Magnetically actuated sensing device
First Claim
1. A magnetically actuated sensing device for controlling an electrical circuit in a physical security monitoring system, said sensing device comprising:
- (a) a switch unit having at least three electrically interconnected reed switches, each one of said reed switches being responsive to a respective predetermined magnetic flux density, presence of said respective predetermined flux density causing magnetic actuation of each respective one of said reed switches;
(b) a plurality of permanent magnet biasing means, one of said permanent magnet biasing means being located adjacent each one of said reed switches for providing said respective predetermined magnetic flux density surrounding each one of said plurality of reed switches, at least one of said plurality of permanent magnet biasing means being located so as to provide magnetic flux in substantial opposition to magnetic flux of at least one other of said plurality of permanent magnet biasing means; and
(c) an actuating unit comprising means for allowing each one of said reed switches to assume a magnetically nonactuated state by reducing the net flux density surrounding each one of said plurality of reed switches sufficiently below said respective predetermined flux density when said actuating unit is in a predetermined position relative to said switch unit.
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Accused Products
Abstract
A magnetically-actuated sensing device for use in security monitoring systems. A switch unit having a plurality of electrically interconnected magnetic reed switches disposed in a predetermined physical relationship is provided for controlling electrical circuits. Each reed switch is biased in a magnetically-actuated state by permanent biasing magnet in close proximity thereto, the biasing magnets being arranged in a predetermined combination of polarity orientations. A corresponding number of permanent actuating magnets with polarity orientators opposing those of the biasing magnets are disposed within an actuating unit so that they overcome the effect of the biasing magnets when the switch unit and actuating unit are in a predetermined physical relationship with each other. The polarity of at least one of the biasing magnets opposes the polarity of other biasing magnets of the device, providing a sensing device which cannot be deceived using only a single permanent magnet to simulate the actuating magnets. Single-pole-double-throw reed switches may be used to give positive signals corresponding to both alignment and misalignment of the actuating unit with the switch unit. Magnetic shielding associated with the switches and actuating magnets allows the device to be factory-adjusted and sealed, and thereafter to be used in environments containing magnetic material without further adjustment.
58 Citations
10 Claims
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1. A magnetically actuated sensing device for controlling an electrical circuit in a physical security monitoring system, said sensing device comprising:
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(a) a switch unit having at least three electrically interconnected reed switches, each one of said reed switches being responsive to a respective predetermined magnetic flux density, presence of said respective predetermined flux density causing magnetic actuation of each respective one of said reed switches; (b) a plurality of permanent magnet biasing means, one of said permanent magnet biasing means being located adjacent each one of said reed switches for providing said respective predetermined magnetic flux density surrounding each one of said plurality of reed switches, at least one of said plurality of permanent magnet biasing means being located so as to provide magnetic flux in substantial opposition to magnetic flux of at least one other of said plurality of permanent magnet biasing means; and (c) an actuating unit comprising means for allowing each one of said reed switches to assume a magnetically nonactuated state by reducing the net flux density surrounding each one of said plurality of reed switches sufficiently below said respective predetermined flux density when said actuating unit is in a predetermined position relative to said switch unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification