Proximity switch

• US 4,380,007 A
• Filed: 05/27/1981
• Issued: 04/12/1983
• Est. Priority Date: 05/27/1980
• Status: Expired due to Fees

• Current Assignee: Playmont AG
• Original Assignee: Playmont AG
• Inventors: Steinegger, Walther
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US06/267,819
• Time in Patent Office: 685 Days
• Field of Search: 178/19, 178/18, 340/365 C, 340/365 R, 340/365 S, 200/181, 200/DIG. 1, 361/288, 400/479.1
• US Class Current: 341/33
• CPC Class Codes: H03K 17/962 Capacitive touch switches

Abstract

The proximity switch has a capacitive sensor which comprises a metallic support mounted on a printed circuit board and supporting, on a surface parallel to said board but facing away from it, a layer made of electrically conductive foam material. The latter nestles against a cover plate made of glass which provides the dielectric of a capacitive sensor actuatable by the stray field of the mains. When this alternating stray field is concentrated by a part of a human body brought into the vicinity of the sensor, the latter will actuate an electronic switch connected to it.

Claims

1. Proximity switch actuated by an alternating electrical field comprising

a circuit-carrying base plate;

at least one capacitively actuatable sensor protruding from said circuit-carrying base plate;

said sensor including

a metallic support having a surface facing away from said base plate,

a layer of electrically conductive foamed material lining said surface of said metallic support.

2. Switch according to claim 1, characterized by a stiff cover plate made of dielectric material, which touches the free surface of the conductive foamed material.

3. Switch according to claim 2, characterized in that the cover plate is made of glass.

4. Switch according to claim 1, 2, or 3 characterized by

additional ones of said sensors each having said foamed material;

free surfaces of said foamed material on said sensors lying essentially in the same plane and each forming an electrode;

each said electrode electrically connected to a circuit on said circuit-carrying base plate, said circuit being actuatable through the action of an alternating electrical field on the corresponding said electrode.

5. Switch according to claim 4, characterized in that said circuits are printed circuits applied on said base plate.

6. Proximity switch according to claim 5, characterized in that each circuit comprises a CMOS-gate, one input of which is connected to the corresponding electrode and, through a diode, to ground, a further input of said gate being connected directly to ground and its output being connected to ground through a capacitor.