Long-core-pipe anti-twist and anti-strain structure multi-stage hydraulic cylinder

Abstract

The application discloses a long-core-pipe anti-twisting and anti-strain structure multistage hydraulic cylinder, which comprises an outer cylinder, a middle cylinder, a piston rod, a middle piston, a middle spacer sleeve, a middle guide sleeve, a core pipe assembly, an inner piston, a piston rod gland and a piston rod guide sleeve. The middle cylinder is slidably arranged in the outer cylinder through the middle piston, the middle spacer sleeve and the middle guide sleeve. The piston rod is slidably arranged in the middle cylinder through the inner piston, the piston rod gland and the piston rod guide sleeve. The core pipe assembly is arranged between the piston rod and the middle cylinder and is used for guiding the piston rod. The multistage hydraulic cylinder adopts a core pipe oil feeding mode, can realize built-in oil passage, avoids external pipe arrangement and reduces the occurrence of knocking and oil leakage. A plurality of guide structures are arranged through the core pipe, the guiding capacity is effectively increased, the strain of the inner wall of the core pipe and the piston rod caused by the flexural deformation of the slender core pipe is avoided, the reliability and stability of the oil cylinder are improved, and the service life of the oil cylinder is prolonged.

Description

Technical Field

[0001] This invention relates to a multi-stage hydraulic cylinder, specifically a multi-stage hydraulic cylinder with a long core tube structure to prevent torsion and tension damage. Background Technology

[0002] With the development of automation and intelligent technology in oil drilling rigs, higher requirements have been placed on the reliability, stability, and sophistication of hydraulic cylinders, especially the lifting hydraulic cylinders used for raising and lowering the derrick and base. Lifting cylinders are characterized by short installation distances and long strokes, requiring high reliability and stability. The oil passage in the rod chamber is typically installed on the lug at the end of the smallest piston rod, and oil is then passed through small holes machined into the inner cylinder wall. Cleaning the burrs in these holes is difficult and can easily scratch the seal, leading to internal leakage. The outer side is connected to the system via hydraulic hoses, which move with the piston rod as it extends and retracts. These hoses are prone to scratches and impacts, causing oil leaks and affecting the normal operation of the hydraulic cylinder.

[0003] Existing multi-stage lifting cylinders for oil drilling rigs generally employ solutions such as connecting the piston rod end with a hydraulic hose, machining small oil passage holes in the cylinder wall of the sleeve, or machining extra-long holes in the inner bore of the intermediate cylinder. Additionally, some multi-stage hydraulic cylinders used in other equipment also employ a core tube return structure; however, the connection between the core tube and the inner bore of the piston rod is only supported by the first guide sleeve at the small end of the piston rod, which serves to prevent communication between the two hydraulic cylinder chambers. The core tube is typically in a cantilevered, drooping state.

[0004] In general, the rod chamber oil passages of lifting hydraulic cylinders are installed on the lugs at the end of the smallest stage piston rod. Oil passages in each stage of the cylinder's rod chamber are accessed through small oil passages machined into the inner cylinder wall. Cleaning these small holes is difficult, as they can easily scratch the seals and cause internal leakage. The outer side is connected to the system via hydraulic hoses. These hoses move with the piston rod as it extends and retracts, making them susceptible to scratches and impacts that can damage them and cause oil leaks, affecting the normal operation of the hydraulic cylinder.

[0005] Some multi-stage cylinders have rod chamber oil passages with extra-long oil passages machined on the cylinder wall of the intermediate piston rod. Machining these oil passages is difficult, and cleaning the inner hole is challenging. When subjected to impact loads, the cylinder wall is prone to deformation, posing a risk of bursting. This type of hydraulic cylinder requires increased cylinder wall thickness, resulting in low material utilization and high manufacturing costs.

[0006] Multi-stage cylinders with core tube structure are also used in engineering machinery such as oil drilling rigs. The core tube and the inner hole of the piston rod are only connected by the first guide sleeve of the small end of the piston rod to support the core tube and block the communication between the two hydraulic cylinders. The core tube is usually a cantilever structure. Due to its own weight, the core tube sags and bends and rubs against the inner hole of the piston rod, producing iron pins that cause internal leakage. After being subjected to pressure impact, the core tube may even twist, which poses a safety hazard. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a multi-stage hydraulic cylinder with a long core tube anti-torsion and anti-tear structure. By using an oil-passing method through the core tube, the oil circuit can be built-in, avoiding external piping and reducing the occurrence of oil leakage due to impact. By arranging multiple sets of guiding structures on the core tube, namely the core tube guiding support is "guide sleeve-floating support guide-sleeve guide", the guiding capacity is effectively increased, avoiding tearing of the core tube and piston rod inner wall caused by the bending deformation of the slender core tube.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: a multi-stage hydraulic cylinder with a long core tube anti-torsion and anti-tension structure, comprising: an outer cylinder, an intermediate cylinder, a piston rod, an intermediate piston, an intermediate spacer sleeve, an intermediate guide sleeve, a core tube assembly, an inner piston, a piston rod cap, and a piston rod guide sleeve. The intermediate cylinder is slidably mounted in the outer cylinder through the intermediate piston, the intermediate spacer sleeve, and the intermediate guide sleeve. The piston rod is slidably mounted in the intermediate cylinder through the inner piston, the piston rod cap, and the piston rod guide sleeve. The core tube assembly is disposed between the piston rod and the intermediate cylinder and is used for guiding the piston rod.

[0009] Furthermore, the cavity inside the outer cylinder is divided into an outer rod chamber and an outer rodless chamber by an intermediate piston. The outer rod chamber has a rod port on its wall, and the outer rodless chamber has a rodless port on its wall. The rod port and the rodless port are located on both sides of the maximum sliding range of the intermediate piston. A hydraulic valve assembly is provided outside the outer cylinder and is connected to the rod port and the rodless port on the outer cylinder through a rigid pipe.

[0010] Furthermore, one end of the intermediate cylinder is provided with an intermediate end cap, and the piston rod with an internal piston is slidably disposed in the intermediate cavity formed by the intermediate cylinder and the intermediate end cap. The intermediate cavity is divided into an intermediate rod cavity and an intermediate rodless cavity by the internal piston. One end of the core tube assembly is fixed on the intermediate end cap on one side of the intermediate cavity, and the other end is slidably installed together with the piston rod.

[0011] Furthermore, the intermediate end cap is provided with an oil passage that connects the outer rodless chamber and the intermediate rodless chamber, and the intermediate piston and the intermediate end cap are provided with an oil passage for connecting the outer rod chamber and the core tube assembly.

[0012] Furthermore, the piston rod includes: a rod end, a cylinder, and an ear ring cover plate. The rod end is connected to the ear ring cover plate through the cylinder to form a piston rod. The internal piston is fitted on the outer ring of the rod end. The rod end and the center of the cylinder are provided with a through hole for installing the core tube assembly. The side wall of the rod end is provided with an oil passage for the intermediate cavity, the cylinder through hole, and the rod end through hole to communicate with each other.

[0013] Furthermore, the internal piston is provided with oil-conducting bushings at both ends.

[0014] Furthermore, the earring cover plate is provided with an air passage for connecting the tube body through hole to the outside air, and an exhaust pressure test connector is installed on the air passage.

[0015] Furthermore, the core tube assembly is installed in the piston rod via a first core tube guide sleeve, a second core tube guide sleeve, a spacer sleeve, a floating guide sleeve baffle, a core tube guide sleeve, a right end support plate, a middle support plate, a left end support plate, and a non-metallic guide ring. The first core tube guide sleeve is installed at the end of the rod's small end through hole near the middle end cap. The second core tube guide sleeve is located at the end of the rod's small end through hole away from the middle end cap via the floating guide sleeve baffle. The spacer sleeve is located in the through hole between the first and second core tube guide sleeves. The left and right ends of the core tube guide sleeve are installed in the through holes in the cylinder via the left and right end support plates, respectively. The middle support plate is located on the core tube guide sleeve between the right and left end support plates.

[0016] Furthermore, a static seal and a dynamic seal are provided between the first guide sleeve of the core tube and the core tube assembly.

[0017] Furthermore, the core tube assembly includes a core tube flange and a sliding core tube. The sliding core tube is mounted on the intermediate end cap via the core tube flange, and the core tube flange is provided with an oil passage for communication between the external rod chamber and the sliding core tube.

[0018] Furthermore, an exhaust pressure test connector is also provided on the side wall of the outer cylinder.

[0019] The beneficial effects of this invention are: by using the core tube for oil passage, the oil circuit can be built-in, avoiding external pipe laying and reducing the occurrence of oil leakage due to impact; by arranging multiple sets of guiding structures on the core tube, namely the core tube guiding support is "guide sleeve-floating support guide-sleeve guide", the guiding capacity is effectively increased, avoiding the scratches on the inner wall of the core tube and piston rod caused by the bending deformation of the slender core tube, improving the reliability and stability of the oil cylinder, and thus increasing its service life. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention; In the diagram: 1. External cylinder barrel; 11. Rodless chamber oil port; 12. Rod chamber oil port; 13. Rigid pipe; 2. Intermediate cylinder; 21. Intermediate end cap; 22. Intermediate piston; 23. Intermediate spacer sleeve; 24. Intermediate guide sleeve; 25. Piston rod gland; 26. Piston rod guide sleeve; 3. Piston rod; 31. Small end of rod; 32. Cylinder body; 33. Ear ring cover plate; 34. First guide sleeve of core tube; 341. Static seal; 342. Dynamic seal; 35. Second guide sleeve of core tube; 36. Spacer sleeve; 37. Floating guide sleeve baffle; 38. Core tube guide sleeve; 391. Right end support plate; 392. Intermediate support plate; 393. Left end support plate; 394. Non-metallic guide ring; 4. Internal piston; 41. Oil passage spacer sleeve; 5. Core tube assembly; 51. Core tube flange; 52. Sliding core tube; 6. Exhaust pressure test connector; 7. Hydraulic valve assembly. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0023] like Figure 1 As shown, a multi-stage hydraulic cylinder with a long core tube anti-torsion and anti-tear structure includes: an outer cylinder 1, an intermediate cylinder 2, a piston rod 3, an intermediate piston 22, an intermediate spacer sleeve 23, an intermediate guide sleeve 24, a core tube assembly 5, an inner piston 4, a piston rod 3 cover 25, and a piston rod 3 guide sleeve 26. The intermediate cylinder 2 is slidably mounted in the outer cylinder 1 through the intermediate piston 22, the intermediate spacer sleeve 23, and the intermediate guide sleeve 24. The piston rod 3 is slidably mounted in the intermediate cylinder 2 through the inner piston 4, the piston rod 3 cover 25, and the piston rod 3 guide sleeve 26. The core tube assembly 5 is disposed between the piston rod 3 and the intermediate cylinder 2 and is used for guiding the piston rod 3.

[0024] The outer cylinder 1 is divided into an outer rod chamber and an outer rodless chamber by an intermediate piston 22. The outer rod chamber has a rod port 12 on its wall and a rodless chamber has a rodless port 11 on its wall. The rod port 12 and the rodless port 11 are located on both sides of the maximum sliding range of the intermediate piston 22. A hydraulic valve assembly 7 is provided outside the outer cylinder 1 and is connected to the rod port 12 and the rodless port 11 on the outer cylinder 1 through a rigid pipe 13. The ports of the hydraulic valve assembly 7 are connected to the main hydraulic system.

[0025] One end of the intermediate cylinder 2 is provided with an intermediate end cap 21. The piston rod 3, which is equipped with an internal piston 4, is slidably disposed in the intermediate cavity formed by the intermediate cylinder 2 and the intermediate end cap 21. The intermediate cavity is divided into an intermediate rod cavity and an intermediate rodless cavity by the internal piston 4. One end of the core tube assembly 5 is fixed on the intermediate end cap 21 on one side of the intermediate cavity, and the other end is slidably installed together with the piston rod 3.

[0026] The intermediate cylinder end cap is connected and fixed to the intermediate cylinder barrel 2 cylinder body 32 by ventilation screws. The interior is a closed structure and the exterior is sealed with an end cap.

[0027] The intermediate end cap 21 is provided with an oil passage that connects the outer rodless chamber and the intermediate rodless chamber. The intermediate piston 22 and the intermediate end cap 21 are provided with an oil passage for connecting the outer rod chamber and the core tube assembly 5.

[0028] The piston rod 3 includes: a small rod end 31, a cylinder 32, and an ear ring cover plate 33. The small rod end 31 is connected to the ear ring cover plate 33 through the cylinder 32 to form the piston rod 3. The internal piston 4 is fitted on the outer ring of the small rod end 31. The small rod end 31 and the cylinder 32 are provided with a through hole for installing the core tube assembly 5. The side wall of the small rod end 31 is provided with an oil passage for the intermediate cavity, the through hole of the cylinder 32, and the through hole of the small rod end 31 to communicate with each other.

[0029] The internal piston 4 has oil-conducting bushings 41 at both ends.

[0030] The earring cover plate 33 is provided with an air passage for connecting the through hole of the cylinder 32 to the outside air. An exhaust pressure test connector 6 is installed on the air passage. The exhaust pressure test connector 6 is connected to the earring cover plate 33 by threads for the exhaust of gas inside the cavity.

[0031] The core tube assembly 5 is installed in the piston rod 3 via a first core tube guide sleeve 34, a second core tube guide sleeve 35, a spacer sleeve 36, a floating guide sleeve baffle 37, a core tube guide sleeve 38, a right end support plate 391, a middle support plate 392, a left end support plate 393, and a non-metallic guide ring 394. The first core tube guide sleeve 34 is installed at the end of the rod small end 31 near the middle end cap 21 through the through hole. The second core tube guide sleeve 35 is located at the end of the rod small end 31 away from the middle end cap 21 through the floating guide sleeve baffle 37. The spacer sleeve 36 is located in the through hole between the first core tube guide sleeve 34 and the second core tube guide sleeve 35. The left and right ends of the core tube guide sleeve 38 are installed in the through holes in the cylinder 32 through the left end support plate 393 and the right end support plate 391, respectively. The middle support plate 392 is located on the core tube guide sleeve 38 between the right end support plate 391 and the left end support plate 393.

[0032] The end of the core tube assembly 5 away from the intermediate end cap 21 is provided with a non-metallic support ring and the core tube guide sleeve 38.

[0033] A static seal 341 and a dynamic seal 342 are provided between the first guide sleeve 34 of the core tube and the core tube assembly 5.

[0034] The first guide sleeve 34 of the core tube is installed on the left end of the small end 31 of the rod by thread. The first guide sleeve 34 of the core tube is statically sealed 341 on the outside and is dynamically sealed 342 on the inside to isolate the hydraulic cylinder oil in the two chambers. The first guide sleeve 34 of the core tube itself is made of ductile iron as the guide ring of the core tube assembly 5.

[0035] The right end of the first guide sleeve 34 of the core tube is increased by multiple spacers to increase the guiding length between the first guide sleeve 34 and the second guide ring of the core tube. The second guide sleeve 35 of the core tube is embedded in the inner hole of the small end 31 of the rod by the pressure of the floating guide sleeve baffle 37 and the left end of the first guide sleeve 34 and the spacer sleeve 36. The inner side of the second guide sleeve 35 of the core tube is left with a gap from the core tube assembly 5, which plays a floating support and guiding role. The non-metallic guide ring 394 is made of non-metallic material. The open structure of the inner hole is embedded in the groove at the right end of the core tube assembly 5, and the outer circle is in contact with the core tube guide sleeve 38 and slides relative to it. Under the support and guidance of the three sets of guiding structures of the first guide sleeve 34, the second guide sleeve 35 and the non-metallic guide ring 394, the core tube assembly 5 is guaranteed to slide relative to the core tube guide sleeve 38 and prevent the core tube assembly 5 from bending and deforming due to its own weight.

[0036] The core tube guide sleeve 38 is fixed to the inner hole of the piston rod 3 by three sets of support plates: right end support plate 391, middle support plate 392, and left end support plate 393. The three sets of support plates are welded and fixed to the core tube guide sleeve 38. The outer ends of the right end support plate 391 and the left end support plate 393 are connected to the stop of the piston rod 3. The inner step is fixed and the outer side is welded to prevent the core tube guide sleeve 38 from twisting and deforming due to pressure impact.

[0037] The core tube assembly 5 includes a core tube flange 51 and a sliding core tube 52. The sliding core tube 52 is mounted on the intermediate end cover 21 through the core tube flange 51. The core tube flange 51 is provided with an oil passage for communication between the external rod chamber and the sliding core tube 52.

[0038] In the core tube assembly 5, the core tube flange 51 is connected to the intermediate cylinder end cover by screws. The core tube flange 51 is welded together with the sliding core tube 52. A seal is provided between the core tube flange 51 and the intermediate end cover 21 to seal the hydraulic oil passages on the left and right sides of the core tube flange 51.

[0039] The outer cylinder 1 is also provided with an exhaust pressure test connector 6 on its side wall. The two ends of the outer cylinder 1 are connected to the cylinder exhaust pressure test connector 6 by threads for the discharge of gas in the cavity.

[0040] The return oil circuit is constructed by a rigid pipe 13 connected to the external rod chamber, which in turn connects to the external rod chamber, the oil passage of the intermediate piston 22, the intermediate cylinder bore, the oil passage of the intermediate end cap 21, the core tube flange 51, the sliding core tube 52, the inner cavity of the piston rod 3 cylinder 32, the oil passage of the piston rod 3 rod small end 31, the oil passage of the oil diaphragm 41, and the rod chamber of the intermediate cylinder. The inlet oil circuit is constructed by a rigid pipe 13 connected to the external rodless chamber, which in turn connects to the external rodless chamber, the oil passage of the intermediate end cap 21, and the rodless chamber of the intermediate cylinder 2. This design makes the return oil circuit more reasonable and compact, avoiding the problem of oil leakage due to bumping or contact with the non-fixed oil passage of the piston rod 3.

[0041] Working principle and implementation scheme: Double rod structure. The outer cylinder 1 is fixed to the structural component. When extended: after oil is introduced through the oil port 12 of the rod chamber on the outer cylinder body, it enters the outer rodless chamber of the outer cylinder 1, pushing out the middle cylinder 2. At the same time, the oil enters the rodless chamber of the middle cylinder 2 through the oil passage on the middle end cap 21. The piston rod 3 is pushed out under the guidance of the inner piston 4 and the core tube assembly 5. When the piston rod 3 is pushed out: the oil in the middle rod chamber of the middle cylinder 2 enters the piston rod 3 cylinder 32 through the oil passage of the oil diaphragm 41 and the rod small end 31. The oil in the piston rod 3 cylinder 32 then flows out from the oil port 12 of the rod chamber of the outer cylinder 1 through the oil passage of the core tube assembly 5, the oil passage of the middle end cap 21, the oil passage of the middle piston 22, and the outer rod chamber. When retracted, the oil flow direction is opposite to that when extended.

[0042] The oil passages of the intermediate cylinder 2 and the core tube assembly 5 are easily manufactured and detachable, facilitating processing and maintenance. A right-end support plate 391, an intermediate support plate 392, and a left-end support plate 393 are installed on the core tube guide sleeve 38 and fixed by welding. Oil holes are opened on the support plates to ensure interconnection of the internal oil passages of the piston rod 3. The inner circle of the support plate is machined based on the outer circle of the core tube guide sleeve 38, and the outer circle of the support plate is interference-fitted into the stop mouths at both ends of the piston rod 3, ensuring the coaxiality of the inner hole of the core tube guide sleeve 38 and the outer circle of the piston rod 3. The end support plate 391 and the left end support plate 393 are welded and fixed to the piston rod 3. The middle support plate 392 does not contact the inner wall of the piston rod 3 to prevent the core tube guide sleeve 38 and the core tube from being twisted and bent due to internal oil pressure. One end of the core tube assembly 5 is fixed to the middle end cover 21. It slides relative to the core tube guide sleeve 38 inside the piston rod 3 through three sets of guide systems to jointly support the reliability of the core tube operation. The three sets of guide systems are the first core tube guide sleeve 34 located at the outer end of the small end 31 of the piston rod 3, the second core tube guide sleeve 35, and the non-metallic guide sleeve 36. It is a support ring; the small end 31 of the rod is provided with a mating stop and threads. The first guide sleeve 34 of the core tube is connected to the outer end of the small end 31 of the piston rod 3 by a screw. The inner hole of the first guide sleeve moves relative to the core tube assembly 5 to provide support and guidance. The dynamic seal 342 of the first guide sleeve 34 of the core tube has the function of blocking the oil passage of the rodless cavity and the rod cavity. The floating guide sleeve baffle 37 is made of metal support material. Its outer circle is embedded in the stop of the small end 31 of the rod. The guide distance between it and the first guide sleeve is increased by multiple spacer sleeves 36 to improve the guide length. The floating guide sleeve baffle 37 and the core tube assembly 5 are connected by threads. The tube assembly 5 moves relative to the sliding core tube 52 through a clearance tolerance fit, which serves to assist in supporting the floating guide sleeve baffle 37. The non-metallic support ring is an open structure embedded in the groove at the end of the sliding core tube 52. The outer circle of the non-metallic support ring moves relative to the inner hole of the core tube guide sleeve 38 with a relative tolerance fit, supporting the end of the sliding core tube 52 and preventing the sliding core tube 52 from bending due to its own weight and cantilever drooping. This solves the problem of scratching caused by the contact between the right end of the core tube and the inner wall of the piston rod 3, ensuring the smooth flow of the multi-stage cylinder oil circuit and the stability of its working performance under lifting conditions.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-stage hydraulic cylinder with a long core tube anti-torsion and anti-tension structure, characterized in that, include: The system comprises an outer cylinder, an intermediate cylinder, a piston rod, an intermediate piston, an intermediate spacer sleeve, an intermediate guide sleeve, a core tube assembly, an inner piston, a piston rod cap, and a piston rod guide sleeve. The intermediate cylinder is slidably mounted in the outer cylinder via the intermediate piston, the intermediate spacer sleeve, and the intermediate guide sleeve. The piston rod is slidably mounted in the intermediate cylinder via the inner piston, the piston rod cap, and the piston rod guide sleeve. The core tube assembly is disposed between the piston rod and the intermediate cylinder and serves to guide the piston rod. The intermediate cylinder is provided with an intermediate end cap at one end. The piston rod with an internal piston is slidably disposed in the intermediate cavity formed by the intermediate cylinder and the intermediate end cap. The intermediate cavity is divided into an intermediate rod cavity and an intermediate rodless cavity by the internal piston. One end of the core tube assembly is fixed on the intermediate end cap on one side of the intermediate cavity, and the other end is slidably installed together with the piston rod. The intermediate end cap is provided with an oil passage that connects the outer rodless chamber and the intermediate rodless chamber, and the intermediate piston and the intermediate end cap are provided with an oil passage for connecting the outer rod chamber and the core tube assembly. The piston rod includes: a rod end, a cylinder, and an ear ring cover plate. The rod end is connected to the ear ring cover plate through the cylinder to form the piston rod. The internal piston is fitted on the outer ring of the rod end. The rod end and the cylinder are provided with a through hole for installing the core tube assembly. The side wall of the rod end is provided with an oil passage for the intermediate cavity, the cylinder through hole, and the rod end through hole to communicate with each other. The core tube assembly is installed in the piston rod via a first core tube guide sleeve, a second core tube guide sleeve, a spacer sleeve, a floating guide sleeve baffle, a core tube guide sleeve, a right end support plate, a middle support plate, a left end support plate, and a non-metallic guide ring. The first core tube guide sleeve is installed at the end of the rod's small end through hole near the middle end cap. The second core tube guide sleeve is located at the end of the rod's small end through hole away from the middle end cap via the floating guide sleeve baffle. The spacer sleeve is located in the through hole between the first and second core tube guide sleeves. The left and right ends of the core tube guide sleeve are installed in the through holes in the cylinder via the left and right end support plates, respectively. The middle support plate is located on the core tube guide sleeve between the right and left end support plates. The non-metallic guide ring is embedded in the end of the core tube assembly, and the outer circle of the non-metallic guide ring slides relative to the core tube guide sleeve.

2. The multi-stage hydraulic cylinder with a long core tube anti-torsion and anti-tension structure according to claim 1, characterized in that, The outer cylinder is divided into an outer rod chamber and an outer rodless chamber by an intermediate piston. The outer rod chamber has a rod port on its wall, and the outer rodless chamber has a rodless port on its wall. The rod port and the rodless port are located on both sides of the maximum sliding range of the intermediate piston. A hydraulic valve assembly is located outside the outer cylinder and is connected to the rod port and the rodless port on the outer cylinder through a rigid pipe.

3. The multi-stage hydraulic cylinder with a long core tube anti-torsion and anti-tension structure according to claim 1, characterized in that, The internal piston is equipped with oil-permeable sleeves at both ends.

4. A multi-stage hydraulic cylinder with a long core tube anti-torsion and anti-tension structure according to claim 1, characterized in that, The earring cover plate is provided with an air passage for connecting the tube body through hole to the outside air, and an exhaust pressure test connector is installed on the air passage.

5. A multi-stage hydraulic cylinder with a long core tube anti-torsion and anti-tension structure according to claim 1, characterized in that, The first guide sleeve of the core tube and the core tube assembly are provided with a static seal and a dynamic seal.

6. A multi-stage hydraulic cylinder with a long core tube anti-torsion and anti-tension structure according to claim 1, characterized in that, The core tube assembly includes a core tube flange and a sliding core tube. The sliding core tube is mounted on the intermediate end cover via the core tube flange. The core tube flange has an oil passage for communication between the external rod chamber and the sliding core tube.

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