PURPOSE: To prevent regenerative material from being over-cooled, by providing an element made of shape memory alloy, which is transformed at the solidifying point of regenerative material or at the temperature slightly lower than that point when the temperature in the material is decreasing, and is returned to the initial shape at the temperature higher than the solidifying point when the temperature is increasing, in the regenerative material.

CONSTITUTION: When a regenerative capsule 1 is cooled down and the temperature is lowered down to the solidifying point or the temperature slightly lower than that point, a stirring element 5 is transformed to produce what is like a swirl flow in a regenerative material 4, so that the regenerative material 4 starts solidifying and is turned into a solid as shown in the figure τ3. The shape transformable temperature of shape memory alloy is higher (t2'>t1') when it is increasing, than the case when it is decreasing, so that the alloy is transformed after the regenerative material 4 is completely liquefied when the material is melted. Further effect can be expected if the capsule is composed of an element 5 supported by a support rod 6 as shown in the figure 1'.