Digital printing system and process

Abstract

A method includes: (i) generating a first image (43) on an intermediate transfer member (ITM) (44), moving the ITM along a first direction (94) to a junction between the ITM and a first substrate (50) to transfer the first image to the first substrate at a first position relative to the ITM, the first image being transferred to a given position on the first substrate, and (ii) for a second image (43a) intended to be produced on the ITM after the first image and transferred to a given position on a second substrate (50): a) specifying a second position with respect to the ITM for the second substrate at the junction point, the second position being offset with respect to the first position, the method comprises the following steps: (a) generating a first image on the ITM in a first direction (73a, 73b), (b) moving a second substrate at least in a second direction (73a, 73b) to a second position, and (c) generating a second image on the ITM in a third position which is to compensate for a difference between the first position and the second position, and transferring the second image to the given position on the second substrate.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 355,614, filed on June 26, 2022, the disclosure of which is incorporated herein by reference. Field of the Invention

[0003] The present invention relates generally to digital printing, and in particular to methods and systems for reducing the footprint of transfer between an intermediate transfer member and a substrate during the printing process. Background of the Invention

[0005] Some printing systems have an intermediate transfer member configured to receive an image and transfer the image to a target substrate. In some cases, a print batch containing a large number (e.g., thousands) of copies of a particular image produced on an intermediate transfer member and transferred to a corresponding number of sheets may result in undesirable imprinting of the edges of the sheets on the intermediate transfer member, such that the edge outline may appear in the printing of another image, such as in the next print batch. This phenomenon may reduce the quality of subsequent images printed in subsequent batches using the same intermediate transfer member. Summary of the invention

[0006] An embodiment of the present invention described herein provides a printing method, the method comprising: (i) producing a first image on a movable intermediate transfer member (ITM) of a printing system, and moving the ITM along a first direction to a junction between the ITM and a first substrate to transfer the first image to the first substrate located at a first position relative to the ITM, the first image being transferred to a given position on the first substrate; and (ii) for a second image intended to be produced on the ITM and transferred to a given position on a second substrate after the first image: (a) specifying a second position relative to the ITM for the second substrate at the junction, the second position being located at a certain offset relative to the first position, (b) moving the second substrate at least in the second direction to a second position, and (c) producing a second image on the ITM at a third position, the third position at least partially compensating for the difference between the first position and the second position, and transferring the second image to a given position on the second substrate.

[0007] In some embodiments, the first substrate and the second substrate have equal sizes, and the first image and the second image are copies of a given image. In other embodiments, the first substrate and the second substrate have different sizes, and the first image and the second image are copies of a given image. In still other embodiments, the second substrate is larger than the first substrate at least along an axis parallel to the second direction.

[0008] In some embodiments, the first direction and the second direction are different from each other. In other embodiments, the first direction includes a printing direction, and the second direction includes a transverse printing direction. In still other embodiments, the first substrate and the second substrate include a first sheet and a second sheet, respectively, and moving the second sheet in at least the second direction includes controlling a sheet alignment assembly (SAA) to move the second sheet to a second position in the second direction before inserting the second sheet into the junction.

[0009] In some embodiments, the first substrate and the second substrate include a first sheet and a second sheet, respectively, the first sheet and the second sheet are stacked in an input stack, and moving the second sheet in at least a second direction includes controlling an input stack centering assembly (PCA) to move the second sheet in the second direction: (i) after the first sheet is moved away from the input stack, and (ii) when the second sheet is located in the input stack. In other embodiments, the method includes controlling an output PCA to move an output stack in the second direction for receiving a second sheet and stacking the second sheet on top of the first sheet in the output stack. In still other embodiments, producing a second image on the ITM at a third position includes controlling: (i) a motion assembly to move one or more print bars of a printing system in the second direction, and (ii) at least one of the print bars to apply droplets of printing fluid to a predefined location on the surface of the ITM.

[0010] According to an embodiment of the present invention, there is further provided a printing system, which includes a printing assembly and a processor. The printing assembly is configured to produce an image on a movable intermediate transfer member (ITM) and transfer the image to a substrate, and the printing assembly includes one or more moving assemblies, and the moving assemblies are configured to move: (i) ITM, (ii) printing assembly, and (iii) substrate. The processor is configured to control a printing component to produce a first image on an ITM, and to move the ITM along a first direction to a junction between the ITM and a first substrate to transfer the first image to the first substrate located at a first position relative to the ITM, the first image being transferred to a given position on the first substrate, and for a second image intended to be produced on the ITM after the first image and transferred to a given position on a second substrate, the processor is configured to: (i) specify a second position relative to the ITM for the second substrate at the junction, the second position being located at a certain offset relative to the first position, and (ii) control the printing component to: (a) move the second substrate at least in the second direction to a second position, (b) produce a second image on the ITM at a third position, 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 given position on the second substrate.

[0011] According to an embodiment of the present invention, a system is also provided, which includes an interface and a processor. The interface is configured to receive digital images intended to be printed as first images and second images on a first substrate and a second substrate in a digital printing system, respectively. The processor is configured to control the printing assembly to: (a) produce a first image on a movable intermediate transfer member (ITM), and (b) move the ITM along a first direction to a junction between the ITM and the first substrate to transfer the first image to the first substrate located at a first position relative to the ITM, the first image being transferred to a given position on the first substrate. For a second image intended to: (a) be produced on the ITM after the first image and (b) be transferred to a given position on a second substrate, the processor is configured to: (i) specify a second position relative to the ITM for the second substrate at a junction, the second position being located at a certain offset relative to the first position; and (ii) control the printing component to: (a) move the second substrate to a second position at least in a second direction, (b) produce a second image on the ITM at a third position, 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 given position on the second substrate.

[0012] The present invention will be more fully understood through the following detailed description of the embodiments of the present invention in conjunction with the accompanying drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic side view of a digital printing system according to an embodiment of the present invention;

[0014] Figure 2A and Figure 2B is a schematic pictorial representation of an imprint formed on a blanket of a digital printing system according to an embodiment of the present invention;

[0015] Figure 3 is a schematic pictorial representation of a sheet alignment assembly of a digital printing system according to an embodiment of the present invention; and

[0016] Figure 4 Schematically shows a method for preventing a previously printed image from being imprinted on a Figure 1 and a flowchart of the blanket method of FIG2 . DETAILED DESCRIPTION

[0017] Overview

[0018] Industrial-scale digital printing often requires printing hundreds or thousands of copies of an image on hundreds or thousands of substrates. Some digital printing systems include a flexible intermediate transfer member (ITM) formed into a loop. The ITM is adapted to move and receive ink droplets to form an image on the surface of the ITM. Subsequently, the moving ITM is engaged with a target substrate (e.g., a sheet) by applying an engagement (e.g., pressing) force to transfer the image to the sheet. This process is repeated hundreds or thousands of times.

[0019] In some cases, a repeatable engagement force applied to one or more edges of a sheet may result in undesirable formation of marks on the ITM (e.g., along the printing axis). In addition, in some cases, the dimensions of the sheet may change during a subsequent print job. In such cases, the outline of the mark may undesirably appear on the surface of a subsequent sheet and, thereby, may reduce the quality of the subsequent printed image. Therefore, it is critical to reduce or even eliminate the formation of such marks on the ITM.

[0020] Embodiments of the invention described herein below provide improved techniques for reducing or preventing marking on ITMs.

[0021] In some embodiments, a digital printing system includes a printing assembly and a processor. The printing assembly includes: (i) an image forming station configured to apply droplets of a printing fluid (e.g., a plurality of colors of ink), (ii) a movable intermediate transfer member (ITM) configured to receive the droplets to produce an image thereon, (iii) an imprinting station configured to engage the ITM with a substrate (e.g., a sheet) to transfer the image to the sheet, and (iv) one or more motion components configured to move: (a) the ITM, (b) the printing assembly, and (c) the sheet.

[0022] In some embodiments, the image forming station directs the droplets to predefined locations on the surface of the mobile ITM so as to produce an image at the predefined location. In addition, the image includes a plurality of color images that are registered with each other so that the image is produced without distortion caused by relative displacement of the droplet positions (i) between the color images and (ii) within each of the color images.

[0023] In some embodiments, the processor is configured to control the printing assembly to produce a first image on the ITM, and move the ITM along a first direction (e.g., a printing direction) to a junction between the ITM and the first sheet to transfer the first image to the first sheet located at a first position relative to the ITM, the first image being transferred to a given position on the first sheet.

[0024] In some embodiments, for a second image intended to be produced on the ITM after the first image and transferred to a given position on the second sheet, the processor is configured to specify a second position relative to the ITM for the second sheet at the junction, the second position being located at a certain offset relative to the first position. The processor is also configured to control the printing assembly to: (i) move the second sheet to the second position at least in a second direction (e.g., a transverse printing direction orthogonal to the printing direction), (ii) produce the second image on the ITM at a third position, 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 given position on the second sheet. It should be noted that changing the position of the sheet on the ITM at the junction reduces or prevents the formation of a mark on the ITM, and thereby correspondingly prevents the formation of a mark outline on a subsequent image printed on a subsequent sheet.

[0025] System Description

[0026] Figure 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 rolling flexible blanket 44 that circulates through an image forming station 60, a drying station 64, an impression station 84, and a blanket handling station 52. In the context of the present invention and in the claims, the terms "blanket" and "intermediate transfer member (ITM)" are used interchangeably and refer to a flexible member including one or more layers used as an intermediate transfer member, the flexible member being formed into an endless loop that is configured to receive, for example, an ink image from an image forming station 60 (hereinafter referred to as an intermediate transfer member). Figure 2A and Figure 2B ) and transferring the ink image to a target substrate, as will be described in detail below.

[0027] In one mode of operation, the image forming station 60 is configured to form a mirror image of the digital image 42 on the upper run of the surface of the blanket 44, the mirror image also referred to herein as the "ink image" (hereinafter referred to as the "ink image"). Figure 2A and Figure 2B The ink image is then transferred to a target substrate (e.g., paper, folding carton, multi-layer polymer, or any suitable flexible packaging in sheet or continuous web form) located below the lower run of blanket 44.

[0028] In the context of the present invention, the term “run” refers to the length or section of blanket 44 between any two given rollers that guide blanket 44 .

[0029] In some embodiments, during installation, blanket 44 can be adhered edge to edge using seam sections (also referred to herein as seams 45) to form a continuous blanket loop (also referred to herein as a closed loop). Examples of methods and systems for seam installation are described in detail in U.S. Patent Application Publication No. 2020 / 0171813, the disclosure of which is incorporated herein by reference.

[0030] In some embodiments, 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 run of blanket 44. In some embodiments, each print bar 62 includes a bank of print heads as wide as the print area on blanket 44 and includes individually controllable print nozzles configured to eject ink and other types of printing fluids onto blanket 44, as described in detail below.

[0031] In some embodiments, image forming station 60 may include any suitable number of print bars 62, which for brevity are also referred to herein as bars 62. Each bar 62 may contain a printing fluid, such as a different colored aqueous ink. The inks typically have visible colors, such as, but not limited to, cyan, magenta, red, green, blue, yellow, black, and white. Figure 1 In the example of , the image forming station 60 includes seven print bars 62, but may include, for example, four print bars 62 of any selected colors such as cyan (C), magenta (M), yellow (Y), and black (K).

[0032] In some embodiments, the printhead is configured to eject ink drops of different colors onto the surface of blanket 44 to form an ink image (not shown) on the surface of blanket 44. In this example, blanket 44 moves along the X-axis of an XYZ coordinate system of system 10, and the ink drops are directed by the printhead, generally parallel to the Z-axis of the coordinate system.

[0033] In some embodiments, different print bars 62 are spaced apart from one another along an axis of movement, also referred to herein as (i) the direction of movement 94 of the blanket 44 or (ii) the printing direction. In this example, the direction of movement of the blanket 44 is parallel to the X-axis, and each print bar 62 extends along the Y-axis of the XYZ coordinates of the system 10. In this configuration, accurate spacing between the bars 62 along the X-axis and synchronization between the ink droplets guiding each bar 62 and the moving blanket 44 are critical to achieving correct placement of the image pattern.

[0034] In the context of the present disclosure and in the claims, the terms "inter-color pattern placement," "pattern placement accuracy," "inter-color registration," "C2C registration," "inter-color position difference," "inter-rod registration," and "color registration" are used interchangeably and refer to any placement accuracy of two or more colors relative to each other.

[0035] In some embodiments, the system 10 includes a heater 66, such as a hot gas or air blower and / or an infrared-based heater with a gas or air blower for flowing the gas or air at any suitable temperature. The heater 66 is positioned between the print bars 62 and is configured to partially dry the ink droplets deposited on the surface of the blanket 44. Such air flow between the print bars can help, for example, (i) reduce condensation at the surface of the print head and / or deal with splatter (e.g., residue or small droplets distributed around the main ink droplets), and / or (ii) prevent the orifices of the inkjet nozzles of the print head from clogging, and / or (iii) prevent ink droplets of different colors on the blanket 44 from undesirably merging with each other.

[0036] In some embodiments, system 10 includes a drying station 64 configured to direct infrared radiation and cool air (or another gas) and / or blow hot air (or another gas) onto the surface of blanket 44. In some embodiments, drying station 64 can include an infrared-based illumination assembly (not shown) and / or an air blower 68 or any other suitable drying device.

[0037] In some embodiments, in the drying station 64, the ink image formed on the blanket 44 is exposed to radiation and / or hot air to more thoroughly dry the ink, thereby evaporating most or all of the liquid carrier and leaving only a layer of resin and colorant that is heated to the point of becoming a tacky ink film.

[0038] In some embodiments, system 10 includes a blanket module 70 (also referred to herein as an ITM module) that includes a rolling flexible ITM, such as blanket 44. In some embodiments, blanket module 70 includes one or more rollers 78, wherein at least one of rollers 78 includes a motion encoder (not shown) configured to record the position of blanket 44 in order to control the position of segments of blanket 44 relative to corresponding print bars 62. In some embodiments, one or more motion encoders may be integrated with additional rollers and other moving components of system 10.

[0039] In some embodiments, the aforementioned motion encoder generally includes at least one rotary encoder configured to generate a rotation-based position signal indicative of the angular displacement of the corresponding roller. It should be noted that in the context of the present invention and in the claims, the terms "indicative of" and "indication" are used interchangeably.

[0040] Additionally or alternatively, blanket 44 may include an integrated encoder (not shown) for controlling the operation of various modules of system 10. One implementation of an integrated motion encoder is described in detail, for example, in PCT International Publication No. WO 2020 / 003088, the disclosure of which is incorporated herein by reference.

[0041] In some embodiments, blanket 44 is guided over rollers 76, 78 and other rollers described herein and over a powered tensioning roller, also referred to herein as a dancer roller assembly 74. Dancer roller assembly 74 is configured to control the slack length of blanket 44 and its movement in a controlled manner. Figure 1 In addition, any stretching of the blanket 44 due to aging will not affect the ink image placement performance of the system 10, and will only require taking up more slack by tensioning the dancer roller assembly 74.

[0042] In some embodiments, the floating roller assembly 74 can be motorized. The configuration and operation of rollers 76 and 78 are described in more detail, for example, in U.S. Patent Application Publication No. 2017 / 0008272 and PCT International Publication No. WO 2013 / 132424 mentioned above, the disclosures of which are incorporated herein by reference in their entirety.

[0043] In some embodiments, the system 10 includes a blanket tension drive roller (BTD) 99 and a blanket control drive roller (BCD) 77, which are powered by respective first and second motors, typically electric motors (not shown), and are configured to rotate about their own first and second axes, respectively.

[0044] 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 into blanket 44 or may include sensors external to blanket 44 that use any other suitable technique to acquire signals indicative of 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 in order to monitor the tension applied to blanket 44 and control the operation of dancer assembly 74.

[0045] In the impression station 84, the blanket 44 passes between the impression cylinder 82 and the pressure cylinder 90, which is configured to carry a compressible blanket (hereinafter Figure 3 In some embodiments, the motion encoder is integrated with at least one of the impression cylinder 82 and the pressure cylinder 90.

[0046] In some embodiments, the system 10 includes a console 12 configured to control multiple modules of the system 10, such as a blanket module 70, an image forming station 60 located above the blanket module 70, and a substrate transport module 80, which is located below the blanket module 70 and includes one or more stamping stations, as will be described below.

[0047] In some embodiments, the console 12 includes a processor 20 (typically a general purpose processor) having a suitable front end and interface circuitry to interface with and receive signals from a controller of the dancer assembly 74 and the controller 54 via a cable 57. Additionally or alternatively, the console 12 may include any suitable type of application specific integrated circuit (ASIC) and / or digital signal processor (DSP) and / or any other suitable type of processing unit configured to perform any type of processing on data processed in the system 10.

[0048] In some embodiments, the controller 54, which is schematically shown as a single device, may include one or more electronic modules mounted on the system 10 at predefined locations. At least one of the electronic modules of the controller 54 may include 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 the control circuit may be programmed with software to implement the functions used by the printing system and store data for the software in the memory 22. For example, the software may be downloaded to the processor 20 and the control circuit in electronic form over a network, or the software may be provided on a non-transitory tangible medium, such as an optical, magnetic, or electronic memory medium.

[0049] In some embodiments, console 12 includes a display 34 configured to display data and images received from processor 20 or input inserted by a user (not shown) using input device 40. In some embodiments, console 12 may have any other suitable configuration, such as the alternative configurations of console 12 and display 34 described in detail in U.S. Pat. No. 9,229,664, the disclosure of which is incorporated herein by reference.

[0050] In some embodiments, processor 20 is configured to display a digital image 42 on display 34 that includes one or more sections (not shown) of image 42 and / or various types of test patterns that may be stored in memory 22 .

[0051] In some embodiments, a blanket treatment station 52 (also referred to herein as a cooling station) is configured to treat the blanket by, for example, cooling the blanket and / or applying a treatment fluid to the outer surface of the blanket 44 and / or washing the outer surface of the blanket 44. At the blanket treatment station 52, the temperature of the blanket 44 may be reduced to a desired temperature level before the blanket 44 enters the image forming station 60. Treatment may be performed by passing the blanket 44 over one or more rollers or blades configured to apply cooling and / or washing and / or treatment fluids to the outer surface of the blanket.

[0052] In some embodiments, blanket treatment station 52 may also include one or more bars (not shown) positioned adjacent to print bar 62 so that treatment fluid may additionally or alternatively be applied to blanket 44 via spraying.

[0053] In some embodiments, processor 20 is configured to receive a signal indicative of a surface temperature of blanket 44, for example from a temperature sensor (not shown), in order to monitor the temperature of blanket 44 and control the operation of blanket processing station 52. Examples of such processing stations are described, for example, in PCT International Publications WO2013 / 132424 and WO2017 / 208152, the disclosures of which are incorporated herein by reference in their entirety.

[0054] exist Figure 1 In the example of FIG. 5 , station 52 is mounted between stamping station 84 and image forming station 60, however, station 52 may be mounted adjacent to blanket 44 at any other or additional suitable location or locations between stamping station 84 and image forming station 60. As described above, station 52 may additionally or alternatively be mounted on a bar adjacent to image forming station 60.

[0055] exist Figure 1 In the example of the embodiment of the present invention, the impression cylinder 82 and the pressure cylinder 90 impress the ink image onto the target flexible substrate (such as the individual sheets 50) which is transported by the substrate transport module 80 from the input stack 86 to the output stack 88 via the impression station 84. In this example, a rotary encoder (not shown) is integrated with the impression cylinder 82.

[0056] In some embodiments, the lower run of the blanket 44 selectively interacts with the impression cylinder 82 at the impression station 84 to emboss the image pattern onto the target flexible substrate compressed between the blanket 44 and the impression cylinder 82 by the pressure of the pressure cylinder 90. Figure 1 In the case of the simplex printer shown (ie printing on one side of the sheet 50), only one embossing station 84 is required.

[0057] In other embodiments, module 80 may include two or more impression cylinders (not shown) to allow duplex printing at one or more locations. The configuration of the two impression cylinders also enables single-sided printing at twice the speed of printing double-sided printed matter. In addition, a large number of mixed single-sided printed matter and double-sided printed matter can also be printed. In alternative embodiments, different configurations of module 80 can be used for printing on continuous web substrates. For example, detailed descriptions and various configurations of duplex printing systems and systems for printing on continuous web substrates are provided in U.S. Patents 9,914,316 and 9,186,884, PCT International Publication WO 2013 / 132424, U.S. Patent Application Publication 2015 / 0054865, and U.S. Provisional Application 62 / 596,926, the disclosures of which are all incorporated herein by reference.

[0058] As briefly described above, a sheet 50 or continuous web substrate (not shown) is carried by the module 80 from an input stack 86 and passes through a nip (not shown) between the impression cylinder 82 and the pressure cylinder 90. Within the nip, the surface of the blanket 44 carrying the ink image is firmly pressed against the sheet 50 (or another suitable substrate), such as by a compressible blanket of the pressure cylinder 90, so that the ink image is impressed onto the surface of the sheet 50 and cleanly separated from the surface of the blanket 44. The sheet 50 is then conveyed to the output stack 88.

[0059] In some embodiments, the system 10 includes a stack centering assembly (PCA) 49 configured to move an input stack 86 of sheets 50 in a movement direction 46. Similarly, the system 10 includes a PCA 47 configured to move an output stack 88 of sheets 50 in a movement direction 48. In this example, the movement directions 46 and 48 are substantially parallel to the Y axis of the XYZ coordinate system, but in other embodiments, at least one of the movement directions 46 and 48 may not be parallel to the Y axis.

[0060] exist Figure 1In the example of FIG. 4 , roller 78 is positioned at the upper run of blanket 44 and is configured to keep blanket 44 taut while traveling adjacent to image forming station 60. In addition, it is particularly important to control the speed of blanket 44 beneath image forming station 60 in order to obtain accurate ejection and deposition of ink droplets to form an image on the surface of blanket 44 by image forming station 60.

[0061] In some embodiments, system 10 includes a motion assembly 51 configured to move one or more printbars 62 in a movement direction 53. In this example, motion assembly 51 is configured to move all of printbars 62 of image forming station 60 together.

[0062] In some embodiments, the system 10 further includes a sheet alignment assembly (SAA) 56 configured to move the sheet 50 prior to inserting the sheet into the imprinting station 84. Figure 3 The structure and functionality of SAA 56 are described in detail in .

[0063] In some embodiments, the movement directions 53 and 73 are substantially parallel to the Y axis of the XYZ coordinate system, but in other embodiments, at least one of the movement directions 53 and 73 may not be parallel to the Y axis. It should be noted that in this example, the movement direction 53 is different from the movement direction 94, which is the movement 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 transverse printing direction, which is generally approximately orthogonal to the printing direction (i.e., the movement direction 94).

[0064] In some embodiments, the impression cylinder 82 periodically engages and disengages the blanket 44 to transfer the ink image from the moving blanket 44 to the 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 aforementioned roller and dancer roller assembly to keep the upper run taut and substantially isolate the upper run of the blanket 44 from mechanical vibrations occurring in the lower run.

[0065] In some embodiments, system 10 includes a printing assembly 31, which includes: (i) an image forming station 60, (ii) a rubber blanket 44, (iii) an impression station 84, and (iv) one or more motion components, such as: (a) a rubber blanket module 70, which is configured to move the rubber blanket 44, (b) a motion assembly 51, which is configured to move one or more print bars 62 of the image forming station 60, and (c) an SAA 56, which is configured to move the sheet 50 in a transverse printing direction before inserting the sheet 50 into the impression station 84, as described in detail above.

[0066] In some embodiments, printing assembly 31 may also include PCAs 49 and 47 that are configured to move input stack 86 and output stack 88, respectively, as described in detail above.

[0067] In some embodiments, the system 10 includes an image quality control station 55 (also referred to herein as an automatic quality management (AQM) system) that functions as a closed-loop inspection system integrated into the system 10. In some embodiments, such as Figure 1 Image quality control station 55 may be positioned adjacent to impression cylinder 82 , as shown, and / or at any other suitable location in system 10 .

[0068] In some embodiments, the image quality control station 55 includes a camera (not shown) configured to acquire one or more digital images of the aforementioned ink images printed on the sheet 50. In some embodiments, the camera can include any suitable image sensor, such as a contact image sensor (CIS) or a complementary metal oxide semiconductor (CMOS) image sensor, and a scanner including a slit having a width of about one meter or any other suitable width.

[0069] In the context of this disclosure and in the claims, the terms "about" or "substantially" used with any numerical values ​​or ranges indicate a suitable dimensional tolerance that allows the part or collection of components to function to achieve its intended purpose as described herein.

[0070] In some embodiments, station 55 may include a spectrophotometer (not shown) configured to monitor the quality of the ink printed on sheet 50 .

[0071] In some embodiments, the digital images acquired by the station 55 are transmitted to a processor (such as the processor 20 or any other processor of the station 55), which is configured to evaluate the quality of the corresponding printed image. Based on the evaluation and the signals received from the controller 54, the processor 20 is configured to control the operation of the modules and stations of the system 10. In the context of the present invention and in the claims, the term "processor" refers to any processing unit (such as the processor 20 or any other processor or controller connected to or integrated with the station 55) that is configured to process the signals received from the camera and / or spectrophotometer of the station 55. It should be noted that the signal processing operations, control-related instructions, and other computing operations described herein may be implemented by a single processor or shared among multiple processors of one or more corresponding computers.

[0072] In some embodiments, station 55 is configured to check the quality of printed images and test patterns to monitor various attributes such as, but not limited to, full image registration with sheet 50 (also referred to herein as image-to-substrate registration), color-to-color (C2C) registration, printed geometry, image uniformity, contour and linearity of color, and functionality of print nozzles. In some embodiments, processor 20 is configured to automatically detect geometric distortion or other errors in one or more of the foregoing attributes.

[0073] In some embodiments, processor 20 is configured to analyze the detected distortion to apply corrective action to the faulty module, and / or feed instructions to another module or station of system 10 to compensate for the detected distortion.

[0074] In some embodiments, the system 10 may print a test mark (not shown) or other suitable feature, for example, at a bevel or edge of the sheet 50. By acquiring an image of the test mark, the station 55 is configured to measure various types of distortion, such as C2C registration, image-to-substrate registration, different widths between colors (referred to herein as "inter-bar width delta" or "inter-color width difference"), various types of local distortion, and front-to-back registration errors (in duplex printing). In some embodiments, the processor 20 is configured to: (i) sort sheets 50 having distortion above a first set of predefined thresholds, for example, to a reject tray (not shown); (ii) initiate corrective action for sheets 50 having distortion above a lower second set of predefined thresholds; and (iii) output sheets 50 having slight distortion, for example, below the second set of thresholds, to an output stack 88.

[0075] In some embodiments, processor 20 is configured to detect deviations in profile and linearity of printed colors based on signals received from the spectrophotometer of station 55 .

[0076] In some embodiments, the processor of station 55 is configured to decide whether to stop the operation of system 10, for example, if the density of distortions is above a specified threshold. The processor of station 55 is also configured to initiate corrective actions in one or more of the modules and stations of system 10, as described above. In some embodiments, the corrective actions may be implemented on the fly (while system 10 continues the printing process), or implemented offline by stopping the printing operation and resolving the problem in the corresponding 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 actions or stop the operation of system 10 if the density of distortions is above a specified threshold.

[0077] Additionally or alternatively, the processor 20 is configured to receive signals, for example from the station 55, indicating additional types of distortions and problems in the printing process of the system 10. Based on these signals, the processor 20 is configured to automatically estimate the pattern placement accuracy level and additional types of distortions and / or defects not mentioned above. In other embodiments, any other suitable method for inspecting the pattern printed on the sheet 50 (or on any other substrate described above) may also be used, such as using an external (e.g., offline) inspection system or any type of measuring device 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.

[0078] For the purpose of illustrating the present invention, the configuration of the system 10 is simplified and provided only by way of example. The components, modules and stations described above in the printing system 10 and additional components and configurations are described in detail in, for example, U.S. Patents 9,327,496 and 9,186,884, PCT International Publications WO 2013 / 132438, WO 2013 / 132424 and WO 2017 / 208152, U.S. Patent Application Publications 2015 / 0118503 and 2017 / 0008272, the disclosures of which are all incorporated herein by reference.

[0079] The specific configuration of system 10 is shown by way of example in order to illustrate certain problems solved by embodiments of the present invention and to demonstrate the application of these embodiments in enhancing the performance of such systems. However, embodiments of the present invention are by no means limited to this particular class of example systems, and the principles described herein may be similarly applied to any other class of printing systems.

[0080] Reduces marking of sheet edges on blanket surface

[0081] Figure 2Ais a schematic pictorial illustration of an undesirably formed mark 58 on a blanket 44 when one or more ink images 43 are produced on the surface of the blanket 44 according to an embodiment of the present invention. In the context of the present disclosure and in the claims, the terms ink image 43, image 43 and grammatical variations thereof are used interchangeably.

[0082] In some cases, a print job may include printing thousands of images, which in this example are copies of a given image (e.g., a digital image 42 generated as an ink image 43), respectively, on thousands of sheets 50. In other words, the same image is printed thousands of times on a panel of blanket 44 and then transferred from blanket 44 to thousands of sheets 50.

[0083] In some embodiments, the impression cylinder 82 periodically engages and disengages the blanket 44, such that at the engaged position (also referred to herein as the engagement point), the impression station 84 is configured to transfer the ink image 43 from the moving blanket 44 to the sheet 50 passing between the blanket 44 and the impression cylinder 82. In some embodiments, during engagement, the impression cylinder 82 and the pressure cylinder 90 are pressed against each other between the left and right edges 18 of the sheet 50 (shown as the imprint 58) and between the dashed lines 75a and 75b of the sheet 50. It should be noted that the image 43 is transferred in the area defined between the dashed lines 75a and 75b and between the imprints 58, rather than in the sections 79a and 79b that are considered to be the edges of the sheet 50. Therefore, a smaller force is applied between the impression cylinder 82 and the pressure cylinder 90 in the sections 79a and 79b than the force applied to the area with the image 43.

[0084] In some cases, a repeatable engagement force applied to the left and right edges 18 of the sheet 50 may result in an undesirable mark 58 being formed along the X-axis of the blanket 44, while a smaller pressure applied between the leading edge 72a and the trailing edge 72b of the sheet 50 does not form a mark along the Y-axis of the blanket 44.

[0085] In some cases, the size of the sheet 50 may change in a subsequent printing operation. For example, in a subsequent printing operation, the size of the subsequent sheet 50 along the Y axis is greater than Figure 2A In such cases, the outline of the imprint 58 (and optionally the image 43) may undesirably appear on the surface of a subsequent sheet 50, for example, on the surface of a subsequent image 43 printed on the surface of the respective subsequent sheet 50. The outline of the imprint 58 may degrade the quality of the subsequent image 43 and, in severe cases, may cause the respective subsequent sheet 50 to be discarded. Therefore, it is critical to reduce and even eliminate the formation of the imprint 58, and Figure 2AA graphic illustration of a method for reducing marking 58 is provided below. In addition, the difference between sheet 50 and subsequent sheets 50 can be in one or both of the X-axis and the Y-axis, and the dimensional ratio between the X-axis and the Y-axis can also be different between sheet 50 and subsequent sheets 50.

[0086] Figure 2B is a schematic pictorial illustration of a method for reducing or eliminating the formation of marks 58 on the surface of blanket 44 according to an embodiment of the present invention.

[0087] In some embodiments, SAA 56 is configured to move the respective sheet 50 in direction 73a or in direction 73b prior to inserting the sheet 50 into imprinting station 84. In this example, directions 73a and 73b are both parallel to the Y axis, but in other embodiments, at least one of directions 73a and 73b may have an orientation other than parallel to the Y axis.

[0088] In an example implementation, the above Figure 1 The techniques described in detail in the first batch of images 43 are sequentially printed on a first batch of sheets 50 (eg, having about 100 sheets 50). Figure 2B In the example of FIG. 4 , the first batch is too small to form an imprint 58 on the blanket 44 . To illustrate that no imprint is formed on the surface of the blanket 44 , the edge 18 appears as a thinner line than the line of the imprint 58 .

[0089] Subsequently, a second batch of images 43a (which are similar to image 43, but referred to herein as image 43a to illustrate that this is a different batch of copies of the same image 43) can be printed separately on a subsequent second batch of sheets 50 (e.g., also having about 100 sheets 50) using the same printing technique (with one difference described herein). In some embodiments, the SAA 56 moves each sheet 50 of the second batch in direction 73a before insertion into the imprinting station 84. It should be noted that due to the movement in direction 73a, all sheets 50 of the second batch are engaged with the blanket 44 in a manner that is offset relative to the position of the sheets 50 of the first batch. As shown in FIG. Figure 2B As shown in the example of FIG. 1 , the positions of the edges 18 a of the sheets 50 of the second batch on the blanket 44 are offset from the positions of the edges 18 a of the sheets 50 of the first batch on the blanket 44 .

[0090] Subsequently, a third batch of images 43b (which are similar to image 43 but are referred to herein as image 43b to illustrate that this is a different batch of copies of the same image 43) are printed on a subsequent third batch of sheets 50 (e.g., also having about 100 sheets 50). Figure 2BIn the example of FIG. 5 , the third batch of sheets 50 are moved by SAA 56 in direction 73 b so that edge 18 b is positioned at a different location on blanket 44 than edges 18 and 18 a. In other words, moving one or more sheets 50 along the Y axis (or in any other suitable direction) changes the location of edges 18, 18 a, and 18 b and reduces or eliminates the formation of marks 58 on the surface of blanket 44.

[0091] Figure 3 is a schematic pictorial representation of a sheet alignment assembly (SAA) 56 of the system 10 in accordance with an embodiment of the present invention.

[0092] In some embodiments, SAA 56 includes one or more side gauges configured to move sheet 50 in directions 73a and 73b as described above. Figure 3 In the example configuration shown, sheet 50 is positioned on two side gauges (SLs) 95a and 95b such that SL 95a moves sheet 50 in direction 73a and SL 95b moves sheet 50 in direction 73b using the techniques described herein.

[0093] In some embodiments, SL 95b includes a generally fixed base plate 83b and a movable plate 93b, which is configured to move in directions 73a and 73b, for example, using a motor 91b controlled by the controller 54 and / or the processor 20. Similarly, SL 95a includes a generally fixed base plate 83a and a movable plate 93a, which is configured to move in directions 73a and 73b, for example, using a motor 91a controlled by the controller 54 and / or the processor 20.

[0094] In some embodiments, when plates 93a and 93b move together in direction 73a, edge 89a of plate 93a pushes edge 18 of sheet 50 in direction 73a, and simultaneously, edge 89b of plate 93b moves in direction 73a so as to maintain the distance between edges 89a and 89b approximately equal to the dimension 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 direction 73b, edge 89b of plate 93b pushes sheet 50 in direction 73b, and simultaneously, edge 89a of plate 93a moves in direction 73b so as to maintain the distance between edges 89a and 89b approximately equal to the dimension of sheet 50 along the Y axis.

[0095] In some embodiments, the SAA includes one or more sensors, such as sensors 97a and 97b, which are configured to generate signals indicating the position of edges 89a and 89b and / or the position of sheet 50, and the processor 20 and / or controller 54 are configured to control the movement of sheet 50 in directions 73a and 73b based on the signals received from sensors 97a and 97b.

[0096] In some embodiments, the bottom plate 83a includes one or more arrays 85a of vacuum holes (VH) 87 configured to adhere the sheet 50 to the surface of the bottom plate 83a when a vacuum is applied to the VH 87. Similarly, the bottom plate 83b includes one or more arrays 85b of vacuum holes (VH) 87 configured to adhere the sheet 50 to the surface of the bottom plate 83b when a vacuum is applied to the VH 87.

[0097] In some embodiments, SAA 56 includes one or more slots 92. In this example, after moving in direction 73a or 73b, system 10 is configured to move each sheet 50 through slot 92 into imprinting station 84 using any suitable technique.

[0098] In some embodiments, SAA 56 includes tracks configured to guide plates 93a and 93b to move in directions 73a and 73b. The tracks may be implemented in slots 92 or using any other suitable structure configured to maintain the specified movement of plates 93a and 93b as described above.

[0099] Now refer to the above Figure 1 In some embodiments, in response to moving a given sheet 50 in direction 73a or 73b as described above, processor 20 is configured to maintain image-to-substrate registration between the image and sheet 50 .

[0100] In some embodiments, processor 20 is configured to control motion assembly 51 to move print bar 62 in direction 53 so that a first image (e.g., Figure 2A and Figure 2B An image 43 of the same batch (after moving the print bar 62) is formed on the first panel of the blanket 44 in a manner that is offset relative to a second previous image 43 of the same batch formed on the second previous panel of the blanket 44 (before moving the print bar 62).

[0101] In some embodiments, processor 20 is configured to control SAA 56 to move sheet 50 (which is intended to receive first image 43) in direction 73 corresponding to movement of print bar 62 in direction 53, so that first image 43 is transferred to the intended location on the surface of the corresponding sheet 50 while maintaining the same image-to-substrate registration between first image 43 and the corresponding sheet 50.

[0102] Additionally or alternatively, processor 20 is configured to move sheet 50 in direction 46 in order to prevent undesired formation of markings 58 .

[0103] In some embodiments, the movement in at least one of directions 46, 73, 53, and 48 is generally between about 1 mm and 100 mm relative to the predefined default position of the corresponding entity. For example, SAA 56 is configured to move sheet 50 so that Figure 2B In the example of FIG. 5 , the distance between edges 18 a and 18 b is approximately 40 mm.

[0104] In an alternative embodiment, movement of the sheet 50 may be used in combination with sequential shifting of the image 43 formed on the rubber blanket 44 to prevent the image 43 from being imprinted on the rubber blanket 44 (also referred to herein as a memory effect), as described in detail, for example, in PCT International Application PCT / IB2022 / 054614, the disclosure of which is incorporated herein by reference.

[0105] Figure 4 is a flow chart schematically illustrating a method for preventing an imprint 58 of a previously printed image 43 from being formed on a blanket 44 according to an embodiment of the present invention.

[0106] The method begins with a first image printing step 100, wherein processor 20 controls the stations and modules of system 10 (e.g., at least the Figure 1 4 and 50) to produce first image 43 on blanket 44. It should be noted that image 43 includes an ink image of digital image 42. In addition, processor 20 is configured to control blanket module 70 to move blanket 44 along direction 94 (parallel to the X-axis) to the junction between blanket 44 and first sheet 50 (described above in Figure 1 4 (described in the foregoing), to transfer the first image 43 to the first sheet 50 located at a first position relative to the blanket 44. It should be noted that the first image 43 is transferred to a given position on (the surface of) the first sheet 50.

[0107] At the position specifying step 102, for the second sheet 50 (also referred to herein as the second sheet 50a, which is similar to the first sheet 50 and follows the first sheet), the processor 20 is configured to specify a second position relative to the blanket 44 at the junction. In some embodiments, the second position is located at a certain offset relative to the first position at least along the transverse printing axis (e.g., the Y axis of the XYZ coordinate system), as described above in Figure 2B Described in detail in .

[0108] At substrate movement 104, processor 20 is configured to control SAA 56 to move second sheet 50 in at least a second direction (e.g., direction 73a or direction 73b, which are typically but not necessarily parallel to the Y axis) to the second position specified in step 102 above. Figure 3 An example configuration of the SAA 56 and the movement operation of the sheet 50 are described in detail in FIG.

[0109] At the second image printing step 106 that ends the method, the processor 20 controls at least the image forming station 60, the motion assembly 51, and the blanket module 70 to produce the 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., in the direction 73a or 73b) so as to produce the second image 43a at a third position on the blanket 44, respectively, the third position will at least partially (and typically completely) compensate for the difference between the first position and the second position of steps 100 and 102 above. In addition, in addition to controlling the SAA 56 (as described above in step 104), the processor 20 also controls the stamping station 84 to transfer the second image 43a to a given position on the second sheet 50, as described above in Figure 2B Described in detail in .

[0110] In other words, to prevent the formation of marks 58 on blanket 44, processor 20 controls assembly 51 to move image forming station 60 in the cross-printing direction (e.g., direction 73a and / or 73b). In addition, to maintain the desired level of image-to-substrate registration, processor 20 controls assembly 56 to move sheet 50 in the same direction and distance to compensate for the movement performed by assembly 51.

[0111] Although the embodiments described herein are primarily directed to digital printing using flexible intermediate transfer members, the methods and systems described herein may also be used in other applications, such as for any type of printing systems and processes having any suitable type of intermediate device (e.g., member) for receiving an image and transferring the image to a target substrate.

[0112] It should be understood that the embodiments described above are cited by way of example, and the present invention is not limited to what has been specifically shown and described above. Rather, the scope of the present invention includes both combinations and sub-combinations of the various features described above, as well as changes and modifications of the features that will occur to those skilled in the art after reading the foregoing description and are not disclosed in the prior art. The documents incorporated by reference into this patent application should be considered an integral part of this application, but in the event that any term defined in these incorporated documents conflicts with a definition explicitly or implicitly made in this specification, only the definition in this specification should be considered.

Claims

1. A printing method, comprising: producing a first image on a movable intermediate transfer member (ITM) of a printing system, and moving the ITM in a first direction to an engagement point between the ITM and a first substrate to transfer the first image to the first substrate at a first position relative to the ITM, the first image being transferred to a given position on the first substrate; as well as For a second image intended to be produced on the ITM and transferred to a second substrate at a given position after the first image: specifying a second position relative to the ITM for the second substrate at the junction, the second position being located at an offset relative to the first position; moving the second substrate at least in a second direction to the second position; as well as The second image is produced on the ITM at a third position that will at least partially compensate for the difference between the first position and the second position and transfer the second image to the given position on the second substrate.

2. The method of claim 1, wherein the first substrate and the second substrate have equal dimensions, and the first image and the second image are copies of a given image.

3. The method of 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 given image.

4. The method of claim 3, wherein the second substrate is larger than the first substrate at least along an axis parallel to the second direction. The method according to claim 1 , wherein the first direction and the second direction are different from each other. The method of claim 5 , wherein the first direction comprises a printing direction and the second direction comprises a transverse printing direction.

7. A method according to any one of claims 1 to 6, wherein the first substrate and the second substrate comprise a first sheet and a second sheet, respectively, and wherein moving the second sheet at least in the second direction comprises controlling a sheet alignment assembly (SAA) to move the second sheet in the second direction to the second position before inserting the second sheet into the joint.

8. A method according to any one of claims 1 to 6, wherein the first substrate and the second substrate respectively include a first sheet and a second sheet, the first sheet and the second sheet are stacked in an input stack, and wherein moving the second sheet in at least the second direction includes controlling an input stack centering assembly (PCA) to move the second sheet in the second direction: (i) after the first sheet is moved away from the input stack, and (ii) when the second sheet is located in the input stack.

9. The method of claim 8, and comprising controlling an output PCA to move an output stack in the second direction for receiving the second sheet and depositing the second sheet on top of the first sheet in the output stack.

10. The method of any one of claims 1 to 6, wherein producing the second image on the ITM at the third position comprises controlling: (i) a motion assembly to move one or more print bars of the printing system in the second direction, and (ii) at least one of the print bars to apply droplets of printing fluid to a predefined location on the surface of the ITM.

11. A printing system comprising: a printing assembly configured to produce an image on a movable intermediate transfer member (ITM) and transfer the image to a substrate, the printing assembly comprising one or more motion assemblies configured to move: (i) the ITM, (ii) the printing assembly, and (iii) the substrate; as well as A processor, the processor being configured to: controlling the printing assembly to produce a first image on the ITM, and moving the ITM in a first direction to a junction between the ITM and a first substrate to transfer the first image to the first substrate at a first position relative to the ITM, the first image being transferred to a given position on the first substrate; as well as For a second image intended to be produced on the ITM and transferred to a second substrate at a given position after the first image, (i) specifying a second position relative to the ITM for the second substrate at the junction, the second position being located at a certain offset relative to the first position; and (ii) controlling the printing assembly to: (a) move the second substrate at least in a second direction to the second position, (b) produce the second image on the ITM at a third position that will at least partially compensate for the difference between the first position and the second position, and (c) transfer the second image to the given position on the second substrate.

12. The printing system of claim 11, wherein the first substrate and the second substrate are of equal size, and the first image and the second image are copies of a given image.

13. The printing system of 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 given image.

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

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

16. The printing system of claim 15, wherein the first direction comprises a printing direction and the second direction comprises a cross-printing direction.

17. A printing system according to any one of claims 11 to 16, wherein the first substrate and the second substrate include a first sheet and a second sheet, respectively, and the printing system includes a sheet alignment assembly (SAA), the SAA being configured to move the second sheet in the second direction to the second position, and wherein the processor is configured to control the SAA to move the second sheet at least in the second direction before inserting the second sheet into the joint.

18. A printing system according to any one of claims 11 to 16, wherein the first substrate and the second substrate respectively include a first sheet and a second sheet, the first sheet and the second sheet are stacked in an input stack, and the printing system includes an input stack centering assembly (PCA), the input PCA is configured to move the second sheet in the second direction, and wherein the processor is configured to control the input PCA to move the second sheet in at least the second direction: (i) after the first sheet is moved away from the input stack, and (ii) when the second sheet is located in the input stack.

19. A printing system according to claim 18, and including an output PCA, which is configured to receive the first sheet and the second sheet and stack them in an output stack, and wherein the processor is configured to control the output PCA to move the output stack in the second direction for receiving the second sheet and stacking the second sheet on top of the first sheet in the output stack.

20. A printing system according to any one of claims 11 to 16, and comprising: (a) a plurality of print bars configured to apply droplets of a printing fluid having a plurality of colors, respectively, and (b) a motion assembly configured to move one or more of the print bars, and wherein the processor is configured to control: (i) the motion assembly to move one or more of the print bars in the second direction, and (ii) at least one of the print bars to apply droplets of the printing fluid to a predefined location on a surface of the ITM.

21. A system comprising: an interface configured to receive a digital image intended to be printed as a first image and a second image on a first substrate and a second substrate, respectively, in a digital printing system; as well as A processor, the processor being configured to: controlling a printing assembly to: (a) produce the first image on a movable intermediate transfer member (ITM), and (b) move the ITM in a first direction to a point of engagement between the ITM and the first substrate to transfer the first image to the first substrate at a first position relative to the ITM, the first image being transferred to a given position on the first substrate; as well as For a second image intended to: (a) be produced on the ITM after the first image and (b) be transferred to a given position on the second substrate, (i) specify a second position relative to the ITM for the second substrate at the junction, the second position being located at a certain offset relative to the first position; and (ii) controlling the printing assembly to: (a) move the second substrate at least in a second direction to the second position, (b) produce the second image on the ITM at a third position that will at least partially compensate for the difference between the first position and the second position, and (c) transfer the second image to the given position on the second substrate.

Images