Note: Descriptions are shown in the official language in which they were submitted.
64
The present invention relates to the general
field of tree-harvesting and mnre specifically to an
improved rotary cutting tool for use on the cutting head
5 assembly of a tree-felling vehicle~
In the past recent years, various types o f
machines for felling trees have been developed. A typical
example is the tree-felling tractor used in large scale
tree-harvesting operations, which is a self-propelled all
10 terrain vehicle specifically designed to operate in forest
areas undcr harsh conditions~ The vehicle is provided
with an articulated boom carrying at its end a cutting
mechanism, designated in the art as "cutting head". The
articulated boom is hydraulically operated and it can be
15 extended and retracted, raised, lowered or swung through
360 degrees allowing to bring the cutting head against a
standing tree to be cut~ The cutting head is provided with
a cutting tool for cutting the trce, as well as with a
grappling mechanism to grasp the tree once the cutting
2 0 phase is completed. The felled tree can then be
manipulated to be deposited on the ground or on 3 trailer
for ultimate transportation to a mill.
As it is known to those skilled in the art,
efficient operation of the cutting head is essential to
25 obtain good harvesting rates. For that r e a s o n
considerable efforts have been devoted by the past to the
design of a highly efficient cutting head that is reliable,
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versatile and inexpensive to build and to operateO ~mong
the various designs that have been proposed, the cutting
head disclosed in tbe United States Patent number
4,446,897 granted on May 8, 19~4 to Koehring Canada
Limited, has found wide acceptance in the industry. The
approach in this patent is to provide a cutting head with a
circular saw mounted to a supporting structure that also
carries a pair of hydraulically operatcd arms. In use, the
cutting head is placed against a standing tree by swinging
sideways the boom of the tree-felling vehicle, and when
the cut of the tree is nearly completed, the arms are closed
to grasp the tree, which is then carried away.
This prior design has not been completely
satisfactory in providing optimum tree-cutting
performance at minimum cost. Its main disadvantage is
that it is rather heavy and it can be used only with large
tree-felling vehicles. Furthermore, it is complex to
operate requiring skill and experience from the operator
of the machine to close the power arms ollly ~VhCIl the
2 0 CUttillg phase is almost completed. If the arms are closed
too early, the tree may splinter because of the higll
bending efforts exerted by the arms. On the other hand,
closing the arms too late results in an inability to retain
the tree in the cutting head.
2 5 In another known design, the clltting head is
equipped with a hydraulically or pneumatically operated
shearing device having a pair of knives that shear-off the
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tree instead of cutting it with a rotary tool. These cutting
heads are inexpensive and operate relatively faster,
however, they are known to cause wood splintering
especially if the knives do not meet exactly in the same
5 plane, which may be the result of wear or of improper
adjustment. The wood splinter damages are to be avoided
because the splinted wood portion of the tree must be cut-
off and treated as waste.
Generally speaking, the prior designs have not
10 been able to meet all the requirements to ensure an easy
and trouble-free operation during adverse tree-
harvesting conditions in forest areas.
An object of this invention is an improved
rotary cutting tool for use with a cutting head of a tree-
15 felling apparatus, allowing to rapidly complete the treecutting operation and which has less tendency to become
clogged with wooden chips, comparatively to prior
designs.
The rotary cutter, in accordance with the
2 0 invention, is of the auger type comprising an clongatcd
generally cylindrical body with spirally extending teeth
having each a sharp cutting edge, the teeth being
separated from one another by relatively smooth
transition faces. Each tooth is provided with a bite limiter
2 5 to control the depth of penetration in the wood. Such bite
limiter allows to achieve a controlled cutting action,
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thereby reducing the possibility of rotor jamming or
clo~ging with wooden chips.
In a preferred embodiment, the bite limiter is in
the form of a projection fornmed on the transition face,
5 extending along the cutting edge of the associated tooth.
The projection is positioned radially inwardly with
respect to the cutting edge7 the distance between the
radial position of the projection and the cutting edge
defining the depth of penetration of the tooth.
Preferably, the cutting rotor, according to the
invention, is used with a cutting head assembly to be
mounted on the cnd of the articulated boom of a tree-
felling vehicle, comprising a tree-carrying frame,
preferably dimensioned to receive and carry a plurality of
15 felled trees. Advantageously, the cutting rotor is
mounted in the lower portion of the tree-carrying frame
to cut a tree low to the ground ior obtaining good wood
product recovery.
A grappling arm assembly is Ill()lllltCd to lhc
2 0 tree-carrying frame, for placcment against olle side of a
tree to bring the tree-carrying frame and the cutting tool
toward the tree. The tree progressively enters the trce-
carrying frame as the cutting of the tree proceeds. When
ttle cutting phase is completed, thc tree is entirely
2 5 supported by the tree-carrying frame.
Preferably, a spring biased clamping arm is
mounted to the tree-carrying frame to securely hold one
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s
or several trees therein when the tree-felling vehicle
progresses in the forest area. The clamping arm is
designed to move out of engagement with the trees in the
tree-carrying frame to allow a freshly cut tree to enter
5 the tree-carrying frame, and then to move back in
position to securely clamp the trees.
Therefore, the invention comprises, in a
general aspect, a wood cutting tool for use on a cutting
headl of a tree-felling vehicle, the cutting tool
1 0 comprising:
- an elongated generally cylindrical body
having a longitudinal axis coinciding with an axis of
rotation of the body; and
- a plurality of teeth on the body, the teeth
15 extending spirally about the longitudinal axis, two
adjacent teeth being separated by a transition face, each
tooth including a sharp cutting edge and a bite limiting
means to limit the penetration of the tooth in the wood.
A preferred embodiment of the present
2 0 invention will now be described in relation to the anllexed
drawings, in which:
Figure 1 is a perspective view of a cutting head
assembly for use with the rotary cutting tool accnrding to
the present invention;
2 5 Figure 2 is an elevational view of a rotary
cutting tool according to the invention;
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Figure 3 is cross-sectional view along lines 3-3
of the cutting tool shown in Figure 2;
Figure 4 is a top plan view of the CUttillg head
assembly according to the present invention; and
5Figures S to 11 illustrate the operation of the
cutting head assembly according to the invention.
Figure 1 of the drawings illustrates a cutting
head assembly 10 designated by the reference numeral 10.
The cutting head assembly is shown attached to the boom
1012 of a tree-felling vehicle which is not illustrated in the
drawings and will not be described in detail because such
vehicles are well known in the art and do not form part of
the present invention.
The cutting head assembly comprises a
15 generally U-shaped tree-carrying frame 14 constructed
from metallic members which are assembled by welding or
by any other appropriate manner. More particularly, the
tree-carrying frame comprises a supporting platform 16
made of heavy gage sheet-metal mollnte(l to ~I metallic
2 0 brace 18 lo provide rigidity. Fron~ the platlorlll lfi pr()Jcct
upwardly a pair of elongated hollow members 2n llaving a
rectangular cross-section, the elongated hollow member
20 at the right in Figure 1 being the largest and being
secured to the extremity of the boom 12 by means of a
2 5 suitable connection (not shown in the drawings) of a type
known in the art. This type of connection allows the
cutting head to be rapidly removed from the boom 12 for
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ser~ice or for installation to another tree-felling vehicle.
To both members 20 are attached a pair of vertically
spaced curved supports 22.
A cutting tool in the form of an auger-type rotor
5 24 with helically extending cutting teeth is mounted to
the lower portion of the tree-carrying frame 14, in front
of the platform 16. The rotor 24 is journaled to the the
brace 18 and it is driven by a hydraulic motor 26 of known
construction mounted in a suitable housing 28. Power to
10 the motor 26 is provided by pressurized fluid supplied by
flexible lines 30 from the hydraulic circuit of the tree-
felling vehic1e. The structure of the rotor 24 will be
described in detail later in conjunction with Figures 2
and 3.
The tree-carrying frame 14 may be
manufactured in different sizes according to the average
trunk diameter of the trees to be cut or according to the
number of trees to be received in the tree-carrying frame
14.
2 0 The tree-carrying frame 14 carries a grappling
arm assembly 32 including a pair of arms 34 secured to a
shaft 38 journaled at its lower end to the housing 2X of
the motor 26, and at its upper end to a bracket 40 welded to
the hollow member 20 mounted to the boom 12.
2 5 Referring in conjunction to Figures 1 and 4, a
clamping arm assembly 42 is mounted on the shaft 38 and
comprises a bracket 44 rotatably mounted to the shaft 38
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between the bracket 40 and the upperrnost tree engaging
arm 34, and a curved clamping arm 46 mounted for
rotation on the bracket 44 about a pin 48. A coil spring 50
having one end attached to the clamping arm 46 and an
5 opposite end secured to the bracket 44 maintains the
clamping arm 46 in the position shown in Figure 1,
against a stop S2 formed on the bracket 44. In other
words, the clamping arm 46 cannot be rotated about the
pin 48 outwardly with respect to the tree-carrying frame
10 14 when the clamping arm 46 is in the position shown in
Figure 4, because it abuts against the stop 52. However,
the clamping arm 46 may be pushed inw;lrdly by
extending the spring 50.
The tree grappling arm assembly 32 may be
15 moved toward and away the tree-carrying frame 14 by
extending or retracting, respectively, a fluid ram 54
(illustrated schematically with dashed lines in ~igure 4)
having an end mounted to a bracket 56 wclded to the tree-
carrying frarne 14, and an opposite en(l mo~ tc(l to the
2 0 grappling arm assembly 32. Similarly, tlle clamping arm
assembly 42 rrlay be pivoted on the shaft 38 by a flui(l ram
S8 (illustrated schematically with dashed lines in Figure
4) having one end mounted to the bracket 44 and an
opposite end mounted to a bracket 60 attached to the tree-
2 5 carrying frame 14 and vertically spaced from the bracket56.
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The f1uid rams 54 and S6 are operated by
pressurized hydraulic fluid supplied from the hydraulic
circuit of the tree-felling vehicle, as it is known in the
art.
S Reference is now made to Figures 2 and 3
illustrating in detail the structure of the rotor 24. The
rotor 24 is made of metallic material, preferably wear
resistant steel and has a generally cylindrical shape. The
cutting rotor 24 is provided with a plurality of helically
extending teeth 62 each inclined in the direction of
rotation of the rotor 24 and terminating with a cutting
edge 100 overhanging a deep flute 102. The teeth 62 are
separated from each other by relatively smooth transition
faces 104, each transition face 104 extending from the
15 cutting edge of a leading tooth toward the flute of a
trailing tooth. On each transition face 104 are grinded
two relatively flat, narrow and oblique surfaces 106 and
108 ~neeting at an obtuse angle to define a projecting
ridge 110 parallel to the associated cutting edge 100 and
2 0 running alon~ the entire length thereof. Tlle ridge 110
extends radially inwardly with respect to the associated
cutting edge 62 to define a bite limiter to control the
penetration of the toolh in the wood. The operation of the
bite limiters is schematically illustrated in Figure 3. The
2 S dashed line 112 illustrates the bottom of the Icerf pro(luced
by the rotor 24 in a tree. Upon rotation of the rotor 24 the
teeth 62 will penetrate the wood until the ridges 110 abat
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on the bottom of the kerf, the rotating movement causing
chips 114 to be peeled away from the wood. Since the
penetration of the t--eth 62 in the wood is limited, there is
little possibility of rotor jamming because the rate of wood
removal by each tooth is strictly controlled.
The depth of penetration of each tooth 62 in the
wood corresponds to the distance between the radial
positions of the cutting edge of the tOOtll 62 and the
associated ridge 110 respectively. Stated otherwise, the
depth of penetration is the distance, considered in cross-
section of the rotor 24, separating two concentric
imaginary circles, namely an inner circle containing all
the ridges 11n of the rotor 24 and an outer circle
containing all the cutting edges 100. By varying the
location of the ridge 110 with respect to the position of
the associated tooth 62, the depth of penetration thereof
may be changed.
It should be appreciated that the bite limiters
may be provided by forming various types of pro jection
on the transition faces 104, the ridges 11() l~cing only thc
most convenient since they are formed by simply
grinding two oblique flats.
The pitch of the teeth 62 is in the range from 10
to 15 degrees approximately. The pitch is defined as the
2 5 angle between a tangent to the cutting edge 100 and the
axis of rotation of the cutting tool.
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The end portions 64 of the rotor 24 are
machined to fit in respective bearings (not shown) in the
brace 18.
The operation of the cutting head 10 according
5 to the invention will now be described in detail with
relatîon to Figures 5 to 11.
For beginning the tree-har~esting operation,
the tree-felling vehicle is driven in position in the forest
area near a standing tree 101 to be cut. The boom 12 of
10 the vehicle is extended to bring the cutting head tO close
to the tree 101, the grappling arm slssembly 32 and the
clamping arm assembly positioned against the tree 101 as
shown in Figure 5. The hydraulic motor 26 is actuated and
the fluid ram 54 is extended to bring the tree carrying
frame 14 against the tree 101 for enga&ement with the
spinning rotor 24 which progressively cuts the tree 101,
as illustratedl in Figure 6. The tree 101 progressively
enters the tree-carrying frame 14 while the cutting ph,lse
proceeds unt;l the cut is completed alld thc tree 10l is
2 0 entirely supported on the platform 16.
The fluid ram 58 is extended to bring the
clamping arm 46 toward the tree 101 for securing same in
the tree-carrying frame 14.
Referring now to Figure 6, to cut anolher tree,
2 5 designated by the reference numeral 200, the grappling
arm assembly 42 is opened and the cutting head 10 is
moved in position so that the grappling arm assembly 32
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is brought against the tree 200. The fluid ram 54 is
extended to bring the tree-carrying frame 14 toward the
tree 200 which is cut by the rotor 24 and loaded in the
tree-carrying frame 14, the tree 200 resting between the
S clamping arm 46 and the grappling arm assembly 32, as
exemplified in Figure 9. The fluid ram 58 is then
retracted so that the arm 46 pivots about the pin 48 to
clear the tree 200 and to spring back in opened position as
shown in Figure I1.
The same steps are repeated to cut another tree
until the tree-carrying frame 14 is filled to capacity.
Although the invention has been described
above with respect to one specific form, it will be evident
to persons skil1ed in the art that it may be refined and
15 modified in various ways. It is therefore wished to have
it understood that the present invention should not be
limited in interpretation except by the terms of the
following claims.
