Browse Prior Art Database

Capacitive Key Switch Having Intimate Contacting Pivot Plate

IP.com Disclosure Number: IPCOM000048820D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Bellamy, RL: AUTHOR [+3]

Abstract

Capacitive key switch 11 includes a pivot plate 13 which is movable upon depression of keybutton 14 to contact circuit board 15. Pivot plate 13 moves under a force provided by spring 17, which is attached thereto and to keybutton 14. Spring 17 buckles upon keybutton depression causing pivot plate 13 to rock downward. This spring action is described in U.S. Patent 4,118,611.

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Capacitive Key Switch Having Intimate Contacting Pivot Plate

Capacitive key switch 11 includes a pivot plate 13 which is movable upon depression of keybutton 14 to contact circuit board 15. Pivot plate 13 moves under a force provided by spring 17, which is attached thereto and to keybutton
14. Spring 17 buckles upon keybutton depression causing pivot plate 13 to rock downward. This spring action is described in U.S. Patent 4,118,611.

In order to insure intimate contact between pivot plate 13 and circuit board 15, a single pivot point 19 on plate 13 is utilized. The pivot point 19 is located under the connection of spring 17 and contacts circuit board 15. Since both circuit board 15 and plate 13 have bottom surfaces which are curved on a large radius, surface contact is established by three points, one being the pivot point and the other two being on the radiused surfaces. This allows better conformity of plate 13 to the surface of card 15. Since the buckling spring 17 can buckle to the left or right of the center line of keybutton 14, a V-notch or radius 21 is cut in the keybutton to receive the spring 17, preventing it from lateral movement which would put an unbalanced lateral force on the plate 13. In this manner, intimate contact between plate 13 and 15 is maintained in the keybutton down position, thereby providing uniform capacitive coupling there between for each keybutton actuation.

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