| 摘要 |
PURPOSE:To inhibit a driven roller from sliding unnecessarily by providing an umbrella-shaped body which is fitted between double wall guide parts by a control shaft. CONSTITUTION:The umbrella-shaped body, e.g. a tapered washer 24 is provided to the control shaft 22 between the double wall type guide parts 172A and 172B, and the tapered part of this washer 24 is directed to the driven roller 19 and fitted on the control shaft 22 while a slight gap which allows associative motion is left. This washer 24 functions to prevent the driven roller 19 from reversing in cooperation with the guide part 172B. For example, when a belt 101 is loose, the driven roller 19 is energized by a spring 23, so the control shaft 22 is moved by the loosing quantity of the belt as shown by an arrow. In this movement, the washer 24 abuts on the guide part 172A, but never impedes the movement of the control shaft 22, thereby maintaining the proper tension state of the belt 101. Consequently, the driven roller 19 is prevented from sliding unnecessary to prevent an abnormal image from being formed. |
