04839474 is referenced by 38 patents and cites 20 patents.

A low profile switch or keypad has one or more touch buttons of circular or polygonal shape in plan formed integrally with and raised from a surrounding membrane of elastomeric material by a wall of resiliently deformable material of thickness and angle relative to the membrane so that the wall can flex under finger pressure on the or each button without deflecting the surrounding membrane. The membrane and at least the periphery of the button are relatively thick and the wall is relatively thin so that deformation during the keystroke is localized in the wall. The length of the wall is about equal to the keystroke and is relatively small compared to the width of the touch button. The junction between the wall and the membrane is located a distance greater than the keystroke above the lower surfaces of the membrane so that the wall passes overcenter during the keystroke resulting in a change in tactile sensation. The underside of each touch button is preferably formed with a convex contact pad dimensioned in relation to the button diameter and travel and the length of wall so that the contact pad makes surface to surface contact with conductors of an underlying circuit board.

Title
Switches and keyboards
Application Number
783927
Publication Number
4839474
Application Date
December 10, 1987
Publication Date
June 13, 1989
Inventor
Brian D Smith
London
GB
Richard P Hayes Pankhurst
London
GB
Agent
Shoemaker and Mattare
Assignee
Key Innovations
GB
IPC
H01H 13/70
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