Printing method and system

Abstract

The method of printing includes applying one or more fluids, including at least a printing fluid, to an intermediate transfer member (ITM) (44) to form an image on the ITM (44). At least a portion of the image is transferred from the ITM (44) to a target substrate (50). Residue of the one or more fluids remaining on the ITM (44) that is not transferred to the target substrate (50) is transferred from the ITM (44) to one or more rotatable elements (112), and the residue is removed from the one or more rotatable elements (112).

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 954,516, filed December 29, 2019, the disclosure of which is incorporated herein by reference.

[0002] The present invention relates generally to digital printing, and more particularly to a method and system for cleaning components of a digital printing system. [Background technology]

[0003] Some printing systems may include an assembly for cleaning the equipment.

[0004] For example, U.S. Patent Application Publication No. 2019 / 0016114 describes a printing device capable of continuously cleaning a transfer member while miniaturizing the device. The printing device includes a cleaning roller configured to apply a cleaning liquid to the transfer member while rotating in contact with the transfer member, a liquid tank configured to store the cleaning liquid such that a portion of the cleaning roller is immersed in the cleaning liquid, and a removal unit configured to remove dirt by contacting a surface of the cleaning roller rotating in the liquid tank. Summary of the Invention [Means for solving the problem]

[0005] One embodiment of the present invention described herein provides a method of printing, the method including applying one or more fluids to an intermediate transfer member (ITM) including at least a printing fluid for forming an image on the ITM. At least a portion of the image is transferred from the ITM to a target substrate. Residue of the one or more fluids remaining on the ITM that is not transferred to the target substrate is transferred from the ITM to one or more rotatable elements, and the residue is removed from the one or more rotatable elements.

[0006] In some embodiments, the one or more rotatable elements are disposed on a first surface of the ITM and include one or more additional rotatable elements disposed on a second surface of the ITM opposite the first surface, where at least a first one of the rotatable elements and at least a second one of the additional rotatable elements face each other, and transferring the residue includes engaging the first and second rotatable elements. In other embodiments, applying at least the printing fluid includes applying a processing fluid to the ITM, and the engaging of the first and second rotatable elements is performed when applying at least one of (i) the processing fluid, and (ii) the printing fluid to the ITM. In yet other embodiments, the engaging of the first and second rotatable elements is performed for a predetermined time interval, and the method includes disengaging the first and second rotatable elements outside of the predetermined time interval.

[0007] In one embodiment, the ITM includes: (i) a first outer layer made from a first material and having a first structure, and (ii) a second outer layer made from a second material and having a second structure, the first and second outer layers being formed for transferring the residue from the first outer layer to the second outer layer. In another embodiment, the ITM includes a first outer layer having a first adhesive force to the residue, and at least one of the first and second rotatable elements includes a second outer layer having a second adhesive force to the residue, whereby the second adhesive force is greater than the first adhesive force, and transferring the residue includes engaging the first and second outer layers.

[0008] In some embodiments, the second outer layer comprises at least an alloy selected from the list consisting of (a) electroless nickel, (b) hard chromium, (c) anodized coating, and (d) a ceramic coating. In other embodiments, the second outer layer has an ISO grade surface roughness between N1 and N4. In yet other embodiments, at least one of the rotatable elements comprises at least an alloy selected from the list consisting of (a) aluminum, (b) a metal alloy, (c) a ceramic compound, and (d) a polymer.

[0009] In one embodiment, removing the residue comprises at least one of: (a) scraping, (b) brushing, and (c) wiping the residue from one or more of the rotatable elements. In another embodiment, removing the residue comprises engagement between at least one surface of each rotatable element and at least one scraper oriented at an angle between 55° and 65° relative to the surface of each rotatable element.

[0010] In some embodiments, the ITM has a given width and at least one of the rotatable elements comprises a roller having a length equal to or greater than the given width. In other embodiments, the one or more rotatable elements are disposed on a first surface of the ITM and include one or more additional rotatable elements disposed on a second surface of the ITM opposite the first surface, where at least a first one of the rotatable elements and at least a second one of the additional rotatable elements face each other, and transferring the residue comprises at least the first and second rotatable elements being continuously engaged with each other at least as the ITM is moved.

[0011] In accordance with one embodiment of the present invention, there is additionally provided a printing system that includes: (a) one or more stations configured to apply one or more fluids, including at least a printing fluid, to an intermediate transfer member (ITM) to form an image on the ITM; (b) an image transfer station configured to transfer at least a portion of the image from the ITM to a target substrate; and (c) an ITM cleaning station (ICLS) configured to (i) transfer residue of the one or more fluids remaining on the ITM that have not been transferred to the target substrate from the ITM to one or more rotatable elements, and (ii) remove the residue from the one or more rotatable elements. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic side view of a digital printing system in accordance with one embodiment of the present invention; [Figure 2A]2 is a schematic side view of a blanket washing station in accordance with an embodiment of the present invention. [Figure 2B] 2 is a schematic side view of a blanket washing station in accordance with an embodiment of the present invention. [Diagram 3] 2 is a flow chart that generally illustrates a method for cleaning residual image that has not been transferred to a target substrate, in accordance with one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Overview Some printing processes may involve using a printing fluid to form an image on a surface of an intermediate substrate, such as one or more members or drums, and transferring the image from the intermediate substrate to a target substrate. In some cases, the printing fluid may not be completely transferred, leaving a residue on the surface of the intermediate substrate. Such residue may contaminate the printing system and reduce the quality of subsequent images printed on the respective target substrate.

[0014] Embodiments of the invention described below provide improved techniques for cleaning an intermediate transfer member (ITM) during operation of a printing system. In some embodiments, a digital printing system includes an image forming station configured to print an image, including ink or any other type of printing fluid, onto the ITM, also referred to herein as a blanket. The digital printing system further includes an image transfer station configured to transfer the image from the ITM to a target substrate, such as a sheet or continuous web substrate.

[0015] In some embodiments, the digital printing system further includes an ITM cleaning station (ICLS) mounted in close proximity to the ITM, the ICLS configured to transfer residue remaining on the ITM that was not transferred to the target substrate from the ITM to one or more rotatable transfer rollers.

[0016] In the context of the present invention and claims, the term "residue" refers to any type of solid, liquid, gas, or any combination thereof that is unintentionally left on the intermediate substrate after the transfer of the image from the ITM to the target substrate. For example, printing fluids, ITM processing fluids, combinations thereof, various types of contaminants, or any other type of material that is not intended to be on the ITM surface after the transfer of the image from the ITM to the target substrate. It should be noted that in some cases, materials, such as processing fluids, may be intentionally applied to the ITM surface and therefore would not be considered residue.

[0017] The ICLS is further configured to remove the residue from each of the one or more transfer rollers using, for example, a scraping blade, and transfer the removed residue debris to a waste container using any suitable transfer technique.

[0018] In some embodiments, the ICLS may include one or more rotatable auxiliary rollers that are directly or indirectly fixed to the chassis of the digital printing system and configured to rotate about an axis, e.g., coupled to an axis at the center of the auxiliary roller. The transfer roller and the auxiliary roller are positioned on opposite sides of the ITM, with each pair of a transfer roller and a corresponding auxiliary roller facing each other.

[0019] In some embodiments, the transfer roller and scraper blade are respectively coupled to first and second arms that are coupled to each other (e.g., using a pin) and to the chassis using a hinge such that each of the arms is configured to rotate about the hinge.

[0020] In some embodiments, the ICLS includes a pneumatic piston assembly that is configured to engage and disengage the transfer roller and the auxiliary roller by moving at least a first arm relative to the auxiliary roller. In the engaged position, the moving ITM rotates the transfer roller to transfer residue to an outer surface of the transfer roller.

[0021] In some embodiments, the outermost layer of the ITM is a "release layer" that has a given adhesion to the printing fluid and residue. The transfer roller includes an outer layer that has an adhesion (to the residue) that is greater than the given adhesion. In such embodiments, at the engaged position, the residue is transferred from the ITM to the transfer roller.

[0022] In some embodiments, the ICLS includes a mechanism for engaging and disengaging scraping blades with the transfer rollers. When engaged, the one or more scraping blades are configured to remove residue from the outer surface of each transfer roller.

[0023] The disclosed techniques improve the quality of printed images by reducing the number of defects formed during the printing process. Additionally, the disclosed techniques improve the productivity of printing systems by (a) cleaning the ITMs during the printing process, and (b) reducing the number of contamination events during the printing process, thus increasing the availability of such systems to produce printed images.

[0024] System Description 1 is a schematic side view of a digital printing system 10 in accordance with one embodiment of the present invention. In some embodiments, system 10 includes a rotating flexible blanket 44 that cycles through an imaging station 60, a drying station 64, an imprinting station 84, an ITM cleaning station (ICLS) 100, and a blanket treatment station 52. In the context of the present invention and in the claims, the terms "blanket" and "intermediate transfer member (ITM)" are used interchangeably to refer to a flexible member including one or more layers that is used as an intermediate member configured to receive an ink image and transfer the ink image to a target substrate, as described in more detail below.

[0025] In an operational mode, imaging station 60 is configured to form a mirror ink image, also referred to herein as an “ink image” (not shown) or simply “image,” of digital image 42 on an upper run of the surface of blanket 44. The ink image is then transferred to a target substrate (e.g., paper, folding carton, multi-layer polymer, or any suitable flexible packaging in the form of a sheet or continuous web) disposed beneath a lower run of blanket 44.

[0026] In the context of the present invention, the term "run" refers to the length or segment of blanket 44 between any two given rollers over which blanket 44 is guided.

[0027] In some embodiments, during installation, the blanket 44 may be attached edge to edge to form a continuous blanket loop (not shown). One example of a method and system for seam installation is described in detail in U.S. Provisional Application No. 62 / 532,400, the disclosure of which is incorporated herein by reference.

[0028] In some embodiments, imaging station 60 typically includes multiple print bars 62, each mounted (e.g., using a slider) on a frame (not shown) that is positioned at a fixed height above the surface of the upper run of blanket 44. In some embodiments, each print bar 62 includes a strip of print head that is the same width as the print area on blanket 44 and includes individually controllable print nozzles.

[0029] In some embodiments, imaging station 60 may include any suitable number of bars 62, and each bar 62 may include a printing fluid, such as a different colored water-based ink. The inks typically have visible colors, such as, but not limited to, cyan, magenta, yellow, and black. In the example of FIG. 1, imaging station 60 includes seven print bars 62, but may include four print bars 62 having any selected color, such as, for example, cyan, magenta, yellow, and black.

[0030] In some embodiments, the print heads 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 .

[0031] In some embodiments, the different print bars 62 are spaced from one another along an axis of movement, also referred to herein as the direction of movement of the blanket 44, represented by arrow 94. In this configuration, precise spacing between the bars 62 and synchronization between the direction of the ink droplets of each bar 62 and the moving blanket 44 is essential to enable precise placement of the image pattern.

[0032] In some embodiments, the system 10 includes a heater, such as a hot gas or air blower 66 and / or an infrared (IR) heater or other suitable type of heater adapted for the printing application. In the example of FIG. 1, the blower 66 is positioned between the print bars 62 and configured to partially dry the ink droplets deposited on the surface of the blanket 44. This flow of hot air between the print bars can help, for example, to reduce condensation on the surface of the print head, and / or to deal with satellites (e.g., residue or small droplets dispersed around the main ink droplets), and / or to prevent clogging of the inkjet nozzles of the print head, and / or to prevent droplets of different color inks on the blanket 44 from unnecessarily intermixing with each other.

[0033] In some embodiments, the system 10 includes a drying station 64 configured to blow hot air (or another gas) onto a surface of the blanket 44. In some embodiments, the drying station includes a blower 68 or any other suitable drying device.

[0034] At drying station 64, the ink image formed on blanket 44 is exposed to radiation and / or hot air to more thoroughly dry the ink, evaporating most or all of the liquid carrier and leaving only a layer of resin and colorant that is heated to the point where it becomes a tacky ink film.

[0035] In some embodiments, the system 10 includes a blanket module 70 that includes a rotating ITM, such as the blanket 44. In some embodiments, the blanket module 70 includes one or more rollers 78, at least one of which includes an encoder (not shown) configured to record the position of the blanket 44 in order to control the position of the sections of the blanket 44 relative to the respective print bars 62. In some embodiments, the encoder of the roller 78 typically includes a rotary encoder configured to generate a rotary-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 claims, the terms "indicative of" and "indication" are used interchangeably.

[0036] Additionally or alternatively, blanket 44 may include an embedded encoder (not shown) for controlling the operation of various modules of system 10. One embodiment of an embedded encoder is described in detail, for example, in U.S. Provisional Application No. 62 / 689,852, the disclosure of which is incorporated herein by reference.

[0037] In some embodiments, blanket 44 is guided over rollers 76 and 78, as well as a powered tensioning roller, also referred to herein as dancer assembly 74. Dancer assembly 74 is configured to control the amount of slack in blanket 44, and its movement is represented diagrammatically by a double-headed arrow. Furthermore, any stretching of blanket 44 with aging will not affect the ink image placement performance of system 10 and will only require further slack to be taken up by tensioning dancer assembly 74.

[0038] In some embodiments, dancer assembly 74 may be motorized. The configuration and operation of rollers 76 and 78 are described in further detail, for example, in U.S. Patent Application Publication No. 2017 / 0008272 and the aforementioned PCT International Publication No. WO2013 / 132424, the disclosures of which are incorporated herein by reference in their entireties.

[0039] 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 sensors may be integrated within blanket 44 or may include sensors external to blanket 44 using any other suitable technique for obtaining signals indicative of the mechanical tension applied to blanket 44. In some embodiments, processor 20 and additional controllers (e.g., shown in FIGS. 2 and 3 below) of system 10 are configured to receive signals generated by the tension sensors to monitor the tension applied to blanket 44 and to control the operation of dancer assembly 74.

[0040] At the impression station 84 , also referred to herein as the image transfer station, the blanket 44 passes between an impression cylinder 82 and a pressure cylinder 90 .

[0041] In some embodiments, the system 10 includes a control console 12 configured to control multiple modules of the system 10, such as a blanket module 70, an image forming station 60 disposed above the blanket module 70, and a substrate transport module 80 disposed below the blanket module 70 and including one or more printing stations, as described below.

[0042] In some embodiments, the console 12 includes a processor 20, typically a general-purpose computer, with appropriate front-end and interface circuitry for interfacing with and receiving signals from the controller of the dancer assembly 74 and the controller 54 via cable 57. In some embodiments, the controller 54, shown diagrammatically as a single device, may include one or more electronic modules mounted at predetermined locations on the system 10. At least one of the electronic modules of the controller 54 may include an electronic device, such as a control circuit or processor (not shown), that is 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 perform functions used by the printing system, and data for the software may be stored in memory 22. The software may be downloaded in electronic form to the processor 20 and control circuitry, for example, via a network, or it may be provided on a non-transitory tangible medium, such as an optical, magnetic or electronic memory medium.

[0043] In some embodiments, the console 12 includes a display 34 configured to display data and images received from the processor 20 or input inserted by a user (not shown) using an input device 40. In some embodiments, the console 12 may have any other suitable configuration, for example, alternative configurations of the console 12 and display 34 are described in detail in U.S. Pat. No. 9,229,664, the disclosure of which is incorporated herein by reference.

[0044] In some embodiments, the processor 20 is configured to display on the display 34 a digital image 42 including one or more segments (not shown) of the image 42 and / or various types of test patterns that may be stored in the memory 22.

[0045] In some embodiments, the blanket treatment station 52, also referred to herein as a cooling station, is configured to treat the blanket, for example, by cooling the blanket and / or applying a treatment fluid to the outer surface of the blanket 44 and / or cleaning the outer surface of the blanket 44. In the blanket treatment station 52, the temperature of the blanket 44 can be reduced to a desired value before the blanket 44 enters the imaging station 60. Treatment can be performed by passing the blanket 44 over one or more rollers or blades configured for cooling and / or cleaning and / or applying a treatment fluid onto the outer surface of the blanket.

[0046] In some embodiments, the blanket treatment station 52 may be located adjacent to the imaging station 60 in addition to or instead of the location of the blanket treatment station 52 shown in Figure 1. In such embodiments, the blanket treatment station may include one or more bars adjacent to the print bar 62, where treatment fluid is applied to the blanket 44 by jets.

[0047] In some embodiments, processor 20 is configured to receive a signal indicative of the surface temperature of blanket 44, for example, from a temperature sensor (not shown), to monitor the temperature of blanket 44 and to control the operation of blanket treatment station 52. Examples of such treatment stations are described, for example, in PCT International Publication Nos. WO 2013 / 132424 and WO 2017 / 208152, the disclosures of which are incorporated herein by reference in their entireties.

[0048] Additionally or alternatively, treatment fluid may be applied to blanket 44 by jetting prior to ink jetting at the imaging stations.

[0049] 1, station 52 is mounted between impression station 84 and imaging station 60, however, station 52 may be mounted adjacent blanket 44 in any other or additional suitable location or locations between impression station 84 and imaging station 60. As previously mentioned, station 52 may additionally or alternatively include a bar adjacent imaging station 60.

[0050] In the example of FIG. 1, impression cylinder 82 presses an ink image onto a target flexible substrate, such as an individual sheet 50 , which has been transported by substrate transport module 80 via impression cylinder 82 from an input stack 86 to an output stack 88 .

[0051] In some embodiments, the lower run of blanket 44 selectively interacts with impression cylinder 82 at impression station 84 to impress an image pattern onto a target flexible substrate compressed between blanket 44 and impression cylinder 82 under the action of pressure from pressure cylinder 90. For the simplex printer shown in FIG. 1 (i.e., printing on one side of sheet 50), only one impression station 84 is required.

[0052] In other embodiments, the module 80 may include two or more impression cylinders to allow one or more double-sided printing. The two impression cylinder configuration also allows single-sided printing to be performed at twice the speed of double-sided printing. In addition, mixed lots of single-sided and double-sided prints can also be printed. In alternative embodiments, a different configuration of the module 80 may be used for printing on a continuous web substrate. Detailed descriptions and various configurations of double-sided printing systems and systems for printing on a continuous web substrate are provided, for example, in U.S. Pat. Nos. 9,914,316 and 9,186,884, PCT International Publication No. WO2013 / 132424, U.S. Patent Application Publication No. 2015 / 0054865, and U.S. Provisional Application No. 62 / 596,926, the disclosures of which are all incorporated herein by reference.

[0053] As briefly described above, a sheet 50 or continuous web substrate (not shown) is conveyed by module 80 from an input stack 86 and passed through a nip (not shown) located between impression cylinder 82 and pressure cylinder 90. Within the nip, a surface of blanket 44 carrying the ink image is pressed firmly against sheet 50 (or other suitable substrate) by, for example, a compressible blanket (not shown) of pressure cylinder 90, thereby imprinting the ink image onto the surface of sheet 50 and cleanly separating it from the surface of blanket 44. Sheet 50 is then conveyed to an output stack 88.

[0054] 1, rollers 78 are positioned on the upper run of blanket 44 and are configured to keep blanket 44 taut as it passes adjacent to imaging station 60. Moreover, it is particularly important to control the speed of blanket 44 under imaging station 60 in order to obtain precise jetting and deposition of ink droplets onto the surface of blanket 44 by imaging station 60, thereby obtaining placement of the ink image.

[0055] In some embodiments, the impression cylinder 82 is periodically engaged and disengaged from the blanket 44 in order to transfer the ink image from the moving blanket 44 to a target substrate passing between the blanket 44 and the impression cylinder 82. In some embodiments, the system 10 is configured to apply a torque to the blanket 44 using the roller and dancer assemblies described above in order to keep the upper run taut and substantially isolate the upper run of the blanket 44 from being affected by mechanical vibrations occurring in the lower run.

[0056] As previously mentioned, the ink image typically includes a printing fluid, such as a water-based ink having multiple colors of ink, and the aforementioned treatment fluid, which is applied to the blanket 44 using the blanket treatment station 52. In some cases, after transferring the ink image from the blanket 44 to the sheet 50, residue may remain on the blanket 44, which may cause, among other things, scratches on the blanket 44 and contamination of the system 10. In some embodiments, the system 10 includes an ITM cleaning station (ICLS) 100, which is typically mounted between the printing station 84 and the blanket treatment station 52. In some embodiments, the ICLS 100 includes one or more pairs of rotatable elements, in this example a pair of rollers, shown generally in mutual engagement. When engaged, the rollers are configured to remove the aforementioned residue from the blanket 44. The ICLS 100 is described in further detail in Figures 2A and 2B below, and the blanket cleaning process is further described in Figure 3 below.

[0057] It should be noted that the components of both the ICLS 100 and the blanket handling station 52 are positioned on either side of the blanket 44 as illustrated in FIG. 1, ie, similar to the components of the transfer station, for example.

[0058] In some embodiments, system 10 includes an image quality control station 55, also referred to herein as an automated quality control (AQM) system, which functions as a closed-loop inspection system integrated within system 10. In some embodiments, station 55 may be located adjacent impression cylinder 82, as shown in FIG. 1, or at any other suitable location within system 10.

[0059] In some embodiments, station 55 includes a camera (not shown) that is configured to capture one or more digital images of the aforementioned ink images printed on 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 that includes a slit having a width of about one meter or any other suitable width.

[0060] In the context of this disclosure and in the claims, the term "about" or "approximately" in relation to any numerical value or range indicates an appropriate dimensional tolerance that enables a part or collection of components to function for its intended purpose as described herein. For example, "about" or "approximately" may refer to a range of values ​​of ±20% of the recited value, e.g., "about 90%" may refer to a range of values ​​from 72% to 100%.

[0061] In some embodiments, station 55 may include a spectrophotometer (not shown) configured to monitor the quality of the ink printed on sheet 50 .

[0062] 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, configured to evaluate the quality of each printed image. Based on that evaluation and signals received from controller 54, processor 20 is configured to control the operation of the modules and stations of system 10. In the context of the present invention and claims, the term "processor" refers to any processing device, such as processor 20 or any other processor or controller connected to or integrated with station 55, that is configured to process signals received from the camera and / or spectrophotometer of station 55. It should be noted that the signal processing operations, control related instructions, and other computational operations described herein may be performed by a single processor or distributed among multiple processors of one or more respective computers.

[0063] In some embodiments, station 55 is configured to inspect the quality of the printed images and test patterns to monitor various attributes such as, but not limited to, perfect image registration with sheet 50, color-to-color (C2C) registration, printed geometry, image uniformity, color profile and linearity, and print nozzle functionality. In some embodiments, processor 20 is configured to automatically detect geometric distortions or other errors in one or more of the aforementioned attributes. For example, processor 20 is configured to compare between a design version of a given digital image (also referred to herein as a "master" or "source image") and a digital image of a printed version of the given image, captured by a camera.

[0064] In other embodiments, processor 20 may apply any suitable type of image processing software, for example to a test pattern, to detect distortions indicative of the aforementioned errors. In some embodiments, processor 20 is configured to analyze the detected distortions to apply corrective action to the malfunctioning module and / or provide instructions to another module or station of system 10 to correct the detected distortions.

[0065] 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 spectrophotometer of station 55 .

[0066] In some embodiments, the processor 20 is configured to detect various types of defects based on the signals acquired by the station 55: (i) defects in the substrate (e.g., the blanket 44 and / or the sheet 50), such as scratches, pinholes, and damaged edges, and (ii) printing-related defects, such as irregular color spots, satellites, and splashes.

[0067] In some embodiments, processor 20 is configured to detect these defects by comparison between sections of the print and respective reference sections of the original design, also referred to herein as the master. Processor 20 is further configured to classify the defects and, based on the classification and predetermined criteria, reject sheets 50 having defects that are not within the specified predetermined criteria.

[0068] In some embodiments, the processor of station 55 is configured to determine whether to stop operation of system 10, for example, if the defect density is above a specified threshold. The processor of station 55 is further configured to initiate corrective action in one or more of the modules and stations of system 10, as described above. Corrective action may be performed on-the-fly (during which system 10 continues the printing process) or offline by stopping printing operations and correcting the problem within the respective module and / or station 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 stop operation of system 10, if the defect density is above a specified threshold.

[0069] Additionally or alternatively, processor 20 is configured to receive signals, for example from station 55, indicative of additional types of defects and problems in the printing process of system 10. Based on these signals, processor 20 is configured to automatically estimate the pattern placement accuracy and the level of additional types of defects not previously mentioned. In other embodiments, any other suitable method for inspecting the patterns printed on sheet 50 (or on any other substrate previously mentioned) may also be used, for example using an external (e.g., offline) inspection system, or any type of measurement fixture and / or scanner. In these embodiments, based on the information received from the external inspection system, processor 20 is configured to initiate any suitable corrective action and / or stop operation of system 10.

[0070] The configuration of system 10 is provided in a simplified manner purely as an example to clarify the present invention. The components, modules and stations described in the printing system 10 described above, as well as additional components and configurations, are described in detail in, for example, U.S. Patent Nos. 9,327,496 and 9,186,884, PCT International Publication Nos. WO2013 / 132438, WO2013 / 132424 and WO2017 / 208152, U.S. Patent Application Publication Nos. 2015 / 0118503 and 2017 / 0008272, the disclosures of which are all incorporated herein by reference.

[0071] The particular configuration of system 10 is shown by way of example to illustrate the particular problems addressed by embodiments of the present invention and to demonstrate the application of these embodiments in enhancing the performance of such systems, but embodiments of the present invention are in no way limited to this particular type of example system, and the principles described herein may be applied to any other type of printing system as well.

[0072] Blanket Washing Station 2A is a schematic side view of an ITM cleaning station (ICLS) 100, in accordance with one embodiment of the present invention. In some embodiments, ICLS 100 includes one or more rotatable elements, in this example, two similar auxiliary rollers 102 coupled to a frame 104, which is mounted on a chassis 105 of system 10.

[0073] In some embodiments, each auxiliary roller 102 has a circular cross-section with a diameter of about 80 mm or any other suitable diameter. In the example of Figure 2A, the auxiliary rollers 102 are fixed to the X and Y axes and are rotated about the Z axis by the blanket 44 as the blanket 44 moves in the direction of movement represented by arrow 94.

[0074] In some embodiments, each auxiliary roller 102 may have a core including an aluminum alloy, such as Al6061-T6, or any other suitable alloy. The core of the auxiliary roller 102 may be covered with an outer layer 103 including any suitable type of soft material, such as ethylene propylene diene monomer (EPDM) rubber having a Shore A hardness ranging between about 20 ShA and about 95 ShA.

[0075] In some embodiments, the ICLS 100 includes one or more additional rotatable elements, in this example two transfer rollers 112 similar to each other, each having a circular cross section and a diameter of about 80 mm. The transfer rollers 112 have a core comprising an aluminum alloy, such as the aforementioned Al6061-T6, or any other suitable alloy, or a ceramic compound or polymer.

[0076] In some embodiments, the center of the transfer roller 112 may be covered with an outer layer 113 comprising electroless nickel with an N2 ISO grade surface roughness. Based on material properties and surface treatment, the outer layer 113 is configured to receive residue transferred from the blanket 44 as described in more detail below.

[0077] Additionally or alternatively, the outer layer 113 may include any other suitable material and roughness level configured to receive the residue transferred from the blanket 44. For example, the outer layer 113 may include electroless nickel, hard chrome, anodized or any other suitable type of ceramic coating. Moreover, the roughness grade of the outer layer 113 may have any suitable ISO grade of surface roughness between N1 and N4.

[0078] In some embodiments, blanket 44 has a given width perpendicular to arrow 94 (e.g., about 1 meter), and at least one (and typically both) of rollers 102 and 112 may have a length that is greater than or equal to the given width of blanket 44.

[0079] As shown in FIG. 2A , the transfer roller 112 and the auxiliary roller 102 are disposed on opposite sides of the blanket 44, facing each other. In this configuration, each pair of rollers 102 and 112 may prevent motion of the blanket 44 along at least the Y axis and allow motion of the blanket 44 along the aforementioned direction of movement, which is substantially parallel to the X axis. In the example of FIG. 2A , the ICLS 100 includes two pairs of rollers 102 and 112. However, in other embodiments, the ICLS 100 may include any other suitable number of rollers 102 and 112 (i.e., one or more pairs of rollers 102 and 112) arranged in any suitable configuration.

[0080] In some embodiments, transfer roller 112 is mounted on a rigid arm 106 that is coupled to chassis 105 and configured to rotate about hinge 107. In some embodiments, ICLS 100 is configured to engage and disengage between rollers 102 and 112, as described in more detail in FIG. 2B below.

[0081] 1 above, blanket 44 receives the ink image from imaging station 60 and transfers the ink image to sheet 50 or any other target substrate. In some cases, after transferring the ink image from blanket 44 to sheet 50, residues may remain on blanket 44, and ICLS 100 is configured to remove these residues by transferring them from blanket 44 to transfer roller 112 of ICLS 100. In some embodiments, the outer surface of blanket 44 includes a release layer (not shown), which is configured to transfer the ink image to sheet 50 and then transfer said residues to transfer roller 112.

[0082] In some embodiments, the pair of engaged rollers 102 and 112 are configured to form a nip through which the blanket 44 passes. The nip formed between the pair of auxiliary rollers 102 and the transfer roller 112 may be substantially similar to the nip formed between the impression cylinder 82 and the pressure cylinder 90, as described in FIG. 1 above, and allows for the transfer of residue from the blanket to the transfer roller.

[0083] In some embodiments, the ICLS 100 includes elements for removing residue transferred to the surface of the outer layer 113 of the transfer roller 112. In some embodiments, these residue removal elements, also referred to herein as residue cleaners, are configured to physically contact the surface of the outer layer 113 to mechanically remove residue as each transfer roller 112 rotates about its own axis.

[0084] In some embodiments, the residue cleaner may include one or more scraping blade assemblies 111 configured to clean residue from each transfer roller 112. In the example of FIG. 2A, two scraping blade assemblies 111 are used to clean each transfer roller 112. In other embodiments, the ICLS 100 may include any other suitable number of scraping blade assemblies 111.

[0085] In one embodiment, a single scraper blade assembly 111 may be sufficient to clean all residue from the surface of the outer layer 113 of each transfer roller 112. In another embodiment, three or more scraper blade assemblies 111 may be used to clean a single transfer roller 112.

[0086] It should be noted that each transfer roller 112 may have an independent number of scraper blade assemblies 111. For example, a first transfer roller 112 may be cleaned using a single scraper blade assembly 111, and a second transfer roller 112 may be cleaned using two or more scraper blade assemblies 111.

[0087] It should be noted that the number of transfer rollers 112, and in particular the number of scraper blade assemblies 111 applied to clean each transfer roller 112, may depend on the printing application and the material applied to the blanket 44.

[0088] In some embodiments, the scraping blade assembly 111 is mounted on a rotatable arm 108 that is coupled to the chassis 105 and configured to rotate about a hinge 107 .

[0089] In other embodiments, the element for removing residue from the transfer roller 112 may include any other suitable type of residue cleaner, such as, but not limited to, a brush, a wiper, or a scrolling down cleaner.

[0090] It should be noted that the ICLS 100 may include one or more types of cleaners applied to each transfer roller 112. For example, scraper blade assemblies 111 and brushes.

[0091] In some embodiments, ICLS 100 is configured to engage and disengage rollers 102 and 112, as described in more detail below in FIG. 2B. In some embodiments, during normal operation of system 10, for example, when at least blanket 44 is being moved, at least one roller 112 and one roller 102 opposite roller 112 are continuously inter-engaged to transfer residue from blanket 44 to roller 112.

[0092] In other embodiments, processor 20 controls ICLS 100 to engage rollers 102 and 112 for a predetermined time interval, such as during image transfer, and to disengage rollers 102 and 112 outside of the predetermined time interval.

[0093] In some embodiments, when the blanket treatment station 52 constantly applies treatment fluid to the surface of the blanket 44 (as described in FIG. 1 above), the ICLS 100 is operated such that the pair of rollers 102 and 112 are constantly engaged to remove residue of the treatment fluid from the surface of the blanket 44.

[0094] In other embodiments, ICLS 100 may always be in the engagement mode, in which all pairs of rollers 102 and 112 are engaged at all times. It should be noted that ICLS 100 can operate non-stop in the engagement mode, but has the ability to disengage one or more pairs of rollers 102 and 112 when such engagement is required. As previously discussed, the engagement and disengagement operations of rollers 102 and 112 are controlled by processor 20.

[0095] Additionally or alternatively, engagement between the pair of rollers 102 and 112 may be performed at least when applying printing fluid (eg, ink) to blanket 24 .

[0096] In other embodiments, one or more (and typically both) pairs of rollers 102 and 112 may be engaged, at least when blanket 44 is being moved in the direction of movement indicated by arrow 94 .

[0097] In an alternative embodiment, instead of the two pairs of rollers 102 and 112 shown in FIG. 2A, the ICLS 100 may include a single pair of rollers 102 and 112. In other words, the ICLS 100 may include one auxiliary roller 102 and one transfer roller 112. In such an embodiment, the processor 20 controls the ICLS 100 to engage the rollers 102 and 112, and in some embodiments, also to disengage the rollers 102 and 112, as described in detail in FIG. 2B below. It should be noted that the embodiments of the present disclosure described for multiple pairs of rollers 102 and 112 are applicable, mutatis mutandis, to any ITM cleaning station, such as the ICLS 100, having the aforementioned single pair of rollers 102 and 112.

[0098] Reference is now made to inset 120, which illustrates scraping blade assembly 111. In some embodiments, scraping blade assembly 111 includes a blade housing 115 and a blade 114. Blade housing 115 is configured to hold blade 114 and may include an aluminum alloy, or any other suitable alloy. Blade 114 may include 1090 steel, or any other suitable alloy adapted for scraping the aforementioned residue from the surface of outer layer 113 of the respective transfer roller 112.

[0099] In some embodiments, processor 20 is configured to control scraping blade assembly 111 to (a) engage blade 114 with the surface of outer layer 113 by moving blade 114 in direction 116, or (b) disengage blade 114 from the surface of outer layer 113 by moving blade 114 in direction 118. In one embodiment, blade housing 115 is configured to engage and disengage blade 114 from the surface of outer layer 113, as described in more detail in FIG. 2B below.

[0100] In some embodiments, during operation of system 10, blanket 44 rotates transfer roller 112 counterclockwise (shown as arrow 109) as blanket 44 moves in the direction of arrow 94. In some embodiments, as imaging station 60 applies ink droplets to blanket 44, processor 20 controls scraper blade assembly 111 to move blade 114 in direction 116 to remove residue from the surface of outer layer 113, as described above. The removed residue debris is transferred to waste tray 110, for example, by gravity, or to any other suitable waste container using any other suitable technique.

[0101] In some embodiments, system 10 may operate without applying ink droplets to blanket 44. For example, during start-up or maintenance of system 10, blanket treatment station 52 may apply the aforementioned treatment fluid to the surface of blanket 44. In such embodiments, processor 20 is configured to control scraper blade assembly 111 to move blade 114 in direction 118 to disengage from the surface of outer layer 113 and prevent the treatment fluid from being removed from outer layer 113.

[0102] It should be noted that after use of the treatment fluid, the processor 20 may control the scraper blade assembly 111 to move the blade 114 in the direction 116 to remove the used treatment fluid from the surface of the outer layer 113.

[0103] In some embodiments, the scraping blade assembly 111 may include any suitable number of blades 114. Specifically, where the ICLS 100 includes a single pair of rollers 102 and 112, the scraping blade assembly 111 may include any suitable number of blades 114. For example, the scraping blade assembly 111 may include one blade 114 (such as the blade shown in inset 120), two blades 114 (as shown in FIG. 2A), or three or more blades 114. Moreover, as previously discussed, even when including a pair of rollers 102 and 112, the blade assembly 111 may include a combination of one or more blades 111 and other cleaning elements, such as brushes.

[0104] 2B is a schematic side view of an engagement and disengagement assembly of ICLS 100, in accordance with one embodiment of the present invention. Note that in FIG. 2B, ICLS 100 is shown without rollers 102 and 112, and without blade 114.

[0105] In some embodiments, ICLS 100 includes a pneumatic piston assembly 123 that is coupled to one end of frame 104 using a screw 141 or any other suitable fastening technique. The other end of piston assembly 123 is coupled to a mount 144 that is hooked onto arm 106 and disposed between dead shafts 135 of transfer rollers 102. Note that while dead shaft 137 of transfer roller 102 appears larger in FIG. 2B than dead shaft 135 of transfer roller 112, the actual diameters of rollers 102 and 112 are similar (e.g., about 80 mm), as described above in FIG. 2A. In some embodiments, piston assembly 123 includes one or more pneumatic pistons (not shown) having any suitable diameter, such as about 40 mm.

[0106] In some embodiments, processor 20 is configured to control piston assembly 123 to disengage rollers 102 and 112 by pushing mount 144 along the Y axis toward waste tray 110. As shown in FIG. 2A above, arms 106 and 108 may rotate about hinge 107 so that transfer roller 112 is moved away from blanket 44 and disengaged from auxiliary roller 102.

[0107] In some embodiments, the ICLS 100 includes one or more gas springs 124 coupled to a hinge 136 mounted on the chassis 105 and a screw 138 configured to secure the arms 106 and 108 to one another. In one embodiment, the gas spring 124 is configured to hold at least the arm 106 during maintenance, such as during replacement of one or more of the rollers 102 and / or 112 and / or replacement of one or more of the blades 114. For example, in a blade replacement, the screw 138 is withdrawn from the ICLS 100 to separate the arms 106 and 108. In a roller replacement, the piston assembly 123 is separated from the mounting 144 and the gas spring 124 allows controlled rotation of the arms 106 and 108 about the hinge 107.

[0108] In other embodiments, the ICLS 100 may include a single pair of rollers 102 and 112, and the one or more gas springs 124 described above may be omitted from the configuration of the ICLS 100. In such embodiments, the pair of rollers 102 and 112 may be positioned in close proximity to the chassis 105, and the piston assembly 123 may be sufficient to urge the mount 144 along the Y axis toward the waste tray 110, as described above. This configuration makes it possible to perform maintenance operations as described above and / or any suitable maintenance operations with respect to the impression cylinder 82, without having the gas springs 124.

[0109] In alternative embodiments, instead of the one or more gas springs 124 described above, the ICLS 100 may include any other suitable type of device configured to secure the arms 106 and 108 to one another.

[0110] Reference is now made to inset 140, which illustrates components of blade housing 115. Note that blade 114 and parts of blade housing 115 have been removed from inset 140 for illustration of elements associated with movement of blade 114 in directions 116 and 118 as described above in inset 120 of FIG. 2A.

[0111] In some embodiments, the blade housing 115 includes a spring 126 coupled to the screw 130 and configured to pull the blade 114 in the direction 116 by rotating the blade housing 115 clockwise about the hinge 132. Additionally or alternatively, the blade housing 115 may include any other suitable type of device, such as, but not limited to, a piston (not shown), configured to apply a controllable and / or adjustable force to pull the blade 114 in the direction 116, as described above with respect to the spring 126.

[0112] In some embodiments, the blade housing 115 includes an eccentric screw 128 having at least two positions. In a first position, the eccentric screw 128 is configured to rotate the blade housing 115 counterclockwise about the hinge 132 to urge the blade 114 in the direction 118. In a second position, the eccentric screw 128 typically does not apply a force to the housing 115 and the spring 126 couples the blade 114 to the surface of the outer layer 113, as previously described and shown in the inset 120 of FIG. 2A above.

[0113] In some embodiments, the processor 20 is configured to control the engagement and disengagement between the blade 114 and the transfer roller 112 by controlling the position of the eccentric screw 130. In such embodiments, when the eccentric screw 130 is in a first position, the blade 114 and the transfer roller 112 are disengaged from one another, whereas when the eccentric screw 130 is in a second position, the blade 114 and the transfer roller 112 are engaged with one another. It is noted that the processor 20 is further configured to position the eccentric screw 130 at any position between the first and second positions.

[0114] In other embodiments, the ICLS 100 may include any other suitable mechanism for controlling the engagement and disengagement between the blade 114 and the transfer roller 112 .

[0115] The particular configuration of ICLS 100 is shown as an example to illustrate the particular problems, such as contamination and scratches, that are addressed by embodiments of the present invention, and to demonstrate the application of these embodiments in enhancing the performance of ICLS 100 and system 10. However, embodiments of the present invention are in no way limited to this particular type of example cleaning station and printing system, and the principles described herein may be applied to other types of cleaning stations and printing systems as well.

[0116] FIG. 3 is a flow chart that generally illustrates a method for cleaning untransferred residue from sheet 50, in accordance with one embodiment of the present invention.

[0117] The method begins with an image printing step 200 in which processor 20 controls image forming station 60 to apply ink droplets to blanket 44 to form an image thereon. In an image transfer step 202, processor 20 controls blanket module 70 and impression station 84 to transfer the image from blanket 44 to sheet 50.

[0118] In some cases, residue that is not transferred to sheet 50 may remain on blanket 44. In a residue transfer step 204, processor 20 controls ICLS 100 to engage rollers 102 and 112 with blanket 44 therebetween to transfer the residue from blanket 44 to one or more rotatable elements, such as transfer roller 112.

[0119] As described above in FIG. 2A , the release layer of blanket 44 is adapted to transfer the (ink image and) residue, and the outer surface of outer layer 113 is adapted to receive the residue so that it is transferred from blanket 44 to one or more transfer rollers 112.

[0120] In some embodiments, the outer surface of outer layer 113 can have a given adhesion to the residue that is greater than the adhesion to the residue of blanket 44. In such embodiments, when rollers 102 and 112 are engaged, the release layer of blanket 44 engages the outer surface of outer layer 113 and the residue is transferred to outer layer 113.

[0121] Completing the method, in a residue removal step 206 , the processor 20 controls the ICLS 100 to engage one or more blades 114 with the outer surface of the outer layer 113 to remove residue from the transfer roller 112 .

[0122] In some embodiments, processor 20 is configured to control ICLS 100 to repeat the above-described method for each new image applied to each section of blanket 44.

[0123] Although the embodiments described herein primarily address methods and apparatus for cleaning residue from the ITM of a digital printing system, the methods and systems described herein may be used in other applications, such as cleaning any type of contamination from any flexible substrate.

[0124] It will therefore be understood that the foregoing embodiments are cited by way of example, and that the present invention is not limited to what has been specifically shown and described herein above. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described above, as well as variations and modifications thereof not disclosed in the prior art, which would occur to one skilled in the art upon reading the foregoing description. Documents incorporated by reference in this patent application are to be considered as integral parts of this application, and only the definitions in this specification are to be considered, except to the extent that any term is defined in these incorporated documents in a manner that is inconsistent with the definitions expressly or implicitly made herein.

Claims

1. A method for producing a recording medium comprising: rotating one or more rollers to move an intermediate transfer member (ITM) disposed on the one or more rollers; applying one or more fluids, including at least a printing fluid, to the ITM to form an image on the ITM; transferring at least a portion of the image from the ITM to a target substrate; engaging (i) one or more rotatable elements disposed on a first side of the ITM, and (ii) one or more additional rotatable elements disposed on a second side of the ITM opposite the first side, wherein both the one or more rotatable elements and the one or more additional rotatable elements are distinct from the one or more rollers that move through the ITM, and wherein at least a first rotatable element of the one or more rotatable elements and at least a second rotatable element of the one or more additional rotatable elements face each other; transferring residue of the one or more fluids remaining on the ITM that was not transferred to the target substrate from the ITM to the one or more rotatable elements; removing the residue from the one or more rotatable elements; A printing method comprising:

2. I. applying the one or more fluids to the ITM further comprises applying a treatment fluid to the ITM; II. Engaging the one or more rotatable elements with the one or more additional rotatable elements is performed at least when applying at least one of: (i) a processing fluid; and (ii) a printing fluid to the ITM; and III. The transferring of the residue includes engaging the first rotatable element with a second rotatable element; The method of claim 1.

3. 3. The method of claim 2, further comprising: engaging the first and second rotatable elements for a predetermined time interval; and disengaging the first and second rotatable elements outside of the predetermined time interval.

4. 4. The method of any one of claims 1 to 3, wherein removing the residue comprises engaging a surface of at least one respective rotatable element with at least one scraper oriented at an angle between 55° and 65° relative to the surface of each rotatable element.

5. A method according to any one of claims 1 to 3, wherein transferring the residue includes at least the first rotatable element and the second rotatable element being continuously engaged with each other at least when the ITM is moved.

6. one or more stations configured to apply one or more fluids, including at least a printing fluid, to an intermediate transfer member (ITM) to form an image on the ITM; an image transfer station including one or more rollers configured to rotate to move the ITM and configured to transfer at least a portion of the image from the ITM to a target substrate; an ITM cleaning station (ICLS) including (a) one or more rotatable elements disposed on a first side of the ITM, and (b) one or more additional rotatable elements disposed on a second side of the ITM opposite the first side, both the one or more rotatable elements and the one or more additional rotatable elements being distinct from the one or more rollers of the image transfer station, and at least a first rotatable element of the one or more rotatable elements and at least a second rotatable element of the one or more additional rotatable elements facing each other, the ICLS configured to (i) transfer residue of the one or more fluids remaining on the ITM that was not transferred to the target substrate from the ITM to the one or more rotatable elements, and (ii) remove the residue from the one or more rotatable elements; a processor configured to control the ICLS to engage the first rotatable element and the second rotatable element to transfer the residue; A printing system comprising:

7. 7. The system of claim 6, wherein the one or more stations are further configured to apply a treatment fluid to the ITM, and the processor is configured to control an ICLS to engage the first rotatable element and the second rotatable element at least when the one or more stations apply at least one of (i) the treatment fluid, and (ii) the printing fluid to the ITM.

8. 7. The system of claim 6, wherein the processor is configured to control the ICLS to engage the first and second rotatable elements for a predetermined time interval and to disengage the first and second rotatable elements outside of the predetermined time interval.

9. 7. The system of claim 6, wherein the ITM includes a first outer layer having a first adhesive force to the residue, and at least one of the first rotatable element and second rotatable element includes a second outer layer having a second adhesive force to the residue, the second adhesive force being greater than the first adhesive force.

10. 10. The system of claim 9, wherein the second outer layer comprises at least an alloy selected from the list consisting of: (a) electroless nickel, (b) hard chromium, (c) anodized coating, and (d) a ceramic coating.

11. The system of claim 9 or 10, wherein the second outer layer has an ISO grade surface roughness between N1 and N4.

12. 11. The system of claim 6, wherein at least one of the rotatable elements comprises at least an alloy selected from the list consisting of: (a) aluminum; (b) a metal alloy; (c) a ceramic compound; and (d) a polymer.

13. The system of any one of claims 6 to 10, wherein the ICLS includes at least one of: (a) a scraper, (b) a brush, and (c) a wiper configured to remove the residue from the one or more rotatable elements.

14. 11. The system of any one of claims 6 to 10, wherein the ICLS is configured to remove the residue by engaging a surface of at least one respective rotatable element with at least one scraper that is oriented at an angle between 55° and 65° relative to the surface of each rotatable element.

15. A system described in any one of claims 6 to 10, wherein the first rotatable element has a first diameter and the second rotatable element has a second diameter equal to the first diameter.

16. A system described in any one of claims 6 to 10, wherein the first rotatable element has a first diameter and the second rotatable element has a second diameter different from the first diameter.

Images