JPH0221538B

PURPOSE:To obtain a prescribed scanning speed through a small-sized motor by using a spring with necessary elastic force as the main driving source for a scanning mechanism, and then using the driving force of a synchronizing motor in combination. CONSTITUTION:A sample plate 2 is mounted on a scanning member 1 at a prescribed position, and the front edge 1F of the scanning member 1 is pressed in against a spring 4 as shown by an arrow (c). At this time, a moving link 9 pressed against an intermediate link 8 is displaced by 90 deg. by the free rotation of a unidirectional clutch 10 and when a microswitch operating plate 7 reaches a position 7', the roller 22R of a microswitch 22 is pressed, turning on a synchronizing motor 16. As the motor 16 rotates at a constant prescribed synchronizing speed, braking operation is performed to allow a driving pulley 11 at a prescribed pulley 11 through a timing belt 15, thus regulating the scanning speed of the scanning member 11. Since the braking force of the motor 16 is nearly equalized to the elastic force of the spring 4, the torque of the motor 16 is reduced to half.