GB493244A - Improvements in thermally actuated switches, relays and apparatus for fire detectionand like purposes - Google Patents

Abstract

493,244. Thermal switches; fire - alarm systems. BLANC, A. Dec. 6, 1937, No. 33682. Convention date, Dec. 8, 1936. [Class 38 (v)] [Also in Group XXI] A fire-alarm system, Fig. 5, comprises a detector D which normally closes the energizing circuit of a relay 16 which maintains open at contacts 27, 29 the circuit from a current source B. On the occurrence of a fire, detector D causes de-energization of relay 16 to complete the circuit to a lamp 31, buzzer 32, bell S and a fire extinguishing device V. All the circuits can be broken by withdrawing a plug 18. The detector D consists in a thermal switch, Fig. 1, comprising a bimetallic spiral 1 adjustably fixed at its centre to a terminal 2 and carrying at its free end an insulating sector 5 provided with contact plates 6 slidable between the jaws of a resilient clip contact 11. On expansion of the spiral 1 the insulating part 5 engages contact 11 and the relay circuit is broken. The relay 16, Fig. 3, has an armature 20 pivoted at 23 and formed with an extension 24 for moving a pair of contact arms 25 against the action of a spring 30. The movable contacts 27 are of clip form and engage on both sides of fixed blade contacts 29. A latch 21 pivoted on the free end of armature 20 is attracted by the core 19 and engages a slot in the core to latch the armature in the energized position and prevent any disturbance due to outside vibration, which object is further served by the construction of the relay and thermal switch contacts.