The present invention relates to a switch that has a positioning member with a protrusion which positions one end of a bimetal plate at a close circuit position and an open circuit position.
Switches generally have two functions, opening the circuit or closing the circuit, and either one is simply a push to a switch button to let the two contact points in the switch box separate from each other or contact with each other. However, in an overridden situation, the switches cannot react by themselves and the current could melt parts in the switches or the electric appliances to result in damage. A bimetal plate is used in the switch box to prevent the situation. Switches with an override interruption structure known to applicant are disclosed in U.S. Pat. No. 5,786,742, 5,223,813, 4,937,548, 4,661,667, 4,931,762, 5,451,729, 4,704,594 and 4,937,548. A thermally deformed bimetal plate is used to open the circuit when the current overrides. However, the action to open the circuit takes time because the structure is so complicated and the two contact points are indirectly operated by the bimetal plate so that there is a possibility for the electric current to destroy the electric equipment when the switch is overridden.
Besides, U.S. Pat. No. 5,933,069 and 5,262,748 each has a simple structure and employs one positioning member connected to an end of the switch button, the other positioning member connected to an inside of the switch box, and a spring connected between the two positioning members. However, it is difficult to assemble the three parts in the switch box and there is friction between the positioning member and the box so that it cannot react immediately if the bimetal plate is worn out. U.S. Pat. No. 5,760,672 provides a simple structure for the switch but the bimetal plate lacks a reliable positioning function to maintain its overridden position.
The present invention intends to provide a switch that has a simple structure and the bimetal plate is positioned when it is deformed.
The primary object of the present invention is to provide a switch that has a bimetal plate which is held at its position after it is deformed due to current overriding.
In accordance with one aspect of the present invention, there is provided a switch comprising a box and a button pivotally connected to a top of the box and two terminal plates respectively extending through a bottom of the box. A positioning member has a fist end fixedly connected to the box and a second end formed with a protrusion. A link has a first end connected to an end of the button and a second end formed with an engaging port. A bimetal plate has a first end fixedly connected to one of the terminal plates and a second end engaged with the engaging port of the link. The second end of the bimetal plate pushes the protrusion of the positioning member when it is moved.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.