PURPOSE: To keep stable contact condition at all times without occurence of gaps between a thermally-sensitive part and a tank by a method wherein a thermal cutout is fixed at the upper part of the tank by attaching screws into which springs are inserted and the thermal cutout moves up and down freely to push the thermally-sensitive part to the tank.

CONSTITUTION: At a tank 6 thermo-stands 18 are fixed and a thermal cutout 12 is fixed at the upper part 17 of the tank to the stands 18 by attaching screws B26 into which springs are inserted and it is so constituted that the thermally- sensitive part 20 of the thermal cutout 12 is pushed to and comes in contact with the upper part 17 of the tank. The thermal cutout 12 moves up and down (arrow) freely along the tank 6 to keep stable contact condition at all times.