Heat motor operated load regulating switch assembly and knob attachment therefor

Abstract

A user adjustable switching controller for duty cycle regulating flow of current to an electrical load such as a resistance heater, particularly for cooking appliances. A load current switch, when closed by a user operated cam also energizes a heat motor which includes a resistive strip attached to one active leg of a U-shaped bi-metal member. In one embodiment the integrally formed load current switch snap spring is securely attached to the heated leg of a U-shaped bi-metal and the moveable contact arm pivoted on the base. The other leg of the U-shaped bi-metal is anchored to a base including one of the load-connecting stationary terminals; and, the anchored leg serves to provide ambient temperature compensation. In another embodiment, the integrally formed blade spring of the moveable contact member is pivoted on the active leg of the U-shaped bi-metal and the moveable contact arm welded to the base. User rotation of the cam deflects a bias spring which acts on the portion of the bi-metal attached to the load switch snap spring to effect closing of the load current switch and energization of the heat motor. Heating of the bi-metal causes warpage which overcomes the bias spring to open the load switch and shut off the heat motor. Cooling of the bi-metal allows the load current switch to re-close repeating the cycle. User adjustment of the cam varies the bias on the snap spring and thus the re-open point of the switch with respect to the cycle, thereby varying the ratio of "on" to "off" time of the load current. The heat motor sub-assembly including the base with the load connecting terminal, the U-shaped bi-metal, the heater and the moveable contact arm and heater connecting chip is pre-fabricated and installed in the controller housing as a unit.

Dependencies are inferred from the claim text.