Actuator using elastic extensible member
An actuator includes an elastic member extensible in axial directions when a pressurized fluid is supplied into the elastic member, and guiding device arranged inwardly of the elastic member and permitting the elastic member to move in the axial directions, but restraining the elastic member from moving in directions intersecting the axial directions. As the actuator is of an air-bag type so that energy of the pressurized fluid can be converted into mechanical movement with high efficiency. The actuator moves only in radial directions without expanding in radial directions, so that a space occupied by the actuator in operation is little.