Original transport apparatus, original transport method and image reading apparatus

Abstract

An original transport apparatus includes an original tray for stacking an original; a feed device for feeding the original to a feeding position; a transport device for transporting the original from the feeding position to a discharge outlet via a reading position; a switchback path disposed adjacent to the discharge outlet for switching back to turn over the original; a re-feed path for guiding the original to the feeding position; and a discharge device disposed at a downstream side of the switchback path for discharging the original to a discharge tray. After both sides of the original are read, the original is fed to the feeding position via the switchback path. The feed device transports the original via the reading position while the original is overlapped with the next original, and the discharge device discharges the first original via the discharge outlet.

What is claimed is:  
     
         1 . An original transport apparatus for transporting originals, comprising: 
 an original tray for stacking the originals,    feed means disposed adjacent to the original tray for feeding the originals stacked on the original tray one by one to a predetermined feeding position,    transport means disposed adjacent to the feed means for transporting one original from the feeding position to a discharge outlet through a reading position,    a switchback path disposed adjacent to the discharge outlet in a discharge direction for switching back the one original to turn over the same,    a re-feed path disposed adjacent to the switchback path for returning the one original to the feeding position after the one original is switched back in the switchback path,    discharge means disposed at a downstream side of the switchback path for discharging the one original after the one original is read, and    means for overlapping the one original with a next original after two sides of the one original are read so that the one original after the two sides of the one original are read is sent to the feeding position via the switchback path, is overlapped with the next original to pass through the reading position without being read, and is discharged by the discharge means via the discharge outlet.    
     
     
         2 . An original transport apparatus according to  claim 1 , wherein said overlap means overlaps the one original with the next original such that a leading edge of the one original is shifted rearwardly from a leading edge of the next original by a predetermined distance.  
     
     
         3 . An original transport apparatus according to  claim 1 , wherein said discharge means includes a pair of discharge rollers capable of rotating at different speeds for discharging the one original after the two sides are read.  
     
     
         4 . An original transport apparatus according to  claim 3 , wherein said pair of the discharge rollers includes a first discharge roller for contacting the one original after the two sides thereof are read, and a second discharge roller for contacting the next original to be read next, said first discharge roller rotating at a speed higher than that of the second discharge roller in discharging the original.  
     
     
         5 . An original transport apparatus according to  claim 3 , wherein said pair of the discharge rollers rotates in a reverse direction for switching back the next original and for transporting the next original to the reading position after the one original, the two sides of which have been read, passes the pair of the discharge rollers.  
     
     
         6 . An original transport apparatus according to  claim 5 , wherein said discharge means further includes a return prevention lever disposed adjacent to the discharge rollers for stopping the one original so that the one original is not switched back when the discharge rollers rotate in the reverse direction.  
     
     
         7 . An original reading method for reading originals, comprising: 
 feeding one original stacked on an original tray to a predetermined feeding position,    transporting the one original from the predetermined feeding position to a predetermined reading position,    reading one side of the one original at the reading position,    switching back the one original after the one side of the one original is read, to turn over the one original,    returning the one original to the feeding position,    reading the other side of the one original at the reading position,    switching back the one original again after two sides of the original are read to turn over the one original,    transferring the one original again to the feeding position,    overlapping the one original with a next original,    transporting the one original and the next original to the reading position in a condition that the one original is overlapped with the next original, one side of the next original being read while the one and next originals are being transported, and    discharging the original.    
     
     
         8 . An original transport method according to  claim 7 , wherein in overlapping the one original with the next original, the one original is overlapped with the next original such that a leading edge of the one original is shifted from a leading edge of the next original rearwardly by a predetermined distance.  
     
     
         9 . An original transport method according to  claim 7 , further comprising after the one side of the next original is read, switching back the next original to transfer the next original to the feeding position.  
     
     
         10 . An original transport method according to  claim 9 , further comprising reading the other side of the next original after the one side thereof is read.  
     
     
         11 . An image reading apparatus comprising: 
 transport means for receiving originals one by one, and transporting the originals sequentially to a predetermined reading position,    reading means for reading one original passing through the reading position,    a switchback path for switching back the one original read at the reading position to change a moving direction thereof to turn over the original,    discharge means for discharging the one original after the one original is read, and    control means for controlling the transport means, the reading means and the discharge means such that the one original is circulated twice through the switchback path for reading two sides of the one original by the reading means; the one original is overlapped with a next original after the two sides of the one original are read and the one and next originals are transferred to the reading position; and the next original overlapped with the one original is read by the reading means.    
     
     
         12 . An image reading apparatus according to  claim 11 , wherein said control means selects a first control mode in which the one original is circulated twice through the switchback path for reading the two sides of the one original by the reading means, the one original is overlapped with the next original after the two sides of the one original are read and the one and next originals are transferred to the reading position, and the next original overlapped with the one original is read by the reading means; or a second control mode in which the one original is circulated twice through the switchback path for reading the two sides of the one original by the reading means, and then a next original is transported to the reading position for reading after the one original is turned over and discharged alone.