A centralizer for a screw pump sucker rod

Abstract

This invention provides a straightening guide for a screw pump sucker rod, comprising: a housing; a plurality of straightening blocks evenly arranged on the outer surface of the housing; a top rod concentrically arranged inside the housing, with ball heads at both ends of the top rod; and connector assemblies disposed at both ends of the housing for connecting an upper sucker rod and a lower sucker rod, respectively. The connector assemblies include a ball-and-socket type connecting seat fixedly connected to the end of the housing and a ball-and-cap connector adapted to the ball-and-socket type connecting seat. The inner wall surface of the ball-and-socket type connecting seat is constructed as a first inner spherical surface, and an inner drive tooth is provided on the first inner spherical surface. The ball-and-cap connector includes a ball-and-cap body, the outer surface of which is provided with radially extending outer drive teeth, and the interior of the ball-and-cap body forms a second inner spherical surface adapted to the ball head. The outer drive teeth and the inner drive teeth mesh to form a meshing pair, allowing the ball-and-cap connector to bend relative to the housing and to straighten the sucker rod via the straightening blocks.

Description

Technical Field

[0001] This invention belongs to the field of oil production engineering in petroleum engineering, and specifically relates to a centralizing guide for the sucker rod of a screw pump. Background Technology

[0002] The surface-driven screw pump oil production system consists of four main parts: a surface drive unit, tubing, sucker rod, and screw pump. The surface drive unit drives the sucker rod to rotate within the tubing. The sucker rod then transmits this rotational motion to the rotor of the screw pump. During the rotation of the screw pump rotor, a series of closed chambers are formed between the rotor and stator. These closed chambers draw in, seal, and pressurize the downhole fluid before discharging it into the tubing and finally to the surface. When the sucker rod rotates within the tubing, it is subjected to centrifugal force, causing it to come into contact with the tubing wall at certain points, resulting in tubing and rod wear. This phenomenon is particularly pronounced in the build-up and stabilization sections of the well, especially in the build-up section where the radius of curvature is small and both the tubing and sucker rod are bent. The bent sucker rod's axes do not coincide during rotation, causing a buckling phenomenon when transmitting torque, which exacerbates tubing and rod wear, leading to tubing perforation and sucker rod breakage. This results in well production losses and hinders the rapid and efficient development of the oilfield.

[0003] Chinese patent document CN113123734A discloses a sucker rod guide, comprising: a centralizing shaft, a centralizing sleeve fitted on the centralizing shaft with both ends of the centralizing shaft extending beyond the centralizing sleeve by a predetermined length. Torque transmission connecting sleeves are fitted at both ends of the centralizing shaft, and a locking connecting sleeve is fitted at the end of the torque transmission connecting sleeve furthest from the centralizing sleeve. A shaft hole is provided inside the sleeve of the torque transmission connecting sleeve near the locking connecting sleeve, and a universal joint recess is provided inside the sleeve of the locking connecting sleeve. A ball joint torque universal joint comprises: a ball head, a torque shaft located on both sides of the ball head and fixedly connected to the ball head, and a shaft. The ball head of the ball joint torque universal joint is installed in the universal joint recess of the locking connecting sleeve, and the torque shaft is inserted into the shaft hole of the torque transmission connecting sleeve. A reducing male connector is fitted onto the shaft of one end of the ball joint torque universal joint, and a reducing female connector is fitted onto the shaft of the other end of the ball joint torque universal joint. Although this sucker rod guide has the functions of straightening and guiding, it cannot transmit rotational torque and easily increases fluid resistance. In addition, this sucker rod guide has no lubrication function, is prone to wear and failure, and has a short service life.

[0004] Chinese patent document CN215805141U discloses an internal torque transmission device for preventing uneven wear of the rod tube in a screw pump. This device includes a male end variable-thread connector for the screw pump sucker rod, an internal transmission spindle, a centralizing block, a universal joint assembly, an internal transmission cylinder, and a female end variable-thread connector. The universal joint assembly is housed within the ball joint cavity of the internal transmission spindle, and both the universal joint assembly and the internal transmission spindle are placed within the internal transmission cylinder. The centralizing block is located outside the internal transmission spindle. The male and female end variable-thread connectors are connected to one end of the internal transmission spindle, and their other ends are connected to the corresponding type of sucker rod. This internal torque transmission device for preventing uneven wear of the rod tube in a screw pump uses a cross-shaped torque guiding transmission principle, resulting in unstable torque transmission. Furthermore, the torque transmission device lacks a lubrication system, making it prone to wear and failure.

[0005] Chinese patent document CN213234979U discloses a screw pump sucker rod guide and centralizer, including a guide rod and a universal head. The universal head is spherical in shape, and a first limiting surface is provided on the spherical surface around the axis of the guide rod. The cross-section of the first limiting surface is a square with chamfers. The universal head has a first guide surface, which is a convex spherical surface. A positioning sleeve has a second limiting surface on its inner wall that matches the first limiting surface. The second limiting surface matches the first limiting surface and transmits torque. A second guide surface, which is a concave spherical surface, is provided. The universal head can swing within the positioning sleeve. The positioning sleeve and the connecting piece are detachably connected. The guide rod can swing relative to the positioning sleeve at an angle α. The torque transmission device of this screw pump sucker rod guide and centralizer is square, resulting in unstable torque transmission. Furthermore, the torque transmission device lacks a lubrication device, making it prone to wear and failure. Summary of the Invention

[0006] To address the technical problems described above, this invention aims to provide a centralizing guide for the sucker rod of a screw pump. This centralizing guide can effectively prevent oil spillage and stagnation in curved well sections, reduce uneven wear between the sucker rod and tubing, and greatly extend the life of the screw pump oil production system, thereby achieving the goal of improving quality and efficiency.

[0007] Therefore, according to the present invention, a straightening guide for a screw pump sucker rod is provided, comprising: a cylindrical outer shell; a plurality of straightening blocks evenly arranged on the outer surface of the outer shell; a push rod concentrically arranged inside the outer shell, the two ends of the push rod being respectively provided with ball heads; and connector assemblies symmetrically arranged at both ends of the outer shell, respectively used to connect an upper sucker rod and a lower sucker rod, the connector assembly comprising a ball-and-socket shaped connecting seat fixedly connected to the end of the outer shell and a ball-and-socket shaped connector adapted to the ball-and-socket shaped connecting seat; wherein, the inner wall surface of the ball-and-socket shaped connecting seat is constructed as a first inner spherical surface, and an inner drive tooth is provided on the first inner spherical surface, the ball-and-socket shaped connector comprising a ball-and-socket body, the outer surface of the ball-and-socket body being provided with radially extending outer drive teeth, and the interior of the ball-and-socket body forming a second inner spherical surface adapted to the ball head, the outer drive teeth and the inner drive teeth being adapted to mesh to form a meshing pair, such that the ball-and-socket shaped connector can bend relative to the outer shell and can straighten the sucker rod by means of the straightening blocks.

[0008] In one embodiment, the spherical cap joint further includes a spherical cap connecting rod connected to the spherical cap body for connecting to a corresponding upper sucker rod or lower sucker rod.

[0009] In one embodiment, the end of the crown connecting rod away from the crown body is provided with an external thread.

[0010] In one embodiment, a high-pressure sealing element is provided between the ball-and-socket connector and the spherical crown joint, and the high-pressure sealing element is located at the connection between the spherical crown body and the spherical crown connecting rod.

[0011] In one embodiment, one end of the ball-and-socket connector is provided with an inner stepped joint, which is fixedly connected to the end of the outer casing by a threaded connection.

[0012] In one embodiment, a high-pressure sealing ring is provided between the inner stepped joint and the end of the outer casing.

[0013] In one embodiment, the straightening block is made of D3O strain rate sensitive material, which allows the straightening block to be in a soft state when it is not in contact with the inner wall of the tubing, and to have a certain rigidity after contacting the inner wall of the tubing to straighten the sucker rod.

[0014] In one embodiment, the plurality of straightening blocks are arranged in a spiral shape and are evenly spaced apart in both the axial and circumferential directions.

[0015] In one embodiment, the outer diameter of the straightening block is larger than the outer diameter of the ball-and-socket connector.

[0016] In one embodiment, the annular space formed between the top rod and the outer housing radially is filled with lubricating oil for lubricating the mating surfaces of the ball-and-socket connector and the spherical crown joint.

[0017] Compared with the prior art, the advantages of this application are:

[0018] The centralizing guide for sucker rods in screw pumps according to the present invention uses D3O strain rate-sensitive centralizing blocks spirally distributed on the outer surface of the outer casing to fit against the inner wall of the tubing, providing good centralization and alignment of the sucker rod string. A toothed spherical universal joint is formed within the joint assembly by the meshing of external drive teeth on the spherical cap body and internal drive teeth in the ball-and-socket connector. This toothed spherical universal joint can non-flexibly transmit the rotational torque of the sucker rod in curved sections, eliminating the buckling phenomenon that occurs when the sucker rod flexibly transmits torque, and reducing contact wear between the tubing and the sucker rod. Furthermore, the entire toothed spherical universal joint forms a closed system, and the meshing transmission mechanism is lubricated throughout the entire process by lubricant. This combines the centralization and alignment functions with the universal torque transmission function of the entire system, ultimately enabling the screw pump well to prevent tubing wear. This allows the centering guide used for the screw pump sucker rod to effectively prevent oil spillage and stagnation in curved well sections, reduce uneven wear between the sucker rod and tubing, and greatly extend the life of the screw pump oil production system, thereby achieving the goal of improving quality and efficiency. Attached Figure Description

[0019] The present invention will now be described with reference to the accompanying drawings.

[0020] Figure 1 The structure of a centralizing guide for a screw pump sucker rod according to the present invention is shown schematically.

[0021] Figure 2 schematically shown Figure 1 The structure of the ball crown joint in the centralizing guide for the sucker rod of a screw pump is shown.

[0022] Figure 3 yes Figure 2 The left view.

[0023] Figure 4 The distribution structure of the straightening blocks on the outer shell is schematically shown.

[0024] In this application, all drawings are schematic and are used only to illustrate the principles of the invention, and are not drawn to scale. Detailed Implementation

[0025] The present invention will now be described with reference to the accompanying drawings. It should be noted that these descriptions are provided merely to illustrate the principles of the invention and do not limit the scope of the invention.

[0026] For ease of understanding, in this application, the end closest to the wellhead is defined as the upper end, upstream end, or similar terms, for example... Figure 1 The left end is defined as the end furthest from the wellhead, while the end furthest from the wellhead is defined as the lower end, downstream end, or similar terms, for example... Figure 1 The right end of the middle.

[0027] Figure 1 The structure of a centralizing guide 100 for a screw pump sucker rod according to the present invention is schematically shown. Figure 1 As shown, the centralizing guide 100 for the sucker rod of a screw pump includes a housing 1, centralizing blocks 2, a push rod 3, and a connector assembly 4. The housing 1 is a cylindrical outer shell 1 with a cavity inside. Multiple centralizing blocks 2 are provided and evenly arranged on the outer surface of the housing 1. The push rod 3 is concentrically arranged within the cavity of the housing 4, and each end of the push rod 3 has a ball head 31. Two connector assemblies 4 are provided and symmetrically arranged at both ends of the housing, used to connect the upper sucker rod and the lower sucker rod (not shown), respectively. The connector assembly 4 includes a ball-and-socket connector 41 fixedly connected to the end of the housing 1 and a ball-and-socket connector 42 adapted to the ball-and-socket connector 41.

[0028] According to the present invention, such as Figure 3 As shown, the inner wall surface of the ball-and-socket connector 41 is constructed as a first inner spherical surface, and radially extending inner drive teeth 411 are provided on the first inner spherical surface. The spherical crown connector 42 includes a spherical crown body 421, and the outer surface of the spherical crown body 421 is provided with radially extending outer drive teeth 4211. The interior of the spherical crown body 421 forms a second inner spherical surface 4212 that is adapted to the ball head 31 at the end of the push rod 3. The outer drive teeth on the spherical crown body 421 and the inner drive teeth 411 in the ball-and-socket connector 41 are adapted to mesh to form a meshing pair, thereby realizing the universal connection between the spherical crown connector 42, the push rod 3 and the outer shell 1, so that the spherical crown connector 42 can be bent relative to the outer shell 1, and the sucker rod can be straightened by the straightening block 2.

[0029] like Figure 2 As shown, the spherical cap connector 42 also includes a spherical cap connecting rod 422 connected to the spherical cap body 421. The spherical cap connecting rod 422 is used to connect to the corresponding upper or lower sucker rod. Preferably, the spherical cap body 421 and the spherical cap connecting rod 422 are constructed as one piece.

[0030] like Figure 2As shown, an external thread 4221 is provided at the end of the spherical cap connecting rod 422 that is away from the spherical cap body 421. The spherical cap joint 42 is adapted to be connected to the corresponding upper or lower sucker rod through the external thread 4221 on the spherical cap connecting rod 422. Preferably, the external thread 4221 is a standard sucker rod thread for connection with conventional sucker rods.

[0031] Preferably, the second inner spherical surface 4212 inside the crown body 421 is a smooth spherical surface, which allows the crown body 421 to fit tightly with the ball head 31 at the end of the top rod 3.

[0032] According to the present invention, the outer drive teeth 4211 on the outer surface of the spherical cap body 421 are machined in a radial shape and coplanar with the axial surface. Multiple outer drive teeth 4211 are provided, and the angles between adjacent outer drive teeth 4211 are set to be equal. Simultaneously, the inner drive teeth 411 on the inner wall surface of the spherical socket connecting seat 41 are machined in a radial shape and coplanar with the axial surface. Multiple inner drive teeth 411 are provided, and the angles between adjacent inner drive teeth 411 are set to be equal, and the angles between them are equal to those between adjacent outer drive teeth 4211. Thus, the outer drive teeth on the spherical cap body 421 and the inner drive teeth 411 in the spherical socket connecting seat 41 are adapted to mesh. When the sucker rod rotates, the outer drive teeth on the spherical cap body 421 and the inner drive teeth 411 in the spherical socket connecting seat 41 adapt to mesh. While transmitting torque, the two can slide relative to each other within a certain spatial angle range around the center of the spherical cap during rotation, thereby preventing the sucker rod from buckling.

[0033] To provide sufficient space for the adaptive transmission between the ball-and-socket connector 41 and the spherical cap connector 42, the radial dimension of the outer transmission teeth 4211 on the outer surface of the spherical cap body 421 along its outer circumference is no greater than one-eighth of the circumference of the spherical surface on which the outer surface of the spherical cap body 421 is located. Similarly, the radial dimension of the inner transmission teeth 411 along the inner wall of the ball-and-socket connector 41 is no greater than one-eighth of the circumference of the spherical surface on which the outer surface of the ball-and-socket connector 41 is located.

[0034] To ensure the sealing between the ball-and-socket connector 41 of the connector assembly 4 and the mating surface with the ball-and-socket connector 42, such as Figure 1As shown, a high-pressure sealing element 5 is provided between the ball-and-socket connector 41 and the spherical crown connector 42. The high-pressure sealing element 5 is sleeved on the spherical crown connector 42 and located at the connection between the spherical crown body 421 and the spherical crown connecting rod 422. The cross-sectional shape of the high-pressure sealing element 5 is approximately a right-angled trapezoid, with the upper base forming the inner surface of the high-pressure sealing element 5, the lower base forming the outer surface, the high side forming the first end face facing the transmission gear, and the inclined side opposite the high side forming the second end face facing the spherical crown connecting rod 422. Preferably, the inner surface is constructed as an arc surface adapted to the outer surface of the spherical crown connector 42, thereby enabling a tight fit with the spherical crown connector 42. The outer surface of the high-pressure sealing element 5 is constructed as an arc surface adapted to the inner surface of the ball-and-socket connector 41, thereby enabling a tight fit with the first inner spherical surface on the inner surface of the ball-and-socket connector 41. Thus, a seal is achieved between the ball-and-socket connector 41 and the spherical crown connector 42. Figure 1 As shown, the ball-and-socket connector 41 is generally cylindrical, with an axial through hole inside for the ball-and-socket connector 422 of the ball-and-socket joint 42 to pass through. The first inner spherical surface is formed on the inner wall of the axial inner end of the ball-and-socket connector 41 (near the end of the outer casing 1).

[0035] In one embodiment, the ball-and-socket connector 41 has an inner stepped joint at its axial inner end, and the inner wall of the inner stepped joint has an internal thread. Meanwhile, both ends of the outer casing 1 have external threads. The ball-and-socket connector 41 is connected to the outer casing 1 by the internal thread through a mating fit between the internal thread and the external thread at the ends, thereby achieving a fixed connection between the ball-and-socket connector 41 and the outer casing 1.

[0036] To ensure the sealing of the connection between the ball-and-socket connector 41 and the outer casing 1, such as Figure 1 As shown, a high-pressure sealing ring 6 is provided between the inner stepped joint and the end of the outer shell 1.

[0037] Preferably, the ball joint 42 can be made of the same steel as the Class D sucker rod.

[0038] According to the present invention, the centralizing block 2 can be made of D3O strain rate sensitive material. This allows the centralizing block 2 to be in a soft state when not in contact with the inner wall of the tubing, and to quickly harden when in contact with the inner wall of the tubing, thus achieving the centralizing function on the one hand, and reducing friction on the other. Therefore, the centralizing block 2 can be in a soft state when not in contact with the inner wall of the tubing, but has a certain rigidity after contact with the inner wall of the tubing, in order to centralize the sucker rod.

[0039] like Figure 4As shown, multiple centralizing blocks 2 are spirally distributed and evenly spaced in both the axial and circumferential directions. The centralizing guide 100 can fit tightly against the inner wall of the tubing through the centralizing blocks 2 and can rotate relative to the tubing, thereby centralizing the sucker rod and minimizing the flow resistance to the fluid inside the tubing.

[0040] The outer diameter of the straightening block 2 is larger than the outer diameter of the ball-and-socket connector 41. This not only effectively ensures the straightening performance of the straightening guide 100 for the sucker rod of the screw pump, but also prevents the ball-and-socket connector 41 from contacting the inner wall of the tubing, thereby avoiding friction between the ball-and-socket connector 41 and the inner wall of the tubing.

[0041] According to the present invention, the annular space formed between the push rod 3 and the outer casing 1 in the radial direction is filled with lubricating oil to lubricate the mating surfaces (including the meshing pair and the sliding pair) of the ball-and-socket connector 41 and the ball-and-socket joint 42. Simultaneously, the presence of the high-pressure sealing element 5 between the ball-and-socket connector 41 and the ball-and-socket joint 42, and the high-pressure sealing ring 6 at the connection between the ball-and-socket connector 41 and the outer casing 1, effectively ensures the sealing of the annular space, thereby preventing lubricating oil leakage. Thus, the entire connector assembly 4, through the meshing of the external drive teeth on the ball-and-socket body 421 and the internal drive teeth 411 in the ball-and-socket connector 41, forms a closed system of a rack-and-tooth ball-and-socket universal joint, and the meshing transmission mechanism is lubricated throughout the entire process by the lubricating oil.

[0042] In practical applications, the centralizing guide 100 for screw pump sucker rods according to the present invention can be used individually on the sucker rod string, or multiple units can be connected in series on the screw pump sucker rod string in curved well sections. After the sucker rod string is lowered into position and the screw pump is started for production, the centralizing guide 100 for the screw pump sucker rod plays a role in centralizing and aligning the sucker rod string. At the same time, the rack-and-tooth spherical universal joint formed by the meshing of the outer drive teeth on the spherical cap body 421 and the inner drive teeth 411 in the spherical socket connecting seat 41 prevents the sucker rod from bending and deforming, prevents the sucker rod from buckling, and ultimately prevents the tubing from wearing unevenly.

[0043] According to the present invention, the centering guide 100 for the sucker rod of a screw pump uses D3O strain rate sensitive centering blocks 2, which are spirally distributed on the outer surface of the outer casing 1, to fit against the inner wall of the tubing, thus providing good centering and alignment for the sucker rod string. A toothed spherical universal joint is formed within the connector assembly 4 by the meshing of the outer drive teeth on the spherical cap body 421 and the inner drive teeth 411 in the ball-and-socket connector 41. This toothed spherical universal joint can transmit the rotational torque of the sucker rod in a curved section non-flexibly, eliminating the bucking phenomenon that occurs when the sucker rod transmits torque through flexible bending, and reducing contact wear between the tubing and the sucker rod. Furthermore, the entire toothed spherical universal joint forms a closed system, and the meshing transmission mechanism is lubricated throughout the entire process by lubricating fluid. This achieves a combination of centering and alignment functions and universal torque transmission, ultimately enabling the screw pump well to prevent tubing wear. This allows the straightening guide 100 used for the sucker rod of the screw pump to effectively prevent oil pumping blockage in curved well sections, reduce uneven wear between the sucker rod and tubing, and greatly extend the service life of the screw pump oil production system, thereby achieving the goal of improving quality and efficiency.

[0044] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0045] 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 connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0046] Furthermore, in the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0047] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A centralizing guide for the sucker rod of a screw pump, comprising: Cylindrical outer shell (1); Multiple straightening blocks (2) are evenly arranged on the outer surface of the outer shell; A push rod (3) is concentrically arranged inside the outer casing, and each end of the push rod is provided with a ball head (31); and The connector assemblies (4) symmetrically arranged at both ends of the outer casing are used to connect the upper sucker rod and the lower sucker rod respectively. The connector assembly includes a ball-and-socket connector (41) fixedly connected to the end of the outer casing and a ball-and-socket connector (42) adapted to the ball-and-socket connector. The inner wall of the ball-and-socket connector is constructed as a first inner spherical surface, and an inner drive tooth (411) is provided on the first inner spherical surface. The spherical crown connector includes a spherical crown body (421), the outer surface of which is provided with radially extending outer drive teeth (4211), and the interior of the spherical crown body forms a second inner spherical surface (4212) adapted to the ball head. The outer drive teeth and the inner drive teeth are adapted to mesh to form a meshing pair, so that the spherical crown connector can bend relative to the outer shell and can straighten the sucker rod through the straightening block. The straightening block is made of D3O strain rate sensitive material, which allows the straightening block to be in a soft state when it is not in contact with the inner wall of the tubing, and to have a certain rigidity after contacting the inner wall of the tubing to straighten the sucker rod.

2. A centralizer for use with a screw pump sucker rod as defined in claim 1, wherein, The spherical crown connector also includes a spherical crown connecting rod (422) connected to the spherical crown body, for connecting to the corresponding upper sucker rod or lower sucker rod.

3. The centralizing guide for the sucker rod of a screw pump according to claim 2, characterized in that, The end of the spherical crown connecting rod away from the spherical crown body is provided with an external thread (4221).

4. The centralizing guide for the sucker rod of a screw pump according to claim 2 or 3, characterized in that, A high-pressure sealing element (5) is provided between the ball-shaped connector and the ball-shaped joint, and the high-pressure sealing element is located at the connection between the ball-shaped body and the ball-shaped connecting rod.

5. The centralizing guide for the sucker rod of a screw pump according to any one of claims 1 to 3, characterized in that, One end of the ball-and-socket connector is provided with an inner stepped joint, which is fixedly connected to the end of the outer shell by a threaded connection.

6. The centralizing guide for the sucker rod of a screw pump according to claim 5, characterized in that, A high-pressure sealing ring (6) is provided between the inner stepped joint and the end of the outer shell.

7. The centralizing guide for the sucker rod of a screw pump according to claim 1, characterized in that, The plurality of straightening blocks are arranged in a spiral shape and are evenly spaced apart in both the axial and circumferential directions.

8. The centralizing guide for the sucker rod of a screw pump according to claim 1, characterized in that, The outer diameter of the straightening block is larger than the outer diameter of the ball-and-socket connector.

9. The centralizing guide for the sucker rod of a screw pump according to claim 1, characterized in that, The annular space formed between the top rod and the outer casing is filled with lubricating oil to lubricate the mating surfaces of the ball-and-socket connector and the spherical crown connector.

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