[0001] The present invention is related to running gears for rail vehicles, and more particularly
for tramway vehicles.
[0002] The present manufacture trend in the field of tramway vehicles is directed towards
an entirely lowered floor or platform, for a better convenience of passenger getting
on and off. In order to achieve this object it is practically necessary to employ
different bogies than the traditional ones, for instance provided with independently
steering axles. Steering axles solve to a relevant extent the problem of the curve
wheel-rail wear, since these axles can be radially adjusted following the curve radius
of the track.
[0003] Axle steering is performed in some cases spontaneously, but more frequently it is
driven by means of suitable mechanical systems, to the aim of ensuring the necessary
intrinsic safety and also to warrant that the wheel set assembly be statically determined
and, therefore, be not negatively affected by any track imperfections.
[0004] The invention is thus more particularly related to a running gear for low-floor rail
vehicles, comprising at least two bodies having each two independent respectively
outer and inner steering axles, with respect to the vehicle configuration, including
respective axle structures rotatably connected to the body around respective central
vertical axis and each carrying a wheel pair, a tow bar pivotally interconnecting
at its ends the two bodies, and drive means for operating curve steering of the axles
of the two bodies.
[0005] A running gear of the above-referenced type is known for instance from US-A-5,277,127,
according to which the axle steering angle is transmitted from one body to the adjacent
body via a longitudinal steering rod, a toggle lever centrally articulated on the
inner axle bridge, a connecting rod and an extension present on one side of the wheel
bridge. Steering is transmitted to the outer axles via a pair of longitudinal drawbars
lying on opposite sides of the longitudinal center line of the vehicle and connected
to each other with a connecting rod, or by an oblique connecting rod, or still by
means of a swing lever supported on one side of the body central area and connected,
via two connecting rods, to corresponding articulation points of the two axle frames.
[0006] As far as steering of the inner axles of the two bodies is concerned, the presently
known systems are not adapted to enable achievement of low curve-radiality errors
of the axles, particularly in the case of tramway vehicles having two bodies and,
therefore, with only two available reference signals.
[0007] The object of the present invention is to provide a running gear for low-floor rail
vehicles of the above-referenced type, which enables to combine high efficiency and
relative simplicity, so as to obtain the lowest possible curve-radiality error of
the axles, particularly in the case of a two-body tramway.
[0008] According to the invention, this object is achieved by virtue of a running gear of
the type set forth at the beginning, essentially characterized in that said drive
means operate steering of the axles of each body through the relative angular displacement
between the tow bar and the bodies, and as a function of the rotation between said
tow bar and the respective body.
[0009] The steering system according to the present invention originates from an analytical
study of the running gear geometry, so as to obtain a steering law upon which the
rotation of the inner axles is driven - and transmitted to the outer axles - following
a unique linear relationship, independent from the curve radius, which shall be disclosed
in detail herebelow. Following simple geometrical evaluations, the system may be simplified
so as to reduce it to a single lever which transmits to the inner axles the rotation
of the tow bar, and a simple rotation reversing member then transmits the same amount
of angle of rotation to the vehicle outer axles.
[0010] The same system can be applied to three-body rail vehicles, suppressing the reversing
member as far as the axles of the central body are concerned, and directly delivering
the steering signal from the closer tow bar of the central body, so as to achieve
extremely reduced radiality errors during curve entry and exit.
[0011] The same system may also be applied to tramway vehicles having a plurality of intermediate
bodies, wherein only the two end bodies are equipped with the rotation reversing member
between the respective axles, while the axles of the intermediate bodies receive the
steering drive from the respective closest tow bars.
[0012] According to a preferred constructive embodiment of the invention, said drive means
comprise two substantially coplanar trapezoid-linkage mechanisms interconnecting,
on opposite sides, the tow bar and the inner axles of the two bodies and each of which
includes;
- a first angled lever arm rigidly connected at one end thereof to the corresponding
articulated end of the tow bar to the respective body,
- a second angled lever arm having a greater length than the first lever arm and rigidly
connected at one end to the axle structure in a spaced relationship from the respective
vertical rotation central axis thereof,
- an oblique bar pivotally connected to the free ends of said first and second lever
arms,
- and wherein the ratio between the length of the first and second lever arms is equal
to a predetermined value.
[0013] The invention contemplates alternative embodiments in connection with said drive
means, among which a solution employing a flying lever mechanism applied to the ends
of the tow bar.
[0014] The running gear according to the invention affords, in comparison to similar known
solutions, the following advantages:
- achievement of a perfect radiality of the axles when running along a curve, independently
of the radius of the curve itself;
- minimization of the maximum radiality error of the axles upon curve entry and exit
phases;
- remarkable efficiency and simplicity of the steering system;
- complete bi-directionality, in the sense that the steering system identically operates
in both advancement directions of the vehicle.
[0015] The invention will now be disclosed in detail with reference to the annexed drawings,
purely provided by way of non limiting example, in which:
- figure 1 is a partial and simplified perspective view of a low-floor two-body tramway
vehicle provided with a running gear according to the invention,
- figure 2 is a simplified top plan view of figure 1,
- figure 3 is a partial lateral elevational view in an enlarged scale according to arrow
III of figure 1,
- figure 4 is a geometrical diagram of figure 2,
- figure 5 is a diagram similar to figure 4 of a first variant of the invention,
- figure 6 is a partial geometrical diagram showing a second variant of figure 4,
- figure 7 is a view similar to figure 4 showing a tramway vehicle having three bodies,
and
- figure 8 is a view similar to figure 7 of a tramway vehicle having a plurality of
bodies.
[0016] The example shown in figures 1 through 3 is related to a tramway vehicle formed by
two bodies generally designated as 1, 2 and interconnected by an intermediate tow
bar 3.
[0017] Each body 1, 2 has a low floor 4 and two respectively inner and outer, with respect
to the vehicle configuration, independent steering axles 5, 6. Assuming that in the
advancing condition of the vehicle the body 1 is placed forwardly and the body 2 is
placed rearwardly with respect to the travel direction, the outer axle 6 and the inner
axle 5 of the body 1 shall be the front axle and the rear axle, respectively, while
the inner axle 5 and the outer axle 6 of the body 2 shall be the front axle and the
rear axle, respectively.
[0018] Each of the inner and outer axles 5, 6 comprises conventionally an axle support structure
or bridge, diagrammatically shown as 7 and carrying a respective coaxial wheel pair
8.
[0019] Each support structure 7 is centrally connected rotatably to the respective body
1, 2 around a respective vertical axis, so as to enable curve steering of the corresponding
axle 5, 6. In the case of the shown example each rotation vertical axis is defined
by a respective journal 9 centrally carried by a rocker lever 10 the opposite ends
of which are connected to the axle structure 7 through a pair of longitudinal arms
11. This arrangement is however to be considered as purely given by way of example.
[0020] The tow bar 3 is connected to the facing ends of the two bodies 1, 2 around respective
central articulated joints 12, 13.
[0021] In order to perform steering of the axles 5, 6, the invention provides a mechanical
drive system which, on one side, guarantees that the complex of the wheels 8 be statically
determined, so as to afford intrinsic safety against negative effects deriving from
any possible track imperfections, and on the other hand enables to obtain a perfect
radial steering of the axles along full curve, independently of the radius of the
curve itself. This steering system has been conceived starting from an analytical
study of the running gear geometry, the explanation of which will now be given with
reference to figure 4, showing the simplified geometrical diagram of the vehicle depicted
in figures 1 through 3.
[0022] In the geometrical diagram of figure 4 the following references have been used:
A = trace of the vertical rotation axis 9 of the outer axle 6 relative to the body
1.
B = trace of the vertical rotation axis 9 of the inner axle 5 relative to the body
1.
C = trace of the articulated joint 12 between the tow bar 3 and the body 1.
D = trace of the articulated joint 13 between the tow bar 3 and the body 2.
E = trace of the vertical rotation axis 9 of the inner axle 5 relative to the body
2.
F = trace of the vertical rotation axis 9 of the outer axle 6 relative to the body
2.
[0023] In the same diagram the following dimensions are also indicated:
a = distance between the vertical rotation axis A, B of the axles 5, 6 of the body
1 and between the vertical rotation axis E, F of the axles 5, 6 of the body 2.
b = distance between the articulated joint C of the tow bar 3 and the vertical rotation
axis B of the inner axle 5 of the body 1, and also distance between the articulated
joint D of the tow bar 3 and the vertical rotation axis E of the inner axle 5 of the
body 2.
c = length of the tow bar 3.

[0024] Lengths
a and
b are same for both bodies 1, 2.
[0025] Further, the following angles are indicated in the geometrical diagram of figure
4.
[0026] δ
A, δ
F = steering angles of the outer axles 6 of the two bodies 1, 2, respectively, measured
with reference to the longitudinal axis thereof.
[0027] δ
B, δ
E = steering angles of the inner axles 5 of the two bodies 1, 2, respectively, measured
with reference to the longitudinal axis thereof.
[0028] σ₁, σ₂ = relative angles between the tow bar 3 and the two bodies 1, 2, respectively,
with reference to the longitudinal axis thereof.
[0029] From the analytical study of the theoretical laws of the steering angles δ
A, δ
B, δ
E, δ
F of the axles 5, 6 as a function of the advancement of the vehicle along a curve,
the constant steering angle to be maintained in full curve, i.e. when

is defined by the following expression:

wherein R is the curve radius.
[0030] The angle σ is as follows:

thus, independently of the curve radius R:

[0031] In view of the above relation, the idea upon which the invention is based consists
of operating steering of the inner axles 5 of each body 1, 2 by means of the relative
angular displacement between the tow bar 3 and the bodies 1, 2, and more particularly
of causing these inner axles 5 to rotate proportionally to the corresponding rotation
between the tow bar 3 and the respective bodies 1, 2, and then transmitting same but
opposite rotation to the outer axles 6 of the two bodies.
[0032] The steering angle of the axles is thus expressed as a function of the rotation angle
of the tow bar 3 by the following linear relations:

Once having fixed the geometrical characteristics
a and
d, the preceding law satisfies radiality in full curve of the axles 5, 6 independently
of the radius R of the curve.
[0033] It is then necessary providing a means to minimize the maximum radiality error of
the axles 5, 6 during the entry and exit phases thereof relative to the curve. Once
having fixed the values
a and
d (i.e. the distance between the inner axle 5 and the outer axle 6 of each body 1,
2 and the distance between the inner axles 5 of the two bodies 1, 2), a geometrical
entity to act upon so as to minimize said maximum error for the four axles still subsists:
it is the magnitude
b, i.e. the distance between the ends of the tow bar 3 corresponding to the articulated
joint C, D, and the vertical rotation axis B, E of the inner axle 5 of each body 1,
2.
[0034] Following a numerical simulation of entry into a curve having a radius R = 15 m,
once having fixed
a and
d, one and only one value of
b was identified which minimizes the maximum error for all four axles 5, 6. It has
been found that the minimum error value which can be achieved is only function of
a and
d. If one or both these values are decreased, the error can be correspondingly reduced.
[0035] In order to operate steering of the inner axles 5 according to the above law

i.e. a control which is proportional to the rotation between the tow bar 3 and
each body 1, 2, the invention is providing, in the case of the embodiment shown in
figures 1 through 4, two simple trapezoid-linkage mechanisms referenced as 14, 15
for the body 1 and for the body 2, respectively.
[0036] The two trapezoid-linkages 14, 15 are substantially coplanar to each other and are
placed, in the case of the shown example, on opposite sides with respect to the longitudinal
center line of the vehicle. However an arrangement (not shown in the drawings) is
also contemplated, according to which the two trapezoid linkages are situated on the
same side with respect to the longitudinal center line of the vehicle.
[0037] Specifically referring to the geometric diagram shown in figure 4, the trapezoid
linkage 14 associated to the body 1 comprises a first angled lever arm 16 rigidly
connected to the articulated end C of the tow bar 3, and a second angled lever arm
17 rigidly connected to the inner axle 5 of the body 1, at a distance from the respective
vertical central rotation axis B, and having a greater length than the first lever
arm 16.
[0038] The two lever arms 16, 17, which in the condition of straightward motion of the vehicle
shown in the drawings are parallel to each other, are pivotally connected at the respective
free ends G, H to an oblique bar 18.
[0039] The ratio between the length of the lever arm 16 (CG) and the length of the first
lever arm 17 (BH) is such that

In the condition of straightward travel shown in the drawings, the oblique bar
18 is arranged perpendicularly to the two lever arms 16, 17: this permits ensuring
a kinematic behaviour which is most close to the linear one, so as to minimize the
non-linearity errors due to the different lengths of the lever arms 16, 17.
[0040] The arrangement of the trapezoid linkage 15 associated to the body 2 is almost identical
to that of the trapezoid linkage 14, but for the fact that the former is placed on
the opposite side relative to the longitudinal vehicle axis. Thus the trapezoid linkage
15 also comprises a first lever arm 16 rigid with the articulated end D of the tow
bar 3 to the body 2, a second lever arm 17 rigidly connected to the inner axle 5 of
the body 2 at a distance from the respective central vertical rotation axis E, and
an oblique bar 18 pivotally connected at I and L, respectively, to the free ends of
the angled lever arms 16 and 17.
[0041] Even in this case the ratio between the length of the arm 16 (DI) and the length
of the arm 17 (EL) is such that:

Actually, in accordance with the structural arrangement shown in figures 1 through
3, the second angled lever arms 17 are not physically present, since the articulations
H and L of the oblique bars 18 of the two trapezoid linkages 14, 15 are directly carried
by the ends, opposite to each other, of the support structures 7 of the inner axle
5 of the body 1 and of the body 2, respectively. Therefore, the second lever arms
17, which are materially depicted in the geometrical diagram of figure 4, simply correspond
to the distance between the articulations H, L and the central vertical rotation axis
B, E of the two inner axles 5.
[0042] For operating steering of the outer axles 6 of the two bodies 1, 2, that as previously
pointed out shall be of the same but opposite entity with respect to that of the inner
axles 5, two oblique rods 19 are provided which interconnect, for each body 1, 2,
respective points of the support structures 7 of the inner axle 5 and of the outer
axle 6 placed on opposite sides with respect to the longitudinal axis of the vehicle.
As shown in the structural arrangement of figures 1 through 3, each rod 19 is articulated
respectively to one end 20 and to the opposite end 21 of the respective rocker levers
10 associated to the two axles 5, 6.
[0043] In operation, the two trapezoid linkages 14, 15 and the two oblique rods 19 operate
and, respectively, transmit curve steering of the axles 5, 6 of the two bodies 1,
2 proportionally to the rotation between the tow bar 3 and these bodies 1, 2, according
to the above specified linear relationship, which enables to achieve almost perfect
radiality of the axles 5, 6 in full curve independently of the radius of the curve
itself, while minimizing the maximum radiality error of the axles during the entry
and exit phases relative to the curve.
[0044] As a matter of fact the above linear relationship

Is a particular case of the following more general law:

wherein the distance
b is selected at will and the following relationship is anyhow valid:

It is thus a matter of determining one or the other of the two variables M, N
through a normal method of optimization of the resulting radiality errors.
[0045] The embodiment of the invention such as previously disclosed, simply employing the
two trapezoid linkages 14, 15, accomplishes the particular condition wherein the length
b is optimized so as to annul the coefficient N.
[0046] However, selecting different values of the length
b, i.e. not annulling the coefficient N, the invention contemplates the possibility
of carrying out a kinematic configuration such as shown in figure 5, or even of employing
a so called "flying lever" mechanism such as diagrammatically depicted in figure 6.
[0047] The embodiment according to figure 5, wherein parts which are identical or similar
to those disclosed with reference to figure 4 are designated by the same reference
numerals, differs therefrom in that each trapezoid linkage 14, 15 further comprises
a second oblique bar 22 pivotally interconnecting the articulation point G, or respectively
I, between the first arm 16 and the oblique bar 18 of the respective trapezoid linkage
14, 15, with a third angled arm 23.
[0048] The third arm 23 associated to the trapezoid linkage 14 of the body 1 is connected
to the other body 2 behind the articulation end D of the tow bar 3 to the body 2,
while the third arm 23 associated to the trapezoid linkage 15 of the body 2 is connected
to the body 1 in front of the corresponding articulation point C of the tow bar 3
to the body 1.
[0049] The "flying lever" mechanism is purely depicted in the form of a geometrical diagram
in figure 6, in which only the tow bar 3 is shown with the articulation ends C and
D thereof to the bodies 1 and 2 of the vehicle.
[0050] This mechanism comprises a first lever 24 and a second lever 25 of which the first
one is articulated to the articulation end C of the tow bar 3 to the body 1, and the
second one is articulated to the articulation end D of the tow bar 3 to the body 2,
and these levers 24 and 25 are placed on opposite sides of the tow bar 3. The levers
24 and 25 are therefore freely rotatable and are connected to the inner axles 5 of
the respective bodies 1, 2 via respective rigid square arms 26, 27, which in turn
are connected to the inner axles 5 of the two bodies.
[0051] Reference numeral 28 designates a flying lever which is oriented generally transversely
to the tow bar 3, and which is articulated at one end 29 thereof to a connecting rod
30 which is in turn articulated to the end 31 of the lever 25. A second connecting
rod 32 pivotally connects the end 33 of the lever 24 with a point 35 of the flying
lever 28 which is spaced apart from the opposite end 36 thereof. A third lever 37,
also articulated in correspondence of the articulation end C of the tow bar 3 to the
body 1, is pivotally connected at the end 38 thereof to the end 36 of the flying lever
28 via a third connecting rod 39.
[0052] In figure 6,
a,
b,
c and
d designate the length of the first lever 24, of the second lever 25, of the third
lever 37 and of the flying lever 28, respectively.
[0053] In operation, the displacements of the points 28 and 35 due to rotations α and β
of the levers 24 and 25 cause a rotation of the flying lever 28. Since, as previously
pointed out, the latter is also connected via the connecting rod 39 to the third lever
37, the final effect is thus a rotation γ of such lever 37 with respect to the tow
bar 3.
[0054] Once having set the values
a,
b,
c,
d, corresponding as explained in the above to the lengths of the various mechanism
components, the following relationships are deriving from geometrical studies:

The above relationships are valid if the flying lever 28 is dimensioned so as
the length thereof is corresponding to the sum of the lengths of the third lever 37
and of the second lever 25, i.e. if

whereby

A law of more general character may be obtained varying the length
d of the flying lever 28.
[0055] Reverting now to the preceding general law of axle steering as a function of the
tow bar 3 rotation:

it is to be pointed out that, according to the above law, the steering angles
δ of the axles were referred to the longitudinal axis of the bodies 1 and 2.
[0056] In the case of the flying lever mechanism, the same law is accomplished referring
the axle steering not to the bodies, but relative to the tow bar 3. For instance,
in the case of the body 1, since the relative rotation between this body and the tow
bar 3 is σ₁, it is:

Wherein δ'
A is in fact the steering angle referred to the tow bar 3.
[0057] It is sufficient to select the lengths
a,
b,
c,
d so as to obtain

The flying lever mechanism shown in figure 6 may be simplified, with equivalent
functional effects, suppressing the first connecting rod 32 and the second connecting
rod 39, and in such a case the flying lever 28 shall be articulated at 35 and 36 directly
to the first lever 34 and to the third lever 37, respectively.
[0058] According to a further simplification, corresponding to the case where the coefficient
N = 0, also the second connecting rod 30 may be suppressed, whereby the end 29 of
the flying lever 28 shall be directly articulated to the second lever 25.
[0059] The invention is applicable not only to tramway vehicles having two bodies, but also
to vehicles provided of three or more bodies.
[0060] Figure 7 shows the embodiment according to figure 4 applied to a tramway vehicle
having three bodies, i.e. with an intermediate body 2a interposed between the bodies
1 and 2, and also having a pair of independent steering axles 5a, 5b. The intermediate
body 2a is connected at one end to the body 1 via a tow bar 3a, and at the other end
to the body 2 via a tow bar 3b, both identical to the tow bar 3 as previously disclosed.
[0061] A trapezoid linkage 14 placed on the side of the body 1, and a trapezoid linkage
15a situated on the side of the intermediate body 2a, are operatively associated to
the tow bar 3a. Likewise, a trapezoid linkage 14a placed on the side of the intermediate
body 2a and a trapezoid linkage 15 situated on the side of the body 2 are operatively
associated to the tow bar 3b.
[0062] The trapezoid linkages 14, 15a, 14a, 15 are exactly same as those previously disclosed
with reference to the trapezoid linkages 14 and 15.
[0063] The axles 5 and 6 of the bodies 1, 2 are interconnected through the reversing bars
19, while no such bar is provided for the intermediate body 2a.
[0064] According to this arrangement, also steering of each of the axles 5a, 5b of the intermediate
body 2a is operated through the angular displacement of the tow bar 3a, 3b which is
closest, and as a function of the rotation thereof, thus achieving extremely reduced
radiality errors during curve entry and exit.
[0065] A similar arrangement is applicable to the case of a vehicle comprising, between
the bodies 1 and 2, a plurality of intermediate bodies 2a.....2n with respective pairs
of independent steering axles 5a, 5b and connected to the adjacent bodies via respective
tow bars 3a.....3n. In such a case each intermediate body 2a......2n is equipped with
respective trapezoid linkages 15a, 14a.......15n,14n, while the reversing bars 19
are even in this case only applied to the end bodies 1 and 2. In practice, therefore,
all of the axles 5a, 5b of the intermediate bodies 2a......2n receive the steering
drive from the tow bar 3a.......3n which is closest thereto.
[0066] Obviously, the arrangement of the steering drive system disclosed with reference
to figure 5 as well as the flying lever system of figure 6 can also be applied to
the case of tramway vehicle having three or more bodies.
[0067] Lastly it is to be pointed out that, in any case, it will be necessary to prevent
negative effects and fouling of the axle steering signals deriving from the movements
of the body relative to the axles in the horizontal plane, due to yielding of the
vehicle lateral suspension. To such effect the vehicle lateral suspension shall normally
be interposed between the body structure and the low floor 4.
[0068] Naturally the details of construction and the embodiments may be widely varied with
respect to what has been disclosed and illustrated, without thereby departing from
the scope of the invention such as defined by the appended claims.
1. A running gear for low-floor (4) rail vehicles comprising at least two bodies (1,
2) each having two independent respectively outer (6) and inner (5) steering axles,
with respect to the vehicle configuration, including respective axle structures (7)
rotatably connected to the body (1, 2) around respective central vertical axis (9;
A, B, E, F) and each carrying a wheel pair (8), a tow bar (3) pivotally interconnecting
at its ends (12, 13; C, D) the two bodies (1, 2), and drive means (14, 15; 24-39;
19) for operating curve steering of the axles (5, 6) of the two bodies (1, 2), characterized
in that said drive means (14, 15; 24-39) operate steering of the axles (5) of each
body (1, 2) through the relative angular displacement between the tow bar (3) and
the bodies, and as a function of the rotation between said tow bar (3) and the respective
body (1, 2).
2. A running gear according to claim 1, characterized in that steering of the inner axles
(5) is operated, and transmitted to the outer axles (6), in accordance to the following
linear relationship:

wherein

and wherein:
δ
B, δ
E: steering angles of the inner axles (5) of the two bodies (1, 2) relative thereto,
δ
A, δ
F: steering angles of the outer axles (6) of the two bodies (1, 2) relative thereto,
σ₁, σ₂: relative angles between the tow bar (3) and the two bodies (1, 2),
a = distance between the central rotation axis (A-B; E-F) of the inner axle (5) and
of the outer axle (6) of each body (1, 2),
d = sum of the length (
c) of the tow bar (3) and the distance (
b) between each articulation end (C, D) of the tow bar (3) and the central rotation
axis (B, E) of the inner axle (5) of the respective body (1, 2).
3. A running gear according to claim 2, characterized in that the distance (
b) between each articulation end (C, D) of the tow bar (3) and the central rotation
axis (B, E) of the inner axle (5) of the respective body (1, 2) is selected and optimized
so that N = 0, and said linear relationship is approximated as follows:

whereby the axles (5, 6) of each body (1, 2) are solely operated through a control
which is proportional to the rotation between the body and the tow bar (3).
4. A running gear according to claim 3, characterized in that said drive means comprise
two substantially coplanar trapezoid linkages (14, 15) interconnecting the tow bar
(3) and the inner axles (5) of the two bodies (1, 2) and each including:
- a first angled lever arm (16) rigidly connected at one end thereof to the corresponding
articulation end (C, D) of the tow bar (3) to the respective body (1, 2),
- a second angled lever arm (17) having a greater length than the first lever arm
(16) and carried by the support structure (7) of the axle (5) at a distance from the
respective central vertical rotation axis (B, E) thereof,
- an oblique bar (18) pivotally connected to said first and second lever arms (16,
17),
wherein the ratio between the lengths of the first arm (16) and of the second
arm (17) is equal to M.
5. A running gear according to claim 4, characterized in that, in the non steered condition
of the axles (5, 6), said first and said second angled lever arms (16, 17) are parallel
to each other and are oriented perpendicularly to the oblique bar (18).
6. A running gear according to claim 2, characterized in that said drive means comprise
two substantially coplanar trapezoid linkages (14, 15) interconnecting the tow bar
(3) and the inner axles (5) of the two bodies (1) and each including:
- a first angled lever arm (16) rigidly connected at one end thereof to the corresponding
articulation end (C, D) of the tow bar (3) to the respective body (1, 2),
- second angled lever arm (17) having a greater length than the first lever arm (16)
and carried by the support structure (7) of the axle (5) at a distance from the respective
central vertical rotation axis (B, E) thereof,
- an oblique bar (18) pivotally connected to said first and second lever arms (16,
17)
wherein the ratio between the lengths of the first arm (16) and of the second
arm (17) is equal to M,
- a pair of oblique rods (22) each pivotally interconnecting the free end of the first
lever arm (16) of the trapezoid linkage (14, 15) associated to one body (1, 2) and
a third angled arm (23) connected to the other body (2, 1) in proximity of the corresponding
articulation end (D, C) of the tow bar (3).
7. A running gear according to claim 2, characterized in that said drive means comprise
a flying lever mechanism applied to the ends of the tow bar (3) and including:
- a first and a second lever (24, 25) each articulated in correspondence of a respective
articulation end (C, D) of the tow bar (3) to the respective body (1, 2), said first
and second lever (24, 25) being arranged on opposite sides of said tow bar (3) and
being connected to the inner axles (5) of the respective bodies (1, 2) via respective
rigid square arms (26, 27),
- a flying lever (28) oriented generally transversally to the tow bar (3),
- a first and a second connecting rod (32, 30) pivotally connecting the first and,
respectively, the second lever (24, 25) with said flying lever (28) at one end (29)
thereof and, respectively, at a point (35) thereof spaced apart from the other end
(36) thereof,
- a third lever (37) articulated in correspondence of one of the articulation ends
(C) of the tow bar (3) to one of the bodies,
- a third connecting rod (39) pivotally connecting said third lever (37) to the other
end (36) of the flying lever (28).
8. A running gear according to claim 7, characterized in that the flying lever (28) has
a length (d) which is equal to the sum of the lengths (b + c) of said second and third levers (25, 24).
9. A running gear according to claim 7, characterized in that the first connecting rod
(32) and the third connecting rod (39) are suppressed, whereby said flying lever (38)
is directly articulated to said first and third levers (24, 37).
10. A running gear according to claim 9, characterized in that also the second connecting
rod (30) is suppressed, whereby said flying lever (28) is directly articulated to
the second lever (25).
11. A running gear according to claim 1, characterized in that said drive means comprise
transmission means (19) for transmitting reversed steering from the inner axles (5)
to the outer axles (6) of the two bodies (1, 2), said transmission means comprising
an oblique reversing rod (19) pivotally connecting the outer and inner axles (5, 6)
of each body (1, 2).
12. A running gear according to claim 11, wherein the vehicle comprises a third body (2a)
interposed between said bodies (1, 2), having a pair of independent steering axles
(5a, 5b) and connected to said two bodies (1, 2) via a pair of tow bars (3a, 3b),
characterized in that said drive means (14, 14a, 15, 15a) are associated to both said
tow bars (3a, 3b) and said transmission means (19) are only associated to said two
bodies (1, 2).
13. A running gear according to claim 11, wherein the vehicle comprises a number of bodies
(2a.....2n) interposed between said two bodies (1, 2), each having a pair of independent
steering axles (5a, 5b) and each of which is connected to the adjacent bodies via
respective tow bars (3a....3n), characterized in that said drive means (14, 14a.....14n,
15, 15a......15n) are associated to each tow bar (3a.....3n) and said transmission
means (19) are only associated to said two bodies (1, 2).