Hydraulic system for a lifting device

Abstract

Hydraulic system for a hydraulic lifting device (1) comprising: - at least one hydraulically piloted valve (2) for controlling the supply of hydraulic fluid to at least one hydraulic consumer (11) of the hydraulic lifting device (1), and - at least one control element (4) for hydraulically piloting the valve (2), wherein the control element (4) is fluidly connected to the hydraulically piloted valve (2) via at least one pilot line (5, 6), and the switching position of the at least one hydraulically piloted valve (2) can be controlled via the at least one pilot line (5, 6) by supplying hydraulic fluid through the control element (4), wherein - in the at least one pilot line (5, 6) between the control element (4) and the at least one hydraulically piloted valve (2) there is at least one reducing element (7) effective in at least one direction, preferably in two directions.8) is arranged and - at least one hydraulic pressure accumulator (9, 10) is fluid-conductingly connected to at least one pilot line (5, 6).

Description

[0001] The invention relates to a hydraulic system for a lifting device having the features of the preamble of claim 1, a hydraulic lifting device having such a hydraulic system and a vehicle having such a lifting device.

[0002] State-of-the-art hydraulic systems for lifting devices with hydraulically pilot-operated valves are prone to resonance phenomena in parts of the lifting device when subject to rapidly changing control inputs. For example, when an actuator is actuated by a hydraulically pilot-operated valve of such a lifting device, this can lead to undesirable oscillation of a crane arm of the lifting device driven by the actuator. With hydraulically pilot-operated valves, such oscillation can, in turn, directly impact the control element and thus lead to uncontrollable oscillation of parts of the lifting device. To bring the lifting device back under control, it must be stopped briefly, which interrupts operation. This problem can occur particularly with decreasing viscosity at higher temperatures of the hydraulic fluid.

[0003] Measures known in the prior art to prevent such oscillation include electronic detection of the control signals emitted by a user and appropriate signal processing for electronically supported implementation of the pilot control. The use of vibration dampers for parts of the lifting device is also known. These dampers disadvantageously increase the loads on the lifting device's actuators by inhibiting mobility, and their breakaway torque can also lead to resonance phenomena. Such measures known in the prior art also incur additional costs and increase the maintenance effort and susceptibility to failure of the hydraulic system and the lifting device.

[0004] US 5 034 892 A discloses a device for suppressing vibrations and wobbly movements when driving a mobile crane according to the preamble of claim 1.

[0005] An operating mode selector switches between a driving mode with active vibration suppression and a working mode. The object of the invention is to provide a hydraulic system, a hydraulic lifting device, and a vehicle with such a hydraulic lifting device in which the aforementioned problems do not occur. In particular, a simple and low-maintenance hydraulic system is to be provided.

[0006] This object is achieved by a hydraulic system having the features of claim 1, a hydraulic lifting device having such a hydraulic system, and a vehicle having such a lifting device. Advantageous embodiments of the invention are defined in the dependent claims.

[0007] The hydraulic system according to the invention can be suitable for a hydraulic lifting device and can comprise at least one valve hydraulically piloted with hydraulic fluid. Such a valve can control the supply of hydraulic fluid to at least one hydraulic consumer of the hydraulic lifting device depending on the switching position of the valve.

[0008] The switching position of such a hydraulically pilot-operated valve can be changed by applying hydraulic fluid to a control input of the valve. The valve can also have several, in particular two, control inputs for switching between switching positions.

[0009] The hydraulic system can further comprise at least one control element for hydraulically piloting the valve, wherein the control element can be fluidly connected to the hydraulically piloted valve via at least one pilot line, and the switching position of the at least one hydraulically piloted valve can be controlled via the at least one pilot line by supplying hydraulic fluid through the control element. The control element can supply a quantity of hydraulic fluid, possibly proportional to a deflection of an operating lever of the control element, to the hydraulically piloted valve via at least one pilot line, thus influencing its switching position.

[0010] It is provided that at least one reducing element acting in at least one direction is arranged in the at least one pilot line between the control element and the at least one hydraulically pilot-controlled valve, and additionally at least one hydraulic pressure accumulator is fluidly connected to at least one pilot line. A reducing element can have a flow resistance for hydraulic fluid that differs from, and in particular is greater than, a conventional hydraulic line.

[0011] By combining at least one reducing element and a hydraulic pressure accumulator, an increase in hydraulic pressure in the pilot line and thus the control behavior of the hydraulically pilot-operated valve can be influenced. In particular, a sudden pressure increase and / or pressure drop, and thus sudden switching of the valve, can be avoided, especially at low hydraulic fluid viscosity.

[0012] Excessively high valve opening speed can lead to resonance phenomena in the lifting device. A gradient in the pressure change of the hydraulic fluid in the pilot line, particularly at a control input of the hydraulically pilot-operated valve, can be flattened by combining at least one reducing element and a hydraulic pressure accumulator.

[0013] Compared to a design with only a single reducing element with a high flow resistance for hydraulic fluid, an additional hydraulic accumulator can allow the use of a reducing element with a lower flow resistance for hydraulic fluid. This enables the hydraulic system to function over a wide operating temperature range. Particularly with high oil viscosities and low temperatures, a design with only a single reducing element with a high flow resistance can only control a hydraulically pilot-operated valve with great effort and imprecisely.

[0014] In principle, the hydraulic pressure accumulator can apply pressure to a pilot line connected to it via a fluid connection. The hydraulically pilot-operated valve may require a certain pilot pressure at its control input to change the switching position, which must be applied by the control element. A hydraulic pressure accumulator connected via a fluid connection to the associated pilot line can influence the pressure to be applied by the control element, in particular, reduce it or cause a delayed pressure build-up and / or pressure reduction.

[0015] The reducing element can preferably act in two directions, i.e., inhibit flow both out of and into a control output of the operating element. Alternatively, the reducing element can be designed as a throttle check valve, which allows a one-way effect.

[0016] In an advantageous embodiment, the at least one reducing element can be arranged between the at least one operating element and the at least one hydraulically pilot-operated valve, and the at least one hydraulic pressure accumulator can be fluidly connected between the at least one reducing element and the at least one hydraulically pilot-operated valve to at least one pilot line. The operating element can supply a quantity of hydraulic fluid, possibly proportional to a deflection of an operating lever of the operating element, to the hydraulically pilot-operated valve via at least one pilot line. With this arrangement of the reducing element and the hydraulic accumulator, hydraulic fluid supplied by the operating element can simultaneously pressurize the hydraulic accumulator and the hydraulic pilot-operated valve after flowing through the reducing element.Conversely, hydraulic fluid displaced from the hydraulically pilot-operated valve can be absorbed in the hydraulic accumulator before it flows through the reducing element to the control element.

[0017] This allows pressure loading of the valve and feedback to the control element to be dampened. A change in the switching position of the hydraulically pilot-operated valve, in which hydraulic fluid flows from the valve into the pilot line, can also be absorbed in the hydraulic accumulator without being inhibited by the reducing element.

[0018] In In an advantageous embodiment of the invention, the at least one reducing element can be arranged serially in the at least one pilot line.

[0019] In In an advantageous embodiment of the invention, the at least one hydraulic pressure accumulator can be arranged parallel to at least one pilot line.

[0020] In an advantageous embodiment of the invention, the at least one operating element can have at least one first control output and one second control output and can comprise at least one operating lever that can be deflected at least between a first and a second position.

[0021] When the operating lever is moved to the first position, for example, from a neutral position, the hydraulic fluid from the first control output can be pressurized. At the same time, the hydraulic fluid from the second control output can be relieved of pressure. Conversely, the second control output can be pressurized while the first control output is simultaneously relieved of pressure. Preferably, the pressure can be released into a tank of the hydraulic system.

[0022] In an advantageous embodiment, the at least one control element can have at least a first control output and a second control output, and the hydraulically pilot-operated valve can have at least a first control input and a second control input. The control outputs and the control inputs can be fluidically connected to one another via at least a first and a second pilot line. For example, the first control output can be connected to the first control input via the first pilot line, and the second control output can be connected to the second control input via the second pilot line. Such an arrangement can be provided for a hydraulically pilot-operated valve that can be switched between at least two switching positions.

[0023] At least one of the pilot lines can be fluidically connected to at least one hydraulic pressure accumulator. It can also be provided that each of the pilot lines is fluidically connected to at least one hydraulic pressure accumulator.

[0024] In an advantageous embodiment, the at least one control element can have at least a first control output and a second control output, and the hydraulically pilot-controlled valve can have at least a first control input and a second control input, wherein the control outputs and the control inputs are fluidly connected to one another via at least one first and one second pilot line. The first and second pilot lines, which can each have at least one reducing element, can be connected to one another via two inlets of a shuttle valve, wherein the at least one hydraulic pressure accumulator can be connected to an outlet of the shuttle valve.

[0025] This allows at least one pressure accumulator to be used for both pilot lines. When pressure is applied to one pilot line by the control element, the connection of the other pilot line to the pressure accumulator can be interrupted by the shuttle valve.

[0026] This makes it possible to change the switching positions of the hydraulically pilot-operated valve even faster, since when the switching position of the hydraulically pilot-operated valve changes, in which hydraulic fluid flows out of the valve into the pilot line, the outflowing hydraulic fluid does not have to work against the pressure accumulator, since its connection can be interrupted by the shuttle valve.

[0027] In an advantageous embodiment, the at least one hydraulic pressure accumulator can be designed as a diaphragm accumulator with an expandable diaphragm and / or as a piston accumulator with a movable piston and / or in the form of an at least partially expandable line for hydraulic fluid. A diaphragm accumulator can, for example, be designed as a metal bellows accumulator.

[0028] In an advantageous embodiment, the at least one hydraulic pressure accumulator can be designed as a piston accumulator with a movable piston, wherein the movable piston can be subjected to force for resetting by a spring and / or a compressed gas. The restoring force can be adjustable by selecting a spring and / or a gas pressure. The spring can preferably be made of a metallic material.

[0029] The piston accumulator can comprise a substantially cylindrical piston, movable relative to the housing, in a substantially cylindrical housing. The piston can divide the housing into a piston chamber, in which pressurized hydraulic fluid can act on the piston, and a spring chamber, in which a spring can be arranged to apply a restoring force.

[0030] A spring for applying force to the piston can be designed in the form of at least one coil spring and / or at least one disc spring. The piston accumulator preferably has a single spring element.

[0031] In one embodiment of the spring for applying force to the piston in the form of a spiral spring, guide means can be arranged at least partially in an inner region of the spring, preventing the spring from buckling during compression. In one embodiment, the guide means can be formed as substantially cylindrical extensions on the piston and / or in or on the housing.

[0032] In a preferred embodiment of the piston accumulator, the piston can have a predeterminable or predetermined opening and / or a predeterminable or predetermined gap to the housing, through which hydraulic fluid can flow at a predeterminable or predetermined flow rate from a piston chamber of the piston accumulator into a spring chamber of the piston accumulator. As a result, a spring arranged in the spring chamber can be substantially completely surrounded by hydraulic fluid, thereby providing effective corrosion protection for the spring. The spring chamber of the piston accumulator can be connected to a tank of the hydraulic system via a relief line.

[0033] In an advantageous embodiment, the at least one reducing element can be designed as a throttle, preferably a fixed throttle with a throttle opening of at least 0.6 millimeters, and / or at least in sections as a hydraulic line with a predetermined or predeterminable flow resistance for hydraulic fluid.

[0034] In an advantageous embodiment, the hydraulically preloadable valve can be designed as a proportional valve or a discrete valve.

[0035] In an advantageous embodiment, the at least one hydraulic actuator can be designed as a hydraulic cylinder, hydraulic motor, or hydraulic rotator. A hydraulic cylinder can be an actuator of a lifting device, for example, for moving a crane arm. A hydraulic cylinder can also be an actuator of a working tool of a lifting device. A hydraulic motor can generally be used to drive a lifting device and / or a working device of a lifting device.

[0036] Protection is also sought for a hydraulic lifting device with a hydraulic system according to one of the preceding claims. Such a hydraulic lifting device can preferably be designed as a crane, in particular as a loading crane or as a timber crane for loading timber.

[0037] Furthermore, protection is sought for a vehicle with a hydraulic lifting device as described above.

[0038] Further details and advantages of the present invention are explained in more detail below with reference to the exemplary embodiments shown in the drawings. Fig. 1 is a schematic representation of an embodiment of a hydraulic system according to the invention, Fig. 2 is a schematic representation of a further embodiment of a hydraulic system according to the invention, Fig. 3 is an embodiment of a hydraulic pressure accumulator, Fig. 4 is an embodiment of a hydraulic lifting device with a hydraulic system according to the Figure 1 , Fig. 5 an embodiment of a vehicle with a lifting device according to the Figure 4 .

[0039] Figure 1shows a schematic representation of an embodiment of a hydraulic system according to the invention, wherein this comprises a valve 2 hydraulically pilot-controlled with hydraulic fluid for controlling a supply of at least one hydraulic consumer 11 of a hydraulic lifting device 1 (see Figure 4 ) with hydraulic fluid and an operating element 4 in the form of a joystick for hydraulic pilot control of the valve 2.

[0040] In the embodiment shown, the operating element 4 has a first control output 41 and a second control output 42. The operating element 4 further has an operating lever 50 which can be deflected at least between a first and a second position. When the operating lever 50 is deflected into the first or second position, pressurization with hydraulic fluid from the first or second control output 41, 42 and pressure relief of the hydraulic fluid, here by pressure relief via a relief connection 43 into a tank 23 of the hydraulic system, of the second or first control output 42, 41 takes place.

[0041] In the illustrated embodiment, the hydraulically pilot-operated valve 2 has a first control input 21 and a second control input 22, wherein the control outputs 41, 42 and the control inputs 21, 22 are fluidly connected to one another via a first and a second pilot line 5, 6. The switching position of the hydraulically pilot-operated valve 2 can be controlled via the at least one pilot line 5, 6 by supplying hydraulic fluid through the control element 4. Hydraulic fluid can be supplied to the control element 4 via a pump 24 at a supply connection 44 from a tank 23 of the hydraulic system.

[0042] In the embodiment shown, reducing elements 7, 8 are arranged in the pilot lines 5, 6 between the operating element 4 and the hydraulically pilot-controlled valve 2, acting at least in one direction, preferably in two directions. Furthermore, each of the pilot lines 5, 6 has at least one hydraulic pressure accumulator 9, 10, which are fluidly connected to the pilot lines 5, 6.

[0043] By combining at least one reducing element 7, 8 and a hydraulic pressure accumulator 9, 10, an increase in the hydraulic pressure in the pilot line 5, 6 and thus a control behavior of the hydraulically pilot-operated valve 2 can be influenced. In particular, a sudden pressure increase and / or decrease at the control inputs 21, 22 and thus a sudden switching of the valve 2 can be avoided.

[0044] In principle, the hydraulic pressure accumulator 9, 10 can apply pressure to a pilot line 5, 6 fluidly connected to it. The hydraulically pilot-controlled valve 2 may require a certain pilot pressure at a control input 21, 22 to change the switching position, which must be applied by the control element 4. A hydraulic pressure accumulator 9, 10 fluidly connected to the associated pilot line 5, 6 can influence the pressure to be applied by the control element 4, in particular reduce it or cause a delayed pressure build-up and / or pressure reduction.

[0045] As shown, the at least one reducing element 7, 8 is arranged between the at least one operating element 4 and the at least one hydraulically pilot-operated valve 2. The at least one hydraulic pressure accumulator 9, 10 is fluidly connected to at least one pilot line 5, 6 between the at least one reducing element 7, 8 and the at least one hydraulically pilot-operated valve 2.

[0046] By means of the operating element 4, a quantity of hydraulic fluid, possibly proportional to the deflection of an operating lever 50 of the operating element 4, can be supplied to the hydraulically pilot-controlled valve 2 via at least one pilot line 5, 6. With the arrangement of the reducing elements 7, 8 and the hydraulic accumulators 9, 10 shown, hydraulic fluid supplied by the operating element 4, after flowing through the corresponding reducing element 7, 8, can simultaneously pressurize the associated hydraulic accumulator 9, 10 and the hydraulic pilot-controlled valve 2 via the corresponding control inlet 21, 22. Conversely, hydraulic fluid displaced from a control inlet 21, 22 of the hydraulically pilot-controlled valve 2 can be absorbed in the corresponding hydraulic accumulator 9, 10 before flowing through the corresponding reducing element 7, 8 to the operating element 4 and from there, if necessary, into the tank 23.

[0047] This allows pressure loading of the valve 2 and feedback to the control element 4 to be dampened. A change in the switching position of the hydraulically pilot-operated valve 2, in which hydraulic fluid flows from a control input 21, 22 of the valve 2 into the corresponding pilot line 5, 6, can also be absorbed in the corresponding hydraulic accumulator 9, 10 without being inhibited by the corresponding reducing element 7, 8.

[0048] In the embodiment shown, the at least one reducing element 7, 8 is arranged serially in the at least one pilot line 5, 6. The at least one hydraulic pressure accumulator 9, 10 is arranged parallel to at least one pilot line 5, 6.

[0049] Figure 2 shows a schematic representation of a further embodiment of a hydraulic system according to the invention, which partially corresponds to the embodiment of the Figure 1 corresponds.

[0050] The first and second pilot lines 5, 6, which can each have a reducing element 7, 8, are, in contrast to the design of the Figure 1 In this embodiment, they are connected to each other via two inlets 31, 32 of a shuttle valve 3, with a hydraulic pressure accumulator 9 being connected to an outlet 33 of the shuttle valve 3.

[0051] This allows a common pressure accumulator 9 to be used for both pilot lines 5, 6.

[0052] As shown, when the first pilot line 5 is pressurized with hydraulic fluid from the first control output 41 by the control element 4, the connection of the second pilot line 6 to the pressure accumulator 9 can be interrupted by the shuttle valve 3. The hydraulic pressure accumulator 9 is thus fluidly connected only to the first pilot line 5.

[0053] When the switching position of the hydraulically pilot-controlled valve 2 changes due to pressurization of the first control input 21, in which hydraulic fluid flows from a control output 22 of the valve 2 into the second pilot line 6, the flowing hydraulic fluid does not have to work against the pressure accumulator 9, since its connection to the corresponding pilot line 5, 6 is interrupted by the shuttle valve 3.

[0054] Figure 3shows a possible embodiment of a hydraulic pressure accumulator 9. In the embodiment shown, the hydraulic pressure accumulator 9 is designed as a piston accumulator with a substantially cylindrical housing 16 and a substantially cylindrical piston 12 that is movable relative to the housing 16, wherein the movable piston 12 is subjected to a force for resetting by a spring 13. A restoring force can be adjusted by selecting a spring 13. In the embodiment shown, the spring 13 is designed in the form of at least one spiral spring. An embodiment in the form of at least one disc spring is also conceivable.

[0055] In a design of the spring 13 for applying force to the piston 12 in the form of the spiral spring shown, guide means 17, 18 can be arranged at least partially in an inner region of the spring 13, which prevent the spring 13 from buckling during compression. The guide means 17, 18 can be designed, as shown, as essentially cylindrical extensions on the piston 12 and in the housing 16.

[0056] The piston 12 can divide the housing 16 into a piston chamber, in which pressurized hydraulic fluid can act on the piston 12, and a spring chamber, in which a spring 13 can be arranged to apply a restoring force.

[0057] The hydraulic pressure accumulator 9 can be connected to the hydraulic system via a hydraulic connection 14.

[0058] As shown, the piston 12 can have an opening 19 and / or a gap 20 to the housing 16, through which hydraulic fluid can flow at a predeterminable or predetermined flow rate from a piston chamber 27 of the piston accumulator into a spring chamber 28 of the piston accumulator. As a result, a spring 13 arranged in the spring chamber 28 can be substantially completely surrounded by hydraulic fluid, thereby providing effective corrosion protection for the spring 13. The spring chamber 28 of the piston accumulator can be connected to a tank 23 of the hydraulic system (not shown) via a relief line connected to a relief connection 15.

[0059] Fig. 4 shows an embodiment of a hydraulic lifting device 1 with a hydraulic system according to the Figure 1 . A design of the hydraulic system according to the Figure 2 is also conceivable.

[0060] In the illustrated embodiment, a hydraulic actuator 11 in the form of a double-acting hydraulic cylinder for lifting the crane arm of the lifting device 1 is connected to an output of the hydraulically pilot-operated valve 2. Depending on the switching position of the hydraulically pilot-operated valve 2, a hydraulic fluid supply to the at least one hydraulic actuator 11 of the hydraulic lifting device can be controlled. The hydraulic fluid can be pumped by a pump 25 from a tank 23 of the hydraulic system.

[0061] To simplify the illustration, corresponding overload valves and load-holding valves of the hydraulic system are not shown. Further designs of the hydraulic actuator 11 in the form of an actuator of a work tool, a hydraulic motor, or a hydraulic rotator are not excluded.

[0062] It can be provided that the hydraulic system has further hydraulically pilot-controlled valves 2 according to the invention for further hydraulic cylinders, actuators or drives of the hydraulic lifting device 1.

[0063] Fig. 5 shows an embodiment of a vehicle 26 with a lifting device 1 according to the Figure 4 . List of reference symbols

[0064] 1 hydraulic lifting device 2 hydraulically pilot-operated valve 3 shuttle valve 4 operating element 5 first pilot line 6 second pilot line 7 reducing element 8 reducing element 9 hydraulic pressure accumulator 10 hydraulic pressure accumulator 11 hydraulic output 12 piston 13 spring 14 hydraulic connection 15 relief connection 16 housing 17 guide means 18 guide means 19 opening 20 gap 21 first control input 22 second control input 23 tank 24 pump 25 pump 26 vehicle 27 piston chamber 28 spring chamber 31 shuttle valve input 31 shuttle valve input 33 shuttle valve output 41First control output 42Second control output 43Relief connection 44Supply connection 50 control levers

Claims

1. Hydraulic system for a hydraulic lifting device (1) comprising - at least one valve (2) hydraulically pilot-controlled using hydraulic fluid for open-loop controlling the supply of hydraulic fluid to at least one hydraulic consumer (11) of the hydraulic lifting device (1) and - at least one operating element (4) for hydraulically pilot-controlling the valve (2), wherein the operating element (4) is connected to the hydraulically pilot-controlled valve (2) via at least one pilot line (5, 6) in a fluid-conducting manner and the switching position of the at least one hydraulically pilot-controlled valve (2) can be open-loop controlled via the at least one pilot line (5, 6) by supplying hydraulic fluid through the operating element (4), characterized in that - at least one reducing element (7, 8) effective in at least one direction, preferably in two directions, is arranged in the at least one pilot line (5, 6) between the operating element (4) and the at least one hydraulically pilot-controlled valve (2), and - at least one hydraulic pressure accumulator (9, 10) is connected in a fluid-conducting manner between the at least one reducing element (7, 8) and the at least one hydraulically pilot-controlled valve (2) with at least one pilot line (5, 6).

2. Hydraulic system according to the preceding claim, wherein the at least one reducing element (7, 8) is arranged in series in the at least one pilot line (5, 6).

3. Hydraulic system according to one of the preceding claims, wherein the at least one hydraulic pressure accumulator (9, 10) is arranged parallel to at least one pilot line (5, 6).

4. Hydraulic system according to one of the preceding claims, wherein the at least one operating element (4) has at least one first control output (41) and one second control output (42) and comprises at least one operating lever (50) which can be deflected at least between one first and one second position, wherein, when the operating lever (50) is deflected into the first or second position, the first or second control output (41, 42) is pressurized with hydraulic fluid and the hydraulic fluid is depressurized, preferably into a tank (23) of the hydraulic system, of the second or first control output (42, 41).

5. Hydraulic system according to one of the preceding claims, wherein the at least one operating element has at least one first control output (41) and one second control output (42) and the hydraulically pilot-controlled valve (2) has at least one first control input (21) and one second control input (22), wherein the control outputs (41, 42) and the control inputs (21, 22) are connected to each other in a fluid-conducting manner via at least one first and one second pilot line (5, 6) and each of the pilot lines (5, 6) is connected in a fluid-conducting manner to at least one hydraulic pressure accumulator (9, 10).

6. Hydraulic system according to one of the preceding claims, wherein the at least one operating element (4) has at least one first control output (41) and one second control output (42) and the hydraulically pilot-controlled valve (2) has at least one first control input (21) and one second control input (22), wherein the control outputs (41, 42) and the control inputs (21, 22) are connected to one another in a fluid-conducting manner via at least one first and one second pilot line (5, 6), and the first and second pilot lines (5, 6) are connected to each other via two inputs (31, 32) of a changeover valve (3), and the at least one hydraulic pressure accumulator (9, 10) is connected to an output (33) of the changeover valve (3).

7. Hydraulic system according to one of the preceding claims, wherein the at least one hydraulic pressure accumulator (9, 10) is designed as a diaphragm accumulator with an expandable diaphragm and / or as a piston accumulator with a movable piston (12) and / or in the form of a line for hydraulic fluid that is expandable at least in sections.

8. Hydraulic system according to one of the preceding claims, wherein the at least one hydraulic pressure accumulator (9, 10) is designed as a piston accumulator with a movable piston (12), wherein the movable piston (12) is acted upon for resetting with a spring (13), preferably in the form of at least one coil spring and / or at least one disc spring, and / or compressed gas.

9. Hydraulic system according to one of the preceding claims, wherein the hydraulic pressure accumulator (9, 10) is designed as a piston accumulator with a movable piston (12) and a spring (13) for resetting the piston (12), wherein the spring (13) is designed in the form of at least one coil spring and guide means (17, 18), preferably in the form of cylindrical extensions, are arranged at least in sections in an inner region of the spring (13) to prevent buckling of the spring (13) during compression.

10. Hydraulic system according to one of the preceding claims, wherein the hydraulic pressure accumulator (9, 10) is designed as a piston accumulator with a housing (16) and a piston (12) movable relative thereto, wherein the piston (12) has a predeterminable or predetermined opening (19) and / or a predeterminable or predetermined gap (20) to the housing (16) for the flow of hydraulic fluid.

11. Hydraulic system according to one of the preceding claims, wherein the at least one reducing element (7, 8) is designed as a throttle, preferably a fixed throttle with at least 0.6 millimeters of throttle opening, and / or at least in sections as a hydraulic line with a predetermined or predeterminable flow resistance for hydraulic fluid.

12. Hydraulic system according to one of the preceding claims, wherein the at least one hydraulic consumer (11) is designed as a hydraulic cylinder, hydraulic motor, or hydraulic rotator.

13. Hydraulic lifting device (1), preferably a crane, particularly preferably a timber crane for loading timber, with a hydraulic system according to one of the preceding claims.

14. Vehicle (26) with a lifting device according to the preceding claim.

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