Sheet discharge device, image forming system, and sheet post-processing device

Abstract

A present sheet post-processing device includes a first tray for stacking a sheet, a processing tray that temporarily stacks conveyed sheets until the number of the sheets reaches a predetermined number, and a discharge mechanism that discharges the sheets stacked on the processing tray onto the first tray. A sheet bundle forming unit divides, when forming a first sheet bundle on the first tray, sheets constituting the first sheet bundle into a plurality of sets and discharges the sheets a plurality of times for each set. At this time, a number of sheets included in a sheet set that constitutes a first sheet bundle and that is discharged at the first time is set smaller than a number of sheets included in a sheet set that constitutes a second sheet bundle and that is discharged at the first time.

What is claimed is: 
     
         1 . A sheet discharge device comprising:
 a first tray for stacking sheets; and   a sheet bundle forming unit that forms a sheet bundle on the first tray, wherein   when forming a first sheet bundle on the first tray, the sheet bundle forming unit divides sheets constituting the first sheet bundle into a plurality of sets and discharges the sheets a plurality of times for each set, and   a number of sheets included in a sheet set that constitutes a first sheet bundle and that is discharged at the first time is set smaller than a number of sheets included in a sheet set that constitutes a second sheet bundle and that is discharged at the first time.   
     
     
         2 . The sheet discharge device according to  claim 1 , wherein
 the sheet bundle forming unit has a buffer part that temporarily retains conveyed sheets until the number of the sheets reaches a predetermined number and a discharge mechanism that discharges the sheets retained in the buffer part onto the first tray.   
     
     
         3 . The sheet discharge device according to  claim 2 , further comprising a conveying path for sheet conveyance, wherein
 the buffer part serves as a second tray for temporarily stacking a sheet conveyed thereto through the conveying path.   
     
     
         4 . The sheet discharge device according to  claim 2 , further comprising a conveying path for sheet conveyance, wherein
 the buffer part serves as a diverging path formed so as to diverge from the conveying path.   
     
     
         5 . The sheet discharge device according to  claim 4 , wherein
 the discharge mechanism switchback-conveys a sheet temporarily retained in the diverging path in the direction opposite to a conveying direction of the sheet to discharge the sheet onto the first tray or switchback-conveys a sheet conveyed to the diverging path in the direction opposite to a conveying direction of the sheet to discharge the sheet onto the first tray through the conveying path.   
     
     
         6 . The sheet discharge device according to  claim 2 , further comprising a conveying path for sheet conveyance, wherein
 the buffer part serves as a second tray for temporarily stacking a sheet conveyed thereto through the conveying path, and   the discharge mechanism discharges a first sheet conveyed thereto through the conveying path onto the first tray as a first sheet set and discharges a sheet temporarily stacked on the second tray onto the first tray as a second or subsequent sheet set.   
     
     
         7 . The sheet discharge device according to  claim 1 , wherein
 when forming a first sheet bundle in one job on the first tray, the sheet bundle forming unit divides sheets constituting the first sheet bundle into a plurality of sets and discharges the sheets a plurality of times such that the number of sheets included in a sheet set that constitutes a first sheet bundle and that is discharged at the first time is set smaller than the number of sheets included in a sheet set that constitutes a second sheet bundle and that is discharged at the first time in the job.   
     
     
         8 . The sheet discharge device according to  claim 1 , further comprising a detection unit that detects presence/absence of a sheet on the first tray, wherein
 when forming, after the detection unit detects that there is no sheet on the first tray, the first sheet bundle to be discharged, the sheet bundle forming unit discharges sheets a plurality of times such that the number of sheets included in a sheet set that constitutes a first sheet bundle and that is discharged at the first time is set smaller than the number of sheets included in a sheet set that constitutes a second sheet bundle and that is discharged at the first time.   
     
     
         9 . An image forming system comprising:
 an image forming unit that forms an image onto a sheet;   a first tray for stacking sheets on each of which an image is formed by the image forming unit; and   a sheet bundle forming unit that forms a sheet bundle on the first tray, wherein   when forming a sheet bundle on the first tray, the sheet bundle forming unit divides sheets constituting the sheet bundle into a plurality of sets and discharges the sheets a plurality of times for each set, and   a number of sheets included in a sheet set that constitutes a first sheet bundle and that is discharged at the first time is set smaller than a number of sheets included in a sheet set that constitutes a second sheet bundle and that is discharged at the first time.