Post-processing apparatus

Abstract

A post-processing apparatus includes a processing tray for stacking a sheet and a detection sensor for detecting the presence or absence of the sheet placed on the processing tray. The post-processing apparatus includes a pinch roller for moving towards the processing tray if the detection sensor does not detect the sheet, and a longitudinal alignment roller configured to rotate by a predetermined amount while sandwiching the sheet in the processing tray with the pinch roller to elongate the sheet. By holding a rear end of the sheet in the processing tray with a paddle section and elongating the sheet towards the downstream side with the longitudinal alignment roller, the presence or absence of the sheet is detected by the detection sensor.

1 . A post-processing apparatus, comprising:
 a processing tray configured to stack a sheet;   a detection sensor disposed on the processing tray and configured to detect a presence or an absence of the sheet placed on the processing tray;   a conveyance roller configured to convey the sheet on the processing tray;   a pressing roller configured to move to the conveyance roller when the detection sensor does not detect the sheet; and   a controller configured to control the conveyance roller to rotate by a predetermined amount while sandwiching the sheet between the conveyance roller and the pressing roller in the processing tray.   
     
     
         2 . The post-processing apparatus according to  claim 1 , further comprising:
 a paddle configured to hold the sheet at an upstream side of the conveyance roller in the processing tray.   
     
     
         3 . The post-processing apparatus according to  claim 2 , wherein the paddle is configured to rotate to convey the sheet to the upstream side. 
     
     
         4 . The post-processing apparatus according to  claim 2 , wherein
 the paddle is configured to hold a load which is larger than a conveyance force of the conveyance roller.   
     
     
         5 . The post-processing apparatus according to  claim 3 , wherein
 the paddle is configured to hold a load which is larger than a conveyance force of the conveyance roller.   
     
     
         6 . The post-processing apparatus according to  claim 1 , wherein:
 the controller is configured to cause the conveyance roller to repeatedly rotate by a predetermined amount, and   the detection sensor is configured to repeatedly detect the absence or the presence of the sheet.   
     
     
         7 . A method of performing post-processing of a sheet, comprising:
 arranging the sheet on a processing tray;   detecting, by a detection sensor disposed on the processing tray, a presence or an absence of the sheet on the processing tray;   conveying, by a conveyance roller, the sheet on the processing tray;   moving a pressing roller to the conveyance roller when the detection sensor detects that the sheet is absent;   causing, by a controller, rotation of the conveyance roller by a predetermined amount, and   sandwiching the sheet between the conveyance roller and the pressing roller in the processing tray while the conveyance roller rotates.   
     
     
         8 . The method according to  claim 7 , further comprising:
 holding the sheet by a paddle at an upstream side of the conveyance roller.   
     
     
         9 . The method according to  claim 8 , further comprising:
 rotating the paddle to convey the sheet to the upstream side of the conveyance roller.   
     
     
         10 . The method according to  claim 8 , further comprising:
 holding, by the paddle, a load which exceeds a conveyance force of the conveyance roller.   
     
     
         11 . The method according to  claim 9 , further comprising:
 holding, by the paddle, a load which exceeds a conveyance force of the conveyance roller.   
     
     
         12 . The method according to  claim 7 , further comprising:
 repeating rotation of the conveyance roller, so as to cause the conveyance roller to rotate by a predetermined amount a plurality of times, and   repeating detection by the detection sensor of the absence or the presence of the sheet.   
     
     
         13 . A post-processing system, comprising:
 a processing tray configured to receive at least one sheet;   a controller configured to receive information indicative of whether the at least one sheet is present in the processing tray from a sensor disposed on the processing tray;   a first roller and a second roller,   the first roller being configured to rotate by a predetermined amount when the at least one sheet is sandwiched between the first roller and the second roller in the processing tray,. wherein the controller is configured to control rotation of the first roller by the predetermined amount   the second roller being configured to move to the first roller when the at least one sheet is not detected on the processing tray; and   a paddle configured to hold the at least one sheet upstream of the first roller in the processing tray, and to press a rear end of the at least one sheet in a direction toward the processing tray when the at least one sheet moves from a standby tray to the processing tray.