| 摘要 |
In a sheet stacking system for stacking plural sheets from a printed sheets output path into at least one sheet stacking tray, including a stack height sensor for detecting the height of the stack of sheets in the tray and controlling a stacking control system; the stack height sensor has an elongated maximum stack height sensing bar, and a sensing bar movement system for intermittently moving the maximum stack height sensing bar into the tray in an operative measurement position on top of the stack of sheets in the tray at a position transversely of the sheet entrance path, with a normal force pressing downwardly against the top of the stack. The stack height sensing bar in this position extends across the top of the stack at the height of the highest level of any portion of the stack, in particular, overlying the sets stapling area. A sensing system is actuated by the height of the stack height sensing bar in this measurement position to provide signals to the stacking control system, which provides a control signal when the maximum stack height in the sheet entrance path to said sheet stacking tray reaches a height which is preset below the height which would obstruct the sheet entrance path. This sensor system can move, to measure several bins, and can also provide a sheet knockdown function.
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