Note: Descriptions are shown in the official language in which they were submitted.
WHEELED VEHICLE HAVING RETRACTABLE DRIVEN TRACKS
Field of the Invention
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
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 means which may include at least two
retractable tracked
drives. A marine drive may include a jet drive. 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 means
may also provide vehicle suspension.
Brief Description of the Drawing
Figure 1 is, in rear perspective partially cut-away view, a four wheeled
vehicle having
retractable driven tracks according to one embodiment.
Description
As seen in Figure 1, a wheeled vehicle 10 includes wheels 12 separated by a
wheel-base A. In
conventional 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 14.
In deep snow conditions, or in other soft terrain conditions in which wheels
12 may bog down,
it assists traction in such terrain to reduce the pressure exerted downwardly
by the wheels.
One way this is accomplished is by using large 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 Figure 1 may be approximately
44 inches in
diameter, thereby reducing their pressure footprint on soft terrain. Another
way to reduce the
pressure footprint is to reduce the tire pressure by actively 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 when it is desired to travel at higher
speed.
The addition of retractable tracks 16 mounted under vehicle 10 provides a
further method of
reducing the pressure footprint of the vehicle. Although a pair of such tracks
16 mounted for
example under the running boards 18 of vehicle 10 do add weight to the
vehicle, the benefit in
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reducing the pressure footprint off-sets the additional weight penalty of the
tracks when the
tracks 16 are deployed so as to engage the snow or other soft terrain.
Although deployment mechanisms other than the actuated linkage illustrated
will work, Figure
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 or boggy
conditions. Thus what is seen in Figure 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. Because
vehicle 10 moves
forwardly in direction B, I refer to the forward end 24a of frame 24 as the
end of frame 24
corresponding with the forward end of vehicle 10. The opposite, rear end of
frame 24 is
referred to herein as rearward end 24b. Frame 24 holds endless track 20 so
that the track is
free to rotate, 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 axles driven at their in board end by a conventional
drive train splitter
(not shown) mounted to vehicle driveshaft 14. The laterally outer ends of the
shafts drive
rotation of one of the 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 in
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 Figure 1, again which is not intended to be
limiting, as other
structures and/or linkages 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 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 extends 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 be a pneumatic cylinder, is pivotally mounted up under
running board
18 at the rearward end 18b of running board 18.
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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 and thus to also raise or lower 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.
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 an alternative embodiment, not intended to be limiting, a scissor linkage
such as for example
scissor linkage 26, and associated selectively actuable actuator may be
provided at each end of
frame 24 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. 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, the
vehicle may be a
two wheeled trailer for towing behind a four wheeled vehicle.
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