Abstract:
A printer includes a pair of feet upon which the printer can rest. A pair of spaced apart and upright legs extends from respective feet. A supply spool is rotationally mounted between the legs and is configured to carry a wound length of print media. A printhead assembly is fast between the legs and defines a passage through which print media unwound from the supply spool can pass. The printhead assembly includes a printhead which can eject ink onto the print medium passing through the passage. An uptake spool is rotationally mounted between the legs and the printed print medium can be wound thereon.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   The present application is a continuation of U.S. application Ser. No. 11/329,167 filed on Jan. 11, 2006, now issued as U.S. Pat. No. 7,152,949, which is a continuation of U.S. application Ser. No., 11/078,321 filed on Mar. 14, 2005, now issued as U.S. Pat. No. 7,011,390, which is a continuation of U.S. application Ser. No. 10/743,759 filed on Dec. 24, 2003, now issued as U.S. Pat. No. 6,916,082, which is a continuation of U.S. application Ser. No. 10/120,351 filed on Apr. 12, 2002, now issued as U.S. Pat. No. 6,672,706, which is a continuation-in-part of U.S. application Ser. No. 09/112,767, now issued as U.S. Pat. No. 6,416,167, the entire contents of which are herein incorporated by reference. The following United States applications and patents are hereby incorporated by reference: 
   
     
       
             
             
             
             
             
             
           
         
             
                 
             
           
           
             
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   FIELD OF THE INVENTION 
   This invention relates to a wide format pagewidth inkjet printer. More particularly, this invention relates to a printing mechanism for a wide format pagewidth inkjet printer and to a wide format pagewidth inkjet printer. 
   BACKGROUND OF THE INVENTION 
   High volume, high resolution printing is an objective that has been sought by the manufacturers of wide format printers for some time. Wide format printers have been available to the public for many years. Examples of popular wide format printers are the Hewlett Packard (HP) 1000/5000, the HP 3000/3500, the Epson 7000/10,000 and many others. 
   These printers all have a traversing printhead that traverses a print medium while depositing ink on the medium. Applicant believes that these printers suffer from inherent disadvantages, particularly when attempts are made to utilize the design of such printers in order to achieve faster printing speeds at high resolutions. 
   Central to the problem of achieving high printing speeds is the ability to achieve a printhead that is capable of generating the necessary number of ink dots at a suitable rate. Further, in order to achieve accurate printing, it is desirable that a row or band of the image be created in as little print cycles as possible, and preferably in a single print cycle. It follows that it is undesirable for a traversing printhead to be used in an attempt to achieve high print speeds and that a single printhead incorporating a suitable number of inkjet nozzles is required. 
   Thermal printheads also referred to as bubble jet printheads and piezoelectric printheads have been available for some time. These suffer from excessive heat build up and energy consumption and have therefore been found by the applicant to not be suitable for use in a pagewidth configuration. A number of disadvantages associated with such printheads are set out in U.S. Pat. No. 6,443,555. 
   The applicant has developed a printhead chip that is capable of producing images having a resolution as high as 1600 dpi. These chips are manufactured using integrated circuit fabrication techniques. Details of the chips are provided in the above referenced applications and patents. Applicant believes that these printhead chips are extremely suitable for use in wide format printers. The reason for this is that such chips operate at extremely high speeds due to the large number of nozzle arrangements required in a single chip and due to the fact that such chips can be driven at an extremely high cyclical rate. 
   The Applicant has been faced with a number of difficulties in order to achieve the effective use of such printhead chips in wide format printers. One particular difficulty identified by the Applicant is the effective control of a number of such printhead chips to achieve accurate printing. This control must incorporate the use of effective image processing tools that are capable of processing stored images at a rate that corresponds with the physical rate of printing achievable by a number of the above printhead chips. 
   Another difficulty that faces the manufacturers of wide format printers are the problems associated with heat build up. This can often result in the necessity for expensive heat extraction devices that add to the complexity of the printer. 
   SUMMARY OF THE INVENTION 
   According to a first aspect of the invention, there is provided a printing mechanism that comprises 
   an elongate support structure; 
   a pair of busbars that are mounted on the support structure; 
   a plurality of printed circuit boards that are mounted on the support structure to be electrically connected to the busbars, each printed circuit board including print engine control circuitry that is configured to control operation of a number of printhead chips; 
   a plurality of ink distribution structures that are mounted on the support structure and connectable to a supply of ink; and 
   a plurality of printhead modules that are mounted on respective ink distribution structures, each printhead module having a carrier and a printhead chip positioned on the carrier, each printhead chip having a plurality of nozzle arrangements that are positioned on a wafer substrate, each nozzle arrangement incorporating a micro-electromechanical actuator for ejecting ink from a nozzle chamber, and being mounted on a respective ink distribution assembly, a number of the printhead chips being connected to the print engine control circuitry such that each nozzle arrangement can receive data signals from the print engine control circuitry. 
   The support structure may include an elongate chassis that is interposed between a pair of end supports, the chassis being shaped to support the printed circuit boards on one side of the chassis and the ink distribution structures on another side of the chassis, with the busbars interposed between the printed circuit boards and said one side of the chassis. 
   Each printhead module may include a flexible printed circuit board that interconnects the printhead chip to the control circuitry. 
   The print engine control circuitry of each printed circuit board may be defined by an integrated circuit. 
   The support structure may include a channel member that is mounted on the chassis and the ink distribution structures may be positioned in a channel defined by the channel member. 
   Each ink distribution structure may define a plurality of ink reservoirs that extend through the ink distribution structure such that ink reservoirs extend a length of the channel member when the ink distribution structures are positioned in the channel. The printing mechanism may include a connecting assembly that is mounted on an endmost ink distribution structure to permit a plurality of ink conduits to be connected to the endmost ink distribution structure with each conduit being in fluid communication with a respective ink reservoir. 
   According to a second aspect of the invention, there is provided a print assembly for a wide format pagewidth inkjet printer, the print assembly comprising 
   an elongate carrier that is mountable on a support structure of the printer and is positioned an operative distance from a platen of the printer; 
   a number of printhead chips that are mounted on the carrier, the printhead chips being provided in a number and configuration such that the printhead chips define a printing zone between the carrier and the platen, the printing zone having a length of at least 36 inches (914 mm), each printhead chip being of the type that incorporates a plurality of nozzle arrangements, each nozzle arrangement being in the form of a micro electromechanical system to achieve the ejection of ink from the nozzle arrangement; and 
   control circuitry that is positioned on the carrier and is operatively connected to the printhead chips to control operation of the printhead chips. 
   According to a third aspect of the invention, there is provided a wide format pagewidth inkjet printer that comprises 
   a support structure; 
   a platen positioned in the support structure; 
   a print assembly positioned operatively with respect to the platen, the print assembly comprising
         an elongate carrier that is mounted on the support structure of the printer and is positioned an operative distance from the platen;   a number of printhead chips mounted on the carrier, the printhead chips being provided in a number and configuration such that the printhead chips define a printing zone between the carrier and the platen, the printing zone having a length of at least 36 inches (914 mm), each printhead chip being of the type that incorporates a plurality of nozzle arrangements, each nozzle arrangement being in the form of a micro electromechanical system to achieve the ejection of ink from the nozzle arrangement; and   control circuitry that is positioned on the carrier and is operatively connected to the printhead chips to control operation of the printhead chips; and       

   a feed mechanism that is positioned on the support structure for feeding a print medium though the printing zone. 

   
     The invention is now described, by way of example, with reference to the accompanying drawings. The following description is not intended to limit the broad scope of the above summary. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, 
       FIG. 1  shows a schematic, three-dimensional view of part of a printing mechanism of a print assembly, in accordance with the invention, of a printer, also in accordance with the invention; 
       FIG. 2  shows a front view of the printing mechanism of  FIG. 1 ; 
       FIG. 3  shows a rear view of the printing mechanism of  FIG. 1 ; 
       FIG. 4  shows a three dimensional, external view of the printer; 
       FIG. 5  shows a schematic, three-dimensional view of operative parts of the printer; 
       FIG. 6  shows a schematic, exploded view of the printer; 
       FIG. 7  shows a schematic, side sectioned view of a portion of the printer incorporating the print assembly; 
       FIG. 8  shows an exploded view of an operative portion of the printing mechanism; 
       FIG. 9  shows a cross sectional view of an operative portion of the printing mechanism; 
       FIG. 10  shows a high-level block diagram of an image processing apparatus of the print assembly; 
       FIG. 11  shows an expanded block diagram of a page expansion unit of the image processing apparatus; 
       FIG. 12  shows a block diagram of the image processing apparatus incorporating the page expansion unit; 
       FIG. 13  shows a schematic, three-dimensional view of part of a printhead chip of the print assembly of the printer, showing one nozzle arrangement of the printhead chip; and 
       FIG. 14  shows a schematic, three-dimensional view of a printhead module that incorporates a printhead chip. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In  FIG. 4 , reference numeral  10  generally indicates a printer, in accordance with the invention. 
   The printer  10  has a support structure  12  that supports a print assembly  14 , also in accordance with the invention, above a substrate. The support structure  12  includes a pair of spaced feet  16  and a leg  18  extending from each foot  16 . The print assembly  14  is mounted on the legs  18  to span the legs  18 . 
   A media tray  20  is positioned between the legs  18 . The media tray  20  is configured to store suitable print media, such as paper  22 . 
   The paper  22  is fed from a media feed mechanism in the form of a media roll  166  through the print assembly  14  and on to a take up spool  24 . An electronics enclosure  26  is also positioned between the legs  18  to enclose various electronic components that are described below. 
   The print assembly  14  includes a lid  28 , with a handle  30 , and a front cover  32 . The lid  28  and front cover  32  are positioned between a pair of end moldings  34 . 
   The print assembly  14  also includes a color TFT LCD  36  with touch screen navigation. A stop button  38  is also provided to enable a user to stop operation of the print assembly  14 . 
   The print assembly  14  and its various components are shown in further detail in the remaining Figures. 
   In  FIGS. 1 to 3 , reference numeral  40  generally indicates a printing mechanism of the print assembly  14 . As can be seen in the drawings, the printing mechanism  40  is segmented. In particular, the printing mechanism  40  includes an image processing apparatus, in accordance with the invention, that includes nine printed circuit boards (PCB&#39;s)  42  connected to each other with corresponding connector blocks  44 . 
   The printing mechanism  40  further includes a printhead  41  having seventy-two printhead modules  46 . Each PCB  42  is configured to control eight printhead modules  46 . It follows that nine PCB&#39;s  42  are provided. The printhead modules  46  are described in further detail below. 
   Each PCB  42  includes a print engine controller (PEC)  48 . The PEC&#39;s  48  are also described in further detail below. 
   Each PCB  42  also includes a memory storage device in the form of memory chips and more particularly in the form of 64 Mbit external DRAM chips  50 . The DRAM chips  50  cooperate with the PEC  48  in a manner that is described below. 
   Further, each PCB  42  includes a quality authentication (QA) chip  52 . Details of a suitable QA chip are set out in the above referenced U.S. Pat. No. 6,362,868 and are therefore not set out in this description. The QA chip  52  serves to inhibit unauthorized refilling of ink in the manner described in U.S. Pat. No. 6,362,868, in addition to other functions such as ensuring the quality of print media used with the printer  10 . 
   An endmost PCB  42  includes a serial connector  54  that permits serial data cables  56  to be connected to the PCB&#39;s  42 . 
   Each PCB  42  is connected to its associated printhead modules  46  with a flexible PCB  58 . 
   The printing mechanism  40  includes a metal chassis  60  that extends between a pair of side moldings  61  that are positioned in the end moldings  34 . The PCB&#39;s  42  are mounted on the chassis  60 . The chassis  60  has a generally U-shaped cross section. A channel  62  of an Invar alloy is positioned on the chassis  60 . 
   A chassis molding  64  of a plastics material is positioned on an outside of the chassis  60  and the channel  62 . Each PCB  42  is mounted on the chassis molding  64 . 
   The chassis molding  64  defines a pair of recesses  66  on an outer side of the chassis molding  64 . The recesses  66  extend a length of the chassis molding  64 . A busbar  68  is positioned in each recess  66 . The busbars  68  are configured to supply electrical power to the PCB&#39;s  42 . 
   An ink reservoir assembly  70  is positioned in the Invar channel  62 . The ink reservoir assembly  70  includes an ink distribution arrangement  72 . Each printhead module  46  is positioned on a respective ink distribution arrangement  72 . In particular, each printhead module  46  is removably mounted on its ink distribution arrangement  72  to facilitate removal and replacement when necessary. 
   The ink reservoir assembly  70  includes a plurality of ink reservoir moldings  76 . Each ink reservoir molding  76  corresponds with an associated printhead module  46 . The ink reservoir moldings  76  are positioned end-to-end along and within the Invar channel  62 . 
   Each ink reservoir molding  76  defines a plurality of elongate ink channels  74 , each accommodating a differently colored ink. Thus, effective elongate ink channels extend a length of the Invar channel  62 . 
   An end cap molding  78  is positioned on an endmost ink reservoir molding  76 . The end cap molding  78  has a plurality of connectors  80  defined thereon and in alignment with respective ink channels  74  when the end cap molding  78  is positioned on said endmost ink reservoir molding  76 . The connectors  80  are connectable to an ink hose connector  82 . The ink hose connector  82  is, in turn, connected to each of a plurality of ink hoses  84 . It follows that each hose  84  is in fluid communication with a respective ink channel  74 . Each hose  84  supplies the ink reservoir assembly  70  with ink of a particular color. For example, the hoses  84  can carry Cyan (C), Magenta (M), Yellow (Y) and Black (K) inks, respectively. In this case, four hoses  84  are provided. Also, each reservoir molding  76  defines four ink channels  74 . Alternatively, the hoses  84  can carry Cyan (C), Magenta (M), Yellow (Y), Red (R), Green (G) and Blue (B) inks, respectively. In this case, six hoses  84  are provided. Also, each reservoir molding  76  then defines six ink channels  74 . Instead of six differently colored inks, the six hoses  84  can carry CMYK and Infrared (IR) inks and a fixative (F) for high speed printing so that the inks can dry rapidly. 
   Each hose  84  is connected to a respective ink container  86  ( FIG. 5 ), so that each hose  84  is connected between an ink container  86  and a particular ink channel  74 . The hoses  84  are connected to their respective containers  86  with T-piece connectors  94  shown in  FIG. 1 . 
   The print assembly  14  includes a plurality of capping devices  88  that correspond with respective printhead modules  46 . Each capping device  88  is displaceable between an operative position in which it serves to cap its respective printhead module  46 , to inhibit drying of ink, and an inoperative position in which ink can be ejected from the printhead module  46 . A camshaft  90  is positioned in the chassis  60 . A translating member  92  interconnects the camshaft  90  and the capping devices  88 , so that rotational movement of the camshaft  90  results in reciprocal movement of the capping devices  88  between their operative and inoperative positions. 
   The camshaft  90  is driven with a suitable motor, indicated generally at  96  in  FIG. 5 . 
   Further detail of the print assembly  14  is shown in  FIG. 7 . As can be seen in this drawing, the front cover  32 , the lid  28  and a rear cover  98  together define a housing  100  for the print assembly  14 . 
   A plurality of ink cartridges  102  is positioned beneath the lid  28 . Each ink cartridge  102  stores one of the inks mentioned above. Each ink cartridge  102  is positioned between a pair of clips  104  so that it can be replaced when necessary. Each ink cartridge  102  and a respective ink reservoir  86  are in fluid communication with each other, when the ink cartridge  102  is received between the clips  104 . 
   A pair of platens, in the form of an upper platen  106  and a lower platen  108  is positioned within the housing  100 . A pair of spaced primary rollers in the form of an upper primary roller  110  and a lower primary roller  112  is provided to displace the paper  22  through the print assembly  14 . The upper roller  110  is positioned at an upper end of the platens  106 ,  108 , while the lower roller  112  is positioned between the platens  106 ,  108 . The rollers  110 ,  112  are configured to drive a sheet of the paper  22  over, consecutively, an inner surface of the lower platen  108  and an outer surface of the upper platen  106 . Thus, the paper  22  passes over the upper roller  110 , while the lower roller  112  is positioned between upwardly and downwardly moving portions of the paper  22 . 
   A brush  114  is pivotally mounted at  116  to the housing  100 . The brush  114  has an arcuate transverse profile that corresponds with the upper primary roller  110 . The brush  114  is positioned in the housing  100  so that the paper  22  can pass between the brush  114  and the housing  100 . 
   A pinch roller  118  is positioned downstream of the brush  114  to bear against the upper primary roller  110 . Thus, when the paper  22  is displaced from between the brush  114  and the upper primary roller  110 , the pinch roller  118  retains the paper  22  against lateral movement. 
   The upper platen  106  defines an upper printing zone  120  and a lower cutting zone  122 . A gap  124  is defined between the upper and lower printing zones  120 ,  122 . A plurality of spiked wheels  126  is partially received through the gap  124  to engage the paper  22  and the lower primary roller  112 . A crossbar  128  is operatively positioned with respect to the spiked wheels  126  to retain the spiked wheels  126  in position. The spiked wheels  126  and the pinch roller  118  are configured so that a suitable tension is set up in the paper  22  when the paper  22  passes over the printing zone  120  of the upper platen  106 . 
   The chassis  60  and channel  62  are positioned above the printing zone  120  of the upper platen  106 . The chassis  60  and the channel  62  are connected to a displacement mechanism  129  so that the chassis  60  and channel  62  can be displaced from the printing zone  120  when necessary. In particular, the chassis  60  and channel  62  are displaceable between an operative position in which the printhead modules  46  are a distance from the printing zone  120  that is suitable for printing and an inoperative position in which the paper  22  can be released from the printing zone  120 . 
   The chassis  60  and channel  62  are connected to the pinch roller  118  with suitable metalwork  130 . Further, the chassis  60  and channel  62  are connected to the crossbar  128 . It follows that, when the displacement mechanism  129  is operated, the pinch roller  118  and the spiked wheels  126  are displaced from the upper platen  106  together with the chassis  60  and the channel  62 . 
   The displacement mechanism  129  includes a camshaft  132  and a pusher  134 . The pusher  134  is connected to the chassis  60  and the channel  62  so that, upon rotation of the camshaft  132 , the chassis  60  and channel  62  are displaced towards and away from the printing zone of the upper platen  106 . 
   Upper idler rollers  136  are rotatably mounted above the upper platen  106  so that the paper  22  is received between the upper platen  106  and the upper idler rollers  136 . 
   A lower, sprung idler roller  138  is mounted on the lower platen  108  to be partially received through a gap  140  defined in the lower platen  108 . The sprung idler roller  138  is configured and positioned to bear against the lower primary roller  112 . Thus, an upwardly moving portion of the paper  22  is gripped, and passes between, the lower primary roller  112  and the sprung idler roller  138 . 
   The print assembly  14  includes a cutting mechanism  142  that is mounted in the housing  100  above the cutting zone  122  of the upper platen  106 . The cutting mechanism includes a cutter  146  that traverses the paper  22  to cut the paper  22 . The cutting mechanism  142  includes an optical sensor  144  so that the cutter  146  can be stopped when it reaches an end of a cutting stroke. The cutting zone  122  defines a cutting formation  148  that cooperates with the cutter  146  to facilitate cutting of the paper  22 . 
   As can be seen in  FIG. 6 , the print assembly  14  includes an air impeller  150  and a motor  152  to drive the air impeller  150 . The air impeller  150  serves to generate an air current within the housing  100  for cooling purposes. An air filter  153  is also positioned in the housing  100  to filter the air passing through the housing  100 . The air impeller  150  also serves to generate the air current to a sufficient extent to minimize the build up of dust on the printhead modules  46 . 
   As can further be seen in  FIG. 6 , the primary rollers  110 ,  112  are connected to a gearbox  154  that is mounted on a bracket  156 . The gearbox  154  and bracket  156  are positioned on one of the legs  18  and covered with one of the end moldings  34 . Thus, the primary rollers  110 ,  112  serve to drive the paper  22  through the print assembly  14 . 
   A printhead bracket  157  is positioned in the housing  100  and extends between the legs  18 . The printhead bracket  157  provides a support structure for the chassis  60  and channel  62 . The printhead bracket  157  also provides a support structure for the upper idler rollers  136 . 
   The housing  100  is shaped to define an opening  158  for passage of the paper  22  into and out of the print assembly  14 . Feed rollers  162  are rotatably mounted on a tie bar  160  that extends between the legs  18 . The feed rollers  162  are positioned so that the paper  22  passes over the feed rollers  162  when the paper is fed into the print assembly  14 . The tie bar  160  also serves a structural purpose in that it provides structural rigidity to the printer  10 . 
   Discharge rollers  164  are rotatably mounted on the upper platen  106 . The discharge rollers  164  are positioned so that the paper  22  passes over the discharge rollers  164  when the paper  22  is fed from the print assembly  14 . 
   Both the media roll  166  and the take up spool  24  are driven with a media roll drive motor  168  and a take up spool drive motor  170 , respectively ( FIG. 5 ). 
   The printer  10  includes a power supply unit  172  that is positioned in the electronics enclosure  26 . The power supply unit  172  is configured to be powered by either al 10V or 220V power supply. Further, the power supply unit  172  is configured so that up to 90 Amps can be drawn from the power supply unit  172 . The power supply unit  172  is connected with power cables  173  to various components of the printer  10 , such as the various drive motors to supply the components with required operational energy. 
   The printer  10  includes an ATX motherboard  174  that is also positioned in the electronics enclosure  26 . A printhead interface card  176  is mounted on the motherboard  174 . The printhead interface card  176  is connected to the nine PCB&#39;s  42  with suitable data cables  178 . Thus, conventional print data supplied to the interface card  176  from the motherboard  174  can be converted into a suitable form for reading by the various PCB&#39;s  42 . 
   The printer  10  includes a hard drive unit  180 . Conveniently, the hard drive unit  180  can have a capacity of 40 Gigabytes. This facilitates the storage of entire images to be printed. The hard drive unit  180  is connected to the motherboard  174  in a conventional fashion. The hard drive unit  180  is a conventional hard drive unit and is therefore capable of storing images in any number of formats, such as the well-known JPEG format. The manner in which the image data is read from the hard drive unit  180  is also conventional. As is set out below, printing of the images is digitally controlled as a result of the printhead technology utilized in this invention. It follows that transferal of image data from the hard drive unit  180  to the PCB&#39;s  42 , via the printhead interface card  176  can take place without the requirement of significant data transformation, in particular, without the requirement of digital to analogue signal conversion. 
   The interface card  176  is also connected to a motor and LCD controller PCB  182  to control operation of the various drive motors and the TFT LCD. Details of such control are set out in the above referenced applications and are therefore not provided in this description. The motor and LCD controller PCB  182  is connected to a cut off switch  184  that is, in turn, connected to the stop button  38  so that operation of the printer  10  can be halted. 
   As can be seen in  FIG. 14 , the printhead modules  46  each include a printhead chip  186 . The printhead chip  186  can be in the form of any of the printhead chips described in the above referenced applications/patents. Each printhead module  46  includes a carrier  187  in which the printhead chip  186  is positioned. The carrier  187  defines a suitable connection zone for the flexible PCB  58  associated with the printhead chip  186 .  FIG. 13  shows a schematic diagram of part of a printhead chip  186  that is suitable for use in the printer  10 . Each printhead module  46  includes what are known as on chip fiducials  258 . The on chip fiducials  258  are essentially in the form of markers to facilitate accurate alignment of the printhead modules  46  in the print assembly  14 . 
   The printhead chip  186  is described in detail in the above referenced U.S. Pat. No. 6,416,167 and will therefore not be described in such detail in this specification. Briefly, however, the chip  186  includes a wafer substrate  188 . A CMOS drive circuitry layer  190  is positioned on the wafer substrate  188  and is connected to the flexible PCB  58 . 
   A plurality of nozzle arrangements  210  is positioned on the CMOS drive circuitry layer  190 . For the purposes of convenience, one such nozzle arrangement  210  is shown in  FIG. 13 . The printhead chip  186  comprises a multiple replication of the nozzle arrangement  210  on the wafer substrate  188 . As set out in the above referenced applications and patents, the printhead chip  186  is the product of an integrated circuit fabrication technique. Replication of components in order to achieve a product is a well-known feature of such a fabrication technique. It follows that the printhead chip  186  can readily be understood by a person of ordinary skill in the field of chip fabrication. 
   Each nozzle arrangement  210  includes a thermal bend actuator  192  that is positioned on the CMOS layer  190  to receive an actuating signal from the CMOS layer  190 . In particular, the thermal bend actuator  192  includes a support post  194  that is mounted on the CMOS layer  190  to extend from the CMOS layer  190 . The thermal bend actuator  192  includes an actuator arm  196  that is fixed to, and extends from, the support post  194 . The actuator arm  196  includes a heating layer  198  in the form of an electrical heating circuit of a material having a coefficient of thermal expansion that is such that the material is capable of performing useful work on a MEMS scale as a result of expansion upon heating. The heating layer  198  is positioned on a layer  200  of a material having a coefficient of thermal expansion that is less than that of the heating layer  198  defining the electrical heating circuit. The heating layer  198  is positioned intermediate the layer  200  and the substrate  188  so that the actuator arm  196  is bent away from the substrate  188  when a current is passed through the heating layer  198 . 
   Nozzle chamber walls  202  are positioned on the CMOS layer  190 . A roof wall  204  is positioned on the nozzle chamber walls  202 . The nozzle chamber walls  202  and the roof wall  204  define a nozzle chamber  206 . The roof wall  204  defines an ink ejection port  208  from which ink is ejected, in use. 
   A paddle member  212  is mounted on the actuator arm  196  to extend into the nozzle chamber  206 . The paddle member  212  is configured and positioned in the nozzle chamber  206  so that, upon displacement of the actuator arm  196 , as described above, ink is ejected from the nozzle chamber  206 . 
   The actuator arm  196  is connected to the CMOS layer  190  through the support post  194  so that the heating layer  198  can receive an electrical signal from the CMOS layer  190 . 
   As can be seen in  FIGS. 3 and 9 , the printhead chips  186  are each positioned at an angle with respect to a straight line running the length of the printing zone  120 . This facilitates a measure of overlap at adjacent ends of the printhead chips  186  to ensure printing continuity. 
   It is clear from the above referenced United States applications and patents that a pagewidth printhead including printhead chips as described above can incorporate up to 84,000 nozzle arrangements. It follows that, by using the printhead chips  186 , it is possible for the print assembly  14  to have over as many as 200,000 nozzle arrangements. It follows that over 200,000 dots can be printed on the paper  22  in the printing zone  120 . In one particular example, the seventy-two printhead chips  186  provide a print width of 57.6 inches with 552 960 nozzle arrangements  210 . 
   The nozzle arrangements  210  of each chip  186  are positioned side-by-side in two rows in a staggered fashion. It follows that true 1600 dpi printing can be achieved with the printhead chips  186 . 
   Each printhead chip  186  therefore includes 7680 nozzle arrangements  210 . Each nozzle arrangement  210  is independently controlled by the PCB  42  to eject a 1-picolitre drop on demand. The integrated circuit fabrication technology used is based on Very Large Scale Integration (VLSI) technology that is fully described in the above referenced applications and patents. As a result of the manufacturing techniques used, each nozzle arrangement  210  can be as little as 32 microns wide. This allows each printhead chip  186  to have a surface area as little as 21 mm 2 . 
   The characteristics of each nozzle arrangement  210  are such that it is capable of being driven at a cyclical rate of up to 80 kHz by its associated PEC  48 . This permits printing of up to 21.6 billion drops per second that provides thirty-five thousand square feet per hour at 1600 dpi. 
   Each printhead chip  186  is connected to its associated PCB  42  with the flexible PCB  58 . It follows that each flexible PCB  58  is connected to the CMOS layer  190  of its associated printhead chip  186 . 
   Each PEC  48  is a page rendering engine application specific integrated circuit (ASIC) that receives input data relating to compressed page images from the printhead interface  176 . The PEC  48  produces decompressed page images at up to six channels of bi-level dot data as output. It will be appreciated that each PEC  48  communicates with eight printhead chips  186  in this example. Each PEC  48  is capable, however, of communication with up to sixteen such printhead chips  186 . In particular, each PEC  48  can address up to sixteen printhead chips in up to six color channels at 15,000 lines/sec. It follows that each PEC  48  allows for a 12.8-inch printhead width for full bleed printing of A3, A4 and letter pages. 
   Each PEC  48  is color space agnostic. This means that the PEC  48  can accept print data in any color. While each PEC  48  can accept contone data as CMYX or RGBX where X is an optional fourth channel, it can also accept contone data in any print color space. Additionally, each PEC  48  is configured to define a mechanism for arbitrary mapping of input channels to output channels. The PEC  48  is also configured for combining dots for ink optimization and the generation of channels based on any number of other channels. In this example, data input is typically based on CMYK for contone printing, K for a bi-level input, fixative, and optional further ink channels. The PEC  48  is also configured to generate a fixative channel for fast printing applications. 
   Each PEC  48  is configured to be resolution agnostic. This means that each PEC  48  simply provides a mapping between input resolutions and output resolutions by means of various scale factors. In this example, the expected output resolution is 1600 dpi. However, the PEC  48  does not store any data to this effect. 
   Each PEC  48  is also configured to be page-length agnostic. Each PEC  48  operates a printing band at a time and a page can have any number of bands. It follows that a “page” can have any reasonable length. 
   Each PEC  48  defines an interface so that it can be synchronized with other PEC&#39;s  48 , as is the requirement with this invention. This allows a simple two-PEC solution for simultaneous A3/A4/Letter duplex printing. This also allows each PEC  48  to be responsible for the printing of only a portion of a page. It will be appreciated that combining synchronization functionality with partial page rendering allows multiple PEC&#39;s to be readily combined for alternative printing requirements including simultaneous duplex printing, wide format printing, commercial printing, specialist high contone resolution printing, and printing applications where more than six ink channels are required. 
   The following table sets out the features of each PEC  48  and its associated benefits. 
   
     
       
             
           
             
             
           
         
             
               TABLE 1 
             
           
           
             
                 
             
             
               Features and Benefits of PEC 
             
           
        
         
             
               Feature 
               Benefits 
             
             
                 
             
             
               Optimized print 
               30 ppm full page photographic quality color 
             
             
               architecture in hardware 
               printing from a desktop PC 
             
             
               0.18 micron CMOS 
               High speed 
             
             
               (&gt;3 million transistors) 
               Low cost 
             
             
                 
               High functionality 
             
             
               1.8 billion dots per 
               Extremely fast page generation 
             
             
               second 
             
             
               15,000 lines per second 
               1.1 A4/Letter pages per PEC chip per second 
             
             
               at 1600 dpi 
             
             
               1 chip drives up to 
               Low cost page-width printers 
             
             
               122,880 nozzles 
             
             
               1 chip drives up to 6 
               99% of printers can use 1 chip per page 
             
             
               color planes 
             
             
               Sophisticated internal 
               Only requires 1 external memory, leading to 
             
             
               memory buffering and 
               low cost systems 
             
             
               caching 
             
             
               JPEG expansion 
               low bandwidth from PC 
             
             
                 
               low memory requirements in printer 
             
             
               Lossless bitplane 
               high resolution text and line art with low 
             
             
               expansion 
               bandwidth from PC (e.g. over USB) 
             
             
               Netpage tag expansion 
               Generates interactive paper 
             
             
               Stochastic dispersed dot 
               Optically smooth image quality 
             
             
               dither 
               No moire effects 
             
             
               Hardware compositor for 
               Pages composited in real-time 
             
             
               6 image planes 
             
             
               Dead nozzle 
               Extends printhead life and yield 
             
             
               compensation 
               Reduces printhead cost 
             
             
               Color space agnostic 
               Compatible with all inksets and image sources 
             
             
                 
               including RGB, CMYK, spot, CIE L*a*b*, 
             
             
                 
               hexachrome, YCrCbK, sRGB and other 
             
             
               Color space conversion 
               Higher quality/lower bandwidth 
             
             
               Computer interface 
               Works with USB1, USB2, IEEE1394 
             
             
               agnostic 
               (Firewire), ethernet, IEEE1284 (Centronics) 
             
             
               Variable page length 
               Print any page length (up to 64 km) 
             
             
               Cascadable in resolution 
               Printers of any resolution 
             
             
               Cascadable in color 
               Special color sets e.g. hexachrome can be used 
             
             
               depth 
             
             
               Cascadable in image size 
               Printers of any width 
             
             
               Cascadable in pages 
               Printers can print both sides simultaneously 
             
             
               Cascadable in speed 
               Very high speed printers can be built 
             
             
               Fixative channel data 
               Extremely fast ink drying without wasteage 
             
             
               generation 
             
             
               Built-in security 
               Revenue models are protected 
             
             
               Undercolor removal on 
               Reduced ink useage 
             
             
               dot-by-dot basis 
             
             
               Does not require fonts 
               No font substitution or missing fonts 
             
             
               for high speed operation 
             
             
               Flexible printhead 
               Many configurations of printheads are 
             
             
               configuration 
               supported by one chip type 
             
             
               Drives Memjet ™ 
               No print driver chips required, results in lower 
             
             
               printheads directly 
               cost 
             
             
               Determines dot accurate 
               Removes need for physical ink monitoring 
             
             
               ink usaege 
               system in ink cartridges 
             
             
                 
             
           
        
       
     
   
   In  FIG. 10 , there is shown a block diagram of the PEC  48 . The PEC  48  includes a micro controller interface in the form of a high-speed interface  214  through which an external micro controller  216  can write to the 64 Mbit DRAM chip  50 . The high-speed interface  214  forms part of a data input means of the PEC  48 . 
   The PEC  48  also includes a control circuitry interface in the form of a low speed serial interface  220  through which the micro controller  216  can access registers of the PEC  48  and the DRAM chip  50 . 
   The PEC  48  also includes page expansion circuitry in the form of a page expansion unit (PEU)  222  that receives data relating to compressed pages and renders it into data relating to bi-level dots. Line loader and line formatter circuitry in the form of a line loader/formatter unit  224  is also provided that formats dots for a given print line destined for a printhead interface  226  that communicates directly with the printhead chips  186  of each printhead module  46 . 
   As can be seen, the PEC  48  performs three basic tasks. These are:
         a) Accepting register and DRAM access commands via the low speed interface  220  (or from the external DRAM chip  50 ).   b) Accepting DRAM write accesses (typically compressed page bands and register command blocks) via the high speed interface  214 .   c) Rendering page bands from the external DRAM chip  50  to the printhead chips  186 .       

   These tasks are independent. However, they do share the external DRAM chip  50 . It follows that arbitration is required. The PEC  48  is configured so that DRAM accesses required for rendering page bands always have the highest priority. 
   The PEC  48  includes control circuitry in the form of a PEC controller  228  that provides external clients with the means to read and write PEC registers, and read and write DRAM in single 32 bit data chunks. 
   The DRAM chip  50  is connected to memory storage control circuitry in the form of an SDRAM controller  234 . In turn, the SDRAM controller  234  is connected to memory storage control circuitry in the form of a DRAM interface unit  236 . 
   The PEC  48  includes a data bus  230  and a low speed serial bus  232 . Both the SDRAM controller  234  and the DRAM interface unit  236  are connected to the low speed serial bus  232 . The PEC controller  228  is connected to the data bus  230 . The PEC controller  228  is also connected to the low speed serial bus  232  via the low speed interface  220 . The high-speed interface  214 , the PEU  222  and the line loader/formatter unit are also connected to the data bus  230 . 
   In use, since the PEC  48  prints page bands from DRAM, a given band B is loaded into DRAM via the high-speed interface  214  before printing can begin. Then, while the PEC  48  is rendering band B via the PEU, band B+1 can be loaded to DRAM. While band B+1 is being expanded and printed, band B+2 can be loaded, and so on. 
   In the following table, the various components of the PEC  48  mentioned above are described briefly. 
   
     
       
             
           
             
             
             
             
           
         
             
               TABLE 2 
             
           
           
             
                 
             
             
               Units within PEC (high level) 
             
           
        
         
             
               unit 
                 
               reference 
                 
             
             
               acronym 
               unit name 
               numeral 
               description 
             
             
                 
             
             
               DIU 
               DRAM 
               236 
               Provides the interface for 
             
             
                 
               interface 
                 
               DRAM read and write access 
             
             
                 
               unit 
                 
               for the various PEC units. 
             
             
                 
                 
                 
               The DIU provides arbitration 
             
             
                 
                 
                 
               between competing units and 
             
             
                 
                 
                 
               passes on DRAM requests to 
             
             
                 
                 
                 
               the SCU. 
             
             
               HSI 
               High speed 
               214 
               Provides external clients 
             
             
                 
               interface 
                 
               (such as the microcontroller) 
             
             
                 
                 
                 
               with the means to write to 
             
             
                 
                 
                 
               DRAM. 
             
             
               LLFU 
               Line loader 
               224 
               Reads the expanded page image 
             
             
                 
               formatter 
                 
               from line store, formatting 
             
             
                 
               unit 
                 
               the data appropriately for 
             
             
                 
                 
                 
               the Memjet printhead. 
             
             
               LSI 
               Low speed 
               220 
               Provides external clients 
             
             
                 
               interface 
                 
               with the means to send 
             
             
                 
                 
                 
               commands to the PCU and 
             
             
                 
                 
                 
               receive register reads. 
             
             
               PCU 
               PEC 
               228 
               Provides external clients 
             
             
                 
               controller 
                 
               with the means to read and 
             
             
                 
                 
                 
               write PEC registers, and 
             
             
                 
                 
                 
               read and write DRAM in 
             
             
                 
                 
                 
               single 32-bit chunks. 
             
             
               PEU 
               Page 
               222 
               Reads compressed page data 
             
             
                 
               expansion 
                 
               and writes out the 
             
             
                 
               unit 
                 
               decompressed form of the 
             
             
                 
                 
                 
               same to DRAM. 
             
             
               PHI 
               Printhead 
               226 
               Is responsible for sending 
             
             
                 
               interface 
                 
               dot data to the Memjet 
             
             
                 
                 
                 
               printhead segments and for 
             
             
                 
                 
                 
               providing line synchroniza- 
             
             
                 
                 
                 
               tion between multiple PECs. 
             
             
               SCU 
               SDRAM 
               234 
               Provides the DIU with access 
             
             
                 
               controller 
                 
               to the external DRAM. 
             
             
                 
               unit 
             
             
                 
             
           
        
       
     
   
   An expanded block diagram of the PEU  222  is shown in  FIG. 11 . In the following table, the various components of the PEU  222  are described briefly. 
   
     
       
             
           
             
             
             
             
           
         
             
               TABLE 3 
             
           
           
             
                 
             
             
               Units within Page Expansion Unit (high level) 
             
           
        
         
             
               unit 
                 
               reference 
                 
             
             
               acronym 
               unit name 
               numeral 
               description 
             
             
                 
             
             
               CDU 
               Contone 
               238 
               Expands JPEG compressed 
             
             
                 
               decoder 
                 
               contone layer and writes 
             
             
                 
               unit 
                 
               decompressed contone to 
             
             
                 
                 
                 
               DRAM 
             
             
               CLBI 
               Contone line 
               240 
               Provides line buffering 
             
             
                 
               buffer 
                 
               between CRU and HCU 
             
             
                 
               interface 
             
             
               CRU 
               Contone 
               242 
               Reads expanded contone 
             
             
                 
               reader unit 
                 
               image from DRAM 
             
             
               DNC 
               Dead nozzle 
               244 
               Compensates for dead 
             
             
                 
               compensator 
                 
               nozzles by error 
             
             
                 
                 
                 
               diffusing dead nozzle 
             
             
                 
                 
                 
               data into surrounding 
             
             
                 
                 
                 
               dots. 
             
             
               DWU 
               Dotline 
               246 
               Writes out the 6 channels 
             
             
                 
               writer unit 
                 
               of dot data for a given 
             
             
                 
                 
                 
               printline to the line 
             
             
                 
                 
                 
               store DRAM 
             
             
               HCU 
               Halftoner 
               248 
               Dithers contone layer 
             
             
                 
               compositor 
                 
               and composites the bi- 
             
             
                 
               unit 
                 
               level spot 0 and 
             
             
                 
                 
                 
               position tag dots. 
             
             
               LBD 
               Lossless 
               250 
               Expands compressed 
             
             
                 
               bilevel 
                 
               bi-level layer. 
             
             
                 
               decoder 
             
             
               SLBI 
               Spot line 
               252 
               Provides line buffering 
             
             
                 
               buffer 
                 
               between LBD and HCU 
             
             
                 
               interface 
             
             
               TE 
               Tag encoder 
               254 
               Encodes tag data into 
             
             
                 
                 
                 
               line of tag dots. 
             
             
               TLBI 
               Tag line 
               256 
               Provides line buffering 
             
             
                 
               buffer 
                 
               between TE and HCU 
             
             
                 
               interface 
             
             
                 
             
           
        
       
     
   
   A first stage in page expansion occurs along a pipeline defined by the CDU  238 /CRU  242 , the LBD  250  and the TE  254 . The CDU  238  expands a JPEG-compressed contone (typically CMYK) layer. The LBD  250  expands a compressed bi-level layer (typically K), and the TE  254  encodes data tags for rendering (typically in IR or K ink) at a later stage. The CLBI  240 , the SLBI  252  and the TLBI  256  receive output data from this stage. 
   The HCU  248  carries out a second stage. The HCU  248  dithers a contone layer and composites position tags and a bi-level spot 0  layer over a resulting bi-level dithered layer. A data stream generated by the HCU  248  is adjusted to create smooth transitions across overlapping segments or printhead chips  186 . The HCU  248  is configured so that a number of options exist for the way in which compositing occurs. This stage can produce up to six channels of bi-level data. It should be noted that not all six channels might be present on the printhead chips  186 . For example, the printhead chips  186  may be CMY only, with K pushed into the CMY channels and IR ignored. Alternatively, the position tags mentioned above may be printed in K if IR ink is not available or for testing purposes. 
   The DNC  244  carries out a third stage. In this stage, the DNC  244  compensates for dead nozzles in the printhead chips  186  by error diff-using dead nozzle data into surrounding dots. 
   Bi-level, six channel dot-data (typically CMYK-IRF) generated in the above stages is buffered and written out to a set of line buffers stored in the off-chip DRAM via the DWU  246 . 
   In a final stage, the dot-data is loaded back from the DRAM, formatted for the printhead, and passed to the printhead interface  226  via a dot FIFO (not shown). The dot FIFO accepts data from the line loader/formatter unit  224  at pclk rate, while the printhead interface  226  removes data from the FIFO and sends it to the printhead chips  186  at a rate of either pclk/4, pclk/2 or pclk. 
     FIG. 12  simply shows the PEC  48  incorporating the exploded PEU  222 . 
   The printing benefits associated with the printhead chips  186  are set out in detail in the above referenced applications and patents. However, some benefits are particularly important when applied to wide printing formats. 
   A particular benefit is the high number of nozzle arrangements  210  per printhead chip  186 . This facilitates extremely rapid printing in that a single print cycle can achieve an image band. It follow that it is not necessary for further print cycles to be used to fill in “missing” dots as is the case with a scanning printhead. 
   The PEC&#39;s  48  provide the necessary synchronized control of the printhead chips  186  as described above. Furthermore, as is clear from a number of the above referenced applications and patents, for example U.S. Pat. No. 6,362,868, the printhead chips  186  allow for the conversion from analogue printing processes to fully digital processes. This allows for a substantial amount of flexibility and speed. Digital control of the printhead chips  186  is by means of the PEC&#39;s  48 . The fact that the PEC&#39;s  48  digitally control the printhead chips  186  allows for the high printing speed of up to 21.6 billion drops per second. In particular, the need for separate printhead chip drivers is removed, which is key to the high printing speed of the chips  186 . 
   The incorporation of the CMOS layer  190  serves to integrate CMOS technology with MEMS technology on each printhead chip  186 . It follows that at least one off-chip connection for each nozzle arrangement  210  is not required. It will be appreciated that such a requirement would make a printhead unreliable and cost-prohibitive to manufacture. 
   A further important advantage associated with the printer  10  is that a width of the printing zone  120  is extremely small when compared to the length. In a particular example, the printing zone  120  can be as little as 0.5 mm thick. It will be appreciated that it is necessary to achieve extremely stable paper movement through the printing zone  120  in order to ensure that accurate printing takes place in the printing zone. The narrow width of the printing zone  120  facilitates minimal control over the paper  22  as it passes through the printing zone. 
   In the event that a substantially wider printing zone were provided, it would be necessary to provide further control over movement of the paper  22  through such a printing zone. This would require such devices as vacuum platens to retain the paper  22  against any form of pivotal or lateral movement as the paper  22  moves through the printing zone. This could greatly increase the cost of the wide format printer. 
   This highlights some reasons why thermal or bubble jet and piezoelectric printheads would not be practical choices when attempting to achieve the printing characteristics of the printer  10 . As set out in the above referenced applications and patents, such printheads are not suitable for providing the high density of nozzle arrangements achieved with the printheads of the above referenced matters. It follows that, in attempting to apply thermal and piezoelectric printheads to a wide format printer, it would be necessary to have a relatively wide printing zone so that overlapping of printheads could occur to the necessary extent. This would immediately raise the problem mentioned above. Still further, especially with the thermal printheads, a suitable cooling system would be required to keep the temperature in the printing zone at a reasonable level. This would also increase the cost to an unacceptably high level. 
   In order to achieve an appreciation of the speed of the printer  10  at a resolution of 1600 dpi, the following comparative table is set out below. It should be noted that the purpose of the following table is simply to illustrate the speed of printing and is not intended to denigrate the various printers used for comparison. 
   
     
       
             
           
             
             
             
             
             
             
             
             
             
           
             
             
             
             
             
             
           
             
             
             
             
             
             
             
             
             
             
             
             
           
         
             
                 
             
             
               Wide Format Printers 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               Memjet 
               OEM Printhead Print Width (inches) 
               38.4 
               44.8 
               51.2 
               57.6 
               64.0 
               70.4 
               76.8 
             
             
                 
               Number of Printhead Chips 
               48 
               56 
               64 
               72 
               80 
               88 
               96 
             
             
                 
               Number of Nozzles 
               368,640 
               430,080 
               491,520 
               552,960 
               614,400 
               675,840 
               737,280 
             
             
                 
               Max. print speed (sq ft/hr at 1600 × 1600 dpi) 
               17,578 
               20,508 
               23,438 
               26,367 
               29,297 
               32,227 
               35,156 
             
             
                 
             
           
        
         
             
                 
               Make 
               Model 
               Resolution 
               Speed 
               Speed Advantage (# of times faster) 
             
             
                 
                 
             
           
        
         
             
               Com- 
               HP 
               1000/5000 
               600 × 600 
               120 
               146 
               171 
               195 
               220 
               244 
               269 
               293 
             
             
               parison 
               HP 
               3000/3500 
               600 × 300 
               72 
               244 
               285 
               326 
               366 
               407 
               448 
               488 
             
             
                 
               Epson 
               7000/10000 
               720 × 720 
               90 
               195 
               228 
               260 
               293 
               326 
               358 
               391 
             
             
                 
               Encad 
               Novajet 800 
               600 × 600 
               96 
               183 
               214 
               244 
               275 
               305 
               336 
               366 
             
             
                 
               Gretag 
               Arizona 
               Draft mode 
               444 
               40 
               46 
               53 
               59 
               66 
               73 
               79 
             
             
                 
               Gretag 
               Arizona 
               309 × 618 
               220 
               80 
               93 
               107 
               120 
               133 
               146 
               160 
             
             
                 
               Colorspan 
               Mach X11 
               600 × 600 
               115 
               153 
               178 
               204 
               229 
               255 
               280 
               306 
             
             
                 
               Canon 
               BJW 9000 
               600 × 1200 
               72 
               244 
               285 
               326 
               366 
               407 
               448 
               488 
             
             
                 
               Mutoh 
               Albatross 
               792 × 792 
               65 
               270 
               316 
               361 
               406 
               451 
               496 
               541 
             
             
                 
               Roland 
               HiFi Jet 
               720 × 720 
               96 
               183 
               214 
               244 
               275 
               305 
               336 
               366 
             
             
                 
               Nur 
               Fresco 
               360 × 360 
               300 
               59 
               68 
               78 
               88 
               98 
               107 
               117 
             
             
                 
             
           
        
       
     
   
   As is known by those of skill in the fabrication of integrated circuits, while a set up cost for the manufacture of an integrated circuit device can be high, the cost of commercial manufacture of such devices is relatively low. It follows that Applicant envisages that the cost of manufacture of a wide format printer in accordance with this invention will be comparable to the cost of manufacture of the wide format printers listed in the above table. 
   It will be apparent to those skilled in the art that many obvious modifications and variations may be made to the embodiments described herein without departing from the spirit or scope of the invention.