EP3377699B1 - Tamping unit and method for tamping a track - Google Patents

Description

Technical field

The invention relates to a tamping unit for tamping a track, with tamping picks which can be immersed in a ballast bed and which can be set into vibration by means of a vibration drive, the vibration drive comprising a housing in which a shaft with an eccentric is arranged so as to be rotatable about a shaft axis and on which Eccentric a transmission element for transmitting a vibration movement is mounted. In addition, the invention relates to a method for tamping a track by means of the tamping unit, the vibration movement generated being transmitted to a pick arm via an auxiliary cylinder.

State of the art

Due to the high loads to which a tamping unit is exposed, the vibration drive must meet special requirements. When immersing the tamping pick in a ballast bed of a track and then compacting the ballast below a threshold, load changes occur that stress the vibration drive. In particular when tamping a non-renewed ballast bed, which is often completely encrusted, high opposing forces act on the tamping pick set in motion by means of a vibration drive. Even in such difficult operating conditions, the vibration drive must maintain the required vibration of the tamping picks with an approximately constant vibration amplitude in order to ensure a constant tamping quality.

For use in tamping units there is therefore one from the patent AT 350 097 B well-known vibration drive, in which an oscillating vibration movement is generated by means of a driven eccentric shaft. With this design, the vibration amplitude is fixed by the dimensioning of the eccentric shaft. The one transferred to the tamping pick via the auxiliary cylinder and pick arms Vibration movement is therefore largely unaffected by the resistance of the ballast bed.

With one from the AT 513 973 A known type, the vibration movement is generated by means of a hydraulic linear drive. Without special measures, an increased ballast bed resistance leads to an undesirable reduction in the vibration amplitude. On the other hand, a hydraulic linear drive enables simple adjustment of the vibration parameters through to a rapid sequence of switch-on and switch-off processes. The latter is more difficult to implement in a known vibration drive with an eccentric axis due to the inertia of the masses in rotation.

Summary of the invention

The invention has for its object to provide an improvement over the prior art for a vibration drive of the type mentioned. Another task is to specify a corresponding method for stuffing a track.

According to the invention, these objects are achieved by a tamping unit according to claim 1 and a method according to claim 12. Further developments can be found in dependent claims.

The eccentric is rotationally and radially displaceably connected to the shaft, the position of the eccentric relative to the shaft being adjustable in the radial direction by means of an adjusting device. In operation, a torque is transmitted by means of the shaft to the eccentric designed as a separate component. The effect on the transmission element is determined by an adjustable center distance between an eccentric axis and the shaft axis. Specifically, the amplitude of the vibration movement which can be transmitted by means of the transmission element is infinitely adjustable. While maintaining the advantages of an eccentric drive, the possibility is created to adjust vibration parameters during operation. A changed distance between the eccentric axis and the shaft axis not only leads to a changed vibration amplitude, but with constant torque also to a changed impact force, which is applied by means of the vibration drive.

An advantageous development of the invention provides that the transmission element is designed as a connecting rod for transmitting an oscillating vibration movement. The connecting rod can then be connected to a linearly guided piston, by means of which the vibration can be transferred to several components.

In a simple form, the shaft has two opposite, mutually parallel flats on a lateral surface, by means of which the eccentric is guided radially. In the direction of rotation, the flattened areas form a positive connection together with correspondingly designed counter surfaces of the eccentric, in order to reliably transmit a torque.

Furthermore, it is advantageous if the adjusting device comprises at least one hydraulic cylinder with a piston, wherein an adjusting force can be exerted on the eccentric by means of the piston. This means that an often already existing hydraulic system can be used to adjust the eccentric relative to the shaft.

The hydraulic cylinder is advantageously arranged in the shaft. This cylinder is connected to a hydraulic line in the shaft, so that the adjustment device is compact and weight-saving.

The hydraulic cylinder is advantageously controlled by means of a pilot-operated check valve. This ensures that the cylinder remains fixed in its position after an adjustment process even if high opposing forces act on the eccentric.

A further development of the invention provides that the adjusting device comprises a further cylinder with a piston for fixing and / or for resetting the eccentric. The eccentric is thus clamped in position between two pistons, which provides a particularly robust fixation. The second piston is also advantageously controlled by means of a pilot-operated check valve.

There is an improvement in the possible uses of the tamping unit if the adjustment device is connected to a control and / or a Control is connected. In this way, the vibration drive of the tamping unit can be automatically adapted to changed conditions during operation.

To generate a feedback after an adjustment process, it is advantageous if the vibration drive comprises a sensor for detecting an instantaneous center distance between the shaft axis and an eccentric axis. In this way it can be checked whether a specified center distance has actually been set or is maintained during operation. Faults can thus be recognized immediately.

It is also advantageous if the vibration drive comprises a sensor for detecting an angular position and / or angular velocity of the shaft. This creates the possibility to determine an actual rotational speed of the shaft at any time and, for example, to give the vibration drive a preferred start or end position. In addition, several vibratory drives can be operated synchronized in this way.

A simple drive variant provides that the shaft is connected to a variable hydraulic motor. In addition to the advantageous use of a hydraulic system that is often already present, a simple adjustment of a vibration frequency is possible by changing the speed of the shaft.

To reduce the power consumption of the vibration drive, it is advantageous if the shaft is coupled to a flywheel. During a vibration cycle, energy is continuously released or absorbed by delayed and accelerated masses. The flywheel serves as a buffer to compensate for these energy fluctuations.

In a method according to the invention for tamping a track by means of a tamping unit described above, the vibration movement generated is transmitted to the respective tamping pick via an auxiliary cylinder and a pick arm, the vibration movement being changed by adjusting the eccentric in relation to the shaft in the radial direction by means of the adjusting device. Specifically, the vibration amplitude is adjusted during operation.

The method is advantageously further developed in such a way that a tamping cycle is formed from a plurality of phases running in succession and that, by means of a control and / or regulation, at least in one phase a different axis distance between the shaft axis and an eccentric axis is set in relation to another phase. Individual phases of the tamping cycle include, for example, lowering the tamping unit, providing the tamping pick, raising the tamping unit and repositioning the tamping unit. Due to the adjustability, the vibration drive is optimally used for the respective phase.

It is advantageous if an axis distance equal to zero is set at least in one phase of the stuffing cycle in order to suspend the vibration for a desired duration regardless of the speed of the shaft. This is particularly useful during repositioning of the tamping unit between two tamping processes to reduce noise and reduce the power consumption of the vibration drive.

In addition, it is advantageous if the shaft is driven at different speeds during a stuffing cycle. In this way, the vibration frequency can be adapted to different requirements during a stuffing cycle. For example, a higher rotational speed is specified during an immersion process because the immersion resistance of a ballast bed is reduced with a higher vibration frequency.

Brief description of the drawings

The invention is explained below by way of example with reference to the accompanying figures. In a schematic representation:

Fig. 1

Tamping unit with two pick arms

Fig. 2

Vibration drive of the tamping unit according to Fig. 1

Fig. 3

Sectional view of the vibration drive in elevation

Fig. 4

Sectional view with eccentric in zero position

Fig. 5

Sectional view with eccentric with maximum center distance

Fig. 6

Version with alternative adjustment device

Fig. 7

Oblique view of the shaft according to Fig. 2

Description of the embodiments

This in Fig. 1 The illustrated tamping unit 1 comprises an adjustable vibratory drive 2 in order to set two opposing tamping pick 3 or tamping pick groups in vibration. Each tamping pick 3 is attached to a pick arm 4. The respective pick arm 4 is pivotally articulated on a lowerable tamping tool carrier 5 and connected to a piston rod of an associated auxiliary cylinder 6. The vibration drive 2, to which each pick arm 4 is connected via the associated auxiliary cylinder 6, is also fastened to the tamping tool carrier 5. A generated vibration is thus transmitted via the respective add-on cylinder 6 to the respective pick arm 4 and the tamping pick 3 attached to it.

As in Fig. 2 can be seen, the vibration drive comprises a shaft 7, which is mounted in a housing 8 with sealed bushings. At least one further sealed bushing is provided for a transmission element 9 to which the auxiliary cylinders 6 of the tamping unit 1 are connected. The shaft 7 is advantageously mounted in the housing 8 by means of roller bearings. The components of the vibration drive 2 cause an oscillating vibration movement 10 during operation. The shaft 7 rotates about a shaft axis 11 and is rotationally connected to an eccentric 12.

The Figures 3-6 show that an axis distance 15 can be set between an eccentric axis 13 and the shaft axis 11 by means of an adjusting device 14. If the center distance 15 is greater than zero, a rotational movement 16 of the shaft 7 and the eccentric 12 is transmitted into the vibratory movement 10 by means of the transmission element 9. In the exemplary embodiment, the transmission element 9 is designed as a connecting rod, which is articulated with a linearly guided piston element 17 connected is. A pin 18 is provided for connecting the piston element 17 to the transmission element 9.

Those components which are to be subjected to the vibration movement 10 can be connected to the piston element 17. In a simpler variant, the respective auxiliary cylinder is mounted directly on the eccentric with a suitable connection and itself functions as a transmission element 9 Fig. 2 Oil-lubricated roller bearing 19 shown between the transmission element 9 and the eccentric 12 is in the Figures 3-6 not shown for the sake of clarity.

The adjusting device 14 advantageously comprises a hydraulic cylinder 20 which is arranged in the shaft 7 and presses a piston 21 against an inner surface of the eccentric 12 seated on the shaft 7. The eccentric 12 can be adjusted relative to the shaft 7 by means of this pressure force. In order to fix or reset the eccentric 12 in its respective position, a further element of the adjusting device 14 generates a counterforce on an opposite inner surface of the eccentric 12. This is, for example, by means of a spring or - as in Fig. 3 shown - applied by means of a further piston 22 of a further cylinder 23.

Instead of a hydraulic adjustment device 14, a mechanical adjustment device (not shown) can be used. This includes, for example, spindles or crankshafts guided in the shaft 7 in order to adjust the position of the eccentric 12 relative to the shaft 7.

The Figures 4 and 5 show a simplified representation of two end positions of the adjustable eccentric 12. In Fig. 4 the center distance 15 between shaft axis 11 and eccentric axis 13 is zero. The rotational movement 16 of the shaft 7 and the eccentric 12 do not lead to any vibration movement here. This setting of the eccentric position thus serves to expose the vibration.

In Fig. 5 a maximum center distance 15 between the shaft axis 11 and the eccentric axis 13 is set. The transmission element 9 designed as a connecting rod then transmits an oscillating vibration movement 10 with a vibration amplitude that corresponds to the maximum center distance 15. With the given kinematic arrangement of the respective auxiliary cylinder 6, of the respective pick arm 4 and of the respective tamping pick 3 results in a desired vibration amplitude at the free end of the tamping pick 3.

By appropriate control of the adjusting device 14, any value between zero and a maximum value can be set for the center distance 15. With the torque remaining the same, a reduced center distance 15 not only leads to a lower vibration amplitude, but also to a higher impact force of the vibration drive 2. This is advantageous for the operation of the tamping unit 1 in order to adapt the effect of the respective vibrating tamping pick 3 to a ballast bed if necessary ,

In an alternative adjustment device 14 according to Fig. 6 the eccentric 12 is not seated on the shaft 7, but is connected to the shaft 7 in a rotationally locking and radially adjustable manner via the adjusting device 14. For example, in the case of a hydraulic design, the free ends of the pistons 21, 22 are pushed into a respective longitudinal groove on an inner surface of the eccentric 12 and fixed in the longitudinal direction by means of fastening means 24. In this way, the pistons 21, 22 serve on the one hand for adjustment in the radial direction and on the other hand as elements of a rotationally locking connection between shaft 7 and eccentric 12.

In the Fig. 7 Shown shaft 7 according to the variant in Fig. 2 has two flats 25, by means of which the eccentric 12 is guided radially. In the area of these flattened portions 25, two hydraulic cylinders 20, 23 are arranged in the shaft 7 as elements of the adjusting device 14. In the installed state, the pistons 21, 22 press against inner surfaces of the eccentric 12, as a result of which it is displaced radially to the shaft axis 11. The inner surfaces of the eccentric 12 slide along the flats 25 of the shaft 7.

Each cylinder 20, 23 is connected to a respective pilot-operated check valve 26 via hydraulic lines arranged in the shaft 7. The check valves 26 are also advantageously arranged within the shaft 7 in order to ensure very short connecting lines between the pilot-operated check valves 26 and the cylinders 20, 23. This will respond quickly Adjustment device 14 allows. In addition, the compressible amount of fluid is minimized, so that the compressibility of a hydraulic fluid used is negligible. The use of two cylinders 20, 23 controlled by means of pilot-operated check valves 26 ensures that the eccentric 12 is securely fixed in its set position relative to the shaft 7.

Supply lines and control lines of the adjusting device 14 are guided, for example, to the outside on an end face 27 of the shaft 7. These rotating lines are connected to a hydraulic system by means of a known rotary feedthrough.

The vibration movement 10 can be adapted to individual phases of a stuffing cycle with the method according to the invention. At the beginning of the tamping cycle, the tamping tool carrier 5 is first lowered. During this phase, the tamping picks 3 are immersed in a ballast bed of a track. The tamping ax 3 vibrate with a vibration frequency of up to 60 Hertz and in the vibration drive 2 the maximum center distance 15 between the shaft axis 11 and the eccentric axis 13 is set. The greatest possible vibration amplitude thus results at the free end of the respective tamping pick 3.

In the next phase, the ballast is compacted below a threshold. The tamping picks 3 lying opposite in the track direction move towards one another with an additional movement, in that each additional cylinder 6 exerts a torque on the associated pimple arm 4. In this case, the additional movement is superimposed on the vibration movement 10 generated by the vibration drive 2. By adjusting the speed of the shaft 7, the vibration frequency is set to 35 Hertz in this phase.

If the shaft 7 is already driven with a maximum torque, the impact force of the tamping pick 3 can be increased in this phase if necessary by slightly reducing the center distance 15 between the shaft axis 11 and the eccentric axis 13. Such a measure may be useful for a heavily encrusted ballast bed. Doing so the center distance 15 is only reduced to such an extent that the resulting reduction in the vibration amplitude remains negligible.

During an oscillation period, the masses of the auxiliary cylinders 6, the pick arms 4 and the tamping pick 3 which are in vibration are first accelerated and braked in one direction and then accelerated and braked in the opposite direction. These vibrational movements therefore continuously lead to the release and absorption of kinetic energy. A large part of this fluctuating energy is temporarily stored in the rotating masses of the shaft 7 and the eccentric 12 which are in constant swing.

Advantageously, the shaft 7 is additionally coupled to a flywheel in order to keep the angular velocity of the rotating masses constant over a period of oscillation, independently of a rotary drive. The power consumption of the vibration drive 2 according to the invention is thus significantly lower than that of a linear vibration drive, which generates a vibration, for example by means of a hydraulic cylinder.

As soon as the compaction process has ended, the tamping picks 3 are pulled out of the ballast bed by lifting the tamping tool carrier 5. The order cylinders 6 are also reset in this phase of the tamping cycle, the vibration is suspended until the tamping pick 3 has penetrated again by setting the center distance 15 between the shaft axis 11 and the eccentric axis 13 to zero.

Specifically, the vibration amplitude is reduced to zero, the vibration frequency remaining constant during this reduction process. Without the eccentric adjustment according to the invention, the shaft 7 would have to be braked in order to suspend the vibration. The vibration drive 2 would inevitably run through low frequency ranges. Components of a tamping machine comprising tamping unit 1 or elements of the track section usually have low natural frequencies, so that undesirable resonances would occur. In addition, a cyclical braking and acceleration of the rotating masses would significantly increase the power consumption of the vibration drive 2.

For the automatic implementation of the changes in the eccentric position made in the individual phases of a stuffing cycle, the adjusting device 14 is controlled by means of a control and / or a regulation. Various sensors can be attached to the tamping unit 1 in order to record vibration parameters such as frequency and amplitude in real time and to report them to the control system. In particular, a sensor for detecting the instantaneous center distance 15 between the shaft axis 11 and the eccentric axis 13 can be provided. A particularly precise setting of the center distance 15 can thus be achieved.

The shaft 7 is driven by means of a hydraulic motor which uses the hydraulic system present in the tamping machine. This provides a sufficiently high torque and the speed is infinitely adjustable.

Claims (15)

1. A tamping unit (1) for tamping a track, having tamping tines (3) which are designed for immersion into a ballast bed and can be set in vibrations by means of a vibration drive (2), wherein the vibration drive (2) comprises a housing (8) in which a shaft (7) including an eccentric (12) is arranged for rotation about a shaft axis (11) and wherein a transmission element (9) for transmitting a vibratory motion (10) is mounted on the eccentric (12), characterized in that the eccentric (12) is connected to the shaft (7) in a rotation-locked and radially displaceable manner, and that the position of the eccentric (12) relative to the shaft (7) is adjustable in radial direction by means of an adjustment device (14).
2. A tamping unit (1) according to claim 1, characterized in that the transmission element (9) is designed as a connecting rod for transmission of an oscillating vibratory motion (10).
3. A tamping unit (1) according to claim 1 or 2, characterized in that the shaft (7) has, at a shell surface, two oppositely positioned parallel flat portions (25) by means of which the eccentric (12) is guided radially.
4. A tamping unit (1) according to one of claims 1 to 3, characterized in that the adjustment device (14) comprises at least one hydraulic cylinder (20) with a piston (21), and that an adjustment force can be exerted upon the eccentric (12) by means of the piston (21).
5. A tamping unit (1) according to claim 4, characterized in that the hydraulic cylinder (20) is arranged in the shaft (7).
6. A tamping unit (1) according to claim 4 or 5, characterized in that the hydraulic cylinder (20) is controlled by means of a pre-controlled check valve (26).
7. A tamping unit (1) according to one of claims 4 to 6, characterized in that the adjustment device (14) comprises a further cylinder (23) having a piston (22) for fixing and/or returning the eccentric (12).
8. A tamping unit (1) according to one of claims 1 to 7, characterized in that the adjustment device (14) is connected to a control and/or a governing device.
9. A tamping unit (1) according to one of claims 1 to 8, characterized in that the vibration drive (2) has a sensor for detecting a momentary axis distance (15) between the shaft axis (11) and an eccentric axis (13).
10. A tamping unit (1) according to one of claims 1 to 9, characterized in that the vibration drive (2) comprises a sensor for detecting an angle position and/or angular velocity of the shaft (7).
11. A tamping unit (1) according to one of claims 1 to 10, characterized in that the shaft (7) is connected to a variable hydraulic motor.
12. A method of tamping a track by means of a tamping unit (1) according to one of claims 1 to 11, wherein the generated vibratory motion (10) is transmitted via a squeezing drive (6) to a tine arm (4), characterized in that the vibratory motion (10) is changed in that the eccentric (12) is adjusted relative to the shaft (7) in radial direction by means of the adjustment device (14).
13. A method according to claim 12, characterized in that a tamping cycle is formed of several phases taking place one after the other, and that during at least one phase, by means of a control and/or governing device, an axis distance (15) between the shaft axis (11) and an eccentric axis (13) is set which is different versus another phase.
14. A method according to clam 13, characterized in that, during at least one phase of the tamping cycle, an axis distance (15) equalling zero is set.
15. A method according to one of claims 12 to 14, characterized in that during a tamping cycle, the shaft (7) is powered with different speeds of rotation.

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