Multiple unit self-holding pushbutton switch - has preloaded contact spring eliminating need for mechanical friction to maintain contact pressure

摘要

A multi-pole switch consists of an insulated housing (1) containing a strip of preloaded steel spring (23) and a number of push-buttons (7, 9, 11, 13). The spring is anchored between each button by clamps (45-47-51, 53), the clamps preloading the spring by bending it across the width into a convex shape. The spring has a length in excess to the housing length, causing one part of the spring to deflect downwards (11). Placed under the spring is a layer of foam rubber or plastic (27) which has an underlay of flexible material (29) coated on the underside with electrical contact material. The bottom of the housing is also fitted with contact material, and covered by an insulaing matrix (31) which has openings at the switch positions (33-35, 37-39). Depression of a button deflects the flexible layer due to pressure exerted by the spring on the foam rubber interface, thus forcing the two contact materials together. Switching speed is relatively independent from operator speed.