Abstract:
An apparatus that comprises a plurality of printing cartridges to reproduce an image, wherein each printing cartridge prints a portion of the image onto a substrate. The apparatus further comprises a media transport for moving the substrate parallel to a first dimension. The printing cartridges are disposed on a carrier in a two dimensional pattern such that the plurality of printing cartridges are able to print on the substrate a line that is perpendicular to the first dimension. Fewer than half of the plurality printing cartridges that print segments of the line that abut each other are adjacent to each other along the first dimension.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application Ser. No. 60/765,353, filed Feb. 3, 2006, and incorporated herein by reference in its entirety. 
     
    
     REFERENCE REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable  
       SEQUENTIAL LISTING  
       [0003]     Not applicable  
       BACKGROUND OF THE INVENTION  
       [0004]     1. Field of the Invention  
         [0005]     The present invention relates generally to printing systems and more particularly to a system that uses a plurality of printing cartridges for high-speed printing.  
         [0006]     2. Description of the Background of the Invention  
         [0007]     Ink jet printing systems use ink jet cartridges that propel a drop of ink to a substrate, such as paper. Some ink jet printing system use a traversing print head, where a print head traverses the width of the paper dropping one or more lines of ink to form a swath of an image along the width of the paper. Upon completion of the swath, the paper is advanced in accordance with the width of the swath and the print head traverses the width of the paper to print a next swath. Traversing head printing systems are generally slower and are used in applications where print speed is not of great importance.  
         [0008]     Other ink jet printing systems use a single fixed printing head. The paper advances under the printing head and the nozzles of the printing head eject drops of ink onto the paper in accordance with the position with paper to print an image. These types of ink jet printing systems are capable of higher print speeds than printing systems which use traversing heads; however, these systems generally use a relatively narrow printing head and, thus are used in applications where a relatively narrow, 1 to 2 inches (2.54-5.08 cm), image is required. Printing heads with larger widths are not commonly used because of the complexity of manufacture and because the entire printing head has to be replaced if any nozzles therein fail.  
         [0009]     To overcome the speed short comings of the traversing head printing systems and the print width limitations of the fixed head printing systems, printing systems have been developed that stitch images printed by multiple, small, fixed printing heads. Typical printing heads comprise nozzles and require more area than necessary for the nozzles. The additional area is needed for mounting points, ink delivery tubing, drive electronics, etc. As such, two printing heads that are to print adjoining portions of an image cannot simply be mounted onto a frame or a carrier abutted against one another. Instead, printing heads are typically mounted onto a carrier in a two dimensional fashion.  FIG. 1  shows a carrier  100  having printing cartridges  102  A-F mounted thereon. Each of the printing cartridges  102 -A through  102 -F comprise print heads  104 -A through  104 -F, respectively, wherein, each print head comprises a number of nozzles controllable to print a swath of an image. Each nozzle in the printing cartridge is controlled individually to eject a drop of ink onto a substrate  106 . In operation, the substrate  106  is transported past the printing cartridges  102  in the direction indicated by the arrow A, while the nozzles that comprise each print head  104  are controlled to eject ink onto the substrate to print a swath in a direction parallel to the paper transport direction (arrow A). The swaths are printed abutting one another to print a stitched image of width W 1  (and represented in  FIG. 1  by a line of text  108 . The carrier shown in  FIG. 1  has a length of D that is at least sufficient to accommodate the number of printing cartridges required to print an image of width W 1 . Typical printing cartridges are able to print between 1 to 1.5 inch (2.54-3.81 cm) swaths. Using such printing cartridges in the configuration shown in  FIG. 1  would enable printing of images that have a width W 1  of 6 to 9 inches (15.24-22.86 cm).  
         [0010]      FIG. 2  shows an arrangement of printing cartridges  202  A-F and  204  A-F on a carrier  200  that has a length D for printing an image that has a width W 2 , that is twice the width of the image printed by the arrangement of printing cartridges shown in  FIG. 1 . Specifically, a first group of six printing cartridges  202  A-F prints a first portion of the image having a width W 1  and a second group of six printing cartridges  204  A-F prints a second portion of the image that also has width W 1 . The two groups printing in concert can produce a stitched image with a width W 2 . As described above in connection with  FIG. 1 , the substrate  206  is transported past the carrier  200  in the direction shown by arrow A such that the nozzles comprising the printing cartridges  202  A-F and  204  A-F eject ink thereon to print an image (illustrated as the line of characters  208 ). The configuration of  FIG. 2  enables printing of images that have a width W 2  of between 12 and 18 inches (30.48-40.72 cm), (if each printing cartridge prints a swatch of between 1 to 1.5 inches, i.e., 2.54-3.81 cm).  
         [0011]     The printing cartridges  202  A-F are typically distributed on the carrier  200  in the dimension parallel to the direction A such that the distance between centers of each pair of printing cartridges that print adjacent swaths of the image (e.g., printing cartridges  202 -A and  202 -B) is equal to the inter-head distance d 1 , which is the distance between adjacent printing cartridges. As shown in  FIG. 2 , printing cartridges  202 -F and  204 -A print adjacent swaths of the image; however, the distance between these printing cartridges is five times the inter-head distance d 1  and, therefore, there are four printing cartridges between cartridge  202 -F and  204 -A in the direction parallel to arrow A.  
         [0012]     Alignment errors or errors in the transport of the substrate  206  may cause a misalignment (i.e., a stitching error) between two swaths of an image that are stitched. If such a misalignment is relatively small, there may not be any perceptible error in the image of the stitched swaths printed by two printing cartridges, especially if the distance between the two printing cartridges is relatively small. In particular, if the distance between the pair of printing cartridges that print abutting swaths of an image is equal to the inter-head distance d 1  then a misalignment error between the cartridges may not result in a perceptible error in the stitching error. As shown in  FIG. 2 , when the two printing cartridges that print abutting swaths are members of the same group (either  202  A-F or  204  A-F) of printing cartridges, the distance therebetween is d 1  (and there are no cartridges between them). The possibility of a perceptible stitching error is significantly greater if the misalignment occurs between two printing cartridges that print abutting swaths, where the two printing cartridges are members of different groups (i.e., between printing cartridges  202 -F and  204 -A). Decreasing the distance between pairs printing cartridges that print abutting swaths of the image reduces this possibility of perceptible stitching error.  
       SUMMARY OF THE INVENTION  
       [0013]     An apparatus for printing that comprises a plurality of printing cartridges and a carrier for mounting the plurality of printing cartridges. The apparatus further comprises a media transport that moves a substrate parallel to a first dimension. The plurality of printing cartridges are disposed on the carrier in a two dimensional pattern, wherein plurality of printing cartridges are able to print a line on the substrate perpendicular to the first dimension. In addition, fewer than half of the plurality of printing cartridges that print segments of the line that abut each other are adjacent to each other along the first dimension.  
         [0014]     Other aspects and advantages of the present invention will become apparent upon consideration of the following detailed description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  shows a prior art arrangement of printing cartridges on a carrier;  
         [0016]      FIG. 2  shows another prior art arrangement of printing cartridges on a carrier;  
         [0017]      FIG. 3  shows an embodiment of a printing carrier having printing cartridges arranged thereon;  
         [0018]      FIG. 4  shows another embodiment of a printing carrier having printing cartridges arranged thereon;  
         [0019]      FIG. 5  shows yet another embodiment a carrier on which printing cartridges are arranged;  
         [0020]     FIGS.  6 A-C are schematic diagrams of an embodiment of a printing system that uses an embodiment of the carrier depicted in  FIGS. 1-5 ;  
         [0021]     FIGS.  7 A-B are schematic diagrams of additional embodiments of printing systems that use the embodiments of the carrier depicted in  FIGS. 1-5 ;  
         [0022]      FIG. 8  depicts still another embodiment of a carrier on which printing cartridges are arranged; and  
         [0023]      FIG. 9  shows of a curved carrier that has slots therein for mounting printing cartridges. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]      FIG. 3  shows a carrier  300  having an arrangement of two groups of printing cartridges  302  A-F and  304  A-F. The maximum distance between any pair of the printing cartridges  302  A-F and  304  A-F that print abutting swaths is two times the inter-head distance d 1 . As was discussed above with reference to  FIG. 2 , reducing the distance between printing cartridges that print abutting swaths also reduces the stitching error. In particular, the distance between printing cartridge  302 -F and  304 -A is twice the inter-head distance d 1  instead of five times d 1  as was the case in the configuration shown in  FIG. 2 . If the print width produced by the individual printing cartridges  202  A-F and  204  A-F used in the configuration shown in  FIG. 2  is identical to the print width individual printing cartridges  302  A-F and  304  A-F, then the maximum width of the image printed by the combination of the cartridges in  FIG. 3  is identical to the maximum width of the image produced using the arrangement of the printing cartridges shown in  FIG. 2 . Arranging cartridges on a carrier such that the number of printing cartridges disposed (in the direction parallel to arrow A) between any two printing cartridges that print abutting swaths of an image is less than the half the number of cartridges in each group affords a reduction in the possibility of stitching error.  
         [0025]      FIG. 4  shows another way of disposing two groups of six cartridges to print a stitched image that has a width identical to that possible by the configurations shown in  FIGS. 2 and 3 . The maximum distance between two heads in the paper transport direction is two times the inter-head distance d 1 . It should be apparent to those skilled in the art, that other configurations are possible to minimize the distance between printing cartridges that print abutting swaths.  
         [0026]      FIG. 5  shows a configuration of three groups on a carrier  500 , wherein each group comprises eight printing cartridges  502  A-H,  504  A-H, and  506  A-F. The printing cartridges  502 ,  504 , and  506  are disposed to minimize the distance between any pair of printing cartridges. In this configuration, the maximum distance between a pair printing cartridges that print abutting swaths is three times the inter-head distance d 1 . If each of the cartridges is able to print 1 to 1.5 inches (2.54-2.81 cm), then this configuration allows a maximum image width between 24 and 36 inches (60.96-91.44 cm).  
         [0027]     Although the configurations shown in  FIGS. 3 and 4  show the distribution of two groups of six printing cartridges on a carrier to minimize the effects of misalignment and transport errors on stitched portions of printed images, other distributions of printing cartridges will be apparent to those skilled in the art. Similarly,  FIG. 5  shows one arrangement of three groups of eight cartridges on a carrier, and other arrangements should be apparent to those skilled in the art. Furthermore, other arrangements of two or more groups of cartridges will be apparent, where the number of cartridges disposed between any two cartridges that print adjacent or abutting swaths is less than half the number of cartridges that comprise the group.  
         [0028]      FIG. 6A  shows a schematic of a printing system that combines a paper transport system and a carrier  602  that has printing cartridges disposed thereon in the manner described above. Specifically, a belt  604  transports a web of paper  606  past the carrier  602 , which is mounted vertically. The carrier  602  and belt  604  are positioned such that the printing cartridges may eject drops of ink onto the paper as the paper is transported.  FIG. 6B  shows a similar configuration to  FIG. 6A  and comprises the carrier  602  and the belt  604  arranged such that the web of paper  606  is transported horizontally therebetween.  FIG. 6C  shows an arrangement for printing on sheets of paper, where a carrier  614  is mounted opposite a belt  610 , which transports sheets of paper  618  A-C past the carrier. As each sheet moves past the printing cartridges that comprise the carrier, the printing cartridges are controlled to eject ink.  
         [0029]      FIG. 7A  shows a carrier  702  that is curved (e.g., a section of a cylinder) instead of planer. The printing cartridges are disposed on the carrier  702  as described above. The carrier  702  and a drum (or cylinder)  704  are positioned such that a web of paper  706  may be transported therebetween. Specifically, rotation of the drum  704  urges the web paper  706  to move in the rotational direction and the printing cartridges comprising the carrier  702  are controlled to eject ink onto the paper to produce an image.  FIG. 7B  shows an arrangement of a first carrier  708  and a second carrier  710  about a drum  712 . The paper is transported between the first and second carriers  708  and  710 , respectively, and the drum. The printing cartridges that comprise the first carrier  708  eject ink onto a portion of the web of paper  714 . The printing cartridges that comprise the second carrier  710  then eject inks onto the same portion of the web of paper  714  when that portion is positioned between the second carrier  710  and the drum. If the printing cartridges that comprise the first carrier  708  are supplied with a first ink color and the printing cartridges that comprise the second carrier  710  are supplied with a second ink color, then the configuration of  FIG. 7B  enables printing of images that have two colors. It should be apparent that additional drum/carrier combinations similar to those shown in  FIG. 7B  may be used subsequently to print images having than more two colors onto the web of paper.  
         [0030]     Details of the mechanical and electrical control systems required enabling the systems shown in FIGS.  6 A-C and FIGS.  7 A-B are known to those skilled in the art.  
         [0031]     Referring once again to  FIG. 3 , in some embodiments, all of the printing cartridges  302  A-F and  304  A-F are supplied with ink having the same color. In other embodiments, the group of cartridges  302  A-F supplied with ink having a first color and  304  A-F may be supplied with ink having a second color. Similarly, in some embodiments a single control system receives a line of image data (e.g., a raster line) and coordinates the ejection of ink accordingly from all of the cartridges mounted on the carrier  300  to reproduce the line on the substrate  306 . In other embodiments, a first control system and a second control system each receive a line of image data. The first control system coordinates ejection of ink from a first group of printing cartridges (e.g., print cartridges  302  A-F) in accordance with the line of image data and the second control system coordinates ejection of ink from a second group of printing cartridges (e.g., printing cartridges  304  A-F) in accordance with the line of image data. In yet another embodiment, a first control system receives a first portion of the line of image data and coordinates the ejection of ink from the first group of printing cartridges in accordance therewith. In this embodiment, the second control system receives a second portion of the line of image data and coordinates the ejection of ink from the second group of printing cartridges in accordance with the second portion.  
         [0032]      FIG. 8  shows an embodiment of a carrier  800  having printing cartridges  802  A-F and  804  A-F arranged thereon. This embodiment is similar to that shown in  FIG. 3 , except that the individual printing cartridges  802  A-F and  804  A-F are mounted at an angle φ with respect to a perpendicular to the transport direction A of the substrate. This arrangement allows the resolution of the image printed by the printing cartridges to be increased. The value of the angle φ depends on the printing cartridge being used. The manufacturer of the printing cartridge may recommend particular values of φ that may be used to print images at various resolutions. For example, in one embodiment positioning the printing cartridges at an angle φ that is between 1.5° and 3° that results in an output resolution of between 600 dots-per-inch (dpi) in the paper transport direction (arrow A) and 300 dpi across the width of the substrate and 600 dpi in both the paper transport direction and the paper width direction.  
         [0033]     Furthermore, mounting the printing cartridges  802  A-F and  804  A-F at an angle also reduces the transient ink supply necessary to each printing cartridge. In particular, if the printing cartridges  802  A-F and  804  A-F are not mounted at an angle (that is, nozzles of these cartridges are collinear with a direction perpendicular to the transport direction of the substrate), then all of the nozzles that comprise a particular print cartridge must be eject ink simultaneously. However, mounting the cartridges at an angle requires only a portion of the nozzles of a particular ink cartridge to eject ink. Reducing the number of nozzles of a printing cartridge that must simultaneously eject a drop of ink reduces both the transient ink supply requirements to the printing cartridge and also the transient power required to force ejection of ink drops from the nozzles of the printing cartridge.  
         [0034]     In one embodiment, the carriers described herein above are milled at a high precision from a block of steel and are tempered to be thermally stable. In other embodiments, the carrier is made out of carbon fiber. In still other embodiments, the carrier Invar (an alloy of iron and nickel) is used to manufacture the carrier. Other materials suitable for manufacturing the carrier will be apparent to those skilled in the art. The arrangements of printing cartridges shown in the figures and described above are locations where printing cartridges may be mounted and provided as templates to show the position of one printing cartridge relative to another. Such positions would be positions where slots are cut into the carrier, and the printing cartridges would be secured into the slots using mounting screws.  FIG. 9  shows an embodiment of a portion of a carrier  900  that is curved. The carrier  900  comprises a first group of slots  902  A-F for allow mounting a first group of six printing cartridges and a second group of slots  904  A-F for mounting a second group of six printing cartridges. The portion of the carrier  900  shown  FIG. 9  also comprises slots  906 -A and  906 -B that are part of the third group of slots. The remaining slots of the third group are not shown. The carrier also comprises mounting holes  908 ,  910 , and  910  for mounting and aligning a printing cartridge that is urged into the slot  902 -A. Typically, screws are used to secure the printing cartridge into the slot. Holes similar to  908 ,  910 , and  912  are associated with the remaining slots.  
         [0035]     The arrangements described above may be used with any type of printing cartridge including those used for desktop ink jet printer, ink jet plotters, industrial ink jet printers, etc. It should be apparent that the embodiments described above are not limited to use with ink jet cartridges, but may be used with other types of printing technologies where image data is stitched across multiple cartridges. For example, the arrangements described above may be used to arrange heads that are used to change magnetic flux on an imaging drum used in magnetography. Similarly, imaging heads may be arranged as described above to expose an imaging drum used in xerography.  
       INDUSTRIAL APPLICABILITY  
       [0036]     Numerous modifications to the present invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is presented for the purpose of enabling those skilled in the art to make and use the invention and to teach the best mode of carrying out same. The exclusive rights to all modifications which come within the scope of the appended claims are reserved.