Patent ID: 7832718

Claim:
A sheet post processing apparatus, comprising: a process tray for aligning and accumulating sheets delivered in succession; staple means disposed on the process tray at a post processing position for post processing the sheets on the process tray, and reciprocally movably arranged in a sheet width direction transverse with a sheet discharging direction of a post processed sheet stack on the process tray; a sheet discharging stacker arranged at a downstream side of the process tray for accumulating and accommodating the post processed sheet stack; and sheet stack delivery means for delivering the post processed sheet stack on the process tray from the process tray to the sheet discharging stacker, the sheet stack delivery means comprising a pushing member which engages the sheet stack on the process tray and transfers the sheet stack in a discharge direction, guide means for guiding the pushing member in the sheet discharging direction along the process tray, and drive means for reciprocally moving the pushing means along the guide means, wherein the pushing member is arranged such that when the sheet stack is delivered to the sheet discharging stacker, the pushing member engages the guide means and moves along the guide means by the drive means, and at a predetermined position, the pushing member is separated from the guide means and is movable in the sheet width direction.