Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02800448 2012-12-21
TREE FELLING AND GRAPPLING HEAD
FIELD OF INVENTION
The present invention relates to a tree felling and grappling head and in
particular to a tree
felling and grappling head for attachment to a boom of vehicle used in
forestry or logging
operations. The head has grapple arms which can grip around the trunk of a
tree, and a saw
that can cut through the tree trunk being gripped by the grapple arms.
BACKGROUND
A tree felling head is attached to the boom of a vehicle and used in the
forestry industry.
Felling heads have been used for severing the tree stem from its stump and
laying the severed
stem on the ground for later extraction from the forest by other means. The
cutting tools used
in felling heads may include circular saws, discs, guillotines and chainsaws.
In the United States
of America and Canada, circular saws and discs are more commonly used because
tree size is
relatively small. Chainsaw cutting mechanisms are typically used for tree
felling operations in
New Zealand where average tree sizes are significantly larger.
Felling heads are also used for grappling or shovelling operations in which
felled stems are
picked up off the ground and repositioned to facilitate more efficient or cost
effective
extraction to a site where the sterns will ultimately be loaded onto
transport, for example trucks
or railway cars.
United States patent 5,390,715 describes an apparatus for cutting and pruning
trees. A grapple
and saw assembly 23 includes a grapple assembly 29 and a saw assembly 50. The
saw assembly
is attached to the output shaft 48a of a rotary hydraulic motor 48. The motor
and the grapple
assembly are attached to a frame 24. The saw assembly includes a chain saw
hydraulic motor
51. A positioning mechanism permits the saw assembly to rotate through an arc
of 360 degrees
independently of movement of the grapple assembly.
1
United States patent 6,374,877 describes a bar saw feller buncher and method
of felling trees.
Harvesting arms 18, 20, 22 are pivotally attached to a frame 12 of a bar saw
felling head 10. A
bar saw 14, includes a saw bar and cutting chain is driven by a motor 16. A
rotary or linear
hydraulic actuator may rotate the bar saw through 90 degrees about the axis of
the chain saw
drive motor 16, or a different axis, to move the saw between a home position,
in which the saw
is housed in an open-sided box 40, and a cocked position.
United States patent 7,311,126 and corresponding New Zealand patent 532008
describe a
grapple head assembly with a grapple 1 and a cut-off chain saw 30. A hydraulic
saw drive
motor 20 is mounted in a head portion 20 of the grapple. The saw bar 42 pivots
about the saw
drive sprocket 25, which is preferably coaxial with a pivot axis of a jaw 4 of
the grapple.
The effectiveness of grappling or shovelling by prior art felling heads is
limited due to the
position of the saw box that houses the cutting mechanism.
In this specification where reference has been made to patent specifications,
other external
documents, or other sources of information, this is generally for the purpose
of providing a
context for discussing the features of the invention. Unless specifically
stated otherwise,
reference to such external documents or such sources of information is not to
be construed as
an admission that such documents or such sources of information, in any
jurisdiction, are prior
art or form part of the common general knowledge in the art.
SUMMARY OF INVENTION
At least one embodiment of the invention provides a tree felling and grappling
head with a
repositionable severing mechanism, or at least to provide the public with a
useful choice.
In a first aspect, there is described a tree felling and grappling head for
gripping and severing a
tree stem, the tree felling and grappling head comprising: a grapple assembly
comprising a
grapple body and opposing grapple arms that define a grapple zone, the grapple
arms being at
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respective opposite sides of the grapple zone; a coupling head by which the
tree felling and
grappling head can be suspended from a supporting device; a saddle that is
rotatably attached to
the coupling head for rotation of the saddle, relative to the coupling hcad,
about a saddle
rotation axis; and a severing assembly comprising a severing assembly body and
a severing
device; wherein: the grapple body is tiltable relative to the saddle through
at least 90 degrees
about a grapple body tilt axis that is substantially perpendicular to the
saddle rotation axis,
between a tree felling configuration and a grappling configuration; the
grapple arms are attached
to the grapple body and extend forward beyond a front face of the grapple body
when the
grapple body is in the tree felling configuration; each of the grapple arms
has a gripping face for
contacting an object when gripped by the grapple arms; a rear portion of the
grapple zone is
adjacent the front face of the grapple body and a forward portion of the
grapple zone is
adjacent free ends of the grapple arms; the severing assembly body is
pivotally attached to the
grapple body at a severing assembly body pivot axis for pivoting relative to
the grapple body,
between a retracted position and an extended position; the severing device is
pivotally attached
to the severing assembly body for pivoting about a severing device pivot axis,
relative to the
severing assembly body, between a stowed position and a range of deployed
positions;
the severing assembly body pivot axis and the severing device pivot axis are
respectively at the
opposite sides of the grapple zone; and the severing device pivot axis is
substantially parallel to
the severing assembly body pivot axis; wherein when the severing device is in
the stowed
position and the severing assembly body is in the retracted position, the
severing device and the
severing assembly body lie substantially behind the front face of the grapple
body, behind the
gripping face of at least one of the grapple arms, or both substantially
behind the front face of
the grapple body and behind the gripping face of at least one of the grapple
arms; and wherein
when the grapple body is in the tree felling configuration and the severing
assembly body is in
the extended position, the severing device pivot axis is positioned forward of
the front face of
the grapple body toward the forward portion of the grapple zone so that the
severing device
can perform a cut in a direction away from the grapple body, with a final
portion of the cut
positioned at or adjacent the forward portion of the grapple zone.
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Preferably, the grapple arms are pivotally attached to the grapple body at
grapple arm pivot axes
for pivoting, relative to the grapple body, between an open arm configuration
and a closed arm
configuration.
Preferably, the severing assembly body pivot axis and at least one grapple arm
pivot axis are a
common axis. In an alternative embodiment, the severing assembly body pivot
axis is different
from any of the grapple arm pivot axes.
Alternatively, the tree felling and grappling may comprise at least two
grapple arms on one side
of the grapple body and at least one opposed grapple arm on the other side of
the grapple body,
wherein the least two grapple arms are pivotally attached to the grapple body
for pivotal
rotation about a first grapple arm pivot axis and the at least one grapple arm
is pivotally
attached to the grapple body for pivotal rotation about a second grapple arm
pivot axis, for
moving the grapple arms between an open arm configuration and a closed arm
configuration,
and the severing assembly body is pivotally attached to the grapple body for
pivotal rotation
about the first grapple arm pivot axis.
Preferably, the saddle is rotatable, relative to the coupling head, through at
least 360 degrees.
Preferably, the grapple arm pivot axes are substantially coplanar and the
grapple body is tillable,
relative to the saddle, through at least 90 degrees, and preferably at least
about 150 degrees, for
moving the grapple arm pivot axes between a substantially horizontal
orientation and a
substantially vertical orientation, when the saddle rotation axis is
substantially vertical.
The housing may house an actuator for moving the severing device between the
stowed
position and the range of deployed positions, and may house an actuator for
moving the
severing assembly body between the retracted position and the extended
position.
Preferably, the severing device is a chain saw, and the chain saw comprises a
bar which carries a
cutting chain and is pivotally attached to the housing for movement of the
chain saw between
the stowed position and the range of deployed positions.
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In a second aspect, there is described a method of using a tree felling and
grappling head as
described above, the method comprising: a. with the severing device in the
stowed position,
positioning the tree felling and grappling head, and closing the grapple arms
to grip a portion of
the stem of a standing tree with the grapple arms; b. with the severing
assembly body in the
extended position, progressively extending the severing device through the
range of severing
positions to sever the stem below the gripped portion; c. retracting the
severing device to the
stowed position; d. allowing the weight of the severed stem to reorient the
tree felling and
grappling head and e. opening the grapple arms to release the severed stem.
Preferably, the method comprises the additional steps of: f. retracting the
severing assembly
body to the retracted position; and g. positioning the tree felling and
grappling head, and closing
the grapple arms to grab the stem of a felled tree with the grapple.
Preferably, the method comprises the further steps of: h. progressively
extending the severing
device through the range of severing positions to sever the grabbed stem; and
i. retracting the
severing device to return the severing device to the stowed position.
Preferably, the method comprises the further steps of: j. relocating the
grabbed stem: and k.
opening the grapple arms to release the grabbed stem.
This invention may also be said broadly to consist in the parts, elements and
features referred to
or indicated in the specification of the application, individually or
collectively, and any or all
combinations of any two or more said parts, elements or features.
To those skilled in the art to which the invention relates, many changes in
construction and
widely differing embodiments and applications of the invention will suggest
themselves without
departing from the scope of the invention as defined in the appended claims.
The disclosures
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and the descriptions herein are purely illustrative and are not intended to be
in any sense
limiting.
The term 'comprising' as used in this specification or in the accompanying
claims means
'consisting at least in part of', that is to say when interpreting statements
in this specification or
in the accompanying claims which include that term, the features, prefaced by
that term in each
statement, all need to be present but other features can also be present.
The term "behind", as used in this specification or in the accompanying claims
to define a
positional relationship of one feature with respect to another feature, is to
be understood as
meaning that one of the features is further back than the other feature, but
is not necessarily
directly in line behind the other feature.
As used herein, the term "and/or" means "and" or "or", or both.
As used herein, "(s)" following a noun means the plural and/or singular forms
of the noun.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments and methods of utilising the invention will be further
described by way
of example only and without intending to be limiting, with reference to the
accompanying
figures in which:
Figure 1 shows a front perspective view of a grappling and severing head
according to
the invention, with a grapple body tilted to an upward position, grapple arms
extended
forwardly in a partially open configuration, a severing assembly body in an
extended position,
and a chain saw in a deployed position;
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CA 02800448 2012-12-21
Figure 2 shows a side perspective view of the grappling and severing head of
Figure 1,
with the grapple body tilted to the upward position, the grapple arms extended
forwardly in a
partially open configuration, the severing assembly body in the extended
position, and the chain
saw in the deployed position;
Figure 3 shows a front perspective view of the grappling and severing head of
Figures 1
and 2, with the grapple body tilted to the upward position, the grapple arms
extended forwardly
in a closed configuration, the severing assembly body in the extended
position, and the chain
.. saw in a stowed position;
Figure 4 shows a perspective view of the grappling and severing head of
Figures 1 to 3,
with the grapple body tilted to the upward position, the grapple arms extended
forwardly in a
partially open configuration, the severing assembly body in the extended
position, and the chain
.. saw in a deployed position;
Figure 5 shows a perspective view of the grappling and severing head of
Figures 1 to 4,
with the grapple body tilted to the upward position, the grapple arms extended
forwardly in a
partially open configuration, the severing assembly body in the extended
position, and the chain
saw in the stowed position;
Figure 6 shows a front view of the grappling and severing head of Figures 1 to
5, with
the grapple body tilted to a downward position, the grapple arms extended
downwardly in the
open configuration, the severing assembly body in the extended position, and
the chain saw in
the stowed position;
Figure 7 shows a rear view of the grappling and severing head of Figures 1 to
6, with
the grapple body tilted to the downward position, the grapple arms extended
downwardly in the
open configuration, the severing assembly body in the extended position, and
the chain saw in
the stowed position;
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Figure 8 shows a sectioned bottom view of the grappling and severing head of
Figures 1
to 7, as seen looking up from below the head and sectioned below the chain saw
but above a
lower wall of a chain saw housing of the severing assembly body, with the
grapple body tilted to
the upward position, the grapple arms extended forwardly in the open
configuration, the
severing assembly body in the extended position, and the chain saw in the
stowed position;
Figure 9 shows a sectioned bottom view of the grappling and severing head of
Figures 1
to 8, as seen looking up from below the head and sectioned below the chain saw
but above the
lower wall of the chain saw housing, with the grapple body tilted to the
upward position, the
grapple arms extending partially forward in the closed configuration, the
severing assembly
body in the extended position, and the chain saw in the stowed position;
Figure 10 shows a front view of the grappling and severing head of Figures 1
to 9, with
the grapple body tilted to the downward position, the grapple arms extended
downwardly in the
.. open configuration, the severing assembly body in the retracted position,
and the chain saw in
the stowed position;
Figure 11 shows a rear view of the grappling and severing head of Figures 1 to
10, with
the grapple body tilted to the downward position, the grapple arms extended
downwardly in the
open configuration, the severing assembly body in the retracted position, and
the chain saw in
the stowed position;
Figure 12 shows a sectioned bottom view of the grappling and severing head of
Figures
1 to 11, as seen looking up from below the head and sectioned below the chain
saw but above
the lower wall of the chain saw housing, with the grapple body tilted to the
upward position, the
grapple arms extended forwardly in the open configuration, the severing
assembly body in the
retracted position, and the chain saw in the stowed position; and
Figure 13 shows a sectioned bottom view of the grappling and severing head of
Figures
1 to 12, as seen looking up from below the head and sectioned below the chain
saw but above
the lower wall of the chain saw housing, with the grapple body tilted to the
upward position, the
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grapple arms extended partially forward in the closed configuration, the
severing assembly body
in the retracted position, and the chain saw in the stowed position.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
Referring to the figures it will be appreciated that the invention may be
implemented in various
forms and modes. The following description of embodiments of the invention is
given by way
of example only.
The figures show a grappling and severing head for use in forestry harvesting
operations and
particularly for gripping and severing a tree stem or trunk. The grappling and
severing head
comprises a grapple assembly 10 and a severing assembly 30.
The grapple assembly 10 comprises a grapple body 11 and three grapple arms 12,
13 and 14.
Each grapple arm extends forward beyond a bed plate 15 at a front face of the
grapple body.
The severing assembly 30 comprises a severing assembly body 31 and a severing
device, such as
chain saw 32, which is attached to the severing assembly body.
The grapple arms 12, 13 and 14 are progressively reconfigurable between an
open arm
configuration shown in Figures 1, 2, 6 to 8 and 10 to 12, and a closed arm
configuration shown
in Figures 3, 7, 9 and 13. Partially-open arm configurations are shown in
Figures 4 and 5.
The severing assembly body 31 is pivotally attached to the grapple body 11 at
pivot 33, shown
in Figures 1, 4 and 5. The severing assembly body is pivotable, relative to
the grapple body,
about a severing assembly body pivot axis at pivot 33 for moving the severing
assembly body 31
between an extended position, shown in Figures 1 to 9, and a retracted
position, shown in
Figures 10 to 13.
The severing assembly body 31 is positioned in its retracted position when the
grapple and
severing head is to be used in a shovelling or grappling mode in which the
grapple and severing
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head grips, and optionally severs, the stem of an already-felled tree. In this
retracted grappling
position, the severing assembly body 31 lies substantially behind the bed
plate 15 at the front
face of the grapple body 11.
The severing assembly body 31 is positioned in the extended position when the
grapple and
severing head is to be used in a felling mode in which the grapple and
severing head grips and
then severs the stem of a standing tree to fell the tree. In this extended
felling position, at least
a substantial portion of the severing assembly body 31 extends in front of the
bed plate 15 at
the front face of the grapple body 11.
The severing assembly body 31 comprises a housing 34. The severing device,
which is
preferably a chain saw 32 as shown in the figures, is moveably attached to the
housing for
movement between a stowed position, shown in Figures 3 and 5 to 13, and a
range of deployed
positions, some of which are shown in Figures 1, 2 and 4. In the stowed
position, the chain
saw 32 is stowed substantially inside the housing 34. In the deployed
positions, a severing
portion of the chain saw extends outside the housing for cutting and severing
a stem held in the
grapple.
The housing 34 houses a first hydraulic actuator or ram 35, partially shown in
Figure 2, 4 and 5,
which is extended and retracted to move the chain saw 32 between the stowed
position and the
range of deployed positions. The housing also houses a second hydraulic
actuator or ram 36,
shown at least partially in Figures 2 and 4, 5, 8, 9, 12 and 13, which is
extended and retracted to
pivot the severing assembly body 31 and move it between its extended position,
shown in
Figures 1 to 9, and its retracted position, shown in Figures 10 to 13.
The chain saw 32 has a bar 37 that carries an endless cutting chain 38 driven
by hydraulic motor
39, via a chain drive sprocket 40 located at the proximal end of the bar, as
best seen in Figures 6
to 9. The chain saw bar is pivotally attached to the housing 34 for pivoting
about the axis of
the chain drive sprocket 40, to pivot the chain saw between the stowed
position and the range
of deployed positions.
CA 02800448 2012-12-21
The chain saw bar 37 pivot axis, at the axis of the chain drive sprocket 40,
is spaced apart from,
and substantially parallel to, the severing assembly pivot axis at pivot 33.
In the embodiment
shown in the figures, these two pivot axes are on opposite sides of the
grapple zone between
the opposing grapple arms. Extension and retraction of the severing assembly
body 31 moves
the pivot axis of the chain saw bar respectively forward and rearward of the
bed plate 15 at the
front of the grapple body 11.
The chain saw motor 39 is housed, as are the actuators 35 and 36, inside the
housing 34 to
protect these components from impacts, for example with other machinery or
with trees, logs
or the ground. Apertures are provided in the walls of the housing for
inspection and servicing
of components in the housing. The apertures are covered, in use, by cover
plates which have
been omitted from the figures to show the internal components.
Two of the grapple arms 12 and 13 are pivotally attached to the grapple body
11 for pivotal
rotation of these two grapple arms, relative to the grapple body, about a
first grapple arm pivot
axis at pivot 16. A third grapple arm 14 opposes the two grapple arms and is
pivotally attached
to the grapple body 11 for pivotal rotation of the third grapple arm, relative
to the grapple
body, about a second grapple arm pivot axis at pivot 17. The three grapple
arms pivot about
the respective pivots to move the grapple arms between the open arm
configuration and the
closed arm configuration.
The grapple arm pivot axes are substantially coplanar and substantially
parallel, and the severing
assembly body pivot axis at pivot 33 and the pivot axis of the two grapple
arms 12 and 13 at
pivot 16 share a common axis provided by a single pivot pin.
The two grapple arms 12 and 13 are a unitary construction and move together
about their
common pivot 16. One end of a link 18 is pivotally attached to the opposing
third grapple arm
14 at a pivot pin 20 located in front of the pivot 17 about which the opposing
third grapple arm
14 rotates. The other end 18A of the link 18 is pivotally attached to a
rearward extension of the
two grapple arms 12 and 13, at a pivot 19 (seen in Figure 5). A hydraulic ram
(not shown) is
housed in the grapple body 11 and is pivotally attached to a rearward
extension of the opposing
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third grapple arm 14 to rotate that arm about its pivot 17. Rotation of the
opposing third
grapple arm 14 is coupled via linkage 18 to simultaneously rotate the two
grapple arms 12 and
13 in an opposite direction about their common pivot 16, to move the three
grapple arms
between the open and closed arm configurations.
The grappling and severing head also comprises a coupling head 50 by which the
grappling and
severing head can be suspended from a supporting device (not shown), such as
the boom of a
vehicle. The grappling and severing head may further comprise a saddle 60 that
is rotatably
attached to the coupling head 50 for unlimited rotation of the saddle through
360 degrees or
more, relative to the coupling head, about a saddle rotation axis at a pivot
pin 62 (an upper end
of which may be seen in Figures 2, 4 and 5). A hydraulic motor 51, shown in
Figures 1 and 3, is
located in the coupling head 50, for rotating the saddle relative to the
coupling head.
The grapple body 11 is pivotally attached to the saddle 60 for tilting of the
grapple body
through at least 90 degrees, and preferably at least 165 degrees, relative to
the saddle, about a
grapple body tilt axis at saddle pivot 61. The grapple body tilt axis at
saddle pivot 61 is
substantially perpendicular to the saddle rotation axis at pivot pin 62.
Two hydraulic rams 22 are connected between respective ram mounts 23 on the
grapple body
11 and respective pivot pins 63 on the saddle 60, and are simultaneously
extended or retracted
to tilt the grapple body relative to the saddle. The rams 22 are extended to
lift the grapple body
to an initial felling position, with the grapple arms extending substantially
horizontally, as shown
in the figures, for gripping the stem of a standing tree about to be felled.
After the stem has
been severed, the rams 22 can be retracted to tilt and lower the grapple body
to a grapple
position to tilt and lower the severed stem to the ground. In the grapple
position, shown in
Figures 10 and 11, the grapple arms 12, 13 and 14 extend downward from the
grapple body 11
which hangs below the saddle 60. With the grapple body in this grapple
position, the grapple
and severing head is useful for further processing of already-felled trees, as
described below.
When the saddle rotation axis is substantially vertical, the grapple body tilt
axis is substantially
horizontal, and the grapple arm pivot axes at the pivots 16, 17 can be moved,
by tilting the
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grapple body 11 relative to the saddle 60 about saddle pivot 61, between a
substantially vertical
orientation, shown in Figures 1 to 5, 8, 9, 12 and 13, (useful when gripping
upright stems or
trunks of trees preparatory to felling) and a substantially horizontal
orientation, shown in
Figures 6, 7, 10 and 11, (useful when grappling felled stems or logs that are
lying, or piled, on
the ground).
Stationary blades 21 are fitted at opposite ends of the bed plate 15 of the
grapple body 11. The
blades are preferably provided with a serrated edge for improving the grip of
the grapple on a
stem, log or tree trunk held between the grapple arms. The serrated blade
edges dig into the
bark of a gripped stem to help prevent the stem from twisting or sliding in
the grapple.
The grappling and severing head described above may be used to process
forestry trees, and is
particularly useful for tree felling operations, for shovel logging, for
putting felled stems though
delimbers or debarkets, for cutting logs to length, for repositioning or
stacking felled trees and
logs, and for loading logs onto transport such a railway cars or truck and
trailer combinations.
The term 'shovel logging' refers to the repeated repositioning of felled
stems, to a position in
readiness for removal from the forest, using an excavator-style machine with a
boom and
grapple head attachment.
In a typical method of using the grappling and severing head described above,
the chain saw 32
is retracted to the stowed position in the housing 34 of the severing assembly
30, the severing
assembly is extended to the felling position, and the grapple arms 12, 13 and
14 are opened to
the open arm configuration, all as shown in the bottom view of Figure 8. The
grapple and
severing head is positioned with the open grapple arms around the stem or
trunk of a standing
tree, and the arms closed, as shown in the bottom view of Figure 9, to grip
the stem or trunk by
the grapple.
The chain saw 32 is then progressively extended outward from the housing 34 to
pivot through
the range of deployed severing positions for cutting through the stem below
the gripping
grapple arms 12, 13 and 14. With the severing assembly body 31 extended to the
felling
position, the chain saw 32 can be progressively extended through the range of
deployed
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severing positions to cut through the tree stem. The cut is completed by
cutting the last
outermost part of the tree stem at the furthermost point from the bed plate 15
of the grapple
body. When completing the cut, the pivoting bar of the chain saw is aligned
approximately
parallel to the bed plate 15 at the front face of the grapple body 11.
When the severing assembly body 31 is in the fully extended position, the
pivoting bar of the
chain saw 32 can be aligned approximately parallel to the bed plate 15 at the
front face of the
grapple body 11 when the saw is about to completely sever a larger diameter
tree stem. When
the cut is about to be completed, it is advantageous for the remaining uncut
segment of the tree
stem to be furthermost from the bedplate and for the chord of the remaining
uncut segment to
be at least approximately parallel to the bed plate.
After severing the stem, the grapple may initially maintain the stem upright.
The chain saw is
retracted to its stowed position in the housing 34 of the severing assembly
30, and the grapple
body and grapple arms partially assist the direction of the falling stem. The
two hydraulic rams
22 controlling the tilt of the grapple body 11, and the hydraulic motor 51
controlling rotation of
the saddle 60, are put in a float mode to allow the weight of the severed stem
to tilt and rotate
the grapple body as the stem falls to the ground. The operator of thc vehicle
boom, from
which the grapple and severing head is suspended, can also move the boom to
help control the
falling tree. The hydraulic ram housed in the grapple body 11 is operated to
open the grapple
arms 12, 13 and 14 and release the grip of the grapple on the stem.
When the severing assembly 30 is retracted to the grappling position, the
chain saw pivot at the
drive sprocket 40 is substantially in line with the bed plate 15, and the
severing assembly is
substantially clear of the grapple arms 12, 13 and 14 which are then free to
grab one or more
felled logs or stems. By stowing the chain saw 32 in the housing 34 and
retracting the severing
assembly substantially behind the bed plate 15 at the front face of the
grapple body, the
severing assembly and chain saw are relatively protected from damage and do
not intrude
substantially into the grappling zone. In this configuration, the grapple and
severing head can
be used to pick up felled stems, for example when shovel logging, sorting or
stacking logs in
readiness for loading, or when loading logs onto transport, or when the
grapple and severing
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head is used in conjunction with a static delimber, without substantial
interference from the
severing assembly.
When the severing assembly is retracted to the grappling position, the chain
saw can be
progressively extended through the range of severing positions to cut through
the log or stem
held by the grapple arms, for example for cutting felled logs to pre-
determined lengths
preparatory to loading onto transport.
It is to be understood that all operations of the grapple and severing head
can be performed
simultaneously and without regard to the operational position or configuration
of any
component part of the grapple and severing head. For example, the grapple arms
12, 13 and 14
can be positioned at either the open arm configuration or the closed arm
configuration, or
anywhere between those two configurations, and the chain saw 32 can be driven
and extended
and retracted, when the severing assembly 30 is positioned in either the
felling or grappling
modes or in any intermediate position between those two modes. Furthermore,
these
operations can be performed for any tilt position of the grapple body 11
relative to the saddle
60, or any rotational position of the saddle 60 relative to the coupling head
50.
In one preferred embodiment of the invention, the maximum stem or log diameter
that can be
cut is 1 metre in the felling configuration and 0.7 metre in the grapple
configuration.
Specific embodiments of the invention have been described above by way of
example only, and
modifications and improvements as would be obvious to those skilled in the art
may be made
to the invention without departing from the scope of the invention as defined
by the following
claims.
In one such modification, the chain saw of the severing device is substituted
by a circular saw,
disc or guillotine. The use of a circular saw or disc may be useful where
typical tree sizes are
relatively smaller, for example in the United States of America or Canada,
than in New Zealand
where chain saw cutting mechanisms are found to be more suitable for the
significantly larger
tree sizes.
CA 02800448 2012-12-21
In another modification, the severing assembly body 31 is moved linearly
instead of pivoting as
described above, to move between a retracted position and an extended
position. Similarly, the
chain saw 32 or other severing device could be moved linearly, relative to the
severing assembly
body 31, instead of pivoting.
It is to be understood that although three grapple arms are shown in the
embodiment described
above, any suitable number of grapple arms may be employed. At least one arm
is moveable to
open and close the grapple.
It is also to be understood that when the severing assembly body is in the
retracted position and
the severing device is in the stowed position, the severing assembly body and
the severing
device lie substantially behind, i.e. further back than, the front face of the
grapple body or lie
substantially behind the gripping face of at least one of the grapple arms,
even when the grapple
arms are in an open-arm configuration, so that the severing assembly body and
the severing
device are clear of the grappling zone, i.e. are clear of a stem or tree or
log being grappled by
the grappling and severing head. When the severing assembly body is in the
retracted position
and the severing device is in the stowed position, a portion or all of either
one or both of the
severing assembly body and the severing device may be positioned to one side
of the grapple
assembly, i.e. behind the gripping face of one of the grapple arms, and/or a
portion or all of
either one or both may be positioned behind the front face of the grapple
body. In these
positions, the severing assembly body and the severing device are relatively
protected from
inadvertent impacts and do not get in the way of the grapple arms when they
are being used in
the grappling or shovelling modes.
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