U.S. patent application number 10/399238 was filed with the patent office on 2004-02-12 for railway wheel/rail noise and wear reduction arrangement.
Invention is credited to Nilsson, Nils-Ake.
Application Number | 20040026526 10/399238 |
Document ID | / |
Family ID | 20281466 |
Filed Date | 2004-02-12 |
United States Patent
Application |
20040026526 |
Kind Code |
A1 |
Nilsson, Nils-Ake |
February 12, 2004 |
Railway wheel/rail noise and wear reduction arrangement
Abstract
A railway wheel/rail squeal suppression, wheel/rail noise
reduction and wear reduction arrangement includes a separate
structure (14) carried by a rail. The separate structure has a
saddle-like profile including a web portion (15) defining a running
surface for supporting the wheel, and two flange portions (16a,
16b). The saddle-like profile is shaped substantially in conformity
with the shape of the railhead, is located on top it and is
mechanically de-coupled therefrom. Resilient means (17) is
interposed between the web portion and the railhead (13). The web
portion (15) has a thickness not less than about twice the
thickness of the flange portions so as to resist detrimental
compression of the resilient means (17) and transfer only a portion
of wheel load to the rail, and the flange portions (16a, 16b) are
connected to the rail so as to transfer a remaining wheel load
thereto.
Inventors: |
Nilsson, Nils-Ake; (Taby,
SE) |
Correspondence
Address: |
DICKSTEIN SHAPIRO MORIN & OSHINSKY LLP
2101 L STREET NW
WASHINGTON
DC
20037-1526
US
|
Family ID: |
20281466 |
Appl. No.: |
10/399238 |
Filed: |
August 18, 2003 |
PCT Filed: |
October 17, 2001 |
PCT NO: |
PCT/SE01/02267 |
Current U.S.
Class: |
238/382 |
Current CPC
Class: |
E01B 2204/01 20130101;
E01B 5/08 20130101; E01B 19/003 20130101 |
Class at
Publication: |
238/382 |
International
Class: |
E01B 019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 18, 2000 |
SE |
0003770-5 |
Claims
1. A railway wheel/rail squeal suppression, wheel/rail noise
reduction and wear reduction arrangement including a separate
structure (14; 14'; 14") carried by a rail having a foot portion
(11), a web portion (12) and a head portion (13) normally
supporting a wheel, the separate structure having a saddle-like
profile including a web portion (15; 15'a) defining a running
surface for supporting the wheel, and two flange portions (16a,
16b), the saddle-like profile being shaped substantially in
conformity with the shape of the head portion, being located on top
of it and being mechanically de-coupled from the head portion, and
resilient means (17) being interposed between the web portion and
the head portion (13), characterized in that the web portion (15;
15'a) has a thickness not less than about twice the thickness of
the flange portions so as to resist detrimental compression of the
resilient means (17) and transfer only a portion of wheel load to
the rail, and that the flange portions (16a, 16b) are connected to
the rail so as to transfer a remaining wheel load thereto.
2. An arrangement according to claim 1, characterized by fastening
and load transmitting means (19, 20, 21, 22; 19, 30) between the
separate structure and the rail.
3. An arrangement according to claim 2, characterized in that a
viscoelastic layer (26a, 26b) is arranged between said fastening
and load transmitting means and said rail.
4. An arrangement according to claim 1, characterized in that the
mass of the separate structure is small in relation to the mass of
the co-oscillating mass of the rail.
5. An arrangement according to any one of the preceding claims,
characterized in that the railhead (13") has reduced cross
sectional dimensions and that the separate structure (14') has
external dimensions corresponding to those of a railhead having
non-reduced dimensions.
6. An arrangement according to any one of the preceding claims,
characterized in that the separate structure includes means (19a,
19b) for attachment to the fastening and load transmitting means
(20, 21; 30a, 30b) carried by the rail.
7. An arrangement according to claim 2, characterized in that the
rail includes integrated means (30a, 30b) for the attachment of the
separate structure.
Description
[0001] The present invention concerns a railway wheel/rail squeal
suppression, wheel/rail noise reduction and wear reduction
arrangement.
[0002] It is well known that railway wheels may cause loud
screeching or squealing noises particularly when running on a
curved rail due to bogie crabbing and wheel flange-to-rail contact.
The noise is normally composed of one or more tonal components that
could alter its sound levels with time in a very annoying way. Such
a noise is usually referred to as wheel/rail squeal and is a
problem in most traffic systems employing track-bound vehicles,
such as trams/streetcars, underground/subway cars and the like.
[0003] Various attempts have been made in the past to reduce
vibrations and structureborne sound associated with wheel/rail
systems, both to reduce noise emissions and to prevent the
formation of ripples in the rail which in turn lead to disturbing
noise, involving measures both on the wheels (U.S. Pat. No.
4,358,148) and the rail (U.S. Pat. Nos. 3,974,963 and
4,203,546).
[0004] Most prior art vibration reduction systems employ masses,
springs and dampeners or visco-elastic layers attached to a wheel
and/or a rail.
[0005] One object of the present invention is to reduce the
wheel/rail squeal and simultaneously reduce the wear of both the
wheel and the rail by measures on the rail. This aspect of the
present invention is based on earlier studies performed by the
inventor utilising non-linear lumped parameter models.
[0006] These studies reveal that a reduced rail mass will affect
the non-linear stick-slip process in such a way that the wheel/rail
squeal is most likely to be totally abolished.
[0007] The inventive idea, thus, as regards the wheel/rail squeal
reduction, resides in reducing the dynamically participating mass
of the rail, and, more precisely, a portion of a rail excited by a
wheel travelling on it.
[0008] It is also well known that railway wheels may cause high
sound levels even when running on a welded straight track. Such a
noise is usually referred to as wheel/rail roar noise and is a
problem in most transportation systems employing rail carried
vehicles, such as trams/streetcars, underground/subway cars
high-speed trains and the like.
[0009] Various attempts have been made in the past to reduce
radiation of airborne sound, vibrations and structureborne sound
associated with wheel/rail systems. These attempts have been
targeting to reduce noise emissions e.g. by screens, by special
wheel designs etc.
[0010] Instead, another object of the present invention is to
reduce the wheel/rail roar noise by measures on the rail and
simultaneously reduce wear of both the wheel and the rail. This
aspect of the present invention is based on various studies which
reveal that an increased compliance in the wheel/rail contact patch
as well as making the contact patch longer, such as occurring when
the wheel or rail is made more compliant, both will work to reduce
the emitted noise level from the wheel/rail system. The increased
compliance will cause the existing roughness in the running
surfaces of the wheel and the railhead to generate smaller
(reduced) forces when the wheel is rolling on the rail, and,
consequently, less noise. The extension of the length of the
contact patch will cause the roughness wavelength, which is small
compared to the length of the contact patch, to be filtered out.
Thereby the excitation forces onto both the wheel and the rail will
be significantly reduced, and, as a consequence, the noise emitted
as well as wear of the wheel and of the rail will be
correspondingly reduced.
[0011] The inventive idea, thus, as regards the wheel/rail roar
noise reduction, resides in increasing the mechanical compliance of
the rail and, more precisely, a portion of a rail excited by a
wheel travelling on it, thereby making the contact patch longer and
the roughness virtually softer thereby reducing the roughness
induced rolling forces onto both the rail and the wheel. The
reduced forces will also significantly reduce the wheel and rail
wear.
[0012] The inventive idea is realised by providing a running
surface on a separate structure disengaged from the railhead on
which a wheel is normally running.
[0013] In practice, there are different ways of embodying this:
[0014] a) A separate structure, preferably a saddle profile
structure, extending in the longitudinal direction of the rail, is
added onto the top, or, head portion of an original rail
section;
[0015] b) A longitudinal groove is cut into a railhead and an inlay
structure is placed in the groove;
[0016] c) An ordinary rail is machined to remove exterior portions
of its head portion, and a separate structure, preferably a saddle
profile structure having exterior dimensions corresponding to the
removed portions is prepared to substitute the removed portion;
[0017] d) A special rail profile and an associated separate
structure, preferably a saddle profile structure, are prepared
having together the profile and dimensions of an ordinary rail
section. In either case, the mass of the separate structure shall
be small in relation to the mass of the rail and be mechanically
de-coupled from the rail, preferably by the interposition of
resilient materials between the rail and the separate
structure.
[0018] Particularly, at the squeal frequency the co-oscillating
mass of the separate structure shall be small in relation to the
co-oscillating mass of the rail, typically in the range of 1:5-20.
Also, the mass per length unit of the separate structure shall be
very small in relation to the mass per length unit of the remainder
of the rail, including possible attachments other than the separate
structure.
[0019] Since the dynamically disengaged structure resting on the
railhead will also reduce the forces generated by the wheel/rail
contact both in the vertical, lateral and longitudinal direction,
also a significant reduction of the wear of the wheel and the rail
will result.
[0020] Japanese Patent Document 2-35102 (A) discloses a rail having
its head crowned with a first layer of a material having sound
absorbing or vibration isolating properties, such as a polymer
material. Outside the first layer there is a damping member formed
by a layer of uniform thickness of a damping alloy such as a
Co-group or a Mn--Cu alloy. The shapes of the layers shown are such
that mounting thereof inevitably involves bending of the layers to
fit the profile of the railhead and, in one embodiment, an upper
portion of the rail web. This, in turn, means that the outer layer,
the damping member, is comparatively weak and not capable of
resisting wheel loads to the extent necessary to avoid overload of
the polymer material. Furthermore, in the embodiment where the two
layers extend downwards along a portion of the rail web and are
attached thereto by means of bolts, there is no possibility that
the wheel loads can be transmitted to the rail by means of the
damping member.
[0021] Embodiments of the present invention will now be described,
reference being made to the accompanying drawings, wherein:
[0022] FIG. 1 is a cross section through a rail provided with a
wheel/rail squeal suppression arrangement including a separate
structure added onto the head portion of the rail according to a
first embodiment;
[0023] FIG. 2 is a perspective view of a section of an arrangement
according to FIG. 1;
[0024] FIG. 3 is a cross section through a variant of the first
embodiment according to FIGS. 1 and 2;
[0025] FIG. 4a shows a cross section through an upper portion of a
normal railhead;
[0026] FIG. 4b shows a cross section through a rail having portions
of its railhead removed and replaced by a separate saddle profile
structure according to a third embodiment of the present
invention;
[0027] FIG. 5 shows a cross section through a rail including a
special rail profile and a saddle profile structure according to a
fourth embodiment of the present invention.
[0028] The rail shown in FIGS. 1-3 is an ordinary rail used for
trams and trains and having a foot portion 11, a web portion 12 and
a head portion 13. In the first embodiment of the invention shown
in FIGS. 1 and 2, a separate saddle profile structure 14 is added
onto the top of the railhead 13 to extend in its longitudinal
direction. This separate structure substantially has the section of
an inverted U having a web portion 15 and two leg portions 16a,
16b. The separate structure is suitably an extruded or continuously
cast profile of aluminium or a forged or hot rolled profile of
wrought steel.
[0029] As seen particularly in FIG. 1, the curvature of the surface
of the separate structure 14 facing the railhead is adapted to the
curvature of the railhead 13 such that these curvatures are
substantially uniform. A supporting layer 17 of a resilient
material, such as rubber, is interposed between the top surface of
the rail head and the separate structure, thus keeping the latter
at a substantially uniform distance a from the rail head. A typical
thickness of the layer 17 is 1-6 mm, preferably 2-3 mm, in a squeal
suppression embodiment, and 1-8 mm, preferably 2-5 mm, in a roar
noise reduction embodiment. It is designed to resist vertical loads
and to ensure lateral flexibility of the separate structure. To
achieve this, the material shall have a high bulk modulus to avoid
"polymer crushing" (less than 30% compression of the rubber
material), and a low modulus of shear to give the important lateral
flexibility. Further, its material properties shall not change
significantly with temperature changes. It is advantageous that the
rubber material exhibits a high material loss factor, typically
.eta..sub.m =0.3-0.9 or more in a squeal suppression embodiment,
and 0.3-0.8 in a roar noise reduction embodiment. A useful material
would be butyl rubber.
[0030] Between the opposed inner sides of the legs 16a, 16b of the
saddle profile structure and the respective sides of the rail head
there may be provided lateral cushions 18a, 18b of a flexible
material soft enough to enable lateral movement of the separate
structure relative to the rail head.
[0031] In order to firmly hold the separate structure 14 in place,
its leg portions 16a, 16b are provided with flanges 19a, 19badapted
to be located in a common, substantially horizontal plane when the
separate structure is mounted onto a rail. Angle irons 20, 21
having substantially perpendicular legs 20a, 20b and 21a, 21b,
respectively, are firmly attached to the web portion 12 of the rail
by means of horizontally spaced bolts 22 extending through the legs
20b, 21b and the web portion 12 and having nuts 22a and bolt heads
22b. The legs 20a, 21a are substantially horizontally aligned and
spaced a small distance b from the flanges 19a, 19b, respectively.
Resilient layers 23a, 23b are interposed between the respective
facing flanges 19a, 19b and legs 20a, 21a to ensure lateral
flexibility of the separate structure relative to the rail head.
Bolts 24, 25 having nuts 24a, 25a and bolt heads 24b, 25b,
respectively, vertically extend through the respective opposed
flanges 19a, 19b and legs 20a, 21a to connect the separate
structure 14 to the angle irons.
[0032] Besides keeping the separate structure to the rail, the
bolts 24, 25 serve to reinstate the galvanic connection between the
wheel of a train and the rail that has been lost by the
interposition of the layer 17 between the mass structure and the
railhead. It is imperative, thus, that the heads and nuts of the
bolts 24, 25 have good electrical contact with the flanges 19a, 19b
and the legs 20a, 21a to ensure galvanic contact to the angle irons
and further into the rail web by means of the bolts 21.
[0033] In order to attenuate vibrations propagating along the web
portion, layers 26a, 26b of a visco-elastic material, such as
polyurethane, may be applied between the web portion 12 and the
legs 20b, 21b, respectively.
[0034] The arrangement shown in FIG. 3 differs from the one
according to FIGS. 1 and 2 only in that the separate structure 14'
is asymmetrical as concerns the thickness of its web portion 15'.
It will be seen thus, that in order to better withstand the load of
a wheel, the web portion 15' has a thickened portion 15'a which is
the portion of the rail on which a wheel is to roll. It will
further be seen, that the adjoining leg portion 16'a is also
somewhat thickened in relation to the opposed leg portion 16'b.
[0035] Although the embodiment according to FIGS. 1-3 will provide
a solution to the noise problem, it involves the drawback that at
least one of a pair of rails will have to be laterally displaced
since adding a structure to a normal rail will influence the track
width.
[0036] The second embodiment of the present invention shown in
FIGS. 4a and 4b sets this drawback aside.
[0037] FIG. 4a shows a section through a railhead 13 of a normal
rail and the upper portion of its web portion 12. A cross-hatched
portion 13' defined by a dash-dotted line indicates portions of the
railhead to be removed in order to reduce the railhead section to
an extent enabling a saddle profile structure having substantially
the exterior dimensions of the original railhead to be mounted onto
the reduced railhead 13" as shown in FIG. 4b.
[0038] Thus, the second embodiment of the present invention shown
in FIG. 4b does not involve a change of the cross section of a
normal rail. As mentioned, this has been accomplished by machining
a normal railhead 13 so as to remove material 13' from the top and
at least one side of the railhead (the one against which the flange
of a railcar wheel bears, although FIGS. 4a and b show both sides
being reduced) leaving a reduced railhead 13", and in that the
removed material has been replaced by a saddle profile structure
14' resembling that shown in FIG. 1, and an interposed elastic
layer 17, substantially according to FIG. 1, although the saddle
profile structure 14' has exterior dimensions corresponding to
those of the non-machined railhead shown in FIG. 4a.
[0039] The saddle profile structure 14' is kept attached to the
remaining rail by equal means as shown in FIG. 1, including flanges
19a, 19b, angle irons 20, 21, bolts 22, 24, 25, and interposed
resilient layers 23a, 23b. Supplementary lateral cushions 18a, 18b
may be interposed between the flanges 16a, 16b of the saddle
profile structure and the lateral sides of the reduced railhead
13".
[0040] The third embodiment of the present invention shown in FIG.
5 utilises a rail section particularly manufactured for the purpose
of enabling mounting thereon of a saddle profile structure.
[0041] Thus, the portion of the rail section where its web portion
12 merges with the railhead has been widened to provide two opposed
shoulders 30a, 30b having flat upper surfaces 31a, 31b,
respectively, corresponding to those of the legs 20a, 20b,
respectively, of the angle irons 20, 21 of FIG. 1. The shoulders
30a, 30b merge with a reduced railhead 13a having substantially the
shape of the remaining railhead 13" of
[0042] FIG. 4b. A saddle profile structure 14", shaped and
imensioned substantially as the one according to FIG. 4b, is
mounted onto the railhead 13a by means of bolts 24, 25 extending
through flanges 19a, 19b of the saddle profile structure 14" and
the shoulders 30a, 30b, respectively. As before, a resilient layer
17 is interposed between the saddle profile structure 14" and the
diminished railhead 13a, and supplementary lateral cushions 18a,
18b may be interposed between the flanges 16a, 16b of the saddle
profile structure and the lateral sides of the reduced railhead
13a.
[0043] As can be seen in the Figures, the web portion 15 of the
separate structures is substantially thicker than its flange
portions. This is to make the web portion stiff enough not to cause
polymer crushing. The ultimate stress limit for useful polymers is
at about 30% compression. In operation, thus, a limit of about 20%
compression should not be exceeded. Under such circumstances, it is
preferred to make the web portion not less than about twice as
thick as the flange portions. This, in turn, means a reduced
deflection of the web portion and, consequently, that only a
portion of the wheel load is absorbed by the resilient layers 23a,
23b so as not to risk causing detrimental polymer crushing, whereas
a remaining portion of the load is transferred from the web portion
through the flange portions to the rail by means of the angle irons
20, 21 and its attachment bolts 22 in the embodiments of FIGS.
1-4b, and straight into the shoulders 30a, 3b in the embodiment of
FIG. 5.
* * * * *