New Nippon Electric Co., Ltd.

Sadayoshi Iwanari

Osamu Umene

Yoshimasa Sakamoto

A thermal fuse comprises an electrically and thermally conductive housing hermetically sealing switch parts of a fusible temperature-sensitive pellet, metallic plates, compression springs and a slidable resilient contact member. The contact member has a center contact portion at its bottom base and a peripheral contact portion with a plurality of tongues extending from the bottom base. The contact member of resilient conductive material is shaped to form a portion sloping over the bottom base and to form peripheral tongues extending relative to the flat surface of the assembled metallic plate when no external force is applied. The shaped contact member with its peripheral tongues has an outer diameter equal to, or smaller than, the inside diameter of the housing when no external force is applied, whereas the application of a biasing force of one of two compression springs to the contact member expands the outer diameter thereof to be larger than the inside diameter of the housing case to maintain a sufficient contact force between the contact member and the housing.

Thermal fuse employing a slidable resilient contact member in a

The present thermal fuse comprises an electrically and thermally conductive housing for hermetically sealing the switching parts and a fusible, temperature sensitive pellet in said housing. The pellet is preferably molded to have a cylindrical shape or body provided with one cavity or several cavities and assembled in the housing, whereby the outside pellet surface contacts the inner surface of the housing. The cavity or cavities take up about 5 to 50 percent of the whole cross sectional area of the pellet. The pellet is made of a mixture of organic and inorganic substances preferably so as to accelerate the fusing function of the pellet when the temperature rises above the melting point of the major component of the organic materials. The cavity or cavities of the pellet greatly facilitate a large and rapid shrinkage in volume and the addition of inorganic substance provides a large thermal conductivity of the pellet, whereby a rapid and exact fuse action is accomplished.

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Kusatsu, Japan

Sadayoshi Iwanari