GB2097845A - A formation of several independently mobile track maintenance machines - Google Patents

Abstract

A mechanised track maintenance train comprising independently mobile maintenance vehicles 3, 4, 5 has a fixed reference line 10 common to all the vehicles and set up section by section alongside the track. Each vehicle has a sensing probe 16, 24, 29 which travels along the reference line, the line being at least twice the overall length of the track maintenance vehicles. The latter may be a ballast cleaner, a tamping and levelling machine, and a vibratory stabiliser. Alternatively a leading tamping and levelling machine may be coupled to the ballast cleaner. <IMAGE>

Description

SPECIFICATION A formation of several independently mobile track maintenance machines This invention relates to a mobile machine formation for improving and, more particularly, correcting the position of a railway track, consisting of several track maintenance machines arranged one behind the other longitudinally of the track and capable of travelling independently of one another, for example a track tamping and levelling machine incorporating a tamping unit, a lifting and - optionally - lining unit and a following track consolidating machine, pickup elements being associated with each of the tools of these machines for bringing the track from its actual position to the required position with the aid of a reference system.

Mobile machine formations of this type are known as "mechanised maintenance trains (MMT)" and are intended in particular to obtain greater accuracy in the position of railway tracks to accommodate high-speed traffic and greater durability of track correction work. Machines of this type which are capable of travelling along the track independently of one another are adapted to one another in terms of their performance and joined together to form a mobile machine formation in order to work on the track, i.e. to correct and stabilise it, fully automatically and economically as it were in a single run, as described for example in the Article on pages 14 and 1 6 of the Journal "Railway Technical Review", 1977/78.In addition to a conventional track tamping, levelling and lining machine equipped with its own reference system, mobile machine formations of the type in question also include for example stabilising machines, consolidating machines and also ploughs and power wrenches. On the one hand, the length of each machine reference system is limited so that it is not possible completely to eliminate relatively long undulations or inaccuracies in the track, whilst on the other hand the final outcome of the work done by a particular machine may be adversely affected by the following machine, particularly in regard to the track position created.

It is already known (cf. G.B. Patent No.

13031 91), that a reference system formed by a laser beam may be fitted to machines for measuring or correcting the position of a railway track of which the tools or adjusting elements are arranged with sensors responding to the laser beam which may be associated with various machines arranged one behind the other. In this case, however, the laser transmitter or receiver is arranged on a travelling track maintenance machine, in particular a track tamping, levelling and lining machine. Although machines of this type have proved to be very successful in practice, they are relatively involved in terms of their construction and are not always robust enough for practical application.

In addition, individual travelling machines equipped with their own fixed reference system, for example travelling consolidating or tamping machines and ballast cleaning machines, are known from G.B. Patents Nos. 1 537198 and 1395231. The tools of these machines are each connected to a probe which is aligned with a straight reference wire fixedly arranged alongside the track in order to carry out the necessary track correction work or to adjust the clearing depth during clearing or takeup of the ballast on the basis of the required level as determined by the reference wire. This known ballast cleaning machine has proved to be very successful in practice.

Now, the object of the present invention is to provide a mobile machine formation of the type described at the beginning by means of which the various track maintenance machines in operation at one and the same time and capable of travelling independently of one another can be better and more accurately co-ordinated with one another.

According to the invention, this object is achieved in that, in the mobile machine formation described at the beginning, a fixed, common reference line designed to be set up section by section alongside the track is associated with the various track maintenance machines and at least one tool and/or one pickup element of each track maintenance machine is connected to a probe designed to slide along the reference line, the length of this reference line corresponding to at least twice the overall length of all the track maintenance machines arranged one behind the other longitudinally of the track. A travelling machine installation constructed in accordance with the invention is particularly simple and yet robust in its construction.On the other hand, it affords the particular advantage that, despite the successive operation of the various track maintenance machines, there is no danger whatever of the result of their work being adversely affected by one another in any way. In addition, the accuracy with which the position of the track is improved and corrected is also increased.In particular, the combination of features according to the invention makes it possible for the first time and by surprisingly simple means to co-ordinate the units and tools associated with the various machines capable of travelling independently of one another with one another in such a way that, despite the different types of work done, the track lies exactly in the required position, particularly over long sections of track, after the last track maintenance machine has completed its work, even in cases where the ballast bed has been completely replaced by the ballast cleaning machine.

One particularly preferred embodiment of the invention is characterised in that at least one tool and/or pickup element of a track maintenance machine capable of travelling in steps along the track, for example a track tamping and levelling machine, and of a track maintenance machine travelling continuously (non-stop) independently of that machine, for example a ballast cleaning machine, is connected to a probe designed to slide along the common reference line.In this way, it is possible for the first time for a track maintenance machine travelling in steps and a track maintenance machine travelling continuously (non-stop) to be guided by a common reference line so that, even with different track maintenance machines of this type, it is possible to obtain a high degree of operational synchronism in their technology by very simple means and, at the same time, to prevent any mutual interference.

In one particularly advantageous embodiment of the invention, the tools and/or pickup elements of a ballast cleaning machine equipped with clearing and, optionally, track lifting and levelling tools and arranged as the first machine in the working direction; a following track tamping and levelling machine equipped with lifting and lining tools and travelling in steps; and of a following stabilising machine travelling continuously (nonstop) and equipped with vibrating tools designed to grip the track are each connected to probes designed -- preferably identically - to slide along the common reference line.With the construction according to the invention, these various track maintenance machines joined together to form more or less the basic arrangement of a so-called mechanised maintenance train provide for a considerable improvement both in accuracy and also in the absence of mutual operational interference by comparison with the hitherto used arrangement working without a common reference line.

In another advantageous embodiment of the invention, the tools and/or pickup elements of a track tamping and levelling machine which is equipped with a tamping unit and lifting tools displaceable in the working direction and which is arranged as the first machine in the working direction; of a ballast cleaning machine connected to that machine and equipped with a clearing tool; of another, following track tamping and levelling machine equipped with lifting and lining tools and of a following stabilising machine equipped with vibrating tools are each connected to probes designed -- preferably identically - to slide along the common reference line.This special construction and arrangement, particularly in conjunction with the track tamping and levelling machine coupled to the ballast cleaning machine, enables the mobile machine formation to be used for working on tracks where the ballast conditions are difficult, for example tracks supported by shallow ballast beds. The accuracy obtainable with this mobile machine formation may be achieved with virtually any required ballast bed in the course of a track levelling operation carried out independently of the ballast cleaning operation. In other words, it is also possible accurately to establish shallow-bedded sections of track in a single operation from cleaning to stabilisation without any predetermined limit values being exceeded or damaging track deformation occurring in the course of the necessary track lifting operations.

One particularly simple and robust embodiment of the invention is characterised in that the common reference line is formed by a straight reference wire designed to be stretched out between fixing or marking posts arranged alongside the track and in that, for setting up and dismantling this reference wire in sections, each marking post is provided at its uppermost part where it receives and holds the wire with a guide member for the free passage of the probes formed by rollers, each guide member being mounted for lateral and vertical displacement on guides. An arrangement such as this is particularly suitable for heavy-duty track work, because the mechanical reference line formed by a stretched wire, although it could equally well be formed by a rollable steel tape, satisfies every requirement.In practice, the length of the intervals separating the marking posts from one another is best selected in such a way that it does not exceed the length of the wire reference system necessary even in the known individual machines, in order in particular to avoid significant, unacceptable sagging. In addition, the local setting up and dismantling of the common reference wire in sections in accordance with the invention may be carried out quickly and safely without any need for additional aids and, in particular, provides for the free and accurate passage of the individual probes.

The one-piece construction according to the invention of the common reference wire, which is designed to be fixed at its ends to reeling or tensioning mechanisms preferably associated with each marking post in both directions of the track, is particularly appropriate and advantageous, for example for a mobile machine formation comprising only two, three or even four different track maintenance machines in which the overall length of the machine formation must not be too great.

According to another aspect of the invention, however, the common reference line may also be formed by a two-piece reference wire which is designed to be fixed at either end to reeling or tensioning mechanisms preferably associated with each marking post in both longitudinal directions of the track. This arrangement is also suitable for a mobile machine formation comprising a relatively large number of different track maintenance machines. In addition, it is possible with this construction of the reference line for the second section of track to be prepared independently of the first section and vice versa, so that the machine formation as a whole may continue working on the track without interruption.

Two examples of embodiment of the invention are described in detail in the following with reference to the accompanying drawings, wherein: Figure 1 is a diagrammatic side elevation of a mobile machine formation comprising three different track maintenance machines constructed in accordance with the invention.

Figure 2 is a diagrammatic plan view.

Figure 3 is an even more diagrammatic plan view of the machine formation as a whole extending beyond the overall length of the reference line.

Figures 4 and 5 are respectively a side elevation and front elevation on a larger scale of a marking post with the common reference wire.

Figure 6 is a highly diagrammatic plan view of another embodiment of a mobile machine formation according to the invention comprising other different types of track maintenance machines and a two-part common reference wire.

Figure 7 shows part of a marking post with the common two-part reference wire.

The travelling machine formation 1 shown in Figures 1 and 2 consists of a ballast cleaning machine 3 (arranged as the first machine in the working direction indicated by the arrow 2), a following track tamping and levelling machine 4 and a stabilising machine 5 following these two machines. The machines 3, 4 and 5, which are adapted to travel independently of one another, form a so-called mechanised maintenance train and are adapted to travel by means of standard undercarriages along a track 8 consisting of sleepers 6 and rails 7, their respective tools and/or pickup elements -- for improving or rather correcting the position of the track -- being aligned with a common straight reference wire 10 designed to be fixedly arranged or set up alongside the track 8 in sections by means of marking posts 9, as will be described in more detail hereinafter.

The ballast cleaning machine 3, which is adapted to travel continuously (non-stop) comprises a set of lifting tools 11, an endless clearing chain 1 2 which surrounds the raised track panel and which is designed for vertical and/or transverse displacement by lifting drives 13 and a following (i.e. in the working direction) set of levelling tools 1 5 designed for displacement by lifting drives 14. The clearing chain 12 is connected to a probe 1 6 which is intended to identify the required position determined by the straight reference wire 10 and which is connected by a control line to a control unit 17 provided on the machine. The control unit 1 7 is additionally connected by a control line to a preferably identical probe 1 6 connected to the levelling tool 1 5.By means of this ballast cleaning machine 3, the bedding ballast below the raised track panel is removed or taken up to a selectable predetermined depth and, optionally, transverse inclination by the clearing chain 12 in conjunction with the probe 16 sliding along the common straight reference wire 10, cleaned in the usual way in a sieve and then reintroduced into the ballast bed in uniform distribution. The bedding ballast is then moved into a position suitable for the subsequent lowering of the track panel by means of the levelling tool 1 5 designed to be controlled by the control system 1 7 in conjunction with a probe 1 6 cooperating with the common straight reference wire 1 0.

The tamping and levelling machine 4 of the mobile machine formation 1 which follows the ballast cleaning machine 3 in the working direction and which can be seen in particular in Figures 1 and 2 is designed to travel along the track in steps in the working direction (arrow 2) for tamping the ballast below the sleepers 6. For each rail 7, this machine 4 comprises a vertically displaceable tamping unit 1 8 which is equipped in particular with tamping tools designed to be moved towards and away from one another and to be vibrated, and -- preceding this tamping unit 18 - a set of lifting and lateral lining tools 21 designed to be activated by hydraulic lifting and lateral lining drives 1 9 and 20.Between the tamping unit 18 and the lifting and lining unit, there is one pickup element 22 per rail 7 which normally consists of a wheel guided for vertical displacement on the rail and on the chassis of the machine and of a pickup rod which is connected to said wheel and which extends up to an on-board straight reference wire 23 determining the required position. A probe 24 connected to the pickup element 23 is associated with the lifting and lateral lining tools 21, one probe 24 being provided for each rail 7. By means of this tamping and levelling machine 4, the track 8 consisting of rails 7 and sleepers 6 is lifted to the required level and, if necessary, laterally shifted in the usual way by means of the lifting and lateral lining tools 21 in conjunction with the on-board straight reference wire 23 and a control unit 25.A continuous comparison with the values obtained with the aid of the control system in conjunction with the onboard straight reference wire 23 may now be made by the probe 24 associated with the tools in conjunction with the common straight reference wire 10 along which the probe 24 slides over a fairly long section of the track for determining the required position. On the other hand, the track 8 may also be lifted and', if necessary, shifted into the required position solely by way of the probe 24 in conjunction with the common straight reference wire 10. By means of the tamping unit 18, the ballast below the track held in the required position by the lifting and lateral lining tools 21 may be tamped and consolidated by closing and vibrating the tamping tools and hence fixed in that position.

The stabilising machine 5 which is shown more clearly in Figure 2 and which is adapted to travel continuously (non-stop) along the track 8 independently of the track tamping and levelling machine 4 comprises two vibrator units equipped with vibrating tools 27 which are arranged one behind the other longitudinally of the track on the chassis of the machine, are mounted for vertical displacement.relative thereto and are connected to a hydraulic lowering drive 26. The vibrating tools 27 which grip the two rails 7 on both sides in the manner of pincer rollers and which, in particular, are designed to be laterally vibrated are vertically and laterally displaceable by drives and are connected to a control system 28 through a standard on-board reference system for either lowering or stabilising the track.Probes 29 are associated with the vibrating tools 27 (preferably between two pairs of vibrating tools per rail), being connected to pickup elements 30 on the one hand for determining the position of the two rails and on the other hand for determining the prescribed position as determined by the common straight reference wire 10. Each of these probes 29 is also connected to the control unit 28.The previously cleaned, levelled (with reference to the common straight reference wire 10), raised (with reference to the straight common reference wire 10 and optionally to the straight reference wire 23) and tamped track is brought by the stabilising machine 5 into a deeper position corresponding to the settlement of the track and stabilised, the probe 29 designed to slide along the common straight reference wire 10 supplying the exact values for the required position which may advantageously be compared with the respective known actual values along these sections of track.

As can clearly be seen in Figures 1 and 2, the common straight reference wire 10 is stretched over a number of marking posts 9 arranged one behind the other alongside the track in the longitudinal direction thereof. These marking posts 9 are designed to be driven in laterally adjacent the track, preferably into the subgrade, and are arranged at intervals apart from one another which are at least sufficiently narrow to prevent the common straight reference wire 10 from sagging. The length of the common straight reference wire 10 is at least twice the total length of all the track maintenance machines 3, 4 and 5 arranged one behind the other, as can be seen particularly clearly in Figure 3, in which the individual machines are shown even more simply and diagrammatically solely in the interests of clarity.

The marking post 9 shown on a larger scale in Figures 5 and 6 consists of a guide member 31 which receives and holds the straight reference wire 10 and which is designed for the free passage of the probes 16, 24 and 29 designed preferably identically in the form of rollers. The guide member 31 is vertically and laterally displaceable by means of guides 32 to enable the straight reference wire to be brought into the correct vertical and lateral position with the aid of the individual guide members 31 of each marking post 9. To enable the common straight reference wire 10 to be set up and dismantled in sections, reeling and tensioning mechanisms 33 and 34 are provided on each marking post 9 so that the straight reference wire may be rolled up or unrolled, tensioned and fixed at its ends in either longitudinal direction of the track.

Each marking post consists essentially of an impact-driven pile 35 to the upper end of which is fixed the guide member 31 which is approximately pointed to rectangular in shape with a groove-like depression at its upper end for accommodating the straight reference wire 10, the angle corresponding to the roller-like configuration of the probes 16, 24 and 29. It is essential for the roller to be able to pass freely over the respective guide members 31. For changing the direction of the straight reference wire, the guide element 31 is formed with a threading opening 36, a nonreturn mechanism 37 being provided for fixing the reeling and tensioning unit 33, 34 consisting of a rotatable roll.Locking devices 38 and 39 are provided on the horizontal and vertical guides 32 for fixing the guide element 31 connected to the impact-driven pile 32 in its required lateral or vertical position.

The illustration of the marking post in Figure 4 corresponds to the illustration on the far right of Figure 1 in which the front end of the straight reference wire 10 is anchored in the marking post 9. In the same way, the rear end of this common one-piece straight reference wire 10 is anchored in the marking post 9 shown on the far left of Figure 1. The other marking posts situated between these two marking posts 9 are merely there to hold and guide the common straight reference wire 10 in conjunction with the respective guide member 31.

The other embodiment of a travelling machine formation 40 which is shown in Figure 6 consists of a track tamping and levelling machine 41 arranged as the first machine in the working direction and -- following this tamping and levelling machine, but coupled thereto - a ballast cleaning machine 42, another track tamping, levelling and lining machine 43 fol!owing the two machines 41 and 42 and adapted to travel in steps and -- coupled to the machine 43 - a stabilising machine 44 adapted to travel continuously (non-stop). The track tamping and levelling machine 41 equipped with lifting tools is coupled to and adapted to travel in conjunction with the ballast cleaning machine 42 which is equipped with a clearing chain and a levelling tool in the same way as in the embodiment illustrated in Figures 1 to 5.The vertically displaceable tamping unit of the machine 41 , which is again equipped with tamping tools designed to be moved towards and away from one another and to be vibrated, is mounted on the machine chassis for displacement longitudinally of the machine to enable the ballast between the individual sleepers to be locally tamped during the common continuous (non-stop) advance of the two machines 41 and 42.

As in the embodiment shown in Figures 1 to 5, the track tamping, levelling and lining machine 43 and the stabilising machine 44 are equipped with one tamping unit per rail, a set of lifting and lateral lining tools, a set of vibrating tools and with the corresponding pickup elements. Again in the same way as in the embodiment shown in Figures 1 to 5, the tools and pickup elements of these four machines 41, 42, 43 and 44 are provided with probes 45 or alternatively such probes are associated with the lifting and lining tools and with the vibrating tools. These probes, which are again in the form of rollers, are designed to slide along and to estabiish the required position of a straight reference wire which, in this embodiment, is in two parts 46, 47.

As can be seen from Figure 7, the respective ends of this two-part straight reference wire 46, 47 are introduced into a threading opening 48 of a marking post 49 and are then stretched by a reeling and tensioning unit and fixed to the marking post substantially in the same way as in Figures 4 and 5. The marking post 49 is thus designed in the same way as the marking post described with reference to'figures 4 and 5.

Accordingly, the probes 45 associated with the machines 41, 42, 43 and 44 may change over from one end to another front end of the wire without any interruption in work. When the last probe reaches the end of the front straight reference wire 47, the rear straight reference wire 46 may be dismantled and reassembled on the next, already prepared marking post preceding the front reference wire 47.These marking posts 49 are again arranged adjacent the track 50 at intervals from one another which on average correspond to at least the length of a machine, the total length of the two-part straight reference wire 46, 47 corresponding at least to twice the total length of all the machines 41, 42, 43 and 44 arranged one behind the other By means of the mobile machine formation 40 shown in Figures 6 and 7, the track preceding the ballast cleaning machine 42 may be raised by the lifting tools of the levelling and tamping machine 41 used as the first machine and the ballast beneath the raised track tamped, so that it is possible to clean even relatively shallow ballast beds without any danger of the track being deformed by excessive lifting.All these correcting operations in conjunction with the levelling or lifting and lateral shifting of the track with the ballast bed may be monitored and adjusted with the aid of the common two-part straight reference wire 46, 47 with a view to bringing the track into the required position.

The mode of operation of the machine formation according to the invention for improving and correcting the position of a track will now be described with reference to Figures 1 to 5: Before the mobile machine formation 1 begins work in an interval between trains, the marking posts 9 required for the one-piece straight reference wire 10 may be driven into the subgrade adjacent the track 8 and vertically and laterally aligned with the aid of the guides and in accordance with the required position of the track as recorded in the track plan. The interval separating the marking posts 9 from one another best corresponds on average to at least the length of one machine.The straight reference wire 10 is then stretched from the reeling and tensioning mechanism 33, 34 of the rearmost marking post 9 (in the working direction of the machine formation 1) up to the leading marking post 9 via the guide members 31, which is done by threading the end of the wire through the threading opening 36 and attaching it to the roll of the reeling and tensioning unit 33, 34. When the individual probes 1 6, 24, 29 of the various track maintenance machines 3, 4 and 5 reach the stretched straight reference wire 10 aligned in accordance with the required position of the track 8, the probe 16; 24 29, which is in the form of a roller, particularly a double-flanged roller, is applied.Thereafter, any positional deviation of the tools 12, 1 5 and pickup elements 22, 30 connected to the probes in relation to the straight reference wire 10 is converted into a corresponding electrical signal which is relayed by the control lines to the associated control units 1 7, 25, 28. These control units are respectively connected to the hydraulic control circuits of the drives 13, 14, 19, 20, 26 activating the various units and tools 12, 15, 21, 27 and remain in action until -- through the following change in position -- no deviation from the required position is detected by the probe.In this connection, it is also possible for example for the probe 16 of the clearing chain 12 to be set up in such a way that no signal is released at a required clearing depth.

When the leading machine 3 of the machine formation 1 reaches the end of the straight reference wire 10 and the machines 4 and 5 come to a stop immediately behind one another, the entire machine formation 1 is stopped. In the meantime, the common straight reference wire 10 is released from the rear and front reeling and tensioning unit 33, 34 and, if possible in contact with the guide members 31, is displaced or tensioned in the working direction indicated by the arrow 2 until the rear end of the reference wire reaches the point immediately behind the probe 29 of the stabilising machine 5 used as the last machine. The two ends are fixed to the reeling and tensioning units 33, 34 of the marking posts 9 situated in this region and placed under tension.

Since the front marking posts 9 were aligned and levelled in accordance with the prescribed level of the track 8 during the work of the machine formation 1, the interrurption in work required for moving the common straight reference wire 10 may be kept very short.

The embodiments described in the foregoing do not limit the invention in any way because the invention lends itself to modification in many respects, particularly in regard to the individual technologies invoived in conjunction with the choice of the various track maintenance machines capable of travelling independently of one another.

On the other hand, any suitable mechanical means designed for particularly rapid setting up and dismantling may be used as the reference line. For example, it is even possible to use a relatively rigid, for example rod-like, reference line or even a guide suitable for use as a rigid wall boundary, particularly in conjunction with a guide rule or the like. In that case, the special design of the probe may also be adapted to these different reference lines. It is essential that these components should on the one hand be simple and robust as far as is possible and, on the other hand, should be suitable for obtaining a corresponding degree of accuracy and also for relatively rapid setting up and dismantling.

Claims (8)

1. A mobile machine formation for improving and, more particularly, correcting the position of a railway track, consisting of several track maintenance machines arranged one behind the other longitudinally of the track and capable of travelling independently of one another, for example a track tamping and levelling machine incorporating a tamping unit, a lifting and optionally - lining unit and a following track consolidating machine, pickup elements being associated with each of the tools of these machines for bringing the track from its actual position to the required position with the aid of a reference system, characterised in that a fixed, common reference line designed to be set up section by section alongside the track is associated with the various track maintenance machines and at least one tool and/or one pickup element of each track maintenance machine is connected to a probe designed to slide along the reference line, the length of this reference line corresponding to at least twice the overall length of all the track maintenance machines arranged one behind the other longitudinally of the track.

2. A machine formation as claimed in Claim 1, characterised in that at least one tool and/or pickup element of a track maintenance machine capable of travelling in steps along the track, for example a track tamping and levelling machine and of a track maintenance machine travelling continuously (non-stop) independently of that machine, for example a ballast cleaning machine is connected to a probe designed to slide along the common reference line.

3. A machine formation as claimed in Claim 1 or 2, characterised in that the tools and/or pickup elements of a ballast cleaning machine equipped with clearing and, optionally, track lifting and levelling tools and arranged as the first machine in the working direction; of a following track tamping and levelling machine equipped with lifting and lining tools and travelling in steps; of a following stabilising machine travelling continuously (nonstop) and equipped with vibrating tools designed to grip the track are each connected to probes designed -- preferably identically - to slide along the common reference line.

4. A machine formation as claimed in Claim 1 or 2, characterised in that the tools and/or pickup elements of a track tamping and levelling machine which is equipped with a tamping unit and lifting tools displaceable in the working direction and which is arranged as the first machine in the working direction; of a ballast cleaning machine connected to that machine and equipped with a clearing tool; and of another following track tamping and levelling machine equipped with lifting and lining tools and of a following stabilising machine equipped with vibrating tools are each connected to probes designed -- preferably identically - to slide along the common reference line.

5. A machine formation as claimed in any of Claims 1 to 4, characterised in that the common reference line is formed by a straight reference wire designed to be stretched out between fixing or marking posts arranged alongside the track and in that, for setting up and dismantling this reference wire in sections, each marking post is provided at its uppermost part where it receives and holds the wire with a guide member for the free passage of the probes (29, 45) formed by rollers, each guide member being mounted for lateral and vertical displacement on guides.

6. A machine formation as claimed in any of Claims 1 to 5, characterised in that the common reference line is formed by a straight reference wire which is designed to be fixed at its ends to reeling or tensioning mechanisms preferably associated with each marking post in both longitudinal directions of the track.

7. A machine formation as claimed in any of Claims 1 to 4, characterised in that the common reference line may be formed by a two-part reference wire which is designed to be fixed at either end to reeling or tensioning mechanisms preferably associated with each marking post in both longitudinal directions of the track.

8. A mobile railway track maintenance machine formation substantially as herein described with reference to Figures 1 to 5 or Figures 6 and 7 of the accompanying drawings.