A rotatable and telescopic composite motion underwater actuator and driving method

Abstract

This invention discloses a rotatable and telescopic composite underwater actuator and its driving method. The actuator includes a hydraulic cylinder, a plunger rod, a motor, a valve block, and a pressure compensation mechanism. The hydraulic cylinder is horizontally arranged and has an internal cavity. The plunger rod is movably installed within the cavity. The valve block is fixedly installed on the outer side of the hydraulic cylinder. The motor is fixedly installed at the front end of the valve block, and the pressure compensation mechanism is fixedly installed at the rear end of the valve block. The pressure compensation mechanism contains a rolling diaphragm for pressure compensation. The rolling diaphragm has a bag-like structure and a built-in balance valve for adjusting the oil flow rate and stabilizing the position of the hydraulic cylinder. The driving method involves changing the flow direction of the oil circuit inside the actuator by rotating the motor forward and backward to achieve the extension and retraction of the plunger rod. This invention has the advantages of simple and compact structure, small size, stable structure, high integration, and easy installation.

Description

Technical Field

[0001] This invention relates to the field of underwater operations, and specifically to a rotatable and telescopic composite motion underwater actuator and its driving method. Background Technology

[0002] With the continuous development of marine engineering and deep-sea exploration, the demand for underwater equipment is increasing. These devices typically need to operate in extreme environments such as high pressure and low temperature, making their reliability and functionality key design considerations. Cover plate opening and closing devices are a crucial component of underwater equipment, playing a vital role in deep-sea exploration, environmental monitoring, and resource development.

[0003] Existing underwater electro-hydraulic actuators typically employ a linear hydraulic transmission structure, where the hydraulic piston rod at the output end can only achieve linear extension and retraction in a single direction. Under most conventional operating conditions, this structure can meet basic push-pull requirements. However, in certain specific underwater applications, such as when simultaneous linear displacement and rotational attitude adjustment are needed in propulsion, control, or execution mechanisms, traditional actuators become insufficient. Due to the lack of synchronous rotation capability, existing products often require additional independent rotating mechanisms or complex multi-axis linkage structures, increasing system size and weight, as well as sealing difficulties, energy consumption, and failure risks. This makes them unsuitable for certain compact, high-reliability, or multi-degree-of-freedom control requirements of underwater equipment. Therefore, existing underwater electro-hydraulic actuators have significant limitations in functional integration and composite motion capabilities, making them unsuitable for underwater operating environments with higher performance requirements. Summary of the Invention

[0004] This invention provides a rotatable and telescopic composite motion underwater actuator and driving method, which can meet the specific needs of cover opening and closing devices in the prior art.

[0005] The technical solution adopted in this invention is:

[0006] I. A Rotatable and Telescopic Composite Motion Underwater Actuator

[0007] The actuator includes a hydraulic cylinder, a piston rod, a motor, a valve block, and a pressure compensation mechanism. The hydraulic cylinder is horizontally arranged and has a cavity inside. The piston rod is movably installed in the cavity. The valve block is fixedly installed on the outer side of the hydraulic cylinder. The motor is fixedly installed at the front end of the valve block, and the pressure compensation mechanism is fixedly installed at the rear end of the valve block. The pressure compensation mechanism has a rolling diaphragm for pressure compensation. The rolling diaphragm has a bag-like structure and contains a balance valve for adjusting the oil flow rate and stabilizing the position of the hydraulic cylinder.

[0008] The hydraulic cylinder includes a front cylinder body, a rear housing, a grooved tube, and a hinged tube assembly. One end of the grooved tube is fixedly connected to the front cylinder body, and the other end of the grooved tube extends into the rear housing with a gap between it and the housing. The cavity opens outward at the end of the front cylinder body away from the grooved tube and is sealed at the end of the rear housing away from the grooved tube. A front cylinder head is fixedly installed on the open side of the front cylinder body, and a rear cylinder head is fixedly installed on the other side of the front cylinder body. The front cylinder head has a hole in the middle to allow a plunger rod to pass through the hole to the outside of the front cylinder body, and the rear cylinder head has a hole in the middle to allow the plunger rod to pass through the hole, pass through the grooved tube, and reach the inside of the rear housing. A hinged tube assembly for connecting to the hydraulic pipeline is fixedly installed on one side of the front cylinder body, and the grooved tube and the front cylinder body are simultaneously fixedly installed on the same side of the valve block.

[0009] The groove tube includes a groove block and a groove body. One end of the groove block is fixedly connected to the front cylinder block, and the other end is fixedly connected to the groove body and the rear housing respectively. The groove block and the front cylinder block are fixedly installed on the same side of the valve block. The groove body extends into the interior of the rear housing and there is a gap between it and the housing. The groove body has an inner cavity for installing the plunger rod.

[0010] The plunger rod has a radially through-hole located near the rear housing. A pin is fixedly installed in the through-hole, and a roller is fitted on each end of the pin after it passes through the two ends of the through-hole. The slide body has two rotationally symmetrical slide grooves along the axis, which penetrate the outer surface of the slide body. Each slide groove is a curved segment that spirals from one end to the other along the axial direction. A roller is installed in each slide groove, so that the movement of the roller in the slide groove drives the movement of the entire plunger rod. The axial arrangement of the slide groove allows the roller to drive the extension and retraction of the entire plunger rod along the axial direction of the slide groove. The curved shape of the slide groove allows the movement of the roller along the curve of the slide groove to drive the rotation of the entire plunger rod. A position switch for sending the position signal of the plunger rod is installed on the slide tube. The curve shape of the slide groove is a sine curve, so that the acceleration of the plunger rod during the rotation cycle is a continuous curve.

[0011] All components of the hydraulic cylinder are sealed with oil seals. A piston is fixedly installed on the outer circumference of the middle part of the plunger rod. The outer circumference of the piston and the inner circumference of the front cylinder body are sealed with a sealing ring. The piston diameter is larger than the opening diameter of the front cylinder head and the opening diameter of the rear cylinder head, thereby limiting the stroke of the plunger rod. The piston and the rear cylinder head divide the hydraulic cylinder into three oil chambers: the first oil chamber, the second oil chamber, and the third oil chamber. One end of the first oil chamber is sealed between the plunger rod and the front cylinder head with an oil seal, and the other end is sealed between the piston and the front cylinder body with a sealing ring. One end of the second oil chamber is sealed between the piston and the front cylinder body with a sealing ring, and the other end is sealed between the plunger rod and the rear cylinder head with an oil seal. One end of the third oil chamber is sealed between the plunger rod and the rear cylinder head with an oil seal, and the other end of the third oil chamber is the sealed end of the rear housing. The front cylinder head and the front cylinder body, the rear cylinder head and the sliding block, the sliding block and the rear housing, and the rear housing and the sliding block are all sealed with sealing rings.

[0012] The valve block has an internal chamber. The output shaft of the motor at the front end of the valve block is connected to the pressure compensation mechanism through the chamber. A hollow connecting block is fixedly installed on one side of the valve block. The hollow part of the connecting block is connected to the valve block chamber. A watertight plug for external control signals is installed on the connecting block. The watertight plug is connected to the drive power supply and the control console. The watertight plug is electrically connected to the motor and the position switch through the connecting block, the valve block, and the slide tube, respectively.

[0013] The pressure compensation mechanism includes a gear pump, a balance valve, an oil tank cover, a liquid level indicator, a diaphragm piston plate, a conical spring, a rolling diaphragm, a clamping ring, and a sealing flange. The gear pump, the sealing flange, and two balance valves are fixedly installed at the rear end of the valve block. The sealing flange is an annular structure that surrounds the gap between the gear pump and the two balance valves inside. The outer periphery of the sealing flange extends backward and the radial dimension gradually decreases. The output shaft of the motor at the front end of the valve block is connected to the gear pump through the chamber, so that the rotation of the motor drives the gear pump to rotate, thereby supplying oil to the oil cylinder.

[0014] The rolling diaphragm is a deformable bag-shaped structure. The rolling diaphragm is intermittently fitted outside the gear pump and the balance valve. The clamping ring is fitted around the outer periphery of the rolling diaphragm so that the bag-shaped end of the rolling diaphragm is pressed against the outer periphery of the sealing flange with a smaller radial dimension. One end of the oil tank cover opening has an internal thread that engages with the thread on the outside of the sealing flange for fixation. The oil tank cover is fitted onto the outer periphery of the sealing flange with a larger radial dimension. The gear pump also has two channels for oil to interact with the rolling diaphragm in one direction. One channel is used for the rolling diaphragm to supply oil to the gear pump, and the other channel is used for the gear pump to discharge oil to the rolling diaphragm.

[0015] The conical spring is axially mounted on the non-open end of the oil tank cover. The top surface of the conical spring abuts against the diaphragm piston plate, and the bottom surface of the conical spring is fixedly connected to the non-open end face of the oil tank cover. The diaphragm piston plate contacts the non-open end of the rolling diaphragm. A circular hole is opened on the non-open end face of the oil tank cover, and a threaded hole is opened in the middle of the diaphragm piston plate. One end of the liquid level indicator rod passes through the circular hole into the oil tank cover and is screwed into the threaded hole in the diaphragm piston plate for fixation. The other end of the liquid level indicator rod extends out of the oil tank cover, so that when the deformation of the rolling diaphragm caused by the change in the amount of oil inside changes, it is transmitted to the liquid level indicator rod through the diaphragm piston plate to visually reflect the change.

[0016] The gear pump has three oil ports: a first oil port, a second oil port, and a third oil port. Two oil passages for oil flow are respectively opened between the valve block and the front cylinder block, namely the first oil passage and the second oil passage. One oil passage for oil flow is opened between the valve block and the slide tube, namely the third oil passage. The two balance valves are the first balance valve and the second balance valve.

[0017] The first oil port of the gear pump is connected to one end of the first balance valve and the control oil port of the second balance valve, respectively. The other end of the first balance valve is connected to one end of the first oil passage. The other end of the first oil passage is connected to the first oil chamber inside the front cylinder block through a hinged pipe member installed on one side of the front cylinder block. The second oil port of the gear pump is connected to one end of the second balance valve and the control oil port of the first balance valve, respectively. The other end of the second balance valve is connected to one end of the second oil passage. The other end of the second oil passage is connected to the second oil chamber inside the front cylinder block. The third oil port of the gear pump is connected to one end of the third oil passage. The other end of the third oil passage is connected to the third oil chamber inside the rear housing and the sliding block.

[0018] The second oil passage is directly connected to the second oil chamber inside the front cylinder block. The first oil passage is connected to the first oil chamber inside the front cylinder block through a hinged pipe component installed on one side of the front cylinder block. Each of the balance valves is a one-way valve and there is also a passage inside the valve that is opened by the valve core.

[0019] The gear pump connects to the first oil chamber inside the front cylinder block via a first oil port, a first balance valve, a first oil passage, and a hinged pipe component, forming two oil circuits: a first oil supply circuit for supplying oil and a first oil return circuit for returning oil. The gear pump also connects to the second oil chamber inside the front cylinder block via a second oil port, a second balance valve, and a second oil passage, forming two oil circuits: a second oil supply circuit for supplying oil and a second oil return circuit for returning oil. Finally, the gear pump connects to the third oil chamber inside the rear housing and the sliding block via a third oil port and a third oil passage, forming a third oil circuit.

[0020] II. A driving method for a rotatable and retractable composite motion underwater actuator

[0021] The driving method is as follows:

[0022] First, start the motor. The motor drives the gear pump to rotate, which causes the oil circuit inside the underwater actuator to circulate and push the plunger rod to rotate and extend, thereby opening the external cover.

[0023] Then, the motor is reversed, which drives the gear pump to rotate in the opposite direction, causing the oil circuit inside the underwater actuator to circulate in the opposite direction, pushing the plunger rod to rotate and retract, thereby closing the external cover.

[0024] Next, the underwater actuator makes judgments and operates in the following manner:

[0025] When the gear pump supplies oil and the piston rod moves at a speed exceeding the preset speed, the oil flow inside the balance valve slows down, thereby slowing down the piston rod and regulating the speed of the cylinder.

[0026] When the gear pump supplies oil and the piston rod moves at a speed not exceeding the preset speed, the balance valve in the return oil circuit remains open because the high-pressure oil in the supply oil circuit pushes the valve core, and the piston rod 1 moves normally.

[0027] When the gear pump does not supply oil, the oil pressure at the control ports of the balance valves on both sides cannot open the valve core. The first / second return oil circuit in each balance valve cannot return oil because the valve core is closed, thus ensuring that the position of the oil cylinder is fixed.

[0028] When the motor is started, the reverse / forward rotation of the motor drives the gear pump to rotate in the reverse / forward direction, causing the gear pump to supply oil to the first oil chamber / second oil chamber through the first oil supply line / second oil supply line, thereby pushing the plunger rod to retract / extend. At the same time, the valve core of the corresponding second balance valve / first balance valve opens, allowing the oil in the second oil chamber / first oil chamber to return to the gear pump through the second return oil line / first return oil line.

[0029] The rotation of the motor drives the gear pump to rotate, thereby starting to supply oil to the first or second oil port. When the first oil port supplies oil, the first oil port supplies oil to the first oil chamber through the first oil supply line as the oil inlet side. The increase of oil in the first oil chamber pushes the piston to move towards the second oil chamber, thereby realizing the movement of the plunger rod towards the rear housing. Under the action of the roller and the slide, it rotates and retracts. The oil pushes the valve core in the second balance valve to move and open the channel in the second balance valve. The channel allows the oil that cannot flow in the second oil chamber due to the second balance valve acting as a one-way valve to flow back to the second oil port through the second return oil line as the return oil side, thereby forming a circulation.

[0030] When the second oil port supplies oil, the second oil port supplies oil to the second oil chamber through the second oil supply line as the oil inlet side. The increase of oil in the second oil chamber pushes the piston to move towards the first oil chamber, thereby realizing the movement of the plunger rod towards the front cylinder. Under the action of the roller and the slide, it rotates and extends. The oil pushes the valve core in the first balance valve to move and open the channel in the first balance valve. The channel allows the oil that cannot flow in the first oil chamber due to the second balance valve acting as a one-way valve to flow back to the first oil port through the first return oil line as the return oil side, thereby forming a cycle.

[0031] When the gear pump supplies oil and the piston rod moves at a speed exceeding the preset speed, the pressure on the inlet side decreases. The pressure difference between the inlet and return sides narrows, causing the valve core opening of the balance valve on the return side to shrink. This obstructs and slows down the flow of oil, thereby slowing down the piston rod and regulating the cylinder's movement speed. When the gear pump does not supply oil, the oil pressure at the control ports of the balance valves on both sides cannot open the valve core. The channel controlled by the valve core inside the balance valve cannot be opened because the valve core is closed. The oil cannot flow because it is disconnected on the return side, thus ensuring that the cylinder position is fixed.

[0032] When the plunger rod extends forward towards the cylinder block, oil is supplied from the third port through the third oil passage to the third oil chamber to balance the pressure. When the plunger rod retracts backward towards the housing, oil is returned from the third oil chamber through the third oil passage to the third port to balance the pressure. When oil overflows, the excess oil flows to the rolling diaphragm through the gear pump. When oil is insufficient, the missing oil flows to the gear pump through the rolling diaphragm, thus achieving pressure compensation.

[0033] The beneficial effects of this invention are:

[0034] The device of this invention has the advantages of simple and compact structure, small size, stable structure, high integration and easy installation. When the underwater equipment needs to open the cover, the opening and closing mechanism can be controlled to start the action. The plunger rod drives the cover plate to extend and rotate. While opening the cover plate, the cover plate is rotated to the side, which improves the opening speed and opening efficiency to ensure the normal operation of subsequent actions.

[0035] 1) The present invention adopts a design of a sliding tube structure, which enables the piston rod of the opening and closing mechanism to extend and rotate according to the predetermined trajectory of the sliding tube, thus having the advantages of fast opening speed and high structural stability.

[0036] 2) This invention addresses the issue of significant seawater pressure inside the structure when operating at higher underwater depths by employing a pressure compensation mechanism to ensure consistent pressure inside and outside the structure. This prevents structural damage caused by excessive pressure differences and reduces the pressure resistance requirements and weight of the structure.

[0037] 3) This invention uses two balance valves to achieve interlocking function, which can realize the control of cylinder speed, stabilize the position of piston rod, and prevent the piston rod from automatically extending or retracting when power is lost or the system is paused, thereby improving the movement stability of piston rod.

[0038] To optimize the opening mechanism, shorten operation time, improve task execution efficiency, and reduce resource consumption, we are researching a modular, highly integrated, simple, high-load-bearing, safe and stable operation mechanism that can balance internal and external seawater pressure. This is of great significance for promoting marine exploration and technological progress. Attached Figure Description

[0039] Figure 1 This is a structural diagram of the device of the present invention;

[0040] Figure 2 This is a structural diagram of the hydraulic cylinder module of the present invention;

[0041] Figure 3 This is a structural diagram of the pump, valve, motor, and pressure compensation device of the present invention.

[0042] Figure 4 This is a structural diagram of the articulated pipe component of the present invention;

[0043] Figure 5 This is the hydraulic circuit and schematic diagram of the present invention.

[0044] In the diagram: 1. Piston rod, 2. Front cylinder head, 3. Front cylinder block, 4. Motor, 5. Valve block, 6. Connecting block, 7. Pressure compensation mechanism, 8. Oil tank cover, 9. Rear housing, 10. Slide tube, 11. Hinge tube assembly, 12. Gear pump, 13. Liquid level indicator rod, 14. Diaphragm piston plate, 15. Conical spring, 16. Rolling diaphragm, 17. Clamping ring, 18. Sealing cover flange, 19. Balance valve, 20. Dust seal, 23. Piston, 26. Pin, 27. Roller, 28. Position switch, 29. Rear cylinder head, 30. Hinge joint, 31. Welded pipe, 32. Hinged joint with hole, 33. Plug, 34. Watertight plug. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] like Figure 1 As shown, the underwater actuator includes a hydraulic cylinder, a plunger rod 1, a motor 4, a valve block 5, and a pressure compensation mechanism 7. The hydraulic cylinder is horizontally arranged, with a cavity inside. The plunger rod 1 is movably installed within the cavity. The valve block 5 is fixedly installed on the outer side of the hydraulic cylinder. The motor 4 is fixedly installed at the front end of the valve block 5 to control the extension, retraction, and rotation of the plunger rod 1. The pressure compensation mechanism 7 is fixedly installed at the rear end of the valve block 5. A rolling diaphragm 16 for pressure compensation is installed inside the pressure compensation mechanism 7. The rolling diaphragm 16 has a bag-like structure and contains a balance valve for adjusting the oil flow rate and stabilizing the position of the hydraulic cylinder.

[0047] The plunger rod 1 has a square hole at its front end and a pair of parallel planes on its outer circumference, which can be used to install a cover plate or other accessories. The lower part of the front cylinder body 3 has four threaded holes, allowing the entire structure to be fixed in underwater equipment.

[0048] like Figure 2 As shown, the hydraulic cylinder includes a front cylinder body 3, a rear housing 9, a sliding tube 10, and a hinged tube component 11. The front cylinder body 3 and the rear housing 9 are coaxially fixedly connected by the sliding tube 10 and screws. One end of the sliding tube 10 is fixedly connected to the front cylinder body 3, and the other end of the sliding tube 10 extends into the interior of the rear housing 9 with a gap between it and the housing 9. The cavity is open outward at the end of the front cylinder body 3 away from the sliding tube 10, and the cavity is sealed at the end of the rear housing 9 away from the sliding tube 10. The front cylinder head 2 is fixedly installed on the open side of the front cylinder body 3 by screws, and the rear cylinder head 29 is fixedly installed on the other side of the front cylinder body 3 by screws. The front cylinder head 2 has a hole in the middle so that the plunger rod 1 passes through the hole to the outside of the front cylinder body 3. The rear cylinder head 29 has a hole in the middle so that the plunger rod 1 passes through the hole, passes through the sliding tube 10, and reaches the interior of the rear housing 9.

[0049] A hinged pipe component 11 for connecting oil pipeline is fixedly installed on one side of the front cylinder block 3 by screws, and a sliding groove pipe 10 and the front cylinder block 3 are fixedly installed on the same side of the valve block 5.

[0050] Specifically, the front cylinder block 3 has four threaded holes on its front end face, and the front cylinder head 2 has four through holes at corresponding positions. The front cylinder head 2 and the front cylinder block 3 can be fixed by screws. The rear cylinder head 29 is located between the front cylinder block 3 and the slide tube 10. The front end face of the slide tube 10 has a cylindrical groove that matches the rear end of the rear cylinder head 29. When the slide tube 10 is fixed to the front cylinder block 3, the rear cylinder head 29 is also fixed. The rear end face of the front cylinder head 2 has four threaded holes, and the slide tube 10 and the rear housing 9 each have four through holes at corresponding positions. Screws can pass through the rear housing 9 and the slide tube 10 in sequence and fix the two to the front cylinder block 3 through threaded connections. The diameter of the piston part in the middle of the plunger rod 1 is slightly larger than the inner diameter of the front cylinder head 2 and the diameter of the rear cylinder head 29, thereby limiting the stroke of the piston rod. The hinge tube component 11 is fixed to the surface of the front cylinder block 3 through a threaded connection.

[0051] The groove tube 10 includes a groove block and a groove body. One end of the groove block is fixedly connected to the front cylinder 3, and the other end is fixedly connected to the groove body and the rear housing 9 respectively. The groove block and the front cylinder 3 are fixedly installed on the same side of the valve block 5. The groove body extends into the interior of the rear housing 9 and there is a gap between it and the housing 9. The groove body has an inner cavity for installing the plunger rod 1.

[0052] The plunger rod 1 has a through hole in the radial direction near the rear housing 9. A pin 26 is fixedly installed in the through hole. After the two ends of the pin 26 pass through the two ends of the through hole, a roller 27 is fitted on each end. The slide body has two slide grooves that are rotationally symmetrical along the axis. The slide grooves penetrate the outer side of the slide body. Each slide groove is a curved segment that spirals from one end to the other along the axial direction. Specifically, each slide groove consists of three segments that are connected sequentially from one end of the slide body to the other end along the axial direction. The two segments on both sides are mainly straight lines parallel to the axial direction and are not located on the same axis. The middle segment is mainly a curve used to smoothly transition between the straight lines on both sides.

[0053] Each groove is fitted with a roller 27, which moves the plunger rod 1 as a whole by moving the roller 27 in the groove. The axial arrangement of the groove allows the plunger rod 1 to extend and retract along the axial direction of the groove by the roller 27. The curved shape of the groove allows the plunger rod 1 to rotate as the roller 27 moves along the curve of the groove. A position switch 28 is installed on the groove tube 10 to send the position signal of the plunger rod 1.

[0054] Specifically, when the opening and closing mechanism is in the opening process, the roller 27 is located in the straight groove of the slide tube 10, and the plunger rod 1 extends straight out in its initial position. When the roller 27 moves to the curved groove of the slide tube 10, the groove forces the roller 27, pin 26, and plunger rod 1 to rotate. At this time, the plunger rod 1 rotates while extending. When the opening is complete, the plunger rod 1 stops moving, completing the opening process. When the opening and closing mechanism is in the closing process, the roller 27 is located in the curved groove of the slide tube 10, and the groove forces the roller 27, pin 26, and plunger rod 1 to rotate. At this time, the plunger rod 1 rotates while retracting. After rotation, the roller 27 is located in the straight groove of the slide tube 10, and the plunger rod 1 retracts straight out in its initial position. When the closing is complete, the plunger rod 1 stops moving, completing the closing process. There is a groove on the rear side of the plunger rod 1, perpendicular to the pin 26. The groove will open with the position on the slide tube 10. The two position switches 28 on the slide tube 10 are designed to send the position signal of the plunger rod 1. Specifically, one position switch 28 is located on the slide block, and the other is located on the side of the slide body near the closed end. When the plunger rod 1 is fully retracted, the plunger rod 1 causes both position switches 28 to close. As the plunger rod 1 extends outward, when the groove at the rear end of the plunger rod 1 moves to the position switch 28 on the slide body, the position switch 28 opens, while the position switch 28 on the slide block remains closed. At this time, the position switches 28 are in a state of one closed and one open. When the plunger rod 1 is fully extended, the groove at the rear end of the plunger rod 1 moves to the position switch 28 on the slide block, causing that position switch 28 to open, while the position switch 28 on the slide body remains open. When fully extended, both position switches 28 are in the open state.

[0055] The groove's curved shape is a sine curve, ensuring that the acceleration of the plunger rod 1 during its rotation cycle is a continuous curve over time. When the rollers 27 on both sides of the plunger rod 1 rotate under force in the groove, the acceleration of the plunger rod 1 during its entire rotation cycle is a continuous curve over time. This curve ensures that the plunger rod 1 rotates smoothly without any sudden acceleration changes during its entire motion from the starting point to the end point.

[0056] All components of the hydraulic cylinder are sealed with oil seals. A piston 23 is fixedly mounted on the outer circumference of the middle part of the plunger rod 1. The outer circumference of the piston 23 and the inner circumference of the front cylinder 3 are sealed by a sealing ring. The diameter of the piston 23 is larger than the opening diameter of the front cylinder head 2 and the opening diameter of the rear cylinder head 29, thereby limiting the stroke of the plunger rod 1. The piston 23 and the rear cylinder head 29 divide the hydraulic cylinder into three oil chambers: the first oil chamber, the second oil chamber, and the third oil chamber. One end of the first oil chamber is sealed between the plunger rod 1 and the front cylinder head 2 by an oil seal, and the other end is open to the outside. The piston 23 and the front cylinder 3 are sealed by a sealing ring. One end of the second oil chamber is sealed by a sealing ring between the piston 23 and the front cylinder 3, and the other end is sealed by an oil seal between the plunger rod 1 and the rear cylinder head 29. One end of the third oil chamber is sealed by an oil seal between the plunger rod 1 and the rear cylinder head 29, and the other end of the third oil chamber is the sealed end of the rear housing 9. The front cylinder head 2 and the front cylinder 3, the rear cylinder head 29 and the sliding block, the sliding block and the rear housing 9, and the rear housing 9 and the sliding block are all sealed by sealing rings.

[0057] Specifically, the inner side of the round hole of the front cylinder head 2 has multiple cylindrical grooves. Dustproof rings 20, oil seals, and wear rings are placed between the front cylinder head 2 and the plunger rod 1. The dustproof rings 20 prevent external dust from entering the oil cylinder. The oil seals 21 consist of two Y-shaped sealing rings placed back to back to achieve dynamic sealing of the oil cylinder. The two wear rings are placed side by side to support the plunger rod 1 while avoiding friction between metals. The outer circular surface of the mating part of the front cylinder head 2 and the front cylinder body 3 has two cylindrical grooves for placing O-rings to ensure static sealing between the front cylinder head 2 and the front cylinder body 3. The piston 23 part in the middle of the plunger rod 1 has a cylindrical groove, and a sealing ring or other sealing element is placed in the middle to form a combined seal, ensuring that the first oil chamber and the second oil chamber are separated as high and low pressure oil chambers.

[0058] Multiple cylindrical grooves are formed on the inner side of the rear cylinder head 29. Wear-resistant rings and oil seals are placed between the rear cylinder head 29 and the plunger rod 1, respectively. The two wear-resistant rings are placed side by side to support the plunger rod 1 while avoiding metal-to-metal friction. The oil seal achieves dynamic sealing of the cylinder. Two cylindrical grooves are formed on the outer circular surface of the part of the rear cylinder head 29 that mates with the front cylinder block 3 to place O-rings and ensure static sealing between the rear cylinder head 29 and the front cylinder block 3. A cylindrical groove is formed on the outer circular surface of the part of the rear cylinder head 29 that mates with the slide tube 10 to place O-rings and ensure static sealing between the rear cylinder head 29 and the slide tube 10. A cylindrical groove is formed on the outer circular surface of the part of the slide tube that mates with the rear housing 9 to place O-rings and ensure static sealing between the slide tube 10 and the rear housing 9.

[0059] like Figure 3As shown, the valve block 5 has a chamber for oil and electrical flow. The output shaft of the motor 4 at the front end of the valve block 5 is connected to the pressure compensation mechanism 7 through the chamber. A hollow connecting block 6 is fixedly installed on one side of the valve block 5. The hollow part of the connecting block 6 communicates with the chamber of the valve block 5. Two watertight plugs 34 are installed on the connecting block 6 for connecting external power and control signals to drive the opening and closing mechanism. The watertight plugs 34 are connected to the drive power supply and the control console to control the movement of the underwater actuator and provide feedback on the current working status. The internal cables of the watertight plugs 34 are electrically connected to the motor 4 and the position switch 28 through the connecting block 6, the valve block 5, and the slide tube 10, respectively.

[0060] The motor 4, valve block 5, connecting block 6, and pressure compensation mechanism 7 are all connected by threads. The valve block 5 has a through hole that corresponds to the hole on the top of the front cylinder 3 and is fixed by threaded connection. The front and rear end faces and sides of the valve block 5 have threaded holes that correspond to the holes of the motor 4, the holes of the pressure compensation device, and the holes of the connecting block 6 and are fixed by threaded connection.

[0061] like Figure 3 As shown, the pressure compensation mechanism 7 includes a gear pump 12, a balance valve 19, an oil tank cover 8, a liquid level indicator rod 13, a diaphragm piston plate 14, a conical spring 15, a rolling diaphragm 16, a clamping ring 17, and a sealing cover flange 18.

[0062] The rear end of the valve block 5 is fixedly mounted with a gear pump 12, a sealing cover flange 18 and two balance valves 19. The sealing cover flange 18 has an annular structure that surrounds the gear pump 12 and the two balance valves 19 within the gap. The outer periphery of the sealing cover flange 18 extends backward and the radial dimension gradually decreases. The output shaft of the motor 4 at the front end of the valve block 5 is connected to the gear pump 12 through the chamber, so that the rotation of the motor 4 drives the gear pump 12 to rotate, thereby supplying oil to the cylinder. Specifically, the motor 4 and the gear pump 12 are fixed together by a coupling sleeve.

[0063] The rolling diaphragm 16 is a deformable bag-shaped structure. The rolling diaphragm 16 is intermittently fitted outside the gear pump 12 and the balance valve 19. The bag opening end of the rolling diaphragm 16 is fitted onto the outer periphery of the sealing flange 18 with a smaller radial dimension. The contact surface between the sealing flange 18 and the rolling diaphragm 16 has multiple sets of grooves to increase the friction between them. The clamping ring 17 is fitted onto the outer periphery of the rolling diaphragm 16 so that the bag opening end of the rolling diaphragm 16 is pressed tightly against the outer periphery of the sealing flange 18 with a smaller radial dimension, further ensuring the sealing performance of the rolling diaphragm 16. One end of the oil tank cover 8 has an internal thread that engages with the thread on the outside of the sealing flange 18 for fixation. The oil tank cover 8 is fitted onto the outer periphery of the sealing flange 18 with a larger radial dimension. The gear pump 12 also has two channels for oil to interact with the rolling diaphragm 16 in one direction. One channel is used for the rolling diaphragm 16 to supply oil to the gear pump 12, and the other channel is used for the gear pump 12 to discharge oil to the rolling diaphragm 16. The gear pump 12 also has a pressure relief circuit inside.

[0064] A conical spring 15 is axially installed on the non-open end of the oil tank cover 8. The top surface of the conical spring 15 abuts against the diaphragm piston plate 14, and the bottom surface of the conical spring 15 is fixedly connected to the non-open end face of the oil tank cover 8. The diaphragm piston plate 14 and the non-open end of the rolling diaphragm 16 are in direct contact to ensure that the rolling diaphragm 16 is subjected to uniform force. A circular hole is opened on the non-open end face of the oil tank cover 8, and a threaded hole is opened in the middle of the diaphragm piston plate 14. One end of the liquid level indicator rod 13 passes through the circular hole into the oil tank cover 8 and is screwed into the threaded hole in the diaphragm piston plate 14 for fixation. The other end of the liquid level indicator rod 13 extends out of the oil tank cover 8, so that when the deformation of the rolling diaphragm 16 due to the change in the amount of oil inside changes, it is transmitted through the diaphragm piston plate 14 to the liquid level indicator rod 13 to intuitively reflect the change.

[0065] Specifically, the bottom of the non-open end of the oil tank cover 8 has a ring of protruding grooves that can hold the large-diameter end of the conical spring 15 in place. The small-diameter end of the conical spring 15 presses against the diaphragm piston plate 14, and the piston plate directly contacts the rolling diaphragm 16, ensuring that the rolling diaphragm 16 is subjected to uniform force. The bottom of the non-open end of the oil tank cover 8 has a round hole, and the middle of the diaphragm piston plate 14 has a threaded hole, through which the liquid level indicator rod 13 can be inserted into the oil tank cover 8 and screwed into the diaphragm piston plate 14 for fixation. When the amount of oil inside the rolling diaphragm 16 changes, the change can be visually reflected by the liquid level indicator rod 13. The bottom of the open section of the oil tank cover 8 has internal threads that can be engaged with the external threads of the sealing flange 18 for fixation.

[0066] The gear pump 12 has three oil ports: a first oil port, a second oil port, and a third oil port. Two oil passages for oil flow are respectively opened between the valve block 5 and the front cylinder 3, namely the first oil passage and the second oil passage. One oil passage for oil flow is opened between the valve block 5 and the slide tube 10, namely the third oil passage. The two balance valves 19 are the first balance valve and the second balance valve, respectively.

[0067] The first oil port of the gear pump 12 is connected to one end of the first balance valve and the control oil port of the second balance valve respectively. The other end of the first balance valve is connected to one end of the first oil passage. The other end of the first oil passage is connected to the first oil chamber inside the front cylinder 3 through the hinged pipe member 11 installed on one side of the front cylinder 3.

[0068] The second oil port of the gear pump 12 is connected to one end of the oil port of the second balance valve and the control oil port of the first balance valve. The other end of the oil port of the second balance valve is connected to one end of the second oil passage. The other end of the second oil passage is connected to the second oil chamber inside the front cylinder block 3.

[0069] The third oil port of gear pump 12 is connected to one end of the third oil passage, and the other end of the third oil passage is connected to the third oil chamber inside the rear housing 9 and the sliding block.

[0070] The second oil passage is directly connected to the second oil chamber inside the front cylinder block 3. The first oil passage is connected to the first oil chamber inside the front cylinder block 3 through the hinged pipe component 11 installed on one side of the front cylinder block 3. Each balance valve 19 is a one-way valve and there is also a passage opened by the valve core inside the valve.

[0071] Specifically, such as Figure 4 As shown, the articulated pipe component 11 includes an articulated joint 30, a welded pipe 31, a perforated articulated joint 32, and a screw plug 33. The welded pipe 31 is a slender, bent tube welded to a hollow cylinder. It is connected to the front cylinder 3 by threads through the articulated joint 30 and the perforated articulated joint 32. The screw plug 33 seals the oil port on the other side of the perforated articulated joint 32 to ensure that the only first oil passage is unobstructed. The contact surface between the welded pipe 31 and the front cylinder 3 has a groove for placing an O-ring to ensure the static seal of the oil pipeline. The contact surface between the welded pipe 31 and the two articulated joints 30 has a groove for placing an O-ring to ensure the static seal of the oil pipeline.

[0072] The first oil port is connected to the first and second balance valves through oil passages inside the valve block 5, and the second oil port is also connected to the first and second balance valves through oil passages inside the valve block 5, thereby regulating the movement speed of the plunger rod 1 and ensuring the fixed position of the cylinder. Each balance valve 19 is also equipped with a safety valve and a safety circuit for pressure relief.

[0073] The gear pump 12 passes through the first oil port, the first balance valve, the first oil passage, and the hinged pipe component 11 in sequence, and finally connects to the first oil chamber inside the front cylinder block 3 to achieve the purpose of supplying / returning oil, forming two oil circuits. The oil circuit used for supplying oil in the first balance valve is the first oil supply circuit, and the oil circuit used for returning oil in the first balance valve is the first oil return circuit.

[0074] The gear pump 12 passes through the second oil port, the second balance valve, the second oil passage, and finally the second oil chamber inside the front cylinder block 3 to supply / return oil, forming two oil circuits. The oil circuit used for supplying oil in the second balance valve is the second oil supply circuit, and the oil circuit used for returning oil in the second balance valve is the second oil return circuit.

[0075] The gear pump 12 supplies / returns oil to the rear housing 9 and the third oil chamber of the sliding block through the third oil port and the third oil passage, thus forming the third oil circuit.

[0076] The driving method for the underwater actuator is as follows:

[0077] First, start the motor. The motor drives the gear pump 12 to rotate, which causes the oil circuit inside the underwater actuator to circulate and push the plunger rod 1 to rotate and extend, thereby opening the external cover. When it is opened to a certain extent, the cover rotates to avoid interfering with the subsequent material release or equipment deployment process.

[0078] Then, the motor is reversed, and the motor drives the gear pump 12 to rotate in the opposite direction, so that the oil circuit in the underwater actuator is formed in the opposite direction to push the piston rod 1 to rotate and retract, thereby closing the external cover. During the closing process, the cover is rotated back to its original position and pressed tightly.

[0079] Next, the underwater actuator makes judgments and operates in the following manner:

[0080] When the gear pump 12 supplies oil and the piston rod 1 moves at a speed exceeding the preset speed, the balance valve 19 slows down the flow of oil inside due to the reduced pressure difference, thereby slowing down the movement speed of the piston rod 1 and achieving the regulation of the cylinder movement speed.

[0081] When the gear pump 12 supplies oil and the piston rod 1 moves at a speed not exceeding the preset speed, the balance valve 19 in the return oil circuit remains open because the high-pressure oil in the supply oil circuit pushes the valve core, and the piston rod 1 moves stably.

[0082] When the gear pump 12 is not supplying oil, the oil pressure at the control ports of the balance valves 19 on both sides cannot open the valve core. The first / second return oil circuit in each balance valve 19 cannot return oil because the valve core is closed, thus ensuring that the position of the oil cylinder is fixed.

[0083] The specific method is as follows:

[0084] like Figure 5As shown, when the motor is started, the reverse / forward rotation of the motor 4 drives the gear pump 12 to rotate in the reverse / forward direction, so that the gear pump 12 supplies oil to the first oil chamber / second oil chamber through the first oil supply line / second oil supply line, thereby pushing the plunger rod 1 to retract / extend. At the same time, the valve core of the corresponding second balance valve / first balance valve opens, so that the oil in the second oil chamber / first oil chamber returns to the gear pump through the second return oil line / first return oil line.

[0085] The rotation of motor 4 drives gear pump 12 to rotate, thereby enabling the first oil port or the second oil port to start supplying oil. When the first oil port supplies oil, the first oil port supplies oil to the first oil chamber through the first oil supply circuit as the oil inlet side. The increase of oil in the first oil chamber pushes piston 23 to move towards the second oil chamber, thereby realizing the movement of plunger rod 1 towards the rear housing 9. Under the action of roller 27 and slide groove, it rotates and retracts. At this time, high pressure is formed on the first oil port side, while the second balance valve connected to the first oil port is at low pressure. The oil flows from high pressure to low pressure, thereby pushing the valve core in the second balance valve to move and open the channel in the second balance valve. The channel allows the oil in the second oil chamber that cannot flow due to the second balance valve acting as a one-way valve to flow back to the second oil port through the second return oil circuit as the return oil side, thereby forming a cycle.

[0086] When the second oil port supplies oil, the second oil port supplies oil to the second oil chamber through the second oil supply line as the oil inlet side. The increase of oil in the second oil chamber pushes the piston 23 to move towards the first oil chamber, thereby realizing the movement of the plunger rod 1 towards the front cylinder 3. Under the action of the roller 27 and the slide groove, it rotates and extends. At this time, a high pressure is formed on the second oil port side, while the first balance valve connected to the second oil port is at low pressure. The oil flows from high pressure to low pressure, thereby pushing the valve core in the first balance valve to move and open the channel in the first balance valve. The channel allows the oil that cannot flow in the first oil chamber due to the second balance valve acting as a one-way valve to flow back to the first oil port through the first return oil line as the return oil side, thereby forming a cycle.

[0087] When the piston rod 1 moves faster than the preset speed, the pressure on the inlet side decreases, reducing the pressure difference between the inlet and return sides. This causes the valve core opening of the balance valve 19 on the return side to narrow, obstructing and slowing the oil flow, thus slowing down the piston rod 1 and regulating the cylinder's movement speed. When the motor 4 loses power or the device is paused (i.e., the gear pump 12 does not supply oil), the oil pressure at the control ports of the balance valves 19 on both sides cannot open the valve core. The valve core-controlled channel inside the balance valve 19 cannot open because the valve core is closed, sealing the oil in both chambers of the cylinder. The oil cannot flow because it is disconnected on the return side, thus ensuring the cylinder position is fixed. However, when the external pressure is too high, the balance valve 19 can automatically push open the internal valve core through its internal circuit, allowing the circuit to open and the oil to flow, releasing the pressure and preventing the cylinder from bursting due to excessive pressure, thus acting as a safety valve.

[0088] When the plunger rod 1 extends forward towards the cylinder block 3, oil is supplied from the third oil port to the third oil chamber through the third oil passage to balance the pressure. When the plunger rod 1 retracts towards the rear housing 9, oil is returned from the third oil chamber to the third oil port through the third oil passage to balance the pressure. When oil overflows, the excess oil flows to the rolling diaphragm 16 through the gear pump 12. When oil is insufficient, the missing oil flows to the gear pump 12 through the rolling diaphragm 16, thereby achieving pressure compensation.

[0089] When the pressure compensation mechanism 7 is subjected to external seawater pressure, the rolling diaphragm 16 is squeezed and deformed, transmitting the external pressure to the internal oil. Since all spaces inside the system are connected, the internal and external pressures can be kept in balance, avoiding structural damage caused by excessive internal and external pressure differences. At the same time, it reduces the pressure resistance requirements of the structure and reduces weight.

Claims

1. A rotatable and telescopic composite motion underwater actuator, characterized in that: The system includes a hydraulic cylinder, a plunger rod (1), a motor (4), a valve block (5), and a pressure compensation mechanism (7). The hydraulic cylinder is horizontally arranged and has a cavity inside. The plunger rod (1) is movably installed in the cavity. The valve block (5) is fixedly installed on the outer side of the hydraulic cylinder. The motor (4) is fixedly installed at the front end of the valve block (5). The pressure compensation mechanism (7) is fixedly installed at the rear end of the valve block (5). A rolling diaphragm (16) for pressure compensation is installed inside the pressure compensation mechanism (7). The rolling diaphragm (16) has a bag-shaped structure and contains a balance valve for adjusting the oil flow rate and stabilizing the position of the hydraulic cylinder. The hydraulic cylinder includes a front cylinder body (3), a rear housing (9), a sliding tube (10), and a hinged tube component (11). One end of the sliding tube (10) is fixedly connected to the front cylinder body (3), and the other end of the sliding tube (10) extends into the rear housing (9) with a gap between it and the housing (9). The cavity opens outward at the end of the front cylinder body (3) away from the sliding tube (10), and the cavity is sealed at the end of the rear housing (9) away from the sliding tube (10). A front cylinder head (2) is fixedly installed on the open side of the front cylinder body (3). A rear cylinder head (29) is fixedly installed on the other side of the front cylinder block (3). The front cylinder head (2) has a hole in the middle so that the plunger rod (1) can pass through the hole to the outside of the front cylinder block (3). The rear cylinder head (29) has a hole in the middle so that the plunger rod (1) can pass through the hole and reach the inside of the rear housing (9) through the grooved tube (10). A hinged tube component (11) for connecting the oil pipeline is fixedly installed on one side of the front cylinder block (3). The grooved tube (10) and the front cylinder block (3) are fixedly installed on the same side of the valve block (5). The groove tube (10) includes a groove block and a groove body. One end of the groove block is fixedly connected to the front cylinder (3), and the other end is fixedly connected to the groove body and the rear housing (9) respectively. The groove block and the front cylinder (3) are fixedly installed on the same side of the valve block (5). The groove body extends into the interior of the rear housing (9) and there is a gap between it and the housing (9). The groove body has an inner cavity for installing the plunger rod (1). The plunger rod (1) has a radial through hole located near the rear housing (9). A pin (26) is fixedly installed in the through hole. Each end of the pin (26) is fitted with a roller (27) after passing through the two ends of the through hole. The slide body has two rotationally symmetrical slide grooves along the axis. The slide grooves penetrate the outer side of the slide body, and each slide groove is a spiral curve segment that rotates from one end to the other along the axis. Each slide groove has a roller (27) installed in it, so that the movement of the roller (27) in the slide groove... The axial arrangement of the groove allows the piston rod (1) to extend and retract along the axial direction of the groove via the roller (27). The curved shape of the groove allows the piston rod (1) to rotate as it moves along the curve of the groove via the roller (27). A position switch (28) for sending the position signal of the piston rod (1) is installed on the groove tube (10). The curved shape of the groove is a sine curve, so that the acceleration of the piston rod (1) during the rotation cycle is a continuous curve. All components of the hydraulic cylinder are sealed with oil seals. A piston (23) is fixedly installed on the outer periphery of the middle part of the plunger rod (1). The outer periphery of the piston (23) and the inner periphery of the front cylinder body (3) are sealed with a sealing ring. The diameter of the piston (23) is larger than the opening diameter of the front cylinder head (2) and the opening diameter of the rear cylinder head (29), thereby limiting the stroke of the plunger rod (1). The piston (23) and the rear cylinder head (29) divide the hydraulic cylinder into three oil chambers: the first oil chamber, the second oil chamber, and the third oil chamber. One end of the first oil chamber is sealed between the plunger rod (1) and the front cylinder head (2) by an oil seal, and the other end is open to the outside. The piston (23) and the front cylinder block (3) are sealed by a sealing ring. One end of the second oil chamber is sealed between the piston (23) and the front cylinder block (3) by a sealing ring, and the other end is sealed between the plunger rod (1) and the rear cylinder head (29) by an oil seal. One end of the third oil chamber is sealed between the plunger rod (1) and the rear cylinder head (29) by an oil seal, and the other end of the third oil chamber is sealed at the rear housing (9). The front cylinder head (2) and the front cylinder block (3), the rear cylinder head (29) and the sliding block, the sliding block and the rear housing (9), and the rear housing (9) and the sliding block are all sealed by sealing rings.

2. The rotatable and telescopic composite motion underwater actuator according to claim 1, characterized in that: The valve block (5) has a chamber inside. The output shaft of the motor (4) at the front end of the valve block (5) is connected to the pressure compensation mechanism (7) through the chamber. A hollow connecting block (6) is fixedly installed on one side of the valve block (5). The hollow part of the connecting block (6) is connected to the chamber of the valve block (5). A watertight plug (34) for external control signal is installed on the connecting block (6). The watertight plug (34) is connected to the drive power supply and the control console. The watertight plug (34) is electrically connected to the motor (4) and the position switch (28) through the connecting block (6), the valve block (5), and the slide tube (10).

3. The rotatable and telescopic composite motion underwater actuator according to claim 2, characterized in that: The pressure compensation mechanism (7) includes a gear pump (12), a balance valve (19), an oil tank cover (8), a liquid level indicator rod (13), a diaphragm piston plate (14), a conical spring (15), a rolling diaphragm (16), a clamping ring (17), and a sealing flange (18). The gear pump (12), the sealing flange (18), and two balance valves (19) are fixedly installed at the rear end of the valve block (5). The sealing flange (18) is an annular structure that surrounds the gap between the gear pump (12) and the two balance valves (19) inside. The outer periphery of the sealing flange (18) extends backward and the radial dimension gradually decreases. The output shaft of the motor (4) at the front end of the valve block (5) is connected to the gear pump (12) through the chamber, so that the rotation of the motor (4) drives the gear pump (12) to rotate, thereby supplying oil to the oil cylinder. The rolling diaphragm (16) is a deformable bag-shaped structure. The rolling diaphragm (16) is intermittently fitted outside the gear pump (12) and the balance valve (19). The clamping ring (17) is fitted around the outer periphery of the rolling diaphragm (16) so that the bag end of the rolling diaphragm (16) is pressed against the outer periphery of the sealing flange (18) with a small radial dimension. One end of the opening of the oil tank cover (8) is threaded and fixed with the thread on the outer side of the sealing flange (18). The oil tank cover (8) is fitted around the outer periphery of the sealing flange (18) with a large radial dimension. The gear pump (12) also has two channels for oil to interact with the rolling diaphragm (16) in one direction. One channel is used for the rolling diaphragm (16) to supply oil to the gear pump (12), and the other channel is used for the gear pump (12) to unload oil to the rolling diaphragm (16). The conical spring (15) is axially mounted on the non-open end of the oil tank cover (8). The top surface of the conical spring (15) abuts against the diaphragm piston plate (14), and the bottom surface of the conical spring (15) is fixedly connected to the non-open end face of the oil tank cover (8). The diaphragm piston plate (14) and the non-open end of the rolling diaphragm (16) are in contact. A round hole is opened on the non-open end face of the oil tank cover (8), and a threaded hole is opened in the middle of the diaphragm piston plate (14). One end of the liquid level indicator rod (13) passes through the round hole and enters the oil tank cover (8), and is screwed into the threaded hole in the diaphragm piston plate (14) for fixation. The other end of the liquid level indicator rod (13) extends out of the oil tank cover (8), so that when the deformation of the rolling diaphragm (16) due to the change in the amount of oil inside changes, it is transmitted through the diaphragm piston plate (14) to the liquid level indicator rod (13) to intuitively reflect the change.

4. The rotatable and telescopic composite motion underwater actuator according to claim 3, characterized in that: The gear pump (12) has three oil ports: a first oil port, a second oil port, and a third oil port. Two oil channels for oil flow are opened between the valve block (5) and the front cylinder (3), namely the first oil channel and the second oil channel. One oil channel for oil flow is opened between the valve block (5) and the slide tube (10), namely the third oil channel. The two balance valves (19) are the first balance valve and the second balance valve, respectively. The first oil port of the gear pump (12) is connected to one end of the first balance valve and the control oil port of the second balance valve, respectively. The other end of the first balance valve is connected to one end of the first oil passage. The other end of the first oil passage is connected to the first oil chamber inside the front cylinder (3) through the hinged pipe member (11) installed on one side of the front cylinder (3). The second oil port of the gear pump (12) is connected to one end of the second balance valve and the control oil port of the first balance valve, respectively. The other end of the second balance valve is connected to one end of the second oil passage. The other end of the second oil passage is connected to the second oil chamber inside the front cylinder (3). The third oil port of the gear pump (12) is connected to one end of the third oil passage. The other end of the third oil passage is connected to the third oil chamber inside the rear housing (9) and the sliding block. The second oil passage is directly connected to the second oil chamber inside the front cylinder (3). The first oil passage is connected to the first oil chamber inside the front cylinder (3) through the hinged pipe component (11) installed on one side of the front cylinder (3). Each of the balance valves (19) is a one-way valve and there is a passage inside the valve that is opened by the valve core. The gear pump (12) passes through the first oil port, the first balance valve, the first oil passage, and the hinged pipe component (11) in sequence, and finally connects to the first oil chamber inside the front cylinder block (3) to supply oil / return oil, forming two oil circuits. The oil circuit used for supplying oil is the first oil supply circuit, and the oil circuit used for returning oil is the first return oil circuit. The gear pump (12) passes through the second oil port, the second balance valve, and the second oil passage in sequence, and finally connects to the second oil chamber inside the front cylinder block (3) to supply oil / return oil, forming two oil circuits. The oil circuit used for supplying oil is the second oil supply circuit, and the oil circuit used for returning oil is the second return oil circuit. The gear pump (12) passes through the third oil port, the third oil passage, and the third oil chamber of the rear housing (9) and the sliding block to form a third oil circuit.

5. A driving method for a rotatable and retractable composite motion underwater actuator as described in any one of claims 1-4, characterized in that, The driving method is as follows: First, start the motor. The motor drives the gear pump (12) to rotate, which causes the oil circuit inside the underwater actuator to circulate and push the piston rod (1) to rotate and extend, thereby opening the external cover. Then, the motor is reversed, and the motor drives the gear pump (12) to rotate in the opposite direction, so that the oil circuit in the underwater actuator is formed in the opposite direction to push the piston rod (1) to rotate and retract, thereby closing the external cover. Next, the underwater actuator makes judgments and operates in the following manner: When the gear pump (12) supplies oil and the piston rod (1) moves at a speed exceeding the preset speed, the oil flow inside the balance valve (19) slows down, thereby slowing down the piston rod (1) and thus controlling the speed of the cylinder. When the gear pump (12) supplies oil and the speed of the piston rod (1) does not exceed the preset speed, the balance valve (19) of the return oil circuit is pushed by the high pressure oil in the supply oil circuit to keep the valve core open, and the piston rod 1 moves normally. When the gear pump (12) does not supply oil, the oil pressure at the control port of the balance valve (19) on both sides cannot open the valve core. The first / second return oil circuit in each balance valve (19) cannot return oil because the valve core is closed, thus ensuring that the position of the oil cylinder is fixed.

6. The driving method for a rotatable and telescopic composite motion underwater actuator according to claim 5, characterized in that, The driving method is specifically as follows: When the motor is started, the reverse / forward rotation of the motor (4) drives the gear pump (12) to rotate in the reverse / forward direction, so that the gear pump (12) supplies oil to the first oil chamber / second oil chamber through the first oil supply line / second oil supply line, thereby pushing the plunger rod (1) to retract / extend. At the same time, the valve core of the corresponding second balance valve / first balance valve opens, so that the oil in the second oil chamber / first oil chamber returns to the gear pump through the second return oil line / first return oil line. The rotation of the motor (4) drives the gear pump (12) to rotate, thereby enabling the first oil port or the second oil port to start supplying oil. When the first oil port supplies oil, the first oil port supplies oil to the first oil chamber through the first oil supply oil passage as the oil inlet side. The increase of oil in the first oil chamber pushes the piston (23) to move towards the second oil chamber, thereby realizing the movement of the plunger rod (1) towards the rear housing (9). Under the action of the roller (27) and the slide groove, it rotates and retracts. The oil pushes the valve core in the second balance valve to move and open the channel in the second balance valve. The channel allows the oil in the second oil chamber that cannot flow due to the second balance valve acting as a one-way valve to flow back to the second oil port through the second return oil passage as the return oil side, thereby forming a cycle. When the second oil port supplies oil, the second oil port supplies oil to the second oil chamber through the second oil supply line as the oil inlet side. The increase of oil in the second oil chamber pushes the piston (23) to move towards the first oil chamber, thereby realizing the movement of the plunger rod (1) towards the front cylinder (3). Under the action of the roller (27) and the slide groove, it rotates and extends. The oil pushes the valve core in the first balance valve to move and open the channel in the first balance valve. The channel allows the oil in the first oil chamber that cannot flow due to the second balance valve acting as a one-way valve to flow back to the first oil port through the first return oil line as the return oil side, thereby forming a cycle.

7. The driving method for a rotatable and telescopic composite motion underwater actuator according to claim 5, characterized in that: When the plunger rod (1) extends forward towards the cylinder block (3), oil is supplied from the third oil port to the third oil chamber through the third oil passage to balance the pressure. When the plunger rod (1) retracts towards the rear housing (9), oil is returned from the third oil chamber to the third oil port through the third oil passage to balance the pressure. When oil overflows, the excess oil flows to the rolling diaphragm (16) through the gear pump (12). When oil is insufficient, the missing oil flows to the gear pump (12) through the rolling diaphragm (16) to achieve pressure compensation.

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