PURPOSE: To reduce the usage of a shape storing alloy by energyzing a toggle joint with the aid of a shape storing spring.

CONSTITUTION: When temperature reaches a level exceeding the transformation point, a shape storing spring 32 produces a elastic restoring force several times larger than that in the martensite phase, causing the force for pulling a toggle joint 20 closer to the stopping part 27 side to be increased. Namely, the toggle joint 20 is displaced in the direction of increasing an opening angle θ, and the θ approaches about 180°, so that it is possible to move a pressuring member 17 to the supporting part 8 side by increasing tensile force due to the shape storing spring 32 to several or several ten times even if said tensile force is small. Hereby, it is possible to obtain pressurizing force equivalent to the conventional one even with the reduced usage of a shape storing alloy material.