Patent ID: 7900905

Claim:
A post-processing apparatus, comprising: a stacker which is adapted to stack a plurality of sheets, wherein the stacker includes: (i) a sheet stopping member which is adapted to align the sheets, (ii) a first paddle member which is arranged adjacent to the sheet stopping member at a first predetermined position regardless of a size of the sheets in a sheet conveyance direction, wherein the first paddle member is arranged to rub a primary sheet and a secondary sheet to move the primary sheet and the secondary sheet toward the sheet stopping member, each of the primary sheet and the secondary sheet being ejected onto the stacker, and (iii) a second paddle member which is arranged to be at more than a first predetermined length from the first paddle member at a second predetermined position regardless of the size of the sheets, wherein the second paddle member is arranged in an opposite direction of the sheet stopping member with respect to the first paddle member so as to have the second paddle member rub the secondary sheet to move the secondary sheet toward the sheet stopping member, the secondary sheet being ejected onto the stacker; an accumulating section which is positioned upstream of the stacker in the sheet conveyance direction to superimpose the plurality of sheets to be supplied to the stacker; a sheet detection section which is positioned downstream of the accumulating section in the sheet conveyance direction to detect a sheet; a post-processing device which is adapted to conduct a post-processing operation for the superimposed sheets ejected onto the stacker; paired conveyance rollers which are adapted to nip the superimposed sheets after the post-processing operation to eject the superimposed sheets onto a sheet ejection tray; and a control section which controls the accumulating section, based on a sheet detection signal sent from the sheet detection section, to superimpose the secondary sheet on the primary sheet in the accumulating section such that a leading section of the primary sheet is positioned toward an upstream side in the sheet conveyance direction at the first predetermined length from a leading section of the secondary sheet, wherein the control section further controls the first paddle member to rub the leading section of the primary sheet which protrudes from the secondary sheet toward the sheet stopping member in the stacker, and still further controls the first paddle member to rub the primary sheet to move toward the sheet stopping member.