Abstract:
A connector is disclosed that includes spring contacts (200) for making a solderless connection to other electrical conductors (310). Each spring contact (200) has a loop contact portion (230) that is supported so that its end regions (232 and 234) are restrained in a direction generally normal to the site of engagement of its arcuate contact surface (236) with the other electrical conductor (310). As a result, the main region (235) of the loop contact portion (230) is essentially rotated rather than compressed when pressed into engagement with the other electrical conductor (310). The desired contact force necessary for a good solderless electric connection is thereby provided.

Description:
FIELD OF THE INVENTION 
     This invention relates to contacts for electrical connectors and within that field to contacts for making a solderless connection to other electrical conductors such as conductive paths on a printed circuit board. 
     BACKGROUND OF THE INVENTION 
     The typical manner in which an electrical connection is established between a discrete conductor and a conductive path on a printed circuit board is by having the discrete conductor pass through a hole that is circumscribed by the conductive path. Solder is then applied to this juncture to envelop both the conductor and the surrounding conductive path and thereby electrically connect one to the other. 
     An example of this type of connection where the discrete conductor is a contact of a connector is disclosed in U.S. Pat. No. 4,186,988 issued to R. J. Kohler on Feb. 5, 1980. As disclosed in that patent, the connector, which is a jack of the type used in telephones, is mounted on an associated printed circuit board by a multiple of cyndrical locking posts. The posts extend downwardly from a surface of the connector that overlies the printed circuit board, and the posts are accommodated by holes in the printed circuit board, 
     Each post includes an upper portion having a diameter that is slightly less than the diameter of the hole that accommodates it and having a height slightly greater than the thickness of the printed circuit board. In addition, each post includes a lower portion having a diameter somewhat larger than the hole in the printed circuit board. Finally, each post is split longitidinally whereby the sides of the post can be deflected inwardly to permit the lower portion to pass through the accommodating hole and then return to an undeflected state when the upper portion is positioned within the hole. The lower portion of each post thereby serves to secure the connector to the printed circuit board. 
     Because of tolerance variations in the thickness of printed circuit boards, the height of the upper portion of each locking post has to be slightly greater than the maximum allowable thickness. There is, therefore, some play between the connector and a printed circuit board of lesser thickness. This play is essentially removed when the spring contacts of the connector are soldered to the printed circuit board. Thus, as is typical, the soldered junctions serve to electrically connect and also physically secure the connector to the printed circuit boards. 
     As a result of the stresses created in performing the securing function and vagaries in the soldering operation, soldered junctions, while generally providing good conductivity, sometimes fail under shock. More significantly, such junctions can sometimes fail in a manner that creates an intermittent open that is difficult to detect. Also of significance in the very competitive world of electronics is that soldering requires an additional processing step that adds to the cost of the product. 
     For these reasons it is desirable to be able to make a solderless connection to conductive paths on a printed circuit board. A solderless connection, however, relies on intimate engagement in order to obtain the desired conductivity across the interface between the two elements. This intimate engagement is made more difficult by the above described tolerance variations in the thickness of printed circuit boards. Each contact of the component being electrically connected to the printed circuit board must not be stressed beyond its yield point when the associated component is mounted on a printed circuit board of maximum thickness. Yet, each contact must provide the necessary contact force when the associated component is mounted on a printed circuit board of minimum thickness. 
     SUMMARY OF THE INVENTION 
     A contact in accordance with the present invention that has this capability comprises a wire spring contact of a connector, such as a jack of the type used in telephones. The jack includes a dielectric housing having a generally rectangular shaped cavity to accommodate a mating plug. The housing further has a planar base portion that serves at the bottom of the cavity and extends laterally both beyond the sides and rear end of the cavity. The bottom surface of the base portion is adapted to overlie the printed circuit board to which each spring contact is to be connected. 
     Each spring contact comprises a linear contact portion at one end that is joined by an intermediate portion to a loop contact portion at the other end. The linear contact portion extends cantilever fashion within the cavity of the housing and serves to make electrical connection with the corresponding contact of the mating plug. The intermediate portion extends within a groove in the bottom and front end of the base portion and serves to generally locate the linear contact portion. The loop contact portion is located within the base portion to the rear of the cavity and serves to engage and make electrical connection with a conductive path of a printed circuit board. 
     The loop contact portion includes first and second end regions. The first end region joins the loop contact portion with the intermediate portion and is situated within an opening in the base portion, the opening extending between the top and bottom surfaces of the base portion. The second end region of the loop contact portion extends adjacent to the first end region and is situated within a groove in the bottom of the base portion. The remainder or the main region of the loop contact portion lies within a slot within the base portion that extends between the top and bottom surfaces of the base portion. The main region extends below the bottom surface of the base portion and includes an arcuate contct surface, which is adjacent to the second end region, that provides the site of enagement with the conductive path on the associated printed circuit board. 
     As a result of this arrangement, the loop contact portion is restrained in a lateral direction between the sides of the slot in the base portion. In addition, both the first and second end regions of the loop contact portion are restrained in a direction generally perpendicular to the conductive path that the loop portion engages. The main region of the loop contact portion, however, is free to be deflected in this direction, and when pressed into engagement with a conductive path, the main region essentially rotates about the first and second end regions. 
     This arrangement provides a higher contact force than is provided by the typical single cantilever contact spring because loading becomes distributed throughout the circumference of the loop contact portion as deflection takes place. Furthermore, since the main region of the loop contact portion is free to be deflected, it primarily rotates rather than being compressed as is the case, for example, with respect to the contact structure disclosed in U.S. Pat. No. 3,842,189 issued on Oct. 15, 1974 to P. D. Southgate. There is therefore no problem with the contact of this invention being stressed beyond its yield point. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a perspective view of an electrical connector embodying the spring contact of the present invention; 
     FIG. 2 is a rear elevation of the connector; 
     FIG. 3 is a bottom view of the connector; 
     FIG. 4 is a sectional view of the connector taken along line 4--4 of FIG. 3; 
     FIG. 5 is the same as FIG. 4 showing the connector mounted on a printed circuit board; and 
     FIG. 6 is a force-deflection diagram for the spring contact of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1 of the drawing, a connector embodying a spring contact in accordance with the present invention includes a dielectric member 100 for supporting a multiple of spring contacts 200. The support member 100 comprises a housing portion 110 upstanding from a planar base portion 120, the housing portion having a cavity 112 for accommodating a mating connector. 
     The base portion 120 serves as the bottom of the cavity 112 and extends beyond the sides of and to the rear of the housing portion 110. The base portion 120 has a top surface 121 and a bottom surfce 122, and four parallel planar slots 123 and 124 respectively extend between the top and bottom surfaces at the front and the rear of the base portion. 
     Referring also to FIGS. 2 and 3, the slots 123 are located within the cavity 112 of the housing portion 110 while the slots 124 are to the rear of the housing portion. In addition, the slots 123 are more closely spaced than the slots 124, the spacing of the slots 123 corresponding to the spacing between the contacts of a modular telephone plug, typically apart, and the spacing of the slots 124 corresponding to the spacing of the conductive paths on a printed circuit board, typically apart. 
     Four grooves 125 in the bottom surface 122 of the base portion 120 respectively extend from the bottom of the slots 123 and flare laterally outward so that the spacing at the rear end of the grooves corresponds to the spacing of the slots 124. The rear end of each groove 125 communicates with a vertical opening 126 that is opened to the top and bottom of the base portion 120. In addition, four grooves 130 in the bottom surface 122 of the base portion 120 respectively extend between the openings 126 and the slots 124. 
     As seen most clearly in FIG. 4, each spring contact 200 comprises a linear contact portion 210 at one end that is joined by an intermediate portion 220 to a loop contact portion 230 at the other end. The linear contact portion 210 extends cantilever-fashion within the cavity 112 of the housing portion 110 of support member 100 and serves to make electrical connection with a corresponding contact of a mating plug (not shown). The intermediate portion 220 extends within one of the grooves 125 in the bottom surface 122 and the associated slot 123 in the front end of the base portion 120 and serves to generally locate the linear contact portion 210. The loop contact portion 230 is located within the portion of the base portion 120 to the rear of the housing portion 110 and serves to engage and make solderless electrical connection with a conductive path 310 on an associated printed circuit board 300 shown in FIG. 5. 
     The loop contact portion 230 includes a first end region 232 and a second end region 234. The first end region 232 joins the loop contact portion 230 with the intermediate portion 220 and is situated within the opening 126 in the base portion 120 to the rear of the groove 125 within which the intermediate portion is situated. The second end region 234 of the loop contact portion 230 extends adjacent to the first end region 232 and is accommodated by the groove 130 in the bottom surface 122 of the base portion 120 to the rear of the opening 126 within which the first end region 232 is situated. 
     The remainder of the loop contact portion 230 comprises a main region 235 that is partially accommodated within the slot 124 in the base portion 120 that is to the rear of the groove 127 in which the second end region 234 is accommodated. The main region 235 extends below the bottom surface 122 of the base portion 120 and includes an arcuate contact surface 236 which is adjacent to the second end region 234. The contact surface 236 provides the site of engagement with the conductive path 310 on the printed circuit 300 (FIG. 5). 
     As a result of the foregoing arrangement, the loop contact portion 230 is restrained in a lateral direction between the sides of the slot 124 at the base portion 120. In addition, both the first and second end regions 232 and 234 of the loop contact portion 230 are restrained in a direction generally normal to the site of enagement of the arcuate contact surface 236 with the conductive path 310 on the printed circuit board 300. The main region 235 of the loop contact portion 230, however, is free to be deflected in this direction and, as shown in FIG. 5, when presssed into engagement with the conductive path 310, the main region essentially rotates abut the first and second end regions 232 and 234. 
     This deflection occurs when the connector is mechanically mounted to the printed circuit board 300 by means of four cylindrical locking posts 127. The posts 127 extend downwardly from the bottom surface 122 of the base portion 120, and the posts are accommodated by holes (not shown) in the printed circuit board 300. 
     As shown most clearly in FIG. 2, each post 127 includes an upper portion 128 having a diameter that is slightly less than the diameter of the hole that accommodates it and having a height slightly greater than the thickness of the printed circuit board 300. In addition, each post includes a lower portion 129 having a diameter somewhat larger than the hole in the printed circuit board 300. Finally, each post 127 is split longitudinally whereby the sides of the lower portion 129 can be deflected inwardly to permit it to pass through the accommodating hole and then return to an undeflected state when the upper portion 128 is positioned within the hole. The lower portion 129 of each post 127 thereby serves to secure the connector to the printed circuit board 300. 
     Referring now to FIG. 6, the force-deflection diagram shown there depicts the deflection of a single loop contact portion 230 in the process of the connector being secured to the printed circuit board 300. That is, it depicts the deflection of the loop contact portion 230 from its position in FIG. 4 to its position in FIG. 5. As the locking posts 127 are pushed downwardly through the accommodating holes in the printed circuit board 300, the deflection of the loop contact portion 230 is increased. This deflection reaches its maximum when the bottom surface 122 (FIG. 4) engages the upper surface of the printd circuit board 300. 
     Once the connector is in place with the lower portion 129 of each locking post 127 returned to its undeflected condition, the downward insertion force is removed from the connector, and the force exerted by the loop contact portion 230 against the printed circuit board 300 moves the connector upwardly until the upper end of the lower portion 129 of the locking posts 127 engages the underside of the printed circit board 300. This takes up any tolerance variation between the thickness of the printed circuit board 300 and the height of the upper portions of 128 of the locking posts 127. The deflection of the loop contact portion 230 is thereby slightly reduced. But the loop contact portion 230, because of the above-described manner in which the spring contact 200 is supported on the support member 100, retains a spring loading in excess of 1.5 pounds. This force provides the contact force neessary to produce a good solderless electrical connection to the conductive path 310 on the printed circuit board 300.