A double-layer sealing structure of an equiaxed crystal vacuum precision casting furnace

Abstract

The utility model discloses a kind of up and down double-layer sealing structure of isometric crystal vacuum precision casting furnace, including the column of lifting mechanism, sleeve, and the sealing assembly being set between the sleeve of column, and sealing assembly is constituted by upper sealing unit and lower sealing unit along the axial distribution of column, upper sealing unit includes upper star type sealing ring, dustproof ring and gland, lower sealing unit includes at least two lower star type sealing ring, guide belt and copper sleeve.The utility model adopts the progressive sealing design of double-layer star type sealing ring, combines the structural advantage of star type sealing ring four lip, realizes the sealing effect of low friction, high dustproof, anti-twist, and the quick replacement of sealing ring is realized by modular assembly structure, without disassembling entire lifting system, effectively prolongs sealing life 3-5 times, reduce maintenance downtime more than 80%, applicable to isometric crystal vacuum precision casting high temperature, dusty, easy sputtering working condition, with significant industrial application value.

Description

Technical Field

[0001] This utility model relates to the field of precision casting sealing equipment technology, and in particular to a double-layer sealing structure for an equiaxed crystal vacuum precision casting furnace, especially suitable for bidirectional dynamic sealing scenarios between the column and sleeve in the casting furnace mold lifting system. This structure can achieve reliable sealing in all dimensions under harsh conditions such as high temperature, dust, and molten metal splashing, while also featuring independent upper and lower maintenance and quick replacement of sealing components, solving the problem of uneven protection at the upper and lower ends in traditional unidirectional seals.

[0002] Equiaxed crystal vacuum precision casting is a core technology in aerospace and high-end equipment manufacturing, obtaining high-performance castings through the precision forming of molten metal in a vacuum environment. The mold lifting system, as the core actuator, directly determines the equipment's lifespan and casting precision through the sealing reliability of its columns and sleeves. The sealing structure must simultaneously prevent dust intrusion from above the furnace and the upward movement of oil and impurities from below, while also withstanding high temperatures and the impact of molten metal splashing. Traditional unidirectional seals can only protect one end, easily leading to seal failure at the other end, becoming a bottleneck restricting equipment stability.

[0003] With increasing demands for casting quality, the need for comprehensive sealing protection in lifting systems has become more prominent. Developing an independent dual-directional sealing structure to achieve simultaneous dustproofing, leak prevention, and rapid maintenance at both ends is of significant practical importance for promoting the upgrading of precision casting equipment. Background Technology

[0004] The mold lifting system is the "central actuator" of the equiaxed crystal vacuum precision casting furnace. The dynamic sealing performance between its column and sleeve directly determines the equipment's operational stability, casting yield, and production economy. Currently, in the casting industry, equipment downtime due to seal failure in this part accounts for as much as 42%, and related maintenance costs account for 18%-25% of the total equipment operating costs. Existing sealing technology has become a core bottleneck restricting the improvement of precision casting efficiency. Specific shortcomings can be discussed from three dimensions: technical principles, operating condition adaptability, and maintenance costs. The risk of bidirectional failure due to the imbalance of protection dimensions: Existing technologies generally adopt an asymmetrical design of "single-stage sealing at the top + natural opening at the bottom". This structure originated from the early casting furnace's requirement of "low dust and low frequency operation", which is completely unsuitable for the current intelligent casting workshop's "high dust and continuous operation" conditions. From the perspective of top protection, traditional single-lip dust seals can only block large dust particles (diameter > 5μm). The blocking rate for nanoscale metal oxide dust (such as Al2O3 and SiO2 dust, diameter 0.1-2μm) generated during the casting process is less than 30%. After this type of dust enters the sealing gap with the reciprocating motion of the column, it mixes with the lubricating grease to form "grind paste", accelerating the wear of the column surface. Data from an aerospace casting company shows that in casting furnaces using this structure, the surface roughness of the column deteriorates from the initial Ra0.4μm to Ra1.2μm within 500 hours, leading to scratches and failure of the sealing lip. From the perspective of lower protection, the open design exposes the lower end of the sleeve directly to ground oil stains, cooling water condensate, and scattered slag particles. During the vacuum pumping process of the furnace body, a negative pressure will be formed at the lower end, forcibly sucking these impurities into the sealing gap. Statistics show that 65% of sealing failures are caused by the upward movement of impurities at the lower end, of which 20% will cause the copper sleeve to seize up, requiring the replacement of the entire lifting system, with a replacement cost of over 80,000 yuan per set.

[0005] A severe mismatch exists between the performance of sealing elements and operational requirements: Existing technologies mostly use nitrile rubber (NBR) O-rings or ordinary lip rings as core seals. These materials and structures are completely inadequate for handling the complex operating conditions of casting furnaces. Regarding temperature adaptability, during normal operation of the casting furnace, the radiant heat from the furnace body stabilizes the temperature of the sealing area at 80-150℃. The instantaneous temperature of the molten metal during pouring can reach 200-250℃. Nitrile rubber exhibits significant elastic decay above 120℃, and after 1000 hours of continuous operation at 150℃, the compression deformation rate reaches 60%-75%, completely losing its sealing ability. While fluororubber is heat-resistant, current technologies only use it for static sealing, not for dynamic lifting scenarios. Regarding sealing reliability, O-rings use a single-lip line contact seal, which is susceptible to uneven contact pressure due to column machining errors (such as roundness error > 0.05mm), creating a "sealing blind zone." Helium mass spectrometry leak detection tests show that structures using O-ring seals are prone to uneven contact pressure under vacuum of 1×10⁻⁶. -3 At Pa, the leakage rate is generally 5×10 -5 Pa·m 3 / s or more, far exceeding the 1×10⁻⁶ required for aerospace castings. -7 Pa·m 3 / s standard. In terms of impact resistance, the O-ring has no buffer structure. When the molten metal splashes slightly due to blockage of the pouring gate (temperature > 1000℃, particle diameter 1-5mm), it will directly burn the seal, causing the seal to fail instantly and causing a sudden drop in the vacuum degree in the furnace. The value of a single scrapped casting can reach hundreds of thousands of yuan.

[0006] High maintenance costs due to structural design flaws: The existing sealing structure adopts an "integral embedded" design, with the seal encased inside the sleeve. Replacement requires disassembling 12 components, including the mold, lifting cylinder, and connecting flange. The entire process requires 2-3 technicians and takes 4-8 hours. Statistics from a company producing 200 tons of aerospace precision castings annually show that its three casting furnaces experience an average downtime of 360 hours per year due to seal replacement. Based on an hourly output value of 8,000 yuan, the direct production loss exceeds 2.88 million yuan. Furthermore, in the traditional structure, the copper sleeve and the sleeve use an interference fit but lack a positioning structure. Installation requires manual calibration, which is prone to circumferential rotation, leading to misalignment of the spiral oil groove and lubrication failure. The average service life of the copper sleeve is only 1,200 hours, with an annual replacement cost exceeding 50,000 yuan per unit. In addition, the existing structure lacks an active chip removal design, and dust accumulation requires the use of a high-pressure air gun for cleaning, which can easily cause dust diffusion and endanger the health of operators. The cost of dust removal equipment that meets the "Emission Standard of Air Pollutants for Foundry Industry" (GB 39726-2020) will increase by an additional 300,000 yuan per workshop.

[0007] To address these issues, some companies have attempted improvements using "multi-layer O-ring stacking" or "unidirectional star-shaped rings + dustproof rings," but none have overcome the core defects: multi-layer O-ring stacking doubles the frictional resistance (friction coefficient increases from 0.3 to 0.6-0.8), increasing drive motor energy consumption by more than 30%, and the gaps between the rings become new "dead zones" for dust accumulation; while unidirectional star-shaped rings solve the friction problem, they still fail to address the lack of protection at the lower end, only extending the seal life from 300 hours to 800 hours, which is insufficient for continuous production. Currently, no sealing structure in the industry can simultaneously achieve "bidirectional protection, high-temperature adaptability, and rapid maintenance," making the development of a comprehensive sealing solution suitable for equiaxed crystal vacuum precision casting furnaces an urgent need.

[0008] Sealing failure in the mold lifting system is a major cause of casting furnace malfunctions. Existing technologies often employ solutions such as "upper end sealing + lower end opening" or "single-layer sealing ring," which have numerous drawbacks. 1. Limited Protection Dimensions: Traditional structures only have a seal at the top, leaving the lower end of the sleeve susceptible to entry of ground oil, metal shavings, or dust drawn in due to the furnace's negative pressure, leading to wear and jamming between the column and the copper sleeve. Data from one company shows that due to dust ingress at the bottom, one-way sealing systems require cleaning every 200-300 hours on average and major overhauls every 800 hours, resulting in high maintenance costs.

[0009] 2. Poor sealing reliability: The single-layer O-ring has uneven contact pressure at the single lip, resulting in a sealing blind zone. Under operating conditions of 80-150℃, the compression deformation rate of nitrile rubber exceeds 60%, and it essentially fails after 1000 hours. It cannot effectively block molten metal splashes, easily causing damage to core components, with single losses exceeding hundreds of thousands of yuan.

[0010] 3. Friction and installation defects: The friction coefficient of the O-ring is 0.3-0.5, which increases the motor energy consumption by 15%-20% and makes it easy to twist and fall off; the seal is hidden inside the system, and replacement requires disassembling the entire lifting system, which takes 4-8 hours. For a casting company with an annual output of 1,000 tons, the annual downtime loss exceeds 2 million yuan.

[0011] Some companies have tried multi-layer O-ring solutions, but simply stacking them does not solve the problem of bidirectional protection, and the frictional resistance is greatly increased, making it easy for dust to accumulate between the rings. Although star-shaped sealing rings have the advantage of low friction with four lips, their current application is limited to unidirectional sealing, and they have not formed a fully coordinated structure, which cannot meet the bidirectional protection requirements of casting furnaces.

[0012] Based on this, the present invention proposes a double-layer independent sealing structure, which solves the defects of the prior art through synchronous protection at the upper and lower ends, core sealing with a star-shaped sealing ring and modular design. Utility Model Content

[0013] To address the shortcomings of existing technologies, the purpose of this utility model is to provide a double-layer sealing structure for an equiaxed crystal vacuum precision casting furnace. The upper and lower sealing units form all-dimensional protection, and the four-lipped advantages of the star-shaped sealing ring achieve low-friction sealing. Combined with the modular design of the upper and lower pressure caps, the sealing components can be quickly replaced without disassembling the lifting system, thus extending the service life and reducing maintenance costs.

[0014] The above-mentioned utility model objective is achieved through the following technical solution: A double-layer sealing structure for an equiaxed crystal vacuum precision casting furnace, applied to a mold lifting system, characterized in that it includes a column of a lifting mechanism, a sleeve sleeved outside the column, and a sealing assembly fixedly disposed between the column and the sleeve. The sealing assembly includes an upper sealing unit and a lower sealing unit distributed from top to bottom along the column axis; The upper sealing unit includes an upper sealing part, an upper pressure cover, and an upper dustproof ring. The upper sealing part is installed between the column and the sleeve. The upper pressure cover is detachably fixed to the top end face of the sleeve and is located above the upper sealing part. The upper dustproof ring has a double-lip structure and is embedded in the inner hole step of the upper pressure cover. Its lip faces away from the sleeve and is interference-fitted with the outer peripheral surface of the column. The lower sealing unit includes a lower sealing part, a lower pressure cover, and a lower dustproof ring. The lower sealing part is installed between the column and the sleeve. The lower pressure cover is detachably fixed to the bottom end face of the sleeve and is located below the lower sealing part. The lower dustproof ring has a double-lip structure and is embedded in the inner hole step of the lower pressure cover. Its lip faces away from the sleeve and is interference-fitted with the outer peripheral surface of the column.

[0015] As a further technical solution of this utility model: the radial gap between the column and the sleeve is 0.5-2mm, the overall axial length of the sealing assembly is 20-50mm, and the distance between the upper sealing unit and the lower sealing unit is 5-15mm. The depth of the upper sealing groove is 3-8mm, and the width is 5-10mm. The cross-section of the upper star-shaped sealing ring is a four-lip star-shaped structure, and its four sealing lips are tightly fitted with the outer peripheral surface of the column and the upper, lower, and inner wall surfaces of the upper sealing groove, respectively. The structural dimensions of the lower sealing groove are the same as those of the upper sealing groove, and the structural parameters of the lower star-shaped sealing ring are the same as those of the upper star-shaped sealing ring. Its sealing lips are tightly fitted with the outer peripheral surface of the column and the upper, lower, and inner wall surfaces of the lower sealing groove.

[0016] As a further technical solution of this utility model: the upper sealing part includes at least two upper star-shaped sealing rings, an upper guide strip and at least one upper copper sleeve. The upper copper sleeve is fixed to the upper copper sleeve mounting groove on the inner wall of the sleeve by interference fit. The upper guide strip is made of polytetrafluoroethylene and is sleeved on the column. The outer peripheral surface of the upper guide strip is slidably fitted with the inner hole surface of the upper copper sleeve. The two upper star-shaped sealing rings are respectively disposed in the upper sealing grooves on the upper and lower sides of the upper copper sleeve.

[0017] As a further technical solution of this utility model: the lower sealing part includes at least two lower star-shaped sealing rings, a lower guide strip and at least one lower copper sleeve. The lower copper sleeve is fixed to the lower copper sleeve mounting groove on the inner wall of the sleeve by interference fit. The lower guide strip is made of polytetrafluoroethylene and is sleeved on the column. The outer peripheral surface of the lower guide strip is in sliding fit with the inner hole surface of the lower copper sleeve. The two lower star-shaped sealing rings are respectively arranged in the lower sealing grooves on the upper and lower sides of the lower copper sleeve.

[0018] As a further technical solution of this utility model: the upper star-shaped sealing ring and the lower star-shaped sealing ring are both made of fluororubber FKM, with a Shore hardness of 65-75HA, a nominal cross-sectional size of 5×5mm-10×10mm, an included angle of 80°-100° for the four lips, a lip height of 1-3mm, and a compression deformation rate of no more than 25% after continuous operation at 250℃ for 1000 hours.

[0019] As a further technical solution of this utility model: the upper dustproof ring and the lower dustproof ring are both made of polyurethane elastomer with a Shore hardness of 80-90HA and an interference fit of 0.1-0.3mm. The inner surface of the dustproof ring is provided with lubrication grooves evenly distributed along the circumference. The depth of the lubrication grooves is 0.2-0.5mm, the width is 0.5-1mm, and the spacing between adjacent lubrication grooves is 3-5mm.

[0020] As a further technical solution of this utility model: both the upper and lower copper sleeves are made of tin bronze, and their inner diameter is 0.05-0.1mm larger than the outer diameter of the column. The inner surface of the copper sleeve is provided with a spiral oil groove, the lead of the spiral oil groove is 10-20mm, the depth is 0.1-0.3mm, and both the upper and lower end faces of the copper sleeve are provided with chamfers, the chamfer angle is 30°-45°, and the chamfer width is 1-2mm.

[0021] As a further technical solution of this utility model: the top of the upper cover is provided with an annular tray mounting platform. The outer diameter of the tray mounting platform is 3-5mm smaller than the outer diameter of the main body of the upper cover. The end face of the tray mounting platform is provided with a positioning pin hole for positioning and cooperating with the top tray of the lifting system. The outer circumferential surface of the upper cover is provided with anti-slip texture. The height of the anti-slip texture is 0.5-1mm and the spacing is 1-2mm.

[0022] As a further technical solution of this utility model: both the upper copper sleeve and the lower copper sleeve are provided with annular chip removal grooves on their outer peripheral surfaces. The depth of the chip removal grooves is 0.5-1mm and the width is 1-2mm. The chip removal grooves are connected to chip removal holes opened on the sleeve wall. The diameter of the chip removal holes is 2-4mm and their axis is perpendicular to the axis of the sleeve.

[0023] As a further technical solution of this utility model: the axial length of the upper guide strip and the lower guide strip is 5-10mm, and an annular sealing lip is provided on their outer circumferential surface. The sealing lip is interference-fitted with the inner hole surface of the copper sleeve, and the interference amount is 0.05-0.1mm. The two ends of the guide strip are provided with a wear-resistant coating. The wear-resistant coating is made of molybdenum disulfide and has a coating thickness of 5-10μm.

[0024] As a further technical solution of this utility model: the inner wall of the sleeve is provided with a positioning groove, and the outer circumferential surface of the copper sleeve is provided with a positioning boss that cooperates with the positioning groove. The height of the positioning boss is 0.5-1mm and the width is 2-3mm.

[0025] In summary, compared with the prior art, the present invention has at least one of the following beneficial technical effects: A comprehensive protection system is constructed to completely solve the problem of bidirectional failure: This utility model achieves comprehensive sealing protection for the lifting system through a symmetrical design of "upper sealing unit + lower sealing unit," fundamentally solving the pain point of "one-end protection, one-end failure" in traditional structures. Regarding upper-end protection, the main lip of the double-lip polyurethane dustproof ring can block more than 95% of large dust particles (diameter > 1μm), while the secondary lip forms a secondary barrier. Combined with the high-temperature grease stored in the inner lubrication groove, the blocking rate for nano-sized metal oxide dust is increased to 99.2%. The four lips of the upper star-shaped sealing ring form four sealing lines with the column surface. Under vacuum conditions, the self-tightening effect of the lips ensures that the leakage rate is stably controlled at 1×10⁻⁶. -7 Pa·m 3 Below / s, far exceeding aerospace industry standards. Regarding lower-end protection, the lower sealing unit is completely symmetrical with the upper structure. The lower dustproof ring effectively blocks the intrusion of ground oil, condensate, and molten slag particles. Combined with the chip removal grooves on the outer circumference of the lower copper sleeve and the chip removal holes on the sleeve, it can quickly remove intruding trace amounts of dust, preventing the formation of "grind paste." Industrial tests show that in casting furnaces using this structure, at dust concentrations of 10mg / m³... 3 After 4000 hours of continuous operation in a workshop environment, the amount of dust accumulation inside the sleeve is only 3% of that in traditional structures, and the surface roughness of the column remains within Ra0.45μm. In addition, the buffer space formed by the 5-15mm spacing between the upper and lower sealing units can absorb the impact energy during molten metal splashing. Under the scenario of 150℃ and molten metal small particles (diameter <3mm) splashing, the seals do not suffer ablation damage, and the protection reliability is improved by more than 10 times.

[0026] 2. Synergistic optimization of materials and structure to achieve a win-win situation of long service life and low friction: This utility model breaks the industry paradox of "positive correlation between sealing reliability and frictional resistance" through the upgrading of core component materials and structural innovation. In terms of service life extension, the star-shaped sealing ring made of fluororubber FKM material has a compression deformation rate of only 18%-25% after 1000 hours of continuous operation at 250℃, which is far lower than the 60%-75% of nitrile rubber O-rings; combined with the spiral oil groove in the inner hole of the tin bronze copper sleeve, long-term lubrication can be achieved, and the oil film retention time is extended from 200 hours in the traditional structure to 1500 hours. The average service life of the star-shaped sealing ring is increased from 300-500 hours to 3000-5000 hours, which is 6-10 times longer. In terms of friction optimization, the four-lip structure of the star-shaped sealing ring reduces the contact area by 40% compared to the O-ring, lowering the coefficient of friction from 0.3-0.5 to 0.08-0.15. The sealing lip on the outer periphery of the PTFE guide strip is interference-fitted with the copper sleeve, ensuring guiding accuracy while avoiding direct metal-to-metal contact. Combined with the molybdenum disulfide wear-resistant coating (coefficient of friction 0.05) on both end faces, the frictional resistance of the entire sealing structure is reduced by more than 55%. Actual application data from a certain enterprise shows that after adopting this structure, the power consumption of the drive motor of the mold lifting system decreased from 11kW to 9kW. Based on an annual operating time of 8000 hours, each furnace can save 17,600 yuan in electricity costs (industrial electricity price 0.25 yuan / kWh). Simultaneously, the positioning groove-boob fit structure between the copper sleeve and the bushing completely prevents circumferential rotation of the copper sleeve, improving the positioning accuracy of the spiral oil groove to within 0.02mm, extending the service life of the copper sleeve from 1200 hours to 6000 hours, and reducing annual replacement costs by 83%.

[0027] 3. Modular design significantly reduces operation and maintenance costs and downtime losses: The detachable pressure cap and symmetrical structure design of this utility model create a "rapid maintenance system," completely changing the traditional "major disassembly and reassembly" mode of seal replacement. When replacing seals, only a torque wrench is needed to remove the bolts of the upper and lower pressure caps (6-8 bolts for the upper pressure cap and 6-8 bolts for the lower pressure cap) to directly remove the dust ring, star-shaped sealing ring, and guide belt. There is no need to disassemble core components such as the mold and lifting cylinder. The entire replacement process takes only 1-1.5 hours, compared to 4-8 hours for the traditional structure, reducing downtime by 75%-87.5%. For a company producing 1000 tons of precision castings annually, after adopting this structure for its 5 casting furnaces, the average annual downtime due to seal replacement was reduced from 400 hours to 50 hours. Based on an hourly output value of 12,000 yuan, this translates to an annual reduction in production losses of 4.2 million yuan. In terms of ease of maintenance, the anti-slip textured design on the outer periphery of the upper pressure cover eliminates the need for special tools during disassembly, and the positioning pin holes ensure that the coaxiality error during pressure cover reinstallation is ≤0.05mm, avoiding manual calibration. The component commonality rate of the upper and lower sealing units reaches 80% (only the upper pressure cover includes the tray mounting platform), reducing the types of spare parts inventory and lowering inventory costs by more than 30%. Furthermore, the active chip removal structure reduces the need for high-pressure air gun cleaning, lowering the workshop dust concentration from 10mg / m³. 3 Reduced to 2 mg / m 3 It complies with GB 39726-2020 standards, which can save the investment and operating costs of additional dust removal equipment, saving 200,000 yuan per workshop in environmental protection costs per year.

[0028] 4. Wide adaptability to various operating conditions, expanding the boundaries of technological applications: This utility model, through flexible adjustment of material selection and structural parameters, can be adapted to different types of casting furnaces and extreme operating conditions, possessing strong promotional value. Regarding temperature adaptability, the star-shaped sealing ring can be made of low-temperature fluororubber (-40℃ to 250℃), suitable for low-temperature alloy casting furnaces; when using perfluoroether rubber, it can withstand temperatures above 300℃, suitable for high-temperature casting scenarios such as titanium alloys. Regarding vacuum adaptability, by increasing the number of lips on the star-shaped sealing ring (e.g., a six-lip structure), the leakage rate can be reduced to 5×10⁻⁶. -8 Pa·m 3 Below / s, meeting the requirements of high vacuum casting furnaces for aerospace applications (1×10 -4 The requirements of Pa) are met. Regarding column size adaptation, by adjusting the inner diameter of the seal, the size of the copper sleeve, and the specifications of the gland, it can adapt to various columns with diameters ranging from 30mm to 120mm, covering the needs of small to large casting furnaces. Currently, this structure has been piloted in three different types of casting enterprises, adapting to aluminum alloy casting furnaces (80-100℃), titanium alloy casting furnaces (150-200℃), and low-temperature alloy casting furnaces (-30℃ to 80℃), respectively. All have achieved a sealing life exceeding 3000 hours and a maintenance cost reduction of over 80%, verifying its wide operating condition adaptability.

[0029] 5. Synergistic Improvement of Structural Safety and Economy: The detailed design of this utility model not only improves sealing performance but also enhances the safety and economy of equipment operation. The 30°-45° chamfer design on the upper and lower end faces of the copper sleeve avoids scratching the sealing lip during assembly, reducing the assembly scrap rate from 15% to 2%. The sealing lip structure of the guide belt prevents grease leakage and avoids contamination of castings, increasing the casting qualification rate by 0.5%-1%. Based on an annual production of 1000 tons of castings and a scrap loss of 5000 yuan / ton, this translates to an annual reduction in scrap loss of 25,000-50,000 yuan. Furthermore, the axial length of this structure is only 20-50mm, which is more compact than traditional sealing structures (axial length 30-60mm). It can directly replace the sealing parts of existing equipment without structural modifications to the lifting system, reducing equipment upgrade costs to below 15,000 yuan / unit, far lower than the 80,000 yuan / unit cost of replacing a new lifting system. This provides an economical and feasible solution for equipment upgrades in small and medium-sized foundry enterprises.

[0030] 6. Long life and low friction: The fluororubber star ring has a 3-5 times longer life, the coefficient of friction is reduced to 0.08-0.15, and the motor energy consumption is reduced by 18%-22%; the copper sleeve and guide belt work together to reduce column wear, with wear amount ≤0.01mm.

[0031] 7. Quick maintenance: The upper and lower pressure plates are detachable, and the seal replacement only takes 1.5 hours, reducing downtime by more than 70%; the chip removal groove and positioning structure improve the ease of installation and reduce the difficulty of maintenance. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall structure of this utility model.

[0033] Figure 2 for Figure 1 A magnified view of part A in the diagram.

[0034] Reference numerals in the attached diagram: 1. Upper star-shaped sealing ring; 2. Upper guide band; 3. Upper copper sleeve; 4. Upper dustproof ring; 5. Upper pressure cap; 6. Column; 7. Sleeve; 8. Lower copper sleeve; 9. Lower guide band; 10. Lower star-shaped sealing ring; 11. Lower dustproof ring; 12. Lower pressure cap; 13. Hex socket head cap bolt; 14. Chip removal hole; 15. Chip removal groove; 16. Positioning groove; 17. Positioning boss; 18. Pallet mounting platform. Detailed Implementation

[0035] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.

[0036] In the description of this utility model, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model 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 utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0038] A double-layer sealing structure for an equiaxed crystal vacuum precision casting furnace is applied to a mold lifting system. It includes a column 6, a sleeve 7 sleeved outside the column 6, and a sealing assembly between the two. The sealing assembly includes an upper sealing unit and a lower sealing unit distributed along the axial direction of the column 6. The distance between the two units is 5-15mm to avoid mutual interference and form a buffer space.

[0039] The upper sealing unit includes an upper sealing part, an upper pressure cover 5, and an upper dustproof ring 4. The upper pressure cover 5 is detachably fixed to the top of the sleeve 7 by M6-M10 hexagonal bolts 13, with 4-8 bolts evenly distributed around the circumference and a tightening torque of 25-40 N·m. The upper dustproof ring 4 is a double-lip polyurethane structure, embedded in the inner hole step of the upper pressure cover 5, with the lip facing away from the sleeve 7, and an interference fit of 0.1-0.3 mm with the column 6. The inner hole lubrication groove stores grease to achieve long-term lubrication. The upper sealing part includes at least two upper star-shaped sealing rings 1, an upper guide band 2, and an upper copper sleeve 3. The upper copper sleeve 3 is interference-fitted to the mounting groove of the upper copper sleeve 3 by 0.02-0.05 mm. The upper guide band 2 is made of polytetrafluoroethylene and has a sliding fit clearance of 0.05-0.1 mm with the inner hole of the upper copper sleeve 3. The two upper star-shaped sealing rings 1 are respectively located in the upper and lower sealing grooves of the upper copper sleeve 3, with the four lips respectively fitting the column 6 and the groove wall.

[0040] The lower sealing unit is symmetrical and coordinated with the upper structure: it includes a lower sealing part, a lower pressure cover 12 and a lower dustproof ring 11. The lower pressure cover 12 is fixed to the bottom of the sleeve 7 by bolts of the same specification. The structural parameters of the lower dustproof ring 11 are the same as those of the upper dustproof ring 4 to achieve dust prevention at the lower end. The lower sealing part includes at least two lower star-shaped sealing rings 10, a lower guide band 9 and a lower copper sleeve 8. The installation method of the lower copper sleeve 8 is the same as that of the upper copper sleeve 3. The mating parameters of the lower guide band 9 and the lower copper sleeve 8 are the same as those of the upper part. The two lower star-shaped sealing rings 10 are respectively located in the upper and lower sealing grooves of the lower copper sleeve 8, and the sealing lips fit tightly.

[0041] The radial clearance between the column 6 and the sleeve 7 is 0.5-2mm to meet the movement requirements and provide installation space; the overall axial length of the sealing assembly is 20-50mm to ensure a compact structure.

[0042] Preferably, both the upper star-shaped sealing ring 1 and the lower star-shaped sealing ring 10 are made of fluororubber FKM material, with a Shore hardness of 65-75HA, a cross-section of 5×5mm-10×10mm, an included angle of 80°-100° for the four lips, a lip height of 1-3mm, and a compression deformation rate of ≤25% after 1000 hours at 250℃, exhibiting excellent high temperature resistance and self-cleaning properties.

[0043] As a preferred option, both the upper dustproof ring 4 and the lower dustproof ring 11 are made of polyurethane elastomer with a Shore hardness of 80-90HA, an interference fit of 0.1-0.3mm at the lip, and a lubrication groove depth of 0.2-0.5mm, a width of 0.5-1mm, and a spacing of 3-5mm, which improves wear resistance and lubrication effect.

[0044] As a preferred option, both the upper copper sleeve 3 and the lower copper sleeve 8 are made of tin bronze, with an inner diameter 0.05-0.1mm larger than that of the column 6. The inner hole spiral oil groove has a lead of 10-20mm and a depth of 0.1-0.3mm. The upper and lower end faces have a 30°-45° chamfer with a width of 1-2mm to avoid scratching the seal and achieve uniform lubrication.

[0045] As a preferred embodiment, the top of the upper cover 5 is provided with a tray mounting platform 18, the outer diameter of which is 3-5mm smaller than that of the main body, and the end face positioning pin hole has a diameter of 3-6mm and a depth of 5-10mm to ensure coaxiality with the top tray; the outer perimeter anti-slip texture has a height of 0.5-1mm and a spacing of 1-2mm for easy disassembly; the lower cover 12 has a symmetrical structure, only omitting the tray mounting platform 18, and the other parameters are the same as those of the upper cover 5.

[0046] Preferably, both the upper copper sleeve 3 and the lower copper sleeve 8 are provided with chip removal grooves 15 on their outer periphery, with a depth of 0.5-1mm and a width of 1-2mm, which are connected to the chip removal holes 14 with a diameter of 2-4mm on the wall of the sleeve 7 to achieve rapid dust discharge; the inner wall of the sleeve 7 is provided with positioning grooves 16, and the outer periphery of the copper sleeve is provided with positioning bosses 17 with a height of 0.5-1mm and a width of 2-3mm to prevent the copper sleeve from rotating circumferentially.

[0047] Preferably, the axial length of both the upper guide band 2 and the lower guide band 9 is 5-10mm, the outer circumferential sealing lip is 0.05-0.1mm over the copper sleeve, and the thickness of the molybdenum disulfide coating on both end faces is 5-10μm, which improves sealing and wear resistance.

[0048] Example 1: Standard bidirectional sealing structure This embodiment is applied to a medium-sized casting furnace, with column 6 having a diameter of 50mm, an operating environment temperature of 80-120℃, and a dust concentration of 0.1-10μm.

[0049] Upper sealing unit: Upper pressure cap 5, 12mm thick, with 6 M8 hexagon socket head caps distributed circumferentially; Upper dustproof ring 4, inner diameter 49.7mm, outer diameter 58mm, lip interference 0.15mm, lubrication groove depth 0.3mm, width 0.8mm, spacing 4mm; Upper copper sleeve 3, made of ZCuSn10Pb1, inner diameter 50.08mm, outer diameter 52mm, length 8mm, fixed with 0.03mm interference, spiral oil groove lead 15mm, depth 0.2mm, 45° chamfer width 1.5mm; Upper guide strip 2, made of PTFE with 15% carbon fiber, length 8mm, outer circumferential sealing lip interference 0.05mm, molybdenum disulfide coating 8μm; Two upper star-shaped sealing rings 1, made of fluororubber, 5×5mm cross-section, four lips with an included angle of 90°, lip height 2mm.

[0050] The lower sealing unit is symmetrical to the upper one: the lower pressure cover 12 is 12mm thick and has 6 M8 bolts; the parameters of the lower dustproof ring 11 are the same as those of the upper dustproof ring 4; the lower copper sleeve 8 has the same structure as the upper copper sleeve 3, and the inner wall of the sleeve 7 is corresponding to the positioning groove 16 and the installation groove; the parameters of the lower guide band 9 are the same as those of the upper guide band 2; the two lower star-shaped sealing rings 10 are exactly the same as those of the upper one.

[0051] The sleeve 7 has an inner diameter of 52.5 mm and a radial clearance of 0.5 mm with the column 6; the upper and lower sealing units are spaced 10 mm apart; the chip removal groove 15 has a depth of 0.8 mm and a width of 1.5 mm; the chip removal hole 14 has a diameter of 3 mm; the positioning groove 16 has a width of 2.5 mm and a depth of 0.8 mm; and the copper sleeve positioning boss 17 matches.

[0052] Assembly steps: 1. Pre-treatment: Clean the surfaces of column 6 and sleeve 7 to remove burrs; apply high-temperature grease (-40℃ to 300℃) to the oil groove of the copper sleeve and the lubrication groove of the guide belt.

[0053] 2. Installation of the lower sealing unit: Press the lower copper sleeve 8 into the mounting groove of the lower copper sleeve 8, and align the positioning boss 17 with the groove; install the lower star-shaped sealing ring 10 into the lower sealing groove; insert the lower guide band 9 into the sleeve 7 after the column 6 is fitted; install the lower star-shaped sealing ring 10 into the corresponding groove; after the lower dustproof ring 11 is embedded in the lower pressure cover 12, fix the bolt to the bottom of the sleeve 7, and tighten the torque to 25 N·m.

[0054] 3. Installation of the upper sealing unit: The upper copper sleeve 3 is press-fitted into the mounting groove of the upper copper sleeve 3; the upper star-shaped sealing ring 1 is installed into the upper sealing groove; the upper guide strip 2 is fitted onto the column 6; the lower star-shaped sealing ring 1 is installed into the corresponding groove; after the dustproof ring 4 is embedded in the upper cover 5, the bolt is fixed to the top of the sleeve 7, and the tightening torque is 25 N·m.

[0055] 4. Subsequent steps: The top tray is fixed to the upper pressure cover 5 by the positioning pin, and the telescopic protective cover is installed.

[0056] Test results: After 4000 hours of continuous operation, the seal was in good condition, the wear of column 6 was less than 0.01mm, the motor energy consumption was reduced by 18%, the time for replacing the seal was 1.5 hours, and the downtime was reduced by 70%.

[0057] Example 2: Enhanced bidirectional sealing structure A double-layer sealing structure for an equiaxed crystal vacuum precision casting furnace differs from Embodiment 1 in that it is applied to a large casting furnace with a column diameter of 80mm, an ambient temperature of 100-150℃, and a high risk of molten metal splashing. The differences from Embodiment 1 are: a 15mm spacing between the upper and lower sealing units; a 15mm thickness for the upper pressure cap 5; eight M10 bolts with a tightening torque of 40 N·m; a 0.2mm interference fit at the lip of the upper and lower dustproof rings 11; a 10mm length for the upper and lower copper sleeves 8; a 0.3mm depth for the spiral oil groove; and a 10μm coating thickness for the upper and lower guide strips 9.

[0058] Test results: The seal remained stable after 3500 hours of continuous operation at 150℃, and no intrusion occurred when there was slight splashing of molten metal. The lifting system was intact.

[0059] Example 3: High Vacuum Bidirectional Sealing Structure A double-layer sealing structure for an equiaxed crystal vacuum precision casting furnace, differing from Embodiment 1 in that it is applied to an aerospace casting furnace with a vacuum degree of 1×10⁻⁶. -3 Pa, column 6 diameter 60mm. The star-shaped sealing ring is a six-lip fluororubber structure with a 7×7mm cross-section, lip angle of 60°, and height of 1.8mm; sealing groove width 8mm; chip removal groove 15 depth 1mm, width 2mm, chip removal hole 14 diameter 4mm; copper sleeve oil groove depth 0.3mm, lead 12mm.

[0060] Test results: Leakage rate < 1×10 -7 Pa·m 3 / s, with stable performance after 5000 hours of continuous operation and a 22% reduction in energy consumption.

[0061] This invention solves the problem of bidirectional protection, addressing industry pain points by combining a star-shaped sealing ring with a bidirectional pressure cap to form a synergistic mechanism of "dustproof at the top and anti-fouling at the bottom," extending the sealing life by 3-5 times and creatively extending the advantages of the star-shaped ring to all-dimensional sealing. This invention employs friction and maintenance innovations, combining a four-lip star-shaped ring, copper sleeve oil groove, and guide strip coating to reduce the friction coefficient to 0.08-0.15, lowering energy consumption by over 18%. The detachable design of the upper and lower pressure caps (12) creatively achieves rapid replacement "without disassembling the lifting system," reducing downtime by 80%. This invention is adaptable to extreme working conditions. The combination of fluororubber, polyurethane, and tin bronze materials, along with the anti-rotation structure of the 17 positioning bosses, allows the seal to operate stably in environments with 250℃ high temperatures and molten metal splashing, breaking through the limitations of traditional seals and creatively improving adaptability to harsh environments.

[0062] The implementation principle of this utility model is as follows: This utility model discloses a double-layer sealing structure for an equiaxed crystal vacuum precision casting furnace, relating to the field of sealing technology for precision casting equipment, and applied to a mold lifting system. It aims to solve the technical problems of easy failure of the unidirectional seal, uneven protection at the upper and lower ends, and high maintenance costs in existing casting furnace lifting mechanisms. The sealing structure includes a column 6, a sleeve 7 fitted outside the column 6, and a sealing assembly between the column 6 and the sleeve 7. The sealing assembly includes an upper sealing unit and a lower sealing unit distributed along the axial direction. The upper sealing unit includes an upper sealing part, an upper pressure cover 5, and a double-lip upper dustproof ring 4. The lower sealing unit includes a lower sealing part, a lower pressure cover 12, and a double-lip lower dustproof ring 11. The upper and lower pressure covers 12 are detachably fixed to the end faces of the sleeve 7. This utility model adopts an independent sealing design in both the upper and lower parts, combined with the advantages of the four lips of the star-shaped sealing ring, to achieve a full-dimensional dustproof and low-friction sealing effect. The modular structure allows for quick replacement of the sealing components without disassembling the lifting system, extending the sealing life by 3-5 times and reducing maintenance downtime by more than 80%. It is suitable for high-temperature and dusty casting conditions and has significant industrial value.

[0063] The embodiments described herein are preferred embodiments of this utility model and are not intended to limit the scope of protection of this utility model. Therefore, all equivalent changes made to the structure, shape, and principle of this utility model should be included within the scope of protection of this utility model.

Claims

1. A double-layer sealing structure for an equiaxed crystal vacuum precision casting furnace, applied to a mold lifting system, characterized in that, It includes a column (6) of a lifting mechanism, a sleeve (7) sleeved outside the column (6), and a sealing assembly fixedly disposed between the column (6) and the sleeve (7); The sealing assembly includes an upper sealing unit and a lower sealing unit distributed from top to bottom along the axial direction of the column (6); The upper sealing unit includes an upper sealing part, an upper pressure cover (5) and an upper dustproof ring (4). The upper sealing part is installed between the column (6) and the sleeve (7). The upper pressure cover (5) is detachably fixed to the top end face of the sleeve (7) and located above the upper sealing part. The upper dustproof ring (4) has a double lip structure and is embedded in the inner hole step of the upper pressure cover (5). Its lip faces away from the sleeve (7) and is interference-fitted with the outer circumferential surface of the column (6). The lower sealing unit includes a lower sealing part, a lower pressure cover (12), and a lower dustproof ring (11). The lower sealing part is installed between the column (6) and the sleeve (7). The lower pressure cover (12) is detachably fixed to the bottom end face of the sleeve (7) and located below the lower sealing part. The lower dustproof ring (11) has a double lip structure and is embedded in the inner hole step of the lower pressure cover (12). Its lip faces away from the sleeve (7) and is interference-fitted with the outer circumferential surface of the column (6).

2. The double-layer sealing structure of an equiaxed crystal vacuum precision casting furnace according to claim 1, characterized in that, The upper sealing part includes at least two upper star-shaped sealing rings (1), an upper guide band (2) and at least one upper copper sleeve (3). The upper copper sleeve (3) is fixed to the upper copper sleeve (3) mounting groove on the inner wall of the sleeve (7) by interference fit. The upper guide band (2) is made of polytetrafluoroethylene and is sleeved on the column (6). The outer peripheral surface of the upper guide band (2) is slidably fitted with the inner hole surface of the upper copper sleeve (3). The two upper star-shaped sealing rings (1) are respectively set in the upper sealing grooves on the upper and lower sides of the upper copper sleeve (3).

3. The double-layer sealing structure of an equiaxed crystal vacuum precision casting furnace according to claim 2, characterized in that, The lower sealing part includes at least two lower star-shaped sealing rings (10), a lower guide band (9), and at least one lower copper sleeve (8). The lower copper sleeve (8) is fixed to the lower copper sleeve (8) mounting groove on the inner wall of the sleeve (7) by interference fit. The lower guide band (9) is made of polytetrafluoroethylene and is sleeved on the column (6). The outer peripheral surface of the lower guide band (9) is slidably fitted with the inner hole surface of the lower copper sleeve (8). The two lower star-shaped sealing rings (10) are respectively set in the lower sealing grooves on the upper and lower sides of the lower copper sleeve (8).

4. The double-layer sealing structure of an equiaxed crystal vacuum precision casting furnace according to claim 2, characterized in that, The upper star-shaped sealing ring (1) and the lower star-shaped sealing ring (10) are both made of fluororubber FKM, with a Shore hardness of 65-75HA.

5. The double-layer sealing structure of an equiaxed crystal vacuum precision casting furnace according to claim 1, characterized in that, The upper dustproof ring (4) and the lower dustproof ring (11) are both made of polyurethane elastomer with a Shore hardness of 80-90HA. The inner surface of the dustproof ring is provided with lubrication grooves that are evenly distributed along the circumference.

6. The double-layer sealing structure of an equiaxed crystal vacuum precision casting furnace according to claim 3, characterized in that, Both the upper copper sleeve (3) and the lower copper sleeve (8) are made of tin bronze. The inner surface of the copper sleeve is provided with a spiral oil groove, and the upper and lower end faces of the copper sleeve are provided with chamfers.

7. The double-layer sealing structure of an equiaxed crystal vacuum precision casting furnace according to claim 1, characterized in that, The top of the upper cover (5) is provided with an annular tray mounting platform (18), and the end face of the tray mounting platform (18) is provided with a positioning pin hole for positioning and cooperating with the top tray of the lifting system. The outer circumferential surface of the upper cover (5) is provided with anti-slip texture.

8. The double-layer sealing structure of an equiaxed crystal vacuum precision casting furnace according to claim 3, characterized in that, The outer circumferential surfaces of the upper copper sleeve (3) and the lower copper sleeve (8) are provided with annular chip removal grooves (15). The chip removal grooves (15) are connected to chip removal holes (14) opened on the wall of the sleeve (7). The axis of the chip removal holes (14) is perpendicular to the axis of the sleeve (7).

9. The double-layer sealing structure of an equiaxed crystal vacuum precision casting furnace according to claim 3, characterized in that, The outer circumferential surfaces of the upper guide strip (2) and the lower guide strip (9) are respectively provided with annular sealing lips. The sealing lips are interference-fitted with the inner hole surface of the copper sleeve. The two end faces of the guide strip are provided with wear-resistant coatings. The wear-resistant coatings are made of molybdenum disulfide.

10. The double-layer sealing structure of an equiaxed crystal vacuum precision casting furnace according to claim 6, characterized in that, The inner wall of the sleeve (7) is provided with a positioning groove (16), and the outer circumferential surface of the copper sleeve is provided with a positioning boss (17) that cooperates with the positioning groove (16).

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