[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.
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).