Cleaning system for moving element of coating device, related coater, coating device and method

Abstract

The present application relates to a cleaning system adapted to clean the outer surface of a roller of a coater (10) adapted to coat and / or print and / or form a layer on a web, the cleaning system comprising:-a robotic arm comprising a holding mechanism; -a cleaning device held on the holding mechanism, the cleaning device being adapted to clean an outer surface of the roller; -a command unit adapted to command the robot arm and the cleaning device to perform a cleaning task of a portion of the outer surface, the command unit being adapted to receive at least one defect characteristic and to trigger a cleaning task in dependence on each received defect characteristic, the defect characteristic being a characteristic of at least one defect of the layer.

Description

Technical Field

[0001] The present application relates to a cleaning system suitable for cleaning a moving element of a coating device, in particular the outer surface of a roller. The present application also provides a coating machine or coating device comprising the cleaning system. The present application also relates to a method for cleaning the outer surface of a moving element of a coating device. Background Art

[0002] Coating machines are used to convert moving webs. One common technique for converting moving webs is coating. This technique requires the use of at least one coating machine.

[0003] This type of coating machine is associated with coating processes that use rollers to apply, treat, coat, print, laminate, or form chemical compositions onto a web. Such a coating machine may also include rollers for driving, carrying, or conveying the web. This coating process allows for coating speeds of typically 100-1000 m / min, but these speeds are hampered by the fact that the quality of the web coating is, in most cases, unsatisfactory.

[0004] Therefore, there is a need for a system suitable for increasing the efficiency of a coating machine. SUMMARY OF THE INVENTION

[0005] To this end, the present description describes a cleaning system suitable for cleaning the outer surface of a moving element, in particular a roller, of a coating installation comprising a coater suitable for coating and / or printing and / or shaping a layer on a web, said cleaning system comprising:

[0006] - a robotic arm comprising a holding mechanism;

[0007] - a cleaning device held on the holding mechanism, the cleaning device being suitable for cleaning the outer surface of the moving element;

[0008] a command unit adapted to command the robot arm and the cleaning device to perform a cleaning task of a portion of the outer surface of the moving element,

[0009] The command unit is adapted to receive at least one defect characteristic and to trigger a cleaning task depending on each received defect characteristic, the defect characteristic being characteristic of at least one defect of the layer.

[0010] This cleaning system is able to improve the efficiency of coating equipment by reducing defects, thus improving the process.The development of this cleaning system was obtained through a research project carried out by the applicant.

[0011] The following section discusses this research project and the different difficulties that needed to be addressed that led to the present application.

[0012] In practice, a thin layer of a solvent-based coating composition is applied to a thin PET web using a very high-speed coater (coating speeds are typically 400-1000 m / min) using multiple rollers. Typically, the thickness of the plastic web is less than 5 μm and the weight basis of the coating layer is 1 g / m 2 (But the target may be 0.5g / m 2 or smaller).

[0013] The efficiency of such a coater is affected by several factors that should be minimized.

[0014] In particular, it is desirable to remove contamination / impurities, scale and ink residues from cylinders (rollers) used in web coating processes.

[0015] In one specific coating process, a coating composition is applied to a moving web by transferring the liquid coating composition from an applicator roller to the web. In this process, a counterroll (or backup roller) performs one or both of the following functions: supporting the web and metering the liquid coating composition into the nip formed between the two rollers. The counterroll is often referred to as a "sleeve" because it is covered by a flexible, smooth, resilient cover. During the coating process, the sleeve may become soiled. Staining of the sleeve has a direct impact on the quality of the coated web.

[0016] At the time, manual cleaning with polishing pads was ineffective in removing deposits such as dirt, dust, solid particles, and especially dried ink splatter. Operator intervention to clean the rollers after detecting defects caused additional delays and increased safety risks. Furthermore, the entire coating system had to be stopped to clean the ink splatter generated during the machine's ramp-up phase, negating the benefits of the ramp-up phase in starting production.

[0017] All of these considerations prompted the applicant to examine the entire coating process and determine that the cleaning process is a critical point for the following reasons.

[0018] Automation of the cleaning process improves quality, safety and productivity.

[0019] In the specific case of producing coated webs using highly flammable solvent-based coating compositions, the coating system must comply with ATEX environments, and the cleaning system must therefore be located in an explosion-proof environment. Consequently, the cleaning environment is restricted due to the presence of highly flammable solvents, and there is an additional explosion risk due to friction with the support rolls and the use of solvents for cleaning.

[0020] Controlling the cleaning process (controlling friction and friction operations) is a goal, especially in ATEX environments. One advantage is the reduced risk of sparks and less leakage of highly flammable solvents.

[0021] However, the cleaning process should also offer other advantages in a non-ATEX environment.

[0022] Another issue is controlling the coating phase by reducing production stoppages, avoiding operator intervention on the rotating drum (also called reel or roll) and improving overall process efficiency.

[0023] Another issue is improving operator safety by avoiding the need to lift heavy objects.

[0024] In particular, operations such as transporting or handling the rollers for offline cleaning of the rollers / cylinders should be avoided.

[0025] This cleaning system is designed to automatically clean rollers used in coating processes. The rollers to be cleaned can be rollers equipped with elastomeric sleeves and can rotate at a maximum speed of 3200 rpm (revolutions per minute).

[0026] The main contaminants are dry materials such as waxes, resins, additives and pigments, and solvents such as 100 / 140 gasoline, toluene, ethyl acetate and methyl ethyl ketone (MEK) can be used for cleaning.

[0027] Semi-solid or solid substances (such as gel or cream) can also be used to wipe the sleeve. In addition, static discharge additives can be added to the cleaning product.

[0028] Assessing the extent of fouling during coating processes is difficult because the components being cleaned are in motion. One goal is to clean the rollers during high-speed production without frequent line stops while ensuring operator safety.

[0029] Therefore, one of the challenges of the research project was to automate this cleaning phase so that operators no longer had to intervene in the rotating drum or stop production for online or offline roller cleaning. The data used to provide the cleaning operation could come from control cameras or any other online control system, such as an online coat weight control unit.

[0030] This results in a cleaning system that is designed to effectively reduce defects caused by dirty cylinders when coating and / or printing and / or forming layers on a web.

[0031] These defects caused by dirty rollers are specific and differ from other types of defects, such as papermaking defects. Specifically, they are repetitive, with the distance between each defect corresponding to the circumference of the roller. Examples include ink voids, streaks, excessive thickness, or smudges.

[0032] According to other aspects of the cleaning system, which are advantageous but not mandatory, the cleaning system may incorporate one or more of the following features, in any technically acceptable combination:

[0033] - the cleaning system further comprises an analysis unit adapted to:

[0034] - receiving data from a sensor, said data being an image of the layer coated and / or printed by the coater, and

[0035] - analyzing said data to detect at least one defect characteristic of at least one defect of said layer.

[0036] - the cleaning device is provided with an interface unit, which is suitable for receiving multiple information about at least one defect of the layer from a user, and the command unit is suitable for commanding the robot arm and the cleaning device also according to the multiple information about at least one defect of the layer.

[0037] The at least one defect characteristic detected by the analyzing unit is the presence or absence of a defect.

[0038] - Each defect is associated with a defect degree, a defect characteristic being the defect degree.

[0039] - The command unit is adapted to trigger a cleaning task when the defect level of a detected defect exceeds a predetermined defect level.

[0040] Each defect of the layer belongs to a respective predetermined defect group, a defect characteristic being the defect group to which the defect belongs, and a region characteristic of the region to be cleaned by the cleaning device is selected based on the defect characteristic.

[0041] - An area feature is the surface of the area to be cleaned.

[0042] One area characteristic is the location of the center of the area to be cleaned, which is preferably selected from three areas: the left part of the moving element, the center part of the moving element and the right part of the moving element.

[0043] The cleaning task is characterized by cleaning parameters, and the command unit is adapted to calculate each cleaning parameter depending on the defect characteristics.

[0044] - the cleaning device comprises a cleaning pad adapted to come into contact with said portion of the outer surface of the moving element, the cleaning pad preferably having an outer surface with foam, in particular melamine foam.

[0045] The cleaning device further comprises a cleaning pad, a solvent reservoir and a pressure unit adapted to deliver solvent from the solvent reservoir to the cleaning pad.

[0046] The present description also relates to a coating machine comprising the cleaning system as described above.

[0047] The present specification also describes a coating device comprising a cleaning system as described above.

[0048] The present description also relates to a method for cleaning the outer surface of a moving element, in particular a roller, of a coating apparatus comprising a coater suitable for coating and / or printing and / or shaping a layer on a web, the method being performed by a cleaning system comprising:

[0049] - a robotic arm comprising a holding mechanism;

[0050] - a cleaning device held on the holding mechanism, the cleaning device being suitable for cleaning the outer surface of the moving element;

[0051] - a command unit adapted to command the robot arm and the cleaning device to perform a cleaning task of a portion of the outer surface of the moving element;

[0052] The method comprises:

[0053] - receiving at least one defect characteristic, said defect characteristic being characteristic of at least one defect of said layer,

[0054] - Trigger a cleaning task based on each received defect characteristic. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Without limiting the purpose of the present application, the present application will be better understood based on the following description corresponding to the accompanying drawings and as illustrative examples. In the drawings:

[0056] - Figure 1 is a side view of the coating equipment,

[0057] - Figure 2 It is a schematic diagram of the coating machine implied in the coating process.

[0058] - Figure 3 is a schematic diagram of the cleaning system, and

[0059] - Figures 4 to 8 Schematic diagrams of implementation examples of different specific coating processes. Detailed Description of the Invention

[0060] Figure 1 A coating device 5 is schematically shown in FIG.

[0061] The coating device 5 is adapted to perform a coating process. Such a process implies the use of all necessary machines that are part of the coating apparatus 5.

[0062] More precisely, the coating process comprises at least the following steps in sequence: web unwinding, coating, and finally rewinding.

[0063] One or more optional steps may be added between coating and rewinding to solidify the coating layer by cooling, drying, curing or otherwise shaping the coating composition.

[0064] Accordingly, the coating device 5 includes at least an unwinder 6 , a rewinder 7 and a coating machine 10 .

[0065] The unwinder 6 and the rewinder 7 are adapted to unwind and rewind a roll of web material at a given speed, respectively.

[0066] Depending on the choice of coating technology, a dryer 8 and / or a curing machine 9 is usually required.

[0067] The dryer 8 and curing machine 9 are adapted to implement a film-forming or dry coating layer formation technique by converting the liquid coating layer applied to the web into a solid coating layer. Depending on the end use of the coated web, the coating cloth can be tack-free or remain tack-free. A protective film or shim can be added to prevent the coil from sticking and further allow for reel unwinding.

[0068] Heat transfer using temperature controlled rollers or air blows, infrared heating, ultraviolet curing, and electron beam radiation are examples of techniques used in film formation.

[0069] The coater 10 is a machine suitable for coating and / or printing and / or shaping a layer on the web 12 .

[0070] Web refers to any film, foil, sheet, etc., in which the length and / or width dimension is at least 10 or 100 times greater than the thickness dimension.

[0071] The web may comprise any long, thin and flexible structure (paper, film, foil, nonwoven, textile, plastic film, metal foil, impregnated textile, prepreg, ...) Optionally, the web has a flat and / or flexible surface.

[0072] Such a flat web can comprise any type of material, such as metal, glass, paper, fabric, leather, plastic, particles, and the like, and can be woven, laminated, or any combination thereof. The flat web can be woven, rough, smooth, or open, such as a mesh. The flat web can comprise a polymer, such as polyester or polyimide. The flat web can be aluminum foil or copper foil. The flat web can be intended to be coated, laminated, embossed, or printed. The flat web can be a multilayer web, i.e., a coated web or laminate.

[0073] Preferably, the flat web is designed and / or intended to be coated, printed, chemically treated, cut, slit, sliced, wound and / or unwound, cured or dried. The uncoated side is intended to come into contact with the outer surface of a roller system (reverse roller 17) for cleaning. The flat web can also come from a formed manufacturing process such as casting, blow molding or extruded film.

[0074] Optionally, the flat web is a belt.

[0075] The flat web can be a drive belt. The flat web can be used to carry objects or drive an element to rotate.

[0076] In general, the coating equipment 5 disclosed herein may include a coating, printing, or any and all types of wire wrapping machines known to those skilled in the art, such as, but not limited to, machines used for calendaring or laminating operations.

[0077] The coating equipment may include one or more coaters to perform by any and all coating techniques, as a single coating technique or in combination.

[0078] Well-known techniques are, for example, gravure coating, porous roller coating, rotary screen printing, flexographic printing, calendering, lamination or embossing.

[0079] Some specific examples are detailed below.

[0080] More information on the implantation of the coating device 5 is evident from documents US 4,270,483, US 3,851,582 and US 5,176,077.

[0081] Figure 2 An example of a coating machine 10 is schematically shown.

[0082] The coater 10 includes an ink reservoir 13 , a coating element 14 , a coating roller 16 , a back roller 17 , and a cleaning system 20 .

[0083] In this example, ink was chosen as a specific possibility for the coating composition.

[0084] The coating roll 16 , also referred to as an applicator roll, may be an engraved roll suitable for coating and / or printing and / or covering a portion of the web 12 with a desired coating layer 15 .

[0085] In this example, an applicator roller 16 applies ink provided by an ink reservoir 13 to the web 12 .

[0086] The metered application from the reservoir 13 to the application roller 16 is ensured by a coating element 14 such as a doctor blade.

[0087] Each of the rollers 16 and 17 is a rotating roller.

[0088] The counter roller 17 may be part of a roller assembly.

[0089] The roller assembly is adapted to allow movement of a web 12 that is intended to be coated with the coating layer.

[0090] The return roll 17 may be a drive roll and may drive the web 12 through the coater.

[0091] The counter roller 17 can also be an idle roller, the rotation of which is ensured by the web. In both cases, the counter roller 17 processes the web 12 on its outer surface 22, thereby dragging the web 12 or metering the coating layer 15.

[0092] The coating device 5 further comprises a sensor 18 .

[0093] The sensor 18 may be located at any position in the coating device 5 . Preferably, the sensor 18 is located at the end of the coating device before the rewinder 7 .

[0094] Sensor 18 is a sensor adapted to capture images or collect data from the coating layer applied to web 12 by coater 10 .

[0095] The data may be a defect map of the web 12 .

[0096] As is apparent from the described examples, the data collected or acquired by the sensors 18 corresponds to quality data.

[0097] Specifically, the sensor 18 may be capable of detecting major and minor defects.

[0098] The purpose of the sensor 18 is to detect the effect of fouling on the web, not to correct it.

[0099] To achieve this, different types of sensors can be used.

[0100] For example, according to the present example, the sensor 18 is a camera vision system, ie, one or more cameras.

[0101] This type of sensor can capture the entire web with a linear camera.

[0102] Other types of sensors require several to cover the entire width of the web with sufficient detail.

[0103] The sensor 18 can also be adapted to the material being used, effectively detecting defects of small size.

[0104] The data collected by the sensors 18 may include information regarding the location of the defect that is transmitted to the cleaning system 20 .

[0105] Other types of sensors can be used, each with different detection techniques and systems.

[0106] For example, a scanning system such as an in-line coat weight measurement may be used, which may use, for example, X-ray or ultrasonic sensors, and which may use transmissive, reflective or both types of sensors.

[0107] Interferometry can also be used, which exploits the interference of waves to extract information.

[0108] This is not an exhaustive list and many types of sensors 18 are contemplated.

[0109] At least one vision sensor may be used, but also capacitance sensors, frequency sensors, air pressure sensors (such as those used for rubber defect detection), or other sensors suitable for the product and process used may be used.

[0110] The type of test depends on the product parameter affected by fouling.

[0111] While camera vision systems are preferred due to their versatility, detection of defects can also be performed by human operators.

[0112] The use of sensors is optional. If necessary, the type of sensor should be selected based on product and / or process characteristics.

[0113] The data collected by the sensor 18 may include, for example, thickness, color changes, surface structure, electrical parameters, geometric parameters, or any other process output. In complex cases, it may be necessary to combine several types of sensors or detection systems to detect the effects of fouling on the web.

[0114] exist Figure 3 In this case, the cleaning system 20 comprises an analyzing unit 28 .

[0115] In other embodiments, analysis unit 28 may not be present, particularly when the output of analysis unit 28 is obtained by another technique (eg, by an operator).

[0116] In this case, the cleaning system 20 is equipped with an interface unit adapted to receive at least one defect characteristic from an operator.

[0117] For the sake of illustration, only the case where the analysis unit 28 is present will be described below.

[0118] In one embodiment, analysis unit 28 is connected to sensor 18 and analyzes the data output of sensor 18 to drive cleaning system 20. In one embodiment, sensor 18 is capable of detecting and identifying defects based on parameters recorded in a database or using a computer.

[0119] The analysis unit 28 is adapted to receive data from the sensor 18. Thus, the data received are images of the layer coated and / or printed by the coater 10.

[0120] The analyzing unit 28 is adapted to analyze the data to detect and identify at least one defect characteristic.

[0121] The cleaning system 20 further includes a robot arm 24 , a cleaning device 26 , and a command unit 30 .

[0122] The robotic arm 24 includes a holding mechanism 32 .

[0123] The cleaning device 26 is adapted to clean the outer surface 22 of the roller 17 .

[0124] The cleaning device 26 can also be used to clean the temperature-controlled roller. Since heat or cold may be used, which can accelerate the curing of the coating composition on the area to be cleaned and make the cleaning process more difficult (the ink cures faster, or the ink melts and the stain spreads...), the cleaning device 26 can include suitable cleaning aids.

[0125] More generally, the cleaning device 26 is adapted to clean the area to be cleaned.

[0126] In this context, “cleaning” means that the cleaning device 26 is adapted to clean the area until it is completely clean, or at least until the relevant defects are completely removed (in sync with the sensor 18 and the analysis unit 28 ).

[0127] The cleaning device 26 may also be adapted to partially clean the area until the relevant defects are reasonably removed according to quality standards.

[0128] This area to be cleaned is characterized by an area feature.

[0129] For example, the location of the center of the area to be cleaned is an area feature.

[0130] This positioning can be simplified to a left portion of the outer surface 22 , a center portion of the outer surface 22 , and a right portion of the outer surface 22 .

[0131] Another example of an area characteristic is the size of the area to be cleaned.

[0132] According to the example described, the cleaning device 26 comprises a cleaning pad 34 adapted to come into contact with a portion of the outer surface 22 of the roller 17 .

[0133] The cleaning pad 34 having an outer surface 36 may be provided with fabric, foam, or any other material that can absorb or retain liquid.

[0134] Preferably, the foam is melamine foam.

[0135] Preferably, the fabric is a microfiber-containing fabric.

[0136] The cleaning pad 34 may be composed of one or more of polyester, polyamide (nylon), wood pulp, cellulose, or cellulosic fibers.

[0137] Cleaning may be performed by wiping or rubbing the outer surface 22 of the roller 17 with a dry or solvent soaked pad.

[0138] The cleaning system 20 may also include a solvent reservoir 38 and a pressure unit 40. The pressure unit 40 may be adapted to send or pour solvent from the solvent reservoir 28 to the cleaning pad 34.

[0139] The solvent reservoir 38 may also be disconnected from the cleaning system 20. In the case where the solvent reservoir is independent of the cleaning system, the cleaning system 20 may soak the cleaning pad 34 in the solvent reservoir 38 to absorb the solvent.

[0140] The cleaning device 26 is held on a holding mechanism 32 of the robot arm 24 .

[0141] The command unit 30 is suitable for commanding the robot arm 24 and the cleaning device 26 to perform a cleaning task of a portion of the outer surface 22 of the roller 17 .

[0142] A cleaning task may correspond to a single operation, several operations or even several repeated operations forming a cleaning cycle.

[0143] The command unit 30 is also capable of controlling the amount of solvent dispensed on the cleaning pad 34 and delivering a regulated amount of solvent.

[0144] Each cleaning task is characterized by cleaning parameters.

[0145] For example, the cleaning parameters are as follows:

[0146] - pressure for cleaning,

[0147] - Crushing time of cleaning products,

[0148] - the space between two smashes,

[0149] - the type of ink used for the layer,

[0150] - the type of solvent used,

[0151] - the technology used by the coater, and

[0152] - Number of cycles (if relevant).

[0153] The cleaning parameters may be stored in a database including a list of defect characteristics.

[0154] A defect characteristic is a characteristic of at least one defect of a layer.

[0155] For example, the defect characteristic refers to whether a defect exists.

[0156] According to another example, the defect characteristic is the defect degree of the defect.

[0157] It is assumed here that each defect is associated with a respective defect severity, such as level 0 no defect, level 1 slight defect, level 2 severe defect, and level 3 very severe defect.

[0158] In particular embodiments, cleaning system 20 may be adapted to selectively clean or not clean a portion of outer surface 22 of roller 17 based on a defect severity value.

[0159] According to another illustration, several defect groups are defined, and each defect of a layer belongs to one defect group.

[0160] Therefore, the defect characteristic is the defect group to which the defect belongs.

[0161] For example, defect groups are groups defined by size ranges, such as small size defects, medium size defects, and large size defects, as a specific example.

[0162] Groups of defects that are similar in appearance and / or size may be used.

[0163] Defect groups can also be divided based on the criticality of the defects.

[0164] This defect criticality is usually defined based on the user's quality standards.

[0165] More generally, a defect group can be a combination of several defect characteristics and associated with the criticality, severity, or severity of the defect or flaw.

[0166] To carry out this classification operation, analysis unit 28 implements a neural network, for example.

[0167] In a variant or supplement, the analysis unit 28 may be provided with a self-learning capability.

[0168] As a specific example, the analyzing unit 28 is adapted to automatically sort the defects and assign the defects to corresponding defect groups.

[0169] The analysis unit 28 is therefore adapted to process the data received from the sensor 18 in accordance with the defect characteristics.

[0170] The command unit 30 is adapted to receive at least one defect characteristic.

[0171] In the present case, the command unit 30 receives at least one defect characteristic from the analysis unit.

[0172] The command unit 30 is adapted to trigger a cleaning task according to each received defect characteristic.

[0173] The operation of the command unit 30 will now be described using several specific use cases.

[0174] As a first example, the command unit 30 triggers a cleaning task depending on the degree of defect.

[0175] For example, the command unit 30 triggers the cleaning task only when the defect level of the detected defect exceeds a predetermined defect level.

[0176] As another example, the command unit 30 selects at least one region feature according to the defect group to which the detected defect belongs.

[0177] In another example, areas to be cleaned can be identified based on defects. The cleaning system is assigned a cleaning "task." The task is triggered visually and stops when the defect disappears.

[0178] The area to be cleaned is precise. Cutting out the area to be cleaned allows intervention at the correct location while preventing the robot from moving along the entire length of the roller. This ensures that contact between the robot and the roller is only for cleaning. This cleaning system 20 allows for a faster response to any problems on the counter roller 17.

[0179] In fact, the reaction time to initiate a cleaning operation is limited by the time required for the web 12 to travel the distance between the roller to be cleaned and the sensor.

[0180] Therefore, the faster the web 12 travels, the faster the cleaning operation can be initiated. The faster defects are annealed, the better the coating quality. During the coating or printing process, the cleaning operation can be carried out while the web 12 is being processed. There is no need to wait for each portion of the web 12 to be removed from the roller 17.

[0181] This also results in a significant reduction in robot movements, saving solvent or saving on solvent pumping and dispensing, thus achieving energy savings.

[0182] Task cleaning mode is also more precise and therefore more efficient because cleaning precise locations avoids lateral movement, displacement or extension of the area to be cleaned. If the pad is moved and pressed simultaneously over a large area, the area to be cleaned may spread and create new defects or move or extend defects.

[0183] The amount of solvent is strictly controlled within the necessary range. Specifically, "displacement fouling" or the generation of secondary defects (excess solvent) is avoided. Fumes from the solvent used for cleaning are also reduced.

[0184] This cleaning system 20 also avoids unnecessary friction of the pads. This increases the safety of the equipment and reduces the risk of fire in ATEX areas. In fact, friction can generate sparks or heat.

[0185] Furthermore, using the cleaning system 20, the strictly necessary amount of solvent is dosing achieved during the cleaning process, since automatic dosing (compared to manual dosing) allows for a healthier environment (air quality) and greater safety for the operator (no need to enter the coating area containing high-speed rotating machines).

[0186] Cleaning system 20 also offers the advantage of controlled and improved cleaning responsiveness. The response time between detecting a defect and cleaning the corresponding area is limited to the distance the film travels between the coating area and the defect detection area. The limiting factor in responsiveness is the roll speed. The faster the film moves, the greater the responsiveness, resulting in less loss or waste. This improves the overall process yield.

[0187] Furthermore, use of this cleaning system 20 can reduce the amount of waste due to defects by 10%.

[0188] The proposed cleaning system is an automated, autonomous and compact system.

[0189] The cleaning system has the advantage of limited system size. This is particularly useful for insertion into confined maneuverable areas. The cleaning system can even reach enclosed, secure areas that are inaccessible to operators.

[0190] The cleaning system also reduces intervention and maintenance. Specifically, there is no need to introduce mobile tools or accessories into the area.

[0191] Downtime is also limited, as the coating line can run continuously at high speed, 24 hours a day, for optimal production.

[0192] The cleaning system also has the advantage of robotic remote tracking for its maintenance / servicing operations.

[0193] Specifically, the cleaning system can be left outside the coating area (operating area), specifically allowing the replacement of used pads and the refilling of solvent tanks in complete safety, as the operator does not need to enter the coating area. These operations can be performed outside the operating area and during shielded time.

[0194] This means that the cleaning system also leads to an overall improvement in working conditions.

[0195] It should be understood that other embodiments and / or use contexts are contemplated for such a cleaning system 20. Specifically, the sensor 18 can be placed after coating, before film formation, or after a dry coating layer is formed.

[0196] The sensor 18 can also be placed before the coating system to remove impurities before the coating operation.The sensor 18 can also be used differently.

[0197] For example, the sensor 18 and the analysis unit 20 may also be used to track the cleaning efficiency, to track the removal of defects or the appearance of new defects or the remaining of defects.

[0198] A map of the coating film can be generated and stored along with information on the location and size of defects that have not yet been removed. This can be used to monitor quality indicators.

[0199] The mapping can be used to check the efficiency of the cleaning system 20 and compare whether there are any remaining defects before and after the start of the robotic task.

[0200] The cleaning system 20 may be the cleaning system disclosed in document US10040101 or the cleaning system disclosed in document US11192149.

[0201] It can also be pointed out that the cleaning system 20 can clean other types of rollers, such as backing rollers, transfer rollers, gravure rollers, metering rollers, idler rollers, rollers in dryers and embossing rollers...

[0202] Thus, the cleaning system 20 is compatible with any and all types of rolls used in web handling film processes.

[0203] In particular, the cleaning system 20 may also be used to clean any conveyor or drive rollers.

[0204] Furthermore, the rollers may actually be conveyor belts carried by the roller assembly.

[0205] In this sense, the element has infinite curvature and thus forms essentially a flat surface.

[0206] More generally, the cleaning system 20 is thus suitable for cleaning the outer surface of any moving element of the coating apparatus 5. Preferably, the cleaning system 20 is implemented in a coating apparatus that is subject to high levels of contamination, such as apparatus for wet coating, printing or lamination.

[0207] The cleaning system 20 can be used for any number of rollers, in particular 3 or 5 roller systems, and is suitable for any type of roller material (eg EPDM, steel, HNBR, tungsten or chrome-plated steel).

[0208] Similarly, the cleaning system 20 may be used with other coating / printing / forming technologies.

[0209] Different versions are used for coating and printing. One might also associate these technologies with surface treatment. These technologies can be categorized by the number of rollers, direction of rotation, and design.

[0210] For example, a common technology is the three-roller system (impregnating roller color deck). A traditional three-roller printing deck is mounted on a pair of frames or consoles and typically consists of a pair of angular bearing blocks for the plate cylinder and a pair of inking roller bearing blocks for the inking rollers (anilox roller and impregnating roller). An ink fountain is often included.

[0211] The cleaning system 20 can also be used for roller coating or rollerless coating.

[0212] In roller coating and related processes, wet coverage is determined by the flow rate of the coating composition and the coating speed. Roller coating is a coating method in which the thickness and uniformity of the coating film are controlled by the flow of fluid in the nip or gap between a pair of rotating rollers. This extends to coating rollers of infinite radius, including those used to cover flat sheets, and to rollers with zero speed, such as those used to cover knives and blades.

[0213] Gravure coating allows covering the web with thin coating layers, down to a few micrometers, typically around 3 μm.

[0214] When applying a thin layer of pigmented backing ink, fouling in the coater can lead to defects in the coated layer: the backing roller becomes soiled with ink, for example from the coating element or the ink reservoir. Roller fouling can be caused by ink splashes, ink in the form of droplets (due to aerodynamic effects, volatility of the components, etc.), misting, leakage, etc. Generally speaking, ink droplets "fly" from the doctor blade chamber, reservoir or application roller to the support roller (material projection).

[0215] The ink then dries more or less quickly, depending on the ink composition, pigments, or solvents used. Excessive dried solid ink on the support roller creates an additional and undesirable local thickness, pushing away the actual coating composition applied to the web. This is where defects such as white spots, voids, or gaps appear on the coated web: locations where the coating composition is missing. These may be referred to as "sleeve defects" because they are caused by fouling of the sleeve.

[0216] When trying to clean the sleeve, using traditional cleaning techniques (robotics) may create new defects. In fact, the fouling area may expand or shift, for example when dried ink spreads on the sleeve.

[0217] Furthermore, the thinner the web to be coated, the more severe the impact of fouling on the quality of the coated web.

[0218] The cleaning system 20 allows for efficient cleaning of the sleeve after detecting and identifying sleeve defects on the coated web 12 in real time.

[0219] Scaling on the sleeve can be detected directly.

[0220] However, proper detection is not achieved when applying dark coating compositions when the sensor 18 is directed towards the roller surface. Depending on the type or back-up roller used, the contrast between the sleeve surface and the fouling area is often too low (black ink on a black cover), or the glossiness of the anilox roller may interfere with fouling detection.

[0221] Furthermore, the rotation of the roll increases the difficulty of finding the scaled areas to be cleaned. Therefore, methods of cleaning the sleeves have been developed that first control the coating layer of the web and then perform a cleaning operation to remove the scale from the sleeve.

[0222] Thanks to the use of cleaning system 20, cleaning does not introduce new defects. Once a defect has appeared, been detected, and identified, cleaning system 20 can be activated. Thus, cleaning system 20 operates as a therapeutic defect treatment system. Furthermore, cleaning system 20 can selectively clean specific areas to be cleaned based on commands from the analysis unit. Cleaning operations are precise and on-demand, starting and stopping as defects appear and disappear.

[0223] The cleaning system 20 can also exhibit 3 degrees of freedom of movement relative to the surface to be cleaned to compensate for the curvature of the roller and its speed. The path of the cleaning device can be sinusoidal, elliptical, orbital, linear...

[0224] Forward roller coating can also benefit from the cleaning system 20.

[0225] With this technique, the web travels over a support roll while an application roll rotates in the same direction as the support roll at the same or a different speed.The coating composition may be supplied through a slot die.

[0226] In another design, a dipping roller can absorb the liquid from the pan and transfer it to the applicator roller, creating a three-roller pan feed system. A third roller can be added to rest against the applicator roller, with the liquid supplied to the nip between them. Any number of rollers can be used, and the rollers can be smooth, chrome-plated steel, or rubber-covered. Ceramic rollers can also be used.

[0227] like Figure 5 As shown, in the case of screen printing, in particular rotary screen printing, the screen is a seamless perforated nickel roller, the degree of perforation being expressed by the mesh number, which represents the number of holes per linear inch. A scraper is mounted inside the perforated roller to supply and distribute the coating composition (paste). The scraper blade pushes the paste through the perforated screen. A whisper blade can smooth the applied coating layer. Related coating techniques include pattern coating, dot coating, ordinary paste coating, foam coating, etc. In rotary screen printing, a cleaning system is suitable for cleaning the outer surface of the roller carrying the web.

[0228] Flexographic printing technology (often called Flexo) can be considered in coating equipment. This technology such as Figure 6 shown.

[0229] This printing technology is a high-quality printing technology for the packaging industry (compared to letterpress, gravure, offset printing). The web to be printed can be packaging material such as paper, plastic film, aluminum foil... Flexo can be used for highly flexible and qualitative printing on a wide range of materials at variable speeds. In flexographic printing, the web can be printed with a pattern defined by an intermediate roller. The area to be cleaned is located on the outer surface of the counter roller, which forms a nip with the intermediate roller. When using an engraved roller ( Figure 7) or micro roller ( Figure 8 ) during coating, a pick-up roller delivers the coating composition from a reservoir to the web. For both coating techniques, increasing the coating speed also increases the tendency of nearby rollers to become contaminated, thereby affecting the surface of the coated web.

[0230] The cleaning system 20 can also be used for kiss coating.

[0231] In kiss coating, the web, traveling in the same direction as or opposite to the applicator roll, may be held against the applicator roll solely by web tension.The roll to be cleaned may be part of a roll assembly used to transport the web.

[0232] The cleaning system 20 can also be used for reverse roll coating.

[0233] In reverse roll coating, the web is fed in the opposite direction from the applicator roll. A support roll (sometimes called a "sleeve"), typically covered with rubber, is used between the web and the applicator roll, which are pressed against each other to meter the coating composition, thereby controlling its thickness or basis weight. The amount of liquid transferred to the web can be controlled by the applicator roll, which is a metering roll that rotates in the opposite direction.

[0234] Several different counter-rotating roll configurations are possible. In many cases, a doctor blade is used to wipe off excess coating from the applicator roll within the doctor blade chamber. This technique allows for metering of liquid coating composition onto the applicator roll shortly after the coating composition is delivered from a reservoir to the applicator roll.

[0235] Cleaning systems can also be used for dip coating, whereby the web is immersed in a liquid. A pair of squeeze rollers is used to remove excess coating from the web. Splashing of the coating composition as it is introduced into and out of the web is a major source of defects due to fouling of nearby rollers.

[0236] The cleaning system 20 can also be used for hot melt coating.

[0237] Other technologies that can benefit from a cleaning system 20 are rod coating, wire wound rod coating (Meyer rod), scraping off excess coating liquid, blade coating, knife coating, air knife coating, dip coating, ...

[0238] In all cases, the cleaning system 20 can improve the efficiency of the coater.

[0239] This is advantageous for many applications: flexible films (printed packaging...), food containers, paper, textiles, technical coatings, prepregs, adhesive tapes, artificial leather production, batteries (electrode plates or primers on conductive surfaces), monochrome printers (screen printing).

[0240] In a specific technical area, thin coated webs are used for thermal transfer printing. For thermal transfer printing, the coated web is cut into narrow ribbons. For high-performance end uses and / or heavy-duty printers, the quality of the ink ribbon is crucial at high printing speeds. Therefore, the quality of the thin coated web directly affects the print quality (print sensitivity, darkness, etc.). This type of ribbon is typically used for printing labels, tags, etc.

[0241] The cleaning system 20 can also be used in the printing industry and in printers (electrophotography, laser printing, thermal transfer printers . . . ).

[0242] The cleaning system 20 can also be used for plastic sheet production: the composition itself is extruded. Plastic sheets can also be produced by coating on a substrate and then peeling from the substrate after curing (peeling).

[0243] Such a cleaning system 20 can also be used for non-flexible webs to be coated / printed, such as in the production of hard floor coverings.

[0244] Cleaning system 20 may also be particularly suitable for high value-added items, demanding end uses requiring a zero-defect product.

[0245] In fact, reducing the number / size of defects and mapping the remaining defects enables the end user to know the location of the defects and / or discard the areas with remaining defects.

[0246] Applying glue or adhesive by any technique such as wet coating or dry lamination may also be valuable, for example in laminating two surfaces using a liquid or pressure sensitive adhesive.

Claims

1. A cleaning system (20) suitable for cleaning the outer surface (22) of a moving element of a coating device (5), said coating device (5) comprising a coater (10) suitable for coating and / or printing and / or shaping a layer on a web (12), said cleaning system (20) comprising: - a robotic arm (24) comprising a holding mechanism (32); a cleaning device (26) held on the holding member (32), the cleaning device (26) being suitable for cleaning the outer surface (22) of the moving element (17); a command unit (30) adapted to command the robot arm (24) and the cleaning device (26) to perform a cleaning task of a portion of the outer surface (22) of the moving element (17), The command unit (30) is adapted to receive at least one defect characteristic, which is characteristic of at least one defect of the layer, and to trigger a cleaning task according to each received defect characteristic.

2. The cleaning system according to claim 1, wherein: The cleaning system (20) further comprises an analyzing unit (28) adapted to: - receiving data from a sensor (18), said data being an image of a layer coated and / or printed by said coater (10), and - analyzing said data to detect at least one defect characteristic of at least one defect of said layer.

3. A cleaning system according to claim 1, wherein the cleaning device (26) is provided with an interface unit, which is suitable for receiving multiple information about at least one defect of the layer from a user, and the command unit (30) is suitable for commanding the robot arm (24) and the cleaning device (26) also based on the multiple information about at least one defect of the layer.

4. The cleaning system according to claim 2, wherein at least one defect characteristic detected by the analyzing unit (28) is the presence or absence of a defect.

5. The cleaning system of claim 1, wherein each defect is associated with a defect degree, one of the defect characteristics being the defect degree.

6. The cleaning system according to claim 5, wherein the command unit (30) is adapted to trigger a cleaning task when the defect level of the detected defect exceeds a predetermined defect level.

7. A cleaning system according to claim 1, wherein each defect of the layer belongs to a corresponding predetermined defect group, a defect characteristic is the defect group to which the defect belongs, and the regional characteristics of the area to be cleaned by the cleaning device (26) are selected based on the defect characteristic.

8. The cleaning system of claim 7, wherein one area characteristic is a surface of the area to be cleaned.

9. The cleaning system of claim 8, wherein one area characteristic is the location of the center of the area to be cleaned.

10. The cleaning system according to claim 9, wherein the positioning of the center of the area to be cleaned is selected from the following three areas: the left part of the moving element (17), the central part of the moving element (17) and the right part of the moving element (17).

11. The cleaning system according to claim 1, wherein the cleaning task is characterized by cleaning parameters, the command unit (30) being adapted to calculate each cleaning parameter depending on the defect characteristics.

12. The cleaning system according to claim 1, wherein the cleaning device (26) comprises a cleaning pad adapted to come into contact with the portion of the outer surface (22) of the moving element (17).

13. The cleaning system according to claim 1, wherein the cleaning pad has an outer surface (22) with foam, in particular melamine foam.

14. The cleaning system of claim 1, wherein the cleaning device (26) further comprises a cleaning pad, a solvent reservoir, and a pressure unit adapted to deliver solvent from the solvent reservoir to the cleaning pad.

15. The cleaning system according to claim 1, wherein the moving element of the coating device (5) is a roller (17).

16. A coating machine (10) comprising the cleaning system (20) according to any one of claims 1 to 15.

17. A coating apparatus (5) comprising the cleaning system (20) according to any one of claims 1 to 15.

18. A method for cleaning an outer surface (22) of a moving element of a coating device (5), the coating device (5) comprising a coater (10) adapted to coat and / or print and / or shape a layer on a web (12), the method being performed by a cleaning system (20), the cleaning system (20) comprising: - a robotic arm (24) comprising a holding mechanism (32); a cleaning device (26) held on the holding member (32), the cleaning device (26) being suitable for cleaning the outer surface (22) of the moving element (17); - a command unit (30) adapted to command the robot arm (24) and the cleaning device (26) to perform a cleaning task of a portion of the outer surface (22) of the moving element (17); The method comprises: - receiving at least one defect characteristic, said defect characteristic being characteristic of at least one defect of said layer, and - Trigger a cleaning task based on each received defect characteristic.

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