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Low Force Displacement Capacitor Actuator for Calico Keyboards

IP.com Disclosure Number: IPCOM000083247D
Original Publication Date: 1975-Apr-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Harris, RH: AUTHOR

Abstract

Illustrated is a capacitive-coupling actuator having snap action, tactile feel, and a low force - displacement characteristic. The key button 1 is depressed by the operator's finger pressure to move the key stem and force application member 2 downward. The key stem 2 has formed legs 3 which engage the upturned edges of a dome element 4. This dome element is normally slightly deformed to lie flat against the upper surface of a dielectric coating 5 above two capacitive-coupling conductors 6 and 7, which are mounted on a substrate 8.

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Low Force Displacement Capacitor Actuator for Calico Keyboards

Illustrated is a capacitive-coupling actuator having snap action, tactile feel, and a low force - displacement characteristic. The key button 1 is depressed by the operator's finger pressure to move the key stem and force application member 2 downward. The key stem 2 has formed legs 3 which engage the upturned edges of a dome element 4. This dome element is normally slightly deformed to lie flat against the upper surface of a dielectric coating 5 above two capacitive-coupling conductors 6 and 7, which are mounted on a substrate 8.

When key button 1 is depressed, bending moments are induced in the peripheral portions of the dome member 4 until it snaps or bows overcenter, as shown in dashed lines in the figure. Upon the release of finger pressure, the dome element 4 is self-restoring and acts as a key stem biasing spring, to return the key button 1 to the up position.

A contamination shield 9 of flexible plastic may be included beneath the key button 1 and over the key stem 2 to eliminate the introduction of liquids or dirt particles, to the active area of the device. Key stem and actuator 2 are maintained in position by a framework 10, which holds each key button 1 centered over a pair of capacitive pads 6 and 7, as shown.

This device has a low profile, which is achieved because of the reduced key travel required, since only small vertical deflections are necessary to introduce sufficient bending mome...