Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02864246 2014-10-01
TITLE OF THE INVENTION
ENDLESS BELT TENSIONER SYSTEM AND METHOD OF USE THEREOF
FIELD OF THE INVENTION
10002] The present application generally relates to an endless belt
tensioner. More precisely, the present application relates to an endless belt
tensioner adapted to change the tension in the endless belt.
BACKGROUND OF THE INVENTION
[0003] Vehicles equipped with endless belt drives are adapted to be used
on various types of grounds. Endless belt drives, or caterpillars, are
replacing, or
complementing, weight supporting wheels to reduce ground contacting pressure
and improve floatation and traction on soft grounds.
10004] Each endless belt is generally installed on a set of wheels and/or
bearing members supporting and positioning the endless belt on the vehicle. At
least one driven tooted wheel, commonly called a sprocket, engages the endless
belt to transmit movement to the endless belt and propel the vehicle. Other
optional endless belt supports can also be used to ensure proper operation of
the
endless belt drive,
CA 02864246 2014-09-17
MTC-088-004-002-CA2
1
2 [0005] The weight-supporting wheels are affixed to a suspension
system
3 adapted to absorb ground imperfections of rugged terrains and provide a
smoother
4 ride to occupants of the vehicle. A wide-travel suspension system
generally allows
the passage of significant ground obstacles. However, wide travel suspensions
6 significantly affect the tension of the endless belt and increase the
risk of
7 disengaging the endless belt from its drive sprocket and/or coming off
its weight
8 supporting wheels. Significant tension in the endless belt also has an
effect on the
9 useful life of the endless belt.
11 [0006] A need, therefore, exists for an improved tensioner
system for the
12 endless belts of all-terrain vehicles.
13
14 SUMMARY OF THE INVENTION
16 [0007] The following presents a simplified summary of the
invention in order
17 to provide a basic understanding of some aspects of the invention. This
summary is
18 not an extensive overview of the invention. It is not intended to
identify key/critical
19 elements of the invention or to delineate the scope of the invention.
Its sole purpose
is to present some concepts of the invention in a simplified form as a prelude
to the
21 more detailed description of exemplary embodiments, which is presented
later.
22
23 [0008] An endless belt tensioner system, and method of use
thereof, of the
24 present invention (including a kit therefor) may, by way of example, be
exploited in
relation to an all-terrain vehicle. However, the tensioner system of the
present
26 invention may be used in relation to other vehicles adapted to serve in
contexts that
27 differ from the embodiments described and illustrated hereinafter.
28
29 [0009] It is to be understood herein that the term all-terrain
vehicle generally
refers to an off-road vehicle although the vehicle could alternatively be used
on the
31 road. It is further understood that the term endless belt generally
refers to a
2
CA 02864246 2014-09-17
MTC-088-004-002-CA2
1 caterpillar-type drive adapted to impart motive power from the vehicle to
the ground
2 by a means that provides a wider ground footprint than a wheel. An
endless belt, or
3 a caterpillar, can be made of articulated steel parts, rubber, composite
materials
4 (woven material and rubber) or other material suitable to this end.
6 [0010] Therefore, one object of the present invention improves
at least some
7 of the deficiencies associated with an endless belt tensioner intended to
be adapted
8 to an all-terrain vehicle.
9
[0011] Another object of the present invention provides an endless belt
11 tensioner system that offers a wide travel suspension while assisting in
preventing
12 the endless belt from coming off its proper operating position.
13
14 [0012] An object of the present invention provides an endless
belt tensioner
system that offers a wide travel suspension while preventing the endless belt
from
16 wearing out prematurely.
17
18 [0013] One object of the present invention provides an endless
belt tensioner
19 system that is hydraulically actuated.
21 [0014] An additional object of the present invention provides an
endless belt
22 tensioner system that allows high suspension travel thereof.
23
24 [0015] One additional object of the present invention provides
an endless belt
tensioner system that requires low maintenance and assists in preventing
debris
26 from influencing its useful life.
27
28 [0016] An additional object of the present invention provides an
endless belt
29 tensioner system that applies tension to the endless belt proportional
to the traction
effort applied to the endless belt.
31
3
CA 02864246 2014-09-17
MTC-088-004-002-CA2
1 [0017] Another additional object of the present invention
provides an endless
2 belt tensioner system that applies distinct tension to each of the
endless belts in
3 proportion with their respective traction effort.
4
[0018] An additional object of the present invention provides an endless
belt
6 tensioner system that applies tension to the endless belts when the
vehicle moves
7 forward and rearward.
8
9 [0019] One other additional object of the present invention
provides a method
of adjusting tension in endless belts in accordance with behaviors of the
vehicle.
11
12 [0020] An aspect of the present invention provides an endless
belt tensioner
13 system that uses a hydraulically actuated tensioner to adjust the
tension of the
14 endless belt.
16 [0021] Another aspect of the present invention provides an
endless belt
17 tensioner system that uses a hydraulic shuttle valve to distribute
hydraulic pressure
18 to the tensioner system.
19
[0022] One aspect of the present invention provides an endless belt
tensioner
21 system that is, at least in part, disposed on the vehicle in a fashion
that prevents the
22 tensioning system from being contaminated by foreign materials.
23
24 [0023] One other aspect of the present invention provides an
endless belt
tensioner system of which the hydraulic portion is disposed inside the frame
and the
26 endless belt contacting wheels are disposed outside the frame and
subjected to
27 foreign material.
28
29 [0024] Another aspect of the present invention provides an
endless belt
tensioner system adapted to be dynamically powered by hydraulic pressure.
31
4
CA 02864246 2014-09-17
MTC-088-004-002-CA2
1 [0025] One another aspect of the present invention provides an
endless belt
2 tensioner system provided with a shuttle valve that hydraulically
actuates the
3 tensioner system when the vehicle moves forward and rearward.
4
[0026] An aspect of the present invention provides a hydraulic endless belt
6 tensioner system that uses a drive hydraulic pressure to tense the
endless belt.
7
8 [0027] An aspect of the present invention provides a hydraulic
endless belt
9 tensioner system for each side of a vehicle, each hydraulic endless belt
tensioner
system being hydraulically coupled with its respective hydraulic drive system.
11
12 [0028] One another aspect of the present invention provides a
hydraulic
13 endless belt tensioner system for each side of a vehicle, each hydraulic
endless belt
14 tensioner system being hydraulically coupled with the hydraulic drive
system
providing the higher pressure therein.
16
17 [0029] Another aspect of the present invention provides a
manually actuated
18 hydraulic endless belt tensioner system.
19
[0030] One aspect of the present invention provides an automatically
21 pressure regulated hydraulic endless belt tensioner system based, at
least in part,
22 on the traction force, the speed of the vehicle, the steering angle, the
longitudinal
23 inclination of the vehicle and/or the transversal inclination of the
vehicle.
24
[0031] An aspect of the present invention provides a hydraulic endless belt
26 tensioner system coupled with a preloading spring providing a non-
hydraulic tension
27 preload to the endless belt.
28
29 [0032] Yet another aspect of the present invention provides, for
a
substantially constant hydraulic pressure, a substantially constant endless
belt
31 contacting wheels pressure over the endless belt contacting wheels
displacement.
5
CA 02864246 2014-09-17
MTC-088-004-002-CA2
1
2 [0033] One additional aspect of the present invention provides
an endless
3 belt tensioner system adapted to apply a tensioning force on a ground-
contacting
4 endless belt of a vehicle, the tensioning force being substantially
proportional to an
endless belt drive force applied to the endless belt to move the vehicle.
6
7 [0034] One aspect of the present invention provides an endless
belt tensioner
8 system comprising a tensioner module adapted to physically apply tension
on an
9 endless belt of a vehicle; a vehicle behavior module adapted to determine
the
behaviors of the vehicle; and a tensioner management module adapted to
position
11 the tensioner module based, at least in part, on outputs provided by the
vehicle
12 behavior module.
13
14 [0035] Another aspect of the present invention provides a
vehicle comprising
at least a pair of ground-contacting endless belts each cooperating with a
tensioning
16 mechanism adapted to determine a tension in the ground-contacting
endless belt,
17 the tensioning mechanism increasing the tension in the ground-contacting
endless
18 belt in function of a speed of the vehicle.
19
[0036] Another aspect of the present invention provides a method for
21 managing a tension of a ground-contacting endless belt on a vehicle, the
method
22 comprising sensing the hydraulic pressure in a drive hydraulic system
adapted to
23 propel the vehicle; adjusting the tension in the ground-contacting
endless belt based
24 at least in part on the sensed hydraulic pressure.
26 [0037] A further aspect of the present specification provides a
spring
27 mechanism that insures a minimum tension in the endless belt during
vehicle
28 operation and non-operation.
29
[0038] Therefore, in accordance with the present invention, there is
provided
31 an endless belt tensioner system adapted to apply a tensioning force on
a ground-
6
CA 02864246 2014-09-17
MTC-088-004-002-CA2
1 contacting endless belt of a vehicle, the tensioning force being
substantially
2 proportional to an endless belt drive force applied to the endless belt
to move the
3 vehicle.
4
[0039] Also in accordance with the present invention, there is provided an
6 endless belt tensioner system comprising: a tensioner module adapted to
physically
7 apply tension on an endless belt of a vehicle; a vehicle behavior module
adapted to
8 determine the behaviors of the vehicle; and a tensioner management module
9 adapted to position the tensioner module based, at least in part, on
outputs provided
by the vehicle behavior module.
11
12 [0040] Further in accordance with the present invention, there
is provided a
13 vehicle comprising at least a pair of ground-contacting endless belt
cooperating with
14 a tensioning mechanism adapted to determine a tension in the ground-
contacting
endless belt, the tensioning mechanism increasing the tension in the ground-
16 contacting endless belt in function of a speed of the vehicle.
17
18 [0041] Still further in accordance with the present invention,
there is provided
19 a method for managing a tension of a ground-contacting endless belt on a
vehicle,
the method comprising:
21
22 [0042] sensing the hydraulic pressure in a drive hydraulic
system adapted to
23 propel the vehicle; and
24
[0043] adjusting the tension in the ground-contacting endless belt based at
26 least in part on the sensed hydraulic pressure.
27
28 [0044] Other objects, aspects, advantages and features of the
present
29 invention will become more apparent upon reading of the following non-
restrictive
description of embodiments thereof, given by way of example only with
reference to
31 the accompanying drawings.
7
CA 02864246 2014-09-17
MTC-088-004-002-CA2
1 BRIEF DESCRIPTION OF THE DRAWINGS
2
3 [0045] Reference will now be made to the accompanying drawings,
showing
4 by way of illustration an illustrative embodiment of the present
invention, and in
which:
6
7 [0046] FIG. 1 is a front-right isometric view of an all-terrain
vehicle;
8
9 [0047] FIG. 2 is a right side elevation view of the all-terrain
vehicle of FIG. 1;
11 [0048] FIG. 3 is an isometric view of a tensioner system of the
all-terrain
12 vehicle of FIG. 1;
13
14 [0049] FIG. 4 is an isometric view of the tensioner system of
FIG. 3;
16 [0050] FIG. 5 is a rear elevation view of the tensioner system
of FIG. 3;
17
18 [0051] FIG. 6 is an exploded isometric view of the tensioner
system of FIG. 3;
19
[0052] FIG. 7 is a side elevation view of the tensioner system of FIG. 3;
21
22 [0053] FIG. 8 is a transversal cross-sectional view of the
tensioner system of
23 FIG. 7;
24
[0054] FIG. 9 is a schematic side elevation view of the tensioner system of
26 FIG. 3 and its effect on the endless belt of FIG. 1;
27
28 [0055] FIG. 10 is a schematic hydraulic circuit illustrating an
embodiment of
29 the present invention;
8
CA 02864246 2014-09-17
MTC-088-004-002-CA2
1 [0056] FIG. 11 is a schematic hydraulic circuit illustrating an
embodiment of
2 the present invention;
3
4 [0057] FIG. 12 is a schematic hydraulic circuit illustrating an
embodiment of
the present invention;
6
7 [0058] FIG. 13 is an angled view of part of a variant all-
terrain vehicle,
8 showing the tensioner system of FIG. 3 provided with a spring mechanism;
and
9
DESCRIPTION OF ILLUSTRATIVE EMBODIMENT(S) OF THE INVENTION
11
12 [0059] The present invention will now be described with
reference to the
13 drawings, wherein like reference numerals are used to refer to like
elements
14 throughout. In the following description, for purposes of explanation,
numerous
specific details are set forth in order to provide a thorough understanding of
the
16 present invention. It may be evident, however, that the present
invention may be
17 practiced without these specific details.
18
19 [0060] Thus, an embodiment of the invention is shown on FIGS. 1
and 2
embodied on an all-terrain vehicle 10. The all-terrain vehicle 10 is
constituted, inter
21 alia, of a passenger compartment 20, a frame 30, a drive system 40, a
power pack
22 50, a hydraulic system 60, a suspension system 70 and a tensioner system
80. The
23 passenger compartment 20 is provided with doors 202 pivotally secured on
each
24 side of a roof portion 204 via hinges 206, windows 208 disposed on the
periphery of
the vehicle 10, a back door 212 and a plurality of lights 210.
26
27 [0061] Manufacturing of the passenger compartment 20 of the
illustrated
28 embodiment is generally made in aluminium material for reasons of
strength and
29 weight. Other materials, like steel, plastic or composite materials,
could be used
within the scope of the present invention.
31
9
CA 02864246 2014-09-17
MTC-088-004-002-CA2
1 [0062] The passenger compartment 20 is mounted to the frame 30
thus
2 forming a monocoque construction that enhances the rigidity and the
strength of the
3 overall vehicle assembly. Most parts of the vehicle assembly can be
fastened,
4 glued, welded, riveted or secured by other suitable means known in the
art of
vehicle manufacturing.
6
7 [0063] The power pack 50 is housed in and secured to the frame
30. The
8 power pack 50 is preferably located low in the frame 30 to keep the
center of gravity
9 of the vehicle 10 as low as possible. Preferably, the power pack 50 is
transversally
centered in the vehicle 10 for reasons of lateral weight distribution. The
longitudinal
11 position of the power pack 50 can vary in accordance with the desired
mass
12 distribution and volume allocation. In this respect, the power pack 50
can be
13 disposed in the center of the vehicle 10 to advantage mass distribution.
14 Alternatively, the power pack 50 can be positioned toward the rear of
the frame 30
to allow maximum room therein for passengers.
16
17 [0064] An internal combustion engine 502, e.g. a diesel or gas
engine,
18 powers a hydraulic system 60 via a rotating or reciprocating hydraulic
pump 602.
19 The internal combustion engine 502 could alternatively power more than one
hydraulic system 60 and/or hydraulic pump 602. A plurality of hydraulic pumps
602
21 and/or hydraulic system 60 might be desirable for reasons of reliability
if the vehicle
22 10 is expected to be used in extreme conditions by offering redundant
systems.
23 More than one hydraulic pump 602 also allows driving independently each
endless
24 belt 404. The pressurized hydraulic system 60 powers hydraulic motors
406 that, in
turn, mechanically power the drive system 40 with drive sprockets 402.
Intermediate
26 planetary gearboxes (not shown) reduce the ratio between each hydraulic
motor 406
27 and its associated sprocket 402. Sprockets 402 of the drive system 40
propel the
28 vehicle 10 by engaging and turning the endless belts 404. Two hydraulic
motors 406
29 are installed in the vehicle 10, each moving one of the two endless
belts 404. The
vehicle 10 is steered by a difference in rotation of the two hydraulic motors
406.
31
CA 02864246 2014-09-17
MTC-088-004-002-CA2
1 [0065] Still referring to FIG. 1 and FIG. 2, the suspension
system 70
2 comprises a plurality of suspension units 702. Each suspension unit 702
uses a
3 double wishbone configuration 704 coupled on a proximal side to the frame
30 of
4 the vehicle 10 and, on a distal side, to a hub 706. The hub 706 pivotally
accommodates a tandem 708 to which are rotatably secured suspension wheels
6 710. Support wheels 712 are provided on an endless belt upper support 714
to
7 maintain the upper side of the endless belt 404 on its way toward the
front of the
8 vehicle 10.
9
[0066] Tension in each endless belt 404 is independently managed by the
11 tensioner system 80. Endless belt contacting wheels 802 are adapted to
move along
12 the radius generated by tension lever 804 about pivot axis 816 to extend
or retract
13 the circumference of its associated endless belt 404. The tensioner
system 80 is
14 adapted to provide proper tension in the endless belt 404 by dynamically
adapting to
operating conditions of the vehicle 10. This aspect of the tensioner mechanism
80
16 will be discussed later in more details.
17
18 [0067] As better seen on FIGS. 3 through 8, it can be
appreciated that the
19 tensioner system 80 is actuated by a hydraulic cylinder 806 attached on
one side to
the frame 30 via an intervening cylinder support 808. The actuation of the
hydraulic
21 cylinder 806 by the hydraulic system 60 procures a desired tension to
the endless
22 belt 404 (illustrated on FIGS. 1 and 2). The hydraulic cylinder 806 is
pivotally
23 coupled on the other side (i.e. piston side), with a rod end 822, to a
primary lever
24 810 that extends from a pivot member 812. The pivot member 812 is
pivotally
secured to the frame 30 by an intervening bearing support 814 adapted to
receive a
26 plurality of ball bearings 824 therein. The two levers 804 are
selectively positioned
27 and pivotally secured to the pivot member 812 at a predetermined angle
thereto with
28 splines 828 (better seen on FIG. 5) or other means to join both parts
while offering
29 angular adjustment thereof. The angular position of the levers 804 can
be changed
by removing the fasteners 826 securing the levers 804 and angularly
repositioning
31 the levers 804 in the splines 828. Two endless belts contacting wheels
802 are
11
CA 02864246 2014-09-17
MTC-088-004-002-CA2
1 rotatably secured to a wheel support 818 (axle), defining a wheel axis
820
2 thereabout, abutting the levers 804 on each end thereof. Each endless
belt
3 contacting wheel 802 is provided with a ball bearing 830 arrangement to
facilitate
4 rotational movements of the endless contacting wheels 802 when the
endless belt
404 rotates.
6
7 [0068] The tensioner system 80 is separated in two portions,
the internal
8 portion 840 and the external portion 842. The internal portion 840 is
disposed inside
9 the frame 30 of the vehicle 10 to protect a portion of the elements of
the tensioner
system 80 against dirt, sand, water and other contaminants. In contrast, the
external
11 portion 842 extends outside the frame 30 of the vehicle 10 and is
therefore not
12 protected against contaminants. The junction between the two portions
840 and 842
13 is made with the levers 804 that are extending outside the frame 30 by
extending
14 out of the bearing support 814. Levers 804 pivot about the pivot axis
816 to apply
tension to the endless belt 404. Sealing of the interface between the internal
portion
16 840 and the external portion 842 is performed with seals 844, which are
best seen
17 on FIGS. 6 and 7, disposed on the circular section of the levers 804. In
so doing,
18 only a portion of the levers 804 and the endless belt contacting wheels
802 are
19 vulnerable to the environment.
21 [0069] It can be appreciated that the bearing support 814 is
sealed to the
22 frame 30 with a series of 0-rings 832 installed on each bolt 834
securing the bearing
23 support 814 to the frame. A gasket 836 is disposed on the periphery of
the bearing
24 support 814 to further seal the bearing support 814 to the frame 30.
26 [0070] Alternatively, the internal portion 840 could be defined
by a casing (not
27 illustrated) adapted to cover components assembled outside the frame 30.
Such an
28 internal portion, despite not being disposed inside the frame 30 of the
vehicle 10 in
29 this alternate embodiment, would be sealed from the environment by the
casing.
Seals 844 could be similarly installed on the levers 804 through the casing
thus
31 allowing pivotal movements of the pivot member 812.
12
CA 02864246 2014-09-17
MTC-088-004-002-CA2
1
2 [0071] Focusing now on FIG. 7 illustrating the limit positions
850 and 852 of
3 the endless belt contacting wheels 802, the tensioner system 80 tenses
the endless
4 belt 404 to the maximum in its extended limit position 850. In contrast,
the tensioner
system 80, in the retracted limit position 852, removes tension in the endless
belt
6 404. A schematic illustration of an exemplary displacement of the endless
belt 404
7 in accordance with the limit positions 850 and 852 of the endless belt
contacting
8 wheels 802 is provided in FIG. 9. It has to be noted that, with the
embodied
9 geometry, for a constant hydraulic pressure, the force applied by the
endless belt
contacting wheels 802 on the endless belt 404 remains substantially constant
over
11 the entire course of the levers 804. This is that the effective lever of
the primary
12 lever 810 and the effective lever of the levers 804 remains
substantially proportional
13 over the entire course of the levers 804.
14
[0072] As mentioned above, one of the objects of the present invention is
to
16 provide sufficient tension in the endless belt 404 to avoid the endless
belt 404 from
17 any slipperage or coming off with respect to the sprocket 402. It also
prevents the
18 endless belt 404 from coming off the weight supporting wheels 710 and
the support
19 wheels 712. Significant tension in the endless belt 404 could be
maintained so that
no slipperage of the endless belt 404 occurs when driven by the sprocket 402.
21 However, the down side is that unnecessary tension in the endless belt
404
22 prevents the suspension system 70 of the vehicle from working in an
optimal
23 fashion. In other words, maximum suspension travel can occur if there is
sufficient
24 slack in the endless belt 404 to allow the suspension system 70 to move.
Unnecessary tension in the endless belt 404 restricts movements of the
suspension
26 system 70 required to provide a smooth ride.
27
28 [0073] A strategy to avoid any slipperage of the sprocket 402
with the endless
29 belt 404 while allowing maximum suspension travel suggests that tension
in the
endless belt 404 should be adapted to specific conditions of use of the
vehicle 10,
31 namely, inter alia, the drive effort to propel the vehicle 10, the speed
of the vehicle
13
CA 02864246 2014-09-17
MTC-088-004-002-CA2
1 10, the centrifugal force of the turning endless belt 404, vehicle self-
pivoting (aka
2 autogiration when each endless belt 404 counter-rotate), the steering
angle, the
3 longitudinal angle of the vehicle 10 and the transversal angle of the
vehicle 10.
4
[0074] The drive effort to propel the vehicle 10 is provided by the
hydraulic
6 system 60. By using corresponding hydraulic pressure in the hydraulic
system 60
7 used to drive the sprocket 402 tensioner system 80 it is possible to
obtain a
8 correlation between the drive effort provided by the sprocket 402 and
tension of the
9 endless belt 404. Increased hydraulic pressure in the drive system caused
by
increased drive effort increases the tension in the endless belt 404 therefore
11 preventing slipperage of the sprocket 402. In contrast, reduction of the
drive effort
12 reduces the hydraulic pressure in the hydraulic system 60, which also
reduces the
13 tension in the endless belt 404. The correlation is dynamic and provides
14 corresponding tension in the endless belt 404 at all time. A spring (as
seen in FIG.
13, described hereinbelow) is alternatively added to the tensioner system 80
to
16 preload the endless belt 404 and provide minimum tension when the
hydraulic
17 pressure in the hydraulic system 60 is under a predetermined threshold.
18
19 [0075] FIG. 10 schematically illustrates a possible embodiment
that provides
a correlation between the drive hydraulic pressure and the tension in the
endless
21 belt 404. The hydraulic layout of FIG. 10 illustrates a power pack 50
that actuates
22 the hydraulic pump 602 to hydraulically power the hydraulic motor 406
which, in
23 turn, rotates the sprocket 402 that is engaged to the endless belt 404
to propel the
24 vehicle 10. The hydraulic cylinder 806 of the tensioner mechanism 80 is
hydraulically connected to the hydraulic circuit powering the hydraulic motor
406.
26 This way, the hydraulic cylinder 806 and the hydraulic motor 406 are
subjected to
27 identical hydraulic pressure. This means the hydraulic cylinder 806
applies more
28 tension to the endless belt 404 when more drive efforts are provided to
the sprocket
29 402.
14
CA 02864246 2014-10-01
MTC-088-004-002-CA2
[0076] Still on FIG, 10, the forward path 604 of hydraulic oil brings
hydraulic power to the hydraulic motor 406 when the vehicle 10 is propelled
forward. Conversely, a rearward path 606 of hydraulic oil brings hydraulic
power
to the hydraulic motor 406 when the vehicle 10 is propelled rearward. The
hydraulic cylinder 806 is hydraulically powered from both paths 604, 606 of
hydraulic oil to tense the endless belt 404 when the vehicle 10 is driven in
both
forward and rearward directions. A shuttle valve 610 is provided between both
paths 604 and 606 of hydraulic oil to ensure that the hydraulic cylinder 806
is
pressurized by the path 604, 606 providing the highest hydraulic pressure
whether the vehicle 10 is driven forward or rearward.
[0077] FIG. 11 illustrates a hydraulic layout having two distinct hydraulic
circuits, i.e. one hydraulic circuit 612 for driving the endless belt 404
disposed on
the left side of the vehicle 10 and another 614 for the endless belt 404
disposed
on the right side of the vehicle 10. Each hydraulic circuit 612, 614 is
pressurized
by the same power source 50 (although more than one power source 50 could
be used without departing from the scope of the present invention) activating
distinct hydraulic pumps 602.1 and 602.2. One hydraulic pump for each
hydraulic
circuit 612, 614 ensures that enough hydraulic pressure is provided to each
hydraulic motor 406.1, 406.2. The quantity and the pressure of hydraulic fluid
in
each hydraulic circuit 612, 614 varies in accordance with the drive effort
(hydraulic fluid pressure), the speed of the vehicle 10 (hydraulic fluid
velocity),
the load of the vehicle 10 and, inter alia, the steering angle if the vehicle
10 turns.
Shuttle valves 610.1 and 610.2 are provided in each hydraulic circuit 612 and
614 between the hydraulic lines 604, 606 to achieve the same purpose as
described above in respect to FIG. 10. Therefore, each hydraulic cylinder 806
will
be respectively actuated by the hydraulic circuit 612 or 614 that drives its
associated endless belt 404. Moreover, the highest hydraulic pressure will
still be
used by each hydraulic path 604, 606 when the endless belts 404 moves either
forwardly or rearwardly.
CA 02864246 2014-10-01
, .
,
MTC-088-004-002-CA2
[0078] Referring now to FIG. 12 illustrating the hydraulic system
of FIG. 11
with an additional shuttle valve 610.3. The shuttle valve 610.3 is provided
between both hydraulic circuits 612, 614 to equally use the absolute highest
hydraulic pressure simultaneously on both hydraulic cylinders 806.1, 806.2.
[0079] The proportional valve can alternately be used to replace
the
shuttle valve 610 and provide only the desired amount of pressure to each
hydraulic cylinder 806. The proportional valve is adapted to receive an
electric
signal about a desired output pressure, if the output pressure is different
than the
electric signal the proportional valve adjusts the output pressure until it
reaches
the desired output pressure. Alternatively, a pilot pressure could be used by
the
proportional valve to determine the amount of pressure that reaches each
hydraulic cylinder 806 through the hydraulic proportional valve. The pilot
pressure can be managed by controllers adapted to manage hydraulic systems
by controllers adapted to manage hydraulic systems.
[0080] With reference to FIG. 13, a spring mechanism 90 has been
added
to each above-described tensioner system 80 to ensure a minimum tension on
the endless belt 404 during operation and non operation. The spring mechanism
90 herein includes a pair pneumatic springs 902, which are compressed between
the frame 30 and a component 904 (for instance, the piston end of the
hydraulic
cylinder 806) that is connected to the mechanism that cause the tension levers
804 to pivot. Therefore, the springs 902 exert pressure in direction 906 onto
the
component 904, which in turn forces the tension levers 804 along direction 908
thereby biasing the contacting wheels 802 against the endless belt 404. The
spring mechanism 90 is thus exemplarily herein coupled with the hydraulic
cylinder 806 through the rod end 822 secured to the primary lever 810. Other
types of springs can be used instead of the present pneumatic springs 902.
16
CA 02864246 2014-09-17
MTC-088-004-002-CA2
1 [0081] The description and the drawings that are presented herein are
meant
2 to be illustrative of the present invention. They are not meant to be
limiting of the
3 scope of the present invention. Modifications to the embodiments
described may be
4 made without departing from the present invention, the scope of which is
defined by
the following claims:
6
7
17
