According to embodiments, a sheet post-processing apparatus includes a processing tray, a vertical alignment section, a horizontal alignment section and a controller. The controller is configured to control the horizontal alignment section to shift the sheet to a first alignment position a predetermined distance from the center of the processing tray in the sheet width direction, control the horizontal alignment section to align the sheet in the sheet width direction at the first alignment position, and control the vertical alignment section to align the sheet in the conveying direction at the first alignment position, control the horizontal alignment section to realign the sheet at the first alignment position.

A printer includes a printing unit, a casing, a scanner unit disposed in an upper portion of the casing, and a discharge unit that, below the scanner unit, is connected to the casing pivotably between a closed position and an open position and that a sheet of paper is discharged to. The discharge unit includes a placement surface for the sheet and a medium support unit capable of supporting the sheet from below while in a state of being protruded from the placement surface. The medium support unit is displaceable between a maximum protruded position and a minimum protruded position. When the amount of protrusion of the medium support unit from the placement surface when the discharge unit is in the open position is less than the amount of protrusion of the medium support unit in the maximum protruded position from the placement surface.

A printer includes a printing unit, a casing, a scanner unit disposed in an upper portion of the casing, and a discharge unit that, below the scanner unit, is connected to the casing pivotably between a closed position and an open position and that a sheet of paper is discharged to. The discharge unit includes a placement surface for the sheet and a medium support unit capable of supporting the sheet from below while in a state of being protruded from the placement surface. The medium support unit is displaceable between a maximum protruded position and a minimum protruded position. When the amount of protrusion of the medium support unit from the placement surface when the discharge unit is in the open position is less than the amount of protrusion of the medium support unit in the maximum protruded position from the placement surface.

An image forming apparatus may comprise the following elements. A stacking unit in which a sheet is stacked. A conveyance unit conveys the sheet. A time-counting unit counts a conveyance time from when the conveyance unit starts to convey the sheet until the sheet arrives at a predetermined position on a conveyance path. A determination unit determines that over stacking has occurred, if the conveyance time of the sheet exceeds a first over stacking threshold value.

An image forming apparatus may comprise the following elements. A stacking unit in which a sheet is stacked. A conveyance unit conveys the sheet. A time-counting unit counts a conveyance time from when the conveyance unit starts to convey the sheet until the sheet arrives at a predetermined position on a conveyance path. A determination unit determines that over stacking has occurred, if the conveyance time of the sheet exceeds a first over stacking threshold value.

This paper sheet processing device (100) for processing paper sheets is provided with: an identification unit (55) for identifying paper sheets; stacking units (60, 210) for stacking paper sheets on the basis of the content of classification types identified by the identification unit (55); and a control unit (50, 135, 550) that reads, from a memory unit (56, 136, 560) in which an upper limit of paper sheets to be stacked by the stacking units (60, 210) are stored in association with the content of classification types, the upper limit for paper sheets that correspond to the content of the classification types of the paper sheets stacked by the stacking units (60, 210), and sets the upper limit for paper sheets to be stacked by the stacking units (60, 210).

This paper sheet processing device (100) for processing paper sheets is provided with: an identification unit (55) for identifying paper sheets; stacking units (60, 210) for stacking paper sheets on the basis of the content of classification types identified by the identification unit (55); and a control unit (50, 135, 550) that reads, from a memory unit (56, 136, 560) in which an upper limit of paper sheets to be stacked by the stacking units (60, 210) are stored in association with the content of classification types, the upper limit for paper sheets that correspond to the content of the classification types of the paper sheets stacked by the stacking units (60, 210), and sets the upper limit for paper sheets to be stacked by the stacking units (60, 210).

When a discharge count has exceeded a specified number of sheets, a sheet discharge device executes a process of moving down a discharge tray by a specified quantity and thereafter moving up the discharge tray until a top-surface detection part outputs a top-surface detection signal, while clocking a move-up time lasting from a move-up start of the discharge tray until output of the top-surface detection signal by the top-surface detection part. When the move-up time is equal to or less than a reference time, the sheet discharge device makes a next sheet discharged while the top-surface detection part outputs the top-surface detection signal; on the other hand, when the move-up time is more than the reference time, the sheet discharge device executes a correction process of moving down the discharge tray before making the next sheet discharged.

When a discharge count has exceeded a specified number of sheets, a sheet discharge device executes a process of moving down a discharge tray by a specified quantity and thereafter moving up the discharge tray until a top-surface detection part outputs a top-surface detection signal, while clocking a move-up time lasting from a move-up start of the discharge tray until output of the top-surface detection signal by the top-surface detection part. When the move-up time is equal to or less than a reference time, the sheet discharge device makes a next sheet discharged while the top-surface detection part outputs the top-surface detection signal; on the other hand, when the move-up time is more than the reference time, the sheet discharge device executes a correction process of moving down the discharge tray before making the next sheet discharged.

A sheet loading device is provided with a sheet ejection portion, a sheet loading portion, a first detection mechanism, a driving device, a second detection mechanism, and a control portion. The driving device drives the sheet loading portion to ascend/descend between an upper surface detection position and a reference position made to descend by a prescribed distance from the upper surface detection position. The second detection mechanism detects that the sheet loading portion is at the reference position. In a case where sheets of the same type are ejected continuously from the sheet ejection portion, the control portion controls beforehand the sheet loading portion to ascend from the reference position to the upper surface detection position and sets a loadable number of sheets of the sheet loading portion in accordance with an ascending time of the sheet loading portion.