Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FELLING HEAD ACCUMULATOR ARM
CROSS-REFERENCE TO RELATED APPLICATION
This claims the benefit of U.S. Provisional Patent Application No. 60/156,213
filed
September 27, 1999.
STATEMENT REGARDING GOVERNMENT SPONSORED
RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to forestry equipment, and in particular to a feller
buncher for felling
and accumulating trees.
DISCUSSION OF THE PRIOR ART
Felling heads are widely used in the logging industry for accumulating in a
vertical position
several freshly cut trees prior to laying down the bundle at once, to be
transported to roadside by
a skidder or forwarder. The felling head is mounted to a heavy duty vehicle,
such as a drive to tree
or swing to tree wheeled or tracked vehicle, for high efficiency logging.
One type of felling head uses a large saw blade disc having peripheral cutting
teeth. The
disc is rotated in a horizontal plane below a butt plate, with the teeth
exposed at the front of the butt
plate. See, for example, the prior art felling head 10 which is illustrated in
Figs. 1-3. Referring
to Figs. 3A-C, an already cut tree T l, cut by blade 12 shown in phantom is
supported on the butt
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plate 14 and held in place by a pivotable accumulator arm 16. As the blade 12
is advanced
through a tree being cut, the butt plate 14 slides under the cut stem and the
stem is stabilized by one
or more pivotable harvesting arms 18. Typically, two harvesting arms 18 are
provided which move
in orison, are vertically spaced apart and are hinged to the frame of the head
to pivot about a
vertical axis on one side of the frame 20, as illustrated. A single
accumulator arm 16 is typically
provided, positioned vertically between the two harvesting arms 18 and hinged
to pivot from the
opposite side of the frame 20.
When the cut of the first tree T 1 is completed, the accumulator arm 16 is
actuated by
extending hydraulic cylinder 22 (Fig. 3A) which has its rod end pivotally
connected at axis 23 to
crank 24 and its base end pivotally connected at axis 21 to the frame 20. The
crank 24 is pivotally
connected at axis 25 of the near end of inner arm 26, which is pivotally
connected at axis 32 to the
frame 20. The crank 24 is pivotally connected at axis 27 to the near end of
link 28, which has its
distal end pivotally connected at axis 38 to the near end of outer arm 30.
Outer arm 30 is pivotally
connected at axis 34 to the distal end of inner arm 26. Extension spring 36
extends between inner
arm 26 and link 28 and keeps the outer arm 30 from being moved relative to the
inner arm 26 until
the inner arm 26 reaches the limit of its movement. As shown in Fig. 3A, when
hydraulic cylinder
22 is fully retracted, the arm 16 is fully open, with inner arm 26 fully open
and outer arm 30
abutting stop 37 of arm 26. When the hydraulic cylinder 22 is extended, it
acts through crank 24,
inner arm 26, link 28 and outer arm 30, to pivot the inner arm 26 inward about
axis 32, and when
arm 26 reaches the limit of its inward movement, to pivot the outer arm 30
inward about axis 34.
After the first tree T 1 of a bundle is severed, the arm 16 is actuated to
hold it in the side
pocket position shown in Fig. 3B, where the butt end of the tree is trapped
against the pocket walls
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39 and the upper part of the trunk is trapped against the fixed upper arms 41,
also known as the
horn. After the next tree T2 is cut, harvesting arms 18 are actuated to pull
the tree into the pocket
while at the same time actuating the arm 16 to withdraw it from the bundle and
bring it back around
the bundle including the newly cut tree. As shown in Fig. 3C, a situation can
occur in which the
outer arm 30 gets trapped by the newly cut tree. As shown in Fig. 3C, the
inner arm 26 is fully
open, but the outer arm is unable to withdraw from the bundle. When this
occurs, the operator
must either try to rearrange the load by jerking the head, or drop the load,
both of which are time
consuming and hard on the equipment.
SUMMARY OF THE INVENTION
The present invention provides a felling head having at least one accumulator
arm for
holding a bundle of two or more cut trees which overcomes the above problems.
The accumulator
armhas an inner arm pivotally connected at its near end to the felling head
frame and an outer arm
pivotally connected to the opposite, distal end of the inner arm. The inner
and outer arms are
driven to close around the bundle and retract from it, as in the prior art. An
accumulator arm of
the invention differs from the prior art in that it includes an aft arm and a
fore arm. The aft amz is
the part of the outer arm that is pivotally connected to the distal end of the
inner arm and is driven
open and closed. The aft arm extends from the pivotal connection with the
inner arm to the fore
amz. The fore arm is pivotally connected to the distal end of the aft arm and
biased by a spring into
an open position in which the fore arm extends from the aft arm as a natural
extension of it. The
fore arm is pivotally connected to the aft arm so that the fore arm can pivot
inwardly against the
bias of the spring away from the open position. Thereby, if the outer arm gets
obstructed, the fore
arm can pivot out of the way to permit powered opening of the outer arm.
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These and other objects and advantages of the invention will be apparent from
the
drawings and detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side plan view of a prior art felling head;
Fig. 2 is a detail perspective view illustrating the accumulator amt of the
prior art felling
head of Fig. 1;
Fig. 3A is a top sectional schematic view of the prior art felling head of
Fig. 1 in a fully
open position, showing the inner arm in section and the crank as if it were
transparent;
Fig. 3B is a view like Fig. 3A, but showing the accumulator arm in a fully
closed position,
I 0 and showing the top plate of the inner arm ;
Fig. 3C is a view like Fig. 3B, but showing the accumulator arm in a jammed
position and
the inner arm transparent;
Fig. 4A is a partial sectional view like Fig. 3A of the same felling head but
with an
accumulator arm of the invention in the fully open position;
Fig. 4B is a view like Fig. 4A, but showing the accumulator amz fully closed,
and showing
the top plate of the accumulator arm and the outer end of the inner arm as if
it were transparent and
partially in section;
Fig. 4C is a view like Fig. 4B, but showing the accumulator arm opening and
the fore-arm
pivoted inward to clear a tree which would otherwise jam the opening of the
accumulator arm, with
all parts of the accumulator arm shown transparent and partially in section
through the inner and
aft arms; and
Fig. 5 is a view like Fig. 2 but of an accumulator arm of the invention.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In Figs. 4A-C, parts of the felling head 50 of the invention which are the
same as parts of
the prior art felling head 10 have been labeled with the same reference
numbers.
Referring to Figs. 4A-C, the only part of the felling head 50 which is
materially different
from the felling head 10 is the accumulator arm 40. The accumulator arm 40 is
the same as the
accumulator arm 16 of the prior art felling head 10 except that the outer arm
45 has a fore arm
portion 42 that swings out of the way if it runs into an obstruction when the
outer arm is opening
up.
Referring to Fig. 2, the outer arm 16 is made of an upper plate 44 and a lower
plate 46,
which are joined by welding to one or more intermediate plates 48. In the arm
40 of the invention,
as shown in Fig. 5, the same type of construction is used for the aft arm
portion 52, the only
differences being that the aft arm 52 is not as long as the arm 16, the aft
arm 52 has the upper and
v
lower plates 44 and 46 bored to mount a shaft and bearings for pivotally
mounting the fore arm 42
to pivot about axis 55 relative to aft arm 52, and the aft arm 52 has a
structure 54 to which one end
of extension spring 56 (Figs. 4A-C) is secured. The total length of the arm
45, including the aft arm
52 and fore arm 42, is approximately equal to the length of the arm 30, so the
length of
accumulator arm 40 is approximately equal to the length of accumulator arm 16.
Spring 56 has its other end secured to the fore arm 42 to bias the arm 42 in
an open
position, shown in Fig. 4A. Fore arm 42 has an outer plate 58 which is wide
enough to overlap
the outer edges of upper and lower plates 44 and 46 at the rear of the fore
arm 42, so as to abut
those plates in the open position and thereby provide a positive stop. Thus,
the fore arm 42 is
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prevented from opening any further than is shown in Figs. 4A and 4B, in which
position it is open
and a natural extension of the aft arm 52.
The arm 40 operates the same as the arm 16 in the positions of Figs. 4A and
4B, which
are analogous to Figs. 3A and 3B. The operation in the situation of Fig. 4C
though, in which the
arm 16 was jammed, is markedly different. Inthat situation, opening movement
of the aft arm 52
(byretracting the hydraulic cylinder 22 shown in Fig. 4C) is permitted to
continue because the fore
arm 42 is pivoted about axis 55 by its abutment with the tree T2. When the tip
of the fore arm 42
clears the tree T2, the spring 56 biases it into the fully open position
relative to aft arm 52. It
should be noted that the spring 56 could be replaced with a torsion spring or
any other means
which biases the fore arm 42 into the open position.
Thereby, the problem in the prior art of the accumulator arm becoming
obstructed by the
second and subsequently cut trees of a bundle accumulated by a felling head is
solved. This is done
in a machine where the entire accumulator arm, including the inner arm and the
outer arm, are
powered when closed and opened, so that the outer arm folds inwardly back over
the inner arm
when it closes and opens back up under power when it is opened. Thereby, the
advantages of an
elbowed arm to accumulate more trees and hold them securely, particularly in a
side pocket felling
head, are achieved, while providing an arm which is less susceptible to
jamming.
A preferred embodiment of the invention has been shown and described in
detail. Many
modifications and variations of the embodiment described will be apparent to
those skilled in the
art. For example, various mechanisms may be used to power the inner and outer
arms opened and
closed. Therefore, the invention is not limited to the embodiment described.
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