Patent ID: 8311473

Claim:
A bookbinding system comprising: an image forming apparatus that forms an image on a sheet; and a bookbinding device that receives the sheet on which an image is formed by the image forming apparatus and includes a punching unit that performs a punching process of forming a punching hole on a sheet; an aligning unit that aligns a plurality of sheets having punching holes; a ring binding unit that mounts, in the punching holes of the sheets aligned by the aligning unit, a ring-shaped binding tool to create a booklet; and a prohibiting unit that, if a sheet received from the image forming apparatus is a punched sheet having a punching hole thereon, causes the punching unit not to perform the punching process on the punched sheet, the prohibiting unit further including a detecting unit to detect whether or not the sheet received from the image forming apparatus is a punched sheet and to determine the size of the sheet received from the image forming apparatus upon detecting that the sheet received from the image forming apparatus is a punched sheet, the detecting unit being arranged upstream of the punching unit in a sheet conveyance path, the detecting unit being arranged on a position wherefrom two adjacent punching holes, among multiple punching holes, can be detected on an end portion of the sheet, and the presence of the holes being detected and a sheet size being determined based on detection results of two punched-hole detection sensors of the detecting unit.