SYSTEM FOR COMPENSATING FOR THE THERMAL EXPANSION OF A CABLE USING BILATIN CUPS

Abstract

THERMAL EXPANSION COMPENSATION SYSTEM FOR A CABLE USING BILADES Thermal expansion compensation system for a main cable (10) comprising a traction axis (14) extending substantially parallel to the longitudinal direction, two tensioning devices (16a, 16b) connected to the main cable and to the traction axis (14) comprising at least two racks (20a, 22a;20b, 22b), arranged on either side of the traction axis (14), at least one bimetallic strip (32a, 32b) comprising two strips formed from materials having different coefficients of thermal expansion, the ends of each bimetallic strip being connected to each of the racks and a substantially central portion of the bimetallic strip being connected to the traction axis (14), the bimetallic strip (32a, 32b) being configured to have a variable curvature depending on its temperature, so as to exert a variable traction force between the traction axis (14) and the rack depending on the temperature. Figure for the abstract: Figure 1a;

Description

Title of the invention: SYSTEM FOR COMPENSATING THE THERMAL EXPANSION OF A CABLE USING BIMETAL STRIPS Technical field of the invention

[0001] The invention relates to a system for compensating for the thermal expansion of a cable and in particular of a cable of a catenary in railway infrastructures. The invention also extends to a cable of a railway catenary comprising such a compensation system. Technological background

[0002] Catenaries are mainly made up of four components including structures, armaments, contact wires, and carrier cables. The structures include the supports, posts and gantries which are used to carry the entire catenary. The catenary includes in particular an armament, generally a carrier cable, an auxiliary cable, a conductive cable called a contact wire allowing contact with the pantograph for mechanical guidance and routing of the current, a set of vertical cables stretched between the carrier cable, the auxiliary cable and the contact wire so as to ensure the linearity of the latter.The catenary arming generally comprises a console supporting the catenary, a console guy wire used more particularly to adjust the height, an anti-sway linked to the auxiliary carrier cable and intended to prevent any inclination of the catenary, this anti-sway being terminated by a return arm linked to the contact wire.

[0003] For reasons of implementation and maintenance of geometry, the catenary is divided into "laying sections" corresponding to a section on which the conductors are uninterrupted. In order to control the geometry, in particular the height of the contact plane and the quality of the capture, the effects of thermal expansion of the conductors can be compensated by a regularization system.

[0004] A known solution to overcome this problem of thermal expansion consists of installing devices at the ends of the cantons which pull on the conductors, and thus ensure a constant mechanical tension and therefore geometry. These devices can be winches or pulleys to which a counterweight is attached, to ensure constant tension, such as for example the Tensorex® device from Pfisterer.

[0005] One of the disadvantages of this solution lies in the installation of these systems at the ends of the cantons which impose a rotation around the system. The length of the cable to be wound is equivalent to the distance to the fixed point multiplied by the coefficient of thermal expansion of the cable and multiplied by the temperature delta.

[0006] In general, on conventional 1500V catenaries, the contact wires are regularized, i.e. thermal expansion is compensated, and the carrier cables are not regularized. As a result, the geometry varies significantly depending on the temperature.

[0007] Another known solution to overcome this problem is to manually take up the tension of the carrying cable of the device. This is a device which is placed in a span of a catenary and which allows, using a screw, to increase the mechanical tension by exerting a three-point bending on the carrying cable.

[0008] The disadvantage is that the adjustment of the mechanical tension is manual, punctual and is not a function of the temperature.

[0009] Another disadvantage of the previous solutions also lies in the constraints necessary to ensure this tension adjustment. In other words, these solutions involve a longitudinal displacement of the carrier cable over the entire length of the section. For example, for a half-section of 750 meters, it is necessary to allow for a displacement due to the expansion of the cable as a function of temperature of approximately 90 centimeters. Also, the suspension chains of the carrier cable do not allow such a displacement. Therefore, regularization of the cables, particularly the carrier cables, would require significant modifications to the existing installations.

[0010] The inventors sought to propose an alternative solution for ensuring the maintenance of a constant or non-constant mechanical tension in a cable and which can equip a catenary type cable in railway infrastructures or an electrical cable type used in energy infrastructures (high voltage lines for example), without difficulty, and without requiring the replacement of these cables. Objectives of the invention

[0011] The invention thus aims to provide a thermal expansion compensation system which overcomes at least some of the drawbacks of known devices.

[0012] The invention aims in particular to provide, in at least one embodiment of the invention, a compensation system which can be mounted on a conductive or non-conductive cable.

[0013] The invention also aims to provide, in at least one embodiment of the invention, a compensation system which can be mounted on a catenary cable without requiring the replacement of the existing catenary structure.

[0014] The invention also aims to provide, in at least one embodiment of the invention, a compensation system allowing regularization of the cable equipped with such a device.

[0015] The invention also aims to provide, in at least one embodiment of the invention, a compensation system which is compact and lightweight.

[0016] The invention also relates to a main carrier cable of a catenary equipped with such a compensation system to further enable regularization of the carrier cable.

[0017] The invention also aims to provide, in at least one embodiment of the invention, a compensation system making it possible to act as a section insulator, i.e. allowing electrical cutting of the catenary. Presentation of the invention

[0018] To this end, the invention relates to a system for compensating for the thermal expansion of a main cable comprising a system for compensating for the thermal expansion of a main cable comprising a first portion of main cable and a second portion of main cable, both of which portions extending in one direction, called the longitudinal direction, and arranged between two separate attachment points, said first and second portion of main cable each being respectively connected to an attachment point, said compensation system being characterized in that it comprises a traction axis extending substantially parallel to the longitudinal direction, a first tensioning device connected on the one hand to said first portion of main cable and on the other hand to the traction axis, and a second tensioning device connected on the one hand to the second portion of main cable and on the other hand to the traction axis,each tensioning device comprising: ,

[0019] - a means of attachment to the main cable;

[0020] - at least two racks, arranged on either side of the traction axis and sen ably parallel to each other in nominal position, each connected to the attachment means by at least one traction arm;

[0021] - at least one bimetallic strip comprising two blades formed from materials having different thermal expansion coefficients, the ends of each bimetallic strip being connected to each of the racks and a substantially central portion of the bimetallic strip being connected to the traction axis, the bimetallic strip being configured to have a variable curvature depending on the temperature of the bimetallic strip, so as to exert a variable traction force between the traction axis and the rack depending on the temperature,

[0022] and in that each bimetallic strip of one of the tensioning devices is oriented so that the traction force exerted by said tensioning device on the traction axis is oriented in a direction opposite to the traction force exerted by the other tensioning device on the traction axis when it is subjected to the same temperature.

[0023] A compensation system according to the invention therefore makes it possible to compensate for the thermal expansion of a main cable. Throughout the text, the term "main cable" refers to a cable which may be a carrier such as, for example, a carrier main or an auxiliary carrier of a catenary, or non-carrying; a conductive cable such as a contact wire for example of a catenary or an energy infrastructure, or non-conductive. The compensation system comprises at least one traction axis for connecting the adjustment device to the main cable.

[0024] The compensation system according to the invention is mechanically linked to the main cable and does not require replacement of the pre-existing cable and is installed directly on the existing cable.

[0025] A compensation system according to the invention makes it possible to adjust the mechanical tension of the main cable when the latter undergoes thermal expansion due to temperature variations. Thus, the compensation system can be added to a cable of an existing infrastructure in order to allow the regulation of the mechanical tension of the main cable according to the variation in temperatures.

[0026] Each bimetallic strip of the system has a variation in curvature as a function of the temperature configured to compensate for the thermal expansion of the main cable. In particular, each bimetallic strip has a curvature that increases as the temperature increases, thanks to the presence of two strips with different thermal expansion coefficients, a first strip and a second strip. The increased curvature of each bimetallic strip applies a mechanical tension between the traction axis and the racks to which it is attached which makes it possible to compensate for the thermal expansion of the main cable. Due to this mechanical tension, the racks move relative to the traction axis and exert a tensile force on the main cable via the traction arms which transmit this tensile force.Since the curvature of the bimetallic strips is influenced by temperature variations, they automatically compensate for the thermal expansion of the main cable due to these same temperature variations. The movements are therefore controlled by the temperature via the bimetallic strip(s).

[0027] The bimetallic strip(s) of each tensioning device are configured to exert a mechanical force on the traction axis opposite the other tensioning device. Thus, the two tensioning devices exert an opposing force on the traction axis, which allows the tensioning devices to each exert opposing forces on the main cable.

[0028] The curvature K of the bimetallic strips is expressed according to the following formula:

[0029] [Math.l] _______________6ElE2(hi + h2)hih2s__________ K ~ E\h2 + 4EiE2h3}h2 + 6E}E2h2h22 + 4E}E2h2hl + E2h2

[0030] With Ei the Young's modulus of the material of the first blade, E2 the Young's modulus of the material of the second blade, hi the thickness of the first blade, h2 the thickness of the second blade, and e the product of the temperature difference by the difference in expansion coefficient between the two materials. The temperature difference is defined as the difference between the temperature to which the bimetallic strip is subjected and a reference temperature of the bimetallic strip at rest, for example the temperature at which the two strips of the bimetallic strip have the same length and the bimetallic strip is therefore straight. The reference temperature can also be a temperature at which the bimetallic strip has a curvature compensating for the mechanical tension at an average temperature of the temperature range that the compensation system seeks to compensate for.

[0031] The bimetallic strips are therefore configured to have a rest position at the reference temperature and a stress position when a temperature difference appears with the reference temperature. The bimetallic strips of the two tensioning devices are preferably identical, with a different orientation for each tensioning device, which makes it possible to obtain two opposing tensile forces compensating for the expansion of the main cable.

[0032] The radius r of curvature is equal to the inverse of the curvature and allows the deflection f of each bimetallic strip to be calculated according to the following formula:

[0033] [Math.2] f = r-(r 2 - L 2 Ÿ' 2

[0034] With 1 the half-length of the bimetallic strip, that is to say half of the total length of the bimetallic strip. The deflection of each bimetallic strip makes it possible to know the relative displacement that the bimetallic strip can compensate for at a given temperature.

[0035] The compensation system according to the invention aims to compensate for the thermal expansion of the main cable. The thermal expansion causes a displacement “d” to be compensated for proportional to the length “a” of the span, in a temperature amplitude “R” targeted by the invention, depending on the coefficient “a” of expansion of the material from which the main cable is formed, generally copper. The formula is as follows:

[0036] [Math.3] d = a*R*a

[0037] In practice, in the context of a conventional railway installation, for example the French railway network, the length "a" of the span is generally of the order of twenty to fifty-four meters, the temperature amplitude "R" is of the order of a few tens of degrees Celsius, and the coefficient "a" of expansion of copper is equal to 17*106K '. The displacement to be compensated is therefore of the order of one to ten centimeters, generally one to five centimeters. The objective is therefore for the deflection of the bimetallic strip to be close to the displacement to be compensated.

[0038] The bimetallic strips allow the tension of the main cable to be taken up without requiring the intervention of an operator when the adjustment is manual and without requiring the entire cable system to be changed. This compensation system therefore saves time while offering a space-saving solution adaptable to any type of cable and infrastructure.

[0039] Preferably, this compensation system is particularly well suited for the conductor cables of a catenary system, being able to adapt to a continuous cable or by cutting the cable or wire to install the system. The installation by keeping the continuous cable is more robust, while the one where the cable is cut makes it possible to form a section insulator by introducing an electrical separation between the two parts of the main cable or contact wire.

[0040] The invention makes it possible to ensure mechanical tension in the event of possible expansion of the main cable and the compensation system does not require fixed attachment to a support corresponding to an attachment point formed, for example, in the case of a catenary by a post.

[0041] Furthermore, the system for compensating for the thermal expansion of a cable according to the invention allows adjustment of the mechanical tension of the main cable without the intervention of an operator. The traction axis allows the main cable to be supported by means of the compensation system during thermal expansion of the main cable.

[0042] The invention also makes it possible to compensate for the thermal expansion of a cable without requiring heavy modifications and adaptations to existing infrastructures.

[0043] Advantageously and according to the invention, the tensioning device comprises a plurality of bimetallic strips, configured to have the same radius of curvature as a function of the temperature of the bimetallic strip.

[0044] According to this aspect of the invention, the bimetallic strips form a bimetallic strip network, on each of the tension devices, the number of bimetallic strips being adapted according to the mechanical stress of each bimetallic strip, in particular when its bending is maximum in the temperature range considered, taking into account a safety margin necessary according to the uses. The calculation of the number of bimetallic strips required can be carried out by calculating the resistance of materials according to the bending stress of each bimetallic strip, or by experimental tests to determine the load causing the bimetallic strip to break.

[0045] Preferably, the number of bimetallic strips on each tensioning device is between 5 and 30 for an application of a system for compensating for the thermal expansion of a main railway cable.

[0046] The length of the racks is determined based on the number of bimetallic strips on each tensioning device and the curvature of the bimetallic strips in the temperature range considered when using the compensation system.

[0047] Advantageously and according to the invention, each bimetallic strip comprises a first strip formed from an alloy of iron and nickel comprising around 36% nickel and 64% iron, and a second strip formed from copper.

[0048] According to this aspect of the invention, the alloy of iron and nickel in the proportions 64%-36% has a low coefficient of thermal expansion particularly suitable for use in a bimetallic strip. Copper is used because it has a higher coefficient of expansion than the alloy of iron and nickel. The alloy of iron and nickel in the proportions described is better known under the name Invar®, in particular Invar 36®.

[0049] Advantageously and according to the invention, each bimetallic strip comprises a fold arranged substantially in its central part.

[0050] According to this aspect of the invention, the folding of the bimetallic strips makes it possible to reduce the total compensation of the compensation system, in particular by reducing the displacement of the racks relative to the traction axis. The use of bimetallic strips with folding makes it possible, with the same thermomechanical parameters, to adapt to smaller cable spans.

[0051] Advantageously and according to the invention, each bimetallic strip comprises a bore arranged substantially in the central part and configured to receive the traction axis.

[0052] According to this aspect of the invention, each bimetallic strip is connected to the traction axis by the bore and can transmit the traction force.

[0053] Advantageously and according to the invention, each traction arm is connected by a pivot connection to the attachment means and by a pivot connection to the rack.

[0054] According to this aspect of the invention, the pivot connections prevent the mechanism from being clamped and allow the movement necessary to compensate for the expansion.

[0055] Advantageously and according to the invention, at least one tensioning device comprises a protective cover, connected to the rack of the tensioning device and extending opposite a rack of the other tensioning device of the compensation system.

[0056] According to this aspect of the invention, the protective cover is used in particular when the device is used on a contact wire (conductor in contact with the pantograph). In this use, the conductor is interrupted under the device and the protective cover serves to ensure the correct guidance of the pantograph under the device in order to protect both the device and the pantograph, thus allowing use on a contact wire without collision with the pantograph or any other object which would slide in a guided manner on the contact wire.

[0057] The invention also relates to a catenary cable equipped with a thermal expansion compensation system according to the invention, configured to compensate for the thermal expansion of said catenary cable arranged between two separate attachment points formed by posts.

[0058] The invention advantageously relates to a catenary cable or conductor wire equipped with a thermal expansion compensation system according to the invention, configured to compensate for the thermal expansion of said conductor cable arranged between two separate attachment points.

[0059] The advantages and technical effects of the compensation system according to the invention apply mutatis mutandis to a catenary cable equipped with a compensation system according to the invention and to a catenary conductor cable equipped with a compensation system according to the invention.

[0060] The invention also relates to a compensation system and a catenary cable equipped with a compensation system according to the invention, characterized in combination by all or part of the characteristics mentioned above or below. List of figures

[0061] Other aims, characteristics and advantages of the invention will appear on reading the following description given solely for non-limiting purposes and which refers to the appended figures in which:

[0062] [Fig.1a] is a schematic top view of a compensation system in position on a main cable, according to a first embodiment of the invention,

[0063] [Fig.lb] is a schematic side view of a compensation system in position on a main cable, according to the first embodiment of the invention,

[0064] [Fig.2a] is a schematic top view of a compensation system in position on a main cable, according to a second embodiment of the invention,

[0065] [Fig.2b] is a schematic side view of a position compensation system on a main cable, according to the second embodiment of the invention,

[0066] [Fig.3a] is a schematic side view of a first embodiment of a bimetallic strip of a compensation system,

[0067] [Fig.3b] is a schematic front view of the first embodiment of a bimetallic strip of a compensation system

[0068] [Fig.4a] is a schematic side view of a second embodiment of a bimetallic strip of a compensation system,

[0069] [Fig.4b] is a schematic front view of the second embodiment of a bimetallic strip of a compensation system, according to a second embodiment of the invention,

[0070] [Fig.5a] is a schematic top view of the operation of a communication system concept comprising the first embodiment of the bimetallic strip.

[0071] [Fig.5b] is a schematic top view of the operation of a communication system concept comprising the second embodiment of the bimetallic strip.

[0072] Detailed description of embodiments of the invention

[0073] In the figures, the scales and proportions are not strictly respected, for the purposes of illustration and clarity. Throughout the detailed description which follows with reference to the figures, unless otherwise indicated, each element of the compensation system is described as it is arranged when it is fixed in the vicinity of a cable main carrier of a catenary connected between two posts forming the attachment points, the attachment points thus delimit a span. In addition, identical, similar or analogous elements are designated by the same references in all figures.

[0074] Figures 1a and 1b schematically represent a compensation system 10a in position on a main cable, according to a first embodiment of the invention, respectively in top and side view.

[0075] Figures 2a and 2b schematically represent a system 10b for compensation in position on a main cable, in particular a current-carrying cable or a contact wire, according to a second embodiment of the invention, respectively in top and side view.

[0076] In the two embodiments shown, the compensation systems 10a, 10b are installed on a main cable 12 which may be, for example, a catenary carrying cable, a contact wire or a current-carrying cable. Only a portion of the main cable 12 is shown, and in [Fig. 1a] in top view, the portion of the main cable arranged below the compensation system is shown in dotted lines for reasons of clarity. The main cable 12 is connected to the attachment points (not visible) and the straight line connecting the two attachment points of the main cable 12 forms a longitudinal direction along which the main cable extends substantially, subject to the action of gravity and thermal expansion. The curvature of the main cable as shown is for illustrative purposes and is not necessarily representative of the curvature of an actual main cable.

[0077] The compensation system comprises a traction axis 14 and two tensioning devices, a first tensioning device 16a connected on the one hand to the main cable 12 by a first attachment means 18a at a first portion 120a of the main cable and on the other hand to the traction axis 14, and a second tensioning device 16b connected on the one hand to the main cable 12 by a second attachment means 18b at a second portion 120b of the main cable and on the other hand to the traction axis 14. According to the embodiment shown in [Fig.2a], the main cable is discontinuous between the first portion 120a of the main cable and the second portion 120b of the main cable. If the main cable is a conductive cable, the compensation system can thus act as a section insulator.

[0078] The first tensioning device 16a comprises two racks, a first rack 20a and a second rack 22a, arranged on either side of the traction axis 14 and substantially parallel to each other in the nominal position. Each rack comprises at least one, here six fasteners 28a for the first rack 20a and six fasteners 30a for the rack 22a making it possible to receive at least one, here six bimetallic strips 32a.

[0079] The second tensioning device 16b comprises two racks, a first rack 20b and a second rack 22b, arranged on either side of the traction axis 14 and substantially parallel to each other in the nominal position. Each rack comprises at least one, here six fasteners 28b for the first rack 20b and six fasteners 30b for the rack 22b for receiving at least one, here six bimetallic strips 32b. The different parts of each tensioning device are designed to be assembled to each other by simple pivot-type connections with an axis and a bore, and are locked by a pin or any other securing device. In the second embodiment of the invention, the tensioning devices each comprise a protective cover 34a, 34b connected to the rack of the tensioning device and extending opposite a rack of the other tensioning device of the compensation system.

[0080] The bimetallic strips 32a and 32b of each tensioning device comprise two strips formed from materials having different coefficients of thermal expansion, in particular in these embodiments a first strip made of Invar 36® having a low coefficient of thermal expansion and a second strip made of copper having a higher coefficient of thermal expansion. The ends of each bimetallic strip 32a, 32b are connected to each of the racks and a substantially central portion of the bimetallic strip is connected to the traction axis 14, each bimetallic strip 32a, 32b being configured to have a variable curvature depending on the temperature of the bimetallic strip, so as to exert a variable traction force between the traction axis and the rack depending on the temperature.The bimetallic strips of the first tensioning device 16a are oriented so that the tensile force exerted by the first tensioning device 16a on the tensile axis 14 is oriented in a direction opposite to the tensile force exerted by the second tensioning device 16b on the tensile axis 14 when it is subjected to the same temperature. The bimetallic strips of the two tensioning devices are preferably identical, with a different orientation. The number of bimetallic strips depends on the mechanical stresses applied to them and their mechanical strength. The tensile axis 14 is for example a cylindrical axis formed of steel or copper in cases where the compensation system does not also serve as a section insulator, otherwise an insulating bar, generally made of silicone-coated fiberglass.

[0081] Each bimetallic strip comprises a substantially central part, called the central part, connected to the traction axis. The portions of the bimetallic strip extending on either side of the central part have lengths called half-length of the bimetallic strip, for example between two and ten centimeters. The thickness of the bimetallic strip is for example less than one millimeter. For example, a half-length of three and a half centimeters and a thickness of the bimetallic strip equal to half a millimeter (a quarter of a millimeter per strip) allow compensation for the thermal expansion of a main cable for a temperature range of around 35°C and a range of twenty meters.

[0082] A first embodiment of a bimetallic strip 32 is shown respectively from the front and from the side in Figures 3a and 3b and a second embodiment of a bimetallic strip 32' is shown respectively from the front and from the side in Figures 4a and 4b.

[0083] In the first embodiment of the bimetallic strip 32 in the nominal position at the reference temperature, the two strips are of identical lengths and the bimetallic strip is therefore straight. A bore 42 arranged in the central part 40 of the bimetallic strip makes it possible to receive the traction axis.

[0084] In the second embodiment of the bimetallic strip 32' in the nominal position at the reference temperature, the two strips are of identical lengths and the bimetallic strip comprises a fold arranged 44 on its central part 40'. A bore 42' arranged in the central part 40' of the bimetallic strip makes it possible to receive the traction axis.

[0085] The bimetallic strips according to the two embodiments comprise systems for attachment to the rack attachments, here bores 46.

[0086] Figures 5a and 5b schematically represent in top view the operation of a compensation system comprising respectively the first embodiment of the bimetallic strip and the second embodiment of the bimetallic strip. The solid lines represent the compensation system in the so-called rest position and the dotted lines represent the compensation system when it is subjected to a temperature difference relative to the temperature of the rest position.

[0087] In the first embodiment of the bimetallic strip, the change in temperature causes a curvature of the bimetallic strip 32a of the first tensioning device 16a and of the bimetallic strip 32b of the second tensioning device 16b, both connected to the traction axis 14. A traction force is then transmitted on the one hand in the first tensioning device 16a to the racks 20a and 22a then to the first attachment means 18a which causes a first displacement La at the first attachment means 18a, and on the other hand on the one hand in the second tensioning device 16b to the racks 20b and 22b then to the second attachment means 18b which causes a second displacement Lb at the second attachment means 18a. The displacements La and Lb are generally equal if the system is balanced and allow the displacement due to thermal expansion of the main cable to be compensated.

[0088] In the second embodiment of the bimetallic strip, the change in temperature causes a curvature of the folded bimetallic strip 32'a of the first tensioning device 16a and of the folded bimetallic strip 32'b of the second tensioning device 16b, both connected to the traction axis 14. A traction force is then transmitted on the one hand in the first tensioning device 16a to the racks 20a and 22a then to the first attachment means 18a which causes a first displacement L'a at the first attachment means 18a, and on the other hand on the one hand in the second tensioning device 16b to the racks 20b and 22b then to the second attachment means 18b which causes a second displacement L'b at the second attachment means 18a. The displacements L'a and L'b are generally equal if the system is balanced and make it possible to compensate for the displacement due to the thermal expansion of the main cable. The displacements with this second embodiment of the bimetallic strip, called folded bimetallic strip, are less than the displacements of the first bimetallic strip, which makes it possible to compensate for a smaller displacement with the same temperature difference, for example for an application on a main cable with a smaller span.

[0089] The operation as described in Figures 5a and 5b is the same when each tensioning device comprises several bimetallic strips.

Claims

Claims

1. System for compensating for the thermal expansion of a main cable (12) comprising a first portion (120a) of main cable and a second portion (120b) of main cable, both of which portions extending in a direction, called the longitudinal direction, and arranged between two separate attachment points, said first and second portion of main cable each being respectively connected to an attachment point, said compensation system being characterized in that it comprises a traction axis (14) extending substantially parallel to the longitudinal direction, a first tensioning device (16a) connected on the one hand to said first portion (120a) of main cable and on the other hand to the traction axis (14), and a second tensioning device (16b) connected on the one hand to the second portion (120b) of main cable and on the other hand to the traction axis (14), each device (16a, 16b) of voltage including: • a means (18a, 18b) for attachment to the main cable; • at least two racks (20a, 22a; 20b, 22b), arranged in on either side of the traction axis (14) and substantially parallel to each other in the nominal position, each connected to the attachment means (18a, 18b) by at least one traction arm (24a, 26a; 24b, 26b); • at least one bimetallic strip (32a, 32b) comprising two strips formed from materials having different thermal expansion coefficients, the ends of each bimetallic strip being connected to each of the racks (20a, 22a; 20b, 22b) and a substantially central portion of the bimetallic strip being connected to the traction axis (14), the bimetallic strip (32a, 32b) being configured to have a variable curvature depending on the temperature of the bimetallic strip, so as to exert a variable traction force between the traction axis (14) and the rack depending on the temperature, and in that each bimetallic strip (32a, 32b) of one of the tensioning devices (16a, 16b) is oriented so that the tensile force exerted by said tensioning device (16a, 16b) on the tensile axis is oriented in a direction opposite to the tensile force exerted by the other device (16a, 16b) of tension on the traction axis when subjected to the same temperature.

2. Compensation system according to claim 1, characterized in that each tension device (16a, 16b) comprises a plurality of bimetallic strips (32a, 32b), configured to have the same radius of curvature as a function of the temperature of the bimetallic strip.

3. Compensation system according to one of claims 1 or 2, characterized in that each bimetallic strip (32a, 32b) comprises a first strip formed from an alloy of iron and nickel comprising around 36% nickel and 64% iron, and a second strip formed from copper.

4. Compensation system according to one of claims 1 to 3, characterized in that each bimetallic strip (32') comprises a fold (44) arranged substantially in its central part.

5. Compensation system according to one of claims 1 to 4, characterized in that each bimetallic strip (32a, 32b) comprises a bore arranged substantially in the central part and configured to receive the traction axis (14).

6. Compensation system according to one of claims 1 to 5, characterized in that each traction arm (24a, 26a; 24b, 26b) is connected by a pivot connection to the attachment means (18a, 18b) and by a pivot connection to the rack.

7. Compensation system according to one of claims 1 to 6, characterized in that at least one tensioning device (16a, 16b) comprises a protective cover (34a, 34b), connected to the rack (20a, 22a; 20b, 22b) of the tensioning device and extending opposite a rack (20a, 22a; 20b, 22b) of the other tensioning device of the compensation system.

8. Catenary cable equipped with a thermal expansion compensation system (10) according to one of claims 1 to 7, configured to compensate for the thermal expansion of said catenary cable arranged between two separate attachment points formed by posts.

Images