Airflow control in printing systems and related devices, systems, and methods

Abstract

To provide address blurring issues.SOLUTION: A printing system comprises a printhead to eject ink to a deposition region through an opening in a carrier plate. A print medium is held against a movable support surface by vacuum suction communicated through platen holes of a vacuum platen, and transported through the deposition region. An airflow control system comprises upstream and downstream valves associated with the printhead, individually addressable channels for the vacuum platen, or both. The upstream and downstream valves are arranged to selectively block and allow the airflow through upstream and downstream sides, respectively, of the opening in the carrier plate. Actuation of the upstream and downstream valves may be controlled based on a location of the print medium. The channels are arranged to selectively control the supply of vacuum suction to respectively corresponding columns of platen holes. Actuation of the channels may be controlled based on a size of the print medium.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] Aspects of the present disclosure relate generally to inkjet printing, and more particularly to inkjet printing systems having media handling devices that utilize vacuum suction to hold and transport print media. Related devices, systems, and methods are also disclosed. [Background technology]

[0002] Introduction In some applications, inkjet printing systems use an ink deposition assembly having one or more printheads and a media transport device for moving print media (e.g., substrates such as sheets of paper, envelopes, or other substrates suitable for being printed with ink) through an ink deposition region (e.g., an area beneath the printheads) of the ink deposition assembly. Inkjet printing systems form printed images on the print media by ejecting ink from the printheads onto the media as the media passes through the deposition region. In some inkjet printing systems, the media transport device uses vacuum suction to help hold the print media against a movable support surface (e.g., a conveyor belt, a rotating drum, etc.) of the transport device. The vacuum suction to hold the print media against the support surface can be achieved using a vacuum source (e.g., a fan) and a vacuum plenum fluidly connecting the vacuum source to a side of the movable support surface opposite the side that supports the print media. The vacuum source creates a vacuum in the vacuum plenum, causing the vacuum suction to pass through holes in the movable support surface that are fluidly connected to the vacuum plenum. When the print media is introduced onto the movable support surface, vacuum suction creates a suction force that holds the print media against the movable support surface. A media transport device that utilizes vacuum suction can enable the print media on the movable support surface to be held firmly in place without slippage while being transported through an ink deposition area below the ink deposition assembly, thereby helping to ensure accurate placement of the print media relative to the print head and a more accurate printed image. Vacuum suction can also enable the print media to be held flat as it passes through the ink deposition area, which can also help to increase the accuracy of the printed image and at the same time help prevent portions of the print media from lifting and impacting portions of the ink deposition assembly, potentially causing jams or damage.

[0003] One problem that can arise in inkjet printing systems that include media transport devices that utilize vacuum suction is unintended blurring of images resulting from airflow induced by the vacuum suction. In some systems, such blurring can occur in portions of the printed image near the edges of the print media. This blurring can occur due to uncovered holes in the media transport device adjacent to one or more of the edges of the print media. In particular, during a print job, the print media are spaced apart on the movable support surface as they are transported in the process direction through the deposition region of the ink deposition assembly, and therefore portions of the movable support surface between adjacent print media are not covered by either print media. This region between adjacent print media is referred to herein as the inter-media zone. Thus, uncovered holes exist in the movable support surface adjacent both the leading and trailing edges of each print media in the inter-media zone.

[0004] Additionally, there may be an area of ​​uncovered holes extending along the inner edge of the print medium. One edge of the print medium is used to register the print medium in the cross-process direction (i.e., the edge is aligned in the cross-process direction with the registration reference line), and this edge is referred to herein as the outer edge. The edge opposite the outer edge is referred to herein as the inner edge. Because the location of the outer edge in the cross-process direction is fixed, the location of the inner edge in the cross-process direction varies depending on the size of the print medium. The vacuum suction holes are generally positioned to extend across approximately the entire width of the deposition area in the cross-process direction so that any size of print medium the system is designed to use, from the minimum size to the maximum size, can be held. As a result, if the print medium currently being printed is smaller than the maximum size, its inner edge may not extend in the cross-process direction far enough to cover all of the holes. Therefore, when smaller print media are used, an area of ​​uncovered holes appears adjacent to the inner edge of the print medium.

[0005] Because the aforementioned holes near the leading, trailing, and inner edges are uncoated, the vacuum in the vacuum plenum induces air to flow through those uncoated holes. This airflow can deflect ink drops, such as satellite drops, as they travel from the print head to the substrate, thereby causing blurring of the image near those edges.

[0006] A need exists to improve the accuracy of drop placement in inkjet printing systems and reduce the appearance of blur in the final printed media product. A further need exists to address the blur problem in a reliable manner while maintaining print and transport speeds in order to provide an efficient inkjet printing system. Summary of the Invention

[0007] Embodiments of the present disclosure may solve one or more of the problems set forth above and / or demonstrate one or more of the desirable features set forth above. Other features and / or advantages may become apparent from the following description.

[0008] According to at least one embodiment of the present disclosure, a printing system includes an ink deposition assembly including a carrier plate and a print head positioned to eject printing fluid through a print head opening in the carrier plate to a deposition region of the ink deposition assembly; a media transport device including a movable support surface, the media transport device configured to hold the print media against the movable support surface by vacuum suction through holes in the media transport device and transport the print media through the deposition region along a process direction; and an airflow control system. The airflow control system includes an upstream valve associated with the print head and a downstream valve associated with the print head. Each of the upstream and downstream valves is movable between an open state and a closed state. In the closed state, the upstream valve blocks airflow through an upstream side of the print head opening, and in the open state, the upstream and downstream are defined based on the process direction. In the closed state, the downstream valve blocks airflow through a downstream side of the print head opening, and in the open state, the downstream valve blocks airflow through a downstream side of the print head opening.

[0009] According to at least one embodiment of the present disclosure, a printing system includes an ink deposition assembly including a carrier plate and a print head positioned to eject printing fluid through print head openings in the carrier plate onto a deposition region of the ink deposition assembly; a media transport device including a movable support surface, the media transport device configured to hold a print medium against the movable support surface by vacuum suction through holes in the media transport device and transport the print medium through the deposition region along a process direction; and an airflow control system. The airflow control system includes a plurality of channels individually transitionable between an on state and an off state, each of the channels associated with at least one row of holes. In the on state, each channel provides vacuum suction to the at least one row of holes, and in the off state, each channel does not provide vacuum suction to the at least one row of holes.

[0010] According to at least one embodiment of the present disclosure, a printing system includes an ink deposition assembly including a carrier plate and a print head positioned to eject printing fluid through a print head opening in the carrier plate to a deposition region of the ink deposition assembly; a media transport device including a movable support surface, the media transport device configured to hold the print media against the movable support surface by vacuum suction through holes in the media transport device and transport the print media through the deposition region along a process direction; and an airflow control system. The airflow control system includes an upstream valve associated with the print head and a downstream valve associated with the print head. Each of the upstream and downstream valves is movable between an open state and a closed state. In the closed state, the upstream valve blocks airflow through an upstream side of the print head opening, and in the open state, the upstream and downstream are defined based on the process direction. In the closed state, the downstream valve blocks airflow through a downstream side of the print head opening, and in the open state, the downstream valve blocks airflow through a downstream side of the print head opening. The airflow control system also includes a plurality of channels individually transitionable between an on state and an off state, each associated with at least one row of holes extending in the process direction, each channel applying vacuum to the associated row of holes when in the on state, and each channel not applying vacuum to the associated row of holes when in the off state.

[0011] According to at least one embodiment of the present disclosure, a method includes transporting a print medium through a deposition area of ​​a print head of a printing system and ejecting a printing fluid from the print head through a print head opening in a carrier plate to deposit ink on the print medium in the deposition area. During transport, the print medium is held against a movable support surface of the media transport device via vacuum suction through holes in the media transport device, the vacuum suction being transmitted to the holes from a vacuum source via a vacuum plenum. The method further includes controlling an airflow control system to selectively block airflow through upstream and downstream sides of the print head opening by selectively actuating an upstream valve and a downstream valve between an open state and a closed state, where upstream and downstream are defined based on the process direction. The upstream valve blocks airflow through the upstream side of the print head opening in a closed state and allows airflow through the upstream side of the print head opening in an open state. The downstream valve blocks airflow through the downstream side of the print head opening in a closed state and allows airflow through the downstream side of the print head opening in an open state. The method may also include controlling the airflow control system to selectively turn on and off individual channels of the plurality of channels, each associated with at least one row of holes extending in the process direction, each channel providing vacuum suction to the associated row of holes in the on state and each channel not providing vacuum suction to the associated row of holes in the off state. [Brief explanation of the drawings]

[0012] The present disclosure can be understood from the following detailed description, either alone or in conjunction with the accompanying drawings. The drawings are included to provide a further understanding of the disclosure, and are incorporated into and constitute a part of this specification. The drawings illustrate one or more embodiments of the present teachings and, together with the description, make clear certain principles and operations. In the drawings:

[0013] [Figure 1A]1A-1C illustrate schematic diagrams of airflow patterns relative to a printhead assembly, transport device, and print media at different stages of print media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting blurring effect on the print media product. [Figure 1B] 1A-1C illustrate schematic diagrams of airflow patterns relative to a printhead assembly, transport device, and print media at different stages of print media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting blurring effect on the print media product. [Figure 1C] 1A-1C illustrate schematic diagrams of airflow patterns relative to a printhead assembly, transport device, and print media at different stages of print media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting blurring effect on the print media product. [Figure 1D] 1A-1C illustrate schematic diagrams of airflow patterns relative to a printhead assembly, transport device, and print media at different stages of print media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting blurring effect on the print media product. [Figure 1E] 1A-1C illustrate schematic diagrams of airflow patterns relative to a printhead assembly, transport device, and print media at different stages of print media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting blurring effect on the print media product. [Figure 1F] 1A-1C illustrate schematic diagrams of airflow patterns relative to a printhead assembly, transport device, and print media at different stages of print media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting blurring effect on the print media product. [Figure 1G] 1A-1C illustrate schematic diagrams of airflow patterns relative to a printhead assembly, transport device, and print media at different stages of print media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting blurring effect on the print media product. [Figure 1H]1A-1C illustrate schematic diagrams of airflow patterns relative to a printhead assembly, transport device, and print media at different stages of print media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting blurring effect on the print media product. [Figure 1I] 1A-1C illustrate schematic diagrams of airflow patterns relative to a printhead assembly, transport device, and print media at different stages of print media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting blurring effect on the print media product. [Figure 1J] 1A-1C illustrate schematic diagrams of airflow patterns relative to a printhead assembly, transport device, and print media at different stages of print media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting blurring effect on the print media product. [Figure 1K] 1A-1C illustrate schematic diagrams of airflow patterns relative to a printhead assembly, transport device, and print media at different stages of print media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting blurring effect on the print media product. [Figure 1L] 1A-1C illustrate schematic diagrams of airflow patterns relative to a printhead assembly, transport device, and print media at different stages of print media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting blurring effect on the print media product.

[0014] [Figure 2] FIG. 1 is a block diagram illustrating components of an embodiment of an inkjet printing system including an airflow control system.

[0015] [Figure 3] FIG. 1 is a schematic diagram of an ink deposition assembly, a media transport device, and an airflow control system of an embodiment of an inkjet printing system.

[0016] [Figure 4A] FIG. 4 is a top plan view of the printhead assembly of the inkjet printing system of FIG. 3. [Figure 4B] FIG. 4 is a plan view of a portion of the inkjet printing system of FIG. 3.

[0017] [Figure 5A] 4B is a cross-sectional view of the inkjet printing system of FIG. 4A, the cross section being taken along D in FIG. 4A. [Figure 5B] 4B is a cross-sectional view of the inkjet printing system of FIG. 4A, the cross section being taken along D in FIG. 4A. [Figure 5C] 4B is a cross-sectional view of the inkjet printing system of FIG. 4A, the cross section being taken along D in FIG. 4A. [Figure 5D] 4B is a cross-sectional view of the inkjet printing system of FIG. 4A, the cross section being taken along D in FIG. 4A. [Figure 5E] 4B is a cross-sectional view of the inkjet printing system of FIG. 4A, the cross section being taken along D in FIG. 4A. [Figure 5F] 4B is a cross-sectional view of the inkjet printing system of FIG. 4A, the cross section being taken along D in FIG. 4A.

[0018] [Figure 6A] FIG. 1 is a cross-sectional view of an inkjet printing system, the cross section being taken along the process direction. [Figure 6B] FIG. 1 is a cross-sectional view of an inkjet printing system, the cross section being taken along the process direction. [Figure 6C] FIG. 1 is a cross-sectional view of an inkjet printing system, the cross section being taken along the process direction. [Figure 6D] FIG. 1 is a cross-sectional view of an inkjet printing system, the cross section being taken along the process direction.

[0019] [Figure 7] FIG. 2 is a plan view from below of a vacuum platen of one embodiment of an inkjet printing system.

[0020] [Figure 8A]8 is a cross-sectional view of the inkjet printing system of FIG. 7, the cross section being taken along line E in FIG. 7. [Figure 8B] 8 is a cross-sectional view of the inkjet printing system of FIG. 7, the cross section being taken along line E in FIG. 7. [Figure 8C] 8 is a cross-sectional view of the inkjet printing system of FIG. 7, the cross section being taken along line E in FIG. 7.

[0021] [Figure 9] 1 is a process flow diagram illustrating one embodiment of a method. DETAILED DESCRIPTION OF THE INVENTION

[0022] As mentioned above, when the inter-media zone is near or below the print head, uncovered holes in the inter-media zone can create cross-flow that can blow ink drops, such as smaller satellite drops formed when ejected from the print head, out of the way and cause image blurring. Similarly, uncovered holes along the inner or outer sides of the print media can also create cross-flow that causes image blurring. To better illustrate some of the phenomena that cause blurring problems, refer to FIGS. 1A-1L. FIGS. 1A, 1D, 1G, and 1J schematically show a print head 10 printing on a print media 5 near the trailing edge TE, leading edge LE, inner edge IE, and middle portion of the print media 5, respectively. 1A, 1D, and 1J are cross sections taken through one of the print heads 10 along the process direction P (the direction in which the moving surface moves the print medium below the print head through the deposition zone, indicated by the y-axis in the figures), and FIG. 1G is a cross section taken through the same print head 10 along a cross-process direction perpendicular to the process direction P (indicated by the x-axis in the figures). FIGS. 1B, 1E, 1H, and 1K show enlarged views of regions A, B, C, and D of FIGS. 1A, 1D, 1G, and 1J, respectively. FIGS. 1C, 1F, 1I, and 1L show enlarged photographs of printed images, including lines printed near the trailing edge TE, leading edge LE, inner edge IE, and middle of a sheet of paper.

[0023] As shown in FIGS. 1A, 1D, 1G, and 1J, an inkjet printing system includes one or more print heads 10 for ejecting ink onto a print medium 5 through print head openings 19 in a carrier plate 11 and a movable support surface 20 for transporting the print medium 5 in a process direction P, which corresponds to the positive y-axis direction in the figures. The movable support surface 20 moves over (e.g., slides along) the top of a vacuum platen 26, providing a vacuum environment on the bottom side of the platen 26. The movable support surface 20 has holes 21, and the vacuum platen 26 has holes 27, which periodically align as the movable support surface 20 moves to expose areas above the movable support surface 20 to the vacuum below the platen 26. In areas where the print medium 5 covers the holes 21, vacuum suction through the aligned holes 21 and 27 generates a force that holds the print medium 5 against the movable support surface 20. However, little or no air flows through these covered holes 21 and 27 because they are blocked by the print medium 5. On the other hand, as shown in Figures 1A, 1D, and 1G, in the inter-media zone 22 and the uncovered area 24 near the inner side IB of the platen 26, the holes 21 and 27 are not covered by the print medium 5, and therefore the vacuum suction draws air in and causes it to flow down through these holes 21 and 27. This creates an airflow, indicated by the dashed arrows in Figures 1A, 1D, and 1G, from the area around the print head 10 toward the uncovered holes 21 and 27 in the inter-media zone 22 and uncovered area 24, with some of the airflow passing underneath the print head 10.

[0024] In FIG. 1A , print medium 5a is printing near its trailing edge TE, so the region where ink is currently being ejected (e.g., ink ejection region A in FIG. 1A ) is located downstream of inter-media zone 22, which is the region between print media 5a and 5b that follows print medium 5b. Upstream and downstream are defined with respect to process direction P. Thus, some of the air drawn toward inter-media zone 22 flows upstream through ink ejection region A. More specifically, vacuum suction from inter-media zone 22 reduces the pressure in the region immediately above inter-media zone 22, e.g., region R1 in FIG. 1A , while the region downstream of print head 10, e.g., region R2 in FIG. 1A , remains at a higher pressure. This pressure gradient causes air to flow upstream from region R2 to region R1, and the airflow crosses through ink ejection region A in FIG. 1A , which is between regions R1 and R2. Airflows such as these that cross through ink ejection regions are referred to herein as crossflows 15. 1A , cross-flow 15 flows upstream due to the relative location of inter-media zone 22 with respect to ink ejection area A, but cross-flow 15 may flow differently if inter-media zone 22 is located elsewhere. Additionally, some cross-flows may arise from sources other than inter-media zone 22, and these cross-flows may flow in various directions. As such, the illustrated cross-flows 15 are merely exemplary and are not meant to be exhaustive of all cross-flows that may occur near print head 10.

[0025] 1B , which includes a close-up of region A, main drops 12 and satellite drops 13 are formed as ink is ejected from print head 10 toward medium 5. Satellite drops 13 are much smaller and have less mass and momentum than main drops 12, and therefore upstream cross-flow 15 tends to affect satellite drops 13 more than main drops 12. Thus, while main drops 12 may land on print medium 5 near their intended deposition locations 16 regardless of cross-flow 15, cross-flow 15 may push satellite drops 13 away from their intended trajectories, causing them to land at unintended locations 17 on medium 5 that are displaced from their intended locations 16. This can be seen in an actual printed image, as shown in FIG. 1C , where the denser / darker line is formed by main drops 12 deposited primarily at the intended location 16, while smaller dots dispersed away from the line are formed by satellite drops 13 blown away from the intended location 16 to land at unintended locations 17, resulting in a blurred or smeared appearance for the printed line. In particular, the blur in FIG. 1C is asymmetrically biased toward the trailing edge TE by cross-flow 15 near the trailing edge TE, which blows primarily upstream. The inter-media zone 22 may also induce other airflows flowing in other directions, such as airflow from the upstream side of the printhead 10 downstream, but these other airflows do not pass through the inkjet region A in the example scenario of FIGS. 1A and 1B and therefore do not contribute to the blurring of the image. Only these airflows that cross the inkjet region are referred to herein as cross-flows.

[0026] 1D-1F illustrate a further situation in which such blurring occurs, this time near the leading edge LE of the print medium 5b. The cause of blurring near the leading edge LE is similar to that described above in connection with the trailing edge TE, except that when printing near the leading edge LE, ink discharge region B is now located upstream of the inter-media zone 22. As a result, crossflow 15 across ink discharge region B originates from the upstream side of the print head 10, e.g., region R3, and flows downstream. Thus, as shown in enlarged view B' of FIG. 1E, which includes an enlarged view of region B, when printing near the leading edge LE, satellite drops 13 are blown downstream (in the positive y-axis direction) toward the leading edge LE of the print medium 5b. As shown in FIG. 1F, this results in asymmetric blurring biased toward the leading edge LE.

[0027] 1G-1I illustrate another situation in which such blurring can occur, this time near the inner edge IE of the print medium 5a. As described above, as used herein, the inner edge is either edge of the print medium opposite the outer edge, which is the edge used to register the print medium in the cross-process direction. As shown in FIG. 1G, the outer edge OE is aligned with the registration reference line (REG). Because the print medium 5a is smaller in the cross-process direction than the maximum size accommodated by the movable support surface 20, holes 21 along the inner edge IE of the print medium are not covered. The area along the inner edge IE that contains the uncovered holes is referred to herein as the uncovered area 24. The cause of the blurring near the inner edge IE is similar to that described above with respect to the trailing edge TE and leading edge LE, except that when printing near the inner edge IE, the cross-flow 15 is induced by the uncovered area 24 rather than the inter-media zone 22, and the ink ejection area is located outside the uncovered area 24. As a result, the cross-flow 15 across ink ejection region C now originates from the outer side of print head 10, e.g., region R5, and flows inward toward region R4. Thus, as shown in close-up view C' of Figure 1H, which includes a close-up of region C, when printing near inner edge IE, satellite drops 13 are blown inward (in the positive y-axis direction) toward inner edge IE of print medium 5b. This results in asymmetric blurring that is biased toward inner edge LE, as shown in Figure 1I.

[0028] In contrast, as shown in FIG. 1J and the close-up view D' in FIG. 1K, which corresponds to the close-up view of region D, when printing away from the edge of the print medium 105, little or no cross-flow 15 may be present because the inter-media zone 22 and uncovered region 24 are too far apart to induce much airflow. Because the cross-flow 15 is absent or weaker away from the edge of the print medium 5 near the uncovered holes in the movable support surface 20, satellite drops 13 in this region are less likely to be blown off course. Thus, as shown in FIGS. 1K and 1L, when printing away from the edge of the print medium 5b, in the "center portion" of the print medium 5b, satellite drops 13 tend to land at locations 18 much closer to their intended locations 16, resulting in much less, if any, noticeable image blurring. The deposition location 18 of the satellite drops 13 may still vary somewhat from the intended location 16 due to other factors affecting the satellite drops 13, but the deviation is less than near the leading edge, trailing edge, or inner edge.

[0029] Embodiments disclosed herein may reduce or eliminate such image blurring by, among other things, utilizing an airflow control system that reduces or eliminates undesirable cross-flow, which tends to result in unacceptable image blurring. With cross-flow reduced or eliminated, satellite drops are more likely to land closer to or at their intended deposition locations, thus reducing the amount of blurring. Airflow control systems according to various embodiments reduce or eliminate cross-flow by selectively blocking airflow through upstream and downstream portions of print head openings in the carrier plate and / or by selectively blocking airflow through individually addressable channels extending along the process direction in the vacuum platen based on the location of the inter-media zone.

[0030] In various embodiments, a valve is provided for each print head to selectively block a gap between the print head and the rim of the print head opening in the carrier plate. An upstream valve is provided upstream of the print head to block the upstream gap between the print head and the rim of the print head opening, and a downstream valve is provided downstream of the print head to block the downstream gap between the print head and the rim of the print head opening (upstream and downstream are defined based on the process direction). Each valve is movable between an open state that allows airflow through the gap and a closed state that blocks airflow through the gap, depending on the location of the inter-media zone. In various embodiments, the valves are actively controlled, e.g., actuated by an actuator to move between the open and closed states. In various other embodiments, the valves are passively controlled, e.g., moved between the open and closed states by suction of the inter-media zone when the valve is near.

[0031] In various embodiments, the valves move between open and closed states based on the location of the inter-media zone, blocking airflow through whichever side of the printhead opening in the carrier plate tends to contribute to cross-flow under current operating conditions and allowing airflow through the other side of the printhead opening to relieve the low pressure above the inter-media zone. Because the side of the printhead opening that tends to contribute to cross-flow at each leading edge and trailing edge changes as the inter-media zone passes the printhead, the upstream and downstream valves alternately open and close based on the position of the inter-media zone as the inter-media zone passes them. For example, when the downstream edge of the inter-media zone (i.e., the trailing edge TE of the print media) is under the printhead as in FIG. 1A , airflow through the downstream side of the corresponding carrier plate opening tends to flow upstream through the ink ejection region, thereby contributing to cross-flow. Meanwhile, in this same situation, airflow through the upstream side of the printhead opening actually helps to relieve cross-flow by helping to counteract the negative pressure above the inter-media zone. In this way, the downstream valve is closed and the upstream valve is open to prevent cross-flow from the downstream side of the print head opening while allowing beneficial airflow through the upstream side of the print head opening. As the inter-media zone continues to move downstream, eventually, the upstream edge of the inter-media zone (i.e., the leading edge LE of the following print media) begins to pass under the print head, as in FIG. 1D , at which point the upstream side of the print head opening becomes the side that contributes to cross-flow, and airflow through the downstream side becomes beneficial. Therefore, the downstream valve changes to an open state and the upstream valve changes to a closed state. In this way, the valves reduce or eliminate cross-flow by blocking airflow from one side of the print head that would otherwise contribute to cross-flow, while allowing airflow from the other side of the print head to help mitigate cross-flow. With cross-flow induced by the inter-media zone reduced or eliminated, satellite drops are more likely to land at or closer to their intended deposition locations near the leading and trailing edges of the print media, thus reducing the amount of blurring.

[0032] In various embodiments, the present disclosure further contemplates the use of individually addressable channels provided in the vacuum platen of a media transport device, the channels extending in the process direction. The channels may be provided in at least an inner side region of the vacuum platen to align with potential uncovered areas of the movable support surface that may appear depending on the size of the print media. Each channel transmits vacuum suction from the vacuum plenum to a corresponding row of platen holes in the vacuum platen. One or more valves are provided for each channel to block airflow through the corresponding channel (also referred to herein as turning the channel off for ease of reference) or allow airflow through the corresponding channel (also referred to herein as turning the channel on for ease of reference). Thus, suction through individual rows of holes can be independently turned on or off by actuating the valve of the corresponding channel. In various embodiments, the individually addressable channels are controlled based on the size of the print media currently being used, such that each channel located within the uncovered area is turned off, thereby preventing suction through each of the uncovered platen holes in the uncovered area. With suction blocked in the uncoated areas, the amount of fogging is reduced because cross-flow otherwise caused by the uncoated areas is reduced or eliminated.

[0033] 2 is a block diagram that schematically illustrates a printing system 100 that utilizes an airflow control system in accordance with one or more embodiments of the present disclosure. The printing system 100 includes an ink deposition assembly 101, a media transport device 103, an airflow control system 150, and a control system 130. These components of the printing system 100 are described in more detail below.

[0034] The ink deposition assembly 101 includes one or more printhead modules 102. For simplicity, one printhead module 102 is shown in FIG. 2 , but any number of printhead modules 102 may be included in the ink deposition assembly 101. In some embodiments, each printhead module 102 may correspond to a particular ink color, such as cyan, magenta, yellow, and black, for example. Each printhead module 102 includes one or more printheads 110 configured to eject printing fluid, such as ink, onto a print medium to form an image. For simplicity, one printhead 110 is shown in FIG. 2 in the printhead module 102, but any number of printheads 110 may be included per printhead module 102. The printhead module 102 may include one or more walls, including a bottom wall, which may be referred to herein as a carrier plate 111. The carrier plate 111 includes a printhead opening 119 through which the printhead 110 is positioned to eject ink. In some embodiments, the carrier plate 111 supports the print head 110. In other embodiments, the print head 110 is supported by other structures. The print head module 102 may also include additional structures and devices to support and facilitate operation of the print head 110, such as ink supply lines, ink reservoirs, electrical connections (not shown), etc., as known in the art.

[0035] As shown in FIG. 2 , the media transport device 103 includes a movable support surface 120, a vacuum plenum 125, and a vacuum source 128. The movable support surface 120 transports the print medium through a deposition region of the ink deposition assembly 101. The vacuum plenum 125 provides vacuum suction to one side (e.g., the bottom side) of the movable support surface 120, and the print medium is supported on the opposite side (e.g., the top side) of the movable support surface 120. Holes 121 through the movable support surface 120 transmit the vacuum suction through the surface 120 such that the vacuum suction holds the print medium against the surface 120. The movable support surface 120 is movable relative to the ink deposition assembly 101, such that as the movable support surface 120 moves, the print medium held against the movable support surface 120 is transported relative to the ink deposition assembly 101. Specifically, movable support surface 120 transports the print medium through a deposition region of ink deposition assembly 101, which is the region where printing fluid (e.g., ink) is ejected onto the print medium, such as the region beneath print head(s) 110. Movable support surface 120 may include any structure that can be actuated to move relative to ink deposition assembly 101, the structure having holes 121 to allow vacuum suction to hold the print medium, such as a belt, drum, etc. Vacuum plenum 125 includes a valve, wall, or any other structure arranged to enclose or define an environment in which a vacuum condition (e.g., a low-pressure condition) is maintained by vacuum source 128, and plenum 125 fluidly couples vacuum source 128 to movable support surface 120 such that movable support surface 120 is exposed to the vacuum condition within vacuum plenum 125. In some embodiments, movable support surface 120 is supported by vacuum platen 126, which may be the top wall of vacuum plenum 125. In such embodiments, the movable support surface 120 is fluidly coupled to the vacuum in the plenum 125 via holes 127 through the vacuum platen 126. In some embodiments, the movable support surface 120 is itself one of the walls of the vacuum plenum 125 and is therefore directly exposed to the vacuum in the plenum 125. The vacuum source 128 may be any device configured to remove air from the plenum 125 to create a low pressure condition within the plenum 125, such as a fan, a pump, or the like.

[0036] The airflow control system 150 includes (a) a valve 151 for controlling airflow around the print head 110, (b) a channel 160 and a channel valve 161 for controlling airflow through the array of holes 127 in the vacuum platen 126, or (c) both the valve 151 and the channel 160 and the channel valve 161. In some embodiments in which a valve 151 is used, an actuator 159 is also provided for moving the valve 151 between an open state and a closed state. As used herein, moving a valve (such as valve 151) between an open state and a closed state may generally be referred to as actuating the valve, specifically moving the valve from an open state to a closed state may be referred to as closing the valve, and specifically moving the valve from a closed state to an open state may be referred to as opening the valve. In some embodiments in which a channel valve 161 is provided, an actuator 169 is also provided for actuating the channel valve 161. For ease of illustration, in FIG. 2 and the following description, airflow control system 150 is shown / described as having both valve 151 and channel 160 and channel valve 161, but it should be understood that in some embodiments, valve 151 may be omitted, and in other embodiments, channel 160 and channel valve 161 may be omitted.

[0037] Each valve 151 is associated with one or more print heads 110, with one valve 151 positioned adjacent the upstream face of each print head 110 and another valve 151 positioned adjacent the downstream face of each print head 110. The valves 151 are positioned to block airflow through a gap between the upstream or downstream face of the print head 110 and the rim of a corresponding print head opening 119 in the carrier plate 111. Each valve 151 is independently movable between an open state and a closed state, as described above. In the closed state, the valve 151 extends across or over an associated gap between the print head 110 and the rim of the print head opening 119 to block airflow through the gap. In the open state, the valve 151 is rotated so that it no longer blocks airflow through the gap. Valves 151 positioned upstream of print head 110 to block airflow through the upstream gap between print head 110 and the rim of print head opening 119 are referred to herein as upstream valves 151 when it is desirable to emphasize their positioning, and valves 151 positioned downstream of print head 110 to block the downstream gap are referred to herein as downstream valves 151 when it is desirable to emphasize their positioning. When their position is not emphasized, upstream and downstream valves are referred to simply as valves.

[0038] As described above, in some embodiments, the airflow control system 150 includes actuators 159 that actively actuate the valves 151. Each actuator 159 is a device configured to drive movement of the valve 151 between an open state and a closed state. The actuators 159 can be of various types, including, but not limited to, hydraulic or pneumatic pistons, solenoids, linear actuators, hydraulic or pneumatic rotary actuators, electric motors, rotary actuators, etc. The actuators 159 may utilize electromotive power, hydraulic power, pneumatic power, or any other desired power source. The actuators 159 may also include various motion-to-force conversion mechanisms or linkages, such as linear-to-rotary conversion mechanisms, rotary-to-linear conversion mechanisms, or any other linkages for translating and / or converting the motion of the actuators 159 into the desired motion of the valves 151.

[0039] In some embodiments, rather than actively actuating valve 151 using actuator 159, valve 151 is passively actuated. For example, valve 151 may be a threshold valve configured to automatically transition to an open state when subjected to a pressure differential above a certain threshold and to automatically transition to a closed state when the pressure differential falls below the threshold. In such embodiments, the presence of an inter-media zone near valve 151 creates a pressure differential that actuates valve 151 to an open state, but the pressure differential decreases as the inter-media zone moves away from valve 151, causing valve 151 to automatically return to a closed state.

[0040] Regardless of whether valve 151 is actively or passively actuated, airflow control system 150 actuates valve 151 (i.e., between a closed state and an open state) based on the location of the inter-media zone. Actuation of valve 151 based on the location of the inter-media zone may be actively controlled via actuator 159 and controller 131 (described further below), or passively controlled using a threshold valve, as described above. Because the leading edge LE and trailing edge TE of the print medium define the boundaries of the inter-media zone, any reference herein to the location of the inter-media zone is equivalent to a reference to the corresponding locations of the leading edge LE and trailing edge TE of print medium 105. Thus, when it is said herein that airflow control system 150 actuates valve 151 based on the location of the inter-media zone, this is equivalent to airflow control system 150 actuating valve 151 based on the location of the leading edge LE and trailing edge TE of the print medium.

[0041] In embodiments in which active actuation of the valves 151 is used, the controller 131 may control the actuator 159 to actuate the valves 151 at times corresponding to specific positions in the inter-media zone, which may be predetermined or dynamically determined. These positions may be defined relative to a reference location or object, such as the printhead opening (or portion thereof), the printhead 110 (or portion thereof), or the valve 151 (or portion thereof), and may hereinafter be referred to as trigger locations. Generally, each downstream valve 151 is controlled to be closed at least while the trailing edge TE of the print medium (i.e., the downstream edge of the inter-media zone) is located under the printhead 110 associated with the valve 151. Conversely, each upstream valve 151 is controlled to be closed at least while the leading edge LE of the print medium (i.e., the upstream edge of the inter-media zone) is located under the printhead 110 associated with the valve 151. In an embodiment where there are multiple print heads 110 per print head module 102 and the print heads 110 are offset in the process direction, in addition to the controls described above, the downstream valve 151d can be controlled to be closed while the trailing edge LE of the print medium is located under an adjacent print head 110 downstream of the print head 110 associated with the valve 151, and the upstream valve 151 can be controlled to be closed while the trailing edge TE of the print medium is located under an adjacent print head 110 upstream of the print head 110 associated with the valve 151.

[0042] More specifically, in some embodiments, each downstream valve 151 is actuated to a closed state when (or before) the downstream edge of the inter-media zone (i.e., the trailing edge TE of the print media) reaches an upstream trigger location associated with the valve 151. The downstream valve 151 can be actuated to an open state when the downstream edge of the inter-media zone reaches a downstream trigger location associated with the valve 151. Conversely, the upstream valve 151 is actuated to a closed state when the upstream edge of the inter-media zone 122 (i.e., the leading edge LE of the print media) reaches an upstream trigger location associated with the valve 151, or when the downstream edge of the inter-media zone reaches a downstream trigger location associated with the valve 151. The downstream valve 151 can be actuated to an open state when the downstream edge of the inter-media zone 122 (i.e., the trailing edge TE of the print media) reaches a downstream trigger location associated with the valve 151. The upstream trigger location associated with valve 151 may be any predetermined location upstream of the deposition region of the print head 110 associated with valve 151, such as the upstream edge of the carrier plate 111, the upstream edge of the print head opening 119, the upstream edge of the print head, and the upstream edge of the ink deposition region of the print head 110. The downstream trigger location may be any predetermined location downstream of the deposition region of the print head 110 associated with valve 151, such as the downstream edge of the ink deposition region of the print head 110, the downstream edge of the print head 110, and the downstream edge of the print head opening 119. The exact timing at which valve 151 transitions between the open and closed states may vary depending on factors such as the actuation speed of actuator 159, the width of the inter-media zone (i.e., the gap distance between adjacent print media), and the velocity of the movable support surface 120. Valve positioning and actuation according to embodiments are discussed in more detail below in connection with FIGS. 4A-9 .

[0043] The airflow control system 150 may include independently addressable channels 160 (channels 160). Each channel 160 corresponds to one or more rows of holes 127 in the platen 126, with the channels and rows of holes 127 extending in the process direction. The channels 160 include structures defining passageways through which vacuum from the vacuum plenum 125 is transmitted to the corresponding holes 127. Channel valves 161 are respectively coupled to the channels 160 to control airflow through the channels 160. When a channel valve 161 is open, airflow is permitted through the corresponding channel 160, thereby enabling vacuum through the corresponding hole 127. This state is referred to herein as the channel 160 being on. When a channel valve 161 is closed, airflow through the channel 160 is stopped, thereby stopping vacuum through the corresponding hole 127. This state is referred to herein as the channel 160 being off. An actuator 169 is operatively coupled to the channel valve 161 for moving the channel valve 161 between an open state and a closed state.

[0044] In some embodiments, a channel 160 is provided for each row of holes 127 in the platen 126. In other embodiments, a channel is provided for only a subset of the rows. If a channel 160 is provided for less than all holes 127, the channel 160 may be provided for rows of holes 127 located along the inner side of the vacuum platen 126, as this is an area that is likely to go uncovered when print media of smaller widths (measured in the cross-process direction) are used. As described above, in a printing system such as printing system 100, the outer edge OE of the print media is aligned with a registration reference line (e.g., REG in FIG. 1G) located on the outer side of the media handling device (e.g., OB in FIG. 1G), and therefore, when smaller print media are used, holes inside the inner edge are not covered.

[0045] While the description herein assumes that the outer edges of the print media are aligned, other alignment schemes can be used. For example, the print media can be centered on the platen 126, in which case uncovered areas can appear along both edges of the print media. While an inside edge system is shown and described for clarity, if other alignment schemes are used, the location of the channel 160 can be adjusted to align with wherever the uncovered areas potentially appear, and the principles of operation are the same regardless of which portion of the platen 126 has the uncovered areas.

[0046] The channel valves 161 operate independently to control which channels 160 are turned off and which channels 160 remain on. The airflow control system 150 can select which channels 160 to turn off based on the size of the print media currently being used (e.g., selected for a print job or currently being printed on). In particular, any channels 160 fluidly coupled to corresponding holes 127 that are not (or will not be) covered by the print media are turned off, and any channels 160 fluidly coupled to corresponding holes 127 that are (or will be) covered by the print media remain on. In this manner, all of the channels 160 fluidly coupled to holes 127 in the uncovered regions 24 are turned off, preventing suction through the holes 127 in the uncovered regions 24 and eliminating cross-flow induced by the uncovered regions 24. Furthermore, because all of the holes 127 covered by the print media can receive vacuum suction, the suction holding force on the print media is maintained at full strength. When the size of the print media being used changes, the airflow control system 150 changes which channels 160 are turned off based on the size of the new print media.

[0047] Referring again to FIG. 2 , the control system 130 includes processing circuitry for controlling the operation of the printing system 100. The processing circuitry may include one or more electronic circuits configured with logic for performing the various operations described herein. The electronic circuitry may be configured with logic for performing the operations by including dedicated hardware configured to perform the various operations, by including software instructions executable by the circuitry for performing the various operations, or any combination thereof. In examples where the logic includes software instructions, the electronic circuitry of the processing circuitry includes a memory device for storing the software and a processor including one or more processing devices capable of executing the instructions, such as, for example, a processor, processor core, central processing unit (CPU), controller, microcontroller, system-on-chip (SoC), digital signal processor (DSP), graphics processing unit (GPU), etc. In examples where the logic of the processing circuitry includes dedicated hardware, in addition to or instead of the processor, the dedicated hardware may include any electronic device configured to perform specific operations, such as an application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), complex programmable logic device (CPLD), discrete logic circuit, hardware accelerator, hardware encoder, etc. Additionally, the processing circuitry may include any combination of dedicated hardware and general-purpose processors and software. In some embodiments, the logic of control system 130 may include logic corresponding to location tracking system 132 and logic corresponding to controller 131, which are described in more detail below.

[0048] As described above, controller 131 is configured to determine when to actuate valve 151. Controller 131 generates signals to actuator 159 to control actuator 159 to move valve 151 at the determined times. Controller 131 may be part of control system 130 and includes one or more electronic circuits configured with logic to perform the operations described herein, as described above in connection with control system 130. While shown as part of control system 130, controller 131 may also be considered part of airflow control system 150 because it controls several operations of airflow control system 150. Certain operations described herein as being performed by airflow control system 150 may also be performed by controller 131. The physical location of the hardware forming controller 131 is not limited.

[0049] Location tracking system 132 may be used to track the location of the inter-media zone and / or print media as the print media is transported through the ink deposition assembly. As used herein, tracking the location of the inter-media zone or print media refers to the system having knowledge, whether direct or inferred, of where the print media is located at various points as the print media is transported through ink deposition assembly 101. Direct knowledge of the location of the inter-media zone or print media may include information obtained by directly observing the print media, for example, via one or more sensors (e.g., edge-detection sensors). Inferred knowledge of the location of the inter-media zone or print media may be obtained by inference from other known information, for example, by calculating how far the print media has moved from a previously known location based on the known velocity of movable support surface 120. In some embodiments, location tracking system 132 may explicitly track the location of the inter-media zone, the leading edge LE of the print media, and / or the trailing edge TE of the print media. In other embodiments, the location tracking system may explicitly track the location of any other portion(s) of the print media. Because the location of the inter-media zone is critically dependent on the location of the print media and the dimensions of the print media (known to the controller), tracking the location of any arbitrary portion of the print media is functionally equivalent to tracking the location of the inter-media zone. In some embodiments, location tracking system 132 may be part of control system 130.

[0050] Most existing printing systems are already configured to track the location of the print media as it is transported through the ink deposition assembly, as knowledge of the location of the print media can help ensure accurate image formation on the print media. As such, various systems for tracking the location of the print media are known in the art. Because such location tracking systems are known, they will not be described in detail herein. In the embodiments disclosed herein, any known location tracking system (or any new location tracking system) can be used to track the location of the print media, and the controller can use this information to determine the location of the leading edge LE and / or trailing edge TE (if not already known).

[0051] 3-8C, specific embodiments of a printing system that may be used as printing system 100 are described. In the following figures and descriptions, indices such as "_1," "_2," etc., are added to the end of the reference numbers of some components. These indices are used when multiple similar components are present and desirably refer to a specific one of those components. However, when components are referred to generically or collectively without the need to distinguish between specific ones, the indices may be omitted. Thus, as an example, as in FIG. 4A, when it is desirable to identify a specific one of valves 351, valve 351 may be labeled and referred to as first valve 351_1, whereas in other instances where it is not desirable to distinguish between multiple valves 351, valve 351 may simply be labeled and referred to as valve 351. Similarly, for some components, "u" or "d" is added to the reference number to indicate an upstream or downstream location relative to the corresponding print head, with upstream and downstream being relative to the process direction as described above.

[0052] FIGS. 3-5F illustrate a printing system 300 that may be used similarly to the printing system 100 described above with reference to FIG. 2. FIG. 3 includes a schematic diagram of a portion of the printing system 300 from a side view. FIG. 4A includes a plan view looking down on the printhead modules 302 and the media transport device 303. In FIG. 4A, some components that are not otherwise visible because they are positioned below other components are shown with dashed or dotted lines. FIGS. 5A-5F include a cross-section of the printing system 300, with the cross-section taken along D in FIG. 4A, and each of FIGS. 5A-5F illustrates a series of states as the print media 305a and 305b are transported past one of the printhead modules 302.

[0053] 3, printing system 300 includes ink deposition assembly 301, media transport device 303, and airflow control system 350, which may be used similarly to ink deposition assembly 101, media transport device 103, and airflow control system 150, respectively, of FIG. 2. Printing system 300 may also include additional components not shown in FIGS. 3-5F, such as a control system (e.g., control system 130).

[0054] In the printing system 300 shown in FIG. 3 , the ink deposition assembly 301 includes four printhead modules 302, each having three printheads 310, as shown in FIG. 4A . As shown in FIG. 3 , the printhead modules 302 are arranged in series along the process direction P above the media transport device 303 so that the print medium 305 is transported sequentially beneath each of the printhead modules 302. As shown in FIG. 4A , the printheads 310 are arranged to eject printing fluid (e.g., ink) through corresponding printhead openings 319 in corresponding carrier plates 311, with the bottom ends of the printheads 310 extending partway through the printhead openings 319. In this embodiment, the printheads 310 are arranged in an offset pattern, with one of the printheads 310 being further upstream or downstream than the other two printheads 310 of the same printhead module 302. In other embodiments, different numbers and / or arrangements of print heads 310 and / or print head modules 302 are used, and those skilled in the art will understand that they can select various such numbers and arrangements as desired.

[0055] In printing system 300, media transport device 303 includes a flexible belt that provides a movable support surface 320. As shown in FIG. 3 , movable support surface 320 is driven by rollers 329 to move along a looped path, a portion of which passes through ink deposition region 323 of ink deposition assembly 301. Further, in this embodiment, vacuum plenum 325 includes a vacuum platen 326 that forms a top wall of plenum 325 and supports movable support surface 320. Platen 326 includes platen holes 327 that allow fluid communication between the interior of plenum 325 and the underside of movable support surface 320.

[0056] In some embodiments, the platen hole 327 may include a channel on its upper side, as seen in the enlarged cutaway view of FIG. 3A, which may increase the opening area of ​​the hole 327 on its upper side. Specifically, the platen hole 327 may include a bottom portion 327a that opens to the bottom side of the platen 326 and a top portion 327b that opens to the top side of the platen 326, with the top portion 327b being a different size and / or shape than the bottom portion 327a. For example, FIGS. 3-5F show embodiments of the platen hole 327, where the top portion 327b is a channel that is elongated in the process direction and the bottom portion 327a is a through-hole with a shorter length and a smaller cross-sectional area (see the enlarged view of FIG. 3A and the dashed lines in FIG. 4A). In some embodiments, multiple holes 327 may share the same top portion 327b; in other words, multiple bottom portions 327a may be connected to the same top portion 327b.

[0057] The holes 321 in the movable support surface 320 are arranged such that each hole 321 is aligned in the process direction (y-axis) with a corresponding collection of platen holes 327. Thus, as the movable support surface 320 moves over (e.g., slides across) the platen 326, each hole 321 periodically moves over its corresponding platen hole 327, resulting in the holes 321 and platen holes 327 being temporarily aligned vertically (i.e., aligned in the z-axis direction). As the holes 321 move over their corresponding platen holes 327, the holes 321 and 327 define openings that fluidly couple the environment above the movable support surface 320 to the low-pressure conditions in the vacuum plenum 325, thereby generating vacuum suction through the holes 321 and 327. This suction generates a vacuum holding force on the print medium 305 when the print medium 305 is disposed over the holes 321.

[0058] As shown in FIGS. 3-5F, airflow control system 350 includes valve 351 and corresponding actuator 359 for actuating valve 351. Valve 351 and actuator 359 may be used similarly to valve 151 and actuator 159 described above in connection with FIG. 2. In printing system 300, as shown in FIGS. 4A-5F, there are two valves 351 per print head 310, including upstream valve 351u for blocking a portion of opening 319 on the upstream side of print head 310 and downstream valve 351d for blocking a portion of opening 319 on the downstream side of print head 310. Thus, in FIG. 4A, first print head 310_1 has upstream valve 351u_1 and downstream valve 351d_1, second print head 310_2 has upstream valve 351u_2 and downstream valve 351d_2, and so on. In FIG. 4A , each valve 351 has its own corresponding actuator 359 for actuating the valve 351. In other embodiments, several valves 351, such as valves 351 aligned with one another in the cross-process direction (e.g., 351u_1 and 351u_3, and 351d_1 and 351d_3), may share the same actuator 359, and the valves 351 may be actuated simultaneously. In embodiments in which multiple valves 351 share the same actuator 359, the actuator 359 may be coupled to the valve 351 via a linkage for transferring the motion of the actuator 359 to each of the associated valves 351. In FIG. 4A , there are three print heads 310, and therefore six valves 351; however, in other embodiments in which a different number of print heads 310 are provided, a different number of valves 351 may be provided, with each print head 310 having two corresponding valves 351.

[0059] As noted above, the valves 351 are positioned such that, when in a closed state, they block airflow through portions of the openings 319. Specifically, each upstream valve 351u is positioned to block airflow through a gap between the upstream side of the print head 310 and the rim of the opening 319 associated with that print head 310, which gap is referred to herein as the upstream gap 319u. Similarly, each downstream valve 351d is positioned to block airflow through a gap between the downstream side of the print head 310 and the rim of the opening 319, which gap is referred to herein as the downstream gap 319d. 3-5F, in the closed state, valve 351 is positioned above and generally parallel to the top of carrier plate 311 (see FIGS. 4B and 5A), with one end of valve 351 contacting (or adjacent to) the top of carrier plate 311 (hereinafter referred to as the carrier plate end of valve 351) and another end of valve 351 contacting (or adjacent to) the side of print head 310 (hereinafter referred to as the print head end of valve 351) so that valve 351 substantially spans the area above gap 319u or 319d and blocks airflow through gap 319u or 319d. See, for example, valves 351d_1, 351u_2, and 351d_2 in FIG. 5A in the closed state. As best seen in FIGS. 4B and 5A, the valves 351 are pivotally coupled to the carrier plate 311 by pivot connections 357 and base plates 356. The base plates 356 are fixed relative to the carrier plate 311, and each pivot connection 357 is rotatably coupled to the base plate 356 and to a corresponding valve 351, thereby enabling rotation (pivoting) of the valves 351 relative to the carrier plate 311. The rotation of the valves 351 may be about an axis of rotation parallel to the cross-process direction. In the embodiment of FIGS. 5A-5E, the pivots 357 are attached to the corresponding valves such that as the valves 351 rotate from a closed state to an open state, the end of the valve 351 near the print head 310 moves toward the carrier plate 311 and away from the print head 310, thereby opening the gaps 319u or 319d.In the open state, valve 351 is non-parallel to the top of carrier plate 311 so that air can pass through gap 319u or 319d past valve 351. See, for example, valve 351u_1 in Figure 5A in the open state.

[0060] In other embodiments, valve 351 may be positioned and configured differently. For example, in the closed state, valve 351 may be positioned entirely within gap 319u or 319d, rather than above gap 319u or 319d. As another embodiment, in the open state, the print head end of valve 351 may rotate upward, away from gap 319u or 319d, rather than downward into gap 319u or 319d. As another embodiment, pivot 357 may be coupled to valve 351 near the print head end of valve 351 or near the center of valve 351, rather than near the carrier plate end of valve 351, resulting in a different location and orientation of valve 351 in the open state.

[0061] Valve 351 may comprise, for example, a solid plate-like structure of one or more materials and may be made of any suitable material, such as metal, plastic, rubber, polymer, etc. In some embodiments, valve 351 comprises metal, which provides sturdiness and wear resistance. In FIG. 4A , valve 351 is generally rectangular, but the shape of valve 351 is not limited thereto. Valve 351 may have any desired shape so long as valve 351 is capable of blocking and unblocking gap 319u or 319d as described herein. In some embodiments, valve 351 comprises a pneumatic oscillating valve.

[0062] Valve 351 can be driven to rotate between open and closed states by actuator 359. In FIG. 3 , actuator 359 is a rotary actuator that drives the rotation of shaft 358, which in turn drives the rotation of a corresponding one of valves 351. In the illustrated embodiment, shaft 358 is directly coupled to (or is an integral part of) pivot 357, which is fixedly attached to valve 351, such that rotation of shaft 358 causes rotation of pivot 357, which in turn causes rotation of valve 351. In other embodiments, actuator 359 can be a linear actuator that imparts linear motion to a drive output, which can drive rotation of valve 351 through a linear-to-rotary conversion mechanism. For example, a linear actuator may be coupled to the end of valve 351 opposite pivot 357 and configured to move that end vertically (i.e., in the Z-axis direction), with pivot 357 then functioning as a translation mechanism to convert this linear motion into rotation of valve 351. As will be appreciated by those skilled in the art, other translation mechanisms, linkages, and actuators can be used in various configurations to impart rotation to valve 351. Any device capable of generating drive output motion (rotational or translational) may be used as actuator 359, such as an electric motor, a hydraulic rotary actuator, a pneumatic rotary actuator, a solenoid, a hydraulic actuator, a pneumatic actuator, an electric motor, etc.

[0063] A variety of valves and actuators, including shapes, sizes, materials, and / or movements, are contemplated as being within the scope of the present disclosure, and one skilled in the art will understand that any valve may be selected as desired, so long as it can be moved between a state that blocks airflow through the gap between the print head and the carrier plate and a state that allows airflow through the gap between the print head and the carrier plate, based on the operating principles disclosed herein.

[0064] As described above, airflow control system 350 is configured to actuate valve 351 with timing based on the position of inter-media zone 322. As described above with respect to valve 151, each valve 351 has an upstream trigger location and an associated downstream location, and valve 351 is moved based on the location of inter-media zone 322 relative to these trigger locations. The above discussion related to timing of actuating valve 151 is applicable to valve 351. In practice, it takes a finite time for valve 351 to move between configurations, and during this time that valve 351 is moving, inter-media zone 322 continues to move. Thus, in some embodiments, to ensure that valve 351 is in the intended configuration when inter-media zone 322 reaches the desired trigger location (the "nominal trigger location"), actuator 359 may be controlled to begin moving valve 351 just before inter-media zone 322 actually reaches the nominal trigger location. In other words, the actual trigger location used to trigger extension or retraction may be offset from the nominal trigger location by some fixed amount to account for the finite time it takes for valve 351 to extend or retract. The offset may be determined using the known velocity of movable support surface 320 and the known deployment time of valve 351.

[0065] The operation of valve 351 and the manner in which valve 351 reduces cross-flow are described in more detail below with reference to FIGS. 5A-5F. FIGS. 5A-5F include cross-sections taken along D in FIG. 4A and illustrate various positions of inter-media zone 322 and the corresponding states of valve 351. In FIGS. 5A-5F, the timing for actuating upstream valve 351u_1 and downstream valve 351u_2 is described; the same timing may be used to actuate valves 351u3 and 351d_3, respectively. Furthermore, although the timing for actuating valve 351 in only one printhead module 302 is described, similar timing may be used to actuate similarly located valves 351 in other printhead modules 302.

[0066] FIG. 5A shows the inter-media zone 322 in a first position. The first position corresponds to the downstream edge of the inter-media zone 322 (i.e., the trailing edge TE of the printing medium 305a) reaching the upstream trigger location associated with the first upstream valve 351u_1. In this example, the upstream trigger location of the first upstream valve 351u_1 is the upstream surface of the carrier plate 311. Therefore, at or before the trailing edge TE of the printing medium 305a is at (i.e., vertically aligned with) the upstream edge of the carrier plate 311, the controller causes the corresponding actuator 359 (not shown) to open the valve 351. Thus, in this state, the valve 351u_1 allows airflow through the upstream gap 319u_1. The other valves 351 are in a closed state, and therefore block airflow through their respective gaps 319u or 319d.

[0067] As the trailing edge TE of the print medium 305a continues to move downstream beneath the print head 310_1, there is a risk that the inter-media zone 322 will induce cross-flow upstream through the deposition region 312 of the print head 310u, as shown in FIG. 5B. However, because the first upstream valve 351u_1 is open, air is allowed to flow downward through the upstream gap 319u_1 toward the inter-media zone 322, as indicated by the dashed line in FIG. 5B. This airflow counteracts some of the suction from the inter-media zone 322 and increases the pressure in the area above the inter-media zone 322. This reduces the strength with which air is pulled from downstream of the print head 310_1, thus reducing the strength of the upstream cross-flow. Furthermore, because the valve 351d_1 is closed, the cross-flow that would otherwise occur through the downstream gap 319d_1 is prevented, as described above in connection with FIG. 1A, thereby further reducing the upstream cross-flow.

[0068] FIG. 5C illustrates the inter-media zone 322 when the downstream edge of the inter-media zone 322 (i.e., the trailing edge TE of the print media 305a) is at the downstream trigger location associated with the valve 351u_1. Specifically, in this example, the downstream trigger location associated with the valve 351u_1 is the downstream surface of the print head 310. Thus, the valve 351u_1 is closed when (or just before) the trailing edge TE of the print media 305a reaches this location. In this configuration, the valve 351u_1 blocks airflow through the upstream gap 319u_1. In other embodiments, rather than closing the valve 351u_1 based on the trailing edge TE reaching the downstream trigger location associated with the valve 351u_1, the valve 351u_1 may be closed based on the leading edge LE reaching the upstream trigger location associated with the valve.

[0069] In the illustrated embodiment, the upstream trigger locations associated with valves 351d_1 and 351u_2 are the same as the downstream trigger location of valve 351u_1, i.e., the downstream face of print head 310_1. Thus, in this embodiment, valve 351u_1 is closed while valves 351d_1 and 351d_2 are open. In other embodiments, the upstream trigger locations associated with valves 351d_1 and 351u_2 are not necessarily the same as the downstream trigger location of valve 351u_1.

[0070] After the timing shown in FIG. 5C , leading edge LE of print medium 305b begins to move under print head 310_1, and printing near its leading edge LE begins, as shown in FIG. 5D . Furthermore, trailing edge TE of print medium 305a begins to move under print head 310_2. Thus, after the state shown in FIG. 5C , there is a risk that inter-media zone 322 will induce both downstream cross-flow through the ink deposition region 312 of print head 310_1 and upstream cross-flow through the ink deposition region 312 of print head 310_2. However, as shown in FIG. 5D , because valves 351d_1 and 351u_2 are open, beneficial airflow can flow through gaps 319d_1 and 319u_2 to counteract the negative pressure from inter-media zone 322 and reduce the intensity of the cross-flow. Additionally, because both valves 351u_1 and 351d_2 are in a closed state, cross-flow that might otherwise occur through gaps 319u_1 and 319d_2 is prevented, thereby further reducing cross-flow.

[0071] FIG. 5E illustrates the inter-media zone 322 when the downstream edge of the inter-media zone 322 (i.e., the trailing edge TE of the print medium 305a) is at the downstream trigger location associated with valve 351d_1, the downstream trigger location associated with valve 351u_2, and the upstream trigger location associated with valve 351d_2. Specifically, in this example, these trigger locations are all the same: the downstream surface of print head 310_2. Thus, when (or just before) the trailing edge TE of the print medium 305a reaches this location, valves 351d_1 and 351u_2 are closed and valve 351d_2 is opened. In other embodiments, rather than closing valves 351d_1 and 351u_2 based on the trailing edge TE reaching the downstream trigger location associated with each valve 351, valves 351d_1 and 351u_2 may be closed based on the leading edge LE reaching the upstream trigger location associated with each valve 351.

[0072] In the illustrated example, the downstream trigger locations associated with valves 351d_1 and 351u_2 will be the same as the upstream trigger location of valve 351d_2, i.e., the downstream face of print head 310_2. However, in other embodiments, these trigger locations are not necessarily the same as one another, and thus valves 351 are not necessarily actuated simultaneously.

[0073] As leading edge LE of print media 305b continues to move under print head 310_2, there is a risk that the inter-media zone will pull cross-flow downstream through the ink deposition region 312 of print head 310_2. However, as shown in FIG. 5F , because downstream valve 351d_2 is in an open state, airflow can flow through gap 319d_2, which is beneficial for countering the negative pressure from inter-media zone 322 and reducing the intensity of the cross-flow. Furthermore, because both valves 351d_1 and 351u_2 are in a closed state, cross-flow that might otherwise occur through gaps 319d_1 and 319u_2 is prevented, thereby further reducing cross-flow.

[0074] After the inter-media zones 322 have completely passed the printhead modules 302, the state of the valves 351 becomes less important from the perspective of reducing cross-flow, as the inter-media zones 322 are likely too far apart to induce significant cross-flow. Thus, after the inter-media zones 322 have moved past their corresponding printhead modules 302, the valves 351 can be in any desired state. For example, valve 351u_1 can be opened and the other valves 351 can be closed to accommodate the appearance of the next inter-media zone 322.

[0075] While airflow control system 350, including valve 351 and actuator 359, is described above in connection with a particular embodiment of printing system 300, it should be understood that other embodiments of printing systems may utilize the same airflow control system 350 or a similar airflow control system. For example, embodiments of printing systems having different configurations of ink deposition assemblies or different configurations of media transport devices may utilize valves similar to valve 351. For example, in embodiments having a different number of printhead modules or printheads than printing system 300, the same airflow control system 350 may be used, except that the number of valves 351 may be modified to account for the number of printhead modules and printheads. In embodiments having a different printhead arrangement than printing system 300, a valve similar to valve 351 may be used, except that the arrangement of valve 351 may be changed to match the printhead arrangement. In embodiments having different media transport devices, the same airflow control system 350 may generally be used without any modification. As such, airflow control system 350, or a similar version thereof, may be utilized in a variety of printing systems in addition to the particular printing system 300 described above.

[0076] Figures 6A-6D show a printing system 600 that may be used similarly to printing system 100 described above with reference to Figure 2. Figures 6A-6D include cross sections of printing system 600, with the cross sections taken along the process direction, and each of Figures 6A-6D shows a series of states as print media 605a and 605b are transported past one of the printhead modules 602.

[0077] Printing system 600 includes an ink deposition assembly, a media transport device 603, and an airflow control system 650, which may be used similarly to ink deposition assembly 101, media transport device 103, and airflow control system 150, respectively, of Figure 2. Printing system 600 may also include additional components, such as a control system (e.g., control system 130).

[0078] The ink deposition assembly includes one or more printhead modules 602, each having one or more printheads 610 that eject printing fluid (e.g., ink) through printhead openings 619 in a carrier plate 611. The printhead modules 602, printheads 610, and carrier plates 611 may be used in the same manner as printhead modules 102, printheads 110, and carrier plates 111, respectively. For simplicity of explanation, only one printhead module 602 is shown, although in practice multiple printhead modules 602 may be provided. Notably, the ink deposition assembly may be configured similarly to ink deposition assembly 301 described above, and therefore, redundant description of its components has been omitted.

[0079] Media transport device 603 includes a vacuum platen 626 having holes 627 and a movable support surface 620 having holes 621. Media transport device 603 may be configured similarly to media transport device 303 described above, and therefore, a redundant description of its components will be omitted.

[0080] In the embodiment of FIGS. 6A-6D, airflow control system 650 includes a threshold valve 651, which can be used similarly to valve 151 described above. Unlike valve 351, which is actively actuated by actuator 359, threshold valve 651 is passively actuated by a pressure differential. When the difference between the pressure on one side of valve 651 (e.g., the top side) and the pressure on the other side of valve 651 (e.g., the bottom side) exceeds a threshold value, valve 651 automatically moves to an open state. Conversely, when the pressure differential is lower than the threshold value, valve 651 moves to a closed state. Thus, in effect, threshold valve 651 tends to block relatively weak airflow (airflow associated with a pressure differential below the threshold) while allowing relatively strong airflow (airflow associated with a pressure differential above the threshold) to pass.

[0081] The threshold valve 651 may be formed from a material that is sufficiently rigid to allow the valve 651 to support its own weight and remain in a blocking position when the pressure differential is below a threshold, yet flexible enough to allow the valve 651 to move, deform, and / or bend to an open position when the pressure differential exceeds a threshold. For example, the valve may be formed from plastic, rubber, silicone, various polymers, thin metals, etc. Additionally, there are commercially available threshold valves that can be used as the threshold valve 651.

[0082] The threshold values ​​used for the threshold valves 651 may be any desired threshold values. In some embodiments, the threshold values ​​may be high enough so that each threshold valve 651 remains closed when the inter-media zone 622 is below the printhead module but relatively far from the valve 651, and low enough so that each threshold valve 651 opens when the inter-media zone 622 is near (e.g., below) the valve 651. More specifically, in some embodiments, the threshold values ​​may be high enough so that each threshold valve 651 remains closed when the inter-media zone 622 is below the printhead module 102 but not directly below the valve 651 itself, and low enough so that each threshold valve 651 opens when the inter-media zone 622 is directly below the valve 651 itself. The optimal values ​​for the threshold values ​​may vary from system to system, depending on the physical characteristics of the system and the desired operation of the overall printing system. Generally, the stronger the suction generated by the inter-media zone, the higher the threshold that can be implemented to trigger the valve, and the suction generated by the inter-media zone can vary from system to system based on the strength of the suction generated by the media transport device, the size of the inter-media zone, the number and size of holes in the movable support surface and vacuum platen, the distance from the movable support surface to the carrier plate, etc. The desired threshold may be determined, for example, by testing different threshold valves 651 in the system and identifying one that obtains a desired result, such as acceptable image blur.

[0083] Like valves 351, each valve 651 is transitionable between an open state and a closed state based on the position of inter-media zone 622. However, as described in more detail below in connection with Figures 6A-6D, rather than a controller tracking the position of inter-media zone 622 and sending signals to activate the valve at the appropriate times, threshold valves 651 are passively and automatically activated by suction in inter-media zone 622 as it passes through valve 651.

[0084] 6A shows a state in which the inter-media zone 622 is not yet under the printhead module 602. Therefore, the vacuum experienced near the printhead 610 is still relatively weak, and the pressure difference between each of the threshold valves 651 is less than the threshold T. For example, the difference between the pressure P2 above the upstream valve 651u_1 and the pressure P1 below the upstream valve 651u_1 is greater than the threshold T, so the valve 651u_1 remains closed. The same applies to the other valves 651.

[0085] As the inter-media zone 622 advances under the printhead module 602, the pressure in the region under the carrier plate 611 near (e.g., immediately above) the inter-media zone 622 drops. Thus, as shown in FIG. 6B , when the inter-media zone 622 is under the first upstream valve 651u_1, the pressure P1 in the upstream gap 619u_1 drops sufficiently so that the pressure difference P2-P1 is greater than the threshold T. Thus, the valve 651u_1 is in an open state, allowing air to flow through the gap 619u_1 toward the inter-media zone 622. This airflow helps counter the suction from the inter-media zone 622, thereby reducing the strength with which air is pulled from downstream of the printhead 610, thereby reducing the strength of the cross-flow. In contrast, because the inter-media zone 622 is not close enough to the valve 651d_1, the pressure difference P4-P3 remains below the threshold T, and the valve 651d_1 remains closed. The same applies to the valve 651u_2. In this way, the valves 651d_1 and 651d_2 block the airflow through the downstream gap 619d_1 and the upstream gap 619u_2, respectively, further reducing the occurrence and intensity of cross-flows.

[0086] As the inter-media zone 622 advances further beneath the printhead module 602, it then eventually moves beneath each of the remaining valves 651d_1, 651u_2, and 651d_2, and once the inter-media zone 622 is close enough to the corresponding valve 651, the pressure difference between the valves 651 becomes large enough that each of the valves 651 automatically opens in sequence due to suction from the inter-media zone 622. As the inter-media zone 622 advances further, it then eventually moves away from each of the valves 651, and once the inter-media zone 622 is sufficiently far from the corresponding valve 651, the pressure difference between the valves 651 becomes small enough that each of the valves 651 automatically closes in sequence.

[0087] For example, FIG. 6C shows a state in which inter-media zone 622 is below valves 651d_1 and 651u_2, such that the pressure differential P4-P3 between these valves 651 is greater than threshold T, and valves 651d_1 and 651u_2 are in an open state. Beneficial airflow is therefore permitted to flow through gaps 619d_1 and 619d_2, counteracting the suction from inter-media zone 622 and reducing the strength of cross-flow. At this same time, inter-media zone 622 is not below valves 651u_1 and 651d_2, such that the pressure differentials P2-P1 and P6-P5 between these valves 651 are both less than threshold T, and valves 651u_1 and 651d_2 are in a closed state. Thus, cross-flow through gaps 619u_1 and 619d_2 is prevented.

[0088] 6D shows a state in which inter-media zone 622 is below valve 651d_2, such that the pressure differential P6-P5 across valve 651d_2 is greater than threshold T, causing valve 651d_2 to be in an open state. Beneficial airflow is therefore permitted to flow through gap 619d_2, counteracting the suction from inter-media zone 622 and reducing the strength of cross-flow. At this same time, inter-media zone 622 is not below any of the other valves 651, so the pressure differentials across those valves 651 are all less than threshold T, causing those valves 651 to be in a closed state. Thus, cross-flow through gaps 619d_1 and 619d_2 is prevented.

[0089] Figures 7-8C show a printing system 700 that may be used similarly to the printing system 100 described above with reference to Figure 2. Figure 7 includes a plan view from below of the vacuum platen 726. Figures 8A-8C include cross sections taken along E in Figure 7, each of which shows a different size print media 705 being printed.

[0090] Printing system 700 includes an ink deposition assembly 701, a media transport device 703, and an airflow control system 750, which may be used similarly to ink deposition assembly 101, media transport device 103, and airflow control system 150, respectively. Printing system 700 may also include additional components, such as a control system (e.g., control system 130).

[0091] The ink deposition assembly 701 includes one or more printhead modules, each having one or more printheads 710 that eject printing fluid (e.g., ink) through printhead openings in a carrier plate 711. The printhead modules, printheads 710, and carrier plates 711 may be used in the same manner as the printhead modules 102, printheads 110, and carrier plates 111, respectively. The ink deposition assembly may be configured in the same manner as the ink deposition assembly 301 described above, and therefore, a redundant description of its components will be omitted.

[0092] Media transport device 703 includes a vacuum platen 726 having holes 727 and a movable support surface 720 having holes 721. Media transport device 703 may be configured similarly to media transport device 303 described above, and therefore, a redundant description of its components will be omitted.

[0093] Airflow control system 750 includes channels 760 and valves 761. Channels 760 are independently addressable, meaning that channels 760 can be independently turned on or off. In this context, a channel 760 being "on" means that airflow is permitted through the holes 727 associated with the channel 760, and a channel being "off" means that airflow is not permitted through the holes 727 associated with the channel 760. Valves 761 are coupled to channels 760 to control whether each channel 760 is on or off (i.e., to control airflow through the channels 760 and their associated holes 727). When a valve 761 is open, airflow is permitted through the corresponding channel 760, and thus vacuum suction through the corresponding holes 727 is enabled (i.e., the channel 760 is on). When valve 761 is closed, airflow through channel 760 is stopped and therefore vacuum suction through the corresponding hole 727 is stopped (ie, channel 760 is off).

[0094] As shown in FIGS. 7-8C , the channels 760 include structures that define a path through which vacuum suction in the vacuum plenum 725 is transferred to a corresponding group of holes 727. In particular, each channel 760 corresponds to at least one row of holes 727 in the platen 726, with both the channels 760 and the rows of holes 727 extending in the process direction (y-axis direction). The channels 760 include one or more openings through which the vacuum suction in the vacuum plenum is transferred to the interior of the channel 760, and a valve 761 is positioned at one opening to selectively fluidly connect the channel 760 to the vacuum plenum. Although the channels 760 are shown in FIGS. 7-8C as elongated, box-like structures (rectangular prisms) each having a valve 761 at one end through which air enters the channel 760, the configuration of the channels 760 and valves 761 is not so limited. The channels 760 and valves 761 may have any shape and configuration that allows them to selectively allow or block airflow between the vacuum plenum and the corresponding group of holes 727. For example, the channels 760 may be recessed into the bottom surface of the platen 726 rather than extending from it. As another example, the valves 761 may be positioned differently, such as on the bottom side of the channels 760 or on the opposite end of the channels 760, to block the outlet end of the channels from the vacuum source. As another example, multiple valves 761 may be provided per channel 760 to reduce the airflow impedance of the channels 760. Furthermore, the group of holes 727 whose airflow is controlled by the channels 760 may, but need not necessarily, include all holes 727 in the corresponding row of holes 727. In some embodiments, the channels 760 control airflow through at least those holes 727 in their corresponding row(s) that are in or near the deposition region of the ink deposition assembly. Those skilled in the art can envision various arrangements of channels, holes, and valves without departing from the scope and principles of operation disclosed herein.

[0095] 7-8C show six channels 760. However, in practice, any number of channels 760 may be provided. In some embodiments, a channel 760 is provided for each row of holes 727 in the platen 726, while in other embodiments, channels 760 are provided for fewer than all rows. In some embodiments where channels 760 are provided for fewer than all rows of holes 727, the channels 760 are positioned to cover the N rows of holes 727 closest to the side of the platen 727 where the uncovered region 724 appears, where N is the number of channels 760. For example, in FIGS. 7-8C , the uncovered region 724 appears on the inner side (IB) of the platen 726, and therefore six channels 760_1 through 760_6 are provided for the six innermost rows of holes 727. In some embodiments, a channel 760 is provided for each row of holes 727, which may possibly be located in the uncovered region 724, taking into account the size of the print media the printing system is configured to use. For example, if the smallest print medium the printing system is configured to use has the innermost K rows of holes 727 left uncoated (K is any integer), then at least K channels 760 may be provided in at least these K rows of holes 727.

[0096] 7-8C, the print medium is aligned with a registration reference line (REG) located on the outer side (OB in FIGS. 7-8C) of the platen 726; therefore, when smaller print media are used, the uncovered area 724 appears on the inner side of the print medium. Thus, in such a system, a channel 760 is provided in the row of holes 727 on the inner side of the platen 726. However, in embodiments in which the print medium is aligned differently, the channel 760 can be repositioned to align with where the uncovered area appears.

[0097] In some embodiments, an actuator is operably coupled to (or is an integral part of) valve 761 to move valve 761 between an open state and a closed state. The actuator is not shown in Figures 7-8C to avoid obscuring other parts. The actuator may be used similarly to actuator 169 described above.

[0098] As shown in FIGS. 8A-8C, the valves 761 can be individually controlled to individually turn on or off channels 760 based on the size of the print medium currently being used (e.g., currently being printed or selected for a currently pending print). For example, as shown in FIG. 8A, the largest print medium 705a the system is designed to use is selected, and the cross-process direction width of this print medium 705a is sufficient to cover all of the rows of holes 727. Thus, in this example, there are no uncovered areas 724, and therefore, moving all of the valves 761 to their open state turns on all of the channels 760. The open state of the valves 761 is indicated in the figures by a circle that schematically represents the open path of the valves 761. In contrast, as shown in FIGS. 7B-7C, when a smaller print medium 705 is used, some of the rows of holes 727 are not covered, and therefore uncovered areas 724 are present. In such a state, each channel 760 within the uncovered region 724 is turned off by moving the corresponding valve 761 to a closed state. The closed state of the valve 761 is indicated schematically in FIGS. 8A-8C by an X superimposed on the valve 761. Thus, for example, in FIG. 8B , a print medium 705b sized such that the innermost two rows of holes 727 are uncovered is used, and therefore the innermost two channels 760_1 and 760_2 are turned off (i.e., valves 761_1 and 761_2 are moved). As another example, in FIG. 7C , the smallest print medium 705c the printing system is designed to use is selected, and therefore all of the channels 760 are off (i.e., all of the valves 761 are in a closed state). The three illustrated states are non-limiting and are used to demonstrate the principles of operation, and one skilled in the art will understand that if other sizes of print media are used that cover a different number of rows of holes 727, a different number of channels 760 may be turned on or off accordingly, such that channels 760 within uncovered areas 724 are turned off and channels 760 not in uncovered areas 724 are turned on.In this manner, suction through holes 727 in uncovered areas 724 is prevented regardless of the size of the print media, thus eliminating cross-flow induced by uncovered areas 724. Furthermore, all of the holes 727 that are covered by the print media can continue to receive vacuum suction, thus maintaining full suction holding force on the print media.

[0099] While airflow control systems 350, 650, and 750 are illustrated and described in the context of a particular embodiment of a printing system, it should be understood that other embodiments of a printing system may utilize the above-described airflow control systems 350, 650, or 750 with or without some minor modifications that would be apparent to one skilled in the art. For example, in printing systems having ink deposition assemblies configured differently from those described above in connection with printing systems 300, 600, and 700 (e.g., different numbers, sizes, shapes, or arrangements of printheads or printhead modules), the above-described airflow control systems 350 and 650 may be used so long as one or more printheads extend through corresponding openings and associated gaps exist upstream and downstream of the printheads through which valves 351 or 651 can selectively block airflow. The number of valves 351 or 651 may be adjusted based on the number of printheads. The shape and size of valve 351 or 651 can be adjusted based on the shape and size of the gap blocking the airflow (which varies depending on the shape and size of the print head and the opening through which the print head extends). Airflow control system 700 can be used regardless of the configuration of the ink deposition assembly, except that the size of channel 760 can vary depending on the size of the ink deposition area. As another example, in printing systems having media transport devices configured differently from those described above with respect to printing systems 300, 600, and 700, airflow control system 750 can be used regardless of the shape, number, or arrangement of holes 727, and regardless of the type or configuration of the movable support surface or vacuum plenum, as long as holes 727 are present to provide vacuum suction to the print media. The number and size of channels 760 can be varied based on the arrangement of holes 727 and the size of the ink deposition area. The airflow control systems 350 and 650 described above can be used regardless of the configuration of the media transport device, as long as the media transport device utilizes vacuum suction to hold the print media. As such, airflow control systems 350, 650, and / or 750 may be utilized, with or without modification, in a variety of printing systems, including but not limited to the specific printing systems described above. Additionally, airflow control systems 350, 650, and / or 750 may be used alone or in combination.

[0100] As described above, a controller (such as controller 131) determines when to activate a valve (such as valve 151 or 351) based on the location of the inter-media zone, and the controller activates the valve when the upstream or downstream edge of the inter-media zone reaches a particular trigger location. In some embodiments, these trigger locations are predetermined and programmed into controller 131. For example, the trigger location may be set to one of the example trigger locations described above. As another example, the trigger location may be determined experimentally by repeatedly printing test images on print media, determining the amount of blur in the image, adjusting the trigger location for activating the valve, and then repeating the process until a desired level of image blur is achieved. The timing that produced the desired level of image blur may then be selected and programmed into the controller as the predetermined timing. In contrast, in some embodiments, the trigger location (and therefore the activation timing based thereon) may be dynamically determined or adjusted during operation of the printing system, for example, based on real-time feedback. As described above, a controller (such as controller 131) may also determine the width of the print medium and actuate a valve (such as valve 161 or 761) based on the width of the print medium. The width of the print medium may be determined based on imaging of the print medium, an edge-detection sensor, or the current known paper size of the print medium.

[0101] FIG. 9 illustrates an embodiment of a method 900 related to dynamically determining a trigger location for actuating a valve (e.g., valve 151 or 351). In one example, method 900 may be automatically performed by a control system of the printing system, such as control system 130 of printing system 100 or the control system of printing system 300. In some examples, the trigger location (and therefore the timing) for actuating a valve may be dynamically adjusted during use of the printing system. In some embodiments, the operations of method 900 and / or other operations described herein may be embodied in machine-readable instructions (also referred to as computer-readable instructions, processor-executable instructions, code, software, programming, etc.) stored on one or more non-transitory machine-readable media (e.g., memory devices), which, when executed by processing circuitry of the printing system, cause the printing system to perform the operations described herein. Method 900 may also be performed by a user of the printing system, for example, by the user placing the printing system in an operational state in which the printing system performs the operations of method 900.

[0102] Block 901 includes printing an image using a printing system including an airflow control system according to various embodiments described herein. In one embodiment, the image may be a test image generated specifically for the process of adjusting valve actuation timing. The test image may include a predetermined pattern or shape (e.g., one or more lines). In another embodiment, the image may not be specific to the process of adjusting valve actuation timing. For example, the image may be part of a regular print job that is not related to the adjustment process.

[0103] Block 902 includes determining the amount of edge blur in the printed image. This may include, for example, obtaining an electronic image of the printed image by scanning or photographing the printed image. The electronic image may then be analyzed to determine the amount of blur in the image. For example, luminance values ​​of portions of the electronic image may be sampled and compared to expected luminance values ​​for those portions (expected luminance values ​​known from the master image data used to print the image), and the amount of difference between the sampled values ​​and the expected values ​​may represent the amount of image blur in the printed image. As another example, the technique for measuring blur disclosed in U.S. Patent Application No. 16 / 818,847, filed March 13, 2020, may be used to determine the amount of edge blur. Any other known image analysis technique may be used to detect blur in an image.

[0104] Block 903 includes adjusting trigger locations associated with the valves based on the determined amount of edge blur. For example, the amount of edge blur may be used as feedback in a control loop, such as a PID control loop, with the trigger location being the control variable. Each valve may have multiple associated trigger locations that need to be set, such as an upstream trigger location and a downstream trigger location, as described above. In some embodiments, some valves may have additional trigger locations, such as multiple different downstream trigger locations. It should be understood that each trigger location corresponds to one or more actuation timings for the valve, as the timing at which the valve is actuated corresponds to the timing at which a portion of the inter-media zone (i.e., the leading edge or trailing edge of the print media defining the inter-media zone) reaches various trigger locations. A given trigger location may be associated with both opening and closing timings for the same valve. For example, a given valve may be opened when the downstream edge of the inter-media zone reaches a given trigger location, and the valve may be closed when the upstream edge of the inter-media zone reaches the same given trigger location. Different valves may have different trigger locations, and different types of actions (eg, opening or closing the valve) may occur based on those trigger locations.

[0105] The trigger locations for all valves may be determined by repeating process 900 multiple times, with one or more trigger locations of one or more valves changing with each iteration. In some examples, the trigger locations of similarly positioned valves may be set based on the learned trigger location of a given valve, thereby avoiding the need to repeat process 900 for each valve in a group of similarly positioned valves. For example, valves aligned in the cross-process direction with one another may all have the same trigger location, so the trigger location(s) of only one of these valves need to be learned, and the others may be set accordingly. As another example, in some embodiments, all upstream valves may have the same relative trigger location. For example, if the downstream trigger location of a given upstream valve is determined to be X mm downstream of the downstream face of the corresponding print head, then the downstream trigger locations of all upstream valves may be set to X mm downstream of the downstream face of their corresponding print head. As another example, the trigger locations of the valves of a first printhead module may be determined by running process 900 one or more times, and then the valves of other printhead modules may be set based on the trigger locations of the respective valves of the first printhead module in the same relative location.

[0106] Although the process 900 is described above in relation to varying the trigger location to learn the value of the trigger location, because the trigger location and the actuation timing are intrinsically linked, the same process 900 can equivalently be described as varying the actuation timing to learn the value of the actuation timing.

[0107] The specification and accompanying drawings illustrating aspects and embodiments of the present invention should not be construed as limiting, but rather define the invention protected by the claims. Various mechanical, compositional, structural, electrical, and operational changes can be made without departing from the spirit and scope of the specification and claims. In some instances, well-known circuits, structures, and techniques have not been shown or described in detail so as not to obscure the invention. Like numbers in two or more figures represent the same or similar elements.

[0108] As used herein, a valve "blocking" a gap between the rim of an opening and the side of a print head refers to positioning the valve relative to the gap so that it substantially covers or spans the gap and is sufficiently close to the carrier plate and print head to prevent airflow through the gap. In this context, a valve "preventing" airflow through the gap means that the valve creates a relatively high impedance state through the gap such that airflow through the gap is significantly reduced compared to a fully open state (e.g., impedance is increased 10 times that of the open state and / or airflow is reduced to about 10% of the open state). In this manner, blocking a gap and preventing airflow does not necessarily require a hermetic seal or strict elimination of all airflow.

[0109] Furthermore, the terms used herein to describe aspects of the present invention, such as spatial and relational terms, have been selected to assist the reader in understanding embodiments of the present invention, but are not intended to limit the present invention. For example, spatial terms such as “upstream,” “downstream,” “below,” “below,” “lower,” “above,” “top,” “inside,” “outside,” “above,” and “below” may be used herein to describe the orientation or spatial relationship of one element or feature to another element or feature, as shown in the figures. These spatial terms are used relative to the pose shown in the figures and are not limited to a particular frame of reference in the real world. Thus, for example, the direction “up” in a figure does not necessarily correspond to “up” in the world frame of reference (e.g., a direction away from the Earth's surface). Furthermore, when a frame of reference different from that shown in the figures is considered, the spatial terms used herein may need to be interpreted differently in that different frame of reference. For example, a direction referred to as “up” with respect to one of the figures may correspond to a direction referred to as “down” with respect to a different frame of reference that is rotated 180 degrees from the frame of reference of the figure. As another example, if a device is flipped 180 degrees in the world frame of reference, as compared to how it appears in a figure, an item described herein as being "above" or "on" a second item associated with the figure would then be "below" or "below" the second item with respect to the world frame of reference. Thus, the same spatial relationship or orientation may be described using different spatial terms, depending on which frame of reference is being considered. Furthermore, the poses of the items shown in the figures have been selected for convenience of illustration and description, but in actual implementations, the poses of the items may differ.

[0110] The term "process direction" refers to a direction parallel to and oriented in the same direction as the axis along which the print media moves as it is transported through the deposition area of ​​the ink deposition assembly. Thus, the process direction is parallel to and oriented along the positive y-axis in the figures.

[0111] The term "cross-process direction" refers to a direction perpendicular to the process direction and parallel to the movable support surface. At any given point, there are two cross-process directions oriented in opposite directions: an "inner" cross-process direction and an "outer" cross-process direction. Thus, considering the reference frame shown in the figures, a cross-process direction is any direction parallel to the x-axis, including directions oriented in either the positive or negative direction along the x-axis. References to the "cross-process direction" herein should be understood to generally refer to any cross-process direction, rather than one specific cross-process direction, unless the context dictates otherwise. Thus, for example, the statement "the valve is movable in the cross-process direction" means that the valve can move in the inward direction, the outward direction, or both.

[0112] The terms "upstream" and "downstream" may refer to a direction parallel to the process direction, with "downstream" referring to a direction oriented in the same direction as the process direction (i.e., the direction in which the print media is transported through the ink deposition assembly), and "upstream" referring to a direction oriented opposite the process direction. In the figures, "upstream" corresponds to the negative y-axis direction, and "downstream" corresponds to the positive y-axis direction. The terms "upstream" and "downstream" may also be used to refer to the relative location of elements, with an "upstream" element being displaced upstream relative to a reference point, and a "downstream" element being displaced downstream relative to a reference point. In other words, an "upstream" element is closer to the beginning of the path the print media takes as it is transported through the ink deposition assembly (e.g., where the print media contacts the movable support surface) than another reference element. Conversely, a "downstream" element is closer to the end of that path (e.g., where the print media leaves the support surface) than another reference element. The reference point of another element to which an "upstream" or "downstream" element is compared may be explicitly stated (e.g., "upstream of the print head") or may be inferred from the context.

[0113] The terms "inner" and "outer" refer to the cross-process direction, with "inner" referring to a direction toward the cross-process direction and "outer" referring to a direction opposite the cross-process direction of "inner." In the figures, "inner" corresponds to the positive x-axis direction and "outer" corresponds to the negative x-axis direction. The terms "inner" and "outer" also refer to relative locations, with "inner" elements displaced inward relative to a reference point and "outer" elements displaced outward relative to a reference point. The reference point may be explicitly stated (e.g., "the inner side of the print head") or may be inferred from the context.

[0114] The term "vertical" refers to a direction perpendicular to the movable support surface within the deposition region. At any given point, there are two vertical directions oriented in opposite directions: an "upward" direction and a "downward" direction. Thus, considering the reference frame shown in the figure, a vertical direction is any direction parallel to the z-axis, including directions oriented in the positive z-axis direction ("up") or the negative z-axis direction ("down").

[0115] The term "horizontal" refers to a direction parallel to (or tangent to) a movable support surface in the deposition zone if the movable support surface is not flat in the deposition zone. Horizontal directions include the process direction and the cross-process direction.

[0116] The term "vacuum" has different meanings in different contexts, ranging from the strict meaning of a space completely devoid of matter to the more general meaning of a relatively low pressure state. In this specification, the term "vacuum" is used in a general sense and should be understood to broadly refer to a state or environment in which the air pressure is lower than a reference pressure, such as ambient or atmospheric pressure. The amount by which the pressure of a vacuum environment must be lower than the reference pressure to be considered a "vacuum" is not limited and may be a small or large amount. Thus, as used herein, "vacuum" includes, but is not limited to, states that may be considered a "vacuum" in the stricter sense of the term.

[0117] The term "air" has different meanings in different contexts, ranging from the strict meaning of the Earth's atmosphere (or a mixture of gases whose composition is similar to that of the Earth's atmosphere) to the more general meaning of any gas or mixture of gases. As used herein, the term "air" is used in a general sense and should be understood to refer broadly to any gas or mixture of gases. This may include, but is not limited to, the Earth's atmosphere, an inert gas such as one of the noble gases (e.g., helium, neon, argon, etc.), nitrogen (N2) gas, or any other desired gas or mixture of gases.

[0118] Additionally, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context dictates otherwise. Furthermore, terms such as "comprises," "comprising," and "includes" specify the presence of stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups. Unless specifically stated otherwise, components described as being coupled may be directly coupled electrically or mechanically, or indirectly coupled through one or more intermediate components. Mathematical and geometric terms are not necessarily intended to be used according to their strict definitions unless the context dictates otherwise, because, for example, those skilled in the art will understand that even if a term also has a strict definition, substantially similar elements that function in a substantially similar manner may readily fall within the scope of the descriptive term.

[0119] Elements and their associated aspects described in detail with reference to one embodiment may, whenever practical, be included in other embodiments in which they are not specifically shown or described. For example, if an element is described in detail with reference to one embodiment but not with reference to a second embodiment, the element may nevertheless be claimed as being included in the second embodiment.

Claims

1. 1. A printing system comprising: an ink deposition assembly including a carrier plate and a print head positioned to eject printing fluid through a print head opening in the carrier plate onto a deposition area of ​​the ink deposition assembly; a media transport device including a movable support surface, the media transport device configured to hold a print medium against the movable support surface by vacuum suction through holes in the media transport device and transport the print medium through the deposition area along a process direction; 1. An airflow control system comprising: an upstream valve disposed upstream of the print head and a downstream valve disposed downstream of the print head, wherein upstream and downstream are defined based on the process direction; each of the upstream valve and the downstream valve is movable between an open state and a closed state; the upstream valve is configured to extend along and block airflow through an upstream gap defined between the print head and a rim of the print head opening in the closed state, and to allow airflow through the upstream gap in the open state; an airflow control system configured such that, in the closed state, the downstream valve extends along and blocks airflow through a downstream gap defined between the print head and the rim of the print head opening, and, in the open state, allows airflow through the downstream gap; the upstream valve and the downstream valve are independently transitionable between the open state and the closed state based on a position of an inter-media zone between adjacent print media held against the movable support surface; a first actuator configured to actuate the upstream valve between the open state and the closed state; a second actuator configured to actuate the downstream valve between the open and closed conditions; a controller configured to cause the first actuator and the second actuator to selectively actuate the upstream valve and the downstream valve between the open state and the closed state based on a position of an inter-media zone between adjacent print media held relative to the movable support surface; The controller is configured to dynamically determine trigger locations for actuating each of the upstream and downstream valves by sensing an amount of image blur in a printed image, and to adjust the trigger locations based on the sensed amount of image blur.

2. The controller controls the first actuator and the second actuator to actuating the upstream valve to the open state when the intermedia zone reaches a first position; actuating the upstream valve to the closed state when the intermedia zone reaches a second position; actuating the downstream valve to the open state when the intermedia zone reaches a third position; The printing system of claim 1 , configured to actuate the downstream valve to the closed state when the inter-media zone reaches a fourth position.

3. The printing system of claim 2 , wherein the fourth location is downstream of the third location, and the third location and the second location are downstream of the first location.

4. The printing system of claim 3 , wherein the second location and the third location are the same location.

5. The printing system of claim 1 , wherein the upstream valve and the downstream valve comprise threshold valves.

6. 6. The printing system of claim 5, wherein vacuum suction from the inter-media zone individually actuates each of the upstream and downstream valves to the open state when the inter-media zone is beneath each of the valves.

7. The printing system of claim 6 , wherein each of the upstream valve and the downstream valve is in the closed state when the inter-media zone is not under the respective valve.

8. 2. The printing system of claim 1, wherein each of the upstream valve and the downstream valve extends along a cross-process direction perpendicular to the process direction and rotates about a rotation axis parallel to the cross-process direction while being actuated between the open state and the closed state.

9. the media transport device includes a vacuum platen, the aperture extending through the vacuum platen; The printing system of claim 1 , wherein the movable support surface comprises a belt configured to move over a surface of the vacuum platen.

10. the airflow control system includes a plurality of channels individually transitionable between an on state and an off state, each of the channels associated with at least one row of the holes extending in the process direction; In the on state, each channel applies vacuum suction to the at least one row of holes; The printing system of claim 1 , wherein in the off state, each channel does not provide vacuum suction to the at least one row of holes.

11. the airflow control system further includes a plurality of channel valves respectively connecting the channels to a vacuum plenum; 11. The printing system of claim 10, wherein each of the channel valves is individually actuatable between an open state and a closed state to place the corresponding channel in the on state and the off state, respectively.

12. The printing system of claim 10 , further comprising a controller configured to selectively place individual ones of the channels in the on and off states based on a size of the print medium.

13. 1. A printing system comprising: an ink deposition assembly including a carrier plate and a print head positioned to eject printing fluid through a print head opening in the carrier plate onto a deposition area of ​​the ink deposition assembly; a media transport device including a movable support surface, the media transport device configured to hold a print medium against the movable support surface by vacuum suction transmitted from a vacuum plenum on a first side of the movable support surface to the print medium on a second side of the movable support surface through holes in the media transport device, the holes being arranged in rows extending in the process direction; and an airflow control system including a plurality of channels individually transitionable between an on state and an off state, each of the channels disposed on the first side of the movable support surface and associated with at least one row of holes, the airflow control system configured to control transfer of vacuum suction from the vacuum plenum to the associated at least one row of holes; a controller configured to selectively place individual ones of the channels in the on and off states based on a size of the print medium; each channel, in the on state, supplies vacuum suction from the vacuum plenum to the at least one row of holes; each channel, in the off state, does not apply vacuum to the at least one row of holes; the airflow control system further includes a plurality of valves respectively connecting the channels to the vacuum plenum; each of the valves is individually actuatable between an open state and a closed state to place the corresponding channel in the on state and the off state, respectively; the controller is configured to dynamically determine respective trigger locations for actuating each of the plurality of valves by sensing an amount of image blur within a printed image, and to adjust each trigger location based on the sensed amount of image blur. Printing system.

14. 1. A printing system comprising: an ink deposition assembly including a carrier plate and a print head positioned to eject printing fluid through a print head opening in the carrier plate onto a deposition area of ​​the ink deposition assembly; a media transport device including a movable support surface, the media transport device configured to hold a print medium against the movable support surface by vacuum suction through holes in the media transport device and transport the print medium through the deposition area along a process direction, the holes being arranged in rows extending in the process direction; 1. An airflow control system comprising: an upstream valve disposed upstream of the print head and a downstream valve disposed downstream of the print head, upstream and downstream valves, wherein upstream and downstream are defined based on the process direction, and each of the upstream and downstream valves is movable between an open state and a closed state; an airflow control system including: a plurality of channels individually transitionable between an on state and an off state, each of the channels associated with at least one row of the holes extending in the process direction; the upstream valve is configured to extend along and block airflow through an upstream gap defined between the print head and a rim of the print head opening in the closed state, and to allow airflow through the upstream gap in the open state; the downstream valve is configured to extend along and block airflow through a downstream gap defined between the print head and the rim of the print head opening in the closed state, and to allow airflow through the downstream gap in the open state; each channel, in the on state, applies vacuum to the associated row of holes; each channel, in the off state, does not apply vacuum to the associated row of holes; a controller, selectively placing individual ones of the channels in the on and off states based on the size of the print medium; individually actuating the valves between the open and closed states based on a position of an inter-media zone between adjacent print media held against the movable support surface; The printing system further comprises a controller configured to dynamically determine respective trigger locations for actuating each of the upstream and downstream valves by sensing an amount of image blur in a printed image, and to adjust each trigger location based on the sensed amount of image blur.

15. 1. A method comprising: transporting a print medium along a process direction through a deposition area of ​​a print head of a printing system, wherein the print medium is held against a movable support surface of a media transport device during the transport via vacuum suction through holes in the media transport device, the vacuum suction being transmitted from a vacuum source to the holes via a vacuum plenum, the holes being arranged in a row extending in the process direction; ejecting a printing fluid from the print head through a print head opening in a carrier plate to deposit the printing fluid onto the print medium in the deposition area; controlling an airflow control system to selectively block airflow through upstream and downstream sides of the print head opening by selectively actuating upstream and downstream valves between open and closed states, wherein upstream and downstream are defined based on the process direction; the upstream valve, in the closed state, blocks airflow through the upstream side of the print head opening, and, in the open state, allows airflow through the upstream side of the print head opening; the downstream valve, in the closed state, blocks airflow through a downstream side of the print head opening, and, in the open state, allows airflow through the downstream side of the print head opening; controlling the airflow control system to selectively turn on and off individual channels of a plurality of channels; each of the channels is associated with at least one row of the holes extending in the process direction; each channel, in the on state, applies vacuum to the associated row of holes; each channel, in the off state, does not apply vacuum to the associated row of holes; Including, selectively actuating the upstream valve and the downstream valve between the open state and the closed state includes selectively actuating the valves based on a position of an inter-media zone between adjacent print media held against the movable support surface; Selectively turning on and off individual channels of the plurality of channels includes selectively turning on and off individual channels of the channels based on a size of the print medium; The method further includes dynamically determining respective trigger locations for actuating each of the upstream and downstream valves by sensing an amount of image blur in a printed image, and adjusting each trigger location based on the sensed amount of image blur.

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