Main parts

1) Insulating paper  2) Conductive housing  3) Bimetal disc 

4) Movable contact  5) Stationary silver contact  6) Base  7) Iron nails

Construction

The stationary silver contact is welded on the base, the movable contact is welded to one end of the bimetal disc, the other end is welded to the housing by iron nails. The movable contact is in close contact with the stationary silver contact under the pre-pressure of the bimetal disc, the base and the housing are isolated by  insulating paper. The current first passes through the movable contacts connected to the housing and bimetal disc,  and then through the stationary silver contacts on the base to form a loop.