Abstract:
A printing fluid refill unit for a print engine includes a reservoir having a variable storage volume for holding an amount of printing fluid, the variable storage volume having a plurality of discrete volumetric increments, each of the discrete volumetric increments having equal volumes, the reservoir further having an actuator for reducing the variable storage volume by one or more of the discrete volumetric increments; a ratchet system forming part of the actuator, the ratchet system effecting variation of the storage volume by a minimum increment of one discrete volumetric increment; an information storage element for storing information on the amount of printing fluid contained in the refill unit and for connecting with an information reader incorporated in the print engine for reading the information stored by the storage element when the refill unit is mounted to the print engine; a selector for activating the actuator to dispense a volume of the printing fluid equal to a selected multiple of the discrete volumetric increments, wherein the information stored by the storage element enables the reader to control the selector so as to derive the selected multiple of the volumetric increments; and a sensor for sensing the position of the ratchet, whereby a remaining volume of ink in the variable storage volume is determined.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present application is a Continuation of U.S. application Ser. No. 11/014,750 filed Dec. 29, 2004, which is a Continuation-In-Part of U.S. application Ser. No. 10/760,254 filed on Jan. 21, 2004, now issued U.S. Pat. No. 7,448,734. 
         [0000]    In the interests of brevity, the disclosure of the parent application is incorporated in its entirety into the present specification by cross reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a high speed print engine for an inkjet printer unit, and more particularly to a system for refilling the print engine with a selected quantity of refill ink. 
       CO-PENDING APPLICATIONS 
       [0003]    The following applications have been filed by the Applicant with the present application: 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
               
             
             
               
                 7,152,972 
                 7,543,808 
                 7,621,620 
                 7,669,961 
                 7,331,663 
               
               
                 7,360,861 
                 7,328,973 
                 7,427,121 
                 7,407,262 
                 7,303,252 
               
               
                 7,249,822 
                 7,537,309 
                 7,311,382 
                 7,360,860 
                 7,364,257 
               
               
                 7,390,075 
                 7,350,896 
                 7,429,096 
                 7,384,135 
                 7,331,660 
               
               
                 7,416,287 
                 7,488,052 
                 7,322,684 
                 7,322,685 
                 7,311,381 
               
               
                 7,270,405 
                 7,303,268 
                 7,470,007 
                 7,399,072 
                 7,393,076 
               
               
                 7,588,301 
                 7,249,833 
                 7,524,016 
                 7,490,927 
                 7,331,661 
               
               
                 7,524,043 
                 7,300,140 
                 7,357,492 
                 7,357,493 
                 7,566,106 
               
               
                 7,380,902 
                 7,284,816 
                 7,284,845 
                 7,255,430 
                 7,390,080 
               
               
                 7,328,984 
                 7,350,913 
                 7,322,671 
                 7,380,910 
                 7,431,424 
               
               
                 7,470,006 
                 7,585,054 
                 7,347,534 
                 7,306,320 
                 7,377,635 
               
               
                 11/014,727 
                 11/014,730 
               
               
                   
               
             
          
         
       
     
         [0004]    The disclosures of these co-pending applications are incorporated herein by reference. 
       CROSS REFERENCES TO RELATED APPLICATIONS 
       [0005]    The following patents or patent applications filed by the applicant or assignee of the present invention are hereby incorporated by cross-reference. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
               
             
             
               
                 7,364,256 
                 7,258,417 
                 7,293,853 
                 7,328,968 
                 7,270,395 
               
               
                 7,461,916 
                 7,510,264 
                 7,334,864 
                 7,255,419 
                 7,284,819 
               
               
                 7,229,148 
                 7,258,416 
                 7,273,263 
                 7,270,393 
                 6,984,017 
               
               
                 7,347,526 
                 7,465,015 
                 7,364,255 
                 7,357,476 
                 11/003,614 
               
               
                 7,284,820 
                 7,341,328 
                 7,246,875 
                 7,322,669 
                 6,623,101 
               
               
                 6,406,129 
                 6,505,916 
                 6,457,809 
                 6,550,895 
                 6,457,812 
               
               
                 7,152,962 
                 6,428,133 
                 7,204,941 
                 7,282,164 
                 7,465,342 
               
               
                 7,278,727 
                 7,417,141 
                 7,452,989 
                 7,367,665 
                 7,138,391 
               
               
                 7,153,956 
                 7,423,145 
                 7,456,277 
                 7,550,585 
                 7,122,076 
               
               
                 7,148,345 
                 7,416,280 
                 7,252,366 
                 7,488,051 
                 7,360,865 
               
               
                 7,628,468 
                 7,334,874 
                 7,393,083 
                 7,475,965 
                 7,578,582 
               
               
                 7,591,539 
                 10/922,887 
                 7,472,984 
                 10/922,874 
                 7,234,795 
               
               
                 7,401,884 
                 7,328,975 
                 7,293,855 
                 7,410,250 
                 7,401,900 
               
               
                 7,527,357 
                 7,410,243 
                 7,360,871 
                 10/922,877 
                 6,746,105 
               
               
                 7,156,508 
                 7,159,972 
                 7,083,271 
                 7,165,834 
                 7,080,894 
               
               
                 7,201,469 
                 7,090,336 
                 7,156,489 
                 7,413,283 
                 7,438,385 
               
               
                 7,083,257 
                 7,258,422 
                 7,255,423 
                 7,219,980 
                 7,591,533 
               
               
                 7,416,274 
                 7,367,649 
                 7,118,192 
                 7,618,121 
                 7,322,672 
               
               
                 7,077,505 
                 7,198,354 
                 7,077,504 
                 7,614,724 
                 7,198,355 
               
               
                 7,401,894 
                 7,322,676 
                 7,152,959 
                 7,213,906 
                 7,178,901 
               
               
                 7,222,938 
                 7,108,353 
                 7,104,629 
                 7,246,886 
                 7,128,400 
               
               
                 7,108,355 
                 6,991,322 
                 7,287,836 
                 7,118,197 
                 7,575,298 
               
               
                 7,364,269 
                 7,077,493 
                 6,962,402 
                 10/728,803 
                 7,147,308 
               
               
                 7,524,034 
                 7,118,198 
                 7,168,790 
                 7,172,270 
                 7,229,155 
               
               
                 6,830,318 
                 7,195,342 
                 7,175,261 
                 7,465,035 
                 7,108,356 
               
               
                 7,118,202 
                 7,510,269 
                 7,134,744 
                 7,510,270 
                 7,134,743 
               
               
                 7,182,439 
                 7,210,768 
                 7,465,036 
                 7,134,745 
                 7,156,484 
               
               
                 7,118,201 
                 7,111,926 
                 7,431,433 
                 09/575,197 
                 7,079,712 
               
               
                 6,825,945 
                 7,330,974 
                 6,813,039 
                 6,987,506 
                 7,038,797 
               
               
                 6,980,318 
                 6,816,274 
                 7,102,772 
                 7,350,236 
                 6,681,045 
               
               
                 6,728,000 
                 7,173,722 
                 7,088,459 
                 09/575,181 
                 7,068,382 
               
               
                 7,062,651 
                 6,789,194 
                 6,789,191 
                 6,644,642 
                 6,502,614 
               
               
                 6,622,999 
                 6,669,385 
                 6,549,935 
                 6,987,573 
                 6,727,996 
               
               
                 6,591,884 
                 6,439,706 
                 6,760,119 
                 7,295,332 
                 7,064,851 
               
               
                 6,826,547 
                 6,290,349 
                 6,428,155 
                 6,785,016 
                 6,831,682 
               
               
                 6,741,871 
                 6,927,871 
                 6,980,306 
                 6,965,439 
                 6,840,606 
               
               
                 7,036,918 
                 6,977,746 
                 6,970,264 
                 7,068,389 
                 7,093,991 
               
               
                 7,190,491 
                 7,511,847 
                 7,663,780 
                 10/962,412 
                 7,177,054 
               
               
                 7,364,282 
                 10/965,733 
                 10/965,933 
                 10/974,742 
                 7,538,793 
               
               
                 6,982,798 
                 6,870,966 
                 6,822,639 
                 6,737,591 
                 7,055,739 
               
               
                 7,233,320 
                 6,830,196 
                 6,832,717 
                 6,957,768 
                 7,170,499 
               
               
                 7,106,888 
                 7,123,239 
                 10/727,162 
                 7,377,608 
                 7,399,043 
               
               
                 7,121,639 
                 7,165,824 
                 7,152,942 
                 10/727,157 
                 7,181,572 
               
               
                 7,096,137 
                 7,302,592 
                 7,278,034 
                 7,188,282 
                 7,592,829 
               
               
                 10/727,180 
                 10/727,179 
                 10/727,192 
                 10/727,274 
                 10/727,164 
               
               
                 7,523,111 
                 7,573,301 
                 7,660,998 
                 10/754,536 
                 10/754,938 
               
               
                 10/727,160 
                 7,369,270 
                 6,795,215 
                 7,070,098 
                 7,154,638 
               
               
                 6,805,419 
                 6,859,289 
                 6,977,751 
                 6,398,332 
                 6,394,573 
               
               
                 6,622,923 
                 6,747,760 
                 6,921,144 
                 10/884,881 
                 7,092,112 
               
               
                 7,192,106 
                 7,374,266 
                 7,427,117 
                 7,448,707 
                 7,281,330 
               
               
                 10/854,503 
                 7,328,956 
                 10/854,509 
                 7,188,928 
                 7,093,989 
               
               
                 7,377,609 
                 7,600,843 
                 10/854,498 
                 10/854,511 
                 7,390,071 
               
               
                 10/854,525 
                 10/854,526 
                 7,549,715 
                 7,252,353 
                 7,607,757 
               
               
                 7,267,417 
                 10/854,505 
                 7,517,036 
                 7,275,805 
                 7,314,261 
               
               
                 7,281,777 
                 7,290,852 
                 7,484,831 
                 10/854,523 
                 10/854,527 
               
               
                 7,549,718 
                 10/854,520 
                 7,631,190 
                 7,557,941 
                 10/854,499 
               
               
                 10/854,501 
                 7,266,661 
                 7,243,193 
                 10/854,518 
                 10/934,628 
               
               
                   
               
             
          
         
       
     
       BACKGROUND OF THE INVENTION 
       [0006]    Traditionally, most commercially available inkjet printers have a print engine which forms part of the overall structure and design of the printer. In this regard, the body of the printer unit is typically constructed to accommodate the print head and associated media delivery mechanisms, and these features are integral with the printer unit. 
         [0007]    This is especially the case with inkjet printers that employ a printhead that traverses back and forth across the media as the media is progressed through the printer unit in small iterations. In such cases the reciprocating printhead is typically mounted to the body of the printer unit such that it can traverse the width of the printer unit between a media input roller and a media output roller, with the media input and output rollers forming part of the structure of the printer unit. With such a printer unit it may be possible to remove the printhead for replacement, however the other parts of the print engine, such as the media transport rollers, control circuitry and maintenance stations, are typically fixed within the printer unit and replacement of these parts is not possible without replacement of the entire printer unit. 
         [0008]    As well as being rather fixed in their design construction, printer units employing reciprocating type printheads are considerably slow, particularly when performing print jobs of full colour and/or photo quality. This is due to the fact that the printhead must continually traverse the stationary media to deposit the ink on the surface of the media and it may take a number of swathes of the printhead to deposit one line of the image. 
         [0009]    Recently, it has been possible to provide a printhead that extends the entire width of the print media so that the printhead can remain stationary as the media is transported past the printhead. Such systems greatly increase the speed at which printing can occur as the printhead no longer needs to perform a number of swathes to deposit a line of an image, but rather the printhead can deposit the ink on the media as it moves past at high speeds. Such printheads have made it possible to perform full colour 1600 dpi printing at speeds in the vicinity of 60 pages per minute, speeds previously unattainable with conventional inkjet printers. 
         [0010]    Such a pagewidth printhead typically requires high precision and high speed paper movement and as such the entire print engine (printhead, paper handling mechanisms and control circuitry etc) must be configured accordingly to ensure high quality output. 
         [0011]    Accordingly, there is a need to provide a print engine having a pagewidth printhead that can be readily employed within a standard body of a printer unit and is constructed in a manner that ensures that all the necessary parts of the print engine are configured in a manner that enables consistent, high speed printing. 
       SUMMARY OF THE INVENTION 
       [0012]    According to an aspect of the present disclosure, a printing fluid refill unit for a print engine includes a reservoir having a variable storage volume for holding an amount of printing fluid, the variable storage volume having a plurality of discrete volumetric increments, each of the discrete volumetric increments having equal volumes, the reservoir further having an actuator for reducing the variable storage volume by one or more of the discrete volumetric increments; a ratchet system forming part of the actuator, the ratchet system effecting variation of the storage volume by a minimum increment of one discrete volumetric increment; an information storage element for storing information on the amount of printing fluid contained in the refill unit and for connecting with an information reader incorporated in the print engine for reading the information stored by the storage element when the refill unit is mounted to the print engine; a selector for activating the actuator to dispense a volume of the printing fluid equal to a selected multiple of the discrete volumetric increments, wherein the information stored by the storage element enables the reader to control the selector so as to derive the selected multiple of the volumetric increments; and a sensor for sensing the position of the ratchet, whereby a remaining volume of ink in the variable storage volume is determined. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    In the drawings: 
           [0014]      FIG. 1  shows a front perspective view of a printer unit employing a print engine according to an embodiment of the present invention; 
           [0015]      FIG. 2  shows the printer unit of  FIG. 1  with the lid open exposing the print engine; 
           [0016]      FIG. 3  shows a schematic of document data flow in a printing system according to one embodiment of the present invention; 
           [0017]      FIG. 4  shows a more detailed schematic showing an architecture used in the printing system of  FIG. 3 ; 
           [0018]      FIG. 5  shows a block diagram of an embodiment of the control electronics as used in the printing system of  FIG. 3 ; 
           [0019]      FIG. 6  shows an exploded perspective view of a print engine according to an embodiment of the present invention; 
           [0020]      FIG. 7  shows the print engine of  FIG. 6  with cartridge unit inserted in the cradle unit; 
           [0021]      FIG. 8  shows the cradle unit of  FIG. 7  with the cover assembly in the closed position; 
           [0022]      FIG. 9  shows a front perspective view of the cartridge unit of  FIG. 7 ; 
           [0023]      FIG. 10  shows a front perspective view of the underside of the cartridge unit of  FIG. 9 ; 
           [0024]      FIG. 11  shows an exploded perspective view of the cartridge unit of  FIG. 7 ; 
           [0025]      FIG. 12  shows an alternative exploded view of the cartridge unit of  FIG. 7 ; 
           [0026]      FIG. 13  shows a front perspective view of the main body of the cartridge unit of  FIG. 7  with the lid assembly removed; 
           [0027]      FIG. 14  shows an exploded front perspective view of the main body of  FIG. 13 ; 
           [0028]      FIG. 15  shows a sectional side view of the main body of  FIG. 13 ; 
           [0029]      FIG. 16  shows an example of an ink storage arrangement for use in the cartridge unit of  FIG. 9  according to one embodiment; 
           [0030]      FIG. 17  shows a cross-sectional view of an ink storage compartment employing the ink storage arrangement of  FIG. 16   
           [0031]      FIG. 18  shows a front perspective view of a printhead assembly suitable for use with the cartridge unit of  FIG. 9 ; 
           [0032]      FIG. 19  shows a front perspective view of the underside of the printhead assembly of  FIG. 18 ; 
           [0033]      FIG. 20  shows an exploded view of the printhead assembly of  FIG. 18 ; 
           [0034]      FIG. 21  shows a cross-sectional end view of the printhead assembly of  FIG. 18 ; 
           [0035]      FIG. 22  shows a simplified schematic depiction of linked integrated circuits according to one embodiment of the present invention; 
           [0036]      FIG. 23  shows a simplified schematic depiction of two linked integrated circuits employing a right angled join; 
           [0037]      FIGS. 24A and 24B  show a schematic depiction of two linked integrated circuits employing an angled join; 
           [0038]      FIG. 25  shows a simplified schematic depiction of two linked integrated circuits employing a vertical offset join; 
           [0039]      FIG. 26  shows a simplified schematic depiction of two linked integrated circuits employing a sloped placement join; 
           [0040]      FIGS. 27A and 27B  show a simplified schematic drawing of two linked integrated circuits employing a dropped triangle nozzle join; 
           [0041]      FIG. 28A  shows a magnified perspective view of an integrated circuit as shown in  FIGS. 27A and 27B  employing a dropped triangle nozzle arrangement; 
           [0042]      FIG. 28B  shows a magnified perspective view of the join between two integrated circuits employing the nozzle arrangement of  FIG. 28A ; 
           [0043]      FIG. 28C  shows an underside view of the integrated circuit of  FIG. 28A ; 
           [0044]      FIG. 29  shows an exploded perspective view of an alternative printhead assembly according to another embodiment of the present invention; 
           [0045]      FIG. 30  shows a partly assembled perspective view of the printhead assembly of  FIG. 29 ; 
           [0046]      FIG. 31  shows a plurality of holes being laser drilled into the adhesive layer of the printhead assembly of  FIG. 29 ; 
           [0047]      FIG. 32  shows a plurality of integrated circuits being arranged along the surface of the adhesive layer of  FIG. 31 ; 
           [0048]      FIGS. 33A-33C  show various views of a portion of an ink distribution member according to a further embodiment of the present invention; 
           [0049]      FIG. 34A  shows a transparent top view of a printhead assembly employing the ink distribution member of  FIGS. 33A-33C  showing in particular, the ink passages for supplying ink to the integrated circuits; 
           [0050]      FIG. 34B  shows an enlarged view of  FIG. 34A ; 
           [0051]      FIG. 35  shows a schematic view of a priming arrangement for priming an ink storage compartment of the present invention; 
           [0052]      FIG. 36  shows a schematic view of an alternative priming arrangement for priming an ink storage compartment of the present invention; 
           [0053]      FIG. 37  shows a schematic view of the priming arrangement of  FIG. 36  with the bypass valve in the closed position; 
           [0054]      FIG. 38  shows a schematic view of yet another alternative priming arrangement for priming an ink storage compartment of the present invention; 
           [0055]      FIG. 39  shows a schematic view of the alternative priming arrangement of  FIG. 38  with the bypass valve in a closed position. 
           [0056]      FIG. 40  shows yet another alternative arrangement for priming the ink storage compartment of the present invention, employing a needle which passes through the side wall of the compartment; 
           [0057]      FIG. 41  shows a vertical sectional view of a single nozzle for ejecting ink, for use with the invention, in a quiescent state; 
           [0058]      FIG. 42  shows a vertical sectional view of the nozzle of  FIG. 41  during an initial actuation phase; 
           [0059]      FIG. 43  shows a vertical sectional view of the nozzle of  FIG. 42  later in the actuation phase; 
           [0060]      FIG. 44  shows a perspective partial vertical sectional view of the nozzle of  FIG. 41 , at the actuation state shown in  FIG. 43 ; 
           [0061]      FIG. 45  shows a perspective vertical section of the nozzle of  FIG. 41 , with ink omitted; 
           [0062]      FIG. 46  shows a vertical sectional view of the of the nozzle of  FIG. 45 ; 
           [0063]      FIG. 47  shows a perspective partial vertical sectional view of the nozzle of  FIG. 41 , at the actuation state shown in  FIG. 42 ; 
           [0064]      FIG. 48  shows a plan view of the nozzle of  FIG. 41 ; 
           [0065]      FIG. 49  shows a plan view of the nozzle of  FIG. 41  with the lever arm and movable nozzle removed for clarity; 
           [0066]      FIG. 50  shows a perspective vertical sectional view of a part of a printhead chip incorporating a plurality of the nozzle arrangements of the type shown in  FIG. 41 ; 
           [0067]      FIG. 51  shows a schematic cross-sectional view through an ink chamber of a single nozzle for injecting ink of a bubble forming heater element actuator type. 
           [0068]      FIGS. 52(A) to 52(C)  show the basic operational principles of a thermal bend actuator; 
           [0069]      FIG. 53  shows a three dimensional view of a single ink jet nozzle arrangement constructed in accordance with  FIG. 22 ; 
           [0070]      FIG. 54  shows an array of the nozzle arrangements shown in  FIG. 53 ; 
           [0071]      FIG. 55  shows a schematic showing CMOS drive and control blocks for use with the printer of the present invention; 
           [0072]      FIG. 56  shows a schematic showing the relationship between nozzle columns and dot shift registers in the CMOS blocks of  FIG. 55 ; 
           [0073]      FIG. 57  shows a more detailed schematic showing a unit cell and its relationship to the nozzle columns and dot shift registers of  FIG. 56 ; 
           [0074]      FIG. 58  shows a circuit diagram showing logic for a single printer nozzle in the printer of the present invention; 
           [0075]      FIG. 59  shows a front perspective view of a lid assembly of a cartridge unit according to an embodiment of the present invention; 
           [0076]      FIG. 60  shows a front perspective view of the underside of the lid assembly of  FIG. 59 ; 
           [0077]      FIG. 61  shows an exploded front perspective view of the lid assembly of  FIG. 59 ; 
           [0078]      FIG. 62  shows a front perspective view of a capper assembly of a cartridge unit according to an embodiment of the present invention; 
           [0079]      FIG. 63  shows an exploded front perspective view of the capper assembly of  FIG. 62 ; 
           [0080]      FIG. 64  shows an exploded front perspective view of the underside of the capper assembly of  FIG. 62 ; 
           [0081]      FIG. 65  shows a sectional end view of the capper assembly of  FIG. 62 ; 
           [0082]      FIG. 66  shows a sectional perspective view of the capper assembly operationally mounted to the cartridge unit of the present invention in a capped state; 
           [0083]      FIG. 67  shows a sectional perspective view of the capper assembly operationally mounted to the cartridge unit of the present invention in an uncapped state; 
           [0084]      FIGS. 68A-68D  show various perspective views of the frame structure of the cradle unit according to an embodiment of the present invention; 
           [0085]      FIG. 69  shows a perspective front view of a cartridge unit support member of the cradle unit according to an embodiment of the present invention; 
           [0086]      FIG. 70  shows a perspective side view of the frame structure of  FIGS. 68A-68D  with the cartridge unit support member of  FIG. 69  attached thereto; 
           [0087]      FIGS. 71A-71B  show various views of the idle roller assembly of the cradle unit according to one embodiment of the present invention; 
           [0088]      FIG. 72  shows a sectional side view of the idle roller assembly of  FIGS. 71A-71B  mounted to the cartridge support member of  FIG. 69 ; 
           [0089]      FIGS. 73A and 73B  show front and back perspective views of the PCB assembly of the present invention having the control circuitry mounted thereto for controlling the print engine of the present invention; 
           [0090]      FIGS. 74A-74C  show various views of the PCB assembly of  FIGS. 73A and 73B  mounted between arm supports; 
           [0091]      FIGS. 75A and 75B  show a support bar assembly for the PCB assembly of  FIGS. 73A and 73B  in accordance with one embodiment of the present invention; 
           [0092]      FIG. 76  shows a perspective view of the support bar assembly of  FIGS. 75A and 75B  assembled to the PCB assembly of  FIGS. 74A-74C ; 
           [0093]      FIGS. 77A and 77B  shows perspective views of the assembly of  FIG. 76  attached to the cradle unit of the present invention; 
           [0094]      FIG. 78A-78C  show various views of the cover assembly of the cradle unit according to an embodiment of the present invention; 
           [0095]      FIG. 79  shows a perspective view of the cover assembly as attached to the cradle unit; 
           [0096]      FIG. 80  shows the print engine of the present invention with the cover assembly in an open position; 
           [0097]      FIG. 81  shows the print engine of the present invention with the cover assembly in a closed position; 
           [0098]      FIG. 82  shows a front perspective view of the push rod assembly in isolation from the cover assembly; 
           [0099]      FIG. 83  shows a perspective view of the foot portion of the push rod assembly of  FIG. 82 ; 
           [0100]      FIG. 84  shows an ink refill unit according to one embodiment of the present invention; 
           [0101]      FIG. 85  shows the ink refill unit of  FIG. 84  in relation to the print engine of the present invention; 
           [0102]      FIG. 86  shows the ink refill unit positioned for refilling ink within the print engine as shown in  FIG. 85 ; 
           [0103]      FIG. 87  shows the cartridge unit as removed from the cradle unit of  FIGS. 85 and 86 ; 
           [0104]      FIG. 88  shows an underside view of the ink refill unit of  FIG. 84 ; 
           [0105]      FIG. 89  illustrates the ink refill unit of  FIG. 84  with its lid assembly removed; 
           [0106]      FIG. 90  shows an exploded view of the various components of the ink refill unit of  FIG. 84 ; 
           [0107]      FIG. 91  illustrates a syringe assembly isolated from the ink refill unit as shown in  FIGS. 89 and 90 ; 
           [0108]      FIG. 92  shows an end perspective view of the syringe assembly as shown in  FIG. 91 ; 
           [0109]      FIG. 93  illustrates a base assembly isolated from the other components of the ink refill unit as shown in  FIGS. 89 and 90 ; 
           [0110]      FIGS. 94A-94C  show an ink distribution system provided by the ink refill unit positioned on the print engine as shown in  FIG. 85 ; 
           [0111]      FIG. 95  shows the ink refill unit with its lid assembly removed in accordance with an alternative embodiment of a syringe assembly; 
           [0112]      FIG. 96  shows an exploded view of the various components of the ink refill unit as shown in  FIG. 95 ; 
           [0113]      FIG. 97  shows a syringe assembly isolated from the ink refill unit as shown in  FIG. 95 ; 
           [0114]      FIG. 98  shows an end sectional view of the syringe assembly as shown in  FIG. 95 ; 
           [0115]      FIG. 99  shows a base assembly isolated from the other components of the ink refill unit as shown in  FIGS. 95 and 96 ; 
           [0116]      FIG. 100  shows yet another embodiment of an ink refill unit suitable for use with the present invention; 
           [0117]      FIG. 101  shows an opposite perspective view of the ink refill unit of  FIG. 100 ; 
           [0118]      FIG. 102  shows an underside view of the ink refill unit of  FIG. 100 ; 
           [0119]      FIG. 103  shows the ink refill unit of  FIG. 100  with its end cap removed; 
           [0120]      FIG. 104  shows an exploded view of the various components of the ink refill unit of  FIG. 100 ; 
           [0121]      FIG. 105  shows the working relationship between the internal components of the ink refill unit as shown in  FIGS. 100 and 104 ; and 
           [0122]      FIG. 106  shows a side sectional view of the ink refill unit of  FIG. 100 . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0123]    As discussed previously, the present invention resides in a print engine  1  that can be readily incorporated into a body of a printer unit  2  to perform the printing functions of the printer unit. 
         [0124]    As shown in  FIGS. 1 and 2 , the printer unit  2 , which incorporates the print engine  1 , may be in any form but typically has a media supply region  3  for supporting and supplying media  8  to be printed by the print engine, and a media output or collection region  4  for collecting the printed sheets of media. The printer unit  2  may also have a user interface  5  for enabling a user to control the operation of the printer unit, and this user interface  5  may be in the form of an LCD touch screen as shown. 
         [0125]    The printer unit  2  typically has an internal cavity  6  for receiving the print engine  1 , and access to the internal cavity may be provided by a lid  7  which is hingedly attached to the body of the printer unit  2 . 
         [0126]    The print engine  1  is configured to be positioned and secured within the printer unit  2  such that media  8  located in media supply region  3  can be fed to the print engine  1  for printing and delivered to the collection region  4  for collection following printing. In this regard, the print engine  1  includes media transport means which take the sheets of media  8  from the media supply region  3  and deliver the media past the printhead assembly, where it is printed, into the media output tray  4 . A picker mechanism  9  is provided with the printer unit  2  to assist in feeding individual streets of media  8  from the media supply  3  to the print engine  1 . 
         [0127]    As shown schematically in  FIG. 3 , in use, the printer unit  2  is arranged to print documents received from an external source, such as a computer system  702 , onto a print media, such as a sheet of paper. In this regard, the printer unit  100  includes means which allow electrical connection between the printer unit  2  and the computer system  702  to receive data which has been pre-processed by the computer system  702 . In one form, the external computer system  702  is programmed to perform various steps involved in printing a document, including receiving the document (step  703 ), buffering it (step  704 ) and rasterizing it (step  706 ), and then compressing it (step  708 ) for transmission to the printer unit  2 . 
         [0128]    The printer unit  2  according to one embodiment of the present invention, receives the document from the external computer system  702  in the form of a compressed, multi-layer page image, wherein control electronics provided within the print engine  1  buffers the image (step  710 ), and then expands the image (step  712 ) for further processing. The expanded contone layer is dithered (step  714 ) and then the black layer from the expansion step is composited over the dithered contone layer (step  716 ). Coded data may also be rendered (step  718 ) to form an additional layer, to be printed (if desired) using an infrared ink that is substantially invisible to the human eye. The black, dithered contone and infrared layers are combined (step  720 ) to form a page that is supplied to a printhead for printing (step  722 ). 
         [0129]    In this particular arrangement, the data associated with the document to be printed is divided into a high-resolution bi-level mask layer for text and line art and a medium-resolution contone color image layer for images or background colors. Optionally, colored text can be supported by the addition of a medium-to-high-resolution contone texture layer for texturing text and line art with color data taken from an image or from flat colors. The printing architecture generalises these contone layers by representing them in abstract “image” and “texture” layers which can refer to either image data or flat color data. This division of data into layers based on content follows the base mode Mixed Raster Content (MRC) mode as would be understood by a person skilled in the art. Like the MRC base mode, the printing architecture makes compromises in some cases when data to be printed overlap. In particular, in one form all overlaps are reduced to a 3-layer representation in a process (collision resolution) embodying the compromises explicitly. 
         [0130]    As mentioned previously, data is delivered to the printer unit  2  in the form of a compressed, multi-layer page image with the pre-processing of the image performed by a mainly software-based computer system  702 . In turn, the print engine  1  processes this data using a mainly hardware-based system as is shown in more detail in  FIG. 4 . 
         [0131]    Upon receiving the data, a distributor  730  converts the data from a proprietary representation into a hardware-specific representation and ensures that the data is sent to the correct hardware device whilst observing any constraints or requirements on data transmission to these devices. The distributor  730  distributes the converted data to an appropriate one of a plurality of pipelines  732 . The pipelines are identical to each other, and in essence provide decompression, scaling and dot compositing functions to generate a set of printable dot outputs. 
         [0132]    Each pipeline  732  includes a buffer  734  for receiving the data. A contone decompressor  736  decompresses the color contone planes, and a mask decompressor decompresses the monotone (text) layer. Contone and mask scalers  740  and  742  scale the decompressed contone and mask planes respectively, to take into account the size of the medium onto which the page is to be printed. 
         [0133]    The scaled contone planes are then dithered by ditherer  744 . In one form, a stochastic dispersed-dot dither is used. Unlike a clustered-dot (or amplitude-modulated) dither, a dispersed-dot (or frequency-modulated) dither reproduces high spatial frequencies (i.e. image detail) almost to the limits of the dot resolution, while simultaneously reproducing lower spatial frequencies to their full color depth, when spatially integrated by the eye. A stochastic dither matrix is carefully designed to be relatively free of objectionable low-frequency patterns when tiled across the image. As such, its size typically exceeds the minimum size required to support a particular number of intensity levels (e.g. 16×16×8 bits for 257 intensity levels). 
         [0134]    The dithered planes are then composited in a dot compositor  746  on a dot-by-dot basis to provide dot data suitable for printing. This data is forwarded to data distribution and drive electronics  748 , which in turn distributes the data to the correct nozzle actuators  750 , which in turn cause ink to be ejected from the correct nozzles  752  at the correct time in a manner which will be described in more detail later in the description. 
         [0135]    As will be appreciated, the components employed within the print engine  1  to process the image for printing depend greatly upon the manner in which data is presented. In this regard it may be possible for the print engine  1  to employ additional software and/or hardware components to perform more processing within the printer unit  2  thus reducing the reliance upon the computer system  702 . Alternatively, the print engine  1  may employ fewer software and/or hardware components to perform less processing thus relying upon the computer system  702  to process the image to a higher degree before transmitting the data to the printer unit  2 . 
         [0136]    In all situations, the components necessary to perform the above mentioned tasks are provided within the control electronics of the print engine  1 , and  FIG. 5  provides a block representation of an embodiment of the electronics. 
         [0137]    In this arrangement, the hardware pipelines  732  are embodied in a Small Office Home Office Printer Engine Chip (SoPEC). As shown, a SoPEC device consists of 3 distinct subsystems: a Central Processing Unit (CPU) subsystem  771 , a Dynamic Random Access Memory (DRAM) subsystem  772  and a Print Engine Pipeline (PEP) subsystem  773 . 
         [0138]    The CPU subsystem  771  includes a CPU  775  that controls and configures all aspects of the other subsystems. It provides general support for interfacing and synchronizing all elements of the print engine  1 . It also controls the low-speed communication to QA chips (which are described below). The CPU subsystem  771  also contains various peripherals to aid the CPU, such as General Purpose Input Output (GPIO, which includes motor control), an Interrupt Controller Unit (ICU), LSS Master and general timers. The Serial Communications Block (SCB) on the CPU subsystem provides a full speed USB1.1 interface to the host as well as an Inter SoPEC Interface (ISI) to other SoPEC devices (not shown). 
         [0139]    The DRAM subsystem  772  accepts requests from the CPU, Serial Communications Block (SCB) and blocks within the PEP subsystem. The DRAM subsystem  772 , and in particular the DRAM Interface Unit (DIU), arbitrates the various requests and determines which request should win access to the DRAM. The DIU arbitrates based on configured parameters, to allow sufficient access to DRAM for all requestors. The DIU also hides the implementation specifics of the DRAM such as page size, number of banks and refresh rates. 
         [0140]    The Print Engine Pipeline (PEP) subsystem  773  accepts compressed pages from DRAM and renders them to bi-level dots for a given print line destined for a printhead interface (PHI) that communicates directly with the printhead. The first stage of the page expansion pipeline is the Contone Decoder Unit (CDU), Lossless Bi-level Decoder (LBD) and, where required, Tag Encoder (TE). The CDU expands the JPEG-compressed contone (typically CMYK) layers, the LBD expands the compressed bi-level layer (typically K), and the TE encodes any Netpage tags for later rendering (typically in IR or K ink), in the event that the printer unit  2  has Netpage capabilities. The output from the first stage is a set of buffers: the Contone FIFO unit (CFU), the Spot FIFO Unit (SFU), and the Tag FIFO Unit (TFU). The CFU and SFU buffers are implemented in DRAM. 
         [0141]    The second stage is the Halftone Compositor Unit (HCU), which dithers the contone layer and composites position tags and the bi-level spot layer over the resulting bi-level dithered layer. 
         [0142]    A number of compositing options can be implemented, depending upon the printhead with which the SoPEC device is used. Up to 6 channels of bi-level data are produced from this stage, although not all channels may be present on the printhead. For example, the printhead may be CMY only, with K pushed into the CMY channels and IR ignored. Alternatively, any encoded tags may be printed in K if IR ink is not available (or for testing purposes). 
         [0143]    In the third stage, a Dead Nozzle Compensator (DNC) compensates for dead nozzles in the printhead by color redundancy and error diffusing of dead nozzle data into surrounding dots. 
         [0144]    The resultant bi-level 5 channel dot-data (typically CMYK, Infrared) is buffered and written to a set of line buffers stored in DRAM via a Dotline Writer Unit (DWU). 
         [0145]    Finally, the dot-data is loaded back from DRAM, and passed to the printhead interface via a dot FIFO. The dot FIFO accepts data from a Line Loader Unit (LLU) at the system clock rate (pclk), while the PrintHead Interface (PHI) removes data from the FIFO and sends it to the printhead at a rate of 2/3 times the system clock rate. 
         [0146]    In the preferred form, the DRAM is 2.5 Mbytes in size, of which about 2 Mbytes are available for compressed page store data. A compressed page is received in two or more bands, with a number of bands stored in memory. As a band of the page is consumed by the PEP subsystem  773  for printing, a new band can be downloaded. The new band may be for the current page or the next page. 
         [0147]    Using banding it is possible to begin printing a page before the complete compressed page is downloaded, but care must be taken to ensure that data is always available for printing or a buffer under-run may occur. 
         [0148]    The embedded USB 1.1 device accepts compressed page data and control commands from the host PC, and facilitates the data transfer to either the DRAM (or to another SoPEC device in multi-SoPEC systems, as described below). 
         [0149]    Multiple SoPEC devices can be used in alternative embodiments, and can perform different functions depending upon the particular implementation. For example, in some cases a SoPEC device can be used simply for its onboard DRAM, while another SoPEC device attends to the various decompression and formatting functions described above. This can reduce the chance of buffer under-run, which can happen in the event that the printer commences printing a page prior to all the data for that page being received and the rest of the data is not received in time. Adding an extra SoPEC device for its memory buffering capabilities doubles the amount of data that can be buffered, even if none of the other capabilities of the additional chip are utilized. 
         [0150]    Each SoPEC system can have several quality assurance (QA) devices designed to cooperate with each other to ensure the quality of the printer mechanics, the quality of the ink supply so the printhead nozzles will not be damaged during prints, and the quality of the software to ensure printheads and mechanics are not damaged. 
         [0151]    Normally, each printing SoPEC will have an associated printer unit QA, which stores information relating to the printer unit attributes such as maximum print speed. The cartridge unit may also contain a QA chip, which stores cartridge information such as the amount of ink remaining, and may also be configured to act as a ROM (effectively as an EEPROM) that stores printhead-specific information such as dead nozzle mapping and printhead characteristics. The refill unit may also contain a QA chip, which stores refill ink information such as the type/colour of the ink and the amount of ink present for refilling. The CPU in the SoPEC device can optionally load and run program code from a QA Chip that effectively acts as a serial EEPROM. Finally, the CPU in the SoPEC device runs a logical QA chip (ie, a software QA chip). 
         [0152]    Usually, all QA chips in the system are physically identical, with only the contents of flash memory differentiating one from the other. 
         [0153]    Each SoPEC device has two LSS system buses that can communicate with QA devices for system authentication and ink usage accounting. A large number of QA devices can be used per bus and their position in the system is unrestricted with the exception that printer QA and ink QA devices should be on separate LSS busses. 
         [0154]    In use, the logical QA communicates with the ink QA to determine remaining ink. The reply from the ink QA is authenticated with reference to the printer QA. The verification from the printer QA is itself authenticated by the logical QA, thereby indirectly adding an additional authentication level to the reply from the ink QA. 
         [0155]    Data passed between the QA chips is authenticated by way of digital signatures. In the preferred embodiment, HMAC-SHA  1  authentication is used for data, and RSA is used for program code, although other schemes could be used instead. 
         [0156]    As will be appreciated, the SoPEC device therefore controls the overall operation of the print engine  1  and performs essential data processing tasks as well as synchronising and controlling the operation of the individual components of the print engine  1  to facilitate print media handling, as will be discussed below. 
       Print Engine 
       [0157]    The print engine  1  is shown in detail in  FIGS. 6-8  and consists of two parts: a cartridge unit  10  and a cradle unit  12 . 
         [0158]    As shown, the cartridge unit  10  is shaped and sized to be received within the cradle unit  12  and secured in position by a cover assembly  11  mounted to the cradle unit. 
         [0159]    The cradle unit  12  is provided with an external body  13  having anchor portions  14  which allow it to be fixed to the printer unit  2  in a desired position and orientation, as discussed above, to facilitate printing. 
         [0160]    In its assembled form as shown in  FIG. 8 , with cartridge unit  10  secured within the cradle unit  12  and cover assembly  11  closed, the print engine  1  is able to control various aspects associated with printing, including transporting the media past the printhead in a controlled manner as well as the controlled ejection of ink onto the surface of the passing media. In this regard, the print engine  2  may also include electrical contacts which facilitate electrical connection with the user interface  5  of the printer unit  2  to enable control of the print engine  1 . 
       Cartridge Unit 
       [0161]    The cartridge unit  10  is shown in detail in  FIGS. 9-12 . With reference to the exploded views of  FIGS. 11 and 12 , the cartridge unit  10  generally consists of a main body  20 , a lid assembly  21 , a printhead assembly  22  and a capper assembly  23 . 
         [0162]    Each of these parts are assembled together to form an integral unit which combines ink storage together with the ink ejection means in a complete manner. Such an arrangement ensures that the ink is directly supplied to the printhead assembly  22  for printing, as required, and should there be a need to replace either or both of the ink storage or the printhead assembly, this can be readily done by replacing the entire cartridge unit  10 . 
         [0163]    As is evident in  FIGS. 9 and 10 , the cartridge unit  10  has facilities for receiving a refill supply of ink to replenish the ink storage when necessary and the cartridge unit itself carries an integral capping assembly  23  for capping the printhead when not in use. 
       Main Body 
       [0164]    The main body  20  of the cartridge unit  10  is shown in more detail in  FIGS. 13-15  and comprises a moulded plastics body which defines a plurality of ink storage compartments  24  in which the various colours and/or types of ink are stored. Each of the ink storage compartments  24  are separated from one another to prevent mixing of the different inks, as is shown more clearly in  FIG. 14 , and extend along the length of the main body  20 . 
         [0165]    There are five ink storage compartments  24  shown, having a square or rectangular shape, with the end compartments being larger than the other compartments. The larger end compartments are intended to store the ink more readily consumed during the printing process, such as black ink or (infrared ink in Netpage applications) whilst the smaller compartments are intended to store the cyan, magenta and yellow inks traditionally used in colour printing. The base  25  of each of the ink storage compartments  24  is provided with a raised portion  26  which surrounds an ink outlet  27 , through which the ink flows for supply to the printhead assembly  22 . The raised portions  26  are typically moulded into the main body  20  and act to separate the outlet  27  from the base  25  of the ink storage compartment  24  to ensure a sufficient flow rate of ink from the compartment  24 . 
         [0166]    In this regard, an air barrier/ink filter  28  made from a fine mesh material is placed over the ink outlet  27 , atop of the raised portions  26 , thereby leaving a space between the filter and the outlet for receiving ink. The air barrier/ink filter  28  is formed such that ink can readily pass through the mesh to the printhead assembly  22  but any air bubbles present in the ink are prevented from passing through. 
         [0167]    As shown in  FIG. 11 , the ink storage compartments  24  are provided with an absorbent material  29  such as a foam for storing the ink. The absorbent material  29  is shaped to conform to the shape of the ink storage compartment  24  and is fitted within the corresponding compartment to be supported on top of the air barrier/ink filter  28 . In this arrangement, the lower surface of the absorbent material  29  is separated from the base  25  of the ink storage compartments via the raised portions  26 . The absorbent material  29  acts to absorb ink supplied to the compartment  24  such that the ink is suspended internally within. The manner in which ink is supplied to the compartment  24  will be discussed in more detail later, however it should be appreciated that the structure of the absorbent material is such that it contains a number of open pores which receive and draw in the ink under capillary action. 
         [0168]    The ink fills the space between the ink filter/air barrier  28  and the outlet  27  thereby forming an ink dam, which is in fluid communication with the ink in the printhead assembly  22  and the ink suspended within the absorbent material  29 . Due to the nature of the absorbent material  29  and the fact that the ink is retained therein under capillary action, a back pressure is created which prevents the ink from freely flowing from the compartment  24  and out the nozzles of the printhead assembly  22 . 
         [0169]    Whilst the use of a foam or sponge material as an absorbent material  29  which stores the ink therein under capillary attraction forces is well established in the art, due to the nature of such materials, their use may cause contaminants to be introduced into the stored ink. These contaminants can then make their way to the ink delivery nozzles of the printhead assembly  22 , causing blockages and therefore (possible irreparable) malfunction of the ink delivery nozzles. Whilst conventional arrangements have typically employed filters and the like in an attempt to protect the nozzles, such filters may themselves become blocked due to the presence of particulate material present in the foam or sponge material. 
         [0170]    In this regard, in an alternative embodiment, the absorbent material  29  may be provided as a block or stack of layers made from a polymer material, such as polycarbonate, acrylic, polysulfone, polystyrene, fluoropolymer, cyclic olefin polymer, cyclic olefin copolymer, etc, having the channels  16  formed therein in the form of a micro-capillary array, as shown in  FIG. 16 , with each channel having an average diameter of about 10 microns or less. 
         [0171]    In this arrangement, the body of the absorbent material  29 , in which the micro-capillary array of the channels  16  is formed, remains stable and rigid at all times. That is, the rigid walls of the channels remain intact during exposure to the ink whereby particulate matter is not introduced into the ink, unlike the cellular or interlaced arrangement of compressible pores within the conventional foam and sponge materials which contribute to contaminant production. 
         [0172]    The absorbent material  29  having the channels  16  formed as a micro-capillary array therein can be arranged within the individual ink storage compartments  24  as shown in  FIG. 17 . An ink trapping layer  17  is provided between the ink filter/air barrier  28  and the absorbent material  29 . The trapping layer  17  absorbs the supplied ink in multiple-directions, thus allowing for the ingress of the ink into the longitudinally orientated channels  16 , and in this regard merely acts as a means for presenting the ink to the channels  16 . The trapping layer  17  may be provided as a foam or sponge material with a thickness substantially less than that of the absorbent material  29 , since the function of the trapping layer is merely to supply ink to the channels  16  of the absorbent material  29  and not to store the ink. 
         [0173]    The ink drawn into and stored within the channels  16  is able to pass to the nozzles of the printhead assembly  22  via the ink trapping layer  17 . The use of foam or sponge material in the ink trapping layer  17  may result in some particulate contamination occurring in the ink. However, this may be minimized by providing the layer with a thickness and density which is just sufficient for absorbing the necessary amount of ink for effective absorption into the channels  16 . In any event, since the ink is effectively stored only in the absorbent material  29 , the contaminant level that may be produced in the ink trapping layer is significantly reduced from the levels produced by the conventional structures. 
         [0174]    A pressed metal chassis  30  is fitted to the underside of the main body via clips  31  formed in the chassis  30  which mate with corresponding clips formed in the main body  20 . The pressed metal chassis  30  is shaped to conform to the underside of the main body  20  and includes a plurality of holes  32  that extend therethrough which are positioned to correspond with the ink outlets  27  of the ink storage compartments  24  such that there is a passage for ink to pass through the chassis  30 . The chassis  30  provides additional stability to the cartridge unit  10  and includes an edge  33  that extends downwardly from the main body  20  which defines a contact region where the flex printed circuit board  52  of the printhead assembly  22  contacts with corresponding electrical contacts  128  in the cradle unit  12 , in a manner which will be described in more detail later in the description. The chassis  30  also has a plurality of elongate recesses  34  formed along its length, through which connecting clips provided on the printhead assembly  22  pass, for connection to the main body  20 , as will be described in more detail below. 
         [0175]    A seal moulding  35  is attached to the chassis  30  to complete and seal the ink flow path from the ink storage compartments  24  through the chassis  30 . The seal moulding  35  is made from an elastomeric material and has a plurality of hollow cylindrical inserts  36  formed along its surface which extend through the holes  32  formed in the chassis  30  and into the ink outlets  27  of each of the ink storage compartments  24 , as shown in  FIG. 15 . The distal ends of the hollow cylindrical inserts  36  abut with the main body  20  to seal the ink outlets  27  and ensure ink flow through the seal moulding  35 . The seal moulding  35  is fixed to the surface of the metal chassis  30  by a lock-fit or a suitable adhesive and acts to provide a substantially planar surface upon which the printhead assembly  22  is attached. The planar surface having a plurality of outlet holes  39  provided therein through which ink can flow to the printhead assembly. 
         [0176]    As is shown in  FIGS. 14 and 15  a flex printed circuit board (PCB) backer  37  is attached to the side of the main body  20  via locating studs  38  and extends over the downwardly projecting edge  33  of the chassis  30 . The flex PCB backer  37  is made from a suitable elastomeric material and provides a backing onto which the flex PCB  52  of the printhead assembly  22  is supported following attachment of the printhead assembly  22  to the main body  20 . As will be discussed in more detail later in the description, the flex PCB  52  from the printhead assembly  22  is provided with a suitable recess which fits over the locating studs  38  such that the electrical dimpled contacts  53  formed on the flex PCB  52  are positioned over the flex PCB backer  37  and extend outwardly therefrom to contact suitable electrical contacts  128  provided in the cradle unit  12 . This arrangement provides some degree of flexibility in this contact region such that appropriate electrical contact can be established between the cradle unit  12  and the cartridge unit  10  to allow the transmission of data and power therebetween to control the ink ejecting nozzles of the printhead assembly  22 . This arrangement also ensures that the forces associated with the contact between the cartridge unit  12  and the cradle unit  10  in this region are carried by the chassis  30  and not transferred to the printhead assembly  22  which could cause damage to the delicate printhead integrated circuits. 
         [0177]    As shown in  FIGS. 13 and 14 , the main body  20  also includes a pair of end supports  40  which extend from the main body  20  in a downward direction with respect to the cartridge unit  10 . The end supports  40  are arranged such that the seal moulding  35  and the flex PCB backer  37  extend along the main body  20  between the two end supports  40 . The purpose of the end supports  40  will be described later in the description. 
       Printhead Assembly 
       [0178]    The printhead assembly  22  is shown in more detail in  FIGS. 18 to 21 , and is adapted to be attached to the underside of the main body  20  to receive ink from the outlet holes  39  formed in the planar surface of the seal moulding  35 . 
         [0179]    As shown more clearly in  FIG. 20 , the printhead assembly  22  comprises an upper moulding  42 , having features which facilitate connection of the printhead assembly to the main body  20  of the cartridge unit  10 . These features are in the form of u-shaped clips  43  that project from the surface of the upper moulding  42 . The clips  43  pass through the elongate recesses  34  provided in the chassis  30  and become captured by lugs (not shown) formed in the main body  20 , thereby securing the printhead assembly  22  to the main body  20 . 
         [0180]    In order to receive ink from the ink storage compartments  24 , the surface of the upper moulding  42  has a plurality of ink inlets  44  which project therefrom. The ink inlets  44  are received within the outlet holes  39  of the seal moulding  35 , when the printhead assembly  22  is secured to the main body  20 , and provide a path for the ink to flow to the printhead integrated circuits for printing. To ensure a sealed connection, the ink inlets  44  are shaped to fit within the outlet holes  39  of the seal moulding  35  and may also be provided with an outer coating that facilitates sealing. 
         [0181]    The upper moulding  42  is made from a liquid crystal polymer (LCP) and is bonded to a lower moulding  45  via an adhesive film  46 . The lower moulding  45  is also made from an LCP and has a plurality of channels  47  formed along its length. Each of the channels  47  are provided to receive ink from one of the ink storage compartments  24 , via an ink inlet  44 , and distribute the ink along the length of the printhead assembly  22  for feeding to the ink delivery nozzles  51  of the printhead assembly  22 . The channels preferably have a width of 1 mm and are separated by walls having a width of 0.75 mm. In the embodiment shown, the lower moulding  45  has five channels  47  extending along its length with each of the ink channels  47  receiving ink from one of the corresponding ink inlets  44 . Such an arrangement ensures that the different inks remain separated throughout the journey from the individual ink storage compartments  24  to the corresponding ink delivery nozzles of the printhead integrated circuit. In this regard, the adhesive film  46  also acts to seal the individual ink channels  47  and prevent cross channel mixing of the ink when the lower moulding  45  is assembled to the upper moulding  42 . 
         [0182]    In order to further distribute the ink from the ink channels  47  of the lower moulding  45  to the printhead integrated circuits (ICs)  50 , an ink distribution member  48  is attached to the lower moulding  45  and acts as an interface between the printhead ICs  50  and the ink channels  47  of the lower moulding  45 . The purpose of the ink distribution member  48  is to provide a flow path for ink to flow from the relatively wide channels  47  to the relatively small and narrow channels  98  formed on the underside of the printhead ICs  50  which feed the ink to the individual ink delivery nozzles  51 . 
         [0183]    In order to appreciate the manner in which the ink distribution member  48  functions to perform millimetric-to-micrometric fluid distribution to the nozzles of the printhead ICs  50 , reference is firstly made to the manner in which the printhead ICs  50  are arranged to form the printing zone of the printhead assembly  22 . 
         [0184]    As alluded to above, the present invention is related to page-width printing and as such the printhead ICs  50  are arranged to extend horizontally across the width of the passing media to deposit ink droplets thereon to create an image. To achieve this, individual printhead ICs  50  are linked together in abutting arrangement across the surface of the ink distribution member  48  of the printhead assembly  22 , as shown simply in  FIG. 22 . The length of an individual printhead IC  50  is around 20-22 mm and as such in order to print an A4/US letter sized page, 11-12 individual printhead ICs  50  may be linked together in abutting fashion. Other printing sizes may also be possible and as such the number of individual printhead ICs  50  required may vary depending upon the application. 
         [0185]    Each printhead IC  50  has a plurality of individual ink delivery nozzles  51  formed therein, the structure and control of which will be described in more detail later. The nozzles  51  within an individual printhead IC  50  are grouped physically to reduce ink supply complexity and wiring complexity, and are also grouped logically to minimize power consumption and to allow a variety of printing speeds. 
         [0186]    As mentioned previously, each printhead IC  50  is able to print five different colours (C, M, Y, K and IR) and contains 1280 ink delivery nozzles  51  per colour, with these nozzles being divided into even and odd nozzles (640 each). Even and odd nozzles for each colour are provided on different rows on the printhead IC  50  and are aligned vertically to perform true 1600 dpi printing, meaning that the nozzles  51  are arranged in 10 rows. The horizontal distance between two adjacent nozzles  51  on a single row is 31.75 microns, whilst the vertical distance between rows of nozzles is based on the firing order of the nozzles, but rows are typically separated by an exact number of dot lines, plus a fraction of a dot line corresponding to the distance the paper will move between row firing times Also, the spacing of even and odd rows of nozzles for a given colour must be such that they can share an ink channel, as will be described below. 
         [0187]    The manner in which individual printhead ICs  50  are linked together in abutting fashion may be performed in a variety of ways. As shown in  FIG. 23 , the simplest way to achieve this linkage of the printhead ICs  50  is to form a rectangular join between adjacent ICs  50 . However, due to the nature of this rectangular join, it may result in a gap between adjacent nozzles at the join interface which could produce a vertical stripe down the printed page of media where no ink is deposited, which may be unacceptable in some printing applications. 
         [0188]    This may be overcome by providing a sloping join as shown in  FIG. 24   a  which provides nozzle overlap at the join interface. As shown by the enlarged view of nozzle rows of a single colour at the interface in  FIG. 24   b , such an arrangement does not produce a visible join along the printing page as discussed above. In this arrangement, the ICs  50  must be perfectly aligned vertically to link in this fashion and as such this may not be always possible. 
         [0189]    To overcome this problem, the ICs  50  may be provided with a vertical offset, as shown in  FIG. 25 . This offset can be seen by the vertical offset between the longitudinal edges of adjacent ICs  50 , and this offset increases with each join along the length of the printhead assembly  22 . For example, if the offset was equivalent to 7 lines of nozzles per join, then for 11 ICs joined in this manner, there would be a total of 10 joins and 70 additional nozzle lines. This then results in an increase in the lines of data storage required for the printhead assembly. To overcome this, each IC  50  may be placed on a mild slope to achieve a constant number of print lines regardless of the number of joins, as shown in  FIG. 26 . It will be appreciated that in this arrangement the rows of nozzles on the ICs  50  are aligned, but the IC is placed in a sloped orientation, such that if all the nozzles were fired at once, the effect would be lots of sloped lines provided on the page of media, however with the nozzles being fired in the correct order relative to the paper movement, a straight line for n dots would be printed, followed by another straight line for another n dots separated by 1 line. 
         [0190]    Yet another system for linking the ICs  50  in abutting fashion is shown in  FIGS. 27   a  and  27   b . In this arrangement, the ICs  50  are shaped at their ends to link together to form a horizontal line of ICs, with no vertical offset between neighboring ICs. A sloping join is provided between the ICs which has a 45 degree angle to the upper and lower chip edges. Typically, the joining edge is not straight and has a sawtooth profile to facilitate positioning, and the ICs  50  are intended to be spaced about 11 microns apart, measured perpendicular to the joining edge. In this arrangement, the left most ink delivery nozzles on each row are dropped by 10 line pitches and arranged in a triangle configuration as shown in  FIG. 27   a  and  FIGS. 28   a  and  28   b . This arrangement provides a degree of overlap of nozzles at the join and maintains the pitch of the nozzles to ensure that the drops of ink are delivered consistently along the printing zone. This arrangement also ensures that more silicon is provided at the edge of the IC  50  to ensure sufficient linkage. Control of the operation of the nozzles is performed by the SoPEC device, however compensation for the nozzles is performed in the printhead, or may also be performed by the SoPEC device, depending on the storage requirements. In this regard it will be appreciated that the dropped triangle arrangement of nozzles disposed at one end of the IC  50  provides the minimum on-printhead storage requirements. However where storage requirements are less critical shapes other than a triangle can be used, for example, the dropped rows may take the form of a trapezoid. 
         [0191]      FIG. 28   a  shows more clearly the upper surface of a portion of the individual ICs. As can be seen bond pads  96  are provided along an edge thereof which provide a means for receiving data and or power to control the operation of the nozzles from the SoPEC of the cradle unit  12 . Fiducials  97  are also provided on the surface of the ICs to assist in positioning and aligning the ICs  50  with respect to each other. The fiducials  97  are in the form of markers that are readily identifiable by appropriate positioning equipment to indicate the true position of the IC  50  with respect to a neighbouring IC  50 , and are strategically positioned at the edges of the IC, proximal the join. As shown in  FIG. 28   b , the fiducials  97  align with corresponding fiducials  97  provided on the surface of a neighbouring IC  50  to ensure alignment of the ICs to appropriate limits, as discussed above. 
         [0192]    The underside of a printhead IC  50  is shown in relation to  FIG. 28   c . As shown, along the underside of the IC  50  there are provided a number of etched channels  98 , with each channel  98  in communication with a pair of rows of nozzles  51 . The channels  98  are about 80 microns wide and extend the length of the IC  50  and include silicon walls  99  formed therein, to divide the channels  98  into portions. The channels are adapted to receive ink from the ink channels  47  of the lower moulding  45  and distribute the ink to the pair of rows of nozzles  51  to eject that ink of a specific colour or type. The partitioning of the channels  98  by the silicon walls  99  ensures that the flow path to the nozzles is not too great thereby reducing the likelihood of ink starvation to the individual nozzles along the length of the IC. In this regard, each portion feeds approximately 128 nozzles and is individually fed a supply of ink. 
         [0193]    Each of the ICs  50  are positioned and secured to the surface of the ink distribution member  48 . As mentioned previously, the ink distribution member delivers the ink from the 1 mm wide channels  47  formed in the lower moulding  45  to the 80 micron wide channels  98  formed in the underside of the printhead ICs  50 . 
         [0194]    The ink distribution member  48  can be configured in a number of forms. In one embodiment the ink distribution member  48  may be in the form of a laminated structure consisting of a number of layers bonded to one another, as described in U.S. Pat. No. 6,409,323 and pending US Application No. 2004/0113997. 
         [0195]    In an alternative embodiment, the ink distribution member  48  may be in a two-part form comprising an intermediate layer  172  and an adhesive layer  173 , as shown in  FIG. 29 . In this arrangement, the intermediate layer  172  is arranged to fit over the exposed channels  47  of the lower moulding  45  to seal the channels  47  and to form a sealed unit with the lower moulding  45 . The intermediate layer  172  has a plurality of holes  174  formed therethrough along its length each of which are aligned with the channels  47  and are spaced at regular intervals along the length thereof. 
         [0196]    As shown more clearly in  FIG. 30 , the holes  174  formed through the intermediate layer  172  which relate to the most central channel  47  of the lower moulding  45  are in the form of small diameter holes equi-spaced at intervals along the length of the intermediate layer  172 . Larger diameter holes  174  are provided which correspond to the other channels  47  of the lower moulding  45 , which are displaced laterally from the most central channel. These holes  174  are similarly equi-spaced along the length of the intermediate layer and micro conduits  176  are provided which extend from the larger diameter holes to terminate at a central region of the intermediate layer  172 , proximal the smaller diameter holes. These conduits  176  distribute the ink from each of the holes  172  to a central region of the intermediate layer to deliver the different types/colours of ink to the channels  98  formed in the underside of the integrated circuits  50 . 
         [0197]    The intermediate layer  172  is also made from a liquid crystal polymer (LCP) which is injection moulded to the appropriate shape and configuration. The intermediate layer  172  is bonded to the lower moulding  45  via a thermal adhesive, such as 3M 816 or Abelflex 5206 or 5205, which is applied between the intermediate layer  172  and the lower moulding  45  and placed in a laminator. 
         [0198]    To facilitate placement and to secure the integrated circuits  50  upon the surface of the intermediate layer  172  a bonding film  175  is applied to the surface of the intermediate layer  172 . The bonding film  175  is in the form of a laminate polymer film which may be a thermoplastic film such as a PET or Polysulphone film, or it may be in the form of a thermoset film, such as those manufactured by AL technologies and Rogers Corporation. The bonding film  175  preferably has co-extruded adhesive layers formed on both sides thereof and is laminated onto the upper surface of the intermediate layer  172   
         [0199]    Following lamination of the bonding layer  175  to the intermediate layer  172 , holes are drilled through the bonding layer  175  to coincide with the centrally located small diameter holes  174 , and the ends of the conduits  176 . This is shown in  FIG. 31 . These holes provide a separate flow passage through the bonding layer  175  for each of the different types of inks, which feed directly to the appropriate channel portions  98  formed on the underside of the integrated circuits  50  for supply to the ink delivery nozzles  51  associated with each channel portion  98 , as discussed above. Fiducial locating marks  177  are also drilled into the surface of the bonding layer to assist in attaching and positioning the ICs  50  thereon. 
         [0200]    In order to attach the ICs  50  to the surface of the bonding layer  175 , the ICs  50  are placed in a die and heated to 170° C. and then pressed into the bonding layer  175  at 40 psi pressure for about 3 seconds. This results in the ICs  50  being thermally bonded to the intermediate layer  172 , as shown in  FIG. 32 . As shown, the fiducial locating marks  177  formed in the surface of the bonding layer  175  aid in positioning the ICs such that the channels  98  formed in the underside of the ICs  50  correctly align with the holes drilled through the bonding layer  175  to provide a flow path for ink to be fed to the nozzles for printing. 
         [0201]    In this embodiment the ink distribution member  48  is in the form of a two part element containing an intermediate layer  172  which fits over the channels  47  formed in the lower moulding  45 , and a bonding layer  175  allowing fluid flow therethrough and which acts to attach the ICs to the surface of the intermediate layer  172 . 
         [0202]    In yet another embodiment, the ink distribution member  48  may be in the form of a one-piece element with the ICs being directly attached to its upper surface. In this regard, rather than providing an intermediate layer  172  having holes  174  that extend therethrough and conduits  176  formed in the upper surface thereof to direct the flow of ink towards the central region of the intermediate layer  172 , the conduits are formed within the body of the ink distribution member  48  such that the upper surface of the ink distribution member only has small diameter holes formed centrally therein for delivering the ink to the undersurface of the ICs. 
         [0203]    The manner in which this is achieved is shown in  FIGS. 33   a - 33   c . These Figures merely show the manner in which the ink can be directed from one of the channels  47  of the lower moulding  45 , and it will be appreciated that the same approach can be similarly applied to deliver ink from the remainder of the channels  47 . 
         [0204]    As shown, the underside of the ink distribution member  48  is provided with a plurality of holes or inlets  180  therein, each having a diameter of approximately 1 mm, which corresponds to the width of the channels  47  provided in the lower moulding  45 . The inlets  180  do not extend through the body of the ink distribution member  48 , but rather extend into the member  48  to a depth of about a ¾ the thickness of the member  48 , as shown in the sectioned view of  FIG. 33   c.    
         [0205]    For the inlets  180  associated with the centre channel  47  of the lower moulding, an outlet  182 , in the form of a 80 micron wide hole, is provided in the uppermost surface of the ink distribution member  48  which extends into the end wall of the inlet  180  to provide a path for the ink to flow out of the ink distribution member. For the inlets  180  associated with the other channels  47  of the lower moulding  45 , a tunnel  181  is provided from a side wall of the inlet  180  within the ink distribution member  48  which acts to direct the flow of the ink received in the inlet through the body of the ink distribution member  48  to a central position therein. An outlet  182 , as described above, is then formed on an uppermost side of the ink distribution member to provide a path for the ink present in the tunnel  181  to exit the ink distribution member at the desired position along the surface of the ink distribution member. The outlets  182  are essentially 80 microns in width, to correspond with the width of the channels  98  provided on the underside of the integrated circuits  50 . 
         [0206]    The ink distribution member  48  of this embodiment is made from a photo-structurable glass-ceramic material, such as Forturan glass. These materials, when exposed to specific levels of pulsed UV laser energy density (fluence), have a photo-chemical reaction which creates a density of nanocrystals within the volume thereof, the density of which is directly proportional to the fluence of the exposed laser beam. In this regard, in order to form the desired inlets  180 , outlets  182  and tunnels  181  connecting the inlets and outlets, the ink distribution member  48  is mounted upon a precision XYZ stage for exposure to a focussed laser beam. Various tools may be used to control the size and shape of the critically exposed volume of the glass structure to ensure that the desired pattern and shape is created within the ink distribution member. Typical exposure times may vary from 15 minutes to 1 hour. 
         [0207]    Following exposure the ink distribution member is loaded into an oven for thermal treatment to aid in causing crystallisation of exposed regions of the glass. The exposed and thermally treated glass is then loaded into a mild etchant for around 7 minutes to etch the exposed regions, however the etch time may vary dependant upon the thickness of the glass and the depth of the cut. The thermal treatment and etching steps may be repeated in order to form the complete ink distribution member as shown in the figures. 
         [0208]    With this arrangement, ink present in the channels  47  of the lower moulding  45  is drawn into the ink distribution member  48  via inlets  180  which are positioned over the channels  47  at regular intervals therealong. Upon entering the inlets  180 , where required, the ink is directed to a central region of the ink distribution member  48  via the above mentioned tunnels  181 , where the ink can then exit the ink distribution member  48  via the outlets  182  at a predetermined position which is aligned with the corresponding channels  98  formed in the underside of the ICs  50 . 
         [0209]    The ICs  50  are secured to the upper surface of the ink distribution member  48  to receive the ink therefrom, using spun coated adhesive applied to the underside of the IC  50 , or by screen printing epoxy on the upper surface of the ink distribution member  48 . In this regard, the fiducials provided on the ICs  50  and on the surface of the ink distribution member  48  assist in positioning the ICs  50  such that the channels  98  formed in the underside of the ICs  50  are aligned with the appropriate outlet  182  formed in the upper surface of the member  48  to receive the correct type/colour of ink. 
         [0210]      FIGS. 34   a  and  34   b  show the manner in which this is arranged to control the delivery of ink from the five channels  47  of the lower moulding  45 . These figures provide a top view of the arrangement and for reasons of clarity, the various elements are shown in outline to indicate the manner in which ink flows between the elements.  FIG. 34   a  is a top view of the arrangement showing the ICs  50  located centrally upon the ink distribution member  48 . The ink distribution member  48  is in turn secured to the lower moulding  45  such that the inlets  180  align with the respective channels  47  at regular intervals along the length thereof to receive ink from the channels  47  for distribution to the ICs  50 . The inlets  180  associated with the central channel  47  are in direct fluid communication with an outlet  182 , which delivers the ink to the underside of the ICs  50 . The inlets  180  associated with the other channels  47  include tunnels  181  formed within the ink distribution member  48  which are in fluid communication with associated outlets  182  disposed remote from the inlets  180  to deliver ink to the underside of the ICs  50 . As is shown, in this arrangement the outlets  182  are centrally arranged on the upper surface of the ink distribution member in a predetermined pattern, with the position of each outlet defining a point at which ink of a specific colour is delivered to the IC  50 . 
         [0211]      FIG. 34   b  is a magnified view of  FIG. 34   a , showing in detail the manner in which the ink is supplied to the underside of the ICs  50 . The channels  98  formed on the underside of the IC  50  are clearly shown, as are the silicon walls  99  provided along the length of the channels  98 , which divide the channels  98  into portions. As shown, the ICs  50  are positioned on the surface of the ink distribution member such that the outlets  182  align with the channels  98  at the junction of the channel portions, namely at the region where the silicon walls  99  are situated. This then ensures that one outlet  182  supplies ink to two channel portions, allowing a regular spacing of outlets to be achieved along the surface of the ink distribution member  48 . 
         [0212]    In the above described embodiment, the ink distribution member  48  is in the form of a on-piece element thereby overcoming the need to provide separate layers and reducing the complexity of the system, as sealing between layers is no longer required. 
         [0213]    Following attachment and alignment of each of the printhead ICs  50  to the surface of the ink distribution member  48 , a flex PCB  52  is attached along an edge of the ICs  50  so that control signals and power can be supplied to the bond bads  96  of the ICs  50  to effect printing. As shown more clearly in  FIG. 20 , the flex PCB  52  folds around the printhead assembly  22  in an upward direction with respect to the cartridge unit  10 , and has a plurality of dimpled contacts  53  provided along its length for receiving power and or data signals from the control circuitry of the cradle unit  12 . A plurality of holes  54  are also formed along the distal edge of the flex PCB  52  which provide a means for attaching the flex PCB  52  to the locating studs  38  formed on the main body  20 , such that the dimpled contacts  53  of the flex PCB  52  extends over the flex PCB backer  37 . The manner in which the dimpled contacts  53  of the flex PCB  52  contact the power and data contacts  128  of the cradle unit  12  is described later. 
         [0214]    A media shield  55  is attached to the printhead assembly  22  along an edge thereof and acts to protect the printhead ICs  50  from damage which may occur due to contact with the passing media. The media shield  55  is attached to the upper moulding  42  upstream of the printhead ICs  50  as shown more clearly in  FIG. 21 , via an appropriate clip-lock arrangement or via an adhesive. When attached in this manner, the printhead ICs  50  sit below the surface of the media shield  55 , out of the path of the passing media. 
         [0215]    As shown in  FIGS. 20 and 21 , a space  56  is provided between the media shield  55  and the upper  42  and lower  45  moulding which can receive pressurized air from an air compressor or the like. As this space  56  extends along the length of the printhead assembly  22 , compressed air can be supplied to the space  56  from either end of the printhead assembly  22  and be evenly distributed along the assembly. The inner surface  57  of the media shield  55  is provided with a series of fins  58  which define a plurality of air outlets evenly distributed along the length of the media shield  55  through which the compressed air travels. This arrangement therefore provides a stream of air across the printhead ICs  50  in the direction of the media delivery which acts to prevent dust and other particulate matter carried with the media from settling on the surface of the printhead ICs, which could cause blockage and damage to the nozzles. 
         [0216]    A cross section of the complete printhead assembly  22  is shown in  FIG. 21 . As shown, ink is received from the ink storage compartments  24  via the ink inlets  44  of the upper moulding  42 , which feed the ink directly into one of the ink channels  47  of the lower moulding  45 . The ink is in turn fed from the ink channels  47  to the ink delivery nozzles  51  of the printhead ICs  50  by way of the ink distribution member  48 . 
         [0217]    As shown in  FIGS. 20 and 21 , the lower moulding  45  is provided with a plurality of priming inlets  59  at one end thereof. Each of the priming inlets  59  communicate directly with one of the channels  47  and provide a means for priming the printhead assembly  22  and the ink storage compartments  24  with ink prior to shipment and use. Various ways in which the priming is achieved will now be described with reference to  FIGS. 35-40 . 
         [0218]      FIG. 35  is a simplified cross-sectional representation of an ink storage compartment  24  as described previously. Ink is primed into the absorbent material  29  through the ink outlet  27  which links the compartment  24  to the channels  47  of the printhead assembly  22 . In this regard, the ink is supplied via the priming inlets  59  along the channels  47  of the lower moulding  45 , with each channel  47  in fluid communication with one ink outlet  27  of an ink storage compartment  24  to deliver ink of a specific type/colour to that ink storage compartment  24 . 
         [0219]    Priming of the ink storage compartments  24  is typically performed prior to shipment of the cartridge unit  10  and as such, an ink source can be temporarily attached to the priming inlets  59 , wherein upon completion of priming, the priming inlets can be capped/sealed. 
         [0220]    As discussed above, priming ink is supplied under pressure to the ink storage compartment  24  via the ink outlets  27 . The priming ink flows into the space between the ink filter/air barrier  28  and the outlet  27 , and is absorbed into the absorbent material  29  through the ink filter/air barrier  28 . As discussed above, due to the porous nature of the absorbent material  29  the ink becomes suspended within the absorbent material due to capillary attraction forces. By keeping the upper surface of the absorbent material  29  dry and exposed to atmospheric pressure through the vent hole  63 , the ink is able to be continually drawn into the pores of the absorbent material  29  via capillary action (as shown by arrows B). 
         [0221]    As discussed above, ink present in the channels  47  of the lower moulding  45  is also supplied to the ink delivery nozzles  51  of the integrated circuits  50 , via the ink distribution member  48 . During the above described priming process, the ink flows to the nozzles  51  to prime the individual nozzles with ink, and due to the capillary action of the absorbent material  29  in the ink storage compartments  24 , a sufficient backpressure is established in the ink supply to prevent leakage of the ink out of the nozzles  51 . 
         [0222]    In this regard, the priming operation is ceased before the absorbent material becomes completely saturated and its upper surface becomes wet with ink, so that the necessary backpressure can be maintained. This may be controlled by limiting the supply of ink or by more sophisticated methods, such as sensing the level of ink within the body. Hydrophobic material may also be used on the surface of the ICs  50  in the vicinity of the nozzles  51  so as to assist in leakage prevention. 
         [0223]    In the above-described arrangement, it may be necessary to maintain the pressure of the supplied ink to be below a level which ensures the ink is not ejected through the nozzle outlets  51  during priming. Practically, this situation may increase the required time necessary to prime the cartridge unit  10 . 
         [0224]    An alternative embodiment for configuring the ink storage compartments  24  which provides a means of substantially obviating the need to limit the ink pressure during priming is illustrated in  FIGS. 35 to 39 . In this embodiment, a bypass fluid path  185  is provided in fluid communication with the ink outlet  27 . 
         [0225]    The bypass fluid path  185  allows the priming ink an additional path into the ink storage compartment  24  where it can be absorbed by the absorbent material  29 . In this regard, the priming ink does not only flow through the ink filter air barrier  28  directly into the absorbent material  29 , but can also flow into at least a portion of a well region  24   a  of the compartment  24 , as illustrated by arrows C in  FIG. 36 . The well region  24   a  is the annular region surrounding the raised portions  26  on the base  25  of the compartments where there is a gap between the base  25  of the compartment  24  and the absorbent material  29 . This well region  24   a  defines a space where the priming ink can be readily delivered via the bypass fluid path  185 . 
         [0226]    With this arrangement, by providing more than one path for the ink to enter the ink storage compartment  24 , a larger surface area of the absorbent material  29  is exposed to the priming ink and as such the ink is drawn into the absorbent material more quickly and the supply pressure of the priming ink can be reduced. 
         [0227]    The path  185  is provided with a bypass valve  186  which is open during initial priming of the cartridge unit  10  and is closed upon completion of the priming operation, as shown in  FIG. 37 . The bypass valve  186  may be provided by way of a variety of arrangements and may be either manually or automatically controlled. For example, the bypass valve  186  may be provided as a manual depression button as illustrated in  FIGS. 38 and 39 . 
         [0228]    In this arrangement, the bypass valve  186  is in the form of a button  187  provided as a flexible portion of the bottom wall of the path  185 . The button  187  may be made from a rubber material and may be connected to the wall of the path  185  via an annular weakened portion  187   a . Initially, and during priming, the button  187  is positioned as shown in  FIG. 38  to allow the priming ink to flow through the path  185 . Once priming is complete, the path  185  is closed by depressing the button  187  into a circular recessed region  188  of the internal wall of the path  185 . In this regard, the button  187  is captured by the lip  189  and retained therein, thereby blocking the bypass valve  186 , as shown in  FIG. 39 . 
         [0229]    It will be appreciated that those skilled in the art will understand that other bypass valve structures are possible and encompassed by the present invention. For example, a simple alternative to the above may be providing the additional fluid path  185  as a compressible silicon tube or the like. 
         [0230]    The bypass valve  186  may be configured to be irreversibly closed once the priming is completed. On the other hand, if refilling of the storage compartments via the priming inlets of the printhead assembly  22  is desired, a bypass valve capable of being opened and closed without limit may be provided. 
         [0231]    Another embodiment of the ink storage compartments  24  which provides an alternative or additional arrangement for priming the compartments  24  with ink is illustrated in  FIG. 40 . 
         [0232]    In this arrangement, a port  190  is provided in at least one of the side walls of each compartment  24  in a position below the upper surface of the absorbent material  29 . The ports  190  are provided for the insertion of a needle  191  from an external ink source syringe or the like (not shown) which penetrates into the absorbent material  29 , and through which the priming ink is supplied into the body. The ports  190  are configured so that the needle  191  supplies the priming ink towards the lower portion of the absorbent material  29 , shown with arrows D in  FIG. 40 , so as to prevent wetting of the uppermost portion of the absorbent material  29 , for the reasons discussed above. 
         [0233]    Each port  190  is provided with a valve  192  which allows penetration of the needle  191  and is sealed when the needle is extracted and at other times. For example, the valve  192  may incorporate an elastomeric seal. 
         [0234]    In this way, the priming ink is delivered directly to the absorbent material  29  and through capillary force is suspended therein for delivery to the nozzles of the printhead assembly  22 , as shown with arrow E in  FIG. 40 . 
         [0235]    The arrangement of this embodiment may be provided independently of those of the above-described embodiments, or may be used in conjunction with those arrangements to provide an additional refilling mechanism for the ink storage compartments  24 . 
       Ink Delivery Nozzles 
       [0236]    An example of a type of ink delivery nozzle arrangement suitable for the present invention, comprising a nozzle and corresponding actuator, will now be described with reference to  FIGS. 41 to 50 .  FIG. 50  shows an array of ink delivery nozzle arrangements  801  formed on a silicon substrate  8015 . Each of the nozzle arrangements  801  are identical, however groups of nozzle arrangements  801  are arranged to be fed with different colored inks or fixative. In this regard, the nozzle arrangements are arranged in rows and are staggered with respect to each other, allowing closer spacing of ink dots during printing than would be possible with a single row of nozzles. Such an arrangement makes it possible to provide a high density of nozzles, for example, more than 5000 nozzles arrayed in a plurality of staggered rows each having an interspacing of about 32 microns between the nozzles in each row and about 80 microns between the adjacent rows. The multiple rows also allow for redundancy (if desired), thereby allowing for a predetermined failure rate per nozzle. 
         [0237]    Each nozzle arrangement  801  is the product of an integrated circuit fabrication technique. In particular, the nozzle arrangement  801  defines a micro-electromechanical system (MEMS). 
         [0238]    For clarity and ease of description, the construction and operation of a single nozzle arrangement  801  will be described with reference to  FIGS. 41 to 49 . 
         [0239]    The ink jet printhead integrated circuit  50  includes a silicon wafer substrate  8015  having 0.35 Micron 1 P4M 12 volt CMOS microprocessing electronics is positioned thereon. 
         [0240]    A silicon dioxide (or alternatively glass) layer  8017  is positioned on the substrate  8015 . The silicon dioxide layer  8017  defines CMOS dielectric layers. CMOS top-level metal defines a pair of aligned aluminium electrode contact layers  8030  positioned on the silicon dioxide layer  8017 . Both the silicon wafer substrate  8015  and the silicon dioxide layer  8017  are etched to define an ink inlet channel  8014  having a generally circular cross section (in plan). An aluminium diffusion barrier  8028  of CMOS metal 1, CMOS metal 2/3 and CMOS top level metal is positioned in the silicon dioxide layer  8017  about the ink inlet channel  8014 . The diffusion barrier  8028  serves to inhibit the diffusion of hydroxyl ions through CMOS oxide layers of the drive electronics layer  8017 . 
         [0241]    A passivation layer in the form of a layer of silicon nitride  8031  is positioned over the aluminium contact layers  8030  and the silicon dioxide layer  8017 . Each portion of the passivation layer  8031  positioned over the contact layers  8030  has an opening  8032  defined therein to provide access to the contacts  8030 . 
         [0242]    The nozzle arrangement  801  includes a nozzle chamber  8029  defined by an annular nozzle wall  8033 , which terminates at an upper end in a nozzle roof  8034  and a radially inner nozzle rim  804  that is circular in plan. The ink inlet channel  8014  is in fluid communication with the nozzle chamber  8029 . At a lower end of the nozzle wall, there is disposed a moving rim  8010 , that includes a moving seal lip  8040 . An encircling wall  8038  surrounds the movable nozzle, and includes a stationary seal lip  8039  that, when the nozzle is at rest as shown in  FIG. 44 , is adjacent the moving rim  8010 . A fluidic seal  8011  is formed due to the surface tension of ink trapped between the stationary seal lip  8039  and the moving seal lip  8040 . This prevents leakage of ink from the chamber whilst providing a low resistance coupling between the encircling wall  8038  and the nozzle wall  8033 . 
         [0243]    As best shown in  FIG. 48 , a plurality of radially extending recesses  8035  is defined in the roof  8034  about the nozzle rim  804 . The recesses  8035  serve to contain radial ink flow as a result of ink escaping past the nozzle rim  804 . 
         [0244]    The nozzle wall  8033  forms part of a lever arrangement that is mounted to a carrier  8036  having a generally U-shaped profile with a base  8037  attached to the layer  8031  of silicon nitride. 
         [0245]    The lever arrangement also includes a lever arm  8018  that extends from the nozzle walls and incorporates a lateral stiffening beam  8022 . The lever arm  8018  is attached to a pair of passive beams  806 , formed from titanium nitride (TiN) and positioned on either side of the nozzle arrangement, as best shown in  FIGS. 44 and 49 . The other ends of the passive beams  806  are attached to the carrier  8036 . 
         [0246]    The lever arm  8018  is also attached to an actuator beam  807 , which is formed from TiN. It will be noted that this attachment to the actuator beam is made at a point a small but critical distance higher than the attachments to the passive beam  806 . 
         [0247]    As best shown in  FIGS. 41 and 47 , the actuator beam  807  is substantially U-shaped in plan, defining a current path between the electrode  809  and an opposite electrode  8041 . Each of the electrodes  809  and  8041  are electrically connected to respective points in the contact layer  8030 . As well as being electrically coupled via the contacts  809 , the actuator beam is also mechanically anchored to anchor  808 . The anchor  808  is configured to constrain motion of the actuator beam  807  to the left of  FIGS. 44 to 46  when the nozzle arrangement is in operation. 
         [0248]    The TiN in the actuator beam  807  is conductive, but has a high enough electrical resistance that it undergoes self-heating when a current is passed between the electrodes  809  and  8041 . No current flows through the passive beams  806 , so they do not expand. 
         [0249]    In use, the device at rest is filled with ink  8013  that defines a meniscus  803  under the influence of surface tension. The ink is retained in the chamber  8029  by the meniscus, and will not generally leak out in the absence of some other physical influence. 
         [0250]    As shown in  FIG. 42 , to fire ink from the nozzle, a current is passed between the contacts  809  and  8041 , passing through the actuator beam  807 . The self-heating of the beam  807  due to its resistance causes the beam to expand. The dimensions and design of the actuator beam  807  mean that the majority of the expansion in a horizontal direction with respect to  FIGS. 41 to 43 . The expansion is constrained to the left by the anchor  808 , so the end of the actuator beam  807  adjacent the lever arm  8018  is impelled to the right. 
         [0251]    The relative horizontal inflexibility of the passive beams  806  prevents them from allowing much horizontal movement the lever arm  8018 . However, the relative displacement of the attachment points of the passive beams and actuator beam respectively to the lever arm causes a twisting movement that causes the lever arm  8018  to move generally downwards. The movement is effectively a pivoting or hinging motion. However, the absence of a true pivot point means that the rotation is about a pivot region defined by bending of the passive beams  806 . 
         [0252]    The downward movement (and slight rotation) of the lever arm  8018  is amplified by the distance of the nozzle wall  8033  from the passive beams  806 . The downward movement of the nozzle walls and roof causes a pressure increase within the chamber  8029 , causing the meniscus to bulge as shown in  FIG. 42 . It will be noted that the surface tension of the ink means the fluid seal  8011  is stretched by this motion without allowing ink to leak out. 
         [0253]    As shown in  FIG. 43 , at the appropriate time, the drive current is stopped and the actuator beam  807  quickly cools and contracts. The contraction causes the lever arm to commence its return to the quiescent position, which in turn causes a reduction in pressure in the chamber  8029 . The interplay of the momentum of the bulging ink and its inherent surface tension, and the negative pressure caused by the upward movement of the nozzle chamber  8029  causes thinning, and ultimately snapping, of the bulging meniscus to define an ink drop  802  that continues upwards until it contacts adjacent print media. 
         [0254]    Immediately after the drop  802  detaches, meniscus  803  forms the concave shape shown in  FIG. 43 . Surface tension causes the pressure in the chamber  8029  to remain relatively low until ink has been sucked upwards through the inlet  8014 , which returns the nozzle arrangement and the ink to the quiescent situation shown in  FIG. 61 . 
         [0255]    Another type of printhead nozzle arrangement suitable for the present invention will now be described with reference to  FIG. 51 . Once again, for clarity and ease of description, the construction and operation of a single nozzle arrangement  1001  will be described. 
         [0256]    The nozzle arrangement  1001  is of a bubble forming heater element actuator type which comprises a nozzle plate  1002  with a nozzle  1003  therein, the nozzle having a nozzle rim  1004 , and aperture  1005  extending through the nozzle plate. The nozzle plate  1002  is plasma etched from a silicon nitride structure which is deposited, by way of chemical vapor deposition (CVD), over a sacrificial material which is subsequently etched. 
         [0257]    The nozzle arrangement includes, with respect to each nozzle  1003 , side walls  1006  on which the nozzle plate is supported, a chamber  1007  defined by the walls and the nozzle plate  1002 , a multi-layer substrate  1008  and an inlet passage  1009  extending through the multi-layer substrate to the far side (not shown) of the substrate. A looped, elongate heater element  1010  is suspended within the chamber  1007 , so that the element is in the form of a suspended beam. The nozzle arrangement as shown is a microelectromechanical system (MEMS) structure, which is formed by a lithographic process. 
         [0258]    When the nozzle arrangement is in use, ink  1011  from a reservoir (not shown) enters the chamber  1007  via the inlet passage  1009 , so that the chamber fills. Thereafter, the heater element  1010  is heated for somewhat less than 1 micro second, so that the heating is in the form of a thermal pulse. It will be appreciated that the heater element  1010  is in thermal contact with the ink  1011  in the chamber  1007  so that when the element is heated, this causes the generation of vapor bubbles in the ink. Accordingly, the ink  1011  constitutes a bubble forming liquid. 
         [0259]    The bubble  1012 , once generated, causes an increase in pressure within the chamber  1007 , which in turn causes the ejection of a drop  1016  of the ink  1011  through the nozzle  1003 . The rim  1004  assists in directing the drop  1016  as it is ejected, so as to minimize the chance of a drop misdirection. 
         [0260]    The reason that there is only one nozzle  1003  and chamber  1007  per inlet passage  1009  is so that the pressure wave generated within the chamber, on heating of the element  1010  and forming of a bubble  1012 , does not effect adjacent chambers and their corresponding nozzles. 
         [0261]    The increase in pressure within the chamber  1007  not only pushes ink  1011  out through the nozzle  1003 , but also pushes some ink back through the inlet passage  1009 . However, the inlet passage  1009  is approximately 200 to 300 microns in length, and is only approximately 16 microns in diameter. Hence there is a substantial viscous drag. As a result, the predominant effect of the pressure rise in the chamber  1007  is to force ink out through the nozzle  1003  as an ejected drop  1016 , rather than back through the inlet passage  1009 . 
         [0262]    As shown in  FIG. 51 , the ink drop  1016  is being ejected is shown during its “necking phase” before the drop breaks off. At this stage, the bubble  1012  has already reached its maximum size and has then begun to collapse towards the point of collapse  1017 . 
         [0263]    The collapsing of the bubble  1012  towards the point of collapse  1017  causes some ink  1011  to be drawn from within the nozzle  1003  (from the sides  1018  of the drop), and some to be drawn from the inlet passage  1009 , towards the point of collapse. Most of the ink  1011  drawn in this manner is drawn from the nozzle  1003 , forming an annular neck  1019  at the base of the drop  16  prior to its breaking off. 
         [0264]    The drop  1016  requires a certain amount of momentum to overcome surface tension forces, in order to break off. As ink  1011  is drawn from the nozzle  1003  by the collapse of the bubble  1012 , the diameter of the neck  1019  reduces thereby reducing the amount of total surface tension holding the drop, so that the momentum of the drop as it is ejected out of the nozzle is sufficient to allow the drop to break off. 
         [0265]    When the drop  1016  breaks off, cavitation forces are caused as reflected by the arrows  1020 , as the bubble  1012  collapses to the point of collapse  1017 . It will be noted that there are no solid surfaces in the vicinity of the point of collapse  1017  on which the cavitation can have an effect. 
         [0266]    Yet another type of printhead nozzle arrangement suitable for the present invention will now be described with reference to  FIGS. 52-54 . This type typically provides an ink delivery nozzle arrangement having a nozzle chamber containing ink and a thermal bend actuator connected to a paddle positioned within the chamber. The thermal actuator device is actuated so as to eject ink from the nozzle chamber. The preferred embodiment includes a particular thermal bend actuator which includes a series of tapered portions for providing conductive heating of a conductive trace. The actuator is connected to the paddle via an arm received through a slotted wall of the nozzle chamber. The actuator arm has a mating shape so as to mate substantially with the surfaces of the slot in the nozzle chamber wall. 
         [0267]    Turning initially to  FIGS. 52(   a )-(c), there is provided schematic illustrations of the basic operation of a nozzle arrangement of this embodiment. A nozzle chamber  501  is provided filled with ink  502  by means of an ink inlet channel  503  which can be etched through a wafer substrate on which the nozzle chamber  501  rests. The nozzle chamber  501  further includes an ink ejection port  504  around which an ink meniscus forms. 
         [0268]    Inside the nozzle chamber  501  is a paddle type device  507  which is interconnected to an actuator  508  through a slot in the wall of the nozzle chamber  501 . The actuator  508  includes a heater means e.g.  509  located adjacent to an end portion of a post  510 . The post  510  is fixed to a substrate. 
         [0269]    When it is desired to eject a drop from the nozzle chamber  501 , as illustrated in  FIG. 52(   b ), the heater means  509  is heated so as to undergo thermal expansion. Preferably, the heater means  509  itself or the other portions of the actuator  508  are built from materials having a high bend efficiency where the bend efficiency is defined as: 
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         [0270]    A suitable material for the heater elements is a copper nickel alloy which can be formed so as to bend a glass material. 
         [0271]    The heater means  509  is ideally located adjacent the end portion of the post  510  such that the effects of activation are magnified at the paddle end  507  such that small thermal expansions near the post  510  result in large movements of the paddle end. 
         [0272]    The heater means  509  and consequential paddle movement causes a general increase in pressure around the ink meniscus  505  which expands, as illustrated in  FIG. 52(   b ), in a rapid manner. The heater current is pulsed and ink is ejected out of the port  504  in addition to flowing in from the ink channel  503 . 
         [0273]    Subsequently, the paddle  507  is deactivated to again return to its quiescent position. The deactivation causes a general reflow of the ink into the nozzle chamber. The forward momentum of the ink outside the nozzle rim and the corresponding backflow results in a general necking and breaking off of the drop  512  which proceeds to the print media. The collapsed meniscus  505  results in a general sucking of ink into the nozzle chamber  502  via the ink flow channel  503 . In time, the nozzle chamber  501  is refilled such that the position in  FIG. 52(   a ) is again reached and the nozzle chamber is subsequently ready for the ejection of another drop of ink. 
         [0274]      FIG. 53  illustrates a side perspective view of the nozzle arrangement.  FIG. 54  illustrates sectional view through an array of nozzle arrangement of  FIG. 53 . In these figures, the numbering of elements previously introduced has been retained. 
         [0275]    Firstly, the actuator  508  includes a series of tapered actuator units e.g.  515  which comprise an upper glass portion (amorphous silicon dioxide)  516  formed on top of a titanium nitride layer  517 . Alternatively a copper nickel alloy layer (hereinafter called cupronickel) can be utilized which will have a higher bend efficiency. 
         [0276]    The titanium nitride layer  517  is in a tapered form and, as such, resistive heating takes place near an end portion of the post  510 . Adjacent titanium nitride/glass portions  515  are interconnected at a block portion  519  which also provides a mechanical structural support for the actuator  508 . 
         [0277]    The heater means  509  ideally includes a plurality of the tapered actuator unit  515  which are elongate and spaced apart such that, upon heating, the bending force exhibited along the axis of the actuator  508  is maximized. Slots are defined between adjacent tapered units  515  and allow for slight differential operation of each actuator  508  with respect to adjacent actuators  508 . 
         [0278]    The block portion  519  is interconnected to an arm  520 . The arm  520  is in turn connected to the paddle  507  inside the nozzle chamber  501  by means of a slot e.g.  522  formed in the side of the nozzle chamber  501 . The slot  522  is designed generally to mate with the surfaces of the arm  520  so as to minimize opportunities for the outflow of ink around the arm  520 . The ink is held generally within the nozzle chamber  501  via surface tension effects around the slot  522 . 
         [0279]    When it is desired to actuate the arm  520 , a conductive current is passed through the titanium nitride layer  517  within the block portion  519  connecting to a lower CMOS layer  506  which provides the necessary power and control circuitry for the nozzle arrangement. The conductive current results in heating of the nitride layer  517  adjacent to the post  510  which results in a general upward bending of the arm  20  and consequential ejection of ink out of the nozzle  504 . The ejected drop is printed on a page in the usual manner for an inkjet printer as previously described. 
         [0280]    An array of nozzle arrangements can be formed so as to create a single printhead. For example, in  FIG. 54  there is illustrated a partly sectioned various array view which comprises multiple ink ejection nozzle arrangements of  FIG. 73  laid out in interleaved lines so as to form a printhead array. Of course, different types of arrays can be formulated including full color arrays etc. 
         [0281]    The construction of the printhead system described can proceed utilizing standard MEMS techniques through suitable modification of the steps as set out in U.S. Pat. No. 6,243,113 entitled “Image Creation Method and Apparatus (IJ 41)” to the present applicant, the contents of which are fully incorporated by cross reference. 
         [0282]    The integrated circuits  50  may be arranged to have between 5000 to 100,000 of the above described ink delivery nozzles arranged along its surface, depending upon the length of the integrated circuits and the desired printing properties required. For example, for narrow media it may be possible to only require 5000 nozzles arranged along the surface of the printhead assembly to achieve a desired printing result, whereas for wider media a minimum of 10,000, 20,000 or 50,000 nozzles may need to be provided along the length of the printhead assembly to achieve the desired printing result. For full colour photo quality images on A4 or US letter sized media at or around 1600 dpi, the integrated circuits  50  may have 13824 nozzles per color. Therefore, in the case where the printhead assembly  22  is capable of printing in 4 colours (C, M, Y, K), the integrated circuits  50  may have around 53396 nozzles disposed along the surface thereof. Further, in a case where the printhead assembly  22  is capable of printing 6 printing fluids (C, M, Y, K, IR and a fixative) this may result in 82944 nozzles being provided on the surface of the integrated circuits  50 . In all such arrangements, the electronics supporting each nozzle is the same. 
         [0283]    The manner in which the individual ink delivery nozzle arrangements may be controlled within the printhead assembly  22  will now be described with reference to  FIGS. 55-58 . 
         [0284]      FIG. 55  shows an overview of the integrated circuit  50  and its connections to the SoPEC device (discussed above) provided within the control electronics of the print engine  1 . As discussed above, integrated circuit  50  includes a nozzle core array  901  containing the repeated logic to fire each nozzle, and nozzle control logic  902  to generate the timing signals to fire the nozzles. The nozzle control logic  902  receives data from the SoPEC device via a high-speed link. 
         [0285]    The nozzle control logic  902  is configured to send serial data to the nozzle array core for printing, via a link  907 , which may be in the form of an electrical connector. Status and other operational information about the nozzle array core  901  is communicated back to the nozzle control logic  902  via another link  908 , which may be also provided on the electrical connector. 
         [0286]    The nozzle array core  901  is shown in more detail in  FIGS. 56 and 57 . In  FIG. 56 , it will be seen that the nozzle array core  901  comprises an array of nozzle columns  911 . The array includes a fire/select shift register  912  and up to 6 color channels, each of which is represented by a corresponding dot shift register  913 . 
         [0287]    As shown in  FIG. 57 , the fire/select shift register  912  includes forward path fire shift register  930 , a reverse path fire shift register  931  and a select shift register  932 . Each dot shift register  913  includes an odd dot shift register  933  and an even dot shift register  934 . The odd and even dot shift registers  933  and  934  are connected at one end such that data is clocked through the odd shift register  933  in one direction, then through the even shift register  934  in the reverse direction. The output of all but the final even dot shift register is fed to one input of a multiplexer  935 . This input of the multiplexer is selected by a signal (corescan) during post-production testing. In normal operation, the corescan signal selects dot data input Dot[x] supplied to the other input of the multiplexer  935 . This causes Dot[x] for each color to be supplied to the respective dot shift registers  913 . 
         [0288]    A single column N will now be described with reference to  FIG. 77 . In the embodiment shown, the column N includes 12 data values, comprising an odd data value  936  and an even data value  937  for each of the six dot shift registers. Column N also includes an odd fire value  938  from the forward fire shift register  930  and an even fire value  939  from the reverse fire shift register  931 , which are supplied as inputs to a multiplexer  940 . The output of the multiplexer  940  is controlled by the select value  941  in the select shift register  932 . When the select value is zero, the odd fire value is output, and when the select value is one, the even fire value is output. 
         [0289]    Each of the odd and even data values  936  and  937  is provided as an input to corresponding odd and even dot latches  942  and  943  respectively. 
         [0290]    Each dot latch and its associated data value form a unit cell, such as unit cell  944 . A unit cell is shown in more detail in  FIG. 58 . The dot latch  942  is a D-type flip-flop that accepts the output of the data value  936 , which is held by a D-type flip-flop  944  forming an element of the odd dot shift register  933 . The data input to the flip-flop  944  is provided from the output of a previous element in the odd dot shift register (unless the element under consideration is the first element in the shift register, in which case its input is the Dot[x] value). Data is clocked from the output of flip-flop  944  into latch  942  upon receipt of a negative pulse provided on LsyncL. 
         [0291]    The output of latch  942  is provided as one of the inputs to a three-input AND gate  945 . Other inputs to the AND gate  945  are the Fr signal (from the output of multiplexer  940 ) and a pulse profile signal Pr. The firing time of a nozzle is controlled by the pulse profile signal Pr, and can be, for example, lengthened to take into account a low voltage condition that arises due to low power supply (in a removable power supply embodiment). This is to ensure that a relatively consistent amount of ink is efficiently ejected from each nozzle as it is fired. In the embodiment described, the profile signal Pr is the same for each dot shift register, which provides a balance between complexity, cost and performance. However, in other embodiments, the Pr signal can be applied globally (ie, is the same for all nozzles), or can be individually tailored to each unit cell or even to each nozzle. 
         [0292]    Once the data is loaded into the latch  942 , the fire enable Fr and pulse profile Pr signals are applied to the AND gate  945 , combining to the trigger the nozzle to eject a dot of ink for each latch  942  that contains a logic 1. 
         [0293]    As shown in  FIG. 58 , the fire signals Fr are routed on a diagonal, to enable firing of one color in the current column, the next color in the following column, and so on. This averages the current demand by spreading it over 6 columns in time-delayed fashion. 
         [0294]    The dot latches and the latches forming the various shift registers are fully static in this embodiment, and are CMOS-based. The design and construction of latches is well known to those skilled in the art of integrated circuit engineering and design, and so will not be described in detail in this document. 
         [0295]    The nozzle speed may be as much as 20 kHz for the printer unit  2  capable of printing at about 60 ppm, and even more for higher speeds. At this range of nozzle speeds the amount of ink than can be ejected by the entire printhead assembly  22  is at least 50 million drops per second. However, as the number of nozzles is increased to provide for higher-speed and higher-quality printing at least 100 million drops per second, preferably at least 500 million drops per second and more preferably at least 1 billion drops per second may be delivered. At such speeds, the drops of ink are ejected by the nozzles with a maximum drop ejection energy of about 250 nanojoules per drop. 
         [0296]    Consequently, in order to accommodate printing at these speeds, the control electronics must be able to determine whether a nozzle is to eject a drop of ink at an equivalent rate. In this regard, in some instances the control electronics must be able to determine whether a nozzle ejects a drop of ink at a rate of at least 50 million determinations per second. This may increase to at least 100 million determinations per second or at least 500 million determinations per second, and in many cases at least 1 billion determinations per second for the higher-speed, higher-quality printing applications. 
         [0297]    For the printer unit  2  of the present invention, the above-described ranges of the number of nozzles provided on the printhead assembly  22  together with the nozzle firing speeds and print speeds results in an area print speed of at least 50 cm 2  per second, and depending on the printing speed, at least 100 cm 2  per second, preferably at least 200 cm 2  per second, and more preferably at least 500 cm 2  per second at the higher-speeds. Such an arrangement provides a printer unit  2  that is capable of printing an area of media at speeds not previously attainable with conventional printer units. 
       Lid Assembly 
       [0298]    The lid assembly  21  of the cartridge unit  10  is shown in  FIGS. 59-61 . The lid assembly  21  is arranged to fit over the main body  20 , thereby sealing each of the ink storage compartments  24 . As such, the lid assembly  21  is shaped to conform to the shape of main body  20  and is attached to the main body via ultrasonic welding, or any other suitable method which provides a sealed connection. 
         [0299]    The outer surface  60  of the lid assembly  21  is provided with a number of ink refill ports  61 , for receiving ink from a refill unit  200  and for directing the refill ink into one of the ink storage compartments  24  of the main body  20 . In the embodiment shown in  FIG. 59 , there are five ink refill ports  61  provided, with each of the refill ports being in fluid communication with one of the five ink storage compartments  24  to facilitate refilling of the associated compartments with ink. 
         [0300]    The ink refills ports  61  are in the form of holes extending through the lid assembly  11  and each hole is provided with a valve fitting  62  made from an elastomeric moulding. The valve fittings  62  act to seal the ports  61  during non refill periods and provide a means for interacting with an outlet of the ink refill unit  200  to ensure controlled transfer of ink between the ink refill unit  200  and the ink storage compartment  24 . In this regard, when an ink refill unit  200  is not in communication with the ink refill ports  61  the valve fittings  62  seal the ink refill ports, and when the ink refill unit  200  is in communication with the ink refill ports, the valve fittings permits transfer of ink from the ink refill unit through the ink refill ports. The manner in which this is achieved is described later in the description. 
         [0301]    The outer surface  60  of the lid assembly  21  also includes a venting arrangement which provides air venting of each ink storage compartment  24 . The venting arrangement consists of individual vent holes  63  which extend into the individual ink storage compartments  24  and channels  64  which extend from the vent holes  63  to the edge of the lid assembly  21 . The channels  64  are preferably etched into the outer surface  60  of the lid assembly and assume a tortuous path in the passage from the vent holes  63  to the edge of the lid assembly. 
         [0302]    As shown in  FIG. 61 , a film  65  is placed over the outer surface  60  of the lid assembly and includes holes  66  formed therein which fit around the ink refill ports  61 . The film  65  may be an adhesive film such as a sticker/label or the like which may also have printed thereon instruction information to assist the user in handling the cartridge unit  10 . When applied to the surface of the lid assembly  21 , the film sits atop the etched channels  64  formed in the outer surface  60 , thereby enclosing the venting passage from the vent hole  63  to the edge of the lid assembly  21  which enables the ink storage compartment to breathe via the tortuous path. 
         [0303]    The underside of the lid assembly  21  is shown in more detail in  FIG. 60  and includes flow channels  67  extending from the underside of the ink refill ports  61  to direct the refill ink into the appropriate ink storage compartment  24 . As shown in  FIG. 61 , a weld membrane  68  is welded to the underside of the ink refill ports  61  and the flow channels  67  to form sealed delivery passages along which the ink passes en route to each of the ink storage compartments  24 . 
         [0304]    The underside of the lid assembly  21 , also includes moulded features or ridges  69  which extend into the ink storage compartments  24  when the lid assembly  21  is sealed to the main body  20 . These moulded features or ridges  69  ensure that an air gap is formed above the absorbent material  29  for venting via the vent hole  63  to assist the absorbent material  29  to function to absorb the ink and retain the ink suspended therein under capillary action. 
         [0305]    As shown in  FIGS. 59 and 60 , extending downwardly from the outer surface  60  of the lid assembly  21  are a pair of guide walls  70 . The guide walls  70  assist in locating the lid assembly  21  on the main body  20  during assembly. The guide walls  70  also have a recessed portion  71  formed therein which acts as a hand grip to assist in handling the cartridge unit during use. 
         [0306]    As shown more clearly in  FIG. 59 , the guide wall  70  that extends along the face of the main body  20  proximal the printhead assembly  22  also includes a series of holes  72  in a lower edge thereof. These holes  72  are arranged to align with and receive the locating studs  38  provided on the main body  20  onto which the flex PCB backer  37  and the flex PCB  52  of the printhead assembly  22  are attached. In this arrangement, when the lid assembly  21  is fixed to the main body  20 , a portion of the flex PCB  52  of the printhead assembly  22  is sandwiched between the guide wall  70  and the flex PCB backer  37 , thereby acting to help retain the flex PCB  52  in position. 
       Capper Assembly 
       [0307]    As discussed previously and shown in  FIGS. 11 and 12 , the main body  20  of the cartridge unit  10  is provided with downwardly projecting end supports  40 . The end supports  40  are integral with the main body  20  and are arranged such that the printhead assembly  22  is positioned between the end supports. Each of the end supports  40  are configured to receive the capping assembly  23  and as such have retaining projections  73  formed on their surfaces to retain the capping assembly  23  in position. 
         [0308]    The capping assembly  23  is shown in more detail in  FIGS. 62 to 67 , and generally consists of a capper chassis  74  which receives the various components of the capping assembly  23  therein. The capper chassis  74  is in the form of an open ended channel having a pair of upwardly extending tongue portions  75  at its ends which are shaped to fit over the end supports  40  of the main body and engage with the retaining projections  73  provided thereon to secure the capper assembly  23  in position. The capper chassis  74  essentially retains the parts of the capper assembly  23  therein, and is made from a suitable metal material, having rigidity and resilience, such as a pressed steel plate. 
         [0309]    The base of the capper chassis  74  is shown more clearly in  FIG. 64  and includes a centrally located removed portion  76  and spring arms  77  extending from either side of the removed portion  76  towards the tongue portions  75 . The spring arms  77  are hingedly fixed to the chassis  74  at the region proximal the removed portion, and are biased inwards of the capper chassis. The spring arms  77  may be made from the same material as the chassis and formed by removing material from the chassis pressing the arms from the base of the chassis. Whilst the spring arms  77  are shown as being integral with the chassis  74 , they may be provided as a separate insert which may be inserted into the open channel of the chassis  74 , as would be appreciated by a person skilled in the art. 
         [0310]    A rigid insert  78  is provided to fit within the chassis  74  to provide added rigidity to the capper assembly  23 . In this regard the insert  78  is made from moulded steel and forms an open u-shaped channel. A lower capper moulding  79  is located within the insert  78  and retained within the insert via engagement of a number of lugs  80  formed along the sides of the lower capper moulding  79  with corresponding holes  81  provided in the sides of the insert  78 . The lower capper moulding  79  is made from a suitable plastic material and forms a body having closed ends and an open top. The ends of the lower capper moulding  79  are provided with air vents  82  which provide a means for air to enter the capper assembly and ventilate the capper assembly. 
         [0311]    The base of the lower capper moulding is provided with a pair of centrally located projections  83  which are received within slots  84  formed in the base of the rigid insert  78 . The projections  83  extend through the rigid insert  78 , beyond its outer base surface to define a region for receiving an electromagnetic button  85 , which is spot welded to the outer base surface of the rigid insert  78  between the projections  83 . The purpose of the electromagnetic button  85  will be discussed in more detail later in the description; however it should be appreciated that the electromagnetic button  85  can be made of any material which is capable of experiencing magnetic attraction forces. 
         [0312]    A strip of absorbent media  86  is provided to fit within the lower capping moulding  79 , and may be made from any type of material capable of absorbing and retaining ink therein, such as urethane foam or the like. The absorbent media  86  is shaped to fit within the lower capper moulding  79  and includes a stepped portion  87  which projects above the lower capper moulding  79  and extends centrally along the length of the absorbent media  86 , as is shown more clearly with regard to  FIGS. 63 and 65 . 
         [0313]    An upper capper moulding  88  is then provided to fit over the lower capper moulding  79  and the absorbent media  86 . The upper capper moulding  88  has essentially two portions, a lower portion  89  which seals along the edges of the lower capper moulding  79  to retain the absorbent media  86  therein, and an upper portion  90  which essentially conforms to the shape of the stepped portion  87  of the absorbent media  86 . The lower portion  89  is made from a rubber or plastics material and has an edge portion which sits along the upper edge of the lower capping moulding  79  and which is attached thereto by an ultrasonic weld or any other suitable attachment means. The upper portion  90  has an open upper surface and is made from a dual shot elastomeric material. The open upper surface is in the form of a rim portion  91  that extends beyond the absorbent media  86  and defines a perimeter seal for sealing the integrated circuits  50  of the printhead assembly  22 , as is shown in relation to  FIG. 65 . The space formed between the upper edge of the rim portion  91  and the absorbent media  86  is the space which seals the integrated circuits  50  of the printhead assembly  22 . 
         [0314]    In this arrangement, the upper capper moulding  88 , absorbent media  86 , lower capper moulding  79  and the rigid insert  78  form a unit which is adapted to fit within the capper chassis  74 . In order to secure the unit in place, a retainer element  92  is provided which fits over the upper capping moulding  88  and is secured to the chassis  74  as shown in  FIG. 62 . 
         [0315]    The retainer element  92  is essentially in the form of an open ended channel which fits over the upper capper moulding  88  and encloses the components therein. A slot  93  is formed in the upper surface of the retainer element  92  through which the upper portion  90  of the upper capper moulding  88  can protrude and the slot is shaped to conform to the shape of the upper portion  90  of the upper capper moulding  88 , as is shown in  FIG. 65 . The upper surface of the retainer element  92  is curved and acts as a media guide during printing, as will be described in more detail later. The retainer element  92  is fixed to the chassis via a snap-fit arrangement whereby lugs  94  formed in the retainer element  92  are received in recesses  95  provided in the chassis  74 . When assembled in this manner, the components of the capper assembly  23  are contained within the retainer element  92  and the chassis  74 , and the electromagnetic button  85  secured to the rigid insert  78  is aligned with the centrally located removed portion  76  of the chassis. 
         [0316]    Upon assembly and attachment of the capper assembly  23  to the end supports  40  of the main body  20 , due to the presence of the spring arms  77  extending inwardly from the base of the chassis  74 , the rigid insert  78  which contains the lower capper moulding  79 , absorbent media  86  and the upper capper moulding  88  therein, is supported on the spring arms  77  and is raised from the base of the chassis  74 . This state is shown in  FIGS. 62 and 65 , and in this state the upper portion  90  of the upper capper moulding  88  protrudes through the slot  93  provided in the retainer element  92 . This state is the capping state, whereby the upper rim portion  91  of the upper capper moulding  88  contacts the printhead assembly  22  and acts as a perimeter seal around the printhead integrated circuits  50 , sealing them within the confined space of the capper assembly  23 . In the capping state, the nozzles  51  of the printhead integrated circuits  50  may fire and spit ink into the absorbent material  86 . The absorbent material  86 , is typically retained in a moist state at all times, such that when the integrated circuits are in the capping state, the nozzles are sealed in a moist environment which prevents ink from drying in the nozzles of the integrated circuits and blocking the nozzles. 
         [0317]    In order to perform printing, the capper assembly  23  must be moved from a capping state to a printing state. This is achieved by causing the rigid insert  78  to act against the spring arms  77  of the chassis  74  and move in a downwards direction, towards the base of the chassis  74 . This movement is caused by applying an electromagnetic force in the vicinity of the base of the capper assembly  23 , proximal the centrally located removed portion  76 . The activation of the electromagnet force attracts the electromagnet button  85  fixed to the underside of the rigid insert  78 , thereby causing the rigid insert, which contains the lower capper moulding  79 , absorbent media  86  and the upper capper moulding  88  therein, to move in a downward direction with respect to the printhead assembly  22 . The centrally located removed portion  76  of the base of the chassis  74  allows the electromagnet button  85  to be fully retracted against the spring arms  77  towards the source of the electromagnetic force. This in turn causes the upper rim portion  91  of the upper capping moulding  88  to retract into the retainer element  92  such that it is flush with the outer surface of the retainer element  92  and does not protrude therefrom. It will be appreciated that the retainer element  92  does not move and is fixed in position. Such a state is referred to as the printing state, and in this state there is a gap formed between the retainer element  92  and the printhead assembly  22  through which the media can pass for printing. In the printing state, the retainer element  92  acts as a media guide and the media contacts the retainer element and is supported on the surface of the retainer element as it passes the printhead assembly for printing. 
         [0318]      FIGS. 66 and 67  show the cartridge unit  10  in the capping state and the printing state respectively. It will be appreciated that due to the action of the spring arms  77 , the capping state is the relaxed state of the capper assembly  23  and whenever printing is not occurring the cartridge unit  10  is in the capping state. In this regard, the cartridge unit  10  is packaged and shipped in the capping state. As such, to move the cartridge unit  10  into a printing state, power must be supplied to an electromagnet, which is located in the cradle unit  12  as described later, to cause the upper capper moulding  88  to retract into the retainer element  92 . In the event of power failure or cessation of power to the printer unit, the electromagnetic force is removed, and the capper assembly  23  returns to the capping state under action of the spring arms  77 , thereby protecting the printhead integrated circuits  50  against prolonged periods of exposure to drying air. 
       Cradle Unit 
       [0319]    The cradle unit  12  is shown in relation to  FIGS. 6-8  and generally consists of a main body  13  which defines an opening for receiving the cartridge unit  10 , and a cover assembly  11  adapted to close the opening to secure the cartridge unit  10  in place within the cradle unit  12 . 
         [0320]    The main body  13  of the cradle unit  12  includes a frame structure  101  as shown in  FIGS. 68   a - 68   d . The frame structure  101  generally comprises two end plates  102  and a base plate  103  connecting each of the end plates  102 . As mentioned previously, each of the end plates  102  is provided with anchor portions  14  formed the base thereof to enable the print engine  1  to be secured in position within the printer unit  2 . A drive roller  104  and an exit roller  105  are mounted between the end plates  102  via mounting bearings  106  and are separated a distance to accommodate the cartridge unit  10  when the print engine  1  is fully assembled. The drive roller  104  and the exit roller  105  are each driven by a brushless DC motor  107  which is mounted to one of the end plates  102  and drives each of the drive and exit rollers via a drive mechanism  108 , such as a drive belt. Such a system ensures that both the drive roller  104  and the exit roller  105  are driven at the same speed to ensure a smooth and consistent passage of the media through the print engine  1 . 
         [0321]    An electromagnet assembly  109  is mounted to the underside of the base plate  103  in a central position as shown most clearly in  FIGS. 68   c  and  68   d . The purpose of the electromagnet assembly  109  is to actuate the capper assembly  23  of the cartridge unit  10 , as previously discussed. A hole  110  is provided in the base plate  103  around the electromagnet assembly  109  to facilitate communication with the electromagnet button  85  on the capper assembly  23 . 
         [0322]    A refill solenoid assembly  111  is mounted to the other end plate  102 , opposite the DC motor  107 , and is provided to operate a refill unit  200  to refill the cartridge unit  10  with refill ink, as will be described later. The refill solenoid assembly  111  is positioned such that an actuator arm  112  extends beyond the upper edge of the end plate  102 , the purpose of which will become apparent later in the description. 
         [0323]    Cartridge unit guides  113  are also mounted to the interior surfaces of each of the end plates  102 . The guides are located at the rear of the cradle unit  12  and assist in positioning the cartridge unit  10  within the cradle unit  12  to ensure that removal and replacement of the cartridge unit  10  is a simple process. To further accommodate the cartridge unit  10 , a cartridge unit support member  114  is mounted between the end plates  102  at the front of the cradle unit  12 . The cartridge unit support member  114  is shown in more detail in  FIG. 69 , and is in the form of a shaped plate fixed to the front portion of the cradle unit  12 . The cartridge unit support member  114  has a pair of clips  115  which fit into recesses  116  formed in the end plates  102  and has further anchor points  117  which enable the cartridge unit support member to be fixed to the end plates  102 , via screws or the like, to form a surface upon which the cartridge unit  10  can be received and supported. The cartridge unit support member  114  together with the cartridge unit guides  113 , defines a space  118  for receiving the cartridge unit  10  therein which conforms to the shape of the cartridge unit  10 , as shown in  FIG. 70 . 
         [0324]    An idle roller assembly  119  is fixed to the cartridge unit support member  114  and includes a plurality of roller wheels  120  which are positioned to contact the surface of the drive roller  104  and rotate therewith. The idle roller assembly  119  is shown in  FIGS. 71   a  and  71   b  and comprises a curved multi-sectioned plate  121  with each section of the plate having a pair of roller wheels  120  provided at its distal end. Each section of the plate  121  is spring loaded against the surface of the cartridge unit support member  114  via a suitable spring means  122 , to allow the roller wheels  120  to move with respect to the surface of the drive roller  104  to accommodate print media therebetween. The idle roller assembly  119  is attached to the under-surface of the cartridge unit support member  114  via clips  123  which are received in corresponding slots  124  formed in the cartridge unit support member  114 , as is shown in  FIG. 72 . Such an arrangement ensures that the media that is presented to the print engine  1  from the picker mechanism  9  of the printer unit  2 , is gripped between the drive roller  104  and the idle roller assembly  119  for transport past the printhead assembly  22  of the cartridge unit  10  for printing. 
         [0325]    The control electronics for the print engine which controls the operation of the integrated circuits  50  of the printhead assembly  22 , as well as the operation of the drive roller  104  and exit roller  105  and other related componentry, is provided on a printed circuit board (PCB)  125  as shown in  FIGS. 73   a  and  73   b . As can be seen, one face of the PCB  125  contains the SoPEC devices  126  and related componentry  127  for receiving and distributing the data and power received, as will be discussed later, whilst the other face of the PCB includes rows of electrical contacts  128  along an edge thereof which provides a means for transmitting the power and data signals to the printhead assembly  22  in a manner to be described below. 
         [0326]    The PCB  125  is mounted between two arms  129 , with each of the arms having a claw portion  130  to receive the PCB  125  in position, as shown in  FIGS. 74   a - 74   c . Each arm  129  is configured to have a substantially straight edge  131  and an angled edge  132  having a protrusion  133  formed thereon. The PCB  125  is positioned between the arms  129  such that the face of the PCB having the electrical contacts  128  formed along the lower edge thereof extends between the substantially straight edges  131  of the arms  129 . 
         [0327]    The upper region of each of the arms  129  includes an upwardly extending finger portion  134  and a spring element  135  is provided for each of the arms  129 , the purpose of the finger portion  134  and the spring element  135  will be discussed in more detail later. 
         [0328]    In order to provide stability to the PCB  125  as it is mounted between the two arms  129 , a support bar  136  is attached to the assembly which acts along the bottom edge of the PCB  125 , on the face that contains the SoPEC devices  126  and the related componentry  127 . This support bar  136  is shown in  FIGS. 75   a - 75   b  and consists of a curved plate  137  made from a suitable material such as steel which has appropriate strength and rigidity properties. The support bar  136  has a contact edge  138  which is arranged to contact the surface of the PCB  125 , along its bottom edge opposite the electrical contacts  128 . The contact edge  138  has a pair of attachment points  139  at its ends which allow the support bar  136  to be secured to the PCB  125  via screws or other suitable attachment means. Locating projections  140 , are also provided to mate with appropriate locating holes in the PCB  125  to assist in correctly position the support bar  136  in place. The contact edge  138  includes an electrical insulator coating  141  along its length which performs the contact between the support bar  136  and the PCB  125 . It will be appreciated that the support bar  136  contacts the surface of the PCB  125  along its&#39; lower edge and provides backing support to the electrical contacts  128  when they come into contact with the corresponding dimple contacts  53  provided on the flex PCB  52  of the printhead assembly  22 . 
         [0329]    The support bar  136  also includes a relatively straight portion  142  which extends substantially horizontally from the contact edge  138 . The straight portion  142  includes a pair of tabs  143  that extend longitudinally from its ends to engage with corresponding slots  144  provided in the arms  129  to further secure the support bar  136  in position. A plurality of star wheels  145  is also provided along the length of the straight portion  142  in a staggered arrangement. The star wheels  145  are secured within slots  146  formed in the straight portion  142  and are provide on spring loaded axles  147  which permits relative movement of the star wheels  145  with respect to the straight portion of the support bar  146 . The star wheels  145  are provided to contact the surface of the exit roller  105  to assist in gripping and removing the printed media from the print engine  1 , as will be discussed below.  FIG. 76  shows the support bar  136  attached to the PCB  125  and arms  129 . 
         [0330]    The arms  129  are attached to a bottom portion of end plates  102  at the pivot point  148  via a screw arrangement as shown in  FIGS. 77   a  and  77   b . In this arrangement the arms  129 , and subsequently the PCB  125  and support bar  136 , is able to pivot about the pivot point  148  between an open position wherein the contacts  128  on the PCB  125  are remote from the dimpled contacts  53  on the flex PCB  52  of the cartridge unit  22 , and a closed position where the contacts  128  on the PCB  125  are in pressing contact with the dimpled contacts  53  on the flex PCB  52  of the cartridge unit  22 . As clearly shown, upon attachment of the arms  129  to the end plates  102 , the star wheels  145  are in contact with the surface of the exit roller  105 , to capture the sheet of media therebetween for removal of the sheet from the print engine  1  to a collection area  4  for collection. 
         [0331]    The cover assembly  11 , as shown in  FIGS. 78   a - 78   c , is attached to the upper portion of the end plates  102  via pivot pins  150  which are received in holes  151  formed in the upper portion of the end plates  102 . The cover assembly  11  is made from a moulded plastic material and the pivot pins  150  are formed proximal to a rear edge of the cover assembly  11  during the moulding process. The pivot pins  150  allow the cover assembly  11  to pivot about the end plates  102  between a closed position, where the cartridge unit  10  is secured within the cradle unit  12 , and an open position, where the cartridge unit  10  can be removed from the cradle unit  12  and replaced. A latch  152  is provided in a front edge  153  of the cover assembly  11 . The latch  152 , has a flexible clip element  154  which is received within a recess  155  provided in the cartridge unit support member  114  when the cover assembly  11  is in the closed position, as shown in  FIG. 81 . The flexible clip element  154  is spring loaded via a spring element (not shown) such that the clip element  154  can be readily depressed to release engagement between it and the recess  155  provided in the cartridge unit support member  114  so that the cover assembly  11  can be pivoted into an open position, as shown in  FIG. 80 . 
         [0332]    Positioned adjacent the pivot pins  150 , on the inside of the cover assembly  11 , are a pair of posts  156 . The posts  156  are arranged substantially alongside the pivot pins  150 , towards the front edge  153  of the cover assembly  11 . The posts  156  are configured such that they are a greater length than the pivot pins  150  and hence extend inwardly a greater distance, to contact the spring element  135  of the arms  129  which support the PCB  125 . 
         [0333]    In this regard, the act of opening and closing the cover assembly  11  also performs the function of bringing the contacts  128  provided on the surface of the PCB  125 , into contact with the corresponding dimpled contacts  53  provided on the flex PCB  52  of the printhead assembly  22 . To achieve this, the cover assembly  11  and the arms  129  are arranged as shown in  FIG. 79 . 
         [0334]    As shown, the cover assembly  11  is attached to the end plates  102  such that the posts  156  extend between the upwardly extending finger portion  134  and the spring element  135  at each end thereof. When the cover assembly  11  is moved to the open position, as shown in  FIG. 80 , the posts  156  act against the upwardly extending finger portion  134  of the arms  129  causing the arms  129 , and the PCB  125 , to pivot away from contact with the dimpled contacts  53  of the flex PCB  52  of the cartridge unit  22 . This movement is due to the swing action of the cover assembly  11  when opened which in turn causes the posts  156  to move in an arcuate direction towards the rear of the print engine  1 . When the cover assembly  11  moves to the closed position as shown in  FIG. 81 , the cover assembly  11  pivots about the pivot pins  150 , causing the posts  156  to move in an arcuate direction towards the front of the print engine  1 . As the posts  156  move, they contact the upright portion of the spring element  135 , causing the PCB  125  and the arms  129  to pivot forward. The spring element  135  has considerable rigidity to transfer the force exerted upon it by the posts  156  into forward movement of the PCB  125  and arms  129  which results in the contacts  128  on the outward lower portion of the PCB  125  to contact the corresponding dimpled contacts  53  provided on the flex PCB  52  of the cartridge unit  10 , which is positioned and supported on the flex PCB backer  37 . As the cover assembly  11  is secured in place by the clip element  154  gripping the recessed portion  155  of the cartridge unit support member  114 , the contacts  128  remain in aligned contact with the dimpled contacts  53 , ensuring that power and data can be transmitted between the SoPEC devices  126  and the integrated circuits  50  of the printhead assembly  22 . Due to the fact that the posts  156  act against the upright portion of the spring element  135 , with the corresponding horizontal portion of the spring element  135  being secured against the arms  129 , there is a return force stored in the spring element  135  such that when the latch  152  of the cover assembly  11  is released the PCB  125  and the arms  129  will begin to pivot away from contact with the dimpled contacts  53  of the flex PCB  52 , breaking electrical contact therebetween and allowing ready removal of the cartridge unit  10 . 
         [0335]    As shown in  FIGS. 78   a - 78   c , the cover assembly  11  includes a centrally located docking port  157  in the form of a hole formed through the cover assembly  11 . The docking port  157  is shaped to enable a refill unit  200  to pass therethrough to dock with the cartridge unit  10  thereby enabling refilling of the cartridge unit  10  with ink, in a manner which will be described below. The docking port  157  has a rim portion  158  upon which a portion of the base of the refill unit  200  is received. Formed within the rim portion  158  of the docking port  157  is an engagement means  159  which engages with the refill unit  200  to retain the refill unit securely in position to facilitate refilling of the cartridge unit  12 . A QA chip reader  160  is also formed in the rim  158  of the docking port  157  to mate with a corresponding QA chip provided in the refill unit  200  to ensure integrity of the refill unit. The manner in which the engagement means  159  and the QA chip reader  160  functions will be described in more detail later in the description. 
         [0336]    Projecting into the docking port  157  via a hole  161  formed in the wall of the rim portion  158 , as shown in  FIG. 78   c , is a push rod  162 . As shown more clearly in  FIG. 82 , the push rod  162  is in the form of an elongate bar member having an end  163  of reduced cross section which extends through the hole  161  in the wall of the rim portion  158 ; and an end having a foot portion  164 , a part of which extends perpendicular to the length of the push rod  162 . The body of the push rod  162 , proximal the foot portion  164 , has a slot  165  formed therein which enables the push rod  162  to be secured to the underside of the cover assembly  11  by way of a screw or the like upon which a push clip  166  is secured. The push clip  166  allows the push rod  162  to move longitudinally with respect to the push clip  166  but prevents any sideways or downward movement of the push rod  162 . A retainer  167  is also provided in the underside of the cover assembly  11  proximal the docking port  157  to retain the push rod in position and to prevent any non-longitudinal movement of the push rod  162 . In this configuration, the pushrod  162  is free to move in a longitudinal direction with respect to its length, such that the end  163  of reduced cross section can enter and be withdrawn from the docking port  157 . A spring element  168  is provided in the slot  165  formed in the push rod  162  and acts to bias the push rod  162  into position, such that its natural position is to have its end  163  extend into the docking port  157 . 
         [0337]    The foot portion  164  of the push rod  162  is shown in more detail in  FIG. 83 . The part of the foot portion  164  which extends perpendicular to the length of the push rod, has a groove  169  formed therein. The surface  170  of the groove is angled towards the end  163  of the push rod, as shown. The foot portion  164  is positioned at the side edge of the cover assembly  11  and extends in a downward direction with respect to the cover assembly  11 . In this position the actuator arm  112  of the refill solenoid assembly  111  mounted on the cradle unit  12  is orientated such that it is aligned with the groove  169  of the foot portion  164 . As the actuator arm  112  is raised by the solenoid assembly  111  in a vertical direction, it travels along the surface  170  of the groove  169  thereby causing the push rod  162  to retract such that the end  163  of the push rod  162  no longer extends into the docking port  157 . Lowering of the actuator arm  112  by the solenoid assembly  111  results in the push rod  162  returning to its naturally biased position under the action of the spring element  168 , whereby the end  163  extends into the docking port  157 . The manner in which the end  163  of the push rod interacts with the refill assembly  200  will be discussed in more detail below, however it should be appreciated that the position of the push rod is controlled by the SoPEC device  126  with regard to the state of operation of the printer unit. 
       Refill Unit 
       [0338]      FIG. 47  illustrates one embodiment of an ink refill unit  200 . The ink refill unit  200  generally comprises a base assembly  202  which houses internal ink refilling components and a lid assembly  204  which fits onto the base assembly  202 . The base and lid assemblies may be moulded from a plastics material and the base assembly may be moulded as a single piece or in sections (as shown in  FIG. 88 ). 
         [0339]    As mentioned previously, the refill unit  200  contains ink and is intended to be used as a means for refilling the ink storage compartments  24  within the cartridge unit  10 . The refill unit  200  is configured to dock with the surface of the cartridge unit  10  in order to transfer the ink it contains into the ink storage compartments  24  of the cartridge unit  10 . For this purpose, the cover assembly  11  of the cradle unit  12  has a docking port  157  formed therein through which the refill unit  200  is able to pass to dock with the upper surface of the print cartridge  10 . 
         [0340]    As discussed previously in relation to the lid assembly  21  of the cartridge unit  10 , the upper surface  60  of the lid assembly  21  has a plurality of ink refill ports  61  formed therein, with each of the individual ink refill ports  61  being in fluid communication with one of the ink storage compartments  24  to deliver ink to that compartment. The position of the individual ink refill ports  61  on the surface of the cartridge unit  10  is specific to the type or colour of ink stored by the cartridge unit, and the position and configuration of the ink refill ports  61  is consistent between different cartridge units. In this regard, each refill unit  200  is configured with a plurality of outlets  206  located in a bottom section  202   a  of the base assembly  202  for docking with the cartridge unit. However in each instance, only one of the outlets is in fluid communication with the supply of ink for distributing ink to an ink storage compartment of the cartridge unit through the corresponding ink refill port, the position of the outlet being dependant upon the type or colour of ink to be supplied from the refill unit. As shown in  FIG. 88 , the refill unit  200  is arranged with one working outlet  208  for the distribution of the particular coloured ink contained in the refill unit to the ink refill port  61  of the correspondingly coloured ink storage compartment  24  in the cartridge unit  10 . That is, if the refill unit  200  contains cyan ink, the working outlet  208  is positioned so as to correspond to the ink refill port  61  of the cyan ink chamber of the cartridge unit  10  when the refill unit is docked with the cartridge unit. 
         [0341]    A clip arrangement  210  is provided on at least one side of the base assembly  202  of the refill unit  200  for securing the refill unit to the print engine during the refilling operation. This ensures reliable and efficient transfer of ink from the refill unit  200  to the cartridge unit as the refill unit  200  is substantially immovable from the print engine until the clip arrangement  210  is disengaged, thereby ensuring a complete seal between the refill unit and the cartridge unit and preventing the possibility of ink spillage or air ingress between the outlet and the ink refill port. 
         [0342]    In this regard, the clip arrangement  210  is formed as a resilient section of the side wall of the base assembly  202  and is movable with respect the remainder of the side wall so as to engage and disengage with a corresponding engagement means  159  provided in the docking port  157  of the cover assembly  11  of the cradle unit. The clip arrangement includes clip portions  212  in the form of projections that project from a resilient arm  214 , the arm  214  being depressible to move into and out of a recess  216  about a pivot region  218 , the pivot region  218  being a weakened region in the surface of the base assembly  202 . In this way, when the bottom section  202   a  of the base assembly  202  is moved into docking engagement with the surface of the cartridge unit by being passed through the docking port  157  of the cover assembly, the engagement means  159  of the cover assembly comes into contact with the clip portions  212 . This contact causes the arm  214  to deflect into the recess  216  as the refill unit is pushed into docking position with the cartridge unit, until the clip portions pass the engagement means  159  of the cover assembly. At this point, the arm  214  is no longer in contact with the engagement means  159  and hence returns to its original position thereby engaging the clip portions  212  with the lip of the engagement means  159 . 
         [0343]    The clip and engagement means of the refill unit and the cover assembly, respectively, are configured so that in the docked (refilling) position, the outlets  206 , and most importantly the working outlet  208 , of the refill unit  200  is snugly positioned on the refill ports of the cartridge unit. 
         [0344]    Once refilling has been completed, the refill unit  200  can be removed from docking engagement with the cartridge unit, by depressing the resilient arm  214  such that the clip portions  212  disengage with the lip of the engagement means. Suitable detail ridges  222  may be provided on the resilient arm  214  to provide grip for a user&#39;s finger(s) to manipulate the clip arrangement  210 . 
         [0345]    The clip arrangement  210  and corresponding engagement portion  110  may be provided on only one side of the refill unit  200  and cover assembly, or may be provided on both (opposite) sides. 
         [0346]    Within the refill unit  200  the ink is stored in a syringe-type assembly  224 . The syringe-type assembly  224  is mounted within the base assembly  202  of the refill unit  200  so as to be covered by the lid assembly  204 . The syringe-type assembly  224  has the necessary capacity to store the amount of ink required for refilling of the ink storage compartments of the cartridge unit. The components of the syringe assembly  224  are most clearly seen in  FIG. 90 . 
         [0347]    A tank  226  is provided in the syringe assembly  224  for storing the ink within the refill unit  200 . The tank  226  has at one end an ejection port  228  through which the ink is ejected for distribution and is sealed at the other end by a syringe seal  230 . The syringe seal  230  is mounted on a plunger  232  which is received within the hollow internal space of the tank  226  to expel the stored ink from the ejection port  228 . The plunger  232  is arranged to be driven into the hollow internal space of the tank  226  under action of a compression spring  234 . The compression spring is provided within the plunger  232  and projects from the plunger to contact with the internal end wall of the base assembly  202  (i.e., opposite the internal end wall adjacent the ejection port  228  of the tank  226 ). In this way, the compression spring  234  applies a constant force to the plunger  232  urging it to plunge towards the interior of the tank  226  when the syringe assembly  224  is housed in the base assembly  202 . 
         [0348]    Control of the plunging operation, and hence control of the delivery of the ink from the refill unit, is provided by ratchet arrangement of the syringe assembly  224 . The ratchet arrangement comprises an actuator rod  236  which mounts at its upper end and an intermediate position towards its lower end to mounting slots  238  provided on the tank  226 . The rod  236  has a pawl  240  projecting from one side thereof between the positions mounted through the slots  238 . The pawl  240  is engageable with a series of grooves providing a ratchet  242  on a side surface of the plunger  232 . 
         [0349]    The rod  236  is rotatable about its long axis so as to engage and disengage the pawl  240  with the ratchet  242 . An actuator spring  244  is provided at the upper end of the rod  236  which acts against the side surface of the plunger  232  so as to bias the pawl  240  into the ratchet  242 . The engagement of the pawl  240  and the ratchet  242  provides sufficient resistance against the plunging of the plunger  232  into the interior of the tank  226  under action of the compression spring  234 . 
         [0350]    Thus, upon initial use of the refill unit  200 , the pawl  240  is engaged with the first groove of the ratchet  242 , thereby preventing the plunger from substantially entering the interior of the tank  226  and in turn providing maximum ink storage capacity within the tank  226 . In order to commence refilling of the cartridge unit, ink must be ejected from the tank  226  through the ejection port  228 . This is achieved through rotation of the rod  236  which disengages the pawl from the first groove. The plunger  232  then enters into the interior of the tank  226  under action of the compression spring, causing ink to be ejected out the ejection port  228 . The pawl  240 , following disengagement with the first groove, engages with the next groove of the ratchet  242  through the return action of the actuator spring  244  against the initial rotation the rod  236 . This causes movement of the plunger  232  within the interior of the tank  226  to stop, thereby stopping delivery of ink from the ejection port  228 . More ink can be ejected from the tank  226  by repeated rotation of the rod  236  and engagement/disengagement of the pawl  240  with the ratchet  242 , thereby providing incremental delivery of ink in controlled amounts. This continues until the pawl engages with the final groove of the ratchet, at which point the ink within the tank  226  has been depleted. 
         [0351]    The rotation of the rod  236  to disengage the pawl  240  is caused by action of an actuator shaft  246  on an arm  248  which projects from the rod. The actuator shaft  246  is housed within the base assembly  202 , as shown in  FIG. 93 , so as to be slidable along its long axis. One end of the actuator shaft  246  is slidable to contact the arm  248  of the rod  236  when the syringe assembly  224  is mounted into the base assembly  202  and the other end of the actuator shaft is slidable to be exposed to the outside of the base assembly through a hole  202   b  formed in one of its end walls. 
         [0352]    In order to perform the refilling operation, the exposed end of the actuator shaft  246  comes into contact with the end of the push rod provided on the underside of the cover assembly, which projects into the docking port of the cover assembly. The manner in which the push rod operates has been discussed in detail above; however, when the refill unit  200  is in its refill position, the solenoid assembly can cause the push rod to extend and push the actuator shaft  246  into contact with the arm  248  of the rod  236  so as to disengage the pawl  240  with the ratchet  242 , following which the push rod returns to its retracted position. Then, once the pawl  240  re-engages through action of the actuator spring  244 , the arm  248  of the rod  236  pushes the actuator shaft  246  back so as to be exposed again for subsequent contact by the push rod. 
         [0353]    More ink is refilled from the refill unit  200  through repeated actuation of the push rod by the solenoid assembly, delivering controlled amounts of refill ink each time. As such, the refill cartridge is provided with the ability to perform multiple refilling operations. 
         [0354]    The status of the amount of the ink stored within the refill unit  200  is monitored by a quality assurance (QA) control chip  250  provided in the base assembly  202 . Initially, the QA chip  250  may store information in a memory thereof such as the ink capacity of the tank  226  (e.g., about 50 ml), the amount of ink which will be ejected from the tank with each pawl/ratchet  240 / 242  shift (e.g., about 6 ml), the colour of the ink stored within the tank and the position of the working outlet  208 . 
         [0355]    In this regard, a sensor or other means is provided connected to the QA chip  250  which senses either the position of the pawl/ratchet or the number of times the rod  236  has been rotated by the actuator shaft  246  or some other mechanism which informs the QA chip  250  of the remaining capacity/number of refills of the refill unit. In this regard, the memory of the QA chip  250  is provided as a rewritable memory. 
         [0356]    The QA chip  250  is provided in an exposed position on the end surface of the base assembly  202 , such as in the vicinity of the hole  202   b  for the actuator shaft  246  (see  FIG. 88 ), so as to align and connect with the corresponding QA chip reader provided within the rim of the docking port of the cover assembly. 
         [0357]    The QA chip reader is connected to a QA chip and/or controller of the print engine. In this way, the QA chip  250  is able to communicate the above-described information to the print engine. For example, the controller of the print engine is able to check whether the ink storage compartment of the cartridge unit containing the ink colour/type which matches the refill unit  200  requires refilling by the amount of at least one pawl/ratchet shift. In response to such determinations, the controller controls the solenoid assembly so as to operate the push rod the appropriate number of times to refill the corresponding ink chamber. 
         [0358]    This communication between the refill unit  200  and the print engine ensures that the correct type/colour of ink and the correct amount of ink is refilled into the correct ink storage compartment. Other checks can be performed also, such as correct positioning of the working outlet  208  on the appropriate refill port of the cartridge unit. 
         [0359]    In order to deliver the refill ink into the refill ports, the working outlet  208  of the refill unit comprises a syringe needle  252  which is connected to the ejection port  228  of the tank  226  through a fluid channel  254  provided on the inner side and bottom surfaces of the base assembly  202 . Sealing between the ejection port  228  and the fluid channel  254  is provided by an O-ring  256 . The syringe needle  252  is arranged to penetrate the valve fittings provided within the corresponding ink refill ports so as to allow the flow of ink into the ink storage compartments. 
         [0360]    As previously mentioned, the valve fittings may be provided as an elastomeric seal which seals the ink storage compartments from the surroundings, thus preventing dust and the like entering the chambers and providing an elastically walled channel through which the syringe needle  252  can pass. 
         [0361]    Sealing between the working outlet  208  and the valve fittings is provided by a seal ring  258  which surrounds the syringe needle  252 . In the refill unit&#39;s isolated state, the syringe needle  252  is protected by the seal ring  258  within the working outlet  208  (see  FIG. 88 ). Whereas, in the refill position, the syringe needle  252  is exposed to the valve fitting by action of valve&#39;s upper surface on the seal ring  258  to push the seal ring into the working outlet  208 . The seal ring  258  is able to ‘ride’ up the syringe needle  252  and upon release from the refill position, the seal ring is returned to its protection position via action of a seal spring  260  situated between the seal ring and the inner surface of the fluid channel  254  above the syringe needle. The seal spring  260  is held to the seal ring  258  with a support washer  262 . 
         [0362]    An exemplary refilling operation is illustrated in  FIGS. 94   a  to  94   c.    
         [0363]    In  FIG. 94   a , the refill unit  200  is in its refilling position with the syringe needle  252  penetrating the valve fittings of an ink storage compartment of the cartridge unit. At the stage shown, ink  264  stored within the tank  226  has been primed into the fluid channel  254  and the syringe needle  252 . Alternatively, the fluid channel  254  may comprise air or other gas at this stage, e.g., before the first refilling operation for the refill unit has been performed. The ink is held within this fluid path without escaping through the syringe needle due to vacuum pressure created in the fluid path. 
         [0364]    Alternatively, a cap may be provided to be either manually or automatically fitted within the working outlet so as to cap the end of the syringe needle. Such a cap additionally provides a means of ensuring that the stored ink does not dry out before the first application and between multiple refill applications. 
         [0365]    In  FIG. 94   b , the actuator arm of the solenoid assembly of the cradle unit is operated to extend the push bar into contact with the actuator shaft  246 , moving the actuator shaft  246  into contact against the arm  248  of the rod  236 . Immediately after this, the push bar returns to its retracted position of  FIG. 94   a . The pawl  240  is then disengaged from the ratchet groove  242 , thus causing the compression spring  234  to depress the plunger  232  into the tank  224  in the direction of arrow A. As a result, ink  264  is ejected from the ejection port  228  and thus through the syringe needle  252  into the ink storage compartment in the direction of arrow B. 
         [0366]    In  FIG. 94   c , the plunger  232  has moved sufficiently for the pawl  240  to engage with the next ratchet groove  242 . At this point, the plunger  232  is stopped and as such the ejection of the ink  264  from the syringe needle  252  ceases. 
         [0367]    The above process may be repeated until the ink chamber  122  is deemed refilled by the controller of the printer unit or until the refill unit  200  is depleted of ink. The status of the amount of ink in the refill unit  200  can be relayed to a user through the operation of an indicator light  266 , such as an LED, provided on the lid assembly  204 . The indicator light  266  is connected to the QA chip  250  when the lid assembly  204  is fitted to the base assembly  202 , and may be operated to illuminate during the refilling operation and cease illumination when this operation is finished and when the refill unit  200  is depleted. Alternatively, the indicator light  266  may be capable of multi-coloured illumination, such that different light colours are used to indicate the particular status of the refill unit  200 , e.g., a green light during refilling; a red light when the refill unit is depleted. 
         [0368]    Power for the indicator light  266  and the QA chip  250  may be provided via the connection with the QA chip reader. Alternatively, a battery may be provided within the refill unit  200  having a power capacity sufficient for operating the unit until the ink is depleted. 
         [0369]    An alternative embodiment of a syringe assembly  268  housed within the refill cartridge  200  is illustrated in  FIGS. 95 to 99 . Like the syringe assembly  224  of the previous embodiment, the syringe assembly  268  is mounted within the base assembly  202  of the refill unit  200  so as to be covered by the lid assembly  204  and has the necessary capacity to store and distribute the amount of ink required for refilling to the print cartridge  102  through the working outlet  208 . 
         [0370]    Like the syringe assembly of the previous embodiment, the syringe assembly  268  is provided with the tank  226  for storing the ink within the refill unit  200 . The tank  226  has at one end the ejection port  228  through which the ink is ejected for distribution and is sealed at the other end by the syringe seal  230 . The syringe seal  230  is mounted on the plunger  232  which plunges into the hollow internal space of the tank  226  to drive the stored ink out of the ejection port  228 . 
         [0371]    The plunger  232  is plunged into the tank  226  through action of a compression spring  270  which is attached at one and about the circumference of the body  232   a  of the plunger  232 . The other end of the spring  270  acts against a ring  232   b  fixed between posts  272  which project from the lower internal surface of the base assembly  202 . In this arrangement, due to the nature compression spring  270 , it acts to constantly bias the plunger  232  towards the interior of the tank  226  when the syringe assembly  268  is housed in the base assembly  202 , as did the earlier described embodiment. 
         [0372]    In this instance, control of the plunging operation is provided by a pawl and ratchet arrangement of the syringe assembly  268 . The pawl and ratchet arrangement comprises an actuator rod  274  which is mounted via pins  274   a , between its upper and lower ends, to mounting slots  276  which project from the lower internal surface of the base assembly  202 . In this way, the rod  274  is able to swing or pivot about the mounted pins  274   a.    
         [0373]    The rod  274  has a pawl  278  at its upper end which is engageable with a series of teeth of a ratchet  280  provided in a circular arrangement at one end of a feed member  282  (best illustrated in  FIG. 98 ). The swinging of the rod  274  enables the pawl to engage and disengage with the ratchet. An actuator spring  284  is provided between a boss  274   b , which projects from the lower end of the rod  274 , and an internal surface of the base assembly to bias the pawl into the ratchet. 
         [0374]    The feed member  282  is in the form of a cylindrical wheel and is mounted at either end to the posts  272  via pins  272   a  which project into axial holes (not shown) in the ends of the feed member  282 . In this way, the feed member  282  is able to rotate about its longitudinal axis. The feed member  282  further comprises a grooved thread  286  about its circumference at the end opposite the ratchet  280 . The grooved thread  286  is used to train a rope  288  about the feed member  282 . One end of the rope is attached to the end of the grooved thread and the other end of the rope attached to, or through, the plunger body  232   a.    
         [0375]    Prior to shipment of the refill unit  200 , the combination of the rope  288  and grooved thread  286  and the ratchet and pawl arrangement is used to initially retract the plunger  232  from the tank  226  so as to provide a space in which to store the ink. In this regard, the feed member  282  is provided with a gear  290  which is able to mesh with an external motor gear or the like. Action of the motor gear rotates the feed member (in a clockwise direction in the arrangement shown in  FIG. 97 ) whilst the pawl is not engaged with the ratchet which causes the rope to be wound about the grooved thread, thus retracting the plunger from the tank  226  against the action of the spring  270 . 
         [0376]    Sufficient rotational force is required to compress the spring  270  and sufficient strength is required in the rope to hold the plunger in place whilst the spring is compressed. Once the plunger has been pulled out of the tank in which position the spring is substantially fully compressed, the pawl is engaged with the nearest tooth of the ratchet. This engagement provides sufficient resistance against the plunging of the plunger  232  into the interior of the tank  226  through action of the compression spring  270 . The tank  226  can then be primed with ink for shipment. 
         [0377]    Thus, upon first use of the refill unit  200 , the pawl  278  is engaged with the tooth of the ratchet  280  which provides maximum ink storage capacity within the tank  226 . As ink is required to be ejected from the tank  226  through the ejection port  228  during a refilling operation, the rod  274  is swung to disengage the pawl with the tooth of the ratchet. This causes the plunger  232  to advance into the tank  226  a set distance thereby ejecting a measured portion of the stored ink through the ejection port  228 . Ejection stops when the pawl  278  engages with the next tooth of the ratchet  280 , which occurs through action of the actuator spring  284  swinging the rod  274  into engagement with the ratchet. 
         [0378]    Additional measured portions of ink can be ejected from the tank  226  by repeated swinging of the rod  274  thereby causing engagement/disengagement of the pawl with the ratchet. This continues until the rope  288  and the compression spring  270  are fully extended at which point the ink within the tank  226  is depleted and the refill unit  200  is spent. 
         [0379]    Similar to the previous embodiment, the swinging of the rod  274  to disengage the pawl  278  can be controlled by way of a slider element provided on the underside of the cover assembly  11  contacting the lower surface of the rod opposite the boss  274   b . As discussed in relation to the previous embodiment, the lid assembly can be configured such that an end of the slider element projects into the docking port  157  and through a hole  202   c  formed in one of the side walls of the base assembly  202  when the refill unit is docked with the cartridge unit  10 . The other end of the slider element may be connected to a refill solenoid assembly which is attached to the cradle unit as described previously. 
         [0380]    In this way, when the refill unit  200  is docked with the cartridge unit  10  and is in a refill position, the slider element can be operated to push the rod  274  so as to disengage the pawl  278  with the ratchet  280 . Then, once the pawl re-engages through action of the actuator spring  284 , the lower end of the rod  274  is repositioned for subsequent contact by the slider element. 
         [0381]    More ink is refilled from the refill unit  200  through repeated sliding of the slider element. Equally, multiple refill operations using the one refill unit  200  can be performed if any one refill operation does not deplete the ink contained therein. As such, the refill unit is provided with the ability to perform multiple refilling operations. 
         [0382]    The clip arrangement  210  and the arrangement of the syringe needle  252  in the working outlet  208  and the QA chip  250  is the same for the refill cartridge incorporating this alternative syringe assembly  268  as that of the previous embodiment. 
         [0383]    With this alternative embodiment of the syringe assembly  268  a larger volume of ink can be stored within the tank  226  of the refill unit  200  (e.g., about 50 ml) whilst retaining a similarly size to that in the previous embodiment. This is because, the space occupied by the pawl and ratchet arrangement is minimised whilst retaining a sufficient number of steps for controlled ejection of ink for refilling. 
         [0384]      FIGS. 100 to 106  illustrate yet another embodiment of an ink refill unit  400  suitable for use with the print engine of the present invention. 
         [0385]    The ink refill unit  400  generally comprises a body assembly  402 , for housing the various internal components necessary for storing and delivering the refill ink, and an end cap assembly  404  which fits onto and caps an end of the body assembly  402 . The body and cap assemblies may be moulded from a plastics material. 
         [0386]    As in the embodiments described above, the refill unit  400  contains ink and is intended to be used as a means for refilling ink storage compartments  24  provided within the cartridge unit  10 . In this regard, the refill unit  400  is configured to dock with the uppermost surface  60  of the cartridge unit  10  to transfer the ink contained therein into one or more of the ink storage compartments  24  of the cartridge unit  10  in the manner as discussed previously. 
         [0387]    In this regard, the refill unit  400  is also arranged with at least one working outlet  408  (see  FIG. 102 ) for distributing a particular colour or type of ink contained in the refill unit to the corresponding ink refill port  61  associated with the desired ink storage compartment  24  of the cartridge unit  10 . That is, if the refill unit  400  contains cyan ink, the working outlet  408  is positioned so as to correspond to the ink refill port  61  associated with the cyan ink storage compartment of the cartridge unit  10  when the refill unit is in its refilling position. 
         [0388]    Although not shown in the drawings, a clip arrangement similar to that of the earlier described embodiment may be provided on the body assembly  402  and within the rim portion  158  of the docking port  157 , to ensure reliable and efficient transfer of ink from the refill unit  400  to the cartridge unit  10 . 
         [0389]    The body assembly  402  of the ink refill unit  400  has capacity to store a sufficient amount of ink required to refill the ink storage compartments  24  of the cartridge unit  10 . The internal components of the body assembly  402  are most clearly seen in  FIGS. 103 to 106 . 
         [0390]    A compressible bellows tank  410  is provided in the body assembly  402  for storing the ink. In this regard, the bellows tank is sealed at one end and is provided with an ejection port  412  at the other end (being the end adjacent the end wall of the body assembly) through which the ink is ejected for distribution. The sealed end of the bellows tank  410  abuts a plunger  414  which is arranged to compress the bellows tank against the end wall of the body assembly to expel the stored ink out of the ejection port  412 . 
         [0391]    The plunger  414  compresses the bellows tank  410  through action of a gear and thread arrangement. The gear and thread arrangement comprises a helical geared thread  416  provided about the circumference of the substantially circular plunger  414  which mates with an elongate drive gear  418  which is mounted within the body assembly  402  and extends along the length thereof, and an internal lead screw thread  420  provided in the substantially cylindrical internal wall of the body assembly (see  FIG. 106 ). The lead screw thread  420  is provided with a gap along the length of the body assembly  402  in which the drive gear  418  sits and is able to come into contact with the gear teeth in the gear thread  416  of the plunger  414 . An elongate protruded region  422  of the body assembly  402  is provided to accommodate the drive gear  418  in this position. 
         [0392]    In this gear and thread arrangement, the plunger  414  is able to rotate so as to move along the lead screw thread  420 . This movement provides the plunging operation of the plunger against the bellows tank. The rotation of the plunger is provided by rotation of the drive gear  418  being imparted to the geared thread  416  of the plunger. The drive gear  418  is held within the protruded region  422  by a pin  418   a  provided on one end of the drive gear which slides into a depression or hole within the internal end wall of the body assembly  402  and a pin  404   a  provided in a corresponding position on the internal surface of the end cap assembly  404  which slides into a corresponding depression  418   b  provided on the other end of the drive gear. Other arrangements are possible however, so long as the drive gear is free to rotate about its long axis. 
         [0393]    The rotation of the drive gear  418  is driven by a motor gear  124  which meshes with the teeth of the drive gear. The motor gear  124  is driven by a motor which may be mounted to the underside of the cover assembly  11  of the cradle unit  12 . In this arrangement, similar to those described in the above alternative embodiments, the motor gear  124  is arranged to project from the surface of the cover assembly to engage with the drive gear  418  through a slot  422   a  in the protruded region  422 . Those of ordinary skill in the art will understand that the motorisation of the gear and thread arrangement may also be provided within the refill unit  400  itself instead of in the cover assembly  11 . 
         [0394]    Control of the plunging operation is provided by the controlling the operation of the motor responsible for rotating the motor gear  124 , and a suitable gearing ratio may be provided for reasonably fine control of the plunger movement. As will be appreciated, the plunging operation provides controlled release of the ink from the bellows tank  410  through its ejection port  412 . 
         [0395]    Upon first use of the refill unit  400 , plunger  414  is fully retracted so as to provide full extension of the bellows tank and hence maximum ink storage capacity in the refill unit  400 . Of course, suitably sized bellows tanks can be provided within the same sized refill units  400  for provided different storage amounts, e.g., 30 ml as opposed to 50 ml, depending on application, the colour of the ink, etc. Then, as ink is required to be ejected from the bellows tank  410  during a refilling operation, the motor may be controlled to rotate the motor gear  124  and the drive gear  418  thereby causing the plunger  414  to compress the bellows tank to eject some of the stored ink through the ejection port  412 . The amount of ink ejected per rotation of the motor gear  124  can be readily ascertained to provide metered release of ink into the cartridge unit  10  as necessary. 
         [0396]    The plunging is continued until the required amount of ink has been ejected into the ink storage compartments of the cartridge unit  10 . For example, in a single-use refill operation, the entire contents of the refill unit  400  would be ejected, however in a multiple-use refill operation, only part of the refill unit&#39;s capacity of ink may be required at one time. In such a multiple-use regime, more ink can be ejected from the bellows tank by repeated plunging operations until the ink within the bellows tank has been depleted. The ink may be dispensed in a series of preselected amounts, e.g., by a series of preselected numbers of turns of the plunger  414 , until the necessary amount of ink has been dispensed, or the plunger  414  may be simply turned until it is determined that the ink chamber has been replenished. 
         [0397]    In order to ensure that the ink does not leak from the ejection port  412  after a refilling operation has been performed and ink remains in the bellows tank for subsequent refills, suitable fluid pressure is retained within the bellows tank  410  at all times. This is achieved by backing-up the plunger  414  by a suitable amount once the refilling operation is complete. This is done by rotating the plunger in the opposite direction so as to allow slight re-expansion of the bellows tank  410 . In this regard, the sealed end of the bellows tank is preferably attached to the plunger and the motor provided in the cover assembly  11  is preferably a bi-directional motor. 
         [0398]    Like the previous embodiments, the status of the amount of the ink stored within the refill unit  400  is monitored by a QA control chip  424  provided in the body assembly  402 . The QA chip  424  is provided in an exposed position on the surface of the end cap assembly  404 , or alternatively on the end surface of the body assembly  402 , so as to align and connect with a QA chip reader  160  provided in the docking port  157  of the cover assembly  11 . The QA chip reader is in turn connected to the SoPEC devices  126  of the cradle unit  12  to enable control of the overall refill operation. In the present embodiment, the QA chip  424  is used to provide information on the amount of ink (and colour, etc) stored in the refill unit  400  at any instant to the SoPEC devices  126 , so that the SoPEC devices can control the motor to rotate the motor gear  124  the appropriate number of times to refill the corresponding ink storage compartment  24 . 
         [0399]    In this regard, a sensor or other means may be connected to the QA chip  424  to sense either the position of the plunger  414  or the number of times the plunger  414  has been rotated by the drive gear  418  which informs the QA chip  424  of the remaining capacity/number of refills of the refill unit  400 . 
         [0400]    As with the first embodiment, the working outlet  408  of the refill unit  400  comprises a syringe needle  426  which is connected to the ejection port  412  of the bellows tank  410  through a fluid channel  428  provided on the outer sides of the body assembly  402  (see  FIG. 102 ). Sealing between the ejection port  412  and the fluid channel  428  is provided by an O-ring  430 . The syringe needle  426  is arranged to penetrate the valve fittings  62  provided within the ink refill ports  61  of the cartridge unit  10  so as to allow the flow of ink into the ink storage compartments  24 . The arrangement and operation of the syringe needle  426  is otherwise the same as in the first embodiment. 
         [0401]    An indicator light (not shown) may be provided on the body assembly  402  of the refill unit  400  connected to the QA chip  424  so as to indicate the status of the amount of ink in the refill unit to a user. Power for the indicator light and the QA chip may be provided via the connection to the contact  130  of the print cradle  100 . Alternatively, a battery may be provided within the refill unit  400  having a power capacity sufficient for operating the unit until the ink is depleted. 
         [0402]    While the present invention has been illustrated and described with reference to exemplary embodiments thereof, various modifications will be apparent to and might readily be made by those skilled in the art without departing from the scope and spirit of the present invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but, rather, that the claims be broadly construed.