Abstract:
In one example, a media guide for use in a printer having a print bar and a print zone adjacent to the print bar includes a movable blocker downstream from the print zone along a media path and movable though a range of motion to block print media from leaving the media path when exiting the print zone,

Description:
BACKGROUND 
       [0001]    In some inkjet printers, a media wide printhead assembly, commonly called a print bar, is used to print on paper or other print media moving past the print bar. Media wide printers usually can print faster than printers in which a narrower printhead assembly is scanned back and forth across the print media. 
     
    
     
       DRAWINGS 
         [0002]      FIG. 1  is a block diagram illustrating an inkjet printer in which examples of a new print media guide may be implemented. 
           [0003]      FIG. 2  is a perspective view illustrating one example of a new media guide configured to block the gap behind the print bar, such as might be used in the printer of  FIG. 1 . 
           [0004]      FIGS. 3 and 4  are side elevation and top down perspective views, respectively, illustrating the print zone in an inkjet printer implementing one example of the new print media guide. The print bar is omitted in  FIG. 4  to better illustrate the media guide. 
           [0005]      FIGS. 5 and 6  illustrate alternate printing positions for the print bar and media guide shown in  FIGS. 3 and 4 . 
           [0006]      FIG. 7  illustrates the media guide shown in  FIGS. 3 and 4  with the print bar in a service position. 
           [0007]      FIG. 8  illustrates the media guide of  FIGS. 3 and 4  blocking the leading edge of a sheet of print media exiting the print zone from leaving the media path. 
           [0008]      FIG. 9  is a top down perspective view illustrating another example of the new media guide. 
           [0009]      FIGS. 10 and 11  illustrate alternate positions for the media guide shown in  FIG. 9 . 
       
    
    
       [0010]    The same part numbers designate the same or similar parts throughout the figures. 
       DESCRIPTION 
       [0011]    Faster printing, media wide printers allow the ink little time to dry before leaving the print zone. Wet ink can cause the leading edge of the print media to curl and cockle as it exits the print zone. A curled or cockled leading edge may curl into any gap between the print bar and downstream parts, causing the media to jam. A new media guide has been developed to block the gap behind the print bar immediately downstream from the print zone so that the print media will not curl into this gap and jam. In one example, the media guide includes a blocker that is biased against the print bar through a range of motion that covers the range of motion of the print bar for changing the spacing between the print bar and the media support platen, such as for thicker (or thinner) media and for duplex printing. Accordingly, examples of the new media guide are described with reference to an inkjet printer using a media wide print bar. However, examples of the new media guide are not limited to media wide print bars or even inkjet printers. Examples of the new media guide might also be implemented in other inkjet type dispensers. The examples shown in the figures and described below, therefore, illustrate but do not limit the invention, which is defined in the Claims following this Description. 
         [0012]    As used in this document, “liquid” means a fluid not composed primarily of a gas or gases; a “platen” means a supporting structure or multiple supporting structures and is not limited to a flat plate; a “printhead” means that part of an inkjet printer or other inkjet type dispenser that dispenses liquid from one or more openings, for example as drops or streams; a “print bar” means a structure or device holding an arrangement of one or more printheads that remains stationary during printing. “Printhead” and “print bar” are not limited to printing with ink but also include inkjet type dispensing of other liquids and/or for uses other than printing. 
         [0013]      FIG. 1  is a block diagram illustrating an inkjet printer  10  in which examples of a new print media guide  12  may be implemented. Referring to  FIG. 1 , printer  10  includes a print bar  14  that includes an arrangement of one or more printheads for dispensing ink on to a sheet or continuous web of paper or other print media  16 . Printer  10  also includes a print media transport mechanism  18  for moving media  16 , an ink supply or multiple supplies  20  for supplying ink to print bar  14 , and a printer controller  22 . Controller  22  represents generally the programming, processor(s) and associated memories, and the electronic circuitry and components needed to control the operative elements of printer  10 . Print media guide  12  is located immediately downstream from print bar  14  along a media path  24  that proceeds from left to right in  FIG. 1 , as indicated by media path arrows  24 . As described in more detail below with reference to the examples shown in  FIGS. 2-11 , media guide  12  blocks the gap behind print bar  14  immediately downstream from print zone  26  so that the leading edge of media  16  will not curl into or otherwise jam at this gap. 
         [0014]      FIG. 2  is a perspective view illustrating one example of a new media guide  12  configured to block the gap behind print bar  14 , such as might be used in the printer of  FIG. 1 .  FIGS. 3 and 4  are more detailed views illustrating a print zone  26  in an inkjet printer  10  implementing a media guide  12  like the one shown in  FIG. 2 . 
         [0015]    Referring first to  FIG. 2 , a media wide print bar  14  includes multiple printheads  28  surrounded by a shroud or other protective structure  30 . Media guide  12  includes a moveable blocker  32  connected to a stationary base  34 . The media path is from left to right in  FIG. 2  as indicated by arrows  24 . Blocker  32  is positioned immediately downstream from print bar  14  and extends across substantially the full width of media path  24  to block print media from the space behind print bar  14 . In this example for guide  12 , blocker  32  pivots on base  34  along a pivot  36 , as indicated by motion arrow  38 . The pivotable blocker  32  is biased against print bar  14  shroud  30  through a range of motion that covers the range of motion of print bar  14  for changing the printhead to platen spacing, such as for thicker (or thinner) media and for duplex printing. Although a single continuous blocker  32  spans the media path in  FIG. 2 , other configurations are possible. For example, multiple discrete blockers spaced apart from one another might be used in some implementations as long as there is sufficient blocking area to effectively block the print media from jamming behind print bar  14 . 
         [0016]    Referring now to the more detailed views of  FIGS. 3 and 4 , print bar  14  positioned over a media support platen  40  defines a print zone  26  in which ink is dispensed on to the paper or other print media  16 . Print bar  14  and media  16  are omitted from the top down perspective view of  FIG. 4  to better illustrate media guide  12 . As best seen in  FIG. 3 , media transport  18  includes print zone entry rollers  42 ,  44  and exit rollers  46 ,  48 . In this example, exit rollers  46  are configured as star wheels  46  that help minimize damaging the ink image on media  16  as it exits print zone  26 . 
         [0017]    In this example for guide  12 , blocker  32  is connected to base  34  at pivot  36 . A torsion spring or other suitable biasing mechanism  50  ( FIG. 4 ) biases the pivotable blocker  32  through a range of motion that covers the range of motion of print bar  14  for changing the spacing between printheads  28  ( FIG. 2 ) and platen  40 , for example to accommodate different thicknesses of print media  16 . In this example, as shown in  FIG. 4 , spring  50  is connected between a stationary base  34  and blocker  32 . Other suitable biasing configurations are possible. The rotational motion of blocker  32  is indicated by arrow  38  in  FIG. 3  and the translational motion of print bar  14  is indicated by arrow  52  in  FIG. 3 . In the example shown in the figures, blocker  32  is biased against print bar  14 , in particular against shroud  30 . While it is expected that blocker  32  will usually be biased against print bar  14  to eliminate any gap behind print bar  14 , it may be adequate or even desirable in some implementations that blocker  32  not contact print bar  14 . 
         [0018]      FIGS. 5 and 6  show different printhead to platen spacing for printing and the corresponding positions for print bar  14  and media guide  12 .  FIG. 7  shows print bar  14  in a servicing position raised far above platen  40  and the corresponding position of media guide  12 . In  FIG. 5 , print bar  14  is lowered to a smaller printhead to platen spacing PPS 1  and spring  50  presses blocker  32  against print bar shroud  30 . In  FIG. 6 , print bar  14  is raised to a larger printhead to platen spacing PPS 2 , blacker  32  has rotated up at the urging of spring  50 , and spring  50  continues to press blocker  32  against print bar shroud  30 . In  FIG. 7 , print bar  14  is raised to a service position too far above platen  40  for printing and outside the range of motion of blocker  32 . Thus, blacker  32  no longer contacts print bar shroud  30 , for example either because the further rotation of blocker  32  is blocked or because spring  50  no longer exerts a biasing force on blacker  32 . 
         [0019]      FIG. 8  illustrates media guide  12  blocking the leading edge  54  of a sheet of print media  16  exiting print zone  26 . Print bar  14  in  FIG. 8  is in the PPS 2  position of  FIG. 6  such as might be used for duplex printing or printing thicker media  16 . Referring to  FIG. 8 , blacker  32  includes a surface  56  that blocks media leading edge  54  from leaving media path  24  downstream from print zone  26  and guides leading edge  54  toward the nip between star wheel  46  and exit roller  48 . 
         [0020]      FIG. 9  illustrates another example of the new media guide  12  in which guide  12  includes a built-in biasing mechanism.  FIGS. 10 and 11  show different printhead to platen spacing for printing and the corresponding positions for print bar  14  and for this example of media guide  12 . Referring to  FIGS. 9-11 , blacker  32  is connected to base  34  through flexible connectors  58 . When flexed, as shown in  FIGS. 10 and 11 , each connector  58  acts as a biasing mechanism that urges blocker  32  against print bar shroud  30 . Blocker  32  and connectors  58  together form guide surface  56  that blocks the leading edge of the print media from leaving media path  24  downstream from print zone  26  and guides the leading edge toward the nip between star wheel  46  and exit roller  48  ( FIG. 8 ). 
         [0021]    As noted at the beginning of this Description, the examples shown in the figures and described above illustrate but do not limit the invention. Other examples are possible. Therefore, the foregoing description should not be construed to limit the scope of the invention, which is defined in the following claims.