PURPOSE: To avoid the generation of an impact noise by locking loads such as a cartridge, doors of a car, a cover of a trunk and so on by an electric motor.

CONSTITUTION: A gear 1b mounted on a rotary shaft 1a of an electric motor 1 is connected to a rotary cam plate 3 through gears 2, 2b, 4, a projecting portion 3b of the rotary cam plate 3 is brought into contact with the left end of a lever 5, a projecting portion 3e is brought into contact with a lever 10 and a lever 7 is pressed to the peripheral surface of the rotary cam plate 3. In this arrangement, loads such as a cartridge 6, doors of a car, a cover of a trunk and so on can be locked with a little labor by the driving force of the electric motor, so that the generation of a large impact noise can be avoided.