Thermally responsive switching device

Abstract

A thermally responsive switching device suitable for use as a motor protector and the like is disclosed. Such device includes a housing assembly consisting of a thermoplastic base and a shallow drawn metallic cover. The base provides sidewalls extending to a peripheral flange against which a flange on the cover is positioned. The thermoplastic material is deformed inwardly around the cover flange to permanently connect the assembly. The switch includes an elongated bimetal snap element supported at one end on the end of a heater in heat exchange relation therewith. The other end of the heater is connected to an external terminal through an opening in the thermoplastic base. The terminal provides a tubular projection extending through the opening and a plurality of inwardly extending, resilient tabs which are welded to the heater. The resilient tabs resiliently bias the heater toward the terminal to ensure that looseness does not occur if the base material shrinks and to accommodate differential thermal expansion to prevent looseness or excessive stresses in the thermoplastic material. A mounting stud is welded to one end of the snap element and a movable contact is welded to the other end. Reinforcing elements cooperate with the stud and the movable contact to sandwich the material of the bimetal therebetween to minimize fatigue inducing stress concentrations.