Safety device for limiting the movement of doors and the like on contact with an obstacle
First Claim
1. A safety device suitable for use in power operated apparatus for producing a safety control signal on contact between an obstacle and at least one part of the apparatus to control the further operation of said apparatus, said safety device comprising a resilient member attachable to a part of an apparatus, at least two electrodes associated with the resilient member and connectable to an electrical supply, means electrically interconnecting said electrodes and capable of passing a current indicative of unobstructed operation of said apparatus and means responsive to deformation of said resilient member following contact therewith to change the electrical conditions prevailing between said electrodes to vary said current and means capable of detecting the variation in current to produce said safety control signal.
2 Assignments
0 Petitions
Accused Products
Abstract
A safety device specially suitable for preventing the further movement of power operated parts such as doors of trams or garage doors on contact with an obstacle for example a human being. A resilient member is attached to the edge of the door and is provided with two electrodes so that a constant small current flows between the electrodes to indicate that the safety device is operational and wherein, on contact with the edge of the door, the resilient member deforms and gives rise to an increased current between the electrodes which is used as a control signal to inhibit further movement of the door. The increased current is achieved either by allowing the two electrodes to contact each other directly thus short circuiting a resistor or by making the resilient member conductive so that its resistance decreases during compression. The resilient member is located within an elongate slot in a rubber moulding having additional airfilled elongate slots for cushioning the edge of the door.
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Citations
23 Claims
- 1. A safety device suitable for use in power operated apparatus for producing a safety control signal on contact between an obstacle and at least one part of the apparatus to control the further operation of said apparatus, said safety device comprising a resilient member attachable to a part of an apparatus, at least two electrodes associated with the resilient member and connectable to an electrical supply, means electrically interconnecting said electrodes and capable of passing a current indicative of unobstructed operation of said apparatus and means responsive to deformation of said resilient member following contact therewith to change the electrical conditions prevailing between said electrodes to vary said current and means capable of detecting the variation in current to produce said safety control signal.
Specification