Abstract:
A funicular intended particularly for transporting heavy loads between an upstream station ( 10 ) and a downstream station ( 12 ), comprises a track ( 14 ), preferably a railway, connecting the upstream station ( 10 ) to the downstream station ( 12 ), a vehicle ( 16 )running on the track ( 14 ) and at least one towing cable ( 30 ) in closed loop having a first towing section ( 32.1 ) passing over a first pulley ( 20.1 ) of the upstream station and over a first return pulley ( 26 ) fixed to the vehicle ( 16 ) and a second towing section ( 32.2 ), in all ways separate from the first towing section and passing over the return pulley ( 26 ) and over a second pulley ( 20.2 ) of the upstream station ( 10 ).

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The invention relates to a funicular, particularly for transporting heavy loads, such as for example confinement hoods for radioactive wastes intended to be buried in an underground site. 
       PRIOR ART 
       [0002]    Document FR 2 954 747 describes a funicular designed to transport radioactive wastes between an upstream overground station and a downstream station of an underground waste landfill facility. An inclined ramp connects the upstream station to the downstream station and materialises a rail transport track and one or several counterweight tracks. A wagon runs on the transport track whereas one or several counterweights run in the opposite direction on the counterweight track. The wagon and the counterweight(s) are connected by two cables that each pass over a driving pulley, in order to give the installation redundancy with a view to increasing its safety. In order to fix an end of each cable to the wagon, the latter is equipped with a winding drum and one gripping jaw per cable. This fixing method, extremely well tried and trusted, nevertheless has the drawback of taxing the cable in a way that accelerates its ageing. 
         [0003]    In in JP 8-133068, a funicular is described, which comprises an upstream station, a downstream station, a circulation track connecting the upstream station to the downstream station, a vehicle rolling on the circulation track, the vehicle being provided with a tension balancing system formed by a drum, to which the ends of two cable sections that link the vehicle to the upstream station are affixed, wherein the two cable sections are wound in opposite directions on the drum, so that the extension of one of the cable sections leads to a rotation of the drum that balances the tensions on the two cable sections. 
         [0004]    In an entirely different context illustrated by document EP 0 692 418 B1, cable cars for transporting passengers are known, comprising two suspension cables arranged on either side of the cabin and above the latter, on which a pendulum carriage on which a cabin is suspended travels, in addition to a closed-loop towing cable, a first section of which is pulled between a first compensation pulley mounted on the cabin and a first idle pulley located in a downstream station, wherein a second section is pulled between the first idle pulley of the downstream station and a first driving pulley situated in an upstream station, wherein a third section is pulled between the first driving pulley and a second compensation pulley mounted on the cabin, wherein a fourth section is pulled between the second compensation pulley and a third compensation pulley mounted on the cabin, wherein a fifth section is pulled between the third compensation pulley and a second driving pulley situated in the upstream station, wherein a sixth section is pulled between the second driving pulley and a second idle pulley situated in the downstream station, wherein a seventh section is pulled between the second idle pulley situated in the downstream station and a fourth compensation pulley mounted on the cabin and wherein an eighth section is pulled between the fourth compensation pulley and the first compensation pulley. The axes of rotation of the compensation pulleys are all vertical, wherein the first and second compensation pulleys are coaxial and located laterally on one side of the cabin whereas the third and fourth compensation pulleys are likewise coaxial, but situated on the other side of the cabin. This arrangement of the suspension cables and of the sections of the towing cable laterally outside and on either side of the cabin makes it possible to increase lateral stability and in particular reduce lateral oscillations while reducing the distance between the carriage and the cabin. Furthermore, the path of the towing cable allows balancing of the traction exerted on the cabin by the sections of cable. This solution is not however intended to be transposed to the transport of heavy loads, since on the one hand, the cabin is suspended and on the other hand, the curved path imposed on the towing cable and particularly its passage over small-diameter compensation pulleys, restricts the section of the cable. 
       DISCLOSURE OF THE INVENTION 
       [0005]    The invention aims to solve the drawbacks of the prior art and propose a device and a method of coupling between a travelling vehicle and a towing cable that dispenses with gripping jaws on the vehicle. 
         [0006]    For this purpose, a first aspect of the invention proposes a funicular comprising an upstream station, a downstream station, a track, preferably a railway, connecting the upstream station to the downstream station, a vehicle running on this track, at least one towing cable in closed loop having a first towing section passing over a first pulley of the upstream station and over a return pulley fixed to the vehicle, a second towing section, in all ways separate from the first towing section and passing over the return pulley and over a second pulley of the upstream station, a first linking section towed between the first pulley of the upstream station and a first pulley of the downstream station, a second linking section towed between the second pulley of the upstream station and a second pulley of the downstream station, a first return section towed between the first pulley of the downstream station and a second return pulley situated on the vehicle and a second return section towed between the second pulley of the downstream station and the second return pulley. 
         [0007]    Replacing the gripping jaws of the prior art with a large-diameter pulley overcomes the potential problems of cable fatigue at the gripping jaw on the vehicle. 
         [0008]    The first towing section and the second towing section of the cable run along the track, preferably substantially parallel to the latter and parallel to each other, spaced apart in a manner that is preferably substantially constant in their portion situated along the track. The towing cable is preferably wound around the first return pulley in a circular arc of more than 120° and of less than 360°, preferably of more than 160°, preferably of less than 200° and preferably of approximately 180°. The diameter of the pulley, which is preferably substantially equivalent to the distance between the first and second towing section of the cable, is dimensioned such as to ensure a maximum radius of curvature of the cable compatible with the section of the cable according to normative provisions. This is the reason why the pulley is large in diameter and in practice has a diameter greater than half and preferably greater than two thirds of the width of the vehicle. 
         [0009]    Preferably, the vehicle comprises at least one undercarriage having a track width for running on the track, wherein the first return pulley has a diameter greater than half of the track width and preferably greater than two thirds of the track width. 
         [0010]    According to one embodiment, the funicular comprises at least one weight for tensioning the cable. The weight(s) can advantageously be arranged in one or two wells so as to obtain an adequate vertical displacement. Each weight is preferably suspended on the associated section of cable by means of a pulley, which preferably has a diameter of at least the same magnitude as that of the return pulley. 
         [0011]    According to one embodiment, the towing cable is wound around the first pulley of the upstream station and around the second pulley of the upstream station in an arc of more than 120° and of less than 360°, preferably of more than 180°, preferably of more than 225° and preferably of more than 240°. 
         [0012]    In order to achieve these wide angles, provision can be made for the cable&#39;s comprising at least one linking section that crosses the first towing section and the second towing section, preferably in a portion of the installation outside the tracks, preferably in a part of the upstream station upstream from the track. 
         [0013]    The funicular is preferably provided with first driving means for the first towing section of the cable and with second driving means for the second towing section of the cable, which are preferably independent. These driving means may comprise motors of any appropriate type, turning driving pulleys and be situated at any appropriate location, particularly in the upstream station or in the downstream station. According to a particularly advantageous embodiment, the first pulley of the upstream station is a driving pulley, the axle of which is driven by a motor and the second pulley of the upstream station is a driving pulley, the axle of which is also driven by a motor. Although it is conceivable to drive both driving pulleys of the upstream station using the same motor, it is preferred to use two different motors in order to provide the installation with a certain redundancy. 
         [0014]    The funicular is preferably provided with at least a first brake to lock the first towing section and a second brake to lock the second towing section. These brakes may be incorporated in the driving means, for example in order to brake and arrest rotation of a towing pulley. They may also involve brakes acting on the cable or a combination of different types of brake. 
         [0015]    These brakes allow the installation to operate in a degraded mode with a single motor if the other motor fails. All that is needed in this case is to block the towing cable associated with the failed motor and drive the vehicle solely using the second towing section and the other motor. 
         [0016]    During operation, the driving means are intended to drive both towing sections of the towing cable. The return pulley, which is capable of rotating, allows balancing of the forces exerted on the towing sections. It may be chosen to control the driving pulleys with a relative motion (i.e. with a difference in rotation speed), so as to impose slow rotation on the return pulley, in order for example to avoid always taxing the same portion of the cable. It may also be chosen to control the driving pulleys such that the return pulley does not rotate during travel, but rotation is imparted to the return pulley during a halt, for example when empty, in the upstream station or in the downstream station. 
         [0017]    In practice, the track defines a path for the vehicle and an axis for this path, which will be merged with a so-called longitudinal axis of the vehicle. The axis of the path is oblique and preferably rectilinear between the upstream station and the downstream station. For the purposes of the description, a second axis, a so-called transverse axis, of the vehicle is defined, horizontal and perpendicular to the longitudinal axis. Finally, a third reference axis is defined, perpendicular to the two preceding axes. 
         [0018]    The vehicle preferably comprises a platform on which the load rests during its transport. In practice, the platform is horizontal, whereas the track forms an angle, preferably constant, with the horizontal. 
         [0019]    The first return pulley rotates around an axis that is positioned on the vehicle, preferably in the part of the vehicle located upstream from the platform, i.e. between the upstream station and the platform. 
         [0020]    The vehicle preferably comprises a chassis bearing the platform and resting on an upstream undercarriage and on a downstream undercarriage, situated longitudinally on either side of the platform, the upstream undercarriage between the platform and the upstream station and the downstream undercarriage between the platform and the downstream station. The axis of rotation of the first return pulley is preferably situated between the upstream undercarriage and the downstream undercarriage, or at least between an upstream longitudinal end of the upstream undercarriage and a downstream end of the downstream undercarriage. 
         [0021]    According to one embodiment, the axis of rotation of the first return pulley can be perpendicular to the longitudinal axis of the vehicle, or preferably oblique in relation to the longitudinal axis, with an angle preferably included between 80° and 100°. Guide rollers may also be provided on the vehicle in order to guide each of the first and second towing sections towards the return pulley. These guide rollers preferably include at least one first guide roller associated with the first towing section and situated above the first towing section, in addition to a second guide roller associated with the second towing section and situated above the second towing section. 
         [0022]    According to a preferred embodiment, the axis of rotation of the first return pulley is perpendicular to a transverse axis of the vehicle, in the median longitudinal vertical plane of the vehicle. 
         [0023]    The two towing sections of the cable are preferably situated in the same plane parallel to the track and perpendicular to a median longitudinal vertical plane of the vehicle. 
         [0024]    Alternatively, it is also conceivable that the axis of rotation may be parallel to the transverse axis of the vehicle. In this case, the plane defined by the longitudinal axis and the axis of rotation is preferably situated close to the centre of gravity of the unloaded vehicle. 
         [0025]    According to one embodiment, the track comprises two parallel rails spaced apart from each other. Preferably, a service corridor is positioned between the two rails. In this case, the first and second towing sections of the cable are preferably arranged in the corridor. 
         [0026]    Both return pulleys are preferably of the same diameter. They may be coaxial and situated approximately halfway between the two longitudinal ends of the vehicle or, according to a preferred embodiment, be non-coaxial and particularly situated longitudinally spaced apart from one another, on either side of the load transport platform, if appropriate. Preferably, the axes of rotation of the return pulleys are non-parallel and preferably secant in a median longitudinal vertical plane of the vehicle. 
         [0027]    According to another aspect of the invention, the latter refers to a method for controlling a funicular as described above, wherein the first towing section and the second towing section are driven at the same linear speed. Control is particularly easy in this case and the return pulley(s) ensures/ensure balancing in the tension of the sections of the cable. 
         [0028]    According to another embodiment, the first towing section and the second towing section are driven so as to cancel the rotation speed of the first return pulley, which can be measured by a return pulley rotation sensor. 
         [0029]    According to another embodiment, the first towing section and the second towing section are driven so as to impose rotation of the first return pulley. 
         [0030]    According to another embodiment, the first towing section and the second towing section are driven so as to cause rotation of the first return pulley without any movement of the vehicle. This cable circulation regimen without movement of the vehicle can be advantageously employed in one of the upstream or downstream stations, in order to ensure that all the portions of the cable are taxed in the same way during the life of the installation. 
         [0031]    According to a degraded operating mode specific to installations with a closed-loop cable, only one of the towing sections is driven, the other being idle, in order to move the wagon at slow speed. 
         [0032]    According to another aspect of the invention, the latter refers to a vehicle designed to run on a railway-type track, particularly a vehicle for a funicular according to the first aspect of the invention, in any of the configurations according to the various different embodiments discussed and comprising a chassis defining a median longitudinal vertical plane. The chassis rests on at least one pendulum running gear, comprising two independent lateral pendulum devices situated on either side of the median longitudinal vertical plane. Each lateral pendulum device comprises:
       a secondary pendulum articulated in relation to the chassis around a horizontal secondary pivot axis and   two primary pendulums, wherein each of the two primary pendulums is articulated in relation to the second pendulum around a horizontal primary pivot axis, wherein the primary pivot axes of the two primary pendulums are spaced apart from each other, longitudinally on either side of the secondary pivot axis, where in each primary pendulum is associated with at least two support rollers designed to run on the railway-type track, each rotating around a rotation axis parallel to the primary pivot axis of the associated primary pendulum and situated longitudinally on either side of the primary pivot axis of the associated primary pendulum.       
 
         [0035]    The arrangement of the primary and secondary pendulums of each lateral pendulum device serves to balance the forces exerted on the support rollers and therefore distribute the vehicle weight over a large number of support rollers. This aspect of the invention is the subject of concomitant submission of another International patent application, to which the reader will refer. 
         [0036]    More generally, the content of the prior applications, the priority of which is claimed in the present application, is integrally included in the present application by reference. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0037]    Further characteristics and advantages of the invention will be clear from reading the following description, made in reference to the appended figures, which show: 
           [0038]      FIG. 1 , a diagrammatic view of a funicular according to an embodiment of the invention; 
           [0039]      FIG. 2 , a side view of a vehicle of the funicular of  FIG. 1 ; 
           [0040]      FIG. 3 , a top view of the vehicle in  FIG. 2 ; 
           [0041]      FIG. 4 , a front view of the vehicle in  FIG. 2 ; 
           [0042]      FIG. 5 , a detailed view of  FIG. 2 ; 
           [0043]      FIG. 6 , an isometric view of a part of an upstream station of the funicular in  FIG. 1 ; 
           [0044]      FIG. 7 , a top view of the upstream station in  FIG. 5 ; 
           [0045]      FIG. 8 , a side view of the upstream station in  FIG. 6 ; 
           [0046]      FIG. 9 , an isometric view of a downstream station of the funicular in  FIG. 1 ; 
           [0047]      FIG. 10 , a top view of the downstream station in  FIG. 1 . 
       
    
    
       [0048]    For greater clarity, identical or similar features are identified by identical reference signs in all the figures. 
       DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0049]    In  FIG. 1 , a diagrammatic and simplified illustration is provided of a funicular comprising an upstream station  10 , a downstream station  12  and a track  14 , preferably a railway, along which a single vehicle  16  travels back and forth, designed to transport a load interchangeably from the upstream station  10  to the downstream station  12  or from the downstream station  12  to the upstream station  10 . The track  14  preferably has a constant incline between the upstream station  10  and the downstream station  12 . 
         [0050]    The upstream station  10  is equipped with two driving pulleys  20 . 1 ,  20 . 2 , powered by motor means  22 . 1 ,  22 . 2 , which may be common or separate for each pulley. 
         [0051]    The downstream station  12  is also equipped with two pulleys  24 . 1 ,  24 . 2 , freely rotating, turning around axes parallel to those of the driving pulleys of the upstream station  10 . 
         [0052]    The vehicle  16  is in turn equipped with two large-diameter return pulleys  26 ,  28 , freely rotating around two axes A, B situated in a median longitudinal median plane P of the vehicle  16 . The return pulleys  26 ,  28  are arranged at a distance from another along the path of the vehicle, one on the side of the upstream station  10  and the other on the side of the downstream station  12 . 
         [0053]    A closed-loop cable  30  is towed between the return pulleys  26 ,  28  of the vehicle  16  and the pulleys  20 . 1 ,  20 . 2 ,  24 . 1 ,  24 . 2  of the upstream and downstream stations. More specifically, the cable  30  comprises a first towing section  32 . 1  towed between the upstream return pulley  26  of the vehicle  16  and a first pulley ( 20 . 1 ) of those of the upstream station  10 , a first linking section  34 . 1  towed between the first driving pulley  20 . 1  and a first pulley of those of the downstream station  24 . 1 , a first return section  36 . 1  towed between the first pulley of the downstream station  24 . 1  and the downstream return pulley  28  situated on the vehicle  16 , a second return section  36 . 2  towed between the downstream return pulley  28  and the second pulley of the downstream station  24 . 2 , a second linking section  34 . 2  towed between the second pulley of the downstream station  24 . 2  situated in the downstream station and the second driving pulley  20 . 2  of the upstream station  10  and a second towing section  32 . 2  between the second driving pulley  20 . 2  and the upstream return pulley  26  of the vehicle  16 , thereby closing the loop. 
         [0054]    Optionally, each of the two linking sections  34 . 1 ,  34 . 2  passes through a tensioning device  38 . 1 ,  38 . 2  comprising an upstream guide pulley  40 . 1 ,  40 . 2 , a downstream guide pulley  42 . 1 ,  42 . 2  and a mobile pulley  44 . 1 ,  44 . 2  bearing a weight  46 . 1 ,  46 . 2  moving in a vertical well  48 . 1 ,  48 . 2 . In the diagrammatic representation in  1 , the spatial orientations of the pulleys and the path of the cable have not necessarily been respected, but will be more readily apparent from  FIGS. 2 to 10 . 
         [0055]    Provision is also made for cable braking devices  49 . 1 ,  49 . 2 , which may for example act on the driving pulleys  20 . 1 ,  20 . 2 ., or on the towing sections  32 . 1 ,  32 . of the cable. 
         [0056]    The vehicle  16 , illustrated in detail in  FIGS. 2 to 5 , comprises a chassis  50  on which a horizontal platform  52  bearing the load  54  is formed. It is possible to define a longitudinal axis X of the vehicle parallel to the direction of the rectilinear path, a transverse axis Y, perpendicular to the above axis and horizontal and a third reference axis Z of the vehicle, perpendicular to the above axes and the track. The chassis  50  rests on an upstream running gear  56  and a downstream running gear  58 . Each running gear is composed of two independent lateral pendulum devices  60 . Each lateral pendulum device  60  comprises a secondary pendulum  62  mounted to pivot around an axis  62 . 1  on a plate  64  fixed to the chassis via two jacks  66  and two primary pendulums  68  articulated in relation to the secondary pendulum  62  around pivot axes  68 . 1  and on each of which two support rollers  70  are mounted running on the track  14  and rotating around axes  70 . 1 . The jacks  66 , which are oriented along axis Z perpendicular to the track  14 , do not have a filtering suspension function, but allow raising of the chassis  50  above the ground for its setting in motion and its lowering in contact with the ground of the track  14  when stationary for the loading and unloading phases in the station or when moving for emergency braking. The pivot axes  68 . 1  of the primary pendulums  68  are arranged longitudinally on either side of the secondary pivot axis  62 . 1  and the rotation axes  70 . 1  longitudinally on either side of the primary pivot axis  68 . 1 , which allows balancing of the forces exerted by the support rollers  70  on the track. On one side of the vehicle, the rollers  70  are cylindrical, whereas on the other, they are provided with lateral guide flanges  70 . 2  to allow compensation for any slight variations in the spacing between the rails. Each roller  70  may also be equipped with a brake  70 . 3 . 
         [0057]    One can see in  FIGS. 2 to 4  the positioning of the two large-diameter return pulleys  26 ,  28 , on the chassis, above the track and rotating around two axes A, B situated in the longitudinal median plane and slightly angled in relation to the axis Z perpendicular to the track. The return pulleys are guided in relation to the chassis  50  by bearings  26 . 1 ,  28 . 1 . spaced apart from one another along the path of the vehicle. In this case, the bearings  26 . 1  of the upstream return pulley  26  linking the vehicle to the upstream station, is situated upstream from the bearings  28 . 1  of the downstream return pulley  28  linking the vehicle to the downstream station  12 . Furthermore, the bearings  26 . 1 ,  28 . 1  are situated longitudinally between the secondary pivot axes  62 . 1  of the upstream running gear  56  and downstream running gear  58 . Guide rollers  72  are arranged along the track to support the cable  30 . Return pulleys  26 ,  28  are arranged above the guide rollers  72 . The chassis  50  is equipped with orientation rollers  74  allowing the cable  30  to be raised and oriented in the oblique plane of the return pulleys  26 ,  28 . 
         [0058]    The vehicle may also be equipped with upstream and downstream driver&#39;s cabins  76 , each provided with a control console  78 . The chassis  50  of the vehicle  16  features wear skids  80  which, when the jacks  66  are lowered, rest on the ground. 
         [0059]      FIGS. 6 to 8  allow visualisation of the path of the cable in the upstream station. The first towing section  32 . 1  enters the station along a path situated essentially in a vertical plane parallel to the axis X of the path from the return pulley  26  to the driving pulley  20 . 1 . The same applies to the second towing section  32 . 2  between the return pulley  26  and the second driving pulley  20 . 2 . On leaving the first driving pulley  20 . 1 , the first linking section  34 . 1  of the cable crosses the two towing sections  32 . 1  and  32 . 2  and is diverted by the upstream guide pulley  40 . 1  towards the mobile pulley  44 . 1  in the well  46 . 1 , re-emerging and being guided by the downstream guide pulley  42 . 1  so as to run along a vertical plane parallel to the path of the vehicle  16 , to the downstream station  12 . The second linking section  34 . 2  follows a similar path, crossing the two towing sections  32 . 1 ,  32 . 2  and being diverted by the upstream guide pulley  40 . 2  towards the mobile pulley  44 . 2  in the well  46 . 2 , re-emerging and being guided by the downstream guide pulley  42 . 2  so as to run along a vertical plane parallel to the path of the vehicle  16 , to the downstream station  12 . Crossing of the linking sections  34 . 1   34 . 2  with the towing sections  32 . 1 ,  32 . 2  in the upstream station  10  ensures contact between the cable  30  and each of the driving pulleys  20 . 1 ,  20 . 2  over more than 180° and in practice over more than 225° and preferably over more than 240°. In this embodiment, the upstream driving pulleys, the downstream guide pulleys and the mobile pulleys have horizontal rotation axes, whereas the driving pulleys have vertical axes. 
         [0060]      FIGS. 9 and 10  illustrate the downstream station  12  equipped with the two pulleys  24 . 1 ,  24 . 2 , freely rotating, turning around vertical axes. The diameters of the driving pulleys  20 . 1 ,  20 . 2  of the upstream station and of the idle pulleys  24 . 1 ,  24 . 2  of the downstream station are preferably substantially identical. As illustrated by  FIGS. 2 to 10 , the linking sections  34 . 1 ,  34 . 2 , in their path along the track  14 , flank the towing sections  32 . 1 ,  32 . 2  and the return sections  36 . 1 ,  36 . 2 . 
         [0061]    The symmetry of the installation is such that in theory, if the two driving pulleys  20 . 1 ,  20 . 2  are driven at equal speed in opposite directions and assuming the dynamic elastic deformations of the cable identical on either side, the vehicle  16  is driven in an ascending or descending direction, without the return pulleys  26 ,  28  rotating. In practice, the conditions for perfect symmetry are not achieved, owing for example to the differences in perimeter of the driving pulleys and rotation of the return pulleys  26 ,  28  allows dynamic balancing of the forces exerted on the sections of the cable  30 . It may also be chosen to control the driving pulleys  20 . 1 ,  20 . 2  with a speed difference, so as to cause constant rotation of the return pulleys  26 ,  28 , as discussed above. This speed difference may be constant or variable, particularly periodically. 
         [0062]    It is also noted that the relative position of the bearings  26 . 1 ,  28 . 1  allows, in case of a slight lack of alignment of the vehicle in relation to the track, generation of a compensating torque on the chassis  50  of the vehicle, thereby bringing the vehicle back into alignment. The positioning of the bearings  26 . 1  upstream from the centre of gravity of the vehicle when empty and upstream from the platform  52  bearing the load  54  also ensures correct orientation of the vehicle on the track, both when loaded and when empty, to the extent that the centre of gravity of the vehicle  16  when empty is in the median longitudinal plane and that the load  54  is also positioned such that its centre of gravity is in the median longitudinal plane. 
         [0063]    In the event of failure of one of the motors  22 . 1 ,  22 . 2 , the corresponding brake  49 . 1 ,  49 . 2  can be operated and the vehicle  16  can be driven at low speed by the other motor. 
         [0064]    In order to control the funicular according to the invention, it is possible to resort to different sensors in order to measure different status variables of the installation and more particularly: sensors measuring the speed or rotation of the driving pulleys  20 . 1 ,  20 . 2 , sensors measuring the speed or rotation of the pulleys  24 . 1 ,  24 . 2  of the downstream station, sensors measuring the speed or rotation of the return pulleys  26 ,  28 , extensometric sensors detecting stretching of the different sections of the cable or some thereof, sensors measuring the resulting force on the axis of the upstream return pulley  26 , sensors measuring the speed of the vehicle  16  and sensors measuring the motor torque of the driving pulleys  20 . 1 ,  20 . 2 . 
         [0065]    Naturally, various modifications are possible. It is possible in particular to double the installation, so as to ensure redundancy in towing. 
         [0066]    The tensioning devices are not necessary positioned on the towing sections, but may be alternatively placed on the linking sections or the return sections. The drive motors may be arranged in the downstream station. Motorisation divided between the two stations may also be contemplated.