Membrane switch with means for preventing contamination of the interior thereof

DETAILED DESCRIPTION The present invention relates to membrane switches using silver conductors and in particular to a means for impeding migration of the silver between conductors.
One purpose is a membrane switch in which silver may be silk screened, printed or painted, in conductive paths, on spaced surfaces of the switch, and wherein the switch is essentially sealed from outside contamination except for a vent passage of substantial length, suitable for equalizing internal and external pressures, which vent passage also interconnects the chambers within the switch where the switching action takes place.
Another purpose is a switch of the type described in which migration of silver between conductors is substantially impeded by retarding moisture film formation upon the surface of the switch assembly.
Another purpose is a switch of the type described in which pressure equalization between interior and exterior portions of the switch is provided with a minimum of air exchange, thereby retarding the admission of contamination into the interior of the switch.
Another purpose is a membrane switch in which the silver conductors are substantially buried in a resin, used for adhesive purposes, to impede silver migration.
Another purpose is a membrane switch in which the switch is substantially or totally sealed, thereby preventing contamination moisture from reaching the interior of the switch, but at the same time providing means for internal and external pressure equalization.
Other purposes will appear in the ensuing specification, drawings and claims.