Spiral isostatic pressing die and forming process of annular filter element

Abstract

The invention provides a spiral isostatic pressing die and a forming process of an annular filter element, and belongs to the technical field of filter element forming. The external structure comprises a spiral outer sleeve and an inner rubber tube which is arranged in an inner cavity of the outer sleeve in a shape follow-up mode, the outer wall of the inner rubber tube is attached to the inner wall of the outer sleeve, a spiral forming cavity is formed in the inner cavity of the inner rubber tube, and a plurality of static pressure holes are formed in the outer sleeve; the internal structure comprises a mold core located in the forming cavity, the mold core is arranged in the forming cavity in the axial direction in a shape follow-up mode, and a filler cavity is formed between the mold core and the inner rubber pipe. The plugging structure comprises two sealing rubber plugs, and the two sealing rubber plugs are detachably installed at the two ends of the filler cavity correspondingly. According to the spiral isostatic pressing die, a spiral filter element can be formed, then preparation of an annular filter element is completed, the process is simpler, the yield is increased, and the hole diameter precision is higher.

Description

Technical Field

[0001] This invention belongs to the field of filter element molding technology, and more specifically, it relates to a spiral isostatic pressing mold and a molding process for annular filter elements. Background Technology

[0002] In the field of industrial filtration and aeration, annular filter cartridges are key components whose performance directly affects fluid treatment efficiency and system stability. Currently, the industry generally uses the traditional straight tube filter cartridge rolling process to manufacture annular aeration filter cartridges. This process requires many cumbersome steps: first, metal powder is made into a straight tube filter cartridge blank, and then the straight tube filter cartridge is bent into an annular shape by manual or mechanical winding. During the process, welding is also required to fix it to maintain the annular structure.

[0003] This traditional process has significant drawbacks: First, it is highly complex, with multiple steps increasing production time and labor costs, and is prone to poor product consistency due to accumulated operational errors. Second, the yield is low, as the straight filter cartridge blank is prone to cracking and deformation due to uneven stress during the rolling process, especially for thin-walled or large-diameter annular filter cartridges, resulting in a high scrap rate. Third, pore size control is difficult, as the mechanical stress during rolling alters the internal pore structure of the filter cartridge, leading to uneven pore size distribution, affecting filtration accuracy and the stability of aeration effect, and consequently impacting the overall operating efficiency of the treatment system. Summary of the Invention

[0004] The purpose of this invention is to provide a spiral isostatic pressing mold, which aims to solve the problems of high process complexity, low yield, and difficulty in pore size control when bending straight tube filter elements into annular filter elements.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a spiral isostatic pressing mold, including an external structure, an internal structure, and a sealing structure; The external structure includes a spiral outer tube and an inner rubber tube conformally disposed within the inner cavity of the outer tube. The outer wall of the inner rubber tube is fitted with the inner wall of the outer tube, and the inner cavity of the inner rubber tube forms a spiral-shaped molding chamber. The outer tube has multiple static pressure holes. The internal structure includes a mold core located within the molding cavity. The mold core is axially conformally disposed within the molding cavity, and a filler chamber for filling metal powder is formed between the mold core and the inner tubing. The sealing structure includes two sealing plugs, which are detachably installed at both ends of the packing chamber, so that they are in an uninstalled state during packing or in an installed state after packing.

[0006] In one possible implementation, when the sealing plug is in an uninstalled state, the two ends of the outer sleeve are respectively provided with first positioning pins radially, the two first positioning pins are parallel to each other, and the first positioning pins pass through the side wall of the outer sleeve and the side wall of the inner tube from the outside to the inside and are inserted into the mold core. The two ends of the outer sleeve are provided with second positioning pins, and the second positioning pins are perpendicular to either of the first positioning pins.

[0007] In one possible implementation, limit blocks are provided at both ends of the second positioning pin, and the two limit blocks can move along the axial direction of the second positioning pin to press against the outer side walls of the outer sleeve that are far apart from each other.

[0008] In one possible implementation, the two end faces of the outer tube are on the same plane, and the two end faces of the outer tube are coaxially provided with an adapter half-groove for adapting to the second positioning pin. The adapter half-groove is respectively opened on the same side end face of the outer tube, the inner tube and the mold core along its length direction.

[0009] In one possible implementation, the two ports of the packing chamber are staggered and their axial projection areas do not overlap.

[0010] In one possible implementation, a plurality of the static pressure holes are symmetrically and coaxially opened on both sides of the outer sleeve.

[0011] In one possible implementation, the sealing plug includes an integrally formed end cap and an insertion sleeve, the diameter of the end cap being larger than the cross-sectional diameter of the packing chamber, and the insertion sleeve being inserted into both ends of the packing chamber and having an interference fit with the packing chamber.

[0012] The beneficial effects of the spiral isostatic pressing mold provided by this invention are as follows: Compared with the prior art, the spiral filling chamber allows metal powder to be directly filled and isostatically pressed to obtain a spiral filter element blank in one step, eliminating cumbersome steps such as straight pipe bending and welding, significantly reducing the time cost and operational complexity caused by process connections, and significantly improving production efficiency. The conformal design of the forming chamber and the mold core ensures that the metal powder is subjected to uniform pressure under isostatic pressing. Multiple static pressure holes on the outer tube ensure that the pressure is evenly transmitted to the inner tube, thereby ensuring that the metal powder in the filling chamber is subjected to consistent stress, avoiding blank defects caused by local stress concentration, effectively reducing the scrap rate, and significantly improving the yield. The metal powder is uniformly pressed in the spiral filling chamber, resulting in a more stable bonding state between powder particles. The pore formation process is less affected by external interference, allowing for precise control of pore size and distribution, ensuring the stability of filter element filtration accuracy and aeration effect, and solving the problem of difficult pore size control in traditional processes. Furthermore, the removable sealing plug design of the sealing structure facilitates the filling of metal powder during the filling process and provides a reliable seal after filling, ensuring that the powder does not leak during isostatic pressing, further guaranteeing the molding quality and providing reliable support for the implementation of the above-mentioned solution. The spiral isostatic pressing mold provided by this invention can form a spiral filter element, thereby completing the preparation of annular filter elements. The process is simpler, the yield is improved, and the pore size accuracy is higher.

[0013] The present invention also provides a molding process for an annular filter element, using the aforementioned spiral isostatic pressing mold, comprising the following steps: S1: When the two sealing plugs are not installed, use a spray gun to spray stainless steel powder into the port of the packing chamber until the packing chamber is full. S2: After installing two sealing plugs at both ends of the packing chamber, place the spiral isostatic mold into the isostatic press for pressing; S3: After the spiral isostatic pressing mold is completed, remove the two sealing plugs, fix the outer sleeve, and spirally pull the mold core and spiral filter element out of the packing chamber. Finally, spirally pull the mold core out of the spiral filter element. S4: Place the spiral filter element on the tray and load it into the vacuum sintering furnace for sintering. S5: After the spiral filter element is sintered, it is taken out of the vacuum sintering furnace, shaped and pressed to form an annular filter element with a reserved opening. The three-way connector is placed in the reserved opening and welded to the two ports of the annular filter element respectively.

[0014] This invention provides a molding process for annular filter elements. Compared with existing technologies, powder filling is performed when the sealing plug is in an uninstalled state. Combined with the structural characteristics of the spiral packing chamber, this allows stainless steel powder to fill the entire chamber more smoothly, reducing filling dead zones caused by complex structures. The use of a spray gun enables dense pre-filling of the powder through pressure control, laying a good foundation for subsequent pressing. Utilizing the uniform pressure characteristics of an isostatic press, combined with the spiral chamber design of the mold, the stainless steel powder is subjected to uniform force in all directions, ensuring consistent density and uniform structure of the molded spiral filter element, avoiding the localized porosity problems that may occur with traditional molding methods. First, the outer sleeve is fixed, then the mold core and spiral filter element are spirally extracted together, and finally the mold core and filter element are separated. This demolding method, adapted to the spiral structure, minimizes external force damage to the filter element during demolding, ensuring the accuracy of the spiral shape. Vacuum sintering eliminates pores and stress inside the filter element, enhancing its structural strength and filtration performance. Shaping and pressing corrects minor deformations after sintering, ensuring the dimensional accuracy of the final annular structure. Welding of the tee joints allows the annular filter element to form a complete fluid channel, meeting practical application requirements. This invention provides a forming process for annular filter elements with a coherent and efficient overall flow. Each step, from powder filling to final forming, is designed around the characteristics of a spiral isostatic pressing mold. This fully utilizes the structural advantages of the mold and, through the synergistic effect of each step, ultimately obtains annular filter elements with uniform density, meeting strength standards, and precise dimensions, while simultaneously ensuring production efficiency and product consistency. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of a spiral isostatic pressing mold in the state without the sealing plug installed, provided by the present invention; Figure 2 A schematic diagram of the structure of a spiral isostatic pressing mold with a sealing plug installed, provided by the present invention; Figure 3 A schematic diagram of the structure of the sealing plug provided by the present invention; Figure 4 This is a schematic diagram of the structure of the mold core provided by the present invention; Figure 5 This is a schematic diagram of the structure of the annular filter element provided by the present invention; Figure 6 A flowchart of the molding process of an annular filter element provided by the present invention.

[0017] In the diagram: 1. Outer sleeve; 2. Inner rubber sleeve; 3. Mold core; 4. Sealing plug; 401. End cap; 402. Insertion sleeve; 5. First positioning pin; 6. Second positioning pin; 7. Limiting block; 8. Static pressure hole; 9. Magnetorheological fluid channel; 10. Pressure sensing plate; 11. Filter element; 12. T-connector. Detailed Implementation

[0018] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0019] Unless otherwise explicitly specified, the use of terms such as "first," "second," or "third" is intended to distinguish different objects, not to describe a specific order.

[0020] Unless otherwise expressly defined, the use of directional terms such as “center,” “lateral,” “longitudinal,” “horizontal,” “vertical,” “top,” “bottom,” “inner,” “outer,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “clockwise,” “counterclockwise,” “high,” and “low” to indicate orientation or positional relationships is based on the orientation and positional relationships shown in the accompanying drawings and is only for the convenience of describing the invention and simplifying the description, and is not intended to 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 limiting the specific scope of protection of the invention.

[0021] Please see Figure 1 and Figure 2 The present invention will now describe a spiral isostatic pressing mold. A spiral isostatic pressing mold includes an external structure, an internal structure, and a sealing structure. The external structure includes a spiral outer tube and an inner tube conformally disposed within the inner cavity of the outer tube. The outer wall of the inner tube fits against the inner wall of the outer tube, and the inner cavity of the inner tube forms a spiral molding chamber. Multiple static pressure holes are provided on the outer tube. The internal structure includes a mold core located within the molding chamber. The mold core is conformally disposed axially within the molding chamber, and a filling chamber for filling metal powder is formed between the mold core and the inner tube. The sealing structure includes two sealing plugs, which are detachably installed at both ends of the filling chamber, allowing them to be in a non-installed state during filling or in an installed state after filling.

[0022] This invention provides a spiral isostatic pressing mold. Compared with existing technologies, it allows metal powder to be directly filled into a spiral-shaped packing chamber, and a spiral filter element blank is obtained in one step after isostatic pressing. This eliminates cumbersome steps such as straight pipe bending and welding, significantly reducing the time cost and operational complexity caused by process connections, and significantly improving production efficiency. The conformal design of the forming chamber and the mold core ensures that the metal powder is subjected to uniform pressure under isostatic pressing. Multiple static pressure holes on the outer tube ensure that the pressure is evenly transmitted to the inner tube, thereby ensuring that the metal powder in the packing chamber is subjected to consistent stress, avoiding blank defects caused by local stress concentration, effectively reducing the scrap rate, and significantly improving the yield. The metal powder is uniformly pressed in the spiral packing chamber, resulting in a more stable bonding state between powder particles. The pore formation process is less affected by external interference, and the pore size and distribution can be precisely controlled, ensuring the stability of filter element filtration accuracy and aeration effect, and solving the problem of difficult pore size control in traditional processes. Furthermore, the removable sealing plug design of the sealing structure facilitates the filling of metal powder during the filling process and provides a reliable seal after filling, ensuring that the powder does not leak during isostatic pressing, further guaranteeing the molding quality and providing reliable support for the implementation of the above-mentioned solution. The spiral isostatic pressing mold provided by this invention can form a spiral filter element, thereby completing the preparation of annular filter elements. The process is simpler, the yield is improved, and the pore size accuracy is higher.

[0023] Please see Figure 1 When the sealing plug is not installed, first locating pins are radially inserted at both ends of the outer sleeve. These two first locating pins are parallel to each other and pass through the sidewalls of the outer sleeve and inner sleeve sequentially from the outside in, eventually inserting into the mold core. This allows for precise radial positioning of the mold core, inner sleeve, and outer sleeve, effectively preventing relative misalignment during filling operations and ensuring the shape and dimensional accuracy of the filling chamber, laying the foundation for uniform filling of metal powder. Second locating pins are also inserted at both ends of the outer sleeve, perpendicular to either of the first locating pins. This further restricts the relative movement of components in another dimension. The second and first locating pins form a three-dimensional positioning system, significantly improving the positioning accuracy of the entire mold structure when the sealing plug is not installed, and reducing problems such as deformation of the filling chamber caused by component misalignment.

[0024] The combination of the first and second locating pins tightly connects the outer sleeve, inner tubing, and mold core into a single unit, enhancing the overall rigidity of the mold in an unsealed state. During operations such as metal powder filling, it effectively resists external forces impacting and disturbing the mold structure, preventing loosening or shaking of components, ensuring a smooth filling process, and reducing the risk of instability affecting filling quality.

[0025] Please see Figure 1The second locating pin has limit blocks at both ends. These limit blocks can move axially along the second locating pin to press against the outer walls of the outer sleeve, which are far apart from each other. As the limit blocks move axially, they can precisely apply pressure to the outer walls of the outer sleeve by adjusting their own positions, creating a clamping force on the entire external structure of the mold. This force promotes a tighter fit between the outer sleeve, inner tube, and mold core, minimizing relative displacement caused by assembly gaps. Especially during metal powder filling, this effectively avoids dimensional deviations in the filling chamber caused by loose components, providing a solid guarantee for subsequent molding accuracy.

[0026] Please see Figure 1 The two end faces of the outer sleeve are on the same plane, and coaxially formed with matching semi-grooves for the second locating pin. These semi-grooves are respectively formed along the length of the outer sleeve, inner tube, and mold core on the same side end face. The matching semi-grooves provide a precise mounting track for the second locating pin. Because the matching semi-grooves of the outer sleeve, inner tube, and mold core are coaxially arranged, it ensures that the second locating pin remains straight when passing through, preventing bending or loosening due to uneven force caused by installation position deviations. Simultaneously, the semi-groove structure matches the shape of the second locating pin, increasing the contact area between the locating pin and each component, making the locating pin less prone to radial wobble during operation, thus ensuring stable positioning.

[0027] Please see Figure 4 The mold core adopts a hollow structure, with embedded magnetorheological fluid channels that allow for fluid circulation through inlets and outlets. Multiple pressure sensors embedded axially on the outer wall are connected wirelessly to an external data acquisition device, forming a dynamic adjustment system. During pressing in the filling chamber, the system operates as follows: After the magnetorheological fluid (a smart material composed of magnetic particles dispersed in a liquid carrier) is introduced into the channels, an external magnetic field generator applies a variable magnetic field. When the magnetic field strength increases, the magnetic particles align in a chain-like structure along the magnetic field direction, making the magnetorheological fluid appear almost solid, thus increasing the mold core rigidity. When the magnetic field strength decreases, the magnetic particles return to a dispersed state, the magnetorheological fluid reverts to a liquid state, and the mold core rigidity decreases accordingly. Meanwhile, the pressure sensor captures pressure changes at different locations within the packing chamber in real time and transmits the data to an external device. The system dynamically adjusts the magnetic field strength based on the pressure distribution to achieve precise adaptation of the core rigidity—increasing the rigidity of the corresponding area when local pressure exceeds the limit to resist the pressure and prevent filter element deformation; reducing rigidity when local pressure is insufficient to allow the chamber space to expand appropriately to enhance the pressing effect, ultimately achieving adaptive pressure balance.

[0028] Leveraging the rapid response characteristics of magnetorheological fluid, the rigidity of the mold core can be adjusted within milliseconds. Combined with real-time feedback from pressure sensing, the pressure difference between points within the chamber can be controlled within 5%, effectively solving the problem of uneven pressure caused by the complex structure of spiral filter elements and reducing defects such as pressing cracks and wall thickness deviations. By adjusting the rigidity of the mold core locally, the molding accuracy of each part of the filter element is made consistent. In addition, there is no need to replace the mold core; simply adjusting the magnetic field strength can adapt to the pressing requirements of filter elements with different densities and spiral parameters, reducing mold replacement costs and time. Finally, the closed-loop control formed by pressure sensing and rigidity adjustment reduces human intervention errors, resulting in smaller deviations in dimensional tolerances of batch products and significantly improving product consistency.

[0029] The two ports of the packing chamber are staggered, and their axial projection areas do not overlap. When installing the sealing plugs, the non-overlapping port structure reduces the risk of interference between the two plugs, making plug installation smoother, the sealing effect more reliable, and reducing seal failure caused by plug collisions. Simultaneously, the non-overlapping port structure provides more flexible removal space for the filter element. Operators can first slowly pull one end of the filter element from the corresponding port, using the gap created by the staggered ports to adjust the filter element angle, avoiding the other end scraping against the inner wall of the mold, and then gradually remove the entire spiral filter element smoothly. This design effectively reduces the risk of interference between the filter element and the mold structure during removal, protecting the integrity of the molded filter element's shape and internal pore structure from damage, while also improving the smoothness of the removal operation and further enhancing production efficiency.

[0030] Specifically, multiple static pressure holes are symmetrically and coaxially arranged on both sides of the outer sleeve, allowing the static pressure medium to enter simultaneously and in equal amounts from both sides. Because the positions and structures of the static pressure holes on both sides are perfectly aligned, the resistance experienced by the medium during flow is essentially the same, ensuring a symmetrical radial distribution of the medium pressure within the mold. This avoids pressure bias caused by unilateral pressure entry, thus ensuring uniform pressure on all parts of the metal powder within the filling chamber. This significantly reduces molding defects caused by uneven pressure, such as insufficient local density or shape distortion. This design also effectively counteracts the lateral force of the static pressure medium on the outer sleeve. When the medium enters from the symmetrical static pressure holes on both sides, the pressure applied to the outer sleeve on both sides is equal in magnitude and opposite in direction, significantly reducing the deformation of the outer sleeve caused by unidirectional force, ensuring the structural stability of the mold, and extending its service life. Especially for molds with special spiral structures, this force balance better maintains the precision of the spiral shape, preventing changes in mold shape due to uneven force during long-term use, which could affect the molding quality of subsequent products.

[0031] Specifically, the walls of the static pressure holes are electropolished, and each static pressure hole is detachably embedded with a porous ceramic filter element. The pore size of the filter element decreases gradually along the direction of media flow. An elastic sealing ring is installed between the filter element and the hole wall of the static pressure hole. The elastic sealing ring is made of hydrogenated nitrile rubber with a Shore hardness of 65-75. The gradient-decreasing porous ceramic filter element forms a multi-stage filtration structure. The large-pore section first intercepts larger impurities to avoid clogging the subsequent small-pore section, while the small-pore section deeply purifies the static pressure media, effectively preventing impurities from entering the mold and contaminating the metal powder, thus ensuring the purity of the molded product. At the same time, the detachable structure allows for quick replacement of the filter element when it becomes clogged or worn, significantly reducing maintenance costs and downtime. The electropolished hole wall surface has extremely high smoothness, which not only significantly reduces media flow resistance and pressure loss, but also prevents the formation of eddies or turbulence in the media, allowing the pressure to be transmitted more smoothly to the inner tube, further improving the uniformity of stress in all areas of the packing chamber. In addition, the elastic sealing ring made of hydrogenated nitrile rubber has excellent oil resistance and aging resistance. Its Shore hardness of 65-75 degrees can not only tightly fit the gap through sufficient elastic deformation to prevent media leakage, but also provide appropriate support to prevent the filter element from shifting under high pressure. The presence of the sealing ring also reduces the corrosion of other parts of the mold caused by media leakage. Combined with the filter element's interception of impurities, it reduces the erosion and corrosion of the hole wall, thus extending the service life of the mold.

[0032] Please see Figure 3 The sealing plug comprises an integrally molded end cap and an insertion sleeve. The diameter of the end cap is larger than the cross-sectional diameter of the packing chamber. The insertion sleeve is inserted into both ends of the packing chamber and is interference-fitted with it. The end cap's larger diameter provides reliable axial restraint during installation, preventing the sealing plug from collapsing or shifting due to hydrostatic pressure, ensuring the stability of the seal. Simultaneously, the fit between the end cap and the outer sleeve's end face forms the first sealing barrier, preventing external impurities from entering or internal powder from overflowing. The interference fit between the insertion sleeve and the packing chamber achieves a tight radial seal. The interference creates continuous contact pressure between the outer wall of the sleeve and the inner wall of the chamber, effectively preventing hydrostatic medium from seeping into the packing chamber from the end gaps, preventing powder contamination by the medium or molding defects due to pressure imbalance. The integrally molded design ensures the connection strength between the end cap and the sleeve, avoiding sealing failures that may be caused by assembly gaps, while simplifying the manufacturing process and ensuring the overall structural consistency of the sealing plug.

[0033] Please see Figure 5 and Figure 6 Based on the same inventive concept, this invention also provides a molding process for an annular filter element, using the aforementioned spiral isostatic pressing mold, including the following steps: S1: When the two sealing plugs are not installed, use a spray gun to spray stainless steel powder into the port of the packing chamber until the packing chamber is full. S2: After installing two sealing plugs at both ends of the packing chamber, place the spiral isostatic mold into the isostatic press for pressing; S3: After the spiral isostatic pressing mold is completed, remove the two sealing plugs, fix the outer sleeve, and spirally pull the mold core and spiral filter element out of the packing chamber. Finally, spirally pull the mold core out of the spiral filter element. S4: Place the spiral filter element on the tray and load it into the vacuum sintering furnace for sintering. S5: After the spiral filter element is sintered, it is taken out of the vacuum sintering furnace, shaped and pressed to form an annular filter element with a reserved opening. The three-way connector is placed in the reserved opening and welded to the two ports of the annular filter element respectively.

[0034] This invention provides a molding process for annular filter elements. Compared with existing technologies, powder filling is performed when the sealing plug is in an uninstalled state. Combined with the structural characteristics of the spiral packing chamber, this allows stainless steel powder to fill the entire chamber more smoothly, reducing filling dead zones caused by complex structures. The use of a spray gun enables dense pre-filling of the powder through pressure control, laying a good foundation for subsequent pressing. Utilizing the uniform pressure characteristics of an isostatic press, combined with the spiral chamber design of the mold, the stainless steel powder is subjected to uniform force in all directions, ensuring consistent density and uniform structure of the molded spiral filter element, avoiding the localized porosity problems that may occur with traditional molding methods. First, the outer sleeve is fixed, then the mold core and spiral filter element are spirally extracted together, and finally the mold core and filter element are separated. This demolding method, adapted to the spiral structure, minimizes external force damage to the filter element during demolding, ensuring the accuracy of the spiral shape. Vacuum sintering eliminates pores and stress inside the filter element, enhancing its structural strength and filtration performance. Shaping and pressing corrects minor deformations after sintering, ensuring the dimensional accuracy of the final annular structure. Welding of the tee joints allows the annular filter element to form a complete fluid channel, meeting practical application requirements. This invention provides a forming process for annular filter elements with a coherent and efficient overall flow. Each step, from powder filling to final forming, is designed around the characteristics of a spiral isostatic pressing mold. This fully utilizes the structural advantages of the mold and, through the synergistic effect of each step, ultimately obtains annular filter elements with uniform density, meeting strength standards, and precise dimensions, while simultaneously ensuring production efficiency and product consistency.

[0035] In step S1, during the injection of stainless steel powder, the two sealing plugs are kept in an uninstalled state. The spray gun is then turned on to inject stainless steel powder into the port of the filling chamber. Simultaneously, the ultrasonic vibration device is activated, allowing vibration to act on the mold. The ultrasonic vibration frequency varies periodically within the range of 20-40kHz. This periodic frequency variation produces different mechanical vibration effects. Low-frequency vibration can propel the stainless steel powder deeper into the filling chamber, while high-frequency vibration helps to break up local agglomerations of the powder, thereby enhancing the powder's fluidity and reducing filling dead zones caused by the complex spiral chamber structure. The combination of periodic ultrasonic vibration and targeted adjustment of the spray gun significantly improves the uniformity of stainless steel powder filling, effectively avoiding cracking and deformation problems that may occur during subsequent pressing due to uneven filling, laying a good foundation for product quality. At the same time, an infrared thermal imager is used to monitor the filling density distribution of stainless steel powder in the filling chamber in real time. Because different powder packing densities create different temperature field distributions, the infrared thermal imager can accurately identify areas where the density is below a preset threshold by capturing these temperature field differences. Once such areas are detected, the spray pressure and angle of the spray gun are adjusted promptly to ensure that stainless steel powder is more accurately applied to low-density areas until the filling chamber is uniformly filled. Real-time monitoring by the infrared thermal imager enables visualization and precise control of the filling process, reducing errors from human judgment. This not only improves filling efficiency and shortens filling time but also avoids waste of stainless steel powder, reduces production costs, and ensures consistency in filling quality across different batches, thereby enhancing overall production stability.

[0036] In the sintering process of step S4, the specific operation is as follows: After placing the spiral filter element on the tray and loading it into the vacuum sintering furnace, the equipment is started to begin sintering. The heating process adopts a gradient mode. First, the first stage of heating is carried out at a rate of 5℃ / min. During this stage, 3-5 pulse currents are applied at regular intervals, with the peak density of the pulse current controlled at 100-150A / mm². Each pulse lasts for 0.5-1s, and the timing of each pulse current application is synchronized with the switching of the inert gas circulation direction in the furnace. When the temperature reaches the set value of the first stage, the second stage of heating begins, and the rate is increased to 10℃ / min. Similarly, during this stage, the pulse current is applied at the above frequency, peak density, and duration, and synchronized with the switching of the inert gas circulation direction. Then, the third stage of heating begins, and the rate is reduced to 5℃ / min. The operation of applying the pulse current and synchronizing with the switching of the gas circulation direction is repeated until the highest temperature required for sintering is reached.

[0037] In the above steps, the gradient heating rate adapts to the physicochemical changes of the filter element at different temperature stages. The initial slower heating rate allows for the smooth discharge of moisture and volatile impurities from the surface of the stainless steel powder particles, avoiding internal stress concentration caused by rapid heating. The accelerated heating rate in the middle stage promotes interparticle diffusion and fusion, improving sintering efficiency. The subsequent slowing down of the rate helps reduce structural defects caused by sudden temperature changes. The synergistic effect of the pulsed current, with its instantaneous high energy, activates the activity of atoms on the particle surface, accelerates the diffusion process, promotes neck growth and pore shrinkage, and improves the density and structural strength of the filter element. Furthermore, the periodic pulsed form avoids excessive sintering of localized areas of the filter element caused by continuous high temperatures. Simultaneously, the application of the pulsed current synchronized with the switching of the inert gas circulation direction ensures that when the local temperature of the filter element rises due to the current, fresh inert gas can promptly remove trace amounts of impurity gas, preventing their deposition on the filter element surface, ensuring the cleanliness of the sintering environment, and further improving the purity and performance of the filter element. In addition, this collaborative process can shorten the overall sintering time, improve production efficiency, and make the performance of each part of the filter element more uniform, thereby enhancing the consistency and reliability of the product.

[0038] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A spiral isostatic pressing mold, characterized in that, This includes the external structure, internal structure, and sealing structure; The external structure includes a spiral outer tube and an inner rubber tube conformally disposed within the inner cavity of the outer tube. The outer wall of the inner rubber tube is fitted with the inner wall of the outer tube, and the inner cavity of the inner rubber tube forms a spiral-shaped molding chamber. The outer tube has multiple static pressure holes. The internal structure includes a mold core located within the molding cavity. The mold core is axially conformally disposed within the molding cavity, and a filler chamber for filling metal powder is formed between the mold core and the inner tubing. The sealing structure includes two sealing plugs, which are detachably installed at both ends of the packing chamber, so that they are in an uninstalled state during packing or in an installed state after packing.

2. The spiral isostatic pressing mold as described in claim 1, characterized in that, When the sealing plug is not installed, the two ends of the outer tube are respectively radially provided with first positioning pins, the two first positioning pins are parallel to each other, and the first positioning pins pass through the side wall of the outer tube and the side wall of the inner tube from the outside to the inside and are inserted into the mold core. The two ends of the outer tube are jointly provided with second positioning pins, and the second positioning pins are perpendicular to either of the first positioning pins.

3. The spiral isostatic pressing mold as described in claim 2, characterized in that, Limiting blocks are provided at both ends of the second positioning pin. The two limiting blocks can move along the axial direction of the second positioning pin to press against the outer side walls of the outer sleeve that are far apart from each other.

4. A spiral isostatic pressing mold as described in claim 2, characterized in that, The two end faces of the outer tube are on the same plane, and the two end faces of the outer tube are coaxially provided with an adaptation half groove for adapting to the second positioning pin. The adaptation half groove is respectively opened on the same side end face of the outer tube, the inner tube and the mold core along its length direction.

5. A spiral isostatic pressing mold as described in claim 4, characterized in that, The two ports of the packing chamber are staggered and their axial projection areas do not overlap.

6. A spiral isostatic pressing mold as described in claim 1, characterized in that, Multiple static pressure holes are symmetrically and coaxially opened on both sides of the outer sleeve.

7. A spiral isostatic pressing mold as described in claim 1, characterized in that, The sealing plug includes an integrally formed end cap and an insertion sleeve. The diameter of the end cap is larger than the cross-sectional diameter of the packing chamber. The insertion sleeve is inserted into both ends of the packing chamber and is interference-fitted with the packing chamber.

8. A molding process for an annular filter element, using a spiral isostatic pressing mold as described in any one of claims 1-7, characterized in that, Includes the following steps: S1: When the two sealing plugs are not installed, use a spray gun to spray stainless steel powder into the port of the packing chamber until the packing chamber is full. S2: After installing two sealing plugs at both ends of the packing chamber, place the spiral isostatic mold into the isostatic press for pressing; S3: After the spiral isostatic pressing mold is completed, remove the two sealing plugs, fix the outer sleeve, and spirally pull the mold core and spiral filter element out of the packing chamber. Finally, spirally pull the mold core out of the spiral filter element. S4: Place the spiral filter element on the tray and load it into the vacuum sintering furnace for sintering. S5: After the spiral filter element is sintered, it is taken out of the vacuum sintering furnace, shaped and pressed to form an annular filter element with a reserved opening. The three-way connector is placed in the reserved opening and welded to the two ports of the annular filter element respectively.

9. The molding process of an annular filter element as described in claim 8, characterized in that, In step S1, during the process of spraying stainless steel powder, ultrasonic vibration is used to assist filling. The frequency of the ultrasonic vibration changes periodically in the range of 20-40kHz. At the same time, the filling density distribution of stainless steel powder in the filling chamber is monitored in real time by an infrared thermal imager. When the local density is detected to be lower than the preset threshold, the spraying pressure and angle of the spray gun are adjusted.

10. The molding process of an annular filter element as described in claim 8, characterized in that, The sintering process in step S4 adopts a combination of gradient heating and pulsed current. The gradient heating rate changes in stages from 5℃ / min to 10℃ / min and then to 5℃ / min. In each heating stage, 3-5 pulsed currents are applied. The peak density of the pulsed current is 100-150 A / mm², and the pulse duration is 0.5-1 s. The timing of the pulsed current application is synchronized with the switching of the circulation direction of the inert gas in the furnace.

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