GB990563A - Improvements in thermally operable electric switch devices - Google Patents

Abstract

990,563. Thermal switches. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. June 21, 1963 [Aug. 7, 1962], No. 30204/62. Heading H2B. In a room thermostat, a thermally responsive bimetallic spiral 24 is separated from contacts 12, 21 and 13, 22 and other parts of the switch which may carry current, by a partition 33. The switch base 1 has four terminals 5, 6, 7 and 8, line terminal 5 being connected through a conducting strip 16, spring 19 and armature 20 to contacts 21, 22. The fixed contacts 12, 13 are connected through conducting bars 10, 11 to terminals 6 and 7. As the room temperature increases, the spiral 24 expands and the free end engages and moves a heat insulating member 23 which opens contacts 12, 21 and closes contacts 13, 22. The contacts 12, 21 may be included in a circuit with a heater. A magnet 24 cooperates with the armature 20 to provide snapaction for the contacts. A pointer, Fig. 3 (not shown), connected to the centre of the spiral 24 and viewed through a window in the casing, adjusts the spiral and thus the setting temperature of the thermostat. Contacts 12 and 13 may also be adjustable. An accelerating heater resistor 31, connected between terminals 6 and 8, is located in a niche 32 which concentrates heat on the spiral. Stops may be provided to limit the movement of the pointer and thus select day and night temperatures for the thermostat.