US Patent 7345568 Dual protection device for circuits

A protection device includes a bi-metallic plate having a first end fixed to a first terminal and a second of the bi-metallic plate has a first contact point so as to contact a second contact point on a first end of a carrier. A contact plate has a first end in contact with a second terminal and a second end of the contact plate is forced to connect to a second end of the carrier by a low melting point metal. When the protection device is overloaded, the bi-metallic plate is bent to separate the first contact point and the second contact point. Besides, if the bi-metallic plate does not bend as expected, the low melting point metal melts to separate the second end of the contact plate and the carrier when a pre-set temperature is reached.