Tamping unit for compacting the underside of the track

Abstract

A tamping unit (4) for compacting the underside of a track (3), comprising paired tamping tools (12) which are mutually capable of a squeezing movement by means of respective squeeze cylinders (16) in which a squeeze piston (17) is arranged to which the working pressure of a first hydraulic circuit (23) can be applied, and in order to superimpose vibrations on the squeeze movement (24), each squeeze cylinder (16) is assigned a vibration piston (30) which is arranged in a pressure intensifier (27) with a primary cylinder (28) and a secondary cylinder (29), so that vibration generation can be carried out at a lower pressure level.

Description

[Technical field]

[0001] The invention relates to a tamping unit for compacting the underside of a track, comprising tamping tools arranged in pairs, which can perform a mutual squeezing movement by means of respective squeeze cylinders, in which a squeeze piston is arranged to which the working pressure of a first hydraulic circuit can be applied, and to which a vibration piston is assigned to each squeeze cylinder in order to superimpose vibrations on the squeeze movement. [Background technology]

[0002] From EP 1 653 003 A1, a tamping unit is known, in which tamping ice axes are moved in pairs to compact the underside of the track. This squeeze movement for compacting the ballast is carried out by hydraulically pressurizable squeeze cylinders. A hydraulic vibration is superimposed on the linear squeeze movement, so that easier penetration into the ballast and improved compaction are achieved.

[0003] AU 517843 A1 describes an improved hydraulic vibration generation, in which in each squeeze cylinder, in addition to the squeeze piston, a vibration piston is arranged for superimposing the squeeze movement on an adjustable vibration, thus allowing the optimization of the parameters required for vibration generation independently of the squeeze movement. Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is to improve a tamping unit of the type mentioned at the beginning in such a way that hydraulic vibration is possible with high energy efficiency. [Means for solving the problem]

[0005] According to the invention, this problem is solved by the features of the independent claim 1. The dependent claims provide advantageous configurations of the invention.

[0006] In the present invention, each vibration piston is arranged in a pressure intensifier (also called a pressure transducer or pressure booster) with a primary and secondary cylinder. In this way, vibration generation can be carried out at a lower pressure level. High pressure occurs only in the secondary cylinder of the intensifier. Lower pressure occurs in the primary cylinder, where the vibration occurs. This results in less energy losses during switching operations. By arranging the pistons for vibration generation in a pressure intensifier separate from the squeeze cylinder, the controllability is improved. For example, the vibration is only active during the penetration operation of the tamping tool into the ballast and during the squeeze operation.

[0007] In a refinement of the invention, the booster is connected to the second hydraulic circuit via a control valve, e.g. an existing hydraulic circuit in the tamping machine, which has a lower pressure level than the first hydraulic circuit, is used, which simplifies the construction and maintenance of the entire hydraulic system.

[0008] In this case, the control valve is advantageously connected to a control device that is arranged to control the control valve by a variable vibration parameter. This modified control arrangement allows each stage of a tamping cycle to be linked to a specific vibration parameter. For example, a vibration frequency of 40-50 Hz is pre-set during the penetration operation of the tamping tool into the ballast. During the squeezing movement, the frequency is reduced to 35 Hz, and when the tamping tool is raised, the vibration is stopped. In addition to a higher energy efficiency, this measure also leads to lower noise emissions during operation. Furthermore, the vibration amplitude can be adapted to the current properties of the ballast bed to be compacted. Setting different vibration amplitudes during the penetration and squeezing operations may be rational.

[0009] In an improved configuration, the control valve is configured as a proportional or servo valve and a stroke measuring sensor is arranged for detecting the piston stroke and / or the piston position. In particular, the position of the oscillating piston in the secondary or primary cylinder of the pressure intensifier is measured thereby. In this case, the control valve is controlled via a control circuit for adjusting the oscillation frequency and / or the oscillation amplitude. It may also be reasonable to adjust it depending on the instantaneous position of the assigned squeeze piston. This makes it possible, for example, to pre-set the oscillation frequency depending on the squeeze stroke. In this case, the squeeze stroke is measured by a further stroke measuring sensor or an angle sensor arranged on the pivot arm. When two hydraulic circuits are used, the oscillation amplitude and frequency can be controlled particularly precisely and efficiently.

[0010] Further advantages are obtained if the intensifier, in particular the secondary cylinder of the intensifier, is arranged directly on the assigned squeeze cylinder. In this way, the amount of hydraulic oil displaced during the oscillation cycle is reduced to a minimum. Correspondingly, less heat loss occurs in the hydraulic circuit. Furthermore, it is ensured that the oscillation parameters remain stable during the squeeze operation, since there are no flexible connecting tubes in the high pressure area.

[0011] In an advantageous configuration, a first and a second pressure intensifier are assigned to each squeeze cylinder, the first pressure chamber of each squeeze cylinder is connected to the pressure chamber of the assigned first pressure intensifier, and the second pressure chamber of each squeeze cylinder is connected to the pressure chamber of the assigned second pressure intensifier. Thus, each squeeze cylinder is assigned a unique vibration circuit. Thus, a unique vibration can be applied to each tamping tool. This is, for example, reasonable in a branched tamping unit with a swiveling pick, so that the tamping pick that is swiveled upward does not vibrate.

[0012] In another advantageous configuration, two pressure intensifiers are assigned to both squeeze cylinders of one tamping tool pair, one pressure intensifier being connected to the first pressure chamber of one squeeze cylinder and the other pressure intensifier being connected to the first pressure chamber of the other squeeze cylinder, which simplifies the construction of the hydraulic system for generating vibrations.

[0013] Advantageously, in this configuration, the second pressure chambers of both squeeze cylinders are connected to a pressure accumulator in which energy is temporarily stored during the vibration cycle, resulting in a high energy efficiency of the entire system.

[0014] In both configurations, the intermediate chambers of both pressure intensifiers are preferably connected to a compensation accumulator or to a pressure-loaded charging line, with corresponding preload pressures in the intermediate chambers ensuring uninterrupted functioning of the pressure intensifiers.

[0015] A further improvement in energy efficiency is achieved in that the flow opening between the squeeze cylinder and the intensifier is larger than the connection opening of the squeeze cylinder to the first hydraulic circuit, which avoids counter-reactions on the first hydraulic circuit when vibrations are active. To generate vibrations, hydraulic oil only needs to be pumped back and forth between the intensifier and the assigned pressure chamber of the squeeze cylinder.

[0016] The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram of a tamping machine on a track. [Diagram 2] FIG. 2 is a schematic diagram of a tamping unit. [Diagram 3] FIG. 1 is a schematic diagram of a configuration in which one squeeze cylinder is provided with two pressure intensifiers. [Figure 4] FIG. 1 is a schematic diagram of a configuration in which one squeeze cylinder pair is provided with two pressure intensifiers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The tamping machine 1 shown in Figure 1 can travel with a rail travelling gear 2 on a track 3, the underside of which is to be compacted, and comprises a tamping unit 4, a refrying unit (lifting / lining unit) 5, an inspection system 6 and a control device 7. The track 3 is a ballasted track in which a track frame formed by sleepers 8 and rails 9 is supported in a ballast bed 10. During the tamping operation, the track frame is lifted to a target position by the refrying unit 5 and, if necessary, moved laterally. The inspection system 6 performs a compensation adjustment of the current position of the track frame according to the target position.

[0019] The target position is determined by penetrating the tamping unit 4 into the ballast bed 10 between the sleepers 8 with a vibrating tamping pick 11 and compacting the ballast below the sleepers 8 by a squeezing action. The tamping tool 12 usually comprises two tamping picks 11 mounted side by side in the pick mount of a pivot lever 13. The pivot arms 13 of the tamping tools 12 located opposite each other are supported in a tongue-like manner on a common tool support 14. This tool support 14 is guided in a unit frame 15 so as to be height-adjustable. The upper ends of the tamping tools 12 are pivoted to the tool support 14 via respective squeeze cylinders 16.

[0020] Each squeeze cylinder 16 is configured as a hydraulic cylinder in which a squeeze piston 17 is connected via a piston rod 18 to the assigned tamping tool 12. A first pressure chamber (piston chamber) 19 can be applied with the working pressure of a first hydraulic circuit 23 via a first connecting opening 21, and a second pressure chamber (annular chamber) 20 can be applied with the working pressure of the first hydraulic circuit 23 via a second connecting opening 22. This working pressure is built up in the first pressure chamber 19 via a switching valve (not shown), so that a squeeze movement 24 of the tamping pick 11 occurs. During the squeeze movement, the squeeze pressure provided in the first hydraulic circuit 23 is thus applied in each first pressure chamber 19.

[0021] In this case, the desired squeeze force is determined by the pressure difference between the first pressure chamber 19 and the second pressure chamber 20 and the ratio of the piston surface 25 adjacent to the first pressure chamber 19 to the annular surface 26 adjacent to the second pressure chamber 20. To return the tamping tool 12, an opening pressure is applied to the second pressure chamber 20 relative to the first pressure chamber 19, taking into account the area ratio. During the penetration operation of the tamping tool 12 into the ballast bed 10, the two pressure chambers 19 are blocked off from the first hydraulic circuit 23. This is done via a changeover valve (not shown) which is connected via lines to the two connecting openings 21, 22.

[0022] According to the invention, at least one pressure intensifier 27 is assigned to each squeeze cylinder 16. In the configuration shown in Fig. 2 and Fig. 3, two pressure intensifiers 27 are assigned to each squeeze cylinder 16. Each pressure intensifier 27 comprises a primary cylinder 28 and a secondary cylinder 29. An oscillating piston 30 is arranged in each pressure intensifier 27. For the purposes of the following description, the piston in the secondary cylinder 29 (secondary piston) is defined as the oscillating piston 30. However, due to the rigid connection by the connecting rod 31, the piston in the primary cylinder 28 (primary piston) 32 may also be considered as the oscillating piston.

[0023] The larger diameter of the primary piston 32 compared to the diameter of the secondary piston 30 determines the pressure conversion ratio of the pressure boosters 27. In the illustrated example, the low system pressure of the second hydraulic circuit 33 is converted via the respective pressure booster 27 into the working pressure which occurs in the first pressure chamber 19 and in the second pressure chamber 20, respectively. The second hydraulic circuit 33 can be supplied from the first hydraulic circuit 23 by means of a corresponding pressure reducer. Preferably, an existing hydraulic circuit with a correspondingly low pressure level is used.

[0024] When dimensioning the intensifier 27, the ratio between the large piston surface 25 and the annular surface 26 of the assigned squeeze piston 17 must be taken into account. In particular, the diameter of the secondary piston 30 is predefined by the volume change occurring during active vibration in the pressure chambers 19, 20 of the assigned squeeze cylinder 16. The primary pistons 32 of the intensifier 27 must be dimensioned in such a way that the same pressure always exists in the adjacent primary pressure chambers 34, i.e. the system pressure of the second hydraulic circuit 33. Thus, the same force acts on each primary piston 32 when pressurized. The length of each primary cylinder 28 and secondary cylinder 29 results from the maximum piston stroke for generating the desired vibration.

[0025] The first pressure chamber 19 of the assigned squeeze cylinder 16 is connected via a first flow opening 35 to the secondary pressure chamber 36 of the first pressure intensifier 27. The second pressure chamber 20 of the assigned squeeze cylinder 16 is connected via a second flow opening 37 to the secondary pressure chamber 36 of the second pressure intensifier 27. The primary pressure chamber 34 is connected via a switching valve 38 to the second hydraulic circuit 33.

[0026] In the simplest case, the switching valve 38 is a 4 / 2-way valve, which alternately switches both boosters 27 to the system pressure of the second hydraulic circuit 33. For this purpose, the switching valve 38 is controlled by the control device 7. The switching instant is determined by a square signal 39. In this way, the squeeze piston 17 in the squeeze cylinder 16 is subjected to vibrations, which result in an oscillatory movement 40 of the tamping pick 11. The frequency and amplitude of the vibrations can be adjusted via the system pressure of the second hydraulic circuit 33 and the square signal 39.

[0027] The flow openings 35, 37 between the secondary cylinder 29 of the intensifier 27 and the pressure chamber 19, 20 of the assigned squeeze cylinder 17 are dimensioned significantly larger than the connection openings 21, 22 to the first working pressure circuit 23. During the penetration operation, the oil inflow or outflow through the connection openings 21, 22 is blocked by a switching valve (not shown). In this case, due to the corresponding dimensioning of the intensifier, the hydraulic oil passes between the respective pressure chamber 19, 20 of the squeeze cylinder 16 and the assigned secondary pressure chamber 36 of the respective intensifier 27. As a result, the squeeze piston 17 in the squeeze cylinder 16 oscillates. This vibration is transmitted via the piston rod 18 to the assigned tamping tool 12.

[0028] During the squeeze operation, the oscillations are maintained because the secondary pressure chamber 36 is filled through the large flow openings 35, 37 between the squeeze cylinder 16 and the intensifier 27 before the reaction time of the integrated overpressure valve is reached. The direct mounting of the intensifier 27 to the assigned squeeze cylinder 16 also ensures that oscillations are maintained, by which damping effects are avoided.

[0029] At the start of operation, the first pressure chamber (piston chamber) 19 is filled and then blocked. The working pressure in the blocked first chamber 19 and the counter pressure applied to the smaller annular surface 26 fill the pressure intensifier 27. The switching valve 38 can then start working full time.

[0030] The intermediate chambers 41 of both intensifiers 27 are connected to one another via a compensation line 42. A compensation accumulator 43 is connected to this compensation line 42, so that a preload pressure (e.g. 5 bar) is applied to the intermediate chamber 41. When vibrations become active, this arrangement compensates even small volume fluctuations in the intermediate chamber 41. Alternatively to this, filling lines with equal preload levels can be used.

[0031] In a refinement of the invention, the switching valve 38 is designed as a servo valve or a proportional valve. At least one piston stroke in the cylinder 16, 28, 29 is detected by a stroke measuring sensor 44. This can be done by direct measurement in the corresponding cylinder 16, 28, 29 or indirectly via the position of the tamping tool 12. A measuring signal corresponding to the piston stroke is fed to a control device 7, which subsequently regulates the vibration as a function of the measuring signal. In this way, a regulation circuit for the desired vibration amplitude is obtained.

[0032] A simplified construction is shown in FIG. 4, where only one pressure intensifier 27 is assigned to each squeeze cylinder 16 of the tamping tools 12 located opposite each other. In particular, each first pressure chamber (piston chamber) 19 is connected to the secondary pressure chamber 36 of the assigned pressure intensifier 27. The application of the system pressure of the second pressure circuit 33 to the primary pressure chamber 34 takes place as in the example shown in FIG. 3. A compensation line 42 with a compensation accumulator 43 or a charging line is also present. Furthermore, a pressure accumulator (hydraulic accumulator) 45 is provided, which is connected to a connecting line 46 of the second pressure chamber (annular chamber) 20.

[0033] During the penetration operation, the pressure in this connecting line 46 and in the second pressure chamber 20 are blocked by a valve (not shown) from the rest of the hydraulic circuit. Pressure peaks occurring during active oscillations are temporarily stored by the pressure accumulator 45. In this case, hydraulic oil is stored in the pressure accumulator 45 at the rising edge of the square signal 39 and released again at the falling edge.

[0034] With the onset of the squeeze action, the connection line 46 and the second pressure chamber 20 are unblocked and the hydraulic fluid can flow back into the first hydraulic circuit 23. The vibrations are then maintained. In this case, the hydraulic fluid continues to be stored in the accumulator 45 with each rising edge of the rectangular signal 39 and is released again at the falling edge of the edge. In this way, heating of the hydraulic fluid due to the action of the vibrations is avoided.

Claims

1. A tamping unit (4) for compacting the underside of a track (3), comprising tamping tools (12) arranged in pairs, the tamping tools (12) being capable of squeezing each other by means of respective squeeze cylinders (16), in each of which a squeeze piston (17) is arranged to which the working pressure of a first hydraulic circuit (23) can be applied, and a vibration piston (30) is assigned to each squeeze cylinder (16) in order to superimpose vibration on the squeezing movement (24), A tamping unit (4), characterized in that the oscillating piston (30) is arranged in a pressure intensifier (27) comprising a primary cylinder (28) and a secondary cylinder (29).

2. 2. The tamping unit (4) according to claim 1, characterized in that the pressure intensifier (27) is connected to a second hydraulic circuit (33) via a control valve (38).

3. 3. The tamping unit (4) according to claim 2, characterized in that the control valve (38) is connected to a control device (7) configured to control the control valve (38) by means of a variable vibration parameter.

4. 4. The tamping unit (4) according to claim 2 or 3, characterized in that the control valve (38) is configured as a proportional valve or a servo valve, and a stroke measuring sensor (44) is arranged for detecting a piston stroke and / or a piston position.

5. 2. The tamping unit (4) according to claim 1, characterized in that the pressure intensifier (27), in particular the secondary cylinder (29) of the pressure intensifier (27), is arranged directly on the assigned squeeze cylinder (16).

6. 2. The tamping unit (4) according to claim 1, characterized in that first and second pressure intensifiers (27) are assigned to each squeeze cylinder (16), the first pressure chamber (19) of each squeeze cylinder (16) is connected to the pressure chamber (36) of the assigned first pressure intensifier (27), and the second pressure chamber (20) of each squeeze cylinder (16) is connected to the pressure chamber (36) of the assigned second pressure intensifier (27).

7. 2. The tamping unit (4) according to claim 1, characterized in that two pressure intensifiers (27) are assigned to both squeeze cylinders (16) of one tamping tool pair, one of the pressure intensifiers (27) being connected to the first pressure chamber (19) of one of the squeeze cylinders (16), and the other of the pressure intensifiers (27) being connected to the first pressure chamber (19) of the other of the squeeze cylinders (16).

8. 8. The tamping unit (4) according to claim 7, characterized in that the second pressure chambers (20) of both squeeze cylinders (16) are connected to a pressure accumulator (45).

9. 9. The tamping unit (4) according to claim 6, wherein the intermediate chambers (41) of both pressure intensifiers (27) are connected to one another via a compensation accumulator (43) or via a pressure-applied filling line.

10. 2. The tamping unit (4) according to claim 1, characterized in that the flow openings (35, 37) between the squeeze cylinder (16) and the pressure intensifier (27) are larger than the connection openings (21, 22) of the squeeze cylinder (16) to the first hydraulic circuit (23).

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