The types of bimetal switches are classified into two, one is a slow make and break type and the other snap-acting type. Here is described a new type of snap-acting bimetal switch which can act by small temperature changes and still has a good contact pressure.
The main parts of this switch are; (1) two curved bimetal strips which are fixed uniaxially and move in opposite direction each other, (2) a floating lever which has an electric contact at its end, and (3) a curved spring. The spring force of outside bimetal acts at the end of the fioating lever by the aid of curved spring and supplies the contact pressure. The other component force balances to the spring force of inside bimetal. When the two bimetals are heated and the amount of their strain energy stored becomes sufficiently large, the floating lever moves and rotates at a high speed, and accordingly the contact opens.
It is apparent that the mechanism of this snap-action can be explained by solving the buckling behaviour of curved bimetal beams. For solving this problem we investigated into the instability of the spring system, setting up an equivalent diagram consisting of simple springs. Thus we introduced the conditions necessary to obtain good snap-acting switches.