AT527175A1 - control of a tamping unit - Google Patents

Abstract

The invention relates to a tamping unit (1) for tamping sleepers (2) of a track (3), with a height-adjustable tool carrier (5) mounted on a unit frame (4), on which tamping tools (6) are mounted that can be pivoted relative to one another, wherein each tamping tool (6) is coupled to a hydraulic auxiliary cylinder (7) and each auxiliary cylinder (7) comprises a piston-side and a rod-side pressure chamber, wherein the piston-side pressure chamber and the rod-side pressure chamber of the respective auxiliary cylinder (7) are controlled by means of a control device (15) via separate control valves (11a, b, c, d; 12a, b). The invention further relates to a method for controlling the auxiliary cylinders of this tamping unit by means of a control device (15), preferably a program-controlled control device.

Description

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control of a tamping unit

The invention relates to a tamping unit for tamping sleepers of a track, with a height-adjustable tool carrier mounted on a unit frame, on which tamping tools are mounted that can be pivoted relative to one another, each tamping tool being coupled to a hydraulic auxiliary cylinder and each auxiliary cylinder comprising a piston-side and a rod-side pressure chamber. The invention further relates to a method for controlling the auxiliary cylinders of this tamping unit by means of a control device, preferably a

program-controlled control device.

Maintaining the correct track positions within a certain tolerance range is a crucial factor for the safe operation of the tracks in a rail network. In order to build tracks with specified track positions or to correct faulty track positions, these are driven over by a maintenance machine. This maintenance machine usually comprises a main frame that moves continuously during operation and a machine frame on which, among other things, a tamping unit is arranged. A control device arranged on the maintenance machine controls

and monitors the tamping unit.

The machine frame can be movable relative to the main frame in order to prevent the units arranged therein from moving relative to the track grid during the processing of the ballast bed and to move them between the processing intervals by at least one sleeper distance in the processing direction.

to move forward.

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The track grid, which is made up of rails and sleepers connected to them, is first moved from the current track position determined beforehand by measurement to the correct track position specified by a lifting and straightening unit connected to the unit frame of the maintenance machine. The tamping picks of the tamping tools, which are mounted on a height-adjustable tool holder and can pivot against each other, then plunge into the ballast bed, with this tool holder in turn being mounted on a unit frame.

of the tamping unit.

By means of a partial closing movement of the tamping tools arranged in pairs, referred to as setting, which is superimposed with a vibration movement with a frequency between 15Hz and 55 Hz, preferably between 30Hz and 40Hz, the ballast below the pre-positioned sleepers is compacted and thus the corrected track position is achieved, if necessary with the aid of

further work steps, fixed.

A common method according to the state of the art for this process, also known as tamping, to maintain a corrected track position is asynchronous constant pressure tamping, which is characterized by a constant tamping force between 2kN and 20kN, preferably between 7kN and 15kN. According to the state of the art, this tamping force is applied by means of auxiliary cylinders as shown in AT 516 547 A4. The piston rods of the auxiliary cylinders exert an auxiliary force on the swivel arms of the tamping tools, which is converted into the

the darning force acting on the darning pick is implemented.

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According to the current state of the art, the oscillating movement superimposed on the adjustment movement is mainly generated mechanically using eccentric shafts. However, solutions are also known that generate such oscillating movements using existing or additional components of the hydraulic circuit.

The piston of the auxiliary cylinder defines a piston-side and a rod-side pressure chamber, the

Volume changes when the piston moves.

Once the tamping tools moved by the positioning have reached their end position, it is necessary to hold this end position for a specified period of time, apart from an oscillating movement that leads to vibration of the tamping picks of the tamping tools in the ballast bed. In this operating case, which is also referred to as clamping the piston, the pressure in both pressure chambers in the positioning cylinder must be kept the same, regardless of whether the positioning force is generated via the piston surface or via the ring surface due to the installation position of the positioning cylinder. The piston can also be clamped before the positioning movement and after tamping, i.e. during the lowering, lifting and further movement of the tool carrier.

take place.

Due to the operating modes of the positioning and clamping of the tamping tools and the possibility of different installation positions of the positioning cylinder, it is necessary to switch the pressure in the pressure chambers and in particular on the counterpressure side between different pressure levels. To avoid cavitation or instabilities in the hydraulic circuit of the positioning cylinder, throttles are arranged in the hydraulic connections of the positioning cylinder according to the state of the art.

which causes excessive acceleration of the piston

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However, this arrangement reduces the overall efficiency of the system. In certain operating cases, a larger number of

adjustable valves required.

The invention is based on the object of providing an improvement over the prior art for a tamping unit of the type mentioned above.

A further object of the invention is to provide a method for controlling the auxiliary cylinders of this tamping unit by means of

a control device.

According to the invention, this object is achieved by the characterizing part of the tamping unit described in claim 1 and the method for controlling the auxiliary cylinders of this tamping unit by means of a control device according to claim 7. Dependent claims give advantageous

embodiments of the invention.

In order to reduce losses and to increase the efficiency of the hydraulic subsystem for controlling the auxiliary cylinders, a tamping unit for tamping sleepers of a track is provided according to the invention, with a height-adjustable tool carrier mounted on an aggregate frame, on which tamping tools that can be pivoted relative to one another are mounted, wherein each tamping tool is coupled to a hydraulic auxiliary cylinder and each auxiliary cylinder comprises a piston-side and a rod-side pressure chamber and the piston-side pressure chamber and the rod-side pressure chamber of the respective auxiliary cylinder are controlled by means of a control device via

controlled by separate control valves.

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This separate control avoids coupling of the control edges of the directional control valves that are usually used to control the pressure chambers of the auxiliary cylinder. The control valves can be designed as seat valves or as slide valves according to principles known from the state of the art. It is advantageous that proportional valves have a positive overlap between

slide and ring grooves of the valve housing.

Advantageously, each pressure chamber is controlled by two control valves, each of which has two connections and is characterized by the two valve end positions, open and closed. Depending on the control and the valve design, intermediate positions can also be realized in addition to these two end positions. A common term for this

Valve type is 2/2 way valve.

An advantageous further development controls each pressure chamber with a control valve known as a 3/3 way valve, which has three connections and is characterized by the valve rest position being closed and the two active valve end positions being open-supplying and open-draining. Open-supplying in this context means that a connection is established between the pressure line and the pressure chamber for the hydraulic medium. In contrast, open-draining means that a connection is established between the pressure chamber and the tank line for the hydraulic medium. The hydraulic medium is

Preferably a hydraulic oil. An improvement would be to have a

Pressure measuring device, preferably a pressure sensor,

which converts the pressure into a signal that the

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Control device provided by this

recognized and processed.

In a preferred development of the tamping unit, a position measuring device is arranged in the vicinity of each piston of the hydraulic auxiliary cylinder. This can either directly detect the position of the piston in the cylinder or measure the position of the swivel arm, for example its deflection angle, in relation to a rest position and thus indirectly determine the current piston position. The position measuring device is preferably an angle sensor. The output signal generated by the position measuring device is made available to the control device, recognized by it and processed by it. The output signals of the measuring devices are advantageously made available to the control device continuously. In an advantageous development, the output signal of the control device is made available at selectable time intervals. In a preferred development, the control device is

a program-controlled control device.

It is advantageous if control methods according to the state of the art are used in this control device. A further improvement provides that control methods for the application of

come.

In the method according to the invention, at least two states of the control valves are switched by means of the control signals of a control device. This control device is preferably a

program-controlled control device.

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In an advantageous further development, measuring devices are arranged on or in the vicinity of the auxiliary cylinders. Temperature measuring devices, preferably temperature sensors, are advantageously arranged in the vicinity of the

pressure chambers arranged.

A preferred development is a method for controlling the auxiliary cylinders of a tamping unit by means of a control device which generates signals for the control valves and outputs them to them based on predetermined target values for the pressures in the pressure chambers and the positions of the pistons of the auxiliary cylinders and the actual values provided by the pressure measuring devices and position measuring device, so that the difference between the predetermined target values and the actual values recorded by the measuring devices becomes smaller and smaller over time. The signal output by the control device is advantageously made available to the control valves continuously. In an advantageous development, the signal output by the control device is sent to the control valves in

selectable time intervals.

A further improvement provides that the setpoint values for the pressures, within the scope of the degrees of freedom determined by the geometry of the auxiliary cylinders and other design conditions, are independent of the setpoint values for

the positions of the cylinder pistons are specified.

A further development provides a method for controlling the auxiliary cylinders of a tamping unit by means of a control device, which, based on predetermined setpoint curves for the pressures in the pressure chambers and the

Position of the piston of the auxiliary cylinders and the

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Pressure measuring devices and position measuring device provided actual values of these pressures and positions, generates signals for the control valves and outputs them to them, so that the absolute value of the difference between the ]Respective current setpoint of the specified setpoint curve and the associated respective actual value recorded by the measuring device arranged for this purpose

remains within a specified range.

In a preferred development of the method, the setpoint curves for the pressures are determined within the scope of the degrees of freedom determined by the geometry of the auxiliary cylinders and other design conditions, independently of the setpoint curves for the positions of the cylinder pistons

specified.

In a further development, a hydraulic medium flows through the pressure chambers of the auxiliary cylinders without the cylinder being moved. Such an operating mode can advantageously be used to change the temperature of the hydraulic medium, for example to increase or decrease it compared to a measured temperature value.

reduce.

The invention is explained below by way of example with reference to the accompanying figures.

in schematic representation:

Fig. 1 An embodiment of the tamping unit with hydraulic auxiliary cylinders; Fig. 2 A maintenance machine on a track with a

tamping unit and a lifting and straightening unit;

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Fig. 3 A control variant of a hydraulic auxiliary cylinder with two 2/2 directional valves per pressure chamber;

Fig. 4 An alternative control variant of a hydraulic auxiliary cylinder with a 3/3

Directional valve per pressure chamber.

Fig. 1 shows a simplified version of a tamping unit 1 in a conventional embodiment. A tool carrier 5 is mounted in a height-adjustable manner in a unit frame 4. In order to enable a tamping pick, which is clamped in a swivel arm of the tamping tool 6, to be inserted into the ballast bed 8 on which the track grid 3 formed from rail and sleeper 2 rests, the tool carrier 5 can be connected to a linear drive along guide rods which are connected to the unit frame 4.

are moved in the vertical direction.

To carry out the positioning movement of the tamping picks arranged in pairs in the ballast bed, each swivel arm of the tamping tool 6 is coupled on the rod side with a hydraulic positioning cylinder 7. The respective hydraulic positioning cylinder 7 is connected with its

Housing connected to the tool carrier 5.

The vibrations for the vibration movement of the tamping tools 6 are generated in the embodiment shown with an eccentric shaft which is mounted in the tool carrier 5

is stored.

A maintenance machine 9 is shown in a simplified manner in Fig. 2 on a track 3. The details of the sleepers 2 of the track and the ballast bed 8 of the superstructure of the

Rail track is omitted.

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A machine frame which is used cyclically during maintenance operation is arranged within a main frame which is not specified in more detail and which, in the case of maintenance operation or transfer journeys, generally moves continuously in one direction. On the one hand, this machine frame carries a lifting and straightening unit 10 and, on the other hand, the tamping unit 1 which, in a different embodiment to that in Fig. 1, is used for the simultaneous

suitable for tamping two or more sleepers 2.

Fig. 3 shows an embodiment of the control of an auxiliary cylinder 7 of a tamping unit 1 according to the invention. In a simplified sectional view of the auxiliary cylinder 7, the piston with the piston rod, the annular surface on the side on which the piston and rod are connected to each other, and the piston surface on the

opposite side of the piston.

The piston-side pressure chamber is therefore defined by a side surface of the auxiliary cylinder, the piston surface and that part of the cylinder jacket that lies between these two surfaces. The rod-side pressure chamber, on the other hand, is defined by the ring surface, the other side surface of the auxiliary cylinder and the part of the cylinder jacket that lies between the

between these two surfaces.

In the embodiment shown, both the piston-side and the rod-side pressure chamber of the auxiliary cylinder are connected to two control valves 1la and 1l1c or 11b and 11d. One of the two control valves 1la or 11b connects the respective pressure chamber to the pressure line P of the hydraulic circuit.

whereas the other control valve 11c or 11d

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The respective pressure chamber is connected to a connection T, which

to the tank or reservoir of the hydraulic medium.

In this embodiment, the respective control valve 1la, 11b, 11c or 11d is a 2/2-way valve with two connections and two valve end positions, between which valve positions can be continuously adjusted based on the control signal. In the illustrated energy-free rest state of the control valves 1l1la, 11b, 11c and 11d, in which they are held by a return spring, the connection between the two valve connections is interrupted and thus no hydraulic medium can be passed through one of the control valves 1lla, 11b, 11c or 11d.

become.

If one of the control valves 1la, 11b, 11c or 11d is activated with the electrical control element against the return spring force, the connection between both valve connections is opened proportionally to the respective control signal and the hydraulic medium can be pumped through the valve connections depending on the pressure levels.

one of the control valves 1la, 11b, 11c or 11d.

The respective pressure chamber can be connected to the pressure line P £ in a fluid-conducting manner by activating the control valve connected to the pressure line, i.e. 11a for the piston-side pressure chamber and 11b for the rod-side pressure chamber. Conversely, the respective pressure chamber can be connected to the tank or reservoir of the hydraulic medium by activating the control valve 11c for the piston-side pressure chamber or 11d for the rod-side pressure chamber. This usually leads to the outflow of the

hydraulic medium from the respective cylinder chamber.

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The pressure measuring devices 13a and 13b are connected in a fluid-conducting manner to the piston-side pressure chamber and the rod-side pressure chamber, respectively, which measure the pressure of the respective pressure chamber and convert it into an electrical signal that can be recognized by the control device 15.

convert.

A position measuring device 14 is arranged in the vicinity of the auxiliary cylinder 7, which provides a position signal that can be read and processed by the control device 15 and from which, with known geometric conditions, the position of the piston in the

Additional cylinder 7 can be closed.

Fig. 4 shows a further embodiment of the control of an auxiliary cylinder 7 according to the invention with the control valves 12a and 12b, whose switching states can be changed by the control device 15. Arrangement of piston and piston rod, as well as determination of piston-side pressure chamber and rod-side pressure chamber

correspond to the embodiment of Fig. 3.

The pressure measuring devices 13a and 13b for measuring the pressures of the piston-side and rod-side pressure chamber and position measuring device 14 for determining the position of the piston in the auxiliary cylinder 7 and the generation of the output signals of these measuring devices, which can be recognized and processed by the control device, work in the same way as in the embodiment variant

of Fig. 3.

However, the design of the

Control circuit in Fig. 4 from that in Fig. 3 thereby,

that the piston-side pressure chamber has a control valve 12a

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and a control valve 12b is assigned to the rod-side pressure chamber.

Both control valves 12a and 12b are characterized by three connections. One of these is connected to the pressure line P, another to the respective pressure chamber of the auxiliary cylinder 7 and the third to the tank or.

reservoir of the hydraulic medium.

In the passive middle position, the valve rest position, of the control valve 12a or 12b, in which the valve slide is held by means of two return springs, whereby one spring is arranged on each side of the valve slide and acts on it with its spring force, there is no connection between the pressure supply connection or tank discharge connection and the pressure chamber connection. In the valve rest position of the control valve 12a or 12b, the hydraulic medium therefore remains in the respective pressure chamber without its quantity being reduced, with the exception of possible losses due to leaks in the

auxiliary cylinder 7 or the supply lines increases or decreases.

If a signal from the control device 15 activates one of the control valves 12a or 12b with the control element on one side against the spring force of the return spring on the opposite side, the control valve 12a or 12b is moved from its closed passive middle position into a

Control signal proportional position.

The switching state of the valve slide on the left side of the middle position connects the pressure line connection P with the respective pressure chamber connection, which may allow the flow of the

hydraulic medium towards the lower pressure level

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is enabled. The connection to the tank remains interrupted.

The position of the valve slide on the right side of the middle position, however, connects the respective pressure chamber with the tank or reservoir of the hydraulic medium, whereby a flow of the hydraulic medium may again occur in the direction of the lower pressure level. In this case, the connection remains

to pressure line P is interrupted.

The subject matter of the invention is not limited to the two embodiments shown as examples. Other variants are possible, such as other types and shapes of control valves as well as the arrangement of other measuring devices for measured variables such as the temperature of

subject matter of the invention.

Other operating modes of the tamping unit are also possible in addition to lowering, positioning, clamping, vibrating and lifting, as well as their combinations with other embodiments of the subject matter of the invention. An example of this is the recuperation of energy in a hydraulic pump-motor unit, which generates the pressure in the hydraulic medium and maintains it in the hydraulic circuit, by utilizing the effect of the gravitational field or other force effects on machine parts.

such as frames, units and their components.

Claims (10)

15 20 25 30 23004 15 patent claims 1. Tamping unit (1) for tamping sleepers (2) of a track (3), with a height-adjustable tool carrier (5) mounted on an aggregate frame (4), on which tamping tools (6) are mounted that can be pivoted relative to one another, wherein each tamping tool is coupled to a hydraulic auxiliary cylinder (7) and each auxiliary cylinder (7) comprises a piston-side and a rod-side pressure chamber, characterized in that the piston-side pressure chamber and the rod-side pressure chamber of the respective auxiliary cylinder (7) are controlled by means of a control device (15) via separate Control valves (1la-d;12a,b) are controlled. 2. Tamping unit according to claim 1, characterized in that each pressure chamber is connected to two control valves (1la,c or 11b,d), each having two connections and through which two End positions open and closed are characterized. 3. Tamping unit according to claim 1, characterized in that each pressure chamber is connected to a control valve (12a or 12b) which has three connections and is characterized by a valve rest position and two active valve end positions. 4. Tamping unit according to one of claims 1 to 3, characterized in that for each pressure chamber a pressure measuring device (13a or 13b), preferably a pressure sensor, is arranged between the at least one control valve and the pressure chamber in order to convert the pressure into a signal that is continuous or in selectable 15 20 25 30 23004 16 Time intervals of the control device (15), preferably a program-controlled control device, for made available, recognized and processed by the latter. 5. Tamping unit according to claim 5, characterized in that a position measuring device (14), preferably an angle sensor, is arranged in the vicinity of each piston of the hydraulic auxiliary cylinder (7) in order to convert the position of the piston in the respective auxiliary cylinder into a signal which is made available continuously or at selectable time intervals to the control device (15), preferably the program-controlled control device. is provided, recognized and processed by the provider. 6. Method for controlling the auxiliary cylinders (7) of a tamping unit (1) according to one of claims 1 to 5, characterized in that at least two states of the control valves are switched by means of control signals of a control device (15), preferably a program-controlled control device. become. 7. Method according to claim 6, characterized in that based on predetermined target values for the pressures in the pressure chambers and the positions of the pistons of the auxiliary cylinders (7) and the actual values of these pressures and positions provided by the pressure measuring devices (13a,b) and position measuring device (14), signals for the control valves (1la-d;12a,b) are generated and transmitted to them continuously or at selectable time intervals. so that the difference between the given 15 20 25 23004 17 setpoints and the values measured via the measuring devices (13a,b,14) recorded actual values becomes smaller over time. 8. Method according to claim 7, characterized in that the setpoint values for the pressures are independent of the setpoint values for the positions of the cylinder pistons. 9. Method according to claim 6, characterized in that, based on predetermined setpoint curves for the pressures in the pressure chambers and the position of the piston of the auxiliary cylinder (7) and the actual values of these pressures and positions provided by the pressure measuring devices (13a,b) and position measuring device (14), signals are generated for the control valves (1la-d,1l12a,b) and output to them continuously or at selectable time intervals, so that the absolute value of the difference between the respective instantaneous setpoint of the predetermined setpoint curve and the associated respective values recorded by the measuring device (13a,b,l14) arranged for this purpose. Actual value remains within a specified range. 10. Method according to claim 9, characterized in that the setpoint curves for the pressures are independent of the setpoint curves for the positions of the cylinder pistons be specified.