An overload protection system

Abstract

The application provides an overload protection system arranged on a crane and driving a winch to act, comprising an oil tank, a pilot overflow valve, a first switch valve, a first control valve group, a second control valve group, a detection component and a motor, a hydraulic pump is arranged on the oil tank, the hydraulic pump is connected with a first port of the motor through an oil inlet pipeline, a second port of the motor is connected with the oil tank through an oil return pipeline, a pilot overflow valve is arranged between the oil inlet pipeline and the oil return pipeline, an oil inlet end of the pilot overflow valve is connected with the oil inlet pipeline, and an oil outlet end of the pilot overflow valve is connected with the oil return pipeline; the first control valve group comprises a first control switch valve, a first control reversing valve and a first control overflow valve; the above structure can adjust the pressure of the overflow valve in an emergency, so that the hydraulic oil circuit can be kept stable, and the winch can be controlled to quickly release the steel wire rope to realize emergency rope abandonment in the emergency.

Description

Technical Field

[0001] This invention relates to the field of winch control system technology, and more specifically to an overload protection system. Background Technology

[0002] A hydraulic winch mainly consists of a hydraulic motor (low-speed or high-speed), a normally closed hydraulic multi-disc brake, a planetary gearbox, a clutch (optional), a drum, a support shaft, a frame, and a rope presser (optional). The hydraulic motor has high mechanical efficiency, large starting torque, and can be equipped with different distributors depending on the working conditions. Valve assemblies can also be designed and directly integrated into the motor distributor, such as those with balance valves, overload valves, high-pressure shuttle valves, speed-regulating directional valves, or other valve assemblies. The brake and planetary gearbox are directly installed inside the drum. The drum, support shaft, and frame are designed according to mechanical requirements, resulting in a simple and reasonable overall structure with sufficient strength and rigidity. Its conventional principle is that the hydraulic motor drives the drum to rotate, and the rotation of the drum winds the wire rope onto it for retraction.

[0003] Chinese patent application No. 202311396506.4, published on April 16, 2024, discloses an overload protection method for hydraulic circuits. This method records the full-load oil pressure values ​​of the winch system under full load operation at different throttle valve openings. Based on the current full-load oil pressure value, it can accurately calculate the oil pressure value for overload exceeding 1.1 times. The throttle valve amplifies the oil pressure in the oil pump and multi-way valve group area of ​​the inlet pipeline, increasing the difference between the full-load and overload oil pressure values. This allows the pressure switch to accurately detect the numerical difference between the full-load and overload oil pressure values, thus enabling the pressure switch to accurately detect whether the winch system is overloaded.

[0004] The document states that the pressure relief valve opens when an overload is detected. However, as with existing technology, the pressure relief valve's regulating pressure is usually preset. When an overload is detected, the valve opens. This means that if the regulating pressure of the valve is high, opening it requires a large hydraulic oil pressure. Adjusting the pressure of the valve also requires stopping the machine, which wastes working time and reduces efficiency. Furthermore, since the adjustment is only done through the valve, it cannot be manually relieved quickly if the valve malfunctions, thus preventing emergency rope abandonment. Summary of the Invention

[0005] This invention provides an overload protection system that can adjust the pressure of the relief valve manually or automatically, thereby ensuring the stability of the hydraulic circuit and the stability of the rope disposal process.

[0006] To achieve the above objectives, the technical solution of the present invention is: an overload protection system, wherein the overload protection system is installed on a crane and drives the winch to operate, comprising an oil tank, a pilot-operated relief valve, a first switching valve, a first control valve group, a second control valve group, a detection component, and a motor. A hydraulic pump is provided on the oil tank, the hydraulic pump is connected to the first port of the motor through an oil inlet pipe, and the second port of the motor is connected to the oil tank through a return oil pipe. A pilot-operated relief valve is provided between the oil inlet pipe and the return oil pipe, the oil inlet end of the pilot-operated relief valve is connected to the oil inlet pipe, and the oil outlet end of the pilot-operated relief valve is connected to the return oil pipe; a first switching valve is provided on the return oil pipe.

[0007] The first control valve group includes a first control switching valve, a first control directional valve, and a first control relief valve. The P and T ends of the first control directional valve are connected to the oil tank, the A end of the first control directional valve is connected to the control end of the first control switching valve, the first port of the first control switching valve is connected to the oil tank through the first control relief valve, and the second port of the first control switching valve is connected to the control oil circuit of the pilot-operated relief valve. The relief pressure of the first control relief valve is less than the control pressure of the control oil circuit of the pilot-operated relief valve.

[0008] The second control valve assembly includes a second control switching valve, a second control directional valve, and a second control relief valve. The P and T ends of the second control directional valve are connected to the oil tank, and the A end of the second control directional valve is connected to the control end of the second control switching valve. The first port of the second control switching valve is connected to the oil tank through the second control relief valve, and the second port of the second control switching valve is connected to the control oil circuit of the pilot-operated relief valve. The relief pressure of the second control relief valve is less than the control pressure of the control oil circuit of the pilot-operated relief valve. The drain pressure of the first control relief valve is less than the drain pressure of the second control relief valve.

[0009] The detection component is communicatively connected to the second control directional valve. The detection component includes an inclination sensor installed on the crane and a force sensor installed on the winch. The inclination sensor and the force sensor are connected to the control terminal of the second control directional valve through a terminal processor. A pressure regulator is also provided at the control terminal of the second control relief valve. The pressure regulator is communicatively connected to the terminal processor.

[0010] The second control terminal of the first switching valve is connected to the A terminal of the first control directional valve and the A terminal of the second control directional valve via the first shuttle valve. The first port of the first switching valve is connected to the second port of the motor via a return oil pipe. The second port of the first switching valve is connected to the oil tank via a return oil pipe. The first control terminal of the first switching valve is connected to the first port and the second port of the first switching valve. The second control terminal of the first switching valve is also connected to the oil tank via the first shuttle valve. The first control terminal of the first switching valve controls the first port and the second port of the first switching valve to connect. The second control terminal of the first switching valve controls the first port and the second port of the first switching valve to disconnect.

[0011] In the above structure, when the rope is being wound up, hydraulic oil output from the oil tank enters the inlet pipe, then passes through the motor and returns to the oil tank via the return pipe, circulating to achieve the rope winding operation. Simultaneously, a first switching valve is installed on the return pipe. When the motor is running normally, the oil tank supplies hydraulic oil to the motor through the inlet pipe, and the hydraulic oil flows into the return pipe. The hydraulic oil in the return pipe flows to the first control terminal of the first switching valve, thereby driving the first switching valve to switch direction and connect the first port and the second port. This connects the return pipe to the oil tank, allowing the hydraulic oil to flow back to the oil tank for circulation. When lifting heavy objects, this is the rope winding state. The tilt sensor detects the crane's working radius, and the force sensor detects the tension of the wire rope during the rope winding state. The current working radius of the crane is compared with the preset working radius, and the current wire rope tension is compared with the preset wire rope tension. When the wire rope tension is too high under the working radius of the crane, the terminal processor drives the second control valve to switch and connect the A end with the P end. The oil tank outputs hydraulic oil to the control end of the second control switch valve through the second control switching valve, causing the second control switch valve to switch and connect the first port and the second port of the second control switch valve. As a result, the control hydraulic oil in the control oil circuit of the pilot-operated relief valve is depressurized through the second control relief valve and flows back to the oil tank, thereby reducing the regulating pressure of the pilot-operated relief valve. At the same time, the terminal processor controls the pressure regulator in real time according to the overturning moment of the crane, thereby driving the second The relief valve's discharge pressure is regulated to ensure the hydraulic oil pressure is neither too high nor too low, keeping the crane's overturning moment within a safe range. This allows for the rapid formation of the internal circulation oil circuit, ensuring both automatic and rapid rope release and stable hydraulic circuit operation. If the hook catches an object that cannot be unhooked during rope retraction, the first control directional valve is manually activated. This directional valve switches, connecting terminals A and P. The oil tank outputs hydraulic oil to the control terminal of the first control switch valve through the first control directional valve. This causes the first control switch valve to switch and connect its first and second ports. Consequently, the control hydraulic oil in the pilot-operated relief valve's control circuit flows back to the oil tank after being depressurized by the first control relief valve. This lowers the regulating pressure of the pilot-operated relief valve. Since the oil pressure in the inlet pipe is greater than the regulating pressure of the pilot-operated relief valve, it drives the valve to open. This allows the hydraulic oil in the inlet pipe to be depressurized through the valve and flow into the return pipe, increasing the oil pressure in the return pipe. This also makes the oil pressure at the end of the motor connected to the return pipe greater than the pressure at the end of the motor connected to the inlet pipe. Due to the overflow effect of the pilot-operated relief valve, a circulation loop is formed between the inlet pipe, the return pipe, and the motor. The tank continues to output hydraulic oil to the inlet pipe, further increasing the amount of hydraulic oil in the circulation loop. This increases the pressure difference across the motor, thereby increasing the motor speed and enabling rapid rope release.

[0012] Furthermore, the tilt sensor and the force sensor are connected to the control terminal of the second control directional valve via a terminal processor; a pressure regulator is also provided at the control terminal of the second control overflow valve, and the pressure regulator is communicatively connected to the terminal processor.

[0013] The above settings allow for convenient pressure regulation of the second control relief valve by using a pressure regulator.

[0014] Furthermore, a second switching valve is provided between the oil inlet end of the pilot-operated relief valve and the oil inlet pipe. The first port of the second switching valve is connected to the oil inlet pipe, and the second port of the second switching valve is connected to the oil inlet end of the pilot-operated relief valve.

[0015] The above settings, by setting a second switching valve, ensure that the oil circuit between the oil inlet pipe and the pilot relief valve is opened only when the pilot relief valve is needed, thereby facilitating the control of the hydraulic system.

[0016] Furthermore, a balance valve assembly is provided on the oil inlet pipe. The balance valve assembly includes a balance relief valve and a balance check valve. The oil inlet end of the balance relief valve is connected to the first port of the motor through the oil inlet pipe, and the oil outlet end of the balance relief valve is connected to the hydraulic pump through the oil inlet pipe. The oil inlet end of the balance check valve is connected to the oil outlet end of the balance relief valve, and the oil outlet end of the balance check valve is connected to the oil inlet end of the balance relief valve.

[0017] The above settings, through the installation of a balance valve assembly, ensure stable hydraulic oil output from the inlet pipe.

[0018] Furthermore, a brake valve is also provided on the motor. The control end of the brake valve is connected to the oil inlet pipe and the oil outlet pipe through a brake reversing valve. The P end of the brake reversing valve is connected to the oil tank, and the A end of the brake reversing valve is connected to the control end of the brake valve. The control end of the brake reversing valve is connected to the oil inlet pipe and the oil outlet pipe.

[0019] The above setup connects the inlet and outlet oil pipes via the control terminal of the brake valve reversing valve. When the winch is to be started, the hydraulic oil in the inlet and outlet oil pipes flows to the control terminal of the brake valve reversing valve and controls the brake valve reversing valve to connect terminal A to terminal P. This causes the hydraulic oil output from the oil tank to flow to the control terminal of the brake valve, thereby driving the brake valve to open and facilitating motor rotation.

[0020] Furthermore, a spring is provided on the second control end of the first switching valve, and the hydraulic oil pressure at the second control end plus the spring pressure is greater than the hydraulic oil pressure at the first control end of the first switching valve.

[0021] The above configuration, by incorporating a spring, ensures that when the first switching valve is to be closed, the hydraulic oil pressure flowing from the oil tank to the second control end of the first switching valve, combined with the spring force, overcomes the hydraulic oil pressure at the first control end of the first switching valve, thereby driving the first switching valve to close and preventing the hydraulic oil from flowing back to the oil tank through the return oil pipe.

[0022] Furthermore, the first port of the first shuttle valve is connected to the A end of the first control directional valve and the A end of the second control directional valve, the second port of the first shuttle valve is connected to the oil tank, and the third port of the first shuttle valve is connected to the second control end of the first switching valve.

[0023] The above configuration, by placing a first shuttle valve between the second control terminal of the first switching valve and the A terminal of the first and second control directional valves, ensures that the hydraulic oil flowing from the second control directional valve to the second control terminal of the first switching valve does not conflict with the hydraulic oil flowing from the oil tank to the second control terminal of the first switching valve. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the hydraulic system of the present invention.

[0025] Figure 2 for Figure 1 Diagram of hydraulic circuit connection at point A.

[0026] Figure 3 for Figure 1 Enlarged view of point B in the middle. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0028] like Figures 1-3As shown, an overload protection system is installed on a crane and drives the winch. It includes an oil tank 1, a pilot-operated relief valve 2, a first switching valve 3, a motor 4, a detection component (not shown), a first control valve group, and a second control valve group. A hydraulic pump (not shown) is installed on the oil tank 1. The hydraulic pump is connected to the first port 41 of the motor 4 via an inlet pipe 11, and the second port 42 of the motor 4 is connected to the oil tank 1 via a return pipe 12. A pilot-operated relief valve 2 is installed between the inlet pipe 11 and the return pipe 12. The inlet end of the pilot-operated relief valve 2 is connected to the inlet pipe 11. The oil outlet is connected to the return oil pipe 12; a first switch valve 3 is provided on the return oil pipe 12. The first port of the first switch valve 3 is connected to the second port 42 of the motor 4 through the return oil pipe 12. The second port of the first switch valve 3 is connected to the oil tank 1 through the return oil pipe 12. The first control terminal 31 of the first switch valve 3 is connected to the first port and the second port of the first switch valve 3. The second control terminal 32 of the first switch valve 3 is connected to the oil tank. The first control terminal 31 of the first switch valve 3 controls the first port and the second port of the first switch valve 3 to connect. The second control terminal 32 of the first switch valve 3 controls the first port and the second port of the first switch valve 3 to disconnect.

[0029] The first control valve group includes a first control switching valve 81, a first control directional valve 82, and a first control relief valve 83. The P and T ends of the first control directional valve 82 are connected to the oil tank 1. The A end of the first control directional valve 82 is connected to the control end 811 of the first control switching valve 81. The first port of the first control switching valve 81 is connected to the oil tank 1 through the first control relief valve 83. The second port of the first control switching valve 81 is connected to the control oil circuit 20 of the pilot-operated relief valve 2. The overflow pressure of the first control relief valve 83 is less than the control pressure of the control oil circuit 20 of the pilot-operated relief valve 2. In this embodiment, the control end 821 of the first control directional valve is connected to a control button (not shown in the figure) in the crane operator's cab via an external circuit. In case of emergency, the operator in the cab can press the control button to drive the first control directional valve to achieve reversal.

[0030] The second control valve assembly includes a second control switching valve 91, a second control directional valve 92, and a second control relief valve 93. The P and T terminals of the second control directional valve 92 are connected to the oil tank 1. The A terminal of the second control directional valve 92 is connected to the control terminal 911 of the second control switching valve 91. The first port of the second control switching valve 91 is connected to the oil tank 1 via the second control relief valve 93. The second port of the second control switching valve 91 is connected to the control oil circuit 20 of the pilot-operated relief valve 2. The relief pressure of the second control relief valve 93 is less than the control pressure of the control oil circuit 20 of the pilot-operated relief valve 2. The discharge pressure of the first control relief valve is less than the discharge pressure of the second control relief valve.

[0031] The detection component is communicatively connected to the second control directional valve 92. The detection component includes a tilt sensor mounted on the crane and a force sensor mounted on the winch. The tilt sensor and force sensor are connected to the control terminal of the second control directional valve 92 via a terminal processor. A pressure regulator 931 is also provided at the control terminal of the second control relief valve 93, and the pressure regulator 931 is communicatively connected to the terminal processor. In this embodiment, the terminal processor is a PLC or CPU, or other device used for information processing; its specific technology is existing and will not be elaborated further here.

[0032] A first shuttle valve 84 is provided between the second control terminal 32 of the first switching valve 3 and the A terminal of the first control directional valve 82 and the A terminal of the second control directional valve 92. The first port 841 of the first shuttle valve 84 is connected to the A terminal of the second control directional valve 92, the second port 842 of the first shuttle valve 84 is connected to the oil tank 1, and the third port 843 of the first shuttle valve 84 is connected to the second control terminal 32 of the first switching valve 3.

[0033] A first shuttle valve 84 is installed between the second control terminal 32 of the first switching valve 3 and the A terminal of the second control directional valve 92. During normal rope winding, hydraulic oil from the control tank 1 enters the second port 842 of the first shuttle valve 84. Since the second control switching valve 92 is closed, the first port 841 of the first shuttle valve 84 cannot supply oil. Therefore, the hydraulic oil in the tank 1 enters the second control terminal 32 of the first switching valve 3 through the second port 842, closing the first switching valve 3 and thus enabling the rope winding operation to be stopped. In case of emergency rope winding, the second control switching valve 92 is open, allowing hydraulic oil from the tank 1 to enter the first port 841 of the first shuttle valve 84 and then flow to the control terminal of the first switching valve 3, closing it and enabling emergency rope winding. This ensures that the hydraulic oil flowing from the second control directional valve 92 to the second control terminal 32 of the first switching valve 3 does not conflict with the hydraulic oil flowing from the tank 1 to the second control terminal 32 of the first switching valve 3.

[0034] A second switching valve 21 is provided between the oil inlet end of the pilot-operated relief valve 2 and the oil inlet pipe. The first port of the second switching valve 21 is connected to the oil inlet pipe 11, and the second port of the second switching valve 21 is connected to the oil inlet end of the pilot-operated relief valve 2. By setting the second switching valve 21, the oil passage between the oil inlet pipe 11 and the pilot-operated relief valve 2 is opened only when the pilot-operated relief valve 2 is needed, thereby facilitating the control of the hydraulic system.

[0035] A balance valve assembly 5 is provided on the oil inlet pipe 11. The balance valve assembly 5 includes a balance relief valve 51 and a balance check valve 52. The oil inlet end of the balance relief valve 51 is connected to the first port 41 of the motor 4 through the oil inlet pipe 11, and the oil outlet end of the balance relief valve 51 is connected to the hydraulic pump through the oil inlet pipe 11. The oil inlet end of the balance check valve 52 is connected to the oil outlet end of the balance relief valve 51, and the oil outlet end of the balance check valve 52 is connected to the oil inlet end of the balance relief valve 51. By setting up the balance valve assembly 5, the hydraulic oil output of the oil inlet pipe 11 is stabilized.

[0036] like Figure 1 As shown, a brake valve 43 is also provided on the motor 4. The control end of the brake valve 43 is connected to the oil inlet pipe and the oil outlet pipe through a brake directional valve 44. The P end of the brake directional valve 44 is connected to the oil tank, the A end of the brake directional valve is connected to the control end of the brake valve, and the K end of the brake directional valve 44 is connected to the oil inlet pipe 11 and the oil outlet pipe 12. When the winch is to be started, the hydraulic oil in the oil inlet pipe 11 and the oil outlet pipe 12 flows to the control end of the brake directional valve 44 and controls the brake directional valve 44 to switch so that the A end connects to the P end. This causes the hydraulic oil output from the oil tank 1 to flow to the control end of the brake valve 43, thereby driving the brake valve 43 to open and facilitating the rotation of the motor 4.

[0037] like Figure 2 As shown, a spring 33 is also provided on the second control end 32 of the first switching valve 3. The hydraulic oil pressure at the second control end 32 plus the pressure of the spring 33 is greater than the hydraulic oil pressure at the first control end 31 of the first switching valve 3. By setting the spring 33, when the first switching valve 3 is to be closed, the hydraulic oil pressure flowing from the oil tank 1 to the second control end 32 of the first switching valve 3 plus the elastic force of the spring 33 overcomes the hydraulic oil pressure at the first control end 31 of the first switching valve 3, thereby driving the first switching valve 3 to close, so that the hydraulic oil cannot flow back to the oil tank through the return oil pipe 12.

[0038] The working principle of this invention is as follows: When the rope is being wound up, hydraulic oil output from the oil tank 1 enters the inlet pipe 11 through the balance check valve 52, then passes through the motor 4 and returns to the oil tank 1 via the return pipe 12, thus circulating to achieve the rope winding operation. Simultaneously, a first switching valve 3 is installed on the return pipe 12. When the motor 4 is rotating normally, the oil tank 1 supplies hydraulic oil to the motor 4 through the inlet pipe 11, and the hydraulic oil flows into the return pipe 12 through the motor 4. The hydraulic oil in the return pipe 12 flows to the first control terminal 31 of the first switching valve 3, thereby driving the first switching valve 3 to switch direction and connect the first port and the second port. This connects the return pipe 12 to the oil tank, allowing the hydraulic oil to flow back to the oil tank 1, achieving circulation. When lifting a heavy object, the crane is in the rope-retracting state. The tilt sensor detects the crane's working radius, and the force sensor detects the wire rope tension during this retracting state. By comparing the crane's current working radius with a preset working radius, and comparing the current wire rope tension with a preset wire rope tension, if the wire rope tension is too high at the crane's working radius, the terminal processor drives the second control valve to switch, connecting end A and end P. The oil tank outputs hydraulic oil through the second control switching valve 92 to the control end 911 of the second control switch valve 91, causing the second control switch valve 91 to switch and connect its first port and second end. This causes the control hydraulic oil in the control circuit 20 of the pilot-operated relief valve 2 to flow back to the oil tank via the second control relief valve 93, thereby lowering the regulating pressure of the pilot-operated relief valve 2. Simultaneously, the terminal processor controls the pressure regulator in real time based on the overturning moment of the crane, thereby driving the relief pressure of the second control relief valve to adjust, ensuring that the hydraulic oil pressure is neither too high nor too low, and that the overturning moment of the crane remains within a safe range. This enables the rapid formation of the internal circulation oil circuit, ensuring both rapid rope release and hydraulic circuit stability. If the hook catches an object that cannot be unhooked during rope retraction, the first control directional valve is manually activated, and the second... A first control directional valve 82 switches to connect end A and end P. The oil tank outputs hydraulic oil to the control end 811 of the first control switch valve 81 through the first control directional valve 82, causing the first control switch valve 81 to switch and connect the first port and the second port of the first control switch valve 81. As a result, the control hydraulic oil of the control oil circuit 20 of the pilot relief valve 2 is depressurized through the first control relief valve 83 and flows back to the oil tank. This reduces the regulating pressure of the pilot relief valve 2. Since the oil discharge pressure of the first control relief valve is less than that of the second control relief valve, the regulating pressure of the pilot relief valve can be reduced to a greater extent, thereby making the oil discharge speed of the hydraulic oil circuit faster.Because the oil pressure in the inlet pipe 11 is greater than the regulating pressure of the pilot-operated relief valve 2, the pilot-operated relief valve 2 is driven to open. This causes the hydraulic oil in the inlet pipe 11 to be depressurized through the pilot-operated relief valve 2 and flow to the return pipe 12, thereby increasing the oil pressure in the return pipe 12. This results in the oil pressure at the end of the motor 4 connected to the return pipe 12 being greater than the oil pressure at the end of the motor connected to the inlet pipe 11. Furthermore, due to the overflow effect of the pilot-operated relief valve 2, a circulation loop is formed between the inlet pipe, the return pipe, and the motor through the pilot-operated relief valve. The oil tank continues to output hydraulic oil to the inlet pipe, further increasing the amount of hydraulic oil in the circulation loop. This increases the pressure difference across the motor 4, thereby increasing the motor 4's speed and enabling rapid rope release.

Claims

1. An overload protection system, wherein the overload protection system is installed on a crane and drives the winch to operate, characterized in that: The system includes an oil tank, a pilot-operated relief valve, a first switching valve, a first control valve group, a second control valve group, a detection component, and a motor. A hydraulic pump is mounted on the oil tank. The hydraulic pump is connected to the first port of the motor via an inlet pipe, and the second port of the motor is connected to the oil tank via a return pipe. A pilot-operated relief valve is installed between the inlet and return pipes. The inlet end of the pilot-operated relief valve is connected to the inlet pipe, and the outlet end of the pilot-operated relief valve is connected to the return pipe. A first switching valve is installed on the return pipe. The inlet end of the pilot-operated relief valve is connected to the inlet pipe. A second switching valve is provided between the two, with its first port connected to the oil inlet pipe and its second port connected to the oil inlet of the pilot-operated relief valve; a balance valve assembly is provided on the oil inlet pipe, the balance valve assembly including a balance relief valve and a balance check valve, the oil inlet of the balance relief valve being connected to the first port of the motor through the oil inlet pipe, the oil outlet of the balance relief valve being connected to the hydraulic pump through the oil inlet pipe, the oil inlet of the balance check valve being connected to the oil outlet of the balance relief valve, and the oil outlet of the balance check valve being connected to the oil inlet of the balance relief valve; The first control valve group includes a first control switching valve, a first control directional valve, and a first control relief valve. The P and T ends of the first control directional valve are connected to the oil tank, the A end of the first control directional valve is connected to the control end of the first control switching valve, the first port of the first control switching valve is connected to the oil tank through the first control relief valve, and the second port of the first control switching valve is connected to the control oil circuit of the pilot-operated relief valve. The relief pressure of the first control relief valve is less than the control pressure of the control oil circuit of the pilot-operated relief valve. The second control valve assembly includes a second control switching valve, a second control directional valve, and a second control relief valve. The P and T ends of the second control directional valve are connected to the oil tank, and the A end of the second control directional valve is connected to the control end of the second control switching valve. The first port of the second control switching valve is connected to the oil tank through the second control relief valve, and the second port of the second control switching valve is connected to the control oil circuit of the pilot-operated relief valve. The relief pressure of the second control relief valve is less than the control pressure of the pilot-operated relief valve control oil circuit. The drain pressure of the first control relief valve is less than the drain pressure of the second control relief valve. The detection component is communicatively connected to the second control directional valve. The detection component includes a tilt sensor mounted on the crane and a force sensor mounted on the winch. The second control terminal of the first switching valve is connected to the A terminal of the first control directional valve and the A terminal of the second control directional valve via the first shuttle valve. The first port of the first switching valve is connected to the second port of the motor via a return oil pipe. The second port of the first switching valve is connected to the oil tank via a return oil pipe. The first control terminal of the first switching valve is connected to the first port and the second port of the first switching valve. The second control terminal of the first switching valve is also connected to the oil tank via the first shuttle valve. The first control terminal of the first switching valve controls the first port and the second port of the first switching valve to connect. The second control terminal of the first switching valve controls the first port and the second port of the first switching valve to disconnect.

2. The overload protection system according to claim 1, characterized in that: The tilt sensor and force sensor are connected to the control terminal of the second control directional valve via a terminal processor; a pressure regulator is also provided at the control terminal of the second control overflow valve, and the pressure regulator is communicatively connected to the terminal processor.

3. The overload protection system according to claim 1, characterized in that: A brake valve is also provided on the motor. The control end of the brake valve is connected to the oil inlet pipe and the oil outlet pipe through a brake reversing valve. The P end of the brake reversing valve is connected to the oil tank, and the A end of the brake reversing valve is connected to the control end of the brake valve. The control end of the brake reversing valve is connected to the oil inlet pipe and the oil outlet pipe.

4. An overload protection system according to claim 1, characterized in that: A spring is also provided on the second control end of the first switching valve. The hydraulic oil pressure at the second control end plus the pressure of the spring is greater than the hydraulic oil pressure at the first control end of the first switching valve.

5. An overload protection system according to claim 1, characterized in that: The first port of the first shuttle valve is connected to the A end of the first control directional valve and the A end of the second control directional valve, the second port of the first shuttle valve is connected to the oil tank, and the third port of the first shuttle valve is connected to the second control end of the first switching valve.

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