Proximity detector between a metallic mass and an element to which is applied an electric voltage

• US 4,845,476 A
• Filed: 12/14/1987
• Issued: 07/04/1989
• Est. Priority Date: 12/17/1986
• Status: Expired due to Fees

• Current Assignee: SARL Societe D'Assistance Technique AUX Industries Electroniques Pneumatiques Hydrauliques Rue Parmentier - BP 19 - 85110 Chantonnay
• Original Assignee: Societe D'Assistance Technique AUX Industries Electroniques Pneumatiques Hydrauliqes
• Inventors: Garnier, Jean C., Rangeard, Gilbert, Thomas, Jean
• Primary Examiner(s): Orsino, Joseph A.
• Assistant Examiner(s): Hofsass, Jeffery A.
• Application Number:
  US07/132,311
• Time in Patent Office: 568 Days
• Field of Search: 340/660, 340/657, 340/561, 324/457, 324/72, 361/179, 361/180
• US Class Current: 340/660
• CPC Class Codes: G01V 3/088 operating with electric fields G01V3/082 takes precedence

Abstract

The present invention relates to a proximity detector between a metallic mass and an element subjected to an electric voltage, with an electric circuit feeding a safety device such as the coil controlling a circuit-breaker, the feed switch of a motor controlling the displacement of the mass, an auditory or visual alarm, or an emergency ground. The circuit includes an element which is normally non-conductive but made conductive when there is a potential appearing on the metallic mass to be protected, or on the antenna in which the electric circuit is fed by a DC autonomous power source. The conductibility of the element whose conductibility is modified by the variation of the electrostatic potential is controlled by the potential at an intermediate point between the metalic mass or the antenna and a pole of the DC source, with interposition between the intermediate point and the pole of a resistive or capacitive element.

Claims

1. In a proximity detector for detecting the proximity of a metallic mass to a live element including an electric circuit for feeding a safety device such as the control coil of a circuit breaker, the power supply switch of a motor controlling displacement of the mass, an alarm, an emergency ground and the like, the improvement wherein

said circuit includes

(a) a DC power supply source (6);

(b) first sensing means (5) for producing a first electrostatic potential upon direct contact of the mass with the live element;

(c) second sensing means (2) for producing a second electrostatic potential when the mass is in close proximity to the live element;

(d) field effect transistor means (8, 8'"'"') for detecting the first and second electrostatic potentials, said field effect transistor means including plural gate means each connected with a terminal of said first and second sensing means respectively and with a pole of said DC power supply source, said field effect transistor means also including a sourcedrain circuit polarized by said DC power supply source;

(e) a resistive element (7) connected between said pole and said terminal of said first sensing means; and

(f) a capacitive element (18) connected between said pole and said terminal of said second sensing means, whereby when at least one of said first and second potentials is altered, the conductibility of said field effect transistor means is modified to produce an output to the safety device.

2. Apparatus as defined in claim 1, and further comprising

(g) bipolar transistor means (13, 13'"'"') connected with said field effect transistor means for producing a current in response to the modified conductibility of said field effect transistor means;

and

(h) thyristor means (16, 16'"'"') connected with the output of said bipolar transistor means for producing an output to the safety device in response to the current of said bipolar transistor means.