U.S. patent number 3,736,968 [Application Number 05/092,581] was granted by the patent office on 1973-06-05 for method and apparatus for processing logs.
This patent grant is currently assigned to Sun Studs, Inc.. Invention is credited to Howard C. Mason.
United States Patent |
3,736,968 |
Mason |
June 5, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
METHOD AND APPARATUS FOR PROCESSING LOGS
Abstract
A method and apparatus for processing logs to obtain an optimum
amount of wood products of predetermined quality from each log. The
method includes the steps of positioning each log along a reference
axis, electronically scanning the log to determine certain of its
dimensions with respect to the reference axis, computing the center
axis of the largest surface of a preselected shape that can be
superimposed within the measured dimensions, and repositioning the
log with the center axis parallel to an index line such as the
cutting line of a predetermined processing equipment. Scanning
arrangements and processing apparatus are disclosed for practicing
the steps of the method in the processing of logs of different
diameters.
Inventors: |
Mason; Howard C. (Oregon City,
OR) |
Assignee: |
Sun Studs, Inc. (Roseburg,
OR)
|
Family
ID: |
22233965 |
Appl.
No.: |
05/092,581 |
Filed: |
November 25, 1970 |
Current U.S.
Class: |
144/357; 144/3.1;
144/400 |
Current CPC
Class: |
B27B
29/00 (20130101); B23D 59/008 (20130101); B27B
1/007 (20130101); B27B 31/06 (20130101) |
Current International
Class: |
B27B
1/00 (20060101); B27B 31/06 (20060101); B27B
31/00 (20060101); B27B 29/00 (20060101); B23D
59/00 (20060101); B27b 001/00 () |
Field of
Search: |
;144/312,209,326,3R
;143/22 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schran; Donald R.
Claims
It is claimed and desired to secure by Letters Patent:
1. A method of processing a log to obtain the optimum amount of
wood products of a selected grade therefrom, comprising the steps
of
positioning the log with respect to a reference location,
scanning the log to determine certain of its dimensions with
respect to the reference location,
plotting in a data processing equipment at least one planar profile
of the dimensions of the log, said profile being taken in a plane
passing through the ends of the log,
computing in a data processing equipment at least the center axis
of the widest parallelogram that can be superimposed within the
plotted profile of the log, and
repositioning the log with the center axis parallel to an index
line of a log processing equipment.
2. Log processing equipment comprising
a saw array aligned with an index line,
aligning means for receiving and holding a log at a reference
location,
photoelectric scanning means spaced from said reference location
for producing an output signal representative of the dimensions of
a log passed by said scanning means,
data processing means connected to said scanning means for
evaluating said output signal and producing a data output signal in
response thereto,
charger means for releasably gripping said log at said reference
location and transporting the log past said scanning means, said
charger means including means responsive to said data output signal
for angularly repositioning said log with respect to said index
line,
a saw carriage, aligned with said index line and movable with
respect to said saw array, for receiving from said charger means
said log when repositioned, and
control means associated with said saw carriage for selectively
moving said carriage with respect to said saw array, said control
means being responsive to said data output signal whereby said log
carried by said saw carriage is divided into cants by the saw array
in accordance with a preselected cutting pattern stored in said
data processing means.
3. Log processing equipment as described in claim 2 further
including
a movable cant chain having means thereon for receiving and holding
cants each at a reference position,
transfer conveyor means for receiving cants produced by said saw
array and conveying said cants onto said cant chain,
cant scanning means for producing a cant output signal
representative of the profile dimensions of a cant passed by said
scanning means while being carried on said cant chain, said profile
being taken along a flat side of said cant,
said data processing means being connected to said cant scanning
means for evaluating said cant output signal and producing a cant
data output signal in response thereto,
a cant sawing station spaced from said cant scanning means,
including a sawing conveyor and a saw array aligned along a second
index line with respect to said sawing conveyor, and
second transfer conveyor means for receiving cants from said cant
chain and conveying said cants onto said sawing conveyor, said
second transfer conveyor means including adjustable cant guide
means responsive to said cant data output signal from said data
processing means for repositioning each cant with respect to said
second index line before sawing thereof by said saw array.
4. The method of claim 1 further including the steps of
dividing the log into cants,
positioning each cant with respect to a cant reference
position,
scanning each cant to measure certain of its dimensions with
respect to the reference position,
plotting in said data processing equipment a planar profile of the
measured dimensions of the cant, said profile being taken along a
flat side of said cant,
computing in said data processing equipment the center axis of the
widest parallelogram that can be superimposed within the plotted
profile of the cant, and
repositioning the cant with the center axis parallel to an index
line of a cant sawing array.
5. A method of processing a log including the steps of
placing the log in a reference position,
scanning the log to measure the diameter of the log at numerous
locations spaced along the length of the log,
plotting in a data processing equipment a profile of the measured
diameters of the log,
computing in said data processing equipment the coordinates with
respect to said reference position of the cylindrical surface
having the largest diameter defined within said plotted profile,
and
repositioning said log with the sides of said cylindrical surface
parallel to an index line of a log processing apparatus.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for the
processing of logs to produce optimum results. More particularly,
the invention is related to a method and apparatus for the
processing of logs of different diameters to obtain the maximum
amount of salable wood products of a predetermined quality from
each log.
In processing logs, such as in peeling veneer or sawing logs into
cut lumber, it is desirable to obtain the maximum amount of salable
wood products of high quality from each log. New saws and saw
arrays, as well as improved methods of treating and softening logs,
are continuously being developed to permit the processing of logs
with a minimum of wood wastage. However, a major problem still
exists in the wood industry in determining how a given log should
be divided in an optimum fashion, and then in automatically
controlling a predetermined processing equipment to divide the log
in the selected fashion.
It is conventional in the lumber industry to reduce logs to cut
lumber by means of a saw array, and a saw carriage that is movable
with respect to the saw array under the control of an operator.
Prior to gripping of a given log in the saw carriage, the log is
positioned with its best side up, as determined from a visual
inspection by the operator. With the log aligned with its best side
up, (i.e., usually the side most free from crooks), the log is
gripped in the saw carriage and moved through the saw array
repeatedly, with cants or flitches of various widths being removed
from the log on each pass as determined arbitrarily by the operator
in accordance with certain rules of thumb.
In such practice, many factors are not considered that should enter
into a determination of the optimum manner of dividing or breaking
down a given log. For example, all logs are tapered from one end to
the other. Consequently, some wastage always occurs in producing
lumber of regular or rectangular dimensions therefrom. Furthermore,
logs are commonly of very irregular and/or elliptical diameter, and
include crooks along their length, as well as depressions or
extensions in their outer surfaces. For obvious reasons, each of
these factors has a significant effect upon the way the log should
be divided to achieve optimum results. Accordingly, it would be
desirable to eliminate operator judgment from the determination of
how to divide each given log, in favor of a system which would
precisely and automatically evaluate all the above factors in
arriving at an optimum solution.
U.S. Pat. No. 3,459,246 to Ottosson represents an advance in the
art in this regard in that it describes an apparatus for sawing
logs that includes an automatically controlled saw array. The
Ottosson system further includes means for examining an incoming
log with a photocell array to determine the smallest diameter of
the log, and uses this information to automatically set the saw
array for dividing the log. In other words, in the Ottosson system,
each log is sawed in accordance with a programmed cutting schedule
determined by the measured minimum diameter of the log. This tends
to reduce the wastage that occurs as a result of log taper, and can
partially compensate for irregularities in the logs surface that
result in a noticeable reduction in the log diameter.
However, the Ottosson system does not include means for
repositioning a log after scanning. Consequently, a crooked log of
a given diameter is processed in the same fashion as a straight log
of the same diameter, with significant wastage resulting.
Furthermore, unnecessary wastage results due to the other factors
such as elliptical diameter and irregular surface depressions and
extensions. Therefore, the Ottosson system does not produce optimum
results in the division of logs into cut lumber.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a method
and apparatus for processing logs that overcomes the disadvantages
of conventional methods.
It is another object of the invention to provide a method for
processing logs to obtain the maximum amount of wood products of a
predetermined quality from a given log.
It is a further object of the invention to provide a method for
processing logs wherein certain dimensions of each log are
accurately measured and the largest surface of a preselected shape
that can be superimposed within the measured dimensions is
determined.
It is yet a further object of the invention to provide apparatus
for repositioning the log with respect to a predetermined
processing equipment for maximum utilization of the wood
encompassed by such surface.
It is yet a further object of the invention to provide novel
apparatus for practicing the method described herein.
The inventor of the method and apparatus described herein has
determined that there is an arithmetical best solution for the
division of each circular area of a different diameter, such as a
log cross section, into rectangular components of a given size or
set of sizes, such as the cross sections of pieces of cut lumber.
The inventor also has found that to obtain the maximum amount of
salable wood products from a given log, it is desirable to measure
accurately certain of the dimensions of the log and to determine
the largest surface of preselected shape that can be superimposed
within the measured dimensions of the log.
If the log is to be reduced to cut lumber or veneer the preselected
surface should have parallel sides. Therefore, if the log is
measured in two dimensions so that a planar profile of the log can
be plotted, a planar surface such as a rectangle or parallelogram
is selected. However, if the log is measured in three dimensions so
that a volumetric representation of the log can be plotted, a
volumetric surface such as a cylinder is selected. In either case,
the largest surface of the preselected form that can be
superimposed within the measured dimensions of the log encompasses
the maximum amount of lumber within the log that can be reduced to
cut lumber of the desired rectangular dimensions or reduced to
veneer. In the event the log is to be divided into irregular
components, an appropriate surface of irregular form could be
selected, although this is not a usual requirement of log
processing systems.
Accordingly, the above objects of the invention are attained by a
method which includes the steps of positioning a log along a
reference axis, scanning the log to determine certain of its
dimensions, computing the center axis of the largest surface of
preselected form (such as a rectangle or a cylinder) that can be
superimposed within the measured dimensions of the log, and
repositioning the log with the center axis parallel to an index
line such as the cutting line of a predetermined processing
equipment, allowing maximum use of the wood encompassed within such
surface. The method can be utilized in producing cut lumber from
logs, or it can be utilized in other log processing operations such
as peeling veneer.
Scanning arrangements and an automatically controlled sawmill are
described for processing logs of different diameters.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the invention will become apparent
from the following detailed description of the invention taken in
conjunction with the accompanying drawings, wherein:
FIG. 1 is a schematic diagram of a sawmill adapted to process
lumber in accordance with the invention;
FIG. 2 is a diagrammatic side elevation view of a scanner and block
charger for positioning logs, of the type used in the apparatus
illustrated in FIG. 1;
FIG. 3 is a partial top elevation view of the scanner and block
charger shown in FIG. 2, illustrating the outline of a log as
initially positioned in the charger;
FIG. 4 is a diagrammatic view of a scan grid illustrating the axial
alignment of a log before scanning and the axial alignment of the
same log as repositioned in the charger of FIG. 2 just prior to
engagement in the saw carriage;
FIG. 5 is a diagrammatic side elevation view of a cant scanner and
charger assembly of the type used for positioning cants in the
sawmill disclosed in FIG. 1;
FIG. 6 is a top elevation view of the cant scanner assembly
illustrated in FIG. 5 with a cant positioned for scanning therein;
and
FIG. 7 is a diagrammatic view of a scan grid illustrating the axial
alignment of a cant before scanning and the axial alignment of the
same cant as repositioned for further processing upon leaving the
cant scanner illustrated in the FIG. 5.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, logs of different diameter are
automatically processed to obtain an optimum amount of salable wood
products of a predetermined quality from each log. Each log is
supplied to a processing apparatus and aligned in a charger along a
reference axis. The log is then examined, such as by a
photoelectric scanning device, to accurately determine certain of
the dimensions of the log.
The scanning can be carried out in numerous ways. One convenient
way of scanning the log is to utilize a single array of
photoelectric scanning devices generally positioned along the
length of the log and oriented to scan the log along one side for
measuring the length of the log and the diameter of the log at
spaced intervals along the length thereof. This permits the
"plotting" of a two-dimensional representation or planar profile of
the log. The term "plotting" is used to mean the orientation of
data representations within data processing equipment and not
physical plotting, although the latter is possible. After the first
scanning operation, the log is repositioned in the log processing
apparatus and divided into subcomponents such as cants or flitches.
The cants or flitches are then rescanned along a flat side prior to
being processed into cut lumber.
Alternatively, a single set of scanning devices can be used, and
the log can be periodically rotated beneath the scanning devices,
to derive a series of readings that measure the spaced diameters of
the log at the different angular positions. This permits the
"plotting" of a three dimensional representation of the log.
In yet another scanning method, two arrays of scanning devices are
positioned along the length of the log, oriented in different
planes (for example, at right angles to each other) to
simultaneously measure the spaced diameters of two different sides
of the log. This method of scanning also permits the "plotting" of
a three dimensional representation of the log.
The dimensional data derived from the scanning devices is supplied
to an electronic data processing unit for evaluation or "plotting."
From the dimensional data, the electronic data processing unit
produces an output that represents the coordinates of the largest
surface of preselected form that can be superimposed within the
measured dimensions of the log taking into account certain
arbitrary factors that relate to the predetermined acceptable
quality of the wood products to be derived from the log. As
previously explained, if the scanning device used in one from which
a planar profile of the log can be "plotted" a planar surface with
parallel sides, such as a rectangle or parallelogram, is selected.
However, if a scanning device is used which produces data from
which a volumetric profile of the log can be "plotted," a
volumetric surface with parallel sides, such as a cylinder, is
selected. In addition, the output of the data processing unit
includes information representing the coordinates of the center
axis of the selected surface. The output signals of the data
processing unit are used to control the repositioning of the log in
a carriage with the calculated center axis parallel to an index
line such as the cutting line of a saw array.
Upon evaluation of the dimensional information the data processing
unit also selects, from a number of possible sawing or processing
patterns that were previously designed by empirical methods and
stored in the processing unit memory, a processing pattern which is
the optimum pattern for the largest surface. Such an optimum
pattern is the pattern that will yield the maximum amount of wood
products of a desired quality from the given log. For example, if
it is desired to divide a log into 2 inch .times. 4 inch studs, the
optimum pattern would produce the greatest possible number of studs
of acceptable quality from the given log. After selection, the
processing program for the selected pattern is automatically
carried out by the processing apparatus under the control of the
data processing unit.
The method described herein can be used with saw arrays for
producing cut lumber from logs, or can be used with other
processing apparatus such as that used for peeling veneer.
One preferred apparatus for practicing the method of the invention
is illustrated in the drawings in the form of a sawmill especially
adapted for sawing logs into cut lumber such as 2 inch .times. 4
inch studs. The sawmill is designed for processing, continuously,
logs of predetermined lengths ranging from 84 to 104 inches and
having different diameters, for example ranging from 5 to 50
inches.
In accordance with the method of the invention, each of the logs,
referred to hereinafter as blocks, is scanned along one side
whereby a planar profile of the dimensions of the log can be
"plotted," and is regarded as including a volume of usable wood
encompassed within the largest parallelogram that can be
superimposed within the measured dimensions. The center axis of the
optimum surface or parallelogram for a given block is also
determined from data obtained during photoelectric scanning of one
side of the log. The best or optimum solution for dividing each
block is the solution that provides the greatest number of cants of
2 inch or 4 inch width and is determined after making allowance for
such lumber grading factors such as acceptable sawing variations,
shrinkage, surfacing, saw kerf, and for allowable wane consistent
with acceptable grade standards. After a block is divided into
cants, the cants are scanned along a flat side whereby a planar
profile of each cant is "plotted." An optimum solution is then
determined for dividing each cant into the maximum number of studs
of 2 inch .times. 4 cross section.
Referring now to FIG. 1, a sawmill 10 is generally illustrated
including a block infeed network 11, a charger and scanner array
12, a saw carriage 14, and a twin band mill 15. The sawmill further
includes an intermediate transfer conveyer arrangement 16
interconnecting the band mill with a cant scanner generally
indicated at 18. A cant guide 19 is arranged between scanner 18 and
a cant processing station 20 that includes a 4 inch gang edger 21
and a 2 inch gang edger 22. A conveyor system generally indicated
at 25 receives cut lumber from the edgers and precedes an
unscrambler 26 and a sorter 27 that ultimately supply sorted lumber
to a stacker 29. A data processing unit generally indicated at 30
is provided for automatically controlling all the components of the
sawmill in a manner explained hereinafter. It should be understood
that the conveyors and chains shown in the drawings are of
conventional design and are schematically illustrated to permit
simplication of the drawings. Suitable power means, not shown, are
associated with each of the conveyors and chains to drive them at
the desired speeds in the directions indicated by the arrows.
Referring more particularly to the components mentioned above,
block infeed network 11 includes a horizontal block infeed chain
35, and an inclined block infeed chain 36 arranged at the rear of
chain 35. Infeed chain 35 is adapted to receive blocks deposited
thereon, for example by means of a lift truck, and both chains are
adapted for transferring blocks therealong. The block infeed
network also includes a horizontal reject chain 38 and a conveyor
39 including end-to-end chains 41, 42 that communicate between
reject chain 38 and a conventional Nicholsen chipper 34. Chains 41,
42 are adapted to receive reject blocks from chain 38 and to
transport such blocks to chipper 34. The chipper is adapted to
reduce the reject blocks into commercially usable chips as a
byproduct of the sawmill. Chains 41, 42 are positioned, as
schematically indicated, at a lower level than block infeed chain
35. Therefore, operator controlled ejection means, not shown, can
be used for transferring reject blocks from the infeed chain to
chain 41 for transport to the chipper.
A conveyor 46 and a transfer chain 47 are arranged to communicate
between chain 41 and a cutoff saw 49, having an infeed roller set
50 associated therewith. The cutoff saw is a conventional unit
adapted for reducing logs to a suitable block size for processing
in the chipper. The sawmill also includes an inclined conveyor
chain 51 adapted to communicate directly with chipper 34.
Referring now to FIGS. 1-3, the block charger and scanner array 12
are particularly illustrated as comprising a block alignment yoke
55 including two sets of vertically opposed V-members or V's 56.
Each set of V's includes a fixed lower V 58 and an upper V 59
adapted for power movement between a closed or clamped position
shown in solid outline in FIG. 2 and an open or retracted position
shown in dotted outline in FIG. 2.
The lower V's are positioned beneath the upper end of chain 36 and
are suitably constructed to receive and support blocks as they
leave the end of chain 36. The upper V's occupy a noninterfering
position when retracted and are adapted for gripping and firmly
clamping blocks against the lower V's when closed. The block is
centered in the V's and retained in a fixed position along a
lengthwise axis that is arbitrarily used as a reference axis during
the scanning operation described hereinafter. It should be apparent
that the reference axis is not coincident with the center axis of
the log, but the reference axis will always pass through the ends
of the log.
The positioning of the upper V's is automatically controlled by
processing unit 30. However, a manually controlled override switch
and a block rotating mechanism, not shown, are provided by which
the V's can be opened and the block rotated for realignment. This
enables each block to be clamped in the block alignment yoke with
its best side up as determined by an operator.
A block charger 60 is provided in conjunction with the alignment
yoke, having arms 62, 64 positioned outwardly on either side of the
V-members to selectively engage the ends of a block clamped within
yoke 55. For this purpose, each charger arm includes an enlarged
outer portion 66 having spikes 67 fastened thereto. Each charger
arm otherwise includes a multiposition stacked hydraulic cylinder
set works 70 adapted for extending the length of the arm,
independently, in increments, such as 1/10th inch increments. The
upper end 69 of each charger arm is secured to a power assembly 72
controlled by processing unit 30. The power assembly is adapted for
moving the arms, selectively, into and out of contact with the ends
of a block in yoke 55. In addition, the power assembly is designed
to pivot the charger arms upwardly, to the position b shown in
dotted outline in FIG. 2, wherein a block carried thereby is
generally positioned along a scanning path indicated at 74. The
power assembly is further adapted for driving the charger arms and
block as a unit whereby the block traverses path 74 through a block
scanner 75 and ultimately is rested in a region adjacent saw
carriage 14 in position c shown in dotted outline in FIG. 2. During
this entire phase of the operation the block is positioned along
the reference axis, running longitudinally of the block, as
determined by the original positioning of the block in the
alignment yoke 55.
Referring to FIGS. 1-3, the block scanner 75 is particularly
illustrated as comprising an upper hood 77 and a lower hood 79
spaced therefrom. The upper hood is positioned above scan line 74
and serves as a housing and reflector for a line source of light
80, such as a neon tube, supported therefrom and extending parallel
to the length of a block oriented in the charger arms. Source 80
produces light of appropriate intensity and direction to illuminate
the upper half of each block as it traverses the scanner. Lower
housing 79 supports a plurality of light responsive elements 82,
such as photocells and electrical circuitry associated therewith.
The photocells are arranged in a line directly beneath light source
80 for exposure thereby, being interspersed at predetermined
intervals along the length of lower hood 79. The photocells are
adapted to produce an electrical output in the presence of light
and to produce no output in the absence of light. Accordingly, the
presence of any portion of a block between light source 80 and each
individual photocell can be detected.
In the preferred embodiment illustrated 55 photocells are utilized
being spaced at 2 inch intervals over a 110 inch span along the
length of the scanner. The output of each photocell is connected to
a conventional electronic unit, not shown, for amplifying the
output of the photocell and supplying the amplified output to
processing unit 30. In the embodiment illustrated, the photocell
array is actuated, by means not shown, upon the approach of the
charger arms and 550 readings are obtained from each photocell
during the traverse of a given block, each reading being taken at a
1/10th inch interval of horizontal travel of the block through the
scanner. The data procured from such a scanning sequence is
supplied to processing unit 30 and utilized in the calculation and
"plotting" of the block dimensions. From such data processing unit
30 calculates the center axis of the largest parallelogram that can
be superimposed within the measured and "plotted" dimensions of the
block and independently controls the operation of the hydraulic set
works 70 of each charger arm 62, 64 to realign the block with the
center axis parallel to an index line, such as a saw line, prior to
engagement in the saw carriage, in a manner explained in more
detail hereinafter.
Saw carriage 14 is of conventional design, including spaced-apart
carriage arms 83, 84 adapted to engage the ends of a block.
Conventional means, not shown, are provided for moving the carriage
arms into engagement with a block and for releasing the arms at the
end of the sawing program. The carriage arms are formed with knife
edges 86 designed to slice into the ends of the block for firm
engagement. The knife edges have recesses 87 formed therein,
located so as to be centered over ends 66 of the charger arms when
a block is engaged by carriage arms 83, 84. This permits gripping
of the block in the saw carriage along the calculated center axis
prior to release of the block by the charger arms.
Conventional means, not shown, are provided for driving the
carriage arms, with a block gripped therein, along an index line
such as a carriage center line or saw line 90 between a start
position 91 indicated in FIG. 1 and a stop position 92.
Intermediate stops at a backstand position 94 are also possible. A
conventional slab chipper 95 is provided having heads 96 arranged
on either side of the carriage center line between the start and
backstand positions for removal of chips from the outer periphery
of the blocks. The spacing of the slab chipper heads is
automatically controlled by unit 30.
Twin band mill 15 is arranged along center line 90 for removing
slabs from either side of a block traversing the center line. The
band mill is of conventional design, comprising a pair of band saws
98, 99. Each band saw includes front and rear cutting edges and is
adapted for selective lateral movement toward or away from center
line 90 in response to signals from processing unit 30. Conveyors
101, 102 and rollers 103, 104 are adapted to receive cants removed
from the blocks on forward passes; and conveyors 107, 108 are
arranged to receive cants removed from the blocks on rearward
passes.
A main outfeed conveyor 110 is provided for receiving cants from
the band mill. The main conveyor communicates with conveyor 107 by
means of a conveyor 112, and with conveyor 108 by means of a series
of conveyors 113, 114, 115. A conveyor 116 is adapted to receive
cants from conveyors 101, 102 and deliver them to the main outfeed
conveyor. Intermediate transfer conveyor 118 is adapted to receive
cants from outfeed conveyor 110 via chain 119 and to deliver such
cants to cant scanner 18.
Referring now to FIGS. 5 and 6, the cant scanner is particularly
illustrated as including a pair of parallel scan chains 121 each
having a plurality of lugs 122 secured thereto in opposed pairs or
sets, and a pair of crowder chains 124 arranged parallel with and
overlying the scan chains. Cants are received on the scan chains
from transfer conveyor 118 and are conveyed thereby through the
cant scanner. The cants, such as cant 130, are arranged on the scan
chains with their length transverse to the direction of movement of
the chain. The cants are also positioned by conventional means with
their worst side up, (i.e., the side having the narrowest strip of
smooth surface) as illustrated in FIGS. 5 and 6.
Lugs 122 on the scan chains extend above the level of the crowder
chains and the crowder chains are operated at a higher speed than
the scan chains. Therefore, each cant is maintained in contact with
a set of lugs on the cant chain during transfer through the cant
scanner. The difference in speeds between the crowder chain and the
cant chain is adjusted to a suitable value to maintain the cants in
firm contact with the lugs.
The cant scanner comprises a hood 131 supported above the cant
chains that serves as a reflector element and as a support for a
plurality of detectors such as photocells 133. A pair of light
sources such as lamps 135, 136 are supported on either side of the
hood arranged to direct light upon the upper surface of each cant
as it is guided beneath the hood. The light from these lamps is
reflected by the smooth surfaces of the cant upwardly to the
photocells. However, any light striking the rough or wane surfaces
of the cant is absorbed or diffused whereby the photocells do not
receive it. Accordingly, the photocells accurately detect the
dimensions of the flat surface on the upper side of the cant. In
the preferred embodiment 55 photocells are utilized, arranged in
line along a 110 inch axis passing through the center of the
scanner hood. As with the block scanner, a scan grid 55 inches wide
is utilized, with measurements of the cant being taken every
one-tenth inch of its transverse of the scan grid. Therefore, the
output data from the photocell array can be supplied to unit 30
where it is processed for calculation of an optimum parallelogram
of wood of uniform thickness in the cant, as well as the center
axis thereof.
A conveyor 140 is provided for receiving cants from the crowder
chain, after scanning, and delivering such cants to a conveyor 142
having a set of cant guides 19 associated therewith. Each cant
guide includes a stop 147 that is independently positioned by a
hydraulic ram 148 at a desired lateral distance from the edge of
conveyor 142. The stops of both cant guides are adjusted, under the
control of processing unit 30, to contact the leading edge of the
cant and to establish a desired alignment for each cant as it is
projected onto conveyor 142. Thus, the cants are realigned or
repositioned with the center axis of the optimum parallelogram
parallel to the cutting line of the edger saws.
A cant chipper 144 is arranged downstream of conveyor 142 for
removing any excess portions of the cants prior to sawing, and a
conveyor 146 is adapted to receive cants leaving the cant chipper.
Four inch gang edger 21 is arranged downstream of conveyor 146. A
transfer conveyor 150 and an edger infeed conveyor 152 are arranged
upstream of 2 inch gang edger 22. A selector fence 156 of
conventional design is associated with conveyor 146. The fence
permits passage of 2 inch cants and controls the transfer of 4 inch
cants to the transfer chain for delivery to the 2 inch gang edger.
Consequently, in the embodiment illustrated, all the cut lumber is
reduced to 2 inch .times. 4 inch studs. It should be apparent,
however, that other sawing arrangements are possible without
departing from the invention.
An outfeed conveyor 160 receives cut lumber from gang edger 21 and
a corresponding outfeed conveyor 162 receives cut lumber from gang
edger 22. The cut lumber is delivered to an unscrambler 26 via a
transfer conveyor 166, a conveyor 167, and a cross conveyor 169.
The unscrambler is of conventional design and provides aligned cut
lumber to a sorter 27 via a transfer conveyor 171.
A conventional stacking unit 29 is located downstream of the
sorter. The stacking unit serves to automatically stack the cut
lumber or studs in predetermined lots for delivery from the
sawmill.
The operation of the sawmill described hereinbefore is
automatically controlled by means of data processing unit 30, with
the exception of certain operator responsive override controls,
such as the block rotating control previously mentioned. Blocks are
transmitted into the mill for processing via the block infeed
conveyors and reach the alignment yoke. When a block drops into the
lower V's of the yoke, the V's automatically close and clamp the
block in a position along a reference axis such as that illustrated
in FIG. 3.
Ordinarily, it is preferred that the block be positioned with the
best side up. Therefore, after the clamping action, if the operator
observes that the block is not so positioned, he can reopen the
V's, rotate the block on the lower V's until its principal
curvature or any excessive surface irregularity is arranged in a
vertical plane. The V's are then permitted to reclamp the block in
that position and the block charger arms automatically grip the
block at each end, in response to processing unit control signals.
The V's then retract allowing the charger arms to pivot the block
upwardly and move it horizontally along the scan path.
As the block approaches the scan zone, the photocell array is
actuated and scanning begins at a point corresponding to the zero
line of the block scan grid schematically represented in FIG. 4.
During the passage of the block through the scan zone, a signal is
generated from each photocell for each one-tenth inch of block
travel through the 55 inch scan zone. As light is occluded by
portions of the block, the recorded signal from each of the blocked
photocells changes whereby the profile of the leading edge of the
block is detected. When the trailing edge of the block passes by a
particular photocell, the signal from that photocell again changes
whereby the profile of the trailing edge of the block is
detected.
When the last point on the trailing side of the block has passed
the photocell array, the data supplied to the processing unit is
used in the computation of the maximum parallelogram which can be
superimposed within the profile dimensions of the block. The center
axis of the maximum parallelogram is also calculated and an
electrical signal representing that center axis is transmitted to
the charger arm set works. As the charger arms approach a position
adjacent the saw carriage, the electrical signal from the
processing unit controls the movement of the calibrated stacked
hydraulic cylinders comprising the set works. The hydraulic
cylinders are extended, individually, until the center axis of the
optimum parallelogram is parallel with the sawing line of the saw
carriage. The center axis can coincide with the sawing line or it
can be offset therefrom by a small distance as is required by the
particular cutting program selected.
With the block properly repositioned, the saw carriage arms close
on each end of the block and the charger arms are released from the
block. The charger arms are then withdrawn to their original
location for handling the next block fed into the sawmill.
Referring now to FIG. 4, a planar profile of a typical block is
shown in solid outline superimposed upon a grid that schematically
represents the block scan grid. The parallelogram having the
greatest width that can be superimposed within the block profile is
represented by parallelogram X and the center axis of parallelogram
X is represented by line Y. Line R.sub.1 represents the position of
the reference axis of the block during scanning and line R.sub.2
represents the position of the reference axis after the block is
repositioned in the saw carriage arms. It should be apparent that
the block is repositioned after scanning so that center axis Y of
parallelogram X is parallel to the base of the scan grid which is,
in turn, parallel to the saw line. As shown, such repositioning
results in the movement of both ends of the block which causes both
angular and lateral adjustment of the reference axis.
Before sawing, the processing unit 30 positions the slab chipper
heads to convert a calculated amount of slab from each side of the
block into chips, in accordance with the appropriate preselected
cutting pattern. As previously mentioned, the sawing pattern for
each particular block is automatically selected by the processing
unit from one of a number of empirically determined cutting
patterns that are retained in the processing unit, a different
pattern being provided for each 1/10th inch difference in width of
the maximum parallelogram.
As the block is passing through the slab chipper, the two band saws
of the twin band mill are moved into position for the first cuts,
also under the control of the processing unit. When the band saws
are positioned, the saw carriage completes its first pass through
the band mill with the first pair of cants being removed, one from
each side of the block, and delivered through the conveyor network
previously described toward the cant scanner. The band saws are
then repositioned for the second cuts and the saw carriage and
block are passed back through the band mill with the second set of
cants being removed and dropped, one on each side of the block.
This process is repeated until the selected cutting program for the
block has been completed. Upon completion, the saw carriage stops
in the backstand position between the band mill and the slab
chipper and releases the remaining section of the block. The saw
carriage then returns to the start position to receive the next
block to be processed.
It should be noted that it is possible for the processing to
include several passes of the block through the slab chipper in
order to remove excess wood such as would occur with a flared
block. This serves to prevent damage to the chipper in the event it
is necessary to remove more wood than the chipper is capable of on
the first pass.
The cants are transferred sequentially from the outfeed conveyor
and indexed onto the lugged scan chains. The cants are positioned
on the intermediate transfer conveyor with their narrow side up as
illustrated in FIG. 6 and are maintained in this relative position
during the remaining sawing operations. Each cant is carried onto
the scan chains and maintained in contact with a set of lugs by the
crowder chain. The position of the cant in contact with the lugs
establishes a reference position for the cant during processing
which is the equivalent of gripping the cant along a reference axis
M as shown in FIG. 6. Each set of lugs retains its cant aligned
along the reference axis M during transfer through the cant
scanner. Therefore, each individual cant can be identified by its
relative position during and after scanning. This facilitates the
"housekeeping" task of the processing unit since a significant
interval occurs between the scanning of a particular cant and the
processing of that cant by the cant chipper and edger saw
arrangement.
The cant scanning operation is similar to the block scanning
operation previously described in that a 55 inch by 110 inch scan
grid is utilized. In the embodiment described, 55 photocells are
utilized, although a different number could be used if desired. The
photocell array is actuated as each set of lugs approaches the zero
line of the scan grid and as the cant traverses the scan line an
output signal is derived from each photocell during each one-tenth
inch of cant movement across the scan grid. As previously
described, when light is reflected from the smooth upper surface of
the cant the photocell produces a positive output. However, when
light strikes the wane portions of the cant or is diffused by a
front or trailing edge of the cant, the photocell produces no
output. Accordingly, an accurate profile of the upper surface of
the cant can be detected and measured.
As with the block scanner, data from each cant is processed in unit
30 and the widest parallelogram of wood of uniform thickness
encompassed within the profile of the cant is determined. Data
representing the center axis of the parallelogram is also
calculated and supplied to the cant guides. In response to this
data, the two adjustable set stops at the edge of the cant guide
conveyor are set to predetermined positions. Accordingly, as the
leading edge of the cant moves onto the conveyor into contact with
these set stops, the cant is automatically positioned with the
center axis of the optimum parallelogram of wood aligned parallel
to the center line of the cant chipper and the edger saws. The cant
is maintained in this alignment during subsequent sawing.
Referring now to FIG. 7, the profile of a typical cant is shown in
solid outline superimposed upon a grid that schematically
represents the cant scan grid. The widest parallelogram that can be
superimposed within the cant profile is represented by
parallelogram K and the center axis of parallelogram K is
represented by line L. Line M.sub.1 represents the position of the
reference axis of the cant during scanning and line M.sub.2
represents the position of the reference axis after the block is
retained on conveyor 142. It should be apparent that the cant is
repositioned after scanning so that the center axis L of
parallelogram K is parallel to the base of the scan line and
parallel to the edger saws. As shown, such repositioning results in
the movement of both ends of the cant, causing both angular and
lateral adjustment of the reference axis.
The processing unit also controls the movement of one or both heads
of the cant chipper to locations which will convert to chips all
except the wood within the widest parallelogram as the cant is
driven through the chipper. As the edged cants leave the chipper
they are carried by conveyor 146 into contact with fence 156. Two
inch cants pass the fence member and are ultimately processed
through a 4 inch gang edger. The 4 inch cants, however, are
transferred by means of transfer conveyor 150 and conveyor 152 for
processing through the 2 inch gang edger.
From these saws, the resulting cut lumber is passed onto the
conveyor systems previously described and on through an unscrambler
into the sorter. Studs from the sorter are usually made up into 7
foot kiln packages in a stacker at the end of the sorter, at which
point they can be rolled out for transport to other areas, such as
the drying kilns.
It should be apparent that in the sawmill described, the processing
units and conveying systems are arranged for convenient handling of
cut lumber. However, other arrangements are possible without
departing from the scope of the invention.
Likewise, the block scanner is particularly designed for
conveniently and accurately handling blocks of 8 foot lengths.
However, other scanning systems and scanning grids could be
utilized so long as the blocks are repositioned along an optimum
cutting axis. As previously mentioned, it is possible to
simultaneously scan the block along two planes to derive a
three-dimensional profile of the block. With such scanning, it is
possible to calculate in a single step the maximum cylindrical
surface that can be superimposed within the dimensions of a block.
The block can then be repositioned with the center axis of the
cylinder parallel to an index line for processing the block into
cut lumber or into veneer.
In addition, with a single scanning array, a block could be
repeatedly passed through the scanner, being rotated a
predetermined amount such as 30.degree., between each pass. This
would produce data from the scanner output which could also be
utilized to derive a three dimensional profile of the block. The
center axis of the largest cylindrical surface that could be
superimposed within the block could be identified and the block
could then be repositioned for processing as previously described.
The disadvantage of such scanning is the additional time required.
In addition, such scanning requires more intricate "housekeeping"
operations in the processing unit. Therefore, such scanning is not
preferred for the processing of cut lumber.
However, it should be apparent that any of the types of scanning
described herein can be used to obtain more wood products from a
given log than was heretofore possible. In addition, the invention
described results in the automatic processing of blocks at a higher
rate than was previously possible with a reduction in
personnel.
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