Hydraulic system and working machine

Abstract

The utility model relates to the field of hydraulic pressure, and discloses a hydraulic system and an operation machine. The hydraulic system comprises a driving oil cylinder and an auxiliary oil cylinder which are both used for being connected with the movable arm and driving the movable arm to swing. The oil pump is connected with the driving oil cylinder and can supply oil to the driving oil cylinder; the number of the energy storage devices is at least two, the energy storage devices are connected with the pressure cavity of the auxiliary oil cylinder through the corresponding first control valves, and the first control valves are used for controlling connection and disconnection of the energy storage devices and the auxiliary oil cylinder. When the movable arm is in different swing ranges, auxiliary driving force can be provided by different energy storage devices, and due to the fact that the energy storage devices are mutually independent, when the movable arm works in the common swing range, the problem that the pressure of the corresponding energy storage devices is reduced due to the fact that part of pressure needs to be divided to drive the movable arm to penetrate through the lower swing range does not exist. And the energy storage device can better provide auxiliary driving force for the movable arm in a common swinging range.

Description

Technical Field

[0001] The utility model relates to the technical field of hydraulics, in particular to a hydraulic system and a working machine. Background Art

[0002] During the operation of a working machine such as an excavator, the lifting and lowering of the boom is controlled by a driving oil cylinder. During the lowering process of the boom, a large amount of gravitational potential energy is released, and the gravitational potential energy of the boom is dissipated through the overflow action of the overflow valve in the hydraulic system. This process generates a large amount of heat, causing the temperature of the hydraulic system to rise.

[0003] In the related art, an accumulator is used to recover the gravitational potential energy of the boom during the lowering process. The swing range of the boom generally includes an upper swing range, a common swing range, and a lower swing range that are sequentially distributed from top to bottom. The accumulator is used to recover the gravitational potential energy of the boom within the entire swing range.

[0004] The working time of the boom within the common swing range is relatively long, and when the boom is operating within the common swing range, the accumulator always needs to allocate part of its energy to drive the boom through the lower swing range, causing the pressure of the accumulator to drop, resulting in a decrease in the driving effect of the accumulator within the common swing range. Summary of the Utility Model

[0005] In view of this, the utility model provides a hydraulic system and a working machine to solve or improve the problem that the driving effect of the accumulator decreases within the common swing range of the boom in the related art.

[0006] In a first aspect, the utility model provides a hydraulic system, including:

[0007] A driving oil cylinder and an auxiliary oil cylinder, both of which are used to be connected to the boom and drive the boom to swing;

[0008] An oil pump, connected to the driving oil cylinder and capable of supplying oil to the driving oil cylinder;

[0009] An energy storage device and a first control valve. The number of the energy storage devices is set to at least two, and the energy storage devices are all connected to the pressure chamber of the auxiliary oil cylinder through the corresponding first control valves. The first control valve is used to control the on-off between the energy storage device and the auxiliary oil cylinder;

[0010] Wherein, the energy storage device is used to store the pressure oil discharged from the auxiliary oil cylinder or supply pressure oil to the auxiliary oil cylinder.

[0011] In an optional embodiment, the hydraulic system further includes a first one-way valve. The liquid inlet of the first one-way valve is connected to the fuel tank, and the liquid outlet of the first one-way valve is connected to the pressure chamber of the auxiliary oil cylinder.

[0012] In an alternative embodiment, the first control valve includes three working positions;

[0013] Wherein, in the first working position, the first control valve disconnects the energy storage device from the auxiliary oil cylinder; in the second working position, the first control valve conducts unidirectionally from the energy storage device to the auxiliary oil cylinder; in the third working position, the first control valve conducts unidirectionally from the auxiliary oil cylinder to the energy storage device.

[0014] In an alternative embodiment, the first control valve is communicatively connected to the operating assembly of the drive oil cylinder, and the first control valve switches working positions in response to the operation signal of the operating assembly.

[0015] In an alternative embodiment, the hydraulic system further includes a relief valve. The inlet of the relief valve is connected to the pressure chamber of the auxiliary oil cylinder, and the outlet of the relief valve is connected to the oil tank.

[0016] In an alternative embodiment, the hydraulic system further includes a pressure detection device. The pressure detection device is connected to the pressure chamber of the auxiliary oil cylinder and is used to detect the pressure value of the pressure chamber of the auxiliary oil cylinder. The relief valve is set as an adjustable relief valve.

[0017] In an alternative embodiment, the hydraulic system further includes a second control valve. The oil pump is connected to the pressure chamber of the auxiliary oil cylinder through the second control valve, and the second control valve is used to control the connection and disconnection between the oil pump and the auxiliary oil cylinder.

[0018] In an alternative embodiment, the hydraulic system further includes a second check valve. The second control valve is connected to the pressure chamber of the auxiliary oil cylinder through the second check valve, and the conduction direction of the second check valve is from the second control valve to the auxiliary oil cylinder.

[0019] In an alternative embodiment, the number of the drive oil cylinders is set to two. The two drive oil cylinders are respectively arranged on both sides of the boom, and the auxiliary oil cylinder is arranged between the two drive oil cylinders.

[0020] In a second aspect, the present invention further provides a working machine, including a boom and the hydraulic system as described above.

[0021] For the hydraulic system provided by the present invention, within different swing ranges of the boom, different energy storage devices can provide auxiliary driving forces. Since the energy storage devices are independent of each other, when the boom works in the common swing range, the corresponding energy storage device does not have the problem that the pressure of the energy storage device drops due to the need to divide part of the pressure to drive the boom through the lower swing range, so that the energy storage device can better provide auxiliary driving force for the boom in the common swing range.

[0022] The working machine provided by the present utility model includes a hydraulic system, and thus includes all the above advantages of the hydraulic system at the same time. Description of the Drawings

[0023] In order to more clearly illustrate the specific embodiments of the present utility model or the technical solutions in the related art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the related art. Obviously, the drawings in the following description are some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 It is a schematic diagram of the swing range of the boom in the embodiment of the present utility model;

[0025] Figure 2 It is a schematic diagram of the structure of the hydraulic system in the embodiment of the present utility model;

[0026] Figure 3 It is a schematic diagram of the relative position relationship between the driving oil cylinder and the auxiliary oil cylinder in the embodiment of the present utility model;

[0027] Figure 4 It is a schematic diagram of the state of the energy storage device when the boom swings to the upper limit position of the upper swing range in the embodiment of the present utility model;

[0028] Figure 5 It is a schematic diagram of the state of the energy storage device when the boom swings to the lower limit position of the lower swing range in the embodiment of the present utility model;

[0029] Figure 6 It is a schematic diagram of the state of the energy storage device when the boom swings to the lower limit position of the common swing range in the embodiment of the present utility model.

[0030] Explanation of the Reference Numerals in the Drawings:

[0031] 1. Driving oil cylinder; 2. Auxiliary oil cylinder; 3. Boom; 4. Oil pump; 5. Energy storage device; 6. First control valve; 601. First working position; 602. Second working position; 603. Third working position; 7. First one-way valve; 8. Relief valve; 9. Pressure detection device; 10. Second control valve; 11. Second one-way valve; a. Upper swing range; b. Common swing range; c. Lower swing range. Detailed Embodiments

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Apparently, the described embodiments are some, but not all, of the embodiments of the present utility model. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0033] In the related art, an accumulator is used to recover the gravitational potential energy of the boom during its downward movement. The swing range of the boom in the vertical direction generally includes an upper swing range a, a common swing range b, and a lower swing range c, which are distributed in sequence from top to bottom. The accumulator is used to recover the gravitational potential energy of the boom within the entire swing range.

[0034] The working duration of the boom within the common swing range b is relatively long. And when the boom is working within the common swing range b, the accumulator always needs to allocate part of its energy to drive the boom through the lower swing range c, causing the pressure of the accumulator to drop, and resulting in a decrease in the driving effect of the accumulator within the common swing range b.

[0035] To solve or improve the technical problem that the driving effect of the accumulator decreases within the common swing range of the boom in the related art, an embodiment of the present utility model provides a hydraulic system and a working machine.

[0036] The following will be combined with Figures 1 to 6 , to describe the hydraulic system provided in the embodiments of the present utility model.

[0037] Specifically, the hydraulic system includes a driving oil cylinder 1, an auxiliary oil cylinder 2, an oil pump 4, an energy storage device 5, and a first control valve 6.

[0038] Among them, both the driving oil cylinder 1 and the auxiliary oil cylinder 2 are used to be connected to the boom 3 and drive the boom 3 to swing. Specifically, the boom 3 is swingably connected to the frame of the working machine. The two ends of the driving oil cylinder 1 are respectively hinged to the frame and the boom 3, and the two ends of the auxiliary oil cylinder 2 are respectively hinged to the frame and the boom 3. For example, the boom 3 is swingably connected to the rotating platform of the frame.

[0039] The oil pump 4 is connected to the driving oil cylinder 1 and can supply oil to the driving oil cylinder 1. For example, the oil pump 4 is connected to the driving oil cylinder 1 through a corresponding control valve and supplies oil to the driving oil cylinder 1 through the control valve, and the control valve can control the telescopic movement of the driving oil cylinder 1.

[0040] The number of energy storage devices 5 is set to at least two. For example, the energy storage device 5 can be set as an accumulator. Each energy storage device 5 is connected to the pressure chamber of the auxiliary oil cylinder 2 through a corresponding first control valve 6. Among them, the pressure chamber of the auxiliary oil cylinder 2 refers to the oil chamber that can make the auxiliary oil cylinder 2 extend when pressure oil is introduced. The first control valve 6 is set as a reversing valve, such as an electromagnetic reversing valve or a hydraulically controlled reversing valve. The first control valve 6 is used to control the on-off between the energy storage device 5 and the auxiliary oil cylinder 2, and the first control valves 6 corresponding to each energy storage device 5 can be independently controlled respectively.

[0041] Among them, the energy storage device 5 is used to store the pressure oil discharged from the auxiliary oil cylinder 2 or supply pressure oil to the auxiliary oil cylinder 2. Specifically, when the energy storage device 5 supplies pressure oil to the auxiliary oil cylinder 2, the auxiliary oil cylinder 2 extends, so as to drive the boom 3 to lift. During the lowering process of the boom 3, the auxiliary oil cylinder 2 is compressed, and the pressure oil discharged from the auxiliary oil cylinder 2 enters the energy storage device 5 and is stored by the energy storage device 5. That is, when the boom 3 is lifted, the energy storage device 5 can provide auxiliary driving force for the boom 3 through the auxiliary oil cylinder 2, reduce the load of the driving oil cylinder 1, and further reduce the load of the oil pump 4, achieving the effect of energy conservation and emission reduction. When the boom 3 is lowered, the energy storage device 5 can recover the gravitational potential energy of the boom 3 through the auxiliary oil cylinder 2.

[0042] In this embodiment, at least two energy storage devices 5 can be used to recover the gravitational potential energy of the boom 3 within the entire swing range. For example, during the process of the boom 3 descending to the lowest position, the first control valves 6 of all the energy storage devices 5 are opened, so that all the energy storage devices 5 can store energy, and the pressures of each energy storage device 5 are the same. In this way, at least two energy storage devices 5 can store energy simultaneously, reducing the energy storage time, thereby improving the energy storage efficiency of the energy storage device 5 during the lowering process of the boom 3 and avoiding the problem that the lowering speed of the boom 3 is too slow, which affects the working efficiency.

[0043] To facilitate the description of the working principle of the hydraulic system, it is assumed that the energy storage device 5 includes a first energy storage device and a second energy storage device. When the boom 3 operates in the lower swing range c, the first energy storage device can be used to provide lifting power for the boom 3, and the first energy storage device can store the gravitational potential energy of the boom 3 within the lower swing range c. When the boom 3 operates in the common swing range b, the energy of the first energy storage device can be released to drive the boom 3 to move to the lower limit position of the common swing range b, and then the second energy storage device can be used to provide lifting power for the boom 3 and store the gravitational potential energy of the boom 3 within the common swing range b. That is, within different swing ranges of the boom 3, different energy storage devices 5 can provide auxiliary driving forces. Since the first energy storage device and the second energy storage device are independent of each other, when the boom 3 operates in the common swing range b, there is no problem that the pressure of the corresponding energy storage device 5 decreases due to the need to divert part of the pressure to drive the boom 3 through the lower swing range c, enabling the energy storage device 5 to better provide auxiliary driving force for the boom 3 within the common swing range b.

[0044] Regarding the situation where the boom 3 operates in the upper swing range a, since the working duration in the upper swing range a is relatively short, the second energy storage device can directly provide the auxiliary driving force. Alternatively, a third energy storage device can also be set to provide the auxiliary driving force, that is, the first energy storage device, the second energy storage device, and the third energy storage device respectively provide auxiliary driving forces within the lower swing range c, the common swing range b, and the upper swing range a.

[0045] In summary, within different swing ranges of the boom 3, different energy storage devices 5 can provide auxiliary driving forces. Since the energy storage devices 5 are independent of each other, when the boom 3 operates in the common swing range b, there is no problem that the pressure of the corresponding energy storage device 5 decreases due to the need to divert part of the pressure to drive the boom 3 through the lower swing range c, enabling the energy storage device 5 to better provide auxiliary driving force for the boom 3 within the common swing range b.

[0046] In addition, by setting at least two energy storage devices 5, when one or some of them are damaged or need to be overhauled, the remaining energy storage devices 5 can provide auxiliary driving forces or recover energy, improving the stability of the hydraulic system. And by setting at least two energy storage devices 5, the energy storage efficiency can be improved and the influence on the lowering speed of the boom 3 can be reduced.

[0047] In some embodiments provided by the present utility model, the hydraulic system further includes a first one-way valve 7.

[0048] Wherein, the liquid inlet of the first one-way valve 7 is connected to the fuel tank, and the liquid outlet of the first one-way valve 7 is connected to the pressure chamber of the auxiliary oil cylinder 2. That is, the conduction direction of the first one-way valve 7 is from the fuel tank to the auxiliary oil cylinder 2.

[0049] In this embodiment, during the normal working process, the hydraulic oil of the energy storage device 5 and the auxiliary oil cylinder 2 cannot return to the fuel tank through the first directional valve, ensuring that the energy storage or energy release of the energy storage device 5 can proceed normally. When the energy storage device 5 is damaged or the first control valve 6 is damaged, resulting in the inability of the hydraulic oil of the energy storage device 5 to enter the auxiliary oil cylinder 2, when the boom 3 is lifted to drive the auxiliary oil cylinder 2 to extend, the auxiliary oil cylinder 2 can suck oil from the fuel tank through the first check valve 7, avoiding the problem of damage caused by the generation of negative pressure or vacuum inside the auxiliary oil cylinder 2.

[0050] In some embodiments provided by the present utility model, the first control valve 6 includes three working positions, namely the first working position 601, the second working position 602, and the third working position 603.

[0051] Among them, in the first working position 601, the first control valve 6 disconnects the energy storage device 5 from the auxiliary oil cylinder 2. In the second working position 602, the first control valve 6 conducts unidirectionally from the energy storage device 5 to the auxiliary oil cylinder 2. In the third working position 603, the first control valve 6 conducts unidirectionally from the auxiliary oil cylinder 2 to the energy storage device 5.

[0052] In this embodiment, when the boom 3 is lifted, the first control valve 6 can be switched to the second working position 602 so that the pressurized oil in the energy storage device 5 can enter the auxiliary oil cylinder 2. When the boom 3 descends, the first control valve 6 can be switched to the third working position 603 so that the pressurized oil in the auxiliary oil cylinder 2 can enter the energy storage device 5. When the working machine stops working or the boom 3 needs to be hovered, the first control valve 6 can be switched to the first working position 601. At this time, the pressurized oil of the energy storage device 5 will not enter the auxiliary oil cylinder 2, and the pressurized oil of the auxiliary oil cylinder 2 will not enter the energy storage device 5, so that the boom 3 can stop more stably.

[0053] In some embodiments provided by the present utility model, the first control valve 6 is communicatively connected to the operating assembly of the drive oil cylinder 1, and the first control valve 6 switches working positions in response to the operation signal of the operating assembly. The operating assembly is used to control the telescoping of the drive oil cylinder 1.

[0054] Optionally, the operation signal of the operating assembly can be an electrical signal. Correspondingly, the first control valve 6 is an electromagnetic directional valve. Or, the operation signal of the operating assembly can also be pilot oil. Correspondingly, the first control valve 6 is a hydraulically controlled directional valve.

[0055] Optionally, when the control component controls the driving oil cylinder 1 to extend, the first control valve 6 switches to the second working position 602 in response to the control signal of the control component; when the control component controls the driving oil cylinder 1 to retract, the first control valve 6 switches to the third working position 603 in response to the control signal of the control component; when the control component controls the driving oil cylinder 1 to stop, the first control valve 6 switches to the first working position 601 in response to the control signal of the control component.

[0056] In this embodiment, the first control valve 6 switches the working position in response to the operation signal of the control component, so that the energy storage device 5 can store the gravitational potential energy of the boom 3 based on the operation of the control component, or provide an auxiliary driving force for the boom 3, so that the energy storage device 5 can drive the auxiliary oil cylinder 2 to act before or at the same time as the driving oil cylinder 1 acts, with a faster response.

[0057] In some embodiments provided by the present utility model, the hydraulic system further includes an overflow valve 8. The inlet of the overflow valve 8 is connected to the pressure chamber of the auxiliary oil cylinder 2, and the outlet of the overflow valve 8 is connected to the fuel tank.

[0058] In this embodiment, when the oil pressure in the pressure chamber of the auxiliary oil cylinder 2 is too high, oil can be drained to the fuel tank through the overflow valve 8 to prevent the pressure of the auxiliary oil cylinder 2 from being too high, which may cause damage to the auxiliary oil cylinder 2 or other components.

[0059] In some embodiments provided by the present utility model, the hydraulic system further includes a pressure detection device 9. The pressure detection device 9 is connected to the pressure chamber of the auxiliary oil cylinder 2 and is used to detect the pressure value of the pressure chamber of the auxiliary oil cylinder 2. The overflow valve 8 is set as an adjustable overflow valve.

[0060] In this embodiment, the pressure value of the auxiliary oil cylinder 2 can be obtained through the pressure detection device 9, so that the auxiliary driving force of the auxiliary oil cylinder 2 can be calculated based on the pressure value. By setting the overflow valve 8 as an adjustable overflow valve 8, the maximum auxiliary driving force of the auxiliary oil cylinder 2 can be adjusted by adjusting the overflow valve 8.

[0061] In some embodiments provided by the present utility model, the hydraulic system further includes a second control valve 10. The oil pump 4 is connected to the pressure chamber of the auxiliary oil cylinder 2 through the second control valve 10, and the second control valve 10 is used to control the on-off between the oil pump 4 and the auxiliary oil cylinder 2.

[0062] In this embodiment, the energy storage device 5 or the auxiliary oil cylinder 2 can be replenished with oil through the oil pump 4.

[0063] In some embodiments provided by the present utility model, the hydraulic system further includes a second one-way valve 11. The second control valve 10 is connected to the pressure chamber of the auxiliary oil cylinder 2 through the second one-way valve 11, and the conduction direction of the second one-way valve 11 is from the second control valve 10 to the auxiliary oil cylinder 2.

[0064] In this embodiment, when it is necessary to replenish the energy storage device 5 or the auxiliary oil cylinder 2 with oil, the second control valve 10 is opened, and the oil from the oil pump 4 can enter the energy storage device 5 or the auxiliary oil cylinder 2 through the second control valve 10 and the second one-way valve 11. After the replenishment is completed, the second control valve 10 is closed. The oil in the energy storage device 5 and the auxiliary oil cylinder 2 is blocked by the second one-way valve 11 and the second control valve 10 and will not return to the oil pump 4. By setting the second one-way valve 11, on the one hand, it can prevent the problem of damage to the second control valve 10 caused by excessive oil pressure. On the other hand, the dual sealing effect of the second one-way valve 11 and the second control valve 10 can better avoid the problem of oil leakage.

[0065] In some embodiments provided by the present utility model, the number of driving oil cylinders 1 is set to two. The two driving oil cylinders 1 are respectively arranged on both sides of the boom 3, and the auxiliary oil cylinder 2 is arranged between the two driving oil cylinders 1.

[0066] In this embodiment, by arranging the two driving oil cylinders 1 on both sides of the boom 3 and arranging the auxiliary oil cylinder 2 between the two driving oil cylinders 1, the forces on both sides of the boom 3 are balanced, and the auxiliary oil cylinder 2 and the driving oil cylinder 1 can jointly drive the boom 3 to lift.

[0067] An embodiment of the present utility model also provides a working machine.

[0068] Specifically, the working machine includes a boom 3 and the hydraulic system as described above.

[0069] The working machine includes a hydraulic system, and thus also includes all the above advantages of the hydraulic system, so it will not be elaborated here.

[0070] It should be noted that the hydraulic system includes but is not limited to excavators, loaders, and cranes.

[0071] Although the embodiments of the present utility model have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present utility model, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A hydraulic system, characterized in that, Comprising: A driving oil cylinder (1) and an auxiliary oil cylinder (2), both of which are used to be connected to the boom (3) and drive the boom (3) to swing; An oil pump (4), connected to the driving oil cylinder (1) and capable of supplying oil to the driving oil cylinder (1); An energy storage device (5) and a first control valve (6), the number of the energy storage devices (5) is set to be at least two, and the energy storage devices (5) are all connected to the pressure chamber of the auxiliary oil cylinder (2) through the corresponding first control valves (6), and the first control valve (6) is used to control the on-off between the energy storage device (5) and the auxiliary oil cylinder (2); Wherein, the energy storage device (5) is used to store the pressure oil discharged by the auxiliary oil cylinder (2) or supply pressure oil to the auxiliary oil cylinder (2).

2. The hydraulic system according to claim 1, wherein The hydraulic system further includes a first one-way valve (7), the inlet of the first one-way valve (7) is connected to the fuel tank, and the outlet of the first one-way valve (7) is connected to the pressure chamber of the auxiliary oil cylinder (2).

3. The hydraulic system according to claim 1, wherein, The first control valve (6) includes three working positions; Wherein, in the first working position (601), the first control valve (6) disconnects the energy storage device (5) from the auxiliary oil cylinder (2), in the second working position (602), the first control valve (6) conducts unidirectionally from the energy storage device (5) to the auxiliary oil cylinder (2), and in the third working position (603), the first control valve (6) conducts unidirectionally from the auxiliary oil cylinder (2) to the energy storage device (5).

4. The hydraulic system according to claim 3, characterized in that, The first control valve (6) is communicatively connected to the operating component of the driving oil cylinder (1), and the first control valve (6) switches the working position in response to the operation signal of the operating component.

5. The hydraulic system according to claim 1, characterized in that, The hydraulic system further includes a relief valve (8), the inlet of the relief valve (8) is connected to the pressure chamber of the auxiliary oil cylinder (2), and the outlet of the relief valve (8) is connected to the fuel tank.

6. The hydraulic system according to claim 5, characterized in that, The hydraulic system further includes a pressure detection device (9), the pressure detection device (9) is connected to the pressure chamber of the auxiliary oil cylinder (2) and is used to detect the pressure value of the pressure chamber of the auxiliary oil cylinder (2), and the relief valve (8) is set as an adjustable relief valve.

7. The hydraulic system according to claim 1, wherein, The hydraulic system further includes a second control valve (10), the oil pump (4) is connected to the pressure chamber of the auxiliary oil cylinder (2) through the second control valve (10), and the second control valve (10) is used to control the on-off between the oil pump (4) and the auxiliary oil cylinder (2).

8. The hydraulic system according to claim 7, characterized in that, The hydraulic system further includes a second one-way valve (11), the second control valve (10) is connected to the pressure chamber of the auxiliary oil cylinder (2) through the second one-way valve (11), and the conduction direction of the second one-way valve (11) is from the second control valve (10) to the auxiliary oil cylinder (2).

9. The hydraulic system according to claim 1, wherein The number of the driving oil cylinders (1) is set to be two, the two driving oil cylinders (1) are respectively arranged on both sides of the boom (3), and the auxiliary oil cylinder (2) is arranged between the two driving oil cylinders (1).

10. An earthmoving machine, characterized in that, Comprising a boom (3) and the hydraulic system according to any one of claims 1-9.

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