GB649011A - Improvements in or relating to thermostats for controlling electrical heating apparatus - Google Patents

Abstract

649,011. Thermal switches. ELECTRIC & MUSICAL INDUSTRIES, Ltd. April 30, 1948, No. 11835. [Class 38(v)] In a thermostat for controlling an electrical heating device, e.g. a room heater and comprising a heat-responsive means and switch arranged to be operated thereby in response to changes in temperature of the room, the heat-responsive means is additionally heated by the heat generated in the leads connected to the switch, so as to reduce the lag between the temperature of the thermostat and that in the neighbourhood of the heating device. The switch 4, which may be of the kind described in Specification 419,917, is mounted on a centrally pivoted lever 3, the lefthand end of which is held against an adjusting cam 7 by a spring 5. A bimetal strip 10 is mounted by screws 12 on a bracket 13 and its right-hand end engages the switch plunger 11, the strip being adjusted by a screw 14 so that the switch 4 is closed. The switch terminals 20, 21 are connected to main terminals 18, 19 by leads 31 and 32, and 33 respectively, the leads 31 32 preferably being of nickel. The heater is connected to terminals 18, 19 if a large current is needed, and to terminal 19, and a terminal 17, between leads 31, 32, if a smaller current is needed. On distortion of the strip 10 due to the combined heating effect of the room temperature and the leads 31 and 32, or 31 alone, the plunger 11 is depressed and the switch 4 opened. The thermostat is carried by a bracket having keyhole slots engaged by studs on the base 1.