阅读说明：本技术 用于铺设铁路轨道的铁轨的方法 (Method for laying a rail of a railway track ) 是由 J-C.皮盖 于 2018-05-18 设计创作，主要内容包括：为了用于使用工作列车(4)铺设铁路轨道的铁轨(12),所述工作列车(4)包括至少一个加热装置(32),所述至少一个加热装置(32)具有至少一个加热区域(28)、一个或多个气体燃烧器(42)以及置于所述一个或多个气体燃烧器(42)与加热区域(28)之间的一个或多个辐射体(44),所述一个或多个辐射体(44)以敞开到加热区域(28)中的开口(46)被穿孔,使所述工作列车(4)沿着铺设方向(100)移动,以使得在每个瞬间,要被固定的铁轨(12)的一部分穿过加热区域(28)；使用加热装置(32)将热量施加到要被固定的铁轨(28)的穿过加热区域(28)的所述部分,通过供应一个或多个气体燃烧器(42),使得没有火焰从加热区域(28)中的开口(46)出来,并且使得施加到铁轨(12)的部分的热量的至少75％、优选至少80％、优选至少85％通过一个或多个辐射体(44)的辐射被传递；在施加热量之后,铁轨(12)的所述部分被固定到在铺设方向(100)上位于加热区域(18)后面的铁路轨道的轨枕(10)。(For use in laying a rail (12) of a railway track using a work train (4), the work train (4) comprising at least one heating device (32), the at least one heating device (32) having at least one heating zone (28), one or more gas burners (42) and one or more radiators (44) placed between the one or more gas burners (42) and the heating zone (28), the one or more radiators (44) being perforated with openings (46) opening into the heating zone (28), moving the work train (4) in a laying direction (100) so that at each instant a portion of the rail (12) to be secured passes through the heating zone (28); applying heat to the portion of the rail (28) to be secured that passes through the heating zone (28) using the heating device (32), by supplying one or more gas burners (42) such that no flame exits from an opening (46) in the heating zone (28), and such that at least 75%, preferably at least 80%, preferably at least 85% of the heat applied to the portion of the rail (12) is transferred by radiation of the one or more radiators (44); after the application of heat, the portion of the rail (12) is fixed to the sleeper (10) of the railway track behind the heating zone (18) in the laying direction (100).)

1. A laying method for laying a rail (12) of a railway track using a work train (4), the work train (4) comprising at least one heating device (32), the heating device (32) having at least one heating zone (28), one or more gas burners (42) and one or more radiators (44) interposed between the one or more gas burners (42) and the heating zone (28), the one or more radiators (44) being perforated with openings (46) opening into the heating zone (28), in which laying method:

-moving the work train (4) along a laying direction (100) so that at each instant a portion of the rail (12) not attached to a tie (8,10) passes through the heating zone (28);

-applying heat to the portion of the rail (12) passing through the heating zone (28) using the heating device (32);

characterized in that the one or more gas burners (42) are supplied such that no flame exits from the opening (46) in the heating zone (28) and such that at least 75%, preferably at least 80%, preferably at least 85% of the heat applied to the portion of the rail (12) is transferred by radiation of the one or more radiators (44).

2. The laying method according to claim 1, characterized in that it involves adjusting, according to one or more control parameters, one or more of the following supply parameters of one or more adjusted burners of said one or more gas burners (42): fuel flow rate, oxidant flow rate, flow rate of the fuel/oxidant mixture.

3. A laying method according to any one of the preceding claims, wherein the one or more gas burners (42) comprise at least two burners, and preferably at least four burners, and wherein the number of activated burners is adjusted according to one or more control parameters.

4. A laying method according to claim 3, wherein the one or more gas burners (42) comprise at least one pair of adjacent gas burners, one of which is positioned behind the other in the laying direction.

5. A laying method according to claim 3 or 4, wherein the one or more gas burners comprise at least one pair of opposed burners located on either side of a mid-plane of the heating zone (28) parallel to the laying direction.

6. A laying method according to any one of claims 2 to 5 wherein the one or more control parameters include one or more of the following measured or estimated parameters: a temperature of the portion of the rail before heating, a temperature of the portion of the rail after heating, a temperature of the portion of the rail during heating, an outdoor ambient temperature, a speed of movement of the work train, a speed of movement of the rail relative to the heating device, a duration of heating, a difference between a measured temperature and a set temperature of the portion of the rail before heating, a difference between a measured temperature and a set temperature of the portion of the rail after heating, a difference between a measured temperature and a set temperature of the portion of the rail when heat is applied, an ambient humidity, or a wind speed.

7. The laying method according to claim 6, characterized in that it involves measuring at least one temperature of said portion of the rail, after the heat has been applied, using a pyrometer (58) arranged in the laying direction (100) at the outlet region (40) of the heating zone (28) or behind the heating zone (28).

8. Method of laying according to claim 6 or 7, wherein the method involves measuring at least one temperature of the portion of rail (12) before applying heat, using a pyrometer (58) arranged at an inlet area (38) of the heating zone (28) or in front of the heating zone (28) in the laying direction (100).

9. A laying method according to any one of claims 6 to 8 wherein the method involves measuring at least one temperature of the portion of the rail (12) whilst applying heat using a pyrometer (58) arranged inside the heating zone (28).

10. Method according to any one of claims 1 to 9, characterized in that the portion of the rail located in the heating zone (28) is lifted from the rail and in that, after the application of heat, the portion of the rail is positioned on the tie and then attached to the tie.

11. A laying method according to any one of the preceding claims wherein the portion of the rail (12) is guided relative to the frame of the work train (4) such that it passes through the heating zone as the work train moves.

12. A laying method according to any one of the preceding claims, wherein the heating device (32) is guided relative to the frame of the work train (4) such that the portion of the rail (12) passes through the heating zone (28) as the work train (4) moves.

13. Method according to any one of the preceding claims, wherein the heating device (32) is guided relative to the portion of the rail (12), preferably by rolling the heating device (32) over the portion of the rail (12), such that the portion of the rail (12) passes through the heating area (28) while the work train (4) is moving.

14. A laying method according to any one of the preceding claims, wherein said portion of the rail (12) is attached to the sleepers (10) of the railway track behind the heating area (18) in the laying direction (100) after the application of heat.

15. Work train (4) for implementing a laying method according to any one of the preceding claims, comprising at least one heating device (32), the heating device (32) having at least one heating zone (28), one or more gas burners (42) and one or more radiators (44) interposed between the one or more gas burners (42) and the heating zone (28), the one or more radiators (44) being perforated with an opening (46) opening into the heating zone (28), the work train (4) comprising:

-pulling means for moving the work train (4) along a laying direction (100) so that at each instant a portion of the rail (12) not attached to a tie (8,10) passes through the heating zone (28);

-supply means for supplying the one or more gas burners (42) such that no flame exits from the openings (46) in the heating zone (28) and such that at least 75%, preferably at least 80%, preferably at least 85% of the heat applied to the portion of the rail (12) is transferred by radiation of the one or more radiators (44).

16. Work train (4) according to claim 15, characterized in that it comprises lifting means for lifting said portion of the rail located in the heating area (28) from the track and positioning means for positioning said portion of the rail on the tie after applying heat before attaching it to the tie.

17. Work train (4) according to claim 15 or 16, characterized in that the heating device (32) comprises one or more heating modules (34), each comprising a heating zone (28), one or more gas burners (42) and one or more radiators (44) placed between the one or more gas burners (42) of a heating module (34) and the heating zone (28) of a heating module (34).

18. Work train (4) according to combined claims 16 and 17, characterized in that at least one of the one or more heating modules (34) is provided with guiding means (48) for guiding said portion of the rail (12) in the heating zone (28) of the guided heating module (34), said guiding means (48) preferably comprising a roller rolling on said portion of the rail (12), the roller preferably supporting the guided heating module (34).

Technical Field

The present invention relates to a method for laying a rail of a railway track, comprising heating the rail, and to a work train for implementing such a laying method.

Background

The rails of a railway track are subject to relatively large temperature variations depending on the season and weather conditions. Due to the increase in temperature, the rails tend to elongate and expand, and conversely, due to the decrease in temperature, the rails tend to contract.

Nowadays, the rails are laid continuously, so that the length cannot be changed under the influence of temperature changes. The rails are attached to the track at an average temperature called the "neutral" temperature, which differs in value depending on the climate zone. When ambient temperatures exceed the average annual level, the unexpanded rails are subjected to compressive forces which tend to push the rails out of their path. Conversely, when the ambient temperature is below the average annual level, the non-contracting rails are subjected to traction forces which tend to pull the track out of its path.

If the temperature of the rails is not controlled while the laying is being carried out, an operation called mechanical "neutralisation" operation must be carried out after the laying and the speed of travel limited until these operations are completed. Mechanical neutralization involves cutting a section from the rail, the thickness of which is a function of the difference observed between the temperature at intervention and the "neutral" temperature of the site, loosening the rail and stretching it to fill the space left by the section that has been removed, then retightening the rail and re-welding, if appropriate. Before this neutralization operation is performed, the travel speed on the track must be limited, most commonly to 50 kph. It will be appreciated that organizing such work during neutralization interventions and during the previous phase between laying the rails and neutralization leads to serious traffic disturbances.

Directly attaching rails that are continuously heated to near or equal to a "neutral" temperature helps to minimize traffic disturbances.

One solution currently used for continuously heating rails requires the use of induction technology. This method helps to obtain sufficient heat accuracy to ensure that the rails are laid within the required tolerance of the "neutral" temperature. This may be referred to as fine direct thermal neutralization. However, the equipment required for intervention is relatively complex, as it requires a generator, and cooling of the power circuit, generator and inductor.

For construction sites where ballast stabilization is required to follow, a thermal "pre-neutralization" procedure is proposed which involves raising the temperature of the rail to a "neutral" temperature sufficiently close to the location prior to attaching it to the ties, but without ensuring that the "neutral" temperature is reached. This "pre-neutralization" advantageously allows immediate resumption of travel at a speed of about 80kph instead of 50kph until the aforementioned final mechanical neutralization operation is performed. One way of performing such thermal pre-neutralization is to sprinkle the hot water on the road, but this solution has operational drawbacks, in particular in terms of efficiency and transport and removal of the water, which reduce its benefits.

Furthermore, document US6308635 proposes heating rails already laid on the ground by using a gas heating module comprising a hot air generator for heating the rails by convection. The convection heating may be supplemented by radiant heating obtained by radiant panels located between the burners and the heating portion of the rails, the radiant panels being perforated to allow flames to pass through them and into the heating chamber where the portion of the rails to be heated is located. However, this substantially convective and secondary radiative heating method is difficult to control, particularly because it depends on the air flow.

Disclosure of Invention

The object of the present invention is to overcome the drawbacks of the prior art and to propose a heating method that provides a high level of performance in terms of efficiency, reliability and operating quality.

To this end, a first aspect of the invention proposes a method of laying a rail of a railway track using a work train comprising at least one heating device having at least one heating zone; one or more gas burners; and one or more radiators disposed between the one or more gas burners and the heating zone, the one or more radiators being perforated with an opening that opens to the heating zone, in which method:

-the work train is moved in the laying direction so that at each instant a portion of the rail passes through the heating zone;

-applying heat to the portion of the rail passing through the heating zone using a heating device, the one or more gas burners being supplied such that no flame exits from an opening in the heating zone and such that at least 75%, preferably at least 80%, preferably at least 85% of the heat applied to the portion of the rail is transferred by radiation of the one or more radiators;

after the application of heat, a portion of the rail is attached to the sleepers of the railway track behind the heating area in the laying direction.

The radiation is substantially in the infrared spectral range, ensuring excellent heating efficiency and low losses. The radiation is not affected by wind or other climatic parameters.

Perforations are useful because they optimize the heating of the radiator, but should not cause convection to dominate when transferring heat to the portion of the rail.

Naturally, the heating power should be adjusted according to the external conditions in order to obtain the desired set temperature of the rail.

According to one embodiment, the invention relates to adjusting one or more of the following combustion parameters, relating to the supply to one or more modulation burners of one or more gas burners, according to one or more control parameters: fuel flow rate, oxidant flow rate, flow rate of the fuel/oxidant mixture.

According to another embodiment, the one or more gas burners comprise at least two burners, and preferably at least four burners, and the number of activated burners is adjusted according to one or more control parameters. In particular, the one or more gas burners may comprise at least one pair of adjacent gas burners positioned one behind the other in the laying direction, and/or the one or more gas burners may comprise at least one pair of opposite burners located on either side of a median plane of the heating zone parallel to the laying direction.

Preferably, the one or more control parameters comprise one or more of the following measured or estimated parameters: the temperature of the portion of the rail before heating, the temperature of the portion of the rail after heating, the temperature of the portion of the rail during heating, outdoor ambient temperature, speed of movement of the work train, speed of movement of the rail relative to the heating device, duration of heating, difference between measured temperature and set temperature of the portion of the rail before heating, difference between measured temperature and set temperature of the portion of the rail after heating, difference between measured temperature and set temperature of the portion of the rail when heating is applied, ambient humidity or wind velocity. In particular, one or more of the following procedures may be performed:

-measuring at least one temperature of a portion of the rail after the heat has been applied, using a pyrometer arranged at or behind an exit region of the heating zone in the laying direction;

-prior to applying heat, measuring at least one temperature of a portion of the rail using a pyrometer arranged at or in front of an inlet region of the heating zone in the laying direction;

-measuring at least one temperature of the portion of the rail while applying heat using a pyrometer arranged inside the heating zone.

According to a particularly advantageous embodiment, the portion of the rail located in the heating area is lifted from the rail and, after the application of heat, is positioned on the tie and then attached to the tie. Lifting a portion of the rail into the heating area helps to better surround the rail, heating it not only from above, but also from the side, and optionally from below, either by direct radiation of one or more radiators, or by indirect radiation reflected from the walls of the heated area of the radiators, so as to apply heat uniformly to the periphery of the portion of the rail and to minimise losses. The fact that the heating zones are separated from the rail, in particular from the sleepers, allows high heating powers to be achieved when required, without risking the rail.

According to an alternative embodiment, the part of the rail located in the heating area is laid on the track. In such cases, care must be taken to ensure that the applied heat is substantially directed towards the rail to minimise the heat applied to other components of the track.

In order to obtain repeatable positioning of the portion of the rail to be attached that passes through the heating zone, in particular one or more of the following procedures may be performed:

-guiding the portion of the rail relative to the frame of the work train such that the portion of the rail passes through the heating area as the work train moves.

-guiding the heating device relative to the frame of the work train such that a portion of the rail passes through the heating zone as the work train moves.

-guiding the heating device relative to the portion of the rail, preferably by rolling the heating device over the portion of the rail such that the portion of the rail passes through the heating area as the work train moves.

According to one embodiment, the work train is moved in the laying direction without stopping.

The laying method according to the invention can be carried out in particular when a new track is first laid or when a renovation or renovation work is carried out. In particular, and according to a preferred aspect of the present invention, it relates to a method for renewing or renewing a railway track, which method comprises inter alia: the old rails are removed and new or renovated rails are laid according to the laying method described above.

According to another aspect of the invention it relates to a rail work train for implementing the method as described above.

In particular, the present invention relates to a work train comprising at least one heating device having at least one heating zone, one or more gas burners, and one or more radiators placed between the one or more gas burners and the heating zone, the one or more radiators being perforated with an opening open to the heating zone, the work train comprising:

-pulling means for moving the work train in the laying direction so that at each instant a portion of the rail not attached to the tie passes through the heating zone;

-supply means for supplying the one or more gas burners such that no flame exits from the opening in the heating area and such that at least 75%, preferably at least 80%, preferably at least 85% of the heat applied to the portion of the rail is transferred by radiation of the one or more radiators.

Preferably, the work train comprises lifting means for lifting the portion of the rail located in the heating area from the track and positioning means for positioning the portion of the rail on the tie after the application of heat and before attaching the portion of the rail to the tie. As previously mentioned, lifting a portion of the rail into the heating area contributes to better surround the rail, heating it not only from above, but also from the side and optionally from below, either by direct radiation of one or more radiators or by indirect radiation reflected from the walls of the heated area of the radiator, so as to apply heat uniformly to the periphery of the portion of the rail and to minimize losses. The fact that the heating zones are separated from the rail, in particular from the sleepers, allows high heating powers to be achieved when required, without risking the rail.

According to one embodiment, the heating apparatus comprises one or more heating modules, each heating module comprising a heating zone, one or more gas burners, and one or more radiators disposed between the one or more gas burners of the heating module and the heating zone of the heating module. Preferably, the one or more heating modules comprise at least one guided heating module provided with guide means for guiding a portion of the rail in the heating area of the guided heating module, the guide means preferably comprising a roller rolling on the portion of the rail, the roller preferably supporting the guided heating module.

Drawings

Other features and advantages of the present invention will become apparent upon reading the following description and upon reference to the accompanying drawings. In the drawings:

FIG. 1 is a schematic illustration of a railway track rail laying site according to the method of the present invention;

FIG. 2 is a detailed schematic view of the worksite of FIG. 1 illustrating heating of a rail to be attached in accordance with the method of the present invention;

FIG. 3 is a schematic view of the top of the heating module of the heating apparatus for carrying out the method of the present invention;

FIG. 4 is a schematic front view of the heating module of FIG. 3;

FIG. 5 is a schematic view of a control unit of the heating module of FIGS. 3 and 4;

fig. 6 is a schematic front view of a heating module according to a first variant;

fig. 7 is a schematic front view of a heating module according to a second variant;

fig. 8 is a schematic front view of a heating module according to a third variant;

for purposes of clarity, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

Detailed Description

Fig. 1 shows an overall view of a railway track renewal site 2 in which a work train 4 (partially shown) is used to remove old rails 6 (the lead block) and old ties 8 and then replace them with new ties 10 and new rails 12, the entire procedure continuing as the train moves forward in the laying direction 100. Work train 4 includes cars 16 resting on bogies 18, 20, with cars 16 traveling on old rail 6 at the front of work train 4 and on new rail 12 at the rear of work train 4. The middle portion of work train 4 rests on tracks 22, and in the absence of rails on track 2 in that portion of the worksite, tracks 22 travel directly over old sleepers 8 before they are removed.

At the front section of the site, the tools allow the old rail 6 to be removed from the ties 8. When they are removed, the old rails 6 are raised and rest on the track ballast 24 on the side of the track. On the next section of the worksite, the old sleepers 8 are exposed, allowing them to be removed using a set of removal tools and replaced with new sleepers 10 using a set of laying tools. Before the work train 4 passes, the new rail 12, which has been arranged on the ground on either side of the track 2, is raised and positioned according to the desired geometry of the new rail 2 and then laid on the new sleeper 10. After the work train 4 passes, the final attachment of the new rail 12 is made by means of rail fasteners.

To prevent or limit the risk of gaps or breaks in the track that may be caused by dimensional changes of the rail 12 due to harsher weather or meteorological conditions, the final attachment of the new or refurbished rail 12 to the ties is done while these metal profile sections reach the average temperature of the laying location (known as the "pre-stressing" or "de-stressing" temperature).

To this end, a section of new or renovated rail 12 to be laid is brought to a set temperature in a conditioning area 28, which is located in front of and close to its attachment area 30, where it is attached to one or more sleepers 10 at 30. When intervention is made at the work site when the ambient temperature is below a set temperature (called "pre-stressing" or "stress-relieving" temperature), this adjustment involves heating the rails, in this case the conditioning zone 28 is a heating zone.

To this end, the invention proposes the use of a heating device 32, schematically illustrated in fig. 2 to 4, which heating device 32 acts substantially by thermal radiation. The heating device 32 comprises at least one heating module 34, which at least one heating module 34 has at least one, preferably at least two, and particularly preferably at least four heating units 36 as shown in fig. 3, which heating units 36 delimit an elongated heating area 28, which heating area 28 is located at a distance from the track and is oriented in the laying direction 100 of the work train 4 and is open at a front end 38 and at a rear end 40. Four heating units 36 are arranged transverse to either side of the heating zone, two closer to the inlet and two closer to the outlet.

Each heating unit 36 includes one or more burners 42 and a unit of radiators 44, with the radiators 44 being disposed between the one or more burners 42 and the heating zone 28. The radiator 44 is preferably perforated by an opening 46 open to the heating zone 28, the opening 46 may be disposed opposite the burner 42 or offset from the burner 42.

Guiding means 48 are provided at the inlet 38 and the outlet 40 of the heating zone 28 of the heating apparatus to guide the rail 12 through the heating zone 28. In the preferred embodiment, the portion of the rail 12 that passes through the heating zone 28 is raised, i.e. vertically at a distance above its final position at the end of the laying process. The heating device itself may be provided with one or more actuators 50 or passive positioning mechanisms for properly positioning the heating device relative to the rail 12 and compensating for positioning variations of the work train 4 relative to the desired trajectory of the track. Preferably, the guiding means 48 comprise rollers that roll on the rail 12 and, where appropriate, support the heating unit 36.

Pyrometers 52 are positioned at the inlet 38 of the heating zone 28, inside the heating zone 28, and the outlet 40 of the heating zone 28, and, where applicable, adjacent the attachment zone 30. These pyrometers 52 are linked to a control unit 54 shown in fig. 5, which control unit 54 receives signals from other sensors 56, such as: a sensor sensing the speed of the work train 4, a sensor sensing the speed of the rail to be attached, an ambient temperature sensor, an atmospheric pressure sensor and/or an ambient humidity sensor. Thus, the control unit 54 is capable of measuring, estimating or calculating one or more of the following parameters: the temperature of the portion of the rail to be attached before heating, the temperature of the portion of the rail to be attached after heating, the temperature of the portion of the rail to be attached during heating, the outdoor ambient temperature, the speed of movement of the work train 4, the speed of movement of the rail relative to the heating means, the amount of heat transferred by the heating means to the portion of the rail.

Furthermore, the control unit 54 contains in its memory a set temperature which may have been input or programmed and which represents a desired "pre-stressed" or "de-stressed" temperature in the attachment area 30, which makes it possible to determine, where applicable, the difference between the set temperature and the measured temperature of the part of the rail to be attached before heating, the difference between the set temperature and the measured temperature of the part of the rail to be attached after heating, or the difference between the set temperature and the measured temperature of the part of the rail to be attached during heating.

Finally, the control unit 54 is linked to: a proportional solenoid valve 58 for regulating the flow rate of oxidant and/or fuel for supplying the burner; the igniter is used for controlling the ignition of the combustor; and proportional solenoid valves 60, 62 for controlling the overall supply of fuel gas from a gas tank 64 and oxidant gas from a compressor 66.

Thus, the heating power of each heating unit may be adjusted in a relatively continuous manner within a range around the nominal value, for example within a range of 50% to 150% of the nominal value, by varying the flow rate of oxidant and/or fuel at the solenoid valves 58, 60, 62. Outside this modulation range, larger variations can be obtained by completely switching off or igniting certain heating units 36.

When the work train 4 is moved in the laying direction 100, the rail 12 to be attached is moved in the opposite direction relative to the heating device 28 and is guided such that at each moment the elevated portion of the rail 12 to be attached passes through the heating zone 28. The positioning of the heating device is adjusted by the actuator 50 or positioning mechanism, if applicable. The radiator 44 is arranged close to the portion of the rail 12 to be attached, and preferably at a distance of less than 20cm, and preferably at a distance of less than 10 cm.

Thus, at each moment, and according to the advance of the work train 4, the portion of rail 12 to be attached passes through the heating zone 28, where it is heated by the heating device 32 before it leaves the heating zone 28 and is conveyed to the attachment zone 30, where it is laid on the ties 10 of the railway track.

The control unit 54 uses a computational algorithm to determine the number of burners 42 and/or the flow rate of oxidant and/or fuel required to heat the rail 12 to be attached, in accordance with all or some of the parameters previously discussed.

In particular, the one or more gas burners 42 are supplied such that radiation through the one or more radiators 44 transfers at least 75%, preferably at least 80%, preferably at least 85% of the heat to the rail, and no flame exits from the openings 46 in the heating zone 28. The only function of the opening 46 is therefore to cause a rapid and uniform heating of the radiator 44.

Preferably, the work train moves in the laying direction without stopping, moving at a speed of practically more than 30 mm/s, preferably more than 100 mm/s.

Naturally, the examples shown in the figures and discussed above are given only as illustrative and non-limiting examples.

The number of heating units 36 and their positioning in each heating module 34 may vary. It is advantageous to have at least two heating units 36 opposite each other on both sides of the heating zone 28 (as shown in fig. 3 and 4), or more generally, to have at least two heating units 36 radiating into the heating zone at different angles. In particular, the advantage of lifting the portion of the rail 12 that passes through the heating zone 28 may be utilised in order to direct at least some of the thermal radiation to the lower face of the rail. In this respect, it is ideally conceivable to arrange three heating units distributed at 120 ° (fig. 6) or four heating units distributed at 90 ° (fig. 7) around the heating zone. A reflective surface 68 (fig. 8) defining part of the heating zone 28 may also be provided to distribute heat around the periphery of the rail. It is also advantageous to arrange a plurality of heating units 36 in succession in the longitudinal direction of advance of the vehicle, as shown in fig. 3, or indeed to have a plurality of heating modules 34, as shown in fig. 2, to allow a stepwise multistage heating. The heating modules 34 arranged in sequence may be directly adjacent or separated by isothermal insulating sections. They may also be separated by open air sections. One or more heating modules 34 may be suspended from the load bearing structure of one of the cars in the middle portion of work train 4. They may also be supported independently by wheels or tracks advancing on the track, if applicable, linked by an open-air coupling.

If appropriate, only some of the gas burners 42 may be equipped with regulating solenoid valves 58.

It is also contemplated that solenoid valves 58 are not proportional, but operate in an on/off mode, with the number of heating units 36 being turned off or on as desired. In this case, it is envisaged that the solenoid valves 60, 62 providing the total supply of fuel and oxidant may be proportional valves to ensure a certain degree of continuity of variation, or they may be on/off valves, in which case the amount of heat applied is adjusted only in stages by varying the number of heating units 36 supplied. Without a proportional solenoid valve, a pulsed operating mode is also conceivable, in which some gas burners 42 are fired intermittently. It is also envisaged to articulate the heating units 36 in such a way that they can be quickly removed from the heating zone 28 when it is desired to reduce the amount of heat transferred to the rail 12 to be laid.

As a variant, the heating unit uses ambient air as oxidant and only the flow rate of the fuel is adjusted. In this case, the solenoid valve 62 and the compressor 66 are omitted. In practice, the fuel gas is propane or LPG fuel.

Depending on the accuracy of the observed adjustment, which will depend on the response time of the heating unit 36, the method according to the invention will be able to be used for thermal pre-neutralization, or even for fine direct thermal neutralization.

When the rail 12 to be attached has been laid on the tie, a heating operation of the rail 12 to be attached can be performed.

The method for heating rails for railway track renovation in which rails are to be replaced, which has been described above, can also be used for rail track renovation in which old rails are re-laid, or for first-time laying.