| 摘要 |
PURPOSE:To eliminate surely a toner cloud by opening a negative pressure generating valve, which is provided in a suction hose below a developing machine, to its full width when the developing machine is operated and closing completely the negative pressure generating valve when another developing machine starts the operation. CONSTITUTION:Suction hoses 18-20 are connected to developing machine housings 5-7, and negative pressure generating valves 22 are inserted to parts A1-A3 in these hoses 18-20. When the operation of one developing machine out of developing machines 2-4 is switched to that of another developing machine, the negative pressure generating valve 22 placed below the former developing machine is held slightly opened for a while after the end of the operation of this developing machine to discharge the toner cloud hanging over in the developing machine housing to the outside of a joining hose 24 through the suction hose by a suction blower 25. |
