SHEET PROCESSING DEVICE, IMAGE FORMATION SYSTEM, AND SHEET BUNDLE ADDITIONAL FOLDING METHOD

摘要

PROBLEM TO BE SOLVED: To prevent a staple needle from being bent at the time of making additional folding with a back of a sheet bundle (booklet) that is saddle stitched.SOLUTION: A saddle stitching bookbinding device 2 includes a holding means which includes a folding roller pair 230 for folding a sheet bundle SB at a folding line part SB1 and a folding plate 215 for pushing the folding line part SB1 into a nip of the folding roller pair 230, and an additional folding roller unit 260 which pressurizes the folding line part SB1 that is folded by the folding means in thickness direction of the sheet bundle SB, for additional folding. Since, at the additional folding, the folding plate 215 protects a staple needle N of the sheet bundle SB from the pressurizing force of the additional folding roller unit 260, the staple needle N is prevented from being bent when additional folding is made with the back of the sheet bundle being saddle stitched.