US 3825881 A
An electrical contact element for gripping and providing electrical contact with a flat conductor includes an integral, bifurcated-shaped segment having a pair of jaw members each of which include teeth formed along inner edges of the jaws. Outer jaw edges extend to an apex along a length thereof. A slot is formed in each jaw at the apex and extends generally inwardly from the apex. The apex is positioned along the length of the jaw at a location for providing that upon the application of a crimping force to the element at the apex, the element will deform near the slot and grip a conductor positioned between the jaws with a force which decreases progressively along the length of the jaw from inner to outer teeth. Deformation of the element results in the establishment of creep resisting forces which lock the jaws to the cable.
Description (OCR text may contain errors)
Patent [191 TERMINATION DEVICE FOR FLAT ELECTRICAL CONDUCTORS [451 July 23, 1974 Primary Examiner-James R. Boler Assistant ExaminerPeter Nerbun  Inventor: Jon Wigby, Sandy Hook, Conn.  Assignee: Burndy Corporation, Norwalk, 5 ABSTRACT I Conn. An electrical contact element for gripping and providing electrical contact with a flat conductor includes an  Ffled' 1972 integral, bifurcated-shaped segment having a pair of  Appl. No.: 319,143 jaw members each of which include teeth formed along inner edges of the jaws. Outer jaw edges extend to an apex along a length thereof. A slot is formed in I each jaw at the apex and extends generally inwardly  d 99 R from the apex. The apex is positioned along the length N 0 ea c 3 6 T of the jaw at a location for providing that upon the applicationof a crimping force to the element at the apex, the element will deform near the slot and grip a  References C'ted I J conductor positioned between the jaws with a force UNITED STATES PATENTS which decreases progressively along the length of the 2,570,753 10/1951 Berg 339/276 T jaw from inner to outer teeth..Deformation of the ele- 3,22l,294 11/1965 Roberts 339/276 T ment results in the establishment of creep resisting 3,259,873 7/1966 Parkinson et al. 339/276 T forces which lock the jaws to the 3,422,391 1/1969 Thomson 339/97 R 6 Claims, 6 Drawing Figures 1. TERMINATION DEVICE FOR FLAT ELECTRICAL CONDUCTORS This invention relates generally to termination devices for electrical conductors. The invention relates more particularly to an improved termination device and contact element for use with a flat electrical conductor.
In one form of electrical cable known variously as a strip, tape or ribbon cable, a plurality of elongated, relatively thin, electrical conductors of rectangular crosssection are closely aligned in parallel and are embedded in a thin, elongated strip of insulating material. Various factors relating to the configuration of this form of electrical cable have made it necessary to provide termination devices which are especially adapted for use with these cables. A typical termination device comprises a plurality of contact elements which are mounted side by side and which extend in longitudinal alignment with a plurality of flat conductors to which electrical connection is to be made. Each contact element includes a first integral, generally bifurcated shaped segment formed at one end of the element for gripping and establishing electrical connection with a conductor of the cable, and, a second integral segment formed at an opposite end of the element for engaging a contact of a mating connector. The bifurcated segment comprises a pair of toothed jaws which are initially spaced apart for receiving an insulated tape cable conductor therebetween and which are crimped together against opposite sides of the cable. Crimping of the toothed jaws causes penetration of the insulation by the teeth thereby effecting electrical connection with the flat conductor and esablishing a mechanical grip on the cable.
While this form of tape cable terminal element has been employed successfully, it has exhibited several limitations which detract from its reliability and performance; For example, the crimped contact element exhibits a stress creep in the metal over a period of time resulting in a relaxation of the mechanical grip on the cable and an interruption of electrical conitnuity with the flat conductor. In addition, the application of an excessive crimping force to the contact element has at times caused the severance of the conductor. Generally that segment of a conductor near the outer teeth of the element severs initially and causes the interruption of electrical continuity between the contact element and the conductor.
Various arrangements have been proposed for overcoming the disadvantages which have accompanied the use of this form of contact element. Stress creep is partially reduced in one arrangement by providing grooves which extend from inner and outer edges of one of the jaws. A creep opposing stress is established upon crimping of the jaw. This arrangement, however, results in cable gripping forces which progressively increase in magnitude outwardly from a throat of the jaw. Greater forces are thereby exerted on the conductor near the outer, teeth and the cable is undesirably severed at times near outermost teeth when excessive crimping forces are applied to the element.
In another termination arrangement, the magnitude of the gripping force exerted by the contact jaws on the conductor progressively decreases from innermost teeth of the jaw to outermost teeth of the jaw. This progressive decrease in gripping force is provided by varying the spacing between the teeth of the crimped jaw. Variable spacing is accomplished by altering the dimensions or shape of the teeth along the length of the jaw. Variations in teeth dimensions or shape however can result in an undesirable skiving characteristic whereby the cable is pinched and is subjected to side wise displacement. A loss of electrical continuity between the element and the conductor can result from this undesired skiving.
Accordingly, it is an object of this invention to provide an improved termination device and contact element for a tape cable. I
Another object of the invention is to provide an improvedcontact element which corrects one or more of the above enumerated disadvantages found in prior contact elements.
Another object of the invention is to provide in a tape cable terminating device a contact element having an improved means for overcoming the loss of grip on a flat conductor resulting from stress creep in the element.
Another object of the invention is to provide in a tape cable terminating device an improved contact element having a toothed jaw wherein gripping forces exerted on a flat conductor which is positioned between the teeth of the jaw decrease progressively from inner to outer teeth of the element.
Another object of the invention is to provide an improved contact element for a flat conductor having means for effecting electrical contact by penetrating insulation of the conductor while avoiding shearing of the conductor.
A further object of the invention is to provide an improved toothed contact element which exerts a grip ping force on a conductor which decreases progressively along the length of the element from inner to outer teeth and which additionally provides a means for overcoming stress creep in the contact element.
In accordance with features of this invention, an electrical contact element for a flat conductor includes an integral, bifurcated-shaped, conductor gripping and contact segment having a pair of jaw members each of which include gripping teeth formed along adjacent inner edges of the jaws, and, outer jaw edges which extend to an apex along their length. A slot is formed in each jaw at the apex and extends generally inwardly from the apex. The apex is located at a position along the length of the jaw for providing that upon the application of a crimping force to the element at the apex, the element will deform near the slot and grip a conductor positioned between the jaws with a force which decreases progressively along the length of the jaw from inner to outer teeth. Gripping forces are thereby exerted on an insulated conductor by inner teeth which establish a firm mechanical connection while a limited penetration sufficient to assure electrical contact with the conductor is provided by outer teeth. This arrangement advantageously avoids the interruption of electrical contact near the outer teeth as a result of the application of excessive gripping forces which have heretofore tended to sever a thin conductor. Additionally, the slots extending from the apex and which deform during crimping provide for a locked gripping of the conductor and resist stress creep in the metal contact element.
These and other objects and features of the invention will become apparent from the following specification and from the drawings wherein:
FIG. 1 is a side elevation view of an uncrimped contact element which is constructed in accordance with features of this invention;
FIG. 2 is a plan view of the contact element of FIG.
FIG. 3 is a front elevation view of the contact element of FIG. 1;
FIG. 4 is a plan view, partly cut away, of a multiconductor tape cable;
FIG. 5 is a side elevation view of the terminal of FIG. 1 subsequent to crimping of a conductor of a tape cable; and
FIG. 6 is a view of a tape cable terminating device constructed in accordance with features of this inventron.
Referring now to FIGS. 1-3 of the drawings, a contact element in accordance with the invention is shown to include a first integral, bifurcated shaped segment referenced generally as 8 and formed at a left end of the element as viewed in FIG. 1. The segment 8 is adapted for gripping and establishing electrical contact with a flat conductor. A second integral segment referenced generally as 9 is formed at the right end of the element as viewed in FIG. 1 for engaging a contact member of a mating connector. The contact element is fabricated of a metal such as beryllium copper, phosphorous bronze or other suitable electrically conductive material which is adapted to take a mechanical set upon the application of crimping forces. For purposes of clarity in the drawings, the contact element is shown greatly enlarged and in practice the segment 8 will have dimensions, for example, on the order of .5 inches in length, 0.2 inches in width, and 0.015 inches in thickness.
The bifurcated segment 8 includes a pair of jaw members l0 and 12. Teeth 14 of uniform configuration and size are formed along an inner edge 15 of the jaw and teeth 16 also of uniform configuration and size are formed along an inner edge 17 of the jaw 12. These teeth are positioned along the length of their respective jaws for providing that when the jaws l0 and 12 are crimped together as seen in FIG. 5, the teeth of the jaws will intermesh. An outer edge 18 of the jaw member 10 defines an extension of the jaw member toward an apex or peak 20. Similarly, an outer edge 22 of the jaw member 12 defines an extension of the jaw member toward an apex or peak 24. A slot 26 is formed in the jaw member 10 which extends generally inwardly from the apex toward the inner edge of the jaw member. A slot 28 is also formed in the jaw member 12 and extends inwardly from the apex 24 toward the inner edge 17. As indicated in greater detail hereinafter, the jaws of the bifurcated segment are crimped against opposite sides of a tape cable and grip the cable and establish electrical connection with an insulated flat conductor of the cable.
The segment 9 which engages and provides electrical continuity with a contact plug member 31 of a mating connector is shown to comprise a receptacle formed by a pair of resilient fingers 32 and 33. These fingers extend transversely from a neck 34 which extend longitudinally from the segment 8. The contact element is fabricated for example by stamping and the fingers 32 and 33 are subsequently formed by folding over segments of the element to form these fingers. The fingers con verge along their length to a constriction 36 and flange outwardly from this constriction to form a guide for the plug element 31 of a mating connector. The fingers resiliently engage the plug contact member 31 which extends longitudinally into the constriction 36. Although the particular form of connector engaging means is shown in the drawing to comprise a receptacle for engaging a plug of a mating connector, other engaging means may be substituted for the receptacle. For example, the contact element may include an integrally formed plug segment as an alternative to the receptacle illustrated.
A relatively flat insulated cable 40 which includes conductive ribbons 42, is positioned between the jaws 10 and 12 of the contact element as illustrated in FIG. 5 and is longitudinally aligned therewith. The conductor extends into a mouth 44 of the contact, which is formed by the outer segments of the jaw members, and toward a throat 46 located inwardly of the teeth 14 and 16. With the flat conductor thus orientated, crimping forces are applied at the apex 20 and 24 as indicated by the arrows causing the teeth of jaw members 10 and 12 to close on the insulation and conductor thereby penetrating the insulation, establishing electrical connection with the conductor and gripping the cable.
Upon the initial application of a crimping force to the contact element at the apex points, the jaws 10 and 12 will rotate about a pivot point located slightly to the right of the throat 46 and will advance toward each other. During the application of this crimping force the outer edges of the jaws begin to deform and flow into the slots 26 and 28. A continued application of the crimping force causes these slots to deform from their initial U-shaped configuration as illustrated in FIG. 1 to a final tear drop shape as illustrated in FIG. 5. Deformation of the jaw segments is accompanied by the creation of compressive forces in the elements along outer edges of the jaws and tension forces along the inner edges of the jaws. The initial pivot point of the jaws which was located near the rear of the throat 46 is advanced by the crimping action from the throat 46 along each of these jaws. The forward displacement of the pivot point provides for initial engagement of the insulated conductor by the inner teeth of the jaws 10 and 12 respectively. The continued application of the crimping force causes subsequent progressive engagement of the cable by outer teeth of the jaws 10 and 12. Upon completion of the crimping operation, the spacing between the uniformly shaped inner teeth is less than the spacing between the uniformly shaped outer teeth as is illustrated in FIG. 5. A progressively decreasing force on the engaged insulated conductor is thereby established from the inner to the outer teeth of the contact element. Application of the crimping force is terminated upon penetration of the insulation and slight contact with the conductor by outer teeth 60 and 62. Greater penetration of the cable will occur between the innermost teeth of the jaws. Thus, while a firm gripping force is applied to the insulated conductor by the toothed jaws, the avoidance of interruption of electrical continuity is assured by limiting the penetration of outer teeth to a penetration of the insulation and slight contact with the conductor. A relatively strong gripping force and electrical continuity between the element and conductor is thus provided. Furthermore, upon termination of the crimping operation the outer edges of the jaws l0 and 12 remain in a compressive state while the inner edges along which the teeth are formed will exist in a tensile state. The advantageous result of this deformation and the compression on the outer edges is the establishment of a force which locks the teeth in contact with the cable and resists creep stress in a contact element.
The described deformation of the jaw members upon the application of crimping forces is accomplished by locating the slotted apexes and 24 at positions along the length of the jaws intermediate the innermost and outermost teeth. The jaw edges extend to an apex which in a preferred embodiment coincide with the slots on each jaw as described above. U-shaped slots 24 and 26 extend inwardly from the apex preferably to a depth equal to about one-third the distance between the apex and the inner edges of the jaws.
FIG. 6 illustrates a terminal device for a flat electrical conductor constructed in accordance with features of this invention. The terminal device includes a receptacle body 70 formed of an electrical insulating material such as phenylene oxide and a cover body 72 similarly formed of an electrical insulating material. The bodies 70 and 72 include a plurality of integrally formed oppositely positioned aligned grooves (not illustrated) for positioning and securing a plurality of contact elements 74 in side by side relationship across the width of the device. The bodies 70 and 72 are secured together by suitable means such as screws 78 or by moulded in place plastic snaplocks thereby restraining thecontact elements in place. Crimping of the contact elements 74 to conductors 40 of the tape cable 42 is accomplished prior to assembly of the terminal device. Crimping is provided in a jig wherein each of the contact elements 74 is aligned with a flat conductor of the cable. In the embodiment of the contact element illustrated, the contact elements 74 are initially positioned for crimping by aligning the elements on a magazine rod 75 which is formed of an electrical insulating material such as nylon. The rod 75 extends through an aperture 76 formed element. The crimping is then effected by the application of a crimping force to the contact elements and the assembled contact elements and rod are positioned in the body 70. The elements 74 can be permanently positioned on the rod before the crimping operation by spiking an edge of each of the elements against the rod 75. An improved contact element and terminal device for a flat conductor has thus been described which advantageously resists stress creep forces and which provides gripping forces which progressively decrease outwardly along the jaws of the contact element from a throat portion of the element. A firm gripping force is thereby applied while the possibility of severing the conductor is substantially reduced.
While I have described and illustrated a particular embodiment of my invention, various modifications may be made thereto by those skilled in the art without departing from the spirit of the invention and the scope of the appended claims.
What is claimed is:
l. A contact element for a terminating device for a flat conductor comprising:
a thin electrically conductive body having a first integral bifurcated-shaped conductor gripping and contact segment and a second integral segment for engaging a contact member of a mating connector;
2. The contact element of claim 1 wherein said bifurcated segment includes a throat formed at a juncture of said jaw members and said teeth extend along said jaws to an inner location, and said apexes are positioned at a longitudinal position intermediate said throat and the inner teeth of said jaws.
3. The contact element of claim 1 wherein said slot has a generally U-shaped configuration.
4. The contact element of claim 1 wherein said teeth are of uniform size and shape.
5. The contact element of claim 1 wherein said element includes a second segment arranged for engaging a control element of a mating connector.
6. A terminating device for a tape cable comprising:
a means for mounting a plurality of contact elements which grip and establish electrical contact with a tape cable and engage a mating connector;
each of said elements comprising a thin, electrically conductive body having a first, integral, bifurcatedshaped conductor gripping and contact segment and a second integral segment for engaging a contact member of a mating connector;
said bifuracted segment having a pair of jaw members each including teeth formed along adjacent inner edges of the jaws;
each of said jaws having outer edges thereof which extend to an apex along their length;
a slot formed in each jaw at the apex and extending generally inwardly from the apex whereby the application of a crimping force at the apex establishes progressive gripping forces which decrease in magnitude from inner to outer teeth of the jaws and establish a stress creep resisting force in the element; and,
a second integral segment for engaging a control element of a mating connector.