Image Number 2 for United States Patent #4375585.
A deformable switch keyboard assembly with a flexible unitary top member, a compressible intermediate switch assembly layer and a bottom member providing mechanical support for the intermediate assembly and mechanical isolation for the switching function.The top member has a plurality of switch site defining regions extending in a first direction and located in a predetermined array to define the keyboard. The intermediate switch assembly has a plurality of switch sites each underlying a different one of the top member projections. The bottom member has first and second sets of projections extending toward the top member, each of the first set of projections underlying a different one of the switch sites and providing a compression contact beneath the intermediate switch assembly when the corresponding top member region is actuated to advance in the first direction. Each of the second set of projections is located intermediate different adjacent ones of the switch sites and is longer than any of the first set of projections in order to provide mechanical isolation between an actuated switch site and the remainder of the switch sites.