Thermostat with positive off position

Details Thermostat with positive off position Thermostat with positive off position

1977-12-20

1979-09-04

Moses, R. L.

Electricity: electrothermally or thermally actuated switches

Thermally actuated switches

With bimetallic element

337 82, 337353, 337361, H01H 3752

Patent

active

041669940

ABSTRACT:
Thermostats for use in electrically heated appliances have a positive off position and are adapted for transition to a low temperature on position within a small amount (approximately one radian) of control shaft rotation. The thermostats comprise a stacked blade assembly including a lower bimetal temperature responsive blade, an intermediate stiff spring blade and an upper less stiff flexible spring blade, with the spring blade having juxtaposed switch contacts thereon and the bimetal blade operating to separate the switch contacts when the set temperature is attained. A control bracket mounted above the stacked blade assembly defines an opening through which a control shaft extends, the control shaft butting against the stiff spring blade and positioning it. The shaft mounts a cam and the control bracket has a depending cam follower for the cam, wherein the spring blade urges the cam against the cam follower. The cam has an on/off transition portion which achieves the transition of the thermostat between its positive off position with the switch contacts separated and a low temperature positive on position with the switch contacts together at good contact pressure. In one embodiment the cam further comprises a temperature adjustment portion for adjusting temperature settings above the low temperature on position. In another embodiment the cam is comprised of a cam bushing which threadably receives the control shaft for temperature adjustment, and the cam bushing and cam shaft are locked together by clutch surfaces for rotating the cam bushing to achieve the off/on transition.

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