Paper Sheet Stacking Apparatus and Image Forming System

Abstract

A paper sheet stacking apparatus, includes: a first tray that stacks a paper sheet; a sheet discharger that discharges a paper sheet supplied from the outside of the apparatus to the first tray; a second tray that receives the paper sheet stacked on the first tray and discharges the received paper sheet to the outside of the apparatus; and a hardware processor that controls operation states of the first tray and the second tray, wherein the first tray and the second tray have: a first operation state in which the first tray is positioned at a paper sheet stacking position; a second operation state in which the paper sheet stacked on the first tray is deliverable to the second tray; and a third operation state in which the first tray that has delivered the paper sheet to the second tray is returned to the paper sheet stacking position.

What is claimed is: 
     
         1 . A paper sheet stacking apparatus, comprising:
 a first tray that stacks a paper sheet;   a sheet discharger that discharges a paper sheet supplied from the outside of the paper sheet stacking apparatus to the first tray;   a second tray that receives the paper sheet stacked on the first tray and discharges the received paper sheet to the outside of the paper sheet stacking apparatus; and   a hardware processor that controls operation states of the first tray and the second tray,   wherein the first tray and the second tray have:   a first operation state in which the first tray is positioned at a paper sheet stacking position at which the paper sheet discharged from the sheet discharger is stacked and the second tray is positioned below the first tray;   a second operation state in which an upper surface of the second tray is positioned above an upper surface of the first tray and the paper sheet stacked on the first tray is deliverable to the second tray; and   a third operation state in which the first tray that has delivered the paper sheet to the second tray is returned to the paper sheet stacking position.   
     
     
         2 . The paper sheet stacking apparatus according to  claim 1 , wherein each of the first tray and the second tray includes a clearance for passing the other tray so that the first tray and the second tray do not interfere with each other on the same plane. 
     
     
         3 . The paper sheet stacking apparatus according to  claim 1 , wherein the first tray reaches a paper sheet delivery position according to a height of the second tray, whereby the first operation state changes to the second operation state. 
     
     
         4 . The paper sheet stacking apparatus according to  claim 3 , wherein in the first operation state, the second tray is positioned below the first tray, and
 the first tray lowers, whereby the first operation state changes to the second operation state.   
     
     
         5 . The paper sheet stacking apparatus according to  claim 3 , wherein a plurality of the second trays is stacked in an up-and-down direction, and the paper sheet delivery position is switched according to a height of the second tray positioned at an uppermost position. 
     
     
         6 . The paper sheet stacking apparatus according to  claim 1 , further comprising a pedestal part that moves between the inside of the paper sheet stacking apparatus and the outside of the paper sheet stacking apparatus, wherein
 the second tray is mounted on the pedestal part.   
     
     
         7 . The paper sheet stacking apparatus according to  claim 6 , wherein the second tray is mounted on the pedestal part in an attachable and detachable manner. 
     
     
         8 . The paper sheet stacking apparatus according to  claim 1 , further comprising a carriage on which the second tray is mounted and that conveys the second tray, wherein
 the carriage is accommodatable inside the paper sheet stacking apparatus.   
     
     
         9 . The paper sheet stacking apparatus according to  claim 1 , further comprising a carriage on which the second tray discharged to the outside of the paper sheet stacking apparatus is mounted and that conveys the second tray. 
     
     
         10 . The paper sheet stacking apparatus according to  claim 1 , wherein the second tray reaches a paper sheet delivery position according to the height of the first tray, whereby the first operation state changes to the second operation state. 
     
     
         11 . The paper sheet stacking apparatus according to  claim 1 , wherein each of the first tray and the second tray reaches a predetermined paper sheet delivery position, whereby the first operation state changes to the second operation state. 
     
     
         12 . An image forming system, comprising:
 an image forming apparatus that discharges a paper sheet on which an image is formed; and   the paper sheet stacking apparatus according to  claim 1  in which the paper sheet discharged from the image forming apparatus is stacked.