Method and machine for tamping a track

Abstract

The invention relates to a method for tamping sleepers (6) of a track section (7) mounted in a ballast bed (5) by means of a tamping unit (9) comprising two opposite tamping tools (17) which, when tamping each sleeper (6), are subjected to vibrations (22), lowered into the ballast bed (5) and moved towards one another by a supply movement (30), while the track section (7) is held in a raised position. A supply speed (v) of at least one tamping tool (17) is monitored by means of an evaluation apparatus (27), wherein, when a predetermined supply time (t1) or a predetermined supply path (s) is reached, a current value (28) of the supply speed (v) is compared with a limit value (29), and wherein a notification signal (31) indicates whether the current value (28) is over the limit value (29). This optionally indicates that a cavity (24) located under the sleeper (6) has not yet been adequately filled.

Description

Technical field

[0001] The invention relates to a method for tamping sleepers of a track bed supported in a ballast bed using a tamping unit comprising two opposing tamping tools which, during tamping of the respective sleeper, are lowered into the ballast bed by vibrations and moved towards each other with an offset motion, while the track bed is held in a raised position. The invention also relates to a tamping machine for carrying out the method. State of the art

[0002] Railway lines with ballasted track require regular track geometry correction, typically using track tamping machines, switch tamping machines, or universal tamping machines. These machines, which move cyclically or continuously along the track, usually comprise a measuring system, a lifting / aligning unit, and a tamping unit. The lifting / aligning unit raises the track to a predetermined position. To fix this new position, tamping tools on the tamping unit are used to tamp and compact track ballast from both sides under each sleeper.

[0003] Various designs are known for tamping units used to tamp the sleepers of a track grid laid in a ballast bed. For example, AT 350 097 B discloses a tamping unit with hydraulic auxiliary drives, which are connected on the one hand to a rotating eccentric shaft for vibration generation and on the other hand to pivoting tamping tools. AT 339 358 B discloses a tamping unit with hydraulic drives that serve in a combined function as auxiliary drives and vibration generators.

[0004] AT 515 801 A4 describes a method for compacting a track ballast bed using a tamping unit, with the aim of specifying a quality index for ballast bed hardness. For this purpose, the actuating force of an actuating cylinder is measured as a function of its travel, and a characteristic value is defined based on the derived energy consumption. However, this characteristic value is of limited significance because a not insignificant portion of energy lost within the system is not taken into account. Furthermore, the total energy actually introduced into the ballast during a tamping process would not allow for a reliable assessment of the ballast bed's condition.

[0005] In a method known from AT 520 056 A1, each vibration cycle generated by a vibratory drive is analyzed for at least one tamping tool. Specifically, during a vibration cycle, the force acting on the tamping tool is recorded over the distance traveled by the tamping tool. Continuous evaluation of these force-displacement curves allows for real-time detection of the condition of the ballast bed and whether sufficient compaction is achieved. Description of the invention

[0006] The invention is based on the objective of improving a method of the type mentioned above in such a way that optimal ballast filling of cavities under the sleepers can be carried out in a simple manner. A further objective of the invention is to provide a corresponding tamping machine.

[0007] According to the invention, these problems are solved by a method according to claim 1 and a machine according to claim 13. Dependent claims specify advantageous embodiments of the invention.

[0008] An evaluation unit monitors the tamping speed of at least one tamping tool. When a predetermined tamping time or distance is reached, the current tamping speed is compared to a limit value, and a signal indicates whether the current value exceeds the limit. During the filling of the voids under the sleepers, a counterforce caused by the friction of the ballast acts on the tamping tools. This counterforce increases as the void is filled and the stiffness of the ballast layer under the sleeper increases. Consequently, the tamping speed decreases at a constant tamping pressure.

[0009] The present invention utilizes this effect to detect the current filling status. If, after a predetermined pre-positioning phase, the current order speed is still above the threshold, a corresponding information signal is issued. For example, a visual or audible signal is emitted. The current filling status can also be indicated by maintaining a signal or by a changing signal upon a status change. In any case, the signal indicates whether, based on a value comparison, the cavity below the threshold has already been sufficiently filled or whether the filling is still insufficient. In the latter case, subsequent measures are taken to achieve optimal filling.

[0010] In a simple version, the signal is fed to a display device to indicate to the operator that a cavity under the threshold currently being tamped is insufficiently filled. This alerts the operator that the current tamping process should be continued and that further tamping operations may be necessary to achieve optimal filling.

[0011] In an improved embodiment of the invention, the signal is fed to a control device of the tamping unit, whereby, in particular, a longer tamping duration and / or a modified tamping force are automatically specified by means of the control device. This eliminates the need for operator intervention to optimize the gravel filling process.

[0012] If necessary, it is advisable for the control unit to automatically initiate another tamping process for the threshold currently being tamped. This measure is particularly advantageous if the available tamping tool travel is insufficient to achieve the desired filling level.

[0013] An advantageous embodiment of the invention is characterized by increasing the frequency of the tamping tool's vibrations when the current value falls below the limit value. For this purpose, the current value is continuously compared with the limit value to detect when an optimal filling state is reached. Only when this optimal filling state is reached do the vibrations transmitted from the tamping tool to the ballast, due to the increased vibration frequency, lead to enhanced temporary dynamic fluidization of the ballast. This so-called ballast flow causes the ballast grains to slide against each other with low friction. The ballast behaves in a fluid-like manner and vibrates independently to a higher density. During the filling phase, this effect is limited due to the lower vibration frequency.The vertical friction between the gravel grains facilitates the filling process because the tamping tools move larger, interlocking ballast packages. This prevents the gravel from flowing around the tamping tools.

[0014] For comparison with the limit value, it is useful to evaluate the current value as the delivery speed at the moment the specified delivery time or delivery distance is reached. This method does not require high computing power from the evaluation unit because no modification of the recorded speed value is necessary.

[0015] In another variant, it can be advantageous to evaluate the current value as an averaged value of the delivery speed over a range of delivery time or delivery distance. This compensates for inaccuracies in speed measurement or irregularities during the delivery process.

[0016] Another approach involves determining the current value as the result of a weighted time or path integral. Less computing power is required if the current value is determined as a weighted sum of several measured values ​​of the feed rate. These methods also compensate for irregularities in the feed process, with certain phases of the feed process being emphasized through appropriate weighting.

[0017] When improving these variants, a weighting is specified depending on a calculated or measured process parameter of the packing operation. This specific weighting enables automated adaptation of the evaluation algorithms to changing packing conditions.

[0018] Advantageously, the penetration work or penetration force during the lowering process of the tamping tool is determined as such a process parameter. Based on this process parameter, an adapted weighting is subsequently derived for calculating the current value of the feed rate.

[0019] Further improvements in the evaluation are achieved when a time-dependent progression of the positioning speed or the positioning distance is fed as input data to a machine learning model. For example, the evaluation system might employ a neural network, a support vector machine, a decision tree, a regression analysis, or a Bayesian network. Additional process variables, such as the lifting value of the track grid or a desired positioning force, can also serve as input data for the model. The model's output provides a current value that can be used to assess the filling condition.

[0020] The tamping machine according to the invention for carrying out one of the specified methods comprises a lifting unit for raising the track grid and a tamping unit for tamping under the raised sleepers. A sensor for detecting the tamping speed is arranged, the sensor being coupled to an evaluation unit. The evaluation unit contains an algorithm that compares a current value of the tamping speed with a limit value. Furthermore, the evaluation unit is configured to output a signal indicating whether the current value exceeds the limit value at the predetermined comparison time. The tamping machine designed in this way enables the optimal filling of the cavities formed under the raised sleepers in a simple manner.

[0021] In a basic training course, the evaluation unit is coupled with a display unit to show a message. The display alerts an operator to an insufficient filling level, whereupon necessary follow-up measures are initiated.

[0022] In a further improvement to the machine, the evaluation unit is coupled with a control unit for the tamping unit. As soon as the control unit receives information about insufficient filling via the signal, measures to further fill the cavities are automatically initiated. For example, the waiting time is extended or another tamping operation is carried out for the current threshold being tamped. Brief description of the drawings

[0023] The invention is explained below by way of example with reference to the accompanying figures. These show, in schematic representation: Fig. 1 Tamping machine Fig. 2 Tamping unit during a lowering process Fig. 3 Tamping tools during filling of a cavity Fig. 4 Tamping tools during compaction of the ballast layer Fig. 5 Graph of the feed rate over time Fig. 6 Determination of the limit value Fig. 7 Determination of the limit value and evaluation of the measured feed rate Description of the embodiments

[0024] The in Fig. 1The illustrated tamping machine 1 is movable on rails 3 of a track 4 by means of rail carriages 2. Sleepers 6, supported in a ballast bed 5, together with the rails 3 attached to them, form a track grid 7. For carrying out the present method, the tamping machine 1 comprises a lifting unit 8 and a tamping unit 9. In addition, a measuring system 10 is arranged for track alignment correction. The units 8 and 9 are adjustable relative to a machine frame 12 via actuators 11. The lifting unit 8 is advantageously also provided for laterally aligning the track grid 7.

[0025] The tamping unit 9 and a machined section of track 4 are in Fig. 2As shown, a tool carrier 14 is guided vertically in an aggregate frame 13. A driven eccentric shaft is arranged on the tool carrier 14 as a vibration drive 15. Two auxiliary drives 16 are articulated to the eccentric shaft. The rotation of the eccentric shaft sets the auxiliary drives 16 into vibration, with the respective eccentricity determining the vibration amplitude.

[0026] Tamping tools 17 are mounted on the tool carrier 14 opposite a sleeper 6 to be tamped. Each tamping tool 17 comprises a tamping lever 18, the upper lever arm of which is connected to the associated auxiliary drive 16. A tamping pick 19 is arranged on the lower lever arm, which plunges into the ballast bed 5 during a tamping operation.

[0027] Fig. 2The tamping unit 9 is shown during a lowering movement 20 of the tamping tools 17, whereby the tamping picks 19 exert a penetrating force 21 on the ballast bed 5. During this process, the vibration drive 15 is active, so that the respective tamping pick 19 is subjected to vibrations 22 via the associated tamping lever 18 and the blocked auxiliary drive 16. The processed section of the track grid 7 is lifted into a predetermined target position by means of the lifting unit 8 with a lifting force 23. This creates cavities 24 under the sleepers 6 that are yet to be tamped, which are to be filled with ballast during a tamping operation. Roller clamps 25 of the lifting unit 8 hold the processed track grid 7 in position until the end of each tamping operation.

[0028] At least one tamping tool 17 is equipped with a sensor 26 for detecting an adjustment speed v. This sensor 26 is coupled to an evaluation unit 27 to compare a current value 28 of the adjustment speed v with a stored limit value (threshold) 29. This comparison is performed continuously or at least at a specific time after the start of an adjustment movement 30. In any case, the result of the comparison performed when a predetermined adjustment time t1 or a predetermined adjustment distance s is reached is subsequently relevant. For this purpose, a corresponding default value for the adjustment time t1 and / or the adjustment distance s is stored in the evaluation unit 27. When this default value is reached, the adjustment movement is usually not yet complete. The total intended adjustment time or the total intended adjustment distance is greater than the default value relevant for the comparison.

[0029] If the relevant value comparison shows that the current value 28 of the approach speed v is still above the limit value 29, a corresponding message signal 31 is issued by the evaluation unit 27. This indicates that the cavity 24 of the currently tamped threshold 6 has not yet been sufficiently filled. An operator receives the corresponding information via a display unit 32, which receives the message signal 31. This enables the operator to initiate measures to optimize the filling of the cavity 24.

[0030] For the automated execution of corresponding measures, the evaluation unit 27 is coupled to a control unit 33 of the tamping unit 9. The signal 31 initially causes the control unit 33 to continue the tamping movement by adjusting the actuating drives 16. It continuously checks whether the current value 28 of the tamping speed v reaches the limit value 29. The maximum possible tamping travel limits this measure. Furthermore, a reserve is necessary so that the ballast pushed under the sleeper 6 during backfilling can be compacted completely. If necessary, as a further measure, the same sleeper 6 is tamped again to ensure optimal filling of the cavity 24. This process is again checked by comparing the current value 28 of the tamping speed v with the limit value 29.

[0031] Shortly before the tamping picks 19 reach the specified immersion depth, the adjusting movement 30 begins through a corresponding activation of the adjusting drives 16. The adjusting process initially fills the cavity 24 located under the threshold 6, as shown in Fig. 3 The tamping picks 19 exert a constant assisting force 34 on the gravel grains because the assisting drives 16, designed as hydraulic cylinders, are subjected to a constant pressure.

[0032] During the filling of the cavity 24, the tamping tools 17 remain subjected to vibrations 22, the vibration frequency being advantageously lower than the frequency during immersion in the ballast bed 5. In this way, the ballast grains remain mobile. The lower frequency prevents excessive fluidization of the ballast grains, thus preventing lateral migration of the ballast grains.

[0033] The start of the adjustment movement 30 is recorded in the evaluation unit 27 in order to compare the current value 28 of the adjustment speed v with the stored limit value 29 when the predetermined adjustment time t 1 is reached. The limit value 29 is determined in advance by theoretical analyses, by a simulation or by an experiment and stored in the evaluation unit 27.

[0034] One way to determine the limit value 29 by means of an experiment is to raise the track grid 7 to the desired lifting value before the actual tamping process begins. In a first step 35, the track grid 7 is raised as described in Fig. 6As shown. During the leveling process, in a second step 36, the leveling speed v and, if applicable, the leveling force 34 are measured. In addition, in a third step 37, the time t 0 is determined from a measurement of the lifting force 23, from which the ballast, due to the complete filling of the cavity 24, pushes the sleeper 6 upwards. At this time t 0, the lifting force 23 decreases and the leveling speed v is reduced. The limit value 29 for the detection, whether the filling process In this example, the speed v measured when the filling is reached corresponds to the point of completion.

[0035] By continuously comparing the current value 28 of the tamping speed v with the limit value 29, the achievement of optimal filling of the cavity 24 is detected during each tamping operation. Advantageously, from this point onward, the frequency of the vibrations 22 of the tamping tools 17 is increased. The increased dynamic excitation enhances the mobility of the ballast grains, causing them to transition into a denser structure. In this way, optimal compaction of the ballast pushed under the sleeper 6 is achieved in the final phase of the tamping operation. The switch from tamping frequency to compaction frequency can also be solely dependent on the distance traveled or on time. A corresponding threshold value is empirically determined in advance by measuring the lifting force 23, as described above.

[0036] In a further development of the invention, the limit value 29 and / or the time t1 for carrying out the comparison with the current value 28 of the tamping speed v is determined as a function of other calculated or measured process variables. For example, the penetration force 21 or the penetration work during the lowering of the tamping picks 19 into the ballast bed 5 is used as such a process variable. The lifting of the track grid 7 by means of the lifting unit 8 and the desired tamping force 34 can also serve as process variables to influence the limit value 29 or the comparison time t1.

[0037] Furthermore, it can be useful to determine an average speed as the current value 28 of the filling speed v. The filling speed v is recorded from the beginning of a filling process, and an average value is continuously calculated. For example, the average speed can be determined by a weighted time or distance integral, or by a weighted sum of several speed measurements. The weighting can be time- or distance-dependent and can be defined depending on the process parameters mentioned above. If the current value 28 determined in this way exceeds the limit value 29, insufficient filling is detected.

[0038] A final compaction process 38 of the filled gravel is in Fig. 4This process only occurs once the preceding backfilling process 39 is complete. Since the resistance of the gravel is lower during backfilling than in the already filled state, the backfilling movement 30 occurs at a higher speed v during backfilling than during the final compaction of the filled gravel, assuming a constant applying force 34.

[0039] The corresponding speed profile is in Fig. 5The process is illustrated. At time t0, when the cavity 24 is completely filled below the threshold 6, the limit value 29 is determined beforehand. In a first example of a filling process, a comparison of the current value 28 of the filling speed v with the limit value 29 is performed for a predetermined filling time t1. In this first example, the current value 28 is still above the limit value 29. This indicates that the filling process 39 is not yet complete. In the second example, the comparison is performed at a later time t1' because a longer filling time is specified. Here, the current value 28' has already fallen below the limit value 29. The comparison provides the information that the filling process 39 is complete.

[0040] The velocity v is measured or estimated, for example, by measuring the adjustment travel at the adjustment cylinder 16, by measuring a pivot angle of the tamping lever 18, or by measuring a volume flow rate of one or more adjustment cylinders 16. In a further development of the invention, the course of the measured or estimated adjustment velocity v is used as input for a machine learning model. For example, a neural network, a support vector machine, a decision tree, a regression analysis algorithm, or a Bayesian network is implemented in the evaluation unit 27.

[0041] Fig. 7A simple evaluation using the evaluation unit 27 is shown. As described above, the limit value 29 is determined and stored beforehand. During each filling operation 40, the filling speed v is recorded. In a comparison operation 41, the current value 28 of the filling speed v is compared with the stored limit value 29. This results in an automated decision as to whether the current filling operation 39 is complete or not. In the case of insufficient filling, a corresponding message signal 31 is issued.

[0042] This ensures that each sleeper 6 is optimally tamped. Only when the cavity 24 under the respective sleeper 6 is completely filled and the compaction of the filled ballast is complete, is the tamping of the next sleeper 6 carried out in the working direction 42. This process is advantageously automated, with the control unit 33 reporting to a machine control system that a tamping operation is complete. Consequently, the machine 1 or a so-called satellite is moved forward by one sleeper division, or, in the case of a multi-sleeper tamping unit 9, by several sleeper divisions.

[0043] If necessary, after a predetermined number of tamping operations or in the event of an obvious change in conditions, the tamping process is interrupted in order to recalculate the limit value 29. This can be useful, for example, if a new ballast layer transitions into an old ballast layer or if the type of sleepers 6 changes. Otherwise, typical changes in track conditions are compensated for by the weightings described, depending on the determined process parameters.

Claims

1. A method for tamping sleepers (6) of a track panel (7), supported in a ballast bed (5), by means of an evaluation device (27) and a tamping unit (9), comprising two tamping tools (17) opposite one another which, during tamping of the respective sleeper (6), are lowered into the ballast bed (5) with vibrations (22) being applied, and are moved towards each other with a squeezing movement (30) while the track panel (7) is held in a raised position, characterized in that the evaluation device (27) is used to monitor a squeezing speed (v) of at least one tamping tool (17), that a current value (28) of the squeezing speed (v) is compared with a limit value (29) when a predefined squeezing time (t1) or a predefined squeezing distance (s) is reached, and that a notification signal (31) indicates whether the current value (28) is above the limit value (29).

2. A method according to claim 1, characterized in that the notification signal (31) is fed to a display device (32) to indicate to an operator an insufficient filling of a void (24) below the current sleeper (6) to be tamped.

3. A method according to claim 1 or 2, characterized in that the notification signal (31) is fed to a control device (33) of the tamping unit (9), and that a longer squeezing time and / or a modified squeezing force (34) is automatically specified, particularly by means of the control device (33).

4. A method according to claim 3, characterized in that the control device (33) automatically triggers a further tamping process for the current sleeper (6) to be tamped.

5. A method according to one of the claims 1 to 4, characterized in that the frequency of the vibrations (22) of the tamping tool (17) is increased when the current value (28) falls below the limit value (29).

6. A method according to one of the claims 1 to 5, characterized in that the squeezing speed (v) at the point in time of reaching the predefined squeezing time (t1) or the predefined squeezing distance (s) is evaluated as the current value (28).

7. A method according to one of the claims 1 to 5, characterized in that a value of the squeezing speed (v) averaged over a range of the squeezing time (t) or the squeezing distance (s) is evaluated as the current value (28).

8. A method according to one of the claims 1 to 5, characterized in that the current value (28) is determined as the result of a weighted time or distance integral.

9. A method according to one of the claims 1 to 5, characterized in that the current value (28) is determined as a weighted sum of several measuring values of the squeezing speed (v).

10. A method according to claim 8 or 9, characterized in that a weighting is predefined depending on a calculated or measured process variable of the tamping process.

11. A method according to claim 10, characterized in that a penetration work or a penetration force (21) is recorded as a process variable during the lowering of the tamping tools (17).

12. A method according to one of the claims 1 to 11, characterized in that a time progression of the squeezing speed (v) or the squeezing distance (s) is fed to a machine learning model as input data.

13. A tamping machine (1) for carrying out a method according to one of the claims 1 to 12, comprising a lifting unit (8) for lifting the track panel (7) and a tamping unit (9) for tamping lifted sleepers (6), characterized in that a sensor system (26) is arranged to record a squeezing speed (v), and that the sensor system (26) is coupled with the evaluation device (27), which is set up for comparing a current value (28) of the squeezing speed (v) with a limit value (29) and for outputting a notification signal (31), indicating whether the current value (28) is above the limit value (29).

14. A tamping machine (1) according to claim 13, characterized in that the evaluation device (27) is coupled with a display device (32) for displaying a notification.

15. A tamping machine (1) according to claim 13 or 14, characterized in that the evaluation device (27) is coupled with a control device (33) of the tamping unit (9).

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