GB426442A - Improvements in or relating to fire-alarm systems - Google Patents

Abstract

426,442. Fire-alarms and fire-extinguishing. FARMER, F. L., 472, Bordesley Green, Birmingham. Feb. 16, 1934, No. 5107. [Classes 47 (i) and 47 (ii)] An operating device for fire or temperature alarms or extinguishing apparatus, preferably connected in parallel with the pushes of a house bell system, comprises a mercury tube 8 having sealed-in contacts 10, 11 and housed in a casing 17, the contact 11 being connected to the bottom 14 of the casing. A contact strip 21 connected to the contact 10 extends inside the casing 17 to a point adjacent the contact 11. A fusible ring 16 is secured within the casing. When the temperature rises, the mercury expands, and bridges the contacts 10, 11, closing the circuit of the bell 3 and indicator board 6, Fig. 4, at 1. If it continues to rise, so that the mercury bursts the tube 8 and falls into the bottom 14, the contacts 11 and 21 are bridged. If a temperature is reached at which the mercury volatilizes, the ring 16 melts and bridges the contacts 11, 21. The pushes of the bell system may be incorporated in the device, as at 23, and the tube 8 may be graduated. Preferably, an extension bell, not shown, is provided for a bedroom or the like. In a modification, Fig. 3, adapted to close at 29, Fig. 4, the circuit of a double pole relay 27 for energizing a solenoid 28 which controls a sprinkler valve 30, the contact 29 is constituted by the end 34 of an expansion tube 32. If the tube 8 bursts, the mercury closes the relay circuit at 11, 34. At the same time, the air in the tube 32 expands. On subsequent cooling, contraction of the air remaining in tube 32 sucks out the mercury from the bottom 14, so that the relay circuit is broken at 11, 34, the solenoid 28 is de-energized, and the supply of water to the sprinkler is cut off.