Capacitance switch

Claim 1

A membrane capacitance switch wherein switch activation produces a change in capacitance detectable by external circuitry, comprising: a substrate sheet, a flexible sheet extending over said substrate sheet, a conductive contact carried by one of said substrate sheet and said flexible sheet, a capacitance element located between said substrate sheet and said flexible sheet and aligned with said contact, said capacitance element comprising an inner insulating layer and first and second outer conductive portions on opposite surfaces of said inner insulating layer, said capacitance element forming a first capacitor, spacing means for spacing said capacitance element from said contact so as to provide an insulating zone between said contact and said first conductive portion, said contact, insulating zone, and first conductive portion being adapted to form a second capacitor electrically in series with said first capacitor, said flexible sheet, spacing means, contact, and first conductive portion all being adapted and located to cause the spacing between said contact and first conductive portion to vary when said flexible sheet is flexed during switch activation and to thereby cause the net capacitance of said first and second capacitors to change to an extent detachable by external circuitry, said spacing means including a spacer layer occupying the space between said flexible layer and said capacitance element, and said capacitance spacing element being bent around said spacer in a fold portion at an end thereof.