Note: Descriptions are shown in the official language in which they were submitted.
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SAFETY WHEEL ASSEMBLY FOR A GUIDED VEHICLE
FIELD OF THE INVENTION
[0001]
The present invention generally relates to the field of run-flat safety
devices for tires used on guided vehicles such as a monorail. More
specifically,
the invention relates to a guide wheel assembly having a safety wheel
positioned
outside the guide wheel where the safety wheel may spin independently from the
guide wheel.
BACKGROUND OF THE INVENTION
[0002]
Punctured, deflated and flat tires have been around for as long as
tires have existed. Flat tires are still a problem today. Whereas a flat tire
may
sometimes simply represent an annoyance, in some other cases, a flat tire may
represent a real threat. To cope with the dangers and annoyances of a flat
tire,
many concepts have been suggested. Some of these concepts use a solid or
somewhat deformable safety wheel placed inside the tire. However, changing the
tire in such an assembly is more cumbersome than when there is no safety
wheel inside the tire. Exterior safety wheels, bolted to the wheel have also
been
suggested. However, this solution still suffers from being somewhat intricate
when it comes time to change a damaged or worn tire, which first requires
disassembling the safety wheel. Moreover, this solution is prone to skidding a
deflated or flat tire and safety wheel on their respective rolling surfaces
since the
tire does not have the same circumference as the smaller safety wheel.
[0003]
There is therefore a need for an improved guide wheel and safety
wheel assembly.
SUMMARY OF THE INVENTION
[0004]
It is an object of the present invention to provide a guide wheel
assembly for a guided vehicle such as a monorail that overcomes or mitigates
one or more disadvantages of known guide wheel assemblies, or at least
provides a useful alternative.
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[0005] The invention provides the advantages of making it possible to
change a damaged or worn tire without having to disassemble the safety wheel.
Moreover, the invention prevents skidding a deflated tire or safety wheel on
the
tire's or safety wheel's respective running surfaces, thereby preventing
further
degrading the tire's or the safety wheel's condition as well as preventing
degrading the running surface on which the tire and safety wheel roll.
[0006] In accordance with an embodiment of the present invention, there
is provided a guide wheel assembly for a bogie of a guided vehicle such as a
monorail vehicle where the monorail vehicle is operative to run on a guide
beam.
The bogie has at least two vertical guide wheel spindles adapted to be located
on
a different side of the guide beam. The guide wheel assembly comprises a hub,
a
guide wheel, a tire and a safety wheel. The hub has a guide wheel mounting
interface and a safety wheel mounting interface spaced apart along its length.
The hub is adapted to be rotatably mounted on one of the guide wheel spindles
of the bogie. The guide wheel is mounted to the hub at the guide wheel
mounting
interface. The tire is mounted on the guide wheel. The safety wheel is
rotatably
mounted on the hub at the safety wheel mounting interface. The safety wheel
spins on a safety wheel bearing, such as a plain bearing, placed between the
safety wheel and the hub. The safety wheel has a smaller circumference than a
circumference of the tire. So in case the tire deflates, the safety wheel is
operative to roll on the beam at a different radial speed than the tire.
[0007] Optionally, the guide wheel may be removably mounted on the hub
and the safety wheel may have a conical web to better clear the tire.
[0008] In accordance with another embodiment of the present invention,
there is provided a bogie for guiding a guided vehicle such as a monorail
vehicle
on a guide beam. The bogie comprises a bogie frame, a load wheel, at least two
guide wheel spindles and corresponding at least two guide wheel assemblies.
The load wheel is attached to the bogie frame and supports the monorail
vehicle
on the guide beam. Each one of the at least two guide wheel spindles extends
vertically downwardly on a different side of the bogie frame. Each guide wheel
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assembly, being mounted to a different guide wheel spindle, is adapted to
contact a different side of the guide beam when in use. Each one of the guide
wheel assemblies comprises a hub, a guide wheel, a tire and a safety wheel.
The
hub has a guide wheel mounting interface and a safety wheel mounting interface
spaced apart along the length of the hub. The guide wheel assemblies are
rotatably mounted to their respective guide wheel spindle through their
respective
hub. The guide wheel is attached to the hub at the guide wheel mounting
interface. The tire is mounted on the guide wheel. The safety wheel is
rotatably
mounted on the hub at the safety wheel mounting interface. The safety wheel
spins on a safety wheel bearing, such as a plain bearing, placed between the
safety wheel and the hub. The safety wheel has a smaller circumference than
that of the tire. Advantageously, if the tire deflates, the safety wheel is
operative
to roll on the side of the beam at a different rotational speed than that of
the tire.
[0009] Optionally, the guide wheel may be removably mounted on the hub
proximate a free extremity of the guide wheel spindle. The safety wheel may
have a conical web. Advantageously the safety wheel may be mounted on the
hub adjacent and in close proximity a spindle mounting interface where the
spindle is connected to the bogie frame.
[0010] In yet another embodiment of the present invention, there is
provided a monorail vehicle adapted to travel on a guide beam. The monorail
vehicle comprises a chassis and two bogies as already described. Each one of
the two bogies are connected to the chassis proximate a different extremity of
the
chassis.
BRIEF DESCRIPTION OF DRAWINGS
[0011] These and other features of the present invention will become more
apparent from the following description in which reference is made to the
appended drawings wherein:
[0012] Figure 1 is a side view of a monorail vehicle on a guide beam
showing a carbody in phantom lines in accordance with an embodiment of the
present invention;
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[0013] Figure 2 is an isometric view of one bogie of the
monorail vehicle of
Figure 1 shown on the guide beam;
[0014] Figure 3 is a top view of the bogie of Figure 2;
[0015] Figure 4 is a side view of the bogie of Figure 2;
[0016] Figure 5 is a cross-sectional front view of a guide
wheel assembly
of the bogie of Figure 2 mounted on a guide wheel spindle.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present invention relates to a guide wheel
assembly for a
guided vehicle such as a monorail vehicle, a bogie for a monorail vehicle
using
such guide wheel assembly and a monorail vehicle using such a bogie.
[0018] Figure 1 is now referred to. A monorail vehicle 10
sits on a guide
beam 12. The monorail vehicle 10 comprises a chassis 14 and two bogies 16.
The bogies 16 are connected to the chassis 14 at its front and rear
extremities to
support and guide the monorail vehicle 10 on the guide beam 12.
[0019] Figures 2 and 3 are now concurrently referred to. Each
bogie 16
comprises a bogie frame 18, a load wheel 20 and at least two guide wheel
assemblies 24. The load wheel 20 supports the monorail vehicle 10 on the guide
beam 12 through the bogie frame 18. The bogie 16 of the present embodiment
uses six guide wheel assemblies 24, which are used to keep the load wheel 20
centered on and aligned with the guide beam 12. The two lower guide wheel
assemblies 25 are also known as stabilizing wheel assemblies since their role
is
also to stabilize the roll of the monorail vehicle 10. Structurally, they are
however
identical to the other guide wheel assemblies 24.
[0020] Figure 4 is now concurrently referred to. To locate
each guide
wheel assembly 24, the bogie 16 is equipped with at least two (six in the case
depicted in the present embodiment) corresponding guide wheel spindles 22.
Figure 4 shows one such guide wheel spindle 22 where the guide wheel
assembly 24 has been removed for clarity. Each one of the guide wheel spindles
22 extends vertically downwardly on both sides of the bogie frame 18. Each
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guide wheel assembly 24, being mounted to a different spindle 22, is adapted
to
contact one of the sides of the guide beam 12.
[0021] Figure 5 is now concurrently referred to. Each one of the guide
wheel assemblies 24 comprises a hub 26, a guide wheel 28, a tire 30 mounted
on the guide wheel 28 and a safety wheel 32 co-axially rotatably mounted to
the
hub 26 and co-axially aligned with the guide wheel 28.
[0022] Each guide wheel assembly 24 is rotatably mounted to its
respective spindle 22 through its respective hub 26, which spins on the
spindle
22 through hub bearings 44. The hub 26 has a guide wheel mounting interface
34 and a safety wheel mounting interface 36 which are spaced apart along the
length (along the longitudinal axis) of the hub 26. The guide wheel mounting
interface 34 may be a conventional wheel mounting interface such as a flange
38
which may use press-fitted studs 40. In conventional fashion, corresponding
holes in the guide wheel 28 may be aligned with the studs 40 so that the guide
wheel 28 may be solidly mounted against the flange 38 of the guide wheel
mounting interface 34 using nuts 42.
[0023] Advantageously, the guide wheel 28 may be removably mounted
on the hub 36 proximate a free extremity 46 of the spindle 22. The free
extremity
46 is understood to be the extremity of the spindle 22 that is not held in the
bogie
frame 18. In case of damage to the guide wheel 28 or to the tire 30, or simply
in
case a worn tire 30 needs replacing, having the guide wheel 28 mounted
proximate the free extremity 46 of the spindle 22 allows an easy disassembly
of
the guide wheel 28 without having to remove the safety wheel 32 from the hub
26. Hence, it is conveniently possible to remove the guide wheel 28 and its
tire
from the hub 26, change the tire 30 much like an automobile tire is changed,
and
reinstall the guide wheel 28 back on the hub 26. It is therefore simpler and
faster
to change the tire 30. The safety wheel 32 may be mounted on the hub 26
adjacent and in close proximity to a spindle mounting interface 47 where the
spindle 22 is mounted to the bogie frame.
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[0024] The safety wheel 32 is rotatably mounted on the hub 26 at the
safety wheel mounting interface 36 through the safety wheel bearing 48. The
safety wheel bearing 48 may be any type of bearing device such as a ball
bearing, roller bearing, sleeve, or simply a coating such as a Teflon
coating. By
mounting the safety wheel 32 independently from the guide wheel 28 and by
allowing the safety wheel 32 to spin independently on the hub 26, it is
possible to
allow some differential rotational speed between the hub 26 and the safety
wheel
32, and therefore between the safety wheel 32 and the guide wheel 28 which
spins with the hub 26. This differential rotational speed between the safety
wheel
32 and the guide wheel 28 is required because the safety wheel 32 has a
smaller
radius, and therefore a smaller circumference, than a working radius, and
therefore a circumference, of the tire 30. Indeed, when adequately inflated
but
unloaded, the tire 30 has a tire radius and a tire circumference. When
adequately
inflated and under load, the tire has an effective working radius which is
smaller
than its unloaded radius. Hence, to prevent unduly contact with the side of
the
guide beam 16 when the monorail vehicle 10 is in operation, the safety wheel
32
has to have a smaller diameter than the working diameter of the tire 30.
[0025] Advantageously, should the tire 30 deflate or become flat, or if
an
unusual large load compresses the tire 30 sufficiently (such as in the case of
higher speeds in a curve or switch or in the case of large lateral winds), the
safety wheel 32 is operative to contact and roll on the side of the beam in
parallel
with the tire 30 and to keep on guiding and/or stabilizing the monorail
vehicle 10
and/or preventing the tire from being overloaded. Because the circumference of
the tire 30 remains the same, whether inflated or flat, and because the tire
still
rolls on the side of the guide beam 16 even when deflated, the rotational
speed
of the tire 30 is lower than the rotational speed of the safety wheel 32. This
differential rotational speed between the safety wheel 32 and the tire 30
therefore
allows a non-skidding simultaneous contact of both the safety wheel 32 and the
tire 30 with the side of the guide beam 16 when the tire 30 is deflated or
flat and
the safety wheel 32 contacts the side of the guide beam 16. Advantageously,
because the safety wheel 32 is rotatably mounted on the hub 26, which itself
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spins on hub bearings 44 over the spindle 22, the safety wheel bearing 48
never
acquires a large rotational speed, but rather simply spins at the differential
rotational speed between the tire 30 and the safety wheel 32. This low
differential
rotational speed allows using cheaper bearings, such as plain bearings, and
advantageously may allow a longer life.
[0026] The safety wheel may have a web 50 which may be either flat,
conical as depicted in Figure 4, or have a curvilinear shape. In any case, it
is
preferable that the web 50 clears the shape of a flat tire 30 in order to
prevent
rubbing against it and degrading a side wall of the tire 30. The conical or
curvilinear web 50 allows having a shorter hub 26 while still clearing the
tire 30.
[0027] The present invention has been described with regard to preferred
embodiments. The description as much as the drawings were intended to help
the understanding of the invention, rather than to limit its scope. It will be
apparent to one skilled in the art that various modifications may be made to
the
invention without departing from the scope of the invention as described
herein,
and such modifications are intended to be covered by the present description.
The invention is defined by the claims that follow.
