US Patent 8136812 Sheet stacker and finisher furnished with the same

Affords sheet stacking device that, in stacking sheets onto a loading tray, enables stacking of the sheets always in the correct posture regardless of the nature of the sheets' surface material. The sheet stacking device includes a tray unit located downstream of a sheet discharging port, a sheet-end regulating member provided on the tray unit, a conveying unit for transporting sheets carried out onto the tray unit though the sheet discharging port, toward the sheet-end regulating member, and a conveyance controller for controlling the conveying unit. In conveying toward the sheet-end regulating member a sheet having been carried onto the tray unit, the conveyance controller varies the running time during which the conveying unit applies conveyance force to the sheet, in accordance with the material nature of the sheet surface.