Automatic document feeder with anti-skew function

Abstract

An automatic document feeder with an anti-skew function is disclosed. The automatic document feeder comprises a pick up roller for feeding documents loaded on a tray, a feed roller for transferring the fed documents toward document scanning means; and an intermediate roller disposed just before the feed roller to transfer the documents toward the feed roller. The Intermediate roller has a document feed speed on a surface thereof faster than that of the feed roller. It is possible to prevent skew from occurring between the REGI roller or the intermediate roller and the feed roller by merely adjusting a linear velocity of the REGI roller or the intermediate roller, thereby improving document feeding performance and extending a lifetime of the device such as a motor since a driving system has no additional load.

1 . An automatic document feeder comprising: 
 a pick up roller for feeding documents loaded on a tray;    a feed roller transferring the fed documents toward document scanning means; and    an intermediate roller disposed just before the feed roller to transfer the documents toward the feed roller,    wherein the intermediate roller has a document feed speed on a surface thereof faster than that of the feed roller.    
     
     
         2 . The automatic document feeder according to  claim 1 , wherein the intermediate roller is a REGI roller for aligning the fed documents.  
     
     
         3 . The automatic document feeder according to  claim 1 , wherein the intermediate roller has a document feed speed on a surface thereof faster than that of the feed roller by about 1˜2%.  
     
     
         4 . An automatic document feeder comprising: 
 a first pick up roller for feeding documents loaded on a tray;    a feed roller transferring the fed documents toward document scanning means;    a first intermediate roller disposed just before the feed roller to transfer the documents toward the feed roller;    a second pick up roller for refeeding the document that having one surface already scanned; and    a second intermediate roller for refeeding the document refed by the second pick up roller toward the feed roller,    wherein the first and second intermediate rollers have a document feed speed on surfaces thereof faster than that of the feed roller.    
     
     
         5 . The automatic document feeder according to  claim 4 , wherein the first intermediate roller is a REGI roller for aligning the fed documents.  
     
     
         6 . The automatic document feeder according to  claim 4 , wherein the first and second intermediate rollers have a document feed speed on the surfaces thereof faster than that of the feed roller by about 1˜2%.  
     
     
         7 . A method of operating an automatic document feeder comprising: 
 picking up documents for feeding documents loaded on a tray;    transferring the documents toward document scanning means via a feed roller; and    transferring the documents toward the feed roller via an intermediate roller disposed just before the feed roller,    wherein the intermediate roller has a document feed speed on a surface thereof faster than that of the feed roller.    
     
     
         8 . The method according to  claim 7 , wherein the intermediate roller is a REGI roller for aligning the fed documents.  
     
     
         9 . The method according to  claim 7 , wherein the intermediate roller has a document feed speed on a surface thereof faster than that of the feed roller by about 1˜2%.