Signalling switch e.g. for fire or end-of-travel detector - includes glass plate carrying conductive strip which is broken in emergency by spring-loaded percussive element

摘要

The detector may be used in a fire alarm or in other sensors in which one alarm condition is to be detected. A conductive strip (2) is applied to a plate glass (1) support which is held between two contacts (3,4) such that the conductive strip completes a circuit between two terminals (12,13). When the alarm condition occurs, the glass plate is broken, and so the circuit through the conductive strip is also broken. In an end-of-travel detector a spring loaded pin (9) is driven into the glass to break it. Since the glass in such a detector forms the base of the conductive strip, it is not easy for the detector to be activated and then returned to its normal condition as is possible with some alarms. The glass support (1) may be broken by a spring (8) and a percussion element (9) which are slidably mounted in a support which is unitary with the housing. Alternatively, a thermally-sensitive strip may be used to break the circuit when a preset temp. is reached.