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Abstract

A heating pad with a thermostatic control circuit coupled to a resistance heating element. The resistance heating element and an acrylic based polymer adhesive are glued between polyester film layers. The film layers and heating element are contained with a plastic sleeve. The thickness and properties of the polyester film and adhesive forms a fuse. The adhesive delaminates the polyester film at excessive temperatures causing the resistance heating element to sever thereby creating an open circuit that halts operation of the heating pad. The thermostatic control circuit includes a hysteresis circuit that compares analog signals across two thin film resistors to provide a control signal to a power controller to selectively vary the power output to the heating element. The thermostatic control circuit is an integrated circuit board disposed within the fused plastic sleeve.

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First Claim