Note: Descriptions are shown in the official language in which they were submitted.
CA 02242538 1999-07-06
Axial-Drive Felling Head
Field of the Invention
The present invention relates to logging machinery and, more particularly, to
an improved
felling head for gripping, cutting and manipulating trees.
Background of the Invention
For many years now, felling heads have replaced the traditional chainsaw in
most logging
operations where trees are ofmedium diameter. The felling head is usually used
to restrain, cut,
accumulate and pile trees in .a single, quick operation. The felling head is
normally mounted on
the end of a suitable tree cutting carrier's manipulator arm, which is, in
turn, mounted to a tractor
or tracked vehicle. The felling head is a much more efficient device than the
traditional hand-
carried chainsaw and, surprisingly, it causes less damage to the environment
because felled trees
are not dragged on the forest floor, crushing and uprooting young stems,
saplings and
undergrowth.
Some felling heads ale especially well-suited for manipulating trees mainly
because they
can be tilted back and forth as well as sideways. In this specification, the
expression "tilted back
and forth" refers to the pitch of the frame as illustrated in Figure 1.
Similarly, the expressions
"tilted sideways" or "side tilt" should be construed to refer to the roll of
the frame about the axis
of rotation of the drive shaft of the motor as illustrated in Figure 6.
The back and forth tilting motion is achieved by a hydraulic actuator normally
installed
on the manipulator arm (or crane). The double attachment of the felling head
to the manipulator
arm allows the felling head to pivot about one of the attachment points while
the hydraulic
actuator pushes or pulls on the other attachment point. This back and forth
tilt (or pitch) makes
it possible for the felling head to position itself parallel to the tree and,
after the cut, to lay the
tree on the ground.
CA 02242538 1999-07-06
In addition to the back and forth pitch, the sideways tilting motion (i.e. the
roll) gives the
felling head greater maneuverability in gripping, cutting and manipulating
trees and thus
increases the potential for producing larger piles of trees in a given period
of time without having
to constantly readjust the position of the tractor. Thus, a highly
maneuverable felling head
increases the efficiency of the logging operation. Furthermore, since the
felled trees can be easily
manipulated and piled in a convenient location for the transporter to pick
them up, the harvesting
minimizes the damage to neighboring trees and saplings.
Although the present description deals primarily with the gripping, cutting
and
manipulating of trees, it should be appreciated by a man skilled in the art
that the felling head
of the present invention could also be used to grip, cut and manipulate wooden
poles (e.g.
telephone poles or power-line poles) or, with a different type of saw blade
practically any tree-
like or pole-like object.
In the prior art, many different types of mechanisms have been used to create
the side
tilting motion of the felling head. Some prior art systems use a pair of
hydraulic actuators
mounted on the felling head that are linked to a large gear, itself linked to
a central gear around
which the tilting motion is achieved. The hydraulic actuators push and pull
simultaneously on
the large gear, thereby rotating the felling head around the central gear. In
this case, the rotation
is limited by the travel of thc; hydraulic actuators to a side tilt rotation
of about 180 degrees.
Other systems use a hydraulic motor and chain arrangement. A hydraulic motor
with a
drive shaft and sprocket is mounted on the felling head and linked with a
chain to a large central
sprocket located at the rotational axis of the felling head. When the motor
sprocket turns, it
induces a side tilting motion to the felling head. This arrangement has a much
larger rotational
range than the hydraulic actuator arrangement described in the previous
paragraph. Its range can
reach 360 degrees.
Other combinations of gear assembly or gears and chains assembly are commonly
used
in the prior art but they all share the same feature of having the components
necessary for the
side-tilt rotation mounted in .a position that is not coaxial with the side-
tilting axis of rotation of
the frame of the felling head.
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These prior art arrangements tend to be bulky, heavy and generally involve
moving parts
that are often exposed to the rigorous environment of the logging field.
Exposed components
such as gears, chains, sprockets or hydraulic actuators, are susceptible to
being hit and damaged.
Open moving parts are prone to becoming tangled in branches. Furthermore, dust
and dirt tend
to clog lubricated moving components and thus these arrangements require
regular maintenance
to avoid breakdowns.
Thus, there is a need in the logging industry for an improved felling head.
Objects and Statement of the Invention
It is therefore an object of the present invention to provide a felling head
that is light and
thus more maneuverable.
It is another object of the present invention to provide a felling head that
is compact.
It is another object of the present invention to provide a felling head that
is mechanically
reliable and requires very little maintenance.
It is another object of the present invention to provide a felling head that
has few moving
parts.
It is another object of the present invention to provide a felling head that
is less
susceptible to damage.
It is another object of the present invention to provide a felling head that
has few
components and is thus easy and inexpensive to manufacture.
As embodied and broadly described herein, the present invention provides a
felling head
for mounting to a suitable tree cutting carrier's manipulator arm for
restraining, cutting and
manipulating trees, the felling head comprising: a frame, a holder for
connecting the frame to the
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manipulator arm; a bearing-like member rotatably connecting the frame to the
holder, the
bearing-like member defining a rotational axis about which the frame may
rotate; and a motor
having a drive shaft rotatable about the rotational axis. The drive shaft is
coupled to the bearing-
like member, whereby, in operation, the motor is adapted to impart rotational
motion to the
frame. Such a coaxial arrangement simplifies the transmission of torque from
the motor to the
frame. By minimizing the size and complexity of the transmission, the
manufacturing cost and
overall weight of the felling head is reduced. Furthermore, by minimizing the
number of
moving parts associated with a transmission system, the reliability of the
overall felling head is
improved and maintenance requirements become less demanding.
Advantageously, the felling head further comprises a gear assembly. A gear
assembly
augments the torque produced by the motor so that a large torque is exerted on
the frame, thus
permitting the manipulation of loads having high inertia.
Advantageously, the motor is mounted to the holder. Without the additional
weight of
the motor, the frame is lighter. Since the frame is lighter, the frame is more
maneuverable and
can achieve higher angular accelerations for a given motor torque rating.
Moreover, since the
frame is lighter, not only is the frame more maneuverable but the amount of
energy dissipated
during operation is less than the energy dissipated had the motor been located
on the frame.
Furthermore, the presence of the motor on the holder simplifies the hydraulic
routing to the
motor which thus leaves the frame unencumbered by hydraulic lines. When
operating amid thick
branches, a felling head without hydraulic lines running from the manipulator
arm to the frame
is less likely to become ensnared or tangled.
Advantageously, the holder defines a cavity in which the motor is at least
partially
housed, the drive shaft protruding from the cavity. Thus, the holder at least
partially protects the
motor from collisions with trees, branches, dirt and other deleterious
elements of the
environment.
Advantageously, the frame defines a cavity in which the gearbox is at least
partially
housed, the gearbox being adapted to cooperate with the drive shaft. Thus, the
frame at least
partially protects the gearbox from collisions with trees, branches, dirt and
other deleterious
elements of the environment.
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Advantageously, the gear assembly comprises a planetary gear. The use of a
planetary
gearbox ensures that a very ;Large gear ratio is obtained between the drive
shaft of the motor and
the frame. In other words, a. planetary gearbox can greatly augment the torque
produced by the
drive shaft of the motor. While the torque necessary to rotate the frame is
large, the torque
required to rotate the frame when gripping a multitude of tall trees can
become enormous. Thus,
a planetary gearbox is preferable to increase the torque output by the drive
shaft of the motor to
a level sufficient to rotate and manipulate both the frame and the frame's
load of trees.
Other objects and features of the invention will become apparent by reference
to the
following description and drawings.
Brief Description of the Draw_ inns
A detailed description of the preferred embodiments of the present invention
is provided
hereinbelow, by way of example only, with reference to the accompanying
drawings, in which:
Figure 1 is a side ele;vational view of a felling head mounted on a typical
tree cutting
earner's manipulator arm in a logging environment;
Figure 2 is a side elevational view of a first embodiment of an axial-drive
felling head
in accordance with the present invention;
Figure 3 is a rear elevational view of the felling head of Figure 2 showing
the details of
the holder;
Figure 4 is a side elevational view of the motor and gear assembly arrangement
of the
felling head of Figure 2;
Figure 5 is a rear elev.ational view of the planetary-type gear assembly of
the felling head
of Figure 2;
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Figure 6 is a rear elevational 'view of the felling head of Figure 2, rotated
about the axis
of rotation of the drive shaft;
Figure 7 is a side ele;vational view of a variant of the felling head of
Figure 2, showing
a motor linked to the frame via a bearing-like member;
Figure 8 is a side elevational view of a second embodiment of the present
invention,
illustrating a felling head wherein the motor is located on the frame and the
gear assembly is
located on the holder;
Figure 9 is a side ele;vational view of a variant of the second embodiment of
Figure 8
wherein a bearing-like member is located on the holder; and
Figure 10 is a top plan view of a path that a tractor could follow to produce
an efficient
and environmentally-conscious tree-piling pattern.
In the drawings, preferred embodiments of the invention are illustrated by way
of
examples. It is to be expressly understood that the description and drawings
are only for the
purpose of illustration and ale an aid for understanding. They are not
intended to be a definition
of the limits of the invention.
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Description of the Preferred Embodiment
Figures 1 and 2 illustrate a first embodiment of a felling head according to
the present
invention designated comprehensively by the reference numeral 10. The felling
head 10 is
mounted to a tilting holder 30 which in turn is normally attached to a
manipulator arm 5 of a tree
cutting earner 4 or other such vehicle. The felling head 10 is made of a frame
20 on which is
typically mounted a plurality of restraining arms 15 used to restrain the
trees as the saw blade
located normally at the base 21 of the frame 20 cuts the bottom part of the
tree trunk. The frame
20 is provided with a transmission arrangement, for example a gear assembly
50. In the
illustrated example, the gear assembly 50 is of planetary type. The planetary
gear assembly 50
is solidly affixed to the tilting holder 30. The tilting holder 30 has a
cavity in which a hydraulic
motor 40 is at least partially housed. The motor 40 is coupled to the gear
assembly 50 via a drive
shaft 45 which transfers the rotary motion of the motor 40 to the gear
assembly 50. Since the
frame 20 is fixed to the outer shell of the gear assembly 50, the frame 20
therefore follows the
rotation of the gear assembly. The frame 20 rotates about the axis of the
drive shaft 45. For the
purposes of this specification, this arrangement is termed "coaxial" since the
axis of rotation of
the drive shaft 45 is in alignment with the axis of rotation of the frame 20.
Furthermore, this
arrangement permits the frame 20 to rotate at least 360 degrees with respect
to the holder 30.
Thus, the felling head 10 cm be maneuvered into practically any posture for
gripping, cutting
and manipulating trees.
In normal use, the tree cutting earner 4 is positioned near a tree 2. The
manipulator arm
5 is extended and the frame :? 0 of the felling head 10 is positioned
preferably parallel to the tree
trunk. Depending on the position of the tractor 4 relative to the tree 2, the
felling head 10 may
need to be tilted backward or forward and/or sideways.
To control the backward and forward motion of the felling head 10, the
operator actuates
the hydraulic actuator 8. The holder 30 is linked to the manipulator arm 5 by
a pivoting point
32 and to the hydraulic actuator 8 at a pivot point 34 of the holder 30. As
the hydraulic actuator
8 pulls or pushes at the pivot point 34, the holder 30 and therefore the
felling head 10 rotate
about the pivoting point 32. l:f the operator needs to tilt the felling head
10 sideways, he actuates
the hydraulic motor 40. The: drive shaft 45 of the motor 40 imparts rotary
motion to the gear
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assembly 50 and therefore to the felling head 10.
When the felling head 10 is properly aligned with the tree 2, the restraining
arms 15 open
and grasp the tree 2. In that name motion, the saw located at the base 21 of
the frame 20 cuts the
tree 2. With the tree cut and. firmly held by the restraining arms 15 of the
felling head 10, the
manipulator arm 5 lifts the tree 2, the motor 40 rotates the frame 20 so that
the length of the tree
is generally parallel to the ground and then, finally, the manipulator arm 5
lays the tree 2 on the
ground in a position that will be easily accessible for the collection vehicle
to pick up and carry
away. To facilitate the pick-up procedure, it is preferable to make neat piles
of trees, having
every tree parallel to each other. This is why the sideways rotation, or roll,
of the felling head
10 is advantageous. Because the felling head 10 is able to tilt sideways, the
operator is able to
place every tree parallel to each other even if he has moved the tree cutting
earner 4 to a new
location.
Figure 10 shows a path that the operator could follow in the logging area. By
positioning
the felled trees in piles that are within range of the middle path, the
heavier machines used to
pick up the trees only have to use the middle path. This has the advantage of
being less damaging
to the small trees and underl;rowth as well as being faster and more
efficient.
In Figure 4, the illustrated hydraulic motor 40 is illustrated enclosed in a
cavity 38 of the
holder 30 where it is protected from tree branches and tree trunks that can
damage the hydraulic
motor 40 or its hydraulic hoses. The gear assembly 50 is at least partially
housed in the frame
10 and also protected from damage. This arrangement creates a lighter frame
than what is
commonly found in the prior art. The weight of the felling head 10 is an
important feature
considering that, when the manipulator arm 5 is fully extended, the weight of
the felling head 10
applies an enormous force to the entire structure of the tree cutting carrier
4. This arrangement
is also very compact and allows the operator to manipulate the felling head 10
in dense wooded
areas without it getting tangled in branches.
Figure 6 shows the filling head 10 rotated sideways about the axis defined by
the drive
shaft 45 of the motor 40 and the central gear 54 (shown in Figure 5) of the
gear assembly 50.
Since the inner workings of a planetary gearbox are understood by those
skilled in the art, suffice
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it to say that the torque of the central gear 54 is transferred to the
intermediate gears 56 which
in turn transfers it to the final gear 52 on which frame 20 is rigidly
attached. Frame 20 rotates
about the axis of rotation of the drive shaft by following the final gear 52.
With this
arrangement, the felling head 10 is capable of at least 360 degrees of
rotation.
Figure 7 illustrates a variant o f the first embodiment of the present
invention in which the
torque produced by the motor 40 is transmitted to the frame 20 via an
intermediate element, for
instance, a bearing-like member 60. This bearing-like member 60 could be a
roller bearing, a
ball bearing, a journal bearing or simply a low-friction shaft-sleeve
arrangement. In this
particular variant, the drive shaft 45 is connected to the bearing-like member
60. The drive shaft
45 of the motor 40 and a central inner gear 66 are coaxial. In other words,
the drive shaft 45 and
the central inner gear 66 share the same axis of rotation. The inner part 64
of the bearing-like
member 60 is affixed to the holder 30 while the outer part 62 is affixed to
the frame 20. The
drive shaft 45 extends through an aperture in the inner part 64 and is linked
to the outer part 62
at the central inner gear 66. 7Che torque of the motor 40 is transferred to
the frame 20 by the drive
shaft 45 and the outer part 6:2 of the bearing-like member 60, thereby
rotating the frame.
Figure 8 shows a second embodiment having a drive shaft 45 that is coaxial
with the axis
of rotation of the frame 20. In this embodiment, the motor 40 is housed in the
frame 20 and is
also aligned with the axis of sideways rotation ofthe frame 20. The gear
assembly 50 is housed
in the cavity 38 of the holder 30. The motor 40 imparts rotational motion to
the drive shaft 45
which in turn imparts rotational motion to the central gear 54. Since the
final gear 52 of the
gearbox 50 is held rigidly onto the holder 30, the rotational movement is
transferred back to the
motor 40, thereby rotating the frame 20. This arrangement simply reverses the
transfer of torque
but is as strong and sturdy as the first: embodiment depicted in Figures 1-7.
Figure 9 illustrates a variant of the second embodiment depicted in Figure 8.
The motor
40 is housed in the frame 20 and is also aligned along the axis of rotation of
the frame 20 of the
felling head 10. Rotational motion of the frame 20 is achieved through the
bearing-like member
60 which is housed in the cavity 38 of the holder 30. The drive shaft 45 of
the motor 40 extends
through an aperture in the inner part 64 and is linked to the outer part 62 at
the central inner gear
66. The motor 40 imparts rotational motion to the drive shaft 45, which in
turn imparts rotational
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motion to the central inner ge;ar 66. Since the outer part 62 of the bearing-
like member 60 is held
rigidly onto the holder 30, th.e rotational movement is transferred back to
the inner part 64 of the
bearing-like member 60, thereby rotating the frame 20.
The above description of preferred embodiments should not be interpreted in a
limiting
manner since other variations, modifications and refinements are possible
within the spirit and
scope of the present invention. The scope of the invention is defined in the
appended claims and
their equivalents.
