Internal circulation pressure maintaining rotary oil cylinder

Abstract

The internal circulation pressure maintaining rotary oil cylinder comprises a piston pull pipe, a cylinder body is installed outside the piston pull pipe, a cover shell is installed at the rear end of the cylinder body, a backflow cavity is formed in the front end of the cylinder body, and a third installation groove opposite to a second installation groove is formed in the side wall of the other side of the backflow cavity; a valve is mounted in the third mounting groove and is mounted on the oil through hole; the valve is provided with a valve body, the valve body is installed in the third installation groove, a penetrating hole penetrating through the valve body is formed in the center of the valve body, a valve rod is arranged on the side, close to the oil inlet part, of the backflow cavity, one end of the valve rod penetrates through the second installation groove and is inserted into the first installation groove, and the other end of the valve rod is inserted into the penetrating hole. The bottom face of the end, close to the first steel ball, of the valve rod sinks inwards to form a spring clamping groove. The problem that when the hydraulic pressure in the oil cylinder is too large, the bearing limit of the oil cylinder and accessories (such as sealing pieces and pipelines) of the oil cylinder is possibly exceeded, and consequently the parts are damaged or invalid is solved.

Description

Technical Field

[0001] The invention relates to the field of rotary oil cylinders, and in particular to an internal circulation pressure-maintaining rotary oil cylinder. Background Art

[0002] At present, the existing rotary cylinder, also known as the hydraulic rotary cylinder, is a tightly assembled accessory that generates very high torque in a small space through hydraulic pressure and can achieve precise and easy control. The rotary cylinder is compactly designed to provide strong torque output in a limited space. Its key components include sealing devices and switch valves. Sealing devices such as sealing rings, sealing ring seats and sealing ring supports are used to prevent hydraulic oil leakage and maintain the sealing of the cylinder. The switch valve is used to control the inlet and outlet and flow rate of hydraulic oil, thereby controlling the movement speed and direction of the rotary cylinder. When the hydraulic pressure in the cylinder is too large, it may exceed the bearing limit of the cylinder and its accessories (such as seals, pipelines, etc.), causing these components to be damaged or fail. In particular, seals may leak due to excessive pressure, thereby affecting the sealing performance of the cylinder. Summary of the invention

[0003] In view of the above problems, the present invention proposes an internal circulation pressure-maintaining rotary oil cylinder, which solves the problem that when the hydraulic pressure in the existing oil cylinder is too high, it may exceed the bearing limit of the oil cylinder and its accessories (such as seals, pipelines, etc.), causing these components to be damaged or fail. In particular, the seals may leak due to excessive pressure, thereby affecting the sealing performance of the oil cylinder.

[0004] The technical solution adopted by the present invention is as follows:

[0005] An internal circulation pressure-maintaining rotary oil cylinder comprises: a piston pulling tube, a cylinder body is arranged outside the piston pulling tube, a cover shell is arranged at the rear end of the cylinder body, a reflux chamber is arranged at the front end of the cylinder body, an oil inlet portion is arranged at the bottom of the cover shell, an oil inlet chamber is arranged in the oil inlet portion, and the oil inlet chamber is connected to the reflux chamber through an oil through hole; an annular baffle is arranged at the front end of the piston pulling tube, the annular baffle is located at a side of the reflux chamber close to the oil inlet portion, a first mounting groove is arranged on the side wall of the lower side of the reflux chamber located at the front end of the cylinder body, a second mounting groove is arranged at a position corresponding to the first mounting groove on the annular baffle, and a third mounting groove arranged opposite to the second mounting groove is arranged on the side wall of the other side of the reflux chamber;

[0006] A valve is installed in the third mounting groove, and the valve is installed on the oil through hole; the valve has a valve body, and the valve body is installed in the third mounting groove. A through hole penetrating the valve body is provided in the center of the valve body, and an inner annular limiting flange is provided in the center of the valve body. A valve stem is provided on the side of the reflux chamber close to the oil inlet part, one end of the valve stem passes through the second mounting groove and is inserted into the first mounting groove, and the other end of the valve stem is inserted into the through hole. A first steel ball is installed in the valve body, and the bottom surface of the valve stem close to the first steel ball is recessed inward to form a spring groove, and a push rod spring is installed in the spring groove, and the end of the push rod spring abuts against the first steel ball, and the end of the spring groove is provided with a first outer limiting flange, and a valve seat is provided at one end of the valve body away from the annular baffle, and an inner groove is provided at one end of the valve seat close to the valve stem, and a protrusion is provided at the center of the inner groove. In the present invention, when the hydraulic oil is released through the switch valve, the pressure in the oil inlet is reduced and the rotation speed of the cylinder body is slowed down. This stage is used to control the speed and direction of rotation. The present invention realizes the control of oil flow through the coordinated action of the valve stem, the first steel ball, the push rod spring and the valve seat and other components, and by adjusting the position of the valve stem, the sealing state between the first steel ball and the valve seat can be controlled, thereby opening or closing the channel for oil circulation. It can adjust the hydraulic pressure difference between the reflux chamber and the oil inlet chamber, thereby preventing the oil inlet chamber from being too high, and avoiding the problem that the hydraulic pressure in the oil cylinder is too high and may exceed the bearing limit of the oil cylinder and its accessories (such as seals, pipelines, etc.), causing these components to be damaged or fail. The valve body of the present invention has a high sensitivity, a long pressure holding time, and an anti-sluggish reaction structure.

[0007] Optionally, the front end of the cylinder body is provided with a first sealing groove close to the front end and a second sealing groove close to the rear end; a first O-ring is provided in the first sealing groove, a second O-ring is provided in the first sealing groove, and the first sealing groove and the second sealing groove are both filled with sealing oil.

[0008] Optionally, the first O-ring has an elliptical cross-section.

[0009] Optionally, an annular groove is provided on the side wall of the second O-ring not in contact with the piston pull tube, and an annular V-groove is provided on the inner wall of the second O-ring in contact with the piston pull tube.

[0010] Optionally, the second O-ring contacts the inner wall of the piston pull tube at one end away from the first sealing groove, and the first slope is provided with a downwardly inclined end away from the first sealing groove, and the annular groove is provided with a second annular slope near the top of the first slope, and the second slope is provided with an upwardly inclined end away from the first sealing groove. The present invention enhances the sealing elasticity of the second O-ring by providing an annular groove and a V-shaped groove to form a pair of deformation and sealing oil accommodating grooves, and the first slope and the second slope further enhance the deformation capacity of the protrusion formed by the two slopes to further prevent oil leakage due to excessive oil pressure and insufficient deformation capacity, and finally form a double-sealed solid oil seal structure. The annular groove is located at one end close to the third groove, and water cannot directly pass through the annular groove and enter the oil cylinder, and the waterproof and dustproof effect is better.

[0011] Optionally, an outer wall at the rear end of the piston pull tube is provided with an external thread, and the thread strength of the piston pull tube is grade 12.9.

[0012] Optionally, a fourth mounting groove is provided on the side wall of the reflux chamber away from the oil inlet part, and a valve hole bolt is installed in the fourth mounting groove, a through hole is provided in the center of the valve hole bolt, a second outer limiting flange is provided at the end of the through hole, a second steel ball is provided in the center of the through hole, the second steel ball is abutted against a spring, a fastening screw is provided at the end of the spring, a threaded groove matching the fastening screw is provided at one end of the through hole, and a liquid storage tank is provided at the end of the valve hole bolt away from the fastening screw; the liquid storage tank is connected to the oil through hole; the elastic coefficient of the spring is smaller than the elastic coefficient of the push rod spring, so that the fourth mounting groove forms a low-pressure holding zone, and the third mounting groove forms a high-pressure holding zone, so that the pressure holding time is longer.

[0013] Optionally, the inner groove is provided with a plurality of through holes on the side wall surrounding the protruding portion.

[0014] Optionally, a first joint and a second joint are mounted on the side wall of the cover body, and a straight joint is detachably mounted on the bottom of the oil inlet portion.

[0015] Optionally, a bearing is mounted on the cylinder body located at the oil inlet portion, and a sleeve piston is mounted on the bearing.

[0016] Beneficial Effects

[0017] 1. The present invention adopts a double-sealed solid oil seal structure at the front end of the cylinder.

[0018] 2. The valve system of the present invention is designed to have a high sensitivity, a long pressure holding time and an anti-sluggish reaction structure.

[0019] 3. The rear end seal of the oil cylinder in the present invention adopts a waterproof design and a rotating oil seal structure.

[0020] 4. The strength of the drawn pipe thread is provided as 12.9 grade. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a three-dimensional structural diagram of the internal circulation pressure-maintaining rotary cylinder of Example 1 of the present invention;

[0022] Figure 2 The inner circulation pressure-maintaining rotary cylinder of embodiment 1 of the present invention Figure 1 A side cross-sectional view of

[0023] Figure 3 The inner circulation pressure-maintaining rotary cylinder of embodiment 1 of the present invention Figure 2 A partial enlarged view of part A;

[0024] Figure 4 The inner circulation pressure-maintaining rotary cylinder of embodiment 2 of the present invention Figure 2 A partial enlarged view of part B;

[0025] Figure 5 The inner circulation pressure-maintaining rotary cylinder of embodiment 3 of the present invention Figure 2 A partial enlarged view of part C;

[0026] Figure 6 It is a partial structural diagram of the internal circulation pressure-maintaining rotary cylinder of embodiment 4 of the present invention;

[0027] Figure 7 The inner circulation pressure-maintaining rotary cylinder of embodiment 4 of the present invention Figure 6 A partial enlarged view of part D.

[0028] The reference numerals in the figures are:

[0029] 1. Piston pull tube, 2. Cylinder body, 3. Cover body, 4. Reflux chamber, 5. Oil inlet chamber, 6. Oil through hole, 7. Annular baffle, 8. First mounting groove, 9. Second mounting groove, 10. Third mounting groove, 11. First joint, 12. Second joint, 13. Oil inlet part, 14. Straight joint, 15. Bearing, 16. Sleeve piston, 17. Valve body, 18. Perforation, 19. Inner annular limit flange, 20. Valve stem, 21. First steel ball, 22. Spring clamping groove, 23. Push rod spring, 24. Flange, 25. Valve seat, 26. Inner groove, 27. Protrusion, 28. Through hole, 29. First sealing groove, 30. Second sealing groove, 31. An O-ring, 32, a second O-ring, 33, an annular groove, 34, a V-groove, 35, a first inclined surface, 36, a second inclined surface, 37, a fourth mounting groove, 38, a valve hole bolt, 39, a through hole 40, a second outer limiting flange, 41, a second steel ball, 42, a spring, 43, a fastening screw, 44, a front cover, 45, a rear cover, 46, a first fastening groove, 47, a second fastening groove, 48, a heat dissipation fastening bolt, 49, a bolt head, 50, a first heat dissipation hole, 51, a second heat dissipation hole, 52, a spiral coil, 53, a first inlet pipe, 54, a second inlet pipe, 55, an adapter, 56, a heat dissipation fin, 57, a bent heat dissipation coil. DETAILED DESCRIPTION

[0030] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0031] In the description of the present invention, unless otherwise specified, "multiple" means two or more than two; the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] Example 1

[0033] The technical solution adopted by the present invention is as follows:

[0034] like Figure 1 , Figure 2 and Figure 3 As shown, the present invention discloses an internal circulation pressure-maintaining rotary oil cylinder, comprising: a piston pull tube 1, an outer wall of the rear end of the piston pull tube is provided with an external thread, and the thread strength of the piston pull tube is 12.9. A cylinder body 2 is arranged outside the piston pull tube, a cover body 3 is arranged at the rear end of the cylinder body, a reflux chamber 4 is arranged at the front end of the cylinder body, an oil inlet 13 is arranged at the bottom of the cover body, an oil inlet chamber 5 is arranged in the oil inlet, and the oil inlet chamber is connected to the reflux chamber through an oil hole 6; an annular baffle 7 is arranged at the front end of the piston pull tube, the annular baffle is located on the side of the reflux chamber close to the oil inlet, a first mounting groove 8 is arranged on the side wall of the lower side of the reflux chamber at the front end of the cylinder body, a second mounting groove 9 is arranged at a position corresponding to the first mounting groove on the annular baffle, and a third mounting groove 10 arranged opposite to the second mounting groove is arranged on the side wall of the other side of the reflux chamber; a first joint 11 and a second joint 12 are arranged on the side wall of the cover body, and a straight joint 14 is detachably arranged at the bottom of the oil inlet. The cylinder body at the oil inlet portion is provided with a bearing 15, and the bearing is provided with a sleeve piston 16. The through-connector in this embodiment is externally connected to a switch valve. A valve is installed in the third mounting groove, and the valve is installed on the oil through hole; the valve has a valve body 17, the valve body is installed in the third mounting groove, a through hole 18 penetrating the valve body is provided in the center of the valve body, an inner annular limiting flange 19 is provided in the center of the valve body, a valve stem 20 is provided on the side of the reflux chamber close to the oil inlet, one end of the valve stem passes through the second mounting groove and is inserted into the first mounting groove, and the other end of the valve stem is inserted into the through hole, a first steel ball 21 is installed in the valve body, the bottom surface of the valve stem close to the first steel ball is inwardly recessed to form a spring clamping groove 22, a tappet spring 23 is installed in the spring clamping groove, the end of the tappet spring abuts against the first steel ball, and a first outer limiting flange 24 is provided at the end of the spring clamping groove, a valve seat 25 is provided at one end of the valve body away from the annular baffle, an inner groove 26 is provided at one end of the valve seat close to the valve stem, a protrusion 27 is provided at the center of the inner groove, and a plurality of through holes 28 communicating with the end of the oil through hole away from the annular baffle are opened on the side wall of the inner groove surrounding the protrusion. The front end of the oil hole is connected to the spring slot, and the through hole is connected to the rear end of the oil hole. The contact area between the protrusion and the first steel ball is small, and the first steel ball can be deflected, so the sealing surface is unstable, which makes the pressure holding time longer.

[0035] During implementation of this embodiment, when the switch valve is opened, the hydraulic oil enters the oil inlet through the oil pipe, pushing the piston to move outward. At this time, the pressure in the oil inlet increases, and the rotary cylinder body begins to rotate due to the torque. The piston continues to move outward, driving the piston of the internal circulation pressure-maintaining rotary cylinder to move outward as well. The sealing device maintains the oil seal in the oil inlet to ensure that the cylinder body can rotate smoothly. When the hydraulic oil is released through the switch valve, the pressure in the oil inlet decreases, and the rotation speed of the cylinder body slows down. This stage is used to control the speed and direction of rotation. The control valve is closed, the hydraulic oil stops entering the oil inlet, the cylinder body stops rotating, and the piston of the oil inlet begins to move inward and returns to the initial position. The present invention realizes the control of oil flow through the coordinated action of components such as the valve stem, the first steel ball, the push rod spring and the valve seat, and can control the sealing state between the first steel ball and the valve seat by adjusting the position of the valve stem, thereby opening or closing the channel for oil circulation. It can adjust the hydraulic pressure difference between the reflux chamber and the oil inlet chamber, thereby preventing the oil inlet chamber from having excessive pressure, and avoiding the problem that the hydraulic pressure in the oil cylinder is too high and may exceed the bearing limit of the oil cylinder and its accessories (such as seals, pipelines, etc.), causing these components to be damaged or fail, and has better dust and water proofing effects.

[0036] This embodiment 2

[0037] like Figure 4 As shown, the difference between this embodiment 2 and embodiment 1 is that the front end of the cylinder body is provided with a first sealing groove 29 near the front end and a second sealing groove 30 near the rear end; a first O-type sealing ring 31 is provided in the first sealing groove, and a second O-type sealing ring 32 is provided in the first sealing groove. The cross section of the first O-type sealing ring is elliptical, and the first sealing groove and the second sealing groove are both filled with sealing oil.

[0038] An annular groove 33 is provided on the side wall of the second O-ring not in contact with the piston draw tube, and an annular V-shaped groove 34 is provided on the inner wall of the second O-ring in contact with the piston draw tube. An annular first inclined surface 35 is provided on the inner wall of the second O-ring in contact with the piston draw tube at an end away from the first sealing groove, and the first inclined surface is provided with an oblique downward inclination toward the end away from the first sealing groove, and an annular second inclined surface 36 is provided on the top of the annular groove near the first inclined surface, and the second inclined surface is provided with an oblique upward inclination toward the end away from the first sealing groove.

[0039] When this embodiment is implemented, the second O-ring is provided with an annular groove and a V-shaped groove to form a pair of deformation and sealing oil accommodating grooves, thereby enhancing the sealing elasticity of the second O-ring. Its first inclined surface and second inclined surface further enhance the deformation capacity of the protrusion formed by the two inclined surfaces, further preventing oil leakage due to excessive oil pressure and insufficient deformation capacity, and finally cooperates with the first O-ring to form a double-sealed solid oil seal structure.

[0040] Embodiment 3

[0041] like Figure 5 As shown, the difference between this embodiment 3 and embodiment 1 is that a fourth mounting groove 37 is provided on the side wall of the reflux cavity away from the oil inlet portion, a valve hole bolt 38 is installed in the fourth mounting groove, a through hole 39 is provided in the center of the valve hole bolt, a second outer limiting flange 40 is provided at the end of the through hole, a second steel ball 41 is provided in the center of the through hole, the second steel ball is abutted against a spring 42, a fastening screw 43 is provided at the end of the spring, and a threaded groove adapted to the fastening screw is provided at one end of the through hole. A liquid reservoir is provided at one end of the valve hole bolt away from the fastening screw; the liquid reservoir is connected to the oil through hole.

[0042] When this embodiment is implemented, the second steel ball moves under the oil pressure and also plays a role in adjusting the pressure balance between the liquid storage tank and the reflux chamber.

[0043] This embodiment 4

[0044] like Figure 6 and Figure 7 As shown, the difference between this embodiment 4 and embodiment 1 is that the cylinder body includes a front cover 44 and a rear cover 45, and there is a gap between the rear cover and the cover body. The outer edge of the front cover is provided with a first fastening groove 46 and a second fastening groove 47, and the first fastening groove and the second fastening groove are both provided with internal threads. The first fastening groove and the second fastening groove are provided with copper heat dissipation fastening bolts 48, and one end of the heat dissipation fastening bolt is provided with a bolt head 49, and the other end of the heat dissipation fastening bolt is provided with a bolt column, and the bolt column is connected to the first heat dissipation hole 50, and the first heat dissipation hole is connected to the second heat dissipation hole 51, and the second heat dissipation hole passes through the bolt column and the bolt head, and the first heat dissipation hole is provided with a spiral coil 52, and the first heat dissipation hole passes through the bottom wall of the bolt, and the bolt head is provided with a first inlet pipe 53, and the inlet pipe is connected to the spiral coil pipe. The outer end of the first inlet pipe is rotated with a second inlet pipe 54, and the connection between the first inlet pipe and the second inlet pipe is provided with a sealing sleeve or an adapter 55. The second inlet pipe is externally connected to a detachable heat sink 56 mounted on the rear cover, and the heat sink is provided with a curved heat sink 57 connected to the second inlet pipe. The spiral pipe, the first inlet pipe, and the second inlet pipe in this embodiment can also be filled with a gas with a high thermal conductivity such as helium.

[0045] When this embodiment is implemented, the copper heat dissipation fastening bolts efficiently and directly dissipate the heat of the cylinder body through the heat dissipation fastening bolt spiral disk, the first inlet pipe, the second inlet pipe, the curved heat dissipation coil and the heat dissipation fins. The spiral coil has a large contact area with the heat dissipation fastening bolts, a large heat dissipation area, and a fast diffusion speed of the gas with high thermal conductivity, so that heat exchange can be better performed through thermal convection and heat transfer.

[0046] The above description is only a preferred embodiment of the present invention, and does not limit the patent protection scope of the present invention. Any equivalent structural transformation made by using the contents of the present invention and the drawings, directly or indirectly used in other related technical fields, is also included in the protection scope of the present invention.

Claims

1. An internal circulation pressure-maintaining rotary cylinder, characterized in that: include: A piston pulling tube, wherein a cylinder body is arranged outside the piston pulling tube, a cover shell is arranged at the rear end of the cylinder body, a reflux chamber is arranged at the front end of the cylinder body, an oil inlet portion is arranged at the bottom of the cover shell, an oil inlet chamber is arranged in the oil inlet portion, and the oil inlet chamber is connected to the reflux chamber through a through hole; an annular baffle is arranged at the front end of the piston pulling tube, the annular baffle is located at a side of the reflux chamber close to the oil inlet portion, a first mounting groove is arranged on the side wall of the lower side of the reflux chamber located at the front end of the cylinder body, a second mounting groove is arranged at a position corresponding to the first mounting groove on the annular baffle, and a third mounting groove arranged opposite to the second mounting groove is arranged on the side wall of the other side of the reflux chamber; A valve is installed in the third mounting groove, and the valve is installed on the oil through hole; the valve has a valve body, and the valve body is installed in the third mounting groove. A through hole penetrating the valve body is provided in the center of the valve body, and an inner annular limiting flange is provided in the center of the valve body. A valve stem is provided on the side of the reflux chamber close to the oil inlet part, one end of the valve stem passes through the second mounting groove and is inserted into the first mounting groove, and the other end of the valve stem is inserted into the through hole. A first steel ball is installed in the valve body, and the bottom surface of the valve stem close to the first steel ball is recessed inward to form a spring groove, and a push rod spring is installed in the spring groove, and the end of the push rod spring abuts against the first steel ball, and the end of the spring groove is provided with a first outer limiting flange, and a valve seat is provided at one end of the valve body away from the annular baffle, and an inner groove is provided at one end of the valve seat close to the valve stem, and a protrusion is provided at the center of the inner groove.

2. The internal circulation pressure-maintaining rotary cylinder according to claim 1, characterized in that: The front end of the cylinder body is provided with a first sealing groove close to the front end and a second sealing groove close to the rear end; a first O-type sealing ring is provided in the first sealing groove, a second O-type sealing ring is provided in the first sealing groove, and the first sealing groove and the second sealing groove are both filled with sealing oil.

3. The internal circulation pressure-maintaining rotary cylinder according to claim 2, characterized in that: The first O-ring has an elliptical cross section.

4. The internal circulation pressure-maintaining rotary cylinder according to claim 2, characterized in that: An annular groove is provided on the side wall of the second O-ring not in contact with the piston pull tube, and an annular V-shaped groove is provided on the inner wall of the second O-ring in contact with the piston pull tube.

5. The internal circulation pressure-maintaining rotary cylinder according to claim 4, characterized in that: The second O-ring seal contacts the inner wall of the piston pull tube at one end away from the first sealing groove and has an annular first slope, the first slope is inclined downwardly at an end away from the first sealing groove, the annular groove is provided with an annular second slope near the top of the first slope, the second slope is inclined upwardly at an end away from the first sealing groove.

6. An internal circulation pressure-maintaining rotary cylinder as claimed in claim 1, 2, 3, 4 or 5, characterized in that: An outer wall at the rear end of the piston pull tube is provided with an external thread, and the thread strength of the piston pull tube is grade 12.

9.

7. An internal circulation pressure-maintaining rotary cylinder as claimed in claim 1, 2, 3, 4 or 5, characterized in that: A fourth mounting groove is provided on the side wall of the reflux chamber away from the oil inlet portion, a valve hole bolt is installed in the fourth mounting groove, a through hole is provided in the center of the valve hole bolt, a second outer limiting flange is provided at the end of the through hole, a second steel ball is provided in the center of the through hole, the second steel ball is abutted against a spring, a fastening screw is provided at the end of the spring, a threaded groove matching the fastening screw is provided at one end of the through hole, a liquid storage tank is provided at the end of the valve hole bolt away from the fastening screw; the liquid storage tank is connected to the oil through hole.

8. The internal circulation pressure-maintaining rotary cylinder according to claim 7, characterized in that: The inner groove is provided with a plurality of through holes on the side wall surrounding the protruding portion.

9. An internal circulation pressure-maintaining rotary cylinder as claimed in claim 1, 2, 3, 4 or 5, characterized in that: The side wall of the cover body is provided with a first joint and a second joint, the bottom of the cover body is provided with an oil inlet, and the bottom of the oil inlet is detachably provided with a straight-through joint.

10. An internal circulation pressure-maintaining rotary cylinder as claimed in claim 1, 2, 3, 4 or 5, characterized in that: A bearing is arranged on the cylinder body located at the oil inlet part, and a sleeve piston is arranged on the bearing.

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