EP3781744B1 - Method for fixing a rail of a rail track with thermal conditioning of a rail portion, and associated rail machine - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to the installation of a rail of a railway track, and more particularly to a thermal conditioning operation of a portion of the rail before its installation. It relates both to a railway machine allowing this thermal conditioning operation and to an immobilization process including this operation. It aims at both the installation of a new rail on a pre-existing track, the installation of a new rail on a new track, and a maintenance operation on a pre-existing rail, which includes a removal operation followed by an operation deposit. The railway machine can be an autonomous machine, a renewal train or a laying train.

STATE OF PRIOR ART

Railway rails are subject to significant temperature variations depending on the seasons and weather conditions. The rails tend to elongate and expand under the effect of a rise in temperature, and, conversely, to contract under the effect of a drop in temperature.

Nowadays, the rails are laid continuously end-to-end welded and thus fixed to the sleepers, so that the rails cannot vary in length due to temperature variations. Under the effect of an increase in the ambient temperature beyond the installation temperature, the rails, unable to expand, undergo a compressive force tending to push the track out of its way. Conversely, under the effect of a drop in temperature below the installation temperature, the rails, unable to contract, are subject to a tensile force tending to pull the track out of its path.

To minimize the impact of temperature variations, we seek to immobilize the rails on the track at a predetermined temperature called "neutral", the value of which differs depending on the climatic regions, and which can correspond for example to an average or median temperature of the place of installation, observed over a long period, if applicable of several years. We are thus assured that the range of variation of stresses inside the rail, and the variation of forces on the track, will be minimized.

In the document EP 0 467 833 A train of works is illustrated comprising an induction heating station for a previously lifted rail, and a zone for immobilizing the rail on the track sleepers with a view to its subsequent fixing using fasteners. Induction heating generates, in a portion of the rail passing through a heating zone of the heating station, an induced current which raises the temperature of the portion of the rail by Joule effect. But the circulation of electrons in the rail is not uniform and we observe a skin effect which is all the more sensitive as the induction frequency increases. This results in a highly inhomogeneous temperature distribution within the rail at the exit from the heating zone. The rail immobilization zone is located at a distance from the heating station, so that the temperature has time to homogenize in the rail, in other words so that the difference between the surface temperature and the temperature in the heart of the rail is lower than a predetermined threshold, the objective being that at the level of the immobilization zone, the rail has reached a homogeneous temperature equal to the predetermined neutral temperature of the location. For example, for a work train traveling at 6 meters per minute, a distance of 17 meters is planned between the exit of the heating station and the rail immobilization zone, which corresponds to a homogenization time of 170 seconds.

Other heating methods can be implemented. It has thus been proposed to expose the rail to infrared radiation. However, we note that infrared radiation penetrates little into the material, and only generates superficial heating, with a skin effect of around 100 nm. Other forms of heating, in particular by spraying water or by exposure to the flame of a burner, have been proposed, but also result in heating limited to the surface of the rail.

Starting from the postulate that it is necessary to wait for the temperature in the rail to homogenize to the neutralization temperature before immobilizing the rail on the sleepers, the idea of the need to provide a homogenization time, and therefore a significant distance between the main heating station and the zone of immobilization of a railway work machine, has established itself in the state of the art.

This provision is, however, not without its drawbacks. It firstly impacts the size of the railway machine, which is provided with means for moving the rail between the heating station and the immobilization zone. Furthermore, measures must be taken to limit and control thermal losses in the space separating the heating zone from the immobilization zone, in order to limit energy consumption and ensure that at the level of the heating zone immobilization, the homogeneous temperature reached is indeed the recorded temperature known as “neutral”. Finally, operational difficulties appear each time the railway machine has to stop unexpectedly, since the portion of rail located between the heating station and the immobilization zone, after a certain time, is no longer at the desired temperature, and that a specific procedure must be implemented each time it is restarted. This is also what led, in the document WO2017/017600A1 , to propose interposing, between the heating device and the immobilization zone, an intermediate section of thermal insulation, or additional thermal treatment aimed at compensating the thermal losses between the heating station and the immobilization zone.

When it is necessary to cool the rail before immobilization, the cooling methods also involve cooling the surface of the rail, therefore non-homogeneous cooling of the rail, with similar difficulties.

To solve these problems, it would theoretically be possible to use technologies allowing uniform heating of the rail, for example by passing a direct current through the rail. But such technology proves difficult to implement in practice.

STATEMENT OF THE INVENTION

The invention aims to remedy the drawbacks of the state of the art and to simplify the immobilization of a rail at a so-called “neutral” set temperature.

• on déplace la machine ferroviaire dans une direction de travail, de manière qu'à chaque instant une portion du rail, non fixée à une traverse de la voie ferrée, traverse une zone de conditionnement thermique d'un dispositif de conditionnement thermique de la machine ferroviaire ;
• on modifie une température d'une région superficielle de la portion du rail traversant la zone de conditionnement thermique à l'aide du dispositif de conditionnement thermique, en générant une distribution de température non homogène dans la portion de rail ; et
• on immobilise la portion du rail sur une traverse de la voie ferrée, après modification de la température de la région superficielle de la portion du rail, mais sans attendre que la distribution de la température dans la portion du rail soit homogénéisée.

To do this, according to a first aspect of the invention, a method of immobilizing a rail of a railway using a railway machine is proposed, according to which:

• the railway machine is moved in a working direction, so that at each instant a portion of the rail, not fixed to a sleeper of the railway track, crosses a thermal conditioning zone of a thermal conditioning device of the railway machine ;
• a temperature of a surface region of the portion of the rail passing through the thermal conditioning zone is modified using the thermal conditioning device, generating a non-homogeneous temperature distribution in the portion of the rail; And
• the portion of the rail is immobilized on a sleeper of the railway track, after modification of the temperature of the surface region of the portion of the rail, but without waiting for the distribution of the temperature in the portion of the rail to be homogenized.

• la conservation de la température moyenne du rail pendant l'homogénéisation ;
• la proportionnalité entre l'allongement du rail et la contrainte moyenne dans la section transversale observée.

The inventors in fact suspected, then verified by calculation and experimental tests, that it was not necessary to wait for the temperature to homogenize in the rail to obtain the desired effect, namely an extension of the rail, or a length of the portion of rail being installed, corresponding to the elongation and length observed at neutral temperature. The theoretical study is based on two results:

• maintaining the average temperature of the rail during homogenization;
• the proportionality between the elongation of the rail and the average stress in the observed cross section.

If we designate by C the thermal capacity of the steel (in J/kg/K), by ρ the density of the steel (in kg/m ³ ), and by V the volume of rail considered (in m ³ ), the thermal energy present in the rail at the outlet of the thermal conditioning zone is, by definition: $$E_0={\displaystyle {\iiint }_V\mathrm{VS}.T_0.\rho .\mathit{dv}}=\mathrm{VS}.\rho .{\displaystyle {\iiint }_V{T}_0.\mathit{dv}}$$

We can define an average temperature of the rail T _{0 avg} such that: $$T_{0\mathit{mev}}=\frac{1}{V}{\displaystyle {\iiint }_V{T}_0.\mathit{dv}}$$

It deduces: $$E_0=\mathrm{VS}.\rho .V.T_{0\mathit{mev}}$$

If we designate by T ₁ = T _{1 avg} the uniform temperature of the rail obtained after homogenization, and by E ₁ the thermal energy of the rail after uniformization, we obtain: $$E_1=\mathrm{VS}.\rho .V.T_{\mathrm{1}\mathit{mev}}$$

However, if we observe that the time constant for homogenization of the temperature (2 to 3 minutes) is very small compared to the time constant for cooling the rail as a whole (100 to 200 minutes), we can consider that the transformation corresponding to homogenization is adiabatic, so that there is conservation of thermal energy. Since then : $$E_0=E_1$$

We therefore have, after simplification: $$T_{0\mathit{mev}}=T_{\mathrm{1}\mathit{mev}}$$

It has thus been established that the average temperature leaving the conditioning zone is equal to the homogenization temperature of the rail.

If we denote by S the surface of the rail section, by E the Young's modulus, and by α is the elongation coefficient of the rail, we can express the average stress in the rail section as follows: $$\sigma =\frac{1}{S}.{\displaystyle {\iint }_S\sigma \left(s\right).\mathit{ds}}=\frac{1}{S}.{\displaystyle {\iint }_{S}E.\alpha .\mathit{\Delta T}\left(s\right).\mathit{ds}}=E.\alpha .\left[\frac{1}{S}.{\displaystyle {\iint }_S\mathit{\Delta T}\left(s\right).\mathit{ds}}\right]$$

We can define a variation in the average temperature Δ T _avg in the rail section, which is equal to the average of the local temperature variations in the rail section so that: $${\mathit{\Delta T}}_{\mathit{mev}}=\frac{1}{S}.{\displaystyle {\iint }_S\mathit{\Delta T}\left(s\right).\mathit{ds}}$$

We then write the average stress as a function of the average temperature variation: $$\sigma =E.\alpha .{\mathit{\Delta T}}_{\mathit{mev}}$$

Furthermore, Hooke's law on elasticity makes it possible to relate the average stress to the relative elongation (neglecting variations in the section): $$\sigma =E.\frac{\mathit{\Delta L}}{L_0}$$

We deduce the relationship of proportionality between the relative elongation and the variation of the average temperature of the section: $$\frac{\mathrm{\Delta }L}{L_0}=\alpha .\mathrm{\Delta }{T}_{\mathit{mev}}$$

In other words, the elongation of a section of the rail is proportional to the average temperature observed in the section of the rail, but independent of the temperature distribution in the section of the rail.

In practice, the railway machine moves in the working direction at a constant speed, which can be described as nominal, for operating conditions. work data (geometry of the track, nature of the work to be carried out). As an indication, this speed is usually in the range of 100 to 1200 m/hour.

Preferably, the portion of the rail is immobilized on the crosspiece for less than 50 seconds, preferably less than 30 seconds after the portion of the rail has left the thermal conditioning zone. It is advantageous for the time which elapses between leaving the thermal conditioning zone and fixing the rail to the crosspiece to be minimal, to limit convective heat exchanges with the ambient environment.

Under certain conditions, the temperature distribution at the exit from the thermal conditioning zone can be very inhomogeneous, and remain very inhomogeneous at the time of immobilization of the rail. For example, it can be seen that at the time of immobilization of the portion of the rail there is a difference of more than 50°C between at least one point on the surface of the portion of the rail and at least one point on the soul of the rail portion.

According to one embodiment, the modification of the temperature of a surface region of the portion of the rail passing through the thermal conditioning zone is such that the average temperature of the portion of the rail at the exit from the thermal conditioning zone is equal to within +/- 5°C, and preferably to within +/-3°C, and preferably to within +/-2°C, and preferably to within +/-1°C, and preferably exactly, at a predetermined set temperature of the installation location.

By average temperature, we mean here the volume integral of the elementary temperatures in the portion of the rail: $$T_{\mathit{mev}}=\frac{1}{V}{\displaystyle {\iiint }_{V}T\left(v\right).\mathit{dv}}$$

Passage through the thermal conditioning zone is accompanied by a heat transfer equal to the quantity of heat necessary to bring the section of rail to an average temperature equal to within +/- 5°C, and preferably to +/ -3°C, and preferably within +/-2°C, and particularly preferably within +/-1°C, and preferably exactly, at a predetermined set temperature of the place of immobilization, at the exit from the thermal conditioning zone.

To the extent that the transition between the exit from the thermal conditioning zone and the immobilization zone is of short duration, we can consider that the thermal exchanges between the rail and the environment are low. Therefore, the modification of the temperature of a superficial region of the portion of the rail crossing the thermal conditioning zone results in a transfer of a quantity of heat equal to the quantity of heat necessary to bring the section of rail, in adiabatic conditions, at a homogenization temperature equal to a temperature within a predetermined tolerance interval, preferably +/-5°C, preferably +/-3°C, preferably +/-2°C , preferably +/-1°C around, and preferably exactly at, a predetermined set temperature.

In other words, the thermal conditioning zone is the place of a transfer of thermal energy which can be positive or negative, and whose value Δ E is equal to the difference between the thermal energy E _A of the front rail entry into the thermal conditioning zone and the thermal energy E _N of the rail in an ideal state at a homogeneous temperature equal to the neutral temperature T _N (or the difference between the thermal energy E _A of the rail before the entry into the thermal conditioning zone and the thermal energy Ec of the rail in a target state at a homogeneous temperature equal to a target temperature T _C equal to the neutral temperature T _N to within +/- 5°C, and preferably to +/-3°C, and preferably within +/-2°C, and particularly preferably within +/-1°C, and preferably exact). By assuming that the rail is in thermal equilibrium with its environment before entering the thermal conditioning zone, therefore at a homogeneous temperature equal to the ambient temperature T _A , we can write: $$\{\begin{array}{c}{E}_{\mathrm{NOT}}=\mathrm{VS}.\rho .V.T_{\mathrm{NOT}}\\ E_{\mathrm{HAS}}=\mathrm{VS}.\rho .V.T_{\mathrm{HAS}}\\ \mathrm{\Delta }E=E_{\mathrm{NOT}}-E_{\mathrm{HAS}}=\mathrm{VS}.\rho .V.\left(T_{\mathrm{NOT}}-T_{\mathrm{HAS}}\right)\end{array}$$

Preferably, the heat exchange device is controlled as a function of one or more control variables, including one or more of the following measured or estimated variables: a temperature of the portion of the rail at the entry into the thermal conditioning zone, a temperature of the portion of the rail at the exit from the thermal conditioning zone, a temperature of the portion of the rail in the thermal conditioning zone, a temperature of the portion of the rail at the level of the zone d immobilization, a temperature of the rail portion after the immobilization zone, an external ambient temperature, a speed of movement of the railway machine, a speed of movement of the rail relative to the thermal conditioning device, a duration of passage in the thermal conditioning zone, a difference between a set temperature and a measured temperature of the portion of the rail before thermal conditioning, a difference between a set temperature and a measured temperature of the portion of the rail after thermal conditioning, a difference between a temperature setpoint and a measured temperature of the portion of the rail during the heat supply, a difference between a setpoint temperature and a temperature of the portion of the rail at the level of the immobilization zone, a difference between a setpoint temperature and a temperature of the rail portion after the immobilization zone, an ambient humidity, or a wind speed.

• au moins une température de la portion du rail après l'apport de chaleur à l'aide d'au moins un thermomètre (par exemple un pyromètre ou un thermocouple) disposé au niveau d'une zone de sortie de la zone de conditionnement thermique ou derrière la zone de conditionnement thermique dans la direction de travail ;
• au moins une température de la portion du rail avant l'apport de chaleur à l'aide d'au moins un thermomètre (par exemple un pyromètre ou un thermocouple) disposé au niveau d'une zone d'entrée de la zone de conditionnement thermique ou devant la zone de conditionnement thermique dans la direction de travail ;
• au moins une température de la portion du rail durant l'apport de chaleur à l'aide d'au moins un thermomètre (par exemple un pyromètre ou un thermocouple) disposé à l'intérieur de la zone de conditionnement thermique ;
• au moins une température de la portion du rail après l'immobilisation, à l'aide d'au moins un thermomètre (par exemple un pyromètre ou un thermocouple) disposé au niveau de la zone d'immobilisation ou après la zone d'immobilisation dans la direction de travail.

According to one embodiment, one or more of the following temperatures are measured:

• at least one temperature of the portion of the rail after the heat supply using at least one thermometer (for example a pyrometer or a thermocouple) arranged at an exit zone of the thermal conditioning zone or behind the thermal conditioning zone in the working direction;
• at least one temperature of the portion of the rail before the heat supply using at least one thermometer (for example a pyrometer or a thermocouple) arranged at an entry zone of the thermal conditioning zone or in front of the thermal conditioning zone in the direction of work;
• at least one temperature of the portion of the rail during the heat supply using at least one thermometer (for example a pyrometer or a thermocouple) placed inside the thermal conditioning zone;
• at least one temperature of the portion of the rail after immobilization, using at least one thermometer (for example a pyrometer or a thermocouple) placed at the level of the immobilization zone or after the immobilization zone in the direction of work.

According to one embodiment, the portion of the rail crossing the thermal conditioning zone is raised relative to the railway track. Where appropriate, the railway machine can be provided with a device for positioning the portion of rail on the track, located between the thermal conditioning device and the zone for immobilizing the portion of rail on a sleeper of the track. In this hypothesis, the positioning device must preferably be compact, so that the corresponding positioning zone is short.

Alternatively, the positioning of the rail portion on the track can be done in the thermal conditioning zone.

According to another alternative embodiment, the portion of the rail crossing the thermal conditioning zone rests on a sleeper of the railway track. The immobilization of the portion of the rail on the sleeper is the operation which immediately follows the crossing of the thermal conditioning zone by the same portion of the rail.

Preferably, the temperature of a surface region of the portion of the rail passing through the thermal conditioning zone is modified, by thermal exchange with a heat source, hot or cold, in particular by thermal radiation, thermal conduction and/or convection, or by alternating electric current induced or generated in the rail portion.

• des moyens de traction aptes à déplacer la machine ferroviaire dans une direction de travail à une vitesse de fonctionnement prédéterminée de 500 m/heure,
• au moins un dispositif de conditionnement thermique comportant au moins une zone de conditionnement thermique disposée de manière qu'à chaque instant, lorsque la machine ferroviaire (4) se déplace dans la direction de travail (100) à la vitesse de fonctionnement prédéterminée, une portion du rail, non fixée à une traverse, traverse la zone de conditionnement thermique ; le dispositif de conditionnement thermique étant apte à modifier une température d'une région superficielle de la portion du rail traversant la zone de conditionnement thermique, en générant une distribution de température non homogène dans la portion de rail ;
• une zone d'immobilisation de la portion du rail sur une traverse de la voie ferrée, située au niveau d'un bogie derrière la zone de conditionnement thermique dans la direction de travail, la zone d'immobilisation étant positionnée à moins de 5 mètres de la zone de conditionnement thermique.

According to another aspect of the invention, it relates to a railway machine comprising:

• traction means capable of moving the railway machine in a working direction at a predetermined operating speed of 500 m/hour,
• at least one thermal conditioning device comprising at least one thermal conditioning zone arranged in such a way that at each instant, when the railway machine (4) moves in the working direction (100) at the predetermined operating speed, a portion of the rail, not attached to a sleeper, crosses the thermal conditioning zone; the thermal conditioning device being capable of modifying a temperature of a superficial region of the portion of the rail passing through the thermal conditioning zone, by generating a non-homogeneous temperature distribution in the rail portion;
• a zone for immobilizing the portion of the rail on a sleeper of the railway track, located at the level of a bogie behind the thermal conditioning zone in the working direction, the immobilization zone being positioned less than 5 meters from the thermal conditioning zone.

Preferably, the thermal conditioning device is able to provide to the rail portion passing through the thermal conditioning zone and/or able to extract from the rail portion passing through the thermal conditioning zone, a greater quantity of heat sufficient to increase and /or reduce the average temperature of the rail portion by at least 5°C, for a UIC60 rail, when the railway machine advances in the working direction at the predetermined operating speed.

According to one embodiment, the railway machine comprises means for modifying the temperature of a surface region of the portion of the rail passing through the thermal conditioning zone, by alternating electric current induced or conducted in the portion of rail, or by exchange thermal with a source of heat, hot or cold, in particular by thermal radiation, thermal conduction and/or convection.

BRIEF DESCRIPTION OF THE FIGURES

• la figure 1, une vue schématique d'un chantier de pose d'un rail de voie de chemin de fer, selon le procédé de l'invention ;
• la figure 2, une vue schématique de détail du chantier de la figure 1, illustrant le conditionnement thermique et la fixation d'une portion de rail suivant le procédé de l'invention ;

Other characteristics and advantages of the invention will emerge on reading the description which follows, with reference to the appended figures, which illustrate:

• there figure 1 , a schematic view of a site for laying a railway track, according to the method of the invention;
• there figure 2 , a schematic detailed view of the construction site of the figure 1 , illustrating the thermal conditioning and fixing of a portion of rail according to the method of the invention;

For greater clarity, identical or similar elements are identified by identical reference signs throughout the figures.

DETAILED DESCRIPTION OF EMBODIMENTS

On the figure 1 an overall view of a railway track renewal site 2 is illustrated, a site on which old rails 6 are removed by means of a renewal train 4 (partially shown). front sector) and old sleepers 8 and their replacement by new sleepers 10 and new rails 12, all continuously as the renewal train 4 advances at constant speed in a working direction 100. The renewal train 4 comprises wagons 16 resting on bogies 18, 20 which run on the old rails 6 in the front part of the renewal train 4 and on the new rails 12 in the rear part of the renewal train 4. Part middle of the renewal train 4 rests on tracks 22 which, in the absence of rails on track 2 in this part of the site, roll directly on the ballast 24 and the old sleepers 8 before their removal.

On a front section of the site, tools allow the old rails 6 to be separated from the sleepers 8. As they are dismantled, the old rails 6 are lifted and placed back on the ballast 24 on the sides of the track. On the next section of the site, the old sleepers 8 are exposed, which makes it possible to carry out their removal using a group of removal tools and their replacement with the new sleepers 10 using a group of installation tools. The new rails 12, which, before the passage of the renewal train 4, were placed on the ground on either side of track 2, on rollers to allow thermal expansion of the rail free of stress towards the front of the train, are lifted and positioned respecting the desired geometry of track 2, before being placed on the new sleepers 10. The immobilization of the new rails 12 is carried out by the weight of the railway machine at the level of the zone of immobilization 26, also called anchoring zone, located at the level of a bogie 20, in the rear part of the renewal train 4. In known manner, the actual fixing of the new rails 12 is carried out downstream, using 'fasteners.

In order to avoid or limit the risk of deterioration of the track under the effect of variations in climatic or weather conditions, it is planned to immobilize the new or renovated rails 12 on the sleepers by carrying these metal profiles to a set temperature, called “neutral”.

For this purpose, the section of new or renovated rail to be installed 12 is brought to a set temperature in a thermal conditioning zone 30 of a thermal conditioning device 32, the thermal conditioning zone 30 being located in front and near of the immobilization zone 26 of the rail on one or more sleepers 10, or even directly contiguous to the immobilization zone 26. If necessary, the immobilization zone 26 itself can be preceded by a positioning zone of the rail , which can be located between the thermal conditioning zone 30 and the immobilization zone 26 (in the hypothesis where the rail is lifted in the thermal conditioning zone) or upstream of the thermal conditioning zone (in the hypothesis where the rail already rests on the new sleepers 10 in the thermal conditioning zone 30 ). Alternatively, the positioning zone of the rail coincides with the immobilization zone 26 or the thermal conditioning zone 30.

When the intervention on the site takes place at a time when the ambient temperature is lower than the so-called “neutral” set temperature, the thermal conditioning includes heating of the rail, the thermal conditioning device 30 is arranged as a heating device, the thermal conditioning zone 30 then being a heating zone. This heating can be carried out by the means usually used, which have in common not to generate a homogeneous distribution of the temperature in the rail, but on the contrary to generate a significant temperature difference between certain heated zones on the surface of the rail or at proximity to the surface of the rail on the one hand, and less heated zones located at the heart of the rail. Heating can in particular be carried out by electrical induction in the rail, by sprinkling with hot water, by infrared radiation, or by exposure to a heat transfer fluid (water, air, steam, combustion gas, flame).

Conversely, when the ambient temperature is higher than the so-called "neutral" set temperature, the thermal conditioning includes cooling of the rail, the thermal conditioning device 30 is arranged as a cooling device, the thermal conditioning zone 30 then being a cooling zone. This cooling can in particular be carried out by exposure to a heat transfer fluid.

Remarkably, the immobilization zone 26 is positioned relative to the thermal conditioning device 32 in such a way that when the renewal train 4 advances in the working direction 100 at the nominal operating speed, the portion of the rail having left the thermal conditioning device 32 with a non-homogeneous temperature distribution reaches its immobilization position on the sleeper in the immobilization zone 26 before a homogenization of the temperature distribution in a cross section of the rail portion has occurred .

For example, the immobilization zone 26 is located less than five meters from the thermal conditioning zone 30, for a renewal train circulating at a nominal speed of 500 m/hour, so that a portion of the rail reaches the immobilization zone 26 less than 36 seconds after leaving the thermal conditioning zone 30.

In practice, it is advantageous to reduce as much as possible the distance between the exit of the thermal conditioning zone 30 and the immobilization zone 26, in order to simplify the restart of the renewal train 4 after a stopping period, by reducing the portion of rail whose temperature is no longer within the tolerance interval authorizing its anchoring, and located between the thermal conditioning zone 30 and the zone immobilization zone 26. It is therefore envisaged in particular that the exit from the thermal conditioning zone 30 can coincide spatially with the immobilization zone 26.

Thermometers 34 are positioned at the entrance to the thermal conditioning zone 30, inside the thermal conditioning zone 30, at the exit from the thermal conditioning zone 30, and if necessary directly near the zone immobilization 26. These thermometers 34 are connected to a control unit 36, which receives signals from other sensors 38 such as, for example: a speed sensor of the renewal train 4, a speed sensor of the rail to be treated , an ambient temperature sensor, an atmospheric pressure sensor, and/or an ambient humidity sensor. The control unit 36 is thus capable of measuring, estimating or calculating one or more of the following parameters: an average temperature of the portion of the rail to be treated before thermal conditioning, an average temperature of the portion of the rail after thermal conditioning, a temperature of the portion of the rail during thermal conditioning, a temperature of the portion of the rail after its anchoring, an external ambient temperature, a speed of movement of the renewal train 4, a speed of movement of the rail relative to the conditioning device thermal, a quantity of heat transmitted to the portion of the rail by the thermal conditioning device.

Furthermore, the control unit 36 contains in memory a set temperature which may have been entered or programmed, and is representative of the neutral temperature sought in the immobilization zone 26, which if necessary allows a determination of a difference between the set temperature and an average temperature of the portion of the rail to be treated before thermal conditioning, a difference between the set temperature and an average temperature of the portion of the rail after thermal conditioning, or a difference between the set temperature and an average temperature of the portion of the rail during conditioning thermal. In known manner, the control unit 36 is capable of modulating the power of the thermal conditioning device.

When the renewal train 4 advances in a working direction 100, the rail to be treated 12 moves, relative to the thermal conditioning device 30, in the opposite direction, and is guided so that at each moment a raised portion of the rail to be treated 12 passes through the thermal conditioning zone 30. If necessary, the positioning of the thermal conditioning device is adjusted using actuators or a positioning mechanism.

This ensures that at each instant, and depending on the progress of the renewal train 4, a portion of the rail to be treated 12 passes through the thermal conditioning zone 30 where, depending on the external conditions, it is heated or cooled by the thermal conditioning device 32, so that the average temperature in the portion of the rail leaving the thermal conditioning zone is equal to the set temperature. The control unit 36 determines by a calculation algorithm, depending on all or part of the parameters discussed previously, the thermal energy which must be transferred to the rail to be treated 12 or which must be extracted therefrom to obtain this average temperature.

As soon as it leaves the thermal conditioning zone 30, and although its temperature is very inhomogeneous, the portion of the rail 12 has reached the elongation corresponding to the elongation of a rail at a homogeneous temperature equal to the set temperature. The portion of the treated rail 12 enters immediately or almost immediately into the immobilization zone 26, where it is immobilized on a sleeper 10 of the railway track, less than 50 seconds, and preferably less than 30 seconds after the exit from the thermal conditioning zone 30. In this short period of time, the losses by convective exchange with the ambient air are negligible.

Naturally, the examples shown in the figures and discussed above are given for illustrative purposes only and are not limiting.

The method of thermal conditioning of the rails which has been described for a railway renovation with replacement of the rails, also applies to a renovation of the track with replacement of the old rails, or for a first installation, or even for a thermal treatment of interview.

What has been described for a renewal train can be transposed to an autonomous railway machine or a laying train.

Claims (10)

1. A method for immobilizing a rail (12) of a railway track (2) using a railway machine (4), in which method:

   - the railway machine (4) is moved in a working direction (100) such that, at each instant, a portion of the rail (12) that is not attached to a sleeper (8, 10) of the railway track (2) passes through a thermal conditioning zone (30) of a thermal conditioning device (32) of the railway machine (4);

   - a temperature of a surface region of the portion of the rail passing through the thermal conditioning zone (30) is modified using the thermal conditioning device (32), by generating a non-homogeneous temperature distribution in the rail portion;

   characterized in that the portion of the rail (12) is immobilized on a sleeper (10) of the railway track after the temperature of the surface region of the portion of the rail has been modified, but without waiting for the distribution of the temperature in the portion of the rail to be homogenized.
2. The immobilization method according to claim 1, characterized in that the portion of the rail (12) is immobilized on the sleeper (10) less than 50 seconds, preferably less than 30 seconds, after the portion of the rail (12) has left the thermal conditioning zone (30).
3. The immobilization method according to either of the preceding claims, characterized in that the modification of the temperature of a surface region of the portion of the rail passing through the thermal conditioning zone (30) is such that the average temperature of the rail portion at the outlet of the thermal conditioning zone (30) is equal to within +/- 5°C, and preferably within +/-3°C, and preferably within +/-2°C, and preferably within +/- 1°C, and preferably exactly, to a predetermined set temperature of the installation site.
4. The immobilization method according to any of the preceding claims, characterized in that the modification of the temperature of a surface region of the portion of the rail passing through the thermal conditioning zone (30) results in a transfer of an amount of heat equal to the amount of heat necessary to bring the rail section, under adiabatic conditions, to a homogenization temperature equal to a temperature within a predetermined tolerance range, preferably +/-5°C, preferably +/-3°C, preferably +/-2°C, preferably +/- 1°C around, and preferably exactly to, a predetermined set temperature.
5. The immobilization method according to any of the preceding claims, characterized in that the portion of the rail (12) passing through the thermal conditioning zone (30) is raised relative to the railway track (2).
6. The immobilization method according to any of the preceding claims, characterized in that the portion of the rail (12) passing through the thermal conditioning zone (30) rests on a sleeper (8, 10) of the railway track (2).
7. The immobilization method according to any of the preceding claims, characterized in that the temperature of a surface region of the portion of the rail passing through the thermal conditioning zone (30) is modified by heat exchange with a hot or cold heat source, in particular by thermal radiation, thermal conduction and/or convection, or by an alternating electric current induced or generated in the rail portion.
8. A railway machine (4) comprising:

   - traction means suitable for moving the railway machine (4) in a working direction (100) at a predetermined operating speed of 500 m/hour;

   - at least one thermal conditioning device (32) comprising at least one thermal conditioning zone (30), the thermal conditioning zone being arranged such that, at each instant, when the railway machine (4) moves in the working direction (100) at the predetermined operating speed, a portion of a rail (12) that is not attached to a sleeper (8, 10) passes through the thermal conditioning zone (30); the thermal conditioning device (32) being suitable for modifying a temperature of a surface region of the portion of the rail passing through the thermal conditioning zone (30) by generating a non-homogeneous temperature distribution in the rail portion;

   - an immobilization zone (26) of the portion of the rail (12) on a sleeper (10) of the railway track, which zone is located in the region of a bogie (20) behind the thermal conditioning zone (30) in the working direction,

   characterized in that the immobilization zone (26) is positioned less than 5 meters from the thermal conditioning zone.
9. The railway machine (4) according to claim 8, characterized in that the thermal conditioning device is suitable for supplying to the rail portion passing through the thermal conditioning zone and/or suitable for extracting from the rail portion passing through the thermal conditioning zone a greater amount of heat sufficient for increasing and/or decreasing, by at least 5°C, the average temperature of the rail portion, for a UIC60 rail, when the railway machine advances in the working direction at the predetermined operating speed.
10. The railway machine (4) according to any of claims 8 to 9,
    characterized in that the railway machine comprises means for modifying the temperature of a surface region of the portion of the rail passing through the thermal conditioning zone (30), by alternating electric current induced or conducted in the rail portion, or by heat exchange with a hot or cold heat source, in particular by thermal radiation, thermal conduction and/or convection.

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