Various "split-tube" contacts of the above-specified type are known in which the tube structure makes it difficult to control the insertion/extraction force, in particular because of excessive tolerance ranges. It is therefore necessary to sort contacts so as to eliminate those which are out-of-range.
In addition, presently manufactured flexible spring contacts do not provide a sufficient safety margin. This drawback is a direct result of the structure and the method of manufacture used for the flexible springs currently in use. The contact end of a spring is obtained by folding a metal part that was initially rectilinear in the longitudinal direction. When the contact end is subjected to radial resilient forces during insertion/extraction operations, it pivots relative to the fixing portion via a fold that acts as a hinge. As a result, stresses are concentrated and the metal is subjected to considerable stress at the fold, which means that its safety factor is insufficient for certain applications, such as space applications.
Furthermore, in a flexible spring contact organized in that way, only the contact end is displaceable and it alone determines the force bearing against the pin of the male contact with which it is required to co-operate (the bearing force being determined in particular by its length and its slope), thereby determining the insertion/extraction force. The remainder of the spring is not involved in determining said force, and as a result, when considered overall, the spring is too rigid for it to be possible to obtain an insertion/extra ction force that is as small as could be desired for making it easy to operate connectors having a large or a very large number of contacts.