A gel paste coating system and control method

Abstract

The application provides a gel paste coating system and a control method, which comprises a mixing and defoaming stage, a constant pressure conveying stage, a discharging coating stage and a finishing and archiving stage. In the mixing and defoaming stage, the vacuum degree in the container is monitored by a temperature and pressure sensor, and after the vacuum degree reaches a preset value and is maintained for a preset time, the next stage is entered; in the constant pressure conveying stage, the pressure is adjusted to a target value and maintained constant according to the feedback signal of the temperature and pressure sensor; in the discharging coating stage, an electric tank bottom valve is opened to make the paste directly released from the bottom of the container to the backing material under the driving of constant gas pressure, the coating conveyor speed is adjusted according to the feedback of the speed sensor, and the coating parameters are adjusted according to the coating pressure distribution feedback of the contact sensor; in the finishing and archiving stage, the process parameters in the whole process are continuously collected at a preset sampling frequency to generate a process curve archive associated with the current batch. The application can realize high-precision coating of high-viscosity gel paste and provide data support for subsequent process amplification.

Description

Technical Field

[0001] This invention relates to the field of gel ointment manufacturing technology, and in particular to a gel ointment coating system and control method. Background Technology

[0002] Gel patches (also known as poultices) are topical medications made by mixing the active pharmaceutical ingredient with a suitable hydrophilic matrix and then coating it onto a backing material. They are applied directly to the skin. Gel patches mainly consist of three parts: a backing layer, a patch layer, and an anti-adhesive layer. With the continuous development of transdermal drug delivery systems and the increasing demands on gel patch manufacturing processes, gel patches have become widely used in daily life.

[0003] In the coating process of gel ointments, traditional methods rely heavily on manual experience, resulting in problems such as low precision in controlling coating amount, uneven coating thickness, and uneven drug content. Process parameters during the trial production stage, such as pressure, speed, and temperature, are difficult to precisely replicate, leading to low production efficiency and significant batch-to-batch quality variations. Furthermore, traditional methods lack comprehensive data recording, failing to provide reliable data for subsequent industrial production.

[0004] In recent years, some technologies have attempted to introduce automated control methods into the coating field. For example, CN201271624Y discloses an automated device for coating rubber plasters, which adds an automatic coating thickness detection device and a control system mainly composed of PLCs. The control system is connected to the servo motors of each execution part. CN102423747A discloses a rubber plaster transfer coating method, in which the coating process is controlled by a PLC controller. The GST type roller-type hydrogel coating and slicing machine adopts a PLC computer control system, human-machine interface operation, photoelectric tracking positioning, automatic material feeding, and has functions such as fault diagnosis, alarm, metering, statistics, printing, and monitoring. The HS-1000 type gel plaster coating machine adopts a non-woven fabric dual-station unwinding, and uses an angular displacement sensor to feedback the position of the floating roller to control the servo motor to adjust the unwinding speed. It is equipped with a magnetic powder brake and a tension detection device to achieve automatic tension adjustment, and the product thickness is monitored through a weight closed-loop control system. Furthermore, existing technologies include intelligent preparation and control systems for gel plasters based on image recognition. These systems use convolutional neural networks to identify defects in coating images, thereby optimizing the process. In the field of hot melt adhesive coating, the integration of PLC and sensor technologies has also been achieved for real-time closed-loop control of coating thickness, temperature, and speed.

[0005] However, the aforementioned existing technologies still have the following shortcomings:

[0006] Firstly, existing intelligent coating equipment is mostly configured for large-scale production lines, resulting in large size and high cost, primarily suitable for large-scale industrial production. For scenarios such as laboratory research and development, formula screening, process exploration, and small-batch pilot production, due to small batch sizes and frequent product switching, large equipment not only has high start-up costs and significant material waste, but also suffers from high inertia and response delays, making it difficult to adapt to the need for rapid parameter adjustments under small-batch conditions. Furthermore, large coating equipment typically employs independent feeding and coating systems, requiring materials to be transported over long distances through pipelines. For high-viscosity gels and pastes, this results in large pipeline residues and difficult cleaning, further limiting its applicability in multi-variety, small-batch scenarios.

[0007] Secondly, the feeding and coating systems of existing coating equipment are often independent. After the paste is prepared in the mixing equipment, it needs to be transferred to a separate hopper or storage container before being fed into the coating machine. For high-viscosity gel pastes, this transfer process not only easily causes material adhesion loss and cross-contamination, but may also introduce air bubbles, affecting coating quality and drug uniformity. Especially in the laboratory research and development stage, the total amount of material in each batch is limited, and the loss during the transfer process can significantly affect the accuracy of the test results.

[0008] Third, while existing technologies disclose PLC control, sensor feedback, and single closed-loop control methods for thickness or speed, they lack a coherent closed-loop control strategy covering the entire process from mixing and degassing to coating and molding. The connection between each process step relies heavily on manual intervention or simple timing control, making it difficult to achieve coordinated adjustment of multiple parameters such as feeding pressure, coating speed, and doctor blade gap. This results in deviations in coating basis weight when speed fluctuates or feeding is unstable. Furthermore, the data recording function of existing equipment is relatively rudimentary, typically only recording setpoints or final results, lacking continuous acquisition and storage of process curves. This makes it difficult to provide accurate and complete data support for subsequent process scale-up and quality backtracking.

[0009] In summary, how to construct a gel coating system and method that can achieve integrated mixing-transportation-coating throughout the entire process, possess multi-parameter collaborative closed-loop control capabilities, provide complete data traceability, and is compact in size and suitable for laboratory research and development as well as small-batch pilot production is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0010] To address the aforementioned technical problems, the technical solution adopted by this invention is as follows:

[0011] According to a first aspect of the present invention, a method for controlling the application of a gel ointment is provided, comprising the following stages performed sequentially:

[0012] Mixing and degassing stage: Start the electric mixer to mix the materials in the gel container. Monitor the vacuum level in the gel container through temperature and pressure sensors. After the vacuum level reaches the preset value and is maintained for the preset time, proceed to the next stage.

[0013] Pressure stabilization and delivery stage: Gas is introduced into the gel container through the pressure regulation module, and the pressure inside the gel container is adjusted to the target value and maintained constant according to the feedback signal of the temperature and pressure sensor.

[0014] Material feeding and coating stage: Start the coating conveyor to transport the backing material, open the electric bottom valve at the bottom outlet of the gel container, so that the paste is released directly from the bottom of the gel container onto the backing material under constant gas pressure, adjust the speed of the coating conveyor according to the actual speed feedback from the speed sensor, and adjust the coating parameters according to the coating pressure distribution feedback from the contact sensor.

[0015] Final recording stage: Close the electric tank bottom valve, continuously collect and store the process parameters of the entire process at the preset sampling frequency, and generate a process curve file associated with the current batch.

[0016] According to a second aspect of the present invention, a gel ointment application system is provided, comprising:

[0017] The gel container has a mixing interface for mounting an electric mixer and a pressurizing interface for connecting a pressure regulating module at the top, and a discharge port at the center of the bottom.

[0018] An electric mixer is installed at the mixing port on top of the gel container, and the mixing blade of the electric mixer extends into the inside of the gel container.

[0019] The pressure regulating module is connected to the pressurization port on the top of the gel container via a pipeline, and is used to introduce pressurized gas into the gel container.

[0020] An electric bottom valve is installed at the outlet at the bottom of the gel container to control the release of the gel.

[0021] A coating conveyor, located below the gel container, is used to carry and transport the backing material.

[0022] A temperature and pressure sensor is installed on the gel container to detect the pressure and temperature inside the gel container.

[0023] A liquid level sensor is installed inside the gel container to detect the distance of the gel from the top of the container.

[0024] A speed sensor, installed on the coating conveyor, is used to detect the conveying speed of the backing material.

[0025] A contact sensor is installed at the coating station of the coating conveyor to detect the position of the backing material and / or the coating pressure distribution.

[0026] A doctor blade is positioned above the coating station of the coating conveyor and is used to control the coating thickness.

[0027] A programmable logic controller (PLC) is electrically connected to an electric mixer, a pressure regulating module, an electric tank bottom valve, a coating conveyor, a temperature and pressure sensor, a speed sensor, a contact sensor, a liquid level sensor, and a scraper, respectively. The PLC is configured to execute the gel ointment coating control method described in the first aspect.

[0028] The present invention has at least the following beneficial effects:

[0029] This invention integrates mixing, degassing, pressure conveying, and coating into a single system. The gel paste container is equipped with a stirring port and a pressurizing port at the top and a discharge port at the center of the bottom. This allows the paste to be mixed and degassed within the same container and then released directly from the bottom to the coating conveyor by top air pressure without the need for transfer. This eliminates the need for separate mixing equipment and paste transfer devices. This not only simplifies the system structure and avoids material adhesion loss and cross-contamination during the transfer process of high-viscosity gel pastes, but also provides a structural basis for system miniaturization. The entire system can operate in small volumes from 0.5L to 20L, meeting the needs of laboratory research and development and small-batch pilot production scenarios. Based on this, the present invention uses the vacuum degree reaching the standard and maintaining it for a preset time as the verification basis for sufficient degassing in the mixing and degassing stage, and the pressure reaching the target value and maintaining it constant in the pressure stabilizing and conveying stage as the verification basis for stable material supply. That is, the automatic condition determination between each stage is based on real-time feedback signals from sensors rather than relying on fixed time or manual judgment, so that the switching timing of each stage between different batches is consistent, avoiding process fluctuations caused by differences in manual judgment or timing deviations, thereby improving the repeatability and consistency of the process between batches.

[0030] Meanwhile, during the material feeding and coating stage, a constant conveying pressure was established and maintained in advance to eliminate the initial coating amount deviation caused by the pressure shock at the start of the feeding process. Speed ​​PID closed-loop control ensured the backing material moved at a uniform speed, and dynamic compensation was performed based on the coating pressure distribution along the width direction detected in real time by the contact sensor. This synergistic control of stable pressure, constant speed, and thickness feedback adjustment effectively improved the consistency of the coating amount per unit area. Furthermore, from the start of the mixing and degassing stage, process parameters were continuously collected at a preset sampling frequency and linked to specific batch storage, generating batch process curve archives containing temperature, pressure, speed, and coating pressure distribution data. This provides traceable data for subsequent scale-up from laboratory to industrial production. All parts in contact with the material feature a hygienic, no-dead-angle design, and can be connected to a CIP online cleaning system for cleaning after coating, facilitating rapid switching between multiple product types.

[0031] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A simplified diagram of a gel ointment coating device system provided by the present invention;

[0034] Figure 2 This is a schematic diagram of a gel ointment coating device system provided in an embodiment of the present invention;

[0035] Figure 3 A flowchart of a gel ointment coating control method provided in an embodiment of the present invention.

[0036] (Symbol Explanation)

[0037] 1-Gel container 1;

[0038] 2- Electric mixer;

[0039] 3-Pressure regulation module;

[0040] 4-Electric tank bottom valve;

[0041] 5-Coating conveyor;

[0042] 6-Programmable Logic Controller;

[0043] 7-Temperature and pressure sensor;

[0044] 8-Speed ​​sensor;

[0045] 9-Contact sensor;

[0046] 10-Scraper;

[0047] 11-Temperature control module;

[0048] 12-Liquid level sensor. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] In the laboratory research and development and small-batch trial production of gel ointments, traditional manual methods often suffer from problems such as low precision in coating amount control, uneven coating thickness, and uneven drug content. Although some existing technologies have attempted to introduce PLC control and sensor feedback into the coating field, such as adding an automatic coating thickness detection device and PLC control system in rubber ointment coating, and achieving closed-loop control of thickness, temperature, and speed by integrating PLC and sensors in hot melt adhesive coating, these technical solutions are mainly aimed at large-scale industrial production scenarios. More importantly, in existing gel ointment coating equipment, the mixing equipment and coating equipment are often independent of each other. After mixing, the ointment needs to be transferred to a separate hopper or storage container before being fed into the coating machine. Its control logic mostly adopts simple time-series control or single-parameter closed-loop control, and the switching between process stages depends on time settings or manual judgment, lacking an automated condition triggering mechanism based on real-time feedback of the material status in the container.

[0051] To address the shortcomings of existing technologies, this invention provides a gel coating device system and control method. The core concept lies in integrating mixing, degassing, pressure conveying, and coating onto a single miniaturized platform. Through segmented condition-triggered control logic based on real-time sensor feedback signals, the control system automatically allows entry into the next stage only after the process parameters of the current stage reach a preset threshold and remain there for a preset time. This enables fully automated closed-loop control and data traceability throughout the entire process from mixing and degassing to coating. Unlike conventional coating processes that rely solely on time settings or manual experience for process switching, this invention automatically determines each stage's switching based on whether the physical quantities monitored in real-time by sensors meet the standards, thus avoiding process fluctuations caused by human error or inaccurate timing.

[0052] The following is in conjunction with the appendix Figures 1 to 3 This section provides a detailed explanation of the system's operating methods and control procedures.

[0053] First Embodiment

[0054] like Figure 1 and Figure 2 As shown, the gel coating device system provided in this embodiment includes: a gel container 1, an electric mixer 2, a pressure regulating module 3, an electric bottom valve 4, a coating conveyor 5, a programmable logic controller 6, a temperature and pressure sensor 7, a speed sensor 8, a contact sensor 9, a scraper 10, a temperature regulating module 11, and a liquid level sensor 12. The main components of this system are described below.

[0055] (a) Gel container

[0056] The gel paste container 1 has a vertical tank structure and is made of 316L stainless steel. The top of the container integrates a stirring port, a pressurizing port, a feed inlet, and a vacuum port. The stirring port, located at the center of the top, is used to install the drive unit and stirring shaft of the electric mixer 2. The pressurizing port connects to the gas supply line of the pressure regulating module 4. The vacuum port connects to a vacuum system (not shown) to achieve negative pressure degassing inside the container. The feed inlet is used to add raw materials such as the gel matrix and active ingredients. The bottom of the container is designed with a conical opening, with the angle between the conical side and the centerline ranging from 55° to 60°. This angle range allows for good flowability of the paste; too small an angle results in a too gentle cone, causing the paste to stagnate on the surface; too large an angle results in a too steep cone, unnecessarily increasing the overall height of the container and affecting equipment stability and ease of operation. The conical opening facilitates the continuous flow of high-viscosity paste towards the bottom center under gravity, reducing the accumulation and residue of paste at the bottom of the container. A discharge port is located at the center of the bottom, equipped with an electric bottom valve 4 to control the release of the paste. The inner wall of the container bottom and the discharge port are smoothly connected by a rounded arc with a radius of 5mm to 10mm. This, combined with the conical constriction structure, avoids dead zones in the paste flow, ensuring smooth and residue-free discharge. The gel paste container body adopts a double-layer jacketed structure design. The inner layer is the paste storage chamber, and the outer layer is a circulating medium jacket. The jacket has a medium inlet and outlet for circulating media such as hot water or heat transfer oil, enabling precise temperature control of the paste. The inner wall of the container is electrolytically polished, with a surface roughness Ra≤0.4μm. Rounded transitions are used at all corners of the inner wall to prevent paste residue and microbial growth, meeting sanitary production requirements.

[0057] The gel paste container of this invention serves as both a mixing container and a pressure conveying container. During the mixing and degassing stage, the gel paste container acts as a mixing container, with an electric mixer 2 stirring and mixing the materials inside. A vacuum system is used to evacuate the inside of the container to achieve negative pressure degassing. During the pressure stabilization and conveying stage and the coating stage, the gel paste container switches to a pressure conveying container. A pressure regulating module introduces pressurized gas into the top space of the container, driving the paste inside to be released downwards from the bottom outlet onto the backing material on the coating conveyor 5. The entire mixing, degassing, conveying, and discharging process is completed within the same container, eliminating the need to transfer the paste between different devices and avoiding adhesion loss and cross-contamination during material transfer.

[0058] The effective volume of the gel paste container ranges from 0.5L to 20L, preferably 20L. This capacity range precisely corresponds to the needs of laboratory research and development and small-batch pilot production of gel pastes: 0.5L-5L is suitable for the laboratory formulation screening and process parameter exploration stage, while 5L-20L is suitable for the small-batch pilot production and pilot-scale amplification research stage. Compared with the batch requirements of existing large-scale coating equipment, which often reach hundreds of kilograms, the small-capacity design of this invention effectively reduces material waste in the research and development stage, lowers experimental costs, and facilitates rapid switching experiments for multiple varieties and small batches.

[0059] In addition, a sensor mounting interface is provided on the top of the gel container 1 for mounting a liquid level sensor 12. The liquid level sensor 12, employing a radar level gauge or ultrasonic level gauge, is mounted on the top of the container with its detection probe facing the liquid level of the gel inside. It is used to detect the liquid level height of the gel in real time and feed the signal back to the analog input module of the programmable controller 6. The programmable controller 6 calculates the remaining volume of the gel in the container based on the liquid level signal and dynamically adjusts the control parameters of the pressure PID control module accordingly. This compensates for changes in pressure control characteristics caused by the increase in the gas space at the top due to the reduction in gel volume, ensuring that the pressure inside the container remains constant during the dispensing process. When the liquid level sensor 12 detects that the remaining gel volume is lower than the preset safe liquid level, the programmable controller 6 issues a warning signal.

[0060] (ii) Electric mixer

[0061] An electric mixer 2 is installed at the mixing port on top of the gel paste container 1. Its drive motor is fixed to the top cover of the container, and the mixing shaft extends vertically into the interior of the gel paste container. The mixing paddle is located in the lower part of the inner cavity of the gel paste container. The mixing paddle adopts a frame-type or anchor-type structure, and the gap between the outer edge of the paddle and the inner wall of the container is a preset distance, such as 5mm-15mm. This structure is suitable for mixing high-viscosity gel pastes, effectively promoting the overall circulation of materials in the container, preventing the paste from adhering and accumulating on the container wall, and facilitating the release and discharge of air bubbles during the mixing process.

[0062] The speed of the electric mixer is steplessly adjustable by a programmable logic controller (PLC) via a frequency converter, with a speed setting range of 0 rpm to 100 rpm. To address the high viscosity of the gel paste, the mixer is equipped with overload protection. When the stirring torque exceeds a preset safety threshold, the PLC automatically cuts off the mixer's power supply to prevent equipment damage. During the mixing and degassing stage, the PLC controls the mixer to operate according to a specific speed-time curve, such as a segmented variable-speed mixing mode of low-speed start-up, medium-speed dispersion, and high-speed shearing, based on the preset process formula. This ensures thorough and uniform mixing of the gel matrix and active ingredients, while simultaneously utilizing a vacuum system to degas the paste.

[0063] The stirring shaft is installed off-center from the gel paste container or uses an eccentric design, combined with a baffle structure, to increase turbulence during stirring and improve mixing uniformity. The contact surfaces between the stirring paddle and the paste are polished, with no sharp edges, facilitating cleaning and reducing paste residue. A mechanical or magnetic seal is installed between the stirring shaft and the top cover of the gel paste container to ensure good sealing performance under both vacuum degassing and positive pressure conveying conditions, preventing outside air from entering or gas leakage from the container.

[0064] (III) Pressure Regulation Module

[0065] The pressure regulating module 3 is connected to the pressurization port at the top of the gel container 1 via a pipeline, and is used to introduce pressurized gas into the container to provide conveying power for the gel to be released from the discharge port at the bottom of the container.

[0066] The pressure regulating module consists of an air compressor, a filter, a precision pressure reducing valve, and an electro-proportional valve connected in series. The air compressor provides compressed air; the filter, with a filtration accuracy of, for example, 0.01 μm, removes oil mist and particulate matter from the compressed air, ensuring that the gas entering the container is clean and uncontaminated, meeting the hygiene requirements for gel ointment production; the precision pressure reducing valve coarsely adjusts the compressor outlet pressure to the set range; the electro-proportional valve, as the final actuator, has its opening controlled by the analog output signal of the programmable logic controller, and is used to steplessly and precisely regulate the gas pressure entering the container. The outlet of the pressure regulating module is connected to the pressurization port on the top of the gel ointment container 1 via a sanitary pipe. A one-way valve is installed on the pipe to prevent the ointment inside the container from flowing back into the air supply line under abnormal circumstances.

[0067] The pressure regulation accuracy of the precision pressure reducing valve can reach within ±0.5% to ±1% of the set value. Taking a set pressure of 0.3MPa as an example, the actual output pressure can be stabilized between 0.297MPa and 0.303MPa, with extremely small pressure fluctuation range. In contrast, the setting error of ordinary pressure reducing valves is usually around ±5% to ±10% of the set value, meaning that when the set pressure is 0.3MPa, the actual output may fluctuate between 0.27MPa and 0.33MPa. Through its internal precision structure feedback regulation mechanism, the precision pressure reducing valve can control the output pressure fluctuation within an extremely narrow range, thereby providing a stable and accurate input air source for the subsequent electro-proportional valve. In the pressure regulation module 3 of this invention, the precision pressure reducing valve and the electro-proportional valve work together. The precision pressure reducing valve is responsible for coarsely adjusting the air source pressure to near the set value and initially stabilizing it. The electro-proportional valve further performs stepless precise adjustment based on the analog signal from the PLC, building upon the precision pressure reducing valve. The two work together to ensure that the compressed air pressure entering the top space of the gel container 1 has extremely high stability and control accuracy.

[0068] The pressure regulating module of this invention performs different pressure control tasks at different working stages of the gel container. During the mixing and degassing stage, the pressure regulating module is in the off state. The vacuum system evacuates the inside of the container through the vacuum port at the top of the gel container. At this time, the pressurization port is used as a safety gas supply port. When the vacuum level inside the gel container exceeds a preset safety lower limit, the programmable logic controller (PLC) controls the electro-proportional valve to slightly open, introducing a small amount of sterile gas into the container to prevent deformation and damage due to excessive negative pressure. During the pressure stabilization and conveying stages and the dispensing and coating stages, the vacuum system is off, and the PLC controls the electro-proportional valve to open according to the set value, introducing pressurized gas into the space at the top of the container. The PLC has a built-in pressure PID regulation module that automatically adjusts the opening of the electro-proportional valve based on the difference between the actual pressure value fed back by the temperature and pressure sensor 7 inside the container and the set pressure value, so that the pressure inside the container quickly reaches the target value and remains constant, with a pressure control accuracy of ±0.5%FS. In view of the characteristics of the 0.5L-20L small volume container of the present invention, the differential time constant Td in the pressure PID parameter of the programmable logic controller is set to a small value to prevent the air pressure from overshooting due to the excessively fast air intake response in the small space, and to ensure that the pressure rise process is smooth and without shock.

[0069] When the temperature and pressure sensor 7 detects that the pressure inside the container exceeds the preset safety threshold, the programmable logic controller automatically closes the electric proportional valve and opens the exhaust solenoid valve connected in parallel with the pressurization interface to quickly release the pressure inside the container to a safe level and prevent the electric tank bottom valve 4 from opening, ensuring system safety.

[0070] With the above configuration, the pressure regulating module can provide a stable, clean, and pulse-free delivery force for high-viscosity gel pastes, ensuring that the paste is smoothly released from the bottom outlet of the container and providing pressure assurance for subsequent precision coating.

[0071] (iv) Electric tank bottom valve

[0072] The electric bottom valve 4 is installed at the outlet at the center of the bottom of the gel paste container 1 to control the release and cut-off of the paste inside the container.

[0073] The electric bottom valve is a pneumatically or electrically driven sanitary diaphragm valve or aseptic bottom valve, with its valve body fixedly connected to the bottom outlet of the container via flange or welding. The core structural feature of this electric bottom valve is that when the valve is closed, the upper surface of the sealing diaphragm is flush with the inner wall of the bottom of the gel container, forming a zero-volume structure with no dead corners and no residue. This structural design allows the gel, after mixing and degassing within the container, to be released vertically downwards from the bottom of the container onto the backing material of the coating conveyor 5 without any pipe bends or dead corners, effectively avoiding material residue and cross-contamination caused by dead zones in the flow at the electric bottom valve and pipe connections.

[0074] The electric bottom valve uses a quick-opening sanitary clamp connection for easy disassembly and cleaning. The internal flow channel of the electric bottom valve is a full-bore structure, with the surface treated by electrolytic polishing and rounded corners. When the electric bottom valve is open, the paste flow is smooth and unobstructed, preventing shear degradation or retention of high-viscosity materials due to abrupt changes in flow. The opening and closing of the electric bottom valve is controlled by a programmable logic controller (PLC) via digital output signals to drive a solenoid valve. The full-open or full-close response time of the electric bottom valve is less than or equal to a preset value, such as 100ms, enabling rapid response and improving the control accuracy at the start and stop of material dispensing, thus avoiding coating deviations caused by delays in valve opening and closing. The electric bottom valve is equipped with a valve position feedback sensor, which feeds back the actual on / off status signal of the electric bottom valve to the PLC's digital input module in real time to confirm the valve's execution status. If no valve position feedback signal is received within a specified time after the electric bottom valve opening command is issued, the PLC issues an alarm signal and stops subsequent coating operations. When used in conjunction with the CIP online cleaning system, the flush diaphragm structure and full-bore flow channel of this electric tank bottom valve ensure that the cleaning fluid fully rinses all contact surfaces inside the valve, eliminating cleaning blind spots and effectively preventing cross-contamination between batches.

[0075] With the above configuration, the electric bottom valve enables a smooth transition of the gel paste from the container to the backing material under the combined action of gravity and top air pressure. It is the core actuator connecting the two key process steps of mixing and degassing and precision coating.

[0076] (v) Coating conveyor

[0077] The coating conveyor 5 is located directly below the gel paste container 1 and is used to carry and transport the backing material, so that the backing material passes through the coating station at a constant speed, receives the paste released from the bottom of the container, and forms a uniform coating layer.

[0078] The coating conveyor is equipped with an unwinding roller, a tensioning roller, a coating platform, a traction roller, and a take-up roller, arranged sequentially along the conveying direction of the backing material. The unwinding roller is used to load and unload the rolled backing material, such as nonwoven fabric or polyester film; the tensioning roller is used to adjust the conveying tension of the backing material to prevent slack or deviation during operation; the coating platform is located directly below the discharge port of the gel paste container and serves as the supporting surface for coating the backing material; the traction roller is located downstream of the coating platform and is driven by a drive motor to provide traction power for the continuous conveying of the backing material; the take-up roller is located at the end of the conveyor and is used to roll the coated finished material into a reel.

[0079] The drive motor is a servo motor, equipped with a servo controller, and controlled by a programmable logic controller (PLC). A speed sensor 811 is installed on the shaft of the traction roller to detect its rotational speed in real time, indirectly reflecting the linear velocity of the backing material, and feeding the speed signal back to the PLC. The PLC has a built-in speed PID control module that automatically adjusts the output frequency of the servo driver based on the difference between the set speed value and the actual speed value fed back by the speed sensor 811, maintaining a constant traction roller speed and ensuring the backing material moves forward at a uniform speed. A tension sensor is installed on the tension roller to monitor the conveying tension of the backing material in real time. When the tension exceeds the preset range, the PLC automatically adjusts the unwinding speed of the unwinding roller or the braking torque of the magnetic powder brake to restore the tension to the set value.

[0080] The upper surface of the coating platform is a smooth, flat plane. A vacuum adsorption chamber is installed inside the platform, and numerous micropores are distributed on the surface. During the coating process, the vacuum adsorption system is activated, adsorbing the backing material onto the upper surface of the coating platform through the micropores. This prevents the backing material from shifting or wrinkling under the pressure of the paste coating, ensuring the stability of the coating dimensions. A scraper 10 is installed above the coating platform, downstream of the gel paste container outlet, to scrape the paste to a preset thickness. A contact sensor 9 is installed above the coating platform, upstream of the scraper 10, to detect whether the backing material is in place and the pressure distribution during paste coating.

[0081] With the above configuration, the coating conveyor, under the control of the programmable controller, transports the backing material to the coating station at a constant speed, receives the paste released from the bottom of the gel container, and sends it out after being scraped and formed by the scraper 10, thus realizing the continuous operation from the release of the paste from the container to the coating formation.

[0082] (vi) Temperature and pressure sensor

[0083] The temperature and pressure sensor 7 is a composite sensor that integrates temperature detection and pressure detection. It is installed on the side wall or top cover of the gel container 1. Its detection probe extends into the container and comes into direct contact with the gel or the gas space inside the container.

[0084] The temperature sensing element is a PT100 resistance temperature detector (RTD), with a temperature range of 0℃-100℃ and an accuracy class of A (±0.15℃), used for real-time monitoring of the temperature of the paste inside the container. The temperature signal is converted into a 4-20mA standard analog current signal by a temperature transmitter and transmitted to the analog input module of the programmable controller (PLC) via a shielded cable. Based on this temperature signal, the PLC controls the flow rate or temperature of the circulating medium within the jacket to maintain the paste temperature within the process setpoint range.

[0085] The pressure sensing element employs a sanitary flat diaphragm pressure transmitter. Its pressure-sensing diaphragm is in direct contact with the medium inside the container, and the diaphragm surface is flush with the inner wall of the container, featuring a dead-angle-free design to prevent paste residue from remaining on the pressure-sensing diaphragm. The pressure transmitter has a range of -0.1MPa to 0.8MPa and outputs a 4-20mA standard analog current signal, which is transmitted to the analog input module of the programmable controller 60 via a shielded cable. The programmable controller automatically switches the pressure sensing range and alarm threshold according to the current process stage: during the mixing and degassing stage, it switches to the negative pressure range (-0.1MPa to 0MPa) to monitor the vacuum level inside the container; during the pressure stabilization and conveying stages and the discharging and coating stages, it switches to the positive pressure range (0MPa to 0.8MPa) to monitor the conveying pressure inside the container. The two ranges correspond to different alarm thresholds. When the detected value exceeds the allowable range for the corresponding stage, the programmable controller issues an alarm signal and executes corresponding safety protection actions.

[0086] The temperature and pressure sensor 7 adopts a sanitary chuck-type mounting structure, which is fixed through the mounting interface on the container wall. A sealing ring is provided between the sensor housing and the mounting interface to ensure that the container maintains good sealing performance under both vacuum and positive pressure conditions. The sensor housing and the metal parts in contact with the medium are all made of 316L stainless steel, and the surface is electrolytically polished to meet the sanitary requirements for gel ointment production.

[0087] With the above configuration, the temperature and pressure sensor 7, as a single composite sensor, realizes real-time monitoring of two key process parameters, temperature and pressure, during the gel coating process, and automatically adapts the detection range according to the process stage, providing real-time and accurate data support for segmented closed-loop control.

[0088] (vii) Speed ​​sensor

[0089] Speed ​​sensor 8 is installed on the drive roller shaft of coating conveyor 5 to detect the conveying speed of backing material in real time.

[0090] Speed ​​sensor 8 employs a non-contact photoelectric encoder or Hall effect sensor, with its detection end positioned opposite the drive roller shaft. The photoelectric encoder detects the rotational angle and speed of the drive roller shaft, outputting pulse signals of corresponding frequencies; the Hall effect sensor detects changes in the magnetic field generated by a magnetic element mounted on the drive roller shaft, also outputting pulse signals. The linear velocity of the drive roller shaft is proportional to the conveying speed of the backing material; therefore, the real-time linear velocity of the backing material can be indirectly obtained by detecting the rotational speed of the drive roller shaft. The pulse signals output by speed sensor 8 are transmitted via a shielded cable to the high-speed counting input module of the programmable controller (PLC), which calculates the actual speed value based on the number of pulses per unit time.

[0091] The programmable controller has a built-in speed PID control module that compares the actual speed value fed back by the speed sensor 8 with the set speed value. Based on the difference, it automatically adjusts the frequency of the drive motor of the coating conveyor 5 to keep the conveying speed of the backing material constant. When the speed sensor 8 detects that the actual speed deviates from the set value, the programmable controller also synchronously adjusts the opening of the electric tank bottom valve 4 or the output pressure of the pressure regulating module 3, so that the feeding rate follows the change in coating speed, realizing coordinated control of feeding and coating.

[0092] With the above configuration, speed sensor 8 provides real-time and accurate detection data for the closed-loop speed control and dynamic matching of the feeding rate of the coating conveyor, and is a key detection link to ensure constant coating speed and consistent coating basis weight.

[0093] (viii) Contact sensor

[0094] The contact sensor 9 is located at the coating station of the coating conveyor 5, upstream of the scraper 10, and is used to detect whether the backing material has reached the predetermined coating position and the pressure distribution during the paste coating process.

[0095] The contact sensor 9 can be a thin-film pressure sensing array or a micro-motion contact sensor group. Its sensing surface is parallel to the conveying plane of the backing material, maintaining a small gap or slight contact with the upper surface of the backing material. The sensor is arranged along the width direction of the coating conveyor, covering the entire width range of the backing material. The contact sensor 9 has densely arranged sensing contacts, capable of simultaneously detecting pressure values ​​at multiple locations along the width direction of the backing material. When the backing material arrives at the coating station, the contact sensor 9 detects the contact pressure of the backing material on the sensing surface and outputs a position signal. When the paste is released onto the backing material and passes under the contact sensor 9, the pressure exerted by the paste on the backing material is transmitted to the sensor through the backing material, and the contact sensor 9 outputs a pressure distribution signal along the width direction in real time.

[0096] The output signal of the contact sensor 9 is transmitted to the analog input module of the programmable controller via a shielded cable. Based on the position signal, the programmable controller determines whether the backing material has reached the predetermined coating position and controls the opening sequence of the electric tank bottom valve 4 accordingly. The electric tank bottom valve is only allowed to open for material discharge after the coating conveyor reaches a stable speed and the contact sensor 9 detects that the backing material is in place, thus avoiding the release of paste onto the conveyor belt without backing material, which would cause material waste and equipment contamination.

[0097] During the coating process, the programmable controller first calculates the average pressure value of each sensing point in the width direction based on the pressure detection values ​​fed back by the contact sensor 9, and then performs the following two judgments:

[0098] (1) Single point deviation judgment: Compare the deviation of the pressure detection value of each sensing point relative to the average value. If the deviation of any sensing point exceeds the preset single point deviation threshold, the abnormal point is removed, indicating that the coating amount in the local area is obviously abnormal, triggering local compensation adjustment for the area, such as adjusting the local gap of the scraper 10 corresponding to the position.

[0099] (2) Overall range determination: After removing abnormal points, calculate the range between the maximum and minimum values ​​of the remaining sensing points. If the range does not exceed the preset overall allowable deviation threshold, the overall coating thickness in the width direction is determined to be uniform. If the range exceeds the preset overall allowable deviation threshold, it indicates that the overall coating fluctuates greatly, triggering the compensation adjustment of the overall process parameters, such as fine-tuning the overall height of the scraper 10 or the opening of the electric tank bottom valve.

[0100] By judging the above two conditions step by step, the programmable controller 6 can distinguish between local anomalies and overall fluctuations, and perform different levels of adjustment accordingly: when the pressure detection values ​​of each sensing point in the width direction simultaneously meet the above two conditions, the coating thickness is determined to be uniform; when either condition is not met, the gap of the scraper 10 or the opening of the electric tank bottom valve 4 is automatically adjusted to compensate according to the judgment result: if the pressure detection value is too high, it indicates that the coating amount is too large, then the programmable controller 6 sends a positive pulse to the stepper motor driver to drive the scraper 10 to move downward by a preset step length to reduce the gap of the scraper 10. This step length is determined by the step angle of the stepper motor, the lead screw, and the microstepping multiple of the driver; if the pressure detection value is too low, it indicates that the coating amount is too small, then the programmable controller 6 sends a reverse pulse to the stepper motor driver to drive the scraper 10 to move upward by a preset step length to increase the gap of the scraper 10. The above adjustment process is carried out step by step in a single preset step size. After each adjustment step is completed, the pressure distribution is re-tested. If the judgment condition is still not met, the next step is adjusted until the pressure distribution is restored to uniformity.

[0101] The single-point deviation threshold and overall permissible deviation threshold mentioned above are both set by the operator based on the rheological properties of the paste, such as viscosity, flowability, and coating thickness accuracy requirements, and are stored as formulation parameters in the programmable controller 6. For the single-point deviation threshold: when the paste viscosity is high, the coating thickness is more sensitive to pressure changes, requiring a smaller deviation threshold, such as ±3% relative to the average value; when the paste viscosity is low, the deviation threshold can be appropriately relaxed, such as ±10% relative to the average value. For the overall permissible deviation threshold: its setting depends on the process requirements for overall uniformity in the width direction, and is usually expressed as the absolute value of the pressure difference, such as 5 kPa, or as a percentage relative to the average value, such as ±5%. A smaller threshold is used for high-precision requirements, and a larger threshold is used for general requirements. The operator can determine the two types of thresholds suitable for a specific formulation through simple experiments.

[0102] With the above configuration, the contact sensor 9 provides a key detection method for determining the position of the backing material and monitoring the coating uniformity in real time during the coating process. It is an important sensing link for realizing multi-variable collaborative control of material feeding, conveying and coating.

[0103] (ix) Scraper

[0104] The scraper 10 is positioned above the coating station of the coating conveyor 5, downstream of the discharge port of the gel paste container 1, and is used to scrape the paste released onto the backing material to a preset thickness.

[0105] The doctor blade 10 mainly consists of a blade holder, a blade, and a height adjustment mechanism. The blade holder is fixedly installed above the coating platform, spanning the entire width of the coating conveyor. The blade is installed at the lower end of the blade holder, and the gap between its lower edge and the upper surface of the backing material determines the coating thickness. The blade is made of stainless steel, with a flat cutting edge. The straightness of the cutting edge is precisely machined to ensure minimal deviation, guaranteeing the consistency of the coating gap at all points along the width, thereby ensuring the lateral uniformity of the coating thickness. The angle between the blade and the conveying direction of the backing material is adjustable to accommodate the coating requirements of pastes of different viscosities.

[0106] The height adjustment mechanism is driven by a stepper motor, whose output shaft is connected to the blade holder via a lead screw drive mechanism. The stepper motor is controlled by a programmable logic controller (PLC), and its rotation angle precisely corresponds to the lifting displacement of the blade holder, enabling micron-level adjustment of the gap between the doctor blade 10 and the coating platform. Based on the coating pressure distribution signal in the width direction fed back by the contact sensor 9, the PLC calculates the deviation between the current actual coating thickness and the target thickness, and sends a corresponding number of pulse signals to the stepper motor driver, driving the stepper motor to rotate forward or backward. The lead screw drive mechanism converts the rotational motion into linear lifting motion of the blade holder, thereby precisely adjusting the gap between the lower edge of the blade and the upper surface of the backing material. When the contact sensor 9 detects that the coating pressure in a certain area is too high, the PLC controls the stepper motor to slightly increase the gap of the doctor blade 10, reducing the coating amount in that area; when the coating pressure is too low, it controls the stepper motor to slightly decrease the gap of the doctor blade 10, increasing the coating amount in that area. During the adjustment process, the stepper motor driver feeds back the actual number of rotation steps of the stepper motor to the programmable controller in real time, forming a position closed loop to ensure the accuracy and repeatability of the scraper 10 gap adjustment.

[0107] Baffles are installed on both sides of the blade to prevent the paste from overflowing from both sides of the width during the scraping process. A paste return channel is installed above the blade holder to guide the excess paste scraped by the scraper 10 back to a container or collection tray.

[0108] With the above configuration, the scraper 10, under the control of the programmable controller, dynamically adjusts the scraping gap according to the coating pressure distribution signal fed back in real time by the contact sensor 9. This works in conjunction with the material feeding rate adjustment and coating speed adjustment to ensure the lateral consistency of the coating weight.

[0109] (x) Programmable Logic Controller

[0110] The programmable logic controller 6 serves as the control core of the system. It is electrically connected to the electric mixer 2, pressure regulating module 3, electric tank bottom valve 4, coating conveyor 5, temperature and pressure sensor 7, speed sensor 8, contact sensor 9, and scraper 10. It is used to receive detection signals from each sensor, execute segmented process control logic, and output control commands to each execution component.

[0111] The programmable logic controller (PLC) uses a Siemens S7-1200 series or equivalent industrial PLC. It integrates a central processing unit, data memory, and communication interface, supports multiple programming languages ​​such as ladder diagrams and structured text, and features high reliability, strong anti-interference capabilities, and flexible on-site programming and debugging functions. The I / O configuration of the PLC is as follows:

[0112] Analog Input Module (AI): Receives temperature and pressure signals from temperature and pressure sensor 7, speed signal from speed sensor 8, and pressure distribution signal from contact sensor 9, converting the continuous analog signals from each sensor into digital quantities for processing by the central processing unit.

[0113] Digital Input Module (DI): Receives the position signal from the contact sensor 9, the valve position feedback signal from the electric tank bottom valve 4, and the switching signals from peripheral devices such as the emergency stop button, limit switch, and tension sensor.

[0114] Analog output module (AO): Outputs a continuous control signal of 0-10V or 4-20mA to the frequency converter of the electric mixer 2 to adjust the mixing speed, and outputs to the electro-proportional valve of the pressure regulating module 3 to precisely control the pressure inside the container.

[0115] Digital Output Module (DO): Outputs switch signals to control the opening and closing of the electric tank bottom valve 4, the start and stop of the coating conveyor 5 drive motor, the forward / reverse pulse output of the stepper motor driver of the scraper 10, and switch actuators such as alarm indicator lights and exhaust solenoid valves.

[0116] The programmable logic controller (PLC) incorporates a pressure PID control module and a speed PID control module, and stores a segmented process control program. This program executes sequentially through the mixing and degassing stage, the pressure stabilization and conveying stage, the material dispensing and coating stage, and the final archiving stage. Switching between stages is based on real-time feedback signals from the temperature and pressure sensor 7, the speed sensor 8, and the contact sensor 9. The PLC also features an industrial Ethernet communication interface for data exchange with the human-machine interface, supporting the downloading and uploading of formula parameters, the display of real-time process curves, and the export of batch process curve files.

[0117] With the above configuration, the programmable logic controller (PLC) achieves coordinated control of all execution components and closed-loop adjustment of all process parameters throughout the gel coating process, ensuring a high degree of automation and process repeatability in the coating process.

[0118] (xi) Vacuum system

[0119] In this invention, the vacuum system is an important component for achieving negative pressure degassing in the mixing and degassing stage of the gel container 1. The vacuum system is a complete air extraction channel extending from the top of the gel container 1 to the external exhaust pipe.

[0120] The vacuum system includes a vacuum pump, vacuum tubing, a vacuum pneumatic valve, a filter, a check valve, and a vacuum pressure switch. The top of the gel container 1 is equipped with a vacuum interface, which is connected sequentially to the vacuum pneumatic valve, filter, and vacuum pump inlet via vacuum tubing. The vacuum pump exhaust port extends to the outdoor or workshop exhaust system via an exhaust pipe. All the above components are connected in sequence according to the airflow direction, forming a complete unidirectional evacuation channel: "container → vacuum pump → exhaust port".

[0121] The pneumatic vacuum valve is installed on the vacuum line, located between the vacuum interface and the vacuum pump. Its switching is controlled by the digital output module of the programmable controller 6. It is used to activate the vacuum pump during the mixing and degassing stage and to shut off the vacuum line during other stages, preventing the pressurized gas introduced by the pressure regulating module 3 from leaking through the vacuum line. A filter is installed between the pneumatic vacuum valve and the vacuum pump to capture trace amounts of paste droplets or dust entrained in the gas extracted from the container, preventing impurities from entering the vacuum pump and causing pump wear or contamination. The filter has a quick-release design, allowing for easy disassembly, cleaning, or filter element replacement. A check valve is installed at the exhaust port of the vacuum pump, with its direction of flow from the vacuum pump to the exhaust line, preventing external air from flowing back into the container through the exhaust line after the vacuum pump stops running. A vacuum pressure switch is installed at the vacuum interface on the top of the container or on the vacuum line near the container. It is used to detect the vacuum level inside the container and transmit the signal to the digital input module of the programmable controller 6 as an auxiliary monitoring signal for the vacuum system's operating status.

[0122] During the mixing and degassing stage, the programmable controller 6 controls the pneumatic vacuum valve to open and starts the vacuum pump. The vacuum pump continuously draws air from inside the container through the vacuum pipeline, creating a negative pressure environment inside the container. The gas inside the container, carrying bubbles generated during the mixing process, flows along the suction channel: the gas enters the vacuum pipeline from the vacuum port at the top of the container, passes through a filter to remove any entrained trace amounts of paste droplets, and then enters the vacuum pump. After being compressed by the vacuum pump, it is discharged to the outside through the exhaust port. During this process, the temperature and pressure sensor 7 switches to the negative pressure range to monitor the vacuum level inside the container in real time and feeds the signal back to the programmable controller 6. When the programmable controller 6 determines that degassing is complete, it first controls the pneumatic vacuum valve to close, cutting off the connection between the container and the vacuum pipeline, and then stops the vacuum pump, keeping the inside of the container sealed in preparation for the subsequent pressure stabilization and delivery stage.

[0123] With the above configuration, the vacuum system realizes the vacuum degassing function inside the gel container 1 with a complete and unidirectional air extraction channel structure. After degassing, the valve is switched to enable the container to bear pressure delivery function. It is a key component to realize the dual use of the container.

[0124] (xii) Jacketed Circulation System

[0125] The jacketed circulation system (not shown) is a standard temperature control module in gel ointment production. It is responsible for heating or cooling the ointment in the gel ointment container 1 to keep the ointment temperature within the process setting range.

[0126] The jacketed circulation system is a closed-loop system consisting of a jacketed container, circulation pipelines, a temperature control module 11, and a control system. The gel container 1 adopts a double-layer jacketed structure, with the inner layer being the gel storage cavity and the outer layer being the circulation medium jacket. The jacket has a medium inlet and a medium outlet, which are connected to the temperature control module 11 via circulation pipelines. Circulation medium, such as hot water, cold water, or heat transfer oil, is driven by the temperature control module 11, enters the jacket through the medium inlet via the circulation pipeline, flows through the internal space of the jacket, exits through the medium outlet, and returns to the temperature control module 11 via the circulation pipeline, forming a complete closed-loop circuit of "temperature control module 11 → circulation pipeline → jacket inlet → jacket interior → jacket outlet → circulation pipeline → temperature control module 11".

[0127] The temperature control module 11 includes a circulating pump, a heater, and a cooler. The circulating pump drives the medium to circulate continuously in a closed loop; the heater heats the medium, and the cooler cools the medium. The temperature control module 11 heats or cools the circulating medium according to the control signal output by the programmable controller 6. When the programmable controller 6 determines that heating is needed, it activates the heater to increase the medium temperature; when it determines that cooling is needed, it activates the cooler to decrease the medium temperature. The control signal for the temperature control module 11 comes from the following sources: the programmable controller 6 receives the actual temperature of the paste inside the container from the temperature and pressure sensor 7, compares it with the target temperature set in the formula, calculates the temperature deviation, and outputs the corresponding heating or cooling control signal to the temperature control module 11, forming a closed-loop temperature control. The temperature control module 11 also has an independent medium temperature sensor to monitor the real-time temperature of the circulating medium and serves as an internal feedback signal to assist the temperature control module 11 in accurately controlling the medium output temperature, forming the internal control loop of the temperature control module 11.

[0128] During the mixing and degassing stage, the jacketed circulation system preheats the paste in the container according to process requirements, bringing it to a suitable mixing temperature, such as 45-50℃, to reduce viscosity and facilitate stirring and vacuum degassing. During the coating stage, the jacketed circulation system continuously maintains a constant paste temperature to prevent viscosity increases due to temperature drops, which could affect coating uniformity. After coating, the jacketed circulation system can circulate cooling medium to cool any remaining paste in the container, facilitating subsequent cleaning operations.

[0129] With the above configuration, the jacketed circulation system achieves precise control of the temperature of the gel paste in the container with a complete closed-loop structure, providing stable temperature conditions for mixing, degassing, and coating, which is an important guarantee for ensuring coating quality and process repeatability.

[0130] Furthermore, in this embodiment, the programmable logic controller is configured to perform the following stages:

[0131] Mixing and degassing stage: Start the electric mixer to mix the materials in the gel paste container. Monitor the vacuum level in the gel paste container through temperature and pressure sensor 7. After the vacuum level reaches the preset value and is maintained for the preset time, proceed to the next stage.

[0132] Specifically, during the mixing and degassing stage, the operator selects the target formula through the human-machine interface, and the programmable logic controller automatically calls the corresponding process parameters for the formula, including stirring speed, target temperature, vacuum setpoint and holding time.

[0133] The programmable logic controller (PLC) first activates the jacket circulation system, introducing a circulating medium at a set temperature into the jacket of the gel container 1 to preheat it. Once the temperature inside the gel container, as indicated by the temperature and pressure sensor 7, reaches the target temperature (e.g., 48°C), the PLC issues a command to start the electric mixer 2, which operates at the speed set in the formula, such as 50 rpm. The operator opens the feed inlet at the top of the gel container and adds the gel matrix, active ingredients, and other raw materials into the container. After adding the materials, the feed inlet is closed, and the electric mixer 2 continues to stir and mix the materials inside the gel container, ensuring that all components are fully and evenly dispersed.

[0134] After stirring and mixing are initiated, the programmable logic controller (PLC) activates the vacuum system, evacuating the container through the vacuum port on top. During this process, the temperature and pressure sensor 7 switches to the negative pressure range (-0.1 MPa to 0 MPa), monitoring the vacuum level inside the container in real time and feeding the signal back to the PLC. The PLC compares the real-time vacuum level with the target vacuum value set in the formula, such as -0.08 MPa. Once the target vacuum value is reached, the PLC starts timing. During timing, the PLC continuously monitors the vacuum level: if the vacuum level remains near the target value (fluctuations not exceeding ±5% of the set value), this vacuum state is maintained until the preset maintenance time ends, indicating that degassing is complete. The preset maintenance time refers to the duration of continuous vacuuming after the target vacuum value is reached; its specific duration is set by the formula, not a fixed value.

[0135] During the mixing and degassing stage, while the vacuum pump continuously removes gas from the gas space within the container, bubbles dissolved in the paste gradually migrate to the paste surface and burst and escape under the pressure difference. This bubble escape process follows Stokes' law: the rising speed of bubbles in a viscous fluid is inversely proportional to the viscosity of the paste. The higher the viscosity of the paste, the slower the bubbles rise and the longer the degassing time required; conversely, the lower the viscosity of the paste, the faster the bubbles rise and the shorter the degassing time required. Therefore, the preset holding time must be adaptively set according to the rheological properties of the paste to ensure that the bubbles have sufficient time to migrate from the interior of the paste to the surface and burst and escape.

[0136] During the formulation development phase, operators determine the shortest effective degassing time for a specific formulation through experiments. The experimental method is as follows: The paste is evacuated under a set vacuum condition, and samples are taken at different time intervals. The density change or residual gas content of the paste is measured using a hydrometer or a gas content analyzer. The time when the density no longer increases (i.e., the gas content no longer decreases) is the shortest effective degassing time required for the formulation. In actual production, this time is multiplied by a certain safety factor, such as 1.2-1.5, and set as the preset hold time for the formulation. Generally, the preset hold time for low-viscosity formulations is approximately 3-5 minutes, and for high-viscosity formulations, it is approximately 5-10 minutes.

[0137] Timing begins once the target vacuum level is reached. Timing continues only if the vacuum level remains within the allowable deviation range of the target value throughout the timing process. If the vacuum level drops below the target value during timing, timing stops and restarts once the vacuum level recovers. This mechanism ensures that the actual degassing time is sufficient to allow for the physical time required for bubble escape, rather than simply relying on a fixed time for switching. This avoids residual bubbles in the paste due to insufficient degassing time, which could affect the quality of subsequent coatings.

[0138] After degassing is complete, the programmable logic controller shuts down the vacuum system and automatically proceeds to the next stage.

[0139] Throughout the mixing and degassing stage, the programmable logic controller continuously uses the temperature signal fed back by the temperature and pressure sensor 7 to control the flow rate of the circulating medium in the jacket through PID closed-loop control, so that the temperature of the paste is always maintained within the allowable deviation range of the temperature set in the formula. This ensures that the active ingredients are mixed evenly under suitable temperature conditions, while preventing the paste from deteriorating due to excessively high temperature or the paste from becoming too viscous due to excessively low temperature, which would affect the mixing effect.

[0140] With the above configuration, the mixing and degassing stage realizes the automated control of material mixing and vacuum degassing, and uses the achievement of vacuum degree and maintenance for a preset time as the judgment condition for the completion of the stage, ensuring that the air bubbles in the paste are fully removed, providing uniform and bubble-free paste raw materials for subsequent precision coating.

[0141] Pressure stabilization and delivery stage: Gas is introduced into the gel container through the pressure regulation module, and the pressure inside the gel container is adjusted to the target value and maintained constant according to the feedback signal of the temperature and pressure sensor 7.

[0142] Specifically, after the mixing and degassing stage is completed, the programmable logic controller automatically shuts down the vacuum system and turns on the pressure regulation module 3 to enter the pressure stabilization and delivery stage.

[0143] The programmable logic controller first retrieves the pressure setting value according to the current formula, such as 0.2-0.4MPa, preferably 0.3MPa, and outputs a control signal to the electro-proportional valve in the pressure regulating module 3, so that clean compressed air passes through the filter, the precision pressure reducing valve and the electro-proportional valve in sequence, and is introduced into the top space of the gel container 1 through the pressurization port on the top of the container.

[0144] During the compressed air introduction process, the temperature and pressure sensor 7 switches to the positive pressure range (0MPa to 0.8MPa) to monitor the gas phase pressure inside the container in real time and feed the signal back to the analog input module of the programmable logic controller (PLC). The PLC has a built-in pressure PID control module, which compares the actual pressure value fed back by the temperature and pressure sensor 7 with the target pressure value set in the recipe, calculates the difference between the two, and automatically adjusts the opening of the electro-proportional valve according to the difference using a PID algorithm.

[0145] Specifically, the pressure PID control module performs the following calculations in each control cycle:

[0146] Compare the actual pressure value PV fed back by the temperature and pressure sensor 7 with the target pressure value SP set in the formula, and calculate the deviation value e=SP-PV;

[0147] Calculate the current deviation value e(n), the integral of the deviation with respect to time ∑e·Δt, and the derivative of the deviation with respect to time Δe / Δt, respectively.

[0148] Multiply the three calculation results by the proportional coefficient Kp, integral coefficient Ki, and differential coefficient Kd respectively, and then sum them to obtain the control output value MV=Kp·e(n)+Ki·∑e·Δt+Kd·Δe / Δt;

[0149] The programmable logic controller (PLC) 6 converts the control output value MV into a 4-20mA analog signal and outputs it to the electro-proportional valve to control the valve spool opening. In this control process, the precision pressure reducing valve, acting as a pre-stage air source treatment element, coarsely adjusts the air source pressure from the air compressor to near the target pressure value, with a deviation not exceeding ±1% of the target value, thus reducing the adjustment burden on the electro-proportional valve. The electro-proportional valve, as the final actuator, continuously adjusts its valve spool opening based on the 4-20mA analog signal output from the PLC 6. This continuous adjustment, unlike the discrete control of on / off valves, further eliminates residual deviations based on the coarse adjustment of the precision pressure reducing valve, achieving precise closed-loop pressure control. Through the cascading cooperation of the precision pressure reducing valve and the electro-proportional valve, the compressed air pressure entering the container precisely follows the target setpoint.

[0150] Throughout the pressure build-up and maintenance process, the aforementioned PID calculation is repeated at a fixed control cycle, such as 50ms, causing the control output value MV to be updated in real time according to the deviation. The opening of the electro-proportional valve is continuously adjusted accordingly: when the actual pressure is lower than the target pressure (i.e., the deviation e is positive), MV increases, the electro-proportional valve opening increases, and the air intake increases; when the actual pressure approaches the target pressure (i.e., the deviation e approaches zero), MV gradually decreases to the equilibrium value, and the electro-proportional valve opening decreases accordingly to the equilibrium position, maintaining a balance between the air intake and system air consumption; when external disturbances cause the actual pressure to deviate from the target value, the deviation e reappears, the PID calculation immediately responds and automatically adjusts MV, ensuring that the actual pressure always follows the target setpoint. Considering the characteristics of the 0.5L-20L small-volume containers of this invention, the differential time constant Td of the pressure PID adjustment module is set to a small value to prevent pressure overshoot due to excessively rapid air intake response in small spaces, ensuring a smooth and shock-free pressure rise process and high pressure control accuracy.

[0151] When the programmable logic controller (PLC) determines that the pressure inside the container has stabilized within the allowable deviation range of the target pressure value and maintains the stabilization time for a preset time, such as 5-10 seconds, the pressure stabilization and delivery stage is completed, and the PLC automatically enters the next stage.

[0152] Throughout the pressure-stabilized delivery phase, the programmable logic controller (PLC) continuously monitors the pressure signal from the temperature and pressure sensor 7 and the liquid level signal from the liquid level sensor 12. Based on the liquid level signal from the liquid level sensor, the PLC calculates the remaining volume Vpaste of the paste within the container and, based on the total container volume Vtotal, calculates the current volume Vgas = Vtotal - Vpaste of the gas space at the top of the container. The PLC stores a calibration curve or mapping table between the gas space volume and the proportional coefficient Kp and integral coefficient Ki of the pressure PID control module. This calibration relationship was pre-obtained through pressure step response tests at different liquid levels and after PID parameter tuning. During the coating process, the programmable controller 6 queries the mapping table in real time based on the current gas space volume Vgas to obtain the optimal Kp and Ki values ​​corresponding to that volume, and dynamically updates the current parameters of the pressure PID control module: when the liquid level drops, causing the gas space volume Vgas to increase, the system inertia increases and the response lag increases. The programmable controller appropriately increases the proportional coefficient Kp according to the mapping relationship to improve the response speed of pressure regulation. The specific increase is determined by querying the mapping table; for example, for every 1L increase in gas space volume, Kp increases by a certain preset percentage. Conversely, when the liquid level is high and the gas space volume is small, Kp returns to its normal value to prevent system overshoot. Through the above liquid level feedforward compensation, the control parameters of the pressure PID control module are matched with the actual operating conditions in the container in real time.

[0153] Based on this, if the pressure inside the container deviates from the target value due to the flow of the paste or temperature changes, a deviation will occur between the actual pressure and the target pressure. The pressure PID adjustment module will recalculate the control output value MV according to the deviation in each control cycle. The programmable controller 6 will convert the updated MV into a 4-20mA analog signal and output it to the electric proportional valve to adjust its valve core opening, increase or decrease the air intake, so that the actual pressure returns to the target value.

[0154] If the temperature and pressure sensor 7 detects that the pressure inside the container exceeds the preset safety threshold, the programmable controller 6 immediately closes the electric proportional valve, opens the exhaust solenoid valve connected in parallel with the pressurization interface for emergency pressure relief, and prevents the electric tank bottom valve 4 from opening, ensuring system safety.

[0155] With the above configuration, the pressure stabilization conveying stage achieves the establishment and maintenance of a stable conveying pressure before material discharge. The pressure reaches the target value and remains constant as the condition for the completion of the stage and the triggering condition for entering the material discharge coating stage. This ensures that the paste is under stable pressure from the beginning of the subsequent material discharge coating process, eliminating the coating amount fluctuation in the start-up stage.

[0156] Material feeding and coating stage: Start the coating conveyor to transport the backing material, open the electric bottom valve at the bottom outlet of the gel container, so that the paste is released directly from the bottom of the gel container onto the backing material under constant gas pressure, adjust the speed of the coating conveyor according to the actual speed feedback from the speed sensor 8, and adjust the coating parameters according to the coating pressure distribution feedback from the contact sensor 9.

[0157] After the pressure stabilization and conveying stage is completed, the programmable logic controller automatically enters the material feeding and coating stage.

[0158] Specifically, the programmable logic controller (PLC) first starts the coating conveyor 5. The servo drive motor of the coating conveyor 5 drives the traction roller to rotate, which in turn drives the unwind roller to release the backing material, allowing the backing material to pass sequentially through the tension roller into the coating platform. During startup, the speed sensor 8 detects the actual linear speed of the backing material in real time and feeds the signal back to the PLC. The PLC's built-in speed PID control module automatically adjusts the output frequency of the servo drive based on the difference between the target speed value set in the formula and the actual speed value fed back by the speed sensor 8, enabling the coating conveyor 5 to quickly reach and maintain the target speed, such as 5 m / min.

[0159] Specifically, during the coating start-up phase, the programmable controller 6 sends a start command to the servo driver of the coating conveyor 5, driving the traction roller to rotate and allowing the backing material to enter the coating platform. During this process, the speed sensor 8 provides real-time feedback of the actual linear velocity PV to the high-speed counting input module of the programmable controller 6.

[0160] The programmable controller 6 has a built-in speed PID adjustment module. This module uses an incremental PID algorithm and performs the following calculations in each control cycle: calculate the current speed deviation e1(n) = SV - PV, where SV is the target speed set by the recipe; combine the speed deviation ev(n-1) of the previous control cycle and the speed deviation e1(n-2) of the control cycle before that, calculate the frequency increment ΔMV1 = Kp·[e1(n) - e1(n-1)] + Ki·e1(n) + Kd·[e1(n) - 2e1(n-1) + e1(n-2)]; the programmable controller 6 accumulates the frequency increment ΔMV1 to the current output frequency, i.e., F(n) = F(n-1) + ΔMV1, and converts the frequency value into a 0~10V voltage command through the analog output module and outputs it to the servo driver to control the servo driver to output the corresponding drive frequency, thereby adjusting the rotation speed of the traction roller. The above PID calculation is repeated with a fixed control cycle, such as 50ms, so that the output frequency is updated in real time according to the speed deviation: when the actual speed is lower than the target speed, ΔMV1 is positive, the output frequency gradually increases, the traction roller accelerates its rotation, and the backing material accelerates its forward movement; when the actual speed approaches the target speed, ΔMV1 gradually decreases to close to zero, the output frequency is maintained at the current value, and the traction roller rotates at a constant speed; when external disturbances cause the actual speed to deviate from the target value, the speed deviation e1(n) reappears, the PID calculation responds immediately and automatically adjusts the output frequency to compensate.

[0161] To prevent speed overshoot caused by excessive accumulation of the integral term due to large initial deviations during startup, the speed PID control module adopts an integral separation strategy: when the absolute value of the speed deviation is greater than a preset deviation threshold, such as 10% of the target speed, the integral coefficient Ki is set to zero, and only the proportional and derivative terms control the speed, thus avoiding excessive accumulation of the integral term when the deviation is large; when the absolute value of the speed deviation is reduced to within the preset deviation threshold, the integral term is resumed, and the integral action is used to eliminate steady-state residual error, ensuring that the steady-state speed fluctuation does not exceed ±0.1 m / min.

[0162] When the actual speed fed back by speed sensor 8 reaches the allowable deviation range of the target speed and remains stable, and when contact sensor 9 detects that the backing material has reached the coating station (i.e., the position signal is valid), the programmable logic controller sends an opening command to the electric bottom valve 4. The electric bottom valve 4 opens rapidly with a millisecond-level response speed. The constant gas pressure (e.g., 0.3 MPa) established and maintained during the pressure stabilization and conveying stage in the gel paste container 1 drives the paste inside the container, causing it to be released vertically downwards from the center outlet at the bottom of the container, directly onto the backing material on the coating conveyor 5 below. During the paste release process, because the pressure inside the container is pre-established and maintained constant, the paste is under stable pressure drive from the beginning of release, avoiding initial coating deviation caused by the impact of the feed pressure.

[0163] After the paste is released onto the backing material, it passes under the scraper 10 as the backing material is conveyed forward. The gap between the lower edge of the scraper 10 blade and the upper surface of the backing material determines the coating thickness. The paste is evenly scraped at this gap to a preset thickness, such as 1.8 mm. The excess paste accumulates on the upstream side of the scraper 10 to form a peak, which continues to participate in the coating process under the shearing action of the scraper 10.

[0164] During the coating process, the programmable logic controller performs multi-variable coordinated control, as follows:

[0165] Speed ​​closed-loop control: Speed ​​sensor 8 monitors the actual linear velocity of the backing material in real time and feeds it back to the programmable logic controller. The speed PID adjustment module continuously compares the actual speed with the target speed. When the actual speed deviates from the target value due to external resistance such as tension fluctuations of the backing material or changes in roller friction, the output frequency of the servo driver is automatically adjusted to compensate, so that the backing material always maintains a uniform speed.

[0166] Feed rate tracking control: Based on the actual speed value fed back by speed sensor 8, the programmable logic controller (PLC) synchronously adjusts the opening of the electric tank bottom valve 4 or the output pressure of the pressure regulating module 3 to ensure the feed rate follows the real-time changes in coating speed, maintaining a constant amount of paste released per unit length of backing material. When only minor adjustments to the feed rate are needed, the output pressure of the pressure regulating module 3 is adjusted first. The PLC 6 automatically adjusts the opening of the electro-proportional valve according to the aforementioned pressure PID regulation logic based on the speed deviation, changing the air pressure at the top of the container to fine-tune the feed rate. The pressure regulation has a fast response speed and is suitable for compensating for small fluctuations. When a significant adjustment to the feed rate is required, the opening of the electric tank bottom valve 4 is adjusted synchronously. The electric tank bottom valve 4 is an electric regulating valve equipped with analog position feedback, and its valve core opening is continuously controlled by a 4-20mA signal output from the analog output module of the PLC 6. The PLC 6 calculates the target opening value based on the ratio of the actual speed value fed back by speed sensor 8 to the reference speed. When the actual speed increases, the valve opening increases synchronously according to the increase in speed; when the actual speed decreases, the valve opening decreases synchronously. The programmable logic controller (PLC) 6 converts the target opening value into a 4-20mA signal and outputs it to the valve positioner of the electric tank bottom valve 4, driving the valve core to move to the target opening position. Simultaneously, the valve positioner feeds back the actual position signal of the valve core, forming a closed-loop opening control to ensure the valve core accurately reaches the target opening. The two work together to ensure the feeding rate precisely follows the coating speed changes. Coating thickness closed-loop control: During the coating process, the contact sensor 9 detects the coating pressure distribution signal at each sensing point in the width direction in real time and feeds it back to the PLC. The PLC calculates the average pressure detection value at each sensing point in the width direction and determines whether the deviation of the pressure value at each point relative to the average value is within the preset allowable deviation threshold. When the pressure detection values ​​at each sensing point in the width direction tend to be consistent, i.e., the maximum deviation does not exceed the preset allowable deviation threshold, the coating thickness is determined to be uniform, and the current doctor blade gap remains unchanged. When the pressure reading in a certain area deviates from the average value by more than a preset allowable deviation threshold, the coating amount in that area is determined to be abnormal. The programmable logic controller (PLC) automatically adjusts the gap of the scraper blade 10 to compensate: if the pressure is too high, indicating that the coating amount in that area is too large, the PLC 6 sends a positive pulse to the stepper motor driver, driving the scraper blade 10 to move downward by a preset step length to reduce the gap; if the pressure is too low, indicating that the coating amount is too small, the PLC 6 sends a reverse pulse to the stepper motor driver, driving the scraper blade 10 to move upward by a preset step length to increase the gap. During the adjustment process, the stepper motor driver provides real-time feedback on the actual number of rotations of the stepper motor to the PLC 6, forming a position closed loop to ensure accurate adjustment each time.

[0167] The three control loops mentioned above are executed in parallel and operate collaboratively in the programmable logic controller to ensure the dynamic matching of the material feeding rate, coating speed and coating thickness during the coating process, so that the coating amount (gram weight) per unit area remains consistent.

[0168] When the programmable logic controller determines that the preset coating length has been reached or receives a stop command, it first closes the electric tank bottom valve 4 to cut off the paste supply. After all the paste under the scraper 10 has been coated, it stops the coating conveyor 5 and releases the pressure in the container, automatically entering the finishing and archiving stage.

[0169] Final recording stage: Close the electric tank bottom valve, continuously collect and store the process parameters of the entire process at the preset sampling frequency, and generate a process curve file associated with the current batch.

[0170] After the material feeding and coating stage is completed, the programmable logic controller automatically enters the final archiving stage.

[0171] During the coating process, when the liquid level sensor 12 detects that the remaining amount of paste in the container is lower than the preset safe liquid level, the programmable controller 6 issues a low liquid level warning signal to prompt the operator to prepare to end the coating.

[0172] Specifically, the programmable logic controller (PLC) first sends a closing command to the electric bottom valve 4. The electric bottom valve 4 closes rapidly with a millisecond-level response, its sealing diaphragm flush with the inner wall of the container bottom, cutting off the source of the paste. Subsequently, the PLC controls the exhaust solenoid valve in the pressure regulating module 3 to open, releasing the residual pressure in the gel paste container 1 to atmospheric pressure. The coating conveyor 5 continues to run for a preset time. Once all the remaining paste below the scraper 10 has been coated onto the backing material and sent out of the coating platform, the coating conveyor 5 stops running. The PLC 6 verifies that the paste in the container has been basically emptied through the signal fed back from the liquid level sensor 11, ensuring complete discharge and preventing residual material from affecting the next batch of production. At this point, the coating operation is complete.

[0173] During the coating process, the programmable logic controller (PLC) continuously collects process parameters throughout the entire process at a preset sampling frequency of no less than 10Hz, starting from the start of the mixing and degassing stage. This includes timestamps, temperature and pressure curves from temperature and pressure sensors 7, speed curves from speed sensors 8, on / off commands and valve position feedback from the electric tank bottom valve 4, the electrical proportional valve opening command sequence from the pressure regulating module 3, and pressure distribution data in the width direction from the contact sensor 9. All collected data is linked in real-time to the current production batch number, forming a complete batch process curve file in chronological order. This file is stored in the PLC's internal memory and synchronously uploaded to the manufacturing execution system via an industrial Ethernet communication interface.

[0174] The batch process curve file comprehensively records the continuous trajectory of each process parameter changing over time throughout the entire coating process of this batch. When conducting subsequent industrial-scale production, R&D personnel can directly retrieve this file to identify the key process parameters and their variation ranges on the pilot-scale equipment. Based on this, they can determine the amplification factor and set values ​​for parameters such as coating speed, feeding pressure, and doctor blade gap in scale-up production. This provides scientific and reliable data support for large-scale production, saving the time and material costs associated with extensive trial and error in traditional empirical scale-up.

[0175] After the coating operation is completed, all parts of the system that come into contact with the material, including the inner wall of the gel paste container 1, the electric tank bottom valve 4, the surface of the coating conveyor 5, and the scraper 10, are designed with a residue-free, hygienic approach. There are no dead zones where material can accumulate. The system can be quickly connected to a CIP (Cleaning In Place) online cleaning system for cleaning. The cleaning solution, under pump pressure, can thoroughly rinse all paste contact surfaces, effectively removing residual paste, preventing cross-contamination between different batches, and facilitating rapid changeover testing for multiple varieties and small batches.

[0176] With the above configuration, the final archiving stage not only achieves complete material cutting and rapid equipment cleaning and preparation after the coating operation is completed, but more importantly, it archives the entire process data in the form of continuous curves and links them to specific batches, providing complete and accurate data support for subsequent process scale-up and quality backtracking.

[0177] In a preferred embodiment of the present invention, the programmable controller 6 also performs the following viscosity adaptive compensation control.

[0178] During the coating process, when the paste flows through the electric tank bottom valve 4 under the top air pressure, its flow rate depends on the paste viscosity, valve opening degree and pressure difference before and after the valve. Specifically, the programmable controller 6 calculates the actual pressure difference ΔP across the electric bottom valve 4 based on the paste temperature signal fed back by the temperature and pressure sensor 7, and the pressure before and after the valve fed back by the first pressure sensor on the upstream side and the second pressure sensor on the downstream side of the electric bottom valve 4. Based on the flow coefficient Cv value corresponding to the current valve opening, combined with the real-time collected pressure difference ΔP and the preset paste density ρ, the actual instantaneous flow rate Qactual through the electric bottom valve 4 in the current control cycle is calculated according to the orifice plate flow formula Q=Cv·√(ΔP / ρ) in fluid mechanics. Based on the flow cross-sectional area S corresponding to the current valve opening and the actual instantaneous flow rate Qactual, the real-time flow velocity v=Qactual / S of the paste is calculated. Then, based on the relationship between the pressure difference ΔP and the flow velocity v under the current valve opening, the apparent viscosity η of the current paste is calculated: η= (ΔP·D²) / (K·L·v), where D is the equivalent diameter of the valve flow channel, K is the valve flow channel shape coefficient, and L is the flow channel length. D, K, and L are all fixed structural parameters given when the valve leaves the factory.

[0179] As an alternative simplification, if the valve structural parameters D, K, and L cannot be accurately obtained, the viscosity change trend can be directly characterized by the ratio of the pressure difference ΔP to the standard pressure difference ΔP0 at the preset reference temperature, i.e., the viscosity change coefficient α = ΔP / ΔP0. The parameters are adjusted using a model-free adaptive method, that is, without establishing an accurate viscosity-pressure mathematical model, the adjustment is made by looking up the correspondence table between the experimentally measured "viscosity change trend" and "optimal PID parameters" to simplify the calculation.

[0180] During the coating process, when the paste temperature decreases or the paste undergoes a rheological change due to shear thinning, its apparent viscosity changes, causing the feed flow rate to drift at the same valve opening, thus affecting the consistency of the coating thickness. To address this, in each control cycle, the programmable controller 6 automatically adjusts the proportional coefficient Kp and integral coefficient Ki of the pressure PID control module based on the calibration relationship between the viscosity change coefficient α and the PID parameters. This calibration relationship is pre-determined experimentally: at different paste temperatures, the pressure response curves corresponding to the viscosity change coefficient α are measured, and the optimal Kp and Ki values ​​are determined through PID parameter tuning, such as the Ziegler-Nichols method, to establish a mapping relationship table between α and Kp, and α and Ki. This calibration relationship is stored in the programmable controller 6 in the form of a mapping table or a fitting function. During real-time control, the programmable controller 6 directly looks up the table or interpolates to calculate the corresponding PID parameters based on the current α value. The specific adjustment method is as follows: when the viscosity increases, the feed flow rate under the same pressure difference decreases, the programmable controller 6 increases the proportional coefficient Kp to improve the response speed of pressure regulation, and at the same time appropriately increases the integral coefficient Ki to eliminate steady-state deviation, ensuring that the valve opening can be adjusted to the target opening in a shorter time; when the viscosity decreases, the feed flow rate under the same pressure difference increases, the programmable controller 6 decreases the proportional coefficient Kp to prevent system overshoot oscillation, and at the same time appropriately decreases the integral coefficient Ki to maintain system stability.

[0181] Through the above viscosity adaptive compensation control, the programmable controller 6 can automatically correct the control parameters of the pressure PID adjustment module according to the real-time viscosity change of the paste, and compensate for the change in feed flow caused by viscosity fluctuation. Thus, when there are differences in viscosity between different batches of paste or when the viscosity changes due to temperature fluctuations during the coating process of the same batch, the coating weight can be kept consistent.

[0182] As a further preferred embodiment of the present invention, the programmable controller 6 or the host computer system communicatively connected to the programmable controller 6 also performs data-driven process parameter self-optimization control.

[0183] After each coating cycle, the programmable logic controller 6 associates and stores the batch process curve files generated during the final archiving stage with the corresponding batch coating quality inspection results, such as thickness uniformity, basis weight deviation, and pressure distribution in the width direction, to build a process database. As production batches accumulate, this database continuously expands, forming a historical process dataset covering multiple formulations and batches.

[0184] Based on this, Gaussian process regression is used to train the process database, establishing a predictive model with process parameters as input and coating quality as output. The predictive model describes the mapping relationship between process parameters and coating quality, specifically in the form: Quality Index = f(Pressure Setpoint, Speed ​​Setpoint, Doctor Blade Gap 10, Paste Temperature, Paste Viscosity) + Noise Term. The function f is modeled non-parametrically using Gaussian process priors, and the noise term represents the combined effect of observation errors and unmodeled disturbances. Before coating a new batch, the operator inputs the characteristic parameters of the current material, such as paste temperature and apparent viscosity, through a human-machine interface. The programmable controller 6 inputs these parameters into the predictive model. With optimal coating quality as the goal, within preset process parameter constraints such as pressure and speed limits, a Bayesian optimization method is used to automatically recommend the optimal combination of process parameters, including pressure setpoint, speed setpoint, and doctor blade gap 10. The operator confirms and executes the recommended combination. During the coating process, the programmable controller 6 continuously inputs real-time collected process parameters and sensor feedback data into the prediction model. The model updates its predicted value for the coating quality of the current batch online. When the predicted value deviates from the target range, it automatically fine-tunes the pressure setpoint and the doctor blade gap 10 to ensure that the actual coating quality always approaches the target value. After each batch of coating is completed, the process data and quality inspection results of the new batch are added to the process database. The prediction model is periodically retrained or incrementally updated, so that the prediction accuracy of the model continuously improves with the accumulation of data, gradually approaching the optimal process window for each formulation.

[0185] With the above configuration, this invention utilizes the process curve archive data accumulated from historical batches to achieve automatic optimization of process parameters through a data-driven approach. This realizes a closed-loop iteration of "data acquisition → model training → parameter recommendation → online optimization → data accumulation," further improving the consistency of coating quality and the efficiency of process development.

[0186] It should be noted that the specific structure, installation position, and connection method of the gel ointment application device system shown in the accompanying drawings and the above embodiments are merely illustrative examples provided to facilitate understanding of the technical solution of the present invention and are not intended to limit the present invention. Those skilled in the art should understand that the accompanying drawings only schematically show some hardware components closely related to the technical solution of the present invention and do not show all auxiliary structures. For other auxiliary hardware structures required to implement the technical solution of the present invention, those skilled in the art can configure and implement them according to actual needs and with reference to existing technologies.

[0187] Furthermore, the specific component models, numerical ranges such as container volume (0.5L to 20L), cone angle (55° to 60°), temperature deviation (±1℃), and control cycle (50ms) mentioned in the above embodiments, as well as the specific component selections such as sanitary diaphragm valves, PT100 thermal resistors, and 4-20mA signal transmission, are all preferred embodiments for implementing the technical solution of this invention, and not limitations on the scope of protection of this invention. After reading this specification, those skilled in the art can fully implement the technical solution of this invention by using other hardware components with equivalent functions or adjusting relevant parameter values ​​according to actual working conditions and design requirements. For example, using other brands of PLC controllers, using different types of temperature sensors such as thermocouples, using pressure transmitters with different ranges, using signal transmission methods with different communication protocols such as 0-10V voltage signals or industrial Ethernet communication, or adjusting the above numerical parameters according to the rheological characteristics of the paste and the coating process requirements, etc., all of which do not depart from the essence of this invention. All technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection of this invention.

[0188] The gel ointment coating device system of the present invention, through the structural design and synergistic cooperation of the above-mentioned components, can produce the following beneficial technical effects compared with the prior art:

[0189] First, it improves the consistency of coating thickness and coating amount.

[0190] This invention establishes and maintains a constant conveying pressure in advance during the pressure-stabilizing conveying stage, allowing the paste to be released from the bottom of the container under constant pressure. A PID closed-loop speed control ensures the backing material moves at a uniform speed. A contact sensor detects the coating pressure distribution along the width direction in real time and performs dynamic compensation. The synergistic effect of stable pressure, constant speed, and thickness feedback adjustment improves the uniformity of the coating amount per unit area in both the width and length directions, overcoming the shortcomings of low precision in coating amount control and uneven coating thickness in manual production.

[0191] Second, it improves the repeatability of the process and the consistency between batches.

[0192] This invention automatically links the four stages of mixing and degassing, pressure stabilization and conveying, material feeding and coating, and final archiving through a condition-triggered mechanism. The next stage can only be triggered after the process parameters of the previous stage have been verified to meet the standards in real time by sensors. Since the switching between stages is not based on fixed time or manual judgment, but rather on automated condition determination based on real-time feedback signals from temperature and pressure sensors, speed sensors, and contact sensors, for example, the mixing and degassing stage uses achieving and maintaining a preset vacuum level as the verification criterion for sufficient degassing, and the pressure stabilization and conveying stage uses reaching and maintaining a constant pressure value as the verification criterion for stable material supply. Therefore, in different batches of coating processes, as long as the condition parameters of each stage are set the same, the switching timing between stages will be consistent, avoiding differences in stage switching timing caused by differences in manual judgment or timing deviations. This results in better repeatability of the coating process between different batches.

[0193] Third, it simplifies the system structure, avoids losses and pollution during material transfer, and achieves equipment miniaturization.

[0194] This invention integrates mixing, degassing, pressure conveying, and coating into a single system. The gel paste container has a stirring and pressurizing interface at the top and a discharge port at the center of the bottom. After mixing and degassing within the same container, the paste is directly released from the bottom to the coating conveyor by top air pressure without transfer, eliminating the need for separate mixing equipment and paste transfer devices in existing technologies, thus simplifying the system structure. Because mixing, degassing, and pressure conveying are completed within the same container, there is no need to transfer the paste between different devices, avoiding material adhesion loss and cross-contamination during the transfer process of high-viscosity gel pastes. Simultaneously, eliminating separate mixing and transfer equipment provides a structural basis for system miniaturization, enabling the entire system to achieve the entire process from mixing to coating in small volumes ranging from 0.5L to 20L, meeting the miniaturization requirements of laboratory research and development and small-batch pilot production scenarios.

[0195] Fourth, it provides traceable data support for process scale-up.

[0196] This invention continuously collects process parameters throughout the entire process at a preset sampling frequency, starting from the start of the mixing and degassing stage. This generates batch process curve archives containing temperature curves, pressure curves, speed curves, valve opening sequences, and coating pressure distribution data, which are then linked to specific batch storage. Unlike existing technologies that only record set values ​​or discrete sampling points, this invention's continuous process curve archives fully record the dynamic trajectory of the actual process, providing data support for subsequent scale-up from laboratory to industrial production.

[0197] Fifth, it facilitates quick switching between multiple product types and cleaning and maintenance.

[0198] All parts of this invention that come into contact with the material, including the inner wall of the gel container which is electrolytically polished and the valve core which is flush with the inner wall of the container bottom when the electric bottom valve is closed, forming a structure without dead angles, are designed with a sanitary grade without dead angles. After coating, it can be connected to a CIP online cleaning system for cleaning, and all surfaces in contact with the paste can be cleaned without manual disassembly.

[0199] Second Embodiment

[0200] This embodiment provides a method for controlling the application of a gel paste, which can be executed by the gel paste application device system described in the first embodiment. Figure 2 As shown, the method includes the following stages executed sequentially.

[0201] Mixing and degassing stage: Start the electric mixer to mix the materials in the gel container. Monitor the vacuum level in the gel container through temperature and pressure sensors. After the vacuum level reaches the preset value and is maintained for the preset time, proceed to the next stage.

[0202] Pressure stabilization and delivery stage: Gas is introduced into the gel container through the pressure regulation module, and the pressure inside the gel container is adjusted to the target value and maintained constant according to the feedback signal of the temperature and pressure sensor.

[0203] Material feeding and coating stage: Start the coating conveyor to transport the backing material, open the electric bottom valve at the bottom outlet of the gel container, so that the paste is released directly from the bottom of the gel container onto the backing material under constant gas pressure, adjust the speed of the coating conveyor according to the actual speed feedback from the speed sensor, and adjust the coating parameters according to the coating pressure distribution feedback from the contact sensor.

[0204] Final recording stage: Close the electric tank bottom valve, continuously collect and store the process parameters of the entire process at the preset sampling frequency, and generate a process curve file associated with the current batch.

[0205] In this embodiment, the specific structure of the gel ointment coating device system, the connection relationship between each component, the working principle, and the control method have been described in detail in the first embodiment, and will not be repeated in this embodiment. Unless otherwise specified, the system components and their control methods involved in each stage of execution shall be implemented with reference to the first embodiment.

[0206] Third Embodiment

[0207] To verify the technical effect of the present invention, the applicant conducted the following comparative experiment using the same material formulation, batch size of 5 liters, backing material, target coating speed of 5 meters per minute, and target coating thickness of 1.5 millimeters.

[0208] The experiment was divided into two groups. The experimental group used the scheme of this invention, with all automatic control functions enabled, including pressure closed-loop control, speed closed-loop control, and coating thickness closed-loop control. The control group used the conventional process, with the closed-loop feedback function disabled, and fixed doctor blade gap, tank pressure, and coating speed were set manually based on experience. Except for the control mode, the experimental conditions were identical for both groups.

[0209] The experiment selected the following five core indicators for comparison.

[0210] The first test was coating uniformity. After coating, nine measurement points were selected at equal intervals along the width of the fabric, and the thickness of the coating layer at each point was measured using a precision thickness gauge. The coefficient of variation was then calculated. Experimental data showed that, due to the lack of automatic adjustment, the control group had a coating thickness coefficient of variation of 8.5%, with significant differences in thickness between the edges and the center. Under closed-loop control, the experimental group's thickness coefficient of variation decreased to 2.3%, a reduction of 73%, and the thickness consistency along the width of the fabric was significantly improved.

[0211] The second test was the consistency of coating pressure distribution. Pressure values ​​at various points along the width direction were directly read from the contact sensors during the coating process. In the control group, due to manually set parameters that could not respond in real time to changes in the paste's flow characteristics, the maximum pressure deviation along the width direction was ±12%, easily resulting in localized high or low pressure. In the experimental group, the pressure values ​​at each point were more consistent, with the maximum deviation controlled within ±4%, a reduction of 67%.

[0212] The third item was the consistency of the ointment content. Following the method for checking the ointment content of gel patches in the Chinese Pharmacopoeia, multiple samples were randomly selected to determine the weight of the ointment per unit area. The control group showed a large deviation in ointment content from different sampling locations, with a relative standard deviation of 6.8%. The experimental group showed a high degree of consistency in ointment content across all sampling points, with the relative standard deviation decreasing to 1.9%, a reduction of 72%, and significantly better intra-batch uniformity than the control group.

[0213] The fourth item is system response speed and stability. The time from startup to reaching a stable coating state and the speed fluctuation curve during the coating process were recorded. The control group showed significant speed overshoot during startup, requiring 8 seconds to reach a stable coating state, and exhibited large speed fluctuations during operation. The experimental group, under speed PID closed-loop control, quickly and smoothly reached the target speed, reaching a stable state in just 2.5 seconds, representing a 69% improvement in response speed. Steady-state speed fluctuation did not exceed ±0.1 m / min, and the operation was smooth and oscillating.

[0214] The fifth item is the finished product qualification rate. This involves counting the number of defective products out of 100 consecutively coated samples due to uneven thickness or air bubbles. The control group had a higher defect rate, with a finished product qualification rate of 87%; the experimental group had a significantly lower defect rate, with a finished product qualification rate increasing to 98%, an increase of 11 percentage points.

[0215] The above comparative experiments demonstrate that the present invention, through multi-variable synergistic control of pressure closed-loop, speed closed-loop, and coating thickness closed-loop, significantly improves the uniformity and batch consistency of gel ointment coating. Compared with conventional open-loop control, the coefficient of variation of coating thickness is reduced by more than 70%, the relative standard deviation of ointment content is reduced from 6.8% to 1.9%, and the finished product qualification rate is increased from 87% to 98%. The above experimental data fully demonstrate that the technical solution of the present invention has significant progress and practical application value compared with the prior art. The present invention also provides an electronic device, including: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being configured to perform the methods described in the embodiments of the present invention.

[0216] This invention also provides a computer-readable storage medium storing computer-executable instructions for performing the methods described in this invention.

[0217] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0218] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for controlling the application of a gel paste, characterized in that, This includes the following stages, executed sequentially: Mixing and degassing stage: Start the electric mixer to mix the materials in the gel container, monitor the vacuum level in the gel container through the temperature and pressure sensor, and enter the next stage after the vacuum level reaches the preset value and is maintained for the preset time. Pressure stabilization and delivery stage: Gas is introduced into the gel container through the pressure regulation module, and the pressure inside the gel container is adjusted to the target value and maintained constant according to the feedback signal of the temperature and pressure sensor; Material feeding and coating stage: Start the coating conveyor to deliver the backing material, open the electric bottom valve at the bottom outlet of the gel container, so that the paste is released directly from the bottom of the gel container onto the backing material under constant gas pressure, adjust the speed of the coating conveyor according to the actual speed feedback from the speed sensor, and adjust the coating parameters according to the coating pressure distribution feedback from the contact sensor. Final recording stage: Close the electric tank bottom valve, continuously collect and store the process parameters of the entire process at the preset sampling frequency, and generate a process curve file associated with the current batch.

2. The gel ointment application control method according to claim 1, characterized in that, The top of the gel container is provided with a stirring interface for mounting the electric mixer and a pressurizing interface for connecting the pressure regulating module; the bottom outlet is located at the center of the bottom of the gel container.

3. The method for controlling the application of gel ointment according to claim 1, characterized in that, During the pressure stabilization and delivery stage, a PID control algorithm is used to automatically adjust the opening of the air intake valve based on the difference between the set pressure value and the actual pressure value fed back by the temperature and pressure sensor, until the pressure reaches the target value and remains constant.

4. The method for controlling the application of a gel paste according to claim 1, characterized in that, During the material feeding and coating stage, a speed PID closed-loop control is used to automatically adjust the drive frequency of the coating conveyor based on the difference between the set speed value and the actual speed value fed back by the speed sensor, so that the backing material moves forward at a uniform speed.

5. The method for controlling the application of a gel paste according to claim 1, characterized in that, During the material feeding and coating stage, there is a preset timing relationship between the opening of the electric tank bottom valve and the start of the coating conveyor. The electric tank bottom valve opens after the coating conveyor reaches a stable speed and the contact sensor detects that the backing material is in place.

6. The method for controlling the application of a gel paste according to claim 1, characterized in that, During the material feeding and coating stage, the opening degree of the electric tank bottom valve or the output pressure of the pressure regulating module is dynamically adjusted according to the actual speed value fed back by the speed sensor, so that the material feeding rate follows the coating speed. At the same time, the doctor blade gap is dynamically adjusted according to the coating pressure distribution signal fed back by the contact sensor, so as to realize multi-variable coordinated control of material feeding rate, coating speed and coating thickness.

7. The method for controlling the application of a gel paste according to claim 1, characterized in that, During the mixing and degassing stage, the temperature and pressure sensor is switched to the negative pressure range to monitor the vacuum level inside the container; during the pressure stabilization and conveying stage and the material dispensing and coating stage, the temperature and pressure sensor is switched to the positive pressure range to monitor the conveying pressure inside the container.

8. The method for controlling the application of a gel paste according to claim 1, characterized in that, During the final recording phase, the process curve file includes timestamps, temperature curves, pressure curves, speed curves, valve opening sequence, and pressure distribution data of the contact sensor.

9. The method for controlling the application of a gel paste according to claim 1, characterized in that, During the material feeding and coating stage, when the contact sensor detects that the coating pressure deviates from the preset range, it automatically adjusts the scraper gap or the opening of the electric tank bottom valve to compensate.

10. A gel-ointment application system, characterized in that, include: The gel container has a mixing interface for mounting an electric mixer and a pressurizing interface for connecting a pressure regulating module at the top, and a discharge port at the center of the bottom. An electric mixer is installed at the mixing port on the top of the gel container, and the mixing paddle of the electric mixer extends into the inside of the gel container; The pressure regulating module is connected to the pressurization port on the top of the gel container via a pipeline, and is used to introduce pressurized gas into the gel container; An electric bottom valve is installed at the outlet at the bottom of the gel container to control the release of the gel. A coating conveyor is positioned below the gel container to carry and transport the backing material; A temperature and pressure sensor is installed on the gel container to detect the pressure and temperature inside the gel container; A liquid level sensor is installed inside the gel container to detect the distance of the gel from the top of the container. A speed sensor, installed on the coating conveyor, is used to detect the conveying speed of the backing material; A contact sensor is installed at the coating station of the coating conveyor to detect the position of the backing material and / or the coating pressure distribution. A doctor blade is positioned above the coating station of the coating conveyor and is used to control the coating thickness. A programmable logic controller (PLC) is electrically connected to an electric mixer, a pressure regulating module, an electric tank bottom valve, a coating conveyor, a temperature and pressure sensor, a speed sensor, a contact sensor, a liquid level sensor, and a scraper, respectively. The PLC is configured to execute the gel ointment coating control method according to any one of claims 1 to 9.

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