Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION
this invention concerns a railway truch and a
flexible roller bearing adapter assembly which provides
fit-up between a bearing journal and a side frame in a
conventional three-piece railway truck such that the
wheelsets can move independently with respect to the side
frames as is required to achieve proper wheelset tracking on
both curved and tangent track. Various benefits are
realized, including reduced flange-to-rail contact and
reduced sliding at the interface between the wheel and rail
running surfaces.
The lnvention contemplates a bearing adapter
assembly which includes elastomeric elements having a form
or geometry that provides for three dimensional support of
the side frame pedestals on the bearing journals in a manner
that permits necessary and controlled bearing journal
translation longitudinally of the side frames in the
pedestal opening through differential deformation of the
elastomer, including compression thereof. The invention
further provides continuously wear-compensated longitudinal
and lateral bearing adapter-to-pedestal constraint.
A conventional three piece railway truck is comprised
of a pair of laterally spaced side frames which are
supported on a pair of longitudinally spaced wheelsets, and
an elongated bolster which extends between the spaced side
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frames and is supported thereon by springs. Practitioners
in the art have continuously sought to improve the
performance of such truchs in an effort to realize improved
truch component service life, reduced rail wear, improved
fuel economy and operating reliability, increased safety,
and other benefits which can result in overall enhancement
of railway rolling stoch performance.
Modern railway truck wheelset roller bearings permit
only very limited wheelset movement with respect to the side
frames. For example, such bearings permit substantially no
lateral freedom for the wheelsets to move laterally with
respect to the truch side frames. More specifically, it is
well hnown that when a conical wheelset of a conventional
truck is displaced laterally on the rails, the wheels roll
on unequal radii. The wheel which rolls on the larger
radius moves ahead of the other wheel thus steering the
wheelset from the laterally displaced position toward the
center position, where the wheels roll on equal radii.
However, as the wheelset continues on its preferred path, it
passes the equilibrium or centered position and moves to a
laterally displaced position on the opposite side of center,
from which the effect of the wheels rolling on unequal radii
again steers the wheelset back toward the centered position.
The wheelset thus continuously rolls along a substantially
sinusoidal path when there is no sliding at the rail-wheel
interface. In order to follow such a sinusoidal path the
wheelsets move with respect to the side frames to either a
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trapezoidal geometry as in radial steering, or a
parallelogram geometry such as commonly occurs when the
truch warps.
Due to the lach of lateral freedom in the roller
bearings, the entire truch will tend to follow such a
sinusoidal path. At higher speeds the motion of an empty
car body will tend to couple with lateral truch oscillations
to produce violent cyclical lateral car body accelerations,
commonly hnown as hunting, which can result in accelerated
wear of rail car components and rails as well as other
undesirable consequences including lading damage.
Conventional prior art truchs also permit the
wheelset bearing journals only very limited longitudinal and
rotational freedom in the horizontal plane with respect to
the side frame pedestals due to bearing adapter-to-side
frame horizontal friction and restricted motion limits. As a
result, the wheelsets of prior art truchs have insufficient
longitudinal freedom at the side frame pedestals to steer to
a radial alignment when traversing curved trach.
Consequently, the wheelsets tend to slide on the rails when
negotiating curved trach. The inability of the wheelsets of
such truchs to steer thus results in severe frictional
rubbing contact between the wheel flanges and the rails,
and accelerated flange and rail head wear on shorter radius
curves. Under such conditions, fuel economy also suffers as
a great deal of energy is dissipated by such rubbing
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contact. More severe flange rubbing also may create a
tendency for the wheel to climb the rail thus precipitating
a derailment. Furthermore, improper wheelset tracking on
curves may also cause or aggravate trach misalignment.
The variable restraining friction and unpredictable
motion limits between the bearing journal adapter and the
side frame pedestal in conventional truchs also results in
traching energy losses on tangent trach. When the wheelsets
of a truch cannot achieve a free rolling alignment on
tangent trach due to asymmetrical tread wear and/or
journal-to-pedestal restraint, the resulting wheel tread
slip and/or flange rubbing causes increased wheelset rolling
energy dissipation.
The art has contemplated truchs which include
resilient wheelset journal suspension to provide greater
freedom of relative motion than in truchs such as those
characterized above. For example, steering truchs are hnown
which use articulating techniques such as mechanical linhage
systems, usually in the form of steering arms, for the
simultaneous control of both wheelsets in the truch. Nearly
all such articulated steering truchs and other hnown truch
designs require resilient journal suspension at the side
frame pedestals. However, to be effective the resilient
suspension must be sufficiently elastic in horizontal shear
to permit the bearing journal to move longitudinally in the
pedestal for steering, and must also be sufficiently stiff
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in the lateral direction so as not to reduce the composite
lateral car body-to-truck spring constant and thereby
encourage low speed empty car hunting. As a result of these
conflicting requirements, hnown resilient journal
suspensions often have yielded either unsatisfactory control
at lower empty car speeds or a limited or ineffective
steering capability. For example, many prior resilient
journal suspensions, commonly the sandwich- configurations
in which elastomer is sandwiched or laminated in alternate
layers with a rigid substrate such as a steel plate, the
available lateral and longitudinal restraint are identical
and therefore unable to accommodate such conflicting
requirements as those specified above.
The prior art has also contemplated the use of
resilient elastomers in conjunction with the bearing
adapters of railway truck wheelsets for load cushioning or
shoch absorption. Some such prior art pertains to truchs
with so-called plane bearings. Patents of interest include
U.S. patents 149,284, 301,510, 1,222,698, 1,904,007,
2,234,413, 2,239,646, 2,842,409, 2,957,733, 3,033,617,
3,098,682, 3,222,111, 4,044,689, and 2,207,848. The above
cited patents are not generally concerned with
journal-to-side frame flexibility for the purpose of
wheelset steering.
B~IEF SUMMARY OF THE INVENTION
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The present invention contemplates a novel and
improved railway truch and bearing adapter apparatus and
method for accommodating and controlling relative motion
between the side frames and the wheelsets of a conventional
three piece railway truch. The invention provides effective
wheelset steering freedom under loaded car conditions as
well as lateral stability for empty cars at higher speeds.
The apparatus of this invention includes a journal
bearing adapter assembly having resilient elastomeric
elements which are confined between the bearing adapter and
the roof of a side frame pedestal opening. The elastomeric
elements, owing to their particular geometry which may be
regarded generally as a wedge shape in a presently preferred
embodiment of the invention, are initially vertically
deformed in compression between a rigid bearing adapter
member and the roof of the side frame pedestal opening under
the side frame weight and the weight carried thereby. The
initial or preload elastomeric deformation provides mutual
restraint, both laterally and longitudinally, between the
bearing journal adapter and the side frame pedestal jaw
thrust lugs, with sufficient lateral and longitudinal
stiffness for confinement of the bearing journals with
respect to the respective pedestal openings.
At the same time the elastic deformation of the
elastomeric elements permits sufficient longitudinal freedom
between the wheelsets and the side frame pedestals that
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wheel/rail triction can move the wheelsets to a radial
position for slip-free traching. However, sufficient motion
restraint is also available to discourage lower speed empty
car hunting. Most importantly, under larger magnitude
loading, which increases wheel/rail frictional forces, the
wheelsets can yaw independently of the side frames.
Accordingly, they can follow both tangent and curved trach
without undue flange-rail contact or higher magnitude
rail-wheel slip or creepage at the running surface of the
rail.
The invention also provides continuous compensation
capability to keep the bearing adapter-to-side frame fit-up
free of excess lateral and longitudinal freedom which would
otherwise develop as a result of progressive wear during the
service life of the bearing adapter. The invention
additionally provides for reduced wear rates in such wearing
components as the pedestal roof and the bearing adapter
assembly as well as reduced potential for bearing damage
resulting from impact loads between the pedestal jaw thrust
lugs and the bearing cup such as may result from train
action forces due to acceleration or brahing or hump yard
operations.
Z5 Accordingly, it is one object of this invention to
provide a novel and improved method and apparatus for
supporting a side frame of a railway truch with respect to a
wheelset journal bearing.
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A more specific object of the invention is to provide
a novel and improved railway truck bearing adapter including
elastomeric elements which provide optimum restraint of
wheelset-to-side frame relative motion for both empty and
loaded car operating conditions.
Another object of the invention is to provide a novel
and improved method of maintaining engagement and
controlling relative motion between the wheelsets and side
frames of a railway truch.
A more specific object of both the apparatus and
method aspects of the invention is to provide a railway
truch bearing adapter assembly with one or more resilient
elastomeric elements that are continuously maintained in a
confined and deformed relationship with respect to the
wheelset and side frame, the elastomeric elements including
portions thereof which are deformed by relative steering and
2~ truch warping motion between the wheelset and side frame and
which tend to resile from the deformed state thus providing
restraint of such relative motion.
Ihese and other objects and further advantages of the
z5 invention will be more readily understood upon consideration
of the following detailed description and the accompanying
drawings, in which:
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~ig. 1 is a side elevation, partially sectioned on
line I-I of Fig. 2, of a fragmentary portion of a railway
truck side frame assembled with a wheelset bearing journal
and a bearing adapter assembly according to one presently
preferred embodiment of the instant invention;
Fig. 2 is a sectioned top plan view tahen on line
II-II of Fig. 1;
~i9. ~ lS a generally schematic side elevation
similar to Fig. 1 and showing longitudinal wheelset movement
with respect to a side frame; and
Flg. 4 is a transverse section tahen generally at the
location of line IV-IV of Fig. 1 and showing an alternative
embodiment of the invention.
~here is generally indlcated at 10 in Fig. 1 a
bearing adapter assembly which is received within a pedestal
opening 1Z of a railway truch side frame 14. Only a
fragmentary end portion of side frame 14 is shown. The
railway truch generally may be a conventional structure
consisting of a pair of laterally spaced side frames 14 each
having pedestal openings 12 adjacent the opposed
longitudinal ends thereof, and each supporting intermediate
the longitudinal ends thereof one respective end of an
elongated bolster (not shown) which extends intermediate the
spaced side frames 14. For purposes of this description,
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the term lateral will refer to the direction of lateral
spaclng between the side frames of a truch (i.e. axially of
the wheelsets) and the term longitudinal will refer to the
direction longitudinally of the side frames.
Each pedestal opening 12 is defined by longitudinally
spaced, downwardly projecting pedestal jaw portions 16 and
18 of side frame 14, and an intervening roof portion 20 such
that a bearing journal 22 of a conventional wheelset 24 may
be received within pedestal opening 12 below roof portion
20. The bearing journal Z2 comprises a roller bearing
assembly 26 which provides a well known rotary interface
between the wheelset axle 27 (Fig. Z) and a cylindrical
bearing cup 28 which encompasses roller bearing assembly Z6.
As is woll hnown, in operation the bearing cup 28 is
non-rotatably engaged with a bearing adapter while the
wheelset 24 is axially rotatable with respect to the
rotationally stationary bearing cup and adapter.
2() For support of the side frame 14 with respect to the
wheelset Z4, bearing journal portion 22 of wheelset 24 is
received within pedestal opening 12 with the bearing adapter
assembly 10 captively retained in engagement with an upper
external surface portion 30 of bearing cup 28 and with an
adjacent downwardly facing surface portion 32 of pedestal
roof 20 which preferably may extend substantially the full
width and length of pedestal roof portion 20.
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More specifically, bearing adapter assembly 10
preferably comprises a rigid bearing adapter member 34 of
cast iron, for example, and an assembly of generally
wedge-shaped elastomeric members 36 which are received in
the assembled configuration into pedestal opening 12 as a
conventional bearing adapter would be received with
conventional longitudinally spaced thrust lugs 11 engaged
within cooperably formed slots 13 (Fig. 2) disposed at the
respective longitudinally opposed ends of the bearing
adapter assembly 10.
La~erally spaced and upwardly projecting flange or
side portions 19 of the adapter member 34 project above the
elevation of pedestal opening roof surface 32 to overlap the
opposed sides of the pedestal opening roof portion 20. The
rigid adapter member 34 also includes a downwardly facing,
generally cylindrical surface portion 38 which is
engageable with the complementary upper surface portion 30
- of bearing cup 28 for support of the bearing adapter
assembly 10 with respect to the wheelset 24.
The exterior periphery of adapter member 34 includes
an upper surface 40 which extends intermediate flanges 19
and includes a centrally located, transversely extending
z5 ridge 42 (Figs. 1 and 2) that extends generally parallel to
the rotary axis X-X of wheelset 24. Engagement surface 40
includes surface portions 44 which extend laterally with
respect to the pedestal opening in confronting relation to
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surface 3Z. Surtace portions 44 also slope downwardly in
opposed longitudinal directions from ridge 42 so as to
diverge downwardly from pedestal roof surface 32. Adjacent
the longitudinally outer end of each surface portion 44 is a
vertically downward step 46, and from the lower end of each
step 46 a further surface portion 44' slopes longitudinally
downwardly and outwardly, and then extends generally
horizontally in the longitudinally outward direction to a
point 48 adjacent respective pedestal jaw inner surfaces 51.
1~ From point 48 a further surface portion 49 of the exterior
periphery of the rigid member 34 extends generally
downwardly adjacent pedestal jaw inner surfaces 51 and is
joined with surface 38 by a lowermost, generally radiused
surface portion 39.
1~
The inner surface configuration of pedestal opening
12 may be essentially conventional as the invention is
intended preferably as a retrofit for conventional three
piece truchs. Accordingly, the various pedestal opening
2~ inner surfaces including surfaces 32 and 51 are not
described in detail here as those versed in the art will be
fully familiar with conventional pedestal opening
configurations and such detailed description thus is deemed
unnecessary. It will suffice to note that the support
surfaces of the pedestal opening 12 cooperate with the above
described exterior surface portions of adapter member 34 to
define an envelope within which the elastomeric elements 36
are received.
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Accordingly, each elastomeric element 36 comprises a
generally wedge-shaped member having diverging upper and
lower surface portions 50 and 52 which are formed so as to
be engageable with surfaces 32 and 44, respectively. Each
elastomeric element 36 is further provided with a step
portion 54 which conforms with respective step 46 and a
vertical surface portion 56 which is provided as a portion
of the throat of slot 13 to be engageable with a confronting
surface 15 of thrust lug 11 in each of pedestal jaws 16 and
18. From Figs. 2 and 4, the elastomeric elements 36 will
also be seen to includs a pair of laterally spaced apart,
upstanding flange portions 58 which are confined laterally
between the lower part of pedestal roof portion 20 (which is
upwardly adjacent to surface 32) and the respective upwardly
projecting flanges 19 of adapter member 34.
In addition, laterally spaced side column portions 59
of elastomeric members 36 extend longitudinally outward
beyond the respective surfaces 56 and are confined between
the opposed lateral sides 13 of the thrust lugs 11,
respectively, and the respective adjacent portions of the
laterally spaced adapter member flange portions 19. The
side column portions 59 also engage surfaces 44' such that
when vertical loading is applied to elastomeric elements 36,
the side column portions 59 deform laterally to laterally
confine the members 36 with respect to thrust lugs 11. The
side frame pedestal thus is elastically confined with
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respect to the wheelset bearing assembly with sufficient
elastic restraint, both initially and throughout bearing
adapter service life, to limit both lateral and longitudinal
side frame pedestal-to-bearing journal freedom.
The following further description comprises not only
structural description but in addition disclosure of the
mode of operation and the method of my invention, described
with reference to Figs. 1 through 4 inclusive. As has been
noted, the instant invention serves to control the freedom
of relative longitudinal and lateral side frame-to-bearing
journal motion thus enhancing empty car lateral stability at
higher speeds; however, the increased lateral and
longitudinal pedestal to bearing journal restraint also
accommodates loaded car wheelset steering freedom.
The disclosed elastic pedestal journal restraints
additionally improve thc roller bearing journal load
environment by offering improved symmetry of bearing
zo loading. They also preclude extreme journal impacts that
occur in conventional side frame journal assemblies which
permit free lateral and longitudinal relative motion between
rigid limits. The invention still further provides
continuous wear compensation whereas in conventional trucks,
the magnitude of impact loads becomes increasingly more
? severe as side frame to adapter lateral and longitudinal
rigid limits wear in service.
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To provlde wear compensation, the wedge-shaped
elastomeric members 36 are retained intermediate the rigid
adapter member 34 and the pedestal roof surface 32 such that
under the loading and deformation thereof in service they
tend to continuously migrate down the slope of surfaces 44
and longitudinally outward into engagement with the opposed
thrust lugs 11. Fit-up and proper confinement thus is
maintained throughout the service life of the bearing
adapter 10, and both lateral and longitudinal elastic
restraint are maintained throughout the service life of the
bearing adapter assembly.
The lnvention also provides the requisite wheelset
freedom to permit the loaded car wheelsets to steer around
trach curves or to independently seek optimum tracking
alignment on tangent trach. The weight of the car, bolster
and side frames loads surfaces 50 of the respective
elastomeric elements 36 in vertical compression. Due to the
described wedge-lihe geometry of the elastomeric elements
2~ 36, the vertical unit pressure supporting the weight of the
car between the mutually engaged pedestal roof 3Z and
surface 50 of the respective elastomeric wedges is greatest
along the thinner section portions of the elastomeric
elements 36 because of the higher unit compression strain in
the thinner elastomeric sections. Thus, the greatest
vertical unit pressure on elastomeric members 36 occurs
adjacent the central ridge 42 of the adapter member 34, and
decreases with progressively greater longitudinal distance
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irom ridge 42 with increasing section thickness of the
elements 36. As will be seen from the disclosure, this
provides an optimized resisting moment for rotation of
adapter member 34. The larger portion of the mass of
elastomer concentrated at longitudinally outer locations,
and the particular geometry of this larger mass as
described, also are effective to restrain longitudinal
translation of the wheelsets by longitudinally oriented
compressive deformation of the elastomer in regions
longitudinally and laterally adjacent to the side frame
pedestal jaw thrust lugs.
Steering loads imposed by the wheelsets 24 on the
bearing adapters 10 deform the elastomeric elements 36
differentially so that the rigid adapter member 34 can
rotate about a center point C located on line L-L (Fig. 3).
Such adapter rotation occurs in response to various force
inputs, including most notably the rail-wheel steering
forces experienced as the wheelsets 24 tend to yaw with
respect to the side frames 14 in negotiation of both tangent
and curved track above described. That is, on curved track
the wheelsets will tend to yaw independently toward their
respective true radial positions as influenced by the wheel
conics and the wheel-rail friction forces, and on tangent
track the wheelsets will yaw with respect to the side frames
as they follow the above-described sinusoidal path. Such
steering forces result in longitudinal translation or fore
and aft motion of the wheelset bearing journals with respect
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to the pedestal openings, which motion is accommodated by
rotation of the bearing adapter member 34 as shown in Fig. 3
about center C from its neutral position on a radial D
(which extends vertically from center C) to a radial E
displaced angularly from the radial D by an angle F.
The elevation of the center of rotation C along line
P-P' is determined by the relative stiffness of the
elastomeric elements 36 in longitudinal shear and in
differential compression. The lower the magnitude of shear
stiffness of the elastomer, the higher along line P-P' the
center of rotation C will fall, tending toward the behavior
of predominantly shear restrained pedestal freedom of
conventional steering truchs.
The instant invention can thus employ a higher shear
resistant material for enhanced lateral and longitudinal
journal control and resultant improved lateral empty car
stability. Additionally, rotational freedom as above
described can now also be achieved with proper elastomeric
element geometry to permit sufficient longitudinal motion of
the bearing journals within the pedestal jaw openings for
response to available loaded car steering force levels.
z~ Variations in the design of elastomeric elements 36
are contemplated to optimize the performance of adapter 10
in both loaded and empty car operation. For example, with a
given elastomeric element design and material, if the wedge
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,g
angle of the elastomeric elements is made larger than the
lncluded angle between the adapter sloping surface 44 and
the pedestal roof surface 32, the resisting moment to
rotation of the adapter member 34 about center C would be
increased. Also, due to a resulting higher vertical
elastomer unit stress near thrust lugs 11, the confinement
for lateral and longitudinal translation of member 34 in the
pedestal opening 12 would also increase.
1~ An optimal design of elastomeric elements 36 might
well include a composite member having a harder and more
durable elastomer at the pedestal roof interface and a lower
hardness elastomer comprising the remainder of the
elastomeric element 36. Such a combination would yield
improved wear resistance at the pedestal roof interface
without reducing the vertical resilience needed for loaded
car steering.
Flg. 4 illustrates a bearing adapter assembly 10'
similar in many salient respects to the assembly 10 as above
described and including pairs of laterally opposed
elastomeric elements 36', each of which has opposed,
generally horizontal lower and upper surface portions which
cooperably engage rigid adapter member 34 and a downwardly
facing engagement surface 32' of pedestal roof portion 20,
respectively. Surface 3Z' diverges laterally upward and
outward from the central vertical plane P-P of the side
frame such that the gravitational preload on members 36'
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tends to bias members 36' laterally outward while also
effecting confinement thereof by longitudinal wedging action
as above described. This bi-directional ~lateral and
longitudinal) wedging action will provide alternative modes
of confinement, restraint, and wear compensation over the
embodiment of Figs. 1-3, and thus affords opportunities to
design for optimal levels of both lateral and longitudinal
elastic restraint.
According to the description hereinabove, the instant
invention provides a novel and improved apparatus and method
for maintaining and stabilizing the relative motion between
railway truch wheelsets and the components supported
thereby, particularly as regards the wheelset steering
responses which have a tendency in conventional cars to
encourage empty car harmonic oscillations.
Of course, the above description pertains only to
certain presently preferred best mode embodiments of the
invention. I have contemplated various alternative and
modified embodiments which would also occur to others versed
in the art, once apprised of my invention. For example, the
elastomeric elements I have described may be reinforced in
various ways to modify the modes and magnitude of elastic
response and restraint provided thereby. Mechanical
reinforcement is but one of many design alternatives that
are contemplated for optimizing lateral and longitudinal
elastic restraint in the context of the invention as
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described. Accordingly, it is intended that the invention
be construed as broadly as permitted by the scope of the
claims appended hereto.
