Sheet folder, post-processing apparatus, image forming apparatus, and image forming system

Abstract

A sheet folder includes a conveyance roller pair, first, second and third folding rollers, a guide, and circuitry. The conveyance roller pair conveys a sheet in a conveyance direction at a first speed. The first folding roller is downstream from the conveyance roller pair. The second and third folding rollers are in contact with the first folding roller to form first and second nips, respectively, with the first folding roller, and rotate along with the first folding roller. The guide is between the conveyance roller pair and the first nip in the conveyance direction, and is changeable between first and second postures. The circuitry is to control the guide to guide the sheet to the first nip and change the posture to the second posture to fold the sheet into the second nip, and control the first folding roller to rotate at a second speed and folds the sheet.

1 . A sheet folder comprising:
 a conveyance roller pair to convey a sheet in a conveyance direction at a first speed;   a first folding roller downstream from the conveyance roller pair in the conveyance direction;   a second folding roller in contact with the first folding roller to form a first nip with the first folding roller, the second folding roller to rotate along with the first folding roller;   a third folding roller in contact with the first folding roller to form a second nip with the first folding roller, the third folding roller to rotate along with the first folding roller;   a guide, between the conveyance roller pair and the first nip in the conveyance direction, the guide being changeable between:
 a first posture to guide the sheet from the conveyance roller pair to the first nip; and 
 a second posture to guide the sheet from the conveyance roller pair to the second nip; and 
   circuitry configured to:   control the guide at the first posture to guide the sheet from the conveyance roller pair to the first nip;   control the guide to change the posture from the first posture to the second posture to fold the sheet into the second nip while the first nip nips the sheet; and   control the first folding roller to rotate at a second speed faster than the first speed of the conveyance roller pair while the second nip nips and folds the sheet.   
     
     
         2 . The sheet folder according to  claim 1 ,
 wherein the circuitry is further configured to:   control the guide at the second posture to guide the sheet from the conveyance roller pair to the second nip;   control the guide to change the posture from the second posture to the first posture to fold the sheet into the first nip while the second nip nips the sheet.   
     
     
         3 . The sheet folder according to  claim 1 ,
 wherein the circuitry is further configured to:   rotate the conveyance roller pair and the first folding roller in a forward direction while the first nip or the second nip nips and folds the sheet to convey the sheet in the conveyance direction; and   rotate the conveyance roller pair and the first folding roller in a reverse direction opposite to the forward direction while the first nip or the second nip nips and folds the sheet.   
     
     
         4 . The sheet folder according to  claim 1 , further comprising:
 a return conveyance path to convey the sheet, nipped between the first folding roller and the third folding roller, from the second nip to an upstream of the conveyance roller pair in the conveyance direction.   
     
     
         5 . The sheet folder according to  claim 4 ,
 wherein the second folding roller faces the first folding roller across a main conveyance path in the conveyance direction,   the third folding roller faces the first folding roller across the return conveyance path branched from the main conveyance path at a branching portion upstream from the first nip in the conveyance direction, and   the return conveyance path joins the main conveyance path at a joining portion upstream from the conveyance roller pair in the conveyance direction, and   the circuitry is further configured to:   control the conveyance roller pair to rotate in a forward direction to convey the sheet in the conveyance direction;   control the first folding roller to rotate in a forward direction to:
 convey the sheet nipped by the first nip in the conveyance direction; and 
 convey the sheet nipped by the second nip from the return conveyance path to the main conveyance path; and 
   control the first folding roller to rotate in a reverse direction opposite to the forward direction to:
 convey the sheet nipped by the first nip in a direction opposite to the conveyance direction; and 
 convey the sheet nipped by the second nip to the return conveyance path. 
   
     
     
         6 . The sheet folder according to  claim 5 ,
 wherein the circuitry is further configured to:   change the guide to the first posture to rotate the conveyance roller pair and the first folding roller at conveyance speeds equal to each other in the forward direction, before a leading end of the sheet passes through the first nip and a folding position of the sheet reaches a given position;   change the guide from the first posture to the second posture in response to arrival of the folding position of the sheet to the given position to rotate the first folding roller in the reverse direction until the folding position of the sheet passes through the second nip, to fold the sheet at the folding position; and   rotate the conveyance roller pair in the forward direction while changing the guide from the second posture to the first posture and rotate the first folding roller in the forward direction at a conveyance speed faster than a conveyance speed of the conveyance roller pair, in response to passage of the folding position of the sheet through the second nip, to unfold a fold line of the sheet at the folding position and eject the sheet.   
     
     
         7 . The sheet folder according to  claim 6 ,
 wherein the circuitry is further configured to:   fold the sheet at multiple folding positions including the folding position shifted in the conveyance direction; and   unfold a fold line at each of the multiple folding positions and eject the sheet.   
     
     
         8 . The sheet folder according to  claim 5 ,
 wherein the circuitry is further configured to:   change the guide to the second posture to rotate the conveyance roller pair in the forward direction and the first folding roller in the reverse direction, before a leading end of the sheet passes through the second nip and a folding position of the sheet reaches a given position;   change the guide from the first posture to the second posture in response to arrival of the folding position of the sheet to the given position to rotate the first folding roller in the forward direction until the folding position of the sheet passes through the first nip, to fold the sheet at the folding position;   rotate the conveyance roller pair in the forward direction while changing the guide from the first posture to the second posture until a given time elapses and rotate the first folding roller in the reverse direction at a conveyance speed faster than a conveyance speed of the conveyance roller pair, in response to passage of the folding position of the sheet through the first nip, to unfold a fold line of the sheet at the folding position and convey the sheet to the return conveyance path; and   change the guide from the second posture to the first posture in response to elapse of the given time to rotate the conveyance roller pair and the first folding roller in the forward direction at conveyance speeds equal to each other, to eject the sheet.   
     
     
         9 . The sheet folder according to  claim 1 ,
 wherein multiple sheets including the sheet is sequentially conveyed from an image forming device, and   the circuitry is further configured to:   cause multiple sheets including the sheet to be sequentially conveyed; and   shift respective folding positions of the multiple sheets in the conveyance direction of the sheet.   
     
     
         10 . A post-processing apparatus comprising:
 the sheet folder according to  claim 1 ; and   a sheet binder to bundle multiple sheets including the sheet provided with a fold line folded by the sheet folder.   
     
     
         11 . An image forming apparatus comprising:
 an image forming device to form an image on a sheet; and   the sheet folder according to  claim 1  to provide a fold line on the sheet on which the image is formed by the image forming device.   
     
     
         12 . An image forming system comprising:
 an image forming apparatus to form an image on a sheet;   a conveyance roller pair to convey a sheet in a conveyance direction of the sheet that has passed the image forming apparatus at a first speed;   a first folding roller downstream from the conveyance roller pair in the conveyance direction;   a second folding roller in contact with the first folding roller to form a first nip with the first folding roller, the second folding roller to rotate along with the first folding roller;   a third folding roller in contact with the first folding roller to form a second nip with the first folding roller, the third folding roller to rotate along with the first folding roller;   a guide between the conveyance roller pair and the first nip in the conveyance direction to change a posture between a first posture that guides the sheet to the first nip and a second posture that guides the sheet to the second nip; and   circuitry configured to:   control the guide at the first posture to guide the sheet from the conveyance roller pair to the first nip;   control the guide to change the posture from the first posture to the second posture to fold the sheet into the second nip while the first nip nips the sheet; and   control the first folding roller to rotate at a second speed faster than the first speed of the conveyance roller pair while the second nip nips and folds the sheet.   
     
     
         13 . The image forming system according to  claim 12 ,
 wherein the circuitry is further configured to:   control the guide at the second posture to guide the sheet from the conveyance roller pair to the second nip; and   control the guide to change the posture from the second posture to the first posture to fold the sheet into the first nip while the second nip nips the sheet.   
     
     
         14 . A sheet folder comprising:
 a conveyance roller pair to convey a sheet in a conveyance direction at a first speed;   a first folding roller downstream from the conveyance roller pair in the conveyance direction;   a second folding roller in contact with the first folding roller to form a first nip with the first folding roller, the second folding roller to rotate along with the first folding roller;   a third folding roller in contact with the first folding roller to form a second nip with the first folding roller, the third folding roller to rotate along with the first folding roller; and   a guide, downstream from the conveyance roller pair in the conveyance direction and having a first guide face facing a first face of the sheet and a second guide face facing a second face of the sheet, the guide being changeable between:
 a first posture to guide the sheet from the conveyance roller pair to the first nip; and 
 a second posture that guides the sheet from the conveyance roller pair to the second nip, 
   wherein the guide is configured to:   guide the sheet at the first posture from the conveyance roller pair to the first nip, and   change the posture from the first posture to the second posture to fold the sheet into the second nip while the first nip nips the sheet; or   guide the sheet at the first posture from the conveyance roller pair to the second nip, and   change the posture from the second posture to the first posture to fold the sheet into the first nip while the second nip nips the sheet.   
     
     
         15 . The sheet folder according to  claim 14 ,
 wherein the first guide face and the second guide face have an interval having an upstream side greater than a downstream side in the conveyance direction.   
     
     
         16 . An image forming apparatus comprising:
 an image forming device to form an image on a sheet; and   the sheet folder according to  claim 14  to provide a fold line on the sheet on which the image is formed by the image forming device.