Patent Publication Number: US-6983697-B2

Title: Printing color layers

Description:
FIELD OF THE INVENTION 
   This invention relates in general to printing color layers and, more particularly, to applying color layers to an intermediate transfer member while the intermediate transfer member is disengaged from an impression drum. 
   BACKGROUND OF THE INVENTION 
   As color printing becomes more ubiquitous, faster color printing becomes more desirable. One of the limiting factors in color printing is the process by which color layers, or separations, are applied to the sheet media being printed. Each color layer is the layer for only one color. 
   In conventional multi-color simplex printing, a color layer is applied to an intermediate transfer member (ITM), or blanket. The color layer is then transferred to print media held by an impression drum (IMP). The print media is held on the IMP for as many cycles as there are colors used. 
   In conventional color printing, four colors are typically used; yellow, magenta, cyan, and black, though other colors and number are sometimes used as well. Where four colors are used, the sheet media is held on the IMP for four cycles. During each cycle, a single color layer is applied to the ITM and then transferred to the sheet media. This process limits the speed at which a sheet of media may be processed. 
   SUMMARY OF THE INVENTION 
   According to principles of the present invention, in one embodiment, an intermediate transfer member is disengaged from an impression drum. Color layers are applied to the intermediate transfer member while a sheet media is transported between the disengaged intermediate transfer member and impression drum. The intermediate transfer member is then engaged with the impression drum. Another sheet media is transported between the intermediate transfer member and the impression drum. The color layers are transferred from the intermediate transfer member onto the sheet media. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a depiction of one embodiment of the present invention printing system. 
       FIGS. 2A and 2B  are a flow chart illustrating one embodiment of the present invention method for printing. 
       FIGS. 3A–3C  illustrates a timing flow diagram of one embodiment of the transport system of the present invention printing system. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Illustrated in  FIG. 1  is one embodiment of printing system  2 . Printing system  2  includes first intermediate transfer member (ITM)  4 , first impression drum (IMP)  6 , application controller  8 , transport system  10 , and optionally second ITM  12 , and second IMP  14 . Printing system  2  is intended for use in printing to sheet media  16 . Examples of sheet media  16  include paper, transparency film, and cardstock. 
   First ITM  4  is any apparatus or system configured to receive a plurality of color layers and transfer the color layers to sheet media  16 . First IMP  6  is any apparatus or system selectively engageable with first ITM  4  and configured to hold sheet media  16  while first ITM  4  transfers color layers onto sheet media  16 . 
   First IMP  6  is engaged with first ITM  4  when they are close enough for ITM  4  to transfer color layers to sheet media  16  held by IMP  6 . First IMP  6  is disengaged with first ITM  4  when there is a gap between first IMP  6  and first ITM  4  such that ITM  4  cannot transfer color layers to sheet media  16  held by IMP  6 . 
   In one embodiment, first IMP  6  is equipped to hold sheet media  16  while sheet media  16  passes over IMP  6 . Commonly known examples of means for holding sheet media  16  include grippers positioned on IMP  6  and a vacuum system within IMP  6 . 
   Second ITM  12  and second IMP  14  are like first ITM  4  and first IMP  6 . Second ITM  12  and second IMP  14  are positioned relative to first ITM  4  and first IMP  6  so that sheet media  16  passes first through first ITM to  4  and first IMP  6 , then through second ITM  12  and second IMP  14 . 
   Application controller  8  is any combination of hardware and executable code configured to apply color layers to first ITM  4  and second ITM  12 . In one embodiment, application controller  8  is configured to apply at least one color layer to first ITM  4  while first ITM  4  is disengaged from first IMP  6 . In one embodiment, application controller  8  is further configured to, with first ITM  4  and first IMP engaged, apply at least one color layer to first ITM  4 . 
   In another embodiment, application controller  8  is further configured to apply at least one color layer to second ITM  12  while second ITM  12  is disengaged from second IMP  14 . In another embodiment, application controller  8  is further configured to apply, with second ITM  12  and second IMP engaged, at least one color layer to second ITM  12 . 
   Transport system  10  is any apparatus or system configured to transport sheet media  16 . In one embodiment, transport system  10  includes feeders  18 ,  20 . Transport system  10  is configured to transport sheet media  16  between first ITM  4  and first IMP  6  and second ITM  12  and second IMP  14 . While between each ITM and IMP pair, sheet media  16  is on the IMP, either for receiving a color layer from the ITM or merely passing through. 
   In one embodiment, transport system  10  is further configured to transport sheet media  16  between first ITM  4  and first IMP  6  while first ITM  4  and first IMP  6  are disengaged. In another embodiment, transport system  10  is further configured to transport sheet media  16  between first ITM  4  and first IMP  6  while applying one of the color layers to first ITM  4 . 
   In another embodiment, transport system  10  is further configured to transport sheet media  16  between second ITM  12  and second IMP  14  while second ITM  12  and second IMP  14  are disengaged. In another embodiment, transport system  10  is further configured to transport sheet media  16  between second ITM  12  and second IMP  14  while applying one of the color layers to second ITM  12 . 
   Optionally, printing system  2  further includes computer  22  and program storage system  24 . Either or both of application controller  8  and transport system  10  may be partially embodied within computer  22 . 
   Computer  22  is any combination of hardware and executable code configured to execute executable code stored in program storage system  24 . Program storage system  24  is any device or system configured to store data or executable code. Program storage system  24  may also be a program storage system tangibly embodying a program, applet, or instructions executable by computer  22  for performing the method steps of the present invention executable by computer  22 . Program storage system  24  may be any type of storage media such as magnetic, optical, or electronic storage media. 
   Program storage system  24  is illustrated in  FIG. 1  as a single device. Alternatively, program storage system  24  may include more than one device. Furthermore, each device of program storage system  24  may be embodied in a different media type. For example, one device of program storage system  24  may be a magnetic storage media while another device of program storage system  24  is an electronic storage media. 
     FIGS. 2A and 2B  are a flow chart representing steps of one embodiment of the present invention. Although the steps represented in  FIGS. 2A and 2B  are presented in a specific order, the present invention encompasses variations in the order of steps. Furthermore, additional steps may be executed between the steps illustrated in  FIGS. 2A and 2B  without departing from the scope of the present invention. 
   One embodiment of the timing and transport system of the present invention printing system  2  is illustrated in  FIGS. 3A–3C  and discussed below in some detail with  FIGS. 2A and 2B  and in more detail after the discussion of  FIGS. 2A and 2B . 
   First ITM is disengaged  26  from first IMP  6 . At least one color layer is applied  28  to first ITM  4 . Optionally, sheet media S 1  is transported  30  between first ITM  4  and first IMP  6  while first ITM  4  and first IMP  6  are disengaged  26 . Optionally, sheet media S 1  is transported between first ITM  4  and first IMP  6  while one of the color layers is applied  28  to first ITM  4 . Color layers applied  28  to first ITM  4  are not transferred to sheet media S 1 . After passing between first ITM  4  and first IMP  6 , sheet media moves toward second ITM  12  and second IMP  14 . 
   First ITM  4  is engaged  32  with first IMP  6 . Sheet media S 2  is transported  34  between first ITM  4  and first IMP  6 . The color layers are transferred  36  from first ITM  4  onto sheet media S 2 . 
   Optionally, with first ITM  4  and first IMP  6  engaged, at least one additional color layer is applying  38  to first ITM  4 . Each additional color layer is transferred  40  to sheet media S 2 . 
   Optionally, second ITM  12  is disengaged  42  from second IMP  14 . At least one color layer is applied  44  to second ITM  12  while second ITM  12  is disengaged  42  from second IMP  14 . Second ITM  12  is then engaged  46  with second IMP  14 . Sheet media S 1  is transported  48  between second ITM  12  and second IMP  14 . The color layers are transferred  50  from second ITM  12  onto sheet media S 1 . 
   Optionally, with second ITM  12  and second IMP  14  engaged, at least one additional color layer is applying  52  to second ITM  12 . Each additional color layer is transferred  54  to sheet media S 1 . 
   Second ITM  12  is disengaged  56  from second IMP  14  after the color layers are transferred  50 ,  54  to sheet media S 1 . At least one color layer is applied  58  to second ITM  12  while second ITM  12  is disengaged  42  from second IMP  14 . Sheet media S 2  is transported  60  between second ITM  12  and second IMP  14  while second ITM  12  and second IMP  14  are disengaged  56 . 
   Tables 1 and 2 illustrate specific examples of timing that may be used to practice the present invention. Table 1 is illustrated by  FIGS. 3A–3C . Table 2 is an alternate embodiment, to the timing example of Table 1. 
   At time t 1 , sheet S 1  is in feeder  18  and a color layer is applied to ITM  4 . The “*” in Tables 1 and 2 indicates that the ITM is being loaded with a color layer while the ITM is disengaged from its IMP. As shown in  FIG. 3A , first ITM  4  and first IMP  6  are disengaged. 
   At time t 2 , ITM  4  remains disengaged from IMP  6  as sheet S 1  is moved onto first IMP  6  and a color layer is applied to ITM  4 . Since ITM  4  and IMP  6  are disengaged, the color layers on ITM  4  are not transferred to sheet S 1 . Also at time t 2 , sheet S 2  is positioned in feeder  18 . 
   At time t 3 , sheet S 1  is transported towards IMP  14 , ITM  4  and IMP  6  engage, and sheet S 2  is transported onto IMP  6 . An additional color layer is applied onto ITM  4  and all three color layers are transferred to sheet S 2 . Additionally, a color layer is applied to ITM  12 . 
   At time t 4 , sheet S 1  is positioned in feeder  20  while another color layer is applied to ITM  12 . Also, another color layer is applied to ITM  4  and transferred to sheet S 2 . 
   At time t 5 , ITM  12  and IMP  14  engage, and sheet S 1  is transported onto IMP  14 . An additional color layer is applied onto ITM  12  and all three color layers are transferred to sheet S 1 . ITM  4  and IMP  6  disengage and sheet S 2  is transported towards IMP  14 . A color layer is applied to ITM  4 , which is intended to be later transferred to Sheet S 4 . Also, sheet S 3  is positioned in feeder  18 . 
   
     
       
         
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
           
             
               TABLE 1 
             
             
                 
             
             
               Position 
               Time 
               t1 
               t2 
               t3 
               t4 
               t5 
               t6 
               t7 
               t8 
               t9 
               t10 
               t11 
               t12 
               t13 
             
             
                 
             
           
          
             
               1 
               Feeder 18 
               S1 
               S2 
                 
                 
               S3 
               S4 
                 
                 
                 
                 
                 
                 
                 
             
             
               2 
               IMP 6 
               * 
               S1* 
               S2 
               S2 
               * 
               S3* 
               S4 
               S4 
                 
             
             
               3 
               Transport 
                 
                 
               S1 
                 
               S2 
                 
               S3 
                 
               S4 
             
             
               5 
               Feeder 20 
                 
                 
                 
               S1 
                 
               S2 
                 
               S3 
                 
               S4 
             
             
               6 
               IMP 14 
                 
                 
               * 
               * 
               S1 
               S1 
               S2* 
               * 
               S3 
               S3 
               S4 
             
             
               7 
               Exit 
                 
                 
                 
                 
                 
                 
               S1 
               S2 
                 
                 
               S3 
               S4 
                 
             
             
               8 
               Exit 
                 
                 
                 
                 
                 
                 
                 
               S1 
               S2 
                 
                 
               S3 
               S4 
             
             
                 
             
          
         
       
     
   
   At time t 6 , another color layer is applied to ITM  12  and is then transferred to sheet S 1 . Sheet S 2  is positioned in feeder  20 , sheet S 3  passes between IMP  6  and ITM  4  while a color layer is applied to ITM  4 , and sheet S 4  is positioned in feeder  18 . 
   At time t 7 , ITM  12  and IMP  14  disengage and sheet S 1  is released from IMP  14 , moving towards the exit. Sheet S 2  passes between ITM  12  and IMP  14  while a color layer is applied to ITM  12 , which is intended for sheets S 3 . Sheet S 3  is transported towards ITM  12  and IMP  14 . ITM  4  and IMP  6  engage, and sheet S 4  is transported onto IMP  6 . An additional color layer is applied onto ITM  4  and all three color layers are transferred to sheet S 4 . 
   At times t 8  and t 9 , sheets S 1  and S 2  exit. As the process of sheets S 3  and S 4  are similar to sheets S 1  and S 2 , further discussion of S 3  and S 4  are omitted. Additionally, although the example illustrated in Table 1 and  FIGS. 3A–3C  shows only four sheets, any number of sheets may be processed using the present invention system and method. 
   Table 2 illustrates another example of a timing chart for use by the present invention system and method. 
   
     
       
         
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             
           
             
               TABLE 2 
             
             
                 
             
             
               Position 
               Time 
               t1 
               t2 
               t3 
               t4 
               t5 
               t6 
               t7 
               t8 
               t9 
               t10 
               t11 
               t12 
               t13 
             
             
                 
             
           
          
             
               1 
               Feeder 18 
               S1 
                 
               S2 
                 
               S3 
                 
               S4 
                 
                 
                 
                 
                 
                 
             
             
               2 
               IMP 6 
               * 
               S1* 
               * 
               S2 
               * 
               S3* 
               * 
               S4 
                 
                 
                 
             
             
               3 
               Transport 
                 
                 
               S1 
                 
               S2 
                 
               S3 
                 
               S4 
                 
                 
             
             
               5 
               Feeder 20 
                 
                 
                 
               S1 
                 
               S2 
                 
               S3 
                 
               S4 
                 
             
             
               6 
               IMP 14 
                 
               * 
               * 
               * 
               S1 
               * 
               S2* 
               * 
               S3 
                 
               S4 
                 
                 
             
             
               7 
               Exit 
                 
                 
                 
                 
                 
               S1 
                 
               S2 
                 
               S3 
                 
               S4 
                 
             
             
               8 
               Exit 
                 
                 
                 
                 
                 
                 
               S1 
                 
               S2 
                 
               S3 
                 
               S4 
             
             
                 
             
          
         
       
     
   
   One advantage of the system and method of the present invention is that in a system with multiple print engines in series, a first sheet media may be transported through the first print engine, without printing to the first sheet media, while the first print applies a color layer to the ITM. The color layer is then transferred to a subsequent sheet media. The time during which the first sheet media passed through the first print engine is used effectively to further the printing process. 
   Two color print engine units can be placed in series with one other so that both units can be printing simultaneously, effectively doubling the output. To fully realize a doubled output speed, each unit must have blank paper present at its input. This requires either a by-pass paper path or a loss of one printing cycle, which would reduce the output to less than twice the speed of a single unit. 
   With this invention, no color print engine cycles are lost while a sheet media is passed through one engine, without receiving color, into a second engine where it will receive color. This allows two color print engines to be placed in series and get double the output of a single standalone engine. 
   The foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention embraces all such alternatives, modifications, and variances that fall within the scope of the appended claims.