Lexmark International, Inc.

International Business Machines Corporation

Edwin T Coleman, Iii

Peter J Mendel

Kenneth H Mimlitch

David Carl Bishop

Steven A Silverstein

Edward E Pollard

William A Abell, Jr

Charles H Lingle

John M Huellemeier

Philip Michael Cullen

Mary L VanArsdall

Adjustable keyboard for a personal computer

First and second membranes carrying contacts located on opposing faces are separated by a third or spacer membrane having holes therein so that a circuit may be completed between the contacts when a force is applied to the first membrane. The first and second membranes and the peripheries of the holes define substantially enclosed switch regions. The first, second and third membrane layers are mechanically held together, without the use of adhesives, in the regions other than the switch regions. Spacer elements are provided between the spacer membrane and one of the first and second membranes. The spacer elements form air pockets such that air may flow between the switch region and the air pockets as the first membrane is depressed and then released. The arrangement provides two advantages. First, it reduces pressure buildup, such as would occur if the membranes were sealed together, when force is applied to the first layer. Secondly, it reduces pressure variations in the switch region where a vacuum would otherwise be created as the first membrane returns to its undepressed position. The contacts thus open more quickly thereby reducing the possibility of contact bounce. The spacer elements might be either conductive or dielectric. If they are conductive they may be applied during the same screening pass that places conductors and contacts on the first or second layer. If they are non-conductive they may be applied during the same screening pass that places a dielectric on the flextail portion of a membrane.

Screened pattern causing gaps around keyboard membrane spacer hole to

A pivoting rocking actuator has a first bottom surface, which comprises two spaced portions, resting on an upper surface of a membrane contact switch assembly when the actuator is in its rest position. The actuator has one end of a buckling spring, which is initially buckled in a selected direction, acting against its upper surface with the other end of the spring acting against a key, which is slidably mounted on a frame, of a keyboard. When the key is depressed, the spring catastrophically buckles in the selected direction to cause initial pivoting of the actuator about a forward edge of each of the spaced portions. This causes a curved bottom surface of the actuator to rotate about a pivot point on the bottom curved surface to close a contact switch of the membrane contact switch assembly. When the key is released, the spring unbuckles at a slower rate than its compression so that there is an initial further rotation of the actuator along the curved bottom surface in the same direction as rotation occurred to close the contact switch. Then, the actuator returns to its rest position to open the contact switch.

Rocking switch actuator for a low force membrane contact switch

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Versailles, KY, United States of America

Edwin T Coleman, Iii