Abstract: A thermally operated snap-acting switch uses a switch arm and tension spring for rotating the switch arm. A thermal-responsive element moves the pivot of theswitch arm relative to the centerline of the spring to actuate the switch. Heater means activates the thermal-responsive element for operating the switch.

Abstract: A thermostatically controlled electric fuel heater for raising the temperature of diesel fuel flowing from a fuel tank to a fuel filter to prevent precipitation of wax crystals in the fuel filter and consequent filter clogging at low ambient temperatures includes a heat conductive tube incorporated as part of the fuel line a short distance upstream of the filter. An electric heating assembly is positioned on the tube and includes an electric resistance heating element helically wound about the tube and controlled by a thermostat responsive to the temperature of the tube and located upstream from the heating element. The thermostat includes a molded plastic frame having a central opening through which the tube passes. The thermostat includes a bimetallic thermal element secured to the frame and arranged to actuate a snap-action switch carried by the frame. The frame includes a baffle for thermally isolating the thermal element from the heating element.

Abstract: A thermal device for controlling the temperature of glow plugs in a diesel engine in which current is applied to the glow plugs from the battery through a relay, the relay in turn being actuated by a thermally controlled switch controlled by a heater. The heater applies heat to the thermal-sensitive switch. The relay also controls current through the heater so that the heater cycles in unison with the glow plugs. The thermally-operated switch includes a bimetallic element which is heated by the heater. The bimetallic element is mounted in the engine block so as to be subject to the same ambient temperature conditions as the glow plugs. A thermal timer responsive to the same ambient temperature conditions includes a resistance heater element energized from the alternator. The thermal timer switch de-energizes the relay when heated to a predetermined temperature.

Abstract: A thermally operated actuator useful as a relay, flasher, circuit breaker, or the like, in which a bimetal element is movable by heating and cooling in response to an electrical resistance heater and/or current passing through the bimetal element. In one form of the invention ambient compensation is achieved by rigidly clamping one end of the bimetal element to provide a cantilever support, and providing a support at the other end that either clamps or pivotally engages the bimetal element and longitudinally compresses the element, causing the element to buckle into a curved configuration. Heat is applied selectively to the bimetal element adjacent either end to produce a snap action change in the shape of the element between two fixed positions. In an alternative form of the invention, two parallel bimetal elements are linked together to provide ambient compensation while still providing the snap action change in shape in response to selectively applied heat.