Alarm device
First Claim
1. An alarm device for indicating unauthorized removal of various objects from a display riser, such objects including bottom surfaces having varying degrees of concavity formed therein, comprising:
- a) a display riser including a housing having a support surface for supporting an object to be displayed;
b) switch means mounted in said housing and having a pair of electrical contacts for closing an electrical circuit when an object is lifted a predetermined distance from the support surface of said housing;
c) a plunger operatively coupled to said switch means and extending upwardly through an opening in the support surface of said housing, said plunger adapted to be depressed by the weight of an object placed thereon for a distance which varies according to the degree of concavity formed in the bottom of the object, and wherein depression of said plunger separates said electrical contacts to provide a throw length spacing having a predetermined limit, thereby setting the alarm; and
d) means for maintaining said throw length substantially constant and independent of the distance said plunger is depressed when said distance is greater than the predetermined limit of said throw length.
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Accused Products
Abstract
Movement or removal of a display object placed on a base is detected by a switch mechanism for closing an electrical circuit, having an elongated plunger and a device for maintaining the throw length of the switch mechanism substantially constant and independent of the distance the plunger is depressed upon setting of the alarm. Detection of extremely short plunger travel is enabled without special adjustments in the plunger length. A "tilt" switch may be added for added sensitivity. A plurality of bases, each with its own switch, may be grouped with a single signalling device to provide an alarm system. Portions of the circuitry may be grouped in modular form for introduction into the base housing.
30 Citations
17 Claims
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1. An alarm device for indicating unauthorized removal of various objects from a display riser, such objects including bottom surfaces having varying degrees of concavity formed therein, comprising:
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a) a display riser including a housing having a support surface for supporting an object to be displayed; b) switch means mounted in said housing and having a pair of electrical contacts for closing an electrical circuit when an object is lifted a predetermined distance from the support surface of said housing; c) a plunger operatively coupled to said switch means and extending upwardly through an opening in the support surface of said housing, said plunger adapted to be depressed by the weight of an object placed thereon for a distance which varies according to the degree of concavity formed in the bottom of the object, and wherein depression of said plunger separates said electrical contacts to provide a throw length spacing having a predetermined limit, thereby setting the alarm; and d) means for maintaining said throw length substantially constant and independent of the distance said plunger is depressed when said distance is greater than the predetermined limit of said throw length. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification