Note: Descriptions are shown in the official language in which they were submitted.
21 96728
ACTUATOR DRIVEN SLEWING MRC~ANISM FOR
TIMBER PROCESSING wo~R~R~n
FIELD OF lNV~N-llON
The present invention relates generally to the field of
timber handling and processing workheads and more
particularly, to an actuator driven slewing mechanism for a
timber felling head that allows for relative rotational
movement between the felling head and a boom or other support
structure to which the felling head is connected.
BACRGROUND OF lNV~lION
It is common in the tree harvesting industry for timber
handling or processing workheads to be mounted on the end of a
boom or other like support structure attached to an all-
terrain vehicle through a swinging link, known in the art as a
dangle connection. This dangle connection enables the
workhead to swivel freely on the end of the boom. Such
machines are capable of a variety of timber handling and
processing functions depending upon the type of workhead
employed. For example, there are workheads which are adapted
to fell trees, delimb trees, remove bark and load or carry
processed logs onto transport vehicles or into storage areas.
It is also common for such machines to use hydraulic cylinders
fixed to the boom to pivot the workhead in a plane aligned
with the boom. In addition, most harvesting machines are
capable of rotating the timber handling workhead about the
boom axis for a total of 30~ or 40~ of rotational movement.
Some harvesting machines, however, are capable of between 180~
and 270~ or more of rotational movement of the timber handling
workhead about the boom axis. The larger degrees of
rotational movement, known to those skilled in this art as
high-angle rotation, have been achieved by a variety of
gearing means including rack and pinion sets driven by
hydraulic cylinders, gearsets wherein the driving pinions are
coupled to hydraulic cylinders, and geartrains driven by
hydraulic motors or a combination of chain drives, planetary
gear reducers and hydraulic motors.
21 Y672~
An example of a prior art harvesting machine designed for
what is termed in the art as "straight-ahead" operation, in
which a workhead is capable of pivotal movement, is provided
by United States Patent No. 4,491,163 issued on January 1,
1985 in the name of Kurelek. This patent teaches that
hydraulic cylinders may be used to drive a crank arm and link
member which in turn rock or swivel the workhead in a vertical
plane aligned with the boom.
Another example of hydraulic cylinders being used to
obtain swivel or swinging motion may be found in United States
Patent No. 5,123,462 issued on June 23, 1992 in the name of
Davision. The harvesting machine according to Davision is a
heavy duty brush cutter used in connection with forestry
management and right-of-way clearing. This patent teaches
that a pair of boom turning cylinders mounted to steel lugs,
which are in turn welded to each side of a cutter boom, swing
the cutter boom from side to side about its vertical turning
axis.
Hydraulic cylinders have also been used in connection
with a timber handling workhead, specifically a tree felling
head, to raise and lower a saw guard of the felling head which
in turn enables the felling of larger diameter trees as .
disclosed in United States Patent No. 4,921,024 issued on May
1, 1990 and identifying as the inventors, Wiemeri and
Mitchell. This patent teaches that extension and retraction
of hydraulically powered pistons causes a moveable guard
portion which is attached to a fixed guard portion by a hinge
to be raised and lowered to selectively expose or overlay a
saw blade.
Gilbert-Tech Inc. of Roberval, Quebec markets a timber
handling workhead, specifically a tree felling head under the
trade-mark GILBERT 1000 Series, which achieves 180~ of
rotational movement. The Gilbert tree felling head is rotated
by two vertically disposed hydraulic cylinders actuating a
21 i672~
gear segment and a pinion gearset. One end of each of the
hydraulic cylinders is pivotally attached to a disc saw
housing of the tree felling head and the other end of each of
the hydraulic cylinders is pivotally attached to the gear
segment in the gearset. Extension and retraction of the
hydraulically powered pistons turns the gear segment which
turns a smaller gear mounted on a bearing and causes a larger
gear to climb around the smaller gear to rotate the tree
felling head freely about the axis of the pinion gear.
In another prior art device, Denharco of Saint Hyacinthe,
Quebec achieves 240~ of rotational movement of a timber
handling workhead, specifically a tree felling head marketed
under the trade-mark DENHARCO CS5500 RTA felling head side
tilt mechanism, by using a conventional chain drive, a
planetary gear reducer and a hydraulic motor. The hydraulic
motor through the gear reducer drives a pinion which in turn
drives the chain to rotate the felling head around the boom
adaptor.
A further example of a prior art device is a tree felling
head marketed by Quadco Equipment Inc. of Montreal, Quebec as
the Model 2OB Centre Tower Saw Head. This device achieves
240~ of rotational movement by using a gearset wherein the
driving pinions are couped to two hydraulic cylinders via
cranks. The gearset resides inside the felling head. The
driving pinions mesh with a larger gear which is attached to
the boom adaptor. The hydraulic cylinders are fed with .
pressurized oil through a hydraulic timing valve to ensure
rotation of the tree felling head. A rotary timing valve
changes the direction of the oil flowing into the hydraulic
cylinders such that the cylinders are either pulling or
pushing on the cranks. When one of the cylinders is at its
maximum torque, the other cylinder is not generating any
torque and visa versa. The cranks translate the linear motion
of the hydraulic cylinders into rotary motion which drives the
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gearset to rotate the tree felling head about the axis of the
boom adaptor.
Quadco has another device which achieves 270~ of
rotational movement of a tree felling head using a
conventional design consisting of two hydraulic motors driving
a geartrain to rotate the felling head.
There are several advantages to harvesting machines
having timber handling or processing workheads with high-angle
rotation. These include the ability to harvest trees at any
angle, which is particularly useful in a blow-down situation,
and the ability to control the fall of the trees. As well,
these machines allow for the flexibility to place the felled
bunches of trees in a particular location for skidding, with
the end result being larger and fewer piled bunches for fast
and easy skidding to the landing. In addition, the skidder
payload is improved without the need for multiple bunching.
Environmentally, high-angle rotation is also advantageous
in that it m; n; mi zes the damage to forest growth and reduces
feller buncher and skidder travel. Less machine travel means
more operator comfort and less machine fatigue.
While the prior art devices capable of high-angle
rotation possess the above-described advantages, generally
they are complex arrangements involving many mechanical parts
which require constant and specific maintenance. For example,
gear segment and pinion gearsets and other types of gearsets
must be serviced and maintained via lubrication and greasing
on a regular basis due to the clogging debris from felled
trees. The complex nature of the gearsets requires speci-fic
maintenance by experienced mechanics and causes down time for
the machine operator. Increased maintenance means higher
operating costs and down time for the machine operator
resulting in decreased productivity and lower profits. As
well, many of the prior art devices do not provide for ready
21 ~6728
s
maintenance access to hydraulic supply lines in a compact
design.
Therefore, there has developed a need for a timber
handling or processing workhead capable of high-angle rotation
which overcomes these disadvantages.
SUMMARY OF lN V~N 1 ION
According to a broad aspect of the present invention,
there is provided a slewing assembly for a timber handling
apparatus of the type having a workhead connected to a support
structure, the workhead being rotatable about a slew axis with
respect to the support structure, the slewing assembly
comprising: (a) a slewing means for relative rotational
movement of the workhead and the support structure about the
slew axis; (b) a drive means for imparting the relative
rotational movement of the workhead and the support structure,
the drive means comprising two actuators, each actuator having
a fixed end and a moveable end, the actuators each provid-ing
means for linearly extending and retracting the moveable ends
thereof with respect to the fixed ends thereof along an
actuating axis, one end of each actuator being rotatably
attached to the workhead and the other end of each actuator
being rotatably attached to the support structure; wherein
each actuator is positioned to apply a force to the slewing
means at a point radially distant from the slew axis thereof
upon extension and retraction of the moveable end of the
actuator with respect to the fixed end of the actuator to
thereby effect the relative rotational movement of the
workhead and the support structure, and wherein the actuators
are each positioned such that the actuating axes associated
therewith do not all intersect the slew axis at the same time
during the relative rotational movement of the workhead and
the support structure.
21 96728
According to another broad aspect of the present
invention, there is provided a slewing assembly for a timber
handling apparatus of the type having a workhead connected to
a support structure, the workhead being rotatable about a slew
axis with respect to the support structure, the slewing
assembly comprising: (a) a slewing mechanism for relative
rotational movement of the workhead and the support structure
about the slew axis; (b) a drive mechanism for imparting the
relative rotational movement of the workhead and the support
structure, the drive mechanism comprising two actuators, ~ach
actuator having a fixed end and a moveable end, the moveable
ends of the actuators each being linearly extendible and
retractable with respect to the fixed ends thereof along an
actuating axis, one end of each actuator being rotatably
attached to the workhead and the other end of each actuator
being rotatably attached to the support structure; wherein
each actuator is positioned to apply a force to the slewing
mechanism at a point radially distant from the slew axis
thereof upon extension and retraction of the moveable end of
the actuator with respect to the fixed end of the actuator to
thereby effect the relative rotational movement of the
workhead and the support structure, and wherein the actuators
are each positioned such that the actuating axes associated
therewith do not all intersect the slew axis at the same time
during the relative rotational movement of the workhead and
the support structure.
With reference to preferred embodiments of the present
invention, the slewing means or slewing mechanism comprises a
first cylindrical bearing surface provided with the support
structure which is in relative rotational contact with a
corresponding second cylindrical bearing surface provided with
the workhead. Preferably, the first cylindrical bearing
surface is an elongate cylindrical extension that is attached
to the support structure, with the cylindrical extension being
received within the second cylindrical bearing surface which
is concentrically disposed therearound. The second
21 9~728
cylindrical bearing surface may be defined by a plurality of
annular bearings.
In one embodiment, the elongate cylindrical extension has
a free terminal end and another terminal end adjacent to the
support structure, and the extension provides a retaining
plate attached to the free terminal end and disposed
substantially normal to the slew axis. The elongate
cylindrical extension further provides an annular shoulder at
the terminal end thereof adjacent to the support structure,
such that the retaining plate and annular shoulder define
opposed thrust bearing surfaces extending radially around the
elongate cylindrical extension. The annular bearings may have
a generally L-shaped cross-sectional configuration to thereby
provide corresponding radially extending surfaces for relative
rotational contact with the thrust bearing surfaces.
Advantageously, the elongate cylindrical extension may be
provided with a through passage for hydraulic supply lines for
timber handling means of the workhead.
According to further preferred embodiments, the slewing
assembly further comprises a sensing means for each actuator,
the sensing means detecting a dead position of the respective
actuator. This dead position is obtained when the actuating
axis of the actuator intersects with the slew axis during the
relative rotational movement of the workhead and its support
structure. Upon detection of the dead position of the
actuator by the sensing means, the direction of linear
translation of the actuator is reversed.
In yet further preferred embodiments, the actuating axis
of each actuator is located in the plane substantially
perpendicular to the slew axis of the workhead. Each actuator
may be rotatably attached at each end thereof by means of a
pin connection. The ends of the actuators which are attached
to the support structure for the workhead are positioned
'~1 q6728
substantially radially equidistant from the slew axis in one
preferred orientation. Likewise, the ends of the actuators
which are attached to the workhead may be positioned
substantially radially equidistant from the slew axis. In an
unrotated position of the workhead, the ends of the actuators
which are attached to the workhead are located on a line which
is substantially parallel to another line on which is located
each of the ends of the two actuators which are attached to
the support structure. Alternatively, the ends of the
actuators which are attached to the support structure may be
positioned at the same location.
The slewing assembly according to preferred embodiments
of the invention may have a drive means or drive mechanism
which provides only two actuators or may alternatively provide
more than two actuators, such as three actuators.
Each of the actuators is preferably a hydraulic cyli~der.
In this manner, each hydraulic cylinder may be made
selectively capable of extension and retraction in a float
mode. In such a float mode, unpressurized hydraulic fluid is
permitted to respectively draw into and drain away from each
cylinder in response to loading thereof.
BRIEF DESCRIPTION OF DRAWINGS
For purposes of illustration and understanding of the
present invention, but not of limitation, reference will be
made to the following drawings in describing various aspects
and preferred embodiments of the present invention, in which:
Figure 1 is a perspective view of a timber handling
workhead, specifically a tree felling head, mounted to a boom
support structure of an all-terrain vehicle, which felling
head comprises the slewing mechanism according to a preferred
embodiment of the present invention;
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Figure 2 is a side elevation of the tree felling head of
Figure 1, showing a boom adaptor for attachment of the felling
head to the boom support structure and showing a linkage means
connected thereto for pivotal movement of the felling head
with respect to the boom support structure;
Figure 3 is a cross-sectional view of the tree felling
head of Figure 2, taken along line 3-3 of Figure 1, showing in
detail the structure of the slewing mechanism according to a
preferred embodiment of the present invention;
Figure 4 is an end elevation of the tree felling head,
partially in cross-section, viewed adjacent the boom support
structure (not shown) and showing the preferred positioning of
two hydraulic cylinders for the slewing mechanism according to
a preferred embodiment of the present invention;
Figure 5 is a side elevation of a cylindrical bearing
surface and boom adaptor of the slewing mechanism shown in
Figure 4, by means of which the tree felling head rotates
about a slew axis with respect to the boom support structure;
Figure 6 is an end elevation of the cylindrical bearing
surface and boom adaptor of Figure 5, viewed adjacent the boom
support structure (not shown);
Figure 7 is a top plan view of the cylindrical bearing
surface and boom adaptor of Figure 5;
Figure 8 is a cross-section of the cylindrical bearing
surface and boom adaptor of Figure 7, taken along the line 8-
8';
Figures 9a, 9b and 9c are schematic diagrams illustrating
the operation of the slewing mechanism of Figure 4, viewed in
end elevation adjacent the boom support structure (not shown),
and displaying in sequence three positions of clockwise
21 9672~ -
movement of the tree felling head as it rotates from an
unrotated or mid-point position, through to a dead or toggle
position associated with one of the hydraulic cylinders of the
slewing mechanism, and ending with a fully rotated clockwise
position.
Figures lOa, lOb and lOc are schematic diagrams
illustrating the operation of the slewing mechanism of Figure
4, viewed in end elevation adjacent the boom support structure
(not shown), and displaying in sequence three positions of
counterclockwise movement of the tree felling head as it
rotates from an unrotated or mid-point position, through to a
dead or toggle position for one of the hydraulic cylinders of
the slewing mechanism, and ending with a fully rotated
counterclockwise position.
Figure 11 is a graph of wrist torque applied to the
slewing mechanism of Figure 4, plotted as a function of
angular displacement of the tree felling head from the mid-
point position;
Figure 12 is a schematic layout of an electrohydraulic
circuit adapted for operating and controlling the hydraulic
cylinders of the slewing mechanism according to a preferred
embodiment of another aspect of the present invention;
Figure 13 is a detailed schematic layout of a bank of
hydraulic control valves and relays associated with the
electrohydraulic circuit of Figure 12; and
Figure 14 is a cross-sectional view of the cylindrical
bearing surface and boom adaptor of the slewing mechanism of
Figure 5, showing a swivel manifold block mounted on the
slewing mechanism for through passage of hydraulic supply
lines from the boom support structure to timber handling means
of the workhead.
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11
Figure 15 is an end elevation of the swivel manifold
block of Figure 14, showing four swivel manifold spools for
the hydraulic supply lines;
Figure 16 is a partial cross-sectional view of the swivel
manifold block of Figure 14, taken along line 16-16' of Figure
15, showing the positioning of a swivel manifold spool within
the block;
Figure 17 is a schematic diagram illustrating an
alternate positioning of the two hydraulic cylinders for the
slewing mechanism, by means of attachment at a common point;
and
Figure 18 is a schematic diagram illustrating the
positioning of three hydraulic cylinders for the slewing
mechanism, again by means of attachment at a common point.
DETATT~Rn DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to Figure 1, the slewing mechanism of the
present invention is shown in a timber handling workhead of
the type having a felling head 40 connected to a support
structure in the form of a boom structure generally shown by
reference numeral 20.
The boom support structure 20 is connected to an all-
terrain vehicle 10 of the kind well known to those skilled in
this art, which includes an operator cab 12, an endless track
driving system 14, and a turntable 16 upon which the cab base
18 is mounted for rotation. The boom support structure 20
includes an inner arm portion 22 and an outer arm portion 24
each portion having a first and second end. The inner arm
portion 22 and the outer arm portion 24 are capable of pivotal
movement relative to one another at the junction of the second
end of the inner arm portion and the first end of the outer
2'1 ~672~
arm portion about pivot location 26. The first end of the
inner arm portion 22 is pivotally mounted to the cab base 18
as at pivot location 28. The second end of the outer arm
portion 24 is pivotally connected to the boom adaptor 50 as at
pivot location 62. Extension and retraction of a hydraulic
actuator 30 causes the inner arm portion 22 to pivot in a
vertical plane about pivot location 28. A further hydraulic
actuator 32 controls the angle between the inner arm portion
22 and the outer arm portion 24. Extension and retraction of
the hydraulic actuator 32 causes the outer arm portion 24 to
pivot in a vertical plane relative to the inner arm portion 22
about pivot location 26.
Turning more specifically to Figures 2 and 3, the felling
head 40 of the preferred embodiment is mounted in a fixed
fashion, known to those skilled in this art, to the end of the
outer arm portion 24 of the boom support structure 20 by means
of a boom adaptor or support structure adaptor 50. A linkage
means, known to those skilled in this art as a crank assembly,
60, is connected to the boom adaptor 50 for pivotal movement
of the felling head about pivot location 62. Crank assembly
60 comprises a link members 64 and a crank arm 70. Link
member 64 has a first end pivotally connected, as at 66, to
the boom adaptor 50 and a second end which is pivotally
connected, as at 68, to one end of crank arm 70. A piston rod
72 of hydraulic cylinder 74 is pivotally connected at its
cylinder end to a bracket 76 on the outer arm portion 24 of
the boom support structure 20. The other end of crank arm 70
is pivotally connected, as at 78, to the outer arm portion 24
of the boom support structure 20, such that the crank arm 70
extends upwards from the outer arm portion 24. Thus,
extension and retraction of piston rod 72 of the hydraulic
cylinder 74 causes crank assembly 60 to pivot the felling head
40 in a vertical plane, aligned with the boom support
structure 20, about the pivot location 62. This downwar~
articulation of the felling head via the crank assembly
provides the felling head with an additional degree of tilt to
21 ~67~8
approach a position that is nearly parallel to the ground when
the boom support structure is at full extension.
The felling head 40 according to a preferred embodiment
of the present invention is a disc saw felling head having an
upright box section structural element 41 acting as a main
member for the entire felling head and timber handling means
in the form of a grappling means and cutting means. The
grappling means consists of a single accumulator arm 42 and
two standard harvesting arms 43, both known to those skilled
in this art. The cutting means is provided in the lower
portion of the felling head and includes a circular saw blade
44 (Figure 1) mounted in a plane perpendicular to the general
longitudinal axis of the felling head. The saw blade 44 is
located within a saw blade housing 45 having a top surface 47
and a bottom surface 49. A saw motor 44A drives the circular
saw blade 44. Two skiis 46 are affixed to the bottom surface
49 of the saw blade housing 45 and a log pusher 48 protrudes
from the front of the saw blade housing as shown in Figures 2
and 3.
Referring to Figures 3 through 8, the slewing means for
rotational movement of the felling head 40 with respect to the
boom support structure 20 is next explained. Those skilled in
this art will readily appreciate that the present invention
may be adapted to other timber handling and processing
apparatus employing various timber handling and processing
means, such as workheads for felling, delimbing, debarking,
bucking, carriage and loading of trees, or combinations
thereof.
The slewing means according to a preferred embodiment of
the present invention comprises a first male cylindrical
bearing surface, provided with the boom support structure,
which is in relative rotational contact with a corresponding
second female cylindrical bearing surface provided with the
felling head. Preferably, the first male cylindrical bearing
21 96728
14
surface is an elongate cylindrical extension 52 that is
attached to the boom support structure 20 by means of the boom
adaptor 50 as shown in more detail in Figure 5. The boom
adapter 50 provides, at one end thereof, means for respective
pivotal attachment to the link member 64 of the crank assembly
60 and to the second arm portion 24 of the boom support
structure 20. Such means for pivotal attachment may be in the
form of a bracket assembly 51.
Preferably, the second female cylindrical bearing surface
is located in a cavity or receptacle 54 (Figure 3) in the
felling head 40. The second female cylindrical bearing
surface is concentrically disposed to receive the first male
cylindrical bearing surface therewithin. Preferably, the
second female cylindrical bearing surface is defined by a
plurality of annular bearings, such as two annular bearings
80, 82, which are housed in the receptacle 54 and which have a
generally L-shaped cross-sectional configuration. This L-
shaped configuration provides axial thrust bearing surfaces
80a, 82a and radial bearing surfaces 80b, 82b on each of the
annular bearings 80, 82, as shown in Figure 5. The annular
bearings may be constructed from brass or some other suitable
material known to those skilled in this art.
The elongate cylindrical extension 52 has a free terminal
end to which is fixedly attached a removable retaining plate
56 by means of bolts 57 or the like, and another terminal end,
adjacent to the boom adaptor 50, around which is disposed an
annular shoulder 58. The removable retaining plate 56 and
annular shoulder 58 together act to constrain the felling head
against excessive longitudinal movement within the receptacle
54 along the direction of the slew axis AA'. The removable
retaining plate 56 and the annular shoulder 58 define opposed
axial thrust bearing surfaces 56a, 58a which extend radially
around the elongate cylindrical extension 52, as shown in
Figure 5. The axial thrust bearing surfaces 56a, 58a
correspond with the respective axial thrust bearing surfaces
21 ~6728
80a, 82a of the annular bearings 80, 82 and are in relative
rotational contact therewith. The elongate cylindrical
extension 52 also defines radial bearing surface 52a which
extends along the longitudinal length thereof, as shown in
Figure 5. The radial bearing surface 52a on the cylindrical
extension 52 corresponds with the respective radial bearing
surfaces 80b, 82b of the annular bearings 80, 82 and are in
relative rotational contact therewith. In a preferred
embodiment of the present invention, the bracket assembly 51,
the elongate cylindrical extension 52, the removable retaining
plate 56 and the annular shoulder 58 are fixed the one to the
other by means of a screwed and welded engagement or the like.
The elongate cylindrical extension 52 may be constructed from
hardened steel or from some other suitable material known to
those skilled in this art. Advantageously, the elongate
cylindrical extension may be made hollow to allow for through
passage of hydraulic supply lines 200 to the timber handling
means of the felling head 40.
The two annular bearings 80 and 82 are concentrically
arranged with respect to the elongate cylindrical extension 52
and are fixed within the receptacle 54 to allow relative
rotational movement between the elongate cylindrical extension
52 and the annular bearings 80, 82 about the slew axis AA', as
shown in Figures 3 and 5. As explained in greater detail
below, this relative rotational movement, upon engagement of
the drive means, produces rotational movement of the felling
head 40 about the slew axis AA~ with respect to the boom
support structure 20. Those skilled in this art will
appreciate that although the described embodiment of the
invention provides annular bearings 80, 82 in the form of
bushings, other bearing surfaces such as those comprisin$
roller or ball bearings could also be adapted for use with the
present invention.
The drive means for imparting the relative rotational
movement of the felling head 40 with respect to the boom
21 96728
16
support structure 20 according to another aspect of the
present invention is described with reference to Figures 4 and
9 to 13. The drive means comprises at least two actuators,
preferably a first hydraulic cylinder 90 having a piston rod
94 and a second hydraulic cylinder 92 having a piston rod 96.
The hydraulic cylinders are of a conventional nature well
known to those skilled in this art, as more fully described
below. These hydraulic cylinders, when used as a means of
rotational drive together with the slewing mechanism according
to the present invention, eliminate the necessity of any form
of gearsets or other transmission gearing to achieve the
desired degree of high-angle rotation. In a preferred
embodiment of the present invention, the cylinder ends of
hydraulic cylinders 90 and 92 are rotatably attached adjacent
the top surface 47 of the saw blade housing 45 of the felling
head 40 by pin connections as at pivot locations 98 and 100
respectively, for instance by means of a pin and a spherical
alloy steel ball bushing or the like. Similarly, the terminal
ends of piston rods 94 and 96 are rotatably attached to the
boom adaptor 50 as at pivot locations 102 and 104,
respectively. Those skilled in this art will appreciate that
the reverse mounting of the hydraulic cylinders may also be
employed according to embodiments of the invention, as is the
mounting of the first cylinder in one orientation and the
second cylinder in the other. The cylinder ends of hydraulic
cylinders 90 and 92 are fixed and the terminal ends of piston
rods 94 and 96 are moveable along an actuating axis of each
hydraulic cylinder. In a preferred embodiment of the
invention, hydraulic cylinders 90 and 92 each have an
actuating axis which is located in a plane substantially
perpendicular to the slew axis of the felling head. The
preferred angular positioning and spatial orientation of
hydraulic cylinders 90 and 92 is described in greater detail
herebelow.
The hydraulic cylinders 90 and 92 are preferably double-
acting in nature, in that the piston rods 94 and 96 are
21 96728
-
17
capable of being driven to retract and extend. The piston
rods of the cylinders achieve powered linear extension and
retraction by way of pressurized fluid chambers of a
conventional nature controlled by electrohydraulic directional
control valves 106 as shown in Figure 3, of the type capable
of handling at least 4000 pounds per square inch, for example,
the valve L9OLS marketed by the VOAC Hydraulics company of Mt.
Prospect, Illinois or the like. Those skilled in this art
will appreciate that hydraulic cylinders 90 and 92 should be
installed such that the cylinders do not ever produce a .
"bottoming out" of the piston rods 94 and 96 at each extreme
end of the cylinder portion, whether the piston rod is fully
extended or fully retracted within the cylinder. In other
words, better mechanical integrity is achieved when the
hydraulic cylinders provide oil relief at each extreme
position of the piston rod, which is the result of the unused
stroke of the piston rod.
With reference to Figures 9(a) to 9(c) and lO(a) to
lO(c), extension and retraction of piston rod 94 of hydraulic
cylinder 90 creates a force along an actuating axis BB'
thereof which is located in a plane substantially
perpendicular to the slew axis AA'. This force is applied to
the slewing means at a point radially distant from the slew
axis AA', to thereby effect the rotational movement of the
felling head 40 with respect to the boom support structure 20.
Similarly, extension and retraction of piston rod 96 of
hydraulic cylinder 92 creates a force along an actuating axis
CC' thereof which is located in a plane substantially
perpendicular to the slew axis AA'. This force is likewise
applied to the slewing means at a point radially distant from
the slew axis AA' to thereby effect the rotational movement of
the felling head 40 with respect to the boom support structure
20. In the preferred embodiment of the present invention, the
extension and retraction of the piston rods of hydraulic
cylinders 90 and 92 are phase timed, or synchronized, by way
of sensing means, preferably in the form of two proximity
- 21 967~
18
sensing devices 108 and 109, shown in Figures 3 and 14, as
described in greater detail herebelow. In what follows,
reference to extension and retraction of hydraulic cylinders
90 and 92 shall mean extension and retraction of the piston
rods 94 and 96 within the cylinders.
In their preferred positioning and orientation, the
cylinder ends of hydraulic cylinders 90 and 92 are rotatably
attached adjacent the top surface 47 of the saw blade housing
45 substantially radially equidistant from the slew axis AA'
as best shown in Figure 4. The distance between the cylinder
ends does not change in the preferred embodiment because the
cylinder ends are fixed to the saw blade housing 45. The
angle ~ between the actuating axis BB' and the line YY'., and
the angle ~' between the actuating axis CC' and the line YY',
as shown in Figure 4, change depending upon the different
phases or synchronization of the extension and retraction of
the hydraulic cylinders. When the felling head 40 is in an
unrotated or midpoint position, as best shown in Figure 4, the
angles a and ~' are equal and were chosen in the preferred
embodiment because this was the angle which provided both firm
structural mounting of the hydraulic cylinders and permitted
rotation of the felling head 40 about the slew axis AA'
without the piston rods 94 and 96 interfering with one another
or traversing the slew axis AA'. In addition, the position of
hydraulic cylinders 90 and 92 was chosen in the preferred
embodiment such that when one cylinder is in its dead or
toggle position, defined in more detail below, the other
cylinder is in the position of applying m~;mllm torque to the
slewing means, as shown in Figures 9(b) and lO(b).
The terminal ends of piston rods 94 and 96 are also
positioned substantially radially equidistant from the slew
axis AA' as shown in Figure 4, and are rotatably attached to
the boom adaptor 50 which is pivotally attached to the boom
support structure 20. Neither the distance between the
terminal ends and the slew axis AA' nor the angle 0, as shown
2~ ~6728
19
in Figure 4, changes in the preferred embodiment during the
different phases or synchronization of the extension and
retraction of the hydraulic cylinders. When the felling head
40 is in an unrotated or midpoint position, as best shown in
Figure 4, the terminal ends of piston rods 94 and 96 are
located in a line that is substantially parallel with a line
which intersects the cylinder ends of the corresponding
hydraulic cylinders 90 and 92. Moreover, hydraulic cylinders
90 and 92 are positioned with the terminal ends of piston rods
94 and 96 being angled towards the slew axis AA'.
The phased timing or synchronization of hydraulic
cylinders 90 and 92 will next be described with reference to
Figures 9(a) to 9(c) and lO(a) to lO(c). In the preferred
embodiment of the present invention, when the felling head 40
is in an unrotated or midpoint position, as shown in Figure
9(a), the terminal ends of piston rods 94 and 96 are each
located at angle of approximately 17~ below the line XX' which
intersects the slew axis AA'. For rotation of the felling
head 40 in a clockwise direction when viewed from the boom
support structure 20, hydraulic cylinder 92 is powered to
retract, and hydraulic cylinder 90 is simultaneously powered
to extend, until the felling head 40 assumes the position as
shown in Figure 9(b). At the position shown in Figure 9(b),
the felling head 40 has rotated approximately 40~ about the
slew axis AA' in a clockwise direction from the unrotated or
midpoint position of Figure 9(a).
The position of the hydraulic cylinders shown in Figure
9(b) defines the dead or toggle position of hydraulic cylinder
92, in that no torque is being applied to the slewing means by
hydraulic cylinder 92. This dead or toggle position occurs
when the actuating axis CC' associated with hydraulic cylinder
92 intersects with the slew axis AA~ during rotational
movement of the felling head 40. In the preferred embodiment
of the invention, a sensing means is used to detect the dead
or toggle position of each of the hydraulic cylinders 90 and
21 9672~
92. The sensing means is described in greater detail below.
When the sensing means detects that hydraulic cylinder 92 has
attained the dead or toggle position, the direction of linear
translation of hydraulic cylinder 92 is reversed so that the
cylinder is thenceforth powered to extend rather than retract.
For the felling head 40 to continue to rotate clockwise from
the position of Figure 9(b), hydraulic cylinder 92, having
attained its dead or toggle position and having now reversed
its direction of linear translation, extends while hydraulic
cylinder 90 simultaneously further extends so that felling
head 40 assumes the fully rotated position as shown in Figure
s(c). Mechanical stops 93 and 95, as shown in Figures 3, 5
and 14, are used on the felling head to prevent it from
rotating beyond the fully rotated position. Mechanical stops
93 and 95 prevent the felling head from rotating beyond the
fully rotated clockwise or counter-clockwise positions shown
in Figures 9(c) and lO(c), by abutment against corresponding
stops 193, 195 located on the boom adaptor. The mechanical
stops are metal weldments or the like.
At the clockwise fully rotated position of the slewing
mechanism, the terminal ends of piston rods 94 and 96 are
still at an angle of approximately 17~ below the line XX' and
the felling head 40 has rotated approximately 100~ about the
slew axis AA' in a clockwise direction from the unrotated or
midpoint position of Figure 9(a). To reverse direction from
the position shown in Figure 9(c), each of hydraulic cylinders
90 and 92 is powered to retract, thereby returning the felling
head 40 towards the position of Figure 9(b). When the
position of Figure 9(b) is attained, again the sensing means
associated with hydraulic cylinder 92 causes cylinder 92 to
reverse direction, whereupon cylinder 92 is powered to extend
rather than retract. The felling head 40 is then returned to
the unrotated or midpoint position set out in Figure 9(a) by
the powered extension of hydraulic cylinder 92 and the
continued powered retraction of hydraulic cylinder 90.
- 21 ~67~8
21
For rotation of the felling head 40 from the
unrotated or midpoint position shown in Figure lO(a) in a
counter-clockwise direction, when viewed from the boom support
structure, hydraulic cylinder 90 is powered to retract and
hydraulic cylinder 92 is simultaneously powered to extend,
until the felling head 40 assumes the position shown in Figure
lO(b). At the position shown in Figure lO(b), the felling
head 40 has rotated approximately 40~ about the slew axis AA~
in a counter-clockwise direction from the unrotated or
midpoint position of Figure lO(a).
The position of the hydraulic cylinders shown in
Figure lO(b) defines the dead or toggle position of hydraulic
cylinder 90, in that no torque is being applied to the slewing
means by hydraulic cylinder 90. This dead or toggle position
occurs when the actuating axis BB' associated with hydraulic
cylinder 90 intersects with the slew axis AA' during
rotational movement of the felling head 40. When the sensing
means associated with hydraulic cylinder 90 detects that the
dead or toggle position has been attained, the direction of
linear translation of hydraulic cylinder 90 is reversed so
that the cylinder is thenceforth powered to extend rather than
retract. For the felling head 40 to continue to rotate
counter-clockwise from the position of Figure lO(b), hydraulic
cylinder 90, having attained its dead or toggle position and
having now reversed its direction of linear translation,
extends while hydraulic cylinder 92 simultaneously further
extends so felling head 40 assumes the fully rotated position
as shown in Figure lO(c). Mechanical stop 95 prevents the
felling head from rotating beyond the fully rotated counter-
clockwise position shown in Figure lO(c).
At the counter-clockwise fully rotated position of the
slewing mechanism, the terminal ends of piston rods 94 and 96
are still at an angle of approximately 17~ below the line XX'
and the felling head 40 has rotated approximately 100~ about
the slew axis AA' in a counter-clockwise direction from the
21 q6728
unrotated or midpoint position of Figure lO(a). To reverse
direction from the position shown in Figure lO(c), each of
hydraulic cylinders 90 and 92 is powered to retract, thereby
returning the felling head 40 towards the position of Figure
lO(b). When the position of Figure lO(b) is attained, again
the sensing means associated with hydraulic cylinder 90 causes
cylinder 90 to reverse direction, whereupon cylinder 90 is
powered to extend rather than retract. The felling head 40 is
then returned to the unrotated or midpoint position set out in
Figure lO(a) by the powered extension of hydraulic cylinder 90
and the continued powered retraction of hydraulic cylinder 92.
In the preferred embodiment, the sensing means for
detecting the dead or toggle position of each hydraulic
cylinder consists of two proximity sensing devices 108 and
109. Sensing device 108 detects position changes of hydraulic
cylinder 90 and sensing device 109 detects position changes of
hydraulic cylinder 92. The proximity sensing devices detect
positional changes through changes in magnetic fields and are
of a conventional nature known to those skilled in this art,
for instance both of the proximity sensing devices in the
preferred embodiment are of the type IAS-20-A13-S made by
Rechner Industries of Germany. Such proximity sensing devices
detect the presence of a metal object which is located within
a distance of approximately 5 millimetres from the device.
Therefore, in a preferred embodiment of the present invention,
a raised portion or a metal end plate 107 (Figure 5),
approximately 3/8 of an inch thick, is affixed by weldment or
the like to extend from the outer end surface of retaining
plate 56. The outer end surface of retaining plate 56 is not
itself within the 5 mm range of the proximity sensors, but the
outer end surface of metal end plate 107 is within said range.
When the metal end plate 107, by rotation of the felling head
40, crosses the field of detection of the proximity sensor,
which occurs when either of hydraulic cylinders 90 and 92 are
in the dead or toggle position, the proximity sensor detects
the presence of the metal end plate and signals a reversal of
21 q6728
-
23
the direction of linear translation of the cylinder in the
dead or toggle position as more fully described below.
When hydraulic cylinder 90 is in the dead or toggle
position, proximity sensing device 108, shown in Figure 3,
detects the presence of the metal end plate 107 and signals
the hydraulic circuit shown in Figure 12 by means of electric
relays 110 to reverse the direction of linear translation of
that cylinder by redirecting the flow of oil into hydraulic
cylinder 90. A similar signal is generated by proximity
sensing device 109 when it detects the presence of the metal
end plate 107 due to hydraulic cylinder 92 being in the dead
or toggle position. Accordingly, the direction of linear
translation of hydraulic cylinder 92 is reversed by
redirecting the flow of oil into that cylinder. Thus, the
effect of reversing the direction of linear translation of a
hydraulic cylinder at the dead or toggle position associated
with that cylinder is to further rotate the felling head 40
about the slew axis AA' such that the felling head reaches its
maximum angle of rotation. Those skilled in this art will
appreciate that other types of sensors may be employed to
effect the above-described sensing means, for example, the
proximity sensor may be substituted by a contact or mechanical
switch. Alternatively, rotary valves or the like may be used
to detect the positional changes of the felling head itself.
The position and spatial orientation of hydraulic
cylinders 90 and 92 as described above allows for the
avoidance of the central zone 99 as schematically shown in
Figures 4, 9 and 10. The central zone 99 allows for passage
of the hydraulic supply lines 200 for the various powered
devices of the workhead, such as the accumulator arm 42 and
the harvesting arms 43, or the saw motor 44A, through the
centre of the elongate cylindrical extension 52 of the boom
adaptor 50 as shown in Figure 14. This preferred central
passage of the hydraulic supply lines is yet another aspect of
the present invention and is achieved by means of a swivel
- 21 ~6728
24
manifold block and spools as described in greater detail
herebelow.
A preferred hydraulic circuit for the felling head 40 of
the present invention is described with reference to Figures
12 and 13. Those skilled in this art will appreciate that
alternative hydraulic circuit layouts may also be used in
order to operate and control the various felling head devices
mentioned above. The preferred circuit 120 for use with the
present invention includes proximity sensor circuits 122a,
122b and float sections 124a,124b, each of which are described
in greater detail below.
With reference to Figure 12, the circuit 120 comprises a
first pressure source 125, such as a hydraulic pump, to supply
hydraulic fluid to a bank 126 of directional control valves
106, which bank includes the float sections 124a, 124b. The
bank 126 in turn is in fluid commlln;cation with clamp
cylinders 128a, 128b and with hydraulic cylinders 90 and 92.
The clamp cylinders respectively actuate the accumulator arm
42 and the harvesting arms 43 of the felling head 40,
previously described. The hydraulic cylinders 90 and 92
actuate the slewing means for the felling head 40, also
previously described.
A second pressure source 130, such as a hydraulic pump,
supplies hydraulic fluid to saw motor 44A. The saw motor 44A
is for driving circular saw blade 44, referred to above. A
check valve 132 is disposed in parallel to the saw motor 44A
to allow for continued operation of the saw motor on power
off. Each of the circuit segments associated with the
hydraulic pumps 125 and 130 provide respective return lines
134 and 136 to tank 137. A drain 138 is provided to tank 144
for actuation solenoids 142 (Figure 13) associated with the
directional control valves 106 of bank 126. Likewise, a case
drain 146 to tank 144 is provided for saw motor 44A.
- 2~ q6728
Turning now to Figure 13, each of the directional control
valves 106 of bank 126 is preferably a four-way, three-
position valve which is biased to the centre position. At the
centre position of each valve 106, the respective cylinders
9o, 92, 128a and 128b are locked hydraulically. At either end
position of the valves 106, hydraulic fluid is supplied so as
to respectively extend and retract the piston rods of each
cylinder. A pair of actuation solenoids 142 is associated
with each of the valves 106 in order to activate the valves
away from their biased centre position. Each activation
solenoid 142 of the said pair is a two-position hydraulic
spool, respectively controlled by means of operator
pushbuttons 148 or the like. In Figure 13, the pushbuttons
for the actuation solenoids of the circuit segments for the
hydraulic cylinders 90 and 92 of the slewing means are shown,
but those that would be associated with clamp cylinders 128a,
128b are omitted for sake of convenience, as those skilled in
this art will readily be able to derive an appropriate
arrangement of operator controls to activate the actuation
solenoids associated with clamp cylinders 128a, 128b.
Each pushbutton 148 for the circuit segment of the
slewing means provides a signal to its associated actuation
solenoid pair 142 through paired relays 110. Each paired set
of relays 110 is powered by a respective proximity sensor 108,
109 as previously described. Thus, when hydraulic cylinder 90
or 92 reaches its dead or toggle position, the relays 110 are
switched, thereby causing power to be discontinued from one
actuation solenoid 142 and supplied to the other actuation
solenoid 142 of the solenoid pair associated with the
particular cylinder 90 or 92. Relays 110 therefore effect the
reversing of direction of linear translation of hydraulic
cylinders 90 and 92 at the dead or toggle position associated
with these cylinders, to allow for further rotation of the
felling head 40 so that it reaches its maximum angle of
rotation, all as previously described.
- - - - - - - - -
26 21 '~6128
The float sections 124a, 124b associated with the
respective hydraulic cylinders 90 and 92 each comprise two
two-way, two-position spools 150. When all of the spools 150
for both cylinders 90 and 92 are activated by means of a
common pushbutton (not shown) or other suitable operator
control means, each port at the central position of the valve
106 is placed in fluid commlln;cation with tank, thereby
permitting each of the hydraulic cylinders 90 and 92 to extend
and retract in a float mode. In this mode, unpressurized
hydraulic fluid may be drawn into and drained away from each
cylinder in response to loading thereof. Those skilled in
this art will appreciate that other means may be employed in
order to implement the above-described float mode, for
instance, the three-position valves 106 of the slewing means
circuit segment may be substituted with valves that provide an
additional position to put each of the relevant ports of the
valve to tank.
In operation, once an operator has felled a tree and has
oriented the felled tree in a desired position by actuation of
the slewing means and boom for the felling head, the operator
may then engage the float mode in order to effect a release of
the hydraulically locked actuators of the slewing means. This
will achieve a damped fall for the tree to the location of
skidding. The float mode therefore enables a skilled operator
to place a felled tree to the ground more quickly, without the
need for operator controlled and powered movements of the
slewing means, provided the operator is ~atisfied with the
expected trajectory of the tree prior to engaging the float
mode. In addition, the skilled operator may use the float
mode to move a felled tree while it is on the ground by
dragging the trunk end of the felled tree to a desired
location for loading or skidding.
With reference to Figure 14, 15 and 16, the elongate
cylindrical extension 52 of the boom adaptor 50 is associated
with a fluid delivery means consisting of a swivel manifold
21 96728
27
block 210 for through passage of hydraulic supply lines 200
for controlling and driving the various powered devices of the
felling head 40. The swivel manifold block 210 is constructed
of ductile iron or the like and comprises a retaining plate
214 which attaches the block to the felling head 40 by means
of bolts 224 or the like and an end plate 226. The swivel
manifold block has been equipped with an aperture 222 for
alignment purposes during assembly.
There are four swivel manifold spools 212 which are
housed within the swivel manifold block 210 as best shown in
Figure 15. The end plate 226 prevents the spool from lateral
movement out of the swivel manifold block as seen in Figure
16. Each swivel manifold spool is substantially cylindrical
and constructed of hardened steel or the like which creates a
bearing surface 212a thereby allowing the spool to rotate
within the swivel manifold block 210. Four hydraulic supply
lines 200 pass through the swivel manifold block 210 and
deliver fluid into each of the four swivel manifold spools via
conduits 228 as shown in Figure 15. The spools are provided
with apertures 218 in fluid commlln;cation with the downstream
hydraulic supply lines for the various powered devices in the
felling head 40. In this way, the swivel manifold block and
spools reduce the torsion that would normally be applied to
the hydraulic supply lines if they were carried to the felling
head 40 or passed through the slewing means uninterrupted.
By using hydraulic cylinders as a means for driving
rotational movement of the felling head 40 with respect to the
boom support structure 20, many of the problems associated
with complex gearset arrangements are eliminated. For
example, wear and tear on the slewing mechanism and the level
of machine maintenance will both be expected to be reduced.
Fewer engaging and locking parts is expected to ml n;m~ ze down
time caused by clogging debris from felled trees which in turn
reduces operating costs and increases productivity.
21 967~8
28
In addition, by providing the swivel manifold block and
spools, the length of the hydraulic supply hoses to the
felling head 40 may be reduced since there is no need for the
rotational movement of the felling head to be accommodated by
slack in the supply hoses. This results in a compact design
which m; n i m; zes hose chaffing and snagging during field use of
the felling head 40.
Finally, those skilled in this art will appreciate that
the inventive concept in any of its foregoing aspects can be
incorporated, adapted or modified in many different
constructions, so that the generality of the preceding
description is not to be superseded by the particularity of
the attached drawings. For instance, as shown schematically
in Figure 17, an alternate positioning for two hydraulic
cylinders 90a, 92a is to attach the actuating rod end of the
cylinders to a common point 300a located on the boom adaptor.
As shown schematically in Figure 18, a further alternative is
the use of three hydraulic cylinders 90b, 92b and 90c whose
actuating rod ends are attached at common point 300a on the
boom adaptor. Thus, these and various other alterations,
modifications or additions may be incorporated into the
various constructions and arrangements of parts and devices
described herein without departing from the spirit or scope of
the present invention.
