Sheet processing apparatus and sheet processing method

Abstract

A sheet is nipped and held by first and second bend forming rollers of which rotation axes are in a direction perpendicular to a sheet conveying direction, the conveying speed of the held portion is made lower than a sheet conveying speed on the upstream side so that a bend is formed on the sheet, the sheet is conveyed toward the bend forming rollers such that the sheet conveying direction to the bend forming rollers passes through a line segment from the rotation axis of the first bend forming roller to a predetermined position on a surface of the first bend forming roller, and the bend formed on the conveyed sheet is pressed from the surface of the sheet in a position on the opposite side of the second bend forming roller with respect to the position where the sheet is in contact with the first bend forming roller.

1 . (canceled) 
     
     
         2 . A sheet processing apparatus comprising:
 a pair of initial conveyance rollers configured to convey a sheet, the pair of initial conveyance rollers defining a virtual line extending along a conveyance path downstream from a first nip formed therebetween such that the virtual line delineates a first side and a second side, the first side and the second side extending perpendicular from the virtual line in opposite directions;   a pair of subsequent conveyance rollers configured to further convey the sheet after receiving the sheet from the pair of initial conveyance rollers by rotating in a forward direction, and to bend the sheet by rotating in a reverse direction while the pair of initial conveyance rollers hold the sheet to form a bent sheet, the pair of subsequent conveyance rollers including a first subsequent conveyance roller and a second subsequent conveyance roller with a second nip formed therebetween such that (i) a subsequent line segment (A) intersects a center of the first subsequent conveyance roller, a center of the second subsequent conveyance roller and the virtual line and, (ii) on an upstream side of the pair of subsequent conveyance rollers, an angle between the virtual line and the subsequent line segment on the first side forms an acute angle; and   a folding line forming unit configured to fold the bent sheet in a folding nip on the second side, the folding line forming unit including (I) a first dedicated folding line forming roller and (II) at least one of (i) a second dedicated folding line forming roller and (ii) the first subsequent conveyance roller.   
     
     
         3 . The sheet processing apparatus according to  claim 2 , wherein the folding line forming unit comprises:
 the first dedicated folding line forming roller and the first subsequent conveyance roller.   
     
     
         4 . The sheet processing apparatus according to  claim 2 , wherein the folding line forming unit comprises:
 the first dedicated folding line forming roller and the second dedicated folding line forming roller that are each independent rollers from the pair of subsequent conveyance rollers.   
     
     
         5 . The sheet processing apparatus according to  claim 2 , wherein
 the pair of initial conveyance rollers are separate rollers from rollers included in the folding line forming unit.   
     
     
         6 . The sheet processing apparatus according to  claim 2 , wherein
 a tangent line crosses the virtual line at an intersection point along a surface of the first subsequent conveyance roller such that, on the upstream side of the pair of subsequent conveyance rollers, the tangent line and the virtual line have one of a right angle and an obtuse angle therebetween.   
     
     
         7 . The sheet processing apparatus according to  claim 2 , wherein
 an initial line segment intersects a center of the first initial conveyance roller, intersects a center of the second subsequent conveyance roller and extends from an upper side of the virtual line opposite the folding line forming unit such that the initial line segment intersects the subsequent line segment on the upper side of the virtual line.   
     
     
         8 . The sheet processing apparatus according to  claim 2 , wherein
 a first straight lines intersects the first nip and the center of the first subsequent conveyance roller and a second straight line intersects the first nip and the second nip such that the virtual line is between the first straight line and the second straight line, and the virtual line intersects with a surface of first subsequent conveyance.   
     
     
         9 . The sheet processing apparatus according to  claim 2 , wherein
 the virtual line and the line segment intersect at an intersection point such that the intersection point therebetween is positioned closer to a third nip associated with the folding line forming unit than the second nip.   
     
     
         10 . A sheet processing apparatus comprising:
 a pair of initial conveyance rollers configured to convey a sheet, the pair of initial conveyance rollers including a first initial conveyance roller and a second initial conveyance roller such that an initial line segment intersects a center of the first initial conveyance roller and a center of the second initial conveyance roller, the pair of initial conveyance rollers defining a perpendicular line extending along a conveyance path downstream from a first nip formed therebetween such that the perpendicular line is perpendicular to the initial line segment and delineates a first side and a second side, the first side and the second side extending perpendicular from the perpendicular line in opposite directions;   a pair of subsequent conveyance rollers configured to convey the sheet conveyed from the pair of initial conveyance rollers by rotating in a forward direction, and to bend the sheet by rotating in a reverse direction while the pair of initial conveyance rollers hold the sheet to form a bent sheet, the pair of subsequent conveyance rollers including a first subsequent conveyance roller and a second subsequent conveyance roller with a second nip formed therebetween such that (i) a subsequent line segment intersects a center of the first subsequent conveyance roller, a center of the second subsequent conveyance roller and the perpendicular line, and (ii) on an upstream side of the pair of subsequent conveyance rollers, an angle between the perpendicular line and the subsequent line segment on the first side forms an acute angle; and   a folding line forming unit configured to fold the bent sheet in a folding nip on the second side, the folding line forming unit including (I) a first dedicated folding line forming roller and (II) at least one of (i) a second dedicated folding line forming roller and (ii) the first subsequent conveyance roller.   
     
     
         11 . The sheet processing apparatus according to  claim 10 , wherein the folding line forming unit comprises:
 the first dedicated folding line forming roller and the first subsequent conveyance roller.   
     
     
         12 . The sheet processing apparatus according to  claim 10 , wherein the folding line forming unit comprises:
 the first dedicated folding line forming roller and the second dedicated folding line forming roller that are each independent rollers from the pair of second conveyance rollers.   
     
     
         13 . The sheet processing apparatus according to  claim 10 , wherein
 the pair of first conveyance rollers are separate rollers from rollers included in the folding line forming unit.   
     
     
         14 . The sheet processing apparatus according to  claim 10 , wherein
 a tangent line crosses the perpendicular line at an intersection point along a surface of the first subsequent conveyance roller such that, on the upstream side of the pair of subsequent conveyance rollers, the tangent line and the perpendicular line have one of a right angle and an obtuse angle therebetween.   
     
     
         15 . The sheet processing apparatus according to  claim 10 , wherein
 an initial line segment intersects a center of the first initial conveyance roller, intersects a center of the second subsequent conveyance roller and extends from an upper side of the perpendicular line opposite the folding line forming unit such that the initial line segment intersects the subsequent line segment on the upper side of the perpendicular line.   
     
     
         16 . The sheet processing apparatus according to  claim 10 , wherein
 a first straight lines intersects the first nip and the center of the first subsequent conveyance roller and a second straight line intersects the first nip and the second nip such that the perpendicular line is between the first straight line and the second straight line, and the perpendicular line intersects with a surface of first subsequent conveyance.   
     
     
         17 . The sheet processing apparatus according to  claim 10 , wherein
 the perpendicular line and the line segment intersect at an intersection point such that the intersection point therebetween is positioned closer to a third nip associated with the folding line forming unit than the second nip.   
     
     
         18 . A sheet processing apparatus comprising:
 a pair of initial conveyance rollers configured to convey a sheet, the pair of initial conveyance rollers including a first initial conveyance roller and a second initial conveyance roller such that an initial line segment intersects a center of the first initial conveyance roller and a center of the second initial conveyance roller, the pair of initial conveyance rollers defining a perpendicular line extending along a conveyance path downstream from a first nip formed therebetween such that the perpendicular line is perpendicular to the initial line segment;   a pair of subsequent conveyance rollers configured to convey the sheet conveyed from the pair of initial conveyance rollers by rotating in a forward direction, and to bend the sheet by rotating in a reverse direction while the pair of initial conveyance rollers hold the sheet to form a bent sheet, the pair of subsequent conveyance rollers including a first subsequent conveyance roller and a second subsequent conveyance roller with a second nip formed therebetween such that (i) the perpendicular line intersects the first subsequent conveyance roller and (ii) the first nip is closer to a center of the second subsequent conveyance roller than to a center of the first subsequent conveyance roller; and   a folding line forming unit configured to fold the bent sheet in a folding nip, the folding line forming unit including (I) a first dedicated folding line forming roller and (II) at least one of (i) a second dedicated folding line forming roller and (ii) the first subsequent conveyance roller.   
     
     
         19 . The sheet processing apparatus according to  claim 18 , wherein the folding line forming unit comprises:
 the first dedicated folding line forming roller and the first subsequent conveyance roller.   
     
     
         20 . The sheet processing apparatus according to  claim 18 , wherein the folding line forming unit comprises:
 the first dedicated folding line forming roller and the second dedicated folding line forming roller that are each independent rollers from the pair of second conveyance rollers.   
     
     
         21 . The sheet processing apparatus according to  claim 18 , wherein the pair of first conveyance rollers are separate rollers from rollers included in the folding line forming unit.