Abstract: A rotating actuator displaces a movable pin between two end positions, at least one of which two end positions is a stop. The actuator comprises an energy buffer, components mutually connecting the energy buffer and the movable pin, a mass capable of storing energy of the energy buffer as kinetic energy, wherein at the end of the displacement in at least one direction the kinetic energy of the mass is stored again in an energy buffer. A locking device blocks the actuator in at least one extreme position when the remaining kinetic energy has been substantially transferred to the energy buffer. The lost energy can be supplied at the end of the movement cycle. Between the energy buffer and the movable pin are situated at least two rotating components, i.e., an actuating element which drives the movable pin between two end positions. The distance between the end positions in relation to each other is not necessarily determined.