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Abstract

A fire detection system includes an elongated liquid filled tube with a fluid coupled alarm switch, with a flexible diaphragm which senses a change from the liquid to vapor phase in the presence of an overheat or fire condition to provide an alarm. To prevent false alarms due to normal expansion of the liquid under changing ambient temperature conditions, a compensator is provided which in one form is a pair of mechanically coupled bellow type containers, filled with the same liquid which will expand at the same rate as the fluid under normal ambient temperature conditions but in a fire condition will resist faster expansion thus causing the alarm switch to be actuated. In another embodiment, a bimetallic bellows is utilized to match the liquid expansion but resist greater vapor pressure. Yet in another embodiment the change in liquid flow rate due to a fire condition is sensed to prevent further accommodation to the normal increase in volume of the liquid. This is done by a flexible diaphragm or a floating seal ball.

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First Claim