EP0207197B1 - Method for the renewing or laying of a railway track - Google Patents

Abstract

A levelling and shifting machine and a transmitter system (1) are used, the latter being installed on a carriage parked on the track and transmitting a spreading beam in the horizontal plane for levelling and a spreading beam in the vertical plane (Fr) for shifting, these beams defining an absolute measuring base. The receivers for levelling and shifting, which are installed on a measuring carriage of the machine, are designed for self-centering relative to the line of incidence of one of the said beams or the other during each measurement. In a curve of the track (3), the vertical beam (Fr) defines a cord of this curve, and the set position of the receiver defines the current value of the pitch of the curve (fm0, fm1 etc). A computer calculates the desired value of the pitch (f0, f1 etc.) and the variation (y0, Y1 etc.) between the two values, the latter variation determining the shifting correction. The measuring interval (G') covered by the machine without a change in the position of the transmitter (1) is selected greater than the length (G) of the cord, and the initial measuring point (A0) is selected on the secant passing through the cord beyond the point of intersection of the beam (Fr) and the track (3), so that the sum of the maximum pitches towards one side and the other is compatible with the travel of the receiver on its measuring carriage.

Description

The invention relates to a method according to the preamble of claim 1.

A machine in the form of a tamper-grader-ripper by means of which this process can be carried out is known from European patent No. 90,098 of the applicant. The transmitter which is constituted by a laser transmitter is designed so that its beam can be rotated on its axis to emit a fan or scanning beam in a vertical plane serving as a reference base for the shifting and a horizontal beam serving as a base. of reference for leveling. The two receivers automatically adjust to the vertical and respectively horizontal beam. This machine advances step by step, from sleepers to sleepers, and at each stop we proceed to leveling then, after having turned the laser transmitter by 90 °, to the shifting. It is also possible to level every two sleepers while the shifting is carried out at each intermediate sleeper.

In curves, it is known to use as the absolute reference line the cord of a section of track which is, in the known machine, formed by a laser beam in a fan or scanning in a vertical plane. This cord extends between the emitter which is on the director rail or axis of the track and the point of intersection of the beam with the director rail or axis of the track. To perform the shift correction, we measure the deflection of this rope, we compare it with the known deflection of the desired curve, and we calculate the difference which is a measure for the lateral displacement of the rails in one or the other. meaning.

So far, the measurement interval for which the transmitter remains fixed while the machine approaches it step by step, is identical to the rope, i.e. the initial measurement in a measurement interval begins at the point of intersection of the beam with the director rail or track axis. This measurement interval corresponding to the rope is limited in length by the condition that the largest arrow must not be greater than the possibility of lateral movement of the receiver on the machine, because this receiver must adjust to the point of impact of the beam, the value of the possible lateral displacement out of the chassis of the machine being generally limited by the prohibition to enter the gauge of the parallel rail so as not to hinder traffic on this rail.

Because of these conditions, in the curves, one is forced to choose relatively short measurement intervals, therefore to frequently move the laser transmitter to define the next measurement interval, which leads to loss of time, increases the number manipulations and decreases the yield of shifting operations.

The present invention provides a method which makes it possible to widen the measurement interval, therefore the interval which can be crossed step by step by the machine without changing the place of the transmitter.

To this end, the method according to the invention is characterized by the features of claim 1.

Preferred embodiments are described in claims 2, 3 and 4.

• La figure 1 représente, schématiquement en vue latérale, l'émetteur laser avec le récepteur pour le nivellement et, en traits mixtes, le faisceau horizontal, et en pointillés le faisceau vertical.
• La figure 2 représente la même vue que la figure 1, mais en plan, avec le récepteur pour le ripage, le faisceau vertical étant dessiné en traits mixtes tandis que le faisceau horizontal est dessiné en pointillés.
• La figure 3 représente, schématiquement, le récepteur laser soit pour le ripage, soit pour le nivellement avec le faisceau laser ajusté.
• La figure 4 représente, schématiquement, une vue transversale de la voie avec les récepteurs de nivellement et de ripage.
• La figure 5 est une vue schématique en perspective illustrant le principe du dispositif avec les deux faisceaux et les deux récepteurs.
• La figure 6 représente, schématiquement, une vue de dessus, sur une section courbée de la voie, dont l'écart par rapport de la courbe théorique indiquée en traits mixtes a été exagéré pour une meilleure compréhension, et sur laquelle on a représenté plusieurs points de mesure pour illustrer le ripage.
• La figure 7 représente une vue partielle agrandie de la section courbée de la voie, selon la figure 6, à un endroit de travail.
• Les figures 8, 8a, 8b représentent des schéma-blocs du dispositif pour trois différentes méthodes de commande des corrections de voie.
• La figure 9 représente, schématiquement, une coupe transversale de la voie au niveau du récepteur pour le ripage, montrant le système de calcul de flèche, et au dessous, le trajet parcouru par ce récepteur sur son support pendant les mesures aux différents points de mesure.

In the following, the invention is explained in more detail using the drawings showing, schematically, an embodiment of the device and preferred details of the device.

• Figure 1 shows, schematically in side view, the laser transmitter with the receiver for leveling and, in phantom, the horizontal beam, and in dotted lines the vertical beam.
• Figure 2 shows the same view as Figure 1, but in plan, with the receiver for shifting, the vertical beam being drawn in dashed lines while the horizontal beam is drawn in dotted lines.
• FIG. 3 schematically represents the laser receiver either for shifting or for leveling with the adjusted laser beam.
• FIG. 4 schematically represents a transverse view of the track with the leveling and shifting receivers.
• Figure 5 is a schematic perspective view illustrating the principle of the device with the two beams and the two receivers.
• FIG. 6 schematically represents a top view, on a curved section of the track, the deviation from the theoretical curve indicated in phantom has been exaggerated for better understanding, and on which several points have been represented to illustrate the shifting.
• Figure 7 shows an enlarged partial view of the curved section of the track, according to Figure 6, at a working place.
• Figures 8, 8a, 8b show block diagrams of the device for three different methods of controlling channel corrections.
• Figure 9 shows, schematically, a cross section of the track at the level of the receiver for shifting, showing the deflection calculation system, and below, the path traveled by this receiver on its support during the measurements at the different measurement points .

The operating principle of a machine making it possible to carry out the process according to the invention will firstly be described by means of FIGS. 1 to 5 for its application to the straight sections of the rails, with a view to explaining the shifting and leveling. Such a machine is moreover described in patent EP No. 90,098. According to this principle, a single laser transmitter 1 is therefore provided, placed in front of a leveling and ripping machine on a railway track, advancing along the arrow ( Fig. 1) and shown diagrammatically in the drawings by a main frame 2. This emitter 1 is suitable for emitting a fan-shaped or directed-scanning beam either horizontally for leveling (beam Fn), and after a rotation of 90 ° or vertically for shifting (beam Fr), a leveling receiver Rn and a shifting receiver Rr being both mounted on the machine, i.e. - say on a front measuring carriage (not shown) of the machine.

In Figure 1 showing a side view of the leveling control device is illustrated by line 3 the old way which must be corrected, the faults of this way were naturally very exaggerated for the understanding of the figure, in dotted lines is illustrated the portion of this old channel which has just been corrected, line 4 represents the new corrected channel and the line in phantom 4 'represents the desired channel which is defined by the axis of the laser which is adjusted, at the start of work, parallel to this desired path.

The device comprises a laser transmitter 1, emitting a horizontal beam Fn and which is mounted on a carriage 5 stationary in a fixed manner, at a location chosen on the old track 3, in front of the machine which is, in the case considered, a tamper-grader-ripper symbolized by the chassis 2 and which will be hereinafter simply designated by machine. This machine is equipped with a known relative measurement base, formed by the points A, B, C on the track, which are defined in a known way, for example by feelers belonging to measuring carriages rolling on the tracks. independent of the bogies of the machine, and suspended below the main chassis 2 of the latter. Point C defined by the rear measuring carriage is on track 4 already corrected. Point A, the position of which in FIG. 1 has been exaggerated, is on the track not yet corrected, this is why the chassis 2 is tilted forward. Point 8 represents the working point which is therefore located near the working elements used to position the track and which are constituted, in the known manner, by shifting and leveling clamps. In Figure 1, point B has just been corrected, as point C is also corrected.

At the height of point A is mounted on the front measuring carriage a laser receiver for leveling Rn which can be adjusted vertically with respect to the chassis of the carriage by means of an adjustment motor Mn. A reference line Ln serves as a relative measurement base for leveling. In the example considered, an element which carries the front end AL of this reference line Ln is fixed to the receiver Rn. This end AL is located above point A. In the present case, this reference line Ln is assumed to be produced by a wire stretched over the measuring carriages. This wire is fixed at point CL situated at the height of point C and controls by its position in a well-known manner, via a control device, the position of the leveling clamps, at point BL, situated at the height of point B .

The laser receiver for leveling Rn, like the laser receiver for shifting Rr which will be discussed below, consists of four photoelectric cells C1 to C4, shown in FIG. 3, and it is designed in such a way that it can be moved to the desired position by means of the adjustment motor Mn as a function of the line of impact of the horizontal laser beam Fn on the cells, the adjustment being carried out as soon as the beam is exactly between the two central cells C2 and C3.

In the case shown in FIG. 1, the adjustment has already been made in such a way that the reference line Ln which had, before correction, the position represented by the line L'n now has the correct position parallel to the axis of the laser. This means that the point AL has moved vertically upwards by the distance x _A , which corresponds to the height by which the track should be lifted at point A, and that the point BL has been corrected vertically by the distance x _B , which defines at the working point the point Bx located exactly on the theoretical line 4 'and on which the track 3 was lifted from the leveling correction ABn by the clamps, BC therefore represents the section of the track corrected while AB represents the uncorrected section.

Of course, this reference line Ln could be formed by any other mechanical means or not, for example a light ray, and the measuring carriages defining the points A and C are not necessarily located below the chassis 2 but can be found on small auxiliary carriages which would roll at a fixed distance at the front, respectively at the rear of the chassis 2.

In FIG. 2, a top view of the shift control device working with a vertical laser beam Fr has been shown in a manner similar to FIG. 1. The shift receiver Rr, installed like the receiver Rn, on the carriage front measurement is adjustable relative to this carriage on a transverse guide according to the vertical beam Fr by means of a motor M. A reference line Lr serves as a relative measurement base for the shifting and is, in the example considered and for the shifts carried out on the rectilinear channels linked to the receiver Rr. The position of the reference line Lr already corrected is shown in FIG. 2 and in dashed lines the reference line L'r to l 'state not corrected. In this view, position A of the reference point includes the two points AG on the left rail and AD on the right rail. At the height of these points AG, AD, the reference line Lr has moved transversely from the gap y _A and at the height of the point B of the gap y _B , which defines the desired position By of the axis of the track which is displaced from the shift correction ΔBr by the controlled clamps.

The pliers for the correction of the horizontal and vertical planes at point B of the machine, are actuated by positioning motors for leveling and shifting, controlled according to the deviations x _B , respectively _YB determined by the bases of relative measurements as shown in Figures 1 and 2.

According to a variant, the reference lines Ln and Lr forming the relative measurement base can also be arranged on the measurement carriages in a fixed manner and therefore independently of the receivers Rn and Rr, for example at the height of the central axis longitudinal of the front (point A) and rear (point C) measuring carriages or at the level of the guide rail. In this case, the deviations x _B , respectively _YB which determine the corrections of the channel are determined, from the deviations x _A and y _A , by the ratios _{XA / XB} and y _A / y _e which depend only on the known distances ÂC and ÂB. These deviations x _A and y _A are given by the position of the receivers Rn and Rr on the basis of measurement relative to point A.

FIG. 4 schematically represents a section of the track and of the front measuring carriage at the level of the leveling receivers Rn and of shifting Rr showing their relative position, and in this precise case it has been assumed that the shifting receiver Rr is located on the central axis of the track while the leveling receiver Rn is located on the director rail which is generally the lowest track in a curve.

In Figure 5 there is shown simultaneously, in perspective, the two systems and we see the horizontal beam Fn and vertical Fr and the two leveling receivers Rn which can move vertically and shifting Rr which can move horizontally. The laser transmitter 1 is located on the axis of the track.

Figure 6 shows the shifting system in a curved section of channel 3 before the correction and, in phantom, the theoretical curve 4 ', known, having the radius R and defining the position in which the channel 3 should be corrected. For the sake of simplification, we have shown in FIG. 6 only the director rail of the track or the central axis of the track, and we have indicated only the point A of the relative measurement base A, B, C (FIG. 2 ) by designating points A _o , A ₁ , A ₂ , A ₃ , A ₄ at the different measurement points where the machine stops. The differences between track 3 and the theoretical curve 4 'are of course largely exaggerated in FIG. 6. The transmitter 1 placed on the track in front of the machine, emits a vertical beam Fr which cuts the curve of the track and forms therefore a secant.

Up to now, according to the conventional method, for the shifting in a curve the rope was chosen as the measurement interval in which the machine moves step by step towards the transmitter without having to change the position of the latter, and the measurement initial was carried out at the intersection of the beam with the guide rail or track axis, in this way there were only the arrows of the rope located on the same side of the rail. The maximum rope was of course limited by the condition that the maximum deflection did not exceed the possible travel of the receiver on the machine.

According to the invention, as shown in FIG. 6, a larger measurement interval G ′ is chosen, which exceeds the chord beyond the point of intersection of the beam with the director rail or axis of the track, up to point A _o which represents, in the example chosen, the place of initial measurement and correction. In FIG. 6, the reference values of the arrows f _o , fl, ... f4 (distance between the theoretical curve 4 ′ and the beam Fr) have been indicated, which are calculated by a calculator UC (FIG. 8), the values arrows fm _o , fm _l , ... fm _{4 '} (distance between the guide rail or axis of the current track and Fr) which are measured, as well as the deviations y _o , y ₁ , ... y4, defined by the differences ^fm o - fo = ^y o, fm _l - f _I = y ₁ etc.

The maximum measurement interval G 'must of course be chosen in such a way that the sum of the maximum left and right arrows which are, in the example considered, the arrows fm _o + fm ₄ , is compatible with the travel of the receiver Rr which always adjusts to the beam Fr.

In practice, if you are on a section of track that does not have too much curvature, you can position the carriage 5 carrying the laser transmitter 1 at a distance of approximately 350 to 400 meters from the machine, therefore larger than so far, and once it has advanced during work too close to the transmitter, the carriage 5 is again moved a distance of about 350 to 400 meters from the machine.

At the start of work, in the measurement interval G ', the machine with the shifting receiver Rr is therefore at point A _o . More precisely, it is the front measuring carriage which is at point A _o . In this initial position, either the current value of the arrow fm _o and therefore the difference fm _o - f _o = y _o are known from the last measurement in the previous measurement interval and can be used to adjust the beam Fr of the laser; or, if the repair begins, the difference y _o is measured directly as the difference from the current position of the track and its desired position, defined, for example by a fixed mark or stake.

During work, the machine follows the curve of track 3 and arrives successively after a distance traveled S1, S2, S3, S4 etc, at points A _{1 '} A ₂ , A ₃ , A ₄ etc, while the shift receiver Rr follows the vertical beam Fr of the laser and therefore always moves automatically on its carriage to the point of impact with the beam Fr. This position of the receiver each time determines the current value of the arrow fm ₁ , fm ₂ , etc.

As the machine advances, at each measurement point A ₁ , A ₂ , etc., the set value of the arrow f _l , f ₂ , etc. which corresponds to the theoretical curve 4 ′ is calculated . For this, we use, as is still explained in relation to FIG. 8, a deflection calculator UC and a unit for measuring the distance traveled UM. The calculator UC calculates the setpoint value of the deflection in a known manner for the curves and all the connection curves, as a function of the geometric data, such as the radius R of the curve, the length G 'of the interval of chosen measurement, data for the variable radius of a connection curve which includes the length L of this curve, etc., and of the path traveled S, and compares it with the measured arrow, therefore the current value of this arrow. From the difference of the two values are calculated the corresponding deviations y ₁ , y ₂ etc.

Of course, if the difference fm - f gives a positive difference y, the movement of the rails takes place in the direction of the beam Fr, as is the case at points A _o , A ₁ A ₂ , A ₄ . If the difference is negative there, the rails are moved in the other direction, as is the case in point A ₃ .

At point A ₂ , in the example shown in FIG. 6, the setpoint value of the arrow f ₂ is zero, because the receiver is precisely at the point of intersection between the theoretical curve 4 'and the beam Fr. The current value of the arrow fm ₂ is equal to the deviation y _z .

To carry out the shifting in a curve, the arrow f _B of the relative measurement base must also be taken into account, as illustrated diagrammatically in FIG. 7 for a working position of the machine. The relative measurement base was indicated with point A (on track 3 not corrected), working point B and point C (on track 4 corrected), the reference line L'r before and Lr after correction, the receiver Rr centered on the beam Fr, which determines the current deflection fm of the absolute measurement base, as well as the difference fm - f = - y _A (f is the reference value of the deflection). The arrow f _B is the distance between the theoretical curve and the reference line forming a chord of this curve. In FIG. 7, the theoretical curve 4 "has been indicated with respect to the relative measurement base with the reference line L'r not yet corrected; the arrow f _B shown therefore relates to this theoretical curve.

The value of this arrow f _B is always known; it is constant in a curve with constant radius, and variable in a connection curve and calculated by a UR computer (Figure 8) as a function of the path traveled.

The procedure for correction of shifting is described in detail by means of FIG. 7 and of FIG. 8 which shows the block diagram of control and command in a curve.

The arrows calculator UC in the absolute measurement base is arranged to calculate the setpoint values of the arrows f at each working place and to generate at its output a signal corresponding to the difference y _A at point A or y _B at point B. For this, we first introduce, before the start of work in a measurement interval G ', the following data: Radius R of the curve of the concerned track, respectively the data for the variable radius of a curve connection; the initial deviation y _o at the point A _o measured in the track, for example, with respect to a fixed mark or stake, and the length of the interval G '.

During the advance of the machine, the variable data are introduced: the path traveled S, measured by a unit of measurement UM; the current value of the deflection fm measured by the receiver Rr as well as the angle of superelevation measured in a known manner by a pendulum Pe. Indeed, the channels to be adjusted are always subject to slope faults and, therefore, it is essential to correct the difference y _A , _YB respectively, as a function of the superelevation at the measurement points. This is done using a Pe pendulum, installed on the relative measurement base.

To carry out a correct shifting at point B, there are two main methods using a reference line Lr either movable or stationary on the machine.

According to the first method, there is provided, as illustrated in FIG. 7, a reference line Lr adjustable independently of the position of the receiver Rr transversely by a motor Mf (FIGS. 8 and 9). In this case at the output of the calculator UC, the difference y _A appears at point A corresponding to the difference fm - f _o , corrected if necessary by a correction depending on the angle a. This difference _YA controls the motor Mf which moves the reference line Lr to point A of this difference y _A. This corresponds to a gap y _B at the working point B, where a stop, or a reference element, is moved with the reference line Lr defining the desired position or set position of the clamps which correct the rails.

In addition, the computer UR calculates the deflection f _B of the relative measurement base from data S and R, respectively L and from the other data for the variable radius of a connection curve. The calculator UR emits an output signal corresponding to this arrow f _B which controls a second motor Mb (FIG. 8). This motor corrects the position of the abovementioned abutment with respect to the reference line Lr by a distance equal to f _B , such that the abutment is now exactly on the theoretical curve 4 '.

Now the clamps which engage the rails are moved from the shift correction AB by a hydraulic drive engaged until the track is at the set position defined by the stop, therefore on the theoretical line 4 '. As shown in FIG. 7, the value AB is equal to the addition of the deviations y _B and yf _B , yf _B representing the distance between the current position of the uncorrected channel 3 and the uncorrected reference line L'r.

According to the other shifting method (FIG. 8a), we work with a stationary reference line Lr, the motor Mf is eliminated, and the computer UC calculates the difference y _B at point B and sends an output signal corresponding to this difference y _B to the motor Mb which also receives the signal corresponding to the arrow f _B calculated by the computer UR. This motor Mb is therefore controlled by the two signals y _B and f _B and causes the stop of this distance y _B and f _{B to move} in the set position.

As a variant, (FIG. 8b), the output signal _YB of the computer UC can be introduced into the computer UR which directly calculates the total displacement y _B + f _B and gives a signal corresponding to the motor Mb.

According to another variant, it is also possible for the calculator UC to send a signal corresponding to the difference y _A to the calculator UR which transforms it into a signal corresponding to the difference y _B at point B. In this case, the calculator UC must not emit a signal y _B.

As an alternative, the calculator UR gives a signal corresponding to f _B to the calculator UC which emits a signal corresponding to the sum y _B + f _B as a control signal to the motor Mb.

In all the cases described above, to carry out the shifting, the hydraulic drive of the clamps which grip the rails is controlled by a signal corresponding to the shifting correction ΔB = y _B + yf _B (FIG. 7) so that the rails are shifted in the setpoint position which is defined by the stop or the reference element in the relative measurement base. The hydraulic drive of the grippers is therefore indirectly controlled by the UC and UR computers.

Alternatively, it is also possible to proceed in the following manner: a position detector is provided which at all times determines the current position of the clamps and therefore of channel 3 and sends a signal relating thereto for the computer UR. This UR computer calculates not only the arrow f _B but also from this arrow f _B and from the signal which represents the current position of channel 3, directly the difference yf _B (FIG. 7). In this case, by renouncing the motor Mb, the clamps are controlled directly by means of the output signal y _B of the calculator UC and the output signal yf _B of the calculator UR, or else from the signal corresponding to the sum y _B + yf _B of the UR computer without the need to use a stop or a movable reference element which determines the set position. The block diagrams corresponding to this way of controlling the hydraulic drive of the grippers would correspond to Figures 8, 8a and 8b with the only modifications that the motor Mb shown would represent the hydraulic drive of the grippers and that the output signal corresponding to the arrow f should be replaced by the signal corresponding to the deviation yf _B.

The unit EC shown in FIG. 8, 8a and 8b, which receives the signal y _A , will be explained during the description of FIG. 10.

FIG. 9 illustrates a sectional view of the track and the front measuring carriage - seen from the front - at point A _o (FIG. 6) and, in dashed lines, at point A ₃ , and this before correction. At the starting point A _o for the shifting of a track sector, in the measurement interval G ', the shifting receiver Rr is moved to the front end of the relative measurement base on the support 6 of the carriage measurement, at a distance from the central axis La of the measuring device (therefore the central longitudinal axis of the measuring carriages) equal to the value of the current deflection fm _o , for example by means of a screw, driven by the motor Mr. The vertical beam Fr is centered at the receiver Rr. The front point AL _O of the reference line is moved on the support 7 of the measuring carriage by the motor Mf of the difference y, therefore of the difference fm _o - f _o in the center of the theoretical path 4 ' _o .

At measurement point A, the receiver Rr has moved on the support 6 by the value of the arrow measured fm ₃ smaller than the theoretical arrow f ₃ , making it possible to calculate the difference y ₃ . In this case, the front end AL ₃ of the relative base is moved on the support 7 of the measuring carriage at the center of the theoretical track 4 ' ₃ ,

Below FIG. 9, the path of the receiver Rr has been shown on its support 6 during the measurements at points A _o and A ₄ . In principle, the maximum width that the transverse support 6 can occupy is generally 3 meters.

The invention is, of course, not limited to the embodiments described and many other variants could be envisaged. The fact that the measurement interval G 'can be chosen to be wider than hitherto also means that the distances between the fixed marks or stakes installed along the track and defining the theoretical route can be greater and therefore that the number of these benchmarks is reduced.

Claims (4)

1. A process for reparing or laying a railroad track using a levelling and shifting machine (2) and, on the one hand, a system (1) transmitting electromagnetic beams, in particular laser beams, installed on a carriage (5) parked on the track (3) or the layout in front of the machine (2) and designed to transmit a first fan-shaped or sweeping beam (Fn) in a horizontal plane for levelling and a second fan-shaped or sweeping beam (Fr) in a vertical plane for shifting, and, on the other hand, installed on a measuring carriage of the machine (2), two receivers (Rn, Rr) for the horizontal beam (Fn) and for the vertical beam (Fr), these receivers (Rn, Rr) being designed for automatic self-centering relative to the line of incidence of one of the said beams or the other during each measurement, in a curve of the track the vertical beam (Fr) defines a cord (G) of this curve, the adjusted position of the shifting receiver (Rr) defining the actual value of the pitch (fm_1' fm₂,..) of the curve, a computer (UC) calcuting at each measuring point (A1, A2,...), in a given measuring interval, the desired value of the pitch (f1, f2,...) and the distance (y₁, Y2... between the two values, this distance determining the shifting correction (AB) to be made, characterized in that the measuring interval (G') travelled by the machine (2) without a change in the position of the transmitter (1) is selected to be greater than the said cord (G), and that the initial measuring point (A_o) is selected on the secant passing through the said cord beyond the point of intersection between the said beam (Fr) and the track (3) at a distance from the point of intersection, this interval being selected so that the total of the maximum pitches towards one side and the other is compatible with the travel of the receiver (Rr) on its measuring carriage.

2. The process as claimed in claim 1, using with the machine a reference line (Lr) of a relative measuring base (A, B, C) which is adjusted automatically as a function of the said distance (yA) at the front point of the said relative measuring base, the said distance being calculated by the said computer (UC) characterized in that the track shifting is controlled, on the one hand, as a function of the adjusted position of this reference line (Lr) at the working point (B) and, on the other hand, as a function of the value of the pitch (fB) of the relative measuring base calculated by a second computer (UR).

3. The process as claimed in claim 1, using with the machine a reference line (Lr) of a relative measuring base (A, B, C), characterized in that the said reference line remains stationary on the machine, and that the track shifting is controlled, on the one hand, as a function of the distance (yB) between the actual position of the reference line (Lr) at the working point (B) and the desired position, this distance (yB) being determined on the basis of the said distance (yA) calculated by the said computer (UC), and, on the other hand, as a function of the pitch (fB) of the relative measuring base calculated by another computer (UR).

4. The process as claimed in claim 3, using in the relative measuring base (A, B, C) a displaceable stop defining the desired position of the track to be corrected, characterized in that the said stop is actuated by a motor (Mb), and that this motor (Mb) is controlled by the two signals corresponding to yB and to fB or by a single signal corresponding to the total yB + fB calculated in one of the computers (UR or UC).

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