Patent ID: 7784778

Claim:
A stacker for use with a sheet, comprising: a sheet stacking section which receives the sheet and stacks the sheet, a stopping member which stops a top edge of the sheet and aligns the sheet, paired paddle-wheels which are structured to separate from and approach each other perpendicular to a sheet conveyance direction to press against the sheet, and convey the sheet to the stopping member; and a control section structured to control the paired paddle-wheels to separate from each other perpendicular to the sheet conveyance direction so that the paired paddle-wheels are arranged on side areas of the sheet, and press against the side areas of the sheet; wherein the control section is further structured to control the paired paddle-wheels to approach each other perpendicular to the sheet conveyance direction so that the paired paddle-wheels are arranged on a center area of the sheet, and press against the center area of the sheet.