US3922050A

US3922050A - Blind, shank expanding electrical terminal structure

Info

Publication number: US3922050A
Application number: US453200A
Authority: US
Inventors: Michael J Lettini; Howard P Stock
Original assignee: Boeing Co
Current assignee: Boeing Co
Priority date: 1974-03-21
Filing date: 1974-03-21
Publication date: 1975-11-25
Anticipated expiration: 1992-11-25
Also published as: BE833449A; GB1470272A; FR2265194B1; FR2265194A1

Abstract

Attaching an electrical terminal to a sheet or body of electrically conducting material coated with a generally nonconducting material to form an electrical terminal structure wherein said electrical terminal makes low-resistance contact to said sheet or body is disclosed. The method of the invention comprises the steps of: drilling a cylindrical hole through said sheet or into said body; inserting a blind, shank expanding terminal comprising an elongated cylindrical shank and a cylindrical, radially expandable sleeve axially mounted on said shank into said drilled hole; and, pulling said shank axially while preventing said sleeve from moving axially so that said sleeve is caused to radially expand into low resistance electrical contact with said sheet or body in the region where the cylindrical periphery of said hole and the cylindrical periphery of said sleeve meet. The apparatus of the invention comprises an improved electrical terminal structure comprising a sheet or body of electrically conducting material and a blind, shank expanding terminal formed of an elongated cylindrical shank and a radially expandable cylindrical sleeve axially mounted on said shank in a manner such that said radially expandable sleeve radially expands when said shank is axially displaced in one direction with respect to said sleeve. Said radially expandable cylindrical sleeve is formed of a material that is electrically compatible with said sheet or body of electrically conducting material.

Description

United States Patent Lettini et al.

[ 1 Nov. 25, 1975 l l BLIND, SHANK EXPANDING ELECTRICAL TERMINAL STRUCTURE [75] inventors: Michael J. Lettini, Mercer Island;

Howard P. Stock, Bellevue, both of Wash.

[73] Assignee: The Boeing Company. Seattle,

Wash.

[22] Filed: Mar. 2]. 1974 [2l] Appl. No: 453,200

{52] US. Cl. .t 339/14 R; 339/220 R; 339/276 R [51] Int. Cl. HOlR 3/06 [58] Field of Search t. 339/14, 220, 276; 85/70 [56] References Cited UNITED STATES PATENTS 2,06l,629 ll/l936 Huck 85/70 Primary E.raminer-Roy Lake Assistant Examinerjones: DeWalden W. Attorney, Agent, or Firm-Christensen. OConnor. Garrison & Havelka [57} ABSTRACT Attaching an electrical terminal to a sheet or body of electrically conducting material coated with a generally nonconducting material to form an electrical terminal structure wherein said electrical terminal makes low-resistance contact to said sheet or body is disclosed The method of the invention comprises the steps of: drilling a cylindrical hole through said sheet or into said body; inserting a blind, shank expanding terminal comprising an elongated cylindrical shank and a cylindrical. radially expandable sleeve axially mounted on said shank into said drilled hole; and. pulling said shank axially while preventing said sleeve from moving axially so that said sleeve is caused to radially expand into low resistance electrical contact with said sheet or body in the region where the cylindrical periphery of said hole and the cylindrical periphery of said sleeve meet. The apparatus of the invention comprises an improved electrical terminal structure comprising a sheet or body of electrically conducting material and a blind shank expanding terminal formed of an elongated cylindrical shank and a radially expandable cylindrical sleeve axially mounted on said shank in a manner such that said radially expandable sleeve radially expands when said shank is axially displaced in one direction with respect to said sleeve. Said radially expandable cylindrical sleeve is formed of a material that is electrically compatible with said sheet or body of electrically conducting material.

13 Claims, 8 Drawing Figures r l l I l l l l l l l l I l I lllllllllll U.S. Paterit Nov. 25, 1975 Sheet 1 of2 3,922,050

q glnumvll BLIND, SHANK EXPANDING ELECTRICAL TERMINAL STRUCTURE BACKGROUND OF THE INVENTION This invention is directed to electrical terminal structures and more particularly to electrical terminal structures including an electrical terminal and a body of electrically conductive material.

Electrical terminal structures, and in particular electrical grounding terminal structures, have found widespread use. These terminal structures are generally adapted to create a point wherein electrical contact is made between one or more electrical conductors and a body of electrically conductive material. Such contact may be necessary for one or more of a variety of reasons. Generally, these reasons fall into two different groups-safety and electrical. The safety group includes safety of the personnel operating the related equipment and safety of the equipment itself. The electrical group includes the electrical requirements of the related equipment.

The safety group may, for example, include the prevention of sparks which could cause an explosion if explosive gases exist in the surrounding environment. Similarly, the safety group may include lightning protection and electrostatic charge dissipation. In other words, the safety group reasons for making electrical contact to a body of electrically conducting material are related either to the direct personnel or equipment harm or the associated personnel or equipment harm that can be caused by electrical energy.

On the other hand, the electrical group reasons for making electrical contact to a body of conductive material relate to the use of the electrical equipment involved. For example, the chassis of electrical equipment is often used to provide electrical return paths. Moreover, in some cases, the chassis or a surrounding shield is used for electromagnetic interference control. Further, often a conductive body of material is utilized to create a particular electrical function, such as a ground plane for an antenna, for example. In any of these cases, it is necessary to provide an electrical contact to a body of electrically conducting material. Usually electrical terminals make contact with the body and electrical conductors are attached to the terminals. As herein used the term electrical terminal structure defines the terminal per se and the surrounding body of electrically conductive material to which the terminal is physically and electrically attached.

The most common prior art electrical terminal used to form an electrical terminal structure, and in particular an electrical grounding terminal structure, comprises a stud in combination with a plurality of washers and nuts. The overall electrical terminal structure using such an electrical terminal is formed by drilling a hole through the body of electrically conductive material to which the terminal is to be attached. Thereafter, the surface of the body of material, around the hole and on one or both sides thereof, is cleaned to remove any nonelectrical coatings. Such nonconductive electrical coatings may comprise a variety of layers of materials or may just consist of a primer coat of paint. Thereafter, a washer and a lock washer are assembled on the stud and the assembly is installed through the hole from the back side of the body of material. Following this installation, a washer and a nut (usually formed of brass) are attached to the stud on the "front" side of the structure. As the nut becomes tightened on the stud, the terminal becomes affixed to the body of electrically conductive material. Following such affixation, the exposed surfaces of the body of electrically conductive material are recoated or reprimed with care being taken to prevent the recoating or the repriming material from impinging on the brass nut and the portion of the stud extending outwardly from the brass nut. Next, electrical terminals are installed on the stud and a further washer and locknut are added. Finally, an inspection of the overall terminal is performed.

The foregoing method of and apparatus for forming an electrical terminal structure, obviously. has a variety of disadvantages. For example, generally eight individual and distinct steps must be performed in order to assemble a multitude of components and create the resultant structure. Because these steps are time comsuming, the labor expense of forming such an electrical terminal structure is greater than desirable.

One of the primary reasons that the labor expense is high relates to the requirement that the body of electrically conductive material be cleaned prior to installation, and reprimed after installation.

In addition to the cost disadvantages of the previously described electrical terminal structure. there exist other disadvantages. For example, both sides of the body to which the terminal is to be attached must be accessible at the time of attachment because the stud head and the brass nut are installed from opposite sides and because both the stud head and the brass nut must be gripped during tightening of the nut on the stud. This initial requirement is not only a disadvantage in and of itself but may also cause problems during the operative life of the terminal structure. Specifically, if the terminal structure loosens during its lifetime, and if the head side is then inaccessible, retightening of the terminal structure becomes extremely difficult. The most common way of retightening this structure requires the use of two nuts to grip the exposed portion of the stud and prevent its rotation while the brass nut is rotated toward the head of the stud. Obviously, such a procedure is time consuming and, therefore, costly. Another related problem of this terminal structure relates to replacement. For example, if the stud becomes nonusable because of corrosion or other reasons (for example, if it breaks off), and if the stud head side of the body of electrical conductive material is inaccessible, replacement is impossible without first obtaining access to the inaccessible side.

Various attempts have been made to produce terminal structures which overcome the disadvantages of the prior art electrical terminal structure described above. One such attempt is described in US. Pat. No. 3,535,673 issued to Gulistan for Electrical Terminal". The electrical terminal described in this patent comprises a stud having a head and a cylindrical collar located adjacent to the head on the threaded side of the stud. The terminal is mounted in a hole formed in an electrically conductive material from the back side thereof. Thereafter, a frustoconical region extending outwardly from the cylindrical region on the side remote from the head is bent downwardly. Electrical contact is made where the sides of the hole and the sides of the cylindrical collar meet.

Obviously, the resultant electrical terminal structure overcomes some of the disadvantages described above. However, certain disadvantages still remain. For example. this terminal must be inserted from the back side of the body of electrically conductive material. Hence. the disadvantages attendant to this method of installation remain. Further. other advantages emerge. For example. the size of the hole and the size of the cylindrical collar must be precisely related (unless the surface is previously cleaned with its related disadvantages) or else the resultant electrical contact is inadequate. While the knurled collar proposed by Gulistan can overcome some of the precision disadvantages such a collar creates other disadvantages. Specifically. such a collar has been found to cause irregularities on the inside of the hole. The stresses built up around these irregularities can cause cracks to radiate out from the edge of the hole. Such cracks are undesirable to say the least and in some industries, such as the aircraft industry, for example. are completely unacceptable.

Other attempts have also been made to provide an electrical terminal structure which overcomes the disadvantages described above. However, prior to the instant invention, these attempts have also been generally unsuccessful. In many cases these attempts have been related to specific structural situations, such as mounting electrical terminals on a circuit board, for example. In other cases, the attempts still require cleaning of one or more of the surfaces of the body of electrical conducting material to which electrical terminal contact is to be made. Thus, prior to the instant invention many of the problems noted above have remained unsolved.

Therefore, it is an object of this invention to provide a new and improved electrical terminal structure.

It is another object of this invention to provide an electrical terminal structure which does not require access to both sides of a body of electrically conductive material during the mounting of an electrical terminal.

It is a further object of this invention to provide an electrical terminal structure that does not require that generally nonconducting materials be cleaned or removed from one or both surfaces of a body of electrically conductive material prior to an electrical terminal device being attached to the body of electrically conductive material.

It is also an object of this invention to provide an electrical conducting terminal that includes a limited number of parts.

It is yet another object of this invention to provide an electrical terminal structure having a low galvanic emf.

It is yet a further object of this invention to provide an electrical terminal structure that includes a body of electrically conductive material and an electrical terminal that has good torque and axial load characteristics, low galvanic emf and does not require access to both sides of the body of electrically conductive material when the electrical terminal is attached thereto.

It is still another object of this invention to provide an electrical terminal structure wherein an electrical terminal is inserted into a hole in a body of electrically conductive material without causing injury to the electrically conductive material surrounding the hole.

It is also another object of this invention to provide an electrical terminal structure wherein the structure is formed by inserting an electrical terminal into a hole in a body of electrically conductive material. said formation requiring the performance of a minimum number of steps.

It is yet a still further object of this invention to provide an electrical terminal structure including an electrical terminal mounted in a body of electrically conductive material in a manner that allows the electrical terminal to be easily replaced by a similar electrical terminal without requiring access to both sides of the body of electrically conductive material.

SUMMARY OF THE INVENTION In accordance with principles of this invention, a method of forming an electrical terminal structure by attaching an electrical terminal to a body of electrically conductive material having a flat surface which may be coated with a generally nonconductive material so that said electrical terminal makes an electrically low resistance contact with said body of electrically conductive material is provided. The method of the invention comprises the steps of: drilling a cylindrical hole through said generally nonconductive material into said body of electrically conductive material; inserting a blind shank expanding terminal comprising a cylindrical shank and a radially expandable cylindrical sleeve axially mounted on said shank into said drilled hole; and, causing said sleeve to radially expand and come into low resistance electrical contact with said body of electrically conductive material in the region where the cylindrical periphery of said hole meets said cylindrical sleeve.

In accordance with further principles of this invention, the shank and sleeve of the blind shank expanding terminal are formed such that said sleeve radially expands when said shank is axially displaced in one direction with respect to said sleeve. Thus, the method of the invention comprises the further step of axially moving said shank with respect to said sleeve.

In accordance with still further principles of this invention, the body of electrically conductive material is a sheet having a front side and a back side and the sleeve includes a collar lying on the front side whereby the method of the invention also comprises the step of causing a portion of the sleeve residing on the back side of said body to expand outwardly as said shank is axially moved with respect to said sleeve so as to form a collar having a diameter greater than the diameter of said hole.

In accordance with still other principles of this invention. an improved electrical terminal structure is provided. The improved electrical terminal structure comprises a body of electrically conductive material having a hole therein and a blind shank expanding terminal mounted in said hole. The blind shank expanding terminal comprises a cylindrical shank including a head and a radially expandable sleeve axially mounted on said shank adjacent to said head, said radially expandable sleeve being adapted to radially expand when said shank is axially displaced in one direction with respect to said sleeve.

In accordance with further principles of this invention, the sleeve is formed of a material that is electrically compatible with said body of electrically conductive material such that the galvanic emf across the materials is less than a predetermined amount such as 0.250 volts, for example.

In accordance with still further principles of this invention, one end of the sleeve of said blind shank expanding terminal comprises a collar end and the other end comprises a thin wall. The thin wall end is adjacent to the head and when the shank is axially displaced in said one direction, the thin wall rolls outwardly. If the body of electrically conductive material is a sheet of such material this outward rolling forms a collar that presses the sheet against the collar forming the other end of said sleeve.

In accordance with other principles of this invention, the body of electrically conductive material is formed of aluminum and the sleeve is formed of either tin coated naval brass or alodine 600 coated aluminum.

In accordance with still other principles of this invention, the diameter of said head is substantially the same as the outer diameter of said thin wall end of said sleeve. Further, said shank includes a splined cylindrical region separated from said head by an undercut region. The diameter of said splined cylindrical region is smaller than the diameter of said head. In addition, a threaded stud extends outwardly from said splined cylindrical region; said head, said splined cylindrical region and said stud being coaxial. Moreover, extending outwardly from said threaded region on the end of said stud remote from said splined region is a coaxial breakaway member. Located between said breakaway member and said stud is an undercut region whereat said breakaway member breaks away from said stud when the force creating the axial movement of said shank with respect to said sleeve reaches a predetermined level, said force being applied to said breakaway member of said shank only.

In accordance with yet other principles of this invention, said sleeve comprises a cylindrical axial aperture having a diameter slightly less than the diameter of said splined cylindrical region of said shank between said splined cylindrical region and said collar of said sleeve and slightly greater than the diameter of said splined cylindrical region where said sleeve surrounds said splined cylindrical region, all diameters being prior to the axial movement of said shaft with respect to said sleeve.

It will be appreciated from the foregoing summary that the invention provides an electrical terminal structure. The electrical terminal structure of the invention comprises a body of electrically conductive material which may be coated with a nonconductive coating and a blind shank expanding electrical terminal mounted in a hole formed in the body of electrically conductive material. The electrical terminal comprises a shank with a head and a sleeve with a perforated collar. During attachment, the shank is axially moved outwardly with respect to the sleeve (and the body of electrically conductive material). This movement causes radial expansion of the sleeve where it lies in the hole and, if the body is a sheet, a collar-like expansion of the sleeve on the side of the body remote from the direction of pull. In this manner the sheet is pressed between the preformed collar and a collar formed by expansion. Electrical contact is made radially, where the sleeve and the side of the hole meet, as opposed to where the surface of the body and a collar or washer meet. Thus, the nonconductive material need not be removed prior to attachment of the blind shank expanding terminal. Yet, even though such material is not removed, a good resistance electrical contact is formed between the terminal and the body or sheet of electrically conductive material.

It will also be appreciated from the foregoing summary that the invention overcomes the abovedescribed disadvantages of prior art electrical terminal structures. Specifically, only a minimum number of installation steps are required by the invention. Thus, the cost of installation is considerably less than is the cost of installing prior art terminals, particularly those that utilize a stud/washer/nut arrangement. In fact, in one instance, it was found that up to a percent reduction in cost without loss of electrical terminal benefits can be achieved using the invention. In addition, access to both sides of the body of electrically conductive material is not required. Further, the terminal can be easily removed and replaced by merely driving the shank in the direction opposite to the pulling direction, drilling out the remaining sleeve and reinstalling a similar terminal in the same hole. Also installation of the terminal does not create irregularities around the hole which could. after installation, create radial cracks extending out from the hole.

In addition to overcoming the disadvantages of prior art electrical terminal structures, none of the advantages of prior art electrical terminal structures are lost by the invention. For example, the electrical terminal structure of the invention has torque and axial load characteristics comparable with prior art structures utilizing a stud/washer/nut arrangement. Further, the sleeve material can be chosen so as to have good (i.e., 0.250 volts or lower) galvanic compatibility with the body of electrically conductive material. For example,

- if the body is formed of aluminum, the sleeve can be formed of tin coated naval brass or alodine 600 coated aluminum. In addition, the thermal shock, current cycling, humidity and vibration characteristics of the inventive terminal structure are as good as, or better than, prior art terminal structures. Further, the oxidation characteristics (which relate to shelf life) of the terminal structure are good, assuming suitable materials are utilized. such as tin coated naval brass or alodine 600 coated aluminum.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing objects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description when taken in conjunction with the accompanying drawings wherein:

FIG. I is an exploded view illustrating one of the most common prior art electrical terminal structures in use;

FIG. 2 is an exploded view illustrating the basic concept of the invention;

FIG. 3 is a side view illustrating a preferred embodiment of an electrical terminal formed in accordance with the invention;

FIG. 4 is a side view partially in section illustrating an electrical terminal of the type illustrated in FIG. 3 being installed in a body of electrically conductive material;

FIG. 5 is a side view partially in section illustrating an electrical terminal structure formed in accordance with the invention;

FIG. 6 is a side view partially in section illustrating in side-by-side relationship an electrical terminal formed in accordance with the invention both prior to and subsequent to installation in a sheet of electrically conductive material;

FIG. 7 is a side view partially in section illustrating an alternate electrical terminal structure formed in accordance with the invention; and,

FIG. 8 is a split side view partially in section illustrating a still further alternate electrical terminal structure formed in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. I is an exploded side view illustrating one of the most common prior art electrical terminal structures. and in particular an electrical terminal grounding structure. The structure illustrated in FIG. 1 comprises a body of electrically conductive material ll. The body of electrically conductive material may be a thin sheet of aluminum, titanium or tin, for example. One or both of the front and rear surfaces may be coated with a

layer

13 and 15 formed of a nonconductive material. such as a paint primer, for example.

Prior to actually installing an electrical terminal of the prior art type in the body 11 illustrated in FIG. I, a cylindrical aperture (hole) 17 is first punched. drilled or in some other manner formed in the body of electrically conductive material 11. Thereafter, the portion of the nonconductive layers in the areas 19 and 2! surrounding the hole 17 on the front and rear surfaces I3 and I5 are removed by any suitable means. Alternatively. and in fact more frequently, a portion of the nonconductive layer surrounding the hole on only one side is removed. In any event, thereafter the electrical terminal is actually installed.

The prior art electrical terminal illustrated in FIG. 1 comprises: a bolt 23; a lock washer 25; a first flat washer 27; a second flat washer 29; a nut 3], preferably formed of brass; one or more electrical terminals 33; a third flat washer and a self-locking retaining nut 37. Prior to passing the threaded shank 39 of the bolt 23 through the hole 17, the lock washer 25 followed by the first flat washer 27 are passed over the shank 39 so as to lie adjacent to the head 41 of the stud 23. Thereafter, this assembly is inserted through the hole 17, upwardly as viewed in FIG. I so that the upper surface of the first flat washer 27 lies in the previously cleaned lower area 21 surrounding the hole 17. In this manner, the first flat washer is brought into electrical contact with the body of electrically conductive material. Thereafter, the second flat washer 29 is mounted about the threaded shank 39 and the brass nut 31 is applied to the shank and tightened. The mounting is such that the second flat washer is also in electrical contact with the body of electrically conductive material 11 because it lies in the upper cleaned area 19 surrounding the hole 17. The remaining exposed cleaned area must then be repainted or reprimed and allowed to dry, being careful not to get paint on the nut or threaded shank. Next, one

or more electrical contacts 33 followed by the third flat washer 35 are mounted about the threaded shank 39. Finally, the retaining nut 37 is installed and tightened. In some cases, where a direct" buildup is desired, the brass nut is eliminated.

It will be observed that the resultant terminal structure illustrated in FIG. I and described above has a variety of disadvantages. For example, because it includes a multitude of components, it is expensive to install. This factor becomes of particular significance when a large number of terminal structures are to be formed. In addition, after partial installation. repriming is required to prevent corrosion and other undesired detri mental effects from occuring. Moreover, a structure of the type illustrated in FIG. I has the disadvantage that access to both sides of the body of electrically conductive material 11 is required during installation of the terminal. In this regard, it should also be noted that if the electrical terminal loosens during use. and if both 8 sides of the body ll are not accessible, it is extremely difficult to retighten the terminal. One way of retightening the structure is to double nut" the threaded shank 39 of the bolt 23 to prevent movement of the bolt and then retighten the brass nut 31. Because such a procedure is time consuming, it is also expensive.

On the other hand, an electrical terminal arrangement of the type illustrated in FIG. 1 has a number of desirable characteristics. For example, it normally has high torque and axial load strength. In addition, the materials used can be chosen to be galvanically compatible with the body of electrically conductive material. Further, it has high thermal shock, current cycling, humidity, vibration and oxidation characteristics. Finally, the overall thermal structure has low electrical resistance. The herein described invention overcomes the above-noted disadvantages of this structure, and related structures, without loss of these desirable advantages.

FIG. 2 illustrates, in exploded form, the basic concept of this invention. The electrical terminal structure illustrated in FIG. 2 comprises a body of electrically conductive material 43, which may be a thin sheet of material. The body or sheet 43 may be coated on one or both sides with a

nonconductive coating

44 or 45, such as primer paint, for example. In addition to the sheet 43, the terminal structure also includes a blind shank expanding terminal 47. The blind shank expanding terminal 47 includes a sleeve 46 axially mounted about an elongated shank 48. The sleeve 46 comprises a cylindrical region 49 (prior to installation) that terminates in a preformed collar 50. The elongated shank comprises a head region 51 and a threaded stud 52. The sleeve 46 includes a cylindrical central aperture which allows it to be mounted about the elongated shank 48 in a manner such that the collar is remote from the head region 51.

In accordance with the invention, a blind shank expanding terminal 47 of the type generally illustrated in FIG. 2 is inserted from one side (above as viewed in FIG. 2) into a cylindrical aperture drilled, punched or in some other manner formed in the sheet of electrically conducting material 43 so that the collar 50 lies against the side from which the terminal is inserted. After such insertion, the sleeve is expanded outwardly by moving the shank 48 upwardly (as viewed in FIG. 2) in the direction of the arrow 53. This expansion presses the outer surface of the sleeve against the sides of the hole where they meet in the region 54. Electrical contact between the sheet 43 and the sleeve 46 occurs in this region 54. In addition, as will be better understood from the following description, the portion of the cylindrical region 49 lying on the back or remote side (the bottom as viewed in FIG. 2) expands or rolls outwardly to some degree. Thus, the sheet of electrically conductive material is pressed between the outwardly rolled portion and the preformed collar 50. Located above the preformed collar 50 is one or more electrical contacts and located above the electrical contact(s) is a flat washer 56 and a self-locking retaining nut 57. The nut presses the contact(s) against the preformed collar 50 to create electrical contact therebetween.

It will be appreciated at this point from the foregoing brief description of the basic concept of the invention, that it overcomes many of the disadvantages of the prior art illustrated in FIG. 1 described above. Specifically, it is rapidly, easily installed. Moreover, the terminal is, inserted from one side of the sheet or body of electrically conductive material. Hence, access to both sides is not necessary. Thus, the terminal is a blind terminal. Because of this advantage the electrical terminal can be easily replaced should it loosen in the hole. Replacement merely requires driving the shank 48 in the direction opposite to the arrow 53. After the shank has been removed, the sleeve 46 can be easily removed by drilling it out in a conventional manner. Thereafter, a similar shank expanding terminal is easily replaced in the same aperture. It will be appreciated that no step of this entire replacement procedure requires access to the back side of the sheet 43.

One more important advantage of the inventive electrical terminal structure illustrated in FIG. 2 should be noted. Specifically, the formation of this structure does not require the removal of any nonconducting material from either surface of the sheet (body) of electrically conducting material 43. Thus, there is no requirement that these surfaces be recoated after the terminal is formed.

FIG. 3 illustrates a preferred embodiment of a blind, shank expanding electrical terminal 59 formed in accordance with the invention prior to insertion into an aperture in a body of electrical conducting material. The blind shank expanding electrical terminal 59 comprises an elongated shank 63 and a sleeve 61. The sleeve 61 includes a preformed collar 67 and the shank includes a threaded stud 69 and a head 65. The sleeve includes a central aperture and is mounted about the elongated shank such that the collar 67 is remote from the head 65 and the cylindrical portion 66 is adjacent to the head.

Extending outwardly from, and coaxial with, the threaded stud 69 on the side remote from the head 65 is a breakaway portion 81. An undercut region 83 is formed where the breakaway portion 81 and the threaded stud meet. The other end of the breakaway region 81 includes a gripping region 85. The breakaway portion 81 is preferably cylindrical and has a diameter smaller than the diameter of the threaded stud 69. The undercut region is formed such that when a sufficient coaxial force between the stud 69 and the breakaway portion is created, the breakaway portion 81 breaks away from the stud. FIG. 4 illustrates a device for creating such a force.

As illustrated in FIG 4, during insertion, the sleeve 61 is inserted into the aperture in the body, which aperture has a diameter generally similar to, or slightly larger than, the outer diameter of the cylindrical portion 66 of the sleeve 61, and condiderably less than the diameter of the collar 67. Thus, the collar 67 lies above (as illustrated in FIG. 4) the upper surface of the sheet of electrically conductive material 43. The head 65, of course, lies on the other side (lower) of the sheet. A suitable tool 9] which includes a cylindrical housing 93 and an axially movable head 95 slidably located inside of the housing is used to attach the electrical terminal 69 to the sheet of electrically conductive material 43. The axially movable head 95 includes an aperture surrounded by means (not shown) adapted to grip the gripping region 85 of the breakaway portion 81, and the lower tip of the cylindrical housing is adapted to press against the upper surface of the preformed collar 67. Normally the electrical terminal is mounted in the tool 91 in this manner before the sleeve is inserted into the aperture in the sheet. In any event. after the sleeve is so inserted, the tool is energized. Such energization causes the tool head 95 to move upwardly in the direction of the arrow 70, as viewed in FIG. 4, while housing 93 remains stationary against the preformed collar 67. This axial force causes the elongated shank 63 to move upwardly. When this movement occurs, the head 65 causes the cylindrical portion 66 of the sleeve 61 to expand radially outwardly in the region where the cylindrical portion is planar with the sheet of electrically conductive material 43. On the back side of the sheet, the cylindrical portion rolls outwardly. After the terminal has deformed in this manner, the continuing tool force causes the breakaway portion 81 to separate from the threaded stud at the undercut region 83. The end result is the electrical terminal structure illustrated in FIG. 5. The rolled portion 99 ofthe sleeve is located on the back side of the sheet 43 and the breakaway portion 81 is not shown. Good electrical conduction between the sleeve and the sheet occurs in the peripheral meeting region designated 10]. The collar compressive forces as well as the radial force prevents axial rotation of the terminal.

If desired, to assist in preventing rotation during attachment of the electrical contacts 55 (FIG. 2) to the terminal, the head can include a suitable depression which allows it to be held against rotation by a suitable means such as a Phillips screwdriver 102 (FIG. 4), for example.

FIG. 6 illustrates. in a side-by side manner, the electrical terminal structure of the invention both prior to the radial and roll expansion of the cylindrical portion 66 of the sleeve 61 and subsequent thereto. In addition, the internal structure of the sleeve and shank is illustrated. More specifically, the left-hand side of FIG. 6 illustrates in cross-section the internal structure of the shank 63 and sleeve 61 prior to radial and roll expansion. Located adjacent to the head 65 of the shank 63 is an undercut region 103. Located above the undercut region 103 (as viewed in FIG. 6) is a knurled cylindrical section 105. The knurled cylindrical region 105 has a diameter slightly greater than the diameter of the undercut region 103. The end of the knurled cylindrical section 105 adjacent to the undercut region 103 is relatively planar whereby a'sharp generally right-angle corner 106 is formed. On the other hand, the end 107 of the knurled cylindrical section 105 remote from the undercut region 103 tapers inwardly. Projecting outwardly from the knurled cylindrical section 105 is the threaded stud 69. The diameter of the threaded stud is less than the diameter of the knurled cylindrical section 105.

The inner surface of the sleeve 61 has two

different diameter regions

108 and 109 and an inwardly curved tip 111. The inwardly curved tip is on the end of the sleeve opposite to the collar 67 and lies in the undercut region 105. The first diameter region 108 is the same or slightly larger than the knurled cylindrical section 103 of the shank 63 and surrounds that portion of the shank. The second diameter region 109 has a diameter slightly smaller than the diameter of the knurled cylindrical section 105 and substantially larger than the diameter of the threaded stud 69. The second diameter region lies between the end of the first diameter region and the prefomed collar end of the sleeve.

During installation, when the shank is axially moved with respect to the sleeve, the head causes the lower portion (as viewed in FIG. 6) of the sleeve to roll outwardly to form the collar 99, as previously described. At the same time, the movement of the knurled cylindrical section 105 causes the second diameter region 109 to expand the sleeve outwardly, as it moves into this region. This outward expansion creates a tight ra dial force against the aperture side walls whereby the previously described electrical contact region 101 is formed. After the terminal achieves the configuration illustrated on the right side of FIG. 6, the breakaway portion 81 breaks away, as previously described.

FIG. 7 illustrates an alternate embodiment of the in vention wherein one or more electrical contacts 112 are located between the preformed collar 67 and the upper surface of the electrical conductive material 43 rather than above the collar, and no threaded stud is included. Rather, the breakaway portion is located next to the knurled cylindrical section. The electrical contacts are mounted in the illustrated position prior to axial movement of the shank. Axial movement of the shank creates the above-described forces. Thus, the FIG. 7 embodiment results in a permanent attachment arrangement, rather than such an arrangement that allows electrical contact to be made and broken. However, the benefits of the invention are not lost. In this case, a low resistance electrical path exists between the cylindrical peripheral contact region 101, and between the electrical contact 112 and the collar 67 where they meet in the region 115.

FIG. 8 illustrates a further alternate embodiment of the invention. In the embodiment illustrated in FIG. 8, the body of electrically conductive material 117 is relatively thick. A nonconductive coating 119 (such as primer paint) may be located on one surface. A dead end cylindrical aperture 121 passes through the nonconductive coating 119 and enters the body 117. The sleeve end of the electrical terminal device is inserted into this aperture so that the collar lies surface-to-surface with the coating 119. Thereafter, the shank is moved upwardly in the direction of the arrow 123. This action creates a radial force which maintains the overall structure in the dead end cylindrical aperture 121. Obviously, no rollover of the sleeve occurs. The greater radial contact surface, which creates a greater radial force, to some extent compensates for this lack.

It will be appreciated from the foregoing description that the invention provides an electrical terminal structure which overcomes the above-described problems of prior art electrical terminal structures. Not only is the apparatus of the invention uncomplicated, its insertion is also uncomplicated and, therefore, inexpensive. There is no requirement the surfaces be cleaned and later reprimed. Rather, all that need be done to form the invention is to drill a hole into or through the electrically conductive material. Thereafter, a blind shank expanding stud is inserted in the hole. A simple well known tool is then utilized to move a shank outwardly with respect to a sleeve. This movement causes the sleeve to radially expand. If the remote end of the sleeve is free, it rolls outwardly. The end result is a tight electrical terminal structure which has good electrical conductivity. The structure also has axial and torque characteristics as good as, or better than, prior art structures, and in particular such structures of the type illustrated in FIG. 1. Further, by a suitable choice of material, good galvanic compatibility is provided. In this regard. good galvanic compatibility, preferably, means a galvanic emf of less than 0.250 volts. For example, a sleeve made of tin coated naval brass (Brass AMS 46l lC /H] will have good galvanic compatibility with an aluminum sheet or body ofelectrically conductive material. Alternatively, an Alodine 600 coating on a 606l-T6 aluminum substrate sleeve can be utilized with a body or sheet of the same nature, if desired. Moreover, other materials can be utilized depending upon the nature of the body or sheet of electrically conductive material. For example, an A151 302 series stainless steel sleeve can be used with a titanium sheet or body. Preferably, the shank is formed of a heat treated steel coated cadmium.

While a preferred embodiment of the invention has been illustrated and described, it will be appreciated by those skilled in the art and others that various changes can be made therein without departing from the spirit and scope of the invention. Hence, the invention can be practiced otherwise than as specifically described herein.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A blind shank expanding threaded electrical grounding terminal structure:

l. a sheet of material having an electrically conductive center and cove red on its first and second sides with generally non-conductive layers, said sheet of material having a cylindrical aperture therein extending through said electrically conductive center and said generally non-conductive layers whereby said electrically conductive center is exposed in the region defined by the periphery of said cylindrical aperture;

. an integrally formed elongated shank co-axially centered in said cylindrical aperture, said elongated shank including:

a. a head located on one end. said head adapted to cause a collar to be formed in a radially expandable sleeve on the second side of said sheet of material in bearing engagement with the nonconductive layer located on said second side;

b. a sleeve expanding region located adjacent to said head, said sleeve expanding region adapted to radially press a radially expandable sleeve into low resistance electrical contact with the portion of said electrically conductive center exposed in the region defined by the periphery of said cylindrical aperture; and,

c. a threaded portion extending axially outwardly from said sleeve expanding region on the opposite side thereof from said head;

3. a radially expandable sleeve mounted about said elongated shank and extending through said sheet of material so as to generally surround said sleeve expanding region, said radially expandable sleeve being in low resistance electrical contact with the portion of said electrically conductive center exposed in the region defined by the periphery of said cylindrical aperture and in low resistance electrical contact with said sleeve expanding region of said elongated shank, said radially expandable sleeve including:

a. a pre-formed collar located in bearing, but nonelectrical, engagement with the non-conductive layer located on the first side of said sheet of material; and.

b. a cylindrical region integral with said collar, said cylindrical region surrounding said sleeve expanding region of said elongated shank and radially pressed by said sleeve expanding region into low resistance electrical contact with the portion of said electrically conductive center exposed in 13 the region defined by the periphery of said cylindrical aperture; and,

c. an outwardly rolled collar portion located in bearing, but non-electrical, engagement with the non-conductive layer located on the second side of said sheet of material, said outwardly rolled collar portion being formed by the head of said elongated shank pressing said sleeve outward in the region thereof lying outside of the cylindrical aperture on said second side;

4. an electrical contact, connected to an electrical conductor at least partially surrounding the part of said threaded portion of said elongated shank located adjacent to said preformed collar on the side thereof remote from the side of said pre-formed collar in bearing engagement with said sheet of material; and,

5. a nut threaded onto said threaded portion so as to press said electrical contact into low resistance electrical contact with said pre-formed collar.

2. A blind shank expanding threaded electrical grounding terminal suitable for mounting in an aperture formed in a body of electrically conductive material to provide a means for electrically connecting ground wires to said body of electrically conductive material in a low galvanic emf manner, said blind shank expanding terminal comprising:

1. an integrally formed elongated shank, said elongated shank including:

a. a head located on one end;

b. a cylindrical longitudinally splined region located adjacent to said head, but spaced therefrom by a narrow undercut region, said splined region adapted to cause a radially expandable sleeve to expand radially outwardly when said sleeve surrounds said splined region and said splined region is axially moved in one direction with respect to said sleeve;

0. a threaded portion extending axially outwardly from said splined region on the opposite side thereof from said head; and,

d. a breakaway gripping extension extending axially outwardly from said threaded region on the opposite side thereof from said splined region; and,

2. a radially expandable sleeve mounted about said elongated shank so as to generally surround said cylindrical splined region, said radially expandable sleeve including:

a. a collar; and,

b. a cylindrical region integral with said collar, said cylindrical region lying adjacent to said head of said elongated shank and said collar being remote therefrom, the portion of said cylindrical region lying adjacent to said head curving inwardly so that the tip thereof lies in said undercut region, said cylindrical region adapted to radially expand outwardly into low resistance electrical contact with the adjacent surface of said aperture in said body of electrically conductive material when said elongated shank is moved axially with respect to said radially expandable sleeve; and,

c. a cylindrical aperture coaxial with said cylindrical region and separated into two regions having different diameters, the first of said diameters being approximately the same as the diameter of said splined region of said elongated shank and surrounding said splined region of said elongated shank prior to the expansion of said radially ex pandable sleeve into low resistance electrical contact, the second of said diameters being slightly smaller than the diameter of said splined region and surrounding said splined region after the expansion of said radially expandable sleeve into low resistance contact with the adjacent surface of said aperture in said body of electrically conductive material.

3. The electrical terminal claimed in claim 2 wherein said radially expandable sleeve is formed of tin coated naval brass.

4. The electrical terminal claimed in claim 2 wherein said radially expandable sleeve is formed of Alodine coated aluminum.

5. In an electrical terminal structure wherein electrical contact, between a sheet or body of electrically conductive material, covered in the region of electrical contact with a layer of non-conductive material, is made via a threaded shaft and an attachment nut, with the threaded shaft being affixed to said sheet or body of electrically conductive material so as to be in low galvanic emf electrical contact therewith, the improvement comprising a blind shank expanding mechanism for affixing said threaded shaft to said sheet or body, said blind shank expanding mechanism comprising:

expansion means integrally formed with said threaded shaft, at one end thereof, for radially expanding a radially expandable sleeve when said sleeve surrounds said expansion means and said expansion means is moved in a predetermined direc tion with respect to said sleeve; and a radially expandable sleeve, including a collar formed at one end, mounted about said expansion means in a position such that said collar is located inwardly of the end of said expansion means nearest said threaded shaft, said radially expandable sleeve further including a cylindrical region integral with said collar, said cylindrical region formed so as to radially expand outwardly when said elongated shank is moved in said predetermined direction with respect to said radially expandable sleeve.

6. The improved electrical terminal structure claimed in claim 5 further including a breakaway region integrally formed with and extending axially outwardly from the end of said threaded shaft remote from the end integrally formed with said expansion means.

7. The improved electrical terminal structure claimed in claim 6 wherein said radially expandable sleeve is formed of tin coated naval brass.

8. The improved electrical terminal structure claimed in claim 6 wherein said radially expandable sleeve is formed of Alodine coated aluminum.

9. A method of creating a threaded electrical terminal in a sheet of material having an electrically conductive center and covered on both sides with generally non-conductive layers, said method comprising the steps of:

forming a cylindrical aperture in said sheet, said cylindrical aperture formed so as to pass through said sheet and expose said electrically conductive center in the region defined by the periphery of said cylindrical aperture;

inserting into said cylindrical aperture a blind shank expanding electrical terminal, said blind shank expanding electrical terminal comprising an elongated shank threaded at one end, and a radially expandable cylindrical sleeve surrounding the other end of said shank, said shank and said sleeve formed such that axial movement of said shank with respect to said sleeve along their common axis in a predetermined direction causes said radially expandable sleeve to expand radially outwardly. said sleeve being formed of a metallic material that is electrically compatible with the electrically conductive center of said sheet of material. said sleeve having an outer diameter sized such that it is surrounded by. but spaced slightly from. said cylindrical aperture when centered in said cylindrical aperture prior to said axial movement, said sleeve including a collar having a diameter greater than the outer diameter of said sleeve surrounding the end of said sleeve nearest said threaded end of said shank, said blind shank expanding electrical terminal being inserted into said cylindrical aperture to a position such that said collar rests against one side of said sheet of material; and.

causing said radially expandable sleeve to radially expand outwardly into low resistance electrical contact with said electrically conductive center of said sheet of material in the region where the cylindrical periphery of said cylindrical aperture and the adjacent peripheral surface of said sleeve meet by axially moving said elongated shank in said prede termined direction with respect to said radially expandable sleeve.

10. The method claimed in claim 9 wherein a portion of said radially expandable sleeve extends outwardly from the side of said sheet of material remote from the side of said sheet against which said collar lies prior to said step of causing said sleeve to radially expand outwardly, and wherein said method includes the further step of causing said portion of said sleeve extending outwardly from the side of said sheet of material remote from the side of said sheet against which said collar lies to simultaneously expand outwardly, as said elongated shank is moved axially with respect to said sleeve to cause said sleeve to radially outwardly. so as to form a further collar on said side of said sheet of material remote from the side of said sheet against which said collar lies.

U. The method claimed in claim 10 wherein said electrical compatibility is such that the galvanic emf across said electrically conductive center of said sheet of material and said radially expandable sleeve lies within the approximate range of O to 0.250 volts.

12. A method of creating a threaded electrical terminal in a body of material having an electrically conductive center and covered on one side with a generally non-conductive layer said method comprising the steps of:

forming a cylindrical aperture in said body, said cylindrical aperture formed so as to pass through said generally non-conductive layer and terminate in said body so as to expose said electrically conductive center in the region defined by the periphery of said cylindrical aperture;

inserting into said cylindrical aperture a blind shank expanding electrical terminal, said blind shank expanding electrical terminal comprising an elongated shank threaded at one end, and a radially expandable cylindrical sleeve surrounding the other end of said shank, said shank and said sleeve formed such that axial movement of said shank with respect to said sleeve along their common axis in a predetermined direction causes said radially expandable sleeve to expand radially outwardly, said sleeve being formed of a metallic material that is electrically compatible with the electrically conductive center of said body of material, said sleeve having an outer diameter sized such that it is surrounded by. but spaced slightly from, said cylindrical aperture when centered in said cylindrical aperture prior to said axial movement, said sleeve including a collar having a diameter greater that the outer diameter of said sleeve surrounding the end of said sleeve nearest said threaded end of said shank. said blind shank expanding electrical terminal being inserted into said cylindrical aperture to a position such that said collar rests against said generally non-conductive layer; and,

causing said radially expandable sleeve to radially expand outwardly into low resistance electrical contact with said electrically conductive center of said body of material in the regian where the cylindrical periphery of said cylindrical aperture and the adjacent peripheral surface of said sleeve meet by axially moving said elongated shank in said predetermined direction with respect to said radially expandable sleeve.

IS. The method claimed in claim 12 wherein said electrical compatibility is such that the galvanic emf across said electrically conductive center of said body of material and said radially expandable sleeve lies within the approximate range of 0 to 0.250 volts.

Claims

1. A blind shank expanding threaded electrical grounding terminal structure: 1. a sheet of material having an electrically conductive center and covered on its first and second sides with generally nonconductive layers, said sheet of material having a cylindrical aperture therein extending through said electrically conductive center and said generally non-conductive layers whereby said electrically conductive center is exposed in the region defined by the periphery of said cylindrical aperture; 2. an integrally formed elongated shank co-axially centered in said cylindrical aperture, said elongated shank including: a. a head located on one end, said head adapted to cause a collar to be formed in a radially expandable sleeve on the second side of said sheet of material in bearing engagement with the non-conductive layer located on said second side; b. a sleeve expanding region located adjacent to said head, said sleeve expanding region adapted to radially press a radially expandable sleeve into low resistance electrical contact with the portion of said electrically conductive center exposed in the region defined by the periphery of said cylindrical aperture; and, c. a threaded portion extending axially outwardly from said sleeve expanding region on the opposite side thereof from said head; 3. a radially expandable sleeve mounted about said elongated shank and extending through said sheet of material so as to generally surround said sleeve expanding region, said radially expandable sleeve being in low resistance electrical contact with the portion of said electrically conductive center exposed in the region defined by the periphery of said cylindrical aperture and in low resistance electrical contact with said sleeve expanding region of said elongated shank, said radially expandable sleeve including: a. a pre-formed collar located in bearing, but non-electrical, engagement with the non-conductive layer located on the first side of said sheet of mateRial; and, b. a cylindrical region integral with said collar, said cylindrical region surrounding said sleeve expanding region of said elongated shank and radially pressed by said sleeve expanding region into low resistance electrical contact with the portion of said electrically conductive center exposed in the region defined by the periphery of said cylindrical aperture; and, c. an outwardly rolled collar portion located in bearing, but non-electrical, engagement with the non-conductive layer located on the second side of said sheet of material, said outwardly rolled collar portion being formed by the head of said elongated shank pressing said sleeve outward in the region thereof lying outside of the cylindrical aperture on said second side; 4. an electrical contact, connected to an electrical conductor at least partially surrounding the part of said threaded portion of said elongated shank located adjacent to said preformed collar on the side thereof remote from the side of said pre-formed collar in bearing engagement with said sheet of material; and, 5. a nut threaded onto said threaded portion so as to press said electrical contact into low resistance electrical contact with said pre-formed collar.

2. a radially expandable sleeve mounted about said elongated shank so as to generally surround said cylindrical splined region, said radially expandable sleeve including: a. a collar; and, b. a cylindrical region integral with said collar, said cylindrical region lying adjacent to said head of said elongated shank and said collar being remote therefrom, the portion of said cylindrical region lying adjacent to said head curving inwardly so that the tip thereof lies in said undercut region, said cylindrical region adapted to radially expand outwardly into low resistance electrical contact with the adjacent surface of said aperture in said body of electrically conductive material when said elongated shank is moved axially with respect to said radially expandable sleeve; and, c. a cylindrical aperture coaxial with said cylindrical region and separated into two regions having different diameters, the first of said diameters being approximately the same as the diameter of said splined region of said elongated shank and surrounding said splined region of said elongated shank prior to the expansion of said radially expandable sleeve into low resistance electrical contact, the second of said diameters being slightly smaller than the diameter of said splined region and surrounding said splined region after the expansion of said radially expandable sleeve into low resistance contact with the adjacent surface of said aperture in said body of electrically conductive material.

2. an integrally formed elongated shank co-axially centered in said cylindrical aperture, said elongated shank including: a. a head located on one end, said head adapted to cause a collar to be formed in a radially expandable sleeve on the second side of said sheet of material in bearing engagement with the non-conductive layer located on said second side; b. a sleeve expanding region located adjacent to said head, said sleeve expanding region adapted to radially press a radially expandable sleeve into low resistance electrical contact with the portion of said electrically conductive center exposed in the region defined by the periphery of said cylindrical aperture; and, c. a threaded portion extending axially outwardly from said sleeve expanding region on the opposite side thereof from said head;

3. a radially expandable sleeve mounted about said elongated shank and extending through said sheet of material so as to generally surround said sleeve expanding region, said radially expandable sleeve being in low resistance electrical contact with the portion of said electrically conductive center exposed in the region defined by the periphery of said cylindrical aperture and in low resistance electrical contact with said sleeve expanding region of said elongated shank, said radially expandable sleeve including: a. a pre-formed collar located in bearing, but non-electrical, engagement with the non-conductive layer located on the first side of said sheet of mateRial; and, b. a cylindrical region integral with said collar, said cylindrical region surrounding said sleeve expanding region of said elongated shank and radially pressed by said sleeve expanding region into low resistance electrical contact with the portion of said electrically conductive center exposed in the region defined by the periphery of said cylindrical aperture; and, c. an outwardly rolled collar portion located in bearing, but non-electrical, engagement with the non-conductive layer located on the second side of said sheet of material, said outwardly rolled collar portion being formed by the head of said elongated shank pressing said sleeve outward in the region thereof lying outside of the cylindrical aperture on said second side;

5. In an electrical terminal structure wherein electrical contact, between a sheet or body of electrically conductive material, covered in the region of electrical contact with a layer of non-conductive material, is made via a threaded shaft and an attachment nut, with the threaded shaft being affixed to said sheet or body of electrically conductive material so as to be in low galvanic emf electrical contact therewith, the improvement comprising a blind shank expanding mechanism for affixing said threaded shaft to said sheet or body, said blind shank expanding mechanism comprising: expansion means integrally formed with said threaded shaft, at one end thereof, for radially expanding a radially expandable sleeve when said sleeve surrounds said expansion means and said expansion means is moved in a predetermined direction with respect to said sleeve; and a radially expandable sleeve, including a collar formed at one end, mounted about said expansion means in a position such that said collar is located inwardly of the end of said expansion means nearest said threaded shaft, said radially expandable sleeve further including a cylindrical region integral with said collar, said cylindrical region formed so as to radially expand outwardly when said elongated shank is moved in said predetermined direction with respect to said radially expandable sleeve.

9. A method of creating a threaded electrical terminal in a sheet of material having an electrically conductive center and covered on both sides with generally non-conductive layers, said method comprising the steps of: forming a cylindrical aperture in said sheet, said cylindrical aperture formed so as to pass through said sheet and expose said electrically conductive center in the region defined by the periphery of said cylindrical aperture; inserting into said cylindrical aperture a blind shank expanding electrical terminal, said blind shank expanding electrical terminal comprising an elongated shank threaded at one end, and a radially expandable cylindrical sleeve surrounding the other end of said shank, said shank and said sleeve formed such that axial movement of said shank with respect to said sleeve along their common axis in a predetermined direction causes said radially expandable sleeve to expand radially outwardly, said sleeve being formed of a metallic material that is electrically compatible with the electrically conductive center of said sheet of material, said sleeve having an outer diameter sized such that it is surrounded by, but spaced slightly from, said cylindrical aperture when centered in said cylindrical aperture prior to said axial movement, said sleeve including a collar having a diameter greater than the outer diameter of said sleeve surrounding the end of said sleeve nearest said threaded end of said shank, said blind shank expanding electrical terminal being inserted into said cylindrical aperture to a position such that said collar rests against one side of said sheet of material; and, causing said radially expandable sleeve to radially expand outwardly into low resistance electrical contact with said electrically conductive center of said sheet of material in the region where the cylindrical periphery of said cylindrical aperture and the adjacent peripheral surface of said sleeve meet by axially moving said elongated shank in said predetErmined direction with respect to said radially expandable sleeve.

10. The method claimed in claim 9 wherein a portion of said radially expandable sleeve extends outwardly from the side of said sheet of material remote from the side of said sheet against which said collar lies prior to said step of causing said sleeve to radially expand outwardly, and wherein said method includes the further step of causing said portion of said sleeve extending outwardly from the side of said sheet of material remote from the side of said sheet against which said collar lies to simultaneously expand outwardly, as said elongated shank is moved axially with respect to said sleeve to cause said sleeve to radially outwardly, so as to form a further collar on said side of said sheet of material remote from the side of said sheet against which said collar lies.

11. The method claimed in claim 10 wherein said electrical compatibility is such that the galvanic emf across said electrically conductive center of said sheet of material and said radially expandable sleeve lies within the approximate range of 0 to 0.250 volts.

12. A method of creating a threaded electrical terminal in a body of material having an electrically conductive center and covered on one side with a generally non-conductive layer, said method comprising the steps of: forming a cylindrical aperture in said body, said cylindrical aperture formed so as to pass through said generally non-conductive layer and terminate in said body so as to expose said electrically conductive center in the region defined by the periphery of said cylindrical aperture; inserting into said cylindrical aperture a blind shank expanding electrical terminal, said blind shank expanding electrical terminal comprising an elongated shank threaded at one end, and a radially expandable cylindrical sleeve surrounding the other end of said shank, said shank and said sleeve formed such that axial movement of said shank with respect to said sleeve along their common axis in a predetermined direction causes said radially expandable sleeve to expand radially outwardly, said sleeve being formed of a metallic material that is electrically compatible with the electrically conductive center of said body of material, said sleeve having an outer diameter sized such that it is surrounded by, but spaced slightly from, said cylindrical aperture when centered in said cylindrical aperture prior to said axial movement, said sleeve including a collar having a diameter greater that the outer diameter of said sleeve surrounding the end of said sleeve nearest said threaded end of said shank, said blind shank expanding electrical terminal being inserted into said cylindrical aperture to a position such that said collar rests against said generally non-conductive layer; and, causing said radially expandable sleeve to radially expand outwardly into low resistance electrical contact with said electrically conductive center of said body of material in the region where the cylindrical periphery of said cylindrical aperture and the adjacent peripheral surface of said sleeve meet by axially moving said elongated shank in said predetermined direction with respect to said radially expandable sleeve.

13. The method claimed in claim 12 wherein said electrical compatibility is such that the galvanic emf across said electrically conductive center of said body of material and said radially expandable sleeve lies within the approximate range of 0 to 0.250 volts.