Patent Publication Number: US-4480385-A

Title: Tool and method for terminating electrical conductors in contact members

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed generally to solderless electrical connections and, more particularly, to a novel tool and method for terminating an insulated conductor into a portion of an electrical contact premounted in an electrical connector. 
     In recent years, increasing numbers of applications have developed in the communications, data processing and transportation industries requiring electrical connectors which provide reliable solderless interconnections with insulated electrical conductors. This demand has perhaps been greatest in the telecommunications industry where miniaturized, high contact density ribbon connectors are used extensively. Connectors of this general type are disclosed in U.S. Pat. Nos. 3,867,005; 3,902,154; and 3,926,498. Because of the great number of individual conductors terminated in these connectors and because of the close spacing between the individual contacts, reliable solder terminations are difficult to achieve, as well as time consuming and costly to maintain and service. For these reasons, insulation-piercing contacts have been developed for use in ribbon connectors and have met with wide acceptance when used to terminate insulated conductors having solid wire cores. Unfortunately, due to the demanding standards in the industry requiring almost negligible change in contact resistance, the insulation-piercing type ribbon connectors have proven unacceptable when used with stranded wire core conductors. Experience has shown that tensile forces applied to the conductors, as well as the cold flow of the insulation surrounding the core, causes the individual strands of the wire core to move and reposition within the insulation-piercing contacts, causing changes in contact resistance. Thus, solder termination ribbon connectors are still used widely with stranded core insulated conductors. 
     Accordingly, a need exists for a ribbon connector which provides a satisfactory solderless termination to stranded core insulated conductors, and preferably both stranded and solid core conductors can be used with the present invention. In addition, in order that the connector be commercially practicable, the termination can be performed with the electrical contact premounted within the connector. 
     One approach to solving these problems is shown in U.S. Pat. No. 4,159,156 which is assigned to the assignee of the present invention. In that patent, an electrical contact member having a terminal portion is premounted in an electrical connector. The terminal portion is formed by an outwardly open channel which has a pair of contact sidewalls and a pair of spaced conductor engaging elements in the form of opposed detents. The tool and method of that patent comprises shearing portions of the actual conductor engaging detent elements and bending the sheared portions onto the conductor. 
     Another termination tool and method is shown in pending U.S. application Ser. No. 042,465, filed May 25, 1979, which is a continuation of parent application Ser. No. 897,076, filed Apr. 17, 1978 and now abandoned and U.S. Pat. No. 4,264,118 which is a continuation of Ser. No. 897,076, both of which are assigned to the assignee of the present invention. In those pending applications, sidewall portions of the contact terminal portion, other than the conductor engaging detent elements (as in U.S. Pat. No. 4,159,156), are sheared and crimped onto the conductor which previously is inserted into the contact channel. However, in this application, a bifurcated termination tool head is employed to perform a two-step terminating operation whereby the conductor first is inserted into the contact and the sidewalls of the contact thereafter are crimped onto the conductor. The disclosure of these two pending applications is incorporated herein by reference for the general purpose of showing types of connector structures with which the present invention is applicable. 
     SUMMARY OF THE INVENTION 
     The present invention, therefore, is directed to a tool and method for terminating insulated conductors into a portion of an electrical contact which may be premounted in an electrical connector, and simultaneously crimping portions of the contact other than the conductor engaging elements thereof onto the conductor to mechanically retain the conductor in electrical engagement with the contact member. 
     In the exemplary embodiment of the invention, the electrical contact member has a terminal portion which is defined by an open channel formed by a pair of contact sidewalls. Two conductor engaging elements in the form of pairs of inwardly directed detents are formed in the contact sidewalls along the channel defined by the terminal portion. 
     The tool includes an insertion and crimping head or member which has insertion means for engaging and inserting a conductor into the contact channel and make electrical engagement between the conductor and the spaced pairs of conductor engaging elements. Crimping means is provided on the member for engaging and shearing wall portions of the contact sidewalls other than the conductor engaging elements simultaneously with the insertion of the conductor by the insertion means, and forming the sheared wall portions onto the inserted conductor within the channel. 
     The insertion means of the tool head includes spaced, generally planar end portions or faces for engaging and inserting the conductor, and the crimping means of the tool is disposed between the spaced insertion portions for shearing wall portions of the contact sidewalls between the spaced conductor engaging elements simultaneously with the insertion of the conductor. 
     The crimping means of the tool head or member includes a pair of curved surface portions for folding the sheared wall portions onto the conductor to mechanically retain the conductor in engagement with the conductor engaging elements. The curved surface portions intersect each other along a common edge portion whereby the centers of curvature of the curved surface portions are sufficiently close to each other to completely fold the sheared contact wall portions onto the conductor without distorting the original contact configuration and without disturbing the connection between the conductor and the contact conductor engaging elements, thereby eliminating many of the problems with prior termination tools and methods of the character described. 
     Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmented perspective view of the termination tool of the present invention spaced above a contact which is shown, premounted in an electrical connector; 
     FIG. 2 is an exploded perspective view, on an enlarged scale, showing the termination tool similar to the showing in FIG. 1, in combination with a subjacent insulated conductor and the terminal portion of a channel shaped contact member; 
     FIG. 3 is a perspective view of the underside of the termination tool of FIGS. 1 and 2, showing the spaced insertion means and the crimping means therebetween; 
     FIG. 4 is a vertical sectional view through the crimping portion of the termination tool; and 
     FIG. 5 is a perspective view of the insulated conductor and contact terminal portion shown in FIG. 2, with the conductor fully inserted and terminated within the terminal portion. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings in greater detail, and first to FIG. 1, the termination tool of the present invention includes a termination member or head, generally designated 10, which is appropriately mounted on a vertically reciprocating support means in a composite tool as is well known in the art. The tool head 10 is movable toward and away from an electrical connector, generally designated 12, which has an electrical contact, generally designated 14, premounted therein. The movement of the tool head 10 is shown generally by the double headed arrow A. Although the invention has been set forth in the Background and Summary portions as having particular utility in a ribbon connector of the type shown in the aforesaid pending applications assigned to the assignee of the present invention, it is to be understood that the invention is contemplated for use with single conductors in a wide range of applications. The electrical connector 12 referred to herein is contemplated to encompass any type of dielectric connector insert 12a (FIG. 1) having an electrical contact 14 mounted therein. 
     Referring to FIGS. 2 and 5 where the terminal portion of the contact member 14 is best shown, the terminal portion has an elongated outwardly open channel configuration formed by a pair of contact sidewalls 14a which are interrupted along their lengths by conductor engaging elements formed by two pairs of opposing, inwardly directed detents 14b. As can be seen in FIGS. 2 and 5, the two opposing pairs of conductor engaging detents 14b are spaced along the length of the channel shaped terminal portion of the contact 14 so that lengths of the sidewalls 14a are disposed therebetween. The sidewalls 14a of the contact terminal portion are joined by a base or bottom wall 14c. 
     The electrical connector 12 and insert 12a are designed to permit crimping and termination of an insulated conductor 16 within the contact 14 while the contact or contacts are mounted in place in the connector. Since the present invention has a wide range of applications, the details of mounting the contact within the connector are not described herein and the disclosures of the aforementioned U.S. Pat. No. 4,159,156 and pending applications Ser. Nos. 042,465 and 897,076 are incorporated herein by reference. 
     The termination tool member or head 10 of the present invention includes insertion means for engaging and inserting the conductor 16 into the channel shaped terminal portion of the contact 14 and make electrical engagement between the conductor 16 and the conductor engaging elements 14b. The insertion means includes a pair of spaced, generally planar end faces 18 (FIG. 3) having generally &#34;H&#34; shapes. These planar end faces are generally coplanar with each other for uniformly engaging the conductor 16 and inserting the conductor between the conductor engaging elements or detents 14b whereby the detents pierce insulation 16a of the conductor 16 and establish electrical termination with a single core or a stranded core 16b of the conductor. These detents 14b create little disturbance of the stranded conductor 16b and practically negligible change in contact resistance. 
     The termination tool member or head 10 also includes crimping means for engaging and shearing wall portions of the contact sidewalls 14a between the conductor engaging detents 14b simultaneously with the insertion of the conductor 16 by the insertion faces 18. More particularly, as best shown in FIGS. 2 and 3, crimping means, generally designated 20, is formed on the underside of the termination head 10 between the insertion faces 18. The crimping means includes a pair of spaced cutting edges 20a on each side of the head for engaging and shearing sidewall portions of the contact sidewalls 14a between the conductor engaging detents 14b. A pair of curved surface portions 20b are disposed between the cutting edges 20a for folding the sheared wall portions of the contact onto the conductor 16 to mechanically retain the conductor in engagement with the conductor engaging detents 14b. 
     Referring to FIG. 5, the terminal portion of a contact 14 is shown with a conductor 16 fully inserted and terminated therein, and with sidewall portions 22 of the contact sidewalls 14a folded onto the conductor. The cutting edges 20a of the crimping means 20 of the termination tool 10 are effective to shear the contact sidewalls, as at 24 in FIG. 5, to leave the sheared wall portions 22 for forming by the curved surfaces 20b onto the conductor 16. 
     As stated heretofore, it is important that there be negligible change in the contact resistance when connections of the character described herein are made. This includes little disturbance of the stranded conductor 16b of the insulated conductor 16. Detent type conductor engaging elements, such as 14b, have been quite effective in maintaining proper contact resistance and little conductor disturbance. However, many crimping operations heretofore performed drastically change the characteristics of the conductor engagement in the areas between the engaging detents 14b. FIG. 4 shows an end view of the curved surface portions 20b of the crimping head 10. The radii of curvature of the curved surface portions are designated by the designation &#34;Y&#34; and the distance between the centers of curvature 26 of the surface portions is designated by the distance &#34;X&#34;. It can be seen that the distance X between the centers 26 of curvature of the pair of curved surface portions 20b is less than twice the radii of curvature of the surface portion. With this construction, the curved surface portions 20b intersect each other along a common edge portion 28 extending lengthwise of the conductor 16 and contact 14. In practice, it has been found effective to form the crimping portion 20 of the tool such that the distance X between the center 26 of curvature of the pair of curved surface portions 20b verses the radii of curvature of the surface portions is on the order of 5:3. 
     With the construction or configuration of the curved surface portions 20b of the crimping means 20 shown in FIG. 4, the sheared wall portions 22 (FIG. 4) of the contact 14 are &#34;gently&#34; folded onto the conductor 15 without disturbing the critical conductor engagement between the insulation piercing detents 14b of the contact. Furthermore, it can be seen from FIG. 4 that the outer portions 30 of the curved surfaces 20b are flared somewhat out of their radii of curvature toward a more tangential direction. The &#34;bending&#34; or &#34;clamping&#34; action of prior crimping tools of the character described herein is eliminated by the vastly improved crimping tool of the present invention. Not only is the crimping action improved, but the crimping operation of the termination method of the present invention is performed and carried out simultaneously with the insertion of the conductor 16 within the contact 14, again resulting in practically negligible change in contact resistance and little or no disturbance of the strands 16b of the insulated conductor 16. 
     It will be understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.