Temp. detector exposed to low ambient pressure - has gas-filled bubble which dilates under reduced pressure and is interposed between double coaxial tube housing

摘要

The detection appts. capable of fluctioning under conditions of differing pressure, comprises a sensitive element e.g a thermistor (11) in a housing with a thin gas-filled bubble (51) to detach the housing when the exterior pressure is reduced. The housing comprises two concentric tubes (39, 44) and the bubble is interposed between the ends of the tubes. The inner tube is held by the bubble and the outer tube frictionally engages a cap (29), such that when the force developed by the dilation of the bubble under reduced pressure, is greater than the frictional force, the simultaneous detachment of the external and internal tubes occurs, thus exposing the element to the external pressure. The bubble may be made from latex and filled with air.