Sheet processing apparatus and image forming system

Abstract

A conveyance unit conveys the sheet to an accumulation portion. A half-folding processing unit includes a folding roller pair and performs a half-folding process on the sheet bundle. A conveyance roller pair conveys the sheet bundle. A square back processing unit performs a square back process on the sheet bundle and includes a pair of clamp portions. A length of a conveyance path from the folding roller pair to the pair of clamp portions is larger than a half of a length of a long side of a sheet of a maximum size. In a state in which conveyance by the conveyance roller pair of a first sheet bundle to be subjected to the square back process is stopped, the conveyance unit conveys at least one sheet included in a second sheet bundle subsequent to the first sheet bundle toward the accumulation portion.

What is claimed is: 
     
         1 . A sheet processing apparatus comprising:
 an inlet portion configured to receive a sheet discharged from an image forming apparatus;   an accumulation portion configured to accumulate sheets;   a conveyance unit configured to convey the sheet received from the inlet portion to the accumulation portion;   a saddle binding unit configured to perform a saddle binding process on a sheet bundle including a plurality of sheets accumulated in the accumulation portion;   a half-folding processing unit including a folding roller pair and a pressing portion and configured to perform a half-folding process on the sheet bundle, the folding roller pair being configured to perform half-folding on the sheet bundle by conveying the sheet bundle while nipping the sheet bundle such that a spine of the sheet bundle is positioned downstream of a fore edge of the sheet bundle, the pressing portion being configured to press the sheet bundle, subjected to the saddle binding process by the saddle binding unit, toward a nip portion of the folding roller pair;   a conveyance roller pair configured to nip and convey the sheet bundle subjected to the half-folding process by the half-folding processing unit; and   a square back processing unit including a pair of clamp portions configured to relatively move with respect to the sheet bundle conveyed by the conveyance roller pair and thus nip the sheet bundle or release nipping of the sheet bundle and a pressing roller provided downstream of the pair of clamp portions in a conveyance direction of the conveyance roller pair and configured to press the spine of the sheet bundle nipped by the pair of clamp portions toward the pair of clamp portions,   wherein the square back processing unit is configured to perform a square back process in which a corner is formed on the spine of the sheet bundle by pressing, by the pressing roller, the spine of the sheet bundle nipped by the pair of clamp portions such that the spine of the sheet bundle protrudes downstream in the conveyance direction with respect to the pair of clamp portions,   wherein a length of a conveyance path from the folding roller pair to the pair of clamp portions is larger than a half of a length of a long side of a sheet of a maximum size capable of being subjected to the square back process by the square back processing unit, and   wherein in a state in which conveyance by the conveyance roller pair of a first sheet bundle to be subjected to the square back process is stopped, the conveyance unit is configured to convey at least one sheet included in a second sheet bundle subsequent to the first sheet bundle toward the accumulation portion.   
     
     
         2 . The sheet processing apparatus according to  claim 1 , further comprising:
 a temporary accumulation portion different from the accumulation portion and configured to temporarily accumulate sheets received from the inlet portion,   wherein the temporary accumulation portion is capable of accumulating at least one sheet included in the second sheet bundle, and   wherein the conveyance unit is configured to convey the at least one sheet included in the second sheet bundle and accumulated in the temporary accumulation portion toward the accumulation portion in the state in which conveyance of the first sheet bundle by the conveyance roller pair is stopped.   
     
     
         3 . The sheet processing apparatus according to  claim 2 , further comprising:
 another accumulation portion different from the accumulation portion and configured to accumulate sheets received from the inlet portion;   an end binding unit configured to perform a binding process on an end portion of a sheet bundle including a plurality of sheets accumulated in the other accumulation portion; and   a switching member configured to switch, between a first conveyance path and a second conveyance path, a path in which a sheet is conveyed,   wherein the first conveyance path is a conveyance path in which a sheet is conveyed from the inlet portion to the other accumulation portion, and the second conveyance path is a conveyance path in which a sheet is conveyed from the inlet portion to the accumulation portion, and   wherein the temporary accumulation portion branches from the first conveyance path at a position closer to the other accumulation portion than to the inlet portion with respect to the switching member.   
     
     
         4 . The sheet processing apparatus according to  claim 1 , further comprising:
 a sheet detection portion configured to detect presence or absence of a sheet in the accumulation portion,   wherein the conveyance unit is configured to start conveyance of at least one sheet included in the second sheet bundle toward the accumulation portion on a basis of a timing at which the half-folding process on the first sheet bundle accumulated in the accumulation portion is started and it is detected that no sheet is present in the accumulation portion by the sheet detection portion.   
     
     
         5 . The sheet processing apparatus according to  claim 1 ,
 wherein, in a case where a first virtual line and a second virtual line are set, the first virtual line being a line passing through a nip of the folding roller pair not nipping the sheet bundle and orthogonal to a first line passing through rotational centers of the folding roller pair and to a width direction of the sheet bundle, the second virtual line being a line passing through a nip of the conveyance roller pair not nipping the sheet bundle and orthogonal to a second line passing through rotational centers of the conveyance roller pair and to the width direction,   the conveyance roller pair is provided such that the second virtual line intersects with the first virtual line and the second virtual line is inclined downward in a vertical direction toward a downstream side in a conveyance direction of the folding roller pair, and   a conveyance path in which the sheet bundle is conveyed between the folding roller pair and the conveyance roller pair is bent such that the sheet bundle conveyed by the folding roller pair is passed on to the conveyance roller pair.   
     
     
         6 . The sheet processing apparatus according to  claim 1 , further comprising:
 another accumulation portion different from the accumulation portion and configured to accumulate a sheet received from the inlet portion;   an end binding unit configured to perform a binding process on an end portion of a sheet bundle including a plurality of sheets accumulated in the other accumulation portion; and   a stacking portion which is capable of moving up and down with respect to the other accumulation portion and configured to support thereon a sheet bundle subjected to the binding process by the end binding unit,   wherein a movement range of the stacking portion overlaps with the folding roller pair in a vertical direction.   
     
     
         7 . An image forming system comprising:
 an image forming unit including an image forming portion configured to form an image on a sheet; and   the sheet processing apparatus according to  claim 1 ,   wherein the sheet processing apparatus performs a square back process on a sheet bundle constituted by sheets on which images have been formed by the image forming portion.