GB563964A - Improvements relating to automatic fire and/or burglar alarm systems - Google Patents

Abstract

563,964. Fire and burglar alarms. ASSOCIATED FIRE ALARMS, Ltd., and McNEIL, E. A. March 2, 1943, No. 3440. [Class 118 (i)] [Also in Group XXI] An automatic fire or burglary alarm system of the kind wherein a tensioned wire, cord, &c., when under the influence of expansion &c. in the case of fire, or a pull &c. in the case of burglary, actuates an electric signalling device, comprises a compensating device including a floating lever and delay-action means such as a dashpot by which after a given time the floating lever which effects the operation of the signalling device will be returned to inoperative position. The tensioned wire 10 is connected by a chain 11 to a rod 13 influenced by a spring 15 to which rod is connected by a pin and slot 17 a floating lever 18 pivoting about a fulcrum 22 carried by the piston-rod 23 of a dashpot 24, the far end of the lever being held floating by two springs 20, 21 and provided with a stud 19 adapted to bear on and close pairs of switch contacts 26, 27 and 28, 29 connected up in parallel to the signalling circuit. Sudden expansion or interference with the wire 10 causes the spring 15 to tilt the floating lever about its pivot 22 so that the stud 19 closes one or other of the pairs of switch contacts 26, 27 or 28, 29, but after a certain interval movement of the dashpot piston 25 enables the spring 20, 21 to restore the end of the floating lever to mid-position and allow the switch contacts to open. Slow variations are taken up by the dashpot without movement of the stud 19. In case of a slow fire causing gradual increase of temperature insufficient to close the contacts, stops may be provided limiting the angular movement of the floating lever or the length of the dashpot cylinder may be arranged so that the travel of the piston 25 is arrested.