Note: Descriptions are shown in the official language in which they were submitted.
~22~
TITLE OF INVENTION
. _ _
SAW TYPE TREE FELLING HEAD ~ND METHOD OF FELLING
TREES UTILI~ING A FELLING HEAD
FIELD OF INVENTION
_~ _ __
This invention relates generally to tree felling
heads and more particularly to impxovements in felling heads
of the type utilizing a saw for cu-tting the tree and a
method of felling trees utilizing the same.
BACKGROUND OF INVENTION
Tree felling heads are well known in the art and
comprise generally a frame having a grapple mounted thereon
for grasping the tree and severing means for cutting the
tree at a position below the grapple. Various different
severing devices are known and have been proposed including
shears, chain saws and circular saws. Shear severing
devices have been proven to be fast and rugged for felling
trees and require relatively little maintenance. There is,
however, considerable concern as to the damage caused to
the tree resulting in substantial wastage at the butt end
and which is a valuable part of the tree. ~aws, on the
other hand, whether they be circular blades or chain saws,
casue substantially less damage but they are fragile
devices requiring frequent sharpening, maintenance and/or
replacement. They are thus considered more costly than
shears.
A principal drawback with saw type tree felling
devices is binding of the saw during severing of the
~2~06
standing tree. To overcome this, pusher arms have been
used as, for example, disclosed in Canadian Patent 898,661
issued April 25, 1972 to Per G. Mellgren, or U. S. Patent
2,341,035 issued February 8, 1944 to P. ~rzelak. The
pusher arm presses against the tree in the direction of
cut forcing the tree to be tilted so as to avoid binding
during the severing operation. This, however, is not
completely accomplished. When the saw makes the final cut
through the tree, the tree thereafter is not supported and
rests on the saw blade causing damage thereto or binding
of the same.
Felling heads incorporating a circular saw or
chain saw are known in the art and while they have the
advantage of making a clean cut thrcugh a tree, they are
not entirely satisfactory in their present design. Often
the tree will slip downwardly in the grapple after it has
been severed causing binding of the saw and/or damage to
the saw.
Another major drawback of felling heads incorporat-
ing a circular saw or chain saw is that the tree is firmlygripped by a grapple on the felling head whereafter the
tree is cut by the severing device. Firmly gripping the
tree by the grapple can cause strain on the tree, tilting
it from its normal growing position and which will result
in damage to the tree during severing and/or binding of
the saw.
SUMMARY OF INVENTION
_ .
A principal object of the present invention is
to provide a felling head having a saw for severing a tree
and positive means for supporting the tree such that it
can not slip downwardly in the grapple after it has been
severed from its roots.
Another object of the present invention is to
provide a tree felling head having a saw with means for
supporting the tree during a severing operation and means
for stabilizing the tree without resorting to the use of a
grapple firmly gripping the same.
In accordance with one aspect of applicant's
invention there is provided a method of felling trees
using a felling head having a saw movably mounted thereon
comprising driving a horizontally disposed sharpened blade
on the felling head partially into the tree from one side
thereof, applying a selected force to the opposite side of
the tree at a position above the cutting member, moving a
driven saw on the felling head through the tree to cut the
same and laterally sliding the severed tree, while in its
vertical position, onto a support plate. In the preferred
embodiment of the invention, the driven saw is moved
through the tree in a direction of the force being applied
to the tree at a position above the sharpened blade.
In accordance with another aspect of the present
invention, there is provided a tree felling head comprising
a frame, a sweep arm mounted on said frame for pressing
~2x~La)~
against the standing tree from one side thereof, a plate
mounted on said frame and having a sharpened edge for
penetrating into the trunk of the standing tree at a position
below the sweep arm and on a side of the tree opposite to
that of the sweep arm and a saw movably mounted on the
frame for cutting through the standing tree in a plane in
close proximity to that of said plate.
Applicant's invention is particularly directed to
a modification to Canadian patent 1,103,130 issued June 16,
1981 and entitled "Accumulator Felling ~ead". In the
patented structure there is an accumulator type grapple and
a pair of shear blades for severing the tree at a position
below the grapple~ One shear blade is fixed to the frame of
the felling head and a flat plate extends rearwardly there-
from laterally across the felling head providing an areafor accumulating trees and supporting the butt end of the
accumulated trees. The other shear blade is mounted on an
arm pivotally attached to the frame and is movable in a
direction toward and away from the fixed shear blade. In
the present invention, the movable shear blade is replaced
by a chain saw pivotally mounted on the arm. When a
standing tree is to be cut the arm is pivoted towards the
fixed shear blade and sufficient force applied as to cause
the fixed shear blade to partially penetrate into the tree.
A sweep arm or sweep arms on the frame are pivoted to
press against the tree at a position above the fixed shear
blade and on an opposite side of the tree. Thereafter, the
- 4 -
~2~
driven saw is plvoted to cut through the tree in a plane
in near proximity to that of the shear blade. When the
tree has been cut through, the fixed shear blade supports
the tree and thus avoids any damage to the saw blade since
the tree can not move downwardly as is the case with prior
art devices. The continual pressure applied by the sweep
arm to the tree avoids any binding of the saw during
cutting and immediately the tree has been severed the
sweep arms move the tree laterally into the tree accumulating
area where it is firmly held by the accumulator grapple arms.
Preferably, the upper edge cut through the tree by
the chain saw is slightly below the upper surface of the
fixed plate so that when the tree is moved laterally it is
also raised slightly, thereby preventing any binding of the
saw. For this purpose the taper on the fixed shear blade
should extend slightly beyond the depth of penetration
of the shear blade into the tree when cutting a standing
tree.
LIST OF DRAWINGS
The invention is illustrated by way of example
with reference to the accompanying drawings wherein:
Figure 1 is an oblique view of the felling head
disclosed in applicant's aforementioned Canadian patent;
Figure 2 is an oblique view of the lower end of
the felling head illustrating the major components detached
and forming the severing device and tree support plate;
~22~0~3~
Figure 3 is an oblique v:iew of a chain saw unit
that can be substituted directly for the movable shear
blade on the felling heads illustrated in Figures 1 and 2;
Figure 4 is an elevational diagrammatic view
illustrating cutting a standing tree with a device provided
in accordance with the present invention; and
Figure 5 is a schematic of the hydraulic circuit
for the felling head having the chain saw unit mounted
thereon.
DESCRIPTION OF PREFERRED EMBODIMENT
In Figure 1 there is illustrated a tree felling
head disclosed in applicant's aforementioned Canadian patent
1,103,130. Figure 2 is a partial view of the lower end of
such felling head representing the commercial embodiment.
The felling head comprises a frame unit 10 pivotally
attachable in a conventional manner by means on the end
of an extendible and retractable boom on a mobile vehicle.
At the upper end of the frame there is an arcuate arm 11
and at the lower end of the frame a plate 12 having a
corresponding arcuate tree retaining arm 13 for retaining
a tree or a plurality of trees severed by the shear
severing mechanism. Trees severed are retained in the
accumulating area by articulated arms 14 pivotally attached
to the frame by pin 15 and consist of a first arm 16 and
a finger member 17 pivotally attached thereto by pin 18.
The arm 16 and finger member 17 are actuated by an
hydraulic cylinder unit 18 and link unit 19. The tree
1221006
support plate 12 has a shear blade 20 attached thereto
with a sharpened edge 21 and which cooperates with a
shear blade 22 mounted on a pivoted arm 23 for severing
the tree. The arm 23 is pivotally attached to the frame
by means of a pivot pin 24 and moved by an hydraulic
cylinder unit 25 (see Figure 3)O A standing tree severed
by the shear blades 20 and 22 is swept from the shear
blades onto the tree supporting plate 12 by a sweep arm
unit 26 which may be a single arm or an upper and lower
arm as illustrated in the drawing. Movement of the sweep
arm is effected by hydraulic cylinder unit 27 shown in
Figure 1 or a pair of cylinders 27A and 27s shown in
Figure 5. The articulated arm 14 la single arm or an
upper arm and lower pair of arms as illustrated in Figure
1) is selectively moved by the single cylinder 18 shown in
Figure 1 or respective ones of a pair of hydraulic cylinder
units 18A and 18B illustrated in Figure 5 and the finger
arms 15 are pivotally moved by the links 19. For further
details on the same, reference may be had to applicant's
aforementioned Canadian patent.
In Figure 3 there is illustrated an arm 23A
which can be substituted for the arm 23 illustrated in
Figures 1 and 2 and pivotally attached to the frame 10 by
pivot pin 24 passing through bushing 30 in the arm 23A.
The arm 23A is connected to the hydraulic cylinder 25
(which at the other end is anchored to frame 10) and
moved thereby about pivot pin 24 in a direction toward
- 7 -
~L22~00~
and away from the blade 20 having the sharpened cutting
edge 21. The arm 23A is channel shaped in cross-se~tion
with the open part of the channel facing blade 20.
Pivotally mounted on bushing 30 is a power driven chain
saw 40 pivotally moved about journal 30 by an hydraulic
cylinder unit 41. The arm 23A has a pair of spaced apart
plates 28 and 29 (see Figure 4) disposed respectively
above and below the chain saw unit defining a channel in
which the chain saw and bar is located prior to a cutting
operation. Plates 28 and/or 29 may have a flat edge for
engaging the tree. Alternatively, plate 28 may have a
sharpened or serrated edge 28A and/or plate 29 may have a
sharpened or serrated edge 29A for penetrating into the
surface of the tree prior to a cutting operation when the
tree is clampingly engaged between cutting member 20 and
arm 23A. Before cutting of the tree is commenced, the
tree is clampingly engaged between the cutting blade 20
and the arm 23A and with sufficient force on arm 23A as
to cause cutting edge 21 of plate 12 to penetrate the tree
as illustrated in Figure 4. In the event plates 28 and/or
29 are provided with a sharpened edge, during such
clamping such edges would penetrate the tree stabili~ing
the entire felling head unit on the standing tree. At
the same time and before cutting of the tree has commenced,
sweep arm 26 is swung against the tree and biased with a
selected force so as to press the tree in the direction
of the tree collecting or accumulating area on the felling
~22~ 6
head. When the tree is firmly grapsed between the arm
23A and shear blade 20 the chain saw is activated and
pivoted by cylinder 41 so as to move the saw through the
tree cutting the same. When the tree has been completely
severed from its roots it is shifted laterally by sweep
arm 36 onto support or butt plate 12.
A schematic of the hydraulics for the felling head
with the saw attachment of Figure 3 is illustrated in
Figure 5. In referring to such Figure, there is illustrated
a pair of hydraulic cylinder units 18A and 18s that actuate
the arms 16 of the tree accumulating mechanism. A pair of
hydraulic cylinders 27A and 27B actuate the sweep arm 26
and operate in conjunction with hydraulic cylinder 25 that
causes the arm 23A to move forward so as to grasp the -tree
between such arm and the shear blade on the accumulating
side of the felling head. A hydraulic motor M drives
the chain saw and actuation thereof is controlled by a
sequence valve SV which causes the same to operate when
the pressure in cylinder 25 builds up to a predetermined
level. The severing pass of the saw, i.e. movement of the
saw blade through the tree, is effected by hydraulic cylinder
41 under the control of a solenoid operated valve 42. Oil
supply for this purpose is taken from the exhaust side of
motor M by way of line 43 under system back pressure
or if required the back pressure built up by a variable
pilo-t operated orifice 44. Pilot pressure for the
actuation of this orifice is taken from the pressure side
1~210~)~
of the motor. Its effect is such that the size of the
orifice varies inversely with the pressure, thus bringing
about maximum cutting speed at all -times. The motor M is
protected by a relief valve 45 and reversal of the motor's
operation is prevented by a check valve 46. The broken
lines 47 are drain lines and bring together the drainage
from the sequence valve SV, the motor M and the exhaust
from cylinder 41. Lubrication for the chain of the chain
saw is taken from this circuit and fed to the saw in an
appropriate manner from a nozzle or orifice 48. The
hydraulic cylinder unit 41 controlling movement of the
chain saw in its pass through the tree is a combination
hydraulic cylinder accumulator unit. A compressible gas
or spring is used as a spring means causing the chain saw
to retract into the housing upon completion of its cut
through the tree.
In order to convert the felling head from a
shear to a saw severing device, pin 24 is removed and the
pivotal connection of cylinder 25 to the arm is disconnected.
The arm 23 is then replaced with arm 23A illustrated in
Figure 3 and the cylinder 25 connected thereto. For the
chain saw arm attachment a smaller cylinder can be used
than that used for the shear blade arm of Figure 1. In the
hydraulic system oil initially flows to the saw arm
cylinder 25 which in turn brings the arm assembly forward
so that the tree to be cut is trapped beween the arm and
the fixed shear blade 20. The sweep arms 26 move at the
-- 10 --
~;~2'L~6
same time as the saw arm and when the pressure builds up
to a selected setting (preferably above 1,000 p.s.i.) the
oil flow shifts via sequence valve 41 to the hydraulic motor
which in turn starts the chain moving on the chain saw bar.
The return line from the motor is linked up with the rod
end line from the saw arm cylinder. The check valve 46
in the circuit prevents the saw motor from running in
reverse. The drain line 47 directly to tank provides a
very low pressure line to relieve the saw motor case, the
lo sequence valve and the saw bar cyllnder.
The saw arm movement is effected by the small
hydraulic cylinder 41. Such cylinder, as previously
mentioned, incorporates therein a gas section the pressure
of which is used to retain the bar in the shelter of the
channel provided in the arm.
From the foregoing, it can be seen the apparatus
when severing a tree does not grasp the tree but instead
applies pressure from one side thereof by sweep arms 26
pushing the tree generally in the direction of the tree
accumulating area. When making a cut with the chain saw
this has a tendency to open up the cut and thus avoid
binding of the saw. The cutting plane of the saw may be
in line with the shear blade 20 or, alternatively, slightly
therebelow. In having the saw slightly below the fixed
shear blade and by having an appropriate tapered edge for
the blade, i.e. one that is perhaps longer than the depth
of penetration, it not only acts as a blade to penetrate the
~2Z1~
tree but also a wedge for lifting the tree. The tree,
after it is severed, is swept into the accumulating area
and by moving up the sharpened edge of the cutting blade
this causes the tree to be lifted slightly as it is moved
laterally into the collecting area. This obviously moves
the butt end of the tree away from the saw preventing any
damage to the saw after the cut has been completed.
In cutting large trees the accumulator arms may
be removed as on large trees only a single tree would be
handled at one time. In this case a tree which has been
cut would be moved laterally by the sweep arm 26 onto plate
12 and a~ainst arcuate arm 11 and the arcua-te wall 13. The
sweep arm would be then utilized to retain the tree in such
area until it has been felled.
Anyone skilled in the art will realize from the
hydraulic circuit shown in Figure 5 that as cutting becomes
more difficult for Motor M there will be a pressure increase
to the motor M and cylinder 27. The increased pressure in
the latter will cause sweep arm 26 to apply more pressure
to the tree, widening the kerf, thus decreasing any tendency
to bind.
The variable orifice 44 is an optional feature as
there may be sufficient system back pressure to accomplish the same
results. Pilot pressure from the pressure side of the motor
causes the orifice size and thus the back pressure which it
creates to vary inversely with the pressure demands of the
motor and thus the pressure applied by cylinder 91 will also
vary inversely.
- 12-
