Louvered contact elements comprise elongate electrically conductive strip members having transverse expanses which are bent or twisted with respect to the strip member so as to provide opposed sets of contact fingers extending outwardly of the strip member. In providing a connector, such contact element is assembled with one set of its contact fingers in engagement with one terminal member and this assembly mates with another terminal member which is engaged by the other contact finger set. Known connectors employ louvered contact elements in flat configuration in conjunction with flat terminal members and in cylindrical configuration in which case the terminal members are of plug and socket configuration, as shown, for example, in Crabbs U.S. Pat. No. 2,217,473 and Neidecker U.S. Pat. No. 3,453,587.
Connectors of louvered contact element type have the capability of maximizing current flow for a given voltage drop between a pair of terminal members by virtue of their increased surface contact area over that attainable by direct mutual engagement of such terminal members. The realization of maximized current flow is dependent, in one aspect, on providing secure retention of the louvered contact element in or on its associated supporting terminal member while at the same time maintaining the intended surface engagement therebetween as called for by design specifications.
Various contact retention measures are presently known. In the above-referenced Crabbs patent, a plug and socket connector arrangement (FIG. 7) embodies a louvered contact element which is retained through a self-biasing arrangement, i.e., the louvered contact element strip member is formed into a cylinder and is nested by its own resilience in an axially extending cylindrical recess formed in the socket with the outwardly extending set of the contact element fingers engaging the recess wall. The plug is engaged by the interiorly extending finger set on insertion in the socket. A like self-biasing arrangement is shown in the above-referenced Neidecker patent. This latter patent also provides for assembly of the contact element in encircling relation to the plug (FIGS. 8 and 9) wherein the strip member is provided with crenellated edges which are bent over axially spaced shoulders of the plug, the plug surface between the shoulders being engaged by the interiorly extending finger set. A variation of this last-discussed technique is shown in Niederer U.S. Pat. No. 3,751,619.
The employment of self-bias for contact element retention in socket terminal members becomes less reliable as socket diameters increase and self-biasing retention forces decrease, thereby increasing the likelihood of unintended contact element removal upon plug manipulation.
Commonly-assigned copending application Ser. No. 503,783 of Johnson et al., filed on Sept. 6, 1974 discloses, in one of its aspects, that louvered contact element self-biased retention in socket terminal members is enhanced by providing respectively dissimilar longitudinal extents for the contact element finger sets. With the shorter length finger set extending to the socket recess wall, the contact element is seated more deeply in the socket and is accordingly better retained by self-bias. Such arrangement also provides lessened spring rate for the longer contact finger set engaging the plug thereby reducing manufacturing tolerances for the connector parts.
In addition to the foregoing arrangements wherein louvered contact elements are retained by self-bias in sockets or by having parts thereof interfittable with plugs, the art has looked to embodiments wherein the contact elements may be positively retained either on the plug or socket terminal members by means apart from the contact elements. Thus, in a present commercial practice, cylindrically formed contact elements are seated on plugs and retention rings are snapped onto the sides of the strip member to force the same onto the plug surface. Further, in literature distributed by Multilam Corporation, Los Altos, California and dated July 12, 1973, arrangements are depicted (pages 9 and 10) wherein a pair of cylinders, apparently dimensioned either to snugly encircle a plug or to snugly nest in a socket are arranged to abut a cylindrically formed louvered contact element therebetween. The cylinders each apparently present a surface to the contact element which is inclined with respect thereto to retain the same in place.
The positive contact element retention inherent in such commercial and literature arrangements is believed to suffer certain disadvantages. For example, contact element replacement is more difficult than in the self-biased and crenellated edge embodiments noted heretofore. In the commercial arrangement, snap rings need be removed. In the literature arrangement, an apparent wedge-fitted cylinder need be removed. Further, in the case of each of these arrangements, it is considered difficult to achieve the aforesaid intended design specification surface engagement between the louvered contact element and its supporting terminal member due to inherent variations in retention forces imposed by the retention elements themselves and/or by the person assembling or reassembling the connector. As will be appreciated, variations in retention forces which displace the web sides of the strip member can adversely affect intended contact finger surface engagement.
Further patents which serve as background material for the subject invention in describing connectors subject to the foregoing operational shortcomings include Deal U.S. Pat. Nos. 3,861,595 and 3,861,776, Burke U.S. Pat. No. 1,901,894, Streib U.S. Pat. No. 2,280,728 and German Pat. No. 1,106,390.