Thermostat

摘要

A thermostat comprises a tube (10) with a switch assembly (12) mounted at a first end of the tube. A rod (14) extends within the tube and is secured to it adjacent its second end (16). The rod (14) has a coefficient of thermal expansion different from that of the tube (10) and is operatively coupled to the switch assembly (12) so as to cause the switch assembly (12) to change state in reaction to a change of temperature of the tube (10). There is carried on the rod (14) a first supporting member (42) formed from a material of a high melting point and a second supporting member (44) formed from a material with a melting point below that temperature which would be dangerous if exceeded in use. A spring (50) is trapped in compression between the first and second supporting members (42,44). An actuating assembly (60,62,64)) is operable under the action of the spring (50) on its release in the event of the second supporting member (44) melting, to cause the switch assembly (12) to change state so as to prevent further heating. <IMAGE>