Abstract:
A method and apparatus for picking the top or the bottom sheet, as desired from a stack of sheets of documents to be scanned using opposed rollers or other members which apply differing amounts of frictional force to opposite faces of the sheet to be picked. The opposed rollers each have substantially the same coefficient of friction and are selectively rotated each in the same direction of rotation but with different torques to apply differential frictional forces to pick the desired sheet from the top or the bottom of the stack.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS IF ANY 
     None. 
     BACKGROUND OF THE INVENTION AND PRIOR ART 
     The present invention relates to a method and apparatus for picking the top or the bottom sheet, as desired, from a stack of sheet documents to be scanned in a document scanning device such as an all in one document scanner, copier and facsimile machine or for stand alone scanners, copiers and facsimile machines and the like. As used herein, the term “document scanning device” is therefore intended to encompass all types of devices in which documents are fed to be scanned and the teachings of this disclosure are accordingly not necessarily limited to all in one or stand alone document scanners, copiers and facsimile machines. 
     Automatic document feeders, particularly for all in one products such as generally described above, require a mechanism which must pick in the correct order of document sheets which are stacked. For facsimile transmission of a multi-page document, the first page picked by the automatic document feeder should be transmitted first to in accordance with conventional first page out facsimile transmission protocol. Conversely, when copying a document, it is conventional to pick and copy the last sheet of the document first in order to assure that the printed output order is correct. This problem is resolved if the user is willing to insert the input documents in one order, e.g., face down for facsimile transmission and in a different order, e.g., face up for simplex (one side) sheet copying. For truly universal operation of an all in one product, not only single sided (simplex) copying, facsimile transmission and scanning should be achievable by the automatic document feeder, but also double sided (duplex) copying, facsimile transmission and document scanning should be achievable without the user being required to stack the document differently depending on the function to be performed. 
     The present invention is directed to an automatic document feeder which has the capability of picking single document sheets to be scanned with the same mechanism which can be easily controlled to either pick from the top or the bottom of the document stack depending on the function to be achieved and without changing the position of the mechanism on the scanning device. 
     SUMMARY OF THE INVENTION 
     In its method aspects, the present invention provides a method of moving a document to be transported to a scan region of a document scanning device from a document stack comprising the steps of: 
     a) picking a single sheet of document from a surface of a stack of sheets of documents by contacting opposite face sides of said sheet with opposed moveable members which apply differing amounts of frictional force to opposite face sides of said sheet; 
     b) rotating a first one of said moveable members with a first torque to apply a first frictional force to the surface of said sheet facing outwardly of said stack; and 
     c) rotating a second one of said moveable members with a second torque to apply a second frictional force to the surface of said sheet which faces said stack, said first torque and force being higher than said second torque and force. 
     In its broadest apparatus aspects, the present invention provides apparatus for feeding documents to be scanned to a document scanning device comprising: 
     a) a support for a stack of documents to be fed to said scanning device; 
     b) a pair of opposed rotary members comprising a sheet pick member and a sheet retard member for contacting opposite face sides of a single sheet of document and applying frictional force thereto; and 
     c) a drive mechanism for rotating said members in the same forward direction of rotation for uppermost sheet picking and in the same reverse direction of rotation for lowermost sheet picking such that an upper one of said members applies more torque and frictional force than a lower one of said members when picking an uppermost sheet from said stack and said lower one of said members applies more torque and frictional force than said upper one of said members when picking a lowermost sheet from said stack. 
     Additionally, the present invention further provides a document scanning device comprising: 
     a) a support for a stack of documents to be scanned; 
     b) spaced guides defining a path of document travel extending from said support through a scanning region past a document scanner to a scanned document output location; 
     c) a document drive apparatus for moving documents to be scanned along said path through said scanning region to said scanned document output location; 
     d) a pair of opposed document contact rollers for picking individual sheets of documents to be scanned from a stack of documents on said support, said rollers comprising a pick roller and a retard roller; and 
     e) a drive mechanism for moving said rollers in the same forward direction of rotation for uppermost sheet picking and in the same reverse direction of rotation for lowermost sheet picking such that an upper one of said rollers applies more torque than a lower one of said rollers when picking an uppermost sheet from said stack and said lower one of said rollers applies more torque than said upper one of said rollers when picking a lowermost sheet from said stack for moving said sheet to be scanned to said path of media travel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic side elevation view of an inclined media stack and picking rollers capable of repeatedly picking single sheets of media from either the top or from the bottom of the media stack and showing the mode of operation for picking the top sheet of media from the stack. 
     FIG. 2 is a schematic side elevation view like FIG. 1 but showing the mode of operation for picking the bottom sheet of media from the stack. 
     FIG. 3 is a side elevation view of a sheet picking apparatus embodying the invention. 
     FIG. 4 is a schematic front elevation view of one form of pick roller drive mechanism for use in the present invention. 
     FIG. 5 is a schematic perspective view of a second form of pick roller drive mechanism for use in the present invention. 
     FIG. 6 is a side elevation view of the roller drive of FIG. 5 showing roller movement during a top sheet pick operation. 
     FIG. 7 is a side elevation view of the roller drive of FIG. 5 showing roller movement during a bottom sheet pick operation. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As seen in FIGS. 1 and 2 which respectively show in schematic form the operation of media pick rollers for picking the top or uppermost one of a stack of sheets of media to be scanned and, in FIG. 2 for picking the lowermost or bottom sheet from the stack, a media feed and support tray  22  is inclined at an angle θ from the horizontal between 0° and 90°, preferably in the range from 15° to 30° such that gravity assists in feeding the stack of media to opposed upper and lower sheet pick rollers  40 ,  42 . It will be understood that although single rollers are shown in the schematic drawings, these rollers may comprise a series of spaced rollers on a common shaft. The uppermost sheet of media from the stack  24  is picked, as shown in FIG. 1, by rotating the upper sheet pick roller  40  in the clockwise direction while rotating the lower roller  42 , also in the clockwise direction, to function as a retard roller for retarding movement of all but the uppermost sheet of media from the stack through the bight between the rollers  40 ,  42 . As is known, the sheet pick rollers  40 ,  42  may be provided with a rubberized or other suitable non-slip surface for gripping the surface of a sheet of paper or other media to be fed to a scan region of a document scanning device. Preferably, the coefficient of friction of the media engaging surfaces of the rollers  40 ,  42  is substantially the same so that by reversing the direction of rotation of the rollers, either one of the rollers may act as a pick roller while the other acts as a retard roller. Picking of the upper sheet single sheet of paper or other media is accomplished in novel fashion according to the invention by rotating the upper roller  40  with a greater amount of torque than the amount of torque applied to the bottom roller  42  as both rotate in the clockwise direction. 
     As seen in FIG. 2, when the lowermost or bottom sheet of paper or other media is to be picked from the stack, the direction of rotation of the rollers  40 ,  42  is reversed such that both rotate in the counterclockwise direction as shown with application of a higher torque to the lower pick roller  42  than the amount of torque applied to the upper pick roller  40 . When picking the lowermost sheet from the stack, the upper roller  40  operates as a retard roller. 
     FIG. 3 is a schematic side elevation view of a document scanning device  10  having a generally flat horizontally extending table or platen surface  12  having a window  14  at one end thereof through which a document to be scanned can be viewed by the scanning components of the device as is conventional. The device has an inclined frame  20  on which a document input or feed tray  22  for holding a stack  24  of documents to be fed to the scanning device is provided. A plurality of paper guides  26 ,  27 ,  28 ,  29  are suitably supported on the frame  20  and define a paper path extending from the media stack  24  to the scan region  14  and thence past a document drive roller  30  and document output roller  32  to a scanned document output location at which a tray  34  is preferably provided for receiving a stack  36  of scanned documents. The apparatus for feeding individual sheets from the stack  24  to the scan region  14  includes the media support or feed tray  22  as well as the upper and lower media pick rollers  40 ,  42  and a suitable drive mechanism for moving the rollers  40 ,  42  in the same forward direction of rotation (e.g., clockwise) for uppermost sheet picking and in the same reverse direction (e.g., counterclockwise) for lowermost sheet picking. The rollers  40 ,  42  must be driven in a manner such that the amount of torque and resulting frictional force applied to the surface of a sheet which faces outwardly of the stack is greater than the amount of torque applied to the roller and resulting frictional force applied to the side of the sheet to be picked which faces the stack. 
     The drive mechanism for rotating the rollers  40 ,  42  can take any one of various forms. One form of drive mechanism is schematically shown in FIG.  4  and employs a small DC motor  46  and transmission  48  to drive shaft  44  on which the top pick roller  40  is mounted via gear  45 . Similarly, a second small DC motor  56  is used to drive the bottom pick roller  42  which is mounted on shaft  54  through a transmission  58 . The motors are operated such that the transmissions  45 ,  48  drive the rollers  40 ,  42  such that the torque and frictional force applied to the document sheet by the retarding roller is significantly less than that of the picking roller. 
     A second form of roller drive is schematically shown in FIGS. 5-7. In this arrangement, a single small DC motor  60  simultaneously provides rotary power to both the upper roller  40  and lower roller  42 . A plurality of upper roller drive gears  62 ,  64 ,  66  and lower roller drive gears  72 ,  74 ,  76  are all mounted on a pivoting shift plate  80  which pivotally moves to a first or lower (clockwise) position as seen in FIG. 6 when drive motor  60  is rotated in the clockwise direction such that the upper drive gears  62 ,  64 ,  66  engage gear  45  to drive the upper shaft  44  and top pick roller  40  while torque limiting gear  84  simultaneously engages and drives the lower shaft  54  via gear  55  to rotate the bottom pick roller  42  at a lower torque when picking the top sheet of media from the stack. 
     FIG. 7 shows the reverse operation for picking the lowermost sheet of media from the stack. In this arrangement, the motor  60  rotates in the reverse (counterclockwise as shown) direction to pivot the shift plate  80  from the position seen in FIG. 6 counterclockwise to the position shown in FIG. 7 such that lower shaft drive gears  72 ,  74 ,  76  directly engage the gear  55  and shaft  54  to power rotate the lower roller  42 . In this position of the transmission, the upper drive gears  62 ,  64 ,  66  are disengaged from the gear  45  while rotary power is transmitted to the upper shaft  44  via gear  45  through the torque limiting gear  84 . With the mechanisms thus far described, the device can pick and scan according to the following table. Simplex and Duplex faxing are exactly the same as simplex and Duplex copying. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Simplex Copy 
                 Duplex Copy 
                 Simplex Fax 
                 Duplex Fax 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 ADF Input Stack Order 
                 
                   
                     
                       
                         N 
                         1 
                       
                     
                             
                     
                         
                     
                   
                 
                 
                   
                     
                       
                         N 
                         1 
                       
                     
                             
                     
                         
                     
                   
                 
                 
                   
                     
                       
                         N 
                         1 
                       
                     
                             
                     
                         
                     
                   
                 
                 
                   
                     
                       
                         N 
                         1 
                       
                     
                             
                     
                         
                     
                   
                 
               
               
                   
               
               
                 Pick Order 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 ADF Output Order 
                 
                   
                     
                       
                         1 
                         N 
                       
                     
                             
                     
                         
                     
                   
                 
                 
                   
                     
                       
                         N 
                         1 
                       
                     
                             
                     
                         
                     
                   
                 
                 
                   
                     
                       
                         N 
                         1 
                       
                     
                             
                     
                         
                     
                   
                 
                 
                   
                     
                       
                         N 
                         1 
                       
                     
                             
                     
                         
                     
                   
                 
               
               
                   
               
               
                 Print Output Order 
                 
                   
                     
                       
                         1 
                         N 
                       
                     
                             
                     
                         
                     
                   
                 
                 
                   
                     
                       
                         N 
                         1 
                       
                     
                             
                     
                         
                     
                   
                 
                 N/A 
                 N/A 
               
               
                   
               
               
                 Note:  
               
               
                 1/N designates the stack with first page on top, N th  page on bottom, facing up.  
               
               
                 N/1 designates the stack with the N th  page on top, first page on bottom, facing down.  
               
               
                 Simplex Fax ADF Output Order is maintained by duplexing the document once.  
               
             
          
         
       
     
     It will be seen that the user never has to change the orientation of the input documents and that the order of the original document stack is always maintained at the scanned document output tray  34 . Additionally, printed copies are delivered when desired in the correct order in which the document pages were scanned. Thus, without user intervention other than by telling the device whether to copy or transmit a facsimile of the scanned document, the disclosed mechanism can selectively pick from the top or bottom of the input document stack to maintain first page output order in all cases of copying, scanning and facsimile transmission. 
     Persons skilled in the art will appreciate that various modifications can be made in the preferred embodiments shown and described above and that the scope of protection is limited only by the wording of the claims which follow. For example, the rollers  40 ,  42  may instead be replaced by belts and the different drive arrangements shown in FIGS. 4-7 can easily be replaced by other roller drives so long as the proper amount of torque is applied to the opposed rollers  40 ,  42  to maintain a torque differential therebetween adequate to prevent misfeed of multiple document sheets as described.