Tamping assembly for tamping a track

Abstract

The invention relates to a tamping assembly (4) for tamping a track (3), comprising tamping tools (12) which are arranged in pairs and can be fed towards one another by means of a relevant feed cylinder (16), wherein: a feed piston (17) to which a hydraulic pressure from a first hydraulic circuit (23) can be applied is located in the relevant feed cylinder (16); and a vibration piston (30) is associated with each feed cylinder (16) in order to superimpose a vibration on a feed movement (24); and the vibration piston (30) is located in a pressure amplifier (27) having a primary cylinder (28) and a secondary cylinder (29). In this way, the vibration generation can be carried out at a lower pressure level.

Description

Technical field

[0001] The invention relates to a tamping unit for tamping a track, with tamping tools arranged in pairs which can be adjusted to each other by means of a respective adjusting cylinder, wherein an adjusting piston which can be acted upon by a hydraulic pressure of a first hydraulic circuit is arranged in the respective adjusting cylinder, and wherein a vibrating piston is assigned to each adjusting cylinder in order to superimpose a vibration on an adjusting movement. State of the art

[0002] From EP 1 653 003 A1, a tamping unit is known in which tamping picks are moved in pairs towards each other to tamp a track. This positioning movement for ballast compaction is carried out with the aid of a hydraulically actuated positioning cylinder. A hydraulic vibration is superimposed on the linear positioning movement to achieve easier penetration into the ballast and improved compaction.

[0003] An improved hydraulic vibration generation system is disclosed in AT 517843 A4. In this system, each auxiliary cylinder is equipped with an auxiliary piston in addition to an auxiliary piston, enabling the superimposition of an auxiliary movement with an adjustable vibration. This allows for the optimization of the parameters required for vibration generation, independent of the auxiliary movement. Description of the invention

[0004] The invention is based on the objective of improving a stuffing unit of the type mentioned above in such a way that hydraulic vibration with high energy efficiency is enabled.

[0005] According to the invention, this problem is solved by the features of independent claim 1. Dependent claims specify advantageous embodiments of the invention.

[0006] The vibrating piston is located within a pressure intensifier (also known as a pressure converter or pressure amplifier) ​​comprising a primary and a secondary cylinder. This design allows for vibration generation at a lower pressure level. High pressures prevail only in the secondary cylinder of the pressure intensifier. Lower pressures are present in the primary cylinder, where the vibration is generated, resulting in minimal energy loss during switching operations. Positioning the vibration-generating piston within a pressure intensifier separate from the secondary cylinder improves controllability. For example, the vibration is activated only during the penetrating of the tamping tools into the ballast and during the subsequent tamping process.

[0007] In a further development of the invention, the pressure booster is connected to a second hydraulic circuit via a control valve. For example, a hydraulic circuit already present in a tamping machine with a lower pressure level than the first hydraulic circuit is used. This simplifies the design and maintenance of the entire hydraulic system.

[0008] Advantageously, the control valve is connected to a control unit configured to actuate the control valve with variable vibration parameters. With this modified control system, each phase of a tamping cycle can be linked to its own vibration parameters. For example, a vibration frequency of 40-50 Hz is set during the penetration phase of the tamping tools into the ballast. During the positioning phase, the frequency is reduced to 35 Hz, and the vibration stops when the tamping tools are raised. In addition to increased energy efficiency, this measure also results in lower noise emissions during operation. Furthermore, the vibration amplitudes can be adapted to the specific properties of the ballast bed being tamped. Specifying different vibration amplitudes for the penetration and positioning phases can also be beneficial.

[0009] In an improved version, the control valve is designed as a proportional or servo valve, incorporating a displacement sensor to detect piston travel and / or piston position. Specifically, this measures the position of the vibrating piston within the secondary or primary cylinder of the pressure booster. The control valve is actuated via a closed-loop control system to regulate the vibration frequency and / or amplitude. Control based on the current position of the associated actuator piston can also be advantageous. This allows, for example, the setting of a vibration frequency dependent on the actuator travel, which is measured by another displacement sensor or an angle sensor mounted on a pivot arm. When using two hydraulic circuits, the vibration amplitude and frequency can be controlled with exceptional precision and efficiency.

[0010] Further advantages arise when the pressure intensifier, particularly its secondary cylinder, is located directly on the associated auxiliary cylinder. This minimizes the amount of hydraulic oil moved during a vibration cycle, resulting in correspondingly low heat losses in the hydraulic circuit. Furthermore, the absence of flexible connecting hoses in the high-pressure section ensures that the vibration parameters remain stable during an auxiliary operation.

[0011] In an advantageous embodiment, each auxiliary cylinder is assigned a first and a second pressure intensifier, wherein a first pressure chamber of the respective auxiliary cylinder is connected to a pressure chamber of the assigned first pressure intensifier, and wherein a second pressure chamber of the respective auxiliary cylinder is connected to a pressure chamber of the assigned second pressure intensifier. In this way, each auxiliary cylinder has its own vibration circuit. Thus, each tamping tool can be subjected to its own vibration. This is useful, for example, in switch tamping units with pivoting tampers, so that the pivoted tamping tines are not set into vibration.

[0012] In another advantageous embodiment, two pressure intensifiers are assigned to the two auxiliary cylinders of a tamping tool pair, wherein one pressure intensifier is connected to a first pressure chamber of one auxiliary cylinder and the other pressure intensifier is connected to a first pressure chamber of the other auxiliary cylinder. This simplifies the design of the vibration-generating hydraulic system.

[0013] In this variant, the second pressure chambers of the two auxiliary cylinders are sensibly connected to a pressure accumulator. During a vibration cycle, energy is temporarily stored in this pressure accumulator, resulting in high energy efficiency for the overall system.

[0014] In both variants, the intermediate chambers of the two pressure intensifiers are advantageously connected to a compensating reservoir or a pressurized filling line. A corresponding pre-charge pressure in the intermediate chambers ensures trouble-free operation of the pressure intensifiers.

[0015] Further energy efficiency is achieved by making the passage openings between the auxiliary cylinders and the pressure boosters larger than the connection openings of the auxiliary cylinders to the primary hydraulic circuit. This prevents any feedback to the primary hydraulic circuit during active vibration. To generate vibration, hydraulic oil is simply pumped back and forth between the pressure boosters and the associated pressure chambers of the auxiliary cylinders. Brief description of the drawings

[0016] The invention is explained below by way of example with reference to the accompanying figures. These show, in schematic representation: Fig. 1 Tamping machine on a track Fig. 2 Tamping unit Fig. 3 Variant with two pressure boosters on an auxiliary cylinder Fig. 4 Variant with two pressure boosters on a pair of auxiliary cylinders Description of the embodiments

[0017] The in Fig. 1 The tamping machine 1 shown is movable on rail carriages 2 along a track 3 to be tamped and comprises a tamping unit 4, a lifting / aligning unit 5, a measuring system 6, and a control unit 7. The track 3 is a ballasted track in which a track grid formed from sleepers 8 and rails 9 is supported in a ballast bed 10. During a tamping operation, the lifting / aligning unit 5 raises the track grid into a target position and, if necessary, shifts it laterally. The measuring system 6 compares the current position of the track grid with the target position.

[0018] The target position is fixed by the tamping unit 4, with vibrating tamping picks 11, penetrating the ballast bed 10 between the sleepers 8 and compacting the ballast under the sleepers 8 with an additional action. A tamping tool 12 typically comprises two tamping picks 11 mounted side by side in pick holders of a pivoting lever 13. The pivoting arms 13 of opposing tamping tools 12 are mounted in a pincer-like manner on a common tool carrier 14. The tool carrier 14 is height-adjustable and guided in a frame 15. The upper ends of the tamping tools 12 are articulated to the tool carrier 14 via respective auxiliary cylinders 16.

[0019] Each auxiliary cylinder 16 is designed as a hydraulic cylinder in which an auxiliary piston 17 is coupled to the associated tamping tool 12 via a piston rod 18. A first pressure chamber (piston chamber) 19 and a second pressure chamber (annular chamber) 20 can be pressurized with a hydraulic pressure from a first hydraulic circuit 23 via a first connection opening 21 and a second connection opening 22, respectively. The hydraulic pressure in the first pressure chamber 19 is increased by means of switching valves (not shown) to cause an auxiliary movement 24 of the tamping picks 11. Thus, during an auxiliary operation, the auxiliary pressure provided in the first hydraulic circuit 23 is present in the respective first pressure chamber 19.

[0020] A pressure difference between the first and second pressure chambers 19, 20 and the ratio of a piston area 25 adjacent to the first pressure chamber 19 to an annular area 26 adjacent to the second pressure chamber 20 determines a desired assisting force. To reset the tamping tools 12, the second pressure chamber 20 is pressurized relative to the first pressure chamber 19 with an opening pressure, taking into account the area ratio. During the penetration of the tamping tools 12 into the ballast bed 10, the two pressure chambers 19 are closed to the first hydraulic circuit 23. This is achieved via switching valves (not shown) which are connected to the two connection openings 21, 22 via lines.

[0021] According to the invention, each auxiliary cylinder 16 is assigned at least one pressure intensifier 27. In the variant according to Fig. 2 and Fig. 3 Each auxiliary cylinder 16 is assigned two pressure intensifiers 27. Each pressure intensifier 27 comprises a primary cylinder 28 and a secondary cylinder 29. A vibrating piston 30 is arranged in each pressure intensifier 27. For the purposes of this explanation, the piston (secondary piston) in the secondary cylinder 28 is defined as the vibrating piston 30. However, due to the rigid coupling by means of a connecting rod 31, the piston (primary piston) 32 in the primary cylinder 28 can also be considered a vibrating piston.

[0022] The larger diameter of the primary piston 32, relative to the diameter of the secondary piston 30, determines the pressure intensifier 27. In this case, the pressure intensifier 27 intensifies a low system pressure from a second hydraulic circuit 33 to the hydraulic pressure prevailing in the first and second pressure chambers 19 and 20, respectively. The second hydraulic circuit 33 can be supplied from the first hydraulic circuit 23 via appropriate pressure reducers. Preferably, an existing hydraulic circuit with a correspondingly low pressure level is used.

[0023] When dimensioning the pressure amplifiers 27, the ratio between the large piston area 25 and the annular area 26 of the associated auxiliary piston 17 must be taken into account. In particular, the diameters of the secondary pistons 30 are determined by the volume changes occurring in the pressure chambers 19, 20 of the associated auxiliary cylinder 16 during active vibration. The primary pistons 32 of the pressure amplifiers 27 must be dimensioned such that the same pressure is always established in adjacent primary pressure chambers 34, namely the system pressure of the second hydraulic circuit 33. In this way, the same force acts on each primary piston 32 when pressurized. The length of the respective primary and secondary cylinders 28, 29 results from the maximum piston stroke required to generate the desired vibration.

[0024] The first pressure chamber 19 of the associated auxiliary cylinder 16 is connected to a secondary pressure chamber 36 of the first pressure intensifier 27 via a first through-hole 35. The second pressure chamber 20 of the associated auxiliary cylinder 16 is connected to the secondary pressure chamber 36 of the second pressure intensifier 27 via a second through-hole 37. The primary pressure chambers 34 are connected to the second hydraulic circuit 33 via a switching valve 38.

[0025] In the simplest case, the switching valve 38 is a 4 / 2-way valve that alternately switches the two pressure boosters 27 to the system pressure of the second hydraulic circuit 33. For this purpose, the switching valve 38 is controlled by the control unit 7, with a square wave signal 39 determining the switching points. In this way, the actuating piston 17 in the actuating cylinder 16 is subjected to a vibration, resulting in a vibrating movement 40 of the plugging picks 11. The frequency and amplitude of the vibration can be adjusted via the system pressure of the second hydraulic circuit 33 and the square wave signal 39.

[0026] The through-holes 35, 37 between the secondary cylinders 29 of the pressure boosters 27 and the pressure chambers 19, 20 of the associated auxiliary cylinder 17 are significantly larger than the connection openings 21, 22 to the first hydraulic pressure circuit 23. During a penetration process, oil flow and outflow through the connection openings 21, 22 are blocked by means of switching valves (not shown). Due to the appropriate dimensions of the pressure boosters, the hydraulic oil is pushed back and forth between the respective pressure chamber 19, 20 of the auxiliary cylinder 16 and the associated secondary pressure chamber 35 of the respective pressure booster 27. As a result, the auxiliary piston 17 vibrates in the auxiliary cylinder 16. This vibration is transmitted to the associated tamping tool 12 via the piston rod 18.

[0027] During an adjustment process, the vibration is maintained because the secondary pressure chambers 36 fill through the large through-holes 35, 37 between the adjustment cylinder 16 and the pressure intensifiers 27 before the built-in pressure relief valves have a sufficient reaction time. Direct mounting of the pressure intensifiers 27 to the associated adjustment cylinder 16 also ensures the maintenance of the vibration by avoiding damping effects.

[0028] At the start of a work operation, the first pressure chamber (piston chamber) 19 is filled and then sealed. The hydraulic pressure in the sealed first chamber 19, combined with a counter-pressure on the smaller annular surface 26, fills the pressure boosters 27. The switching valve 38 can then begin operating at any time.

[0029] The intermediate chambers 41 of the two pressure intensifiers 27 are connected to each other via a compensating line 42. A compensating reservoir 43 is connected to the compensating line 42 so that the intermediate chambers 41 are pressurized with a pre-charge pressure (e.g., 5 bar). When vibration is activated, the slight volume fluctuations of the intermediate chambers 41 are compensated for by this arrangement. Alternatively, a filling line with the same pre-charge pressure level can be used.

[0030] In a further development of the invention, the switching valve 38 is designed as a servo valve or proportional valve. A displacement sensor 44 detects at least one piston movement within a cylinder 16, 28, 29. This can be done by direct measurement within the respective cylinder 16, 28, 29 or indirectly via the position of the tamping tools 12. A measurement signal corresponding to the piston movement is supplied to the control unit 7. Subsequently, the vibration is controlled by the control unit 7 as a function of the measurement signal. In this way, a control loop is created for a desired vibration amplitude.

[0031] A simplified structure is in Fig. 4 As shown, each auxiliary cylinder 16 of opposing tamping tools 12 is assigned only one pressure intensifier 27. Specifically, each first pressure chamber (piston chamber) 19 is connected to the secondary pressure chamber 36 of the assigned pressure intensifier 27. The primary pressure chambers 34 are pressurized with the system pressure of the second pressure circuit 33 as shown in the example. Fig. 3 A compensating line 42 with compensating reservoir 43 or a filling line is also present. In addition, there is a pressure accumulator (hydraulic battery) 45, which is connected to a connecting line 46 of the second pressure chambers (ring chambers) 20.

[0032] During a penetration process, the pressure in this connecting line 46 and in the second pressure chambers 20 is isolated from the rest of the hydraulic circuit by means of valves (not shown). The pressure peaks generated during active vibration are temporarily stored by means of the pressure accumulator 45. Hydraulic oil is stored in the pressure accumulator 45 on the rising edge of the square wave signal 39 and released again on the falling edge.

[0033] At the start of an adjustment process, the lock on the connecting line 46 and the second pressure chambers 20 is released, and hydraulic oil can flow back into the first hydraulic circuit 23. The vibration is maintained, with hydraulic oil continuing to be stored in the pressure accumulator 45 with each rising edge of the square wave signal 39 and released again on the falling edge. In this way, heating of the hydraulic oil as a result of the applied vibration is prevented.

Claims

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

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

3. A tamping unit (4) according to claim 2, characterized in that the control valve (38) is connected to a control device (7) that is set up to actuate the control valve (38) with variable vibration parameters.

4. A tamping unit (4) according to claim 2 or 3, characterized in that the control valve (38) is designed as a proportional or servo valve, and that a distance sensor (44) is arranged to detect a piston travel and / or a piston position.

5. A tamping unit (4) according to one of the claims 1 to 4, characterized in that the pressure amplifier (27), in particular the secondary cylinder (29) of the pressure amplifier (27), is arranged directly on the assigned squeezing cylinder (16).

6. A tamping unit (4) according to one of the claims 1 to 5, characterized in that each squeezing cylinder (16) is assigned a first and a second pressure amplifier (27), that a first pressure chamber (19) of the respective squeezing cylinder (16) is connected with a pressure chamber (36) of the assigned first pressure amplifier (27), and that a second pressure chamber (20) of the respective squeezing cylinder (16) is connected with a pressure chamber (36) of the assigned second pressure amplifier (27).

7. A tamping unit (4) according to one of the claims 1 to 5, characterized in that the two squeezing cylinders (16) of a tamping tool pair are assigned two pressure amplifiers (27), that the one pressure amplifier (27) is connected with a first pressure chamber (19) of the one squeezing cylinder (16), and that the other pressure amplifier (27) is connected with a first pressure chamber (19) of the other squeezing cylinder (16).

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

9. A tamping unit (4) according to one of the claims 6 to 8, characterized in that intermediate chambers (41) of both pressure amplifiers (27) are connected via a compensating accumulator (43) or via a filling line applied with pressure.

10. A tamping unit (4) according to one of the claims 1 to 9, characterized in that outlet openings (35, 37) between the squeezing cylinders (16) and the pressure amplifiers (27) are larger than connection openings (21, 22) of the squeezing cylinders (16) to the first hydraulic circuit (23).

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