Test sockets of the type described herein are used in electrical and/or burn-in (heated) testing of electronic components prior to their ultimate mounting in an electronic device of which they are to become a part.  It is necessary in such a test socket that the contact pins of the component not be damaged by insertion or withdrawal from the test socket, that insertion and withdrawal be accomplished rapidly and without undue forces being exerted on the component or the test socket and that reliable electrical contact be made with every contact pin of the component. 
There is described in U.S. Pat.  No.  3,763,459 a zero or low insertion force socket with which integrated circuits and electronic components in devices such as dual-in-line packages can be easily inserted, tested and evaluated, and thereafter easily withdrawn.  This type of device is known as a high cycle or test socket, as opposed to a connector mounted on a circuit board and into which the package will be inserted to remain for an extended length of time. 
The socket disclosed in the aforementioned patent is comprised of a housing of three stacked members.  The middle member moves back and forth between the upper and lower members that are fastened together.  U-shaped contact elements are positioned in the socket with the two contact arms extending up through aligned openings in the middle and upper members.  The contact arms are in the open position, i.e., spaced apart in the relaxed position.  The openings through which the contact arms extend have a concave surface portion so that upon moving the middle member axially, the contact arms are brought into engagement with the component leads positioned therebetween and are wrapped around them partially by the concave surfaces to effect good electrical contact.  Axial movement of the middle member is produced by a cam attached to a rod which may be the socket, the force required to move the middle member may be excessive.