Therm-o-disc, Incorporated

Emil R Plasko

James A Tennant

Ronald A Nixon

Marc A Peoples

A self-contained unitary thermal cutoff switch assembly having a hollow sealed switch housing formed by a collector and a lid that serve as the switch contacts. Separating the collector and the lid is a plastic insulating liner that generally follows the inside contour of the collector. The lid is held in place at the open end of the collector by folding over the top lip of the collector which will, at the same time, fold over the insulator in a U-shape about the edge of the lid and hold and insulate the lid in a spaced relationship with the collector. A shape memory collector formed as a straight piece of wire is located between the lid and the side of the collector opposite the lid. The wire is held in alignment by an opening through the insulator which supports an end portion of the wire adjacent to the bottom of the collector. When the thermal cutoff is subjected to a temperature equal to or greater than the recovery temperature of the shape memory conductor, the conductor will change to its recovered shape and open the circuit. If a high resistance circuit through the open thermal cutoff switch is required, the plastic insulator may be molded of a partially conductive compound by using a mixture such as polypropylene and carbon black.

Thermal cutoff switch

A heating element control includes a ceramic substrate having a resistance circuit thereon of a material having a positive temperature coefficient. A first comparator compares the resistance of the circuit with a first known resistance to control a signal light. A second comparator compares the resistance of the circuit with a second known resistance to control a heating element.

Heating element control

Wires and a thermistor are isolated from the interior surface of a metal tube by a ceramic tube and a ceramic spacer to protect the thermistor and prevent breakdown of insulation on the wires.

Temperature sensing apparatus

A thermal cutoff includes a housing having a resistive coating bonded thereto, and defining a heater for heating the thermal cutoff to its firing temperature.

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Lexington, OH, United States of America

Emil R Plasko