Robertshaw Controls Company

White-Westinghouse Corporation

George L Hetrick

Calvin J Holtkamp

Richard Warren

An oven control for self-cleaning ovens provides a hydraulic sensing system having a wafer-like bellows. The position of the bellows is adjusted by a face cam on a control shaft in the BAKE and BROIL modes of operation. The bellows also controls the temperature of the oven for SELF-CLEANING. However, the face cam does not determine the SELF-CLEANING temperature. A door lock operator switch is also operated by the bellows, but is connected so that the adjusted position of the bellows does not affect the door lock operating temperature. Three separate calibration adjustments are provided. The first calibrates the operating temperature in the BAKE and BROIL modes of operation. The second calibrates the SELF-CLEANING temperature, and the third calibrates the door lock operating temperature. A bimetal ambient temperature compensator is provided to compensate for variations in the ambient temperature of the control.

Oven thermostat

A thermal cycling switch has an insulated housing carrying a centrally located rotating cam. The cam operates a first ON/OFF switch connectable between a pair of contacts that are connected to one side of a load and one power line. The rotary cam also moves an adjusted contact mounted on an adjustable arm which cooperates with a cyling arm contact to operate as another switch between the other side of the load and another power line. The cycling arm includes a bimetal member which is electrically insulated at the base, as well as a current conducting strip formed of pure nickel metal extending along the low expansion side of the bimetal member. The metal strip is heated by a separate resistance wire wrapped around an insulated cover on the metal strip and connected across the load so that whenever the load is energized from the power lines, the metal strip is heated to produce an initial biasing force causing the contacts to close in opposition to the thermal expansion of the bimetal, which tends to cause the contacts to open.

Thermal cycling switch

A sensor, located to respond to the temperature of the cooking platform and having a positive temperature coefficient of resistance throughout a range of temperatures up to the maximum selected safe operating temperature of the platform, is connected to a thermal cycling control switch and provides an increasing resistance with an increasing platform temperature to effect a wattage limiting control of the heating element supplying heat to the platform.

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Mansfield, OH, United States of America

George L Hetrick