Abstract: A power actuator comprises an enclosure (5) separated by transverse partitions (6) into two sections (7, 8) which are filled in succession with a heat-transfer agent. A load-bearing casing (1) the walls of which are made of a material possessing a "form-remembering" ability is arranged along the longitudinal axis of the enclosure (5). At a definite temperature the walls of the load-bearing casing (1) deflect inwardly, thereby reducing the internal volume of the load-bearing casing (1). The transverse partitions are made of an elastic material and are installed for coming in contact with the external surfaces of the walls of the casing (1) when their position is changed.