Patent ID: 8146904

Claim:
A sheet processing apparatus comprising: a sheet stack tray which provides an inclined sheet stack surface on which a sheet is stacked; a regulating member, having a regulating surface disposed opposite the inclined sheet stack surface, which is movable toward the inclined sheet stack surface so as to decrease a clearance between the regulating surface and the inclined sheet stack surface, and thereby regulate the sheet stacked on the inclined sheet stack surface; a clamping member which clamps an upper portion of the sheet stacked on the inclined sheet stack surface; a pair of folding rollers which performs a folding process to the sheet stacked on the sheet stack tray, the pair of folding rollers being disposed on a side to which the pair of folding rollers faces the inclined sheet stack surface at a predetermined distance from the inclined sheet stack surface; and a controller which controls movement of the clamping member and movement of the regulating member so that, the clamping member clamps the upper portions of the sheet after the regulating member regulates the sheet, and the regulating member moves to increase the clearance between the regulating surface and the inclined sheet stack surface while the upper portion of the sheet is clamped by the clamping member.