Keyboard with concave and convex domes

Claim 1

A keyboard comprising a first sheet of flexible and resilient insulator plastic, a first circuit pattern supported on the underside of said sheet, said first circuit pattern having contactors and circuit lines of electrically conductive material, said circuit lines selectively coupled to said contactors, a first plurality of snappable convex domes and at least one concave dome formed in said first sheet, each dome supporting a contactor of said first circuit pattern, an insulator spacer having a plurality of openings in register with said concave and convex domes and of a size to selectively permit the domes to extend into said openings, a second sheet of insulator plastic supporting a second circuit pattern, said second circuit pattern having contacts and circuit lines of electrically conductive material, said circuit lines selectively coupled to said contacts in register with said openings, and means for continuously holding said first sheet, spacer and second sheet together whereby said concave dome extends into said spacer opening in register therewith and said contactor supported thereby is urged against a contact of said second circuit pattern in register therewith, said first circuit pattern contactors supported by said convex domes capable of being snapped into said spacer openings to selectively engage other contacts of said second circuit pattern by depression of said convex domes, said contactors of said first circuit pattern being supported on the interior of said convex domes and on the exterior of said at least one concave dome, and at least the contactor supported by said at least one concave dome being interconnected by a circuit line to a contactor supported by at least one of said convex domes.