TOUCH SENSITIVE ELECTRONIC SWITCH

• US 3,737,670 A
• Filed: 07/09/1971
• Issued: 06/05/1973
• Est. Priority Date: 07/09/1971
• Status: Expired due to Term

• Current Assignee: Willis A. Larson
• Original Assignee: Willis A. Larson
• Inventors: Larson, Willis A.
• Primary Examiner(s): Schaefer, Robert K.
• Assistant Examiner(s): Smith, William J.
• Application Number:
  US05/161,948
• Time in Patent Office: 697 Days
• Field of Search: 200/DIG.2,159B,DIG.1,159R 307/112,116 317/123P,DIG.1
• US Class Current: 307/116
• CPC Class Codes: H03K 17/9645 Resistive touch switches
• CPC Class Codes: H03K 17/965 Switches controlled by moving an element forming part of the switch
• CPC Class Codes: Y10S 200/02 Body attached switches

Abstract

In order to provide sensitive, touch responsive electronic switching, a pair of electrodes disposed in a unique configuration are coupled to a high gain amplifier such that relatively high resistance bridging across the electrodes will result in a positive switching condition at the output terminals of the high gain amplifier. In a first preferred embodiment of the invention, the pair of electrodes comprises a first centrally disposed electrode encompassed by a second, circular electrode disposed concentrically to, but longitudinally offset from the first electrode. Thus, the pair of electrodes substantially conform to the contour of an operator'"'"''"'"'s finger which sets up a relatively high resistance path between the two electrodes when both are touched. The finite galvanic skin resistance is sensed and differentiated from the substantially infinite resistance normally existing between the two electrodes by high current gain amplification to provide a sharp change in current flow through a load connected to the output terminals of the high gain amplifier. The sharply differentiated state of the output terminals of the high gain amplifier may be utilized to control switching functions in any manner desired in subsequent stages. For use in environments in which the atmosphere may be contaminated or which may require the use of gloves by the switch operators, a membrane which has, on its underneath side, a conductive coating, is disposed over the pair of electrodes to perform the bridging function when the membrane is pressed against the electrodes.

Claims

1. Electrical Switch Apparatus operable by the lateral bridging of the switch electrodes by the skin resistance of an operator, comprising in combination:

insulating media having a top surface;

first electrode means immovably arranged with the insulating media with the top surface of the first electrode exposed to the finger of an operator upon the top surface of the insulating media;

second electrode means immovably arranged with the insulating media laterally around and about the first electrode with the top surface of the second electrode exposed to the finger of an operator upon the top surface of the insulating media laterally from the first electrode and with the top surface of the second electrode arranged above the level of the top surface of the first electrode in a manner that the finger of an operator touches the second electrode before contact is made between the finger and the first electrode to thereby allow good contact of the operator'"'"''"'"'s finger with the second electrode before contact is made with the first electrode and thereby allow the harmless groundiNg of the usual alternating voltage induced from an external source into an operator'"'"''"'"'s body and allow a direct current path to be set up laterally between the first electrode and the second electrode as soon as the finger of the operator touches the first electrode.

2. The electrical switch of claim 1 wherein the first electrode comprises a disc.

3. The electrical switch of claim 2 wherein the second electrode comprises an annulus surrounding the disc of the first electrode.

4. The electrical switch apparatus of claim 3, wherein the insulating media comprises a housing.

5. The electrical switch apparatus of claim 4, wherein the housing includes:

space for a direct current amplifier; and

coupling means for connecting the first and second electrodes to the input terminals of any direct current amplifier within the housing space.

6. The electrical switch apparatus of claim 1 comprising means for coupling the first and second electrodes to input terminals of an amplifier.

7. The electronic switch apparatus of claim 1 wherein the height difference between the level of the top surface of the first electrode and the level of the top surface of the second electrode is sufficient to establish a desired touch threshold for the switch.

8. Electronic switch apparatus operable by the bridging of the switch electrodes by the skin resistance of an operator, comprising in combination:

insulating media having a top surface;

first electrode means laterally immovably arranged with the insulating media with the top surface of the first electrode exposed to the finger of an operator upon the top surface of the insulating media;

second electrode means laterally immovably arranged with the insulating media and the first electrode laterally around and about, spaced, and insulated from the first electrode with the top surface of the second electrode exposed to the finger of an operator upon the top surface of the insulating media laterally from the first electrode and with the top surface of the second electrode arranged above the level of the top surface of the first electrode in a manner that the finger of an operator touches the second electrode before contact is made between the finger and the first electrode to thereby allow good contact of the operator'"'"''"'"'s finger with the second electrode before contact is made with the first electrode and thereby allow the harmless discharge of voltage in an operator'"'"''"'"'s body and allow a direct current path to be set up laterally between the first electrode and the second electrode as soon as the finger of the operator touches the first electrode;

first means for providing an electrical connection to the first electrode; and

second means for providing an electrical connection to the second electrode.

9. The electronic switch apparatus of claim 8 wherein the first connection means comprises means for providing an electrical connection between the first electrode and the input of a direct current amplifier.

10. The electronic switch apparatus of claim 9 wherein the second connection means comprises means for providing an electrical connection between the second electrode and a means for supplying DC voltage to the direct current amplifier.

11. The electronic switch apparatus of claim 10 wherein the height difference between the level of the top surface of the first electrode and the level of the top surface of the second electrode is sufficient to establish a desired touch threshold for the switch.

12. The electronic switch apparatus of claim 8 wherein the second connection means comprises means for providing an electrical connection between the second electrode and a means for supplying DC voltage to the direct current amplifier.

13. The electronic switch apparatus of claim 9 wherein the height difference between the level of the top surface of the first electrode and the level of the top surface of the second electrode is sufficient to establish a desired touch threshold for the switch.

14. The electronic switCh apparatus of claim 8 wherein the height difference between the level of the top surface of the first electrode and the level of the top surface of the second electrode is sufficient to establish a desired touch threshold for the switch.

15. The electrical switch apparatus of claim 1 wherein the top surface of the first electrode extends from the top surface of insulating media and wherein the top surface of the second electrode extends from the top surface of the insulating media.

16. The electronic switch apparatus of claim 8, wherein the top surface of the first electrode extends from the top surface of insulating media and wherein the top surface of the second electrode extends from the top surface of the insulating media.