Self-rotating type damping sucker rod centralizer

Abstract

The invention discloses a self-rotating type damping sucker rod centralizer which comprises an upper rod body (12) and a lower rod body (9), the upper rod body (12) is connected with an upper movable coupling (1), the lower rod body (9) is connected with a lower movable coupling (3), the upper rod body (12) is screwed with a screw rod (15) of the lower rod body (9) through a threaded hole (16), centralizing sleeves are arranged on the outer sides of the upper rod body (12) and the lower rod body (9), and the centralizing sleeves are connected with the upper movable coupling (1) and the lower movable coupling (3). An oil guide groove (2) is formed in the outer side of the centralizing sleeve, shoulders (4) are arranged at the two ends of the inner side of the centralizing sleeve respectively, the shoulders (4) are sealed with the upper movable coupling (1) and the lower movable coupling (3) respectively, a connecting block (13) is further arranged in the middle of the inner side of the centralizing sleeve, and the connecting block (13) is connected with centralizing sleeve helical teeth (14) through splines. When a sucker rod strokes up and down, the shock absorption effect can be achieved through the spring, the helical teeth are prevented from being impacted, and the service life of the centralizer is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of oil drilling equipment, in particular to a self-spinning shock-absorbing sucker rod centralizer. Background Art

[0002] In the sucker rod pumping system, the sucker rod is a key component connecting the ground drive equipment and the downhole pump. Its stability and operation effect directly affect the production efficiency of the oil well. However, in actual application, the relative movement between the sucker rod and the oil pipe may cause eccentric wear, which may seriously reduce the strength and service life of the sucker rod and the oil pipe. Eccentric wear will not only cause the sucker rod to break and the oil pipe wall to wear, but may also cause oil pipe leakage, thereby affecting the normal production and safety of the oil well. Especially after the oil field enters the high water content development stage, the downhole oil-water ratio continues to rise, the working environment of the pumping system becomes more severe, the depth of the oil well increases, and the pumping frequency increases, which greatly aggravates the eccentric wear problem between the sucker rod and the oil pipe.

[0003] At present, major domestic oil fields are facing different types and relatively simple structures of centralizers when using sucker rod centralizers. These devices have exposed different degrees of deficiencies in the actual production process. For example, the steel wheel type centralizer is prone to cracking the oil pipe in a short period of time because its contact surface with the oil pipe changes from rolling to sliding. In addition, in high water-content oil wells, steel rollers are easily corroded, resulting in jamming, which in turn affects normal operation. The design of the movable centralizer includes two parts fastened to the sucker rod, but as the use time goes by, due to friction and wear, the preload force gradually decreases, causing the centralizer to slide on the rod body, and may eventually fall off, losing the proper straightening effect.

[0004] In addition, the centralizing coupling is a nylon centralizing body added to the sucker rod coupling. Due to the limited space in the oil pipe, the nylon body is usually thin, and is limited by the design of the coupling, it is easy to fall off due to wear, causing the pump to get stuck. The traditional self-spinning centralizer is centralized by the meshing of the helical teeth, but during the up and down strokes, the huge impact force generated by the direct contact of the helical teeth can easily cause the helical teeth to break, resulting in the failure of the centralizing function.

[0005] Therefore, it is necessary to invent a self-spinning shock-absorbing sucker rod centralizer to effectively solve the problems of poor sealing effect, unstable connection, and impact on rigid connections of various parts of the existing centralizer. Summary of the invention

[0006] The present invention provides a self-spinning shock-absorbing sucker rod centralizer to solve the problems that the traditional centralizer cannot fully play its role under high load, high-speed pumping and complex geological conditions, and is prone to cause oil pipe wear and sucker rod breakage.

[0007] The present invention is implemented by adopting the following technical scheme: a self-rotating shock-absorbing sucker rod centralizer, comprising an upper rod body and a lower rod body, wherein the upper rod body is connected to an upper movable coupling, and the lower rod body is connected to a lower movable coupling, and the upper rod body is screwed to the screw of the lower rod body through a threaded hole, and a centralizing sleeve is arranged on the outer side of the upper rod body and the lower rod body, and an oil guide groove is arranged on the outer side of the centralizing sleeve, and shoulders are arranged at both ends of the inner side, and the shoulders form a seal with the upper movable coupling and the lower movable coupling respectively, and a connecting block is also arranged in the middle part of the inner side of the centralizing sleeve, and the connecting block is connected to the helical teeth of the centralizing sleeve through a spline.

[0008] Furthermore, the lower rod body is provided with lower rod body bevel teeth and a lower rod body spring, a lower rod body spring sleeve is provided on the outer side of the lower rod body spring, a lower rod body bevel tooth adjustment screw sleeve is provided on the lower rod body bevel teeth, and a lower movable coupling adjustment screw sleeve is also provided on the lower rod body.

[0009] Furthermore, the lower movable coupling is in threaded contact with the lower movable coupling adjusting screw sleeve, the lower movable coupling adjusting screw sleeve is connected with the lower rod body spring sleeve through a slide groove, the lower rod body spring sleeve is connected with the lower rod body helical tooth adjusting screw sleeve through a slide groove, and the lower rod body helical tooth adjusting screw sleeve is connected with the lower rod body helical teeth through a spline.

[0010] Furthermore, the outer side of the lower rod body spring is in sliding contact with the lower rod body spring sleeve, the inner side is in contact with the lower rod body, the left side is in contact with the lower movable coupling adjusting screw sleeve, and the right side is in contact with the lower rod body helical tooth adjusting screw sleeve.

[0011] Furthermore, the upper rod body is provided with upper rod body bevel teeth and an upper rod body spring, an upper rod body spring sleeve is provided on the outer side of the upper rod body spring, an upper rod body bevel tooth adjustment screw sleeve is provided on the upper rod body bevel teeth, and an upper movable coupling adjustment screw sleeve is also provided on the upper rod body.

[0012] Furthermore, the upper movable coupling is in threaded contact with the upper movable coupling adjusting screw sleeve, the upper movable coupling adjusting screw sleeve is connected with the upper rod body spring sleeve through a slide groove, the upper rod body spring sleeve is connected with the upper rod body bevel tooth adjusting screw sleeve through a slide groove, and the upper rod body bevel tooth adjusting screw sleeve is connected with the upper rod body bevel teeth through a spline.

[0013] Furthermore, the outer side of the upper rod body spring is in sliding contact with the upper rod body spring sleeve, the inner side is in contact with the upper rod body, the left side is in contact with the upper rod body helical tooth adjusting screw sleeve, and the right side is in contact with the upper movable coupling adjusting screw sleeve.

[0014] Furthermore, the upper movable coupling is connected to the external thread on the upper rod end through an internal thread hole, and the lower movable coupling is connected to the external thread on the lower rod end through an internal thread. Both sides of the upper movable coupling and the lower movable coupling have threaded holes for connecting the sucker rod.

[0015] Furthermore, the centralizing sleeve is streamlined in shape and is provided with spiral oil guide grooves parallel to each other. The outer side of the centralizing sleeve is made of reinforced nylon composite material, and the inner side is made of AOC alloy.

[0016] The beneficial effects of the present invention are: The present invention uses the rod body up and down strokes to make the teeth mesh, and the oil guide groove of the centralizing sleeve assists in generating tangential force, so that the centralizing sleeve spins in the well, reducing eccentric wear with the pipeline, and solves the problem of aggravated eccentric wear between the existing centralizer and the pipeline in harsh environments.

[0017] The invention realizes threaded connection with the sucker rod through the upper and lower couplings, thereby solving the problem that the existing centralizer falls off and jams the pump due to the decrease of pre-tightening force.

[0018] The present invention reduces the impact of the sucker rod on the helical teeth during the up and down strokes by introducing a spring, and adjusts the screw sleeve to perform secondary sealing inside the centralizer through the spring sleeve, thereby reducing the risk of corrosion inside the centralizer, extending the service life of the centralizer, and also improving the oil production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0020] Figure 1 This is a schematic diagram of the oil guide groove structure of the centralizing sleeve; Figure 2 This is a schematic diagram of the interior of the righting sleeve; Figure 3 It is the cross-section of the upper rod body; Figure 4 It is the cross-section of the lower rod; Figure 5 It is the tooth meshing diagram; Figure 6 It is a partial cross-sectional view of the centralizer coupling; Figure 7 It is a schematic diagram of a spring sleeve and a coupling adjusting screw sleeve; Figure 8 It is a schematic diagram of the helical teeth of the rod body and the helical teeth adjusting sliding sleeve; Fig. 9 It is the overall cross-sectional view of the centralizer; In the figure, 1-upper movable coupling; 2-oil guide groove; 3-lower movable coupling; 4-shoulder; 5-slide groove; 6-lower rod body oblique tooth adjusting screw sleeve; 7-lower rod body spring; 8-upper movable coupling adjusting screw sleeve; 9-upper rod body; 10-lower rod body oblique teeth; 11-upper rod body spring sleeve; 12-lower rod body; 13-connecting block; 14-straightening sleeve oblique teeth; 15-screw; 16-threaded hole. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0023] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0024] See also Figures 1 to 9 A self-spinning shock-absorbing sucker rod centralizer comprises an upper rod body 12 and a lower rod body 9, wherein the upper rod body 12 is connected to an upper movable coupling 1, and the lower rod body 9 is connected to a lower movable coupling 3. The upper rod body 12 is screwed to a screw 15 of the lower rod body 9 through a threaded hole 16. A centralizing sleeve is arranged on the outer side of the upper rod body 12 and the lower rod body 9, an oil guide groove 2 is arranged on the outer side of the centralizing sleeve, and shoulders 4 are arranged at both ends of the inner side, and the shoulders 4 are respectively sealed with the upper movable coupling 1 and the lower movable coupling 3. A connecting block 13 is also arranged in the middle part of the inner side of the centralizing sleeve, and the connecting block 13 is connected to the helical teeth 14 of the centralizing sleeve through a spline.

[0025] In this embodiment, the lower rod body 9 is provided with a lower rod body helical tooth 10 and a lower rod body spring 7, the lower rod body spring sleeve is provided on the outer side of the lower rod body spring 7, the lower rod body helical tooth 10 is provided with a lower rod body helical tooth adjusting screw sleeve 6, and the lower rod body 9 is also provided with a lower movable coupling adjusting screw sleeve. The lower movable coupling 3 is in contact with the lower movable coupling adjusting screw sleeve through a thread, the lower movable coupling adjusting screw sleeve is connected with the lower rod body spring sleeve through a slide groove 5, the lower rod body spring sleeve is connected with the lower rod body helical tooth adjusting screw sleeve 6 through the slide groove 5, and the lower rod body helical tooth adjusting screw sleeve 6 is connected with the lower rod body helical tooth 10 through a spline. The outer side of the lower rod body spring 7 is in sliding contact with the lower rod body spring sleeve, the inner side is in contact with the lower rod body 9, the left side is in contact with the lower movable coupling adjusting screw sleeve, and the right side is in contact with the lower rod body helical tooth adjusting screw sleeve 6.

[0026] In this embodiment, the upper rod body 12 is provided with an upper rod body bevel tooth and an upper rod body spring, an upper rod body spring sleeve 11 is provided on the outer side of the upper rod body spring, an upper rod body bevel tooth adjusting screw sleeve is provided on the upper rod body bevel tooth, and an upper movable coupling adjusting screw sleeve 8 is also provided on the upper rod body 12. The upper movable coupling 1 is in contact with the upper movable coupling adjusting screw sleeve 8 through a thread, the upper movable coupling adjusting screw sleeve 8 is connected with the upper rod body spring sleeve 11 through a slide groove, the upper rod body spring sleeve 11 is connected with the upper rod body bevel tooth adjusting screw sleeve through a slide groove, and the upper rod body bevel tooth adjusting screw sleeve is connected with the upper rod body bevel tooth through a spline. The outer side of the upper rod body spring is in sliding contact with the upper rod body spring sleeve 11, the inner side is in contact with the upper rod body 12, the left side is in contact with the upper rod body bevel tooth adjusting screw sleeve, and the right side is in contact with the upper movable coupling adjusting screw sleeve 8.

[0027] In this embodiment, the upper rod body 12 and the lower rod body 9 are connected to the upper movable coupling 3 and the lower movable coupling 1 respectively by applying thread glue on the threads, and the upper rod body 12 and the lower rod body 9 are respectively inserted from the two ends of the straightening sleeve, and the threads are tightened. The upper and lower sucker rods are respectively connected to the external threads of the upper movable coupling 3 and the lower movable coupling 1, and they are installed at the eccentric wear position of the rod pipe. The inner thread of the coupling adjustment screw sleeve (including the upper movable coupling adjustment screw sleeve 8 and the lower movable coupling adjustment screw sleeve) is connected to the outer thread of the movable coupling (the upper movable coupling 3 and the lower movable coupling 1), and the coupling adjustment screw sleeve can be adjusted in position through the outer thread of the movable coupling. The spring sleeve (including the upper rod body spring sleeve 11 and the lower rod body spring sleeve) realizes axial movement by cooperating with the movable coupling slide groove. The spring sleeve cooperates with the rod body adjustment screw sleeve and the coupling adjustment screw sleeve to form a seal to prevent the liquid in the well from flowing into the spring sleeve.

[0028] In this embodiment, the upper movable coupling 1 is connected to the external thread of the upper rod body 12 through an internal thread hole, and the lower movable coupling 3 is connected to the external thread of the lower rod body 9 through an internal thread. Both sides of the upper movable coupling 1 and the lower movable coupling 3 have threaded holes for connecting the sucker rod. Furthermore, there is a spring in the spring sleeve, the inner side of the spring is close to the sucker rod, and the outer side is in contact with the spring sleeve. The outer diameter of the spring is larger than the movable coupling. When the spring is squeezed, the spring can be limited to achieve the purpose of shock absorption, reduce the impact on the helical teeth when mating, and extend the service life. The other side of the spring sleeve is mated with the rod body adjusting screw sleeve through a sliding groove, and the rod body adjusting screw sleeve and the rod body helical teeth are mated through splines.

[0029] In this embodiment, the straightening sleeve is streamlined in shape and is provided with spiral oil guide grooves 2 that are parallel to each other. The outer material of the straightening sleeve is reinforced nylon composite material, and the inner material is AOC alloy. Furthermore, the helical teeth of the straightening sleeve are matched with the connecting block 13 through splines. There is a certain phase angle between the helical teeth of the upper and lower rod bodies. When they are engaged with the inner helical teeth of the sliding sleeve (straightening sleeve) (straightening sleeve helical teeth 14), the rod body generates a tangential force on the sliding sleeve, causing the sliding sleeve to self-rotate in the same direction. There is an oil guide groove on the outer side of the straightening sleeve. When the oil flows through the outer oil guide groove and flows through the straightening device, it generates a tangential force on the straightening device. The force is in the same direction as the tangential force generated between the helical teeth, which is conducive to the self-rotation of the sliding sleeve during operation. The helical teeth at both ends of the inner side of the sliding sleeve are symmetrical and can be matched with the helical teeth on the upper and lower rod bodies (including the upper rod body helical teeth and the lower rod body helical teeth 10). The large inner diameter of the sliding sleeve cooperates with the outer side of the movable coupling to form a seal.

[0030] The working principle of the present invention is: The present invention relies on the force generated by the up and down strokes of the sucker rod, and the helical teeth (including the upper rod body helical teeth, the lower rod body helical teeth 10 and the helical teeth 14 of the helical sleeve) cooperate to make the straightening sleeve spin. The sucker rod is threadedly connected through the upper movable coupling 1 and the lower movable coupling 3, respectively. The upper rod body 12 and the lower rod body 9 are respectively inserted from both ends of the straightening sleeve and screwed together through the threaded hole 16 and the threaded rod 15. The upper rod body 12 is threadedly connected to the upper movable coupling 1, and the lower rod body 9 is threadedly connected through the lower movable coupling 3.

[0031] When the sucker rod is in the upward stroke, the straightening sleeve and the oil pipe are subjected to force in the vertical direction of eccentric wear. At this time, the spring (including the upper rod body spring and the lower rod body spring 7) is subjected to the axial force decomposed from the initial meshing of the rod body helical teeth (including the upper rod body helical teeth and the lower rod body helical teeth 10) and the straightening sleeve helical teeth 14 gears. The spring is in contact with the helical teeth adjusting screw sleeve and is compressed. The helical teeth adjusting screw sleeve slides along the slide groove. At this time, the tangential force generated by the helical teeth meshing is not enough to make the straightening sleeve spin. The upward stroke continues. When the spring sleeve is matched with the coupling adjusting screw sleeve through the slide groove, the axial displacement of the rod body helical teeth and the straightening sleeve helical teeth 14 is restricted and begins to mesh. The spring is longer than the spring sleeve. When fully meshed, the helical teeth adjusting screw sleeve contacts the spring and unloads part of the impact force. At this time, the tangential force generated by the helical teeth meshing makes the straightening sleeve spin. At the same time, during the whole process, the liquid flows through the straightening sleeve oil guide groove 2, generating the same tangential force as when the helical teeth mesh, promoting the straightening sleeve to spin in the well. When the sucker rod is in the downward stroke, the upper rod body 12 moves downward, at which time the spring rebounds, pushing the helical tooth adjusting screw sleeve and the helical teeth of the rod body back to the initial meshing position, and at the same time causing the lower rod body 9 to repeat the above steps, thereby achieving continuous self-spin.

[0032] When the sucker rod makes an up and down stroke, the helical tooth adjusting screw sleeve and the coupling adjusting screw sleeve cooperate with the spring sleeve slide groove, the coupling adjusting screw sleeve and the helical tooth adjusting screw sleeve cooperate with the spring sleeve as the first layer of sealing, and the centralizing sleeve shoulder 4 and the upper movable coupling 1 and the lower movable coupling 3 serve as the second layer of sealing, which has a better sealing effect and can improve the working stability of the centralizer under harsh conditions.

[0033] The invention provides a self-spinning shock-absorbing sucker rod centralizer, which can reduce eccentric wear on the pipeline under the condition of good sealing effect, and can use the spring to achieve shock absorption effect during the up and down strokes of the sucker rod to prevent the helical teeth from impact, thereby extending the service life of the centralizer.

[0034] It should be noted that the terms "connection" and "setting" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "connection" and "setting" may explicitly or implicitly include one or more of the features. Moreover, the terms "connection", "setting" and the like are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. And for the aforementioned embodiments, for the sake of simple description, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited to the described order of actions, because according to the present application, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification belong to preferred embodiments, and the actions involved are not necessarily required by the present application.

[0035] For the aforementioned embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the order of the actions described, because according to the present application, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily required by the present application.

[0036] The above embodiments describe the basic principles and main features of the present invention and the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the changes and modifications made by those skilled in the art shall be within the scope of protection of the appended claims of the present invention without departing from the spirit and scope of the present invention.

Claims

1. A self-spinning damping sucker rod centralizer, characterized in that: The invention comprises an upper rod body (12) and a lower rod body (9), wherein the upper rod body (12) is connected to an upper movable coupling (1), and the lower rod body (9) is connected to a lower movable coupling (3). The upper rod body (12) is screwed to a screw (15) of the lower rod body (9) through a threaded hole (16). A straightening sleeve is arranged on the outer side of the upper rod body (12) and the lower rod body (9). An oil guide groove (2) is arranged on the outer side of the straightening sleeve, and shoulders (4) are arranged at both ends of the inner side. The shoulders (4) respectively form a seal with the upper movable coupling (1) and the lower movable coupling (3). A connecting block (13) is also arranged in the middle of the inner side of the straightening sleeve, and the connecting block (13) is connected to the helical teeth (14) of the straightening sleeve through a spline.

2. A self-spinning damping sucker rod centralizer as claimed in claim 1, characterized in that: The lower rod body (9) is provided with lower rod body oblique teeth (10) and a lower rod body spring (7), a lower rod body spring sleeve is provided outside the lower rod body spring (7), a lower rod body oblique teeth adjusting screw sleeve (6) is provided on the lower rod body oblique teeth (10), and a lower movable coupling adjusting screw sleeve is also provided on the lower rod body (9).

3. A self-spinning damping sucker rod centralizer as claimed in claim 2, characterized in that: The lower movable coupling (3) is in threaded contact with the lower movable coupling adjusting screw sleeve, the lower movable coupling adjusting screw sleeve is connected to the lower rod body spring sleeve via a slide groove (5), the lower rod body spring sleeve is connected to the lower rod body helical tooth adjusting screw sleeve (6) via the slide groove (5), and the lower rod body helical tooth adjusting screw sleeve (6) is connected to the lower rod body helical tooth (10) via a spline.

4. A self-spinning damping sucker rod centralizer as claimed in claim 3, characterized in that: The lower rod body spring (7) is in sliding contact with the lower rod body spring sleeve on the outside, in contact with the lower rod body (9) on the inside, in contact with the lower movable coupling adjusting screw sleeve on the left side, and in contact with the lower rod body oblique tooth adjusting screw sleeve (6) on the right side.

5. The self-spinning damping sucker rod centralizer according to claim 1, characterized in that: The upper rod body (12) is provided with an upper rod body bevel tooth and an upper rod body spring, an upper rod body spring sleeve (11) is provided outside the upper rod body spring, an upper rod body bevel tooth adjustment screw sleeve is provided on the upper rod body bevel tooth, and an upper movable coupling adjustment screw sleeve (8) is also provided on the upper rod body (12).

6. A self-spinning damping sucker rod centralizer as claimed in claim 5, characterized in that: The upper movable coupling (1) is in threaded contact with the upper movable coupling adjusting screw sleeve (8); the upper movable coupling adjusting screw sleeve (8) is connected to the upper rod body spring sleeve (11) via a slide groove; the upper rod body spring sleeve (11) is connected to the upper rod body helical tooth adjusting screw sleeve via a slide groove; and the upper rod body helical tooth adjusting screw sleeve is connected to the upper rod body helical teeth via a spline.

7. A self-spinning damping sucker rod centralizer as claimed in claim 6, characterized in that: The upper rod body spring is in sliding contact with the upper rod body spring sleeve (11) on the outside, in contact with the upper rod body (12) on the inside, in contact with the upper rod body oblique tooth adjustment screw sleeve on the left side, and in contact with the upper movable coupling adjustment screw sleeve (8) on the right side.

8. The self-spinning damping sucker rod centralizer according to claim 1, characterized in that: The upper movable coupling (1) is connected to the external thread on the end side of the upper rod body (12) via an internal thread hole, and the lower movable coupling (3) is connected to the external thread on the end side of the lower rod body (9) via an internal thread hole. Both sides of the upper movable coupling (1) and the lower movable coupling (3) are provided with threaded holes for connecting the sucker rod.

9. The self-spinning damping sucker rod centralizer according to claim 1, characterized in that: The centralizing sleeve is streamlined in shape and is provided with mutually parallel spiral oil guide grooves (2); the outer side of the centralizing sleeve is made of reinforced nylon composite material, and the inner side is made of AOC alloy.

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