PURPOSE: To suppress vibration at the time of the opening and closure of the shutter and exert no adverse influence upon the laser, etc., of a printer by letting an opening/ closing mechanism part be in operation against the frictional resistance of a damper either by the excitation of a solenoid or by the energizing force of a spring.

CONSTITUTION: When the shutter 1 is opened, the solenoid 3 is excited, a link 2B is pushed up by the armature 3A of the solenoid 3 to rotate a shaft 2A, and a link 2C is rotated to open the shutter 1. At this time, the spring force of the spring body 4 and the frictional resistance of the damper 5 are transmitted to the opening/closing mechanism part 2 through the shaft 2A, so the opening/closing mechanism part 2 operates against the spring force of the spring body 4 and the frictional resistance of the damper 5. When the shutter 1 is closed, on the other hand, the solenoid 3 is turned OFF and the shutter 1 is closed under its own weight and the spring energizing force of the spring body 4. At this time, the opening/closing mechanism part 2 operates against the frictional resistance of the damper 5. The vibration of the shutter 1 is therefore reducible through the vibration absorbing operation of the damper 5, so the adverse influence of the vibration of the shutter is eliminated.