| 摘要 |
PURPOSE: To release tension of a belt by means of small operation force by binding both ends of a tension spring to movable points and arranging a cam for positioning a yoke fixing one end of the spring. CONSTITUTION: When a lever 28 is turned clockwise around a pivot screw, a cam 40 presses a rotational element 38, so that the rotational element 38 and a finger 36 are pressed downward and a yoke plate 22 is moved downward. In this way, a belt roller 42 journalled onto a supporting part protruded forward from the yoke plate 22 is moved downward toward a rear roller 48 journalled to a base 12. Consequently, tension of a sand paper belt wound between the belt rollers 42, 48 is released and the belt is replaced. In this process, a distance between the fingers 34, 36 serving as fixing parts for a spring 32 is kept constant in all the positions of the operation lever 28. Therefore, an operation force for the lever 28 can be decreased and a load of the spring 32 can be kept constant, so that replacement of the belt can be carried out smoothly. |
