Sheet bundle binding processing apparatus and image forming system having the same

A sheet bundle binding processing apparatus, comprising:

• a sheet discharging path through which sheets having difference lengths in a direction perpendicular to a sheet discharging direction are discharged in center reference;
• a processing tray on which sheets fed from the sheet discharging path are stacked;
• an aligning device which aligns the sheets stacked on the processing tray at a reference position in the direction perpendicular to the sheet discharging direction;
• a staple binding unit which staple-binds a sheet bundle on the processing tray;
• a press binding unit which press-binds a sheet bundle on the processing tray without using a staple;
• a stapler shifting device which moves the staple binding unit between a plurality of different binding positions;
• and
• a controller which controls the aligning device and the stapler shifting device,
• wherein the controller is capable of selecting from either an aligning operation to perform positional aligning in center reference or an aligning operation to perform positional aligning in side reference, when causing the aligning device to align sheets having different lengths in the direction perpendicular to the sheet discharging direction, and
• the controller causes sheets to be aligned in center reference in a processing mode to perform staple binding on a plurality of sheet positions, to be aligned in side reference in a processing mode to perform staple binding on a sheet corner, and to be positioned at a binding position with the sheet bundle being moved in the direction perpendicular to the sheet discharging direction after sheets are aligned in side reference or center reference in a processing mode to perform press binding on a sheet corner.