Sheet processing apparatus and sheet folding method and image forming apparatus

Abstract

According to one embodiment, a sheet processing apparatus pushes, with a folding plate, a sheet bundle held by a stacker into a nip portion formed by a first folding roller and a second folding roller and forms a fold. The first folding roller includes a first folding section configured to come into contact with the second folding roller and form the nip portion and a first groove configured to form a gap between the first groove and the second folding roller in a state in which the first folding section is in contact with the second folding roller. The first groove is formed in a position where an end in the width direction of a sheet bundle of a predetermined size pushed in by the folding plate passes.

1 . A sheet processing apparatus comprising:
 a stacker configured to hold a sheet bundle; and   a folding plate configured to push the sheet bundle held by the stacker into a nip portion formed by the first folding roller and the second folding roller, wherein   the first folding roller includes a first folding section and a first groove, the first folding section being configured to come into contact with the second folding roller and form the nip portion, and the first groove being configured to form a gap between the first groove and the second folding roller in a state in which the first folding section is in contact with the second folding roller and being formed in a position where an end in a width direction of a sheet bundle of a predetermined size, on which a fold is formed, passes, and   the second folding roller forms a fold on the sheet bundle in cooperation with the first folding roller.   
     
     
         2 . The apparatus according to  claim 1 , wherein the second folding roller includes:
 a second folding section configured to come into contact with the first folding section of the first folding roller and form the nip portion; and   a second groove configured to form the gap between the second groove and the first folding roller in a state in which the first folding section and the second folding section are in contact with each other.   
     
     
         3 . The apparatus according to  claim 2 , wherein the second groove is formed in a position where the end in the width direction of the sheet bundle of the predetermined size pushed in by the folding plate passes. 
     
     
         4 . The apparatus according to  claim 3 , wherein
 the predetermined size is a plurality of sizes, and   a plurality of the first and second grooves are formed for each of the predetermined sizes.   
     
     
         5 . The apparatus according to  claim 4 , further comprising an aligning member configured to align, before the sheet bundle is pushed by the folding plate, a width direction of the sheet bundle stacked by the stacker. 
     
     
         6 . The apparatus according to  claim 5 , further comprising:
 an acquiring section configured to acquire a size of a sheet stacked on the stacker; and   a controller configured to determine whether the size of the sheet acquired by the acquiring section corresponds to the predetermined size and, if the acquired size of the sheet does not correspond to the predetermined size, before the folding plate pushes the sheet bundle into the nip portion, move the sheet bundle to a predetermined position where at least one of both ends in a width direction of the sheet bundle passes the gap.   
     
     
         7 . The apparatus according to  claim 6 , wherein the controller moves the sheet bundle to the predetermined position via the aligning member. 
     
     
         8 . A sheet processing method for a sheet processing apparatus including: a first folding roller including a folding section configured to come into contact with a second folding roller and form, in a state in which the folding section is in contact with the second folding roller, a nip portion and a groove configured to form a gap between the groove and the second folding roller and in a position where an end in a width direction of a sheet bundle of a predetermined size passes; and a folding plate configured to push a sheet bundle held by a stacker into the nip portion and form a fold, the method comprising:
 acquiring a size of a sheet of the sheet bundle;   determining whether the acquired size of the sheet corresponds to the predetermined size; and   moving, if the acquired size of the sheet does not correspond to the predetermined size, before the folding plate pushes the sheet bundle into the nip portion, the sheet bundle to a predetermined position where at least one of both ends in a width direction of the sheet bundle passes the gap.   
     
     
         9 . The method according to  claim 8 , wherein the second folding roller includes:
 a second folding section configured to come into contact with the first folding section of the first folding roller and form the nip portion; and   a second groove configured to form the gap between the second groove and the first folding roller in a state in which the first folding section and the second folding section are in contact with each other.   
     
     
         10 . The method according to  claim 8 , further comprising aligning a width direction of a sheet bundle stacked by the stacker before the folding plate pushes the sheet bundle. 
     
     
         11 . The method according to  claim 10 , further comprising moving the sheet bundle to the predetermined position with an aligning member configured to align the width direction of the sheet bundle stacked by the stacker. 
     
     
         12 . An image forming apparatus comprising:
 an image forming section configured to form an image on a sheet;   a stacker configured to hold a sheet bundle subjected to image formation;   a folding plate configured to push the sheet bundle held by the stacker into a nip portion formed by the first folding roller and the second folding roller, wherein   the first folding roller includes a first folding section and a first groove, the first folding section being configured to come into contact with the second folding roller and form the nip portion, and the first groove being configured to form a gap between the first groove and the second folding roller in a state in which the first folding section is in contact with the second folding roller and being formed in a position where an end in a width direction of a sheet bundle of a predetermined size, on which a fold is formed, passes, and   the second folding roller forms a fold on the sheet bundle in cooperation with the first folding roller.   
     
     
         13 . The apparatus according to  claim 12 , wherein the second folding roller includes:
 a second folding section configured to come into contact with the first folding section of the first folding roller and form the nip portion; and   a second groove configured to form the gap between the second groove and the first folding roller in a state in which the first folding section and the second folding section are in contact with each other.   
     
     
         14 . The apparatus according to  claim 13 , wherein the second groove is formed in a position where the end in the width direction of the sheet bundle of the predetermined size pushed in by the folding plate passes. 
     
     
         15 . The apparatus according to  claim 14 , wherein
 the predetermined size is a plurality of sizes, and   a plurality of the first and second grooves are formed for each of the predetermined sizes.   
     
     
         16 . The apparatus according to  claim 15 , further comprising an aligning member configured to align, before the sheet bundle is pushed by the folding plate, a width direction of the sheet bundle stacked by the stacker. 
     
     
         17 . The apparatus according to  claim 16 , further comprising:
 an acquiring section configured to acquire a size of a sheet stacked on the stacker; and   a controller configured to determine whether the size of the sheet acquired by the acquiring section corresponds to the predetermined size and, if the acquired size of the sheet does not correspond to the predetermined size, before the folding plate pushes the sheet bundle into the nip portion, move the sheet bundle to a predetermined position where at least one of both ends in a width direction of the sheet bundle passes the gap.   
     
     
         18 . The apparatus according to  claim 17 , wherein the controller moves the sheet bundle to the predetermined position via the aligning member.