Hydraulic valve arrangement of a tamping unit tool

Abstract

The invention relates to a hydraulic valve arrangement (13) for positioning a tamping unit tool (8A, 8B), comprising a hydraulic valve (15) with control lines (145, 146), inlet lines (141, 142), outlet lines (143, 144) and at least two switching end positions, a hydraulic actuator (7, 7A, 7B) with two separate pressure chambers (72, 73), a piston and an associated actuating element (71), and a hydraulic line network (14) with a high-pressure port (17) and a low-pressure port (18), wherein the hydraulic valve (15) is connected by means of the hydraulic line network (14) on the inlet side to the high-pressure and low-pressure ports (17, 18) and on the outlet side to the two pressure chambers (72, 73) of the hydraulic actuator (7), and wherein the hydraulic valve (15) is hydraulically actuated by means of two control oil ports (X, Y). is directly connected, with a first output line (143) connected to a first pressure chamber (72),a hydraulic control line (145) branches off and is connected to the first of the control oil connections (X), and from a second output line (144), which is connected to a second pressure chamber (73), another hydraulic control line (146) branches off and is connected to the second of the control oil connections (Y), whereby, due to a pronounced oscillation of the volume flow regime, a periodic movement of the actuating element (71) of the hydraulic actuator (7, 7A, 7B) characterized by frequency and offset is established.

Description

[0001] The invention relates to a hydraulic valve arrangement for positioning a tamping unit tool comprising a hydraulic valve with control lines, inlet lines, outlet lines and at least two switching end positions, a hydraulic actuator with two separate pressure chambers, a piston and an actuating element connected thereto, and a hydraulic line network with a high-pressure and a low-pressure connection, wherein the hydraulic valve is connected on the inlet side to the high-pressure and low-pressure connections and on the outlet side to the two pressure chambers of the hydraulic actuator by means of the hydraulic line network.

[0002] Tamping units are used to relocate and compact the ballast of the ballast layer of a railway track below sleepers, which together with the rails attached to them form a track grid on which the wheels of a rail vehicle roll.

[0003] In addition to tamping units that process the ballast bed of only one sleeper before being moved a sleeper distance further in the direction of work by a rail vehicle designed as a track construction machine, on which they are attached, there are also multi-sleeper tamping units for the simultaneous processing of the ballast bed of two, three or four sleepers.

[0004] However, the widths of most known tamping units for processing a sleeper are greater than the sleeper spacing, making it impossible to arrange a number n of identical units in such a way as to tamp a corresponding number n of sleepers simultaneously.

[0005] EP 3 239 398 A1 discloses a tamping unit for a track tamping machine, wherein each tamping tool designed as a rocker arm of a tamping tool pair of the tamping unit is assigned a hydraulic cylinder which forms both the auxiliary drive and the vibration drive.

[0006] AT 525 272 A4 discloses a tamping unit for tamping a track with tamping tools arranged in pairs, which can be positioned relative to each other by means of a respective positioning cylinder, wherein a positioning piston is arranged in the respective positioning cylinder and a vibration piston is assigned to each positioning cylinder in order to superimpose a vibration on a positioning movement.

[0007] The use of fully hydraulic tamping units, which generate the vibration of the tamping tools using hydraulic actuators instead of an eccentric shaft, enables such a reduction in the construction width that the construction width of a tamping unit module for a sleeper does not exceed a sleeper spacing.

[0008] High amplitude and frequency volume flow regimes are required to generate vibrations.

[0009] When using proportional valves with electromagnetic control, these can at best be provided in reduced quality, resulting in undesirable drops in vibration amplitude or vibration frequency.

[0010] Such a regulated proportional valve with electromagnetic control for vibration generation according to the state of the art therefore limits the operationally permissible ranges of amplitude and frequency of the volume flow regime.

[0011] The invention is based on the objective of providing an improvement over the prior art for a hydraulic valve arrangement for positioning a tamping unit tool of the type mentioned above.

[0012] In particular, the aim is to achieve an extension of the restrictions regarding amplitude and frequency of the volume flow regime generated by the hydraulic valve arrangement, while maintaining a width of a tamping unit module of no more than one threshold spacing.

[0013] Furthermore, it is an object of the invention to disclose a method for operating the valve arrangement.

[0014] Finally, the use of the hydraulic valve arrangement according to the invention in a tamping unit and in a track construction machine should be mentioned.

[0015] According to the invention, these problems are solved by a hydraulic valve arrangement according to claim 1, a tamping unit according to claim 6, a rail vehicle according to claim 7 and a method according to claim 8.

[0016] Dependent claims specify advantageous embodiments of the invention.

[0017] A hydraulic valve arrangement for positioning a tamping unit tool comprises a hydraulic valve with control lines, inlet lines, outlet lines and at least two switching end positions, a hydraulic actuator with two separate pressure chambers, a piston and an associated actuating element, and a hydraulic line network with a high-pressure and a low-pressure connection, wherein the hydraulic valve is connected on the inlet side to the high-pressure and the low-pressure connections and on the outlet side to the two pressure chambers of the hydraulic actuator by means of the hydraulic line network, and the hydraulic valve is directly hydraulically switched by means of two control oil connections, wherein a hydraulic control line branches off from a first outlet line, which is connected to a first pressure chamber, and is connected to the first of the control oil connections, and from a second outlet line, which is connected to a second pressure chamber,a further hydraulic control line branches off and is connected to the second of the control oil connections.

[0018] The hydraulic valve is arranged as the main valve between the hydraulic actuator and the sources and sinks of the hydraulic medium, in particular a hydraulic oil, and is connected to the aforementioned other components of the overall arrangement by means of hydraulic lines of the hydraulic piping network.

[0019] Hydraulic sources are in particular hydraulic pumps or hydraulic motor-pump units, which are driven by electric generators or by internal combustion engines.

[0020] In the case of an open hydraulic circuit, a hydraulic sink is a tank into which the hydraulic medium is fed and from which the hydraulic medium is drawn.

[0021] In a closed hydraulic circuit, the hydraulic sink corresponds to the low-pressure port of the hydraulic pump or the motor-pump unit.

[0022] To change the dynamics of the volume flow regime in the hydraulic piping network, storage tanks for the hydraulic medium can also be arranged at one or more points in the hydraulic circuit.

[0023] In this case, the control oil ports of this hydraulic valve are directly connected to its working ports, whereby changes in the volume flow regime at the valve outputs are fed back to the control inputs.

[0024] The volume flow regime for the hydraulic actuators of the tools of a stuffing unit exhibits a pronounced oscillation when controlled with the valve arrangement according to the invention.

[0025] Higher switching forces of a directly switched hydraulic valve result in shorter switching times compared to electromagnetically switched valve designs.

[0026] This hydraulic valve arrangement therefore allows for higher vibration amplitudes and higher vibration frequencies compared to prior art designs.

[0027] Another advantage of this valve arrangement is that vibration generation using exclusively hydraulic components offers increased reliability compared to an embodiment with electromagnetic switching elements of the hydraulic valve.

[0028] In a preferred embodiment, the hydraulic valve, which connects the hydraulic actuator to the high-pressure port and the low-pressure port via a hydraulic piping network, is a proportional valve with two inputs, two outputs and two discrete switching end positions.

[0029] It is advantageous if at least one further hydraulic valve is arranged in at least one of the hydraulic control lines between the branch of at least one of the output lines of the first hydraulic valve and at least one of the control oil connections of this first hydraulic valve.

[0030] By inserting at least one additional hydraulic valve, an indirect connection is created between one of the working ports of the first hydraulic valve and one of its control ports.

[0031] In this arrangement of hydraulic valves, the control signals of this electromagnetically actuated additional hydraulic valve do not include the fundamental oscillation of the pronounced oscillation of the volume flow regime resulting from the feedback, thus resulting in more favorable control engineering properties.

[0032] In particular, the hydraulic valve arrangement exhibits a lower control deviation compared to state-of-the-art designs, and only additional disturbances need to be compensated for.

[0033] Such disturbances affect the steady-state vibration operation of the tamping tool pairs of a tamping unit during the tamping process or arise due to other external factors such as the oil temperature, the lubrication conditions, especially of bearings and guides, as well as the aging of parts and elements of the unit and the machine involved in the tamping process.

[0034] Preferably, the at least one further hydraulic valve comprises an inlet, an outlet and two switching end positions, and it is advantageous if the further hydraulic valve can be continuously adjusted between a first passive switching end position and a second active switching end position by means of manual and / or electromagnetic actuation.

[0035] Furthermore, it is advantageous if the first passive switching end position of the additional hydraulic valve interrupts the return of hydraulic medium from at least one of the output lines to at least one of the control oil connections of the first hydraulic valve, and if in the second active switching end position of the additional hydraulic valve a throttled return of the hydraulic medium takes place.

[0036] By arranging this additional, throttling hydraulic valve, the duration during which the first hydraulic valve remains in one of its switching end positions, or the duration between switching from one switching end position to another and the subsequent switching from the other switching end position to a further switching end position, which in the case of two switching end positions is again the first switching end position, can be varied.

[0037] Preferably, the hydraulic actuators of a tamping unit and / or a tamping unit module are controlled by the hydraulic valve arrangement according to the invention.

[0038] By controlling a tamping unit module by means of the hydraulic valve arrangement according to the invention, it is possible to realize this tamping unit module with a width b AM that corresponds to or is less than a threshold distance.

[0039] It is advantageous if rail vehicles or rail vehicle combinations with working units for the construction or maintenance of a railway track have a tamping unit or an arrangement of tamping unit modules as a working unit, which is controlled by means of the hydraulic valve arrangement according to the invention.

[0040] The total construction width B AM in the machining direction of an arrangement of n tamping unit modules results in a threshold spacing ds of the following: B AM ≤ n ⋅ d s .

[0041] With such a construction width B AM, tamping units can also be realized that tampe more than four sleepers simultaneously, i.e. in particular tamping units for the synchronous tamping of a sleeper number n=5, n=6, n=7, etc.

[0042] Even with multi-sill tamping units with n≤4, it is advantageous to use tamping unit modules with a unit width b AM smaller than the sill spacing ds, because these tamping unit modules are symmetrically and uniformly constructed, unlike the prior art.

[0043] The arrangement of n of these identical tamping unit modules with symmetrical design in a multi-sleeper tamping unit reduces the forces acting on the unit frame and machine and results in smoother and quieter operation.

[0044] To determine the total width B AM of a multi-sleeper tamping unit, the frame in which these tamping unit modules are arranged must also be taken into account.

[0045] Advantageously, a method for operating a hydraulic valve arrangement according to the invention provides that, due to the connection of the hydraulic valve output lines with the hydraulic valve control lines, a time-varying volume flow regime is generated, which causes an oscillation of the actuating element of the controlled hydraulic actuator characterized by amplitude and frequency.

[0046] It is advantageous if the frequency f of the periodic movement of the actuating element of the hydraulic actuator is set due to the control of at least one of the two further hydraulic valves.

[0047] It is particularly advantageous if the method is designed in such a way that the frequency f of the periodic movement of the actuating element of the hydraulic actuator is set due to the synchronous control of the two other hydraulic valves.

[0048] Furthermore, it is advantageous to adjust the offset of the periodic movement of the actuating element of the hydraulic actuator due to the control of at least one additional hydraulic valve.

[0049] It is particularly advantageous if the method for operating a hydraulic valve arrangement according to the invention makes it possible to adjust the offset of the periodic movement of the actuating element of the hydraulic actuator by means of an opposing control of the two further hydraulic valves.

[0050] By adjusting the offset of the periodic movement of the hydraulic actuator's actuating element, a directed movement can be superimposed on the periodic movement.

[0051] Thus, by controlling the hydraulic actuators of a tamping unit, a tamping unit module or an arrangement of tamping unit modules by means of the hydraulic valve arrangement according to the invention, both assisting movements and vibrations of the tamping tool pairs can be realized.

[0052] The invention is explained below in an exemplary manner with reference to the accompanying figures.

[0053] They show, in schematic representation: Fig. 1 A tamping unit with two linear actuators for performing the positioning movement and the vibration of the tamping tool pairs. Fig. 2 An embodiment of the hydraulic valve arrangement according to the invention for positioning a tamping unit tool. Figure 1 Fig. 3 Arrangement of n=5 tamping unit modules with a width b AM of at most one sleeper spacing ds in a common frame. Fig. 4 Rail vehicle train with the tamping unit module arrangement. Figure 3

[0054] Figure 1 shows a tamping unit 1 with a half-lowered pair of tamping tools 8A, 8B over a sleeper 10, which is connected to a rail 9 by means of a rail fastening 12 and forms a track grid which is supported on a ballast layer 11.

[0055] The stuffing unit 1 comprises a frame 2 to which the cylinder of a linear actuator 3 is attached.

[0056] This linear actuator 3 serves to vertically lower the tamping tools 8A, 8B from a rest position, in which the tamping picks of the tamping tools 8A, 8B are located above the ballast layer 11, into a working position, in which the tamping picks of the tamping tools 8A, 8B are immersed to a sufficient depth in the ballast layer 11 to redistribute the ballast of the ballast layer 11 below the sleeper 10.

[0057] For this purpose, a slide 4, which is moved in a vertical direction along guide rods 5A, 5B connected to the frame 2, is connected to a tool carrier 6 and to the actuating element of the linear actuator 3.

[0058] The tamping tool pairs 8A, 8B are rotatably mounted on the carrier 6, wherein the upper end of the lever arm of the respective tamping tool 8A, 8B is rotatably connected to the rod-shaped actuating element of the corresponding linear actuator 7A, 7B.

[0059] Movements of the rod-shaped actuating elements of the linear actuators 7A, 7B are transmitted by the lever arms of the tamping tool pairs 8A, 8B to their tamping picks and are responsible for both the staking movement and the vibration of the tamping picks.

[0060] The cylindrical housings of these linear actuators 7A, 7B are rotatably connected to the carrier 6.

[0061] Since the distance d 1 from the point of application of the force F 1 by the linear actuators 7A, 7B to the pivot point of the lever arms of the tamping tools 8A, 8B is less than the distance d 2 from the pivot point to the point of transmission of the force F 2 to the ballast of the ballast layer 11 by the tamping picks of the tamping tools 8A, 8B due to the narrow embodiment of the tamping unit 1 shown, and because the force F 1 is applied at an angle α to the normal to the line connecting the point of force application and the pivot point, it is necessary to transmit a force F 1 from the linear actuators 7A, 7B to the tamping tools 8A, 8B that is greater than the force F 2 acting on the ballast.

[0062] The force F 1 to be applied is determined using the following formula, provided that the values ​​for F 2 , d 1 , d 2 and α are known or given: F 1 = 1 cos α . d 2 d 1 ⋅ F 2

[0063] One embodiment of the hydraulic valve arrangement 13 according to the invention comprises a linear hydraulic actuator 7 with an actuating element 71 formed from a piston and rod, which separates the cylindrical space for the hydraulic medium into a rod-side pressure chamber 72 and a piston-side pressure chamber 73, is Figure 2 to be taken.

[0064] The hydraulic valve arrangement 13 comprises, in addition to this hydraulic actuator 7, a hydraulic valve 15, whose inputs P, T are connected by means of lines 141, 142 of the hydraulic line network 14 to a hydraulic high pressure port 17 and a low pressure port 18.

[0065] The outputs A, B of this hydraulic valve 15 are connected to the pressure chambers 72, 73 of the hydraulic actuator 7 by means of the lines 143, 144 of the hydraulic line network 14.

[0066] From branching points of these connecting lines 143, 144, the valve outputs A, B are also routed back via the further hydraulic valves 16A, 16B and the control lines 145, 146 to the control inputs X, Y of the first hydraulic valve 15.

[0067] The first hydraulic valve 15 is a proportional valve with two inlet ports P, T and two outlet ports A, B.

[0068] The control oil connections X, Y allow switching between the two switching end positions of this 2 / 2-way valve, wherein the embodiment of the hydraulic valve 15 provides that the movable valve spool engages when one of the two switching end positions is reached.

[0069] In a first switching end position, the hydraulic valve 15 connects, on the one hand, the hydraulic high-pressure line connection 17 to the rod-side pressure chamber 72 of the hydraulic actuator 7 via the line 141 and the line 143, and on the other hand, the piston-side pressure chamber 73 to the hydraulic low-pressure connection 18 via the lines 144 and 142.

[0070] In this first switching end position, the actuating element 71 of the hydraulic actuator 7 moves to the right, whereby the volume of the rod-side pressure chamber 72 increases and that of the piston-side pressure chamber 73 decreases simultaneously.

[0071] Due to the pressure conditions in the lines 143, 144, which act on the control oil ports X, Y of the first hydraulic valve (main valve) 15 by means of the further hydraulic valves (hydraulic control valves) 16A, 16B and the control lines 145, 146, the valve spool is subsequently moved from the first to the second switching end position when the control valves 16A, 16B are in the fluid-conducting switching position until it locks into this switching end position.

[0072] By means of the second switching end position, the first hydraulic valve 15 connects fluid-conducting on the one hand the hydraulic high-pressure port 17 to the piston-side pressure chamber 73 by means of lines 141 and 144 and on the other hand the rod-side pressure chamber 72 to the hydraulic low-pressure port 18 by means of lines 143 and 142.

[0073] This second switching end position results in a movement of the actuating element 72 to the left, with a simultaneous increase in the volume of the piston-side pressure chamber 73 and a decrease in that of the rod-side pressure chamber 72.

[0074] Additionally, due to the now changed pressure conditions in the lines 143, 144, which, in the case of fluid-conducting hydraulic control valves 16A, 16B, act on the control lines 145, 146 and thus on the control oil connections X, Y of the main valve 15, the valve spool is then moved away from the second switching end position until it locks back into the first switching end position.

[0075] In the fluid-conducting switching position of the control valves 16A, 16B, a periodically changing volume flow regime of the hydraulic medium in the lines 143, 144 is established due to the control of the main valve 15, and consequently a periodic oscillating movement of the actuating element 71 of the hydraulic actuator 7.

[0076] The hydraulic control valves 16A, 16B each have an input port and an output port as well as a passive switching end position and an active switching end position, between which switching can be carried out continuously by means of an electromagnetic control or by a manual actuating element.

[0077] The passive switching end position is held in position by a mechanical spring, and the control and actuation must overcome the spring force to switch to the active switching end position.

[0078] The passive switching end position of the control valves 16A, 16B interrupts the respective feedback of the outputs A, B of the main valve 15 to its control oil connections X, Y and thus prevents the oscillation of the volume flow regime and the actuating element 71.

[0079] The active switching end position of the control valves 16A, 16B establishes a connection between the outputs A, B and the control oil connections X, Y of the main valve 15 by means of adjustable throttling.

[0080] The control valves 16A, 16B thus allow the frequency and offset of the vibrations of the volume flow regime and therefore of the movements of the actuating element 71 of the hydraulic actuator 7 to be set.

[0081] When setting the frequency f and offset of the periodic movement of the actuating element 71, it should be noted that due to the generally different effective areas of the hydraulic actuator 7, the corresponding sensitivities of the other hydraulic valves 16A, 16B may differ.

[0082] A tamping unit 1', comprising a number n>4 of tamping unit modules 1A, 1B, 1C, 1D, 1E with a module width b AM , is in Figure 3 arranged in a common frame 2' above a section of railway track.

[0083] This rail track is characterized, among other things, by a track grid consisting of rails 9 which are mounted on sleepers 10A, 10B, 10C, 10D, 10E, 10F by means of rail fastenings 12, whereby the following relationship applies to the distance ds between the sleepers: d s ≥ b AM

[0084] Despite the common frame 2', the tamping tool pairs 8A, 8B of these tamping unit modules 1A, 1B, 1C, 1D, 1E can be lowered independently of one another into the sleeper compartments and the ballast layer 11 of the superstructure (not shown) by means of the vertically acting hydraulic actuators 3A, 3B, 3C, 3D, 3E according to tamping methods from the state of the art and / or innovative tamping methods, in order to achieve the most favorable result possible for the production of a specified and / or the correction of an existing track position.

[0085] A multi-sill tamping unit 1'' with five tamping unit modules 1A, 1B, 1C, 1D, 1E, as described in Figure 3 shown are for the synchronous tamping of up to five sleepers 10, 10A, 10B, 10C, 10D, 10E of the track grid of a railway track and with a total construction width B AM , is in Figure 4 arranged on vehicle part 19B of a rail vehicle unit 19.

[0086] The rail vehicle unit 19 consists of a power car 19A with a pantograph-type current collector 20 for supplying electrical consumers, in particular traction drive and work unit drive, by means of an overhead electrical line (not shown).

[0087] The power car 19A moves on the rails 9 of a railway track by means of a rail bogie 21A and is positively connected to a vehicle part 19B, in particular by means of coupling devices.

[0088] The vehicle section 19B carries the multi-sleeper tamping unit 1" and is supported on the rails 9 of a rail track by means of the bogies 21B, 21C, 21D.

[0089] The bogies 21B, 21C, 21D either have their own traction drives or the vehicle section 19B of the rail vehicle assembly 19 is moved on the rail track by means of the power car 19A, while the multi-sleeper tamping unit 1" establishes a predetermined track position or corrects a measured existing track position according to specifications.

[0090] The subject matter of the invention disclosed by the claims is not limited to the exemplary embodiments shown.

[0091] In particular, further variants of hydraulic valve arrangements 13, combinations of tamping unit modules 1, 1', 1" and of rail vehicle assemblies 19 are included by the following claims.

Claims

1. Hydraulic valve arrangement (13) for positioning a tamping unit tool (8A, 8B) comprising a hydraulic valve (15) with control lines (145, 146), inlet lines (141, 142), outlet lines (143, 144) and at least two switching end positions, a hydraulic actuator (7, 7A, 7B) with two separate pressure chambers (72, 73), a piston and an associated actuating element (71) as well as a hydraulic line network (14) with a high-pressure port (17) and a low-pressure port (18), wherein the hydraulic valve (15) is connected by means of the hydraulic line network (14) on the inlet side to the high-pressure and low-pressure ports (17, 18) and on the outlet side to the two pressure chambers (72, 73) of the hydraulic actuator (7), characterized by the fact thatThe hydraulic valve (15) is directly hydraulically switched by means of two control oil connections (X, Y), wherein a hydraulic control line (145) branches off from a first output line (143), which is connected to a first pressure chamber (72), and is connected to the first of the control oil connections (X), and from a second output line (144), which is connected to a second pressure chamber (73), another hydraulic control line (146) branches off and is connected to the second of the control oil connections (Y), whereby, due to a pronounced oscillation of the volume flow regime, a periodic movement of the actuating element (71) of the hydraulic actuator (7, 7A, 7B) is established, characterized by frequency and offset.

2. Hydraulic valve arrangement (13) according to claim 1, characterized by the fact thatThe hydraulic valve (15), which connects the hydraulic actuator (7, 7A, 7B) to the high pressure port (17) and the low pressure port (18) via the hydraulic line network (14), is a proportional valve (15) with two inputs (P, T), two outputs (A, B) and two discrete switching end positions.

3. Hydraulic valve arrangement (13) according to one of claims 1 or 2, characterized by the fact that at least one further hydraulic valve (16A, 16B) is arranged in at least one of the hydraulic control lines (145, 146) between the branch of at least one of the output lines (143, 144) of the first hydraulic valve (15) and at least one of the control oil connections (X, Y) of this hydraulic valve (15).

4. Hydraulic valve arrangement (13) according to claim 3, characterized by the fact thatthe at least one further hydraulic valve (16A, 16B) having an input, an output and two switching end positions, wherein it is continuously adjustable between a first passive switching end position and a second active switching end position by means of manual and / or electromagnetic actuation.

5. Hydraulic valve arrangement (13) according to claim 4, characterized by the fact that The first passive switching end position interrupts the return of hydraulic medium from at least one of the output lines (143, 144) to at least one of the control oil connections (X, Y) of the first hydraulic valve (15) and in the second active switching end position a throttled return of the hydraulic medium takes place.

6. Tamping unit (1, 1', 1'') with tamping tools (8A, 8B) coupled to hydraulic actuators (7, 7A, 7B), characterized by the fact that the hydraulic actuators (7, 7A, 7B) are controlled by a hydraulic valve arrangement (13) according to one of claims 1 to 5.

7. Rail vehicle (19, 19A, 19B) and / or rail vehicle combination (19) with working units for the construction and / or processing of a railway track, characterized by the fact that at least one of the working units is a tamping unit (1, 1', 1'') according to claim 6.

8. Method for operating a hydraulic valve arrangement (13) according to any one of claims 1 to 5 characterized by the fact that Due to the connection of the hydraulic valve output lines (143, 144) with the hydraulic valve control lines (145, 146), a time-varying volume flow regime is generated, which causes an oscillation of the actuating element (71) of the controlled hydraulic actuator (7, 7A, 7B) characterized by amplitude and frequency.

9. Method according to claim 8 characterized by the fact thatThe frequency of the periodic movement of the actuating element (71) of the hydraulic actuator is set (7, 7A, 7B) by controlling at least one further hydraulic valve (16A, 16B) according to one of claims 3 to 5.

10. Method according to one of claims 8 or 9 characterized by the fact that The offset of the periodic movement of the actuating element (71) of the hydraulic actuator (7, 7A, 7B) is set by controlling at least one further hydraulic valve (16A, 16B) according to one of claims 3 to 5.

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