Dual cylinder hydraulic system for hoisting apparatus and hoist

Abstract

The present application belongs to the technical field of engineering machinery and provides a double-cylinder hydraulic system for a hoisting machine and the hoisting machine. The double-cylinder hydraulic system comprises a double-oil-cylinder unit and a control valve unit. The double-oil-cylinder unit comprises a primary oil cylinder and a secondary oil cylinder. The rod cavity of the primary oil cylinder is in communication with the rod cavity of the secondary oil cylinder. The control valve unit comprises a first reversing valve and a second reversing valve. The first reversing valve is used to select the direction of system pressure oil to the rod cavity of the primary oil cylinder. The second reversing valve is used to select one of the rod cavities of the primary oil cylinder and the secondary oil cylinder to return oil and the other one to hold pressure. The system uses two reversing valves to control the oil inlet and return of the primary oil cylinder and the secondary oil cylinder respectively, which can realize non-synchronous and synchronous retraction control of the two oil cylinders, thereby increasing the extension mode of the double oil cylinder.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of engineering machinery, and particularly relates to a double-cylinder hydraulic system for a hoisting machine and the hoisting machine. BACKGROUND

[0002] In order to realize the hoisting performance of the crane under multiple working conditions, the telescopic arm of the crane needs to have multiple telescopic modes to cope with different load working conditions. The existing telescopic arm with a small number of sections is generally driven by only one oil cylinder. When the number of sections of the telescopic arm exceeds a certain number, in order to ensure that the telescoping stroke of the oil cylinder can meet the telescopic length of the telescopic arm, some manufacturers use two-stage oil cylinders or even three-stage oil cylinders.

[0003] In the existing two-stage oil cylinder type crane, due to the structure of the oil cylinder and the limitation of the passage of the reversing valve, the telescopic arm can only realize sequential extension and synchronous retraction, and the telescopic mode is very single. SUMMARY

[0004] In view of the above defects or deficiencies, the present application provides a double-cylinder hydraulic system for a hoisting machine and a hoisting machine, aiming to solve the technical problem of single telescopic mode of the existing two-stage oil cylinder type crane.

[0005] To achieve the above-mentioned purpose, the present application provides a double-cylinder hydraulic system for a hoisting machine, which comprises a double-oil-cylinder unit and a control valve unit. The double-oil-cylinder unit comprises a primary oil cylinder and a secondary oil cylinder, and the rod cavity of the primary oil cylinder is in communication with the rod cavity of the secondary oil cylinder. The control valve unit comprises a first reversing valve and a second reversing valve. The first reversing valve is used to selectively guide the system pressure oil to the rod cavity of the primary oil cylinder. The second reversing valve is used to selectively control the return oil of one of the rodless cavities of the primary oil cylinder and the secondary oil cylinder, and the other one is pressure holding.

[0006] In the embodiment of the present application, the second reversing valve is provided with a first oil port side and a second oil port side. The first oil port side is connected to the intermediate oil circuit for return oil. The second oil port side is connected to the first working oil circuit and the second working oil circuit. The first working oil circuit and the second working oil circuit are in communication with the rodless cavities of the primary oil cylinder and the secondary oil cylinder, respectively. The second reversing valve is provided with a first valve position and a second valve position. The first valve position is configured to make the first working oil circuit and the intermediate oil circuit conductive and the second working oil circuit pressure holding. The second valve position is configured to make the second working oil circuit and the intermediate oil circuit conductive and the first working oil circuit pressure holding.

[0007] In the embodiment of the present application, an overflow protection oil circuit is provided between the first oil port side of the second reversing valve and the system return oil circuit. A first overflow valve is provided on the overflow protection oil circuit. The first valve position is configured to make the first working oil circuit and the intermediate oil circuit conductive, and the second working oil circuit and the overflow protection oil circuit conductive. The second valve position is configured to make the second working oil circuit and the intermediate oil circuit conductive and the first working oil circuit cut off.

[0008] In the embodiment of the present application, the second reversing valve is further provided with a third valve position, and the third valve position is configured to make the first working oil path and the second working oil path both conductive to the intermediate oil path.

[0009] In the embodiment of the present application, the first reversing valve is provided with a third oil port side and a fourth oil port side, the third oil port side is connected to the system oil inlet path and the system oil return path, the fourth oil port side is connected to the intermediate oil path, and the first reversing valve is provided with a fourth valve position and a fifth valve position; wherein the fourth valve position is configured to make the system oil return path conductive to the intermediate oil path, and the fifth valve position is configured to make the system oil inlet path conductive to the intermediate oil path.

[0010] In the embodiment of the present application, a third working oil path is further provided between the rodless cavity of the primary oil cylinder and the fourth oil port side of the first reversing valve, the fourth valve position is configured to make the system oil return path conductive to the intermediate oil path, and the fifth valve position is configured to make the system oil inlet path conductive to the third working oil path.

[0011] In the embodiment of the present application, a second overflow valve is provided between the intermediate oil path and the system oil return path, and / or between the third working oil path and the system oil return path.

[0012] In the embodiment of the present application, an oil pressure balancing unit is respectively provided on the rodless cavity working oil path of the primary oil cylinder and the secondary oil cylinder, and the oil pressure balancing unit is provided with a throttling channel for controlling the oil outlet rate of the rodless cavity of the primary oil cylinder and the secondary oil cylinder.

[0013] In the embodiment of the present application, the first reversing valve and the second reversing valve are hydraulic control reversing valves.

[0014] To achieve the above-mentioned purpose, the present application further provides a crane, wherein the crane comprises the double-cylinder hydraulic system for hoisting equipment according to the above.

[0015] Through the above technical solution, the double-cylinder hydraulic system for hoisting equipment provided by the embodiment of the present application has the following beneficial effects:

[0016] The present system controls the oil return of the rodless cavity of the primary oil cylinder and the rodless cavity of the secondary oil cylinder by adopting the second reversing valve, and can realize synchronous retraction control and non-synchronous retraction control of the two-stage oil cylinder, thereby increasing the extension mode of the double oil cylinder.

[0017] Other features and advantages of the present application will be described in detail in the following specific embodiment part. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate the

[0019] Figure 1 is a structural schematic diagram of a first embodiment of a double-cylinder hydraulic system for a hoisting machine according to an embodiment of the present application;

[0020] Figure 2 is a schematic diagram of oil port positions of a first reversing valve according to an embodiment of the present application;

[0021] Figure 3 is a structural schematic diagram of a second embodiment of a double-cylinder hydraulic system for a hoisting machine according to an embodiment of the present application.

[0022] BRIEF DESCRIPTION OF DRAWINGS

[0023] 1 double-cylinder unit; 11 primary oil cylinder; 12 secondary oil cylinder; 21 second reversing valve; 211 first valve position; 212 second valve position; 213 third valve position; 22 first reversing valve; 221 fourth valve position; 222 fifth valve position; 223 first oil port; 224 second oil port; 225 third oil port; 226 fourth oil port; 227 fifth oil port; 228 sixth oil port; 23 third reversing valve; 31 intermediate oil line; 32 first working oil line; 33 second working oil line; 34 overflow protection oil line; 341 first overflow valve; 35 system oil inlet line; 36 system oil return line; 37 third working oil line; 38 fourth working oil line; 41 balance valve; 42 speed regulating valve; 51 first solenoid valve; Yla first solenoid; Ylb second solenoid; 52 second solenoid valve; Yl third solenoid; 53 third solenoid valve; Y3 fourth solenoid; 61 system overflow valve; 62 second overflow valve. DETAILED DESCRIPTION

[0024] The specific embodiments of the present application will be described in detail hereinafter with reference to the drawings. It should be understood that the specific embodiments described herein are merely illustrative and explanatory and are not intended to limit the present application.

[0025] A double-cylinder hydraulic system for a hoisting machine according to the present application will be described below with reference to the drawings.

[0026] The present application provides a double-cylinder hydraulic system for a hoisting machine, as shown in Figure 1 , Figure 2 and Figure 3 A double-cylinder hydraulic system for a hoisting machine according to the present application will be described below with reference to the drawings.

[0027] The double-cylinder unit 1 comprises a primary cylinder 11 and a secondary cylinder 12, and the rod cavity of the primary cylinder 11 is communicated with the rod cavity of the secondary cylinder 12.

[0028] The control valve unit comprises a first reversing valve 22 and a second reversing valve 21, the first reversing valve 22 is used for guiding the system pressure oil to the rod cavity of the primary cylinder 11, and the second reversing valve 21 is used for selectively controlling one of the rodless cavities of the primary cylinder 11 and the secondary cylinder 12 to return oil and the other to be pressure blocked.

[0029] Through the reversing of the first reversing valve 22, the pressure oil in the system inlet oil way 35 can be guided to the rod cavity of the primary cylinder 11, and thus the pressure oil in the rod cavity of the primary cylinder 11 can theoretically flow into the rod cavity of the secondary cylinder 12 due to the communication between the rod cavities of the primary cylinder 11 and the secondary cylinder 12.

[0030] When the system pressure oil enters the rod cavity of the primary cylinder 11, if it is required to control the primary cylinder 11 to retract alone, it is only needed to control the second reversing valve 21 to reverse, so that the rodless cavity of the primary cylinder 11 normally returns oil and the rodless cavity of the secondary cylinder 12 is pressure blocked, and thus the primary cylinder 11 can normally perform the retraction action due to the normal return of the rodless cavity of the primary cylinder 11, and the secondary cylinder 12 can keep the current posture due to the pressure blocking of the rodless cavity of the secondary cylinder 12. Similarly, when it is required to control the secondary cylinder 12 to retract alone, it is only needed to control the second reversing valve 21 to reverse, so that the rodless cavity of the secondary cylinder 12 normally returns oil and the rodless cavity of the primary cylinder 11 is pressure blocked, and when it is required to control the two cylinders to retract simultaneously, it is only needed to control the second reversing valve 21 to reverse, so that the rodless cavities of the primary cylinder 11 and the secondary cylinder 12 both normally return oil.

[0031] In summary, through the adoption of the second reversing valve 21 to control the return of the rodless cavities of the primary cylinder 11 and the secondary cylinder 12 respectively, the system can realize the synchronous retraction control and the non-synchronous retraction control of the two cylinders, thereby increasing the extension and retraction modes of the double cylinder.

[0032] In the embodiment of the present application, the pressure blocking can be realized in the mode of cutting off the working oil way of the rodless cavity, or a second overflow valve 62 is arranged between the working oil way of the rodless cavity and the system return oil way 36.

[0033] As Figure 1 and Figure 3As shown, in the embodiment of the present application, the second reversing valve 21 is provided with a first oil port side and a second oil port side, the first oil port side can refer to the side of the second reversing valve 21 with P and T ports, and the second oil port side can refer to the side of the second reversing valve 21 for connecting with the execution unit. The first oil port side is connected with the intermediate oil line 31 for oil return, and the second oil port side is connected with the first working oil line 32 and the second working oil line 33, which are respectively communicated with the rodless cavity of the primary oil cylinder 11 and the rodless cavity of the secondary oil cylinder 12. The second reversing valve 21 is provided with a first valve position 211 and a second valve position 212, the first valve position 211 is configured to make the first working oil line 32 conductive with the intermediate oil line 31 and the second working oil line 33 be pressure blocked, and the second valve position 212 is configured to make the second working oil line 33 conductive with the intermediate oil line 31 and the first working oil line 32 be pressure blocked. The intermediate oil line 31 can be directly connected to the system oil return line 36, or connected to the first reversing valve 22, and the intermediate oil line 31 is connected to the system oil return line 36 through the reversing of the first reversing valve 22.

[0034] When the system pressure oil enters the rod cavity of the primary oil cylinder 11, if it is needed to control the primary oil cylinder 11 to retract alone, only the second reversing valve 21 is controlled to reverse to the first valve position 211, at this time the rodless cavity of the primary oil cylinder 11 returns oil normally through the first working oil line 32 and the intermediate oil line 31, the primary oil cylinder 11 retracts normally, the secondary oil cylinder 12 is in a pressure blocking state, and the secondary oil cylinder 12 keeps still. If it is needed to control the secondary oil cylinder 12 to retract alone, only the second reversing valve 21 is controlled to reverse to the second valve position 212, at this time the rodless cavity of the secondary oil cylinder 12 returns oil normally through the second working oil line 33 and the intermediate oil line 31, the secondary oil cylinder 12 retracts normally, the primary oil cylinder 11 is in a pressure blocking state, and the primary oil cylinder 11 keeps still.

[0035] As shown in Figure 1 and Figure 3 In the embodiment of the present application, the second reversing valve 21 is further provided with a third valve position 213, the third valve position 213 is configured to make the first working oil line 32 and the second working oil line 33 both conductive with the intermediate oil line 31. The intermediate oil line 31 can be connected with the first reversing valve 22, and the first reversing valve 22 can select to guide the system pressure oil to the intermediate oil line 31 or return oil for the intermediate oil line 31. Among them, in the third valve position 213, the rodless cavities of the primary oil cylinder 11 and the secondary oil cylinder 12 both return oil normally, and the primary oil cylinder 11 and the secondary oil cylinder 12 retract synchronously. By setting the third valve position 213, the two oil cylinders can be realized to extend synchronously or retract synchronously.

[0036] As shown in Figure 1 and Figure 3As shown, in the embodiment of the present application, an overflow protection oil circuit 34 is arranged between the first oil port side of the second reversing valve 21 and the system return oil circuit 36, and a first overflow valve 341 is arranged on the overflow protection oil circuit 34. The first valve position 211 is configured to connect the first working oil circuit 32 and the intermediate oil circuit 31, and the second working oil circuit 33 and the overflow protection oil circuit 34. The second valve position 212 is configured to connect the second working oil circuit 33 and the intermediate oil circuit 31, and cut off the first working oil circuit 32, or the second valve position 212 is configured to connect the second working oil circuit 33 and the intermediate oil circuit 31, and connect the first working oil circuit 32 and the overflow protection oil circuit 34. In the process of independent retraction of the primary oil cylinder 11, the position between the telescopic arms is maintained by pressure blocking of the rodless cavity of the secondary oil cylinder 12. If there is a load on the telescopic arm, it will cause the working oil pressure of the rodless cavity of the secondary oil cylinder 12 to be very large. In order to ensure system safety, the second working oil circuit 33 and the overflow protection oil circuit 34 can be controlled to be connected when the first working oil circuit 32 and the intermediate oil circuit 31 are connected, so that the pressure of the rodless cavity of the secondary oil cylinder 12 can be safely relieved when the pressure exceeds the limit, avoiding pipe or cylinder burst. Compared with arranging a system overflow valve 61 on the system inlet oil circuit 35, this connection mode has faster response speed and high protection capability for the oil cylinder. The circuit is suitable for load sensing system and can reduce overflow flow and save energy. The cross-sectional area of the cavity of the primary oil cylinder 11 is larger than that of the secondary oil cylinder 12, and it can bear higher load. Therefore, in order to avoid the situation that the telescopic arm retracts out of control, the state of the first working oil circuit 32 can be preferably set to cut off. Of course, in some scenarios, the second valve position 212 can be configured to connect the second working oil circuit 33 and the intermediate oil circuit 31, and the first working oil circuit 32 and the overflow protection oil circuit 34.

[0037] As shown in Figure 1 and Figure 3 As shown, in the embodiment of the present application, the first reversing valve 22 is provided with a third oil port side and a fourth oil port side, the third oil port side is connected with the system inlet oil circuit 35 and the system return oil circuit 36, and the fourth oil port side is connected with the intermediate oil circuit 31. The first reversing valve 22 is provided with a fourth valve position 221 and a fifth valve position 222. The fourth valve position 221 is configured to connect the system return oil circuit 36 and the intermediate oil circuit 31, and the fifth valve position 222 is configured to connect the system inlet oil circuit 35 and the intermediate oil circuit 31.

[0038] Further, the third working oil path 37 is further provided between the rod cavity of the primary oil cylinder 11 and the fourth oil port side of the first reversing valve 22, the fourth valve position 221 is configured to be communicated between the system return oil path 36 and the intermediate oil path 31, and the system inlet oil path 35 and the third working oil path 37, the fifth valve position 222 is configured to be communicated between the system inlet oil path 35 and the intermediate oil path 31, and the system return oil path 36 and the third working oil path 37. Through the two valve positions of the first reversing valve 22 and the three valve positions of the second reversing valve 21, the two oil cylinders can be synchronously extended, synchronously retracted, individually extended, and individually retracted.

[0039] When it is required to control the primary oil cylinder 11 and the secondary oil cylinder 12 to be synchronously retracted, the first reversing valve 22 is controlled to switch to the fourth valve position 221, and the second reversing valve 21 is controlled to switch to the third valve position 213, at this time, the system pressure oil enters into the rod cavity of the primary oil cylinder 11 and the rod cavity of the secondary oil cylinder 12, the rodless cavity of the primary oil cylinder 11 and the rodless cavity of the secondary oil cylinder 12 return oil through the intermediate oil path 31 and the system return oil path 36, and the two oil cylinders are synchronously retracted.

[0040] When it is required to control the primary oil cylinder 11 and the secondary oil cylinder 12 to be synchronously extended, the first reversing valve 22 is controlled to switch to the fifth valve position 222, and the second reversing valve 21 is controlled to switch to the third valve position 213, at this time, the system pressure oil enters into the rodless cavity of the primary oil cylinder 11 and the rodless cavity of the secondary oil cylinder 12 through the intermediate oil path 31, and the rod cavity of the primary oil cylinder 11 and the rod cavity of the secondary oil cylinder 12 return oil through the third working oil path 37, and the two oil cylinders are synchronously extended.

[0041] When it is required to control the primary oil cylinder 11 to be individually retracted, the first reversing valve 22 is controlled to switch to the fourth valve position 221, and the second reversing valve 21 is controlled to switch to the first valve position 211, at this time, the system pressure oil enters into the rod cavity of the primary oil cylinder 11 and the rod cavity of the secondary oil cylinder 12 through the third working oil path 37, the rodless cavity of the primary oil cylinder 11 returns oil individually through the intermediate oil path 31, the primary oil cylinder 11 is individually retracted, the rodless cavity of the secondary oil cylinder 12 is in a pressure holding state, and the secondary oil cylinder 12 remains stationary.

[0042] When it is required to control the secondary oil cylinder 12 to be individually retracted, the first reversing valve 22 is controlled to switch to the fourth valve position 221, and the second reversing valve 21 is controlled to switch to the second valve position 212, at this time, the system pressure oil enters into the rod cavity of the primary oil cylinder 11 and the rod cavity of the secondary oil cylinder 12 through the third working oil path 37, the rodless cavity of the secondary oil cylinder 12 returns oil individually through the intermediate oil path 31, the secondary oil cylinder 12 is individually retracted, the rodless cavity of the primary oil cylinder 11 is in a pressure holding state, and the primary oil cylinder 11 remains stationary.

[0043] When the first-stage oil cylinder 11 needs to be controlled to extend alone, the first switching valve 22 is switched to the fifth valve position 222, and the second switching valve 21 is switched to the first valve position 211. At this time, the system pressure oil enters the rodless chamber of the first-stage oil cylinder 11 alone through the intermediate oil line 31, the rod chamber of the first-stage oil cylinder 11 returns oil through the third working oil line 37, the first-stage oil cylinder 11 extends alone, and the rodless chamber of the second-stage oil cylinder 12 has no pressure oil input, so the second-stage oil cylinder 12 remains stationary.

[0044] When the second-stage oil cylinder 12 needs to be controlled to extend alone, the first switching valve 22 is switched to the fifth valve position 222, and the second switching valve 21 is switched to the second valve position 212. At this time, the system pressure oil enters the rodless chamber of the second-stage oil cylinder 12 alone through the intermediate oil line 31, the rod chamber of the second-stage oil cylinder 12 returns oil through the third working oil line 37, the second-stage oil cylinder 12 extends alone, and the rodless chamber of the first-stage oil cylinder 11 has no pressure oil input, so the first-stage oil cylinder 11 remains stationary.

[0045] As shown in Figure 1 and Figure 3 , in the embodiment of the present application, a second overflow valve 62 can be arranged between the intermediate oil line 31 and the system return oil line 36, and / or between the third working oil line 37 and the system return oil line 36, to ensure the safety of system operation.

[0046] As shown in Figure 1 and Figure 3 , in the embodiment of the present application, the rodless chamber working oil lines of the first-stage oil cylinder 11 and the second-stage oil cylinder 12 are respectively provided with an oil pressure balancing unit, and the oil pressure balancing unit is provided with a throttling passage for controlling the oil outlet rate of the rodless chamber of the first-stage oil cylinder 11 and the second-stage oil cylinder 12.

[0047] Specifically, as shown in Figure 1 , the oil pressure balancing unit can be a balancing valve 41. The first working oil line 32 is provided with a first balancing valve 41, and the first balancing valve 41 has a first one-way valve position and a first throttling valve position. The first one-way valve position is configured to be conductive when the hydraulic oil flows to the rodless chamber of the first-stage oil cylinder 11 and to be cut off in the opposite direction. The first throttling valve position has a throttling passage for controlling the flow rate of the hydraulic oil. The switching control end of the first balancing valve 41 is hydraulically connected to the third working oil line 37. When the first-stage oil cylinder 11 needs to be retracted, the third working oil line 37 is high pressure, and the first balancing valve 41 will be switched to the first throttling valve position to control the return rate of the first working oil line 32, thereby ensuring the smooth retraction of the first-stage oil cylinder 11.

[0048] Similarly, the second working oil path 33 is provided with a second balance valve 41, the second balance valve 41 has a second one-way valve position and a second throttle valve position, the second one-way valve position is configured to be open when the hydraulic oil flows to the rodless cavity of the secondary oil cylinder 12 and be closed in the opposite direction, the fourth working oil path 38 is provided between the rod cavity of the primary oil cylinder 11 and the rod cavity of the secondary oil cylinder 12, and the switching control end of the second balance valve 41 is hydraulically connected to the fourth working oil path 38. When the third working oil path 37 is filled with oil, the fourth working oil path 38 is high pressure, and the second balance valve 41 will switch to the second throttle valve position to ensure that the secondary oil cylinder 12 retracts smoothly.

[0049] Of course, as Figure 3 shown, the oil pressure balance unit can also be a speed regulating valve 42 with a one-way open channel and a throttling channel, the one-way open channel can ensure that the system pressure oil smoothly enters the rodless cavity of the primary oil cylinder 11 and the rodless cavity of the secondary oil cylinder 12 when the oil cylinder is extended, and the throttling channel can adjust the retraction speed of the oil cylinder when the oil cylinder is retracted.

[0050] In the embodiment of the present application, the first switching valve 22 and the second switching valve 21 can be liquid-controlled switching valves.

[0051] Specifically, as Figure 1 and Figure 2 shown, the liquid control pilot oil path of the second switching valve 21 is controlled by the first electromagnetic valve 51, the first electromagnetic valve 51 is also a switching valve, the switching of the first electromagnetic valve 51 is controlled by the first electromagnet Y1a and the second electromagnet Y1b at both ends, when the first electromagnet Y1a is powered, the second switching valve 21 switches to the first valve position 211, when the second electromagnet Y1b is powered, the second switching valve 21 switches to the second valve position 212, and when the first electromagnet Y1a and the second electromagnet Y1b are both de-energized, the second switching valve 21 remains in the third valve position 213 in the middle position.

[0052] The pilot oil path of the first switching valve 22 can be controlled by the second electromagnetic valve 52 and the third electromagnetic valve 53 respectively, or by one electromagnetic valve, the second electromagnetic valve 52 is provided with a third electromagnet Y1, and the third electromagnetic valve 53 is provided with a fourth electromagnet Y3, when the third electromagnet Y1 is powered, the first switching valve 22 switches to the fourth valve position 221, when the fourth electromagnet Y3 is powered, the first switching valve 22 switches to the fifth valve position 222, and when both are de-energized, the first switching valve 22 is in the middle position of the closed valve position.

[0053] When it is necessary to control the extension of the primary oil cylinder 11 alone, the first electromagnetic valve 51 and the fourth electromagnetic valve are powered.

[0054] When it is necessary to control the extension of the secondary oil cylinder 12 alone, the second electromagnetic valve 52 and the fourth electromagnetic valve are powered.

[0055] When the two oil cylinders need to be controlled to extend simultaneously, the fourth electromagnetic valve is powered on, and the first electromagnetic valve 51 and the second electromagnetic valve 52 are both powered off.

[0056] When the first-stage oil cylinder 11 needs to be controlled to retract alone, the first electromagnetic valve 51 and the third electromagnetic valve 53 are powered on.

[0057] When the second-stage oil cylinder 12 needs to be controlled to retract alone, the second electromagnetic valve 52 and the third electromagnetic valve 53 are powered on.

[0058] When the two oil cylinders need to be controlled to retract simultaneously, the third electromagnetic valve 53 is powered on, and the first electromagnetic valve 51 and the second electromagnetic valve 52 are both powered off.

[0059] As shown in FIGS. ​ and ​ In the embodiment of the present application, the first reversing valve 22 can be a three-position six-way valve and includes a first oil port 223, a second oil port 224, and a third oil port 225 on the third oil port side, and a fourth oil port 226, a fifth oil port 227, and a sixth oil port 228 on the fourth oil port side. The first oil port 223 is connected to the system oil inlet line 35, the fourth oil port 226 is connected to the third reversing valve 23, the oil outlet of the third reversing valve 23 is connected back to the third oil port 225, and the pilot control end of the third reversing valve 23 is hydraulically connected to the hydraulic line between itself and the fourth oil port 226. The second oil port 224 is connected to the system oil return line 36, the fifth oil port 227 and the sixth oil port 228 are connected to the third working oil line 37 and the intermediate oil line 31, respectively. The third reversing valve 23 is normally kept in the closed valve position, and when the pilot control end of the third reversing valve 23 is under high pressure, the third reversing valve 23 is self-locked in the open valve position. Among them, the first reversing valve 22 is in the third valve position 213 and the fourth valve position 221, the first oil port 223 and the fourth oil port 226 are open, and in the middle closed valve position, the first oil port 223 and the fourth oil port 226 are closed. By providing the third reversing valve 23, the self-locking pressure holding performance of the oil cylinder can be ensured when the first reversing valve 22 is in the middle closed valve position, and the oil cylinder from retracting.

[0060] To achieve the above object, the present application further provides a crane, wherein the crane comprises a double-cylinder hydraulic system for a hoisting machine according to the above description. Since the crane adopts all the technical solutions of the above embodiments, it at least has the beneficial effects brought by the above embodiments, which will not be repeated here.

[0061] The crane of the present application can be a multi-section arm crane of double-cylinder rope arrangement structure.

[0062] In conclusion, the double-cylinder hydraulic system in the application can realize the synchronous extension and retraction control and the independent extension and retraction control of the double-cylinder unit 1 through two groups of reversing valves, thereby increasing the number of working modes of the oil cylinder and reducing the number of valve groups used.

[0063] In the description of the application, it should be understood that the terms "first", "second" are used only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can be explicitly or implicitly included at least one of the features. In the description of the application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0064] In the application, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and other terms should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrated; it can be mechanical connection, or electrical connection or communication with each other; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise specifically limited. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0065] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0066] Although the embodiments of the application have been described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the application.

Claims

1. A dual cylinder hydraulic system for a lifting appliance characterised in that, The double-cylinder hydraulic system for a lifting machine comprises: a double-cylinder unit (1) comprising a primary cylinder (11) and a secondary cylinder (12), a rod cavity of the primary cylinder (11) being communicated with a rod cavity of the secondary cylinder (12); and a control valve unit comprising a first directional valve (22) and a second directional valve (21), the first directional valve (22) being used for controlling oil inlet and outlet of the rod cavity of the primary cylinder (11), the second directional valve (21) being used for selectively controlling oil return of one of the rod cavity of the primary cylinder (11) and the rod cavity of the secondary cylinder (12) and pressure holding of the other one; the second directional valve (21) is provided with a first oil port side and a second oil port side, the first oil port side being connected with an intermediate oil line (31) for oil inlet and outlet, the second oil port side being connected with a first working oil line (32) and a second working oil line (33), the first working oil line (32) and the second working oil line (33) being respectively communicated with the rod cavity of the primary cylinder (11) and the rod cavity of the secondary cylinder (12), the second directional valve (21) being provided with a first valve position (211), a second valve position (212) and a third valve position (213); the first valve position (211) is configured to make the first working oil line (32) and the intermediate oil line (31) conductive and the second working oil line (33) pressure holding, the second valve position (212) is configured to make the second working oil line (33) and the intermediate oil line (31) conductive and the first working oil line (32) pressure holding, and the third valve position (213) is configured to make the first working oil line (32) and the second working oil line (33) both conductive with the intermediate oil line (31).

2. The dual cylinder hydraulic system for hoisting equipment according to claim 1, characterized in that, an overflow protection oil line (34) is arranged between the first oil port side of the second directional valve (21) and a system oil return line (36), a first overflow valve (341) is arranged on the overflow protection oil line (34), the first valve position (211) is configured to make the first working oil line (32) conductive with the intermediate oil line (31) and the second working oil line (33) conductive with the overflow protection oil line (34), and the second valve position (212) is configured to make the second working oil line (33) conductive with the intermediate oil line (31) and the first working oil line (32) cut off.

3. The dual cylinder hydraulic system for hoisting equipment of claim 1, wherein, the first directional valve (22) is provided with a third oil port side and a fourth oil port side, the third oil port side being connected with a system oil inlet line (35) and a system oil return line (36), the fourth oil port side being connected with the intermediate oil line (31), the first directional valve (22) being provided with a fourth valve position (221) and a fifth valve position (222); wherein, the fourth valve position (221) is configured to make the system oil return line (36) conductive with the intermediate oil line (31), and the fifth valve position (222) is configured to make the system oil inlet line (35) conductive with the intermediate oil line (31).

4. The dual cylinder hydraulic system for hoisting equipment according to claim 3, characterized in that, The third working oil path (37) is further arranged between the rod cavity of the primary oil cylinder (11) and the fourth oil port side of the first reversing valve (22), the fourth valve position (221) is configured to connect the system oil return path (36) and the intermediate oil path (31), and the system oil inlet path (35) and the third working oil path (37) are connected, the fifth valve position (222) is configured to connect the system oil inlet path (35) and the intermediate oil path (31), and the system oil return path (36) and the third working oil path (37) are connected.

5. The dual cylinder hydraulic system for hoisting equipment according to claim 4, characterized in that, A second overflow valve (62) is arranged between the intermediate oil path (31) and the system oil return path (36), and / or between the third working oil path (37) and the system oil return path (36).

6. The dual cylinder hydraulic system for hoisting apparatus according to any one of claims 1 to 5, characterized by, An oil pressure balancing unit is arranged on the rodless cavity working oil path of the primary oil cylinder (11) and the secondary oil cylinder (12) respectively, and the oil pressure balancing unit is provided with a throttling channel for controlling the oil outlet rate of the rodless cavity of the primary oil cylinder (11) and the secondary oil cylinder (12).

7. The dual cylinder hydraulic system for hoisting apparatus according to any one of claims 1 to 5, characterized by, The first reversing valve (22) and the second reversing valve (21) are liquid-controlled reversing valves.

8. A crane, characterized in that A double-cylinder hydraulic system for a lifting device, comprising any one of the double-cylinder hydraulic systems according to claims 1 to 7.

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