GB692605A - Automatically and manually operable electric fire alarm switches - Google Patents

Abstract

692,605. Thermal switches; switch covers. LEVY, M. Sept. 3, 1951. No. 20798/51. Class 38(v) A fire-alarm switch comprises contacts 35, 49 normally held open by a fragile plate 20 which is held in place by fusible means, the contacts closing when the fusible means melt or when the plate is broken. The plate is held on a seating 19 by a flanged ring 21 which is secured by fusible pieces 23 screwed to the body 15. The movable contact 49 is formed on the end of a wire 46 which is bent to engage the inner surface of the plate 20 and is mounted by a screw 42. If the plate is broken, or pieces 23 melt, the wire 46 can move to the Fig. 4 position to close a signal circuit. The pieces 23 may be replaced by loops connecting the ring and the body, Fig. 6 (not shown), and the ring may be split axially, the ends of the two parts being fusibly held together (Figs. 7, 8 (not shown). Alternatively, the ring may comprise two abutting annulae 121, 221, Fig. 9, joined by fusible links 23c. In a further arrangement, the plate is retained by fusible washers arranged on screws threaded into the body, Figs. 10 to 14 (not shown). A hammer 52, on a chain 51 suspended from a hook 50, is provided for breaking the plate 20, which may be of glass with a "FIRE" sign behind it.