Capacitance switch

• US 4,373,122 A
• Filed: 10/16/1981
• 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:
  US06/311,915
• Time in Patent Office: 480 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 switch in which a capacitance spacing element is bent around an end of a spacer centrally relieved for strain relief.

Claims

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

a substrate sheet,

a flexible sheet extending over said substrate sheet,

a conductive contact carried by one of said substrate sheet and said flexible sheet,

a capacitance element located between said substrate sheet and said flexible sheet and aligned with said contact,

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 said contact so as to provide an insulating zone between said contact and said first conductive portion,

said contact, insulating zone, and first conductive portion being adapted to form a second capacitor electrically in series with said first capacitor,

said flexible sheet, spacing means, contact, and first conductive portion all being adapted and located to cause the spacing between said contact and first conductive portion to vary when said flexible sheet is flexed during switch activation and to thereby cause the net capacitance of said first and second capacitors to change to an extent detachable by external circuitry,

said spacing means including a spacer layer occupying the space between said flexible layer and said capacitance element, and

said capacitance spacing element being bent around said spacer in a fold portion at an end thereof.

2. The switch of claim 1 in which said spacer comprises adhesive material.

3. The switch of claim 2 in which said spacer is centrally semi-circularly relieved adjacent said fold portion.

4. The switch of claim 3 in which the transverse edges of the end of said spacer including said relieved portion of said spacer engages said fold portion.

5. The switch of claim 2 in which said spacer is centrally relieved adjacent said fold portion.