Hydraulic actuator suitable for seawater environment

Abstract

The utility model belongs to the field of fluid automation control, and discloses a hydraulic actuator suitable for a seawater environment, which comprises a box body, the box body is provided with a piston rod hole and a cylinder barrel guide hole, a piston rod penetrates through the piston rod hole, a rack is arranged in the middle of the piston rod, and a gear meshed with the rack is arranged in the box body. One end of each hydraulic cylinder barrel is in sealed connection with the corresponding cylinder barrel guide hole, and the other end of each hydraulic cylinder barrel is in sealed connection with a hydraulic cylinder head; pistons are fixed at two ends of the piston rod; the hydraulic cylinder head is coaxially provided with a stroke adjusting structure, and one end of the stroke adjusting structure makes contact with the end face of the piston rod. The two hydraulic cylinder heads are provided with a first oil port and a second oil port which are communicated with the hydraulic cylinder barrel respectively, and circulation of hydraulic oil is achieved. On the premise that it is guaranteed that the hydraulic actuator is compact in structure, small in size and light in weight, the structural length of the actuator is shortened as much as possible, the seawater corrosion resistance safety coefficient is increased, the switch action time is controlled within 0.3 second, and the hydraulic actuator is suitable for automatic batch production.

Description

Technical Field

[0001] This utility model relates to a hydraulic actuator suitable for seawater environments, with rapid switching action, and suitable for automated mass production, belonging to the field of fluid automation control. Background Technology

[0002] Currently, hydraulic actuators on the market have a protection rating of only IP65, and most of them have a switching action time of more than 2 seconds. They are also large in size and heavy in weight, making it difficult to meet the demanding working conditions where there is limited installation space in offshore platforms, ship bilge water systems, and ship ballast tanks, and where there are extremely high requirements for the switching speed, hydraulic cylinder leakage level, and seawater corrosion resistance of the actuators.

[0003] Common hydraulic actuators use internal bore positioning for the hydraulic cylinder barrel and cylinder head. After the hydraulic cylinder head encounters multiple high-speed impacts, the hydraulic cylinder head (such as...) Figure 1 The outer circular boss (as shown) is prone to generating metal shavings due to friction with the inner wall of the hydraulic cylinder, causing hydraulic oil contamination and premature damage to the hydraulic oil seal. The coating at the joint between the hydraulic cylinder head and the cylinder barrel is also susceptible to damage after repeated high-speed impacts, posing a corrosion risk. Most common hydraulic actuators use polyurethane Y-rings, rubber O-rings, or a combination of rubber as the primary sealing material for hydraulic oil seals. The linear velocity of these conventional hydraulic oil seals is less than 0.5 m / s, resulting in a longer switching time for the hydraulic actuator. While replacing the hydraulic oil seal with a stepped hydraulic seal with a linear velocity of 5 m / s or greater speeds up the switching time, it also leads to a larger leakage rate and poor pressure holding effect, creating a potential hazard for the hydraulic actuator operating without maintenance for extended periods. Utility Model Content

[0004] To solve the above-mentioned technical problems, the purpose of this utility model is to provide a hydraulic actuator suitable for seawater environments.

[0005] To address the aforementioned problems, this invention provides a hydraulic actuator suitable for seawater environments. The actuator includes a housing with a piston rod hole penetrating both ends. A cylinder guide hole is located near the side of the housing. A piston rod, moving along the penetration direction, passes through the piston rod hole. A rack is located in the middle of the piston rod. A rotatable gear is located inside the housing, meshing with the rack. Hydraulic cylinders are fitted at both ends of the piston rod. One end of the hydraulic cylinder is sealed to the cylinder guide hole, and the other end is sealed to a hydraulic cylinder head. Pistons, symmetrically positioned relative to the housing, are fixed at both ends of the piston rod. The inner side of the piston is sealed to the piston rod, and the outer side is movably sealed to the inner wall of the hydraulic cylinder. A stroke adjustment structure is coaxially arranged on the hydraulic cylinder head, with one end of the structure contacting the piston rod end face. The two hydraulic cylinder heads are respectively provided with a first oil port and a second oil port communicating with the hydraulic cylinders, enabling the flow of hydraulic oil.

[0006] According to this utility model, one end of the hydraulic cylinder head is provided with a guide sealing groove, the inner hole of the guide sealing groove fits with the outer diameter of the hydraulic cylinder barrel, and is movably connected to the inner wall of the hydraulic cylinder barrel in a sealing manner.

[0007] According to this utility model, the stroke adjustment structure is an adjusting screw; the end face of the hydraulic cylinder head is provided with a threaded hole, the adjusting screw passes through the threaded hole and is directly opposite the end of the piston rod inside the hydraulic cylinder, and a cap-shaped sealing nut is fitted on the end of the adjusting screw away from the hydraulic cylinder, and the cap-shaped sealing nut is sealed to the hydraulic cylinder head.

[0008] According to this utility model, the inner side of the adjusting screw extends into the inner cavity of the hydraulic cylinder, while the outer side of the adjusting screw is exposed outside the hydraulic cylinder head.

[0009] According to this utility model, the outer circumference of the piston is provided with a support ring and a hydraulic oil seal, and the piston is sleeved on the piston rod.

[0010] According to this utility model, both ends of the piston rod are stepped shafts, the shape of the inner hole in the middle of the piston is the same as the shape of the stepped shafts at both ends of the piston rod, one end face of the stepped hole of the piston abuts against the end face of the stepped shaft of the piston rod, and is screwed together with the piston rod by threads, and a nut is fitted on the other side of the piston, and the piston is tightened onto the stepped shaft by the nut.

[0011] According to this utility model, the adjusting screw is fitted with a sealing nut on the outside of the hydraulic cylinder head. The sealing nut is located between the cap-shaped sealing nut and the hydraulic cylinder head, and both ends of the sealing nut are respectively sealed to the cap-shaped sealing nut and the hydraulic cylinder head.

[0012] According to this utility model, the housing is further provided with a stepped hole in the radial direction, the stepped hole including a lower shaft hole and an upper shaft hole, and an oil groove is provided in the lower shaft hole of the stepped hole; an upper shaft and a lower shaft are respectively provided on both sides of the gear, the lower shaft end is provided with a shaft hole for driving the valve stem, and the upper shaft end is provided with an interface for NAMUR installation standard; a gear cover is fitted on the upper shaft, the inner side of the gear cover is sealed and rotatably connected to the upper shaft, the outer side of the gear cover is sealed and rotatably connected to the inner wall of the housing, and the lower shaft of the gear extends into the lower shaft hole of the housing, and the lower shaft is sealed and rotatably connected to the lower shaft hole of the housing.

[0013] According to this utility model, the gear cover is further provided with a stepped outer circle, a stepped shaft hole and a flange. One end of the stepped outer circle is connected to one end of the flange. The stepped shaft hole is divided into an inner hole and an outer hole. The inner hole is the hole in the middle of the stepped outer circle and the outer hole is the hole in the middle of the flange. The inner hole of the stepped hole of the gear cover is fitted onto the upper shaft of the gear. The flange of the gear cover is fixed to the top of the housing. The lower end face of the gear is in close contact with the lower shaft hole end face of the housing. The lower end face of the gear cover restricts the radial movement of the upper end face of the gear. The outer hole of the stepped hole of the gear cover is sealed by an oil gauge.

[0014] According to this utility model, further, the plane on one radial side of the housing is provided with screw holes around the lower shaft hole of the stepped hole, and the plane on the other radial side of the housing is provided with screw holes for installing the gear cover and screw holes for installing the valve feedback device bracket around the upper shaft hole of the stepped hole. A flat bolt is fixed in the screw hole for installing the gear cover, and a sealing bolt is sealed in the screw hole for installing the valve feedback device bracket.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. This utility model, while ensuring that the hydraulic actuator is compact, small in size and light in weight, shortens the structural length of the actuator as much as possible, improves the safety factor against seawater corrosion, and controls the switching action time to within 0.3 seconds, and is suitable for automated mass production.

[0017] 2. The structure of this utility model is short: the seal can only move axially on the bottom plane of the guide sealing groove of the hydraulic cylinder head and the side of the groove hook, and the height of the hook is only 45% of the diameter of the O-ring wire and the thickness is only 25% of the diameter of the O-ring wire, which greatly shortens the length of the hydraulic cylinder and makes the hydraulic actuator structure as short as possible.

[0018] 3. The hydraulic cylinder of this utility model adopts external guide positioning: both ends of the hydraulic cylinder adopt external guide positioning, so that no metal structure of the hydraulic cylinder head can contact the inner wall of the cylinder during installation or use, ensuring that the inner wall of the cylinder is smooth and flat and that the hydraulic oil is free from iron filings.

[0019] 4. The switching action of this utility model is rapid: a support ring is provided at the front end of the piston to facilitate the introduction and installation of the piston, and two hydraulic seals are provided at the rear end of the piston. The hydraulic oil seals here are preferably hydraulic stepped seals composed of PTFE and O-rings with a linear velocity of 5 m / s or more. The first hydraulic stepped seal is used to scrape off excess oil film, and the second hydraulic stepped seal is used for sealing and pressure maintenance. This allows the actuator switching action time to be controlled within 0.3 seconds as much as possible. Without improving the manufacturing precision of the parts, the internal leakage of the piston-type single-acting hydraulic cylinder specified in JB / T10205-2010 standard can be controlled within 30% of the specified value.

[0020] 5. The fully sealed structure of this utility model: All parts subjected to internal and external air pressure are sealed with O-rings or ED sealing rings, and sealant is applied to the mating surfaces near the actuator to fill the gaps. Then, anti-corrosion coating is sprayed on the outer surface of the actuator, so that the actuator not only has diving function, but also has high corrosion resistance, which meets the needs of use in the confined space and highly corrosive environment of offshore platforms, ship bilge water systems, ship ballast tanks, etc.

[0021] 6. The present invention has a compact structure: the gear and gear shaft are made as one piece, and the pitch circle diameter of the gear is minimized as much as possible while ensuring that the tooth surface and shaft have sufficient strength. This reduces the external dimensions of the housing and the linear motion stroke of the piston rod, thereby ensuring that the actuator has the characteristics of compact structure and light weight.

[0022] 7. Precise stroke limiting of this utility model: An adjusting screw is installed in the threaded hole of the cylinder head of the hydraulic cylinder. By rotating the adjusting screw, the depth of the adjusting screw into the inner cavity of the hydraulic cylinder can be controlled, thereby limiting the axial position of the piston rod. The rotation angle of the gear is controlled by the rack located on the piston rod, so as to achieve precise stroke limiting of the actuator.

[0023] 8. Emergency manual switch control function of this utility model: In the event of hydraulic power failure, the piston rod is moved by rotating the adjusting screw so that its end face inside the hydraulic cylinder moves. The rack set on the piston rod meshes with the gear to control the rotation angle of the gear, thereby realizing the emergency manual switch control function of the valve.

[0024] 9. Low-temperature resistance of this utility model: Key components such as hydraulic cylinder barrel, adjusting bolt, gear, and housing are all made of low-temperature resistant materials, which can ensure that the product is suitable for low-temperature environments of -20℃.

[0025] 10. The wired feedback valve position signal of this utility model: A valve feedback device bracket mounting hole is provided on the top of the housing for mounting a valve feedback device bracket; the upper shaft of the gear is provided with a NAMUR standard mounting interface. By removing the oil level indicator and sealing nut from the top of the actuator, the rotating shaft of the valve feedback device can be inserted into the NAMUR standard mounting interface located on the upper shaft of the gear and fixed to the valve feedback device bracket, thus realizing wired feedback of the valve position signal. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the hydraulic cylinder head of a hydraulic actuator in the prior art;

[0027] Figure 2 This is a schematic diagram of the hydraulic cylinder head of a hydraulic actuator suitable for seawater environments according to the present invention;

[0028] Figure 3 This is a schematic diagram of the disconnected cross-sectional structure of a hydraulic actuator suitable for seawater environments according to the present invention;

[0029] Figure 4 for Figure 3 A magnified view of a portion of the image;

[0030] Figure 5 for Figure 3 A schematic diagram of the CC cross-section structure.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1-Box body, 2-Piston rod, 3-Hydraulic cylinder barrel, 4-Piston, 5-Nut, 6-Hydraulic cylinder head, 7-Screw, 8-Sealing nut, 9-First cap-shaped sealing nut, 10-Gear, 11-Gear cover, 12-Oil level indicator, 13-Flat bolt, 14-Sealing bolt, 16-First hydraulic oil seal, 17-Second hydraulic oil seal, 18-Support ring, 19-First O-ring, 20-Second O-ring, 21-First ED sealing ring, 22-Second ED sealing ring, 24-Third O-ring, 25-Fourth O-ring, 26-Fifth O-ring, 27-Adjusting screw. Detailed Implementation

[0033] To make this utility model more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings:

[0034] This utility model provides a hydraulic actuator suitable for seawater environments, such as... Figures 3-5 As shown, it includes a housing 1, which has piston rod holes arranged along the axial direction on opposite sides of the left and right end faces. Here, left and right are opposite. Figure 3Regarding the display direction; a cylinder guide hole is provided on the side of the piston rod hole near the housing 1, and threaded holes for installing the hydraulic cylinder 3 are provided around the cylinder guide hole; a stepped hole is provided radially on the housing 1, the stepped hole including a lower shaft hole and an upper shaft hole, the lower shaft hole of the stepped hole is provided with an oil groove and a third O-ring 24; the radially lower surface of the housing 1 is the lower plane, and the radially upper surface of the housing 1 is the upper plane. The lower plane is provided with screw holes of ISO5211 standard around the lower shaft hole of the stepped hole, and the upper plane is provided with threaded holes for installing the gear cover 11 around the upper shaft hole of the radial stepped hole and fixed with flat bolts 13. It is also provided with threaded holes for installing the valve feedback bracket and sealed with sealing bolts 14.

[0035] A hydraulic cylinder 3 is connected to the cylinder guide hole of the housing 1. A hydraulic cylinder head 6 is connected to the end of the hydraulic cylinder 3 away from the housing 1. The hydraulic cylinder head 6 is provided with screw holes. The hydraulic cylinder 3 is positioned by the hydraulic cylinder head 6 and the cylinder guide hole on the housing 1, and is fixed to the side of the housing 1 with screws 7. The two hydraulic cylinder heads 6 are respectively provided with a first oil port A and a second oil port B communicating with the inner cavity of the hydraulic cylinder 3. Hydraulic oil flows into the inner cavity of the hydraulic cylinder 3 through the first oil port A and the second oil port B, respectively.

[0036] A piston rod 2 passes through the piston rod hole of the housing 1, and a rack is provided in the middle of the piston rod 2; the piston 4 is sleeved on the piston rod 2, and the two are threaded together and fixed by a nut 5. A first O-ring 19 is provided on the stepped hole of the piston 4, and a first hydraulic oil seal 16, a second hydraulic oil seal 17 and a support ring 18 are provided on the outer circle of the piston 4. The support ring 18 is in contact with the inner wall of the hydraulic cylinder 3.

[0037] Specifically, the stepped shafts at both ends of the piston rod 2 are divided into two parts: a small shaft with a smaller diameter on the side farther from the middle and a large shaft with a larger diameter on the side closer to the middle. The shape of the inner hole in the middle of the piston 4 is the same as the outline of the stepped shafts at both ends of the piston rod 2, so as to realize the connection and cooperation between the two. One side of the piston 4 is screwed onto the stepped shaft of the piston rod 2 by the thread engagement, and the nut 5 is located on the other side of the piston 4, and the piston 4 is pressed tightly onto the stepped shaft by the nut 5.

[0038] An adjusting screw 27 is inserted into the threaded hole of the hydraulic cylinder head 6. The inner side of the adjusting screw 27 extends into the inner cavity of the hydraulic cylinder barrel 3 to limit or adjust the axial position of the piston rod 2, while the outer side is exposed outside the hydraulic cylinder head 6.

[0039] A sealing nut 8 is threaded onto the outer periphery of the adjusting screw 27. A first ED sealing ring 21 is provided on the front side (the side closer to the hydraulic cylinder 3), while no sealing ring is provided on the back side (the side away from the hydraulic cylinder 3). The sealing nut 8 has a threaded hole in the axial direction. The front side of the sealing nut 8 with the first ED sealing ring 21 is in close contact with the end face of the hydraulic cylinder head 6, preventing hydraulic oil from leaking out from the mating surface between the front side of the sealing nut 8 and the hydraulic cylinder head 6. A first cap-shaped sealing nut 9 is fitted onto the outside of the adjusting screw 27 through a threaded hole. A second ED sealing ring 22 is provided on the front side of the first cap-shaped sealing nut 9, and a threaded hole is provided in the axial direction. The front side with the second ED sealing ring 22 is in close contact with the back side of the sealing nut 8, preventing hydraulic oil from leaking out from the mating surface between the front side of the cap-shaped sealing nut 9 and the back side of the sealing nut 8.

[0040] Gear 10 and its two side shafts are integrally formed. Gear 10 is located on the outer circumference of the shaft. On the shaft, there are upper and lower shafts on both sides of gear 10. The lower shaft end is provided with a shaft hole for driving the valve stem, and the upper shaft end is provided with a NAMUR installation standard interface. Gear cover 11 has a stepped outer circle, a stepped shaft hole, and a flange. One end of the stepped outer circle is connected to one end of the flange. The stepped shaft hole is divided into an inner hole and an outer hole. The inner hole is the hole in the middle of the stepped outer circle, and the outer hole is the hole in the middle of the flange. The stepped outer circle is provided with a fourth O-ring 25 for mating with the upper shaft hole of the housing 1. The stepped shaft hole is provided with an oil groove and a fifth O-ring 26 for mating with the upper shaft of gear 10. The flange is provided with screw holes for installing flat bolts 13. The lower shaft of gear 10 extends into the lower shaft hole of housing 1, and the lower end face of gear 10 is in close contact with the end face of the lower shaft hole of housing 1. The inner hole of the stepped hole of the gear cover 11 is fitted onto the upper shaft of the gear 10 and fixed to the top of the housing 1 by a flat bolt 13. The lower end face of the gear cover 11 restricts the radial movement of the upper end face of the gear 10, thereby ensuring that the gear 10 can only rotate by meshing with the teeth of the intermediate rack of the piston rod 2. The outer hole of the stepped hole of the gear cover 11 is sealed by an oil gauge 12.

[0041] According to the Mechanical Design Handbook - Connection and Fastening Chapter, the formula for calculating bolt torque is T = kFd, where F is the preload, i.e., the axial force of the bolt, T is the torque, k is the torque coefficient, and d is the nominal diameter of the bolt. Substituting the data, the axial force of the bolt can be obtained.

[0042] The threaded hole diameter of the cylinder head of the hydraulic cylinder 3 should be 33-75% of the inner diameter of the hydraulic cylinder 3, and the engagement length of the threaded hole should be set to 8-14P to improve the load capacity of the threaded hole. Under the premise of ensuring a threaded hole machining accuracy of not less than 6H, it is recommended to use a pressing method to machine the threaded hole, thereby improving the strength of the thread surface. Under the premise of ensuring an external thread machining accuracy of not less than 6h, it is recommended to use a rolling method to machine the adjusting screw 27, thereby improving the strength of the thread surface. The thrust that can be used to move the piston rod 2 should be controlled within 25% of the theoretical data of the axial force of the adjusting screw 27.

[0043] The working principle of this utility model is as follows: The actuator of this utility model has the conventional start-stop control function, such as... Figure 3 As shown: When the hydraulic power source is normal, hydraulic oil is input into the first oil port A. The hydraulic oil is injected into the inner cavity of the left hydraulic cylinder 3 through the oil passage of the hydraulic cylinder head 6. The hydraulic cylinder head 6 and the hydraulic cylinder 3 are sealed by the second O-ring 20. The hydraulic cylinder head 6 and the sealing nut 8 are sealed by the first ED sealing ring 21. The sealing nut 8 and the cap-shaped sealing nut 9 are sealed by the second ED sealing ring 22. This pushes the left piston 4 to push the piston rod 2 to the right. The hydraulic oil in the right hydraulic cylinder 3 is discharged from the second oil port B. The rack set on the piston rod 2 controls the gear 10 to rotate counterclockwise through the meshing motion with the gear 10, realizing the normal opening function of the valve by the hydraulic actuator.

[0044] Similarly, hydraulic oil is input into the second oil port B. The hydraulic oil is injected into the inner cavity of the right hydraulic cylinder 3 through the oil passage of the hydraulic cylinder head 6. The hydraulic cylinder head 6 and the hydraulic cylinder 3 are sealed by the second O-ring 20, the hydraulic cylinder head 6 and the sealing nut 8 are sealed by the first ED sealing ring 21, and the sealing nut 8 and the cap-shaped sealing nut 9 are sealed by the second ED sealing ring 22. This pushes the right piston 4 to push the piston rod 2 to the left. The hydraulic oil in the left hydraulic cylinder 3 is discharged from the first oil port A. The rack on the piston rod 2 controls the gear 10 to rotate clockwise through the meshing motion with the gear 10, realizing the normal closing function of the hydraulic actuator on the valve.

[0045] The actuator of this utility model has a precise control function for the conventional opening and closing stroke: An adjusting screw 27 is installed in the threaded hole of the hydraulic cylinder head 6 located on the left side of the housing 1. By rotating the adjusting screw 27, the depth of the adjusting screw 27 into the hydraulic cylinder 3 can be adjusted. The end face of the adjusting screw 27 limits the leftward movement of the piston rod 2. The rack set on the piston rod 2 meshes with the tooth surface of the gear 10 to precisely limit the stopping angle of the gear 10 when it rotates counterclockwise, thereby achieving the precise limitation function of the actuator stroke.

[0046] Similarly, an adjusting screw 27 is installed in the threaded hole of the hydraulic cylinder head 6 located on the right side of the housing 1. By rotating the adjusting screw 27, the depth of the adjusting screw 27 inserted into the hydraulic cylinder 3 can be adjusted. The end face of the adjusting screw 27 restricts the rightward movement of the piston rod 2. The rack set on the piston rod 2 meshes with the tooth surface of the gear 10 to precisely limit the stopping angle of the gear 10 when rotating clockwise, thereby achieving the precise limitation function of the actuator stroke.

[0047] Emergency manual switch control function: When there is no hydraulic oil input at the first oil port A, remove the cap-shaped sealing nut 9 on the left side. By rotating the adjusting screw 27, the end face of the adjusting screw 27 inside the hydraulic cylinder 3 pushes the piston rod 2 to the right. The rack on the piston rod 2 meshes with the gear 10, controlling the gear 10 to rotate counterclockwise, thus achieving manual operation to open the valve in an emergency. Similarly, when there is no hydraulic oil input at the second oil port B, remove the cap-shaped sealing nut 9 on the right side. By rotating the adjusting screw 27, the end face of the adjusting screw 27 inside the hydraulic cylinder 3 pushes the piston rod 2 to the left. The rack on the piston rod 2 meshes with the gear 10, controlling the gear 10 to rotate clockwise, thus achieving manual operation to close the valve in an emergency.

[0048] The actuator of this utility model has a wired signal feedback function: the top of the housing 1 is provided with a valve feedback device bracket mounting hole. The valve feedback device bracket can be installed by removing the sealing screw 14; the oil level indicator 12 can be removed and the rotating shaft of the valve feedback device can be inserted into the NAMUR standard mounting hole located on the upper shaft of the gear 10 and fixed on the valve feedback device bracket, so that the valve position signal can be fed back through the wired line.

[0049] The above description is merely a preferred embodiment of this utility model and is not intended to limit this utility model in any form or substance. It should be noted that those skilled in the art can make several improvements and additions without departing from this utility model, and these improvements and additions should also be considered within the protection scope of this utility model. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of this utility model are equivalent embodiments of this utility model. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of this utility model still fall within the scope of the technical solution of this utility model.

Claims

1. A hydraulic actuator suitable for seawater environments, characterized in that, The device includes a housing with a piston rod hole penetrating both ends. A cylinder guide hole is located near the side of the housing. A piston rod, moving along the injection direction, passes through the piston rod hole. A rack is located in the middle of the piston rod. A gear meshing with the rack is located inside the housing. Hydraulic cylinders are fitted at both ends of the piston rod. One end of the hydraulic cylinder is sealed to the cylinder guide hole, and the other end is sealed to a hydraulic cylinder head. Pistons, symmetrically positioned relative to the housing, are fixed at both ends of the piston rod. The inner side of the piston is sealed to the piston rod, and the outer side of the piston is sealed to the inner wall of the hydraulic cylinder. A stroke adjustment structure is coaxially arranged on the hydraulic cylinder head, with one end of the stroke adjustment structure contacting the end face of the piston rod. The two hydraulic cylinder heads are respectively provided with a first oil port and a second oil port communicating with the hydraulic cylinders to allow hydraulic oil flow.

2. A hydraulic actuator suitable for seawater environments as described in claim 1, characterized in that, One end of the hydraulic cylinder head is provided with a guide sealing groove, the inner hole of the guide sealing groove fits with the outer diameter of the hydraulic cylinder barrel, and is movably connected to the inner wall of the hydraulic cylinder barrel in a sealing manner.

3. A hydraulic actuator suitable for seawater environments as described in claim 1, characterized in that, The stroke adjustment structure is an adjusting screw; the end face of the hydraulic cylinder head is provided with a threaded hole, the adjusting screw passes through the threaded hole and is directly opposite the end of the piston rod inside the hydraulic cylinder, and a cap-shaped sealing nut is fitted on the end of the adjusting screw away from the hydraulic cylinder, and the cap-shaped sealing nut is sealed to the hydraulic cylinder head.

4. A hydraulic actuator suitable for seawater environments as described in claim 3, characterized in that, The inner side of the adjusting screw extends into the inner cavity of the hydraulic cylinder, while the outer side of the adjusting screw is exposed outside the hydraulic cylinder head.

5. A hydraulic actuator suitable for seawater environments as described in claim 1, characterized in that, The piston has a support ring and a hydraulic seal on its outer circumference, and the piston is fitted onto the piston rod.

6. A hydraulic actuator suitable for seawater environments as described in claim 1, characterized in that, Both ends of the piston rod are stepped shafts. The shape of the inner hole in the middle of the piston is the same as the shape of the stepped shafts at both ends of the piston rod. One end face of the stepped hole of the piston abuts against the end face of the stepped shaft of the piston rod and is screwed together with the piston rod by threads. A nut is fitted on the other side of the piston, and the piston is tightened onto the stepped shaft by the nut.

7. A hydraulic actuator suitable for seawater environments as described in claim 3, characterized in that, The adjusting screw is located on the outside of the hydraulic cylinder head and is fitted with a sealing nut. The sealing nut is located between the cap-shaped sealing nut and the hydraulic cylinder head, and both ends of the sealing nut are respectively sealed to the cap-shaped sealing nut and the hydraulic cylinder head.

8. A hydraulic actuator suitable for seawater environments as described in claim 1, characterized in that, The housing has a stepped hole in the radial direction, which includes a lower shaft hole and an upper shaft hole. An oil groove is provided in the lower shaft hole of the stepped hole. An upper shaft and a lower shaft are provided on both sides of the gear. The lower shaft end is provided with a shaft hole for driving the valve stem. The upper shaft end is provided with an interface for NAMUR installation standard. A gear cover is fitted on the upper shaft. The inner side of the gear cover is sealed and rotatably connected to the upper shaft. The outer side of the gear cover is sealed and rotatably connected to the inner wall of the housing. The lower shaft of the gear extends into the lower shaft hole of the housing and is sealed and rotatably connected to the lower shaft hole of the housing.

9. A hydraulic actuator suitable for seawater environments as described in claim 8, characterized in that, The gear cover has a stepped outer circle, a stepped shaft hole, and a flange. One end of the stepped outer circle is connected to one end of the flange. The stepped shaft hole is divided into an inner hole and an outer hole. The inner hole is the hole in the middle of the stepped outer circle, and the outer hole is the hole in the middle of the flange. The inner hole of the stepped hole of the gear cover is fitted onto the upper shaft of the gear. The flange of the gear cover is fixed to the top of the housing. The lower end face of the gear is in close contact with the lower shaft hole end face of the housing. The lower end face of the gear cover restricts the radial movement of the upper end face of the gear. The outer hole of the stepped hole of the gear cover is sealed with an oil gauge.

10. A hydraulic actuator suitable for seawater environments as described in claim 8, characterized in that, The plane on one radial side of the housing has screw holes around the lower shaft hole of the stepped hole, and the plane on the other radial side of the housing has screw holes around the upper shaft hole of the stepped hole for installing a gear cover and screw holes for installing a valve feedback device bracket. A flat bolt is fixed in the screw hole for installing the gear cover, and a sealing bolt is sealed in the screw hole for installing the valve feedback device bracket.

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