Printing unit with air guides to optimize airflow

Abstract

The printing unit includes a base plate defining an elongated slot extending across a media supply path, an elongated printhead positioned within the slot and printing on a printing medium supplied along the media supply path, an aerosol extractor positioned downstream of the printhead in the media supply direction and generating airflow through the printing zone associated with the printhead, and air guides protruding from the underside of the base plate toward the media supply path. The air guides are positioned at both ends of the printhead and include respective guide walls for directing the airflow toward the aerosol extractor.

Description

Technical Field

[0001] The present invention relates to a high-speed printing unit. The present invention has been mainly developed to optimize print quality in digital inkjet printers.

Background Art

[0002] Inkjet printers that employ Memjet's (registered trademark) page-wide technology are commercially available for many different printing applications, such as desktop printers, digital inkjet printers, and wide-format printers. Memjet (registered trademark) printers typically have a length of at least 200 mm and include one or more fixed inkjet printheads that are replaceable by the user. For example, a desktop label printer includes a single user-replaceable full-color printhead, a high-speed inkjet printer includes a plurality of user-replaceable monochrome printheads aligned along the media supply direction, and a wide-format printer includes a plurality of user-replaceable printheads arranged in an alternating, partially overlapping configuration so as to be disposed across a wide-format media supply path.

[0003] Analog printers have conventionally been used for relatively large-volume printing where the cost of producing a dedicated printing plate is economically justified. In recent years, single-pass digital inkjet printing has become increasingly used for relatively small-volume printing in industrial printing systems. Digital inkjet printing avoids the high setup costs required for producing a printing plate and allows each print job to be tailored to a specific customer. It is desirable for existing web supply systems for analog printing systems to be adaptable, for example, to incorporate a "drop-in" inkjet module in place of an offset printing station.

[0004] Memjet® printing technology uses a system where rows of print chips are butted together at their edges to form a printhead that spans the entire page width, making it ideal for reducing the overall span of the printing zone along the media supply direction. Each print chip has four or five active nozzle rows, which can be used for redundant printing.

[0005] U.S. Patent No. 10,857,821 (as incorporated herein by reference) describes a printing system having an array of configurable print modules, each having a monochrome printhead configured for single-pass printing. For example, by arranging four print modules along a media path, full-color (CMYK) printing with five times the redundancy in each color plane can be achieved. The system described in U.S. Patent No. 10,857,821 provides OEMs with flexibility in inkjet press design and high-quality, high-speed printing using five times the redundancy. However, to achieve full-color printing, the print modules must be aligned and spaced along the media supply path. This imposes a requirement on the media supply system to match all colors, resulting in relatively high setup costs for OEMs. Nevertheless, these costs are significantly lower than those of other page-wide printing systems that use overlapping or very large print chips to achieve single-pass printing.

[0006] U.S. Patent No. 10,293,609 (the contents of which are incorporated herein by reference) describes a full-color page-wide printhead having two rows of butted print chips that receive ink from a common manifold. The printhead has double redundancy in each ink color, provided by four active nozzle rows in each row of print chips.

[0007] U.S. Patent Application No. 18 / 309,412, filed on 28 April 2023 (the contents of which are incorporated herein by reference), describes a printing unit with a cantilevered aerosol extractor.

[0008] U.S. Patent Publication No. 2022 / 0324239 (the contents of which are incorporated herein by reference) describes a printing unit comprising overlapping upstream and downstream printheads and an aerosol extractor.

[0009] It would be desirable to provide a low-cost printing unit that optimizes aerosol extraction and airflow through one or more printing zones, thereby optimizing print quality. [Overview of the project]

[0010] In the first embodiment, a printing unit is provided, and this printing unit is A base plate that defines an elongated slot extending across the media supply path, A long, narrow print head positioned within a slot and printing on printing media supplied along a media supply path, An aerosol extractor is positioned downstream of the printhead in the media supply direction and generates airflow through the printing zone associated with the printhead, It includes an air guide that protrudes from the lower surface of the base plate toward the media supply path, Air guides are positioned at both ends of the printhead and include guide walls to direct airflow toward the aerosol extractor.

[0011] The printing unit according to the first embodiment has the advantage of optimizing the airflow through the print zone of the print head. By minimizing the range in which air is drawn in from the lateral region upstream of the print head, a more unidirectional (approximately parallel to the media supply direction) airflow through the print zone is obtained. This has the resulting advantage of improving print quality, especially when printing with relatively large PPS (print head-to-paper spacing), for example, PPS of 3 mm or more.

[0012] Preferably, the guide wall extends upstream from the aerosol extractor, at least partially along the short sides on both sides of the slot.

[0013] Preferably, the guide wall extends parallel to the medium supply direction.

[0014] Preferably, the guide wall extends upstream of the print head and slot.

[0015] Preferably, the aerosol extractor extends into the gap between the base plate and the medium supply path.

[0016] Preferably, the lower surface of the aerosol extractor and the lower surface of the air guide are on substantially the same plane.

[0017] Preferably, the aerosol extractor includes at least one suction nozzle or slit located less than 30 mm downstream from the print head.

[0018] Preferably, the aerosol extractor extends over at least the same length as the row of ink ejection nozzles of the printhead.

[0019] Preferably, the guide walls extend along both ends of the printhead and partially along the downstream side of the printhead toward the side edge of the aerosol extractor.

[0020] Preferably, the printing unit includes first and second print heads arranged in an alternating overlapping arrangement configuration. The first and second print heads are arranged in respective first and second slots. The first and second print heads each have respective first and second aerosol extractors. The first and second aerosol extractors are arranged at respective downstream edges of the first and second slots. At both ends of each of the first and second print heads, first and second sets of air guides are arranged.

[0021] Preferably, the first print head is the upstream print head in the media supply direction, and the second print head is the downstream print head.

[0022] Preferably, the first print head is part of the first inkjet module, and the second print head is part of the second inkjet module.

[0023] Preferably, the first and second inkjet modules are mounted on the unit chassis in opposite front-to-back orientations.

[0024] Preferably, the first aerosol extractor has a configuration different from that of the second aerosol extractor.

[0025] Preferably, the first aerosol extractor is asymmetric in plan view and includes a manifold arm having a finger portion arranged between the first and second print heads.

[0026] Preferably, the first set of air guides has a configuration different from that of the second set of air guides.

[0027] In a second aspect, a printing unit is provided, the printing unit including a unit chassis for mounting on a media supply path, The first and second elongated print heads attached to the unit chassis and arranged to overlap across the media supply path, with the second print head being downstream of the first print head in the media supply direction, the first and second elongated print heads; A first aerosol extractor arranged downstream of the first print head in the media supply direction, extending into the gap between the unit chassis and the media supply path, and generating an air flow through the first printing zone associated with the first print head, the first aerosol extractor; A second aerosol extractor arranged downstream of the second print head and the first aerosol extractor in the media supply direction, extending into the gap between the unit chassis and the media supply path, and generating an air flow through the second printing zone associated with the second print head, the second aerosol extractor; The first and second aerosol extractors are arranged at the same distance from their respective first and second print heads.

[0028] The printing unit according to the second aspect has the advantage of realizing an optimal air flow through the first and second printing zones associated with the first and second print heads. By arranging each aerosol extractor immediately downstream of and at the same distance from its respective print head, similar air flow characteristics are obtained in each printing zone, thereby achieving more uniform printing across the entire media supply path and enabling effective aerosol extraction from each printing zone.

[0029] Preferably, a part of the first aerosol extractor is arranged between the first and second print heads along the media supply direction.

[0030] Preferably, the first aerosol extractor is asymmetric in plan view and includes a manifold arm having a finger portion arranged between the first and second print heads.

[0031] Preferably, the finger portion has a width of less than 50 mm along the medium supply direction.

[0032] Preferably, the first and second aerosol extractors have different configurations.

[0033] Preferably, the first and second aerosol extractors have overlapping portions along the medium supply direction.

[0034] Preferably, the first and second aerosol extractors are positioned along the media supply direction at a distance of less than 30 mm from the first and second print heads, respectively.

[0035] Preferably, the first print head is part of the first inkjet module, and the second print head is part of the second inkjet module.

[0036] Preferably, the first and second inkjet modules are mounted on the unit chassis, facing in opposite directions relative to each other.

[0037] Preferably, the printing unit comprises first and second sets of air guides associated with each first and second aerosol extractor, the air guides having guide walls for directing airflow toward each aerosol extractor.

[0038] Preferably, the first set of air guides has a guide wall that extends upstream of the first aerosol extractor in the medium supply direction.

[0039] Preferably, the second set of air guides has guide walls that extend upstream of the second aerosol extractor in the medium supply direction.

[0040] Preferably, the lower surfaces of the first and second aerosol extractors and the lower surfaces of the first and second sets of air guides are on substantially the same plane.

[0041] In this specification, the term “inkjet module” means an assembly of components including an inkjet printhead, such as an elongated printhead configured for single-pass printing (known in the art as a “page-wide” or “line-head” printhead). An inkjet module typically includes one or more of the following to provide a fully integrated inkjet system: maintenance components such as cappers and / or wipers; mechanisms for moving the printhead and / or maintenance components; ink supply components such as pumps, valves, and ink connectors; and electronic circuits for supplying power and / or data to the printhead.

[0042] In this specification, the term "ink" means any printing fluid that can be printed from an inkjet printhead. The ink may or may not contain colorants. That is, the term "ink" may include conventional dye-based or pigment-based inks, infrared inks, fixatives (e.g., precoats and finishers), 3D printing fluids, solar inks, biofluids, sensing fluids, and the like.

[0043] In this specification, the term “attached” includes both direct attachment and indirect attachment via an intermediary. [Brief explanation of the drawing]

[0044] Hereinafter, specific embodiments of the present invention will be described as merely illustrative examples with reference to the accompanying drawings. [Figure 1] Figure 1 is a top perspective view of the printing unit. [Figure 2] Figure 2 shows the printing unit with the cover of the first (upstream) inkjet module removed. [Figure 3] Figure 3 is a bottom perspective view of the printing unit. [Figure 4]Figure 4 is a bottom perspective view of a single print head and its corresponding air guide and aerosol extractor. [Modes for carrying out the invention]

[0045] Referring to Figures 1 and 2, a printing unit 100 is shown, comprising a pair of opposing first (upstream) and second (downstream) inkjet modules 1A and 1B, rotatably mounted on a unit chassis 102 in a forward and reverse direction. Each inkjet module 1 is described in detail in the applicant's U.S. application No. 18 / 309,004, filed on April 28, 2023, which is incorporated herein by reference. Essentially, each inkjet module 1 comprises a module chassis 10 for rotatably mounting on the unit chassis 102, a printhead carrier 30 containing its respective printhead 3 and associated electronics, a lift mechanism (not shown) for moving the printhead carrier closer to and further away from the media supply path relative to the module chassis, and cappers and wipers (not shown) for servicing the printheads.

[0046] The printing unit 100 is similar to that described in U.S. Patent Application No. 18 / 309,412, filed on April 28, 2023, but differs in that the opposing upstream and downstream inkjet modules 1A, 1B, and consequently the upstream and downstream printheads 3A, 3B, are arranged in an overlapping configuration to perform monochrome printing with 8x redundancy, typically on relatively wide media. In contrast, the tandem configuration described in U.S. Patent Application No. 18 / 309,412 has opposing upstream and downstream inkjet modules that are perfectly aligned with respect to the media supply direction, and typically performs full-color printing with 4x redundancy and high quality. Each printhead 3 is of the type described in U.S. Patent No. 10,293,609 (the contents of which are incorporated herein by reference) and has two rows of butt-aligned print chips that receive ink from a common manifold. However, it will be understood that any single-pass printhead can be used in the printing unit 100.

[0047] Referring to Figure 3, the upstream and downstream print heads 3A and 3B (collectively referred to as "print head 3") are visible on the underside of the printing unit 100. The print heads 3A and 3B are indicated by their printing positions, which protrude through their respective opening slots defined by the C-shaped base plate 12 of each module chassis 10. The upstream and downstream aerosol extractors 212A and 212B (collectively referred to as "aerosol extractors 212") are located immediately downstream of the respective print heads 3A and 3B in the media supply direction indicated by arrow M. By positioning the aerosol extractors 212 close to each print head 3, the accumulation of ink aerosols downstream of the print heads can be avoided, and the airflow through each printing zone can be optimized. Typically, each aerosol extractor 212 is located at a distance of less than 40 mm, for example, less than 20 mm, from each print head 3. Each aerosol extractor 212 has a suction portion 222 (e.g., a suction slit or suction nozzle) adjacent to its respective print head 3, and this suction portion extends over at least the same area as the nozzle row that defines each printing zone of the print head.

[0048] As shown in Figure 3, the upstream and downstream aerosol extractors 212A and 212B inevitably have different configurations due to the geometric constraints of the downstream area of ​​the printing zone and the need to minimize the distance between the upstream and downstream print heads 3A and 3B along the media supply direction M (e.g., less than 100 mm or less than 80 mm apart). Therefore, the upstream aerosol extractor 212A is typically asymmetrical and has a manifold arm 213 and a relatively narrow (e.g., less than 50 mm wide) finger portion 214 extending into the space between the upstream and downstream print heads 3A and 3B (see Figure 4). On the other hand, the downstream aerosol extractor 212B has fewer geometric constraints and spreads out almost symmetrically in plan view to optimize uniform airflow across the entire downstream printing zone.

[0049] Air guides 4, which protrude downward from each base plate 12, are positioned on both sides of each print head 3. Each air guide 4 has a guide wall 6 that extends upstream from each aerosol extractor 212 and is configured to guide the airflow through each printing zone toward the aerosol extractor.

[0050] Figure 4 shows the upstream printhead 3A alone, along with the corresponding baseplate 12, aerosol extractor 212, and air guide 4. The guide wall 6 of the air guide 4 extends upstream of the printhead, parallel to the media supply direction M, thereby facilitating a unidirectional airflow parallel to the media supply direction through the printing zone towards the aerosol extractor 212. This unidirectional airflow through the printing zone is advantageous for optimizing print quality.

[0051] In the absence of the air guide 4, the aerosol extractor 212 tends to draw in air not only from the upstream region aligned with the print head 3, but also from the upstream lateral region offset from the print head. Therefore, the air guide 4 is effective in optimizing the airflow through the printing zone by minimizing the intake of air from those lateral regions.

[0052] A further advantage of the air guide 4 is that all nozzles receive a similar airflow, resulting in more uniform drying of the inkjet nozzles across the entire printhead. Without the air guide, nozzles at the edges of the printhead tend to receive oblique airflow from laterally offset areas, causing them to dry out more easily than nozzles located in the center of the printhead. Relatively high drying of the edge nozzles is undesirable when nozzle drying is controlled by wet-hold ejection (see, for example, U.S. Patent No. 9,545,787 assigned to the present applicant). This is because it would require more frequent wet-hold ejection (KWS) for all nozzles in the printhead to address the relatively more prone-to-drying edge nozzles. Minimizing KWS is desirable for optimizing print quality, and therefore the air guide also works to reduce the KWS requirements of the printhead.

[0053] Further optimization of airflow is achieved by extending the guide walls 6 in an L-shape from both ends of the printhead, partially along the downstream side of the printhead (i.e., perpendicular to the media supply direction M) to contact the side edges of the aerosol extractor 212. In this way, the aerosol extractor 212 is positioned downstream of the printhead 3, with both sides contacting the guide walls 6, and these guide walls extend continuously around and upstream of the aerosol extractor, preferably to the upstream side of the printhead. This configuration further minimizes the air drawn in from areas other than the upstream region aligned with the printhead, as best shown in Figure 4.

[0054] It will be understood that the specific configuration of the air guide 4 may vary depending on the geometric and / or mechanical constraints within the printing unit. However, print quality is generally improved by using air guides 4 that extend at least partially along both ends of the print head 3 and direct airflow parallel to the media supply direction M toward each aerosol extractor 212.

[0055] Naturally, the present invention is described for illustrative purposes only, and it should be understood that modifications of details are possible within the scope of the invention as defined in the appended claims.

Claims

1. A printing unit, A base plate that defines an elongated slot extending across the media supply path, A long, narrow print head is positioned within the aforementioned slot and prints on a printing medium supplied along the aforementioned medium supply path, An aerosol extractor is positioned downstream of the print head in the media supply direction and generates airflow through the printing zone associated with the print head, The base plate is equipped with an air guide that protrudes from the lower surface of the base plate toward the medium supply path, A printing unit characterized in that the air guides are positioned at both ends of the print head and each includes a guide wall for directing the airflow toward the aerosol extractor.

2. A printing unit according to claim 1, characterized in that the guide wall extends at least partially along the short sides on both sides of the slot upstream from the aerosol extractor.

3. A printing unit according to claim 1, characterized in that the guide wall extends parallel to the media supply direction.

4. A printing unit according to claim 1, characterized in that the guide wall extends upstream of the print head and the slot.

5. A printing unit according to claim 1, characterized in that the aerosol extractor extends into the gap between the base plate and the medium supply path.

6. A printing unit according to claim 1, characterized in that the lower surface of the aerosol extractor and the lower surface of the air guide are substantially on the same plane.

7. A printing unit according to claim 1, characterized in that the aerosol extractor includes at least one suction nozzle or suction slit located less than 30 mm downstream from the print head.

8. A printing unit according to claim 1, characterized in that the aerosol extractor extends over at least the same area as the row of ink ejection nozzles of the print head.

9. A printing unit according to claim 8, characterized in that the guide wall extends along both ends of the print head and partially extends downstream of the print head toward the side edge of the aerosol extractor.

10. The printing unit according to claim 1 comprises a first and a second print head arranged in a configuration in which parts of them overlap in an alternating manner, The first and second print heads are arranged in their respective first and second slots. The first and second print heads each have their own first and second aerosol extractors, The first and second aerosol extractors are positioned at the downstream edges of the first and second slots, A printing unit characterized in that a first and second set of air guides are positioned at both ends of each of the first and second print heads.

11. A printing unit according to claim 10, characterized in that the first print head is an upstream print head in the media supply direction, and the second print head is a downstream print head.

12. A printing unit according to claim 11, characterized in that the first print head is part of a first inkjet module, and the second print head is part of a second inkjet module.

13. A printing unit according to claim 11, characterized in that the first and second inkjet modules are mounted on the unit chassis in opposite directions from each other.

14. A printing unit according to claim 13, characterized in that the first aerosol extractor has a different configuration from the second aerosol extractor.

15. A printing unit according to claim 14, characterized in that the first aerosol extractor comprises a manifold arm having a finger portion that is asymmetrical in plan view and positioned between the first and second print heads.

16. A printing unit according to claim 13, characterized in that the air guide of the first set has a different configuration from the air guide of the second set.

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