AN ELECTRICAL KEYBOARD

1,274,162. Retractive switches. INTERNATIONAL BUSINESS MACHINES CORP. 19 April, 1971 [16 Feb., 1970], No. 20970/71. Heading H1N. [Also in Division B6F] An electric contact making keyboard comprises a base 10 with an array of first electrical contacts 12, 12A spaced thereon. An apertured insulating layer 14 overlays the base, and a diaphragm 18 overlays the insulating layer. Second electrical contacts 20, 20A are spaced on the underside of the diaphragm in registration with first contacts 12, 12A, via the apertures in layer 14. An apertured guide plate 24 is provided above and spaced from the diaphragm 18. Each aperture has a plunger 22 with a wider and larger upper portion 22A and a second narrower and lower portion 22B which is in registration with the first and second contacts. At least the lower portion of plunger 22 comprises an elastomeric material. An elastomeric nomenclature sheet on the upper surface of the guide plate 24, seals the mechanism against dust and dirt. An apertured metal plate 30 holds the nomenclature sheet in position and prevents the accidental triggering of the keyboard.