Post-processing device and image forming apparatus

Abstract

A post-processing device includes a sheet-bundle forming unit that stacks plural sheets and forms a sheet bundle; a binding unit that forms a cut and a tongue in the sheet bundle and binds the sheet bundle by inserting the tongue into the cut; a transport unit that transports the sheet bundle; and a stack unit that stacks the sheet bundle. The binding unit includes first and second binding mechanisms that bind first and second sheet bundles at first and second sides in a direction intersecting with a transport direction of the sheet bundle, respectively. The post-processing device further includes an arrangement mechanism that arranges the first and second sheet bundles at different positions on the stack unit in the direction intersecting with the transport direction so that a tongue formed in one of the first and second sheet bundles is shifted from the other sheet bundle.

What is claimed is: 
     
         1 . A post-processing device, comprising:
 a sheet-bundle forming unit that stacks a plurality of sheets and forms a sheet bundle;   a binding unit that forms a cut in part of the sheet bundle formed by the sheet-bundle forming unit, forms a tongue in the sheet bundle by cutting part of the sheet bundle into a predetermined shape so that a first end remains uncut and continues to the sheet bundle, and binds the sheet bundle by folding the tongue and inserting a second end of the tongue into the cut;   a transport unit that transports the sheet bundle bound by the binding unit; and   a stack unit that stacks the sheet bundle transported by the transport unit,   wherein the binding unit includes
 a first binding mechanism that binds a first sheet bundle at a first side in a direction intersecting with a transport direction of the sheet bundle, and 
 a second binding mechanism that binds a second sheet bundle at a second side in the direction intersecting with the transport direction of the sheet bundle, and 
   wherein the post-processing device further comprises an arrangement mechanism that arranges the first sheet bundle bound by the first binding mechanism and the second sheet bundle bound by the second binding mechanism at different positions on the stack unit in the direction intersecting with the transport direction of the sheet bundle so that a tongue formed in one of the first and second sheet bundles respectively bound by the first and second binding mechanisms is shifted from the other sheet bundle.   
     
     
         2 . The post-processing device according to  claim 1 , wherein the arrangement mechanism arranges the first sheet bundle bound by the first binding mechanism at one of a plurality of positions on the stack unit in the direction intersecting with the transport direction of the sheet bundle so that the tongue of the first sheet bundle does not contact a tongue of another first sheet bundle. 
     
     
         3 . The post-processing device according to  claim 2 , wherein the arrangement mechanism arranges the second sheet bundle bound by the second binding mechanism at one of a plurality of positions on the stack unit in the direction intersecting with the transport direction of the sheet bundle so that the tongue of the second sheet bundle does not contact a tongue of another second sheet bundle. 
     
     
         4 . The post-processing device according to  claim 1 , wherein the binding unit binds the sheet bundle so that a longitudinal direction of the tongue inserted into the cut extends along the transport direction of the sheet bundle. 
     
     
         5 . The post-processing device according to  claim 1 , wherein the transport unit transports the sheet bundle in a direction in which the first end of the tongue of the sheet bundle bound by the binding unit is located downstream of the second end in the transport direction of the sheet bundle. 
     
     
         6 . The post-processing device according to  claim 1 , wherein the first binding mechanism binds the first sheet bundle so that a second end of the tongue formed by the first binding mechanism is arranged at one of front and back sides of the first sheet bundle on the stack unit and a second end of a tongue formed by the second binding mechanism is arranged at the other of front and back sides of the second sheet bundle on the stack unit. 
     
     
         7 . An image forming apparatus, comprising:
 an image forming mechanism that respectively forms a plurality of images on a plurality of sheets;   a sheet-bundle forming unit that stacks the plurality of sheets with the images formed by the image forming mechanism, and forms a sheet bundle;   a binding unit that forms a cut in part of the sheet bundle formed by the sheet-bundle forming unit, forms a tongue in the sheet bundle by cutting part of the sheet bundle into a predetermined shape so that a first end remains uncut and continues to the sheet bundle, and binds the sheet bundle by folding the tongue and inserting a second end of the tongue into the cut;   a transport unit that transports the sheet bundle bound by the binding unit; and   a stack unit that stacks the sheet bundle transported by the transport unit,   wherein the binding unit includes
 a first binding mechanism that binds a first sheet bundle at a first side in a direction intersecting with a transport direction of the sheet bundle, and 
 a second binding mechanism that binds a second sheet bundle at a second side in the direction intersecting with the transport direction of the sheet bundle, and 
   wherein the image forming apparatus further comprises an arrangement mechanism that arranges the first sheet bundle bound by the first binding mechanism and the second sheet bundle bound by the second binding mechanism at different positions on the stack unit in the direction intersecting with the transport direction of the sheet bundle so that a tongue formed in one of the first and second sheet bundles respectively bound by the first and second binding mechanisms is shifted from the other sheet bundle.   
     
     
         8 . The image forming apparatus according to  claim 7 ,
 wherein the binding unit includes
 the first binding mechanism that binds the first sheet bundle at the first side in the direction intersecting with the transport direction of the sheet bundle, and 
 the second binding mechanism that binds the second sheet bundle at the second side in the direction intersecting with the transport direction of the sheet bundle, and 
   wherein the image forming apparatus further comprises a rotation unit that rotates an orientation of the images formed on the sheets by the image forming mechanism, in accordance with whether the first binding mechanism performs the binding processing or the second binding mechanism performs the binding processing.   
     
     
         9 . The image forming apparatus according to  claim 8 , further comprising a switch unit that switches a formation order of the images on the sheets forming the sheet bundle by the image forming mechanism, in accordance with whether the first binding mechanism performs the binding processing or the second binding mechanism performs the binding processing.