DEVICE FOR INDICATING A PRESSURE OR FORCE

Abstract: A device for indicating a pressure or force applied to, for example, push-buttons, door edge sensors, pressure sensitive doormats or position detecting equipment in general, the device comprising one or more channels (3, 6) in an elastic material. One or more of the channels (3) contain a sound transmitter/receiver combination (4, 5) with electric lead-ins, the combination establishing, in normal operation, a sound communication between the sound transmitter and the sound receiver. Upon application of an external force on the elastic material of the channel (3), the channel is compressed such that the sound communication is interrupted.

Description: DEVICE FOR INDICATING A PRESSURE OR FORCE The present invention relates to a device for in¬ dicating a pressure or force, with possible fields of application such as push-buttons, door edge sensors, pressure sensitive doormats or position detecting equip- ment in general. Various indication techniques are used, for example on motor operated doors where a person entering through the doorway may be in danger of getting caught at the front or lower edge of the door. Different methods are used to reduce such danger, but none of them functions in a fully satisfactory manner. The functional problems are frequently caused by the incapacity of the devices to distinguish between unauthorised obstacles and the normal surroundings. Furthermore, mechanical type switching arrangements are frequently used which comprise switching plates of metal, and therefore also oxidation is a great problem. In addition, excessive contact stress may cause lasting deformation of this type of metal plate, which hardly is of advantage to the function. The device according to the invention comprises one or more channels in an elastic material, e.g. rubber, one or more of said channels containing a sound-conducting compressible medium, such as air, as well as a sound transmitter at one end and a sound receiver at the other end. By sound are here meant frequencies lower than the ultrasonic frequency. The channel or channels are adapted to be included or integrated in rubber strips or the like, for example in door sealing strips of an elastic material, also in existing, conventional door sealing strips. The strip can be mounted in curves since the channel conducts acoustic energy. This makes it possible to use a low power input, which causes a break of the channel to be indicated as an obstacle. If the channel is compressed anywhere along its length by an obstacle, the sound path through the medium is inter¬ rupted. The same occurs with any type of fault in the device proper, e.g. power failure, short-circuiting of the lead-ins or puncture of a channel. The device thus is self-regulating in that the operating means is rendered inoperative on power failure. Moreover, the switching principle may well be used in explosive surroundings since no spark is formed when the switch is closed. The device will be described in more detail below, reference being had to the accompanying drawing and a preferred embodiment, the drawing showing a part of a garage door or industrial gate 1 whose lower edge is provided with a rubber strip 2 having a channel 3. The channel is air-filled, and contains a sound trans¬ mitter 4, such as an oscillator (<20 kHz), and a receiver 5 of the sound from the sound transmitter. The transmitter and the receiver may be of conventional type and are each arranged at one end of the channel and provided with lead-ins in an electric circuit comprising a current source S and a gate operating means M. In the strip 2 and parallel to the channel 3, a further channel 6 (de¬ formation channel) may extend which is intended to be deformed upon braking of the gate so as not to damage the obstacle which caused the deformation of the channel 3. It is shown at 7 that a force F is applied, and it appears that the channel 3 is deformed before the channel 6, as indicated above. When the channel 3 is deformed, the sound path between the sound transmitter and the sound receiver is interrupted and, consequently, the current to the operating means of the gate 1 is inter¬ rupted, whereupon the deformation channel 6 can be de¬ formed upon braking of the gate.

Claims: CLAIMS 1. A device for indicating a pressure or force applied to, for example, push-buttons, door edge sensors, pressure sensitive doormats or position detecting equip¬ ment in general, c h a r a c t e r i s e d in that it comprises one or more channels (3, 6) in an elastic material, that one or more of said channels (3) contain a sound transmitter/receiver combination (4, 5) with electric lead-ins, said combination establishing, in normal operation, a sound communication between the sound transmitter and the sound receiver, and that said channel (3) is compressed upon application of an external force on the elastic material so as to interrupt the sound communication. 2. A device as claimed in claim 1, c h a r a c t e r i s e d in that the sound transmitter is of a type emitting sound having a frequency lower than the ultra¬ sonic frequency.

Inventors: JOENSSON BERT OVE, JOENSSON, BERT, OVE
Applicants: JOENSSON BERT OVE, JOENSSON, BERT, OVE
Application year: 1986
Main classification: E05F15
IPC codes: E05F15, F16P3, G08B13