Self-locking mechanism and casing head for petroleum wellhead

Abstract

The invention relates to the technical field of casing heads, and discloses a self-locking mechanism and a casing head for a petroleum wellhead, the self-locking mechanism comprises a primary casing head body, a secondary casing head body and a self-locking unit, the secondary casing head body is arranged at the upper part of the primary casing head body, and the self-locking unit is arranged at the upper end of the primary casing head body; the self-locking unit is triggered when the second-stage casing head body is installed on the first-stage casing head body, and the second-stage casing head body is locked. According to the self-locking mechanism and the casing head for the petroleum wellhead, the self-locking unit is arranged between the first-stage casing head body and the second-stage casing head body, when the second-stage casing head body is installed on the first-stage casing head body, the rack is extruded to move downwards, the rack pushes the sleeve to rotate, and therefore the lock pin is pushed to move and be locked; the lock pin is inserted into the clamping groove of the second-stage casing head body, so that the second-stage casing head body and the first-stage casing head body are fixed.

Description

Technical Field

[0001] This invention relates to the field of casing head technology, and more specifically, to a self-locking mechanism and a casing head for oil wellheads. Background Technology

[0002] The wellhead is the surface part of an oil well where the equipment used to control and guide the extraction of oil, gas, and water fluids is installed. It is a key node connecting the oil well to surface facilities. The casing head is the lowest part of the wellhead, used to suspend the casing and seal the wellhead to prevent formation fluid leakage. The casing head connects different sections of the casing.

[0003] The casing head is one of the core components of the drilling wellhead assembly, primarily used to fix the wellhead structure and perform multiple functions. As a key hub connecting the downhole casing string to surface equipment, it not only suspends the weight of all casing layers except the surface casing, but also prevents pressure cross-contamination by sealing the casing annular space, ensuring well control safety. During the drilling phase, the casing head provides the installation foundation for the blowout preventer (BOP), while during the oil production phase, it transitions to connecting the tubing head and the Christmasleigh (or Christmas tree).

[0004] Patent document CN113107412B discloses a pressure-resistant and corrosion-resistant multi-stage bushing head with interchangeable hangers of different styles. It comprises a base, a multi-stage bushing head tee, mandrel-type bushing hangers of different specifications, slip-type bushing hangers, and matching sealing collars, wing valves, threaded flanges, pressure gauge assemblies, threaded connections, and seals. A mandrel-type bushing hanger with an extended neck can be installed in the central hole above the multi-stage bushing head tee, and a slip-type bushing hanger can also be installed in each. The central hole, BT sealing ring, and grease injection valve of each bushing head tee above the next stage can seal the extended neck above the mandrel-type bushing hanger of the next stage, and can also seal the upper end of the bushing held by the slip-type bushing hanger through the matching sealing collar. Furthermore, the non-metallic materials in the seals are all fluororubber or highly saturated hydrogenated nitrile rubber. This makes it more suitable for use in complex well conditions and wells with high pressure, high corrosion, and high temperature differences.

[0005] In existing multi-stage bushing heads, adjacent bushing heads are connected by bolts, which is inconvenient to install and disassemble, time-consuming and labor-intensive, increasing the time required for installing and disassembling bushing heads and affecting work efficiency.

[0006] Therefore, it is necessary to propose a self-locking mechanism and a casing head for oil wellheads to solve the problems existing in the prior art. Summary of the Invention

[0007] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. The summary section of this invention is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0008] To address the aforementioned problems, the present invention provides a self-locking mechanism, comprising a primary sleeve head body, a secondary sleeve head body, and a self-locking unit. The secondary sleeve head body is disposed on the upper part of the primary sleeve head body, and the self-locking unit is disposed on the upper end of the primary sleeve head body. The self-locking unit is triggered when the secondary sleeve head body is installed onto the primary sleeve head body, thereby locking the secondary sleeve head body.

[0009] Preferably, the self-locking unit includes a sleeve rotatably disposed on the side wall of the primary bushing head body, a locking pin disposed inside the sleeve, and the locking pin moving radially along the primary bushing head body. An annular snap-fit ​​groove is opened on the outer circumference of the lower end of the secondary sleeve head body, and one end of the locking pin snaps into the snap-fit ​​groove.

[0010] Preferably, multiple self-locking units are arranged along the circumferential direction of the primary sleeve head body.

[0011] Preferably, a through groove is formed on the side wall of the sleeve, the side wall of the through groove is a spiral surface, and a limiting groove is formed at one end of the through groove near the center of the first-stage sleeve head body, the side wall of the limiting groove is perpendicular to the axis of the sleeve. A pin is provided on the outer circumference of the locking pin, and the pin is slidably disposed in the through groove and the limiting groove.

[0012] Preferably, a gear is provided on the circumferential surface of the sleeve at the end away from the center of the first-stage sleeve head body; An annular groove is formed on the upper end face of the primary sleeve head body, and a groove is formed at the bottom of the annular groove. A rack is slidably arranged in the groove, and the rack is meshed with a gear.

[0013] Preferably, a first spring is provided in the groove, with the upper end of the first spring connected to the lower end of the rack and the lower end of the first spring connected to the bottom surface of the groove.

[0014] Preferably, a toothed ring is provided at a distance from the groove within the annular groove, and the toothed ring meshes with the gear.

[0015] Preferably, an axial groove is formed on the outer circumference of the locking pin along the axial direction, a limiting hole is formed on the side wall of the first-stage sleeve head body, a limiting block is set in the limiting hole, and the axial groove and the limiting block are connected in cooperation.

[0016] Preferably, a clearance groove is formed on the lower end face of the secondary sleeve head body at a position corresponding to the rack, and multiple second springs are arranged in an array on the bottom surface of the clearance groove. An annular pressure plate is slidably arranged in the clearance groove, and one end of the second spring away from the bottom surface of the clearance groove is connected to the annular pressure plate.

[0017] The present invention also provides a casing head for oil wellheads, including the self-locking mechanism described above.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: The self-locking mechanism and casing head for oil wellheads described in this invention have a self-locking unit between the primary casing head body and the secondary casing head body. When the secondary casing head body is installed on the primary casing head body, the rack is squeezed downwards, the rack pushes the sleeve to rotate, thereby pushing the locking pin to move and lock. The locking pin is inserted into the snap-fit ​​groove of the secondary casing head body, thus fixing the secondary casing head body to the primary casing head body.

[0019] The self-locking mechanism and casing head for oil wellheads described in this invention, along with other advantages, objectives, and features of this invention, will be partly apparent from the following description and partly understood by those skilled in the art through study and practice of the invention. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the self-locking mechanism disclosed in this invention; Figure 2 This is a cross-sectional structural schematic diagram of the self-locking mechanism disclosed in this invention; Figure 3 This is a schematic diagram of the structure of the self-locking unit disclosed in this invention; Figure 4 This is a schematic diagram of the sleeve and locking pin disclosed in this invention; Figure 5 This is a schematic diagram of the locking pin structure disclosed in this invention; Figure 6 This is a schematic diagram of the gear ring disclosed in this invention; Figure 7 This is a schematic diagram of the structure of the primary sleeve head body disclosed in this invention; Figure 8 This is a cross-sectional structural schematic diagram of the self-locking unit disclosed in this invention; Figure 9 This is a schematic diagram of the structure of the secondary bushing head body, the second spring, and the pressure plate disclosed in this invention. Figure 10This is an exploded structural diagram of the primary bushing head body and self-locking unit disclosed in this invention. Figure 11 This is a cross-sectional structural schematic diagram of the secondary sleeve head body disclosed in this invention.

[0021] The components are as follows: 1. Primary sleeve head body; 2. Secondary sleeve head body; 3. Self-locking unit; 4. Sleeve; 5. Locking pin; 6. Snap-fit ​​groove; 7. Through groove; 8. Helical surface; 9. Limiting groove; 10. Pin; 11. Gear; 12. Annular groove; 13. Groove; 14. Rack; 15. First spring; 16. Gear ring; 17. Axial groove; 18. Limiting hole; 19. Limiting block; 20. Clearance groove; 21. Second spring; 22. Annular pressure plate; 23. Drive plate; 24. Drive plate groove; 25. Cone; 26. Cover plate; 27. Square hole. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, so that those skilled in the art can implement it based on the description.

[0023] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0024] like Figures 1-11 As shown, the present invention provides a self-locking mechanism, including a primary sleeve head body 1, a secondary sleeve head body 2, and a self-locking unit 3. The secondary sleeve head body 2 is disposed on the upper part of the primary sleeve head body 1, and the self-locking unit 3 is disposed on the upper end of the primary sleeve head body 1. The self-locking unit 3 is triggered when the secondary sleeve head body 2 is installed on the primary sleeve head body 1, and locks the secondary sleeve head body 2.

[0025] Furthermore, the self-locking unit 3 includes a sleeve 4 rotatably disposed on the side wall of the first-stage sleeve head body 1, a locking pin 5 disposed inside the sleeve 4, and the locking pin 5 moving radially along the first-stage sleeve head body 1. An annular snap-fit ​​groove 6 is opened on the outer circumferential surface of the lower end of the secondary sleeve head body 2, and one end of the locking pin 5 is snapped into the snap-fit ​​groove 6.

[0026] Furthermore, multiple self-locking units 3 are arranged along the circumferential direction of the primary sleeve head body 1.

[0027] Furthermore, a through groove 7 is opened on the side wall of the sleeve 4. The side wall of the through groove 7 is a spiral surface 8. A limiting groove 9 is opened at one end of the through groove 7 near the center of the first-stage sleeve head body 1. The side wall of the limiting groove 9 is perpendicular to the axis of the sleeve 4. A pin 10 is provided on the outer circumference of the locking pin 5, and the pin 10 is slidably disposed in the through groove 7 and the limiting groove 9.

[0028] Furthermore, a gear 11 is provided at one end of the circumferential surface of the sleeve 4 that is away from the center of the first-stage sleeve head body 1; An annular groove 12 is formed on the upper end face of the primary sleeve head body 1, and a groove 13 is formed at the bottom of the annular groove 12. A rack 14 is slidably arranged in the groove 13, and the rack 14 is meshed with a gear 11.

[0029] Furthermore, a first spring 15 is provided in the groove 13, with the upper end of the first spring 15 connected to the lower end of the rack 14 and the lower end of the first spring 15 connected to the bottom surface of the groove 13.

[0030] Furthermore, a gear ring 16 is provided at a distance from the groove 13 within the annular groove 12, and the gear ring 16 is meshed with the gear 11.

[0031] Furthermore, an axial groove 17 is formed on the outer circumference of the locking pin 5 along the axial direction, and a limiting hole 18 is formed on the side wall of the first-stage sleeve head body 1. A limiting block 19 is provided in the limiting hole 18, and the axial groove 17 and the limiting block 19 are connected in cooperation.

[0032] Furthermore, a clearance groove 20 is formed on the lower end face of the secondary sleeve head body 2 at a position corresponding to the rack 14. Multiple second springs 21 are arranged in an array on the bottom surface of the clearance groove 20. An annular pressure plate 22 is slidably arranged inside the clearance groove 20. One end of the second spring 21 away from the bottom surface of the clearance groove 20 is connected to the annular pressure plate 22.

[0033] The present invention also discloses a casing head for oil wellheads, including the self-locking mechanism described in the above technical solutions.

[0034] The working principle of the above technical solution: It includes a primary bushing head body 1, a secondary bushing head body 2, and a self-locking unit 3. The secondary bushing head body 2 is located on the upper part of the primary bushing head body 1, and the self-locking unit 3 is located on the upper end of the primary bushing head body 1. The self-locking unit 3 is triggered when the secondary bushing head body 2 is installed on the primary bushing head body 1, and locks the secondary bushing head body 2. The self-locking unit 3 is located on the upper part of the primary bushing head body 1. When the secondary bushing head body 2 is connected to the primary bushing head body 1, the secondary bushing head body 2 presses down on the self-locking unit 3, and the self-locking unit 3 locks the secondary bushing head body 2 onto the primary bushing head body 1.

[0035] The self-locking unit 3 includes a sleeve 4 rotatably disposed on the side wall of the first-stage sleeve head body 1, a locking pin 5 disposed inside the sleeve 4, and the locking pin 5 moving radially along the first-stage sleeve head body 1. An annular snap-fit ​​groove 6 is opened on the outer circumferential surface of the lower end of the secondary sleeve head body 2, and one end of the locking pin 5 is snapped into the snap-fit ​​groove 6.

[0036] A through groove 7 is opened on the side wall of the sleeve 4. The side wall of the through groove 7 is a spiral surface 8. A limiting groove 9 is opened at one end of the through groove 7 near the center of the first-stage sleeve head body 1. The side wall of the limiting groove 9 is perpendicular to the axis of the sleeve 4. A pin 10 is provided on the outer circumference of the locking pin 5, and the pin 10 is slidably disposed in the through groove 7 and the limiting groove 9.

[0037] An axial groove 17 is formed on the outer circumference of the locking pin 5 along the axial direction. A limiting hole 18 is formed on the side wall of the first-stage sleeve head body 1. A limiting block 19 is set in the limiting hole 18. The axial groove 17 and the limiting block 19 are connected in a mating manner. The sleeve 4 is rotatably disposed in the limiting hole 18. The limiting hole 18 is a stepped hole. The diameter of the hole at the end near the outer wall of the first-stage sleeve head body 1 is smaller than the diameter at the end away from the outer wall of the first-stage sleeve head body 1. The sleeve 4 is rotatably disposed in the stepped hole with a larger diameter in the limiting hole 18. One end of the sleeve 4 with the gear 11 contacts the shoulder of the limiting hole 18. The shoulder provides axial support force for the sleeve 4.

[0038] A locking pin 5 is provided inside the sleeve 4. The diameter of the locking pin 5 is adapted to the smaller diameter of the stepped hole of the limiting hole 18. It is slidably set inside the smaller diameter of the stepped hole. The limiting block 19 is set on the side wall of the smaller diameter of the stepped hole. The limiting block 19 is connected to the axial groove 17, so that the locking pin 5 moves radially along the first-stage sleeve head body 1.

[0039] A through groove 7 is opened on the side wall of the sleeve 4. The through groove 7 is spiral and the side wall of the through groove 7 is a spiral surface 8. When the sleeve 4 rotates, the spiral surface 8 can push the pin 10. Since the locking pin 5 cannot rotate due to the restriction of the limiting block 19, it can only move along the axial direction. Therefore, the spiral surface 8 of the through groove 7 can push the locking pin 5 to move towards the center of the first-stage sleeve head body 1. The locking pin 5 extends out of the side wall of the first-stage sleeve head body 1 and enters the snap-fit ​​groove 6, thereby locking the second-stage sleeve head body 2 and connecting the second-stage sleeve head body 2 with the first-stage sleeve head body 1.

[0040] Multiple self-locking units 3 are arranged along the circumference of the primary sleeve head body 1. When the locking pin 5 locks the secondary sleeve head body 2, the self-locking units 3 arranged in the circumferential array will push out the locking pin and get stuck in the locking groove 6 in each direction of the circumference, so that the connection between the secondary sleeve head body 2 and the primary sleeve head body 1 is more stable.

[0041] One end of the locking pin 5 inserted into the snap-fit ​​groove 6 is set as a cone. The lower side wall of the snap-fit ​​groove 6 is provided with an inclined surface with the same inclination angle as the cone of the locking pin. When the locking pin 5 is inserted into the snap-fit ​​groove 6, the cone end of the locking pin 5 cooperates with the inclined surface of the snap-fit ​​groove 6, so that the locking pin 5 exerts downward pressure on the lower side wall of the snap-fit ​​groove 6, thereby improving the connection stability of the secondary sleeve head body 2.

[0042] A limiting groove 9 is opened at one end of the through groove 7 near the center of the primary sleeve head body 1. The side wall of the limiting groove 9 is perpendicular to the axis of the sleeve 4. After the sleeve 4 rotates by a corresponding angle, when the locking pin 5 locks the secondary sleeve head body 2 from all directions of the circumference through the snap-fit ​​groove 6, the position of the rotation of the sleeve 4 causes the pin 10 to enter the limiting groove 9. The side wall of the limiting groove 9 is perpendicular to the axis of the sleeve 4. At this time, the limiting groove 9 presses against the pin 10, preventing the pin 10 from retracting, thereby tightly locking the secondary sleeve head body 2.

[0043] To improve the stability of the position of the pin 10 limited by the limiting groove 9, a micro groove can be provided on the side wall of the limiting groove 9 away from the center of the primary sleeve head body 1, so that the pin 10 enters into the micro groove and prevents the pin 10 from sliding out of the limiting groove 9. The depth of the micro groove is very small, which can prevent the pin 10 from sliding out. When performing reverse operation and disassembling the secondary sleeve head body 2, it will not generate a large resistance to the reversal of the sleeve 4.

[0044] A gear 11 is provided on the circumferential surface of the sleeve 4 at one end away from the center of the first-stage sleeve head body 1; An annular groove 12 is formed on the upper end face of the primary sleeve head body 1, and a groove 13 is formed at the bottom of the annular groove 12. A rack 14 is slidably arranged in the groove 13 and meshes with a gear 11. The upper end of the rack 14 extends to the outside of the annular groove 12. When the secondary sleeve head body 2 is installed on the primary sleeve head body 1 from the top, the lower end face of the secondary sleeve head body 2 contacts the upper end of the rack 14. The secondary sleeve head body 2 moves downward, and the rack 14 moves downward. The movement of the rack 14 drives the gear 11. The rotation of the gear 11 drives the sleeve 4 to rotate. The sleeve 4 pushes the pin 10 to move through the spiral surface 8 of the through groove 7 until the limiting groove 9 rotates to the position where the pin 10 enters the limiting groove 9, thus completing the locking.

[0045] A first spring 15 is installed in the groove 13. The upper end of the first spring 15 is connected to the lower end of the rack 14, and the lower end of the first spring 15 is connected to the bottom surface of the groove 13. When locking the secondary sleeve head body 2, the rack 14 moves downward and compresses the first spring 15, causing the first spring 15 to shorten and store energy. When disassembling the secondary sleeve head body 2, the secondary sleeve head body 2 no longer squeezes the rack 14, and the rack 14 returns to its original position under the elastic force of the first spring 15. The self-locking unit 3 can be used in the next installation.

[0046] A gear ring 16 is provided at intervals between the annular groove 12 and the groove 13. The gear ring 16 meshes with the gear 11. After the sleeve head is used, the secondary sleeve head body 2 and the primary sleeve head body 1 are disassembled. At this time, the gear ring 16 is rotated, causing the gear 11 to rotate in the opposite direction. The gear 11 drives the sleeve 4 to rotate in the opposite direction, causing the pin 10 to enter the through groove 7 from the limiting groove 9. The sleeve 4 continues to rotate, and the inner wall of the through groove 7 and the side wall opposite to the spiral surface 8 push the locking pin 5 to move away from the center end of the primary sleeve head body 1. The end of the locking pin 5 is withdrawn from the snap-fit ​​groove 6, and the secondary sleeve head body 2 can be directly removed. This saves the work of tightening and loosening multiple bolts during installation and disassembly, and improves the work efficiency during installation and disassembly.

[0047] A drive plate 23 is fixedly installed on the outer circumferential wall of the gear ring 16. When disassembling the secondary bushing head body 2, the drive plate 23 can be pushed manually. For large bushing heads, a drive unit can be installed on the outer wall of the primary bushing head body 1 to push the drive plate.

[0048] A drive plate groove 24 is formed on the side wall of the primary bushing head body 1 at a position corresponding to the drive plate 23. When the gear ring 16 rotates, the drive plate 23 moves in the drive plate groove 24. The drive plate groove 24 is connected to the annular groove 12. The drive plate 23 and the gear ring 16 can be connected by threads. After the gear ring 16 is placed into the annular groove 12, the drive plate 23 is then inserted into the drive plate groove 24 and connected to the gear ring 16.

[0049] A cover plate 26 is detachably installed on the end face of the primary bushing head body 1. A square hole 27 is provided on the cover plate 26 opposite to the rack 14. The rack 14 extends from the square hole 27 to the upper part of the primary bushing head body 1. The cover plate 26 can seal the annular groove 12 to prevent debris and dust from entering the annular groove and ensure that the components in the annular groove 12 work normally.

[0050] During disassembly, the reverse rotation of gear 11 causes rack 14 to move upward. To prevent the movement of rack 14 from interfering with the disassembly of the secondary sleeve head body 2, a clearance groove 20 is provided on the lower end face of the secondary sleeve head body 2 at a position corresponding to rack 14. Multiple second springs 21 are arranged in an array on the bottom surface of clearance groove 20. An annular pressure plate 22 is slidably arranged in clearance groove 20. One end of the second spring 21 away from the bottom surface of clearance groove 20 is connected to the annular pressure plate 22. When gear 11 reverses, rack 14 moves upward and pushes the annular pressure plate 22 upward. The annular pressure plate 22 squeezes the second spring 21, causing the annular pressure plate 22 to enter the clearance groove 20, giving rack 14 space to move upward.

[0051] When the secondary bushing head body 2 is installed, the annular pressure plate 22 also contacts the top of the rack 14. In order for the annular pressure plate 22 to squeeze the rack 14 and make the rack 14 move downward, the elastic force of the second spring 21 is greater than the elastic force of the first spring 15. When the secondary bushing head body 2 is installed, the annular pressure plate 22 can overcome the elastic force of the first spring 15 under the action of the elastic force of the second spring 21 and push the rack 14 to move downward.

[0052] The elastic force of the second spring 21 needs to compress the first spring 15 and overcome the resistance of the rack 14. Without contraction, it pushes the rack 14 to move and drives the gear 11 to rotate, thereby driving the sleeve 4 to rotate and push the locking pin 5 to move axially through the helical surface 8, so that the locking pin 5 is inserted into the snap-fit ​​groove 6, thereby locking the secondary sleeve head body 2. The elastic force of the second spring 21 should be greater than the elastic force of the first spring and the resistance of the rack 14 moving downward.

[0053] During disassembly, the torque applied to the drive plate 23 by the drive unit can push the gear 11 through the gear ring 16, causing the gear 11 to drive the sleeve 4 to reverse, pulling the locking pin 5 out of the snap-fit ​​groove 6. At the same time, the torque applied to the drive plate 23 must also overcome the elastic force generated by the second spring 21 on the rack 14 to push the annular pressure plate 22 upward. During this process, the first spring 15 provides auxiliary elastic force, using the rack 14 to move upward to press the annular pressure plate 22 into the clearance groove 20. The clearance groove 20 provides clearance space for the rack 14 to move upward, preventing the rack 14 from not moving, which would cause the secondary sleeve head body 2 and the primary sleeve head body 1 to be locked and unable to be disassembled.

[0054] The drive unit can be selected based on the springs of the second spring 21 and the first spring 15.

[0055] Both the primary casing head body 1 and the secondary casing head body 2 have an inner cavity for installing a hanger. The hanger can be a spindle-type casing hanger or a slip-type casing hanger.

[0056] The types and installation methods of the suspension devices are existing technologies and will not be elaborated here.

[0057] The lower part of the secondary sleeve head body 2 is a cone 25. The cone 25, like the secondary sleeve head body, has a hollow cavity inside. The upper part of the primary sleeve head body 1, corresponding to the cone 25, has a tapered hole. The shape of the tapered hole is adapted to the shape of the cone 25. The tapered hole and the cone 25 can make the secondary sleeve head body 2 and the primary sleeve head body 1 automatically center, improving the stability of the installation.

[0058] A sealing groove is formed along the circumferential direction on the cone 25, and a sealing ring is set in the sealing groove to seal the connection between the secondary casing head body and the primary casing head body. The sealing ring can be a circular sealing ring, a rectangular sealing ring, or an X-type metal sealing ring. The sealing ring is existing technology, and different types of sealing rings suitable for downhole pressure can be selected.

[0059] The beneficial effects of the above technical solution are as follows: The self-locking mechanism and casing head for oil wellheads of the present invention include a self-locking unit between the primary casing head body and the secondary casing head body. When the secondary casing head body is installed on the primary casing head body, the rack is squeezed downwards, and the rack pushes the sleeve to rotate, thereby pushing the locking pin to move and lock. The locking pin is inserted into the snap-fit ​​groove of the secondary casing head body, thus fixing the secondary casing head body to the primary casing head body.

[0060] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, 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. Therefore, they should not be construed as limitations on this invention.

[0061] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0062] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. Other modifications can be easily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A self-locking mechanism, characterized in that, It includes a primary bushing head body (1), a secondary bushing head body (2), and a self-locking unit (3). The secondary bushing head body (2) is located on the upper part of the primary bushing head body (1), and the self-locking unit (3) is located on the upper end of the primary bushing head body (1). The self-locking unit (3) is triggered when the secondary bushing head body (2) is installed on the primary bushing head body (1) and locks the secondary bushing head body (2).

2. The self-locking mechanism according to claim 1, characterized in that, The self-locking unit (3) includes a sleeve (4) rotatably disposed on the side wall of the first-stage sleeve head body (1), and a locking pin (5) is disposed inside the sleeve (4). The locking pin (5) moves radially along the first-stage sleeve head body (1). An annular snap-fit ​​groove (6) is opened on the outer circumference of the lower end of the secondary sleeve head body (2), and one end of the locking pin (5) is snapped into the snap-fit ​​groove (6).

3. The self-locking mechanism according to claim 2, characterized in that, Multiple self-locking units (3) are arranged along the circumference of the primary sleeve head body (1).

4. The self-locking mechanism according to claim 2, characterized in that, A through groove (7) is opened on the side wall of the sleeve (4). The side wall of the through groove (7) is a spiral surface (8). A limiting groove (9) is opened at one end of the through groove (7) near the center of the first-stage sleeve head body (1). The side wall of the limiting groove (9) is perpendicular to the axis of the sleeve (4). A pin (10) is provided on the outer circumference of the locking pin (5), and the pin (10) is slidably disposed in the through groove (7) and the limiting groove (9).

5. The self-locking mechanism according to claim 4, characterized in that, A gear (11) is provided on the circumferential surface of the sleeve (4) at one end away from the center of the first-stage sleeve head body (1). An annular groove (12) is provided on the upper end face of the primary sleeve head body (1), and a groove (13) is provided at the bottom of the annular groove (12). A rack (14) is slidably arranged in the groove (13), and the rack (14) is meshed with a gear (11).

6. The self-locking mechanism according to claim 5, characterized in that, A first spring (15) is provided in the groove (13). The upper end of the first spring (15) is connected to the lower end of the rack (14), and the lower end of the first spring (15) is connected to the bottom surface of the groove (13).

7. The self-locking mechanism according to claim 5, characterized in that, A toothed ring (16) is provided in the annular groove (12) at intervals from the groove (13), and the toothed ring (16) meshes with the gear (11).

8. The self-locking mechanism according to claim 7, characterized in that, An axial groove (17) is provided on the outer circumference of the locking pin (5) along the axial direction. A limiting hole (18) is provided on the side wall of the first-stage sleeve head body (1). A limiting block (19) is provided in the limiting hole (18). The axial groove (17) and the limiting block (19) are connected in cooperation.

9. The self-locking mechanism according to claim 8, characterized in that, A clearance groove (20) is opened on the lower end face of the secondary sleeve head body (2) at a position corresponding to the rack (14). Multiple second springs (21) are arranged in an array on the bottom surface of the clearance groove (20). An annular pressure plate (22) is slidably arranged in the clearance groove (20). One end of the second spring (21) away from the bottom surface of the clearance groove (20) is connected to the annular pressure plate (22).

10. A casing head for oil wellheads, characterized in that, Includes the self-locking mechanism according to any one of claims 1-9.

Images