Floating loop, hydraulic control system and aerial work platform

Abstract

The utility model discloses a floating loop, a hydraulic control system and an aerial work platform, and relates to the technical field of hydraulic control. The floating loop comprises a first reversing valve, a first shuttle valve, a pressure reducing valve, a second reversing valve, a floating multi-way valve, a bidirectional balance valve and a floating oil cylinder; an oil inlet of the first reversing valve and an oil inlet of the pressure reducing valve are respectively connected with an oil outlet of the electro-hydraulic proportioning pump, an oil outlet of the first reversing valve and an oil drainage port of the pressure reducing valve are respectively connected with the hydraulic oil tank, and a control oil port of the first reversing valve is connected with an oil outlet of the pressure reducing valve and an oil inlet of the second reversing valve through the first shuttle valve; an oil outlet of the second reversing valve is connected with a two-way balance valve through a floating multi-way valve, and the two-way balance valve is connected with a floating oil cylinder; wherein the electro-hydraulic proportioning pump is driven by a speed regulating motor. The floating loop solves the problem that when a traditional floating loop is directly applied to a system of an adjustable-speed motor and an electro-hydraulic proportioning pump, constant-pressure standby cannot be achieved or standby pressure is too high.

Description

Technical Field

[0001] This utility model belongs to the field of hydraulic control technology, and in particular relates to a floating circuit, a hydraulic control system and an aerial work platform. Background Technology

[0002] Aerial work platforms are equipment used for working at heights and are widely used in construction, power, and municipal industries. Their hydraulic control systems mainly consist of: a power source, luffing circuit, telescopic circuit, turntable circuit, leveling circuit, boom circuit, work platform swing circuit, steering circuit, and floating circuit. Existing electrification retrofit solutions for aerial work platforms simply replace the engine with an electric motor; the control system still uses a load-sensitive system. This solution fails to effectively address the problem of large throttling losses in the valve control system, and the electric motor operates at a fixed speed, causing the hydraulic pump to operate in a low-displacement range under certain working conditions, resulting in low pump efficiency. Taking a 28-meter aerial work platform as an example, the energy losses of the electric motor, hydraulic pump, and multi-way valve are 23%, 25%, and 9%, respectively. These significant energy losses severely impact the operational endurance of the aerial work platform.

[0003] Currently, the load-sensitive control systems widely used in aerial work platforms have the following main drawbacks:

[0004] ① The motor speed is fixed and there is no real-time control of the motor speed. If the required flow rate is too large and exceeds the limit of the pump, the flow supply of the hydraulic control system cannot be guaranteed.

[0005] ② The efficiency of electric motors and pumps is relatively low under certain operating conditions. The main manifestations are: the electric motor operates at a fixed speed, and the efficiency of the electric motor is low under partial load and no-load conditions; under low flow conditions, the pump is often in the small displacement range, and the efficiency of the hydraulic pump is low.

[0006] ③ The overall efficiency of the motor and pump is difficult to maintain at its highest level under different operating conditions: Because the pressure and flow of the hydraulic system are constantly changing, the efficiency of the pump and motor are constantly changing, which makes it difficult for the overall efficiency of the two to maintain its highest level under different operating conditions.

[0007] ④ Because load-sensitive systems require a pressure difference to regulate the pump outlet flow, throttling energy loss is unavoidable.

[0008] Therefore, considering the use of a variable speed motor to drive an electro-hydraulic proportional pump as the electro-hydraulic power source can basically eliminate the throttling loss of the hydraulic system. By constantly adjusting the motor speed and pump displacement, the goal of keeping the hydraulic system efficiency at its highest under different working conditions can be achieved, thereby improving the overall energy utilization efficiency of the hydraulic system. This is also the idea of ​​further enhancing the energy-saving potential of the hydraulic system under the variable speed and variable displacement control method. Utility Model Content

[0009] The purpose of this invention is to provide a floating circuit, a hydraulic control system, and an aerial work platform to solve the problem that traditional floating circuits cannot achieve constant pressure standby or have excessively high standby pressure when using a power source of a speed-regulating motor and an electro-hydraulic proportional pump.

[0010] This utility model solves the above-mentioned technical problems through the following technical solution: a floating circuit applied to an aerial work platform, the floating circuit including a first directional valve, a first shuttle valve, a pressure reducing valve, a second directional valve, a floating multi-way valve, a bidirectional balance valve, and a floating cylinder; the oil inlet of the first directional valve and the oil inlet of the pressure reducing valve are respectively connected to the oil outlet of an electro-hydraulic proportional pump, the oil outlet of the first directional valve and the oil drain port of the pressure reducing valve are respectively connected to a hydraulic oil tank, the control oil port of the first directional valve is connected to the oil outlet of the pressure reducing valve and the oil inlet of the second directional valve through the first shuttle valve; the oil outlet of the second directional valve is connected to the bidirectional balance valve through the floating multi-way valve, and the bidirectional balance valve is connected to the floating cylinder; wherein, the electro-hydraulic proportional pump is driven by a speed-regulating motor.

[0011] Furthermore, a throttling element is provided in the oil line between the pressure reducing valve and the second directional valve. The throttling element is a fixed throttling orifice or a variable throttling orifice.

[0012] Furthermore, a filter is also provided at the oil outlet of the electro-hydraulic proportional pump.

[0013] Furthermore, the speed-regulating motor is a three-phase asynchronous motor.

[0014] Based on the same concept, this utility model also provides a hydraulic control system, including the floating circuit described above.

[0015] Furthermore, the hydraulic control system also includes a luffing circuit, which includes a main valve assembly, a switching valve, a proportional throttle valve, and a luffing cylinder. The inlet of the main valve assembly is connected to the outlet of the electro-hydraulic proportional pump, the control port of the main valve assembly is connected to the first shuttle valve in the floating circuit, and the outlet of the main valve assembly is connected to the luffing cylinder. A switching valve is provided in the oil line between the main valve assembly and the rodless chamber of the luffing cylinder. The first end of the proportional throttle valve is connected to the oil line between the main valve assembly and the rodless chamber of the luffing cylinder, and the second end of the proportional throttle valve is connected to the oil line between the main valve assembly and the rod chamber of the luffing cylinder.

[0016] Furthermore, the main valve assembly includes a pressure compensation valve, a variable amplitude multi-way valve, a second shuttle valve, and a third shuttle valve. The inlet of the pressure compensation valve is connected to the outlet of the electro-hydraulic proportional pump. The control port of the pressure compensation valve is connected to the first shuttle valve in the floating circuit through the second shuttle valve. The outlet of the pressure compensation valve is connected to the first port of the variable amplitude multi-way valve. The second and third ports of the variable amplitude multi-way valve serve as the outlets of the main valve assembly. The two ends of the third shuttle valve are respectively connected to the second port of the variable amplitude multi-way valve, and the third shuttle valve is also connected to the second shuttle valve.

[0017] Furthermore, the main valve assembly includes a cartridge valve and a third directional valve. The inlet of the cartridge valve is connected to the outlet of the electro-hydraulic proportional pump, and the outlet of the cartridge valve is connected to the first port of the third directional valve. The second and third ports of the third directional valve serve as the outlets of the main valve assembly. The fourth port of the third directional valve is connected to the hydraulic oil tank. The outlet of the cartridge valve is also connected to the first shuttle valve in the floating circuit.

[0018] Furthermore, the hydraulic control system also includes a telescopic circuit, a turntable circuit, a leveling circuit, a boom circuit, a swing circuit, and a steering circuit; the telescopic circuit, turntable circuit, leveling circuit, and steering circuit are respectively connected to the oil outlet of the electro-hydraulic proportional pump; the boom circuit and the swing circuit are respectively connected to the leveling circuit; the first shuttle valve in the floating circuit is also connected to the luffing circuit, telescopic circuit, turntable circuit, leveling circuit, and steering circuit.

[0019] Based on the same concept, this utility model also provides an aerial work platform, including the hydraulic control system described above.

[0020] Beneficial effects

[0021] Compared with the prior art, the advantages of this utility model are:

[0022] The floating circuit of this invention is applied to a hydraulic control system that uses a speed-regulating motor and an electro-hydraulic proportional pump as power sources. This floating circuit has a constant pressure standby function at the pump outlet, which meets the performance requirements of rapid floating and leveling during walking conditions. It solves the problem that traditional floating circuits cannot achieve constant pressure standby or have excessively high standby pressure when directly used in new hydraulic systems. Attached Figure Description

[0023] To more clearly illustrate the technical solution of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only one embodiment of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of a hydraulic control system with a multi-way valve in the functional circuit of this utility model embodiment;

[0025] Figure 2 This is a schematic diagram of a hydraulic control system in which the functional circuit of this utility model uses a cartridge valve.

[0026] Explanation of reference numerals in the attached diagram: 1-Speed-regulating motor, 2-Electro-hydraulic proportional pump, 3-Filter, 10-Floating circuit, 11-First directional valve, 12-First shuttle valve, 13-Pressure reducing valve, 14-Throttle element, 15-Second directional valve, 16-Floating multi-way valve, 17-Floating cylinder, 18-Two-way balance valve, 20-Luffing circuit, 21-Luffing multi-way valve, 22-Third shuttle valve, 23-Second shuttle valve, 24-Switch valve, 25-Proportional throttle valve, 26-Luffing cylinder, 27-Cartridge valve, 28-Third directional valve, 29-Pressure compensation valve, 30-Telescopic circuit, 40-Turntable circuit, 50-Leveling circuit, 60-Flying boom circuit, 70-Swing circuit, 80-Steering circuit. Detailed Implementation

[0027] The technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0028] The technical solutions of this application will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0029] Example 1

[0030] To address the issues of low motor and pump efficiency and energy loss due to the need for a pressure differential to adjust pump outlet flow in load-sensitive control systems for aerial work platforms, this paper proposes a power source consisting of a variable-speed motor 1 and an electro-hydraulic proportional pump 2 driven by the variable-speed motor 1. The outlet flow of the electro-hydraulic proportional pump 2 is controlled based on the desired flow rate (i.e., the required flow rate corresponding to the electrical signal output by the operating handle). The real-time overall efficiency of the power source is determined based on the real-time torque of the variable-speed motor 1, the real-time outlet pressure of the electro-hydraulic proportional pump 2, and the real-time outlet flow rate. This efficiency is then used to control the speed of the variable-speed motor 1 and the displacement of the electro-hydraulic proportional pump 2, achieving joint regulation of motor speed and pump displacement under different flow rates and pressures. This improves the efficiency of the variable-speed motor 1 and the electro-hydraulic proportional pump 2 while ensuring the required flow rate under actual working conditions. It solves the problems of throttling losses caused by the need for a pressure differential to adjust output flow in traditional load-sensitive pumps, and the difficulty in maintaining the highest overall efficiency of the motor and pump under different working conditions, thus reducing system energy loss. By jointly regulating the speed of the variable-speed motor 1 and the displacement of the electro-hydraulic proportional pump 2, power matching between the two is achieved. For example, during idling and no-load operation, the speed of the variable-speed motor 1 is reduced, decreasing its output power and energy loss. Under low-flow conditions, the output flow rate of the electro-hydraulic proportional pump 2 is increased, preventing it from operating in the low-displacement range and improving its efficiency, thus enhancing the overall efficiency of the power source. The power source employing a variable-speed motor and an electro-hydraulic proportional pump solves the throttling losses caused by the need for a pressure difference to regulate the output flow rate in traditional load-sensitive pumps, reducing system energy loss.

[0031] When traditional floating circuits are directly applied to hydraulic control systems powered by a speed-regulating motor 1 and an electro-hydraulic proportional pump 2, they cannot achieve constant pressure standby, thus failing to meet the requirements for rapid floating leveling performance during travel. Based on this technical problem, this invention improves the floating circuit to adapt to the power source of a speed-regulating motor 1 and an electro-hydraulic proportional pump 2, achieving rapid floating leveling control.

[0032] like Figure 1 and Figure 2 As shown, the floating circuit 10 provided in this embodiment includes a first directional valve 11, a first shuttle valve 12, a pressure reducing valve 13, a second directional valve 15, a floating multi-way valve 16, a bidirectional balance valve 18, and a floating cylinder 17. The inlet of the first directional valve 11 and the inlet of the pressure reducing valve 13 are respectively connected to the outlet of the electro-hydraulic proportional pump 2. The outlet of the first directional valve 11 and the drain port of the pressure reducing valve 13 are respectively connected to the hydraulic oil tank. The control port of the first directional valve 11 is connected to the outlet of the pressure reducing valve 13 and the inlet of the second directional valve 15 through the first shuttle valve 12. The outlet of the second directional valve 15 is connected to the bidirectional balance valve 18 through the floating multi-way valve 16. The bidirectional balance valve 18 is connected to the floating cylinder 17. In this embodiment, the first directional valve 11 is a two-position two-way directional valve.

[0033] When the system is idling, the output flow of the electro-hydraulic proportional pump 2 flows into the hydraulic oil tank through the pressure reducing valve 13. The output flow of the electro-hydraulic proportional pump 2 is greater than the internal leakage of the electro-hydraulic proportional pump 2 to satisfy the internal leakage of the electro-hydraulic proportional pump 2. The excess flow flows into the hydraulic oil tank through the pressure reducing valve 13.

[0034] When the system is in floating operation, the output flow of the electro-hydraulic proportional pump 2 is divided into two paths: one path flows to the inlet of the first directional valve 11, and the other path, after passing through the pressure reducing valve 13, is further divided into two paths: one path flows through the second directional valve 15, the floating multi-way valve 16, and the bidirectional balance valve 18 into the floating cylinder 17; the other path flows through the first shuttle valve 12 to the control port of the first directional valve 11. The opening condition of the first directional valve 11 is that the outlet pressure of the electro-hydraulic proportional pump 2 is greater than or equal to the control port pressure and the spring force. For example, if the output pressure of the pressure reducing valve 13 is 45 bar and the spring force is 32 bar, then the opening pressure of the first directional valve 11 is 77 bar. After the floating command is output, the outlet pressure of the electro-hydraulic proportional pump 2 remains constant at the sum of the output pressure of the pressure reducing valve 13 and the spring force, and the inlet pressure of the floating multi-way valve 16 remains constant at the output pressure of the pressure reducing valve 13. When the external load or terrain changes, the hydraulic oil quickly enters the floating cylinder 17, allowing it to make fine adjustments in the floating state to maintain vehicle stability, i.e., constant pressure standby, achieving back pressure. After the first directional valve 11 is opened, if the floating cylinder 17 has a flow requirement, the flow will flow to the floating cylinder 17, and the excess flow will be released through the first directional valve 11; if the floating cylinder does not respond, the fixed flow of the electro-hydraulic proportional pump 2 will be released through the first directional valve 11.

[0035] In a specific embodiment of this utility model, a throttling element 14 is also provided in the oil line between the pressure reducing valve 13 and the second reversing valve 15. The throttling element 14 is a fixed throttling orifice or a variable throttling orifice to achieve flow regulation.

[0036] In a specific embodiment of this utility model, a filter 3 is also provided at the oil outlet of the electro-hydraulic proportional pump 2 to filter out impurities in the oil.

[0037] In a specific embodiment of this utility model, the speed regulating motor 1 is a three-phase asynchronous motor, and the speed control method of the speed regulating motor 1 is vector control.

[0038] Example 2

[0039] like Figure 1 and Figure 2As shown, the hydraulic control system for aerial work platforms provided in this embodiment includes a luffing circuit 20 and a floating circuit 10 as in Embodiment 1 of this utility model. The luffing circuit 20 includes a main valve assembly, a switching valve 24, a proportional throttle valve 25, and a luffing cylinder 26. The inlet of the main valve assembly is connected to the outlet of the electro-hydraulic proportional pump 2, the control port of the main valve assembly is connected to the first shuttle valve 12 in the floating circuit 10, and the outlet of the main valve assembly is connected to the luffing cylinder 26. A switching valve 24 is provided in the oil line between the main valve assembly and the rodless chamber of the luffing cylinder 26. The first end of the proportional throttle valve 25 is connected to the oil line between the main valve assembly and the rodless chamber of the luffing cylinder 26, and the second end of the proportional throttle valve 25 is connected to the oil line between the main valve assembly and the rod chamber of the luffing cylinder 26. In this embodiment, the switching valve 24 is a two-position two-way switching valve 24.

[0040] The main valve assembly of this utility model has two implementation methods, such as... Figure 1 As shown, in the first embodiment, the main valve assembly includes a pressure compensation valve 29, a variable amplitude multi-way valve 21, a second shuttle valve 23, and a third shuttle valve 22. The oil inlet of the pressure compensation valve 29 is connected to the oil outlet of the electro-hydraulic proportional pump 2. The control oil port of the pressure compensation valve 29 is connected to the first shuttle valve 12 in the floating circuit 10 through the second shuttle valve 23. The oil outlet of the pressure compensation valve 29 is connected to the first port of the variable amplitude multi-way valve 21. The second and third ports of the variable amplitude multi-way valve 21 serve as the oil outlets of the main valve assembly. The two ends of the third shuttle valve 22 are respectively connected to the second port of the variable amplitude multi-way valve 21, and the third shuttle valve 22 is also connected to the second shuttle valve 23.

[0041] When performing the luffing upward movement, the output flow of the electro-hydraulic proportional pump 2 flows into the rodless chamber of the luffing cylinder 26 through the pressure compensation valve 29, the luffing multi-way valve 21, and the switching valve 24; when performing the luffing downward movement, the oil in the rodless chamber of the luffing cylinder 26 enters the rod chamber of the luffing cylinder 26 through the switching valve 24 and the proportional throttle valve 25 under the action of the boom's own load.

[0042] The hydraulic control system also includes a telescopic circuit 30, a turntable circuit 40, a leveling circuit 50, a boom circuit 60, a swing circuit 70, and a steering circuit 80. The outlet of the electro-hydraulic proportional pump 2 is connected to the main valve assemblies in the floating circuit 10, the luffing circuit 20, the telescopic circuit 30, the turntable circuit 40, the leveling circuit 50, and the steering circuit 80. The boom circuit 60 and the swing circuit 70 are respectively connected to the leveling circuit 50. The main valve assemblies of the telescopic circuit 30, the turntable circuit 40, the leveling circuit 50, and the steering circuit 80 are similar to the main valve assembly of the luffing circuit 20, and all include a pressure compensation valve 29, a luffing multi-way valve 21, a second shuttle valve 23, and a third shuttle valve 22. The first shuttle valve 12 in the floating circuit 10 is connected to the second shuttle valve in the luffing circuit 20. The second shuttle valve in the luffing circuit 20 is connected to the second shuttle valve in the telescopic circuit 30. The second shuttle valve in the telescopic circuit 30 is connected to the second shuttle valve in the turntable circuit 40. The second shuttle valve in the turntable circuit 40 is connected to the second shuttle valve in the leveling circuit 50. The second shuttle valve in the leveling circuit 50 is connected to the second shuttle valve in the steering circuit 80. When the boom is in motion, the first shuttle valve 12, the second shuttle valve 23, and the third shuttle valve 22 select the maximum pressure at the outlet of each multi-way valve during boom motion and apply this maximum pressure to the control port of the first directional valve 11. The first directional valve 11 operates in the left position, closing this oil circuit to prevent the outlet pressure of the electro-hydraulic proportional pump 2 from being released through the first directional valve 11.

[0043] like Figure 2 As shown, in the second embodiment, the main valve assembly includes a cartridge valve 27 and a third directional valve 28. The inlet of the cartridge valve 27 is connected to the outlet of the electro-hydraulic proportional pump 2, and the outlet of the cartridge valve 27 is connected to the first port of the third directional valve 28. The second and third ports of the third directional valve 28 serve as the outlets of the main valve assembly. The fourth port of the third directional valve 28 is connected to the hydraulic oil tank. In this embodiment, the third directional valve 28 is a three-position four-way directional valve.

[0044] When performing the luffing upward movement, the output flow of the electro-hydraulic proportional pump 2 flows into the rodless chamber of the luffing cylinder 26 through the pressure cartridge valve 27, the third directional valve 28, and the switching valve 24; when performing the luffing downward movement, the oil in the rodless chamber of the luffing cylinder 26 enters the rod chamber of the luffing cylinder 26 through the switching valve 24 and the proportional throttle valve 25 under the action of the boom's own load.

[0045] The main valve assemblies of the telescopic circuit 30, turntable circuit 40, leveling circuit 50, and steering circuit 80 are similar to those of the luffing circuit 20, all including a cartridge valve 27 and a third directional valve 28. The first shuttle valve 12 in the floating circuit 10 is connected to the outlet of the cartridge valves in the luffing circuit 20, telescopic circuit 30, turntable circuit 40, leveling circuit 50, and steering circuit 80. During boom movement, the first shuttle valve 12 feeds back the outlet pressure of the cartridge valve 27 to the control port of the first directional valve 11. The first directional valve 11 operates in the left position, closing this oil circuit and preventing the outlet pressure of the electro-hydraulic proportional pump 2 from being released through the first directional valve 11.

[0046] The above description only discloses specific embodiments of the present utility model, but the protection scope of the present utility model is not limited thereto. Any changes or modifications that can be easily conceived by those skilled in the art within the technical scope disclosed in the present utility model should be included within the protection scope of the present utility model.

Claims

1. A floating circuit applied to an aerial work platform, characterized in that: The floating circuit includes a first directional valve, a first shuttle valve, a pressure reducing valve, a second directional valve, a floating multi-way valve, a bidirectional balance valve, and a floating cylinder. The inlet of the first directional valve and the inlet of the pressure reducing valve are respectively connected to the outlet of the electro-hydraulic proportional pump. The outlet of the first directional valve and the drain port of the pressure reducing valve are respectively connected to the hydraulic oil tank. The control port of the first directional valve is connected to the outlet of the pressure reducing valve and the inlet of the second directional valve through the first shuttle valve. The outlet of the second directional valve is connected to the bidirectional balance valve through the floating multi-way valve. The bidirectional balance valve is connected to the floating cylinder. The electro-hydraulic proportional pump is driven by a speed-regulating motor.

2. The floating loop according to claim 1, characterized in that: A throttling element is also provided in the oil line between the pressure reducing valve and the second directional valve. The throttling element is a fixed throttling orifice or a variable throttling orifice.

3. The floating circuit according to claim 1, characterized in that: A filter is also provided at the oil outlet of the electro-hydraulic proportional pump.

4. The floating loop according to claim 1, characterized in that: The speed-regulating motor is a three-phase asynchronous motor.

5. A hydraulic control system, characterized in that: The system includes a floating loop as described in any one of claims 1 to 4.

6. The hydraulic control system according to claim 5, characterized in that: The system also includes a luffing circuit, which comprises a main valve assembly, a switching valve, a proportional throttle valve, and a luffing cylinder. The inlet of the main valve assembly is connected to the outlet of the electro-hydraulic proportional pump, the control port of the main valve assembly is connected to the first shuttle valve in the floating circuit, and the outlet of the main valve assembly is connected to the luffing cylinder. A switching valve is provided in the oil line between the main valve assembly and the rodless chamber of the luffing cylinder. The first end of the proportional throttle valve is connected to the oil line between the main valve assembly and the rodless chamber of the luffing cylinder, and the second end of the proportional throttle valve is connected to the oil line between the main valve assembly and the rod chamber of the luffing cylinder.

7. The hydraulic control system according to claim 6, characterized in that: The main valve assembly includes a pressure compensation valve, a variable amplitude multi-way valve, a second shuttle valve, and a third shuttle valve. The inlet of the pressure compensation valve is connected to the outlet of the electro-hydraulic proportional pump. The control port of the pressure compensation valve is connected to the first shuttle valve in the floating circuit through the second shuttle valve. The outlet of the pressure compensation valve is connected to the first port of the variable amplitude multi-way valve. The second and third ports of the variable amplitude multi-way valve serve as the outlets of the main valve assembly. The two ends of the third shuttle valve are respectively connected to the second port of the variable amplitude multi-way valve, and the third shuttle valve is also connected to the second shuttle valve.

8. The hydraulic control system according to claim 6, characterized in that: The main valve assembly includes a cartridge valve and a third directional valve. The inlet of the cartridge valve is connected to the outlet of the electro-hydraulic proportional pump, and the outlet of the cartridge valve is connected to the first port of the third directional valve. The second and third ports of the third directional valve serve as the outlets of the main valve assembly. The fourth port of the third directional valve is connected to the hydraulic oil tank. The outlet of the cartridge valve is also connected to the first shuttle valve in the floating circuit.

9. The hydraulic control system according to any one of claims 5 to 8, characterized in that: The system also includes a telescopic circuit, a turntable circuit, a leveling circuit, a boom circuit, a swing circuit, and a steering circuit; the telescopic circuit, turntable circuit, leveling circuit, and steering circuit are respectively connected to the oil outlet of the electro-hydraulic proportional pump; the boom circuit and the swing circuit are respectively connected to the leveling circuit; the first shuttle valve in the floating circuit is also connected to the luffing circuit, the telescopic circuit, the turntable circuit, the leveling circuit, and the steering circuit.

10. An aerial work platform, characterized in that: The working platform includes a hydraulic control system as described in any one of claims 5 to 9.

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