GB616416A - Improvements in or relating to electric fire-alarms - Google Patents

Abstract

616,416. Thermal switches. SMITH, D. O., and GODDARD, J. A. Sept. 5, 1946, No. 26686. [Class 38 (v)] The gas-filled capsule 10 of. a fire-alarm switch is brazed at its centre to a strip 12 screwed to an insulating ring 11, and on its other side to a contact disc 16 co-operating with an adjustable contact pin 22. The pin is screwed to a spring-arm 21 secured to a conducting bridge 18 attached to the ring 11 which carries terminals 39, 41. A slotted insulating block 26 screwed beneath the bridge carries a stud contact 35 connected by a lead 38 to the terminal 39, and a spring-urged plunger contact 29 having at one end a nose 30 engaging a trigger 31 on the spring-arm 21. A lead 42 connects the bridge 18 with the terminal 41, and the strip 12 is connected to the terminal 39 by a lead 40. As the capsule expands the disc 16 engages the pin 22 thereby closing the alarm circuit ; further expansion causes the spring-arm 21 to release the plunger 29 to complete an alternative circuit through the stud 35 and the bridge should the capsule burst. The time interval between the closures is adjustable by a screw 45. A push-button 33 resets the switch which may be enclosed by a casing 50 and a slotted top cover, Fig. 4 (not shown).