Note: Descriptions are shown in the official language in which they were submitted.
CA 02 612 35 6 2 0 0 7 ¨11¨ 2 7
File number: 11038-090
Revision: As Filed
Date: 2007/11/27
Title of the Invention
[0001] Traction Assembly with Trail Compensating System.
Cross-Reference to Related Applications
[0002] There are no cross-related applications.
Field of the Invention
[0003] The present invention generally relates to traction assemblies used as
wheel
replacement for wheeled vehicles. More particularly, the present invention
relates to
traction assemblies used as wheel replacement for the wheels that steer
vehicles.
Background of the Invention
[0004] Nowadays, there are an ever-increasing number of people who enjoy
riding all-
terrain vehicles and other similar off-road vehicles, either in trails or even
on totally
uncharted terrain.
[0005] In order to further adapt the vehicles to the increasing variety of
terrains onto
which they are ridden, companies have started to offer traction assemblies
which can be
used to replace wheels on wheeled vehicles.
[0006] Traction assemblies generally comprise a frame, a sprocket wheel, idler
and/or
road wheels and an endless track disposed therearound. By using an endless
track instead
of a tire, a traction assembly generally provides increased floatation and
better traction to
the vehicle. However, since the ground contacting area (hereinafter "contact
patch") of
the endless track of the traction assembly is generally significantly larger
than the contact
patch of a regular tire, and since the steering and suspension systems of the
vehicle were
initially designed and configured to accommodate wheels and not traction
assemblies,
- 1 -
CA 02612356 2014-03-18
File number 11038-090
steering and other driving characteristics of the traction assembly-equipped
vehicle are
generally affected, sometimes even negatively.
[0007] Indeed, it has been discovered that when the steerable wheels of
certain all-terrain
vehicles are replaced by traction assemblies, the steering of these vehicles
was negatively
affected by the fact that the trail of each traction assembly varied in
opposite direction
during steering manoeuvres. As it is known in the art, the trail of a traction
assembly (or
a wheel) generally affects the stability of the vehicle. Hence, during
steering of these
vehicles, as the trail of one traction assembly diminishes, the trail of the
other traction
assembly increases, thereby rendering the vehicle particularly unstable in
curves.
[0008] Hence, there is a need for a novel traction assembly which improves
riding
condition when traction assemblies are used to replace existing steerable
wheels on
vehicles.
Objects of the Invention
[0009] Accordingly, a main aspect of the present invention is to provide a
traction
assembly having a trail compensating system adapted to compensate for
variations in the
trail of the traction assembly when the latter is pivoted during steering
manoeuvres.
[0010] Other and further objects and advantages of the present invention will
be obvious
upon an understanding of the illustrative embodiments about to be described or
will be
indicated in the appended claims, and various advantages not referred to
herein will occur
to one skilled in the art upon employment of the invention in practice.
Summary of the Invention
[0011] The aforesaid and other objectives of the present invention are
realized by
generally providing an improved traction assembly particularly adapted to
replace the
front or steerable wheels of a wheeled vehicle.
- 2 -
CA 02612356 2014-03-18
File number 11038-090
[0012] The object of the present invention involves a traction assembly that
can
preferably replace a wheel on wheeled vehicle. The traction assembly thus
involves a
vehicle with a frame and at least one traction axle. Preferably, the traction
assembly can
replace steerable wheels on either side of the front portion of the vehicle.
[0013] More particularly, the traction assembly comprises a sprocket wheel and
a
longitudinally extending traction band cooperating therewith. The sprocket
wheel is
preferably fixedly attached by means known in the art to the traction axle (or
the wheel
hub) of the vehicle. The traction assembly also comprises a support structure
or frame,
preferably, but not exclusively in the form of a slider bar on which idler
wheels are
preferably mounted. These idlers wheels are preferably mounted at the
extremities of the
support structure. A plurality of road wheels can also be mounted on either
side and along
the support structure to increase the stability of the traction band.
[0014] In accordance with the invention, the traction assembly further
comprises a trail
compensating system which generally prevents the trail of the traction
assemblies to
either increase or diminish when the traction assemblies are steered.
[0015] As used hereinabove and hereinafter, the term "trail" generally refers
to the
horizontal distance, measured along the ground, between the geometrical center
of the
contact patch of the traction assembly (or of the wheel) and the intersection
point
between the projection of the steering rotation axis and the ground when
viewed from the
side. The concept of "trail", which is generally known in the mechanical art,
is also
known to have material effect on the steering and handling of a vehicle.
[0016] Hence, the trail compensating system is generally comprised of an
elongated
member or mechanism which is pivotally mounted, at its first end, generally,
but not
exclusively, to the front portion of the traction assembly, and at its second
end, to the
vehicle at a point which is, contrary to the prior art, preferably located
longitudinally
behind the steering axis.
- 3 -
CA 02612356 2007-11-27
File number: 11038-090
Revision: As Filed
Date: 2007/11/27
[0017] The features of the present invention which are believed to be novel
are set forth
with particularity in the appended claims.
Brief Description of the Drawings
[0018] The above and other objects, features and advantages of the invention
will
become more readily apparent from the following description, reference being
made to
the accompanying drawings in which:
[0019] Figure 1 is an internal side view of a traction assembly.
[0020] Figure 2 is an internal side view of a traction assembly, without the
trail
compensating system, during a right turn.
[0021] Figure 3 is an internal side view of a traction assembly, without the
trail
compensating system, during a left turn.
[0022] Figure 4 is a side view of a traction assembly, with the trail
compensating system
according to the invention, as installed on the front right wheel hub of a
vehicle.
[0023] Figure 5 is an internal side view of a traction assembly, schematically
with the
trail compensating system, during a right turn.
[0024] Figure 6 is an internal side view of a traction assembly, schematically
with the
trail compensating system, during a left turn.
Detailed Description of the Preferred Embodiment
[0025] A novel traction assembly with a trail compensating system will be
described
hereinafter. Although the invention is described in terms of specific
illustrative
embodiments, it is to be understood that the embodiments described herein are
by way of
example only and that the scope of the invention is not intended to be limited
thereby.
[0026] Referring first to Fig. 1, a traction assembly 100, in accordance with
the present
invention, generally comprises a sprocket wheel 110 fixedly mounted to the
wheel hub or
axle which is operationally connected to the suspension and steering system 20
of the
vehicle. The traction assembly 100 also comprises a frame structure 120 to
which idler
-4-
CA 02612356 2014-03-18
File number 11038-090
wheels 130 and road wheels 140 are pivotally mounted. Finally, disposed around
the
sprocket wheel 110, the idler wheels 130 and the road wheels 140 is a
longitudinally
extending endless track 150 preferably made of elastomeric material.
[0027] Generally, traction assemblies 100 can be used to replace wheels on
wheeled
vehicles in order to provide improved floatation and traction. However, since
the
vehicles onto which traction assemblies 100 are generally installed were
initially
designed to use wheels for propulsion and for steering, the suspension and
steering
systems 20 of these vehicles were designed accordingly. Hence, to provide
certain
driving and steering characteristics to the vehicle 10, the steering axes 21
of wheeled
vehicles are generally at an angle. The angle is generally determined to
generate a certain
trail for the wheels. Also, due to the overall symmetry of the circular
wheels, the rotation
of the wheels around the angled steering axes generally does not affect the
trail of the
wheels.
[0028] However, when the front and/or steerable wheels of a wheeled vehicle
are
replaced by traction assemblies 100, the suspension and steering systems 20 of
the
vehicle are generally not modified to particularly accommodate the traction
assemblies
100. Hence, when a formerly wheeled vehicle 10 equipped with traction
assemblies 100
is steered, the traction assemblies 100 pivot around the steering axis 21 of
the suspension
and steering system 20 of the vehicle 10. However, contrary to a wheel which
is
essentially symmetric, a traction assembly is not symmetric. This difference
generally
affects the steering behaviour of the vehicle.
[0029] Referring now to Fig. 2, when, for example, a prior art front right
traction
assembly 100 is steered to the right, thus away from the vehicle, the traction
assembly
100 pivots around the steering axis 21, as would a regular wheel. However,
since the
steering axis 21 is angled and since the traction assembly 100 is not
symmetric, the front
portion of the traction assembly 100 rises, displacing at the same time the
contact patch
170' toward the rear of the traction assembly 100 and thereby altering the
trail of the
traction assembly 100.
- 5 -
CA 02 612 35 6 2 0 0 7 ¨11¨ 2 7
File number: 11038-090
Revision: As Filed
Date: 2007/11/27
[0030] On the contrary, referring now to Fig. 3, when, for example, a prior
art front right
traction assembly 100 is steered to the left, thus toward the vehicle, the
traction assembly
pivots around the steering axis 21. However, in this case, instead of rising,
the front
portion of the traction assembly 100 descends, displacing at the same time the
contact
patch 170" toward the front of the traction assembly 100 and thereby altering
the trail of
the traction assembly 100.
[0031] As the skilled addressee would understand, when a vehicle is steered,
for
example, to the right, the front right traction assembly 100 will behave as
the traction
assembly 100 shown in Fig. 2 since the traction assembly will be pivoted away
from the
vehicle. However, the front left traction assembly 100 will behave as the
traction
assembly 100 shown in Fig. 3, since the traction assembly 100 will be pivoted
toward the
vehicle. Consequently, as the front portion of the right traction assembly 100
will rise,
the front portion of the left traction assembly 100 will descend.
[0032] By varying the trail of each traction assembly 100 is opposite
direction, steering
behaviour of the vehicle will be negatively affected. Moreover, when the
phenomenon
described above is combined with the weight transfer due to centrifugal forces
that
naturally occurs when a vehicle engages a curve, the resulting steering
behaviour of the
vehicle can be fatally affected.
[0033] Referring now to Fig. 4, in order to generally compensate for the
variations in the
trail of the traction assemblies 100 during steering manoeuvres, the traction
assembly 100
is shown equipped with the trail compensating system 160. In the present
preferred
embodiment, the trail compensating system also serves as an anti-rotation
system.
Accordingly, as shown in Fig. 4, the trail compensating system 160 can be an
elongated
mechanism which can be resiliently compressed or extended in order to absorb
rotational
movements of the traction assembly 100 around the axis of rotation of the
traction axle of
the vehicle 10. Still, the trail compensating system 160 could alternatively
be an
elongated member. The present invention is not so limited.
- 6 -
CA 02 612 35 6 2 0 0 7 ¨11¨ 2 7
File number 11038-090
Revision: As Filed
Date: 2007/11/27
[0034] As shown in Fig. 4, the trail compensating system 160 is generally an
elongated
structure (e.g. a member or a mechanism) which is pivotally connected, at its
first end,
generally to a point 161 on the front portion of the traction assembly 100,
and at its
second end, to a pivot point 163, located on the suspension and steering
system 20, which
is longitudinally displaced with respect to the point 162 which is aligned
with the steering
axis 21.
[0035] By so connecting the front portion of the traction assembly 100 to a
pivot point
163 longitudinally displaced generally behind the point 162, a trail
compensating effect
occurs and the position of the contact patch 170 of both the front right and
front left
traction assemblies 100 remain essentially unchanged when the vehicle 10 is
steered,
thereby maintaining the trail of the front right and front left traction
assemblies 100.
[0036] For example, as shown in Fig. 5, when the front right traction assembly
100
equipped with a trail compensating system 160 (not shown for clarity) is
steered to the
right, the front portion of the traction assembly 100 does not rise and
therefore the
position of the contact patch 170 and the trail of the traction assembly 100
remains
essentially unchanged.
[0037] Similarly, as shown in Fig. 6, when the front right traction assembly
100 equipped
with a trail compensating system 160 (not shown for clarity) is steered to the
left, the
front portion of the traction assembly 100 does not descend and therefore the
position of
the contact patch 170 and the trail of the traction assembly 100 remains also
essentially
unchanged.
[0038] Hence, by generally preventing displacements of the contact patch 170
of each
traction assembly 100 during steering manoeuvres, the trail of each traction
assembly 100
remains essentially unchanged and the driving and steering behaviour of the
vehicle are
not negatively affected.
- 7 -
CA 02612356 2007-11-27
File number: 11038-090
Revision: As Filed
Date: 2007/11/27
[0039] Understandably, the skilled addressee shall understand that the trail
compensating
system 160 is efficient essentially only flat surfaces. Indeed, the trail
compensating
system 160 generally does not prevent displacements of the contact patch 170
of a
traction assembly 100 when the latter is on uneven surfaces or when the whole
traction
assembly 100 pivots around the rotation axis of the axle.
[0040] Furthermore, it is to be understood that the position of the point 161
on the front
portion of the traction assembly 100 and the position of the pivot point 163
on the
suspension and steering system 20 shown in the figures are given for example
purpose
only. As the skilled addressee would understand, the exact position of the
point 161 on
the traction assembly 100 and the exact position of the pivot point 163 on the
suspension
and steering system 20 can vary according to the particular configuration or
geometry of
the traction assembly 100 and to the particular configuration or geometry
(e.g. steering
axis inclination) of the suspension and steering system 20. For example, in a
different
embodiment, the point 161 could be located on the rear portion of the traction
assembly
100 whereas the point 163 would correspondingly be located in front of the
steering axis
21. The present invention is not so limited.
[0041] While illustrative and presently preferred embodiments of the invention
have been
described in detail hereinabove, it is to be understood that the inventive
concepts may be
otherwise variously embodied and employed and that the appended claims are
intended to
be construed to include such variations except insofar as limited by the prior
art.
- 8 -
