(19)
(11) EP 0 365 489 A2

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication:
25.04.1990 Bulletin 1990/17

(21) Application number: 89830271.6

(22) Date of filing: 20.06.1989
(51) International Patent Classification (IPC)5B61F 5/44
(84) Designated Contracting States:
AT BE CH DE ES FR GB GR IT LI LU NL SE

(30) Priority: 19.10.1988 IT 6794088

(71) Applicant: FIAT FERROVIARIA S.p.A.
I-10138 Torino (IT)

(72) Inventor:
  • Santanera, Oreste
    I-10025 Pino Torinese (Torino) (IT)

(74) Representative: Buzzi, Franco et al
c/o Jacobacci-Casetta & Perani S.p.A. Via Alfieri, 17
10121 Torino
10121 Torino (IT)


(56) References cited: : 
   
       


    (54) A bogie with steering axles for railway vehicles


    (57) A bogie for railway vehicles has steering axles (5) connected horizontally to the frame (4) (of the body or of the bogie proper) by means of levers, connecting rods, tie rods and struts (9) which permit longitudinal forces but not torques to be transmitted between the axles and the frame. For steering purposes, the two axles may be independent of each other or may be connected to each other and/or to the bogie frame and/or to the vehicle body. A retaining device (24) is also provided for modifying the resilient characteristic of the steering movement of the axles, so as to adapt it to the line and the preselected speed range.




    Description


    [0001] The present invention relates in general to bogies for railway vehicles. It must be stated that, in the course of the following description and claims, the term "bogie" means an assembly of two axles (each with two wheels) with their respective bushes, suspensions, connections, etc., whether the assembly is connected directly to the vehicle body (a two-axle vehicle) or is connected to a frame (in this case the "bogie frame") to form an "bogie proper" and therefore a vehicle including a body and two bogies or n bodies and n + 1 bogies (an articulated vehicle).

    [0002] The bogies of railway vehicles are fundamental elements of railway technology and are called upon to provide an ever-increasing performance in the development of rail services.

    [0003] This development tends towards a continual increase in quality and quantity.

    [0004] The main quality characteristic is a reduction in time, that is, an increase in speed. The main quality characteristic is an increase in traffic intensity insofar as it is compatible with maintenance.

    [0005] The bogies for modern vehicles must therefore permit ever greater speeds with low track aggression. This must be possible both on new lines (direct lines with special routes and few bends) and on many of the lines using old routes.

    [0006] These different requirements are normally satisfied by the provision of vehicles with characteristics which are at best suitable for one particular situation (for example, for high speed) and attempts to adapt them to the requirements of other types for use (for example, service on tortuous lines).

    [0007] In traditional bogies in which the various components are interconnected by resilient elements with fixed characteristic, the need for adaptation is felt particularly in the definition of the resilience of the connections between the axles (with bushes) and the bogie frame, in the X (longitudinal), Y (transverse) and Z (vertical) directions.

    [0008] These connections are among the principal factors affecting the good or bad stability of the bogie on bends and its ability to adapt to curves. In fact, whilst, for travelling round curves, the reduction of the angle of attack of the wheel relative to the track to the minimum possible requires that the axles be connected to the bogie frame with considerable freedom of movement, particularly pivoting (a freedom which must also exist in the presence of traction and braking forces), high-speed travel in a straight line or on large-radius curves requires more rigid connections between the axles and the frame in order to avoid snaking movements of an amplitude and frequency such as to cause the flanges to knock against the rails.

    [0009] Bogies for satisfying the first requirement (ease of adaptation to curves) have already been proposed, in which the bushes of the axles are connected to the structure of the bogie so as to enable it to steer, that is, to be oriented radially while travelling round bends. However, the bogies with steering axles proposed up to now have found few practical applications, due mainly to difficulties in their adaptation to modern requirements for high-speed travel in a straight line or on large-radius curves.

    [0010] The object of the present invention is to enable the production of bogies with steering axles which provide the best response to the conflicting requirements specified above by means of suitable variations, which can easily be carried out in practice, of the basic parameter constituted by the resilience of the longitudinal connections (in the X direction) between the bushes and the structure of the bogie.

    [0011] According to the invention, this object is achieved by virtue of the concept defined in Claim 1.

    [0012] Further subordinate and alternative characteristics of the invention are defined in the subclaims 2 to 8.

    [0013] Further characteristics of the invention will become clear from the detailed description which follows with reference to the appended drawings, provided by way of non-limiting example, in which:

    Figure 1 is a schematic side elevational view of a bogie with steering axles for railway vehicles, according to the invention,

    Figure 2 is a schematic plan view from above, taken on the arrow II of Figure 1,

    Figure 3 Is a view similar to Figure 2, partially-sectioned and on an enlarged scale,

    Figure 4 is a longitudinal section taken on the line IV-IV of Figure 3, and

    Figure 5 shows a detail of Figure 3 on an enlarged scale.



    [0014] With reference to the drawings, a bogie for a railway vehicle is generally indicated 1 and is intended to be articulated to the body of the vehicle in a manner which is known and therefore not illustrated in detail in the drawings. The articulation to the body, which is arranged in the central region of the bogie 1, is generally indicated 2 in Figure 1. Resilient secondary suspension members 3 are associated therewith in known manner.

    [0015] The bogie 1 is constituted, also in conventional manner, by a rigid or deformable frame 4 (in the latter case, for improving vertical adaptability to the track) carrying two axles 5 with respective wheels 6.

    [0016] The two axles 5 are provided with respective bushes 7 at their ends and primary suspension springs 8 are interposed between the bushes and the frame 4.

    [0017] The bogie 1 also includes members (not shown in the drawings) for transmitting traction and braking forces to the body, braking equipment, and possibly motors and their transmissions: these elements are generally conventional and, for brevity, will not therefore be described.

    [0018] According to the invention, the two axles 5 are connected horizontally to the frame 4 by means of respective kinematic mechanisms, generally indicated 9, which permit longitudinal forces acting along a longitudinal axis X (parallel to the axis of the track), but not torques, to be transmitted between the axles 5 and the frame 4.

    [0019] Each of the two kinematic mechanisms 9 includes a pair of longitudinal connecting rods 10, each of which is articulated at one end 11a to one of the bushes 7 and at the opposite end 11b to a respective right-angled lever 12 which is articulated centrally to the frame 4 about a vertical pin 13 with a cylindrical articulation.

    [0020] Each right-angled lever 12 has a transverse arm 14 (that is, an arm parallel to the transverse axis Y of the bogie 1) to which the articulation end 11b of the respective connecting rod 10 is connected, and a longitudinal arm 15 (that is, an arm parallel to the longitudinal axis X of the bogie 1) which extends from the side opposite the respective connecting rod 10. The ends 12′ of the longitudinal arms 15 of the right-angled levers 12 of each kinematic mechanism 9 are interconnected by means of a transverse rod 16 parallel to the transverse axis Y of the bogie 1. As is clear from Figures 2 and 3, by virtue of the arrangement described above, the two cross members 16 associated with the two kinematic mechanisms 9 extend near the transverse centreline of the bogie 1.

    [0021] The articulations 11a, 11b and 12′ are conveniently provided with resilient joints, not illustrated, as are the articulations between the pins 13 and the right-angled levers 12.

    [0022] The invention provides for the connection of the two cross members 16 in various alternative or combined ways. In particular, the latter are connectible to each other, to the frame 4 of the bogie 1, and to the frame of the body.

    [0023] In the first case, the connection between the two cross members 16 can be achieved by means rigid or resilient members, with the possible addition of shock-absorbers. The embodiment illustrated shows an example of a resilient connection achieved (as shown in greater detail in Figure 3) by means of a cylinder 17 whose axis is parallel to the transverse axis y of the bogie 1 (and therefore parallel to the cross members 16) and within which a piston-rod unit 18 is axially slidable against the action of springs 19. The rod 18 and the opposite end of the cylinder 17 from the rod 18 react against respective bearing surfaces 20 which project longitudinally from the two cross members 16.

    [0024] In the second case, the connection between the cross members 16 and the frame 4 of the bogie 1 is achieved by means of a transmission lever 21 with a central fulcrum 22 in the central region of one of the cross members 16 and an end fulcrum 23 on the frame 4. In this case, the resilient interconnection 17-20 between the two cross members 16 is also present and a retaining device 24 is also provided which is operable selectively to lock the transmission lever 21 in a central position (shown in the drawings) in which it is aligned with the longitudinal axis X of the bogie 1, so as consequently to stop the movement of the cross members 16 and hence the pivoting of the right-angled levers 12. The retaining device 24, which is shown in greater detail in Figure 5, comprises two cylinders 25 fixed to the frame 4 of the bogie 1 symmetrically and on opposite sides of a longitudinal appendage 26 of the transmission lever 21, the appendage extending from the side opposite the fulcrum 23. The two cylinders 25 are aligned with each other parallel to the transverse axis Y of the bogie 1, and respective pistons 36 sealingly slidable in the cylinders are subject on one side to the action of one or more thrust springs 27 and on the opposite side to the action of a pressurised fluid, normally air, supplied by a source, not illustrated. A rod or strut 28 is fixed to each piston 36 and projects sealingly from the respective cylinder 25 so as to cooperate with the appendage 26 of the transmission lever 21 in the manner explained below.

    [0025] In the presence of air pressure in the cylinders 25, the two pistons 36, with their struts 28, are kept in the retracted rest configuration shown in the drawings, in which they do not interfere with the appendage 26 of the lever 21 and the latter is therefore free to move with the cross members 16 and the respective right-angled levers 12.

    [0026] In the absence of pressurised air in the two cylinders 25, the springs 27 urge the two structs 28 against the opposite sides of the appendage 26 of the lever 21 and therefore tend to keep the latter in the central position shown in the drawings, so as to prevent the movement of the cross-members 16 and the respective right-angled levers 12.

    [0027] In the third case, the retaining device 24 is omitted and the transmission lever 21 is connected to the body of the vehicle at 29, in a region intermediate its fulcra 22 and 23, by means of a vertical shaft 30 with two universal joints. The shaft 30 may be replaced by an equivalent device for the transmission of torque only, whereby the pivoting movements between the body and the bogie force the lever 21 to pivot about the fulcrum 23 and hence the fulcrum 22 to be displaced transverse the longitudinal axis C of the bogie 1. Since, as stated, the fulcrum 22 is connected to one of the cross members 16, and since the two cross members 16 are interconnected by the resilient device 17-20, the body-bogie pivoting is transformed into two equal and opposite pivoting movements of the axles 5, which therefore assume a radial arrangement.

    [0028] According to a further and simpler embodiment of the invention, it is possible to eliminate any connection of the cross members 16 (and hence of the two kinematic mechanisms 9) to each other, as well as their connection to the frame 4 of the bogie 1 and to the body of the vehicle.

    [0029] The main advantages resulting from the conformation of the bogie according to the invention may be summarised as follows:

    1) the axles are connected horizontally to the frame (of the body or of the bogie proper) by means of levers, connecting rods, tie rods, and struts which are designed to permit the transmission of longitudinal forces (that is, forces directed along an axis parallel to the axis of the track) but not torque between the axles and the frame;

    2) within the above-mentioned design, the resilience values of the primary suspension (transverse and longitudinal) and all the articulations which connect the bushes to the frame (by means of connecting rods, levers, tie rods, and struts) enable: the grading of the stiffnesses of the longitudinal and transverse connections of the axles to the frame; the attribution of the desired resilient characteristic to the pivoting motion (in a horizontal plane) of each axle relative to the frame, which in practice is not affected by the presence of traction or braking forces;

    3) the resilient characteristic of the pivoting motion (in a horizontal plane) of each axle relative to the frame of the bogie depends: on the longitudinal resilience of the primary suspensions of each bush; on the radial resilience of the articulations of the connecting rods, levers, tie rods, and struts connecting the bushes, and on the cylindrical resilience of the articulations which come into play when the right-angled levers pivot;

    4) the movements of the right-angled levers, as a result of longitudinal movements of the bushes of each axle in the opposite direction, give rise to parallel movements of the transverse rods which, since they are located near the transverse axis of the bogie, can easily be interconnected so that the pivoting movements of the two axles of the bogie can be connected with suitable resilience;

    5) the two transverse rods can also be locked selectively to the frame of the bogie, so as to change the resilient characteristics of the pivoting motion of the axles in order to adapt it to the line and to the preselected speed range;

    6) the lever which is used for any locking of the transverse rods can also be connected to the body of the vehicle (in the case of vehicles "with bogies") by a cardan shaft system, thus achieving the pivoting of the axles in dependence on the angle of pivoting between the body and the bogies (and therefore on the radius of the curve).



    [0030] The operation of the bogie 1 according to the invention will now be explained below with reference to the various embodiments described above.

    [0031] (Case I) - In the absence of any connection of the cross members 16 to each other or to the frame 4 or the body of the vehicle, each of the two axles 5 is independent and connected to the bogie 1 only by means of the respective primary suspension 8, the connecting rods 10, the right-angled levers 12 and the transverse rods 16 which are free, that is, as stated, are connected neither to each other, nor to the frame 4, nor to the vehicle body.

    [0032] In this case, each axle 5 is free to pivot relative to the frame 4 under the action of the forces developed between the wheels 6 and the rails which are opposed by the forces and torques, which may be very small, which oppose the movements of the unit constituted by the axles 5, the connecting rods 10, the right-angled levers 12, and the transverse rods 16.

    [0033] (Case II) - In this case, as explained above, the two transverse rods 16 are interconnected by the resilient device 17-20 (or by an equivalent rigid device). Under the action of the active and passive forces referred to in Case I, the two axles 5 pivot, as a result of the connection 17-20, through angles which are equal (or almost equal if, as in the case described, the connection 17-20 is resilient) and opposite. The axle which has the greater tendency to adopt a radial position can contribute to the radial positioning of the other.

    [0034] (Case III) - In this case, the bogie 1 is provided with a connection between the two kinematic mechanisms 9 and the frame 4, as well as with the retaining device 24.

    [0035] In this case, even during running, the same bogie can assume the following two arrangements:
    III₁: in the presence of compressed air in the cylinders 25, the transmission lever 21 and hence the transverse rods 16 are free and the axles 5 can therefore move (especially pivot) relative to the frame 4 of the bogie 1, both by the radial deformation of all the resilient articulations 11a, 11b, 12′ and by the pivoting of the right-angled levers 12 and the articulations associated with the pins 13.

    [0036] In this case, the resistance which the axle must overcome in order to move radially is slight.

    [0037] III₂: in the absence of compressed air in the cylinders 25, the two struts 28 are urged, under the action of the springs 27, against the appendage 26 of the transmission lever 21. The latter is therefore restrained in the central position shown in the drawings, and the movement of the transverse rods 16 is prevented. Consequently, the right-angled levers 12 cannot pivot and the axles 5 can move longitudinally and pivot relative to the frame 4 of the bogie 1 only by the radial deformation of the resilient articulations 11a, 11b and 12′.

    [0038] In this case, the resilience (particularly in the sense of pivoting) of the connections of the axles 5 to the frame 4 of the bogie 1 is low; stability at speed is improved and the ability to adapt radially to bends is reduced.

    [0039] A change from one of the arrangements III₁ - III₂ to the other can be effected easily by means of conventional solenoid valves which are activated or de-activated in dependence on the speed or the type of line.

    [0040] (Case IV) - The bogie 1 is provided with a connection between the kinematic mechanisms 9 and the body of the vehicle by means of the transmission lever 21 and the shaft 30, whilst the retaining device 24 is absent. In this case, pivoting between the body and the bogie 1 causes, by means of the lever 21 and the kinematic mechanisms 9, equal and opposite pivoting of the two axles 5 which are therefore steered independently of any other movement (vertical, transverse, longitudinal) of the secondary suspension 3.

    [0041] Naturally, the details of construction and forms of embodiment of the bogie may be varied widely with respect to those described and illustrated, without thereby departing from the scope of the present invention. Thus, for example, although the above description relates to its application to a bogie proper, it is equally applicable (except Case IV described above) in the case of the direct application of the assembly of two axles, with the respective bushes, suspensions and connections, to the body of a railway vehicle.


    Claims

    1. A bogie for railway vehicles, comprising a bogie structure and a pair of axles provided with respective end bushes connected to the bogie structure so that the axles can be steered, characterised in that the two bushes (7) of each axle (5) are connected to the bogie structure (4) by means of a respective kinematic mechanism (9) for transmitting longitudinal forces between the axle (5) and the bogie structure (4), including:
    - a pair of longitudinal connecting rods (10) each of which is articulated at one end (11a) to a respective bush (7) of the axle (5),
    - a pair of right-angled levers (12) articulated to the bogie structure (4) about respective vertical axes (13) and each having a transverse arm (14) which is articulated to the other end (11b) of the corresponding connecting rod (10) and a longitudinal arm (15) which extends in the opposite direction from the connecting rod (10),
    - a cross member (16) which pivotably interconnects the longitudinal arms (15) of the two right-angled levers (12).
     
    2. A bogie according to Claim 1, characterised in that the articulation ends (11a, 11b, 12′) of each connecting rod (10) and each right-angled lever (12) are provided with respective resilient joints.
     
    3. A bogie according to Claim 1 or Claim 2, characterised in that the cross members (16) of the two kinematic mechanisms (9) associated with the bushes (7) of the two axles (5) are free with respect to each other and to the bogie structure (4).
     
    4. A bogie according to Claim 1 or Claim 2, characterised in that the cross members (16) of the two kinematic mechanisms (9) associated with the bushes (7) of the two axles (5) are interconnected so that a displacement of one of the cross members (16) in one direction causes a corresponding displacement of the other cross member in the same direction and therefore the pivoting of the axles (5) in opposite senses.
     
    5. A bogie according to Claim 4, characterised in that the two cross members (16) are interconnected by means of a resilient device (17-20).
     
    6. A bogie according to Claim 4 or Claim 5, characterised in that the cross members (16) of the two kinematic mechanisms (9) associated with the bushes (7) of the two axles (5) are also connected to the bogie structure (4) by means of a transmission lever (21) carried centrally by one of the cross members (16) and having one end (23) articulated to the bogie structure (4), a retaining device (24) being associated with the opposite end (26) of the transmission lever (21) and being operable selectively to lock the transmission lever (21) relative to the bogie structure (4) in a central position in which it is aligned with the longitudinal axis (X) of the bogie (1).
     
    7. A bogie according to Claim 6, characterised in that the retaining device (24) comprises a pair of fluid actuators (25) arranged transversely and symmetrically on opposite sides of the end (26) of the transmission lever (21) and driving respective struts (28) which are movable between inoperative, retracted positions in which they do not interfere with the transmission lever (21) and advanced positions in which they lock the transmission lever (21) in the central position.
     
    8. A bogie according to Claim 4 or Claim 5, in which the bogie is pivotably connected to a body of a railway vehicle, characterised in that the cross members (16) of the two kinematic mechanisms (9) associated with the bushes (7) of the two axles (5) are also connected to the bogie structure (4) and the vehicle body by means of a transmission lever (21) which has a first fulcrum (22) on one of the cross members (16) and a second fulcrum (23) on the bogie structure (4), and a cardan-type vertical connecting device (30) which interconnects the vehicle body and the lever (21) at a position (29) intermediate the two fulcra (22) and (23).
     




    Drawing