Method and system for compacting a track ballast bed

Abstract

A method for compacting a track ballast bed (10) by means of a tamping unit (3) which has a tool carrier (13) and tamping tools (15) mounted thereon and having tamping tines (17), wherein a plurality of method steps are carried out, specifically positioning the tamping tines (17) above the surface (20) of the track ballast bed (10), lowering the tool carrier (13) by means of a height adjustment drive (14), with the tamping tines (17) plunging into the track ballast bed (10), adjusting the tamping tools (15) by means of adjustment drives (16), with the tamping tines (17) moving towards one another, and resetting the tamping tools (15) and lifting the tool carrier (13), with the tamping tines (17) being moved away from one another and being pulled out of the track ballast bed (10), wherein a ballast bed surface point (33) at which a shaft (34) of the tamping tine (17) projects out of the track ballast bed (10) is determined by means of a computing unit (22) for the respective tamping tine (17) at the end of the adjustment, and wherein the height adjustment drive (14) and the adjustment drives (16) are actuated in coordination with one another by means of a control device (19) such that the respective tamping tine (17) is moved through the associated ballast bed surface point (33). As a result, the compacted track ballast bed (10) is affected as little as possible while the tamping tines (17) are being pulled out.

Description

[0001] 1

[0002] Method and system for compacting a track ballast bed

[0003] The invention relates to a method for compacting a track ballast bed using a tamping unit comprising a tool carrier and tamping tools with tamping picks mounted thereon, wherein several process steps are carried out, namely positioning the tamping picks above the surface of the track ballast bed, lowering the tool carrier by means of a height adjustment drive, whereby the tamping picks penetrate the track ballast bed, advancing the tamping tools by means of advancing drives, whereby the tamping picks are moved towards each other, and repositioning the tamping tools and raising the tool carrier, whereby the tamping picks are moved away from each other and withdrawn from the track ballast bed. The invention also relates to a corresponding system for carrying out the method.

[0004] On a track with a ballast bed, the track geometry deteriorates over time due to traffic loads and weather conditions. A tamping machine is used to restore the desired track geometry. Such a machine is movable along the track and comprises a lifting and aligning unit and a tamping unit with tamping picks.

[0005] This method is used to fix the track bed, consisting of rails and sleepers, after a lifting and straightening process. During this process, vibrating tamping picks are inserted into the track ballast on both longitudinal sides of a sleeper and aligned with each other. Each tamping pick has a downward-tapering shaft, at the end of which a pick plate is positioned transversely to the direction of placement. During the placement process, ballast is first pushed into a cavity created by lifting the sleeper. After this filling, the ballast is compacted by continuous vibration of the tamping picks, thus creating a durable sleeper support.

[0006] Such a process is described, for example, in AT 520056 A1. The tamping process is divided into individual phases. In a first phase, a tool carrier with tamping tools is lowered, with tamping picks plunging into sleeper compartments located next to a sleeper. While still being lowered, a second phase begins with an approach movement, whereby the tamping picks move towards the sleeper. The lowering of the tool carrier ends when the tamping pick ends have reached a defined penetration depth, and the approach movement continues. In a third phase, the movement is reversed. The tool carrier, along with the tamping tools, is moved upwards, and a return movement causes the opposing tamping tools, arranged in a pincer-like fashion, to open.

[0007] The invention is based on the objective of improving a method of the type mentioned above in such a way that, after a tamping process, optimal compaction of the track ballast bed is achieved, in particular with an approximately uniform ballast bed surface. Furthermore, it is an objective of the invention to provide a corresponding system for carrying out the method.

[0008] These problems are solved by the features of independent claims 1 and 8. Dependent claims specify advantageous embodiments of the invention. 3

[0009] According to the invention, a computing unit determines, upon completion of the positioning process, a point on the ballast surface where a shaft of the tamping pick protrudes from the track ballast. A control device coordinates the height adjustment drive and the positioning drives in such a way that the respective tamping pick is moved through the assigned point on the ballast surface. During this predetermined movement, a lower endpoint of the respective tamping pick moves along a predetermined trajectory through the assigned point on the ballast surface. Preferably, the trajectory for the respective tamping pick is predetermined such that the geometric centroids or area centroids of the cross-sections of the tamping pick move approximately through a center of the assigned point on the ballast surface.

[0010] The coordinated upward movement of the tool carrier and the return movement of the tamping tools minimizes the impact on the compacted track ballast during the withdrawal of the tamping picks. So-called tamping holes are largely prevented, leaving an almost uniform ballast surface after the tamping picks are removed.

[0011] Without the adaptation of the tamping process according to the invention, two scenarios are possible, each with more or less significant disadvantages. In the first scenario, the return movement is delayed relative to the upward movement, causing the tamping picks, which are still positioned, to move upwards. This throws ballast upwards, onto the tops of the sleepers, into the area of ​​the rail fastenings, and onto the rail heads. The ballast density deteriorates in the spaces between the sleepers, and pronounced tamping holes are formed. Furthermore, the lateral resistance of the track is reduced. In the second scenario, the upward movement of the tool carrier is delayed relative to the return movement of the tamping tools. The resulting opening movement of the tamping picks in the track ballast bed causes ballast to be pushed away from the sleeper.The ballast compaction under the sleeper decreases because the already compacted ballast can flow away towards the opening tamping picks. This also results in inhomogeneous compaction and reduced lateral resistance of the track.

[0012] These disadvantages are avoided by moving the respective tamping pick through the associated point on the ballast surface. This determined point on the ballast surface, at which the tamping pick protrudes from the track ballast at the end of the tamping process, can be considered the imaginary intersection of the tamping pick shaft with the ballast surface. The center of this point on the ballast surface is then the geometric centroid or centroid of this intersection. Below the ballast surface, the pick shaft and the attached pick plate displace the ballast. This displaced ballast volume decreases continuously during the withdrawal of the tamping pick from the track ballast according to the invention.

[0013] The preferred trajectory for the lowest endpoint of the respective tamping pick of a line is through the geometric centroids or area centroids of the cross-sections of the 5 in the auxiliary position.

[0014] The pick shaft is approximated so that the lower sections of the pick shaft and the pick plate are essentially moved by the imaginary intersection of the pick shaft with the gravel bed surface when being pulled out.

[0015] This means that the ballast compaction achieved by the initial placement of the ballast remains largely unaffected by the withdrawal of the tamping picks in the final phase of the tamping process. The ballast in the respective sleeper bay is not loosened because ballast displacement is minimized. Subsequent filling of tamping holes is largely avoided. Furthermore, no ballast is thrown upwards onto the sleeper tops, rail fastenings, and rails. Ballast particles on the sleeper tops and rail fastenings can cause dangerous ballast flying when a rail vehicle passes over them at high speed. With the method according to the invention, subsequent sweeping of the ballast from the sleepers and rail fastenings is unnecessary. Likewise, the risk of damage to wheels and rails from ballast particles on the track surfaces is eliminated.

[0016] Overall, the remaining homogeneous ballast compaction in the sleeper bays and under the sleepers results in high lateral resistance of the sleepers. The track geometry remains stable for a long time, thus extending the intervals between necessary track geometry corrections.

[0017] In a further development of the method, a swivel drive arranged on the respective tamping tool is controlled by the control device for laterally pivoting one of the tamping picks, wherein the tamping pick with a lateral 24009

[0018] 6

[0019] The tamping pick is moved by pivoting through the corresponding area of ​​the ballast surface. Such laterally pivoting tamping picks are useful for working on turnouts and track crossings. In areas with limited clearance between sleepers, rails, guard rails, switch blades, and other track components, individual tamping picks are pivoted upwards so that only the remaining picks penetrate into free areas of the track ballast. The penetrating tamping picks are generally not oriented vertically downwards, but rather slightly inclined with their plates towards the rails. This achieves particularly good compaction of the ballast below the crossing points of rails and sleepers. A high-quality support for the sleepers is especially important there to prevent them from tilting under load.By pivoting sideways back during the pulling process, the lower end of each tamping pick moves through the associated ballast bed surface area, and the compacted zone under the sleepers remains unaffected.

[0020] Advantageously, the current position of each tamping pick is determined by means of a sensor arrangement. In a simpler version, the respective tamping pick position is derived solely from control signals of the height adjustment drive and the auxiliary drives, taking into account the known geometric and kinematic conditions. The drives are, for example, designed as hydraulic cylinders with discrete piston adjustment. In the improved method, the sensor arrangement enables precise and reliable detection of the respective pick position in a simple manner. With the known pick position at the end of the auxiliary movement, further calculations are then performed using the 24009

[0021] 7

[0022] The calculation unit calculates the point on the surface of the ballast bed where the shaft of the tamping pick protrudes from the track ballast bed.

[0023] Preferably, output data from the sensor arrangement is transmitted to the control unit, whereby the respective tamping pick is moved along an assigned trajectory in a controlled manner. In particular, a lower endpoint of the respective tamping pick is moved along the trajectory. The control system enables precise movement along the predefined trajectory even in the presence of disturbances.

[0024] With a further improvement, the respective tamping tool is returned to a final position after the associated tamping pick has been completely withdrawn from the track ballast. Setting a large opening width on the opposing tamping picks thus has no effect on the withdrawal process of the respective tamping pick. This is particularly useful with irregular sleeper spacing and when tamping under double sleepers.

[0025] Preferably, the tamping picks are subjected to vibration during lowering, ordering, and resetting and lifting. Continuous vibration of the tamping picks during these process steps mobilizes the gravel particles within their area of ​​influence. This reduces resistance when inserting and positioning the tamping picks. Furthermore, a higher compaction of the gravel particles is achieved during positioning. When withdrawing the tamping picks, the vibration causes the mobilized gravel particles to immediately fill the volume displaced by each pick. 24009

[0026] 8

[0027] This effect is enhanced if the tamping picks are vibrated at a higher frequency during resetting and lifting than during positioning. The increased frequency causes the gravel grains directly adjacent to each tamping pick to enter a flow-like state, resulting in particularly efficient filling of the volume released by the tamping picks.

[0028] The system according to the invention for carrying out one of the described methods comprises a tamping unit with a tool carrier height-adjustable by means of a height-adjusting drive, on which tamping tools with tamping picks for immersion in a track ballast bed are mounted by means of auxiliary drives, wherein a computing unit is provided for determining a point on the ballast surface at which a shaft of the respective tamping pick protrudes from the track ballast bed at the end of the insertion, and wherein a control device is arranged for the coordinated control of the height-adjusting drive and the auxiliary drives such that the respective tamping pick is moved through the associated point on the ballast surface. With this system, which is set up for carrying out the method according to the invention, a high quality of the processed track is achieved.A stable track geometry is achieved in accordance with the specifications, exhibiting particularly high lateral displacement resistance. This is because, after tamping a sleeper, the compaction result is not adversely affected when the tamping pick is withdrawn. With system improvements, the dimensions of the tamping unit are stored in a memory unit assigned to the control unit and / or the processing unit. This allows for a simple calculation, based on control signals from the height adjustment drive and the auxiliary drives, of the points on the ballast surface where the tamping picks protrude from the ballast at the end of each tamping operation. In the simplest case, the distance to the ballast surface is estimated based on empirical data and stored in the processing unit.Preferably, the impact of the respective tamping pick on the gravel bed surface is detected based on the resistance encountered, and the current position of the tamping pick relative to the gravel bed surface is derived from this.

[0029] Furthermore, in a further development of the system, a swivel drive for laterally pivoting the associated tamping pick is arranged on each tamping tool. During the withdrawal of the tamping picks from the ballast bed, the respective swivel drive is controlled by the control unit in such a way that the respective tamping pick is moved through the associated point on the ballast bed surface.

[0030] In a further improvement, a sensor array is installed to detect the current position of each tamping pick. This allows the position of each tamping pick relative to the ballast bed to be directly determined at the end of a tamping operation. From the measurement results of the sensor array, the positions of the ballast surface points where the tamping picks protrude from the ballast bed are calculated, and subsequently, the trajectories of the tamping picks as they are withdrawn from the ballast bed are derived.

[0031] Advantageously, the sensor arrangement comprises several sensors, with each of the drives for changing the position of the respective tamping pick being assigned a motion sensor and / or a displacement sensor and / or a rotation angle sensor. Using these sensors, and taking into account the known geometric and kinematic conditions, the current position of the respective tamping pick in a spatial reference frame can be determined.

[0032] Preferably, the sensor arrangement is coupled to the control unit, wherein a controller for the regulated control of the drives is provided in the control unit. With this configuration of the system, a controlled movement of the respective tamping pick is achieved, particularly during the withdrawal of the tamping picks from the ballast bed.

[0033] In a preferred embodiment, the respective auxiliary drive is connected on the one hand to the associated tamping tool and on the other hand to a vibratory drive. The vibratory drive ensures vibration generation with a stable amplitude. In another embodiment, the respective auxiliary drive is configured to generate both the auxiliary movement and the vibratory movement. For example, a hydraulic cylinder is controlled by a servo or proportional valve, whereby cyclic pressure pulses are superimposed on the pressure applied for the auxiliary movement. 24009

[0034] 11

[0035] In a further improvement of the system, a distance sensor is arranged to detect the distance to the ballast bed surface. From the detected distance between the distance sensor and the ballast bed surface, the position of the respective tamping pick relative to the ballast bed surface can be derived by the processing unit, taking into account the known geometric and kinematic conditions. Preferably, the distance sensor is arranged directly on the tamping unit, for example on the tool carrier or on the unit frame, and coupled to the processing unit.

[0036] The invention is explained below by way of example with reference to the accompanying figures. These show, in schematic representation:

[0037] Fig. 1 System with a tamping machine arranged on a track section;

[0038] Fig. 2 Tamping unit with tamping picks immersed in a track ballast bed in side view;

[0039] Fig. 3 Tamping unit with tamping picks immersed in a track ballast bed in front view;

[0040] Fig. 4 Stuffing unit in side view;

[0041] Fig. 5 Side view of auxiliary drive;

[0042] Fig. 6 Tool carrier in side view;

[0043] Fig. 7 Stuffing tool with stuffing pick in side view;

[0044] Fig. 8 Stuffing unit with raised tool carrier in

[0045] Side view;

[0046] Fig. 9 Stuffing unit with lowered tool carrier in

[0047] Side view;

[0048] Fig. 10 Stuffing unit with lowered tool carrier in

[0049] Front view;

[0050] Fig. 11 Pulling process opposite

[0051] Darning pick; 24009

[0052] 12

[0053] Fig. 12 Darning pick in front view;

[0054] Fig. 13 Darning pick according to Fig. 12 in a side view.

[0055] The system 1 shown in Fig. 1 comprises a tamping machine 2 with a tamping unit 3 and a lifting and aligning unit 4. The units 3 and 4 are arranged on a machine frame 5, which is supported on rail bogies 6 and can be moved on a track 7. A track grid, consisting of sleepers 8 and rails 9 attached to them, rests in a track ballast bed 10. During a processing operation, the track grid is lifted section by section by means of the lifting and aligning unit 4 and laterally aligned, and fixed in the predetermined position by means of the tamping unit 3.

[0056] The exemplary stuffing unit 3 in Figures 2-7 comprises a unit frame 11, which is laterally displaceable and preferably rotatable about a vertical axis on the machine frame 5 by means of a rotary device. Vertical guides 12 for a tool carrier 13 are arranged on the unit frame 11. A height adjustment drive

[0057] The tool carrier 13 is height-adjustable along these guides 12 relative to the aggregate frame 11. Two opposing tamping tools are mounted on the tool carrier 13.

[0058] 15 are mounted in a pincer-like manner. Each tamping tool 15 forms a pivoting lever, the upper end of which is connected to an associated auxiliary drive 16. At the free lower end of each tamping tool 15, two tamping picks 17 are arranged side by side. In a simpler version, only one tamping pick 17 is arranged on each tamping tool 15. 24009

[0059] 13

[0060] Preferably, the auxiliary drives 16 are designed as hydraulic cylinders. Extension of the respective piston rod causes the tamping picks 17 to be positioned relative to each other. Furthermore, the auxiliary drives 16 are coupled to a vibratory drive 18. The vibratory drive 18 comprises, in particular, an eccentric shaft on which the auxiliary drives 16 are mounted. During operation, a rotation of the eccentric shaft is transmitted via the auxiliary drives 16 into oscillating vibratory movements of the tamping tools 15.

[0061] The drives 14, 16, 18 of the tamping unit 3 are controlled by a control device 19. Preferably, the control device 19 comprises a microcontroller in which a control program for the coordinated control of the individual drives 14, 16, 18 is configured.

[0062] A tamping process is divided into several process steps that are repeated cyclically. In a first process step, the tamping picks 17 are positioned above the ballast bed surface 20. For this purpose, the tamping machine 2 is moved along the track until the respective tamping pick 17 is located above a sleeper bay.

[0063] In the next step, the tool carrier 13 is lowered, whereby the vibrating tamping picks 17 plunge into the track ballast 10. The lowering process is completed as soon as the lower ends of the tamping picks 17 have reached a predetermined immersion depth. Typically, an upper pick plate edge 21 is located just below the underside of a sleeper. The vibration frequency during immersion is, for example, 45 Hz, which particularly stimulates the mobility of the individual ballast grains. 24009

[0064] 14

[0065] The positioning of the tamping tools 15 begins during or immediately after the final lowering phase. The positioning drives 16 extend and push the upper lever arms of the tamping tools 15 apart, thereby positioning the tamping picks 17 attached to the lower lever arms. The vibration continues, but at an optimal frequency of 35 Hz for moving and compacting the ballast grains.

[0066] In the final stage of the tamping process, a reverse movement takes place, whereby the tool carrier 13 is raised and the auxiliary drives 16 are retracted. The advantages of the method according to the invention come into play in this final stage. The current position and orientation of the respective tamping pick 17 at the end of the auxiliary operation is important in this respect.

[0067] To determine the position of each tamping pick 17, a computing unit 22 is arranged in the control device 19 or as a separate device. Geometric and kinematic data of the tamping unit 3 are stored in this computing unit 22. This will be discussed in more detail with reference to Figures 4-7.

[0068] On the tool carrier 13, a horizontal distance a between the two bearing points 23 of the tamping tools 15 and a vertical distance b between these bearing points 23 and a center 24 of the vibratory drive 18 are taken into account. The respective tamping tool 15 is considered in a starting position with a vertically oriented tamping pick 17. Here, a horizontal distance c and a vertical distance d between the pivot bearing point 25 and an upper bearing eye 26 for connection with the 24009 are initially considered.

[0069] The associated auxiliary drive 16 is important. In addition, there is a distance e between the pivot bearing point 25 and the lower end of a tamping pick holder 27, and a free length f of the tamping pick 17 attached to the tamping pick holder 27. This results in a total length of the lower lever arm of the tamping tool 15. Another dimension for the calculations is the shaft diameter g of the tamping pick 17. The decisive factor here is the shaft diameter g at the point to which the tamping pick 17 typically penetrates the track ballast 10.

[0070] Further data for calculating the position of the tamping picks 17 are the current length h of the height adjustment drive 14 and the current length i of the respective auxiliary drive 16. From these variable lengths h and i, the current position of the associated tamping tool 15 is determined. Preferably, each drive 14, 16 is assigned its own displacement sensor for detecting the current drive position. Alternatively, a rotary encoder can be arranged in the respective pivot bearing 28, the output data of which indicates the current position of the associated tamping tool 15 relative to the tool carrier 13.

[0071] Further data is added in a further development with laterally pivoting tamping picks (Figs. 8-10). Here, swivel drives 29 are arranged between the upper swivel arm of the respective tamping tool 15 and the associated pick holder 27. The distances between the additional bearing points 30 of the pick holders 27 are stored in the computing unit 22. In addition, the variable lengths of the swivel drives 29 are supplied to the computing unit 22, whereby rotary encoders can also serve as an alternative. 24009

[0072] 16

[0073] In Fig. 8, the further developed tamping unit 3 with the tamping picks 17 is positioned above the ballast bed surface 20. The lower ends 31 of the tamping picks are highlighted with markings in the illustration. An optimized trajectory 32 is specified for these tamping pick ends 31 when the tamping picks 17 are withdrawn. For this purpose, at the end of each insertion process, a ballast bed surface location 33 is first determined for each tamping pick 17, at which a shaft 34 of the tamping pick 17 protrudes from the track ballast bed 10. This determination of the ballast bed surface locations 33 is carried out in the processing unit 22 with the data ai described above, based on the given geometric and kinematic relationships.

[0074] Figure 11 shows several successive positions of the tamping picks 17 pulled from the track ballast 10. To determine the respective ballast surface point 33, the distance between the respective tamping tool 15 and the ballast surface 20 is used. In the simplest case, this distance is estimated based on experience. Preferably, the position of the height adjustment drive 14 is recorded when the tamping picks 17 strike the ballast surface 20 during the insertion process. The distance can then be derived from this using the stored geometric data. In a further development, a separate distance sensor 35 is arranged to determine the distance to the ballast surface 20.

[0075] At the end of the insertion process, the lower tamping pick ends 31 are located at their lowest points. Here, the 24009 values ​​determined by the calculation unit 22 are shown.

[0076] 17

[0077] The gravel bed surface locations 33 are visible as intersection surfaces 36 of the associated pick shaft 34 and the gravel bed surface 20. Each of these gravel surface locations 33 has a geometric centroid 37, which forms the center of this gravel surface location 33. The predetermined trajectory 32 of the respective lower tamping pick end 31 preferably runs through this center.

[0078] The method according to the invention provides that the respective tamping pick 17 is moved through the associated ballast bed surface area 33. This requirement is met if the respective lower end of the tamping pick 31, through the coordinated control of the height adjustment drive 14 and the auxiliary drives 16, moves along a continuous trajectory through the associated cross-sectional area 36 when the tamping pick 17 is withdrawn. Preferably, the first and second derivatives of the trajectory are continuous, so that the respective tamping pick 17 performs a smooth movement without lateral displacement while being withdrawn from the track ballast bed 10. The lower end of the tamping pick 31 moves essentially along a line through the geometric centroids of the cross-sections along the pick shaft 34.

[0079] Only when the respective tamping pick 17 has been completely pulled out of the track ballast bed 10, is a final reset of the auxiliary drives 16 carried out so that a desired opening width w is set for the next tamping process.

[0080] Figures 12 and 13 show an advantageous embodiment of the respective tamping pick 17 for further improving its removal from the track ballast bed 10. In the front view (Fig. 12) it can be seen that the upper 24009

[0081] 18

[0082] The edges of the pickaxe plate 21 slope outwards from the base of the shaft. The side view (Fig. 13) also shows that the pickaxe plate has a ridge with sloping surfaces on its upper surface. These downward-sloping surfaces deflect the gravel grains laterally as the tamping pick 17 is pulled out of the gravel bed 10. These paths of movement of the gravel grains are indicated by arrows. The special shape of the upper edges of the pickaxe plate largely prevents gravel grains from being moved upwards together with the tamping pick 17.

Claims

19 Patent claims 1. Method for compacting a track ballast bed (10) using a tamping unit (3) which has a tool carrier (13) and tamping tools (15) with tamping picks (17) mounted on it, comprising the process steps: - Positioning the tamping picks (17) above the surface (20) of the track ballast bed (10) , - Lowering of the tool carrier (13) by means of a height adjustment drive (14) , whereby the tamping picks (17) dip into the track ballast bed (10), - Positioning the tamping tools (15) by means of positioning drives (16), whereby the tamping picks (17) are moved towards each other, - Resetting the tamping tools (15) and raising the tool carrier (13) , wherein the tamping picks (17) are moved away from each other and pulled out of the track ballast bed (10), characterized in that, by means of a calculating unit (22) for the respective tamping pick (17) at the end of the positioning, a ballast bed surface location (33) at which a shaft (34) of the tamping pick (17) protrudes from the track ballast bed (10) is determined and that, by means of a control device (19), the height adjustment drive (14) and the positioning drives (16) are controlled in such a coordinated manner that the respective tamping pick (17) is moved through the associated ballast bed surface location (33).

2. Method according to claim 1, characterized in that a pivoting drive (29) arranged on the respective tamping tool (15) is controlled by the control device (19) for laterally pivoting one of the tamping picks (17) and that the tamping pick (17) is equipped with a lateral 20 The pivoting movement is carried out by the associated gravel bed surface point (33).

3. Method according to claim 1 or 2, characterized in that a current position of the respective tamping pick (17) is determined by means of a sensor arrangement.

4. Method according to claim 3, characterized in that output data from the sensor arrangement are transmitted to the control device (19) and that the respective tamping pick (17) is moved in a controlled manner along an assigned trajectory (32).

5. Method according to one of claims 1 to 4, characterized in that the respective tamping tool (15) is returned to a final position after the associated tamping pick (17) has been completely withdrawn from the track ballast bed (10).

6. Method according to one of claims 1 to 5, characterized in that the tamping picks (17) are subjected to vibration during lowering, ordering, resetting and raising.

7. Method according to claim 6, characterized in that the vibration of the tamping picks (17) during resetting and lifting is carried out at a higher frequency than during positioning.

8. System (1) for carrying out a method according to one of claims 1 to 7, comprising a stuffing unit (3) with a tool carrier (13) height-adjustable by means of a height adjustment drive (14), on which by means of 21 The auxiliary drives (16) pivotable tamping tools (15) with tamping picks (17) for immersion in a track ballast bed (10) are mounted, characterized in that a calculating unit (22) is provided for determining a ballast bed surface point (33) at which a shaft (34) of the respective tamping pick (17) protrudes from the track ballast bed (10) at the end of the positioning, and that a control device (19) is provided in such a way as to coordinate the control of the height adjustment drive (14) and the auxiliary drives (16) such that the respective tamping pick (17) is moved through the associated ballast bed surface point (33).

9. System (1) according to claim 8, characterized in that dimensions (ai) of the stuffing unit (3) are stored in a storage unit.

10. System (1) according to claim 8 or 9, characterized in that a pivoting drive (29) for laterally pivoting the associated tamping pick (17) is arranged on the respective tamping tool (15).

11. System (1) according to one of claims 8 to 10, characterized in that a sensor arrangement is provided for detecting a current position of the respective tamping pick (17).

12. System (1) according to claim 11, characterized in that each of the drives (14, 16, 29) for changing the position of the respective tamping pick (17) is assigned a motion sensor and / or a displacement sensor and / or a rotation angle sensor. 22 13. System (1) according to claim 11 or 12, characterized in that the sensor arrangement is coupled to the control device (19) and that a controller for controlled control of the drives (14, 16, 29) is provided in the control device (19).

14. System (1) according to one of claims 1 to 13, characterized in that the respective auxiliary drive (16) is connected on the one hand to the associated tamping tool (15) and on the other hand is coupled to a vibration drive (18).

15. System (1) according to one of claims 1 to 14, characterized in that a distance sensor (35) is arranged for detecting the distance of the gravel bed surface (20).

Images