Vacuum cooling and setting device for pvdf pipes

Abstract

The application relates to the technical field of pipe material preparation, in particular to a vacuum cooling and shaping device for PVDF pipe material. The device comprises a vacuum cooling box, a sizing sleeve and a temperature control mechanism. The first vacuum cooling chamber and the second vacuum cooling chamber which are independent of each other are arranged in the vacuum cooling box along the pipe material conveying direction. The second vacuum cooling chamber can be further divided into a front chamber and a rear chamber. The sizing sleeve is arranged at the inlet end of the vacuum cooling box. The temperature control mechanism comprises independent temperature control components which respectively act on the sizing sleeve and the two vacuum cooling chambers. The device is also provided with a cooling medium supply mechanism. Through the independent temperature control and gradient temperature design of the multi-chamber, the device realizes the gentle cooling of the PVDF pipe material, effectively eliminates the transverse lines on the outer surface, improves the smoothness of the inner and outer walls, fully releases the residual stress, avoids the concave pipe wall during welding, and meets the stringent requirements of high-end fields such as semiconductors on the PVDF pipe material.

Description

Technical Field

[0001] This application relates to the field of pipe manufacturing technology, and in particular to a vacuum cooling and shaping device for PVDF pipes. Background Technology

[0002] Polyvinylidene fluoride (PVDF) pipes are widely used in high-end fields such as semiconductors, photovoltaics, and high-purity chemicals due to their excellent chemical resistance, high purity, and good mechanical properties. These pipes are typically produced using an extrusion molding process, where vacuum cooling and shaping is a crucial step determining the final dimensional accuracy, surface quality, and internal structure of the pipe. This step involves cooling and shaping the high-temperature extruded pipe blank in a vacuum sizing sleeve, allowing it to solidify rapidly and reach the predetermined outer diameter.

[0003] However, PVDF, as a semi-crystalline polymer, is characterized by high crystallinity, a narrow processing window, high melt viscosity, and significant shrinkage. In existing technologies, common vacuum cooling and shaping equipment often employs relatively simple cooling methods, such as rapid cooling of the tube blank via water cooling or spraying. This cooling method easily leads to excessive temperature differences between the inner and outer layers of the tube blank, and uneven cooling rates, resulting in a series of defects. Specifically, the outer surface of the tube is prone to periodic transverse striations, and the surface finish of both the inner and outer walls is difficult to meet the extremely high requirements for high-purity applications (e.g., inner wall roughness Ra < 0.25 μm). Simultaneously, rapid and uneven cooling accumulates significant residual stress within the tube wall. These residual stresses not only affect the long-term dimensional stability of the tube but are also released during subsequent hot plate welding and other processing, resulting in concave tube walls in the weld area and irregular weld bead morphology, severely impacting the sealing reliability and service life of the pipeline system.

[0004] Therefore, developing a vacuum cooling and shaping device that can achieve controllable and gentle cooling and effectively release stress has become an urgent technical problem to be solved in order to improve the quality of high-end PVDF pipes. Utility Model Content

[0005] To address one or more of the above-mentioned problems, this application provides a vacuum cooling and shaping device for PVDF pipes, comprising: The vacuum cooling chamber has at least two independent chambers arranged sequentially along the pipe conveying direction, namely a first vacuum cooling chamber and a second vacuum cooling chamber located downstream of the first vacuum cooling chamber. A sizing sleeve, which is installed at the inlet end of the vacuum cooling box, is used to initially shape the outer diameter of the incoming pipe. The temperature control mechanism includes a first temperature control mechanism, a second temperature control mechanism, and a third temperature control mechanism. The first temperature control mechanism acts on the sizing sleeve to control its temperature. The second temperature control mechanism acts on the first vacuum cooling chamber to independently control its temperature. The third temperature control mechanism acts on the second vacuum cooling chamber to independently control its temperature. A cooling medium supply mechanism is located inside the vacuum cooling chamber and is used to spray cooling medium onto the outer surface of the pipes passing through the vacuum cooling chamber.

[0006] According to the vacuum cooling and shaping equipment for PVDF pipes provided in this application, the first temperature control mechanism is an oil temperature control system, which is configured to maintain the working temperature of the sizing sleeve between 50°C and 150°C.

[0007] According to the vacuum cooling and shaping equipment for PVDF pipes provided in this application, the second temperature control mechanism is configured to maintain the temperature of the cooling medium in the first vacuum cooling chamber between 40°C and 80°C.

[0008] According to the vacuum cooling and shaping equipment for PVDF pipes provided in this application, the second vacuum cooling chamber is divided into a front chamber and a rear chamber along the pipe conveying direction.

[0009] According to the vacuum cooling and shaping equipment for PVDF pipes provided in this application, the third temperature control mechanism is configured to control the temperature of the cooling medium in the front chamber between 30°C and 70°C, and to control the temperature of the cooling medium in the rear chamber between 60°C and 100°C.

[0010] According to the vacuum cooling and shaping equipment for PVDF pipes provided in this application, the cooling medium supply mechanism includes a water pump, a spray pipe, and a nozzle disposed on the spray pipe.

[0011] According to the vacuum cooling and shaping equipment for PVDF pipes provided in this application, the second temperature control mechanism includes a first heater and a first temperature sensor disposed in the first vacuum cooling chamber.

[0012] According to the vacuum cooling and shaping equipment for PVDF pipes provided in this application, the second temperature control mechanism further includes a first mechanical temperature control valve and a first float valve. The first mechanical temperature control valve is used to regulate the discharge of the cooling medium in the first vacuum cooling chamber, and the first float valve is used to maintain the liquid level of the cooling medium in the first vacuum cooling chamber.

[0013] According to the vacuum cooling and shaping equipment for PVDF pipes provided in this application, the third temperature control mechanism includes a second heater disposed in the second vacuum cooling chamber, and a second temperature sensor and a third temperature sensor disposed respectively corresponding to the front chamber and the rear chamber.

[0014] According to the vacuum cooling and shaping equipment for PVDF pipes provided in this application, the third temperature control mechanism further includes a first heat exchanger and a second heat exchanger. The first heat exchanger is used to perform secondary temperature control on the cooling medium supplied to the front chamber, and the second heat exchanger is used to perform secondary temperature control on the cooling medium supplied to the rear chamber.

[0015] According to the vacuum cooling and shaping equipment for PVDF pipes provided in this application, the third temperature control mechanism further includes a second mechanical temperature control valve and a second float valve. The second mechanical temperature control valve is used to regulate the discharge of the cooling medium in the second vacuum cooling chamber, and the second float valve is used to maintain the liquid level of the cooling medium in the second vacuum cooling chamber. According to the vacuum cooling and shaping equipment for PVDF pipes provided in this application, the third temperature control mechanism further includes a first solenoid valve and a second solenoid valve. The first solenoid valve is used to control the external condensate flowing to the first heat exchanger, and the second solenoid valve is used to control the external condensate flowing to the second heat exchanger.

[0016] The above-mentioned one or more technical solutions provided in this application include at least the following technical effects: The PVDF pipe vacuum cooling and shaping equipment provided in this application, through the integrated structure of independent temperature control for the sizing sleeve and multiple independently temperature-controlled chambers in the vacuum cooling box, enables precise and gradual temperature management throughout the entire cooling process of PVDF pipes after extrusion. The equipment first employs an oil temperature control system in the sizing sleeve stage to maintain a mild initial cooling environment, effectively preventing uneven crystallization and transverse lines on the high-temperature pipe blank surface caused by rapid cooling, while also initially releasing the initial stress generated during extrusion molding. Subsequently, the pipe enters multiple vacuum cooling chambers separated by a thermally insulated and sealed structure. Each chamber is equipped with an independent temperature control mechanism and a cooling medium injector. By setting a specific temperature gradient—high initially, then low, and finally slightly increasing at the end—this segmented temperature control mechanism ensures a more uniform and gradual temperature change between the inner and outer layers of the pipe during cooling. This not only significantly improves the smoothness of the outer surface and eliminates transverse lines, but also promotes the gradual and sufficient release of residual stress inside the pipe.

[0017] Furthermore, this equipment perfectly suits the physical properties of PVDF as a semi-crystalline polymer. PVDF crystallizes rapidly and has high crystallinity. If the cooling rate is too fast or uneven, the molecular chain segments are quickly "frozen" in a disordered state, resulting in a wide distribution of crystalline regions and numerous defects. Macroscopically, this manifests as a rough surface, poor gloss, and significant internal locking stress. This equipment extends the time window for the tube blank surface to remain in a highly elastic state by setting a 50-150℃ heat preservation zone in the sizing sleeve, allowing the molecular chains more opportunities to align in an orderly manner, forming more complete and uniformly sized crystalline regions, thereby improving surface gloss from the source. After entering the vacuum cooling chamber, the 40-80℃ cooling environment in the first chamber avoids a temperature gap with the sizing sleeve, achieving a smooth transition in the cooling curve. The second chamber is further divided into a front section (30-70℃) and a rear section (60-100℃). This design is particularly crucial: the front section continues to cool to consolidate the shaping effect, while the intentional increase in temperature in the rear section is not for heating but to create a "stress relaxation window." Within the temperature range of 60-100℃, the mobility of PVDF molecular chain segments is enhanced, sufficient to overcome local conformational energy barriers. This allows molecular chain segments that were frozen and in a non-equilibrium state during the initial cooling process to rearrange and relax, thereby effectively dissipating microscopic internal stress. This "cooling-heating" cyclic treatment is essentially an online heat treatment of the pipe, achieving the dual goals of stress release and dimensional stability.

[0018] Therefore, the beneficial effects of this equipment are multi-layered and effectively meet the needs of high-end industries. It directly solves the long-standing problems of appearance defects and internal stress in PVDF pipe production, eliminating horizontal lines on the outer wall, significantly improving the smoothness of the inner wall, and reducing the roughness of the inner wall of small pipes, far exceeding the stringent requirements of the semiconductor industry. A more profound impact is that, due to the effective release of residual stress in the pipe, it exhibits excellent dimensional stability during subsequent hot plate welding, completely avoiding the phenomenon of concave pipe walls in the weld area, and resulting in full, outwardly curved weld beads, greatly improving the sealing reliability and long-term service life of the pipeline system. This equipment provides crucial process equipment support for the production of high-precision, high-purity, and high-reliability PVDF pipes, and has significant industrial application value. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1This is a cross-sectional structural schematic diagram of a vacuum cooling and shaping device for PVDF pipes provided in some embodiments of this application; Figure 2 This is a structural schematic diagram of another cross-section of the vacuum cooling and shaping equipment for PVDF pipes provided in some embodiments of this application.

[0021] Figure label: 1. Vacuum cooling chamber; 11. First vacuum cooling chamber; 12. Second vacuum cooling chamber; 121. Front chamber; 122. Rear chamber; 13. First partition component; 14. Second partition component; 2. Sizing sleeve; 3. Temperature control mechanism; 31. First temperature control mechanism; 32. Second temperature control mechanism; 321. First heater; 322. First temperature sensor; 323. First mechanical temperature control valve; 324. First float valve; 33. Third temperature control mechanism; 331. Second heater; 332a. Second temperature sensor; 332b. Third temperature sensor; 333. Second mechanical temperature control valve; 334. Second float valve; 335a. First heat exchanger; 335b. Second heat exchanger; 336a. First solenoid valve; 336b. Second solenoid valve; 41a. First water pump; 41b. Second water pump; 42. Sprinkler pipe; 43. Sprinkler head. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0024] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are 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, and therefore should not be construed as a limitation of this application.

[0025] 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.

[0026] The following is in conjunction with the appendix Figure 1 and Figure 2 This application provides a detailed description of the specific implementation method of the vacuum cooling and shaping equipment for PVDF pipes. This equipment is specifically designed for cooling and shaping PVDF pipes after extrusion molding. Through a scientific structural layout and precise temperature control, it effectively improves problems such as poor surface quality and residual stress that occur when processing PVDF pipes using traditional equipment, ensuring the processing accuracy and performance of the pipes.

[0027] The equipment includes a vacuum cooling chamber 1, inside which at least two independent chambers are arranged sequentially along the conveying direction of the PVDF pipe: a first vacuum cooling chamber 11 and a second vacuum cooling chamber 12, separated by a first partition 13. The second vacuum cooling chamber 12 is located downstream of the first vacuum cooling chamber 11; that is, after being processed in the first vacuum cooling chamber 11, the PVDF pipe continues to flow into the second vacuum cooling chamber 12 to complete the subsequent cooling and shaping process. Each chamber adopts an independent structural design, effectively avoiding mutual interference of temperature environments within different chambers. This provides reliable structural support for segmented temperature control, ensuring that each cooling process can proceed stably under preset temperature conditions, and preventing fluctuations in cooling effect due to cross-temperature influences.

[0028] A sizing sleeve 2 is installed at the inlet end of the vacuum cooling box 1. The core function of the sizing sleeve 2 is to initially shape the outer diameter of the high-temperature molten PVDF tube blank that has just been extruded from the extruder. Through its own structural constraints, it ensures that the tube blank can maintain the preset outer diameter size during the subsequent cooling process, providing a basic guarantee for the dimensional accuracy of the final product. Considering the characteristics of PVDF material itself, such as fast crystallization speed and narrow processing window, if the temperature of the sizing sleeve 2 is too low, the surface of the high-temperature tube blank is prone to uneven crystallization due to rapid cooling, which will lead to the formation of transverse lines. At the same time, it will also cause stress concentration inside the tube blank. Therefore, the sizing sleeve 2 needs to be used in conjunction with a special temperature control structure to adjust its working temperature to adapt to the processing requirements of PVDF material.

[0029] To achieve precise temperature control throughout the entire process, the equipment is equipped with a complete temperature control mechanism 3, which specifically includes a first temperature control mechanism 31, a second temperature control mechanism 32, and a third temperature control mechanism 33. These three mechanisms correspond to different controlled objects and form a collaborative working system. The first temperature control mechanism 31 directly acts on the sizing sleeve 2, adjusting its temperature in real time to ensure the high-temperature PVDF tube blank is in a slow cooling environment during the initial shaping stage. This reduces surface striations and initially alleviates internal stress in the tube blank. The second temperature control mechanism 32 is specifically used to independently regulate the temperature of the first vacuum cooling chamber 11, ensuring the tube entering the chamber is cooled at a suitable temperature, preventing further stress accumulation due to sudden cooling. The third temperature control mechanism 33 independently controls the temperature of the second vacuum cooling chamber 12, creating a gradient with the temperature of the first chamber 11 to achieve an orderly transition in the tube cooling process.

[0030] The structural design and collaborative working mode of the above-mentioned components enable the PVDF pipe to undergo controllable temperature changes throughout the cooling and shaping process. This achieves precise control of the outer diameter, reduces surface defects through slow cooling and segmented temperature control, and gradually releases internal stress. This provides favorable conditions for avoiding pipe wall concavity and ensuring weld bead morphology in subsequent welding processes. In particular, it can meet the stringent requirements of the semiconductor industry for high-purity PVDF pipe inner wall smoothness, thereby improving the product's qualification rate and applicability.

[0031] In a specific example, the first partition 13, namely the sealing flange, is used to control the vacuum pressure of each chamber separately.

[0032] In some embodiments, the first temperature control mechanism 31 adopts an oil temperature control system design, that is, the oil temperature is controlled by a mold temperature controller, and the oil is circulated to heat the sizing sleeve 2. This design can accurately regulate the working temperature of the sizing sleeve 2 and keep it stably within the range of 50°C to 150°C. The oil temperature control system, with its excellent temperature stability and heat transfer uniformity of the heat transfer oil, is a preferred solution for meeting the processing requirements of PVDF materials. It establishes a connection with the sizing sleeve 2 through a preset heat transfer medium circulation pipeline, allowing the heat transfer oil to flow evenly through the temperature regulation channel of the sizing sleeve 2, achieving efficient heat transfer and stable temperature control.

[0033] In a specific example, the oil temperature control system includes a heating module, a circulation drive module, a temperature detection module, and an adjustment module. The heating module precisely heats the heat transfer oil. The circulation drive module uses a circulation pump to deliver the heated heat transfer oil to the inner jacket layer of the sizing sleeve 2. During the circulation of the heat transfer oil within the jacket layer, it transfers heat to the working surface of the sizing sleeve 2. The temperature detection module collects the temperature data of the heat transfer oil in real time and feeds the data back to the adjustment module. The adjustment module dynamically adjusts the output power of the heating module according to the preset temperature value, ensuring that the working temperature of the sizing sleeve 2 remains stable within the set range of 50℃ to 150℃. This closed-loop temperature control design effectively avoids the impact of temperature fluctuations on processing quality, enabling the sizing sleeve 2 to continuously provide a stable initial shaping environment for the PVDF tube blank, further ensuring the surface finish and dimensional accuracy of the tube, while also creating favorable conditions for the gradual release of stress.

[0034] Taking into account the inherent characteristics of PVDF material—rapid crystallization and narrow processing window—the working temperature range of 50℃ to 150℃ has been specifically optimized. If the temperature of the sizing sleeve 2 is below 50℃, the high-temperature molten PVDF billet will experience uneven surface crystallization due to excessively rapid cooling after contact with the sizing sleeve 2, leading to transverse defects in the pipe wall. Simultaneously, significant stress concentration will occur inside the billet due to the sudden temperature drop. If the temperature is above 150℃, it will be difficult to achieve initial cooling and shaping of the billet, potentially causing fluctuations in the outer diameter and affecting subsequent processing accuracy. This temperature range provides a gentle and stable initial cooling environment for the billet, ensuring the sizing sleeve 2's constraint and shaping effect on the billet's outer diameter while slowing down the cooling rate of the billet surface, avoiding surface defects caused by uneven crystallization. Simultaneously, it gradually releases the initial stress generated inside the billet during extrusion molding, laying the foundation for subsequent deep cooling and stress release in the vacuum cooling chamber.

[0035] In some embodiments, the vacuum cooling and shaping equipment for PVDF pipes is equipped with a cooling medium supply mechanism. This cooling medium supply mechanism is integrally located inside the vacuum cooling chamber 1, and its arrangement path is adapted to the pipe conveying trajectory of each chamber. It can continuously spray cooling medium onto the outer surface of the PVDF pipes as they sequentially pass through the first vacuum cooling chamber 11 and the second vacuum cooling chamber 12. The cooling medium supply mechanism specifically includes a water pump, a spray pipe 42, and nozzles 43. The cooling medium is provided by an external temperature control unit (TCU). The water pump delivers the cooling medium to the spray pipe 42 through pipelines, and then the nozzles 43 on the spray pipe 42 evenly spray it onto the surface of the PVDF pipes, ensuring sufficient contact between the cooling medium and the outer surface of the pipes and guaranteeing cooling uniformity. The cooling medium supply mechanism forms a stable connection with the internal structure of the vacuum cooling chamber 1, ensuring that it maintains its predetermined installation position during equipment operation and avoiding the impact of vibration and other factors on spraying accuracy.

[0036] From a functional perspective, the cooling medium supply mechanism uniformly sprays cooling medium onto the outer surface of the pipe through nozzles 43, providing direct cooling and causing the pipe temperature to gradually change along the conveying direction. This, combined with the independent temperature control mechanisms 3 of each chamber, forms a synergistic cooling system. Considering the high requirements of PVDF material for cooling uniformity, the circumferential distribution design of the nozzles 43 effectively avoids uneven crystallization caused by excessively rapid local cooling rates, reducing the generation of surface defects in the pipe and creating a stable temperature environment for stress release. Furthermore, continuous and uniform cooling medium spraying helps maintain the pipe's dimensional stability during the cooling process, avoiding dimensional deviations caused by uneven temperature gradients and further ensuring the pipe's outer diameter accuracy.

[0037] In a specific example, water can be used as the cooling medium. The spray pipes 42 of the cooling medium supply mechanism are arranged at intervals along the pipe conveying direction inside the vacuum cooling chamber 1. Each group of spray pipes 42 is circumferentially distributed around the pipe conveying path, and multiple nozzles 43 are evenly arranged on the spray pipes 42 to ensure that the cooling medium can evenly cover the outer surface of the pipe from multiple angles. Each spray pipe 42 is connected to a water pump through a pipeline, and the water pump realizes the unified supply and distribution of the cooling medium. This layout not only ensures that the pipes in the first vacuum cooling chamber 11 and the second vacuum cooling chamber 12 can obtain sufficient cooling medium, but also adapts to the temperature control requirements of different chambers, so that the cooling process and temperature control are precisely coordinated, thereby improving the overall cooling and shaping effect of the pipe.

[0038] In a specific example, the cooling medium supply mechanism can employ two independent configurations to achieve more precise zoned cooling. Specifically, it includes a first water pump 41a and a second water pump 41b, along with corresponding spray pipes and nozzles. Each system independently completes the delivery and spraying of the cooling medium. The first water pump 41a is dedicated to supplying the cooling medium to the first vacuum cooling chamber 11, while the second water pump 41b is dedicated to supplying the cooling medium to the two sections of the second vacuum cooling chamber 12. This independent configuration effectively avoids mutual interference between the temperature and flow rate of the cooling medium in different vacuum cooling chambers, ensuring precise maintenance of the mild cooling environment in the first vacuum cooling chamber 11 and the gradient cooling temperature in the second vacuum cooling chamber 12. This further improves the uniformity of cooling and temperature control accuracy of the pipes in each chamber, providing a more reliable guarantee for optimizing the surface finish of the pipes and fully releasing internal stress.

[0039] In some embodiments, based on the semi-crystalline nature of PVDF material, its narrow processing window, and its susceptibility to stress concentration due to sudden temperature changes, the second temperature control mechanism 32 is further configured to stably maintain the temperature of the cooling medium in the first vacuum cooling chamber 11 between 40°C and 80°C. This temperature range has been specifically optimized to avoid problems such as uneven crystallization, surface striations, and internal stress accumulation caused by excessively low cooling medium temperatures leading to sudden cooling of the pipe after initial shaping by the sizing sleeve 2, while also preventing situations where excessively high temperatures prevent effective cooling of the pipe and affect subsequent shaping efficiency and dimensional accuracy. By controlling the cooling medium temperature within this range, a mild and continuous cooling environment can be provided for the pipe, ensuring the stability of the pipe's outer diameter while gradually releasing the internal stress remaining from the sizing stage. Combined with the uniform spraying of the cooling medium supply mechanism, this further improves the smoothness of the pipe's outer surface, laying a solid foundation for subsequent deep cooling and stress release in the second vacuum cooling chamber 12.

[0040] In some embodiments, to further improve the accuracy and stability of temperature control in the first vacuum cooling chamber 11, the second temperature control mechanism 32 adopts a modular design, specifically including a first heater 321, a first temperature sensor 322, a first mechanical temperature control valve 323, and a first float valve 324, all of which are integrated and installed inside the first vacuum cooling chamber 11, and form a closed-loop system for coordinated control through pipeline connection and signal transmission. The first heater 321 is positioned near the delivery pipeline of the cooling medium supply mechanism, and can directly heat the cooling medium entering the first vacuum cooling chamber 11 to ensure that the temperature of the cooling medium quickly approaches the preset standard. The first temperature sensor 322 is fixed in the key area where the cooling medium contacts the pipe in the first vacuum cooling chamber 11. It can capture the actual temperature change of the cooling medium in real time and generate a detection signal, which is fed back to the main control unit of the equipment. The first mechanical temperature control valve 323 is connected in series in the discharge pipeline of the cooling medium. Its core function is to control the discharge and discharge flow of the cooling medium according to the set temperature. The first float valve 324 is installed in the first vacuum cooling chamber 11 and is used to control the replenishment flow of the cooling medium according to the liquid level in the chamber to maintain a stable liquid level.

[0041] In a specific example, the closed-loop control process of the second temperature control mechanism 32 is as follows: The main control unit presets the target temperature of the cooling medium in the first vacuum cooling chamber 11. The cooling medium is delivered to the spray pipe 42 by the water pump 41a and evenly sprayed onto the surface of the pipe through the nozzle 43. The first temperature sensor 322 feeds back the collected cooling medium temperature data to the main control unit in real time. When the detected temperature is below 40°C, the main control unit will synchronously instruct the first heater 321 to increase the heating power and raise the cooling medium temperature. When the detected temperature is above 80°C, the first mechanical temperature control valve 323 automatically opens to discharge excess high-temperature cooling medium. At this time, the first float valve 324 detects the drop in the liquid level in the chamber and automatically opens to replenish the cooling medium, ensuring that the liquid level in the chamber is maintained at the preset height, forming a complete closed-loop control of temperature and liquid level. This refined structural design and control logic ensures that the cooling environment in the first vacuum cooling chamber 11 is always adapted to the cooling requirements of the PVDF pipe, effectively guaranteeing the consistency of processing quality.

[0042] In some embodiments, to meet the requirements of gradient temperature control and stress release during the cooling process of PVDF pipes, the second vacuum cooling chamber 12 is further divided into a front chamber 121 and a rear chamber 122 along the pipe conveying direction by a second partition 14. The two chambers adopt independent structural designs, are temperature-isolated from each other, and avoid temperature interference between the front chamber 121 and the rear chamber 122, providing a structural basis for independent temperature control. This segmented design allows the second vacuum cooling chamber 12 to form differentiated temperature zones, enabling the pipe to undergo a preset temperature change process as it passes through the two chambers sequentially. This ensures the continuity of cooling and shaping while gradually releasing stress through a reasonable temperature transition, solving the stress concentration problem caused by traditional single-chamber cooling.

[0043] In some embodiments, based on the core requirements of the semi-crystalline nature of PVDF material and stress release, the third temperature control mechanism 33 is further configured with a differentiated temperature control mode, namely, the temperature of the cooling medium in the front chamber 121 is stably controlled between 30°C and 70°C, while the temperature of the cooling medium in the rear chamber 122 is stably controlled between 60°C and 100°C. This temperature gradient setting has been specifically optimized. The temperature of the front chamber 121 is lower than the cooling medium temperature of the first vacuum cooling chamber 11, which can achieve a further stable decrease in the pipe temperature, continuously consolidate the outer diameter shaping effect, and avoid new stress caused by a sudden drop in temperature. The temperature of the rear chamber 122 is higher than that of the front chamber 121, forming a tempering-type temperature change of "cooling down-heating up". This design can effectively activate the molecular activity inside the PVDF material, promote the full release of residual internal stress, and fundamentally solve problems such as pipe wall concavity and irregular weld bead morphology that occur during pipe welding.

[0044] In some embodiments, to achieve precise temperature control within the second vacuum cooling chamber 12, the third temperature control mechanism 33 adopts a modular integrated design of "shared basic temperature control + segmented secondary precision control." Specifically, it includes a second temperature sensor 332a corresponding to the front chamber 121, a third temperature sensor 332b corresponding to the rear chamber 122, a second heater 331 shared by both chambers, a second mechanical temperature control valve 333, a second float valve 334, and a first heat exchanger 335a and a second heat exchanger 335b adapted to the two chambers respectively, as well as a first solenoid valve 336a and a second solenoid valve 336b. All components are installed inside the second vacuum cooling chamber 12, forming a collaborative working system through structural assembly and signal transmission, ensuring both the uniformity of the basic temperature control and achieving differentiated and precise adjustment of segmented temperatures.

[0045] The second heater 331 is arranged around the main water supply pipeline leading from the cooling medium supply mechanism to the second vacuum cooling chamber 12. It is used to uniformly heat the cooling medium flowing into the two chambers, ensuring that the temperature of the cooling medium approaches the preset range first, laying a stable foundation for subsequent segmented precise control. The second temperature sensor 332a is fixed in the core area where the cooling medium contacts the pipe in the first chamber 121, and the third temperature sensor 332b is fixed in the corresponding area in the second chamber 122. They respectively collect the temperature data of the cooling medium in the two chambers in real time and generate independent detection signals, providing accurate basis for their respective temperature control. The second mechanical temperature control valve 333 is connected in series on the main cooling medium discharge pipeline of the second vacuum cooling chamber 12. It is used to comprehensively control the discharge and discharge flow of the cooling medium based on the temperature feedback of the two chambers, maintaining... The overall balance of the cooling medium in the chamber is maintained; the second float valve 334 is installed in the second vacuum cooling chamber 12 to control the supply flow of the cooling medium according to the overall liquid level in the chamber, ensuring a continuous and stable supply of the cooling medium and avoiding the impact of liquid level fluctuations on the cooling effect; the first heat exchanger 335a is connected in series in the branch water supply pipeline of the front chamber 121, and the second heat exchanger 335b is connected in series in the branch water supply pipeline of the rear chamber 122, respectively, to perform secondary precise temperature control of the cooling medium in the corresponding chambers and achieve temperature fine-tuning; the first solenoid valve 336a corresponds one-to-one with the first heat exchanger 335a, and the second solenoid valve 336b corresponds one-to-one with the second heat exchanger 335b. Both are used to control the on / off of external condensate water, thereby independently adjusting the heat exchange efficiency of the corresponding heat exchanger, and finally achieving differentiated temperature control of the two chambers.

[0046] In some embodiments, the spray pipe 42 of the cooling medium supply mechanism is also divided into a front spray pipe and a rear spray pipe, corresponding to the front chamber 121 and the rear chamber 122 respectively. The water supply pipeline is designed as a "main line + branch" structure. After the main water supply pipeline is uniformly heated by the second heater 331, it branches into two independent branch water supply pipelines, which lead to the two chambers respectively. The first heat exchanger 335a is connected in series in the front branch water supply pipeline, and the second heat exchanger 335b is connected in series in the rear branch water supply pipeline, forming a temperature control architecture of "unified heating + segmented secondary temperature control". This structural design not only ensures the basic temperature requirements of the cooling medium, but also enables independent temperature control of the two chambers through segmented components, avoiding mutual temperature interference between the two chambers. This provides a reliable structural basis for independent temperature control, allowing the second vacuum cooling chamber 12 to form a differentiated temperature zone of "cooling-heating". As the pipe passes through the two chambers in sequence, it undergoes a preset temperature change process, ensuring the continuity of cooling and shaping, and gradually releasing stress through reasonable temperature transition. This effectively solves the stress concentration problem caused by traditional single-chamber cooling.

[0047] In a specific example, the closed-loop control process of the third temperature control mechanism 33 is as follows: The main control unit presets the target temperature of the cooling medium in the front chamber 121 (30℃ to 70℃) and the target temperature of the cooling medium in the rear chamber 122 (60℃ to 100℃). The cooling medium is transported to the main water supply pipeline by the water pump 41b, and after being uniformly heated by the second heater 331, it flows into the two branch water supply pipelines respectively. The cooling medium in the front branch water supply pipeline is subjected to secondary temperature control by the first heat exchanger 335a, and is then evenly sprayed onto the surface of the pipe in the front chamber 121 through the nozzle of the front spray pipe. The cooling medium in the rear branch water supply pipeline is subjected to secondary temperature control by the second heat exchanger 335b, and is then evenly sprayed onto the surface of the pipe in the rear chamber 122 through the nozzle of the rear spray pipe.

[0048] The second temperature sensor 332a collects the cooling medium temperature data of the front chamber 121 in real time and feeds it back to the main control unit. When the detected temperature is below 30°C, the main control unit controls the second heater 331 to appropriately increase the heating power, while reducing the opening of the first solenoid valve 336a to reduce the heat exchange efficiency and quickly raise the temperature of the front cooling medium to the preset range. When the detected temperature is above 70°C, the main control unit keeps the power of the second heater 331 unchanged, increases the opening of the first solenoid valve 336a, introduces more external condensate into the first heat exchanger 335a, and exchanges heat with the cooling medium in the front branch water supply pipeline to achieve rapid cooling.

[0049] Meanwhile, the third temperature sensor 332b collects the cooling medium temperature data of the downstream chamber 122 in real time and feeds it back to the main control unit. When the detected temperature is below 60℃, the main control unit controls the second heater 331 to increase the heating power and simultaneously reduces the opening of the second solenoid valve 336b to reduce heat exchange loss and quickly increase the temperature of the downstream cooling medium. When the detected temperature is above 100℃, the main control unit increases the opening of the second solenoid valve 336b to quickly cool the downstream cooling medium through the second heat exchanger 335b. During this process, if the average temperature of the cooling medium in the two chambers is higher than the preset threshold, the second mechanical temperature control valve 333 automatically opens to discharge excess high-temperature cooling medium, and the second float valve 334 automatically opens to replenish the cooling medium after detecting a drop in the liquid level in the chamber, maintaining a stable liquid level.

[0050] This closed-loop control design of "unified basic heating + segmented secondary precise temperature control" can achieve differentiated temperature control of the two chambers with only a second heater and segmented components. This ensures that the two chambers always maintain their respective preset temperature ranges. The tube is first cooled and solidified in the first chamber 121 in the second vacuum cooling chamber 12, and then heated in the second chamber 122 to release stress through tempering. This completes a continuous cooling and solidification process, further improving the dimensional accuracy, surface quality and welding performance of the tube, and meeting the stringent requirements of high-purity PVDF tubes in high-end fields such as semiconductors.

[0051] In actual operation, the specific working process of the vacuum cooling and shaping equipment for PVDF pipes provided in this application is as follows: After the PVDF tube blank in a high-temperature molten state is extruded by the extruder, it first enters the sizing sleeve 2 located at the inlet end of the vacuum cooling box 1. At this time, the first temperature control mechanism 31, i.e. the oil temperature control system, is activated simultaneously. It controls the circulation of heat transfer oil through the mold temperature controller. The heating module of the cooling medium supply mechanism precisely heats the heat transfer oil. The circulation pump of the circulation drive module delivers the heated heat transfer oil to the inner jacket layer of the sizing sleeve 2. When the heat transfer oil circulates in the jacket layer, it evenly transfers heat to the working surface of the sizing sleeve 2. The temperature detection module collects the temperature data of the heat transfer oil in real time and feeds it back to the adjustment module. The adjustment module dynamically adjusts the output power of the heating module according to the preset value, so that the working temperature of the sizing sleeve 2 is stably maintained between 50℃ and 150℃. Under the structural constraint of the sizing sleeve 2, the tube blank completes the initial shaping of the outer diameter. At the same time, in this mild and slow cooling environment, the initial stress generated by extrusion molding is initially released, avoiding the formation of surface horizontal lines.

[0052] After the initial shaping of the pipe is completed, it enters the first vacuum cooling chamber 11 along the conveying direction. This chamber is separated from the second vacuum cooling chamber 12 by the first partition component 13, i.e., a sealing flange, to ensure that the vacuum pressure and temperature do not interfere with each other. At this time, the second temperature control mechanism 32 starts to work. Its modular combination of the first heater 321, the first temperature sensor 322, the first mechanical temperature control valve 323, and the first float valve 324 works in concert. The main control unit presets the target temperature (40℃ to 80℃) of the cooling medium in the first vacuum cooling chamber 11. The first water pump 41a of the cooling medium supply mechanism delivers cooling water, which is used as the cooling medium, to the spray pipe 42 of the chamber. The water is then evenly sprayed onto the surface of the pipe through the evenly distributed nozzles 43 on the spray pipe 42. Sensor 322 is fixed in the critical area where the cooling medium and the pipe come into contact in the chamber. It captures the actual temperature change of the cooling medium in real time and generates a detection signal to feed back to the main control unit. When the detected temperature is below 40°C, the main control unit synchronously instructs the first heater 321 to increase the heating power and raise the temperature of the cooling medium. When the detected temperature is above 80°C, the first mechanical temperature control valve 323 automatically opens to discharge excess high-temperature cooling medium. At this time, the first float valve 324 automatically opens to replenish the cooling medium after detecting the drop in the liquid level in the chamber, ensuring that the liquid level in the chamber is maintained at the preset height, forming a complete closed-loop control of temperature and liquid level. The pipe cools down steadily in this mild and continuous cooling environment, further releasing the internal stress remaining in the sizing stage, while improving the surface finish.

[0053] After cooling, the pipe continues to enter the second vacuum cooling chamber 12. This chamber is divided into a front chamber 121 and a rear chamber 122 by a second partition 14. The two chambers are temperature-isolated from each other. The spray pipes 42 of the cooling medium supply mechanism are correspondingly divided into front spray pipes and rear spray pipes. The water supply pipeline is designed with a "main + branch" structure. The third temperature control mechanism 33 adopts a modular integrated design of "shared basic temperature control + segmented secondary precision control" and begins operation. The second water pump 41b of the cooling medium supply mechanism delivers cooling water to the main water supply pipeline of the second vacuum cooling chamber 12. After being uniformly heated by the second heater 331 shared by the two chambers, the water flows into two independent branch water supply pipelines. The cooling water in the front branch water supply pipeline is subjected to secondary temperature control by the first heat exchanger 335a and then sprayed by the front spray pipe. The cooling medium is evenly sprayed onto the surface of the pipe in the front chamber 121. The second temperature sensor 332a corresponding to the front chamber 121 collects the temperature data of the cooling medium in real time and feeds it back to the main control unit. When the detected temperature is below 30°C, the main control unit controls the second heater 331 to appropriately increase the heating power, while reducing the opening of the first solenoid valve 336a to reduce the heat exchange efficiency, and quickly raises the temperature of the front cooling medium to the preset range of 30°C to 70°C. When the detected temperature is above 70°C, the main control unit keeps the power of the second heater 331 unchanged, increases the opening of the first solenoid valve 336a, and introduces more external condensate into the first heat exchanger 335a to exchange heat with the cooling medium in the front branch water supply pipeline to achieve rapid cooling. The pipe continues to cool down in this range to consolidate the shaping effect and ensure accurate and stable outer diameter dimensions.

[0054] The pipe then enters the rear chamber 122 of the second vacuum cooling chamber 12. Cooling water from the rear branch water supply pipe, after secondary temperature control by the second heat exchanger 335b, is evenly sprayed onto the pipe surface through the nozzles of the rear spray pipe. The third temperature sensor 332b in the corresponding rear chamber 122 collects the cooling medium temperature data in real time and feeds it back to the main control unit. When the detected temperature is below 60℃, the main control unit controls the second heater 331 to increase the heating power while simultaneously reducing the opening of the second solenoid valve 336b to reduce heat exchange losses and rapidly increase the temperature of the rear cooling medium. When the detected temperature is above 100℃, the main control unit increases the opening of the second solenoid valve 336b, rapidly cooling the rear cooling medium through the second heat exchanger 335b, thus maintaining the cooling medium temperature in the rear chamber 122 stably between 60℃ and 100℃, forming a "cooling-heating" tempering temperature change, stimulating… The molecular activity within the active PVDF material promotes the full release of residual internal stress. During this process, a second mechanical temperature control valve 333, shared by both chambers, is connected in series on the main cooling medium discharge pipeline of the second vacuum cooling chamber 12. It is comprehensively regulated based on the average temperature feedback from the second temperature sensors 332a and 332b. When the average temperature is higher than the preset threshold, it automatically opens to discharge excess high-temperature cooling medium. A second float valve 334 is installed in the second vacuum cooling chamber 12. It automatically controls the supply flow of cooling medium based on the overall liquid level in the chamber, ensuring a continuous and stable supply of cooling medium and avoiding the impact of liquid level fluctuations on the cooling effect. After the entire cooling and shaping process is completed, the pipe is output smoothly, the horizontal lines on its outer wall are completely eliminated, the smoothness of the inner wall meets the requirements of high-end fields such as semiconductors, the residual stress is greatly reduced, and there will be no concave pipe wall phenomenon during subsequent hot plate welding. The weld bead shape is regular and full.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A vacuum cooling and shaping device for PVDF pipes, characterized in that, include: The vacuum cooling chamber has at least two independent chambers arranged sequentially along the pipe conveying direction, namely a first vacuum cooling chamber and a second vacuum cooling chamber located downstream of the first vacuum cooling chamber. A sizing sleeve, which is installed at the inlet end of the vacuum cooling box, is used to initially shape the outer diameter of the incoming pipe. The temperature control mechanism includes a first temperature control mechanism, a second temperature control mechanism, and a third temperature control mechanism. The first temperature control mechanism acts on the sizing sleeve to control its temperature. The second temperature control mechanism acts on the first vacuum cooling chamber to independently control its temperature. The third temperature control mechanism acts on the second vacuum cooling chamber to independently control its temperature. A cooling medium supply mechanism is located inside the vacuum cooling chamber and is used to spray cooling medium onto the outer surface of the pipes passing through the vacuum cooling chamber.

2. The vacuum cooling and shaping equipment for PVDF pipes according to claim 1, characterized in that, The first temperature control mechanism is an oil temperature control system, which is configured to maintain the working temperature of the sizing sleeve between 50°C and 150°C.

3. The vacuum cooling and shaping equipment for PVDF pipes according to claim 1, characterized in that, The second temperature control mechanism is configured to maintain the temperature of the cooling medium in the first vacuum cooling chamber between 40°C and 80°C.

4. The vacuum cooling and shaping equipment for PVDF pipes according to claim 1, characterized in that, The second vacuum cooling chamber is divided into a front chamber and a rear chamber along the pipe conveying direction.

5. The vacuum cooling and shaping equipment for PVDF pipes according to claim 4, characterized in that, The third temperature control mechanism is configured to control the temperature of the cooling medium in the front chamber between 30°C and 70°C, and to control the temperature of the cooling medium in the rear chamber between 60°C and 100°C.

6. The vacuum cooling and shaping equipment for PVDF pipes according to claim 1, characterized in that, The cooling medium supply mechanism includes a water pump, a spray pipe, and nozzles mounted on the spray pipe.

7. The vacuum cooling and shaping equipment for PVDF pipes according to claim 1, characterized in that, The second temperature control mechanism includes a first heater and a first temperature sensor disposed within the first vacuum cooling chamber.

8. The vacuum cooling and shaping equipment for PVDF pipes according to claim 7, characterized in that, The second temperature control mechanism further includes a first mechanical temperature control valve and a first float valve. The first mechanical temperature control valve is used to regulate the discharge of the cooling medium in the first vacuum cooling chamber, and the first float valve is used to maintain the liquid level of the cooling medium in the first vacuum cooling chamber.

9. The vacuum cooling and shaping equipment for PVDF pipes according to claim 1, characterized in that, The third temperature control mechanism includes a second heater disposed in the second vacuum cooling chamber, and a second temperature sensor and a third temperature sensor disposed respectively corresponding to the front chamber and the rear chamber.

10. The vacuum cooling and shaping equipment for PVDF pipes according to claim 9, characterized in that, The third temperature control mechanism further includes a first heat exchanger and a second heat exchanger. The first heat exchanger is used to perform secondary temperature control on the cooling medium supplied to the front chamber, and the second heat exchanger is used to perform secondary temperature control on the cooling medium supplied to the rear chamber.

11. The vacuum cooling and shaping equipment for PVDF pipes according to claim 9, characterized in that, The third temperature control mechanism also includes a second mechanical temperature control valve and a second float valve. The second mechanical temperature control valve is used to regulate the discharge of the cooling medium in the second vacuum cooling chamber, and the second float valve is used to maintain the liquid level of the cooling medium in the second vacuum cooling chamber.

12. The vacuum cooling and shaping equipment for PVDF pipes according to claim 10, characterized in that, The third temperature control mechanism further includes a first solenoid valve and a second solenoid valve. The first solenoid valve is used to control the external condensate flowing to the first heat exchanger, and the second solenoid valve is used to control the external condensate flowing to the second heat exchanger.

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