PURPOSE: To reduce the impulsive noise of a gear due to a pinch cam and a press-fixing spring force by providing the pinch cam with a first cam curve and a second cam curve which are continuous.

CONSTITUTION: A press-fixing cam part of a pinch cam 5 is provided with the first cam curve 5b1 and the second cam curve 5b2 as a cam radius change part. When a slide part 7a of a press-fixing cam follower 7 is slided while following up the first cam curve 5b1 of the pinch cam 5, only a return spring 11 is expanded. When the slide part 7a is slided while following up the second cam curve 5b2 of the pinch cam 5, not only the return spring 11 but also a press-fixing spring 8 is expanded because a pinch roll 2 is abutted on a capstan shaft 1. When the slide part 7a comes to a maximum cam radius part 5c of the pinch cam 5 thereafter, expansion of the return spring 11 and the press- fixing spring 8 is stopped to complete press-fixing of the pinch roll 2.