A wire drawing furnace air pressure compensation system, a multi-stage micro-pore sealing device and a control method

Abstract

The application provides a wire drawing furnace air pressure compensation system, a multi-stage micro-pore sealing device and a control method. The multi-stage micro-pore sealing device comprises a sealing sleeve, a hollow channel is arranged in the sealing sleeve for the passage of an optical fiber, the hollow channel comprises an upper channel, at least two air blowing channels and a lower channel, the adjacent two air blowing channels are communicated through a buffer channel, a plurality of air outlet holes are arranged on the circumferential direction of the side wall of the air blowing channel, a hollow air inlet chamber is formed between the side wall of the hollow channel and the outer side wall of the sealing sleeve, an air inlet hole is formed on the outer side wall of the sealing sleeve and communicated with the air inlet chamber, and the airflow from the air inlet hole flows out through the air outlet hole after passing through the air inlet chamber to form a seal for the optical fiber in the hollow channel. The multi-stage micro-pore sealing device has strong equalization ability for local airflow unevenness, can ensure the uniformity and stability of the outlet air curtain even if the eccentricity of the optical fiber preform rod is high, and solves the problem of airflow disturbance caused by the deviation of the preform rod.

Description

Technical Field

[0001] This invention relates to the field of optical fiber production technology, and in particular to a gas pressure compensation system for a drawing furnace, a multi-stage micropore sealing device, and a control method. Background Technology

[0002] Fiber optic drawing refers to the process of heating and melting fiber preforms of a certain diameter using drawing equipment and drawing them into optical fibers with specific geometric requirements. The heating equipment for the molten fiber preform (commonly known as a fiber drawing furnace) is one of the core pieces of equipment in the fiber drawing process. This equipment directly affects several important technical parameters of the optical fiber, such as geometric parameters, fiber attenuation, fiber strength, and polarization mode dispersion. Traditional fiber drawing furnaces mainly use resistance heating or induction heating methods, and introduce inert gases (such as helium) to create a protective atmosphere to prevent oxidation of the graphite components at high temperatures and maintain a stable temperature field.

[0003] The core heating element inside the fiber drawing furnace is typically made of high-purity graphite, which undergoes a violent oxidation reaction when in contact with oxygen at operating temperatures exceeding 2000℃. If the furnace is not properly sealed, external air can infiltrate through the furnace opening gaps, causing the graphite surface to become porous and powdery. This not only significantly shortens its lifespan and increases production costs, but the carbon powder particles produced by oxidation also adhere to the molten fiber surface, forming defects and severely degrading the fiber's mechanical strength. Fiber drawing requires a highly uniform and stable temperature distribution within the furnace; any airflow fluctuations will disrupt the thermal equilibrium. A good sealing system ensures that the inert protective gas (such as helium) forms a stable laminar flow along a predetermined path, providing an ideal environment for the uniform melting of the fiber preform. Conversely, sealing failure leads to abnormal furnace pressure fluctuations, causing the airflow to change from laminar to turbulent, resulting in temperature field fluctuations and ultimately causing abnormal geometric parameters such as fiber diameter fluctuations and excessive cladding roundness. This stability is fundamental to achieving the excellent optical performance of optical fibers, such as low attenuation and high bandwidth.

[0004] Existing wire drawing furnace sealing technologies primarily seal the furnace inlet, and these technologies are relatively mature. However, the sealing technology at the outlet is less mature. For example, CN219507828U uses a non-contact air curtain sealing device. The air curtain seal used in this method has poor stability. When the preform's axis shifts during the drawing process, it can lead to uneven gaps at the furnace inlet, causing airflow disturbances and furnace pressure fluctuations. Secondly, a single air curtain structure has limited ability to compensate for pressure changes and cannot effectively maintain constant furnace pressure. This can easily cause instability in the temperature and airflow fields within the wire drawing furnace, thereby affecting the fiber diameter and cladding roundness. These defects can directly lead to a decrease in fiber quality and a shortened equipment lifespan.

[0005] In addition, the existing gas pressure regulation system of wire drawing furnace has a slow response. The commonly used open-loop control or simple threshold control is difficult to quickly compensate for pressure changes at the millibar level, resulting in an excessively long recovery time. Summary of the Invention

[0006] The main objective of this invention is to provide a gas pressure compensation system for a fiber drawing furnace, as well as its multi-stage microporous sealing device and control method, which aims to improve the sealing performance of the fiber optic furnace outlet side.

[0007] To achieve the above objectives, the present invention provides a multi-stage microporous sealing device for a wire drawing furnace pressure compensation system, comprising a sealing sleeve installed sealingly below the bottom opening of the wire drawing furnace. The sealing sleeve has a hollow channel inside for optical fibers to pass through. The hollow channel includes an upper channel, at least two air blowing channels, and a lower channel that are sequentially connected and coaxially arranged from top to bottom. Adjacent air blowing channels are connected by a buffer channel. Multiple air outlets are provided in the circumferential direction of the sidewall of the air blowing channel. A hollow air inlet chamber is formed between the sidewall of the hollow channel and the outer wall of the sealing sleeve. An air inlet hole communicating with the air inlet chamber is opened on the outer wall of the sealing sleeve. The airflow entering from the air inlet hole flows out through the air outlet hole after passing through the air inlet chamber to seal the optical fiber in the hollow channel.

[0008] Preferably, the air blowing channel is in the shape of an inverted frustum.

[0009] Preferably, the pore density on the sidewall of the air blowing channel is 200 pores / cm². 2 ~400 holes / cm 2 The sidewall opening ratio of the air blowing channel is 25%~35%, and the diameter of the air outlet is 0.1mm~0.5mm.

[0010] Preferably, the buffer channel includes a first transition section in the shape of a cylinder and a second transition section above it in the shape of an upright frustum. The bottom end face of the first transition section is connected to the top end face of the lower air blowing channel, and the top end face of the second transition section is connected to the bottom end face of the upper air blowing channel.

[0011] Preferably, both the upper channel and the lower channel are cylindrical in shape, with the diameter of the upper channel being larger than that of the lower channel, and the diameter of the lower channel being smaller than that of the bottom surface of the buffer channel.

[0012] Preferably, the height of the buffer channel is 20mm~40mm, and the height of the air intake chamber is 100mm~200mm.

[0013] Preferably, the plurality of air outlets are evenly arranged in the circumferential direction of the air blowing channel; the thickness of the sidewall of the hollow channel and the outer sidewall of the sealing sleeve are both 5mm~12mm.

[0014] Preferably, all of the air blowing channels have the same shape and size.

[0015] The present invention also proposes a pressure compensation system for a wire drawing furnace, including the aforementioned multi-stage microporous sealing device, and further including a pressure sensor, a controller, and a mass flow controller. The end of the pressure sensor extends into the interior of the wire drawing furnace to collect the actual pressure signal inside the furnace. The inlet side of the mass flow controller is connected to the gas source, and the outlet side of the mass flow controller is connected to the air inlet of the multi-stage microporous sealing device. The controller is electrically connected to the control terminals of the pressure sensor and the mass flow controller to control the air inlet flow of the multi-stage microporous sealing device according to the measured pressure.

[0016] This invention further proposes a control method based on the above-mentioned gas pressure compensation system for wire drawing furnace, comprising the following steps:

[0017] After the wire drawing furnace starts running, set the furnace pressure to the initial set pressure value;

[0018] The control pressure sensor acquires the actual pressure value inside the furnace in real time and sends the actual pressure value inside the furnace to the controller;

[0019] The controller calculates the current signal based on the actual pressure value inside the furnace according to its internal preset algorithm, and sends the current signal to the mass flow controller to control the air intake flow of the multi-stage microporous sealing device to the preset value.

[0020] The actual pressure value inside the furnace is updated in real time.

[0021] When the actual pressure value inside the furnace is less than the target micro-positive pressure value, the controller updates the current signal to increase the air intake flow of the multi-stage microporous sealing device.

[0022] When the actual pressure value inside the furnace is greater than the target micro-positive pressure value, the controller updates the current signal to reduce the air intake flow of the multi-stage microporous sealing device.

[0023] The gas pressure compensation system for wire drawing furnace proposed in this invention has the following beneficial effects:

[0024] 1. Powerful "homogenization" capability: Through the air inlet chamber and multiple air outlets of at least two air blowing channels, high-speed air intake can be converted into uniform laminar flow, generating adjustable air curtain resistance. Even if the optical fiber preform has an eccentricity of up to ±2mm, the uniformity and stability of the outlet air curtain can be guaranteed, thus completely solving the problem of airflow disturbance caused by preform offset.

[0025] 2. The multi-stage air blowing channel improves the sealing performance at the outlet of the wire drawing furnace, which can greatly reduce the consumption of inert gas, saving 15%-20% of inert gas.

[0026] 3. The use of a sealed sleeve to create a constant micro-positive pressure environment can effectively isolate air intrusion, prevent the graphite heating element from oxidizing, and extend its service life by more than 30%.

[0027] 4. A constant micro-positive pressure environment is created by using a sealed sleeve, forming a stable airflow and temperature field inside the drawing furnace. The furnace pressure fluctuation range is ±0.25-0.6kPa, which greatly improves the consistency of the optical fiber's geometric parameters. The optical fiber diameter fluctuation range can be controlled within ±0.2μm, and the cladding non-circularity is better than 0.3%.

[0028] 5. The gas pressure compensation system of this drawing furnace has strong compatibility. It can be adapted to preforms of different diameters and drawing speeds through PLC program, reducing the need to replace hardware components, improving production efficiency, and bringing considerable economic benefits due to its reduced consumption of protective gas. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the gas pressure compensation system for the wire drawing furnace of the present invention;

[0030] Figure 2 This is a three-dimensional structural diagram of the multi-stage microporous sealing device in the gas pressure compensation system of the wire drawing furnace of the present invention;

[0031] Figure 3 This is a top view schematic diagram of the multi-stage microporous sealing device in the gas pressure compensation system of the wire drawing furnace of the present invention;

[0032] Figure 4 This is a cross-sectional view of the multi-stage microporous sealing device in the gas pressure compensation system of the wire drawing furnace of the present invention;

[0033] Figure 5 This is a schematic cross-sectional view of the optical fiber produced by the first embodiment of the drawing furnace pressure compensation system of the present invention;

[0034] Figure 6 This is a schematic cross-sectional view of the optical fiber produced by the second embodiment of the drawing furnace gas pressure compensation system of the present invention;

[0035] Figure 7 This is a flowchart illustrating the control method of the gas pressure compensation system for the wire drawing furnace of the present invention.

[0036] In the diagram, 1-optical fiber, 2-multi-stage microporous sealing device, 21-upper channel, 22-air blowing channel, 23-lower channel, 24-buffer channel, 25-air outlet, 26-air inlet, 27-air inlet chamber, 3-fixed base, 4-drawing furnace, 5-quartz sealing barrel, 6-sealing quartz ring, 7-tail bar, 8-air inlet, 9-mass flow controller, 10-pressure sensor, 11-controller.

[0037] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0038] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0039] It should be noted that in the description of this invention, the terms "lateral," "longitudinal," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] This invention proposes a gas pressure compensation system for a wire drawing furnace.

[0041] Reference Figures 1 to 4 A pressure compensation system for a wire drawing furnace includes a multi-stage microporous sealing device 2, a pressure sensor 10 (which can be a high-precision sensor with its probe extending directly into the high-temperature working zone inside the wire drawing furnace 4), a controller 11 (a programmable logic controller), and a mass flow controller 9 (MFC). The end of the pressure sensor 10 extends into the wire drawing furnace 4 to collect the actual pressure signal inside the furnace. The inlet side of the mass flow controller 9 is connected to a gas source (an inert gas, such as high-purity helium), and the outlet side of the mass flow controller 9 is connected to the air inlet 26 of the multi-stage microporous sealing device 2. The controller 11 is electrically connected to the control terminals of the pressure sensor 10 and the mass flow controller 9 to control the air inlet flow of the multi-stage microporous sealing device 2 according to the measured pressure.

[0042] The multi-stage microporous sealing device 2 includes a sealing sleeve installed below the bottom opening of the drawing furnace 4. The sealing sleeve has a hollow channel inside for optical fibers to pass through. The hollow channel includes an upper channel 21, at least two air blowing channels 22, and a lower channel 23 that are connected sequentially from top to bottom and coaxially arranged. Adjacent air blowing channels 22 are connected by a buffer channel 24. Multiple air outlets 25 are provided on the circumferential direction of the side wall of the air blowing channel 22. A hollow air inlet chamber 27 is formed between the side wall of the hollow channel and the outer wall of the sealing sleeve. An air inlet hole 26 communicating with the air inlet chamber 27 is opened on the outer wall of the sealing sleeve. The airflow entering from the air inlet hole 26 passes through the air inlet chamber 27 and flows out through the air outlet hole 25 to seal the optical fiber in the hollow channel.

[0043] The upper part of the wire drawing furnace 4 is sealed by components such as the quartz sealing barrel 5 and the sealing quartz ring 6, while the lower part is sealed by the multi-stage microporous sealing device 2, together forming a complete sealing system, thereby achieving sealing at both the top and bottom.

[0044] The barometric pressure sensor 10 has a range of 0-200 kPa and an accuracy of ±0.1% FS. The mass flow controller 9 has a range of 0-50 SLM and an accuracy of ±0.5%-0.8% FS.

[0045] The multi-stage micropore sealing device 2 is installed at the bottom of the drawing furnace 4 using a dedicated fixed base 3. The fixed base 3 is rigidly connected to the furnace body and achieves an airtight seal through a flange. The multi-stage micropore sealing device 2 is made of high-temperature resistant (referring to resistance to temperatures exceeding 800 degrees Celsius) and oxidation-resistant materials (such as high-nickel chromium alloys, stainless steel, silicon nitride ceramics, cast iron, carbon steel, etc.).

[0046] Specifically, in this embodiment, referring to Figure 4 The air blowing channel 22 is in the shape of an inverted frustum (an inverted frustum refers to a frustum with its large end facing upwards). The air blowing channel 22 with the inverted frustum shape structure, together with the annularly distributed air outlets 25, improves the sealing performance.

[0047] In this embodiment, the pore density on the sidewall of the air blowing channel 22 is 200 pores / cm². 2 ~400 holes / cm 2 Preferably 300 pores / cm 2 The sidewall opening ratio of the air blowing channel 22 is 25%~35%, preferably 30%, and the diameter of the air outlet 25 is 0.1mm~0.5mm, preferably 0.2mm. This parameter setting precisely ensures sealing performance, guaranteeing the uniformity and stability of the outlet air curtain even with an eccentricity of up to ±2mm in the optical fiber preform, thus completely solving the problem of airflow disturbance caused by preform misalignment.

[0048] Specifically, refer to Figure 4 The buffer channel 24 includes a first transition section in the shape of a cylinder and a second transition section above it, which is in the shape of an upright frustum (an upright frustum refers to a frustum with its large end facing down). The bottom surface of the first transition section is connected to the top surface of the lower air blowing channel 22, and the top surface of the second transition section is connected to the bottom surface of the upper air blowing channel 22. This structural arrangement of the buffer channel 24 ensures a stable transition of airflow between the upper and lower air blowing channels 22.

[0049] Reference Figure 4Both the upper channel 21 and the lower channel 23 are cylindrical, with the diameter of the upper channel 21 being larger than that of the lower channel 23, and the diameter of the lower channel 23 being smaller than the diameter of the bottom surface of the buffer channel 24 (the end face of the bottom surface near the lower channel 23). This shape design reduces air leakage and minimizes the amount of sealing gas used, while also ensuring the airtightness of the drawing furnace opening. In this embodiment, the height of the buffer channel 24 is 20mm~40mm, and the height of the air inlet chamber 27 is 100mm~200mm. This height setting further optimizes the gas flow path and further ensures the airtightness of the drawing furnace opening. The inner wall of the air inlet chamber 27 is polished to reduce flow resistance. Multiple air outlets 25 are evenly arranged circumferentially in the blowing channel 22 to achieve uniform sealing. All blowing channels 22 have the same shape and size, which facilitates production and manufacturing.

[0050] In this embodiment, the hollow channel includes an upper channel 21, at least two air blowing channels 22, and a lower channel 23, which are connected sequentially from top to bottom and coaxially arranged. A buffer channel 24 is provided between the two air blowing channels 22. The lower air blowing channel 22 performs preliminary throttling and diffusion on the high-speed airflow from the MFC, breaking up large vortices. After the airflow enters the buffer channel 24, its kinetic energy decreases, its pressure energy is restored, and it is homogenized. Subsequently, the airflow is further "combed" into a uniform laminar flow through the upper air blowing channel 22. This structure is equivalent to a "pneumatic filter," which can transform the pulsating or uneven airflow that may exist at the inlet into an extremely stable outlet flow, improving the sealing performance of the wire drawing furnace outlet side.

[0051] Furthermore, the thickness of the sidewalls of the hollow channel and the outer wall of the sealing sleeve are both 5mm to 12mm. Too thick a thickness would result in an excessively heavy structure, while too light a thickness would compromise the overall structural strength. This thickness range is chosen to strike a balance between lightness and stability.

[0052] The working process of this wire drawing furnace pressure compensation system is as follows: After the system starts, initialization is performed first: the target micro-positive pressure value P required for the wire drawing process is set in controller 11. set (e.g., 101.5 kPa), and set an initial flow rate Q for the mass flow controller 9 based on historical experience. init (For example, 8 L / min). After the wire drawing process begins, the system enters a real-time monitoring and adjustment cycle: the pressure sensor 10 collects the actual pressure value P inside the furnace at a frequency of 10-100 times per second. actual The signal is transmitted in real time to the controller 11 via the analog input module. The controller 11 internally runs a PID control algorithm. Based on the algorithm output, the controller 11 sends a 4-20mA standard current signal to the mass flow controller 9, precisely instructing it to adjust the gas flow rate to the new set value. For example, if P is detected... actual<P set If the flow rate is high, the flow rate increases linearly; conversely, if the flow rate is low, the flow rate decreases. Inert gas, precisely regulated by the mass flow controller 9, enters the multi-stage microporous sealing device 2 at a flow rate of 5-20 L / min and undergoes the aforementioned multi-stage stabilization process. Finally, the gas flowing out from the uppermost blowing channel 22 forms a large-area, uniformly velocity umbrella-shaped laminar flow curtain below the furnace opening. The flow resistance of this curtain has a good linear relationship with the inlet flow rate. By finely controlling the flow rate, its resistance can be precisely controlled, thereby offsetting pressure fluctuations caused by external disturbances or internal process changes, and "locking" the furnace pressure near the set value. The response time of the entire adjustment process is less than 3 seconds, effectively controlling furnace pressure fluctuations within P... set Within ±0.5%.

[0053] The gas pressure compensation system for wire drawing furnace proposed in this invention has the following beneficial effects:

[0054] 1. Strong "homogenization" capability: Through the air inlet chamber 27 and then through multiple air outlets 25 of at least two air blowing channels 22, high-speed air intake can be converted into uniform laminar flow, generating adjustable air curtain resistance. Even if the optical fiber preform has an eccentricity of up to ±2mm, the uniformity and stability of the outlet air curtain can be guaranteed, thus completely solving the problem of airflow disturbance caused by preform offset.

[0055] 2. The use of a multi-stage air blowing channel 22 improves the sealing performance at the outlet of the wire drawing furnace, which can greatly reduce the consumption of inert gas, saving 15%-20% of inert gas;

[0056] 3. The use of a sealed sleeve to create a constant micro-positive pressure environment can effectively isolate air intrusion, prevent the graphite heating element from oxidizing, and extend its service life by more than 30%.

[0057] 4. A constant micro-positive pressure environment is created by using a sealed sleeve, forming a stable airflow and temperature field inside the drawing furnace 4. The furnace pressure fluctuation range is ±0.25-0.6kPa, which greatly improves the consistency of the optical fiber's geometric parameters. The optical fiber diameter fluctuation range can be controlled within ±0.2μm, and the cladding non-circularity is better than 0.3%.

[0058] 5. The gas pressure compensation system of this drawing furnace has strong compatibility. It can be adapted to preforms of different diameters and drawing speeds through PLC program, reducing the need to replace hardware components, improving production efficiency, and bringing considerable economic benefits due to its reduced consumption of protective gas.

[0059] The following two examples illustrate the gas pressure compensation system for this wire drawing furnace.

[0060] Example 1

[0061] In this embodiment, the drawing furnace pressure compensation system is used to produce G.652.D standard single-mode optical fiber. The cross-sectional diagram of the single-mode optical fiber is shown below. Figure 5 As shown.

[0062] In this embodiment, the sidewalls of the sealing sleeve and the hollow channel are both made of 316L stainless steel through precision wire cutting and laser drilling. The sealing sleeve and the sidewalls forming the hollow channel are made of the same material, facilitating integral molding and simplifying the manufacturing process. In this embodiment, the height of the buffer channel 24 is 40mm. The sealing sleeve is sealed to the 60mm diameter outlet flange at the bottom of the drawing furnace 4 via its top flange. The pressure sensor 10 is an absolute pressure ceramic capacitive pressure sensor 10, with its threaded probe (M20×1.5) screwed into a dedicated interface on the sidewall of the drawing furnace 4, positioning the pressure-sensing diaphragm approximately 200mm below the heating zone inside the furnace to accurately reflect the working area pressure. The mass flow controller 9MFC consists of a high-purity helium cylinder, a pressure reducing valve, a precision filter, and a mass flow controller 9 connected in series. The outlet of the mass flow controller 9 is connected to the inlet 26 of the sealing sleeve via a φ6mm EP-grade stainless steel hose. The controller 11 is centered around an industrial PLC controller 11. Its analog input module receives 4-20mA signals from the barometric pressure sensor 10, and its analog output module sends 4-20mA control signals to the MFC, forming a closed loop.

[0063] The specific parameters of the gas pressure compensation system for this wire drawing furnace are shown in the table below.

[0064] Table 1. Parameters of Core Components of the Gas Pressure Compensation System for Wire Drawing Furnaces

[0065]

[0066] The level spacing refers to the height of the buffer channel 24.

[0067] Operating procedures: During normal wire drawing operation, the operator only needs to set the target pressure value P on the PLC controller 11. set (e.g., 101.5 kPa) and pressure control zone (e.g., ±0.5 kPa). After startup, the system enters fully automatic operation. Its closed-loop control logic is as follows: the pressure sensor 10 samples the furnace pressure P at a frequency of 10 Hz. actual ; Controller 11 calculates the deviation e(t) = P actual -P set and the rate of change; the PID control algorithm outputs a control signal u(t); the MFC receives u(t) and linearly adjusts the helium output flow rate Q. For example, when P actual Below P setAs u(t) increases, Q increases, and more gas flows through the two-stage microporous device. The gas is divided into multiple fine streams as it passes through the first-stage microporous system. These streams mix and become evenly pressurized in the buffer chamber, and then further "sorted" through the subsequent blowing channel 22, ultimately forming a uniform and stable laminar gas curtain at the furnace opening. The resistance of this gas curtain is positively correlated with the flow rate Q. An increase in flow rate means a stronger "blocking" effect of the gas curtain on the gas inside the furnace, thereby increasing P... actual Recovery.

[0068] This drawing furnace pressure compensation system is used to draw G.652.D standard single-mode optical fiber (preform diameter 80mm, drawing speed 1500 m / min). Its key process parameters are compared below:

[0069] 1. Furnace pressure stability: The range of pressure fluctuation inside the furnace has been narrowed from 101.5±3.0 kPa under manual control to 101.5±0.5 kPa;

[0070] 2. Fiber geometric performance: Fiber diameter fluctuation (standard deviation) has been optimized from ±0.8μm to within ±0.3μm;

[0071] 3. The out-of-roundness of the cladding layer improved from an average of 0.6% to below 0.3%;

[0072] 4. Equipment and Cost: The stable micro-positive pressure environment effectively curbs air intrusion, significantly slows down the oxidation of the graphite heating element surface, and extends the estimated lifespan by more than 30%. At the same time, the consumption of inert gas (helium) is reduced by 15% due to the avoidance of overcompensation.

[0073] Example 2

[0074] In this embodiment, the drawing furnace gas pressure compensation system is used for hollow anti-resonant optical fibers, and its fiber cross-section diagram is shown below. Figure 6 As shown. Because hollow optical fibers are extremely susceptible to distortion and collapse during the drawing process due to airflow or pressure disturbances, this example incorporates several design improvements based on Example 1, with the core objective of achieving ultimate pressure stability and airflow uniformity.

[0075] The difference between this embodiment and Embodiment 1 is that a three-stage air blowing channel is used (Embodiment 1 uses a two-stage air blowing channel). At the same time, the material of the sealing sleeve and the side wall of the hollow channel is upgraded to Inconel 718 to withstand potentially higher local temperatures and reduce thermal deformation.

[0076] To generate a finer and more uniform airflow, the diameter of the air outlet 25 was reduced to 0.1 mm, and the pore density was increased to 400 pores / cm³. 2The open area ratio is approximately 31%. A three-stage air blowing channel is adopted, with an inlet chamber 27 height of 280 mm and a stage spacing of 30 mm, thus providing a longer airflow homogenization path. All outlet holes 25 are electrolytically polished after processing to ensure smooth inner walls and prevent turbulence. The gas supply system uses high-purity helium gas with a purity of 99.9999%, as its higher thermal conductivity is beneficial for uniform furnace temperature. Two MFCs are used for parallel gas supply, one for basic flow rate (0-15 SLM) and the other for fine-tuning flow rate (0-5 SLM), which, when combined, can achieve high-resolution flow rate adjustment of 0.05 SLM. The key components and their parameters in this embodiment are shown in Table 2.

[0077] Table 2 Parameters of Core Components in Example 2

[0078]

[0079] Operating steps: To begin the wire drawing operation, the operator only needs to set the target pressure value P on the PLC controller 11. set Due to the complex microstructure of the hollow antiresonant optical fiber, the target furnace pressure was set to 100.8 kPa, slightly lower than atmospheric pressure, to reduce the stress on the internal microstructure. After startup, the system entered fully automatic operation. Pressure sensor 10 sampled the furnace pressure P at a frequency of 10 Hz. actual PLC calculates the deviation e(t) = P actual -P set The rate of change; the PID control algorithm outputs the control signal u(t); the mass flow controller 9 receives u(t) and linearly adjusts the helium output flow rate Q.

[0080] This embodiment employs a dual MFC parallel system to achieve high-resolution flow regulation of 0.05 SLM, ensuring pressure control accuracy of ±0.25 kPa. Furthermore, during the wire drawing process, if the controller 11 detects a pressure change exceeding 1.0 kPa within one second, the system automatically reduces the wire drawing speed to a safe value and locks the current MFC flow rate. Simultaneously, after passing through the three-stage ultra-dense air blowing channels 22, the resulting "air wall" has a lower and more uniform flow velocity, effectively isolating external environmental vibrations and airflow noise from interfering with furnace stability, providing a near-static "air" environment for the perfect formation of microstructures.

[0081] The gas pressure compensation system of this drawing furnace was applied to the drawing of a typical 5-tube hollow anti-resonant optical fiber, and the following results were obtained:

[0082] 1. Furnace pressure stability: The working pressure inside the furnace is stably controlled at 100.8±0.2 kPa.

[0083] 2. Uniformity of fiber microstructure: Under an electron microscope, the shape regularity, size consistency and arrangement periodicity of all air hole microstructures on the cross-section of the fiber are more than 99% similar to those of the preform, with no obvious deformation or hole collapse.

[0084] 3. Optical performance: Thanks to the well-preserved microstructure, the transmission loss of the optical fiber in the 1550nm window is significantly reduced from the initial 2dB / km to below 1dB / km.

[0085] Example 1 above demonstrates the universal value of this drawing furnace pressure compensation system in improving the quality, efficiency and economic benefits of traditional optical fiber production; Example 2 illustrates that this drawing furnace pressure compensation system, through targeted design, can meet the extreme requirements of environmental stability for the manufacturing of cutting-edge special optical fibers, especially hollow optical fibers, thereby verifying the strong technical inclusiveness and upgrade potential of this invention.

[0086] The present invention also proposes a multi-stage microporous sealing device for a wire drawing furnace gas pressure compensation system.

[0087] In this preferred embodiment, refer to Figures 2 to 4 A multi-stage microporous sealing device for a wire drawing furnace pressure compensation system includes a sealing sleeve installed below the bottom opening of the wire drawing furnace 4. The sealing sleeve has a hollow channel inside for optical fibers to pass through. The hollow channel includes an upper channel 21, at least two air blowing channels 22, and a lower channel 23 arranged coaxially from top to bottom. Adjacent air blowing channels 22 are connected by a buffer channel 24. Multiple air outlets 25 are provided on the circumferential direction of the sidewall of the air blowing channel 22. A hollow air inlet chamber 27 is formed between the sidewall of the hollow channel and the outer wall of the sealing sleeve. An air inlet hole 26 communicating with the air inlet chamber 27 is opened on the outer wall of the sealing sleeve. The airflow entering from the air inlet hole 26 flows out through the air outlet hole 25 after passing through the air inlet chamber 27 to seal the optical fibers in the hollow channel.

[0088] Specifically, in this embodiment, the air blowing channel 22 is in the shape of an inverted frustum. The pore density on the sidewall of the air blowing channel 22 is 200~400 pores / cm², the opening rate of the sidewall of the air blowing channel 22 is 25%~35%, and the diameter of the air outlet 25 is 0.1mm~0.5mm. The buffer channel 24 includes a first transition section in the shape of a cylinder and a second transition section above it in the shape of an upright frustum. The bottom end face of the first transition section is connected to the top end face of the lower air blowing channel 22, and the top end face of the second transition section is connected to the bottom end face of the upper air blowing channel 22. Both the upper channel 21 and the lower channel 23 are cylindrical. The diameter of the upper channel 21 is larger than the diameter of the lower channel 23, and the diameter of the lower channel 23 is smaller than the diameter of the small end bottom face of the buffer channel 24.

[0089] The height of the buffer channel 24 is 20mm~40mm, and the height of the air inlet chamber 27 is 100mm~200mm. Multiple air outlets 25 are evenly arranged in the circumferential direction of the air blowing channel 22. All buffer channels 24 have the same shape and size.

[0090] The present invention also proposes a control method for a gas pressure compensation system for a wire drawing furnace.

[0091] Reference Figure 7 This invention proposes a control method based on the above-mentioned gas pressure compensation system for a wire drawing furnace, comprising the following steps:

[0092] Step S10: After the drawing furnace 4 starts running, set the furnace pressure value to the initial set pressure value;

[0093] Step S20: Control the pressure sensor 10 to acquire the actual pressure value inside the furnace in real time, and send the actual pressure value inside the furnace to the controller 11;

[0094] In step S30, the controller 11 calculates the current signal based on the actual pressure value inside the furnace according to its internal preset algorithm, and sends the current signal to the mass flow controller 9 to control the mass flow controller 9 to control the air intake flow of the multi-stage microporous sealing device 2 to the preset set value.

[0095] Step S40: Update the obtained actual pressure value inside the furnace in real time; when the obtained actual pressure value inside the furnace is less than the target micro-positive pressure value, execute step S50; when the obtained actual pressure value inside the furnace is greater than the target micro-positive pressure value, execute step S60.

[0096] In step S50, the controller 11 updates the current signal to increase the air intake flow of the multi-stage microporous sealing device 2.

[0097] In step S60, the controller 11 updates the current signal to reduce the air intake flow of the multi-stage microporous sealing device 2.

[0098] In this control method, during initial setup, the target pressure is set to 101.0~102.0 kPa and the initial flow rate is set to 8 SLM~15 SLM.

[0099] The control method proposed in this invention employs an intelligent closed-loop control system based on real-time feedback, which can respond to minute pressure changes at the millibar level in a sub-second manner, achieving dynamic pressure balance and significantly reducing the furnace pressure fluctuation range from more than ±5% in the traditional method to within ±0.5%.

[0100] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A multi-stage microporous sealing device for a wire drawing furnace pressure compensation system, characterized in that, The device includes a sealing sleeve installed below the bottom opening of a wire drawing furnace. The sealing sleeve has a hollow channel inside for optical fibers to pass through. The hollow channel includes an upper channel, at least two air blowing channels, and a lower channel arranged coaxially from top to bottom. Adjacent air blowing channels are connected by a buffer channel. Multiple air outlets are provided on the circumferential direction of the sidewalls of the air blowing channels. A hollow air inlet chamber is formed between the sidewall of the hollow channel and the outer wall of the sealing sleeve. An air inlet hole communicating with the air inlet chamber is provided on the outer wall of the sealing sleeve. Airflow entering through the air inlet hole passes through the air inlet chamber and exits through the air outlet hole to seal the optical fiber in the hollow channel. The buffer channel includes a first transition section in the shape of a cylinder and a second transition section above it in the shape of an upright frustum. The bottom surface of the first transition section is connected to the top surface of the lower air blowing channel, and the top surface of the second transition section is connected to the bottom surface of the upper air blowing channel.

2. The multi-stage microporous sealing device for the gas pressure compensation system of the wire drawing furnace as described in claim 1, characterized in that, The air blowing channel is shaped like an inverted frustum.

3. The multi-stage microporous sealing device for the gas pressure compensation system of the wire drawing furnace as described in claim 1, characterized in that, The pore density on the sidewall of the air blowing channel is 200 pores / cm². 2 ~400 holes / cm 2 The sidewall opening ratio of the air blowing channel is 25%~35%, and the diameter of the air outlet is 0.1mm~0.5mm.

4. The multi-stage microporous sealing device for the gas pressure compensation system of the wire drawing furnace as described in claim 2, characterized in that, Both the upper and lower channels are cylindrical in shape, with the diameter of the upper channel being larger than that of the lower channel, and the diameter of the lower channel being smaller than that of the bottom surface of the buffer channel.

5. The multi-stage microporous sealing device for the gas pressure compensation system of the wire drawing furnace as described in claim 1, characterized in that, The height of the buffer channel is 20mm~40mm, and the height of the air intake chamber is 100mm~200mm.

6. The multi-stage microporous sealing device for the gas pressure compensation system of the wire drawing furnace as described in claim 1, characterized in that, The multiple air outlets are evenly arranged in the circumferential direction of the air blowing channel; the sidewalls of the hollow channel and the outer sidewalls of the sealing sleeve are both 5mm to 12mm thick.

7. The multi-stage microporous sealing device for the gas pressure compensation system of a wire drawing furnace as described in any one of claims 1 to 6, characterized in that, All the described air blowing channels are identical in shape and size.

8. A gas pressure compensation system for a wire drawing furnace, characterized in that, The multi-stage microporous sealing device, including the gas pressure compensation system for a wire drawing furnace as described in any one of claims 1 to 7, further includes a gas pressure sensor, a controller, and a mass flow controller. The end of the gas pressure sensor extends into the interior of the wire drawing furnace to collect the actual pressure signal inside the furnace. The inlet side of the mass flow controller is connected to the gas source, and the outlet side of the mass flow controller is connected to the air inlet of the multi-stage microporous sealing device. The controller is electrically connected to the control terminals of the gas pressure sensor and the mass flow controller to control the air inlet flow of the multi-stage microporous sealing device according to the measured pressure.

9. A control method based on the gas pressure compensation system of the drawing furnace according to claim 8, characterized in that, Includes the following steps: After the wire drawing furnace starts running, set the furnace pressure to the initial set pressure value; The control pressure sensor acquires the actual pressure value inside the furnace in real time and sends the actual pressure value inside the furnace to the controller; The controller calculates the current signal based on the actual pressure value inside the furnace according to its internal preset algorithm, and sends the current signal to the mass flow controller to control the air intake flow of the multi-stage microporous sealing device to the preset value. The actual pressure value inside the furnace is updated in real time. When the actual pressure value inside the furnace is less than the target micro-positive pressure value, the controller updates the current signal to increase the air intake flow of the multi-stage microporous sealing device. When the actual pressure value inside the furnace is greater than the target micro-positive pressure value, the controller updates the current signal to reduce the air intake flow of the multi-stage microporous sealing device.

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