A high torque gas seal oil casing thread joint

Abstract

This invention relates to the field of oil casing pipe joint technology, and in particular to a high-torsion gas-tight oil casing pipe threaded joint, comprising an internally threaded pipe body, an externally threaded pipe body, an inner liner, and an externally threaded ring. The inner wall of the internally threaded pipe body has a first receiving groove, and the inner wall of the externally threaded pipe body has a second receiving groove. The bottom outer wall of the inner liner fits against the inner wall of the first receiving groove, and the top outer wall of the inner liner fits against the inner wall of the second receiving groove. The externally threaded ring is fixedly connected to the outer wall of the inner liner. The outer walls of the externally threaded pipe body and the externally threaded ring are threadedly connected to the inner wall of the internally threaded pipe body. This invention, through the combined structure of the internally threaded pipe body, externally threaded pipe body, inner liner, and externally threaded ring, combined with the double-threaded connection design between the internally threaded pipe body, externally threaded pipe body, and inner liner, effectively improves the torsional strength of the joint. The multi-stage sealing structure works synergistically to ensure the airtightness of the joint under high-temperature and high-pressure environments.

Description

Technical Field

[0001] This invention relates to the field of oil casing pipe joint technology, and in particular to a high torsion-resistant gas-sealed oil casing pipe threaded joint. Background Technology

[0002] In the process of oil and gas exploration and development, casing and tubing are key equipment for constructing oil and gas well passages. Since casing and tubing typically need to be connected into tubing strings that can reach lengths of several kilometers, threaded joints, as crucial components connecting the tubing, directly affect the safety and reliability of the entire tubing string. As oil and gas exploration and development extend to deep wells, ultra-deep wells, and high-temperature, high-pressure, and corrosive environments, higher requirements are placed on the connection strength and sealing performance of threaded joints.

[0003] Existing oil casing threaded fittings are mainly divided into two categories: API standard threaded fittings and special threaded fittings. API standard threaded fittings mainly rely on the metal-to-metal contact between thread grease and the thread itself to achieve a seal, but their torsional resistance and airtightness often fail to meet requirements under extreme operating conditions. Although special threaded fittings improve performance by adding metal-to-metal sealing structures and optimizing thread forms, they still have many shortcomings in practical applications.

[0004] Specifically, in existing threaded joints, the threads are prone to deformation or slippage under high torque, leading to connection failure. Furthermore, under complex downhole conditions (such as axial tension, compression, bending, and temperature changes), fretting wear or gaps can easily occur between the sealing surfaces, resulting in gas leakage. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the threaded connection method in the related technology is prone to loosening under vibration environment, lacks an effective anti-loosening mechanism, is difficult to guarantee long-term sealing reliability, and its torsional resistance is difficult to meet the requirements.

[0006] To solve the above technical problems, the present invention provides the following technical solution: a high anti-torsion gas-sealing oil sleeve threaded joint, comprising an internally threaded tube body, an externally threaded tube body, an inner liner tube, and an externally threaded ring, wherein a first receiving groove is formed on the inner wall of the internally threaded tube body, a second receiving groove is formed on the inner wall of the externally threaded tube body, the bottom outer wall of the inner liner tube is attached to the inner wall of the first receiving groove, the top outer wall of the inner liner tube is attached to the inner wall of the second receiving groove, and the externally threaded ring is fixedly connected to the outer wall of the inner liner tube. The outer wall of the externally threaded pipe body and the outerly threaded ring are connected to the inner wall of the internally threaded pipe body.

[0007] As a preferred embodiment of the high anti-torsion gas-sealed oil sleeve threaded joint of the present invention, wherein: the inner wall of the internal threaded pipe is provided with a first inclined conical surface, and the bottom of the external threaded ring is provided with a second inclined conical surface corresponding to the first inclined conical surface, and the first inclined conical surface and the second inclined conical surface are interference fit.

[0008] As a preferred embodiment of the high anti-torsion gas-sealed oil sleeve threaded joint of the present invention, wherein: the inner wall of the inner threaded pipe body is further provided with a sealing ring, and the second inclined cone surface at the bottom of the outer threaded ring passes through the inner side of the sealing ring.

[0009] As a preferred embodiment of the high torsion-resistant gas-tight oil sleeve threaded joint of the present invention, wherein: the top of the internal threaded pipe body is provided with a shoulder and a female sealing surface, and the external threaded pipe body is provided with a shoulder groove and a male sealing surface corresponding to the shoulder position, the shoulder is inserted into the inner wall of the shoulder groove, and the female sealing surface and the male sealing surface are interference fit.

[0010] As a preferred embodiment of the high anti-torsion gas-sealed oil sleeve threaded joint of the present invention, wherein: a first inclined bevel is provided on the outer side of the shoulder at the top of the internal threaded pipe body, and a second inclined bevel is provided on the outer side of the shoulder groove at the bottom of the external threaded pipe body, and the first inclined bevel and the second inclined bevel are adapted to each other.

[0011] As a preferred embodiment of the high anti-torsion gas-tight oil sleeve threaded joint of the present invention, wherein: the outer wall of the internal threaded pipe is fixedly connected to a first retaining ring, the outer wall of the first retaining ring is provided with an external thread, the outer wall of the external threaded ring is fixedly connected to a second retaining ring, and the outer wall of the second retaining ring is slidably connected to an outer sleeve, the top of the outer sleeve is slidably connected to the outer wall of the internal threaded pipe, the bottom inner wall of the outer sleeve is provided with an internal thread, and the outer wall of the first retaining ring is threadedly connected to the bottom inner wall of the outer sleeve, and the bottom of the first retaining ring is provided with a second tapered section.

[0012] As a preferred embodiment of the high torsion-resistant gas-tight oil sleeve threaded joint of the present invention, wherein: a first through hole is provided on the outer sleeve, and a plurality of second through holes are provided on the second retaining ring, the second through holes being evenly distributed in a ring on the second retaining ring, and a pin is inserted into the inner wall of the first through hole and the second through hole, and the inner wall of the first through hole and the second through hole is interference-fitted with the pin.

[0013] As a preferred embodiment of the high torsion-resistant gas-sealing oil sleeve threaded joint of the present invention, the bottom of the pin is provided with a tapered head, and the top of the pin is fixedly connected with a mushroom head.

[0014] As a preferred embodiment of the high anti-torsion gas-sealed oil sleeve threaded joint of the present invention, wherein the inner diameter of the threaded tube body and the outer threaded ring at the end away from the second retaining ring gradually shrinks.

[0015] As a preferred embodiment of the high anti-torsion gas-sealed oil sleeve threaded joint of the present invention, wherein: the inner liner tube is provided with a third inclined cone surface and a fourth inclined cone surface at both ends, the bottom of the first receiving groove is provided with a fifth inclined cone surface that cooperates with the third inclined cone surface, and the top of the second receiving groove is provided with a sixth inclined cone surface that cooperates with the fourth inclined cone surface.

[0016] The beneficial effects of this invention are as follows: This invention utilizes a combined structure of an internally threaded pipe body, an externally threaded pipe body, an inner liner, and an externally threaded ring, along with a double-threaded connection design between the internally threaded pipe body, the externally threaded pipe body, and the inner liner, which helps to improve the torsional strength of the joint. Through the coordinated operation of a multi-stage sealing structure (threaded seal, conical seal, elastic seal, and end face seal), the airtightness of the joint is ensured under high temperature and high pressure environments.

[0017] Insert the pin into the aligned first and second through holes. The pin is press-fitted with the inner walls of the first and second through holes to form a mechanical locking mechanism. When external vibration or alternating loads attempt to loosen and rotate the external threaded tube body and external threaded ring relative to the internal threaded tube body, the rotational torque will be transmitted to the thread friction torque between the outer tube and the first retaining ring through the second retaining ring, providing a portion of the torsional strength. Moreover, the pin has locked the outer tube. Unless the pin is sheared (which requires extremely large shearing force, far exceeding normal working conditions), the outer tube cannot rotate, enabling the joint to withstand severe vibration and alternating loads, enhancing torsional strength, and maintaining a stable connection state for a long time. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure in an embodiment of this disclosure.

[0019] Figure 2 This is a cross-sectional view of the internally threaded pipe body in an embodiment of this disclosure.

[0020] Figure 3 This is a cross-sectional view of the externally threaded pipe body in an embodiment of this disclosure.

[0021] Figure 4 This is a cross-sectional view of the inner lining tube in an embodiment of this disclosure.

[0022] Figure 5 For the embodiments of this disclosure Figure 1 Enlarged diagram of point A in the middle.

[0023] Figure 6 This is a cross-sectional view of the second retaining ring in an embodiment of this disclosure.

[0024] Figure 7 This is a schematic diagram of the assembly of the internally threaded tube body and the inner liner tube in an embodiment of this disclosure.

[0025] Figure 8 This is a schematic diagram of the assembly of the internally threaded tube body, the externally threaded tube body, and the inner liner tube in the embodiments of this disclosure.

[0026] Reference numerals: 1-Internal threaded tube body; 11-First receiving groove; 111-Fifth inclined conical surface; 12-First inclined conical surface; 13-Sealing ring; 14-Shoulder; 141-First inclined bevel; 15-Female sealing surface; 16-First retaining ring; 16-Second conical section; 2-External threaded tube body; 21-Second receiving groove; 211-Sixth inclined conical surface; 22-Shoulder groove; 221-Second inclined bevel; 23-Male sealing surface; 3-Inner liner tube; 31-Third inclined conical surface; 32-Fourth inclined conical surface; 4-External threaded ring; 41-Second inclined conical surface; 42-Second retaining ring; 421-Second through hole; 43-Outer sleeve; 431-First through hole; 44-Pin; 441-Conical head; 442-Mushroom head. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0028] Example 1, referring to Figures 1 to 4 This embodiment provides a high torsion-resistant gas-tight oil sleeve threaded joint, including an internally threaded tube body 1, an externally threaded tube body 2, an inner liner tube 3, and an externally threaded ring 4. The inner wall of the internally threaded tube body 1 is provided with a first receiving groove 11, the inner wall of the externally threaded tube body 2 is provided with a second receiving groove 21, the bottom outer wall of the inner liner tube 3 is attached to the inner wall of the first receiving groove 11, the top outer wall of the inner liner tube 3 is attached to the inner wall of the second receiving groove 21, and the outer wall of the inner liner tube 3 is fixedly connected to the externally threaded ring 4. In this embodiment, the internally threaded tube body 1 is the female end component of the connector, used to receive and connect the externally threaded tube body 2. The externally threaded tube body 2 is the male end component of the connector, used to screw into the internally threaded tube body 1 to achieve connection. Its exterior is provided with threads, a sealing structure, and a positioning structure. A first receiving groove 11 is formed on the inner wall of the internally threaded tube body 1 to receive the bottom of the inner liner tube 3. The shape of the first receiving groove 11 is adapted to the outer wall of the bottom of the inner liner tube 3, achieving radial positioning of the inner liner tube 3. The bottom of the first receiving groove 11 is provided with a fifth inclined conical surface 111, used to cooperate with the third inclined conical surface 31 of the bottom of the inner liner tube 3. A second receiving groove 21 is formed on the inner wall of the externally threaded tube body 2 to receive the top of the inner liner tube 3. The shape of the second receiving groove 21 is adapted to the outer wall of the top of the inner liner tube 3, achieving radial positioning of the inner liner tube 3. The top of the second receiving groove 21 is provided with a sixth inclined conical surface 211, used to cooperate with the fourth inclined conical surface 32 of the top of the inner liner tube 3, achieving precise positioning and sealing.

[0029] Furthermore, the internally threaded pipe body 1 is made of high-quality alloy steel. The inner wall thread of the internally threaded pipe body 1 adopts a trapezoidal thread or a special sealing thread, which has the characteristics of strong load-bearing capacity and good sealing performance. The first inclined conical surface 12 and the female sealing surface 15 are precision machined, with a surface roughness Ra of no more than 0.8 μm to ensure the sealing effect. The externally threaded pipe body 2 is preferably made of the same or similar material as the internally threaded pipe body 1 to ensure the consistency of the coefficient of thermal expansion. The outer wall thread of the externally threaded pipe body 2 matches the inner wall thread of the internally threaded pipe body 1, adopting a trapezoidal thread or a special sealing thread. The surface roughness Ra of the male sealing surface 23 is no more than 0.8 μm to ensure the sealing effect with the female sealing surface 15.

[0030] Furthermore, the inner liner 3 is a transitional connector placed between the internally threaded tube body 1 and the externally threaded tube body 2, used to achieve coaxial positioning and a sealing barrier function for the two tube bodies. The bottom of the inner liner 3 is inserted into the first receiving groove 11 of the internally threaded tube body 1, and the top is inserted into the second receiving groove 21 of the externally threaded tube body 2. The outer wall of the middle section is fixedly connected to the externally threaded ring 4. The inner liner 3 connects the internally threaded tube body 1 and the externally threaded tube body 2 into a whole, and its tube wall forms a physical barrier to prevent gas leakage. The inner liner 3 is preferably made of high-strength alloy steel, and its inner and outer walls are precision machined to ensure the fitting accuracy with the receiving grooves. The surface roughness Ra of the third inclined conical surface 31 and the fourth inclined conical surface 32 is not greater than 1.6μm to ensure the sealing effect. The inner liner 3 and the externally threaded ring 4 are fixedly connected by interference fit or welding to ensure that there is no relative movement between the two.

[0031] The external threaded tube body 2 and the external threaded ring 4 are connected to the inner wall of the internal threaded tube body 1 by the external thread.

[0032] In this embodiment, the external threaded ring 4 is a threaded connector fixed to the outer wall of the inner liner tube 3, used for threaded connection with the internally threaded tube body 1 to form a double-threaded connection structure. The external threaded ring 4 is fixedly sleeved on the outer wall of the inner liner tube 3, and its outer wall has threads that mesh with the inner thread of the internally threaded tube body 1. The external threaded ring 4 and the externally threaded tube body 2 are screwed into the internally threaded tube body 1 together to form a double-threaded connection structure, which increases the meshing area and load-bearing capacity of the threads.

[0033] In this embodiment, the traditional one-piece connector is decomposed into four main components: an internally threaded tube body 1, an externally threaded tube body 2, an inner liner tube 3, and an externally threaded ring 4. The internally threaded tube body 1 serves as the female end of the connector, with threads on its inner wall for connection with the male end of the externally threaded tube body 2. The externally threaded tube body 2 serves as the male end of the connector, with threads on its outer wall for screwing into the internally threaded tube body 1. The inner liner tube 3 is positioned between the internally threaded tube body 1 and the externally threaded tube body 2, serving as a transition connection and a sealing barrier. The external threaded ring 4 is fixed to the outer wall of the inner liner tube 3, forming a double threaded connection structure together with the external threaded tube body 2. This is beneficial to improving the torsional strength and sealing performance of the joint. Moreover, the inner liner tube 3, as an independent sealing element, forms a metal barrier with its fit with the inner wall of the first receiving groove 11, effectively blocking the channel for gas leakage along the thread gap and increasing axial strength. The double threaded connection structure formed by the external threaded ring 4 and the external threaded tube body 2 increases the meshing area of ​​the threads and disperses the torque load, thereby significantly improving the torsional strength of the joint.

[0034] Example 2, refer to Figures 1 to 8 This embodiment is based on the previous embodiment, but differs from the previous embodiment in that...

[0035] Reference Figure 2 The inner wall of the internally threaded tube body 1 is provided with a first inclined conical surface 12, and the bottom of the externally threaded ring 4 is provided with a second inclined conical surface 41 corresponding to the first inclined conical surface 12. The first inclined conical surface 12 and the second inclined conical surface 41 are interference-fitted.

[0036] In this embodiment, the first inclined conical surface 12 is disposed at the end of the threaded area on the inner wall of the internally threaded tube body 1, and is in the shape of an annular conical surface. It is used to make an interference fit with the second inclined conical surface 41 at the bottom of the externally threaded ring 4 to form a metal-to-metal main sealing structure. The cone angle of the first inclined conical surface 12 is usually designed to be 10° to 20° to ensure that sufficient radial interference can be generated during tightening, while avoiding excessive assembly stress.

[0037] Reference Figure 2 The inner wall of the internally threaded tube body 1 is also provided with a sealing ring 13, and the bottom of the externally threaded ring 4 has a second inclined cone surface 41, which passes through the inner side of the sealing ring 13.

[0038] In this embodiment, the sealing ring 13 is disposed on the inner wall of the internally threaded pipe body 1, located inside the first inclined conical surface 12, and is used to cooperate with the second conical section 42 at the bottom of the externally threaded ring 4 to form an elastic sealing structure. The second inclined conical surface 41 is disposed at the bottom of the externally threaded ring 4, located inside the second inclined conical surface 41, and is shaped like a frustum of a cone, used to pass through the inner side of the sealing ring 13. The outer diameter of the second inclined conical surface 41 gradually increases from the bottom to the top. When it passes through the sealing ring 13, it will expand the sealing ring 13, so that the sealing ring 13 is tightly attached to the inner wall of the internally threaded pipe body 1, forming an elastic sealing structure. The sealing ring 13 is preferably made of rubber, polytetrafluoroethylene, or metal elastic material. Rubber sealing rings have good elasticity and sealing performance, but limited temperature resistance; polytetrafluoroethylene sealing rings have good corrosion resistance and temperature resistance; metal elastic sealing rings are suitable for high temperature and high pressure environments. The cross-sectional shape of the sealing ring 13 can be O-shaped, V-shaped, or U-shaped, selected according to specific working conditions.

[0039] In one embodiment, the external threaded ring 4 is made of high-quality alloy steel and undergoes heat treatment to obtain good comprehensive mechanical properties. The outer thread of the external threaded ring 4 matches the inner thread of the internal threaded tube body 1, employing a trapezoidal thread or a special sealing thread form. The second inclined conical surface 41 is precision machined with a surface roughness Ra of no more than 0.8 μm to ensure a sealing effect with the first inclined conical surface 12. The inner diameter of the thread on the end of the external threaded ring 4 away from the second retaining ring 42 gradually narrows, forming a conical thread structure, which causes radial interference during tightening, enhancing the tightness and sealing of the threaded connection.

[0040] Reference Figure 2 The top of the internally threaded pipe body 1 is provided with a shoulder 14 and a female sealing surface 15. The externally threaded pipe body 2 is provided with a shoulder groove 22 and a male sealing surface 23 corresponding to the position of the shoulder 14. The shoulder 14 is inserted into the inner wall of the shoulder groove 22, and the female sealing surface 15 and the male sealing surface 23 are interference fit.

[0041] In this embodiment, a shoulder 14 is located at the top (innermost end) of the internally threaded pipe body 1, and is an annular protrusion used to mate with the shoulder groove 22 of the externally threaded pipe body 2, providing axial positioning. A first inclined bevel 141 is provided on the outer side of the shoulder 14, forming an inclined guide surface to facilitate smooth insertion of the shoulder groove 22 of the externally threaded pipe body 2. The inclination angle of the first inclined bevel 141 is typically designed to be 30° to 45° to balance the guiding effect and structural strength. A female sealing surface 15 is located on the inner side of the shoulder 14, and is an annular conical surface used to interfere with the male sealing surface 23 of the externally threaded pipe body 2, forming an end-face sealing structure. The cone angle of the female sealing surface 15 is typically designed to be 15° to 25° to ensure sufficient sealing pressure is generated when the shoulder 14 contacts the shoulder groove 22. The male sealing surface 23 is located on the inner side of the shoulder groove 22, and is an annular conical surface used to interfere with the female sealing surface 15 of the internally threaded pipe body 1, forming an end-face sealing structure. The cone angle of the male sealing surface 23 matches the cone angle of the female sealing surface 15, typically ranging from 15° to 25°. In practice, the sealing effect of the end face seal depends on the cone angle, surface roughness, and tightening torque of the sealing surfaces. The cone angle is typically designed to be 15° to 25°, and the surface roughness Ra is no greater than 0.8 μm. The tightening torque should ensure sufficient sealing pressure between the female sealing surface 15 and the male sealing surface 23, while avoiding excessive assembly stress.

[0042] Reference Figure 2 The shoulder 14 at the top of the internally threaded tube 1 is provided with a first inclined bevel 141 on the outside, and the shoulder groove 22 at the bottom of the externally threaded tube 2 is provided with a second inclined bevel 221 on the outside. The first inclined bevel 141 and the second inclined bevel 221 are compatible with each other.

[0043] In this embodiment, a shoulder groove 22 is formed at the bottom (i.e., the outermost end) of the externally threaded pipe body 2, and is in the shape of an annular groove. It is used to mate with the shoulder 14 of the internally threaded pipe body 1 to provide axial positioning. A second inclined bevel 221 is provided on the outer side of the shoulder groove 22, which is in the shape of an inclined guide surface and is adapted to the first inclined bevel 141 of the shoulder 14 to facilitate assembly and alignment. The inclination angle of the second inclined bevel 221 is the same as that of the first inclined bevel 141, which is usually 30° to 45°.

[0044] Reference Figure 2 The outer wall of the internally threaded tube body 1 is fixedly connected to the first retaining ring 16, the outer wall of the first retaining ring 16 is provided with external threads, the outer wall of the externally threaded ring 4 is fixedly connected to the second retaining ring 42, and the outer wall of the second retaining ring 42 is slidably connected to the outer sleeve 43. The top of the outer sleeve 43 is slidably connected to the outer wall of the internally threaded tube body 1, the bottom inner wall of the outer sleeve 43 is provided with internal threads, and the outer wall of the first retaining ring 16 is threadedly connected to the bottom inner wall of the outer sleeve 43. The bottom of the first retaining ring 16 is provided with a second tapered section 161.

[0045] In this embodiment, the first retaining ring 16 is fixedly connected to the outer wall of the internally threaded tube body 1, and is in the shape of an annular protrusion. Its outer wall has external threads for engaging with the internal threads at the bottom of the outer sleeve 43 to achieve the locking mechanism. The first retaining ring 16 and the internally threaded tube body 1 can be integrally formed, or they can be fixed by welding or threaded connection. The second tapered section 161 facilitates the guide joint's movement through narrow environments.

[0046] Reference Figure 3 and Figure 6 The outer sleeve 43 has a first through hole 431, and the second retaining ring 42 has multiple second through holes 421. The second through holes 421 are evenly distributed in a ring on the second retaining ring 42. A pin 44 is inserted into the inner wall of the first through hole 431 and the second through hole 421, and the inner wall of the first through hole 431 and the second through hole 421 is press-fitted with the pin 44.

[0047] In this embodiment, the second retaining ring 42 is fixedly connected to the outer wall of the external threaded ring 4, and is in the shape of an annular protrusion, used to cooperate with the outer sleeve 43 to realize the connection of the locking mechanism. The second retaining ring 42 has multiple second through holes 421, which are evenly distributed annularly on the second retaining ring 42, for inserting the pin 44 to lock the position of the outer sleeve 43. The outer sleeve 43 has a cylindrical structure and is fitted onto the outer wall of the second retaining ring 42. Its top is slidably connected to the outer wall of the internally threaded tube body 1, and its bottom inner wall has internal threads. The outer sleeve 43 is used to connect the first retaining ring 16 and the second retaining ring 42 to realize the locking function. The outer sleeve 43 has a first through hole 431, for aligning with the second through hole 421 of the second retaining ring 42 before inserting the pin 44.

[0048] Reference Figure 5 The bottom of the pin 44 is provided with a tapered head 441, and the top of the pin 44 is fixedly connected to a mushroom head 442.

[0049] In this embodiment, the pin 44 is used to lock the relative position of the outer sleeve 43 and the second retaining ring 42, preventing the outer sleeve 43 from accidentally rotating and loosening. The pin 44 specifically includes a conical head 441 and a mushroom head 442. The conical head 441 is located at the bottom of the pin 44 and is conical in shape, facilitating the smooth insertion of the pin 44 into the first through hole 431 and the second through hole 421. The mushroom head 442 is fixedly connected to the top of the pin 44 and is disc-shaped or hemispherical, facilitating the removal of the pin 44.

[0050] In practice, the externally threaded tube body 2 and the externally threaded ring 4 are screwed into the internally threaded tube body 1 until the specified tightening torque is reached. Then, the outer sleeve 43 is rotated to slide along the outer wall of the second retaining ring 42 until the internal thread at the bottom of the outer sleeve 43 contacts the external thread of the first retaining ring 16. The outer sleeve 43 is then rotated to thread it into the first retaining ring 16 and tightened. Finally, the tapered head 441 of the pin 44 is aligned with the first through hole 431 of the outer sleeve 43 and the second through hole 421 of the second retaining ring 42, and the pin 44 is inserted to complete the locking. When disassembly is required, the pin 44 is first pulled out, then the outer sleeve 43 is rotated in the opposite direction to separate it from the first retaining ring 16, and then the externally threaded tube body 2 and the externally threaded ring 4 are rotated in the opposite direction to complete the disassembly.

[0051] Reference Figure 1 The inner diameter of the threads of the external threaded tube body 2 and the external threaded ring 4 at the end away from the second retaining ring 42 gradually shrinks.

[0052] In practice, due to the gradual contraction of the inner diameter of the thread on the end of the external threaded ring 4 furthest from the second retaining ring 42 (tapered thread design), the thread engagement is relatively loose and the rotational resistance is small in the initial screwing stage. As the screwing depth increases, the thread engagement gradually tightens and the rotational torque gradually increases. This progressive engagement design facilitates assembly operations and ensures a tight final connection. When the external threaded ring 4 is screwed into the internal threaded pipe body 1, the tapered thread structure generates radial interference, causing the thread teeth to fit tightly and enhancing the thread sealing effect. The reliability of the thread seal depends on the machining accuracy of the thread and the tightening torque. The thread tolerance grade is usually controlled within 6H / 6g, and the tightening torque is determined according to the pipe diameter and thread type to ensure sufficient contact pressure between the thread teeth. When the outer sleeve 43 is tightened, the threads on its inner wall generate a frictional locking force with the threads of the first retaining ring 16, restricting the rotational freedom of the outer sleeve 43 relative to the first retaining ring 16. Since the outer sleeve 43 is also fitted onto the second retaining ring 42, and the second retaining ring 42 is fixedly connected to the external threaded ring 4, the outer sleeve 43 restricts the rotational freedom of the external threaded ring 4 and the external threaded tube body 2 relative to the internal threaded tube body 1 through the second retaining ring 42, and can also protect the joint.

[0053] Reference Figure 4 The inner liner tube 3 is provided with a third inclined cone surface 31 and a fourth inclined cone surface 32 at both ends. The bottom of the first receiving groove 11 is provided with a fifth inclined cone surface 111 that cooperates with the third inclined cone surface 31. The top of the second receiving groove 21 is provided with a sixth inclined cone surface 211 that cooperates with the fourth inclined cone surface 32.

[0054] In this embodiment, the first inclined conical surface 12 is disposed at the end of the threaded region on the inner wall of the internally threaded pipe body 1, and the second inclined conical surface 41 is disposed at the bottom of the externally threaded ring 4. When the externally threaded ring 4 is screwed into the internally threaded pipe body 1, the second inclined conical surface 41 and the first inclined conical surface 12 generate radial interference, forming a metal-to-metal main sealing structure. The sealing effect of the conical surface seal depends on the cone angle, surface roughness, and interference amount of the conical surface. The cone angle is usually designed to be 10° to 20°, the surface roughness Ra is not greater than 0.8μm, and the interference amount is determined according to the pipe diameter and working pressure, typically 0.1mm to 0.3mm.

[0055] During assembly, apply thread grease to the external threads of the externally threaded tube body 2 and the externally threaded ring 4. Align the externally threaded tube body 2 with the open end of the internally threaded tube body 1, aligning the first inclined bevel 141 with the second inclined bevel 221. Rotate the externally threaded tube body 2 to screw it into the internally threaded tube body 1, referring to... Figure 7 During the screwing process, the second inclined conical surface 41 of the external threaded ring 4 gradually contacts and interferes with the first inclined conical surface 12 of the internal threaded tube body 1, forming a conical seal; the second inclined conical surface 41 passes through the sealing ring 13, expanding the sealing ring 13 to form an elastic seal; the shoulder 14 inserts into the shoulder groove 22, and the female sealing surface 15 contacts and interferes with the male sealing surface 23, forming an end face seal. Continue rotating the external threaded tube body 2 until the specified screwing torque is reached. At this time, the fourth inclined conical surface 32 of the inner liner tube 3 and the sixth inclined conical surface 211 of the external threaded tube body 2 are tightly fitted, achieving positioning and sealing of the top of the inner liner tube 3, as shown in the figure. Figure 8 Rotate the outer sleeve 43, allowing it to slide along the outer wall of the second retaining ring 42 until the internal thread at the bottom of the outer sleeve 43 contacts the external thread of the first retaining ring 16. Continue rotating the outer sleeve 43 until it is threadedly connected to and tightened with the first retaining ring 16. Align the tapered head 441 of the pin 44 with the first through hole 431 of the outer sleeve 43 and the second through hole 421 of the second retaining ring 42, insert the pin 44, and complete the locking. In practice, the tightening torque is determined based on the pipe diameter, thread type, and working pressure, and is typically within ±10% of the recommended tightening torque. After inserting the pin 44, check whether the pin 44 is fully inserted and whether the mushroom head 442 is tightly against the outer wall of the outer sleeve 43.

[0056] The combined structure of the internally threaded tube body 1, the externally threaded tube body 2, the inner liner tube 3, and the externally threaded ring 4, along with the double-threaded connection design, enhances the torsional strength of the joint. A multi-stage sealing structure (threaded seal, conical seal, elastic seal, and end face seal) works synergistically to ensure the airtightness of the joint under high temperature and high pressure conditions. Inserting the pin 44 into the aligned first and second through holes, with the pin 44 interfering with the inner walls of the first and second through holes, creates mechanical positioning. The presence of the pin 44 completely eliminates the rotational freedom of the outer tube 43 relative to the second retaining ring 42. Even under external vibration, the outer tube 43 cannot rotate out, thus ensuring the reliability of the locking mechanism. This effectively prevents thread loosening and improves the long-term stability of the connection.

[0057] Multi-stage sealing specifically includes: First-level sealing: The threaded seal is the first sealing barrier formed. When the externally threaded pipe body 2 and the externally threaded ring 4 are screwed into the internally threaded pipe body 1, the threads begin to contact. Due to the contraction design of the thread inner diameter, radial interference occurs between the threads. Thread grease fills the gaps between the threads, forming the first line of defense with the metal contact surface, preventing the intrusion of external media.

[0058] The second-stage seal is a conical seal. As the screw-in depth increases, the second inclined conical surface 41 at the bottom of the external threaded ring 4 gradually approaches the first inclined conical surface 12 on the inner wall of the internal threaded pipe body 1. When they come into contact, due to the geometric characteristics of the conical surfaces, the axial screw-in force is converted into a huge radial interference force. The second inclined conical surface 41 and the first inclined conical surface 12 form an interference fit, and the metal surfaces undergo slight elastic deformation, forming a high-strength metal-to-metal seal. The metal interference fit greatly enhances the gas tightness of the entire joint, enabling the sealing structure to withstand extremely high internal pressure, making it the core main seal.

[0059] The third-stage seal: Simultaneously or slightly after the formation of the elastic seal and the conical seal, the second inclined conical surface 41 at the bottom of the external threaded ring 4 begins to insert into the inner side of the sealing ring 13 on the inner wall of the internally threaded pipe body 1. The outer diameter of the second inclined conical surface 41 gradually increases from the bottom to the top. When it passes through the inner side of the sealing ring 13, it generates a radial spreading force on the sealing ring 13. After the sealing ring 13 is spread open, its outer surface is in close contact with the inner wall of the internally threaded pipe body 1, and its inner surface is in close contact with the outer wall of the second inclined conical surface 41. This elastic sealing structure has excellent compensation capabilities, can adapt to manufacturing tolerances, temperature changes, and pressure fluctuations, and ensures long-term reliability of the seal.

[0060] The fourth level of sealing: The end face seal is the final sealing barrier and a sign that the assembly is complete. When the externally threaded tube 2 is screwed into its final position, the shoulder 14 at the top of the internally threaded tube 1 inserts into the inner wall of the shoulder groove 22 at the bottom of the externally threaded tube 2. At this point, the female sealing surface 15 contacts the male sealing surface 23. Due to the axial limiting effect of the shoulder 14 and the shoulder groove 22, further screwing will generate a huge axial compressive force, causing the female sealing surface 15 and the male sealing surface 23 to form an interference fit. This end face sealing structure not only provides a sealing function but also plays a role in precisely controlling the tightening position and preventing structural damage caused by over-tightening.

Claims

1. A high-torsion-resistance gas-tight oil sleeve threaded joint, characterized in that, The device includes an internally threaded tube body (1), an externally threaded tube body (2), an inner liner tube (3), and an externally threaded ring (4). The inner wall of the internally threaded tube body (1) is provided with a first receiving groove (11), and the inner wall of the externally threaded tube body (2) is provided with a second receiving groove (21). The bottom outer wall of the inner liner tube (3) is attached to the inner wall of the first receiving groove (11), and the top outer wall of the inner liner tube (3) is attached to the inner wall of the second receiving groove (21). The outer wall of the inner liner tube (3) is fixedly connected to the externally threaded ring (4). The outer wall of the external threaded tube body (2) and the external threaded ring (4) are threaded to the inner wall of the internal threaded tube body (1).

2. The high torsion resistance gas-tight oil sleeve threaded joint as described in claim 1, characterized in that: The inner wall of the internally threaded tube (1) is provided with a first inclined cone surface (12), and the bottom of the externally threaded ring (4) is provided with a second inclined cone surface (41) corresponding to the first inclined cone surface (12). The first inclined cone surface (12) and the second inclined cone surface (41) are interference fit.

3. The high torsion resistance gas-tight oil sleeve threaded joint as described in claim 1, characterized in that: The inner wall of the internally threaded tube (1) is also provided with a sealing ring (13), and the bottom of the externally threaded ring (4) has a second inclined cone surface (41) that passes through the inner side of the sealing ring (13).

4. The high torsion resistance gas-tight oil sleeve threaded joint as described in claim 1, characterized in that: The top of the internally threaded pipe body (1) is provided with a shoulder (14) and a female sealing surface (15). The externally threaded pipe body (2) is provided with a shoulder groove (22) and a male sealing surface (23) corresponding to the shoulder (14). The shoulder (14) is inserted into the inner wall of the shoulder groove (22), and the female sealing surface (15) and the male sealing surface (23) are press-fitted.

5. The high torsion-resistant gas-tight oil sleeve threaded joint as described in claim 4, characterized in that: The shoulder (14) at the top of the internally threaded tube (1) is provided with a first inclined bevel (141) on the outside, and the shoulder groove (22) at the bottom of the externally threaded tube (2) is provided with a second inclined bevel (221) on the outside, and the first inclined bevel (141) and the second inclined bevel (221) are adapted to each other.

6. The high torsion-resistant gas-tight oil sleeve threaded joint as described in claim 1, characterized in that: The outer wall of the internally threaded tube body (1) is fixedly connected to the first retaining ring (16), the outer wall of the first retaining ring (16) is provided with external threads, the outer wall of the externally threaded ring (4) is fixedly connected to the second retaining ring (42), and the outer wall of the second retaining ring (42) is slidably connected to the outer sleeve (43). The top of the outer sleeve (43) is slidably connected to the outer wall of the internally threaded tube body (1), the bottom inner wall of the outer sleeve (43) is provided with internal threads, and the outer wall of the first retaining ring (16) is threadedly connected to the bottom inner wall of the outer sleeve (43). The bottom of the first retaining ring (16) is provided with a second tapered section (161).

7. The high torsion-resistant gas-tight oil sleeve threaded joint as described in claim 6, characterized in that: The outer sleeve (43) has a first through hole (431), and the second retaining ring (42) has multiple second through holes (421). The second through holes (421) are evenly distributed in a ring on the second retaining ring (42). The inner walls of the first through hole (431) and the second through hole (421) have pins (44) inserted into them, and the inner walls of the first through hole (431) and the second through hole (421) are interference-fitted with the pins (44).

8. The high torsion-resistant gas-tight oil sleeve threaded joint as described in claim 7, characterized in that: The bottom of the pin (44) is provided with a tapered head (441), and the top of the pin (44) is fixedly connected to a mushroom head (442).

9. The high torsion-resistant gas-tight oil sleeve threaded joint as described in claim 1, characterized in that: The inner diameter of the threaded tube body (2) and the external threaded ring (4) gradually shrinks at the end away from the second retaining ring (42).

10. The high torsion resistance gas-tight oil sleeve threaded joint as described in claim 1, characterized in that: The inner liner tube (3) is provided with a third inclined cone surface (31) and a fourth inclined cone surface (32) at both ends. The bottom of the first receiving groove (11) is provided with a fifth inclined cone surface (111) that cooperates with the third inclined cone surface (31). The top of the second receiving groove (21) is provided with a sixth inclined cone surface (211) that cooperates with the fourth inclined cone surface (32).

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