Patent ID: 7905474

Claim:
A sheet finisher comprising: a saddle stitch unit configured to stitch a center of a sheet bundle in which printed sheets are bundled; a fold unit configured to fold the center stitched by the saddle stitch unit and to form a fold line; and a fold reinforcing unit configured to reinforce the fold line formed by the fold unit and to include; a roller unit that includes a first roller and a second roller, and moves along a direction of the fold line while nipping and pressing the fold line of the sheet bundle transported from the fold unit by the first roller and the second roller; a drive unit configured to include a single motor to move the roller unit along the direction of the fold line from a standby position located at a position separate from an end of the sheet bundle; a nip unit that includes a first nip plate and a second nip plate, and configured to nip the sheet bundle transported from the fold unit at a position between the fold line and the fold unit, the first nip plate and the second nip plate being opened in a thickness direction of the sheet bundle when the roller unit is located at the standby position, and the first nip plate and the second nip plate being closed to nip the sheet bundle when the roller unit reinforces the fold line after the sheet bundle is transported between the first nip plate and the second nip plate, a positional relation between the first nip plate and the fold unit being fixed, the sheet bundle transported from the fold unit being placed on the first nip plate, and the second nip plate being kept substantially parallel to the first nip plate, and being driven to be opened and closed in the thickness direction of the sheet bundle by the single motor.