Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Field of the Invention
The present invention relates to peeling of wood
bolts, more particularly, the present invention relates to
peeling of tapered wood bolts by cutting same on a taper.
8ackground of the Present Invention
The production of veneer for a variety of
different purposes including plywood manufacture, lamin-
ated veneer lumber or, in some cases, oriented strand
lumber, it is common practice to mount wooden bolts on a
lathe and rotate same around an axis substantially
parallel to the longitudinal axis of the tree from which
the bolt was formed, i.e. with the annual rings extending
circumferentially about the axis of rotation. In such
systems as is well known the cutting edge of the knife is
mounted substantially parallel to the axis of rotation and
is held in this parallel orientation as it is advanced
toward the axis as the log is peeled thereby to produce a
substantially uniform thickness veneer (there will be some
deviation due to defects, etc) and a substantially right
cylindrical core when the peeling operation is completed.
It will be apparent that as peeling occurs since the knife
edge remains parallel to the axis of rotation, the veneer
produced is of uniform thickness and the length of each
side edge of the veneer is the same so there is little
tendency for the veneer to curl.
It is also been suggested to cut tapered veneers
particularly for the production of the walls of a bucket
by mounting the blade on an arm and pivoting the arm
around a center pin located axially spaced from the end of
the bolt. Such devices are shown in U.S. patent 767,466
issued August 16, 1904 to Wolfinger and U.S. patent
qk
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1,209,052 issued December 19, 1916 to Sinclair. These
devices cut on a taper so that the veneer produced is
necessarily thicker at one end than other and with one
side edge longer than the other so the veneer will tend to
curl.
U.S. patent 1,957,166 issued May 1, 1934 to
Hartzell also discloses a concept of cutting a veneer
basically in the same manner as some pencil sharpeners
operate.
It is common practice to sense the bolt as it
approaches the lathe to provide an indication of the taper
and shape of the bolt and then to grip the bolt in a
particular fashion so that it may be mounted in the lathe
in a selected position to determine the location of the
axis of rotation of the bolt in the lathe and thereby to
maximize the amount of veneer produced from a given bolt.
In modern lathes, the peeling knive is mounted
on a knife carriage which in turn is mounted on a pair of
side blocks one at each end of the carriage. The side
blocks are mounted in tracks and are advanced by a suit-
able feed mechanism one at each side of the machine
controlled to advance the carriage with the knife substan-
tially parallel to the axis of rotation of the bolt, i.e.
with both axial ends of the knife travelling at the same
speed. In many of the modern machines, the rate of advance
or degree of advancement of each side block is continuous-
ly measured to ensure that the knife carriage presents the
knife edge substantially parallel to the axis of rotation
throughout the peeling operation. In many cases, such a
system includes independent hydraulic drives for each side
block, measuring the displacement of each side block and
controlling the operation of the hydraulics to ensure that
the side blocks are properly aligned to maintain the knife
edge as above described.
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It has been known on startup to cut veneer with
the blade misaligned so that the cutting radius at one end
of the block is shorter than at the other thereby produc-
ing a veneer longer on one side than the other forcing the
same to curve. Such a condition while known to happen
could not be tolerated for any significant length of time
and thus was corrected immediately.
Brief Description of Present Invention
Is an object of the present invention to provide
a system for increasing the mount of veneer attainable
when peeling a tapered bolt.
It is a further object of the present invention
to provide a system permitting cutting of a veneer from a
bolt at an angle to the axis of rotation of the bolt so
that the blade for cutting the veneer is more nearly
parallel to the grain of wood thereby increase the effec-
tive of length of strands that may be formed therefrom.
Broadly, the present invention relates to a
method and apparatus for peeling of the veneer from a
tapered wood block by sensing the shape of the block
rotating the block about a rotational axis in a veneer
lathe having a cutting edge and peeling a veneer from the
block with said cutting edge, the improvement comprising
independently adjusting the opposite axial ends of said
cutting edge in accordance with the shape of said wood
block so that said edge is not parallel to the axis of
rotation at least at the commencement of the peeling
operation and is set at an angle to said axis of rotation
in accordance with said taper so that the end of said edge
adjacent the larger diameter (butt) end of said block is
spaced farther from said axis of rotation of said block
then the opposite end of said edge.
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One embodiment of the invention, the cutting
angle of the knife to the axis of rotation will be
substantially equal to or less than the angle of taper of
the wood block as sensed by the sensing mean, i.e. the
cone angle and the said cutting angle will be held
substantially constant until peeling veneer from the block
is completed so that a substantially uniform cross-
sectional thickness veneer is formed and a conical core
remains after completion of the peeling.
In a second embodiment of the present invention,
the said cutting angle is less than the angle of taper of
the wood block as sensed by sensing means, i.e. less than
the cone angle which results in peeling a veneer thicker
on one side edge than on the other. Under these conditions
of peeling, i.e. cutting to produce a tapered thickness
veneer, the angle of the blade or cutting edge to the axis
of rotation of the block changes as peeling proceeds
thereby to produce a veneer that is thicker on one edge
than on the other. In one arrangement the angle continu-
ously changes and is controlled based on the overall size
of the bolt, cone angle, diameter, etc, to provide a
substantially right cylindrical core when the peeling
operation is completed and a veneer having a substantially
constant difference in thickness at is two side edges.
In a second arrangement the knife is initially
set to cut to produce veneer with say the maximum toler-
able difference in thickness from side to side until the
side blade edge is substantially parallel to said axis of
rotation and then the blade edge is maintained substan-
tially parallel to said axis of rotation until the peeling
operation is completed. This manner of operation results
in minimum curl of the veneer produced and produces
substantially uniform thickness veneer during a signifi-
cant portion of the peeling operation.
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In all of the above, the veneer formed will tend
to curve since the cutting radius at the base of the cone
is larger than that at the opposite end of the block and
thus a greater length of veneer tends to be peeled from
the larger diameter end of the block. The amount of curl
that can be tolerated will depend on the equipment and the
end use to which the veneer is to be applied. It is the
intention to clip the veneer as appropriate before the
curvature has built up beyond the acceptable limit.
Brief Description of the Drawings
Further features, objects and advantages will be
evident from the following detailed description of the
preferred embodiment of the present invention taken in
conjunction with the accompanying drawings in which:
Figure 1 is a schematic illustration of the
operation of the present invention.
Figure 2 is a schematic planned view of a lathe
to which the present invention has been applied.
Figure 3 is a schematic representation of the
conventional peeling operation.
Figure 4 is a schematic representation of a
tapered peeling operation.
Figure 5 is a schematic illustration of a taper-
ed peeling operation producing a tapered veneer during at
least a portion of the peeling operation.
Figure 6 is a section through a veneer produced
following the methods illustrated in Figures 3 and 4.
Figure 7 is a section through a tapered veneer
portion produced following the method illustrated in
Figure 5.
Figure 8 is a partial planned view of a veneer
cut using the techniques illustrated in Figures 4 or 5.
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Description of the Preferred Embodiments
The concept of the present invention is indicat-
ed by the box diagram of Figure 1. A wooden block enters
the scanning and positioning station 1, is scanned and its
shape recognized. It is then positioned on a carriage and
carried into the lathe where as indicated by station
number 2 it is centered and mounted for rotation. Next
the knife feed moves the knife into position to cut or
peel veneer from the block as it is rotated as indicated
by the station 3. To this point, the description describes
basically what happens in the prior art. When practicing
the present invention, the sensed shape of the log carried
out in station 1 is transmitted to the knife feed as indi-
cated in the station 3 and the axial ends of the knife are
independently advanced to set the cutting angle of the
knife cutting edge relative to the axis of rotation of the
block the lathe, so that the edge of the knife is substan-
tially parallel to the outer surface of the block, i.e. to
the basic cone or conical shape sensed by the sensing mean
so that one edge of the knife is spaced farther from the
axis of rotation of the block than the other. The knife
is so set for each block and thereby cuts veneer along the
taper whereby the length of the veneer cut at the end of
the knife farther from the axis of rotation is longer than
that cut at the end of the knife cut closer to the axis of
rotation. The veneer so formed is clipped into suitable
lengths for the purpose to which the veneer is to be
applied as indicated by the station 4 before its curvature
reaches an unacceptable level.
The present invention will become more clear by
reference to Figure 2. In this drawing the blocks of wood
are fed into the peeling lathe 10 on conveyor 12 with
their longitudinal axis generally perpendicular to the
direction of movement as indicated by arrow 11. Each
wooden block (not shown) is sensed by sensor schematically
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indicated at 14 which senses the shape of the block,
activates a positioner 16 which may rotate the log to
facilitate scanning of its shape by scanner 14 then clamps
the log in a selected orientation for delivery to the
lathe 10. The positioner 16 positions the bolt or tapered
block or bolt clamped therein into the rotating mechanism
of lathe 10 which may be composed of chucks schematically
indicated at 18 and 20 mounted in the frame 22 of the
lathe and which are axial as indicated by the arrows 24
and 26 and rotatable as indicated by the arrows 28 and 30
mounted. The chucks 18 and 20 mount the log or block and
rotate it on an axis as determined by the sensor 14 and as
positioned by the positioner 16 aligned with the rotation-
al axis indicated by the dot dash line 32 of the chuck.
The information relating to the shape of the log
and how it is mounted with its center rotation on the
center line or axis 32 is fed to a control computer 34 via
the line 35 to control the angular position and advance-
ment of the knife 36 as will be described hereinbelow.
The knife as schematically illustrated at 36 is
mounted in a knife carriage 38 the opposite ends of which
are mounted in a side block 40 and 42 respectively which
in turn are guided for movement on suitable guide slides
or the like, schematically illustrated at 44 and 46
respectively.
Block 40 is driven by a suitable drive means
such as the hydraulic cylinder means 48 the piston rod 50
of which is connected to the block 40 to move the block 40
backward and forward along the slide 44 as indicated by
the arrow 52. The movement of the rod or shaft 50 is
measured by a suitable measuring means 54 which communi-
cates this information to the control computer 34 so that
the position of the block 40 is known at all times.
Similarly, the hydraulic cylinder 56 operates the shaft or
piston 58 to move the block 42 back and forth along the
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track or slide 46 as indicated by the arrow 60. The posi-
tion or movement of the shaft 58 is similarly monitored by
a sensor 62 and this information fed to the control or
main computer 34 via line 64 so that the position of the
block 42 is also always known. The control computer 34
controls independently via lines 66 and 68 the hydraulic
cylinders or the like 48 and 56 respectively.
when a tapered log or block is centered and
rotated along the axis 32 the knife blocks 40 and 42 are
independently advanced to bring the cutting edge into the
proper cutting angle relative to the axis 32 in accordance
with the information provided by the sensor 14. Assuming
the larger end of the block mounted for rotation around
the axis 32 is adjacent to chuck 20 then the block 40 is
advanced toward the axis 32 into a position relative to
the block 200 indicated by the dash lines so that the
cutting edge 70 is now at an angle A to the axis 32. This
angle A is determined by the shape of the log or block
turning in the lathe. The angle A may correspond with the
sensed cone angle of the block as it rotates on axis 32.
In one embodiment of the present invention, both ends of
the knife, i.e. the knife blocks 40 and 42 are then
advanced simultaneously at essentially the same rate as is
conventional practice to continue cutting at the angle A
relative to the axis of rotation and produce a uniform
thickness veneer product, but with one side edge longer
than the other so the veneer tends to curl.
It should be noted that in conventional lathes
the cutting edge 70 is normally positioned in a horizontal
plane containing the axis of rotation 32 so that the angle
A is measured in that horizontal plane. In conventional
operation, the edge 70 would be held substantially
parallel to the axis of rotation 32.
In conventional operation as shown in Figure 5,
the volume bounded by the outside surface of the bolt or
block 72 as indicated by the lines 74 would be cut away as
indicated by the cross-hatched areas 76 to produce a right
cylindrical section having its sides as indicated by the
lines 78 defining the inside portion of the anular section
76. The volume represented by the cross-hatched section
76 is generally wasted and the central right cylindrical
section is peeled via the knife 30 along lines such as
those indicated at 80 to reduce the size of the block to a
cylindrical core generally indicated at 82 having the
cylindrical volume between the two dotted lines 84, i.e.
the volume between the lines 78 and 84 produces usable
veneer whereas the volume 82 in the core and the volume
formed by the hollow frustro conical section 76 are all
wasted.
When practicing one embodiment of the present
invention as illustrated in Figure 4, the knife 30 is set
at an angle A to the axis of rotation 32 by relatively
moving one axial end relative to the other which as illus-
trated is preferably substantially the same angle as the
conical shape of the outside wall 74 of the bolt 72. The
knife is then advanced into the bolt or block 72 with the
side blocks 40 and 42 advancing at substantially the same
speed so that a substantially uniform thickness veneer is
produced, i.e. the angle A is held constant. This opera-
tion is continued until the bolt is reduced to the frustro
conical shape as indicated by the dash lines 86 which
indicate the outer surface of a frustro conical core 88
that will be left when the peeling operation is complet-
ed. It will be noted that extra waste material in the
core, i.e. the difference in material in a right cylindri-
cal core as indicated at 82 in Figure 3 and the frustro
conical core indicated at 88 in Figure 4 is the volume of
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the hollow frustro conical section between the walls 90
and the frustro conical outside walls 86 of the conical
core 88, i.e. the volume indicated by the hatched areas
92.
S It will be apparent that the hatched volume of
the hollow cone 92 is significantly less than that of the
hollow cone 76 and thus the amount of usable veneer
obtained is significantly greater (by better than 5~O and
generally better than 7~) than the amount of veneer
obtainable when cutting in the manner described in Figure
3.
In both Figures 3 and 4, the veneer formed as
indicated at 94 in Figure 6 has the same thickness
throughout its width, i.e. both side edges are of the same
thickness.
The cutting pattern illustrated ~in Figure 5 is
significantly different from that of Figure 4. In this
arrangement, at least the veneer cut from a tapered bolt
72 is also tapered, i.e. it is thicker at the larger dia-
meter end of the bolt than at the smaller diameter end of
the bolt. This difference in thickness will be determined
by the difference in diameter of the bolt at the larger
diameter end relative to the smaller diameter end, i.e.
the cone angle of the bolt being turned around axis 32.
When cutting such a tapered veneer in one manner
of operation, the rate of advance of the two blocks 40 and
42 will be controlled so that in the illustrated arrange-
ment (wherein the larger end of the bolt is adjacent to
block 42) after the initial alignment of the edge 70 rela-
tive to the outer wall 74 of the bolt 72, the block 42
advances more quickly than does the block 40 so that the
veneer produced is thicker at the larger end 96 of the
bolt 72 than at the smaller end 98 thereby to produce a
tapered veneer, i.e. a veneer cut thicker adjacent the end
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96 than adjacent the end 98. Preferably, this difference
in thickness is such that when the outer surface of the
core 100 left when peeling is complete as indicated by the
lines 102 is reached, the knife blade edge 70 will be
substantially parallel to the axis of rotation 32 to
thereby leave a substantially right cylindrical core 102
and minimize wastage.
In some cases it may be desirable to cut
initially to produce veneer having the maximum tolerable
thickness difference from one side to the other to form
the bolt into a substantially right cylindrical shaped
indicated by the dot sash line 104 in Figure S as soon as
possible or in any event well before peeling is completed
and then to cut veneer of uniform thickness (not tapered)
through the remainder of the peeling of the bolt, i.e.
between the lines 102 and 104. This technique will result
in a minium curling of the veneer. Alternatively the
tapered cutting may also be controlled to maintain the
difference in thickness at opposite sides of the veneer
constant so that the veneer produced in the peeling of
that bolt all has substantially the same tapered thickness
profile regardless of its location in the bolt being peel-
ed. Obviously the above alternatives are not absolute and
one may operate somewhere in between if desired and in
some cases finish leaving a tapered core.
It will be apparent that the initial angular
position of the blade edge 70 as indicated by the angle A
when practicing in accordance to the embodiment illustrat-
ed in Figure 5 may be slightly different than that shown
in Figure 4 in that it will be slightly less so that the
depth of cut at the large diameter end 96 will be deeper
than at the small diameter end 98 of the block 72.
The tapered veneer cut when practicing according
to Figure 5 is as above indicated thicker at one end than
the other so that the thickness of the narrow end would be
4~
t- while the thickness at the thicker end would be t+ and
the thickness at the middle would be equal to t so that
the average or nominal thickness of the veneer would be
the same as the nominal thickness t of the veneer of
Figure 6.
It will be apparent that when practicing the
invention as taught in Figures 4 and 5 the length of the
veneer cut at the thick end or larger end 96 will be long-
er than the veneer cut at the smaller end 98 so that the
veneer formed as indicated 104 will tend to curve as
indicated by the lines 106 and 108 at opposite ends of the
veneer corresponding to the ends 96 and 98 respectively of
the block. This veneer may be clipped to suitable lengths
depending on the end purpose to which it will be used. If
it is to be used to make strand lumber, it will be clipped
relatively closely as indicated by the line 110 to produce
a plurality of strips or strands 112. If the veneer 104
or 94 made for example in accordance with Figure 4 embodi-
ment is to be used for other purposes where wider sections
would be preferred the spacing between the cutoff sections
may be significantly larger provided the arc is not suffi-
cient to interfere with subsequent operations of the
equipment, i.e. the veneer 104 or 94 could be severed
along lines spaced as indicated at 114 from the lead end
116 of the veneer say every 2 feet.
Having described the invention, modifications
will be evident to those skilled in the art without
departing from the spirit of the invention as defined in
the appended claims.
