PVA film blowing machine air ring structure

Abstract

The utility model relates to PVA blown film machine technical field, concretely is PVA blown film machine air ring structure, including air ring main part, the inside of air ring main part is provided with first air flue and second air flue, is separated through partition piece between first air flue and second air flue, first air flue and second air flue are annular structure, and the partition piece includes expansion section and contraction section, so that the air inlet space of first air flue is greater than the air outlet space, and the air inlet space of second air flue is less than the air outlet space. In the PVA blown film machine air ring structure, double air flue annular design + gradual change flow channel, realize air flow accurate distribution: the first air flue and second air flue in the inside of air ring main part are annular structure, cooperate the expansion section and contraction section of partition piece, make the first air flue form the gradual change structure of " air inlet space big, air outlet space small", and the second air flue forms the reverse gradual change structure of " air inlet space small, air outlet space big".

Description

Technical Field

[0001] This utility model relates to the field of PVA blown film machine technology, and more specifically, to the air ring structure of a PVA blown film machine. Background Technology

[0002] PVA Definition: Polyvinyl alcohol (PVA) water-soluble film, or simply PVA film, is a high-performance, biodegradable, and environmentally friendly packaging material. Its main component is PVA resin, polymerized from vinyl alcohol monomers. It possesses excellent water solubility, biodegradability, gas barrier properties, transparency, and antistatic properties, making it widely used in pharmaceutical packaging, agricultural coating, and many other fields. The blown film method, as the mainstream production process for PVA water-soluble films, offers advantages over the casting method in terms of stable product quality, high production efficiency, and lower cost. However, it still needs to address inherent challenges such as the close proximity of PVA resin decomposition and processing temperatures, high melt viscosity, poor fluidity, and slow cooling rate.

[0003] In the PVA blown film production process, the air ring, as a core component for cooling and shaping the film bubble, directly determines the thickness uniformity, appearance quality, and production stability of the PVA water-soluble film. Due to the high cooling sensitivity of PVA melt, differences in cooling rates can easily lead to uneven film crystallization, thus affecting key properties such as water solubility. Therefore, the airflow control precision of the air ring is required to be far greater than that of ordinary plastic blown film. However, existing PVA blown film machines generally use the structural design of general plastic blown film equipment, which has the following specific defects: Poor cooling uniformity and insufficient adaptability: Existing air rings mostly adopt a single air duct or a simple double-layer air duct design, lacking a precise airflow guiding structure, resulting in uneven circumferential distribution of cooling air, with airflow velocity fluctuations exceeding 20%. For PVA films with high viscosity and narrow forming windows, excessively rapid local cooling can easily cause film shrinkage and wrinkling, while insufficient cooling leads to film sagging and displacement, directly causing film thickness differences exceeding 5%, and failing to meet the differentiated cooling requirements of PVA water-soluble films with different thicknesses (0.01-0.1mm). Although some double-layer air rings have internal and external air ducts, the lack of a gradual change design in the flow channel cross-section results in insufficient airflow stability, further exacerbating the problem of uneven film cooling. Low cooling efficiency restricts production capacity: The slow cooling rate of PVA melt places high demands on the heat dissipation efficiency of the air ring, but existing air rings generally suffer from poor airflow rectification and rapid attenuation of air velocity at the outlet. Most air rings use multi-hole outlets or wide-gap designs, resulting in air pressure loss of up to 30%, failing to form a high-speed, uniform cooling airflow layer. This leads to a prolonged film bubble cooling and setting time of over 30 seconds, reducing production efficiency by 40% compared to the theoretical value. Furthermore, untimely cooling easily causes film bubble adhesion, film breakage, and other malfunctions, especially in PVA blown film processes with die temperatures of 140-155℃, where the downtime rate can reach as high as 15%. Utility Model Content

[0004] The purpose of this invention is to provide a PVA blown film machine air ring structure to solve the problem mentioned in the background art that existing air rings mostly adopt a single air duct or a simple double-layer air duct design, and the airflow channel lacks a precise flow guiding structure, resulting in uneven distribution of cooling air in the circumference.

[0005] To achieve the above objectives, this utility model provides a PVA blown film machine air ring structure, including an air ring body. The air ring body has a first air duct and a second air duct inside. The first air duct and the second air duct are separated by a separator. Both the first air duct and the second air duct are annular structures. The separator includes an expansion section and a contraction section, such that the air inlet space of the first air duct is larger than the air outlet space, and the air inlet space of the second air duct is smaller than the air outlet space.

[0006] This design constructs the core cooling flow channel using a "dual-ring air duct + gradient separator": the first and second air ducts inside the main air ring are separated by a separator, forming independent annular airflow channels. The expansion and contraction sections of the separator act on the two air ducts respectively—for the first air duct, the expansion section increases the intake space, while the contraction section reduces the exhaust space, resulting in a "wide intake, narrow exhaust" structure; for the second air duct, the opposite is true, with the expansion section on the intake side and the contraction section on the exhaust side, forming a "narrow intake, wide exhaust" structure. This design follows the principles of airflow dynamics: "wide intake, narrow exhaust" can achieve airflow pressurization and acceleration through channel contraction, while "narrow intake, wide exhaust" can achieve airflow stabilization and reduced impact through channel expansion, thereby differentiating and controlling the cooling air between the inner and outer layers.

[0007] Preferably, the first air duct is located inside the partition, one end of the first air duct is provided with a first annular air inlet, and the other end of the first air duct is provided with an inner air outlet.

[0008] This design clearly defines the spatial location (inside the separator) and port structure of the first air duct: a first annular air inlet is provided at the inlet end, and an inner air outlet is provided at the outlet end, forming an airflow path of "annular air inlet - inner air outlet". The inner layout allows the cooling air of the first air duct to act directly on the inner surface of the membrane bubble. With the "wide inlet and narrow outlet" structure, the cooling air is converged in an annular manner after passing through the first annular air inlet, accelerated along the contraction channel, and finally blown directionally to the inner side of the membrane bubble from the inner air outlet, achieving precise cooling of the inner side.

[0009] Preferably, the second air duct is located outside the partition, with a second annular air inlet at one end and an air outlet at the other end.

[0010] This configuration corresponds to the first air duct, clearly defining the second air duct as located outside the separator. A second annular air inlet is provided at the inlet end, and an outlet air outlet is provided at the outlet end, forming an airflow path of "annular air inlet - outer outlet". The outer layout allows the cooling air from the second air duct to cover the outer surface of the membrane bubble. Combined with the "narrow inlet, wide outlet" structure, the cooling air enters through the narrow opening of the second annular air inlet, then diffuses smoothly along the extended flow channel, and is evenly blown outwards from the outlet air outlet to the outer side of the membrane bubble, achieving stable cooling on the outer side.

[0011] Preferably, a guide ring is installed on the main body of the air ring near the first annular air inlet, and an inner air inlet is provided in the middle of the guide ring.

[0012] This feature involves installing a guide ring near the first annular air inlet on the main body of the air duct. Its core function is "airflow guidance and supplementation": the inner air inlet in the middle of the guide ring can directly introduce external cooling air, while the annular structure of the guide ring can guide the airflow to the first annular air inlet, forming a dual airflow supply path of "inner air inlet supplementation + guide ring air guidance", ensuring that the first air duct receives a sufficient and stable airflow source and avoiding cooling blind spots in the first annular air inlet due to insufficient local airflow.

[0013] Preferably, the outer wall of the guide ring is provided with a threaded portion, the air ring body is provided with a threaded opening, and the threaded portion of the guide ring is threadedly connected to the threaded opening on the air ring body.

[0014] This design achieves a threaded connection between the guide ring and the main body of the air ring through a threaded engagement of the threaded portion on the outer wall of the guide ring. The threaded structure has a "rotatable adjustment" feature: rotating the guide ring changes its axial position within the main body of the air ring—when screwed in, the guide ring is closer to the first annular air inlet, which can reduce the air inlet gap and enhance the airflow pressurization effect; when screwed out, the air inlet gap widens and the airflow resistance decreases, allowing for flexible adjustment of the airflow volume and air pressure in the first air duct.

[0015] Preferably, the guide ring is provided with a guide slope near the first air duct to guide the airflow to the inner air outlet for ejection.

[0016] This feature includes a guide slope on the side of the guide ring near the first air duct. This slope follows the fluid mechanics principle of "sloping surface guidance": the cooling air entering from the first annular air inlet is guided by the slope and its airflow direction is changed from "radial inflow" to "directional flow along the slope towards the inward air outlet". This avoids the airflow directly impacting the air duct wall and causing energy loss, while ensuring that the airflow is evenly integrated into the first air duct and reducing airflow eddies.

[0017] Preferably, a heat insulation pad is installed on the outer side of the air outlet end of the air ring body, and a connecting seat is installed at the air inlet end of the air ring body, and the connecting seat is connected and fixed to the blown film machine host.

[0018] This setup incorporates auxiliary structures designed to protect against high-temperature effects and ensure equipment stability: a heat insulation pad is installed at the air outlet of the air ring (near the die of the blown film machine) to block the high temperature from the die from being conducted to the air ring, thus preventing the cooling air in the air duct from being preheated; a connecting seat is installed at the air inlet to fix the air ring to the blown film machine, ensuring that the air ring, die, and film bubble are coaxial and preventing airflow deviation caused by installation misalignment.

[0019] Preferably, the connection between the extended section and the contracted section is a rounded corner structure.

[0020] This feature incorporates a rounded corner structure at the connection between the expansion and contraction sections of the separator, replacing the existing right-angle structure. According to fluid mechanics principles, right-angle structures easily lead to the formation of vortices and energy loss at the turning points; rounded corner structures allow the airflow to transition smoothly along the curved surface, reducing airflow impact and vortices, lowering wind pressure loss, and maintaining airflow stability.

[0021] Compared with the prior art, the beneficial effects of this utility model are as follows: In this PVA blown film machine's air ring structure, a dual-air-duct annular design combined with a gradient flow channel achieves precise airflow distribution. Both the first and second air ducts within the main body of the air ring are annular structures. Combined with the expansion and contraction sections of the separator, the first air duct forms a gradient structure with a large intake space and a small exhaust space, while the second air duct forms a reverse gradient structure with a small intake space and a large exhaust space. This design can rectify and pressurize the cooling air for both the inner and outer layers: the first air duct (inner side) increases the air velocity at the inner outlet through a contraction flow channel, ensuring uniform coverage of the cooling air inside the film bubble; the second air duct (outer side) reduces airflow impact through an expansion flow channel, resulting in a stable distribution of airflow at the outer outlet. The combined effect of these two elements leads to a more uniform circumferential airflow velocity distribution, effectively improving the problem of large airflow fluctuations in existing technologies. For PVA melts with high viscosity and narrow forming window, it can effectively avoid membrane bubble wrinkling caused by excessively rapid local cooling and membrane bubble sagging caused by excessively slow cooling, significantly improve the thickness uniformity and appearance quality of PVA water-soluble film, and at the same time ensure the consistency of film material crystallization, avoiding the impact of core properties such as water solubility on uneven cooling. Rounded corner transitions reduce airflow eddies and further optimize airflow stability: The connection between the expansion and contraction sections of the separator adopts a rounded corner structure. Compared with the right-angle air duct design in the existing technology, it can significantly reduce the impact and eddy phenomenon of airflow at the flow channel turning point, reduce airflow energy loss, and allow the cooling air to act on the membrane bubble surface in a more stable laminar flow state, further improving cooling uniformity, especially suitable for the stringent requirements of PVA water-soluble membranes for a stable cooling environment.

[0022] The constricted flow channel design of the first air duct enhances the air pressure at the inner outlet, while the expanded flow channel design of the second air duct increases the coverage of the outer outlet. The combination of these two features allows the cooling air to quickly form a highly efficient cooling airflow layer enveloping the film bubble, significantly reducing air pressure loss. Simultaneously, the heat insulation pad installed at the air outlet of the air ring effectively blocks high-temperature conduction from the blown film die, preventing preheating of the cooling air within the air duct and ensuring stable initial cooling air temperature, further improving heat dissipation efficiency. Based on this, the cooling and setting speed of the PVA film bubble is significantly accelerated, effectively shortening the production cycle, increasing the production capacity of PVA water-soluble films, and addressing the problem of low cooling efficiency in existing technologies. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of this utility model; Figure 2 This is a schematic diagram of the flow guide ring in this utility model; Figure 3 This is a schematic diagram of the structure of the separator in this utility model; The meanings of the labels in the diagram are as follows: 1. Air ring body; 11. First air duct; 111. First annular air inlet; 112. Inner air outlet; 12. Second air duct; 121. Second annular air inlet; 122. Outer air outlet; 2. Guide ring; 21. Inner air inlet; 22. Threaded part; 23. Guide slope; 3. Separator; 31. Expansion section; 32. Contraction section; 4. Heat insulation pad; 5. Connecting seat. Detailed Implementation

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0025] This utility model provides a PVA blown film machine air ring structure, such as Figures 1-3 As shown, the device includes a main body 1 of the air ring. The interior of the main body 1 of the air ring has a first air duct 11 and a second air duct 12. The first air duct 11 and the second air duct 12 are separated by a separator 3. Both the first air duct 11 and the second air duct 12 are annular structures. The separator 3 includes an extension section 31 and a contraction section 32, which makes the air intake space of the first air duct 11 larger than the air outlet space, and the air intake space of the second air duct 12 smaller than the air outlet space.

[0026] In use, the core cooling flow channel is constructed through a "double-ring air duct + gradient separator 3": the first air duct 11 and the second air duct 12 inside the air ring body 1 form an independent annular airflow channel with the separator 3 as the boundary; the expansion section 31 and the contraction section 32 of the separator 3 act on the two air ducts respectively—for the first air duct 11, the expansion section 31 expands the space on the air intake side and the contraction section 32 shrinks the space on the air outlet side, making the first air duct 11 have a "wide inlet and narrow outlet" structure; for the second air duct 12, the opposite is true, with the expansion section 31 located on the air intake side and the contraction section 32 located on the air outlet side, forming a "narrow inlet and wide outlet" structure. This design follows the principle of airflow dynamics: "wide inlet and narrow outlet" can achieve airflow pressurization and acceleration through flow channel contraction, while "narrow inlet and wide outlet" can achieve airflow stabilization and reduced impact through flow channel expansion, thereby differentiating and controlling the cooling air of the inner and outer layers.

[0027] Effects: Addressing the high viscosity and cooling sensitivity of PVA melt, the dual-channel gradient structure solves the problems of uneven airflow and inability to control airflow in existing single-channel systems. The pressurization and acceleration of the first channel 11 ensures strong cooling airflow to the inside of the membrane bubble, preventing the PVA melt from sagging due to insufficient cooling on the inside. The stabilization and impact reduction of the second channel 12 ensures uniform cooling airflow coverage on the outside of the membrane bubble, preventing excessively rapid cooling on the outside and subsequent wrinkling. Simultaneously, the annular structure of the first and second channels 12 ensures consistent circumferential distribution of cooling airflow, preventing uneven crystallization of the PVA water-soluble film due to cooling differences, thereby guaranteeing the core properties of the membrane material, such as water solubility and thickness uniformity.

[0028] In this embodiment, the first air duct 11 is located inside the partition 3. One end of the first air duct 11 is provided with a first annular air inlet 111, and the other end of the first air duct 11 is provided with an inner air outlet 112.

[0029] In use, the spatial location (inside the separator 3) and port structure of the first air duct 11 are clearly defined: the air inlet end is provided with a first annular air inlet 111, and the air outlet end is provided with an inner air outlet 112, forming an airflow path of "annular air inlet - inner air outlet". The inner layout allows the cooling air of the first air duct 11 to act directly on the inner surface of the membrane bubble. With the "wide inlet and narrow outlet" structure of the first air duct 11, the cooling air is gathered in an annular shape through the first annular air inlet 111, accelerated along the contraction channel of the first air duct 11, and finally blown directionally to the inner side of the membrane bubble from the inner air outlet 112, achieving "precise inner cooling". Effect: Addressing the pain points of "difficulty in cooling the inner side of the PVA blown film and easy adhesion due to excessive temperature" in PVA blown film production, the inner design of the first air duct 11 fills the gap of the existing air ring which "emphasizes external cooling and neglects internal cooling": the inner air outlet 112 acts directly on the inner side of the film bubble, which can quickly remove the heat inside the PVA melt and avoid the film bubble adhesion caused by residual high temperature on the inner side; the first annular air inlet 111 ensures that the airflow is uniformly integrated into the first air duct 11 in the circumferential direction, avoids uneven internal cooling caused by insufficient local air intake, further improves the cooling consistency of the inner and outer sides of the PVA water-soluble film, and reduces the risk of film deformation.

[0030] Specifically, the second air duct 12 is located outside the partition 3. One end of the second air duct 12 is provided with a second annular air inlet 121, and the other end of the second air duct 12 is provided with an outlet air vent 122.

[0031] In use, corresponding to the first air duct 11, the second air duct 12 is located outside the separator 3. The air inlet end is provided with a second annular air inlet 121, and the air outlet end is provided with an outlet 122, forming an airflow path of "annular air inlet - outer air outlet". The outer layout allows the cooling air of the second air duct 12 to cover the outer surface of the membrane bubble. Combined with the "narrow inlet and wide outlet" structure of the second air duct 12, the cooling air enters through the narrow opening of the second annular air inlet 121 and then diffuses smoothly along the extended flow channel of the second air duct 12, and is evenly blown to the outer side of the membrane bubble from the outlet 122, achieving "smooth cooling on the outer side".

[0032] Effect: To address the issue of "susceptibility to wrinkling due to airflow impact" on the outer side of PVA membrane bubbles, the "narrow inlet and wide outlet + outer air outlet" design of the second air duct 12 solves the defects of "large airflow impact and uneven coverage" in existing outer air ducts: The expanded flow channel of the second air duct 12 changes the airflow from "high-speed impact" to "stable coverage", avoiding surface wrinkling of PVA melt due to the impact of outer airflow; the second annular air inlet 121 and the outer air outlet 122 work together to ensure uniform circumferential cooling on the outer side of the membrane bubble, preventing thickness differences in the PVA water-soluble film due to differences in outer cooling, and improving the appearance quality of the membrane material.

[0033] Furthermore, a guide ring 2 is installed on the main body 1 of the air ring near the first annular air inlet 111, and an inner air inlet 21 is provided in the middle of the guide ring 2.

[0034] In use, a guide ring 2 is installed on the main body 1 of the air ring near the first annular air inlet 111. Its core function is "airflow guidance and supplementation": the inner air inlet 21 in the middle of the guide ring 2 can directly introduce external cooling air, and at the same time, the annular structure of the guide ring 2 can guide the airflow to the first annular air inlet 111, forming a dual airflow supply path of "inner air inlet 21 supplementing air + guide ring 2 guiding airflow", ensuring that the first air duct 11 obtains a sufficient and stable airflow source, and avoiding the first annular air inlet 111 from having a cooling blind zone due to insufficient local airflow.

[0035] Effect: In response to the problem of insufficient air intake in the first air duct 11 of the existing air ring, which easily affects the cooling efficiency due to air shortage, the guide ring 2 is designed to provide a stable airflow guarantee for the first air duct 11: the cooling air supplemented by the inner air inlet 21 can enhance the air volume of the first air duct 11, especially suitable for the need of thick PVA water-soluble film to "require stronger internal cooling"; the air guiding effect of the guide ring 2 avoids the dispersion and waste of airflow, improves the airflow utilization rate of the first air duct 11, ensures the stability of the internal cooling intensity of the PVA film bubble, and reduces the decrease in cooling efficiency caused by insufficient air intake.

[0036] Furthermore, the outer wall of the guide ring 2 is provided with a threaded portion 22, and the air ring body 1 is provided with a threaded opening. The threaded portion (22) of the guide ring 2 is threadedly connected to the threaded opening on the air ring body 1.

[0037] In use, the threaded portion 22 on the outer wall of the guide ring 2 engages with the threaded opening of the air ring body 1 to achieve a threaded connection. The threaded structure has a "rotatable adjustment" characteristic: rotating the guide ring 2 can change its axial position within the air ring body 1—when screwed in, the guide ring 2 is closer to the first annular air inlet 111, which can reduce the air inlet gap and enhance the airflow pressurization effect of the first air duct 11; when screwed out, the air inlet gap expands and the airflow resistance decreases, realizing flexible adjustment of the airflow volume and air pressure of the first air duct 11. Results: This solves the problem of existing air rings having "fixed cooling parameters and being unable to adapt to PVA film materials of different thicknesses": When producing thin PVA water-soluble films, screwing in the guide ring 2 enhances the air pressure of the first air duct 11, which can quickly cool the thin film and prevent overheating; when producing thick films, screwing out the guide ring 2 increases the air intake of the first air duct 11, meeting the need for thick films to "require more cooling air"; the air duct can be adjusted without disassembling it, which greatly shortens the debugging time for switching PVA film material specifications, reduces transition material loss, and improves production flexibility.

[0038] Furthermore, the guide ring 2 is provided with a guide slope 23 near the first air duct 11 to guide the airflow to the inner air outlet 112 for ejection.

[0039] In use, a guide slope 23 is set on the side of the guide ring 2 near the first air duct 11. This slope follows the fluid mechanics principle of "slope guidance": the cooling air entering from the first annular air inlet 111 is guided by the guide slope 23 and changes the airflow direction, changing from "radial inflow" to "directional flow along the guide slope 23 to the inner air outlet 112", avoiding the airflow from directly impacting the wall of the first air duct 11 and causing energy loss, while ensuring that the airflow is evenly integrated into the first air duct 11 and reducing airflow eddies. Effects: To address the problems of "turbulent airflow and large pressure loss" in existing airflow guiding structures, the guide slope 23 improves the airflow quality of the first air duct 11: directional airflow reduces airflow eddies and avoids uneven cooling inside the PVA film bubble due to airflow turbulence; reducing pressure loss ensures that the cooling air of the first air duct 11 maintains sufficient intensity and avoids a decrease in the cooling rate of the PVA melt due to pressure attenuation; at the same time, the uniformly integrated airflow further ensures consistent circumferential cooling of the first air duct 11 and reduces the fluctuation of the PVA water-soluble film thickness.

[0040] Furthermore, a heat insulation pad 4 is installed on the outer side of the air outlet end of the air ring body 1, and a connecting seat 5 is installed at the air inlet end of the air ring body 1. The connecting seat 5 is connected and fixed to the blown film machine host.

[0041] During use, auxiliary structures are designed from two aspects: "preventing the influence of high temperature" and "equipment fixation": heat insulation pad 4 is installed on the outside of the air outlet of the air ring body 1. The heat insulation material properties of the heat insulation pad 4 are used to block the high temperature of the blown film machine die from being conducted to the air ring body 1, so as to prevent the cooling air in the first air duct 11 and the second air duct 12 from being preheated; a connecting seat 5 is installed at the air inlet of the air ring body 1. The air ring body 1 is connected and fixed to the blown film machine host through the connecting seat 5, so as to ensure that the air ring body 1 is coaxial with the die and the film bubble, and to avoid the airflow deviation of the first air duct 11 and the second air duct 12 caused by installation deviation. Effects: Addressing the issues of "high temperature at the die opening affecting cooling air temperature and installation deviation causing cooling offset" in PVA blown film production: The heat insulation pad 4 prevents preheating of the cooling air, ensuring stable initial cooling air temperature in the first air duct 11 and the second air duct 12, improving the cooling efficiency of the PVA melt, and preventing slow film bubble setting due to increased cooling air temperature; the precise fixing of the connecting seat 5 ensures that the air ring body 1 and the film bubble are coaxial, preventing the cooling air in the first air duct 11 and the second air duct 12 from being biased to one side, causing the PVA water-soluble film to cool too quickly on one side, further improving the uniformity of the film material, while enhancing the stability of equipment operation and reducing failures caused by loose installation.

[0042] Furthermore, the connection between the extended section 31 and the contracted section 32 is a rounded corner structure.

[0043] In use, a rounded corner structure is adopted at the connection between the extended section 31 and the contracted section 32 of the separator 3, replacing the existing right-angle structure. According to the principles of fluid mechanics, a right-angle structure is prone to causing vortices to form in the airflow at the turning point, resulting in energy loss; the rounded corner structure allows the airflow to transition smoothly along the arc surface, reducing airflow impact and vortices, reducing the wind pressure loss in the first air duct 11 and the second air duct 12, and maintaining airflow stability. Effects: This solves the problem of "right-angle turns causing airflow turbulence" in existing separators: rounded corner transitions reduce airflow eddies, ensuring that the cooling air in the first air duct 11 and the second air duct 12 maintains a stable flow, avoiding localized cooling abnormalities in PVA membrane bubbles due to airflow turbulence; reducing air pressure loss allows the cooling air in the first air duct 11 and the second air duct 12 to maintain sufficient intensity, improving the cooling speed of the PVA melt, while reducing airflow impact damage to the surface of the PVA membrane bubble, ensuring the smoothness of the membrane material, and further improving the quality of PVA water-soluble membrane products.

[0044] When the air ring structure of this utility model is used in a PVA blown film machine, the specific working process of the air ring can be divided into four stages, depending on the PVA blown film production scenario: "airflow introduction - flow channel distribution - film bubble cooling - adjustment and adaptation". The detailed process is as follows: Phase 1: Airflow Introduction and Preliminary Distribution After the PVA blown film machine starts, the cooling air generated by the cooling fan is divided into two paths and enters the air ring: The first airflow flows into the first air duct 11: part of the cooling air enters directly through the first annular air inlet 111 and is guided by the guide slope 23 on the side of the guide ring 2 near the first air duct 11. The airflow changes from "radial inflow" to "directional flow to the inner air outlet 112", avoiding energy loss caused by the airflow impacting the wall of the first air duct 11. At the same time, another part of the cooling air enters from the inner air inlet 21 and then merges with the airflow guided by the guide slope 23 at the auxiliary air inlet end on the side of the air ring body 1 before entering the first air duct 11. The second airflow flows to the second air duct 12: the remaining cooling air enters the second air duct 12 directly through the second annular air inlet 121 on the outside of the air ring body 1. Since the second annular air inlet 121 corresponds to the extension section 31 of the separator 3, the airflow initially converges here, preparing for subsequent stable diffusion. Phase 2: Airflow distribution and state regulation within the dual air ducts Airflow regulation within the first air duct 11: The airflow entering the first air duct 11 flows along the contraction section 32 inside the separator 3. Due to the "wide inlet, narrow outlet" structural characteristics of the first air duct 11, the airflow gradually increases in pressure and speed during the channel contraction process, forming a "high-speed, strong airflow". If producing thin PVA water-soluble films, the guide ring 2 can be rotated clockwise to engage with the threaded part 22 of the air ring body 1, reducing the gap between the guide ring 2 and the first annular air inlet 111, further enhancing the airflow pressurization effect. If producing thick PVA water-soluble films, the guide ring 2 can be rotated counterclockwise to expand the air inlet gap, increase the airflow inflow, and meet the "high airflow" cooling requirements of thick films. Airflow regulation within the second air duct 12: The airflow entering the second air duct 12 flows along the extension section 31 outside the separator 3. Due to the "narrow inlet, wide outlet" structural characteristics of the second air duct 12, the airflow gradually slows down and diffuses during the expansion process, changing from "high-speed impact airflow" to "stable covering airflow," thus avoiding direct impact of the airflow on the outer side of the PVA membrane bubble, which could cause wrinkles. At the same time, the rounded corner structure at the connection between the extension section 31 and the contraction section 32 of the separator 3 ensures that the airflow smoothly transitions along the arc surface in both air ducts, without generating vortices, thus ensuring stable airflow. Stage 3: Cooling process of PVA membrane bubble by airflow When PVA raw material is plasticized by an extruder, it is extruded from the die and inflated to form a film bubble. At this time, the cooling airflow of the air ring acts synchronously on the film bubble: Internal cooling: The "high-speed strong airflow" in the first air duct 11 blows directionally from the inner air outlet 112 to the inner surface of the membrane bubble. Since the inner air outlet 112 is distributed in a ring around the inner side of the membrane bubble, the airflow covers the circumference evenly, which can quickly remove the heat inside the PVA melt, avoid adhesion due to high temperature residue on the inner side of the membrane bubble, and promote rapid shaping of the inner side of the membrane bubble, ensuring uniform crystallization on the inner side of the PVA water-soluble film. External cooling: The "smooth covering airflow" in the second air duct 12 blows evenly from the outlet air vent 122 to the outer surface of the membrane bubble. The airflow wraps around the outer side of the membrane bubble at a low impact speed, slowly and comprehensively removing the heat from the outer side of the membrane bubble, preventing the PVA melt from shrinking and wrinkling due to excessive cooling on the outer side. At the same time, it works in synergy with the internal cooling to ensure that the cooling rate of the inner and outer sides of the membrane bubble is consistent, reducing the thickness difference of the membrane material. Anti-interference guarantee: During this process, the heat insulation pad 4 at the air outlet of the air ring body 1 blocks the high temperature at the die opening, preventing the cooling air temperature in the air duct from rising and maintaining the initial cooling capacity of the cooling air; the connecting seat 5 fixes the air ring body 1 to the blown film machine host, ensuring that the air ring and the film bubble are coaxial, and the airflow always acts perpendicularly on the surface of the film bubble without deviation, further ensuring cooling uniformity. Stage 4: Dynamic adaptation and adjustment during production During the continuous production of PVA blown film, cooling parameters can be dynamically adjusted via the guide ring 2 based on film quality feedback, such as whether the film bubble is wrinkled or whether the thickness is uniform. If sagging is found due to insufficient cooling on the inner side of the membrane bubble, the guide ring 2 can be finely adjusted to increase the air intake of the inner air inlet 21 and enhance the airflow intensity of the first air duct 11. If wrinkles are found on the outside of the membrane bubble, the total air intake of the second air duct 12 can be finely adjusted by the fan. Combined with the flow stabilization effect of the "narrow inlet and wide outlet" flow channel, the impact of the outer airflow can be further reduced. When switching between different specifications of PVA water-soluble film production, it is only necessary to adjust the air inlet gap by rotating the guide ring 2 through the threaded part 22, without disassembling the air ring, which greatly shortens the debugging time and ensures production continuity. In summary, the entire process revolves around the characteristics of PVA melt, which is "sensitive to cooling and prone to wrinkling and adhesion." Through the precise distribution, regulation, and stabilization of airflow, efficient and uniform cooling of PVA film bubbles is achieved, ensuring the high-quality production of PVA water-soluble films.

[0045] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A PVA blown film machine air ring structure, comprising an air ring body (1), characterized in that: The air ring body (1) is provided with a first air duct (11) and a second air duct (12) inside. The first air duct (11) and the second air duct (12) are separated by a separator (3). The first air duct (11) and the second air duct (12) are both annular structures. The separator (3) includes an extension section (31) and a contraction section (32), so that the air intake space of the first air duct (11) is larger than the air outlet space, and the air intake space of the second air duct (12) is smaller than the air outlet space.

2. The PVA blown film machine air ring structure according to claim 1, characterized in that: The first air duct (11) is located inside the partition (3). One end of the first air duct (11) is provided with a first annular air inlet (111), and the other end of the first air duct (11) is provided with an inner air outlet (112).

3. The PVA blown film machine air ring structure according to claim 1, characterized in that: The second air duct (12) is located outside the partition (3). One end of the second air duct (12) is provided with a second annular air inlet (121), and the other end of the second air duct (12) is provided with an outlet air vent (122).

4. The PVA blown film machine air ring structure according to claim 1, characterized in that: The air ring body (1) is equipped with a guide ring (2) near the first annular air inlet (111), and an inner air inlet (21) is provided in the middle of the guide ring (2).

5. The PVA blown film machine air ring structure according to claim 4, characterized in that: The outer wall of the guide ring (2) is provided with a threaded part (22), and the wind ring body (1) is provided with a threaded opening. The threaded part (22) of the guide ring (2) is threadedly connected to the threaded opening on the wind ring body (1).

6. The PVA blown film machine air ring structure according to claim 4, characterized in that: The guide ring (2) is provided with a guide slope (23) near the first air duct (11) to guide the airflow to the inner air outlet (112) for ejection.

7. The PVA blown film machine air ring structure according to claim 1, characterized in that: A heat insulation pad (4) is installed on the outside of the air outlet end of the air ring body (1), and a connecting seat (5) is installed at the air inlet end of the air ring body (1). The connecting seat (5) is connected and fixed to the blown film machine host.

8. The PVA blown film machine air ring structure according to claim 1, characterized in that: The connection between the extended section (31) and the contracted section (32) is a rounded corner structure.

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