(I2) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(19) World Intellectual Property Organization
`International Bureau
`
`MWWWWWWWWWMWWMWWM
`
`(43) International Publication Date
`7 September 2001 (07.09.2001)
`
`(10) International Publication Number
`
`PCT
`
`WO 01/64444 Al
`
`(51) International Patent Classification’:
`2/155
`
`B4IJ 2/I 45,
`
`(21) International Application Number:
`
`PCT/AU0lI00216
`
`(22) International Filing Date:
`
`2 March 2001 (02.03.2001)
`
`(25) Filing Language:
`
`(26) Publication Language:
`
`English
`
`English
`
`(30) Priority Data:
`PQ 5959
`
`2 March 2000 (02.03.2000)
`
`AU
`
`(71) Applicant for all designated States except US): SILVER-
`BROOK RESEARCH PTY LTD [AU/AU]: 393 Darling
`
`Street, Balmain, New South Wales 2041 (AU).
`
`(72) Inventor; and
`(75) InventorlApplicant (for US only): SILVERBROOK,
`Kia [AU/AU]; Silverbrook Research Pty Ltd, 393 Darling
`Street, Balmain, New South Wales 204] ‘ (AU).
`
`(74) Agent: SILVERBROOK, Kia; Silverbrook Research Pty
`Ltd, 393 Darling Street, Balmain, New South Wales 2041
`(AU).
`
`(81) Designated States (national): AE, AG, AL, AM, AT, AU,
`AZ, BA, BB, BG, BR, BY, BZ, CA, CH, CN, CR, CU, CZ,
`DE, DK, DM, DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR,
`HU, ID, IL. IN, IS. JP, KE, KG, KP, KR, KZ, LC, LK, LR,
`LS, LT. LU, LV, MA, MD, MG, MK, MN, MW, MX, MZ,
`NO. NZ, PL, PT. RO. RU, SD, SE, SG, SI, SK. SL, TJ. TM,
`TR, T1‘, TZ, UA, UG, US, UZ, VN, YU. ZA, ZW.
`
`Designated States (regional): ARIPO patent (GH, GM,
`KE, LS, MW, MZ, SD, SL, SZ, TZ, UG, ZW), Eurasian
`patent (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), European
`patent (AT, BE, CH, CY, DE, DK, ES, Fl, FR, GB, GR, IE,
`IT, LU, MC, NL, PT, SE, TR), OAPI patent (BF, BJ. CF,
`CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG).
`
`Pub“shed_
`with international search report
`
`For rwo-letter codes and other abbreviations, refer to the "Guid-
`ance Notes an Codes and Abbreviations "appearing at the begin-
`ning ofeach regular issue ofthe PCT Gazette.
`
`(54) Title: OVERLAPPING PRINTHEAD MODULE ARRAY CONFIGURATION
`
`—:—j—-1—_1
`
`— 1
`
`:
`-1-
`
`j‘—
`
`_——T———j._.__
`
`_.
`
`—_—
`1.-
`
`‘-
`
`j—j
`
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`-1-
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`————T.—-—j
`
`.1-—_—
`
`4444A1
`
`52
`
`3
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`(57) Abstract: A modular pagewidth printhead for a digital ink jet printer having a metal chassis (1) where modules (2) are arranged
`in an overlapping configuration to preserve continuity between the printing from adjacent replaceable modules (2). The printhead
`has an ink reservoir (4), a flexible PCB (10) and busbar(1l). The printhead chips (3) such as MEMJET on each module (2) receive
`print data from TAB films (6). The TAB films (6) extend from the same side of each of the MEMJETchips (3) to allow for a relatively
`compact printhead design. The chips (3) are configured so that predominately all of the chips (3) in the array have, at most, one end
`obscured by the end of an adjacent chip (3). The configuration includes overlapping and inclining the printheads with respect to the
`support beam. This reduces the amount that the TAB films (6) need to narrow or "neck" in order to avoid the obscuring adjacent end.
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`WO 01/64444
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`PCT/AU01/00216
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`OVERLAPPING PRINTHEAD MODULE ARRAY CONFIGURATION
`
`Field of the Invention.
`
`The invention relates broadly to digital inkjet printers and in particular to digital
`
`ink jet printers configured to print the entire width of a page simultaneously.
`
`Co-Pending Applications.
`
`Various methods, systems and apparatus relating to the present invention
`
`are disclosed in the following co—pending applications filed by the applicant or assignee
`
`of the present invention on 24 May 2000:
`
`PCT/AUOO/0057 8
`
`PCT/AU00/00579
`
`PCT/AU00/00581
`
`PCT/AU00/005 80
`
`PCT/AUOO/005 82
`
`PCT/AUOO/00587
`
`PCT/AU00/00588
`
`PCT/AU00/005 89
`
`PCT/AU00/005 83
`
`PCT/AU00/00593
`
`PCT/AU00/00590
`
`PCT/AU00/00591
`
`PCT/AUOO/00592
`
`PCT/AU00/005 S4
`
`PCT/AU00/00585
`
`PCT/AU00/O05 86
`
`PCT/AUO0/00594
`
`PCT/AU00/00595
`
`PCT/AU00/00596
`
`PCT/AU00/00597
`
`PCT/AUOO/00598
`
`PCT/AU00/005 16
`
`PCT/AU00/00517
`
`PCT/AU00/005 1 1
`
`The disclosures of these co—pending applications are incorporated herein by cross-
`
`reference. Also incorporated by cross—reference, is the disclosure of a cb~filed PCT
`
`-application, PCT/AU01/00217 (deriving priority from Australian Provisional Patent
`
`Application No. PQ5957).
`
`Background of the Invention.
`
`Traditionally, inkjet printers have used a printing head that traverses back and forth A
`
`across the width of a page as it prints. Recently, it has been possible to form printheads
`
`that extend the entire width of the page so that the printhead can remain stationary as the
`
`page is moved past it. As pagewidth printheads do not move back and forth across the
`
`page, much higher printing speeds are possible.
`
`Pagewidth printheads are typically micro electro mechanical systems (MEMS)
`
`devices that are manufactured in a manner similar to silicon computer chips.
`
`In this
`
`process, the ink nozzles and ejector mechanisms are formed in a series of etching and
`
`deposition procedures on silicon wafers.
`
`RECTIFIED SHEET (RULE 91)
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`As an industry standard, the silicon wafers are produced in 6 or 8 inch diameter
`
`disks. Consequently only a small strip across the diameter of each wafer can be used to
`
`produce printing chips of sufficient width for pagewidth printing. As a large part of
`
`these wafers are essentially wasted, the production costs of pagewidth printhead chips
`
`- are relatively high.
`
`The costs are further increased because the chip defect rate is also relatively high.
`
`Faults will inevitably occur during silicon chip manufacture and some level of attrition is
`
`always present. A single fault will render an entire pagewidth chip defective, as is the
`
`case with any silicon chip production. However, because the pagewidth chip is larger
`
`than regular chips, there is a higher probability that any particular pagewidth chip will be
`
`defective thereby raising the defect rate as a whole in comparison to regular silicon chip
`
`production.
`
`To address this, the pagewidth printhead may be formed from a series of separate
`
`printhead modules. Using a number of adjacent printhead modules permits full
`
`pagewidth printing while allowing a much higher utilization of the silicon wafer. This
`
`lowers the printhead chip defect rate because a fault will cause a relatively smaller
`
`‘ printhead chip to be rejected rather than a full pagewidth chip. This in turn translates to
`
`lower production costs.
`
`Each printhead chip carries an array of nozzles which have mechanical structures
`
`with sub—rnicron thickness. The nozzle assemblies use thermal bend actuators that can
`
`rapidly eject ink droplets sized in the Pico litre (X 1042 litre) range.
`
`The microscopic scale of these structures causes problems when butting a series
`of printhead modules end to end in order to form a pagewidth printhead. Microscopic
`
`irregularities on the end surfaces of each chip prevent them from perfectly abutting the
`
`end surface on an adjacent chip. This causes the spacing between the end nozzles of two
`
`. adjacent printhead chips to be different from adjacent nozzles on a single printhead chip.
`The gaps between adjacent printhead chips can lower the resultant print quality.
`
`To eliminate the gaps, some modular pagewidth printheads use two adjacent lines
`
`of regularly spaced printhead modules. The lines are out of register with each other and
`
`the ends of a printhead module in one line overlaps with the ends of two adjacent
`
`modules in the other line. This removes the gaps from the resultant printing but also
`
`provides redundant nozzles in the areas of overlap. The print data to the overlapping
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`nozzles is allocated between the adjacent chips so that these areas are not printed twice
`
`which would otherwise have adverse affects on the print quality.
`
`A digital controller is connected to each of the printhead module chips via a TAB
`
`(tape automated bond) film. The TAB film is substantially the same width as the chip
`
`and this causes difficulties when mounting the chips to a support structure within the
`
`printer.
`
`It is preferable that the TAB films for each chip extend from the same side as
`
`this permits a more compact and elegant printhead design. However, this arrangement
`
`requires the TAB films from each of the chips in one of the lines to narrow or ‘neck’ in
`
`order to fit past the restriction caused by the overlapping ends of the adjacent chips in the
`
`other line. Producing and installing TAB films that narrow down enough is complex and
`
`difficult. To avoid this, the TAB films can extend from one side of the chips in one line
`
`and from the opposite side of the chips in the other line. However, as discussed above
`
`this gives the overall printhead greater bulk that can complicate the paper path through
`
`the printer as well as hamper capping the printheads when the printer is not in use.
`
`Summary of the Invention.
`
`Accordingly, the present invention provides a modular printhead for a inkjet
`
`printer, the modular printhead including:
`
`a support frame;
`
`a plurality of printhead modules mounted to the support frame, each module
`
`having an elongate array of ink nozzles extending substantially linearly across the width
`
`of the module such that there is overlap between the elongate arrays of adjacent modules
`
`with respect to the direction of paper movement; wherein,
`
`the modules are arranged such that a first side of each of the nozzle arrays faces 4
`
`toward a first side of the support frame; such that,
`
`therespective first sides of predominantly all of the nozzle arrays have at most
`
`one end portion obscured from the first side of the support frame by the nozzle array of
`
`an adjacent module.
`
`Preferably, the respective first sides of each of the nozzle arrays have at most one
`
`end portion obscured from the first side of the support frame by the nozzle array of an
`
`adjacent module.
`
`By inclining the printhead chips with respect to the support beam and configuring
`
`them to overlap with respect the to paper direction, the TAB films for each chip can
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`extend from the same side. This allows the printhead design to remain relatively
`
`compact while avoiding the need to significantly narrow or ‘neck’ most if not all the
`
`TAB films.
`
`Preferably, the modules are mounted to the support frame along a substantially
`
`straight mounting line such that each of the elongate arrays extends in a direction
`
`inclined to the mounting line of the modules.
`
`In a further preferred form, the mounting
`
`line is normal to the paper direction.
`
`Preferably, the printhead is digitally controlled such that print data sent to the
`
`overlapping portions of adjacent modules is shared between the ink nozzles of the
`
`adjacent modules to avoid double printing of the same data.
`
`In a particularly preferred form, the digital controller starts to place print data
`
`with the nozzles in an adjacent module at the one edge of the overlapping portion, and
`
`ramps up the data directed to the nozzles of the adjacent module stochastically until all
`
`the print data is directed to the adjacent module at the opposing edge of the overlapping
`
`portion.
`
`A Preferably, the printhead is a pagewidth printhead.
`
`In a furtherpreferred form, the printhead modules are adapted to be individually
`
`removed and replaced. To achieve this the printhead modules may be conveniently
`
`adapted for snap—locking engagement with the support frame.
`
`It will be appreciated that the adjacent positioning of a ntunber of small modular
`
`printheads permits full pagewidth printing while allowing a much higher utilization of
`
`the silicon wafer. Furthermore, the defect rate is effectively lower because a single fault
`
`will mean that a relatively smaller printhead chip will be rejected rather than a large full
`
`pagewidth printhead chip. Accordingly, the production costs per chip are significantly
`
`reduced.
`
`By providing each modular printhead with snap—locl< formations, it is convenient to
`
`individually remove and replace defective modules.
`
`Brief Description of the Drawings.
`
`A preferred embodiment of the present invention will now be described by way of
`
`example only with reference to the accompanying drawings in which:
`
`Figure 1 schematically shows a series of printhead modules abutting end to end to
`
`form a pagewidth printhead;
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`Figure 2 shows an enlarged View of the junction between two adjacent printhead
`
`modules shown in Figure 1;
`
`Figure 3 schematically shows the printhead modules configured in an overlapping
`
`relationship with TAB films extending from both sides of the printhead chips;
`
`Figure 4 schematically shows the printhead modules configured in an overlapping
`
`relationship with TAB films extending from only one side of the printhead chips such
`
`that every second TAB film is narrowed;
`
`Figure 5a schematically shows the printhead modules configured in an overlapping
`
`relationship in accordance with the present invention;
`
`Figure 5b schematically shows an alternative configuration of the printhead
`
`. modules in an overlapping relationship in accordance with the present invention;
`
`Figure Scschematically shows another alternative configuration of the printhead
`
`modulesrin an overlapping relationship in accordance with the present invention;
`
`Figure 5d schematically shows one more configuration of the printhead modules in
`
`an overlapping relationship in accordance with the present invention;
`
`Figure 6 schematically shows a single printhead chip in relation to the paper path;
`
`Figure 7 schematically shows the overlap region between two adjacent modules;
`
`Figure 8 is a perspective view showing the underside of a modular printhead
`
`according to the present invention;
`
`Figure 9 shows a rear view of the modular printhead at Figure 8;
`
`Figure 10~is a plan View of the modular printhead shown in Figure 8;
`
`Figure 11 is a front view of the modular printhead shown in Figure 8;
`
`Figure 12 is an underneath View of the modular printhead shown in Figure 8;
`
`Figure 13 is a left end View of the modular printhead shown in Figure 8;
`
`Figure 14 is a perspective View of the underside of a modular printhead with
`
`several of the printhead modules removed;
`
`Figure 15 shows an exploded perspective view of a printhead module;
`
`Figure 16 shows an underside View of a printhead module;
`
`Figure 17 shows an end View of a printhead module; and
`
`Figure 18 shows a cross-sectional view of the modular printhead shown in Figure
`
`8.
`
`Detailed Description of the Preferred Embodiment.
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`Referring to Figures 1
`
`to 4, prior art arrangements for modular pagewidth
`
`printheads are shown.
`
`In Figure 1, the printhead chips (3) of each module (not shown)
`
`are simply abutted end to end across the printhead support beam (not shown). As shown
`
`in the enlarged view of Figure 2, the ink nozzles are laterally spaced at a distance x along
`
`the chip. However, the microscopic irregularities in the ends of the chips (3) are enough
`
`to alter the normal spacing between the nozzles such that the end nozzles on adjacent
`
`chips are laterally spaced by a greater distance y. This adversely affects the print quality
`
`and can result in a blank line or void in the resultant printing.
`
`Figure 3 shows the printhead chips (3) arranged in an overlapping configuration to
`
`avoid any gaps between the printing from adjacent modules. The digital controller-(not
`
`shown) shares the print data amongst the overlapping nozzles of the adjacent printhead
`
`chips so that print data is not printed twice. The TAB films (6) from each chip (3)
`
`extend from opposing sides of each adjacent chip, in order to avoid having to narrow the
`
`TAB film (6) to every second chip (3) as shown in Figure 4. However, with the TAB
`
`films (6) extending from both sides of the chip array, the printhead becomes much wider
`
`which complicates the printer design, and in particular the paper path.
`
`Referring to Figures 5a to 5d, various suitable configurations of the chip array are
`
`shown. To be suitable, the array must allow the TAB film to extend from the same side
`
`of each chip with little or no narrowing required while maintaining the chips in an
`
`overlapping relationship with respect to the paper direction. This is achieved by v
`
`ensuring that the TAB film side of each chip is only obscured at one end, if at all. For
`
`.
`
`illustrative purposes, the obscured areas of the chips are shaded.
`
`The arrangement shown in Figure 5a offers the best configuration in terms of
`
`compact printhead design as well as overall printer design. The printhead chips (3) are
`
`inclined relative to the support beam or at least the line along which the modules (2) are
`
`mounted. This allows the printhead chips (3) to overlap with respect to the paper path
`
`while the TAB films (6) extend from the same side of each chip without being
`
`significantly narrowed. The support beam extends normal to the paper direction so that
`
`the printing occurs over a minimal
`
`length of the paper path so that
`
`the overall
`
`dimensions of the printer are reduced.
`
`The present invention will now be described with particular reference to the
`
`Applicant’s MEMJETTM technology, various aspects of which are described in detail in
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`7
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`the cross referenced documents.
`
`It will be appreciated that MEMJETTM is only one
`
`embodiment of the invention and used here for the purposes of illustration only. It is not
`
`to be construed as restrictive or limiting in any way on the extent of the broad inventive
`
`concept.
`
`A MEMJETTM printhead is composed of a number of identical printhead
`
`modules (2) described in greater detail below. Throughout the description and the cross
`
`references the array of ink ejecting nozzles on each module has been variously referred
`
`to as a ‘printhead chip’, ‘chip’ or ‘segment’. However, from a fair reading of the whole
`
`‘ specification in the context of the cross references, the skilled artisan will readily
`
`‘ appreciate that these integers are essentially the same.
`
`A MEMJETTM printhead is a drop-on-demand 1600 dpi inkjet printer that
`
`’ produces bi-level dots in up to 6 colors to produce a printed page of a particular width.
`
`Since the printhead prints dots at 1600 dpi, each dot is approximately 22.5p.m in
`
`' diameter, and the dots are spaced 15.875ttm apart. Because the printing is bi-level, the
`
`input image is typically dithered or error—diffused for best results.
`
`Typically a MEMIETTM printhead for a particular application is page-
`
`. width. This enables the printhead to be stationary and allows the paper to move past the
`
`printhead. Figure 8 illustrates a typical configuration. 21mm printhead modules are
`
`placed together after manufacture to produce a printhead of the desired length (for
`
`example 15 modules can be combined to form a 12-inch printhead), with overlap as
`
`desired to allow for smooth transitions between modules. The modules are joined
`
`3 together by being placed on an angle such that the printhead chips (3) overlap each other,
`
`as shown in Figure 5. The exact angle will depend on the width of the MEMJETTM
`
`module and the amount of overlap desired, but the vertical height is in the order of lmm,
`
`which equates to 64 dot lines at 1600 dpi.
`
`Each chip has two rows of nozzles for each color, an odd row and an even
`
`row. If both rows of cyan nozzles were to fire simultaneously, the ink fired would end
`
`up on different physical lines of the paper: the odd dots would end up on one line, and
`
`the even dots would end up on another. Likewise, the dots printed by the magenta
`
`nozzles would end up on a completely different set of two dot lines. The physical
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`distances between nozzles is therefore of critical importance in terms of ensuring that the
`
`combination of colored inks fired by the different nozzles ends up in the correct dot
`
`position on the page as the paper passes under the printhead.
`
`The distance between two rows of the same color is 32um, or 2 dot rows.
`
`This means that odd and even dots of the same color are printed two dot rows apart. The
`
`distance between rows of one color and the next color is 128nm, or 8 dot lines apart. If
`
`nozzles for one color’s dot line are fired at time T, then nozzles for the corresponding
`
`dots in the next color must be fired at time T + 8 dot—lines. We can generalize the
`relationships between corresponding nozzles from different rows by defining two
`
`variables:
`
`D1 = distance between the same row of nozzles between two colors = 8
`
`D2 = distance between two rows of the same color in dot-lines = 2
`
`Both D1 and D2 will always be integral numbers of dot rows. We can now
`
`say that if the dot row of nozzles is row L, then row 1 of color C is dot-line:
`
`L — (C~1) D1
`
`and row 2 of color C is dot-line:
`
`L — (C—1)D1 - D2
`
`The relationship between color planes for a given odd/even dot position
`
`in Table 1. for an example 6-color printhead. Note that if one of the 6 colors is fixative it
`
`20
`
`should be printed first.
`
`Table 1. Relationship between different rows of nozzles
`
`Color
`
`u
`
`' 2:2, D]=8
`
`I (
`
`fixative)
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`‘-
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`I
`
`1
`
`ven nozzle
`
`I ~D1
`
`(black)
`
`I‘ ‘D“”2
`'
`
`' *""“D2
`
`3
`
`ven nozzle
`
`I
`
`—
`
`24
`
`magenta)
`
`: 26
`
`‘
`
`(cyan)
`
`Ven nozzle
`
`I —4D1
`
`5
`
`ven nozzle
`
`I
`
`— 5D1
`
`— 40
`
`(infrared)
`
`Each of the colored inks used in a printhead has different characteristics
`in terms of viscosity, heat profile etc. Firing pulses are therefore generated independently
`
`for each color.
`
`In addition, although coated paper may be used for printing, fixative is
`
`required for high speed printing applications on plain paper. When fixative is used it
`
`should be printed before any of the other inks are printed to that dot position. In most
`
`cases, the fixative plane represents an OR of the data for that dot position, although it
`
`does depend on the ink characteristics. Printing fixative first also preconditions the paper
`
`so that the subsequent drops will spread to the right size.
`
`Figure 6 shows more detail of a single printhead chip (3) in the module
`
`array, considering only a single row of nozzles for a single color plane. Each of the
`
`printhead chips (3) can be configured to produce dots for multiple sets of lines. The
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`leftmost d nozzles (d depends on the angle that the modules is placed at) produce dots
`
`for line 11, the next d nozzles produce dots for line n-J , and so on.
`
`I
`
`If a printhead chip (3) consists of 640 nozzles in a single row of odd or
`
`even nozzles (totalling 1280 nozzles of a single color) and the angle of printhead chips
`
`(3) placement produces a height difference of 64 lines (as shown in Figure 5), then d=10.
`
`This means that the module (2) prints 10 dots on each of 64 sets of lines. If the first
`
`dotline was line L, then the last dotline would be dotline L-63.
`
`As can be seen by the placement of adjacent modules (2) in Figure 7, the
`
`corresponding row of nozzles in each modules produces dots for the same set of 64 lines,
`
`10
`
`just horizontally shifted. The horizontal shift is an exact number of dots. Given S
`
`printhead chips (3), then a given print cycle produces dS dots on the same line. If S = 15,
`
`then dS = 150.
`
`Although each 21mm printhead chip (3) prints 1600 dpi bi—level dots over
`
`a different part of page to produce the final image, there is some overlap between
`
`printhead chips (3), as shown in Figure 11. Given a particular overlap distance, each
`
`printhead chips (3) can be considered to have a lead—in area, a central area, and a lead—out
`
`area. The lead-out of one chip (3) corresponds to the lead—in of the next. The central
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`area of a chip (3) is that area that has no overlap at all. Figure 11 illustrates the three
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`areas of a chip (3) by showing two overlapping chips in terms of aligned print—lines.
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`Note that the lead—out area of chip S corresponds to the lead—in area of chip S+1.
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`When producing data for the printhead, care must be taken when placing
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`dot data into nozzles corresponding to the overlap region. If both nozzles fire the same
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`data, then twice as much ink will be placed onto the pages in overlap areas. Instead, the
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`dot data generator should start placing data into chip S at the start of the chip overlap
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`region while removing the data from the corresponding nozzles in chip S+1, and ramp
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`stochastically across the overlap area so that by the end of the overlap area, the data is all
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`allocated to nozzles in chip S+1.
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`In addition, a number of considerations must be made when wiring up a
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`printhead. As the width of the printhead increases, the number of modules (2) increases,
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`and the number of connections also increases. Each chip (3) has its own Dn connections
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`(C of them), as Well as SrClk and other connections for loading and printing.
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`When the number of chips is small it is reasonable to load all the chips (3)
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`simultaneously by using a common SrClk line and placing C bits of data on each of the
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`Dn inputs for the chips. In a 4—chip 4 color printer, the total number of bits to transfer to
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`the printhead in a single SrClk pulse is 16. However for a Netpage (see cross references)
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`enabled (C=6) 12-inch printer, S=15, and it is unreasonable to have 90 data lines running
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`from the print data generator to the printhead.
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`Instead, it is convenient to group a number of chip (3) together for loading
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`‘purposes. Each group of chips (3) is small enough to be loaded simultaneously, and
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`share a SrClk. For example, a 12-inch printhead can have 2 chip groups, each chip group
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`containing 8 chips (3). 48 Dn lines can be shared for both groups, with 2 SrClk lines,
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`one per chip group.
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`As the number of chip groups increases, the time taken to load the
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`printhead increases. When there is only one group, 1280 load pulses are required (each
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`pulse transfers C data bits). When there are G groups, 1280G load pulses are required.
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`The connection between the data generator and the printhead is at most 80 MHz.
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`If G is the number of chip groups, and L is the largest number of chips in
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`a group, the printhead requires LC Drz lines and G SrClk lines. Regardless of G, only a
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`single LSyncL line is required — it can be shared across all chips.
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`Since L chips in each chip group are loaded with a single SrClk pulse, any
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`printing process must produce the data in the correct sequence for the printhead. As an
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`example, when G=2 and L=4, the first SrClk0 pulse will transfer the Dn bits for the next
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`print cycle's dot 0, 1280, 2560 and 3840. The first SrClk] pulse will transfer the D11 bits
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`for the next print cycle’s dot 5120, 6400, 7680, and 8960. The second SrClk0 pulse will
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`transfer the Dn bits for the next print cycle’s dot 1, 1281, 2561, and 3841. The second
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`SrClk] pulse will transfer the D12 bits for the next print cycle's dot 5121, 6401, 7681 and
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`8961.
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`After 1280G SrClk pulses (1280 to each of SrClk0 and SrClk1), the entire
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`line has been loaded into the printhead, and the common LSyncL pulse can be given at
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`the appropriate time.
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`As described above , the nozzles for a given chip (3) do not all print out
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`on the same line. Within each color there are d nozzles on a given line, with the odd and
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`even nozzles of the group separated by D2 dot—lines. There are D1 lines between
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`corresponding nozzles of different colors (D1 and D2 parameters are further described in
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`Section and Section ). The line differences must be taken into account when loading
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`data into the printhead. Considering only a single chip group, Table 2. shows the dots
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`transferred to chip n of a printhead during the a number of pulses of the shared SrClk.
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`Table 2. Order of dots transferred to chip S in a modular printhead
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`128OS+2d+ I
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`And so on for all 1280 SrClk pulses to the particular chip group.
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`With regards to printing, we print 10C nozzles from each chip in the
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`lowest speed printing mode, and 80C nozzles from each chip in the highest speed
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`15
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`printing mode.
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`S = chip number
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`D1 = number of lines between the nozzles of one color and the next (likely = 7-10)
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`D2 = number of lines between two rows of nozzles of the same color (likely = 2)
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`d = number of nozzles printed on the same line by a given chip
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`While it is certainly possible to wire up chips in any way, this document
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`only considers the situation where all chips fire simultaneously. This is because the low-
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`speed printing mode allows low—power printing for small printheads (e.g. 2-inch and 4-
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`inch), and the controller chip design assumes there is sufficient power available for the
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`large print sizes (such as 8-18 inches). It is a simple matter to alter the connections in
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`the printhead to allow grouping of firing should a particular application require it.
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`‘When all chips are fired at the same time IOCS nozzles are fired in the
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`low-speed printing mode and 8OCS nozzles are fired in the high-speed printing mode.
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`A chip produces an analog line of feedback used to adjust the profile of
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`the firing pulses. Since multiple chips are collected together into a printhead, it is
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`effective to share the feedback lines as a tri—state bus, with only one of the chips placing
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`the feedback information on the feedback lines at a time.
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`The printhead is constructed from a number of chips as described in the
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`previous sections. It assumes that for data loading purposes, the chips have been grouped
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`into G chip groups, with L chips in the largest chip group. It assumes there are C colors
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`in the printhead. It assumes that the firing mechanism for the printhead is that all chips
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`fire simultaneously, and only one chip at a time places feedback information on a
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`common tri—state bus. Assuming all these things, Table 3 lists the external connections
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`that are available from a printhead:
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`Table 3. Printhead connections
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`I clk
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`1
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`-- 'mingsignalsinprinthead
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`hase Locked Loop clock for generation 0
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`A
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`‘ “*“°g
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`g“’““d
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`I egative actuator supply
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`ositive actuator supply
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`I egative logic supply
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`ositive logic supply
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`Referring to Figures 8 to 18, the modular printhead has a metal chassis (1) which is
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`fixedly mounted within a digital inkjet printer (not shown). Snap-locked to the metal
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`chassis (1) are a plurality of replaceable printhead modules (2). The modules (2) are
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`sealed units with four separate ink channels that feed a printhead chip (3). As bestiseen
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`in figure 7, each printhead module (2) is plugged into a reservoir moulding (4) that
`supplies ink to the integrally moulded funnels (5).
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`The ink reservoir (4) may itself be a modular component so the entire modular
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`printhead is not necessarily limited to the width of a page but may extend to any
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`arbitrarily chosen width.
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`Referring to Figures 15 to 18, the printhead modules (2) each comprise a printhead
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`chip (3) bonded to a TAB film (6) accommodated and supported by a micro moulding
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`(7). This is, in turn, adapted to mate with a cover moulding (8). The printhead chip (3)
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`is a MEMS (micro electro mechanical System) device. Typically, MEMJETTM chips
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`print cyan, magenta, yellow and black (CMYK) ink. This provides color printing at an
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`image resolution of 1600 dots per inch (DPI) which is the accepted standard for
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`photographic image quality.
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`If there is a defect in the chip it usually appears as a line or void in the printing. If
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`the printhead were to be formed from a single chip then the entire printhead would need
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`replacement. By modularising the printheads there is less probability that any particular
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`printhead module will be defective. It will be appreciated that the replacement of single
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`printhead modules and the greater utilisation of silicon wafers provide a significant
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`saving in production and operating costs.
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`The TAB film (6) has a slot to accommodate the MEMJETTM chip (3) and gold
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`plated contact pads (9) that connect with the flex PCB (flexible printed circuit board)
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`(10) and busbar (11) to get data and power respectively to the printhead. The busbars
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`(11) are thin fingers of metal strip separated by an insulating strip. The busbar sub-
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`assembly (11) is mounted on the underside of the side wall ink reservoir (4).
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`The flex PCB (10) is mounted to the angled side wall of the reservoir (4). It wraps
`beneath the side wall of the reservoir (4) and up the external surface carryi