Tamping unit and method for tamping a group of adjacent sleepers of a track

Abstract

The invention relates to a tamping unit (7) for tamping a group of adjacent sleepers (4, 4a-4e) of a track (3), with tamping tools (17) arranged one behind the other in a working direction (16), wherein the respective tamping tool (17) is pivotably mounted on a height-adjustable tool carrier (14) about an associated pivot axis (18), and wherein auxiliary drives (22b) of individual tamping tools (17) are designed for a first auxiliary movement (25b) and for an opposite second auxiliary movement (25c). Each tamping tool (17m, 17m1, 17m2) arranged between a foremost tamping tool (17v) and a rearmost tamping tool (17h) is assigned an auxiliary drive (22b) designed for two auxiliary movements (25b, 25c) in opposite directions.In this way, each of the tamping tools (17) arranged one behind the other is arranged in a row with tamping tools (17) arranged next to it for sole immersion into a sleeper intermediate space (28).

Description

Technical area

[0001] The invention relates to a tamping unit for tamping a group of adjacent sleepers on a track, comprising tamping tools arranged one behind the other in a working direction. Each tamping tool is pivotably mounted on a height-adjustable tool carrier about an associated pivot axis. Positioning drives for individual tamping tools are configured for a first positioning movement and for an opposite second positioning movement. For tamping a respective sleeper, several tamping tools are arranged side by side in a row at several locations. Furthermore, the invention relates to a method for operating the tamping unit. State of the art

[0002] To restore or maintain a specified track position, ballasted tracks are regularly tamped using a tamping machine. The tamping machine travels along the track and raises the track grid, formed by sleepers and rails, to a desired level using a lifting / leveling unit. The new track position is secured by tamping the sleepers using a tamping unit. The tamping unit comprises tamping tools with tamping picks that, subjected to vibration during the tamping process, plunge into the ballast bed and are moved towards each other using adjusting drives. In the process, ballast is pushed under the respective sleeper and compacted. Tamping machines, in particular, use tamping units to simultaneously tampe a group of adjacent sleepers. Such tamping units are known, for example, from US 3 589 297 A, EP 3 207 179 B1, EP 3 545 134 B1 or EP 3 237 681 B1.The high processing speed achieved in this way makes it possible to work through a track in short closure periods.

[0003] A generic tamping unit is known from EP 0 775 779 A1. In this unit, several tamping tools are mounted one behind the other on separately height-adjustable tool carriers. The tamping tools on one of these tool carriers are assigned positioning cylinders which are designed for a first positioning movement and a second, opposite positioning movement. Each tamping cycle consists of two successive sub-sequences during which tamping tools immerse themselves in the sleeper compartments of the track, are positioned relative to one another, and then raised. In the first sub-sequence, tamping tools immerse themselves directly next to one another in the same sleeper compartment, and the first positioning movement occurs. In the second sub-sequence, tamping tools once again immerse themselves in two sleeper compartments, and the opposite second positioning movement occurs. In this way, all sleepers in the group currently being processed are tamped. Description of the invention

[0004] The invention is based on the object of improving a tamping unit of the type mentioned above to achieve efficient operation. Furthermore, the ballast in the sleeper compartments and the tamping unit itself are to be protected during a tamping process. A further object of the invention is to provide a corresponding method.

[0005] According to the invention, these objects are achieved by the features of independent claims 1 and 9. Dependent claims specify advantageous embodiments of the invention.

[0006] Each tamping tool arranged between a frontmost tamping tool and a rearmost tamping tool is assigned an adjusting drive designed for two adjusting movements in opposite directions. For tamping the respective sleeper at several points, several tamping tools are arranged next to one another in a row. According to the invention, each of the tamping tools arranged one behind the other is arranged in a row with tamping tools arranged next to it for sole insertion into a sleeper gap. Usually, four tamping tools, each with two tamping picks, are arranged next to one another in each row. During a tamping process, two tamping tools per row on either side of a respective rail of the track insert into a sleeper gap in order to undertamp a sleeper adjacent to the respective sleeper gap.

[0007] In conventional tamping units for the simultaneous tamping of several adjacent sleepers, two tamping tools, arranged directly behind one another or diagonally offset from one another, penetrate the ballast bed in at least one sleeper gap. The tamping tools vibrate to loosen the ballast bed during the penetration process. However, wear can occur due to the close proximity of the vibrating tamping tools within the same sleeper gap. Between the vibrating tamping tools in close proximity within the same sleeper gap, increased ballast abrasion, even fragmentation, occurs. The tamping tools themselves are also subject to increased wear due to this stress.

[0008] The increased formation of fines in the ballast bed has an adverse effect on the elasticity of the track, the ballast modulus, and the shear strength of the ballast. Track stability deteriorates due to the increasing inhomogeneity and reduced drainage of the ballast. This results in additional stress on the superstructure and the rail vehicles traveling on the track. Furthermore, the fines harden the ballast bed, making it difficult for the tamping tools to penetrate during subsequent tamping work and increasing the loads on the tamping unit.

[0009] All of these disadvantages are avoided by the invention. Although the tamping tools arranged side by side in a row are subjected to vibration and plunge into the same sleeper gap, these tamping tools are spaced far enough apart that the forces exerted by these tools on the ballast grains do not cause destructive stresses on the ballast. Therefore, during a tamping process using the tamping unit according to the invention, far fewer ballast fines are formed, resulting in a durable track bed with high resistance to lateral displacement. The ballast mode and the gravity strength of the ballast bed are maintained. The protection of the ballast and the improved drainage of the ballast bed result in longer ballast cleaning and replacement intervals.

[0010] In addition, penetration resistance is lower because only the ballast in front of one row of tamping picks needs to be displaced in each intermediate compartment. This reduces the mechanical stress on the tamping unit and the wear on the tamping picks, resulting in longer service and maintenance intervals. The lower penetration resistance allows for smoother penetration into the ballast bed with a lower lowering speed of the tamping tools. This reduces the plunge shock that occurs when the tamping pick tips hit the ballast surface and can lead to the splitting of ballast grains.

[0011] Further advantages include reduced noise emissions, lower energy consumption, and lower vibration loads on the equipment, the track bed, including the track electronics, and the operating personnel. Compared to a conventional tamping unit, far fewer ballast grains are thrown up when the tamping tools are pulled out of the ballast bed, thus eliminating so-called tamping holes. The ballast tools require less work to fill the cavities created under the sleepers during the track lifting process.

[0012] Advantageously, all tamping tools arranged one behind the other are mounted on a common tool carrier, so that only one height adjustment drive is required to lower and raise the tamping tools together. Compared to conventional tamping units, the number of moving components is reduced, resulting in reduced component wear.

[0013] In a preferred embodiment, all adjacent pivot axes of the tamping tools arranged one behind the other are spaced apart by a distance that approximates a sleeper pitch of the track to be tamped. If the tamping unit is intended for tamping tracks with different sleeper pitches, an average of these sleeper pitches is selected to determine the distance between the adjacent pivot axes. Adjustments to larger or smaller sleeper pitches are made by slightly pivoting the respective tamping tool before a penetration process. The uniform adjustment movements of all tamping tools resulting from this arrangement lead to optimal filling of cavities beneath the sleepers to be tamped. In addition, tracks with a small sleeper pitch or with particularly wide sleepers are easy to process.Even with a small sleeper gap width, an optimal tamping process is achieved because more than half the gap width is available for the adjustment path and only one row of picks penetrates into the respective sleeper gap at a time.

[0014] In one variant of the invention, the respective auxiliary drive is a hydraulic cylinder for simultaneously generating vibration and an auxiliary movement. Pulsating pressure on the respective hydraulic cylinder at a frequency between 30 Hz and 45 Hz requires a hydraulic system with servo or proportional valves and continuous displacement measurement of the respective piston rod. If necessary, an oil cooling system must be adapted to dissipate the heat generated by the pulsating pressure.

[0015] In another preferred variant of the invention, the respective auxiliary drive is coupled to the associated tamping tool on the one hand and mounted on an eccentric shaft for generating vibration on the other. This vibration generation by means of a rotating eccentric shaft leads to high process reliability because the vibration amplitude is maintained even with larger reaction forces from the ballast bed.

[0016] An improvement to this variant is achieved by a configuration in which all auxiliary drives of the tamping tools arranged one behind the other are mounted on a common eccentric shaft. This is particularly useful in a version with a common tool carrier. Due to the reduced complexity of using only one vibration drive, component wear and the risk of malfunctions are reduced.

[0017] Advantageously, the respective auxiliary drive is mounted on the eccentric shaft with an adjustable eccentricity, allowing the vibration amplitude to be adjusted while the eccentric shaft's rotation drive is running. The respective eccentricity can be reduced to zero to completely eliminate vibration. A corresponding adjustability of the eccentricity is described in AT 517999 A1. Alternatively, the auxiliary cylinders mounted on the eccentric shaft can be depressurized to eliminate vibration of the associated tamping tools. The tamping tools, immersed in the ballast bed, are held in position by the adjacent ballast.

[0018] In a particularly efficient development of the invention, four tamping tools are arranged one behind the other, with all tamping tools being arranged symmetrically with respect to a plane of symmetry running perpendicular to the working direction. The middle tamping tools with respect to the working direction are each coupled to a support cylinder for two opposing support cylinders. In addition, the tamping picks of these middle tamping tools have pick plates with two working surfaces facing away from each other. With such a tamping unit, three adjacent sleepers can be tamped in one tamping cycle. Compared to a conventional tamping unit for simultaneously tamping three sleepers, the new tamping unit comprises fewer support drives, thereby reducing wear and the risk of malfunctions.

[0019] In another advantageous development of the invention, three tamping tools are arranged one behind the other, with the frontmost and rearmost tamping tools, in particular, being arranged symmetrically with respect to a plane of symmetry running perpendicular to the working direction. Here, the middle tamping tool is coupled to the positioning cylinder for two opposing positioning movements and features a pick plate with two opposing working surfaces. In the area of the pivot axis, an upper lever arm of the middle tamping tool is tilted forwards or backwards and coupled to the inclined positioning cylinder. With this configuration of the tamping unit, two sleepers can be efficiently tamped in one tamping cycle.

[0020] In the method according to the invention for operating the tamping unit, the tamping tools arranged one behind the other perform the following movements during a tamping cycle: simultaneous immersion of all tamping tools in the sleeper compartments of the track to be tamped under vibration, wherein each of the tamping tools arranged one behind the other in a row with tamping tools arranged next to it immerses alone in a sleeper compartment (28), positioning a first group of tamping tools under vibration, wherein this first group includes all tamping tools with an associated adjustment drive for two adjustment movements and wherein these tamping tools carry out the first adjustment movement, positioning a second group of tamping tools under vibration, wherein this second group also includes all tamping tools with an associated adjustment drive for two adjustment movements and wherein these tamping tools carry out the second adjustment movement, and simultaneous lifting of all tamping tools.In this way, all sleepers in the currently processed sleeper group are tamped with a single plunge of the tamping tools. Repeated plunges, with the associated stress on the ballast, are not necessary. After the tamping cycle is completed, the tamping unit is moved in the working direction to the next group of sleepers to be tamped, and a new tamping cycle begins.

[0021] In an alternative method for operating the tamping unit with four tamping tools arranged one behind the other, the following process steps are carried out one after the other: the tamping unit is positioned over a group of three sleepers; a tamping operation is carried out with a single adjustment movement by lowering the tamping tools, under-tamping the first and third sleepers of the group (seen in the working direction), and raising the tamping tools; the tamping unit is moved further in the working direction by one sleeper pitch; a further tamping operation is carried out with the single adjustment movement; the tamping unit is moved further in the working direction by three sleeper pitches; a further tamping operation is carried out with the single adjustment movement.

[0022] This process variant ensures that the sleepers are tamped in a way that is particularly gentle on ballast. Short description of the drawings

[0023] The invention is explained below by way of example with reference to the accompanying figures. They show schematically: Fig. 1: Track construction machine with a tamping unit on a track in a side view; Fig. 2: Tamping unit for tamping a group of three sleepers; Fig. 3: Track with tamping unit in a front view; Fig. 4: Tamping unit for tamping a group of two sleepers during a dipping process of the tamping tools into a ballast bed; Fig. 5: Tamping unit according to Fig. 4 during a first setting process; Fig. 6 Tamping unit according to Fig. 4 during a second setting process; Fig. 7 Tamping unit according to Fig. 2 during a first setting process; Fig. 8 Tamping unit according to Fig. 2 during a second setting process; Fig. 9Procedure sequence when operating the tamping unit according to Fig. 2 with acyclic forward movement of the tamping unit in the working direction. Description of the embodiments

[0024] The Fig. 1 The track construction machine 1 shown is designed as a tamping machine for tamping sleepers 4 stored in a ballast bed 2 of a track 3. The track construction machine 1 comprises a machine frame 6 supported on rail bogies 5, on which a tamping unit 7 is arranged. By means of this tamping unit 7, a group of several adjacent sleepers 4 can be tamped during a tamping process. Furthermore, the track construction machine 1 comprises a lifting and straightening unit 8 for lifting and straightening the track grid formed from sleepers 4 and rails 9. A measuring system 10 records the current rail position.

[0025] The tamping unit 7 is attached to the machine frame 6 by means of an adjusting device 11. It comprises a unit frame 12 with guides 13. A tool carrier 14 is mounted on the guides 13 for height adjustment by means of a height adjustment drive 15. Several tamping tools 17 are mounted on the tool carrier 14, one behind the other, pivotable about a respective pivot axis 18 with respect to a working direction 16. The adjacent pivot axes 18 are spaced apart by a distance a that approximates a sleeper pitch t of the track 3 to be tamped.

[0026] Each tamping tool 17 comprises a pivot lever 19 with an upper and a lower lever arm relative to the associated pivot axis 17. At least one tamping pick 20 is arranged on the lower lever arm. Preferably, two tamping picks 20 are mounted side by side in a tamping pick holder 21 of the respective tamping tool 17. The upper lever arm is pivotally connected to a first end of an auxiliary drive 22. A second end of the auxiliary drive 22 is mounted on an eccentric shaft 23 of a vibration drive 24. The respective auxiliary drive 22 is preferably a hydraulic cylinder connected to a hydraulic system of the track construction machine 1.

[0027] In the example shown, all auxiliary drives 22 of the tamping tools 17 arranged one behind the other are mounted on the same eccentric shaft 23. Specifically, each auxiliary drive 22 is mounted on an associated eccentric shaft section with its own eccentricity. An adjustable sleeve is mounted on each of these eccentric shaft sections to adjust the respective eccentricity. A corresponding mechanism is described in AT 517999 A1.

[0028] In a variant not shown, the respective auxiliary drive 22 is attached directly to the tool carrier 14 and configured to simultaneously generate a vibration and an auxiliary movement 25. As with the eccentric shaft 23 with adjustable eccentricity, various vibration parameters are also adjustable in this variant. In particular, the vibration can be switched on and off at any time. Another possibility is to suspend the vibration transmission of the eccentric shaft 23 by depressurizing the respective auxiliary drive 22. The associated tamping tool 17, immersed in the ballast bed 2, is then held in position by the adjacent ballast.

[0029] Fig. 2 shows the tamping unit 7 in a configuration with four tamping tools 17h, 17m1, 17m2, 17v arranged one behind the other. With respect to the working direction 16, two middle tamping tools 17m1, 17m2 are arranged between the rearmost tamping tool 17h and the frontmost tamping tool 17v. The arrangement of the four tamping tools 17h, 17m1, 17m2, 17v is symmetrical with respect to a plane of symmetry 26 running perpendicular to the working direction 16. The respective auxiliary drive 22a of the frontmost tamping tool 17v and the rearmost tamping tool 17h is designed for only one auxiliary movement 25a. During an auxiliary movement, the corresponding auxiliary drive 22a is extended, so that the associated tamping tines 20 are advanced in the direction of the middle tamping tools 17m1, 17m2.

[0030] The respective tamping drive 22b of the middle tamping tools 17m1, 17m2 is configured for a first tamping movement 25b and for an opposite second tamping movement 25c. Both the extension and retraction of the respective tamping drive 22b cause a corresponding tamping movement 25b, 25c. The associated tamping picks 20 have pick plates with two opposing working surfaces 27, by means of which the ballast can be mobilized in both directions. In this way, the middle tamping tools 17m1, 17m2 can be used to tamper both the sleeper 4 positioned in front of and behind them.

[0031] In the front view in Fig. 3 It can be seen that four tamping tools 17 are arranged side by side in a row. During a tamping process, these four tamping tools 17 of the same row tamper the respective sleeper 4 at four points on both sides of the two rails 9 of the track 3. In a tamping unit according to Fig. 2 Four rows are arranged one behind the other. According to the invention, each of these four rows of tamping tools is designed to be inserted exclusively into a currently assigned sleeper intermediate compartment 28. For control, the respective drives 15, 22, 24 are coupled to a control device 29. This allows, for example, the vibration of a respective tamping tool 17 to be switched on and off.

[0032] A variant of the tamping unit 7 with three tamping tools 17h, 17m, 17v arranged one behind the other is shown in Fig. 4 shown. Here, only one middle tamping tool 17m is formed between the frontmost tamping tool 17v and the rearmost tamping tool 17h for two adjusting movements 25b, 25c in opposite directions. The frontmost tamping tool 17v and the rearmost tamping tool 17h are arranged symmetrically with respect to the plane of symmetry 26 running perpendicular to the working direction 16. The upper lever arm of the middle tamping tool 17m is bent backward relative to the lower lever arm, so that extending and retracting the associated adjusting drive 22b causes a pivoting movement about the associated pivot axis 18.

[0033] During a dipping process, all tamping tools 17h, 17m, 17v are subjected to vibration. Fig. 4 shows the tamping tools 17h, 17m, 17v immediately after immersing themselves in the ballast bed 2 for tamping the second sleeper 4b and the third sleeper 4c of the four sleepers 4a-4d shown. The first sleeper 4a was already tamped during the previous tamping cycle. This completed tamping is marked by hatching. The tamping pick tips of the rearmost tamping tool 17h and the middle tamping tool 17m are set to a first opening width o1, which is larger than the sleeper pitch t. The middle tamping tool 17m thus immerses itself in the ballast bed 2 in the area between an intermediate compartment center 30 and the adjacent sleeper 4c. This ensures that with both subsequent adjusting movements 25b, 25c, approximately the same amount of ballast is pushed under the respective sleeper 4. Accordingly, evenly compacted ballast cushions form under all tamped sleepers 4.Preferably, the opening width o1 corresponds to the threshold pitch t plus an expected adjustment path.

[0034] The rearmost 17h and the middle tamping tool 17m form a first group, which are placed first. The corresponding process for tamping the second sleeper 4b shown is shown in Fig. 5 shown. For this first tamping movement 25a, 25b, the tamping drive 22a of the rear tamping tool 17h is extended and the tamping drive 22b of the middle tamping tool 17m is retracted. With tamping hydraulic cylinders, this is preferably done with the same system pressure, with the piston surfaces being coordinated so that both tamping tools 17h, 17m exert the same tamping force on the ballast. The corresponding tamping tools 17h, 17m are subjected to vibration in order to further compact the ballast pushed under the sleeper 4b. In the case of the front tamping tool 17v, the vibration is preferably switched off during this time. However, it may also be useful to continue to subject the front tamping tool 17v to vibration in order to loosen encrusted ballast for the subsequent second tamping process. During the first adjustment movement 25b, the middle tamping tool 17m uses almost the entire width b of the sleeper intermediate compartment 28.In the end position, the tamping pick tips of the middle 17m and the front tamping tool 17v have a second opening width o2, which essentially corresponds to the first opening width o1 (. Fig. 6 ).

[0035] Immediately thereafter, the third sleeper 4c shown is tamped by the second tamping process, for which the middle tamping tool 17m and the front tamping tool 17v form a second group. The front tamping tool 17v is moved toward the middle tamping tool 17m with the designated tamping movement 17a. At the same time, the tamping drive 22b of the middle tamping tool 17m is extended, resulting in the second tamping movement 25c toward the front tamping tool 17v. In the case of tamping hydraulic cylinders, a second system pressure is applied to account for the surface difference between the piston surface and the annular surface of the hydraulic cylinder. The system pressures as well as the piston and annular surfaces are coordinated so that all tamping tools 17h, 17m, and 17v exert the same tamping force on the ballast.

[0036] During the second adjustment process, both the frontmost tamping tool 17v and the middle tamping tool 17m are subjected to vibration. Meanwhile, the rearmost tamping tool 17h remains in a reset position without vibration to avoid damaging the sleeper support of the already tamped sleeper 4b. At the end of this second adjustment process, all tamping tools 17h, 17m, and 17v are pulled together from the ballast bed 2, with the middle tamping tool 17m and the frontmost tamping tool 17v being returned to their initial position with the first opening width o1. Subsequently, the tamping unit 7 moves forward in the working direction 16 to the next two sleepers 4 to be tamped.

[0037] The Figuren 7 und 8 show a corresponding sequence with four tamping tools 17h, 17m1, 17m2, 17v arranged one behind the other. During the tamping process shown, three of the five sleepers 4b-4e shown are tamped. The first sleeper 4a shown was already tamped beforehand. All four tamping tools 17h, 17m1, 17m2, 17v are subjected to vibration during an immersion process and form the first group for the first adjustment process. Starting from an immersion position with a first opening width o1, the rearmost 17h and the first middle tamping tool 17m1 as well as the frontmost 17v and the second middle tamping tool 17m2 are adjusted to one another. All tamping tools 17h, 17m1, 17m2, 17v are subjected to vibration. The auxiliary drives 22a of the rearmost tamping tools 17h and 17v are extended. The auxiliary drives 22b of the middle tamping tools 17m1 and 17m2 are retracted.In the case of auxiliary hydraulic cylinders, an initial system pressure is applied.

[0038] In an end position of this first tamping process, the second sleeper 4b and the fourth sleeper 4d are completely tamped and the two middle tamping tools 17m1, 17m2 have a second opening width o2 which is slightly larger than the first opening width o1. As a result, almost the entire intermediate compartment width b can be used for the second tamping movement. Immediately after the first tamping process, the second tamping process takes place with the second tamping movement 25c of the middle tamping tools 17m1, 17m2 in the opposite direction. Only the middle tamping tools 17m1, 17m2 are subjected to vibration so that the sleeper supports of the already tamped sleepers 4b, 4d are not affected. The associated tamping drives 22b are extended, whereby in the case of tamping hydraulic cylinders, a second system pressure is applied.The first and second system pressures are coordinated so that all tamping tools 17h, 17m1, 17m2, and 17v exert the same tamping force on the ballast during the respective tamping process. The result of the second tamping process is the tamping of the third sleeper 4c. Subsequently, all tamping tools 17h, 17m1, 17m2, and 17v are raised and reset. After a forward movement of the tamping unit 7 in the working direction 16 by three times the sleeper pitch 3 t, the next tamping cycle begins.

[0039] Fig. 9shows an alternative working method of the tamping unit 7 with four tamping tools 17h, 17m1, 17m2, 17v arranged one behind the other. During each tamping process, only the rearmost 17h and the first middle tamping tool 17m1, as well as the frontmost 17v and the second middle tamping tool 17m2, are positioned relative to each other. After each tamping process, the tamping unit 7 is alternately moved forward by the sleeper pitch t and by three times the sleeper pitch 3 t in the working direction 16. In this way, two sleepers 4 are tamped during each tamping process, with one sleeper 4 located between these sleepers 4.

[0040] This alternative working method is particularly gentle on the ballast and on tamping unit 7. It is ideally used at track sections with difficult conditions. Thus, one advantage of tamping unit 7, with four tamping tools 17h, 17m1, 17m2, and 17v arranged one behind the other, is the ability to perform both this alternative working method and the previously described method for tamping all three sleepers during a single tamping operation.

Claims

1. A tamping unit (7) for tamping a group of adjacent sleepers (4, 4a-4e) of a track (3), with tamping tools (17) arranged one behind the other in a working direction (16), with the respective tamping tool (17) being mounted on a height-adjustable tool carrier (14) so as to be able to pivot about an associated pivot axis (18) , and with squeezing drives (22b) of individual tamping tools (17) being designed for a first squeezing movement (25b) and for an opposite second squeezing movement (25c), and with a plurality of tamping tools (17) being arranged next to one another in a row at a plurality of points for tamping a respective sleeper (4), characterized in that each of the tamping tools (17, 17v, 17h, 17m, 17m1, 17m2) arranged one behind the other is arranged in a row with the tamping tools (17, 17v, 17h, 17m, 17m1, 17m2) arranged next to them for sole penetration of a sleeper crib (28), and in that each tamping tool (17m, 17m1, 17m2) arranged between a foremost tamping tool (17v) and a rearmost tamping tool (17h) is assigned a squeezing drive (22b) designed for two squeezing movements (25b, 25c) in opposite directions.

2. A tamping unit (7) according to claim 1, characterized in that all tamping tools (17, 17h, 17m, 17m1, 17m2, 17v) arranged one behind the other are arranged on a common tool carrier (14).

3. A tamping unit (7) according to claim 1 or 2, characterized in that all adjacent pivot axes (18) of the tamping tools (17, 17h, 17m, 17m1, 17m2, 17v) arranged one behind the other have a distance (a) from one another which approximates a sleeper spacing (t) of the track (3) to be tamped.

4. A tamping unit (7) according to one of the claims 1 to 3, characterized in that the respective squeezing drive (22) is a hydraulic cylinder for simultaneously generating a vibration and a squeezing movement (25).

5. A tamping unit (7) according to one of the claims 1 to 3, characterized in that the respective squeezing drive (22, 22a, 22b) is coupled to the associated tamping tool (17, 17h, 17m, 17m1, 17m2, 17v) on the one hand and mounted on a, in particular, common eccentric shaft (23) for vibration generation on the other.

6. A tamping unit (7) according to claim 5, characterized in that the respective squeezing drive (22, 22a, 22b) is mounted on the eccentric shaft (23) with an adjustable eccentricity.

7. A tamping unit (7) according to one of the claims 1 to 6, characterized in that four tamping tools (17h, 17m1, 17m2, 17v) are arranged one behind the other and, in particular, all tamping tools (17h, 17m1, 17m2, 17v) are arranged symmetrically with respect to a plane of symmetry (26) running perpendicular to the working direction (16).

8. A tamping unit (7) according to one of the claims 1 to 6, characterized in that three tamping tools (17h, 17m, 17v) are arranged one behind the other and, in particular, the foremost (17v) and the rearmost tamping tool (17h) are arranged symmetrically with respect to a plane of symmetry (26) running perpendicular to the working direction (16).

9. A method for operating a tamping unit (7) according to one of the claims 1 to 8, characterized in that the tamping tools (17, 17h, 17m, 17m1, 17m2, 17v) arranged one behind the other perform the following movements during a tamping cycle: - Simultaneous penetration of sleeper cribs (28) of the track (3) to be tamped by all tamping tools (17, 17h, 17m, 17m1, 17m2, 17v) under vibration application, with each of the tamping tools (17, 17v, 17h, 17m, 17m1, 17m2) arranged one behind the other in a row with tamping tools (17, 17v, 17h, 17m, 17m1, 17m2) arranged next to them penetrating a sleeper crib (28) alone, - Squeezing of a first group of tamping tools (17, 17h, 17m, 17m1, 17m2, 17v) under vibration application, with all the tamping tools (17m, 17m1, 17m2) with an associated squeezing drive (22b) for two squeezing movements (25b, 25c) belonging to this first group and with these tamping tools (17m, 17m1, 17m2) performing the first squeezing movement (25b), - Squeezing of a second group of tamping tools (17, 17h, 17m, 17m1, 17m2, 17v) under vibration application, with all the tamping tools (17m, 17m1, 17m2) with an associated squeezing drive (22b) for two squeezing movements (25b, 25c) also belonging to this second group and with these tamping tools (17m, 17m1, 17m2) performing the second squeezing movement (25c), - Simultaneous lifting of all (17, 17h, 17m, 17m1, 17m2, 17v) tamping tools.

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