| 摘要 |
PURPOSE:To exactly prevent a foreign matter from adhering to the surface of a developing member, by providing a shutter member for holding an outside exposed surface of the developing member, in an open position, in a developing action position, and holding said surface in a closed position, in a non-developing action position. CONSTITUTION:When a semi-rotation driving of a cam 21 is started in a state that a developing device A is held in a developing action position against a drum B, the inside surface of a rear side lug 18 receives a pressing force by a raised part of the cam, and a base plate 12, namely, the developing device A moves backward against the drum B. At the time point when the semi-rotation of the cam 21 has been ended, its retreat amount becomes maximum, and the developing device A is switched to a non-developing action position where it has been saved as prescribed against the drum B (a developing sleeve 2 has been separated as prescribed from the surface of the drum B). On the other hand, as for a shutter member 9 which has been held in an open position, a shutter member opening/closing mechanism is operated at the time point being near an end period of a retreat process by interlocking with a retreat motion of the developing device A, executes a closing turn without interfering with the surface of the drum B, and the shutter member is held in a closed position where the surface of the developing sleeve has been hidden.
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