CN116981572A

CN116981572A - Cleaning of inkjet nozzles in digital printing systems

Info

Publication number: CN116981572A
Application number: CN202280021679.5A
Authority: CN
Inventors: 本锡安·兰达; R·拉勒扎; H·卡林斯基; A·摩尔达维斯基; D·巴夫利; N·弗罗因德; R·维尔克
Original assignee: Landa Corp Ltd
Current assignee: Landa Corp Ltd
Priority date: 2021-03-18
Filing date: 2022-03-13
Publication date: 2023-10-31

Abstract

A system (10) having a printing position and a non-printing position, the system (10) including an image forming station (60) and a wiping assembly (200, 400). The image forming station (60) includes at least a nozzle plate (61) having one or more nozzles (166, 166a, 166b, 166 c) configured to apply drops of a printing fluid to a surface of one or more substrates (44) to produce one or more images thereon. The wiper assembly (200, 400) is positioned at least partially in the gap (141) between the nozzle plate (61) and the one or more substrates (44) and is configured to (i) make physical contact with the nozzle plate (61) and (ii) remove residues of printing fluid from at least one of the nozzles (166, 166a, 166b, 166 c) when the system (10) is in the printing position.

Description

Cleaning of inkjet nozzles in digital printing systems

Cross Reference to Related Applications

The present application claims the benefit of U.S. provisional patent application 63/162,577 filed on day 3, month 18 of 2021 and U.S. provisional patent application 63/214,286 filed on day 6, month 24 of 2021, the disclosures of which are incorporated herein by reference in their entireties.

Technical Field

The present application relates generally to digital printing systems, and in particular to methods and systems for preventing clogging of inkjet nozzles in digital printing systems.

Background

Various techniques have been disclosed for maintaining the cleanliness and function of nozzles in inkjet printing systems.

For example, japanese patent application publication 2000103086a describes an inkjet printer having an inkjet head and a transfer belt. The ink jet head includes a plurality of nozzles for ejecting ink onto a transfer belt and further transferred onto recording paper. The maintenance unit is used for a maintenance process of the inkjet head, including a pull-out roller, a roller, and a maintenance sheet (wiping sheet). The maintenance sheet is pulled out from the maintenance unit by a pull-out roller, and then the print head moves upward. The roller and the pull-out roller serve as a pull-out member for horizontally pulling out the maintenance sheet. When the take-up roller is driven to rotate, the maintenance sheet is moved from the supply roller to the take-up roller by the pull-out roller. When the maintenance sheet moves, the nozzle surface is wiped by the maintenance sheet and a wiping operation occurs.

Us patent 10,449,767 describes a liquid ejection device comprising: the liquid ejecting apparatus includes a liquid ejecting head ejecting liquid from nozzles arranged on a nozzle surface, a wiping member having a longitudinal shape capable of contacting the nozzle surface, a contact portion capable of contacting a side of the wiping member opposite to the side in contact with the nozzle surface, and a conveying mechanism conveying the wiping member, wherein the contact portion has a first contact portion which is separated from the wiping member when the wiping member is conveyed by the conveying mechanism and contacts the wiping member when the wiping member is driven to contact the nozzle surface, and a second contact portion which contacts the wiping member when the wiping member is conveyed by the conveying mechanism.

Us patent 8,888,230 describes a fluid ejection device comprising: a fluid ejection head including nozzle rows each having a plurality of nozzles and ejecting a fluid onto a medium, the fluid ejection apparatus being capable of performing a flushing operation in which the fluid is ejected to an absorbing member for absorbing the fluid ejected from the nozzles, wherein the absorbing member is a linear member extending along the nozzle rows and is relatively movable to a position retracted from a flight path of the fluid ejected from the nozzles.

Us patent 5,557,307 describes a cleaning line for inkjet printing nozzles. The adsorbent material is mounted on a nozzle plate of an inkjet printer to collect foreign ink and particles that may clog nozzle orifices of the printer. In an inkjet printer, ink droplets are ejected from an array of orifices in a nozzle plate in a printer head. During droplet ejection, ink is sprayed or deposited around the orifices. Ink droplets are deposited on the web adjacent the nozzles and a mist from the ink droplets is fluctuated back to cover the face of the nozzle plate. Such ink coatings may attract particles that tend to clog the nozzle orifice. By positioning the adsorbing material in close proximity to the nozzle orifice array, the material adsorbs and removes ink covering the nozzle plate before the ink blocks the orifices of the nozzles. The wire is one example of an adsorbent material. The wire slides in a groove across the face of the nozzle plate to wick away ink coating and particles on the nozzle plate. The dispenser spool on one side of the printer head provides clean wire to the printer head and the rewind spool on the other side of the printer head pulls the wire through the nozzle plate and out of the dispenser spool.

Chinese patent application publication 100553982C describes an inkjet coating apparatus comprising a spray head having a plurality of nozzles, the solution of which is sprayed onto a substrate by means of an inkjet, and a wipe having the shape of an absorption band. The wipes are discarded to the discharge gear release mechanism in front of the nozzle face of the spray head and the wipes are pressed against the roller on the nozzle face.

Disclosure of Invention

Embodiments of the invention described herein provide a system having a printing position and a non-printing position, the system including an image forming station and a wiping assembly. The image forming station includes at least a nozzle plate having one or more nozzles configured to apply drops of printing fluid to a surface of one or more substrates to produce one or more images thereon. The wiper assembly is positioned at least partially in the gap between the nozzle plate and the one or more substrates and is configured to (i) make physical contact with the nozzle plate and (ii) remove residue of printing fluid from at least one of the nozzles when the system is in the printing position.

In some embodiments, the system includes (i) a transport assembly configured to move one or more substrates relative to a nozzle plate, and (ii) a processor configured to control: (a) The transport assembly moves the one or more substrates, and (b) the wiper assembly removes residue from at least one of the nozzles while the one or more substrates are moved by the transport assembly. In other embodiments, in the printing position, the processor is configured to maintain a constant throughput of producing one or more images, including during removal of residue by the wiper assembly. In still other embodiments, one or more substrates include an Intermediate Transfer Member (ITM) configured to receive droplets for producing one or more images and transfer the one or more images to a target substrate, and the transport assembly includes an ITM module configured to move the ITM relative to the image forming station to produce the one or more images.

In one embodiment, the one or more substrates comprise one or more sheets or continuous webs, and the transport assembly comprises a substrate transport module configured to move the one or more sheets or continuous webs relative to the image forming station to produce one or more images thereon. In another embodiment, the image forming station includes at least a first print bar having one or more first nozzles and a second print bar having one or more second nozzles, and in the print position, the wiping assembly is configured to remove residue from at least one of the first nozzles while at least one of the second nozzles is applying liquid droplets. In yet another embodiment, in the printing position, a gap between the nozzle plate and the one or more substrates is maintained while (i) applying the droplets and (ii) removing the residue.

In some embodiments, the wiping assembly includes a wiping element configured to remove residue by wiping the residue of the printing fluid from at least one orifice of at least one of the nozzles. In other embodiments, the wiping element comprises a strip configured to hold a cleaning fluid and make physical contact with the nozzle plate by self-adhesion to the nozzle plate. In still other embodiments, the tape comprises: (a) A residue removal layer configured to remove residues of printing fluid from the nozzle plate, and (b) a compressible layer coupled to the residue removal layer and configured to: (i) Absorbs and contains the cleaning fluid when in contact with the cleaning fluid, and (ii) releases at least a portion of the cleaning fluid when a compressive force is applied to the strip material.

In one embodiment, the wiping assembly is configured to position the web over at least one of the nozzles when the image forming station is not applying drops to the substrate. In another embodiment, the strip is configured to cover the nozzle and the compressible layer is configured to maintain moisture in the strip so as to prevent solidification of residue or another substance on the nozzle. In yet another embodiment, the ribbon is configured to: (i) Maintaining a predetermined amount of cleaning fluid for wiping residues disposed on the nozzles, and (ii) absorbing additional residues of printing fluid not disposed on the nozzles.

In some embodiments, the additional residue comprises at least one of a vapor and an aerosol of the printing fluid, and the wiping element is configured to absorb at least one of a vapor and an aerosol of the printing fluid not disposed on the nozzle. In other embodiments, the wiping assembly is configured to move the wiping element within the gap between the nozzle and the one or more substrates for at least one of: (i) Wiping residue disposed on at least one of the nozzles, and (ii) absorbing additional residue of printing fluid located between the nozzle and the one or more substrates. In still other embodiments, the wiping assembly is configured to move the wiping element in a first direction during a first time interval and to move the wiping element in a second direction during a second time interval.

In one embodiment, the nozzles are arranged along a first axis and across a second axis, and at least one of: (i) The first direction is parallel to the first axis, and (ii) the second direction is parallel to the second axis. In another embodiment, one or more substrates are moved in a direction of movement, a first direction being parallel to the direction of movement, and a second direction being orthogonal to the direction of movement. In yet another embodiment, the processor is configured to control the wiper assembly to move the wiper element in at least one of the first and second directions as at least one of the nozzles ejects printing fluid toward the one or more substrates.

In some embodiments, the first time interval is greater than the second time interval. In other embodiments, the first time interval overlaps with one or more second time intervals. In still other embodiments, the first direction is orthogonal to the second direction.

In one embodiment, the processor is configured to control the wiper assembly to (i) move the wiper element in a first direction at a first speed, and (ii) move the wiper element in a second direction at a second speed different from the first speed. In another embodiment, the second speed is at least five times greater than the first speed. In yet another embodiment, the one or more substrates comprise a flexible substrate having a first portion for receiving the one or more printing fluids and a second portion positioned between the first image and the second image, and the processor is configured to control (i) movement of the flexible substrate in a direction of movement, and (ii) movement of the wiping element in a second direction parallel to the direction of movement of the flexible substrate as the second portion passes adjacent the one or more nozzles.

In some embodiments, the processor is configured to control the wiper assembly to move the wiper element in a second direction that is parallel to the direction of movement of the flexible substrate when the one or more nozzles are not applying liquid droplets. In other embodiments, at least part of the wiping element is positioned within the gap between at least one of the nozzles and the second portion during at least part of the second time interval. In yet other embodiments, the processor is configured to: (i) Controlling the image forming station to apply the liquid drops when the first portion passes adjacent the one or more nozzles and not apply the liquid drops when the second portion passes adjacent the one or more nozzles, and (ii) controlling the wiping element to move the wiping element to wipe residue from the nozzles when the processor controls the one or more nozzles not to apply the liquid drops.

In one embodiment, the flexible substrate includes an intermediate transfer member configured to receive the liquid droplets to form an image at the image forming station and transfer the image to the target substrate. In another embodiment, the second portion is configured to be connected between two ends of the first portion so as to form a loop comprising the first portion and the second portion. In yet another embodiment, the one or more substrates include a first sheet configured to receive the first image and a second sheet configured to receive the second image, and the processor is configured to: the wiping assembly is controlled to move the wiping element in a second direction after the first image is formed and before the second image is formed while at least one of the first sheet and the second sheet is moved within the system.

In some embodiments, the system includes a cleaning system configured to remove one or more of the residues from the wiping element. In other embodiments, the image forming station includes one or more printheads, each printhead including one or more nozzles, and the system includes a substrate transport module configured to move a substrate in a printing direction to form an image thereon, the one or more printheads having a first axis parallel to the printing direction and a second axis perpendicular to the printing direction, and the wiper assembly is configured to remove residue from the nozzles of at least one of the printheads by moving the wiper element along the first axis of the one or more printheads. In still other embodiments, the wiping assembly is configured to remove residue from at least one of the nozzles while moving the wiping element along the second axis of the printhead.

In one embodiment, the wiping assembly is configured to remove residue from at least one of the nozzles while the substrate transport module moves the substrate in the printing direction. In another embodiment, the wiping assembly is configured to remove residue from at least one of the nozzles when the nozzles are not applying droplets to the substrate. In yet another embodiment, at least one of the one or more printheads includes a nozzle plate having a first portion and a second portion without nozzles and a third portion between the first portion and the second portion and including nozzles, and the wiping assembly is configured to move the wiping element from the first portion through the third portion to the second portion at least along the first axis.

In some embodiments, the wiping component is configured to move the wiping element along the second axis when the wiping element is positioned over the first portion or the second portion. In other embodiments, the wiping assembly is configured to move the wiping element continuously back and forth along the first axis between the first and second portions at a predetermined frequency. In still other embodiments, the substrate has a plurality of first portions and a plurality of second portions alternately positioned along the substrate in the direction of movement, the image forming stations are configured to form a plurality of images on the plurality of first portions, respectively, when each of the first portions faces the image forming station, the wiping assembly is configured to move the wiping element back and forth along the first axis when the second portions face the image forming station, and the predetermined frequency includes a discrete number of second portions facing the image forming station.

In one embodiment, the predetermined frequency is defined by a time interval. In another embodiment, the substrate comprises a flexible substrate having a first end and a second end coupled by a seam portion to form a loop, the flexible substrate moving in a loop in a printing direction, each of the loops being defined as when the seam portion faces the image forming station, and the predetermined frequency comprises a discrete number of loops. In yet another embodiment, the wiping assembly is configured such that the wiping element: (i) The first motion profile is used to move along a first axis and the second, different motion profile is used to move along a second axis.

In some embodiments, the first motion profile comprises a continuous motion profile and the second motion profile comprises a discrete motion profile.

There is additionally provided, in accordance with an embodiment of the present invention, a tape comprising: (a) A residue removal layer configured to remove residues of printing fluid from one or more nozzles of the printing system, and (b) a compressible layer coupled to the residue removal layer and configured to: (i) Absorbs and contains the cleaning fluid when in contact with the cleaning fluid, and (ii) releases at least a portion of the cleaning fluid when a compressive force is applied to the strip material.

In some embodiments, one or more nozzles are formed in the nozzle plate, and the residue removal layer is configured to receive at least a portion of the cleaning fluid from the compressible layer and self-adhere to the nozzle plate to make physical contact with the one or more nozzles. In other embodiments, the ribbon includes a core layer coupled to the compressible layer and configured to tighten the ribbon in a given plane when tension is applied to the ribbon. In still other embodiments, the core layer is implemented within the fluid-containing layer such that the fluid-containing layer has a first outer surface and a second outer surface facing each other, and the core layer is positioned between the first surface and the second surface.

In one embodiment, the first outer surface is coupled to the residue removal layer, and the tape comprises a polyethylene base layer coupled to the second outer surface of the fluid-containing layer and configured to perform at least one of: (i) Tightening the strip in a given plane when tension is applied to the strip, and (ii) retaining at least a portion of the cleaning fluid within the fluid-containing layer when compression force is not applied to the strip. In another embodiment, the polyethylene base layer comprises polyethylene terephthalate (PET). In yet another embodiment, the tape is moved in at least one of a first direction and a second direction parallel to the given plane, and the core layer and the polyethylene base layer are configured to tighten the tape in the first direction and the second direction.

In some embodiments, the printing system includes a first nozzle having a first print residue and a second nozzle having a second print residue, and at least one of the residue removal layer and the fluid-containing layer is configured to compensate for a topography difference between the first nozzle and the second nozzle so as to adhere between (i) the residue removal layer and (ii) at least the first nozzle and the second nozzle to remove the first print residue and the second print residue.

There is additionally provided, in accordance with an embodiment of the present invention, a method comprising: in a system having a printing position and a non-printing position, droplets of a printing fluid are applied to a surface of one or more substrates using one or more nozzles of a nozzle plate to produce one or more images thereon. A wiper assembly positioned at least partially in a gap between the nozzle plate and the one or more substrates when the system is in the printing position is applied to: (i) Physical contact with the nozzle plate, and (ii) removal of residue of printing fluid from at least one of the nozzles.

The invention will be more fully understood from the following detailed description of embodiments of the invention, taken in conjunction with the accompanying drawings, in which:

drawings

FIG. 1 is a schematic side view of a digital printing system according to an embodiment of the present invention;

FIG. 2 is a schematic side view of a wiping assembly and cleaning station according to an embodiment of the invention;

fig. 3A, 3B and 3C are schematic illustrations of a web moving relative to a surface of a bottom portion of a print bar of a digital printing system according to an embodiment of the present invention.

FIG. 4 is a schematic illustration of a wiping component according to an embodiment of the invention;

FIG. 5 is a schematic cross-sectional view of a strip material according to an embodiment of the present invention;

FIG. 6 is a schematic cross-sectional view of a strip being extruded in an extrusion assembly according to an embodiment of the present invention;

FIGS. 7A and 7B are schematic illustrations of a wiping assembly according to an embodiment of the invention;

FIG. 8 is a flow chart schematically illustrating a method for removing residue from a nozzle of a digital printing system, in accordance with an embodiment of the present invention; and

fig. 9 is a flow chart schematically illustrating a method for forming an image and removing residue from nozzles of a print bar of a digital printing system, in accordance with an embodiment of the present invention.

Detailed Description

SUMMARY

Inkjet-based digital printing systems typically produce an ink image by applying (e.g., jetting or spraying) a printing fluid, such as ink, to a substrate through nozzles.

One problem in such printing systems is that ink residues may condense and clog at least a portion of the nozzles, which may lead to defects and/or distortions in the subsequently printed image. For example, partial blockage of the orifice of the nozzle may divert the next ink drop to fall on the substrate at a different location than expected. As another example, a complete blockage of a nozzle may result in a lack of ink at a desired location on the substrate.

In principle, it is possible to periodically stop printing to perform a maintenance procedure in order to remove the ink residues before solidification occurs on the nozzles. However, such planned or unplanned maintenance reduces the availability and utilization of the printing system and thus reduces the throughput of the system.

Embodiments of the present invention described below provide methods and systems for preventing distortion of a printed image on a substrate by removing ink residues without stopping the printing operation of an inkjet-based digital printing system. The disclosed technology is also referred to herein as the instant removal of ink residues.

In some embodiments, a digital printing system includes an image forming station that includes a plurality of print bars. Each print bar has a plurality of print heads arranged along a long axis of the print bar, and each print head has a nozzle plate having three portions: (i) A central portion positioned at the center of the nozzle plate along the long axis and comprising an array of nozzles for ejecting ink drops (or any other suitable printing fluid) on the substrate, and (ii) two side portions, typically without nozzles, positioned at the sides of the central portion along the long axis.

In some embodiments, the image forming station is configured to apply ink drops to the substrate while the substrate is moving relative to the printhead. The substrate has: (i) A first portion intended to receive ink droplets to form an image on a substrate, and (ii) a second portion, (also referred to herein as a non-printable portion or area) generally positioned to alternate between the first portions. The second portion does not receive ink drops and is not used to form an image thereon. In some embodiments, one of the second portions may include a seam portion described in detail below.

In some embodiments, the substrate is moved in a direction of movement to a print bar proximate the image forming station to receive ink drops on the first portion. In this example, the direction of movement is orthogonal to the long axis of the print bar. In such embodiments, the first and second portions alternately face the print bar when the substrate is moved.

In some embodiments, the processor of the digital printing system is configured to control the image forming station to: (i) Directing ink droplets through the nozzle to the substrate when the first portion of the substrate faces the print bar, and (ii) avoiding ejection of ink droplets to the substrate when the second portion faces the print bar.

In some embodiments, the digital printing system includes a residue removal assembly, also referred to herein as a Wiping Assembly (WA), for each print bar, controlled by a processor and configured to wipe ink residues from the nozzles of the respective print bar. WA comprises a strip and is configured to move the strip in two directions over portions of the nozzle plate. In this example, when the nozzle ejects ink drops on the first portion, the WA is configured to continuously move the ribbon over one side portion of the nozzle plate along the long axis such that the ribbon does not interfere with the ejection process of the ink drops.

In some embodiments, when the substrate is moving and at least one of the second portions faces the print bar, the processor is configured to control the WA to move the web at least along a short axis of the print bar, the short axis being generally parallel to the direction of movement of the substrate. In such embodiments, the ribbon moves along the minor axis: (i) from a first side portion of the nozzle plate, (ii) through the nozzles of the central portion to wipe ink residue from the nozzles, and (iii) to a second side portion of the nozzle plate. Note that the web only moves along the minor axis when one of the second portions faces the print bar and the nozzles are not ejecting ink drops. Furthermore, the WA is configured to move the web along the short axis fast enough so that the web moves away from the central portion of the printhead before the next first portion of the substrate faces the print bar and the nozzle ejects ink drops toward the substrate.

In some embodiments, the processor is configured to schedule the frequency of movement of the web along the minor axis of the print bar while continuously moving the web along the major axis of the print bar. In such embodiments, when the processor controls the WA to perform the next wiping operation of the ink residue, the WA is configured to move the ribbon in the opposite direction along the minor axis. In this example, the opposite direction is designated from the second side portion of the nozzle plate to the first side portion of the nozzle plate through the nozzles of the center portion. In other words, the processor is configured to control the WA to move the web back and forth along the minor axis of the print bar at any suitable frequency while continuously moving the web along the major axis of the print bar.

In some embodiments, the wiping frequency may include any suitable discrete number of second portions, e.g., wiping once every ten second portions, or a predefined time interval, e.g., ink wiping is performed every minute, or a combination thereof, or using any other suitable scheduling technique.

In some embodiments, the image forming station includes a plurality of print bars for a plurality of colors of ink, respectively. For example, the system may include (i) a Print Bar (PB) for applying a cyan ink, referred to herein as cyan PB, and (ii) a Print Bar (PB) for applying a magenta ink, referred to herein as magenta PB. Each print bar includes a plurality (e.g., tens of thousands) of nozzles configured to apply (e.g., by jetting or spraying) ink drops of a respective color (e.g., cyan or magenta) to a first portion of a substrate. Note that the digital printing system is configured to apply any number of ink colors, such as four or seven different colors. For conceptual clarity, this example of two colors of ink is provided by way of example.

In some embodiments, the substrate may include (i) a target substrate, such as a sheet or continuous web, configured to receive droplets to produce an image directly from an image forming station, or (ii) a flexible Intermediate Transfer Member (ITM), also referred to herein as a blanket, configured to receive ink droplets to produce an image, and subsequently transfer the image to the target substrate. In this example, the blanket has two ends and a seam portion for coupling between the ends, so that the blanket is designed in a loop shape. In some embodiments, the processor controls the given print bar to temporarily stop applying ink to the blanket as the blanket is moved in the direction of movement and the aforementioned seam portion (or any other second portion) faces the given print bar. After the seam portion passes the given print bar, the processor controls the given print bar to resume applying ink to the blanket.

In some embodiments, each print bar includes a separate WA having a ribbon. For example, the web of a given WA moves, especially over the nozzle plate below a given print bar, in the gap between the given print bar and the substrate, at least in both directions as described above. The non-printable portion may include non-printable areas between images on a blanket or continuous web, or between sheets in a direct printing system, for example. Note that at the same time, the processor is configured to control at least one of the other print bars of the system to apply ink drops to the substrate while the web wipes ink residue from a given print bar, as described in detail above.

For example, when the seam portion of the blanket passes under (i.e., faces) the cyan PB, the processor is configured to control the first WA to remove ink residues from the nozzles of the cyan PB while the magenta PB nozzles apply ink drops to another portion of the substrate. Subsequently, as the seam portion of the blanket passes under the magenta PB, the processor is configured to control the second WA to remove ink residues from the nozzles of the magenta PB while the cyan PB nozzles apply ink drops to the substrate. Note that maintenance work to remove ink residue from the nozzles is performed while the system is printing an image on the blanket (i.e., on the fly).

In some embodiments, the processor is configured to control the wiper assembly to move the web along the minor axis of the print bar for wiping the nozzles as the seam portion passes under a given print bar. As described above for the second section, the wiping assembly is configured to move the web along the minor axis of the print bar fast enough to finish wiping the nozzles before the seam portion passes under the print bar.

In some embodiments, the web is configured to perform wiping in a limited space between the print bar and the blanket, and has a self-supporting tensioning mechanism, also referred to herein as self-adhesion or self-adhesive force, for adhering to the nozzles as the web is moved by the wiping assembly. The self-adhesion is in particular configured to compensate possible topography differences between nozzles of different printheads of the print bar, as will be described in the following detailed description.

In some embodiments, the tape comprises a multilayer stack comprising: (i) A residue removal layer configured to be positioned over a nozzle plate of the printhead as the tape moves and wipe residue from the nozzles, (ii) a compressible layer having an upper surface and a lower surface; the upper surface is coupled to the residue removal layer, and the compressible layer is configured to contain water to improve adhesion between the tape and the nozzle (and for another purpose described below), (iii) a core layer implemented between the upper and lower surfaces of the compressible layer and configured to improve dimensional stability of the tape in the presence of tension applied to the tape by the wiping assembly, and (iv) a polyethylene terephthalate (PET) layer coupled to the lower surface of the compressible layer and configured to: improving dimensional stability of the web, sealing the compressible layer to prevent leakage of water to the blanket, and improving flexibility of the web to adhere to the nozzles of the print bar. For example, the layers of the tape are described in more detail in fig. 5 of the present disclosure.

In some embodiments, the web may be movable between (i) a supply drum configured to supply clean web for wiping the residue and (ii) a receiving drum configured to receive the web after wiping the ink residue from the nozzles. This configuration (also referred to herein as a reel-to-reel configuration) requires replacement of the supply drum when the entire cleaning tape is used.

In other embodiments, the web may be moved in a closed loop between the print bar and a cleaning station configured to remove ink residue from the web using any suitable technique. In this example, the cleaning station includes a plurality of water tanks, each containing water and coupled to a megasonic transducer configured to vibrate the water within the tank to assist in removing ink residue from the ribbon. In some embodiments, the cleaning system may include a squeezing mechanism positioned between adjacent water containers for squeezing at least a portion of the water with residues and other contaminants contained in the strip from the strip. The cleaning station is also described in detail below.

In some embodiments, after megasonic cleaning, the ribbon is moved into a pressing assembly for pressing some of the water contained in the ribbon, thereby removing ink residues (and other types of contaminants) that may remain in the ribbon after megasonic cleaning.

Note that a portion of the water remains in the compressible layer after extrusion in order to maintain sufficient moisture in the strip to perform several operations described below. In the context of the present disclosure and in the claims, the term extrusion refers to the operation of applying a compressive force to a strip.

In some embodiments, the tape may be used to cap the orifices of the printing nozzles when the print bar is idle and no ink is applied to the substrate. The humidity of the web prevents the ink residue on the printing nozzles from condensing. Furthermore, in both the idle and printing positions of the system, the compressible layer is configured to absorb and contain vapors and aerosols of the ink suspended between the print bar and the blanket, as well as contaminants, to prevent it from solidifying on the nozzles of the print bar.

In some embodiments, the web is sufficiently moist to be wiped and self-adhesion of the web is achieved by adhesion between the water contained in the web and the nozzle plate of each print head of the print bar described above.

The disclosed technology improves the print quality of inkjet printing systems by reducing the amount of defects and distortions caused by nozzle clogging of the print bar. Furthermore, the disclosed technology improves the productivity of inkjet printing systems by cleaning the nozzles on the fly, i.e., while the printing system is continuously printing images on a substrate.

System description

Fig. 1 is a schematic side view of a digital printing system 10 according to an embodiment of the present invention. In some embodiments, system 10 includes a rolling flexible blanket 44 that circulates through image forming station 60, drying station 64, impression station 84, and blanket processing station 52. In the context of the present invention and in the claims, the terms "blanket" and "Intermediate Transfer Member (ITM)" are used interchangeably and refer to a flexible member comprising one or more layers that are used as intermediate members formed in an endless loop configured to receive an ink image, for example, from image forming station 60 and to transfer the ink image to a target substrate, as will be described in detail below.

In one mode of operation, image forming station 60 is configured to form a mirrored ink image of digital image 42, also referred to herein as an "ink image" (not shown) or for brevity as an "image", on an upper run of the surface of blanket 44. The ink image is then transferred to a target substrate (e.g., paper, a folded paper box, a multi-layer polymer, or any suitable flexible package in the form of a sheet or continuous web) located below the lower run of blanket 44.

In the context of the present invention, the term "run" refers to the length or section of blanket 44 between any two given rolls of guiding blanket 44.

In some embodiments, during installation, blanket 44 may be adhered edge-to-edge using seam portion 45 to form a continuous blanket loop. Examples of methods and systems for installing seams are described in detail in U.S. patent application publication 2020/0171813, the disclosure of which is incorporated herein by reference.

In some embodiments, image forming station 60 generally includes a plurality of print bars 62, each mounted on a frame (not shown) at a fixed height above the surface of the upper run of blanket 44. In some embodiments, each print bar 62 includes a print head belt that is as wide as the print area on blanket 44 and includes individually controllable print nozzles, for example, as shown in fig. 3A and 3C below.

In some embodiments, image forming station 60 may include any suitable number of print bars 62, also referred to herein as bars 62 for brevity. Each bar 62 may contain a printing fluid, such as a different color aqueous ink. The ink typically has a visible color such as, but not limited to, cyan, magenta, red, green, blue, yellow, black, and white. In the example of fig. 1, the image forming station 60 includes seven print bars 62, but may include, for example, four print bars 62 having any selected color, such as cyan (C), magenta (M), yellow (Y), and black (B).

In some embodiments, the printheads are configured to eject ink droplets of different colors onto the surface of blanket 44 to form an ink image (not shown) on the surface of blanket 44. In this example, blanket 44 moves along the X-axis of the XYZ coordinate system of system 10 and the ink drops are directed by the print head, generally parallel to the Z-axis of the coordinate system.

In some embodiments, the different print bars 62 are spaced apart from each other along a movement axis, also referred to herein as (i) the direction of movement 94 of the blanket 44 or (ii) the printing direction. In this example, the direction of movement of blanket 44 is parallel to the X-axis, and each print bar 62 extends along the Y-axis of system 10. In this configuration, it is critical to achieve proper placement of the image pattern that the exact spacing between rods 62 along the X-axis and the synchronization between the ink drops directed at each rod 62 and the moving blanket 44.

In the context of the present disclosure and in the claims, the terms "inter-color pattern placement", "pattern placement accuracy", "inter-color registration", "C2C registration", "inter-color position difference", "inter-rod registration", and "color registration" are used interchangeably and refer to any placement accuracy of two or more colors relative to each other.

In some embodiments, the system 10 includes a heater 66, such as a hot gas or air blower and/or an infrared-based heater with a gas or air blower for flowing gas or air at any suitable temperature. Heater 66 is positioned between print bars 62 and is configured to partially dry ink drops deposited on the surface of blanket 44. This air flow between the print bars may help, for example, (i) reduce condensation at the surface of the print head and/or handle splash points (e.g., residues or droplets distributed around the primary ink drops), and/or (ii) prevent the ink jet nozzles of the print head from clogging, and/or (iii) prevent the different colored ink drops on blanket 44 from undesirably fusing with one another.

In some embodiments, system 10 includes a wiper assembly, also referred to herein as a wiper, configured to remove residues of printing fluid that remain on the nozzles of each print bar 62 after the printing fluid is applied to blanket 44. In such embodiments, each print bar 62 may have a separate wiper assembly for removing residue of the printing fluid. Embodiments of the wiping assembly are shown and described in detail in figures 2 through 7B below.

In some embodiments, system 10 includes a drying station 64 configured to direct infrared radiation and cooling air (or another gas) and/or blow hot air (or another gas) onto the surface of blanket 44. In some embodiments, drying station 64 may include an infrared-based illumination assembly (not shown) and/or an air blower 68 or any other suitable drying device.

In some embodiments, in drying station 64, the ink image formed on blanket 44 is exposed to radiation and/or hot air to more thoroughly dry the ink, thereby evaporating most or all of the liquid carrier and leaving only a layer of resin and colorant heated to the point of becoming a tacky ink film.

In some embodiments, system 10 includes a blanket module 70 (also referred to herein as an ITM module) that includes a rolling flexible ITM, such as blanket 44. In some embodiments, blanket module 70 includes one or more rollers 78, wherein at least one of rollers 78 includes a motion encoder (not shown) configured to record the position of blanket 44 in order to control the position of a portion of blanket 44 relative to a corresponding print bar 62. In some embodiments, one or more motion encoders may be integrated with additional rollers and other moving components of system 10.

In some embodiments, the aforementioned motion encoder generally comprises at least one rotary encoder configured to generate a rotation-based position signal indicative of the angular displacement of the respective roller. It should be noted that in the context of the present invention and in the claims, the terms "indicative" and "indicative" are used interchangeably.

Additionally or alternatively, blanket 44 may include an integrated encoder (not shown) for controlling the operation of the various modules of system 10. One embodiment of an integrated motion encoder is described in detail, for example, in PCT International publication WO 2020/003088, the disclosure of which is incorporated herein by reference.

In some embodiments, blanket 44 is directed over rollers 76, 78 and other rollers described herein, as well as over a power tensioning roller, also referred to herein as dancer assembly 74. Dancer assembly 74 is configured to control the relaxed length of blanket 44 and its movement is schematically represented by the double-headed arrow in FIG. 1. In addition, any stretching of blanket 44 due to aging will not affect the ink image placement performance of system 10, and will only need to take up more slack by tensioning dancer assembly 74.

In some embodiments, dancer assembly 74 may be motorized. The configuration and operation of the rollers 76 and 78 are described in more detail, for example, in U.S. patent application publication 2017/0008272 and in the above-mentioned PCT international publication WO 2013/132424, the disclosures of which are incorporated herein by reference in their entirety.

In some embodiments, system 10 includes a blanket tension drive roller (BTD) 99 and a blanket control drive roller (BCD) 77 that are powered by respective first and second motors, typically electric motors (not shown), and are configured to rotate about their own axes, respectively.

In some embodiments, system 10 may include one or more tension sensors (not shown) disposed at one or more locations along blanket 44. The tension sensor may be integrated into blanket 44 or may include a sensor external to blanket 44 that uses any other suitable technique to acquire a signal indicative of the mechanical tension applied to blanket 44. In some embodiments, processor 20 and additional controllers of system 10 are configured to receive signals generated by tension sensors to monitor tension applied to blanket 44 and control operation of dancer assembly 74.

In the impression station 84, the blanket 44 passes between the impression cylinder 82 and a pressure cylinder 90 configured to carry a compressible blanket (not shown). In some embodiments, the motion encoder is integrated with at least one of the impression cylinder 82 and the pressure cylinder 90.

In some embodiments, system 10 includes a control console 12 configured to control a plurality of modules of system 10, such as a blanket module 70, an image forming station 60 located above blanket module 70, and a substrate transport module 80 located below blanket module 70, and one or more imprint stations, as will be described below.

In some embodiments, console 12 includes a processor 20 (typically a general purpose processor) having suitable front end and interface circuitry for interfacing with and receiving signals from a controller of dancer assembly 74 and with controller 54 via cable 57. Additionally or alternatively, console 12 may include any suitable type of Application Specific Integrated Circuit (ASIC) and/or Digital Signal Processor (DSP) and/or any other suitable type of processing unit configured to perform any type of processing on data processed in system 10.

In some embodiments, the controller 54, schematically illustrated as a single device, may include one or more electronic modules mounted on the system 10 at predefined locations. At least one of the electronic modules of the controller 54 may include electronic devices, such as control circuitry or a processor (not shown), configured to control the various modules and stations of the system 10. In some embodiments, the processor 20 and control circuitry may be programmed with software to implement the functions used by the printing system and to store data for the software in the memory 22. For example, the software may be downloaded to the processor 20 and control circuitry in electronic form, over a network, or the software may be provided on non-transitory tangible media, such as optical, magnetic, or electronic memory media.

In some embodiments, console 12 includes a display 34 configured to display data and images received from processor 20 or input inserted by a user (not shown) using input device 40. In some embodiments, the console 12 may have any other suitable configuration, such as an alternative configuration of the console 12 and display 34 is described in detail in U.S. patent 9,229,664, the disclosure of which is incorporated herein by reference.

In some embodiments, processor 20 is configured to display digital image 42 on display 34, including one or more segments (not shown) of image 42 and/or various types of test patterns that may be stored in memory 22.

In some embodiments, blanket processing station 52 (also referred to herein as a cooling station) is configured to process a blanket by, for example, cooling the blanket and/or applying a processing fluid to an outer surface of blanket 44 and/or cleaning an outer surface of blanket 44. At blanket processing station 52, the temperature of blanket 44 may be reduced to a desired temperature level before blanket 44 enters image forming station 60. The treatment may be performed by passing blanket 44 over one or more rollers or blades configured to apply cooling and/or cleaning and/or treatment fluids to the outer surface of the blanket.

In some embodiments, blanket processing station 52 may also include one or more bars (not shown) positioned adjacent to print bar 62 such that processing fluid may additionally or alternatively be applied to blanket 44 by spraying.

In some embodiments, processor 20 is configured to receive signals indicative of the surface temperature of blanket 44, for example, from a temperature sensor (not shown), in order to monitor the temperature of blanket 44 and control the operation of blanket processing station 52. Examples of such processing stations are described, for example, in PCT international publications WO 2013/132424 and WO 2017/208152, the disclosures of which are incorporated herein by reference in their entirety.

In the example of fig. 1, station 52 is mounted between impression station 84 and image forming station 60, but station 52 may be mounted adjacent blanket 44 at any other or additional suitable location or locations between impression station 84 and image forming station 60. As described above, additionally or alternatively, station 52 may be mounted on a pole adjacent to image forming station 60.

In the example of fig. 1, the impression cylinder 82 and the pressure cylinder 90 impress an ink image onto a target flexible substrate (such as each sheet 50) that is transported by the substrate transport module 80 from the input stack 86 to the output stack 88 via the impression station 84. In this example, a rotary encoder (not shown) is integrated with the impression cylinder 82.

In some embodiments, the lower run of blanket 44 selectively interacts with impression cylinder 82 at impression station 84 to imprint the image pattern onto the target flexible substrate compressed between blanket 44 and impression cylinder 82 by the pressure action of pressure cylinder 90. In the case of the simplex printer shown in fig. 1 (i.e., printing on one side of sheet 50), only one impression station 84 is required.

In other embodiments, module 80 may include two or more impression cylinders (not shown) to permit one or more duplex prints. The configuration of two impression cylinders also enables single sided printing at twice the speed of printing a double sided print. In addition, a large number of mixed single-sided and double-sided prints can be printed. In alternative embodiments, different configurations of modules 80 may be used for printing on a continuous web substrate. Detailed descriptions and various configurations of duplex printing systems and systems for printing on continuous web substrates are provided, for example, in U.S. patent 9,914,316 and 9,186,884, PCT international publication WO 2013/132424, U.S. patent application publication 2015/0054865, and U.S. provisional application 62/596,926, the disclosures of which are incorporated herein by reference.

As briefly described above, the sheet 50 or continuous web substrate (not shown) is carried by the module 80 from the input stack 86 through a nip (not shown) between the impression cylinder 82 and the pressure cylinder 90. Within the nip, the ink image bearing surface of blanket 44 is firmly pressed against sheet 50 (or against another suitable substrate), such as by a compressible blanket of pressure cylinder 90, so that the ink image is stamped onto the surface of sheet 50 and cleanly separated from the surface of blanket 44. Subsequently, the sheet 50 is conveyed to the output stack 88.

In the example of fig. 1, roller 78 is positioned at the upper run of blanket 44 and is configured to hold blanket 44 taut as it passes adjacent image forming station 60. Furthermore, it is particularly important to control the speed of blanket 44 below image forming station 60 in order to obtain accurate ejection and deposition of ink droplets to form an image on the surface of blanket 44 by image forming station 60.

In some embodiments, impression cylinder 82 periodically engages and disengages from blanket 44 in order to transfer an ink image from moving blanket 44 to a target substrate passing between blanket 44 and impression cylinder 82. In some embodiments, system 10 is configured to apply torque to blanket 44 using the foregoing roller and dancer roller assemblies in order to keep the upper run taut and substantially isolate the upper run of blanket 44 from mechanical vibrations occurring in the lower run.

In some embodiments, the system 10 includes an image quality control station 55 (also referred to herein as an Automatic Quality Management (AQM) system) that functions as a closed loop inspection system integrated in the system 10. In some embodiments, image quality control station 55 may be positioned adjacent to impression cylinder 82 (as shown in fig. 1) or at any other suitable location in system 10.

In some embodiments, the image quality control station 55 includes a camera (not shown) configured to acquire one or more digital images of the aforementioned ink images printed on the sheet 50. In some embodiments, the camera may include any suitable image sensor, such as a Contact Image Sensor (CIS) or a Complementary Metal Oxide Semiconductor (CMOS) image sensor, and a scanner including a slit having a width of about one meter or any other suitable width.

In the context of the present disclosure and in the claims, the term "about" or "approximately" as used in any numerical value or range indicates a suitable dimensional tolerance that allows a portion or collection of components to function for their intended purpose, as described herein.

In some embodiments, station 55 may include a spectrophotometer (not shown) configured to monitor the quality of ink printed on sheet 50.

In some embodiments, the digital images acquired by station 55 are transmitted to a processor, such as processor 20 or any other processor of station 55, which is configured to evaluate the quality of the respective printed images. Based on the evaluation and the signals received from the controller 54, the processor 20 is configured to control the operation of the modules and stations of the system 10. In the context of the present invention and in the claims, the term "processor" refers to any processing unit configured to process signals received from the camera and/or spectrophotometer of station 55, such as processor 20 or any other processor or controller connected to or integrated with station 55. It should be noted that the signal processing operations, control related instructions, and other computing operations described herein may be implemented by a single processor or shared among multiple processors of one or more respective computers.

In some embodiments, station 55 is configured to check the quality of the printed image and test pattern in order to monitor various properties, such as, but not limited to, full image registration with sheeting 50 (also referred to herein as image-to-substrate registration), inter-color (C2C) registration, print geometry, image uniformity, color profile and linearity, and print nozzle functionality. In some embodiments, the processor 20 is configured to automatically detect geometric distortion or other errors in one or more of the foregoing attributes.

In some embodiments, processor 20 is configured to analyze the detected distortion to apply corrective action to the failed module and/or to feed instructions to another module or station of system 10 to compensate for the detected distortion.

In some embodiments, the system 10 may print test marks (not shown) or other suitable features, for example, at a bevel or edge of the sheet 50. By acquiring images of the test marks, station 55 is configured to measure various types of distortions, such as C2C registration, image-to-substrate registration, different widths between colors (referred to herein as "inter-bar width increments" or "inter-color width differences"), various types of local distortions, and recto-verso registration errors (in duplex printing). In some embodiments, the processor 20 is configured to: (i) Sorting sheets 50 having a distortion above a first set of predefined thresholds to, for example, reject trays (not shown); (ii) Initiating a corrective action on the sheet 50 having a distortion above a second set of lower predefined thresholds; and (iii) output sheet 50 having a slight distortion, for example, below the second set of thresholds, to output stack 88.

In some embodiments, processor 20 is configured to detect deviations in the profile and linearity of the printed colors based on signals received from the spectrophotometers of station 55.

In some embodiments, the processor of station 55 is configured to decide whether to stop operation of system 10, for example, if the density of distortion is above a specified threshold. The processor of station 55 is also configured to initiate corrective actions in one or more of the modules and stations of system 10, as described above. In some embodiments, corrective action may be performed on-the-fly (while system 10 continues the printing process), or off-line by stopping the printing operation and solving problems in the respective modules and/or stations of system 10. In other embodiments, any other processor or controller of system 10 (e.g., processor 20 or controller 54) is configured to initiate corrective action or cease operation of system 10 if the density of the distortion is above a specified threshold.

Additionally or alternatively, processor 20 is configured to receive signals indicative of additional types of distortion and problems in the printing process of system 10, such as from station 55. Based on these signals, the processor 20 is configured to automatically estimate the pattern placement accuracy level and additional types of distortion and/or imperfections not mentioned above. In other embodiments, any other suitable method for inspecting the pattern printed on the sheet 50 (or on any other substrate described above) may also be used, such as using an external (e.g., off-line) inspection system or any type of measuring instrument and/or scanner. In these embodiments, based on information received from the external inspection system, processor 20 is configured to initiate any suitable corrective action and/or cease operation of system 10.

For the purpose of illustrating the invention, the configuration of the system 10 is simplified and provided by way of example only. The components, modules and stations described above in printing system 10, as well as additional components and configurations, are described in detail, for example, in U.S. patent 9,327,496 and 9,186,884, PCT international publications WO 2013/132438, WO 2013/132424 and WO 2017/208152, and U.S. patent application publications 2015/0118503 and 2017/0008272, the disclosures of which are incorporated herein by reference in their entirety.

The particular configuration of system 10 is shown by way of example to illustrate certain problems addressed by embodiments of the present invention and to demonstrate the application of these embodiments in enhancing the performance of such systems. However, embodiments of the present invention are in no way limited to this particular kind of exemplary system, and the principles described herein may be similarly applied to any other kind of printing system.

Control of cleanliness of printing nozzles using a wiping assembly and its cleaning station figure 2 is a schematic side view of a Wiping Assembly (WA) 200 and Cleaning Station (CS) 100 according to an embodiment of the invention. In the context of the present disclosure and in the claims, the terms "WA 200", "residue removal assembly", and "wiper 200" are used interchangeably and refer to an assembly for removing printing fluid residue remaining on the nozzles of print bar 62 after the printing fluid is applied to blanket 44 or any other substrate.

Note that WA 200 and CS100 are not shown to the same scale in fig. 2 for the sake of expression and conceptual clarity. For example, based on the X, Y and Z-axis coordinate system shown in FIG. 2, the length of the print bar 62 along the Y-axis is approximately 1 meter, while the overall size of the CS100 is between approximately 30 cm and 70 cm. For the sake of detailed description, CS100 is presented larger in fig. 2, and WA 200 is described in more detail in fig. 4 below.

In some embodiments, the system 10 includes a plurality of WAs 200. In this example, the system 10 includes a separate WA 200 for each print bar 62 shown in fig. 1 above, but in other embodiments, the system 10 may include any suitable number of wipers, each having any suitable configuration. For example, (i) a single wiper assembly may be used to clean the nozzles of all print bars 62 of system 10, or (ii) at least one print bar 62 may have multiple wipers.

In some embodiments, WA 200 includes a belt 111 configured to move in direction 144 (described in detail below) within gap 141 between print bar 62 and blanket 44. The web 111 moves in the direction 144 to wipe ink residue and other types of residue from the nozzles of the print bar 62. Note that each print bar 62 of system 10 has a separate web 111 for wiping residue from the nozzles of the respective print bar 62.

In this example, blanket 44 moves in a direction of movement 94 (shown in FIG. 1 above) parallel to the X-axis of system 10. In some embodiments, ribbon 111 moves in a direction 144 generally parallel to the Y-axis of system 10, and also moves in additional directions parallel to the X-axis, as will be described in detail below in fig. 3A, 3B, and 3C. In other words, at a first time interval, the ribbon 111 is moved along one axis (e.g., the Y-axis), and at a second, different time interval, the ribbon 111 is moved along both axes (e.g., the X-axis and the Y-axis) simultaneously. Furthermore, WA 200 is configured to (i) move web 111 along the Y-axis (which is also parallel to the long axis of print bar 62 and orthogonal to direction of movement 94 of blanket 44) using a continuous motion profile, and (ii) move web 111 along the X-axis (which is also parallel to both the short axis of print bar 62 and direction of movement 94 of blanket 44) using a discrete motion profile. Embodiments related to the foregoing motion profile are described in detail below in fig. 3A-3C. In other embodiments, the ribbon 111 may move independently in the first and second directions or simultaneously in the first and second directions.

In some embodiments, after a given portion of the strip material 111 is wiped off residues on the nozzle, the given portion of the strip material 111 is diverted by one or more reciprocating pulleys 230 (described in detail below in fig. 4) to move in the direction 150 and for insertion into the CS100 to remove the residues. Subsequently, a given portion of the web 111 that has been cleaned of residues in the CS100 is moved in a direction 140, and subsequently, the given portion of the web 111 is diverted by one or more reciprocating pulleys 210 (described in detail below in fig. 4) for insertion between the blanket 44 and the print bar 62. WA 200 then repeatedly wipes the residue from the nozzles by moving in direction 144 (typically but not necessarily parallel to the Y-axis) and also simultaneously moving parallel to the X-axis (typically but not necessarily parallel to the direction of movement of blanket 44), followed by moving web 111 for cleaning as described above.

In some embodiments, the above-described cycle of residue wiping and web cleaning may be repeated during the printing cycle without stopping the printing operation, i.e., on-the-fly. In some cases, after the printing fluid is applied (e.g., sprayed) from the nozzles of the print bar 62, residues of the printing fluid may remain on the surface of a given nozzle and condense to create undesirable clusters. The clusters may (i) partially block the openings of the nozzles, which may result in C2C registration errors caused by disturbances in the steering angle of subsequent printing fluid ejected from a given nozzle toward blanket 44, or (ii) fully block (i.e., fully block) the nozzles, which may result in, for example, ink missing at one or more locations on the image, or (iii) undesirable defects, such as particles, being formed when the clusters are ejected onto or fall onto the printed image.

In some embodiments, the tape 111 (which is described in detail in fig. 5 below) is configured to remove and collect residue from the nozzles of the print bar 62 and release the collected residue into the CS100, as will be described herein.

In some embodiments, the Cleaning Station (CS) 100 includes a plurality of containers of suitable cleaning fluids. In this example, five or more Water Containers (WCs) 122 (referred to herein as WCs 122a, 122b, 122c, 122d, 122e, and 122 f) are configured to hold any suitable type of water 120, such as, but not limited to, deionized water.

In some embodiments, CS100 is configured to perform acoustic-based removal of residue from ribbon 111 (also referred to herein as acoustic cleaning). In this example, CS100 includes five or more (e.g., six) Megasonic Transducers (MTs) 106 coupled to five or more (e.g., six) WC's 122a-122f and one or more generators (not shown), respectively. Each MT 106 is configured to generate a sound field having a suitable frequency, for example, between about 0.6MHz and 5MHz, and in particular about 1.6MHz, within the water 120 contained in the respective WC. In some embodiments, MT 106 of CS100 may include any suitable type of transducer. Note that MT 106 or any other type of ultrasonic or megasonic transducer is configured to agitate water 120 in order to assist in removing contaminants, such as, paint or other residue, from ribbon 111. In other embodiments, CS100 may also include any other suitable type of agitator for removing wiping residue and other contaminants from ribbon 111 in lieu of or in addition to the transducers described above. In alternative embodiments, residues and other contaminants may be removed from the strip 111 by extruding the strip 111 as the strip 111 passes between rollers 108 described below.

In some embodiments, the CS100 includes a water inlet pipe 101 configured to fill the WC 122f with clean water 120 and a water outlet pipe 104 configured to receive water 120 exiting the WC 122a of the CS100 that is generally contaminated with the above-described residue. In the context of the present disclosure and in the claims, the term "clean" means that the water container has a small amount of residue in the water 120, and the term "dirty" means that the water container has a large amount of residue in the water 120.

In the configuration shown in fig. 2, the WCs 122 are arranged in a stepwise manner such that water 120 flows from WC 122f through all of the WCs 122 to WC 122a and then overflows to the drain pipe 104. For example, when filling WC 122f, water 120 overflows to WC 122e at overflow point 102. Similarly, when the WC 122a, which is the last water container, is filled, the water 120 overflows in the direction 105 toward the drain pipe 104 through the overflow point 103.

In some embodiments, the CS100 includes a conveyor 147 having a plurality of rollers 108 positioned within the WC 122 and outside the WC 122 and configured to convey the strip 111 through the WC 122 of the CS 100. Note that each pair of rollers 108 is also configured to squeeze water 120 that is immersed in the strip 111 and contains the above-described residues and other contaminants. In this example, a given portion of the strip 111 carrying the residue wiped from the nozzle is moved in the direction 107 to insert into the WC 122a, the WC 122a having more residue than any other WC 122 of the CS 100. After a first acoustic cleaning within WC 122a, the given part is moved via a pair of rollers 108 in direction 109 to exit WC 122a and again in direction 107 into WC 122 b. Note that the amount of residue in WC 122b is generally lower than the amount of residue in WC 122a because (i) WC 122a receives tape 111 with residue directly wiped from the nozzles of print bar 62 and (ii) WC 122b receives a water stream from WC 122c, which residue is generally less than WC 122 b. Furthermore, when entering WC 122b, the strip 111 has less residue than the amount of residue when entering WC 122a, as some of the residue has been removed by WC 122 a.

In some embodiments, processor 20 and/or controller 54 are configured to control the speed of ribbon 111, e.g., in direction 144 and in directions 107 and 109. The speed of the strip 111 in directions 107 and 109 controls the amount of water 120 absorbed by the strip 111, and the speed of the strip 111 in direction 144 (and the other direction shown in fig. 3A and 3B below) controls the time that a given portion of the strip 111 contacts a given nozzle for the wiping process.

In some embodiments, the ribbon 111 is moved through the CWs 122c, 122d, 122e, and 122f for additional acoustic cleaning, and then retracted from the WC 122f in the direction 116. Based on the above principle, WC 122f is the cleanest water reservoir in CW 122 that receives clean water from the water inlet pipe 101, and WC 122a is the dirtiest water reservoir in CW 122 that overflows water 120 to the water outlet pipe 104. Thus, CS100 is configured to remove residue from strip 111 that is wiped off the nozzle.

In some embodiments, after being pulled out of WC 122f in direction 116, the strip 111 is diverted by rollers 118 and moved into a squeeze assembly 110 configured to squeeze a majority of the water 120 remaining within the strip 111. In some embodiments, the extrusion assembly 110 includes rotatable drums 112 and 114 that are configured to rotate about their own axes for extrusion operations, which are briefly described above and described in further detail in FIG. 6 below.

In some embodiments, the extrusion assembly 110 further includes a controllable piston 117 and a shaft 119 configured to control the amount of water 120 extruded from the strip 111 by controlling the distance between the drums 112 and 114. In such embodiments, the smaller distance between drums 112 and 114 reduces the amount of water 120 that remains within ribbon 111 after the extrusion process.

In other embodiments, CS100 may also include any other suitable type of one or more cleaning fluids in place of or in addition to water 120.

In other embodiments, the compression assembly 110 may include any other suitable technique for controlling the compression level in place of the piston 117 and shaft 119.

In some embodiments, the cleaning station 100 includes a Tensioning Assembly (TA) 130 configured to apply tension to the strip 111 to keep the strip 111 taut at least during the extrusion process and as the strip 111 moves in the direction 140 toward the reciprocating pulley 210 (as described above). In this example, TA 130 includes a controllable piston 132 and rollers 134, 136, and 138. The piston 132 is configured to move along the Z-axis to control the position of the roller 136 along the Z-axis to apply a specified tension to the ribbon 111. For example, in the event that the strip 111 is not sufficiently tensioned, the piston 132 is moved along the Z-axis to increase the distance between (i) the roller 136 and (ii) the rollers 134 and 138, thereby increasing the tension applied to the strip 111 and causing the strip 111 to be sufficiently tensioned.

In some embodiments, TA 130 is configured to control the tension applied to ribbon 111 during the entire cycle of residue wiping (within WA 200) and residue cleaning (within CS 100).

In other embodiments, TA 130 may also include a spring (not shown) or any other suitable mechanism for controlling the tension applied to ribbon 111, in lieu of or in addition to at least piston 132 and roller 136. Additionally or alternatively, at least one of the systems 10, WA 200, and CS100 may include one or more tensioning assemblies for controlling the level of tension of the strap 111 along the cycle described above.

In some embodiments, the cleaning station 100 and the components 110 and 130 are controlled by the processor 20 and/or the controller 54 of the system 10. In other embodiments, the cleaning station 100 and one or more of the components 110 and 130 may be controlled by one or more controllers (not shown) of the CS100, for example, which are controlled by the processor 20 and/or the controller 54.

In an alternative embodiment, WA 200 may include two drums (not shown) rather than using a closed loop as described above to clean residue from strip 111. The first drum provides a clean web 111 for wiping residue from the print bar 62 and the second drum receives the web 111 after wiping residue from the print bar 62. This configuration is also referred to herein as reel-to-reel. Note that the clean ribbon may be moved through a reservoir of cleaning fluid, such as water 120, and a squeeze assembly (e.g., squeeze assembly 110) for containing a predetermined amount of water 120 within the compressible layer 300 of the ribbon 111. As shown in fig. 2 and 5 above, the water contained within compressible layer 300 may be used to adhere tape 111 to all nozzles of print bar 62 and to remove residue from the nozzles.

Fig. 3A, 3B and 3C are schematic illustrations of the tape 111 moving relative to the bottom surface of portions 170 and 172 of the nozzle plate 61 of the respective printheads of the print bar 62 according to an embodiment of the present invention. Each print head of the print bar 62 has a nozzle plate 61 that includes portions 170 and 172 and a nozzle array described in detail below.

Note that fig. 3A, 3B, and 3C show a bottom view of print bar 62 and a sequence of positions of seam portion 45 and web 111 of blanket 44 moving relative to print bar 62.

In some embodiments, operation of WA 200, and in particular movement of web 111, is synchronized with the firing time intervals and non-firing time intervals of respective print bars 62 of system 10. In such embodiments, when a given print bar 62 ejects printing fluid (e.g., ink) onto blanket 44 (through the nozzles), the web does not wipe the nozzles. However, during the non-firing time interval, a given WA 200 of a given print bar 62 is configured to move its given web 111 to wipe the nozzles of the given print bar 62.

The following embodiments of fig. 3A-3C describe how movement of the ribbon 111 is controlled based on the position of the seam portion 45. In other words, wiping of the nozzles of the print bar 62 is performed during the non-jetting time interval, e.g., as the seam portion 45 of the blanket 44 passes adjacent to (e.g., beneath) the print bar 62, such that the nozzles of the print bar do not jet printing fluid toward the blanket 44. Note that the same technique applies when other portions of blanket 44 pass under print bar 62. For example, when the portion of blanket 44 between the two portions designated to receive ink drops to create an image thereon (e.g., between the images of the two sheets) passes under print bar 62, the nozzles do not jet printing fluid, and at the same time, web 111 may be used to wipe the nozzles.

Referring now to fig. 3A-3C, a snapshot of blanket 44 is shown with seam portion 45 (schematically defined between solid lines 143 and 145) moving relative to print bar 62.

In fig. 3A, seam portion 45 has not reached print bar 62, in fig. 3B seam portion 45 has reached print bar 62 and faces nozzles 166, 166a, and 166B, and in fig. 3C seam portion 45 has passed print bar 62 and continued toward other print bars 62 and/or drying station 64.

In some embodiments, print bar 62 includes a plurality of printheads, shown as arrays of nozzles 166, 166a, and 166b and portions 170 and 172. In this example, portions 170 and 172 are typically made of a ceramic material, are positioned on sides (e.g., edges) of nozzle 166, and are substantially flush with nozzles 166, 166a, and 166 b. Further, portions 170 and 172 typically have no nozzles and are therefore not configured to eject printing fluid.

In the example of fig. 3A, nozzles 166, 166a, and 166b apply printing fluid (e.g., ink drops) to blanket 44 in direction 171 (generally orthogonal to the direction of blanket movement and parallel to the Z-axis). Meanwhile, blanket 44, shown in phantom, moves in a direction of movement 94 (parallel to the X-axis) and belt 111 moves in a direction 144 parallel to the Y-axis.

In some embodiments, print bar 62 has a width 180 between about 40mm and 42mm, and the array of nozzles 166, 166a, and 166b has a width 182 between about 12mm and 14 mm. Based on widths 180 and 182, portions 170 and 172 each have a width between approximately 13mm and 15 mm.

In some embodiments, ribbon 111 has a width 184 between about 12mm and 14mm, which is substantially similar to width 182 and slightly smaller than the width of portions 170 and 172. Note that in such embodiments, web 111 is not positioned between (i) nozzles 166, 166a, and 166b and (ii) blanket 44 when moving in direction 144, and thus does not block printing fluid ejected in direction 171 from nozzles 166, 166a, and 166b toward the surface of blanket 44.

During operation of the system 10, such as during a printing process, the solid line 143 passes adjacent the print bar 62. Solid line 143 indicates a first edge of seam portion 45 that is an integral part of blanket 44 and thus moves with blanket 44 toward print bar 62. In some embodiments, when the first edge of the seam portion 45 is a predetermined distance from the nozzles 166, 166a, and 166b, the processor 20 is configured to control the WA 200 to move the ribbon 111 in the direction 160 generally parallel to the X-axis. In the context of the present disclosure and in the claims, direction 160 is parallel to the direction of movement of blanket 44 (also referred to herein as the printing direction), and direction 144, which is orthogonal to the printing direction, is also referred to herein as the printing cross direction. In addition, print bar 62 has (i) a major axis parallel to the Y-axis and direction 144, and (ii) a minor axis parallel to the X-axis and direction 160. Thus, in some embodiments, WA 200 is configured to move ribbon 111 substantially parallel to the long axis of print bar 62 (i.e., in direction 144) and also substantially parallel to the short axis of print bar 62 (i.e., in direction 160).

In some embodiments, the predetermined distance is determined by processor 20 based on the speed of movement of blanket 44 and other parameters of system 10. Note that in such an embodiment WA 200 moves ribbon 111 in directions 144 and 160 simultaneously. In this example, the speed of movement of ribbon 111 in direction 144 is between about 1 mm/sec and 20 mm/sec, while the speed of movement of ribbon 111 in direction 160 is significantly higher, for example, at any suitable speed greater than 750 mm/sec.

Note that widths 180, 182, and 184, the configuration of print bar 62 and ribbon 111, and the speed of ribbon 111 in directions 144 and 160 are provided by way of example and may vary. In other embodiments, at least one of print bar 62 and web 111 can have any other suitable configuration and/or width, and WA 200 can move web 111 at different speeds in at least one of directions 144 and 160. Further, in this example, directions 144 and 160 are orthogonal to each other, but in other embodiments, directions 144 and 160 may have any other suitable angle therebetween.

In alternative embodiments, system 10 may also include any other suitable type of wiping element or any other suitable type of residue removal assembly for removing residues of printing fluid from nozzles 166, 166a, and 166b, such as a suitable cleaning fluid sprayer or any other contact or non-contact cleaning device, in lieu of or in addition to web 111.

In the example of fig. 3A-3C, print bar 62 includes a plurality of arrays of nozzles 166, 166a, and 166b and portions 170 and 172 arranged in a plurality of printheads along a Y axis and across an X axis. In other embodiments, nozzles 166, 166a, and 166b and portions 170 and 172 may be arranged using any suitable configuration other than a plurality of printheads, for example, print bar 62 may include a single printhead having a length of print bar 62 (e.g., about 1 meter).

Referring now to FIG. 3B, there is shown the time interval in which seam portion 45 of blanket 44 is aligned with the array of nozzles 166, 166a and 166B in the Z-axis. In other words, seam portion 45 passes adjacent to the array of nozzles 166, 166a, and 166b, and faces the array of nozzles 166, 166a, and 166b, in this example, by a distance of gap 141 (e.g., between about 1mm and 2 mm).

In some cases, at least two of the printheads of print bar 62 may not be perfectly flush with each other, such as in the Z-axis. For example, a plate including an array of nozzles 166a may be positioned about 0.05mm higher along the Z-axis than a plate including an array of nozzles 166 b. In this case, when a given web (other than web 111) moves in direction 144, the given web, which is sufficiently taut, may hover without contacting nozzles 166b, and thus, residues of printing fluid may not be wiped by web 111 from at least some of nozzles 166 b.

In some embodiments, the tape 111 is configured to have self-adhesion, which is described in detail below in fig. 5 and is also referred to herein as a self-supporting tensioning mechanism, to make contact with all of the nozzles of all of the printheads of the print bar 62. Please note that

In some embodiments, web 111 is configured to be sufficiently taut to fit within the limited space between blanket 44 and the print head of print bar 62 when moving in directions 144 and 160. However, based on self-adhesion, the tape 111 is configured to adhere to (i.e., make contact with) all of the nozzles (e.g., nozzles 166, 166a, and 166 b) of the print bar 62 and wipe residue from the all of the nozzles. Note that one or more forces (e.g., tensile forces) are applied to ribbon 111 in the XY plane (e.g., along the X-axis and Y-axis) as it moves in at least one of directions 144 and 160. In some embodiments, the tape 111 is configured to adhere to the surface of the nozzle plate 61 based on self-adhesion without any force applied to the tape 111 or print bar 62 along the Z-axis. In other words, when a lateral pulling force is applied to the tape along the X-axis and/or the Y-axis, the tape 111 is configured to adhere to the nozzle plate of the print bar 62 without any vertical force being applied to the tape and/or the print bar. As described above, the adhesion mechanism in the Z-axis is also referred to herein as the self-adhesive or self-supporting force of the tape to the nozzle plate of the print head of print bar 62. Furthermore, the amount and type of fluid (e.g., water 120) contained within compressible layer 300 may also be used to improve the adhesion of tape 111 to all nozzles of print bar 62, and to remove (also referred to herein as wiping) residues from the nozzles.

In some embodiments, based on self-adhesion, the tape 111 is configured to compensate for topographical differences between different nozzles of the print bar 62 and adhere to each nozzle of the print bar 62 to remove residue therefrom. In some embodiments, the adhesion mechanism is achieved by a multi-layer structure of the ribbon 111, as described in detail below in fig. 5.

In some embodiments, the distance between blanket 44 (which is taut and moves in the direction of movement) and print bar 62 (e.g., gap 141) is typically between about 1mm and 1.5mm during the printing operation, but in other embodiments gap 141 may be greater or less than the above-described range. Furthermore, the strip 111 has a thickness of about 0.1mm and is typically in physical contact with: (i) portion 170 (as shown in fig. 3A), or (ii) nozzles 166, 166a, and 166B (as shown in fig. 3B), or (iii) portion 172 (as shown in fig. 3C), and is located between print bar 62 and blanket 44.

As described above in fig. 2, the ribbon 111 moves within the gap 141 such that the thickness of the ribbon 111 is significantly smaller (e.g., between about 5 and 15 times) as compared to the gap 141. Further, as described above in fig. 3A, the width 184 of the ribbon 111 is sized such that the ribbon or any portion thereof does not cover the nozzles when the ribbon 111 is moved only in the direction 144. Further, as described above, the width 182 of the array of nozzles 166, 166a, and 166b is sufficiently small (e.g., about 12.9 mm) and the speed of movement of the web 111 in the direction 160 is sufficiently fast (e.g., about 8 meters per second) to end the wiping of the nozzles in about 50 milliseconds, which is generally shorter than the time interval that the seam portion 45 passes under the nozzles of the print bar 62.

In some embodiments, WA 200 moves web 111 between portions 170 and 172, and when seam portion 45 faces print bar 62, nozzles 166 do not jet printing fluid toward blanket 44, and web 111 wipes residues of printing fluid from nozzles 166.

In some embodiments, when at least a portion of seam portion 45 faces one or more nozzles 166, tape 111 covers one or more nozzles 166 to remove residues of printing fluid. As shown in FIG. 3B, when seam portion 45 is fully facing width 182, the entire width 182 of strip 111 is positioned over nozzle 166. Note that WA 200 is configured to move web 111 in both directions 144 and 160 as seam portion 45 approaches print bar 62 (as shown in fig. 3A) and faces print bar 62 (as shown in fig. 3B).

In some embodiments, processor 20 and/or controller 54 are configured to control the direction and speed of movement of ribbon 111, e.g., the speed in directions 144 and 160. The speed of web 111 in directions 144 and 160 controls the time that a given portion of web 111 contacts a given nozzle of print bar 62 for the wiping process.

Referring now to fig. 3C, the position of the web 111 relative to the print bar 62 and the seam portion 45 is shown. In some embodiments, after seam portion 45 of blanket 44 passes print bar 62 and continues to move toward other print bars 62 and/or drying station 64, WA 200 has completed wiping of nozzles 166 and moved web 111 to portion 170 of print bar 62. As shown in fig. 3C, the solid line 145 indicating the second rear end of the joint portion 45 moves in the moving direction and no longer faces the print bar 62. In some embodiments, image forming station 60 resumes jetting printing fluid from nozzles 166 toward blanket 44 in direction 171 to form the next image on blanket 44.

In some embodiments, the time interval shown in fig. 3A-3C is between about 20 milliseconds (msec) and 300msec as the strip 111 moves from portion 170 to portion 172 via nozzle 166. For example, when the blanket is moving in the direction of movement 94 at a speed of between about 2.5 m/s and 4 m/s, the time interval for moving the strip 111 between sections 170 and 172 is about 50msec.

In some embodiments, WA 200 is configured to move web 111 during the operating time of system 10 while system 10 ejects drops of printing fluid and forms an image (i.e., instant) on blanket 44. In addition, blanket 44 moves to receive an image from image forming station 60 while web 111 wipes residue from nozzles 166. In such embodiments, WA 200 of system 10 is configured to clean residues while system 10 continues the printing operation.

In principle, it is possible to maintain the printing operation of the system 10 and to perform the residue wiping in the maintenance mode. However, the maintenance mode reduces the productivity of the system 10, which does not print during maintenance. In some embodiments, based on the disclosed techniques, maintenance operations (e.g., removal of residues of printing fluid from nozzles 166) are performed on-the-fly as system 10 prints images on blanket 44.

In some embodiments, WA 200 continues to move web 111 only in direction 144 after seam portion 45 passes print bar 62, and when seam portion 45 again approaches print bar 62 (after completing the cycle of blanket 44 shown in fig. 1 above), WA 200 is configured to move web 111 in direction 161 opposite direction 160 so as to wipe nozzles 166, 166a, and 166b of print bar 62. In the example of fig. 3C, the arrow showing direction 161 is a dashed line to illustrate that web 111 moves in direction 161 only when seam portion 45 is proximate print bar 62, as described above. Note that in such an embodiment, the ribbon 111 moves in the reverse order, i.e., from fig. 3C to fig. 3A, such that the ribbon moves in direction 144 and direction 161. In other words, WA 200 is configured to move ribbon 111 in directions 144 and 160. Direction 144 is parallel to the long axis of the print bar and direction 160 is parallel to the short axis of the print bar 62. In this example, residue removal is arranged every time seam portion 45 passes adjacent print bar 62, also referred to herein as a cycle of blanket 44. In this example, (i) web 111 moves only in direction 144 when seam portion 45 is not adjacent print bar 62, and (ii) web 111 moves in both directions 144 and 160 when seam portion 45 passes adjacent print bar 62. Accordingly, web 111 moves back and forth between sections 170 and 172 and completes one back and forth movement in two cycles of blanket 44.

In some embodiments, WA 200 is configured to apply different motion profiles, e.g., a continuous motion profile and a discrete motion profile, as ribbon 111 is moved in directions 144 and 160. In the context of the present disclosure and in the claims, the term "continuous motion" refers to uninterrupted motion at a predetermined speed, and the term "discrete motion" refers to movement that occurs only at predetermined time intervals, which typically, but not necessarily, repeatedly occurs at a predefined frequency.

In the continuous motion profile WA 200, the ribbon 111 is moving in direction 144 at a relatively low speed (e.g., less than about 20 mm/sec). In the discrete motion profile WA 200, the ribbon 111 is moved in the direction 160 at a relatively high speed (e.g., greater than about 750 millimeters/second). As described above, the two motion profiles may be performed simultaneously or separately.

In some cases, blanket 44 may have a temperature of about 80 degrees celsius, while nozzles 166, 166a, and 166b may have a lower temperature, for example, between about 30 degrees celsius and 35 degrees celsius. In this case, printing fluid and other substances may evaporate from blanket 44 and condense and subsequently solidify on one or more of nozzles 166, 166a, and 166b, and may at least partially block one or more orifices of nozzles 166, 166a, and 166 b.

In some embodiments, web 111 may be used to cap nozzles 166, 166a, and 166b when image forming station 60 is in its non-operational mode or maintenance mode (e.g., no drops are applied to blanket 44). In such embodiments, WA 200 is configured to position web 111 to cover nozzles 166, 166a, and 166B, as shown in fig. 3B, such that web 111 prevents vapors and/or aerosols of printing fluid and other materials from adhering to nozzles 166, 166a, and 166B of print bar 62. In some embodiments, processor 20 and/or controller 54 are configured to control WA 200 to move in direction 144 (at any suitable speed) to continuously wipe the nozzles. In other embodiments, processor 20 and/or controller 54 are configured to control WA 200 to place web 111 in contact with the nozzles and to keep web 111 from moving in directions 144 and/or 160 to protect the nozzles from contamination by vapors or aerosols when image forming station 60 is not applying drops of printing fluid to blanket 44.

Note that the presence of water 120 in ribbon 111 increases the humidity between ribbon 111 and nozzles 166, 166a, and 166b, thereby preventing the residue of printing fluid from solidifying on the nozzles. This mechanism works in both cases, (i) when the web 111 is moving (e.g., in direction 144 and/or 160) and contacts the nozzles of the print bar 62, and (ii) when the web 111 is stationary and contacts the nozzles of the print bar 62. In other words, the humidity of the strip 111 prevents the printing fluid from solidifying on the nozzles.

In some embodiments, frequent wiping of the nozzles of each print bar 62 of system 10, such as every 10 seconds, or every 1 minute, or every 2 minutes, helps to maintain the specified function of the nozzles and reduces the frequency of maintenance operations in which system 10 does not print images. The inventors have found that using the disclosed techniques significantly reduces the amount of defects in the printed image. For example, when WA 200 is used and the disclosed techniques are applied, the number of missing nozzles and total blocked nozzles (when the orifices of the nozzles are fully blocked) and the number of offset nozzles (when the orifices of the nozzles are partially blocked) may decrease by one to two orders of magnitude over time.

In the context of the present disclosure and in the claims, the terms "blocking" and "clogging" are used interchangeably, and the terms "orifice of a nozzle" and "nozzle" are used interchangeably.

In other embodiments, the techniques described in this disclosure may be applied to direct printing systems mutatis mutandis. For example, when ink or other printing fluid is directly ejected onto a sheet or any other suitable substrate, the web 111 may be used to clean residue from the printing nozzles between (i) printing a first image on a first sheet and (ii) printing a second (similar or different) image on a second subsequent sheet.

In some embodiments, wiping of the nozzles of the system 10 may be performed at any suitable frequency and may be arranged per a predefined number of images and/or sheets or based on a predefined time interval (e.g., per a predefined number of minutes), or using any other suitable criteria defining a wiping frequency. In other words, when images are printed sequentially on multiple sheets, the printing system may wipe the nozzles for a short time interval after printing the images on a first sheet before starting printing the images on a second sheet that follows the first sheet. In addition, the same techniques can be used when printing images sequentially on a continuous substrate (such as a web). In such a process, nozzle cleaning (e.g., wiping of ink residues) may be performed when a portion or segment of the web between two successive images (one already printed image and the next to be printed image) is positioned very close to the printing nozzles. For example, when a portion of the continuous substrate between two successive images passes under the nozzle.

As described above, the cleaning frequency may be performed after each image or after every selected number of images. Note that also in the case of both direct printing described above (printing on a separate sheet, or printing on a continuous substrate), the wiping of the nozzles is performed during the printing process, without the need to stop the operation of the printing system, and without reducing the print output of the (direct) printing system. Furthermore, the same techniques may be used to wipe residue from printheads in other types of indirect printing systems, for example, the printing system may include a drum to transfer one or more images to a target substrate in lieu of or in addition to blanket 44.

Fig. 4 is a schematic illustration of a Wiping Assembly (WA) 200 according to an embodiment of the invention. In some embodiments, WA 200 includes a Mechanical Assembly (MA) 222 configured to move ribbon 111 in direction 140 from Tension Assembly (TA) 130, as shown in fig. 2 above. MA 222 is also configured to divert ribbon 111 for wiping nozzles 166, 166a, and 166b and portions 170 and 172 of print bar 62, as shown in fig. 3A-3C above.

In some embodiments, WA 200 also includes a Mechanical Assembly (MA) 255 configured to move ribbon 111 with MA 222 to wipe the nozzles and surfaces of print bar 62 as previously described. WA 255 is also configured to divert strip material 111 in direction 150 to Cleaning Station (CS) 100, as shown in fig. 2 above. MA 222 and MA 255 are described in detail below in inset diagrams 201 and 251, respectively.

In some embodiments, WA 200 includes a shaft 202 coupled between MA 222 and MA 255 and configured to rotate Clockwise (CW) and counterclockwise (CCW) to move the ribbon back and forth in directions 160 and 161, as described in fig. 3A-3C above. Note that WA 200 is configured to move ribbon 111 in the following manner: (i) Moving in direction 144 at first time intervals, which is typically performed at least as long as image forming assembly 60 applies drops of printing fluid to blanket 44 (when web 111 is positioned over portions 170 and 172), and (ii) moving alternately in directions 160 and 161 at second shorter time intervals (e.g., about 50msec in each direction 160 and 161) for wiping residues of printing fluid from nozzles 166, 166a and 166b as web 111 passes between portions 170 and 172. For example, the length of ribbon 111 may be between about 2 meters and 4 meters, and the speed of movement in direction 144 may be about 10 millimeters/second or between about 1 millimeter/second and 20 millimeters/second, as described above. The second time interval is about 50msec and the speed of movement of the ribbon 111 in the direction 160 is between about 800 mm/sec and 900 mm/sec. Thus, the ratio between the first time interval and the second time interval may vary and may depend on, among other parameters, the wiping frequency (defined by the number of images), the length and speed of the ribbon 111.

In some embodiments, the ratio between the speeds of movement of ribbon 111 in directions 160 and 144 (also referred to herein as the speed ratio) may be between about 8 (e.g., 800/100) and 900 (e.g., 900/1). In other embodiments, the ribbon 111 may be moved using any other suitable speed ratio between about 5 and 10000.

In one embodiment of the disclosed technique, wiping of the nozzles is performed only as the seam portion passes through the image forming station 60. In this embodiment, web 111 is moved in direction 160 in one cycle of blanket 44 (as shown in FIG. 1 above), then web 111 is moved in the opposite direction 161 in the next cycle of blanket 44, and this alternating cycle repeats as long as image forming station 60 is in operation (e.g., continuing to apply drops to moving blanket 44. Furthermore, in such embodiments, the first time interval overlaps with one or more second time intervals (typically more than one).

Referring now to the illustration 201, the structure of the MA 222 is shown in detail. In some embodiments, MA 222 includes motor 204, typically a servo brushless motor or any other suitable motor, configured to rotate belt 209 between pulleys 206 and 208 for rotating shaft 202.

In some embodiments, MA 222 includes gear 226 and track 224, both of which include respective saw tooth structures that are interwoven with each other. Gear 226 is configured to rotate with shaft 202 to move rail 224 back and forth in linear motion along direction 220, which is generally parallel to direction 140 and, in this example, also parallel to directions 160 and 161. Note that when the shaft 202 and gear 226 rotate clockwise, the track 224 moves in the direction 140, and when the shaft 202 and gear 226 rotate counterclockwise, the track 224 moves in a direction opposite the direction 140.

In some embodiments, MA 222 includes robotic arm 216 configured to move with track 224. Reciprocating pulleys 210, including rollers 211, 212, 213, and 214, are mounted on arm 216 by their respective hinges and are configured to move ribbon 111 from moving in direction 140 (before MA 222) to moving in direction 144 and in directions 160 and 161 (after MA 222), as shown in fig. 3A-3C above.

In some embodiments, ribbon 111 moves into roller 211 along direction 140 and turns to direction 144 as it enters roller 212. Subsequently, the web 111 enters rollers 213 and 214 for maintaining a specific tension of the web 111 while wiping the residues of printing fluid from the nozzles 166, 166a and 166 b.

Referring now to inset 251, MA 255 is shown. In some embodiments, MA 255 includes gears 246 and rails 244, which are similar to gears 226 and rails 224 of MA 222. Gear 246 is coupled to and rotates with shaft 202 to move track 244 in direction 240 generally parallel to direction 220. The reciprocating pulley 230 is mounted on a robotic arm 236 that moves back and forth in a direction 240 via a track 244 to alternately move the roller 111 in directions 160 and 161. Note that gears 226 and 246 are each coupled to shaft 202 such that when processor 20 and/or controller 54 control motor 205 to rotate a belt (CW or CCW), tracks 224 and 244 move together to move ribbon 111 in directions 160 or 161, as described above. In addition, when seam portion 45 is not immediately adjacent print bar 62, the web moves in direction 144, but not in directions 160 or 161.

In some embodiments, the reciprocating pulley 230 includes a plurality of rollers, in this example rollers 232 and 233 configured to maintain a specified tension applied to the ribbon 111 as it moves in the direction 144, and a roller 234 for diverting the direction of the ribbon 111. The reciprocating pulley 230 may include additional rollers, such as roller 235 shown in the general view of fig. 4, configured to divert the ribbon 111 for movement in the direction 150.

In some embodiments, MA 255 includes an arm 237 coupled between arm 236 and roller 234 and configured to adjust the position of roller 234. In some embodiments, MA 222 may include an arm (which is almost completely hidden in illustration 201) similar to arm 237 and configured to adjust the position of roller 212. Such an arm may be used to replace the ribbon 111 during maintenance operations of the WA 200, or to adjust the tension applied to the ribbon 111, or to adjust the direction of movement of the ribbon 111, or for any other suitable function.

In other embodiments, the motor 204 of the MA 222 may be directly coupled to the pulley 208 for rotating the gear 226 and the shaft 202.

The particular configuration of WA 200 is shown by way of example to illustrate certain problems addressed by embodiments of the present invention and to demonstrate the application of these embodiments in enhancing the performance of such systems. However, embodiments of the present invention are in no way limited to this particular kind of example of a wiper assembly, and the principles described herein may be similarly applied to any other kind of mechanism for controlling the removal of residues of printing fluid from nozzles of the system 10 or from nozzles and/or other components of other kinds of printing systems.

Fig. 5 is a schematic cross-sectional view of a ribbon 111 according to an embodiment of the invention. In some embodiments, the tape 111 includes a core layer 303 made of a textile, commercially known as a scrim, made of cotton or linen, and configured to act as the backbone of the tape 111 to improve its mechanical properties. For example, core 303 is configured to increase the tensile strength of ribbon 111 against the tension applied by WA 200 and to prevent plastic deformation and/or tearing of ribbon 111.

In some embodiments, the core layer 303 comprises a woven array of fibers, and in this example, the array of fibers is arranged in a cross-shaped configuration, or interwoven using any other suitable configuration. The core 303 is configured to provide dimensional stability to the ribbon 111 when the WA 200 applies tension to the ribbon 111.

In some embodiments, the fibers of the core layer 303 may include a mixture of polyester and water-based polyurethane.

In some embodiments, ribbon 111 includes compressible layer 300 configured to contain a fluid, such as water 120 and other fluids described herein. The compressible layer 300 has a total thickness of between about 300 μm and 900 μm, or any other suitable thickness, in this example about 600 μm. Note that when a force, such as a compressive force, is applied to ribbon 111, for example, in extrusion assembly 110, particularly in the Z-axis, the thickness of compressible layer 300 decreases and at least some fluid is forced out of compressible layer 300. Such an embodiment is described in detail in fig. 6 below, for example.

In some embodiments, the compressible layer 300 may include a front layer 302 and a back layer 304, both including three-dimensionally entangled polyester microfibers and configured to absorb and contain the aforementioned fluids. In the context of the present disclosure and in the claims, the term ultrafine fibers refers to fibers having a suitable diameter (e.g., between about 2 μm and 6 μm).

In other embodiments, compressible layer 300 may include any other suitable type of material, such as a polyethylene-based material.

In some embodiments, the microfibers of the compressible layer 300 may be impregnated with a water-based polyurethane in the spaces between the microfibers, thereby imparting a soft and highly flexible texture to both the front layer 302 and the back layer 304 of the compressible layer 300. In some embodiments, microfibers are configured to reduce or prevent static electricity at least as web 111 moves relative to print bar 62 and/or blanket 44.

In some embodiments, core layer 303 may be integrated with compressible layer 300 using any suitable technique, such as by applying water pressure and merging between compressible layer 300 and core layer 303, or by coupling between core layer 303 and the front and back layers using any suitable technique. In the example of fig. 5, the thickness of front layer 302 is between about 400 μm and 500 μm, while the thickness of back layer 304 is between about 200 μm and 100 μm, such that the combined thickness of layers 302 and 304 remains at about 600 μm. Note that in this example, layers 302 and 304 constitute compressible layer 300 with core layer 303 therebetween.

In some embodiments, the tape 111 includes a wipe layer 301 coupled to a surface of the front layer 302 using any suitable coupling technique. In this example, layer 301 is made of a suitable elastic material, typically a polymer having an ultra-low fiber density. In other embodiments, layer 301 may include any other material suitable for wiping residues of printing fluid from nozzles 166, 166a, and 166 b. In some embodiments, layer 301 has a thickness between about 50 μm and 500 μm, in this example, layer 301 has a thickness of about 200 μm.

In some embodiments, ribbon 111 comprises a polyethylene base layer, referred to herein as layer 305, having any suitable thickness between about 10 μm and 200 μm. In this example, layer 305 comprises or is made of polyethylene terephthalate (PET) (commercially known as polyester) and has a thickness of about 35 μm.

In some embodiments, layer 305 is coupled to back layer 304 of compressible layer 300 using any suitable technique, such as gluing by applying a thermal Polyurethane (PTU) or any other suitable type of glue (not shown) between layers 304 and 305.

In some embodiments, the above-described multilayer structure provides sufficient tensile strength to the ribbon 111 such that the ribbon 111 does not undesirably elongate by undergoing plastic deformation or creep of the material. Note that core layer 303 and layer 305, which is made of PET, increase the mechanical strength of ribbon 111 to remain taut and withstand the tension applied by WA 200. In other words, layers 303 and 305 tighten ribbon 111 in the X and Y axes and increase the resistance of ribbon 111 to the tension applied by WA 200.

As described above in fig. 3B, the tape 111 is configured to compensate for topographical differences between different nozzles (e.g., nozzles 166a and 166B) of the print bar 62 and is adhered to each nozzle of the print bar 62 to remove residue therefrom. In some embodiments, the above-described multi-layer structure provides the ribbon 111 with the ability to compensate for the above-described topographical differences. In this example, the combination of (i) layer 301 (which is resilient), (ii) compressible layer 300 (which acts as a reservoir of water (e.g., water 120) received from CS 100), and (iii) layer 305 is configured to conform to and compensate for topographical differences (e.g., in the Z-axis) between the different printheads of print bar 62. The adhesion of water 120, the flexibility of layer 301, and the tensile strength and flexibility of layer 305 provide self-adhesion to ribbon 111, allowing contact with nozzle plate 61 and wiping of residue from all of the nozzles (e.g., nozzles 166, 166a, and 166 b) of print bar 62.

In some embodiments, layer 305 is configured to seal against web 111 in order to prevent undesired leakage or dripping of water 120 from web 111 to surface blanket 44. Such dripping may cause, among other things, undesirable defects or other distortions in the image formed on blanket 44. Furthermore, by retaining the desired amount of water 120 within compressible layer 300, layer 305 enhances the self-adhesive force of ribbon 111, as the adhesive force of water 120 helps layer 301 (which is wet or damp) adhere to the nozzle plate of print bar 62, and more specifically to nozzles 166, 166a, and 166b.

In some embodiments, when print bar 62 is idle (e.g., no drops of printing fluid are applied to blanket 44), layer 305 also seals web 111 when the nozzles are capped, as described above in fig. 3C. Note that a sufficient amount of water 120 within the ribbon 111 is necessary to cap the process and/or procedure and to dissolve any residue that forms on the nozzles of the print bar 62.

The specific construction and multilayer structure of the strip 111 is shown by way of example to illustrate certain problems addressed by embodiments of the present invention and to demonstrate the use of these embodiments in enhancing the performance of such systems. However, embodiments of the present invention are in no way limited to this particular kind of example multilayer structure, and the principles described herein may similarly be implemented using other kinds of materials, number of layers, thickness of each layer, and mechanical, physical, and chemical properties of each layer and stacked layers. Furthermore, the embodiments described above in relation to web 111 may be applied to any other kind of printing system.

Fig. 6 is a schematic cross-sectional view of a ribbon 111 being extruded in an extrusion assembly 110, according to an embodiment of the present invention. In some embodiments, the extrusion assembly 110 includes drums 112 and 114 described above in fig. 2. In this example, roller 114 rotates clockwise as indicated by arrow 311 and drum 112 rotates counterclockwise as indicated by arrow 312.

In some embodiments, at least the compressible layer 300 is soaked with water 120 and has a thickness of about 600 μm or even higher due to the volume captured by the water 120 when the strip 111 is pulled from the WC 122 f. In some embodiments, the compressible layer 300 is configured to contain about 300 grams per square meter (g/m) when soaked ² ) To 950g/m ² Is added to the water 120. In this example, compressible layer 300 contains about 575g/m ² 。

In some embodiments, the thickness of compressible layer 300 is reduced to any suitable thickness between about 150 μm and 350 μm as ribbon 111 is inserted between drums 112 and 114. In this example, the thickness of the compressible layer 300 is reduced to a thickness 310 of about 250 μm, and the amount of water 120 contained within the compressible layer 300 is reduced to about 225g/m ² 。

In other words, in this example, approximately 60% of the water 120 is extruded from the ribbon 111. Note that the ribbon 111 is flexible, and thus, after the ribbon 111 exits from the extrusion assembly 110, the cavities within the compressible layer 300 (and other layers) of the ribbon 111 are typically filled with an environmental fluid, such as, but not limited to, air surrounding the extrusion assembly 110. Further, as web 111 moves between blanket 44 and image forming station 60, compressible layer 300 (and other layers) of web 111 are configured to absorb aerosols and vapors of printing fluid present between blanket 44 and print bar 62.

Based on the above embodiment, when moving along the bottom portion of the nozzle plate within the gap between blanket 44 and image forming station 60 (e.g., gap 141 shown in fig. 2 above), ribbon 111 is configured to perform at least one of the following operations: (i) all nozzles adhered to print bar 62 and moving in directions 144 and/or 160 to wipe residue of printing fluid from nozzles 166, 166a, and 166b, (ii) absorb and contain various types of vapors and aerosols that may undesirably deposit on one or more of nozzles 166, 166a, and 166b, (iii) retain some humidity on the surfaces of nozzles 166, 166a, and 166b, and portions 170 and 172 of print bar 62 to prevent undesirable deposition and/or solidification of material around print bar 62, (iv) buffer between nozzles 166, 166a, and 166b and the aforementioned environment, particularly when print bar 62 is not applying droplets of printing fluid to blanket 44 (e.g., when both print bar 62 and system 10 may be in idle and/or standby positions), and (v) remove the aforementioned residue and other contaminants in water reservoir 122 of cleaning station 100.

In some embodiments, processor 20 and/or controller 54 are configured to control the amount of water 120 remaining in ribbon 111 after extrusion by controlling the distance between drums 112 and 114 (also referred to herein as rollers). For example, the distance between drums 112 and 114 is controlled by applying a force in direction 315, such as by piston 117 and shaft 119 described above in fig. 2.

Fig. 7A is a schematic illustration of a Wiping Assembly (WA) 400 shown in top view, according to another embodiment of the invention. In some embodiments, WA 400 may be used in system 10 in addition to or in place of WA 200 described above in fig. 2-4.

In some embodiments, WA 400 includes a track 402, which may have a longitudinal axis parallel to the Y-axis or in any other orientation. WA 400 includes a slider 404 configured to move in the Y-axis and slide along track 402.

In some embodiments, WA 400 includes blade 406, which is made of a lightweight and durable material (such as tungsten carbide), and is coupled to slider 404 using an adhesive bond, for example.

In some embodiments, WA 400 includes a wiper pad 408 coupled to blade 406, for example, by gluing. Wiper pad 408 is made of any material suitable for removing residues of printing fluid from nozzles 166, 166a, and 166b of print bar 62.

In some embodiments, blade 406 of WA 400 is configured to push wiper pad 408 toward nozzles 166, 166a, and 166B of print bar 62 as it moves along print bar 62 in order to compensate for topographical differences (e.g., in the Z-axis) between different printheads of print bar 62, as described above in fig. 3B and 5.

In some embodiments, after wiping nozzles 166, 166a, and 166b of print bar 62, wiper pad 408 may be cleaned using any suitable technique to remove the foregoing residue.

Fig. 7B is a schematic illustration of WA 400 shown in bottom view in accordance with another embodiment of the present invention.

In some embodiments, blade 406 has a first edge coupled to slider 404 and a second edge coupled to wiper pad 408. This configuration allows the second edge to move along the Z-axis to conform to the topography of the print head of print bar 62.

The particular construction of WA 400 is shown by way of example to illustrate certain problems addressed by embodiments of the present invention and to demonstrate the application of these embodiments in enhancing the performance of such systems. However, embodiments of the present invention are in no way limited to this particular type of exemplary wiping assembly 400, and the principles described herein may be similarly applied to any other type of residue removal apparatus.

In other embodiments, the wiper pad may be mounted on a cable (not shown), with or without a blade or any other suitable carrier. In such embodiments, rollers and/or pulleys and/or drums and/or any other suitable type of equipment may be used to move the cable.

Fig. 8 is a flow chart schematically illustrating a method for removing residue from nozzles 166, 166a, and 166b of one or more print bars 62 of system 10, in accordance with an embodiment of the present invention.

The method begins with a printing step 500 in which droplets of a printing fluid are applied from one or more first nozzles and a second nozzle to a moving substrate to create an image thereon. In this example, the moving substrate includes a blanket 44, which is an intermediate transfer member. In other embodiments, the moving substrate may comprise a target substrate, such as one or more sheets or continuous webs, that receive the image directly from the nozzles of the print bar. Such embodiments may be implemented in a direct printing system.

In some embodiments, a first nozzle may be positioned in a first print bar 62 and a second nozzle may be positioned in a second, different print bar 62 of the system 10. Note that each print bar 62 has an individual WA 200 that includes an individual strip 111 for wiping residue from the nozzles of the respective print bar. In the context of this specification, the first WA 200 is configured to wipe nozzles of the first print bar 62, and the second WA 200 is configured to wipe nozzles of the second print bar 62.

In a first residue removal step 502, processor 20 and/or controller 54 moves web 111 of second WA 200 (or any other type of residue removal assembly) for removing residues from one or more second nozzles (e.g., nozzles 166, 166a, and 166b of a second print bar) while a first nozzle (e.g., of a first print bar) applies printing fluid and a substrate (e.g., blanket 44) moves.

Note that steps 500 and 502 may be performed simultaneously. In some embodiments, web 111 of second WA 200 wipes residues of printing fluid from one or more second nozzles of second print bar 62 of system 10 as one or more first nozzles of first print bar 62 of system 10 apply droplets of printing fluid to blanket 44. For example, the nozzles of the magenta print bar may apply magenta ink to blanket 44 while WA 200 of the cyan print bar may move web 111 in both directions 144 and 160 to wipe the residue of cyan ink from the nozzles of the cyan print bar. As shown in fig. 3A-3C above, wiping of the nozzles of the cyan print bar may be performed while seam portion 45 is positioned between blanket 44 and the cyan print bar (e.g., shown as print bar 62 in fig. 3A-3C above).

In a residue cleaning step 504, processor 20 and/or controller 54 are configured to move web 111 carrying residues removed from nozzles of the cyan print bar to a cleaning station (e.g., CS 100) to remove residues from web 111 while at least one of the magenta and cyan nozzles applies drops of printing fluid to blanket 44.

In other embodiments, WA 200 may include two drums (not shown) instead of cleaning residue from strip 111. The first drum provides a clean web 111 for wiping residue from the print bar 62 and the second drum receives the web 111 after wiping residue from the print bar 62. Note that the clean ribbon may be moved through a reservoir of cleaning fluid, such as water 120, and a squeeze assembly (e.g., squeeze assembly 110) for containing a predetermined amount of water 120 within the compressible layer 300 of the ribbon 111. As shown in fig. 2 and 5 above, the water contained within compressible layer 300 may be used to adhere tape 111 to all nozzles of print bar 62 and to remove residue from the nozzles.

In a second residue removal step 506 that ends the method, processor 20 and/or controller 54 moves web 111 of WA 200 (or any other type of residue removal assembly) to remove residues from one or more first nozzles (e.g., nozzles of a magenta print bar) while a second nozzle (e.g., nozzles of a cyan print bar) applies a printing fluid (e.g., cyan ink) to blanket 44, which is moving to create an ink image.

In the above-described embodiment, each print bar 62 has an individual WA 200 such that as seam portion 45 passes between a given print bar 62, a given WA 200 of a given print bar 62 wipes residues of printing fluid from the nozzles of a given print bar 62 while the nozzles of one or more of the other print bars 62 (e.g., nozzles 166, 166a, and 166 b) continue to apply printing fluid to blanket 44 according to the printing scheme of the particular image formed on blanket 44.

Accordingly, it should be appreciated that steps 500-506 of the method depicted in FIG. 8 may be performed in a plurality of cycles. These cycles may be performed at least as long as image forming system 60 applies any type of drop (such as, but not limited to, ink) to blanket 44. Further, one or more of steps 500-506 may be performed concurrently.

For example, in one embodiment, the residue wiping of step 502 may be performed in one portion of the web 111 while another portion of the web 111 is cleaned as described in step 504. In another embodiment, residue wiping may be performed on first print bar 62 while one or more nozzles of one or more of the other print bars 62 of system 10 apply the respective printing fluid to blanket 44, as described in steps 502 and 506 of the method.

In some embodiments, the techniques disclosed in the method of fig. 8 and described in detail above in fig. 2-6 improve the productivity of system 10 by performing maintenance on-the-fly (i.e., when system 10 prints images on blanket 44 and/or transfers images to a target substrate, such as, but not limited to, sheet 50).

Fig. 9 is a flowchart schematically illustrating a method for forming an image and removing residues from the nozzles 166, 166a and 166b of the print bar 62 according to an embodiment of the present invention.

The method begins with a substrate movement step 600 in which a suitable intermediate or target substrate is moved along a movement direction 94. In this example, the substrate includes a blanket 44 having one or more first portions, each of which is intended to receive ink drops to form the aforementioned image thereon, as described in detail in fig. 1 above, for example.

In some embodiments, blanket 44 also includes one or more second portions that are alternately positioned between the first portions. The second portion does not receive ink drops or other printing fluid and is not intended to form an ink image thereon. In such embodiments, one of the second portions may include a seam portion 45.

Note that due to the alternating arrangement of the first and second portions, the first and second portions alternately pass adjacent print bar 62 as blanket 44 moves in movement direction 94. In other words, as blanket 44 moves in direction 94, the first portion faces print bar 62 for a first time interval and the second portion faces print bar 62 for a second time interval after the first time interval. This sequence repeats (along the endless loop of blanket 44) as long as blanket 44 moves in movement direction 94, such that the next first portion faces print bar 62 and subsequently the next second portion faces print bar 62.

In image forming step 602, as blanket 44 is moved in direction of movement 94 and one of the first portions of blanket 44 faces print bar 62, nozzles 166, 166a, and 166b apply (e.g., eject) printing fluid (in this example, ink drops) to a surface facing the first portion of print bar 62.

In a residue removal step 604, while blanket 44 is moving in direction 94 and one of the second portions of blanket 44 faces nozzles 166, 166a, and 166B of print bar 62, processor 20 and/or controller 54 moves web 111 at least in direction 160 (e.g., using the discrete motion profile described above in fig. 3A-3B), and typically also in direction 144 (e.g., using the continuous motion profile described above in fig. 3A-3B), to remove residues of printing fluid from nozzles 166, 166a, and 166B of print bar 62. Note that step 604 may be performed using any suitable frequency, for example blanket 44 may have eleven (11) first portions and eleven (11) second portions.

In the first embodiment, step 604 may be performed when each of the second portions faces print bar 62 (i.e., after each image is formed, and ten times for each cycle of blanket 44, as defined when seam portion 45 passes adjacent print bar 62). In a second embodiment, step 604 may be performed when every fifth second portion faces print bar 62 (i.e., typically occurs twice for each cycle of blanket 44). In a third embodiment, step 604 may be performed only when seam portion 45 is facing print bar 62 (i.e., occurs once for each cycle of blanket 44).

Additionally or alternatively, step 604 may be performed using any other suitable arrangement or frequency, such as every predefined time interval. For example, every about ten seconds, or about thirty seconds, or about five minutes, or about one hour. Note that the frequency may be constant or may vary in conjunction with other operations performed on the system 10, for example, between Preventative Maintenance (PM) operations. For example, a relatively low frequency in the first day after the PM (e.g., every ten minutes), and a high frequency in the last day before the next PM (e.g., every five minutes).

In other embodiments, WA 200 is configured to position web 111 over the nozzles of print bar 62 when print bar 62 is in the idle position (e.g., no ink is applied to blanket 44) so as to prevent solidification of printing fluid residue or any other undesirable matter on nozzles 166, 166a, and 166b and/or on the orifices thereof.

In a tape removal step 606 that ends the method, WA 200 moves tape 111 away from the nozzles of print bar 62. In some embodiments, step 606 is typically performed when blanket 44 is moved and one of the first portions faces a nozzle of print bar 62 to receive ink drops and form an image, such as described above in fig. 3A-3B.

Although the embodiments described herein relate primarily to digital printing systems having intermediate transfer members, the methods and systems described herein may also be used in other applications, such as in any kind of direct printing system that uses inkjet nozzles for two-dimensional and three-dimensional printing applications.

It will thus be appreciated that the embodiments described above are cited by way of example, and that the present application is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present application includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art. Documents incorporated by reference into this patent application should be considered as an integral part of the present application, but in the event that any terms defined in these incorporated documents conflict with definitions made explicitly or implicitly in this specification, only the definitions in this specification should be considered.

Claims

1. A system having a printing position and a non-printing position, the system comprising:

an image forming station comprising at least a nozzle plate having one or more nozzles configured to apply drops of a printing fluid to a surface of one or more substrates to produce one or more images thereon; and

a wiper assembly positioned at least partially in a gap between the nozzle plate and the one or more substrates and configured to (i) make physical contact with the nozzle plate and (ii) remove residue of the printing fluid from at least one of the nozzles when the system is in the printing position.

2. The system of claim 1, comprising: (i) A transport assembly configured to move the one or more substrates relative to the nozzle plate; and (ii) a processor configured to control: (a) The transport assembly moves the one or more substrates, and (b) the wiping assembly removes the residue from at least one of the nozzles while the one or more substrates are moved by the transport assembly.

3. The system of claim 2, wherein in the print position the processor is configured to maintain a constant throughput of producing the one or more images, including during removal of the residue by the wiper assembly.

4. The system of claim 2, wherein the one or more substrates comprise an Intermediate Transfer Member (ITM) configured to receive the droplets for producing the one or more images and transfer the one or more images to a target substrate, and wherein the transport assembly comprises an ITM module configured to move the ITM relative to the image forming station to produce the one or more images.

5. The system of claim 2, wherein the one or more substrates comprise one or more sheets or a continuous web, and wherein the transport assembly comprises a substrate transport module configured to move the one or more sheets or the continuous web relative to the image forming station to produce the one or more images thereon.

6. The system of claim 1, wherein the image forming station comprises at least a first print bar having one or more first nozzles and a second print bar having one or more second nozzles, and wherein in the print position the wiper assembly is configured to remove the residue from at least one of the first nozzles while at least one of the second nozzles is applying the liquid droplets.

7. The system of claim 1, wherein the gap between the nozzle plate and the one or more substrates is preserved while (i) applying the droplets and (ii) removing the residue at the printing location.

8. The system of any one of claims 1-7, wherein the wiping assembly comprises a wiping element configured to remove the residue of the printing fluid by wiping the residue from at least one orifice of at least one of the nozzles.

9. The system of claim 8, wherein the wiping element comprises a strip configured to hold a cleaning fluid and make physical contact with the nozzle plate by self-adhesion to the nozzle plate.

10. The system of claim 9, wherein the ribbon comprises: (a) A residue removal layer configured to remove a residue of printing fluid from the nozzle plate, and (b) a compressible layer coupled to the residue removal layer and configured to: (i) Absorbing and containing a cleaning fluid when in contact with the cleaning fluid, and (ii) releasing at least a portion of the cleaning fluid when a compressive force is applied to the strip material.

11. The system of claim 10, wherein the wiper assembly is configured to position the tape over at least one of the nozzles when the image forming station is not applying the drops to the substrate.

12. The system of claim 11, wherein the tape is configured to cover the nozzle, and wherein the compressible layer is configured to maintain humidity in the tape so as to prevent the residue or another substance on the nozzle from solidifying.

13. The system of claim 9, wherein the ribbon is configured to: (i) Maintaining a predetermined amount of the cleaning fluid for wiping the residue disposed on the nozzles, and (ii) absorbing additional residue of the printing fluid not disposed on the nozzles.

14. The system of claim 11, wherein the additional residue comprises at least one of a vapor and an aerosol of the printing fluid, and wherein the wiping element is configured to absorb at least one of the vapor and aerosol of the printing fluid not disposed on the nozzle.

15. The system of claim 8, wherein the wiper assembly is configured to move the wiper element within a gap between the nozzle and the one or more substrates for at least one of: (i) Wiping the residue disposed on at least one of the nozzles, and (ii) absorbing additional residue of the printing fluid located between the nozzle and the one or more substrates.

16. The system of claim 8, wherein the wiper assembly is configured to move the wiper element in a first direction during a first time interval and to move the wiper element in a second direction during a second time interval.

17. The system of claim 16, wherein the nozzles are arranged along a first axis and across a second axis, and wherein at least one of: (i) The first direction is parallel to the first axis, and (ii) the second direction is parallel to the second axis.

18. The system of claim 16, wherein the one or more substrates move in a direction of movement, wherein the first direction is parallel to the direction of movement, and wherein the second direction is orthogonal to the direction of movement.

19. The system of claim 16, wherein the processor is configured to control the wiper assembly to move the wiper element in at least one of the first and second directions as at least one of the nozzles ejects the printing fluid toward the one or more substrates.

20. The system of claim 16, wherein the first time interval is greater than the second time interval.

21. The system of claim 16, wherein the first time interval overlaps one or more second time intervals.

22. The system of claim 16, wherein the first direction is orthogonal to the second direction.

23. The system of claim 16, wherein the processor is configured to control the wiper assembly to (i) move the wiper element in the first direction at a first speed, and (ii) move the wiper element in the second direction at a second speed different from the first speed.

24. The system of claim 23, wherein the second speed is at least five times greater than the first speed.

25. The system of claim 16, wherein the one or more substrates comprise a flexible substrate having a first portion for receiving the one or more printing fluids and a second portion located between the first and second images, and wherein the processor is configured to control (i) the flexible substrate to move in a direction of movement, and (ii) the wiping element to move in the second direction parallel to the direction of movement of the flexible substrate when the second portion passes adjacent one or more nozzles.

26. The system of claim 25, wherein the processor is configured to control the wiper assembly to move the wiper element in the second direction parallel to the direction of movement of the flexible substrate when the one or more nozzles are not applying the liquid droplets.

27. The system of claim 25, wherein at least a portion of the wiping element is positioned within a gap between at least one of the nozzles and the second portion during at least a portion of the second time interval.

28. The system of claim 25, wherein the processor is configured to: (i) Controlling the image forming station to apply the liquid droplets when the first portion passes adjacent the one or more nozzles and not apply the liquid droplets when the second portion is adjacent the one or more nozzles, and (ii) controlling the wiping assembly to move the wiping element to wipe the residue from the nozzles when the processor controls the one or more nozzles not to apply the liquid droplets.

29. The system of claim 25, wherein the flexible substrate comprises an intermediate transfer member configured to receive the liquid droplets to form an image at the image forming station and transfer the image to a target substrate.

30. The system of claim 25, wherein the second portion is configured to be connected between two ends of the first portion so as to form a loop comprising the first portion and the second portion.

31. The system of claim 16, wherein the one or more substrates comprise a first sheet configured to receive the first image and a second sheet configured to receive the second image, and wherein the processor is configured to: the wiping assembly is controlled to move the wiping element in the second direction after the first image is formed and before the second image is formed while at least one of the first sheet and the second sheet is moved within the system.

32. The system of claim 8, comprising a cleaning system configured to remove one or more of the residues from the wiping element.

33. The system of claim 1, wherein the image forming station comprises one or more printheads, each printhead comprising one or more of the nozzles, and the system comprises a substrate transport module configured to move the substrate in a printing direction to form the image thereon, wherein the one or more printheads have a first axis parallel to the printing direction and a second axis perpendicular to the printing direction, and wherein the wiping assembly is configured to remove the residue from the nozzles of at least one of the printheads by moving a wiping element along the first axis of the one or more printheads.

34. The system of claim 33, wherein the wiper assembly is configured to remove the residue from at least one of the nozzles while moving the wiper element along the second axis of the printhead.

35. The system of claim 33, wherein the wiper assembly is configured to remove the residue from at least one of the nozzles while the substrate transport module moves the substrate in the printing direction.

36. The system of claim 33, wherein the wiper assembly is configured to remove the residue from at least one of the nozzles when the nozzles are not applying the droplets to the substrate.

37. The system of claim 33, wherein at least one of the one or more printheads comprises a nozzle plate having a first portion and a second portion without nozzles and a third portion between the first portion and the second portion and including the nozzles, and wherein the wiper assembly is configured to move the wiper element from the first portion through the third portion to the second portion at least along the first axis.

38. The system of claim 37, wherein the wiper assembly is configured to move the wiper element along the second axis when the wiper element is positioned over the first or second portion.

39. The system of claim 37, wherein the wiper assembly is configured to continuously move the wiper element back and forth between the first and second sections along the first axis at a predetermined frequency.

40. The system of claim 39, wherein the substrate has a plurality of first portions and a plurality of second portions alternately positioned along the substrate in the direction of movement, wherein the image forming stations are configured to form a plurality of images on the plurality of first portions, respectively, when each of the first portions faces the image forming station, wherein the wiping assembly is configured to move the wiping element back and forth along the first axis when the second portions face the image forming station, and wherein the predetermined frequency comprises a discrete number of the second portions facing the image forming station.

41. The system of claim 39, wherein the predetermined frequency is defined by a time interval.

42. The system of claim 39, wherein the substrate comprises a flexible substrate having a first end and a second end coupled by a seam portion to form a loop, wherein the flexible substrate moves in the printing direction in cycles, each of the cycles being defined as when the seam portion faces the image forming station, and wherein the predetermined frequency comprises a discrete number of the cycles.

43. The system of claim 33, wherein the wiper assembly is configured to cause the wiper element to: (i) Moving along the first axis using a first motion profile and moving along the second axis using a different second motion profile.

44. The system of claim 33, wherein the first motion profile comprises a continuous motion profile and the second motion profile comprises a discrete motion profile.

45. A strip material, comprising:

a residue removal layer configured to remove residues of printing fluid from one or more nozzles of the printing system; and

a compressible layer coupled to the residue removal layer and configured to: (i) Absorbing and containing a cleaning fluid when in contact with the cleaning fluid, and (ii) releasing at least a portion of the cleaning fluid when a compressive force is applied to the strip material.

46. The tape of claim 45, wherein the one or more nozzles are formed in a nozzle plate, and wherein the residue removal layer is configured to receive at least a portion of the cleaning fluid from the compressible layer and self-adhere to the nozzle plate to make physical contact with the one or more nozzles.

47. The tape according to any one of claims 45 and 46, comprising a core layer coupled to the compressible layer and configured to tighten the tape in a given plane when tension is applied to the tape.

48. The tape of claim 47, wherein the core layer is implemented within a fluid-containing layer such that the fluid-containing layer has a first outer surface and a second outer surface facing each other, and the core layer is positioned between the first surface and the second surface.

49. The tape of claim 48, wherein the first outer surface is coupled to the residue removal layer and the tape comprises a polyethylene base layer coupled to the second outer surface of the fluid-containing layer and configured to perform at least one of: (i) Tightening the strip in the given plane when the tension is applied to the strip, and (ii) retaining at least a portion of the cleaning fluid within the fluid-containing layer when a compressive force is not applied to the strip.

50. The tape according to claim 49, wherein the polyethylene base layer comprises polyethylene terephthalate (PET).

51. The tape according to claim 49, wherein the tape is moved in at least one of a first direction and a second direction parallel to the given plane, and wherein the core layer and the polyethylene base layer are configured to tighten the tape in the first direction and the second direction.

52. The tape of claim 49, wherein the printing system comprises a first nozzle having a first print residue and a second nozzle having a second print residue, and wherein at least one of the residue removal layer and the fluid-containing layer is configured to compensate for topography differences between the first nozzle and the second nozzle so as to adhere between (i) the residue removal layer and (ii) at least the first nozzle and the second nozzle to remove the first print residue and the second print residue.

53. A method, comprising:

in a system having a printing position and a non-printing position, droplets of a printing fluid are applied to a surface of one or more substrates using one or more nozzles of a nozzle plate to produce one or more images thereon; and

Applying a wiper assembly positioned at least partially in a gap between the nozzle plate and the one or more substrates when the system is in the printing position to: (i) Physical contact with the nozzle plate, and (ii) removal of residue of the printing fluid from at least one of the nozzles.

54. The method of claim 53, comprising: (i) Moving the one or more substrates relative to the nozzle plate, and (ii) removing the residue from at least one of the nozzles while moving the one or more substrates.

55. The method of claim 54, wherein maintaining a constant throughput of producing the one or more images at the print location comprises during removal of the residue by the wiper assembly.

56. The method of claim 54, wherein the one or more substrates comprise an Intermediate Transfer Member (ITM) for receiving the droplets for producing the one or more images and transferring the one or more images to a target substrate, and moving the ITM to produce the one or more images.

57. The method of claim 54, wherein the one or more substrates comprise one or more sheets or a continuous web, and moving the one or more sheets or the continuous web to produce the one or more images thereon.

58. The method of claim 53, wherein the gap between the nozzle plate and the one or more substrates is preserved while (i) applying the droplets and (ii) removing the residue at the printing location.

59. The method of any of claims 53-58, wherein removing the residue comprises applying a wiping element to wipe the residue of the printing fluid from at least one orifice of at least one of the nozzles.

60. The method of claim 59, wherein the wiping element comprises a strip for holding a cleaning fluid and making physical contact with the nozzle plate by self-adhesion to the nozzle plate.

61. The method of claim 59, wherein applying the wiping assembly comprises moving the wiping element within a gap between the nozzle and the one or more substrates for at least one of: (i) Wiping the residue disposed on at least one of the nozzles, and (ii) absorbing additional residue of the printing fluid located between the nozzle and the one or more substrates.

62. The method of claim 59, wherein applying the wiping component comprises moving the wiping element in a first direction during a first time interval, and moving the wiping element in a second direction during a second time interval.

63. The method of claim 62, wherein the nozzles are arranged along a first axis and across a second axis, and wherein at least one of: (i) The first direction is parallel to the first axis, and (ii) the second direction is parallel to the second axis.

64. The method of claim 62, wherein the one or more substrates move in a direction of movement, wherein the first direction is parallel to the direction of movement, and wherein the second direction is orthogonal to the direction of movement.

65. The method of claim 62, wherein applying the wiping component comprises: the wiping element is moved in at least one of the first direction and the second direction as at least one of the nozzles ejects the printing fluid toward the one or more substrates.

66. The method of claim 62, wherein the first time interval is greater than the second time interval.

67. The method of claim 62, wherein the first time interval overlaps one or more second time intervals.

68. The method of claim 62, wherein the first direction is orthogonal to the second direction.

69. The method of claim 62, wherein applying the wiping component comprises: (i) Moving the wiping element in the first direction at a first speed, and (ii) moving the wiping element in the second direction at a second speed different from the first speed.

70. The method of claim 69 wherein the second speed is at least five times greater than the first speed.

71. The method of claim 62, wherein the one or more substrates comprise a flexible substrate having a first portion for receiving the one or more printing fluids and a second portion between the first image and the second image, wherein moving the one or more substrates comprises moving the flexible substrate in a direction of movement, and wherein applying the wiping assembly comprises moving the wiping element in the second direction parallel to the direction of movement of the flexible substrate as the second portion passes adjacent one or more nozzles.

72. The method of claim 71, wherein applying the wiping component comprises: the wiping element is moved in the second direction parallel to the direction of movement of the flexible substrate when the one or more nozzles are not applying the liquid droplets.

73. The method of claim 71, wherein during at least a portion of the second time interval, at least a portion of the wiping element is positioned within a gap between at least one of the nozzles and the second portion.

74. The method of claim 71, wherein applying the droplet comprises: applying the liquid droplets when the first portion passes adjacent the one or more nozzles and not when the second portion is adjacent the one or more nozzles, and wherein applying the wiping assembly comprises: when the one or more nozzles are controlled not to apply the droplets, the wiping element is moved to wipe the residue from the nozzles.

75. The method of claim 71, wherein the second portion is connected between two ends of the first portion so as to form a loop comprising the first portion and the second portion.

76. The method of claim 75, wherein the one or more substrates comprise a first sheet for receiving the first image and a second sheet for receiving the second image, and wherein applying the wiping assembly comprises: the wiping element is moved in the second direction after the first image is formed and before the second image is formed while at least one of the first sheet and the second sheet is moved within the system.

77. The method of claim 59, comprising removing one or more of the residues from the wiping element.