ELASTIC WHEEL FOR RAILWAY VEHICLES
Field of the Art
The present invention relates to an elastic wheel for
railway vehicles, particularly designed for urban railway
vehicles such as trams, subways or light rails.
State of the Art
Elastic wheels are commonly used in trams or in another
type of railway vehicles which run primarily in urban areas.
These wheels are designed for damping vibrations resulting
from rolling and reducing the noise produced to the greatest
possible extent.
Elastic wheels conventionally consist of an elastomer,
in the form of a single annular block or in the form of a set
of individual blocks, which is inserted in a housing defined
between the tread, the wheel center, and a ring compressing
the elastomer against the wheel center. The ring is usually
fastened to the wheel center by means of a set of lock bolts.
The objective that is sought by means of the arrangement
of the elastomer in the housing defined between the ring, the
wheel center and the tread is to attain a suitable flexibility
to vibration damping ratio.
There is a wide range of these elastic wheels on the
market, for example, German patent DE 3,328,321 discloses an
elastic wheel having an elastomer formed by a set of rubber
blocks which are arranged in a virtually horizontal manner in
the housing defined between the tread, the wheel center, and
the retaining ring. In this case, the elastomer has a very
open V shape with an angle of about 15° with respect to the
horizontal, the horizontal being understood as a line
approximately parallel to the axis of the wheel.
Such elastic wheels have low rigidity in the axial
direction because the elastomer works under shear forces in
that direction. Low axial rigidity has a negative influence on
the dynamic behavior of the train and can cause early

deterioration of the elastomer due to the high deformations
experienced during service.
To improve rigidity of such elastic wheels in the axial
direction, the solution disclosed in patent document WO
9520499 proposes inserting metal parts into the elastomer so
that they can work under compression in the axial direction.
In this regard, the solution of European patent document EP
679,540 is also known, which discloses having an elastomer
formed by rubber-coated metal blocks that are alternated
between blocks made of only rubber.
These two solutions improve rigidity of the elastic
wheel in the axial direction by means of hardening the
elastomer, but some of the damping properties are lost by
reducing the amount of elastomer, and noise attenuation, which
is one of the features inherent to elastic wheels, is
therefore decreases. Furthermore, they are complex solutions
that increase the cost of manufacturing the rubber blocks and
the elastic wheel.
Another type of elastic wheel is proposed in European
patent document EP 489,455, in which a V-shaped elastomer is
inserted in the housing defined between the tread, the wheel
center, and the retaining ring with an angle of 60° with
respect to the horizontal. This solutipn assures high enough
axial rigidity, but it has a complex geometry affecting the
manufacturing cost. In this solution, the elastomer consists
of a single annular block through which there extend screws
attaching the wheel center and the retaining ring. This
solution requires manufacturing a different mold for each
elastic wheel design. Furthermore, it is a rather non-
versatile solution, because a change in wheel diameter
requires developing specific molds for manufacturing the
single annular block of the elastomer. On the other hand, it
is necessary to make grooves having a complex geometry to
assure robust attachment between the elastomer and metal
parts, which affects the cost of machining the metal parts.

Another solution for an elastic wheel is proposed in
German patent document DE 2,428,078, which has an elastomer
formed by two annular blocks that are virtually parallel to
one another. In this case, the elastomeric material works
under shear forces in the radial direction of the wheel, so
its radial rigidity is lower. In this case, the elastic wheel
is devised for very specific applications, where the wheel is
subjected to low loads.
It is therefore necessary to develop an elastic wheel
which has a simple and economic structure, and assures good
axial and radial rigidity features.
Object of the Invention
The present invention proposes an elastic wheel that can
be applied to railway vehicles traveling in urban areas, such
as subways, trams or light rails.
This elastic wheel object of the invention is formed by
a tread and a wheel center defining a housing for the
insertion of an elastomer that is compressed by a retaining
ring which is attached to the wheel center by means of
attachment screws, the elastomer being formed by a plurality
of V-shaped elastic blocks.
The housing defined between the tread, the wheel center
and the retaining ring, in which the elastic blocks are
compressed, has two oblique walls belonging to the wheel
center and to the retaining ring, respectively, forming an
angle of between 48° and 52° with respect to the horizontal,
and preferably an angle of 50°. In addition, the oblique walls
of the wheel center and of the retaining ring end in
respective inclined sections on which the vertices of the V-
shaped elastic blocks are supported, said inclined sections
forming an angle of between 2° and 10° with respect to the
horizontal.
A simple and low-cost elastic wheel is thereby obtained,
and given its constructive and functional features, said
elastic wheel is preferably applied for the function for which

it is intended, assuring good axial and radial rigidity
conditions.
Description of the Drawings
Figure 1 shows a partial cross-section view of an
elastic wheel according to the invention.
Figure 2 is an enlarged detail of the housing in which
the elastomer of the wheel is introduced.
Figure 3 shows a side view of the elastic wheel.
Detailed Description of the Invention
Figure 1 shows a cross-section view of the set of
elements forming the elastic wheel object of the present
invention. The elastic wheel has the form of a body of
revolution generated about the axis (R) of the wheel and
consists of a tread (1) , which is the part of the wheel
traveling on the running rail, and a wheel center (2) or wheel
hub.
Between the tread (1) and the wheel center (2) there is
defined a housing in which an elastomer is inserted under
compression, said elastomer being retained by a ring (3) which
is attached to the wheel center (2) by means of attachment
screws (4) that do not interfere with the elastomer, being
located below it. The elastomer retained in the housing is
formed by a plurality of V-shaped blocks (5) made from a
completely elastic material, providing the wheel with high
damping capacity.
The housing where the elastic blocks (5) are compressed
is defined by two oblique walls (2.1, 3.1) belonging to the
wheel center (2) and to the retaining ring (3), respectively,
each of said oblique walls (2.1, 3.1) having an angle (α) of
between 48° and 52° with respect to the horizontal, preferably
an angle (α) of 50°, which allows assuring good axial and
radial rigidity of the elastic wheel, horizontal being
understood as a line parallel to the axis (R) of the wheel.
Furthermore, the oblique walls (2.1, 3.1) of the wheel
center (2) and the retaining ring (3) end in respective

inclined sections (2.2, 3.2) forming an angle (β) of between
2° and 10° with respect to the horizontal. The vertices of the
V-shaped elastic blocks (5) are supported on these inclined
sections (2.2, 3.2) of the wheel center (2) and the retaining
ring (3), such that assembly and disassembly of the elastic
blocks (5) is made easier as a result of the slightly conical
zone defined between them. It is thereby achieved that the
elastic blocks (5) are more homogenously seated in the wheel
center (2) and that the compression stress applied by the
retaining ring (3) during assembly is also homogenous.
Furthermore, this zone defined by the inclined sections (2.2,
3.2) prevents bends in the material of the elastic blocks (5).
With this arrangement of the elastic blocks (5),
confined between the tread (1), the oblique walls (2.1, 3.1)
and the inclined sections (2.2, 3.2) of the wheel center (2)
and the retaining ring (3), minimum axial rigidity of 40 KN/mm
is assured, and radial rigidity sufficient for bearing large
loads during service is in turn assured.
The use of elastic blocks (5) provides enormous
versatility and a huge competitive advantage with respect to
elastic wheel solutions with a single annular block. In fact,
it enables making significant changes to the wheel design
without having to make a new mold; and by including a
sufficient number of elastic blocks (5), behaviour during
service is equivalent to that of said solutions with a single
annular block.
Furthermore, the elastic blocks (5) are compressed
between 20 and 30% with respect to their original size in the
assembly arrangement, this high level of compression assuring
a robust attachment between said elastic blocks (5) and the
metal parts of the tread (1), wheel center (2) and retaining
ring (3). Unwanted movements between parts during service are
thereby avoided without having to machine complex grooves in
metal parts.

inclined sections (2.2, 3.2) forming an angle (P) of between
2° and 10° with respect to the horizontal. The vertices of the
V-shaped elastic blocks (5) are supported on these inclined
sections (2.2, 3.2) of the wheel center (2) and the retaining
ring (3) , such that assembly and disassembly of the elastic
blocks (5) is made easier as a result of the slightly conical
zone defined between them. It is thereby achieved that the
elastic blocks (5) are more homogenously seated in the wheel
center (2) and that the compression stress applied by the
retaining ring (3) during assembly is also homogenous.
Furthermore, this zone defined by the inclined sections (2.2,
3.2) prevents bends, in the material of the elastic blocks (5).
With this arrangement of the elastic blocks (5) ,
confined between the tread (1), the oblique walls (2.1, 3.1)
and the inclined sections (2.2, 3.2) of the wheel center (2)
and the retaining ring (3), minimum axial rigidity of 40 KN/mm
is assured, and radial rigidity sufficient for bearing large
loads during service is in turn assured.
The use of elastic blocks (5) provides enormous
versatility and a huge competitive advantage with respect to
elastic wheel solutions with a single annular block. In fact,
it enables making significant changes to the wheel design
without having to make a new mold; and by including a
sufficient number of elastic blocks (5), behaviour during
service is equivalent to that of said solutions with a single
annular block.
Furthermore, the elastic blocks (5) are compressed
between 20 and 30% with respect to their original size in the
assembly arrangement, this high level of compression assuring
a robust attachment between said elastic blocks (5) and the
metal parts of the tread (1), wheel center (2) and retaining
ring (3). Unwanted movements between parts during service are
thereby avoided without having to machine complex grooves in
metal parts.

CLAIMS
1.- An elastic wheel for railway vehicles, formed by a
tread (1) and a wheel center (2), defining a housing for the
insertion of an elastomer that is compressed by a retaining
ring (3) which is attached to the wheel center (2) by means of
attachment screws (4), and in which the elastomer is formed by
a plurality of V-shaped elastic blocks (5), characterized in
that the housing defined between the tread (1), the wheel
center (2) and the retaining ring (3), in which the elastic
blocks (5) are compressed, has two oblique walls (2.1, 3.1)
belonging to the, wheel center (2) and to the retaining ring
(3), respectively, forming an angle (a) of between 48° and 52°
with respect to jthe axis (R) of the wheel, and in that the
oblique walls (2.1, 3.1) end in respective inclined sections
(2.2, 3.2) on which the vertices of the V-shaped elastic
blocks (5) are supported, said inclined sections (2.2, 3.2)
forming an angle ((5) of between 2° and 10° with respect to the
axis (R) of the wheel.
2.- The elastic wheel for railway vehicles according to
claim 1, characterized in that the angle (a) formed by the
oblique walls (2.1, 3.1) of the wheel center (2) and the
retaining ring (3) is 50° with respect to the axis (R) of the
wheel.
3.- The elastic wheel for railway vehicles according to
claim 1, characterized in that the elastic blocks (5) are
compressed in the assembly arrangement between 20% and 30%
with respect to their original size.