Patent ID: 8662489

Claim:
A sheet stacking apparatus comprising: a discharge unit configured to discharge a sheet to be conveyed; a stacking tray configured to stack the sheet discharged by the discharge unit; an acquisition unit configured to acquire shift information for designating a stacking position of the sheet in a sheet width direction which is orthogonal to a sheet conveyance direction to sort a set of a copy; a shift control unit configured to control, in response to the shift information acquired by the acquisition unit representing stacking in a first position, the stacking position of the sheet in the sheet width direction so that the sheet is stacked in the first position, to control, in response to the shift information representing stacking in a second position, the stacking position of the sheet in the sheet width direction so that the sheet is stacked in the second position, and to control, in response to the shift information representing neither the first position nor the second position and the sheet not being stacked on the stacking tray, the stacking position of the sheet in the sheet width direction so that the sheet is stacked in a third position between the first position and the second position; and an alignment unit configured to align the sheet staked on the stacking tray, wherein the alignment unit moves to a position corresponding to the stacking position of the sheet controlled by the shift control unit and abuts on a side edge of the sheet in the sheet width direction to align the sheet, wherein, in response to a first sheet being stacked on the first position and shift information of a second sheet, which is subsequent to the first sheet, not indicating either the first position or the second position, the shift control unit controls a stacking position of the second sheet to stack the second sheet on the second position, and, in response to the first sheet being stacked on the second position and the shift information of the second sheet not indicating either the first position or the second position, the shift control unit controls the stacking position of the second sheet to stack the second sheet on the first position.