Double-cylinder hydraulic system for hoisting apparatus and crane

Abstract

The invention belongs to the technical field of engineering machinery, and provides a double-cylinder hydraulic system for a hoisting instrument and a crane, the double-cylinder hydraulic system comprises a double-oil-cylinder unit and a control valve unit, the double-oil-cylinder unit comprises a first-stage oil cylinder and a second-stage oil cylinder, a rod cavity of the first-stage oil cylinder is communicated with a rod cavity of the second-stage oil cylinder, and a rod cavity of the second-stage oil cylinder is communicated with a rod cavity of the first-stage oil cylinder; the control valve unit comprises a first reversing valve and a second reversing valve, the first reversing valve is used for selectively guiding system pressure oil to a rod cavity of the first-stage oil cylinder, the second reversing valve is used for selectively controlling one of a rodless cavity of the first-stage oil cylinder and a rodless cavity of the second-stage oil cylinder to return oil, and the other one of the rodless cavity of the first-stage oil cylinder and the rodless cavity of the second-stage oil cylinder builds pressure. According to the system, the two reversing valves are adopted for controlling oil inlet and oil return of the first-stage oil cylinder and the second-stage oil cylinder respectively, asynchronous and synchronous retraction control of the two-stage oil cylinders can be achieved, and therefore the telescopic mode of the two oil cylinders is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of engineering machinery, and in particular relates to a double-cylinder hydraulic system for lifting equipment and a crane. Background Art

[0002] In order to achieve the lifting 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 conditions. Existing telescopic arms with fewer sections are generally driven by only one cylinder. When the number of sections of the telescopic arm exceeds a certain number, in order to ensure that the telescopic stroke of the cylinder can meet the extension length of the telescopic arm, some manufacturers will use two-stage cylinders or even three-stage cylinders.

[0003] In the existing two-stage cylinder crane, due to the cylinder structure and the channel limitation of the reversing valve, the telescopic arm can only be extended sequentially and retracted synchronously, and the telescopic mode is very simple. Summary of the invention

[0004] In view of the above-mentioned defects or shortcomings, the present invention provides a double-cylinder hydraulic system and a crane for lifting equipment, aiming to solve the technical problem of the single telescopic mode of the existing two-stage cylinder crane.

[0005] To achieve the above-mentioned purpose, the present invention provides a double-cylinder hydraulic system for lifting equipment, the double-cylinder hydraulic system for lifting equipment includes a double-cylinder unit and a control valve unit, the double-cylinder unit includes a primary cylinder and a secondary cylinder, the rod chamber of the primary cylinder is connected to the rod chamber of the secondary cylinder, the control valve unit includes a first reversing valve and a second reversing valve, the first reversing valve is used to selectively direct the system pressure oil to the rod chamber of the primary cylinder, the second reversing valve is used to selectively control one of the rodless chamber of the primary cylinder and the rodless chamber of the secondary cylinder to return oil, and the other to hold pressure.

[0006] In an embodiment of the present invention, 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 an intermediate oil circuit for oil return, the second oil port side is connected to a first working oil circuit and a second working oil circuit, the first working oil circuit and the second working oil circuit are respectively connected to a rodless chamber of a first-stage oil cylinder and a rodless chamber of a second-stage oil cylinder, and the second reversing valve is provided with a first valve position and a second valve position; wherein the first valve position is configured such that the first working oil circuit is connected to the intermediate oil circuit and the second working oil circuit is pressurized, and the second valve position is configured such that the second working oil circuit is connected to the intermediate oil circuit and the first working oil circuit is pressurized.

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

[0008] In an embodiment of the present invention, the second reversing valve is further provided with a third valve position, and the third valve position is configured so that both the first working oil circuit and the second working oil circuit are connected to the intermediate oil circuit.

[0009] In an embodiment of the present invention, 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 circuit and the system oil return circuit, the fourth oil port side is connected to the intermediate oil circuit, 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 connect the system oil return circuit with the intermediate oil circuit, and the fifth valve position is configured to connect the system oil inlet circuit with the intermediate oil circuit.

[0010] In an embodiment of the present invention, a third working oil circuit is also provided between the rod chamber of the first-stage oil cylinder and the fourth oil port side of the first reversing valve, the fourth valve position is configured so that the system return oil circuit is connected to the intermediate oil circuit, and the system oil inlet circuit is connected to the third working oil circuit, and the fifth valve position is configured so that the system oil inlet circuit is connected to the intermediate oil circuit, and the system return oil circuit is connected to the third working oil circuit.

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

[0012] In an embodiment of the present invention, an oil pressure balancing unit is respectively provided on the working oil circuit of the rodless chamber of the first-stage oil cylinder and the second-stage oil cylinder, and the oil pressure balancing unit is provided with a throttling channel for controlling the oil outlet rate of the rodless chamber of the first-stage oil cylinder and the second-stage oil cylinder.

[0013] In an embodiment of the present invention, the first reversing valve and the second reversing valve are hydraulically controlled reversing valves.

[0014] To achieve the above object, the present invention further provides a crane, wherein the crane comprises the double-cylinder hydraulic system for lifting equipment described above.

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

[0016] The system uses a second reversing valve to control the oil return of the rodless chamber of the first-stage oil cylinder and the rodless chamber of the second-stage oil cylinder respectively, which can realize synchronous retraction and asynchronous retraction control of the two-stage oil cylinder, thereby increasing the telescopic mode of the double oil cylinder.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide an understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation of the present invention. In the accompanying drawings:

[0019] Figure 1 is a structural schematic diagram of a first implementation mode of a double-cylinder hydraulic system for lifting equipment according to an embodiment of the present invention;

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

[0021] Figure 3 1 is a schematic structural diagram of a second implementation manner of a double-cylinder hydraulic system for lifting equipment according to an embodiment of the present invention.

[0022] Description of Reference Numerals

[0023] 1. Double cylinder unit; 11. First cylinder; 12. Second 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 circuit; 32. First working oil 33, second working oil circuit; 34, overflow protection oil circuit; 341, first overflow valve; 35, system oil inlet circuit; 36, system oil return circuit; 37, third working oil circuit; 38, fourth working oil circuit; 41, balance valve; 42, speed control valve; 51, first solenoid valve; Y1a, first electromagnet; Y1b, second electromagnet; 52, second solenoid valve; Y1, third electromagnet; 53, third solenoid valve; Y3, fourth electromagnet; 61, system overflow valve; 62, second overflow valve. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0025] The double-cylinder hydraulic system for lifting equipment of the present invention will be described below with reference to the accompanying drawings.

[0026] The present invention provides a double-cylinder hydraulic system for lifting equipment, such as Figure 1 , Figure 2 and Figure 3 As shown, the double cylinder hydraulic system for lifting equipment includes:

[0027] The double cylinder unit 1 comprises a primary cylinder 11 and a secondary cylinder 12, wherein the rod chamber of the primary cylinder 11 is connected to the rod chamber of the secondary cylinder 12; and

[0028] The control valve unit includes a first reversing valve 22 and a second reversing valve 21. The first reversing valve 22 is used to direct the system pressure oil to the rod chamber of the first-stage cylinder 11, and the second reversing valve 21 is used to selectively control the return oil of one of the rodless chambers of the first-stage cylinder 11 and the rodless chambers of the second-stage cylinder 12, and hold the pressure in the other.

[0029] By reversing the first reversing valve 22, the pressure oil in the system oil inlet circuit 35 can be directed to the rod chamber of the first-stage cylinder 11. Since the rod chamber of the first-stage cylinder 11 is connected to the rod chamber of the second-stage cylinder 12, the pressure oil entering the rod chamber of the first-stage cylinder 11 can theoretically also flow into the rod chamber of the second-stage cylinder 12.

[0030] When the system pressure oil enters the rod chamber of the primary oil cylinder 11, if it is necessary to control the primary oil cylinder 11 to retract alone, it is only necessary to control the second reversing valve 21 to reverse, so that the rodless chamber of the primary oil cylinder 11 returns oil normally, and the rodless chamber of the secondary oil cylinder 12 is pressurized. Since the rodless chamber of the primary oil cylinder 11 returns oil normally, the primary oil cylinder 11 can perform the retraction action normally, and since the rodless chamber of the secondary oil cylinder 12 is pressurized, the secondary oil cylinder 12 will remain in the current posture. Similarly, when it is necessary to control the secondary oil cylinder 12 to retract alone, it is only necessary to control the second reversing valve 21 to reverse, so that the rodless chamber of the secondary oil cylinder 12 returns oil normally, and the rodless chamber of the primary oil cylinder 11 is pressurized; when it is necessary to control the two oil cylinders to retract at the same time, it is only necessary to control the second reversing valve 21 to reverse, so that the rodless chambers of the primary oil cylinder 11 and the secondary oil cylinder 12 both return oil normally.

[0031] In summary, the system uses the second reversing valve 21 to control the return oil of the rodless chamber of the first-stage cylinder 11 and the rodless chamber of the second-stage cylinder 12 respectively, which can realize synchronous retraction control and asynchronous retraction control of the two-stage cylinders, thereby increasing the telescopic mode of the dual cylinders.

[0032] In the embodiment of the present invention, the pressure holding can be achieved by controlling the working oil circuit of the rodless chamber to be cut off, or by providing a second overflow valve 62 between the working oil circuit of the rodless chamber and the system return oil circuit 36 ​​.

[0033] like Figure 1 and Figure 3As shown, in the embodiment of the present invention, the second reversing valve 21 is provided with a first oil port side and a second oil port side, the first oil port side may refer to the side of the second reversing valve 21 having the P and T ports, and the second oil port side may refer to the side of the second reversing valve 21 for connecting with the execution unit. The first oil port side is connected to the intermediate oil circuit 31 for oil return, and the second oil port side is connected to the first working oil circuit 32 and the second working oil circuit 33, the first working oil circuit 32 and the second working oil circuit 33 are respectively connected to the rodless chamber of the first oil cylinder 11 and the rodless chamber of the second 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 so that the first working oil circuit 32 is connected to the intermediate oil circuit 31 and the second working oil circuit 33 is pressed, and the second valve position 212 is configured so that the second working oil circuit 33 is connected to the intermediate oil circuit 31 and the first working oil circuit 32 is pressed. The intermediate oil circuit 31 may be directly connected to the system oil return circuit 36 ​​, or connected to the first reversing valve 22 , and the intermediate oil circuit 31 may be connected to the system oil return circuit 36 ​​by reversing the first reversing valve 22 .

[0034] When the system pressure oil enters the rod chamber of the primary oil cylinder 11, if it is necessary to control the primary oil cylinder 11 to retract alone, it is only necessary to control the second reversing valve 21 to reversing to the first valve position 211. At this time, the rodless chamber of the primary oil cylinder 11 returns oil normally through the first working oil circuit 32 and the intermediate oil circuit 31, the primary oil cylinder 11 retracts normally, the secondary oil cylinder 12 is in a pressure-holding state, and the secondary oil cylinder 12 remains stationary. If it is necessary to control the secondary oil cylinder 12 to retract alone, it is only necessary to control the second reversing valve 21 to reversing to the second valve position 212. At this time, the rodless chamber of the secondary oil cylinder 12 returns oil normally through the second working oil circuit 33 and the intermediate oil circuit 31, the secondary oil cylinder 12 retracts normally, the primary oil cylinder 11 is in a pressure-holding state, and the primary oil cylinder 11 remains stationary.

[0035] like Figure 1 and Figure 3 As shown, in an embodiment of the present invention, the second reversing valve 21 is further provided with a third valve position 213, and the third valve position 213 is configured so that both the first working oil circuit 32 and the second working oil circuit 33 are connected to the intermediate oil circuit 31. The intermediate oil circuit 31 can be connected to the first reversing valve 22, and the first reversing valve 22 can choose to direct the system pressure oil to the intermediate oil circuit 31 or to return oil to the intermediate oil circuit 31. Among them, in the third valve position 213, the rodless chamber of the first oil cylinder 11 and the rodless chamber of the second oil cylinder 12 both return oil normally, and the first oil cylinder 11 and the second oil cylinder 12 retract synchronously. By setting the third valve position 213, the two oil cylinders can be extended or retracted synchronously.

[0036] like Figure 1 and Figure 3As shown, in the embodiment of the present invention, an overflow protection oil circuit 34 is provided between the first oil port side of the second reversing valve 21 and the system oil return circuit 36, and a first overflow valve 341 is provided on the overflow protection oil circuit 34. The first valve position 211 can be configured so that the first working oil circuit 32 is connected to the intermediate oil circuit 31, and the second working oil circuit 33 is connected to the overflow protection oil circuit 34, the second valve position 212 is configured so that the second working oil circuit 33 is connected to the intermediate oil circuit 31, and the first working oil circuit 32 is cut off, or the second valve position 212 is configured so that the second working oil circuit 33 is connected to the intermediate oil circuit 31, and the first working oil circuit 32 is connected to the overflow protection oil circuit 34. During the process of the single retraction of the primary oil cylinder 11, the position between the telescopic booms is maintained by the rodless chamber pressure of the secondary oil cylinder 12. If there is a load on the telescopic boom, the rodless chamber working oil pressure of the secondary oil cylinder 12 will be very large. In order to ensure the safety of the system, 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 when the rodless chamber pressure of the secondary oil cylinder 12 exceeds the limit, the pressure can be safely relieved to avoid the bursting of the pipeline or the oil cylinder. Compared with setting the system overflow valve 61 on the system oil inlet circuit 35, this connection method has a faster response speed and a high protection ability for the oil cylinder. The circuit is suitable for load-sensitive systems and can achieve the effect of reducing overflow flow and saving energy. Among them, the cavity-free cross-sectional area of ​​the first oil cylinder 11 is larger than that of the second oil cylinder 12, and the load it can bear is also higher. Therefore, when the second oil cylinder 12 retracts alone, in order to avoid the situation of uncontrolled boom retraction, 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 also be configured so that the second working oil circuit 33 is connected to the intermediate oil circuit 31, and the first working oil circuit 32 is connected to the overflow protection oil circuit 34.

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

[0038] Furthermore, a third working oil circuit 37 is provided between the rod chamber 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 so that the system return oil circuit 36 ​​is connected to the intermediate oil circuit 31, and the system inlet oil circuit 35 is connected to the third working oil circuit 37, and the fifth valve position 222 is configured so that the system inlet oil circuit 35 is connected to the intermediate oil circuit 31, and the system return oil circuit 36 ​​is connected to the third working oil circuit 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 extended synchronously, retracted synchronously, extended separately, and retracted separately.

[0039] When it is necessary to control the synchronous retraction of the first-level cylinder 11 and the second-level cylinder 12, the first reversing valve 22 can be controlled to switch to the fourth valve position 221, and the second reversing valve 21 can be controlled to switch to the third valve position 213. At this time, the system pressure oil enters the rod chamber of the first-level cylinder 11 and the rod chamber of the second-level cylinder 12, and the rodless chamber of the first-level cylinder 11 and the rodless chamber of the second-level cylinder 12 return oil through the intermediate oil circuit 31 and the system return oil circuit 36, and the two cylinders are synchronously retracted.

[0040] When it is necessary to control the first-stage cylinder 11 and the second-stage cylinder 12 to extend synchronously, 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 the rodless chamber of the first-stage cylinder 11 and the rodless chamber of the second-stage cylinder 12 through the intermediate oil circuit 31, and the rod chamber of the first-stage cylinder 11 and the rod chamber of the second-stage cylinder 12 return oil through the third working oil circuit 37, and the two cylinders are extended synchronously.

[0041] When it is necessary to control the first-level cylinder 11 to retract alone, 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 the rod chamber of the first-level cylinder 11 and the rod chamber of the second-level cylinder 12 through the third working oil circuit 37, and the rodless chamber of the first-level cylinder 11 returns oil alone through the intermediate oil circuit 31. The first-level cylinder 11 retracts alone, the rodless chamber of the second-level cylinder 12 is in a pressure-holding state, and the second-level cylinder 12 remains stationary.

[0042] When it is necessary to control the secondary oil cylinder 12 to retract independently, 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 the rod chamber of the primary oil cylinder 11 and the rod chamber of the secondary oil cylinder 12 through the third working oil circuit 37, and the rodless chamber of the secondary oil cylinder 12 returns oil independently through the intermediate oil circuit 31, the secondary oil cylinder 12 retracts independently, the rodless chamber of the primary oil cylinder 11 is in a pressure-holding state, and the primary oil cylinder 11 remains stationary.

[0043] When it is necessary to control the primary oil cylinder 11 to extend alone, it is only necessary to control the first reversing valve 22 to switch to the fifth valve position 222, and control the second reversing valve 21 to switch to the first valve position 211. At this time, the system pressure oil enters the rodless chamber of the primary oil cylinder 11 alone through the intermediate oil circuit 31, and the rod chamber of the primary oil cylinder 11 returns oil through the third working oil circuit 37. The primary oil cylinder 11 extends alone, and the rodless chamber of the secondary oil cylinder 12 has no pressure oil input, and the secondary oil cylinder 12 remains stationary.

[0044] When it is necessary to control the secondary oil cylinder 12 to extend alone, it is only necessary to control the first reversing valve 22 to switch to the fifth valve position 222, and control the second reversing valve 21 to switch to the second valve position 212. At this time, the system pressure oil enters the rodless chamber of the secondary oil cylinder 12 alone through the intermediate oil circuit 31, and the rod chamber of the secondary oil cylinder 12 returns oil through the third working oil circuit 37. The secondary oil cylinder 12 extends alone, and the rodless chamber of the primary oil cylinder 11 has no pressure oil input, and the primary oil cylinder 11 remains stationary.

[0045] like Figure 1 and Figure 3 As shown, in an embodiment of the present invention, a second overflow valve 62 may be provided between the intermediate oil circuit 31 and the system return oil circuit 36, and / or between the third working oil circuit 37 and the system return oil circuit 36 ​​to ensure safe operation of the system.

[0046] like Figure 1 and Figure 3 As shown, in an embodiment of the present invention, an oil pressure balancing unit is respectively provided on the rodless chamber working oil circuit of the first-stage oil cylinder 11 and the second-stage oil cylinder 12, and the oil pressure balancing unit is provided with a throttling channel 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, Figure 1 As shown, the oil pressure balancing unit can be a balancing valve 41. A first balancing valve 41 is provided on the first working oil circuit 32. The first balancing valve 41 has a first one-way valve position and a first throttle 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 cut off in the reverse direction. The first throttle valve position has a throttling channel for controlling the flow rate of the hydraulic oil. The reversing control end of the first balancing valve 41 is hydraulically connected to the third working oil circuit 37. When the first-stage oil cylinder 11 needs to retract, the third working oil circuit 37 is high pressure, and the first balancing valve 41 will switch to the first throttle valve position to control the oil return rate of the first working oil circuit 32, thereby ensuring the smooth retraction of the first-stage oil cylinder 11.

[0048] Similarly, a second balancing valve 41 is provided on the second working oil circuit 33, and the second balancing 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 conductive when the hydraulic oil flows to the rodless chamber of the secondary oil cylinder 12 and cut off in the reverse direction. A fourth working oil circuit 38 is provided between the rod chamber of the primary oil cylinder 11 and the rod chamber of the secondary oil cylinder 12, and the reversing control end of the second balancing valve 41 is hydraulically connected to the fourth working oil circuit 38. When the third working oil circuit 37 is fed with oil, the fourth working oil circuit 38 is high pressure, and the second balancing valve 41 will switch to the second throttle valve position to ensure the smooth retraction of the secondary oil cylinder 12.

[0049] Of course, if Figure 3 As shown, the oil pressure balancing unit can also be a speed regulating valve 42 with a one-way conducting channel and a throttling channel. The one-way conducting channel can ensure that the system pressure oil smoothly enters the rodless cavity of the first-stage cylinder 11 and the rodless cavity of the second-stage cylinder 12 when the cylinder is extended, and the throttling channel can adjust the retraction speed of the cylinder when the cylinder is retracted.

[0050] In the embodiment of the present invention, the first reversing valve 22 and the second reversing valve 21 may be hydraulically controlled reversing valves.

[0051] Specifically, Figure 1 and Figure 3 As shown, the hydraulically controlled pilot oil circuit of the second reversing valve 21 is controlled by the first solenoid valve 51, and the first solenoid valve 51 is also a reversing valve. The reversing of the first solenoid valve 51 is controlled by the first electromagnet Y1a and the second electromagnet Y1b at both ends. When the first electromagnet Y1a is energized, the second reversing valve 21 switches to the first valve position 211. When the second electromagnet Y1b is energized, the second reversing valve 21 switches to the second valve position 212. When the first electromagnet Y1a and the second electromagnet Y1b are both de-energized, the second reversing valve 21 remains in the third valve position 213 in the middle position.

[0052] The pilot oil circuit of the first reversing valve 22 can be controlled by the second solenoid valve 52 and the third solenoid valve 53 respectively, and can be controlled by one solenoid valve. The second solenoid valve 52 is provided with a third electromagnet Y1, and the third solenoid valve 53 is provided with a fourth electromagnet Y3. When the third electromagnet Y1 is energized, the first reversing valve 22 switches to the fourth valve position 221. When the fourth electromagnet Y3 is energized, the first reversing valve 22 switches to the fifth valve position 222. When both are de-energized, the first reversing valve 22 is in the middle stop valve position.

[0053] When it is necessary to control the primary oil cylinder 11 to extend alone, the first solenoid valve 51 and the fourth solenoid valve are energized.

[0054] When it is necessary to control the secondary oil cylinder 12 to extend alone, the second solenoid valve 52 and the fourth solenoid valve are energized.

[0055] When it is necessary to control the two oil cylinders to extend simultaneously, the fourth solenoid valve is energized, and the first solenoid valve 51 and the second solenoid valve 52 are both de-energized.

[0056] When it is necessary to control the primary oil cylinder 11 to retract alone, the first solenoid valve 51 and the third solenoid valve 53 are energized.

[0057] When it is necessary to control the secondary oil cylinder 12 to retract alone, the second solenoid valve 52 and the third solenoid valve 53 are energized.

[0058] When it is necessary to control the two oil cylinders to retract simultaneously, the third solenoid valve 53 is energized, and the first solenoid valve 51 and the second solenoid valve 52 are both de-energized.

[0059] like Figure 1 and Figure 2 As shown, in the embodiment of the present invention, 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, a third oil port 225 located on the third oil port side, and a fourth oil port 226, a fifth oil port 227 and a sixth oil port 228 located on the fourth oil port side. The first oil port 223 is connected to the system oil inlet 35, the fourth oil port 226 is connected to the third reversing valve 23, and the oil outlet of the third reversing valve 23 is connected back to the third oil port 225. The pilot control end of the third reversing valve 23 is hydraulically connected to the hydraulic pipeline between itself and the fourth oil port 226. The second oil port 224 is connected to the system oil return 36, and the fifth oil port 227 and the sixth oil port 228 are connected to the third working oil circuit 37 and the intermediate oil circuit 31 respectively. The third reversing valve 23 maintains the shut-off valve position under normal conditions. When the pilot control end of the third reversing valve 23 is high pressure, the third reversing valve 23 is self-locked in the conduction valve position. 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 connected, and in the middle stop valve position, the first oil port 223 and the fourth oil port 226 are cut off. By setting the third reversing valve 23, the self-locking and pressure-holding performance of the oil cylinder can be guaranteed when the first reversing valve 22 is in the middle stop valve position, and the oil cylinder can be prevented from retracting.

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

[0061] The crane of the present invention may be a multi-section boom crane with a double-cylinder rope row structure.

[0062] In summary, the dual-cylinder hydraulic system of the present invention can realize the synchronous extension and extension control of the dual-cylinder unit 1 only through two sets of reversing valves, which not only increases the number of working modes of the cylinder, but also has a compact structure and uses fewer valve groups. At the same time, by setting an overflow protection oil circuit 34 on the second reversing valve 21, the system can overload the working oil circuit of the cylinder with a faster response speed when the cylinder retracts alone. Furthermore, by setting an oil pressure balancing unit, the system can control the retraction speed of the cylinder when it retracts, ensure the smooth retraction of the cylinder, and reduce system jitter.

[0063] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0064] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0065] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. 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 present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0066] Although the embodiments of the present invention have been described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A double-cylinder hydraulic system for lifting equipment, characterized in that: The double-cylinder hydraulic system for lifting equipment comprises: A double cylinder unit (1) comprises a primary cylinder (11) and a secondary cylinder (12), wherein a rod chamber of the primary cylinder (11) is connected to a rod chamber of the secondary cylinder (12); and The control valve unit comprises a first reversing valve (22) and a second reversing valve (21), wherein the first reversing valve (22) is used to selectively direct the system pressure oil to the rod chamber of the first-stage oil cylinder (11), and the second reversing valve (21) is used to selectively control the return of oil from one of the rodless chamber of the first-stage oil cylinder (11) and the rodless chamber of the second-stage oil cylinder (12), and to hold the pressure in the other.

2. The double-cylinder hydraulic system for lifting equipment according to claim 1, characterized in that: The second reversing valve (21) is provided with a first oil port side and a second oil port side, the first oil port side is connected to an intermediate oil circuit (31) for oil return, the second oil port side is connected to a first working oil circuit (32) and a second working oil circuit (33), the first working oil circuit (32) and the second working oil circuit (33) are respectively connected to the rodless chamber of the first oil cylinder (11) and the rodless chamber of the second oil cylinder (12), and 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 such that the first working oil circuit (32) is connected to the intermediate oil circuit (31) and the second working oil circuit (33) is pressurized, and the second valve position (212) is configured such that the second working oil circuit (33) is connected to the intermediate oil circuit (31) and the first working oil circuit (32) is pressurized.

3. The double-cylinder hydraulic system for lifting equipment according to claim 2, characterized in that: An overflow protection oil circuit (34) is provided between the first oil port side of the second reversing valve (21) and the system oil return circuit (36); a first overflow valve (341) is provided on the overflow protection oil circuit (34); the first valve position (211) is configured such that the first working oil circuit (32) is connected to the intermediate oil circuit (31), and the second working oil circuit (33) is connected to the overflow protection oil circuit (34); the second valve position (212) is configured such that the second working oil circuit (33) is connected to the intermediate oil circuit (31) and the first working oil circuit (32) is blocked.

4. The double-cylinder hydraulic system for lifting equipment according to claim 2, characterized in that: The second reversing valve (21) is further provided with a third valve position (213), and the third valve position (213) is configured so that both the first working oil circuit (32) and the second working oil circuit (33) are in conduction with the intermediate oil circuit (31).

5. The double-cylinder hydraulic system for lifting equipment according to claim 2, characterized in that: 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 to a system oil inlet circuit (35) and a system oil return circuit (36), the fourth oil port side is connected to the intermediate oil circuit (31), and 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 oil return circuit (36) with the intermediate oil circuit (31), and the fifth valve position (222) is configured to connect the system oil inlet circuit (35) with the intermediate oil circuit (31).

6. The double-cylinder hydraulic system for lifting equipment according to claim 5, characterized in that: A third working oil circuit (37) is also provided between the rod chamber of the first-stage oil cylinder (11) and the fourth oil port side of the first reversing valve (22); the fourth valve position (221) is configured so that the system return oil circuit (36) is connected to the intermediate oil circuit (31), and the system oil inlet circuit (35) is connected to the third working oil circuit (37); the fifth valve position (222) is configured so that the system oil inlet circuit (35) is connected to the intermediate oil circuit (31), and the system return oil circuit (36) is connected to the third working oil circuit (37).

7. The double-cylinder hydraulic system for lifting equipment according to claim 6, characterized in that: A second overflow valve (62) is provided between the intermediate oil circuit (31) and the system oil return circuit (36), and / or between the third working oil circuit (37) and the system oil return circuit (36).

8. The double-cylinder hydraulic system for lifting equipment according to any one of claims 1 to 7, characterized in that: An oil pressure balancing unit is respectively provided on the rodless chamber working oil circuit of the first-stage oil cylinder (11) and the second-stage oil cylinder (12), and the oil pressure balancing unit is provided with a throttling channel for controlling the oil outlet rate of the rodless chamber of the first-stage oil cylinder (11) and the second-stage oil cylinder (12).

9. The double-cylinder hydraulic system for lifting equipment according to any one of claims 1 to 7, characterized in that: The first reversing valve (22) and the second reversing valve (21) are hydraulically controlled reversing valves.

10. A crane, characterized in that: The invention comprises a double-cylinder hydraulic system for lifting equipment according to any one of claims 1 to 9.

Images