Note: Descriptions are shown in the official language in which they were submitted.
f~783~
BACKGROUND OF THE INVENTION
This invention pertains to the field of rotary cutt0rs more specifically to the field
of cutters adapted for separating bark from the hardwood of a tree.
In the field of sawmill operation it is necessary, as one of the steps for preparing
a tree for further use that the outer bark coating of the tree be separated from the tree.
While the technology appears to draw from the field of wood chippers and adzes, it is
distinct in that while it is necessary to remove the bark by abrading, it is deleterious to
the tree to cut significantly into the wood. Thus a cutting head or adz which is equally
adapted to chipping wood as well as bark is unsatisfactory for the use.
Two major forms of debarkers are in common use. Typically each depends upon
the fact that the shear strength of the bark is weakest in the cambium layer between the
wood and the bark.
Once such form of machine is known as the hol!ow rotor type in which a pluralityof arms, swing mounted to a rotary collar extend inward scraping tangentially in a spiral
around the exterior of the tree which is fed through the center of the collar. Typical
such cutters are shown in U.S. Patent 4,231,406 to Jonsson and U.S. Patent 4,709,737
to Jonsson.
More commonly used form of debarker is the so-called rosser-head debarker in
which a log is traversed past a rotating cylindrical cutter head which rotates against
the log, parallel to the axis of the log. As the log is rotated against the head various
forms of cutters upon the rosser-head are depended upon to tangentially shear the bark
from the log. Typical such prior constructure shown in the Salem rosser-head debarker
and the debarkers manufactured by Fulghum Industries, and the Forest Tool Company.
2~783~
A typical debarker of the radial arm type is manu~actured by Valone, Kone,
Brunette, Inc.
2~78355
SUMMARY OF THE INVENTION
This invention relates to an improved debarking head for a rosser-head type
debarker.
Rosser-head debarkers are all characterized in comprising a substantially
strong metal cylinder affixed to a powered rotating axis which is parallel to the
longitudinal axis of a tree to be debarked with periodically extending cutter teeth on the
cylindrical outer surface of the debarker head. The impacts upon these cutter teeth are
such that they require frequent resetting or replacement and it is difficult to get even
two to three months use from a typical debarker head in full industrial usage.
We have discovered a form of pattern and tooth for rosser-type debarker head
which produces bark chips which can be directly used for boiler field fuel, being small
enough to feed through conveyor and piping system. Further, the particular pattern of
the debarker head cutting teeth of our invention produces more uniform chips and a
smoother more uniform log surface yielding more lumber as opposed to the prior art
rosser-head teeth which create a flailing action removing large barks and large chunks
and creating extensive wood splintering. The existence of wood splintering requires a
sawmill to remove more wood in the first slabbing operation. Further, inasmuch as slab
removed and squaring up a log are typically reduced to wood chips to be used in the
manufacture of composite building materials, it has been found that the particular
pattern of our head produces a smoother finish on the slab and thus a greater quality
and yield of marketable chips.
The debarker head of our invention comprises a plurality of rounded, indexable
cutting teeth spaced in patterns of repeated rows running axially the length of the
~783~
cyllndrical surface, each tooth being spaced along the cylindrical surface so that the
total cutting shadow produced by a single rotation of the head creates a uniform round
toothed scalloped effect. Each tooth is shadowed by adjacent offset teeth so that only
the portion of the round tooth outside of a cord representing essentially one-sixth of the
circumference of the tooth is exposed to direct cutting impact. The remainder of the
round tooth is shadowed by adjacent cutter teeth. As a result, the debarker head of our
invention produces a uniform scalloped cut producing both a shallow and smooth cut
upon the log with limited splintering and reducing the impact on the teeth so that tooth
life is significantly extended.
By shadowing the teeth so that only one-sixth of the tooth circumference is
exposed to cutting ax, the head may be renewed by simply providing the teeth as
round inserts which may be indexed or rotated when worn exposing a new fresh
cutting surface rather than requiring total replacement. Further this produces six
cutting surfaces as opposed to the more typical three or four cutting surfaces in prior art
insert cutters.
It is found that the combination of limited cutting surface, repeatedly indexable
rotatable cutting inserts for overcoming wear, and the uniform offsetting providing a
scalloped smooth cut pattern significantly increases the life span of the cutting head. It
also produces a much smoother chip in the bar suitable for direct feed to typical
boilers, as well as producing a more uniform and smooth slab which increases theultimate productivity and quality of wood chips from the reduced slab during
subsequent sawmill operations upon the timber.
3 ~ 3
Further, by providing for multiple rotating of the teeth, the debarker head may be
sharpened effectively without requiring it to be removed from the machine and without
requiring tool maker's skills for removal and sharpening of individual teeth. Thus, an
operator may keep his debarker running even through normal sharpening cycles.
It is thus an object of this invention to provide a rotary debarker head which has
a significantly increased working life span for removal and rebuilding over debarker
heads of the prior art.
It is a further object of this invention to disclose the form of a debarker headwhich may be more easily resharpened and placed back into operation than prior art
debarker heads.
It is a further object of this invention to disclose a debarker head having
significantly decreased downtime for resharpening as opposed to prior art debarker
heads.
It is a further object of the invention to disclose a rotary debarker head whichproduces a far more uniform bark chip.
It is a further object of the invention to disclose a debarker head which produces
a much smoother and more uniform log for further timber or lumber cutting operation.
These and other objects of the invention may be more clearly seen from the
detailed description of the preferred embodiment which follows:
207835~
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a view of a Rosser type debarker head in use in a debarking machine
on a log.
Figure 2 is a sidD view of the inventive debarker head mounted for rotation on a
axle.
Figure 3 is an end view of the inventive debarker head.
Figure 4 is a cross section view of the inventive debarker head.
Figure 5 is an exploded view of the insert and tooth of the invention.
Figure 6 is a depiction of the scalloped cutting pattern of the invention.
Figure 7 is an unfolded depiction of the pattern of the rows of teeth on the
surface of the debarker teeth.
Figure 8 is an end, cross section view of a log on a debarker using the
invention.
2~7835~
DETAILED DESCF~IPTION OF THE PREFERRED EMBODIMENT
This invention relates specifically to the form of debarker head 2 known as
rosser type debarker heads utilized in machinery as to the form as shown in the figures.
A rosser type debarker head 2 differs from a swinging arm debarker head
principally in that the machine is of the form in which a cylindrical debarker head 2
have a plurality of cutters 4 extending axially from its outer surface 6. It is mounted for
rotation upon a rotational axle 8 suspended on a pivoting or swinging arm 6 which may
be brought close to or away from or ride upon a log 12 which is supported and spun
within a plurality of log support wheels 14 or rollers 14, the debarker head 2 being
normally positioned over the log 12, forming a grip on the log between the debarker
head 2 and the log support rollers 14.
The log support rollers 14 are typically angled or textured so as to force the log
12 to, as the log 12 rotates under the debarker head 2, move laterally so that the entire
length of the log 12 passes at a controllable rate or uniform rate under the debarker
head 2 as the debarker head 2 rotates. Alternatively, this may be accomplished by
providing wheels or pushers 16 to push the log under the debarker head.
The above applies to Mor Bark KTM Debarker. A typical Rosser Head
Debarker uses rollers 14 to revolve the log 12 and mounts the rotary head
apparatus 2 on a carriage (not shown) that feeds laterally down the log 12.
Rosser type debarker heads, as with other debarkers, function by
chipping away bark. With high speed rotation of the debarker head 2, the
individual cutters 4, radiating axially from the cylindrical surface 6 of the
2~783~
de~arker head 2, break into the bark 18 of the log. This causes the bark 18
to shear, preferably along the weaker cambium layer 20 which exists in a
tree between the bark 18 and the wood 22 of the tree. Rosser type
debarkers are typically used in the lumber industry where it is desired that
the wood 22 of the tree be maintained in as smooth a condition as possible
as the peeled log 12 is to be sawn into timber, lumber and the like. Bark
chips 24 have no structural strength and thus are not of use for
incorporation in composite material but rather are typically used as a
feedstock for boilers and power plants within the lumber mill.
In order to be so used as feed products 24 the chips must be of a
uniform small size, but not a powder, and must be adapted to the size found
most desirable for powered feed in preexisting machinery provided for
feeding chips to the boilers and power plants of a lumber mill. Thus, if
chips 24, as provided from a debarker, are too large, or are strips or the
like, these chips 24 must be further cut. This adds to the cost of
processing and feed for the boiler. If the chips are too small or powdered
they may not be fed to the boilers and their economic value is lost, equally
increasing the cost of lumber processing.
2~83~
Referring to the drawings, I show in the form of my improved rosser
type debarker head a cylindrical rosser type debarker head 2 having
mounted thereupon a plurality of cutting elements 4 of a unique form
described as follows. Each of the individual cutting elements 4 is formed
of an extended, extruded welded base member 26 extending axially out from
the cutter head 2. Each base member 26 terminates in a curved, radiused
outer end 28 having a bottom receiving face 30 for receiving a hardened
cutting inse~t 32. Means 34 are provided within each base member or tooth
26 for fastening a cutter insert 32 to the tooth 26. Such means are well
understood to those in the toolmaker's art, and typically are in the form of
a faced receiving receptacle 36 for mating with the back 38 of a provided
cylindrical hardened cutter insert 32 or disk shaped hardened cutter insert
32. A central receiving threaded aperture 40 receives a stud or screw 42
for fastening the cutter insert 32.
Thus the active part of each individual tooth 36 which forms the
active cutting face 44, is a curved shaped cutter insert 32. Preferably this
insert 32 is of a form having a circular outer edge, a slightly convex upper
face 38 for mating with the debarker tooth 36 and having a flat, bottom
cutting face 44.
1 0
~û783~5
The debarker tooth 36 itself is typically formed of a casting, being
widest at its base 46 where the debarker tooth 36 is attached to the head 2
and being narrower behind the insert 32 so that the debarker tooth insert
322 forms the sole point of contact or impact with bark 18 and the log 12
during operation of the debarker. Along a half radius of the debarker tooth
36, typically for a distance equal to about one percent of the radius of the
debarker insert 32, the tooth 26 is cut away, forming a cutter edge masked
gap 27, so as to expose only a an angled section of the radial edge of the
cutter insert 32 .
The cutter insert 32 itself is preferably made as a strong metal
support member 35 having recesses into which carbide insets 33 are
secured, forming a cutter insert 32 which has an optimun combination of
toughness, from the support mernber 35 and hardness, from the carbide
insets 33, and having a round outer periphery and a center hole 40 for
adopting and receiving a securing bolt 42 or stud 42 so as to be held to the
debarker tooth 26. The debarker tooth 26 being radiused to match the upper
radius of the cutter insert 32, the insert 32 fits within the debarker tooth
26 and resists shifting out of place under impact and load.
, ,
2~7~3~5
The carbide insets 33 are overlapped 33A so that around the
preimeter of the cutter insert 32 there is, at all angles, a carbide faced
cutting surface 44. This continuous carbide faced cutting surface 44 then
permits the repeated indexing of the insert 32.
- By making the insert 32 in a round or
1~
~783~
curved configuration, it is continuously indexable, that is, it may be
rotated about its mouunting bolt 42 as mounted on the debarker tooth to
expose unused cutter radial edge, effectively renewing the sharpness of the
cutter tooth 26. For the preferred round cutter insert 32, this rotation
preferably is by a periodic amount. In contrast to prismatic inserts, there
is no requirement that the insert 32 be precisely aligned with its mount,
and thus indexing of the inserts 32 of the invention does not require the
skilled toolmaker craft work of prior art cutter inserts.
A typical debarker tooth 26 for the preferred embodiment of the
debarker head 2, the debarker head 2 having a cylindrical radius of 3-1/2
inches, is positioned so that the outer edge of the cutter insert 32 is at its
maximum extent 45, a little less than a 6 inch radius; and each cutter
insert 32 is of a 2 inch radius.
- Each individual debarker tooth 26 is installed around the outer
surface 6 of the debarker head 2 in serrated rows 48, a plurality of
debarker teeth 26 being in each row, and each row 48 being laterally offset
so that in total, as the debarker head 2 is rotated, the outer edge or cutting
toe 45 of each successive cutter insert 32 is offset from all other cutting
2~7~3~
inserts 32 of the head 2 a uniform amount. This, of course, is established
by the portioning of the debarker teeth 26 on the debarker head 2.
The number of debarker teeth 26 upon the debarker head 2, the offset
of the debarker teeth 26 and the diameter of each individual debarker tooth
insert 32 are mutually chosen such that the offset between the position of
adjacent debarker teeth inserts 32, as the debarker head 2 is rotated, is
substantially equal to 1/6 of the circumference of each individual cutter
insert 32.
Referring to the figures, it can be seen that this form of offset
creates a shallow scalloped pattern in which any individual debarker cutter
insert 32 defines a cutting arc or cutting edge 45 that is substantially
equal to 1/6 of the circumference of the individual debarker insert 32.
In use, the head 2 of the invention is assembled by inserting and
clamping the inserts 32 within the debarker teeth 26. The inventive
debarker head 2 is then installed as a standard rosser head debarker head in
a rosser type debarker. For debarking, a log 12 is placed into the rosser
type debarker and rotated, the debarker head 2 being rotated against the log
and brought into contact therewith. The unique scalloped cutting pattern
50 caused by the combination of the offset of the individual debarker head
1 4
~a7~35~
teelh 26 and the round cut and shape of each individual cutting insert 32
provides a shallow, uniform cut pattern within the bark as the debarker
head 2 cuts into the bark 18.
Further, the depth of the cut 52 is controlled by the impact pattern of
adjacent debarker inserts 32 as the debarker head 2 rotates. The depth of
cut is maintained substantially at a radius of the debarker active cutting
edge 45, which is the cordal section of the debarker insert subtended to
form a 1/6 circumference. Only that 1/6 portion of the debarker insert 32
actually impacts the log and is subjected to wear and impact forces; as the
debarker head rotates rapidly against the log, the shoulder 54 of the
adjacent debarker teeth 26 prevents the cut depth 52 from being any deeper
than the depth where adjacent shoulders 54 overlap. This is a showing
effect, where the shoulder of adjacent debarker teeth 54 in essence
- .
overlap in their rotational path to form non-cutting or shadow regions,
limiting the depth of cut.
It is found that this cutting pattern 50 produces a uniform small
sized bark chip 24 which is ideally suited for feeding to the typically found
boiler feeding machinery within a lumber and sawmill.
2~7~55
It is further found that the controlled depth 52 o~ the cut occurring
as a result of the shadowing effect of the adjacent offset debarker teeth
26 as the debarker head 2 is rotated, combined with the round face or
curved aspect presented by the debarker cutter insert 32, produces a
minimum of splintering within the underlying wood 22 and provides a
uniformly, relatively smooth surface. As an example, within the sizes
given above for the embodiment of the invention having two inch diameter
inserts 32, that is, teeth of a one inch radius) the actual cutting depth is
approximately .37 inch and thus the scalloped pattern 50 produced along
the log 12 upon removal of the bark 18 is that of a smoothly undulating
pattern having a maximum depth of about .37 inch. This pattern eliminates
the substantial splintering and shredding typically found with the flat
edged cutting teeth of the prior art debarker heads.
Inasmuch as the nonuniform outer surface of the log must be sawn
off, or slabbed, in order to render the log into a square or rectangular shape
for sawing into lumber, this minimization of splintering and cutting in the
outer surface of the log minimizes the waste inherent in these sawn outer
portions of the log or slabs.
Further, inasmuch as the primary economic use of the slab is~ 3~5
chipped by a wood chipper for incorporation into various composite and
particle boards, it has been found that slabs that have been debarked by the
inventive debarker head 2, having the smoothly scalloped outer surface
produced by the inventive debarker head 2, produce a higher quality, more
uniform chip, having a higher economic value within the particle board
after market.
It may be appreciated that extreme forces are imposed upon a rosser
head debarker during the process of debarking, and the resulting wear is
very heavy. In prior art debarkers, the debarker head must be taken out of
service and the cutters replaced and resharpened so frequently that,
typically, the normal life span of a debarker head in use is three months.
By providing the debarker cutting edges as curved inserts 32, either
round or provided in various curves to provide the desirable scalloped and
offset effect 3 above stated, I have discovered that, in lieu of the inserts
32 having to be totally replaced, the bolt 42 may be loosened and the
inserts 32 rotated providing a new cutting surface. For the round inserts
32 of the preferred embodiment, this permits six rotations of the tooth
before the debarker head 2 must be taken out of service and all the inserts
2~78355
32 replaced. This compares with the prior art fixed teeth which require
the head to be taken completely out of service and sharpened by a skilled
tool maker.
Further, unlike the prismatic inserts of the prior art, since the cutter
inserts of the current invention are smoothly arced shapes, relatively
unskilled labor can easily loosen, reposition and retighten the inserts 32
while the debarker head is installed on the machine. This compares with
the extensive downtime necessary for removal of the debarker head
required in the prior art, to permit removal and positioning of prismatic
inserts which must be exactly aligned within a cutting tool.
Thus the life span of the inventive debarker head 2 is up to six times
that of a debarker head with regular cutting teeth and up to twice that of a
debarker head with inserts of the prior art. Further, the scalloped pattern
50 and limited cutting edge 45 exposure of the inserts 32 permits a harder
insert 32 to be used (harder inserts being more brittle) with less danger of
impact and breakage. This is shown by the production of more uniformly
sized chips which shows a more uniform impact loading upon the teeth.
The overall result is a debarker head whose life span may be measured in
years rather than in months.
1 8
As an example, the initial prototype version of the inventive a~e~a7rl~e~5
head was placed into test service to determine its life span. When removed
for inspection after a year and one-half's test usage, it was found to be
still serviceable; this compares to a three month life span for a typical
rosser head debarker head of the prior art.
It can thus be seen that the debarker head 2 disclosed here represents
a considerable improvement over the prior ar~. It is preferred that the
rosser head debarker of the invention use round inserts, although it can be
seen that many advantages of the head would occur with curved inserts.
Further, the exact form of the round inserts and the form of the support
tooth permits many variations in detail.
For this reason this invention extends to those wider equivalents and
variations in the form of a rosser type debarker head as are inherent in the
claims.
1 9
