Sealing structure of high-pressure-resistant threaded connecting piece

Abstract

The invention discloses a high-pressure-resistant threaded connecting piece sealing structure which comprises a hole body, a shaft body and an O-shaped sealing ring, the shaft body is inserted into the hole body, the hole body and the shaft body are connected through threads to form a screwing structure, the front end of the shaft body is in clearance fit with the hole body, a sealing annular groove is formed in the front end of the shaft body, and the O-shaped sealing ring is arranged in the sealing annular groove. The O-shaped sealing ring has compression amount after being installed, a second conical surface is arranged in the hole body, a first conical surface corresponding to the second conical surface is arranged on the shaft body, and the second conical surface and the first conical surface are attached to form a conical sealing pair under the action of axial pressing force of the shaft body and the hole body. The conical sealing pair is used for preventing the O-shaped sealing ring from being squeezed into a fit clearance under high pressure to cause damage, and the formed sealing structure is a static sealing structure, is not suitable for dynamic sealing of reciprocating or rotating motion, is suitable for a high-pressure hydraulic or pneumatic system with the working pressure exceeding 21 MPa, and is particularly suitable for aerospace equipment.

Description

Technical Field

[0001] This invention relates to the field of sealing technology for connectors, specifically a high-pressure resistant threaded connector sealing structure. Background Technology

[0002] In high-reliability hydraulic and pneumatic systems such as aviation and aerospace, O-rings are widely used in static sealing applications. Their structural design typically follows industry standards such as HB / Z4-95 "Design Requirements for O-rings and Sealing Structures," employing a hole-shaft clearance fit and rectangular sealing grooves. This type of structure is suitable for operating pressures not exceeding 21 MPa and offers advantages such as simple structure, convenient installation, and excellent sealing performance.

[0003] However, as aerospace equipment develops towards higher pressures, the operating pressure of systems is increasing daily, and traditional sealing structures are gradually revealing the risk of seal failure under high pressure. Especially under operating conditions exceeding 21 MPa, O-rings are prone to being pushed into the bore-shaft mating clearance by pressure, resulting in rupture or ring shedding and seal failure. Even with PTFE protective rings, insufficient material strength can lead to plastic failure under continuous high pressure, failing to effectively prevent O-ring damage.

[0004] In some technologies, patent document CN201116634Y mainly addresses the sealing and ease of assembly / disassembly requirements of pipeline unions, achieving sealing through a conical surface fit combined with an O-ring. However, it lacks a mechanism to suppress O-ring failures such as extrusion and shearing under pressure, and does not address structural limiting designs to prevent O-ring extrusion and other failures in the bore-shaft fit under high-pressure conditions. Document CN104265880A focuses on the configuration of the conical sealing head and the sealing method, but it is unclear whether it incorporates the combined approach of "O-ring groove + conical sealing pair for O-ring anti-extrusion limiting." Indeed, document CN101645560B still pertains to the improvement of end-face sealing groove structure. It does not propose a method for forming a conical sealing pair on the low-pressure side and using this conical sealing pair as a physical barrier to limit and prevent O-ring extrusion in high-pressure static sealing scenarios with significantly increased working pressure (e.g., exceeding 21MPa). It also lacks systematic limitations on key engineering constraints such as the range of hole-shaft clearance fit, conical surface roughness, and machining accuracy. Therefore, in high-pressure hydraulic or pneumatic systems, there may still be problems with insufficient sealing reliability due to O-ring extrusion damage.

[0005] Patent document US7600649B1 discloses a core idea that involves actively reducing or filling the mating gap at the location of the O-ring under high temperature / high pressure conditions through structural or material means, in order to prevent the O-ring from being pushed into the gap by pressure after softening. However, the above solutions often rely on the specific deformation of the components under pressure / heat or on the expansion of the backup ring and materials to "dynamically reduce the gap." The requirements for structural and material matching are high. Moreover, the approach does not involve forming a conical sealing pair by fitting the conical surfaces of the bore and shaft together, and using this conical sealing pair to form a physical barrier on the low-pressure side to limit the O-ring and prevent it from being extruded. Therefore, in the static sealing scenario for threaded connections, there are still limitations in terms of structural complexity, manufacturing consistency, and assembly controllability.

[0006] Therefore, existing sealing structures are no longer sufficient to meet the long-term stable sealing requirements of high-pressure systems. Especially in the aerospace field, higher requirements are placed on sealing safety, pressure resistance, and lifespan. There is an urgent need to develop a new sealing structure that is more protective and adaptable to high-pressure conditions in order to effectively solve the problem that traditional sealing rings are easily damaged by compression. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the existing defects and provide a high-pressure resistant threaded connection sealing structure. Through the first conical surface and the second conical surface, a tightly fitting conical sealing pair is formed under the action of axial clamping force, so as to effectively limit the O-ring seal. This structure can significantly suppress the extrusion deformation of the sealing ring in the gap direction under high pressure environment, and avoid system leakage or failure due to sealing ring damage. It can effectively solve the problems in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a high-pressure threaded connector sealing structure, comprising a bore, a shaft, and an O-ring. The shaft is inserted into the bore, and the bore and shaft are provided with axial clamping force through a pre-tightening structure. The pre-tightening structure is a swivelable structure formed by a threaded connection or a spring assembly. The front end of the shaft is clearance-fitted with the bore. The front end of the shaft is provided with a sealing annular groove, and the O-ring is disposed in the sealing annular groove. The O-ring is compressed after being inserted. A second conical surface is provided in the bore, and a first conical surface corresponding to the second conical surface is provided on the shaft. The second conical surface and the first conical surface fit together under the axial clamping force of the shaft and the bore to form a conical sealing pair. This conical sealing pair is used to prevent the O-ring from being squeezed into the fitting gap under high pressure and thus damaged. The formed sealing structure is a static sealing structure and is not suitable for dynamic sealing of reciprocating or rotating motion. This structure is suitable for high-pressure hydraulic or pneumatic systems with working pressures exceeding 21 MPa, and is especially suitable for aerospace equipment.

[0009] Furthermore, the cone angle of the first cone is 60° to 90°, and the second cone has the same angle as the first cone, with a cone length of 0.3-1mm.

[0010] Furthermore, when the pretensioning structure is a spring assembly, the spring assembly includes a helical spring, a disc spring, or a wave spring.

[0011] Furthermore, the O-ring is made of synthetic rubber, selected from fluororubber, nitrile rubber, or EPDM rubber.

[0012] Furthermore, the surface roughness Ra of the first and second conical surfaces is no greater than 0.8 μm. The surface roughness and machining accuracy requirements are good, so that the O-ring seal will not be scratched or cut when passing through the orifice.

[0013] Furthermore, the clearance fit between the shaft and the bore is in the range of 0.01 mm to 0.1 mm.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention forms a tightly fitting conical sealing pair through the first and second conical surfaces under axial clamping force, effectively limiting the O-ring seal. This structure can significantly suppress the extrusion deformation of the seal in the gap direction under high pressure, avoiding system leakage or failure due to seal breakage. It is especially suitable for high-pressure hydraulic and pneumatic systems with working pressure exceeding 21MPa. The conical surfaces are located on the low-pressure side, further reducing the pressure difference on the seal and improving the overall sealing performance and structural safety.

[0015] 2. Compared with existing sealing structures that rely on protective rings, this invention achieves anti-extrusion function through the structure itself, eliminating the need for additional PTFE or other protective rings. This avoids the risk of protective rings easily deforming or failing in traditional structures, reducing structural complexity and the number of components. At the same time, the structural design takes into account both processing feasibility and assembly convenience, adapting to a fitting accuracy of 0.01mm to 0.1mm gaps, ensuring a highly efficient and reliable sealing effect without increasing manufacturing difficulty. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the shaft structure of the present invention; Figure 3 This is a schematic diagram of the hole structure of the present invention; Figure 4 This is a schematic diagram of another form of sealing structure for the fit between the shaft and the bore of the present invention; Figure 5 This is a schematic diagram of the original sealing structure of the present invention with a protective ring. Figure 6 This is a schematic diagram comparing the sealing state of the sealing structure of the present invention and the original sealing structure after being subjected to high pressure.

[0017] In the diagram: 1. Hole body, 2. Shaft body, 3. O-ring seal, 4. Conical sealing pair, 5. Sealing annular groove, 6. First conical surface, 7. Second conical surface, 8. Protective ring. Detailed Implementation

[0018] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are 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 a limitation of this invention. Example 1

[0019] Please see Figure 1-6 This invention provides a technical solution: a high-pressure resistant threaded connector sealing structure, comprising a bore 1, a shaft 2, and an O-ring 3. The shaft 2 is inserted into the bore 1, and the bore 1 and shaft 2 are provided with axial clamping force through a pre-tightening structure. The pre-tightening structure is a swivelable structure formed by a threaded connection or a spring assembly. The front end of the shaft 2 is clearance-fitted with the bore 1. The front end of the shaft 2 is provided with a sealing annular groove 5, and the O-ring 3 is disposed in the sealing annular groove 5. After the O-ring 3 is installed, it has a compression amount. The bore 1 is provided with... A second conical surface 7 is provided, and a first conical surface 6 corresponding to the second conical surface 7 is provided on the shaft body 2. The second conical surface 7 and the first conical surface 6 are fitted together under the axial clamping force of the shaft body 2 and the bore body 1 to form a conical sealing pair 4. The conical sealing pair 4 is used to prevent the O-ring seal 3 from being squeezed into the mating gap under high pressure and causing damage. The sealing structure formed is a static sealing structure and is not suitable for dynamic sealing of reciprocating or rotating motion. It is suitable for high-pressure hydraulic or pneumatic systems with working pressure exceeding 21MPa, and is especially suitable for aerospace equipment.

[0020] This embodiment relies on the conical sealing pair 4 as the core structure. By designing the first conical surface 6 and the second conical surface 7 as mating surfaces with matching cone angles, after the hole body 1 and the shaft body 2 are pre-tightened by threaded engagement, the conical surfaces fit tightly together to form a highly reliable static seal. The conical sealing pair is preferably positioned close to the low-pressure side to form an effective physical barrier, inhibiting the O-ring seal 3 from being squeezed out towards the hole-shaft gap under high pressure. The O-ring seal 3 is placed in the sealing annular groove 5 at the front end of the shaft body 2 and has a moderate amount of compression. It provides initial sealing force under the compressed state, and is limited by the conical sealing pair to avoid its rupture, ring cutting, or failure due to high pressure load.

[0021] Through this structural design, the sealing ring can effectively maintain its integrity and sealing function under static conditions, significantly enhancing its resistance to compression under high pressure. Compared with traditional solutions that rely on protective rings, this invention avoids plastic deformation or structural failure caused by insufficient strength of the protective ring material, simplifies the overall structure, and improves the integration and reliability of the sealing components. In addition, this sealing structure supports high-precision sealing with a mating gap of 0.01mm to 0.1mm, ensuring that the sealing requirements of high-end applications such as aerospace are met without increasing the difficulty of processing.

[0022] In one possible implementation, the cone angle of the first cone 6 is 60° to 90°, and the second cone 7 has the same angle as the first cone 6, with a cone length of 0.3-1 mm.

[0023] This implementation further optimizes the structural stability of the conical sealing pair 4 by specifying the range of conical angles and the setting of the fitting length. The conical angle is between 60° and 90°, which can improve its compressive strength while maintaining sufficient fitting area. The conical length of 0.3-1mm helps to achieve effective fitting and prevent leakage. The consistent conical angle ensures full contact between the first conical surface 6 and the second conical surface 7, improving the sealing effect and mechanical interlocking stability.

[0024] By controlling the cone angle and the fitting length, the limiting effect and resistance to pressure deformation of the sealing pair are significantly enhanced, effectively avoiding damage or failure of the sealing surface caused by uneven local stress. At the same time, the controllability of processing and the consistency of assembly are improved, and the reliability and service life of the overall sealing structure are enhanced.

[0025] The cone angle and length can be adjusted according to the specific pressure level of the application; for example, for higher pressure scenarios, the cone angle can be appropriately reduced or the cone length can be increased to enhance structural stability; for medium pressure applications, a more lenient parameter range can be used to simplify processing and reduce costs.

[0026] In one possible implementation, when the preload structure is a spring assembly, the spring assembly includes a helical spring, a disc spring, or a wave spring.

[0027] Optionally, a spring assembly is provided at the swivelable structure formed by the threaded connection between the bore 1 and the shaft 2 to provide auxiliary axial clamping force or compensate for the axial clamping force. Through the preload and rebound characteristics of the elastic element, the first conical surface 6 and the second conical surface 7 can maintain a continuous contact state when the axial preload fluctuates due to factors such as assembly tolerances, temperature changes, vibration, or pressure pulsation. This ensures that the conical sealing pair 4 is in a stable sealing and limiting condition, improving the reliability and service life of the sealing structure under high pressure conditions. This solution uses a spring assembly instead of the traditional threaded engagement method to achieve the required axial preload for the conical sealing pair 4. The spring assembly has a flexible adjustment function, which can automatically compensate for gap changes caused by thermal expansion and contraction or micro deformation, keep the sealing surface in continuous contact, and thus maintain a constant sealing effect.

[0028] Using spring assemblies simplifies assembly processes, reduces human error, and improves the system's adaptability to vibration or temperature fluctuations, extending its service life. They are particularly suitable for high-reliability sealing systems that require quick disassembly or installation in confined spaces, offering greater flexibility and maintainability.

[0029] In one possible implementation, the O-ring 3 is made of synthetic rubber, selected from fluororubber, nitrile rubber, or EPDM rubber. By selecting different types of synthetic rubber materials to make the O-ring 3, its corrosion resistance, pressure resistance, and resilience can be improved for different media and operating temperature conditions. Fluororubber is suitable for high temperature and highly corrosive environments, nitrile rubber performs well in mineral oils, and EPDM rubber performs well in ozone and water environments.

[0030] A variety of materials can cover a wider range of working conditions, improve system adaptability, extend the service life of seals, reduce replacement frequency, and enhance the overall system stability and economy.

[0031] In one possible implementation, the surface roughness Ra of the first conical surface 6 and the second conical surface 7 is no greater than 0.8 μm. The conical surface roughness and machining accuracy requirements are good, protecting the O-ring 3 from being scratched or cut when passing through the orifice. The high surface precision of the conical surface design ensures that the sealing mating surfaces produce stable and lasting linear contact during mating, avoiding mechanical damage to the sealing ring caused by microscopic protrusions or roughness on the surface. The surface roughness Ra≤0.8 μm ensures smoothness and tight mechanical mating. This can significantly reduce the risk of scratching and cutting during the sealing ring assembly process, improve the initial sealing success rate and long-term sealing reliability, and reduce maintenance frequency and system leakage probability.

[0032] The surface quality of the conical surface can also be further optimized by polishing, electrochemical deburring or coating treatment; for automated batch processing, CNC grinding technology can be used to ensure processing consistency.

[0033] In one possible implementation, the clearance fit between the shaft 2 and the bore 1 is in the range of 0.01 mm to 0.1 mm. Appropriately controlling the clearance between the shaft 2 and the bore 1 helps to provide sufficient structural limiting space while ensuring smooth assembly, and avoids the seal ring from being squeezed in by high pressure and breaking due to excessive clearance. This range takes into account both the feasibility of processing and manufacturing and the stability of sealing performance.

[0034] Controlling the gap within this range helps improve the compressive strength and positioning accuracy of the sealing structure, while ensuring a smooth sealing assembly process and reducing the risk of abnormal stress on the sealing ring.

[0035] As attached Figure 5 and 6 As shown, the original O-ring 3 will be squeezed into the mating gap under high pressure. When the pressure reaches a certain value, the O-ring 3 will be squeezed and damaged. Even if a protective ring 8 is set on the low-pressure side, the protective ring 8 is usually made of polytetrafluoroethylene (PTFE). PTFE is a plastic with low hardness. When the pressure continues to increase to a certain value, it will also be squeezed and damaged, which will cause the protective ring 8 to be squeezed into the gap and damaged, resulting in sealing failure.

[0036] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A high pressure resistant threaded connection seal structure comprising a hole body (1), a shaft body (2) and an O-ring (3), characterized in that: The shaft body (2) is inserted into the hole body (1), and the hole body (1) and the shaft body (2) provide an axial compression force through a pre-tightening structure, the pre-tightening structure is a screwable structure or a spring assembly formed by screwing, the front end of the shaft body (2) is in clearance fit with the hole body (1), the front end of the shaft body (2) is provided with a sealing annular groove (5), an O-shaped sealing ring (3) is arranged in the sealing annular groove (5), the hole body (1) is provided with a second taper surface (7), the shaft body (2) is provided with a first taper surface (6) corresponding to the second taper surface (7), and the second taper surface (7) and the first taper surface (6) are in close fit to form a tapered sealing pair (4) under the action of the axial compression force of the shaft body (2) and the hole body (1).

2. A high pressure threaded connection seal as claimed in claim 1, characterized in that: The taper angle of the first taper surface (6) is 60° to 90°, the angle of the second taper surface (7) is the same as that of the first taper surface (6), and the length of the taper surface is 0.3-1mm.

3. A high pressure threaded connection seal as defined in claim 1, wherein: When the pre-tightening structure is a spring assembly, the spring assembly comprises a spiral spring, a disc spring or a wave spring.

4. A high pressure threaded connection seal as defined in claim 1, wherein: The material of the O-shaped sealing ring (3) is synthetic rubber, and the material is selected from fluoroelastomer, nitrile rubber or ethylene-propylene-diene rubber.

5. A high pressure threaded connection seal as defined in claim 1, wherein: The surface roughness Ra of the first taper surface (6) and the second taper surface (7) is not greater than 0.8μm.

6. A high pressure threaded connection seal as defined in claim 1, wherein: The clearance fit range of the shaft body (2) and the hole body (1) is 0.01mm to 0.1mm.

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