Sheet processing apparatus

A method for transporting sheets of a sheet processing apparatus having a tray to hold a first sheet, a second sheet and a third sheet which are fed thereon, and a transport device configured to transport the first sheet, the second sheet and the third sheet onto the tray via a transport path having a sheet transport guide that guides the first sheet, the second sheet and the third sheet onto the tray, the sheet transport guide including a sheet supporting surface, the transport device having a press member that is openable and closable with respect to the sheet supporting surface and a transport roller that is rotatable in a normal direction and in a reverse direction which is opposite to the normal direction, the method comprising:

• rotating the transport roller in the normal direction to transport the first sheet to a predetermined position and stopping the rotation to stop the first sheet at the predetermined position while the press member is closed,
• opening the press member to insert the first sheet between the press member and the sheet supporting surface,
• rotating the transport roller in the reverse direction to transport the first sheet from the predetermined position to a first position in the transport path while the press member is opened,
• closing the press member to press the first sheet against the sheet supporting surface to hold the first sheet at the first position until transportation of the third sheet has started,
• rotating the transport roller in the normal direction to transport the second sheet to the predetermined position and stopping the rotation to stop the second sheet at the predetermined position while the press member is closed,
• opening the press member to insert the second sheet between the press member and the sheet supporting surface,
• rotating the transport roller in the reverse direction to transport the second sheet from the predetermined position to a second position in the transport path while the press member is opened,
• closing the press member to press the second sheet against the sheet supporting surface to hold the second sheet at the second position, while the second sheet is superimposed on the first sheet held at the first position, until transportation of the third sheet has started,
• rotating the transport roller in the normal direction to transport the third sheet to a third position and to be superimposed on the second sheet held at the second position, and
• rotating the transport roller in the normal direction to transport the first sheet, the second sheet and the third sheet together onto the tray after the third sheet is transported to the third position,
• wherein the second position is at an upstream side of the first position and the third position, in a sheet transport direction toward the tray, and
• wherein the transport roller is rotated in the normal direction to transport the first sheet, the second sheet and the third sheet in the sheet transport direction and is rotated in the reverse direction to transport the first sheet and the second sheet in a direction opposite to the sheet transport direction.