Tamping unit and method for tamping a track

Abstract

The invention relates to a tamping unit (7) for tamping a track (4), comprising tamping tines (19) which can be driven into a track ballast bed (10) and are each arranged in a tine mounting (16) of a tamping tool (15) which can be moved relative to the track ballast bed (10) by actuating drives (14, 17). In each tamping tine (19) and / or the associated tine mounting (16) there is a high-frequency actuator (23) for generating vibrations. This reduces the penetration resistance compared to conventional tamping operations, which are commonly carried out with a much lower vibration ranging from 35 Hz to 60 Hz.

Description

[0001] Tamping unit and method for tamping a track

[0002] The invention relates to a tamping unit for tamping a track with tamping picks that can be immersed in a track ballast bed, each pick being arranged in a pick holder of a tamping tool that can be moved relative to the track ballast bed by actuators. The invention also relates to a method for operating the tamping unit.

[0003] From EP 3 631 087 A1, a tamping machine and a method for compacting a track ballast bed are known. The tamping machine comprises a tamping unit and a lifting and aligning unit. A track section brought into a target position by the lifting and aligning unit is fixed by means of the tamping unit. Tamping picks attached to pivot levers penetrate the track ballast bed between the track sleepers and are aligned with each other. To reduce the penetration resistance, the tamping picks are subjected to vibration. Preferably, the pivot levers are connected to an eccentric shaft via an auxiliary drive, with rotation of the eccentric shaft causing the vibration of the tamping picks. In another embodiment, vibration generators are arranged in the bearing points of the pivot levers. Sensors are arranged on the tamping picks or on pick holders of the tamping unit, by means of which the compaction of the track ballast bed is monitored.

[0004] EP 3 953 527 Al of fenbart specifies a tamping pick with an integrated sensor for a tamping unit. A longitudinal bore for receiving a sensitive element of the sensor is arranged in the pick shaft. During a tamping process, this sensor detects a measured value occurring in the tamping pick, the evaluation of which is used to improve subsequent tamping processes.

[0005] The EP 1 653 003 A2 of fenbart describes a tamping process in which hydraulic actuators power both the positioning and vibration movements of the tamping picks. The vibration frequency during positioning is typically 35 Hz. During penetration of the tamping picks into the track ballast, the vibration frequency is briefly increased, for example to 60 Hz. This facilitates easier penetration of the tamping picks, particularly in encrusted ballast.

[0006] The invention is based on the objective of improving the tamping unit of the type mentioned above in such a way that individual phases of a tamping process, in particular the penetration of the tamping picks into the track ballast bed, are optimized. A further objective of the invention is to provide a corresponding method.

[0007] These problems are solved by the features of independent claims 1 and 9. Dependent claims specify advantageous embodiments of the invention.

[0008] According to the invention, a high-frequency actuator for generating vibrations is arranged in each tamping pick and / or in the associated pick holder. Activating the high-frequency actuators sets the tamping picks into high-frequency vibrations. As soon as the tamping picks penetrate the track ballast, these high-frequency vibrations are transmitted to the ballast grains in the effective area of ​​the tamping picks. This reduces the penetration resistance compared to conventional tamping processes, which are carried out solely with vibration in the range of 35 Hz to 60 Hz. Preferably, the application of high-frequency vibrations occurs in addition to conventional vibration generation. Particularly when the tamping picks penetrate the track ballast, the application of high-frequency vibrations alone can also be advantageous.Compared to conventional vibration, the ballast grains are vibrated at a lower amplitude, resulting in reduced lateral displacement of the ballast grains when entering the track bed. Simultaneously, the mobilization of the ballast grains by the high-frequency vibrations leads to lower penetration resistance. Compared to conventional tamping processes, a reduction in penetration effort of approximately 15% is possible with new ballast. Even greater reductions in penetration effort can be achieved with older ballast.

[0009] Preferably, the respective high-frequency actuator is configured to generate mechanical vibrations with a frequency of at least 1000 Hz, and in particular at least 16000 Hz. At frequencies above 16000 Hz, these are usually referred to as ultrasonic vibrations. The frequency is selected depending on the properties of the existing vibration-capable system. The aim is to transfer a high kinetic energy to the gravel grains, whereby the vibrations generated by the high-frequency actuator should produce the largest possible vibration amplitude at the free end of the respective tamping pick, on which a pick plate is arranged. However, the vibration amplitude remains significantly lower than with conventional vibration application, where the amplitude values ​​are in the range of 5 mm.Advantageously, the arrangement of the respective high-frequency actuator makes the associated tamping pick part of a vibrating system which, when excited by the high-frequency actuator, develops a mode shape, with the high-frequency actuator being arranged, in particular, at an antinode of this mode shape. A local amplitude maximum of the excited vibrations occurs at the antinode. The frequency for exciting the vibrating system and the positioning of the respective high-frequency actuator are coordinated such that a maximum vibration amplitude also results at the free end of the associated tamping pick.

[0010] In a preferred embodiment of the invention, the respective high-frequency actuator is coupled in a cavity of the associated tamping pick to a mass body that is movable relative to the tamping pick. When the high-frequency actuator is activated, relative movements between the tamping pick and the mass body cause the high-frequency vibrations of the corresponding tamping pick. Tamping picks designed in this way can be combined with a conventional tamping unit. Only appropriate wiring needs to be retrofitted in the area of ​​the respective tamping pick holder, and a control device for controlling the high-frequency actuators needs to be installed.

[0011] Preferably, a cable connection is arranged between the respective high-frequency actuator and a connector for coupling with a control device. For example, a longitudinal bore is provided in a pick shaft of the respective stuffing pick, at the end of which the high-frequency actuator is positioned. A connector is arranged at the opening of the longitudinal bore and connected to the high-frequency actuator via a cable 5. After these components are mounted, the longitudinal bore is preferably filled with a filler material to protect the cable and the connections.

[0012] In another advantageous embodiment of the invention, the respective high-frequency actuator is arranged on a surface of the associated tamping pick holder. This facilitates connection to a control device. Furthermore, this arrangement can be combined with conventional tamping picks. Advantageously, the pick holder is set off from the rest of the pivot lever by a reduction in cross-section and, together with the tamping pick, forms a vibrating system that can be excited by means of the high-frequency actuator. For example, a metal ring arranged around a holding section of the respective tamping pick is provided as the movable mass element.

[0013] Preferably, the respective high-frequency actuator is a piezoelectric actuator. Such an actuator can be operated within the intended frequency range and has a compact design for placement within the tamping pick or pick holder. Furthermore, high-performance versions can generate sufficient kinetic energy to ensure adequate mobilization of the ballast grains, even under strong counterforces from encrusted ballast. The piezoelectric actuator typically consists of individual, pre-sintered ceramics bonded together in a stack. The ceramic stack is integrated into a housing with a preload and delivers high forces at high frequencies without wear. 24012

[0014] 6

[0015] In another variant, the respective high-frequency actuator is an electrostatic actuator that delivers sufficiently high kinetic energy within the intended frequency range. Such an electrostatic actuator comprises several electrodes that are movably arranged. The high-frequency oscillations are generated, as with the piezoelectric actuator, by applying a corresponding alternating voltage.

[0016] In the inventive method for operating the tamping unit, the respective high-frequency actuator is activated by a control device during the immersion of the associated tamping pick into a track ballast bed. This reduces the necessary penetration work by mobilizing the ballast grains and bringing them into a fluid-like state. The result is lower penetration resistance because the ballast grains, set into high-frequency vibrations, can change their position without noticeable frictional losses.

[0017] In an advantageous further development of the method, the respective high-frequency actuator is activated by the control device during the withdrawal of the associated tamping pick from the track ballast. The tamping pick is pulled out of the ballast along a predetermined trajectory, whereby the vibrating ballast grains are further compacted and wear on the tamping pick is reduced. So-called tamping holes are avoided because the mobilized ballast grains immediately fill the space released by the tamping pick. 24012

[0018] 7

[0019] The invention is explained below by way of example with reference to the accompanying figures. These show, in schematic representation:

[0020] Fig. 1 Tamping machine on a track;

[0021] Fig. 2 Stuffing unit in a side view;

[0022] Fig. 3 Darning pick with a high-frequency actuator in the pick shaft;

[0023] Fig. 4 tamping pick according to Fig. 3 in a pick holder of a tamping tool;

[0024] Fig. 5. Dotting pick in a pick holder which has a high-frequency actuator.

[0025] The tamping machine 1 shown in Fig. 1 comprises a machine frame 2, which is supported on rail chassis 3 and is movable on a track 4. A lifting and aligning unit 5 is attached to the machine frame 2. Behind it, with respect to a working direction 6, a tamping unit 7 is arranged which is laterally adjustable relative to the machine frame 2 and, in particular, rotatable about a vertical axis.

[0026] Track 4 comprises a track grid consisting of track sleepers 8 and track rails 9 attached to them, which is supported in a track ballast bed 10. When the tamping machine 1 is operated, the track grid is brought into a target position by means of the lifting and aligning unit 5 and fixed in this target position by means of the tamping unit 7.

[0027] The exemplary tamping unit 7 in Fig. 2 comprises a unit frame 11 with vertical guides 12 for a tool carrier 13, which can be vertically displaced relative to the unit frame 11 by means of a height adjustment drive 14. Opposing tamping tools 15 are pivotably mounted on the tool carrier 13. Each tamping tool 15 comprises 24012

[0028] Figure 8 shows a pivot lever with a lower lever arm that includes a pick holder 16. An upper lever arm is connected via an auxiliary drive 17 to a vibratory drive 18 arranged on the tool carrier 13. For example, the auxiliary drive 17, designed as a hydraulic cylinder, is mounted on an eccentric shaft of the vibratory drive 18. In this case, a rotation of the eccentric shaft is transmitted via the respective auxiliary drive 17 into a vibratory movement of the associated tamping tool 15. In a variant not shown, the respective hydraulic cylinder is designed as both an auxiliary drive 17 and a vibratory drive 18 and is directly articulated to the tool carrier 13.

[0029] The respective pick holder 16 serves to attach a darning pick 19, which comprises a pick shaft 20 and a pick plate 21 at a lower end. Preferably, an upper retaining section 22 of the darning pick 19 is designed as a cone and clamped in a corresponding inner surface of the pick holder 16. A clamping force is applied, for example, by means of a screw.

[0030] During a tamping operation, the tool carrier 13 with the tamping tools 15 is moved towards the track ballast bed 10 by activating the height adjustment drive 14. The vibrating tamping picks 19 penetrate the track ballast bed 10, and an adjustment movement occurs when a predetermined penetration depth is reached or shortly before. During this movement, the adjustment drives 17 push the upper lever arms of the tamping tools 15 apart, thereby moving the tamping picks 19 towards each other. This adjustment movement causes the ballast to be displaced towards the track sleeper 8 to be tamped. This fills the cavity located under the 24012

[0031] 9

[0032] The track sleeper 8 is formed as a result of the lifting of the track grid by the lifting and aligning unit 5. Subsequently, the vibration transmission of the tamping picks 19 to the ballast grains leads to a sustained compaction of the newly formed sleeper support.

[0033] The vibratory drive 18 generates vibrations at a frequency of 35 Hz during the positioning process. For the immersion process, the frequency is increased to 45 Hz, for example, to reduce the immersion resistance by increasing the mobilization of the gravel particles. However, vibration generation via an eccentric shaft or a fully hydraulic vibration generation using a hydraulic positioning cylinder does not allow for an arbitrarily increased vibration frequency.

[0034] Therefore, according to the invention, a high-frequency actuator 23 for generating vibration is arranged in the respective tamping pick 19 and / or in the associated pick holder 16. This makes vibration frequencies of well over 1000 Hz achievable, particularly in the ultrasonic range from 16000 Hz or 20000 Hz. The high-frequency vibrations are generated by bending movements of the components involved, especially the tamping pick 19. The achievable vibration amplitude is lower than the amplitude achieved by means of the vibration drive 18. Nevertheless, the high-frequency vibration transfers a high kinetic energy to the ballast grains, thereby significantly reducing the friction between them.

[0035] Preferably, the vibration at this high frequency takes place during the immersion of the tamping picks 19 into the track ballast bed 10. This reduces the penetration resistance compared to the conventional 24012.

[0036] 10

[0037] Vibration is applied by means of the vibration drive 18. By applying a penetration force F and a penetration distance s, the penetration work for the respective tamping pick 19 decreases as it penetrates the track ballast bed 10. With new gravel, the penetration force is reduced by approximately 15% compared to a conventional penetration process. With old, especially encrusted, gravel, the penetration force is greater and the reduction in penetration work is up to 20%.

[0038] The extraction of the tamping picks 19 from the track ballast bed 10 after the ballast placement and compaction process is also improved by applying high-frequency vibration. The respective tamping pick 19 is pulled out of the ballast along a predetermined trajectory, while the ballast grains are kept in motion at a high frequency. The volume released by the tamping pick is filled by the mobilized ballast grains. This further compacts the ballast at these points, preventing so-called tamping holes. In addition, the reduced friction minimizes wear on the tamping picks 19 during extraction.

[0039] The advantages are achieved in various applications. For example, the vibration applied by the vibration drive 18 is kept constant at 35 Hz throughout the entire packing process, and the high-frequency vibration is activated during the insertion and withdrawal phases of the packing pick 19. In another variant, the frequency of the vibration drive 18 is also adjusted during the insertion phase.

[0040] 11 increased, for example to 45 Hz. It may also be advantageous to omit the vibration drive 18 and to apply the vibration exclusively by means of the high-frequency actuators 23 in all phases of the stuffing process.

[0041] A first exemplary embodiment of the high-frequency vibration application is shown in Figures 3 and 4. Here, the high-frequency actuator 23 is arranged in a cavity of the plug 19. For this purpose, a longitudinal bore leads from above through the plug shaft 20 to the mounting point of the high-frequency actuator 23. For example, the high-frequency actuator 23 is glued in place with its own housing in the cavity at the end of the longitudinal bore, with a cable connection 24 leading to a connector 25 at the upper end of the plug shaft 20 for supplying and controlling the high-frequency actuator 23. Preferably, the longitudinal bore is filled with a filler material 26 after assembly.

[0042] A movable mass 27 is connected to the high-frequency actuator 23. This mass 27, preferably made of a high-density metal, is set into high-frequency vibrations by the activated high-frequency actuator 23. The high-frequency actuator 23 exerts a supporting force on the tamping pick 19, thereby subjecting it to the vibrations.

[0043] The modified tamping pick 19 resembles a oscillating beam clamped at one end, which exhibits vibrations with mode shapes when excited. In Fig. 3, the first mode shape 28 and the second mode shape 29 are shown to the right of the tamping pick 19. The latter has an antinode 30 at which the deflection curve reaches a local amplitude maximum. Preferably, the frequency and arrangement of the high-frequency actuator 23 are matched such that the high-frequency actuator 23 is located at the antinode 30 and that the free end of the tamping pick 19 reaches an amplitude maximum. In this way, optimal transfer of the kinetic energy through the pick plate 21 to the gravel grains is achieved.

[0044] In the exemplary embodiment, the direction of the high-frequency oscillation corresponds to the direction of vibration generated by the vibration drive 18. In another embodiment, the high-frequency oscillations are excited by the high-frequency actuator 23 in such a way that the direction of oscillation and the direction of vibration generated by the vibration drive 18 form an angle of up to 90°. The respective tamping pick 19 then oscillates at a low frequency (e.g., 35 Hz) in the longitudinal direction of the track and at a high frequency (e.g., 16 kHz) in the transverse direction. Another variant provides for a high-frequency torsional oscillation of the respective tamping pick 19. In this case, the high-frequency actuator 23 generates angular momentum about a longitudinal axis of the associated tamping pick 19, so that the pick plate 21 performs rotational movements oscillating about this longitudinal axis.

[0045] The tamping pick 19, which is attached to the pick holder 16, is connected to a control unit 33 via a plug connection 31 and a cable 32. Preferably, a distributor 34 coupled to the control unit 33 is arranged on the tool carrier 13 and connected to the high-frequency actuators 23 of the tamping tools 15 via the flexible cables 32. This embodiment has the advantage that existing tamping units 7 can also be combined with the new invention without modifying the tamping tools 15. Only the modified tamping picks 19 and the control unit 33 are required.

[0046] High-frequency actuators 23 require a set up control unit 33.

[0047] A second embodiment is shown in Fig. 5. Here, a conventional tamping pick 19 is attached to the respective pick holder 16. In this variant, the pick holders 16 are modified compared to conventional tamping tools 15. Preferably, the respective lever arm above the pick holder 16 is tapered so that the pick holder 16, together with the tamping pick 19, is capable of oscillation relative to the rest of the pivot lever. The high-frequency actuator 23 arranged in the pick holder 16 excites this oscillating system. Here, too, the frequency and arrangement of the high-frequency actuator 23 are preferably matched such that the high-frequency actuator 23 is located at an antinode 30 of a mode shape and an amplitude maximum occurs at the free end of the tamping pick 19.

[0048] In the pick holder 16, an annular recess is arranged around the retaining section 22. The high-frequency actuator 23 is positioned on an inner surface of this recess and connected to a movable mass 27. This mass 27 is, for example, a metal ring arranged around the retaining section 22. The activated high-frequency actuator 23 sets the mass 27 into vibration, bearing against the inner wall of the pick holder 16. This subjects the vibrating system, including the pick 19, to the high-frequency vibrations.

[0049] In one embodiment not shown, several high-frequency actuators 23 are arranged for applying vibration to the respective tamping pick 19. For example, 24012

[0050] 14 One of the high-frequency actuators 23 is arranged in the tamping pick 19, and another high-frequency actuator 23 is arranged in the associated pick holder. The excitation frequencies and the positions of the high-frequency actuators 23 are coordinated such that interferences cause a maximum vibration amplitude at the free end of the tamping pick 19.

[0051] Preferably, the respective high-frequency actuator 23 is designed as a piezoelectric actuator. Such a ceramic actuator converts electrical energy directly into linear movements with high speed and high force. This makes it possible to achieve mechanical vibrations in the high ultrasonic range. The piezoelectric actuator is supplied with electrical energy and controlled via the cable connection 24.

[0052] In another embodiment, the respective high-frequency actuator 23 is designed as an electrostatic actuator. Such an electrostatic actuator is constructed from several electrode layers and insulation layers and deforms when an electrical voltage is applied. The actuator is connected on one side to the tamping pick 19 or the pick holder 16 and on the other side to the mass body 27. By applying a high-frequency alternating voltage, the mass body 27 and the oscillating system with the tamping pick 19 are set into vibration.

[0053] Other high-frequency actuators 23, which have a sufficiently small form factor and can generate mechanical vibrations at high frequency, are also suitable for carrying out the present invention. In particular, the 24012

[0054] 15 each high-frequency actuator 23 designed as a component with its own housing and arranged by means of an adhesive or screw connection on the respective plugging pick 19 or on the respective pick holder 16 .

Claims

16 Patent claims 1. Tamping unit (7) for tamping a track (4) with tamping picks (19) which can be immersed in a track ballast bed (10) and which are each arranged in a pick holder (16) of a tamping tool (15) which can be displaced relative to the track ballast bed (10) by actuators (14, 17), characterized in that a high-frequency actuator (23) for generating vibration is arranged in the respective tamping pick (19) and / or in the associated pick holder (16).

2. Stuffing unit (7) according to claim 1, characterized in that the respective high-frequency actuator (23) is configured to generate mechanical vibrations with a frequency of at least 1000 Hz, in particular at least 16000 Hz.

3. Stuffing unit (7) according to claim 1 or 2, characterized in that, by the arrangement of the respective high-frequency actuator (23), the associated stuffing pick (19) is part of a vibrating system which, when excited by means of the high-frequency actuator (23), forms a mode shape (29), wherein the high-frequency actuator (23) is in particular arranged at an antinode (30) of this mode shape (29).

4. Stuffing unit (7) according to one of claims 1 to 3, characterized in that the respective high-frequency actuator (23) is coupled in a cavity of the associated stuffing pick (19) with a movable mass body (27).

5. Stuffing unit (7) according to claim 4, characterized in that a cable connection (24) is arranged between the respective high-frequency actuator (23) and a plug connection (31) for coupling with a control device (33).

6. Stuffing unit (7) according to one of claims 1 to 3, characterized in that the respective high-frequency actuator (23) is arranged on a surface of the associated pick holder (16).

7. Stuffing unit (7) according to one of claims 1 to 6, characterized in that the respective high-frequency actuator (23) is a piezoelectric actuator.

8. Stuffing unit (7) according to one of claims 1 to 6, characterized in that the respective high-frequency actuator (23) is an electrostatic actuator.

9. Method for operating a tamping unit (7) according to one of claims 1 to 8, characterized in that the respective high-frequency actuator (23) is activated by means of a control device (33) during an immersion process of the associated tamping pick (19) into a track ballast bed (10).

10. Method according to claim 9, characterized in that the respective high-frequency actuator (23) is activated by means of the control device (33) during the withdrawal of the associated tamping pick (19) from the track ballast bed (10).

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