Image forming apparatus, sheet finisher, and method for driving stacking tray

Abstract

An image forming apparatus according to the present invention includes a printer, a stapler, a stacking tray, a driving mechanism, a detecting unit, a storage unit, and a controller. The printer prints image data on a sheet. The stapler staples a sheet bundle including the sheet. The stacking tray receives the sheet bundle at a standby position. The driving mechanism lifts and lowers the stacking tray. The detecting unit detects an upper surface of the sheet bundle on the stacking tray. The storage unit stores number of sheet bundles on the stacking tray. The controller controls the driving mechanism to increase a distance from the detecting unit to the stacking tray at the standby position according to an increase in the number stored in the storage unit.

1 . An image forming apparatus comprising:
 a printer configured to print image data on a sheet;   a stapler configured to staple a sheet bundle, the sheet bundle including the sheet;   a stacking tray configured to receive the sheet bundle at a standby position;   a driving mechanism configured to lift and lower the stacking tray;   a detecting unit configured to detect an upper surface of the sheet bundle on the stacking tray;   a storage unit configured to store the number of sheet bundles on the stacking tray; and   a controller configured to control the driving mechanism to increase a distance from the detecting unit to the stacking tray at the standby position according to an increase in the number stored in the storage unit.   
     
     
         2 . The apparatus according to  claim 1 , wherein the storage unit stores the number of sheets included in the sheet bundle, and the controller controls the driving mechanism to reduce the distance according to an increase in the number of sheets included in the sheet bundle stored in the storage unit. 
     
     
         3 . The apparatus according to  claim 1 , wherein the controller controls the driving mechanism to increase the distance according to an increase in a size of the sheet. 
     
     
         4 . The apparatus according to  claim 1 , wherein the controller controls the driving mechanism to keep the distance if the number is equal to or smaller than a specified value. 
     
     
         5 . The apparatus according to  claim 1 , wherein the controller controls the driving mechanism to change the distance corresponding to a thickness of a plurality of sheet bundles. 
     
     
         6 . A sheet finisher comprising:
 a stapler configured to staple a sheet bundle, the sheet bundle including a sheet;   a stacking tray configured to receive the sheet bundle at a standby position;   a driving mechanism configured to lift and lower the stacking tray;   a detecting unit configured to detect an upper surface of the sheet bundle on the stacking tray;   a storage unit configured to store number of sheet bundles on the stacking tray; and   a controller configured to control the driving mechanism to increase a distance from the detecting unit to the stacking tray at the standby position according to an increase in the number stored in the storage unit.   
     
     
         7 . The finisher according to  claim 6 , wherein the storage unit stores the number of sheets included in the sheet bundle, and the controller controls the driving mechanism to reduce the distance according to an increase in the number of sheets included in the sheet bundle stored in the storage unit. 
     
     
         8 . The finisher according to  claim 6 , wherein the controller controls the driving mechanism to increase the distance according to an increase in a size of the sheet. 
     
     
         9 . The finisher according to  claim 6 , wherein the controller controls the driving mechanism to keep the distance if the number is equal to or smaller than a specified value. 
     
     
         10 . The finisher according to  claim 6 , wherein the controller controls the driving mechanism to change the distance corresponding to a thickness of a plurality of sheet bundles. 
     
     
         11 . A method for driving a stacking tray comprising acts of:
 stapling a sheet bundle, the sheet bundle including a sheet; and   controlling driving of a stacking tray to increase a distance from a detecting unit that detects an upper surface of the sheet bundle on the stacking tray to the stacking tray at a standby position according to an increase in number of sheet bundles on the stacking tray.   
     
     
         12 . The method according to  claim 11 , wherein the act of controlling controls the driving of the stacking tray to reduce the distance according to an increase in the number of sheets included in the sheet bundle. 
     
     
         13 . The method according to  claim 11 , wherein the act of controlling controls the driving of the stacking tray to increase the distance according to an increase in a size of the sheet. 
     
     
         14 . The method according to  claim 11 , wherein the act of controlling controls the driving of the stacking tray to keep the distance if the number is equal to or smaller than a specified value. 
     
     
         15 . The method according to  claim 11 , wherein the act of controlling controls the driving of the stacking tray to change the distance corresponding to a thickness of a plurality of sheet bundles.