Tubular sheathed electric heater with an overheat safety device

Claim 1

A tubular heater comprising: a tubular sheath, an electric heater coil enclosed within said tubular sheath, a cavity within said tubular sheath, a safety device for turning off power to said electric heater coil of said tubular heater when the tubular heater overheats, said safety device including an electrically conductive tube in said cavity having said electric heater coil electrically connected to one end of said tube and extending away from said tube through said tubular sheath, a rod-shaped member made of a material which is thermally deformable at a certain temperature, said rod-shaped member being located in said tube and extending from said one end of said tube along a length of said tube and said rod-shaped member projecting from an open end of said tube, a normally closed switching arrangement located externally of said tubular sheath and connected in series with said tube and arranged to be actuated by movement of said rod-shaped member projecting from the open end of the tube due to the rod-shaped member undergoing deformation at the certain temperature so that the rod-shaped member acts upon said switching arrangement to turn off said heater coil of said tubular heater, said rod-shaped member in said tube being affected by excessive temperatures of said heater coil.