Snap action thermally responsive switch

Abstract

A thermally responsive switch comprises a housing enclosing a contact arm bearing a fixed contact and a thermally responsive snap-acting element designed to move and return with snap action depending upon the degree of switch self-generated heat or the ambient temperature. One end of the snap-acting element carries a movable contact and its other end is the supporting portion connected to a metallically elastic member mounted in the housing. To a stationary member integrated with the housing, an end support element and a central support element are respectively mounted. The end support element engages the supporting portion of the snap-acting element against the elastically urging force of the elastic member to push in one direction, while the central support element engages a middle portion of the snap-acting element to push in the opposite direction. In this arrangement, the metallically elastic member is urged to engage the end support element elastically intermediate the snap-acting element, and at the same time, urging the snap-acting element in the direction its movable contact travels for opening the contacts. This configuration makes it possible that each of the two support elements engage the snap-acting element with a certain pressure when the thermally snap-acting element respectively moves and returns.