lifting mechanism

Abstract

The application provides a lifting mechanism, which comprises a battery, an electric motor, a hydraulic pump, an oil tank, an oil cylinder, a working device and a proportional valve or an on-off valve. In an energy recovery mode, the hydraulic fluid drives the hydraulic pump to work in a hydraulic motor mode, and then drives the electric motor to work in a generator mode and charges the battery. Before the proportional valve or the on-off valve is switched from the one-way flow position to the two-way flow position, the hydraulic pump is operated to increase the pressure in the hydraulic pipeline between the hydraulic pump and the proportional valve or the on-off valve. By increasing the pressure in the hydraulic pipeline, the low-pressure hydraulic fluid in the pipeline can be prevented from increasing the pressure due to the communication with the high-pressure fluid in the oil cylinder and being compressed in volume at the moment when the proportional valve or the on-off valve is switched from the one-way flow position to the two-way flow position, so that the working device can be prevented from suddenly dropping, and the safety performance and the operation feeling of the lifting mechanism are improved.

Description

Technical Field

[0001] This invention relates to the field of mechanical technology, and more specifically to a lifting mechanism. Background Technology

[0002] Lifting mechanisms are widely used in high-altitude operations and cargo handling. With technological advancements, electrically driven lifting mechanisms are becoming increasingly prevalent. To extend battery life, the potential energy of the descending working device within the lifting mechanism is converted into electrical energy to charge the battery. However, this conversion of potential energy into electrical energy may pose certain safety hazards. Summary of the Invention

[0003] In view of this, the embodiments of this application aim to provide a lifting mechanism to improve the safety performance of the lifting mechanism. Before the proportional valve or switching valve switches from a unidirectional flow position to a bidirectional flow position, the hydraulic pump operates to increase the pressure in the hydraulic line between the hydraulic pump and the proportional valve or switching valve. By pressurizing the hydraulic line, a sudden drop in hydraulic fluid caused by a large pressure difference across the proportional valve or switching valve can be avoided at the moment of switching.

[0004] This application provides a lifting mechanism, which includes a battery, an electric motor, a hydraulic pump, an oil tank, an oil cylinder, and a working device. The lifting mechanism includes a lifting mode, a holding mode, and a lowering mode, wherein the lowering mode includes an energy recovery mode. In the energy recovery mode, hydraulic fluid drives the hydraulic pump to operate as a hydraulic motor, which in turn drives the electric motor to operate as a generator and charge the battery. A proportional valve or a switching valve is provided in the oil line between the hydraulic pump and the oil cylinder. The proportional valve or switching valve has a unidirectional flow position and a bidirectional flow position that allow hydraulic fluid to flow unidirectionally from the hydraulic pump to the oil cylinder. In the lifting and holding modes, the proportional valve or switching valve is in the unidirectional flow position. In the lowering mode, the proportional valve or switching valve is in the bidirectional flow position. Before the proportional valve or switching valve switches from the unidirectional flow position to the bidirectional flow position, the hydraulic pump operates to increase the pressure in the hydraulic line between the hydraulic pump and the proportional valve or switching valve.

[0005] After the hydraulic pump operates and increases the pressure in the hydraulic pipeline, the proportional valve or switching valve switches from a one-way flow position to a two-way flow position, switching the lifting mechanism to the lowering mode. This avoids the situation where the pressure difference on both sides of the proportional valve or switching valve is too large when switching from a one-way flow position to a two-way flow position, which would cause the volume of hydraulic fluid in the pipeline to decrease and thus cause the working device to suddenly drop. This avoids the user on the working device feeling like they are falling, and thus ensures that the working device descends smoothly after switching to the lowering mode.

[0006] In one embodiment, the lifting mechanism further includes a control device that, upon receiving a descent command, controls the hydraulic pump to operate to increase the pressure in the hydraulic line between the hydraulic pump and the proportional valve or the switching valve to be equal to the pressure of the cylinder or the pressure difference between the cylinder and the hydraulic line to be less than a predetermined value.

[0007] The smaller the pressure difference across the proportional valve or switching valve, the more stable the working device will be. Therefore, after receiving the descent command, the hydraulic pump will run to pressurize the hydraulic pipeline until the pressure difference across the proportional valve or switching valve is less than the predetermined value, which can further ensure that the working device will not experience a sudden drop and eliminate potential safety hazards.

[0008] In one embodiment, the lifting mechanism further includes a control device that controls a proportional valve or switching valve to switch from a unidirectional flow position to a bidirectional flow position when the pressure difference between the cylinder and the hydraulic line is less than a predetermined value.

[0009] In one embodiment, the lifting mechanism further includes a control device that controls a proportional valve or on / off valve to switch from a unidirectional flow position to a bidirectional flow position after the hydraulic pump has been running for a predetermined time.

[0010] The predetermined speed and predetermined time are stored in the control device in advance. The predetermined speed and predetermined time are determined by detecting the pressure difference on both sides of the proportional valve or the switching valve, and then by adjusting the lifting mechanism to determine the pressure increase value in the hydraulic pipeline connected to the lower end of the proportional valve and the switching valve at different speeds for the predetermined time of hydraulic pump operation. The speed and predetermined time of hydraulic pump operation are determined by continuous adjustment.

[0011] In one embodiment, a proportional valve or a switching valve is located on the hydraulic line between the hydraulic pump and the cylinder, close to the cylinder.

[0012] In one embodiment, the descent mode includes a non-energy recovery mode. When the proportional valve or switching valve is a proportional valve, in the energy recovery mode, the descent speed of the working device is controlled by the electric motor; in the non-energy recovery mode, the descent speed of the working device is set by the opening degree of the proportional valve or switching valve.

[0013] In one embodiment, the descent mode also includes a non-energy recovery mode; the lifting mechanism also includes a flow limiting valve disposed between the cylinder and the proportional valve or the on / off valve, the flow limiting valve being used to limit the maximum descent speed of the working device.

[0014] In this application, a flow limiting valve is used to provide throttling resistance to limit the maximum descent speed of the hydraulic fluid, thereby limiting the maximum descent speed of the working device and ensuring the safety of the lifting mechanism.

[0015] In one embodiment, the flow limiting valve is positioned close to the cylinder outlet.

[0016] This application ensures that, by installing a flow limiting valve at the cylinder outlet, the working device can descend smoothly even if a rupture occurs at any point in the hydraulic pipeline of the lifting mechanism, thus ensuring the safety of the lifting mechanism.

[0017] In one embodiment, the throttling resistance of the flow limiting valve in the second position is greater than that in the first position; when the pressure difference across the flow limiting valve is greater than a predetermined pressure difference, the flow limiting valve switches from the first position to the second position.

[0018] The position of the flow limiting valve is controlled by the pressure difference on both sides of the flow limiting valve. The flow limiting valve adjusts the maximum descent speed of the hydraulic fluid by switching between the first and second positions of the flow limiting valve, thereby adjusting the descent speed of the working device.

[0019] In one embodiment, the flow limiting valve is in a first position in energy recovery mode and in a second position in non-energy recovery mode.

[0020] In energy recovery mode, the pressure difference across the flow limiting valve is less than a predetermined pressure difference; in non-energy recovery mode, the pressure difference across the flow limiting valve is greater than the predetermined pressure difference. In this application, since the flow limiting valve includes a first throttling orifice of fixed size, the pressure difference across the flow limiting valve is positively correlated with the flow rate passing through the flow limiting valve. Therefore, the position of the flow limiting valve can be switched when the pressure difference (or flow rate) across the flow limiting valve is abnormal, ensuring a smooth descent of the working device.

[0021] In energy recovery mode, the potential energy of the hydraulic fluid needs to be converted into the kinetic energy of the electric motor, and then into electrical energy. Therefore, the throttling resistance between the hydraulic fluid in the cylinder and the hydraulic lines needs to be low to facilitate the conversion of the hydraulic fluid's potential energy into kinetic energy to drive the electric motor. In non-energy recovery mode, the potential energy is consumed at the throttling orifice and converted into heat energy. The hydraulic fluid flows slowly and uniformly to the oil tank to ensure a smooth descent of the working device. Therefore, assuming the lifting mechanism is functioning correctly, in energy recovery mode, the flow control valve is in the first position with low throttling resistance, while in non-energy recovery mode, the flow control valve is in the second position with high throttling resistance.

[0022] In one embodiment, the flow limiting valve includes a first throttling orifice and a selector valve connected together. The selector valve has a connected position and a throttling position where the second throttling orifice is active. When the selector valve is in the connected position, the flow limiting valve is in the first position; when the selector valve is in the throttling position, the flow limiting valve is in the second position.

[0023] In one embodiment, the size of the second throttling orifice is smaller than the size of the first throttling orifice.

[0024] When the pressure difference across the flow limiting valve is greater than the predetermined pressure difference, the selector valve switches from the connected position to the throttling position, that is, from the first throttling orifice to the second throttling orifice, thereby limiting the descent speed of the working device through the second throttling orifice.

[0025] In one embodiment, in energy recovery mode, the descent speed of the working device is controlled by an electric motor; in non-energy recovery mode, the maximum descent speed of the working device is set by a second throttle orifice.

[0026] In one embodiment, the selector valve further includes a spring, wherein the selector valve is in the connected position when the pressure difference across the flow limiting valve is less than a predetermined pressure difference set by the spring, and the selector valve is in the throttling position when the pressure difference across the flow limiting valve is greater than the predetermined pressure difference set by the spring.

[0027] In one embodiment, the flow-limiting valve includes a proportional valve capable of continuously adjusting the flow resistance.

[0028] In one embodiment, the maximum permissible opening of the proportional valve is set according to the real-time cylinder pressure based on pre-calibrated data; or it is set directly according to the maximum permissible cylinder pressure of the working device.

[0029] In one embodiment, the descent mode also includes a non-energy recovery mode, and the lifting mechanism also includes a throttle valve. In the energy recovery mode, the descent speed of the working device is controlled by a motor; in the non-energy recovery mode, the descent speed of the working device is set by the size of the orifice of the throttle valve; when the working device experiences abnormal descent, the maximum descent speed of the working device is set by a flow limiting valve.

[0030] In non-energy recovery mode, the descent speed of the hydraulic fluid can be controlled by a throttle valve. The flow control valve remains in the open position under normal operating conditions (including lifting mode, holding mode, energy recovery mode, and non-energy recovery mode), switching to the throttle position only in abnormal situations such as hydraulic line rupture. This configuration reduces the frequency of flow control valve switching and the duration it remains in the throttle position, thereby extending its service life and ensuring the safety of the entire lifting mechanism. Compared to flow control valves, throttle valves are less expensive and easier to replace; installing a throttle valve between the directional valve and the oil tank can further reduce costs.

[0031] In one embodiment, the lifting mechanism further includes a throttle valve. In both energy recovery mode and non-energy recovery mode, the flow limiting valve is in a first position, and when the working device experiences an abnormal descent, the flow limiting valve is in a second position.

[0032] In one embodiment, the lifting mechanism further includes a reversing valve for selectively connecting the cylinder to the hydraulic pump or the oil tank to switch between energy recovery mode and non-energy recovery mode, and a throttle valve is disposed between the reversing valve and the oil tank.

[0033] In this application, the cylinder and the hydraulic pump are connected in the energy recovery mode, and the cylinder and the oil tank are connected in the non-energy recovery mode.

[0034] In one embodiment, the lifting mechanism further includes a control device configured to switch the position of the directional valve under predetermined conditions to switch the cylinder from the connected hydraulic pump to the connected oil tank, thereby switching from an energy recovery mode to a non-energy recovery mode.

[0035] In one embodiment, the predetermined condition includes any one of the following: the battery charge is greater than a predetermined value; battery failure; motor failure; and other system failures.

[0036] In one embodiment, the lifting mechanism also includes a steering device, wherein a directional valve always connects one of the hydraulic pump and the oil tank to the steering device and the other to the oil cylinder.

[0037] In one embodiment, the lifting mechanism includes two or more hydraulic cylinders, and a corresponding flow limiting valve is provided close to the outlet of each hydraulic cylinder. Each flow limiting valve is connected to a proportional valve or a switching valve.

[0038] The lifting mechanism of this application includes two or more hydraulic cylinders, which can increase the maximum load capacity of the lifting mechanism.

[0039] In one embodiment, each flow limiting valve is connected to a proportional valve or a switching valve; the lifting mechanism also includes an overflow valve connected in parallel with the proportional valve or the switching valve.

[0040] In one embodiment, the lifting mechanism is an aerial work platform or a forklift.

[0041] This application provides a lifting mechanism in which, in energy recovery mode, hydraulic fluid drives a hydraulic pump to operate as a hydraulic motor, which in turn drives an electric motor to operate as a generator and charge a battery. In non-energy recovery mode, a flow limiting valve restricts the maximum descent speed of the working device. Before the proportional valve or switching valve switches from a unidirectional flow position to a bidirectional flow position, the hydraulic pump operates to increase the pressure in the hydraulic line between the hydraulic pump and the proportional valve or switching valve. By pressurizing the hydraulic line, the accelerated descent caused by a large pressure difference across the proportional valve or switching valve can be avoided at the moment the proportional valve or switching valve switches from a unidirectional flow position to a bidirectional flow position, thereby preventing sudden descent of the working device and improving the safety performance of the lifting mechanism. Attached Figure Description

[0042] Figure 1 The diagram shown is a schematic hydraulic principle diagram of a lifting mechanism provided in an embodiment of this application.

[0043] Figure 2 The diagram shown is a schematic circuit diagram of a lifting mechanism provided in an embodiment of this application.

[0044] Figure 3 The diagram shown is a schematic hydraulic principle diagram of a lifting mechanism provided in an embodiment of this application.

[0045] Explanation of reference numerals in the attached figures

[0046] 1-Flow limiting valve; 11-First throttle orifice; 12-Selector valve; 121-Second throttle orifice; 122-Spring; 2-Proportional valve or on / off valve; 21-One-way flow position; 22-Two-way flow position; 3-Directional control valve; 4-Electric motor; 5-Hydraulic pump; 6-Battery; 8-Cylinder; 7-Control device; 9-Oil tank; 10-Relief valve; 20-Steering device; 101-Throttle valve; 102-Pressure sensor. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Generally, lifting mechanisms include lifting, holding, and lowering modes. In lifting mode, the working device moves upward under the action of hydraulic cylinders; in holding mode, the working device remains essentially stationary; and in lowering mode, the working device moves downward. The lifting mechanism controls the height of the working device by switching between different modes, thus transferring goods or personnel carried by the working device from high to low or vice versa.

[0049] Because the battery capacity of the lifting mechanism is limited, it cannot meet the needs of all-day operation. Therefore, it needs to be charged during weekdays, limiting the working time of the lifting mechanism on weekdays. To improve the utilization rate of the electrically driven lifting mechanism, it is required that the charging mechanism not charge during weekdays and then charge the battery at night. To this end, the lowering mode of the lifting mechanism in this application embodiment includes an energy recovery mode, in which the potential energy of the lowering device of the lifting mechanism is converted into electrical energy to extend the battery's usage time.

[0050] However, lifting mechanisms with energy recovery modes still pose safety hazards during use. In holding mode, the pipeline pressure between the cylinder and the proportional valve or switching valve is high. The proportional valve or switching valve and the hydraulic pump are connected via a hydraulic pipeline, which is relatively long, and the pipeline pressure between them is low. When switching from holding mode to lowering mode, the proportional valve or switching valve instantly switches from a unidirectional flow position to a bidirectional flow position. This causes the high-pressure pipeline on one side of the proportional valve or switching valve to connect with the low-pressure pipeline on the other side, resulting in a sudden increase in pressure in the low-pressure pipeline. This compresses the hydraulic fluid in the low-pressure pipeline, causing the working device to suddenly descend, potentially leading to safety issues such as personnel falling or damage to goods.

[0051] In view of this, one embodiment of this application provides a lifting mechanism, which can at least solve the safety problem caused by the sudden descent of the working device when the proportional valve or switching valve switches from a unidirectional flow position to a bidirectional flow position.

[0052] It should be understood that the lifting mechanism in this application can be a mechanical device used for lifting, carrying goods, or for personnel working at heights, such as an aerial work platform or a forklift. In this embodiment, an aerial work platform is used as an example for illustration; specifically, the lifting mechanism is a scissor lift platform.

[0053] Figure 1 The diagram shown is a schematic hydraulic principle diagram of a lifting mechanism provided in an embodiment of this application. Figure 1 As shown, the lifting mechanism may include a steering system and a lifting system. This application primarily addresses the safety issues caused by the sudden descent of the working device of the lifting mechanism. To better illustrate the technical problem solved by this application, Figure 1 The image focuses on the hydraulic circuitry of the lifting system, omitting parts of the drive and steering systems.

[0054] like Figure 1 As shown, a lifting mechanism according to one embodiment of this application includes: a proportional valve or switching valve 2, a directional valve 3, an electric motor 4, a hydraulic pump 5, a battery 6, a hydraulic cylinder 8, an oil tank 9, and a working device (not shown). The hydraulic cylinder 8, the proportional valve or switching valve 2, the directional valve 3, the hydraulic pump 5, and the oil tank 9 are connected sequentially via hydraulic lines. The lifting mechanism also includes a steering device 20, which is connected to the hydraulic pump 5 or the oil tank 9 via the directional valve 3.

[0055] The lifting mechanism in this application includes a lifting mode, a holding mode, and a lowering mode. The lowering mode includes two modes: energy recovery mode and non-energy recovery mode.

[0056] Optionally, as another embodiment, the lifting mechanism may further include a flow limiting valve 1 disposed between the cylinder 8 and the proportional valve or on / off valve 2. The flow limiting valve 1 is used to provide throttling resistance to adjust the maximum flow rate of the hydraulic fluid in the hydraulic line. The throttling resistance of the flow limiting valve 1 in the second position is greater than the throttling resistance in the first position.

[0057] The proportional valve or on / off valve 2 includes a one-way flow position 21 that allows hydraulic fluid to flow unidirectionally from the hydraulic pump 5 to the flow control valve 1, and a two-way flow position 22. For example, the proportional valve or on / off valve 2 is a two-position, two-way valve.

[0058] The directional control valve 3 switches between energy recovery mode and non-energy recovery mode by selectively connecting the cylinder 8 to the hydraulic pump 5 or the oil tank 9. For example, the directional control valve 3 is a two-position four-way valve that connects one of the hydraulic pump 5 and the oil tank 9 to the steering device 20 and the other to the cylinder 8.

[0059] In lifting mode, the flow limiting valve 1 is in the first position, the proportional valve or switching valve 2 is in the one-way flow position 21 that allows hydraulic fluid to flow unidirectionally from the hydraulic pump 5 to the flow limiting valve 1, and the directional valve 3 is in the position that connects the hydraulic pump 5 and the cylinder 8. The oil tank 9, hydraulic pump 5, directional valve 3, proportional valve or switching valve 2, flow limiting valve 1 and cylinder 8 are connected sequentially through hydraulic lines. The hydraulic fluid in the oil tank 9 enters the cylinder 8 under the action of the hydraulic pump 5, pushing the telescopic rod in the cylinder 8 upward to raise the working device.

[0060] In holding mode, the positions of flow limiting valve 1 and proportional valve or switching valve 2 are the same as in lifting mode. The directional valve 3 is in the position that connects hydraulic pump 5 and cylinder 8 or in the position that connects oil tank 9 and cylinder 8. Hydraulic pump 5 stops working and the working device is held at a certain height.

[0061] In the energy recovery mode of the descent mode, the flow limiting valve 1 is in the first position with low flow resistance, the proportional valve or switching valve 2 is in the bidirectional flow position 22, and the directional valve 3 is in the position connecting the hydraulic pump 5 and the cylinder 8. The cylinder 8, flow limiting valve 1, proportional valve or switching valve 2, directional valve 3, hydraulic pump 5, and oil tank 9 are connected sequentially through hydraulic lines. The hydraulic fluid in the cylinder 8 flows sequentially through the flow limiting valve 1, proportional valve or switching valve 2, and directional valve 3, driving the hydraulic pump 5 to operate as a hydraulic motor before flowing into the oil tank 9, which in turn drives the motor 4 to operate as a generator and charge the battery 6. The speed of the hydraulic pump 5 is controlled by controlling the speed of the motor 4, thereby controlling the flow rate of the hydraulic fluid and the descent speed of the working device. In short, the descent speed of the lifting mechanism is controlled by the motor 4. Traditional fixed orifice designs set the maximum descent speed according to the maximum load, and the descent speed of the working device will inevitably be slower when unloaded / not fully loaded. By controlling the descent speed of the working device through the electric motor 4, it can be ensured that the descent speed can be maximized, whether it is fully loaded or unloaded / partially loaded, allowing for more flexible adjustment of the descent speed and maximizing work efficiency.

[0062] In the non-energy recovery mode of the descent mode, the flow limiting valve 1 is in the high flow resistance second position, the proportional valve or switching valve 2 is in the bidirectional flow position 22, and the directional valve 3 is in the position connecting the oil tank 9 and the oil cylinder 8. The oil cylinder 8, the flow limiting valve 1, the proportional valve or switching valve 2, the directional valve 3, and the oil tank 9 are connected sequentially through hydraulic lines. The hydraulic fluid in the oil cylinder 8 flows into the oil tank 9 after passing through the flow limiting valve 1, the proportional valve or switching valve 2, and the directional valve 3 in sequence.

[0063] The hydraulic pump 5 can operate as a hydraulic motor. In lifting mode, the hydraulic pump 5 rotates forward to pump hydraulic fluid from the oil tank 9 into the oil cylinder 8, thereby pushing the extension rod of the oil cylinder 8 upward to raise the working device. In the energy recovery mode of descent mode, the hydraulic pump 5 reverses under the action of hydraulic fluid potential energy to drive the motor 4 to operate as a generator to generate electricity.

[0064] Battery 6 can be a lithium-ion battery. On one hand, battery 6 provides electrical energy to the lifting mechanism, for example, in lifting mode, it provides electrical energy to drive motor 4. On the other hand, in energy recovery mode, battery 6 is charged to store the electrical energy generated by motor 4 (which operates as a generator in this mode).

[0065] Figure 2 The diagram shown is a schematic circuit diagram of a lifting mechanism provided in one embodiment of this application. Figure 1 and Figure 2 As shown, the lifting mechanism includes a control device 7, which is electrically connected to the battery 6, the motor 4, the reversing valve 3, and the proportional valve or switching valve 2.

[0066] The control device 7 may include one or more controllers, such as a motor controller, a valve controller, or a main controller that determines the motor speed / direction and valve based on operator input and control logic, as long as these functions are implemented.

[0067] like Figure 1 and Figure 2 As shown, the control device 7 is configured to enter the lifting mode in response to receiving a lifting command. This switches the lifting mechanism from the holding mode or the lowering mode to the lifting mode. Specifically, in response to receiving a lifting command, the control device 7 controls the proportional valve or switching valve 2 to switch to the one-way flow position 21, controls the directional valve 3 to be connected to the hydraulic cylinder 8 and the hydraulic pump 5, and controls the motor 4 to drive the hydraulic pump 5 to pump hydraulic fluid from the oil tank 9 into the hydraulic cylinder 8, thereby pushing the telescopic rod in the hydraulic cylinder 8 upwards, lifting the working device directly or indirectly connected to the telescopic rod.

[0068] The control device 7 is also configured to switch the proportional valve or on / off valve 2 to the bidirectional flow position 22 in response to receiving a descent command, thereby switching the lifting mechanism from the holding mode to the descent mode.

[0069] The control device 7 is also configured to switch to descent mode after increasing the pressure in the hydraulic lines in response to receiving a descent command. In holding mode, the pressure between the cylinder 8 and the proportional valve or switching valve 2 is higher, while the pressure in the line between the proportional valve or switching valve 2 and the hydraulic pump 8 is lower. Therefore, when switching from holding mode to descent mode, if the pressure in the line between the proportional valve or switching valve 2 and the hydraulic pump 8 is not increased beforehand, the high-pressure oil on the upper side will connect with the low-pressure line on the lower side the instant the proportional valve or switching valve 2 switches to the bidirectional flow position 22. This causes the pressure in the low-pressure line on the lower side to increase instantaneously, compressing the hydraulic fluid in the low-pressure line. The working device will then suddenly descend, giving the user on the working device a feeling of falling, which affects the user experience.

[0070] Specifically, increasing the pressure in the hydraulic lines can be achieved by increasing the pressure in the hydraulic line between the hydraulic pump 5 and the proportional valve or switching valve 2, so that the pressure difference between the hydraulic line pressure between the hydraulic pump 5 and the proportional valve or switching valve 2 and the pressure in the cylinder 8 is less than a predetermined value, or so that the hydraulic line pressure between the hydraulic pump 5 and the proportional valve or switching valve 2 and the pressure in the cylinder 8 are the same or substantially the same. The predetermined value can be determined based on factors such as the precision of the lifting mechanism. This avoids an excessive pressure difference across the proportional valve or switching valve 2 at the moment it switches from the unidirectional flow position 21 to the bidirectional flow position 22, which would cause the hydraulic fluid to descend rapidly, thus ensuring a smooth descent of the working device after switching to the descent mode.

[0071] Specifically, upon receiving a descent command, the control device 7 controls the hydraulic pump 5 to operate, thereby increasing the pressure in the hydraulic lines. When the pressure difference between the cylinder 8 and the hydraulic lines is less than a predetermined value, or when the hydraulic pump 5 has been operating for a predetermined time, the control device 7 controls the proportional valve or switching valve 2 to switch to the bidirectional flow position 22, so that the lifting mechanism switches to the descent mode.

[0072] For example, after receiving a descent command, the control device 7 controls the proportional valve or on / off valve 2 to switch from a one-way flow position 21 to a two-way flow position 22 after the hydraulic pump has been running for a predetermined time.

[0073] For example, after receiving a descent command, the control device 7 switches from the unidirectional flow position 21 to the bidirectional flow position 22 when the pressure difference between the upper and lower ends of the proportional valve or the switching valve is less than a predetermined value or equal to 0.

[0074] The control device 7 is configured to switch the position of the directional valve 3 under predetermined conditions, causing the cylinder 8 to switch from being connected to the hydraulic pump 5 to being connected to the oil tank 9, thereby switching from energy recovery mode to non-energy recovery mode. In other words, the position of the directional valve 3 is switched based on whether energy recovery is required by the lifting mechanism. Specifically, the predetermined conditions include any of the following: the battery 6 has a charge greater than a predetermined value, the battery 6 is faulty, the motor 4 is faulty, or other system circuit faults. The predetermined conditions can also be receiving control commands from the operator, allowing the operator to manipulate the working device as needed.

[0075] For example, when the battery 6 has a charge level greater than 80%, the control device 7 controls the lifting mechanism to switch from energy recovery mode to non-energy recovery mode. Specifically, charging the battery 6 when its charge level is greater than a predetermined value will cause the battery 6 to overheat and shorten its lifespan. Therefore, switching to non-energy recovery mode when the battery 6 has a charge level greater than the predetermined value can extend the lifespan of the battery 6 and reduce the operating cost of the lifting mechanism.

[0076] For example, when motor 4 fails, control device 7 switches the lifting mechanism from energy recovery mode to non-energy recovery mode. Specifically, in the event of a motor 4 failure, the hydraulic fluid descent speed cannot be controlled via motor 4 to control the descent speed of the working device. Therefore, switching to non-energy recovery mode ensures a smooth descent of the working device when motor 4 fails.

[0077] In one embodiment, the control device 7 is configured to switch from energy recovery mode to non-energy recovery mode according to a user input command.

[0078] The control device 7 is also configured to control the descent speed of the hydraulic fluid by controlling the resistance of the electric motor 4 in energy recovery mode.

[0079] like Figure 1As shown, the flow limiting valve 1 provides throttling resistance to limit the maximum descent rate of the hydraulic fluid, thereby limiting the maximum descent rate of the working device. Specifically, the flow limiting valve 1 has two states: a first position and a second position. The throttling resistance of the flow limiting valve 1 in the second position is greater than that in the first position. When the pressure difference across the flow limiting valve 1 exceeds a predetermined pressure difference, the flow limiting valve 1 switches from the first position to the second position. Thus, by switching the first and second positions of the flow limiting valve 1, the maximum descent rate of the hydraulic fluid is adjusted, thereby regulating the descent rate of the working device.

[0080] Furthermore, the position of the flow limiting valve 1 is adjusted according to the pressure difference across the flow limiting valve 1. Under normal circumstances, in energy recovery mode, the pressure difference across the flow limiting valve 1 is less than the predetermined pressure difference, and the flow limiting valve 1 is in the first position; in non-energy recovery mode, the pressure difference across the flow limiting valve 1 is greater than the predetermined pressure difference, and the flow limiting valve 1 is in the second position.

[0081] In special circumstances, such as when the downstream hydraulic hose breaks, the flow rate of hydraulic oil flowing out of cylinder 8 increases sharply, causing an abnormal pressure difference on both sides of flow control valve 1. When the pressure difference on both sides of flow control valve 1 is greater than the predetermined pressure difference, flow control valve 1 switches to the second position with greater throttling resistance to limit the flow rate of hydraulic fluid, thus preventing the working device from accelerating its descent under special circumstances.

[0082] The flow limiting valve 1 in this embodiment is positioned close to the outlet of the hydraulic cylinder 8, which improves the stability of the lifting mechanism. Specifically, if the flow limiting valve 1 and the hydraulic cylinder 8 are connected by a hydraulic line, the flow limiting valve 1 will not function if that hydraulic line ruptures, meaning it cannot limit the accelerated descent of the working device, threatening the safety of personnel on the working device. Therefore, by installing the flow limiting valve 1 at the outlet of the hydraulic cylinder 8, this application ensures that the flow limiting valve 1 functions even if any part of the hydraulic line ruptures, allowing the working device to descend smoothly and ensuring the safety of the lifting mechanism.

[0083] In energy recovery mode, the potential energy of the hydraulic fluid needs to be converted into the kinetic energy of the electric motor 4 and then into electrical energy. Therefore, the throttling resistance between the hydraulic fluid in cylinder 8 and the hydraulic lines needs to be small so that the potential energy of the hydraulic fluid can be converted into kinetic energy to drive the electric motor 4. In non-energy recovery mode, the potential energy is consumed in the throttling orifice and converted into heat energy. The hydraulic fluid flows slowly and uniformly to the oil tank 9 to ensure the smooth descent of the working device. Therefore, assuming no malfunction in the lifting mechanism, in energy recovery mode, the flow limiting valve 1 is in the first position with low throttling resistance, and in non-energy recovery mode, the flow limiting valve 1 is in the second position with high throttling resistance.

[0084] In one embodiment of this application, the flow limiting valve 1 includes a first throttling orifice 11 and a selector valve 12 connected together. The selector valve 12 includes a second throttling orifice 121, the size of which is smaller than that of the first throttling orifice 11. The flow limiting valve 1 has a connected position and a throttling position where the second throttling orifice 121 is active. The throttling resistance of the flow limiting valve 1 in the connected position is less than that in the throttling position. When the flow limiting valve 1 is in the first position, the selector valve 12 is in the connected position. When the flow limiting valve 1 is in the second position, the selector valve 12 is in the throttling position, and the maximum flow rate of the hydraulic fluid is limited by the second throttling orifice 121. That is, the maximum descent speed of the working device is limited by the second throttling orifice 121. This ensures the safety performance of the lifting mechanism.

[0085] In one embodiment of this application, the selector valve 12 further includes a spring 122. When the pressure difference across the flow limiting valve 1 is less than a predetermined pressure difference set by the spring 122, the selector valve 12 is in the connected position; when the pressure difference across the flow limiting valve 1 is greater than the predetermined pressure difference set by the spring 122, the selector valve 12 is in the throttling position. Specifically, a branch between the first throttling orifice 11 and the outlet of the cylinder 8 is connected to the side of the selector valve 12 away from the spring 122, and the side of the flow limiting valve 1 away from the cylinder is connected to the side of the selector valve 12 where the spring 122 is located via a branch. When the pressure difference across the flow limiting valve 1 is too large, the pressure difference of the hydraulic fluid across the selector valve 12 is greater than the elastic force of the spring 122 connected to the first side of the selector valve 12, thereby compressing the spring 122 and switching the selector valve 12 from the connected position to the throttling position.

[0086] By using a hydraulically controlled flow limiting valve 1 to limit the maximum descent speed of the working device, potential malfunctions such as power outages or sensor failures that may occur with solutions using electrically controlled valves and sensors can be avoided, resulting in a higher safety level and a longer service life.

[0087] Although the flow limiting valve 1 in this embodiment includes a first throttling orifice 11 and a selector valve 12, which can achieve automatic switching in response to differential pressure at a lower cost, a proportional valve can also be used as the flow limiting valve, as long as it has a connecting position and a throttling position. When using a proportional valve, the throttling resistance can be continuously adjusted, thereby continuously adjusting the maximum descent speed of the working device and improving control accuracy. When the flow limiting valve 1 is a proportional valve, its valve core position can be controlled according to the pressure in the cylinder detected by the pressure sensor. Specifically, the maximum allowable opening of the proportional valve can be set by calibration, thus limiting the maximum descent speed at that pressure. If the weight of the working device (platform) (corresponding to the cylinder pressure) is large, the maximum allowable opening of the proportional valve is small; if the platform weight is small, the maximum allowable opening of the proportional valve is correspondingly large. Of course, calibration is not required, and the maximum allowable opening of the proportional valve can be directly set according to the pressure of the platform's maximum allowable load.

[0088] It is understood that the terms "large" and "small" regarding throttling resistance mentioned in this invention are relative and do not limit the specific range of resistance. It is sufficient that the throttling resistance at the second position is greater than the throttling resistance at the first position (which can be zero).

[0089] It should be understood that the proportional valve or switching valve 2 can be either a proportional valve or a switching valve.

[0090] In one embodiment, when the proportional valve or switching valve 2 is a proportional valve, it can not only switch between the one-way flow position 21 (that is, the opening of the proportional valve is the minimum) and the two-way flow position 22 (that is, the opening of the proportional valve is the maximum), but also adjust the throttling resistance by adjusting the opening of the proportional valve, thereby adjusting the descent speed of the working device and improving the control accuracy.

[0091] Specifically, in the energy recovery mode of the descent mode, the proportional valve or switching valve 2 is in the bidirectional flow position 22, and the descent speed of the working device is controlled by the motor 4; in the non-energy recovery mode of the descent mode, the descent speed of the working device can be set by the opening degree of the proportional valve or switching valve 2; when the working device descents abnormally, the maximum descent speed of the working device is set by the flow limiting valve 1.

[0092] When the proportional valve or switching valve 2 is a proportional valve, even if the pipeline between the proportional valve or switching valve 2 and the oil tank 9 is ruptured, the proportional valve or switching valve 2 can still control the descent speed of the working device. If the hydraulic pipeline between the proportional valve or switching valve 2 and the flow limiting valve 1 is ruptured, and the proportional valve or switching valve 2 cannot control the descent speed of the working device, the flow limiting valve 1 controls the throttling resistance, thereby controlling the descent speed of the working device.

[0093] Figure 3 The diagram shown is a schematic hydraulic principle diagram of a lifting mechanism provided in an embodiment of this application. Figure 3 As shown, the difference between this embodiment and the previous embodiment is that the lifting mechanism in this embodiment also includes a throttle valve 101 disposed between the reversing valve 3 and the oil tank 9.

[0094] The specific position of the throttle valve 101 can be adjusted arbitrarily between the reversing valve 3 and the oil tank 9. For example... Figure 3As shown, the throttle valve 101 is located on the hydraulic line near the lower end of the directional valve 3. The orifice size of the throttle valve 101 is smaller than the size of the second throttle orifice 121. The throttle valve 101 can be a simple valve with a throttle orifice, or it can be provided by any valve that provides throttling function (such as a proportional valve). Specifically, the difference from the first embodiment is that, in non-energy recovery mode, the descent speed of the hydraulic fluid can be controlled by the throttle valve 101 (instead of the flow limiting valve 1). The flow limiting valve 1 is always in the connected position under normal operating conditions (including lifting mode, holding mode, energy recovery mode, and non-energy recovery mode), and only switches to the throttle position in abnormal situations such as hydraulic line rupture. With this setting, the switching frequency of the flow limiting valve 1 and the duration of the flow limiting valve 1 in the throttle position can be reduced, thereby extending the service life of the flow limiting valve 1 and ensuring the safety of the entire lifting mechanism. Compared with the flow limiting valve 1, the throttle valve 101 is lower in cost and easier to replace, and setting the throttle valve 101 between the directional valve 3 and the oil tank 9 can reduce costs. In lifting mode, holding mode, and energy recovery mode, the hydraulic fluid does not pass through the hydraulic pipeline between the directional valve 3 and the oil tank 9. The throttle valve 101 is located between the directional valve 3 and the oil tank 9 and will not affect the normal flow of hydraulic fluid in the lifting mechanism in lifting mode, holding mode, and energy recovery mode.

[0095] This embodiment shows two hydraulic cylinders 8, with a corresponding flow limiting valve 1 installed immediately adjacent to the outlet of each cylinder 8. Using two hydraulic cylinders 8 increases the maximum load of the lifting mechanism. The number and model of the hydraulic cylinders 8 can be adjusted adaptably according to the specific application scenario of the lifting mechanism.

[0096] In addition, an overflow valve 10 is provided in parallel with the proportional valve or the on / off valve 2.

[0097] It should be understood that the lifting mechanism can be adapted and adjusted based on the principles of the embodiments of this application as needed. Some components in the lifting mechanism can be removed or added, and the models of each component in the lifting mechanism can be adjusted as needed. In one embodiment, the steering system and the lifting system are controlled separately without switching through the reversing valve 3. In another embodiment, pressure sensors and speed sensors can be added to the lifting mechanism, and multiple hydraulic cylinders 8 can be used to increase the maximum load of the lifting mechanism.

[0098] From the foregoing disclosure, the accompanying drawings, and the claims, it will be understood that the lifting mechanism according to embodiments of the present invention has many possibilities and advantages compared to the prior art. Those skilled in the art will further recognize that further modifications and alterations can be made to the hydraulic unit according to the present invention without departing from the spirit and scope of the invention. Therefore, such modifications and alterations are within and covered by the claims. It should be further understood that the foregoing examples and embodiments are for illustrative purposes only, and various modifications, alterations, or combinations of embodiments thereof suggested to those skilled in the art should be included within the spirit and scope of this application.

Claims

1. A lifting mechanism, comprising: The system comprises a battery (6), an electric motor (4), a hydraulic pump (5), an oil tank (9), an oil cylinder (8), and a working device. The lifting mechanism includes a lifting mode, a holding mode, and a lowering mode. The lowering mode includes an energy recovery mode. In the energy recovery mode, hydraulic fluid drives the hydraulic pump (5) to operate as a hydraulic motor, which in turn drives the electric motor (4) to operate as a generator and charge the battery (6). The feature is that a proportional valve or switching valve (2) is provided in the oil line between the hydraulic pump (5) and the cylinder (8). The proportional valve or switching valve (2) has a one-way flow position (21) and a two-way flow position (22) that allow hydraulic fluid to flow unidirectionally from the hydraulic pump (5) to the cylinder (8). In the lifting mode and the holding mode, the proportional valve or switching valve (2) is in the one-way flow position (21). In the lowering mode, the proportional valve or switching valve (2) is in the two-way flow position (22). Before the proportional valve or switching valve (2) switches from the one-way flow position (21) to the two-way flow position (22), the hydraulic pump (5) operates to increase the pressure in the hydraulic line between the hydraulic pump (5) and the proportional valve or switching valve (2). The descent mode also includes a non-energy recovery mode; the lifting mechanism also includes a flow limiting valve (1), which is located between the oil cylinder (8) and the proportional valve or switching valve (2). The flow limiting valve (1) is used to limit the maximum descent speed of the working device. The lifting mechanism also includes a throttle valve (101). In the energy recovery mode, the descent speed of the working device is controlled by the electric motor (4). In the non-energy recovery mode, the descent speed of the working device is set by the size of the orifice of the throttle valve (101). When the working device experiences abnormal descent, the maximum descent speed of the working device is set by the flow limiting valve (1).

2. The lifting mechanism according to claim 1, characterized in that, It also includes control devices, When the control device receives a descent command, it controls the hydraulic pump (5) to operate so as to increase the pressure in the hydraulic line between the hydraulic pump (5) and the proportional valve or switching valve (2) to be equal to the pressure of the cylinder (8) or the pressure difference between the cylinder (8) and the hydraulic line to be less than a predetermined value.

3. The lifting mechanism according to claim 1, characterized in that, It also includes control devices, When the pressure in the hydraulic line between the hydraulic pump (5) and the proportional valve or switching valve (2) is increased to be equal to the pressure of the cylinder (8), or when the pressure difference between the cylinder (8) and the hydraulic line is less than a predetermined value, the control device controls the proportional valve or switching valve (2) to switch from the one-way flow position (21) to the two-way flow position (22).

4. The lifting mechanism according to claim 1, characterized in that, It also includes a control device that controls the proportional valve or switching valve (2) to switch from the unidirectional flow position (21) to the bidirectional flow position (22) after the hydraulic pump (5) has been running for a predetermined time.

5. The lifting mechanism according to claim 1, characterized in that, The proportional valve or switching valve (2) is located on the hydraulic pipeline between the hydraulic pump (5) and the cylinder (8) at a position close to the cylinder (8).

6. The lifting mechanism according to claim 1, characterized in that, The descent mode includes a non-energy recovery mode. When the proportional valve or switching valve (2) is a proportional valve, in the energy recovery mode, the descent speed of the working device is controlled by the electric motor (4). In the non-energy recovery mode, the descent speed of the working device is set by the opening degree of the proportional valve or the switching valve (2).

7. The lifting mechanism according to claim 1, characterized in that, The flow limiting valve (1) is positioned close to the outlet of the oil cylinder (8).

8. The lifting mechanism according to claim 1, characterized in that, The throttling resistance of the flow limiting valve (1) in the second position is greater than that in the first position; when the pressure difference across the flow limiting valve (1) is greater than a predetermined pressure difference, the flow limiting valve (1) switches from the first position to the second position.

9. The lifting mechanism according to claim 8, characterized in that, In the energy recovery mode, the flow limiting valve (1) is in the first position; in the non-energy recovery mode, the flow limiting valve (1) is in the second position.

10. The lifting mechanism according to any one of claims 1-9, characterized in that, The flow limiting valve (1) includes a first throttling orifice (11) and a selector valve (12) connected together. The selector valve (12) has a connected position and a throttling position in which the second throttling orifice (121) is active. When the selector valve (12) is in the connected position, the flow limiting valve (1) is in the first position; when the selector valve (12) is in the throttling position, the flow limiting valve (1) is in the second position.

11. The lifting mechanism according to claim 10, characterized in that, The size of the second throttling orifice (121) is smaller than the size of the first throttling orifice (11).

12. The lifting mechanism according to claim 11, characterized in that, In the energy recovery mode, the descent speed of the working device is controlled by the electric motor (4); in the non-energy recovery mode, the maximum descent speed of the working device is set by the second throttle orifice (121).

13. The lifting mechanism according to claim 10, characterized in that, The selector valve (12) also includes a spring (122). When the pressure difference across the flow limiting valve (1) is less than a predetermined pressure difference set by the spring (122), the selector valve (12) is in the connected position; when the pressure difference across the flow limiting valve (1) is greater than the predetermined pressure difference set by the spring (122), the selector valve (12) is in the throttling position.

14. The lifting mechanism according to any one of claims 7-9, characterized in that, The flow limiting valve (1) includes a proportional valve capable of continuously adjusting the flow resistance.

15. The lifting mechanism according to claim 14, characterized in that, The maximum allowable opening of the proportional valve is set according to the real-time cylinder pressure based on the pre-calibrated data; or it can be set directly according to the maximum allowable cylinder pressure of the working device.

16. The lifting mechanism according to claim 8, characterized in that, The lifting mechanism also includes a throttle valve (101). In both the energy recovery mode and the non-energy recovery mode, the flow limiting valve (1) is in the first position. When the working device experiences an abnormal descent, the flow limiting valve (1) is in the second position.

17. The lifting mechanism according to claim 1, characterized in that, The lifting mechanism also includes a reversing valve (3), which is used to selectively connect the cylinder (8) to the hydraulic pump (5) or the oil tank (9) to switch the energy recovery mode and the non-energy recovery mode. The throttle valve (101) is located between the reversing valve (3) and the oil tank (9).

18. The lifting mechanism according to claim 17, characterized in that, The lifting mechanism also includes a control device; The control device is configured to switch the position of the directional valve (3) under predetermined conditions to switch the cylinder (8) from being connected to the hydraulic pump (5) to being connected to the oil tank (9) in order to switch from the energy recovery mode to the non-energy recovery mode.

19. The lifting mechanism according to claim 18, characterized in that, The predetermined conditions include any one of the following: the battery (6) has a charge greater than a predetermined value; the battery (6) is faulty; the motor (4) is faulty; and other system faults.

20. The lifting mechanism according to claim 17, characterized in that, The lifting mechanism also includes a steering device (20), and the reversing valve (3) always connects one of the hydraulic pump (5) and the oil tank (9) to the steering device (20) and the other to the oil cylinder (8).

21. The lifting mechanism according to claim 1, characterized in that, The lifting mechanism includes two or more hydraulic cylinders (8), and a corresponding flow limiting valve (1) is provided close to the outlet of each hydraulic cylinder (8). Each flow limiting valve (1) is connected to the proportional valve or the switching valve (2).

22. The lifting mechanism according to claim 1, characterized in that, The lifting mechanism also includes an overflow valve (10) connected in parallel with the proportional valve or switching valve (2).

23. The lifting mechanism according to claim 1, characterized in that, The lifting mechanism is an aerial work platform or a forklift.

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