Note: Descriptions are shown in the official language in which they were submitted.
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TANDEM WHEEL ASSEMBLY AND MOBILE SILVICULTURAL APPARATUS
INCLUDING THE SAME
Field of the invention:
The present invention relates to an improved tandem wheel assembly.
More particularly, the present invention relates to a tandem wheel assembly
with
an improved power transmission shaft and to a mobile silvicultural apparatus
provided with such a tandem wheel assembly, generally a pair of such tandem
wheel assemblies, the apparatus being used for carrying out various harvesting
applications. The present tandem wheel assembly may be used on other types of
apparatuses and vehicles, and in various other different fields, such as
construction, mining, agriculture and the like.
Background of the invention:
20
Wheel assemblies, and in particular, wheel assemblies known as "tandem"
wheel assemblies, because each wheel assembly generally comprises "a. pair of
wheels, as well as the corresponding power transmission mechanisms used
therewith, are well known in the art.
Indeed, these wheel assemblies may be used on various different types of
vehicles and/or apparatuses and enable them to travel over uneven and/or
rugged terrain for carrying out different applications, depending on the field
for
which they are intended.
Figure 1 shows a typical example of a conventional tandem wheel
assembly and corresponding power transmission mechanism. Such a
conventional tandem wheel assembly is commercialized by a German company
called NAF. This type of assembly is used widely on mobile silvicultural
apparatuses employed for carrying out harvesting applications.
As shown, the tandem wheel assembly comprises a segment including
gears 103 at the entrance (some gears have been omitted for sake of clarity),
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which are typically located at the center of the tandem. The gears 103 are
generally mounted in a profiled recess which is sealed in an air-tight manner
so
as to enable the gears to continuously soak in lubrication means, such as an
oil
bath, for example. The gears, placed in series, enable to transmit the power
coming from the transmission, for the propulsion of the vehicle, up to the
wheels
of said vehicle. In order to maximize the comfort of a user in the vehicle
during
the displacement thereof on a land to be worked, such as a forest, for
example,
fihe tandem is mounted on the frame of the vehicle by means of a large ball
bearing enabling the tandem to rotate about ifs center.
As can be easily understood from Figure 1, the transmittal of power
coming from the transmission and being redirected towards the wheels is
normally carried out as follows: a driving shaft 105 with universal joints
originates
from the exit of the transmission in order to get to the entrance of the
central gear
box, and a gear pair 107 transmits the power into the power firansmission
shafts
109 directed towards the gears 103 of the tandem.
It is also known in the art that the distance "L" between the supports of a
power transmission shaft 109 is generally large. Indeed, the more a
silvicultural
apparatus is wide, the more this distance "L" becomes substantial.
A substantial problem associated with the above-mentioned type of
tandem wheel assembly is that it is not intended to efficiently receive and
cooperate. with hydraulic motors for driving the mobile silvicultural
apparatus. This
is particularly true when the ground-clearing portion of a front unit of the
apparatus is substantially high with respect to the ground on which the
apparatus
travels.
Tandem wheel assemblies with hydraulic motors are known in the art, and
generally comprise an hydraulic motor mounted onto the tandem support frame,
and being operatively connected to the wheels by means of a corresponding
power transmission system for imparting motion to the wheels via a power
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transmission shaft. However, the conventional power transmission shaft is a
single, rigid and elongated shaft, which during normal working conditions is
subjected to substantial loads, particularly when there is a misalignment in
certain
components of the tandem wheel assembly (e.g. large central bearing) as a
result
of the apparatus travelling over rugged andlor uneven terrain. Consequently,
the
life span of such a power transmission shaft is fairly small, requiring
considerable
maintenance and/or replacement, which is costly and thus disadvantageous.
Known to the Applicant are the following US patents and patent
applications which describe various wheel assemblies: 3,154,163; 3,349,863;
3,360,068; 3,471,166; 3,476,200; 3,481,418; 3,693,743; 3,810,516; 3,831,961;
4,222,578; 4,417,634; 4,647,067; 4,804,205; 4,824,418; 4,869,556; 5,191,952;
5,211,610; 5,339,611; 5,482,326; 5,911,286; 6,012,724; 6,193,007 B1; 6,625,967
B1; 6,698,478 B2; 200210092687 A1; and 2004/0060271 A1; as well as German
patent application No. 3828332 A1.
However, none of these documents seem to teach a tandem wheel
assembly which resolves the above-discussed problems, namely 'in regards to
the use of an hydraulic motor within a restrained space (i.e. small distance
"L") or
the shod life span of the power transmission shaft 109.
Hence, in light of the aforementioned, there is a need for an improved
tandem wheel assembly which, by virtue of its design and components, would be
able to overcome some of the above-discussed prior art problems.
Summary of the invention:
The object of the present invention is to provide a tandem wheel assembly
which satisfies some of the above-mentioned needs and which is thus an
improvement over other related tandem wheel assemblies known in the prior art.
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In accordance with the present invention, the above object is achieved, as
will be easily understood, with a tandem wheel assembly for use with a mobile
apparatus, the tandem wheel assembly comprising:
a support frame for mounting onto a base frame of the mobile apparatus;
a pair of wheels pivotally mounted onto the support frame;
a motor mounted onto the support frame for providing power to the wheels
so as to impart a rotation of fihe wheels; and
a power transmission system operatively connected between the motor
and the wheels for transmitting power from the motor to said wheels, the power
transmission system comprising a rotatable power transmission shaft having
first
and second components each having a longitudinal axis, said first and second
components being connected to each other via coupling means for enabling the
first and second components to rotate together as part of the rotatable power
transmission shaft, white allowing the longitudinal axis of the second
component
to be displaced at an angle with respect to the longitudinal axis of the first
component, so as to sustain a transversal load component subjected to said
rotatable power transmission shaft.
Preferably, the coupling means comprise:
a plurality of longitudinal splines provided about a peripheral outer surface
of an end portion of the first component, the longitudinal splines extending
in a
direction substantially parallel to the longitudinal axis of the first
component; and
a plurality of corresponding longitudinal slots provided about a peripheral
inner surface of an end portion of the second component, the longitudinal
slots
extending in a direction substantially parallel to the longitudinal axis of
the second
component;
wherein the longitudinal splines of the first component are shaped and
sized so as to be removably insertable into the corresponding longitudinal
slots of
the second component, so as to have the first and second components rotate
together about their respective longitudinal axes while allowing the
longitudinal
axis of the second component to be displaced at an angle with respect to the
longitudinal axis of the first component.
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According to another aspect of the invention, there is also provided a
mobile sylvicultural apparatus for travelling over a given terrain for
carrying out
harvesting work on said terrain, the mobile sylvicultural apparatus
comprising:
5 a steerable wheeled base frame comprising a horizontally extending
ground-clearing section, and first and second opposite vertical side sections;
harvesting means mounted to the steerable wheeled base frame for
carrying out harvesting work on the terrain when the sfeerable wheeled support
frame travels thereover;
at least one tandem wheel assembly for imparting motion to the steerable
wheeled base frame, the least one tandem wheel assembly comprising:
a support frame mounted onto the steerable wheeled base frame of
the mobile sylvicultural apparatus;
a pair of wheels pivotally mounted onto the support frame;
a motor mounted onto the support frame for providing power to the
wheels so as to impart a rotation of the wheels; and
a power transmission system operatively connected between the
motor and the wheels for transmitting power from the motor to said wheels,
the power transmission system comprising a rotatable power transmission
shaft having first and second components each having a longitudinal axis,
said first and second components being connected to each other via
coupling means for enabling the first and second components to rotate
together as part of the rotatable power transmission shaft, while allowing
the longitudinal axis of the second component to be displaced at an angle
with respect to the longitudinal axis of the first component, so as to sustain
a transversal load component subjected to said rotatable power
transmission shaft; and
control means for controlling the steerable wheeled base frame, the
harvesting means, and the at least one tandem wheel assembly.
According to another aspect of the invention, there is also provided a
rotatable power transmission shaft pivotally mounted about supports of a
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corresponding power transmission system, the power transmission shaft having
first and second components each having a longitudinal axis, said first and
second components being connected to each other via coupling means for
enabling the first and second components to rotate together as part of the
rotatable power transmission shaft, while allowing the longitudinal axis of
the
second component to be displaced at an angle with respect to the longitudinal
axis of the first component, so as to sustain a transversal load component
subjected to said rotatable power transmission shaft.
The objects, advantages and other features of the present invention will
become more apparent upon reading of the following non-restrictive description
of a preferred embodiment thereof, given for the purpose of exemplification
only,
with reference to the accompanying drawings.
Brief description of the drawings:
Figure 1 is a fop sectional view of a tandem wheel assembly and
corresponding transmission mechanism according to the prior art.
Figure 2 is a top sectional view of a tandem wheel assembly according to a
first preferred embodiment of the present invenfiion.
Figure 3 is an exploded view of what is shown in Figure 2, and better
illustrating the first and second components of the power transmission shaft.
Figure 4 is a side view of the first component of the power transmission
shaft shown in Figure 3.
Figure 5 is a front plan view of what is shown in Figure 4.
Figure 6 is a rear plan view of what is shown in Figure 4.
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Figure 7 is a side view of the second component of the power transmission
shaft shown in Figure 3.
Figure 8 is a front plan view of what is shown in Figure 7.
Figure 9 is a side view of the abutment ring of the power transmission shaft
shown in Figure 3.
Figure 10 is a front plan view of what is shown in Figure 9.
Figure 11 is a side view of the abutment ring of Figure 9, and the second
component of Figure 7, assembled onto the first component of Figure 4, so as
to
form the power transmission shaft of the tandem wheel assembly shown in Figure
2.
Figure 12 is a front plan view of what is shown in Figure 11.
Figure 13 is a rear plan view of what is shown in Figure 11.
Figure 14 is another side view of what is shown in Figure 11, the second
component being shown now displaced at an angle with respect to the first
component.
Figure 15 is a partial front plan view of a base frame of a mobile apparatus
provided with a pair of tandem wheel assemblies according to the present
invention.
Detailed description of a preferred embodiment of the invention:
In the following description, the same numerical references refer to similar
elements. The embodiments shown in Figures 2-15 are preferred.
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Moreover, although the' present invention was primarily designed as a
tandem wheel assembly for use with a mobile sylvicultural apparatus for
harvesting applications and the like, it may be used on other types of wheel
assemblies, having only one wheel for example, as well as on other types of
apparatuses and vehicles, and in various other different fields, such as
construction, mining, agriculture and the like, as apparent to a person
skilled in
the art. For this reason, expressions such as "tandem", "sylvicultural",
"harvesting", "trees", "brush", etc., used herein should not be taken as to
limit the
scope of the present invention and includes all other kinds of objects and/or
applications with which the present invention could be used and may be useful.
As will also be easily understood, the coupling means of the assembly 1
according to the present invention is not necessarily limited to crowned
splines
and slots, and may take on other suitable embodiments, as apparent to a person
skilled in the art.
Moreover, in the context of the present invention, the expressions
"tandem" and "wheel assembly", as well as any other equivalent expressions
and/or compound words thereof, may be used interchangeably. The same
applies for any other mutually equivalent expressions, such as "tandem" and
"support frame" for example, as well as "transmission shaft" and "driving
shaft",
as also apparent to a person skilled in the art.
In addition, although the preferred embodiment of the present invention as
illustrated in the accompanying drawings comprises various components such as
bearings, sealing joints, rings, bolts, etc., and although the preferred
embodiment
of the tandem wheel assembly 1 and corresponding parts as shown consist of
certain geometrical configurations as explained and illustrated herein, not
all of
these components and geometries are essential to the invention and thus should
not be taken in their restrictive sense, i.e. should not be taken so as to
limit the
scope of the present invention. It is to be understood, as also apparent to a
person skilled in the art, that other suitable components and cooperations
thereinbetween, as well as other suitable geometrical configurations may be
used
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for the tandem wheel assembly 1 and corresponding parts according to the
present invention, as will be briefly explained herein and as can be easily
inferred
herefrom, without departing from the scope of the present invention.
Broadly described, the present invention, as illustrated in the
accompanying drawings, relates to an improved tandem wheel assembly 1, and
to a mobile apparatus provided with such an assembly 1. Typically, a mobile
apparatus comprises a pair of such tandem wheel assemblies 1, generally one
tandem wheel assembly 1 (each assembly 1 having preferably two wheels) on
each side of a front unit of the apparatus, as can be easily understood when
referring to Figures 2, 3 and 15.
According to the preferred embodiment of the present invention, the mobile
apparatus is a mobile "sylvicultural" apparatus, such as the ones described in
Applicant's US patent Nos. 6,550,505 and 6,698,478, which are intended to
carry
out various types of "harvesting" applications, such as land clearing, for
example,
and the like, the content of these patents being incorporated herein by
reference.
Indeed, broadly described, and as can be easily understood when referring
to Figure 15, the mobile sylvicultural apparatus according to the present
invention
is preferably used for travelling over a given terrain for carrying out
harvesting
work on said terrain, and preferably comprises a steerable wheeled base frame
3
comprising a horizontally extending ground-clearing section 5, and first and
second opposite vertical side sections 7; harvesting means (or "manipulating"
means - not shown) mounted to the steerable wheeled base frame 3 for carrying
out harvesting work on the terrain when the steerable wheeled support frame 3
travels thereover; at least one tandem wheel assembly 1 for imparting motion
to
the steerable wheeled base frame 3; and control means (not shown) for
controlling the steerable wheeled base frame, the harvesting means, and the at
least one tandem wheel assembly 1.
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According to the present invention, and as better shown in Figures 2 and
3, the tandem wheel assembly 1 comprises a support frame 11 (also referred to
simply as "tandem") for mounting onto the base frame 3 of the mobile
apparatus;
a pair of wheels 13 pivotally mounted onto the support frame 11 about a
5 corresponding pivot axis; a motor 15 (preferably, an hydraulic motor 15)
mounted
onto the support frame 11 for providing power to the wheels 13 so as to impart
a
rotation to the wheels 13; and a power transmission system 17 operatively
connected between the motor 15 and the wheels 13 for transmitting power from
the motor 15 to said wheels 13. As shown in Figure 3, and better illustrated
in
10 Figures 4-14, the power transmission system 17 comprises a rotatable power
transmission shaft 19 having first and second components 19a, 19b, each having
a longitudinal axis 21, 23, said first and second components 19a, 19b being
connected to each other via coupling means 25 for enabling the first and
second
components 19a, 19b to rotate together as part of the rotatable power
transmission shaft 19, while allowing fihe longitudinal axis 23 of the second
component 19b (i.e. the second component 19b) to be displaced at an angle 8
with respect to the longitudinal axis 21 of the first component 19a (i.e. the
first
component 19a), as better shown in Figure 14, so as to be able to better
sustain
a transversal load component subjected to said rotatable power transmission
shaft 19, as can be easily understood by a person skilled in the art.
Preferably, as better shown in Figures 4-8, and as can be easily
understood when referring to Figures 11-14, the coupling means 25 comprise a
plurality of longitudinal splines 27 provided about a peripheral outer surface
of an
end portion of the first component 19a, the longitudinal splines 27 extending
in a
direction substantially parallel to the longitudinal axis 21 of the first
component
19a (see Figs. 4-6); and a plurality of corresponding longitudinal slots 29
provided
about a peripheral inner surface of an end portion of the second component
19b,
the longitudinal slots 29 extending in a direction substantially parallel to
the
longitudinal axis 23 of the second component 19b (see Figs. 7 and 8). The
longitudinal splines 27 of the first component 19a are shaped and sized so as
to
be removably insertable into the corresponding longitudinal slots 29 of the
second
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component 19b, so as to have the first and second components 19a, 19b rotate
together about their respective longitudinal axes 21, 23 white allowing the
longitudinal axis 23 of the second component 19b to be displaced at an angle 8
with respect to the longitudinal axis 21 of the first component 19a, as can be
easily understood when comparing Figures 11 and 14. The splines 27 and the
slots 29 (defined by other neighboring splines, as can be easily understood)
are
preferably made by a suitable manufacturing process, such as machining for
example, as apparent to a person skilled in the art.
Preferably also, the coupling means 25 comprise an abutment ring 31
mounted about a corresponding peripheral recess 33 of the first component 19a
for abutting against the end portion of the second component 19b so as to
delimit
the positioning of the second component 19b with respect to the first
component
19a, as can be easily understood when referring to Figures 4, 9 and 11. The
inside bore of the abutment ring 31 preferably has tapered sections
complementary to the end portions of the first and second components with
which
it cooperates, as better shown in Figures 9, 11 and 14.
Preferably also, the first and second components 19a, 19b are tubular
components, and along with the abutment ring 31, and the other components of
the tandem wheel assembly 1, are preferably made of suitable materials, and
provided with suitable lubrication means, if need may be, as apparent to a
person
skilled in the art.
As better shown in Figures 4 and 5, the other end portion of the first
component 19a is also preferably provided with a plurality of longitudinal
splines
provided about a peripheral outer surface of said another portion of the first
component 19a, said longitudinal splines extending in a direction
substantially
parallel to the longitudinal axis 21 of the first component 19a and destined
to
cooperate with the motor 15, as apparent to a person skilled in the art.
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Preferably also, as can be easily understood when referring to Figures 7
and 13, the other end portion of the second component 19b is provided with a
plurality of gear teeth 35 provided about a peripheral outer surface of said
another portion of the second component 19b, for cooperating with the tandem
support frame 11, as also apparent to a person skilled in the art.
The tandem wheel assembly 1 according to its preferred embodiment, as
better shown in Figures 2 and 3, and as apparent to a person skilled in the
art,
preferably comprises the following components: a pair of tires or wheels 13; a
tandem support frame 11; a securing bearing 37 of the tandem; a self-aligning
bearing 39; a power transmission or driving shaft 19; a tapered roller bearing
41;
a base frame of the vehicle; a sealing joint 43; a tapered roller bearing 45;
a
retaining ring 47; a hydraulic motor 15; a securing bolt 49 of the bearing on
tandem; a securing bolt 51 of the bearing of the tandem on frame of vehicle;
and
a securing bolt 53 of the hydraulic motor 15 (some gears 103 in the tandem 11
have been omitted for sake of clarity).
As may now be better appreciated, the present invention is a substantial
improvement over the prior art in that, as aforementioned, an important aspect
of
the present invention resides in the fact that instead of having a single,
rigid and
elongated transmission shaft as is the case with conventional tandem wheel
assemblies, the tandem wheel assembly 1 according to the present invention
comprises an improved transmission shaft 19 having at least two parts or
components 19a, 19b, as better shown in Figures 3-14. The above-described
coupling means' 25 enable these two components 19a, 19b of the power
transmission shaft 19 to be connected together and thus rotate in unison, as
the
transmission shaft 19 rotafies, to carry out its normal driving function,
while at the
same time, enabling these two components 19a, 19b to be unaligned (i.e.
displaced at an angle 8) with respect to each other, as better shown in Figure
14,
in order to have a "flexible zone" in the transmission shaft 19, and thus be
able to
better support loads and/or displacements to which the transmission shaft 19
of
wheel assembly 1 may be subject to. Thus, the complementary crowned splines
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27 and corresponding slots 29 offer a suitable flexibility to the power
transmission
shaft 19, i.e. enable to achieve a large misalignment between the first and
second
components 19a, 19b, within a more restrained space (smaller distance "L'.' -
see
Fig. 2), which is also very advantageous, particularly when using hydraulic
motors
15 in tandem wheel assemblies 1.
It is worth mentioning once again that although the present invention was
primarily intended for silvicultural applications, the present tandem wheel
assembly 1, and the apparatus provided with such an assembly 1, may be used
in other fields and for other applications, such as for mining applications,
agricultural applications, and the like, as apparent to a person skilled in
the art,
without departing from the scope of the present invention. Furthermore,
according
to the present invention, the power transmission shaft 19 and corresponding
first
and second components 19a, 19b, with abutment ring 31, etc., such as the ones
briefly described herein and such as the ones exemplified in the accompanying
drawings, could be used as a power transmission shaft 19 in other types of
wheels assemblies, such a single-wheel assemblies, as can be easily understood
by a person skilled in the art. Further, as aforementioned, other suifiable
coupling
means 25 for connecting the first and second components 19a, 19b, in the
manner described herein, may be used according to the present invention, as
apparent to a person skilled in the art.
Of course, numerous modifications could be made to the above-described
embodiments without departing from the scope of the invention, as defined in
the
appended claims.
