Downhole hydraulic clutch device

Abstract

The present invention relates to the technical field of tools for oil and gas drilling, and is a downhole hydraulic clutch device, which includes a transmission shaft with an axial flow channel, a clutch assembly and an outer cylinder, and the clutch assembly is mounted on the outer side of the lower part of the transmission shaft. The present invention has a reasonable and compact structure and is easy to use. During normal operation, the power output by the screw drill is directly transmitted to the drill bit through the transmission shaft, so that the drill bit can perform normal rock breaking work; when the drill bit is stuck, the liquid inlet pressure in the upper cavity of the piston is first increased, so that the piston pushes the clutch shaft to further compress the compression spring, and then the transmission convex teeth at the lower end of the clutch shaft are inserted into the corresponding transmission groove on the outer ring platform, and finally the outer cylinder drives the transmission shaft to rotate together through the clutch shaft, breaking the stuck state of the drill bit; when the drill bit resumes normal operation again, the liquid inlet pressure in the upper cavity of the piston is reduced, and the spring pushes the clutch shaft to move up and back to the equilibrium position under the action of the spring restoring force, which has the characteristics of safety, labor saving, simplicity and high efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas drilling tools, and is a downhole hydraulic clutch device. Background Art

[0002] In the process of oil and gas drilling, geological exploration, and mining drilling, directional wells, horizontal wells, high-angle wells, and large-reach wells are increasingly widely used, which puts forward higher requirements for drilling technology. In the process of directional drilling, the country mainly uses a sliding drilling system powered by a mud motor to implement drilling operations. At this time, the screw drill drives the drill bit to rotate and drill, while the drill string itself does not rotate. However, due to the weight of the power drill and the drill bit, it will lie flat at the bottom of the well, resulting in large friction resistance and difficulty in effectively applying drilling pressure. Therefore, during the drilling of hard formations, the drill bit will be stuck and the screw drill will be blocked due to insufficient torque; on the premise of meeting the drilling design, some well sections can adopt composite drilling technology, that is, when the downhole drill bit torque is insufficient, the torque can be transmitted to the drill bit through the drill string to break the stuck state, and in normal working conditions, the screw drill is used to drive the drill bit to rotate and drill, which has a positive effect on reducing friction and torque loss. Summary of the invention

[0003] The present invention provides a downhole hydraulic clutch device, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problems existing in the drilling process of existing directional wells, horizontal wells, high-angle wells and large-reach wells, such as the power drilling tools and drill bits lying flat on the bottom of the well due to their own weight, resulting in large friction resistance and difficulty in effectively applying drilling pressure, and the drill bit getting stuck due to insufficient torque.

[0004] The technical solution of the present invention is achieved through the following measures: a downhole hydraulic clutch device, comprising a transmission shaft with an axial flow channel, a clutch assembly and an outer cylinder, the clutch assembly is mounted on the outer side of the lower part of the transmission shaft, the outer side of the clutch assembly is transmission-connected with the outer cylinder with the upper end located below the transmission shaft, and the clutch assembly can move up and down relative to the outer cylinder, at least one pressure relief hole that passes through inside and outside is provided along the circumference of the transmission shaft corresponding to the position above the clutch assembly, an outer ring platform is provided on the outer side of the lower end of the transmission shaft corresponding to the position below the outer cylinder, the lower end of the clutch assembly can form a transmission connection with the upper side of the outer ring platform, and a drill bit connection groove is provided on the inner side of the lower end of the transmission shaft.

[0005] The following are further optimizations and / or improvements to the above technical solutions:

[0006] The above-mentioned clutch assembly may include a spring, a spring plug and a clutch shaft with an axial channel. The clutch shaft is sleeved on the outer side of the lower part of the transmission shaft, and a transmission ring platform is provided on the upper end of the clutch shaft. The outer side of the transmission ring platform is transmission-connected to the inner side of the lower part of the outer cylinder, and the transmission ring platform can move up and down relative to the outer cylinder; a spring plug sleeved on the outer side of the clutch shaft is fixedly installed on the inner side of the lower end of the outer cylinder, and a spring is sleeved on the transmission shaft at a position corresponding to the upper side of the spring plug and the lower side of the transmission ring platform; at least two transmission cams are evenly distributed along the circumference of the lower end of the clutch shaft, and a transmission groove with a shape matching the transmission cam is provided on the upper side of the outer ring platform corresponding to each transmission cam position.

[0007] The outer side of the transmission ring may be provided with an external spline, the inner side of the lower part of the outer cylinder may be provided with an internal spline meshing with the external spline, and the lower end of the external spline is located below the upper end of the internal spline.

[0008] The clutch assembly may further include a piston, and a piston sleeved on the outer side of the transmission shaft is fixedly mounted on the upper end of the clutch shaft.

[0009] The clutch assembly may further include a first sealing ring and a second sealing ring. At least one first sealing ring is spaced apart from top to bottom between the piston and the outer tube, and at least one second sealing ring is spaced apart from top to bottom between the piston and the transmission shaft.

[0010] The above may also include a filter screen. At least one communicating hole that passes through inside and outside is provided along the circumference of the outer cylinder corresponding to the lower position of the clutch assembly. A filter screen is fixedly installed on the inner side of the outer end of each communicating hole.

[0011] The above may also include a conversion joint with an axial channel, and a conversion joint sleeved on the upper part of the transmission shaft is fixedly installed on the inner side of the upper end of the outer cylinder.

[0012] The present invention has a reasonable and compact structure and is easy to use. During normal operation, the power output by the screw drill is directly transmitted to the drill bit through the transmission shaft, so that the drill bit can perform normal rock breaking work; when the drill bit is stuck, the liquid inlet pressure in the upper cavity of the piston is increased first, so that the clutch shaft is pushed by the piston to further compress the compression spring, and then the transmission convex teeth at the lower end of the clutch shaft are inserted into the corresponding transmission grooves on the outer ring platform, and finally the outer cylinder drives the transmission shaft to rotate together through the clutch shaft, thereby breaking the stuck state of the drill bit; when the drill bit resumes normal operation again, the liquid inlet pressure in the upper cavity of the piston is reduced, and under the action of the spring restoring force, the spring pushes the clutch shaft to move up and back to the equilibrium position. By using the present invention, when the torque of the downhole drill bit is insufficient, the torque is transmitted to the drill bit through the outer cylinder to release its stuck state, and in normal working state, the drill bit is driven to rotate and drill through the transmission shaft, which has a positive effect on reducing friction and reducing torque loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Attached Figure 1 It is a schematic diagram of the main cross-sectional structure of the best embodiment of the present invention.

[0014] Attached Figure 2 For attachment Figure 1 Schematic diagram of the three-dimensional structure of the transmission shaft.

[0015] Attached Figure 3 For attachment Figure 1 Schematic diagram of the three-dimensional structure of the outer cylinder.

[0016] Attached Figure 4 For attachment Figure 1 Schematic diagram of the enlarged three-dimensional structure of the clutch shaft.

[0017] The codes in the accompanying drawings are: 1 is a transmission shaft, 2 is an outer cylinder, 3 is a pressure relief hole, 4 is an outer ring, 5 is a spring, 6 is a spring plug, 7 is a clutch shaft, 8 is an outer spline, 9 is an inner spline, 10 is a transmission convex tooth, 11 is a transmission groove, 12 is a piston, 13 is a filter screen, 14 is a connecting hole, 15 is a conversion joint, 16 is a first sealing ring, 17 is a second sealing ring, and 18 is a drill bit connecting groove. DETAILED DESCRIPTION

[0018] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0019] In the present invention, for the convenience of description, the relative position relationship of each component is described according to the attached Figure 1 The positional relationships such as front, back, top, bottom, left, and right are described according to the layout directions of the drawings in the specification.

[0020] The present invention will be further described below in conjunction with embodiments and drawings:

[0021] As attached Figure 1 , 2 As shown in Figures 3 and 4, the downhole hydraulic clutch device includes a transmission shaft 1 with an axial flow channel, a clutch assembly and an outer cylinder 2. The clutch assembly is mounted on the outer side of the lower part of the transmission shaft 1. The outer side of the clutch assembly is transmission-connected with the outer cylinder 2 whose upper end is located below the transmission shaft 1, and the clutch assembly can move up and down relative to the outer cylinder 2. At least one pressure relief hole 3 that penetrates inside and outside is provided along the circumference of the transmission shaft 1 corresponding to the position above the clutch assembly. An outer ring platform 4 is provided on the outer side of the lower end of the transmission shaft 1 corresponding to the position below the outer cylinder 2. The lower end of the clutch assembly can form a transmission connection with the upper side of the outer ring platform 4. A drill bit connecting groove 18 is provided on the inner side of the lower end of the transmission shaft 1.

[0022] According to the needs, in order to facilitate the connection between the transmission shaft 1 and the power output end of the screw drill, a thread is provided on the outer side of the upper end of the transmission shaft 1; in order to facilitate the disassembly and replacement of the drill bit, a thread can be provided on the inner side of the drill bit connection groove 18; the transmission connection between the outer cylinder 2 and the clutch assembly, which can rotate and move up and down relatively, can be a square shaft transmission, a hexagonal shaft transmission, a guide flat key or a spline transmission in the prior art; the transmission connection between the lower end of the clutch assembly and the outer ring platform 4 can be a friction clutch transmission, a tooth clutch transmission or a gear clutch transmission in the prior art; the clutch state between the lower end of the clutch assembly and the outer ring platform 4 can be achieved by applying drilling fluids of different pressures on the upper and lower sides of the clutch assembly. When high-pressure drilling fluid is applied to the upper side of the clutch assembly, the clutch assembly moves downward and is engaged with the outer ring platform 4. The outer ring platform 4 is connected to the clutch assembly for transmission, and then the outer cylinder 2 will apply additional torque to the transmission shaft 1, so that the transmission shaft 1 rotates with the outer cylinder 2. When high-pressure drilling fluid is applied to the lower part of the clutch assembly, the clutch assembly is separated from the outer ring platform 4, and the transmission shaft 1 can only be subjected to the torque directly transmitted by the screw drill. The separation state between the lower end of the clutch assembly and the outer ring platform 4 can also be achieved by setting an elastic component on the clutch assembly, and then separating the clutch assembly from the outer ring platform 4 through the restoring force of the elastic component. Considering that the separation speed of the clutch assembly and the outer ring platform 4 in the present invention does not affect the normal operation of the drill bit, in order to reduce hydraulic pipelines and control valves to save costs, the separation of the separation assembly and the outer ring platform 4 is achieved by setting an elastic component on the separation assembly.

[0023] During use, the upper end of the transmission shaft 1 can be first fixedly installed together with the power output shaft of the screw drill, and then the lower end of the transmission shaft 1 can be connected to the upper end of the drill bit, so that the power output of the screw drill can be directly transmitted to the drill bit, so that the drill bit can perform normal rock breaking work. At this time, the drilling fluid (low-pressure drilling fluid) will flow to the drill bit through the axial flow channel of the transmission shaft 1; the outer cylinder 2 and the outer shell of the screw drill are fixedly installed together, so that the outer cylinder 2 can drive the clutch assembly to rotate synchronously, and the drilling fluid (low-pressure drilling fluid) will flow from the screw drill into the outer cylinder 2, but at this time the drilling fluid pressure is balanced with the elastic force of the elastic component on the clutch assembly, and the clutch assembly and the outer ring 4 on the transmission shaft 1 are in a separated state, and will not rotate with the transmission shaft 1 nor move up and down relative to the transmission shaft 1; when the drill bit is stuck The hysteresis first increases the drilling fluid pressure from the wellhead (so that the drilling fluid pump pumps out high-pressure drilling fluid) and then increases the liquid inlet pressure in the upper cavity of the clutch assembly. The high-pressure drilling fluid will push the clutch assembly to compress the elastic component and connect its lower end to the upper side of the outer ring platform 4 through transmission. Finally, the outer cylinder 2 drives the transmission shaft 1 to rotate together through the clutch assembly to release the stuck state of the drill bit. When the drill bit can work normally again, the drilling fluid pressure at the wellhead is reduced (the drilling fluid pump is adjusted back to normal working state), so that the pressure on the upper side of the clutch assembly is slowly reduced. The elastic component slowly pushes the clutch assembly upward to the equilibrium position through its restoring force. In this process, the excess drilling fluid in the upper cavity of the clutch assembly can be fed into the axial flow channel in the transmission shaft 1 through the pressure relief hole 3 to supply the drill bit, thereby avoiding the inability of the clutch assembly to be reset due to pressure buildup. The present invention has a reasonable and compact structure and is easy to use. When the torque of the downhole drill bit is insufficient, the torque is transmitted to the drill bit through the outer cylinder 2 to release the stuck state of the drill bit. When the downhole drill bit is in a normal working state, the drill bit is driven to rotate and drill through the transmission shaft 1, which has a positive effect on reducing friction, reducing torque loss and avoiding pressure build-up in the screw drill.

[0024] The above-mentioned downhole hydraulic clutch device can be further optimized and / or improved according to actual needs:

[0025] As attached Figure 1 , 2As shown in Figures 3 and 4, the clutch assembly includes a spring 5, a spring plug 6 and a clutch shaft 7 with an axial channel. The clutch shaft 7 is sleeved on the outer side of the lower part of the transmission shaft 1, and a transmission ring stage is provided on the upper end of the clutch shaft 7. The outer side of the transmission ring stage is transmission-connected to the inner side of the lower part of the outer cylinder 2, and the transmission ring stage can move up and down relative to the outer cylinder 2; a spring plug 6 sleeved on the outer side of the clutch shaft 7 is fixedly installed on the inner side of the lower end of the outer cylinder 2, and a spring 5 is sleeved on the transmission shaft 1 at a position corresponding to the upper side of the spring plug 6 and the lower side of the transmission ring stage; at least two transmission cams 10 are evenly distributed along the circumference of the lower end of the clutch shaft 7, and a transmission groove 11 with a shape matching the transmission cam 10 is provided on the upper side of the outer ring stage 4 corresponding to the position of each transmission cam 10. According to the requirements, the transmission connection between the outer cylinder 2 and the transmission ring table can be a square shaft transmission, a hexagonal shaft transmission, a guide flat key or a spline transmission in the prior art; the spring 5 can be a compression spring, a combined compression spring or a disc spring combination in the prior art, and a compression spring is used in this embodiment; to facilitate the disassembly and assembly of the spring plug 6, the spring plug 6 and the outer cylinder 2 can be connected by a thread, and a hexagonal or square wrench table can be provided on the outer side of the lower end of the spring plug 6.

[0026] During use, when low-pressure drilling fluid is passed into the cavity on the upper side of the clutch shaft 7, the low-pressure drilling fluid will push the clutch shaft 7 downward to compress the spring 5, but at this time the pressure exerted downward by the drilling fluid is equal to the restoring force of the spring 5, so that the clutch shaft 7 is in a balanced state and the transmission convex tooth 10 at its lower end and the transmission groove 11 on the upper side of the outer ring platform 4 are in a separated state; when high-pressure drilling fluid is passed into the cavity on the upper side of the clutch shaft 7, the high-pressure drilling fluid will further push the clutch shaft 7 to compress the spring 5, and finally the transmission convex tooth 10 will be inserted into the corresponding transmission groove 11, so that the torque on the outer cylinder 2 is transmitted to the transmission shaft 1 through the clutch shaft 7. and the drill bit, thereby breaking the stuck state and restoring normal operation of the drill bit; when the drill bit resumes normal production, the liquid inlet pressure in the upper cavity of the clutch shaft 7 is restored to normal working state (low pressure state) to reduce the pressure in the upper cavity of the clutch shaft 7. At this time, under the action of the spring restoring force, the spring 5 pushes the clutch shaft 7 upward to separate from the outer ring platform 4. The clutch shaft 7 will compress the low-pressure drilling fluid during the upward movement, and the compressed low-pressure drilling fluid can flow into the axial flow channel in the transmission shaft 1 through the pressure relief hole 3 and flow toward the drill bit. Finally, the clutch shaft 7 will restore the equilibrium state again until the drill bit is stuck again and repeat the above action.

[0027] As attached Figure 1 , 3 As shown in 4, an external spline 8 is provided on the outer side of the transmission ring, and an internal spline 9 meshing with the external spline 8 is provided on the inner side of the lower part of the outer cylinder 2, and the lower end of the external spline 8 is located below the upper end of the internal spline 9.

[0028] During use, through the arrangement of the external spline 8 and the internal spline 9, the clutch shaft 7 can rotate synchronously with the outer cylinder 2 (that is, the torque on the outer cylinder 2 is transmitted to the clutch shaft 7), and the clutch shaft 7 can also move up and down relative to the outer cylinder 2. The spline transmission has the characteristics of smooth transmission, high load-bearing capacity, good centering and good guiding.

[0029] As attached Figure 1 As shown, the clutch assembly also includes a piston 12, and the upper end of the clutch shaft 7 is fixedly mounted with the piston 12 sleeved on the outer side of the transmission shaft 1. By such an arrangement, leakage of high-pressure drilling fluid from the spline connection gap can be reduced, and work efficiency can be improved; in addition, processing the piston 12 and the clutch shaft 7 separately can reduce processing difficulty, reduce processing procedures, and save processing costs.

[0030] As attached Figure 1 As shown, the clutch assembly further includes a first sealing ring 16 and a second sealing ring 17, at least one first sealing ring 16 is provided between the piston 12 and the outer cylinder 2, and at least one second sealing ring 17 is provided between the piston 12 and the transmission shaft 1. By such an arrangement, when the high-pressure drilling fluid flows into the upper cavity of the piston 12, leakage of the high-pressure drilling fluid from the gap between the piston 12 and the outer cylinder 2 and the transmission shaft 1 can be reduced, thereby improving the working efficiency of the clutch assembly.

[0031] As attached Figure 1 As shown, it also includes a filter screen 13, and at least one connecting hole 14 that penetrates inside and outside is provided along the circumference of the outer cylinder 2 corresponding to the lower position of the clutch assembly, and a filter screen 13 is fixedly installed on the inner side of the outer end of each connecting hole 14. According to the requirements, the fixing method of the filter screen 13 and the outer cylinder 2 can be welding, threaded connection or fixing through a hole clamping spring. In this embodiment, a filter screen installation groove and a clamping spring groove are provided on the inner side of the outer end of each connecting hole 14, and then the filter screen 13 is fixed in the filter screen installation groove through a hole clamping spring 19. This is mainly because the filter screen 13 uses a steel wire mesh in the prior art at a lower cost, and the hole clamping spring 19 is easy to disassemble and assemble or the standard part procurement cost is low. During use, when the piston 12 pushes the clutch shaft 7 downward to compress the spring 5, the liquid in the cavity of the spring 5 can quickly flow out through the connecting hole 14, reducing the resistance of pushing the clutch shaft 7; the filter screen 13 can prevent large particles of impurities in the well from entering the spring cavity, preventing large particles of impurities from hindering the normal operation of the spring 5.

[0032] As attached Figure 1As shown, it also includes a conversion joint 15 with an axial channel, and the conversion joint 15 which is sleeved on the upper part of the transmission shaft 1 is fixedly installed on the inner side of the upper end of the outer cylinder 2. According to the needs, a square or hexagonal wrench stand can also be provided on the outer side of the middle part of the conversion joint 15, so as to facilitate the connection of the present invention with the screw drill by a wrench; the inner diameter of the axial channel of the conversion joint 15 should be larger than the outer diameter of the transmission shaft 1, so that the drilling fluid can flow into the outer cylinder 2 through the annulus between the conversion joint 15 and the transmission shaft 1. Through such a setting, it is convenient for the outer cylinder 2 to be directly connected to the screw drill housing through the conversion joint 15, avoiding the modification of the screw drill housing, thereby saving the cost of improving other parts.

[0033] The above technical features constitute the best embodiment of the present invention, which has strong adaptability and best implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A downhole hydraulic clutch device, characterized in that The invention comprises a transmission shaft with an axial flow channel, a clutch assembly and an outer cylinder. The clutch assembly is sleeved on the outer side of the lower part of the transmission shaft. The outer side of the clutch assembly is transmission-connected with the outer cylinder with the upper end located below the transmission shaft, and the clutch assembly can move up and down relative to the outer cylinder. At least one pressure relief hole that penetrates inside and outside is arranged along the circumference of the transmission shaft corresponding to the upper position of the clutch assembly. An outer ring platform is arranged on the outer side of the lower end of the transmission shaft corresponding to the lower position of the outer cylinder. The lower end of the clutch assembly can form a transmission connection with the upper side of the outer ring platform, and a drill bit connection groove is arranged on the inner side of the lower end of the transmission shaft. The clutch assembly comprises a spring, a spring plug, a piston and a clutch shaft with an axial channel. The clutch shaft is sleeved on the outer side of the lower part of the transmission shaft. The upper end of the clutch shaft is provided with a transmission Ring platform, the outer side of the transmission ring platform is connected to the inner side of the lower part of the outer cylinder, and the transmission ring platform can move up and down relative to the outer cylinder; a spring plug is fixedly installed on the inner side of the lower end of the outer cylinder and is sleeved on the outer side of the clutch shaft, and a spring is sleeved on the transmission shaft at the position between the upper side of the spring plug and the lower side of the transmission ring platform; a piston is fixedly installed on the upper end of the clutch shaft and is sleeved on the outer side of the transmission shaft; at least two transmission convex teeth are evenly distributed along the circumference of the lower end of the clutch shaft, and a transmission groove with a matching shape is provided on the upper side of the outer ring platform corresponding to each transmission convex tooth position; at least one connecting hole that passes through inside and outside is provided along the circumference of the outer cylinder corresponding to the lower position of the clutch assembly, and a filter is fixedly installed on the inner side of the outer end of each connecting hole; During use, the upper end of the transmission shaft is first fixedly installed with the power output shaft of the screw drill, and then the lower end of the transmission shaft is connected to the upper end of the drill bit, and the power output of the screw drill is directly transmitted to the drill bit, so that the drill bit can perform normal rock breaking work. At this time, the low-pressure drilling fluid flows to the drill bit through the axial flow channel of the transmission shaft; the outer cylinder is fixedly installed with the outer shell of the screw drill, so that the outer cylinder can drive the clutch shaft to rotate synchronously. At this time, the drilling fluid can flow from the screw drill into the outer cylinder through the pressure relief hole on the transmission shaft; when low-pressure drilling fluid is passed into the cavity on the upper side of the clutch shaft, the low-pressure drilling fluid will push the clutch shaft compression spring downward, but at this time the downward pressure exerted by the drilling fluid is equal to the spring restoring force, so that the clutch shaft is in a balanced state, and the transmission convex teeth at its lower end and the transmission grooves on the upper side of the outer ring platform are When the clutch shaft is in a separated state, the high-pressure drilling fluid will further push the clutch shaft compression spring to insert the transmission convex teeth into the corresponding transmission grooves, so that the torque on the outer cylinder is transmitted to the transmission shaft and the drill bit through the clutch shaft, so that the drill bit breaks the stuck state and resumes normal operation. When the drill bit resumes normal operation, the liquid inlet pressure in the cavity on the upper side of the clutch shaft is restored to a low-pressure state, reducing the pressure in the cavity on the upper side of the clutch shaft. At this time, under the action of the spring restoring force, the spring pushes the clutch shaft upward to separate from the outer ring platform. The clutch shaft compresses the low-pressure drilling fluid during its upward movement. The compressed low-pressure drilling fluid flows into the axial flow channel in the transmission shaft through the pressure relief hole and flows toward the drill bit. The clutch shaft resumes a balanced state again until the drill bit is stuck again and the above action is repeated.

2. The downhole hydraulic clutch device according to claim 1, characterized in that An external spline is arranged on the outer side of the transmission ring platform, an internal spline meshing with the external spline is arranged on the inner side of the lower part of the outer cylinder, and the lower end of the external spline is located below the upper end of the internal spline.

3. The downhole hydraulic clutch device according to claim 1 or 2, characterized in that The clutch assembly also includes a first sealing ring and a second sealing ring. At least one first sealing ring is spaced apart from top to bottom between the piston and the outer tube, and at least one second sealing ring is spaced apart from top to bottom between the piston and the transmission shaft.

4. The downhole hydraulic clutch device according to claim 1 or 2, characterized in that It also includes a conversion joint with an axial channel. The inner side of the upper end of the outer cylinder is fixedly installed with a conversion joint sleeved on the upper part of the transmission shaft.

5. The downhole hydraulic clutch device according to claim 3, characterized in that It also includes a conversion joint with an axial channel. The inner side of the upper end of the outer cylinder is fixedly installed with a conversion joint sleeved on the upper part of the transmission shaft.

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