KEYBOARD ACTUATING MECHANISM FOR DIAPHRAGM ELECTRIC SWITCH CONTACT ARRAY

1298290 Retractive switches INTERNATIONAL BUSINESS MACHINES CORP 21 Dec 1970 [23 Jan 1970] 60508/70 Heading H1N A switch comprises a fixed contact 27; a movable contact 24 mounted on a diaphragm 23 and an actuating member 20 located on the other side of the diaphragm to the contacts and having a projection 21 facing the diaphragm whereby on depression of the actuating member which is of elastic material the projection urges the contacts into engagement. The contacts 24, 27 are gold-plated copper laid on polyester diaphragms 23, 30; a separator sheet 25 having holes aligned with the contacts is placed between them. The actuating member is of solid neoprene and besides projections 21 has further, shorter projections 22 which limit travel and prevent damage to the contacts or diaphragm 23. Above the actuating member rests a thick block 16 of soft closed-cellular neoprene and above this, resting on a rigid aluminium frame 15 is an actuator sheet 10, 14 of polyurethane elastomer having raised portions 11 marked with indicia (Fig. 2, not shown). The sheet 10 can be readily removed and replaced by another bearing alternative indicia. The block 16 gives the switches a suitable "feel" and allows pretravel and overtravel. The stop projections 22 may be arranged in a circle or a square depending upon the shape of the raised operating portions 11; they may be discrete projections or a continuous ring surrounding the projection 21. More than one projection 21, each operating a pair of contacts, may be associated with a group of projections 22 below a single portion 11.