Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to railway vehic~es having
trucks which are equipped with wheelsets which are pivotally
mounted to the truck. The wheelsets are guided to a radial
alignment during travel of the railway vehicle along
circular curved track.
Railway trucks having steerable axles to achieve
radial alignment are well-known in the art. Various mechan-
isms have been provided to steer the axles to a radial
alignment.
In some trucks equipped for radial alignment of the
wheelsets each wheelset is mounted in a steering yoke. The
yokes are interconnected. Typically these mechanisms make
use of the yaw motion of the car body relative to the truck
centre line to create the steering motions. In such trucks,
forces are created in a lateral direction on the outboard
yoke and reacted through a reference link and lateral link
to the truck side frame. In experience it has been found
that the mechanical advantage of this system demanded the
production of relatively large forces in order to generate
the required steering motions and maintain them against the
influences of wheel/rail forces, particularly those acting
at the flange of the wheels when flange rail contact occurs
and also the oscillatory forces generated during hunting.
The stiffness, which can be designed into these type of
components making up the mechanical linkage, is usually such
that steering accuracy is inadequate and stability against
hunting oscillations is unsatisfactory.
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A new linkage has been developed to overcome these
deficiencies. According to the new linkage steering motions
are created without utilization of the truck frame for any
pivotal connections.
The steering mechanism of this invention may be
mounted on an existing truck having axles mounted in inter-
connected yokes. The mechanism is offset laterally from the
centre line of the truck. It is advantageous to offset the
mechanism as far as practical.
According to the invention there is provided a
steering mechanism for use on a railway vehicle having a car
body mounted on at least two trucks. At least one of the
trucks has inboard and outboard wheelsets, each of the
wheelsets being mounted in a yoke. The inboard and outboard
yokes are pivotally interconnected. Each of the wheelsets is
affixed to the truck in such a manner as to be adapted for
relative pivotal movement with respect to the truc]c about a
general vertical axis. The mechanism further includes a
steering mechanism for guiding the wheelsets to a radial
alignment when the vehicle is travelling on circular curved
track. The mechanism comprises a steering link connected to
the car body and a steering lever which is pivotally
connected to the steering link. A linkage mechanism inter-
connects the steering lever and the inboard and outboard
yokes whereby relative longitudinal movement of the car
body/steering link connection point with respect to the
truck when moving from tangent track to circular track
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causes relative and opposite pivotal movement of the inboard
and outboard yokes whereby the wheelsets assume a radial
configuration when on curved track.
A more complete understanding of the invention may
be had by reference to the attached drawings and description
which illustrate preferred embodiments of the invention and
in which:
Figure 1 illustrates in side view, a truck
incorporating a preferred embodiment of the steering
mechanism of this invention.
Figure 2 illustrates, in plan view, the truck of
Figure 1 with the steering mechanism of this invention in
the position for negotiating tangent track.
Figure 3 illustrates, in plan view, the truck of
Figure 1 with the steering mechanism of this invention in
the position for negotiating curved track.
When a railroad vehicle moves from tangent track to
circular curved track there is relative rotation between the
car body and the trucks supporting the car body typically at
either end of the railroad vehicle. In view of the relative
rotation of the truck and car body, a point remote from the
centre line of the car body will appear to move in the long-
itudinal direction with reference to the truck as well as
having slight motion in the lateral direction. The longitud-
inal component of such motion is directly related to the
radius of curvature and is used in this invention as the
steering input to guide the wheelsets to a radial configura-
tion.
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Generally speaking, the mechanism may be mounted on
typical wheelset yokes and is offset laterally from the
centre line of the truck as far as practical. A bracket may
be attached to the outboard yoke which bracket carries the
lower pivot for a vertical steering lever which is thereby
connected to it. At a point on the steering lever, inter-
mediate between its upper and lower ends, a steering rod is
connected to the bracket by means of a pivotal connection
and this steering rod is similarly attached to the inboard
yoke through a bracket carrying a pivot connection. The top
of the steering lever is connected to a longitudinal
steering link through a pivot connection and the other end
of that link is connected to the car body.
As t:he car l~ody swivel3 relative to the truck the
steering link is moved fore and aft relative to points on
the truck, thus pivoting the steering lever and forcing the
yokes apart or together. Because the yokes are pinned
together at the centre of the truck, the action of the
steering mechanism is to cause the wheelset/yoke assemblies
to rotate relative to one another into a steered alignment.
Correct proportioning of the lever ratio ensures that true
radial alignment is achieved on circular curves.
Figure 1 illustrates a truck generally at 10 having
a steering mechanism according to this invention installed
thereon. The truck comprises an outboard wheelset 12 and an
inboard wheelset 14. Each wheelset, as will be understood by
those familiar with railroad art, comprises an axle and a
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pair of flanged conical wheels fixed thereto such that the
axle and wheels turn at the same radial speed. Such conical
wheelsets if permitted appropriate freedom will move to a
radial configuration when travelling on curved tracks.
However, as also well understood by t:hose familiar with this
art, such single wheelsets are unstable and will continue to
hunt when travelling on either tangent track or on curved
track.
In the truck 10 as illustrated in Figure 1 the
wheelsets are mounted in yokes. The outboard yoke is
indicated at 16 and the inboard yoke at 18. The truck frame
is indicated generally at 20.
A bracket 30 is attached to outboard yoke 16. The
bracket 30 comprises a pivotal connection 32 at a convenient
portion of the bracket. A substantially vertical steering
lever 34 is pivotally connected to bracket 30 at pivotal
connection 32. The steering lever 34 has a pivotal connect-
ion 36 at its upper end. A steering link 40 is pivotally
connected to steering lever 34 at the pivotal connection 36.
The steering link 40 is attached to the car body, which is
not illustrated, at connection 42.
The bracket 30, steering lever 34 and steering link
40 are all located laterally as remote as possible from the
centre line of the vehicle. The location of the steering
mechanism is dictated by the configuration of the truck
frame, the yokes and the configuration of bracket 30. The
advantage of having the mechanism remote as far as possible
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from the centre line is that larger motions are available
for more accurate steering inputs.
The steering lever 34 has a pivotal connection 44
which is intermediate the pivotal connections 32 and 36. A
steering rod 46 is pivotally connected to the steering lever
34 at pivotal connection 44. The steering rod 46 is pivot-
ally connected to a bracket 48 at pivotal connection 50.
~racket 48 is affixed to the inboard steering yoke 18.
The outboard steering yoke 16 and the inboard
steering yoke 18 are pivotally connected to each other at
17 for relative pivotal movement.
With respect to the Figure it may be appreciated
that the connection 42 will move longitudinally as the truck
pivots with respect to the car body. Assuming that the
connection 42 moves to the left in the Figure, the steering
lever 34 will be caused to pivot about the pivotal connect-
ion 32. This in turn causes the steering rod 46 to be drawn
to the left with respect to the pivotal connection 32. Thus,
on this side of the truck the two wheels illustrated of
wheelsets 12 and 14 respectively will be moved towards each
other and thus accomplish a turn with the centre of
curvature in front of the sheet. Similarly movement in the
other direction will cause the wheels illustrated in the
drawing to move further apart accomplishing a turn in the
direction with the radius of curvature behind the sheet.
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It will be obvious to those skilled in the art that
the mechanism may be duplicated on either side of the truck
to provide a redundant steering mechanism.
Various other modifications and changes will occur
to those skilled in the art without departing from the scope
of the invention as defined in the attached claims.
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