Sheet post-processing device and image forming system provided with the same

Abstract

A sheet post-processing device comprises: a processing tray; a discharge tray; and a discharge rollers pair. The discharge rollers pair is constituted by a discharge roller which contacts the uppermost surface of sheets stacked in the processing tray and a discharge roller which contacts the lowermost surface of the sheets stacked in the processing tray). The sheet post-processing device discharges a sheet from the processing tray to the discharge tray by rotating the discharge rollers pair in the forward direction, and causes the sheet to be drawn into the processing tray by rotating the discharge roller in the reverse direction in a state in which the rotation of the discharge roller is stopped.

1 . A sheet post-processing device, comprising:
 a processing tray that accepts and loads thereon a prescribed number of sheets;   a discharge tray that is disposed on a downstream side of the processing tray in a sheet conveyance direction, and onto which sheets loaded on the processing tray are discharged; and   a discharge roller pair that is composed of a discharge roller that comes in contact with an uppermost surface of sheets loaded on the processing tray and a discharge roll that comes in contact with a lowermost surface of the sheets loaded on the processing tray,   wherein   a sheet is discharged from the processing tray onto the discharge tray by forwardly rotating the discharge roller pair, and a sheet is drawn in on the processing tray by reversely rotating the discharge roller in a state where the discharge roll is stopped from rotating.   
     
     
         2 . The sheet post-processing device according to  claim 1 , further comprising:
 a roller holder that is swingable and rotatably supports the discharge roller,   wherein the roller holder swings so that the discharge roller is selectively disposed at a retracted position away from the discharge roll and a contact position where the discharge roller comes in contact with the discharge roll.   
     
     
         3 . The sheet post-processing device according to  claim 2 , further comprising:
 a biasing member that biases the roller holder downward,   wherein in drawing in a sheet on the processing tray, the discharge roller is disposed at the contact position by using only a self-weight of the roller holder, and   in discharging a sheet onto the discharge tray, the discharge roller is disposed at the contact position by, besides using the self-weight of the roller holder, biasing the roller holder downward using the biasing member.   
     
     
         4 . The sheet post-processing device according to  claim 1 , wherein
 the discharge roll rotates forwardly following rotation of the discharge roller, and   a one-way mechanism is provided that restricts reverse rotation of the discharge roll.   
     
     
         5 . The sheet post-processing device according to  claim 1 , wherein
 the processing tray is provided so as to be inclined downward toward a downstream side with respect to a direction in which a sheet is drawn in on the processing tray.   
     
     
         6 . An image forming system, comprising:
 the sheet post-processing device according to  claim 1 ; and   an image forming apparatus that is joined to the sheet post-processing device, forms an image on a sheet, and conveys the sheet on which the image has been formed to the sheet post-processing device.