A hydraulic circuit for controlling a press moving table ram

Abstract

The utility model discloses a kind of hydraulic circuit for controlling press mobile workstation oil cylinder, including hydraulic system oil tank, mobile workstation control oil cylinder, be set on the rodless cavity oil path of oil cylinder rodless cavity quick liquid inlet electromagnetic reversing valve, be set on the rod cavity oil path rod cavity plug-in double-stage electromagnetic overflow liquid discharge valve, and parallel in oil cylinder rodless cavity oil path for slow control and accurate positioning electro-hydraulic proportional reversing valve;Oil cylinder two cavity oil path is also respectively provided with pressure sensor, high pressure maintenance ball valve and oil supplement check valve.The utility model separates quick and slow control oil path by, adopt small-bore proportional valve cooperation displacement sensor to realize positioning function, reduce cost while effectively eliminating hydraulic impact;Double-stage overflow valve has back pressure control and high pressure locking function, oil supplement valve prevents negative pressure damage, maintenance ball valve is convenient to maintain, overall improve the adaptability, reliability of system under quick, slow, locking and forging various working conditions.

Description

Technical Field

[0001] This utility model relates to the field of hydraulic control technology, specifically a hydraulic circuit for controlling the oil cylinder of a press moving worktable. Background Technology

[0002] In heavy forging press operations, the hydraulic cylinder controlling the movement of the worktable needs to adapt to three working conditions: rapid movement, precise positioning when stopping, and locking during forging. The existing hydraulic systems for moving worktables of fast forging presses mostly adopt the following two schemes: (1) Using ordinary electromagnetic directional valves to control the direction and flow valves to adjust the speed. Although this scheme can achieve basic forward and backward movements, it has a response lag problem, and the positioning accuracy is difficult to meet the usage requirements. (2) Using proportional valve control. This scheme is more reasonable for controlling the moving worktable of small-tonnage fast forging presses, but for large-tonnage fast forging presses, due to the large cylinder diameter and high required flow of the moving worktable cylinders, it is necessary to select cartridge proportional directional valves with large flow rates, which leads to increased costs.

[0003] The existing technology has the following disadvantages: (1) When the worktable starts and stops, an "impact phenomenon" is likely to occur, which will lead to mold positioning deviation or component wear. Moreover, the circuit locking performance is poor. After long-term operation, the worktable is prone to displacement due to leakage, which is more obvious under heavy load conditions. (2) Some circuits can only achieve single speed control, which cannot adapt to the multi-condition requirements of the press such as "rapid movement - arbitrary position stop - precise centering". In addition, the cylinder diameter is different for presses of different tonnages, which is not universal enough. (3) The impact of forging is severe. The anvil is prone to generate an impact several times the rated pressure when it contacts the workpiece, which causes the worktable to move a small distance. This can easily cause the pressure in one side of the cylinder to drop suddenly, resulting in cavitation, which can damage the seals, cause equipment vibration, and shorten the service life.

[0004] Therefore, there is an urgent need for a hydraulic control circuit for the worktable of a large-tonnage press that can solve the start-stop shock, achieve precise control under multiple working conditions, have good load adaptability, and be cost-effective. Utility Model Content

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a safe, reliable, low-cost hydraulic circuit applicable to the control cylinders of press worktables of different tonnages. This circuit solves the problem of start-stop impact on the worktable of a high-speed forging press, achieving stable operation; and through the cooperation of displacement sensors, electromagnetic directional valves, and proportional valves, it achieves precise positioning to adapt to different working conditions; and through the application of a replenishing valve, it solves the problem of poor load adaptability during the operation of a moving worktable.

[0006] To achieve the above objectives, this utility model provides the following technical solution: a hydraulic circuit for controlling the cylinder of a press moving worktable, including a hydraulic system oil tank, wherein the hydraulic system oil tank is connected to the moving worktable control cylinder via an oil circuit, and a rodless chamber rapid liquid inlet solenoid valve for rapid liquid inlet is provided on the oil circuit of the rodless chamber of the moving worktable control cylinder, wherein the oil inlet of the rodless chamber rapid liquid inlet solenoid valve is connected to the system pressure oil source, and its oil outlet is connected to the rodless chamber of the moving worktable control cylinder; The rod chamber of the control cylinder for the mobile workbench is equipped with a rod chamber cartridge-type two-stage electromagnetic overflow drain valve for rapid oil return. The inlet of the rod chamber cartridge-type two-stage electromagnetic overflow drain valve is connected to the rod chamber of the control cylinder for the mobile workbench, and its outlet is connected to the hydraulic system oil tank. An electro-hydraulic proportional directional valve for slow speed control and positioning is also connected in parallel on the oil circuit of the rodless chamber of the mobile worktable control cylinder. The oil inlet of the electro-hydraulic proportional directional valve is connected to the system pressure oil source, and its working oil port is connected to the rodless chamber and the rod chamber of the mobile worktable control cylinder, respectively. The rod chamber and rodless chamber oil circuits of the control cylinder for the moving worktable are respectively equipped with rod chamber pressure sensors and rodless chamber pressure sensors for pressure detection. The rod-side and rodless-side oil circuits of the control cylinder of the mobile workbench are respectively connected to a high-pressure maintenance ball valve for the rodless-side chamber and a high-pressure maintenance ball valve for the rod-side chamber, which are used for draining oil during maintenance.

[0007] Preferably, the control signal input terminal of the electro-hydraulic proportional directional valve is connected to the displacement sensor signal, and the displacement sensor is used to detect the displacement of the moving worktable of the high-speed forging press.

[0008] Preferably, the rod chamber and rodless chamber oil circuits of the mobile worktable control cylinder are respectively equipped with a rod chamber oil replenishment check valve and a rodless chamber oil replenishment check valve for preventing negative pressure oil replenishment. The oil inlets of the rod chamber oil replenishment check valve and the rodless chamber oil replenishment check valve are connected to the oil replenishment source, and their oil outlets are respectively connected to the rod chamber and the rodless chamber of the mobile worktable control cylinder.

[0009] Preferably, the rodless chamber oil circuit of the control cylinder of the moving worktable is further provided with a rodless chamber cartridge-type two-stage electromagnetic overflow drain valve, which is symmetrical to the rod chamber cartridge-type two-stage electromagnetic overflow drain valve, for overpressure protection and back pressure control when the rodless chamber returns oil.

[0010] Preferably, both the rod-type cartridge-type two-stage electromagnetic overflow drain valve and the rodless-type cartridge-type two-stage electromagnetic overflow drain valve are two-stage pressure control structures, each including a low-pressure overflow valve and a high-pressure overflow valve, and are switched and controlled by a solenoid valve.

[0011] Preferably, the rod chamber of the control cylinder for the moving worktable is further provided with a rod chamber rapid liquid inlet solenoid valve that is symmetrical to the rodless chamber rapid liquid inlet solenoid valve structure, for liquid inlet control when the cylinder retracts rapidly.

[0012] Preferably, the system also includes a programmable controller, which is connected to the rodless chamber rapid liquid inlet solenoid directional valve, the rod chamber cartridge-type two-stage solenoid overflow valve, the electro-hydraulic proportional directional valve, the displacement sensor, the rod chamber pressure sensor, and the rodless chamber pressure sensor, respectively.

[0013] The working process of this utility model is as follows: When the hydraulic cylinder of the worktable extends rapidly, the quick-acting directional valve on the rodless side of the cylinder is energized and opens, and the return oil bipolar solenoid relief valve on the rod side is simultaneously energized and opens. The high-pressure oil output by the variable pump enters the rodless chamber of the cylinder through the high-flow-rate two-way cartridge directional valve and the electro-hydraulic proportional directional valve. The hydraulic oil in the rod chamber of the cylinder enters the oil tank through the return oil bipolar solenoid relief valve, realizing the rapid forward movement of the worktable. When the worktable needs to stop, the swing angle of the variable pump decreases and the output flow decreases. At the same time, the quick-acting directional valve on the rodless side is de-energized and closes, and the return oil bipolar solenoid relief valve on the rod side is also de-energized and closes. At this time, only the slow-moving electro-hydraulic proportional directional valve is energized. The electro-hydraulic proportional valve receives the feedback signal from the displacement sensor and gradually closes the hydraulic valve port when the worktable is about to stop, avoiding the impact caused by the sudden cut-off of hydraulic oil when the large flow stops.

[0014] During forging, all solenoid valves in the control circuit are de-energized. When the worktable shifts due to a severe impact, the pressure on one side of the cylinder suddenly increases due to the compression of the hydraulic fluid, while a negative pressure is generated on the other side. Hydraulic oil is then replenished through the check valve on the negative pressure side.

[0015] To ensure the smooth operation of the hydraulic cylinder on the workbench and prevent "creeping" phenomenon, the hydraulic return circuit of the cylinder system is designed with a double-pole electromagnetic relief valve. When the cylinder is actuated, the double-pole electromagnetic relief valve in the oil return side chamber is energized. At this time, the relief valve with lower pressure is in the working state, providing stable back pressure for the smooth operation of the cylinder. When the hydraulic cylinder on the workbench is in a stopped state for forging work, the double-pole electromagnetic relief valve is de-energized, and the relief valve with higher set pressure is in the working state.

[0016] When the equipment is shut down and the hydraulic cylinders or valve groups on the workbench need to be repaired, first open the inspection ball valve so that the hydraulic oil on both sides of the cylinder and in the pipeline connecting the cylinder flows into the oil tank through the high-pressure inspection ball valve before carrying out repair and disassembly work, in order to avoid waste caused by oil leakage and environmental pollution.

[0017] The beneficial effects of this utility model are as follows: (1) This utility model uses parallel ordinary large-diameter electromagnetic directional valves to handle rapid oil inlet and outlet, while only using smaller-diameter electro-hydraulic proportional directional valves to handle the final slow-speed adjustment and positioning. This design avoids the problem of large-tonnage presses having to use expensive large-flow cartridge proportional valves due to their large flow requirements, significantly reducing system costs. At the same time, the control principle of this circuit is clear, the two chambers of the cylinder are symmetrically controlled, and the valve block is easy to integrate. For cylinders with different cylinder diameters and speed requirements, only the hydraulic valves of the corresponding diameter need to be matched as needed, which has good versatility and adaptability.

[0018] (2) This utility model forms a complete control system through a displacement sensor and an electro-hydraulic proportional directional valve, which can detect the position of the worktable in real time and dynamically adjust the valve port, so that the worktable can smoothly decelerate and accurately position after rapid movement, effectively eliminating the hydraulic shock caused by the sudden switching of traditional directional valves, and the positioning accuracy can reach ±1 mm. In addition, the specially designed two-stage electromagnetic overflow drain valve provides adjustable back pressure when the oil cylinder is actuated, eliminating the "creeping" phenomenon under heavy load and low speed; when stopped, it provides high pressure locking to prevent the worktable from shifting under forging impact, meeting the needs of multiple working conditions of the press.

[0019] (3) This utility model, by setting oil replenishment check valves in the rod-side and rodless-side chambers, can automatically replenish oil when negative pressure is generated on one side of the cylinder due to forging impact, effectively preventing cavitation, protecting the seals, and extending the cylinder's lifespan. The dual-stage electromagnetic overflow drain valve also has overload protection function, and can quickly release pressure when the system pressure is abnormal. In particular, the high-pressure maintenance ball valves set in the oil lines of the two cylinder chambers make it easy to drain the oil in the pipeline and cylinder back to the oil tank during maintenance, achieving clean, environmentally friendly, and leak-free maintenance, greatly reducing maintenance difficulty and cost. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the hydraulic control principle of this utility model; Figure 2 This is a schematic diagram of the hydraulic integrated control valve group of this utility model; In the diagram: 1. Hydraulic system oil tank; 2.1. Rodless chamber high-pressure maintenance ball valve; 2.2. Rod chamber high-pressure maintenance ball valve; 3.1. Rod chamber quick-inlet solenoid directional valve; 3.2. Rodless chamber quick-inlet solenoid directional valve; 4. Electro-hydraulic proportional directional valve; 5.1. Rod chamber cartridge-type two-stage solenoid overflow drain valve; 5.2. Rodless chamber cartridge-type two-stage solenoid overflow drain valve; 6.1. Rod chamber replenishing check valve; 6.2. Rodless chamber replenishing check valve; 7.1. Rod chamber pressure sensor; 7.2. Rodless chamber pressure sensor; 8. Moving worktable of the fast forging press; 9. Displacement sensor; 10. Moving worktable control cylinder. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings.

[0022] like Figure 1-2 As shown, this utility model provides a hydraulic circuit for controlling the cylinder of the moving worktable of a press. The power source of this circuit relies on the variable pump of the hydraulic system of the fast forging press. Oil is drawn from the main system pressure oil circuit (port P in the figure) through pipelines and valve groups to simplify the configuration.

[0023] The hydraulic circuit actuator is a moving worktable control cylinder 10. The rodless chamber of this cylinder is connected to the system pressure oil source via three parallel oil circuits: the first is a rapid inlet oil circuit, sequentially connected to the rodless chamber rapid inlet solenoid directional valve 3.2; the second is a slow control and reversing oil circuit, connected to an electro-hydraulic proportional directional valve 4; and the third is a replenishment oil circuit, connected to a rodless chamber replenishment check valve 6.2. The rodless chamber oil circuit is also equipped with a rodless chamber pressure sensor 7.2 for pressure monitoring, a rod chamber high-pressure maintenance ball valve 2.2 for maintenance oil drainage, and a rodless chamber cartridge-type two-stage solenoid overflow drain valve 5.2 for return oil back pressure control and overpressure protection.

[0024] The rod chamber of the control cylinder 10 for the movable worktable is connected to the system via corresponding symmetrical oil circuits: a rapid inlet oil circuit is connected to a rapid inlet solenoid directional valve 3.1 for the rod chamber; a slow control oil circuit is connected through another working port of the electro-hydraulic proportional directional valve 4; and a replenishment oil circuit is connected to a replenishment check valve 6.1 for the rod chamber. The rod chamber oil circuit is also equipped with a rod chamber pressure sensor 7.1, a high-pressure maintenance ball valve 2.2 for the rod chamber, and a cartridge-type two-stage solenoid overflow drain valve 5.1 for the rod chamber. All return oil eventually converges into the return oil circuit (port T in the diagram) and flows back to the hydraulic system oil tank 1.

[0025] The system also includes a displacement sensor 9, which is installed on the moving worktable 8 of the fast forging press to detect the actual displacement of the worktable in real time. A replenishment oil tank or low-pressure oil source located near the hydraulic system oil tank 1 provides clean replenishment oil to the rod chamber replenishment check valve 6.1 and the rodless chamber replenishment check valve 6.2.

[0026] A programmable logic controller (PLC) serves as the electrical control system. Its signal input terminals are connected to displacement sensor 9, rod chamber pressure sensor 7.1, and rodless chamber pressure sensor 7.2, respectively. Its control output terminals are connected to the electromagnets of rodless chamber rapid liquid inlet solenoid directional valve 3.2, rod chamber rapid liquid inlet solenoid directional valve 3.1, electro-hydraulic proportional directional valve 4, rod chamber cartridge-type two-stage solenoid overflow drain valve 5.1, and rodless chamber cartridge-type two-stage solenoid overflow drain valve 5.2, respectively, to control the operation of each valve according to the preset program and feedback signals.

[0027] The system works as follows: 1) Rapid extension working condition When the worktable 8 needs to move forward rapidly, the PLC issues a command. The rodless chamber rapid liquid inlet solenoid directional valve 3.2 is energized and switches to the left-hand position. At the same time, the solenoid Y1 of the rod chamber cartridge-type two-stage solenoid overflow valve 5.1 is energized, causing its pilot valve to switch and the main valve core to open. At this time, the overflow pressure of the main valve core is set by the parallel low-pressure overflow valve. The high-pressure, high-flow-rate oil output from the variable pump mainly enters the rodless chamber of the cylinder 10 through the rodless chamber rapid liquid inlet solenoid directional valve 3.2 with a larger diameter. Meanwhile, the electro-hydraulic proportional directional valve 4 can receive a small control signal from the PLC as needed, open to a certain degree, assist in oil inlet, and make preliminary interventions in the movement. Under the piston push, the oil in the rod chamber of the cylinder overcomes the stable back pressure set by the rod chamber cartridge-type two-stage solenoid overflow valve 5.1 and flows smoothly back to the oil tank 1, thereby realizing the high-speed and smooth extension of the worktable.

[0028] 2) Deceleration and positioning conditions When the worktable needs to operate at its working speed or be precisely positioned at a predetermined location, the PLC controls the variable displacement pump to reduce its displacement and decrease the output flow. Simultaneously, the rodless chamber rapid inlet solenoid directional valve 3.2 de-energizes and closes, cutting off the rapid oil inlet pathway. The rod chamber cartridge-type two-stage solenoid overflow valve 5.1 remains energized (Y1), providing stable back pressure. At this time, the movement of the worktable is entirely controlled by the electro-hydraulic proportional directional valve 4. The displacement sensor 9 continuously feeds back the real-time detected worktable position signal to the PLC. The PLC compares this feedback signal with the target position and precisely adjusts the magnitude and direction of the control current output to the electro-hydraulic proportional directional valve 4, thereby controlling the valve opening and the direction of fluid flow. As the worktable approaches the target position, the PLC controls the electro-hydraulic proportional directional valve 4 to gradually close its valve, achieving smooth deceleration and ultimately stopping the worktable at the target position with an accuracy of ±1mm. This process avoids hydraulic shock caused by sudden cut-off of large flow rates.

[0029] 3) Forging and locking conditions When the press enters the forging process, and the worktable 8 needs to remain stationary and withstand a huge impact, the PLC de-energizes all active control valves (rodless chamber rapid liquid inlet solenoid directional valve 3.2, rod chamber rapid liquid inlet solenoid directional valve 3.1, electro-hydraulic proportional directional valve 4, and the solenoid Y1 of the two-stage overflow valves 5.1 and 5.2). At this time, the two rapid liquid inlet oil circuits and the main oil circuit of the electro-hydraulic proportional directional valve 4 are cut off. In the de-energized state, the pilot valves of the rod chamber cartridge-type two-stage solenoid overflow valve 5.1 and the rodless chamber cartridge-type two-stage solenoid overflow valve 5.2 reset, and the overflow pressure of the main valve core is switched to be set by the parallel high-pressure overflow valve, effectively preventing the worktable from "moving" due to internal system leakage or external impact. If the forging force is abnormally large, causing the oil pressure on one side to exceed the set value of the high-pressure overflow valve, the valve will open to release pressure, protecting the cylinder and pipeline safety.

[0030] 4) Rapid retraction mode Its principle is symmetrical to rapid extension. The PLC controls the electromagnet Y2 of the rod chamber rapid liquid inlet solenoid directional valve 3.1 and the rodless chamber cartridge-type two-stage solenoid overflow drain valve 5.2 to be energized. The oil from the variable pump enters the rod chamber of the cylinder through the rod chamber rapid liquid inlet solenoid directional valve 3.1, and the oil in the rodless chamber returns to the cylinder under low pressure back pressure through valve 5.2, realizing the rapid retraction of the worktable.

[0031] 5) Fault protection and maintenance conditions Overload protection: When the pressure on either side of the cylinder abnormally increases due to mechanical jamming or other malfunctions of the worktable, the pressure sensor of the corresponding chamber (rod chamber pressure sensor 7.1 or rodless chamber pressure sensor 7.2) will detect the pressure peak signal in real time and transmit it to the PLC. The PLC immediately outputs a signal to energize the solenoid Y1 or Y2 of the cartridge-type two-stage electromagnetic overflow valve on the corresponding side, forcing its main valve core to switch to the low-pressure overflow state and open quickly to release pressure with a large flow rate, thereby protecting the cylinder and the entire hydraulic system.

[0032] Equipment Maintenance: When it is necessary to disassemble the control cylinder 10 of the movable workbench or related valve groups for maintenance, the maintenance personnel should first open the rodless chamber high-pressure maintenance ball valve 2.1 and the rod chamber high-pressure maintenance ball valve 2.2. At this time, most of the hydraulic oil in the pipes connecting the two chambers of the cylinder and in the cylinder can flow back to the hydraulic system oil tank 1 by its own weight or through other auxiliary means. After the oil is drained, safe and clean disassembly and assembly operations can be carried out, effectively avoiding the waste and environmental pollution caused by hydraulic oil leakage during traditional disassembly methods.

[0033] System Integration and Debugging: For ease of installation and maintenance, all hydraulic valves in the hydraulic circuit described in this utility model, excluding cylinders, sensors, and oil tanks, including directional valves, relief valves, check valves, ball valves, etc., can be integrated and installed on one or more hydraulic valve blocks according to functional modules. The valve blocks have pre-installed standard pressure ports P, return ports T, drain ports L, replenishment ports R, and working ports A and B connecting to the two chambers of the cylinder. Before the system is put into initial use, the target position points of the workbench, the fast / slow speed switching points, the control parameters of the proportional valve, and the high and low pressure setting values ​​of the two-stage relief valve must be set through the PLC's human-machine interface. The signals from the rod chamber pressure sensor 7.1 or the rodless chamber pressure sensor 7.2 and the displacement sensor 9 need to be zeroed and range calibrated to ensure control accuracy.

[0034] This invention cleverly combines a high-flow switching valve with a low-flow proportional valve in parallel, along with a cartridge-type relief valve with dual high and low pressure settings, an automatic oil replenishment valve, pressure feedback protection, and a convenient maintenance structure, to create a comprehensive hydraulic control solution that is fast, reliable, safe, and easy to maintain. It is particularly suitable for the control requirements of the moving worktable of a large-tonnage high-speed forging press.

[0035] The above are merely preferred embodiments of this utility model. It should be noted that, for those skilled in the art, based on the technical teachings provided by this utility model and as common knowledge in the field of hydraulics, other equivalent modifications and improvements can be made, and these should also be considered within the scope of protection of this utility model.

Claims

1. A hydraulic circuit for controlling the cylinder of a press moving worktable, characterized in that... The system includes a hydraulic system oil tank (1), which is connected to a movable worktable control cylinder (10) via an oil circuit. The rodless chamber oil circuit of the movable worktable control cylinder (10) is equipped with a rodless chamber rapid liquid inlet solenoid valve (3.2) for rapid liquid inlet. The oil inlet of the rodless chamber rapid liquid inlet solenoid valve (3.2) is connected to the system pressure oil source, and its oil outlet is connected to the rodless chamber of the movable worktable control cylinder (10). The rod chamber of the mobile worktable control cylinder (10) is equipped with a rod chamber cartridge-type two-stage electromagnetic overflow drain valve (5.1) for rapid oil return. The oil inlet of the rod chamber cartridge-type two-stage electromagnetic overflow drain valve (5.1) is connected to the rod chamber of the mobile worktable control cylinder (10), and its oil outlet is connected to the hydraulic system oil tank (1). The rodless chamber oil circuit of the mobile worktable control cylinder (10) is also equipped with an electro-hydraulic proportional directional valve (4) for slow control and positioning. The oil inlet of the electro-hydraulic proportional directional valve (4) is connected to the system pressure oil source, and its working oil port is connected to the rodless chamber and the rod chamber of the mobile worktable control cylinder (10) respectively. The rod chamber and rodless chamber oil circuits of the control cylinder (10) of the mobile worktable are respectively equipped with a rod chamber pressure sensor (7.1) and a rodless chamber pressure sensor (7.2) for pressure detection. The rod chamber and rodless chamber of the control cylinder (10) of the mobile worktable are respectively connected to a rodless chamber high-pressure maintenance ball valve (2.1) and a rod chamber high-pressure maintenance ball valve (2.2) for draining oil during maintenance.

2. The hydraulic circuit for controlling the moving worktable of a press according to claim 1, characterized in that: The control signal input terminal of the electro-hydraulic proportional directional valve (4) is connected to the displacement sensor (9), which is used to detect the displacement of the moving worktable (8) of the fast forging press.

3. A hydraulic circuit for controlling the moving worktable of a press according to claim 1 or 2, characterized in that: The rod chamber and rodless chamber oil circuits of the mobile worktable control cylinder (10) are respectively equipped with a rod chamber oil replenishment check valve (6.1) and a rodless chamber oil replenishment check valve (6.2) for preventing negative pressure oil replenishment. The oil inlets of the rod chamber oil replenishment check valve (6.1) and the rodless chamber oil replenishment check valve (6.2) are connected to the oil replenishment source, and their oil outlets are respectively connected to the rod chamber and the rodless chamber of the mobile worktable control cylinder (10).

4. The hydraulic circuit for controlling the moving worktable of a press according to claim 3, characterized in that: The rodless chamber oil circuit of the control cylinder (10) of the moving worktable is also equipped with a rodless chamber cartridge double-stage electromagnetic overflow drain valve (5.2) which is structurally symmetrical to the rod chamber cartridge double-stage electromagnetic overflow drain valve (5.1), for overpressure protection and back pressure control when the rodless chamber returns oil.

5. A hydraulic circuit for controlling the moving worktable of a press according to claim 4, characterized in that: Both the rod-type cartridge-mounted two-stage electromagnetic overflow drain valve (5.1) and the rodless cartridge-mounted two-stage electromagnetic overflow drain valve (5.2) are two-stage pressure control structures, each including a low-pressure overflow valve and a high-pressure overflow valve, which are switched and controlled by a solenoid valve.

6. A hydraulic circuit for controlling the moving worktable of a press according to claim 5, characterized in that: The rod chamber of the control cylinder (10) of the moving worktable is also equipped with a rod chamber rapid liquid inlet electromagnetic reversing valve (3.1) which is structurally symmetrical with the rodless chamber rapid liquid inlet electromagnetic reversing valve (3.2) and is used for liquid inlet control when the cylinder retracts rapidly.

7. A hydraulic circuit for controlling the moving worktable of a press according to claim 6, characterized in that: It also includes a programmable controller, which is connected to the rodless chamber rapid liquid inlet solenoid directional valve (3.2), the rod chamber cartridge-type two-stage solenoid overflow drain valve (5.1), the electro-hydraulic proportional directional valve (4), the displacement sensor (9), the rod chamber pressure sensor (7.1) and the rodless chamber pressure sensor (7.2) respectively.

Images