GB931493A - Improvements in or relating to temperature responsive electric switches - Google Patents

Abstract

931,493. Thermal switches. GRAVINER MANUFACTURING CO. Ltd., and WILKIN. SON SWORD Ltd. Dec. 7, 1960 [Dec. 11, 1959], No. 42111/59. Class 38 (5). A temperature-responsive switch for stopping the fuel supply to a fluid fuel burner in the absence of a flame, comprises a metal body 11 and a probe 10 of flame-resistant, high thermal expansion material, e.g. " Nimonic " (Registered Trade Mark), enclosing a rod 12 of low expansion material, for example, ceramic, refractory material, or preferably silica. The relative positions of the rod 12 and probe 10 are adjusted either by a set-screw, or as shown by a short rod 9 fixed during manufacture. Mounted in body 11 is a platform 13, of channelshaped cross-section, which carries a fixed contact 18 on a saddle 19 insulated from the platform by mica 20. A spring blade 16 carrying a contact 17 is fixed at one end to the platform and its other end is engaged in a notch 15a in a rod 15. Contact 18 is electrically connected by a lead 21 to the centre contact 23 of a coaxial connector formed at one end of the casing 11, the casing acting as the outer contact. Modifications are described wherein contacts are normally closed and open on heating. Both the contacts may be carried on spring blades, or either or both may be independently mounted and actuated by the blades.