Sheet processing apparatus and image forming apparatus having the same

Abstract

An adsorption standby unit is provided upstream in the sheet conveying direction of a sheet stacking portion, which stacks sheets to be processed thereon. During processing of sheets on the sheet stacking portion, the next sheet to be processed is adsorbed and put in a standby state by the adsorption standby unit, so that the sheet can be retained and put in a standby state without switching the sheet back.

1 . A sheet processing apparatus operable to process sheets, comprising: 
 a sheet stacking portion configured to stack the sheets to be processed thereon;    a sheet conveying path facilitating conveying a sheet to be processed to the sheet stacking portion;    a sheet conveying portion disposed in the sheet conveying path; and    an adsorption standby unit disposed in the sheet conveying path, the adsorption standby unit configured to adsorb a next sheet to be processed so as to be put in a standby state during processing of the sheets on the sheet stacking portion,    wherein the adsorption standby unit adsorbs an end of the sheet conveyed to the sheet conveying path by the sheet conveying portion.    
   
   
       2 . The sheet processing apparatus according to  claim 1 , further comprising: 
 a step portion disposed upstream of the sheet conveying path,    wherein the adsorption standby unit is provided in the step portion.    
   
   
       3 . The sheet processing apparatus according to  claim 2 , wherein the adsorption standby unit adsorbs the trailing end portion in the sheet conveying direction of the next sheet to be processed along a sheet stacking surface of the step portion.  
   
   
       4 . The sheet processing apparatus according to  claim 2 , wherein the step portion has a depth which prevents a sheet next to the adsorbed sheet adsorbed by the adsorption standby unit from abutting the trailing end in the sheet conveying direction of the adsorbed sheet during proceeding towards the sheet conveying path.  
   
   
       5 . The sheet processing apparatus according to  claim 1 , further comprising: 
 a detection sensor configured to detect a sheet conveyed to the sheet conveying path; and    a controller controlling driving of the sheet conveying portion so as to stop the trailing end in the sheet conveying direction of the next sheet to be processed at a position opposing the adsorption standby unit in accordance with a signal from the detection sensor.    
   
   
       6 . The sheet processing apparatus according to  claim 1 , wherein the adsorption standby unit adsorbs the sheet by air adsorption.  
   
   
       7 . The sheet processing apparatus according to  claim 1 , wherein the adsorption standby unit adsorbs the sheet by electrostatic adsorption.  
   
   
       8 . The sheet processing apparatus according to  claim 6 , wherein the adsorption standby unit adsorbs a plurality of sheets by shifting the trailing ends in the sheet conveying direction of the sheets.  
   
   
       9 . The sheet processing apparatus according to  claim 1 , further comprising a controller which controls a sheet adsorbing force of the adsorption standby unit to correspond to at least one of the material, size, and weight of the sheet.  
   
   
       10 . An image forming apparatus comprising: 
 an image forming portion configured to form images on a sheet;    a sheet processing apparatus processing the sheet having images formed thereon by the image forming portion, the sheet processing apparatus including: 
 a sheet stacking portion configured to stack the sheets to be processed thereon;  
 a sheet conveying path facilitating conveying a sheet to be processed to the sheet stacking portion;  
   a sheet conveying portion disposed in the sheet conveying path; and 
 an adsorption standby unit disposed in the sheet conveying path, the adsorption standby unit configured to adsorb a next sheet to be processed so as to be put in a standby state during processing of the sheets on the sheet stacking portion,  
 wherein the adsorption standby unit adsorbs an end of the sheet conveyed to the sheet conveying path by the sheet conveying portion.  
   
   
   
       11 . The image forming apparatus according to  claim 10 , wherein the sheet processing apparatus further includes: 
 a step portion disposed upstream of the sheet conveying path,    wherein the adsorption standby unit is provided in the step portion.    
   
   
       12 . The image forming apparatus according to  claim 11 , wherein the adsorption standby unit adsorbs the trailing end portion in the sheet conveying direction of the next sheet to be processed along a sheet stacking surface of the step portion.  
   
   
       13 . The image forming apparatus according to  claim 11 , wherein the step portion has a depth which prevents a sheet next to the adsorbed sheet adsorbed by the adsorption standby unit from abutting the trailing end in the sheet conveying direction of the adsorbed sheet during proceeding towards the sheet conveying path.  
   
   
       14 . The image forming apparatus according to  claim 10 , further comprising: 
 a detection sensor configured to detect a sheet conveyed to the sheet conveying path; and    a controller controlling driving of the sheet conveying portion so as to stop the trailing end in the sheet conveying direction of the next sheet to be processed at a position opposing the adsorption standby unit in accordance with a signal from the detection sensor.    
   
   
       15 . The image forming apparatus according to  claim 10 , wherein the adsorption standby unit adsorbs the sheet by air adsorption.  
   
   
       16 . The image forming apparatus according to  claim 10 , wherein the adsorption standby unit adsorbs the sheet by electrostatic adsorption.  
   
   
       17 . The image forming apparatus according to  claim 15 , wherein when the adsorption standby unit adsorbs a plurality of sheets by shifting the trailing ends in the sheet conveying direction of the sheets.  
   
   
       18 . The image forming apparatus according to  claim 10 , further comprising a controller which controls a sheet adsorbing force of the adsorption standby unit to correspond to at least one of the material, size, and weight of the sheet.