Machine and method with tamping assembly

Abstract

The present invention relates to a machine (1) comprising a tamping assembly (7) for simultaneously compacting the underside of a number of sleepers (4) of a track (3) positioned directly one behind the other by means of a number of tamping units (14) arranged one behind the other in the longitudinal direction (17) of the machine, each tamping unit (14) comprising a height-adjustable tool support (15) on which are supported opposing tamping tools (18), the tamping tools (18) being connected via squeeze cylinders (20) to a vibratory drive (19) arranged on the tool support (15). In the present invention, each vibration drive device (19) has an eccentric shaft (25) with a first eccentric disk (27) and a second eccentric disk (28), and the symmetry axes (29, 30) of the first and second eccentric disks (27, 28) and a common rotation axis (25) develop two eccentric planes (31, 32) that form a relative angle (δ) with each other, a first squeeze cylinder (20) is supported on the first eccentric disk (27), and an opposing second squeeze cylinder (20) is supported on the second eccentric disk (30), and the cylinder axes (33) of the opposing squeeze cylinders (20) form a position angle (β) that is close to the relative angle (δ) of the eccentric planes (31, 32).

Description

[Technical Field]

[0001] The invention relates to a machine with a tamping assembly for simultaneously compacting the underside of a number of sleepers of a track positioned directly one behind the other by means of a number of tamping units arranged directly one behind the other in the longitudinal direction of the machine, each tamping unit having a height-adjustable tool support on which opposing tamping tools are supported, the tamping tools being connected via squeeze cylinders to a vibratory drive arranged on the tool support.Furthermore, the invention relates to a method for operating the machine. [Background technology]

[0002] To restore or maintain a preset track position, the track including the ballast bed is regularly processed by a tamping machine. In this case, the tamping machine travels along the track and lifts the track stiles formed by the sleepers and rails to the desired level using a lifting / leveling unit. The new track position is fixed by compacting the undersides of the sleepers using a tamping assembly. The tamping assembly includes a tamping tool with a tamping pick. During the tamping operation, the picks are vibrated and sink into the ballast bed, bringing them closer together. In this case, the ballast is compacted under each sleeper.

[0003] In particular, track tamping machines use a tamping assembly to tamp the undersides of several sleepers simultaneously. The high processing speeds achieved in this way allow continuous operation of one track with short maintenance intervals. Furthermore, modern tamping machines are superior in that they have a low abrasive effect on the ballast as well as the tamping assembly.

[0004] AU 513034 A1 discloses a machine as described above that has at least two tamping units arranged one after the other. Each tamping unit is arranged on a common unit support so that its height is adjustable. A tamping cycle is initiated by lowering the tamping units together. The lowering of adjacent tamping units together to compact the undersides of adjacent sleepers in the machine longitudinal direction is performed with a time delay. This facilitates, in particular, the sinking of directly adjacent tamping ice axes that sink into a common sleeper section. Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to improve the machine of the type described at the beginning so that, in addition to reduced wear, lower noise emissions are achieved. Furthermore, it is desired to provide a corresponding method for operating the improved machine. [Means for solving the problem]

[0006] According to the invention, this problem is solved by the features of the independent claims 1 and 12. The dependent claims describe advantageous configurations of the invention.

[0007] In the present invention, each vibratory drive device includes an eccentric shaft with a first eccentric disk and a second eccentric disk, and the axes of symmetry of the first and second eccentric disks and a common axis of rotation define two eccentric planes that form a relative angle with each other. A first squeeze cylinder is supported on the first eccentric disk, and an opposing second squeeze cylinder is supported on the second eccentric disk, with the cylinder axes of the opposing squeeze cylinders forming a position angle that approximates the relative angle of the eccentric planes. In this way, the angular positions of the eccentric disks and the squeeze cylinders are coordinated with each other, thereby achieving mass compensation in the vibrating assembly parts. In particular, the inertial forces of the synchronously vibrating tamping tools are canceled out. This allows the tamping assembly to operate quieter.

[0008] The squeeze cylinders are not oriented horizontally, so that the relative angle is not equal to 180°. With the squeeze cylinders pivoted at an angle, the arrangement according to the invention ensures that the tamping tools oscillate optimally with synchronous reversals. In particular, the vibrations of the two opposing tamping tools undergo a phase shift that results in the simultaneous arrival of their respective reversal points. The acceleration and deceleration forces of the oscillating mass of the tamping tool and the oscillating partial mass of the squeeze cylinder cancel each other out.

[0009] The tamping ice axes, arranged at the lower free ends of the tamping tool, oscillate in a correspondingly synchronized manner with maximum relative movement. This ensures maximum energy input into the ballast bed without causing troublesome reaction vibrations in the tool support and the associated unit suspension. This reduces the vibration load on the assembly and the machine. This protects not only the components of the tamping assembly, but also the ballast particles of the ballast bed to be compacted. The targeted vibration supply into the ballast bed, combined with mass compensation, reduces noise emissions compared to known tamping assembly designs.

[0010] Advantageously, each tamping unit has at least one squeeze cylinder whose cylinder axis is directed obliquely downwards, in particular at an angle of more than 20° to the horizontal. This allows a particularly narrow design of the individual tamping units in the longitudinal direction of the machine, so that tracks with small sleeper pitches can also be processed simultaneously by all tamping units.

[0011] In an advantageous refinement, each eccentric shaft is coupled to a spring mass. During operation, the eccentric shafts are driven together with the spring mass at a preset rotational speed, with the spring mass acting as a stabilizing force on the rotational speed. In particular, the reaction moment of the vibrating squeeze cylinder and tamping tool during the vibration cycle is compensated for by the kinetic energy temporarily stored in the spring mass. In this case, the vibration amplitude of the tamping tool remains constant regardless of the stiffness of the ballast bed.

[0012] To further improve the mass compensation, the rotating unit formed by the eccentric shaft and the spring mass is configured so that a common center of gravity of mass is located on the opposite side of the axis of symmetry of both eccentric disks relative to the rotation axis, so that the rotating unit acts as a compensation mass for the moving masses of the squeeze cylinders of the opposing tamping tools.

[0013] In an advantageous feature of the invention, the tamping assembly comprises front and rear tamping units with squeeze cylinders arranged asymmetrically relative to one another in the longitudinal direction of the machine, and an intermediate tamping unit with squeeze cylinders arranged symmetrically relative to one another. The intermediate tamping unit has a particularly narrow structural configuration, which allows the undersides of sleepers with small sleeper spacing to be compacted simultaneously. The front and rear tamping units also have a narrow structural configuration in the halves facing the intermediate tamping unit. The halves of the front and rear tamping units opposite the intermediate tamping unit use a wider structural configuration in order to achieve a larger opening width between the opposing tamping tools.

[0014] In accordance with this feature of the invention, the front and rear tamping units each have an eccentric shaft with a different eccentricity, whereby the different leverage ratios and the different eccentricities of the opposing tamping tools are matched to one another so that the vibration amplitudes of the freely vibrating tamping pick ends are the same.

[0015] Advantageously, the opposing tamping tools of the front and rear tamping units are supported on the assigned tool supports by vertically spaced pivot supports, the supports of the tamping tools facing the middle tamping unit preferably being arranged deeper, which allows for a narrower construction without changing the leverage ratio.

[0016] Furthermore, it is advantageous if the front and rear tamping units each have a half facing the intermediate tamping unit, which half is configured correspondingly to the symmetrical half of the intermediate tamping unit. This simplifies the construction of the tamping assembly and facilitates the control of the individual tamping units. Furthermore, the number of various interchangeable parts is reduced.

[0017] Advantageously, the intermediate tamping unit and the halves of the front and rear tamping units facing the intermediate tamping unit are each connected to a first squeeze pressure system, and the halves of the front and rear tamping units opposite the intermediate tamping unit are each connected to a second squeeze pressure system. The different squeeze pressure systems allow for equal static and dynamic squeeze forces to be achieved for all tamping tools.

[0018] Another improvement specifies that the half of each front or rear tamping unit opposite the middle tamping unit is equipped with a squeeze cylinder with a larger stroke, which tamps the underside of double tuck sleepers. This makes the tamping assembly flexible and capable of processing all sleeper configurations that occur on the track section.

[0019] Furthermore, it is advantageous if a number of tamping tools arranged side by side transversely to the longitudinal direction of the machine, including their assigned tamping cylinders, together form a controllable tamping group. This applies to tamping units arranged side by side that tamper the undersides of the sleepers on both sides of both rails of the track. During operation, the tamping groups are controlled together, thereby ensuring a uniform compaction action along the sleepers.

[0020] In the method for operating the aforementioned machine according to the present invention, the vibration drive and squeeze cylinder of each tamping unit are controlled so that the position angle of the squeeze drive varies within a range near the relative angle of the eccentric plane of the assigned eccentric shaft. Thus, during the tamping operation, the instantaneous position angle remains close to the relative angle. In particular, at intermediate pivot positions of the squeeze drive, the position angle corresponds to the relative angle. In this case, the vibrating masses of each tamping assembly vibrate correspondingly and synchronously. This achieves mass compensation, which minimizes the load on the unit and noise generation.

[0021] A refinement of the method specifies that each eccentric shaft is driven by an assigned vibration drive motor, and that all vibration drive motors are controlled by one common control device for synchronous operation, whereby the vibration movements of the tamping units are coordinated with one another and the smoothness of operation of the entire tamping unit is optimized.

[0022] Furthermore, it is advantageous to drive each eccentric shaft at a variable speed depending on the height position of the assigned tamping unit. Before the tamping operation, all tamping units are positioned above the track in a starting position. In this position, the speed of each eccentric shaft remains reduced in order to further reduce noise generation. Only by changing the height position during the lowering operation does the operating speed during the sinking operation increase to a higher speed than during the squeezing operation.

[0023] Another refinement specifies controlling squeeze groups arranged side by side transversely to the longitudinal direction of the machine with one common control signal, thus achieving a uniform compaction action along one sleeper.

[0024] Advantageously, during the squeezing operation, a first squeezing pressure is applied to the intermediate tamping unit and to the halves of the front and rear tamping units facing the intermediate tamping unit, respectively, and a second squeezing pressure is applied to the halves of the front and rear tamping units opposite the intermediate tamping unit, respectively. The different squeezing pressures ensure equal static and dynamic squeezing forces for all tamping tools.

[0025] The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic diagram of a machine with a tamping assembly. [Figure 2]FIG. 1 is a schematic side view of a tamping assembly for simultaneously tamping the undersides of three sleepers. [Figure 3] FIG. 10 is a schematic side view of an intermediate tamping unit. [Figure 4] 4 is a schematic diagram of the kinematics according to FIG. 3. [Figure 5] 4 is a schematic diagram of the kinematics according to FIG. 3 in several working positions. [Figure 6] FIG. 10 is a schematic side view of the front and rear tamping units. [Figure 7] FIG. 7 is a schematic diagram of the kinematics according to FIG. 6. [Figure 8] 7A-7C are schematic diagrams of the kinematics according to FIG. 6 in several working positions. [Figure 9] FIG. 2 is a schematic side view of an eccentric shaft. [Figure 10] FIG. 2 is a schematic plan view of an eccentric shaft. [Figure 11] FIG. 2 is a schematic front view of a tamping assembly. [Figure 12] FIG. 1 is a schematic diagram of a tamping assembly for simultaneously tamping the undersides of four sleepers. DETAILED DESCRIPTION OF THE INVENTION

[0027] The machine 1 shown in Figure 1 is configured as a track tamping machine for simultaneously tamping the undersides of three sleepers out of a plurality of sleepers 4 supported on a ballast bed 2 of a track 3. The machine 1 comprises a machine frame 6 supported on a rail running gear 5. A tamping assembly 7 is attached to the machine frame 6. Furthermore, the machine 1 comprises a lifting / leveling unit 8 for lifting and leveling a track stile formed by the sleepers 4 and the rail 9. A measuring system 10 detects the instantaneous rail position.

[0028] The tamping assembly 7 is attached to the machine frame 6 by means of a position adjustment device 11. The tamping assembly 7 comprises a unit frame 12 with guides 13 and a number of tamping units 14. In a variant not shown, each tamping unit 14 is assigned its own unit frame 12. Each tamping unit 14 comprises a tool support 15 supported on the assigned guide 13 so as to be height-adjustable by means of a height adjustment drive 16. Tamping tools 18 are pivotably supported on each tool support 15 and are opposite each other in the longitudinal machine direction 17.

[0029] Furthermore, a vibration drive 19 is arranged on each tool support 15. A tamping tool 18 is connected to this vibration drive 19 via a squeeze cylinder 20. Each tamping tool 18 has a pivotable lever 21 with an upper lever arm and a lower lever arm. This pivotable lever 21 is supported on the assigned tool support 15 by a pivotable support 22. The upper lever arm is connected to the assigned squeeze cylinder 20. Two tamping ice axes 23 are usually attached to the free lower lever arm.

[0030] In the starting position (FIG. 2), the opposing tamping picks 23 of each tamping unit 14 are equally spaced from one another relative to a central vertical plane 24. The distance between the central vertical planes 24 of adjacent tamping units 14 corresponds to the minimum sleeper pitch t of the sleepers 4 whose undersides are to be tamped. The dimensioning of the tamping units 14 in the machine longitudinal direction 17 therefore depends on this minimum sleeper pitch t.

[0031] The intermediate tamping unit 14, located between the front and rear tamping units 14, has a narrow design in the longitudinal direction 17 of the machine. This requirement is achieved by the squeeze cylinders 20, which are oriented obliquely downwards. Only the halves of the front and rear tamping units 14 facing the intermediate tamping unit 14 are shaped accordingly; the other halves have squeeze cylinders 20 oriented approximately horizontally. This provides a larger pivot range for the assigned tamping tools 18. The increased separation between the opposing tamping ice axes 23, which can be achieved in this way, allows for a larger sleeper pitch t or the adaptation of double sleepers, the underside of which is to be compacted.

[0032] The structure of the intermediate tamping unit 14 will be explained in detail with reference to Figures 3 to 5. Figure 4 shows a kinematic model of the tamping unit 14 shown in Figure 3. Figure 5 shows this kinematic model 3 in three working positions. An eccentric shaft 25 of the vibration drive 19 is supported on the tool support 15. During operation, this eccentric shaft 25 rotates about a rotation axis 26. The eccentric shaft 25 is equipped with two eccentric disks 27, 28 that are offset from one another. The symmetry axes 29, 30 of these two eccentric disks 27, 28 have respective eccentricities e1, e2 relative to the rotation axis 26.

[0033] Furthermore, the axes of symmetry 29, 30 and the axis of rotation 26 extend through two eccentric planes 31, 32 that form a relative angle δ with respect to each other. The cylinder axes 33 of the squeeze cylinders 20 form a position angle β. Opposite squeeze cylinders 20 are arranged symmetrically in the intermediate tamping unit 14. Each cylinder axis 33 is inclined downward at an angle α relative to the horizontal. This angle α is at least 20°. Ideally, the angle α is set within the range of 30° to 50°, which ensures optimal force transmission in addition to a narrow structural form.

[0034] During the tamping operation, the tilt angle α and the position angle β change slightly due to the vibration and squeeze movements. For clarity, FIG. 5 shows different positions of the squeeze cylinder 20 when the eccentric shaft 25 is stationary. The solid lines indicate the squeeze position of the tamping tool 18. In the illustrated position, the cylinder axis 33 is located within the eccentric planes 31 and 32, so that the position angle β is equal to the relative angle δ. For clarity, the eccentricities e1 and e2 are shown as being excessively large compared to the remaining dimensions. The circular movement of the pivot point of the squeeze cylinder 20 that occurs during one rotation of the eccentric shaft 25 is not taken into account in the drawing. The effect of this circular movement on the position change of the cylinder axis 33 can be ignored relative to the effect of the squeeze movement caused by the piston movement.

[0035] When the eccentric shaft 25 starts to rotate during operation, the eccentric planes 31 and 32 also rotate together, with the relative angle δ remaining unchanged. The position angle β is determined by the range β min ~β max During the squeezing operation, the squeeze cylinder 20 pivots slightly about the symmetry axes 29, 30 of the eccentric discs 27, 28. In FIG. 5, both extreme positions are shown by dashed and dashed lines, respectively. The value of the position angle β always remains close to the value of the relative angle δ. In the optimum kinematic configuration of the tamping unit 14, the value of the relative angle δ during operation always lies within the value range β of the position angle β. min ~β max It's inside.

[0036] The corresponding kinematic relationships for the front and rear tamping units 14 are shown in Figures 6 to 8. In these figures, unlike the intermediate tamping units 14, the squeeze cylinders 20 and tamping tools 18 are arranged asymmetrically. The pivoting levers 21 assigned to the different squeeze cylinders 20 are adapted accordingly. On the side facing the intermediate tamping unit 14, the cylinder axes 33 of the squeeze cylinders 20 are oriented obliquely downwards at an inclination angle α to the horizontal.

[0037] As is clear from Figure 8, the intermediate positions of both squeeze cylinders 20 for each pivot range do not occur simultaneously. In the illustrated squeeze position (solid line), the shorter squeeze cylinder 20 is in the intermediate position, and the longer squeeze cylinder 20 is in the downward pivoted end position. In this position, the minimum position angle β min During the return movement of the tamping tool 18, the longer squeeze cylinder 20 passes through an intermediate position where the position angle β corresponds to the value of the relative angle δ of the eccentric shaft 25. After the return movement, the position angle β reaches a maximum value β max Therefore, the value of the position angle β is in the range β around the value of the relative angle δ of the eccentric planes 31, 32 during the squeeze and return movements. min ~β max It fluctuates within.

[0038] To ensure approximately equal leverage ratios on both sides, the pivoting supports 22 are arranged at a distance from one another in the vertical direction on the tool support 15. The longer construction of the approximately horizontally oriented squeeze cylinders 20 allows for a larger squeeze stroke. This allows the position angle β to be increased to a larger value range β min ~β max It fluctuates within.

[0039] 9 and 10 show the eccentric shaft 25 for the front or rear tamping unit 14 in detail. The cutting guide lines are clear in FIG. 9 for the cross-sectional view shown in FIG. 10. A first eccentric disk 27 is located midway along the eccentric shaft 25. A shorter squeeze cylinder 20, oriented diagonally downwards, is supported on this first eccentric disk 27. The second eccentric disk 28 is split into two, with partial eccentric disks located on either side of the first eccentric disk 27. The longer squeeze cylinder 20 is supported by its fork-shaped ends on the second eccentric disk 28. Both squeeze cylinders 20 are shown in dash-dot lines in FIGS. 9 and 10.

[0040] In the position shown, the cylinder axis 33 of the squeeze cylinders 20 is contained in the eccentric planes 31, 32. In this case, the vibration swing of both squeeze cylinders 20 reaches the outer reversal point simultaneously. As the eccentric shaft 25 continues to rotate, the ends of the squeeze cylinders 20 that are supported on the eccentric disks 27, 28 move in opposite directions. The synchronous vibration swing sufficiently compensates for the vibrating masses. This applies in particular to the synchronously vibrating tamping ice axe 23.

[0041] Mass compensation is enhanced by a spring mass 34 that rotates together with the eccentric shaft 25 around the same rotation axis 26. The eccentric shaft and spring mass 34 form a rotating unit with a mass center of gravity 35 that is located approximately in the plane of symmetry 36 of both eccentric planes 31, 32. The mass center of gravity 35 is spaced apart from the rotation axis 26 and located opposite the axes of symmetry 29, 30 of both eccentric disks 27, 28. The spring mass 34 with its eccentric mass center of gravity 35 acts against the inertial force of the vibrating squeeze cylinder 20. The dimensions of the spring mass 34 are tailored to the mass of the squeeze cylinder 20. For example, the spring mass 34 is formed as a disk. This disk is flattened or grooved in one place to obtain the eccentric mass center of gravity 35.

[0042] In the illustrated eccentric shaft 25 for the front or rear tamping unit 14, the eccentricities e1, e2 are different from each other, resulting in equal amplitudes at the free end of the tamping pick 23. In the eccentric shaft 25 for the middle tamping unit 14, both eccentricities e1, e2 are equal due to the symmetrical arrangement.

[0043] As can be seen in FIG. 11 , each rail 9 of the track 3 is assigned two tamping units 14 that can be lowered independently of one another. The tamping assembly 7 therefore comprises four tamping units 14 arranged side by side in a row. In each tamping unit 14, the corresponding eccentric shaft 25 is driven by a vibration drive motor 37. All vibration drive motors 37 are controlled by a common control device 38, which ensures synchronous operation. In this way, vibrations of the individual tamping units 14 cancel each other out. This minimizes vibrations transmitted from the tamping assembly 7 to the machine frame 6.

[0044] In a simplified variant (not shown), each rail 9 is assigned a combined tamping unit 14 with an inner-rail tamping tool 18 and an outer-rail tamping tool 18. In this case, the tamping assembly 7 comprises two combined tamping units 14 arranged next to each other in a row.

[0045] To compact the underside of the sleepers 4, tamping units 14 arranged side by side form a squeeze group. The tamping ice axes 23 of this squeeze group are lowered together and brought close together (two squeeze groups per row). A tamping assembly 7 with four rows of tamping units 14 arranged directly one behind the other is shown in FIG. 12. This results in eight squeeze groups that are controlled together. The squeeze group of the middle tamping unit 14 and the squeeze groups of the front and rear tamping units 14 adjacent to it are supplied with pressure by a first squeeze pressure system 39. The front and rear squeeze groups are supplied with pressure by a second squeeze pressure system 40.

[0046] Thus, during the squeeze operation, different squeeze pressures are applied to the squeeze groups, each set to a different size, which are adjusted to each other so as to generate equal static and dynamic squeeze forces for all tamping ice axes 23. For a uniform squeeze operation along the sleeper 4, each squeeze group is controlled by one common control signal.

Claims

1. A machine (1) comprising a tamping assembly (7) for simultaneously compacting the undersides of a number of sleepers (4) of a track (3) positioned directly one behind the other by means of a number of tamping units (14) arranged one behind the other in a longitudinal direction (17) of the machine, each tamping unit (14) comprising a height-adjustable tool support (15) on which are supported tamping tools (18) opposite each other, the tamping tools (18) being connected via squeeze cylinders (20) to a vibrating drive (19) arranged on the tool support (15), Each of the vibratory drives (19) comprises an eccentric shaft (25) having a first eccentric disk (27) and a second eccentric disk (28), wherein the symmetry axes (29, 30) of the first and second eccentric disks (27, 28) and a common axis of rotation (25) extend through two eccentric planes (31, 32) that form a relative angle (δ) with each other, a first squeeze cylinder (20) is supported on the first eccentric disk (27) and an opposing second squeeze cylinder (20) is supported on the second eccentric disk (28), and cylinder axes (33) of the opposing squeeze cylinders (20) form a position angle (β) that is close to the relative angle (δ) of the eccentric planes (31, 32).

2. 2. The machine (1) according to claim 1, characterized in that each tamping unit (14) comprises at least one squeeze cylinder (20), the cylinder axis (33) of which is directed obliquely downwards, in particular at an inclination angle (α) of more than 20° relative to the horizontal.

3. 3. Machine (1) according to claim 1 or 2, characterized in that each of said eccentric shafts (25) is connected to a spring mass (34).

4. 4. The machine (1) according to claim 3, characterized in that the eccentric shaft (25) and the spring mass (34) form a rotating unit having a center of gravity (35) of mass located on the opposite side of the axis of rotation (26) from the axes of symmetry (29, 30) of both eccentric disks (27, 28).

5. 5. The machine (1) according to any one of claims 1 to 4, characterized in that the tamping assembly (7) comprises front and rear tamping units (14) with squeeze cylinders (20) arranged asymmetrically with respect to one another, and an intermediate tamping unit (14) with squeeze cylinders (20) arranged symmetrically with respect to one another.

6. The front and rear tamping units (14) have different eccentricities (e １ , e ２ 6. The machine (1) according to claim 5, characterized in that it has one eccentric shaft (25) each having a axially extending shaft.

7. 7. The machine (1) according to claim 5 or 6, characterized in that the front and rear tamping units (14) each have a tamping tool (18) facing each other, the tamping tool (18) being supported on the assigned tool support (15) by means of vertically spaced pivot supports (22).

8. 8. The machine (1) according to claim 5, wherein the front and rear tamping units (14) each have a half facing the intermediate tamping unit (14), which half is configured corresponding to a symmetrical half of the intermediate tamping unit (14).

9. 9. The machine (1) according to claim 8, wherein the intermediate tamping unit (14) and the halves of the front and rear tamping units (14) facing the intermediate tamping unit (14) are each connected to a first squeeze pressure system (39), and the halves of the front and rear tamping units (14) opposite the intermediate tamping unit (14) are each connected to a second squeeze pressure system (40).

10. 10. The machine (1) according to claim 8 or 9, characterized in that the half of each of the front or rear tamping units (14) opposite to the intermediate tamping unit (14) is equipped with a squeeze cylinder (20) with a larger stroke, by means of which the underside of the double sleeper is compacted.

11. 11. The machine (1) according to claim 1, characterized in that a plurality of tamping tools (18) arranged side by side transversely to the longitudinal machine direction (17) together form a controllable squeeze group, including an assigned squeeze cylinder (20).

12. A method for operating a machine (1) according to any one of claims 1 to 11, comprising: a method for controlling the vibration drive device (19) and the squeeze cylinder (20) of each of the tamping units (14) so ​​that the position angle (β) varies within a range around the relative angle (δ) of the eccentric planes (31, 32) of the assigned eccentric shaft (25).

13. 13. The method according to claim 12, characterized in that each eccentric shaft (25) is driven by an assigned vibration drive motor (37), and all vibration drive motors (37) are controlled by one common control device (38) for synchronous operation.

14. 14. Method according to claim 12 or 13, characterized in that squeeze groups arranged next to each other transversely to the longitudinal machine direction (17) are controlled by one common control signal.

15. 15. The method according to claim 10, wherein during the squeezing operation, a first squeezing pressure is applied to the intermediate tamping unit (14) and the halves of the front and rear tamping units (14) facing the intermediate tamping unit (14), and a second squeezing pressure is applied to the halves of the front and rear tamping units (14) opposite the intermediate tamping unit (14).

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