Method and apparatus for forming curved cants for curve sawing in an active gangsaw

A gangsaw in-feed mechanism for positioning a cant and feeding the cant generally longitudinally into a 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 translatable skewable chipping heads lying generally in first and second generally parallel vertical planes laterally opposed on either side of the feed path, a method for opening opposed generally vertical longitudinal faces so as to form curved longitudinal profiles on laterally opposed sides of the cant according to an optimized profile solution, so as to feed the cant into the gangsaw along a generally linear feed path for curve sawing in the gangsaw, having the steps of longitudinally translating and positioning the cant along the feed path between said chipping heads, laterally translating and simultaneously skewing the chipping heads, according to the optimized profile solution, into cutting engagement with the laterally opposed sides of the cant so as to open the opposed generally vertical longitudinal faces and form the curved longitudinal profiles by aligning the chipping heads so as to align the first and second planes at an angle of attack generally parallel to the instantaneous tangent of the optimized profile solution at an instantaneous location of the cutting engagement, and feeding the cant from between the chipping heads along a generally linear portion of the feedpath into the gangsaw.

FIELD OF THE INVENTION 
This invention relates to a method and a device for forming 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 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 apparatus 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 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 
minimize 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 centering system that guides a 
cant into a secondary break-down machine with chipping heads or saws. This 
centering action results in the cant following a path very closely 
parallel to the center line of the cant, thus resulting in split taper 
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, U.S. Pat. 
No. 4,373,563 and Lundstrom, Canadian Patent No. 2,022,857. Both the 
Kenyan and Lundstrom devices use mechanical means to center the cant 
during curve sawing and thus disparities on the surface of the cant such 
as scars, knots, branch stubs and the like tend to disturb the machining 
operation and 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 surfaces, and the shape produced may 
be unacceptably bowed. 
Thus in the prior art, so called arc-sawing was developed. See for example 
U.S. Pat. Nos. 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 machine the cant, based, in part, on the cant profile 
information. Arc sawing techniques solve the mechanical centering problems 
encountered with curve sawing but limit the recovery possible from a cant 
by constraining the cut solution to a radial form. 
Applicant is also aware of U.S. Pat. No. 4,373,563, U.S. Pat. No. 
4,572,256, U.S. Pat. No. 4,690,188, U.S. Pat. No. 4,599,929, U.S. Pat. No. 
4,881,584, U.S. Pat. No. 5,320,153, U.S. Pat. No. 5,400,842 and U.S. Pat. 
No. 5,469,904, which are all designs that relate to the curve sawing of 
cants. Eklund, U.S. Pat. No. 4,548,247, teaches laterally translating 
chipping heads ahead of the gangsaws. Dutina, U.S. Pat. No. 4,599,929 
teaches slewing and skewing of gangsaws for curve sawing. 
It has been found that optimized lumber recovery is best obtained for most 
if not all cants if a unique cutting solution is determined for every 
cant. It is assumed that the cant has been faced on two opposed 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, the cant may then be turned 90 degrees so that the curve is now 
turned on to the side and the cant is transferred with its two flat 
surfaces facing up and down. Then the cant is passed through a scanner for 
scanning. 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 apparatus that can allow the 
use of modern disc type chipping heads in a curve sawing system by having 
the discs skewing as well as translating 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 
from cants and in particular irregular or crooked cants by employing a 
"best" curve and a unique cutting solution for each cant. 
To achieve these objectives a two sided cant is positioned and accurately 
guided or 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, 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. 
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 changing its path so as to generally produce no unintended slabs 
or tailings. 
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 
upstream 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 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 
optimize recovery based on measured or sensed cant shape, lumber value, 
operator input and mill requisites, and to remove bulges, horns or flares 
from a cant. 
The method and apparatus consists of, first, an indexing 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 
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. 
An optimizing 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 optimum breakdown solution 
to the various machines to control the movement of the cant and the 
machine segments to produce the designated gangsaw products. 
Immediately following the lateral or horizontal scanner is a sequencing 
transfer that 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 queue up the cant for release onto the positioning apparatus. 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 optimum feeding starting 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 
flares on cants prior to curve sawing. Active chipping heads may also be 
employed immediately 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 maintain 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 
determined 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. 
In combination to creating the third and fourth face the apparatus includes 
a saw cluster mounted on a splined arbor. The saw cluster and arbor are 
capable of at least translating, left or right of the flow (i.e. the 
lineal path) and, in a preferred embodiment, capable of both translating 
and skewing, depending on the amount of maximum 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 maintain 
the saw blades position in relation to the arbor as the cant is fed 
through the saw cluster, thus sawing the cant into boards utilizing the 
optimized profile. In summary, in a device for removing bulges, horns or 
flares on a cant, and in a device 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 translatable 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 longitudinal 
profiles on laterally opposed sides of the cant according to an optimized 
profile solution so as to feed the cant into the gangsaw along a generally 
linear feed path for curve sawing in the gangsaw includes the steps of (a) 
longitudinally translating and positioning the cant along the feed path 
between the chipping heads, (b) laterally translating and simultaneously 
skewing the chipping heads, according to the optimized profile solution, 
into cutting engagement with the laterally opposed sides of the cant so as 
to open the opposed generally vertical longitudinal faces and form the 
curved longitudinal profiles by aligning the plane of the chipping heads 
at an angle of attack so as to be generally parallel to the instantaneous 
tangent of the optimized profile solution at the instantaneous 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 feedpath into the gangsaw. Advantageously, in combination with this 
method, the gangsaw may be actively translated and, in a preferred 
embodiment, 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 chipping heads slightly diverge in a downstream 
direction. 
The method further may include the step of translating 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 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 mechanism for 
positioning a cant and feeding the cant generally longitudinally into a 
gangsaw along a feed path, wherein the cant is longitudinally translated 
and positioned through the gangsaw in-feed mechanism with the cant's 
planar faces generally horizontal, where the mechanism has laterally 
opposed laterally translatable skewable chipping heads lying generally in 
first and second generally parallel vertical planes laterally opposed on 
either side of the feed path for laterally translating 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 longitudinal profiles by aligning the chipping heads so as to align 
the first and second planes generally parallel to the instantaneous 
tangent of the optimized profile solution at an instantaneous location of 
the cutting engagement. 
Advantageously, the chipping heads are adjusted to adjust the angle of 
attack by a toe-in angle so that the first and second planes slightly 
diverge in a downstream direction. 
In one aspect of the invention, the optimized profile solution causes one 
or both of the chipping heads to be translated 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-type chipping heads. 
In a preferred 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 during chipping. 
The invention provides other advantages which will be made clear in the 
description of the preferred embodiments.

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 apparatus is 
seen in FIGS. 1-4 and generally indicated by the reference numeral 10. 
As best seen in FIG. 2, a scanner indexing transfer 12 receives cant 14, 
better seen in FIG. 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 indexing transfer 12. The cant is then transferred 
to a sequencing transfer 26. When ducker E28 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. 
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 of jump 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 actuated 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 towards chipping head 
apparatus 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 10a is positioned by cylinder 44 for adjustment of thickness 
of cant 14, and cylinder 46 rotates chipping head 10a about 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 translated 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 
second sleeve 70 is mounted to chipping head mount 62, which is slidably 
mounted on track 72. Track 72 is fixed to carriage 50. 
Chipping head 10a is powered by and rotatably mounted on, chipping head 
driven bearing mount 62a. Chipping head 10b 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 apparatus 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 is fed through chipping head apparatus 10, 
chipping head apparatus 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 maintain 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 optimum angle of attack aligns the plane of the 
chipping head so as to be generally parallel to the instantaneous 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 downstream side of the chipping heads 
from being dragged across the downstream cant surfaces which would cause 
the planar face to be further cut or scuffed, making the surface concave. 
A toe-in angle .alpha. (seen in FIG. 3) of approximately 1.degree. or 
2.degree. may prevent such scuffing. 
The chipping head apparatus 10 translates laterally, that is, parallel to 
direction C, seen in FIG. 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 FIG. 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 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 maintaining 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 94 for transfer downstream for 
further processing. 
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.