Note: Descriptions are shown in the official language in which they were submitted.
CA 02763754 2012-01-06
DEBARKING CHAIN WITH PASSING LINKS
This application is a division of Canadian Patent Application No. 2,604,986,
filed
April 12, 2006.
FIELD OF THE INVENTION
The present invention relates to an apparatus used for removal of bark and
limbs
from logs, more specifically, to a flail-type, debarking chain apparatus
wherein the
debarking chain includes passing links that rotate with respect to adjacent
chain
links during use. The invention also relates to debarking devices that include
a
plurality of debarking chains having passing links.
BACKGROUND OF THE INVENTION
It is well known that bark and small limbs can be removed from logs in a
debarking
device by passing the log between a set of rapidly rotating, upper and lower
debarking drums in the debarking device, each of which have a plurality of
debarking
chains, also called flail chains. The debarking chains repetitively strike the
surface
of the log with significant force at a high rate of speed, effectively tearing
away any
small limbs and virtually all of the bark on the log in preparation for a
chipping
operation in which the log is chipped into small pieces appropriate for
further
processing into wood pulp for paper manufacturing or the manufacturing of
composite products such as chip board, oriented strand board and engineered
lumber.
Logs are conveyed lengthwise through the debarking device along a
predetermined
feed plane. The upper drum is located above the feed plane and the lower drum
is
CA 02763754 2012-01-06
located below the feed plane, each at a distance from the feed plane to allow
the
debarking chains, or flail chains, together to clear bark and limbs from the
entire
surface of the log. It will be appreciated that each set of debarking chains,
associated with respective debarking drums, must reach at least the midpoint
of the
sides of the log. Some debarking devices have additional debarking drums some
of
which are fix drums and some of which are often "floating" drums.
[0005] It will be appreciated that in prior designs, the debarking chains
consist of elongated
or oblong chain links that have projected wear life based primarily upon
stress
applied to the u-shaped end portion of the respective chain links as these
links
repetitively strike the outer surface of the logs and as these links strike
each other
when the links recoil following such impacts. This projected wear life
dictates
frequency of debarking chain replacement. It will be appreciated that any
extension
of the projected wear life of a set of debarking chains will reduce cost for
debarking
operations in that extended use will reduce the number of chains used per unit
of
logs debarked or wood chips generated.
[0006] In normal use, a set of debarking chains are generally attached to a
debarking drum,
used for a predetermined amount of time or until any links are worn to a
predetermined amount of wear near the point of breakage based on periodic
inspection of the debarking chain, and then disconnected, flipped end to end,
before
being reattached and used again for another set amount of time or
predetermined
amount of wear.
[0007] Debarking is important in chipping operations, because this processing
step
minimizes the residual amount of bark mixed into wood chips from subsequent
chipping operations. Wood chips are less desirable for pulping operations when
they contain bark that is not removed from logs before the logs are chipped.
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CA 02763754 2012-01-06
[0008] A greater fear in these operations, however, is that the debarking
chains will break
and damage the chipper. This is one of the key reasons that operators
carefully
avoid extending the use of a set of debarking chains beyond the projected wear
life
for the chains. If any of the chains break and any of the metal links get into
the
chipper, which is generally rotating at a very high rate of speed, any
consequent
damage to the chipper can result in added operating costs due to machine
downtime
and needed replacement parts. Additionally, there exists the risk that
breaking links
may cause link debris to enter adjacent machinery, causing further damage and
downtime.
[0009] For these and other reasons, it will be appreciated that there is a
practical need to
increase the projected debarking chain wear life, thereby reducing chain
replacement cost per unit of processed wood products, along with associated
costs
of replacement materials and machine downtime.
[0010] The present invention provides improvements which address these and
other
limitations associated with the prior art.
SUMMARY OF THE INVENTION
[0011] The present invention is preferably a debarking chain configured for
attachment to a
debarking drum; the debarking chain including a plurality of interconnected
chain
links, each chain link being a continuous strand of chain material surrounding
and
defining a central opening through which the continuous strand of any
adjacent,
interconnected chain links pass; the plurality of interconnected chain links
including
at least one passing link, the passing link being constructed and arranged to
permit
the passing link to turn with respect to both adjacent chain links in such a
manner
that allows impact and stress on the passing link, created by being struck by
adjacent or next to adjacent chain links and/or the tree, to be distributed
about the
continuous strand making up the passing link. In preferred embodiments, the
debarking chain will also include at least one drum attachment chain link; the
drum
attachment chain link being at a first end of a debarking drum and being
constructed
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CA 02763754 2012-01-06
and arranged to be secured to the debarking drum. The debarking chain will
preferably have a drum attachment chain link at each end of the debarking
chain,
preferably an oblong chain link constructed to correspond to an opening in an
outer surface of the debarking drum in which an end link of a debarking chain
can
be inserted and secured in existing debarking drums. Alternatively, debarking
chains having all links be passing links may be used in a debarking drum
configured to accept passing links. The present invention also includes a
debarking drum including a plurality of such debarking chains, as well as a
debarking device having a debarking drum of the type disclosed above,
preferably
a plurality of such debarking drums. In preferred embodiments, this device
will also
include or be associated with a chipping device constructed and arranged to
chip a
wood log into small wood chips suitable for further processing in the pulp or
composite lumber industries, respectively. It will be appreciated that it is
important
to remove bark from such logs prior to the chipping operation in this process.
[0011.1] In accordance with one aspect of the present invention, there is
provided a
method of making a debarking chain having a passing link, the method
comprising:
providing a debarking chain including a plurality of interlocking welded
oblong
chain links; each interlocking welded oblong chain link having an inner
perimeter
having at least two straight portions; and reshaping one of the interlocking
welded
oblong chain links into a passing link by applying sufficient force to at
least one
interlocking welded oblong chain link so as to change the two straight
portions of
the inner perimeter of the at least one interlocking welded oblong chain link
to
become more rounded.
[0012] These and various other advantages and features of novelty which
characterize
the present invention are pointed out with particularity in the claims annexed
hereto and forming a part hereof. However, for a better understanding of the
invention, its advantages and objects obtained by its use, reference should be
made to the drawings which form a further part hereof, and to the accompanying
descriptive matter, in which there is illustrated and described a preferred
embodiment of the present invention.
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CA 02763754 2012-01-06
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] In the drawings, in which corresponding reference numerals and letters
indicate
corresponding parts of the various embodiments throughout the several views,
and
in which the various embodiments generally differ only in the manner described
and/or shown:
[0014] FIG. 1 is a side elevation providing a schematic illustration of a
"prior art"
debarking/delimbing apparatus;
4a
CA 02763754 2012-01-06
[0015] FIG. 2 is a side elevation providing a schematic illustration of a
debarking/delimbing/chipping apparatus of the present invention utilizing
debarking
chains having passing links;
[0016] FIG. 3 is a perspective view of an alternate debarking drum 222 of the
present
invention showing a rod 228 that is removed so that the debarking chains 226
secured by the rod 228 can be detached from the debarking drum 222 and
replaced
or flipped;
[0017] FIG. 4 is a cross sectional view of the alternate debarking drum 222
illustrated in
FIG. 3 as seen from the line 4-4 of FIG. 3;
[0018] FIG. 5 is a top view illustrating an alternate debarking chain 326 of
the present
invention having five links, two of which are passing links 340;
[0019] FIG. 6 is a top view illustrating an alternate debarking chain 426 of
the present
invention having seven links, two of which are passing links 440;
[0020] FIG. 7 is a top view illustrating an alternate debarking chain 526 of
the present
invention having seven links, four of which are passing links 540;
[0021] FIG. 8 is a top view illustrating an alternate debarking chain 626 of
the present
invention having six links, two of which passing links 640;
[0022] FIG. 9 is a top view illustrating an alternate debarking chain 726 of
the present
invention having eight links, six of which, i.e. every link except the two end
links, is a
passing link 740;
[0023] FIG. 10 is a top view illustrating an alternate debarking chain 826 of
the present
invention having eleven links, where five of eleven links, namely every
alternate link
starting from the penultimate link at either end of the chain, are passing
links 840;
CA 02763754 2012-01-06
[0024] FIG. I IA Is a top view illustrating an alternate debarking chain 926
of the present
invention each having nine links, four of which, the second and third links
from each
end, are passing links 940; the alternate debarking chain is the same as those
chains used in Test No. 3, reported in Example I, below;
[0025] FIG. 11 B is a top view illustrating an alternate debarking chain 1026
of the present
invention having nine links, all of which are passing links 1040; and
[0026] FIG. 12 is a bar graph graphically illustrating the data reported in
Table 1, discussed
in Example I, below.
DETAILED DESCRIPTION
[0027] Debarking devices are commonly used in the wood pulp and composite
lumber
industries to remove bark and small limbs from the surface of a log prior to
chipping
the log. As illustrated in the prior art illustration of FIG. 1, one known
embodiment of
a debarking/delimbing apparatus 10 includes upper and lower debarking units 14
and 16, respectively, having a plurality of debarking chains 26. Each
debarking
chain 26 is constructed of multiple elongated or oblong chain links 34, which
are
used to flail the surface of a log 12 to remove bark and small limbs. The wear
life of
prior art debarking chains is limited by the impact and wear on the respective
chain
links at the point where adjacent or next to adjacent oblong chain links 34
make
contact with adjacent and next to adjacent links when the chain 26 strikes the
log 12.
The elongated shape of such links is believed to lead to repetitive wear from
such
stress and such impacts, generally in the same place on the inside and outside
surfaces of the rounded portion in the u-shaped end of each link 34. This
repetitive
wear diminishes the material in these areas and also places repetitive stress
upon
these areas resulting in a higher degree of metal fatigue; all of which
results in a
limitation on the useful life of such debarking chains 34.
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CA 02763754 2012-01-06
[0028) The prior art debarking/delimbing apparatus 10 shown in FIG. 1 is
representative of
other similar prior art devices, which also have upper and lower debarking
units 14,
16. In many cases, such similar prior art devices will include additional
debarking
units (not shown) spaced away from the first two units 14, 16. In many cases,
the
upper debarking unit 14 is a "floating" unit and the lower unit 16 is in a
fixed position,
as these respective units 14, 16 are. The term "floating" is used to describe
a self-
adjusting ability. As logs 12 of different diameters are inserted into the
debarking
machine 14, the debarking machine 14 will pivot up or down in order to accept
the
log 12 while still remaining close enough to the log 12 in order to
debark/delimb.
Each debarking unit 14, 16 generally includes a debarking drum 20a, 20b having
a
cylindrical plate (not shown) similar to the cylindrical plate 222, shown in a
debarking
drum 220 of the present invention illustrated in FIG. 3, in which the plate
222 has a
series of chain receiving openings or pockets 224 in which an end link 236 of
each
debarking chain 226 can be received and subsequently secured by a securing rod
228, secured by various means known in the art within openings 229 within a
hub or
hubs 230. The hubs 230, through which a rotating shaft 232 is also secured,
permit
the debarking drums 20a, 20b to rotate relative to a housing 33. The securing
rods
228 are often secured within respective hubs 230 by threaded fasteners (not
shown)
secured to reciprocally thread ends on the debarking drum (not shown).
[00291 It will be appreciated that the debarking drums 20a, 20b rotate at a
very high rate of
speed and that the debarking chains 26 strike the logs 12 with great force as
the
logs 12 enter the debarking/delimbing apparatus 10. A great deal of this force
is
directed to points along the inner and outer perimeter of the surface of each
of the
respective chain links as they strike adjacent and next to adjacent links. It
is
commonly observed by persons familiar with debarking/delimbing operations that
this is especially the case for the link that is the second from the end
closest to the
7
CA 02763754 2012-01-06
log of any secured debarking chain 26 and also for the link that is third from
the end.
Indeed, wear to the point of breakage is most often observed in the prior art
debarking chains at the second or third link from the end farthest from the
drum and
closest to the log. The reason for these second and third links of the prior
art being
most prone to wear and breakage is generally believed to be as follows: 1) the
end
link closest to the log is free to rotate about its contact area with the
adjacent second
link. Therefore, impact on the inner and outer circumferential surfaces of the
end
link is distributed, whereas the contact point on the second link associated
with
impact from the end link is largely confined to the u-shaped radius of the end
of the
second link closest to the end link. 2) the end link also strikes the outside
surface of
the u-shaped end of the third link, while the inside surface of the u-shaped
end of the
second link impacts the inside surface of the u-shaped end of the third link,
thus
creating wear in an area of the third link, confined in the prior art
debarking chains,
to the inside and outside perimeters of the u-shaped end closest to the log.
This is
the main reason that debarking chains are disconnected and then "flipped" end
for
end, before being reconnected and used again, because "flipping" the chain
concentrates the wear on the links at the other end of the debarking chain
and,
thereby, extending the wear life for each of debarking chains used in this
way.
[0030] It will be appreciated, however, that, except for unsecured end links
36, oblong links
such as those included in the prior art debarking chains 26, shown in FIG. 1,
do not
readily change orientation, turn or rotate with respect to each other during
use; and
the wear and stress from the impact of the respective links 34 is generally
concentrated in the rounded, u-shaped ends of these oblong links. It is an
object of
the present invention to more equally distribute the stress and wear
associated with
the repetitive impact to the entire inner and outside perimeter of links along
the
length of a debarking chain and particularly along the inner and outer
perimeter of
8
CA 02763754 2012-01-06
the second and third links at the end of each chain where the wear and stress
of
such impacts is concentrated.
V
[0031] Referring now also to FIGS. 2 and 3 the present invention preferably
includes a
preferred debarking chain 126, and a preferred debarking drum 120a, 120b and a
preferred debarking/delimbing/chipping apparatus 110, each of which includes a
number of preferred debarking chains such as debarking chain 126, each of
which
preferably includes at least one "passing" link 140. Preferred debarking
chains 126,
shown in FIG. 2, each have a plurality of passing links 140. In the embodiment
shown in FIG. 2, each of the links of each of the debarking chains 126 are
passing
links 140 except for the links 136 at each end of each of the respective
debarking
chains 126. This embodiment of the invention has the end links 136 that are
elongated, oblong links 134, like those in the prior art debarking chains 26
shown in
FIG. 1. It is believed that it is important for the end links 136 at each end
of these
certain preferred debarking chains 126 of the present invention, to be oblong
link so
that these end links 136 will fit easily into chain receiving openings or
pockets (not
shown) similar to the pockets 224 shown in FIG. 3 that are common in debarking
units that are presently used through out the wood chipping/wood pulping
industry.
It will be appreciated, however, that a redesigned debarking drum, including a
connecting member to connect alternate debarking chains of the present
invention
(not shown), that are made entirely of passing links, are envisioned as
falling within
the scope of the present invention.
[0032] As defined herein, a "passing" link is a chain link that can
substantially rotate,
substantially turn or substantially change its orientation with respect to any
immediately adjacent link or links during use as one of a series of links in a
debarking chain, when the chain is used as a debarking chain in a flailing or
9
CA 02763754 2012-01-06
debarking operation, without necessarily rotating, turning or changing its
orientation
more than 900, and thereby vary its point of engagement with any adjacent
links to
= which it is interconnected, such that any impact, wear or stress upon the
link due to
interaction with such adjacent links occurring during such flailing or
debarking
operations will be distributed over a range of impact or wear points along the
inner
and outer perimeter of the link. A "passing" link, preferably, will not have a
u-shaped
end, such as the lengthwise ends of an oblong link 34, 134 that, due to the
close
proximity of the respective sides of the u-shaped end, limit the frequency of
any
events during such flailing operations in which such a link will change its
orientation
to its adjacent links. It will be appreciated that "passing" links will have
an inner
perimeter, surrounding an open space in the center of the link that will be
arcuate in
at least three different regions of this inner perimeter that may or may not
be
separated by substantially straight inner perimeter surfaces. Ideally, in the
most
preferred embodiments, the inner perimeter will be a continuously arcuate
inner
perimeter that is substantially round. In the most preferred embodiments,
passing
links will be round or substantially round links so that they can be easily
reoriented
with respect to adjacent links with out being limited by any inner perimeter
regions
that are either "straight" or without a "turning" or arcuate inner perimeter
surface.
[0033] It will be appreciated that it is difficult to cost effectively make a
perfectly round chain
link, therefore, passing links are also envisioned to include generally
rounded chain
links that have more than two rounded inner perimeter regions, which could be
immediately adjacent to one another, that allow the link to easily reorient
itself with
respect to both of two adjacent links during a flailing operation when such a
link is
not the end link adjacent only to a single link.
CA 02763754 2012-01-06
[0034] It will be appreciated that passing links are preferably made from
elongated or
oblong links welded steel, which are preferably made of carbon steel or other
steel
alloy, that are "bumped" or struck or pressed with sufficient force on at
least two
sides or on one side against a generally immovable object, in a manner that
permits
the shape of the link to become more rounded or arcuate on the surface of the
inner
perimeter of the link when the force is applied. In preferred processes, the
link will
be "bumped" simultaneously on opposite ends of a oblong link so that the long
straight sides of the link will bend, creating a region along the inner
perimeter of the
link, proximate an area where the inner perimeter was previously straight,
where this
region is now bent or arcuate. This bumping step can be repeated or controlled
until
a desired degree of "roundness" is obtained. Alternatively, the link may be
placed in
a press, preferably a'hydraulic press that will place sufficient force on
opposite ends
of the oblong link to bend the straight sides. Alternatively, a specialized
press or
"bumping" device that initially directs force to two opposing sides, but
eventually
directs force to a plurality of sides of such a link could be designed to
produce more
evenly rounded links that are most preferred. Alternatively, any link can be
reshaped by forcing the link downward along an elongated device having an
increasing diameter or dimension that can expand the distance between any two
surfaces along the inner perimeter of the link, thereby creating a rounded or
arcuate
surface along a previously straight region of the inner perimeter.
Alternatively, a
debarking chain may be formed by taking a chain consisting entirely of passing
links
and "bumping" or reforming some of the passing links in order to make oblong
links.
[0035] It will be appreciated that debarking chains can be made up entirely of
passing links
(see e.g. Fig 11 B). It is believed that such chain will be generally unusable
with
present technology, because the debarking drums, that are in current use
and/or
production, generally require end links that are oblong in order to be
received in the
11
CA 02763754 2012-01-06
"pocket" and secured to the drum. In the future, however, it is envisioned
that
debarking drums will either be equipped with a securing device that will
connect with
debarking chains outside of the "pocket" or the "pockets" will be enlarged so
that
they will be able to receive a passing link or such other rounded link as may
be
attached to the end of a chain of a part of the end of a chain of the present
invention.
Furthermore, although a passing link need not be perfectly round in order to
pass
through and adjacent links and turn with respect thereto, round links are
certainly
passing links. For that reason, a continuous chain made up entirely of round
links
can be a debarking chain of the present invention, because eventually it is
believed
the market will change and debarking drums will either be made to accept
rounded
links or connecting members will be used to engage large end links to
debarking
drums. Therefore, it is believed that debark chains of the present invention
made
entirely of passing links in an important aspect of the present invention.
[0036) Alternately, a chain made entirely of round links can be used to make
debarking
chains for the debarking drums most commonly used today, by shaping or
"bumping" round links until specific links, most preferably the end links, are
oblong in
situations where oblong links are needed to be interconnected with present day
debarking drums.
[0037] The present invention enables users of the preferred debarking chains
to expect an
increase in the wear life of the debarking chain links by incorporating at
least one
passing link, preferably at least two adjacent passing links near each end and
in
certain embodiments, more than two and as many as all of the links other than
the
end links, and in certain situations, where the debarking drum includes
separate
chain connecting mechanisms or compatible flail drum pockets (not shown) that
will
accept a rounded passing link, all of the links can be passing links. In
preferred
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CA 02763754 2012-01-06
embodiments a passing link is generally a chain link that is substantially
round in
shape. Substantially round links can randomly pass through adjacent links,
turning
its orientation with respect to such adjacent links thereby randomly changing
the
wear or impact point where the respective adjacent or next to adjacent links
engage
the passing link during repeated flailing events during debarking operations.
The
wear or impact points will preferably be randomly distributed around the inner
and
outer perimeter of the passing link. The result of such a random turning or
reorientation of the passing link with respect to its adjacent links will
preferably be a
more evenly distributed wear of the passing links, thereby extending debarking
chain
wear life as compared to standard debarking chains consisting of elongated
oblong
links.
[0038] As noted above, a debarking apparatus 110 of the present invention,
incorporating
debarking chains 126 having passing links 140 is illustrated in FIG. 2. The
debarking/delimbing apparatus 110 preferably includes upper and lower
debarking
drums I 20a and 120b, respectively. Each debarking drum 120a and 120b,
preferably includes multiple debarking chains 126 preferably including both
elongated links 134 and passing links 140, which are used to flail the surface
of a log
112 to remove bark and small limbs (not shown). Also included in preferred
embodiments is an adjacent wood chipper 150, located behind the debarking
drums
120a and 120b. In one preferred embodiment of the present invention, the wood
chipper 150 is located close enough to the upper debarking drum 120a that
debris
from a failed chain link may enter the wood chipper 150, causing costly damage
and
machine downtime. Although it is common practice to replace debarking chains
126
prior to the end of their expected, projected or observed wear life, the
expected wear
life may be extended by incorporating passing links, thereby realizing a cost
savings
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CA 02763754 2012-01-06
associated with less equipment down time and more chips per change-out of
debarking chains.
[00391 The embodiment of the present invention shown in FIG. 2 includes
passing links 140
to reside at any point within any debarking chain 126 except at the end links
136 on
either end of the debarking chain 126. These links 136 can be used to connect
the
respective debarking chain 126 to the remaining portion of respective
debarking
drum 120a, 120b. At the connecting end of each debarking chain 126, an
elongated
chain link 134 is generally required, for most existing debarking devices, in
order to
allow the end link 136 to fit within a pocket 224 of the type shown in FIG. 3
that are
commonly provided in existing prior art drum cylinders 222 like that shown in
FIG. 3.
10040] FIG. 3 illustrates an alternate debarking drum assembly 220 of the
present invention.
The debarking drum 220 has an outer surface or cylindrical plate 222 having a
plurality of chain securing openings or pockets 224 in which an end link 236
can be
secured. The debarking drum assembly 220 is configured to allow the end links
236
of the debarking chains 226 to fit into the pockets 224, along an axis
perpendicular
to the length of the debarking drum assembly 220. The end link 236 of each
debarking chain 226 that resides within the pocket 224 is secured by a
securing rod
228 that is preferably configured to slide through securing openings 229 in
hubs 230
at each of two ends of the cylindrical plate 222 or perhaps at a single end in
other
embodiments, such that it can reside within the cylindrical plate 222 of the
debarking
drum 220 along an axis parallel to that of the debarking drum 220 and inserted
such
that it passes through the end link 136 each of the attached debarking chains
226.
Each debarking chain 232 in the debarking drum assembly 220 is preferably
constructed to rotate about the shaft or axis 232 at a high rate of speed.
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CA 02763754 2012-01-06
[0041] A cut away view from the illustration shown in FIG. 3 is, shown in FIG.
4 showing the
debarking drum assembly 220 in greater detail. The end link 236 of each
debarking
chain 226 that passes through the openings or pockets 224 is preferably
fastened to
a rod 228 secured between hubs 230 at each end of the drum assembly 220.
[0042] Various embodiments of alternate debarking chain configurations are
illustrated in
FIGS. 2-10. In FIG. 2, the debarking chains 126 each have seven chain links,
five of
which are passing links 140 and two of which, namely the end links 136, are
elongated links 134 that are elongated and narrower than the passing links
140. In
FIG. 3 and 4, an alternate debarking chain 226 is shown each having eight
chain
links, only one of which is a passing link 240. FIG. 5 illustrates an
embodiment of
the present debarking chain 326 having five links, two of which adjacent to
each end
link 336 are passing links 340. FIG. 6 illustrates an embodiment of the
present
debarking chain 426 having seven links, two of which, the second fink from the
end
on each side, are passing links 440. FIG. 7 illustrates an embodiment of the
present
debarking chain 526 having seven links; four of which, the second and third
links
from each end, are passing links 540. FIG. 8 illustrates an embodiment of the
present debarking chain 626 having six links, only two of which, the second
links
from each end, are passing links 640. FIG. 9 illustrates a further embodiment
of the
present debarking chain 726 having eight links, six of which, each of the
links
between the end links 736, are passing links 740. FIG. 10 illustrates yet
another
embodiment of the present debarking chain 826 having eleven links, five of
which,
every other link after either of the end links 836, are passing links 840.
FIG. 11A
illustrates a further alternate embodiment of the debarking chain 936 of the
present
invention that was prepared for testing purposes in the tests that are
reported below
in Example I. This chain 926 has nine chain links, four of which are passing
links
CA 02763754 2012-01-06
940. Passing links 940 are the second and third link in from each of the two
end
links 936.
[0043] It will be appreciated that preferred debarking chains will have an
oblong link 134 in
both end positions to accommodate the limitations of existing debarking drum
devices that have pockets for securing such chains that generally require an
oblong
link 134. Any of the links may be passing links, however. In alternate
embodiments,
the debarking chains of the present invention can have as many as five, six,
seven,
eight, nine, ten, eleven, twelve, thirteen, fourteen or fifteen links. In
alternate
embodiments, passing links may be used to connect the debarking chain to in
debarking drums that may be plausibly developed to accommodate the debarking
chain with passing links on both ends. Such a debarking chain 1026, in which
all of
the chain links are passing links a1040, is shown in Fig. 11 B.
[0044] One embodiment of the present invention includes passing links
constructed of
through hardened steel for increased wear life. In other embodiments, all of
the links
will be through hardened, although other known methods of hardening the welded
steel links can also be employed.
[0045] As will become apparent to those skilled in the art, there are numerous
variations in
the configuration of the debarking chains containing at least one passing link
which
is within the spirit and scope of the present invention. The length of the
chains,
number and location of passing links and oblong links are by no means limited
to the
configurations described herein. Additionally, different arrangements and
organization of the various components are also possible.
[0046] EXAMPLE I.
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CA 02763754 2012-01-06
[0047] Three types of debarking chain were tested at a debarking/chipping
facility placing
the experimental debarking chains test on the lower flail drum of a Petersen
Pacific
Debarker Chipper. The types of debarking chain tested were:
[0048] Test No. I - Belt furnace heat treated debarking chains having eight
0.656 inch
strand diameter links with an increased Rockwell hardness.
[0049] Test No. 2 - Link induction furnace heat treated debarking chains
having eight 0.656
inch strand diameter links. The link induction furnace heat treated links are
believed
to have hard ends and softer sides that the belt furnace heat treated links
used in
Test No. 1.
[0050] Test No. 3 - Prototypes of the debarking chain of the present invention
having
passing links as the second and third links from each end of 9-link (0.656
inch strand
diameter links) debarking chains. Each of the passing links were bumped in a
Piranha Punch (Model: SEPP 35 Punch 35 ton hydraulic press from Piranha,
Hutchinson, KS) to round the straight sides of the links so that the links
became
substantial rounded. The intent is to allow these links to rotate, thus
distributing the
impact point such that the typical high wear areas at each end of the second
link and
at the base (radius closest to the log) of the third link will be minimized.
[0051] All chain types resulted in more loads per change-out of lower front
flail drum
debarking chain than was typical for the test site. The number of loads
achieved
were 13, 14 and 14 for Tests No. 1, No. 2, and No. 3 respectively. (typical
performance was to achieve 12 loads - 6 loads before flipping the chain end
for end
and 6 loads after flipping).
[0052] TEST RESULTS:
[0053] Test No. 1 chains performed well, even though it was clear to all
parties present that,
due to the way logs were loaded into the debarker/chipper, the chains on the
far left
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CA 02763754 2012-01-06
of the flail drum (when viewed from the end of the machine where the logs were
fed)
experienced excessive wear. This forced the chains to be flipped well before
the
average wear would have required it had the logs been fed in a more balanced
fashion. The chain experienced more even wear across the full width of the
flail
drum for all subsequent testing after these first six loads.
[0054] Test No. 2 chains performed very well in terms of wear, however, they
also had the
highest number of chain segments with broken and missing links.
[0055] Test No. 3 chains performed very well. These chains had the most number
of loads
after flipping and the only reason they were replaced after 14 loads is
because they
had "grown" or expanded in length to the point that they were beginning to
strike the
housing of the flail drum (debarking chains lengthen as interlink wear
occurs).
Operators, on-site supervisors and key management personnel were very
impressed
with the prototype Test No. 3 chain. The results indicated that the inclusion
of
passing links extend the usable wear life of the debarking chain by
distributing the
impact points, thereby eliminating the localized areas of wear.
[00561 METHODS:
[0057] A Peterson Pacific Model 5000g debarking/chipping machine was used in
the
testing. A test of further prototypes will follow in which debarking chain
similar to
that in Test No. 3, will be tested but having only eight links rather than
nine with the
second and third links from each end bumped into a passing link configuration.
The
intent is to start a bit shorter so "growth" does not force the chains to be
changed
out. Additional testing will be conducted with the experimental chain on all
three flail
drums (we had chosen the worst case scenario, lower front flail drum, as the
first
test platform).
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CA 02763754 2012-01-06
[0058] It is projected that an average increase of one load of chips being
produced before
and after flipping the chains at a debarking/chipping operation having nine in-
field
debarking/chipping machines, would result in an annual savings in the cost of
debarking chain of about $350,000. Achieving two more loads before and two
more
loads after flipping is projected to result in a $700,000 savings. It is
suggested that
this estimate is conservative because it does not take into account the down
time
and additional labor associated with changing out the debarking chain.
Clearly,
improving the performance of debarking chain is an important matter for
debarking
chain users. The monthly cost of operating one debarking/chipping machine, in
the
winter in a northern North American environment is estimated to be about
$26,000
for debarking chain and $23,000 for fuel.
[0059] Other pertinent information:
- Logs being chipped were mainly aspen, some Russian poplar. The logs were
frozen. Aspen and Russian Poplar are considered a hardwood.
- The diameter at the base of the logs ranged from 5" to 21 ". The average
diameter was about 8-10 inches.
- Each load was 40 to 41 metric tons of chips.
- High wear chains were moved to low wear areas of the flail drum and low wear
chains were moved to high wear areas when the chain is flipped.
- The bark content was measured for each load and reported back to the foreman
of the debarking operations. The quality of the chips achieved during testing,
averaging less than I% bark content, was within specification.
- The lower front flail drum was rotating at 637 rpm.
- If all goes as anticipated in any test sequence, it takes 1 to 1-1/2 hours
to fill a 2-
trailer load.
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CA 02763754 2012-01-06
The debarking operation operates in 2 twelve hour shifts, typically 6 days a
week.
Other debarking chain currently being used is Campbell, Rud (made in Brazil)
and Honnetaler. The Honnetaler chain was produced at Vistec Chain Company
in the Ukraine.
It became clear that the closer the passing links are to being truly round,
the
longer the wear. The prototype links were somewhat square, which limited the
freedom to rotate and reduced the benefit of rotating.
[0060] The following data in Table 1, below, provides a relative indicator of
the performance
of debarking chain expressed in terms of the number of loads per millimeter of
wear.
Wear is determined by subtracting the average smallest diameter of the 2nd
link
from an original diameter of 0.656 inches. Also shown is the number of broken
segments of debarking chain per load. This data is also shown graphically in
FIG.
12.
[0061] It is noted that the loads per millimeter of wear for Test No.1 before
the chains were
flipped is somewhat overstated due to excessive wear occurring on debarking
chain
segments on the left side (as viewed from the front of the debarking machine).
This
excessive wear of chains on the left side of the flail drum is associated with
the way
logs were loaded into the machine. Since chains that were in the middle and on
the
right side of the flail drum were minimally worn, the average smallest
diameter of the
second link is overstated. If the logs were loaded in a more balanced fashion,
the
average smallest diameter of the second link would have been lower (that is,
the
average wear would have been higher), and more loads would have been achieved
before flipping.
CA 02763754 2012-01-06
Table No. 1. DEBARKING CHAIN PERFORMANCE EXPRESSED IN TERMS OF LOADS
PER MILLIMETER OF WEAR AND BROKEN CHAIN SEGMENTS PER LOAD
TEST NO. 1 2 3
0.656 X 8 BELT 0.656 X 8 0.656 X 9 WITH
CHAIN TYPE FURNACE HIGHER INDUCTION HEAT PASSING LINKS
ROCKWELL HARDNESS TREAT
NO. BEFORE FLIP 6 7 6
LOADS
NO. AFTER FLIP LOADS 7 7 8
BEFORE FLIP AVG 2ND
LINK SMALLEST 0.522 0.552 0.520
DIAMETER (INCHES)
AFTER FLIP AVG 2ND
LINK SMALLEST 0.466 0.521 0.506
DIAMETER (INCHES)
BEFORE FLIP AVG 2ND 3.40 2.64 3.45
LINK WEAR (MM)
AFTER FLIP AVG 2ND 4.83 3.43 3.81
LINK WEAR (MM)
NO. OF CHAIN
SEGMENTS WITH 10 35 13
BROKEN OR MISSING
LINKS
BEFORE FLIP LOADS 1.8 2.6 1.7
PER MM OF WEAR
AFTER FLIP LOADS 1.5 2.0 2.1
PER MM OF WEAR
BROKEN CHAIN 0.77 2.50 0.93
SEGMENTS PER LOAD
[0062] It is to be understood, however, that even though numerous
characteristics and
advantages of the present invention have been set forth in the foregoing
description,
together with details of the structure and function of the invention, the
disclosure is
illustrative only, and changes may be made in detail, especially in matters of
shape,
size and arrangement of parts within the principles of the invention to the
full extent
indicated by the broad general meaning of the terms in which the appended
claims
are expressed.
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