Sheet conveying device that separates multi-fed sheets, and image reading apparatus

Abstract

A sheet conveying device which makes it possible to facilitate separation of multi-fed sheets. A separation pad and a separation roller separate sheets from a sheet bundle placed on a sheet tray, on a one-by-one basis. A pull-off roller section formed by a pair of conveying rollers nips and conveys a fed sheet. The two conveying rollers of the pull-off roller section have rotational axes extending in respective different directions. A registration roller further conveys the sheet conveyed by the pull-off roller section. One roller of the pull-off roller section is disposed such that the roller conveys a sheet in a direction in which the sheet is to be conveyed by the registration roller, and the other roller of the pull-off roller section is disposed such that the roller conveys a sheet obliquely with respect to the sheet conveying direction of the registration roller.

1 . A sheet conveying device comprising:
 a sheet feed unit configured to feed a sheet from a plurality of sheets placed on a sheet tray, on a one-by-one basis, by separating the sheets;   a first conveying unit having a pair of conveying rollers configured to convey the sheet fed from said sheet feed unit in a state nipped therebetween, the conveying rollers having rotational axes extending in respective different directions; and   a second conveying unit configured to further convey the sheet conveyed by said first conveying unit,   wherein one roller of the conveying roller pair is disposed such that the roller conveys the fed sheet in a direction in which the sheet is to be conveyed by said second conveying unit, and the other roller of the conveying roller pair is disposed such that the roller conveys the sheet obliquely with respect to the sheet conveying direction of said second conveying unit.   
     
     
         2 . The sheet conveying device according to  claim 1 , further comprising a multi-feed determination unit configured to determine whether or not multi-feed has occurred in which the sheet conveyed by said first conveying unit is in a state overlapping another sheet, and
 a control unit configured to be operable when said multi-feed determination unit determines that multi- feed has occurred, to perform control such that rotation of one roller of the conveying roller pair nipping the multi-fed sheets is stopped or decelerated.   
     
     
         3 . The sheet conveying device according to  claim 2 , further comprising a sheet width detection unit disposed close to said first conveying unit and configured to detect a sheet width in a direction intersecting with a sheet conveying direction of said first conveying unit, and
 wherein said multi-feed determination unit determines whether or not multi-feed has occurred, based on a change in the sheet width which is detected by said sheet width detection unit during sheet conveyance by said first conveying unit.   
     
     
         4 . The sheet conveying device according to  claim 3 , wherein said sheet width detection unit comprises a plurality of detectors arranged in the direction intersecting with the sheet conveying direction of said second conveying unit. 
     
     
         5 . The sheet conveying device according to  claim 1 , further comprising a switching unit configured to switch the conveying roller pair between a contact state in which one roller and the other roller of the conveying roller pair are brought into contact with each other and a separation state in which the one roller and the other roller of the conveying roller pair are spaced from each other. 
     
     
         6 . The sheet conveying device according to  claim 5 , wherein in synchronism of the sheet reaching the conveying roller pair, said switching unit switches the conveying roller pair held in the separation state in advance to the contact state. 
     
     
         7 . The sheet conveying device according to  claim 1 , wherein the one roller of the conveying roller pair and the other of the conveying roller pair are configured to have respective different conveying forces. 
     
     
         8 . The sheet conveying device according to  claim 7 , further comprising a guide member for guiding the plurality of sheets which are placed on the sheet tray, a portion of said guide member with which a sheet bundle side is brought into contact being angled with respect to the sheet conveying direction. 
     
     
         9 . The sheet conveying device according to  claim 8 , wherein a direction in which a sheet is conveyed by the one roller of the conveying roller pair is the same as the sheet conveying direction of said second conveying unit, and the conveying force of the one roller of the conveying roller pair is larger than the conveying force of the other roller of the conveying roller pair. 
     
     
         10 . An image reading apparatus comprising:
 a sheet tray on which a plurality of sheets are placed;   a sheet feed unit configured to feed a sheet from the sheets placed on said sheet tray, on a one-by-one basis, by separating the sheets;   a first conveying unit having a pair of conveying rollers configured to convey the sheet fed from said sheet feed unit in a state nipped therebetween, the conveying rollers having rotational axes extending in respective different directions;   a second conveying unit configured to further convey the sheet conveyed by said first conveying unit; and   a reading unit configured to read an image from the sheet conveyed by said second conveying unit,   wherein one roller of the conveying roller pair is disposed such that the roller conveys the fed sheet in a direction in which the sheet is to be conveyed by said second conveying unit, and the other roller of the conveying roller pair is disposed such that the roller conveys the sheet obliquely with respect to the sheet conveying direction of said second conveying unit.