Printing unit with ink jet modules connected in series

Abstract

A printing unit includes a unit chassis and a pair of opposed inkjet modules mounted in series on the unit chassis in forward and reverse orientations, each inkjet module having a respective printhead and at least one of: a cover and a wiper. Each printhead includes a first row of print chips and a second row of print chips mounted on an integral surface of a respective ink manifold, the first row of print chips and the second row of print chips having a plurality of print chips interfacing end-to-end along a length of the printhead. The printheads are fully aligned with respect to the media feed direction for printing from the pair of printheads in four ink colors.

Description

Field of the Invention

[0001] The present invention relates to a high-speed printing unit which is developed mainly to minimize the width of the printing area and optimize the printing quality of a full-color digital inkjet printer so that each ink color has multiple redundancies. Background of the Invention

[0003] Available on the market Pagewidth technology inkjet printers are used in many different printing applications, including desktop printers, digital inkjet presses, and wide format printers. The printer typically includes one or more user-replaceable fixed inkjet printheads having a length of at least 200 mm. For example, a desktop label printer includes a single user-replaceable full color, a high-speed inkjet printer includes a plurality of user-replaceable monochrome printheads aligned along the media feed direction, and a wide format printer includes a plurality of user-replaceable printheads arranged in a staggered overlapping arrangement so as to span the wide format media feed path.

[0004] Conventionally, analog printing presses are used for relatively large print runs, where the cost of producing dedicated printing plates is economically feasible. Industrial printing systems are increasingly using single-pass digital inkjet printing for relatively smaller print runs. Digital inkjet printing avoids the high set-up costs of producing printing plates and allows each print job to be customized for a specific customer. Ideally, a web-fed system for an existing analog printing system should be adaptable so that a "plug-and-play" inkjet module can be used instead of, for example, an offset printing station. It is therefore desirable for the inkjet module to occupy a minimum of space relative to the media feed direction, while allowing full-color printing at high speeds with optimal print quality.

[0005] The printing technology uses several rows of end-to-end print chips to construct a page-width print head, which is very suitable for reducing the total span of the printing area along the media feed direction. Each print chip has five rows of nozzles, which can be used for 5-fold redundant printing in a monochrome print head.

[0006] US10,857,821 (the contents of which are incorporated herein by reference) describes a printing system with a configurable array of print modules, each having a corresponding monochrome print head configured for single-pass printing. Four print modules can be arranged along the media path for full-color (CMYK) printing, with 5-fold redundancy in each color plane. Although the system described in US10,857,821 provides OEMs with flexibility in the design of inkjet printers, as well as high-quality and high-speed printing using 5-fold redundancy, the print modules must be aligned and spaced along the media feed path to achieve full-color printing. This places requirements on the media feed system, which needs to align all colors, and therefore, the OEM's set-up costs are relatively high. However, these costs are still much lower than alternative page-width printing systems that use overlapping print chips or very large print chips to achieve single-pass printing.

[0007] US 10,293,609 (the contents of which are incorporated herein by reference) describes a full-color page width printhead having two rows of butt-jointed print chips receiving ink from a common manifold. The printhead has two-fold redundancy in each ink color through four active nozzle rows in each row of print chips.

[0008] It is desirable to provide a low-cost printing unit with multiple redundancies in each ink color, which minimizes the span of the printing zone along the media feed direction to achieve four-color (CMYK) printing. It is further desirable to provide such a printing unit, which allows access to the printhead for replacement, simplifies the printhead alignment and setting procedures, and enables printing with variable printhead-to-paper spacing (PPS) while optimizing print quality. SUMMARY OF THE INVENTION

[0010] In a first aspect, a printing unit is provided, the printing unit comprising:

[0011] unit chassis; and

[0012] a pair of opposing inkjet modules mounted in series on the unit chassis in forward and reverse orientations, each inkjet module having a respective printhead and optionally at least one of: a cap and a wiper,

[0013] in:

[0014] Each printhead includes two rows of print chips mounted on an integral surface of a corresponding ink manifold, each row of print chips including a plurality of print chips butted end-to-end along the length of the printhead;

[0015] A row of print chips is supplied with only one ink color from its corresponding manifold; and

[0016] The print heads are fully aligned with respect to the media feed direction for printing in four ink colors from the pair of print heads.

[0017] The printing unit according to the first aspect advantageously provides a highly compact printing system for full color printing with multiple redundancy and a narrow print zone span. The printing unit is therefore very suitable for use as a "plug and play" unit in existing media feed systems currently used for analog printing. In essence, the printing unit acts as a "micro inkjet printer" in that it achieves similar print quality to existing inkjet printers with an array of monochrome print heads, but at a fraction of the space and cost.

[0018] Preferably, the first row of printing chips and the second row of printing chips on each of the print heads have 180 degree rotational symmetry.

[0019] In one embodiment, each row of the print chip is supplied with only one ink color from its corresponding manifold.This embodiment maximizes speed by potentially utilizing all nozzle rows in a 5-channel print chip.

[0020] In an alternative embodiment, a first row of print chips in one print head prints two colors of ink, and a second row of print chips in the print head prints the same two colors of ink. This alternative embodiment maximizes print quality by using staggered compensation nozzle groups to hide printing artifacts caused by these compensation nozzle groups.

[0021] Preferably, the compensating nozzle groups are adjacent chip bonding areas. Preferably, those compensating nozzle groups in the first row of printing chips are offset (or misaligned) from the compensating nozzle groups in the second row of printing chips with respect to the media feed direction.

[0022] Preferably, each compensating nozzle group includes a downshifted nozzle row offset from the main nozzle row in each print chip, the print chip being configured to delay or advance ejection of the downshifted nozzle row relative to the main nozzle row.

[0023] Preferably, each printhead is asymmetrically disposed toward the front of its respective inkjet module, and wherein opposing inkjet modules in forward and reverse orientations position the pair of printheads in a relatively close arrangement and the pair of caps in a relatively distant arrangement.

[0024] Preferably, the span of the printing zone along the medium feeding direction is less than 20 cm.

[0025] Preferably, each row of printing chips has at least quadruple redundancy, whereby aligned nozzles of at least four nozzle rows are able to print onto the same pixel location.

[0026] Preferably, the pair of inkjet modules are pivotally mounted on the unit chassis for pivotally moving the inkjet modules toward and away from each other.

[0027] Preferably, in the clamshell closed configuration, the printing unit is configured for printing, and in the clamshell open configuration, the respective front face of each inkjet module is accessible for printhead replacement.

[0028] Preferably, each inkjet module is independently pivotable relative to the unit chassis.

[0029] Preferably, each inkjet module comprises a module chassis having a base plate with rear and end walls extending upwardly from the base plate.

[0030] Preferably, each substrate is C-shaped in plan view, having a pair of lateral arms extending parallel to the media feed direction from opposite ends of a longitudinal base member extending perpendicularly to the media feed direction, and each substrate defines an open longitudinal slot for receiving a corresponding print head.

[0031] Preferably, the opposing inkjet modules in the forward and reverse orientations have opposing C-shaped base plates such that the pair of open longitudinal slots are closely positioned relative to the pair of longitudinal base members.

[0032] Preferably, the second inkjet module in the reverse orientation is rotated 180 degrees relative to the first inkjet module in the forward orientation.

[0033] In a second aspect, there is provided a method for redundantly printing in four colors from a first print head and a second print head aligned along a media feed direction, each of the first print head and the second print head having respective first and second rows of print chips butted end to end, the first row of print chips and the second row of print chips having 180 degrees of rotational symmetry, the method comprising the steps of:

[0034] supplying a first ink and a second ink to a first print head;

[0035] printing a first ink material from a first aligned nozzle row of first and second rows of print chips of a first print head;

[0036] printing a second ink material from a second aligned nozzle row of the first and second rows of print chips of the first print head;

[0037] supplying a third ink and a fourth ink to the second print head;

[0038] printing a third ink from a third aligned nozzle row of the first and second rows of print chips of the second print head; and

[0039] printing a fourth ink material from a fourth aligned nozzle row of the first and second rows of print chips of the second print head,

[0040] Wherein, in each of the first print head and the second print head, the compensation nozzle groups in the first and second rows of printing chips are offset along the medium feeding direction.

[0041] The method according to the second aspect advantageously hides the printing artifacts caused by the compensation nozzle group at the chip bonding area, as described below in conjunction with Fig. 9 as described.

[0042] Preferably, each printing chip comprises a corresponding compensation nozzle group at one end thereof adjacent to an adjacent printing chip.

[0043] Preferably, the compensating nozzle group comprises a downshifted nozzle row offset from the main nozzle row in the corresponding print chip.

[0044] Preferably, the ejection of the downshifted nozzle row is advanced or delayed relative to the corresponding main nozzle row in each print chip.

[0045] Preferably, the first row of printing chips in each print head advances the ejection of the corresponding downwardly shifted nozzle row, and the second row of printing chips retards the ejection of the corresponding downwardly shifted nozzle row, and vice versa.

[0046] Preferably, each compensation nozzle group in the first row of printing chips is aligned with the main nozzle row in the second row of printing chips along the medium feeding direction.

[0047] Preferably, at the bonding area between adjacent chips, printing of each ink is shared between one or more nozzle rows of the compensation nozzle group in the first printing chip row and one or more nozzle rows of the main nozzle row in the second printing chip row.

[0048] Preferably, printing artifacts caused by the compensation nozzle group in the first row of printing chips are masked by the main nozzle row in the second row of printing chips.

[0049] Preferably, for each printing chip, two nozzle rows print only one ink material.

[0050] In one embodiment, each print chip includes five nozzle rows, with the center nozzle row not receiving any ink.

[0051] In a related third aspect, there is provided a printing assembly comprising:

[0052] A print head having corresponding first and second rows of printing chips butted end to end, the first row of printing chips and the second row of printing chips having 180 degree rotational symmetry;

[0053] a first ink reservoir in fluid communication with first aligned nozzle rows of first and second print chip rows;

[0054] a second ink reservoir in fluid communication with the second aligned nozzle rows of the first and second print chip rows;

[0055] The compensation nozzle groups in the first and second rows of printing chips are offset along the medium feeding direction.

[0056] Preferably, each printing chip comprises a corresponding compensation nozzle group at one end thereof adjacent to an adjacent printing chip.

[0057] Preferably, the compensating nozzle group comprises a downshifted nozzle row offset from the main nozzle row in the corresponding print chip.

[0058] Preferably, the ejection of the downshifted nozzle row is advanced or delayed relative to the corresponding main nozzle row in each print chip.

[0059] Preferably, the first row of print chips advances the ejection of the corresponding downwardly shifted nozzle row, and the second row of print chips retards the ejection of the corresponding downwardly shifted nozzle row, and vice versa.

[0060] Preferably, each compensation nozzle group in the first row of printing chips is aligned with the main nozzle row in the second row of printing chips along the medium feeding direction.

[0061] Preferably, at the bonding area between adjacent chips, printing of each ink is shared between one or more nozzle rows of the compensation nozzle group in the first printing chip row and one or more nozzle rows of the main nozzle row in the second printing chip row.

[0062] Preferably, printing artifacts caused by the compensation nozzle group in the first row of printing chips are masked by the main nozzle row in the second row of printing chips.

[0063] Preferably, for each printing chip, two nozzle rows print only one ink material.

[0064] Of course, it should be understood that the preferred embodiments described above in conjunction with the first, second and third aspects are also applicable to any one of the first, second and third aspects where relevant.

[0065] As used herein, the term "inkjet module" refers to an assembly of components that includes an inkjet printhead, such as an elongated printhead configured for single-pass printing (referred to in the art as a "page-width" or "line-head" printhead). An inkjet module typically includes one or more of the following components to provide a fully integrated inkjet system: maintenance components, such as caps and / or wipers; mechanisms for moving the printhead and / or maintenance components; ink delivery components, such as pumps, valves, ink connectors, etc.; and electronic circuitry for supplying power and / or data to the printhead.

[0066] As used herein, the term "ink" refers to any printing fluid that can be printed from an inkjet printhead. The ink may or may not contain a colorant. Accordingly, the term "ink" may include conventional dye-based or pigment-based inks, infrared inks, color fixatives (e.g., pre-coatings and finishing agents), 3D printing fluids, solar inks, biofluids, sensor fluids, and the like.

[0067] As used herein, the term "mounting" includes both direct mounting and indirect mounting via intervening parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0069] Figure 1 is a perspective view of a printing unit mounted on a supporting chassis;

[0070] Figure 2 It is a stereogram of a separate printing unit;

[0071] Figure 3 The bottom portion is a portion of the printing unit;

[0072] Figure 4 is a perspective view of the printing unit in the clamshell open position;

[0073] Figure 5 is a top view of the print unit in the clamshell open position;

[0074] Figure 6 is a bottom-up stereogram of the printing unit;

[0075] Figure 7 is an enlarged bottom perspective view of the suction manifold and print head;

[0076] Figure 8 is a plan view of a portion of a print head;

[0077] Fig. 9 is an enlarged plan view of the chip bonding area in the print head;

[0078] Fig.10 is a front top perspective view of the inkjet module when the print head is in a lowered position;

[0079] Fig.11 yes Figure 1 A rear bottom perspective view of the inkjet module shown;

[0080] Fig.12 is a front top perspective view of the inkjet module when the print head is in a raised position;

[0081] Fig.13is a perspective view of a portion of an inkjet module, wherein a carriage is shown in a transparent manner to reveal a sleeve bushing;

[0082] Fig.14 showing a portion of a printhead carrier with the printhead insert assembly removed;

[0083] Fig.15 is a top perspective view of an inkjet module, showing a lifting mechanism;

[0084] Fig.16 An inkjet module is shown with an end wall removed to expose a capping assembly and a cover shell;

[0085] 17A to 17C is a side view of the engagement between a cam guide of a cover assembly and a rocker arm of a cover housing;

[0086] Fig.18 is a top perspective view of the print head embedding seat assembly in a closed position;

[0087] Fig.19 is a top perspective view of the print head embedding seat assembly in an open position;

[0088] Fig. 20 yes Figure 8 A bottom perspective view of the print head embedment seat assembly shown;

[0089] Fig.21 is a perspective view of the print head inserted into the embedding seat;

[0090] Fig. 22 A separate insert seat is shown in an open position;

[0091] Fig.23 is a plan view of a portion of an insert seat;

[0092] Fig.24 is a perspective view of a portion of a modified print head insert assembly;

[0093] Fig.25 is a bottom perspective view of a modified printing unit having gap bars;

[0094] Fig.26 is a top perspective view of the modified printing unit in a clamshell open configuration;

[0095] Fig. 27 is a side view showing a printing area of ​​a modified printing unit;

[0096] Fig.28 is a bottom perspective view of a modified printing unit having an alternative gap bar with a polymer film;

[0097] Fig.29 yes Fig.28 a side view of the modified printing unit shown; and

[0098] Fig.30 yes Fig.28 A schematic side view of a modified printing unit is shown in the printing position. DETAILED DESCRIPTION

[0099] Printing unit

[0100] refer to Figure 1 , shows a printing unit 200, which is mounted on a support chassis 202, which is configured to feed the medium through the printing unit along the medium feeding direction M. The printing unit 200 (in Figure 2 The unit chassis 204 includes a pair of opposed upstream and downstream inkjet modules 1A and 1B, which are mounted in series on the unit chassis in forward and reverse orientations. A single inkjet module 1 is described in detail below.

[0101] Each inkjet module 1 comprises a module chassis 10 which is pivotally mounted on chassis side bars 205 of a unit chassis 204 about a corresponding pair of module pivots 206 located at opposite sides of the module chassis. Thus, each inkjet module 1 is pivotable about a pivot axis perpendicular to the media feed direction M. The upstream inkjet module 1A and the downstream inkjet module 1B of the printing unit 200 are pivotally movable toward and away from each other, so that the printing unit can be configured to be in a clamshell closed configuration ( Figure 1 and Figure 2 ) for printing and in a clamshell open configuration ( Figure 4 and Figure 5 ) for printhead replacement and / or maintenance. Each module chassis 10 has an open respective front face that facilitates access to the internal components of each individual inkjet module 1 in a clamshell open configuration by virtue of the relative relationship of the inkjet modules in the printing unit (i.e., one inkjet module is rotated 180 degrees relative to another inkjet module). Gas struts 208 interconnect each module chassis 10 with chassis side bars 205 to provide a damped eccentric pivot mechanism for each inkjet module 1.

[0102] exist Figures 1 to 5 In the illustrated embodiment, the upstream inkjet module 1A and the downstream inkjet module 1B are independently pivotable, so that one or both inkjet modules can be pivoted. However, those skilled in the art will appreciate that other pivoting mechanisms may also be employed, whereby the pair of module chassis 10 are mechanically coupled, so that both inkjet modules must be pivoted to the clamshell open position. These and other pivoting mechanisms will be apparent to those skilled in the art.

[0103] Each individual inkjet module 1 is a fully integrated unit, including a corresponding print head 3 and a cap and wiper for maintaining the print head. Each print head 3 is of the type described in US10,293,609 (the contents of which are incorporated herein by reference) and includes two rows of print chips 5 mounted on the integral surface of the corresponding ink manifold. Each row of print chips 5 includes a plurality of print chips butted end to end along the length of its corresponding print head 3. Each inkjet module 1 prints two colors of ink from the two rows of print chips 5 of its corresponding print head 3. In addition, the print heads 3 of the pair of inkjet modules 1 mounted in series on the unit chassis 204 are fully aligned with respect to the media feed direction M, so that the printing unit 200 is configured for redundant full-color printing of four ink colors (CMYK). The redundancy of each color channel is provided by a plurality of aligned nozzle rows (e.g., 3, 4 or 5 nozzle rows) in each print head 3, which are fully aligned along the media feed direction M and print the same color ink. Thus, each set of aligned nozzles is able to print to the same pixel location during a single print pass from the fixed print head 3 to provide redundancy for each color.

[0104] The module chassis 10 of each inkjet module 1 has an elongated base plate 12, with a rear wall 14 and a pair of opposing end walls 16 extending upwardly from the base plate. Each base plate is C-shaped in plan view, with a pair of lateral arms 18 extending parallel to the media feed direction from opposite ends of a longitudinal base member 20 extending perpendicularly to the media feed direction. Thus, each base plate 12 defines an open longitudinal slot 22 for receiving a corresponding print head 3. Figure 2 In the embodiment, the print head 3 is raised above the substrate 12 for capping and / or wiping. Figure 6 In the process, the print head is lowered through the slot 22 to perform printing.

[0105] The upstream and downstream inkjet modules 1A and 1B in the printing unit 200 in the respective forward and reverse orientations have the opposite C-shaped base plates 12 so that the pair of open longitudinal slots 22 are closely positioned relative to the pair of longitudinal base members 20. Accordingly, the print heads 3 received through the respective slots 22 are relatively closely arranged so that the printing area (in Figure 3 The total span of the printing zone Z (indicated by the double-headed arrow Z) along the medium feeding direction M is minimized. For example, in the printing unit 200, the span of the printing zone Z including the two print heads 3 can be less than 20 cm, less than 150 cm or less than 125 cm.

[0106] refer to Figures 3 to 5, the base plate 12 also serves as a reference plate for each inkjet module 1 by means of a referenced engagement with a chassis reference block 210 protruding inwardly from a corresponding chassis side bar 205. Each chassis reference block 210 serves as a common reference for the opposing lateral arms 18 in the pair of base plates 12. The chassis reference block 210 provides a z reference for each inkjet module 1 and has an x ​​reference feature and a y reference feature for overall reference of the inkjet module along the x-axis and the y-axis. The printhead embedding seat provides fine adjustment of the relative deflection of the printhead 3 around the θz axis, as will be explained in further detail below.

[0107] exist Figure 6 , the printing unit 200 is shown in its printing position, wherein both print heads 3 protrude through respective slots 22 of the substrate 12. An aerosol extractor 212 is mounted to the rear end bar 207 of the unit chassis 204 and extends below the substrate 12 of the downstream inkjet module 1B towards the downstream print heads relative to the media feed direction M. The aerosol extractor 212 is cantilevered by being pivotally mounted to the rear end bar 207 via a spring-loaded pivot mount 214 and has a free end close to the downstream print heads 3.

[0108] The aerosol extractor 212 includes a duct arm 216 extending from a vacuum port 218 at one end and connected at an opposite end to a suction manifold 220. The duct arm 216 and the suction manifold 220 have a generally low height profile with a flat lower surface extending parallel to the plane of the substrate 12. In its rest position, the aerosol extractor 212 is biased against the substrate 12 of the downstream inkjet module 1 and extends parallel to the media feed path to occupy a minimum space between the substrate and, for example, a platen for supporting print media.

[0109] The suction manifold 220 is coextensive with the slot 22 and has a plurality of suction nozzles 222 for extracting aerosol from near the print zone. The suction nozzles 222 are configured to direct the airflow through the print zone generally in the same direction as the media feed direction M. Thus, the aerosol extractor 212 not only serves to remove ink mist, but also helps to stabilize the vortices associated with the droplet stream in the print zone during printing. The substrate 12 of the upstream inkjet module 1A helps to provide a uniform airflow through the print zone, which is optimal for stabilizing the vortices associated with the droplet stream ejected from the print head 3. The airflow provided by the aerosol extractor 212 can be further optimized by, for example, optional gap bars having corresponding plates positioned between the print heads 3 to provide a more uniform airflow between the print heads and through the print zone (see Figure 25 to Figure 27 ).

[0110] The printing unit 200 can be configured to print at different jetting distances relative to the print medium (referred to in the art as printhead-to-paper spacing or PPS) by adjusting the height of the printhead 3 using a lift mechanism in each inkjet module 1. Height adjustment of the printhead 3 typically disrupts the optimized airflow through the print zone. However, in the printing unit 200, the cantilevered aerosol extractor 212 enables adjustment of the height of the suction nozzle proximate to the downstream printhead. In particular, reference is now made to Figure 7 , the front tab portion 224 connected to the suction manifold 220 is positioned to dock with the print head insert 102 supporting the downstream print head 3. Therefore, when the downstream print head 3 is lowered, the docking engagement of the print head insert 102 with the tab portion 224 causes the suction manifold 220 to pivot against the bias of the pivot mount 218, thereby reducing the height of the suction nozzle 222 commensurate with the height of the print head 3. When the print head 3 is raised, the bias of the pivot mount 218 causes the suction manifold 220 to rise with the print head. In this way, the printing unit 200 is suitable for variable PPS printing with optimized aerosol extraction and optimized airflow through the printing zone.

[0111] Ink tube

[0112] In one embodiment, the print heads 3 can be piped so that each row of print chips 5 (where each print chip 6 has multiple aligned nozzle rows for redundant printing) receives only one color of ink. With four rows of print chips 5 on two print heads 3, full color (CMYK) redundant printing can be achieved using all nozzle rows in each print chip. In this way, the printing unit 200 can emulate a conventional inkjet printer (e.g., FujiFilmJPress 750S) with a monochrome inkjet print bar, but with a much narrower print zone (and lower cost) than conventional systems.

[0113] However, to maximize print quality, Figure 8 and Fig. 9 In the alternative embodiment shown, the printing unit 200 can utilize the inherent architecture of each print head 3, which has two rows of 180-degree rotationally symmetrical print chips 5. As described in US 10,293,609, the first row of print chips 5A and the second row of print chips 5B in each print head 3 include four color channels, whereby each individual print chip 6 in a row can be supplied with two colors of ink. Therefore, the two print heads 3 in the printing unit 200 can be considered to have 8 color channels (two color channels for each row of print chips 5) for printing four different inks (CMYK).

[0114] A fundamental problem that is prevalent in any pagewidth printing system with multiple print chips is that print quality is degraded at the bond area between print chips 6. Inevitably, the pagewidth printhead requires some form of compensation to print over the chip bond area using, for example, electronic stitching techniques, mechanical positioning of the chips, dedicated chip designs that enable chip docking, or a combination thereof. In the printhead 3, print quality issues are generally minimized by virtue of the physical proximity of adjacent chips and a proprietary chip architecture with a "downshifted nozzle row" (see, e.g., US 7,290,852, the contents of which are incorporated herein by reference). Depending on the orientation of the print chip 6, the nozzles in the downshifted nozzle row fire either delayed or advanced relative to the main nozzle row to provide seamless integration between adjacent print chips. However, in In the print head, printing artifacts may still exist due to the downward shift of the nozzle row, especially in certain printing modes, as described in WO2022 / 053258.

[0115] The printing unit 200 has two available color channels for each ink color, allowing the print head 3 to be routed to mask any printing artifacts caused by the bonding area between adjacent print chips 6. Basically, each color of ink is assigned to a first color channel of the first row 5A print chips 6 in a forward orientation, and to a second color channel of the second row 5B print chips 6 in a reverse orientation (i.e., an orientation rotated 180 degrees relative to the first row 5A print chips). In this manner, the compensating nozzle groups 8A (e.g., downshifted nozzle rows) in the first row 5A print chips are offset from the compensating nozzle groups 8B in the second row 5B print chips. Therefore, any printing artifacts caused by the downshifted nozzle rows 8A in the first row of print chips 5A are minimized by the corresponding (i.e., aligned) nozzles from the main nozzle area 7B in the second row of print chips 5B. Similarly, any printing artifacts caused by the downshifted nozzle rows 8B in the second row of print chips 5B are minimized by the corresponding (i.e., aligned) nozzles from the main nozzle area 7A in the first row of print chips 5A.

[0116] exist Fig. 9 In the printhead 3 shown, the first row of print chips 5A has two cyan (C) nozzle rows (each nozzle row has "odd" and "even" sub-rows) and two yellow (Y) nozzle rows. As described in US10,293,609, the middle nozzle row (N) is not used to provide separation between color channels and minimize ink mixing on the nozzle plate. Similarly, the second row of print chips 5B has two cyan (C) nozzle rows and two yellow (Y) nozzle rows. For each color (e.g., cyan), there are four nozzles aligned along the media feed direction to provide 4-fold redundancy. However, as described in US10,293,609, the middle nozzle row (N) is not used to provide separation between color channels and minimize ink mixing on the nozzle plate. Similarly, the second row of print chips 5B has two cyan (C) nozzle rows and two yellow (Y) nozzle rows. For each color (e.g., cyan), there are four nozzles aligned along the media feed direction to provide 4-fold redundancy. However, as described in US10,293,609, the middle nozzle row (N) is not used. Fig. 9As shown, only two cyan dots originate from the down-shifted nozzle row 8A of the first row of print chips 5A; the other two cyan dots originate from the main nozzle row 7B of the second row of print chips 5B. Similarly, the aligned yellow (Y) dots originate from the down-shifted nozzle row 8A of the first row of print chips 5A and the main nozzle row 7B of the second row of print chips 5B.

[0117] Accordingly, it should be understood that the 180 degree rotational symmetry of the first row of print chips 5A and the second row of print chips 5B in the same print head 3 allows hiding or at least minimizing the printing artifacts originating from the downshifted nozzle row 8. This complementary arrangement of the first row of print chips 5A and the second row of print chips 5B in each print head 3 combined with a suitable ink routing sequence advantageously maximizes the printing quality in a printing unit 200 having two print heads. Each print head 3 receives two colors of ink, but both inks are supplied to the two rows of print chips 5 in the corresponding print head.

[0118] Inkjet Module

[0119] For completeness, reference will now be made to Figures 10 to 24 A single inkjet module 1 is described for use in series in a printing system 200 .

[0120] like Fig.10 As shown, the inkjet module 1 includes a chassis 10 having an elongated substrate 12, wherein a rear wall 14 and a pair of opposite end walls 16 extend upwardly from the substrate. In addition to providing structural rigidity to the chassis 10, the rear wall 14 also serves as a support for mounting various fluid components (e.g., pinch valves 15 and pumps 17) and electronic components (e.g., module controller PCB 19) on its front and rear faces. The opening in the rear wall 14 allows fluid connections to be made from the rear face of the inkjet module 1 without the need for access from above. An opening may also be provided for accessing the screw adjuster of any print head embedding seat 102 in the printing unit 200 in situ using a suitable tool (not shown), as will be explained in further detail below.

[0121] The base plate 12 is generally C-shaped in plan view, having a pair of transverse arms 18 extending from opposite ends of a longitudinal base member 20 along a nominal x-axis of the inkjet module 1. An open longitudinal slot 22 defined between the transverse arms 18 extends parallel to the longitudinal axis along a nominal y-axis of the inkjet module 1 and is configured to receive an elongated printhead 3. Thus, the printhead 3 is positioned asymmetrically in the inkjet module 1 toward its front side, such that the printheads are positioned closely together in the printing unit 200. The printhead 3 can be lowered through the slot 22 for printing, or raised above the base plate 12 for maintenance (e.g., capping and / or wiping).

[0122] A pair of posts 24 extend upwardly from the lateral arms 18 of the substrate 12 at opposite ends of the open longitudinal slot 22. Each post 24 is anchored to the substrate 12 at its lower end and fixed to the respective end wall 16 at its upper end. A pair of brackets 26 are slidably engaged with the posts 24 via respective sleeve bushings 28 inserted into each bracket. Each sleeve bushing 28 is slidably movable relative to the respective post 24, thereby allowing the bracket 26 to move vertically linearly toward and away from the substrate 12 along the nominal z-axis of the inkjet module 1. A flange portion 25 located at the lower end of each sleeve bushing 28 is secured to each bracket 26 and references its respective bracket relative to the substrate 12 in the printhead lowered position ( Fig.10 ).

[0123] An elongated printhead carriage 30 is fixedly supported between the carriages 26 and is linearly slidable therewith. The printhead carriage 30 includes spaced-apart front and rear carriage plates 32 interconnecting the carriages 26 and defining a cavity 34 therebetween for accommodating electronic components that supply power and data to the printhead 3. Brackets 38 interconnect the upper portions of the carriage plates 32, and a pair of carriage reference blocks 40 interconnect the lower portions of the carriage plates. The carriage reference blocks 40 are positioned at opposite longitudinal ends of the printhead carriage 30, facing the respective carriages 26. The supported printhead carriage 30, in combination with the sleeve bushing 28, the column 24 and the chassis 10, provides a robust support structure for the printhead 3. The printhead 3 itself is fixed in a complementary insert 102 to form a printhead insert assembly 100, which is mounted to the carriage reference block 40 via a screw fastener 42 engaged with the insert.

[0124] The print head 3 can be moved in the printing position ( Fig.10 ) and maintenance position ( Fig.12 ) between the substrate 12 and the print head 3. The lifting mechanism also enables the height of the print head 3 to be adjusted relative to the print medium when in the printing position. Fig.15 As best shown, the lift mechanism includes a pair of lead screws 44 that are rotatably mounted to the base plate 12 and extend upwardly parallel to the post 24. Each lead screw 44 has a corresponding lead nut 46 that is fixedly connected to a corresponding carriage via a lead nut connector 48. The lead screws 44 are rotatable by interconnected pulley belt assemblies 50 that are operably connected to a common lift motor 52. Accordingly, the printhead 3 can be raised and lowered by actuation of the lift motor 52, which causes the lead screws 44 to rotate simultaneously via the pulley belt assembly 50, thereby raising or lowering the printhead carrier 30 that is connected to the lead nuts 46 via the carriage 26.

[0125] like Fig.12As best shown, the inkjet module 1 includes a wiper carriage 54 resting at one end of the longitudinal slot 22, the wiper carriage having a microfiber wiping web 56. In the printhead raised position, the wiper carriage 54 can be moved longitudinally along the length of the printhead 3 by a wiper moving mechanism 57 mounted on a longitudinal wiper support 55 to wipe ink and debris off the printhead surface. In the printhead lowered position ( Fig.10 ), a bracket in the bracket 26 having a bracket top 27 and bracket side walls 29 shields the wiper carriage 54. Thus, the bracket top 27 and bracket side walls 29 provide at least some protection from ink mist and / or debris that may contaminate the wiper carriage 54 via the open front face of the inkjet module 1 during printing.

[0126] The inkjet module 1 further includes a capping assembly 60 which rests toward the rear wall 14 and which is linearly slidably movable along a transverse capping track 62 toward and away from the printhead 3 by a rack and pinion mechanism 64. The capping assembly 60 includes a capping base 66 slidably engaged with the capping track 62, a peripheral printhead cap 68 mounted on the capping base, and cam guides 70 fixedly mounted to the capping base at opposite ends of the printhead cap. Fig.12 In the parked (covered) position of the capping assembly shown, the printhead cap 68 is covered by a cover shell 72 which is pivotally mounted to the rear wall 14 of the chassis 10. The cover shell 72 takes the form of a rigid plate which seals against the peripheral seal 69 of the printhead cap 68 and maintains a humid environment within the printhead cap when the printhead cap is not used to cap the printhead 3. The wiper moving mechanism 57 is mounted on a wiper support 55 which is fixedly attached to the rear wall 14, directly above the cover shell 72.

[0127] When capping the printhead, the capping assembly 60 is moved laterally away from the cover shell 72 to align with the printhead 3, and the lifting mechanism is used to gently lower the printhead onto the printhead cover 68 to the capping position. As the printhead is raised, the capping assembly 60 moves laterally backward toward the rear wall 14 to engage the cam rear surface 73 of the cam guide 70 with the engagement node 77 of the corresponding rocker arm 74 at each end of the cover shell. The rocker arm 74 is pivotally mounted to the rear wall 14 and allows the cover shell 72 to pivot upward when engaged with the cam guide 70, thereby enabling the capping assembly 60 to slide and move under the cover shell. Once the capping assembly 60 reaches its rearmost parking position, the cover shell 72 is pivoted downward back to the covering position with the help of the profile of the cam guide 70 and the rocker arm 74, in which the printhead cover 68 is covered by the cover shell.

[0128] Fig.17A The cam rear surface 73 of the cam guide 70 is shown engaging the engagement node 77 of the rocker arm 74 as the closure assembly 60 approaches the rear wall 14 . Fig. 17BThe rocker arm 73 is shown pivoting upwardly as the closure assembly transitions to its covering position. Fig. 17C The capping assembly 60 is shown in its rearmost parked position, with the swing arm 74 pivoted back to a horizontal plane and the print head cap 68 covered by the cover shell 72. When capping the print head, the capping assembly 60 is moved from Fig. 17C Its parked position is shown sliding towards the print head 3. The cam front surface 75 of the cam guide 70 engages with the engagement node 77 of the rocker arm 74 to pivot the rocker arm upwards and allow the capping assembly to slide towards the print head 3.

[0129] As mentioned above, now refer to Fig.12 and Fig.13 , the printhead carrier 30 defines a cavity 34 between its front and rear plates 32. The cavity 34 accommodates a supply module 80, which includes front and rear PCBs 82 for supplying power and / or data to the printhead 3. A cooling fan 84 is positioned between the PCBs 82 for cooling the electronic components using cool air drawn into the cavity 34 from the upper side of the printhead carrier 30. The bracket 38 defining the top portion of the printhead carrier 30 has an open truss structure that allows cool air to pass through the cavity 34 and circulate between the PCBs 82. The supply module 80 further includes an ink connector 86 for engaging with complementary ink ports 88 at opposite ends of the printhead 3. The supply module 80 forms an ink connection and an electrical connection with the printhead 3 when the printhead (fixed in its printhead embedding seat assembly 100) is mounted on the printhead carrier 30, as will be explained in more detail below.

[0130] Fig.18 and Fig.19 The print head insert assembly 100 is shown separately. Fig.18 As shown, the insert seat is in its closed position, wherein the print head 3 can be inserted and fixed in the insert seat 102 and is surrounded by the insert seat from all sides. Fig.19 , the insert seat 102 is in its open position, which allows the print head 3 to be removed from the insert seat, but the premise is that the print head insert seat assembly 100 is completely removed from the print head carrier 30. In other words, the print head 3 must be combined with the insert seat 102 to form the print head insert seat assembly 100, and then the print head (e.g., a replacement print head) can be installed in the inkjet module 1 by fastening the insert seat 102 to the print head carrier 30, thereby forming a printing module 81, which includes the print head carrier 30, the supply module 80, the insert seat 102 and the print head 3 fastened to each other.

[0131] The insert 102 is configured to be removably fastened to the printhead carrier 30 via a pair of screw fasteners 42 that extend vertically through the height of the printhead carrier 30. Each screw fastener 42 has a screw lever 43 and a screw tip, with the screw lever having an end accessible to the user from above the printhead carrier 30 and the screw tip protruding through a recessed opening 41 ( Fig.14 ). The upper surface of the insert seat 102 has a pair of reference pins 104, which are configured for complementary engagement with the recessed openings 41 of the carrier reference block 40. To install the print head insert seat assembly 100, each screw fastener 42 passes through the hollow hole 105 of the corresponding reference pin 104 and is screwed into the threaded nut insert 106 of the insert seat 102. Therefore, the print head insert seat assembly 100 can be securely fixed to the print head carrier 30 by accurate reference control by complementary reference engagement between the reference pins 104 and the recessed openings 41 in each carrier reference block 40. The insert seat 102 enables the use of relatively large reference pins 104 that are separate from the print head 3 to perform highly accurate and repeatable reference between the print head carrier 30 and the print head insert seat assembly 100.

[0132] The printhead insert assembly 100 is screwed and fastened to the printhead carrier 30 via the carrier reference block 40, while forming an ink connection and an electrical connection between the printhead 3 and the supply module 80. The ink ports 88 at opposite ends of the printhead 3 are raised to engage with the ink connectors 86 of the supply module 80. Similarly, electrical contacts 109 extending along opposite longitudinal sides of the printhead 3 are electrically contacted with complementary PCB contacts 89 of corresponding PCBs 82 in the supply module 80. During installation of the printhead insert assembly 100, the spring-biased PCB mounting plate 90 of the supply module 80 allows the PCBs 82 to flex laterally away from each other when the printhead 3 is raised between the PCBs. The spring bias provides a reliable electrical connection, while the required insertion force (for both the ink connection and the electrical connection) is provided by the screw fastener 42, which can be easily operated by the user using the screw lever 43. Accordingly, this arrangement eliminates the movable supply assembly and the two-stage ink and electrical connections described in US 10,967,638.

[0133] The print head insert assembly 100 can be in the print head lowered position ( Fig.10 ) or print head raised position ( Fig.12 ) is fastened to the printhead carrier 30, depending on which configuration is more accessible in the particular modular setting of the inkjet module 1. Fig.14 As shown, the printhead cartridge assembly 100 has been removed in the printhead lowered position.

[0134] Reference now Fig.19 and Fig. 22 , the insert seat 102 can be configured in the insert seat open position for removal and insertion of the print head. The insert seat 102 includes a first longitudinal side bar 110 and a second longitudinal side bar 112 extending parallel to opposite longitudinal sides of the print head 3, and a pair of shorter transverse end bars 114, which interconnect each end of the longitudinal side bars to define a rectangular (oblong) insert seat cavity 115. The first longitudinal side bar 110 and the end bar 114 are fixed, while the second longitudinal side bar 112 can move toward and away from the first longitudinal side bar between the open position and the closed position.

[0135] Each end bar 114 has a dowel pin 116 that receives the movable second longitudinal side bar 112. Sliding movement of the second longitudinal side bar 112 relative to the fixed dowel pin 116 provides relative linear movement of the second longitudinal side bar toward and away from the first longitudinal side bar 110.

[0136] The movement of the second longitudinal side bar 112 is achieved by a locking mechanism that configures the insert seat 102 in a closed position or an open position. The locking mechanism includes a pair of insert seat levers 120, each of which is pivotally attached to a corresponding end bar 114 and has a pivot axis perpendicular to the horizontal plane of the insert seat (i.e., parallel to the direction of ejection of droplets from the print head 3). Each insert seat lever 120 defines a cam slot 122, which engages with a corresponding follower pin 124, which extends parallel to the pivot axis at opposite ends of the second longitudinal side bar 112. By means of the cam engagement between the cam slot 122 and the follower pin 124, the pivotal movement of each insert seat lever 120 away from its corresponding end bar 114 causes the second longitudinal side bar 112 to move linearly away from the first longitudinal side bar 110 so as to open the insert seat 102. Conversely, pivotal movement of each insert seat lever 120 toward the corresponding end bar 114 moves the second longitudinal side bar 112 linearly toward the first longitudinal side bar 110 to lock the insert seat 102 closed. Each insert seat lever 120 has a finger grip portion 126 at the end opposite the pivot axis for the user to actuate the locking mechanism.

[0137] The insert 102 is configured to form an ink mist seal around the print head 3 in its closed position. The ink mist seal prevents ink mist from entering the supply module 80, thereby protecting the sensitive electronic circuit system on the PCB 82 from being contaminated by any ink mist generated during the printing process. The ink mist seal includes a pair of opposed first and second longitudinal lips 130 that protrude inwardly toward the print head from the corresponding first and second longitudinal side bars 110 and 112. Each lip 130 engages with a longitudinal edge region 132 of the print head 3 to form a portion of the ink mist seal.

[0138] In order to insert the print head 3 into the insert seat 102, the insert seat is first configured to its open position, such as Fig. 22 Then tilt the print head at an angle ( Fig.21 ) is guided laterally toward the first longitudinal side bar 110 into the open insert seat cavity 115. The first longitudinal flange 134 on one side of the print head 3 is first held at an angle below the longitudinal lip 130 of the first longitudinal side bar 110 to overlap the lip, and then the print head is rotated about its longitudinal axis into a plane parallel to the plane of the insert seat. The print head datums 136 located at opposite ends of the print head 3 are aligned with the complementary insert seat datums 138 ( Fig.23 ) to accurately and repeatably position the print head within the insert.

[0139] When the print head 3 is correctly positioned in the opened insert ( Fig.19 ), the insert seat lever 120 pivots inwardly to close the second longitudinal side rod 112 and lock the insert seat 102 into its closed position, thereby forming a locked print head insert seat assembly 100 ( Fig.18 ). Closure of the insert seat 102 moves the longitudinal lip 130 of the second longitudinal side bar 112 toward the print head 3 to complete the ink mist seal, wherein each longitudinal flange 134 of the print head is positioned below and overlaps its corresponding longitudinal lip.

[0140] The complete print head insert seat assembly 100 can then be fixed to the print head carrier 30 using the screw fastener 42 as described above. When the print head is removed, the reverse procedure is followed, whereby the print head insert seat assembly 100 is removed from the print head carrier 30, the insert seat lever 120 is used to open the insert seat, and the print head 3 is removed from the opened insert seat 102 at an angle.

[0141] Print head deflection adjustment in the printing unit 200

[0142] In the printing unit 200, the alignment of the upstream and downstream print heads 3 is critical to ensure optimal print quality. Although the above-described reference arrangement within each inkjet module 1 and between a pair of inkjet modules in the printing unit 200 provides robust positioning of the print head 3, in a printing system including multiple print heads, small misalignments between the print heads are inevitable to some extent, especially when the print heads are replaceable. It is usually possible to electronically compensate for non-optimal alignment of the print heads along the x-axis, y-axis and z-axis (if necessary, using information obtained from test patterns during system setup).

[0143] However, skew misalignment between print heads is more difficult to compensate electronically, so it is often minimized mechanically to optimize print quality. Figure 5 and Fig.10The nominal coordinate system shown, skew misalignment refers to the rotational misalignment of one print head relative to the other print head about the z-axis. Of course, ideally, the two print heads should be parallel.

[0144] Fig.24 A modified printhead insert assembly 150 is shown, which includes a modified printhead insert 152 and a printhead 3, and the printhead insert assembly is suitable for correcting the skew misalignment between a pair of printheads in a printing unit 200. In the modified printhead insert 152, a cantilever spring 154 is formed at one end of the printhead insert by a micro-machined slot 156 defined in the first (fixed) longitudinal side bar 110. A screw adjuster 158 received by a threaded opening in the first longitudinal side bar 110 is engaged with the cantilever spring 154 to push the cantilever spring toward and away from the printhead 3. Since the printhead 3 is referenced relative to the cantilever spring 154, when the screw adjuster 158 is screwed along the x-axis, the screw adjuster can apply a slight rotational movement to one end of the printhead 3 via the movement of the cantilever spring 154. Accordingly, the screw adjuster 158 can be used to perform fine skew adjustment on the printhead 3 in situ.

[0145] Typically, in the printing unit 200, the print head 3 of one inkjet module is considered to be a reference print head, relative to which the deflection of the other print head is adjusted. Therefore, only one of the print head inserts needs to have a cantilever spring 154 and a screw adjuster 158, but in practice it is convenient for both print head inserts to be identical.

[0146] As described above, the screw adjustment 158 ​​is preferably accessible when the printing module 200 is set up for use. Therefore, the rear wall 14 of each module chassis 10 typically has a suitable window that is visible when the printing unit 200 is in its clamshell closed position (e.g., Figure 1 ), the window enables external access to the rotary adjuster 158 (whether in the printhead raised position or the printhead lowered position).

[0147] Optimized airflow through the print zone

[0148] It is known to optimize the airflow through the print zone during high-speed printing to improve print quality, especially for high PPS printing, i.e., a print head-to-paper spacing (PPS) greater than about 1 mm (e.g., 1 mm to 10 mm or 1 mm to 5 mm). For example, US 6,997,538 (granted to Hewlett-Packard Development Company, LP) describes an inkjet printer having a device for generating an airflow through the print zone along the direction of media travel. The airflow is generated using an upstream blower, a downstream aspirator, or a combination thereof. Subsequent research by the applicant has confirmed the importance of controlling the airflow through the print zone as a means for optimizing print quality. Uniform airflow creates a pressure gradient across the print zone, which tends to stabilize vortices associated with the jetted ink droplet stream. These vortices are generated by the interaction between the ink droplet stream and the Couette flow caused by the moving print medium. In the absence of a forced airflow through the print zone to generate a pressure gradient, the vortices tend to drift, thereby producing a unique printing artifact known as a "tiger stripe" or "wood grain" effect.

[0149] refer to Figure 25 to Figure 27 , showing a modified printing system 300, which is similar to the above combined Figures 1 to 6 Printing system 200 is described, but with gap bars 302 located in the space between upstream and downstream printheads 3A and 3B of upstream and downstream inkjetting modules 1A and 1B, respectively. Where relevant, like reference numerals are used to indicate like features in printing system 200 and modified printing system 300.

[0150] The gap bar 302 extends between the opposing side bars 205 of the unit chassis 204, i.e., parallel to the end bars 207 and the longitudinal axis of the upstream printhead 3A and the downstream printhead 3B. The gap bar 302 includes a polymer plate 304 attached to the underside of the metal support bar 306, the polymer plate defining a flat lower surface that is positioned at substantially the same height relative to the print medium 301 as the lower surface of the printheads 3A and 3B. In some embodiments, the height of the gap bar 302 and / or the polymer plate 304 is adjustable to match the relative heights of the polymer plate and the printheads 3A and 3B.

[0151] The polymer sheet 304 has a width dimension that extends substantially completely across the space between the upstream printhead 3A and the downstream printhead 3B (e.g., spanning at least 70%, at least 80%, or at least 90% of the inter-printhead space) and a length dimension that is at least coextensive with the printheads. By filling the inter-printhead space in this manner, a relatively uniform airflow is provided from the upstream print zone 305, through the downstream print zone 307, and toward the suction nozzle 222 of the aerosol extractor 212 ( Fig. 27 ). This optimized airflow advantageously stabilizes the vortices associated with the ink droplet streams ejected from the printheads 3A and 3B, thereby minimizing the misalignment of stray satellite droplets and optimizing print quality. In the absence of the gap bars 302, the airflow is less uniform and the suction nozzle 222 has minimal impact on the upstream print zone 305, instead drawing air primarily from the inter-printhead space and surroundings.

[0152] Additionally, the polymer sheet 304 advantageously minimizes condensation of ink mist on the gap bars 302. For example, condensation on a metal surface may undesirably drip onto the print media and contaminate the printed image.

[0153] like Fig.26 As best shown, the upper surface of the support bar 306 has a pair of recessed portions 308 configured to receive complementary portions of the upstream inkjet module 1A and the downstream inkjet module 1B. Specifically, when the printing unit 300 is in its clamshell closed position, the carriage side wall 29 of each inkjet module is received in the corresponding recessed portion 308.

[0154] It should be understood that the gap bars 302 can be used to reference each inkjet module relative to the unit chassis 204. Figure 25 to Figure 27 In the embodiment shown, the datuming of each inkjet module 1 is achieved via a respective magnetic datum 310, which is fastened to each module chassis 10 and engages with a complementary chassis datum block in the form of an electromagnet 312. Thus, a reliable datuming of each inkjet module 1 relative to the unit chassis 204 is achieved via magnetic attraction, as described in US 11,376,869, the contents of which are incorporated herein by reference. The release of the inkjet module 1 from the respective printing position can be controlled by the electromagnet 312.

[0155] refer to Figures 28 to 30 , shows a variation of the gap bar 302, in which an elastically deformable polymer film 320 is attached to the lower surface of the support rod 306 instead of the polymer plate 304. The film 320 has a first wing 322A and a second wing 322B, which extend upstream and downstream from the longitudinal edge of the support rod 306 relative to the media feed direction, respectively. Fig.28 and Fig.29 As shown, in its non-deformed configuration, the membrane 320 is generally planar, with its plane extending parallel to the print medium 301. However, downward movement of the printing module (with the corresponding insert seat 102) toward the print medium 301 causes the upstream wing portion 322A and the downstream wing portion 322B of the membrane 320 to bend downward toward the print medium by virtue of engagement with the corresponding insert seats of the upstream inkjet module 1A and the downstream inkjet module 1B ( Fig.30). Accordingly, each of the upstream wing portion 322A and the downstream wing portion 322B functions as an elastic wing that can be bent toward the print medium 301 via engagement with the corresponding embedding seat 102.

[0156] Since the membrane 320 is attached along the longitudinal middle portion of the support rod 306 via the retaining pins 324, the membrane 30 Fig.30 The printing position shown adopts a concave profile between the upstream print head 3A and the downstream print head 3B. The engagement between the insert seat 102 and the corresponding wings 322A and 332B forms a partial seal therebetween, which is sufficient to minimize airflow through the space between the upstream print head 3A and the downstream print head 3B. Figure 25 to Figure 27 Compared to the arrangement shown, membrane 320 provides a more effective seal across the space between the upstream printhead 3A and the downstream printhead 3B because the polymer sheet 304 can only partially extend across the space depending on the height of the printhead relative to the print medium 301. Membrane 320 can accommodate a range of different printhead heights while still maintaining an effective seal and optimizing airflow through the print zone.

[0157] From the above content and Fig.30 It will be further understood that the insert seat 102 corresponding to the downstream print head 3B is simultaneously connected to the downstream wing portion 322B and the tab portion 224 of the aerosol extractor 212 (see Figure 7 This dual function of the insert seat 102 is particularly advantageous for optimizing the airflow through the print zone by controlling the height of the suction nozzle 222 to match the height of the print head 3B and the configuration of the membrane 320.

[0158] It will of course be understood that the present invention has been described by way of example only and that modifications of detail may be made within the scope of the invention as defined in the appended claims.

Claims

1. A printing unit, comprising: Unit chassis; as well as a pair of opposed inkjet modules, the pair of opposed inkjet modules being mounted in series on the unit chassis in forward and reverse orientations, each inkjet module having a corresponding print head, in: Each printhead includes a first row of print chips and a second row of print chips mounted on an integral surface of a corresponding ink manifold, the first row of print chips and the second row of print chips comprising a plurality of print chips butted end-to-end along the length of the printhead; as well as The printheads are fully aligned with respect to a media feed direction for printing in four ink colors from the pair of printheads.

2. The printing unit according to claim 1, wherein: Each of the rows of print chips is supplied with only one ink color from its corresponding manifold.

3. The printing unit according to claim 1, wherein: The first row of printing chips and the second row of printing chips on each of the print heads have 180 degree rotational symmetry.

4. The printing unit according to claim 3, wherein: The first row of printing chips in one print head prints two colors of ink, and the second row of printing chips in the print head prints the same two colors of ink.

5. The printing unit according to claim 3, wherein: The compensating nozzle groups of adjacent bonding areas in the first row of printing chips are offset from the compensating nozzle groups of adjacent bonding areas in the second row of printing chips relative to the medium feeding direction.

6. The printing unit according to claim 4, wherein: Each compensating nozzle group includes a downshifted nozzle row offset from a main nozzle row in each print chip, the print chip being configured to delay or advance firing of the downshifted nozzle row relative to the main nozzle row.

7. The printing unit according to claim 1, wherein: Each printhead is asymmetrically disposed toward a front side of its corresponding inkjet module, and wherein the opposing inkjet modules in the forward and reverse orientations position the pair of printheads in a relatively close arrangement and the pair of caps in a relatively distant arrangement.

8. The printing unit according to claim 7, wherein: The span of the printing area along the medium feeding direction is less than 20 cm.

9. The printing unit according to claim 8, wherein: Each row of printing chips has at least quadruple redundancy, whereby aligned nozzles of at least four nozzle rows are able to print onto the same pixel location.

10. The printing unit according to claim 1, wherein: The pair of inkjet modules are pivotally mounted on the unit chassis for pivotally moving the inkjet modules toward and away from each other.

11. The printing unit according to claim 10, wherein: In the clamshell closed configuration, the printing unit is configured for printing, and in the clamshell open configuration, the respective front face of each inkjet module is accessible for printhead replacement.

12. The printing unit according to claim 11, wherein: Each inkjet module is independently pivotable relative to the unit chassis.

13. The printing unit according to claim 1, wherein: Each inkjet module includes a module chassis having a base plate with a rear wall and end walls extending upwardly from the base plate.

14. The printing unit according to claim 13, wherein: Each substrate is C-shaped in plan view, having a pair of lateral arms extending parallel to the media feed direction from opposite ends of a longitudinal base member extending perpendicular to the media feed direction, and each substrate defines an open longitudinal slot for receiving a corresponding print head.

15. The printing unit according to claim 14, wherein: The opposing inkjet modules in the forward and reverse orientations have opposing C-shaped base plates such that the pair of open longitudinal slots are proximately positioned relative to the pair of longitudinal base members.

16. The printing unit according to claim 1, wherein: The second inkjet module in the reverse orientation is rotated 180 degrees relative to the first inkjet module in the forward orientation.

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