Plastic film blowing forming device and forming method

Abstract

The invention relates to the technical field of plastic film production equipment, in particular to a plastic film blowing forming device and method. A die head; the film blowing forming mechanism is used for film blowing forming of the thin film; the cooling mechanism is used for cooling the film bubbles; the die head is arranged at the tail end of the screw extruder, the film blowing forming mechanism is arranged on the die head, and the cooling forming mechanism is arranged above the die head. And the arranged stabilizing disc utilizes the air holes in the side face to discharge air flow introduced into the film bubbles to the side face, annular air flow is formed, outward radial supporting force is provided for the interiors of the film bubbles, and therefore the situation that the film bubbles shake due to interference of the external environment is reduced, and the quality of the plastic film is improved. The arranged pressure release valve can control the air pressure in the film bubble, so that the air pressure in the film bubble is kept in a set range, meanwhile, the fan continuously supplies air into the film bubble to form a stable pressure environment, and fluctuation of the internal pressure caused by fluctuation of the air supply amount of the fan is reduced.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of plastic film production equipment, in particular to a plastic film blowing forming device and a forming method. BACKGROUND

[0002] The plastic film blowing forming is a high-efficiency and widely-applied film manufacturing process, and the basic process comprises the following steps: plastic raw materials are melted and plasticized through a screw extruder, are extruded into a tubular embryo through an annular die, air is then injected into the tubular embryo to make the tubular embryo blow into a film bubble, the film bubble is cooled and shaped through a cooling air ring, and the film bubble is then pulled, flattened and rolled into a film product.

[0003] In the process, the stability of the film bubble is the core key to determining the product quality and production efficiency. In the prior art, the shape of the film bubble is mainly maintained by establishing a static pressure environment higher than the ambient atmospheric pressure in the film bubble.

[0004] However, in the prior art, only the internal static pressure is relied on to form a suspended and soft air column, and in the production process, the film bubble is extremely susceptible to influences from factors such as slight fluctuations of the material flow of the extruder, uneven air flow of the external cooling air ring and air flow disturbance of the workshop environment, thereby generating low-frequency periodic oscillation or non-periodic drift. The oscillation will directly lead to problems such as uneven longitudinal thickness and surface quality reduction of the finally-formed film. In view of this, the application provides a plastic film blowing forming device and a forming method. SUMMARY

[0005] The application aims to provide a plastic film blowing forming device and a forming method, which solve the problems in the background art.

[0006] To achieve the above-mentioned purpose, the application provides the following technical scheme. A plastic film blowing forming device comprises a screw extruder. A die is arranged at the end of the screw extruder. A film blowing forming mechanism is arranged on the die. A cooling mechanism is arranged above the die. The die is arranged at the end of the screw extruder, the film blowing forming mechanism is arranged on the die, and the cooling forming mechanism is arranged above the die.

[0007] Preferably, the film blowing forming mechanism comprises a support pipe, the support pipe is fixedly connected to the die, the support pipe is arranged through the die, a stabilizing disc is rotatably connected to the top end of the support pipe, and air holes are arranged on the side surface of the stabilizing disc.

[0008] Preferably, the support pipe is fixedly connected with a support disc outside, the stabilizing disc is rotationally connected to the support disc, a groove corresponding to the structure of the support disc is formed in the bottom end of the stabilizing disc, and an impeller is fixedly connected to the bottom end of the stabilizing disc and connected to the inside of the groove.

[0009] Preferably, a pressure stabilizing hole is fixedly connected to the support disc, a pressure relief valve is connected to the inside of the pressure stabilizing hole, the support pipe comprises an air inlet pipe and an air outlet pipe, the air inlet pipe is in communication with the stabilizing disc, and the film blowing forming mechanism further comprises a fan connected to the air inlet pipe.

[0010] Preferably, the cooling and temperature reducing mechanism comprises a support tower arranged outside the die head, a moving frame slidingly connected to the support tower, and a cooling ring rotationally connected to the moving frame, and a rotating assembly for driving the cooling ring is arranged on the moving frame.

[0011] Preferably, the cooling ring has a "Fang" shaped structure in cross section, a communication pipe is fixedly connected to the moving frame and in communication with the cooling ring, and the other end of the communication pipe is in communication with the air outlet pipe.

[0012] Preferably, the rotating assembly comprises a gear ring fixedly connected to the outside of the cooling ring, a gear rotationally connected to the moving frame and in engagement with the gear ring, and a motor one fixedly connected to the moving frame and having an output end fixedly connected to the gear.

[0013] Preferably, a water tank is fixedly connected to the bottom end of the moving frame, circular air holes corresponding to each other are formed in the top end of the water tank and the bottom end of the cooling ring, the water tank is in communication with the cooling ring through the circular air holes, an ultrasonic oscillation sheet is connected to the inside of the water tank, an infrared temperature measuring device is fixedly connected to the moving frame, and a lifting assembly is arranged on the support tower.

[0014] Preferably, the lifting assembly comprises a lead screw rotationally connected to the support tower and in engagement with the moving frame, and a motor two fixedly connected to the support tower and having an output end fixedly connected to the lead screw.

[0015] A plastic film blowing forming method comprises the following steps: S1, raw material extrusion, melting and extruding the plastic raw material through a screw extruder into a tubular shape in a die head; S2, film blowing forming, the fan blows air into the film bubble to form a high pressure environment in the film bubble to keep the shape of the film bubble; S3, cooling and temperature reducing, the cooling and temperature reducing mechanism forms an annular air flow outside the film bubble to uniformly cool the film bubble; S4, traction and winding, the steel roller and the rubber roller combination realize uniform traction through pressure adjustment, and winding is realized through the winding roller.

[0016] By the above technical scheme, the application provides a plastic film blowing forming device and a forming method, which have at least the following beneficial effects: (1) The stabilizing disc is provided with air vents on the side surface, which can discharge the airflow in the film bubble to the side surface, form a ring-shaped airflow, and provide an outward radial supporting force for the inside of the film bubble, thereby reducing the shaking of the film bubble caused by the interference of the external environment and improving the quality of the plastic film.

[0017] (2) The pressure relief valve can control the air pressure in the film bubble, keep the air pressure in the film bubble within a set range, and continuously supply air to the inside of the film bubble through the fan to form a stable pressure environment, thereby reducing the fluctuation of the internal pressure caused by the fluctuation of the air supply amount of the fan.

[0018] (3) The ultrasonic oscillation sheet can atomize the cooling water, evaporate the liquid droplets formed by atomization on the surface of the film bubble, thereby dissipating the heat on the surface of the film bubble, improving the cooling effect of the film bubble, and the adjustable circular air hole structure can control the amount of atomized liquid droplets, thereby conveniently adjusting the cooling efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings, which are included to provide a further understanding of the application, constitute a part of this application: Figure 1 Structure diagram of the application Figure 1 ; Figure 2 Structure diagram of the application Figure 2 ; Figure 3 Structure diagram of the cooling and temperature reducing mechanism of the application Figure 4 Internal structure diagram of the cooling and temperature reducing mechanism of the application Figure 1 ; Figure 2 Internal structure diagram of the cooling and temperature reducing mechanism of the application Figure 6 ; Figure 5 Enlarged diagram of A in the application Figure 7 ; Figure 8 Structure diagram of the film blowing forming mechanism of the application Figure 9 Internal structure diagram of the film blowing forming mechanism of the application Figure 8 Enlarged diagram of B in the application Figures 1-9

[0020] ​In the figure: 1, screw extruder; 2, die head; 3, film blowing forming mechanism; 31, support pipe; 311, air inlet pipe; 312, exhaust pipe; 32, stabilizing disc; 33, air hole; 34, support disc; 35, groove; 36, impeller; 37, pressure stabilizing hole; 38, pressure relief valve; 39, fan; 4, cooling mechanism; 41, support tower; 42, moving frame; 43, cooling ring; 44, rotating assembly; 441, gear ring; 442, gear; 443, motor one; 45, communication pipe; 46, water tank; 47, ultrasonic oscillation sheet; 48, infrared temperature measuring device; 49, lifting assembly; 491, lead screw; 492, motor two; 5, bubble. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0022] Embodiment 1 A plastic film blowing forming device, as shown in the figure, comprises a screw extruder 1; the screw extruder 1 is provided with a die head 2 at the end, and the die head 2 is provided with a film blowing forming mechanism 3 for film blowing forming. Figures 1-6

[0023] Specifically, the film blowing forming mechanism 3 comprises a support pipe 31, which is fixedly connected to the die head 2 and passes through the die head 2, and is used for supporting part of the structure of film blowing forming. The support pipe 31 is arranged at the center position of the die head 2. After the molten plastic extruded from the screw extruder 1 is shaped into a tubular structure in the die head 2, the tubular plastic rises along the outer wall of the support pipe 31. The support pipe 31 is rotatably connected to a stabilizing disc 32 at the top end, and the stabilizing disc 32 is provided with air holes 33 on the side surface. The stabilizing disc 32 is used for stabilizing the bubble 5 of film blowing forming, reducing the shaking of the bubble 5 in the process of moving upward, improving the overall stability and the balance of thickness, and communicating with the support pipe 31. The stabilizing disc 32 discharges the air in the inside of the stabilizing disc 32 outward from the air holes 33. The rotating structure can make the air discharged from the air holes 33 form a ring structure, so as to stabilize the bubble 5. At the same time, the height of the stabilizing disc 32 is at the cooling line of the bubble 5, which provides radial support force for the bubble 5, so as to suppress the swing of the bubble 5.

[0024] ​In addition, a support disk 34 is fixedly connected to the outside of the support tube 31, and a stabilizing disk 32 is rotatably connected to the support disk 34. The support disk 34 supports the stabilizing disk 32, allowing it to rotate stably in the horizontal direction. A groove 35 corresponding to the structure of the support disk 34 is provided at the bottom of the stabilizing disk 32. The groove 35 forms a cavity, facilitating the guidance and discharge of air from inside the membrane bubble 5 when the pressure inside exceeds a preset value. An impeller 36 is fixedly connected to the bottom of the stabilizing disk 32, and is connected inside the groove 35. The impeller 36 can be driven to rotate by the airflow inside the groove 35. The impeller 36 has a concave structure, ensuring that the airflow can only drive the impeller 36 from a set direction.

[0025] Based on this, a pressure stabilizing hole 37 is fixedly connected to the support plate 34. The pressure stabilizing hole 37 is used to stabilize the gas pressure inside the membrane bubble 5 and to discharge gas when the internal gas pressure is too high. A pressure relief valve 38 is connected inside the pressure stabilizing hole 37. The pressure relief valve 38 is used to control the air pressure inside the membrane bubble 5 and can only be opened when the set gas pressure is exceeded. The support pipe 31 includes an air inlet pipe 311 and an air outlet pipe 312. The air inlet pipe 311 is interconnected with the stabilizing plate 32 and is used to introduce air into the membrane bubble 5, so that the membrane bubble 5 is kept at a set high pressure state and thus expands the membrane bubble 5. The air outlet pipe 312 is interconnected with the inside of the groove 35, and the air outlet pipe 312 and the pressure stabilizing hole 37 are respectively set at both ends of the support plate 34, so that a gas pressure difference is formed inside the groove 35 and the air flows to drive the impeller 36. The blown film forming mechanism 3 also includes a fan 39 connected to the air inlet pipe 311. The fan 39 is used to continuously introduce gas into the membrane bubble 5.

[0026] Example 2 like ​ As shown, based on Example 1, a cooling mechanism 4 is provided above the mold head 2 to cool the film bubble 5.

[0027] In this embodiment, the cooling mechanism 4 includes a support tower 41, which is located outside the mold head 2. The support tower 41 supports the entire cooling mechanism 4. A transparent protective plate is provided on the side of the support tower 41 to protect the membrane bubble 5. A movable frame 42 is slidably connected to the support tower 41, and a cooling ring 43 is rotatably connected to the movable frame 42. The movable frame 42 supports the cooling ring 43. A circular through hole is provided on the inner side of the movable frame 42, and the radius of the circular through hole is larger than the radius of the membrane bubble 5, allowing the cooling ring 43 to rotate inside the circular through hole. A rotating assembly 44 is provided on the movable frame 42 to drive the cooling ring 43. The rotating assembly 44 drives the movable frame 42 to rotate and adjust its position.

[0028] Further, the cooling ring 43 is in the shape of a "Fang" character, and the Fang-shaped cooling ring 43 can form a containing cavity for mixing the atomized droplets and the cooling air. Cooling holes are formed in the inner side of the cooling ring 43, and the cooling holes are in the shape of strips, and the direction of the air flow discharged from the cooling holes is the same as the tangent direction of the film bubble 5. The moving frame 42 is fixedly connected with a communication pipe 45, the communication pipe 45 is in communication with the cooling ring 43, the other end of the communication pipe 45 is in communication with the exhaust pipe 312, and the communication pipe 45 is used to guide the gas discharged from the inside of the film bubble 5 into the containing cavity of the cooling ring 43. Since the communication pipe 45 is directly in communication with the inside of the film bubble 5, when the gas pressure in the film bubble 5 fluctuates under the condition that the air supply amount of the fan 39 is constant, the cooling air amount provided by the cooling ring 43 changes synchronously to adapt to the film bubble 5, thereby reducing the probability of the film bubble 5 shaking.

[0029] It is worth noting that the rotating assembly 44 includes a gear ring 441 fixedly connected to the outer side of the cooling ring 43, and the moving frame 42 is rotatably connected with a gear 442 engaged with the gear ring 441. The gear 442 is used to cooperate with the gear ring 441 and drive the rotation of the cooling ring 43. The moving frame 42 is fixedly connected with a motor 443, the output end of the motor 443 is fixedly connected with the gear 442, and the motor 443 is used to drive the rotation of the gear 442, so that the cooling ring 43 can be rotated through the meshing gear ring 441.

[0030] On this basis, the moving frame 42 is fixedly connected with a water tank 46 at the bottom end, and the top end of the water tank 46 and the bottom end of the cooling ring 43 are provided with circular air holes corresponding to each other. The dislocation of the circular air holes can be realized by the rotation of the cooling ring 43, so that the opening of the circular air hole can be conveniently adjusted. The water tank 46 is in communication with the cooling ring 43 through the circular air hole, the water tank 46 contains cooling water, and the water tank 46 is connected with a water inlet pipe for supplementing the cooling water in the water tank 46. The communication pipe 45 is coiled and stacked in the bottom end of the water tank 46, so that the cooling water can be used to cool and cool the air in the communication pipe 45, thereby improving the cooling effect of the film bubble 5. The water tank 46 is connected with an ultrasonic oscillation sheet 47, which can ultrasonic atomize the cooling water to form atomized droplets. Since the water tank 46 is in communication with the cooling ring 43, the atomized droplets can be mixed with the cooling air to form a high-humidity cooling air ring to cool the film bubble 5.

[0031] It is worth mentioning that the mobile frame 42 is fixedly connected with an infrared temperature measuring device 48, the infrared temperature measuring device 48 is electrically connected with the motor 1 443, the infrared temperature measuring device 48 can detect the temperature of the film bubble 5 surface in real time, and adjust the opening of the circular air hole according to the detected temperature, so that the content of the atomized liquid droplets in the cooling air flow blown out by the cooling ring 43 is self-adaptively adjusted according to the temperature of the film bubble 5 surface, so that the cooling efficiency of the film bubble 5 is in the set range interval, avoiding the surface temperature of the film bubble 5 from fluctuating sharply to affect the quality of the film bubble 5, in the embodiment, the infrared temperature measuring device 48 selects an infrared radiation thermometer.

[0032] Further, the support tower 41 is provided with a lifting assembly 49, the lifting assembly 49 can adjust the position of the mobile frame 42, so that the cooling height of the cooling ring 43 can be conveniently controlled. The lifting assembly 49 includes a lead screw 491 rotatably connected to the support tower 41, the lead screw 491 is engaged with the mobile frame 42, the lead screw 491 can drive the engaged mobile frame 42 to move up and down along the lead screw 491, in addition, the lead screw 491 has a self-locking function, after driving the mobile frame 42, the mobile frame 42 can be kept at a set height. At the same time, the support tower 41 is also provided with a guide rod parallel to the lead screw 491, for guiding the movement of the mobile frame 42, the mobile frame 42 is slidingly connected to the guide rod. The support tower 41 is fixedly connected with a motor 2 492, the output end of the motor 2 492 is fixedly connected with the lead screw 491, the motor 2 492 can drive the lead screw 491.

[0033] The plastic blowing film forming device in the application uses plastic to melt and extrude through the screw extruder 1, and forms a film bubble 5 after forming through the die head 2. The fan 39 continuously introduces air into the stabilizing disc 32 through the air inlet pipe 311, and the air in the stabilizing disc 32 is discharged from the air holes 33 to the film bubble 5. The air pressure in the film bubble 5 continuously increases and expands the film bubble 5 by air pressure. When the air pressure in the film bubble 5 is greater than a set value, the pressure relief valve 38 is opened by the air pressure, and the internal air flows into the groove 35. Because the air pressure inside the groove 35 near the stabilizing hole 37 is higher than that near the air outlet pipe 312, the air inside the groove 35 flows from the stabilizing hole 37 to the air outlet pipe 312. The air drives the stabilizing disc 32 to rotate by the impeller 36 in the process of flowing, so that the air discharged from the air holes 33 forms an air ring to stabilize the film bubble 5. After the air is discharged from the air outlet pipe 312, it flows into the cooling ring 43 through the connected communication pipe 45 and after being cooled in the communication pipe 45 immersed in the cooling water. As the air pressure in the cooling ring 43 gradually increases, the air is discharged from the cooling ring 43 to form a cooling air flow and cool the film bubble 5. At the same time, the ultrasonic oscillation sheet 47 atomizes the cooling water into atomized droplets, which flow into the cooling ring 43 from the circular air holes and mix with the cooling air flow. After the atomized droplets flow to the surface of the film bubble 5, they evaporate to cool and lower the temperature of the film bubble 5. In the process of cooling, the infrared temperature measuring device 48 detects the temperature of the surface of the film bubble 5 in real time, and controls the motor 1 443 according to the detected temperature. The motor 1 443 drives the gear ring 441 and the cooling hole to rotate through the gear 442. When the temperature detected by the infrared temperature measuring device 48 increases, the opening degree of the circular air hole increases to increase the amount of atomized droplets and improve the cooling efficiency. When the temperature detected by the infrared temperature measuring device 48 decreases, the opening degree of the circular air hole decreases to reduce the amount of atomized droplets and reduce the cooling efficiency.

[0034] Example 3 A plastic blowing film forming method, comprising the following steps: The main raw material plastic particles are mixed with functional additives in a precise ratio, and are sent into the hopper of the extruder through a vacuum feeding machine. The screw in the extruder rotates to forwardly convey and compact the solid particles. In the compression section and the metering section of the screw, the material is subjected to the double action of external heating and internal shearing, and is completely melted into a uniform viscous flow state melt. The metering section of the screw pushes the melt uniformly, at a constant pressure and quantity, to the die head 2. After the plastic melt from the extruder enters the annular die head 2, the melt is uniformly distributed in the flow channel inside the die head 2, is extruded from the annular die lip gap, and forms a vertical upward hollow thin-walled tube blank.

[0035] The fan 39 blows air at a certain pressure from the support pipe 31 in the center of the die head 2 into the inside of the tube blank, so that the tube blank rapidly expands to form a film bubble 5.

[0036] The cooling mechanism 4 sprays high-speed, uniform cold air circulation onto the outer surface of the membrane bubble 5, causing the heat of the membrane bubble 5 to dissipate rapidly.

[0037] The film bubble 5 first passes through a herringbone clamp and is flattened to form a double-layer flat film. The flattened film is clamped by a pair of traction rollers with a constant linear speed and pulled upward. Finally, the film is wound into a roll by a winding machine.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A plastic blown film forming device, characterized in that: It includes a screw extruder (1); a die head (2); a film blowing forming mechanism (3) for film blowing forming; a cooling mechanism (4) for cooling the film bubble (5); The die head (2) is arranged at the end of the screw extruder (1), the film blowing forming mechanism (3) is arranged on the die head (2), and the cooling forming mechanism is arranged above the die head (2).

2. The plastic blown film forming device according to claim 1, characterized in that: The film blowing forming mechanism (3) includes a support pipe (31), the support pipe (31) is fixedly connected to the die head (2), the support pipe (31) is arranged through the die head (2), a stabilizing disk (32) is rotatably connected to the top end of the support pipe (31), and air vent holes (33) are formed on the side surface of the stabilizing disk (32).

3. The plastic blown film forming device according to claim 2, characterized in that: A support disk (34) is fixedly connected to the outside of the support pipe (31), the stabilizing disk (32) is rotatably connected to the support disk (34), a groove (35) corresponding to the structure of the support disk (34) is formed at the bottom end of the stabilizing disk (32), an impeller (36) is fixedly connected to the bottom end of the stabilizing disk (32), and the impeller (36) is connected inside the groove (35).

4. The plastic blown film forming apparatus according to claim 3, characterized in that: A pressure stabilizing hole (37) is fixedly connected to the support disk (34), a pressure relief valve (38) is connected inside the pressure stabilizing hole (37), the support pipe (31) includes an air inlet pipe (311) and an exhaust pipe (312), the air inlet pipe (311) is communicated with the stabilizing disk (32), and the film blowing forming mechanism (3) further includes a blower (39) connected to the air inlet pipe (311).

5. The plastic blown film forming apparatus according to claim 1, characterized in that: The cooling mechanism (4) includes a support tower (41), the support tower (41) is arranged outside the die head (2), a moving frame (42) is slidably connected to the support tower (41), a cooling ring (43) is rotatably connected to the moving frame (42), and a rotating component (44) for driving the cooling ring (43) is arranged on the moving frame (42).

6. The plastic blown film forming apparatus according to claim 5, characterized in that: The cross section of the cooling ring (43) is in a "C" - shaped structure, a connecting pipe (45) is fixedly connected to the moving frame (42), the connecting pipe (45) is communicated with the cooling ring (43), and the other end of the connecting pipe (45) is communicated with the exhaust pipe (312).

7. A plastic blown film forming apparatus according to claim 5, characterized in that: The rotating component (44) includes a toothed ring (441) fixedly connected to the outside of the cooling ring (43), a gear (442) meshing with the toothed ring (441) is rotatably connected to the moving frame (42), and a motor one (443) is fixedly connected to the moving frame (42), and the output end of the motor one (443) is fixedly connected to the gear (442).

8. A plastic blown film forming apparatus according to claim 5, characterized in that: A water tank (46) is fixedly connected to the bottom end of the moving frame (42), circular air holes corresponding to each other are formed at the top end of the water tank (46) and the bottom end of the cooling ring (43), the water tank (46) is communicated with the cooling ring (43) through the circular air holes, an ultrasonic vibration sheet (47) is connected inside the water tank (46), an infrared temperature measuring device (48) is fixedly connected to the moving frame (42), and a lifting component (49) is arranged on the support tower (41).

9. A plastic blown film forming apparatus according to claim 8, characterized in that: The lifting assembly (49) includes a lead screw (491) rotatably connected to a support tower (41), the lead screw (491) meshing with a moving frame (42), and a motor (492) fixedly connected to the support tower (41), the output end of the motor (492) being fixedly connected to the lead screw (491).

10. A method for plastic blown film forming, used in a plastic blown film forming apparatus as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Raw material extrusion: The plastic raw material is melted and extruded into the die head (2) through the screw extruder (1) to form a tube; S2, blown film forming, the blower (39) blows air into the film bubble (5) and creates a high-pressure environment inside the film bubble (5) to keep the film bubble (5) in shape; S3. Cooling and cooling mechanism (4) forms an annular airflow on the outside of the membrane bubble (5) to uniformly cool the membrane bubble (5); S4. Traction and winding: The combination of steel roller and rubber roller achieves uniform traction through pressure adjustment, and is wound up by winding roller.

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