Overload protection system for crane

Abstract

The utility model provides a crane overload protection system, which is arranged on a crane and drives a winch to act, and comprises 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, 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, the pilot-operated overflow valve is arranged between the oil inlet pipeline and the oil return pipeline, the oil inlet end of the pilot-operated overflow valve is connected with the oil inlet pipeline, and the oil outlet end of the pilot-operated 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; according to the structure, under the emergency condition, the pressure of the overflow valve can be adjusted, so that it is guaranteed that a hydraulic oil way can be kept stable, and under the emergency condition, a winch is controlled to quickly loosen a steel wire rope to achieve emergency rope abandoning.

Description

Technical Field

[0001] The utility model relates to the technical field of winch control systems, and particularly relates to an overload protection system for a crane. Background Technique

[0002] A hydraulic winch mainly consists of a hydraulic motor (low-speed or high-speed motor), a hydraulic normally closed multi-disc brake, a planetary gearbox, a clutch (optional), a drum, a support shaft, a frame, a rope pressing device (optional), etc. The hydraulic motor has high mechanical efficiency, large starting torque, and can be equipped with different flow dividers according to working conditions. It can also be designed with a valve group directly integrated on the motor flow divider as needed, such as a valve group with a balance valve, an overload valve, a high-pressure shuttle valve, a speed regulating and reversing valve, or other performance valve groups. The brake, planetary gearbox, etc. are directly installed inside the drum. The drum, support shaft, and frame are designed according to mechanical requirements. The overall structure is simple and reasonable and has sufficient strength and rigidity. Its conventional principle is to drive the drum to rotate through the hydraulic motor, and wind the steel wire rope onto the drum for retraction through the rotation of the drum.

[0003] In the patent document with the Chinese patent application number 202311396506.4 and the publication date of April 16, 2024, an overload protection method for a hydraulic oil circuit is disclosed, which records the full-load oil pressure values of the winch system when the throttle valve is at different opening degrees; thus, the oil pressure value more than 1.1 times the overload can be calculated under the current full-load oil pressure value, and the calculation is accurate; the throttle valve amplifies the oil pressure in the oil inlet pipeline in the area of the oil pump and the multi-way valve group, making the increase between the full-load oil pressure value and the overload oil pressure value, and then the pressure switch can accurately detect the numerical difference between the full-load oil pressure value and the overload oil pressure value; thus, the pressure switch can accurately detect whether there is an overload in the winch system.

[0004] When the overload is detected in this document, the pressure relief valve will be opened. However, as in the prior art of this document, the adjustment pressure of the pressure relief valve is generally preset in advance. When the overload is detected, the pressure relief valve will be opened. In this way, if the adjustment pressure of the pressure relief valve is relatively large, a relatively large hydraulic oil pressure is required to open the pressure relief valve. If the pressure of the pressure relief valve needs to be adjusted, the machine needs to be stopped first, which is likely to waste working time and reduce efficiency. In addition, it only adjusts through the pressure relief valve. When the pressure relief valve has problems, it cannot be quickly relieved manually, so emergency rope abandonment cannot be carried out. Summary of the Invention

[0005] The utility model provides an overload protection system for a crane, which can adjust the pressure of the overflow valve manually or automatically, so as to ensure the stability of the hydraulic oil circuit and the stability of the whole rope abandonment process.

[0006] To achieve the above object, the technical solution of the present utility model is: a crane overload protection system, the overload protection system is arranged on the crane and drives the winch to act, and 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 provided on the oil tank. The hydraulic pump is connected to the first port of the motor through an oil inlet pipeline. The second port of the motor is connected to the oil tank through an oil return pipeline. A pilot-operated relief valve is provided between the oil inlet pipeline and the oil return pipeline. The oil inlet end of the pilot-operated relief valve is connected to the oil inlet pipeline, and the oil outlet end of the pilot-operated relief valve is connected to the oil return pipeline. A first switching valve is provided on the oil return pipeline.

[0007] The first control valve group includes a first control switching valve, a first control reversing valve and a first control relief valve. The P port and the T port of the first control reversing valve are connected to the oil tank. The A port of the first control reversing 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. 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 group includes a second control switching valve, a second control reversing valve and a second control relief valve. The P port and the T port of the second control reversing valve are connected to the oil tank. The A port of the second control reversing 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. 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 reversing valve. The detection component includes an inclination sensor arranged on the crane and a force sensor arranged on the winch. The inclination sensor and the force sensor are connected to the control end of the second control reversing valve through a terminal processor. A pressure regulator is further provided at the control end of the second control relief valve. The pressure regulator is communicatively connected to the terminal processor.

[0010] The second control end of the first switching valve is connected to the A end of the first control reversing valve and the A end of the second control reversing valve through a first shuttle valve. The first port of the first switching valve is connected to the second port of the motor through an oil return pipeline, and the second port of the first switching valve is connected to the oil tank through an oil return pipeline. The first control end of the first switching valve is connected to the first port and the second port of the first switching valve. The second control end of the first switching valve is also connected to the oil tank through a first shuttle valve. The first control end of the first switching valve controls the communication between the first port and the second port of the first switching valve, and the second control end of the first switching valve controls the disconnection between the first port and the second port of the first switching valve.

[0011] In the above structure, when taking in the rope, the oil tank outputs hydraulic oil which enters the oil inlet pipeline, then passes through the motor and enters the oil tank through the oil return pipeline to complete the operation of taking in the rope. At the same time, a first switch valve is provided on the oil return pipeline. When the motor is rotating normally, the oil tank transports hydraulic oil to the motor through the oil inlet pipeline and the hydraulic oil in the oil return pipeline flows to the first control end of the first switch valve, thereby driving the first switch valve to change its direction and connecting the first port and the second port. As a result, the oil return pipeline is connected to the oil tank and the hydraulic oil can flow back to the oil tank to achieve circulation. When operating to lift a heavy object, at this time it is in the state of taking in the rope. The inclination sensor detects the working radius of the crane, and the force measuring sensor detects the tension of the wire rope in the state of taking in the rope. By comparing the current working radius of the crane with the pre-set working radius, and comparing the current wire rope tension with the pre-set wire rope tension, when the wire rope tension is too large under the working radius of the crane, the terminal processor drives the second control valve to change its direction and makes the A end communicate with the P end. The oil tank outputs hydraulic oil to the control end of the second control switch valve through the second control reversing valve, causing the second control switch valve to change its direction and connect the first port and the second port of the second control switch valve. As a result, the control hydraulic oil of the control oil circuit of the pilot-operated relief valve is depressurized and flows back to the oil tank through the second control relief valve, 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 tipping moment of the crane, thereby driving the regulation of the bleeding pressure of the second control relief valve to ensure that the oil pressure of the hydraulic oil is neither too high nor too low, and ensuring that the tipping moment of the crane can be within a safe range, so as to enable the rapid formation of the internal circulation oil circuit, ensure rapid automatic rope release while also ensuring the stability of the hydraulic oil circuit; if when taking in the rope, the hook hooks an object that cannot be unhooked, manually make the first control reversing valve conduct. The first control reversing valve changes its direction to make the A end communicate with the P end. The oil tank outputs hydraulic oil to the control end of the first control switch valve through the first control reversing valve, causing the first control switch valve to change its direction and connect the first port and the second port of the first control switch valve. As a result, the control hydraulic oil of the control oil circuit of the pilot-operated relief valve is depressurized and flows back to the oil tank through the first control relief valve, thereby reducing the regulating pressure of the pilot-operated relief valve. Since the oil pressure in the oil inlet pipeline is greater than the regulating pressure of the pilot-operated relief valve, it drives the pilot-operated relief valve to open. As a result, the hydraulic oil in the oil inlet pipeline is depressurized through the pilot-operated relief valve to the oil return pipeline, thereby increasing the oil pressure on the oil return pipeline and making the oil pressure at the end of the motor connected to the oil return pipeline greater than the oil pressure at the end of the motor connected to the oil inlet pipeline. And due to the overflow effect of the pilot-operated relief valve, a circulation loop is formed between the oil inlet pipeline, the oil return pipeline and the motor through the pilot-operated relief valve. The oil tank continues to output hydraulic oil to the oil inlet pipeline, further increasing the hydraulic oil in the circulation loop, thereby increasing the pressure difference at both ends of the motor, and then increasing the rotation speed of the motor to achieve rapid rope release.

[0012] Further, the inclination sensor and the force sensor are connected to the control end of the second control reversing valve through the terminal processor; a pressure regulator is also provided at the control end of the second control overflow valve, and the pressure regulator is communicatively connected to the terminal processor.

[0013] With the above settings, the pressure of the second control overflow valve can be conveniently adjusted by setting the pressure regulator.

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

[0015] With the above settings, by setting the second switching valve, the oil circuit between the oil inlet pipeline and the pilot-operated overflow valve is opened only when the pilot-operated overflow valve needs to be used, thus facilitating the control of the hydraulic system.

[0016] Further, a balance valve group is provided on the oil inlet pipeline. The balance valve group includes a balance overflow valve and a balance check valve. The oil inlet end of the balance overflow valve is connected to the first port of the motor through the oil inlet pipeline, the oil outlet end of the balance overflow valve is connected to the hydraulic pump through the oil inlet pipeline, the oil inlet end of the balance check valve is connected to the oil outlet end of the balance overflow valve, and the oil outlet end of the balance check valve is connected to the oil inlet end of the balance overflow valve.

[0017] With the above settings, by setting the balance valve group, the hydraulic oil output of the oil inlet pipeline is stable.

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

[0019] With the above settings, by connecting the control end of the brake valve reversing valve to the oil inlet pipeline and the oil outlet pipeline, when starting the winch, the hydraulic oil of the oil inlet pipeline and the oil outlet pipeline flows to the control end of the brake reversing valve and controls the brake reversing valve to reverse so that the A port communicates with the P port, so that the hydraulic oil output from the fuel tank flows to the control end of the brake valve, thereby driving the brake valve to open and facilitating the rotation of the motor.

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

[0021] With the above settings, by setting the spring, when the first switching valve is to be closed, the hydraulic oil pressure in the second control end of the first switching valve flowing from the fuel tank plus the elastic force of the spring overcomes the hydraulic oil pressure at the first control end of the first switching valve, thereby driving the first switching valve to close, so that the hydraulic oil cannot flow back to the fuel tank through the oil return pipeline.

[0022] Further, the first port of the first shuttle valve is connected to the A end of the first control reversing valve and the A end of the second control reversing valve, the second port of the first shuttle valve is connected to the fuel tank, and the third port of the first shuttle valve is connected to the second control end of the first switching valve.

[0023] With the above settings, by arranging the first shuttle valve between the second control end of the first switching valve and the A ends of the first control reversing valve and the second control reversing valve, the hydraulic oil flowing through the second control reversing valve to the second control end of the first switching valve and the hydraulic oil flowing from the fuel tank to the second control end of the first switching valve will not conflict with each other. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0025] Figure 2 is Figure 1 the internal hydraulic circuit connection diagram at A in

[0026] Figure 3 is Figure 1 the enlarged view of B in DETAILED DESCRIPTION OF THE EMBODIMENTS

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

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

[0029] The first control valve group includes a first control switching valve 81, a first control reversing valve 82, and a first control overflow valve 83. The P port and the T port of the first control reversing valve 82 are connected to the oil tank 1. The A port of the first control reversing 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 overflow valve 83. The second port of the first control switching valve 81 is connected to the control oil circuit 20 of the pilot-operated overflow valve 2. The overflow pressure of the first control overflow valve 83 is less than the control pressure of the control oil circuit 20 of the pilot-operated overflow valve 2. In this embodiment, the control end 821 of the first control reversing valve is connected to a control button (not shown in the figure) in the crane cab through an external circuit. When an emergency occurs, the staff presses the control button in the cab to drive the first control reversing valve to reverse.

[0030] The second control valve group includes a second control switching valve 91, a second control reversing valve 92, and a second control overflow valve 93. The P port and the T port of the second control reversing valve 92 are connected to the oil tank 1. The A port of the second control reversing valve 92 is connected to the control end 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 through the second control overflow valve 93. The second port of the second control switching valve 91 is connected to the control oil circuit 20 of the pilot-operated overflow valve 2. The overflow pressure of the second control overflow valve 93 is less than the control pressure of the control oil circuit 20 of the pilot-operated overflow valve 2. The oil discharge pressure of the first control overflow valve is less than the oil discharge pressure of the second control overflow valve.

[0031] The detection component is communicatively connected to the second control reversing valve 92. The detection component includes an inclination sensor disposed on the crane and a force sensor disposed on the winch. The inclination sensor and the force sensor are connected to the control end of the second control reversing valve 92 through a terminal processor. A pressure regulator 931 is further provided at the control end of the second control overflow valve 93, and the pressure regulator 931 is communicatively connected to the terminal processor. In this embodiment, the terminal processor is a device for processing information such as a PLC or a CPU, which is a prior art and will not be elaborated here.

[0032] A first shuttle valve 84 is provided between the second control end 32 of the first switching valve 3, the A end of the first control reversing valve 82, and the A end of the second control reversing valve 92. The first port 841 of the first shuttle valve 84 is connected to the A end of the second control reversing 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 end 32 of the first switching valve 3.

[0033] By providing the first shuttle valve 84 between the second control end 32 of the first switching valve 3 and the A end of the second control reversing valve 92. When the rope is being wound in the normal state, the hydraulic oil of the control oil tank 1 enters through the second port 842 of the first shuttle valve 84. Since the first port 841 of the first shuttle valve 84 cannot supply oil because the second control switching valve 92 is in the closed state, the hydraulic oil in the oil tank 1 enters the second control end 32 of the first switching valve 3 through the second port 842, causing the first switching valve 3 to close, thereby realizing the ability to close the rope winding operation when winding the rope. When an emergency rope winding is required, since the second control switching valve 92 is in the conducting state, the hydraulic oil of the oil tank 1 enters the first port 841 of the first shuttle valve 84 through the second control switching valve 92 and then flows into the control end of the first switching valve 3 to cause the first switching valve 3 to close, thereby realizing the emergency rope winding. And it ensures that the hydraulic oil flowing from the second control reversing valve 92 to the second control end 32 of the first switching valve 3 does not conflict with the hydraulic oil flowing from the oil tank 1 to the second control end 32 of the first switching valve 3.

[0034] A second switching valve 21 is provided between the oil inlet end of the pilot-operated overflow valve 2 and the oil inlet pipeline. The first port of the second switching valve 21 is connected to the oil inlet pipeline 11, and the second port of the second switching valve 21 is connected to the oil inlet end of the pilot-operated overflow valve 2. By providing the second switching valve 21, the oil path between the oil inlet pipeline 11 and the pilot-operated overflow valve 2 is opened only when the pilot-operated overflow valve 2 needs to be used, thus facilitating the control of the hydraulic system.

[0035] A balance valve group 5 is provided on the oil inlet pipeline 11. The balance valve group 5 includes a balance overflow valve 51 and a balance check valve 52. The oil inlet end of the balance overflow valve 51 is connected to the first port 41 of the motor 4 through the oil inlet pipeline 11, and the oil outlet end of the balance overflow valve 51 is connected to the hydraulic pump through the oil inlet pipeline 11. The oil inlet end of the balance check valve 52 is connected to the oil outlet end of the balance overflow valve 51, and the oil outlet end of the balance check valve 52 is connected to the oil inlet end of the balance overflow valve 51. By providing the balance valve group 5, the hydraulic oil output of the oil inlet pipeline 11 is made stable.

[0036] As Figure 1 shown, a brake valve 43 is further provided on the motor 4. The control end of the brake valve 43 is connected to the oil inlet pipeline and the oil outlet pipeline through a brake reversing valve 44. The P port of the brake reversing valve 44 is connected to the fuel tank, the A port of the brake reversing valve is connected to the control end of the brake valve, and the control end K of the brake reversing valve 44 is connected to the oil inlet pipeline 11 and the oil outlet pipeline 12. By connecting the control end K of the brake valve reversing valve 44 to the oil inlet pipeline 11 and the oil outlet pipeline 12, when starting the winch, the hydraulic oil in the oil inlet pipeline 11 and the oil outlet pipeline 12 flows to the control end of the brake reversing valve 44 and controls the brake reversing valve 44 to reverse so that the A port communicates with the P port, so that the hydraulic oil output from the fuel tank 1 flows to the control end of the brake valve 43, thereby driving the brake valve 43 to open, facilitating the rotation of the motor 4.

[0037] As Figure 2 shown, a spring 33 is further provided on the second control end 32 of the first switch 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 switch valve 3. By providing the spring 33, when closing the first switch valve 3, the hydraulic oil pressure flowing from the fuel tank 1 into the second control end 32 of the first switch valve 3 plus the elastic force of the spring 33 overcomes the hydraulic oil pressure at the first control end 31 of the first switch valve 3, thereby driving the first switch valve 3 to close, so that the hydraulic oil cannot flow back to the fuel tank through the oil return pipeline 12.

[0038] Working principle of the utility model: When taking in the rope, the oil tank 1 outputs hydraulic oil, which enters the oil inlet pipeline 11 through the balanced check valve 52, then passes through the motor 4 and enters the oil tank 1 through the oil return pipeline 12 to realize the rope-taking-in operation. At the same time, a first switching valve 3 is provided on the oil return pipeline 12. When the motor 4 rotates normally, the oil tank 1 transports hydraulic oil to the motor 4 through the oil inlet pipeline 11 and flows into the oil return pipeline 12 through the motor 4. The hydraulic oil in the oil return pipeline 12 flows to the first control end 31 of the first switching valve 3, thereby driving the first switching valve 3 to change direction and connect the first port and the second port. As a result, the oil return pipeline 12 is connected to the oil tank, and the hydraulic oil can flow back to the oil tank 1 to realize circulation. When operating to lift a heavy object, at this time, it is in the rope-taking-in state. The inclination sensor detects the working radius of the crane, and the force-measuring sensor detects the tension of the wire rope in the rope-taking-in state. By comparing the current working radius of the crane with the pre-set working radius, and comparing the current wire rope tension with the pre-set wire rope tension, when the wire rope tension is too large under the working radius of the crane, the terminal processor drives the second control valve to change direction and makes the A end communicate with the P end. The oil tank outputs hydraulic oil to the control end 911 of the second control switch valve 91 through the second control change-over valve 92, so that the second control switch valve 91 changes direction and connects the first port and the second port of the second control switch valve 91. As a result, the control hydraulic oil of the control oil circuit 20 of the pilot-operated relief valve 2 is depressurized and flows back to the oil tank through the second control relief valve 93. As a result, the regulating pressure of the pilot-operated relief valve 2 becomes lower. At the same time, the terminal processor controls the pressure regulator in real time according to the tipping moment of the crane, thereby driving the relief pressure of the second control relief valve to be adjusted, ensuring that the oil pressure of the hydraulic oil is neither too large nor too small, and ensuring that the tipping moment of the crane can be within a safe range, so that an internal circulation oil circuit can be quickly formed, ensuring fast rope releasing while also ensuring the stability of the hydraulic oil circuit; If the hook hooks an object that cannot be unhooked during the rope-taking-in state, manually make the first control change-over valve conduct, and the first control change-over valve 82 changes direction to make the A end communicate with the P end. The oil tank outputs hydraulic oil to the control end 811 of the first control switch valve 81 through the first control change-over valve 82, so that the first control switch valve 81 changes direction and connects 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-operated relief valve 2 is depressurized and flows back to the oil tank through the first control relief valve 83. As a result, the regulating pressure of the pilot-operated relief valve 2 becomes lower. Since the relief pressure of the first control relief valve is less than the relief pressure of the second control relief valve, therefore, the regulating pressure of the pilot-operated relief valve can be reduced to a greater extent, so that the oil discharge speed of the hydraulic oil circuit is faster;Since the oil pressure in the oil 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. As a result, the hydraulic oil in the oil inlet pipe 11 is relieved through the pilot-operated relief valve 2 to the oil return pipe 12, thereby increasing the oil pressure in the oil return pipe 12 and making the oil pressure at the end of the motor 4 connected to the oil return pipe 12 greater than the oil pressure at the end of the motor connected to the oil inlet pipe 11. And due to the overflow effect of the pilot-operated relief valve 2, a circulating circuit is formed among the oil inlet pipe, the oil return pipe and the motor through the pilot-operated relief valve. The oil tank continues to output hydraulic oil to the oil inlet pipe, further increasing the hydraulic oil in the circulating circuit, thus increasing the pressure difference between the two ends of the motor 4, and then increasing the rotational speed of the motor 4 to achieve rapid rope release.

Claims

1. An overload protection system for a crane, the overload protection system is arranged on the crane and drives the winch to operate, and is characterized in that: It 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 provided on the oil tank. The hydraulic pump is connected to the first port of the motor through an oil inlet pipeline. The second port of the motor is connected to the oil tank through an oil return pipeline. A pilot-operated relief valve is provided between the oil inlet pipeline and the oil return pipeline. The oil inlet end of the pilot-operated relief valve is connected to the oil inlet pipeline, and the oil outlet end of the pilot-operated relief valve is connected to the oil return pipeline. A first switching valve is provided on the oil return pipeline. The first control valve group includes a first control switching valve, a first control reversing valve, and a first control relief valve. The P port and the T port of the first control reversing valve are connected to the oil tank. The A port of the first control reversing 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. 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 group includes a second control switching valve, a second control reversing valve, and a second control relief valve. The P port and the T port of the second control reversing valve are connected to the oil tank. The A port of the second control reversing 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. 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. The detection component is communicatively connected to the second control reversing valve. The detection component includes an inclination sensor provided on the crane and a force sensor provided on the winch. The second control end of the first switching valve is connected to the A port of the first control reversing valve and the A port of the second control reversing valve through a first shuttle valve. The first port of the first switching valve is connected to the second port of the motor through the oil return pipeline. The second port of the first switching valve is connected to the oil tank through the oil return pipeline. The first control end of the first switching valve is connected to the first port and the second port of the first switching valve. The second control end of the first switching valve is also connected to the oil tank through a first shuttle valve. The first control end of the first switching valve controls the first port and the second port of the first switching valve to be connected. The second control end of the first switching valve controls the first port and the second port of the first switching valve to be disconnected.

2. The overload protection system of a crane according to claim 1, wherein: The inclination sensor and the force sensor are connected to the control end of the second control reversing valve through a terminal processor. A pressure regulator is also provided at the control end of the second control relief valve. The pressure regulator is communicatively connected to the terminal processor.

3. The overload protection system of a crane according to claim 1, characterized in that: A second switching valve is provided between the oil inlet end of the pilot-operated relief valve and the oil inlet pipeline. The first port of the second switching valve is connected to the oil inlet pipeline, and the second port of the second switching valve is connected to the oil inlet end of the pilot-operated relief valve.

4. The overload protection system for a crane according to claim 1, wherein: A balance valve group is provided on the oil inlet pipeline. The balance valve group 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 pipeline, and the oil outlet end of the balance relief valve is connected to the hydraulic pump through the oil inlet pipeline. 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.

5. The overload protection system of a crane according to claim 1, characterized in that: A brake valve is further provided on the motor. The control end of the brake valve is connected to the oil inlet pipeline and the oil outlet pipeline through a brake reversing valve. The P port of the brake reversing valve is connected to the fuel tank, the A port of the brake reversing valve is connected to the control end of the brake valve, and the control end of the brake reversing valve is connected to the oil inlet pipeline and the oil outlet pipeline.

6. The overload protection system for a crane according to claim 1, characterized in that: A spring is further 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.

7. The overload protection system for a crane according to claim 1, characterized in that: The first port of the first shuttle valve is connected to the A port of the first control reversing valve and the A port of the second control reversing valve. The second port of the first shuttle valve is connected to the fuel tank, and the third port of the first shuttle valve is connected to the second control end of the first switching valve.

Images