AUTOMATED PORTABLE RAIL REPAIR MACHINE FOR IN SITU REPAIR OF DEFECTS IN RAIL TRACK AND METHOD

Field of the Invention

The invention relates to a device for repairing rail track and a method for the same, particularly to an automated machine for the in-situ repair of defects or restoration of damage in rail track, which may be undertaken on plain line track, wing rails and crossing nose sections.

Background to the Invention

Due to the nature of use of rail tracks, defects occur in the rails over time. This may be due to weather conditions and/or trains passing over the rails and, of course, the quality of the rails themselves.

Hitherto, in order to repair such defects, a team of people are sent to the location of the defect and repairs are carried out manually. These repairs require the team to manually heat the rails using a gas torch, normally a propane powered torch, to heat the rail to around 343 degrees centigrade, primarily to reduce the rate of cooling to ensure desirable microstructure in the heat-affected zone of the repaired or restored area; however, as the heating is a manual process carried out with a gas torch, accurate control of temperature to which rail is heated has proved difficult and impractical . Subsequent to heating the track, the defect is manually ground out using a grinder or gouged out by flame curing. Once the defect has been removed, either a welding torch is employed to fill in the missing section with weld or, in some situations, thermite procedure is used to quickly fill-in the ground section. Once the defect in the rail is filled, the rail needs to be shaped to get the profile close to that of adjacent sections. The shaping is a manual process that is often undertaken using grinding wheels and although quality of the blending operation is strongly dependent on the dexterity of the operator, consistency of results is not often achieved.

The manual use of a gas torch and/or thermite in repair process is time-consuming and raise concerns of safety for the track worker. Furthermore, the profile of the rail track after the repair is complete is often different from that of the rest of the rail, thereby increasing the risk for further damage to the rail from the significantly increased dynamic forces imparted by the wheel as a result of misaligned rail geometry across the repaired area. Similarly, once the excavated section has been filled, uncontrolled, and sometimes rapid, cooling of the rail can result in the formation of martensite, which can weaken the repaired section.

Repairs may be required to plain rails, also known as stock rails, which are straight or curved sections or rail, or they may be required at junctions between respective tracks that allow train wheels to cross from one track to another, including wing rails and nose sections, which are together known as frogs.

Methods of repairing rails have been previously proposed, for example in EP 1878528 (Corus UK Limited) and WO2012114083 (Mirage Machines Limited); however, such methods can result in inconsistent repairs with susceptibility to undesirable microstructures. Additionally, the methods can be time-consuming because of the need for the attachment and detachment of tools and parts.

Summary of the Invention Accordingly, the present invention is directed to an automated portable rail repairing machine for in situ repair of defects in rail track, the machine comprising a chassis to which are connected wheels, wherein also the connected to the chassis are: a rail track excavation apparatus arranged to excavate material from a rail track; and a rail track welding apparatus arranged to apply material to an excavated part of a rail track.

Where reference is made to repairs and/or restoration, it will be appreciated that all terms may be relevant. Thus, where a rail is described as being “repaired”, that may be a repair or a restoration, and vice versa.

Thus, in accordance with the present invention, a rail track repair machine is provided that can automatically undertake in-situ repair of discrete defects or restoration of damaged areas of standard rail track and the wing rails and nose of railway crossings, or frogs. The machine has both excavation apparatus and welding apparatus affixed to the chassis. Such an automated machine can allow for the in-situ repair of defects or restoration, for example, once a defect or damaged area has been identified, the automated rail repair machine of the present invention can be mounted upon the rail track and moved into position over the defect, after which the repair process can be automatically undertaken. The device is able to excavate the defect and then fill-in the excavated section with fresh material, with the finished repair being a close, and potentially near-perfect, match to the desired profile of the track. The automated machine reduces the time required to repair defects and so reduces emissions compared with conventional manual processes while at the same time increasing availability of the track for the purposes for which it was installed.

The excavation apparatus may comprise at least one milling cutter, or milling machine, to excavate the section to be removed from the rail. These cutters are especially useful in tight spaces, for example, when milling the crossing nose. Clearly, whilst standard track is substantially symmetrical, the crossing nose has a different shape from other parts of the track, with its triangular front end. Similarly, the profile and dimensions of the wing rail that is associated with the crossing nose must be taking into account when reconstructing a rail. The device of the present invention creates a safer manner in which defects are repaired and reduces the risks associated with manual excavation and welding processes. The welding may be undertaken by any viable welding process, particularly arc welding processes, for example, flux-cored arc welding or gas metal arc welding. The weld process restores the excavated section in order to provide a better and more consistent repair of rail track, compared with existing methods. Furthermore, the process is more efficient and so reduces the down-time of the rail track. Providing a fully automated process provides consistency over existing techniques.

A processor may control the repair process so that the machine and the repair can be fully automated and controlled precisely through a programmable logic controller with an executable program.

In order to carry out the repairs accurately, it is advantageous that prior to the repair being undertaken, the machine is fixed in place, relative to the defect. Therefore, the machine may further comprise a clamping mechanism to clamp the machine in a location and hold it securely in place essential for all subsequent operations. Such a clamping mechanism may comprise at least two location securing clamps for securing the machine to the rail track to be repaired, and, preferably, there are four or more clamps. In one arrangement, the clamps may be arranged so that a first clamp, or set of clamps secure the machine onto a first rail track, and a second clamp, or set of clamps, secure the machine onto a second rail track. By clamping the machine in place using a plurality of clamping mechanisms, the machine can be held securely, thereby allowing accurate repairs to the rail track. It is advantageous that the clamps operate simultaneously to secure the machine in place, preferably being controlled by software that can align the clamping. Furthermore, sensors may be provided to ensure that the clamps are operated in a manner to provide a desired angle of the chassis relative to the rail track. The clamping mechanism can allow the chassis to be arranged in a secure position, which can then allow in-situ excavation of identified defects. Thus, secure synchronised multi-point clamping can be employed for precise squareness, thereby ensuring accurate positioning of active equipment heads, such as the welding head and the milling head. It will be appreciated that clamping the machine to a frog section of rail is less straightforward; however, the use of a plurality of clamps that can simultaneously contact the track allows the machine to fix to a frog section. Thus, whilst the position, shape and number of clamps may vary, when fixing a frog section, there are still a plurality of clamps that engage the track in a synchronised operation to hold the machine firmly in place. A welding earth may be arranged to be part of the clamp section. This allows the welding earth to be automatically connected to the rail.

Preferably, the machine further comprises at least one cast block heater, with the cast block heater having a first position and a second position, wherein, when in the second position, the at least one cast block heater is arranged adjacent the rail track in order to heat the same. More preferably, the cast block heaters work in pairs, with each of the pair of cast block heaters being positioned on respective sides of the rail track. The heaters can be moved from a first position, in which they are held away from the rail track, to a second position, wherein they are adjacent the rail track. In the second position, the pair of cast block heaters can heat the rail track from both sides. The cast block heaters preferably extend beyond the defect on both sides of the rail and allow a more controlled heating and cooling of the rail. Heating beyond the section that is being repaired or restored creates a thermal envelope, thereby allowing control over the section itself and the adjacent material. This can provide the necessary heat input to areas surrounding the section to be repaired to provide the desired microstructure in the finished track. By controlling the heating and cooling of the rail and the weld repair, the integrity of the finished repair is greater than using a manual process and/or a gas torch. The cast block heaters can be arranged to fit underneath the rail head in order to heat the rail from the underside. Unlike the manual process, the arrangement of the present invention allows the rail head to be accessible during the excavation and repair stages, whilst also being able to maintain more uniform heating of the rail. The extension of the cast block heaters to beyond the length of the area to be repaired allows a thermal barrier to be set up at either end of the repaired area and thereby reduce the rate of cooling within the heat affected zone and ensure the desired microstructure. The control over the heating and cooling of the rail reduces the risk of martensite formation during the repair process.

In one arrangement, least two location securing clamps are provided for securing the machine to the rail track to be repaired and to a second rail, and the machine further may further comprise a block heater unit having two or more cast block heaters with one arranged on each side of the rail to be repaired. The cast block heaters can have a first position and a second position, wherein, when in the second position, the cast block heater is arranged laterally adjacent the rail track in order to heat the same, such that the rail to be repaired can be heated from both lateral sides.

The rail track excavation apparatus and the rail track welding apparatus may be positioned on the chassis and both focussed upon the same repair zone when the device is secured to the rails. As such, they may be mounted on the chassis to both focus on the same section, or they may be moved into the repair zone when required; however, once clamped in place, it is preferable that the chassis is not moved until the work is completed.

It is preferred that there are at least two pairs of cast block heaters provided on the machine, one for each of the rails. Having two pairs of cast block heaters reduces the need to reposition the heater for each of the rails. The cast block heaters may be powered from a source on the machine, for example, the same power source as that used for the welding process. Alternatively, a separate power source may be provided for the cast block heaters.

In an additional or alternative arrangement, an induction heating probe can be employed to heat the rail. The induction heating probe may be arranged in front of the track welding apparatus so that heating is achieved prior to the weld deposition. The induction heating probe can be arranged to move at the desired time interval in front of the welding apparatus to heat the rail across its width, or it may be moved across the rail to heat the rail prior to welding. Again, a thermal barrier, or thermal envelope can be created adjacent the area upon which welding is to occur. The thermal barrier at the wide end of a crossing nose can be achieved by traversing the probe in this region until the welding operation is complete. The position of the heating probe relative to the welding apparatus may, in some arrangements, be adjusted. Similarly, it may be desirable to adjust the position of the induction heater relative to the rail, including the height of the probe above the rail. In one arrangement, it may be desirable to have more than one induction heating probe so that the rail can be heated in a particular manner and/or from a certain direction.

Due to the control of the heating and cooling rates that comes with using the cast block heaters or the induction heating probe of the present invention, repair of more hardenable, premium rail steel grades is possible. Hitherto, such grades cannot be reliably repaired due to the lack of control in the cooling of the post-repair weld material. A low preheat temperature can provide a safety platform to compensate for the wide range of temperatures of rails in track at different times of the year, thereby allowing the machine and system of the present invention to obtain a more consistent finish to repairs, regardless of the environmental conditions, particularly the weather conditions. Thus, the rail may be heated to a temperature of, or less than, 120 degrees centigrade. The heating may be undertaken in stages, for example, providing a preheat of between 60 degrees and 80 degrees for carbon steel rails or up to 1 0 degrees for premium grade alloyed rail steels.

Advantageously, a rail track profile measurement system is provided on the machine, and, in one arrangement, the profile measurement system comprises at least two lasers that are arranged to measure the shape and contours of surface of the rail track. The lasers are employed to scan the track and to measure the surface profile thereof, so that the system can create a model, which is preferably, a three-dimensional model of the rail head. Discrete laser measurements can be first computed to derive a smooth transversal profile of the rail and then to project that profile across to the corresponding points measured on the other side of the repaired area. Thus, measurements of the track are taken beyond the section to be repaired or restored so that the profile of the finished track runs smoothly to the adjacent track. The profile measurements may be taken several millimetres beyond the section that is identified to be worked upon, so that the finished profile can be blended with the parent rail on either side of the repaired length. By accurately matching the profile of the track along its length, the risk of discontinuity experienced by the passing wheels is minimised. Therefore, the profile measurement system can be used to obtain the desired positional movement of the milling cutter to ensure a good blend across the repaired area and adjacent sections. Thus, the profile of the section to be excavated can be modelled and, once the repair process is complete the profile of the repaired length can be matched closely to the modelled profile. Thus, the risk of future defects caused by the surface of the rail being mis-aligned is reduced. It will be appreciated that other measurement and/or scanning arrangements may be employed and/or more than two lasers may be included in the profile measurement system to improve the modelling of the rail head.

In some arrangements, for example, where a repair or restoration is undertaken on a frog section, it may be preferred to employ a single point laser measurement system. This may be used to accurately detect the tip of the nose crossing and to follow the two edges of the triangular shape of the nose. These detected edges can then be used to establish a theoretical and actual nose tip. The location of the actual nose tip can then be used to identify one end of a wing rail to be repaired or restored.

It is particularly useful that the machine further comprises a temperature sensor arranged to monitor the temperature of the rail track during the repair process. By monitoring the temperature of the rail track during the repair process, the reprofiling of the repaired area can be better executed to achieve the desired near-perfectly blended profile across the repaired length. Furthermore, the welding process can be undertaken at the correct temperatures, rather than over-heating the track, thereby ensuring consistent repair integrity, reducing carbon emissions and making the process more efficient. Preferably, the temperature sensor is a non-contact temperature sensor, which allows the temperature to monitored without interfering with the milling or welding processes.

The track welding apparatus can be used to allow for a multi-layer deposition that can fill a milled section. The deposition can use a flux cored arc weld process and it may use a controlled square weave pattern. A square weave pattern provides an accurate coverage of the evacuated cavity. A sacrificial layer may be applied to the filled cavity to ensure the required heat input to control the cooling rate and resulting microstructure in the heat affected zone. Achieving robust deposition may depending upon a combination of factors, including the low preheat process, development of a thermal envelop around the repair and control of a welding parameters, such as volts, welding speed, stick-out length, square weave traverse and step over distances.

In respect of crossing noses and wing rails made from carbon-manganese rail steels, a controlled square weave pattern can be undertaken for these types of track sections, although it will be appreciated that the non-symmetrical shape and the dimensions of the crossing nose require different control from standard track. This may be partly addressed by way of developing the thermal envelope by us of an induction heating probe, which can be arranged a predetermined distance ahead of a welding gun, which forms part of the welding apparatus for deposition of material. By knowing the rate at which the rail cools and the distance between the induction probe and the welding gun, a repair and restoration process can be determined. In respect of crossing noses and wing rails made from austenitic manganese steels that require the temperature rise from weld deposition to be restricted preferably to below 200°C, the weld deposition pattern may be changed from square weave to long stringer beads placed side by side to restore the excavated cavity. Furthermore, it may be beneficial to follow the welding gun with air knives at a desire time interval to ensure temperature rise is controlled to below the desired level.

The invention extends to a method of repairing a defect in a rail track comprising the steps of: providing rail repair machine as set out herein; positioning the rail repair machine over the defect to be repaired and locking the machine in an appropriate location to repair the defect; excavating the defect area; and welding the excavated section to return the track to a desired profile, which may be substantially the same shape as the sections adjacent the defect.

The method of repairing a defect in a rail track uses the device of the present invention to automatically excavate and weld the track in situ. The relevant parts of the machine may be moved into, and out of, a repair zone, as required, so that they are in the desired position when needed.

It is preferable that the profile of an adjacent track section to the defect is measured prior to the excavation beginning, and the newly welded material can be matched to substantially the same profile as the adjacent section. Furthermore, it is particularly preferable that the profile of the track on both sides of the defect to be repaired is measured to create a three- dimensional template. Thus, the profile measurement system is used, which may comprise lasers, to create a three-dimensional model that the machine can employ to create a desired profile for the finished weld. The laser system enables measurement of the distance to the rail surface and thereby ensure correct stick-out length of the wire and its positioning on the rail surface. Thus, the desired profile can be calculated and matched in order to achieve a high-quality repair. By cutting the weld wire to the required stick-out length, the present invention can account for any changes in rail profile due to welding heat.

It is advantageous that cast block heaters are employed to heat the rail track at the location of the defect, and it may be that the temperature of the rail track is monitored repeatedly during the repair process. Using cast block heaters, that can fit to the profile of the track and preferably can fit to the underside of the rail head, provides and efficient and effective heating mechanism to ensure that the rails are heated to the correct temperature for the repair. The heat can be provided primarily by conduction into the track and this can help to further ensure that the temperature is maintained during the repair process, which may be particularly beneficial in cold environments where the temperature would otherwise drop rapidly upon removal of a gas torch.

In one preferred embodiment, the defect in the rail track is marked prior to the positioning of the rail repair machine over the defect. The defect in the rail can be marked in advance so that the machine of the present invention can be accurately positioned. The marking may be in the form of a substance being applied to the track at the position of the defect, for example white paint, which can be applied manually in advance. Not only does this allow the machine to be positioned accurately, but it also enables the scanning and profiling of the track to be more easily undertaken by creating a surface upon which the contours may be more accurately identified. The welding gun may be moved in a square weave pattern.

In order improve the quality of the repair, it is advantageous that after weld has been applied, a peening process of the welded layer is undertaken to ensure efficient removal of the slag formed to protect the molten weld pool. This peening process can be important to minimise/eliminate the risk of a stress-raising defect that would subsequently grow under the passage of wheels and lead to transverse rail fracture. Automation of the peening process through the controlled square weave movement can deliver a more thorough removal of slag debris. Additionally, there are benefits of imparting compressive stresses particularly in the intermediate layers during the repair process. In a similar manner to the welding gun, other elements, such as the peening mechanism may follow a square weave pattern or another pattern to ensure that the repair is of high quality.

The excavation apparatus, which may be a milling machine, can be employed to reprofile the finished repair. Using the milling machine, in combination with the modelled rail head profile, the rail head can be reprofiled to a finish that reduces the risk of future damage to the rail. The resulting repair may be a blended profile across the rail head and the sections adjacent the repaired region, thereby providing a relatively smooth track for train wheels. As the profile measurement, or scan, takes account of the track adjacent the section being worked upon, a smooth finished profile can be calculated so that the milling machine can reprofile the track one the deposition stage has been completed. The process of reprofiling a wing rail is similar to that of standard rails; however, reprofiling a crossing nose section is more complicated. Initially, the height of the restored crossing nose will need to be as close to the height of the restored wing rail as possible, and, preferably, identical. Thereafter, the profile at the wide end of the crossing nose will need to be blended into the profile of the unrestored portion. Then, the crown profile all along the weld restored length of the nose will, advantageously, be the optimised profile determined through vehicle dynamic simulations. As such, these requirements are addressed in a process wherein: restoring the of the wing rail first denotes the height of the restored wing rail as the datum, which can then be used to determine the desired nose height; the measured profile of the crossing nose can then be used beyond the restored length to position the milling cutter accordingly; and the coordinates of the optimised profile are used to provide executing instructions for the positioning of the milling cutters.

Thus, the milling instructions for the crossing nose are calculated from the wing rail, which results in a smoother finished junction to minimise impact loading from wheel transfer on to or from the crossing nose.

Traditionally, standard profile templates are employed, which can result in large differences in the actual profiles of the track.

In one embodiment, the arrangement may be provided with one or more air knives. The air knife, or air knives, may be employed to cool the rail and/or to remove debris. This provides a method of cooling the rail to the required temperature prior to reprofiling in a quick and efficient manner, thereby reducing the repair time. It may be that some repairs, such as those to the frog section, cooling may be undertaken after the placement of each stringer bead. This can help to control the inter bead and inter pass temperature.

As will be understood, the repair or restoration of standard rails can be undertaken at a fixed distance, according to the rail gauge. Thus, the repair zone, which may be a restoration zone and which is the area upon which the milling apparatus and the welding apparatus can be focussed, may be at a known position on one rail or the other rail. As a result, the operative elements may be moveable from one side of the chassis to the other, depending upon the position of the rail upon which the machine is focussed. Where the repair or restoration of crossings is undertaken, the repair zone, may be at a position between the rails. Therefore, it may be necessary for the repair zone to be moveable transversely in a continuous fashion, rather than a discrete fashion. This enables the repair zone to be positioned anywhere across the width of the rails.

It will be appreciated that heating of rail track may be undertaken using at least one cast block heater and thus the present invention may extend to a rail track heating device comprising cast block heater. The cast block heater may be as described herein but employed independently from the rail track repair machine. Preferably, the cast block heater is provided with a profile to match, or substantially match the profile of at least a portion of rail track, thereby enabling the track to be heated by placing the cast block heater adjacent the rail to be heated. The cast block heater may be provided with power from a device upon which it is mounted, which may itself be provided with wheels so that it can roll along the tracks.

The present invention may extend to the cast block heater arrangement for heating rail track, and, it may further extend to the positioning of swarf trays adjacent the cast block heater arrangement.

Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 shows a rail repair machine in accordance with a first embodiment of the present invention;

Figure 2 shows a flow chart illustrating an embodiment of the repair process of the present invention;

Figures 3a, 3b and 3c show the cask block heater arrangement of the present invention in a first and second position in 3a and 3b, respectively, with a diagram showing a sectional view in 3 c;

Figure 4 is a perspective view of a second embodiment of the present invention;

Figure 5 is a further view of the device shown in Figure 4; and

Figure 6 shows an arrangement of the excavation and deposition elements of a machine according to the present invention. Detailed Description of Exemplary Embodiments

The figures show a rail repair machine 10 comprising a chassis 12 upon which various elements are mounted. The chassis 12 is provided with wheels 14 to engage with a rail 16 and allow movement of the machine 10 there along.

The chassis 12 is further provided with clamps that can be activated to secure the machine 10 on the rails 16, thereby restricting, or preventing, movement of the machine 10 relative to the rails 16. Thus, the machine 10 can be held in place relative to the rail 16 whilst a repair is carried out.

The clamping mechanism comprises four hydraulically operated clamps positioned at different locations upon the chassis. The clamps are synchronised using software to engage the rails and ensure that the machine 10 is centralised and secured on the rails 16. The synchronisation is undertaken by software to ensure that the clamps are applied equally and accurately to ensure that the machine 10 is positioned securely in place, or that the clamps are applied as needed to align the machine 10 correctly.

Further arranged on the chassis 12 is a cast block heater arrangement 18. In this heater arrangement, two cast block heaters 20 are arranged on respective side of the rail 16. The heaters 20 are shaped to have a profile that follows that of the rail 16 and the underside of the rail head. The cast block heaters 20 have a first position arranged with a gap between the cast block heaters 20 in which the rail 16 sits, and a second position in which the gap between the cast block heaters 20 is reduced, thereby bringing the cast block heaters 20 closer to the respective sides of the rail 16. When in the second position, the cast block heaters 20 heat the rail due to conduction of heat into the rail 16.

Arranged on the sides of the cast block heaters 20 that are distal from the rail 16 are swarf trays 22. The swarf trays 22 are positioned so as to catch any debris or swarf that is generated during the repair process, which may include metal particles or weld material. By providing swarf trays 22 adjacent the cast block heaters and underneath the rail head in a repair zone, the repair process can be more readily automated and waste material collected to reduce the risk of injury and to increase the efficiency of the repair process. Furthermore, the collected debris may be recycled.

A laser scanning system is provided on the chassis 12 that comprises a pair of lasers that are directed towards the rail in the repair zone, the repair zone being a location within the machine, when in use, at which the defect to be repaired is located. The lasers are arranged so as to be able to scan the surface of the rail head and to measure various parameters of the rail head, for example, the surface shape and/or profile. The scanning system can be used to produce a three-dimensional electronic model of the rail head, including the measured heights and contours of the rail.

A computer numerical control milling machine is arranged on the chassis and is able to be positioned adjacent the defect. The milling machine is provided with multiple cutting edges that can be adjusted. Thus, the cutting edges can be arranged to reduce set up times, extend the tool life and to increase productivity by removing the defect accurately and with a shape that allows a high-integrity weld to be deposited in the repair process. Furthermore, the same milling tool can be used for reprofiling the weld repaired area by software control of the tool in a manner similar to that deployed in computer-numeric-control milling operations.

Further mounted upon the chassis is a welder. The welder is arranged to be positioned such that when the defect has been excavated by the milling machine, the welding machine can repair the rail track and fill the excavated portion or section with fresh material. The welder is provided with a source of consumable welding wire that is automatically snipped to the desired stick-out length. The weld wire is held in a spool and can be dispensed as required. Advantageously, two wire straighteners are provided that can correct any inconsistencies of wire feed from the spool. Furthermore, the welding gun may be provided with a pre-set welding angle, incorporating a direct connection to the wire feeder. Precise control of wire stick-out length is obtained by using a laser distance sensor that feeds forward the length of weld material required to activate an automatic wire snipper to cut the weld wire to the required stick-out length. Thus, the welder is able to calculate the required stick-out length, by taking account of any change in rail shape that occurs during the heating of the rail before and during the welding process, which may occur due to heating of the rail. Scrap wire can be received in a specifically provided tray for later disposal in an appropriate manner. The welding gun traverses the rail in a square weave pattern with prescribed and precisely controlled parameters of traverse, step-over distance, and welding speeds. Following completion of deposition of a layer, the deposit is allowed to cool naturally for a short fixed period of time to facilitate detachment of slag. A pneumatically operated peening gun is then traversed over the deposited layer in a similar weave pattern to ensure effective removal of slag. A low-pressure air nozzle is provided such that it can follow the peening gun to deliver a blast of air at high volume and low pressure to blow away slag debris that may remain after the peening operation. The peening gun and air nozzle can be arranged within the spindle of the milling machine and can be controlled by a processor.

The machine 10 is provided with a generator on the chassis 12 that is employed to provide power to the various elements of the machine, including the cast block heaters 20, the scanning system, the welder and the milling machine. Furthermore, a processor is provided to control the various parts of the machine 10 and to enable the steps of the repair to be carried out in the correct sequence and times The processor provides precise control of all weld parameters in order to provide a high integrity weld deposit. Various further sensors and elements may be arranged to provide the processor with information on the repair and the repair process.

One or more air knives may be arranged within the machine and directed towards the rail for more rapid cooling down to the desired temperature prior to reprofiling.

As shown in the flow chart of Figure 2, the method of operating the rail repair machine begins with positioning the machine above a defect and using the clamping mechanism to hold the machine securely in place against the rails.

Once the rail repair machine 10 is securely located, a temperature sensor is employed to monitor the rail temperature. As the integrity of the weld repair is strongly influenced by the thermal history of the weld, the machine 10 of the present invention monitors the temperature of the rail and the weld repair throughout the process. Having measured the temperature of the rails, the lasers of the measurement system are employed to measure the profile of the rail. By measuring the profile of the rail, a three-dimensional model is created to which the finished rail should conform. The lasers are arranged at a known pre-determined angle and the traverse across the rail head taking measurements therealong. Once the profile has been measured, this is stored and is used later to control the movement of the milling cutter to deliver a near-perfect blend of profile across the repaired area.

Excavation of the identified defect can be initiated immediately following measurement of rail profile. However, temperature of rail is measured to establish the start point of monitoring of thermal history through the repair stages. The CNC milling machine that is mounted upon the chassis automatically excavates the defect in the rail head. The computer- controlled excavation ensures the shape and dimensions of the excavated section are within set parameters. Thus, the shape and the depth of the excavated portion can be designed to impart the required camber and radii that improve the weld integrity. The CNC milling machine is able to repair defects of up to 100mm long and up to 15mm deep. Whilst it is envisaged that longer and deeper defects could be repaired, for example, defects up to 200mm long and 25mm deep, most repairs are within the aforementioned dimensions. However, the machine can be programmed to repair longer and deeper defects, if necessary. Shallower milling may be used for sections such as a crossing nose.

The cast block heaters 22 are moved from the first position in which the gap between the heaters is greater, to the second position in which the cast block heaters are adjacent and in contact with the rail. As can be seen in Figure 3b, the cast block heaters fit under the rail head in order to heat the rail transversely from both sides and from the underside of the rail head. The cast block heaters 22 are sized to be longer than the section being repaired so that the rail is also heated and maintained at the desired temperature on both sides of the section to be repaired along the axis of the rail. This is a novel approach involving the creation of a thermal barrier immediately adjacent to the edge of the repaired length and thereby slow the rate of cooling within the heat affected zone to ensure the desired pearlitic microstructure. The cast block heaters 22 are powered by the welding generator that is housed on the chassis, thereby removing the need for gas to be supplied to heat the rails. The engagement of the rail head by the cast block heaters 22 from both sides of the rail permits rapid and more uniform heating to a low pre-soak temperature of 60 to 80 degrees centigrade, although the temperature may, in some cases, by up to 120 or 140 degrees centigrade. The cast block heaters 22 can be retained in place throughout the process, thereby allowing the cooling rate to be accurately controlled. Furthermore, as the cast block heaters 22 extend axially to each side of the defect, a thermal barrier for heat conduction away from the repair region is also established. It will be appreciated that weld restoration could be undertaken using the process of this invention but without employing any preheat, but this will increase the risk of undesirable hard microstructures. Hence, the low preheat process provides the additional assurance for high integrity repairs.

Once the measured temperature of the rail reaches a value within the specified range of 60°C and 80°C and more favourably at the higher end of the specified range, the weld restoration process can be initiated. In preparation, the welding gun is positioned over the wire snipper 17 and the wire extended into the device to permit cutting precisely to the specified wire stick-out length which is an important parameter for the control of weld integrity. Furthermore, this length incorporates the influence of rail distortion resulting from welding heat input.

In the arrangement shown in Figures 4 and 5, a crossing repair and/or restoration machine 30 is shown, which is intended for repairing and/or restoration of rails at crossing sections, for example wing rails and nose sections. The machine 30 comprises a chassis 32 upon which is mounted wheel and brake assemblies 33. As with the embodiment shown in Figures 1 to 3c, the wheels mount the chassis upon the rail and a clamping mechanism is provided that can be used to lock the machine 30 onto the rails to prevent in advertent movement of the machine 30, when in use.

Again, as with the embodiment shown in Figures 1 to 3c, the machine is further provided with milling apparatus 34 and welding apparatus 36. The welding apparatus is provided with a source of weld wire within a reel housing 38. The wire can be provided on a spool within the housing 38 and the wire is provided to the welding apparatus when required, in order to deposit a layer of weld upon the track being repairs or restored. Wire snipping apparatus is also provided to cut and shape the weld wire in order to obtain a consistent deposition of weld material.

The milling apparatus 34 and the welding apparatus 36 are arranged to focus upon a repair zone and then can be moved along the rail as required. Additionally, the chassis allows for the milling apparatus and the welding apparatus 36 to be moved transversely across the rails to the desired position. Additionally, so that repairs can be undertaken over a linear section of rail, the milling apparatus 34 and the welding apparatus 36 can be moved longitudinally along the chassis, which is to say, parallel to the rails, whilst the machine is clamped in place. The longitudinal adjustment section 38 allows for movement longitudinally with respect to the rails, and the transverse adjustment section 40 allows for movement transversely with respect to the rails. Due to the shape of crossing sections in rails, the transverse adjustment section may allow movement beyond the wheels of the chassis 32.

As set out in relation to the machine of figures 1 to 3c, the machine of figures 4 and 5 can be used to plot the dimensions of the rail and to scan and model the profile of the rail. Subsequent to modelling the rail, the excavation and restoration of the rail can be undertaken in a similar manner to that described above and herein. The heating of the rail can be accomplished by way of an induction heater.

Figure 6 shows the excavation and deposition elements that can be present in a machine according to the present invention. This section of the machine may be provided with a milling cutter, blast cleaning tubes, air knives, a peening gun and a welding gun. These can be arranged as shown in the figures, with the milling cutter be arranged in front of the air knives and blast cleaning tubes and with the peening gun and welding gun following the milling cutter.

The welding process comprises deposition of a sufficient number of layers to restore the excavated cavity followed by an additional sacrificial layer as a source of heat input to achieve the desired microstructure in the heat affected zone of the penultimate layer. Thus, in the example of a 10 mm excavation, three restoration layers plus a sacrificial layer are needed to complete the repair. Each restoration layer starts with the snipping of the wire to the prescribed wire stick-out length. This is then followed by positioning of the welding gun at a bottom corner of the excavated cavity and the welding progresses following a square weave path. The width of each traverse across the width of the rail is reduced by a fixed distance to ensure no overflow of molten weld bead. The speed of welding along the traverse and at step over at the end of the traverse are precisely controlled to ensure uniformity of weld bead shape and size. In the case of restoration of crossings made from cast austenitic manganese steel, the control of temperature is achieved through use of long stringer beads that are cooled by air knives that follow the welding gun at the desired time interval.

The welding process, which can allow for multi-layer deposition of weld material, may involve automation of various processes therein. In some cases, a bulb may develop on the end of the weld wire that required removal to ensure a reliable weld when using the wire again. Therefore, it may be required to remove the end of the weld wire by employing a wire snipper, and a wire scrap tray may be arranged to catch the removed tip, which can then be disposed of later. In some arrangements, a laser distance sensor can be used to assist with feeding forward the wire to the required length, after which an automatic wire snipped can cut the wire to the required length. Twin wire straighteners may be used to prepare the wire, although the shape of the wire stick out length may vary, which can affect the positioning of the weld bead, which could reduce the quality and integrity of the finished weld. Thus, in some arrangements, a three-dimensional block can be used to calibrate the shape of the wire stick out length and to make corresponding adjustment to the wire to provide a more accurate positioning of the wire tip in advance of welding.

Once the deposition of a layer is complete, the weld deposit is allowed to cool naturally to allow the slag to detach from the metal deposit. The peening operation is automatically initiated at the end of the prescribed period of natural cooling. Peening follows a square weave pattern similar to the welding gun operation and is followed by a nozzle blowing air at high volume-low flow rate to ensure complete removal any slag layer.

The automated process sequence of wire snipping, square weave welding, square weave peening, and air-blow cleaning is repeated to deliver the number of welding and sacrificial layers prescribed for the excavated depth.

Once the weld is complete, the surface temperature of as welded area is likely to be in excess of 250°C. Prior to finishing the reprofiling of the repaired section of the rail the temperature should be less than 50°C. Therefore, the air knives are repeatedly traversed over the repair area to reduce the temperature. Once the appropriate temperature of the rail is detected, subsequent reprofiling can be undertaken. The air knives may also assist in cleaning the rail and removing debris and/or swarf that may have accumulated on or around the rail. The debris can be collected in the swarf trays.

The reprofiling may be undertaken by the milling machine. Furthermore, the laser scanning system may be used to ensure that the profile of the repaired rail matches the desired profile that is created during the three-dimensional modelling process. Corrections to the reprofiling may be undertaken if the rail head is scanned after the weld process and the profile is not substantially in conformity with the modelled profile. In some arrangements, the excavation apparatus and deposition apparatus may be moveable in three axes, thereby allowing movement along the rail, transversely across the rail and, substantially vertically closer to or away from the rail.

It is envisaged that the rail track repair machine is transported to the repair site on board a specialist maintenance train, a suitable road-rail vehicle or it may be provided with its own propulsion system. Preferably, the machine can be accurately positioned over an identified defect. For maximum flexibility of deployment, a road-rail vehicle suitably modified to house the discrete defect repair machine, associated power source, hydraulic and pneumatic equipment, and the process controller is the preferred mode for transporting the repair machine to work site.

The temperature sensor, which is preferably a non-contact temperature sensor, can be used to measure temperatures at selected locations through the various process states to ensure the integrity of the repair.

The peening gun and air nozzle can be arranged within the spindle of the milling machine and can be controlled by a processor.

The air knife, or knives, and/or cast block heater arrangement may be employed independently of the rail repair machine.

Different rail materials can be accommodated using the device and process of the present invention. For example, cast austenitic manganese steel may be used in crossings, which may require a different approach compared to standard carbon manganese rails. As an example, it may be necessary to maintain the temperature of the substrate below 200 degrees centigrade despite heat input from the weld metal. As such, it might be that no pre-heating is required. Additionally, use of a square weave pattern may be too heat intensive and so the square weave pattern may be adapted to control the heat input. In such a circumstance, long stringer beads may be employed to provide a longer cooling time prior to the deposition of subsequent weld beads. Similarly, air knives may be arranged behind the welding gun, with the air knives being activated after a short, predetermined time interval to allow the deposited weld bead to be rapidly cooled. In some arrangements, further cooling time can be achieved during a preening cycle on the return journey of the welding head from the far end of the deposited weld bead, particularly where air knives are arranged to travel in front of the peening gun. It will be appreciated that the process can be undertaken without the temperature variations and interruptions that occur with existing systems, which can result in a better quality finish. The air knives can be arranged to focus upon the same repair zone, for example, being directed towards the position where weld is deposited.

One or more features of one or more embodiments described herein may be incorporated into other embodiments also described herein.