A coating cavity exhaust structure, system, and method for in-mold coating processes

Abstract

The present application relates to a mold exhaust structure, system and method for in-mold coating process, which aims to significantly reduce bubble and air trapping phenomenon by precisely controlling gas exhaust and fluid filling, and improve the appearance quality and functionality of the product. The exhaust structure includes a coating cavity, a feeding device, a first flow channel, an exhaust assembly, a second flow channel and a transition flow channel. The second flow channel has a smaller flow area than the coating cavity, which increases the fluid flow resistance; the transition flow channel is designed in an arc shape, and the included angle between the tangent line and the vertical direction gradually increases, which optimizes the gas exhaust path. In addition, the system integrates a human-computer interaction unit, a control unit, a first pressure sensor and a second pressure sensor. When the second pressure sensor detects a value greater than 0 bar, the exhaust assembly is closed, and the pressure maintaining and filling stage is entered until the coating is completed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of surface treatment of plastic products, and in particular to a coating cavity exhaust system and control method for in-mold coating process. BACKGROUND

[0002] In the surface treatment process of plastic products, in-mold coating technology is widely used because it can complete the coating process of products directly inside the coating cavity. This technology not only improves production efficiency, but also significantly reduces environmental pollution. However, during the in-mold coating process, if the air inside the coating cavity and the reaction gas generated by the reaction of the molding coating (such as PUR / PUA polyurethane or polyurea coating) cannot be effectively exhausted in time, it will cause defects such as air trapping and bubbles on the surface of the product, which will seriously affect the appearance quality and functionality of the product.

[0003] In the existing in-mold coating technology, although there are some exhaust measures, due to the lack of an efficient exhaust control system, on the one hand, the good flow performance of the coating used in the coating process may hinder the effective exhaust of the gas, causing air bubbles or air trapping inside the product, affecting the quality and appearance of the product; the fast-flowing coating may not be able to uniformly fill the cavity, causing underfilling or overfilling in some parts of the product, affecting the overall performance and consistency of the product. On the other hand, the existing exhaust measures cannot select the appropriate exhaust timing according to the internal pressure of the coating cavity, resulting in poor exhaust effect, which further causes the appearance quality of the product to be not guaranteed. In addition, the existing exhaust scheme is often only suitable for a specific type of coating cavity, with limited scope of application, and cannot meet the diversified production needs. SUMMARY

[0004] In view of one or more of the problems existing in the prior art, the first aspect of the present application provides a coating cavity exhaust structure for in-mold coating process, comprising a second flow channel, a transition flow channel, a first flow channel and an exhaust assembly, the coating cavity, the second flow channel, the transition flow channel and the first flow channel are sequentially communicated,

[0005] wherein the flow area of the second flow channel is smaller than the flow area of the coating cavity;

[0006] The transition flow channel is an arc-shaped flow channel, and the angle of the inclination angle of the transition flow channel gradually decreases along the fluid flow direction;

[0007] The first flow channel comprises an inflow end and an outflow end, the inflow end of the first flow channel is connected with the transition flow channel, and the outflow end of the first flow channel is connected with the exhaust assembly;

[0008] The first flow channel forms at least one bending part for increasing the fluid flow resistance.

[0009] The first aspect of the present application provides a coating cavity exhaust structure for an in-mold coating process. By providing a bending portion in the first flow channel, the gas discharge is promoted, the defects such as bubbles and trapped gas on the surface of the product caused by gas accumulation are reduced, and the fluid flow resistance is increased, so that the coating can be more uniformly filled in the coating cavity, avoiding the problems of local underfilling or excessive filling, and improving the appearance quality and functionality of the product.

[0010] By increasing the second flow channel with smaller flow area, the fluid flow resistance is further increased to ensure uniform filling of the fluid in the coating cavity, especially suitable for coatings with excellent fluidity (such as PUR / PUA polyurethane or polyurea coatings), avoiding the problems of local excessive filling or underfilling caused by rapid flow.

[0011] At the same time, by means of smooth transition of the arc-shaped transition flow channel and gradual decrease of the angle of the transition flow channel (i.e. the angle between the tangent of the transition flow channel and the vertical direction gradually increases), the turbulence and pressure loss of the fluid when turning are reduced, making it easier for gas to be carried out and discharged, further reducing the occurrence of bubbles or trapped gas, and gradually changing the flow direction of the fluid to avoid unstable flow caused by sudden direction change, improving the stability and consistency of the coating process.

[0012] Preferably, the second flow channel has a height of 0.05mm to 5mm and a width of 0.1mm to 8mm.

[0013] By setting the height of the second flow channel to 0.05mm to 5mm and the width to 0.1mm to 8mm, the fluid flow resistance can be accurately controlled. At the same time, the narrow design of the second flow channel increases the turbulence of the fluid, which helps to separate the gas from the coating and carry it out, thereby improving the gas discharge efficiency and reducing the occurrence of bubbles or trapped gas. When the height of the second flow channel is less than 0.05mm or the width is greater than 8mm, the fluid flow resistance will be too large, making it difficult for the coating to pass through the second flow channel, which may cause local overfilling and increase the risk of flow channel being blocked by impurities or solidified coating, resulting in the system unable to work normally; when the height of the second flow channel is greater than 5mm or the width is less than 0.1mm, the fluid flow resistance will be reduced, making the coating flow into the coating cavity quickly, which may cause local underfilling or uneven filling, affecting the product quality, and reducing the turbulence of the fluid, which is not conducive to the separation of gas from the coating and carrying it out, reducing the gas discharge efficiency and increasing the risk of bubbles or trapped gas.

[0014] Preferably, the angle of the transition flow channel changes from 50° to 1° along the fluid flow direction.

[0015] Preferably, the bending portion is at least one of a U-shaped bending portion, an L-shaped bending portion, and an S-shaped bending portion.

[0016] The U-shaped bending part, the L-shaped bending part and the S-shaped bending part can be selected or combined according to actual needs to more accurately adjust the flow resistance of the fluid and ensure uniform filling of the coating in the coating cavity, and are particularly suitable for coatings with different viscosities and flowabilities.

[0017] Preferably, an overflow well is arranged between the bending part of the first flow channel and the exhaust assembly, which can receive the coating to be applied when the fluid contains the coating to be applied, thereby preventing the coating to be applied in the fluid from entering the exhaust assembly.

[0018] By adding the overflow well, the excess coating overflowing from the first flow channel can be received, preventing the coating from directly flowing out of the exhaust assembly and polluting the mold or affecting the coating quality. By receiving the excess coating through the overflow well, the overflow well can protect the exhaust assembly from being blocked by the coating, ensure the normal operation of the exhaust assembly, and prolong the service life of the exhaust assembly.

[0019] Preferably, the exhaust assembly comprises an exhaust valve and an exhaust valve drive connected with the exhaust valve for controlling the opening and closing of the exhaust valve.

[0020] The exhaust valve drive controls the opening and closing of the exhaust valve, realizing the automatic control of the exhaust valve, reducing the need for manual intervention, and improving the production efficiency.

[0021] The second aspect of the present application provides a coating cavity exhaust system for an in-mold coating process, comprising the coating cavity exhaust structure provided in the first aspect, and further comprising a human-computer interaction unit, a control unit, a first pressure sensor and a second pressure sensor.

[0022] The human-computer interaction unit is electrically connected with the control unit, and is used for inputting instruction data information by a user.

[0023] The control unit is electrically connected with the feeding device, and is used for controlling the start and stop of the feeding action of the feeding device.

[0024] The control unit is electrically connected with the exhaust assembly, and is used for controlling the opening and closing of the exhaust assembly.

[0025] The first pressure sensor is arranged on the coating cavity wall at the connection position of the feeding device, and is electrically connected with the control unit, and is used for detecting the pressure value in the coating cavity and transmitting the pressure value to the control unit.

[0026] The second pressure sensor is arranged at the inflow end of the first flow channel, and is electrically connected with the control unit, and is used for detecting the pressure value at the inflow end of the first flow channel and transmitting the pressure value to the control unit.

[0027] The second aspect of the present application provides a coating cavity exhaust system for an in-mold coating process, which can not only conveniently input instruction data information through a man-machine interaction unit to realize automatic control of the system, but also can accurately control the opening and closing timing of the exhaust valve, reduce the occurrence of air bubbles and air trapping, improve the appearance quality and functionality of the product, and can also flexibly adjust the feeding speed of the feeding device and the opening and closing time and frequency of the exhaust assembly according to different coating process requirements, suitable for various types of coating cavities and coatings, and enhance the adaptability and flexibility of the system.

[0028] The third aspect of the present application provides a coating cavity exhaust method for an in-mold coating process, which is executed by the coating cavity exhaust system for an in-mold coating process described above, and the method comprises:

[0029] presetting a pressure value in the control unit through the man-machine interaction unit;

[0030] opening the exhaust assembly to make the coating cavity communicate with the outside;

[0031] feeding the coating paint into the coating cavity by the feeding device;

[0032] detecting the pressure value by the first pressure sensor and the second pressure sensor and transmitting it to the control unit;

[0033] when the pressure value detected by the second pressure sensor is greater than 0 bar, the control unit controls the exhaust assembly to close the gas discharge;

[0034] during the process of feeding the coating paint into the coating cavity by the feeding device, the pressure value detected by the first pressure sensor received by the control unit can reach the preset value.

[0035] The coating cavity exhaust method for an in-mold coating process provided by the third aspect of the present application can reduce the occurrence of air bubbles and air trapping by setting a preset pressure value, real-time monitoring the pressure change in the coating cavity by the first pressure sensor, detecting the pressure value of the first flow channel inflow end by the second pressure sensor, closing the exhaust assembly at the time point when the pressure value detected by the second pressure sensor is greater than 0 after the cavity pressure growth reaches the preset value, and continuing to maintain pressure filling after completing the gas discharge, which improves the appearance quality and functionality of the product. The whole process is automatically completed by the control system, and the user only needs to input the preset pressure value through the man-machine interaction unit, which reduces the need for manual intervention and improves the production efficiency. The control unit can flexibly adjust the feeding speed of the feeding device and the opening and closing time and frequency of the exhaust assembly according to different coating process requirements, suitable for various types of coating cavities and coatings, and enhance the adaptability and flexibility of the system.

[0036] Preferably, the preset pressure value is any value between 20 bar and 120 bar.

[0037] Different preset pressure values can be optimized for different coating viscosity, fluidity and other characteristics to ensure the best coating effect. By setting a reasonable preset pressure value, the gas can be discharged at the appropriate time point, reducing the occurrence of air bubbles and trapped gas, and improving the appearance quality and functionality of the product.

[0038] Preferably, the coating temperature is 30-90℃ and the viscosity is 100-300cps.

[0039] The coating cavity exhaust method for in-mold coating process provided by the present application is suitable for coating materials of different temperatures and viscosities, i.e., it can meet the needs of different production processes, has wide applicability and flexibility, and improves production efficiency and economic benefits.

[0040] Preferably, the feeding device delivers the coating material to the coating cavity at a delivery speed of 5-700g / min.

[0041] The delivery speed of 5-700g / min covers a wide range from very low speed to high speed, and is suitable for different types of coating processes and coating characteristics. By setting a reasonable delivery speed, the uniform distribution of the coating material in the coating cavity can be ensured, avoiding the problems of local underfilling or overfilling, and improving the appearance quality and functionality of the product.

[0042] Preferably, the temperature inside the coating cavity is 80-130℃ when the feeding device delivers the coating material to the coating cavity.

[0043] Higher temperature can accelerate the curing reaction of the coating material, shorten the curing time, and improve the production efficiency. For some thermosetting coating materials, such as polyurethane or polyurea coating materials, appropriate temperature rise can promote crosslinking reaction and obtain better coating performance.

[0044] The operation principle of the coating cavity exhaust system for in-mold coating process provided by the present application is as follows:

[0045] Initial state preparation:

[0046] The injection molding machine completes the mold closing operation, and the substrate is fixed inside the mold to form a coating cavity.

[0047] The control unit initializes the system, and the user sets the preset pressure value and other necessary parameters (such as the feeding speed) through the human-machine interaction unit to ensure that all components are in standby state.

[0048] Start exhaust:

[0049] The control unit controls the exhaust valve driving member to act, opens the exhaust valve, and connects the coating cavity with the outside world, so that the air in the coating cavity can be smoothly discharged. At this time, the initial pressure in the coating cavity is about 0bar.

[0050] Feeding:

[0051] The control unit starts the feeding device to deliver the coating material (e.g. polyurethane or polyurea coating material) through the mixing head and the feeding flow channel into the coating cavity. At the same time, ingredients such as isocyanate (ISO) and polyol (Poly) are delivered into the mixing head.

[0052] Pressure detection:

[0053] The first pressure sensor monitors the pressure change in the coating cavity in real time, and the second pressure sensor monitors the pressure change at the inflow end of the first flow channel in real time, and transmits these data to the control unit.

[0054] Closing the exhaust valve:

[0055] When the pressure value detected by the second pressure sensor is greater than 0 bar, it indicates that the coating material has begun to enter the first flow channel.

[0056] At this time, the control unit controls the exhaust valve drive to act, so that the exhaust valve is closed and gas discharge is stopped, thereby entering the pressure maintaining filling stage.

[0057] Pressure maintaining filling:

[0058] The control unit continues to control the feeding device to deliver the coating material, and performs pressure maintaining filling until the filling of the coating material is completed.

[0059] In the above process, the pressure value detected by the first pressure sensor can reach the pressure value (e.g. any value between 20 bar and 120 bar) set by the user in advance.

[0060] Cooling and solidification and mold opening:

[0061] After filling is completed, the product undergoes a cooling and solidification process in the mold.

[0062] Finally, the injection molding machine performs mold opening operation to take out the product that has been coated.

[0063] It should be understood that the technical solutions of various aspects of the present application can be independent of each other, or can be mutually referenced, and the beneficial effects achieved by each aspect and the corresponding feasible embodiments can be mutually referenced, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0064] The accompanying drawings are used to provide further understanding of the present application, and constitute a part of the specification, together with the embodiments of the present application, to explain the present application, and do not constitute a limitation on the present application. In the drawings:

[0065] Figure 1 is a structural schematic diagram of the coating cavity exhaust structure for in-mold coating process provided by an exemplary embodiment of the present application;

[0066] Figure 2 is a structural diagram of a coating cavity exhaust structure for an in-mold coating process according to another example embodiment of the present application;

[0067] Figure 3 is a structural diagram of a coating cavity exhaust structure for an in-mold coating process according to yet another example embodiment of the present application;

[0068] Figure 4 is a structural diagram of a coating cavity exhaust structure for an in-mold coating process according to still another example embodiment of the present application;

[0069] Figure 5 is a structural diagram of a coating cavity exhaust system for an in-mold coating process according to an example embodiment of the present application;

[0070] Figure 6 is a flow chart of a coating cavity exhaust method for an in-mold coating process according to an example embodiment of the present application;

[0071] Figure 7 is a mold cavity pressure change diagram of a coating cavity exhaust method for an in-mold coating process according to an example embodiment of the present application;

[0072] Figure 8 is a product appearance effect diagram of a coating cavity exhaust method for an in-mold coating process according to an example embodiment of the present application;

[0073] Figure 9 is a mold cavity pressure change diagram of a coating cavity exhaust method for an in-mold coating process according to an example embodiment of the present application;

[0074] Figure 10 is a product appearance effect diagram of a coating cavity exhaust method for an in-mold coating process according to an example embodiment of the present application;

[0075] Figure 11 is a mold cavity pressure change diagram of a coating cavity exhaust method for an in-mold coating process according to an example embodiment of the present application;

[0076] Figure 12 is a product appearance effect diagram of a coating cavity exhaust method for an in-mold coating process according to an example embodiment of the present application;

[0077] Figure 13 is a mold cavity pressure change diagram of a coating cavity exhaust method for an in-mold coating process according to an example embodiment of the present application;

[0078] Figure 14is a product appearance effect diagram of a coating cavity exhaust method for an in-mold coating process provided by an example embodiment of the present application;

[0079] Figure 15 is a mold cavity pressure change diagram of a coating cavity exhaust method for an in-mold coating process provided by the present application;

[0080] Figure 16 is a product appearance effect diagram of a coating cavity exhaust method for an in-mold coating process provided by the present application;

[0081] Figure 17 is a mold cavity pressure change diagram of a coating cavity exhaust method for an in-mold coating process provided by the present application;

[0082] Figure 18 is a product appearance effect diagram of a coating cavity exhaust method for an in-mold coating process provided by the present application;

[0083] Figure 19 is a mold cavity pressure change diagram of a coating cavity exhaust method for an in-mold coating process provided by the present application;

[0084] Figure 20 is a product appearance effect diagram of a coating cavity exhaust method for an in-mold coating process provided by the present application.

[0085] Reference Signs:

[0086] 1. Coating cavity

[0087] 2. Feeding device; 21. Mixing head; 22. Feeding runner

[0088] 3. First runner; 31. Inflow end; 32. Outflow end; 33. Bending portion; 34. Overflow well

[0089] 4. Exhaust assembly; 41. Exhaust valve; 42. Exhaust valve driving member

[0090] 5. Second runner

[0091] 6. Transition runner

[0092] 100. Human-machine interaction unit; 200. Control unit; 300. First pressure sensor; 400. Second pressure sensor DETAILED DESCRIPTION

[0093] Embodiments of this application will now be described in detail, examples of which are illustrated in the accompanying drawings. The components of the embodiments of this application described and shown in the drawings herein can be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application.

[0094] Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0095] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0096] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0097] The following will combine Figure 1 and Figure 20 The technical solutions of this application are clearly and completely described. Obviously, the described embodiments are only some embodiments of this application, not all embodiments.

[0098] Figure 1 This is a schematic diagram of a coating cavity venting structure for in-mold coating process provided in an exemplary embodiment of this application; Figure 2 This is a schematic diagram of a coating cavity venting structure for in-mold coating process provided in another exemplary embodiment of this application.

[0099] The first aspect of this application provides a venting structure for a coating cavity in an in-mold coating process, see reference. Figure 1 and Figure 2 As shown, it includes a feeding device 2 connected to the coating cavity 1, a first flow channel 3, and an exhaust assembly 4.

[0100] The inflow end 31 of the first flow channel 3 is in communication with the coating cavity 1 for receiving fluid.

[0101] In some specific examples, the fluid received by the first flow channel 3 can be overflowed coating paint or gas inside the coating cavity 1.

[0102] When the feeding device 2 starts to feed coating paint into the coating cavity 1, the air inside the coating cavity 1 will be forced to flow into the first flow channel 3; when the coating paint is transitionally fed, the coating paint will also flow into the first flow channel 3.

[0103] In some specific examples, referring to Figure 2 The communication position of the feeding device 2 with the coating cavity 1 corresponds to the communication position of the first flow channel 3 with the coating cavity 1, i.e. they can be located on the front and back sides or left and right sides or upper and lower sides of the coating cavity 1 respectively, or other corresponding two sides, so that the coating paint can flow through the substrate in the coating cavity before reaching the inflow end 31 of the first flow channel 3.

[0104] In some specific examples, the cross-sectional shape of the first flow channel 3 can be circular or other irregular shapes.

[0105] In some specific examples, the fluid received by the first flow channel 3 can be overflowed coating paint or gas inside the coating cavity 1.

[0106] The exhaust assembly 4 is arranged at the outflow end of the first flow channel 3 for discharging gas.

[0107] In some specific examples, the discharged gas can be air inside the coating cavity 1 or other gas generated by the coating paint.

[0108] At least one bending portion 33 is formed on the first flow channel 3 for increasing the flow resistance of the fluid. The bending portion promotes the discharge of gas, reduces the defects such as bubbles and trapped air on the surface of the product caused by the accumulation of gas, and at the same time increases the flow resistance of the fluid, so that the coating paint can be more uniformly filled in the coating cavity, avoiding the problems of local underfilling or excessive filling, and improving the appearance quality and functionality of the product.

[0109] In some specific examples, the feeding device 2 is in communication with the mixing head 21, the mixing head 21 is in communication with the feeding flow channel 22, and the feeding flow channel 22 is in communication with the coating cavity 1, so as to realize the operation of feeding the coating paint from the feeding device 2 into the mixing head 21 for mixing, and then feeding into the coating cavity 1 through the feeding flow channel 22.

[0110] Figure 3 is a structural schematic view of a coating cavity exhaust structure for in-mold coating process provided by another exemplary embodiment of the present application.

[0111] In some embodiments of the first aspect, referring to Figure 1 and Figure 3 the coating cavity exhaust structure for the in-mold coating process further comprises a second flow channel 5 and a transition flow channel 6.

[0112] The second flow channel 5 directly communicates with the coating cavity 1, enabling fluid to flow from the coating cavity 1 into the second flow channel 5. The cross-sectional area of the second flow channel 5 is significantly smaller than that of the coating cavity 1, which increases the flow resistance of the fluid and effectively controls the flow speed of the fluid, ensuring uniform filling of the fluid in the coating cavity, especially for coatings with excellent fluidity (such as PUR / PUA polyurethane or polyurea coatings), avoiding the problem of local overfilling or underfilling caused by rapid flow.

[0113] The second flow channel 5, the transition flow channel 6, and the first flow channel 3 are sequentially connected, forming a continuous flow channel system. In particular, the transition flow channel 6 is an arc-shaped flow channel, and the inclination angle of the transition flow channel gradually decreases along the direction of the coating flow.

[0114] The inclination angle of the transition flow channel refers to the inclination angle of the transition flow channel relative to the horizontal plane, which gradually decreases along the direction of the coating flow. In other words, the tangent of the arc-shaped transition flow channel gradually increases the angle formed with the vertical direction. This design not only guides the smooth turning of the fluid, reduces turbulence and pressure loss, but also promotes effective separation and discharge of gas. For example, when the coating flows from the coating cavity 1 to the first flow channel 3, the arc-shaped design of the transition flow channel 6 enables the fluid to smoothly change the flow direction, avoiding unstable flow caused by sudden direction changes, thereby improving the stability and consistency of the coating process.

[0115] In some specific examples, the coating cavity 1, the second flow channel 5, the transition flow channel 6, and the first flow channel 3 are sequentially connected and can be fixedly connected to each other by welding or other means, or can be fixed by screws or other detachable means.

[0116] In some embodiments of the first aspect, the height of the second flow channel 5 is 0.05mm to 5mm, and the width is 0.1mm to 8mm. In some specific examples, the height of the second flow channel 5 can be 0.05mm, 0.1mm, 0.2mm, 0.3mm, 0.5mm, 1mm, 1.5mm, 2mm, 3mm, 4mm, 5mm, etc. The width of the second flow channel 5 can be 0.1mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, etc.

[0117] In this embodiment, by limiting the height and width of the second flow channel 5, the flow resistance of the fluid can be accurately controlled. At the same time, the narrow design of the second flow channel 5 increases the turbulence of the fluid, which helps the gas to separate from the coating and be carried out, thereby improving the gas discharge efficiency and reducing the occurrence of bubbles or trapped gas. When the height of the second flow channel 5 is less than 0.05 mm or the width is greater than 8 mm, the fluid flow resistance will be too large, making it difficult for the coating to pass through the second flow channel 5, which may cause local overfilling and increase the risk of the flow channel being blocked by impurities or solidified coating, resulting in the system unable to work normally; when the height of the second flow channel 5 is greater than 5 mm or the width is less than 0.1 mm, the fluid flow resistance will be reduced, causing the coating to flow into the coating cavity quickly, which may result in local underfilling or uneven filling, affecting product quality, and reducing the turbulence of the fluid, which is not conducive to the separation of gas from the coating and being carried out, reducing the gas discharge efficiency and increasing the risk of bubbles or trapped gas.

[0118] In some embodiments of the first aspect, the angle of the inclination angle of the transition flow channel 6 varies from 50° to 1° in the direction of the coating flow.

[0119] In some specific examples, the angle can gradually decrease from 30°, 35°, 40°, 45°, 48°, 49° or 50° to 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, 11° and the like.

[0120] The angle of the inclination angle can adapt to different coating and different coating injection speeds, allowing the coating to smoothly transition from the second flow channel with a height of 0.05-5 mm and a width of 0.5-8 mm to the first flow channel, reducing turbulence and pressure loss when turning, ensuring smooth and smooth flow, and also allowing gas to be more easily carried out and discharged, further reducing the occurrence of bubbles or trapped gas.

[0121] Figure 4 is a structural schematic diagram of a coating cavity exhaust structure for an in-mold coating process provided by another exemplary embodiment of the present application.

[0122] In some embodiments of the first aspect, referring to Figure 4 , the curved portion 33 is at least one of a U-shaped curved portion, an L-shaped curved portion and an S-shaped curved portion.

[0123] In this embodiment, U-shaped curved portion, L-shaped curved portion and S-shaped curved portion can be selected or used in combination according to actual needs, to more accurately adjust the flow resistance of the fluid and ensure uniform filling of the coating in the coating cavity, especially for different viscosity and flowability of the coating.

[0124] In some specific examples, the bending portion 33 can include a U-shaped bending portion, an L-shaped bending portion, and an S-shaped bending portion, and the number of the bending portions can be 1, 2, 3, or more. In addition, the bending portion can include a U-shaped bending portion and an L-shaped bending portion, or an L-shaped bending portion and an S-shaped bending portion, or a U-shaped bending portion and an S-shaped bending portion, or a U-shaped bending portion, an L-shaped bending portion, and an S-shaped bending portion.

[0125] In some embodiments of the first aspect, the bending portion 33 of the first flow channel 3 is provided with an overflow well 34 between the overflow well 34 and the exhaust assembly 4, which can receive excess coating paint overflowing from the first flow channel 3, prevent the paint from flowing directly from the exhaust assembly 4, polluting the mold or affecting the coating quality, and at the same time protect the exhaust assembly 4 from being blocked by the paint, ensure the normal work of the exhaust assembly 4, and prolong the service life of the exhaust assembly 4.

[0126] In some specific examples, the overflow well 34 can be a cylindrical or other irregularly shaped container for storing the overflowed coating paint.

[0127] In some embodiments of the first aspect, the exhaust assembly 4 includes an exhaust valve 41 and an exhaust valve drive 42 connected to the exhaust valve 41 for controlling the opening and closing of the exhaust valve 41, thereby realizing the automatic control of the exhaust valve 41, reducing the need for manual intervention, and improving the production efficiency.

[0128] In some specific examples, the exhaust valve 41 can be a core-pulling valve.

[0129] Figure 5 is a structural schematic diagram of a coating cavity exhaust system for an in-mold coating process provided by an exemplary embodiment of the present application.

[0130] The second aspect of the present application provides a coating cavity exhaust system for an in-mold coating process, referring to Figure 5 , which includes the coating cavity exhaust structure described in the first aspect of the embodiment, and further includes a human-computer interaction unit 100, a control unit 200, and a first pressure sensor 300 and a second pressure sensor 400.

[0131] The human-computer interaction unit 100 is electrically connected to the control unit 200, providing a friendly operation interface for the user, allowing the user to conveniently input various instruction data information, such as preset pressure values, feeding speeds, etc. For example, the user can set specific coating parameters through a touch screen or a keyboard, ensuring that the system can be accurately controlled according to the needs.

[0132] The control unit 200 is electrically connected with the feeding device 2 and the exhaust assembly 4, and is responsible for coordinating the work of each component. According to the instruction data information input by the user, the control unit 200 controls the start-stop action of the feeding device 2 to ensure that the paint enters the coating cavity 1 at the appropriate time point. For example, when using polyurethane paint with moderate viscosity, the control unit can start the feeding device according to the set speed to ensure uniform distribution of the paint.

[0133] The control unit 200 is also responsible for controlling the opening and closing action of the exhaust assembly 4 to ensure that the gas is exhausted at the appropriate time point. For example, when the pressure in the coating cavity 1 reaches the preset value, the control unit 200 will immediately close the exhaust assembly 4 to prevent excessive exhaust from affecting the coating quality.

[0134] In some specific examples, the control unit 200 is electrically connected with the exhaust valve driving part 42 of the exhaust assembly 4, thereby controlling the opening and closing of the exhaust valve 41.

[0135] The first pressure sensor 300 is arranged on the cavity wall of the coating cavity 1 at the connection with the feeding device 2, and is electrically connected with the control unit 200, for real-time detection of the pressure value in the coating cavity 1 and transmission of data to the control unit 200. This real-time monitoring mechanism realizes closed-loop control, ensuring the stability and consistency of the coating process.

[0136] The first pressure sensor 400 is arranged at the inflow end 31 of the first flow channel 3, and is electrically connected with the control unit 200, for real-time detection of the pressure value at the inflow end 31 of the first flow channel 3 and transmission of data to the control unit 200.

[0137] The second aspect of the present application provides a coating cavity exhaust system for in-mold coating process, which not only can conveniently input instruction data information through the man-machine interaction unit 100 to realize automatic control of the system, but also can accurately control the opening and closing time of the exhaust assembly 4, reduce the occurrence of bubble and air trapping phenomenon, improve the appearance quality and functionality of the product, and can flexibly adjust the feeding speed of the feeding device 2 and the opening and closing time and frequency of the exhaust assembly 4 according to different coating process requirements, suitable for various types of coating cavities 1 and coating paints, and enhance the adaptability and flexibility of the system.

[0138] Figure 6 The present application is an example embodiment of a coating cavity exhaust method for in-mold coating process.

[0139] The third aspect of the present application provides a coating cavity exhaust method for in-mold coating process, as shown in the figure, the method is executed by the above-mentioned coating cavity exhaust system for in-mold coating process, comprising: Figure 6

[0140] ​S100, presetting a pressure value in the control unit through the human-computer interaction unit.

[0141] In some embodiments, the preset pressure value is any value between 20 bar and 120 bar, such as 20 bar, 25 bar, 30 bar, 40 bar, 50 bar, 60 bar, 70 bar, 80 bar, 90 bar, 100 bar, 110 bar, 115 bar, 120 bar, etc. Different preset pressure values can be moderately optimized and adjusted for different coating viscosity, fluidity, product gram weight, and coating wall thickness, etc. to ensure the best coating effect. By setting a reasonable preset pressure value, the pressure in the coating cavity can be established and monitored in real time, so that the product in the coating cavity can be fully filled, and the appearance quality and functionality of the product are improved. For example: a lower preset pressure value is suitable for coatings or products with low gram weight, poor fluidity, low viscosity, and slow flow rate, reducing flow resistance and ensuring smooth filling. A higher preset pressure value is suitable for special processes that require rapid filling, or coatings with good fluidity, high viscosity, high temperature, and fast flow rate, and products with large gram weight, ensuring uniform distribution of the coating in a short time.

[0142] In some specific examples, the user can also input the speed of the feeding device conveying the coating to the control unit through the human-computer interaction unit.

[0143] S200, the coating cavity is communicated with the outside world, and the feeding device conveys the coating to the coating cavity.

[0144] In some specific examples, step S200 includes:

[0145] S201, the control unit sends an instruction to the exhaust assembly to open it, ensuring that the coating cavity is communicated with the outside world and allowing gas to be smoothly discharged.

[0146] S202, after the exhaust assembly is opened, the control unit starts the feeding device to begin conveying the coating to the coating cavity.

[0147] In some embodiments, the user can set the feeding speed to be 5 g / min to 700 g / min,

[0148] In this embodiment, the conveying speed of 5g / min to 700g / min covers a wide range from very low speed to high speed, suitable for different types of coating processes and coating characteristics. The flow rate of the feeding device can be 5g / min, 700g / min or a value between them, such as 50g / min, 100g / min, 200g / min, 300g / min, 400g / min, 500g / min, 600g / min, 700g / min, etc., depending on the actual coating weight of the product. By setting a reasonable conveying speed, the uniform distribution of the coating in the coating cavity can be ensured, avoiding the problems of local underfilling or overfilling, and improving the appearance quality and functionality of the product.

[0149] In some embodiments, the preset pressure value of the mold exhaust system for the in-mold coating process is 20bar to 120bar, suitable for products with in-mold coating process of 5g-5000g, i.e. whether it is a 5g coating product or a 5000g coating product, to ensure that the pressure in the coating mold cavity is completed when the coating process is 20bar-120bar, i.e. to obtain a relatively perfect coating product.

[0150] In some embodiments, the coating temperature is 30℃ to 90℃, and the viscosity is 100cps to 300cps. For example, the coating temperature can be 30℃, 31℃, 32℃, 35℃, 40℃, 50℃, 60℃, 70℃, 80℃, 85℃, 88℃, 89℃, 90℃, etc. The viscosity can be 100cps, 105cps, 110cps, 120cps, 150cps, 200cps, 250cps, 280cps, 290cps, 295cps, 300cps, etc.

[0151] This embodiment is suitable for coating coatings with different temperatures and viscosities, i.e. it can meet the needs of different production processes, has wide applicability and flexibility, and improves production efficiency and economic benefits.

[0152] In some embodiments, the internal temperature of the coating cavity is 80℃ to 130℃ when the feeding device delivers the coating coating to the coating cavity. For example, the internal temperature of the coating cavity can be 80℃, 81℃, 82℃, 85℃, 90℃, 100℃, 110℃, 120℃, 125℃, 128℃, 129℃, 130℃, etc.

[0153] In this embodiment, higher temperature can accelerate the curing reaction of the coating, shorten the curing time, and improve the production efficiency. For some thermosetting coatings, such as polyurethane or polyurea coatings, appropriate temperature rise can promote crosslinking reaction and obtain better coating performance.

[0154] S300, the first pressure sensor and the second pressure sensor detect the pressure value and transmit it to the control unit.

[0155] When the paint enters the coating cavity, the air inside is extruded, which causes the pressure value to change, and the first pressure sensor transmits the detected pressure change to the control unit.

[0156] At the same time, the second pressure sensor monitors the pressure value of the first flow channel inflow end in real time and transmits it to the control unit.

[0157] S400, when the control unit determines that the pressure value detected by the second pressure sensor is greater than 0 bar, the control unit controls the exhaust assembly to close the gas discharge.

[0158] The second pressure sensor detects the pressure value of the first flow channel inflow end, and the exhaust assembly is closed at the time point when the second pressure sensor detects that the pressure value is greater than 0, and the gas discharge is completed. After continuing to fill the pressure, the occurrence of bubbles and trapped gas is reduced, and the appearance quality and functionality of the product are improved; the whole process is automatically completed by the control system, reducing the need for manual intervention and improving production efficiency; the control unit can flexibly adjust the feeding speed of the feeding device and the opening and closing time and frequency of the exhaust assembly according to different coating process requirements, suitable for various types of coating cavities and paints, and enhance the adaptability and flexibility of the system.

[0159] S500, continue to fill the pressure until the coating process is completed, and the pressure value detected by the first pressure sensor during the coating process can reach the preset pressure value.

[0160] During the process of feeding the coating paint into the coating cavity until the entire coating process is completed, the pressure value detected by the first pressure sensor received by the control unit can reach the preset pressure value, which can ensure that the required pressure value has been established for this coating process, thereby guaranteeing the good effects such as the density and no bubbles of the prepared coating product.

[0161] The following is a specific embodiment of a coating cavity exhaust method for in-mold coating process provided by the present application:

[0162] The equipment and material information used in the following examples of the present application:

[0163] Substrate raw material: transparent PC2067;

[0164] Coating raw material: Liming PUR 8001;

[0165] The coating cavity used for testing: crystal handle in-mold coating cavity;

[0166] The first flow channel used for testing has an L-shaped bend;

[0167] The angle range of the angle formed by the tangent of the transition runner used in the test and the vertical direction is 1° to 50°;

[0168] The equipment used in the test: Krauss Maffei injection molding machine and in-mold coating equipment, mold temperature control system;

[0169] The process conditions of the following examples of the present application are tested as follows:

[0170] Substrate raw material temperature: transparent PC2067 260℃-310℃

[0171] Coating raw material: Liming PUR 8001A.B 50℃-80℃

[0172] Vacuum degree of coating raw material: ≤-0.3Bar-≤-0.4Bar

[0173] Pressure of coating pouring: ISO feed pressure: 165Bar, Poly feed pressure: 170bar

[0174] Example 1

[0175] Initial state: the injection molding machine completes the mold closing operation, the substrate is fixed inside the mold, a coating cavity 1 is formed between the mold and the substrate, the width of the second runner 5 is 2mm, and the height is 1mm. The control unit 200 initializes the system, and the user sets the pressure preset value in the control unit 200 through the man-machine interaction unit 100 to 50bar, ensuring that all components are in standby state;

[0176] The control unit 200 controls the exhaust valve driving part 42 to act, so that the exhaust valve 41 is opened, and the coating cavity 1 is communicated with the outside, ensuring that the air in the coating cavity 1 can be discharged; when the exhaust valve 41 is opened, the initial pressure in the coating cavity 1 is about 0bar;

[0177] The control unit 200 controls the feeding device 2 to start, and the polyurethane coating with a temperature of 70℃ and a viscosity of 170cPs is transported into the coating cavity 1 with a temperature of 110℃ through the mixing head 21 and the feed runner 22 at a speed of 34g / min, at the same time, isocyanate (ISO) and polyol (Poly) are transported into the mixing head, the ISO feed flow is: 23g / s; the Poly feed flow is: 11g / s;

[0178] The first pressure sensor 300 monitors the pressure change in the coating cavity 1 in real time, the second pressure sensor 400 monitors the pressure change at the inflow end 31 of the first runner 3 in real time, and transmits the detected pressure data to the control unit 200;

[0179] When the second pressure sensor detects that the pressure value is greater than 0, the control unit 200 controls the exhaust valve driving part 42 to act, so that the exhaust valve 41 is closed;

[0180] The control unit 200 controls the feeding device 2 to continue feeding the coating material, and performs pressure maintaining filling until the filling of the coating material is completed.

[0181] In the above process, the pressure value detected by the first pressure sensor 300 received by the control unit 200 can reach the pressure value 50 bar set by the user in advance.

[0182] After the filling is completed, cooling and solidification are performed, the coating cavity is opened, and the coated product is taken out.

[0183] Example 2

[0184] Initial state: the injection molding machine completes the mold closing operation, the substrate is fixed inside the mold, the coating cavity 1 is formed between the mold and the substrate, the width of the second flow channel 5 is 8 mm, and the height is 2.5 mm. The control unit 200 initializes the system, the user sets the pressure preset value in the control unit 200 through the human-computer interaction unit 100 to 120 bar, and ensures that all components are in standby state;

[0185] The control unit 200 controls the exhaust valve driving member 42 to act, so that the exhaust valve 41 is opened, and the coating cavity 1 is communicated with the outside, so that the air in the coating cavity 1 can be exhausted; when the exhaust valve 41 is opened, the initial pressure in the coating cavity 1 is about 0 bar;

[0186] The control unit 200 controls the feeding device 2 to start, and the polyurethane coating material with a temperature of 70℃ and a viscosity of 170 cPs is fed into the coating cavity 1 with a temperature of 110℃ through the mixing head 21 and the feeding flow channel 22 at a speed of 34 g / min, at the same time, isocyanate (ISO) and polyol (Poly) are fed into the mixing head, the ISO feeding flow rate is 23 g / s, and the Poly feeding flow rate is 11 g / s;

[0187] The first pressure sensor 300 monitors the pressure change in the coating cavity 1 in real time, the second pressure sensor 400 monitors the pressure change at the inflow end 31 of the first flow channel 3 in real time, and transmits the detected pressure data to the control unit 200;

[0188] When the second pressure sensor detects that the pressure value is greater than 0, the control unit 200 controls the exhaust valve driving member 42 to act, so that the exhaust valve 41 is closed;

[0189] The control unit 200 controls the feeding device 2 to continue feeding the coating material, and performs pressure maintaining filling until the filling is completed.

[0190] In the above process, the pressure value detected by the first pressure sensor 300 received by the control unit 200 can reach the pressure value 120 bar set by the user in advance.

[0191] After filling, cooling and solidification, the coating cavity is opened and the coated product is taken out.

[0192] Example 3

[0193] Initial state: the injection molding machine completes the mold closing operation, the substrate is fixed inside the mold, the coating cavity 1 is formed between the mold and the substrate, the width of the second flow channel 5 is 4 mm, and the height is 4.5 mm. The control unit 200 initializes the system, and the user sets the pressure preset value in the control unit 200 through the human-computer interaction unit 100 to 20 bar, ensuring that all components are in standby state;

[0194] The control unit 200 controls the exhaust valve driving part 42 to act, so that the exhaust valve 41 is opened, and the coating cavity 1 is communicated with the outside, ensuring that the air in the coating cavity 1 can be discharged; when the exhaust valve 41 is opened, the initial pressure in the coating cavity 1 is about 0 bar;

[0195] The control unit 200 controls the feeding device 2 to start, and the polyurethane coating with a temperature of 70℃ and a viscosity of 170cPs is delivered into the coating cavity 1 with a temperature of 110℃ at a speed of 34g / min through the mixing head 21 and the feeding flow channel 22, at the same time, isocyanate (ISO) and polyol (Poly) are delivered into the mixing head, the ISO feeding flow is 23g / s, and the Poly feeding flow is 11g / s;

[0196] The first pressure sensor 300 monitors the pressure change in the coating cavity 1 in real time, and the second pressure sensor 400 monitors the pressure change at the inflow end 31 of the first flow channel 3 in real time, and transmits the detected pressure data to the control unit 200;

[0197] When the second pressure sensor detects that the pressure value is greater than 0, the control unit 200 controls the exhaust valve driving part 42 to act, so that the exhaust valve 41 is closed;

[0198] The control unit 200 controls the feeding device 2 to continue to deliver the coating, and carries out pressure maintaining filling until the filling is completed.

[0199] In the above process, the pressure value detected by the first pressure sensor 300 received by the control unit 200 can reach the pressure value 20bar preset by the user;

[0200] After filling, cooling and solidification, the coating cavity is opened and the coated product is taken out.

[0201] Example 4

[0202] Initial state: the injection molding machine completes the mold closing operation, the substrate is fixed inside the mold, the coating cavity 1 is formed between the mold and the substrate, the width of the second flow channel 5 is 0.1mm, and the height is 0.05mm. The control unit 200 initializes the system, and the user sets the pressure preset value in the control unit 200 to 120bar through the man-machine interaction unit 100, ensuring that all components are in standby state;

[0203] The control unit 200 controls the exhaust valve driving member 42 to act, so that the exhaust valve 41 is opened, and the coating cavity 1 is communicated with the outside, ensuring that the air in the coating cavity 1 can be discharged; when the exhaust valve 41 is opened, the initial pressure in the coating cavity 1 is about 0bar;

[0204] The control unit 200 controls the feeding device 2 to start, and the polyurethane coating with a temperature of 70℃ and a viscosity of 170cPs is delivered into the coating cavity 1 with a temperature of 110℃ at a speed of 34g / min through the mixing head 21 and the feeding flow channel 22, at the same time, isocyanate (ISO) and polyol (Poly) are delivered into the mixing head, the ISO feeding flow is 23g / s, and the Poly feeding flow is 11g / s;

[0205] The first pressure sensor 300 monitors the pressure change in the coating cavity 1 in real time, the second pressure sensor 400 monitors the pressure change at the inflow end 31 of the first flow channel 3 in real time, and transmits the detected pressure data to the control unit 200;

[0206] When the second pressure sensor detects that the pressure value is greater than 0, the control unit 200 controls the exhaust valve driving member 42 to act, so that the exhaust valve 41 is closed;

[0207] The control unit 200 controls the feeding device 2 to continue to deliver the coating, and performs pressure maintaining filling until the filling is completed;

[0208] In the above process, the pressure value detected by the first pressure sensor 300 received by the control unit 200 can reach the pressure value 120bar set by the user in advance;

[0209] After the filling is completed, the cooling and solidification are performed, the mold of the coating cavity is opened, and the coated product is taken out.

[0210] Comparative example 1

[0211] Initial state: the injection molding machine completes the mold closing operation, the substrate is fixed inside the mold, the coating cavity 1 is formed between the mold and the substrate, the width of the second flow channel 5 is 0.1mm, and the height is 6mm. The control unit 200 initializes the system, and the user sets the pressure preset value in the control unit 200 to 20bar through the man-machine interaction unit 100, ensuring that all components are in standby state;

[0212] The control unit 200 controls the exhaust valve driving member 42 to act, so that the exhaust valve 41 is opened, so that the coating cavity 1 is communicated with the outside world, and the air in the coating cavity 1 can be discharged; when the exhaust valve 41 is opened, the initial pressure in the coating cavity 1 is about 0 bar;

[0213] The control unit 200 controls the feeding device 2 to start, and the polyurethane coating with a temperature of 70°C and a viscosity of 170 cPs is transported into the coating cavity 1 with a temperature of 110°C at a speed of 34 g / min through the mixing head 21 and the feeding flow channel 22, and at the same time, isocyanate (ISO) and polyol (Poly) are transported into the mixing head, the ISO feeding flow is 23 g / s, and the Poly feeding flow is 11 g / s.

[0214] The first pressure sensor 300 monitors the pressure change in the coating cavity 1 in real time, and transmits the detected pressure data to the control unit 200.

[0215] At this time, since the width of the second flow channel 5 is 0.1 mm and the height is 5.1 mm, the coating directly enters the overflow well from the overflow flow channel area after filling the product, and does not bring pressure change, thereby causing the coating layer not to be completely filled, and the pressure in the mold is not enough, causing bubbles to be not effectively discharged. The product coating layer appearance is poor.

[0216] Comparative Example 2

[0217] Initial state: the injection molding machine completes the mold closing operation, the substrate is fixed in the mold, the coating cavity 1 is formed between the mold and the substrate, the width of the second flow channel 5 is 8.5 mm, and the height is 0.03 mm. The control unit 200 initializes the system, and the user sets the pressure preset value in the control unit 200 through the man-machine interaction unit 100 to 130 bar, so that all components are in standby state;

[0218] The control unit 200 controls the exhaust valve driving member 42 to act, so that the exhaust valve 41 is opened, so that the coating cavity 1 is communicated with the outside world, and the air in the coating cavity 1 can be discharged; when the exhaust valve 41 is opened, the initial pressure in the coating cavity 1 is about 0 bar;

[0219] The control unit 200 controls the feeding device 2 to start, and the polyurethane coating with a temperature of 70°C and a viscosity of 170 cPs is transported into the coating cavity 1 with a temperature of 110°C at a speed of 34 g / min through the mixing head 21 and the feeding flow channel 22, and at the same time, isocyanate (ISO) and polyol (Poly) are transported into the mixing head, the ISO feeding flow is 23 g / s, and the Poly feeding flow is 11 g / s.

[0220] The first pressure sensor 300 monitors the pressure change in the coating cavity 1 in real time, and the second pressure sensor 400 monitors the pressure change at the inflow end 31 of the first flow channel 3 in real time, and transmits the detected pressure data to the control unit 200;

[0221] When the second pressure sensor detects a pressure value greater than 0, the control unit 200 controls the exhaust valve drive 42 to act, so that the exhaust valve 41 is closed;

[0222] The control unit 200 controls the feeding device 2 to continue feeding the coating material, and performs pressure maintaining filling until the filling is completed;

[0223] In the above process, the pressure value detected by the first pressure sensor 300 received by the control unit 200 can reach the pressure value 130bar preset by the user;

[0224] After the filling is completed, cooling and solidification are performed, the coating cavity is opened, and the coated product is taken out.

[0225] Comparative Example 3

[0226] Initial state: The injection molding machine completes the mold closing operation, the substrate is fixed inside the mold, the coating cavity 1 is formed between the mold and the substrate, the width of the second flow channel 5 is 1mm, and the height is 6mm. The control unit 200 initializes the system, and the user sets the pressure preset value in the control unit 200 through the human-computer interaction unit 100 to 10bar, and ensures that all components are in standby state;

[0227] The control unit 200 controls the exhaust valve drive 42 to act, so that the exhaust valve 41 is opened, so that the coating cavity 1 is communicated with the outside, and the air in the coating cavity 1 can be discharged; When the exhaust valve 41 is opened, the initial pressure in the coating cavity 1 is about 0bar;

[0228] The control unit 200 controls the feeding device 2 to start, and the polyurethane coating with a temperature of 70℃ and a viscosity of 170cPs is fed into the coating cavity 1 with a temperature of 110℃ through the mixing head 21 and the feeding flow channel 22 at a speed of 34g / min, at the same time, isocyanate (ISO) and polyol (Poly) are fed into the mixing head, the ISO feeding flow rate is 23g / s, and the Poly feeding flow rate is 11g / s;

[0229] The first pressure sensor 300 monitors the pressure change in the coating cavity 1 in real time, and the second pressure sensor 400 monitors the pressure change at the inflow end 31 of the first flow channel 3 in real time, and transmits the detected pressure data to the control unit 200;

[0230] When the second pressure sensor detects a pressure value greater than 0, the control unit 200 controls the exhaust valve drive 42 to act, so that the exhaust valve 41 is closed;

[0231] The control unit 200 controls the feeding device 2 to continue feeding the paint and to perform pressure maintaining filling until the filling is completed.

[0232] In the above process, the pressure value detected by the first pressure sensor 300 received by the control unit 200 can reach the pressure value 10 bar preset by the user.

[0233] After the filling is completed, cooling and solidification are performed, the coating cavity is opened, and the coated product is taken out.

[0234] From the above Examples 1 to 4 and Comparative Examples 1 to 3, it can be seen that:

[0235] The pressure change graph during the coating process of Example 1 is shown in Figure 7 The final product is shown in Figure 8 It can be seen that in Example 1, under the condition that the width of the second flow channel 5 is 2 mm, the height is 1 mm, and the preset pressure value is 50 bar, better pressure maintaining filling can be performed, the bubbles in the paint layer of the product are effectively discharged, and the product appearance is good.

[0236] The pressure change graph during the coating process of Example 2 is shown in Figure 9 The final product is shown in Figure 10 It can be seen that in Example 2, under the condition that the width of the second flow channel 5 is 8 mm, the height is 2.5 mm, and the preset pressure value is 120 bar, better pressure maintaining filling can be performed, the bubbles in the paint layer of the product are effectively discharged, and the product appearance is good.

[0237] The pressure change graph during the coating process of Example 3 is shown in Figure 11 The final product is shown in Figure 12 It can be seen that in Example 3, under the condition that the width of the second flow channel 5 is 4 mm, the height is 5 mm, and the preset pressure value is 20 bar, better pressure maintaining filling can be performed, the bubbles in the paint layer of the product are effectively discharged, and the product appearance is good.

[0238] The pressure change graph during the coating process of Example 4 is shown in Figure 13 The final product is shown in Figure 14 It can be seen that in Example 4, under the condition that the width of the second flow channel 5 is 0.1 mm, the height is 0.05 mm, and the preset pressure value is 120 bar, the paint performs better pressure maintaining filling, the coating is dense, the surface has no bubbles and air trapping, and the product appearance is good.

[0239] The pressure change graph during the coating process of Comparative Example 1 is shown in Figure 15 The final product is shown in Figure 16As shown, in the comparative example 1, under the condition that the width of the second runner 5 is 0.1 mm, the height is 5.1 mm, and the preset pressure value is 130 bar, the overflow resistance is not enough, so that the coating directly flows into the overflow well after being filled, the cavity pressure does not change, the coating layer is not completely filled, the mold pressure is not enough to cause the bubbles to be effectively discharged, and finally the product coating layer appearance is poor.

[0240] The pressure change diagram during coating of the comparative example 2 is as shown in Figure 17 The final product is as shown in Figure 18 As shown, in the comparative example 2, under the condition that the width of the second runner 5 is 8.5 mm, the height is 0.03 mm, and the preset pressure value is 130 bar, the product coating layer bubbles can be discharged, but the overflow well appears overflow and flash, and the product and overflow area have the mold support defect.

[0241] The pressure change diagram during coating of the comparative example 3 is as shown in Figure 19 The final product is as shown in Figure 20 As shown, in the comparative example 3, under the condition that the width of the second runner 5 is 1 mm, the height is 6 mm, and the preset pressure value is 10 bar, the coating filling degree is not enough, so that the product surface appears bubbles, air trapping and other adverse effects.

[0242] According to the above examples and comparative examples, when the coating cavity has a certain overflow resistance, even if the width of the second runner 5 is 0.1-8 mm, and the height is 0.05-5 mm, when the second pressure sensor 400 detects that the pressure value is greater than 0 bar, that is, the coating flows into the first runner 3, the exhaust valve is closed, the pressure filling is carried out, and the pressure value detected by the first pressure sensor 300 during the entire coating process can reach the preset pressure value, so that the coating layer is more dense, and the adverse effects such as bubbles and air trapping are reduced.

[0243] It should be noted that the technical solutions in each embodiment of the present application can be combined with each other, but the basis for mutual combination is that it can be realized by ordinary skilled in the art; when the combination of technical solutions is contradictory or cannot be realized, it should be considered that the combination of technical solutions does not exist, that is, it is not within the protection scope of the present application.

[0244] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A venting method for a venting structure of a coating cavity used in in-mold coating processes, characterized in that, The exhaust structure includes a second flow channel, a transition flow channel, a first flow channel, and an exhaust assembly. The coating cavity, the second flow channel, the transition flow channel, and the first flow channel are sequentially connected. Wherein, the flow cross-sectional area of ​​the second flow channel is smaller than the flow cross-sectional area of ​​the coating cavity; The transition channel is an arc-shaped channel, and the angle of inclination of the transition channel gradually decreases along the fluid flow direction; The first flow channel includes an inlet end and an outlet end. The inlet end of the first flow channel is connected to the transition flow channel, and the outlet end of the first flow channel is connected to the exhaust assembly. The first flow channel has at least one bend to increase fluid flow resistance; The exhaust method includes: The pressure value is preset in the control unit through the human-computer interaction unit; The exhaust system is opened, allowing the painting chamber to connect with the outside world; The feeding device delivers coating material into the coating chamber; The first and second pressure sensors detect the pressure values ​​and transmit them to the control unit. When the pressure value detected by the second pressure sensor is greater than 0 bar, the control unit controls the exhaust assembly to shut off gas emission; During the process of the feeding device conveying coating material into the coating chamber, the pressure value detected by the first pressure sensor received by the control unit can reach the preset pressure value. The first pressure sensor is disposed on the wall of the coating chamber at the connection point with the feeding device. The first pressure sensor is electrically connected to the control unit and is used to detect the pressure value in the coating chamber and transmit it to the control unit. The second pressure sensor is disposed at the inflow end of the first flow channel and is electrically connected to the control unit. It is used to detect the pressure value at the inflow end of the first flow channel and transmit it to the control unit.

2. The venting method for the venting structure of the coating cavity in in-mold coating process according to claim 1, characterized in that, The second flow channel has a height of 0.05 mm to 5 mm and a width of 0.1 mm to 8 mm.

3. The venting method for the venting structure of the coating cavity in in-mold coating process according to claim 1, characterized in that, Along the fluid flow direction, the angle of the transition channel varies from 50° to 1°.

4. The venting method for the venting structure of the coating cavity in in-mold coating process according to claim 1, characterized in that, The curved portion is at least one of a U-shaped curved portion, an L-shaped curved portion, and an S-shaped curved portion.

5. The venting method for the venting structure of the coating cavity in in-mold coating process according to claim 1, characterized in that, An overflow well is provided between the bend of the first flow channel and the exhaust assembly. When the fluid contains coating material, the overflow well can be used to catch the coating material, thereby preventing the coating material in the fluid from entering the exhaust assembly.

6. The venting method for the venting structure of the coating cavity in in-mold coating process according to claim 1, characterized in that, The exhaust assembly includes an exhaust valve and an exhaust valve driver, the exhaust valve driver being connected to the exhaust valve and used to control the opening and closing of the exhaust valve.

7. The venting method for the venting structure of the coating cavity in in-mold coating process according to claim 1, characterized in that, The preset pressure value is any value between 20 bar and 120 bar.

8. The venting method for the venting structure of the coating cavity in in-mold coating process according to claim 1, characterized in that, The coating temperature is 30°C to 90°C, and the viscosity is 100 cps to 300 cps.

9. The venting method for the venting structure of the coating cavity in in-mold coating process according to claim 1, characterized in that, The control unit controls the feeding device to deliver the coating material into the coating chamber at a speed of 5g / min to 700g / min.

10. The venting method for the venting structure of the coating cavity in in-mold coating process according to claim 1, characterized in that, When the control unit controls the feeding device to deliver coating material into the coating chamber, the internal temperature of the coating chamber is between 80°C and 130°C.

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