Capacitance switch

• US 4,373,124 A
• Filed: 05/11/1982
• Issued: 02/08/1983
• Est. Priority Date: 01/26/1981
• Status: Expired due to Fees

• Current Assignee: W H Brady Company
• Original Assignee: W H Brady Company
• Inventors: Frame, Norman J.
• Primary Examiner(s): Little, Willis
• Application Number:
  US06/377,264
• Time in Patent Office: 273 Days
• Field of Search: 200/159 B, 200/5 A, 200/292, 200/284, 340/365 C
• US Class Current: 200/600
• CPC Class Codes: H01H 13/702 with contacts carried by or formed from layers in a multilayer structure, e.g. membrane switches
• CPC Class Codes: H01H 13/703 characterised by spacers between contact carrying layers
• CPC Class Codes: H01H 13/785 characterised by the material of the contacts, e.g. conductive polymers
• CPC Class Codes: H01H 2201/026 non precious
• CPC Class Codes: H01H 2207/002 Conductive rubber; Zebra
• CPC Class Codes: H01H 2207/004 Printed circuit tail
• CPC Class Codes: H01H 2207/01 from bottom to top layer
• CPC Class Codes: H01H 2209/038 transparent
• CPC Class Codes: H01H 2209/06 transparent
• CPC Class Codes: H01H 2209/082 transparent
• CPC Class Codes: H01H 2211/004 Adhesive
• CPC Class Codes: H01H 2211/006 Individual areas
• CPC Class Codes: H01H 2227/004 Membrane
• CPC Class Codes: H01H 2227/006 Spacer
• CPC Class Codes: H01H 2227/008 Substrate
• CPC Class Codes: H01H 2227/01 Adhesive
• CPC Class Codes: H01H 2227/018 Printed contacts; Metal foil
• CPC Class Codes: H01H 2229/012 Vacuum deposition
• CPC Class Codes: H01H 2229/028 Adhesive
• CPC Class Codes: H01H 2231/004 CRT
• CPC Class Codes: H01H 2239/006 : Containing a capacitive switch or usable as such
• CPC Class Codes: H03K 17/98 : having a plurality of control members, e.g. keyboard

Abstract

A capacitance-type switch in which an integral capacitance spacer layer element extends over and is severally movable toward and away from separate contact elements of separate switches.

Claims

1. A capacitance switch wherein switch activation produces a change in capacitance detectable by external circuitry, comprising:

a substrate,

a movable layer extending over said substrate,

a plurality of conductive contacts carried by one of said substrate and said movable layer, said contacts defining a plurality of switch zones,

a capacitance element located between said substrate and said movable layer and extending through said plurality of switch zones,

said capacitance element comprising

an inner insulating layer and

first and second outer conductive portions on opposite surfaces of said inner insulating layer,

said capacitance element forming a first capacitor,

spacing means for spacing said capacitance element from each said contact so as to provide insulating zones between each said contact and said first conductive portion,

said contacts, insulating zones, and first conductive portion being adapted to form a plurality of second capacitors each electrically in series with said first capacitor,

said movable layer, spacing means, contacts, and first conductive portion all being adapted and located to cause the spacing between a selected said contact and first conductive portion to vary when said movable layer is moved during switch activation and to thereby cause the net capacitance of said first capacitor and the selected second capacitor to change to an extent detectable by external circuitry, and

said spacing means including one or more spacing elements occupying the space between said movable layer and said capacitance element.

2. The capacitance switch of claim 1 wherein said switch is a membrane switch and said movable layer is a flexible sheet.

3. The capacitance switch of claim 2 wherein said membrane switch has a plurality of capacitance elements each extending through a plurality of switch zones.