EP0147218A2

EP0147218A2 - Insulation piercing compression connector

Info

Publication number: EP0147218A2
Application number: EP84309046A
Authority: EP
Inventors: Sydney Levy
Original assignee: Thomas and Betts Corp
Current assignee: ABB Installation Products Inc
Priority date: 1983-12-29
Filing date: 1984-12-21
Publication date: 1985-07-03
Also published as: AU3708384A; AU557587B2; EP0147218A3; JPS60221977A

Abstract

An insulation piercing electrical connector (20) includes a plurality of insulation piercing projections (38) which engage and secure the conductor (14) in compressive electrical contact. The insulation piercing projections (38) extend from resiliently deformable cantilevered contact arms (34) which are deflectable into contact with an insulated wire (14). A plurality of intersecting slots (44) are formed by the insulation piercing projections (38) which compressively secure the conductor (14) therein.

Description

FIELD OF THE INVENTION:

The invention relates generally to insulation piercing electrical terminals for insulated wire and more particularly to an electrical terminal having insulation piercing projections for contacting the conductor of the wire and compressively retaining the conductor therein.

BACKGROUND OF THE INVENTION:

The use of insulation piercing and insulation displacing contacts is widespread in the electrical wire terminating industry. The advantage of such contacts is that insulated wire need not be stripped of the insulation prior to termination. This of course saves both installation time and expense as no stripping tools need be employed.
Most of the insulation displacing contacts (I.D.C.) used today are of the "U"-shaped or forked variety, having a pair of upwardly extending tines which form therebetween a slot for receipt of the insulated wire. These IDC's make contact along the internal marginal edges of the slot, with the tines acting as pre-loaded cantilevered beams which deflect slightly outwardly upon insertion of the wire into the slot. These "U"-shaped IDC's thus spread open to receive the wire, pierce the insulation and electrically contact the conductor.
While this technique has proven successful in many applications, it does have certain disadvantages. As the wire is inserted between spreading tines the conductor, upon termination will be seated between the spreading tines. In time, such connection may tend to become loose and the electrical continuity may be intermittent. This problem is especially prevalent when terminating stranded wire as the strands have a tendency upon termination, to move outwardly away from the bottom portion of the U-shaped contact toward the wider portion of the spreading tines. Thus, the strands may not be adequately electrically engaged in the slot.
The use of U-shaped or forked terminals is well known for terminating solid conductor wire. Examples of these connectors are shown in U.S. Patent No. 3,117,829 issued on January 14, 1964 and in U.S. Patent No. 3,058,088 issued on October 9, 1962. As can be seen in these references the "U"-shaped contact engages the cable at substantially 90° and spans the diameter thereof. The tines then deform in some manner to accommodate the solid conductor therebetween
Other insulation displacing terminals are known to employ a plurality of radially extending cantilevered contacts which contact the conductor at plural locations. Such contacts are shown in U.K. Patent Specification 1,109,914, French Patent 1,312,525 and German Patent 468,535. These terminals have cantilevered members with IDC end portions, which are designed to pierce only partially into the cable and make conductive contact with the conductor. However as the contacts do not substantially extend into the conductor region of the cable, there is only minimal surface contact with the conductor.

SUMMARY OF THE INVENTION:

It is an object of the present invention to provide an insulation displacing terminal having contact members which pierce the wire insulation and contact the conductor in compressive relation, establishing an effective electrical connection therebetween.
It is a further object to provide a series of slots, formed between the contact members, which secure the conductor therein to compress the conductor of the wire.
In the effective attainment of these and other objects the present invention contemplates providing an electrical terminal for an insulated wire conductor which includes a plurality of insulation displacing contacts. The contacts pierce the insulation and contact the conductor. A plurality of slots are formed between the contacts which support and engage the conductor in compressive fashion, thus establishing an effective compressive electrical connection.

BRIEF DESCRIPTION OF THE DRAWINGS:

Fig. 1 shows in perspective view the electrical connector of the present invention in an open position, for receipt of an extent of insulated stranded wire.
Fig. 2 is the connector of Fig. 1, shown in the closed or connected position.
Fig. 3 is a partial longitudinal sectional showing of the connected wire and connector of Fig. 2 taken along the lines III-III.
Fig. 4 is a cross-sectional showing of the wire and the connector taken along the line IV-IV of Fig. 1.
Fig. 5 is a cross-section of connector and wire of Fig. 2, taken along the line V-V.

DESCRIPTION OF THE PREFERRED EMBODIMENTS:

Referring to Fig. 1 a section of electrical cable 10 is shown comprising an outer insulative jacket 12 made of plastic or similar material, surrounding a conductor 14. The present invention terminates stranded conductors 16 which collectively form conductor 14.
Connector 20 is a two-piece member comprising an outer housing or sleeve 22 and a conductive member 24. Sleeve 22 is an elongate hollow cylindrical structure having a central bore 26. Sleeve 22 slidably frictionally receives conductive member 24 as will be described in detail hereinafter. In the present illustrative embodiment sleeve 22 is constructed of steel or similar metal, however it is also contemplated that sleeve 22 may be constructed of a non-conductive, suitably rigid material such as glass-filled plastic or ceramic as sleeve 22 need not be in conductive contact with conductive member 24.
Conductive member 24 has an elongate body having a terminal end portion 28, a frusto-conical central region 30, and a cylindrical insulation displacing contact portion 32 at the end axially opposite terminal end portion 28. As shown in the drawings, terminal end portion 28 is in the form of a pin for insertion into a mating socket of a similar wire connector. The present invention also contemplates forming a socket or other terminal shape in place of the pin shown in the drawings.
Insulation displacing contact portion 32 includes four identical contact arms 34 which extend in cantilevered fashion from and circumferentially around a cylindrical body section 36 adjacent frusto-conical region 30. Contact arms 34 are formed from cylindrical insulation displacing contact portion 32 and are resiliently deformable. Cylindrical body section 36 as well as cantilever contact arms 34, in compressed position, have an outer diameter which is closely dimensioned to the inner diameter of sleeve 22 to permit sleeve 22 to frictionally slide thereover. Referring additionally to Fig. 4, each of the unsupported ends of cantilevered contact arms 34_'includes a transversely extending insulation piercing projection 38. Referring to one of the projections 38 as representative of the four identical projections, it can be seen that projection 38 is a wedge-shaped member having a pair of substantially perpendicular side edges 40 and 41 which intersect and form an insulation piercing point 42. The remaining edge 43 of the wedge-shaped projection 42 is arcuate at the juncture with cantilevered arm 34.
Connector 20 is connected to cable 10 by inserting a cable end 21 (Fig. 1) among the spread apart cantilevered contact arms 34 and into cylindrical body section 36 until it abuts against the interior walls of the frusto-conical section 30. In this position, sleeve 22 is slidably moved in the direction shown by arrow A over body section 36. Further movement of sleeve 22 in the direction of arrow A, will force sleeve 22 into engagement with the base of cantilevered contact arms 34. Still further progression of sleeve 22 will urge contact arms 34 inwardly toward cable 10. The points 42 of the four projections 38 will pierce the insulative jacket 12 of cable 10 and contact the conductor 14. As the insulation piercing projections 38 are progressively pressed inwardly by the inward deflection of cantilevered contact arms 34, the strands 16 forming conductor 14 will be displaced. Initially, the strands 16 substantially occupy the inner cross-sectional area of cable jacket 12. Movement of insulation piercing projections 38 displaces the strands into an increasingly smaller cross-sectional area. As a result of such displacement the strands 16 will be progressively compressed between the respective opposed side walls 40 and 41 of the insulation piercing projections. As shown in Figs. 2, 3 and 5, when sleeve 22 is moved fully along conductive member 24, adjacent the projections 38, cantilevered contact arms 34 will be fully deflected and projections 38 will have fully pierced cable insulation 12 and will compressively confine the strands 16 of conductor 14.
Referring to Figs. 3 and 5 the resulting compressive connection is shown. In fully progressed position sleeve 22 will lie adjacent the distal end of conductive member 24. The insulation piercing projections 38, which have been radially, inwardly disposed by movement of sleeve 22, engage strands 16 within elongate rectangular slots 44 formed by the opposed side edges 40 and 41 of adjacent respective projections 38. As above described, the side edges 40 and 41 of each projection 38 are substantially normal to the other. In fully compressed position, slots 44 defined by and between adjacent edges, have substantially parallel side walls and extend radially from a central locus 45 coincident with the central axis of the connector 20.
Each compressed slot 44 is bounded on longitudinal sides by opposed side walls 40 and 41 of two adjacent projections 38. The slots 44 are further bounded on their transverse sides by the central locus 45 and by the outer jacket 12. Thus it can be appreciated that strands 16, upon compression by the movement of projection 38, will be retained and compressed in the four elongate rectangular slots 44. Since each adjacent wall 40 and 41 of such projections 38 is disposed parallel to each other, the compression will be uniform across the length of each slot 44 i.e., radially from locus 45 to jacket 12. Thus the slots 44 will have a slot width, between two adjacent side walls 40 and 41, which decreases upon movement of projections 38. Unlike spreading tines of U-shaped contacts or contacts having areas between the blades which are not defined by parallel sides, the present invention prevents tendency for the strands 16 to move radially outwardly from the central locus 45 upon connection. The conductor strands 16 are compressed without radial movement into a cross-shaped area defined by slots 44 which is substantially less than the original circular cross-sectional area by which the strands normally occupy, as shown in Fig. 4. The movement of projections 38, in addition to compressing strands 16 into slots 44 also slightly deforms the strands 16 so as to provide for their accommodation in the smaller cross-sectional area.
Since the strands 16 are bounded within the slots 44 as defined above, the connection formed, will be gas tight preventing oxidation of the strands 16 at the point of connection. Further, as the strands are securely retained in the slots 44 presenting relative movement therebetween, the electrical connection will be permanent and not subject to intermittent contact.
As shown and described herein the present invention employs four right angle projections 38 which upon compression form four extending perpendicular slots 44 extending from locus 45 at 90° orientation from the adjacent slot. It is however contemplated that the present invention may also include other numbers of projections such as those which can have side edges formed at 120° thus providing three slots into which the strands 16 can be compressed. It is noted however that in each case regardless of the number of slots, the side edges forming the slot will have parallel longitudinal sides thus preventing any radially outward migration of the strands upon connection. Other similar arrangements will also become evident to one skilled in the art.
Further it is contemplated that plural conductive members 24 can be mounted in a single housing, in a multi-pin arrangement, for mass termination upon movement of the housing relative to such plural conductive members 24.
While the above invention is described primarily for use with stranded wire it should be appreciated that the present invention may also be employed with wire having a solid conductor.
Various other modifications to the foregoing disclosed embodiment will be evident to those skilled in the art. Thus, the particularly described preferred embodiment is intended to be illustrative and not limited thereto. The true scope of the invention is set forth in the following claims.

Claims

1. A connector for an electrical cable having a stranded conductor surrounded by an insulative casing comprising:

a housing having a central opening therethrough; and

an elongate conductive member slidably received in said housing, said conductive member having a terminal portion at one end thereof and an insulation displacing portion at the other end thereof for electrical connection with said conductor, said insulation displacing portion including a plurality of resilient cantilevered members for surrounding said cable, each said member including an inwardly directed insulation piercing projection, each of said'projections having a pair of intersecting side edges, said cantilevered members being deflectable upon slidable engagement of said housing with said conductive member to deflect inwardly toward said cable to move said insulation piercing projection into said cable to displace said strands in said casing and conductively contact said strands of said conductor, said side edges of said insulation piercing projections forming therebetween a plurality of elongate conductor compression slots, extending outwardly from a central locus, for compressively retaining said displaced strands of said conductor therein.

2. A connector in accordance with claim 1 wherein said slots have elongate side walls defined by said side edges of adjacent insulation piercing projections and wherein said walls of each slot are substantially parallel.

3. A connector in accordance with Claim 1 or Claim 2 wherein said conductive member includes four cantilevered members thereby forming four slots extending from said central locus, each slot radially extending from said locus at 90° orientation with respect to the adjacent slot.

4. A connector in accordance with claim 3 wherein said insulation piercing projections extend substantially transversely from said cantilevered portions.

5. A connector in accordance with claim 4 wherein said insulation piercing projections extend from the unsupported end of said cantilevered members.

6. A connector in accordance with claim 5 wherein said housing is an elongate member having a central longitudinal bore therethrough defining said opening, said conductive member being progressively insertable into said housing bore for relative movement of said housing toward said insulation piercing projections to resiliently deflect said cantilevered members toward said cable and into insulated displacing contact with said conductors.

7. An electrical terminal for terminating an insulated conductor comprising:

an elongate conductive member having a terminal end and a conductor engaging end for receipt of one end of said insulated conductor;

said conductive member including a plurality of resiliently deformable insulation displacing elements for electrically engaging said conductor upon said resilient deformation;

said plural insulation displacing elements forming plural outwardly extending conductor retaining slots, said slots each having a width which is decreased upon deformation of said insulation displacing elements and having parallel side walls defined by said insulation displacing elements for maintaining a uniform compressive force on a cross-sectional area of said conductor;

means for resiliently deforming said insulation displacing elements.

8. A terminal in accordance with claim 7 wherein said conductive member includes a plurality of cantilevered contact arms defining said insulation displacing elements said cantilevered contact arms be_g deflectable toward said insulated conductor and responsive to said deforming means.

9. A terminal in accordance with claim 8 wherein each of said plurality of cantilevered contact arms includes an insulation piercing projection, said insulation piercing projections of each said cantilevered contact arms forming said conductor retaining slots.

10. A terminal for electrical cable having an outer insulative jacket surrounding a plurality of conductive strands defining an inner cross-sectional area, said terminal comprising:

a cylindrical housing having a central bore therethrough;

an elongate conductive member insertably received in said bore of said cylindrical housing, said conductive member being cylindrical about a central longitudinal axis and having at one axial end a terminal end portion and at the other end a plurality of resiliently deformable cantilevered arms for surrounding said cable, each of said cantilevered arms including a wedge-shaped insulation piercing projection having a pair of side edges forming at their intersection an insulation piercing point, said cantilevered arms being deflectable inwardly toward said central axis upon insertion of said conductive member into said housing to move said insulation piercing projections into conductive contact with the strands of said cable, said side edges of said insulation piercing projection, upon said movement of said projections, forming therebetween a plurality of elongate slots extending radially from said central axis, said slots each having parallel longitudinal sides defined by adjacent side edges of said projections, said slots collectively defining a cross-sectional strand retaining area less than said inner cross-sectional area.