Note: Descriptions are shown in the official language in which they were submitted.
WHEELED VEHICLE HAVING RETRACTABLE DRIVEN TRACKS
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to United States Provisional Patent
Application No. 63/002,831
filed on March 31, 2020 and to Canadian Patent Application No. 3,077,569 filed
on March 31,
2020, both entitled "Wheeled Vehicle Having Retractable Driven Tracks", the
entirety of which
are incorporated herein by reference.
TECHNICAL FIELD
This invention relates generally to wheeled vehicles and in particular to a
retractable driven
track system which is mountable under such vehicles for use in snow or other
soft-terrain
conditions.
BACKGROUND
It is known to employ endless tracks on either side of a land vehicle, such as
a conventional
military tank, for increased traction as compared to wheels having resilient
tires when used on
soft terrain such as mud and snow. However, tracked vehicles have drawbacks
such as
damaging the terrain under the tracks when the vehicle is turning for example,
thus rendering
tracked vehicles generally unsuitable for use on conventional paved roads.
The published application by Gibbs Technologies Limited under Publication No.
WO
2007/141515, which published December 13, 2007, discloses an amphibious
vehicle having a
bow, a stern and land propulsion which may include at least two retractable
tracked drives.
The tracks are retractable above the water line for marine travel. The tracks
may be full length
dual tracks or half tracks. Wheels may be provided for land travel, and may be
retractable. The
tracks may retract vertically, or by rotation about a longitudinal axis.
Hydraulic rams used to
retract the land propulsion may also provide vehicle suspension.
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SUMMARY
The present invention is a retractable driven track system for urging motion
of a wheeled
vehicle driven over soft terrain. As disclosed herein, in one embodiment, not
intended to be
limiting, the system includes a frame, a flexible endless track mounted on the
frame for
rotation of the endless track along an underside of the wheeled vehicle, and a
pivotable linkage
coupled at a lower end thereof to the frame, and adapted for coupling at an
upper end thereof
to the underside of the wheeled vehicle. A selectively actuable actuator,
adapted to cooperate
between the underside of the wheeled vehicle and one of the frame or the
linkage, is provided
to selectively lower and raise the frame and the endless track relative to the
underside of the
wheeled vehicle. This allows the track to be selectively engaged and
disengaged, respectively,
with the soft terrain. A drive is also provided, cooperating with, for
selectively driven rotation
of, the endless track relative to the frame to urge at least forward motion of
the vehicle when
the track is driven by the drive and the track is engaged with the soft
terrain.
In a preferred embodiment the linkage includes at least one scissor linkage.
The selectively
actuable actuator, when actuated, expands or contracts, or put another way,
extends or
retracts, the scissor linkage so as to correspondingly lower and raise the
frame. In the
illustrated embodiment, the actuator is a pneumatically driven cylinder so
that extension of the
actuator causes the scissor linkage to extend, and retraction of the actuator
causes the scissor
linkage to retract. Again, this is not intended to be limiting as other
actuators would also work
as would be known to one skilled in the art.
As seen in the illustrations, which show a track on a selectively elevatable
frame on both sides
of a vehicle, the system in one aspect includes a pair of frames and
corresponding tracks,
linkages, actuators and drives mountable on opposite sides of the vehicle so
as to be laterally
spaced apart across the underside of the vehicle, wherein each of the tracks,
when so mounted,
extends longitudinally along the underside of the vehicle.
In the illustrated embodiment, again not intended to be limiting, the vehicle
is a four wheeled
vehicle having a single wheel in each of the four corners of the vehicle so as
to define a
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longitudinally extending wheelbase between front and rear wheels on each side
of the vehicle.
The pair of linkages, actuators, frames and tracks are mounted along the
wheelbase on each
side of the vehicle between corresponding front and rear wheels of the vehicle
so that, when
lowered to engage the soft terrain, the left-side track is between and aligned
with the front and
.. rear wheels on the left side of the vehicle, and the right-side track is
between and aligned with
the front and rear wheels on the right side of the vehicle. Thus the linkages,
actuators, frames
and tracks may be characterized as being mounted substantially flush along
each corresponding
side of the vehicle, and further may be mounted centrally, relative to the
longitudinal
wheelbase dimension, between the front and rear wheels on each side of the
vehicle.
.. In other embodiments, the track, frame, linkage and actuator pair may be
laterally inset from
the sides of the vehicle, or may be a single track, frame, linkage and
actuator system aligned
longitudinally along the longitudinally extending centerline of the vehicle.
In yet other
embodiments, the vehicle may be a two wheeled trailer, and the linkage, the
actuator, the
frame and the track are mounted centrally under the trailer, for example
either centrally along
the length of the trailer, or centrally in the sense of being on the
longitudinally extending
centerline of the trailer, or both.
In the illustrated embodiments, in a first embodiment the scissor linkage is a
single scissor
linkage mounted at a first end of the frame, and further comprising at least
one cross member,
and preferably two cross members, pivotally mounted, at lower ends thereof, at
a second end
of the frame opposite the first end, and wherein upper ends of the cross
members are adapted
to pivotally mount to the underside of the vehicle above the first end of the
frame, whereby the
frame is selectively vertically translatable at both the first and second ends
of the frame by
corresponding first and second actuators, wherein the second actuator is
coupled to the second
end of the frame, and adapted for mounting to the underside of the vehicle for
the selective
vertical translation of the second end of the frame.
In a second exemplary embodiment, not intended to be limiting, instead of
using at least one
cross member, a pair of the scissor linkages and corresponding first and
second actuators are
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coupled to opposite ends of the frame and adapted for mounting to the
underside of the
vehicle.
Although the present system has been described above as being a system which
is ready, or
adapted for, mounting to the underside of the vehicle, it is intended to be
within the scope of
the present disclosure to include the vehicle per se as part of the system in
further
embodiments of the system.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is, in rear perspective right-side partially cut-away view, a four
wheeled vehicle having
retractable driven tracks according to one embodiment.
FIG. 2 is, in rear perspective left-side partially cut-away view, a four
wheeled vehicle having
retractable driven tracks according to a second embodiment.
DESCRIPTION
As seen in FIG. 1, a wheeled vehicle 10 includes four wheels 12, two laterally
spaced apart at
the rear of the vehicle and two having the same lateral spacing at the front
of the vehicle. The
front and rear wheels are separated by a wheel-base A. In conventional wheeled
vehicles 10, all
four wheels 12 may be driven wheels, driven by the vehicle's motor via a drive
train which
typically includes a drive shaft who's position is generally indicated by
reference arrow 14.
In deep snow conditions, or in other soft terrain conditions in which wheels
12 may bog down,
it assists the wheels' traction in such terrain to reduce the pressure exerted
downwardly by the
weight of the vehicle acting on the wheels. One way this is accomplished is by
using over-size
wheels having a large diameter and a large corresponding width so as to
increase the wheel
footprint on the terrain. For example, and without intending to be limiting,
wheels 12 in FIG. 1
may be approximately 44 inches in diameter, thereby reducing their pressure
footprint on soft
terrain as compared to conventional smaller diameter tires. Another way to
reduce the
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pressure footprint is to reduce the tire pressure in the vehicle tires by
deflating the tires when
in snow, mud, or otherwise boggy terrain. This again increases the size of the
tire's footprint
and reduces the pressure per unit area exerted on the ground. This also
typically then requires
that the tires be re-inflated once clear of the boggy or snowy terrain when it
is desired to travel
at higher speed.
The addition of retractable tracks 16 mounted under vehicle 10 provides an
advantageous
method of reducing the pressure footprint of the vehicle acting on the vehicle
tires. Although a
pair of such tracks 16 mounted for example under the running boards 18 on
either side of
vehicle 10 do add weight to the vehicle, the benefit in reducing the pressure
footprint off-sets
the additional weight penalty of the tracks when the tracks 16 are deployed
downwardly so as
to engage the snow or other soft terrain.
Although deployment mechanisms other than the actuated linkage illustrated in
FIG. 1 will
work, such as the alternative actuating linkage shown in FIG. 2, FIG. 1 is
provided as an example
of a driven track system for selectively raising and lowering a driven endless
track 20 so as to
raise track 20 up tucked closely under the vehicle for on-road or higher speed
travel, and to
lower track 20 to engage soft terrain, for example in snow, mud or boggy
conditions.
Thus what is seen in FIG. 1 by of example, and without intending to be
limiting, is a driven
endless track 20, such as may be found on snow-mobiles, supported on bogeys or
rollers 22
mounted on a frame 24. Frame 24 is rigid and may, as seen, be rectangular and
planar so as to
be approximately parallel with a notional ground surface F on which the tires
rest. Because
vehicle 10 moves forwardly in direction B, the end of frame 24 corresponding
with the forward
end of vehicle 10 is referred to as the forward end 24a of frame 24. The
opposite, rearmost end
of frame 24 is indicated as rearward end 24b.
Frame 24 holds endless track 20 so that the track is free to rotate about the
ends of the frame
24a and 24b, for example in direction C when track 20 is driven to assist in
forward motion of
vehicle 10. The force to drive the rotation of track 20 comes, in one example,
from relatively
short laterally extending drive axles (not shown) driven at their in-board end
by a conventional
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drive train splitter (not shown) mounted to the vehicle driveshaft indicated
generally by arrow
14. The laterally outer ends of the drive shafts drive rotation of one of the
in-board sprockets
engaging the track.
Other drive arrangements would also work. For example, each track 20 could be
driven by a
dedicated electric motor, for example mounted within the orbit of the track,
or a pair of tracks
20 could be driven by a single electric motor. The tracks 20 could also be
driven by a hybrid
arrangement of electric drive and mechanical drive. Alternatively, tracks 20
could be
hydraulically driven, with the hydraulic motor located within the orbit of the
tracks, for example
in the space of a sprocket, and with the hydraulic pump located elsewhere in
the vehicle.
In the illustrated example of FIG. 1, again which is not intended to be
limiting, as other
structures and/or linkages such as seen by way of example in FIG. 2 would also
work, a single
scissor linkage 26 is located at the forward end 24a of frame 24, mounted
between forward end
24a and the corresponding forward end 18a of running board 18. The upper ends
of upper links
26a are pivotally mounted under forward end 18a. The lower ends of lower links
26b are
pivotally mounted to forward end 24a of frame 24. The lower ends of upper
links 26a are
pivotally mounted to the upper ends of lower links 26b. Cross-bracing (not
shown) may be
provided between the pairs of upper links and between the pair of lower links.
A rigid cross-
member 28 extends laterally between the lower ends of upper links 26a where
pivotally
connected to lower links 26b.
In this example, which again is not intended to be limiting, a pair of
parallel rigid struts 30
extend between, and are pivotally mounted to, the forward end 18a of running
board 18 and
the rearward end 24b of frame 24. A cross member 30a provides a brace
extending laterally
between struts 30 at approximately half way along the length of struts 30. An
upper cylinder
32, which may for example be a pneumatic cylinder, is pivotally mounted at its
rearward end up
under running board 18, and is pivotally mounted at its forward end to cross
member 28. A
lower cylinder 34, which may for example also be a pneumatic cylinder, is
pivotally mounted up
under running board 18 at the rearward end 18b of running board 18. The lower
end of lower
cylinder 34 is pivotally mounted to either the struts 30 or to cross member
30a.
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Upper cylinder 32 provides the scissor linkage actuator to collapse or extend
the vertical height
(dimension D) of scissor linkage 26 to thereby correspondingly raise or lower
the forward end
24a of frame 24. This raises or lowers the forward end of track 20. Lower
cylinder 34 provides
the strut actuator to swing the struts 30 in direction E to raise or lower the
rearward end 24b of
frame 24 and thus to raise or lower the rearward end of track 20. Cylinders 32
and 34 thereby
provide for selective and independent control by the operator, e.g. the driver
of vehicle 10, of
the height and orientation of track 20 above ground level F. The operator
merely has to control
the pressure in cylinders 32 and 34, or otherwise the position of the tracks
as indicated by
corresponding sensors (not shown).
In alternative embodiments, again without intending to be limiting, the
scissor linkages could
be replaced with linkage arms, for example in a parallelogram arrangement
using a pair of
arms. Further, the tracks could be positioned in board under the vehicle; for
example in the
cavities on either side of the drive shaft.
Advantageously, the cylinder pressures or track positions are displayed to the
operator, for
example digitally or by analog display, and a means to actively adjust the
cylinder pressures or
track position is provided to the operator. For example, a driver may be
provided a joy-stick
controller which, depending on the actuation of the joy-stick by the driver,
controls extension
or retraction of the cylinders. The cylinders may form part of a vehicle
suspension system to
coordinate the deployment of the retractable tracks 16 as part of balancing of
the vehicle 10 to
maximize traction and minimize and balance the vehicle's pressure footprint.
In the alternative embodiment of FIG. 2, not intended to be limiting, scissor
linkages such as for
example scissor linkages 26 and 26' are pivotally mounted at ends 24a and 24b
of frame 24, it
again being understood that a pair of such retractable tracks are mounted on
both sides of
vehicle 10. This differs from the embodiment of FIG. 1 in that instead of the
use of a single
scissor linkage for one end of frame 24 and the use of struts 30 for the
opposite end of frame
24 as in FIG. 1, in FIG. 2 mirror image scissor linkages 26, 26' are used at
ends 24a, 24b of frame
24 mounted up under the corresponding ends of running boards 18. Thus as seen
in FIG. 2,
selectively actuable actuators 32 and 32' are mounted under running boards 18,
so as to criss-
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cross each other. Actuator 32' is mounted aft along running boards 18 and is
pivotally coupled,
so as to actuate, scissor linkages 26 at the forward end of frame 24. Actuator
32' is mounted up
under the forward ends of running boards 18, pivotally coupled so as to
actuate scissor linkages
26' at the rearward end of frame 24. A pivotally mounted strut 30, connecting
the frame of
vehicle 10 or running boards 18 to frame 24, may be employed on either side of
vehicle 10 to
stabilize and guide the vertical translation of track 20 during actuation of
actuators 32, 32'.
Reference to more than one running board 18, and associated actuators and
scissor linkages, is
a reference to running boards 18, actuators 32,32', and scissor linkages
26,26' on either side of
vehicle 10.
In a further alternative embodiment the tracks or track 20 may be mounted
under the vehicle,
laterally inset from the sides of the vehicle, for example mounted along or
under the
longitudinally extending centerline of the vehicle.
In some embodiments the vehicle may have other than four wheels. For example,
it is intended
to be within the scope of the present disclosure that the vehicle may be for
example a two or
four wheeled trailer, for example for towing behind a four wheeled vehicle,
such that one or
more retractable tracks such as seen in FIGS. 1 and 2 are mounted under the
trailer. In the case
of a two wheeled trailer, one or a pair of retractable tracks such as
described above may be
mounted under the trailer, in front or behind the tires, or between the tires
in the center of the
trailer. In some embodiments the trailer may have drive axles to move itself.
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