Sheet processing apparatus for storing supplied sheets while preceding sheet are processed

A sheet processing apparatus, comprising:

• a processing tray on which the sheets are stacked;
• a processing unit which processes the sheets stacked on the processing tray;
• a sheet holding portion which stores supplied sheets while preceding sheets stacked on the processing tray are processed by the processing unit;
• a sheet discharging rotary member which conveys the supplied sheets stored in the sheet holding portion to the processing tray in a conveying direction;
• an abutment stopper, provided in the sheet holding portion, against which the upstream edges of the supplied sheets abut;
• a return roller which moves the supplied sheets in a direction opposite to the conveying direction to abut the upstream edges of the sheets against the abutment stopper;
• and
• a holding member which holds the supplied sheets in the sheet holding portion with their upstream edges in a conveying direction thereof abutted against the abutment stopper until the last sheet of the sheets to be stored is supplied in the sheet holding portion,
• wherein the sheet discharging rotary member conveys the stored sheets to the processing tray from the sheet holding portion when a downstream edge in the conveying direction of the last sheet of the sheets to be stored has projected from the downstream edges of the sheets held in the sheet holding portion by a predetermined amount.