A seven-roller double-sided coating unit with doctor blade and a coating method

Abstract

The application discloses a seven-roller double-sided coating unit with a scraper, which comprises a rack, wherein a second coating group, an air floatation turning roller and a first coating group are sequentially arranged along the feeding direction of a base material on the rack. The seven-roller double-sided coating unit with a scraper and a coating method provided by the application realize the synchronous coating function of coating different coating liquids on the two sides of the base material in one feeding process through the sequential arrangement of the second coating group, the air floatation turning roller and the first coating group and the setting of the seven rollers forming an upper-lower asymmetric double coating group, solve the problems of the secondary feeding scratch of the coating layer, the mutual invasion of solvents, the high energy consumption and the high working hours caused by the coating of one side first and then the coating of the other side after drying in the prior art, and achieve the technical effects of one-time forming of the two sides, no scratch and mottling on the coating surface and great improvement of the production efficiency.

Description

Technical Field

[0001] This invention relates to the field of coating equipment technology, specifically to a seven-roller double-sided coating unit with a doctor blade and a coating method. Background Technology

[0002] Release paper is a functional paper material made by coating the surface of base paper with a release agent. Double-sided release paper requires coatings of different types and amounts on both sides of the substrate. For example, an organosilicon release agent is coated on the front to form a release layer, and an antistatic liquid or primer is coated on the back. The dry silicone coating amount of the release layer is only 0.3g / m² to 1.5g / m², which is an ultra-thin precision coating.

[0003] Currently, there are two main processes for double-sided coating of release paper. The first is two-coating: one side is coated first, dried, and then the other side is coated. During the second coating, the first coating layer passes through the drive roller and guide roller multiple times, which can easily cause defects such as scratches, uneven surface, and damage. The solvent can also corrode the first coating layer, and this process is energy-intensive, time-consuming, and wasteful. The second is simultaneous double-sided coating, such as the "Multi-roller Double-sided Coating Unit and Coating Method" disclosed in Chinese patent application CN110732453A. This method uses two sets of symmetrical coating rollers, each consisting of a metering roller, a transfer roller, and a coating roller. The coating liquid is placed in an open coating liquid tank, and the coating amount is controlled by the gap between the rollers. Although this structure achieves double-sided coating in a single feed, it does not solve the problems of wet coating turning, being crushed and stuck to the roller surface during transport, and lacks tension detection function. In summary, existing equipment struggles to simultaneously handle double-sided differentiated coating, ultra-thin layer precision metering, non-contact conveying of wet coatings, and stable tension control, resulting in unstable product release force, easy coating damage, and high scrap rate. Summary of the Invention

[0004] This application proposes a seven-roller double-sided coating unit with a doctor blade and a coating method, which has the advantages of double-sided one-time forming, non-contact turning and conveying of wet coating, and closed-loop tension control. It solves the technical problems in the existing double-sided coating process of release paper, such as damage to the coating due to the second feeding of material after coating and baking, solvent mutual invasion, high energy consumption and high time, as well as the damage to the wet coating due to turning and contact when coating both sides at the same time, insufficient coating amount control accuracy, uneven coating thickness and high scrap rate caused by unstable tension.

[0005] To achieve the above objectives, this application adopts the following technical solution: a seven-roller double-sided coating unit with a scraper, comprising a frame, wherein a second coating group, an air-bearing steering roller and a first coating group are sequentially arranged on the frame along the material feeding direction of the substrate; The first coating assembly includes a first back roller, an anilox roller, an upper transfer roller, and a closed-type doctor blade assembly. The two ends of the anilox roller, the upper transfer roller, and the closed-type doctor blade assembly are rotatably mounted on translation slides provided on both sides of the frame. The second coating unit includes a second back roller, a feed roller, and a metering transfer roller. The two ends of the feed roller and the metering transfer roller are rotatably mounted on adjustable slides on both sides of the frame.

[0006] Furthermore, the first back roller is rotatably mounted on the frame and its axial position is fixed. The anilox roller rolls in contact with the upper transfer roller, and the upper transfer roller rolls in contact with the substrate wrapped around the first back roller to coat the second coating liquid onto the second surface of the substrate. The closed doctor blade assembly is sealed in contact with the roller surface of the anilox roller and forms a closed storage cavity for holding the second coating liquid with the anilox roller. A receiving groove for receiving dripping coating liquid is provided below the anilox roller.

[0007] Furthermore, the second back roller is rotatably mounted on the frame and its axial position is fixed. The lower half of the conveyor roller is immersed in a material tank containing the first coating liquid. The metering transfer roller is disposed between the conveyor roller and the second back roller. One side of the metering transfer roller rolls and adheres to the conveyor roller, and the other side rolls and adheres to the substrate wrapped around the second back roller, so as to coat the first coating liquid onto the first surface of the substrate.

[0008] Furthermore, the air-bearing steering roller is disposed between the second coating group and the first coating group. The roller surface of the air-bearing steering roller is provided with air vents. The inner cavity of the air-bearing steering roller is connected to the air outlet of the hot air device via a rotary joint. Both ends of the air-bearing steering roller are floatingly mounted on the frame via floating arms. The floating arms are connected to a balancing component. The frame is equipped with a displacement sensor for detecting the swing position of the floating arms.

[0009] Furthermore, the enclosed scraper assembly includes a scraper cavity with an open side. An upper scraper and a lower scraper, which are sealed and fitted to the roller surface of the anilox roller, are respectively installed on the upper and lower edges of the open side of the scraper cavity. Sealing blocks that match the curvature of the roller surface of the anilox roller are installed at both ends of the scraper cavity, so that the scraper cavity and the anilox roller form the enclosed storage cavity. The scraper cavity has an inlet and a return outlet that are connected to the feeding device. A flipping shaft is connected to both ends of the scraper cavity.

[0010] Furthermore, the translation slide is slidably mounted on the frame along the linear slide rail, and is driven to move along the linear slide rail by the slide drive screw. The two ends of the anilox roller are rotatably mounted on the translation slide through separate bearing seats. A lifting cylinder for driving the upper transfer roller to rise and fall is installed on the translation slide.

[0011] Furthermore, the first back roller and the second back roller are each driven by an independent servo motor. The displacement sensor is electrically connected to the controller. The controller adjusts the rotational speed ratio of the first back roller and the second back roller according to the floating arm position signal detected by the displacement sensor, so that the substrate tension between the second coating group and the first coating group remains constant.

[0012] Furthermore, the metering transfer roller includes an air-expanding roller core and a rubber roller sleeve fitted outside the air-expanding roller core. The roller surface of the air-expanding roller core is provided with an air-expanding key strip and an air-expanding rebound bladder. The outer wall of the inner end of the air-expanding rebound bladder is adhered to the inner wall of the air-expanding roller core, and the air-expanding rebound bladder is connected to the inner cavity of the air-expanding roller core. The outer end of the air-expanding rebound bladder is connected to the air-expanding key strip.

[0013] A coating method with a doctor blade-type seven-roller double-sided coating unit includes the following steps: S1. Adjusting the machine: According to the width of the substrate and the coating amount requirements, adjust the bonding pressure of the closed doctor blade assembly to the anilox roller, set the outlet air temperature and outlet air pressure of the hot air device, add the first coating liquid into the material tank, and introduce the second coating liquid into the closed storage chamber. S2, Paper threading: The substrate is wrapped around the second back roller in sequence, and then non-contactly bypassed the air-float steering roller with the first coating layer facing the roller surface of the air-float steering roller, and then wrapped around the first back roller before being led out. S3, First coating: Start the equipment and increase the speed. The material roller carries the first coating liquid from the material tank. After being metered by the metering transfer roller, it is coated on the first side of the substrate. At the same time, the hot air device supplies hot air to the air-float turning roller. The hot air flows out through the vent to form an air cushion. The first coating layer of the substrate is supported by the air cushion and passes around the air-float turning roller non-contactly. The hot air pre-dries the first coating layer. S4. Second coating: The closed doctor blade assembly works with the anilox roller to meter the second coating liquid in a closed manner. The anilox roller transfers the metered second coating liquid to the upper transfer roller, which coats the second side of the substrate. The substrate is then drawn out and enters the subsequent drying process. S5. Tension closed-loop control: During the coating process, the displacement sensor detects the position of the floating arm in real time, and the controller adjusts the speed ratio between the first back roller and the second back roller according to the detection signal to keep the substrate tension between the two coating groups constant.

[0014] The present invention has the following beneficial effects: 1. This application provides a seven-roller double-sided coating unit and coating method with a doctor blade. By arranging the second coating group, the air-float steering roller and the first coating group in sequence along the material feeding direction, and setting the seven rollers to form an asymmetrical double coating group, the synchronous coating function of coating different coating liquids on both sides of the substrate in one feeding is realized. This solves the problems of secondary feeding scratches on the coating, solvent cross-contamination, high energy consumption and high labor time caused by coating one side first, drying and then coating the other side in the prior art. It achieves the technical effect of double-sided one-time forming, no scratches or mottling on the coating surface and greatly improved production efficiency.

[0015] 2. The seven-roller double-sided coating unit and coating method with doctor blade provided in this application achieve the functions of closed-loop supply of the second coating liquid and precise measurement by the doctor blade through the cooperation of the closed doctor blade assembly and the anilox roller to form a closed material storage chamber. This solves the problems of easy splashing, easy mixing of air bubbles, and large fluctuations in coating amount when coating ultra-thin release layers of release paper with open feeding. It achieves the technical effect of stable control of coating amount deviation and coating without streaks and bubbles.

[0016] 3. The seven-roller double-sided coating unit and coating method with a scraper provided in this application, through the cooperation of the air holes of the air-bearing steering roller and the hot air device, as well as the linkage of the floating arm, displacement sensor and two back roller servo drive, a single component realizes three functions at the same time: non-contact steering of the wet coating surface, hot air pre-drying of the first coating surface, and real-time detection of tension between the two coating pressure zones. It solves the problems of the wet coating surface being crushed and stuck when it turns through the guide roller, as well as the problem of substrate stretching deformation and uneven coating thickness caused by the traction speed difference between the two coating groups. It achieves the technical effect of constant substrate tension and uniform double-sided coating thickness. Attached Figure Description

[0017] The accompanying drawings, which form part of this specification, illustrate embodiments disclosed in this application and, together with the specification, serve to explain the principles disclosed in this application.

[0018] This disclosure will become clearer with reference to the accompanying drawings and the following detailed description, wherein: Figure 1 This is a schematic diagram of the overall structure of this application; Figure 2 This is a cross-sectional view of this application; Figure 3 This is a cross-sectional view of the metering transfer roller of this application; Figure 4 This is a cross-sectional view of the closed scraper assembly of this application; Figure 5 This is an exploded view of the structure of the second coating group of this application; Figure 6 This is a schematic diagram of the structure of the air-float steering roller of this application; Figure 7This is an exploded view of the structure of the first coating group of this application; Figure 8 This is a flowchart of the method used in this application.

[0019] In the diagram: 1. Frame; 2. First coating unit; 21. Anilox roller; 22. Enclosed doctor blade assembly; 221. Doctor blade cavity; 222. Upper doctor blade; 223. Lower doctor blade; 224. Sealing block; 225. Feed inlet; 226. Return inlet; 227. Tilting shaft; 228. Doctor blade clamping airbag; 23. Upper transfer roller; 231. Lifting cylinder; 24. First back roller; 25. Receiving trough; 26. Translation slide; 261. Linear slide rail; 262. Slide drive screw; 26 3. Separable bearing housing; 264. Lifting groove; 3. Second coating group; 31. Material conveyor roller; 32. Metering transfer roller; 321. Air-expanded roller core; 322. Rubber roller sleeve; 323. Air-expanded key bar; 324. Air-expanded rebound bladder; 33. Second back roller; 34. Material trough; 341. Constant temperature jacket; 35. Adjustable slide; 4. Air-float steering roller; 41. Vent hole; 42. Rotary joint; 43. Floating arm; 44. Balancing component; 45. Displacement sensor; 5. Substrate; 6. Controller. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] Please see Figure 1 -Appendix Figure 8 As shown, a seven-roller double-sided coating unit with a scraper includes a frame 1 and a controller 6. The frame 1 is provided with a second coating group 3, an air-bearing steering roller 4 and a first coating group 2 arranged sequentially along the feeding direction of the substrate 5.

[0022] See appendix Figure 1 Appendix Figure 2 Appendix Figure 4 and attached Figure 7 As shown, the first coating group 2 includes a first back roller 24, an anilox roller 21, an upper transfer roller 23, and a closed doctor blade assembly 22. Translation slides 26 located at the first coating group 2 are provided on both sides of the frame 1.

[0023] The translation slide 26 is a rectangular frame slide, slidably connected to a linear guide rail 261, which is mounted on the frame 1. The frame 1 is also equipped with a slide drive screw 262 for driving the translation slide 26 along the linear guide rail 261. The extension direction of the linear guide rail 261, i.e., the movement direction of the translation slide 26, is the direction of the center line connecting the anilox roller 21 and the first back roller 24. The translation slide 26 is also equipped with a separate bearing seat 263 and a lifting groove 264.

[0024] The two ends of the first back roller 24 are rotatably mounted on the frame 1, so the position of the axis of the first back roller 24 is fixed. The first back roller 24 is driven by an independent servo motor driven by a planetary reducer, which serves as the main reference roller for the linear speed of the whole machine.

[0025] An anilox roller 21 is positioned diagonally above the first back roller 24, with the line connecting its center to the first back roller 24 forming an angle of approximately 45° with the horizontal plane. The anilox roller 21 rolls in contact with the upper transfer roller 23, distributing the coating liquid from its surface onto the upper transfer roller 23. The amount of coating transferred can be finely adjusted by changing the linear velocity ratio between the surfaces of the anilox roller 21 and the upper transfer roller 23. Both ends of the anilox roller 21 are rotatably mounted in a separable bearing housing 263 via bearings. The separable bearing housing 263 means that the upper cover and base of the bearing housing are detachable; after removing the upper cover, the bearings fitted inside the base and the rollers connected to the bearings can be removed. The anilox roller 21 is driven by an independent servo motor.

[0026] The upper transfer roller 23 is located between the anilox roller 21 and the first back roller 24. The substrate 5 moves between the upper transfer roller 23 and the first back roller 24. One side of the upper transfer roller 23 rolls and adheres to the anilox roller 21, and the other side of the upper transfer roller 23 rolls and adheres to the substrate 5, thereby coating the second coating liquid onto the second surface of the substrate 5. The bearing seats at both ends of the upper transfer roller 23 are slidably installed in the lifting groove 264. A lifting cylinder 231 is installed on the translation slide 26, and the piston rod end of the lifting cylinder 231 is connected to the bearing seat connected to the upper transfer roller 23. Therefore, the upper transfer roller 23 can move as a whole with the translation slide 26, or it can be lifted and lowered separately along the lifting groove 264 under the drive of the lifting cylinder 231, realizing the pressing and depressurization between the upper transfer roller 23 and the first back roller 24. During pressing, the bonding pressure of the upper transfer roller 23 on the substrate 5 is adjusted by the air pressure of the lifting cylinder 231.

[0027] The enclosed doctor blade assembly 22 is sealed and fitted to the roller surface of the anilox roller 21, forming a closed storage cavity for holding the second coating liquid. The enclosed doctor blade assembly 22 includes a doctor blade cavity 221, an upper doctor blade 222, a lower doctor blade 223, and a sealing block 224. One side of the scraper cavity 221 is open and faces the surface of the anilox roller 21. The upper scraper 222 and the lower scraper 223 are respectively installed on the upper and lower edges of the open side of the scraper cavity 221. The contact tangential angle between the scraper blade and the surface of the anilox roller 21 is 25° to 30°. The lower scraper 223 is a metering scraper, which is responsible for the metering function of scraping off excess coating liquid from the surface of the anilox roller 21. The upper scraper 222 is a sealing scraper, which is responsible for the sealing function. The back of both the upper scraper 222 and the lower scraper 223 is provided with a scraper pressing airbag 228 arranged along the entire length. By inflating the airbag and adjusting the air pressure inside the airbag, the scraper blade can be evenly pressed against the roller surface and the pressure between the scraper blade and the roller surface can be adjusted. Two arc-shaped sealing blocks 224 are installed at both ends of the scraper cavity 221. The outer arc surface of the sealing block 224 matches the arc of the anilox roller 21 and elastically fits the roller surface. The upper scraper 222, the lower scraper 223, and the two sealing blocks 224 together seal the open side of the scraper cavity 221, forming a sealed storage cavity between the scraper cavity 221 and the anilox roller 21. The scraper cavity 221 has a feed inlet 225 at the bottom and a return outlet 226 at the top. In actual application, the feed inlet 225 is connected to the feed tank storing the second coating liquid via a metering pump, and the return outlet 226 returns the liquid to the feed tank via a hose. The second coating liquid circulates between the storage cavity and the feed tank, maintaining a slight positive pressure of 0.02MPa to 0.05MPa inside the cavity to prevent air from entering and generating bubbles. The scraper cavity 221 is connected to two ends with a rotating shaft 227. By driving the rotating shaft 227 to rotate, the scraper cavity 221 can be rotated, so that the open side of the scraper cavity 221 is rotated downward to a vertically downward state, which facilitates the pouring out of the second coating liquid in the scraper cavity 221. In practical applications, the rotating shaft 227 can be driven downward by manual operation, a rotating cylinder, or a rotating motor gear set.

[0028] Below the anilox roller 21, a receiving trough 25 is provided to collect dripping coating liquid. Suspended directly below the anilox roller 21 and the enclosed doctor blade assembly 22, the receiving trough 25 has a recovery port at its lowest point connected to a return pipe. In practical applications, the return pipe is connected to the supply tank via a return pump. A liquid level sensor can be installed inside the receiving trough 25, electrically connected to the controller 6. When the recovered coating liquid in the receiving trough 25 accumulates to a set level, the controller 6 starts the return pump to pump the coating liquid back to the supply tank for recycling. The pump stops when the liquid level drops to the lower limit. To facilitate cleaning, the receiving trough 25 is designed to be detachable or can be pulled out from the side of the frame 1 using a drawer-like sliding rail.

[0029] In this application, the translation slide 26 has three points defined by limit switches or servo position points: Working position: The upper transfer roller 23 is pressed against the first back roller 24, and the anilox roller 21 is bonded to the upper transfer roller 23, and the whole machine is in the coating state; Paper feeding position: The slide table moves back about 100mm to 150mm, and a paper feeding channel with a width of about 100mm to 150mm is formed between the upper transfer roller 23 and the first back roller 24. At the same time, the lifting cylinder 231 can lift the upper transfer roller 23 to facilitate paper feeding and the passage of the joint after paper cutting. Maintenance position: The slide table retracts to the end of the stroke, and the anilox roller 21 is retracted to the operating space outside the frame 1. At this time, the top cover of the separable bearing seat 263 can be loosened, and the anilox roller 21 can be lifted out along the axial direction for cleaning or replacement. The rubber roller is removed from the pressing state to avoid permanent indentation caused by long-term static pressure.

[0030] See appendix Figure 1 Appendix Figure 2 Appendix Figure 3 and attached Figure 6 As shown, the air-floating steering roller 4 is a hollow roller. The surface of the air-floating steering roller 4 is provided with ventilation holes 41. A rotary joint 42 is installed in the shaft head at one end of the air-floating steering roller 4. The rotary joint 42 can be connected to the air outlet of the hot air device. The hot air device can be composed of a centrifugal fan, an electric heater and an air filter. The hot air device supplies clean hot air with adjustable temperature and pressure to the inner cavity of the air-floating steering roller 4. Hot air flows out evenly along the entire roller surface through the vent 41, forming a support air cushion of a certain thickness between the roller surface of the air-bearing guide roller 4 and the substrate 5, so that the wet coating surface of the substrate 5 does not come into contact with the roller surface when it passes around the air-bearing guide roller 4. While forming the air cushion to support the substrate 5, the hot air continuously blows on the wet coating of the first side of the substrate 5 to pre-dry it, so that the surface of the coating loses its fluidity before reaching the first coating group 2, avoiding the influence of water and solvent in the coating on the subsequent front coating, and also reducing the load on the subsequent drying device. The outlet air temperature is adjusted according to the type of coating liquid: 50℃~80℃ for water-based coating liquid and 30℃~45℃ for solvent-based coating liquid, to prevent the solvent from evaporating too early and causing the coating surface to form a skin.

[0031] The shaft ends of the air-bearing steering roller 4 are respectively installed at one end of the left and right floating arms 43. The middle part of the floating arm 43 is hinged to the frame 1 through a hinge shaft. The other end of the floating arm 43 is connected to the balance member 44. The balance member 44 can be a balance cylinder, tension spring, etc. In the attached drawings of this application, a balance cylinder is used. The piston rod of the balance cylinder is hinged to the floating arm 43. The set air pressure of the balance member 44 determines the floating support force of the air-bearing steering roller 4 on the substrate 5, thereby setting the reference tension of the substrate section between the second coating group 3 and the first coating group 2. The frame 1 is also equipped with a displacement sensor 45 to detect the swing angle of the floating arm 43. The displacement sensor 45 can be a grating displacement sensor, wire encoder, etc. When the substrate tension between the two coating groups increases, the substrate presses against the air-bearing steering roller 4, the air cushion thickness decreases, and the floating arm 43 swings to one side; when the tension decreases, the floating arm 43 swings back to the other side under the action of the balance member 44; the displacement sensor 45 transmits the real-time position signal of the floating arm 43 to the controller 6.

[0032] Therefore, the air-bearing steering roller 4 possesses three functions simultaneously: first, non-contact air cushion steering to protect the wet coating; second, hot air pre-drying of the first surface coating; and third, as a floating tension roller to detect tension fluctuations between the two coating zones in real time and as a feedback element for tension closed-loop control. Simultaneously, the air cushion pressure and temperature can be adjusted according to the substrate and coating liquid type. Low air cushion pressure adapts to low-basis-weight thin paper to prevent wobbling, while high pressure adapts to high-basis-weight substrates to ensure stable adhesion. Different states of the same component adapt to different working conditions. Furthermore, in practical applications, to further improve the pre-drying effect of the air-bearing steering roller 4 on the first surface coating of the substrate 5, the size and position of the air-bearing steering roller 4 can be customized. Since the wrap angle between the substrate 5 and the air-bearing steering roller 4 determines the contact time of the air cushion layer between the substrate 5 and the air-bearing steering roller 4, the larger the wrap angle, the longer the contact time, and the longer the pre-drying time of the hot air on the first coating of the substrate 5. At the same time, an air-bearing steering roller 4 of a specific diameter can be customized according to the required pre-drying time of the substrate and coating liquid, and the horizontal position of the air-bearing steering roller 4 can be adjusted during installation to change the wrap angle between the substrate 5 and the air-bearing steering roller 4, thereby adjusting the pre-drying effect of the hot air on the first coating.

[0033] See appendix Figure 1 Appendix Figure 2 Appendix Figure 6 As shown, the second coating group 3 includes a feed roller 31, a metering transfer roller 32, and a second back roller 33.

[0034] A material trough 34 is provided below the material roller 31. The two ends of the material trough 34 are connected to the frame 1. The material trough 34 contains a first coating liquid. The first coating liquid in this application is a coating liquid for the non-release surface of the release paper, such as an aqueous antistatic primer. A constant temperature jacket 341 is provided in the inner wall of the material trough 34. Constant temperature water or heat transfer oil at 20℃~40℃ is circulated in the jacket to keep the temperature and viscosity of the coating liquid stable. The two ends of the material trough 34 are also provided with end baffles that can slide along the roller axis, so that the effective feeding width can be adjusted according to the width of the substrate.

[0035] The lower part of the conveyor roller 31 is immersed in the first coating liquid in the material tank 34. In actual application, the immersion depth of the conveyor roller 31 in the first coating liquid can be adjusted by adjusting the liquid level in the material tank 34. The conveyor roller 31 is driven by an independent servo motor. When the conveyor roller 31 rotates, it carries the coating liquid to adhere to the roller surface.

[0036] The two ends of the second back roller 33 are rotatably mounted on the frame 1 through bearings, so the axial position of the second back roller 33 is fixed. In addition, the second back roller 33 is driven by an independent servo motor, and the speed of the servo motor is controlled by the controller 6.

[0037] A metering transfer roller 32 is disposed between the feed roller 31 and the second back roller 33. One side of the metering transfer roller 32 rolls and adheres to the feed roller 31, while the other side rolls and adheres to the substrate 5. When the feed roller 31 rotates, the liquid material on its surface is evenly distributed onto the surface of the metering transfer roller 32. When the substrate 5 passes between the metering transfer roller 32 and the second back roller 33, the second back roller 33 coats the surface of the substrate 5 with the liquid material.

[0038] See appendix Figure 1 Appendix Figure 2 Appendix Figure 5 As shown, adjustable slides 35 are installed on the left and right sides of the frame 1 at the second coating group 3. The adjustable slides 35 are horizontal slides with graduated screws, and their translation direction is along the line connecting the centers of the material roller 31 and the metering transfer roller 32. Two sets of slides are provided on the adjustable slides 35. The two ends of the material roller 31 are rotatably mounted on one set of slides via bearings, and the two ends of the metering transfer roller 32 are rotatably mounted on the other set of slides via bearings. Each set of slides is equipped with a threaded shaft. By adjusting the position of each set of slides via the threaded shaft, the bonding gap between the material roller 31 and the metering transfer roller 32, as well as the bonding pressure between the metering transfer roller 32 and the second back roller 33, can be adjusted respectively.

[0039] See appendix Figure 2 Appendix Figure 3 and attached Figure 5As shown, the metering transfer roller 32 includes an air-expanding roller core 321 and a rubber roller sleeve 322 fitted over the air-expanding roller core 321. The roller surface of the air-expanding roller core 321 is provided with an air-expanding key strip 323 and an air-expanding rebound bladder 324; a portion of the outer wall of the inner end of the air-expanding rebound bladder 324 is adhered to the inner wall of the air-expanding roller core 321, and the air-expanding rebound bladder 324 communicates with the inner cavity of the air-expanding roller core 321. The outer end of the air-expanding rebound bladder 324 is connected to the air-expanding key strip 323. After compressed air is introduced through the air pipe at the shaft end of the air-expanding roller core 321, the outer end of the air-expanding rebound bladder 324 bulges outward, pushing the air-expanding key strip 323 into the corresponding keyway on the inner wall of the tightening rubber roller sleeve 322, thus combining the air-expanding roller core 321 and the rubber roller sleeve 322 into a single roller. After deflating, the air-expanding rebound bladder 324 retracts, causing the air-expanding key strip 323 to retract into the air-expanding roller core 321, separating the air-expanding roller core 321 from the rubber roller sleeve 322. The rubber roller sleeve 322 can then be axially removed from the air-expanding roller core 321 for replacement. In practical applications, when it is necessary to change the type of the first coating liquid, such as changing from an antistatic primer to an adhesive primer, the metering transfer roller 32 can be replaced in a short time, avoiding cross-contamination between different coating liquids.

[0040] In this application, the feeding path of the substrate 5 is as follows: the substrate 5 enters the coating unit via the inlet guide roller from the unwinding device, first wrapping around the second back roller 33 of the second coating group 3 from bottom to top, with the first side of the substrate 5 facing the metering transfer roller 32, and the first side coating is completed at the metering transfer roller 32 and the second back roller 33; then the substrate 5 moves obliquely upward to the air-bearing turning roller 4, and passes around the air-bearing turning roller 4 with the first side coating layer facing the roller surface of the air-bearing turning roller 4, relying on the air cushion blown from the roller surface to achieve non-contact turning and changing of the surface; after changing the surface, the substrate 5 continues to move upward to wrap around the first back roller 24 of the first coating group 2, at this time the second side of the substrate 5 faces outward, and the second side coating is completed at the first back roller 24; finally, the substrate 5 is drawn out from the top of the first back roller 24 and directly enters the subsequent drying device. Throughout the entire feeding path, the wet coating never directly contacts any roller surface.

[0041] The controller 6 uses a PLC and is equipped with a touch screen. Its input terminals are connected to the displacement sensor 45, the liquid level sensor in the receiving tank 25, each limit switch, and each pressure sensor. Its output terminals are connected to the servo drivers of the first back roller 24, the second back roller 33, the anilox roller 21, and the conveyor roller 31, as well as the hot air device, the feeding metering pump, the return pump, and the solenoid valves of each cylinder. The overall machine linear speed is based on the first back roller 24 as the primary reference and the second back roller 33 as the secondary reference. The controller 6 compares the actual position of the floating arm 43 detected by the displacement sensor 45 with the set position corresponding to the reference tension. After PID calculation, it fine-tunes the speed of the second back roller 33, that is, adjusts the speed ratio between the second back roller 33 and the first back roller 24. The adjustment range is generally within ±2% of the linear speed, so that the substrate tension between the two coating groups is always kept near the set value, avoiding excessive stretching and deformation or loosening and wrinkling of the substrate, and ensuring the uniformity of the double-sided coating thickness.

[0042] The seven rollers in the coating unit of this application are: an anilox roller 21, an upper transfer roller 23, and a first back roller 24 belonging to the first coating group 2; a feed roller 31, a metering transfer roller 32, and a second back roller 33 belonging to the second coating group 3; and an air-bearing steering roller 4 located between the two coating groups. Among them, the first back roller 24 and the second back roller 33 are the two reference rollers of the whole machine, with fixed axial positions and driven by independent servo motors respectively; the remaining rollers are arranged around these two reference rollers and can be close to or far away from them.

[0043] Working principle: Adjustment: According to the product process sheet, select the anilox roller 21 and clamp it onto the translation slide 26. Adjust the adjustable slides 35 on both sides to make the pressing gap between the feed roller 31 and the metering transfer roller 32 and the bonding pressure between the metering transfer roller 32 and the second back roller 33 reach the process value. Inflate the scraper pressing airbag 228 to the set pressure. Set the outlet air temperature and outlet air pressure of the hot air device and the set air pressure of the balance component 44. Inject the first coating liquid into the material tank 34, start the feeding metering pump to introduce the second coating liquid into the closed storage chamber and exhaust the air in the chamber.

[0044] Paper feeding: Move the translation slide 26 back to the paper feeding position, lift the upper transfer roller 23 with the lifting cylinder 231, and guide the substrate 5 to wrap around the second back roller 33, around the air-bearing steering roller 4, wrap around the first back roller 24 and then lead it to the drying device; then move the translation slide 26 forward to the working position and lock it, and the upper transfer roller 23 descends to press.

[0045] Operation: The entire machine synchronously accelerates to the process speed. The first coating liquid in the feed trough 34 is metered through the pressure gap between the feed roller 31 and the metering transfer roller 32, and then uniformly coated on the back side (first side) of the substrate 5 on the second back roller 33 by the metering transfer roller 32. The hot air device continuously supplies hot air to the air-float turning roller 4. The wet coating on the back side of the substrate 5 is non-contactly bypassed by the air-float turning roller 4 to complete the face change, and at the same time, the hot air pre-dries the wet coating. After the face change, the substrate 5 enters the first back roller 24. The second coating liquid in the closed doctor blade assembly 22 is accurately metered by the lower doctor blade 223 and stored in the mesh of the anilox roller 21. The anilox roller 21 transfers the coating liquid to the upper transfer roller 23, and the upper transfer roller 23 uniformly coats the front side (second side) of the substrate 5. The coated substrate 5 is then led out into the drying device. Throughout the operation, the displacement sensor 45 provides real-time feedback on the position of the floating arm 43, and the controller 6 performs closed-loop fine-tuning of the rotation speed of the second back roller 33 to maintain constant substrate tension; the liquid level sensor monitors the liquid level in the receiving tank 25 and automatically pumps back the dripping coating liquid.

[0046] Shutdown and Maintenance: When shutting down, the metering pump stops, and the drive shaft 227 causes the scraper cavity 221 to flip downward to the return position. The remaining material in the cavity flows by gravity to the receiving trough 25 and is then drawn back into the feeding bucket. The translation slide 26 moves back to the maintenance position, and the rubber rollers disengage from the pressure. When it is necessary to change the coating liquid type, the metering transfer roller 32 is lifted out as a whole, or after venting, only the rubber roller sleeve 322 is pulled out for replacement.

[0047] See appendix Figure 1 -Appendix Figure 8 As shown, the coating method provided in this application, which includes a doctor blade type seven-roller double-sided coating unit, specifically includes the following steps: S1. Adjusting the machine: Based on the width and coating amount requirements of the substrate 5, adjust the bonding pressure of the closed doctor blade assembly 22 to the anilox roller 21, set the outlet temperature and outlet pressure of the hot air device, add the first coating liquid into the material tank 34, and introduce the second coating liquid into the closed storage chamber. S2, Paper threading: The substrate 5 is wrapped around the second back roller 33 in sequence, and then non-contactly passes around the air-float turning roller 4 with the first coating layer facing the roller surface of the air-float turning roller 4. After wrapping around the first back roller 24, it is led out. S3, First coating: The equipment is started and the speed is increased. The material roller 31 carries the first coating liquid from the material trough 34. After being metered by the metering transfer roller 32, it is coated on the first side of the substrate 5. At the same time, the hot air device supplies hot air to the air-floating turning roller 4. The hot air flows out through the vent 41 to form an air cushion. The first coating layer of the substrate 5 is supported by the air cushion and passes around the air-floating turning roller 4 without contact. The hot air pre-dries the first coating layer. S4. Second coating: The closed doctor blade assembly 22 and the anilox roller 21 work together to meter the second coating liquid in a closed manner. The anilox roller 21 transfers the metered second coating liquid to the upper transfer roller 23, which coats the second side of the substrate 5. The substrate 5 is then taken out and enters the subsequent drying process. S5. Tension closed-loop control: During the coating process, the displacement sensor 45 detects the position of the floating arm 43 in real time, and the controller 6 adjusts the speed ratio between the first back roller 24 and the second back roller 33 according to the detection signal to keep the tension of the substrate 5 between the two coating groups constant.

Claims

1. A seven-roller double-sided coating unit with a doctor blade, comprising a frame (1), characterized in that, The frame (1) is provided with a second coating group (3), an air-bearing steering roller (4) and a first coating group (2) in sequence along the material feeding direction of the substrate (5). The first coating unit (2) includes a first back roller (24), an anilox roller (21), an upper transfer roller (23) and a closed-type doctor blade assembly (22). The two ends of the anilox roller (21), the upper transfer roller (23) and the closed-type doctor blade assembly (22) are rotatably mounted on translation slides (26) provided on both sides of the frame (1). The second coating unit (3) includes a second back roller (33), a feed roller (31) and a metering transfer roller (32). The two ends of the feed roller (31) and the metering transfer roller (32) are rotatably mounted on adjustable slides (35) provided on both sides of the frame (1).

2. The seven-roller double-sided coating unit with doctor blade as described in claim 1, characterized in that, The first back roller (24) is rotatably mounted on the frame (1) and the axial position of the first back roller (24) is fixed. The anilox roller (21) rolls and adheres to the upper transfer roller (23). The upper transfer roller (23) rolls and adheres to the substrate (5) wrapped around the first back roller (24) to coat the second coating liquid onto the second surface of the substrate (5). The closed doctor blade assembly (22) is sealed and adhered to the roller surface of the anilox roller (21) and forms a closed storage cavity for holding the second coating liquid with the anilox roller (21). A receiving groove (25) for receiving dripping coating liquid is provided below the anilox roller (21).

3. The seven-roller double-sided coating unit with doctor blade as described in claim 2, characterized in that, The second back roller (33) is rotatably mounted on the frame (1) and the axial position of the second back roller (33) is fixed. The lower half of the conveyor roller (31) is immersed in the material tank (34) containing the first coating liquid. The metering transfer roller (32) is disposed between the conveyor roller (31) and the second back roller (33). One side of the metering transfer roller (32) rolls and adheres to the conveyor roller (31), and the other side rolls and adheres to the substrate (5) wrapped around the second back roller (33) so as to coat the first coating liquid onto the first surface of the substrate (5).

4. The seven-roller double-sided coating unit with doctor blade as described in claim 3, characterized in that, The air-bearing steering roller (4) is disposed between the second coating group (3) and the first coating group (2). The roller surface of the air-bearing steering roller (4) is provided with a vent hole (41). The inner cavity of the roller of the air-bearing steering roller (4) is connected to the air outlet of the hot air device through a rotary joint (42). The two ends of the air-bearing steering roller (4) are floatingly mounted on the frame (1) through floating arms (43). The floating arms (43) are connected to a balance component (44). The frame (1) is equipped with a displacement sensor (45) for detecting the swing position of the floating arms (43).

5. The seven-roller double-sided coating unit with doctor blade according to claim 4, characterized in that, The enclosed scraper assembly (22) includes a scraper cavity (221) with one side open. An upper scraper (222) and a lower scraper (223) that are sealed and fitted to the roller surface of the anilox roller (21) are respectively installed on the upper and lower edges of the open side of the scraper cavity (221). Sealing blocks (224) that match the curvature of the roller surface of the anilox roller (21) are installed at both ends of the scraper cavity (221). A feed inlet (225) and a return inlet (226) connected to the feeding device are provided on the scraper cavity (221). A flipping shaft (227) is connected to both ends of the scraper cavity (221). Scraper clamping airbags (228) are provided on the back of both the upper scraper (222) and the lower scraper (223).

6. The seven-roller double-sided coating unit with doctor blade as described in claim 5, characterized in that, The translation slide (26) is slidably mounted on the frame (1) along the linear slide rail (261) and is driven to move along the linear slide rail (261) by the slide drive screw (262). The two ends of the anilox roller (21) are rotatably mounted on the translation slide (26) through the separate bearing seats (263). The translation slide (26) is equipped with a lifting cylinder (231) for driving the upper transfer roller (23) to rise and fall.

7. The seven-roller double-sided coating unit with doctor blade as described in claim 6, characterized in that, The first back roller (24) and the second back roller (33) are driven by independent servo motors. The displacement sensor (45) is electrically connected to the controller (6). The controller (6) adjusts the rotational speed ratio of the first back roller (24) and the second back roller (33) according to the position signal of the floating arm (43) detected by the displacement sensor (45), so that the tension of the substrate (5) between the second coating group (3) and the first coating group (2) remains constant.

8. The seven-roller double-sided coating unit with doctor blade as described in claim 7, characterized in that, The metering transfer roller (32) includes an air-expanding roller core (321) and a rubber roller sleeve (322) sleeved outside the air-expanding roller core (321). The roller surface of the air-expanding roller core (321) is provided with an air-expanding key strip (323) and an air-expanding rebound bladder (324). The outer wall of the inner end of the air-expanding rebound bladder (324) is adhered to the inner wall of the air-expanding roller core (321), and the air-expanding rebound bladder (324) is connected to the inner cavity of the air-expanding roller core (321). The outer end of the air-expanding rebound bladder (324) is connected to the air-expanding key strip (323).

9. A coating method using the seven-roller double-sided coating unit with doctor blade as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Adjusting the machine: According to the width and coating amount requirements of the substrate (5), adjust the bonding pressure of the closed scraper assembly (22) on the anilox roller (21), set the outlet temperature and outlet pressure of the hot air device, add the first coating liquid into the material tank (34), and introduce the second coating liquid into the closed storage chamber. S2, Paper threading: The substrate (5) is wrapped around the second back roller (33) in sequence, and then wrapped around the air-float turning roller (4) without contact with the first coating layer facing the roller surface of the air-float turning roller (4), and then pulled out after wrapping around the first back roller (24); S3, First coating: Start the equipment and increase the speed. The material roller (31) carries the first coating liquid from the material tank (34). After being metered by the metering transfer roller (32), it is coated on the first side of the substrate (5). At the same time, the hot air device supplies hot air to the air-floating turning roller (4). The hot air flows out through the vent (41) to form an air cushion. The first coating layer of the substrate (5) is supported by the air cushion and passes around the air-floating turning roller (4) without contact. The hot air pre-dries the first coating layer. S4, Second coating: The closed doctor blade assembly (22) and the anilox roller (21) work together to perform closed metering of the second coating liquid. The anilox roller (21) transfers the metered second coating liquid to the upper transfer roller (23), which coats the second side of the substrate (5). The substrate (5) is then drawn out and enters the subsequent drying process. S5. Tension closed-loop control: During the coating process, the displacement sensor (45) detects the position of the floating arm (43) in real time, and the controller (6) adjusts the speed ratio between the first back roller (24) and the second back roller (33) according to the detection signal so that the tension of the substrate (5) between the two coating groups remains constant.

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