Protecting digital printing system components

Abstract

To provide systems and methods for protecting elements of a digital printing system from potential damage from foreign matter conveyed by moving parts of the printing system, which are suitable for protecting elements of indirect printing systems using an intermediate transfer member.SOLUTION: A printing system comprises: an intermediate transfer member; an image-forming station comprising a print bar disposed over a surface of the ITM; a conveyer for driving rotation of the ITM; a detection system configured to detect foreign matter 5 transported to a detection location upstream of the image-forming station; and a response system operatively coupled to the detection system to respond to the detection of the foreign matter by performing at least one collision-prevention action to prevent a potential collision between the foreign matter and the print bar.SELECTED DRAWING: Figure 13B

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent application claims the benefit of U.S. Provisional Patent Application No. 62,591,847, filed Nov. 29, 2017, which is incorporated by reference in its entirety.

[0002] The present invention relates to a system and method for protecting components of a digital printing system from potential damage from foreign objects carried by moving parts of the printing system, and in particular, the present invention is suitable for protecting components of an indirect printing system that uses an intermediate transfer member. [Background technology]

[0003] Various printing devices have previously been proposed that use an indirect inkjet printing process, in which an inkjet printhead is used to print an image on the surface of an intermediate transfer member, which is then used to transfer the image to a substrate. The intermediate transfer member (ITM) can be a rigid drum or a flexible belt, also called a blanket (e.g., guided via rollers or attached to a rigid drum). Foreign objects can be inadvertently transferred by the ITM towards the inkjet printhead at high speeds, which can cause damage to the printhead if not avoided. Summary of the Invention

[0004] The present disclosure relates to printing systems, e.g., digital printing systems having a moving intermediate transfer member (ITM), e.g., a flexible ITM (e.g., blanket) mounted on a number of rollers (e.g., belt) or via a rigid drum (e.g., drum-mounted blanket), and methods of operating the printing systems.

[0005] An ink image is formed on a surface of the moving ITM (e.g., by drop deposition at an imaging station) and then transferred to a substrate, which may comprise paper, plastic, metal, or any other suitable material. To transfer the ink image to the substrate, the substrate is pressed between at least one impression cylinder and the area of ​​the moving ITM where the ink image is to be located, at which point the transfer station (also called a printing station) is said to be engaged.

[0006] For a flexible ITM mounted on multiple rollers, the printing station typically includes, in addition to the impression cylinder, a pressure cylinder or roller whose outer surface may optionally be compressible. A flexible blanket or belt passes between two such cylinders, which may be selectively engaged or disengaged, usually as the distance between the two is increased or decreased. One of the two cylinders may be in a fixed position in space, and the other cylinder may be moved towards or away from it (e.g., the pressure cylinder may be movable or the impression cylinder may be movable), or the two cylinders may each move towards or away from the other. For a rigid ITM, the drum (on which the blanket may optionally be mounted) constitutes the secondary cylinder that engages or disengages the impression cylinder.

[0007] For clarity, the word rotation is used herein to describe the movement of the ITM in the printing press in the printing direction, regardless of whether the movement is locally linear, locally rotational, or other at various locations in the printing press. For rigid ITMs having a drum shape or drum support, the motion of the ITM is rotational. The printing direction is defined by the movement of the ink image from the imaging station to the printing station. Unless the context clearly indicates otherwise, the terms upstream and downstream may be used hereinafter with respect to relative positions with respect to the printing direction.

[0008] Some embodiments relate to a printing system, specifically an image forming station including an intermediate transfer member (ITM) including a flexible endless belt mounted on a number of guide rollers, an image forming station including a print bar disposed over a surface of the ITM, the print bar configured to form ink images on the surface of the ITM by droplet deposition, a conveyor driving rotation of the ITM at a fixed rotational speed in a printing direction to transport the ink images toward the print station where they are transferred to a substrate, a detection system configured to detect foreign objects transported by the rotating ITM to a detection position upstream of the image forming station and downstream of the print station, and a response system operably coupled to the detection system to respond to detection of the foreign object by performing at least one collision prevention action to prevent a potential collision between the foreign object and the print bar.

[0009] In various embodiments, a printing system may include an intermediate transfer member (ITM) including a flexible endless belt mounted on a number of guide rollers; an image forming station including a print bar disposed over a surface of the ITM, the print bar configured to form ink images on the surface of the ITM by droplet deposition; a conveyor driving rotation of the ITM at a fixed rotational speed in a printing direction to transport the ink images toward the print station where they are transferred to a substrate; a detection system configured to detect foreign objects transported by the rotating ITM to a detection location upstream of the image forming station and downstream of the print station; collision prediction circuitry that predicts a potential collision and / or the likelihood of a potential collision between the foreign object and the print bar; and a response system operably coupled to the prediction circuitry to respond to a prediction of a potential collision by performing at least one collision prevention action to prevent a potential collision between the foreign object and the print bar.

[0010] In some embodiments, the printing system includes an intermediate transfer member (ITM) comprising a flexible endless belt mounted on a number of guide rollers, an imaging station including a print bar disposed over a surface of the ITM, the print bar configured to form ink images on the surface of the ITM by droplet deposition, a conveyor driving rotation of the ITM at a fixed rotational speed in a printing direction to transport the ink images towards a printing station where they are transferred to a substrate, and a mechanical detection system detecting material transported by the rotating ITM at a detection location upstream of the imaging station and downstream of the printing station, the mechanical detection system detecting a ... downstream of the printing station, the mechanical detection system detecting a material transported by the rotating ITM at a detection location downstream of the printing station, the mechanical detection system detecting a material transported by the rotating ITM at a detection location upstream of the imaging station and downstream of the printing station, the mechanical detection system detecting a material transported by the rotating ITM at a detection location downstream of the printing station, the mechanical detection system detecting a material transported by the rotating ITM at a detection location downstream of the printing station, the mechanical detection system detecting a material transport The ITM may include an elongated blade disposed across the width of the ITM, a linking element including one of a tension spring and a barotropic piston (the linking element links the blade to a rigid frame), and at least one of a limit switch and a camera, wherein a gap G2 between the ITM and an edge of the blade adjacent the ITM is smaller than a gap G1 between the print bar and the ITM, and at a detection position, the ITM is extended over an upstream guide roller, a mechanical detection system, and a response system operably coupled to the detection system to respond to detection of a foreign object by performing at least one collision prevention action to prevent a potential collision between the foreign object and the print bar.

[0011] In various embodiments, the printing system may include an intermediate transfer member (ITM) including a flexible endless belt mounted on a number of guide rollers, an imaging station including a print bar disposed over a surface of the ITM with a minimum gap of G1 therebetween, the print bar being configured to form ink images on the surface of the ITM by droplet deposition, a conveyor driving rotation of the ITM at a fixed rotational speed in a printing direction to transport the ink images towards the printing station where they are transferred to a substrate, a detection system configured to detect foreign objects transported by the rotating ITM to a detection position upstream of the imaging station and downstream of the printing station, and a response system operably coupled to the detection system to respond to detection of the foreign object by performing a collision prevention action within a response time to prevent a potential collision between the foreign object and the print bar, the collision prevention action may include lifting the print bar to a height at least twice the gap G1, the response system may include an electric actuator, and the response time may be defined by a speed of the rotating ITM and a distance from the detection position to the imaging station along a path of movement of the ITM in the printing direction. In some embodiments, the collision prevention action can include raising the print bar to a height at least 5 times the gap G1, hi some embodiments, the collision prevention action can include raising the print bar to a height at least 10 times the gap G1.

[0012] In embodiments, a printing system includes an intermediate transfer member (ITM) including a flexible endless belt mounted on a number of guide rollers; an imaging station including a print bar disposed over a surface of the ITM, the print bar configured to form ink images on the surface of the ITM by droplet deposition; a conveyor that drives rotation of the ITM at a fixed rotational speed in a printing direction to transport the ink images toward a printing station where they are transferred to a substrate; and a mechanical detection system that detects material transported by the rotating ITM at a detection location upstream of the imaging station and downstream of the printing station, the mechanical detection system including an elongated blade disposed lengthwise across the width of the ITM, and a linking element including one of a tension spring and a barotropic piston (the linking element may be configured to link the blade to a rigid frame). a mechanical detection system linked to the ITM and at least one of a limit switch and a camera, a gap G2 between the ITM and an edge of the blade proximate the ITM being smaller than a gap G1 between the print bar and the ITM, and at a detection location, the ITM is extended on an upstream guide roller; and a response system operatively coupled to the detection system to respond to detection of the foreign object by performing a collision prevention action within a response time to prevent a potential collision between the foreign object and the print bar, the collision prevention action can include lifting the print bar to a height at least twice the gap G1, the response system can include an electric actuator, and the response time can be defined by a speed of the rotating ITM and a distance from the detection location to the imaging station along a path of travel of the ITM in the print direction. In some embodiments, the collision prevention action can include lifting the print bar to a height at least five times the gap G1. In some embodiments, the collision prevention action can include lifting the print bar to a height at least ten times the gap G1.

[0013] In some embodiments, the detection system can include one of a laser transmitter, an imaging system, an acoustic detection system, and a mechanical detection system. In some embodiments, the detection system can include a detection element disposed adjacent the ITM at the detection location and oriented in a cross-printing direction. The detection element can include one of a laser beam, a musical string, and an elongated blade.

[0014] In some embodiments, the gap G2 between the sensing element and the ITM can be smaller than the gap G1 between the print bar and the ITM. The gap G2 can be no more than 90% of the gap G1. In some embodiments, the gap G2 can be no more than 70% of the gap G1. In some embodiments, the gap G2 can be no more than 70% of the gap G1.

[0015] In embodiments, at the detection location, the ITM is stretched on the upstream guide roller. The printing system can define an x-axis, a y-axis, and a z-axis, where the x-axis and z-axis are parallel to the floor, perpendicular to each other, and together define a plane, the y-axis is perpendicular to the plane, a vector tangent to the ITM at the detection location in the print direction has only a y-axis dimension, the detection element has at least a z-axis dimension, and the gap G2 has only an x-axis dimension. A distance from the detection location to the imaging station along the travel path of the ITM in the print direction can be less than 10% of the total length of the ITM. This distance can be less than 5% of the total length of the ITM. This distance can be less than 2% of the total length of the ITM. In embodiments, the fixed rotational speed can be between 1 / 10 and 1 / 2 revolutions per second. In some embodiments, the fixed rotational speed can be between 1 / 8 and 1 / 4 revolutions per second.

[0016] The detection system according to embodiments may include a geometric detection system configured to detect an impact between the detection element and the foreign object. In embodiments, the detection system and response system may be configured to make the execution of at least one collision prevention action conditional on the intensity of the impact between the foreign object and the detection element exceeding a predetermined threshold. The detection system and response system may be configured to make the execution of at least one collision prevention action conditional on a calculated prediction of the intensity of a future impact between the foreign object and the print head exceeding a predetermined threshold.

[0017] In embodiments, the at least one collision prevention action includes lifting the print bar. The lifting of the print bar can be to a height of at least two times, or at least five times, or at least ten times the height of the gap G1. In some embodiments, the lifting of the print bar can be to a height of at least five times the height of the gap G1. In some embodiments, the lifting of the print bar can be to a height of at least ten times the height of the gap G1.

[0018] According to various embodiments, the foreign matter may include at least one of a transparent treatment coating applied to the surface of the ITM downstream of the printing station and upstream of the detection location, a silicon-containing material contained in a surface release layer of the ITM, dried ink, substrate material, cleaning fluid, and cooling solution.

[0019] In some embodiments, the at least one preventive action can include moving the surrogate to a position upstream of the print bar to ensure that the foreign object impacts the surrogate rather than the print bar. In some embodiments, a response time for prevention of a potential collision between the foreign object and the print bar can be defined by a speed of the rotating ITM and a distance from a detection position to the imaging station along a path of movement of the ITM in the print direction, and the detection and response systems can be configured to ensure that the at least one collision preventive action is performed within the response time. The response time can be less than 1 second. The response time can be less than 500 milliseconds. The response time can be less than 200 milliseconds. In some embodiments, the at least one collision preventive action can further include stopping rotation of the ITM.

[0020] According to various embodiments of the present invention, a mechanical detection system for detecting foreign objects carried by a rotating intermediate transfer member (ITM) in a printing system (a printing system including an image forming station where an ink image is formed on the ITM and a printing station where the ink image is transferred to a substrate) can include an elongated blade, a linkage means including a spring (the linkage means links the blade to a rigid frame), and at least one of a limit switch and a camera.

[0021] In some embodiments, a mechanical detection system for detecting foreign objects carried by a rotating intermediate transfer member (ITM) in a printing system (a printing system including an image forming station where an ink image is formed on the ITM and a printing station where the ink image is transferred to a substrate) can include an elongated blade, a spring connecting the blade to a rigid frame, and at least one of a limit switch and a camera.

[0022] In some embodiments, a mechanical detection system for detecting foreign objects carried by a rotating intermediate transfer member (ITM) in a printing system (a printing system including an image forming station where an ink image is formed on the ITM and a printing station where the ink image is transferred to a substrate) can include an elongated blade, a resilient intermediary element connecting the blade to a rigid frame, and at least one of a limit switch and a camera.

[0023] In embodiments, the machine detection system may be disposed at a detection location facing the ITM downstream of the printing station and upstream of the imaging station. An edge of the elongated blade proximate the ITM may be disposed with a gap therefrom such that a particle of foreign matter larger than the gap in a direction perpendicular to the surface of the ITM at the detection location will impact the edge of the elongated blade. The machine detection system may be configured to detect an impact between the foreign matter and the elongated blade. The detection may include at least one of contacting a limit switch and determining an angle of the blade from the image. The machine detection system may be further configured to signal a response system to initiate a collision prevention response to prevent a collision between the foreign matter and a component of the imaging station. The signaling of the response system may be contingent upon an intensity of the impact between the foreign matter and the elongated blade exceeding a predetermined threshold. In some embodiments, the machine detection system may further include a pivot.

[0024] Some embodiments relate to a method of operating a printing system, specifically a printing system in which a print bar forms ink images on a rotating intermediate transfer member (ITM) that are subsequently transported by the ITM to a printing station where they are transferred to a substrate, the method can include detecting a foreign object transported by the rotating ITM at a detection location upstream of the imaging station and downstream of the printing station, and responding to the detection by performing at least one collision prevention action to prevent a potential collision between the foreign object and the print bar. The detection can be accomplished by using a detection system including one of a laser transmitter, an image processing system, an acoustic detection system, and a mechanical detection system. The detection can be accomplished by using a detection system including a detection element positioned adjacent the ITM at the detection location and oriented in a cross-printing direction. The detection element can include one of a laser beam, a musical string, and an elongated blade.

[0025] In embodiments of the method, a gap G2 between the sensing element and the ITM can be smaller than a gap G1 between the print bar and the ITM. The gap G2 can be not more than 90% of the gap G1. In some embodiments, the gap G2 can be not more than 70% of the gap G1. In some embodiments, the gap G2 can be not more than 70% of the gap G1. In embodiments of the method, the ITM can be stretched over a guide roller upstream of the sensing location.

[0026] According to some embodiments of the method, the printing system defines an x-axis, a y-axis, and a z-axis, where the x-axis and z-axis are parallel to the floor, perpendicular to each other, and together define a plane, the y-axis is perpendicular to the plane, a vector tangent to the ITM at the detection position in the printing direction has only a y-axis dimension, the detection element has at least a z-axis dimension, and the gap G2 has only an x-axis dimension.

[0027] In embodiments of the method, the distance from the detection location along the path of movement of the ITM in the print direction to the imaging station can be less than 10% of the total length of the ITM. The distance can be less than 5% of the total length of the ITM. The distance can be less than 2% of the total length of the ITM. The fixed rotational speed can be between 1 / 10 revolutions per second and 1 / 2 revolutions per second. In some embodiments, the fixed rotational speed can be between 1 / 8 revolutions per second and 1 / 4 revolutions per second.

[0028] In some embodiments, the detecting may be accomplished using a machine detection system configured to detect an impact between the detection element and the foreign object. In some embodiments, the response to the detection may be conditioned on the strength of the impact between the foreign object and the detection element exceeding a predetermined threshold. In some embodiments, the response to the detection may be conditioned on a calculated prediction of the strength of a future collision between the foreign object and the print head exceeding a predetermined threshold.

[0029] In embodiments of the method, the at least one collision prevention action can include lifting the print bar. The lifting of the print bar can be to a height of at least two times the gap G1. In some embodiments, the lifting of the print bar can be to a height of at least five times the gap G1. In some embodiments, the lifting of the print bar can be to a height of at least ten times the gap G1.

[0030] In some embodiments of this method, the foreign object may include at least one of a clear treatment coating applied to a surface of the ITM downstream of the print station and upstream of the detection location, a silicon-containing material in a surface release layer of the ITM, dried ink, substrate material, a cleaning fluid, and a cooling solution. In some embodiments of this method, the at least one preventative action includes moving the surrogate to a position upstream of the print bar to ensure that the foreign object impacts the surrogate rather than the print bar.

[0031] In embodiments of this method, a response time for prevention of a potential collision between the foreign object and the print bar may be defined by a speed of the rotating ITM and a distance from a detection location along a path of travel of the ITM in the print direction to the imaging station, and a response may be achieved such that at least one collision prevention action is performed within the response time. The response time may be less than 1 second. The response time may be less than 500 milliseconds. The response time may be less than 200 milliseconds.

[0032] In some embodiments of the method, the at least one collision prevention action may further include stopping rotation of the ITM.

[0033] In embodiments, the printing system includes an intermediate transfer member (ITM) including a flexible endless belt mounted on a number of guide rollers; an imaging station including a print bar disposed over a surface of the ITM, the print bar configured to form ink images on the surface of the ITM by droplet deposition; a conveyor that drives rotation of the ITM at a fixed rotational speed in a printing direction to transport the ink images toward a printing station where they are transferred to a substrate; and a mechanical detection system that detects foreign objects transported by the rotating ITM at a detection location upstream of the imaging station and downstream of the printing station (the mechanical detection system may include an elongated blade disposed lengthwise across the width of the ITM and a tension spring and a barometric pressure resistor piston). the link element including one of a limit switch and a camera for imaging the elongated blade and imaging circuitry for detecting an orientation of the elongated blade by analyzing the output of the camera (wherein a gap G2 between the ITM and an edge of the blade proximate the ITM is less than a gap G1 between the print bar and the ITM, and at the detection position, the ITM is extended over an upstream guide roller); and a response system operatively coupled to the detection system for responding to detection of the conveyed foreign object by performing at least one collision prevention action to prevent a potential collision between the foreign object and the print bar.

[0034] In embodiments, the printing system includes an intermediate transfer member (ITM) including a flexible endless belt mounted on a number of guide rollers; an imaging station including a print bar disposed over a surface of the ITM, the print bar configured to form ink images on the surface of the ITM by droplet deposition; a conveyor that drives rotation of the ITM at a fixed rotational speed in a printing direction to transport the ink images towards a printing station where they are transferred to a substrate; a mechanical detection system that detects foreign objects transported by the rotating ITM at a detection location upstream of the imaging station and downstream of the printing station (the mechanical detection system includes an elongated blade disposed lengthwise along the width of the ITM; an expandable linking element (the expandable linking element is resilient and / or has pneumatic or hydraulic force based resistance and includes one of a tension spring and a pneumatic resistance piston, the expandable linking element links the blade to a rigid frame); and at least one blade orientation detector that detects an orientation of the elongated blade or its rotation. at least one of a limit switch and a camera (wherein a gap G2 between the ITM and the edge of the blade adjacent the ITM is smaller than a gap G1 between the print bar and the ITM, and at the detection position, the ITM is extended over the upstream guide roller); and a response system operatively coupled to the detection system to respond to detection of the transported foreign object by performing at least one collision prevention action to prevent a potential collision between the foreign object and the print bar.

[0035] In some embodiments, the expandable linking element comprises a spring. In some embodiments, the expandable linking element comprises a pneumatic or hydraulic piston. In some embodiments, the blade orientation detector comprises a limit switch that detects the orientation of the blade. In some embodiments, the blade orientation detector comprises a camera that images the elongated blade and imaging circuitry that detects the orientation of the elongated blade by analyzing the output of the camera. In some embodiments, the blade orientation detector is magnetic (non-limiting examples use reed switches or proximity switches). In some embodiments, the blade orientation detector comprises an encoder,

[0036] In various embodiments, the printing system includes an intermediate transfer member (ITM) comprising a flexible endless belt mounted on a number of guide rollers, an imaging station including a print bar positioned over a surface of the ITM with a minimum gap of G1 therebetween, the print bar being configured to form ink images on the surface of the ITM by droplet deposition, a conveyor driving rotation of the ITM at a fixed rotational speed in a printing direction to transport the ink images toward the printing station where they are transferred to a substrate, a detection system configured to detect foreign objects transported by the rotating ITM to a detection position upstream of the imaging station and downstream of the printing station, and a print bar lift system operably coupled to the detection system to respond to detection of the detected transported foreign object by lifting the print bar to prevent potential collisions between the detected transported foreign object and the print bar.

[0037] In some embodiments, the response system includes an electrical actuator. In some embodiments, the lifting of the print bar occurs within a response time defined by the speed of the rotating ITM and the distance from the detection location to the imaging station along the path of travel of the ITM in the print direction. In some embodiments, the lifting of the print bar is to a height of at least two times the gap G1. In some embodiments, the lifting of the print bar can be to a height of at least five times the gap G1. In some embodiments, the lifting of the print bar can be to a height of at least ten times the gap G1.

[0038] The invention will now be further described, by way of example, with reference to the accompanying drawings, in which dimensions of components and features shown in the figures have been chosen for convenience and clarity of presentation and are not necessarily drawn to scale. [Brief description of the drawings]

[0039] [Figure 1] FIG. 1 is an elevational view of a printing system according to embodiments. [Diagram 2] FIG. 2 is an elevational view showing components of a printing system according to embodiments. [Diagram 3] FIG. 2 is an elevational view showing components of a printing system according to embodiments. [Figure 4A] FIG. 1 is a perspective view illustrating an example of a detection system according to embodiments. [Figure 4B] FIG. 1 is a perspective view illustrating an example of a detection system according to embodiments. [Figure 4C] 1A-1D are two alternative elevation views illustrating components of a detection system according to embodiments. [Figure 5A] FIG. 2 is an elevational view showing components of a detection system according to embodiments. [Figure 5B] FIG. 2 is an elevational view showing components of a detection system according to embodiments. [Figure 5C] FIG. 2 is an elevational view showing components of a detection system according to embodiments. [Figure 5D]FIG. 2 is an elevational view showing components of a detection system according to embodiments. [Figure 6A] FIG. 2 is a perspective view illustrating another example of a detection system according to embodiments. [Figure 6B] 6B are two alternative elevational views showing components of the detection system shown in FIG. 6A. [Figure 6C] FIG. 1 is a perspective view illustrating another example of a detection system according to embodiments. [Figure 7] FIG. 1 is a perspective view illustrating another example of a detection system according to embodiments. [Figure 8A] FIG. 1 is a perspective view illustrating another example of a detection system according to embodiments. [Figure 8B] 8B are two alternative elevational views showing components of the detection system shown in FIG. 8A. [Figure 9] 4 is a flow chart illustrating a method of operation of a printing press including a detection system according to embodiments. [Figure 10] 4 is a flow chart illustrating a method of operation of a printing press including a detection system according to embodiments. [Figure 11] 4 is a flow chart illustrating a method of operation of a printing press including a detection system according to embodiments. [Figure 12] 4 is a flow chart illustrating a method of operation of a printing press including a detection system according to embodiments. [Figure 13A] FIG. 2 is an elevational view illustrating components of a printing system including a detection system according to embodiments. [Figure 13B] FIG. 2 is an elevational view illustrating components of a printing system including a detection system according to embodiments. [Figure 14A] FIG. 2 is an elevational view illustrating components of a printing system including a detection system according to embodiments. [Figure 14B] FIG. 2 is an elevational view illustrating components of a printing system including a detection system according to embodiments. [Figure 15] 4 is a flow chart illustrating a method of operation of a printing press including a detection system according to embodiments. [Figure 16A] FIG. 2 is an elevational view showing components of a detection system according to embodiments. [Figure 16B] FIG. 2 is an elevational view showing components of a detection system according to embodiments. [Figure 16C] FIG. 2 is an elevational view showing components of a detection system according to embodiments. [Figure 16D] FIG. 2 is an elevational view showing components of a detection system according to embodiments. [Figure 17A] FIG. 2 is an elevational view illustrating components of a printing system including a detection system according to embodiments. [Figure 17B] FIG. 17B is a perspective view showing components of the detection system shown in FIG. 17A. [Figure 18A] FIG. 2 is an elevational view showing components of a printing system according to embodiments. [Figure 18B] FIG. 2 is a plan view illustrating components of a printing system according to embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] The present invention will now be described, by way of example only, with reference to the accompanying drawings. The drawings will now be described in particular detail, with the emphasis being that the illustrated details are by way of example and are for illustrative discussion only of preferred embodiments of the invention, and are presented to provide what is believed to be the most useful and readily understood explanation of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, and this description taken together with the drawings will make apparent to those skilled in the art how the various forms of the invention may be actually implemented. Similar reference numerals are generally used throughout the drawings to designate similar elements.

[0041] For convenience, in the context of the description herein, various terms are presented here. To the extent that definitions are provided, whether explicit or implicit, here or elsewhere in this application, such definitions will be understood to be consistent with usage of the defined terms by those of skill in the art. Moreover, such definitions should be interpreted in the broadest possible sense consistent with such usage.

[0042] For purposes of this disclosure, "electronic circuitry" is intended to broadly describe any combination of hardware, software, and / or firmware. Electronic circuitry may include executable code modules (i.e., stored on a computer-readable medium) and / or firmware element(s) and / or hardware element(s), including but not limited to field programmable logic array (FPLA) element(s), hardwired logic element(s), field programmable gate array (FPGA) element(s), and application specific integrated circuit (ASIC) element(s). Any instruction set architecture may be used, including but not limited to reduced instruction set computer (RISC) architecture and / or complex instruction set computer (CISC) architecture. Electronic circuitry may be located at a single location or distributed among multiple locations, in the latter case, the various circuitry elements may be in wired or wireless electronic communication with each other.

[0043] In various embodiments, the ink image is first applied to a surface of an intermediate transfer member (ITM) and then transferred from the surface of the intermediate transfer member to a substrate (i.e., a sheet substrate or a web substrate). For purposes of this disclosure, the terms "intermediate transfer member," "image transfer member," and "ITM" are synonymous and may be used interchangeably. The location where the ink is applied to the ITM is referred to as the "imaging station." In many embodiments, the ITM includes a "belt," "endless belt," or "blanket," and these terms are used interchangeably with ITM.

[0044] The section or area of ​​the printing press where the ink image is transferred to the substrate is the "printing station." It should be understood that for some printing systems, there may be more than one printing station. In some embodiments of the invention, the intermediate transfer member is formed as a belt including a reinforcing or support layer coated with a release layer. In a non-limiting example, the reinforcing layer may be a fabric that is fiber reinforced to be substantially inextensible along its length. By "substantially inextensible" is meant that during any cycle of the belt, the distance between any two fixed points on the belt does not change to an extent that affects image quality. However, the length of the belt may change with temperature or over a longer period of time with aging or fatigue. Across its width, the belt may have a low degree of elasticity to help it remain taut and flat as it is pulled through the imaging stations. A suitable fabric may have, for example, longitudinal glass fibers woven, stitched, or otherwise held together with transversely oriented cotton fibers.

[0045] For an endless intermediate transfer member, the "length" of the ITM is defined as its circumference.

[0046] Referring now to the drawings, Figure 1 is a schematic diagram of a printing system 100 for indirect printing according to some embodiments of the present invention. The system of Figure 1 includes an intermediate transfer member (ITM) 210 that includes a flexible endless belt mounted on a number of guide rollers 232, 240, 250, 253, 242. In another example (not shown), the ITM 220 is a drum or a belt wrapped around a drum. While this figure illustrates aspects of a particular configuration relevant to the discussion of the present invention, the illustrated configuration is not limited to the presented number and arrangement of rollers, nor to the shapes and relative dimensions, all of which are provided herein for convenience in illustrating the system components in a clear manner.

[0047] 1, ITM 210 rotates in a clockwise direction relative to the figure. The direction of belt movement defines an upstream direction and a downstream direction. Rollers 242 and 240 are positioned upstream and downstream, respectively, of image-forming station 212, and thus roller 242 may be referred to as the "upstream roller" and roller 240 may be referred to as the "downstream roller." Printing system 100 further includes: (a) an imaging station 212 including print bars 222A-222D (each designated one of C, MY, and K), each print bar including an inkjet print head(s) 223 as shown in FIG. 3 , the imaging station 212 configured to form (e.g., by droplet deposition thereon) an ink image (not shown) on a surface of the ITM 210; (b) a drying station 214 for drying the ink image; (c) a printing station 216 where the ink image is transferred from the surface of the ITM 210 to a sheet 231 or web substrate (only a sheet substrate is shown in FIG. 1 ); In the particular, non-limiting example of FIG. 1 , the printing station 216 includes an impression cylinder 220 and a blanket / pressure cylinder 218 carrying a compressible blanket 219; (d) a cleaning station 258 upstream from the printing station (which may include a cleaning brush, as shown in FIG. 1, which is just one example of a cleaning solution that may be used in the system), where residual material (e.g., a processing coating and / or an ink image or portions thereof, or other residual material) is cleaned from the surface of the ITM 210; and (e) A processing station 260 upstream from the printing and washing stations (wherein a layer of a liquid processing formulation (e.g., an aqueous processing liquid) is applied to the ITM surface; in one example, the processing liquid may include a dilute solution of a charged polymer. Further includes:

[0048] 1 may not be required. For example, the cooling station and cleaning station may be combined into a single station that may also fulfill the cooling function of cooling the ITM before continuing to the imaging station 212.

[0049] An example of a processing station 260 is shown generally in FIG.

[0050] In the particular non-limiting embodiment of Figure 2, the ITM 210 is moved from right to left as shown (i.e., as part of the bottom run of a clockwise rotation) as represented by arrow 2012 over a doctor blade, generally designated 2014, which is suitably mounted within a tank 2016. In Figure 2, the doctor blade 2014 is formed from a rigid bar having a smooth, neat cylindrical surface that extends across the entire width of the ITM 210.

[0051] Prior to passing over the doctor blade 2014, the underside (i.e., bottom run) of the ITM 210 is coated with an excess of processing formulation (e.g., solution) 2030. The manner in which the excess processing formulation (e.g., solution) is applied to the ITM 210 is not fundamental to the invention, and the ITM 210 could, for example, simply be submerged in a tank containing liquid and passed over a fountain 1128 of processing formulation (e.g., solution) 2030 as shown in Figure 2, or alternatively be sprayed by an upward jet (not shown).

[0052] As shown in this figure, the ITM 210 has a coating 2030 of liquid that is thicker or significantly thicker than desired as it approaches the doctor blade 2014. The function of the doctor blade 2014 is to remove excess liquid 2031 from the ITM 210 and ensure that the remaining liquid is spread evenly and uniformly across the surface of the ITM 210. In a non-limiting example, the doctor blade 2014 can be urged towards the ITM 210 while the ITM 210 is maintained under tension.

[0053] Those skilled in the art will appreciate that the treatment liquid may be applied to the ITM by other means and that excess liquid 2031 may be removed by other means.

[0054] A variety of materials may be used in the operation of a digital indirect printing system such as that described herein. Examples of materials include inks and ink components, substrates (paper, plastic, metal, or any other material to be printed onto), wash solution(s), cooling solution(s), and treatment formulation(s).

[0055] In another example, the ITM 210 may include a surface release layer that includes silicone and silicone-based materials. Any of the above materials, alone or in combination, may dry, chip, flake, crumble, or otherwise create foreign, unwanted particles within the physical confines of the printing system. Such foreign particles may, for example, adhere to the sticky surface of the treatment formulation 2030 and form a thin layer on the surface of the ITM 210. The ITM 210 may cycle or rotate at high speeds through the various stations that make up the printing system, picking up such particles via physical adhesion, chemical adhesion, or electrostatics, and transporting the particles in the printing direction at speeds of greater than 1.5 m / s, greater than 2.5 m / s, or greater than 3 m / s.

[0056] Referring now to FIG. 3, some embodiments of the printing system are shown in further detail. The print heads 223 are shown disposed above the ITM 210 at a height or gap G1 above the surface. For convenience and clarity, the print heads 223 are shown as contiguous in FIG. 3 and subsequent figures, but they need not be contiguous and in some embodiments, there may be spacing between adjacent print heads and other equipment, such as heaters, may be juxtaposed between adjacent print heads. G1 may be set as a minimum gap to take into account irregularities in the layer of treatment formulation 2030 on the surface of the ITM 210, or may be an average or typical gap taking into account such irregularities, or may be defined based on consideration of the specifications of the printing system and its various components, including, but not exhaustively, concentration, jetting distance, or droplet size. Such irregularities may be on the order of a few microns or tens of microns, depending on multiple factors, such as, for example, the design of the processing station 260. The gap G1 may be on the order of hundreds of microns, 1000 microns, or more than 1000 microns. In the example shown in this figure, a particle of foreign material 301 is carried by the ITM 210 as it rotates in the direction indicated by the arrow 2012 (also referred to as the print direction). The particle 301 can be larger than the gap G1 in at least one dimension or height above the surface of the ITM 210. The term "height above the surface of the ITM 210" refers to a dimension that is substantially perpendicular to the surface of the ITM 210, even if the ITM is "vertical" with respect to the ground, such as the cross section of the ITM opposite the particle 301 in FIG. 3. If the particle 301 continues to be carried by the ITM 210 until it reaches the imaging station 212 or vice versa, the particle 301 will or potentially will collide with one or more of the print bars 222A-222D, specifically the print head 223 therein. If the particle 301 has sufficient mass or sufficient momentum, the particle 301 may cause damage to the print head 223 or components thereof as a result of such a collision.Alternatively, even if no damage occurs to the print head 223 elements, particles may become stuck or lodged in or on them.

[0057] It may be desirable to detect such a potential collision before it occurs, and for that purpose, in accordance with the present invention, a detection system 310 is provided upstream of the imaging station 212. The detection system 310 is preferably configured to detect all particles of foreign matter 301 before all potential future collisions with elements of the imaging station 212. The detection system 310 is more preferably configured to detect all such particles of foreign matter 301 having at least a predetermined strength of collision and a predetermined probability of collision with an element of the imaging station 212, and further configured such that the particles of foreign matter 301 are detected in time to take collision prevention or avoidance actions.

[0058] In FIG. 3, it can be seen that the detection system 310 is located at a position L1 upstream of the upstream roller 242 (meaning that at least the elements of the detection system 310 face the position L1 on the ITM 210). In other embodiments, the detection system is located at a position L2 where the ITM 210 meets the upstream roller 242, where the ITM 210 is vertical and the normal vector to the ITM 210 is horizontal. It may be desirable to detect the foreign object at the position where the ITM 210 contacts the roller, since the ITM 210 tends to be under tension, which may smooth out irregularities in the surface of the ITM 210 itself or in the thin coating of the treatment 2030 formulation thereon, which may otherwise complicate effective detection of the foreign object. In some alternative embodiments, the detection system is located at a position L3, 90° clockwise around the upstream roller 242 in the print direction, i.e., a position on the upstream roller 242 where the ITM 210 is horizontal and the normal vector to the ITM 210 is vertical. In another alternative embodiment, the detection system is located at a position L 4 downstream of the upstream roller 242 and upstream of the imaging station 212 .

[0059] The location on the ITM 210 that faces the detection system 310 is referred to herein as the "detection location." In embodiments in which the detection system 310 includes a detection element (not shown in FIG. 3), the term "detection location" specifically refers to the location on the ITM that faces the detection element.

[0060] 4A includes a perspective view from "top" to "right" looking downstream and "down" the image-bearing surface of the ITM 210, the terms "top" and "down" being used relative to the non-limiting example where the ITM 210 is locally horizontal in the area of ​​the detection system 310e. As this figure shows, this perspective view may be defined by an X-axis, a Y-axis, and a Z-axis, where the X-axis and the Z-axis are parallel to a floor (not shown), are orthogonal to each other, and together define a plane, and the y-axis is orthogonal to that plane. Thus, as used herein, "horizontal" has the meaning of being disposed in or on an xz-plane that is parallel to the floor, and "vertical" as used herein has the meaning of being disposed orthogonal to the Y-direction, specifically the XZ-plane. As discussed above, the ITM 210 can be locally horizontal or locally vertical in the area of ​​the detection system (e.g., the detection system 310e). It should be noted here that all other perspectives, FIG. 4B, FIG. 5, FIG. 6A, FIG. 6C, FIG. 7, FIG. 8A, and FIG. 17B utilize this same perspective to show their respective embodiments.

[0061] In the embodiment shown in Figure 4A, the detection system 310 includes a mechanical detection system 310e that includes a blade 410 that is elongated, oriented in a cross-printing direction, and displaced having a proximal edge 421 adjacent the ITM 210 with a gap G2 therebetween as shown in Figure 4C. Although each edge of the blade 410 is illustrated as being flat or curved in the various figures, these shapes are not critical and the edges of the blade 410 can have any shape. If the detection position is selected to be a position where the ITM 210 is vertical, for example, the mechanical detection system 310e is positioned facing either position L1 or position L2 (shown in FIG. 3), the blade 410 will be horizontal during normal operation of the printing system without any impact from foreign objects, as shown in FIG. 4C. If instead the detection position is selected to be a position where the ITM 210 is horizontal, for example, the mechanical detection system 310e is positioned facing either position L3 or position L4 (shown in FIG. 3), the blade 410 will be vertical during normal operation of the printing system without any impact from foreign objects, as shown in FIG. 4C. As shown in FIG. 4A, the width of the blade 410 extends along most of the width of the ITM 210, and as shown in FIG. 4B, the blade 410 can include multiple adjacent blades 410 provided side by side across the width of the ITM 210, with a gap G4 between each pair of adjacent blades 410. In some embodiments, the total width of all of the blades 410, excluding gap G4, is at least 99% of the width of the ITM 210. In some embodiments, the total width of all of the blades 410, excluding gap G4, is at least 99.5% of the width of the ITM 210. In some embodiments, the total width of all of the blades 410, excluding gap G4, is at least 99.7% of the width of the ITM 210.

[0062] Blade 410 is preferably a "floating blade," meaning that when blade 410 is struck by a foreign particle 301 carried by ITM 210 at the proximal edge 421 or on the face of blade 401 near the proximal edge 421 (e.g., point P1 in FIG. 5A), the rotational motion of the proximal edge 421 is relatively unconstrained.

[0063] Figure 5A shows a non-limiting example of a floating blade 410 having a proximal edge 421 adjacent or facing a surface of the ITM 210 and displaced therefrom by a gap G2 therebetween, as shown in Figure 7C. It should be understood that Figures 5A, 5B, 5C, and 5D all depict the ITM 210 as being locally vertical and the blade 410 as being horizontal for convenience only, and that in some embodiments, the opposite is true, and thus the relative orientation of the major elements shown in these figures is merely for illustrating the structural and functional aspects of the various system elements shown. As shown, the blade 410 is disposed on a pivot mechanism 411 fixedly mounted to a rigid frame element 415a and is pivotable with a degree of freedom indicated by arrow 414. Considering that FIG. 5A is an elevational view, those skilled in the art will appreciate that the arrow 414 indicates a pivot or rotation about an axis that is perpendicular to the vector of the print direction 2012 and parallel to the width dimension of the ITM 210, as will be explained. FIG. 5A illustrates the XY axes so that the print direction 2012 can be understood to be upward in the Y direction (which XY axes are illustrated in the perspective of FIG. 5A as including the Z axis, which cannot be seen because FIG. 5a is a two-dimensional projection). It can be seen that the cross section of the blade 410 extends lengthwise in the X direction from the distal edge 422 to the proximal edge 421, and the thickness of the blade 410 is shown in the Y direction. Thus, the width of the blade 410 is necessarily in the Z direction (not shown). Similarly, the width of the ITM 210 is in the Z direction, and the axis of rotation of the blade 410 about the pivot mechanism 411 is similarly disposed in the Z direction. Thus, the pivot axis extends across the width of the blade 410. In other embodiments (not shown), the pivot mechanism 411 can be an integral part of the rigid frame element 415a, for example an elongated spike or an elongated triangle of rigid frame element 415a material, such as metal, having the same arrangement and function as the pivot mechanism 411, which is shown in this figure as a separate element.

[0064] The pivot mechanism 411 can have a sharp triangular-top edge, as shown for convenience in the drawings, or it can be, for example, a rounded edge, so long as the blade 410 is free to pivot thereon as described above with respect to the degree of freedom arrow 414. The distal edge 422 of the blade 410 is linked to the rigid frame element 415b by a linking means 416, which in this example comprises a tension spring. The linking means 416 acts to keep the blade 410 horizontal and define the exact vertical position of its proximal edge in its rest configuration (meaning during normal operation of the printing system without any impact between a foreign object and the blade 410), including position, length, and tension. In some alternative embodiments, the linking means 416 can include a pneumatic piston and cylinder (not shown). The linking means 416 acts to limit, reduce, or damp the downward movement of the distal edge 422 of the blade 410 when an upward force is applied to the proximal 421 edge of the blade 410. While the above discussion has been used to describe an example where the blade 410 is horizontal when the linking means 416 is in a rest position, one skilled in the art will appreciate that in other embodiments, the linking means 416 can operate to maintain a position of the blade 410 that is not horizontal, i.e., where the distal edge 422 is higher than the proximal edge 421 or vice versa. Such determination of the exact angle of rest of the blade 410 in a rest configuration is not exhaustive and is made by the system designer when considering parameters such as the allocated space, the dimensions of the blade 410, and the mechanical characteristics of the linking means 416. Similarly, it should be appreciated that the mechanical detection system 310e can place the blade 410 at a vertical or near vertical angle of rest when the ITM 210 is positioned vertically in a position that is locally horizontal.

[0065] Blade 410 is preferably configured such that it cannot lift and lose contact with pivot mechanism 411 when an upward force (which, if encountered, would reduce the downward movement of the distal edge) is applied to the proximal edge. For example, the weight of blade 410 can be adjusted for this, or additional weight can be added to the blade, either generally or alternatively locally along the area of ​​pivot mechanism 411. Alternatively, blade 410 can be connected to pivot mechanism 411 in a manner that gives blade 410 the freedom to pivot in the direction indicated by arrow 414, but does not restrict rotational movement within a desired range. This connection (not shown) is not exhaustive and can include any known mechanical connector, including nails, rivets, bolts, screws, steel wire snare, restraining brackets, or bearings. Alternatively, blade 410 can be "held down" onto pivot mechanism 411 by a mechanical member (not shown) fixedly attached to a rigid frame element, such as rigid frame element 415b.

[0066] The detection system 310e shown in FIGS. 5A, 5B, 5C, and 5D measures the extension H of the particles 301, 302 from the surface of the ITM 210. 301 (i.e., H in FIG. 5A , which is referred to as “height” “above” the surface when the ITM 210 is horizontal. 3015B , the foreign particle 302 is smaller than the gap G2 and passes through the blade 410 without impacting the blade 410, whereas the larger particle 301 is larger than G2 and impacts the blade 410. It can thus be seen that the value of the gap G2, i.e., the proximity of the blade 410 to the surface of the ITM 210, is a design choice based at least in part on the assumption that a foreign particle protruding from the surface of the ITM 210 that is less than the value of G2 will not collide with the print head 222, or that the likelihood of a collision is so low that it can be "negligible."

[0067] In Figure 5C, which illustrates a later detection system 310e than Figure 5A or 5B, it can be seen that a foreign particle 301 impacts a proximal edge 421 of a blade 410, causing the blade 410 to pivot on pivot mechanism 411, imparting a "counterclockwise" (with respect to this non-limiting illustrated example) rotational force to the blade 410 and causing a downward movement of a distal edge 422 of the blade 410. The linking means 416 limits or dampens the downward movement of the distal edge 422, such that the downward movement of the distal edge 422 caused by a foreign particle 301 impacting the distal edge 422 of the blade 410 is limited in extent depending on the strength of the impact.

[0068] According to embodiments, the mechanical detection system includes a blade orientation detector that identifies the orientation of the blade and / or detects the deflection of the blade, for example, after a foreign object carried by the ITM impacts the blade and causes it to pivot. The blade orientation detector may include any combination of mechanical, magnetic, optical, electronic, and software elements. An example of a mechanical component of the blade orientation detector is a limit switch. As shown in the non-limiting examples of FIGS. 5A, 5B, 5C, and 5D, the mechanical detection system 310e may further include a limit switch 412 configured to switch on or facilitate a current when physically contacted by the trailing edge 422 of the blade 410. In a properly designed mechanical detection system 301e, the limit switch 412 and other components of the system are configured such that the limit switch 412 becomes contacted by the distal edge 422 as a result of an impact (between the foreign particle 301 and the proximal edge 421) of sufficient strength to ensure the execution of an action that prevents a potential future collision of the particle 301 with the print head. The current switched on or facilitated by the limit switch 412 can be used to automatically execute an action, as described below. An example of a suitable limit switch 412 is a miniature snap action switch, such as the "Micro Switch™" product, known in the electronics and mechanical industries. The term micro switch is used interchangeably herein with other known terms, such as limit switch or snap action switch, to mean any electrical switch that is actuated by a physical force, for example, through the use of a tipping point mechanism.

[0069] Minimum impact strength “INT MIN " is used herein to mean the minimum impact strength between a foreign object and the print head that has the potential to cause damage to the print head. Minimum Impact Strength INT MINmay represent or be calculated by either momentum or force, the value of which may be calculated by the system designer or, alternatively, determined empirically through trial and error or after the fact. For example, the designer may calculate or determine that the impact strength resulting from a collision with the print head by a particle of foreign matter having a mass of 5 milligrams moving (i.e., carried by an ITM) at a velocity of 2 meters per second will be the minimum impact strength that can damage the print head. The particle has a momentum of 10 mg-m / sec. If the particle strikes the print head, which is stationary, and decelerates to a velocity of 0 in 1 millisecond, the stopping force acting on the particle should be 10 g-m / sec / sec (for the sake of a simplified example, this ignores the effects of deformation of both the particle and the print head, and assumes that the print head is not moving). Thus, the minimum impact strength INT for this example is MIN can be expressed as either 10 mg-m / sec particle momentum or 10 g-m / sec / sec impact force. The strength of the impact between a foreign object and a detector or detection element, such as the proximal edge 421 of the blade 410, can be used to predict the strength of potential future collisions between the foreign object and the print head, and thus, INT MIN may be used in determining the minimum impact strength between a foreign particle 301 and the proximal edge 421 of the blade 410 that must trigger action to avoid or prevent future collisions.

[0070] For example, the blade 410 may be caused to contact the limit switch 412 and trigger a collision prevention action. MIN It will be apparent to one skilled in the art that a safety factor can be taken so that the minimum impact strength derived from can be set to an impact strength less than the actual theoretical or empirical minimum impact strength that would cause printhead damage. Thus, the minimum impact strength discussed in connection with Figures 5C and 5D can be determined based on the momentum or impact force (i.e., INT) actually required for a foreign particle to cause damage to the printhead, depending on the desired safety margin. MIN) or any other fraction. 301 It will be appreciated by those skilled in the art that an impact will occur only if the amount of extension of a foreign object such as is greater than the gap G2 between the detector (proximal edge 421 of blade 410) and the surface of ITM 201.

[0071] The link means 416 is connected to a minimum collision strength constant INT MIN such that an impact having an intensity equal to or greater than INT moves the terminal edge downward to an extent that the terminal edge contacts and activates limit switch 412 at contact point C1. MIN Preferably, the shock absorber 410 is configured such that an impact having an intensity less than INT will not cause the terminal edge to move downwardly (or in some embodiments will prevent the terminal edge from moving downwardly) to the extent that the terminal edge would contact and activate the limit switch 412. This can be accomplished, for example, by selecting a tension spring having appropriate characteristics of length and tension. As can be seen from the figures, the impact intensity of FIG. 5C is approximately INT MIN In FIG. 5D, the impact intensity is less than INT MIN , the trailing edge of the blade 410 actually contacts the limit switch 412 at contact point C1.

[0072] 6A shows an embodiment in which the detection system 310 includes a laser-based detection system 310a including a miniature laser transmitter 151, a miniature laser receiver 152, respective bases 155a and 155b, and pre-programmed electronic circuitry 160 that processes signals from the laser transmitter 151 and the laser receiver 152 and calculates whether a foreign particle 301 that interrupts or traverses the laser beam 154 as it is carried by the rotating ITM 210 has a sufficient size and mass when considered together with the transport velocity of the particle 301 to ensure or trigger an anti-collision response that will be in effect before the particle 301 reaches the imaging station 212. In this embodiment, the laser beam 154 is parallel to the surface of the ITM 210, traverses the width of the ITM 210, and is displaced from the ITM 210 by a height or gap G2 shown in FIG. Examples of suitable laser beam detection systems for this embodiment are the LV-S71 and LV-S72 Small Beam Spot Thrubeam laser sensors available from Keyence Corporation of America, Itasca, Illinois, USA. In any of the embodiments herein, gap G2 is preferably smaller than gap G1, which characterizes the gap between print head 223 and ITM 210 to predict future or potential collisions with print head 223 of foreign particle 301 of a size equal to or greater than G1 or somewhat smaller than G1. For example, the value of gap G2 can be set to no more than 50%, no more than 70%, or no more than 90% of the value of G1, or alternatively, can be set to at least 50%, at least 70%, or at least 90% of the value of G1.

[0073] 6C, the laser detection system 310b can include a miniature laser transmitter 151, a base 155a, a laser reflector 153, and pre-programmed electronic circuitry 160 that processes signals from the laser transmitter 151 and calculates whether a foreign particle 301 that interrupts or traverses the laser beam 154 as it is transported by the rotating ITM 210 has a sufficient size and mass, when considered along with the transport velocity of the particle 301, to ensure or trigger a collision prevention response that must be in effect before the particle 301 reaches the imaging station 212. An example of a suitable laser detection system for this embodiment is the LV-S61 Small Beam Spot Retro-Reflective Laser Sensor, available from Keyence Corporation of America, Itasca, Illinois, USA.

[0074] In one example, the blade orientation detector can include a camera and image processing software. Figure 7 illustrates an embodiment in which the detection system 310 includes a visual camera system 310c including one or more line-of-sight cameras 163, at least one lateral mount 157, an opposing mount 157a, and pre-programmed electronics 161 that processes images from the one or more cameras 163 and calculates whether the foreign object particle 301 imaged by the one or more cameras 163 has a sufficient size and mass when considered together with the transport velocity of the particle 301 on the ITM 210 to ensure or trigger a collision prevention response that should be in effect before the particle 301 reaches the imaging station 212. As can be seen from this figure, one or more cameras 163 can be deployed to the side of the ITM 210 to image the moving surface of the ITM 210, and in addition or instead, one or more cameras can be deployed opposite or facing the moving ITM 210 at a distance that takes into account the capture angle of the camera 163 and the width of the ITM 210, and it will be apparent to one skilled in the art of imaging systems that the coverage of the ITM 210 can be split widthwise among multiple cameras 163 to allow cameras to be placed closer to the ITM 210. An example of a suitable camera for this embodiment is the In-Sight® Micro 8000 series smart camera available from Cognex Corporation of Natick, Massachusetts, USA. The visual cameras referred to herein can record still images and / or video.

[0075] In another embodiment shown in Figures 8A and 8B, the detection system 310 includes an acoustic-based detection system 310d including a string 164 including a flexible member held under tension by, for example, adjustable string attachment elements 158a and 158b. The string 164 can include a single material, for example nylon or steel, or multiple materials where a first material, for example a copper alloy, is wrapped around a core material, for example steel or nylon. The string 164 can alternatively or additionally include other materials, with the objective of the material selection being vibration at a desired pitch or range of pitches and a desired amplitude or range of amplitudes when struck by a foreign particle 301 carried by the rotating ITM 210. As shown in Figure 8B, the string is preferably displaced from the surface of the ITM 210 with a gap G2 therebetween across the width of the ITM 210 such that the attachment elements 158a and 158b are located on opposite sides of the ITM 210. The acoustic-based detection system 310c preferably further includes a microphone 165 and pre-programmed electronic circuitry 162 which processes the tones generated by the strings 164 and calculates whether a foreign particle 301 that impacts the strings 164 as it is transported by the rotating ITM 210 has sufficient size and mass when considered together with the transport velocity of the particle 301 to ensure or trigger an anti-collision response that must be in effect before the particle 301 reaches the imaging station 212.

[0076] Referring now to FIG. 9 , in some embodiments, a method of operating a printing system includes: a) Step S01: forming an ink image on a surface of an ITM 210 by droplet deposition; b) Step S02: conveying an ink image toward a printing station; c) Step S03: transferring an ink image to a substrate; d) Step S04: Detecting the presence of a foreign object carried by the rotating ITM; e) Step S05: Preventing potential collisions between the foreign object and the print head by taking action in response to detection in S04. Includes.

[0077] In some embodiments, not all of the steps of this method are required.

[0078] In some embodiments, step S04 is performed by a detection system including at least one of a laser detector system, an image processing system including a visual camera, an acoustic detection system, and a machine detection system. Examples of suitable laser detector systems are discussed above with respect to Figures 6A, 6B, and 6C. Examples of suitable image processing systems including a visual camera are discussed above with respect to Figure 7. Examples of suitable acoustic detector systems are discussed above with reference to Figures 8A and 8B. Examples of suitable machine detection systems are discussed above with respect to Figures 4A, 4B, 4C, 5A, 5B, 5C, and 5D.

[0079] In some embodiments, step S05 includes performing collision avoidance action within an acceptable response time, which is the amount of time that elapses between detection of the foreign object and arrival of the foreign object at the location of the print head or at a point on the ITM 210 facing the print head. This acceptable response time for prevention of a potential collision is defined by the rotational speed of the ITM as well as the distance along the ITM surface between the detection location (where the presence of the foreign object is detected) and the print head (or an upstream location on the ITM surface facing the print head). The response time can be less than 1 second, less than 500 milliseconds, or less than 200 milliseconds.

[0080] In FIG. 10, a method of operating a printing system such as that discussed above with reference to FIG. 9 includes determining whether the expected strength of a potential collision with a print head is greater than or equal to a minimum collision strength INT MINIt can be seen that the calculation, determination or designed-in pass / fail Q1 of whether the expected intensity of the potential collision exceeds a predetermined threshold can be resolved with reference to the discussion of the detection system including the blade 410 discussed above with reference to FIGS. 4A, 4B, 4C, 5A, 5B, 5C and 5D, depending on the result, the method can include no response in step S09, i.e., no action to prevent the potential collision, or instead, performing a collision prevention action in step S05. The calculation or determination can be performed by a detector system including electronic circuitry including programmed instructions such as those discussed above with reference to FIGS. 6A, 6B, 6C, 7, 8A and 8B. The designed-in pass / fail of whether the expected intensity of the potential collision exceeds a predetermined threshold can be resolved with reference to the discussion of the detection system including the blade 410 discussed above with reference to FIGS. 4A, 4B, 4C, 5A, 5B, 5C and 5D.

[0081] In some embodiments, step S05 of preventing a potential collision includes raising the print head before the foreign object can impact the print head.

[0082] In some embodiments, step S05 of preventing potential collisions includes moving the surrogate to a position upstream of the print head so that the foreign object will collide with the surrogate rather than the print head.

[0083] FIG. 11 illustrates a method of operating a print head, comprising: a) Step S11: forming an ink image on a surface of the ITM 210 by droplet deposition; b) conveying the ink image towards a printing station (S12); c) a step S13 of transferring the ink image to a substrate; d) detecting an impact between the sensing element and a foreign object carried by the rotating ITM; and e) a step S15 of responding to the impact detection by performing at least one collision prevention action; 1 shows an embodiment including:

[0084] In some embodiments, not all of the steps of this method are required.

[0085] An example of an apparatus suitable for performing step S14 of detecting an impact between a sensing element and a foreign object carried by the rotating ITM 210 is any of the embodiments discussed above in connection with Figures 4A, 4B, 4C, 5A, 5B, 5C, and 5D.

[0086] In some embodiments, step S15 includes performing a collision avoidance action within the amount of time that elapses between detection of the foreign object and arrival of the foreign object at a position on the print head or a point on the ITM facing the print head before the print head is lifted away from the ITM. This acceptable response time for preventing a potential collision is defined by the rotational speed of the ITM as well as the distance along the ITM surface between the position where the presence of the foreign object is detected and an upstream position on the print head or the ITM surface facing the print head. The response time can be less than 1 second, less than 500 milliseconds, or less than 200 milliseconds.

[0087] In FIG. 12, a method of operating a print head, such as that discussed above with reference to FIG. 11, is shown in which the expected strength of a potential collision with the print head is determined to be a minimum collision strength INT MIN It can be seen that the design-in pass / fail Q2 of whether the expected intensity of a potential collision exceeds a predetermined threshold can include a no response, i.e., no action to prevent a potential collision, in step S19, or instead, execution of a collision prevention action in step S15, depending on the result, the method can include a no response, i.e., no action to prevent a potential collision, in step S19, or instead, execution of a collision prevention action in step S15. The design-in pass / fail of whether the expected intensity of a potential collision exceeds a predetermined threshold can be resolved with reference to the discussion of the detection system including blade 410 discussed above with reference to Figures 4A, 4B, 4C, 5A, 5B, 5C, and 5D.

[0088] In some embodiments, step S15 of preventing a potential collision includes raising the print head before the foreign object can impact the print head.

[0089] In some embodiments, step S15 of preventing potential collisions includes moving the surrogate to a position upstream of the print head so that the foreign object will collide with the surrogate rather than the print head.

[0090] 13A and 13B, an embodiment of some components of the printing system 100 is shown, including a detection system 310e, such as any of the systems shown in FIGS. 4A, 4B, 4C, 5A, 5B, 5C, and 5D. The detection system 310e is positioned such that the proximal edge 421 of the blade 410 is at the opposite position L2. FIG. 13A shows the state of the system at time=T1 when the foreign particle 301 is still upstream of the detection position L2 and the blade 410 is still horizontal. FIG. 13B shows the state of the system at time=T2 after the particle 301 impacts the proximal edge of the blade 410, causing it to pivot and, further, after the impact, the particle 301, which continues to be transported by the ITM 210, reaches a position where a collision with the print head 223 could potentially occur. The strength of the impact is measured by the INT, as in the example shown in FIG. 5D. MIN Because it was greater, its strength was sufficient for the distal edge 422 of the blade 410 to overcome the resistance of the linking means 416 and contact the micro-switch 412 at contact point C1.

[0091] The contact with the micro switch 412 is the impact detection in step S14 of FIG. 12, and Q2, i.e., the designed-in “impact intensity is the threshold value INT MIN13A is an example of an indication in which "exceeds T2" is answered in the affirmative. The collision prevention action according to step S15 of FIG. 12 was performed before T2, i.e., before the end of the allowable response time which ends when the particle 301 (which impacted the blade 410) reaches the print head 223. The collision prevention action performed included raising the print bars 222 along with the print head 223 before the foreign object can collide with the print head. The gap between the print head 223 and the ITM 210 is no longer equal to G1 as in FIG. 13A, but is G3 which is greater than G1. In one example, G1 is 1 mm and G3 is 15 mm. In another example, G1 is 2 mm and G3 is between 4 mm and 10 mm. In yet another example, G1 is 800 microns and G3 is 8 mm. In the embodiment shown in this figure, the print bar frame 225 was used to simultaneously raise all of the print bars 222 as part of the collision prevention action. In an alternative embodiment (not shown), one or more individual print bars 222 may be raised in a manner similar to that described above if sufficient for the particular printing system design to prevent collisions.

[0092] In the embodiment shown in FIG. 14A, the pre-programmed electronic circuitry 160 provided in various embodiments for detection discussed herein is in electrical communication with an electrical actuator 229 configured to raise the print bar 222 by raising the print bar frame 225. Thus, a calculation or determination is made by the pre-programmed electronic circuitry 160, such as the designed-in pass / fail Q1 “strength of the collision is a threshold INT” discussed with reference to FIG. MINWhen "exceeds" is resolved in the affirmative and it is desired to prevent a potential collision between the foreign object and the print head as in step S05 of Figure 10, the electrical actuator 229 can be used to lift the print head 223 further from the surface of the ITM 210, for example to a predetermined distance of G3. In this discussion of Figure 14A, it is apparent that preprogrammed electronic circuitry 160 can be replaced by preprogrammed electronic circuitry 161 or preprogrammed electronic circuitry 162 depending on the respective embodiment of the detection system 310a, 310b, 310c, or 310d selected.

[0093] In the embodiment shown in FIG. 14B, the limit switch 412 provided in the various embodiments for impact detection discussed herein is in electrical communication with an electrical actuator 229 configured to raise the print bar 222 by raising the print bar frame 225. Thus, for example, the designed-in pass / fail Q2 “impact intensity is greater than or equal to the threshold INT” discussed with reference to FIG. MIN When "exceeds" is resolved affirmatively in that the limit switch 412 has been contacted by the blade 410 at contact point C1, as discussed above, and it is desired to respond to the impact detection by performing at least one collision prevention action, such as step S15 of FIG. 12, the electric actuator 229 can be used to lift the print head 223 away from the surface of the ITM 210, for example to a predetermined distance G3.

[0094] An example of a suitable electric actuator for any of the above embodiments is the Model PA-15 High-Speed ​​Linear Actuator available from Progressive Automations, Richmond, British Columbia, Canada. However, any high speed actuator capable of performing collision prevention action within the response time is suitable. Those skilled in the art will appreciate that multiple electric actuators may be required to effectively lift the print bar within an acceptable response time, and that a pneumatic actuator can replace the electric actuator. Furthermore, it will be apparent to a system designer that the use of a piston actuator is a design choice disclosed by way of example and is only one of multiple possible forms of effectively lifting the print bar, and that any form of mechanical device can be designed to achieve the same result of quickly lifting the print bar within an acceptable response time.

[0095] FIG. 15 illustrates a method for operating a printing system. a) Step S21: Detecting an impact between a blade element of the detection system and a foreign object carried by the rotating ITM; b) Step S22: The expected strength of a potential collision with the print head is compared to a predetermined threshold INT MIN conditioned on a positive resolution of a designed-in pass / fail Q6 of whether or not the foreign object exceeds the ITM limit, responding to the impact detection by lifting the print bar away from the ITM in a time less than the time it takes for the foreign object to reach the print bar, whereby in the event of a negative resolution of pass / fail Q6 the method includes a non-response of step S29; c) Step S23: The predicted intensity of a potential collision with the print head is determined to be equal to or greater than a predetermined threshold INT of maximum collision intensity that requires further responsive collision prevention action. MAX and, conditional on a positive resolution to decision Q7 of whether or not rotation of the ITM is exceeded, further responding to the shock detection by stopping rotation of the ITM, whereby in the event of a negative resolution of decision Q7 the method includes no further response in step S30. 1 shows an embodiment including:

[0096] In some embodiments, not all of the steps of this method are required.

[0097] In some embodiments, step S23 of further responding to the impact detection by stopping rotation of the ITM may be based at least in part on an operator decision regarding the resolution of decision Q7.

[0098] The method of Figure 15 may be better understood in light of the following discussion of Figures 16A, 16B, 16C, and 16D, which show a set of embodiments in which the rotational motion of the blade 410 of the machine detection system 310f is imaged by a line-of-sight camera 191 and the images captured by the camera 191 are processed by pre-programmed electronic circuitry 167. Thus, the camera 191 and electronic circuitry 167 of Figures 16A, 16B, 16C, and 16D replace the limit switch 412 of Figures 5A, 5B, 5C, and 5D, but all of the other illustrated components are structurally and operationally identical.

[0099] In FIG. 16A, the machine detection system 310f is "waiting" for an impact and the foreign particle 301 can be seen as being transported by the ITM 210 in the printing direction, i.e., toward the imaging station and its print bar and print head (all not shown in FIG. 16A).

[0100] Figure 16B shows the mechanical detection system 310f at a later time than Figure 16A, where it can be seen that a foreign particle 301 has impacted the proximal edge 421 of the blade 410, causing the blade 410 to pivot on the pivot mechanism 411, imparting a "counterclockwise" rotational force to the blade 410 and causing a downward movement of the distal edge of the blade 410 to an angle θ1 below the horizontal. The linkage means 416 is connected to a minimum impact intensity constant INT MINIt is preferred that an impact having a magnitude equal to or greater than this is configured to allow the terminal edge 422 to move downwardly to an extent that detection of the terminal edge 422 by the camera 191 and preprogrammed electronic circuitry 167 triggers responsive collision prevention action.

[0101] In Figure 16B, the impact strength is INT MIN is less than INT MIN are explained above and have the same meaning and purpose here. In the example of FIG. 16B, the camera 191 captures an image of the blade 410 pivoted an angle θ1 from the horizontal, and the electronic circuitry 167 determines that the pivot angle θ1 corresponds to an INT MIN 15, i.e., Q6 in FIG. 15, is resolved to the negative and the "no response" step S29 is executed instead of the "response" step S22.

[0102] Figure 16C illustrates a scenario in which the impact of particle 301 with blade 410 has a greater intensity than the impact of Figure 16B. This is evidenced by the larger (from Figure 16B) rotation angle θ2 (i.e., θ2>θ1), and indeed, when this angle is captured by camera 191, electronic circuitry 167 determines, for example by using a pre-programmed look-up table of angles and impact intensities, that the impact of this scenario is greater than the INT MIN , and therefore Q6 in FIG. 15 is resolved in the affirmative. This lookup table determines that the angle θ2 is greater than INT MAX 15 to resolve Q7 in the negative, and thus may be further used to determine that the "no response" step S30 is executed rather than the "further response" step S23. MAX is another value calculated based on the momentum of the particle at the time of impact or the force of the impact, and indicates impacts that are likely to cause a more severe level of damage to imaging station components.

[0103] Figure 16D illustrates a scenario in which the impact of particle 301 with blade 410 has a greater intensity than either of the impacts of Figures 16B and 16C. This is evidenced by the even larger rotation angle θ3 (i.e., θ3 ≥ θ2), and indeed when this angle is captured by camera 191, electronic circuitry 167 determines, for example by using a pre-programmed look-up table of angles and impact intensities, that the impact in this scenario is greater than the INT MIN is greater than (thus resolving Q6 in Figure 15 in the affirmative), INT MAX 15. The metric determines that the metric has a greater strength than the metric that the metric is greater than (thus resolving Q7 in FIG. 15 in the affirmative).

[0104] The preprogrammed electronic circuitry 167 of the embodiment shown in Figures 16A, 16B, 16C, and 16D may be configured to trigger a responsive collision prevention action, for example, by providing an electrical impulse to the electrical actuator 229 of Figure 14A configured to lift the print bar 222 by raising the print bar frame 225. It is apparent that in any discussion of Figure 14A, the preprogrammed electronic circuitry 160 may be replaced with the preprogrammed electronic circuitry 167 depending on the respective embodiment of the detection system 301 selected. The preprogrammed electronic circuitry 167 of the embodiment shown in Figures 16A, 16B, 16C, and 16D may be further configured to trigger a further responsive collision prevention action, for example, by automatically stopping rotation of the ITM 210 or displaying or sounding an alarm indicating to an operator that rotation of the ITM 210 must be stopped.

[0105] 17A and 17B show an alternative embodiment in which a collision prevention or avoidance action according to any of the embodiments disclosed herein includes moving a surrogate 307 in front of (upstream from) the print head 223 within a response time, thereby preventing the foreign particle 301 from colliding with the print head 223. Instead, the foreign object collides with the surrogate. As shown in these figures, the surrogate 307 is preferably an elongated member positioned along the surface of the ITM 210 in the width direction, far enough away from the surface of the ITM 210 so as not to impede the movement of the ITM 210 and to not scrape the dried treatment formulation 2030 (shown in FIG. 2) from the ITM 210, and close enough (preferably with a gap of less than G2) to ensure impact and eventual removal of the foreign object. In both FIG. 17A and FIG. 17B, it can be seen that the time is T2 and the surrogate 307 has been deployed in response to the impact of the foreign particle 301 with the blade 410.

[0106] FIG. 18A shows an alternative embodiment in which a surrogate 307 in the form of an elongated member disposed widthwise along the surface of the ITM 210 is stored in a position above the surface of the ITM 210 (i.e., while "waiting" for an impact detection that requires responsive collision prevention action) and reaches the stored position by pivoting using a hinge 309.

[0107] FIG. 18B, which is a plan view of a section of the ITM 210 upstream of the imaging station 212 shown in FIG. 18A, illustrates another alternative embodiment in which a surrogate 307 in the form of an elongated member is disposed along the surface of the ITM 210 in the width direction and is quickly slid into position across the width of the ITM 210 from a stored position away from the side of the ITM 210 by an electric actuator (not shown) or other suitable mechanical means, the surrogate 307 having the ability to move back and forth in the direction indicated by arrow 901. In some embodiments, the surrogate 307 includes protrusions 311 configured to remove any particles 301 of foreign matter that collide with the surrogate from the surface of the ITM 210 when the surrogate 307 is retracted from being disposed across the surface of the ITM 210 in the width direction after a potential collision with the print head 223 has been deflected (by the foreign matter instead colliding with the surrogate).

[0108] The present invention has been described using detailed descriptions of embodiments of the invention that are provided by way of example and are not intended to limit the scope of the invention. The described embodiments include different features, not all of which are required in all embodiments of the invention. Some embodiments of the invention utilize only some of the features or possible combinations of features. Those skilled in the art will envision variations of the described embodiments of the invention and embodiments of the invention that include different combinations of the features mentioned in the described embodiments.

[0109] In the description and claims of this disclosure, the verbs "comprise," "include," and "have" and their cognates are used to indicate that the object or objects of the verb are not necessarily an exhaustive list of members, components, elements, or parts of the subject or subjects of the verb. As used herein, the singular forms "a," "an," and "the" include plurals unless the context clearly dictates otherwise. For example, the term "a marking" or "at least one marking" may include a plurality of markings.

Claims

1. 1. A printing system comprising: a. an intermediate transfer member (ITM) comprising a flexible endless belt mounted on a plurality of guide rollers; b. an imaging station including a print bar disposed over a surface of the ITM, the print bar configured to form an ink image on the surface of the ITM by droplet deposition; c. a conveyor for driving rotation of the ITM in a printing direction to transport the ink images towards a printing station where they are transferred to a substrate; d. a cleaning station located upstream of the imaging station where residual material is cleaned from the surface of the ITM; e. a processing station located downstream of the cleaning station and upstream of the imaging station, where a layer of a liquid processing formulation is applied to a surface of the ITM; f. a detection system configured to detect foreign objects carried by the rotating ITM at a detection location upstream of said imaging station and downstream of said printing station; g. a response system operatively coupled to said detection system for responding to detection of said foreign object by performing at least one collision prevention action to prevent a potential collision between said foreign object and said print bar, said detection system including a detection element disposed at said detection location; I. the detection system is configured to quantify the intensity of an impact between (i) the foreign object if present at the detection location and impacting therewith, and (ii) the detection element; II. The response system is configured to condition the at least one collision prevention action on the quantified intensity of the impact exceeding a threshold value; A response system; A printing system comprising:

2. 2. The printing system of claim 1, wherein: (i) the plurality of guide rollers includes a first guide roller and a second guide roller both disposed downstream of the cleaning station and upstream of the imaging station; and (ii) the ITM is oriented vertically between the first guide roller and the second guide roller.

3. 3. The printing system of claim 2, wherein the first guide roller is disposed upstream of the second guide roller, and the detection system is configured to detect the foreign object when the foreign object is disposed on or above the second guide roller.

4. 3. The printing system of claim 2, wherein the detection system is configured to detect the foreign object when the foreign object is disposed on the ITM at a position between the first guide roller and the second guide roller, where the ITM is vertically oriented.

5. The printing system of claim 4 , wherein the detection system is configured to detect the foreign object when the foreign object is located downstream of the processing station and upstream of the imaging station.

6. The printing system of claim 1 , wherein the detection system is configured to detect the foreign object when the foreign object is located downstream of the processing station and upstream of the imaging station.

7. The printing system of claim 2 , wherein the processing stations are deployed in a position in which the ITM is oriented horizontally.

8. 3. The printing system of claim 2, wherein the treatment station includes a vertically oriented blade positioned below the ITM in a position where the ITM is oriented horizontally, the vertically oriented blade forming a layer of the liquid treatment formulation from the ITM by removing excess liquid from the ITM that has been previously applied to the ITM.

9. 2. The printing system of claim 1, wherein the treatment station includes a vertically oriented blade positioned below the ITM in a position where the ITM is oriented horizontally, the vertically oriented blade forming a layer of the liquid treatment formulation from the ITM by removing excess liquid from the ITM that has been previously applied to the ITM.

10. 10. The printing system of claim 1, wherein the detection system includes a blade oriented horizontally in a balanced position, the detection being contingent on a vertically moving foreign object rotating the blade from its horizontally oriented balanced position.

11. 1. A method of operating a printing system, the printing system including: (i) an intermediate transfer member (ITM) including a flexible endless belt mounted on a plurality of guide rollers; and (ii) an image forming station including a print bar disposed over a surface of the ITM, the method comprising: operating the print bar at the imaging station to form an ink image on a surface of the ITM by droplet deposition; b. transferring said ink image to a substrate at a printing station in a manner that leaves behind residual material, said method comprising the following steps, all performed prior to step (a): i. cleaning the surface of the ITM of residual material remaining from a previous print cycle at a cleaning station located upstream of the imaging station; ii. applying a layer of a liquid treatment formulation to a surface of the ITM at a treatment station located downstream of the cleaning station and upstream of the imaging station; iii. using a detection element to detect foreign objects, if any, carried by the rotating ITM at a detection location upstream of said imaging station and downstream of said printing station; iv. performing at least one collision prevention action responsive to and conditional on the result of the detection of the foreign object to prevent a potential collision between the foreign object and the print bar, I. said detecting includes quantifying an intensity of impact between (i) said foreign object if present at said detection location and impacting therewith, and (ii) said detection element; II. The at least one collision prevention action is conditioned on the quantified intensity of the impact exceeding a threshold; And, and A method comprising:

12. 12. The method of claim 11, wherein (i) the plurality of guide rollers includes a first guide roller and a second guide roller both disposed downstream of the cleaning station and upstream of the imaging station, and (ii) the ITM is oriented vertically between the first guide roller and the second guide roller.

13. 13. The method of claim 12, wherein the first guide roller is disposed upstream of the second guide roller, and the foreign object, if present, is detected when disposed on or above the second guide roller.

14. 13. The method of claim 12, wherein the foreign object, if present, is detected when disposed between the first guide roller and the second guide roller.

15. 15. The method of claim 14, wherein the foreign object, if present, is detected when it is located downstream of the processing station and upstream of the imaging station.

16. A method according to any one of claims 11 to 13, wherein the foreign object, if present, is detected when it is located downstream of the processing station and upstream of the image forming station.

17. 12. The method of claim 11, wherein forming the layer of liquid treatment formulation is performed using a vertically oriented blade positioned below the ITM in a position where the ITM is oriented horizontally, the vertically oriented blade forming the layer of liquid treatment formulation by removing excess liquid from the ITM that has been previously applied to the ITM.

18. 13. The method of claim 12, wherein forming the layer of liquid treatment formulation is performed using a vertically oriented blade positioned below the ITM in a position where the ITM is oriented horizontally, the vertically oriented blade forming the layer of liquid treatment formulation by removing excess liquid from the ITM that has been previously applied to the ITM.

19. 12. The method of claim 11, wherein said detecting is performed with a rotatable blade oriented horizontally in an equilibrium position, and said detecting is conditioned on a vertically moving foreign object causing said blade to rotate from its horizontally oriented equilibrium position.

20. 1. A printing system comprising: a. an intermediate transfer member (ITM) comprising a flexible endless belt mounted on a plurality of guide rollers; b. an imaging station including a print bar disposed over a surface of the ITM, the print bar configured to form an ink image on the surface of the ITM by droplet deposition; c. a conveyor for driving rotation of the ITM in a printing direction to transport the ink images towards a printing station where they are transferred to a substrate; d. a cleaning station located upstream of the imaging station where residual material is cleaned from the surface of the ITM; e. a processing station located downstream of the cleaning station and upstream of the imaging station, where a layer of a liquid processing formulation is applied to a surface of the ITM; f. a detection system configured to detect foreign objects carried by the rotating ITM at a detection location upstream of the imaging station and downstream of the cleaning station; g. a response system operatively coupled to said detection system for responding to detection of said foreign object by performing at least one collision prevention action to prevent a potential collision between said foreign object and said print bar, I. the detection system includes a detection element disposed at the detection location; II. the detection system is configured to detect the foreign object when the foreign object is located downstream of the processing station and upstream of the imaging station; A response system; A printing system comprising:

21. The system described in claim 20, wherein the detection position is downstream of the processing station.

22. A system described in any one of claims 20 to 21, wherein the ITM is oriented vertically at the detection position.

23. 1. A method of operating a printing system, the printing system including: (i) an intermediate transfer member (ITM) including a flexible endless belt mounted on a plurality of guide rollers; and (ii) an image forming station including a print bar disposed over a surface of the ITM, the method comprising: operating the print bar at the imaging station to form an ink image on a surface of the ITM by droplet deposition; b. transferring said ink image to a substrate at a printing station in a manner that leaves behind residual material, said method comprising the following steps, all performed prior to step (a): i. cleaning the surface of the ITM of residual material remaining from a previous print cycle at a cleaning station located upstream of the imaging station; ii. applying a layer of a liquid treatment formulation to a surface of the ITM at a treatment station located downstream of the cleaning station and upstream of the imaging station; iii. detecting foreign matter, if any, carried by the rotating ITM at a detection location upstream of said imaging station and downstream of said cleaning station; iv. performing at least one collision prevention action responsive to and conditional on the result of the detection of the foreign object to prevent a potential collision between the foreign object and the print bar; and Including, The method wherein the foreign object, if present, is detected when it is located downstream of the processing station and upstream of the imaging station.

24. The method described in claim 23, wherein the detection position is downstream of the processing station.

25. A method described in any one of claims 23 to 24, wherein the ITM is oriented vertically at the detection position.

Images