Note: Descriptions are shown in the official language in which they were submitted.
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CROSS REFERENCE TO RELATED APPLICATIONS
This application is related to the subject
matter in United States Patent 4,153,265 and Canadian Patents
1,108,998; 1,102,843; and 1,102,371. Certain of the structure
disclosed in this application is disclosed and claimed in my
Canadian Patent 1,109,098.
BACKGROUND OF THE INVENTION
) The inventions described in the afore-mentioned
related applications relate to self-propelled vehicles used
primarily to transport long loads, such a.s whole trees or tree
trunks across roadless terrain. More specifically, such prior
applications relates, as does this application, to rubber tired
; vehicles that have wheel suspension mechanisms which provide
balanced weight between its wheels and additionally permits
adjustment of the steady state position of the main bed frame
of the vehicle relative to a longitudinal roll axis to permit
compensation for the vehicle position when operating continuously
on the side of a hill, and also to facilitate unloading of the
vehicle by a side dumping action in either direction.
In summary, such vehicle comprises an elongated bed
frame that forms the backbone of the vehicle. This frame is
balanced on the central portion of modular front and rear wheel
i assemblies, preferably each having four quadrilaterally spaced
wheels. The quad wheel suspension system is designed to provide
a freedom of movement of each wheel about mutually perpendicular
roll and pitch axes that are vertically spaced one above the
other. The quad wheel assemblies are pivotally mounted on the
bed so as to be movable about a roll axis which is parallel to and
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OI 14964
beneath the longitudinal axis of the main frame element. On
the lower or pitch axis of each quad wheel assembly, two walking
beam members, each carrying a pair of steerable wheels, are
rockably mounted in a balanced relationship. Thus, the walking
beams may rock about the pitch axis of the quad wheel assembly
while the quad wheel assembly itself may pivot about the roll
axis. A mechanical interconnection of the quad wheel assemblies
comprises a pair of tubular torque transmission members that
extend from one quad wheel assembly toward the other an~ are
interconnected by a novel linkage system which continuously
adjusts the position of the longitudinal bed frame about the
roll axis to lie intermediate the positions of the quad wheel
assemblies. Additionally, the linkage incorporates two power
extensible links by which the steady state position of the
longitudinal bed frame member relative to the roll axis may
be selectively determined by the operator.
In accordance with the invention specifically dis-
closed in my aforementioned Canadian Patent no. 1,109,098,
a unique mounting of each wheel with respect to the walking
beam member permits a driving motor and brake to be incorporated
in the wheel mounting mechanism for imparting required rota-
tional movements to the wheel and, additionally, an electrical
or hydraulic actuator is also incorporated in the mounting to
impart individually controlled steering movements to the
particular wheel. As described in my aforementioned Canadian
Patent No. 1,109,098, sensors are provided which generate
signals respectively proportional to the rotational velocity
of the wheel and to the angle of turn of the particular wheel.
These sensor signals are inputs to a microprocessor and are
compared with the turning pocition and
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rotational velocity of the wheel required to effect a particular
attitude and movement of the vehicle, and compensating signals
are then fed to the driving motor for the wheel and the turning
actuator to cause the wheel velocity and wheel position to
correspond to that required to effect a desired attitude of the
vehicle.
A vehicle equipped with this combination of fea-
tures has numerous advantages over prior art off-road vehicles.
The individual control of the velocity and the turning angle
of each wheel permits the vehicle to be manipulated through any
selected one of a plurality of unusual movements or attitudes,
most of which are completely incapable of accomplishment by any
vehicle equipped with conventional driving and steering mechanisms.
Any vehicle as heretofore described requires an operator's cab
which is preferably in an elevated position relative to the
terrain being traversed, and a power source such as a gasoline or
diesel engine driving a hydraulic pump, and, if electric propul-
sion and steering control is to be employed, an electrical
generator of sufficiant capacity to provide the required trac-
tion and steering power. Hence, the operator's cab and the .
power unit are relatively massive in size and become a factor in
the overall design of the vehicle in order to keep such units
from interfering with the load carrying capability of the
vehicle and at the same time, to prevent the operator's cab por-
tion or the power unit portion of the vehicle from engaging pxo-
jections on the ground or overhead and interfering with the
mobility of the vehicle.
When the vehicle of the type heretofore described
is to be employed for harvesting trees, it is quite efficient
to provide a tree severing and handling means on the vehicle t
( ( OI 14964
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so that when the vehicle is driven to the vicinity of the tree
to be harvested, the tree can be engaged by a suitable clamping
mechanism carried on the end of a beam, severed by a suitable
cut-off means, and then the whole tree moved by the clamping
mechanism and beam to a position lying within the cradles pro-
vided on the elongated frame element of the vehicle. Such tree
handling elements must, however, be disposed on the vehicle in
such fashion as to not interfere with either the load carrying
ability or the mobility over the rough terrain where such vehicles
are to be employed.
Lastly, it is desirable that the operator's cab
be capable of adjustment about a horizontal axis so that the
operator is in a substantially upright position, particularly
when severing and loading trees.
~ large number of vehicles have heretofore been
proposed to be employed in the direct harvesting of trees. If
a whole tree, ranging in height up to eighty feet, or the whole
trunk thereof is to be bodily removed from a forest, the vehicle
to transport such whole trees or trunks necessarily has to have
considerable length. Prior art vehicles employed for such purpose
have generally resorted to an articulated vehicle used as a skidding
tractor or employed as a prime mover with one or more trailers
pivotally connected to the prime mover. Such load carrying vehicles
could obviously only be loaded with ~ whole treb when all of the
trailed units were in substantial longitudinal alignment and severe
binding, resulting in actual breakage of the tree, would occur when-
ever the vehicle was steered through any reasonable degree of turn
in travelling from the harvesting site to a processing station.
The long rigid load represented by a bundle of whole trees
superimposed on the structure effectively prevented any relative
horizontal pivotal movement of the articulated trailer units
113~8~ ~
and, as a result, the vehicle either became hung-up on obstruc-
tions around which the vehicle could not be steered or, portions
of the tree load were broken by the forced turning movements
of the articulated trailer unit. Backing of the vehicle was also
very difficult.
Additionally, such prior art units suffered from
the fact that the operator's control cab was generally in a fixed
vertical position with respect to the vehicle. If this position
were high, then the operator had to be continuously on *he alert
to steer around trees which were to be left standing or over-
hanging rock formations. If the operator's cab were left in a
lowered position, it would tend to hang-up on obstructions on
the ground as the vehicle traversed the uneven rugged terrain that
is associated with three harvesting operations. Similar problems
were encountered with the power unit for such vehicles which
necessarily is relatively massive in size and has to be located
on the vehicle so that it does not interfere with the load
carrying capacity of the vehicle nor permit the power unit to
be impacted by upstanding ridges or rocks on the terrain over
which the vehicle is traversed.
Lastly, if the vehicle was cross-wise on a slope,
the operator's cab would be tilted, to the discomfort and incon-
venience of the operator.
OBJECTS OF THE INVENTION
Accordingly, it is an object of this invention to
provide a vehicle having a single elongated frame element suspended
on a pair of quad wheel assemblies of massive rubber tires, with
each wheel being individually provided with traction power
and steering power and adjustably mounted relative to the
frame so as to permit the vehicle to traverse roadless terrain,
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and providing on the forward end of such vehicle a platform
which is selectively adjustable in height relative to the frame,
hence, relative to the ground, and which platfoxm carries an
operator's cab and, additionally, if desired, a tree engaging
boom, permitting the vehicle to engage a whole tree, sever it .
and place the tree between load carrying cradles mounted on
the elongated frame element.
A particular object of this invention is to provide
a tree harvesting vehicle having individual power means for
driving and steering each wheel of two quad wheel assemblies
which support a single el'ongated frame element of the vehicle
and each'wheel is mounted for movement about both a roll axis
parallel to the eIongated frame and a pitch axis perpendicular
to the longitudinal frame to permit the vehicle to traverse
natural terrain, and including means for adjusting the angular
position of the longitudinal frame element relative to the roll
axis of the vehicle so that the operator's platform, carried
on one end of the elongated frame, may at any time be positioned
in a relatively horizontal plane regardless of the slope of
the terrain on which the vehicle wheels may be .operating.
A further object of this invention is to provide a
self contained, self propeIled off-road vehicle having a plurality
of power means on the vehi'cle for individually driving and
steering each of a multiplicity of wheels, plus power means
for adjusting the vertical position of an operator's cab, plus
power means for operating a tree engaging boom and lastly,
power means for adjusting the vertical position of a power
producing unit which is shiftably mounted on the rear end of
the vehicle.
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Other objects and advantages of the invention will
become apparent to those skilled in the art from the following
detailed description, taken in conjunction with the annexed
sheets of drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side elevational schematic view of a
tree harvesting and transport vehicle embodying this invention.
Figure 2 is a plan view of Figure l.
Figure 3 is a perspective view of the major compo-
nents of the wheel suspension, driving and steering mechanismfor the vehicle of Figure 1.
Figure 4 is a perspective view of the roll control
mechanism interconnecting the front and rear wheel assemblies.
DESCRIPTION OF PREFERRED EMBODIMENT
The vehicle illustrated in the drawings is a trans-
portation vehicle for forwarding a load of whole trees from
a harvesting area in a forest to a processing area adjacent to
a road. Additionally, the illustrated vehicle is provided
with a tree severing and loading boom so that the entire
harvesting operation can be accomplished by a single vehicle.
Referring to the drawings, it will be seen that the
vehicle 1 comprises an elongated rigid tubular main frame 20,
including a plurality of load carrying cradle assemblies 22
spaced along its length and adapted to carry a plurality of
long objects, such as whole trees or tree trunks. Each cradle
22 comprises a transverse beam 23 having uprights 22a pivotally
secured to each end and latched in a vertical position by a
convention mechanism (not shown).
Front and rear quad wheel assemblies 24, 26 are
respectively attached to the elongated bed frame 20 by journals
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BZ
so as to be pivotally movable about a longitudinal roll axis
disposed parallel to and beneath the elongated bed frame.
A ro]l control linkage means 28 interconnects the quad
whee] assemblies with each other and with the elongated main
frame 20 so as to control their rélative positions about the
roll axis during operation over rough terrain.
At the front end of the vehicle 1, an operator's
platform 10 is provided and is secured to the front end of
bed frame 20 by a pair of parallel links 11 and 12 which are
pivoted on appropriate horizontal axis pivot pins lla and
12a, which are in turn supported by spaced, depending flanges
10a on platform 10. The other ends of links 11 and 12 are
pivotally secured to a U-shaped casting 20a secured to the
front end o~ the elongated main frame 20. The vertical position
of platform 10 is controlled by a hydraulic cylinder 14 which
is mounted in a trunion bearing 20b secured to the elongated
frame 20 and pivotally connected by piston rod 14b to an
upstanding bracket llb riyidly secured to the upper platform
supporting link 11. In this manner, the vertical height
of the platform 10 relative to the ground may be selectively
adjusted by actuation of the cylinder 14. Incidentally, when
ever this description refers to a hydraulic cylinder, it should
be understood that an electrically powered linear actuator may
be substituted therefor.
On the top surface of platform 10, a conventional turn-
table 13 is journalled for rotation about a vertical axis.
An operator's cab 15 is mounted on top of turntable 13 within
which all of the controls for the vehicle 1 are provided, as
well as an operator's seat (not shown). A lateral projection
13a of the turntable 13 provides a horizontal axis pivotal
mounting bracket 16a for a conventional articulated tree
handling bo~m 16. A plurality of hydraulic cylinders
'6~ and 16^ opcrat~ bctween the various articulated
g
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elements of boom 16 so as to permit the end of the boom to
be moved by the operator ~rom a position closely adjacent
the ground to a loading position passing over the top of the
cab 15 to deposit harvested trees in the load carrying cradles
22.
A conventional tree severing and engaging mechanism
17 is provided on the end of thearticulated boom 16 and its
position about a transverse horizontal axis is controlled by
a cylinder 17a and links 17b and 17c. The tree severing and
engaging mechanism 17 includes a suitable power actuated cut-
off means ~not shown). The construction of the tree engaging
and severing mechanism 17 forms no part of this invéntion and
hence will not be described in further detail. Suffice it to
say, such mechanism has the capability of engaging a tree to
be harvested, severing the tree near the ground and then, while
still engaged with the tree, the articulated boom 16 can be
operated by the various cylinders 16a, 16b and 17a to lift
the severed tree over the platform 10 and the operator's cab 15
and deposit the severed tree in the load carrying cradles 22
provided on the elongated frame 20.
Suitable operator controlled motor means (not shown)
are provided for turning turntable 13 about its vertical axis.
Hence, the tree engaging mechanism 17 can be swung horizontally
into engagement with a tree and the operator's cab is concurrently
moved, so that the operator's view is always aligned with the
tree to be harvested.
At the rear end of the elongated bed frame 20, a
power unit platform 80 is adjustably mounted for movement in
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113~2
a vertical plane by a pair of parallel links 81 and 82, which
are secured to appropriate pivots 83 provided in an end
casting 20d secured to the end of the main frame 20. A
hydraulic cylinder 84 suitably mounted in a trunion bearing
20e secured to the top of the rear end of the bed frame 20,
controls the vertical position of the power unit platform 80
by having its piston rod 84a pivotally connected to an up- ¦
standing bracket 81a secured to one of the parallel links 81.
In this manner, the vertical position of the power unit plat-
form 80 may be selectively adjusted to an elevated position
in order to clear obstacles on the terrain during either the
forward or rearward movement of the vehicle, or to a lowered
position adjacent the ground to permit convenient servicing of
the power unit 85 mounted thereon.
All of the power required for the operation of the
vehicle is provided by the power unit 85 mounted on platform
80 and such unit will normally comprise either a gasoline
or diesel engine driving both a large hydraulic pump to pro-
vide pressured fluid for the operation of all hydraulic cy-
linders involved in the vehicle and an electrical generator
for providing electrical power for the control circuits and
for providing traction and steering power to the wheels, if
electric motors are employed to operate same.
In the drawings, it will be noted that the front
and rear quad wheel assemblies 24 and 26 are substantially
identical to one another, so for the sake of brevity, the
similar portions will be described with respect to one of
them only. ~ccordingly, attention is directed to Figure 3 of
the drawings wherein the details of the front quad wheel
assembly 24 are illustrated.
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~ he suspension system for the ~ront quaù uheel
assembly includes a main pivot block 46 which is pivotally
suspended beneath the tubular main frame 20 between a pair
of depending blocks 20g, thus providing pivotal movement
about a longitudinal horizontal roll axis which is parallel
to and slightly below the axis of the tubular main frame 20.
Such pivotal mounting is not shown but is entirely convention-
al. A torque transmission tube 94 extends rearwardly from
the main pivot block 46 and is co-movable therewith about the
vehicle roll axis. A similar tube 95 extends forwardly from
the rear quad wheel assembly and the adjacent ends of tubes
94 and 95 are respectively interconnected by a roll control
linkage mechanism 28 to be hereinafter described.
The bottom portion of main pivot block 46 is provi-
ded with a pair of laterally projecting horizontal pivot pins
46a which respectively provide pivotal mounting for a pair of
walking beams 48 which are of identical configuration except
that they are mounted in reversed positions on the pivot pins
46a. Each walking beam 48 is of a generally truncated W-
shaped configuration in plan view including a central trun-
cated inverted V-shaped portion 48a defining the bearing for
the pivotal mounting on pin 46a, and identical angularly dis-
posed tubular end elements 48b which provide mountings for
steerable wheel units 60 of the quad wheel assemblies. The
horizontal angle of elements 48b determines the maximum wheel
turning angle.
A wheel mounting assembly 60 is secured to each
free end of walking beam 48, and, as described in detail in
my Canadian Patent No. 1,109,098, each wheel mounting
assembly 60 includes a main hollow housing 62 and a
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radially extending axle housing portion 64 connected to
housing 62 by a conventional anti-friction swing bearing unit
(not shown) to provide steering movements. On one side of
housing 62 an integral collar 65 is formed to permit the
; convenient rigid mounting of the housing 62 to the respective
tubular end 48b of the walking beam 48.
On the free end of axle housing portion 64 there
is mounted a wheel hub member 70 and the hub member 70 not
only provides for conventional mounting of a large, rubber
0 tired, ground engaging wheel 72 on its periphery, but also with-
in such hub mounts a conventional planetary trans~ission for
driving such wheel at reduced speed from a drive shaft which
is axially disposed within the hub 70 and the axle housing 64
and driven by an electric or hydraulic motor 74 co-axially
mounted on main housing 64.
A hydraulic or electric steering motor 80 is
suitably mounted on the top of the main housing 62, and effects
steering movements of axle housing 64 through a speed reduc-
tion mechanism (not shown).
The details of the controls for the rotation,
braking and turning of each wheel 72 are described in my
Canadian Patent No. 1,109,098.
From the description thus ~ar, it is also apparent
that each quad wheel assembly 24, 26 is suspended relative to
the main frame 20 in such fashion that the frame 20 may pivot
relative to the quad wheel assemblies about a roll axis which
is parallel to and slightly beneath the main frame 20. Con-
currently, the wheels on each side of the quad wheel assembly
may freely move in a vertical plane about a transverse hori-
zontal pivot axis defined by the walking beam pivot pin 46a.
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11.348~ `
Moreover, due to the "W" shape of each walking beam 48,
steering movements of each of the wheels up to a thirty degree
angle may be accomplished in either direction without inter-
ference with the suspension, the main frame or the load
carrying cradles of the vehicie.
The relative angular movement of the quad wheel
assemblies 24, 26 with respect to each other and to the
elongated bed frame assembly 21 is regulated by a roll control
linkage 28, centrally located on the vehicle, that causes
equal loading to be imposed on each quad wheel assembly, and
also causes tke bed frame assembly to be rotated proportion-
ately, preferably one half the total angular displacement
between the front and rear quad wheel assemblies, as exists
at any one time. Angular displacement between the quad wheel
assemblies relative to the roll axis obviously occurs during
operation on uneven terrain or over boulders. The ground under
the front quad wheel assembly may be laterally and possibly
oppositely inclined to the ground under the rear quad wheel
assembly, such as might occur while the vehicle is traversing
a ditch at an angle.
Referring now to Figure 4, the roll control linkage
28 will be described in greater detail. The rearward end of
torque tube 94 and the forward end of torque tube~95 are
suitably journalled in a depending frame block 20m and are
`~ 25 disposed in co-axially aligned relationship approximately in
the center of the elongated main frame 20. Immediately above
the ends of the torque tubes 94, 95, the frame 20 is provided
with a pair of upstanding pivot ears 20n which support a pivot
pin 33a which traverses the center portion of a transverse
frame titlt lever 33. On each end of frame tilt lever 33 a
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1~348~
longitudinal connecting lever 35 is centrally mounted for
pivotal movement about a horizontal axis. Additionally, on
each end portion of torque tubes 94 and 95, there are
respectively rigidly secured primary transverse actuating
levers 96 and 97 and the ends of these levers are in general
vertical alignment respectively with the ends of the connecting
levers 35. A plurality of links 37 are provided respectively
having their ends connected by a universal joint connection
to the aligned ends of primary levers 96 and 97 and the
connecting levers 35. Thus, any pivotal movement of one of
the quad wheel assemblies 24, 26 relative to the other will
result in a pivoting movement of the associated primary lever
96, 97, which in turn effects a tilting movement of the main
tilt control lever 33 to shift the position of the main frame
32 approximately one-half the amount of pivotal displacement
of the quad wheel assembly relative to the roll axis. Thus,
a very effective control of the movements of the main frame
about the roll axis in response to much larger movements of
the quad wheel assemblies is achieved and, in effect, the
roll control mechanism 28 provides for balancing the effects
of terrain induced rotations of the two quad wheel assemblies
in opposite directions about the roll axis.
Concurrently, the roll control linkage effects a
transfer of forces between the two quad wheel assemblies to
equalize the loading thereon during movements about the roll
axis.
While the modification of this invention heretofore
described is particularly useful in the hauling of long, stiff
objects, such as tree lengths, or pipes having a length on the
order of 60 feet, in some woodland operations, particularly as
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~13~38Z`
practiced in Canada, it is more desirable to employ an off-road
vehicle for bringing out loads of fresh cut whole trees. A
load of this type does permit some angular shifting of the load
supporting cradles as the transporting vehicle navigates diffi- ¦
cult terrain areas.
While the load supporting cradles 22 may be rigidly
secured to main frame 20, I prefer to utilize the illustrated
construction (Fig. 3) wherein the transverse beam 23 of the
cradle is pivotally mounted to the top surface of the main frame
20. Such pivotal mounting is provided by a pair of upstanding
ears 20h and a pivot pin 23a which traverses the cross-beam 23.
Each cross-beam 23 is effectively secured for co-movement with
the main pivot block 46 of the quad wheel assembly by a pair of
parallel links 40, each of which has a bifurcated end 40a
pivotally connected by a transverse pin 4Ob to the cross-beam
!: 23, and the other end 40c pivotally connected between a pair
of bifurcated ears 46b provided on the main pivot block 46
and traversed by a pivot pin 46c.
It may be desirable to form the load supporting
beams 23 with the outer ends inclined upwardly as shown at
23a in Figure 3, in order to provide additional clearance for
the quad wheel assembly. The important thing is that as each
quad wheel assembly moves about the roll axis to traverse the
terrain, a corresponding pivotal movement of the load support-
ing cradles is imparted by virtue of the parallelogram linkageconnection of the cross-beams 23 to the main pivot block 46.
At the same time, the roll control linkage 28 is still opera-
tive to effectively balance out oppositely directed inclinations
of the front and rear quad wheel assemblies and thus reduce to
a minimum the pivotal movements of the tubular bed frame 20
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113~382
~bout the roll axis.
The advantage of this construction is a significant
reduction in the height of the load carrying cradles relative
to the main frame, hence lowering the center of gravity of
the load.
A further feature of this invention is the addition
to the roll control lever assemblage 28 of a pair of power
actuated stabilizing links which permit the operator to adjust
the static position of the tubular main frame 20, hence the
operator's platform 10, relative to the roll axis. Referring
to Figure 4, such links may comprise power actuated exten-
sible elements 43 which are respectively connected between
the extreme ends of the tilt control lever 33 and the bifur-
cated ends of lateral projections 20k formed on a depending
block 2~m provided on the underside of the tubular bed frame
i~ 20. As the one stabilizing link 43 is extended by the appli-
cation of either hydraulic or electric power thereto, the
other link 43 is retracted so that the net effect is that the
frame 20 is rotated and the load supporting cradles or cross-
beams 23 are shifted laterally and angularly with respect to
the roll axis. Thus, the load may be maintained in a sub-
stantially horizontal position, even though the vehicle is
being operated continuously on a hillside. This capability for
adjusting the static angular position of the load carrying
cradles relative to the roll axis provides additional sta-
bility to the vehicle and hence permits larger loads to be
safely carried along a relatively steep hillside,
Of equal importance is the fact that the adjustment
of the position of the main frame 20 with respect to the roll
axis by the selective actuation of the extensible links 43 is
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11~32~8~3~
of great value in permitting the operator's platform to be
maintained in a substantially horizontal position irrespective
of t~e slope of the terrain on which the vehicle may be located.
Thus, even though the vehicle is operating along the side of
a relatively steep slope, the operator's platform 10 may be
maintained in a substantially horizontal position, resulting
in the tree-engaging element 17 on the end of boom 16 being
generally vertically disposed, hence, more readily engagable
with trees growing on the slope which normally grow vertically,
irrespective of the slope. On the other hand, if the harvest-
ing vehicle approaches a tree which is growing at an angle,
the selective adjustment of the stabilizing links 43 by the
operator will permit the main frame 20 and the platform 10
to be tilted relative to the supporting wheels so that the
tree engaging mechanism 17 is more accurately aligned with the
slope of the tree to be harvested.
It will also be apparent that an extreme extension
of either of the stabilizing links 43 can advantageously effect
the dumping of the load on a selected side of the vehicle. The
vertical rails 22a of each cradle are pivotally mounted on the
ends of the transverse beam and only latched in the upright
position so that they may be readily dropped for unloading. It
should be recognized that when dumping is accomplished in this
manner, the operator's cab is tilted to the same degree. The
dumping of the load is then accomplished by tilting of the load
carrying cradles 22 with respect to the main frame 20. This can be
conveniently accomplished by utilizing power actuated extensible
elements as the links 40 which interconnect the transverse
beams 23 of the load carrying cradles 22 with the vehicle
suspension. The extension of one link 40 while the other link
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113~88~`
is retracted will permit the selective dumping of the load on
either side of the vehicle~ During all other operations, the
extensible elements 40 are maintained in a fixed length
position.
It will be very apparent to those skilled in the
art that the flexibility, hence efficiency, of the described
tree harvesting vehicle is outstanding. Not only will the
vehicle traverse rough roadless terrain, but major components
of the vehicle, namely the operator's platform, the tree en-
gaging mechanism and the power supply can all be vertically
raised to clear upstanding obstructions or lowered to clear
overhanging obstructions. Under all operating conditions, the
operator's cab may be maintained by the operator in a substan-
tially vertical normal position, regardless of the contour of
the terrain over which the vehicle is traversing or on which
i it is stationary, thus insuring not only maximum comfort to
the operator, but minimum interference with his operation of
the vehicle. At any time that a particular tree is to be
harvested, the tree engaging ~echanism 17 can be swung
horizontally by virtue of the turntable 13 to engage the tree
~; without requiring the movement of the entire vehicle and the
operator's cab moves concurrently with the tree engaging
elements of the machine, thus affording the operator unimpeded
vision of the harvesting operation.
Modifications of the invention herein descri~ed
and illustrated will be apparent to those skilled in the art
` and it is intended that the scope of the invention be deter-
mined solely by the appended claims.
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