EP0124300A2

EP0124300A2 - Connector for coaxial cable

Info

Publication number: EP0124300A2
Application number: EP84302305A
Authority: EP
Inventors: Joseph P. Slachetka
Original assignee: Thomas and Betts Corp
Current assignee: ABB Installation Products Inc
Priority date: 1983-04-05
Filing date: 1984-04-04
Publication date: 1984-11-07
Also published as: EP0124300A3; AU2619084A; JPS607083A

Abstract

A connector for providing field installable connections of a data transmitting coaxial cable includes a plug portion (32) housing an electrical contact (36) and a body portion (46) including a camming element (48). The body portion (46) is attached through a strain relief member (50, 52) to a coaxial cable (12), the inner conduction (18) of such cable (12) being exposed. The electrical contact (36) on the plug portion (32) includes a pair of spaced elastically deflectable walls (40, 42) defining an opening (44) for free receipt of the cable inner conductor (18). As the plug (32) and body (46) portions are coupled, preferably by tightening of threaded portions (32b, 38, 46b), a cam surface (48c) on the camming element (48) engages the deflectable contact walls (40, 42) and radially compresses such walls into contact with the cable inner conductor (18), thereby establishing electrical connection thereto.

Description

FIELD OF THE INVENTION:

This invention relates to an electrical connector and more particularly to a connector adapted for use with coaxial cables and which may be readily installed in the field.

BACKGROUND OF THE INVENTION:

With the recent advent of flat conductor cable systems, need has arisen for an undercarpet signal transmission system for connection to data terminals and the like. As the customary raceway or ductwork for cable routing and protection found in traditional electrical power distribution and data systems is not present, the undercarpet environment for data cable systems not only requires a cable capable of withstanding mechanical abuse but also a cable design having a height profile that provides unobtrusive installation. In addition to cable construction, consideration must also be given to the interconnections of such cables and the techniques involved in making such interconnections.
The art has seen the development of a low profile coaxial data cable as indicated, for example, in our U.S. Patent No. 4404425, entitled "Cable Assembly for Undercarpet Signal Transmission" issued on 13th September,1983In an effort, however, to maintain a low cable profile, while yet meeting the required impedance characteristics, the inner conductor of such coaxial cable is typically very thin, on the order of 28-30 AWG, and readily bendable without much rigidity. As is known, connection of such coaxial cable, in view of the thin cable inner conductor, is more difficult than standard coaxial cable and often connection to computer terminals is made through intermediate printed circuit boards which house standard connectors. It is also known that the use of printed circuit boards may be eliminated to allow direct connection to data terminals providing the electrical contacts of the connectors are soldered or crimped to the coaxial cable inner conductors. Such soldering or crimping usually occurs in a factory installation or requires special tooling.
While such soldering and crimping techniques are not suitable for field installable interconnections, it has been found that the commonly used resilient split finger arrangement for connection of contact elements in connector components is also not acceptable in view of the relative softness of the cable inner conductor. Such split finger connection devices, which are designed for resilient interference fit with connector contacts, are shown, for example, in U.S. Patents 4,377,320; 3,936,125; and 3,439,294.
A connector that is readily field installable by ordinary electrician's tools and that provides effective connection to the relatively soft inner cable conductor is highly desirable, in particular, where office layouts and planning dictate changes in the location of the office equipment.

SUMMARY OF THE INVENTION:

It is an object of the present invention to provide an improved electrical connector for connection to a conductor in an electrical cable.
It is another object of the invention to provide a connection apparatus in an electrical connector for disconnectably establishing electrical connection between a cable conductor and a termination contact.
In accordance with the invention, the electrical connector comprises a body having a generally central aperture for receipt therein of an exposed conductor of an electrical cable. A plug is included having means cooperatively coupling the body, the coupling means providing for relative movement between the body and the plug during coupling. The plug has a generally central aperture in substantial alignment with the body aperture. An elongate conductive contact is provided, the contact being disposed in the plug aperture and having a termination end and a conductor receiving end. The conductor receiving end faces the body and has elastically deflectable walls defining an opening for receipt of the cable conductor therein. The walls are movable from a first normally open position wherein the opening is of expanse sufficient to freely receive the cable conductor therein to a second closed position wherein the opening is less than the cross-sectional extent of the cable conductor. Further in the connector, means is supported by the body for engaging the conductor receiving end of the contact and moving the deflectable walls from the first position to the second position during the coupling of the plug and body, such that upon completion of the coupling, electrical connection may be established between the cable conductor and the contact.
In the preferred form, the connector is particularly adapted for connection use with a coaxial cable of the type having an inner conductor and an outer conductor spaced by a layer of insulation and a jacket of insulation about the outer conductor. A plug subassembly and a body subassembly threadably coact to form the connector. The plug subassembly houses the contact with the deflectably movable walls and the body subassembly includes a camming element having a cam surface thereon adapted to engage the deflectable contact walls during threadable assembly of the connector to thereby cause engagement of such contact walls with the coaxial cable inner conductor that passes through the body subassembly. A strain relief member is included for attachment to the coaxial cable insulation jacket and for holding the cable and thereby the inner conductor in a fixed position relative to the connector body subassembly.

BRIEF DESCRIPTION OF THE DRAWING:

Figure 1 is a perspective view illustrating the particularly useful application of the present invention in enabling connection from an undercarpet coaxial data cable directly to a cathode ray tube of a computer terminal.
Figure 2 is a perspective end view of the flat coaxial cable with which the present invention is particularly useful.
Figure 3 is an exploded elevation view of the connector of the present invention, showing the various components thereof and a coaxial cable for connection thereto.
Figure 4 is a side elevation view, partially broken away to reveal interior details, of a plug subassembly and body subassembly in accordance with a preferred connector assembly arrangement, the subassemblies being shown detached.
Figure 5 is a view of the connector strain relief portion, inclusive of a cable clamp, as seen along viewing lines 5-5 of Figure 2.
Figure 6 is an enlarged view of the connector contact conductor receiving end freely receiving the cable conductor prior to full coupling between the connector plug and body.
Figure 7 is a view of Figure 6 wherein the connector coupling and assembly is complete and electrical connection is established between the cable conductor and the connector contact.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT:

Referring now to the drawing, there is shown in Figure 1 a particularly preferred use of the connector of the present invention. As illustrated therein, a coaxial connector, generally designated as numeral 10, terminates a flat coaxial cable 12 for direct connection to a cathode ray tube 14 which may be part of a computer terminal or other data transmission equipment. The flat coaxial cable 12 in preferably of the type having a generally low profile (less than 0.100 inch) for installation on a floor surface beneath carpet tiles 16 or similar floor covering. As shown in detail in Figure 2, the data cable 12 comprises an inner conductor 18 encircled by a layer of insulation 20, a drain wire 22 and an electrically conductive outer sheath 24 surrounding the drain wire 22 and the layer of insulation 20, the drain wire being in electrical contact with the conductive sheath 24. The inner conductor 18 is typically formed of copper and has a diameter of about 28-30 AWG. An outer jacket 26 of insulation having a generally trapezoidal configuration encases the conductive outer sheath 24. Other cross-sectional configurations of the jacket 26 may also be used. Such a cable 12 is more fully described in our U.S. Patent No. 4404425 entitled "Cable Assembly for Undercarpet Signal Transmission", issued on 13th September, 1983.
Turning now to both Figures 3 and 4, the components of the electrical connector 10 are shown, respectively, in exploded and assembled form. In accordance with a preferred connector assembly procedure, the upper components shown in Figure 3 are joined into a separate plug subassembly, generally designated as 28, and the lower components, exclusive of the data cable 12, are joined into a separate body subassembly, generally indicated as 30. The plug subassembly 28 comprises an elongate, generally cylindrical conductive plug 32, an insulator 34, an electrically conductive contact 36 and a threaded coupling 38. The plug 32 is a conventional part, having interior threads (not shown) at end 32a for connection to an external device, such as a cathode ray tube, and is commercially available, for example, as TNC-79525 from Amphenol, Oak Brook, Illinois. Other suitable plugs of the bayonet type, for example, Amphenol part BNC-31-4541, may also be used. The contact 36 is elongate, of generally cylindrical configuration, and is preferably made of a suitably conductive material, such as brass, and preferably plated with silver. The contact 36 has a termination end 36a which, as depicted, may comprise a pin-type member or a suitable socket-type member, not shown. At the other longitudinal end, the contact 36 includes a conductor receiving end 36b which comprises a pair of axially extending, transversely spaced walls 40 and 42 defining therebetween a slotted opening 44. Each of the walls is supported in cantilevered fashion at the base 44a of the opening and is elastically deflectable toward the opposing wall at the free and unsupported end thereof. The opening 44 is formed to have lateral extent slightly greater (about several thousandths of an inch) than the diameter of the cable inner conductor 18 to freely receive such conductor 18 therein as will be described. The walls 40 and 42 are elastically movable upon application of a radial or transverse force thereto effectively reducing the opening to a transverse extent less than the diameter of the inner conductor 18. As such, when the conductor 18 is placed therebetween and the walls 40 and 42 are deflected under application of a transverse force, a compressive force by the walls will be applied to the inner conductor 18 establishing electrical contact thereto. Upon release of the transverse force on the walls 40 and 42, these walls will return to their original position due to their spring characteristics. While the opening 44 is shown as comprising a single axial extending slot, it should be appreciated that multiple slots, thereby defining multiple spring fingers, may also be used.
In the plug subassembly as depicted in Figure 4, the contact 36 resides in the central aperture 34a of the insulator 34, the insulator 34 being seated in the central aperture 38a of the threaded coupling 38 between the contact 36 and inner wall of the coupling 38. The coupling 38 has exterior threads 38b which are threadably connected to interior threads 32b of the plug 32 to thereby form the plug subassembly 28 as illustrated. The coupling 38 also has exterior threads 38c for coupling to the body subassembly 30, as will be described. In the subassembly, the free ends of deflectable contact walls 40 and 42 extend axially beyond the end transverse surface 28a of the plug assembly to facilitate connection to the cable inner conductor, as will be described. These projecting ends 40a and 42a of the deflectable walls are preferably tapered toward the mouth of the opening 44, the outer peripheral surface of such tapered ends 40a and 42a defining a generally frustroconical surface with the smaller diameter of such frustroconical surface being at the distal ends of the walls.
Still referring to Figures 3 and 4, the body subassembly 30 comprises a conductive body 46, an insulative bushing 48, a cable strain relief inclusive of a cable support 50 and a cable clamp 52. While the body 46 and bushing 48 are generally cylindrical, the cable support 50 has a generally trapezoidal cross-section, as depicted in Figure 5, to accommodate the flat cable 12. The cable support 50 is preferably formed from a unitary strip of spring-like metal, such as phosphor bronze, folded at one of the marginal edges 50a and left slightly open at the other marginal edge 50b to allow a snap-on type connection to the body 46, as will be detailed. At one end of the cable support 50, there are provided upper and lower protrusions 50c and 50d for attachment to the knob portion 46a of the body 46. Marginal cutouts 50e and 50f are formed in the cable support 50, such cutouts being laterally spaced less than the width of the cable 12 such that upon insertion of the cable the marginal edges of the cable jacket are exposed at the cutouts 50e and 50f. The cable clamp 52 has projecting legs 52a and 52b adapted to be inserted into the cutouts 50e and 50f to engage the cable jacket and to provide compression to the cable support 50.
The body 46, as indicated, has a protruding knob portion 46a and a nut portion 46b having internal threads 46c. In the preferred arrangement, the knob portion 46a and the nut portion 46b are joined for relative rotative movement.
Prior to being coupled to the body subassembly 30 and ultimately to the complete connector 10, the data cable is prepared as shown in Figure 3. A portion of the outer insulation jacket 26 and the conductive sheath 24 (not shown) are removed to thereby expose the drain wire 22 and the insulated inner conductor 18. The insulation layer 20 is removed from the end portion of the inner conductor 18, the length of the insulation from the cable jacket 26 being slightly longer than the exposed length of the drain wire 22. In attaching the subassembly 30 to the prepared cable 12 as shown in Figure 4, the cable support 50 is initially slid onto the cable jacket 26. The inner conductor 18, insulation layer 20 and the drain wire 22 are fed into an inner aperture 46d of the body 46. The insulative bushing 48 is provided with an inner aperture 48a that is slightly greater than the outer diameter of the insulation layer 20. In inserting the bushing 48 into the body aperture 46d, the inner conductor 18 and the insulation layer 20 thereon pass through the bushing aperture 48c while the drain wire 22 lies exteriorly of the bushing 48. Upon continued insertion of the bushing 48 into the body 46, the drain wire 22 is wedged between the outer bushing wall and the inner wall of the body 46. The bushing 48 is suitably seated as a bushing flange 48b abuts against an interior portion of the knob portion 46a. As the drain wire 22 is in intimate contact with the conductive body 46, electrical connection is thereby established between the body 46, the drain wire 22 and the conductive sheath 24 of the cable 12. The cable support 50 is then slid along the cable 12 toward the body 46 until the knob portion 46a is snapped into the cable support protrusions 50c and 50d. The cable clamp 52 is then attached thereby establishing the cable strain relief and holding the cable and its conductors in a fixed position relative to the body 46.
In accordance with the invention, the bushing 48, preferably formed of a suitable plastic, serves as a camming element in providing the electrical connection between the cable 12 and the connector 10. At the end of the bushing 48 adjacent the flange 48b, a cam surface 48c is provided. The cam surface 48c is generally frustroconical in configuration and corresponds to the tapered, frustroconical shape of the projecting contact walls 40a and 42a. In the body subassembly, the cam surface 48c is radially spaced from and is in circumscribing position about the inner conductor 18.
The joining of the plug subassembly 28 and the body subassembly 30 to form the connector 10 and the establishment of the electrical connection between the cable inner conductor 18 and the connector contact 36 is best understood by reference to Figure 4 and Figures 6 and 7. In bringing the two subassemblies 28 and 30 together the inner conductor 18 is fed into the opening 44 of the contact 36 at its conductor receiving end 36b while the exterior threads 38c of the coupling 38 are inserted into the interior threads 46c of the body 46. This is the position as shown in Figure 6 wherein the inner conductor 18 is freely received in the opening 44 between the deflectable contact walls 40 and 42. Upon threadably tightening the body and plug subassemblies together, the bushing 48 and the contact 36 are moved axially relative to each other until the bushing cam surface 48c strikes the tapered contact ends 40a and 42a. Continued threadably tightening then causes the cam surface 48c to apply a radial force to the contact ends 40a and 42a thereby elastically deflecting the contact walls 40 and 42 about the opening base 44a until contact is established with the inner conductor 18, as shown in Figure 7. Upon completion of the threadable tightening, the contact walls 40 and 42 are in compressed relation against the inner conductor 18. Transverse surface 28a serves as a stop surface to abut the bushing flange 48c to prevent overtightening. Disconnection is effected by reversing the threading operation whereby upon separation of the subassemblies the elastically deflectable contact walls 40 and 42 revert to the normally open position.
Having described the structure and operation of the preferred embodiment of the electrical connector 10 herein, it should now be appreciated that a simply assembled, field installable coaxial cable connector is provided whereby electrical connection may be made directly from the coaxial cable to the desired computer terminal or the like. It should also be understood, however, that the invention described herein may have applicability within its contemplated scope in making connections to cables other than coaxial cables in undercarpet cable systems. To this extent, various modifications may be made to the connector of the present invention. For example, while threaded coupling of the plug and body subassemblies is desirably provided, such coupling may be effected by other known coupling techniques, such as with snap-type connections having cooperative detent structure.
Having described the preferred embodiment of the invention herein, it should be appreciated that various other modifications to the foregoing particularly described invention will now be evident to those skilled in the art. Accordingly, the preferred embodiment as described herein is intended in an illustrative rather than a limiting sense. The true scope of the invention is set forth in the following claims.

Claims

1. An electrical connector for connection to an exposed conductor (18) in an electrical cable (12), comprising:

a body (46)having a generally central aperture for receipt therein of said exposed conductor (18);

a plug (32) having means'(32b,38,46b) cooperatively coupling said body (46), said coupling means (32b,38,46b) providing for relative movement between said body (46) and plug (32) during coupling, said plug (32) further having a generally central aperture in substantial alignment with said body aperture;

an elongate conductive contact (36) disposed in said plug aperture, said contact (36) having a termination end (36a) and a conductor receiving end (36b), said conducting receiving end (36b) facing said body (46), said conductor receiving end (36b) having elastically deflectable walls (40,42) defining an opening (44) for receipt of said cable conductor (18) therein, said walls (40,42) being movable from a first normally open position wherein said opening (44). is of expanse sufficient to freely receive said cable conductor (18) therein to a second closed position wherein said opening (44) is less than the cross-sectional extent of said cable conductor (18); and

means (48) supported by said body (46) for engaging the conductor receiving end (36b) of said contact (36) and moving said deflectable walls (40,42) from said first position to said second position during the coupling of said plug (32) and said body (46), such that upon completion of such coupling electrical connection may be established between said cable conductor and said contact (36).

2. An electrical connector according to Claim 1, wherein said means (48) for engaging the conductor receiving end of said contact includes a cam surface (48c).

3. An electrical connector according to Claim 2, wherein said engaging means (48) comprises an insulative member (48) having a generally central aperture extending therethrough for passage of said cable conductor (18), said cam surface (48c) being disposed on said insulative member (48) adjacent an end portion thereof.

4. An electrical connector according to Claim 3, wherein the outer surfaces (40a,42a) of said deflectable walls (40,42) taper toward the central axis of said contact (36) at the longitudinal end thereof.

5. An electrical connector according to Claim 4, wherein said cam surface (48c) on said insulative member (48) tapers correspondingly with the taper on said contact (36), such that upon engagement of said contact (36) and insulative member (48), the tapered conductor receiving end (36b) of said contact (36) is in engagement with the tapered cam surface (48c) interiorly thereof.

6. An electrical connector according to any preceding Claim, wherein said conductor receiving end opening (44) includes an axially extending slot.

7. An electrical connector according to any preceding Claim, wherein said body (46) includes a strain relief portion (50,52) for attachment to said cable (12).

8. An electrical connector according to any one of Claims 3 to 5 or Claim 6 as dependent on Claim 3 or Claim 7 as dependent on Claim 3, wherein said exposed cable conductor (18) for connection thereto is an inner conductor (18) of a coaxial cable of the type having an outer conductor (24) and a layer of insulation (20) between said inner conductor (18) and said outer conductor (24), and wherein said connector further includes means (22) for electrically connecting said body (46) and said outer conductor (24).

9. An electrical connector according to Claim 8, wherein said electrical cable (12) is of the type including a drain wire (22) in electrical contact with said outer conductor (24) and wherein said means for electrically connecting said body (46) and said outer conductor (24) includes the wedging of said drain wire (22) between said insulative member (48) and an inner wall of said body such that said drain wire (22) is in intimate contact with said body (46).

10. An electrical connector according to any preceding Claim, wherein said coupling means (32b,38,46b) includes threadably interconnectable portions (46b,32b) on said body (46) and said plug (32).