A seal ring set and seal structure for a hydraulic damper

Abstract

The application relates to a sealing ring set for a hydraulic damper, comprising two first combined sealing rings for being installed between a piston and an inner circumferential surface of a cylinder body and one second combined sealing ring for being installed between a piston rod and a cylinder cover, the first combined sealing ring comprises a first outer ring and two first inner rings, and the second combined sealing ring comprises a second inner ring and two second outer rings; the application also provides a sealing structure for the hydraulic damper, which comprises the sealing ring set, a cylinder, a cylinder cover, a piston and a piston rod. The sealing ring set is made of metal material, the adaptability is enhanced, and the stability is higher. The metal material is good in wear resistance and is not prone to being damaged, the service life of the sealing ring set is prolonged, the maintenance period is prolonged, and the sealing ring set for the hydraulic damper can also play the roles of supporting and fixing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydraulic dampers, in particular to a sealing ring set and sealing structure for a hydraulic damper. BACKGROUND

[0002] A hydraulic damper is a mechanical device used to prevent damage to a building, device or pipeline caused by an interference force. The hydraulic damper is a vibration damping device that is sensitive to speed, and when an external interference force occurs, it controls the movement of the hydraulic cylinder piston by means of a special structure valve to suppress the influence of periodic load and impact load on the pipeline or device. Under normal working conditions, it also needs to adapt to the requirements of the thermal expansion and contraction of the device and pipeline. Hydraulic dampers are widely used in the construction, nuclear power, thermal power and other industries. They are mainly used to prevent damage to pipelines or devices caused by impact loads such as earthquakes, water hammers, air hammers and wind loads.

[0003] The working process of a hydraulic damper is divided into two states, rigid and flexible. When the pipeline or device is normally thermally expanded, it can move slowly and almost no damping force is provided, which is flexible. When the load is transient, the piston rod will be relatively fixed in the cylinder, providing a reverse resistance equal to the transient load, which will suppress the vibration of the pipeline or device and reduce the amplitude, thereby protecting the pipeline or device. At this time, it is rigid. This transient load is the rated load designed for the damper. Two key core technologies in hydraulic dampers are the design of a special structure valve and the design of a sealing ring set.

[0004] In order to meet the characteristics of the hydraulic damper, the sealing ring used on the damper piston needs to be able to completely seal the gap between the piston and the cylinder when subjected to an impact force, and to form the gap again after the impact force is absorbed, which helps the piston to move as needed. In the prior art, the sealing ring used for the piston of the hydraulic damper is made of non-metallic material, which has relatively high requirements for the use environment and conditions. Non-metallic sealing rings used in high temperature and low temperature working conditions are expensive and have a short service life, and require a lot of maintenance work. In addition, when the damper changes from rigid to flexible, the non-metallic sealing ring cannot quickly release the gap after expansion, so the non-metallic sealing ring has a single function and only serves as a seal, and the resistance is relatively large. SUMMARY

[0005] In order to solve the above technical problems, the purpose of the present application is to provide a sealing ring set and sealing structure for a hydraulic damper.

[0006] The above object of the present application is achieved by the following technical scheme: a sealing ring set for a hydraulic damper, comprising two first combined sealing rings for being installed between a piston and an inner circumferential surface of a cylinder body and one second combined sealing ring for being installed between a piston rod and a cylinder cover, the first combined sealing ring comprises a first outer ring and two first inner rings, the first outer ring comprises a first circular ring body, first annular inner tapered surfaces are symmetrically arranged on the left and right sides of the inner circumferential surface of the first circular ring body in the radial direction, the first inner ring comprises a second circular ring body, first annular outer tapered surfaces are arranged on the outer circumferential surface of the second circular ring body, and the two first inner rings are symmetrically arranged on the left and right sides of the inside of the first circular ring body through the cooperation of the first annular outer tapered surfaces and the first annular inner tapered surfaces respectively.

[0007] The second combined sealing ring comprises a second inner ring and two second outer rings, the second inner ring comprises a third circular ring body, second annular outer tapered surfaces are symmetrically arranged on the left and right sides of the outer circumferential surface of the third circular ring body in the radial direction, the second outer ring comprises a fourth circular ring body, second annular inner tapered surfaces are arranged on the inner circumferential surface of the fourth circular ring body, and the two second outer rings are symmetrically arranged on the left and right sides of the outside of the third circular ring body through the cooperation of the second annular inner tapered surfaces and the second annular outer tapered surfaces respectively.

[0008] Further, the first inner ring, the first outer ring, the second inner ring and the second outer ring are all made of metal material.

[0009] Further, the first inner ring, the first outer ring, the second inner ring and the second outer ring are all made of 65Mn spring steel.

[0010] Further, a plurality of first axial inner holes are arranged on the inner side surface of the first inner ring in the circumferential direction, the two first inner rings are arranged in the first outer ring, and first springs are installed in the first axial inner holes at the corresponding positions of the two first inner rings.

[0011] Further, the first spring is made of 55CrSiA spring steel.

[0012] Further, a plurality of second axial inner holes are arranged on the inner side surface of the second outer ring in the circumferential direction, the two second outer rings are arranged outside the second inner ring, and second springs are installed in the second axial inner holes at the corresponding positions of the two second outer rings.

[0013] Further, the second spring is made of 55CrSiA spring steel.

[0014] A sealing structure for a hydraulic damper, comprising a sealing ring group, a cylinder, a cylinder head, a piston, and a piston rod for the hydraulic damper, wherein the piston is arranged in the cylinder body, a cylinder head is provided at the front end of the cylinder body, a through hole is provided in the center of the cylinder head, a piston rod is provided at the front end of the piston, the front end of the piston rod extends out of the cylinder head from the through hole, and the piston and the piston rod move axially back and forth in the cylinder; two first combined sealing rings are provided between the piston and the inner circumferential surface of the cylinder body, and one second combined sealing ring is provided between the piston rod and the cylinder head.

[0015] Furthermore, an annular protrusion is provided on the outer circumferential surface of the piston, and a first combined sealing ring is respectively mounted on the outer circumferential surface of the piston on the left and right sides of the annular protrusion, wherein the two first inner rings of the first combined sealing ring are respectively mounted on the outer circumferential surface of the piston, and the outer circumferential surface of the first outer ring is slidably fitted with the inner circumferential surface of the cylinder body; a gasket and a first locking nut are sequentially mounted on the outer side of each first combined sealing ring, and the first locking nut and the annular protrusion limit the axial movement freedom of the second combined sealing ring;

[0016] A first annular groove and a second annular groove are sequentially provided on the right side of the through hole of the cylinder cover, and the inner diameters of the through hole, the first annular groove and the second annular groove increase sequentially. A second combined sealing ring is provided in the first annular groove, and the second inner ring is sleeved on the outer circumference of the piston rod. The outer circumferences of the two second outer rings are slidably fitted with the inner circumference of the first annular groove of the cylinder cover. A second locking nut is provided in the second annular groove, and the step surface formed by the second locking nut, the through hole and the first annular groove limits the axial movement freedom of the second combined sealing ring.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The sealing ring assembly for a hydraulic damper of the present invention includes two first combination sealing rings for installation between the piston and the inner circumferential surface of the cylinder body and one second combination sealing ring for installation between the piston rod and the cylinder head, wherein the first outer ring and the two first inner rings of the first combination sealing rings are slidably fitted together via the first annular inner conical surface and the first annular outer conical surface, and the second outer ring and the second inner ring are slidably fitted together via the second annular inner conical surface and the second annular outer conical surface. When the load borne by the piston rod and the piston does not meet the rated load requirements, the two first combination sealing rings and the one second combination sealing ring assembly will not undergo significant deformation. At this time, the hydraulic oil in the cavities on both sides of the piston in the cylinder can pass freely, and the damper can move freely. When the piston rod and the piston are subjected to sudden tensile and compressive loads that reach the rated load requirements, the two first combination sealing rings and the one second combination sealing ring can achieve the effect of completely sealing the gap between the piston and the cylinder, and the gap between the piston rod and the cylinder head.

[0019] The sealing ring set for hydraulic damper of the present application is made of full metal material. Since the metal has better performance than the non-metallic material widely used at present in high temperature and low temperature environment, the sealing ring set made of full metal enhances the adaptability and has higher stability. The metal material has good wear resistance and is not easy to be damaged, prolonging the service life of the sealing ring set and extending the maintenance cycle. The metal sealing ring set enhances the safety and stability of the equipment while reducing the manufacturing and later maintenance cost. The sealing ring set for hydraulic damper of the present application can also play the role of supporting and fixing. BRIEF DESCRIPTION OF DRAWINGS

[0020] The drawings described herein are intended to provide further understanding of the present application, form a part of the application, and the illustrative examples of the present application and the description thereof are used to explain the present application and do not constitute improper limitation of the present application.

[0021] Figure 1 The figure is a structural schematic diagram of the sealing ring set for hydraulic damper of the present application, wherein Figure 1 (a) is a structural schematic diagram of the first combined sealing ring of the sealing ring set for hydraulic damper of the present application, which is also the first embodiment of the present application; Figure 1 (b) is a structural schematic diagram of the second combined sealing ring of the sealing ring set for hydraulic damper in the first embodiment of the present application;

[0022] Figure 2 is a structural schematic diagram of the first outer ring in the first embodiment of the present application;

[0023] Figure 3 is a structural schematic diagram of the first inner ring in the first embodiment of the present application;

[0024] Figure 4 is a structural schematic diagram of the sealing structure for hydraulic damper in the second embodiment of the present application;

[0025] Figure 5 is a structural schematic diagram of the first combined sealing ring of the sealing ring set for hydraulic damper in the third embodiment of the present application;

[0026] Figure 6 is a structural schematic diagram of the first inner ring in the third embodiment of the present application;

[0027] Figure 7 is a structural schematic diagram of the second combined sealing ring of the sealing ring set for hydraulic damper in the third embodiment of the present application;

[0028] Figure 8 is a structural schematic diagram of the sealing structure for hydraulic damper in the fourth embodiment of the present application;

[0029] In the figure: 1. first outer ring, 11. first circular body, 12. first annular inner cone, 2. first inner ring, 21. second circular body, 22. first annular outer cone, 23. first axial inner hole, 3. second inner ring, 31. third circular body, 32. second annular outer cone, 4. second outer ring, 41. fourth circular body, 42. second annular inner cone, 43. second axial inner hole, 5. first spring, 6. second spring, 7. oil cylinder, 8. cylinder head, 81. through hole, 82. first annular groove, 83. second annular groove, 831. threaded ring groove, 9. piston, 91. annular protrusion, 10. piston rod, 20. gasket, 30. first locking nut, 40. second locking nut. DETAILED DESCRIPTION

[0030] Example 1

[0031] like Figures 1-3 As shown, a sealing ring assembly for a hydraulic damper includes two first combined sealing rings for installation between a piston and a peripheral surface of a cylinder body, and a second combined sealing ring for installation between a piston rod and a cylinder head, wherein the first combined sealing ring includes a first outer ring 1 and two first inner rings 2, wherein the first outer ring 1 includes a first annular body 11, and first annular inner conical surfaces 12 are radially symmetrically provided on the left and right sides of the inner peripheral surface of the first annular body 11, and the first inner ring 2 includes a second annular body 21, and a first annular outer conical surface 22 matching the first annular inner conical surface 12 is provided on the outer peripheral surface of the second annular body 21, and the two first inner rings 2 are symmetrically placed on the left and right sides of the interior of the first annular body 11 through the first annular outer conical surfaces 22 matching the first annular inner conical surface 12;

[0032] The second combined sealing ring includes a second inner ring 3 and two second outer rings 4, the second inner ring 3 includes a third annular body 31, and second annular outer conical surfaces 32 are radially symmetrically provided on the left and right sides of the outer circumference of the third annular body 31. The second outer ring 4 includes a fourth annular body 41, and a second annular inner conical surface 42 matching the second annular outer conical surface 32 is provided on the inner circumference of the fourth annular body 41. The two second outer rings 4 are symmetrically placed on the left and right sides of the outside of the third annular body 31 through the second annular inner conical surface 42 and the second annular outer conical surface 32.

[0033] The first inner ring 2, the first outer ring 1, the second inner ring 3 and the second outer ring 4 are all made of metal.

[0034] The metal material is 65Mn spring steel.

[0035] Example 2

[0036] Reference Figure 4A sealing structure for a hydraulic damper, comprising a cylinder 7, a cylinder cover 8, a piston 9, a piston rod 10, and the sealing ring set for a hydraulic damper described in Embodiment One, the piston 9 is arranged in the cylinder body of the cylinder 7, the cylinder body of the cylinder 7 is provided with the cylinder cover 8, the center of the cylinder cover 8 is provided with a through hole 81, the front end of the piston 9 is provided with the piston rod 10, the front end of the piston rod 10 extends out of the cylinder cover 8 from the through hole 81, and the piston 9 moves back and forth along the axial direction in the cylinder 7 together with the piston rod 10; two first combined sealing rings are arranged between the piston 9 and the inner circumferential surface of the cylinder body of the cylinder 7, and one second combined sealing ring is arranged between the piston rod 10 and the cylinder cover 8.

[0037] An annular protrusion 91 is arranged on the outer circumferential surface of the piston 9, and a gap is formed between the annular protrusion 91 and the inner circumferential surface of the cylinder 7, one first combined sealing ring is respectively sleeved on the outer circumferential surface of the piston 9 on the left and right sides of the annular protrusion 91, wherein the two first inner rings 2 of the first combined sealing ring are respectively sleeved on the outer circumferential surface of the piston 9, and the outer circumferential surface of the first outer ring 1 is slidably attached to the inner circumferential surface of the cylinder body of the cylinder 7; a gasket 20 and a first locking nut 30 (threadedly connected between the first locking nut 30 and the outer circumferential surface of the piston 9) are sequentially arranged on the outer side of each first combined sealing ring, and the first locking nut 30 and the annular protrusion 91 limit the axial movement freedom degree of the second combined sealing ring;

[0038] A first annular groove 82 and a second annular groove 83 are sequentially arranged on the right side of the through hole 81 of the cylinder cover 8, the inner diameters of the through hole 81, the first annular groove 82, and the second annular groove 83 sequentially increase, a threaded processing ring groove 831 is arranged in the second annular groove 83 to realize the threaded processing of the second annular groove 83, a second combined sealing ring is arranged in the first annular groove 82, the second inner ring 3 is sleeved on the outer circumferential surface of the piston rod 10, the outer circumferential surfaces of the two second outer rings 4 are slidably attached to the inner circumferential surface of the first annular groove 82 of the cylinder cover 8, and a second locking nut 40 (threadedly connected between the second locking nut 40 and the second annular groove 83) is arranged in the second annular groove 83, and the second locking nut 40 and the stepped surface formed by the through hole 81 and the first annular groove 82 limit the axial movement freedom degree of the second combined sealing ring.

[0039] Embodiment Three

[0040] Reference Figures 5-7 The difference from Embodiment One is that:

[0041] A plurality of first axial inner holes 23 are arranged on the inner side surface of the first inner ring 2 in the circumferential direction, the two first inner rings 2 are arranged in the first outer ring 1, and the first springs 5 are arranged in the first axial inner holes 23 at the corresponding positions of the two first inner rings 2.

[0042] The first spring 5 is made of 55CrSiA spring steel. The first spring 5 provides elastic force for the separation of the two first inner rings 2.

[0043] A plurality of second axial inner holes 43 are arranged on the inner side of the second outer ring 4 in the circumferential direction. The two second outer rings 4 are arranged outside the second inner ring 3, and the second springs 6 are installed in the second axial inner holes 43 at the corresponding positions of the two second outer rings 4.

[0044] The second spring 6 is made of 55CrSiA spring steel. The second spring 6 provides elastic force for the separation of the two second outer rings 4.

[0045] Example Four

[0046] Reference Figure 8 A sealing structure for a hydraulic damper, comprising a cylinder 7, a cylinder cover 8, a piston 9, a piston rod 10, and the sealing ring set for a hydraulic damper described in Example Three. The piston 9 is arranged in the cylinder body of the cylinder 7, the front end of the cylinder body of the cylinder 7 is provided with the cylinder cover 8, the center of the cylinder cover 8 is provided with a through hole 81, the front end of the piston 9 is provided with the piston rod 10, the front end of the piston rod 10 extends out of the cylinder cover 8 from the through hole 81, and the piston 9 moves back and forth in the cylinder 7 along the axial direction together with the piston rod 10; two first combined sealing rings are arranged between the piston 9 and the inner circumferential surface of the cylinder body of the cylinder 7, and one second combined sealing ring is arranged between the piston rod 10 and the cylinder cover 8.

[0047] An annular protrusion 91 is arranged on the outer circumferential surface of the piston 9, and a gap is formed between the annular protrusion 91 and the inner circumferential surface of the cylinder 7. One first combined sealing ring is sleeved on the outer circumferential surface of the piston 9 on the left and right sides of the annular protrusion 91, respectively. Among them, the two first inner rings 2 of the first combined sealing ring are sleeved on the outer circumferential surface of the piston 9, and the outer circumferential surface of the first outer ring 1 is slidably attached to the inner circumferential surface of the cylinder body of the cylinder 7. A gasket 20 and a first locking nut 30 (threadedly connected between the outer circumferential surface of the piston 9 and the first locking nut 30) are sequentially installed on the outer side of each first combined sealing ring. The first locking nut 30 and the annular protrusion 91 limit the axial movement freedom degree of the second combined sealing ring.

[0048] The first annular groove 82 and the second annular groove 83 are sequentially arranged on the right side of the through hole 81 of the cylinder cover 8, the inner diameters of the through hole 81, the first annular groove 82 and the second annular groove 83 increase sequentially, the threaded processing ring groove 831 is arranged in the second annular groove 83, the threaded processing of the second annular groove 83 is realized, the second combined sealing ring is arranged in the first annular groove 82, the second inner ring 3 is sleeved on the outer circumferential surface of the piston rod 10, the outer circumferential surfaces of the two second outer rings 4 are slidably attached to the inner circumferential surface of the first annular groove 82 of the cylinder cover 8, the second locking nut 40 is arranged in the second annular groove 83 (the second locking nut 40 is threadedly connected with the second annular groove 83), and the second locking nut 40 and the through hole 81 and the first annular groove 82 form a stepped surface to limit the axial movement degree of freedom of the second combined sealing ring.

[0049] The sealing ring set for the hydraulic damper in the embodiment one and the embodiment two comprises two first combined sealing rings and one second combined sealing ring, the first outer ring 1 and the two first inner rings 2 of the first combined sealing ring are slidably attached through the first annular inner taper surface 12 and the first annular outer taper surface 22, the second outer ring 4 and the second inner ring 3 are slidably attached through the second annular inner taper surface 42 and the second annular outer taper surface 32, and the taper angle, the taper width and the sizes of the first outer ring 1, the first inner ring 2, the second outer ring 4 and the second inner ring 3 can be designed according to the size of the rated load of the hydraulic damper.

[0050] When the piston rod 10 and the piston 9 do not bear the load value reaching the rated load requirement, the first inner rings 2 of the two first combined sealing rings can slide along the surface of the piston 9, and since the first inner rings 2 are limited in the axial degree of freedom by the annular protrusions 91 on the piston 9 and the first locking nut 30 on both sides of the first inner rings 2, the two first inner rings 2 can only slide in the limited position. When the piston rod 10 and the piston 9 bear the sudden tensile and compressive load reaching the rated load requirement, the load transmitted to the first combined sealing ring through the internal hydraulic oil will make the two first inner rings 2 relatively slide, and the first annular inner taper surface 12 between the first annular outer taper surface 22 of the first inner ring 2 and the first outer ring 1 will make the first outer ring 1 uniformly expand radially outward, the diameter of the outer surface of the first circular ring body 11 of the first outer ring 1 increases, and thus the gap between the piston 9 and the oil cylinder 7 is completely sealed; after the impact force borne by the piston rod 10 and the piston 9 is absorbed, the two first inner rings 2 simultaneously move outward and separate, and the first outer ring 1 returns to the state before expansion, at which time the piston 9 returns to the movable state.

[0051] 1 second combined seal ring group is arranged between the cylinder cover 8 and the piston rod 10, the second outer ring 4 can slide along the inner surface of the through hole 81 in the cylinder cover 8, the two sides of the two second outer rings 4 rely on the step surface of the stepped hole of the cylinder cover 8 and the second locking nut 40 to limit the freedom degree in the axial direction, so that the two second outer rings 4 can only slide in the defined position space. When the piston rod 10 and the piston 9 are subjected to sudden tensile and compressive load reaching the rated load requirement, the load transmitted to the second combined seal ring group through the internal hydraulic oil will make the two second outer rings 4 slide relatively, and due to the action of the second annular inner taper surface 42 of the second outer ring 4 and the second annular outer taper surface 32 of the second inner ring 3, the second inner ring 3 will be uniformly compressed radially inward, the diameter of the inner surface of the third circular ring body 31 of the second inner ring 3 is reduced, so as to achieve the effect of completely sealing the gap between the piston rod 10 and the cylinder cover 8. When the impact force borne by the piston rod 10 and the piston 9 is absorbed, the two second outer rings 4 move outward and separate at the same time, and the second inner ring 3 returns to the state before compression, at this time the piston rod 10 returns to the movable state.

[0052] When the load borne by the piston rod 10 and the piston 9 does not reach the rated load requirement, the two first combined seal ring groups and the second combined seal ring group will not be deformed obviously, at this time the hydraulic oil in the two cavities on both sides of the piston 9 in the oil cylinder 7 can pass freely, and the damper can move freely.

[0053] The above only describes the preferred examples of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made to the present application shall be included in the protection scope of the present application.

Claims

1. A sealing ring assembly for a hydraulic damper, characterized in that: It includes two first combined sealing rings for installation between the piston and the inner circumferential surface of the cylinder body and a second combined sealing ring for installation between the piston rod and the cylinder head, the first combined sealing ring includes a first outer ring and two first inner rings, the first outer ring includes a first annular body, and first annular inner conical surfaces are radially symmetrically provided on the left and right sides of the inner circumference of the first annular body, the first inner ring includes a second annular body, and a first annular outer conical surface matching the first annular inner conical surface is provided on the outer circumferential surface of the second annular body, and the two first inner rings are symmetrically placed on the left and right sides of the interior of the first annular body through the first annular outer conical surface matching the first annular inner conical surface; The second combined sealing ring includes a second inner ring and two second outer rings, the second inner ring includes a third annular body, and second annular outer conical surfaces are radially symmetrically provided on the left and right sides of the outer circumference of the third annular body. The second outer ring includes a fourth annular body, and a second annular inner conical surface matching the second annular outer conical surface is provided on the inner circumference of the fourth annular body. The two second outer rings are symmetrically placed on the left and right sides of the outside of the third annular body through the second annular inner conical surface matching the second annular outer conical surface. The first inner ring, the first outer ring, the second inner ring and the second outer ring are all made of metal; The first inner ring, the first outer ring, the second inner ring and the second outer ring are all made of 65Mn spring steel; A plurality of first axial inner holes are provided on the inner side surface of the first inner ring along the circumferential direction, two first inner rings are placed inside the first outer ring, and first springs are installed in the first axial inner holes at corresponding positions of the two first inner rings; A plurality of second axial inner holes are provided on the inner side surface of the second outer ring along the circumferential direction. The two second outer rings are placed outside the second inner ring. Second springs are installed in the second axial inner holes at corresponding positions of the two second outer rings.

2. A sealing ring assembly for a hydraulic damper according to claim 1, characterized in that: The first spring is made of 55CrSiA spring steel.

3. A sealing ring assembly for a hydraulic damper according to claim 1, characterized in that: The second spring is made of 55CrSiA spring steel.

4. A sealing structure for a hydraulic damper, comprising a sealing ring assembly for a hydraulic damper according to any one of claims 1 to 3, characterized in that: It also includes an oil cylinder, a cylinder head, a piston, and a piston rod. The piston is arranged in the oil cylinder body. A cylinder head is provided at the front end of the oil cylinder body. A through hole is provided in the center of the cylinder head. A piston rod is provided at the front end of the piston. The front end of the piston rod extends out of the cylinder head from the through hole. The piston and the piston rod move back and forth axially in the oil cylinder; two first combined sealing rings are provided between the piston and the inner circumferential surface of the oil cylinder body, and a second combined sealing ring is provided between the piston rod and the cylinder head.

5. A sealing structure for a hydraulic damper according to claim 4, characterized in that: An annular protrusion is provided on the outer circumferential surface of the piston, and a first combined sealing ring is respectively mounted on the outer circumferential surface of the piston on the left and right sides of the annular protrusion, wherein the two first inner rings of the first combined sealing ring are respectively mounted on the outer circumferential surface of the piston, and the outer circumferential surface of the first outer ring is slidably fitted with the inner circumferential surface of the cylinder body; a gasket and a first locking nut are sequentially mounted on the outer side of each first combined sealing ring, and the first locking nut and the annular protrusion limit the axial movement freedom of the second combined sealing ring; A step hole is provided on the right side of the through hole of the cylinder cover, a second combined sealing ring is provided in the first annular groove of the step hole, the second inner ring is sleeved on the outer circumferential surface of the piston rod, the outer circumferential surfaces of the two second outer rings are slidably fitted with the inner circumferential surface of the first annular groove of the cylinder cover, a second locking nut is provided in the second annular groove of the step hole, and the second locking nut and the step surface of the step hole limit the axial movement freedom of the second combined sealing ring.

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