GB242252A - Improvements in thermostatic regulating devices for electric heat-producing apparatus - Google Patents

Abstract

242,252. Aktiebolaget Birka Regulator. Nov. 3, 1924, [Convention date]. Thermostats. - The current to the electrical heater 2 is regulated by a main thermal switch 6 and an auxiliary thermal switch 7, the latter being arranged near the heater so as to open its contacts 14 when the heater reaches a certain temperature and thereby removes a short-circuit from the heating coil 10 of the main switch, which then opens and closes its contacts 8 in a well-known manner so as to reduce the supply of current to the heater 2 to a suitable amount. The switches 6, 7 are preferably both of the bimetallic kind as shown. The auxiliary switch 7 comprises two springs 12, 13 carrying contracts 14, the strip 13 being engaged by the head of a screw 16 which is adjustably secured in the bimetallic member 15. The main switch 6 is enclosed in a receptacle 11 which is evacuated or filled with an inert gas. In a modification both switches are enclosed in such receptacles or they may be enclosed together in one receptacle which is placed in thermal relation to the heater 2. In this latter case, should the auxiliary switch 7 fail to act, the main switch 6 will still open its contacts, though at a somewhat higher temperature.