ELECTRONIC SWITCH ACTUATED BY PROXIMITY OF THE HUMAN BODY

• US 3,764,819 A
• Filed: 03/15/1972
• Issued: 10/09/1973
• Est. Priority Date: 03/16/1971
• Status: Expired due to Term

• Current Assignee: Harro Muller
• Original Assignee: Harro Muller
• Inventors: Muller, Harro
• Primary Examiner(s): Schaefer, Robert K.
• Assistant Examiner(s): Ginsburg, M.
• Application Number:
  US05/234,952
• Time in Patent Office: 573 Days
• Field of Search: 307/116 200/DIG.1 340/258C
• US Class Current: 307/116
• CPC Class Codes: H03K 17/945 Proximity switches H03K17/96 takes precedence
• CPC Class Codes: H03K 17/955 using a capacitive detector

Abstract

An improved contact-less electronic switch, adapted to be actuated by the approach of a human hand, with a capacitive probe insulated against the chassis and installed in the zone of approach, and connected to a capacitance detecting circuit which delivers a switching signal when the capacitance is increased by the approach of a hand, wherein the improvement comprises that the switch remains unaffected by the approach of all other substances, such as metals or insulating materials.

Claims

1. In an electronic switching arrangement actuated in a contactless manner by the approach of a portion of a human body, having a capacitive probe which is insulated from a support chassis, and connected to a capacitance measuring circuit which delivers a signal when a certain increase of the capacitance is caused by a predetermined approach of the portion of the human body into the electric field of the capacitive probe, the improvement which comprises an inductive probe disposed in the proximity of said capacitive probe, means whereby said inductive probe forms a portion of an oscillator circuit and having a magnetic field, the magnetic field of said inductive probe permeated the electric field of said capacitive probe, said inductive probe being connected to an inductive measuring circuit, said inductive measuring circuit being adjusted to deliver a switching signal indicative of the presence of a metal object at a predetermined distance from said support chasses, and chassis, capacitance measuring circuit being adjusted to deliver a switching signal only when the metal object is closer to said support chassis than the predetermined distance, means connected to receive switching signals from said inductive and capacitance measuring circuits and delivering an output signal only if the said capacitance measuring circuit supplies a switching signal and the measuring circuit associated with the inductive probe does not supply such a switching signal.

2. An arrangement as defined in claim 1, wherein are provided to adjust the sensitivity of the said capacitance measuring circuit to deliver a signal on the approach of an electrically conducting body, but not by the approach of a body of insulating material.

3. An arrangement as defined in claim 1, wherein said capacitive probe is mounted on said support chassis and said chassis is grounded and forms the counter-electrode of said capacitive probe.

4. An arrangement as defined in claim 1, wherein said inductive probe consists of a coil mounted on the legs of a U-shaped high frequency iron core and said capacitive probe consists of a metal plate disposed to lie between the two legs of said iron core but in spaced relationship thereto.

5. An arrangement as defined in claim 1, wherein said capacitive proBe and said inductive probe are supplied by the same oscillator and means whereby the damping of the oscillator is used as a measure of the degree of approach of a metal part.

6. An arrangement as defined in claim 1, wherein means are provided whereby the initial capacitance of the said capacitive probe is neutralized.

7. In an electronic switching arrangement comprising a switch actuated in a contact-less manner by the approach of a portion of a human body, comprising a coil divided into two partial windings, means including one of said windings connected to a capacitor to form an oscillator circuit of an oscillator, the other of said windings being connected to a capacitive probe and applying an electrical potential thereto;

said capacitive probe being connected to a capacitance voltage converter circuit;

said converter circuit being connected to a trigger;

said trigger having a response threshold which is above the level of the signal supplied by said converter circuit in the absence of an object in a zone proximate to the switch and means whereby said response threshold of said trigger is exceeded when a portion of a human body is in the zone proximate to the switch.

8. An arrangement as defined in claim 7, wherein said capacitance converter circuit comprises a diode pump.

9. An arrangement as defined in claim 7, wherein means are provided whereby the response threshold of said trigger is adjustable.

10. An arrangement as defined in claim 7, wherein means are provided whereby the regenerative feedback factor of said oscillator is adjustable.

11. In a electronic switching arrangement including a switch actuated in a contact-less manner by the approach of a portion of a human body comprising a high frequency iron pot core, a coil disposed in said core, said coil being tapped to provide two partial windings, one of said partial windings being larger than the other of said partial windings, said one of said partial windings being arranged in space non-symmetrically with respect to said other of said partial windings;

means including said coil connected to a capacitor to form an oscillator circuit of an oscillator;

said coil being connected to a capacitance converter circuit;

said converter circuit being connected to a trigger;

said trigger having a response threshold which is above the level of the signal supplied by said converter circuit in the absence of an object in a zone proximate to the switch and means whereby said response threshold of said trigger is exceeded when a portion of a human body is in the zone proximate to the switch.

12. An arrangement as defined in claim 11, wherein said other of said partial windings is disposed outside of said one of said partial windings.

13. An arrangement as defined in claim 11, wherein said other of said partial windings is disposed inside said one of said partial windings.