Hoist safety protection device, crane and hoist safety control method

Abstract

A kind of hoisting safety protection device, crane and hoisting safety control method, the hoisting safety protection device includes luffing oil cylinder, telescopic oil cylinder, control valve group and operating valve, operating valve is used to introduce pressure oil into luffing oil cylinder, telescopic oil cylinder, and the oil in luffing oil cylinder, telescopic oil cylinder is introduced into oil return tank to realize oil return, control valve group is used to connect or disconnect telescopic oil cylinder rodless chamber with oil tank, to relieve pressure when telescopic oil cylinder rodless chamber and oil tank are communicated.The hoisting safety protection device, crane and hoisting safety control method of the embodiment of the application, can relieve pressure to telescopic oil cylinder rodless chamber according to the pressure of luffing oil cylinder rodless chamber, so that telescopic oil cylinder cannot stretch out, thereby play the role of preventing telescopic overload, and without using torque limiter and other electronic components, can adapt to outdoor harsh environment, therefore cost is lower, service life is longer, and failure rate is lower.

Description

Technical Field

[0001] This invention relates to the field of lifting machinery technology, and in particular to a lifting safety protection device, a crane, and a lifting safety control method. Background Technology

[0002] Truck-mounted cranes typically change the working point or lifting point by extending, retracting, and tilting the boom. During these movements, the lever arm of the boom and the load changes, consequently altering the torque on the boom and the tipping moment on the vehicle. To prevent tipping, safety controls are necessary.

[0003] Currently, electrical control is commonly used for crane safety management. Specifically, a pressure sensor detects the pressure in the rodless chamber of the luffing cylinder. When the pressure exceeds the rated value, the pressure sensor sends a signal to a torque limiter. The torque limiter then determines the appropriate limiter and sends a signal to control the hydraulic system's telescopic mechanism, which is connected to an electromagnetic unloading valve assembly. This unloads the hydraulic system's telescopic mechanism, preventing overloading and reducing the likelihood of overturning or other accidents. However, on the one hand, torque limiters are costly and have limited installation space, hindering widespread adoption. On the other hand, cranes operate outdoors for extended periods in harsh and complex environments, resulting in relatively short lifespans and higher failure rates for electronic components. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a lifting safety protection device, a crane, and a lifting safety control method that are low in cost, have a long service life, and a low failure rate.

[0005] To achieve the above objectives, the present invention provides a lifting safety protection device, including a luffing cylinder, a telescopic cylinder, a control valve assembly, and an operating valve. The operating valve is used to introduce pressurized oil into the luffing cylinder and the telescopic cylinder, and to return the oil in the luffing cylinder and the telescopic cylinder to the return oil tank. The control valve assembly is used to connect or disconnect the rodless chamber of the telescopic cylinder from the oil tank, so as to release pressure when the rodless chamber of the telescopic cylinder is connected to the oil tank.

[0006] Optionally, the luffing cylinder includes a first luffing cylinder, and the control valve group connects the rodless chamber of the telescopic cylinder to the oil tank to relieve pressure when the pressure in the rodless chamber of the first luffing cylinder exceeds a set pressure value.

[0007] Optionally, the luffing cylinder includes multiple luffing cylinders, including a first luffing cylinder and a second luffing cylinder. When the pressure in the rodless chamber of at least one of the multiple luffing cylinders exceeds a set pressure value, the control valve group connects the rodless chamber of the telescopic cylinder to the oil tank to relieve pressure.

[0008] Optionally, the control valve assembly includes a first shuttle valve and a reversing valve. The first inlet and the second inlet of the first shuttle valve are respectively connected to the rodless chamber of the luffing cylinder. The outlet of the first shuttle valve is connected to the control end of the reversing valve to control the reversing valve to switch directions. The reversing valve includes a first port and a second port. The first port is connected to the oil tank, and the second port is connected to the rodless chamber of the telescopic cylinder. The reversing valve has a first position and a second position. In the first position, the first port and the second port are connected. In the second position, the first port and the second port are disconnected.

[0009] Optionally, the control valve assembly includes a valve body, a small valve stem, a large valve stem, an elastic element, and a stop member. The valve body has a first oil port and a second oil port. The small valve stem and the large valve stem are movably disposed within the valve body to connect or disconnect the first oil port and the second oil port. The oil outlet of the first shuttle valve is connected to the control chamber of the small valve stem to push the small valve stem to move by pressurized oil, thereby pushing the large valve stem to move. The elastic element is disposed at one end of the large valve stem opposite to the small valve stem to abut against the large valve stem to set a set pressure value. The stop member abuts against the other end of the elastic element to limit the position of the elastic element.

[0010] Optionally, the abutment is movably configured to adjust the position of the elastic element in order to adjust the preload of the elastic element.

[0011] Optionally, the valve body further includes a first valve core cavity, a second valve core cavity, and a pressure relief port. The large valve stem is movably disposed within the first valve core cavity. A slot communicating with the first oil port is formed on the large valve stem. The slot communicates with or disconnects from the second oil port as the large valve stem moves. The first valve core cavity includes a pressure relief cavity that is sealed and isolated from the slot. The pressure relief cavity communicates with the pressure relief port, which is connected to the oil tank. The small valve stem is movably disposed within the second valve core cavity. The small valve stem separates the second valve core cavity into the control cavity to form the control end.

[0012] This application also provides a crane including the above-mentioned lifting safety protection device.

[0013] This application also provides a crane safety control method for controlling a crane. The crane includes a luffing cylinder, a telescopic cylinder, a control valve group, and an operating valve. The operating valve is used to introduce pressurized oil into the luffing cylinder and the telescopic cylinder, and to return the oil in the luffing cylinder and the telescopic cylinder to the return oil tank. The control valve group is used to connect or disconnect the rodless chamber of the telescopic cylinder from the oil tank. The luffing cylinder includes a first luffing cylinder. The method determines whether to connect the rodless chamber of the telescopic cylinder to the oil tank to relieve pressure based on the pressure in the rodless chamber of the first luffing cylinder.

[0014] Optionally, when the pressure in the rodless chamber of the first luffing cylinder exceeds a set pressure value, the control valve group controls the connection between the rodless chamber of the telescopic cylinder and the oil tank to release pressure.

[0015] This application also provides a crane safety control method for controlling a crane. The crane includes a luffing cylinder, a telescopic cylinder, a control valve group, and an operating valve. The operating valve is used to introduce pressurized oil into the luffing cylinder and the telescopic cylinder, and to return the oil in the luffing cylinder and the telescopic cylinder to the return oil tank. The control valve group is used to connect or disconnect the rodless chamber of the telescopic cylinder from the oil tank. The luffing cylinder includes multiple luffing cylinders, including a first luffing cylinder and a second luffing cylinder. The method determines whether to connect the rodless chamber of the telescopic cylinder to the oil tank to relieve pressure based on the pressure in the rodless chamber of the multiple luffing cylinders.

[0016] Optionally, when the pressure in the rodless chamber of at least one of the plurality of luffing cylinders exceeds a set pressure value, the control valve group controls the connection between the rodless chamber of the telescopic cylinder and the oil tank to release pressure.

[0017] In the lifting safety protection device, crane, and lifting safety control method of this application, the pressure of the rodless chamber of the luffing cylinder can be controlled to release the pressure of the rodless chamber of the telescopic cylinder, so that the telescopic cylinder cannot extend, thereby preventing telescopic overload. Moreover, it does not require the use of electronic components such as torque limiters, can adapt to harsh outdoor environments, and therefore has low cost, long service life, and low failure rate. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a structural schematic diagram of a truck-mounted crane.

[0020] Figure 2 This is a schematic diagram of the lifting safety protection device provided in the first embodiment of the present invention.

[0021] Figure 3 for Figure 2 A schematic diagram of the control valve assembly of the crane safety protection device shown from one angle.

[0022] Figure 4 for Figure 2 Another angle schematic diagram of the control valve group of the crane safety protection device shown.

[0023] Figure 5 for Figure 4 Sectional view along the AA direction.

[0024] Figure 6 for Figure 4 Sectional view along the BB direction.

[0025] Figure 7 This is a schematic diagram of a lifting safety protection device provided in the second embodiment of the present invention.

[0026] Figure 8 This is a schematic diagram of a lifting safety protection device provided in the third embodiment of the present invention. Detailed Implementation

[0027] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. Based on the description of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention.

[0028] In the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0029] The terms “first,” “second,” “third,” etc., are used merely to distinguish numerical values ​​or elements with similar properties, rather than to indicate or imply relative importance or a specific order.

[0030] The terms “include,” “comprising,” or any other variation thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0031] First Embodiment

[0032] The first embodiment of the present invention provides a crane safety protection device for cranes. Please refer to [reference needed]. Figure 1 The crane includes a turntable 91, a first boom 92 and a second boom 93. The first boom 92 can be luffed under the drive of the first luffing cylinder 11, and the second boom 93 can be luffed under the drive of the second luffing cylinder 13. The second boom 93 is a telescopic boom, and the second boom 93 can be extended and retracted under the drive of the telescopic cylinder 15.

[0033] Please refer to Figure 2 The lifting safety protection device of the first embodiment includes a first luffing cylinder 11, a second luffing cylinder 13, a telescopic cylinder 15, a control valve group 17, and an operating valve 19. The operating valve 19 is used to introduce pressurized oil into the first luffing cylinder 11, the second luffing cylinder 13, and the telescopic cylinder 15, and to return the oil in the first luffing cylinder 11, the second luffing cylinder 13, and the telescopic cylinder 15 to the return oil tank. The control valve group 17 is used to determine whether to connect the rodless chamber of the telescopic cylinder 15 to the oil tank 21 to relieve pressure based on the pressure in the rodless chamber of the first luffing cylinder 11 and the second luffing cylinder 13. Specifically, the first luffing cylinder 11 is used to drive the luffing of the first boom of the crane, the second luffing cylinder 13 is used to drive the luffing of the second boom of the crane, and the telescopic cylinder 15 is used to drive the telescopic boom of the crane to extend and retract. Specifically, the lifting safety protection device of this embodiment can be applied to cranes that are truck-mounted cranes, mobile cranes, or crawler cranes, as long as the crane has a luffing mechanism and a telescopic mechanism.

[0034] The lifting safety protection device in this embodiment can depressurize the rodless chamber of the telescopic cylinder according to the pressure control of the rodless chamber of the luffing cylinder, so that the telescopic cylinder cannot extend, thereby preventing telescopic overload. Moreover, it does not require the use of electronic components such as torque limiters, can adapt to harsh outdoor environments, and therefore has low cost, long service life, and low failure rate.

[0035] In this embodiment, the control valve 19 is connected to the rodless and rod chambers of the first luffing cylinder 11, the rodless and rod chambers of the second luffing cylinder 13, and the rodless and rod chambers of the telescopic cylinder 15. The control valve 19 is also connected to a hydraulic pump (not shown) to supply pressurized oil provided by the hydraulic pump to the first luffing cylinder 11, the second luffing cylinder 13, and the telescopic cylinder 15. Specifically, taking the first luffing cylinder 11 as an example, the control valve 19 may include a directional valve. Through the reversing of the directional valve, the first luffing cylinder 11 can have several working states: Pressure oil enters the rodless chamber of the first luffing cylinder 11 through the control valve 19, and pressure oil in the rod chamber returns through the control valve 19, causing the first luffing cylinder 11 to extend; pressure oil enters the rod chamber of the first luffing cylinder 11 through the control valve 19, and pressure oil in the rodless chamber returns through the control valve 19, causing the first luffing cylinder 11 to retract; the control valve 19 disconnects the first luffing cylinder 11 from the hydraulic pump, pressure oil does not enter the first luffing cylinder 11, and the first luffing cylinder 11 does not operate. Similarly, the second luffing cylinder 13 and the telescopic cylinder 15 can also have the above-mentioned working states, which will not be described in detail here.

[0036] In this embodiment, when the pressure in the rodless chamber of at least one of the first luffing cylinder 11 and the second luffing cylinder 13 exceeds the set pressure value, the control valve group 17 connects the rodless chamber of the telescopic cylinder 15 to the oil tank 21 to release pressure.

[0037] Specifically, the control valve assembly 17 includes a first shuttle valve 171 and a reversing valve 173. The first inlet A and the second inlet B of the first shuttle valve 171 are respectively connected to the rodless chambers of the first luffing cylinder 11 and the second luffing cylinder 13. The outlet of the first shuttle valve 171 is connected to the control end of the reversing valve 173 to control the reversing valve 173 to switch directions. The reversing valve 173 includes a first port T and a second port P. The first port T is connected to the oil tank 21, and the second port P is connected to the rodless chamber of the telescopic cylinder 15. The reversing valve 173 has a first position and a second position. In the first position, the first port T and the second port P are connected, and in the second position, the first port T and the second port P are disconnected. When the pressure in the rodless chamber of the first luffing cylinder 11 and the second luffing cylinder 13 does not reach the set pressure value, the reversing valve 173 is in the second position, and the pressurized oil can normally enter the rodless chamber of the telescopic cylinder 15 through the control valve 19, causing the telescopic cylinder to extend. When the pressure in the rodless chamber of the first luffing cylinder 11 or the second luffing cylinder 13 exceeds the set pressure value, the oil enters the first shuttle valve 171 from the first oil inlet A or the second oil inlet B, and reaches the control end of the reversing valve 173, pushing the valve core of the reversing valve 173 to move, thereby switching the reversing valve 173 from the second position to the first position. The oil in the rodless chamber of the telescopic cylinder 15 flows into the oil tank 21 through the reversing valve 173, depressurizing the telescopic cylinder 15, and the telescopic cylinder 15 cannot extend.

[0038] Specifically, the set pressure value of the control valve assembly 17 is adjustable.

[0039] In this embodiment, please refer to Figures 3 to 6 The control valve assembly 17 includes a valve body 174, a small valve stem 176, a large valve stem 178, an elastic element 180, and an abutment element 182. The valve body 174 has a first oil port T and a second oil port P. The small valve stem 176 and the large valve stem 178 are movably disposed within the valve body 174 to connect or disconnect the first oil port T and the second oil port P. The oil outlet of the first shuttle valve 171 is connected to the control chamber of the small valve stem 176 so that the small valve stem 176 can be moved by pressure oil, thereby pushing the large valve stem 178 to move. The elastic element 180 is disposed at the end of the large valve stem 178 opposite to the small valve stem 176 to abut against the large valve stem 178 to set a set pressure value. The abutment element 182 abuts against the other end of the elastic element 180 to limit the position of the elastic element 180. It is understandable that the small valve stem 176 can also be omitted. The oil outlet of the first shuttle valve 171 is connected to the control chamber of the large valve stem 178, and the large valve stem 178 can be moved directly by the pressure oil. Since the flow rate of the first oil port T and the second oil port P limits the cross-sectional area of ​​the large valve stem 178, directly moving the large valve stem 178 will require a large elastic coefficient of the elastic element 180, which is not conducive to the selection of the elastic element 180. However, by setting the small valve stem 176, the elastic element 180 with a smaller elastic coefficient can be selected.

[0040] Specifically, the abutment 182 is movably configured to adjust the position of the elastic element 180, thereby adjusting the preload of the elastic element 180 and thus adjusting the set pressure value. Specifically, the abutment 182 may be an adjusting screw.

[0041] Specifically, the valve body 174 also has a first valve core cavity 1741, a second valve core cavity 1743, and a pressure relief port L. A large valve stem 178 is movably disposed in the first valve core cavity 1741. A slot 1781 communicating with the first oil port T is formed on the large valve stem 178. The slot 1781 communicates with or disconnects from the second oil port P as the large valve stem 178 moves. The first valve core cavity 1741 includes a pressure relief cavity 1745 sealed and isolated from the slot 1781. The pressure relief cavity 1745 communicates with the pressure relief port L, which is connected to the oil tank 21. A small valve stem 176 is movably disposed in the second valve core cavity 1743. The small valve stem 176 divides the second valve core cavity 1743 into a control cavity and a small cavity. The control cavity forms the control end of the reversing valve 173. By connecting the pressure relief port L to the oil tank 21, the oil that inevitably leaks into the pressure relief chamber 1745 (i.e. the right end of the large valve stem 178) from the slot 1781 can flow into the oil tank through the pressure relief port L, thus preventing the large valve stem 178 from failing to reach the rightmost end of the first valve core chamber 1741 and forming a dead zone.

[0042] Specifically, the first shuttle valve 171 includes a shuttle valve core 1711. When the pressures at both the first inlet A and the second inlet B are less than a set pressure value, both the first inlet A and the second inlet B are disconnected from the outlet. When the pressure at the first inlet A is greater than the set pressure value, pressurized oil pushes the shuttle valve core 1711 to move, connecting the first inlet A and the outlet, and the pressurized oil reaches the outlet of the first shuttle valve 171. When the pressure at the second inlet B is greater than the set pressure value, pressurized oil pushes the shuttle valve core 1711 to move, connecting the second inlet B and the outlet, and the pressurized oil reaches the outlet of the first shuttle valve 171.

[0043] Second Embodiment

[0044] The structure of the lifting safety protection device in the second embodiment of the present invention is basically the same as that in the first embodiment. Please refer to [the relevant documentation]. Figure 7 The difference lies in that the lifting safety protection device in the second embodiment does not include the second luffing cylinder 13 and the first shuttle valve 171. The rodless chamber of the first luffing cylinder 11 is directly connected to the control end of the reversing valve 173. When the pressure in the rodless chamber of the first luffing cylinder 11 is greater than the set pressure value, the reversing valve 173 is pushed to switch from the second position to the first position, and the rodless chamber of the telescopic cylinder 15 is depressurized.

[0045] Third Embodiment

[0046] The structure of the lifting safety protection device in the third embodiment of the present invention is basically the same as that in the first embodiment. Please refer to [the relevant documentation]. Figure 8 The difference lies in that the lifting safety protection device in the third embodiment includes a first luffing cylinder 11, a second luffing cylinder 13, and a third luffing cylinder 23, and also includes a second shuttle valve 25. The rodless chambers of the first luffing cylinder 11 and the second luffing cylinder 13 are respectively connected to the two inlets of the second shuttle valve 25. The outlet of the second shuttle valve 25 and the rodless chamber of the third luffing cylinder 23 are respectively connected to the first inlet A and the second inlet B of the first shuttle valve 171. The outlet of the first shuttle valve 171 is connected to the control end of the reversing valve 173. It can be understood that the lifting safety protection device may also include more luffing cylinders, which can be set as needed. As long as the pressure in the rodless chamber of any one of the multiple luffing cylinders is greater than the set pressure value, the reversing valve 173 can be pushed to switch from the second position to the first position, and the pressure in the rodless chamber of the telescopic cylinder 15 will be released.

[0047] It is understandable that the lifting safety protection device may also include multiple telescopic cylinders, and the rodless chambers of the multiple telescopic cylinders are all connected to the second oil port P of the reversing valve 173.

[0048] Fourth embodiment

[0049] The present invention also provides a crane that includes any of the above-described lifting safety protection devices. Specifically, the crane can be a truck-mounted crane, a crawler crane, or a mobile crane.

[0050] Fifth Embodiment

[0051] The present invention also provides a crane safety control method for controlling a crane. The crane includes a luffing cylinder, a telescopic cylinder 15, a control valve group 17, and an operating valve 19. The operating valve 19 is used to introduce pressurized oil into the luffing cylinder and the telescopic cylinder 15, and to introduce the oil in the luffing cylinder and the telescopic cylinder 15 into the return oil tank 21 to achieve oil return. The control valve group 17 is used to connect or disconnect the rodless chamber of the telescopic cylinder 15 from the oil tank 21. The luffing cylinder has only a first luffing cylinder 11. The pressure in the rodless chamber of the first luffing cylinder 11 determines whether to connect the rodless chamber of the telescopic cylinder 15 to the oil tank 21 to relieve pressure.

[0052] In this embodiment, when the pressure in the rodless chamber of the first variable amplitude cylinder 11 exceeds the set pressure value, the control valve group 17 controls the connection between the rodless chamber of the telescopic cylinder 15 and the oil tank 21 to release pressure.

[0053] It is understood that the specific structure of the control valve group 17 in this embodiment can be the same as that of the control valve group 17 in the first embodiment, and will not be described again here.

[0054] Sixth Embodiment

[0055] This application also provides a crane safety control method for controlling a crane. The crane includes a luffing cylinder, a telescopic cylinder 15, a control valve group 17, and an operating valve 19. The operating valve 19 is used to introduce pressurized oil into the luffing cylinder and the telescopic cylinder 15, and to introduce the oil in the luffing cylinder and the telescopic cylinder 15 into the return oil tank 21 to achieve oil return. The control valve group 17 is used to connect or disconnect the rodless chamber of the telescopic cylinder 15 from the oil tank 21. The luffing cylinder includes multiple luffing cylinders, including a first luffing cylinder 11 and a second luffing cylinder 13. The method determines whether to connect the rodless chamber of the telescopic cylinder 15 to the oil tank 21 to relieve pressure based on the pressure in the rodless chamber of the multiple luffing cylinders.

[0056] In this embodiment, when the pressure in the rodless chamber of at least one of the multiple luffing cylinders exceeds the set pressure value, the control valve group 17 controls the connection between the rodless chamber of the telescopic cylinder 15 and the oil tank 21 to release pressure.

[0057] It is understood that the specific structure of the control valve group 17 in this embodiment can be the same as that of the control valve group 17 in the first embodiment, and will not be described again here.

[0058] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A safety protection device for a hoisting apparatus, characterized in that The control valve group (17) is used for connecting or disconnecting the rodless cavity of the telescopic oil cylinder (15) and the oil tank (21) to achieve pressure relief when the rodless cavity of the telescopic oil cylinder (15) is connected with the oil tank (21); The control valve group (17) includes a first shuttle valve (171), a reversing valve (173), a valve body (174), a small valve rod (176), a large valve rod (178), an elastic member (180) and an abutting member (182); the first oil inlet (A) and the second oil inlet (B) of the first shuttle valve (171) are connected with the rodless cavities of the variable amplitude oil cylinders respectively, and the oil outlet of the first shuttle valve (171) is connected with the control end of the reversing valve (173) to control the reversing of the reversing valve (173); the reversing valve (173) includes a first oil port (T) and a second oil port (P), the first oil port (T) is connected with the oil tank (21), and the second oil port (P) is connected with the rodless cavity of the telescopic oil cylinder (15); the reversing valve (173) includes a first position and a second position; in the first position, the first oil port (T) and the second oil port (P) are connected; in the second position, the first oil port (T) and the second oil port (P) are disconnected; the first oil port (T) and the second oil port (P) are arranged on the valve body (174), the small valve rod (176) and the large valve rod (178) are movably arranged in the valve body (174) to connect or disconnect the first oil port (T) and the second oil port (P), the oil outlet of the first shuttle valve (171) is connected with the control cavity of the small valve rod (176) to drive the small valve rod (176) to move by pressure oil, and then drive the large valve rod (178) to move; the elastic member (180) is arranged at the end of the large valve rod (178) opposite to the small valve rod (176) to abut against the large valve rod (178) to set a set pressure value, and the abutting member (182) abuts against the other end of the elastic member (180) to limit the position of the elastic member (180).

2. The safety device according to claim 1, wherein The variable amplitude oil cylinder includes a first variable amplitude oil cylinder (11), and the control valve group (17) connects the rodless cavity of the telescopic oil cylinder (15) with the oil tank (21) to achieve pressure relief when the pressure of the rodless cavity of the first variable amplitude oil cylinder (11) exceeds a set pressure value.

3. The safety device according to claim 1, wherein The variable amplitude oil cylinder includes a plurality of variable amplitude oil cylinders, and the plurality of variable amplitude oil cylinders include a first variable amplitude oil cylinder (11) and a second variable amplitude oil cylinder (13); the control valve group (17) connects the rodless cavity of the telescopic oil cylinder (15) with the oil tank (21) to achieve pressure relief when the pressure of the rodless cavity of at least one of the plurality of variable amplitude oil cylinders exceeds a set pressure value.

4. The safety device according to claim 1, wherein The abutting member (182) is movably arranged to adjust the position of the elastic member (180) to adjust the pre-tightening force of the elastic member (180).

5. A safety device according to claim 4, wherein the safety device is arranged to be activated by the load. The valve body (174) is further provided with a first valve core cavity (1741), a second valve core cavity (1743) and a pressure relief port (L), the large valve rod (178) is movably arranged in the first valve core cavity (1741), the large valve rod (178) is provided with a slot (1781) in communication with the first oil port (T), the slot (1781) is in communication or disconnected with the second oil port (P) with the movement of the large valve rod (178); the first valve core cavity (1741) comprises a pressure relief cavity (1745) sealed from the slot (1781), the pressure relief cavity (1745) is in communication with the pressure relief port (L), and the pressure relief port (L) is connected to the oil tank (21); the small valve rod (176) is movably arranged in the second valve core cavity (1743), and the small valve rod (176) separates the second valve core cavity (1743) into the control cavity to form the control end.

6. A crane, characterized in that The lifting safety protection device comprises the lifting safety protection device according to any one of claims 1-5. The lifting safety protection device comprises the lifting safety protection device comprises the lifting safety protection device according to any one of claims 1-5.

7. A hoist safety control method for controlling a hoist, characterized by, The crane comprises a luffing cylinder, a telescopic cylinder (15), a control valve group (17) and a control valve (19) for introducing pressure oil into the luffing cylinder and the telescopic cylinder (15) and introducing oil in the luffing cylinder and the telescopic cylinder (15) into an oil tank (21) to realize oil return, the control valve group (17) is used for connecting or disconnecting the rodless cavity of the telescopic cylinder (15) and the oil tank (21), the control valve group (17) comprises a first shuttle valve (171), a reversing valve (173), a valve body (174), a small valve rod (176), a large valve rod (178), an elastic element (180) and an abutting element (182), the first inlet (A) and the second inlet (B) of the first shuttle valve (171) are connected to the rodless cavity of the luffing cylinder respectively, the oil outlet of the first shuttle valve (171) is connected to the control end of the reversing valve (173) to control the reversing of the reversing valve (173), the reversing valve (173) comprises a first oil port (T) and a second oil port (P), the first oil port (T) is connected to the oil tank (21), the second oil port (P) is connected to the rodless cavity of the telescopic cylinder (15), the reversing valve (173) comprises a first position and a second position, in the first position, the first oil port (T) and the second oil port (P) are connected, in the second position, the first oil port (T) and the second oil port (P) are disconnected, the first oil port (T) and the second oil port (P) are arranged on the valve body (174), the small valve rod (176) and the large valve rod (178) are movably arranged in the valve body (174) to connect or disconnect the first oil port (T) and the second oil port (P), the oil outlet of the first shuttle valve (171) is connected to the control cavity of the small valve rod (176) to push the small valve rod (176) to move by pressure oil, and then push the large valve rod (178) to move, the elastic element (180) is arranged at the end of the large valve rod (178) opposite to the small valve rod (176) to abut against the large valve rod (178) to set a set pressure value, the abutting element (182) abuts against the other end of the elastic element (180) to limit the position of the elastic element (180), the luffing cylinder comprises a first luffing cylinder (11), whether the rodless cavity of the telescopic cylinder (15) is connected to the oil tank (21) to release pressure is determined according to the pressure of the rodless cavity of the first luffing cylinder (11).

8. The hoist safety control method according to claim 7, characterized by, When the pressure of the rodless cavity of the first luffing cylinder (11) exceeds the set pressure value, the control valve group (17) controls the rodless cavity of the telescopic cylinder (15) to be connected to the oil tank (21) to release pressure.

9. A hoist safety control method for controlling a hoist, characterized by, The crane comprises a luffing cylinder, a telescopic cylinder (15), a control valve group (17) and a control valve (19) for introducing pressure oil into the luffing cylinder, the telescopic cylinder (15) and introducing oil in the luffing cylinder, the telescopic cylinder (15) into an oil tank (21) to realize oil return, the control valve group (17) is used for connecting or disconnecting the rodless cavity of the telescopic cylinder (15) and the oil tank (21), the control valve group (17) comprises a first shuttle valve (171), a reversing valve (173), a valve body (174), a small valve rod (176), a large valve rod (178), an elastic element (180) and an abutting element (182); the first inlet (A) and the second inlet (B) of the first shuttle valve (171) are connected to the rodless cavity of the luffing cylinder respectively, the oil outlet of the first shuttle valve (171) is connected to the control end of the reversing valve (173) to control the reversing of the reversing valve (173); the reversing valve (173) comprises a first oil port (T) and a second oil port (P), the first oil port (T) is connected to the oil tank (21), the second oil port (P) is connected to the rodless cavity of the telescopic cylinder (15), the reversing valve (173) comprises a first position and a second position, when the first position, the first oil port (T) and the second oil port (P) are connected, when the second position, the first oil port (T) and the second oil port (P) are disconnected; the first oil port (T) and the second oil port (P) are arranged on the valve body (174), the small valve rod (176) and the large valve rod (178) are movably arranged in the valve body (174) to connect or disconnect the first oil port (T) and the second oil port (P), the oil outlet of the first shuttle valve (171) is connected to the control cavity of the small valve rod (176) to move the small valve rod (176) by pressure oil, and then move the large valve rod (178), the elastic element (180) is arranged at the end of the large valve rod (178) opposite to the small valve rod (176) to abut against the large valve rod (178) to set a set pressure value, the abutting element (182) abuts against the other end of the elastic element (180) to limit the position of the elastic element (180); The luffing cylinder comprises a plurality of luffing cylinders, the plurality of luffing cylinders comprise a first luffing cylinder (11) and a second luffing cylinder (13), whether the rodless cavity of the telescopic cylinder (15) is connected to the oil tank (21) to release pressure is determined according to the pressure of the rodless cavity of the plurality of luffing cylinders.

10. The hoist safety control method according to claim 9, characterized by, When the pressure of the rodless cavity of at least one of the plurality of luffing cylinders exceeds the set pressure value, the control valve group (17) controls the rodless cavity of the telescopic cylinder (15) to be connected to the oil tank (21) to release pressure.

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