Tamping Unit and Method for Tamping Sleepers of a Track

The invention relates to a tamping unit segment for tamping sleepers of a track, with tamping tools mounted on a height-adjustable tool carrier opposite one another with respect to a vertical centre plane, which are each connected to a squeeze drive for generating a squeezing movement. Additionally, the invention relates to a tamping unit which comprises the corresponding tamping unit segment and a method for operating the tamping unit segment.

A generic tamping unit segment and a tamping unit with several corresponding tamping unit segments are known from AT 522456 A4. To achieve a narrow design, two hydraulic cylinders are arranged one above the other as squeeze drives. The respective hydraulic cylinder is aligned approximately horizontally and presses an upper lever arm of the assigned tamping tool outwards during a squeezing process. The lower lever arms of the tamping tools with the tamping tines attached thereto are squeezed towards each other. An oscillatory movement is superimposed on the squeezing movement by means of a correspondingly set-up hydraulic control system. A pulsating pressure is applied to one chamber of the hydraulic cylinder. Alternatively, the squeeze drives for vibration application are connected to an eccentric drive.

A tamping unit with tamping unit segments for tamping a plurality of sleepers is also disclosed in AT 520267 A1, with squeezing cylinders arranged in an interlocked manner being connected to a vibration drive via bracket-like transmission elements. The resulting narrow design (e.g. maximal 550 mm extension in the longitudinal direction of the track) allows a plurality of tamping unit segments to be linked together to form an inline tamping unit that can be used to tamp a plurality of adjacent sleepers simultaneously. Compared to conventional tamping units, the interlocked arrangement of the squeezing cylinders requires further design adjustments to prevent unfavourable load conditions.

The object of the invention is to improve a tamping unit segment of the kind mentioned above in such a way that a narrow design is made possible and unfavourable load conditions are prevented. A further object of the invention is to indicate a method for operating the corresponding tamping unit segment.

According to the invention, these objects are achieved by the features of independent claimsand. Dependent claims indicate advantageous embodiments of the invention.

A lever arm with a connecting part projecting over the centre plane is arranged on each tamping tool, with the connecting part of the respective lever arm being connected to the assigned squeeze drive. The centre plane divides the tamping unit segment into two halves, with the respective tamping tool and the squeeze drive of the opposite tamping tool being arranged in each half. This arrangement results in an almost symmetrical design of all drive and transmission elements, with an optimized load situation during operation. The interlocked arrangement of the lever arms is also possible without interfering torsional loads if the connecting parts are designed accordingly. Advantageously, the respective squeeze drive is arranged above the tamping tool coupled to the other squeeze drive. In addition to the narrow design, the arrangement according to the invention also provides optimum force transmission from the respective squeeze drive to the assigned tamping tool.

In a preferred embodiment, the one lever arm protrudes through a fork-shaped opening of the other lever arm. When the lever arm is forked up, both fork ends form the connecting part for connection to the assigned squeeze drive. In this way, torsional moments and asymmetrical loads are prevented.

In a further improvement, an effecting axis of the respective squeeze drive forms an acute angle with the centre plane, in particular an angle of up to 30°. The effecting axis determines the direction of the force acting on the assigned tamping tool from the squeeze drive. An almost vertical effecting axis favours a narrow design of the tamping unit segment and an optimal force transmission. The connecting parts and the bearing points at which the tamping tools are mounted on the tool carrier are at approximately the same height in order to achieve the best leverage effect.

In a preferred variant, each squeeze drive is connected to an eccentric shaft of a vibration drive. This results in a high level of process reliability because a vibration amplitude specified by the eccentrics of the eccentric shaft is maintained, even with large counterforces of a fouled ballast bed. The squeeze drives transmit the vibration to the assigned tamping tools to optimize penetration of the ballast bed and ballast compaction under the sleepers.

Advantageously, equalizing masses are arranged on the eccentric shaft. This compensates for vertical vibrations that could be caused by the oscillating masses of the squeeze drives. However, vertical vibrations can also be used specifically to improve the penetration process in the ballast bed.

In an alternative variant, each squeeze drive is set up as a hydraulic cylinder for generating a vibration superimposed on the squeezing movement. The respective hydraulic cylinder is mounted directly on the tool carrier and is actuated via a servo or proportional valve.

Advantageously, each squeeze drive is coupled to a distance sensor to record an actuating distance. In this way, the squeeze drives can be actuated depending on the distance. This allows easy adjustment to different sleeper distances or to twin sleepers by adjusting the opening width of the tamping tools before penetration of the ballast bed. The distance sensor is also used for hydraulic vibration generation.

In a further improvement, each squeeze drive is coupled to an adjustable limit stop device in such a way that with a retracting of the respective tamping tool, a limit stop element can be moved against a limit stop. In this way, the retracting of the tamping tools is stopped by the limit stop device.

In an advantageous further development, the respective limit stop device comprises a spindle and a limit stop element arranged to rotate thereon. With this, the opening width of the tamping tools can be exactly set in the retracted state.

In a further improvement, the respective limit stop device comprises an adjustable distance element which can be moved by means of an actuating mechanism from a pivoted-out position to a position between the limit stop and the limit stop element. Depending on the position of the distance element, different opening widths can be set in order to adjust to twin sleepers or changed sleeper spacings.

In a simple embodiment, each tamping tool comprises a tamping tine holder with two tamping tines fastened therein. With this, track sections without turnouts and crossings can be efficiently tamped with high quality.

In an another advantageous embodiment, at least one tamping tine of the respective tamping tool is arranged in a tamping tine holder that can be tilted upwards. The corresponding tamping tines can be tilted up in turnouts and crossings as well as in the event of obstacles in the track to prevent a collision with rails, sleepers, or track obstacles. The other tamping tines of the respective tamping unit segment can still be inserted into free areas of a turnout or a crossing and squeezed.

In a tamping unit for achieving a higher working performance, a plurality of the tamping unit segments described are usefully arranged one behind the other for simultaneous tamping of adjacent sleepers of the track, with each tamping unit segment in particular being able to be adjusted in height separately by means of an assigned height-adjustment drive. The linking together of the tamping unit segments in narrow design also allows tamping of adjacent sleepers with small sleeper distances.

In the method according to the invention for operating the tamping unit segment described, the tamping tools inserted into a ballast bed are squeezed during a squeezing process by pulling the connecting part of the respective lever arm upwards by means of the assigned squeeze drive. This squeezing movement takes place with optimum force exerted by the respective squeeze drive on the assigned tamping tool. If there is an eccentric drive, the vibration is also transmitted to the tamping tools with process reliability.

In the method for operating a tamping unit with a plurality of tamping unit segments arranged one behind the other, a respectively assigned limit stop device is adjusted in at least some of the squeeze drives to adjust to a changed sleeper spacing by moving a distance element between a limit stop and a limit stop element using an actuating mechanism. This makes it possible, for example, to quickly change the starting positions of the tamping tines during a transition between concrete sleepers and wooden sleepers.

show a tamping unit segmentwith a tool carrier, which is arranged in a unit frameso as to be adjustable in height by means of a height-adjustment drive. The unit frameis preferably arranged to shift and rotate on a machine frame of a tamping machine. Tamping toolsopposite one another are mounted at two bearing pointsof the tool carrierwith respect to a vertical centre plane. The respective tamping toolcomprises a tamping tine holderin which two tamping tinesare fastened next to each other. According to the invention, a lever armof the respective tamping toolprojects over the centre planewith a connecting part. An assigned squeeze driveis connected to this connecting part. The connecting partis designed, for example, as an articulated eye and forms a revolute joint with a fork end of the squeeze drive.

In the embodiment example shown, the connecting partsand the bearing pointsare approximately at the same height, resulting in an optimum leverage effect. The squeeze drivesare designed as hydraulic cylinders (e.g.mm piston diameter andmm rod diameter) and are aligned approximately vertically upwards. Additionally, electric linear drives can be used as squeeze drives. Preferably, an effecting axisof the squeeze driveforms an acute angle α with the centre plane, in particular in a range from 0° to 30°, in particular from 1° to 20°, in particular from 5° to 15°. This results in improved force transmission from the squeeze drivesto the lever armsas the indicated areas become narrower.

The invention further comprises other embodiment variants. For example, the bearing pointsand the lever armsare arranged in an upper area of the tool carrierand the squeeze drivesare aligned downwards. In another variant, the bearing pointsare arranged in the lower area of the tool carrierand the lever armsare guided so far upwards that the squeeze drivescan be aligned downwards.

Advantageously, the squeeze drivesare mounted on a common eccentric shaft. A central shaft section with a first eccentric and two shaft sections with a second eccentric on either side thereof are formed between two bearing points of the eccentric shaft. One of the two squeeze drivescomprises an eye endthat is arranged laterally offset with respect to an axis of symmetryand is mounted on the centre shaft section of the eccentric shaft. The other squeeze drivehas a fork-shaped split eye end. With this split eye end, the squeeze driveis mounted on the shaft sections with the second eccentric. The effecting axisforms an angle α, for example, of 10° with the centre planeso that optimum force transmission to the lever armsis achieved with sufficient freedom of movement of the squeeze drives. An electric or hydraulic rotary driveis connected to the eccentric shaft. When the eccentric shaftis rotating, the eccentrics cause a vibration that is transmitted to the tamping toolsby means of the squeeze drives. For example, a rotational speed ofrevolutions per second results in a vibration frequency of 35 hertz. The vibration frequency can be adjusted by changing the rotational speed. For example, the vibration frequency is increased during a penetration process of the tamping tines(e.g. 45 Hz). To reduce the noise emission and the vibration load, the rotational speed of the rotary driveis reduced when the tamping tinesare not in the ballast bed. For quickly adjusting the vibration frequency, an electric rotary drive, in particular, is suitable.

The angular positions of the two eccentrics are coordinated in such a way that the tamping toolscan be set to vibrate in a diametrically opposed manner. To prevent vertical vibrations, the oscillating masses of the squeeze drivesand of the lever armsare compensated for by equalizing masseson the eccentric shaft. Both eccentrics are 2 mm, for example, which results in a resulting vibration amplitude at the end of the assigned tamping tine(e.g. 4.6 mm) via a lever ratio (e.g. 1:2.3) of the respective tamping tool.

In the variant shown, each squeeze drivedesigned as a hydraulic cylinder comprises an adjustable limit stop devicethat limits the stroke of the hydraulic cylinder. With this, an opening widthwith which the tamping tinespenetrate a ballast bed can be set. In this way, it is possible to adjust the opening widthto a changed sleeper spacingor to twin sleepers.

The respective limit stop deviceis explained in detail with reference to. The squeeze driveon the left inis shown with the split eye end. The limit stop devicecomprises a limit stoparranged on the cylinder body. An extension armwith a spindlealigned parallel to the piston rodis fastened to the piston rod. The spindleis guided through the limit stop. A threaded nut is arranged at the free end of the spindleas a limit stop element, advantageously secured with a lock nut. The starting position of the assigned tamping tooland thus the opening widthcan be set by turning the threaded nut.

In a further development, a distance elementis mounted on the limit stopby means of a pivot pin. The pivot pinis coupled to an actuating mechanismso that the distance elementcan be pivoted from a pivoted-out position to a position between the limit stopand the limit stop element. In the pivoted-in position, the distance elementacts as a limit stop for the limit stop element, which reduces the stroke of the hydraulic cylinder. This makes it easy to set two different starting positions of the assigned tamping toolusing the distance element. In, the distance elementis shown with continuous lines in the pivoted-in position and with a dotted line in the pivoted-out position.

A variant without an eccentric shaftis shown in. Here, the squeeze drivesare mounted directly on the tool carrier. Modified hydraulic cylinders, which are also set up to generate the vibration, are used. In operation, cyclical vibration movements are superimposed on a squeezing movement by a pulsating actuation of a servo or proportional valve. The respective squeeze driveis aligned approximately vertically and comprises a distance sensorfor recording a piston travel. This provides distance-dependent actuation of the hydraulic cylinder. The distance sensoris also used to limit the stroke and thus to determine the opening width. In this embodiment, the effecting axisand the axis of symmetryof the respective squeeze drivecoincide. During a squeezing or retracting process, the alignment of the axle,changes minimally due to the rotary movement of the assigned tamping tool.

A tamping unitfor a turnout tamping machine or universal tamping machine is shown in. Each tamping toolcomprises two tamping tine holderswhich can be tilted by means of tilting drives. In this way, each tamping tinecan be tilted upwards separately to prevent a collision with an obstacle when lowering the tamping unit segment. In this variant, the respective tamping toolis extended upwards so that the tilting drivescan be mounted to articulate on the tamping tool. In, an eccentric shaftis arranged to generate the vibration. The tamping toolswith tamping tinesthat can be tilted up can also be combined with the hydraulic cylinders shown in.

A tamping unitfor simultaneously tamping a plurality of adjacent sleepersof a trackis shown in. Here, several tamping unit segmentsare guided in three rows one behind the other on guide rodsof a common unit frame. This unit frameis arranged to shift on the machine frame of a tamping machine by means of carriersaligned transversely to the track. The compact design of the tamping unit segmentsenables this arrangement, in which the tamping tinesof adjacent tamping unit segmentspenetrate the same sleeper crib. The sleeper spacing(sleeper distance) of the sleeperssupported on the ballastdetermines the opening widthof the tamping unit segments. Each railof the trackis assigned two tamping unit segmentsper row, so that each row consists of four tamping unit segments. The tamping unitshown comprises a total of twelve tamping unit segments, which are separately height-adjustable. In a variant not shown, each tamping unit segmentis arranged in its own unit frame, with the unit framesbeing mounted on the machine frame of the tamping machine so as to be adjustable relative to one another.

show starting positions of the tamping toolsof the tamping unitshown in. In, the tamping toolsare set for tamping concrete sleepers.shows the starting positions of the tamping toolsfor tamping wooden sleepers. The sleeper distanceof the concrete sleepersis greater than the sleeper distanceof the wooden sleepers. The starting positions are preferably set by means of the described limit stop devices.

For example, the distance elementsremain in the pivoted-out position for concrete sleepers. For tamping wooden sleepers, the distance elementsare brought into the stop position so that the opening widths of the opposing tamping toolsare reduced. The setting of the respective limit stop elementon the assigned spindleis used for fine adjustment. On the one hand, this allows the maximum possible squeezing distance of the tamping unit segmentsarranged on the inside. On the other hand, fine setting prevents tamping toolsof adjacent tamping unit segmentsfrom colliding. A fine-setting process is carried out once for adjusting the tamping tine positions at concrete sleepersand at wooden sleepers.

Alternatively, distance-dependent actuation of the squeeze drivesis provided. For this purpose, each squeeze driveis assigned a distance sensorfor recording the piston travel. During a retracting process, the current position of the respective tamping toolis recorded via the distance sensor. The retracting process ends when the specified opening width or tamping tool position is reached.

With hydraulic squeeze drives, the concrete sleepersand the wooden sleepersare tamped with the same hydraulic pressures, with each tamping unit segmentbeing connected to a common hydraulic system with a uniform system pressure. A retracting process of the respective tamping tooltakes place by simultaneously pressurizing both pressure chambers with the system pressure. For a squeezing process, the pressure in the pressure chamber on the piston side (larger piston area) is reduced by means of an actuated hydraulic valve. The squeezing force results from the pressure difference and the ratio between the larger piston area on the piston side and the smaller rod-shaped ring area. The piston always remains hydraulically clamped.