Pushbutton capacitive transducer

Abstract

An electro-mechanical transducer for use in keyboards and the like which incorporates a capacitance change utilization concept. The transducer includes a plunger assembly reciprocably disposed in a housing therefor, in operative disposition over capacitance forming areas on an insulated substrate. The plunger assembly includes a key button disposed on one end of a shaft, an intermediate flange on the shaft and a flange at the other end of the shaft. The intermediate flange is positioned adjacent a frusto-conical elastomeric return spring and also serves as a resilient stop for the shaft. A compressible foam or sponge-like material having a thin, flexible metalized dielectric material on its lower portion, is mounted on the lower surface of the other flange. Actuation of the shaft downwardly toward the substrate causes the dielectric material to bridge the capacitance forming areas related thereto to cause a change in capacitance and transfer of energy therebetween. The metalized dielectric material is highly flexible to allow it to readily conform to irregularities in the capacitance forming area.

Dependencies are inferred from the claim text.