| 摘要 |
There are plural subunits having a positional relationship that at least one of the subunits is located at such a position as to obstruct an operation of replacing another. There are provided positioning portions that are provided on the main body frame and position the respective subunits, and a subunit releasing mechanism that moves at least an outside subunit from a positioning and fixing position to a prescribed releasing position or a subunit fixing mechanism that holds the outside subunit at a prescribed releasing position and moves it from the released position to a prescribed, positioning and fixing position. Also provided is an axial movement prohibiting portion that prohibits in advance axial movement of a subunit before it is positioned. Further, a two-direction positioning portion is allowed to position a subunit preferentially over a one-direction positioning portion.
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