WO1999022170A1

WO1999022170A1 - Pipe joints

Info

Publication number: WO1999022170A1
Application number: PCT/IL1998/000522
Authority: WO
Inventors: Moshe Kotzer
Original assignee: Moshe Kotzer
Priority date: 1997-10-29
Filing date: 1998-10-28
Publication date: 1999-05-06
Also published as: AU9642798A

Abstract

A pipe joint system which includes first and second tubular members (12, 14) each having an end portion (42, 56) arranged for connection to the other, wherein at least the end portion (42) of the first tubular member (12) is formed of a recoverable plastic, so as to be selectively deformable and thus enable the end portions (42, 56) of the first and second tubular members (12, 14) to be fitted together in a mating arrangement; and bi-directional gripping apparatus (45) having outwardfacing and inwardfacing surfaces configured to be disposed between opposing surfaces of the end portions (42, 56) of the first and second tubular members (12, 14) when fitted together, the outwardfacing and inwardfacing surfaces defining textured contact portions (52) which are formed of a material that has a hardness greater than that of the opposing surfaces of the end portions (42, 56) of the first and second tubular members (12, 14).

Description

PIPE JOINTS

FIELD OF THE INVENTION The present invention relates to the joining of tubular members generally, and in particular, to the joining of tubular members of which at least one is plastic.

DEFINITIONS

Unless specifically mentioned otherwise, the terms "recoverable" and "cold recoverable" are used in the following specification and claims to mean a plastic body which, under certain conditions, has the property or tendency of recovering its original shape at environmental temperatures after undergoing deformation, also at environmental temperatures, and wherein the recovery may be induced by elastic or any other forces existent in the material, including those caused by mechanical memory effects.

The term "tubular member" is employed throughout the present specification and claims to include all pipes, tubes, conduits, as well as the tubular free ends of various fittings with which a connection or joint with another tubular member may be sought.

BACKGROUND OF THE INVENTION

There exist various types of pipe joints and connectors therefor, especially for pipes used in supplying fluids, such as main water pipes, gas lines, oil lines, or domestic water pipes. These generally include a number of lengths of pipe which are connected together, and which may also have various fittings, such as at T-junctions and at valve connections. All of these connections should be fluid-tight, and as simple and inexpensive as possible. A particular problem in providing suitable joints, however, is that the pipe ends are often smooth, and that the joint itself must therefore be provided by applying pressure between a connector element and the pipe end, and by sealing therebetween.

One solution is by providing various interlocking elements which grip onto the end of a pipe, and which, by connecting to an external pressure member, such as a pressure ring or band, serve to become sealed with the pipe. Disadvantages of this type of connection include the large number of parts required, and the relatively complicated construction thereof. Other, more sophisticated methods of connection, such as that described in US Patent No. 3,972,548 to Roseen, call for fusing together two elements made of cross-linked polymers. US Patent No. 4,070,044 to Carrow, also provides a pipe connection between two pipes, at least one of which is formed of a cross-linked polymer. The end of the pipe formed of a cross-linked polymer is deformed so as to fit over the end of the other pipe. A heat-cross-linkable polymer layer is also inserted between the pipe ends. Accordingly, after the pipes have been fitted together, application of heat to the joint region causes the outer pipe end to shrink back to its 'memory' size, so as to press-fit the cross-linking polymer layer between the two pipe ends, with the aim of providing a strong, fluid-tight joint.

Yet a further method employs electrofusion devices, in which there is provided a sleeve having a current carrying electrical heating coil embedded in an inner wall thereof. The sleeve is open ended, and ends of plastic pipes that it is sought to join are inserted into the sleeve. Application of a voltage across the coil causes it to become heated, thereby to cause the inner sleeve layer and an outer surface of the pipes, to melt, thereby fusing together.

There is also known in the art, as disclosed by US Patent 2,967,067 to Singer, a joint for pipes and tubes employing a metal socket or sleeve prepared with annular ribs of tooth-shaped cross section that grip and seal a soft or flexible pipe or tube forced therein. While the joint can be applied to a plain pipe end, the socket must be machined in advance, which does not allow the joint to be used in the field without significant prior preparation.

Amongst further techniques known in the art which employ memory properties of plastic in order to form joints, are techniques which include the use of "mechanical" and "thermal" memory phenomena, as they apply to polymer-based materials. In brief, the main difference between mechanical memory and thermal memory is that, whereas mechanical memory provides for cold deformation of a pipe end and subsequent recovery of the pipe end after removal of a deformation force, thermal memory provides for application of heat to the pipe end and deformation of the softened, heated pipe end, freezing of the pipe end, and reapplication of heat, which causes a recovery of the pipe end to its original shape.

By way of example of joints formed using mechanical memory effects, German patent publication no. 4025840 describes the joining of polyolefin pipes to a connecting piece, employing this phenomenon. Pipes are joined in a process in which one end of a polyolefin pipe is expanded and fitted over a connecting piece. The pipe end, whose internal diameter is smaller than the outer diameter of the connector, is reversibly expanded at room temperature by means of a spreader mandrel to an internal diameter greater than the outer diameter of the connector; the spreader is removed and the pipe and connector are fitted together, after which the connector is attached firmly to the pipe by reversing the expansion. Medium density and cross-linked polyolefins in particular are cold formed and they tend to revert to their original shape. The expanded pipe thereafter shrinks back again.

Reference is now made to US Patent No. 4,927,184 to Bourjot et al, entitled "Pipes Based on Polyolefin Resin for Manufacturing Pipelines and Couplings for Assembling Them", as an example of joints produced using thermal memory effects. In addition to describing the use of multi-layer hot welding devices for joining multi-layer polyolefin pipes, wherein both the device and the pipes each have a layer of thermoplastic resin and a layer of cross-linked polyolefin resin, this patent also describes the use of heat to soften the end of a first pipe end, after which it can be easily expanded and placed over a second pipe end. As the heated pipe end cools, it attempts to return to its previous size.

In considering the merits of prior art devices which employ mechanical or thermal memory phenomena, a number of disadvantages arise.

In the case of devices employing mechanical memory effects, the mechanical memory of a pipe will cause it to seek to shrink back to its original shape when the elastic limit of the pipe has not been exceeded. This effect is observed mostly with cross-linked polyethylene and the above phenomenon of shrinking occurs at environmental temperatures typically in a range from -20 to 50°C. The gradual shrinkage of the material occurs over a period of several minutes up to approximately one hour, depending on the dimensions of the pipes, the materials used, and the environmental conditions. Since the shrinking back of an expanded pipe using mechanical memory typically occurs relatively quickly, there will often be a need for the expansion to be performed on site where a pipe is sought to be joined with another pipe or pipe fitting. For reasons well appreciated by persons skilled in the art, it is however, most desirable to provide a product which is formed to its maximum extent on the production floor, and which requires a minimum amount of skill and effort in the field.

Similarly, where the phenomenon of thermal memory is employed, thermal recovery requires the use of a heat source on-site. Additionally, thermoplastic materials limit the use of thermal memory techniques to the melting point of the plastic. A further disadvantage of using thermal memory techniques, is that irreversible damage may be caused to the pipe. In addition to the above-described disadvantages, the strength of a joint formed using memory effects, is often compromised when using plain, smooth pipe ends. In order to increase the strength of a joint so formed, specially prepared pipe ends possessing surface features are often required to be provided.

For the various reasons cited above, none of the above-described prior art methods and apparatus facilitate high quality, relatively simple, connection and sealing of pipes, as proposed in the present invention.

SUMMARY OF THE INVENTION

The present invention seeks to provide a novel pipe connection system and method of joining tubular members generally, which utilize, in conjunction with plastic mechanical memory effects, a bi-directional gripping apparatus. The system and method of use, provide for a simple to form, inexpensive, and highly reliable pipe connection thereby overcoming disadvantages of known art.

In particular, the present invention seeks to provide a method of, and apparatus for, connecting tubular members which have plain or smooth ends, which may be totally devoid of any surface features that might otherwise help to facilitate a mechanical connection between the two pipe ends.

The present invention also seeks to provide a relatively inexpensive and convenient-to-use tool for the purpose of expanding the free ends of tubular members to which it is sought to attach other tubular members or fittings, on site.

Further, the present invention seeks to provide a method of preparing a plastic tubular member for connection to another tubular member by use of mechanical memory effects, wherein cold deformation of the free end of an elastic tubular member is not required to be performed on site, and the recovery stage is delayed until a desired time, this time preferably being such time as the tubular members to be joined are ready for assembly.

There is thus provided, in accordance with an embodiment of the invention, a pipe joint system which includes: first and second tubular members each having an end portion arranged for connection to the other, wherein at least the end portion of the first tubular member is formed of a recoverable plastic, so as to be selectably deformable and thus to enable the end portions of the first and second tubular members to be fitted together in a mating arrangement; and bi-directional gripping apparatus having outward-facing and inward-facing surfaces configured to be disposed between opposing surfaces of the end portions of the first and second tubular members when fitted together, the outward-facing and inward-facing surfaces defining textured contact portions which are formed of a material that has a hardness greater than that of the opposing surfaces of the end portions of the first and second tubular members, wherein, after deformation of the end portion of the first tubular member, and after fitting together of the end portions of the first and second tubular members and the bi-directional gripping apparatus, the end portion of the first tubular member seeks to recover its non-deformed shape, thereby to apply a radial force to the bi-directional gripping apparatus and to the end portion of the second tubular member, and thereby to press the gripping apparatus between the opposing surfaces of the end portions, such that the contact portions of the inward-facing and outward-facing surfaces of the gripping apparatus become lockingly engaged with the opposing surfaces of the end portions, thereby to lock together the first and second tubular members.

Additionally, in accordance with an embodiment of the invention, the gripping apparatus includes a ring member having generally cylindrical side walls, the side walls having formed thereon the contact portions.

Further, in accordance with an embodiment of the invention, the ring member is configured to form a fluid-tight seal with the first and second tubular members.

Additionally, in accordance with an embodiment of the invention, the cylindrical side walls have at least one elongate opening formed therein so as to permit generally radial deformation of the ring member in response to a radial force applied thereto.

Further, in accordance with an embodiment of the invention, the ring member is formed of a polymer.

Additionally, in accordance with an embodiment of the invention, the ring member is at least partially formed of an elastomer.

Further, in accordance with an embodiment of the invention, the gripping apparatus includes a plurality of discrete gripping elements having formed thereon the contact portions. Additionally, in accordance with an embodiment of the invention, the textured contact portion of at least one of the outward-facing and inward-facing surfaces of the gripping apparatus is further formed so as to allow relative axial translation between the first and second tubular members in a predetermined direction only.

Further, in accordance with an embodiment of the invention, the first tubular member is formed of polyethylene.

Additionally, in accordance with an embodiment of the invention, the first tubular member is formed of cross-linked polyethylene.

Further, in accordance with an embodiment of the invention, the end portion of the first tubular member is configured, following deformation thereof, for attachment exteriorly about the end portion of the second tubular member, and the end portion of the first tubular member is shrinkable.

Alternatively, in accordance with another embodiment of the invention, the end portion of the first tubular member is configured, following deformation thereof, for attachment interiorly of the end portion of the second tubular member, and the end portion of the first tubular member is expandable.

Additionally, in accordance with an embodiment of the invention, the second tubular member is also formed of a recoverable plastic.

Further, in accordance with an embodiment of the invention, a predetermined one of the first and second tubular members is a connector sleeve having free end portions and the system also includes a third tubular member similar to the other of the first and second tubular members, and the free end portions of the connector sleeve are configured for connecting the end portions of the others of the tubular members.

Additionally, in accordance with an embodiment of the invention, there is provided sealing apparatus configured to be disposed between the opposing surfaces of the end portions of the first and second tubular members when fitted together, thereby to form a fluid-tight seal therebetween.

Further, in accordance with an embodiment of the invention, there is provided stopping apparatus operative to limit a relative axial translation between the first and second tubular members to a predetermined distance.

Additionally, in accordance with one embodiment of the invention, there is provided a generally cylindrical releasing device operative to release the contact portions from gripping engagement with the opposing surfaces of the end portions of the first and second tubular members, thereby to allow relative axial translation in any direction.

Further, in accordance with an embodiment of the invention, there is provided expansion apparatus for expanding a free end portion of a plastic tubular member, which includes an adjustable expansion head which defines an outward-facing cylindrical contact region parallel to an axis, and an actuator mechanism for selectively applying a force relative to the axis so as to cause a desired lateral expansion of the contact region while retaining the contact region cylindrical, and parallel to the axis, wherein, when located in the end portion of a tubular member, the contact region is operative to apply radially outward forces thereto, so as to cause expansion thereof.

Additionally, in accordance with an embodiment of the invention, there is also provided a recovery delay apparatus for preventing recovery of an elastically deformed end portion of a tubular member, until after a desired time has elapsed after deforming thereof, wherein the recovery delay apparatus includes a support ring which defines a generally cylindrical contact surface for braced engagement with the deformed end portion of the tubular member, to prevent at least a partial recovery thereof, and the recovery delay apparatus also includes apparatus for permitting selectable release of the support ring, thereby facilitating its disengagement from the deformed end portion.

In accordance with another embodiment of the invention, there is provided a method of employing bi-directional gripping apparatus for connecting first and second tubular members formed of plastic, each having end portions arranged for connection to each other, wherein the bi-directional gripping apparatus has outward-facing and inward-facing surfaces configured to be disposed between opposing surfaces of the end portions of the first and second tubular members when fitted together, the outward-facing and inward-facing surfaces defining textured contact portions which are formed of a material that has a hardness greater than that of the opposing surfaces of the end portions of the first and second tubular members, and wherein the method includes the following steps: a) deforming the end portion of the first tubular member to a size such that it can be fitted together with the second tubular member in a mating arrangement, and thereby causing the end portion of the first tubular member to become recoverable; b) fitting together the first and second tubular members in mating relationship so as to enclose between opposing surfaces thereof the bi-directional gripping apparatus; and c) allowing the end portion of the first tubular member to partially recover its non-deformed size, such that it applies a radial force to the gripping apparatus and to the end portion of the second tubular member, thereby to compress the gripping apparatus between opposing surfaces of the end portions of the first and second tubular members, such that the contact portions of the inward-facing and outward-facing surfaces of the gripping apparatus become lockingly engaged with the opposing surfaces of the end portions, thereby to lock together the first and second tubular members.

Additionally, in accordance with an embodiment of the invention, step b) also includes the sub-step of placing a generally ring-shaped sealing element such that it becomes disposed between opposing surfaces of the end portions of the first and second tubular members when these are fitted together, thereby to provide a fluid-tight seal therebetween.

Further, in accordance with an embodiment of the invention, step a) includes mechanically deforming the end portion at environmental temperatures, and step c) includes allowing recovery of the end portion, also at environmental temperatures.

Additionally, in accordance with an embodiment of the invention, step a) includes radially expanding the end portion of the first tubular member, step b) includes fitting the end portion of the first tubular member about the end portion of the second tubular member, and step c) includes allowing the end portion of the first tubular member to contract relative to the end portion of the second tubular member.

Alternatively, in accordance with another embodiment of the invention, step a) includes radially contracting the end portion of the first tubular member, step b) includes inserting the end portion of the first tubular member into the end portion of the second tubular member, and step c) includes allowing the end portion of the first tubular member to expand relative to the end portion of the second tubular member.

In accordance with yet a further embodiment of the invention, there is provided a method of preparing a plastic tubular member formed of a cold recoverable material for connection to another tubular member, which includes: mechanically deforming a free end portion of the plastic tubular member so as to allow mating thereof with a free end portion of the other tubular member, thereby to set up recovery forces in the free end portion of the plastic tubular member, urging it to recover its original size; bracing the free end portion of the plastic tubular member against recovery; and permitting at least partial recovery of the free end portion of the plastic tubular member after a desired time period has elapsed after said step of deforming.

Additionally, in accordance with an embodiment of the invention, the step of mechanically deforming is performed at environmental temperatures.

Further, in accordance with an embodiment of the invention, the step of bracing includes applying recovery-resistant forces to the free end portion of the plastic tubular member opposite to the recovery forces, thereby to delay recovery of the free end portion of the plastic tubular member.

Additionally, in accordance with an embodiment of the invention, the step of mechanically deforming includes expanding the free end portion of the plastic tubular member, and the step of bracing includes inserting a generally cylindrical recovery delay apparatus inside the free end portion of the plastic tubular member, thereby to brace the free end portion of the plastic tubular member against contraction.

Alternatively, in accordance with an embodiment of the invention, the step of mechanically deforming includes compressing the free end portion of the plastic tubular member, and the step of bracing includes placing a generally cylindrical recovery delay apparatus about the free end portion of the plastic tubular member, thereby to brace the free end portion of the plastic tubular member against expansion.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood and appreciated from the following detailed description, taken in conjunction with the drawings, in which:

Fig. 1 is a schematic cross-sectional view of a simple pipe joint formed in accordance with a preferred embodiment of the invention;

Fig. 2 is a schematic cross-sectional view of an alternative pipe connection, also formed in conjunction with the present invention;

Fig. 3 is a schematic view of a T-connection employing a plurality of pipe connections as seen in Fig. 2;

Fig. 4A is a detailed cross-sectional view depicting a pair of tubular members to be joined, prior to their full assembly;

Fig. 4B is a view similar to that of Fig. 4 A, but following assembly;

Fig. 4C is an enlarged detail of a portion of the joint of Fig. 4B; Fig. 5 is an isometric view of the bi-directional gripping member seen in Figs. 4A-4C;

Fig. 6 is an isometric view of a bi-directional gripping member formed in accordance with an alternative embodiment of the invention;

Fig. 7 is a pictorial representation of a pipe end having placed thereon a plurality of bi-directional gripping elements for use in accordance with an embodiment of the present invention;

Fig. 8A is an enlarged cross-sectional view of a portion of a pipe joint to be formed between two tubular members in accordance with an embodiment of the invention, prior to full assembly, and employing a bi-directional gripping member which may be similar to any of those seen in Figs. 9A, 9B and 9C;

Fig. 8B is a view similar to that of Fig. 8 A, but following assembly;

Figs. 9 A, 9B and 9C are isometric views of bi-directional gripping members formed in accordance with further embodiments of the invention;

Fig. 10 is a schematic cross-sectional view of a pipe joint formed in accordance with yet a further embodiment of the invention;

Figs. 1 1 A and 1 IB are cross-sectional views of a joint formed between two tubular members in accordance with another embodiment of the invention, prior to and subsequent to full assembly, respectively, and employing an additional reinforcement ring formed of a recoverable material;

Fig. 12A is a detailed cross-sectional illustration showing a partially assembled pipe joint, formed in accordance with a further embodiment of the present invention, but prior to full engagement and joining of all the parts thereof;

Fig. 12B is an isometric view of the bi-directional gripping member seen in the pipe joint of Fig. 12 A;

Fig. 13 A is a detailed cross-sectional illustration showing portions of a pair of tubular members to be joined in accordance with an alternative embodiment of the present invention, prior to their full assembly;

Fig. 13B is an isometric view of the bi-directional gripping member seen in Fig. 13 A;

Fig. 14A is a detailed cross-sectional illustration showing a pipe joint formed in accordance with a further alternative embodiment of the present invention; Fig. 14B is an isometric view of the bi-directional gripping member seen in the pipe joint of Fig. 14 A;

Fig. 15 is a schematic side-sectional view of expansion apparatus, useful in a method of the invention, in a retracted position;

Fig. 16 is a schematic side-sectional view of the expansion apparatus of Fig. 15 in an expanded position; _. ^•

Fig. 17 is a front elevational view of the apparatus of Figs. 15 and 16, taken in the direction of arrow 3 in Fig. 16;

Fig. 18 is a schematic side-sectional view of expansion apparatus, formed in accordance with another embodiment of the invention, in a retracted position;

Fig. 19 is a schematic side-sectional view of the expansion apparatus of Fig. 18 in a fully expanded position;

Fig. 20 is a cross-sectional view of the apparatus of Figs. 18 and 19, taken along line 6-6 in Fig. 19;

Figs. 21 A and 21B are views similar to those of Figs. 19 and 20, respectively, but showing use of an adapter ring;

Fig. 22 is a graph showing force applied versus the displacement angle of the expansion head of the apparatus of Figs. 18-21B;

Fig. 23 A is a plan view of a deformed free end portion of a plastic tubular member prepared by use of a recovery delay method in accordance with an alternative embodiment of the invention;

Figs. 23B and 23C are cross-sectional views of the free end portion of Fig. 23A, taken along line B-B therein, using recovery delay apparatus constructed and operative in accordance with an embodiment of the invention, seen in a recovery delay position, and after contraction of the apparatus, respectively;

Fig. 24 is a cross-sectional view similar to Fig. 23B, but illustrating the use of recovery delay apparatus constructed and operative in accordance with another embodiment of the invention;

Fig. 25A is a cross-sectional view similar to Figs. 23B and 24, but illustrating the use of recovery delay apparatus constructed and operative in accordance with a further embodiment of the invention; Fig. 25B is a cross-sectional view similar to that of Fig. 25A, but illustrating the recovery delay apparatus in a collapsed state;

Fig. 26A is a plan view of the deformed free end portion of a plastic tubular member prepared by use of a recovery delay method in accordance with an alternative embodiment of the invention; and

Fig. 26B is a cross-sectional view of the free end portion seen in Fig. 26A, taken along line B-B therein.

DETAILED DESCRIPTION OF THE INVENTION

The present invention seeks to provide an improved system for production of a high-strength, preferably fluid-tight pipe joint, wherein the system of the invention includes improved apparatus and method for connecting tubular members together so as to form the pipe joint As seen from the description below, in addition to the provision of bi-directional gripping apparatus, at least one of the tubular members employed in the system of the present invention is typically formed of a cold recoverable material, at least a portion of which is either expanded or compressed prior to its connection with another tubular member, so as to enable utilization of the mechanical memory effects stored therein.

The system of the invention further includes improved apparatus and method for deformation of a free end portion of a tubular member formed of a cold recoverable material, as well as improved apparatus and method for optionally delaying the recovery stage of a deformed tubular member until a desired time, thereby enabling prior off site preparation of components of a pipe joint

More specifically, the apparatus employed in the preparation of a pipe joint formed in accordance with the system of the present invention, includes

(i) apparatus for connecting two tubular members, as described hereinbelow in conjunction with Figs. 1-14B;

(ii) apparatus for expansion of a tubular member, as described hereinbelow in conjunction with Figs. 15-22; and

(iii) apparatus for optionally delaying the recovery of an expanded or compressed tubular member, as described hereinbelow in conjunction with Figs. 23 A-26B.

Referring now to Fig. 1, there is seen a pipe joint, referenced generally 10, formed in accordance with a preferred embodiment of the invention. Pipe joint 10 is formed between first and second tubular members, respectively referenced 12 and 14, which it is sought to connect, thereby to provide a high strength, preferably fluid-tight joint.

In accordance with the present invention, first member 12 is typically formed of a recoverable plastic, having mechanical memory properties which may be usefully exploited in forming joints in accordance with the present invention. Accordingly, while first member 12 may be formed of any suitable polymer, such as polyethylene, it is most preferably formed of cross-linked polyethylene (PEX), which has greater recovery characteristics at environmental temperatures than non-cross-linked polyethylene. First member 12 may alternatively be formed so as to have plural layers of polyethylene, of which at least one is cross-linked polyethylene.

Second member 14 may be formed of any suitable, plastic material, which is not necessarily recoverable.

It will be appreciated from the description below, that, regardless of the precise type of plastic from which the first and second members are made, the particular advantage of the present invention lies in the fact that it facilitates the joining together of "plain" tubular members which have no surface features, such as ridges, grooves, protrusions or the like, which might otherwise facilitate their connection to each other.

Referring now to Fig. 2, there is seen a pipe connection, referenced generally 20, in which a sleeve member 22 is used, in accordance with the present invention, to connect two tubular members, referenced 24' and 24", in end to end fashion. In this embodiment, each end 26 of sleeve member 22 is joined to an end portion 28' or 28" of an associated tubular member 24' or 24", respectively, so as to define a joint thereat, referenced generally 10'. It will be appreciated that joint 10' is formed in substantially the same manner as joint 10, seen in Fig. 1, that sleeve member 22 has similar properties and generally corresponds to first tubular member 12, and that tubular members 24' and 24" have similar properties and generally correspond to second tubular member 14.

Referring now to Fig. 3, there is seen a T-connection, referenced generally 30, in which a plurality of sleeve members 22 are used to connect a plurality of tubular members, referenced 34', 34" and 34'" to a T-member 36. In this embodiment, each end 26 of sleeve member 22 is joined to an end portion 38', 38" or 38'" of an associated tubular member 34', 34" and 34'", respectively, or to a respective end portion 37', 37" or 37'" of T-member 36, so as to define a joint thereat, referenced generally 10'. It will be appreciated that joints 10' are formed in substantially the same manner as joint 10, seen in Fig. 1, and joint 10', seen in Fig. 2, and that tubular members 34', 34" and 34'" and T-member 36 have similar properties and generally correspond to tubular members 14, 24' and 24" as described above.

It is thus seen that the joint 10 of Fig. 1 represents a general case which can be applied to many different connection arrangements, including variously configured arrangements not specifically described herein, and that the connections shown and described in conjunction with Figs. 2 and 3, are merely representative of this fact.

Details of joint 10 of the invention, is now described in conjunction with Figs. 4A-6, below.

Referring initially to Figs. 4A and 4B, joint 10 of Fig. 1 is shown in enlarged detail, prior to and after full assembly. While only joint 10 is shown and described herein, it will be appreciated that this represents a general case which relates also to joints 10' (Figs. 2 and 3), as well as to joints of various other connection arrangements which may be formed in conjunction with the present invention.

As seen in Figs. 4A and 4B, joint 10 includes first and second tubular members 12 and 14, which have end portions, respectively referenced 42 and 44, which are arranged for connection to each other. There is also provided, and disposed between end portions 42 and 44, gripping apparatus in the form of a bi-directional gripping member 45, having outward-facing and inward-facing textured contact portions. In the present example, gripping member 45 is a gripping ring whose contact portions are embodied by inward-facing and outward-facing gripping barbs or teeth 52. Typically, there is also provided a sealing element 60 which, in the present example, is an O-ring.

As indicated in Fig. 4 A, first member 12 initially has an interior diameter D_a, which at end portion 42 of first member 12, is seen to have been expanded to D . The outer diameter of end portion 44 of second member 14 is D , which is significantly smaller than Da, although preferably greater than D_a. Gripping member 45 has a gross, tip-to-tip diameter D_c, which is typically smaller than D_d, such that barbs 52 do not obstruct initial mating of the ends of the tubular members 12 and 14.

As described in greater detail below in conjunction with a method of the invention, expansion of end portion 42 of first member 12 is provided for, such that the expanded end portion 42 seeks to recover its original shape at environmental temperatures so that the interior diameter of end portion 42 returns, at the very least, to a diameter smaller than D_c, and preferably also to a diameter smaller than exterior diameter D_b of end portion 44 of second tubular member 14.

As seen in Figs. 4B and 4C, the mechanical memory contraction of end portion 42 of first tubular member 12 about gripping member 45 and end portion 44 of second tubular member 14, causes barbs 52 of gripping member 45 to penetrate into opposing inward-facing and outward-facing surfaces of end portions 42 and 44, thereby to lock tubular members 12 and 14 together. It is also seen that, at the same time as gripping member is compressed between first and second members 12 and 14, sealing element 60 also becomes compressed therebetween, thereby to form a fluid-tight seal at the resulting joint.

Referring now also to Fig. 5, the method of the invention is facilitated, in particular, by means of the bi-directional gripping member 45, which, as described above, is configured to be disposed between end portion 42 of first tubular member 12 and end portion 44 of second tubular member 14. Gripping member 45 has outward-facing and inward-facing surfaces, generally referenced 46 and 48 respectively, and, as seen in Figs. 4A-4C, is configured for placement over end portion 44 of second tubular member 14 in accordance with a method of the invention.

It is noted that, while the contact portions of gripping member 45 may take the form of sharp protrusions or barbs 52 as illustrated in Figs. 4A-4C and 5, they may alternatively be embodied in other ways such as are described below generally in conjunction with Figs. 8A-14B.

It is also noted that a further aspect of gripping member 45 is that the contact portions thereof are made of a material that has a hardness greater than that of an inward-facing surface 56 (Figs. 4 A and 4C) of the first tubular member 12, and greater also than that of an outward-facing surface 58 of second tubular member 14. Typically, gripping member 45 is made of metal, although it may alternatively be made of a sufficiently flexible, hardened plastic, such as acetal.

As will be appreciated from the description below, in a case in which only one of a pair of pipes to be connected in the field is formed of a recoverable material, it is desired that gripping member 45 be deformable. In the example described above in conjunction with Figs. 4A-4C, gripping member 45 is formed so as to be contractible.

In accordance with the present embodiment, therefore, gripping member 45 preferably has formed therein longitudinal openings 59 (Fig. 5), ensuring that when a generally uniform, inward radial force is applied to the ring, it contracts generally inwardly, in the region of the openings 59.

In accordance with an alternative embodiment of the invention, however, there may be provided a gripping ring 145, which as seen in Fig. 6, is generally similar to ring 45 (Fig. 5), but which does not have longitudinal openings 59 formed therein. In this embodiment, ring 145 may be formed from a band 147 of a material which has elastic properties, such as EPDM, and into which are embedded barbs or teeth 152, formed of metal, or of another sufficiently hard material for the purpose of the invention.

Referring now briefly to Fig. 7, there may alternatively be provided, in place of gripping members 45 (Fig. 5) and 145 (Fig. 6), a plurality of bi-directional gripping elements 45'. Gripping elements 45' may be of similar structure, and serve a purpose similar to that of members 45 and 145, and are thus not specifically detailed herein.

It will be appreciated however, that in accordance with an embodiment of the invention, it is possible, and may even be desirable, to mount elements 45' onto a pipe end 44' as seen in Fig. 7, as a stage of production, rather than as one of the assembly stages in the field. By way of example, pipe end 44' could be softened by heating, such that gripping elements 45' could then simply be pressed onto the outer surface thereof. Upon cooling of the pipe end 44', elements 45' would remain fastened thereto, and another pipe end (not shown) could then be expanded, placed thereover, and shrunk thereabout, so as to lock the two pipe ends together.

Alternatively, elements 45' could be similarly fastened onto an interior surface of a pipe end, such as an interior surface corresponding to inward-facing surface 56 of end portion 42 of Fig. 4 A. Thereafter, the pipe end with its attached gripping elements, could be joined to another pipe end or tubular member, by placement thereover and contraction thereabout.

It will be appreciated, that in both of the above cases employing gripping elements 45', the outer pipe end is preferably provided as an expandable tubular end portion, having mechanical memory properties similar to those of end portion 42 of first member 12 (FIGS. 4A-4C) which facilitate contraction or shrinking about the inner pipe end of the joint after placement thereover. Alternatively, however, like joints may be formed using a compressible inner pipe end which possesses mechanical memory properties capable of facilitating recovery expansion of the inner pipe end after cold deformation thereof and placement within the outer pipe end of the joint. Such joints employing cold recoverable inner tubular portions, are described generally hereinbelow in conjunction with Fig. 10 as well as Figs. HA and 11B.

Referring now once more to Figs. 4A and 5, and in accordance with one embodiment of the present invention, the internal diameter, D_a, of end portion 42 of first tubular member 12 is initially smaller than the "gross" exterior diameter, D_c, of gripping member 45. Following expansion, however, the internal diameter, O ~, of end portion 42 of first tubular member 12, is greater than the "gross" exterior diameter, D_c, of gripping member 45, such that it can be fitted thereover when gripping member 45 is positioned on the end portion 44 of second tubular member 14. In the present embodiment, D_c is measured between the tips of diametrically opposed outward-facing barbs 52. This is preferred so that the outward-facing barbs 52 do not prevent the two tubular members 12 and 14 from being fitted together.

Thus, referring once again to Figs. 4A-4C, in accordance with the present embodiment of the invention, joint 10 is formed in accordance with the following method steps: a) Deforming the end portion 42 of the first tubular member 12 to a size such that it can be fitted together with the end portion 44 of the second tubular member 14 in a mating arrangement, and thereby causing the end portion 42 of the first tubular member 12 to become recoverable. b) Fitting together end portions 42 and 44 of the first and second tubular members 12 and 14 in mating relationship so as to enclose between opposing surfaces thereof the bi-directional gripping member 45. c) Allowing the end portion 42 of the first tubular member 12 to partially recover its non-deformed size, such that it applies a radial force to the gripping member 45 and to the end portion 44 of the second tubular member 14, thereby to compress the gripping member between opposing surfaces of the end portions 42 and 44 of the first and second tubular members 12 and 14, such that the contact portions of the inward-facing and outward-facing surfaces of the gripping apparatus become lockingly engaged with the opposing surfaces of the end portions, thereby to lock together the first and second tubular members.

In cases where end portion 42 is formed of a cold recoverable material as previously described, step a) of deforming the end portion 42 of first tubular member 12, could be achieved for example, by mechanically stretching the end portion 42 at environmental temperatures - such as with the aid of expansion apparatus described hereinbelow in conjunction with Figs. 15-22. In such a case, step c) may be performed by allowing end portion 42 to undergo at least partial recovery at environmental temperatures, under the influence of mechanical memory effects.

Thus, in allowing mechanical recovery of the end portion 42 of first tubular member 12 of the present embodiment in accordance with step c), the recoverable end portion 42 is operative to apply an inward radial force to the gripping member 45, and to the end portion 44 of the second tubular member 14, thereby to cause the gripping member 45 to contract inwardly about the outward-facing surface 58 of the end portion 44 of the second tubular member 14 so as to become locked together therewith, and, further, to cause the inward-facing surface 56 of the end portion 42 of the first tubular member 12 to become locked together with the outward-facing surface 46 of the gripping member 45.

It will be appreciated by persons skilled in the art, that the above general method steps a) to c), are equally applicable to formation of a pipe joint as described below in conjunction with Fig. 10, wherein step a) includes the step of radially contracting the end portion of the first tubular member, step b) includes the step of inserting the contracted end portion of the first tubular member into the end portion of the second tubular member, and step c) includes the step of allowing the contracted end portion of the first tubular member to expand relative to the end portion of the second tubular member. Preferably in such an embodiment, the first tubular member is formed of a cold recoverable material enabling mechanical deformation and subsequent recovery of its end portion at environmental temperatures.

Similarly it will be appreciated, that method steps a) to c) may be applied to an embodiment of the invention as described hereinbelow in conjunction with Figs. 11A and 1 IB, wherein both the inner and outer tubular members used to form a pipe joint, are formed of a recoverable material, thereby allowing for cold deformation and mechanical memory recovery of each member at environmental temperatures.

It will further be appreciated by persons skilled in the art that, optionally, different steps or portions thereof, may be performed at different locations - such as in the factory or in the field. By way of example, recovery delay apparatus as described hereinbelow in conjunction with Figs. 23A-26B, may optionally be employed together with related method steps, so as to delay the cold recovery of a portion of a tubular member which has undergone mechanical deformation. Such apparatus and associated method steps may be useful in cases where advance off-site preparation of a free end portion of a cold recoverable tubular member is expedient.

It will further be appreciated that, gripping member 45 may be expandable, such as by virtue of longitudinal openings 59 (Fig. 5), so as to enable the use of a gripping member 45 of a given diameter, in conjunction with tubular members of different sizes, including those which may be larger than the initial size of gripping member 45.

Preferably, in addition to the above method steps, a suitable, generally ring-shaped sealing element 60, of the "O-ring" or any other preferred type, is placed onto the end portion 44 of the second tubular member 14 in order to ensure that a good, fluid-tight seal is provided. Sealing element 60 is preferably arranged between the free edge 43 (Fig. 4A) and the gripping member 45. Accordingly, as the end portion 42 of the first tubular member 12 contracts, the sealing element 60 becomes compressed between the end portions of first and second tubular members 12 and 14, thereby sealing any space or gap that may remain.

In accordance with a further embodiment of the invention, however, the bi-directional gripping member of the invention may also function as a fluid-tight sealing element. One example of this is when the gripping member is provided as a band 147 (Fig. 6) of an elastomeric material. A further example is shown and described hereinbelow in conjunction with Figs. 11A and 1 IB, in which the illustrated gripping member 445 has formed thereon, one or more inward-facing unbroken ridges 447, and an unbroken outward-facing ridge 449. It will be appreciated that ridges 447 and 449 are operative to bite into respective opposing surfaces of first and second tubular members 412 and 414, and are thus able to provide a fluid-tight seal therewith, without requiring additional sealing means. Referring once again to Fig. 4B, it is seen that in the case of joint 10, the locking provided between the two members 12 and 14 is dependent on their interaction with the gripping member 45. More particularly, it will be appreciated that the protrusions 52 provided on the gripping member are required to be of a shape and hardness that will cause them to frictionally or mechanically engage the end portions of the tubular members between which the gripping member 45 is compressed, as the outer tubular member 12 contracts and seeks to regain its former size. Thus, while the protrusions 52 are exemplified herein as barbs, they may alternatively be any other type of feature which will provide purchase or gripping between the gripping member 45 and the associated surfaces of the members to be joined.

By way of example, gripping member 45 may include protrusions in the form of circumferential ridges as are described below in conjunction with Figs. 8A-9C and 11A-11B, or may include alternatively formed textured contact portions as is described in conjunction with Figs. 12A-14B. In some cases, the requisite purchase or gripping effect may even be achieved where the contact portions of gripping member 45 are simply provided as roughened surfaces (not shown). Similarly, in accordance with a further embodiment of the invention, the second tubular member may, in fact, have simply a surface formed with depressions and/or ridges which will themselves provide ample purchase for protrusions 52 of gripping member 45 once the gripping member is compressed thereabout.

It is noted however, that the contact portions of gripping member 45 preferably include protrusions which are of a shape and hardness that will cause them to become embedded into the end portions of the tubular members between which the gripping member is compressed.

In the description set out hereinbelow, various embodiments of the invention, which include alternative configurations of the invention's gripping apparatus, are described in conjunction with Figs. 8A-14B. For purposes of completeness, it is noted that these embodiments are intended to serve as non-limiting examples only, and should not be taken to limit the scope of the invention in any way

It is further noted, that joints 210, 310, 410, 510, 530 and 550 as described below, may be easily applied to a variety of connection arrangements, which include, but are not limited, to the connection arrangements depicted in Figs. 2 and 3 above, wherein any suitable combination of joints 210, 310, 410, 510, 530 and 550 may be substituted for joints 10' illustrated therein.

Referring now to Figs. 8A and 8B, there is seen in enlarged detail, a pipe joint, referenced generally 210, formed in accordance with an alternative embodiment of the invention, prior to and following full assembly. Pipe joint 210 is formed between first and second tubular members, respectively referenced 212 and 214, which it is sought to connect, thereby to provide a fluid-tight joint. First and second tubular members 212 and 214 of joint 210 have end portions, respectively referenced 242 and 244, which are arranged for connection to each other. End portions 242 and 244 may be connected to each other using method steps corresponding to those described above in relation to the connection of end portions 42 and 44 of tubular members 12 and 14 in the formation of joint 10.

Referring still to Figs. 8A and 8B, it is seen that in accordance with the present embodiment of the invention, joint 210 is provided by use of a cylindrical gripping member 245 which is arranged between end portions 242 and 244 of tubular members 212 and 214, respectively. Gripping member 245 has inward-facing and outward-facing textured contact portions referenced 246 and 248, which in the present embodiment are constituted by circumferential inward-facing and outward-facing toothed ridges, respectively referenced 247 and 249. Optionally, gripping member 245 includes a stopping portion, referenced 250 whose function is described in greater detail below. There is also preferably provided, a sealing element 260 which, in the present example, is a cylindrical sealing element not of the O-ring type, and is mounted onto a free end 243 of second tubular member 414 without connection to gripping member 245.

Considering now gripping member 245 in more detail, reference is also made to Figs. 9 A, 9B, and 9C, which illustrate isometric views of alternative embodiments of the gripping member. For purposes of clarity, these alternative embodiments are collectively referred to herein as gripping member 245, so as to denote features common to the various embodiments illustrated in Figs. 9A-9C. Conversely, specific reference to one or more of gripping members 245', 245" and 245'" is made where it is sought to denote the individual feature or features of a particular embodiment.

Referring generally to the various embodiments of gripping member 245 illustrated in Figs. 9A-9C, it is noted that the gripping members 245', 245" and 245'" illustrated therein, generally have the same hardness requirements as gripping member 45 of joint 10 (Fig. 5), shown and described hereinabove, and these are therefore not described again herein. It is also of particular note that the outward-facing ridges 249 are formed so as to be positioned in a generally 'forward' orientation, towards the free edge 241 of first tubular member 212 (Figs. 8 A and 8B), and the inward-facing ridges 247 are formed so as to be positioned in an opposing orientation, towards the free edge 243 of second tubular member 214. These orientations ensure that, once a joint has been formed, the ridges 247 and 249 resist pulling apart of the two tubular members 212 and 214 by, in certain cases, becoming even further embedded into the respective surfaces being gripped thereby, even at environmental temperatures.

It should also be noted that following the assembly of joint 210 (Fig. 8B), the width of the space between opposing surfaces 256 and 258 of first and second tubular members 212 and 214, is preferably less than the total breadth of gripping member 245, taken from the peaks of circumferential ridges 247 and 249 on either side thereon. This ensures that joint 210 has good mechanical stability.

Referring now to Figs. 9A and 9B in more specific detail, it is noted that in addition to possessing circumferential ridges, gripping members 245' and 245" are preferably also formed with longitudinal openings as seen in these drawings.

More specifically, in accordance with the example seen in Fig. 9 A, gripping member 245' preferably has formed therein a plurality of longitudinal openings referenced 159', which ensure that when a generally uniform, inward radial force is applied to the gripping member, it contracts generally inwardly, in the region of the openings 159', thereby facilitating its stable positioning upon a tubular end portion such as end portion 244 of second tubular member 214 (Figs. 8A and 8B). Similarly, openings 159' are operative to facilitate expansion of gripping member 245', upon application of a generally uniform, outward radial force to the gripping member, thereby to facilitate stable positioning inside a tubular end portion, such as end portion 242 of first tubular member 212 (Figs. 8 A and 8B). It is noted that in addition to facilitating placement of gripping member 245' upon or within an end portion of a tubular member, openings 159' are also operative to facilitate locking engagement of gripping member 245' about or within a portion of tubular member, in a similar fashion to openings 59 of gripping member 45 described hereinabove in conjunction with Figs. 4A-5.

Referring now briefly to Fig. 9B by way of comparison, alternative gripping member 245" may be used in place of gripping member 245'. Gripping member 245" is generally similar to gripping member 245' (Fig. 9A), except that gripping member 245" is a split ring, having a single split 159" provided therein, so that it may be easily placed either into first tubular member 212 or onto second tubular member 214. It will be appreciated that like longitudinal openings 59 (Fig. 5) and 159' (Fig. 9A), split 159" also provides a convenient means to enable gripping member 245" to expand in response to a radially outward force, or contract in response to a radially inward force, as described above in accordance with a method of the invention.

Turning now to Fig. 9C, there is illustrated therein, a gripping member 245'" which may be used as a further alternative in place of gripping members 245' and 245". As seen in Fig. 9C, gripping member 245'" is generally similar to gripping members 245' and 245", but does not have longitudinal openings formed therein. In this embodiment, gripping member 245'" may be formed from a material harder than that of first and second tubular members 212 and 214 which need not be elastic. It should also be noted that in this embodiment, the internal diameter of gripping member 245"', as measured across the peaks of inward-facing circumferential ridges 247'", is typically less than the external diameter of second tubular member 214, and the external diameter of gripping member 245'", as measured across the peaks of outward-facing circumferential ridges 249'", is typically greater than the internal diameter of first tubular member 212.

In accordance with the present embodiment, to form joint 210, gripping member 245'" is forced over end portion 244 of second tubular member 214 via free end 243 (Figs. 8A and 8B). Thereafter, end portion 242 of first tubular member 212 is forced over gripping member 245'" at least until it completely encompasses the gripping member 245'". Alternatively, if gripping member 245'" includes a stopping portion 250 as shown in Figs. 8 A and 8B with gripping member 245, first tubular member 212 is forced over gripping member 245'" until its free end 241 engages the stopping portion 250. In the present embodiment, circumferential ridges 247'" and 249'" are unbroken, and thus may also provide a sealing function, so that no separate sealing member such as sealing element 260 (Figs. 8A and 8B) is required.

It will be appreciated that whilst gripping member 245'", as described, may be used to provide a joint 210 without requiring either or both of tubular members 212 and 214 to be formed of an elastically deformable material, nevertheless, in cases where either or both of these tubular members are in fact formed of a cold recoverable material, the elastic deformation thereof, and subsequent cold recovery, in accordance with a method of the invention, will be operative to enhance the mechanical stability of joint 210 as previously described hereinabove.

Referring now to Fig. 10, there is seen a pipe joint, referenced generally 310, formed in accordance with a further alternative embodiment of the invention. Pipe joint 310 is formed between first and second tubular members, respectively referenced 312 and 314, which it is sought to connect, thereby to provide a high strength, preferably fluid-tight joint.

First and second tubular members 312 and 314 are similar to first and second tubular members 12 and 14, shown and described above in conjunction with Figs. 1 and 4A-4C, and are thus not specifically described again herein in detail. Similarly, a deformable gripping member 345 and a suitable sealing element 360 are employed in the present embodiment, also as shown and described hereinabove.

It is seen that the sole difference between the presently illustrated joint 310 and joint 10 of Figs. 1 and 4A-4C, is that, whereas, in order to form joint 10, first tubular member 12 is expanded in order to fit the tubular members together, and is thereafter placed over gripping member 45 and second tubular member 14, this is not the case in the present embodiment.

In the present embodiment, the external diameter of first tubular member 312 is initially larger than the internal diameter of gripping member 345. After contracting, however, the external diameter of first tubular member 312 is smaller than the internal diameter of gripping member 345, such that it can be fitted therein when gripping member 345 is positioned inside the end portion of second tubular member 314, generally coaxially therewith, as seen in Fig. 10.

Accordingly, joint 310 is formed by contracting an end portion 342 of first tubular member 312, placing gripping member 345 and sealing element 360 either thereon or inside an end portion 344 of second tubular member 314 - which alternatives, as seen in the drawing, are substantially equivalent to each other - and thereafter inserting the contracted end portion 342 of first tubular member 312 into the end portion 344 of second tubular member 314. The joint is then left so as to allow end portion 342 of first tubular member 312 to expand, thereby applying a radially outward force to the gripping member 345 and to end portion 344 of second tubular member 314, thus causing the protrusions 352 thereof to become embedded in the opposing outward-facing and inward-facing surfaces 353 and 355 of end portions 342 and 344, respectively, so as to cause mechanical engagement therebetween. Sealing element 360 is also compressed therebetween, thereby to provide a fluid-tight sealing thereat.

As previously noted, it will be appreciated that joint 310 is by way of example only, and that the various joint configurations shown and described above in conjunction with Figs. 2 and 3, as well as other pipe joints, may be formed in accordance with the present embodiment of the invention. It will also be appreciated that the gripping apparatus used to form joint 310, is not limited to the configuration of gripping member 345 as illustrated in Fig. 10, but may alternatively include any suitable gripping member including those depicted in Figs. 7, 8A-9C, and 1 1A-14B. Furthermore, it will be appreciated that recovery delay apparatus, particularly as described hereinbelow in conjunction with Figs. 26A and 26B, may optionally be employed to delay the cold recovery of a contracted end portion 342 of first tubular member 312, where desired.

Referring now to Figs. 11A and 1 IB in more detail, there is shown a joint arrangement, referenced generally 410, formed in accordance with a further embodiment of the present invention. The joint is seen prior to full assembly in Fig. 11 A, and following assembly in Fig. 1 IB.

Joint arrangement 410 includes first and second tubular members 412 and 414, each of which is formed of a recoverable material, as described above in conjunction with any of Figs. 1-10. Members 412 and 414 have respective end portions, 442 and 444, which are arranged for connection to each other. First tubular member 412 may either be a connector sleeve 22, as shown and described above in conjunction with Figs. 2 and 3, or the end of a length of pipe or tube which it is sought to join to second tubular member 414. Similarly, second tubular member 414 may be any free end of any sort of pipe, tube or connector, to which it is sought to join first tubular member 412. Arrangement 410 also includes a bi-directional gripping member 445, which has formed thereon generally circumferential inward-facing and outward-facing toothed ridges, respectively referenced 447 and 449. Since, in the present embodiment, both the first and second tubular members 412 and 414 are formed from recoverable materials, gripping member 445 is not required to be deformable, and may be formed of any suitable rigid material. A further advantage resulting from this fact is that the inward-facing and outward-facing toothed ridges 447 and 449 are operative, in addition to their locking function, to provide a fluid-tight seal between the gripping member 445 and the tubular members 412 and 414, thereby obviating the need for an additional sealing ring.

In order to further strengthen the joint seen in Figs. 11 A and 1 IB, there may also be provided a reinforcement ring 460. Reinforcement ring 460 is also formed of a recoverable material, and is preferably mounted onto the end portion 442 of first tubular member 412 in the factory. Ring 460 may for example, have pre-deformation inner and outer diameters similar to that of first and second tubular members 412 and 414, which in the present example, are approximately equal prior to deformation of tubular members 412 and 414.

By way of non-limiting example, end portion 442 of first tubular member 412 together with reinforcement ring 460, may be mechanically expanded, such as with the aid of expansion apparatus described hereinbelow in conjunction with Figs. 15-22, thereby to adopt the relatively expanded position seen in Fig. 1 1A. End portion 444 of second tubular member 414 may then be mechanically compressed so as to allow mounting thereon of gripping member 445, prior to recovery of member 414. Thereafter, expanded end portion 442 and attached ring 460 may be placed over compressed end portion 444 and attached gripping member 445. Upon subsequent recovery of the tubular members and reinforcement ring, the first tubular member 412 and attached ring 460 contract towards their original, pre-expanded shapes, while the second tubular member 414 expands towards its non-compressed shape. In so doing, ridges 447 and 449 of gripping member 445 bite into adjacent opposing surfaces of end portions 442 and 444, as seen in Fig. 1 IB, thereby to cause gripping member 445 to become locked with first and second tubular members 412 and 414, and thereby also to provide a fluid-tight seal therewith.

Optionally, recovery delay apparatus as described hereinbelow in conjunction with Figs. 23A-26B, may be employed where desired, so as to facilitate the prior off-site preparation of tubular members 412 and 414 and associated reinforcement ring 460. Turning now to Figs. 12 A, 13 A and 14A generally, there are seen therein, detailed cross-sectional views of various pipe joint components, illustrated at various stages of assembly. In general terms, each of the resulting pipe joints 510, 530 and 550 incorporates a gripping member, which in contrast to the gripping members already described hereinabove, has non-uniform inward-facing and outward-facing textured contact portions. It is noted that gripping members 525, 545 and 565, as illustrated and described herein in conjunction with Figs. 12B, 13B, and 14B, respectively, are provided as non-limiting examples only, and gripping members incorporating any suitable combination of textured contact portions, are contemplated as falling within the scope of the invention.

It is further noted that in the context of the present invention, joints 510, 530 and 550 are preferably formed using mechanical memory effects arising from the mechanical deformation and cold recovery of either or both of the tubular members used to form a respective joint. It is of additional note however, that, for reasons evident from the description below, gripping members 525, 545 and 565, and similar such bi-directional gripping apparatus, have the particular advantage of facilitating highly mechanically stable joints, even where mechanical memory effects are not employed in the joint formation process.

Referring now more specifically to Fig. 12 A, there is seen, in detailed cross-section, a pipe joint, referenced generally 510, formed in accordance with an embodiment of the present invention, prior to full assembly. Pipe joint 510 is formed between first and second tubular members, respectively referenced 512 and 514, which it is sought to connect in a fluid-tight arrangement.

First and second tubular members 512 and 514 of joint 510 have end portions, respectively referenced 522 and 524, which are arranged for connection to each other. Gripping apparatus, in the form of a cylindrical gripping member, referenced 525, is provided between end portions 522 and 524, and shown in an isometric view in Fig. 12B. Gripping member 525 has an inward-facing textured contact portion 526 and an outward-facing textured contact portion 528. In the present embodiment, these contact portions are constituted by circular rows of inward-facing and outward-facing gripping teeth 626 and 628, respectively. These gripping teeth may have any profile that provides suitable gripping. In the present example, inward-facing gripping teeth 626 are rounded and outward-facing gripping teeth 628 are pointed, as shown in Fig. 12B, but this is strictly by way of example; the gripping apparatus may be embodied by any suitable combination of tooth profiles. There is preferably also provided a sealing element 520 (Fig. 12 A) which, in the present example, is cylindrical and is connected to cylindrical gripping member 525 by barbs 627 thereon. In the present embodiment, there may also optionally be provided on cylindrical gripping member 525, a stopping portion 515 which serves to limit the insertion of cylindrical gripping member 525 into first tubular member 512 to a predetermined distance as shown in Fig. 12 A.

It is of particular note that the outward-facing teeth 628 are formed so as to be positioned in a generally 'forward' orientation, towards free edge 612 of end portion 522 of first tubular member 512, and the inward-facing teeth 626 are formed so as to be positioned in an opposing orientation, towards free edge 614 of end portion 524 of second tubular member 514. These orientations ensure that, once the members comprising a joint enter engagement, teeth 626 and 628 allow relative axial movement of the tubular members in only one predetermined direction and resist pulling apart of the two tubular members 512 and 514. Additionally, in certain cases, teeth 626 and 628 may become embedded into the respective surfaces 518 and 516 being gripped thereby. Accordingly, teeth 626 and 628 are made of a material that has a hardness greater than that of inward-facing surface 516 of first tubular member 512, and greater also than that of outward-facing surface 518 of second tubular member 514. They may be made of metal or, alternatively, of a sufficiently flexible, hardened plastic, such as acetal.

Gripping teeth 626 and 628 may be integrally formed with gripping member 525 or may be mounted thereon, as long as there is sufficient elasticity in their orientation, as described above, so that they allow relative axial movement in the predetermined direction and resist it in the other direction. In accordance with an alternative embodiment of the invention, gripping member 525 may be formed from a material which has elastic properties, such as EPDM, and into which are embedded teeth 626 and 628 formed of metal, or of another sufficiently hard material for the purpose of the present invention.

Referring again to Fig. 12 A, cylindrical sealing element 520 is attached to gripping member 525 with barbs 627, also shown in Fig. 12B, and has a tapered end 621 which extends beyond the end of gripping member 525. It may be formed of any suitably elastic material such as rubber that can be compressed and that will sealingly engage with another smooth surface. Its outward-facing surface 622 engages inward-facing surface 516 of end portion 522 of first tubular member 512 in a fluid-tight seal. When second tubular member 514 is fully inserted into joint 510, its end portion 524 engages tapered end 621 of sealing element 520 to complete a fluid-tight seal between tubular members 512 and 514. It should be noted that the specific form of, and sealing method employed by, sealing element 520, are shown strictly by way of example, and that any suitable sealing element is included within the scope of the present invention.

While, as noted above, gripping member 525 may be embodied by any suitable combination of tooth profiles, the arrangement of pointed and rounded teeth in the present example, represents a preferred combination. As is seen in the drawing, inward-facing surface 516 of end portion 522 of first tubular member 512 engages sealing element 520 before it engages pointed outward-facing gripping teeth 628 of gripping member 525, whereas outward-facing surface 518 of end portion 524 of second tubular member 514 engages sealing element 520 after it engages rounded inward-facing gripping teeth 626 of gripping member 525. Since pointed teeth 628 will tend to scratch or otherwise affect the tube surface which they engage more than rounded teeth 626, the present arrangement of teeth profiles is operative to provide better sealing than the opposite arrangement.

It is worth noting that free edge 614 of end portion 524 of second tubular member 514 may optionally be chamfered to facilitate its insertion into gripping member 525, as shown in Fig. 12A.

In the embodiment of the present invention shown in Fig. 12A, gripping member 525 also includes stopping portion 515 which serves to limit the insertion of cylindrical gripping member 525 into first tubular member 512 to a predetermined distance. Stopping portion 515 is a radial extension at the end of gripping member 525 which may be a complete ring, as shown in Fig. 12B, or one or more portions of the circumference thereof. When gripping member 525 is fully inserted into first tubular member 512, free edge 612 of tubular member 512 engages stopping portion 515 of gripping member 525 as shown in the drawing, thereby preventing deeper insertion.

It will be appreciated that, in accordance with one aspect of the present embodiment, it is possible, and may even be desirable, to mount gripping member 525 onto first tubular member 512 as a stage of production, rather than as one of the assembly stages in the field. This may be wherein gripping member 525 is first inserted into first tubular member 512, and second tubular member 514 is then inserted therein as shown in Fig. 12 A, or the opposite case (not shown) wherein gripping member 525 is first fitted over a first tubular member and the resulting assembly is then inserted into a second tubular member.

Referring now to Fig. 13 A, there is seen, in cross-section, components of a pipe joint, referenced generally 530, prior to their assembly in accordance with a further embodiment of the present invention. Pipe joint 530 is formed between first and second tubular members, respectively referenced 532 and 534, which it is sought to connect, thereby to provide a fluid-tight joint.

First and second tubular members 532 and 534 of joint 530 have end portions, respectively referenced 542 and 544, which are arranged for connection to each other. There is also provided, between end portions 542 and 544, a cylindrical gripping member 545, shown in isometric view in Fig. 13B, having outward-facing and inward-facing textured contact portions 546 and 548. In the present embodiment, the outward-facing contact portion 546 is constituted, by way of example, by pointed teeth 646 similar to teeth 628 described above in conjunction with Figs. 12A and 12B. The inward-facing contact portion 548 in the present example is embodied by barbs 648 which lockingly mount gripping member 545 onto outward-facing surface 536 of end portion 542 of first tubular member 532. There is also provided a sealing element 540 which, in the present example, is cylindrical and is mounted onto free edge 632 of first tubular member 532 without connection to gripping member 545. In the present embodiment, there is also optionally provided on cylindrical gripping member 545, a stopping portion 535 which serves to limit to a predetermined distance, the insertion of first tubular member 532 with cylindrical gripping member 545 mounted thereon, into second tubular member 534.

Teeth 646 and stopping portion 535 in the present example function in similar fashion to teeth 626 and 628 and stopping portion 515 in Figs. 12A and 12B and so are not specifically described herein.

In the present example, cylindrical sealing element 540 is formed, as above, of any suitably elastic material such as rubber, that can be compressed and that will sealingly engage with another smooth surface. It is mounted onto free end 632 of first tubular member 532 and seals therewith, and has an O-ring-like cylindrical protrusion 641 for sealing engagement with second tubular member 534 when inserted therein. In the present example, sealing element 540 is not connected to gripping member 545, but it is positioned by a radially-inward extending portion 643 which overlaps free edge 632 of first tubular member 532, as shown in Fig. 13 A. It is also worth noting that, in the present example, free edge 634 of end portion 544 of second tubular member 534 is optionally chamfered internally, to facilitate the insertion thereinto of first tubular member 532 with gripping member 545 and sealing element 540 mounted thereon, as shown in Fig. 13A.

Referring now to Fig. 13B, there is seen, an isometric view of cylindrical gripping member 545. In accordance with the present example, gripping member 545 preferably has formed therein longitudinal openings 549, ensuring that when a generally uniform, outward radial force is applied to gripping member 545, it expands generally outwardly, in the region of the openings 549. This allows barbed contact portion 548 to be freely positioned for locking onto outward-facing surface 536 of end portion 542 of first tubular member 532 without barbs 648 damaging or otherwise affecting any other part of tube surface 536. Alternatively, gripping member 545 may be formed of a hard material which can be deformed plastically, rather than elastically, so that it can easily be positioned for locking onto outward-facing surface 536 of end portion 542 of first tubular member 532. After being suitably positioned, a generally uniform, inward radial force may be applied to gripping member 545, so as to further deform it, such that it lockingly engages tube surface 536.

In a further alternative embodiment (not shown), gripping member 545 may be formed, without longitudinal openings 549, of a material which has elastic properties, such as EPDM, and into which are embedded barbs 648 and teeth 646, formed of metal or of another sufficiently hard material for the purpose of the invention. In this embodiment, gripping member 545 may be temporarily expanded generally outwardly by the application of a generally uniform, outward radial force thereto, thereby allowing free positioning of gripping member 545 as in the previous example, before releasing it to return to its original size.

In yet a further alternative embodiment, end portion 542 of first tubular member 532 may be formed of a material which has elastic properties, allowing it to be temporarily contracted generally inwardly by the application of a generally uniform, inward radial force thereto, thereby allowing its free insertion into gripping member 545 for positioning therein, before releasing it to return to its original size. It should be noted that in all of the above examples, barbed contact portion 548 of gripping member 545, must be positioned on tube surface 536, prior to engaging toothed contact portion 546 and surface 538 of second tubular member 534.

Referring now to Fig. 14 A, there is seen, in cross-section, a pipe joint, referenced generally 550, formed in accordance with a further alternative embodiment of the present invention. Pipe joint 550 is formed between first and second tubular members, respectively referenced 552 and 554, which it is sought to connect, thereby to provide a fluid-tight joint.

First and second tubular members 552 and 554 of joint 550 have end portions, respectively referenced 562 and 564, which are arranged for connection to each other. There is also provided between end portions 562 and 564, a cylindrical gripping member 565, shown in isometric view in Fig. 14B, which has first and second cylindrical gripping portions, referenced 570 and 572 respectively. As is further illustrated in Fig. 14B, first cylindrical gripping portion 570 has an outward-facing textured contact portion 566 and an inward-facing textured contact portion 568. In the present embodiment, the inward-facing contact portion 568 is constituted, by way of example, by rounded teeth 668 similar to teeth 626 described above in conjunction with Figs. 12A and 12B. The outward-facing contact portion 566 in the present example, is embodied by barbs 666 which lockingly engage gripping member 565 within end portion 562 of first tubular member 552 via its inward-facing surface 556. There is also provided a sealing element 560, which, in the present example, is cylindrical and is mounted onto gripping member 565 via a second barbed surface 667 formed upon second cylindrical portion 572 of the gripping member.

It should be noted that, in the example shown in Figs. 14A and 14B, barbed contact portion 566 is formed on the outward-facing surface of gripping member 565, and is lockingly mounted onto the inward-facing surface 556 of end portion 562 of first tubular member 552. By way of comparison, in the example shown in Figs. 13A and 13B, barbed contact portion 548 is formed on the inward-facing surface of gripping member 545, and is lockingly mounted onto the outward-facing surface 536 of end portion 542 of first tubular member 532. Accordingly, all the alternative embodiments described above for freely positioning barbed contact portion 548 of gripping member 545 upon first tubular member 532 - such as via expansions and contractions of joint components employing longitudinal openings in gripping member 545, or via suitable elastic material - may be applied to the present example by inverting inward and outward directions and by interchanging expansions and contractions. Thus, they are not specifically described herein. It should, however, be noted that in the these examples as well, barbed contact portion 566 of gripping member 565 should be positioned on tube surface 556 prior to engaging toothed contact portion 568 and an outward-facing surface 558 of second tubular member 554.

Considering now sealing element 560 in more detail, the present example employs yet a further type of cylindrical sealing element which seals on inward-facing surface 556 of first tubular member 552 with a smooth cylindrical portion 661 of the sealing element, and seals on outward-facing surface 558 of second tubular member 554 with tilted ring-shaped portions 663, as seen in Fig. 14 A. It should again be noted however, that any suitable form of sealing element is contemplated as falling within the scope of the present invention.

Referring still to Fig. 14A, there is seen, a cylindrical joint disengagement tool 595 which axially encircles second tubular member 554. Joint disengagement tool 595 may be a single integral cylindrical piece, in which case it is preferably installed on second tubular member 554 when forming joint 550, or it may be made of one deformable piece or of two or more pieces that combine to make a complete cylinder that can be assembled around second tubular member 554 when it is sought to disengage joint 550. As seen in the drawing, joint disengagement tool 595 is a smooth cylinder with a diameter intermediate between the external diameter of second tubular member 554 and the internal diameter of first cylindrical gripping portion 570 of gripping member 565, not considering gripping teeth 668. It is long enough, axially, so that when it is fully inserted along second tubular member 554 into joint 550, it comes between outward-facing surface 558 of second tubular member 554 and all gripping teeth 668, thereby disengaging them therefrom. The generally "forward" orientation of gripping teeth 668 towards free edge 654 of end portion 564 of second tubular member 554, allows this disengagement to be reversible, without damaging either gripping member 565 or outward-facing surface 558 of second tubular member 554. With joint disengagement tool 595 so inserted, it is possible to remove second tubular member 554 from first tubular member 552 and gripping member 565, thereby releasing joint 550.

It will be appreciated, as was mentioned in relation to the embodiment of the present invention depicted in Fig. 12 A, that, in accordance with the respective embodiments of the present invention shown in Figs. 13 A and 14A, wherein one of the contact portions of the respective gripping member is embodied by barbs, it is possible, and may even be desirable, to mount the gripping member via its barbs, onto the associated first tubular member, as a stage of production rather than as one of the assembly stages in the field.

It will further be appreciated that, where mechanical deformation and cold recovery of either or both tubular members of a joint is employed to assist in the formation of any of joints 510, 530 or 550, recovery delay apparatus and related method steps, as described hereinbelow in conjunction with Figs. 23 A-26B, may optionally be utilized so as to facilitate off-site preparation of a tubular joint member or members.

Turning now to Figs. 15, 16 and 17, there is seen therein, apparatus referenced 700, constructed in accordance with an embodiment of the system of the present invention, and operative to expand a free end portion of a tubular member. As will be appreciated from the description below, apparatus 700 may be utilized in association with many of the embodiments already described hereinabove, wherein expansion of a tubular member is required or desired. Similarly, apparatus 800, as described below in conjunction with Figs. 18-21B, may serve for expansion of a tubular member in relation to previously described embodiments.

Referring for the moment only to Figs. 15, 16 and 17, apparatus 700 is illustrated for use in expanding a free end portion 722 of a tubular member 712, such as is depicted in dashed lines in Figs. 15 and 16. Tubular member 712 is formed generally similar to first tubular member 12, shown and described above in conjunction with Figs. 1 and 4A-4C, in that it is made of any suitable resilient material, such as plastic, having mechanical memory characteristics. Figs. 15 and 16 respectively illustrate tubular member 712 prior to and following expansion.

Apparatus 700 typically includes an adjustable expansion head 716, a power source 718 mounted onto a base member 720, and an actuator member or head 721, which is connected to power source 718 via a power transfer portion 724.

Expansion head 716 defines an outward-facing generally cylindrical contact region 726 which is formed parallel to an axis 728. In more detail, it is seen that expansion head 716, as seen particularly in Fig. 17, is formed of a plurality of segmental expansion elements 716', each mounted onto a linked support 730 via a hinged connection 732. Each expansion element 716' defines an outward-facing segmental contact surface 726', which, together with the contact surfaces 726' of the other expansion elements 716', constitutes the contact region 726. Each expansion element 716' further defines an inward-facing segmental inclined surface 734, inclined at a predetermined angle α to the axis 728.

Actuator member 721 is seen to be generally conical, such that it defines a conical contact surface 736 (Figs. 16 and 17) which tapers, also at angle α, towards front ends 737 of expansion elements 716', when in the retracted orientation seen in Fig. 15.

Power source 718 may be a suitable pneumatic or hydraulic power source, or. a mechanical system, such as a worm gear system, or the like.

Linked support 730 is constituted by base member 720 and a plurality of elongate connector members 738, which are mutually parallel and are of substantially equal length. Base member 720 may be of any suitable shape, and is located at the rear of the apparatus 700, and transversely to axis 728. Connector members 738 extend between front hinge locations 732 and rear hinge locations 742, whereat they are connected to base member 720. At least three hinge locations 732 and 742 are provided, arranged along an arc of greater than 180°, and spaced preferably equally about axis 728. In the present example, seen in Fig. 17, four pairs of hinge locations 732 and 742 are provided, spaced apart at 90° intervals.

As seen in Figs. 15, 16 and 17, there are preferably also provided one or more resilient compression members 744, such as a rubber belt, or the like, for applying to the expansion elements 716' a radially inward compressive force. This serves to retain the expansion elements 716' in a retracted orientation, in the absence of a radially outward force of greater magnitude.

In general, operation of power source 718 causes a linear translation of actuator head 721 along axis 728, thereby to cause a lateral expansion of expansion head 716, as described below. It is a particular feature of the present embodiment that operation of power source 718 causes a desired lateral widening of the contact region 726 defined by expansion head 716, while maintaining the generally cylindrical form thereof, and thus also the parallel orientation thereof with respect to axis 728. It will thus be appreciated that, when the expansion head 716 is located within free end portion 722 of tubular member 712, the contact region 726 is operative to apply forces thereto, in radially outward directions only, so as to cause an evenly distributed radial expansion of the free end portion 722.

It is also a particular feature of the present embodiment that hinge locations 732 and 742 define respective pivot axes 733 and 743, and that both the mounting of expansion elements 716' at pivot axes 733 and the mounting of connector members 738 at pivot axes 743 are with a single degree of rotational freedom only. Hinge locations 732 are formed such that pivot axes 733 are arranged in a common plane 735 (Figs. 15 and 16), perpendicular to axis 728, and so as to be spaced equidistantly from axis 728. Similarly, hinge locations 742 are formed such that pivot axes 743 are also arranged in a common plane 745 (Figs. 15 and 16), parallel to plane 735, and so as to be spaced equidistantly from axis 728. This geometric arrangement, in conjunction with the above-described geometry of expansion elements 716' and of actuator head 721, limits the movement of expansion elements 716' to a substantially radial motion only, as actuator head 721 advances along axis 728, substantially preventing movement of these elements 716' in any other direction.

Accordingly, in order to expand free end portion 722 of tubular member 712, expansion head 716, in its retracted position shown in Fig. 15, is inserted into end portion 722. Power source 718 is then operated so as to move actuator head 721 along axis 728, in the direction indicated by arrow 746 (Fig. 16), such that conical contact surface 736 thereof slides along the inward-facing inclined surfaces 734 of expansion elements 716', thereby forcing them radially apart, as indicated by arrows 748. In the present example, the diameter of contact region 726 is shown to be just slightly smaller than the interior diameter of free end portion 722 of tubular member 712, such that contact surfaces 726' contact the interior of free end portion 722 even after a small amount of expansion of actuator head 716. This is by way of example only, however, and, within predetermined ranges, apparatus 700 of a predetermined size may be used for expansion of different sizes of tubular members, up to a predetermined maximum size.

As actuator head 721 is displaced successively further along axis 728, expansion elements 716' continue to be displaced further apart, until - in the present example - contact surfaces 726' engage the inward-facing surface of tubular member 712 so as to expand free end portion 722, to a desired size.

Subsequently, after a desired expansion of free end portion 722 has been achieved, actuator head 721 is withdrawn along axis 728, such that the compressive force applied to expansion elements 716' by compression member 744, causes them to contract together, so as to permit removal of the expansion head 716, and of the apparatus 700, from tubular member 712. A desired fitting, pipe, or other tubular member that is sought to fit together with member 712, may then be inserted into the expanded free end portion 722.

Referring now to Figs. 18-20, there is shown therein, expansion apparatus, referenced 800, constructed in accordance with an alternative embodiment of the invention, and operative for expanding a free end 822 of a tubular plastic member 812. Some portions of apparatus 800 are similar, at least in function, if not in form, to those shown and described above in conjunction with apparatus 700, and are therefore not specifically described again hereinbelow. These similar portions are denoted in Figs 18-20, for ease of understanding, by reference numerals which are similar to their counterpart portions in the embodiment of Figs. 15-17, but which commence with a "8" prefix in place of a "7" prefix.

In the present embodiment, each expansion element 816' defines front and rear portions, respectively referenced 860 and 862, each element 816' being connected to a connector member 838 at hinge location 832 via rear portion 862.

Actuator member 821 is mounted for selectable movement along the axis 828 between the expansion elements 816' Actuator member 821 is connected to each expansion element 816' by means of two intervening sets of parallel intermediate connector members 938, so as to form, together with each expansion element 816' and the two intervening pairs of connector members 938, a parallelogram arrangement Each 'set' of connector members 938 is typically either a single member or, as in the present example, it may be a pair of members

It is a particular feature of the present embodiment that hinge locations 832 and 842 define respective pivot axes 833 and 843, and that both the mounting of expansion elements 816' at pivot axes 833 and the mounting of connector members 838 at pivot axes 843 are with a single degree of rotational freedom only. Hinge locations 832 are formed such that pivot axes 833 are arranged in a common plane 835 (Figs. 18 and 19), perpendicular to axis 828, and so as to be spaced equidistantly from axis 828. Similarly, hinge locations 842 are formed such that pivot axes 843 are also arranged in a common plane 845 (Figs. 18 and 19), parallel to plane 835, and so as to be spaced equidistantly from axis 828. This geometric arrangement, in conjunction with the above-described parallelogram arrangement, limits the movement of expansion elements 816' to a substantially radial motion only, as actuator head 821 advances along axis 828, substantially preventing movement of these elements 816' in any other direction.

In operation, a generally forward axial movement of the actuator member 821, as indicated by arrow 846 (Fig. 19), away from the base member 820, causes a pivoting of the intermediate connector members 938 - as shown by arrows 847 (Fig. 19) - towards the generally perpendicular position relative to the axis 828 seen in Fig. 19. This forces the expansion elements 816' radially apart, as indicated by arrows 848, thereby also causing expansion of the tubular member free end portion 822, generally as described above in conjunction with Figs. 15-17.

Referring now briefly to Figs. 21 A and 2 IB, there is shown therein, apparatus 800 which has located thereon an expandable adapter ring, referenced 850. Adapter ring 850 may be any suitable elastic structure, and may be formed of a suitable elastomer, or any other expandable structure. Different sizes of adapter ring 850 may be used so as to effectively increase the diameter of the contact region 826 (Fig. 18 and 19), thereby enabling expansion apparatus 800 of a given size, to be used with a range of sizes of tubular members 812. As a further option, several such rings may be used concentrically, so as to successively increase the effective maximum diameter of expansion.

Referring now briefly to Fig. 22, there is shown a graph of maximum radial force that can be exerted by the expansion head 816, versus the angular displacement between the actuator member 821 and the expansion head 816. This angular displacement is depicted in Fig. 18 by the letter β, and can vary between 0 and 90°. As clearly seen in the graph of Fig. 22, the force exerted increases considerably towards the end of a forward 'stroke' of actuator member 821. This phenomenon can be used to great advantage for expansion of pipe end portions, particularly those formed of especially stiff material, and particularly, when employing apparatus 800 to expand a pipe end having a diameter which is just smaller than the diameter of the expansion head 816 at its point of maximum expansion. In such a case, after expansion has been achieved by opening the expansion head 816 to its maximum extent, successive adapter rings 850 can be placed concentrically on expansion head 816, each time effectively increasing its diameter, and thus enabling a step-by-step expansion of the free end portion 822 of tubular member 812. Further advantages afforded by use of adapter ring 850 include the fact that its use serves to spread the expansion force applied by expansion head 816, over substantially the entire tubular member engaged thereby, thereby ensuring generally uniform expansion of the tubular member, and also serving to protect the interior surface thereof.

It will be appreciated that, while adapter ring 850 has been shown and described in conjunction with apparatus 800, it may also be used in conjunction with apparatus 700, shown and described above in conjunction with Figs. 15-17.

Referring now to Figs. 23A-26B generally, there is seen illustrated recovery delay apparatus, constructed for use in the system and method of the present invention, and operative for optionally delaying the cold recovery of a portion of tubular member which has undergone mechanical deformation by means of cold expansion or cold compression. Such apparatus may be useful in cases where advance off-site preparation of a free end of a cold recoverable tubular member by deformation thereof is expedient, so that the tubular member in its deformed state may be stored with the aid of recovery delay apparatus until such time as it is needed in the field.

It is noted that the exemplary recovery delay apparatus, shown and described hereinbelow in conjunction with Figs. 23A-26B, are all generally sleeve-shaped or ring-like. It will be appreciated however, that this is for example only, and that recovery delay apparatus intended to fall within the scope of the present system of the invention, may also be constituted by members of other suitable configurations which are either hollow or solid in form.

Referring now to Figs. 23 A - 23 C, there is seen the prepared free end 1022 of a plastic tubular member 1012 which, in the present example, is seen to have been expanded. It is seen that recovery of the free end 1022 is prevented by the location of a recovery delay device, constituted in the present embodiment by a support ring 1045. Support ring 1045 is formed of a material which is strong, and which preferably also has a relatively high modulus of elasticity. Suitable materials include steel and aluminum, and a suitable plastic such as U-PVC.

Support ring 1045 has a slit 1004 (Fig. 23 A) which extends across the entire width thereof, formed by free edges 1006a and 1006b. In use, support ring 1045 is inserted into the prepared free end 1022 after expansion thereof, so as to brace the free end against contraction. More precisely, it will be understood that ring 1045 is used to apply recovery-resistant forces to the free end of the tubular member, which are opposite and at least equal to the recovery forces in the deformed end, thereby to delay recovery thereof until a desired time, i.e. until connection of the plastic tubular member to another tubular member or pipe fitting.

An opening 1008 (also seen in hidden detail in Fig. 23 A) is formed along slit 1004, so as to enable extraction of ring 1045 by insertion into opening 1008 of any suitably shaped tool, such as a screwdriver 1010, and a lateral pivoting of the tool while located in the opening 1008, so as to pry loose one of free edges 1006a or 1006b. This pivoting, indicated by arrow 1011 (Fig. 23B), causes one of the free edges to be retracted inwardly of the other edge, as seen in Fig. 23C. Subsequently, ring 1045 may be easily removed from the free end 1022. In the absence of the support ring 1045, the mechanical memory of the free end 1022 causes it to recover its original shape, as desired.

Referring now to Fig. 24, there is seen a prepared free end 2022 of a plastic tubular member, in which is located a recovery delay device 2002 constructed and operative in accordance with another embodiment of the apparatus of the present invention. The delay device 2002 is formed of a support ring 2045, which may be formed of a material similar to those of ring 1045 (Figs. 23A-23C), and which has a longitudinal opening 2059, into which a spacer 2006 has been inserted. In use, support ring 2045 is inserted into the free end 2022 after expansion thereof, and spacer 2006 is placed in opening 2059, thereby to brace the support ring 2045, and thus also the free end 2022 against contraction. Subsequent removal from opening 2059 of the spacer 2006, which may optionally be attached to the ring 2045, causes a partial inward contraction or collapse of the ring, following which it may be easily removed from the free end 2022, allowing recovery thereof.

Spacer 2006 may be formed as a simple peg, and it may also have a hole 2008 formed therein in order to facilitate attachment thereto of a suitable gripping tool, or insertion thereinto of a piece of wire or string, so as to enable spacer 2006 to be pulled easily, possibly without requiring use of any tool.

Referring now briefly to Figs. 5, 9A and 9B in conjunction with Fig. 24, it may be seen that support ring 2045 of recovery delay device 2002, may, in accordance with various further embodiments of the invention, be embodied by a bi-directional gripping member, which is configured to be disposed between the end portions of two plastic tubular members sought to be connected generally as described above. By way of example, support ring may be formed identical to, or substantially similar to, one of bi-directional gripping members 45 (Fig. 5), 245' (Fig. 9A) or 245" (Fig. 9B).

It will be appreciated from the above description, that in such embodiments, wherein support ring 2045 is provided as a bi-directional gripping member, the support ring may serve a dual purpose - namely, it may function as a recovery delay device substantially as described above, and also as a bi-directional gripping member thus also forming an integral part of the connection. Support ring 2045 may thus be formed of any suitable metal, hard plastic, or other suitable material.

It will further be appreciated, that openings 59 (Fig. 5), 159' (Fig 9A) or split 159" of gripping members 45, 245' or 245", as the case may be, are operative to function as openings 2059 of ring 2045, thereby to permit compression of the support ring 2045 when located between a pair of assembled tubular member ends, following removal of any spacers such as spacer 2006 (Fig. 24) therefrom.

Thus, in accordance with a method of the invention, a recovery delay device 2002 in the form of a dual purpose support ring and gripping member 2045, as described above, may be inserted into an expanded free end 2022 of a cold recoverable tubular member, so as to delay recovery thereof. During assembly in the field, a second tubular free end (not seen) is inserted into support ring and gripping member 2045, whereupon removal of any spacers 2006 placed within openings 2059 of the ring 2045, will enable the expanded free end 2022 to contract about the second tubular free end and ring 2045 disposed therebetween, under the influence of mechanical memory recovery forces. As the free end 2022 seeks to recover its original shape, its contraction will be operative to compress support ring and gripping member 2045 between the two tubular free ends, thereby locking the two free ends together.

Referring now to Figs. 25A and 25B, there is seen a prepared free end 4022 of a plastic tubular member, in which is located a recovery delay device 4002 constructed and operative in accordance with yet another embodiment of the apparatus of the invention. The delay device 4002 may be formed of a material similar to those of ring 1045 (Figs. 23A-23C), and is formed as a ring 4045 with an integral, inwardly collapsible portion, indicated generally at 4010. The collapsible portion is typically defined by the provision of preferably one outward -facing groove 4011, surrounded by a pair of inward-facing grooves 4014. Grooves 401 1 and 4014 function as integral hinges, and thereby define a pair of selectably rotatable arc portions 4013. A grip element 4016 extends inwardly from collapsible portion 4010 opposite the outward-facing groove 4011.

It will be appreciated that, while the provision of integral hinges is most convenient, grooves 4011 and 4014 may, alternatively, be replaced by non-integral hinges.

In use, delay device 4002 is inserted into the free end 4022 after expansion thereof, such that the free end is prevented from contracting. Removal of delay device 4002, prior, to assembly of free end 4022 with the end of another tubular member, is facilitated by pulling inwardly on grip element 4016, as shown by arrow 4018. This causes arc portions 4013 to rotate inwardly about grooves 401 1 and 4014, as illustrated by arrows 4020, thereby effectively constituting an inward collapse of collapsible portion 4010, enabling removal of delay device 4002 from the free end 4022.

Referring now to Figs. 26A and 26B, there is seen a prepared free end 5022 of a plastic tubular member 5012 which, in the present example, is seen to have been compressed. It is seen that recovery of the free end 5022 is prevented by the location of a recovery delay device 5002, constituted in the present embodiment by a support ring 5045. Support ring 5045 may be formed of any material described above in conjunction with Figs. 23A-23C.

Support ring 5045 is a split, sleeve-shaped member which defines an opening 5059 between a pair of opposing free edges 5031 and 5033, which respectively have formed thereon, alternating pluralities of knuckles referenced 5032 and 5034. When the knuckle pluralities 5032 and 5034 are brought into mating engagement with each other, they together define a barrel 5036 through which a locking pin 5038 may be inserted, thereby to become locked together. A gripping ring 5040 may be attached to locking pin 5038 for ease of its withdrawal from barrel 5036.

In use, a fully assembled delay device 5002 - with the knuckle pluralities 5032 and 5034 locked together via locking pin 5038 - is placed around the free end 5022 after compression thereof, such that the free end is prevented from expanding to its original size. Extraction of locking pin 5038 from barrel 5036, prior to insertion of free end 5022 into the end of another tubular member for assembly therewith, permits removal of delay device 5002 from free end 5022, so as to allow a desired recovery of the free end 5022.

Referring now briefly to Figs. 23A-26B in general, it is a feature of the present invention that, preferably, the various forms of recovery delay apparatus shown and described hereinabove, are typically not damaged during use, and may thus be reused several times.

In accordance with a further aspect of the system of the invention, however, any suitable recovery delay method may be performed in conjunction with a simple support ring formed of a brittle material, such as a brittle plastic or ceramic, which, while not being reusable, has the advantage of being cheap to manufacture and easy to remove from a braced pipe end, merely by breaking.

It will be appreciated by persons skilled in the art that the scope of the present invention is not limited to what has been particularly shown and described hereinabove, merely by way of example. The scope of the present invention is limited, rather, solely by the claims, which follow:

Claims

1. A pipe joint system which includes: first and second tubular members each having an end portion arranged for connection to the other, wherein at least said end portion of said first tubular member is formed of a recoverable plastic, so as to be selectably deformable and thus to enable said end portions of said first and second tubular members to be fitted together in a mating arrangement; and bi-directional gripping apparatus having outward-facing and inward-facing surfaces configured to be disposed between opposing surfaces of said end portions of said first and second tubular members when fitted together, said outward-facing and inward-facing surfaces defining textured contact portions which are formed of a material that has a hardness greater than that of said opposing surfaces of said end portions of said first and second tubular members, wherein, after deformation of said end portion of said first tubular member, and after fitting together of said end portions of said first and second tubular members and said bi-directional gripping apparatus, said end portion of said first tubular member seeks to recover its non-deformed shape, thereby to apply a radial force to said bi-directional gripping apparatus and to said end portion of said second tubular member, and thereby to press said gripping apparatus between said opposing surfaces of said end portions, such that said contact portions of said inward-facing and outward-facing surfaces of said gripping apparatus become lockingly engaged with said opposing surfaces of said end portions, thereby to lock together said first and second tubular members.

2. A pipe joint system according to claim 1, wherein said contact portions of said gripping apparatus include a plurality of protrusions.

3. A pipe joint system according to claim 2, wherein said plurality of protrusions includes at least one of the group consisting of:

(i) a plurality of barbs; and (ii) at least one ridge.

4. A pipe joint system according to claim 1, wherein said gripping apparatus includes a ring member having generally cylindrical side walls, said side walls having formed thereon said contact portions.

5. A pipe joint system according to claim 4, wherein said ring member is configured to form a fluid-tight seal with said first and second tubular members.

6. A pipe joint system according to claim 4, wherein said cylindrical side walls have at least one elongate opening formed therein so as to permit generally radial deformation of said ring member in response to a radial force applied thereto.

7. A pipe joint system according to claim 4, wherein said ring member is formed of a polymer.

8. A pipe joint system according to claim 4, wherein said ring member is at least partially formed of an elastomer.

9. A pipe joint system according to claim 5, wherein said contact portion of said inward-facing surface of said ring member defines at least one substantially unbroken circumferential inward-facing rib, and said contact portion of said outward-facing surface of said ring member defines at least one substantially unbroken circumferential outward-facing rib, wherein said ribs are configured to become sealingly engaged with said opposing surfaces of said end portions, thereby to form a seal together with said first and second tubular members.

10. A pipe joint system according to claim 4, wherein said contact portions of said gripping apparatus include a plurality of protrusions, and wherein said plurality of protrusions is formed of a material that has a hardness greater than that of said ring member and is mounted resiliently thereon.

11. A pipe joint system according to claim 1, wherein said gripping apparatus includes a plurality of discrete gripping elements having formed thereon said contact portions.

12. A pipe joint system according to claim 1, wherein said textured contact portion of at least one of said outward-facing and inward-facing surfaces is further formed so as to allow relative axial translation between said first and second tubular members in a predetermined direction only.

13. A pipe joint system according to claim 12, wherein said contact portions of said gripping apparatus include a plurality of protrusions which protrude resiliently from said outward-facing and inward-facing surfaces at a generally acute angle thereto and extend generally in said predetermined direction so that they are operative to resist relative axial translation between said first and second tubular members in the direction opposite to said predetermined direction.

14. A pipe joint system according to claim 13, wherein said plurality of protrusions includes at least one of the group consisting of:

(i) a plurality of pointed teeth; (ii) a plurality of rounded teeth; (iii) a plurality of barbs; and (iv) at least one ridge.

15. A pipe joint system according to claim 1, wherein said first tubular member is formed of polyethylene.

16. A pipe joint system according to claim 15, wherein said first tubular member is formed of cross-linked polyethylene.

17. A pipe joint system according to claim 1, wherein said end portion of said first tubular member is configured, following deformation thereof, for attachment exteriorly about said end portion of said second tubular member, and wherein said end portion of said first tubular member is shrinkable.

18. A pipe joint system according to claim 1, wherein said end portion of said first tubular member is configured, following deformation thereof, for attachment interiorly of said end portion of said second tubular member, and wherein said end portion of said first tubular member is expandable.

19. A pipe joint system according to claim 1, wherein said second tubular member is also formed of a recoverable plastic.

20. A pipe joint system according to claim 1, wherein a predetermined one of said first and second tubular members is a connector sleeve having free end portions and said system also includes a third tubular member similar to the other of said first and second tubular members, and wherein said free end portions of said connector sleeve are configured for connecting said end portions of the others of said tubular members.

21. A pipe joint system according to claim 1, and also including sealing apparatus configured to be disposed between said opposing surfaces of said end portions of said first and second tubular members when fitted together, thereby to form a fluid-tight seal therebetween.

22. A pipe joint system according to claim 21, wherein said sealing apparatus includes a generally ring-shaped sealing element which when disposed between said opposing surfaces of said end portions of said first and second tubular members when fitted together, becomes compressed between said first and second tubular members so as provide a fluid-tight seal therebetween.

23. A pipe joint system according to claim 22, wherein said sealing element is integrally formed with said gripping apparatus.

24. A pipe joint system according to claim 1, and also including stopping apparatus operative to limit a relative axial translation between said first and second tubular members to a predetermined distance.

25. A pipe joint system according to claim 4, and also including stopping apparatus operative to limit a relative axial translation between said first and second tubular members to a predetermined distance, wherein said stopping apparatus includes at least one stopping portion formed on said ring member.

26. A pipe joint system according to claim 25, wherein said ring member has generally ring-shaped first and second ends and said stopping portion includes at least one radial protrusion formed at one of said first and second ends of said ring member along at least a portion of its circumference.

27. A pipe joint system according to claim 1, wherein said gripping apparatus includes a ring member having generally cylindrical side walls, said side walls having formed thereon said textured contact portions, wherein said textured contact portion of at least one of said outward-facing and inward-facing surfaces of said gripping apparatus is further formed so as to allow relative axial translation between said first and second tubular members in a predetermined direction only, and wherein said textured contact portions of said gripping apparatus include a plurality of protrusions which protrude resiliently from said outward-facing and inward-facing surfaces at a generally acute angle thereto and extend generally in said predetermined direction so that they are operative to resist relative axial translation between said first and second tubular members in the direction opposite to said predetermined direction, and also including a generally cylindrical releasing device having at least one segment along its circumference wherein said at least one segment forms a complete circle having a diameter that is intermediate between that of one of said outward-facing and inward-facing surfaces of said gripping apparatus and that of one of said opposing surfaces of said end portions of said first and second tubular members and an axial length at least as long as that of said ring member, operative to be inserted between said resilient protrusions and said opposing surfaces of said end portions of said first and second tubular members, thereby to release said contact portions from gripping engagement with said opposing surfaces and thereby to allow relative axial translation in any direction.

28. A pipe joint system according to claim 1, and also including expansion apparatus for expanding said end portion of said first tubular member which includes: an adjustable expansion head which defines an outward-facing cylindrical contact region parallel to an axis; and an actuator mechanism for selectively applying a force relative to said axis so as to cause a desired lateral expansion of said contact region while retaining said contact region cylindrical, and parallel to said axis, wherein, when located in said end portion of said first tubular member, said contact region is operative to apply radially outward forces thereto, so as to cause expansion thereof.

29. A pipe joint system according to claim 1, and also including recovery delay apparatus for preventing recovery of a deformed said end portion of said first tubular member, until after a desired time has elapsed after deforming thereof, wherein said recovery delay apparatus includes: a support ring which defines a generally cylindrical contact surface for braced engagement with said deformed end portion of said first tubular member, to prevent at least a partial recovery thereof, and apparatus for permitting selectable release of said support ring, thereby facilitating its disengagement from said deformed end portion.

30. A pipe joint system according to claim 28, and also including recovery delay apparatus for preventing recovery of a deformed said end portion of said first tubular member, until after a desired time has elapsed after deforming thereof, wherein said recovery delay apparatus includes: a support ring which defines a generally cylindrical contact surface for braced engagement with said deformed end portion of said first tubular member, to prevent at least a partial recovery thereof, and apparatus for permitting selectable release of said support ring, thereby facilitating its disengagement from said deformed end portion.

31. For use in a connection between first and second tubular members formed of plastic, each having an end portion arranged for connection to the other, wherein at least the end portion of the first tubular member is formed of a recoverable plastic, so as to be selectably deformable and thereby to enable the end portions of the first and second tubular members to be fitted together in a mating arrangement, bi-directional gripping apparatus having outward-facing and inward-facing surfaces configured to be disposed between opposing surfaces of the end portions of the first and second tubular members when fitted together, said outward-facing and inward-facing surfaces defining textured contact portions which are formed of a material that has a hardness greater than that of the opposing surfaces of the end portions of the first and second tubular members, wherein, after deformation of the end portion of the first tubular member, and after fitting together of the end portions of the first and second tubular members and said bi-directional gripping apparatus, the end portion of the first tubular member seeks to recover its non-deformed shape, thereby to apply a radial force to said bi-directional- gripping apparatus and to the end portion of the second tubular member, and thereby to press said gripping apparatus between the opposing surfaces of the end portions, such that said contact portions of said inward-facing and outward-facing surfaces of said gripping apparatus become lockingly engaged with the opposing surfaces of the end portions, thereby to lock together the first and second tubular members.

32. Gripping apparatus according to claim 31 , wherein said contact portions include a plurality of protrusions.

33. Gripping apparatus according to claim 32, wherein said plurality of protrusions includes at least one of the group consisting of:

(i) a plurality of barbs; and (ii) at least one ridge.

34. Gripping apparatus according to claim 31, which includes a ring member having generally cylindrical side walls, said side walls having formed thereon said contact portions.

35. Gripping apparatus according to claim 34, wherein said ring member is configured to form a fluid-tight seal with the first and second tubular members.

36. Gripping apparatus according to claim 34, wherein said cylindrical side walls have at least one elongate opening formed therein so as to permit generally radial deformation of said ring member in response to a radial force applied thereto.

37. Gripping apparatus according to claim 34, wherein said ring member is formed of a polymer.

38. Gripping apparatus according to claim 34, wherein said ring member is at least partially formed of an elastomer.

39. Gripping apparatus according to claim 35, wherein said contact portion of said inward-facing surface of said ring member defines at least one substantially unbroken circumferential inward-facing rib, and said contact portion of said outward-facing surface of said ring member defines at least one substantially unbroken circumferential outward-facing rib, wherein said ribs are configured to become sealingly engaged with the opposing surfaces of the end portions, thereby to form a seal together with the first and second tubular members.

40. Gripping apparatus according to claim 34, wherein said contact portions include a plurality of protrusions, and wherein said plurality of protrusions is formed of a material that has a hardness greater than that of said ring member and is mounted resiliently thereon.

41. Gripping apparatus according to claim 31, which includes a plurality of discrete gripping elements having formed thereon said contact portions.

42. Gripping apparatus according to claim 31, wherein said textured contact portion of at least one of said outward-facing and inward-facing surfaces is further formed so as to allow relative axial translation between the first and second tubular members in a predetermined direction only.

43. Gripping apparatus according to claim 42, wherein said contact portions include a plurality of protrusions which protrude resiliently from said outward-facing and inward-facing surfaces at a generally acute angle thereto and extend generally in said predetermined direction so that they are operative to resist relative axial translation between the first and second tubular members in the direction opposite to said predetermined direction.

44. Gripping apparatus according to claim 43, wherein said plurality of protrusions includes at least one of the group consisting of:

45. For use with a plastic tubular member formed of a recoverable material and having a mechanically deformable free end portion configured for connection to a free end portion of another tubular member, expansion apparatus for expanding the mechanically deformable free end portion, which includes: an adjustable expansion head which defines an outward-facing cylindrical contact region parallel to an axis; and an actuator mechanism for selectively applying a force relative to said axis so as to cause a desired lateral expansion of said contact region while retaining said contact region cylindrical, and parallel to said axis, wherein, when located in the free end portion of a plastic tubular member, said contact region is operative to apply radially outward forces thereto, so as to cause expansion thereof.

46. Expansion apparatus according to claim 45, wherein said apparatus further includes a linked support arrangement for supporting said expansion head and said actuator mechanism, and said expansion head includes a plurality of segmental expansion elements, each mounted onto said linked support arrangement via hinged connections, and wherein each said expansion element defines an outward-facing segmental contact surface.

47. Expansion apparatus according to claim 46, wherein said linked support arrangement, said expansion elements and said actuator mechanism are configured so as to retain the segmental contact surfaces equidistant from and parallel to said axis.

48. Expansion apparatus according to claim 47, wherein said linked support arrangement includes: a rigid base member arranged transverse to said axis and having formed thereon at least three hinge locations, arranged along an arc of greater than 180┬░ and spaced equidistantly about said axis; and at least three parallel elongate connector members of equal length and having first and second ends, wherein each said first end is hingedly connected to one of said hinge locations, and each said second end is hingedly connected to one of said segmental expansion elements.

49. Expansion apparatus according to claim 48, wherein said expansion head further defines an inward-facing conical region oriented at a predetermined angle relative to said axis, such that each said expansion element defines an inward-facing segmental inclined surface, also inclined at the predetermined angle to said axis, wherein each expansion element defines a rear portion and a front contact portion terminating in a front end, wherein each said second end of said connector members is connected to said expansion element at said rear portion thereof, wherein said actuator mechanism includes an actuator member mounted for selectable movement along said axis between said base member and said front ends of said expansion elements, wherein said actuator member has a generally conical shape formed symmetrically about said axis and tapering towards a front end thereof, adjacent to said expansion head, wherein said actuator member is operative, when forced axially away from said base member and towards said front ends of said expansion elements, to contact said inward-facing inclined surfaces of said segmental expansion elements so as to force them radially apart, and wherein said expansion elements are prevented by said hinged connection thereof to said connector members from undergoing both linear translation and angular translation parallel to said axis.

50. Expansion apparatus according to claim 49, and also including resilient compression apparatus for applying to said expansion elements a radially inward compressive force thereby to retain said expansion elements in a retracted orientation, in the absence of a radially outward force of greater magnitude.

51. Expansion apparatus according to claim 48, wherein each said expansion element defines rear and front portions, and said second end of each said connector member is connected to said rear portion of one of said expansion elements, wherein said actuator mechanism includes an actuator member mounted for selectable movement along said axis between said expansion elements, and is connected to each said expansion element by means of an intervening pair of parallel intermediate connector members, such that said actuator member defines, together with each said expansion element and said intervening pair of connector members, a parallelogram arrangement, such that, regardless of the axial position of said actuator member with respect to said expansion elements, said segmental contact surfaces are always retained parallel to said axis, and wherein said actuator member is operative, when forced axially away from said base member and towards said front portions of said expansion elements, to rotate said intermediate connector members towards a generally perpendicular position relative to said axis, thereby to force said expansion elements radially apart

52. Expansion apparatus according to claim 49, wherein said actuator mechanism also includes a displacement power source for selectively displacing said actuator member along said axis

53 Expansion apparatus according to claim 45, and further including an adapter element for coaxial placement about said expansion head, thereby to increase the diameter of said contact region

54. For use with a plastic tubular member formed of a recoverable material and having a mechanically deformed free end portion configured for connection to a free end portion of another tubular member, recovery delay apparatus for preventing recovery of the deformed free end portion until after a desired time has elapsed following deforming thereof, which includes: a support ring which defines a generally cylindrical contact surface for braced engagement with the deformed free end portion to prevent recovery thereof, and apparatus for permitting selectable release of said support ring, thereby facilitating its disengagement from the deformed free end portion.

55. Recovery delay apparatus according to claim 54, wherein said support ring is made from a material having a high modulus of elasticity.

56. Recovery delay apparatus according to claim 54, wherein the mechanically deformed free end portion is an expanded free end portion, and said support ring is configured for placement inside the free end portion, thereby to brace it against contraction.

57. Recover^' delay apparatus according to claim 56, wherein said support ring is a split ring having a pair of edges which are arranged for touching engagement when said support ring is positioned inside the free end portion.

58. Recovery delay apparatus according to claim 57, wherein said apparatus for permitting selectable release of said support ring includes apparatus for permitting inward displacement of a selected one of said edges relative to the other of said edges, thereby to enable release of said support ring from the free end portion.

59. Recovery delay apparatus according to claim 56, wherein said support ring includes a compressible bi-directional gripping ring having at least one opening formed therein, and wherein said recover}' delay apparatus also includes at least one spacer for insertion into at least one of said openings, thereby to brace said gripping ring against the interior surface of the expanded free end portion.

60. Recovery delay apparatus according to 56, wherein said support ring has a first hinge location and a pair of second hinge locations spaced thereabout so as to define a pair of arc portions between said first hinge location and said second hinge locations, and said apparatus for permitting selectable release includes apparatus for applying a radially inward pulling force to said arc portions, thereby to cause said arc portions to pivot towards each other about said first hinge location, and, further, to pivot inwardly about said second hinge locations, away from the interior surface of the expanded free end portion of the tubular member, thereby to release it

61 Recovery delay apparatus according to claim 54, wherein the mechanically deformed free end portion is a compressed free end portion, and said support ring is configured for placement about the free end portion, thereby to brace it against expansion

62 Recovery delay apparatus according to claim 61, wherein said support ring is a split sleeve member, and said recovery delay apparatus also includes selectably releasable apparatus for locking said split slee\ e member about the compressed free end portion, thereby to brace it against expansion

63 Recovery delay apparatus according to claim 62, wherein said split sleeve has a pair of opposing free edges and said apparatus for locking includes alternating pairs of knuckles formed on said opposing free edges of said split sleeve member, said pairs of knuckles being operative to define a barrel when arranged in mating engagement together with each other, and a selectably removable locking pin for insertion into said barrel.

64 A method of employing bi-directional gripping apparatus for connecting first and second tubular members formed of plastic, each having end portions arranged for connection to the other, wherein at least the end portion of the first tubular member is formed of a recoverable plastic, and wherein the bi-directional gripping apparatus has outward-facing and inward-facing surfaces configured to be disposed between opposing surfaces of the end portions of the first and second tubular members when fitted together, the outward-facing and inward-facing surfaces defining textured contact portions which are formed of a material that has a hardness greater than that of the opposing surfaces of the end portions of the first and second tubular members, and wherein the method includes the following steps: a) deforming the end portion of the first tubular member to a size such that it can be fitted together with the second tubular member in a mating arrangement, and thereby causing the end portion of the first tubular member to become recoverable; b) fitting together the first and second tubular members in mating relationship so as to enclose between opposing surfaces thereof the bi-directional gripping apparatus; and c) allowing the end portion of the first tubular member to partially recover its non-deformed size, such that it applies a radial force to the gripping apparatus and to the end portion of the second tubular member, thereby to compress the gripping apparatus between opposing surfaces of the end portions of the first and second tubular members, such that the contact portions of the inward-facing and outward-facing surfaces of the gripping apparatus become lockingly engaged with the opposing surfaces of the end portions, thereby to lock together the first and second tubular members.

65. A method according to claim 64, and wherein said step b) also includes the sub-step of placing a generally ring-shaped sealing element such that it becomes disposed between opposing surfaces of the end portions of the first and second tubular members when these are fitted together, thereby to provide a fluid-tight seal therebetween.

66. A method according to claim 64, wherein said step a) includes mechanically deforming the end portion at environmental temperatures, and said step c) includes allowing recovery of the end portion, also at environmental temperatures.

67. A method according to claim 64, wherein said step a) includes radially expanding the end portion of the first tubular member, said step b) includes fitting the end portion of the first tubular member about the end portion of the second tubular member, and said step c) includes allowing the end portion of the first tubular member to contract relative to the end portion of the second tubular member.

68. A method according to claim 64, wherein said step a) includes radially contracting the end portion of the first tubular member, said step b) includes inserting the end portion of the first tubular member into the end portion of the second tubular member, and said step c) includes allowing the end portion of the first tubular member to expand relative to the end portion of the second tubular member.

69. A method according to claim 64, wherein said step a) of deforming the end portion of the first tubular member includes mechanically deforming the end portion of the first tubular member, thereby to set up recovery forces therein urging the end portion to recover to its original size, and wherein said step a) also includes the steps of: bracing the end portion of the first tubular member against recovery; and removal of the bracing from the end portion of the first tubular member after a desired time period has elapsed after said step of deforming.

70. A method of preparing a plastic tubular member formed of a cold recoverable material for connection to another tubular member, which includes: mechanically deforming a free end portion of the plastic tubular member so as to allow mating thereof with a free end portion of the other tubular member, thereby to set up recovery forces in the free end portion of the plastic tubular member, urging it to recover its original size; bracing the free end portion of the plastic tubular member against recovery; and permitting at least partial recovery of the free end portion of the plastic tubular member after a desired time period has elapsed after said step of deforming.

71. A method according to claim 70, wherein said step of mechanically deforming is performed at environmental temperatures.

72. A method according to claim 70, wherein said step of bracing includes applying recovery-resistant forces to the free end portion of the plastic tubular member opposite to the recovery forces, thereby to delay recovery of the free end portion of the plastic tubular member.

73. A method according to claim 70, wherein said step of mechanically deforming includes expanding the free end portion of the plastic tubular member, and said step of bracing includes inserting a generally cylindrical recovery delay apparatus inside the free end portion of the plastic tubular member, thereby to brace the free end portion of the plastic tubular member against contraction.

74. A method according to claim 73, wherein the recovery delay apparatus has at least one opening formed therein, and said step of bracing includes inserting a spacer into the at least one opening.

75. A method according to claim 70, wherein said step of mechanically deforming includes compressing the free end portion of the plastic tubular member, and said step of bracing includes placing a generally cylindrical recovery delay apparatus about the free end portion of the plastic tubular member, thereby to brace the free end portion of the plastic tubular member against expansion

76. A method according to claim 70, wherein the plastic tubular member is formed of polyethylene.

77. A method according to claim 70, wherein the plastic tubular member is formed of cross-linked-polyethylene.