Hydraulically-controlled three-roller centering device

Abstract

The utility model discloses a hydraulically-controlled three-roller centering device which comprises an oil supply pipeline, an oil return pipeline, a control valve, an overflow valve and a hydraulic cylinder used for driving centering rollers to be closed or opened. Wherein the hydraulic cylinder is internally provided with a first oil cavity and a second oil cavity, the first oil cavity is used for feeding oil when the centering roller is driven to be closed towards the center of a penetrating hole, the second oil cavity is used for feeding oil when the centering roller is driven to be opened towards the periphery, an oil inlet of the control valve is connected with the oil supply pipeline, and an oil return opening of the control valve is connected with the oil return pipeline. A first working oil port of the control valve is connected with the first oil cavity, a second working oil port of the control valve is connected with the second oil cavity, and an inlet of the overflow valve is connected with the first oil cavity. According to the three-roller centering device, when the centering rollers cannot be opened towards the periphery, the centering rollers can be forcibly opened through the hollow billets so that the hollow billets can enter the space between the centering rollers, the hollow billets and the ejector rods can be prevented from being bent, and the three-roller centering device can be prevented from being damaged by collision.

Description

Technical Field

[0001] The utility model relates to a three-roll centering device controlled by hydraulic pressure. Background Art

[0002] At present, the three-roll centering device is one of the essential devices in the piercing and rolling process of seamless steel pipes. The specific structures of a three-roll centering device are respectively disclosed in Chinese patents with publication numbers CN209318606U, CN202192100U, and CN105750341B. There are three centering rolls in the three-roll centering device, and the three centering rolls can gather and close towards the piercing center or open towards the surroundings under the telescopic drive of a hydraulic cylinder. And according to the opening amplitude of the three centering rolls, it can be divided into two states: small opening and large opening.

[0003] During the piercing and rolling process of seamless steel pipes, when the mandrel is not close to the centering rolls, the three centering rolls hold the mandrel and rotate with the mandrel. When the mandrel approaches the centering rolls, the hydraulic cylinder drives the three centering rolls to open slightly so that the mandrel can enter the middle of the three centering rolls. After the piercing and rolling is completed, the hydraulic cylinder drives the three centering rolls to open widely.

[0004] However, in the actual working process, when the mandrel approaches the centering rolls, occasionally due to signal failures or valve jamming and other problems, the hydraulic cylinder cannot perform telescopic actions. Furthermore, the hydraulic cylinder cannot drive the three centering rolls to open slightly. At this time, after the mandrel approaches the centering rolls, it will forcibly push into the middle of the three centering rolls. However, since the hydraulic cylinder cannot perform telescopic actions, the three centering rolls cannot open towards the surroundings either. At this time, the mandrel cannot push open the three centering rolls, which will cause the mandrel and the mandrel rod to be severely bent, and will also cause the three-roll centering device to be damaged, resulting in equipment failures. Summary of the Utility Model

[0005] The technical problem to be solved by the utility model is to overcome the defects of the prior art and provide a three-roll centering device controlled by hydraulic pressure, which can forcibly push open the centering rolls through the mandrel when the centering rolls cannot open towards the surroundings so that the mandrel can enter between the centering rolls, thereby avoiding the mandrel and the mandrel rod from being bent and also avoiding the three-roll centering device from being damaged.

[0006] To solve the above technical problem, the technical solution of the utility model is: a three-roll centering device controlled by hydraulic pressure, including an oil supply pipeline, an oil return pipeline, a control valve, an overflow valve, and a hydraulic cylinder for driving the centering rolls to close or open;

[0007] The hydraulic cylinder has a first oil cavity for oil inlet when driving the centering rolls to close towards the piercing center and a second oil cavity for oil inlet when driving the centering rolls to open towards the surroundings;

[0008] The oil inlet of the control valve is connected to the oil supply pipeline, the oil return port of the control valve is connected to the oil return pipeline, the first working oil port of the control valve is connected to the first oil chamber, the second working oil port of the control valve is connected to the second oil chamber, and the control valve is used to control the flow direction and flow rate of the oil fluid so as to control the telescopic movement of the hydraulic cylinder;

[0009] The inlet of the overflow valve is connected to the first oil chamber, and the outlet of the overflow valve is connected to the oil return pipeline.

[0010] Furthermore, the three-roll centering device with hydraulic control further includes a hydraulic lock;

[0011] The first working oil port of the control valve is connected to the first oil chamber through the hydraulic lock;

[0012] The second working oil port of the control valve is connected to the second oil chamber through the hydraulic lock;

[0013] The inlet of the overflow valve is connected to the pipeline between the first oil chamber and the hydraulic lock.

[0014] Furthermore, the three-roll centering device with hydraulic control further includes a pressure reducing valve, and the oil inlet of the control valve is connected to the oil supply pipeline through the pressure reducing valve; wherein, the inlet of the pressure reducing valve is connected to the oil supply pipeline, and the outlet of the pressure reducing valve is connected to the oil inlet of the control valve.

[0015] Furthermore, the three-roll centering device with hydraulic control further includes a hydraulic station, the oil supply pipeline is connected to the oil supply port of the hydraulic station, and the oil return pipeline is connected to the oil return port of the hydraulic station.

[0016] Furthermore, the overflow valve is a stacked overflow valve.

[0017] Furthermore, the control valve is a proportional valve.

[0018] Furthermore, the three-roll centering device with hydraulic control further includes a first swing arm, a second swing arm, a third swing arm, a first gear, a second gear, a third gear, a mounting seat and three centering rollers;

[0019] The first swing arm is rotatably connected to the mounting seat around a first rotating shaft;

[0020] The second swing arm is rotatably connected to the mounting seat around a second rotating shaft;

[0021] The third swing arm is rotatably connected to the mounting seat around a third rotating shaft;

[0022] The cylinder block of the hydraulic cylinder is hinged to the mounting seat, and the piston rod of the hydraulic cylinder is hinged to the first swing arm so that the hydraulic cylinder drives the first swing arm to rotate during the telescopic process;

[0023] The first centering roller is connected to the first swing arm, the second centering roller is connected to the second swing arm, and the third centering roller is connected to the third swing arm. The three centering rollers are distributed on a circle centered on the center of the perforation;

[0024] The first gear is fixedly connected to the first swing arm and the center of the first gear coincides with the first rotating shaft;

[0025] The second gear is fixedly connected to the second swing arm and the center of the second gear coincides with the second rotating shaft;

[0026] The third gear is fixedly connected to the third swing arm and the center of the first gear coincides with the third rotating shaft;

[0027] The second gear and the third gear are respectively directly or indirectly meshed and driven with the first gear. When the first swing arm rotates, the second gear and the third gear are driven to rotate by the first gear, and then the second swing arm and the third swing arm are driven to rotate, and then the three centering rollers are driven to gather and close to the center of the perforation or open to the surroundings.

[0028] Further, the second gear is directly meshed with the first gear.

[0029] Further, the three-roller centering device controlled by hydraulic pressure further includes a fourth gear rotatably connected to the mounting seat. The fourth gear is meshed with the second gear, and the third gear is meshed with the fourth gear.

[0030] Further, the first oil chamber in the hydraulic cylinder is a rodless chamber, and the second oil chamber in the hydraulic cylinder is a rod chamber.

[0031] After adopting the above technical solution, the flow direction and flow rate of the hydraulic oil can be controlled by the control valve to control the extension and retraction of the hydraulic cylinder. When injecting oil into the first oil chamber, oil enters the first oil chamber and oil exits the second oil chamber. At this time, the piston rod of the hydraulic cylinder moves towards the second oil chamber, and the hydraulic cylinder drives the centering rollers to gather and close towards the piercing center. When injecting oil into the second oil chamber, oil enters the second oil chamber and oil exits the first oil chamber. At this time, the piston rod of the hydraulic cylinder moves towards the first oil chamber, and the hydraulic cylinder drives the centering rollers to open outwards. Specifically, there are three centering rollers. When the capillary tube approaches the centering rollers, oil should be injected into the second oil chamber so that the piston rod of the hydraulic cylinder moves towards the first oil chamber, and then the hydraulic cylinder drives the three centering rollers to open outwards, so that the capillary tube can enter the middle of the three centering rollers. At this time, if the hydraulic cylinder cannot perform telescopic actions due to signal failure or valve jamming, etc., the hydraulic cylinder will not be able to drive the three centering rollers to open outwards. At this time, the three centering rollers are in a gathered and closed state. After the capillary tube approaches the centering rollers, it cannot smoothly enter between the three centering rollers but will forcefully push into the middle of the three centering rollers. When the capillary tube pushes into the middle of the three centering rollers, it will apply an outward expanding force to the centering rollers to force the three centering rollers to open outwards. This expanding force will be transmitted to the hydraulic cylinder and generate a reaction force on the hydraulic cylinder to forcibly drive the piston rod of the hydraulic cylinder towards the first oil chamber, resulting in the oil in the first oil chamber being forcibly compressed and the pressure in the first oil chamber increasing. When the pressure in the first oil chamber rises to the opening pressure of the relief valve, the relief valve is opened, and then the oil in the first oil chamber can flow through the relief valve and be discharged into the return oil pipeline, so that the first oil chamber is depressurized and the piston rod of the hydraulic cylinder can move towards the first oil chamber. At this time, the hydraulic cylinder is forcibly pushed open and the centering rollers are also forcibly pushed outwards by the capillary tube, so that the capillary tube can enter between the three centering rollers. To sum up, by setting the relief valve, when a failure occurs and the centering rollers cannot open outwards, the capillary tube can forcibly push open the centering rollers so that the capillary tube can enter between the centering rollers, thereby avoiding the capillary tube and the ejector rod from being bent, avoiding the three-roller centering device from being damaged, and also enabling the operator to gain time for parking treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic structural diagram of the hydraulic control part of the three-roller centering device with hydraulic control of the present utility model;

[0033] Figure 2 is a schematic structural diagram of the mechanical structure part of the three-roller centering device with hydraulic control of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] In order to make the content of the present utility model easier to be clearly understood, the following further detailed description of the present utility model will be given according to specific embodiments in conjunction with the accompanying drawings.

[0035] As Figure 1 , 2 shown, a three-roll centering device controlled by hydraulic pressure includes an oil supply pipeline 1, an oil return pipeline 2, a control valve 3, a relief valve 4, and a hydraulic cylinder 6 for driving the centering rolls 5 to close or open.

[0036] The hydraulic cylinder 6 has a first oil chamber 7 for oil inlet when driving the centering rolls 5 to close towards the piercing center and a second oil chamber 8 for oil inlet when driving the centering rolls 5 to open towards the surroundings.

[0037] The oil inlet of the control valve 3 is connected to the oil supply pipeline 1, the oil return port of the control valve 3 is connected to the oil return pipeline 2, the first working oil port of the control valve 3 is connected to the first oil chamber 7, the second working oil port of the control valve 3 is connected to the second oil chamber 8, and the control valve 3 is used to control the flow direction and flow rate of the oil fluid so as to control the telescopic movement of the hydraulic cylinder 6.

[0038] The inlet of the relief valve 4 is connected to the first oil chamber 7, and the outlet of the relief valve 4 is connected to the oil return pipeline 2. Specifically, controlling the flow direction and flow rate of the oil fluid through the control valve 3 can control the extension and retraction of the hydraulic cylinder 6. When injecting oil into the first oil chamber 7, oil enters the first oil chamber 7 while oil exits from the second oil chamber 8. At this time, the piston rod of the hydraulic cylinder 6 moves towards the second oil chamber 8 and the hydraulic cylinder 6 drives the centering rolls 5 to gather and close towards the piercing center. When injecting oil into the second oil chamber 8, oil enters the second oil chamber 8 while oil exits from the first oil chamber 7. At this time, the piston rod of the hydraulic cylinder 6 moves towards the first oil chamber 7 and the hydraulic cylinder 6 drives the centering rolls 5 to open towards the surroundings.

[0039] More specifically, there are three centering rollers 5. When the capillary tube approaches the centering rollers 5, oil should be injected into the second oil chamber 8 so that the piston rod of the hydraulic cylinder 6 moves towards the first oil chamber 7, and then the hydraulic cylinder 6 drives the three centering rollers 5 to open outwards, enabling the capillary tube to enter the space between the three centering rollers 5. At this time, if the hydraulic cylinder 6 cannot extend or retract due to signal failure or valve jamming, etc., the hydraulic cylinder 6 will not be able to drive the three centering rollers 5 to open outwards. At this time, the three centering rollers 5 are in a gathered and closed state. After the capillary tube approaches the centering rollers 5, it cannot smoothly enter the space between the three centering rollers 5 but will forcefully push into the middle of the three centering rollers 5. When the capillary tube pushes into the middle of the three centering rollers 5, it will exert an outward expanding force on the centering rollers 5 to force the three centering rollers 5 to open outwards. This expanding force will be transmitted to the hydraulic cylinder 6 and generate a reaction force on the hydraulic cylinder 6 to forcibly drive the piston rod of the hydraulic cylinder 6 towards the first oil chamber 7, causing the oil in the first oil chamber 7 to be forcibly compressed and thus increasing the pressure in the first oil chamber 7. When the pressure in the first oil chamber 7 rises to the opening pressure of the overflow valve 4, the overflow valve 4 is opened, and then the oil in the first oil chamber 7 can flow through the overflow valve 4 and be discharged into the return oil pipeline 2, relieving the pressure of the first oil chamber 7 and enabling the piston rod of the hydraulic cylinder 6 to move towards the first oil chamber 7. At this time, the hydraulic cylinder 6 is forcibly pushed open and the centering rollers 5 are also forcibly pushed outwards by the capillary tube, enabling the capillary tube to enter the space between the three centering rollers 5. In summary, by setting the overflow valve 4, when a failure occurs and the centering rollers 5 cannot open outwards, the capillary tube can forcibly push open the centering rollers 5 so that the capillary tube can enter the space between the centering rollers 5, thereby avoiding the capillary tube and the ejector rod from being bent, avoiding damage to the three-roller centering device, and also enabling the operator to gain time for parking treatment.

[0040] In this embodiment, the hydraulic cylinder 6 can be an oil cylinder with a displacement sensor.

[0041] As Figure 1 shown, the three-roller centering device controlled by hydraulic pressure can further include a hydraulic lock 9;

[0042] The first working oil port of the control valve 3 is connected to the first oil chamber 7 through the hydraulic lock 9;

[0043] The second working oil port of the control valve 3 is connected to the second oil chamber 8 through the hydraulic lock 9;

[0044] The inlet of the overflow valve 4 is connected to the pipeline between the first oil chamber 7 and the hydraulic lock 9; Specifically, the first working oil port and the second working oil port are respectively connected to the hydraulic lock 9, and the hydraulic lock 9 is also respectively connected to the first oil chamber 7 and the second oil chamber 8.

[0045] As Figure 1 shown, the hydraulically controlled three-roll centering device may further include a pressure reducing valve 10, and the oil inlet of the control valve 3 is connected to the oil supply pipeline 1 through the pressure reducing valve 10; wherein, the inlet of the pressure reducing valve 10 is connected to the oil supply pipeline 1, and the outlet of the pressure reducing valve 10 is connected to the oil inlet of the control valve 3; specifically, the opening pressure of the overflow valve 4 is greater than the outlet pressure of the pressure reducing valve 10.

[0046] Specifically, the hydraulically controlled three-roll centering device may further include a hydraulic station, the oil supply pipeline 1 is connected to the oil supply port of the hydraulic station, and the oil return pipeline 2 is connected to the oil return port of the hydraulic station.

[0047] In this embodiment, the overflow valve 4 is a stacked overflow valve, which mainly functions as a passive safety unloading; the control valve 3 is a proportional valve.

[0048] As Figure 2 shown, the hydraulically controlled three-roll centering device may further include a first swing arm 11, a second swing arm 12, a third swing arm 13, a first gear 14, a second gear 15, a third gear 16, a mounting seat 17 and three centering rollers 5;

[0049] The first swing arm 11 is rotatably connected to the mounting seat 17 around a first rotating shaft;

[0050] The second swing arm 12 is rotatably connected to the mounting seat 17 around a second rotating shaft;

[0051] The third swing arm 13 is rotatably connected to the mounting seat 17 around a third rotating shaft;

[0052] The cylinder body of the hydraulic cylinder 6 is hinged to the mounting seat 17, and the piston rod of the hydraulic cylinder 6 is hinged to the first swing arm 11 so that the hydraulic cylinder 6 drives the first swing arm 11 to rotate during the telescopic process;

[0053] The first centering roller 5 is connected to the first swing arm 11, the second centering roller 5 is connected to the second swing arm 12, the third centering roller 5 is connected to the third swing arm 13, and the three centering rollers 5 are distributed on a circumference centered on the perforation center;

[0054] The first gear 14 is fixedly connected to the first swing arm 11 and the center of the first gear 14 coincides with the first rotating shaft;

[0055] The second gear 15 is fixedly connected to the second swing arm 12 and the center of the second gear 15 coincides with the second rotating shaft;

[0056] The third gear 16 is fixedly connected to the third swing arm 13, and the center of the first gear 14 coincides with the third rotating shaft;

[0057] The second gear 15 and the third gear 16 are respectively in meshing transmission with the first gear 14 directly or indirectly. When the first swing arm 11 rotates, the second gear 15 and the third gear 16 are driven to rotate by the first gear 14, and then the second swing arm 12 and the third swing arm 13 are driven to rotate, thereby driving the three centering rollers 5 to gather and close towards the piercing center or open towards the surroundings.

[0058] As Figure 2 shown, the second gear 15 is directly meshed with the first gear 14.

[0059] As Figure 2 shown, the hydraulic control three-roller centering device may further include a fourth gear 18 rotatably connected to the mounting seat 17. The fourth gear 18 is meshed with the second gear 15, and the third gear 16 is meshed with the fourth gear 18, so that the third gear 16 is indirectly in meshing transmission with the first gear 14 through the second gear 15 and the fourth gear 18. In this embodiment, the first oil chamber 7 in the hydraulic cylinder 6 is a rodless chamber, and the second oil chamber 8 in the hydraulic cylinder 6 is a rod chamber.

[0060] Specifically, when oil is injected into the first oil chamber 7, oil enters the first oil chamber 7 and oil exits the second oil chamber 8. At this time, the piston rod of the hydraulic cylinder 6 moves towards the second oil chamber 8 and extends outwards, thereby driving the first swing arm 11 and the first gear 14 to rotate clockwise. The first gear 14 drives the second gear 15 and the second swing arm 12 to rotate counterclockwise. The second gear 15 drives the third gear 16 and the third swing arm 13 to rotate counterclockwise through the fourth gear 18, thereby driving the three centering rollers 5 to gather and close towards the piercing center. Further specifically, when oil is injected into the second oil chamber 8, oil enters the second oil chamber 8 and oil exits the first oil chamber 7. At this time, the piston rod of the hydraulic cylinder 6 moves towards the first oil chamber 7 and retracts inwards, thereby driving the first swing arm 11 and the first gear 14 to rotate counterclockwise. The first gear 14 drives the second gear 15 and the second swing arm 12 to rotate clockwise. The second gear 15 drives the third gear 16 and the third swing arm 13 to rotate clockwise through the fourth gear 18, thereby driving the three centering rollers 5 to open towards the surroundings.

[0061] More specifically, when the capillary tube has not approached the centering roller 5, the hydraulic cylinder 6 drives the three centering rollers 5 to tightly hold the ejector rod. At this time, the pressure in the first oil chamber 7 is 7.5 MPa, and the opening pressure of the overflow valve 4 is set to 15 MPa. When the capillary tube approaches the centering roller 5 and the hydraulic cylinder 6 cannot perform telescopic movement due to signal failure or valve jamming, etc., the hydraulic cylinder 6 will not be able to drive the three centering rollers 5 to open outwards. At this time, the three centering rollers 5 are in a gathered and closed state. After the capillary tube approaches the centering roller 5, it cannot smoothly enter between the three centering rollers 5 but will forcefully push into the middle of the three centering rollers 5. When the capillary tube pushes into the middle of the three centering rollers 5, it will apply an outward spreading force to the centering rollers 5 to force the three centering rollers 5 to open outwards, thereby forcing the first swing arm 11 to rotate counterclockwise, forcing the second swing arm 12 to rotate clockwise, and forcing the third swing arm 13 to rotate clockwise. This spreading force will be transmitted to the hydraulic cylinder 6 and generate a reaction force on the hydraulic cylinder 6 to forcibly drive the piston rod of the hydraulic cylinder 6 to retract, thereby compressing the oil in the first oil chamber 7 to increase the pressure in the first oil chamber 7. When the oil pressure in the first oil chamber 7 gradually rises above 15 MPa, the overflow valve 4 is opened. Then, the oil in the first oil chamber 7 can flow through the overflow valve 4 and be discharged into the oil return pipeline 2, so that the first oil chamber 7 is depressurized and the piston rod of the hydraulic cylinder 6 can move towards the first oil chamber 7 and retract. At this time, the hydraulic cylinder 6 is forcibly pushed open and the centering rollers 5 are also forcibly pushed outwards by the capillary tube, so that the capillary tube can enter between the three centering rollers 5. To sum up, by setting the overflow valve 4, when a failure occurs and the centering rollers 5 cannot open outwards, the centering rollers 5 can be forcibly pushed open by the capillary tube so that the capillary tube can enter between the centering rollers 5, thereby avoiding the capillary tube and the ejector rod from being bent, avoiding the three-roller centering device from being damaged, and also being able to buy time for the operator to perform a stop operation.

[0062] In summary, controlling the flow direction and flow rate of the hydraulic fluid through the control valve 3 can control the extension and retraction of the hydraulic cylinder 6. When injecting oil into the first oil chamber 7, oil enters the first oil chamber 7 while oil exits the second oil chamber 8. At this time, the piston rod of the hydraulic cylinder 6 moves towards the second oil chamber 8 and the hydraulic cylinder 6 drives the centering rollers 5 to gather and close towards the piercing center. When injecting oil into the second oil chamber 8, oil enters the second oil chamber 8 while oil exits the first oil chamber 7. At this time, the piston rod of the hydraulic cylinder 6 moves towards the first oil chamber 7 and the hydraulic cylinder 6 drives the centering rollers 5 to open outwards. Specifically, there are three centering rollers 5. When the capillary tube approaches the centering rollers 5, oil should be injected into the second oil chamber 8 so that the piston rod of the hydraulic cylinder 6 moves towards the first oil chamber 7, and then the hydraulic cylinder 6 drives the three centering rollers 5 to open outwards, so that the capillary tube can enter between the three centering rollers 5. At this time, if the hydraulic cylinder 6 cannot perform telescopic movement due to signal failure or valve jamming, etc., the hydraulic cylinder 6 will not be able to drive the three centering rollers 5 to open outwards. At this time, the three centering rollers 5 are in a gathered and closed state. After the capillary tube approaches the centering rollers 5, it cannot smoothly enter between the three centering rollers 5 but will forcefully push into the middle of the three centering rollers 5. When the capillary tube pushes into the middle of the three centering rollers 5, it will apply an outward opening force to the centering rollers 5 to force the three centering rollers 5 to open outwards. This opening force will be transmitted to the hydraulic cylinder 6 and generate a reaction force on the hydraulic cylinder 6 to forcibly drive the piston rod of the hydraulic cylinder 6 towards the first oil chamber 7, resulting in the oil in the first oil chamber 7 being forcibly compressed and thus increasing the pressure in the first oil chamber 7. When the pressure in the first oil chamber 7 rises to the opening pressure of the relief valve 4, the relief valve 4 is opened. Then, the oil in the first oil chamber 7 can flow through the relief valve 4 and be discharged into the oil return pipeline 2, so that the first oil chamber 7 is depressurized and the piston rod of the hydraulic cylinder 6 can move towards the first oil chamber 7. At this time, the hydraulic cylinder 6 is forcibly opened and the centering rollers 5 are also forcibly pushed outwards by the capillary tube, so that the capillary tube can enter between the three centering rollers 5. In summary, by setting the relief valve 4, when a failure occurs and the centering rollers 5 cannot open outwards, the capillary tube can forcibly push open the centering rollers 5 so that the capillary tube can enter between the centering rollers 5, thereby avoiding the capillary tube and the ejector rod from being bent, and also avoiding the three-roller centering device from being damaged, and can also gain time for the operator to perform a stop operation.

[0063] In the specific embodiments described above, the technical problems solved, technical solutions, and beneficial effects of the present utility model have been further described in detail. It should be understood that the above are only specific embodiments of the present utility model and are not used to limit the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A hydraulically controlled three-roller centering device, characterized in that: It comprises an oil supply pipeline (1), an oil return pipeline (2), a control valve (3), an overflow valve (4), and a hydraulic cylinder (6) for driving a centering roller (5) to close or open; The hydraulic cylinder (6) has a first oil chamber (7) for supplying oil when driving the centering roller (5) to close toward the center of the perforation, and a second oil chamber (8) for supplying oil when driving the centering roller (5) to open toward the periphery. The oil inlet of the control valve (3) is connected to the oil supply pipeline (1), the oil return port of the control valve (3) is connected to the oil return pipeline (2), the first working oil port of the control valve (3) is connected to the first oil chamber (7), and the second working oil port of the control valve (3) is connected to the second oil chamber (8). The control valve (3) is used to control the flow direction and flow rate of the oil and thus control the telescopic action of the hydraulic cylinder (6); The inlet of the overflow valve (4) is connected to the first oil chamber (7), and the outlet of the overflow valve (4) is connected to the oil return pipeline (2).

2. The hydraulically controlled three-roller centering device according to claim 1, characterized in that: Also includes a hydraulic lock (9); The first working oil port of the control valve (3) is connected to the first oil chamber (7) through the hydraulic lock (9); The second working oil port of the control valve (3) is connected to the second oil chamber (8) through the hydraulic lock (9); The inlet of the overflow valve (4) is connected to the pipeline between the first oil chamber (7) and the hydraulic lock (9).

3. The hydraulically controlled three-roller centering device according to claim 1, characterized in that: It also comprises a pressure reducing valve (10), through which the oil inlet of the control valve (3) is connected to the oil supply pipeline (1); wherein the inlet of the pressure reducing valve (10) is connected to the oil supply pipeline (1), and the outlet of the pressure reducing valve (10) is connected to the oil inlet of the control valve (3).

4. The hydraulically controlled three-roller centering device according to claim 1, characterized in that: It also comprises a hydraulic station, wherein the oil supply pipeline (1) is connected to the oil supply port of the hydraulic station, and the oil return pipeline (2) is connected to the oil return port of the hydraulic station.

5. The hydraulically controlled three-roller centering device according to claim 1, characterized in that: The overflow valve (4) is a superimposed overflow valve.

6. The hydraulically controlled three-roller centering device according to claim 1, characterized in that: The control valve (3) is a proportional valve.

7. The hydraulically controlled three-roller centering device according to claim 1, characterized in that: It also includes a first swing arm (11), a second swing arm (12), a third swing arm (13), a first gear (14), a second gear (15), a third gear (16), a mounting seat (17) and the three centering rollers (5); The first swing arm (11) is rotatably connected to the mounting seat (17) around a first rotation axis; The second swing arm (12) is rotatably connected to the mounting seat (17) around a second rotation axis; The third swing arm (13) is rotatably connected to the mounting seat (17) around a third rotation axis; The cylinder body of the hydraulic cylinder (6) is hinged on the mounting seat (17), and the piston rod of the hydraulic cylinder (6) is hinged to the first swing arm (11) so that the hydraulic cylinder (6) drives the first swing arm (11) to rotate during the extension and retraction process; The first centering roller (5) is connected to the first swing arm (11), the second centering roller (5) is connected to the second swing arm (12), the third centering roller (5) is connected to the third swing arm (13), and the three centering rollers (5) are distributed on a circumference with the perforation center as the center; The first gear (14) is fixedly connected to the first swing arm (11) and the center of the first gear (14) coincides with the first rotating shaft; The second gear (15) is fixedly connected to the second swing arm (12) and the center of the second gear (15) coincides with the second rotating shaft; The third gear (16) is fixedly connected to the third swing arm (13) and the center of the first gear (14) coincides with the third rotating shaft; The second gear (15) and the third gear (16) are respectively directly or indirectly meshed with the first gear (14) for transmission. When the first swing arm (11) rotates, the first gear (14) drives the second gear (15) and the third gear (16) to rotate, thereby driving the second swing arm (12) and the third swing arm (13) to rotate, thereby driving the three centering rollers (5) to gather and close toward the perforation center or open to the surroundings.

8. The hydraulically controlled three-roller centering device according to claim 7, characterized in that: The second gear (15) is directly meshed with the first gear (14).

9. The hydraulically controlled three-roller centering device according to claim 8, characterized in that: It also includes a fourth gear (18) rotatably connected to the mounting seat (17), the fourth gear (18) meshing with the second gear (15), and the third gear (16) meshing with the fourth gear (18).

10. The hydraulically controlled three-roller centering device according to claim 1, characterized in that: The first oil chamber (7) in the hydraulic cylinder (6) is a rodless chamber, and the second oil chamber (8) in the hydraulic cylinder (6) is a rod chamber.

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