Hydraulic system capable of achieving double-axle steering of shear forklift

Abstract

The utility model discloses a hydraulic system capable of realizing double-axle steering of a shear forklift, which comprises a hydraulic pump, a motor, a control valve group, a first steering oil cylinder and a second steering oil cylinder, the hydraulic pump and the motor are used for providing hydraulic power, and the first steering oil cylinder and the second steering oil cylinder are respectively connected to a front axle and a rear axle of the shear forklift. The control valve set comprises a master control electromagnetic valve, a one-way valve, a pressure compensation throttling valve, a lifting electromagnetic valve, a plurality of dampers, a first electric proportional electromagnetic valve and a second electric proportional electromagnetic valve. According to the utility model, the problem that the scissor forklift cannot work in a narrow space or under a complex working condition is solved, and a steering function capable of steering independently is added; the double-axle synchronous steering of the scissor forklift can be realized, and the turning radius of the scissor forklift is reduced through different matching of the steering angles of the front axle and the rear axle.

Description

Technical Field

[0001] This utility model belongs to the technical field of hydraulic steering systems for scissor lifts, and in particular, relates to a hydraulic system that enables dual-axle steering of scissor lifts. Background Technology

[0002] Aerial work platform scissor lifts are a common and widely used type of aerial work equipment. They achieve lifting and movement through hydraulic systems or electric motors and are widely used in installation, maintenance, and high-altitude operations in industries such as municipal engineering, industrial plants, commercial premises, logistics warehousing, and power.

[0003] Existing scissor lift steering systems typically control the front wheel rotation via a single front wheel cylinder. The fixed damping in these systems cannot dynamically adjust flow based on load or operating conditions, resulting in a limited steering speed and an inability to achieve precise control. This leads to inflexible operation, especially at low speeds or in complex scenarios, causing instability in steering control. Furthermore, while scissor lifts using this technology are simple in structure, easy to operate, and have low manufacturing and maintenance costs, they have a large turning radius, making them unsuitable for use in confined workspaces.

[0004] A patent with publication number CN106640854A discloses a hydraulic system for a bidirectional shuttle bus, used for locking the axles and power steering. The bidirectional shuttle bus includes two axles located at its front and rear sides, two sets of locking mechanisms capable of locking the two axles respectively, and two sets of power steering mechanisms capable of power steering the two axles respectively. The hydraulic system includes a hydraulic tank, a locking circuit, and a power steering circuit. The hydraulic tank includes a locking tank and a power steering tank; the power steering tank is located inside the locking tank; the locking circuit connects the locking tank to the two locking mechanisms; and the power steering circuit connects the power steering tank to the two power steering mechanisms. This patent only supports steering on one axle while the other axle is locked, failing to achieve coordinated steering between the two axles, resulting in a large turning radius and unsuitability for operations in confined spaces. Utility Model Content

[0005] This invention addresses the common problem in existing scissor lift steering systems, which typically control the front wheel rotation via a single front wheel cylinder. The fixed damping in these systems prevents dynamic flow adjustment based on load or operating conditions, resulting in a limited steering speed and an inability to achieve precise control. This leads to inflexible operation, particularly in low-speed or complex scenarios, ultimately causing instability in scissor lift steering. Furthermore, while scissor lifts using this technology are simple in structure, easy to operate, and have low manufacturing and maintenance costs, they suffer from a large turning radius, making them unsuitable for confined workspaces. This invention proposes a hydraulic system that enables dual-axle steering for scissor lifts.

[0006] A hydraulic system enabling dual-axle steering of a scissor lift truck includes a hydraulic pump and a motor for providing hydraulic power, and a control valve assembly, a first steering cylinder, and a second steering cylinder, which are respectively connected to the front and rear axles of the scissor lift truck. The control valve assembly includes a master solenoid valve, a check valve, a pressure-compensated throttle valve, a lifting solenoid valve, multiple damping valves, a first electro-proportional solenoid valve, and a second electro-proportional solenoid valve. The inlet of the master solenoid valve is connected to the hydraulic pump, and its outlet is connected to the inlets of the lifting solenoid valve, the first electro-proportional solenoid valve, and the second electro-proportional solenoid valve, respectively. The pressure-compensated throttle valve is connected in series in the inlet path of the second electro-proportional solenoid valve.

[0007] The oil inlet and outlet of the first steering cylinder are connected to the oil outlet of the hydraulic pump via a first electro-proportional solenoid valve; the oil inlet and outlet of the second steering cylinder are connected to the oil outlet of the hydraulic pump via a second electro-proportional solenoid valve.

[0008] Furthermore, there are four dampers in total. Dampers one and two are respectively installed in the oil inlet and oil return lines of the first steering cylinder, and dampers three and four are respectively installed in the oil inlet and oil return lines of the second steering cylinder.

[0009] Furthermore, damping one, damping two, damping three, and damping four are all adjustable damping.

[0010] Furthermore, the piston rod ends of the first and second steering cylinders are respectively connected to the front and rear axles of the scissor lift via hinge mechanisms.

[0011] Furthermore, the master control solenoid valve is a two-position two-way solenoid valve, whose oil outlet is connected to the lifting solenoid valve, the first electro-proportional solenoid valve, and the second electro-proportional solenoid valve when energized, and connected to the oil tank when de-energized.

[0012] Furthermore, the lifting solenoid valve is a two-position four-way solenoid valve, with its inlet connected to the outlet of the master control solenoid valve, its return port connected to the oil tank, and its working port connected to the lifting circuit.

[0013] Furthermore, it also includes a first relief valve and a second relief valve, which are connected in parallel and connected to two packing cylinders. The first relief valve controls the maximum pressure of the entire hydraulic system, and the second relief valve limits the maximum pressure of the steering circuit separately.

[0014] Furthermore, the master control solenoid valve and the lifting solenoid valve are linked to control the lifting function: when the master control solenoid valve and the lifting solenoid valve are energized at the same time, the oil enters the lifting circuit through the CSE port; when only the master control solenoid valve is energized, the oil flows to the steering control circuit.

[0015] Furthermore, the hydraulic system supports a crab-like movement mode: by synchronously controlling the deflection of the first and second steering cylinders in the same direction, the scissor lift can achieve diagonal translation.

[0016] Furthermore, the check valve is located at the outlet of the hydraulic pump to prevent the hydraulic oil from flowing in the opposite direction.

[0017] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0018] 1. This utility model includes a hydraulic pump and a motor for providing hydraulic power, and also includes a control valve group, a first steering cylinder, and a second steering cylinder, which are respectively connected to the front and rear axles of the scissor lift. The control valve group includes a master solenoid valve, a check valve, a pressure-compensated throttle valve, a lifting solenoid valve, multiple damping valves, a first electro-proportional solenoid valve, and a second electro-proportional solenoid valve. By independently controlling the two steering cylinders, synchronous steering of the scissor lift's two axles can be achieved. By matching the different steering angles of the front and rear axles, the turning radius of the scissor lift can be reduced, enabling it to operate in narrow spaces or complex working conditions.

[0019] 2. By combining different steering angles of the front and rear wheels of the two hydraulic cylinders, the scissor lift can stop more accurately at the target position. The scissor lift using the hydraulic system of this invention has higher steering function reliability; when one steering function malfunctions, the other remains normal, and relying on this normal steering function, the scissor lift can still perform steering actions. Attached Figure Description

[0020] Figure 1 This is a hydraulic schematic diagram of a hydraulic system that enables dual-axle steering in a scissor lift truck.

[0021] In the above diagram, 1. Main control solenoid valve; 2. Check valve; 3. Lifting solenoid valve; 4. First electro-proportional solenoid valve; 5. Damping 1; 6. First steering cylinder; 7. Damping 2; 8. Damping 3; 9. Second steering cylinder; 10. Damping 4; 11. Second electro-proportional solenoid valve; 12. Pressure-compensated throttle valve; 13. Second relief valve; 14. First relief valve; 15. Oil tank; 16. Hydraulic pump; 17. Motor. Detailed Implementation

[0022] To clearly illustrate the technical features of this utility model, the following detailed description is provided through specific embodiments and in conjunction with the accompanying drawings.

[0023] Many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0024] Furthermore, in the description of this utility model, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0025] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0026] In this utility model, unless otherwise expressly specified and limited, the first feature "on" or "below" the second feature may be in direct contact with the first and second features, or indirect contact through an intermediate medium. In the description of this specification, references to terms such as "an embodiment," "some embodiments," "example," "specific example," or "some examples" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0027] Example 1

[0028] like Figure 1As shown, a hydraulic system enabling dual-axle steering of a scissor lift includes a hydraulic pump 16 and a motor 17 for providing hydraulic power. It also includes a control valve assembly, a first steering cylinder 6, and a second steering cylinder 9. The first steering cylinder 6 and the second steering cylinder 9 are respectively connected to the front and rear axles of the scissor lift. The control valve assembly includes a master solenoid valve 1, a check valve 2, a pressure-compensated throttle valve 12, a lifting solenoid valve 3, multiple damping valves, a first electro-proportional solenoid valve 4, and a second electro-proportional solenoid valve 11. The inlet of the master solenoid valve 1 is connected to the hydraulic pump 16, and its outlet is connected to the inlets of the lifting solenoid valve 3, the first electro-proportional solenoid valve 4, and the second electro-proportional solenoid valve 11, respectively. The pressure-compensated throttle valve 12 is connected in series in the inlet path of the second electro-proportional solenoid valve 11.

[0029] The inlet and outlet of the first steering cylinder 6 are connected to the outlet of the hydraulic pump 16 via the first electro-proportional solenoid valve 4; the inlet and outlet of the second steering cylinder 9 are connected to the outlet of the hydraulic pump 16 via the second electro-proportional solenoid valve 11. The first electro-proportional solenoid valve 4 controls the extension and retraction displacement of the first steering cylinder 6 by adjusting the input current, the pressure-compensated throttle valve 12 maintains a constant flow to the solenoid valve, and the second electro-proportional solenoid valve 11 controls the extension and retraction displacement of the second steering cylinder 9. The two cylinders are independently adjusted to achieve differentiated matching of the dual-axle steering angle.

[0030] In this embodiment, the hydraulic pump 16 is driven by the motor 17 and connected to the oil tank 15 via the check valve 2, pumping oil from the oil tank 15 into the system. When the main control solenoid valve 1 is energized, the hydraulic system builds up pressure, and the oil enters the steering circuit through the check valve 2, flowing through the first electro-proportional solenoid valve 4 and the second electro-proportional solenoid valve 11. At the same time, the second relief valve 13 and the first relief valve 14 respectively limit the maximum pressure of the steering circuit and the system. When the system pressure exceeds the set value, the relief valve opens, guiding the excess oil back to the oil tank 15 to prevent overload. Front axle steering unit: The first electro-proportional solenoid valve 4 is connected to the first steering cylinder 6. The first electro-proportional solenoid valve 4 controls the flow rate into the first steering cylinder 6 by adjusting the input current. Its inlet and return oil circuits are respectively equipped with damping 5 and damping 7 to adjust the steering speed. Rear axle steering unit: The second electro-proportional solenoid valve 11 controls the second steering cylinder 9 in the same way. Its inlet and return oil circuits are equipped with damping elements 8 and 10, respectively. A pressure-compensated throttle valve 12 ensures a constant flow to the second electro-proportional solenoid valve 11, resulting in more precise cylinder displacement control. All four dampers are adjustable; by changing the flow area of ​​the damping orifice or the specifications of the damping plug, the flow resistance of the hydraulic oil is adjusted in real time, thereby controlling the system's operating speed and motion smoothness.

[0031] One-way valve 2 serves a protective function, preventing the pressure oil in the steering section from flowing back into the hydraulic pump 16 and damaging it. The master control solenoid valve 1 is a two-position, two-way solenoid valve; its outlet is connected to the lifting solenoid valve 3, the first electro-proportional solenoid valve 4, and the second electro-proportional solenoid valve 11 when energized, and connected to the oil tank 15 when de-energized. The lifting solenoid valve 3 is a two-position, four-way solenoid valve; its inlet is connected to the outlet of the master control solenoid valve 1, its return port is connected to the oil tank 15, and its working port is connected to the lifting circuit.

[0032] The working principle is as follows: When the master control solenoid valve 1 is energized, the system builds up pressure. By independently adjusting the extension and retraction of the two cylinders, the steering angles of the front and rear axles are differentiated to suit different steering requirements and minimize the turning radius. The turning radius of the dual-axle independent control is reduced by 40% compared to the single-axle system. The first electro-proportional solenoid valve 4 enables high-precision steering of the front axle, making it suitable for operation in narrow alleyways.

[0033] Example 2

[0034] like Figure 1 As shown, a hydraulic system enabling dual-axle steering of a scissor lift includes a hydraulic pump 16 and a motor 17 for providing hydraulic power. It also includes a control valve assembly, a first steering cylinder 6, and a second steering cylinder 9. The first steering cylinder 6 and the second steering cylinder 9 are respectively connected to the front and rear axles of the scissor lift. The control valve assembly includes a master solenoid valve 1, a check valve 2, a pressure-compensated throttle valve 12, a lifting solenoid valve 3, multiple damping valves, a first electro-proportional solenoid valve 4, and a second electro-proportional solenoid valve 11. The inlet of the master solenoid valve 1 is connected to the hydraulic pump 16, and its outlet is connected to the inlets of the lifting solenoid valve 3, the first electro-proportional solenoid valve 4, and the second electro-proportional solenoid valve 11, respectively. The pressure-compensated throttle valve 12 is connected in series in the inlet path of the second electro-proportional solenoid valve 11.

[0035] The oil inlet and outlet of the first steering cylinder 6 are connected to the oil outlet of the hydraulic pump 16 via the first electro-proportional solenoid valve 4, respectively; the oil inlet and outlet of the second steering cylinder 9 are connected to the oil outlet of the hydraulic pump 16 via the second electro-proportional solenoid valve 11, respectively.

[0036] This embodiment improves the safety of the steering function by using redundant design to ensure that steering can still be completed in the event of a single axle failure. The master control solenoid valve 1 and the lifting solenoid valve 3 work together to control the lifting function: when both are energized, hydraulic fluid enters the lifting circuit through the CSE port, and the lifting solenoid valve 3 controls the direction of the hydraulic cylinder's movement; when only the master control solenoid valve 1 is energized, the hydraulic fluid flows to the steering control circuit. When the master control solenoid valve 1 is energized and the lifting solenoid valve 3 is de-energized, the hydraulic fluid flows to the first electro-proportional solenoid valve 4 and the pressure-compensated throttle valve 12. When the master control solenoid valve 1 and the second electro-proportional solenoid valve 11 are energized, the hydraulic fluid passes through the pressure-compensated throttle valve 12 to the second electro-proportional solenoid valve 11, and the flow rate through the pressure-compensated throttle valve 12 is a constant value.

[0037] The first relief valve 14 is connected in parallel with the second relief valve 13 via the lifting solenoid valve 3. When the first steering cylinder 6 cannot operate due to a malfunction of the first electro-proportional solenoid valve 4 or a blockage in the oil circuit, the second steering cylinder 9 can still be independently controlled via the second electro-proportional solenoid valve 11. At this time, the second electro-proportional solenoid valve 11 switches to full-flow mode, increasing the steering angle input of the second steering cylinder 9, allowing the scissor lift to complete the turning action solely by steering the rear axle. Conversely, if the second steering cylinder 9 or the second electro-proportional solenoid valve 11 malfunctions, the first electro-proportional solenoid valve 4 takes over the rear axle flow distribution, limiting the speed through damping, allowing the first steering cylinder 6 to still operate independently. The system maintains stable flow through the pressure-compensated throttle valve 12, avoiding pressure fluctuations caused by single-axle operation. Furthermore, the dual pressure protection of the first relief valve 14 and the second relief valve 13 further enhances system reliability and significantly improves the operational safety of the scissor lift under complex working conditions.

[0038] Example 3

[0039] This embodiment achieves diagonal translation (crab mode) of the scissor lift by synchronously controlling the dual-axle hydraulic cylinders. The specific implementation is as follows: When the scissor lift needs to move laterally, the first electro-proportional solenoid valve 4 and the second electro-proportional solenoid valve 11 simultaneously receive control signals in the same direction, causing oil to enter the same-side chambers of the first steering cylinder 6 and the second steering cylinder 9. For example, when oil enters the rodless chambers of both cylinders simultaneously, the front and rear axle tires synchronously deflect to the left; conversely, they deflect to the right. Damping precisely adjusts the cylinder movement speed to ensure consistent steering angles of the dual axles. The pressure-compensated throttle valve 12 maintains a constant flow rate, preventing asynchronous steering due to load changes. In this mode, the scissor lift can translate diagonally, greatly improving maneuverability in narrow spaces such as between racks, while the redundant steering design ensures the safety of the crab mode.

[0040] Obviously, the above-described embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A hydraulic system enabling dual-axle steering of a scissor lift truck, comprising a hydraulic pump and a motor for providing hydraulic power, characterized in that, It also includes a control valve assembly, a first steering cylinder, and a second steering cylinder, with the first and second steering cylinders respectively connected to the front and rear axles of the scissor lift. The control valve assembly includes a master solenoid valve, a check valve, a pressure-compensating throttle valve, a lifting solenoid valve, multiple damping valves, a first electro-proportional solenoid valve, and a second electro-proportional solenoid valve. The inlet of the master solenoid valve is connected to a hydraulic pump, and its outlet is connected to the inlets of the lifting solenoid valve, the first electro-proportional solenoid valve, and the second electro-proportional solenoid valve, respectively. The pressure-compensating throttle valve is connected in series in the inlet path of the second electro-proportional solenoid valve. The oil inlet and outlet of the first steering cylinder are connected to the oil outlet of the hydraulic pump via a first electro-proportional solenoid valve; the oil inlet and outlet of the second steering cylinder are connected to the oil outlet of the hydraulic pump via a second electro-proportional solenoid valve.

2. The hydraulic system for realizing dual-axle steering of a scissor lift truck according to claim 1, characterized in that, There are four dampers in total. Dampers 1 and 2 are respectively installed in the oil inlet and return lines of the first steering cylinder, and dampers 3 and 4 are respectively installed in the oil inlet and return lines of the second steering cylinder.

3. A hydraulic system for realizing dual-axle steering of a scissor lift truck according to claim 2, characterized in that, Damping 1, Damping 2, Damping 3, and Damping 4 are all adjustable damping.

4. A hydraulic system for realizing dual-axle steering of a scissor lift truck according to claim 1, characterized in that, The piston rod ends of the first and second steering cylinders are respectively connected to the front and rear axles of the scissor lift via hinge mechanisms.

5. A hydraulic system for realizing dual-axle steering of a scissor lift truck according to claim 1, characterized in that, The master control solenoid valve is a two-position two-way solenoid valve. When energized, its oil outlet is connected to the lifting solenoid valve, the first electro-proportional solenoid valve, and the second electro-proportional solenoid valve. When de-energized, it is connected to the oil tank.

6. A hydraulic system for realizing dual-axle steering of a scissor lift truck according to claim 1, characterized in that, The lifting solenoid valve is a two-position four-way solenoid valve. Its oil inlet is connected to the oil outlet of the master control solenoid valve, its oil return port is connected to the oil tank, and its working oil port is connected to the lifting circuit.

7. A hydraulic system for realizing dual-axle steering of a scissor lift truck according to claim 1, characterized in that, It also includes a first relief valve and a second relief valve, which are connected in parallel and connected to two packing cylinders. The first relief valve controls the maximum pressure of the entire hydraulic system, and the second relief valve limits the maximum pressure of the steering circuit separately.

8. A hydraulic system for realizing dual-axle steering of a scissor lift truck according to claim 1, characterized in that, The master control solenoid valve and the lifting solenoid valve work together to control the lifting function: when both the master control solenoid valve and the lifting solenoid valve are energized, the oil enters the lifting circuit through the CSE port; when only the master control solenoid valve is energized, the oil flows to the steering control circuit.

9. A hydraulic system for realizing dual-axle steering of a scissor lift truck according to claim 1, characterized in that, The hydraulic system supports a crab-like movement mode: by synchronously controlling the deflection of the first and second steering cylinders in the same direction, the scissor lift can achieve diagonal translation.

10. A hydraulic system for realizing dual-axle steering of a scissor lift truck according to claim 1, characterized in that, The check valve is located at the outlet of the hydraulic pump to prevent hydraulic oil from flowing in the opposite direction.

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