Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR FORMING CURVED CANTS FOR CURVE
SAWING IN AN ACTIVE GANGSAW
Field of the Invention
This mvention relates to a method and a device for form;ng curved cants and for
sawing lumber from curved or straight cants, and in particular relates to a cant forming and
feeding system, for the forming of a curved four sided cant, from a two sided cant for the
0 breakdown of the cant in an active curve sawing gangsaw according to an optimized profile for
optimum sawing of lumber, and to a method and a~paldllls for removing flares from lumber.
Background of the Invention
A canted log, or "cant", by definition has first and second opposed cut planar faces.
In the prior art, cants were fed straight through a profiler or gangsaw so as to produce at least a
third planar face, or multiple boards, either approximately parallel to the center line of the cant,
so called split taper sawing, or approximately parallel to one side of the cant, so called full taper
sawing; or at a slope somewhere between split and full taper sawing. For straight cants, using
2 o these methods for volume recovery of the lumber can be close to optimal. However, logs often
have a curvature and usually a curved log will be cut to a shorter length to minimi7P the loss of
recovery due to this curvature. Consequently, in the prior art, various curve sawing techniques
have been used to overcome this problem so that longer length lumber with higher recovery may
be achieved.
Curve sawing typically uses a mechanical centPring system that guides a cant into
a secondary break-down m~rhine with chipping heads or saws. This cPntPring action results in the
cant following a path very closely parallel to the center line of the cant, thus resulting in split taper
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chipping or sawing of the cant. Cants that are curve sawn by this technique generally produce
longer, wider and stronger boards than is typically possible with a straight sawing technique where
the cant has significant curvature.
Curve sawing techniques have also been applied to cut parallel to a curved face of
a cant, i.e. full taper sawing. See for example Kenyan, United States Patent No. 4,373,563 and
Lundstrom, C~n~ n Patent No. 2,022,857. Both the Kenyan and Lundstrom devices use
mechanical means to center the cant during curve sawing and thus tli~p~rities on the surface of the
cant such as scars, knots, branch stubs and the like tend to disturb the m~t~hining operation and
lo produce a "wave" in the cant. It has also been found that full taper curve sawing techniques,
because the cut follows a line approximately parallel to the convex or concave surface of the cant,
can only produce lumber that mimics these surf~.~es, and the shape produced may be unacceptably
bowedO
Thus ;n the prior art, so called arc-sawing was developed. See for example United
States Patent, 5,148,847 and 5,320,153. Arc sawing was developed to saw irregular swept cants
in a radial arc. The technique employs an electronic evaluation and control unit to determine the
best semi-circular arc solution to m~hine the cant, based, in part, on the cant profile information.
Arc sawing techniques solve the mechanical centering problems encountered with curve sawing
2 o but limit the recovery possible from a cant by constraining the cut solution to a radial form.
Applicant is also aware of United States patent number 4,373,563, United States
patent number 4,572,256, United States patent number 4,690,188, United States patent number
4,599,929, United States patent number 4,881,584, United States patent number 5,320,153, United
2 5 States patent number 5,400,842 and United States patent number 5,469,904, which are all designs
that relate to the curve sawing of cants. Eklund, United States Patent number 4,548,247, teaches
laterally tr~n~l~ting chipping heads ahead ofthe gangsaws. Dutina, United States patent number
4,599,929 teaches slewing and skewing of gangsaws for curve sawing.
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It has been found that optimized lumber recovery is best obtained for most if not
all cants if a unique cutting solution is detçrmined for every cant. The cant has been faced on two
sides in a previous device, by first rotating the cant so that the curved portion of the cant is turned
up so that the cant is formed in the straightest line allowable with the cant then being turned 90
degrees so that the curve is now turned on to the side and the cant is transferred with it's two flat
surfaces now facing up and down. Then the cant is then passed through a scanner, for sc~nnin~
and for each cant a "best" curve is determined, which in some instances is merely a straight line
parallel to the center line of the cant, and in other instances a complex curve that is only vaguely
related to the physical surfaces of the cant.
It is an object of the invention to produce an a~pa~us that can allow the use ofmodern disc type chipping heads in a curve sawing system by having the discs skewing as well
as tr~n~l~ting to follow the optimum profile of the cant, while producing the highest quality of
chips, which in of themselves have resale value in the market, or to remove flares from lumber in
advance of the lumber passing into a curve sawing active machine center such as active chipping
heads and an active sawbox.
It is also an object of the present invention to improve recovery of lumber fromcants and in particular irregular or crooked cants by employing a "best" curve and a unique cutting
2 o solution for each cant.
To achieve these objectives a two sided cant is positioned and accurately guidedor driven through a pair of dynamic conforming opposing chipping heads, to form a four sided
cant just prior to a gangsaw where the four sided cant is then curve sawn into lumber by a cluster,
2 5 or clusters of saws which follow the optimized curved profile of the cant as the cant is directed
into the saw clusters in a straight line.
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It is another object of the present invention to provide a curve sawing system that
moves the cant through the chipping heads and gangsaw linearly without ch~nging its path so as
to generally produce no l-nintçn~ed slabs or t~iling~
It is further an object of the present invention to provide capabilities of the chipping
heads to move away from the cant in the event of a large bulge or horn in the cant, to prevent
unequal chipping forces from forcing the cant off its optimized path, or, as stated above, using
active ~lle~ll chipping heads to remove bulges, horns or flares in the cant. In one aspect of the
invention, the chipping heads would also be capable of angling into the flow and plunging back
o in to the cant (if the bulge was in the middle of the cant for example). This action would create a
short slab that could then be easily handled after exiting the gangsaw. If the slab to be formed was
excessively long so as to be difficult to handle, then the chipping head might be plunged into the
slab to in effect pre-buck the slab into desired lengths.
Summary of the Invention
The method and apparatus of the present invention for forming curved cants for
curve sawing in an active gangsaw, is for the purpose of cutting boards from a curved, tapered or
straight cant in a manner designed to O~lillliGe recovery based on measured or sensed cant shape,
2 o lumber value, operator input and mill requisites, and to remove bulges, horns or flares from a cant.
The method and appal~lus consists of, first, an intlexing transfer which temporarily
holds the cant in a stationary position by a row of retractable duckers, or other means, for
regulated release onto a sequencing transfer. The sequencing transfer then feeds the cants singly
2 5 through a lateral or horizontal scanner, where the scanner reads the profile of the cant and sends
the data to a decision processor. It is understood that within the scope of the present invention,
the sequencing transfer and lateral scanner could be replaced with a lineal scanner.
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An optimi7ing algorithm in the decision processor generates three dimensional
models from the cant's measurements, calculates a complex "best" curve related to the intricate
contours of the cant, and selects a breakdown solution including a cut description that represents
the highest value combination of products which can be produced from the cant. Data is then
transmitted to a programmable logic controller (PLC) that in turn sends motion control
information related to the opLilllUlll breakdown solution to the various m~ ine~ to control the
movement of the cant and the machine segments to produce the design~ted gangsaw products.
Immediately following the lateral or hol;zoll~al scanner is a sequencing transfer that
0 also includes a plurality of rows of retractable duckers and/or pin stops that hold the cant
temporarily for timed queued release so as to ~ueue up the cant for release onto the positioning
a~al~us. The positioning apparatus includes a chainbed (which utilizes a sharpchain) with driven
overhead pressrolls which hold the cant onto the chain-bed, or alternately, a group of driven
bedrolls, also with driven overhead press rolls. The positioning apparatus has a skewbar, with
skewbar pins that positions the cant for the o~ llulll feeding sta~ting position for feeding into the
chipping heads, and the subsequent or downstream gangsaw.
Upstream active chipping heads may be employed to remove bulges, horns or flareson cants prior to curve sawing. Active chipping heads may also be employed immediately
2 o upstream of a sawbox, where the chipping heads are capable of moving in and out following the
curve of the cant as the cant moves lineally past the chipping heads, the cant always moving in a
fixed lineal path. The chipping heads are also capable of skewing left or right of the linear path
of the cant so as to m~int~in a optimum angle of attack (normally a small degree of toe-in) at all
times as the cant moves past the chipping heads. The degree the chipping heads are adjusted is
2 5 detçrmined by the specific curvature of the cant which defines the need, as the angle of the cant
will change in relation of the chipping heads to the amount of curve in the cant as the cant is fed
lineally through the chipping heads. The chipping heads are thus constantly adjusting the angle
of attack, thus producing a non-concave surface of the face being created by the chipping heads.
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In combination to creating the third and fourth face the al,~alus includes a sawcluster mounted on a splined arbor. The saw cluster and arbor are capable of at least tr~n~l~ting~
left or right of the flow (i.e. the lineal path) and, in a ~ r~ d embodiment, capable of both
tr~n~l~ting and skewing, depending on the amount of m~xhllu~ll curve desired so as to position the
saws within the saw cluster, at the optimum angle of attack so as to follow the precise curvature
of the cant or otherwise according to an optimized cutting solution, as the cant moves through the
gangsaw in a fixed linear path. The saw blades are held perpendicular to the arbor by saw blade
guides, which contact the sides of the saw blades to m~int~in the saw blades position in relation
to the arbor as the cant is fed through the saw cluster, thus sawing the cant into boards lltili7ing
the optimized profile~
In summary, in a device for removing bulges, horns or flares on a cant, and in adevice where a gangsaw has an in-feed mechanism for positioning a cant and feeding the cant
generally longitudinally into the gangsaw along a feed path, wherein the cant is oriented with its
planar faces generally horizontal, and wherein the in-feed mechanism has laterally opposed
laterally tr~n~l~t~ble skewable chipping heads which may advantageously be of the disc-type
laterally opposed on either side of the feed path, the method of the present invention for opening
opposed generally vertical longitudinal faces so as to form curved longit~l-lin~l profiles on laterally
opposed sides of the cant according to an optimi~d profile solution so as to feed the cant into the
2 o gangsaw along a generally linear feed path for curve sawing in the gangsaw includes the steps of
(a) longitudinally tr~n~l~ting and positioning the cant along the feed path between the chipping
heads, (b) laterally tr~n~l~ting and simultaneously skewing the chipping heads, according to the
optimi7e~1 profile solution, into cutting engagement with the laterally opposed sides of the cant
so as to open the opposed generally vertical lon~itutlin~l faces and form the curved longitudinal
2 5 profiles by ~ n;ng the plane of the chipping heads at an angle of attack so as to be generally
parallel to the in~t~nt~nPous tangent of the optimized profile solution at the in~t~nt:~neous location
of the cutting engagement of the chipping heads with the cant, (c) feeding the cant from between
the chipping heads along a generally linear portion of the fee~lp~th into the gangsaw.
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Advantageously, in combination with this method, the gangsaw may be actively tr:~n~l~ted and,
in a ple~lled embo~liment, also actively skewed according to an optimized curve sawing profile.
The method may further include the step of adjusting the angle of attack by a toe-in
angle whereby the first and second planes slightly diverge in a downstream direction.
The method further may include the step of tr~n~l~tin~ one or both of chipping
heads away from the cant so as to partially disengage the cutting engagement for sensed bulges
or horns in the cant whereby a risk of de-positioning of the cant by unequal chipping forces is
o reduced.
The method may further include the step of plunging one or both of the chipping
heads into the cant so as to pre-buck slabs.
The method may be accomplished by a gangsaw in-feed meçh~ni~m for positioning
a cant and feeding the cant generally longitll-lin~lly into a gangsaw along a feed path, wherein the
cant is longitll(lin~lly tr~n~l~ted and positioned through the gangsaw in-feed mech~ni~m with the
cant's planar faces generally hofi~o~ l, where the meçh~ni~m has laterally opposed laterally
tr~n~l~t~hle skewable chipping heads lying generally in first and second generally parallel vertical
2 o planes laterally opposed on either side of the feed path for laterally tr~n~l~ting and simultaneously
skewing of the chipping heads, according to an optimized profile solution, into cutting
engagement with the laterally opposed sides of the cant so as to open opposed generally vertical
longitudinal faces and form opposed curved longitll-lin~l profiles by ~ligning the first and second
planes so as to be generally parallel to the in~t~nt~neous tangent of the optimized profile solution
2 5 at an in~t~nt~neous location of the cutting engagement.
Advantageously, the chipping heads are adjusted to adjust the angle of attack bya toe-in angle so that the first and second planes slightly diverge in a downstream direction.
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In one aspect of the invention, the opli~ ed profile solution causes one or both of
the chipping heads to be tr~n~l~ted away from the cant so as to partially disengage the cutting
engagement for sensed bulges or horns in the cant whereby a risk of de-positioning of the cant by
unequal chipping forces is reduced.
Advantageously, said partial disengagement is symmetric on either side of the cant
so as to equalize forces applied to the sides of the cant.
In one embodiment, the optimized profile solution may cause one or both of the
chipping heads to be plunged into the cant so as to pre-buck slabs.
Advantageously, in the above method and device, the chipping heads are disc-tvpechipping heads.
In a plcr~,led embodiment sensing means are provided between the chipping heads
and the gangsaw so as to verify the actual position of the cant prior to the cant entering the
gangsaw to allow adjustment of the active gangsaw in the event the cant has moved or shifted
.
durmg chlppmg.
The invention provides other advantages which will be made clear in the
2 o description of the prcrelled embo-liment~.
Brief Description of the Drawings
The invention will be better understood by reference to drawings, wherein:
Figure l is a side elevation section view according to a pre~lled embodiment of
the invention, taken along section line l-l in Figure 2.
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Figure 2 is a plan view of the curve sawing system of the present invention.
Figure 3 ;s an enlarged view of Figure 2.
Figure 4 is an enlarged section of the side elevation section view of Figure 1.
Figure 5 is perspective view of a two s;ded curved cant.
Detailed Description of the Preferred Embodiment
Referring to the drawing figures wherein similar characters of reference represent
corresponding parts in each view, the cant chipping al)p~dlus is seen in Figures 1-4 and generally
indicated by the reference numeral 10.
As best seen in Figure 2, a scanner indexing transfer 12 receives cant 14, better
seen in Figure 5, from the mill and begins to index cant 14 towards scanner 16 in direction A.
Ducker A18 receives cant 14. When ducker B20 on the scanner indexing transfer 12 becomes
available cant 14 is sequenced from ducker A18 to ducker B20. Cant 14 is sequenced from ducker
B20 to ducker C22, when ducker C22 becomes available. Ducker C22 is mounted upstream of
scanner 16.
When ducker D24 becomes available cant 14 is released by ducker C22, so that
cant 14 is passed through scanner 16 and scanned. Cant 14 moves to ducker D24 on scanner
in-lexing transfer 12. The cant is then transferred to a sequencing transfer 26. When ducker E28
2 5 on cant sequencing transfer 26 becomes available cant 14 is sequenced from ducker D24 to ducker
E28. When ducker F30 on cant sequencing transfer 26 becomes available, cant 14 is sequenced
from ducker E28 to ducker F30.
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Positioning table 34 has park zone pins 32. When park zone pins 32 become
available, cant 14 is sequenced from ducker F30 to park zone pins 32 on positioning table 34.
When positioning table 34 becomes available park zone pins 32 lower and a set ofjump chains 36 are elevated from beneath table 34 and move cant 14 to skew bar pins 38a on skew
bar 38 and thus onto positioning driven table rollers 40 (or other in-feed means). Jump chains 36
lower and a group of driven overhead pressrolls 42 ~ct~-~te~l by means of pressroll cylinders 42a,
press down so as to hold a constant pressure on cant 14 against table rollers 40. Skew bar pins 38a
lower and driven table rollers 40 and driven overhead press rolls 42 feed cant 14 in direction B
0 towards chipping head appald~us 10.
Chipping head apparatus 10 positions chipping head 10a and chipping head 10b
in the correct starting position to accept the end of cant 14. Chipping head 1 Oa is positioned by
cylinder44foradjll~tm~ntofthicknessofcant 14,andcylinder46rotateschippinghead 10aabout
pin 48 to adjust the angle of attack of the chipping head 10a. Chipping heads 10a and 10b are
mounted on carriage 50. Cylinder 52 rotates chipping head 10b about pin 54 for adjustment of
the angle of attack of chipping head 10b. Carriage 50 tr~n~l~ted relative to cant 14, that is,
perpendicular to the flow of cant 14 in direction B, by cylinder 56, so as to form the optimized
curve on cant 14.
One end of cylinder 52 is attached to chipping head mount 58. The other end of
cylinder 52 is attached to pin 60 mounted to carriage 50. One end of cylinder 46 is attached to
chipping head mount 62. The other end of cylinder 46 is attached to pin 64. Pin 64 is mounted
to sleeve 66. Sleeve 66 is slidably mounted on track 68. Track 68 is fixed to carriage 50. A
2 5 second sleeve 70 is mounted to chipping head mount 62, which is slidably mounted on track 72.
Track 72 is fixed to carriage 50.
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Chipping head 1 Oa is powered by and rotatably mounted on, chipping head driven
bearing mount 62a. Chipping head 1 Ob is powered by, and rotatably mounted on, chipping head
driven bearing mount 58a. Carriage 50 is mounted on sleeves 74 and 76. Sleeves 74 and 76 are
slidably mounted on tracks 78 and 80. Thus, cylinder 56 may be actuated to move carriage 50
perpendicular to the flow direction of cant 14.
Once chipping head a~p~dllls 10 has been adjusted for thickness and for the
starting position, and the angle of attack of chipping heads 10a and 10b has been adjusted for
starting, power is applied to driven table rollers 40 and driven overhead press rolls 42 to feed cant
14 into chipping heads 10a and 10b. As cant 14 ;s fed through chipping head apparatus 10,
chipping head a~dlus 10 is constantly adjusted by cylinder 56 to follow the optimized curvature
of cant 14. Simultaneously, chipping heads 10a and 10b are being angled by cylinders 46 and 52
to m~int~in the optimum angle of attack of chipping heads 10a and 10b in relation to the curvature
of the cant as it is being fed through chipping heads 10a and 10b. It has been found that the
optimurn angle of attack aligns the plane of the chipping head so as to be generally parallel to the
eous tangent of the optimized profile solution at the location of the cutting engagement
of the chipping head with the cant. Preferably, the angle of attack is adjusted to include a slight
toe-in of the chipping head to prevent scuffing i.e. to prevent the do~~ am side of the chipping
heads from being dragged across the downstream cant surfaces which would cause the planar face
2 o to be further cut or scuffed, making the surface concave. A toe-in angle ~ (seen in Figure 3) of
approximately 1 ~ or 2 ~ may prevent such scuffing.
I~e chipping head appal~lus 10 tr~nel~tes laterally, that is, parallel to direction C,
seen in Figure 3, by actuation of cylinder 56 to form the optimized curve on cant 14, as cant 14
is fed through chipping heads 10a and 10b. As cant 14 moves into saw clusters 84 and 86 on
gangsaw 82, (as best seen in Figure 1), saw clusters 84 and 86 also move in direction C, delayed
in time so as to match the form of cant 14 after it has been shaped by chipping heads 10a and 10b.
Saw clusters 84 and 86 may also, in one embodiment, skew in direction D if the optimized
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curve-sawn curvature desired is too great given the machine constraints such as the diameter of
saws 88 within saw clusters 84 and 86.
The saw blade clusters 84 and 86 are held by saw blade guides 84c and 86c fixed
in relation to saw arbor 84a and 86a as saw blades 84b and 86b spin. Cant 14 is fed through
gangsaw 82 by overhead driven pressrolls 90, actuated by press roll cylinders 90a, which press
cant 14 onto driven lower bed rolls 92, whereby cant 14, now boards (not shown), is drawn
through saw blade clusters 84 and 86 while m~ g a linear feed. Cant 14, now boards (not
shown), are driven out of gangsaw 82 by driven press rolls 90, and onto gangsaw outfeed rollcase
1 o 94 for transfer downstream for further proces~ing.
As will be apparent to those skilled in the art in the light of the foregoing
disclosure, many alterations and modifications are possible in the practice of this invention
without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to
be construed in accordance with the substance defined by the following claims.
