Patent Publication Number: US-7901032-B2

Title: Printer having moveable printhead and capping/purging member

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 11/778,563 filed Jul. 16, 2007, which is a continuation of U.S. application Ser. No. 11/003,601 filed on Dec. 6, 2004, now issued as U.S. Pat. No. 7,255,419, all of which are herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates in general terms to an inkjet printer and, in particular to pagewidth printhead assemblies with associated capping mechanisms and or nozzle purging systems. By “pagewidth” printhead assembly it is meant an assembly having a printhead with a length which extends across substantially the full width of the media (paper, card, textile or other) to be printed and which, whilst remaining in a stationary position, is controlled to deposit printing ink across the full print width of advancing print media. 
     CO-PENDING APPLICATIONS 
     The following applications have been filed by the Applicant simultaneously with U.S. application Ser. No. 11/778,563: 
     
       
         
           
               
               
               
               
               
               
             
               
                   
               
             
            
               
                 7,364,256 
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                 7,258,416 
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                 11/003,614 
                 7,284,820 
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     The disclosures of these co-pending applications are incorporated herein by reference. 
     CROSS REFERENCES TO RELATED APPLICATIONS 
     The following patents or patent applications filed by the applicant or assignee of the present invention are hereby incorporated by cross-reference. 
     
       
         
           
               
               
               
               
               
             
               
                   
               
             
            
               
                 6,623,101 
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     BACKGROUND OF THE INVENTION 
     Inkjet printers have a series of nozzles from which individual ink droplets are ejected to deposit on print media to form desired printed images. The nozzles are incorporated in various types of printheads and their proper functioning is critical to the creation of quality images. Thus, any partial or total blockage of even a single nozzle may have a significant impact on a printed image, particularly in the case of a pagewidth printer. 
     The nozzles are prone to blockage due to their exposure to ever-present paper dust and other particulate matter and due to the tendency of ink to dry in the nozzles during, often very short, idle periods. Prior to ejection, the ink forms a meniscus at the nozzle opening. Exposure to air (frequently warm) evaporates the ink solvent to leave a solid deposit that can block the nozzle. 
     Servicing systems are conventionally employed for maintaining the functionality of printheads. Such systems provide capping, purging and or wiping. Capping involves the covering of idle nozzles to preclude exposure of ink to drying air. Purging is normally effected by evacuating a capping chamber, thereby sucking deposits from the printhead that block or have the potential to block the nozzles. Wiping is performed in conjunction with the capping and/or purging functions and involves gently sweeping a membrane across the face of the printhead. 
     Most conventional inkjet printers use a reciprocating printhead which is traverses across the width of a momentarily stationary page or portion of print media. In these printers, service stations are provided at one side of the printing zone and, on command, the printhead is traversed to the service station where it is docked while servicing is performed and or the printer is idle. 
     The above described servicing system is not feasible for pagewidth printers because of the stationary printhead assembly that extends across the full width of the printing zone. The printhead assembly effectively defines the print zone and it cannot be moved outside of that zone for servicing. Furthermore, a pagewidth printhead has a significantly larger surface area and contains a vastly greater number of nozzles than a conventional inkjet printhead, especially in the case of a large format printer. These factors dictate that the servicing of printheads requires an entirely different approach to that of conventional scanning type printheads. 
     SUMMARY OF THE INVENTION 
     In a first aspect the present invention provides an inkjet printer comprising:
         at least one pagewidth printhead having a plurality of ink ejection nozzles;   a capping/purging member having a length corresponding substantially to that of the printhead;   a first actuating mechanism arranged to move the printhead in an arcuate first direction between first, second and third positions; and   a second actuating mechanism arranged to move the capping/purging member in an arcuate second direction opposite to the first direction to cap the nozzles of the printhead when the printhead is in the second position and to permit purging of ink from the nozzles when the printhead is in the third position.       

     Optionally, the capping/purging member is formed effectively as a one-piece member. 
     Optionally, the capping/purging member comprises conjoined member portions having an aggregate length corresponding substantially to that of the printhead. 
     Optionally, the capping/purging member comprises a body portion, a lip portion formed from an elastomeric material, a capping cavity surrounded by the lip portion, and a purging chamber surrounded by the lip portion. 
     Optionally, the purging chamber is connected to a suction device. 
     Optionally, the printer comprises two opposed pagewidth printheads, wherein the first actuating mechanism is arranged to effect relative movement of the printheads between the first and second positions and the second actuating mechanism is arranged to interpose the capping/purging member between the printheads when the printheads are in the second position. 
     Optionally, the printheads are offset. 
     Optionally, the printer comprises a carrier positioned adjacent the printhead which carries the capping/purging member, wherein the second actuating mechanism is arranged to pivot the carrier to move the capping/purging member. 
     Optionally, the capping/purging member comprises a lip portion that is formed integrally with a body portion, and a cavity surrounded by the lip portion, the lip portion being peripherally configured to surround the nozzles on the printhead and the body portion having a length corresponding substantially to that of the printhead. 
     An illustrative embodiment of the 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 diagrammatic representation of a printer that incorporates a printhead assembly having two substantially identical printheads, 
         FIG. 2  shows a perspective view of one of the printheads as seen in the direction of a printing zone of the printhead, 
         FIG. 3  shows a sectional end view of one of the printheads, 
         FIG. 4  shows a perspective view of an end portion of a channelled support member removed from the printhead of  FIG. 3  and fluid delivery lines connected to the support member, 
         FIG. 5  shows an end view of connections made between the fluid delivery lines and the channelled support member of  FIG. 4 , 
         FIG. 6  shows a printed circuit board, with electronic components mounted to the board, when removed from a casing portion of the printhead of  FIG. 3 , 
         FIGS. 7A , B and C show in block diagrammatic form a capping mechanism that is applicable to a printhead assembly having two printheads, 
         FIG. 8  shows a perspective view of a capping member of a type suitable for use in the mechanism shown in  FIGS. 7A , B and C, 
         FIGS. 9A , B and C show in block diagrammatic form a capping mechanism that is applicable to a printhead assembly having two printheads, 
         FIGS. 10A , B and C show in block diagrammatic form a capping mechanism that is applicable to a printhead assembly having two printheads, 
         FIG. 11  shows a perspective view of a capping member of a type suitable for use in the mechanisms shown in  FIGS. 10A , B and C, 
         FIGS. 12A  and B show in block diagrammatic form a capping mechanism that is applicable to a printhead assembly having a single (Simplex) printhead, 
         FIGS. 13A  and B show in block diagrammatic form a capping/purging mechanism that is applicable to a printhead assembly having a single (Simplex) printhead, 
         FIGS. 14A  and B show in block diagrammatic form a capping mechanism that is applicable to a printhead assembly having an offset duplex printhead arrangement, 
         FIGS. 15A  and B show in block diagrammatic form a capping mechanism that is applicable to a printhead assembly having a single (Simplex) printhead, 
         FIGS. 16A  and B show in block diagrammatic form a capping/purging mechanism that is applicable to a printhead assembly having a single (Simplex) printhead, 
         FIGS. 17A , B and C show in block diagrammatic form a capping mechanism that is applicable to a printhead assembly having two printheads, 
         FIGS. 18A , B, C and D show in block diagrammatic form a capping/purging mechanism that is applicable to a printhead assembly having two pagewidth printheads, 
         FIG. 19  shows a perspective view of a capping/purging member of a type suitable for use in the mechanism shown in  FIGS. 18A  to D, 
         FIGS. 20A  and B show in block diagrammatic form a turret mounted capping/purging mechanism that is applicable to a printhead assembly having a single printhead, 
         FIG. 21  shows a perspective view of a capping member of a type suitable for use in the mechanism shown in  FIGS. 20A  and B, 
         FIGS. 22A  and B show in block diagrammatic form a turret mounted capping/purging mechanism that is applicable to a printhead assembly having a single printhead, 
         FIG. 23  shows a perspective view of a capping member of a type suitable for use in the mechanism shown in  FIGS. 22A  and B, 
         FIGS. 24A , B and C show in block diagrammatic form a capping/purging mechanism that is applicable to a printhead assembly having a single printhead, 
         FIG. 25  shows a perspective view of a capping member of a type suitable for use in the mechanism shown in  FIGS. 24A  and B, 
         FIGS. 26A  and B show in block diagrammatic form an embodiment of the capping mechanism, being one that is applicable to a printhead assembly having two printheads, 
         FIGS. 27A  and B show in block diagrammatic form an embodiment of the capping mechanism, being one that is applicable to a printhead assembly having two printheads, 
         FIGS. 28A  and B show in block diagrammatic form an embodiment of the capping mechanism, being one that is applicable to a printhead assembly having two printheads, 
         FIGS. 29A , B and C show in block diagrammatic form a capping mechanism that is applicable to a printhead assembly having two printheads, and 
         FIG. 30  shows a perspective view of a capping member of a type suitable for use in the mechanisms shown in  FIGS. 29A , B and C. 
         FIG. 31  shows, in perspective, a sectional view of a portion a printhead chip that is mounted to the printhead and which incorporates printing fluid delivery nozzles and nozzle actuators, 
         FIG. 32  shows a vertical section of a single nozzle in a quiescent state, 
         FIG. 33  shows a vertical section of a single nozzle in an initial activation state, 
         FIG. 34  shows a vertical section of a single nozzle in a later activation state, 
         FIG. 35  shows a perspective view of a single nozzle in the activation state shown in  FIG. 34 , 
         FIG. 36  shows in perspective a sectioned view of the nozzle of  FIG. 13 , 
         FIG. 37  shows a sectional elevation view of the nozzle of  FIG. 13 , 
         FIG. 38  shows in perspective a partial sectional view of the nozzle of  FIG. 33 , 
         FIG. 39  shows a plan view of the nozzle of  FIG. 32 , 
         FIG. 40  shows a view similar to  FIG. 39  but with lever arm and moveable nozzle portions omitted, 
         FIG. 41  illustrates data flow and functions performed by a print engine controller (“PEC”) that forms one of the circuit components shown in  FIG. 6 , 
         FIG. 42  illustrates the PEC of  FIG. 41  in the context of an overall printing system architecture, and 
         FIG. 43  illustrates the architecture of the PEC of  FIG. 41 . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT 
     As illustrated in  FIG. 1 , a pagewidth printhead assembly  50  composed of two substantially identical pagewidth printheads  51  is mounted within a printer  52 , although it will be understood from the following description that the printhead assembly might comprise a single printhead. The printer is shown in outline because it may be constituted by any one of a large number of printer types; including desk-top, office, commercial and wide format printers. Also, the printer may incorporate a single sheet feed system or a roll-feed system for print media (not shown), and it may be arranged for printing alpha-numeric, graphical or decorative images, the latter being relevant to the printing of textiles and wall coverings. 
     Each of the printheads  51  may, for example, be in the form of that which is described in the Applicant&#39;s co-pending U.S. Patent Applications listed in the cross-references section above and all of which are incorporated herein by reference. But other types of pagewidth printheads (including thermal or piezo-electric activated bubble jet printers) that are known in the art may alternatively be employed. 
     As illustrated in  FIGS. 2 to 6  for exemplification purposes, each of the printheads  51  comprises four printhead modules  55 , each of which in turn comprises a unitary arrangement of: 
     a) a plastics material support member  56 , 
     b) four printhead micro-electro-mechanical system (MEMS) integrated circuit chips  57  (referred to herein simply as “printhead chips”), 
     c) a fluid distribution arrangement  58  mounting each of the printhead chips  57  to the support member  56 , and 
     d) a flexible printed circuit connector  59  for connecting electrical power and signals to each of the printhead chips  57 . 
     However, it will be understood that each of the printheads  51  may comprise substantially more than four modules  55  and/or that substantially more than four printhead chips  57  may be mounted to each module. 
     Each of the chips (as described in more detail later) has up to 7680 nozzles formed therein for delivering printing fluid onto the surface of the print media and, possibly, a further 640 nozzles for delivering pressurised air or other gas toward the print media. 
     The four printhead modules  55  are removably located in a channel portion  60  of a casing  61  by way of the support member  56 , and the casing contains electrical circuitry  63  mounted on four printed circuit boards  62  (one for each printhead module  55 ) for controlling delivery of computer regulated power and drive signals by way of flexible PCB connectors  63   a  to the printhead chips  57 . As illustrated in  FIGS. 1 and 2 , electrical power and print activating signals are delivered to one end of the two printheads  51  by way of conductors  64 , and printing ink and air are delivered to the other end of the two printheads by fluid delivery lines  65 . 
     The printed circuit boards  62  are carried by plastics material mouldings  66  which are located within the casing  61  and the mouldings also carry busbars  67  which in turn carry current for powering the printhead chips  57  and the electrical circuitry. A cover  68  normally closes the casing  61  and, when closed, the cover acts against a loading element  69  that functions to urge the flexible printed circuit connector  59  against the busbars  67 . 
     The four printhead modules  55  may incorporate four conjoined support members  56  or, alternatively, a single support member  56  may be provided to extend along the full length of the printhead  51  and be shared by all four printhead modules. That is, a single support member  56  may carry all sixteen printhead chips  57 . 
     As shown in  FIGS. 3 and 4 , the support member  56  comprises an extrusion that is formed with seven longitudinally extending closed channels  70 , and the support member is provided in its upper surface with groups  71  of millimetric sized holes. Each group comprises seven separate holes  72  which extend into respective ones of the channels  70  and each group of holes is associated with one of the printhead chips  57 . Also, the holes  72  of each group are positioned obliquely across the support member  56  in the longitudinal direction of the support member. 
     A coupling device  73  is provided for coupling fluid into the seven channels  70  from respective ones of the fluid delivery lines  65 . 
     The fluid distribution arrangements  58  are provided for channelling fluid (printing ink and air) from each group  71  of holes to an associated one of the printhead chips  57 . Printing fluids from six of the seven channel  70  are delivered to twelve rows of nozzles on each printhead chip  57  (ie, one fluid to two rows) and the millimetric-to-micrometric distribution of the fluids is effected by way of the fluid distribution arrangements  58 . For a more detailed description of one arrangement for achieving this process reference may be made to the co-pending U.S. Patent Applications referred to previously. 
     An illustrative embodiment of one printhead chip  57  is described in more detail, with reference to  FIGS. 9 to 18 , toward the end of this drawing-related description; as is an illustrative embodiment of a print engine controller for the printheads  51 . The print engine controller is later described with reference to  FIGS. 19 to 21 . 
     A print media guide  74  is mounted to each of the printheads  51  and is shaped and arranged to guide the print media past the printing zone, as defined collectively by the printhead chips  57 , in a manner to preclude the print media from contacting the nozzles of the printhead chips. 
     The fluids to be delivered to the printheads  51  will be determined by the functionality of the printer  52 . However, as illustrated, provision is made for delivering six printing fluids and air to the printhead chips  57  by way of the seven channels  70  in the support member  56 . The six printing fluids may comprise: 
     Cyan (C) printing ink 
     Magenta (M) printing ink 
     Yellow (Y) printing ink 
     Black (K) printing ink 
     Infrared (IR) ink 
     Fixative. 
     The filtered air will in use be delivered at a pressure slightly above atmospheric from a pressurised source (not shown) that is integrated in the printer. 
     Having identified the salient features of the pagewidth printheads, different aspects and embodiments will now be illustrated diagrammatically with reference to the capping arrangements shown in  FIGS. 7A to 30 . In the different aspects shown, the same reference numerals have been used to denote features that are similar or have some concordance with corresponding features in the other aspects. 
     In the mechanism shown in  FIG. 7A , two (duplex) printheads  51  are located adjacent one another and together define a gap  80  through which print media is transported in the direction indicated by arrow  81 . However, it will be understood that the invention may be applied equally to a printer having a single printhead. 
     Two capping members  82  are located adjacent the printheads and are inclined at an angle of approximately 40 degrees to the direction of print media feed. 
     When capping is required, for example between successive print runs, the printheads  51  are turned in an arcuate direction through  40  degrees to the position shown in  FIG. 7B . Thereafter, the capping members  82  are moved rectilinearly, in the directions of arrows  83 , to the positions shown in  FIG. 7C  where the capping members are located in nozzle capping engagement with the printhead chips  57  on each of the printheads  51 . 
     Actuating mechanisms  84  and  85 , as shown in block diagrammatic form in  FIGS. 7B and 7C , are employed for effecting the described movements of the printheads  51  and capping members  82 . These mechanisms may comprise geared motor drives, pneumatic actuators or other such mechanisms as are known in the art for effecting movement of relatively small mechanical devices. 
     With the mechanism as illustrated in  FIGS. 7A to 7C , the print media may be maintained in position between the printheads  51  during the capping operation. Also, the capping members  82  are moved in directions normal to the respective printheads  51 , thereby avoiding any potential for rubbing between the capping members and the printing zone of the printheads. 
     Each of the capping members  82  has a configuration as shown in  FIG. 8  or an adaptation of that configuration. Thus, each of the capping members  82  comprises a body portion  100  and, moulded onto or otherwise secured to the body portion, a capping portion having an integrally formed lip portion  101  which surrounds a cavity  102 . The body portion  100  is formed from a metal such as aluminium or from a rigid plastics material, and the capping portion (including the lip portion  101 ) is formed from an elastomeric material. 
     The lip portion  101  is peripherally configured to surround the printhead chips  57  collectively and the adjacent region of the printing zone of each or the printheads  51 . Also, the cavity  102  may be provided or be lined with a hydrophobic material or a hydrophilic material, depending upon the function of the capping member and whether fluid that is purged from the printhead is to be expelled from or retained in the capping member 
     Each of the capping members  82  may be formed as a one-piece member with a length that corresponds with that of a printhead to be capped or it may be formed from conjoined shorter-length portions that have an aggregate length corresponding to that of the printhead. 
     In the mechanism shown in  FIG. 9A , two (duplex) printheads  51  are located adjacent one another and together define a gap  80  through which print media is transported in the direction indicated by arrow  81 . However, it will be understood that the invention has equal application to a printer having a single printhead. 
     Two capping members  82  are located adjacent the printheads and are inclined at an angle of approximately 40 degrees to the direction of print media feed. 
     When capping is required, for example between successive print runs, the printheads  51  are turned in an arcuate direction through  40  degrees to the position shown in  FIG. 9B . Thereafter, the capping members  82  are moved rectilinearly, in the lateral direction of arrows  83 , to the positions shown in  FIG. 9C  where the capping members are located in nozzle capping engagement with the printhead chips  57  on each of the printheads  51 . 
     Actuating mechanisms  84  and  85 , as shown in block diagrammatic form in  FIGS. 9B and 9C , are employed for effecting the described movements of the printheads  51  and capping members  82 . These mechanisms may comprise geared motor drives, pneumatic actuators or other such mechanisms as are known in the art for effecting movement of relatively small mechanical devices. 
     With the mechanism as illustrated in  FIGS. 9A to 9C , the print media may be maintained in position between the printheads  51  during the capping operation. 
     Each of the capping members  82  has a configuration as shown in  FIG. 8  described in detail above. 
     In the mechanism shown in  FIG. 10A , two (duplex) printheads  51  are positioned one above the other to define a gap  80  through which print media is passed, in the direction of arrow  88 , during a printing operation. A single capping member  82  having opposed capping faces  86  is positioned adjacent the printing heads and slightly above the path of the print media. 
     When capping is required, any print media that is positioned in the printer is moved in the direction of arrow  88  by rollers  89  and the upper printhead  51  is raised (relative to the lower printhead) by an actuating mechanism  87 , as indicated in  FIG. 10B . The capping member  82  is then moved rectilinearly by an actuating mechanism  90  to the position shown in  FIG. 10C , where it is interposed between the printheads  51  and located in nozzle capping engagement with the printhead chips  57  on both of the printheads. Positive engagement between the capping member  82  and the two printheads is effected by lowering the upper printhead  51  onto the capping member  82 . 
     The actuating mechanisms  87  and  90 , as shown in block diagrammatic form in  FIGS. 10B and 10C  and as employed for effecting the described movements of the printheads  51 , may comprise geared motor drives, pneumatic actuators or other such mechanisms as are known in the art for effecting movement of relatively small mechanical devices. 
     The capping member  82  is double sided, having in effect two capping portions  86 , and has a configuration as shown in  FIG. 11 . Thus, the capping member  82  comprise a body portion  100  and, moulded onto or otherwise secured to upper and lower faces of the body portion, a capping portion having an integrally formed lip portion  101  which surrounds a cavity  102 . The body portion  100  is formed from a metal such as aluminium or from a rigid plastics material, and the capping portion (including the lip portion  101 ) is formed from an elastomeric material. 
     The lip portion  101  is peripherally configured to surround the printhead chips  57  collectively and the adjacent region of the printing zone of each or the printheads  51 . Also, the cavity  102  may be provided or be lined with a hydrophobic material or a hydrophilic material, depending upon the function of the capping member and whether fluid that is purged from the printhead is to be expelled from or retained in the capping member. 
     The capping member  82  may be formed, effectively, as a one-piece member with a length that corresponds with that of the printhead to be capped or it may be formed from conjoined shorter-length portions that have an aggregate length corresponding to that of the printhead. 
       FIGS. 12A  and B illustrate a capping mechanism that is appropriate to a printer having a single (simplex) printing head  51 . 
     As illustrated, a capping member  82  is initially located below the plane of print media feed  81  through the printer and, following the extraction of any print media in the direction indicated by arrow  84 , the capping member is moved rectilinearly upward by an actuating mechanism  83  to the position shown in  FIG. 12B  where it is located in nozzle capping engagement with the printhead chips  57  on the printhead  51 . 
     The actuating mechanism  83  may comprise a geared motor drive, pneumatic actuator or other such mechanism as is known in the art for effecting movement of relatively small mechanical devices. 
     The capping member  82  is moved in a direction normal to the printhead  51 , thereby avoiding any potential for rubbing between the capping member and the printing zone of the printhead. 
     The capping member  82  has a configuration as shown in  FIG. 8  described in detail above. 
       FIGS. 13A  and B illustrate a capping/purging mechanism that is appropriate to a printer having a single (simplex) printing head  51 . 
     As illustrated, a capping member  82  is initially located below the plane of print media feed  81  through the printer and, following the extraction of any print media in the direction indicated by arrow  80 , the capping member is moved rectilinearly upward by an actuating mechanism  83  to the position shown in  FIG. 13B  where it is located in nozzle capping engagement with the printhead chips  57  on the printhead  51 . 
     The actuating mechanism  83  may comprise a geared motor drive, pneumatic actuator or other such mechanism as is known in the art for effecting movement of relatively small mechanical devices. 
     The capping member  82  doubles as a purging member and it incorporates a chamber  84  that communicates by way of a port  85  with a cavity  86 . An extractor tube  87  extends into the chamber  84  and is connected to a suction pump or other such device  88  within the printer for sucking purged material from the nozzle environment of the printhead  51 . 
     The capping member  82  is moved by the actuating mechanism  83  in a direction normal to the printhead  51 , thereby avoiding potential for rubbing between the capping member and the printing zone of the printhead. 
     The capping member  82  has a configuration as shown in  FIG. 8  described in detail above. 
       FIGS. 14A  and B illustrate a capping mechanism that is appropriate to a printer having two (Duplex) offset printheads  51 . The printheads are orientated in mutually opposite directions and are arranged to deliver ink onto opposite faces of print media as it is transported between the printheads 
     As illustrated, capping members  82  are initially located in vertical spaced relationship to the respective printheads  51  and, thus, are located one at each side of the plane  81  of print media feed through the printer. Following the extraction of any print media from between the printheads  51 , the capping members are moved rectilinearly in mutually opposite vertical directions by actuating mechanisms  80 , to the positions shown in  FIG. 14B , where they are located in nozzle capping engagement with the printhead chips  57  on the respective printheads  51 . 
     Each of the actuating mechanisms  80  may comprise a geared motor drive, pneumatic actuator or other such mechanism as is known in the art for effecting movement of relatively small mechanical devices. 
     The capping members  82  are moved in a direction normal to the printheads  51 , thereby avoiding any potential for rubbing between the capping members and the printing zone of the printheads. 
     Each of the capping members  82  has a configuration as shown in  FIG. 8  described in detail above. 
       FIGS. 15A  and B illustrate a capping mechanism that is appropriate to a printer having a single (simplex) printing head  51 . 
     As illustrated, a capping member  82  is initially located below the plane of print media feed  81  through the printer and, following the extraction of any print media in the direction indicated by arrow  80 , the capping member is moved arcuately upwardly by an actuating mechanism  83  to the position shown in  FIG. 15B  where it is located in nozzle capping engagement with the printhead chips  57  on the printhead  51 . 
     The actuating mechanism  83  may comprise a geared motor drive, pneumatic actuator or other such mechanism as is known in the art for effecting movement of relatively small mechanical devices. 
     The capping member  82  is moved in a direction approximately normal to the printhead  51 , thereby avoiding any potential for significant rubbing between the capping member and the printing zone of the printhead. 
     The capping member  82  has a configuration as shown in  FIG. 8  described in detail above. 
       FIGS. 16A  and B illustrate a capping/purging mechanism that is appropriate to a printer having a single (simplex) printing head  51 . 
     As illustrated, a capping member  82  is initially located below the plane  81  of print media feed through the printer and, following the extraction of any print media in the direction indicated by arrow  80 , the capping member is moved arcuately in an upward by an actuating mechanism  83  to the position shown in  FIG. 16B  where it is located in nozzle capping engagement with the printhead chips  57  on the printhead  51 . 
     The actuating mechanism  83  may comprise a geared motor drive, pneumatic actuator or other such mechanism as is known in the art for effecting movement of relatively small mechanical devices. 
     The capping member  82  doubles as a purging member and it incorporates a chamber  84  that communicates by way of a port  85  with a cavity  86 . An extractor tube  87  extends into the chamber  84  and is connected to a suction pump or other such device  88  within the printer for sucking purged material from the nozzle environment of the printhead  51 . 
     The capping member  82  is moved by the actuating mechanism  83  in a direction that is approximately normal to the printhead  51 , thereby avoiding potential for significant rubbing between the capping member and the printing zone of the printhead. 
     Each of the capping members  82  has a configuration as shown in  FIG. 8  described in detail above. 
     In the mechanism shown in  FIG. 17A , two (duplex) printheads  51  are located adjacent one another and together define a gap  80  through which print media is transported in the direction indicated by arrow  81 . However, it will be understood that the invention may be applied equally to a printer having a single printhead. 
     Two capping members  82  are located adjacent the printheads and are inclined at an angle of approximately 40 degrees to the direction of print media feed. 
     When capping is required, for example between successive print runs, the printheads  51  are turned in an arcuate first direction through  40  degrees to the position shown in  FIG. 17B . Thereafter, the capping members  82  are turned in an arcuate second direction, that is opposite to that of the first direction, to the positions shown in  FIG. 17C  where the capping members are located in nozzle capping engagement with the printhead chips  57  on each of the printheads  51 . 
     Actuating mechanisms  83  and  84 , as shown in block diagrammatic form in  FIGS. 17B and 17C , are employed for effecting the described movements of the printheads  51  and capping members  82 . These mechanisms may comprise geared motor drives, pneumatic actuators or other such mechanisms as are known in the art for effecting movement of relatively small mechanical devices. 
     With the mechanism as illustrated in  FIGS. 17A to 17C , the print media may be maintained in position between the printheads  51  during the capping operation. 
     Each of the capping members  82  has a configuration as shown in  FIG. 8  described in detail above. 
     In the mechanism shown in  FIG. 18A  to D, two (duplex) printheads  51  are located adjacent one another and together define a gap  80  through which print media is transported in the direction indicated by arrow  81 . Two capping/purging members  82  are located adjacent the printheads and are inclined with respect to the direction of print media feed. 
     When capping is required, for example between successive print runs, the printheads  51  are turned in an arcuate first direction from a non-capping first position to a second position as shown in  FIG. 18B . 
     Thereafter, the capping/purging members  82  are turned in an arcuate second direction, opposite to that of the first direction, through to the second position shown in  FIG. 18C . In this second position capping portions  85  of the capping/purging members  82  are located in nozzle capping engagement with the printhead chips  57  on each of the printheads  51 . 
     Actuating mechanisms  83  and  84 , as shown in block diagrammatic form in  FIGS. 18B to 18D , are employed for effecting the described movements of the printheads  51  and the capping/purging members  82 . These actuating mechanisms may comprise geared motor drives, pneumatic actuators or other such mechanisms as are known in the art for effecting movement of relatively small mechanical devices. 
     The capping/purging member  82  incorporates a purging chamber  86  (see  FIG. 18D ) that is arranged to receive material that is purged from the nozzles in the printing head chips  57 . An extractor tube  87  extends into the chamber  86  and is connected to a suction pump or other such device  88  within the printer  52  for sucking material that is purged from the nozzle environment of the printhead. 
     If purging is required following capping of the printhead chips  57  on the printheads  51 , the printheads  51  are turned in the first direction through a further angle, as shown in  FIG. 18D , to a third position. At this third position the printhead chips  57  are located adjacent the chambers  86  and purging of the nozzles is effected. 
     If purging is required independently of capping, the printheads  51  will be turned though the full extent from the first to the third position by the actuating mechanisms  83 , and the capping/purging members  82  will be turned in the opposite direction by the actuating mechanisms  84 , so that the printhead chips  57  will align with the purging chambers  86 . 
     The capping and/or purging operations may be performed in the above described apparatus without interfering with the movement of print media. Thus, the print media may be maintained in position between the printheads  51  during the capping and purging operation. 
     Each of the capping/purging members  82  has a configuration as shown in  FIG. 19 . Thus, each of the capping/purging members  82  comprises a body portion  100  and, moulded onto or otherwise secured to the body portion, a capping portion having an integrally formed lip portion  101  which surrounds the cavity  85  and the purging chamber  86 . The body portion  100  is formed from a metal such as aluminium or from a rigid plastics material, and the capping portion (including the lip portion  101 ) is formed from an elastomeric material. 
     The lip portion  101  is peripherally configured to surround the printhead chips  57  collectively and the adjacent region of the printing zone of each or the printheads  51  during both the capping and the purging operations. 
     Each of the capping/purging members  82  may be formed as a one-piece member with a length that corresponds with that of a printhead to be capped or it may be formed from conjoined shorter-length portions that have an aggregate length corresponding to that of the printhead. 
     The mechanism that is illustrated in  FIGS. 20A  and B comprises a rotatable turret  90  that is positioned vertically below a single printhead  51 , although it will be understood that two turrets might be employed in association with two arcuately moveable printheads if a duplex printhead assembly were to be employed. The turret  90  has a generally triangular configuration in cross-section and it extends (into the page as illustrated) for substantially the full longitudinal length of the printhead  51 . The turret carries a platen  91 , a capping portion  92  and a purging chamber  93  on its respective faces. 
     When positioned adjacent (ie, just below) the printing head  51 , the platen  91  provides support for normal print media feed through the printer. When capping and/or purging is required, the turret  90  is initially lowered by a first actuating mechanism  94  and is rotated by a second actuating mechanism  95  to position the capping member  92  or the purging chamber  93  in alignment with the printhead  51 . Thereafter, the turret is again raised by the actuating mechanism  94  to the position shown in  FIG. 20B . 
     When the purging chamber  96  is located in contact with the printhead chips  57 , purging may be effected and the purged material be sucked out by way of an extractor tube  96  that is connected to a suction device  97 , such as a pump, in the printer. 
     The actuating mechanisms  94  and  95 , as shown in block diagrammatic form, may comprise geared motor drives, pneumatic actuators or such other mechanisms as are known in the art for effecting movement of relatively small mechanical devices. 
     The capping member  92  and the purging chamber  93  as mounted to the turret  90  may each have the configuration as illustrated in  FIG. 21 . The illustrated member in each case comprises a body portion  100  and, moulded onto or otherwise secured to the body portion, a capping portion or purging chamber having an integrally formed lip portion  101  that surrounds a cavity  102 . The body portion  100  is formed from a metal such as aluminium or from a rigid plastics material, and the capping or purging portion (including the lip portion  101 ) is formed from an elastomeric material. 
     The lip portion  101  is peripherally configured to surround the printhead chips  57  collectively and the adjacent region of the printing zone of each or the printheads  51 . In the case of the purging chamber  93 , an aperture  103  is provided (or a plurality of such apertures are provided) in the cavity  102  to connect with the extractor tube  96  by way of a port  104  and a central bore  105  of the turret  90 . 
     The capping member/purging chamber  92 / 93  may be formed as a one-piece member with a length that corresponds with that of the printhead  51  to be capped or it may be formed from conjoined shorter-length portions that have an aggregate length corresponding to that of the printhead. 
     As an alternative to the use of the purging chamber  93 , the nozzles  57  may be purged directly into an aperture or a ported recess (herein referred to as a purging chamber) in the turret when the turret is rotated to the appropriate position. 
     The mechanism that is illustrated in  FIGS. 22A  and B comprises a rotatable turret  90  that is positioned vertically below a single printhead  51 , although it will be understood that two turrets might be employed in association with two arcuately moveable printheads if a duplex printhead assembly were to be employed. The turret  90  has an axially extending body portion  91 , a longitudinally extending flat land portion  92  and a longitudinally extending eccentric land portion  93 . 
     The eccentric land portion  93  of the turret carries a longitudinally extending capping member  94  that extends for substantially the full length of the printhead  51 . Also, a purging chamber  95  is located within the turret  90  and opens to the flat land portion  92  by way of a port  96 . 
     The flat land portion  92  of the turret effectively forms a platen and, when the turret is in the position shown in  FIG. 22A , the land  92  constitutes the lower margin of a passageway through which print media is fed during a printing operation. Thus, when positioned adjacent (ie, just below) the printhead  51 , the platen as defined by the land  92  provides support for normal print media feed through the printer. 
     When capping is required, for example between successive print runs, the turret  90  is rotated to the position shown in  FIG. 22B  and, due to the eccentric positioning of the capping member  94  on the turret  90 , the capping member is moved from a non-capping first position ( FIG. 22A ) to a second position ( FIG. 22B ) at which the capping member  94  is located in nozzle capping engagement with the printhead chips  57  on the printhead  51 . 
     An actuating mechanism  97  is provided for effecting required rotation of the turret  90 . That mechanism may comprise a geared motor drive, a pneumatic actuator or such other mechanism as is known in the art for effecting movement of relatively small mechanical devices. 
     When purging of the nozzles is to be effected, the turret is rotated to the position shown in  FIG. 22A , such that the port  96  is located below the nozzles, and purged material is directed into the purging chamber  95  by way of the port  96 . Purged material be sucked out of the purging chamber  95  by way of an extractor tube  97  that is connected to a suction device  98 , such as a pump, in the printer. 
     The capping member  94  as mounted to the turret  90  may have the configuration as illustrated in  FIG. 23 . The illustrated member comprise a body portion  100  and, moulded onto or otherwise secured to the body portion, a capping portion having an integrally formed lip portion  101  which surrounds a cavity  102 . The body portion  100  is formed from a metal such as aluminium or from a rigid plastics material, and the capping portion (including the lip portion  101 ) is formed from an elastomeric material. 
     The lip portion  101  is peripherally configured to surround the printhead chips  57  collectively and the adjacent region of the printing zone of each or the printheads  51 . Also, the cavity  102  may be provided or be lined with a hydrophobic material or a hydrophilic material, depending upon the function of the capping member and whether fluid that is purged from the printhead is to be expelled from or retained in the capping member. 
     The capping member  94  may be formed as a one-piece member with a length that corresponds with that of the printhead  51  to be capped or it may be formed from conjoined shorter-length portions that have an aggregate length corresponding to that of the printhead. 
       FIGS. 24A , B and C diagrammatically illustrate a capping/purging mechanism applicable to a printer having a single printhead  51 . However, it will be understood that the mechanism might be adapted to a duplex printer, for example by separating or pivoting the printheads when capping and/or purging is required. 
     The mechanism that is illustrated in  FIGS. 24A  to C comprises a carrier  90  which is positioned vertically below and in confronting relationship to the printhead  51 . The carrier incorporates a chamber  92  and it has a longitudinal length corresponding substantially to that of the printhead. 
     A longitudinally extending capping member  93  is pivotally mounted to the carrier  90  and it too has a longitudinal length corresponding substantially to that of the printhead  51 . 
     An actuating mechanism  94  is provided and arranged to effect pivoting of the capping member  93  from a non-capping first position as indicated in  FIG. 24B  to a second position, as indicated in  FIGS. 24A and 24C , at which the capping member is located in nozzle capping engagement with the printhead chips  57 . 
     The actuating mechanism  94  may comprise a geared motor drive, a pneumatic actuator or such other mechanism as is known in the art for effecting movement of relatively small mechanical devices. 
     When capping is required, for example between successive print runs, the capping member  93  may simply be pivoted from the first to the second position, as described above, without effecting any movement of the carrier  90 . In this case the carrier would be located a small distance below the printhead  51  and, in effect, define the lower margin of a passage through which print media is transported during a normal printing operation. In an alternative arrangement (not shown), the carrier  90  might be positioned well below the printhead  51  when the capping member  93  is in the first position and a further actuating mechanism would then be provided for elevating the carrier to the required capping position. 
     When purging of the nozzles is to be effected, the capping member  93  is pivoted to the position shown in  FIG. 24B  and purged material is directed into the purging chamber  92 . The purged material will be sucked out of the purging chamber  92  by way of an extractor tube  96  that is connected to a suction device  95 , such as a pump, in the printer. In an alternative arrangement (not shown) purged material may be directed through apertures in the capping member when the capping member  93  is located in the second position shown in  FIGS. 24A  and C. 
     The capping member  93  as pivotally mounted to the carrier  90  may have the configuration illustrated in  FIG. 25 . The illustrated member comprises a body portion  100  and, moulded onto or otherwise secured to the body portion, a capping portion having an integrally formed lip portion  101  that surrounds a cavity  102 . The body portion  100  is formed from a metal such as aluminium or from a rigid plastics material, and the capping portion (including the lip portion  101 ) is formed from an elastomeric material. 
     The lip portion  101  is peripherally configured to surround the printhead chips  57  collectively and the adjacent region of the printing zone of each or the printheads  51 . Also, the cavity  102  may be provided or be lined with a hydrophobic material or a hydrophilic material, depending upon the function of the capping member and whether fluid that is purged from the printhead is to be expelled from or retained in the capping member. 
       FIGS. 26A  and B diagrammatically illustrate duplex printheads  51  but it will be understood that one of the printheads might be replaced with a platen that would define a lower margin of a passage for print media and act as a support for the capping member that is to be described 
     As illustrated in  FIGS. 26A  and B, the two printing heads  51  are positioned in confronting relationship and are separated by a gap  80  through which print media (not shown) is fed during a printing operation. When capping is required, for example between successive print runs, any print media that is present between the printheads  51  will be retracted by rollers  81  in the direction of arrow  82 , and a capping member  83  will be directed into the gap  80  and be positioned in nozzle capping engagement with all of the printhead chips  57  that are mounted to both of the printheads. 
     The capping member  83  is directed into the gap  80  by way of a ramp or chute  84  and an actuating mechanism  85  is employed for propelling the capping member into the desired position. The actuating mechanism may comprise a geared motor drive, pneumatic actuator or other such mechanism as is known in the art for effecting movement of relatively small mechanical devices. 
     The capping member is dimensioned to cover the confronting surfaces of the printheads  51  and, thus, it has a depth (in the direction of arrow  82 ) approximately equal to that of the printhead  51  and a width (in the direction into the page) which is approximately equal to the length of the printheads. 
     The capping member  83  may be formed from various types of materials that have a sheet-like form and are flexible. The sheet-like form is required in order that the capping member might be inserted into the relatively narrow gap  80  that will normally be present between the printheads  51 , and flexibility is required to enable the creation of an effective capping seal between the capping member and the printheads. 
     The material from which the capping member  83  is formed will be dependent upon whether simple capping is required or whether the capping member is required also to absorb and carry purged ink and other material away from the printing zone of the printheads. For simple capping the material might be selected for hydrophobic properties, and when required to assist in purging functions the material might be selected for hydrophilic properties. The former material might comprise a closed cell thermoplastics material and the latter material might comprise and open cell silicone material. 
     In any event, the material from which the capping member is formed will normally exhibit a degree of compressibility in order that a positive reactive force might be established and maintained between the printheads and the capping member during the capping operation. Alternatively or additionally, the capping member  83  might be formed from layered sheets, so that a fluid (ie, a liquid or a gas) might be directed into the region between the layers to change the effective thickness of the capping member. A fluid delivery mechanism  86  is shown in  FIG. 26B  for this purpose. 
       FIGS. 27A  and B diagrammatically illustrate a simplex printhead arrangement but it will be understood that the invention also applies to a duplex arrangement, in which case the illustrated platen would be replaced with a lower printhead. 
     The mechanism that is illustrated in  FIGS. 27A  and B is suitable for use in conjunction with a wide format printer having a single printhead  51 . A platen  86  and the single printhead  51  define a gap  81  through which the print media is fed, in the direction of arrow  82 . 
     A capping member  83  is provided in the form of a replaceable roll  84  of sheet material of a type to be described (by way of example) and, when a capping operation is to be performed, for example between print runs, the following operations are performed: 
     1. Print media is advanced beyond the printhead assembly in the direction of arrow  82 . 
     2. The platen  80  is lowered by an actuating mechanism  85 . 
     3. The sheet-like capping member  83  is fed through the gap  81  from the roll  84 . 
     4. The platen  80  is raised by the actuating mechanism  85  to position the capping member  83  in nozzle capping engagement with the printhead chips  57 . 
     When capping is no longer required and a purging operation, if any, has been completed, the spent capping member  83  is separated from the roll  84  by a cutter mechanism  86  and the capping member is drawn from the gap  81  in the direction opposite to that indicated by arrow  82 . 
     Feeding of the capping member  83  into and out from the gap  81  may be effected manually or mechanically, depending upon the size and required operating speed of the printer of which the capping mechanism forms a part. 
     When the capping mechanism as illustrated is employed in a wide format printer, the cutter mechanism  86  may comprise one that typically is used to effect the cutting of print media that is fed through the printer from a roll of the print media. 
     The actuating mechanism  85  may comprise a geared motor drive, pneumatic actuator or other such mechanism as is known in the art for effecting movement of relatively small mechanical devices. 
     The capping member is dimensioned to cover the confronting surfaces of the printheads  51  and, thus, it has a width (in the direction into the page) which is approximately equal to the length of the printheads. 
     The capping member  83  may be formed from various types of materials that have a sheet-like form and are flexible. The sheet-like form is required in order that the capping member might be inserted into the relatively narrow gap  81  that will normally be present between the printhead  51  and the platen  80  (or between two printheads in the case of a duplex assembly), and flexibility is required to enable the creation of an effective capping seal between the capping member and the printhead(s). 
     The material from which the capping member  83  is formed will be dependent upon whether simple capping is required or whether the capping member is required also to absorb and carry purged ink and other material away from the printing zone of the printhead. For simple capping the material might be selected for hydrophobic properties, and when required to assist in purging functions the material might be selected for hydrophilic properties. The former material might comprise a closed cell thermoplastics material and the latter material might comprise and open cell silicone material. 
     In any event, the material from which the capping member is formed will normally exhibit a degree of compressibility in order that a positive reactive force might be established and maintained between the printheads and the capping member during the capping operation. Alternatively or additionally, the capping member  83  might be formed from layered sheets, so that a fluid (ie, a liquid or a gas) might be directed into the region between the layers to change the effective thickness of the capping member. 
       FIGS. 28A  and B diagrammatically illustrate a simplex printhead arrangement but it will be understood that the invention also applies to a duplex arrangement, in which case the illustrated platen would be replaced with a lower printhead. 
     The mechanism that is illustrated in  FIGS. 28A  and B is suitable for use in conjunction with a wide format printer having a single printhead  51 . A platen  80  and the single printhead  51  define a gap  81  through which the print media is fed, in the direction of arrow  82 . 
     A capping member  83  is provided in the form of a portion of a replaceable roll  84  of sheet material of a type to be described (by way of example), and a take-up reel  85  is provided for storing spent sheet material  83  following a capping and/or purging operation. 
     When a capping operation is to be performed, for example between print runs, the following operations are performed: 
     1. Print media is advanced beyond the printhead assembly in the direction of arrow  82  or, if required, is retracted in the opposite direction. 
     2. The platen  80  is lowered by an actuating mechanism  86 . 
     3. The sheet-like capping member  83  is fed through the gap  81  from the roll  84  to the take-up reel  85 . 
     4. The platen  80  is raised by the actuating mechanism  86  to position the capping member  83  in nozzle capping engagement with the printhead chips  57 . 
     When capping is no longer required and a purging operation, if any, has been completed, the spent capping member portion of the capping material  83  is moved through the gap  81  and wound onto the take-up reel  85 . 
     Feeding of the capping member  83  into and out from the gap  81  may be effected manually or mechanically, depending upon the size and required operating speed of the printer of which the capping mechanism forms a part. 
     The actuating mechanism  85  may comprise a geared motor drive, pneumatic actuator or other such mechanism as is known in the art for effecting movement of relatively small mechanical devices. 
     The roll  84  of sheet-like capping material has a width (in the direction into the page) which is approximately equal to the length of the printheads. 
     The capping member  83  may be formed from various types of materials that have a sheet-like form and are flexible. The sheet-like form is required in order that the capping member might be inserted into the relatively narrow gap  81  that will normally be present between the printhead  51  and the platen  80  (or between two printheads in the case of a duplex assembly), and flexibility is required to enable the creation of an effective capping seal between the capping member and the printhead(s). 
     The material from which the capping member  83  is formed will be dependent upon whether simple capping is required or whether the capping member is required also to absorb and carry purged ink and other material away from the printing zone of the printhead. 
     For simple capping the material might be selected for hydrophobic properties, and when required to assist in purging functions the material might be selected for hydrophilic properties. The former material might comprise a closed cell thermoplastics material and the latter material might comprise and open cell silicone material. 
     In any event, the material from which the capping member is formed will normally exhibit a degree of compressibility in order that a positive reactive force might be established and maintained between the printheads and the capping member during the capping operation. Alternatively or additionally, the capping member  83  might be formed from layered sheets, so that a fluid (ie, a liquid or a gas) might be directed into the region between the layers to change the effective thickness of the capping member. 
     In the mechanism shown in  FIGS. 29A-C , two (duplex) printheads  51  are positioned one above the other to define a gap  80  through which print media is passed, in the direction of arrow  81 , during a printing operation. A single capping member  82  having opposed capping faces  83  is positioned adjacent the printing heads and slightly above the path of the print media. 
     When capping is required, any print media that is positioned in the printer is moved in the direction of arrow  84  by rollers  85  and the upper printhead  51  is raised (relative to the lower printhead) by an actuating mechanism  86 , as indicated in  FIG. 29B . The capping member  82  is then moved rectilinearly by an actuating mechanism  87  to the position shown in  FIG. 29C , where it is interposed between the printheads  51  and located in nozzle capping engagement with the printhead chips  57  on both of the printheads. Positive engagement between the capping member  82  and the two printheads is effected by lowering the upper printhead  51  onto the capping member  82 . 
     The actuating mechanisms  86  and  87 , as shown in block diagrammatic form in  FIGS. 29B and 29C  and as employed for effecting the described movements of the printheads  51 , may comprise geared motor drives, pneumatic actuators or other such mechanisms as are known in the art for effecting movement of relatively small mechanical devices. 
     The capping member  82  may, as illustrated in  FIG. 30 , comprise a single-sided member when required to cap a single printhead  51  or it may, for the capping function illustrated in  FIGS. 7A  to C, be double sided. In either case, the capping side or portion of the member has a configuration as shown in  FIG. 30 . 
     As illustrated, the capping member  82  has a body portion  90  onto which is moulded or otherwise secured a capping portion having an integrally formed lip portion  91  which surrounds a cavity  92 . The body portion  90  is formed from a metal such as aluminium or from a rigid plastics material, and the capping portion (including the lip portion  91 ) is formed from an elastomeric material. 
     The lip portion  91  is peripherally configured to surround the printhead chips  57  collectively and the adjacent region of the printing zone of each or the printheads  51 . Also, the cavity  92  may be provided or be lined with a hydrophobic material or a hydrophilic material, depending upon the function of the capping member and whether fluid that is purged from the printhead is to be expelled from or retained in the capping member. 
     The capping member  82  may be formed as a one-piece member with a length that corresponds with that of the printhead to be capped or it may be formed from conjoined shorter-length portions that have an aggregate length corresponding to that of the printhead. 
     The interior or underside of the capping member as illustrated in  FIG. 30  may be formed with a cavity or chamber (a “purging chamber”) for receiving material that is purged from a printhead during a purging operation. Purged material may be directed into the purging chamber either by way of the cavity  92  or by way of a separate route. 
     One of the printhead chips  57  is now described in more detail with reference to  FIGS. 31 to 40 . 
     As indicated above, each printhead chip  57  is provided with  7680  printing fluid delivery nozzles  150 . The nozzles are arrayed in twelve rows  151 , each having  640  nozzles, with an inter-nozzle spacing X of 32 microns. Adjacent rows are staggered by a distance equal to one-half of the inter-nozzle spacing so that a nozzle in one row is positioned mid-way between two nozzles in adjacent rows. Also, there is an inter-nozzle spacing Y of 80 microns between adjacent rows of nozzles. 
     Two adjacent rows of the nozzles  150  are fed from a common supply of printing fluid. This, with the staggered arrangement, allows for closer spacing of ink dots during printing than would be possible with a single row of nozzles and also allows for a level of redundancy that accommodates nozzle failure. 
     The printhead chips  57  are manufactured using an integrated circuit fabrication technique and, as previously indicated, embody micro-electromechanical systems (MEMS). Each printhead chip  57  includes a silicon wafer substrate  152 , and a 0.42 micron 1P4M 12 volt CMOS micro-processing circuit is formed on the wafer. Thus, a silicon dioxide layer  153  is deposited on the substrate  152  as a dielectric layer and aluminium electrode contact layers  154  are deposited on the silicon dioxide layer  153 . Both the substrate  152  and the layer  153  are etched to define an ink channel  155 , and an aluminium diffusion barrier  156  is positioned about the ink channel  155 . 
     A passivation layer  157  of silicon nitride is deposited over the aluminium contact layers  154  and the layer  153 . Portions of the passivation layer  157  that are positioned over the contact layers  154  have openings  158  therein to provide access to the contact layers. 
     Each nozzle  150  includes a nozzle chamber  159  which is defined by a nozzle wall  160 , a nozzle roof  161  and a radially inner nozzle rim  162 . The ink channel  155  is in fluid communication with the chamber  159 . 
     A moveable rim  163 , that includes a movable seal lip  164 , is located at the lower end of the nozzle wall  160 . An encircling wall  165  surrounds the nozzle and provides a stationery seal lip  166  that, when the nozzle  150  is at rest as shown in  FIG. 35 , is adjacent the moveable rim  163 . A fluidic seal  167  is formed due to the surface tension of ink trapped between the stationery seal  166  and the moveable seal lip  164 . This prevents leakage of ink from the chamber whilst providing a low resistance coupling between the encircling wall  165  and a nozzle wall  160 . 
     The nozzle wall  160  forms part of lever arrangement that is mounted to a carrier  168  having a generally U-shaped profile with a base  169  attached to the layer  157 . The lever arrangement also includes a lever arm  170  that extends from the nozzle wall and incorporates a lateral stiffening beam  171 . The lever arm  170  is attached to a pair of passive beams  172  that are formed from titanium nitride and are positioned at each side of the nozzle as best seen in  FIGS. 31 and 38 . The other ends of the passive beams  172  are attached to the carriers  168 . 
     The lever arm  170  is also attached to an actuator beam  173 , which is formed from TiN. This attachment to the actuator beam is made at a point a small but critical distance higher than the attachments to the passive beam  172 . 
     As can best be seen from  FIGS. 31 and 38 , the actuator beam  173  is substantially U-shaped in plan, defining a current path between an electrode  174  and an opposite electrode  175 . Each of the electrodes  174  and  175  is electrically connected to a respective point in the contact layer  154 . The actuator beam  173  is also mechanically secured to an anchor  176 , and the anchor  176  is configured to constrain motion of the actuator beam  173  to the left of  FIGS. 32 to 34  when the nozzle arrangement is activated. 
     The actuator beam  173  is conductive, being composed of TiN, but has a sufficiently high electrical resistance to generate self-heating when a current is passed between the electrodes  174  and  175 . No current flows through the passive beams  172 , so they do not experience thermal expansion. 
     In operation, the nozzle is filled with ink  177  that defines a meniscus  178  under the influence of surface tension. The ink is retained in the chamber  159  by the meniscus, and will not generally leak out in the absence of some other physical influence. 
     To fire ink from the nozzle, a current is passed between the contacts  174  and  175 , passing through the actuator beam  173 . The self-heating of the beam  173  causes the beam to expand, and the actuator beam  173  is dimensioned and shaped so that the beam expands predominantly in a horizontal direction with respect to  FIGS. 32 to 34 . The expansion is constrained to the left by the anchor  176 , so the end of the actuator beam  173  adjacent the lever arm  170  is impelled to the right. 
     The relative horizontal inflexibility of the passive beams  172  prevents them from allowing much horizontal movement of the lever arm  170 . However, the relative displacement of the attachment points of the passive beams and actuator beam respectively to the lever arm causes a twisting movement that, in turn, causes the lever arm  170  to move generally downwardly with a pivoting or hinging motion. However, the absence of a true pivot point means that rotation is about a pivot region defined by bending of the passive beams  172 . 
     The downward movement (and slight rotation) of the lever arm  170  is amplified by the distance of the nozzle wall  160  from the passive beams  172 . The downward movement of the nozzle walls and roof causes a pressure increase within the chamber  159 , causing the meniscus  178  to bulge as shown in  FIG. 33 , although the surface tension of the ink causes the fluid seal  167  to be stretched by this motion without allowing ink to leak out. 
     As shown in  FIG. 40 , at the appropriate time the drive current is stopped and the actuator beam  173  quickly cools and contracts. The contraction causes the lever arm to commence its return to the quiescent position, which in turn causes a reduction in pressure in the chamber  159 . The interplay of the momentum of the bulging ink and its inherent surface tension, and the negative pressure caused by the upward movement of the nozzle chamber  159  causes thinning, and ultimately snapping, of the bulging meniscus  178  to define an ink drop  179  that continues outwardly until it contacts passing print media. 
     Immediately after the drop  179  detaches, the meniscus  178  forms the concave shape shown in  FIG. 34 . Surface tension causes the pressure in the chamber  159  to remain relatively low until ink has been sucked upwards through the inlet  155 , which returns the nozzle arrangement and the ink to the quiescent situation shown in  FIG. 34 . 
     As can best be seen from  FIG. 35 , the printhead chip  57  also incorporates a test mechanism that can be used both post-manufacture and periodically after the printhead assembly has been installed. The test mechanism includes a pair of contacts  180  that are connected to test circuitry (not shown). A bridging contact  181  is provided on a finger  182  that extends from the lever arm  170 . Because the bridging contact  181  is on the opposite side of the passive beams  172 , actuation of the nozzle causes the bridging contact  181  to move upwardly, into contact with the contacts  180 . Test circuitry can be used to confirm that actuation causes this closing of the circuit formed by the contacts  180  and  181 . If the circuit is closed appropriately, it can generally be assumed that the nozzle is operative. 
     As stated previously the integrated circuits of the printhead chips  57  are controlled by the print engine controller (PEC) integrated circuits of the drive electronics  63 . One or more PEC integrated circuits  100  is or are provided (depending upon the printing speed required) in order to enable page-width printing over a variety of different sized pages or continuous sheets. As described previously, each of the printed circuit boards  62  carried by the support moulding  66  carries one PEC integrated circuit  190  ( FIG. 41 ) which interfaces with four of the printhead chips  57 , and the PEC integrated circuit  190  essentially drives the integrated circuits of the printhead chips  57  and transfers received print data thereto in a form suitable to effect printing. 
     An example of a PEC integrated circuit which is suitable for driving the printhead chips is described in the Applicant&#39;s co-pending U.S. patent application Ser. Nos. 09/575,108, 09/575,109, 09/575,110, 09/607,985, 09/607,990 and 09/606,999, which are incorporated herein by reference. However, a brief description of the circuit is provided as follows with reference to  FIGS. 41 to 43 . 
     The data flow and functions performed by the PEC integrated circuit  190  are described for a situation where the PEC integrated circuit is provided for driving a printhead  51  having a plurality of printhead modules  55 ; that is four modules as described above. As also described above, each printhead module  55  provides for six channels of fluid for printing, these being:
         Cyan, Magenta and Yellow (CMY) for regular colour printing;   Black (K) for black text and other black or greyscale printing;   Infrared (IR) for tag-enabled applications; and   Fixative (F) to enable printing at high speed.       

     As indicated in  FIG. 41 , images are supplied to the PEC integrated circuit  190  by a computer, which is programmed to perform the various processing steps  191  to  194  involved in printing an image prior to transmission to the PEC integrated circuit  190 . These steps will typically involve receiving the image data (step  191 ) and storing this data in a memory buffer of the computer system (step  192 ) in which image layouts may be produced and any required objects may be added. Pages from the memory buffer are rasterized (step  193 ) and are then compressed (step  194 ) prior to transmission to the PEC integrated circuit  190 . Upon receiving the image data, the PEC integrated circuit  190  processes the data so as to drive the integrated circuits of the printhead chips  57 . 
     Due to the page-width form of the printhead assembly, each image should be printed at a constant speed to avoid creating visible artifacts. This means that the printing speed should be varied to match the input data rate. Document rasterization and document printing are therefore decoupled to ensure the printhead assembly has a constant supply of data. In this arrangement, an image is not printed until it is fully rasterized and, in order to achieve a high constant printing speed, a compressed version of each rasterized page image is stored in memory. 
     Because contone colour images are reproduced by stochastic dithering, but black text and line graphics are reproduced directly using dots, the compressed image format contains a separate foreground bi-level black layer and background contone colour layer. The black layer is composited over the contone layer after the contone layer is dithered. If required, a final layer of tags (in IR or black ink) is optionally added to the image for printout. 
     Dither matrix selection regions in the image description are rasterized to a contone-resolution bi-lev bitmap which is losslessly compressed to negligible size and which forms part of the compressed image. The IR layer of the printed page optionally contains encoded tags at a programmable density. 
     Each compressed image is transferred to the PEC integrated circuit  190  where it is then stored in a memory buffer  195 . The compressed image is then retrieved and fed to an image expander  196  in which images are retrieved. If required, any dither may be applied to any contone layer by a dithering means  197  and any black bi-level layer may be composited over the contone layer by a compositor  198  together with any infrared tags which may be rendered by the rendering means  199 . The PEC integrated circuit  190  then drives the integrated circuits of the printhead chips  57  to print the composite image data at step  200  to produce a printed image  201 . 
     The process performed by the PEC integrated circuit  190  may be considered to consist of a number of distinct stages. The first stage has the ability to expand a JPEG-compressed contone CMYK layer. In parallel with this, bi-level IR tag data can be encoded from the compressed image. The second stage dithers the contone CMYK layer using a dither matrix selected by a dither matrix select map and, if required, composites a bi-level black layer over the resulting bi-level K layer and adds the IR layer to the image. A fixative layer is also generated at each dot position wherever there is a need in any of the C, M, Y, K, or IR channels. The last stage prints the bi-level CMYK+IR data through the printhead assembly  50 . 
       FIG. 42  shows the PEC integrated circuit  190  in the context of the overall printing system architecture. The various components of the architecture include:
         The PEC integrated circuit  190  which is responsible for receiving the compressed page images for storage in a memory buffer  202 , performing the page expansion, black layer compositing and sending the dot data to the printhead chips  57 . The PEC integrated circuit  190  may also communicate with a master Quality Assurance (QA) integrated circuit  203  and with an ink cartridge Quality Assurance (QA) integrated circuit  204 . The PEC integrated circuit  190  also provides a means of retrieving the printhead assembly characteristics to ensure optimum printing.   The memory buffer  202  for storing the compressed image and for scratch use during the printing of a given page. The construction and working of memory buffers is known to those skilled in the art and a range of standard integrated circuits and techniques for their use might be utilized.   The master integrated circuit  203  which is matched to the ink cartridge QA integrated circuit  204 . The construction and working of QA integrated circuits is also known to those skilled in the art and a range of known QA processes might be utilized.       

     The PEC integrated circuit  190  effectively performs four basic levels of functionality:
         Receiving compressed pages via a serial interface such as an IEEE 1394.   Acting as a print engine for producing an image from a compressed form. The print engine functionality includes expanding the image, dithering the contone layer, compositing the black layer over the contone layer, optionally adding infrared tags, and sending the resultant image to the integrated circuits of the printhead chips.   Acting as a print controller for controlling the printhead chips  57  and the stepper motors  102 ,  108  and  111  of the printing system.   Serving as two standard low-speed serial ports for communication with the two QA integrated circuits. In this regard, two ports are used, and not a single port, so as to ensure strong security during authentication procedures.       

     These functions are now described in more detail with reference to  FIG. 21 , which provides a more specific, exemplary illustration of the PEC integrated circuit architecture. 
     The PEC integrated circuit  190  incorporates a simple micro-controller CPU core  204  to perform the following functions:
         Perform QA integrated circuit authentication protocols via a serial interface  205  between print images.   Run stepper motors of the printing system via a parallel interface  206  during printing to control delivery of the print media to the printer for printing.   Synchronize the various components of the PEC integrated circuit  190  during printing.   Provide a means of interfacing with external data requests (programming registers, etc).   Provide a means of interfacing with the printhead assemblies&#39; low-speed data requests (such as reading characterization vectors and writing pulse profiles).   Provide a means of writing portrait and landscape tag structures to an external DRAM  207 .       

     In order to perform the image expansion and printing process, the PEC integrated circuit  190  includes a high-speed serial interface  208  (such as a standard IEEE 1394 interface), a standard JPEG decoder  209 , a standard Group 4 Fax decoder  210 , a custom half-toner/compositor (HC)  211 , a custom tag encoder  212 , a line loader/formatter (LLF)  213 , and a printhead interface  214  (PHI) which communicates with the printhead chips  57 . The decoders  209  and  210  and the tag encoder  212  are buffered to the HC  211 . The tag encoder  212  allocates infrared tags to images. 
     The print engine function works in a double-buffered manner. That is, one image is loaded into the external DRAM  207  via a DRAM interface  215  and a data bus  216  from the high-speed serial interface  208 , while the previously loaded image is read from the DRAM  207  and passed through the print engine process. When the image has been printed, the image just loaded becomes the image being printed, and a new image is loaded via the high-speed serial interface  208 . 
     At the aforementioned first stage, the process expands any JPEG-compressed contone (CMYK) layers, and expands any of two Group 4 Fax-compressed bi-level data streams. The two streams are the black layer and a matte for selecting between dither matrices for contone dithering. At the second stage, in parallel with the first, any tags are encoded for later rendering in either IR or black ink. 
     Finally, in the third stage the contone layer is dithered, and position tags and the bi-level spot layer are composited over the resulting bi-level dithered layer. The data stream is ideally adjusted to create smooth transitions across overlapping segments in the printhead assembly and ideally it is adjusted to compensate for dead nozzles in the printhead assemblies. Up to six channels of bi-level data are produced from this stage. 
     However, it will be understood that not all of the six channels need be activated. For example, the printhead modules  55  may provide for CMY only, with K pushed into the CMY channels and IR ignored. Alternatively, the position tags may be printed in K if IR ink is not employed. The resultant bi-level CMYK-IR dot-data is buffered and formatted for printing with the integrated circuits of the printhead chips  57  via a set of line buffers (not shown). The majority of these line buffers might be ideally stored on the external DRAM  207 . In the final stage, the six channels of bi-level dot data are printed via the PHI  214 . 
     The HC  211  combines the functions of half-toning the contone (typically CMYK) layer to a bi-level version of the same, and compositing the spot1 bi-level layer over the appropriate half-toned contone layer(s). If there is no K ink, the HC  211  functions to map K to CMY dots as appropriate. It also selects between two dither matrices on a pixel-by-pixel basis, based on the corresponding value in the dither matrix select map. The input to the HC  211  is an expanded contone layer (from the JPEG decoder  205 ) through a buffer  217 , an expanded bi-level spot1 layer through a buffer  218 , an expanded dither-matrix-select bitmap at typically the same resolution as the contone layer through a buffer  219 , and tag data at full dot resolution through a buffer (FIFO)  220 . 
     The HC  211  uses up to two dither matrices, read from the external DRAM  207 . The output from the HC  211  to the LLF  213  is a set of printer resolution bi-level image lines in up to six colour planes. Typically, the contone layer is CMYK or CMY, and the bi-level spot1 layer is K. Once started, the HC  211  proceeds until it detects an “end-of-image” condition, or until it is explicitly stopped via a control register (not shown). 
     The LLF  213  receives dot information from the HC  211 , loads the dots for a given print line into appropriate buffer storage (some on integrated circuit (not shown) and some in the external DRAM  207 ) and formats them into the order required for the integrated circuits of the printhead chips  57 . More specifically, the input to the LLF  213  is a set of six 32-bit words and a Data Valid bit, all generated by the HC  211 . 
     As previously described, the physical location of the nozzles  150  on the printhead chips is in two offset rows  151 , which means that odd and even dots of the same colour are for two different lines. In addition, there is a number of lines between the dots of one colour and the dots of another. Since the six colour planes for the same dot position are calculated at one time by the HC  211 , there is a need to delay the dot data for each of the colour planes until the same dot is positioned under the appropriate colour nozzle. The size of each buffer line depends on the width of the printhead assembly. A single PEC integrated circuit  190  may be employed to generate dots for up to 16 printhead chips  57  and, in such case, a single odd or even buffer line is therefore 16 sets of 640 dots, for a total of 10,240 bits (1280 bytes). 
     The PHI  214  is the means by which the PEC integrated circuit  190  loads the printhead chips  57  with the dots to be printed, and controls the actual dot printing process. It takes input from the LLF  213  and outputs data to the printhead chips  57 . The PHI  214  is capable of dealing with a variety of printhead assembly lengths and formats. 
     A combined characterization vector of each printhead assembly  50  and  51  can be read back via the serial interface  205 . The characterization vector may include dead nozzle information as well as relative printhead module alignment data. Each printhead module can be queried via a low-speed serial bus  221  to return a characterization vector of the printhead module. 
     The characterization vectors from multiple printhead modules can be combined to construct a nozzle defect list for the entire printhead assembly and allows the PEC integrated circuit  190  to compensate for defective nozzles during printing. As long as the number of defective nozzles is low, the compensation can produce results indistinguishable from those of a printhead assembly with no defective nozzles. 
     Some of the features of a pagewidth printhead that incorporates the chip and the print engine controller which have been described above are summarised as follows: 
     1. The printhead will normally have at least four color channels. 
     2. The printhead will normally incorporate at least 1400 ink delivery nozzles per inch of print width for each color. 
     3. The printhead may incorporate a total of at least 50,000 nozzles. 
     4. The dot printing processing rate and the drop deposition rate of the printhead may be of the order of 10 9  sec −1  or greater. 
     5. The volume deposited per drop may be of the order of 2×10 −12  l or less. 
     6. The energy level expenditure per drop ejection may be of the order of 200×10 −9  J. or less. 
     It will be understood that the constructional and operating principles of the printer of the present invention may be realised with various embodiments. Thus, variations and modifications may be made in respect of the embodiments as specifically described above by way of example.