GB401805A - Improvements in electrical fire alarms - Google Patents

Abstract

401,805. Thermal switches. VIGILANT AUTOMATIC FIRE ALARM CO., Ltd., 183, Cashel Street, Christchurch, New Zealand. July 9, 1932, No. 19469. Convention date, July 10, 1931. [Class 38 (v).] Relates to fusible switches for fire alarm systems wherein operation of the switch due to heat first allows a closed circuit to open, and then causes an open circuit to be closed. A base 1, Fig. 1, with a cover 7, carries an insulating plate 2 on which are mounted terminal posts 8, 11, 13. The post 8 carries a spring contact 9 which is held, by a rod 18 and a fusible retainer, in contact with a lower contact point 10 on the post 11. The post 13 carries a spring contact 14 which lies between the contact 9 and an upper contact 15 on the post 11. The rod 18 is guided in an adjustable tube 22, Fig. 8, and is connected at its lower end to a screw 25 projecting from a heat-collecting vane 25a. The vane has a slot 25c free to slide on a pin 25d carried by a sleeve 26 below the tube 22, but is retained in its lowered position by fusible metal 27 engaging recesses 25b in the vane. When the metal fuses, the rod 18 is free to rise, releasing the spring contact 9. In a modification, Fig. 5, the rod 18 is connected to a screw 25 having a wedge-shaped end embedded in fusible metal 27. In either construction, the tension of the rod 18 can be adjusted by rotating the tube 22. Specification 326,189, [Class 38 (v), Electric switches &c.], is referred to.