Digital printing system and method

Abstract

The method comprises: (i) generating a first image (43) on an intermediate transfer member (ITM) (44), moving the ITM along a first direction (94) to an engagement point between the ITM and a first substrate (50), and transferring the first image to the first substrate disposed at a first position with respect to the ITM, wherein the first image is transferred to a predetermined position on the first substrate; and (ii) for a second image (43a) generated on the ITM after the first image and intended to be transferred to a predetermined position on a second substrate: (a) at the engagement point, designating a second position with respect to the ITM for the second substrate, the second position being an offset position with respect to the first position; (b) moving the second substrate at least in a second direction (73a, 73b) to the second position; and (c) generating the second image at a third position on the ITM, the third position at least partially compensating for the difference between the first position and the second position, and transferring the second image to the predetermined position on the second substrate.

Description

Technical Field

[0001] Cross - reference to related applications This application claims priority from U.S. Provisional Patent Application No. 63 / 355614, filed on June 26, 2022, the disclosure of which is incorporated herein by reference.

[0002] Field of the Invention The present invention generally relates to digital printing, and more particularly to methods and systems for reducing signatures (signatures) transferred between an intermediate transfer member and a substrate during a printing process.

Background Art

[0003] Background of the Invention Some printing systems have an intermediate transfer member that is configured to receive an image and transfer this image to a target substrate. In some cases, a print batch that includes a very large number (e.g., thousands) of copies of a particular image that is generated on the intermediate transfer member and transferred to each sheet can cause an undesired formation of imprints of the edges of the sheets on the intermediate transfer member, such that the edge silhouette may appear in the prints of other images, for example in the next print batch. This phenomenon can degrade the quality of subsequent images printed using the same intermediate transfer member in subsequent batches.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Patent Document 10

Patent Document 11

Patent Document 12

Patent Document 13

Patent Document 14

Summary of the Invention

Means for Solving the Problems

[0005] One preferred example of the invention described herein provides a method of printing, the method comprising: (i) generating a first image on a movable intermediate transfer member (ITM) of a printing system and moving the ITM along a first direction to an engagement point between the ITM and a first substrate to transfer the first image to the first substrate disposed at a first position relative to the ITM, wherein the first image is transferred to a predetermined position on the first substrate; and (ii) for a second image generated on the ITM after the first image and intended to be transferred to a predetermined position on a second substrate: (a) specifying, at the engagement point, a second position relative to the ITM for the second substrate, the second position being offset relative to the first position; (b) moving the second substrate at least in a second direction to the second position; and (c) generating the second image at a third position on the ITM, the third position at least partially compensating for the difference between the first position and the second position, and transferring the second image to the predetermined position on the second substrate.

[0006] In some preferred examples, the first substrate and the second substrate have equal sizes, and the first and second images are copies of a predetermined image. In other preferred examples, the first substrate and the second substrate have different sizes, and the first and second images are copies of a predetermined image. In still other preferred examples, the second substrate is larger than the first substrate along an axis parallel to at least the second direction.

[0007] In some preferred examples, the first direction and the second direction are different from each other. In other preferred examples, the first direction includes a printing direction, and the second direction includes a direction intersecting the printing direction. In still other preferred examples, the first and second substrates each include a first and a second sheet, and moving the second sheet at least in the second direction includes controlling a sheet alignment assembly (SAA) to move the second sheet in the second direction to the second position before the second sheet is inserted at the engagement point.

[0008] In one preferred example, the first and second substrates each include a first and a second sheet, these sheets are stacked in the input stack, and moving the second sheet at least in the second direction controls the input pile centering assembly (PCA) to move the second sheet in the second direction when (i) after the first sheet has left the input stack and (ii) when the second sheet is disposed within the input stack. In another preferred example, the method includes controlling the output PCA to move the output stack in the second direction to receive the second sheet and stack it on the first sheet within the output stack. In yet another preferred example, generating the second image at the third position on the ITM includes: (i) controlling the motion assembly to move one or more print bars of the printing system in the second direction and (ii) controlling at least one of the print bars to apply droplets of the printing liquid to a predetermined position on the surface of the ITM.

[0009] According to one preferred example of the present invention, a printing system including a printing assembly and a processor is additionally provided. The printing assembly is configured to generate an image on a movable intermediate transfer member (ITM) and transfer this image to a substrate. The printing assembly includes one or more motion assemblies, and these motion assemblies are configured to move: (i) the ITM, (ii) the printing assembly, and (iii) the substrate. The processor controls the printing assembly to generate a first image on the ITM, move the ITM along a first direction to an engagement point between the ITM and a first substrate, and transfer the first image to the first substrate disposed at a first position relative to the ITM. The first image is transferred to a predetermined position on the first substrate. For a second image intended to be generated on the ITM after the first image and transferred to a predetermined position on a second substrate, the processor: (i) designates a second position relative to the ITM for the second substrate at the engagement point, and the second position is a position offset from the first position; (ii) controls the printing assembly to: (a) move the second substrate at least in a second direction to the second position, (b) generate the second image at a third position on the ITM, and the third position at least partially compensates for the difference between the first position and the second position, and (c) transfer the second image to a predetermined position on the second substrate.

[0010] According to one preferred example of the present invention, a system including an interface and a processor is further provided. The interface is configured to receive, in a digital printing system, digital images intended to be printed on a first and a second sheet as a first and a second image, respectively. The processor controls a printing assembly to: (a) generate a first image on a movable intermediate transfer member (ITM), (b) move the ITM along a first direction to an engagement point between the ITM and a first substrate, and transfer the first image to the first substrate disposed at a first position with respect to the ITM, and the first image is transferred to a predetermined position on the first substrate. For a second image intended to be generated on the ITM after the first image and transferred to a predetermined position on a second substrate, the processor: (i) designates, at the engagement point, a second position with respect to the ITM for the second substrate, the second position being an offset position with respect to the first position, and (ii) controls the printing assembly to: (a) move the second substrate at least in a second direction to the second position, (b) generate the second image at a third position on the ITM, the third position at least partially compensating for the difference between the first position and the second position, and (c) transfer the second image to a predetermined position on the second substrate.

[0011] The present invention will be more fully understood from the detailed description of its embodiments, which are to be interpreted in conjunction with the drawings.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Best Mode for Carrying Out the Invention

[0013] Detailed Description of Embodiments Overview Industrial-scale digital printing generally requires printing hundreds or thousands of copies of each of hundreds or thousands of images onto substrates. Some digital printing systems include a flexible intermediate transfer member (ITM) formed in a loop. This ITM is configured to move and receive ink droplets to form an image on the surface of the ITM. Thereafter, the moving ITM engages a target substrate (e.g., a sheet) by applying an engaging force (e.g., pressure) to transfer the image to the sheet. This process is repeated hundreds or thousands of times.

[0014] In some cases, the repeated engaging force applied to one or more edges (ends) of the sheet may cause an undesired formation of an imprint on the ITM (e.g., along the printing axis). Further, in some cases, the size of the sheet may change in subsequent printing operations. In such cases, it is undesirable for the silhouette of the imprint to appear on the surface of subsequent sheets, which can degrade the quality of subsequent printed images. Therefore, it is important to reduce and even eliminate the formation of such imprints on the ITM.

[0015] The embodiments of the invention described hereinafter in this specification provide an improved technique for reducing or preventing the formation of imprints on the ITM.

[0016] In some embodiments, a digital printing system comprises a printing assembly and a processor. The printing assembly comprises (i) an imaging station configured to apply droplets of printing fluid (e.g., multi-color inks), (ii) a movable intermediate transfer member (ITM) configured to receive the droplets and generate an image on the intermediate transfer member, (iii) an impression (pressing, pressure coating) station configured to engage the ITM and a substrate (e.g., a sheet) to transfer the image to the sheet, and (iv) one or more motion assemblies configured to move (a) the ITM, (b) the printing assembly, and (c) the sheet.

[0017] In some embodiments, the imaging station directs droplets to a predetermined location on the surface of the moving ITM to generate an image at the predetermined location. Further, the image is composed of a plurality of color images that are aligned with each other to generate an image without distortion caused by (i) relative displacement between the color images and (ii) the positions of the droplets within each color image.

[0018] In some embodiments, the processor controls the printing assembly to generate a first image on the ITM, move the ITM along a first direction (e.g., the printing direction) to an engagement point between the ITM and a first sheet, and transfer the first image to the first sheet disposed at a first position relative to the ITM, and the first image is transferred to a predetermined position on the first sheet.

[0019] In some embodiments, for a second image intended to be generated on the ITM after the first image and transferred to a predetermined position on the second sheet, the processor designates, at the engagement point, a second position on the ITM for the second sheet, the second position being an offset position relative to the first position. The processor further controls the printing assembly to (i) move the second sheet at least along a second direction (e.g., a direction intersecting the printing direction, which is orthogonal to the printing direction) to the second position, (ii) generate the second image at a third position on the ITM, the third position at least partially compensating for the difference between the first position and the second position, and (iii) transfer the second image to the predetermined position on the second sheet. Note that changing the position of the sheet on the ITM at the engagement point reduces or prevents the formation of an imprint on the ITM, thereby preventing the formation of the silhouette of the imprint on each subsequent image printed on a subsequent sheet.

[0020] Description of the System FIG. 1 is a schematic side view of a digital printing system 10 according to an embodiment of the present invention. In some embodiments, the system 10 includes a rotating flexible blanket 44 that circulates through an image forming station 60, a drying station 64, an impression station 84, and a blanket processing station 52. In the context of the present invention and in the claims, "blanket" and "intermediate transfer member (ITM)" are used interchangeably to refer to a flexible member having one or more layers used as an intermediate transfer member, the flexible member being configured to receive an ink image (shown in FIGS. 2A and 2B below) from, for example, the image forming station 60 and form the ink image in an endless loop configuration for transfer to a target substrate, which will be described in detail below.

[0021] In the operation mode, the image forming station 60 is configured to form an ink mirror image of the digital image 42, also referred to herein as an "ink image" or simply an "image" (shown in FIGS. 2A and 2B below), on the upper running surface of the surface of the blanket 44. Thereafter, the ink image is transferred to a target substrate (e.g., paper, folding cardboard box, multilayer polymer, or any suitable flexible package in the form of a sheet or continuous fabric) disposed below the lower running surface of the blanket 44.

[0022] In the context of the present invention, a "running surface" refers to the length or portion of the blanket 44 between any two given rollers, on which the blanket 44 is guided.

[0023] In some embodiments, during installation, a seam portion, also referred to herein as a seam 45, can be used to adhere the ends of the blanket 44 to form a continuous blanket loop, also referred to herein as a closed loop. An example of a method and system for seam installation is described in U.S. Patent Application Publication No. 2020 / 171813 (Patent Document 1).

[0024] In some embodiments, the image forming station 60 generally includes a plurality of print bars 62, each of which is mounted on a frame (not shown) positioned at a fixed height above the surface of the upper running surface of the blanket 44. In some embodiments, each print bar 62 includes a strip of print heads of the same width as the printing area of the blanket 44 and individually controllable printing nozzles configured to eject ink and other types of printing fluids onto the blanket 44, which will be described in detail below.

[0025] In some embodiments, the image forming station 60 can include any suitable number of print bars 62, also referred to herein as bars 62 for simplicity. Each bar 62 can include a printing fluid such as aqueous inks of different colors. This ink generally has visible colors such as cyan (blue - green), magenta (red - purple), red, green, blue, yellow, black, and white, but is not limited to these colors. In the example of FIG. 1, the image forming station 60 includes seven print bars 62, but can include, for example, four print bars 62 having any selected colors such as cyan (C), magenta (M), yellow (Y), and black (K).

[0026] In some embodiments, the print head is configured to eject ink droplets of different colors onto the surface of the blanket 44 to form an ink image (not shown) on the surface of the blanket 44. In this example, the blanket 44 is moved along the X - axis of the XYZ coordinate system of the system 10 to direct the ink droplets generally parallel to the Z - axis of the coordinate system by the print head.

[0027] In some embodiments, different print bars 62 are spaced apart from each other along a movement axis, also referred to herein as (i) the direction of movement of the blanket 44 or (ii) the printing direction. In this example, the direction of movement of the blanket 44 is parallel to the X - axis, and each print head 62 extends along the Y - axis of the XYZ coordinate system of the system 10. In this configuration, the exact spacing between the bars 62 along the X - axis, and the synchronization of directing the ink droplets of each bar 62 and moving the blanket 44 are essential for the proper placement of the image pattern.

[0028] In the context of this disclosure and in the claims, "pattern placement between colors", "pattern placement accuracy", "color - to - color registration", "C2C (color - to - color) registration", "color - to - color positional difference", "bar - to - bar registration", and "color registration" are used interchangeably and refer to any placement accuracy of two or more colors relative to each other.

[0029] In some embodiments, system 10 includes a high-temperature gas or hot air (hot air, heated air) blower, and / or a heater 66 such as an infrared-based heater with a gas blower or fan to flow gas or air at any suitable temperature. The heater 66 is disposed between the printed bars 62 and is configured to partially dry the ink droplets deposited on the surface of the blanket 44. Such an air flow between the printed bars serves, for example, to (i) reduce concentration on the surface of the print head and / or to process contaminants (e.g., residues or small droplets distributed around the main ink droplets), and / or (ii) prevent clogging of the orifices of the inkjet nozzles of the print head, and / or (iii) prevent the undesired mixing of droplets of different colors of ink on the blanket 44.

[0030] In some embodiments, system 10 includes a drying station 64, which is configured to direct infrared radiation and cooling air (or other gas), and / or to blow hot air (or other gas) onto the surface of the blanket 44. In some embodiments, the drying station 64 can include an infrared-based illumination assembly (not shown) and / or an air blower 68, or any other suitable drying device.

[0031] In some embodiments, within the drying station 64, the ink image formed on the blanket 44 is exposed to radiation and / or hot air to more fully dry the ink, evaporate most or all of the liquid carrier, leaving only a layer of resin and colorant heated to the point of becoming a sticky ink thin film (film).

[0032] In some embodiments, system 10 includes a blanket module 70, also referred to herein as an ITM module, and the blanket module 70 includes a rotary flexible ITM such as blanket 44. In some embodiments, the blanket module 70 includes one or more rollers 78, and at least one of the rollers 78 includes a motion encoder (not shown), and the motion encoder is configured to record the position of the blanket 44 and control the position of a section of the blanket 44 relative to each print bar 62. In some embodiments, one or more motion encoders can be integrated with additional rollers and other movable components of system 10.

[0033] In some embodiments, the motion encoder described above generally includes at least one rotary encoder, and the rotary encoder is configured to generate a rotation-based position signal indicating the angular displacement of each roller. Note that in the context of the present invention and in the claims, "indicating" and "indicating" are used interchangeably.

[0034] In addition or alternatively, the blanket 44 can include an integrated encoder for controlling the operation of various modules of the system 10. One implementation of an integrated motion encoder is described in detail, for example, in International Publication No. WO 2020 / 003088 (Patent Document 2), and the disclosure is incorporated herein by reference.

[0035] In some embodiments, the blanket 44 is guided over rollers 76, 78, and other rollers described herein, and over drive tension rollers, also referred to herein as dancer assemblies 74. The dancer assembly 74 is configured to control the length of slack in the blanket 44, and its movement is schematically indicated by double-headed arrows in FIG. 1. Further, any elongation of the blanket 44 over time need only be compensated for by tightening the dancer assembly 74 to remove additional slack without affecting the ink image placement performance of the system 10.

[0036] In some embodiments, the dancer assembly 74 can be motor-driven. The construction and operation of rollers 76 and 78 are described in further detail, for example, in U.S. Patent Application Publication No. 2017 / 0008272 (Patent Document 3), and International Publication No. 2013 / 132424, the disclosures of which are incorporated herein by reference in their entirety.

[0037] In some embodiments, the system 10 includes a blanket tension drive (BTD) 99 and a blanket control drive (BCD) 77, which are powered by respective first and second motors, generally electric motors (not shown), and are each configured to rotate about their respective first and second axes.

[0038] In some embodiments, system 10 can include one or more tension sensors (not shown) disposed at one or more positions along blanket 44. These tension sensors can be integrated within blanket 44 or can include sensors external to the blanket that use any other suitable technique for obtaining 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 the tension sensors, monitor the tension applied to blanket 44, and control the operation of dancer assembly 74.

[0039] At impression station 84, blanket 44 passes between impression cylinder 82 and pressure cylinder 90, which is configured to carry a compressible blanket (shown in FIG. 3 below). In some embodiments, a motion encoder is integrated with at least one of impression cylinder 82 and pressure cylinder 90.

[0040] In some embodiments, system 10 includes a control console 12 that is configured to control a plurality of modules of system 10, such as blanket module 70, imaging station 60 disposed above blanket module 70, and substrate transport module 80, which is disposed below blanket module 70 and includes one or more impression stations, which are described below.

[0041] In some embodiments, the console 12 includes a processor 20, generally a general-purpose processor, with appropriate front-end and interface circuitry, and these front-end and interface circuits interface with and receive signals from the dancer assembly 74 and the controller 54 via cable 57. Additionally or alternatively, the controller 12 can include any suitable type of application-specific integrated circuit (ASIC) and / or digital signal processor (DSP) and / or any other suitable type of processing device configured to perform any type of processing on the data processed within system 10.

[0042] In some embodiments, the controller 54, schematically shown as a single device, can include one or more electronic modules mounted at a predetermined location on system 10. At least one of the electronic modules of the controller 54 can include an electronic device such as a control circuit or a processor (not shown), and this electronic device is configured to control the various modules and stations of system 10. In some embodiments, the processor 20 and the control circuit can be programmed with software to perform the functions used by the printing system and store data for the software in the memory 22. This software can be downloaded, for example, in electronic form to the processor 20 and the control circuit over a network, or can be provided on a non-transitory tangible medium such as an optical medium, a magnetic medium, or an 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 inputs written by a user (not shown) using the input device 40. In some embodiments, the console 12 can have any other suitable configuration. For example, alternative configurations of the console 12 and the display 34 are described in U.S. Patent No. 9,229,664 (Patent Document 5), and are incorporated herein by reference to its disclosure.

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

[0045] In some embodiments, a blanket processing station 52, also referred to herein as a cooling station, is configured to process the blanket 44, for example, by cooling the blanket 44, and / or by applying a processing fluid to the outer surface of the blanket 44, and / or by cleaning the outer surface of the blanket 44. In the blanket processing station 52, the temperature of the blanket 44 can be reduced to a desired temperature level before the blanket 44 enters the image forming station 60. This process can be performed by passing the blanket 44 over one or more rollers configured to apply a cooling fluid and / or a cleaning fluid and / or a processing fluid to the outer surface of the blanket.

[0046] In some embodiments, the blanket processing station 52 can further include one or more bars (not shown) disposed adjacent to the print bar 62, whereby, in addition to or instead of the above, a processing fluid can be applied to the blanket 44 by spraying.

[0047] In some embodiments, the processor 20 is configured to receive a signal indicative of the surface temperature of the blanket 44 from, for example, a temperature sensor (not shown), monitor the temperature of the blanket 44, and control the operation of the blanket processing station 52. Examples of such processing stations are described, for example, in Patent Document 4 and International Publication No. 2017 / 208152 (Patent Document 6), and are incorporated herein by reference to these disclosures.

[0048] In the example of FIG. 1, the station 52 is implemented between the impression station 84 and the image forming station 60, but the station 52 can be implemented adjacent to the blanket 44 at any other or additional suitable position between the impression station 84 and the image forming station. As described above, the station 52 can alternatively or additionally be implemented on a bar adjacent to the image forming station 60.

[0049] In the example of FIG. 1, the impression cylinder 82 and the pressure cylinder 90 press an ink image onto a target flexible substrate such as an individual sheet 50 that is conveyed by the substrate conveyance module 80 from the input stack 86 through the impression station 84 to the output stack 88. In this example, a rotary encoder (not shown) is integrated with the impression cylinder 82.

[0050] In some embodiments, the lower running surface of the blanket 44 interacts with the impression cylinder 82 at the impression station 84 to press an image pattern onto the target flexible substrate, and the target flexible substrate is pressed between the blanket 44 and the impression cylinder 82 by the action of the pressure of the pressure cylinder 90. In the case of the single-sided (simplex) printer shown in FIG. 1 (i.e., printing on one side of the sheet 50), only one impression station is required.

[0051] In other embodiments, module 80 includes two or more impression cylinders (not shown) to enable one or more double-sided prints. The configuration of two impression cylinders also enables 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 an alternative embodiment, different configurations of module 80 can be used to print on a continuous web substrate. A detailed description and various configurations of double-sided printing systems and systems for printing on continuous web substrates are provided, for example, in U.S. Patent No. 9,914,316 (Patent Document 7), No. 9,186,884 (Patent Document 8), Patent Document 4, U.S. Patent Application Publication No. 2015 / 0054865 (Patent Document 9), and U.S. Provisional Patent Application No. 62 / 596,926 (Patent Document 10), and are incorporated herein by reference in their entirety.

[0052] Briefly as described above, the sheet 50 or a continuous web substrate (not shown) is conveyed by module 80 from input stack 86 and passes through a nip (not shown) disposed between impression cylinder 82 and pressure cylinder 90. Within the nip, the surface of blanket 44 carrying the ink image is firmly pressed against sheet 50 (or against another suitable substrate), for example, by the compressible blanket of pressure cylinder 90, whereby the ink image is pressed onto the surface of sheet 50 and cleanly separated from the surface of blanket 44. Thereafter, sheet 50 is conveyed to output stack 88.

[0053] In some embodiments, system 10 includes a pile centering assembly (PCA) 49, and PCA 49 is configured to move the input stack 86 of sheet 50 in the moving direction 46. Similarly, system 10 includes PCA 47, and PCA 47 is configured to move the output stack 88 of sheet 50 in the moving direction 48. In this example, the moving directions 46 and 48 are substantially parallel to the Y-axis of the XYZ coordinate system. However, in other embodiments, at least one of the moving directions 46 and 48 can be non-parallel to the Y-axis.

[0054] In the example of FIG. 1, roller 78 is disposed on the upper running surface of blanket 44 and is configured to maintain blanket 44 in a tensioned state as blanket 44 passes adjacent to imaging station 60. Further, below imaging station 60, it is particularly important to control the speed of blanket 44 to obtain accurate ejection and deposition of ink droplets for forming an image on blanket 44 by imaging station 60.

[0055] In some embodiments, system 10 includes a motion assembly 51, and motion assembly 51 is configured to move one or more print bars 62 in the moving direction 53. In this example, motion assembly 51 is configured to move all of the print bars 62 of imaging station 60 together.

[0056] In some embodiments, system 10 further includes a sheet alignment assembly (SAA) 56, and SAA 56 is configured to move sheet 50 before sheet 50 is inserted into impression station 84. The structure and function of SAA 56 will be described in detail in FIG. 3 below.

[0057] In some embodiments, the moving directions 53 and 73 are substantially parallel to the Y-axis of the XYZ coordinate system. However, in other embodiments, at least one of the moving directions 53 and 73 can be made non-parallel to the Y-axis. Note that in this example, the moving direction 53 is different from the moving direction 94, which is the moving direction of the blanket 44 and is also referred to herein as the printing direction (generally parallel to the X-axis of the XYZ coordinate system). More specifically, for this example, the SAA 56 is configured to move the sheet 50 in a direction intersecting the printing direction, and the direction intersecting the printing direction is generally approximately orthogonal to the printing direction (i.e., the moving direction 94).

[0058] In some embodiments, the impression cylinder 82 periodically engages with and disengages from the blanket 44 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 torque to the blanket 44 using the rollers and dancer assembly described above to maintain the tension of the upper running surface and isolate the upper running surface of the blanket 44 from being affected by mechanical vibrations generated within the lower running surface.

[0059] In some embodiments, the system 10 includes a printing assembly 31, and the printing assembly 31 includes: (i) an image forming station 60, (ii) a blanket 44, (iii) an impression station 84, and (iv) one or more motion assemblies, such as: (a) a blanket module 70 configured to move the blanket 44, (b) a motion assembly 51 configured to move one or more of the print bars 62 of the image forming station 60, and (c) an SAA 56 configured to move the sheet 50 in a direction intersecting the printing direction before the sheet 50 is inserted into the impression station 84, which has been described in detail above.

[0060] In some embodiments, the printing assembly 31 can also include PCAs 49 and 47, which are configured to move the input stack 86 and the output stack 88 respectively, as described in detail above.

[0061] In some embodiments, the system 10 includes an image quality control station 55, also referred to herein as an automatic quality management (AQM) system, which functions as a closed-loop inspection system integrated within the system 10. In some embodiments, as shown in FIG. 1, the image quality control system 55 can be disposed adjacent to the impression cylinder 82 or at any other suitable location within the system 10.

[0062] In some embodiments, the image quality control system 55 includes a camera (not shown) configured to acquire one or more digital images of the ink images printed on the sheet 50 described above. In some embodiments, the camera can include any suitable image sensor, such as a contact image sensor (CIS) or a complementary metal oxide semiconductor (CMOS), and a scanner having a slit with a width of about one meter or other suitable width.

[0063] In the context of the present invention and in the claims, "about" or "approximately" indicates, for any value or range, an appropriate dimensional tolerance that allows a component or a set of components to function for its intended purpose as described herein.

[0064] In some embodiments, the station 55 can include a spectrophotometer (not shown) configured to monitor the quality of the ink printed on the sheet 50.

[0065] In some embodiments, the digital images acquired by the station 55 are sent to the processor 20 or any other processor of the station 55, and this processor is configured to evaluate the quality of each printed image. Based on this 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 device such as the processor 20 or any other processor or controller connected to or integrated with the station 55, and such processing devices are configured to process the signals received from the camera and / or spectrophotometer of the station 55. Note that the signal processing operations, control-related instructions, and other computational operations described herein can be executed by a single processor or shared among the respective multiple processors of one or more computers.

[0066] In some embodiments, the station 55 is configured to inspect the quality of the printed images and test patterns, and monitor various attributes (but not limited to these) such as the overall alignment of the image with the sheet 50, also referred to herein as image-substrate alignment, color-to-color (C2C) alignment, printed geometric shapes, image uniformity, color profiles 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 above-described attributes.

[0067] In some preferred examples, the processor 20 is configured to analyze the detected distortion, apply corrective actions to malfunctioning modules, and / or issue commands to other modules or stations of the system 10 to compensate for the detected distortion.

[0068] In some embodiments, system 10 can print a test mark (not shown) or other suitable features, such as chamfers (bevels) or margins of sheet 50. By acquiring an image of the test mark, station 55 can perform C2C alignment, image-substrate alignment, different widths between colors referred to herein as "Δ bar-bar width" or "color-color width difference", various types of local distortions, and various types of distortions such as surface-back surface alignment errors (in double-sided printing). In some embodiments, processor 20 is configured to: (i) sort sheet 50 having distortions exceeding a first set of predetermined thresholds, for example, to a reject tray; (ii) initiate a correction operation for sheet 50 having distortions exceeding a second, lower set of predetermined thresholds; and (iii) output sheet 50 having minor distortions, for example, below the second set of thresholds, to an output stack.

[0069] 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.

[0070] In some preferred examples, the processor of station 55 is configured to determine, for example, whether the operation of system 10 should be stopped if the density of the distortion exceeds a specified threshold. The processor of station 55 is further configured to initiate a correction operation for one or more of the modules and stations of system 10 as described above. In some embodiments, the correction operation can be performed on-the-fly (while system 10 is continuing the printing process) or offline by stopping the printing operation in each module and / or station of system 10 to solve the problem. In other embodiments, any other processor or controller of system 10 is configured to initiate a correction operation or stop the operation of system 10 if the density of the distortion exceeds a specified threshold.

[0071] In addition to, or alternatively to, the processor 20 is configured to receive signals indicative of additional types of distortion and problems in the printing process of the system 10, for example, from the station 55. Based on these signals, the processor 20 is configured to automatically estimate the level of pattern placement accuracy and additional types of distortion and / or defects not described above. In other embodiments, any other suitable method of inspecting the patterns printed on the sheet 50 (or any suitable substrate described above) can be used, for example, an external (e.g., offline) inspection system, or any type of measuring jig and / or scanner. In these embodiments, based on the information received from the external inspection system, the processor 20 is configured to initiate any suitable corrective action and / or stop the operation of the system 10.

[0072] For clarity of the present invention, the configuration of the system 10 is simplified and provided as a mere example. The components, modules, and stations within the system 10 described above, and additional components and configurations, are described, for example, in U.S. Patent No. 9,327,496 (Patent Document 11) and Patent Document 8, International Publication No. 2013 / 132438 (Patent Document 12), Patent Document 4, and Patent Document 6, U.S. Patent Application Publication No. 2015 / 0118503 (Patent Document 13) and Patent Document 3, and are incorporated herein by reference in their entirety.

[0073] 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, a particular configuration of the system 10 is shown as an example. However, embodiments of the present invention are in no way limited to this particular type of system example, and the principles described herein can be equally applied to other types of printing systems.

[0074] Reduce the imprint of the sheet edge on the blanket surface FIG. 2A is a schematic pictorial view of an imprint 58 undesirably formed on blanket 44 while forming one or more ink images 43 on the surface of blanket 44, according to one embodiment of the present invention. In the context of this disclosure, and in the claims, ink image 43, image 43, and its grammatical variations (variations) are used interchangeably.

[0075] In some cases, a printing job may involve printing thousands of images, which, in this example, is a copy of a given image (e.g., digital image 42 generated as ink image 43) onto each of thousands of sheets 50. In other words, the same image is printed thousands of times onto the panel of blanket 44 and then transferred onto thousands of sheets 50.

[0076] In some embodiments, impression cylinder 82 periodically engages and disengages from blanket 44 such that, at an engagement position (also referred to herein as an engagement point), impression station 84 is configured to transfer ink image 43 from moving blanket 44 to sheet 50 passing between blanket 44 and impression cylinder 82. In some embodiments, during engagement, impression cylinder 82 and pressure cylinder 90 press against each other between the left end 18 and the right end 18 (shown as imprint 58) of sheet 50 and between straight lines 75a and 75b of sheet 50. Note that image 43 is transferred within the region defined between straight lines 75a and 75b and within imprint 58 and is not transferred within portions 79a and 79b that are considered margins of sheet 50. Accordingly, within portions 79a and 79b between impression cylinder 82 and pressure cylinder 90, a smaller force is applied compared to the force applied to the region having image 43.

[0077] In some cases, the repeatable engaging force applied to the left and right ends 18 of the sheet 50 can cause the formation of an undesired imprint 58 along the X-axis of the blanket 44, whereas the smaller pressure applied between the leading end 72a and the trailing end 72b of the sheet 50 does not form an imprint along the Y-axis of the blanket 44.

[0078] In some cases, the size of the sheet 50 can be changed in subsequent printing jobs. For example, in a subsequent printing job, the size of the subsequent sheet 50 along the Y-axis is larger than the size of the sheet 50 along the Y-axis shown in FIG. 2A. In such a case, it is undesirable for the silhouette of the imprint 58 (and optionally, the image 43) to appear on the surface of the subsequent sheet 50, for example, on the surface of the subsequent image 43 printed on each surface of the subsequent sheet 50. The silhouette of the imprint 58 can degrade the quality of the subsequent image 43, and in severe cases, each of the subsequent sheets 50 may have to be discarded. Therefore, it is important to reduce and even eliminate the formation of the imprint 58, and FIG. 2A below provides a pictorial view of a method for reducing the imprint 58. Further, the difference between the sheet 50 and the subsequent sheet 50 can be in one or both of the X-axis and the Y-axis, and the size ratio between the X-axis and the Y-axis can also be different between the sheet 50 and the subsequent sheet 50.

[0079] FIG. 2B is a schematic pictorial view of a method for reducing or eliminating the formation of the imprint 58 on the surface of the blanket 44 according to an embodiment of the present invention.

[0080] In some embodiments, before the sheet 50 is inserted into the impression station 84, the SAA 56 is configured to move each sheet 50 to the orientation 73a or the orientation 73b. In this example, both the orientations 73a and 73b are parallel to the Y-axis, but in other embodiments, at least one of the orientations 73a and 73b can have an orientation other than parallel to the Y-axis.

[0081] In an implementation example, the first batch of the image 43 described in detail in FIG. 1 can be sequentially printed on each sheet of the first batch of sheets 50 (for example, having about 100 sheets 50). In the example of FIG. 2B, the first batch is too small to form the imprint 58 on the blanket 44. The edge 18 appears within a line width thinner than the line width of the imprint 58, indicating that the imprint is not formed on the surface of the blanket 44.

[0082] Thereafter, the same printing technique can be used with one difference described herein to print a second batch of the image 43a (which is similar to the image 43 but is referred to herein as the image 43a, indicating that this batch is a different batch of copies of the same image 43) on each sheet of a second batch of subsequent sheets 50 (for example, also having about 100 sheets 50). In some embodiments, before being inserted into the impression station 84, the SAA 56 moves each sheet 50 of the second batch to the orientation 73a. Note that due to the movement in the orientation 73a, all the sheets 50 of the second batch are offset with respect to the position of the first batch of sheets 50 of the sheet 50 and engage with the blanket 44. As shown in the example of FIG. 2B, the position of the edge 18a of the sheet 50 of the second batch on the blanket 44 has an offset with respect to the position of the edge 18 of the sheet 50 of the first batch on the blanket 44.

[0083] Thereafter, a third batch of the image 43b (similar to the image, but referred to herein as image 43b, indicating that this batch is a different batch of copies of the same image 43) can be printed on each sheet of a third batch of subsequent sheets 50 (which also has, for example, about 100 sheets 50). In the example of FIG. 2B, the third batch of sheets 50 is moved by the SAA 56 to orientation 73b, whereby the edge 18b is positioned at a position on the blanket 44 that is different from the positions of edges 18 and 18a. In other words, moving one or more sheets along the Y-axis (or in another suitable orientation) can change the positions of edges 18, 18a, and 18b to reduce or eliminate the formation of the imprint 58 on the surface of the blanket 44.

[0084] FIG. 3 is a schematic pictorial view of a sheet alignment assembly (SAA) 56 of the system 10 according to an embodiment of the present invention.

[0085] In some embodiments, the SAA 56 includes one or more side lays (lateral alignment devices) configured to move the sheet 50 to orientations 73a and 73b as described above. In the configuration example shown in FIG. 3, the sheet 50 is positioned on both side lays (SL: side lay) 95a and 95b, whereby, using the techniques described herein, the SL 95a moves the sheet 50 to orientation 73a and the SL 96b moves the sheet 50 to orientation 73b.

[0086] In some embodiments, the SL 95b includes a substrate 83b and a movable plate (flat plate) 93b, the substrate 83b generally being stationary and the movable plate 93b being configured to move to orientations 73a and 73b using, for example, a motor 91b controlled by a controller 54 or a processor 20. Similarly, the SL 95a includes a substrate 83a and a movable plate 93a, the substrate 83a generally being stationary and the movable plate 93a being configured to move to orientations 73a and 73b using, for example, a motor 91a controlled by a controller 54 or a processor 20.

[0087] In some embodiments, when plates 93a and 93b move together in orientation 73a, edge 89a of plate 93a presses edge 18 of sheet 50 in orientation 73a, and at the same time, edge 89b of plate 93b moves in orientation 73a to maintain the distance between edges 89a and 89b approximately equal to the size of sheet 50 along the Y-axis (e.g., the distance between edges 18 of sheet 50). Similarly, when plates 93a and 93b move together in orientation 73b, edge 89b of plate 93b presses sheet 50 in orientation 73b, and at the same time, edge 89a of plate 93a moves in orientation 73b to maintain the distance between edges 89a and 89b approximately equal to the size of sheet 50 along the Y-axis.

[0088] In some embodiments, the SAA includes one or more sensors such as sensors 97a and 97b, which are configured to generate signals indicating the positions of edges 89a and 89b and / or the position of sheet 50, and the processor 20 and / or the controller 54 are configured to control the movement of orientations 73a and 73b of sheet 50 based on the signals received from sensors 97a and 97b.

[0089] In some embodiments, substrate 83a includes one or more arrays 85 of suction holes (VH: vacuum hole) 87, and the VH87 is configured to suck sheet 50 onto the surface of substrate 83a when a vacuum acts on the VH87. Similarly, substrate 83b includes one or more arrays 85b of suction holes (VH) 87, and the VH87 is configured to suck sheet 50 onto the surface of substrate 83b when a vacuum acts on the VH87.

[0090] In some embodiments, the SAA 56 includes one or more slits 92. In this example, after moving in orientation 73a or 73b, the system 10 moves each sheet 50 into the impression station 84 through the slit 92 using any suitable technique.

[0091] In some embodiments, SAA56 has rails that are configured to guide plates 93a and 93b as they move in directions 73a and 73b. The rails can be in the form of slits 92 or any other suitable structure configured to maintain the specified movement of plates 93a and 93b as described above.

[0092] Referring now to FIG. 1, in some embodiments, in response to moving a given sheet 50 in directions 73a and 73b as described above, processor 20 is configured to maintain an image-substrate alignment between the image and sheet 50.

[0093] In some embodiments, processor 20 is configured to control motion assembly 51 to move print bar 62 in direction 53 such that a first image (e.g., image 43 of FIGS. 2A and 2B above) is formed offset from a previous second image of the same batch formed on a previous second panel of blanket 44 (before movement of print bar 62) onto a first panel of blanket 44 (after movement of print bar 62).

[0094] In some embodiments, processor 20 is configured to control SAA56 to move sheet 50 in direction 73 corresponding to the movement of print bar 62 in direction 53 such that first image 43 is transferred to an intended position on the surface of each sheet 50 while maintaining the same image-substrate alignment between first image 43 and each sheet 50.

[0095] In addition or alternatively, processor 20 is configured to move sheet 50 in direction 46 to prevent an undesired formation of imprint 58.

[0096] In some embodiments, at least one of the movements in directions 46, 73, 53, and 48 is about 1 mm to 100 mm relative to the default position of each entity. For example, SAA56 is configured to move the sheet 50 as in the example of FIG. 2B, and the distance between edges 18a and 18b is about 40 mm.

[0097] In an alternative embodiment, the movement of the sheet 50 is used with the sequential shift of the image 43 formed on the blanket 44 to prevent the imprint of the image 43 on the blanket 44, which is also referred to herein as the memory effect. This is described in detail, for example, in International Application No. PCT / IB2022 / 054614 (Patent Document 14), and is incorporated herein by reference to its disclosure.

[0098] FIG. 4 is a flowchart schematically showing a method for preventing the formation of an imprint 58 of a previously printed image 43 on a blanket 44 according to an embodiment of the present invention.

[0099] This method starts from the first image printing step 100, where the processor 20 controls the stations and modules of the system 10 (e.g., at least the image forming module 60 and the blanket module 70 described in detail above in FIG. 1) to generate the first image 43 on the blanket 44. The image 43 consists of an ink image of the digital image 42. Further, the processor 20 controls the blanket module 70 to move the blanket 44 along the direction 94 (parallel to the X-axis) to the engagement point (described above in FIG. 1) between the blanket 44 and the first sheet 50, and transfers the first image 43 to the sheet 50 disposed at the first position with respect to the blanket 44. The first image 43 is transferred to a predetermined position on the surface of the first sheet 50.

[0100] In position specifying step 102, for the second sheet 50 (also referred to herein as the second sheet 50, which is similar to the first sheet 50 and follows the first sheet 50), the processor 20 is configured to specify a second position for the blanket 44 at the engagement point. In some embodiments, as described above in FIG. 2B, the second position is offset from the first position along at least an axis in the direction intersecting the printing direction (e.g., the Y-axis of the XYZ coordinate system).

[0101] In substrate moving step 104, the processor 20 is configured to control the SAA 56 to move the second sheet 50 to the second position specified in step 102 above in at least a second orientation (e.g., orientations 73a or 73b, which are generally parallel to the Y-axis but not necessarily so). The configuration example of the SAA 56 and the operation of moving the sheet 50 are described in detail in FIG. 3 above.

[0102] In the second image printing step 106 that completes the above method, the processor 20 controls at least the image forming station 60, the motion assembly 51, and the blanket module 70 to generate a second image 43a on the blanket 44. In some embodiments, the processor 20 controls the motion assembly 51 to move the image forming station 60 (e.g., to orientation 73a or 73b) to generate the second image 43a at a third position on the blanket 44, and the third position at least partially (generally completely) compensates for the difference between the first position and the second position in steps 100 and 102 above. Further, in addition to controlling the SAA 56 (as described above in step 104), the processor 20 controls the impression station 84, as described in detail in FIG. 2B above, to transfer the second image 43a to a predetermined position on the second sheet 50.

[0103] In other words, to prevent the formation of the imprint 58 on the blanket 44, the processor 20 controls the assembly 51 to move the image forming station 60 in the direction intersecting the printing direction (e.g., the orientations 73a and / or 73b). Then, to maintain the required level of image - substrate alignment, the processor 20 controls the assembly 56 to move the sheet 50 in the same direction by the same distance to compensate for the movement executed by the assembly 51.

[0104] The embodiments described herein mainly address digital printing using a flexible intermediate transfer member. However, the methods and systems described herein can also be used for other applications, such as in any suitable type of printing system and process having any suitable type of intermediate device (e.g., member) for receiving an image and transferring this image to a target substrate.

[0105] The above - described embodiments are cited as examples, and it is clear that the present invention is not limited to what has been specifically illustrated and described above. Rather, the scope of the present invention includes both the combinations and sub - combinations of the various features described above, as well as their variations and modifications, which can be conceived by those skilled in the art upon reading the above description and are not disclosed in the prior art. The documents incorporated by reference in this patent application should be considered an essential part of this application. However, except when any term is defined in these incorporated documents in a manner that conflicts, either explicitly or implicitly, with the definitions made herein, only the definitions herein should be considered.

Claims

Claim 1 A method of printing, comprising: generating a first image on a movable intermediate transfer member (ITM) of a printing system, and moving the ITM in a first direction along to an engagement point between the ITM and a first substrate, and transferring the first image to the first substrate disposed at a first position with respect to the ITM, wherein the first image is transferred to a predetermined position on the first substrate; with respect to a second image generated on the ITM after the first image and intended to be transferred to a predetermined position on a second substrate, designating, at the engagement point, a second position with respect to the ITM for the second substrate, the second position being offset from the first position; moving the second substrate at least in a second direction to the second position; generating the second image at a third position on the ITM, the third position at least partially compensating for a difference between the first position and the second position, and transferring the second image to a predetermined position on the second substrate; and a method including the above steps. Claim 2 The method according to claim 1, wherein the first substrate and the second substrate have equal sizes, and the first image and the second image are copies of a predetermined image. Claim 3 The method according to claim 1, wherein the first substrate and the second substrate have different sizes, and the first image and the second image are copies of a predetermined image. Claim 4 The method according to claim 3, wherein the size of the second substrate along an axis parallel to at least the second direction is larger than that of the first substrate. Claim 5 The method according to claim 1, wherein the first direction and the second direction are different from each other. Claim 6 The method according to claim 5, wherein the first direction includes a printing direction, and the second direction includes a direction intersecting the printing direction. Claim 7 The method according to any one of claims 1 to 6, wherein the first substrate and the second substrate each include a first sheet and a second sheet, and moving the second sheet at least in the second direction includes controlling a sheet alignment assembly (SAA) to move the second sheet in the second direction to the second position before the second sheet is inserted at the engagement point. Claim 8 The first substrate and the second substrate each include a first sheet and a second sheet, the first sheet and the second sheet are stacked in an input stack, and moving the second sheet at least in the second direction controls an input pile centering assembly (PCA) to (i) after the first sheet has left the input stack and (ii) when the second sheet is disposed within the input stack, move the second sheet in the second direction, the method according to any one of claims 1 to 6.

9. The method according to claim 8, comprising controlling an output PCA to move an output stack in the second direction to receive the second sheet and stack it on the first sheet within the output stack.

10. Generating the second image at the third position on the ITM includes (i) controlling a motion assembly to move one or more print bars of the printing system in the second direction and (ii) controlling at least one of the print bars to apply droplets of printing fluid to a predetermined position on the surface of the ITM, the method according to any one of claims 1 to 6.

11. A printing system comprising a printing assembly and a processor, the printing assembly is configured to generate an image on a movable intermediate transfer member (ITM) and transfer the image to a substrate, the printing assembly includes one or more motion assemblies, the motion assemblies are configured to (i) move the ITM, (ii) move the printing assembly, and (iii) move the substrate, the processor is, controlling the printing assembly to generate a first image on the ITM, moving the ITM along a first direction to an engagement point between the ITM and a first substrate, and transferring the first image to the first substrate disposed at a first position relative to the ITM, the first image being transferred to a predetermined position on the first substrate. For a second image intended to be generated on the ITM after the first image and transferred to a predetermined position on the second substrate, (i) at the engagement point, a second position with respect to the ITM is specified for the second substrate, the second position being a position offset with respect to the first position, and (ii) the printing assembly is controlled to (a) move the second substrate to the second position at least in a second direction, (b) generate the second image at a third position on the ITM, the third position at least partially compensating for the difference between the first position and the second position, and (c) transfer the second image to the predetermined position on the second substrate is configured to a printing system

12. The printing system according to claim 11, wherein the first substrate and the second substrate have equal sizes, and the first image and the second image are copies of a predetermined image

13. The printing system according to claim 11, wherein the first substrate and the second substrate have different sizes, and the first image and the second image are copies of a predetermined image

14. The printing system according to claim 13, wherein the size of the second substrate along an axis parallel to at least the second direction is larger than that of the first substrate

15. The printing system according to claim 11, wherein the first direction and the second direction are different from each other

16. The printing system according to claim 15, wherein the first direction includes a printing direction, and the second direction includes a direction intersecting the printing direction

17. The first substrate and the second substrate each include a first sheet and a second sheet, the printing system includes a sheet alignment assembly (SAA), the SAA being configured to move the second sheet to the second position in the second direction, the processor is configured to control the SAA to move the second sheet in the second direction before the second sheet is inserted at the engagement point The printing system according to any one of claims 11 to 16

18. The first substrate and the second substrate each include a first sheet and a second sheet, the first sheet and the second sheet being stacked in an input stack, the printing system includes an input pile centering assembly (PCA), the input PCA being configured to move the second sheet in the second direction The processor is configured to control the input PCA to move the second sheet in the second direction (i) after the first sheet has left the input stack and (ii) when the second sheet is disposed within the input stack. The printing system according to any one of claims 11 to 16.

19. The printing system includes an output PCA, and the output PCA is configured to receive the first sheet and the second sheet and stack them within the output stack. The processor is configured to control the output PCA to move the output stack in the second direction to receive the second sheet and stack it on the first sheet within the output stack. The printing system according to claim 18.

20. The printing system includes (a) a plurality of print bars and (b) a motion assembly. The plurality of print bars are configured to apply droplets of each color of a printing liquid having a plurality of colors. The motion assembly is configured to move one or more of the print bars. The processor is configured to (i) control the motion assembly to move one or more of the print bars in the second direction and (ii) control at least one of the print bars to apply droplets of the printing liquid to a predetermined position on the surface of the ITM. The printing system according to any one of claims 11 to 16.

21. A system comprising an interface and a processor, The interface is configured to receive, in a digital printing system, digital images intended to be printed on a first substrate and a second substrate as a first image and a second image, respectively. The processor is configured to control a printing assembly to generate the first image on a movable intermediate transfer member (ITM), and (b) move the ITM along a first direction to an engagement point between the ITM and the first substrate to transfer the first image to the first substrate disposed at a first position with respect to the ITM, and the first image is transferred to a predetermined position on the first substrate. The processor is further configured to, for the second image intended to be (a) generated on the ITM after the first image and (b) transferred to a predetermined position on the second substrate, (i) at the engagement point, specify a second position for the second substrate relative to the ITM, the second position being an offset position relative to the first position, and (ii) control the printing assembly to: (a) move the second substrate at least in a second direction to the second position, (b) generate the second image at a third position on the ITM, the third position at least partially compensating for the difference between the first position and the second position, and (c) transfer the second image to the predetermined position on the second substrate. System.

Images