Thermostat with bimetal compensating element

摘要

An electric switch that is temperature responsive is provided for operation in a temperature range that is substantially above normal ambient temperature. A pair of contacts are mounted on respective first and second spring members. The second spring member includes a bimetal compensating portion at the distal end thereof. The second contact is mounted on the compensating portion so that upon increasing the temperature of the switch structure, the second contact moves toward engagement with the first contact to eliminate initial overshoot and to compensate for variable contact weld size between the contacts. An operating bimetal assembly in direct contact with the heated surface being monitored is used to break the contacts. The bimetal assembly includes a bimetal base element and a metal element butt-welded to the distal end thereof. The metal element carries a ceramic button to engage the first or upper spring member to move the first contact. An adjusting rod engages a dimple on the second spring member adjacent the point where the bimetal compensating portion is butt-welded to the spring member. The operating bimetal assembly and the two spring members are mounted and separated by an insulator stack. In an alternative embodiment, the bimetal compensating portion is mounted on the end of a full length second spring member. The compensating portion extends back along the second spring member and directly engages an adjustment rod. As the temperature of the bimetal compensating portion is increased, the second contact moves toward engagement with the first contact in the same manner.