Field sensor
First Claim
1. A field sensor control mechanism for detecting obstructions in front of the leading edges of linearly moving motor-operated sliding elevator doors, comprising at least two insulated electrodes mounted in a leading edge of a slidable door at different levels;
- means, including a first capacitor and a first inductor, forming a first oscillating circuit electrically connected to one of said electrodes;
means, including a second capacitor and a second conductor, forming a second oscillating comparison circuit electrically connected to the other of said electrodes and having a base oscillating frequency at least substantially the same as that of said first circuit; and
means including a feedback winding and an amplifier connected in circuit with said first and second circuits and operative for so coupling said first and second circuits that the oscillations of said first circuit vary as a function of capacitance changes in said electrodes.
1 Assignment
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Accused Products
Abstract
A field sensor control mechanism for doors and the like has two or more insulated electrodes mounted at different levels in the leading edge of a door or the like. A first oscillating circuit is connected with one of these electrodes and a second oscillating circuit, separate from the first one and serving as a comparison circuit for the same, is connected to the other electrode. The two circuits have base oscillating frequencies which are either identical or differ only slightly from one another. The circuits are so coupled to one another that the oscillations of the first circuit vary as a function of capacitance changes taking place in the electrodes.
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Citations
10 Claims
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1. A field sensor control mechanism for detecting obstructions in front of the leading edges of linearly moving motor-operated sliding elevator doors, comprising at least two insulated electrodes mounted in a leading edge of a slidable door at different levels;
- means, including a first capacitor and a first inductor, forming a first oscillating circuit electrically connected to one of said electrodes;
means, including a second capacitor and a second conductor, forming a second oscillating comparison circuit electrically connected to the other of said electrodes and having a base oscillating frequency at least substantially the same as that of said first circuit; and
means including a feedback winding and an amplifier connected in circuit with said first and second circuits and operative for so coupling said first and second circuits that the oscillations of said first circuit vary as a function of capacitance changes in said electrodes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- means, including a first capacitor and a first inductor, forming a first oscillating circuit electrically connected to one of said electrodes;
Specification