| 摘要 |
PROBLEM TO BE SOLVED: To improve the visibility and taking out performance of sheets on a lower-stage tray. SOLUTION: This sheet stacking device 500 is provided with an upper-stage tray 18a and the lower-stage tray 18b which are liftable/lowerable and on which sheets discharged from an upper discharge port 834 are stacked; and with a lower position detection sensor S4a for detecting that the upper-stage tray 18a is lifted to a first position above the upper discharge port 834. The sheet stacking device 500 is further provided with an upper position detection sensor S4b for detecting that the upper face of a sheet on the upper-stage tray 18a or the upper-stage tray 18a having no stacked sheets is lifted to a second position above the first position. A clearance (L) between the first and second positions is set below the maximum stacking height (H) of sheets stacked on the upper-stage tray 18a. When sheets are stacked on the lower-stage tray 18b, the upper-stage tray 18a is retracted and lifted above the upper discharge port 834. After one of the lower position detection sensor S4a and the upper position detection sensor S4b performs detection operation, the lifting is stopped in the position when the other performs detection operation. COPYRIGHT: (C)2008,JPO&INPIT
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