Abstract:
Provided is an ink supply bag for a printhead cartridge. The supply bag includes two profiled panels arranged generally coplanar and co-terminally attached to form an ink holding chamber, along with a folded leaf spring biasing said chamber into an expanded position. The supply bag further includes a connector assembly operatively arranging said chamber in fluid communication with ink supply channels of the printhead cartridge.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
   This application is a continuation application of U.S. patent application Ser. No. 11/293,792 filed on Dec. 5, 2005, now issued U.S. Pat. No. 7,438,399, all of which are herein incorporated by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to an inkjet printhead cartridge having an ink supply which maintains substantially constant negative pressure at the ink ejection nozzles of a printhead of the cartridge. 
   CO-PENDING APPLICATIONS 
   The following applications have been filed by the Applicant simultaneously with the present application: 
   
     
       
             
             
             
             
             
             
           
         
             
                 
             
           
           
             
               11/293,800 
               11/293,802 
               11/293,801 
               11/293,808 
               11/293,809 
               11/293,832 
             
             
               11/293,838 
               11/293,825 
               11/293,841 
               11/293,799 
               11/293,796 
               11/293,797 
             
             
               11/293,798 
               11/293,804 
               11/293,840 
               11/293,803 
               11/293,833 
               11/293,834 
             
             
               11/293,835 
               11/293,836 
               11/293,837 
               11/293,794 
               11/293,839 
               11/293,826 
             
             
               11/293,829 
               11/293,830 
               11/293,827 
               11/293,828 
               7,270,494 
               11/293,823 
             
             
               11/293,824 
               11/293,831 
               11/293,815 
               11/293,819 
               11/293,818 
               11/293,817 
             
             
               11/293,816 
               11/293,820 
               11/293,813 
               11/293,822 
               11/293,812 
               7,357,496 
             
             
               11/293,814 
               11/293,793 
               11/293,842 
               11/293,811 
               11/293,807 
               11/293,806 
             
             
               11/293,805 
               11/293,810 
             
             
                 
             
           
        
       
     
   
   The disclosures of these co-pending applications are incorporated herein by reference. 
   CROSS REFERENCES TO RELATED APPLICATIONS 
   Various methods, systems and apparatus relating to the present invention are disclosed in the following U.S. patents/patent applications filed by the applicant or assignee of the present invention: 
                                                   6,750,901   6,476,863   6,788,336   7,249,108   6,566,858   6,331,946       6,246,970   6,442,525   7,346,586   09/505,951   6,374,354   7,246,098       6,816,968   6,757,832   6,334,190   6,745,331   7,249,109   7,197,642       7,093,139   10/636,263   10/636,283   10/866,608   7,210,038   7,401,223       10/940,653   10/942,858   7,364,256   7,258,417   7,293,853   7,328,968       7,270,395   11/003,404   11/003,419   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       7,357,477   11/003,463   7,364,255   7,357,476   11/003,614   7,284,820       7,341,328   7,246,875   7,322,669   11/246,676   11/246,677   11/246,678       11/246,679   11/246,680   11/246,681   11/246,714   11/246,713   7,399,057       11/246,671   11/246,704   11/246,710   11/246,688   7,399,054   11/246,715       7,367,648   7,370,936   7,401,886   11/246,708   7,401,887   7,384,119       7,401,888   7,387,358   7,413,281   10/922,842   10/922,848   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   10/815,628   7,278,727   10/913,373       10/913,374   7,367,665   7,138,391   7,153,956   10/913,380   10/913,379       10/913,376   7,122,076   7,148,345   11/172,816   11/172,815   11/172,814       10/407,212   7,252,366   10/683,064   7,360,865   6,746,105   11/246,687       11/246,718   7,322,681   11/246,686   11/246,703   11/246,691   11/246,711       11/246,690   11/246,712   11/246,717   7,401,890   7,401,910   11/246,701       11/246,702   11/246,668   11/246,697   11/246,698   11/246,699   11/246,675       11/246,674   11/246,667   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   10/760,246       7,083,257   7,258,422   7,255,423   7,219,980   10/760,253   10/760,255       7,367,649   7,118,192   10/760,194   7,322,672   7,077,505   7,198,354       7,077,504   10/760,189   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   7,303,930       11/246,672   7,401,405   11/246,683   11/246,682   7,246,886   7,128,400       7,108,355   6,991,322   7,287,836   7,118,197   10/728,784   7,364,269       7,077,493   6,962,402   10/728,803   7,147,308   10/728,779   7,118,198       7,168,790   7,172,270   7,229,155   6,830,318   7,195,342   7,175,261       10/773,183   7,108,356   7,118,202   10/773,186   7,134,744   10/773,185       7,134,743   7,182,439   7,210,768   10/773,187   7,134,745   7,156,484       7,118,201   7,111,926   10/773,184   7,018,021   7,401,901   11/060,805       11/188,017   11/097,308   11/097,309   7,246,876   11/097,299   11/097,310       7,377,623   7,328,978   7,334,876   7,147,306   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   6,290,349       6,428,155   6,785,016   6,870,966   6,822,639   6,737,591   7,055,739       7,233,320   6,830,196   6,832,717   6,957,768   09/575,172   7,170,499       7,106,888   7,123,239   10/727,181   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   10/727,159   10/727,180   10/727,179       10/727,192   10/727,274   10/727,164   10/727,161   10/727,198   10/727,158       10/754,536   10/754,938   10/727,160   10/934,720   7,171,323   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   11/039,866   7,173,739   6,986,560   7,008,033       11/148,237   7,222,780   7,270,391   7,195,328   7,182,422   7,374,266       10/854,522   10/854,488   7,281,330   10/854,503   7,328,956   10/854,509       7,188,928   7,093,989   7,377,609   10/854,495   10/854,498   10/854,511       7,390,071   10/854,525   10/854,526   10/854,516   7,252,353   10/854,515       7,267,417   10/854,505   10/854,493   7,275,805   7,314,261   10/854,490       7,281,777   7,290,852   10/854,528   10/854,523   10/854,527   10/854,524       10/854,520   10/854,514   10/854,519   10/854,513   10/854,499   10/854,501       7,266,661   7,243,193   10/854,518   10/854,517   10/934,628   7,163,345       10/760,254   10/760,210   7,364,263   7,201,468   7,360,868   10/760,249       7,234,802   7,303,255   7,287,846   7,156,511   10/760,264   7,258,432       7,097,291   10/760,222   10/760,248   7,083,273   7,367,647   7,374,355       10/760,204   10/760,205   10/760,206   10/760,267   10/760,270   7,198,352       7,364,264   7,303,251   7,201,470   7,121,655   7,293,861   7,232,208       7,328,985   7,344,232   7,083,272   11/014,764   11/014,763   7,331,663       7,360,861   7,328,973   11/014,760   7,407,262   7,303,252   7,249,822       11/014,762   7,311,382   7,360,860   7,364,257   7,390,075   7,350,896       11/014,758   7,384,135   7,331,660   11/014,738   11/014,737   7,322,684       7,322,685   7,311,381   7,270,405   7,303,268   11/014,735   7,399,072       7,393,076   11/014,750   11/014,749   7,249,833   11/014,769   11/014,729       7,331,661   11/014,733   7,300,140   7,357,492   7,357,493   11/014,766       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   11/014,717   11/014,716   11/014,732       7,347,534   11/097,268   11/097,185   7,367,650                    
The disclosures of these applications and patents are incorporated herein by reference.
 
   BACKGROUND OF THE INVENTION 
   Negative pressure is required at ink ejection nozzles of inkjet printheads so that undesired ink ejection or leakage is prevented when the nozzles are not being operated to print. Ink supply arrangements to ink ejection nozzles which provide such negative pressure are known. U.S. Pat. No. 4,422,084 discloses several examples of such ink supply arrangements. One of the disclosed arrangements positions a spring within an ink tank which regulates the collapse of the ink tank. However, each of the disclosed arrangements and other conventional arrangements do not provide constant negative pressure at the nozzles. As a result, some ink ejection or leakage may still occur. 
   SUMMARY OF THE INVENTION 
   The present invention provides a spring within collapsible ink bags of the ink supply arrangement wherein the spring is configured to provide substantially constant negative pressure at the ink ejection nozzles of the printhead. In particular, a compression spring is used having a free length which provides this substantially constant negative pressure. 
   In a first aspect the present invention provides an inkjet printhead cartridge, comprising:
         an inkjet printhead having a plurality of ink ejection nozzles;   at least one ink bag containing ink for distribution to the nozzles via a fluid path between the ink bag and the nozzles, the ink being primed in the fluid path and nozzles so as to be ejected by the nozzles, in use, thereby depleting the ink contained in the ink bag, the ink bag being configured to collapse as the ink is depleted;   a body for housing the ink bag and the printhead, the ink bag being attached to the body at a wall opposite a wall of the ink bag facing the printhead; and   a biasing member arranged in the ink bag to apply outwardly directed force on at least the wall of the ink bag facing the printhead,   wherein the biasing member is configured to maintain substantially constant negative pressure at the nozzles as the ink is depleted from the ink bag.       

   Optionally, the biasing member incorporates a compression spring. 
   Optionally, the compression spring has a free length equal to the height from the attached wall of the ink bag to the nozzles plus a height of a negative ink head necessary to provide said negative pressure. 
   Optionally, the free length is 141 millimeters and the height from the attached wall of the ink bag to the nozzles is 41 millimeters. 
   Optionally, said walls of the ink bag have an area of 30 millimeters by 50 millimeters and the compression spring has a spring constant of 14.7 Newtons per meter. 
   Optionally, the compression spring is made of stainless steel. 
   Optionally, the body is arranged to be removably engageable with a printer. 
   Optionally, the printer comprises a print controller for operating the nozzles of the printhead, said operation causing ink ejection and the depletion of ink from the ink bag. 
   Optionally, the non-collapsed ink bag has a fluid volume of at least 15 milliliters. 
   Optionally, the fluid path connects the ink bag to at least 6400 nozzles of the printhead. 
   Optionally, each nozzle of the printhead is configured to eject an ink drop having a volume of about 1.2 picoliters. 
   Optionally, the nozzles of the printhead are arranged so as to print at a resolution of 1600 dots per inch. 
   In a further aspect there is provided an inkjet printhead cartridge, comprising three of said ink bags. 
   Optionally, a first ink bag contains magenta ink, a second ink bag contains cyan ink and a third ink bag contains yellow ink. 
   Optionally, the fluid path of the first ink bag connects the first ink bag to 12800 nozzles of the printhead, the fluid path of the second ink bag connects the second ink bag to 12800 nozzles of the printhead, and the fluid path of the third ink bag connects the third ink bag to 6400 nozzles of the printhead. 
   Optionally, the printhead has 32000 nozzles. 
   Optionally, the printhead is a pagewidth printhead, having a pagewidth of 100.9 millimeters. 
   Optionally, the printhead comprises 5 linked printhead integrated circuits arranged to span the pagewidth, each printhead integrated circuit having 6400 nozzles arranged in rows. 
   Optionally, the fluid path of each ink bag connects the respective ink bag to at least two nozzle rows of each printhead integrated circuit. 
   Optionally, the fluid path of first ink bag connects the first ink bag to four nozzle rows of each printhead integrated circuit, the fluid path of second ink bag connects the second bag to four nozzle rows of each printhead integrated circuit, and the fluid path of third ink bag connects the third ink bag to two nozzle rows of each printhead integrated circuit. 
   In a second aspect the present invention provides a printhead assembly comprising:
         at least one printhead integrated circuit having a plurality of ink ejection nozzles; and   an ink distribution support mounting the, or each, printhead integrated circuit, the ink distribution support being arranged, in use, to distribute ink to the nozzles, the printhead assembly being arranged to be mounted to a printer at the ink distribution support, wherein the ink distribution support is provided with at least one reference feature, the, or each, reference feature serving to provide information on the location of the nozzles upon mounting of the printhead assembly to the printer.       

   Optionally, the ink distribution support is an elongate support, and the, or each, printhead integrated circuit is mounted to extend longitudinally along the elongate support. 
   Optionally, the, or each, printhead integrated circuit is mounted along the elongate support so that the nozzles create a printing zone which extends across a pagewidth. 
   Optionally, the pagewidth is 100.9 millimeters. 
   Optionally, the, or each, reference feature is arranged beyond the longitudinal extent of the printing zone. 
   Optionally, the elongate support is formed as a molding, and the, or each, reference feature is molded as part of the support molding. 
   Optionally, at least one reference feature is provided at either longitudinal end of the elongate support. 
   Optionally, the, or each, reference feature is configured to cooperate with a corresponding complementary feature of the printer upon mounting of the printhead assembly to the printer, the cooperation providing the information on the location of the nozzles. 
   Optionally, the at least one reference feature is a slot in the ink distribution support. 
   Optionally, the complementary feature of the printer is a mesa feature configured to cooperate with the slot in the ink distribution support. 
   Optionally, the at least one reference feature is a flat surface of a plurality of corners of the ink distribution support. 
   Optionally, a plurality of the reference features are provided, one of the reference features being a slot in the ink distribution support and the other reference features being a flat surface of a plurality of corners of the ink distribution support. 
   Optionally, the printhead integrated circuit is formed from a silicon wafer. 
   Optionally, the ink distribution support is a molding formed from liquid crystal polymer. 
   Optionally, the liquid crystal polymer of the ink distribution support has thermal expansion characteristics similar to those of the silicon of the printhead integrated circuit. 
   Optionally, the, or each, printhead integrated circuit has at least 6400 nozzles. 
   In a further aspect there is provided a printhead assembly, comprising 32000 nozzles spanned over the, or each, printhead integrated circuit. 
   In a further aspect there is provided a printhead assembly further comprising five printhead integrated circuits which are arranged to span a pagewidth. 
   Optionally, the pagewidth is 100.9 millimeters. 
   Optionally, the nozzles of the printhead integrated circuit are arranged to print at a resolution of 1600 dots per inch. 
   In a third aspect the present invention provides a printing cartridge for an inkjet printer, the cartridge comprising:
         an ink supply; and a printhead assembly comprising at least one printhead integrated circuit having a plurality of ink ejection nozzles and an ink distribution support mounting the, or each, printhead integrated circuit, the ink distribution support being arranged, in use, to distribute ink from the ink supply to the nozzles,   wherein the printing cartridge is mounted to the printer at the ink distribution support, and wherein the ink distribution support is provided with at least one reference feature, the, or each, reference feature serving to provide information on the location of the nozzles upon mounting of the printing cartridge to the printer.       

   Optionally, the ink distribution support is an elongate support, and the, or each, printhead integrated circuit is mounted to extend longitudinally along the elongate support. 
   Optionally, the, or each, printhead integrated circuit is mounted along the elongate support so that the nozzles create a printing zone which extends across a pagewidth. 
   Optionally, the pagewidth is 100.9 millimeters. 
   Optionally, the, or each, reference feature is arranged beyond the longitudinal extent of the printing zone. 
   Optionally, the elongate support is formed as a molding, and the, or each, reference feature is molded as part of the support molding. 
   Optionally, at least one reference feature is provided at either longitudinal end of the elongate support. 
   Optionally, the, or each, reference feature is configured to cooperate with a corresponding complementary feature of the printer upon mounting of the printing cartridge to the printer, the cooperation providing the information on the location of the nozzles. 
   Optionally, the at least one reference feature is a slot in the ink distribution support. 
   Optionally, the complementary feature of the printer is a mesa feature configured to cooperate with the slot in the ink distribution support. 
   Optionally, the at least one reference feature is a flat surface of a plurality of corners of the ink distribution support. 
   Optionally, a plurality of the reference features are provided, one of the reference features being a slot in the ink distribution support and the other reference features being a flat surface of a plurality of corners of the ink distribution support. 
   Optionally, the printhead integrated circuit is formed from a silicon wafer. 
   Optionally, the ink distribution support is a molding formed from liquid crystal polymer. 
   Optionally, the liquid crystal polymer of the ink distribution support has thermal expansion characteristics similar to those of the silicon of the printhead integrated circuit. 
   Optionally, the, or each, printhead integrated circuit has at least 6400 nozzles. 
   Optionally, the printhead assembly comprises 32000 nozzles spanned over the, or each, printhead integrated circuit. 
   In a further aspect there is provided a printing cartridge wherein the printhead assembly comprises five printhead integrated circuits which are arranged to span a pagewidth. 
   Optionally, wherein the pagewidth is 100.9 millimeters. 
   Optionally, the nozzles of the printhead integrated circuit are arranged to print at a resolution of 1600 dots per inch. 
   In a fourth aspect the present invention provides an inkjet printer comprising:
         a body configured to receive a printhead assembly, the printhead assembly comprising at least one printhead integrated circuit having a plurality of ink ejection nozzles and an ink distribution support mounting the, or each, printhead integrated circuit, the ink distribution support being arranged, in use, to distribute ink to the nozzles; and   at least one mounting feature on the body for mounting the printhead assembly at the ink distribution support, the, or each, mounting feature being configured to cooperate with a corresponding complementary reference feature of the ink distribution support upon mounting of the printhead assembly to the printer, the cooperation providing information on the location of the nozzles.       

   Optionally, the ink distribution support is an elongate support, and the, or each, printhead integrated circuit is mounted to extend longitudinally along the elongate support. 
   Optionally, the, or each, printhead integrated circuit is mounted along the elongate support so that the nozzles create a printing zone which extends across a pagewidth. 
   Optionally, the pagewidth is 100.9 millimeters. 
   Optionally, the, or each, reference feature of the ink distribution support is arranged beyond the longitudinal extent of the printing zone and the, or each, mounting feature is arranged to correspond with the corresponding reference feature. 
   Optionally, the printhead assembly is incorporated in a printing cartridge, and the body of the printer has a cartridge receiving slot for removably receiving the printing cartridge. 
   Optionally, the at least one mounting feature is arranged in the cartridge receiving slot. 
   Optionally, the at least one mounting feature is a mesa feature arranged in the cartridge receiving slot. 
   Optionally, the complementary reference feature of the ink distribution support is a slot configured to cooperate with the mesa feature. 
   Optionally, the at least one mounting feature is at least one protrusion arranged in the cartridge receiving slot. 
   Optionally, the complementary reference feature of the ink distribution support is a flat surface of a plurality of corners of the ink distribution support which is configured to cooperate with the protrusions. 
   Optionally, a plurality of the mounting features are provided, one of the mounting features being a mesa feature arranged in the cartridge receiving slot and the other mounting features being protrusions arranged in the cartridge receiving slot. 
   In a further aspect there is provided a printer, a plurality of the complementary reference features of the ink distribution support are provided, one of the reference features being a slot in the ink distribution support configured to cooperate with the mesa feature, and the other reference features being a flat surface of a plurality of corners of the ink distribution support which are configured to cooperate with the protrusions. 
   In a further aspect there is provided a printer, further comprising print control circuitry for controlling operation of the ink ejection nozzles. 
   Optionally, the print control circuitry is configured to use the information of the location of the nozzles to control said operation. 
   In a further aspect there is provided a printer, further comprising print control circuitry for controlling operation of the ink ejection nozzles of the received printing cartridge. 
   Optionally, the print control circuitry is configured to use the information of the location of the nozzles to control said operation. 
   Optionally, the print control circuitry incorporates an electrical connection interface arranged in the cartridge receiving slot for communicating power and data to the nozzles of the received printing cartridge via electrical contacts of the printhead assembly. 
   Optionally, the electrical connection interface defines at least one further mounting feature configured to cooperate with a further complementary reference feature of the printing cartridge. 
   Optionally, the further complementary reference feature of the printing cartridge is a surface adjacent the electrical contacts of the printhead assembly which is configured to cooperate with the electrical connection interface. 
   In a fifth aspect the present invention provides a method of locating a printhead assembly on a printer, the method comprising the steps of:
         providing a printhead assembly comprising at least one printhead integrated circuit having a plurality of ink ejection nozzles and an ink distribution support mounting the, or each, printhead integrated circuit, the ink distribution support being arranged, in use, to distribute ink from the ink supply to the nozzles;   mounting the printhead assembly to the printer by bringing at least one reference feature provided on the ink distribution support into cooperation with a corresponding complementary feature of the printer; and   determining from the cooperation the location of the nozzles.       

   Optionally, the ink distribution support is an elongate support, and the, or each, printhead integrated circuit is mounted to extend longitudinally along the elongate support. 
   Optionally, the, or each, printhead integrated circuit is mounted along the elongate support so that the nozzles create a printing zone which extends across a pagewidth. 
   Optionally, the, or each, reference feature is arranged beyond the longitudinal extent of the printing zone. 
   Optionally, the elongate support is formed as a molding, and the, or each, reference feature is molded as part of the support molding. 
   Optionally, the moulding is formed from liquid crystal polymer. 
   Optionally, the printhead integrated circuit is formed from a silicon wafer. 
   Optionally, the liquid crystal polymer of the ink distribution support has thermal expansion characteristics similar to those of the silicon of the printhead integrated circuit. 
   Optionally, at least one reference feature is provided at either longitudinal end of the elongate support. 
   Optionally, the at least one reference feature is a slot in the ink distribution support. 
   Optionally, the mounting step comprises cooperating the slot in the ink distribution support with a mesa feature of the printer. 
   Optionally, the at least one reference feature is a flat surface of a plurality of corners of the ink distribution support. 
   Optionally, the mounting step comprises cooperating the flat surfaces of the ink distribution support with protrusions of the printer. 
   In a sixth aspect the present invention provides a printing cartridge comprising:
         a body configured to removably engage with an inkjet printer;   a printhead assembly mounted to the body, the printhead assembly comprising at least one printhead integrated circuit having a plurality of ink ejection nozzles and a support member mounting the, or each, printhead integrated circuit, the nozzles being operated, in use, to print on media by ejecting ink thereon; and   a capping mechanism for capping the nozzles during non-operation; and   a mounting arrangement for commonly mounting the printhead assembly and capping mechanism to the body, the support member of the printhead assembly being directly mounted to the body and the capping mechanism being directly mounted to the support member.       

   Optionally, the support member is an ink distribution support which is arranged, in use, to distribute ink to the nozzles. 
   Optionally, the ink distribution support is an elongate support, and the, or each, printhead integrated circuit is mounted to extend longitudinally along the elongate support. 
   Optionally, the, or each, printhead integrated circuit is mounted along the elongate support so that the nozzles create a printing zone which extends across a pagewidth. 
   Optionally, the pagewidth is 100.9 millimeters. 
   Optionally, the capping mechanism comprises an elongate capper having a capping zone which is commensurate with the printing zone. 
   Optionally, the mounting arrangement incorporates a fixing arrangement arranged beyond the longitudinal extent of the printing and capping zones at one end of the elongate support and capper and a confining arrangement arranged beyond the longitudinal extent of the printing and capping zones at the other end of the elongate support and capper. 
   Optionally, the fixing arrangement incorporates aligned holes through each of the cartridge body, printhead assembly and capping mechanism, a first pin configured to pass through each of the holes and a locking member for locking the first pin within the holes. 
   Optionally, the confining arrangement incorporates aligned slots through each of the cartridge body, printhead assembly and capping mechanism, a second pin configured to pass through each of the slots and a biasing member for locking the second pin within the slots and biasing the cartridge body, printhead assembly and capping mechanism together at the second pin whilst allowing relative movement of the cartridge body, printhead assembly and capping mechanism. 
   Optionally, the ink distribution support is provided with at least one reference feature, the, or each, reference feature serving to provide information on the location of the nozzles upon mounting of the printing cartridge to the printer. 
   Optionally, the, or each, reference feature is arranged beyond the longitudinal extent of the printing zone. 
   Optionally, the, or each, reference feature is configured to cooperate with a corresponding complementary feature of the printer upon mounting of the printing cartridge to the printer, the cooperation providing the information on the location of the nozzles. 
   Optionally, the, or each, reference feature is arranged at the fixed end of the ink distribution support. 
   Optionally, the printhead integrated circuit is formed from a silicon wafer. 
   Optionally, the ink distribution support is a molding formed from liquid crystal polymer. 
   Optionally, the liquid crystal polymer of the ink distribution support has thermal expansion characteristics similar to those of the silicon of the printhead integrated circuit. 
   Optionally, the, or each, printhead integrated circuit has at least 6400 nozzles. 
   Optionally, the printhead assembly comprises 32000 nozzles spanned over the, or each, printhead integrated circuit. 
   In a further aspect theres provided a printing cartridge, the printhead assembly comprises five printhead integrated circuits which are arranged to span a pagewidth. 
   Optionally, the pagewidth is 100.9 millimeters. 
   In a seventh aspect the present invention provides an ink priming arrangement for an inkjet printhead, the inkjet printhead having a plurality of ink ejection nozzles, the priming arrangement comprising:
         an ink bag containing ink for distribution to the nozzles via a fluid path between the ink bag and the nozzles;   a force applicator arranged to apply inwardly directed force on at least one exterior wall of the ink bag so as to reduce an available fluid volume of the ink bag, thereby causing ink to flow from the ink bag to the nozzles along the fluid path; and   a biasing member arranged in the ink bag to apply outwardly directed force on at least one interior wall of the ink bag so as to restrain the reduction of available fluid volume of the ink bag,   wherein the biasing member is configured so as to apply the outwardly directed force only once the available fluid volume of the ink bag has been reduced to a predetermined volume.       

   Optionally, the biasing member incorporates a leaf spring. 
   Optionally, the leaf spring is made from a material having shape-memory characteristic. 
   Optionally, the material is Mylar. 
   Optionally, the leaf spring is formed by folding an elongate arcuate piece of the material about an approximate centre line orthogonal to the longitudinal extent thereof so that the leaf spring exhibits an outwardly directed spring restoring force. 
   Optionally, the leaf spring is formed so as to have a folded longitudinal length and radius of curvature which result in the leaf spring being able to float within the ink contained in the ink bag prior to the application of the inwardly directed force by the force applicator. 
   Optionally, the ink bag is configured to have an available fluid volume of at least 19 milliliters. 
   Optionally, the ink bag is configured to have an available fluid volume of at least 23 milliliters. 
   Optionally, the predetermined available fluid volume is at least 15 milliliters. 
   Optionally, the fluid path connects the ink bag to at least 6400 nozzles of the printhead. 
   Optionally, each nozzle of the printhead is configured to eject an ink drop having a volume of about 1.2 picoliters. 
   Optionally, the nozzles of the printhead are arranged so as to print at a resolution of 1600 dots per inch. 
   In a further aspect there is provided an ink priming arrangement, comprising three of said ink bags. 
   Optionally, a first ink bag contains magenta ink, a second ink bag contains cyan ink and a third ink bag contains yellow ink. 
   Optionally, the fluid path of the first ink bag connects the first ink bag to 12800 nozzles of the printhead, the fluid path of the second ink bag connects the second ink bag to 12800 nozzles of the printhead, and the fluid path of the third ink bag connects the third ink bag to 6400 nozzles of the printhead. 
   Optionally, the printhead has 32000 nozzles. 
   Optionally, the printhead is a pagewidth printhead, having a pagewidth of 100.9 millimeters. 
   Optionally, the printhead comprises five linked printhead integrated circuits arranged to span the pagewidth, each printhead integrated circuit having 6400 nozzles arranged in rows. 
   Optionally, the fluid path of each ink bag connects the respective ink bag to at least two nozzle rows of each printhead integrated circuit. 
   Optionally, the fluid path of first ink bag connects the first ink bag to four nozzle rows of each printhead integrated circuit, the fluid path of second ink bag connects the second bag to four nozzle rows of each printhead integrated circuit, and the fluid path of third ink bag connects the third ink bag to two nozzle rows of each printhead integrated circuit. 
   In an eighth aspect the present invention provides a method of priming an inkjet printhead, the inkjet printhead having a plurality of ink ejection nozzles, the method comprising the steps of:
         providing an ink bag containing ink for distribution to the nozzles via a fluid path between the ink bag and the nozzles;   applying inwardly directed force on at least one exterior wall of the ink bag so as to reduce an available fluid volume of the ink bag, thereby causing ink to flow from the ink bag to the nozzles along the fluid path; and   arranging a biasing member in the ink bag so that the biasing member applies outwardly directed force on at least one interior wall of the ink bag so as to restrain the reduction of available fluid volume of the ink bag only once the available fluid volume of the ink bag has been reduced to a predetermined volume.       

   Optionally, the biasing member incorporates a leaf spring. 
   Optionally, the leaf spring is made from a material having shape-memory characteristic. 
   Optionally, the material is Mylar. 
   Optionally, the leaf spring is formed by folding an elongate arcuate piece of the material about an approximate centre line orthogonal to the longitudinal extent thereof so that the leaf spring exhibits an outwardly directed spring restoring force. 
   Optionally, the leaf spring is formed so as to have a folded longitudinal length and radius of curvature which result in the leaf spring being able to float within the ink contained in the ink bag prior to the application of the inwardly directed force by the force applicator. 
   Optionally, the ink bag is configured to have an available fluid volume of at least 19 milliliters. 
   Optionally, the predetermined available fluid volume is at least 15 milliliters. 
   Optionally, the ink bag is configured to have an available fluid volume of at least 23 milliliters. 
   Optionally, the fluid path connects the ink bag to at least 6400 nozzles of the printhead. 
   Optionally, each nozzle of the printhead is configured to eject an ink drop having a volume of about 1.2 picoliters. 
   Optionally, the nozzles of the printhead are arranged so as to print at a resolution of 1600 dots per inch. 
   Optionally, the ink bag contains one of magenta ink, cyan ink and yellow ink. 
   Optionally, the printhead is a pagewidth printhead, having a pagewidth of 100.9 millimeters. 
   In a ninth aspect the present invention provides an ink supply arrangement for an inkjet printhead, the inkjet printhead having a plurality of ink ejection nozzles, the ink supply arrangement comprising:
         at least one ink bag containing ink for distribution to the nozzles via a fluid path between the ink bag and the nozzles, the ink being primed in the fluid path and nozzles so as to be ejected by the nozzles, in use, thereby depleting the ink contained in the ink bag, the ink bag being configured to collapse as the ink is depleted;   a body for housing the ink bag and the printhead, the ink bag being attached to the body at a wall opposite a wall of the ink bag facing the printhead; and   a biasing member arranged in the ink bag to apply outwardly directed force on at least the wall of the ink bag facing the printhead,   wherein the biasing member is configured to maintain substantially constant negative pressure at the nozzles as the ink is depleted from the ink bag.       

   Optionally, the biasing member incorporates a compression spring. 
   Optionally, the compression spring has a free length equal to the height from the attached wall of the ink bag to the nozzles plus a height of a negative ink head necessary to provide said negative pressure. 
   Optionally, the free length is 141 millimeters and the height from the attached wall of the ink bag to the nozzles is 41 millimeters. 
   Optionally, said walls of the ink bag have an area of 30 millimeters by 50 millimeters and the compression spring has a spring constant of 14.7 Newtons per meter. 
   Optionally, the compression spring is made of stainless steel. 
   Optionally, the body is incorporated in a printhead cartridge. 
   Optionally, the printhead cartridge is removably engageable with a printer. 
   Optionally, the non-collapsed ink bag has a fluid volume of at least 15 milliliters. 
   Optionally, the fluid path connects the ink bag to at least 6400 nozzles of the printhead. 
   Optionally, each nozzle of the printhead is configured to eject an ink drop having a volume of about 1.2 picoliters. 
   Optionally, the nozzles of the printhead are arranged so as to print at a resolution of 1600 dots per inch. 
   In a further aspect there is provided an ink supply arrangement, comprising three of said ink bags. 
   Optionally, a first ink bag contains magenta ink, a second ink bag contains cyan ink and a third ink bag contains yellow ink. 
   Optionally, the fluid path of the first ink bag connects the first ink bag to 12800 nozzles of the printhead, the fluid path of the second ink bag connects the second ink bag to 12800 nozzles of the printhead, and the fluid path of the third ink bag connects the third ink bag to 6400 nozzles of the printhead. 
   Optionally, the printhead has 32000 nozzles. 
   Optionally, the printhead is a pagewidth printhead, having a pagewidth of 100.9 millimeters. 
   Optionally, the printhead comprises 5 linked printhead integrated circuits arranged to span the pagewidth, each printhead integrated circuit having 6400 nozzles arranged in rows. 
   Optionally, the fluid path of each ink bag connects the respective ink bag to at least two nozzle rows of each printhead integrated circuit. 
   Optionally, the fluid path of first ink bag connects the first ink bag to four nozzle rows of each printhead integrated circuit, the fluid path of second ink bag connects the second bag to four nozzle rows of each printhead integrated circuit, and the fluid path of third ink bag connects the third ink bag to two nozzle rows of each printhead integrated circuit. 
   An embodiment of a printhead cartridge that incorporates features of the present invention is now described by way of example with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
       FIG. 1  shows a top elevational perspective view of a printhead cartridge of a printer; 
       FIG. 2  shows a bottom elevational perspective view of the printhead cartridge; 
       FIG. 3  shows a perspective view of the printer; 
       FIG. 4  shows a cross-sectional view of the printer taken along the line I-I of  FIG. 3 ; 
       FIG. 5  shows an exploded view of the printhead cartridge; 
       FIG. 6  shows an isolated view of a printhead of the printhead cartridge; 
       FIG. 7  illustrates an arrangement of printhead integrated circuits of the printhead; 
       FIG. 8  illustrates an arrangement of ink ejection nozzles of the printhead integrated circuits; 
       FIG. 9  illustrates a nozzle triangle of the printhead; 
       FIG. 10  illustrates data and power connections between the printhead cartridge and a cradle unit of the printer; 
       FIG. 11  shows a top elevational, partial cross-sectional view of the printhead taken about line II-II of  FIG. 6 ; 
       FIG. 12  shows a bottom elevational, partial cross-sectional view of the printhead taken about line II-II of  FIG. 6 ; 
       FIG. 13  shows a side cross-sectional view of the printhead taken about line II-II of  FIG. 6 ; 
       FIG. 14  shows a partial side cross-sectional view of the printhead cartridge taken about line III-III of  FIG. 1 ; 
       FIG. 15  shows an isolated view of an ink supply bag of the printhead cartridge; 
       FIG. 16  illustrates a folded leaf spring as removed from the ink bag; 
       FIG. 17  illustrates the leaf spring unfolded; 
       FIG. 18  illustrates an alternative biasing arrangement of the ink bag; 
       FIGS. 19A and 19B  illustrate priming of ink into the printhead and a capping position of a capper of the printhead cartridge; 
       FIG. 20  shows an isolated view of the capper; 
       FIG. 21  shows a cross-sectional view of an operational arrangement of actuator features of the capper with a capping mechanism of the printer; 
       FIG. 22  illustrates a non-capping position of the capper; 
       FIG. 23  illustrates assembly of the printhead and capper to a body of the printhead cartridge; 
       FIG. 24  illustrates a coordinate system of the printhead cartridge; 
       FIGS. 25 and 25A  illustrate reference features of the printhead cartridge; and 
       FIGS. 26 ,  26 A,  26 B and  26 C illustrate alignment of the printhead cartridge with the printer. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
   A printer  100  is provided which is intended for use as a digital photo color printer and is dimensioned to print 100 millimeter by 150 millimeter (4 inch by 6 inch) photos whilst being compact in size and light in weight. As will become apparent from the following detailed description, reconfiguration and dimensioning of the printer could be carried out so as to provide for other printing purposes. 
   The printer  100  of the illustrated photo printer embodiment has dimensions of 18.6 cm (W); 7.6 cm (H); 16.3 cm (D), and a weight of less than two Kilograms. The compact and lightweight design of the printer provides portability and ease of use. 
   The printer  100  may be easily connected to a PC via USB (such as a USB 1.1 port for USB 2.0 compatible PCs) and to digital cameras and other digital photo equipment, such as electronic photo albums and cellular telephones, via USB or PictBridge. Direct printing is available when using Pictbridge compatible digital photo equipment. This enables quick and convenient printing of digital photo images. 
   Connection to external power is used, preferably to mains power via a 12 Volt; 2 Amp (or 24 Volt; 1 Amp) DC power converter. However, the printer may be configured to operate from an internal power source. The printer is configured to efficiently use power, operating at a maximum power consumption of 36 Watts. 
   The printer  100  has three core components: a printhead cartridge  200  having a printhead and ink supply; a printer or cradle unit  400  which supports the printhead cartridge and has a media transport mechanism for transporting print media past the printhead; and a media supply cartridge  600  for supplying the media to the printer. 
   The present invention is concerned with the printhead cartridge  200 , and therefore detailed description of the cradle unit and media supply cartridge is not provided herein. A full description of a suitable cradle unit and media supply cartridge for use with the printhead cartridge  200  is described in the Applicant&#39;s simultaneously co-filed U.S. patent application Ser. Nos. 11/293,794, 11/293,839, 11/293,826, 11/293,829, 11/293,830, 11/293,827, 11/293,828, 11/293,795, 11/293,823, 11/293,827, 11/,293,831, 11/293,815, 11/293,819, 11/293,818, 11/293,817, 11/293,816 and the entire contents of which are hereby incorporated by reference. 
   The printhead cartridge  200  is an assembly having the necessary components for operation as a printer when mounted to the printer or cradle unit having a media supply. 
   The printhead cartridge  200  has a body  202  which is shaped to fit securely in a complementarily shaped printhead cartridge  200  support of the cradle unit (see  FIGS. 1 and 4 ). The body  202  of printhead cartridge  200  houses a printhead  204  and an ink supply  206  for supplying ink to the printhead  204  and has a capper  208  for capping the printhead  204  when the printhead  204  is not in use. 
   The printhead  204  comprises an ink distribution support  210  which is used to mount the printhead  204  to the printhead cartridge body  202  and distribute ink from the ink supply  206  arranged in the body  202  to the printhead  204 . The capper  208  is also mounted to the printhead cartridge body  202  via the ink distribution support  210  so as to be located beneath the mounted printhead  204  relative to the ink supply  206 . A media path  212  (see arrow of  FIG. 4 ) is formed between the printhead  204  and the capper  208  for the transport of print media past the printhead  204  when the capper  208  is not capping the printhead  204 . 
   In the illustrated embodiment, the printhead is a pagewidth inkjet printhead. By using a pagewidth printhead it is unnecessary to scan the printhead across print media. Rather, the printhead remains stationary with the print media being transported therepast for printing. By operating the printhead to continuously print as the print media is continuously fed past the printhead (so called ‘printing-on-the-fly’), the need to stall the media feed for each print line is obviated, therefore speeding up the printing performed. 
   The printer incorporating the printhead  204  of the printhead cartridge  200  is configured to print a full colour page in at most two seconds, which provides high-speed printing of about 30 pages per minute. This high speed printing is performed at high quality as well, with a resolution of at least 1600 dots per inch being provided by the printhead. Such a high resolution provides true photographic quality above the limit of the human visual system. 
   This is achieved by forming the printhead from thousands of ink ejection nozzles  214  across the pagewidth, e.g., about 100 millimeters for 4 inch by 6 inch photo paper. In the illustrated embodiment, the printhead incorporates 32,000 nozzles. The nozzles  214  are preferably formed as Memjet™ or microelectomechanical inkjet nozzles developed by the Applicant. Suitable versions of the Memjet™ nozzles are the subject of a number of the applicant&#39;s patent and pending patent applications, the contents of which is incorporated herein by cross reference and the details of which are provided in the cross reference table above. 
   Brief detail of a printhead suitable for use in the printhead cartridge  200  is now provided. The printhead is formed as a ‘linking printhead’  216  which comprises a series of individual printhead integrated circuits (ICs)  218 . A full description of the linking printhead, its control and the distribution of ink thereto is provided in the Applicant&#39;s co-pending U.S. application Ser. Nos. 11/014,769, 11/014,729, 11/014,743, 11/014,733, 11/014,754, 11/014,755, 11/014,765, 11/014,766, 11/014,740, 11/014,720, 11/014,753, 11/014,752, 11/014,744, 11/014,741, 11/014,768, 11/014,767, 11/014,718, 11/014,717, 11/014,716, 11/014,732, and 11/014,742, all filed Dec. 20, 2004 and U.S. application Ser. Nos. 11/097,268, 11/097,185, 11/097,184, all filed Apr. 4, 2005 and the entire contents of which are incorporated herein by reference. In the illustrated embodiment, the linking printhead  216  has five printhead ICs  218  arranged in series to create a printing zone  219  of a 100.9 millimeter pagewidth. 
   Each printhead IC incorporates a plurality of nozzles  214  positioned in rows  220  (see  FIG. 7 ). The nozzle rows  220  correspond to associated ink colours to be ejected by the nozzles  214  in that row  220 . The illustrated embodiment has ten such rows  220  arranged in groups of two adjacent rows  220   a - e  for five colour channels  222   a - e . However, other arrangements may be used. In the illustrated arrangement, each printhead IC has 640 nozzle per row, 1280 nozzles per colour channel, 6400 nozzles per IC and therefore 32000 nozzles for the five ICs of the printhead. Of course, a different number of printhead ICs, including less or more than five printhead ICs may be used. 
   The nozzles  214  are arranged in terms of unit cells  224  containing one nozzle  214  and its associated wafer space. In order to provide the print resolution of 1600 dots per inch, an ink dot pitch (DP) of 15.875 microns is required. By setting each unit cell to have dimensions of twice the dot pitch wide by five times the dot pitch high and arranging the unit cells  224  in a staggered fashion as illustrated in  FIG. 8 , this print resolution is achieved. 
   Due to this necessary staggered arrangement of the nozzles  214  discontinuity is created at the interface between the adjacent printhead ICs  218 . Such discontinuity will result in discontinuity in the printed product causing a reduction in print quality. Compensation of this discontinuity is provided by arranging a triangle  226  of nozzle unit cells  224  displaced by 10 dot pitches at the interface of each adjacent pair of printhead ICs  218  (see  FIG. 9 ). 
   The nozzle triangles  226  allow the adjoining printhead ICs  218  to be overlapped which allows continuous horizontal spacing between dots across the multiple printhead ICs  218  along the printhead and therefore compensates for any discontinuity. The vertical offset of the nozzle triangle  226  is accounted for by delaying the data for the nozzles  214  in the nozzle triangle  226  by 10 row times. The serially arranged nozzles rows  220  and nozzle triangles  226  of the printhead ICs  218  together make up the printing zone  219  of the printhead. 
   The transfer of data and power to the printhead nozzles is controlled by print control circuitry of the cradle unit when the printhead cartridge  200  is inserted therein. Connection of power and data is made to the printhead  204  via engagement and electrical connection of a connection interface of the cradle unit and a connection panel  228  of the printhead cartridge  200  (see  FIGS. 1 and 4 ). 
   The connection panel  228  comprises a plurality of electrical contacts  230  positioned on a flexible printed circuit board  232 . The flexible printed circuit board  232  is mounted to the ink distribution support  210  so as to wrap around one longitudinal edge thereof to expose the electrical contacts  230  to the connection interface of the cradle unit and to connect the contacts to the nozzles of the printhead  204  (see  FIGS. 6 and 13 ). The specific connections made between the printer/cradle unit and the printhead  204  are illustrated in  FIG. 10 . In the illustrated embodiment, 40 contacts are provided in the connection panel at a pitch of 2.54 millimeters. The power (V POS ) and data delivered via these contacts is bussed to pins of the printhead ICs  218  and a quality assurance (QA) chip  234  of the printhead cartridge  200 . The QA chip  234  is provided for ink quality assurance and defines technical compatibility between the printhead cartridge  200  and printer/cradle unit. 
   The QA chip  234  is configured to track usage of the nozzles, the number of prints that have been performed by the printhead cartridge  200  and the amount of ink remaining in the ink supply  206 . This information is used to ensure that the printhead cartridge  200  is only used by a predetermined usage model. Such a usage model limits the use-lifetime of the printhead cartridge  200  in order to maintain consistent print quality. 
   For example, the model may either be a page-limited model which sets the number of pages which can be printed using the printhead cartridge  200  (e.g., 200 photo pages) or an ink-limited model which sets a maximum number of pages that can be printed without depleting the ink of the (non-refillable) ink supply  206 . In this way, the printhead cartridge  200  is caused to be operational within the operational lifetime of the printhead nozzles  214  and within the supply of ink for full colour printing. Other suitable models for ensuring consistent print quality may also be used. 
   The QA chip  234  may also be configured to store additional information related to the manufacture of the printhead cartridge  200 , including manufacture date, batch number, serial number, manufacturing test results (e.g., a dead nozzle map), etc. 
   The print control circuitry of the cradle unit interrogates the QA chip  234  via the connection interface and connection panel to read all available information, and uses the results to control the operation of the printer. 
   In controlling the printhead, the print control circuitry controls the supply of firing power to the nozzles in order to control the ejection of ink onto the passing print media. Each nozzle is configured to eject an ink drop having a volume of about 1.2 picoliters and a velocity of about eight meters per second. In order to consistently eject drops having these parameters, the power routed to the printhead by the cradle unit is regulated at the connection interface. The regulated power is restricted to have variations of less than 100 millivolts in the 5.5 Volts; 3.5 Amp supplied to the printhead from the 12 Volt; 2 Amp power supply. Variations of this order have negligible effect on drop ejection and therefore the firing pulse width supplied by the print control circuitry can be constant. 
   Firing of the nozzles may also cause brief peaks in the current consumption. These peaks are accommodated by the inclusion of energy storage circuitry in the connection interface of the cradle unit. Further energy storage can also be provided on the printhead  204  in the form of decoupling capacitors  236  on the flexible printed circuit board  232  (see  FIGS. 11 and 13 ). 
   As discussed earlier, five colour channels  222   a - e  are provided in the printhead  204 . In the illustrated embodiment, the channels comprise two magenta ink channels, two cyan ink channels and one yellow ink channel. In order to distribute ink from the supply of the magenta, cyan and yellow inks to the nozzle rows, the ink distribution support  210  has three ink paths  238  as illustrated in  FIGS. 11 to 13 . The three ink paths  238  include a magenta ink path  238   m , a cyan ink path  238   c  and a yellow ink path  238   y.    
   The ink paths  238  are formed by the cooperation of an upper portion  240  and a lower portion  242  of the ink distribution support  210 . The upper and lower portion  240 , 242  are preferably molded portions having details  240   a , 242   a  for forming the ink paths  238 . Preferably, the upper and lower portion are molded from liquid crystal polymer, which is inert to the ink and can be configured to have thermal expansion characteristics similar to those of silicon which is used in the printhead ICs  218 . The upper and lower portion  240 , 242  are bonded to one another to provide a seal for the ink paths  238 . 
   The printhead  204  is an assembly of the ink distribution support  210  and the linking printhead  216  in which the linking printhead  216  is adhesively mounted to the ink distribution support  210  by a polymer sealing film  244 . The sealing film  244  has a plurality of through-holes  244   a  which correspond to, and align, with conduits  238   a  from each of the ink paths  238  to the underside of the lower portion  242  of the ink distribution support  210  and associated ink delivery inlets in the underside of each printhead IC of the linking printhead  216 . The sealing film  244  provides an effective seal between the ink path  238   a  and the printhead ink delivery inlets to prevent the wicking and mixing of ink between the different nozzle rows and individual nozzles. It is noted that the magenta and cyan ink paths  238   m  and  238   c  each have conduits  238   a  for feeding ink to two of the five colour channels of the linking printhead  216 . 
   The flexible printed circuit board  232  is mounted to a flange  246  of the upper portion  240  of the ink distribution support  210  so that contact pads  232   a  of the flexible printed circuit board  232  are able to communicate data and power signals to each of the printhead ICs  218  via pads provided along one edge of the printhead ICs  218  (see  FIGS. 12 and 13 ). 
   A media shield  248  is also mounted to the ink distribution support  210  along the opposite edge of the linking printhead  216  to the flexible printed circuit board  232 . In the illustrated embodiment, the media shield  248  is mounted via an adhesive film  250 , however other arrangements are possible. The media shield  248  is configured to maintain the passing media at a predetermined distance from the nozzles  214  of the linking printhead  216 . This prevents damage being caused to the nozzles by contact of the media with the nozzles. The media shield  248  is preferably a molding formed of liquid crystal polymer. As can be seen from  FIG. 12 , the media shield  248  is spaced from the surface of the ink distribution support  210  by details  248   a . A space  248   b  provided by the details  248   a  provides the predetermined distance of the print media from the nozzles  214 . 
   In the illustrated embodiment, the ink paths  238  of the ink distribution support  210  each have a conical or cylindrical inlet member  238   b  for fluid connection to an associated ink bag  252  of the ink supply  206  (see  FIG. 14 ). Three ink bags  252  are provided, a magenta ink bag, a cyan ink bag and a yellow ink bag. The ink bags  252  are positioned in a base  202   a  of the body  202  of the printhead cartridge  200  which is enclosed by a lid  202   b . The base and lid of the body are preferably plastics moldings having clip details for snap fitting the lid to the base. 
   One of the ink bags  252  is illustrated in  FIG. 15 . The ink bag is formed of two profiled panels  252   a  which are sealed together to make an ink holding chamber  252   b . The ink holding chamber  252   b  of each ink bag is dimensioned to hold an ink volume of at least 19 milliliters up to about 23 milliliters and is configured to be collapsible so as to reduce the available ink volume. The sealed panels  252   a  seal about a connector assembly  254  and a folded leaf spring  256 . The connector assembly  254  is used for both filling of the ink bag with the required ink volume during manufacture of the printhead cartridge  200  and connecting the ink bag  252  with the inlet member  238   b  of the respective ink path  238  of the ink distribution support  210 . 
   Distribution of ink from the ink bag  252  to the ink paths  238  via the connector assembly  254  is performed through an outlet  254   c  of the connector assembly  254 . The cylindrical outlet  254   c  is fitted with a coupling seal  254   d  which has ring details on the exterior cylindrical surface for preventing ink from leaking between the outlet&#39;s inner surface and the coupling seal, and ring details on the interior cylindrical surface for preventing ink from leaking between the coupling seal and the outer surface of the inlet member of the ink path (see  FIG. 14 ). 
   Filling of the ink bag and priming of ink into the connector assembly  254  is performed by injecting ink into an access hole  254   e  of the connector assembly  254 . Air within the ink bag/connector assembly is able to escape through an outlet  254   b  during filling. Once filled, a ball seal  254   a  seals the outlet  254   b  and the coupling seal  254   d , which is provided with a cover seal (not shown), is positioned in the outlet  254   c  to seal off the access hole, as illustrated in  FIG. 14 . Air is undesired within the ink bag and connector assembly  254  so as to prevent air from entering the ink distribution support  210  and the nozzles  214 . Air or other gases may cause printing problems due to the microscopic size of the nozzles. A suitable air filter (not shown) may also be incorporated within the connector assembly  254  to exclude any air present in the ink bag from entering the ink distribution system. 
   The connector assembly  254  is mounted within the interior of the cartridge body base  202   a  by engaging clips  254   f  of the connector assembly  254  with details  202   c  in the base  202   a  which sealingly engages the outlets of the connector assemblies with the inlet members  238   b  of the respective ink paths  238  (see  FIG. 14 ). 
   The folded leaf spring  256  of each bag  252  is formed by folding an elongate plate  256   a  about a centrally disposed slot  256   b  (see  FIGS. 16 and 17 ). The elongate plate  256   a  is dimensioned so that when folded it fits within the sealed ink bag  252 . The elongate plate  256   a  is formed so as to be resilient to the folding and the folding is performed so as to create a curvature in the folded plate. This creates a folded leaf spring which is resistant to an inwardly directed force and which in turn applies an outwardly directed force. A leaf spring having a spring constant equivalent to 1.2 Newtons across an eight millimeter distance between the faces is suitable. Mylar is a suitable material for the leaf spring for its shape memory characteristics. When Mylar is used the folded leaf spring may be thermally formed. Other spring materials may be used, such as stainless steel. 
   The use of the leaf springs  256  within the ink bags  252  provides negative fluid pressure at the nozzles of the printhead  204  when the ink bags  252  are connected to the nozzles and the ink has been fully primed to the nozzles from the ink bags  252 . Negative fluid pressure is created by the leaf spring exerting outwardly directed force on the interior walls of the ink bag panels  252   a . Negative fluid pressure is desired at the nozzles to ensure that uncontrolled ejection or leakage of ink from the nozzles does not occur. 
   A negative pressure head of about −100 millimeters is required to effectively prevent ink from leaking at the nozzles. The illustrated leaf springs  256  may cause fluctuations in the negative pressure head as ink is depleted from the ink bags  252  and therefore the ink volume decreases. 
   In an alternative embodiment, coil springs or like compression springs  258  may be used in place of the leaf springs  256 . The use of a suitably configured compression spring  258  within the ink bag  252 , and attachment of the ink bag  252  to the underside of the lid  202   b  of the cartridge body  202  with suitable adhesive, ensures that a constant negative pressure head is created at the nozzles independent of the ink volume in the ink bags  252 . A suitably configured compression spring, for an ink bag of area 30 millimeters by 50 millimeters, is a spring having the required free length and a spring constant of 14.7 Newtons per meter. 
   The required free length is a combination of a free length of 100 millimeters and the height of the printhead cartridge  200  (e.g., from the attached point of the top of the ink bag  252  to the ink ejection plane of the nozzles). In the illustrated embodiment, the printhead cartridge  200  has a height of 41 millimeters from the interior of the lid  202   b  to the nozzles of the printhead  204 , resulting in a free length of 141 millimeters for the compression spring  258  (see  FIG. 18 ). 
   In the present embodiment, the leaf springs  256  also facilitate the priming of ink from the ink bags  252  to the connected nozzles. Priming is performed before packaging of the printhead cartridge  200  for distribution, and ensures that ink is situated throughout the operational system thereby removing any air or particulate matter in the system prior to printing. In order to prime ink into each of the ink paths  238  of the ink distribution support  210  and nozzles  214 , the ink bags  252  are effectively overfilled with ink. That is, the printing volume of ink within each ink bag is set to be less than a 19 milliliter volume. A priming volume of about four milliliters is needed from each ink bag for priming the system. Thus, a printing volume of at least 15 milliliters is provided in each ink bag. 
   In practice, an additional volume of up to four milliliters is made available in each ink bag in order to account for the inability of the ink bags to be completely collapsed due to the non-zero width of the fully folded (i.e., compressed) leaf spring. 
   In order to prime the priming volume into the ink paths and nozzles, force is applied with a suitable force applicator to the exterior surface of one or both panels  252   a  of the ink bags  252 , as shown by the arrow in  FIG. 19A . In order to provide effective priming, the folded leaf springs  256  are configured to contact the interior surfaces of the ink bags  252  only once the printing volume has been reached in the ink bag. That is, the leaf springs  256  effectively float within the overfilled ink bags  252  prior to priming being performed. The force applicator is arranged to apply the inwardly directed priming force until the resistance caused by the outwardly directed force of the leaf spring is encountered, as shown by the arrows in  FIG. 19B . In this way, negative pressure is immediately created at the primed nozzles. 
   As illustrated in  FIGS. 19A and 19B , a cap  260  of the capper  208  is at its capping position on the nozzles of the printhead  204  during the priming operation so as to capture any primed ink which is ejected from the nozzles during priming. 
   The manner in which the cap of the capper caps the printhead nozzles and the operation of the capper is described in the Applicant&#39;s co-pending U.S. patent application Ser. Nos. 11/246,676, 11/246,677, 11/246,678, 11/246,679, 11/246,680, 11/246,681, and 11/246,714, all filed Oct. 11, 2005 and the entire contents of which are hereby incorporated by reference. 
   For ease of understanding, a brief excerpt of the description provided in these co-pending Applications is now provided. 
   Referring to  FIGS. 19A to 22 , the cap  260  of the capper  208  comprises an elastically deformable elongate pad  262  having a contact surface  262   a  mounted on a elongate support  264  which has lugs or actuation features  266  protruding from each longitudinal end. The support  264  is housed within an elongate housing  268  so that the lugs  266  protrude through slots  268   a  in the housing at each longitudinal end thereof. The housing is mounted to the ink distribution support  210  of the printhead  204  so as to align the pad  262  of the cap  260  with the printhead ICs  218  and the contact surface  262   a  of the pad  262  is configured to form a capping zone which is commensurate with the printing zone  219  of the printhead  204 . Preferably the housing and support are formed as moldings from plastic or like material. 
   The support is slidably movable within the slots  268   a  of the housing  268 , allowing the pad  262  to be slid relative to the housing  268 . The extent of the pad&#39;s slidable movement is defined by the length of the slots  268   a  due to the contact of the lugs  266  with the slot walls. At the upper extent of movement, the cap  260  is placed in its capping position (see  FIG. 21 ) and at the lower extent of movement, the cap  260  is placed in its non-capping position (see  FIG. 22 ). The range of movement may be from about 1.5 millimeters to about 2.6 millimeters, thereby ensuring unobstructed passage of the print media along the media path  212 . 
   A pair of springs  272  is fixed to the bottom wall of the housing  268  to bias the cap  260  into the capping position. In the capping position, the contact surface  262   a  of the pad  262 , which defines the capping zone  270 , sealingly engages with the nozzles  214  of the printhead  204  across the entire printing zone  219 , thereby capping or covering the nozzles. This capping isolates the ink within the nozzles from the exterior, thereby preventing evaporation of water from the primed ink from the nozzles and the exposure of the nozzles to potentially fouling particulate matter during non-operation of the printhead. In the non-capping position, the contact surface  262   a  is disengaged from the nozzles, as illustrated in  FIG. 22 , allowing printing to be performed. 
   When the printhead cartridge  200  is mounted to the cradle unit  400 , the lugs  266  of the support  264  engage with a cam  402  of a capping mechanism of the cradle unit  400 , as illustrated in  FIG. 21 . Rotation of the cam  402 , under control of the print control circuitry of the cradle unit  400 , causes linear sliding movement of the support  264  and, hence, the pad  262 , under control of the springs  272 . Accordingly, the pad  262  may be moved reciprocally between its capping position and its non-capping position. The springs  272  are positioned to ensure that all parts of the contact surface  262   a  of the pad  262  move at the same rate with respect to the printhead  204 . 
   By configuring the capper to be normally capping the printhead in its rest position, i.e., without requiring any electronic mechanism to hold the capper in its capping position, the potential of such an electronic mechanism failing, and therefore uncapping the printhead, is prevented. 
   As previously mentioned, the linking printhead  216  and capper  208  are commonly mounted to the body  202  of the printhead cartridge  200  via the ink distribution support  210 . The ink distribution support  210  is mounted to the cartridge body  202  at mounting zones  210   a  of the support arranged at either longitudinal end of the printing zone  219  of the linking printhead  216  (see  FIG. 6 ). The mounting zones  210   a  are formed as widened sections of the upper and lower portion  240 , 242  of the ink distribution support  210 . These widened sections are easily molded as part of the upper and lower moldings. 
   The mounting zone  210   a  at one end of the ink distribution support  210  (e.g., the right hand end as depicted in  FIG. 23 ) is formed with a through-hole  210   b  which aligns with a corresponding through-hole  268   b  formed in a tab  268   c  extending from the capper housing  268 , as illustrated in  FIG. 23 . These through-holes  210   b , 268   b  of the ink distribution support  210  and capper  208  further align with a similarly positioned through-hole (not shown) provided in the body  202  of the printhead cartridge  200 . 
   The mounting zone  210   a  at the other end of the ink distribution support  210  (e.g., the left hand end as depicted in  FIG. 23 ) is formed with a slot  210   c  (see  FIG. 6 ) which aligns with a corresponding slot  268   d  formed in a tab  268   e  extending from the capper housing  268 , as illustrated in  FIG. 23 . These slots  210   c , 268   d  of the ink distribution support  210  and capper  208  further align with a similarly positioned slot (not shown) provided in the body  202  of the printhead cartridge  200 . 
   A pin  274  is passed through each of the aligned holes at the first end of the printing and capping zones and is locked in place so as to fix the printhead  204  and capper  208  to the cartridge body  202  by a locking member  276 , such as a clip (e.g., an E-clip is illustrated). 
   A second pin  278  is passed through the aligned slots at the second end of the printing and capping zones and is locked in place with a biasing member  280 . The biasing member  280  is arranged to bias the cartridge body  202 , printhead assembly  204  and capper  208  together at the second pin  278  whilst allowing relative movement of the cartridge body  202 , printhead assembly  204  and capper  208 . The illustrated biasing member is a sprung clip  280 , however other arrangements may be used. 
   In this way, relative movement of the components of the printhead cartridge  200  is accommodated whilst maintaining a secure mount of, and proper alignment between, the components. In the illustrated embodiment, the slots are configured so as to accommodate movement along the longitudinal direction of the printhead  204  and capper  208  (i.e., in the X-direction of the coordinate system illustrated in  FIG. 24 ). Such longitudinal movement may occur during the performance of printing due to thermal expansion of the linking printhead silicon and the ink distribution support liquid crystal polymer. As well as maintaining alignment, accommodating such thermal expansion alleviates the effect of stresses on the fragile printhead ICs. 
   Other slotted and/or confining arrangements are possible, so long as proper alignment of the components is maintained throughout the movement accommodated by these arrangements. 
   Whilst proper alignment of the printhead  204  and capper  208  are assured by the mounting arrangement, the exact position of the nozzles of the mounted printhead  204  must be known to perform high quality printing when the printhead cartridge  200  is inserted in the cradle unit  400 . The requirement for this information is exacerbated by the small tolerances allowed by the 100.9 millimeter printing zone  219  of the linking printhead  216  for printing across the 100 millimeters of printable area of four inch wide photo paper. 
   This information is provided by the cooperation of X, Y and Z datums (in accordance with the coordinate system illustrated in  FIG. 24 ) arranged as reference features of the printhead cartridge  200  with complementary mounting features of the cradle unit  400 . A “datum” is defined as a reference position against which other features are located, within given tolerances. 
   In the illustrated embodiment, the three following key aspects of the printhead cartridge-cradle unit alignment are referenced to the X, Y and Z datums: 
   (1) the surface of the print media that the media transport mechanism of the printer presents to the printhead cartridge; 
   (2) the electrical contacts of the flexible printed circuit board on the printhead cartridge; and 
   (3) the cartridge retention points used to hold the cartridge to the cradle unit. 
   The cooperation of the reference features of the printhead cartridge  200  and the mounting features of the printer is arranged to restrict the movement of the printhead cartridge  200 , so as to keep within the tight tolerances. 
   As illustrated in  FIGS. 25 and 25A , the X datum corresponds to a centreline of a slot  282  in the mounting zone  210   a  of the ink distribution support  210  at the fixed end of the printhead  204  and capper  208  (e.g., at the right hand end as depicted in  FIG. 25A ) which is located immediately adjacent the flexible printed circuit board  232  (see also  FIG. 6 ). The Y datum corresponds to a line  284  across the printhead cartridge  200  just above the electrical contacts  230  of the flexible printed circuit board  232 , at which point the exterior surface of the printhead cartridge body  202  is at a slight angle to the vertical (e.g., in the illustrated embodiment a clearance angle of five degrees is provided). The Z datum corresponds to four flat surfaces  286  on the corners of the upper portion  240  of the ink distribution support  210  which face the cradle unit  400  (i.e., the corners of the underside of the upper portion  240  as depicted in  FIG. 25A , which is the same surface in which the slot  282  of the X datum is defined; see also  FIG. 6 ). 
   In this way, the X, Y and Z datums are located as close as possible to the printing zone  219  of the printhead  204  in order to reduce the effect of accumulated tolerances across multiple components. Providing these reference features on the printhead itself, allows the printhead to be self referencing, which in turn accommodates the aforementioned tight tolerances. Other referencing arrangements are possible so long as the small tolerances are accommodated. 
   An example of the manner in which these reference features cooperate with complementary mounting features of the cradle unit is illustrated in  FIGS. 26 ,  26 A,  26 B and  26 C. The X datum slot  282  of the printhead cartridge  200  is received in a complementary shaped mesa feature  404  situated within a cartridge receiving slot  406  of the cradle unit  400  (see  FIGS. 4 and 26B ). The Y datum angled surface  284  of the printhead cartridge  200  is held against a protrusion  408  situated across the cartridge receiving slot  406  of the cradle unit  400  (see  FIG. 26A ). The cradle unit protrusion  408  is the part of the connection interface which carries the electrical contacts of the print control circuitry and power supply for connection to the contacts  230  of the flexible printed circuit board  232 . The Z datum flat surfaces  286  locate on protrusions  410  within the cartridge receiving slot  406  of the cradle unit  400  (see  FIG. 26C ). 
   By locating the X datum slot, one end of the Y datum line and two of the Z datum flat surfaces at the fixed end of the printhead and capper, the exact location of each of the reference features can be known throughout movement of the printhead and capper at the confined end. The print control circuitry of the printer uses the cooperation of these reference features of the printhead cartridge  200  with the known positions of the mounting features of the cradle unit  400  in order to control the firing of the nozzles. 
   Once the printhead cartridge  200  has been inserted into the cartridge receiving slot  406  of the cradle unit  400  to make the above described cooperative connections, the printhead cartridge  200  is held in place by a lid  412  of the cradle unit  400  (see  FIGS. 3 and 4 ). In the illustrated embodiment, correct alignment and contact can be maintained by configuring the lid  412  of the cradle unit  400  to exert a vertical force of about 20 Newtons to the lid of the printhead cartridge body  202  (with a similar force being required to be exerted by a user to insert the printhead cartridge  200 ), and by configuring the slant angle of the printhead cartridge body  202  at the Y datum line  284  to cause the connection protrusion  408  of the cradle unit  400  to exert a horizontal force of about 45 Newtons to the electrical contacts  230  of the flexible printed circuit board  232 . 
   In order to ensure that the printhead cartridge  200  may only be used with a printer/cradle unit which is properly configured to operate the printhead cartridge  200 , it is possible to arrange a key feature  288  on the printhead cartridge  200 , as illustrated in  FIGS. 2 and 26 , for example, which only allows the printhead cartridge  200  to be inserted into a printer/cradle unit having a complementary key feature. Such ‘branding’ of the printhead cartridge  200  and printer/cradle unit can be carried out after manufacture. 
   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.