Patent Publication Number: US-8978563-B2

Title: Motor-driven bogie for a streetcar

Description:
This claims priority to French Application No. 07 54311, filed Apr. 5, 2007 through international application PCT/FR2008/050437, filed Mar. 14, 2008, the entire disclosures of which are hereby incorporated by reference herein. 
     The invention relates in general to railway vehicles, particularly trams. 
     More precisely, according to a first aspect, the invention relates to a powered bogie for a railway vehicle, the bogie being of the type comprising:
         a chassis;   two front wheels transversely spaced apart from one another and two rear wheels transversely spaced apart from one another, the front and rear wheels being connected to the chassis, the front wheels being longitudinally spaced apart from the rear wheels;   at least one driving motor;   transmission means comprising a front reducing gear for coupling the front wheels to the or a motor and a rear reducing gear for coupling the rear wheels to the or a motor.       

     BACKGROUND OF THE INVENTION 
     Such a bogie is known from document FR-A-2 604 676, which describes a tram comprising a body and at least one powered bogie. This bogie comprises a single motor fixed below the body and offset longitudinally forwards relative to the bogie chassis. The front reducing gear is placed between the two front wheels and is coupled directly to the motor. The rear reducing gear is placed outside the wheels and is driven via the front reducing gear. 
     Such a bogie has the advantage of allowing a low central corridor to be arranged in the chassis of the body, allowing access without a step to the entire tram. By contrast, the integration of the motor into the structure of the body beyond the bogie region is restrictive, because it prevents the provision of seats or of an access door above the motor. Moreover, driving the two reducing gears in series is complex from a mechanical point of view. 
     SUMMARY OF THE INVENTION 
     Within this context, the object of the invention is to propose a powered bogie which allows a wide low corridor to be arranged in the chassis of the body, but which is mechanically less complex and easier to integrate into the body of the tram. 
     For this purpose, the invention relates to a powered bogie for a railway vehicle of the aforementioned type, characterised in that the or each motor is mounted on the bogie chassis, the front and rear reducing gears being arranged between, on the one hand, a longitudinal plane midway between the two front wheels and midway between the two rear wheels and, on the other hand, a longitudinal plane passing through the front wheel and the rear wheel situated on the same, first transverse side of the bogie. 
     The bogie may also exhibit one or more of the features below, taken individually or in any of the technically feasible combinations:
         the front and rear reducing gears are arranged in positions symmetrical to one another about a transverse plane midway between the front and rear wheels;   the bogie comprises a single driving motor aligned longitudinally between the front and rear reducing gears;   the bogie comprises two driving motors aligned longitudinally between the front and rear reducing gears;   the bogie comprises front and rear wheel braking elements and secondary suspension components suitable for suspending a railway vehicle body on the bogie chassis, the braking elements and the secondary suspension components being situated outside the bogie relative to the wheels;   the bogie comprises primary suspension components situated between the transmission means and the bogie chassis, the primary suspension components being placed inside the bogie relative to the wheels; and   at least some primary suspension components are low components, each situated entirely below a level between 200 mm and 400 mm relative to the rolling plane of the bogie, for front and rear wheels with a diameter of 590 mm.       

     According to a second aspect, the invention relates to a railway vehicle comprising:
         a body which is elongate in shape in a principal direction, provided with a body chassis;   at least one bogie of the type described above, connected to the body and arranged below the body chassis;   the body chassis comprising a first raised portion above the front and rear wheels situated on the first transverse side of the bogie and above the front and rear reducing gears, a second raised portion at least above the front and rear wheels situated on a second transverse side of the bogie opposite the first, and a lowered portion forming a circulation corridor, substantially parallel to the principal direction, between the first and second raised portions.       

     The railway vehicle may also have one or more of the following features:
         the circulation corridor is offset transversely towards the second raised portion relative to a median plane of the body and parallel to the principal direction;   the bogie is connected to the body by pivot connection means;   the bogie is non-pivoting relative to the body;   the circulation corridor extends from the front and rear reducing gears to the front and rear wheels situated on the second side of the bogie; and   the bogie comprises primary suspension components arranged directly inside the bogie relative to the front and rear wheels situated on the second side of the bogie, the circulation corridor extending from the front and rear reducing gears to said primary suspension components.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the invention will emerge from the description given below, for guidance and not by way of limitation, with reference to the accompanying drawings in which: 
         FIG. 1  is a cross-sectional view of a tram comprising a bogie according to a first embodiment of the invention, the section through the bogie being taken along the arrows I-I of  FIG. 2 ; 
         FIG. 2  is a schematic plan view of the bogie of  FIG. 1 ; 
         FIG. 3  is a view similar to that of  FIG. 3 , for a second embodiment of the invention; 
         FIG. 4  is a view similar to that of  FIG. 1 , for the second embodiment of the invention; 
         FIG. 5  is a side view of a front portion of the bogie of  FIG. 3 , showing in detail the structure of a low primary suspension component of said bogie, the two connecting rods of the suspension component being illustrated at rest in solid lines and in dashed and dotted lines after having been moved under the effect of vertical loading applied to the wheel from bottom to top, and 
         FIG. 6  is a cross-sectional view of an articulation of the upper connecting rod of  FIG. 5 , viewed along the incidence of the arrows VI. 
     
    
    
     DETAILED DESCRIPTION 
     The tram  10  illustrated in  FIG. 1  comprises for example a body  12  which is elongate in shape in a principal direction, provided with a body chassis  14 , and two bogies  16 , each connected to the body  12  and arranged beneath the chassis  14 . The body  12  comprises an inner space for passengers  18 , delimited towards the bottom by the chassis  14 , and seats  20  attached to the chassis  14 . The seats  20  are typically arranged in several rows extending perpendicular to the principal direction. The seats are oriented in such a way that the passengers seated in the seats are looking in the principal direction. 
     The bogies  16  are suitable for supporting and guiding the body  12  when the tram travels along a track. 
     In a first embodiment of the invention, each bogie comprises, as shown schematically in  FIG. 2 :
         a bogie chassis  22 ;   two front wheels  24  and two rear wheels  26 ;   a driving motor  28 ;   transmission means  30  suitable for transmitting the torque generated by the motor  28  to the front wheels  24  and the rear wheels  26 ;   primary suspension components  32  and  33 , and secondary suspension components  34 ;   front and rear brakes  36  and  38 .       

     The chassis  22  typically comprises two longitudinal side members (not shown), and two transverse cross members (not shown) attached rigidly to one another. Only the outer contour of the chassis  22  is shown in  FIG. 2 . The contour is represented by dashed lines. 
     The front wheels  24  are coaxial, spaced transversely from one another, and are connected to the chassis  22 . Similarly, the rear wheels  26  are coaxial, spaced transversely from one another, and connected to the chassis  22 . 
     The front wheels  24  are spaced longitudinally from the rear wheels  26 . 
     The transmission means  30  comprise for example a front axle  40  connecting the front wheels  24  to one another in rotation and a front reducing gear  42  for coupling the front wheels  24  to the motor  28 . The front reducing gear  42  transmits the torque from the motor  28  to one of the front wheels  24 , the torque being transmitted from said wheel to the other front wheel  24  by the front axle  40 . In a variant, the front reducing gear  42  transmits the torque from the motor  28  to the axle  40 , which entrains the two front wheels  24 . 
     The transmission means  30  also comprise a rear axle  44  connecting the two rear wheels  26  to one another in rotation and a rear reducing gear  46  for coupling the rear wheels  26  to the motor  28 . As at the front, the rear reducing gear  46  transmits the torque from the motor  28  to one of the rear wheels  26  or to the rear axle  44 . 
     Each of the axles  40  and  44  is guided in rotation by two axle boxes  45 , arranged directly inside the wheels associated with the axle and extending only over a portion of the transverse length of the axle. In a variant, each of the axles  40  and  44  comprises a rotating shaft connected to the wheels in rotation, and a casing providing mechanical rigidity for the axle and guiding the rotating shaft in rotation. The casing extends virtually from one of the wheels associated with the axle to the other. 
     The motor  28  and the front  42  and rear  46  reducing gears are mounted on the bogie chassis  22  and are therefore independent from the body  12 . They are arranged between, on the one hand, a longitudinal plane P 1  midway between the two front wheels  24  and midway between the two rear wheels  26  and, on the other hand, a longitudinal plane P 2  passing through the front wheel  24  and the rear wheel  26  situated on the same, first transverse side of the bogie  16 . 
     The plane P 1  is, as shown in  FIG. 2 , equidistant from the two front wheels  24  and equidistant from the two rear wheels  26 . It generally corresponds to the median longitudinal plane of the bogie  16 . The motor  28  and the reducing gears  42  and  46  are preferably situated as close as possible to the plane P 2 . 
     Moreover, the positions of the front  42  and rear  46  reducing gears are symmetrical to one another about a transverse plane P 3  midway between the front and rear wheels  24  and  26 . As shown in  FIG. 2 , the plane P 3  is equidistant from the respective axes of rotation of the front wheel  24  and the rear wheel  26  situated on the first side of the bogie. It is also equidistant from the respective axes of rotation of the front wheel  24  and the rear wheel  26  situated on the second side of the bogie opposite the first. 
     The motor  28 , the front reducing gear  42  and the rear reducing gear  46  are aligned longitudinally, the motor  28  being placed longitudinally between the reducing gears  42  and  46 . The motor  28  is equidistant from the two axles  40 ,  44 . 
     The front and rear reducing gears  42  and  46  are different from one another and are chosen to drive the front and rear wheels in the same direction of rotation. 
     The front reducing gear  42  is attached rigidly to the front axle box  45  situated on the first side, or to the casing of the front axle  40 , as appropriate. Likewise, the rear reducing gear  46  is attached rigidly to the rear axle box  45  situated on the first side, or to the casing of the rear axle  44 , as appropriate. 
     The bogie  16  comprises four primary suspension components  32  and  33 , suitable for suspending the bogie chassis  22  on the axles  40  and  44 . 
     Two primary suspension components  32  are situated vertically above the front  42  and rear  46  reducing gears, and are situated between the reducing gears  42  and  46  and the bogie chassis  22  ( FIG. 1 ). 
     Two further primary suspension components  33  are arranged between the plane P 1  and the wheels  24 ,  26  situated on the second side of the bogie, as close as possible to the wheels. 
     In the casing of axles mounted in axle boxes  45 , the two components  33  are arranged between the front and rear axle boxes  45  and the bogie chassis  22 . In the casing of axles with a shaft and a casing, the two components  33  are arranged between the casings of the front and rear axles  40  and  44  and the bogie chassis  22 . 
     The primary suspension components  32  and  33  are rubber/metal sandwiches of the type described in FR-1 536 401. They each comprise a plurality of layers of a resilient material such as rubber, and a plurality of metal plates inserted between the layers of resilient material and adhering to said layers. Each of the components  32  and  33  is chevron-shaped. 
     The primary suspension components  33  each have a transverse width of approximately 100 mm. The components  32  each have a transverse width of 300 mm and a height such that the bogie chassis  22 , above the primary suspension component  32 , is situated at a height of 500 to 550 mm above the rolling plane P 5  of the bogie, for wheels with diameters when new of 590 mm. 
     The bogie typically comprises four secondary suspension components  34 , each consisting of a spiral spring inserted between the bogie chassis  22  and the body chassis  14 . 
     The four secondary suspension spiral springs  34  are arranged symmetrically about the planes P 1  and P 3 . Two springs  34  are placed on the first side of the bogie, transversely outside the bogie relative to the wheels  24  and  26 . The two other spiral springs  34  are arranged on the second side of the bogie, transversely outside said bogie relative to the wheels  24  and  26 . The spiral springs  34  are situated longitudinally between the front  24  and rear  26  wheels. 
     The front brake  36  is arranged on the first side of the bogie, transversely outside the bogie relative to the wheels  24  and  26  situated on the first side. The rear brake  38  is arranged on the second side of the bogie, transversely outside said bogie relative to the wheels  24  and  26  situated on the second side. 
     As shown in  FIG. 1 , the body chassis  14  has a first raised portion  48  in line with the front and rear wheels  24 ,  26  situated on the first transverse side of the bogie, and above the motor  28  and the front and rear reducing gears  42  and  46 . It comprises a second raised portion  50  above the front and rear wheels  24  and  26  situated on the second transverse side of the bogie, and a low portion  52  between the first and second raised portions  48  and  50 . 
     In the first embodiment of the invention, the second raised portion  50  covers the chevron-shaped primary suspension components  33 . 
     The first portion  48  is relatively wider than the second perpendicular to the principal direction, because it covers not only the wheels but also the reducing gears and the motor. The low portion  52  forms a circulation corridor inside the body, said corridor being substantially parallel to the principal direction. The corridor is offset transversely towards the second raised portion  50  relative to the median plane P 4  of the body  12  and extends parallel to the principal direction. 
     The circulation corridor is situated at a level of approximately 480 mm relative to the rolling plane of the bogie. Viewed in a plane perpendicular to the principal direction, it extends virtually from the reducing gears  42  and  46  or the motor  28  to the primary suspension components  33  situated on the second side. It is therefore particularly wide, and is approximately 750 mm wide in the non-pivoting version of the bogie. 
     Each row of seats of the body  12  comprises for example three seats  20 , two seats  20  arranged side by side above the first raised portion  48  and a single seat  20  situated above the second raised portion  50 . The seats  20  hardly overhang within the corridor and thus hardly encroach on the width of the corridor. 
     The bogie  16  may be mounted so as to be pivoting or non-pivoting on the body  12 . A pivoting bogie is connected to the body  12  by pivot connection means about an axis substantially perpendicular to the rolling plane P 5  of the tram and can fit in the curved path followed by the tram. The maximum pivoting amplitude of the bogie relative to the body is approximately 12°. 
     A non-pivoting bogie is connected to the body by connection means allowing very limited pivoting about an axis perpendicular to the rolling plane, generally of less than 2°. 
     It will be noted that the longitudinal direction of the bogie is substantially parallel to the principal direction of the body in the casing of a fixed bogie. In the casing of a pivoting bogie, the longitudinal direction of the bogie is parallel to or forms an angle of less than 12° with the principle direction of the body, the inclination varying as a function of the course of the path followed by the tram. 
     A second embodiment of the invention will now be described in relation to  FIGS. 3 to 6 . Identical elements or elements performing the same function in the first and second embodiments will be denoted by the same reference numerals. Only the points in which the second embodiment differs from the first will be detailed. 
     As shown in  FIG. 3 , the bogie  16  comprises two motors, a front motor  54  coupled to the front reducing gear  42  and a rear motor  56  coupled to the rear reducing gear  46 . The positions of the front and rear reducing gears  42  and  46  are substantially the same as in the embodiment of  FIG. 2 . The front and rear motors  54  and  56  are arranged in positions symmetric to one another about the plane P 3 . They are placed between the reducing gears  42  and  46  and are aligned longitudinally with the reducing gears  42  and  46 . 
     The bogie  16  only comprises a total of two spiral springs  34  instead of four. The two springs  34  are arranged in the plane P 3  in such a way as to be symmetrical to one another about the plane P 1  and are placed outside the bogie relative to the wheels  24 ,  26 . 
     As can be seen in  FIG. 3 , the primary suspension components  61  situated on the side of the bogie are low components. 
     The front primary suspension component  61  comprises:
         two connecting rods  62  and  64 , connected to the chassis  22  by first connection points  66  and  68  respectively, and to the axle box  45  by second connection points  70  and  72  respectively;   a resilient component  74  inserted between the two connecting rods  62  and  64  to define at least the vertical stiffness of the primary suspension component  61 .       

     The two connecting rods  62  and  64  are placed in the same vertical plane, in other words in the same plane perpendicular to the rolling plane P 5  of the bogie, the connecting rod  62 , situated above the connecting rod  64 , being referred to as the upper connecting rod and the connecting rod  64  being referred to as the lower connecting rod in the description that follows. 
     At rest, the two connecting rods  62  and  64  are substantially parallel to one another and extend in a longitudinal direction corresponding substantially to the direction of the side members of the chassis  22 . They are therefore perpendicular to the axle  40 . Between the first and second respective connection points thereof the connecting rods  62  and  64  have substantially the same longitudinal length. 
     As shown in  FIG. 5 , the two connecting rods  62  and  64  are offset longitudinally relative to one another when the primary suspension component  61  is at rest and also when it is under load. Therefore, as shown in  FIG. 5 , the upper connecting rod  62  is offset to the right of  FIG. 5 , in other words towards the chassis  22  relative to the lower connecting rod  64 . In order to distribute the load between the two connecting rods  62  and  64 , the second connection points  70  and  72  of the upper and lower connecting rods  62  and  64  are offset longitudinally on either side of the axle  40 . Thus, in the embodiment of  FIG. 5 , the connection point  70  of the upper connecting rod is offset relative to the central transverse axis of the axle  40  by a distance d towards the chassis  22 . Symmetrically, the connection point  72  of the lower connecting rod  64  is offset symmetrically relative to the central axis of the axle  40  by the same distance d in the longitudinal direction, opposite the chassis  20 . With this arrangement, there is an even distribution of the load between the two connecting rods  62  and  64  when the resilient component  74  is centred between the connection points  66  and  68 , in other words when the centre of the component  74  is placed equidistant from the points  66  and  68  on the straight line passing through the two points  66  and  68 . 
     At rest, the connecting rods  62  and  64  extend substantially horizontally, in other words substantially parallel to the rolling plane P 5  of the bogie, and are situated entirely at a vertical level lower than the highest point  76  of the axle box  45 . The highest point  76  of the axle box is the point of this box situated highest relative to the rolling plane of the bogie. 
     The resilient component  74  is a rubber/metal sandwich of the type described in patent application FR-1 536 401. The resilient component  74  comprises a plurality of rubber layers  76  parallel to one another, a plurality of metal plates  78  inserted between the layers of rubber  76 , and metal end plates  80  arranged at the bottom and top of the sandwich. The plates  78  and  80  are parallel to one another and parallel to the layers of rubber  76 . Each layer of rubber  76  is therefore arranged between two metal plates  78  and/or  80  and adheres to said plates. 
     The axis of compression of such a resilient component is perpendicular to the plates  78  and  80  and to the layers of rubber  76 . 
     Such a sandwich has a substantial stiffness both in compression and in shearing, in other words in response respectively to a load applied in a direction perpendicular to the plane of the plates  78 ,  80  and layers  76 , and parallel to the plane of said plates and layers. 
     The upper and lower connecting rods  62  and  64  each comprise a lateral extension  82  and  84  respectively, defining mutually opposite support surfaces  86  and  88  respectively, for the resilient component  74 . The resilient component  74  is held between the surfaces  86  and  88 . Said surfaces  86  and  88  are parallel to one another, the end plates  80  being placed on the support surfaces and rigidly attached thereto. 
     The support surfaces  86  and  88  are oriented in such a way that the axis of compression of the resilient component  74  forms an angle β of between 0° and 90° relative to the axis passing through the first connection points  66  and  68  of the two connecting rods. Preferably, the angle β is between 20° and 50°, and typically has a value of 30°. 
     The two connecting rods  62  and  64  are connected to the axle box  45  of the bogie by second connection points thereof  70  and  72  respectively by means of resilient cylindrical articulations. The two connecting rods are connected to the bogie chassis  22  at the first connection points thereof  66  and  68  respectively, and also by cylindrical resilient articulations. 
     The connecting rods  62  and  64  comprise at each of the connection points  66 ,  68 ,  70  and  72  a transverse axis end  90  engaged in a cylindrical opening  92  arranged, depending on circumstances, either in the axle box  45 , or in the bogie chassis  22  (see  FIG. 6 ). A cylindrical resilient sleeve  94 , for example of natural or synthetic rubber, is inserted between the axis end  90  and the peripheral wall of the opening  92 . The axis end  90 , the opening  92  and the sleeve  94  are coaxial, in terms of the transverse axis. The sleeve  94  adheres by an inner face to the axis end  90  and by an outer face to the peripheral wall of the opening  92 . 
     The rear low primary suspension component  61  is similar to the front low primary suspension component  61 . Each component  61  is situated at rest entirely below a level between 200 mm and 400 mm above the rolling plane P 5  of the bogie, preferably between 250 mm and 350 mm and typically having a value of 300 mm for wheels with a diameter when new of 590 mm. 
     The operation of the above suspension component will now be described briefly. 
     Under the effect of a load or a fault in the track which causes the wheel  24  to rise, the connecting rods  62  and  64  drive the axle box  45  in a vertical movement. The unit formed by the chassis  22 , the two connecting rods  62  and  64  and the axle box  45 , connected by the connection points  66 ,  68 ,  70  and  72 , forms a parallelogram. 
     When the wheel  24  is subject to a vertical load F from bottom to top, for example in the casing of a fault in the track, the connecting rods  62  and  64  each take up part of the load F at the second connection points thereof  70  and  72  respectively, because said first connection points are placed on either side of the axle. The distribution of the load between the two connecting rods is a function of the position of the resilient component  74  between the connection points  66  and  68 . 
     Under the effect of this load, the connecting rods  62  and  64  pivot upwards relative to the chassis  22  about the first connection points  66  and  68 , in other words clockwise in  FIG. 5 . Under the effect of this pivoting, the support surfaces  86  and  88  tend to draw closer. In the embodiment in  FIG. 1 , for which the angle β has a value of about 30°, the pivoting of the connecting rods  62  and  64  leads to both a compression load and a shearing load being applied to the resilient component  74 . For an angle β of 90°, the resilient component works purely in compression. For an angle β of 0°, the resilient component works purely in shearing. 
     In parallel, the connecting rods  62  and  64  pivot relative to the axle box  45  about the second connection points  70  and  72 , which move vertically upwards as illustrated with dashed and dotted lines in  FIG. 5 . Of course, the axle box  45  and the highest point thereof  76  are also subject to a vertical movement upwards, which is not illustrated in  FIG. 5 . The connecting rods  62  and  64  pivot clockwise in  FIG. 5  relative to the axle box  45  and remain at a level lower than the highest point  76  of the axle box, which has moved upwards. 
     The pivoting of the connecting rods  62  and  64  leads to torsion, for each connecting rod, of the resilient sleeves  60  of the first and also the second connection point. 
     In the second embodiment of the invention, the second raised portion  50  of the floor of the body  14  only covers the wheels  24  and  26  situated on the second side. The low primary suspension components  61  are placed below the circulation corridor  52 , which is itself situated, relative to the rolling plane P 5  of the bogie, at a level between 280 mm and 480 mm, preferably between 330 mm and 430 mm, and typically having a value of 380 mm. 
     In this casing, the circulation corridor extends, viewed in a plane perpendicular to the principal direction, virtually from the reducing gears  42  and  46  or the motor  28  to the wheels  24  and  26  situated on the second side. It is 900 mm wide in the casing of a non-pivoting bogie and 650 mm wide in the casing of a pivoting bogie. 
     The bogie and railway vehicle described above have many advantages. 
     Because the motor or motors are mounted on the chassis, the drive train for transmission between the motor or motors and the wheels is shorter and mechanically simpler. Moreover, as the front and rear reducing gears are arranged, on the one hand, between the longitudinal plane midway between the wheels of the vehicle and the longitudinal plane passing through the wheels situated on the first side of the bogie, it is possible to arrange a particularly wide low circulation corridor in the body chassis. When the primary suspension components situated on the second side are chevron-shaped rubber/metal sandwiches, the corridor extends between, on the one hand, the reducing gears and, on the other hand, the primary suspension components situated on the second side, and is approximately 750 mm wide, in the casing of a non-pivoting bogie. 
     When the primary suspension components situated on the second side are low components, the corridor extends from the reducing gears to the wheels situated on the second side and is approximately 900 mm wide for a non-pivoting bogie and approximately 650 mm wide for a pivoting bogie. 
     When the primary suspension components situated on the second side are of the conventional type, for example chevron-shaped rubber/metal sandwiches, the transverse width thereof must be reduced in such a way as to maintain the width of the corridor, since the components are not covered by the corridor. This constraint no longer exists when primary suspension components of the low type are used, since these components are below the corridor. 
     The symmetrical arrangement of the motor or motors and reducing gears relative to the transverse plane midway between the wheels facilitates this arrangement. 
     The or each of the two driving motors of the bogie may advantageously be aligned longitudinally between the two reducing gears. The or each motor and the reducing gears have substantially the same dimensions transversely, so that there is a large free space between the or each motor and the reducing gears, on the one hand, and the wheels situated on the second side of the bogie to allow the body circulation corridor to pass through. 
     The brakes and secondary suspension springs of the bogie are placed outside the bogie relative to the wheels, so as not to impede the passage of the body circulation corridor. 
     Because of the arrangement of the motors and reducing gears on the bogie, the vehicle may have a particularly wide low corridor between two raised portions of the floor, suitable for accommodating up to four rows of three seats without encroaching on the corridor in the casing of a narrow body (less than 2400 mm wide), or twelve seats above the bogie. In the casing of a wider body (more than 2400 mm wide), it is possible to arrange four rows of four seats above the bogie without encroaching on the corridor, or sixteen seats in total. In this casing, two seats are arranged above the raised portion  48  and two more above the raised portion  50 . 
     Because the reducing gears are assembled on the same side of the bogie, the circulation corridor is offset relative to the median plane of the body and parallel to the principal direction of the body. 
     The architecture of the bogie allows said bogie to be mounted under the body either pivoting about a pivot substantially perpendicular to the rolling plane of the vehicle, or not pivoting, in other words with an angular clearance of less than or equal to 2° relative to the body. 
     The bogie of FR-A-2 604 676 can only be non-pivoting relative to the body, because the motor is mounted under the body. The reducing gears which mechanically connect the motor to the axles could not tolerate changes of 12° in the orientation of the axles relative to the motor. 
     Because the primary suspensions are placed between the wheels, in other words inside and not outside the bogie relative to the wheels, it is possible to lower the side walls  60  of the body substantially to the axis of the wheels, or even lower, while giving them with a curved shape. As shown in  FIG. 1 , the walls  60  are not flat but, on the contrary, are slightly curved, and have a convexity turned towards the outside of the body. Moreover, this arrangement of the primary suspensions facilitates access to the wheels and brake discs to maintain or replace them. 
     The bogie and vehicle described above may have many variants. 
     The secondary suspensions of the bogie may be of any type, and may comprise for example spiral springs or chevron resilient devices. The bogie, both in the first and in the second embodiment, may comprise two or four secondary suspension components. 
     The axles connecting the front wheels and the rear wheels in rotation may be of any type. They may be of the cranked type, as described in EP-0 911 239. They may also be of the uncoupled type, as described in the application with filing number FR 06 00834. 
     The seats  20  situated above the raised portion  50  of the chassis may be oriented perpendicular to the seats  20  situated above the raised portion  48 , in other words in such a way that the passengers are seated with their backs to the side wall  60 . 
     All the primary suspension components may be of the chevron type. Conversely, all the primary suspension components may be low components situated entirely below a level of approximately 300 mm relative to the rolling plane of the bogie, for wheels with a diameter of 590 mm. 
     The railway vehicle may be a light vehicle of the tram type, or a heavier vehicle, for example a train for long or short journeys.