Sheet finishing apparatus and sheet finishing method

Abstract

A sheet finishing apparatus includes an outer wall having a discharge port of sheets; a movable tray on which the sheets discharged from the discharge port are stacked, the movable tray vertically moving along the outer wall according to a stack amount of the sheets; a curl sensor that detects a curled state of the sheets before the sheets are discharged from the discharge port; and a control unit that controls at least one of a discharge speed of the sheets and a position of the movable tray according to the detected curled state of the sheets.

1 . A sheet finishing apparatus comprising:
 an outer wall having a discharge port of sheets;   a movable tray on which the sheets discharged from the discharge port are stacked, the movable tray vertically moving along the outer wall according to a stack amount of the sheets;   a curl sensor that detects a curled state of the sheets before the sheets are discharged from the discharge port; and   a control unit that controls at least one of a discharge speed of the sheets and a position of the movable tray according to the detected curled state of the sheets.   
     
     
         2 . The device according to  claim 1 , wherein
 the curl sensor detects whether the sheet is in a downward curled state in which both ends or one end of the sheet is downward curved, an upward curled state in which both ends or one end of the sheet is upward curved, or a state in which the sheet is not curled.   
     
     
         3 . The device according to  claim 2 , wherein
 the curl sensor further detects the amount of upward or downward curl.   
     
     
         4 . The device according to  claim 2 , wherein
 when the sheet is downward curled, the control unit sets a discharge speed to be lower than a standard discharge speed when the sheet is not curled, and   when the sheet is upward curled, the control unit sets the discharge speed to be higher than the standard discharge speed.   
     
     
         5 . The device according to  claim 3 , wherein
 when the sheet is downward curled, the control unit sets a discharge speed to be lower than the standard discharge speed by a speed proportional to the amount of downward curl, and   when the sheet is upward curled, the control unit sets the discharge speed to be higher than the standard discharge speed by a speed proportional to the amount of upward curl.   
     
     
         6 . The device according to  claim 2 , wherein
 when the sheet is downward or upward curled, the control unit sets a height difference between a highest position of the sheets stacked on the movable tray and a position of the discharge port to be smaller than a standard height difference when the sheet is not curled.   
     
     
         7 . The device according to  claim 3 , wherein
 when the sheet is downward or upward curled, the control unit sets a height difference between a highest position of the sheets stacked on the movable tray and a position of the discharge port to be smaller than a standard height difference when the sheet is not curled by an amount proportional to the amount of curl.   
     
     
         8 . The device according to  claim 1 , wherein
 the curl sensor is a reflective optical sensor disposed on a transport path through which the sheets pass before being discharged from the discharge port, and detects that the sheets are downward curled, upward curled, or not curled, from a pattern of a change in reflection intensity with time while the sheets pass through the transport path.   
     
     
         9 . The device according to  claim 2 , wherein
 when a given number of downward curled sheets are consecutively discharged, the control unit sets a maximum stack amount of the movable tray to be smaller than a maximum stack amount set at that time, and when a total number of sheets stacked on the movable tray arrives at the set maximum stack amount, the control unit stops the discharge of the sheets.   
     
     
         10 . The device according to  claim 2 , wherein
 when a given number of upward curled sheets are consecutively discharged, the control unit sets a maximum stack amount of the movable tray to be larger than a maximum stack amount set at that time, and when a total number of sheets stacked on the movable tray arrives at the set maximum stack amount, the control unit stops the discharge of the sheets.   
     
     
         11 . A sheet finishing method comprising:
 providing an outer wall having a discharge port of sheets;   vertically moving a movable tray on which the sheets discharged from the discharge port are stacked, along the outer wall having the discharge port according to a stack amount of the sheets;   detecting a curled state of the sheets before the sheets are discharged from the discharge port by a curl sensor; and   controlling at least one of a discharge speed of the sheets and a position of the movable tray according to the curled state of the sheets, which is detected by the curl sensor.   
     
     
         12 . The method according to  claim 11 , wherein
 whether the sheet is in a downward curled state in which both ends or one end of the sheet is downward curved, an upward curled state in which both ends or one end of the sheet is upward curved, or a state in which the sheet is not curled, is detected by the curl sensor.   
     
     
         13 . The method according to  claim 12 , further comprising:
 detecting the amount of upward or downward curl by the curl sensor.   
     
     
         14 . The method according to  claim 12 , wherein
 when the sheet is downward curled, a discharge speed is set to be lower than a standard discharge speed when the sheet is not curled, and   when the sheet is upward curled, the discharge speed is set to be higher than the standard discharge speed.   
     
     
         15 . The method according to  claim 13 , wherein
 when the sheet is downward curled, a discharge speed is set to be lower than the standard discharge speed by a speed proportional to the amount of downward curl, and   when the sheet is upward curled, the discharge speed is set to be higher than the standard discharge speed by a speed proportional to the amount of upward curl.   
     
     
         16 . The method according to  claim 12 , wherein
 when the sheet is downward or upward curled, a height difference between a highest position of the sheets stacked on the movable tray and a position of the discharge port is set to be smaller than a standard height difference when the sheet is not curled.   
     
     
         17 . The method according to  claim 13 , wherein
 when the sheet is downward or upward curled, a height difference between a highest position of the sheets stacked on the movable tray and a position of the discharge port is set to be smaller than a standard height difference when the sheet is not curled by an amount proportional to the amount of curl.   
     
     
         18 . The method according to  claim 11 , wherein
 the curl sensor is a reflective optical sensor disposed on a transport path through which the sheets pass before being discharged from the discharge port, and detects that the sheets are downward curled, upward curled, or not curled, from a pattern of a change in reflection intensity with time while the sheets pass through the transport path.   
     
     
         19 . The method according to  claim 12 , wherein
 when a given number of downward curled sheets are consecutively discharged, a maximum stack amount of the movable tray is set to be smaller than a maximum stack amount set at that time, and when a total number of sheets stacked on the movable tray arrives at the set maximum stack amount, the discharge of the sheets stops.   
     
     
         20 . The method according to  claim 12 , wherein
 when a given number of upward curled sheets are consecutively discharged, a maximum stack amount of the movable tray is set to be larger than a maximum stack amount set at that time, and when a total number of sheets stacked on the movable tray arrives at the set maximum stack amount, the discharge of the sheets stops.