An alarm system comprising an elongate and flexible pressure line adapted to be charged with a selected line pressure; switching means coupled to the line and responsive to a pressure change in the line to create alarm signal; union means inserted in frictional sealing engagement within said line and having a bore which maintains the fluid continuity of the line; and spring-biased retaining means circumscribing said line and applying a selected clamping force to seal said union means in said line. The union means are arranged to break the seal of the line in response to an emergency condition, to thereby lower the line pressure and activate an alarm.
This is a division of application Ser. No. 368,609 filed June 11, 1973, and now abandoned in favor of continuation application Ser. No. 595,874, filed July 14, 1975.
A temperature sensor has a flexible nylon tube connected by a fluid-tight coupling to a metal bellows within a metal housing. The interior of the tube and bellows is filled with a pressurized liquid whose critical temperature corresponds to a threshold temperature to be sensed. The pressurized liquid holds the bellows extended, holding an actuating piston back against the action of a spring. When the threshold temperature is reached, the liquid in the tube must boil and ruptures the tube, causing the bellows to collapse and the actuating piston to move. A projecting actuator then mechanically initiates a response such as the closing of a damper in an air-conditioning duct.
