Patent Publication Number: US-2010107923-A1

Title: Primary Suspension Device for a Railway Vehicle Bogie

Description:
The invention generally relates to suspension devices for a rail vehicle. 
     More precisely, according to a first aspect, the invention relates to a device for suspending a first element on a second element of a rail vehicle, of the type comprising: 
     two longitudinal connection rods, each connected via a first connection location to the first element, and via a second connection location to the second element, 
     a resilient member which is interposed between the two connection rods in order to define at least the vertical stiffness of the suspension device. 
     BACKGROUND 
     Such a device is known from CH-192 957, in which the resilient member is formed by two tall helical springs which are arranged in parallel in a casing which is formed by two telescopic portions. Each of the two portions of the casing is fixed to one of the connection rods. 
     Such a suspension device is able to support a heavy load, but has a great height. It cannot be accommodated below a carriage with a low floor, in particular below a tramway carriage having a lowered travel corridor. 
     SUMMARY OF THE INVENTION 
     An object of the present invention provides a primary suspension device having a reduced vertical spatial requirement. 
     The present invention provides a primary suspension device characterised in that the two connection rods are longitudinally offset relative to each other. 
     The suspension device may also have one or more of the features below, taken individually or according to any technically possible combination: 
     the two connection rods are substantially parallel with each other and have, between their first and second respective connection locations, substantially the same length longitudinally; 
     the or each resilient member is a sandwich comprising a plurality of layers of a resilient material and a plurality of metal plates which are interposed between the layers of resilient material and which are adhesively-bonded to the resilient layers; 
     the two connection rods are positioned in the same vertical plane; 
     the or each resilient member has a compression axis which forms an angle β between 0° and 90° with respect to an axis which extends through the first connection locations of the two connection rods; 
     the first element is a chassis of a bogie of the rail vehicle and the second element is an axle or an axle box of the bogie; 
     each of the two connection rods is connected to the axle or the axle box of the bogie at the second connection location thereof by means of a cylindrical resilient articulation and to the chassis of the bogie at the first connection location thereof also by means of a cylindrical resilient articulation; 
     the connection rods extend perpendicularly relative to the axle and the cylindrical resilient articulations have axes parallel with the axle; 
     the second connection locations of the two connection rods are longitudinally offset in a symmetrical manner at one side and the other of the axle; 
     the two connection rods are arranged at a vertical level lower than the apex of the axle or the axle box; and 
     the first element is a rail vehicle body and the second element is a chassis of a bogie of the rail vehicle which is positioned below the body. 
     According to a second aspect, the present invention provides a rail vehicle bogie comprising at least one suspension device which has the above features. 
     According to a third aspect, the present invention provides a rail vehicle comprising at least one suspension device which has the above features. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the invention will be appreciated from the detailed description which is given below, by way of non-limiting example, with reference to the appended Figures, in which: 
         FIG. 1  is a partially sectioned side view of a portion of a bogie comprising a primary suspension according to the invention, the connection rods being illustrated with solid lines in the idle state and being illustrated with broken lines when the wheel associated with the primary suspension is subject to an upward vertical force; 
         FIG. 2  is a plan view corresponding to  FIG. 1 ; and 
         FIG. 3  is a section of the resilient articulation of one of the connection rods, taken along the line of incidence of the arrows III-III of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The bogie  10  illustrated partially in  FIG. 1  comprises two front wheels  12 , and two rear wheels, front axles  14  and rear axles (not shown) which rotatably connect the front wheels  12  and rear wheels to each other, respectively, a chassis  16 , for each front and rear wheel, an axle box  18  which forms a bearing for rotatably guiding the corresponding axle, for each front and rear wheel, a primary device  20  for suspending the chassis  16  on the corresponding axle box  18 , and a secondary device  22  which is capable of suspending the body of a rail vehicle on the chassis  16 . 
     The chassis  16  is typically formed by longitudinal members and cross-members which are rigidly fixed to each other, the cross-members extending parallel with the axles and the longitudinal members perpendicularly relative to the axles. 
     The axle boxes  18  of the two wheels associated with the same axle are arranged between the two wheels. The axle box  18  associated with a wheel is arranged in the immediate proximity of this wheel, towards the inner side of the bogie relative to the wheel. The axle box  18  comprises an outer casing  24  through which the axle  14  extends and a bearing, in particular a roller bearing, which is interposed between the axle and the casing  24 . 
     Each axle box  18  is arranged substantially in continuation of a longitudinal member of the chassis  16 , as illustrated in  FIG. 2 . 
     Each secondary suspension device  22  is interposed between the body of the rail vehicle supported by the bogie and the chassis  16  of the bogie. It is capable of suspending the body on the chassis  16 . 
     Each primary suspension device  20  comprises two connection rods  26  and  28  which are connected by respective first connection locations  30  and  32  to the chassis  16 , and by respective second connection locations  34  and  36  to the casing  24  of the axle box and a resilient member  38  which is interposed between the two connection rods  26  and  28  in order to define at least the vertical stiffness of the primary suspension device  20 . 
     The two connection rods  26  and  28  are positioned in the same vertical plane, that is to say, in the same plane perpendicular relative to the travel plane of the bogie, the connection rod  26 , located above the connection rod  28 , being referred to in the following description as the upper connection rod, and the connection rod  28  as the lower connection rod. 
     In the idle state, the two connection rods  26  and  28  are substantially parallel with each other and extend in a longitudinal direction which corresponds substantially to the direction of the longitudinal members of the chassis  16 . They are thus perpendicular relative to the axle  14 . The connection rods  26  and  28  have, between their first and second respective connection locations, substantially the same longitudinal length. 
     As illustrated in  FIG. 1 , the two connection rods  26  and  28  are longitudinally offset relative to each other when the primary suspension device  20  is in the idle state and also when it is under load. In this manner, the upper connection rod  26  is offset towards the right-hand side of  FIG. 1 , that is to say, towards the chassis  16  relative to the lower connection rod  28 . In order to distribute the load on the two connection rods  26  and  28 , the second connection locations  34  and  36  of the upper and lower connection rods  26  and  28  are longitudinally offset at one side and the other of the axis of the axle  14 . In this manner, in  FIG. 1 , the connection location  34  of the upper connection rod is offset relative to the center transverse axis of the axle  14  by a distance D towards the chassis  16 . Symmetrically, the connection location  36  of the lower connection rod  28  is offset relative to the center axis of the axle  14  by a same distance d in the longitudinal direction, away from the chassis  16 . With this arrangement, there is an equal distribution of the load between the two connection rods  26  and  28  when the resilient member  38  is centered between the connection locations  30  and  32 , that is to say, when the center of the member  38  is positioned at an equal distance from the points  30  and  32  on the straight line which extends via the two points  30  and  32 . 
     In the idle state, the connection rods  26  and  28  extend substantially horizontally, that is to say, substantially parallel with the travel plane of the bogie and are entirely located at a vertical level lower than the apex  40  of the casing of the axle box. The apex  40  of the casing of the axle box is the point of this casing located at the highest point relative to the travel plane of the bogie. 
     The resilient member  38  is a rubber/metal sandwich of the type described in the patent application FR-1 536 401. The resilient member  38  comprises a plurality of mutually parallel rubber layers  42 , a plurality of metal plates  44  which are interposed between the rubber layers  42 , and metal end plates  46  which are arranged at the base and at the peak of the sandwich. The plates  44  and  46  are mutually parallel and are parallel with the rubber layers  42 . Each rubber layer  42  is thus arranged between two metal plates  44  and/or  46  and is adhesively-bonded to these plates. 
     The compression axis of such a resilient member is perpendicular relative to the plates  44  and  46  and the rubber layers  42 . 
     Such a sandwich has a defined stiffness both in terms of compression and shearing, that is to say, in response to a force which is applied in a direction perpendicular relative to the plane of the plates  44 ,  46  and layers  42 , and parallel with the plane of these plates and these layers, respectively. 
     The upper and lower connection rods  26  and  28  each comprise a respective lateral extension  48  and  50 , which define facing abutment surfaces  52  and  54 , respectively, for the resilient member  38 . The resilient member  38  is engaged between the surfaces  52  and  54 . These surfaces  52  and  54  are mutually parallel, the end plates  46  being pressed on the abutment surfaces and rigidly fixed thereto. 
     The abutment surfaces  52  and  54  are orientated in such a manner that the compression axis of the resilient member  38  forms in a reference position an angle β of between 0° and 90° relative to the axis which extends via the first connection locations  30  and  32  of the two connection rods. Preferably, the angle β is between, for example, 20° and 60° and is typically 30°. 
     The two connection rods  26  and  28  are connected to the axle box  18  of the bogie with their respective second connection locations  34  and  36  via cylindrical resilient articulations. The two connection rods are connected to the chassis  16  of the bogie at their first connection locations  30  and  32 , respectively, also via cylindrical resilient articulations. 
     The connection rods  26  and  28  comprise, at each of the connection locations  30 ,  32 ,  34  and  36 , a transverse shaft end  56  which is engaged in a cylindrical hole  58  which is provided, depending on the circumstances, either in the axle box or in the chassis  16  of the bogie (see  FIG. 3 ). A cylindrical resilient sleeve  60 , for example, of synthetic or natural rubber, is interposed between the shaft end  56  and the peripheral wall of the hole  58 . The shaft end  56 , the hole  58  and the sleeve  60  are coaxial, and have a transverse axis. The sleeve  60  is adhesively-bonded via an inner face to the shaft end  56  and via an outer face to the peripheral wall of the hole  58 . 
     The operation of the suspension described above will now be set out in detail below. 
     Under the effect of a load or a lack of track which causes the wheel  12  to lift, the connection rods  26  and  28  drive the axle box  32  in a vertical movement. The assembly comprised of the chassis  16 , the two connection rods  26  and  28  and the axle box  18 , which are connected by the connection locations  30 ,  32 ,  34 ,  36  and  38 , constitutes a deformable parallelogram. 
     When the wheel  12  is subject to an upward vertical force F, in the event of a lack of track, for example, the connection rods  26  and  28  each absorb a fraction of the force F at their second respective connection locations  34  and  36 , owing to the fact that these first connection locations are placed at one side and the other of the axle. The distribution of the force between the two connection rods  26  and  28  is dependent on the position of the block between the points  30  and  32 . 
     Under the effect of this force, the connection rods  26  and  28  pivot upwards relative to the chassis  16  about first connection locations  30  and  32 , that is to say, in the clockwise direction in  FIG. 2 . Under the effect of these pivoting actions, the abutment surfaces  52  and  54  tend to move towards each other. In the embodiment of  FIG. 1 , for which the angle β is approximately 30°, the pivoting of the connection rods  26  and  28  leads to both a compression force and a shearing force being applied to the resilient member  38 . For an angle β of 90°, the resilient member operates with pure compression. For an angle β of 0°, the resilient member operates with pure shearing. 
     In parallel, the connection rods  26  and  28  pivot relative to the axle box  18  about the second connection locations  34  and  36  which move vertically upwards, as illustrated in  FIG. 1  with broken lines. Of course, the axle box  18  and the apex  40  thereof are also subject to a vertical upward movement. The connection rods  26  and  28  pivot in the clockwise direction in  FIG. 1  relative to the axle box  18  and remain at a level lower than the apex  40  of the axle box, which is moved upwards. 
     The pivoting of the connection rods  26  and  28  brings about torsion, for each connection rod, of the resilient sleeves  60  of the first connection location and the second connection location. 
     The vertical stiffness Kz of the primary suspension relative to the wheel is therefore the result of three components: the stiffness of the resilient member  38 , the torsion stiffness of the cylindrical resilient articulations at the connection locations  30 ,  32 ,  34  and  36  and finally the radial stiffness of the cylindrical resilient articulations at the connection locations  30 ,  32 ,  34  and  36 . The vertical stiffness Kz relative to the wheel may be expressed in the following manner: 
         Kz= 1/(1 /Kzr+ 1 /Kzp )+ Kzt    
       with 
         Kzr= 2.(½ .KAr ) 
         Kzp= 4.((sin β) 2   .KPc +(cos β) 2   .KPs )(1 /L ) 2    
         Kzt= 4.( KAt/L   2 ) 
     Kzr being the contribution of the radial stiffness of the cylindrical resilient articulations to the stiffness of the primary suspension relative to the wheel, 
     Kzp being the contribution of the resilient member  38  to the stiffness of the primary suspension relative to the wheel, 
     Kzt being the contribution of the torsion of the cylindrical resilient articulations to the stiffness of the primary suspension relative to the wheel, 
     KAr being the radial stiffness of the cylindrical resilient articulations, 
     KPc being the compression stiffness of the resilient member  38 , 
     KPs being the shearing stiffness of the resilient member  38 , 
     L being the length of the connection rods between the first connection location and the second connection location, 
     2l being the distance which separates the first respective connection locations of the two connection rods, and 
     KAt being the torsion stiffness of the cylindrical resilient articulations  38 . 
     If the wheel  12  is subject to a transverse force Fy (see arrow Fy in  FIG. 2 ), each of the connection rods  26  and  28  tends to pivot about an axis which is substantially vertical relative to the axle casing  14  in the region of the second articulation point thereof, and also relative to the chassis  16  in the region of the first articulation point thereof. In this manner, at each connection location, the shaft end  56  of the connection rod tends to become misaligned relative to the cylindrical housing  58 , and pivots about a vertical axis (see arrow Ω of  FIG. 3 ). 
     The transverse stiffness of the primary suspension relative to the wheel may be expressed in the following manner: 
         Ky= 1/(1 /Kya+ 1 /Kyc ), 
       with 
         Kya= 2.(½ .KAa ), 
         Kyc= 4.( KAc/L   2 ), 
     Kya being the contribution of the axial stiffness of the cylindrical resilient articulations to the transverse stiffness of the primary suspension, 
     Kyc being the contribution of the conical stiffness of the cylindrical resilient articulations to the transverse stiffness of the primary suspension, 
     KAa being the axial stiffness of a cylindrical resilient articulation, and 
     KAc being the conical stiffness of a cylindrical resilient articulation. 
     The longitudinal stiffness of the primary suspension relative to the wheel may be expressed in the following manner: 
         Kx= 2.(½ .KAr ). 
     The rolling stiffness of the axle is expressed in the following manner: 
     
       
      
       Ktetax=Ktetac+Ktetad  
      
     
       with 
       Ktetac=2.KAc, and 
         Ktetad= 2 .Kz .( d/ 2) 2    
     Ktetac being the contribution of the conical stiffness of the cylindrical resilient articulations to the rolling stiffness of the axle, 
     Ktetad being the contribution of the transverse center distance of the axes to the rolling stiffness of the axle, and 
     d being the center distance between the primary suspensions associated with the two wheels of the same axle along a direction parallel with the axle. 
     A rolling movement of the axle corresponds to a rotation movement of this axle about an axis substantially parallel with the movement direction of the bogie. In this instance, each connection rod  26  and  28  tends to pivot about an axis parallel with the movement direction of the bogie (indicated with a dot-dash line R in  FIG. 2 ) relative to the axle box  18  in the region of the second connection location, and relative to the chassis  16  in the region of the second connection location. In this manner, at each of the connection locations, the shaft end  56  tends to become misaligned relative to the cylindrical hole  58  and pivots about the axis R. 
     An embodiment of a primary suspension device as described above will now be set out, suitable for a bogie which has a load of, for example, approximately five tonnes per wheel. 
     The connection rods  26  and  28  each have a length L of approximately 400 mm between their respective first and second connection locations. The lever arm  1  is approximately 170 mm, the angle β is approximately 60°. The center distance d between the primary suspensions of the same axle is approximately 1.09 m. The resilient member has a compression stiffness KPc of 3×10 6 N/m and shearing stiffness KPs of 0.15×10 6 N/m. 
     The cylindrical resilient articulations each have a radial stiffness KAr of approximately 175×10 6 N/m, axial stiffness KAa of approximately 65×10 6 N/m, and torsion stiffness KAt of 4300 m.N/rd, and conical stiffness KAc of approximately 0.3×10 6  m.N/rd. 
     The primary suspension has, in this instance, a vertical stiffness relative to the wheel Kz of approximately 174×10 4 N/m, a stiffness parallel with the axle relative to the wheel Ky of substantially 670×10 4 N/m and a stiffness relative to the wheel in the movement direction of the bogie Kx of substantially 175×10 6 . The rolling stiffness of the axle is approximately 1.93×10 6  m.N/rd. 
     In the idle state, the primary suspension device has a height which is substantially 300 mm. 
     The suspension device described above has a number of advantages. 
     One advantage occurs when the two connection rods are longitudinally offset relative to each other when the suspension device is in the rest state which allows the spacing to be increased between the first respective connection locations of the two connection rods, without increasing the height of the suspension device. This in turn allows resilient members with a larger degree of flexibility to be accommodated, without increasing the height of the suspension device. 
     Selecting a rubber/metal sandwich as a resilient member also contributes to allowing the suspension to absorb a greater vertical load for a specific vertical suspension space. 
     Resilient members of the rubber/metal sandwich type may be more compact than the helical springs which are conventionally used. 
     Furthermore, rubber/metal sandwiches may operate with compression and with shearing, while a helical spring can only operate with compression. It is thus possible to arrange the resilient member of the rubber/metal sandwich type with an angle β which is significantly different from 90°, which contributes to reducing the height of the suspension. 
     Furthermore, for the same spatial requirement, and in particular in an arrangement in which the rubber/metal sandwich operates principally with compression, the suspension device may absorb more load vertically than with a resilient member which includes a helical spring. 
     The use of a rubber/metal sandwich allows the angle β to be selected freely and thus allows variable vertical stiffnesses of the suspension to be obtained for the same connection rod positioning. 
     Furthermore, the greater the longitudinal spacing between the two connection rods, the closer the compression axis of the resilient member is to the vertical (for a fixed angle β), and therefore the greater the possibility of increasing the cross-section of the member perpendicularly relative to the compression axis thereof, and therefore the volume thereof, without increasing the height of the suspension. Alternatively, it is possible to thereby reduce the height of the suspension, without reducing the volume of the resilient member. 
     In this manner, the use of two offset connection rods and a rubber/metal sandwich allows each primary suspension device to be arranged so that it is located entirely below the apex of the axle box or the axle, if necessary. Each device may have, for example, a height of between 200 mm and 400 mm, preferably between 250 mm and 350 mm and typically 300 mm. 
     A preferred position of the connection rods involves their being longitudinally offset in a symmetrical manner at one side and the other of the axle, which allows the connection rods to be evenly loaded in the event of vertical stresses on the wheels when the resilient member is located half-way between the first connection locations of the connection rods, as explained above. 
     The use of cylindrical resilient articulations to connect the connection rods to the chassis on the one hand and to the axle box on the other hand may also be particularly advantageous. These articulations are arranged with axes parallel with the axle, which allows the increase of the stiffness parallel with the axle of the primary suspension, under the action of the conical stiffnesses of the cylindrical resilient articulations, the vertical stiffness of the primary suspension under the action of the torsion stiffnesses of the cylindrical resilient articulations, and the anti-rolling stiffness of the axle also under the action of the conical stiffnesses of the cylindrical resilient articulations. 
     This final point is particularly significant when the primary suspensions are placed between the wheels of the same axle, in which case the inherent rolling stiffness linked to the transverse center distance between axles is low, taking into account the reduced distance which separates the right-hand and left-hand suspensions of the axle. 
     Furthermore, the use of cylindrical resilient articulations and a rubber/metal sandwich confers on the primary suspension a sufficient level of damping to allow vertical shock-absorbers to be dispensed with in the primary suspension. 
     Furthermore, the height adjustment of the suspension can be carried out by arranging wedges between the rubber/metal sandwich and the abutment surfaces of the connection rods. 
     The suspension device described above may have a number of variants. 
     The lower and upper connection rods may not be perpendicular relative to the axle but instead may extend parallel with the axle. 
     In another construction variant, the resilient member  38  may not be a rubber/metal sandwich but instead a helical spring or any other type of resilient member. 
     Also in a further variant of the invention, the connection rods may be connected to the first and second elements not by means of cylindrical resilient articulations but instead by any other type of articulation, for example, by means of spherical joints. 
     Also in an additional manner, it is possible to arrange the connection rods  26  and  28  in such a manner that the second connection locations of these rods are not symmetrical relative to the axle  14 . 
     Owing to the spatial requirement and architecture of the bogie, the resilient member may be offset with respect to the connection rods, in an upward or downward direction, to the left or to the right relative to the position illustrated in  FIG. 1 . 
     In the case of bogies which comprise fixed axles on which the wheels are rotatably mounted, the connection rods  26  and  28  can be connected via their second respective connection locations  34  and  36  directly to the axles. The connection rods may also be connected, via their first connection location to other fixed components of the bogie, for example, to braking members. 
     In the case of bogies which are provided with the axles comprising a rotating shaft which connects the wheels in terms of rotation, and a housing which provides the mechanical stiffness of the axle and the rotational guiding of the rotating shaft, the connection rods  26  and  28  can be connected to the housing via their second connection locations  34  and  36 , respectively. The housing, in this instance, extends practically over the entire length of the axle, from one wheel to the other. 
     The device may comprise a plurality of resilient members  38  which are interposed in parallel between the two connection rods. 
     The primary suspension devices may not be arranged towards the inner side of the bogie relative to the wheels, but instead immediately at the outer side of the bogie relative to the wheels. 
     The suspension device may be integrated in a secondary suspension of the bogie, the second element in this instance being the chassis of the bogie, the first element being the body of the rail vehicle in the case of a non-pivoting bogie, and being the bogie bolster in the case of a bogie which pivots relative to the body. 
     The suspension devices described above may be used on bogies for any type of rail vehicle, for example, tramways, or any type of train.