Abstract:
A printhead is provided having an elongate support having a plurality of internal webs protruding from a base section to define a plurality of parallel fluid supply channels, a shim supported by the support and defining a plurality of rows of openings through which fluid from respective supply channels is supplied, and a plurality of elongate printhead modules supported serially on the shim. Each module defines a plurality of fluid supply passages through which fluid passes to fluid ejection nozzles from respective rows of the openings. Either end of each module defines complementary formations such that adjacent modules nest together.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. application Ser. No. 12/563,967 filed Sep. 21, 2009, which is a continuation of U.S. application Ser. No. 11/730,788 filed Apr. 4, 2007, now issued U.S. Pat. No. 7,604,314, which is a continuation of U.S. application Ser. No. 10/990,527 filed on Nov. 18, 2004, now issued as U.S. Pat. No. 7,210,762, which is a continuation of U.S. application Ser. No. 10/803,922 filed on Mar. 19, 2004, now issued as U.S. Pat. No. 6,830,315, which is a continuation of U.S. application Ser. No. 09/609,140 filed on Jun. 30, 2000, now issued as U.S. Pat. No. 6,755,513 all of which are herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to the field of ink jet printing systems, and more specifically to a support structure and ink supply arrangement for a printhead assembly and such printhead assemblies for ink jet printing systems. 
     DESCRIPTION OF THE PRIOR ART 
     Micro-electromechanical systems (“MEMS”), fabricated using standard VLSI semi-conductor chip fabrication techniques, are becoming increasingly popular as new applications are developed. Such devices are becoming widely used for sensing (for example accelerometers for automotive airbags), inkjet printing, micro-fluidics, and other applications. The use of semi-conductor fabrication techniques allows MEMS to be interfaced very readily with microelectronics. A broad survey of the field and of prior art in relation thereto is provided in an article entitled “The Broad Sweep of Integrated Micro-Systems”, by S. Tom Picraux and Paul McWhorter, in IEEE Spectrum, December 1998, pp 24-33. 
     In PCT Application No. PCT/AU98/00550, the entire contents of which is incorporated herein by reference, an inkjet printing device has been described which utilizes MEMS processing techniques in the construction of a thermal-bend-actuator-type device for the ejection of a fluid, such as an ink, from a nozzle chamber. Such ink ejector devices will be referred to hereinafter as MEMJETs. The technology there described is intended as an alternative to existing technologies for inkjet printing, such as Thermal Ink Jet (TIJ) or “Bubble Jet” technology developed mainly by the manufacturers Canon and Hewlett Packard, and Piezoelectric Ink Jet (PIJ) devices, as used for example by the manufacturers Epson and Tektronix. 
     While TIJ and PIJ technologies have been developed to very high levels of performance since their introduction, MEMJET technology is able to offer significant advantages over these technologies. Potential advantages include higher speeds of operation and the ability to provide higher resolution than obtainable with other technologies. Similarly, MEMJET Technology provides the ability to manufacture monolithic printhead devices incorporating a large number of nozzles and of such size as to span all or a large part of a page (or other print surface), so that page width printing can be achieved without any need to mechanically traverse a small printhead across the width of a page, as in typical existing inkjet printers. 
     It has been found difficult to manufacture a long TIJ printhead for full-page width printing. This is mainly because of the high power consumption of TIJ devices and the problem associated therewith of providing an adequate power supply for the printhead. Similarly, waste heat removal from the printhead to prevent boiling of the ink provides a challenge to the layout of such printhead. Also, differential thermal expansion over the length of a long TIJ-printhead my lead to severe nozzle alignment difficulties. 
     Different problems have been found to attend the manufacture of long PIJ printheads for large- or full-page-width printing. These include acoustic crosstalk between nozzles due to similar time scales of drop ejection and reflection of acoustic pulses within the printhead. Further, silicon is not a piezoelectric material, and is very difficult to integrate with CMOS chips, so that separate external connections are required for every nozzle. 
     Accordingly, manufacturing costs are very high compared to technologies such as MEMJET in which a monolithic device may be fabricated using established techniques, yet incorporate very large numbers of individual nozzles. Reference should he made to the aforementioned PCT application for detailed information on the manufacture of MEMJET inkjet printhead chips; individual MEMJET printhead chips will here be referred to simply as printhead segments. A printhead assembly will usually incorporate a number of such printhead segments. 
     While MEMJET technology has the advantage of allowing the cost effective manufacture of long monolithic printheads, it has nevertheless been found desirable to use a number of individual printhead segments (CMOS chips) placed substantially end-to-end where large widths of printing are to be provided. This is because chip production yields decrease substantially as chip lengths increase, so that costs increase. Of course, some printing applications, such as plan printing and other commercial printing, require printing widths which are beyond the maximum length that is practical for successful printhead chip manufacture. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present disclosure, an inkjet printhead assembly includes an elongate support having a plurality of internal webs protruding from a base section to define a plurality of parallel ink supply channels; a shim mounted on the support and defining a plurality of rows of openings through which ink from respective supply channels is provided; and a plurality of elongate printhead modules mounted serially on the shim. Each module includes a carrier carrying a printhead. Each carrier defines a plurality of ink supply passages through which ink passes to the printhead from respective rows of the openings. Either end of each carrier defines complementary formations such that adjacent pairs of the carriers nest together. The plurality of internal webs protrude from the base section to define a semicircular recess in which the shim is received. The shim is received in the semicircular recess such that the each of the plurality of rows respectively align with one of the plurality of parallel ink channels. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a perspective view of one embodiment of an inkjet printhead assembly according to the invention; 
         FIG. 2  is a perspective view of the inkjet printhead assembly shown in  FIG. 1 , with a cover component (shield plate) removed; 
         FIG. 3  is an exploded perspective view of a part only of the inkjet printhead assembly shown in  FIG. 1 ; 
         FIG. 4  is a perspective partial view of a support extrusion forming part of the inkjet printhead assembly shown in  FIG. 3 ; 
         FIG. 5  is a perspective view of a sealing shim forming part of the inkjet printhead assembly shown in  FIG. 3 ; 
         FIG. 6  is a perspective view of a printhead segment carrier shown in  FIG. 3 ; 
         FIG. 7  is a further perspective view of the printhead segment carrier shown in  FIG. 6 ; 
         FIG. 8  is a bottom elevation of the printhead carrier shown in  FIGS. 6 and 7  (as viewed in the direction of arrow “X” in  FIG. 6 ); 
         FIG. 9  is a top elevation of the printhead carrier shown in  FIGS. 6 and 7  (as viewed in the direction of arrow “Y” in  FIG. 6 ); 
         FIG. 10  is a cross-sectional view of the printhead carrier of  FIGS. 6 and 7  taken at station “B-B” in  FIG. 8 ; 
         FIG. 11  is a cross-sectional view of the printhead carrier of  FIGS. 6 and 7  taken at station “A-A” in  FIG. 8 ; 
         FIG. 11A  is an enlarged cross-sectional view of the seating arrangement of a printhead segment at the print carrier as per detail “E” in  FIG. 11 ; 
         FIG. 12  is a cross-sectional view of the printhead carrier of  FIGS. 6 and 7  taken at station “D-D” in  FIG. 8 ; 
         FIG. 13  is an external perspective view of an end cap of the inkjet printhead assembly shown in  FIG. 1 ; 
         FIG. 14  is an internal perspective view of the end cap shown in  FIG. 13   
         FIG. 15  is an external perspective view of a further end cap of the inkjet printhead assembly shown in  FIG. 1 ; 
         FIG. 16  is an internal perspective view of the end cap shown in  FIG. 15 ; 
         FIG. 17  is a perspective view (from the bottom) of the printhead assembly shown in  FIG. 1 ; 
         FIG. 18  is a perspective view of a part assembly of a support profile and modified sealing shim which are alternatives to those shown in  FIGS. 4 and 5 ; 
         FIG. 19  is a perspective view showing a molding tool and illustrating the basic arrangement of die components for injection molding of the printhead carrier shown in  FIGS. 6 and 7 ; 
         FIG. 20  is a schematic cross-section of the injection molding tool shown in  FIG. 19 , in an open position; and 
         FIG. 21  is a schematic transverse cross-section of the injection molding tool shown in  FIG. 19 , in a closed position, taken at a station corresponding to the station “A-A” in  FIG. 8 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows in perspective view an inkjet printhead assembly  1  according to one aspect of the invention and, in phantom outline, a surface  2  on which printing is to be effected. In use, the surface  2  moves relative to the assembly  1  in a direction indicated by arrow  3  and transverse to the main extension of assembly  1  (this direction is hereinafter also referred to as the transverse direction of the assembly  1 ), so that elongate printhead segments  4 , in particular MEMJET printhead segments such as described in the above-mentioned PCT/AU98/00550, placed in stepped overlapping sequence along the lengthwise extension of assembly  1  can print simultaneously across substantially the entire width of the surface. The assembly  1  includes a shield plate  5  with which the surface  2  may come into sliding contact during such printing. Shield plate  5  has slots  6 , each corresponding to one of the printhead segments  4 , and through which ink ejected by that printhead segment  4  can reach surface  2 . 
     The particular assembly  1  shown in  FIG. 1  has eleven printhead segments  4 , each capable of printing along a 2 cm printing length (or, in other words, within a printing range extending 2 cm) in a direction parallel to arrow  7  (hereinafter also called the lengthwise direction of the assembly  1 ) and is suitable for single-pass printing of a portrait A4-letter size page. However, this number of printhead segments  4  and their length are in no way limiting, the invention being applicable to printhead assemblies of varying lengths and incorporating other required numbers of printhead segments  4 . 
     The slots  6  and the printhead segments  4  are arranged along two parallel lines in the lengthwise direction, with the printing length of each segment  4  (other than the endmost segments  4 ) slightly overlapping that of its two neighboring segments  4  in the other line. The printing length of each of the two endmost segments  4  overlaps the printing length of its nearest neighbour in the other row at one end only. Thus printing across the surface  2  is possible without gaps in the lengthwise direction of the assembly. In the particular assembly shown, the overlap is approximately  1 mm at each end of the 2 cm printing length, but this figure is by no means limiting. 
       FIG. 2  shows assembly  1  with the shield plate  5  removed. Each printhead segment  4  is secured to an associated one printhead segment carrier  8  that will be described below in more detail. Also secured to each printhead segment  4  is a tape automated bonded (TAB) film  9  which carries signal and power connections (not individually shown) to the associated printhead segment  4 . Each TAB film  9  is closely wrapped around an extruded support profile  10  (whose function will be explained below) that houses and supports carriers  8 , and they each terminate onto a printed circuit board (PCB)  11  secured to the profile  10  on a side thereof opposite to that where the printhead segments  4  are mounted, see also  FIG. 3 . 
       FIG. 3  shows an exploded perspective view of a part only of assembly  1 . In this view, three only of the printhead segment carriers  8  are shown numbered  8   a ,  8   b  and  8   c , and only the printhead segment  4  associated with printhead segment carrier  8   a  is shown and numbered  4   a . The TAB film  9  associated therewith is terminated at one end on an outer face of the printhead segment  4  and is otherwise shown (for clarity purposes) in the unwound, flat state it has before being wound around profile  10  and connected to PCB  11 . As can be seen in  FIG. 3 , printhead segment carriers  8  are received (and secured), together with an interposed sealing shim  25 , in a slot  21  of half-circular cross-sectional shape in profile member  10  as will be explained in more detail below. 
       FIG. 4  illustrates a cross-section of the profile member  10  (which is preferably an aluminum alloy extrusion). This component serves as a frame and/or support structure for the printhead segment carriers  8  (with their associated printhead segments  4  and TAB films  9 ), the PCB  11  and shield plate  5 . It also serves as an integral ink supply arrangement for the printhead segments  4 , as will become clearer later, 
     Profile member  10  is of semi-open cross-section, with a peripheral, structured wall  12  of uniform thickness. Free, opposing, lengthwise running edges  16 ′,  17 ′ of side wall sections  16  and  17  respectively of wall  12  border or delineate a gap  13  in wall  12  extending along the entire length of profile member  10 . Profile member  10  has three internal webs  14   a ,  14   b ,  14   c  that stand out from a base wall section  15  of peripheral wall  12  into the interior of member  10 , so as to define together with side wall sections  16  and  17  a total of four (4) ink supply channels  20   a ,  20   b ,  20   c  and  20   d  which are open towards the gap  13 . The shapes, proportions and relative arrangement of the webs and wall sections  14   a - c ,  16 ,  17  are such that their respective free edges  14   a ′,  14   b ′,  14   c ′ and  16 ′,  17 ′, as viewed in the lengthwise direction and cross-section of profile member  10 , define points on a semi-circle (indicated by a dotted line at “a” in  FIG. 4 ). In other words, an open slot  21  of semicircular cross-sectional shape is defined along one side of profile member  10  that runs along its extension, with each of the ink supply channels  20   a - d  opening into common slot  21 . 
     Base wall section  15  of profile member  10  also includes a serrated channel  22  opening towards the exterior of member  10 , which, as best seen in  FIG. 3 , serves to receive fastening screws  23  to fixedly secure PCB  11  onto profile member  10  in a form-fitting manner between free edges  24  (see  FIG. 4 ) of longitudinally extending curved webs  107  extending from the base wall section  15  of profile member  10 . 
     Referring again to  FIG. 3 , sealing shim  25  is received (and secured) within the half-circular open slot  21 . As best seen in  FIGS. 3 and 5 , shim  25  includes four lengthwise extending rows of rectangular openings  26  that are equidistantly spaced in peripheral (widthwise) direction of shim  25 , so that three lengthwise-extending web sections  27  between the aperture rows (of which two are visible in  FIG. 5 ) are located so as to be brought into abutting engagement against the free edges  14   a ′,  14   b ′ and  14   c ′ of webs  14   a ,  14   b ,  14   c  of profile member  10  when shim  25  is received in slot  21 . As can be gleaned from  FIG. 4 , the free edges  16 ′ and  17 ′ of side wall sections  16 ,  17  of profile member  10  are shaped such as to provide a form-lock for retaining the lengthwise extending edges  28  of shim member  25  as a snap fit. In other words, once shim  25  is mounted in profile member  10 , it provides a perforated bottom for slot  21 , which allows passage of inks from the ink supply channels  20   a - d  through apertures  26  in shim  25  into slot  21 . A glue or sealant is provided where shim webs  27  and edges  28  mate with the free edges  14   a ′,  14   b ′,  14   c ′,  16 ′ and  17 ′ of profile member  10 , thereby preventing cross-leakage between ink supply channels  20   a - d  along the abutting interfaces between shim  25  and profile member  10 . It will be noted from  FIG. 5  that not all apertures  26  have the same opening size. Reference numerals  26 ′ indicate two such smaller apertures, the significance of which is described below, which are present in each aperture row at predetermined aperture intervals. A typical size for the full-sized apertures  26  is 2 mm×2 mm. The shim is preferably of stainless steel, but a plastics sheet material may also be used. 
     Turning next to  FIGS. 6-12 , these illustrate in different views and sections a typical printhead segment carrier  8 . Carrier  8  is preferably a single micro-injection molded part made of a suitable temperature and abrasion resistant and form-holding plastics material. (A further manufacturing operation is carried out subsequent to molding, as described below.) As best seen in  FIGS. 6 and 7 , the overall external shape of carrier  8  can be described illustratively as a diametrically slit half cylinder, with a half-circular back face  91 , a partly planar front face  82  and stepped end faces  83 .  FIG. 8  shows a plan view of back face  91  and  FIG. 9  shows a plan view of front face  82 . 
     Carrier  8  has a plane of symmetry halfway along, and perpendicular to, its length, that is, as indicated by lines marked “b” in  FIGS. 8 and 10  which lie in the plane. Line “b” as shown in  FIG. 8  extends in a direction that will hereinafter be described as transverse to the carrier  8 . (When the carrier  8  is installed in the assembly  1 , this direction is the same as the transverse direction of the assembly  1 .) Lines marked “c” in  FIGS. 8, 9, 11 and 12  together similarly indicate the position of an imaginary plane which lies between two sections of the carrier  8  of different length and whose overall cross-sectional shapes are quarter circles. Line “c” as shown in  FIG. 9  extends in a direction that will hereinafter be described as lengthwise in the carrier  8 . (When the carrier  8  is installed in the assembly  1  this direction is the same as the lengthwise direction of the assembly  1 .) These sections will hereinafter be referred to as the shorter and longer “quarter cylinder” sections  8 ′ and 8″, respectively, to allow referenced description of features of the carrier  8 . 
     Each stepped end face  83  includes respective outer faces  84 ′ and  85 ′ of quarter-circular-sector shaped end walls  84  and  85  and an outer face  86 ′ of an intermediate step wall  86  between and perpendicular to end walls  84 ,  85 . This configuration enables carriers  8  to be placed in the slot  21  of profile  10  in such a way that adjoining carriers  8  overlap in the lengthwise direction with the step walls  86  of pairs of neighbouring carriers  8  facing each and overlapping. Such an “interlocking” arrangement is shown in  FIG. 2 , wherein it is apparent that every one of the eleven (11) carriers  8  has an orientation, relative to its neighbouring carrier or carriers  8 , such that faces  84 ′ and  85 ′ of each carrier lie adjacent to faces  85 ′ and  84 ′, respectively, of its neighbouring carrier(s)  8 . In other words, each carrier  8  is so oriented in relation to its neighbouring carrier(s) as to be rotated relatively by 180° about an axis perpendicular to the face  82 . In essence, neighbouring carriers  8  will align along a common lengthwise-oriented plane defined between the step walls  86  of adjoining carriers  8 , shorter and longer quarter cylinder sections  8 ′ and  8 ″ of adjoining carriers  8  alternating with one another along the extension of slot  21 . 
     Turning now in particular to  FIGS. 7, 9, 11 and 11   a , front face  82  of carrier  8  includes on the shorter quarter cylinder section  8 ′ a planar surface  81 . Formed in surface  81  are two handling (i.e. pick-up) slots  87  whose purpose is described below. On the longer quarter cylinder section  8 ″, front face  82  incorporates a mounting or support surface  88  recessed with respect to edges  89  of sector-shaped end walls  84  that are co-planar with the surface  81 . As best seen in  FIG. 11 , mounting surface  88  recedes in slanting fashion from a point on the back face  91  of the longer quarter cylinder section  8 ″ towards an elongate recess  90  extending lengthwise between walls  84 . Recess  90  is of constant transverse cross-section along its length and is shaped to receive in form-fitting manner one printhead segment  4 .  FIG. 11 a    shows, schematically only, printhead segment  4  in position in recess  90 . Mounting surface  88  is provided to accommodate in flush manner with respect to the surface  81  the terminal end of TAB film  9  connected to printhead segment  4 , as is best seen in  FIG. 3 . Due to the opposing orientations of neighbouring carriers  8  along the extension of assembly  1 , the TAB films  9  associated with any two neighbouring carriers  8  lead away from their respective segments  4  in opposite transverse directions, as can be seen in  FIG. 2 . 
     Referring now to  FIGS. 6, 7, 8, 10 and 11  in particular, four rows of ink galleries or ink supply passages  92   a  to  92   d  of generally quadrilateral cross-section are formed within the printhead segment carrier  8 . The ink galleries  92   a  to  92   d  act as conduits for ink to pass from the ink supply passages  20   a  to  20   d , respectively, via openings  26  in the shim  25 , to the printhead segment  4  mounted in recess  90  of the printhead segment carrier  8 . Galleries  92   a - 92   d  extend in quasi-radial arrangement between the half-cylindrical back face  91  of carrier  8  and recess  90  located in the longer quarter cylinder section  8 ″ at front face  82 . The expression “quasi-radial” is used here because recess  90  is not located at a transversely central position across carrier  8 , but is offset into the longer quarter cylinder section  8 ″, so that the inner ends of galleries  92   a - 92   d  are similarly off-set, as further described below. Each gallery  92  has a rectangular opening  93  at back face  91 . All rectangular openings  93  have the same dimension in a peripheral direction of face  91  and are equidistantly spaced around the periphery of back face  91 . Moreover, the openings  93  are symmetrically located on opposing sides of the boundary between shorter quarter cylinder section  8 ′ and longer quarter cylinder section  8 ″, as represented in  FIG. 11  by the line marked “c”. All openings  93  in the shorter quarter cylinder section  8 ′ are of the same dimension, and equispaced, in the lengthwise direction. This also applies to the openings  93  in the longer quarter cylinder section  8 ″, except that openings  93 ′ in the longer quarter cylinder section  8 ″ which correspond to endmost galleries  92   a ′ and  92   b ′ are of smaller dimension in the lengthwise direction than the other galleries  92   a  and  92   b , respectively. 
     By way of further description of how the galleries  92   a  to  92   d  are formed, printhead segment carrier  8  includes a set of five (5) quasi-radially converging walls  95  which converge from back face  91  towards recess  90  at front face  82  and two of which define the faces  81  and  88 . The walls  95  perpendicularly intersect seven (7) generally semi-circular and mutually parallel walls  97  that are equidistantly spaced apart in lengthwise extension of carrier  8 . Of walls  97 , the two endmost ones extending into the shorter quarter cylinder section  8 ′ provide the end walls  85  of stepped end faces  83 , thereby defining twenty-four (24) quasi-radially extending ink galleries  92   a  to  92   d , of quadrilateral cross-section, in four lengthwise-extending rows each of six galleries. The walls  97  are parallel to and lie between end walls  84 . 
       FIG. 12  shows a cross-section through one of the lengthwise end portions of longer quarter cylinder section  8 ″ of carrier  8 . By comparison with  FIG. 11  (which shows a cross-section through the main body of carrier  8 ), it will be seen that the quasi-radially extending walls  95  bordering end gallery  92   a ′ have the same shape as walls  95  which border galleries  92   a , whereas gallery  92   b ′ is bounded on one side by intermediate step wall  86  and by a wall  108 .  FIG. 12  also shows a wall  111  and a wall formation  112  on the wall  86 , the purpose of which is explained below. 
     Converging walls  95  are so shaped at their radially inner ends as to define four ink delivery slots  96   a  to  96   d  which extend lengthwise in the carrier  8  and which open into the recess  90 , as best seen in  FIGS. 11 and 11   a . The slots  96   a  to  96   d  extend between the opposite end walls  84  of longer quarter cylinder section  8 ″ and pierce through the inner parallel walls  97 , including the endwise opposite walls  97  which form the end walls  85  of the shorter cylinder section  8 ′.  FIG. 12  shows how slots  96   a  to  96   d  extend and are formed within the end portions of the longer quarter cylinder section  8 ″, where the slots  96   a  to  96   d  are defined by the terminal ends of two of walls  95 , walls  108 ,  111  and wall formation  112 , wall formation  112  in effect being a perpendicular lip of intermediate step wall  86 . 
     The widths and transverse positioning of the ink delivery slots  96   a  to  96   d  are such that when a printhead segment  4  is received in recess  90 , a respective one of the slots  96   a - 96   d  will be in fluid communication with one only of four lengthwise oriented rows of ink supply holes  41  on rear face  42  of printhead segment  4 , compare  FIG. 11 a   . Each row of ink supply holes  41  corresponds to a row of printhead nozzles  43  running lengthwise along the front face  44  of printhead segment  4 . In the schematic representation of segment  4  in  FIG. 11 a   , the positions of holes  41  and nozzles are indicated by dots, with no attempt made to show their actual construction. Reference to PCT Application No. PCT/AU98/00550 will provide further details of the make-up of segment  4 . Accordingly, each of the ink galleries of a specific gallery row  92   a  to  92   d  is in fluid communication with one only of the rows of ink supply holes  41 . Once a printhead segment  4  is form fittingly received in recess  90  and sealingly secured with its rear face  42  against the terminal inner ends of walls  95 , and wall formations  108 ,  111  and  112  (using a suitable sealant or adhesive), cross-communication and ink bleeding between slots  96   a - 96   d  via recess  90  is not possible. 
     When a carrier  8  is installed in its correct position lengthwise in the slot  21  of profile  10 , compare  FIG. 3 , each opening  93  in its back face  91  aligns with one of the openings  26  in the shim  25 . Smaller openings  26 ′ in the shim  25  correspond to openings  93 ′ of the smaller galleries  92   a ′ and  92   b ′ of carrier  8 . Therefore, each one of the ink supply channels  20   a  to  20   d  is in fluid communication with one only of the rows of ink galleries  92   a  to  92   d , respectively, and so with one only of the slots  96   a  to  96   d  respectively and only one of the rows of ink supply holes  41 . A suitable glue or sealant is provided at mating surfaces of the shim  25  and the carrier  8  to prevent leakage of ink from any of the channels  20   a  to  20   d  to an incorrect one of the galleries  92 , as described further below. The symmetrical location (mentioned above) of openings  93  on back face  91  of carrier  8 , which is matched by the openings  26  in shim  25 , enables the carrier  8  to be received in the slot  21  in either of the two orientations shown in  FIG. 3 , with in both cases each row of ink galleries  92   a  to  92   d  aligning with one only of the ink supply channels  20   a  to  20   d.    
     As mentioned above, the longer quarter cylinder section  8 ″ of carrier  8  has two galleries  92   a ′ and  92   b ′ at each lengthwise end that have no counterpart in the shorter section  8 ′. These galleries  92   a ′ and  92   b ′ provide direct ink supply paths to that part of their associated ink delivery slots  96   a  and  96   b  located in the longer quarter cylinder section  8 ″, and thus to the ink supply holes  41  of the printhead segment  4  that are located near the lengthwise terminal ends of segment  4  when secured within recess  90 . There are no corresponding quasi-radial galleries to supply ink to the end regions of the slots  96   c  and  96   d . However, it is desirable to provide direct ink supply to the end portions of the other two slots  96   c  and  96   d  as well, without reliance on lengthwise flow within the slots  96   c  and  96   d  of ink that has passed through galleries  92   c  and  92   d  respectively. This is ensured by provision of ink supply chambers  99   c  and  99   d  which are shown in  FIG. 12  and which supply ink to the slots  96   c  and  96   d , respectively. Chambers  99   c  and  99   d  are bounded by the walls  84 ,  86 , and wall formations  108 ,  111  and  112 , are open towards slots  96   c  and  96   d , respectively, and are in fluid communication through holes  113  and  114  in an endmost wall  97  with endmost ones of ink galleries  92   c  and  92   d , respectively. The holes  113  and  114  have outlines shaped to match the transverse cross-sectional shapes of the chambers  99   c  and  99   d , respectively, as shown in  FIG. 12 , and the means whereby holes  113  and  114  are formed is described below. 
       FIGS. 13 and 14  show a first end cap  50  which is sealingly secured to an open terminal longitudinal end of profile member  10 , as may be seen in  FIGS. 1 and 2 . Cap  50  is molded from a plastics material and it incorporates a generally planar wall portion  51  that extends perpendicularly to a lengthwise axis of profile member  10 . Four tubular stubs  55   a - 55   d  are integrally moulded with planar wall portion  51  on side  52  of wall portion  51  which will face away from support profile  10  when end cap  50  is secured thereto. On the planar wall side  53  which will face the longitudinal terminal end of support profile  10  (see  FIG. 14 ), four hollow-shaped stubs  57   a - 57   d  are integrally moulded with planar wall portion  51 . As best seen in  FIG. 14 , ink supply conduits  56   a  to  56   d  are defined within tubular stubs  55   a  to  55   d  respectively, extend through planar wall portion  51 , and open within shaped stubs  57   a  to  57   d , respectively, located on the other sides of cap  50 . 
     The shape of each one of the insert stubs  57   a  to  57   d , as seen in transverse cross-section, corresponds respectively to one of the ink supply channels  20   a  to  20   d  of support profile so that, when cap  50  is secured to the terminal axial end of support profile  10 , the walls of stubs  57   a - 57   d  are received form-fittingly in ink supply channels  20   a - 20   d  to prevent cross-migration of ink therebetween. The face  53  abuts a terminal end face of the profile  10 . Preferably, glue or a sealant can be applied to the mating surfaces of profile  10  and cap  50  to enhance the sealing function. 
     The tubular stubs  55   a - 55   d  serve as female connectors for pliable/flexible ink supply hoses (not illustrated) that can be connected thereto sealingly, thereby to supply ink to the integral ink supply channels  20   a - 20   d  of support profile  10 . 
     A further stub  58 , D-shaped in transverse cross-section, is integrally molded to planar wall portion  51  at side  53 . In completed assembly  1 , the curved wall  71 , semi-circular in transverse cross-section, of retaining stub  58  seals against the inside surface of shim  25 , with the terminal edge of shim  25  abutting a peripheral ridge  72  around the stub  58 . Preferably, to avoid cross-migration of ink among channels  20   a  to  20   d , an adhesive or sealant is provided between the shim  25  and wall  71 . The stub  58  assists in retaining the shim  25  in slot  21 . 
     A second end cap  60 , which is shown in  FIGS. 15 and 16 , is mounted to the other end of the profile  10  opposite to cap  50 . Cap  60  has insert stubs  67   a  to  67   d  and a retaining stub  68  identical in arrangement and shape to stubs  57   a  to  57   d  and stub  58 , respectively, of end cap  50 . Insert stubs  67   a  to  67   d  and retention stub  68  are integrally molded with a planar wall portion  61 , and in the completed assembly  1  seal off the individual ink supply channels  20   a - 20   d  from one another, to prevent cross-migration of ink among them. Wall  77  of the retention stub  68  abuts the shim  25  in the same way as described above. A sealant or adhesive is preferably used with end cap  60  in the same way (and for the same purpose) as described above in respect of end cap  50 . 
     Whereas end cap  50  enables connection of ink supply hoses to the printhead assembly  1 , end cap  60  has no tubular stubs on exterior face  62  of planar wall portion  61 . Instead, four tortuous grooves  65   a  to  65   d  are formed on exterior face  62 , and terminate at holes  66   a  to  66   d , respectively, extending through wall portion  61 . Each one of holes  66   a  to  66   d  opens into a respective one of the channels  20   a  to  20   d  so that when the cap  60  is in place on the profile  10 , each one of the grooves  65   a  to  65   d  is in fluid communication with a respective one of the channels  20   a  to  20   d . The grooves  65   a - 65   d  permit bleeding-off of air during priming of the printhead assembly  1  with ink, as holes  66   a - 66   d  permit air expulsion from the ink supply channels  20   a - 20   d  of support profile  10  via grooves  65   a - 65   d . Grooves  65   a - 65   d  are capped under a translucent plastic film  69  bonded to outer face  62 . Translucent plastic film  69  thus also serves the purpose of allowing visual confirmation that the ink supply channels  20   a - 20   d  of profile  10  are properly primed. For charging the ink supply channels  20   a - 20   d  with ink, film  69  is folded back (as shown in  FIG. 15 ) to partially uncover grooves  65   a - 65   d , so that displaced air may bleed out as ink enters the grooves  65   a - 65   d  through holes  66   a - 66   d . When ink is visible behind film  69  in each groove  65   a - 65   d , film  69  is folded towards face  62  and bonded against face  62  to sealingly cover face  62  and so cap-off grooves  65   a - 65   d  and isolate them from one another. 
     Referring to  FIG. 17  (and see also  FIGS. 3 and 4 ), the printed circuit board (PCB)  11  locates between edges  24  formed on profile  10 , and is secured by screw fasteners  23  which engage with the serrations in elongate channel  22  of support profile  10 . The PCB  11  contains three surface mounted halftoning chips  73 , a data connector  74 , printhead power and ground busbars  75  and decoupling capacitors  76 . Side walls  16 ,  17  of support profile  10  are rounded near the edges  24  to avoid damage to the TAB films  9  when these are wound about profile  10 . The electronic components  73  and  76  are specific to the use of MEMJET chips as the printhead segments  4 , and would of course, if other another printhead technology were to be used, be substituted with other components as necessitated by that technology. 
     The shield plate  5  illustrated in  FIG. 1 , which is a thin sheet of stainless steel, is bonded with sealant such as a silicon sealant onto the printhead segment carriers  8 . The shield plate  5  shields the TAB films  9  and the printhead segments  4  from physical damage and also serves to provide an airtight seal around the printhead segments  4  when the assembly  1  is capped during idle periods. 
     The multi-part layout of the printhead assembly  1  that has been described in detail above has the advantage that the printhead segment carriers  8 , which interface directly with the printhead segments  4  and which must therefore be manufactured with very small tolerances, are separate from other parts, including particularly the main support frame (profile  10 ) which may therefore be less tightly toleranced. As noted above, the printhead segment carriers  8  are precision injection micro-moldings. Moldings of the required size and complexity are obtainable using existing micromolding technology and plastics materials such as ABS, for example. Tolerances of +/−10 microns on specified dimensions are achievable including the ink supply grooves  96   a - 96   d , and their relative location with respect to the recess  90  in which the printhead segments  4  are received. Such tolerances are suitable for this application. Other material selection criteria are thermal stability and compatibility with other materials to be used in the assembly  1 , such as inks and sealants. The profile  10  is preferably an aluminum alloy extrusion. Tolerances specified at +/−100 microns have been found suitable for such extrusions, and are achievable as well. 
       FIGS. 19, 20 and 21  are schematic representations only, intended to provide an understanding of the construction of an injection molding die used in the manufacture of a printhead segment carrier  8 . A multi-part die  100  is used, having a fixed base die part  104 , which in use defines the face  82 , recess  90  and slots  96   a  to  96   d  of the carrier  8 , and a multi-part upper die part  102 . The upper die part  102  is closed against the base part  104  for molding, and includes a part  101  with multiple fingers  101   a  which in use form the galleries  92   b  (including galleries  92   b ′) and parts  106  which are fixed relative to part  101 . Also included in the upper part  102  are die parts  103  which are movable relative to the part  101  and which have fingers  103   a  to form the remaining galleries  92   a ,  92   c  and  92   d . Parts  103  seat against parts  106  when molding is underway. Spaces between the fingers  101   a  and  103   a  correspond to the walls  97 . In use of the die  100 , terminal tips of the fingers  101   a  and  103   a  close against blades  105  which in use form the ink supply slots  96   a - 96   d  of carrier  8  and which are mounted to male base  104  to be detachable and replaceable when necessary. Base die part  104  also has inserts  104   a  which in use form the pickup slots  87 . Because zero draft is preferred on the stepped end faces  83  in this application, the die  100  also has two movable end pieces (not shown, for clarity) which in use of the die  100  are movable generally axially to close against the upper die part  102  and which are shaped to define the end faces  84 ′,  85 ′ and  86 ′ of carrier  8 .  FIG. 21  shows a schematic transverse cross-section of the mold  100  when closed, with areas in black corresponding to the carrier  8  being molded. 
     As was mentioned above, the two opposite end portions of the larger quarter cylinder section of carrier  8  incorporate two ink supply chambers  99   c  and  99   d  (see  FIG. 12 ) to provide ink to the ink supply slots  96   c  and  96   d  in that region of the carrier  8 . These chambers  99   c  and  99   d  and associated communication holes  113  and  114  in parallel walls  97  that lead into the neighbouring galleries  92   c  and  92   d , are formed in an operation subsequent to molding, by laser cutting openings of the required shape in the end walls  84  and the neighbouring inner parallel walls  97  from each end. The openings cut in end walls  84  are only necessary so as to access the inner walls  97 , and are therefore subsequently permanently plugged using appropriately shaped plugs  115  as shown in  FIG. 6 . 
     Extrusions usable for profile  10  can be produced in continuous lengths and precision cut to the length required. The particular support profile  10  illustrated is 15.4 mm—25.4 mm in section and about 240 mm in length. These dimensions, together with the layout and arrangement of the walls  16  and  17  and internal webs  14   a  to  14   c , have been found suitable to ensure adequate ink supply to eleven (11) MEMJET printhead segments  4  carried in the support profile to achieve four-color printing at 120 pages per minute (ppm). Support profiles with larger cross-sectional dimensions can be employed for very long printhead assemblies and/or for extremely high-speed printing where greater volumes of ink are required. Longer support profiles may of course be used, but are likely to require cross-bracing and location into a more rigid chassis to avoid alignment problems of individual printhead segments, for example in the case of a wide format printer of 54″ (1372 mm) or more. 
     An important step in manufacturing (and assembling) the assembly  1  is achieving the necessary, very high level of precision in relative positioning of the printhead segments  4 , and here too the construction of the assembly  1  as described above is advantageous. A suitable manufacturing sequence that ensures such high relative positioning of printheads on the support profile will now be described. 
     After manufacture and successful testing of an individual printhead segment  4 , its associated TAB film  9  is bumped and then bonded to bond pads along an edge of the printhead segment  4 . That is, the TAB film is physically secured to segment  4  and the necessary electrical connections are made. The terms “bumped” and “bonded” will be familiar to persons skilled in the arts where TAB films are used. The printhead carrier  8  is then primed with adhesive on all those surfaces facing into recess  90  that mate and must seal with the printhead segment  4 , see  FIG. 11 a   , i.e. along the length of the radially-inner edges of walls  95 ,  108  and  111 , the face of formation  112  and on inner faces of walls  84 . The printhead segment  4  is then secured in place in recess  90  with its TAB film  9  attached. Extremely accurate alignment of the printhead segment  4  within recess  90  of printhead segment carrier  8  is not necessarily required (but is preferred), because relative alignment of all segments  4  at the support profile  10  is carried out later, as is described below. The assembly of the printhead segment  4 , printhead segment carrier  8  and TAB film  9  is preferably tested at this point for correct operation using ink or water, before being positioned for placement in the slot  21  of support profile  10 . 
     The support profile  10  is accurately cut to length (where it has been manufactured in a length longer than that required, for example by extrusion), faced and cleaned to enable good mating with the end caps  50  and  60 . 
     A glue wheel is run the entire length of semi-circular slot  21 , priming the terminal edges  14   a ′,  14   b ′,  14   c ′ of webs  14   a - 14   c  and edges  16 ′,  17 ′ of profile side walls  16 ,  17  with adhesive that will bond the sealing shim  25  into place in slot  21  once sealing shim  25  is placed into it with preset distance from its terminal ends (+/−10 microns). The shim  25  is snap-fitted into place at edges  16 ′,  17 ′ and the glue is allowed to set. Next, end caps  50  and  60  are bonded into place whereby (ink channel sealing) insert stubs  57   a - 57   d  and  67   a - 67   d  are received in ink channels  20   a - 20   d  of profile  10 , and faces  71  and  77  of retention stubs  58  and  68 , respectively, lie on shim  25 . This sub-assembly provides a chassis in which to successively place, align and secure further sub-assemblies (hereinafter called “carrier subassemblies”) each consisting of a printhead segment carrier  8  with its respective printhead segment  4  and TAB film  9  already secured in place thereon. 
     A first carrier sub-assembly is primed with glue on the back face  91  of its printhead segment carrier  8 . At least the edges of walls  95  and  86  are primed. A glue wheel, running lengthwise, is preferably used in this operation. After priming with glue, the carrier sub-assembly is picked up by a manipulator arm engaging into pick-up slots  87  on front face  82  of carrier  8  and placed next to the stub  58  of end cap  50  (or the stub  68  of cap  60 ) at one end of slot  21  in profile  10 . The glue employed is of slow-setting or heat-activated type, thereby to allow a small level of positional manipulation of each carrier subassembly, lengthwise in the slot  21 , before final setting of the glue. With the first carrier subassembly finally secured to the shim  25  within the slot  21 , a second carrier sub-assembly is then picked up, primed with glue as above, and placed in a 180-degree-rotated position (as described above, and as may be seen in  FIG. 3 ) next to the first carrier sub-assembly onto shim  25  and within the slot  21 . The second carrier sub-assembly is then positioned lengthwise so that there is correct lengthwise relative positioning of its printhead segment  4  and the segment  4  of the previously-placed segment  4 , as determined using suitable fiducial marks (not shown) on the exposed front surface  44  of each of the printhead segments  4 . That is, lengthwise alignment is carried out between successive printhead segments  4 , even though it is the printhead segment carrier  8  that is actually manipulated. This relative alignment is carried out to such (sub-micron) accuracy as is required to match the printing resolution capability of the printhead segments  4 . Finally, the bonding of the second carrier sub-assembly to shim  25  is completed. The above process is then repeated with further carrier sub-assemblies being successively positioned, aligned, and bonded into place, until all carrier subassemblies are in position within the slot  21  and bonded in their correct positions. 
     The shield plate  5  has a thin film of silicon sealant applied to its underside and is mated to the printhead segment carriers  8  and TAB films  9  along the entire length of the printhead assembly  1 . By suitable choice of adhesive properties of the silicon sealant, the shield plate  5  can be made removable to enable access to the printhead segment carriers  8 , printhead segments  4  and TAB films  9  for servicing and/or exchange. 
     A sub-assembly of PCB  11  and printhead control and ancillary components  73  to  76  is secured to profile  10  using four screws  23 . The TAB films  9  are wrapped around the exterior walls  16 ,  17  of profile  10  and are bumped and bonded (i.e. physically and electrically connected) to the PCB  11 . See  FIG. 17 . 
     Finally, the completed assembly  1  is connected at the ink inlet stubs  55   a - d  of end cap  50  to suitable ink supplies, primed as described above and sealed using sealing film  69  of end cap  60 . Power and signal connections are completed and the inkjet printhead assembly  1  is ready for final testing and subsequent use. 
     It will be apparent to persons skilled in the art that many variations of the above-described assembly and components are possible. For example,  FIG. 18  shows a shim  125  that is substantially the same as shim  25 , including having openings  126  and  126 ′ corresponding to the openings  26  and  26 ′ in shim  25 , save for longitudinally extending rim webs  128  which, when the shim  125  is mounted to a support profile  110 , abut in surface-engaging manner against the outside of the terminal ends of side walls  116 ,  117  of profile  110  instead of being snap-fittingly received between them as is the case with shim  25 . This arrangement permits wider tolerances to be used in the manufacture of the support profile  110  without compromising the mating capability of the shim  125  and the profile  110 . 
     In yet another possible arrangement, the shim  25  could be eliminated entirely, with the printhead segment carriers  8  then bearing and sealing directly on the edges  14   a ′- 14   c ′ and  16 ′,  17 ′ of the webs  14   a - 14   c  and side walls  16 ,  17  at slot  21  of support profile  10 . 
     It will be appreciated by persons skilled in the art that still further variations and modifications may be made without departing from the scope of the invention. The embodiments of the present invention as described above are in no sense intended to be restrictive.