Abstract:
A method and apparatus for bi-directionally transporting sheet stock in a marking engine by disposing idler rolls on opposite sides of a drive roll on movable idler roll decks for forming forward and reverse nips and feeding sheets from opposite directions into the nips and providing for moving the idler rolls away from opposite sides of the drive roll for jam clearance.

Description:
BACKGROUND 
     The present disclosure relates to transport of print media and particularly print media in sheet form as is employed in photocopiers and office printers. The disclosure particularly relates to digital image printing in print engines arranged for parallel processing, as for example, printing in plural print engines and for duplex printing on both sides of a print media sheet. 
     In print engines arranged for parallel processing, it is often the case that the transport of sheet print media will by-pass one or more print engines in order to print concurrently on another print engine. However, the transport path must also include a provision for reversing the direction and movement of the sheet print media for duplex printing. Thus, the transporters propelling the sheets for moving the sheet print media through the designated path must provide for bi directional movement. Heretofore, such bi directional print sheet media movement has been provided by individual transporters disposed in the media path with one transporter arranged to provide print sheet media movement in a forward direction such as for bypass and simplex printing, and another transporter disposed to arrange for print sheet media movement in the reverse direction such as for duplex printing. The transporters are typically each comprised of a series of nip rollers driven by a belt powered by an individual single direction of rotation drive motor. Thus, the functionality of bi directional print sheet media movement in a print engine has been somewhat complex and costly because of the need for plural print sheet media transporters. 
     It has therefore been desired to reduce the complexity and cost of a sheet transport digital print engine arrangement for parallel printing employing bypass capability and providing for duplex printing on opposite sides of print sheet media. 
     BRIEF DESCRIPTION 
     The present disclosure describes a print sheet media transporter for providing movement of sheets through a transport or printing path and particularly for bi directional transport in digital print engines. The single bi directional transporter employs a single drive motor rotating in one direction for driving a belt which is connected to a plurality of spaced drive rolls, each of which has idler rolls disposed on opposite sides thereof for rotating the idler rolls in opposite directions. The combination of the drive roll and oppositely disposed idler rolls forms a pair of nips which are capable of propelling the print sheet media in opposite directions when fed to the oppositely disposed nips. The bi directional print transporter of the present disclosure thus replaces two separately driven unidirectional print sheet media transporters thereby reducing the complexity and cost of the equipment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a pictorial view of a digital printing arrangement with multiple print engines and illustrates the path of movement of the print sheet media for both printing and bypass transport; 
         FIG. 2  is a perspective view of the bi directional transporter of the present disclosure; 
         FIG. 3  is a perspective view of the transporter of  FIG. 2  taken from the back or motor drive side thereof; 
         FIG. 4  is a view illustrating the bi directional paper paths through the transporter of  FIG. 2 ; 
         FIG. 5  is a perspective view of two of the drive rolls and associated oppositely disposed idler rollers of the transporter of the present disclosure; 
         FIG. 6  is an enlarged detailed view of one of the drive rolls and idlers of  FIG. 5 ; 
         FIGS. 7A and 7B  are view similar to  FIG. 6  showing the unidirectional nip arrangement of prior art print sheet media transporter; 
         FIG. 8  is a view similar to  FIG. 1  showing the arrangement of the plural unidirectional print sheet media transporters of the prior art equipment; 
         FIG. 9  is a side view of the transporter of the present disclosure with the idler roller deck shown open; and, 
         FIG. 10  is a perspective view of the transporter of  FIG. 9  in the open condition. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 8 , a known arrangement for a digital print engine is indicated generally at  1  and includes an incoming print sheet media path for the printing function in the engine  1  as denoted by the dashed line adjacent the black arrow  2 . The engine  1  includes a print media sheet bypass path indicated in dashed outline adjacent the black arrow  3  for bypassing the engine  1  and transporting the print sheet media outwardly through the discharge rollers  4 . For the printing function, the print sheet media is processed through the print engine and is subsequently fed along the path indicated in dashed outline adjacent the black arrow  5 . The print engine may include multiple print heads or photoreceptors indicated generally at  6  for marking primary colors to effect color printing. Upon completion of the printing function and movement along the path in the direction indicated by the arrow  5 , the print media is discharged through the rollers  4  in the case of simplex printing. For effecting duplex printing, the print sheet media is transported along the path shown in dashed outline in a reversed direction as indicated by the adjacent black arrow  7  for recycling through the path  2  and printing on the opposite side of the print sheet media. The transporters for effecting the movement of the print sheet media in either the printing or transport mode are shown in the box  8  which contains a plurality of transporters  9 ,  10  arranged serially, with one of the transporters  9  operative for effecting movement of the print sheet media in the forward direction as denoted by the dashed arrow  11 . Whereas, the separate transporter  10  is operative for effecting movement of the print sheet media in the reverse direction indicated by the dashed arrow  12  for effecting duplex printing. Each of the transporters  9 ,  10  has its own individual drive motor denoted  17 ,  18  respectively. 
     Referring to  FIG. 7A , the nip roller drive arrangement of the prior art transporter  9  of  FIG. 8  is shown wherein the belt driven drive roll  13  cooperates with an idler roller  14  for propelling the print sheet media (paper) in the forward direction. 
     Referring to  FIG. 7B , the nip roller arrangement of the prior art transporter  10  of  FIG. 8  is shown wherein a motor driven drive roll  15  cooperates with an idler roll  16  for propelling the print sheet media (paper) in a reverse direction. 
     Referring  FIG. 1 , a digital print engine indicated generally at  20  according to the present disclosure is operative to receive print sheet media from a sheet feeder (not shown) through entrance nip rollers  21  along a path indicated by dashed line adjacent the dashed black arrow  22  for feeding paper through the print engine and outputting the paper along the path indicated by the dashed outline denoted by the dashed black arrow  26 . The print engine  20  may include plural print heads or photoreceptors for color printing as indicated generally at  24 . The paper may either be discharged through the nip rollers  28  in the case of simplex printing or sent along a reverse path indicated by the dashed black arrow  30  and recycled along the path adjacent arrow  22  for duplex printing on the opposite side of the paper. The print engine  20  also includes a path for bypassing the printing function along a dashed outline path adjacent the black arrow denoted  32  wherein the paper proceeds directly from the inlet to the discharge rollers  28 . The print engine  20  has the single transporter enclosed in a dashed box indicated generally at  34  which is operative to effect the bi directional movement of the paper feed with a single drive motor  36  illustrated in  FIG. 1  in the reduced size perspective view of the transporter  34 . 
     Referring to  FIG. 2 , the bi directional transporter  34  of the present disclosure is shown with one single direction of rotation drive motor  36  for effecting the bi directional movement of the print sheet media through the mechanism. 
     Referring to  FIG. 3 , the transporter  34  is shown in perspective view from the motor side with the cover removed to show the motor drive shaft  40  with a belt  42  engaged therewith for driving shaft pulleys  44 ,  46  respectively. A second belt  47  is disposed over shaft pulley  46  and a third spaced shaft pulley  48 . 
     Referring to  FIGS. 3 ,  5 ,  9  and  10 , the motor  36  of the bi directional transporter  34  is mounted on a plate  52  attached to a platform or deck  54  upon which the shafts driven by pulleys  44 ,  46 ,  48  are mounted. The shaft pulleys  46 ,  48  respectively connected to drive shafts  56 ,  58  which have mounted respectively thereon a plurality of axially spaced drive rolls  60 ,  62 . 
     Each of the drive rolls  60 ,  62  has disposed on opposite sides thereof idler rolls denoted respectively  62 ,  64  for shaft  56  and  66 ,  68  for shaft  58 . One set of idler rolls for shaft  58  is shown in greater detail in  FIG. 6  in which the black arrows indicate the path of the bi directional paper feed. 
     The transporter  34  may have a modular construction wherein the idler rollers  64 ,  68  for shafts  56  and  58  respectively and similarly for idler rollers provided on the shaft connected to pulley  44  are mounted on an upper platform  70 . The idler rollers  62 ,  66  and similar idler rollers for the shaft  44  are mounted on a lower platform or deck  72  which platforms  70 ,  72  may be opened from the drive roll deck  54  for jam clearance. 
     The present disclosure thus describes a bi directional feed sheet print media transporter which provides the bi directional movement of the print sheet media with only a single drive motor rotating in one direction. The transporter of the present disclosure thus provides less complexity and lower cost for a digital print engine employing sheet print media where bi directional sheet transport is required. 
     It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.