Abstract:
A system for guiding a vehicle along a guiding rail includes a guide roller device, with at least one rolling bearing roller and at least one lateral roller having a diameter and shape contacting the rail so that the lateral roller has the same speed at a point of contact with the rail as the central bearing roller on a rolling surface on the rail. The system can be used for tramways.

Description:
The invention relates to a system for guiding a vehicle along at least one guiding rail, having a rolling surface and at least one side surface of which constitutes a guiding surface, of the type which has a guiding roller device configured to cooperate with the rolling surface and the side surface and having a rolling bearing part intended for being in rolling contact by its peripheral surface with the upper rolling surface of the rail and at least one side part capable of coming into contact with the side surface of the rail facing it. 
     BACKGROUND 
     Systems of this type are already known. These systems are suitable for cooperating with one or two rails, and their roller device has a rolling bearing surface and at least one side part in the form of a flange which is rotationally connected with the bearing part, projects radially towards the exterior, and comes in contact with the guiding surface of the rail. 
     This known guiding system has the disadvantage that the contact of the side surfaces of the flanges forming the cheeks with the surfaces of the rail head facing them involves friction between the surfaces in contact and thus wear and tear on both the rail and the roller. 
     The invention aims to propose a guiding system that palliates this disadvantage. 
     SUMMARY OF THE INVENTION 
     To attain this objective, in the roller device according to the invention the rolling part and the side part are configured such that the side part, at its point of contact with the rail, has the same speed as the central part at the site of its rolling surface on the rail. 
     According to one characteristic of the invention, the roller device has at least one rolling support roller and at least one side roller forming the side part and of which the diameter and shape of the side surface intended for coming into contact with the rail are chosen such that the side roller, at its point of contact with the rail, has the same speed as the central support roller at the site of its rolling surface on the rail. 
     According to one characteristic of the invention, the roller device has at least one rolling support roller and at least one side roller forming said side part and of which the diameter and shape of the side surface intended for coming into contact with the rail are chosen such that the side roller, at its point of contact with the rail, has the same speed as the central support roller at the site of its rolling surface on the rail. 
     According to another characteristic of the invention, the vehicle is guided along two parallel guiding rails, of which the exterior side surfaces constitute the guiding surfaces, characterized by the fact that it has a support roller and a side roller for each guiding rail. 
     According to yet another characteristic of the invention, the roller device has three rollers, a central roller and two side rollers forming said side parts and of which the diameter and the shape of the side surface intended for coming into contact with the rail are chosen such that the side rollers, at their point of contact with the rail, have the same speed as the central support roller at the site of its rolling surface on the rail. 
     According to yet another characteristic of the invention, the areas of contact of the side rollers have, in radial section, a convex profile, advantageously in an arc shape, and the contact surfaces of the rail are essentially planar. 
     According to yet another characteristic of the invention, a side roller is rotationally synchronized with the central roller. 
     According to yet another characteristic of the invention, the means of synchronization of the rotation speed of a side roller with the rotation speed of the central roller comprises teeth, associated respectively with the side roller and with the central roller, which mesh with one another. 
     According to yet another characteristic of the invention, a set of teeth is mounted on its support by a means allowing sliding between the teeth and the support when a relative force exceeding a predetermined threshold is exceeded. 
     According to yet another characteristic of the invention, the means of synchronization of the rotation speed of a side roller with the rotation speed of the central roller is the belt-and-pulley type. 
     According to yet another characteristic of the invention, the means of synchronization of the rotation speed of a side roller with the rotation speed of the central roller comprises a ring made out of a nondeformable solid material which comes in contact with a bearing surface of the central roller so as to ensure the rotation of the side roller by friction with the central roller. 
     According to yet another characteristic of the invention, the central roller is formed by a ring rotating freely and maintained by a support device connected to the support shaft. 
     According to yet another characteristic of the invention, the support device comprises rollers for support of the ring that come in rolling contact with an internal annular surface of the ring. 
     According to yet another characteristic of the invention, the system has two rollers, each of which has a radial external part intended for coming into contact with a side surface of the head of the rail and a radial internal part intended for coming into contact with the upper surface of the rail head, the two rollers being arranged in a V-shaped configuration. 
     According to yet another characteristic of the invention, the system has two rollers, each of which has a radial external part intended for coming into contact with a side surface of the head of the rail and a radial internal part intended for coming into contact with the upper surface of the rail head, and one of the rollers has a peripheral ring intended for coming into contact with an annular surface of the other roller so as to ensure the rotation of the roller by friction with the roller. 
    
    
     
       BRIEF DESCRIPTION OF DRAWING FIGURES 
       The invention will be better understood and other aims, characteristics, details and advantages of it will appear more clearly in the course of the following description that references the appended drawings, which are given by way of example to illustrate several embodiments of the invention and in which: 
         FIG. 1  is a perspective view of a guiding system according to the invention; 
         FIG. 2  is a section view in the vertical plane through line II-II of  FIG. 1 ; 
         FIG. 3  is a view of the roller device in the direction of arrow III-III of  FIG. 1 ; 
         FIGS. 4 to 7  are section views similar to  FIG. 2  and show three implementation variations of a first embodiment of the invention; 
         FIG. 8  is a section view similar to  FIG. 2 , of a second embodiment of a roller device according to the invention; 
         FIG. 9  is a section view similar to  FIG. 2 , of an improvement in the embodiment of  FIG. 2 ; 
         FIG. 10  is a section view similar to  FIG. 2 , of a fourth embodiment of the roller device according to the invention; 
         FIG. 11  is a perspective view of another embodiment of the guiding system according to the invention; 
         FIG. 12  is a partial vertical section of another embodiment of the invention; 
         FIG. 13  is a section view, perpendicular to the rail, of yet another embodiment of the guiding system according to the invention; 
         FIG. 14  is a section view according to line XIV-XIV of  FIG. 13 ; 
         FIG. 15  is a section view, perpendicular to the rail, of yet another embodiment of the invention; 
         FIG. 16  is a section view, perpendicular to the rail, of yet another embodiment of the guiding system according to the invention; 
         FIG. 17  is a section view, perpendicular to the rail, of yet another embodiment of the guiding system according to the invention; and 
         FIG. 18  is a section view, perpendicular to the rail, of yet another embodiment of the guiding system according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a guiding system according to the invention that makes it possible to guide a vehicle advantageously on tires rolling on a roadway, using a single rail. 
     In the example represented, the system has roller device  1  engaged on rail  2  that constitutes a mechanical contact roller mounted at fork-shaped end  4  of arm  5  whose other end is mounted so as to pivot around horizontal shaft  6  on a part within the form of frame  7  which is itself mounted so as to pivot around vertical shaft  8  fixed between two parallel support brackets  9  and  10  associated with axle  11  for support of two wheels of the vehicle equipped with the guiding system according to the invention. By means of load maneuver and application system  14  inserted between support frame  7  and arm  5 , the latter can be made to pivot around shaft  6  in order to bring it in or out of engagement with rail  3 . System  14  allows roller device  1  to be applied on the rail with an adjustable force. 
     Provided at the end of each axle is pivoting lever  16  with two arms  17 ,  18 , the pivot pin of which is supported by the axle and contains, at the site of the pivot pin but oriented perpendicularly, the axis of rotation of wheel  12 . Thus, lever  16  forms a triangle of orientation of the wheel. As  FIG. 1  clearly shows, connecting rod  19  is inserted between front end  21  of support frame  7  and the free end of one of the arms, in the present case arm  17 , of guiding triangle  16 . Connecting rod  19  extends parallel to axle  11 . Another connecting rod  22  interconnects the free ends of the other two arms  18  of the two guiding triangles  16 . 
     It is easily understood that any change in orientation of the rail, such as a curvature of rail  2 , is transmitted by roller device  1  to arm  5  and brings about a pivoting of the latter about its vertical shaft  8 , which leads to a change in orientation of wheels  12  by the intermediary connecting rods  19 ,  22  and guiding triangles  16 . 
     Different embodiments of roller device  1  according to the invention will be described below with reference to  FIGS. 2 to 10 . 
       FIG. 2  shows a first variation of a first embodiment of roller device  1  according to the invention. This device has three separate rollers, namely central roller  24  and two side rollers  25  and  26  on either side of it. The three rollers are mounted so as to rotate on crankshaft  28  produced as a single piece, which has central part  29  for support of central roller  24  and a part on the right and on the left, respectively  30  and  31 . Parts  30  and  31  are inclined relative to the axis of central part  29  so that rollers  25  and  26  are inclined, relative to central roller  24 , towards one another at the site of rail  2 . Rollers  24 ,  25 ,  26  are mounted on their shaft parts,  29 ,  30  and  31 , respectively, via rolling bearings,  33 ,  34 ,  35  respectively. Inclined shaft parts  30 ,  31  are held in support parts  37 ,  38  engaged in limbs  40  of fork  4 , with insertion of elastomer layer  40 ,  41 . 
     Rail  2  in the example represented has head  42  as a part connected to base  43  by narrower intermediate part  44 . Head  42  of the rail has planar horizontal surface  45  and two side surfaces  46 ,  47  that are inclined towards one another in the direction of base  43 . 
     Central roller  24  has cylindrical exterior surface  49  by which it comes in rolling contact with upper horizontal surface  45  of rail  2 . Side rollers  25 ,  26  have a larger diameter than the diameter of central roller  24  so that radial external parts  51 ,  52  of the side surfaces oriented towards rail  2  project at the site of the rail, beyond peripheral surface  49  of central roller  24  so that they can come into contact with the inclined side surfaces, respectively  46 ,  47 , of head  42  of the rail. The separation of side contact surfaces  51 ,  52  of rollers  25 ,  26  is greater than the width of rail head  42  so that when one surface is in contact with the rail head, the other is separated from the head, as  FIG. 2  clearly shows. 
     According to an essential characteristic of the invention, annular contact surfaces  51 ,  52  are convex and advantageously have, according to the radial section in  FIG. 2 , an arc shape, which is diagrammatically indicated with broken lines. Consequently, the contact between surfaces  51 ,  52  of the rollers and side surfaces  46 ,  47  is essentially a pin-point and therefore frictionless contact. In the figure, the pin-point contact area of convex surface  52  of roller  26  with side surface  47  of rail head  42  is designated by  54 . Furthermore, the radial distance between the axes of inclined arm parts  30 ,  31  and the areas of contact, such as area  54  of convex surfaces  51 ,  52  of rollers  25 ,  26 , is equal to the radial separation between the axis of middle part  29  and peripheral rolling surface  49  of central roller  24 . 
     In order to prevent any differential speed between roller  24  rolling continually on rail  2  and side rollers  25 ,  26  during contact between the rollers and rail head  42 , after a certain time of no contact the roller device has a means for synchronization of the rollers by driving the side rollers with the central roller. In the case of  FIG. 2 , this driving is brought about by means of a gear. For this purpose, central roller  24  has, on each of its side surfaces, a ring of radial teeth, and each side roller  25 ,  26  has, on its surface facing it, a complementary toothed ring, respectively  57 ,  58 . As the figure shows, the teeth are tapered, and each set of side-roller teeth meshes with a set of central-roller teeth at the site of their part just above the rail. 
     It should also be noted that  FIG. 2  shows at  60  the groove in the roadway that houses head  42  of rail  2 , and the width of which is chosen so as to allow the engagement of the lower radial external parts of side rollers  25 ,  26 . 
     It is observed, moreover, that in order to protect roller device  1  from penetration by foreign bodies and dirt, the device is provided with protective casing  62 , which covers and surrounds the space between the surfaces facing one another of the side rollers and of the central roller. 
       FIG. 4  shows another execution variation of roller device  1  of  FIG. 2 . In this implementation variation of device  1 , central roller  24  has, on its periphery, strip  63  made of synthetic material whose exterior cylindrical peripheral surface constitutes rolling surface  42  of the roller. This layer of synthetic material inserted between the central roller and the rail provides sound insulation. 
       FIG. 5  shows another implementation possibility of the sound insulation. In this case, central roller  24  is provided with elastomer layer  64  for sound insulation situated inside of the roller extending over the whole width of the roller, parallel to its axis. In order also to provide sound insulation at the site of side rollers  25 ,  26 , these rollers are produced in two parts, a central part in the form of hub  66  and annular exterior part  67 , with insertion of insulating elastomer layer  68  between these two parts. Given that the hub has radial projection  69  beyond the lower edge of exterior annular part  67 , insulating layer  68  has an L-shaped profile so that the sound insulation effect is optimal. 
     In the implementation variation of the first embodiment represented in  FIG. 6 , a layer of sound insulation noted  71  is arranged under the area of contact of side rollers  24 ,  25  with side surfaces  46 ,  47  of rail head  42 , and the areas of contact are, for this purpose, produced as separate annular elements, curved as a consequence. These elements  72 ,  73  are connected onto the rollers, with insertion of sound insulating layers  71 . 
       FIG. 7  shows another embodiment of roller device  1  of the invention. In this case, the upper surface of the rail head is no longer planar as in  FIGS. 1 to 6 , but rather has circumferential recess  75 , symmetrical with respect to the longitudinal vertical plane of symmetry, whose bottom  76  is planar and constitutes the rolling path. The exterior side contact surfaces of the head  77 ,  78 , are planar and inclined away from one another toward the roadway. Inclined surfaces  77 ,  78  extend toward the base of rail  2  beyond the level of bottom  76 . 
     In order to be able to roll on bottom surface  76  of the rail, roller  24  has a stepped peripheral surface whose projecting middle part constitutes rolling tread  80 . 
     In this embodiment, side rollers  25 ,  26  can be rotationally connected with central roller  24  and extend in a plane parallel to the plane of the central roller. In other words, the rollers are no longer inclined as in the first embodiment. Consequently, shaft  28  is a straight shaft. By making side contact surfaces  51 ,  52  of the side rollers come into contact with contact surfaces  77 ,  78  of rail head  42  at the bottom  76  of the rail, the distances of the contact points  54  from the axis of the side rollers is identical to the distance of rolling surface  80  of the central roller from its axis of rotation, which has the consequence that the speeds of the side rollers at their contact point  54  and of the central roller at the site of its rolling surface  80  are identical. 
       FIG. 8  illustrates a third embodiment of roller device  1  according to the invention. This embodiment has in common with  FIGS. 2 to 5  the fact that side rollers  25 ,  26  are inclined and independent rollers. This embodiment is distinguished from the first by the means for synchronization of the rotations of these side rollers, from central roller  24 . The rotation of the side rollers by the central roller occurs by means of a device with belts and pulleys. The rotation of central roller  24  is transmitted by first belt  82  to pulley  83 , which is rotationally connected with shaft  84  bearing two other pulleys  85 ,  86 , which are also rotationally connected with shaft  84 . Each of the two pulleys  85 ,  86  transmits the rotation of shaft  84  via belt  87 ,  88  to the corresponding side roller  25 ,  26 . Return pulleys  89 ,  90  are provided so as to ensure the appropriate orientation of the belts at the site of the rollers. 
       FIG. 9  illustrates a possibility for performing the synchronization also by gearing of the inclined rollers. For this purpose, rack rings  57 ,  58  are mounted, constituting bevel gears on the internal side surfaces of side rollers  25 ,  26  so that in case of the presence of a resistance to the rotation of a ring greater than a threshold value, the ring can slide over its support surface. For this purpose, as  FIG. 9  shows, bevel gear  57  has axial annular extension  92  on which annular part  93 , made of bronze, for example, which has an L-shaped cross section, is fastened by screw  94 . Free limb  95  of part  93  is pressed against side support surface  96  of roller  25  by spring element  98  produced, in the example represented, as a torus made of elastomer, with insertion of a washer  99 , spring element  98  being housed in connected annular part  100 . This part has a cross section in the shape of an L, one limb of which is attached on support surface  96  of the roller, while the edge of the other limb is curved so as to form groove  101  for housing of spring element  98 . 
       FIG. 10  illustrates a fourth embodiment of roller device  1  according to the invention, in two slightly different variations which are indicated on the left and on the right of the axis of symmetry of central roller  24 . 
     In this embodiment, side rollers  25 ,  26  are independent of roller  24  but are mounted so as to rotate on shaft parts  30 ,  31 , which are parallel to shaft part  28 , for support of the central roller. This roller device is suitable for rolling on rail head  42  whose rolling surface is planar as in the case of  FIG. 2 . In contrast, the side surfaces by which the side rollers are intended to come into contact with the rail are inclined in the manner represented in  FIG. 7  and therefore bear the references  77  and  78 . So that the rotation speeds of the rollers at points of contact  54  with rail head  42  can be identical to the rotation speed at the site of peripheral rolling surface  49  of central roller  24 , on one hand, and so that the rotational synchronization of side rollers  25 ,  26  on central roller  24  can be ensured, on the other hand, the axes of rotation of the side rollers are offset from the axis of rotation of the central roller, and the latter has a toothed ring  104 ,  105  on each side on its periphery, which meshes with inwardly-toothed ring  106 ,  107  associated with side rollers  25 ,  26 . Toothed rings  104 ,  105  of the central roller, on one hand, and rings  106 ,  107  of the side rollers, on the other hand, are not concentric and mesh with one another on the side of rail  2  with a certain speed-reducing ratio. So as to ensure a certain flexibility of the rotational synchronization of the rollers, each of rings  106 ,  107  is mounted on its roller via two plates  109 , made of bronze, for example, in such a way as to obtain a connection by friction between the roller and the ring. 
     The bronze friction plates are applied against the side surfaces of the ring respectively under the effect of spring element  108  inserted between a support surface of the roller and added annular element  110  which rests on one of plates  109 , the other plate being arranged between the ring and another bearing surface connected with the roller. 
       FIG. 11  illustrates another embodiment of the support arrangement for roller device  1 . The arrangement according to  FIG. 11  is distinguished from that shown in  FIG. 1  by the fact that arm  5  is part of a parallelogram, which has the advantage that roller device  1 , during its vertical movement, always moves by translation without any angular movement. For this purpose, fork  4  for holding the roller device is joined at  112  to arm  5 , and two additional arms  113  are provided that are joined by one end to tabs  114  situated at the front of fork  4  and by their other end to support frame  7 . 
     The guiding system according to the invention has been described in the preceding by means of several embodiments given only as examples. Multiple modifications can nevertheless be made to this system without leaving the scope of the invention. 
     The preceding description showed that the guiding system for a vehicle, according to the invention, is made up of a mechanical actuating contact roller which is, on one hand, attached to the steering elements of the vehicle and which, on the other hand, rolls on the rail. The system is particularly suitable for equipping streetcars that run on tires and on rails. When such a streetcar enters a curve, the roller rolling on the rail is deflected towards the inside of the curve. Since the roller is connected to an arm, the arm pivots around its vertical axis of rotation. Assuming a certain angle, the arm influences the orientation of the wheels of the vehicle in such a way as to reduce the angle of the arm. This kinematic chain makes it possible to transmit the forces necessary for changing direction, the direction-change information being assumed on the side surfaces of the rail. The side rollers of this device make it possible to take up the forces without bringing about friction. In effect, the rollers behave like wheels. The contact between the rail and the rollers is a pin-point and frictionless contact. The invention ensures continual synchronization of the rollers. In order to ensure a certain flexibility of the synchronization and to allow, if necessary, immobilization of one of the two side rollers or the set of rollers in case of the presence of an obstacle, the invention proposes a transmission by adhesion, several implementation possibilities of which have been described as examples. Given that the contact between the central roller and the rail, on one hand, and between the side rollers and the rail, on the other hand, does not occur by friction but only by rolling, the system generates only a small amount of noise. This noise is further reduced by inserting a layer of elastomer between the rolling treads of the central roller and of the side rollers and the support of the roller device, the layer of elastomer functioning as sound insulation. The use of inclined rollers is advantageous because it requires only a narrow slot in the roadway. 
     The invention has been described in the preceding by way of example in several embodiments and execution variations suitable for cooperating with a single guiding rail. Of course, the invention also encompasses systems designed for cooperating with several rails, for example, two rails as illustrated in  FIG. 12 . In this figure are the two rails  116 ,  117 , the vehicle being equipped with two roller devices  118 ,  119  situated on either side of the vehicle  120 . Each roller device  118 ,  119  corresponds to half of roller device  1 , that is, it has rolling support roller  122  corresponding in its configuration and operation to roller  24  of  FIGS. 2 to 10  and an inclined side roller  124 ,  125 , whose configuration and operation correspond, respectively, to the two side rollers  25  and  26 . Rollers  118  and  119  can both have the structural and operational characteristics presented in the description of roller device  1  in its different execution variations. It is observed that side rollers  124 ,  125  cooperate with the respective exterior side surfaces of the rails in the manner that side rollers  25 ,  26  cooperate with guiding rail  2 . 
     In order to illustrate the large number of implementation possibilities of the invention, four additional embodiments will be described below with reference to  FIGS. 13 to 17 . 
     The embodiment represented in  FIGS. 13 and 14  has three roller components intended for coming into contact with single rail  2 , namely central roller component  128  intended for rolling on the upper surface of the rail and two side rollers  129  and  130 , each intended for coming in rolling contact with a side surface of head  42  of the rail. The three roller components rotate around crankshaft  132 , the central component around central portion  133 , and the two side rollers  129 ,  130  around a shaft portion, respectively  134 ,  135 . 
     Central component  128  is a ring, which is kept within its portion  133  of the shaft of rotation via device  137 . This device has two parallel plates  138 ,  139  connected with shaft portion  133  via two plates  140 ,  141  made of an elastically deformable material, arranged on either side of central shaft portion  133  parallel to the rail, in order to obtain a dampening effect and to apply pre-stressing on ring  128 . Each of plates  138 ,  139  has, on its exterior surface, in its upper part, two casters  143 ,  144  arranged on either side of the vertical axis of symmetry of the roller, as seen in  FIG. 14 , via shaft end  146  inclined upward and connected with the corresponding plate. 
     As  FIG. 14  shows, the two casters  143 ,  144  borne by plate  138  or  139  are arranged such that they come into contact with radial internal and inclined peripheral surface  145  or  146  of ring  128  in order to form a V whose summit is in the middle. The inclination of the contact surfaces is parallel to the inclination of support shafts  147  of the casters that, as seen, are inclined as a consequence so as to provide a four-point support in the upper part of the ring. 
     Each side roller  129 ,  130  has hub  148  which, at the free end of shaft portion  134 ,  135  and rotationally connected with the hub, has ring  149  whose convex radial exterior part  150  comes in rolling contact with one of the two side surfaces of head  42  of rail  2 . At the axial interior end, hub  148  has ring  153  rotationally connected with the hub and produced from steel or any other material. As  FIG. 13  shows, ring  153  is arranged such that its peripheral surface  154  comes in contact with inclined peripheral internal surface  145 ,  146  of ring  128  in order to create another two support points in the interior part of the ring as close as possible to the rail. 
     According to an advantageous characteristic of the invention, side rollers  129 ,  130  are rotated by friction with central ring  128  due to the contact of rings  153  of the two rollers on the internal surface of the ring. A speed-reducing ratio between ring  153  and surface  146  make it possible to have the same linear speed at the different points of contact. 
     The embodiment represented in  FIG. 15  has three rollers, central roller  155  and two side rollers  156  and  157 , all three cooperating with the same rail  2 , the central roller being in rolling contact on the upper surface of the rail, and the two side rollers coming into contact with the side surfaces of the head of the rail, as described above for the preceding embodiments. 
     The particularity of the embodiment according to  FIG. 15  lies in the fact that the rotational synchronization of side rollers  156  and  157  occurs by contact of ring  159  of each roller, similar to ring  153  of the embodiment in  FIGS. 13 and 14 , but in this case in rolling contact with inclined and annular bearing surface  161 , provided on the corresponding side of central roller  155  as seen in  FIG. 15 , this central roller having inclined annular contact surface  161  on each side. 
     Each ring  159  has a composite structure having, between two radial internal and external annular elements  163  and  164 , annular element  165  made of an elastically deformable material functioning as dampener and for tight application of the ring on side bearing surface  161  of central roller  155  in the area closest to rail  2 , in order to ensure the effect of driving by friction. The diameters of rings  159  and the diameter of surface  161  make it possible to have the same speed at the points of contact. 
     The embodiment represented in  FIG. 16  has the particularity of having only two rollers  167 ,  168  arranged in a V-shaped configuration and each having two axially peripheral rings, internal  170  and external  171 , respectively, ring  170  coming into pin-point contact with the side surface of head  42  of rail  2  and ring  171  with the upper surface of the rail. So that there is no difference in the linear speeds at the areas of contact, point of contact  172  of exterior ring  170  and point of contact  173  of interior ring  171  have the same radial distance from the axis of inclined support shaft portion  174  of crankshaft  175 . 
     The embodiment illustrated in  FIG. 17  also has only two rollers  177 ,  178  arranged in a V-shaped configuration. One of the rollers, in the example represented, roller  177 , has two areas axially separated from one another on its periphery, one area  180  intended for coming into pin-point contact with one of the two side surfaces of head  42  of rail  2 , whereas the other area  181  comes into rolling contact on the upper surface of the head of the rail, in a manner similar to the two rings  170  and  171  of rollers  167  and  168  in the embodiment of  FIG. 16 . 
     However, unlike this embodiment, the other roller  178  of the embodiment in  FIG. 17  has axial internal ring  183  comparable with ring  159  of the embodiment of  FIG. 15 , which, however, rests on inclined annular bearing surface  184  machined in side surface  185  of roller  177 . Roller  178  also has external ring  186  which comes in contact with the other side surface of head  42  of the rail. As in the case of ring  159  of  FIG. 15 , ring  183  has elastically deformable layer  187  which ensures pressed application of the ring on its bearing surface  184  in order to ensure rotational driving by friction. 
     It should be noted that in all the embodiments of  FIGS. 13 to 17  in which the synchronization of the rotation speeds occurs by frictional contact, a disengagement effect is produced when the friction exceeds a predetermined value, for example, in case of obstruction or an obstacle to the rotation of one of the parts in contact. 
     The large number of examples just described clearly illustrates the specificity of the invention which consists of ensuring frictionless rolling contacts of the rollers with the rail, with the advantage of requiring only small grooves in the roadway without danger for light vehicles and cycles. The axes of rotation of the rollers are generally inclined with respect to the horizontal and have toric surfaces providing pin-point contacts with the rail. 
       FIG. 18  shows yet another embodiment. 
     According to this one, the guiding system has central roller  188  and two side rollers  189  and  190 . Central roller  188  is rotationally guided on shaft  192  by rolling bearings  194 . Each side roller is rotationally guided by ball bearing  196 , on a hub  198 . This hub is connected to shaft  192  by means of shaft  200 . The synchronization of the side roller with respect to the central roller occurs by friction of ring  202  of the roller on central roller  188 . 
     Given that each of hubs  198  is connected to shaft  192 , when side roller  189  or  190  comes in contact with the rail, the side roller rotates around shaft  200 . This rotation makes it possible to detach friction ring  202  from central roller  188 . Thus, the side roller in contact is no longer synchronized with the central roller but rather with the rail.