Abstract:
A termination element for electrical connectors and method for making the same. The elements have a wire receiving portion defined by spaced-apart sides in which opposing jaws are formed. The jaws are cut and formed from the sidewalls to present a uniform angular lead-in for the wire being inserted and are spaced and coined to facilitate compression and deformation of the wire upon insertion.

Description:
This is a continuation of application Ser. No. 589,308 filed June 23, 1975, now abandoned, which is a division of application Ser. No. 443,678 filed Feb. 19, 1974. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a solderless termination system. In particular, it relates to the type of such systems where a wire is engaged and held by blades or jaws. In further particular, it relates to the type of such systems adapted for insulation piercing as well as engaging and holding a wire. 
     2. Description of the Prior Art 
     Electrical termination systems are known in myriad forms and sizes. The type of system of interest in the present description provides, as a means for retaining a wire, a pair of facing blades or jaws which may be, before insertion of a wire, in a contact or appropriately spaced apart. Conventionally, blades are adapted to grip a wire between them for mechanical and electrical contact. Often, a lead-in portion is provided where the contact portion of the blades opens to provide convenient positioning and gradual gripping of the wire. Such structures as are shown in the prior art may also enable the insulation surrounding the wire to be pierced as it is inserted between the blades. Common applications of such termination systems are in splicing wires and in the wire terminating end of connectors. 
     There are a number of factors and problems important in an acceptable insulation piercing solderless termination system. Some of these factors and problems are more pronounced with regard to so called miniature termination systems or high density systems where elements are quite close together. 
     One of the most important (if not the most important) performance factors relates to contact resistance. More accurately, this factor relates to the change in contact resistance between the terminated wire and the terminating system after being subject to time and hostile environments. 
     The physical strength and durability of the connection between the wire and the termination system is also important. 
     Other factors relate to manufacturability and within that general subject, to the level of confidence found for terminations passing the various acceptance tests. It should be understood that with high volume production, the number of faulty pieces should be small and predictable with high level of confidence. 
     The termination system described below has been found to perform very well under a variety of physical and electrical performance conditions and to meet the needs for manufacturability. In terms of change in contact resistance, under hostile environments and use tests, excellent results have been obtained. 
     It is further notable that termination systems of the type herein described have both civilian and military uses and are particularly used in telephone systems. Production and utilization volumes are high and reliability requirements within the performance parameters specified by users are very stringent. In one exemplary application, the criterion set is that, under the defined test conditions, no more than 1 out of 10,000 terminations may exceed a change in contact resistance of 0.25 milliohms at the 95% confidence level. 
     SUMMARY OF THE INVENTION 
     The invention comprises an electrical termination system in which the wire receiving portion is defined by spaced apart sides for receiving a wire between them and at least one pair of formed-in jaws in the sides. The jaws are formed opposite each other presenting a narrowed space between them. The formed-in jaws are integral with the sides at each of their lateral extremities. In a further aspect, a lead-in portion is provided by notching the sides at the jaws establishing an angle to the upper edge of the jaws to aid in locating the wire and directing it into the jaws. In the area which contacts the wire, the lead-in edge desirably has a transition portion which comprises a coined edge in order to present to an entering wire a smoothly angled embossing surface. In addition, the jaws may be freed at their lower ends. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a preferred embodiment of the termination system of the invention. 
     FIG. 2 is a perspective view of another preferred embodiment of the termination system of the invention as embodied in a ribbon type contact element. 
     FIG. 3 is a perspective view of the contact element of FIG. 2 installed in a high density connector body. 
     FIG. 4 is a partial top view of the preferred embodiment of the invention. 
     FIG. 5 is an enlarged partial section end view of the preferred embodiment of the invention through V--V of FIG. 4. 
     FIG. 6 is a sectional end view through VI--VI of FIG. 4 of the termination system with a wire installed, and illustrating in phantom the wire prior to installation. 
     FIG. 7 shows a top view of the invention employed for splicing parallel wires. 
     FIG. 8 shows a top view of the invention employed for butt splicing. 
     FIG. 9 is a photomicrograph of a longitudinal cross section of 24 gauge wire inserted in a termination system. The insulation does not appear in the picture. 
     FIG. 10 is a photomicrograph of a right angle cross section view of 24 gauge wire inserted in a termination system. The insulation does not appear in the picture. 
     FIG. 11 is an enlarged photomicrograph of a longitudinal cross section, as shown in FIG. 9. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the drawings, in FIG. 1, the termination system is illustrated without reference to any specific application. In FIGS. 7 and 8 the termination system is schematically illustrated as employed as a splicing means for parallel wires and butting wires, respectively. 
     In FIGS. 2 and 3, the system is illustrated as employed as a termination or wire receiving end of a ribbon type contact element 1. FIG. 3 shows how such a contact element may be used in a high density connector system. 
     By this, it should be evident that the invention has wide utility as a terminating system. However, it is emphasized that the greatest advantages are seen when it is used in a miniaturized application where there is required strength, reliability and manufacturability of very small parts made from otherwise relatively weak materials. 
     Referring to FIG. 1, the termination system illustrated has spaced apart generally parallel sides 2 and a bottom 3 forming an elongated wire receiving channel. Pairs of oppositely facing formed-in jaws 4, 4a are formed-in and integral with each of the sides 2. Two pairs of jaws 4, 4a are shown although one pair or more than two pair could be used. By formed-in, it is meant that the metal of the sides is not cut or otherwise interrupted but is, rather, stretched and/or bent and thereby formed into the continuous curved jaws attached to and integral with the sides 2 at each of its lateral extremities. Thus, the jaws 4, 4a present laterally smoothly curved opposing formations having working faces 5, 5a as shown. 
     In order to best explain the lead-in portion 6, 6a of the terminating system, it is helpful to describe some of the steps in making the system. Basically, it is punched, bent and formed from flat sheets. The lead-in 6, 6a is preferably made by punching a V-shaped notch prior to the forming-in of the jaws (and also before bending up the sides) so that after the jaw is formed, the upper edge 7, 7a of the sides extends angularly downward and inward following the plan of the jaw and as best seen in FIGS. 4, 5 and 6. 
     As shown in FIG. 1, slots 8, 8a are formed in the sides 2 in order to free the lower end of the jaws 4, 4a from the sides. As shown in FIGS. 2, 4 and 5 the slot 8, 8a is a piece of the sheet removed at the bend in the channel between the sides 2, 2a and the bottom 3. With the particular embodiment shown here involving a 90° bend and the bottom 3 being very close to the lower end of the jaws, it is very important to free the lower end of the jaws in order to prevent excessive stretching and random formations of the metal. It may be possible, where more free area is available below the jaw, to omit freeing it, although the freeing is still preferred. 
     As can be seen in the photomicrograph of FIGS. 9 and 11 a substantially smooth continuous distortion of the wire is achieved by this system. Referring to FIG. 5, in order to facilitate such a smooth distortion, the lead-in portion has a transition area 9, 9a to change the angle of the edge to present an angled embossing surface to the wire at the upper edge of the jaw in the working area. It may be formed by a coining operation in the formation of the piece where the edge 7, 7a has its angle changed to follow the shape of the lead-in portion 6, 6a as seen in FIG. 5. This transition area 9, 9a is so designated because it is an area of transition from contact, by a wire being inserted, with the upper edge 7, 7a of the jaw to contact with its working face 5, 5a. Thus, the transition area is formed at the innermost area of the jaw defined by the working face 5, 5a of the jaw. The transition area, presenting an angled embossing surface, tends to cause compressive forces on the wire, aiding in the desirable relatively smooth distortion of the wire when it is eventually fully inserted. Without the transition area, a sharp corner at the upper edge of the jaw over the working faces 5, 5a would be presented to a wire which would tend to shear and sharply shape the wire. 
     The lead-in area 6, 6a including the coined transition portion is preferably at about a 45° angle to horizontal. It may be preferable to make the transition area present an even steeper angle to a wire between the upper edge and the working face of the jaw in order to enhance its transition effect. Other methods may be employed to form the transition area 9, 9a such as by forming the V notch of the lead-in area with an angled edge instead of a square cut edge. It is intended to define the transition area therefor as effecting a smooth continuation of the upper edge and into transition to the working face of the jaw. 
     It is for many applications important to provide some strain relief in combination with this termination system. A strain relief means suitable with the present termination system shown at 13 in FIG. 2 and 3. This strain relief is fully described in co-pending application, Ser. No. 443,730, now U.S. Pat. No. 3,902,154. 
     In the preferred commercial embodiment, such as illustrated in FIGS. 2 and 3 for a ribbon type contact element, the contact element may be formed from 0.006 inch cadmium bronze sheet. The contact will usually be gold plated either in its entirety or selectively on the mating portion, or both fully and selectively plated. In a primary use in telephone systems employing 24 gauge and/or 26 gauge solid insulated wire, the space between the jaws can be about 0.007 inch. 
     The tab 14 is provided to hold the contact element in place in the insulating connector body. A similar tab 15 is formed up in the butt splicing embodiment of FIG. 8 to hold the part in place in an associated body member. 
     FIG. 3 shows part of a 50 contact polarized ribbon type connector. This is a type of high density connector commonly used in rack-and-panel and cable-to-cable applications in telephone systems. In an exemplary case, the contact elements are on 0.085 inch centers. The contact elements 1 are mounted in two parallel rows in the insulator 10 between the ribs 11. The contact elements 1 reside in channels defined, at the wire termination end, by ribs 11. The ribs 11 provide support for the sides 2, 2a of the termination systems, serving to rigidly back the sides 2 in order to prevent their spreading apart when a wire is inserted. 
     To use the connector, the completed connector is held firmly and wires inserted either singly or multiply, one into each contact element. 
     An exact procedure and means for inserting the wire is more fully described in co-pending application, Ser. No. 502,085, which has been abandoned in favor of pending divisional application Ser. No. 585,308, now U.S. Pat. No. 4,001,931 and pending continuation application Ser. No. 586,453, now U.S. Pat. No. 3,965,558. For the present description, it is sufficient to understand that the wire 12 is positioned as shown in FIG. 6 over the channel and, with a tool designed to do so, evenly pushed down into the channel. 
     As can be appreciated, the smoothly angled configuration of the upper edge 7, 7a of the jaw will contact the insulation on the wire and, as the wire is pushed downward, will tear through the insulation. As the wire progresses downward and the metal of the wire itself contacts the jaws commencing past the transition area 9, 9a and to the working faces 5, 5a, it will be deformed to eventually mate intimately with the jaw working faces 5, 5a. The primary distortion of the wire is an inward compression or embossing with some upward displacement of metal. The photomicrographs of FIGS. 9 and 10 show the configuration of the jaw and the wire as it resides in place. An intimate, largely compressive contact of the wire with the jaws is evident. In the horizontal direction, as shown in FIG. 9, the metal is distorted inward in a smoothly curved pattern preserving the axially fibrous structure of the wire and avoiding stress concentration points. In the vertical direction, while some upward displacement is seen, nevertheless, the embossing nature of the distortion can be seen. 
     In an intensive series of tests involving a variety of hostile environments, thermal cycling, thermal shock, thermal aging and physical strength and durability the termination system performed well according to criteria relevant to telecommunications applications. 
     While the above description relates to certain embodiments now known to and preferred by the inventors, it is possible for persons skilled in the art to make certain additions, changes and modifications. It is intended by the appended claims to cover such additions, changes and modifications as fall within the scope and spirit of the invention.