Thermal cut-off fuse

A self-restoring type thermal cut-off fuse for making electric continuity between first and second lead wires extended out of a housing when the temperature of the ambience is lower than a prescribed temperature and breaking said electric continuity when said temperature rises above the prescribed temperature, which thermal cut-off fuse comprises an electrically conductive contact means adapted to move between first and second positions in a hollow space of said housing and, while at said first position, remain in contact with both first and second terminal portions electrically connected within said housing respectively to said first and second lead wires and, while at said second position, separate from at least one of said first and second terminal portions;

• a temperature-sensitive member tightly sealed in a space on the side of the first position of said contact means within the hollow space of said housing so as to abut one surface of said contact means, said temperature-sensitive member having the property of retaining a solid state under normal conditions and, at the prescribed temperature, melting with increase in volume and, on falling to a temperature lower than said prescribed temperature, solidifying with loss of volume;
• and resilient energizing means adapted to keep said contact means energized at all times in the direction from the second position to the first position and possessed of energizing force insufficient to overcome the force which said temperature-sensitive member generates upon melting with increase in volume in the direction of causing the surface of said temperature-sensitive member abutting said contact means to move said contact means to the second position and sufficient to energize said contact means to the first position at the time said temperature-sensitive member solidifies with loss of volume.