Sheet processing apparatus and image forming system having the same

Abstract

To provide a sheet processing apparatus capable of preventing interference between a next sheet to be conveyed and a discharge claw member after a sheet bundle is discharged by the discharge claw member and reducing the occurrence of a conveyance jam due to curling or buckling of the front end of the next sheet. A sheet processing apparatus includes: a first support guide integrally provided at the upstream end portion in a sheet conveying direction of a discharge unit, which discharges a sheet placed on a processing tray by pushing the rear end portion of the sheet in the sheet conveying direction, and configured to support the downstream front end portion in the conveying direction of a sheet to be conveyed onto the processing tray; and an aligning unit that aligns the sheet on the processing tray in a sheet width direction perpendicular to the conveying direction.

1 . A sheet processing apparatus comprising:
 a conveying unit that conveys a sheet in a predetermined conveying direction;   a processing tray on which the sheet conveyed by the conveying unit is placed;   a discharge unit that discharges the sheet placed on the processing tray by pushing a rear end portion of the sheet in the sheet conveying direction;   a stack tray on which the sheet discharged by the discharge unit is placed;   an aligning unit that aligns the sheet on the processing tray in a sheet width direction perpendicular to the conveying direction;   a first support guide integrally provided at an upstream end portion of the discharge unit in the conveying direction and configured to support a downstream front end portion in the conveying direction of a sheet to be conveyed onto the processing tray; and   a controller that controls the discharge unit and aligning unit, wherein   the controller controls, after a sheet is discharged from the processing tray to the stack tray, the first support guide to support the downstream front end portion in the conveying direction of a next sheet to convey the sheet onto the processing tray.   
     
     
         2 . The sheet processing apparatus according to  claim 1 , wherein
 the discharge unit is configured to reciprocate between a waiting position not to contact the sheet on the processing tray and a discharge position to discharge the sheet on the processing tray to the stack tray, and   the controller controls the discharge unit to return to the waiting position at a first timing after it reaches the discharge position, when the size of the sheet is equal to or more than a predetermined value, and controls the discharge unit to return to the waiting position at a second timing later than the first timing after it reaches the discharge position, when the size of the sheet is less than a predetermined value.   
     
     
         3 . The sheet processing apparatus according to  claim 1 , wherein
 in a shift mode to shift the sheet placed on the processing tray with the aligning unit in the width direction by a predetermined distance, the controller controls, after a sheet is discharged from the processing tray to the stack tray, the second support guide to support the downstream front end portion in the conveying direction of a next sheet to convey the sheet onto the processing tray, and   in a straight discharge mode to discharge the sheet placed on the processing tray to the stack tray without shifting the sheet, the controller controls, after a sheet is discharged from the processing tray to the stack tray, the first support guide to support the downstream front end portion in the conveying direction of a next sheet to be conveyed onto the processing tray.   
     
     
         4 . The sheet processing apparatus according to  claim 3 , wherein
 the discharge unit is configured to reciprocate between a waiting position not to contact the sheet on the processing tray and a discharge position to discharge the sheet on the processing tray to the stack tray, and   the controller controls the discharge unit to return to the waiting position at a first timing after it reaches the discharge position, when the basis weight of the sheet is equal to or more than a predetermined value, and controls the discharge unit to return to the waiting position at a second timing later than the first timing after it reaches the discharge position, when the basis weight of the sheet is less than a predetermined value.   
     
     
         5 . The sheet processing apparatus according to  claim 3 , further comprising a conveying detection unit that detects a sheet conveying amount by the sheet conveying unit, wherein
 the controller sets, based on the conveying amount detected by the conveying detection unit, the second timing to an estimated time point or later at which, after the discharge unit reaches the discharge position, the downstream front end portion in the conveying direction of a next sheet to be discharged onto the processing tray reaches the first support guide.   
     
     
         6 . The sheet processing apparatus according to  claim 4 , wherein
 the discharge unit includes a first discharge claw that moves within a first section in the conveying direction and a second discharge claw configured to be movable at the downstream side of the first section in the conveying direction by the same drive source as that for the first discharge claw, and   the first support guide is provided on the second discharge claw.   
     
     
         7 . An image forming system comprising:
 an image forming apparatus that forms an image on a sheet; and   a sheet processing apparatus that stacks and processes sheets fed from the image forming apparatus, wherein   the sheet processing apparatus is the apparatus as claimed in  claim 1 .