Printing system with dampers to vary vacuum suction through vacuum plenum and related devices, systems and methods

Abstract

To provide devices capable of transporting print media with proper suction.SOLUTION: A printing system 100 comprises one or more print heads arranged to eject ink to a deposition region. Print media are held by vacuum suction in contact with a movable support surface, which transports the print media though the deposition region. The vacuum suction is communicated from a vacuum source to the movable support surface via a vacuum plenum. An airflow control system comprises one or more dampers arranged in the vacuum plenum to control the airflow between the vacuum source and the movable support surface. The dampers have an adjustable impedance to the airflow through the damper. The airflow control system is configured to adjust the impedance of the damper based on a detected condition of the printing system. A detected condition of the printing system may include, for example, a sensed pressure in the vacuum plenum.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] Aspects of the present disclosure generally relate to inkjet printing, and more specifically, to an inkjet printing system having a media transport device that utilizes vacuum suction to hold and transport a printing media. Related devices, systems, and methods are also disclosed.

Background Art

[0002] In some applications, an inkjet printing system uses an ink deposition assembly having one or more print heads, and a medium transport device for moving a printing medium (e.g., multiple sheets of paper, envelopes, or other substrates suitable for printing with ink) through the ink deposition area of ​​the ink deposition assembly (e.g., the area below the print heads). The inkjet printing system forms a printed image on the printing medium by ejecting ink from the print heads onto the medium as the medium passes through the deposition area. In some inkjet printing systems, the medium transport device utilizes vacuum suction to help hold the printing medium in contact with a movable support surface of the transport device (e.g., a conveyor belt, a rotating drum, etc.). Vacuum suction for holding the printing medium in contact with the support surface can be achieved using a vacuum source (e.g., a fan) and a vacuum plenum, which is fluidly coupled to the side of the moving surface opposite to the side supporting the printing medium. The vacuum source creates a vacuum state within the vacuum plenum, causing vacuum suction through holes in the movable support surface fluidly coupled to the vacuum plenum. When a printing medium is introduced onto a movable support surface, vacuum suction generates a suction force that holds the printing medium in contact with the support surface. A medium transport device utilizing vacuum suction allows the printing medium to be reliably held in place without slippage as it is transported through the ink deposition region beneath the ink deposition assembly, thereby helping to ensure precise positioning of the printing medium relative to the print head, and thus more accurate printed images. Vacuum suction can also allow the printing medium to be held flat as it passes through the ink deposition region, which can also help increase the accuracy of the printed image and prevent any portion of the printing medium from rising and hitting any part of the ink deposition assembly, potentially causing clogging or damage.

[0003] One problem that can occur in inkjet printing systems, including media transport devices that utilize vacuum suction, is unintended smudging of the image caused by the airflow induced by the vacuum suction. In some systems, such smudging can occur in portions of the printed image, particularly near the edges of the printing medium. This smudging can result from uncovered holes in the media transport device adjacent to one or more of the edges of the printing medium. In particular, during a printing job, the printing media are separated from each other on movable support surfaces as they are transported through the deposition area of ​​the ink deposition assembly, and therefore portions of the movable support surface between adjacent printing media are not covered by any of the printing media. This region between adjacent printing media is referred to herein as the inter-media zone. Thus, uncovered holes exist on the movable support surface adjacent to both the leading and trailing edges of each printing medium within the inter-media zone. Furthermore, the holes for vacuum suction are generally positioned to extend across approximately the entire width of the deposition area in the cross-process direction (i.e., perpendicular to the direction of transport of the printing medium through the deposition area), so that the holes can accommodate any size of printing medium for which the system is designed to be used, from the smallest to the largest size. However, if the printing medium currently being printed is smaller than the maximum size, the holes do not need to extend sufficiently in the cross-process direction to cover all holes along the inboard or outboard edges of the printing medium (depending on which side of the printing medium is registered). Therefore, holes adjacent to the inboard or outboard edges of the printing medium also do not need to be covered. Because these holes near the front edge, rear edge, inboard edge, and / or outboard edge are uncovered, the vacuum of the vacuum plenum guides air to flow through these uncovered holes. This airflow can deflect ink droplets as they travel from the print head to the substrate, thus causing image smudging near their edges.

[0004] There is a need to improve the precision of droplet placement in inkjet printing systems and reduce smudging in the appearance of the final printed media product. Furthermore, there is a need to address the smudging problem in a reliable manner while maintaining printing and transport speeds to provide efficient inkjet printing systems. [Overview of the project]

[0005] Embodiments of this disclosure may solve one or more of the problems described above and / or demonstrate one or more of the desirable features described above. Other features and / or advantages may become apparent from the following description.

[0006] According to at least one embodiment of the present disclosure, the printing system comprises an ink deposition assembly, a medium transport device, and an airflow control system. The ink deposition assembly comprises one or more print heads arranged to eject ink into the deposition area of ​​the ink deposition assembly. The medium transport device comprises a vacuum source, a vacuum plenum, and a movable support surface. The medium transport device is configured to hold a printing medium in contact with the movable support surface by vacuum suction through a hole in the movable support surface and to transport the printing medium along the process direction through the deposition area. The vacuum suction is communicated from the vacuum source to the hole via the vacuum plenum. The airflow control system comprises one or more dampers located within the vacuum plenum. The dampers have an adjustable impedance to the airflow through the damper between the vacuum source and the hole. The airflow control system is configured to adjust the impedance of the dampers based on the detected state of the printing system.

[0007] According to at least one embodiment of the present disclosure, the method includes transporting one or more printing media through a deposition area of ​​a print head of a printing system, and injecting a printing fluid from the print head to deposit ink onto the printing media in the deposition area. The printing media are held in contact with a movable support surface of the media transport device via vacuum suction through a hole in the media transport device, the vacuum suction communicating from a vacuum source to the hole via a vacuum plenum. The method further includes controlling an airflow control system to dynamically adjust the impedance of a damper located in the vacuum plenum based on a detected state of the printing system. The impedance of the damper controls the airflow between the vacuum source and the hole. [Brief explanation of the drawing]

[0008] This disclosure can be understood from the following detailed description, either alone or together with the accompanying drawings. The drawings are included to provide a further understanding of this disclosure, are incorporated herein, and constitute part of this specification. The drawings illustrate one or more embodiments of this teaching and, together with the description, illustrate specific principles and operations. In the drawings,

[0009] [Figure 1A] This paper schematically illustrates the airflow patterns on the print head assembly, transport devices, and print media during different stages of media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting streaking effects on the printed media product. [Figure 1B] This paper schematically illustrates the airflow patterns on the print head assembly, transport devices, and print media during different stages of media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting streaking effects on the printed media product. [Figure 1C] This paper schematically illustrates the airflow patterns on the print head assembly, transport devices, and print media during different stages of media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting streaking effects on the printed media product. [Figure 1D] This paper schematically illustrates the airflow patterns on the print head assembly, transport devices, and print media during different stages of media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting streaking effects on the printed media product. [Figure 1E] This paper schematically illustrates the airflow patterns on the print head assembly, transport devices, and print media during different stages of media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting streaking effects on the printed media product. [Figure 1F] This paper schematically illustrates the airflow patterns on the print head assembly, transport devices, and print media during different stages of media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting streaking effects on the printed media product. [Figure 1G] This paper schematically illustrates the airflow patterns on the print head assembly, transport devices, and print media during different stages of media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting streaking effects on the printed media product. [Figure 1H] This paper schematically illustrates the airflow patterns on the print head assembly, transport devices, and print media during different stages of media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting streaking effects on the printed media product. [Figure 1I] This paper schematically illustrates the airflow patterns on the print head assembly, transport devices, and print media during different stages of media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting streaking effects on the printed media product. [Figure 1J] This paper schematically illustrates the airflow patterns on the print head assembly, transport devices, and print media during different stages of media transport through the ink deposition area of ​​a conventional inkjet printing system, and the resulting streaking effects on the printed media product. [Figure 1K] Schematically illustrate the airflow patterns with respect to the printhead assembly, transport device, and print media, and the resulting blurring effect in the print media product, between different stages of print media transport through the ink deposition area of a conventional inkjet printing system. [Figure 1L] Schematically illustrate the airflow patterns with respect to the printhead assembly, transport device, and print media, and the resulting blurring effect in the print media product, between different stages of print media transport through the ink deposition area of a conventional inkjet printing system.

[0010] [Figure 2] It is a block diagram illustrating the components of an embodiment of an inkjet printing system including an airflow control system.

[0011] [Figure 3] [[ID=第十六]]It is a schematic illustration diagram of the components of an embodiment of an inkjet printing system.

[0012] [Figure 4A] It is a plan view of an embodiment of a damper. [Figure 4B] It is a plan view of an embodiment of a damper.

[0013] [Figure 5A] It is a plan view of an embodiment of a damper. [Figure 5B] It is a plan view of an embodiment of a damper.

[0014] [Figure 6A] It is a plan view of an embodiment of a damper. [Figure 6B] It is a plan view of an embodiment of a damper.

[0015] [Figure 7A] It is a plan view of an embodiment of a damper. [Figure 7B] It is a plan view of an embodiment of a damper. [Modes for carrying out the invention]

[0016] In the drawings and descriptions herein, numerical indices such as "_1" and "_2" are appended to the end of the reference numbers of some components. When there are multiple similar components and it is desirable to represent a specific one of them, the same base reference number is used, and a different indice is appended to it to distinguish the individual components. However, when components are referred to generally or collectively without the need to distinguish specific ones, the indice may be omitted from the base reference number. For example, when it is desired to identify a specific one of the print media 5, as shown in Figure 1A, print media 5 may be labeled and referred to as the first print media 5_1, but in other cases where it is not desired to distinguish between multiple print media 5, it may simply be labeled and referred to as print media 5.

[0017] As described above, when the intermediary zone is near or below the print head, uncovered holes within the intermediary zone can form transverse flows that can cause satellite droplets to deviate from their course, potentially leading to image streaking. Similarly, uncovered holes along the inboard or outboard side of the printing medium can also form transverse flows that can cause image streaking. To illustrate some of the phenomena that cause streaking in more detail, refer to Figures 1A to 1F. Figures 1A, 1D, 1G, and 1J schematically illustrate the print head 10 printing on the printing medium 5 near the trailing edge TE, leading edge LE, inboard edge, and near the center, respectively. Figures 1A, 1D, and 1J are cross-sections taken through the print head 10 along the process direction (y-axis direction in the figures), while Figure 1G is a cross-section taken through the same print head 10 along a cross-process direction perpendicular to the process direction (x-axis direction in the figures). The example in Figure 1G illustrates an embodiment having three print heads in series along the x-direction, with one canceling out the other two. Figures 1B, 1E, 1H, and 1K illustrate enlarged views of areas A, B, C, and D in Figures 1A, AD, 1B, and 1J, respectively. Figures 1C, 1F, 1I, and 1L illustrate enlarged photographs of a printed image, which includes lines printed on the trailing edge TE, leading edge LE, inboard edge, and near the center of the paper sheet.

[0018] As shown in Figures 1A, 1D, 1G, and 1J, the inkjet printing system comprises one or more print heads 10 for ejecting ink onto a printing medium 5 through print head openings 19 in a carrier plate 11. The inkjet printing system also comprises a movable support surface 20 for transporting the printing medium 5 in the process direction P, corresponding to the positive y-axis direction in the figures. The movable support surface 20 slides along the top of a vacuum platen 26, and a vacuum environment is provided on the bottom side of the platen 26. The movable support surface 20 has holes 21, and the vacuum platen 26 has platen holes 27. The holes 21 and 27 periodically align as the movable support surface 20 moves, thereby exposing the area above the movable support surface 20 to the vacuum below the platen 26. In areas where the printing medium 5 covers the holes 21, the vacuum suction through the aligned holes 21 and 27 generates a force that holds the printing medium 5 in contact with the movable support surface 20. However, little to no air is drawn into these covered holes 21 and 27 because they are shielded from the environment above the movable support surface 20 by the printing medium 5. On the other hand, as shown in Figures 1A, 1D, and 1G, the holes 21 and 27 are not covered by the printing medium 5 in the inter-medium zone 22 (see Figures 1A and 1D) and the uncovered area 24 near the inboard side IB of the platen 26 (see Figure 1G), and therefore vacuum suction draws air from above the movable support surface 20 so that it flows down through these holes 21 and 27. This generates an airflow indicated by the dashed arrows in Figures 1A, 1D, and 1G, which flows from the area around the print head 10 toward the uncovered holes 21 and 27 in the inter-medium zone 22 and the uncovered area 24, with some of the airflow passing beneath the print head 10.

[0019] In Figure 1A, the printing medium 5_1 is printed near its rear edge TE, and therefore the area where ink is currently being ejected ("ink ejection area") (e.g., area A in Figure 1A) is located downstream of the intermediary zone 22 (upstream and downstream are defined with respect to the process direction P). Thus, some of the air being drawn towards the intermediary zone 22 flows upstream through the ink ejection area below the print head 10. More specifically, the vacuum suction from the intermediary zone 22 reduces the pressure in the area immediately above the intermediary zone 22, e.g., area R1 in Figure 1A, while the area downstream of the print head 10, e.g., area R2 in Figure 1A, remains at a higher pressure. This pressure gradient causes the air to flow upstream from area R2 to area R1, with the airflow traversing through a portion of the ink ejection area (e.g., area A in Figure 1A) located between areas R1 and R2. Such airflows that cross the ink ejection area are referred to herein as transverse flows 15. In Figure 1A, the transverse flows 15 flow upstream, but in other situations, the transverse flows 15 may flow in different directions.

[0020] As shown in Figure 1B, enlarged view A', which includes an enlarged view of region A in Figure 1A, when ink is ejected from the print head 10 toward the medium 5, a main droplet 12 and satellite droplets 13 are formed. The satellite droplets 13 are much smaller than the main droplets 12 and have less mass and momentum, and therefore the upstream transverse flow 15 tends to affect the satellite droplets 13 more than the main droplets 12. Thus, the main droplets 12 may land on the printing medium 5 near their intended deposition site 16 regardless of the transverse flow 15, but the transverse flow 15 may push the satellite droplets 13 away from their intended trajectory, resulting in the satellite droplets landing at an unintended location 17 on the medium 5, which is displaced from the intended location 16. The consequences of such transverse flow and the resulting misplaced droplets can be seen in the actual printed image in Figure 1C, where areas 16' of denser print dots corresponding to the intended print lines are formed by droplets (e.g., generally main droplets 12), which are mainly deposited in their intended locations, while areas 17' of sparser dots dispersed away from the lines are formed by droplets (e.g., generally satellite droplets 13), which are sprayed away from their intended locations and land in unintended locations. The resulting image has a smudged or smudged appearance relative to the print lines. In particular, the smudging in Figure 1C is asymmetrically biased towards the trailing edge TE, which is likely an expected consequence of transverse flow 15 near the trailing edge TE, which is mainly sprayed upstream. The intermediate zone 22 may also induce other airflows flowing in other directions, such as downstream airflow from the upstream side of the print head 10, but these other airflows do not pass through the areas where the ink is being sprayed in the scenario currently illustrated and therefore do not contribute to image smudging. Only these airflows that cross the ink ejection area are referred to as transverse flows in this specification.

[0021] Figures 1D to 1F schematically illustrate another situation in which such streaking occurs, this time near the leading edge LE of the printing medium 5_2. The cause of streaking near the leading edge LE is the same as that described above in relation to the trailing edge TE, except that when printing near the leading edge LE, the ink ejection area is located upstream of the inter-medium zone 22. As a result, the transverse flow 15 across the ink ejection area originates from the upstream side of the print head 10, for example from area R3, and flows downstream to area R4. Therefore, when printing near the leading edge LE of the printing medium 5_2, as shown in enlarged view B' of Figure 1E, including an enlarged view of area B in Figure 1D, the satellite droplets 13 tend to be ejected downstream (in the positive Y-axis direction) toward the leading edge LE of the printing medium 5_2 and land at unintended locations 17, while the main droplets 12 tend to land at or near the intended locations 16. As shown in Figure 1F, this effect results in asymmetrical blurring biased toward the leading edge LE of the print medium (i.e., the denser regions 16' of print dots corresponding to the line are formed by the sparser regions 17' of print dots that are dragged away from the line toward the leading edge LE).

[0022] Figures 1G to 1I illustrate yet another situation in which such streaking can occur, this time near the inboard edge IE of the printing medium 5, due to uncovered holes 21 and 27 in that region. The cause of streaking near the inboard edge IE is the same as that described above in relation to the trailing edge TE and leading edge LE, except that when printing near the inboard edge IE, the ink ejection area is located outboard, in the uncovered areas 24 of holes 21 and 27 in the movable support surface 20 and platen 26. As a result, the transverse flow 15 across the ink ejection area originates here from the outboard side of the print head 10, for example, from region R5, and flows in the inboard direction toward region R6. Therefore, when printing near the inboard edge IE, as shown in enlarged view C' of Figure 1H, including an enlarged view of region C in Figure 1G, the satellite droplets 13 are sprayed inboard (in the positive y-axis direction) toward the inboard edge IE of the printing medium 5, landing in unintended locations 17 rather than the intended locations 16 where the main droplets 12 land. As shown in Figure 1I, such transverse flow patterns are expected to result in asymmetrical streaking biased toward the inboard edge IE (i.e., denser areas 16' of printed dots corresponding to lines are formed by sparser areas 17' of printed dots dragging away from lines toward the inboard edge IE). In this example, the printing medium is registered to one side of the printing system (i.e., the outboard side), and therefore, it is assumed that the image streaking will appear on the inboard edge IE. However, in some systems, the printing medium can be centered on a movable support surface, in which case uncovered holes (and therefore streaks) may appear on both sides of the printing medium.

[0023] In contrast, as shown in Figure 1K, enlarged view D', which corresponds to Figure 1J and the enlarged view of region D in Figure 1J, when the print is further away from the edge (rear, front, or inboard) of the printing medium 105, the inter-medium zone 22 and the uncovered region 24 are too far apart to induce much airflow, so the transverse flow 15 is little to no. Since the transverse flow 15 is further away from the edge of the printing medium 5, and is absent or weak, satellite droplets 13 in this region are less likely to be sprayed off course. Therefore, as shown in Figures 1K and 1L, when the print is further away from the edge of the printing medium 5, satellite droplets land at the intended location 16 or at a location 18 that is quite close to the intended location 16, resulting in less image smudging. The deposition location 18 of the satellite droplet may still deviate somewhat from the intended location 16 due to other factors affecting the satellite droplet 13, but the deviation is smaller than that near the leading or trailing edge. Figure 1L illustrates an image obtained as a result of a situation like those in Figures 1J and 1K, showing printed lines representing droplets landing at the intended location 16', with some droplets landing at location 18', sufficiently close to the intended location 16'. The resulting image does not show any significantly noticeable blurring or smudges of the lines.

[0024] Embodiments disclosed herein can reduce or eliminate image blurring, in particular, by utilizing an airflow control system that reduces or eliminates transverse flow. With transverse flow reduced or eliminated, satellite droplets are more likely to land near or at their intended deposition sites, thus reducing the amount of blurring. Airflow control systems according to various embodiments reduce or eliminate transverse flow by dynamically adjusting the vacuum suction through the vacuum plenum in real time based on the current state. In particular, one or more dampers are provided in the vacuum plenum between the vacuum source and the vacuum platen, and the dampers have openings of adjustable size to provide a larger or smaller airflow impedance between the vacuum source and the vacuum platen. By increasing the impedance of the damper (i.e., making the opening smaller), the rate at which air is drawn from the vacuum plenum to the vacuum source is reduced, thus resulting in an increase in pressure within the vacuum plenum. Conversely, by decreasing the impedance of the damper (i.e., making the opening larger), the rate at which air flows out of the vacuum plenum is increased, thus reducing the pressure within the vacuum plenum. An airflow control system can dynamically adjust the damper impedance (i.e., opening size) to obtain the optimal or desired pressure in the vacuum plenum based on the monitoring status of the printing system. For example, the airflow control system may include a pressure monitor positioned in the vacuum plenum, which can adjust the impedance based on the measured pressure in the vacuum plenum to achieve a desired target pressure.

[0025] Controlling the pressure within the vacuum plenum in this manner can help reduce transverse flow while ensuring that an appropriate pressing force is applied to the printing medium. The lower the pressure within the vacuum plenum, the stronger the vacuum suction through the holes in the movable support surface. Therefore, a relatively low pressure within the vacuum plenum results in a relatively strong transverse flow drawn through the uncoated holes, but also a relatively strong pressing force applied to the printing medium. Conversely, a relatively high pressure within the vacuum plenum results in a relatively weak transverse flow through the uncoated holes, but also a relatively weak pressing force. Therefore, the intensity of the pressing force and the intensity of the transverse flow change in a generally inverse manner to the pressure within the vacuum plenum. Thus, in some embodiments, the pressure inside the vacuum plenum is controlled to a level just sufficient to provide an appropriate pressing force, or near it, but not lower, in order to reduce the intensity of the transverse flow as much as possible while ensuring an appropriate pressing force. By controlling the pressure within the vacuum plenum to remain at or near this pressure, the lack of restraint that could otherwise occur when allowing strong transverse flow and pressure changes can be avoided.

[0026] One difficulty with conventional printing systems can be providing and maintaining optimal pressure within the vacuum plenum, such as the pressure described above. Given the fixed strength of suction from the vacuum source, the pressure within the vacuum plenum does not necessarily remain constant throughout a printing job or from one printing job to the next. The pressure within the vacuum plenum depends not only on the strength of suction from the vacuum source but also on the airflow impedance through the movable support surface, which varies depending on the current conditions. In particular, the impedance through the movable support surface varies depending on how many holes are covered by the printing medium. The more holes covered, the greater the impedance through the movable support surface, and therefore, if no countermeasures are taken, the pressure within the vacuum plenum will be lower (i.e., the vacuum suction will be stronger). Conversely, the fewer holes covered, the lower the impedance through the movable support surface, and therefore, if no countermeasures are taken, the pressure within the vacuum plenum will be higher. Therefore, when a relatively small number of holes are covered, such as when the first printing medium is mounted on a movable support surface or when a relatively small printing medium is used, the pressure in the vacuum plenum will be relatively high (i.e., the vacuum suction will be relatively low) (assuming no countermeasures are taken). However, later, when additional printing medium is mounted on the movable support surface and / or the size of the printing medium changes, and more holes are covered, the pressure in the vacuum plenum will be relatively low (i.e., the vacuum suction will be relatively high) (assuming no countermeasures are taken). Thus, if no countermeasures are taken, the pressure inside the vacuum plenum will then tend to fluctuate from time to time, based on the number of holes currently covered by the printing medium.

[0027] Because the pressure inside the vacuum plenum can change from time to time, even though the vacuum source provides a fixed suction strength, in some systems the suction strength of the vacuum source may need to be fixed at a level high enough to ensure proper pressing even in the worst-case scenario (i.e., relatively few holes are covered). However, the suction strength that ensures proper pressing in the worst-case scenario will be higher than the suction required to ensure pressing in other scenarios, such as when more holes are covered by the printing medium. Therefore, to ensure proper pressing under all conditions, the suction strength provided will exceed what is required in some conditions. In such conditions where more suction is provided than necessary, the relatively strong suction will cause relatively strong transverse flow, and thus image blurring.

[0028] The above problems are addressed by embodiments disclosed herein by dynamically adjusting the pressure within the vacuum plenum as a change in state. More specifically, the impedance of the damper can be dynamically adjusted to ensure that a desired pressure is maintained within the vacuum plenum. Because the pressure is adjusted as needed, the strength of the suction provided to the movable support surface can be maintained at a desired level, not too high or too low, in all relevant environments, regardless of the changed state. Thus, embodiments disclosed herein can provide adequate restraint (including in the worst-case scenario) without supplying excessive suction in scenarios requiring less suction. For example, when relatively few holes in the movable support surface are covered, the damper can provide a relatively low impedance (i.e., a larger opening) and thus offset any increase in pressure within the vacuum plenum that may otherwise occur due to many uncovered holes. This ensures that the pressure within the vacuum plenum remains low enough to provide adequate restraint despite many uncovered holes. As more holes in the movable support surface are covered, this tends to decrease the pressure in the vacuum plenum, as described above. However, this decrease in pressure can be sensed, and the damper can be dynamically adjusted to offset the decrease in pressure. Specifically, as more holes are covered, the damper can be controlled to provide a relatively high impedance, which tends to increase the pressure in the plenum, thus offsetting the decrease in pressure caused by the covering of more holes. Therefore, the net effect of adjusting the damper in the manner described above is that the pressure in the vacuum plenum can be maintained at or near the target value, despite the change in the number of holes covered. Thus, rather than providing a higher suction intensity than required in some environments to ensure that sufficient suction is provided in the worst-case scenario, in the embodiments disclosed herein, the desired amount of suction through the holes can be maintained in all environments by controlling the pressure in the vacuum plenum.

[0029] Referring now to Figure 2, an embodiment of the printing system is described in more detail. Figure 2 is a schematic block diagram illustrating a printing system 100 that utilizes the airflow control system described above. The printing system 100 comprises an ink deposition assembly 101 for depositing ink onto a printing medium, a medium transport assembly 103 for transporting the printing medium through the ink deposition assembly 101, and a control system 130 for controlling the operation of the printing system 100. These components of the printing system 100 are described in more detail below. In addition, various components of the printing system 100 are involved in controlling the airflow around the print head, and therefore these components can be collectively referred to as the airflow control system 150, as will be further described below.

[0030] The ink deposition assembly 101 comprises one or more printhead modules 102. For simplicity, one printhead module 102 is illustrated in Figure 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 specific ink color, such as cyan, magenta, yellow, and black. Each printhead module 102 comprises one or more printheads 110 configured to spray a printing fluid, such as ink, onto a printing medium to form an image. In Figure 2, for simplicity, one printhead 110 is illustrated in the printhead module 102, but any number of printheads 110 may be included per printhead module 102. The printhead module 102 may comprise one or more walls, including a bottom wall, which may be referred to herein as a carrier plate. The carrier plate may comprise printhead openings, and the printheads 110 are arranged to spray ink through the printhead openings. In some embodiments, the carrier plate supports the printheads 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, as known in the art, such as ink supply lines, ink reservoirs, and electrical connections, to support the print head 110 and to facilitate the operation of the print head 110.

[0031] As shown in Figure 2, the media transport device 103 comprises a movable support surface 120, a vacuum plenum 125, a vacuum source 128, and one or more dampers 151. The movable support surface 120 transports the printing medium through the deposition area of ​​the printing assembly 101. The vacuum plenum 125 supplies vacuum suction to one side of the movable support surface 120 (e.g., the bottom side), and the printing medium is supported on the opposite side of the movable support surface 120 (e.g., the top side). Holes 121 passing through the movable support surface 120 communicate vacuum suction through the surface 120, and as a result, the vacuum suction presses the printing medium in contact with the surface 120. The movable support surface 120 is movable relative to the printing assembly 101, and therefore, as the movable support surface 120 moves, the printing medium held in contact with the movable support surface 120 is transported relative to the printing assembly 101. Specifically, the movable support surface 120 transports the printing medium through the deposition area of ​​the printing assembly 101, which is an area on the printing medium where the printing fluid (e.g., ink) is sprayed, such as the area below the print head 110. The movable support surface 120 can be driven to move relative to the printing assembly 101 and may comprise any structure having holes 121 that allow vacuum suction to press down on the printing medium. Such a structure may include, but is not limited to, a belt, one or more rotatable drums, etc. Those skilled in the art are familiar with the various movable support structures used in printing systems for transporting printing medium.

[0032] The vacuum plenum 125 comprises baffles, walls, or any other structure arranged to surround or define an environment in which a vacuum state (e.g., a low-pressure state) is maintained by a vacuum source 128, and the plenum 125 is fluidly coupled to a movable support surface 120, thereby exposing the vacuum state within the vacuum plenum 125. In some embodiments, the movable support surface 120 is supported by a vacuum platen 126, which may be the upper wall of the vacuum plenum 125. In such embodiments, the movable support surface 120 is fluidly coupled to the vacuum within the plenum 125 through platen holes 127 passing 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 within the plenum 125. The vacuum source 128 may be any device configured to remove air from the plenum 125 to create a low-pressure state within the plenum 125, such as a fan or pump.

[0033] The damper 151 is provided within the vacuum plenum 125 between the vacuum source 128 and the vacuum platen 126 and / or the movable support surface 120. The damper 151, along with a baffle or wall coupled to the damper 151, divides the vacuum platen 125 into two separate compartments: a lower compartment adjacent to the vacuum source 128 and an upper compartment adjacent to the vacuum platen 126 and / or the movable support surface 120. Given this arrangement, the lower compartment should have a pressure difference depending on the impedance of the damper 151 and the impedance through the movable support surface 120, and should have a lower pressure than the upper compartment at any given time. Each damper 151 has one or more adjustable openings through which the vacuum source 128 is installed in fluid communication with the portion of the vacuum plenum 125 above the damper 128, or in other words, through which the lower compartment of the vacuum plenum 125 is coupled to communicate with the upper compartment of the vacuum plenum 125. The size of the opening of damper 151 can be dynamically adjusted, thereby changing the airflow impedance between the lower and upper compartments. A smaller opening results in a larger impedance, and vice versa. Damper 151 may comprise, for example, an iris damper, a slide-slot damper (also called a guillotine damper), a opposed-blade damper (also called a blade damper or louver damper), a butterfly pan damper, an inlet vane damper, or any other device having an opening of adjustable size. Exemplary embodiments of such dampers are described in more detail below with reference to Figures 4A to 6B. Damper 151 may also be operably coupled to one or more actuators (not illustrated) to automatically actuate damper 151 and change the size of the opening of damper 151.

[0034] The control system 130 includes a processing circuit for controlling the operation of the printing system 100. The processing circuit may include one or more electronic circuits configured with logic for performing the various operations described herein. The electronic circuit may be configured with logic for performing the operations by including dedicated hardware configured to perform the various operations, by including software instructions that can be executed by the circuit to perform the various operations, or by any combination thereof. In an example where the logic includes software instructions, the electronic circuit of the processing circuit includes a memory device for storing software and a processor, which includes one or more processing devices capable of executing instructions, such as 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 a processing circuit includes dedicated hardware in addition to, or instead of, a processor, the dedicated hardware may include any electronic devices configured to perform a specific operation, such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), complex-programmable logic devices (CPLDs), discrete logic circuits, hardware accelerators, and hardware encoders. The processing circuit may also include any combination of dedicated hardware and software for a general-purpose processor.

[0035] The processing circuitry of the control system 130 also comprises, among other things, airflow control logic 155. The airflow control logic 155 controls the impedance of the damper 151, for example, by generating a control signal (e.g., a digital or analog electrical signal) that causes an actuator associated with the damper 151 to change the size of the opening of the damper 151. In some embodiments, the airflow control logic 155 dynamically controls the impedance of the damper 151 based on detected conditions. Dynamically controlling impedance means automatically and variably adjusting the impedance in substantially real-time in response to changing conditions. Automatically in this context, adjustment means that no specific manual intervention by the user is required at the moment a particular adjustment is triggered or achieved. However, automatic does not necessarily exclude other more common user inputs that may be prior conditions for commonly occurring adjustments, such as the user turning on the system, starting a print job, or selecting settings that allow for common adjustments, but which are not for triggering or achieving a specific adjustment. Adjusting impedance in substantially real-time means that the adjustment occurs relatively immediately after the occurrence of the change or stimulus leading to the adjustment, e.g., within a few seconds or less. In some embodiments, the airflow control logic 155 is configured to detect conditions and make resulting adjustments during the normal printing operation of the printing system 100, such as while the printing medium is mounted on a movable support surface 120, while the printing medium is being transported, or while the printing fluid is being deposited. This is in contrast to impedance adjustments that may occur during manufacturing, testing, initialization, shutdown, maintenance, or other such non-printing operations.

[0036] As described above, the airflow control logic 155 controls the impedance of the damper 151 based on the currently detected state. In some embodiments, the detected state includes the pressure in the upper compartment of the vacuum plenum 125. For example, a pressure sensor 153 may be provided in the upper compartment of the vacuum plenum 125, and the output signal of the pressure sensor may be operably coupled to the airflow control logic 155 to provide the airflow control logic 155 with a pressure measurement. The airflow control logic 155 may include logic that implements a control algorithm and thus functions as a controller. A target pressure may be set, and the controller may automatically adjust the impedance so that the sensed pressure is maintained at or near the target pressure (i.e., within a predetermined threshold). In one embodiment, if the sensed pressure is lower than the target pressure (or exceeds a lower threshold amount), the controller may increase the impedance to some extent, and if the sensed pressure is higher than the target pressure (or exceeds a higher threshold amount), the controller may decrease the impedance to some extent. If the sensed pressure is within the target pressure (or threshold), the controller may leave the impedance at its current value. In some embodiments, the amount by which the impedance increases or decreases may be a fixed, predetermined amount, meaning that the controller raises or lowers the impedance in separate steps of a fixed size until the sensed pressure is at or near the target pressure. In other embodiments, the amount by which the impedance increases or decreases may be variably set based on various variables / parameters such as the magnitude of the difference between the sensed pressure and the target pressure, the history of the sensed pressure, the direction and rate of change of the sensed pressure (i.e., the derivative over time), or any other desired variables known in the art.

[0037] One possible embodiment of the control algorithm is a proportional-integral-derivative (PID) control algorithm, but such is not limiting, and other known control algorithms well known to those skilled in the art may also be used. When implementing a PID control algorithm, pressure may be the control variable of the sensed process variable and impedance (i.e., opening size). As the sensed pressure changes, the airflow control logic 155 automatically adjusts the impedance in response to maintain the pressure at or near a desired setpoint (i.e., target pressure).

[0038] The setpoint or target pressure may be a predetermined value programmed into the airflow control logic 155 before normal operation. For example, the pressure setpoint may reflect the maximum pressure in the upper compartment of the vacuum plenum 125, which still allows for proper holding of the printing medium. This pressure may be determined experimentally during the design or manufacture of the printing system 100, for example, by iteratively setting the pressure setpoint of the upper compartment and determining whether the printing medium is properly held at that setpoint.

[0039] In some embodiments, the detected state, based on adjustments to the damper 151, includes, in addition to or instead of, the number, size, and / or location of the printing media currently on the movable support surface 120, in addition to the sensed pressure. The number / size / location of the printing media reflects the amount (e.g., ratio) of holes in the movable support surface 120 currently covered by the printing media, and determines the pressure (at least partially) in the upper section of the vacuum plenum 125, as described above. Therefore, the number / size / location of the printing media can be used as a substitute for the pressure in the plenum, and controlling the impedance of the damper 151 based on the number / size / location of the printing media may allow the pressure in the vacuum plenum to be maintained at or near a target pressure. Therefore, in some embodiments, the control algorithm / controller described above may use the number, size, and / or location of the printing media as a sensed process variable, in addition to or instead of the sensed pressure. In some embodiments, the number, size, and / or location of the printing media are used directly by the controller as sensed process variables (i.e., sensed state of the system), in other words, the determination of whether to increase or decrease the impedance is directly based on these variables. In other embodiments, the controller may use these variables to determine other information, and the impedance adjustment is then based on this other information. For example, the airflow control logic 155 may be estimated from the number, size, and / or location of the printing media and the amount (percentage) of holes in the movable support surface 120 currently covered by the printing media, and the impedance adjustment may then be directly based on the determined amount (percentage) of holes.

[0040] Therefore, the airflow control logic 155 can control the impedance of the damper 151 based on the detected state of the system (e.g., sensed pressure, number / size / location of printing media, amount of covered holes, etc.) in order to maintain a desired pressure within the vacuum plenum 125 despite the changing conditions. This makes it possible to maintain a relatively high pressure within the vacuum plenum even under changing conditions, and thus reduce the strength of suction through the uncovered holes, and thus reduce the strength of transverse flow while remaining low enough to ensure proper holding of the printing media. For example, when a relatively small number of holes are covered, such as when a small number of printing media and / or small printing media are on the movable support surface 120, the damper 151 may be adjusted to provide a relatively low impedance, which tends to reduce the pressure in the upper section of the vacuum plenum 125 and thus offset the increase in pressure that otherwise occurs due to many uncovered holes. When a relatively large number of holes 121 are covered, such as when many and / or large printing media are on a movable support surface 120, the damper 151 may be adjusted to provide a relatively high impedance, which tends to increase the pressure in the upper compartment of the vacuum plenum 125 and thus offset the pressure reduction that otherwise occurs due to some uncovered holes.

[0041] In some embodiments, the detected state based on adjustments to the damper 151 includes information about the current print job, such as the image content of the image to be printed, the type of print medium used, quality settings, or other settings. Some types of image content may be more sensitive to image fringing induced by transverse flow. For example, images printed close to the edge of the print medium (e.g., images with smaller page margins) are more likely to experience the types of fringing described herein, while images farther from the edge of the print medium (e.g., images with larger page margins) may be less likely to experience fringing. As another example, certain types of image content, such as barcodes, small writing, and fine lines, may be more adversely affected when image fringing occurs. Therefore, the airflow control logic 155 monitors the image content of the image being printed and may reduce the system impedance (and thus increase airflow and vacuum suction) when an image less sensitive to image smudging (such as an image not near the edges) is being printed, and increase the impedance (and thus decrease airflow and vacuum suction) when an image more sensitive to image smudging (such as an image near the edges or an image with sensitive types such as a barcode) is being printed. The airflow control logic 155 also monitors the settings selected for the print job and may change the impedance accordingly. For example, a higher quality setting may result in a higher impedance setting, reducing airflow and therefore reducing smudging (along with setting a lower transport speed to avoid lift-off of the printing medium due to lower suction). Furthermore, different types of printing media may require different levels of vacuum suction to remain flat in contact with the movable support surface without edge lift-off, wrinkling, or curling. For example, a relatively rigid and / or thicker substrate may be more resistant to wrinkling or curling than a more flexible and / or thinner substrate, and therefore more vacuum suction may be required to hold the relatively flexible and / or thin substrate flat in contact with a movable support surface.Therefore, the airflow control logic 155 may monitor the type or printing medium being used and adjust the impedance accordingly (i.e., a higher impedance for printing media that require less suction to remain flat, and a lower impedance for printing media that require more suction to remain flat).

[0042] In some embodiments, the airflow control logic 155 may consider multiple states of the system and base the impedance adjustment on those multiple states. In particular, any of the states described above may be used in any combination. For example, in some embodiments, detected states related to information about the current print job (e.g., image content, media type, settings, etc.) may be considered in combination with detected states related to the plenum pressure (e.g., sensed pressure, number / size of print media, amount of uncovered holes, etc.). For example, the airflow control logic 155 may variably adjust the target pressure used by the control algorithm based on information about the current print job, and then variably adjust the impedance of the damper 151 based on the target pressure and the pressure-related states described above.

[0043] Figure 3 illustrates another embodiment of the printing system 300, which may be used as the printing system 100 described above with reference to Figure 2. Figure 3 includes a schematic illustrating a portion of the printing system 300 from a side view.

[0044] As illustrated in Figure 3, the printing system 300 comprises an ink deposition assembly 301, a medium transport device 303, and an airflow control system 350, which can be used as the ink deposition assembly 101, medium transport device 103, and airflow control system 150 described above with reference to Figure 2, respectively. The printing system 300 may also comprise additional components not illustrated in Figure 3, such as a control system (e.g., control system 130) including airflow control logic (e.g., airflow control logic 155).

[0045] In the printing system 300, the ink deposition assembly 301 comprises four printhead modules 302, with each module 302 having three printheads 310 (two printheads 110 are visible in Figure 3, and the third printhead is hidden behind one of the other printheads 110), as shown in Figure 3. The printhead modules 302 are arranged in series along the process direction P above the medium transport device 303, and as a result, the printing medium 305 is transported through the ink deposition area 323 of the ink deposition assembly, i.e., directly below each of the printhead modules 302. The printheads 310 are positioned to eject a printing fluid (e.g., ink) through corresponding openings in corresponding carrier plates, with the bottom ends of the printheads 310 extending partway into the openings. In this embodiment, the print heads 310 are arranged in a counter-attack pattern where two print heads 310 are aligned in the cross-process direction (only one is visible in Figure 3), and one of the print heads 310 is counter-attacked further upstream or downstream than the other two print heads 310, with the counter-attack print head positioned between the other two print heads 310 in the cross-process direction. In other embodiments, different numbers and / or arrangements of print heads 310 and / or print head modules 302 are used.

[0046] In the printing system 300, the media transport device 303 includes a flexible belt that provides a movable support surface 320. As shown in Figure 3, the movable support surface 320 is driven by rollers 329 (the number and arrangement in Figure 3 are not limiting as recognized by those skilled in the art) and moves along a looped path, with a portion of the path passing through the ink deposition area 323 of the ink deposition assembly 301. Furthermore, in this embodiment, the vacuum plenum 325 includes a vacuum platen 326 that forms the upper wall of the plenum 325 and supports the movable support surface 320. The platen 326 includes platen holes 327 that allow fluid communication between the interior of the plenum 325 and the underside of the movable support surface 320.

[0047] In some embodiments, the platen hole 327 may include a channel on its upper side, as seen in the enlarged cutout 3A in Figure 3, which may increase the area of ​​the opening of the upper hole 327. Specifically, the platen hole 327 may include a bottom portion 327a opening to the bottom side of the platen 326 and an upper portion 327b opening to the top side of the platen 326, with the upper portion 327b being sized and / or formed differently from the bottom portion 327a. For example, Figures 3 to 6C illustrate embodiments of the platen hole 327, where the upper portion 327b is a channel extending in the process direction, while the bottom portion 327a is a through-hole that extends less and has a smaller cross-sectional area (see enlarged view D in Figure 3). In some embodiments, multiple holes 327 may share the same upper portion 327b, or in other words, multiple bottom portions 327a may be coupled to the same upper portion 327b. Referring to this specification, an airflow zone 351 that blocks the hole 327 means that at least the bottom portion 327a of the hole 327 is blocked.

[0048] The holes 327 are arranged in columns extending in the process direction P and in rows extending in the cross-process direction (the x-direction shown in Figure 3), with each column comprising a group of holes 327 aligned with each other in the process direction P, and each row comprising one or more groups of holes 327 aligned with each other in the cross-process direction. In some embodiments, the columns and rows are arranged in a regular grid, while in other embodiments, the columns and rows are arranged in other patterns that do not form a regular grid.

[0049] The holes 321 in the movable support surface 320 are arranged such that each hole 321 aligns with the corresponding collection of platen holes 327 in the process direction P (y-axis direction). In other words, in the printing system 300, each hole 321 aligns with one of the rows of platen holes 327. Therefore, as the movable support surface 320 slides across the platen 326, each hole 321 in the movable support surface 320 periodically moves over the corresponding platen holes 327, resulting in the movable support surface holes 321 and platen holes 327 being temporarily aligned vertically (i.e., aligned in the z-axis direction). As the hole 321 of the movable support surface 320 moves over the corresponding platen hole 327, the holes 321 and 327 fluidly couple the environment above the movable support surface 320 to a low-pressure state within the vacuum plenum 325, thus defining an opening that generates vacuum suction through the holes 321 and 327. This suction generates a vacuum pressing force on the printing medium 305 when the printing medium 305 is positioned above the hole 321.

[0050] As shown in Figure 3, the airflow control system 350 includes a damper 351. The damper 351 in Figure 3 may be used as the damper 151 described above in relation to Figure 2. An exemplary arrangement of three dampers 351 is illustrated in Figure 3, but in other embodiments, any number of dampers 351 may be provided, and they may have different sizes, shapes, and locations than those illustrated. As shown in Figure 3, the damper 351 and one or more baffles 352 are positioned within the vacuum plenum 325 between the vacuum source 328 (e.g., a fan, pump, etc.) and the vacuum platen 326. The damper 351 and baffles 352 separate the vacuum plenum 325 into an upper section 325a and a lower section 325b and control the airflow between these sections 325a, 325b. Thus, the damper 351 controls the strength of the suction provided from the vacuum source 328 to the holes 327 in the vacuum platen 326. Each damper 351 has one or more openings 354 (shown by dashed lines in Figure 3) and connects the upper section 325a to the lower section 325b. The size of the openings 354 can be changed by an actuator (not illustrated), and thus the impedance of the damper 351 is changed. The structure and function of the damper 351 are the same as those of the damper 151, and therefore a further detailed explanation of them is omitted.

[0051] The airflow control system 350 is configured to control the impedance of the damper 351 based on the currently detected state. For example, the airflow control system 350 includes a pressure sensor 353 located in the upper compartment 325a. The pressure sensor 353 senses (periodically or continuously) the pressure in the upper compartment 325a and communicates information indicating the sensed pressure to the controller of the airflow control system 350 (not illustrated). The controller of the airflow control system 350 may be similar to the airflow control logic 155 described above and may control the impedance of the damper 351 (i.e., control the size of the opening 354) based on the pressure information as described above with respect to the airflow control logic 155.

[0052] Exemplary embodiments of various types of dampers, specifically dampers 451, 551, and 651, are described below in more detail with reference to Figures 4A to 6B. Dampers 451, 551, and 651 can be used as damper 151 or 351. The control and operation of dampers 451, 551, and 651 may be similar to those of dampers 151 and 351 described above, and therefore, a redundant explanation is omitted.

[0053] Figures 4A and 4B illustrate an exemplary damper 451. The damper 451 is an iris-type damper and comprises several tapered blades 456 arranged circumferentially around a substantially circular opening in a baffle 452, the narrow end of each blade 456 facing toward the center of the opening, and the broad end of each blade 456 pivotally attached to the baffle 452. The blades 452 are positioned so that they interact collectively to define the opening 454. For example, the blades 452 may partially overlap each other and / or be positioned at adjacent edges to define the opening 454. The size of the opening 454 is changed by pivoting each of the blades 452, thus reducing the size of the opening 454 by moving the narrow ends of the blades 452 closer together, or increasing the size of the opening 454 by moving the narrow ends of the blades 452 further apart. In the illustrated example, the blade 452 is approximately triangular in shape, but other shapes can be used instead. In Figures 4A and 4B, one hidden portion of the blade 456 is shown by a dashed line. As illustrated, one end of the blade 456 is coupled to a pivot shaft 457 fixed to the baffle 452. The other end of the blade 456 is coupled to a ring 458 via a linkage mechanism 460. The ring 458 is rotated about its central axis by an actuator 459, and this rotation of the ring 458 is converted into a pivot of the blade 456 via the linkage mechanism 460 and the pivot shaft 457. For example, the transition from the state illustrated in Figure 4A to the state illustrated in Figure 4B can be achieved by rotating the ring 458 counterclockwise (direction R). The actuator 459 may be an electric motor, a solenoid, a hydraulic or pneumatic piston, or any other device capable of imparting motion to the ring 448. For example, if actuator 459 drives a rotational output, ring 458 may include a gear ring that interacts with the rotational drive output to convert the rotation of the output into the rotation of ring 458.As another example, if actuator 459 is a linear actuator, the linear motion output of actuator 459 may be coupled to one side of ring 458, and as a result the translation of the linear motion output is converted into rotation of ring 458. Other known types of iris dampers familiar to those skilled in the art may be used as damper 451.

[0054] Figures 5A and 5B illustrate another embodiment of a damper that can be used according to embodiments of the present disclosure, which may be referred to as a slide-slot damper or guillotine damper. In Figures 5A and 5B, the damper 551 comprises a plate 561 having several slots 562 or other openings. The plate 561 is positioned in contact with a baffle 552, and the slots 562 partially or completely overlap the corresponding slots 563 in the baffle 552. The opening 554 is defined by the overlap of the slots 562 and 563. The size of the opening 554 is changed by moving the plate 561 relative to the slots 563, thereby changing the degree of overlap between the slots 562 and 563. When the slots 562, 563 are fully aligned and overlapping, the size of the opening 554 is maximized. As the slots move from their aligned position, the size of the opening decreases to the point where slots 562 and 563 are not aligned at all and the opening 554 does not exist (i.e., is closed). The actuator 559 imparts movement to the plate 561, causing it to move relative to the baffle 552 (for example, left and right in the orientations of Figures 5A and 5B). For example, the actuator 559 may be a solenoid, a hydraulic or pneumatic piston, a rotary actuator with a rotary-to-linear conversion mechanism (e.g., an electric motor), or any other device capable of imparting translational motion to the plate 561.

[0055] Figures 6A and 6B illustrate yet another embodiment of a damper, which may be referred to as a blade damper, and which can be used in conjunction with the embodiments of the present disclosure. The damper 651 in Figures 6A and 6B is a so-called opposing blade damper and comprises several blades 664 extending parallel to each other across an opening 667 in a baffle 552. The blades 664 are pivotally coupled to the baffle 552 at both ends by pivot shafts 668. The opening 654 is defined by the open space between and around the blades 664. In other words, the opening corresponds to the portion of the opening 667 that is not closed by the blades 664. The blades 664 have a wide surface with width w (see Figure 6B) and a narrow surface with thickness t (see Figure 6A), and therefore the space between the blades 664 can be changed by rotating the blades 664 around their pivot shafts 668. In other words, rotating the blades 664 changes the amount of the opening 667 that is closed by the blades 664. For example, in Figure 6A, the blades 664 are oriented with their narrow faces parallel to the baffle 652, and therefore there is a relatively wide gap between each blade 664 (i.e., the blades 664 do not close the opening 667 very much). However, in Figure 6B, the blades are oriented with their widths substantially parallel to the baffle 652, and therefore the gap between the blades 664 is relatively narrow (i.e., the blades 664 close most of the opening 667, or in some embodiments, all of the opening 667). Therefore, the size of the opening 654 can be changed by rotating the blades 664. One end of each blade 664 can all be coupled to an arm 665, and as a result, translation of the arm rotates all the blades 664 together. The arm 665 is coupled to an actuator 659 that drives the translation of the arm. Therefore, the actuator 659 can control the rotation of the blades 664 and, therefore, the size of the opening 654. For example, the actuator 559 may be a solenoid, a hydraulic or pneumatic piston, a rotary actuator with a rotary-to-linear conversion mechanism (e.g., an electric motor), or any other device capable of imparting motion to the arm 665.

[0056] Figures 7A and 7B illustrate yet another embodiment of a damper that can be used in conjunction with the embodiments of the present disclosure. The damper 751 in Figures 7A and 7B is a so-called butterfly flat-pan damper and comprises a pan 757 coupled to a pivot shaft 755 that extends across an opening 767. The pivot shaft is rotatable, and as the pivot shaft rotates, the pan rotates. The opening 754 is defined by the open space between the pan 757 and the rim of the opening 767. As the pan 757 rotates, the space between the pan 757 and the rim of the opening 767 decreases, thus reducing the size of the opening 754. For example, in Figure 7A, the pan 757 is oriented at a relatively steep angle with respect to the baffle 752, and therefore there is a relatively wide gap between the pan 757 and the rim of the opening 767. However, in Figure 7B, the dish 757 is oriented close to the baffle 752 so as to be parallel to it, and therefore the gap between the dish 757 and the rim of the opening 767 is relatively narrow (i.e., the dish 757 closes most of the opening 767, or in some embodiments, closes all of the opening 767). Therefore, the size of the opening 754 can be changed by rotating the dish 757 (via the rotation of the pivot axis). The pivot axis 756 is coupled to an actuator 759 that drives the rotation of the pivot axis 756. For example, the actuator 559 may be a solenoid, a hydraulic or pneumatic piston, a rotary actuator with a rotary-to-linear conversion mechanism (e.g., an electric motor), or any other device capable of imparting motion to the pivot axis 756.

[0057] This specification and the accompanying drawings illustrating aspects and embodiments of the present invention should not be construed as limiting claims defining the protected invention. Various mechanical, compositional, structural, electrical, and operational modifications can be made without departing from the spirit and scope of this description and claims. In some examples, well-known circuits, structures, and techniques are not shown or described in detail so as not to obscure the invention. Similar numbers in two or more figures represent the same or similar elements.

[0058] Furthermore, the technical terms used herein to describe aspects of the invention, such as spatial and relational terms, are selected to assist the reader in understanding embodiments of the invention, but are not intended to limit the invention. For example, spatial terms such as “upstream,” “downstream,” “directly below,” “below,” “lower,” “up,” “up,” “inboard,” “outboard,” “up,” and “down” may be used herein to describe directions or spatial relationships of one element or feature to another, as illustrated in the figures. These spatial terms are used in relation to the orientation illustrated in the figures and are not limited to any particular reference frame of the real world. Therefore, for example, the direction “up” in the figures does not necessarily have to correspond to “up” in a world reference frame (e.g., away from the Earth’s surface). Furthermore, if a different reference frame is considered to be other than that illustrated in the figures, the spatial terms used herein may need to be interpreted differently in the different reference frame. For example, a direction referred to as “up” for one of the figures may correspond to a direction referred to as “down” with respect to a different reference frame rotated 180 degrees from the reference frame of the figure. As another example, when comparing with the method illustrated in the figure, if the device rotates 180 degrees within the world reference frame, an item described herein as being "above" or "on top of" a second item related to the figure may be "below" or "directly below" the second item with respect to the world reference frame. Therefore, depending on which reference frame is considered, the same spatial relationship or orientation may be described using different spatial terms. Furthermore, while the orientation of an item illustrated in the figure is chosen for the convenience of illustration and explanation, in implementations, the item may take a different orientation.

[0059] The term "process direction" refers to the direction parallel to and aligned with the axis along which the printing medium moves as it is transported through the deposition area of ​​the ink deposition assembly. Therefore, the process direction is parallel to the y-axis in the diagram and aligns with the positive y-axis direction.

[0060] The term “cross-process direction” refers to a direction that is perpendicular to the process direction and parallel to the movable support surface. At any given point, there are two cross-process directions: the “inboard” cross-process direction and the “outboard” cross-process direction. Therefore, considering the reference frame illustrated in the figure, the cross-process direction is any direction parallel to the x-axis, including the direction that points in the positive or negative direction along the x-axis. References to “cross-process direction” in this specification should generally be understood to refer to any of the cross-process directions, rather than one specific cross-process direction, unless otherwise stated by context. Therefore, for example, the statement “the valve is movable in the cross-process direction” means that the valve can move in the inboard direction, the outboard direction, or both directions.

[0061] The terms “upstream” and “downstream” can also refer to directions parallel to the process direction, with “downstream” referring to the direction in the same direction as the process direction (i.e., the direction in which the printing medium is transported through the ink deposition assembly), and “upstream” referring to the direction in the opposite direction to the process direction. In the diagram, “upstream” corresponds to the negative y-axis direction, while “downstream” corresponds to the positive y-axis direction. The terms “upstream” and “downstream” can also be used to describe the relative location of elements, with “upstream” elements being displaced upstream relative to a reference point, and “downstream” elements being displaced downstream relative to a reference point. In other words, “upstream” elements are closer than some other reference elements to the beginning of the path the printing medium takes as it is transported through the ink deposition assembly (e.g., where the printing medium joins the movable support surface). Conversely, “downstream” elements are closer than some other reference elements to the end of the path (e.g., where the printing medium leaves the support surface). The reference point for other elements being compared to the “upstream” or “downstream” element may be explicitly stated (e.g., “upstream side of the print head”) or inferred from the context.

[0062] The terms "inboard" and "outboard" refer to opposite sides of a media transport device along the cross-process direction. "Outboard" refers to the side of the media transport device closest to the registration point where the edges of the print medium are registered. "Inboard" refers to the side of the media transport device opposite to the outboard side. For example, in Figures 6A and 6B, the outboard side of the media transport device is labeled OB, and the inboard side of the media transport device is labeled IB. The terms "inboard" and "outboard" are also used to represent the cross-process direction, with "inboard" referring to the cross-process direction from the outboard side to the inboard side, and "outboard" referring to the cross-process direction from the inboard side to the outboard side. In the figures, "inboard" corresponds to the positive x-axis direction, while "outboard" corresponds to the negative x-axis direction. The terms "inboard" and "outboard" also refer to relative locations, with "inboard" elements displaced in the inboard direction relative to a reference point, and "outboard" elements displaced in the outboard direction relative to a reference point. The reference point can be explicitly stated (e.g., "the inboard side of the print head") or inferred from the context. Therefore, for example, "the inboard side of the carrier plate" refers to the side of the carrier plate that is further inboard relative to another side of the carrier plate. In systems where the printing medium is not edge-registered (e.g., the printing medium is centered), any side of the system can be referred to as the outboard side, and the opposite side as the inboard side.

[0063] The term "perpendicular" refers to a direction perpendicular to a movable support surface within a deposition area. At any given point, there are two perpendicular directions: an "upward" direction and a "downward" direction. Therefore, considering the reference frame illustrated in the figure, the perpendicular direction is any direction parallel to the z-axis, including the direction in the positive z-axis direction ("up") or the negative z-axis direction ("down").

[0064] The term "horizontal" refers to a direction parallel to (or tangent to, if the movable support surface is not flat within the deposition area) a movable support surface within the deposition area. The horizontal direction includes the process direction and the cross-process direction.

[0065] The term "vacuum" has various meanings in different contexts, ranging from its strict meaning of space devoid of all matter to its more general meaning of a relatively low-pressure state. In this specification, the term "vacuum" is used in its general sense and should be understood to broadly represent a state or environment in which the air pressure is lower than some reference pressure, such as ambient pressure or atmospheric pressure. The amount by which the pressure in a vacuum environment should be lower than the reference pressure considered a "vacuum" is not limited and can be small or large. Therefore, as used herein, "vacuum" may include, but is not limited to, states that could be considered a "vacuum" under the more strict meaning of the term.

[0066] The term “air” has various meanings in various 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 a more general meaning of any gas or mixture of gases. In this specification, the term “air” is used in its general sense and should be understood to broadly represent any gas or mixture of gases. This may include, but is not limited to, the Earth’s atmosphere, noble gases (e.g., helium, neon, argon, etc.), inert gases such as one of nitrogen (N2) gases, or any other desired gas or mixture of gases.

[0067] In addition, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context indicates otherwise. Terms such as “comprises,” “comprising,” and “includes” specify the presence of the described features, processes, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, processes, operations, elements, components, and / or groups. Unless otherwise specifically stated, components described as combined may be directly coupled electrically or mechanically, or they may be 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 of the explanation indicates otherwise, as a person skilled in the art will understand that substantially similar elements, for example, functioning in substantially similar ways, may easily fall within the scope of descriptive terminology, even if the terms also have strict definitions.

[0068] Elements described in detail with reference to one embodiment and their related aspects may, whenever practical, be included in other embodiments not specifically illustrated or described. For example, if an element is described in detail with reference to one embodiment and not described with reference to a second embodiment, the element may still be claimed as being included in the second embodiment.

Claims

1. 1. A printing system comprising: an ink deposition assembly comprising one or more printheads arranged to eject ink into a deposition area of ​​the ink deposition assembly; a media transport device comprising a vacuum source, a vacuum plenum, and 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 movable support surface and to transport the print medium along a process direction through the deposition region, the vacuum suction communicating from the vacuum source through the vacuum plenum to the holes; an airflow control system comprising a damper disposed within the vacuum plenum, the damper having an adjustable impedance to airflow through the damper between the vacuum source and the aperture, the airflow control system comprising: a sensed pressure within the vacuum plenum; the amount of said holes currently covered by print media; the number of print media currently being transported by the movable support surface; or Image content related to the current print job; 4. The printing system of claim 3, wherein the impedance of the damper is dynamically adjusted based on one or more of:

2. the vacuum plenum includes a vacuum platen supporting the movable support surface, the vacuum platen including platen holes for providing the vacuum suction from the vacuum plenum to the holes in the movable support surface; the airflow control system includes a damper unit consisting of one or more dampers disposed in the vacuum plenum between the vacuum platen and the vacuum source, wherein all air flowing between the vacuum platen and the vacuum source passes through the one or more dampers of the damper unit, the damper being one of the one or more dampers; the damper unit has an adjustable impedance to airflow through the one or more dampers, the impedance controlling airflow between the vacuum source and each of the platen holes; 2. The printing system of claim 1, wherein the airflow control system is configured to adjust the impedance of the damper unit to control airflow through all of the platen holes based on a detected condition of the printing system.

3. The printing system of claim 2, wherein the airflow control system is configured to dynamically adjust the impedance of the damper based on the detected condition.

4. a pressure sensor in the vacuum plenum, the pressure sensor configured to sense pressure in the vacuum plenum; The printing system of claim 2 , wherein the detected condition includes the pressure sensed by the pressure sensor.

5. The printing system of claim 4 , wherein the airflow control system is configured to adjust the impedance of the damper to maintain a target pressure in the vacuum plenum.

6. the vacuum plenum being separated at least in part by the damper unit into a first section fluidly coupled to the vacuum source and a second section fluidly coupled to the aperture in the movable support surface; the first section and the second section are configured to be placed in fluid communication through the damper; The printing system of claim 4 , wherein the pressure sensor is in the second compartment.

7. The printing system of claim 2 , wherein the detected condition includes the amount of the pores in the movable support surface currently covered by the print media.

8. 8. The printing system of claim 7, wherein the airflow control system is configured to adjust the impedance of the damper unit in response to a change in an amount of the pores of the movable support surface currently covered by the printing medium to maintain a target pressure in the vacuum plenum.

9. The printing system of claim 2 , wherein the detected condition includes the image content associated with the current print job.

10. The damper unit includes a plurality of dampers, the vacuum plenum being separated at least in part by the plurality of dampers into a first section fluidly coupled to the vacuum source and a second section fluidly coupled to the apertures in the movable support surface; The printing system of claim 2 , wherein the first compartment and the second compartment are configured to be placed in fluid communication through the damper.

11. the vacuum plenum being separated at least in part by the damper into a first section fluidly coupled to the vacuum source and a second section fluidly coupled to the aperture in the movable support surface; The printing system of claim 2 , further comprising: the first compartment and the second compartment configured to be placed in fluid communication through the damper unit.

12. The printing system of claim 2 , wherein the one or more dampers of the damper unit are at least one of an iris damper, a slide shutter damper, a blade damper, or a butterfly dish damper.

13. 3. The printing system of claim 2, wherein the one or more dampers of the damper unit include one or more openings, and the air flow control system is configured to adjust the impedance of the dampers by adjusting a size of the one or more openings.

14. 14. The printing system of claim 13, wherein the airflow control system further comprises an actuator operably coupled to the damper unit, the actuator configured to adjust the size of the one or more openings.

15. The printing system of claim 2, wherein the movable support surface comprises a belt configured to move relative to the vacuum platen.

16. 1. A method comprising: transporting one or more print media through a deposition region of a print head of a printing system, the print media being held during the transport against a moveable support surface of a media transport device via vacuum suction through an aperture in the media transport device, the vacuum suction communicating from a vacuum source to the aperture via a vacuum plenum; ejecting a printing fluid from the print head to deposit the ink on the print medium in the deposition area; a sensed pressure within the vacuum plenum; the amount of said holes currently covered by print media; the number of print media currently being transported by the movable support surface; or Image content related to the current print job; detecting a condition including one or more of: and controlling an airflow control system to dynamically adjust an impedance of a damper disposed within the vacuum plenum based on the detected condition, whereby the impedance of the damper is adjusted to: the sensed pressure in the vacuum plenum; the amount of the holes currently covered by print media; the number of print media currently being transported by the movable support surface; or said image content relating to a current print job; and (c) controlling the temperature of the heating element in response to a change in one or more of the temperature, The method of claim 1, wherein the impedance of the damper controls air flow between the vacuum source and the hole.

17. The vacuum plenum includes a vacuum platen supporting the movable support surface, the vacuum platen including platen holes for providing the vacuum suction from the vacuum plenum to the holes in the movable support surface; Controlling the airflow control system to dynamically adjust the impedance of the damper based on the detected condition includes controlling the airflow control system to dynamically adjust an impedance of a damper unit including one or more dampers disposed within the vacuum plenum based on the detected condition, the one or more dampers including the damper; 17. The method of claim 16, wherein the damper unit is located between the vacuum platen and the vacuum source, and all air flowing between the vacuum platen and the vacuum source passes through the damper unit, and the impedance of the damper controls air flow between the vacuum source and each of the platen holes.

18. 20. The method of claim 17, wherein dynamically adjusting the impedance of the damper unit comprises adjusting a size of one or more openings of the one or more dampers using an actuator operably coupled to the damper unit.

19. sensing a pressure within the vacuum plenum, the detected condition comprising the sensed pressure; 20. The method of claim 17, wherein dynamically adjusting the impedance of the damper unit comprises adjusting the impedance of the damper unit to maintain the sensed pressure at or near a target pressure.

20. determining a covered hole volume constituting the holes of the movable support surface currently covered by the print medium, wherein the detected condition includes the covered hole volume; 18. The method of claim 17, wherein dynamically adjusting the impedance of the damper unit comprises adjusting the impedance of the damper in response to changes in the amount of covered holes to maintain a target pressure in the vacuum plenum.

21. determining a number of the print media currently being transported by the movable support surface, the detected condition including the number of the print media; The method of claim 17 , wherein dynamically adjusting the impedance of the damper unit comprises adjusting the impedance of the damper in response to a change in the number of the print media.

22. determining image content or system settings associated with a current print job, wherein the detected conditions include one or more of the image content or the system settings; 20. The method of claim 17, wherein dynamically adjusting the impedance of the damper unit comprises adjusting the impedance of the damper in response to changes in one or more of the image content or the system settings.

Images