Sheet processing apparatus and image forming apparatus

Abstract

When a sheet bundle formed on a processing tray descends in a sheet bundle conveying path by a sheet bundle conveying mechanism while a front edge of the sheet bundle is nipped, a band sheet is circled to a front edge side and overlaid to front and back surfaces. The band sheet is perforated at a plurality of positions by a cutter and, thereafter, cut to a necessary length. Both edges of the band sheet are stapled integratedly with the sheet bundle by a stapler main body also serving as a stapling of the sheet bundle. If the band sheet is not torn at the perforation, its contents cannot be browsed. Therefore, security holding performance of the sheet bundle is raised.

1 . A sheet processing apparatus comprising:
 a tying member supplying portion which supplies a tying member, the tying member is wound around a sheet bundle formed by a plurality of sheets and ties the sheet bundle;   a binding unit which binds the sheet bundle integratedly with the tying member wound around the sheet bundle; and   a control portion which changes a length of the tying member to be supplied by the tying member supplying portion according to a thickness of the sheet bundle.   
     
     
         2 . An apparatus according to  claim 1 , further comprising a winding portion which winds the sheet bundle with the supplied tying member,
 wherein the winding portion overlays both edges of the tying member so as to coincide with an edge portion on the side of one side of the sheet bundle.   
     
     
         3 . An apparatus according to  claim 1 , further comprising:
 a cutting portion which cuts the supplied tying member from a tying material,   wherein the control portion calculates a necessary length of the tying member from the thickness of the sheet bundle and a sheet size of the sheet bundle, and controls the cutting portion so as to cut the tying material to the necessary length.   
     
     
         4 . An apparatus according to  claim 3 , wherein the control portion controls the cutting portion so as to form a perforation at a specific position of the tying member. 
     
     
         5 . An apparatus according to  claim 3 , wherein a process which makes the cutting easy has previously been performed to the tying material at a plurality of positions in a longitudinal direction. 
     
     
         6 . An apparatus according to  claim 1 , wherein the tying member has a width shorter than a length of one side of the sheet bundle. 
     
     
         7 . An apparatus according to  claim 1 , wherein the tying member supplying portion encloses a plurality of types of tying materials having different widths. 
     
     
         8 . An apparatus according to  claim 7 , wherein
 the binding unit binds the sheet bundle at a plurality of binding positions, and   the tying member supplying portion supplies different tying members according to intervals among the plurality of binding positions.   
     
     
         9 . An apparatus according to  claim 1 , further comprising a bundle forming portion which forms the sheet bundle by overlaying the received sheets,
 wherein the binding unit binds the sheet bundle formed by the bundle forming portion in a booklet shape.   
     
     
         10 . An apparatus according to  claim 9 , further comprising a sheet bundle conveying mechanism which moves the sheet bundle from the bundle forming portion and positions the sheet bundle for the binding unit; and
 a winding portion which winds the sheet bundle with the supplied tying member,   wherein the winding portion winds the tying member around the sheet bundle in association with the movement of the sheet bundle which is performed by the sheet bundle conveying mechanism.   
     
     
         11 . An image forming apparatus comprising:
 an image forming portion which forms images onto a sheet; and   a sheet processing apparatus which processes the image formed sheet,   wherein the sheet processing apparatus has a tying member supplying portion, the tying member is wound around a sheet bundle formed by a plurality of sheets and ties the sheet bundle;   a binding unit which binds the sheet bundle integratedly with the tying member wound around the sheet bundle; and   a control portion which changes a length of the tying member to be supplied by the tying member supplying portion according to a thickness of the sheet bundle.   
     
     
         12 . An apparatus according to  claim 11 , further comprising a cutting portion, provided for the sheet processing apparatus, which cuts the tying member to be supplied from a tying material,
 wherein the control portion calculates a necessary length of the tying member based on the thickness of the sheet bundle and a sheet size of the sheet bundle, and controls the cutting portion so as to cut the tying material to the necessary length.