Note: Descriptions are shown in the official language in which they were submitted.
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HIGH SPEED PLANER HEAD
Field of the Invention
The present invention relates to a high speed planer head, such as for use in
commercial manufacturing of construction lumber and finished wood products.
Background
The finish on construction lumber, such as cut from logs into 2 X 4, 2 X 6, 2
X
12, and 4 X 4 nominal dimensions, has become increasingly important as a
result of the
trend for such construction lumber to be sold in retail outlets, such as the
large home
improvement chain stores, to "do-it-yourself ' (DIY) consumers. While
construction
lumber is typically covered with sheet rock or gypsum board and so is not
visible in
finished construction, DIY consumers often select and purchase construction
lumber
primarily on the basis of surface-finish. Accordingly, 'well finished
construction lumber
can command a premium price, and construction lumber that is not well finished
may be
difficult to sell.
Commercial planer heads include a plurality of elongate knives spaced
circumferentially on a cylindrical hub rotating at high speed. The elongate
axes of the
knives are typically, but not necessarily, aligned with the axis of rotation.
The wood
travels relative to the head in a direction perpendicular to the axis of
rotation of the hub,
the knives cutting a surface on the wood. The resulting surface finish is
affected by a
number of factors, e.g., the extent to which the planer head is in balance,
the density of
knives on the planer head, the speed of rotation, the speed of travel of the
wood, and the
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ability of the apparatus to efficiently keep chips away from the cutting
surface as it is
being cut.
Standard practice provides for statically balancing the knives and knife
assemblies
carned by the hub as well as dynamically balancing the hub and the shaft to
which the
hub is attached (or with which the hub is integrally formed). The speed of
rotation of the
head is set as high as practical, and the speed of travel of the wood is set
as high as
possible while still providing acceptable surface finish, to increase the
speed of
production. Some "chip marks" occur as a result of chips remaining on the
cutting
surface as the wood is being cut and have been accepted in the prior art.
With a given degree of balancing and speed of rotation of the planer head,
increasing the speed of wood travel to obtain further efficiency increases
will decrease the
quality of the surface finish, and it would be advantageous either to be able
to increase the
speed while maintaining the quality of surface finish, or maintain the speed
and improve
the quality of the surface finish.
One means for increasing the surface quality given the limitations noted above
is
to increase the frequency of cutting by increasing the density of knives on
the planer head.
Particularly, the parallel and circumferentially distributed cutting edges of
the knives
should be spaced as close together as possible. However, each knife must be
removable
so that the knife can be sharpened or replaced. The knives are typically
clamped in knife
assemblies by screws. The screws may bear on a block of metal called a "gib"
that it tum
bears on the knife, the end of the screw may bear directly on the knife, or
the screw may
extend into a collar that wedges against the knife. In all cases, the
construction
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methodology places limits on the potential for increasing the density of the
knives.
Typically, prior art knives have a straight cutting edge and one or two
radiused or
semi-circularly curved cutting edges at respective ends of the straight
cutting edge.
Where only one curved cutting edge is employed, the knives are alternated in
upside-
down and right-side-up position so that two knives together cut respective
opposite
corners of the wood and each knife cuts the straight face of the wood so that
the straight
face of the wood is twice cut. In either case, a straight cutting edge is
physically merged
with a curved cutting edge. In a process known as "jointing," used for
sharpening the
knives as the knives are installed in the planer head and as the head is
rotating, wherein a
fixed stone is introduced against the rotating knives, what is known in the
art as "relief ' is
lost for the outer portions of the curved cutting edges. This lack of relief
results in
hammering the wood at the corners, degrading surface finish.
Another problem in the prior art is adjusting the planer head between cutting
an
article of wood from green wood stock to cutting an article of the same
nominal size from
dry wood stock, and vice-versa. This has required replacing the complete
planer head,
which is costly.
There is a need, therefore, for a high speed planer head provided according to
the
present invention that solves the aforementioned problems and provides
additional
features and advantages.
Summary of the Invention
The invention disclosed herein is a high speed planer head. According to one
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aspect of the invention a hub and a threaded member are provided. The hub is
axially
disposed for rotation about an axis and has a pocket for receiving a first
knife against a
supporting wall of the pocket. The threaded member has a frustoconical ramping
portion
for producing a wedging force against the knife when the threaded member is
threaded
into a threaded hole in the hub.
According to another aspect of the invention, a second hub for carrying a
second
knife is provided, the second hub preferably being bolted to the first hub to
that the hubs
can be disassembled. The first knife preferably has two linear cutting edges
and the
second knife preferably has at least two curvilinear cutting edges.
The second knife preferably has two linear cutting edges and the second knife
preferably has at least two curvilinear cutting edges and more preferably has
four
concave, semi-circular cutting edges that are spaced apart from one another
with 90
degree rotational symmetry.
Brief Description of the Drawings
Figure 1A is side elevation of a prior art planing apparatus.
Figure 1B is a top view of the planing apparatus of Figure 1A.
Figure 2 is an end view of a prior art planer head for use in the apparatus of
Figures 1A and 1B.
Figure 3 is more detailed end view of the planer head of Figure 2.
Figure 4A is a pictorial view of an alternative prior art planer head.
Figure 4B is a pictorial view of two collars used in the planer head of Figure
4A.
4
d
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Figure 5 is an end view of a face-cutting planer head according to the present
invention.
Figure 6 is more detailed end view of the planer head of Figure 5.
Figure 7 is a pictorial view of a preferred knife for use in the planer head
of Figure
5.
Figure 8A is a cross-sectional view of an unfinished article of lumber.
Figure 8B is a cross-sectional view of the article of lumber of Figure 8A in a
finished condition.
Figure 9A is a pictorial view of side-cutting planer head according to the
present
invention.
Figure 9B is a side elevation of the planer head of Figure 8A.
Figure 10 is an exploded view of a preferred configuration of the planer head
of
Figure 8A.
Figure 11 is an end view of a corner-cutting planer head according to the
present
invention.
Figure 12A is a pictorial view of a front side of a corner-cutting knife
according to
the present invention for use in end portions of the planer head of Figure 9A.
Figure 12B is a pictorial view of a back side of the knife of Figure 12A.
Figure 13A is a cross-sectional schematic view of an article of lumber being
cut
with a corner-cutting knife having a full 1/4 round cutting edge in perfect
alignment.
Figure 13B is a cross-sectional schematic view of the article of lumber of
Figure
12A cut with the knife of Figure 13A in imperfect alignment.
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Figure 14A is a plan view of two knives according to the present invention,
comparing dimensions thereof for cutting an article of lumber from dry and
green stock.
Figure 14B is an end view of an article of lumber shown with finished corners
produced by the two knives of Figure 14A.
Figure 14C is a plan view of a positioning, according to the present
invention, of
the two knives of Figure 14A for finishing the article of lumber as shown in
Figure 14B.
Figure 15A is a schematic view of the knife of Figures 12A and 12B showing
geometric constructions useful for defining the configuration of the knife
according to the
present invention.
Figure 15B is a schematic view of a prior art knife corresponding to the
schematic
view of Figure 15A.
Figure 16A is a pictorial view of the knife shown in Figures 12A and 12B
showing line segments used to describe the shape of a beveled surface of the
knife
according to the present invention.
Figure 16B is a partially cut-away cross-sectional view of the knife of Figure
16A
taken along a line 16B-16B thereof.
Figure 16C is a partially cut-away cross-sectional view of the knife of Figure
16A
taken along a line 16C-16C thereof.
Figure 16D is a partially cut-away cross-sectional view of the knife of Figure
16A
taken along a line 16D-16D thereof.
Figure 17A is a schematic view of a face-cutting knife cutting an article of
lumber
showing an attack relief angle according to the prior art.
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Figure 17B is a schematic view of a corner-cutting knife according to the
present
invention shown relative to the article of lumber of Figure 17A.
Detailed Description of a Preferred Embodiment
Figures 1A and 1B show two orthographic views (side and top, respectively) of
a
high speed planing apparatus 10. The apparatus 10 has a table 12 for
supporting an
article of wood 14 that travels horizontally on the table. At least four
planer heads 16 are
provided: one (16a) above the article of wood (hereinafter "top"), one (16b)
below the
article of wood (hereinafter "bottom"), one (16c) to one side of the article
of wood and
one (16d) to the other side of the article of wood (hereinafter "side"). Each
planer head
rotates about a respective axis of rotation "Ra," "Rb," "Rc," and Rd." As a
result of this
rotation, in conjunction with travel of the wood 14 relative to the planer
heads, each
planer head cuts a corresponding surface on the article of wood, so that a top
surface, a
bottom surface, and two opposing side surfaces are cut. An object of this
process is to
produce a surface having a high surface quality; however, it is not essential
that the
planing apparatus be used to produce a finished surface.
Figure 2 shows an end view of one (17a) of the planer heads 16. The head 17a
has an axis of rotation "R." A hub 18 of the head 17a carries a plurality of
circumferentially spaced apart knives 20 and associated gibs 22 in
corresponding pockets
19 of the hub. Figure 3 shows one of the pockets 19a in more detail. A knife
20a and its
associated gib 22a are disposed in the pocket 19a. A screw 24 is threadably
received
through a hole in the hub 18 and a terminating end 24a thereof extends outside
the hub
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and bears against the gib 22a which, in turn, bears against the knife 20a.
This clamping
force clamps the knife against a supporting wall l9as of the pocket 19a. A
minimum
circumferential spacing "S" is required between adjacent knives to provide
space for
accessing and removing the screw 24a in the direction of the arrow "A."
Figure 4a is a pictorial view of an alternative prior art planer head 17b,
showing a
knife 20b removed therefrom. The knife 20b is clamped in a pocket 19b in the
head 17b
by an axially directed screw 24z extending through an upper collar 25a and
into a
corresponding lower collar 25b. Referring in addition to Figure 4B, the
collars 25 include
corresponding tamped planar portions 25ap (not visible in Figure 4A) and 25bp
for
mating with corresponding tamped planar portions 22b-upper and 22b-lower of a
gib
portion 22b of the knife 20b that functions analogously to the gib 22a of the
knife 20a.
Rather than bearing against the knife as does the gib 22a, the gib portion 22b
is integrally
attached to the knife and supports the knife, which is cantilevered therefrom.
Therefore,
the gib portion 22b must be particularly large and robust to withstand the
required forces,
1 S as compared to the gib 22a.
One of the collars (25a) is adapted to receive the head of the screw 242 and
the
other collar (25b) includes threads "Th" adapted to receive the threads of the
screw.
Inserting the screw through the collar 25a and tightening the screw into the
collar 25b
forces the collars together, wedging the collars against the tamped planar
portions of the
knife and thereby forcing the knife against a back surface 19b5 of the pocket
19b, to
clamp the knife to the planer head. This construction provides an advantage
over the
planer head 17a described immediately above in providing the capability to
move the
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knives closer to one another and therefore achieve denser knife spacing.
However, this
density is limited by the dimensions of the collars and the gib portions 22b,
all of which
must be robustly sized in order to withstand the required forces.
Turning to Figure 5, an end view of a face-cutting planer head 26 according to
the
present invention is shown. A hub 28 of the head 26 carries a plurality of
circumferentially spaced apart knives 30. Each knife 30 is disposed in an
associated
pocket 31 and has an associated gib 32. As best seen in Figure 6, showing a
portion of
the periphery of the hub 28 in greater detail, a screw 34 has a threaded
portion for
threading into a hole 35 in the hub. The threaded portion terminates in a
terminating end
34a that is, preferably, contained within the hub and, in any event, is not
used to exert a
force on either the gib or the knife. Rather, the screw 34 according to the
present
invention has a tamping shoulder portion 34b which in a preferred embodiment
of the
invention is of frustoconical shape. The tamping portion 34b exerts increasing
wedging
force (in the direction indicated by the arrow "b") against the gib 32 as the
screw is
1 S tightened, the gib in turn transmitting this wedging force against the
knife, to clamp the
knife in place against a supporting wall 31c of the pocket 31, and against the
gib, to force
the gib against a front side 40 of the knife and a bottom 31b of the pocket
31. The screw
34 is shown with a male tightening member 34c; however, a female tightening
member
may also be used. Moreover, a female tightening member has been determined not
to
become loaded with wood waste during operation and the female configuration
provides
for greater clearance and so may, therefore, be preferable.
An angle ~ defines the ramp angle of the of the tamping portion 34b of the
screw
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34, This ramp angle provides a mechanical advantage in translating a
tightening force
applied to thread the screw into the hole 35 into a clamping force bearing
against the gib
and, in turn, the knife. A small ramp angle ~ increases the advantage;
however, if the
ramp angle ~ is too small, too little range of movement of the gib will be
provided to
accommodate manufacturing tolerances between the screw, gib and knife, along
with the
additional elastic compression of the parts necessary to exert the required
clamping force.
It has been found that the ramp angle ~ is preferably in the range of about 10
- 25
degrees.
The combination of the screw 34 and gib 32 clamp each knife 30 in the planer
10. head 26. The gib 32 need be no more robust than the gib 22a described
above in
connection with the head 17a. The screw 34 in essentially incorporating the
function of
the collars 25 of the head 17b can be of smaller overall dimensions than the
corresponding screw and collar combination, and the gib 32 need not be as
strong and
therefore may be smaller and, particularly, thinner than the corresponding gib
portion
22b. Thence, the screw and gib according to the present invention provide
minimum
sized components for clamping knives in a planar head, providing for maximum
density
of spacing of the knives and, therefore, a maximum degree or quality of
surface finish.
Referring to Figure 7, the knives 30 are preferably provided with dual,
opposed,
cutting edges 36a and 36b and corresponding deflector ridges 38a and 38b such
as
described in Schmatjen, U.S. Patent No. 5,819,826 that project from the front
side 40 of
the knife and extend parallel to an elongate axis "L" of the knife. The
deflector ridges
define a channel 42 having a channel surface 42a. The channel 42 is
effectively a recess
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in the front side of the knife, which may be provided in other configurations,
such as a
keyway. The knives 30 also have a back surface 44 that is received against the
supporting
wall 31 c of the pocket 31.
The recess provided, in the preferred embodiment, by the deflector ridges 38
and
the associated channel 42 define an interlocking feature adapted for
interlocking with the
gib 32, providing a double-sided, indexable knife system that securely and
positively
holds the knife in the associated pocket. Particularly, as seen in Figure 6,
for use with the
preferred knife 30, the gib is adapted so that one of the deflector ridges 38a
is disposed
outside a toe 39 of the gib at one end of the toe, the other end of the toe
being defined by
a recess 41 shaped to receive the other deflector ridge 38b. The channel 42 as
bounded
by the deflector ridges defines a recess that, along with the relatively
projecting toe of the
gib 32, provide interlocking means which cooperate to index and further
securely hold the
knife 30 in position against the gib 32.
Referring back to Figure 7, the knife 30 has an elongate axis "L" and, a line
perpendicular to the elongate axis "L" and passing through the cutting edges
36 of the
knife defines a transverse axis "TA" of the knife. Now referring back to
Figure 5, the gib
32 associated with the pocket wall 31c defines an orientation of the axis "TA"
for the
knife as installed in the hub 28. This orientation can be specified as an
angle 8, relative
to a radial line "RL" extending through the axis of rotation "R" of the head.
The angle 8,
establishes the axis "TA." The angle 8, is optimized to provide a desired
angle of attack
for the knife and is preferably in the range of 10 - 30 degrees.
The hole 35 for receiving the threaded portion of the screw 34 has an elongate
11
A -
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axis "EA" that makes an angle 62 relative to the radial line "RL." The angle
82 is
optimized to direct the clamping force against the knife. The angle 82 is
preferably in the
range of 10 - 20 degrees and is determined without regard to the angle 8,,
i.e., the axes
"EA" and "TA" rotate together as the angle 8, is varied.
S The planer head 26 provides several outstanding advantages. One advantage is
that the manner described above for clamping each knife 30 provides for much
denser
spacing of the knives as compared to the prior art. The screw 34 may be
accessed and
removed from essentially a radial direction rather than a circumferential
direction, so that
the spacing between the knives need not provide space for screw access or
removal as
was required in the prior art. This denser spacing of the knives, by itself,
improves
surface finish. Moreover, this improved surface finish can be traded off, to
any extent
desired, to achieve higher production throughput by increasing the speed of
travel of the
wood being cut.
The mechanical advantage provided by the screw 34 has been found to decrease
the number of screws required to achieve a given clamping force. This provides
for less
machine downtime, since fewer screws need to be loosened or removed in order
to
remove a knife for replacement or repair. This mechanical advantage also makes
the
screw less prone to loosening, so that clamping is made more secure.
It is also recognized by the present inventor that each of the knives 30 may
be
made very thin (dimension "t" in Figure 7), so that, from material
considerations, it
becomes economical to dispose of the knives rather than repair them. For
example, for a
typical knife that is 7/8" wide (dimension "w" in Figure 7) and arbitrarily
long (e.g.,
12
a
CA 02525900 2005-02-04
anywhere from 1" to 48"), a representative dimension "t" is only 0.082".
Employing
disposable knives further reduces machine downtime as well as the cost of
providing and
operating machines used for knife repair. The ability to make the knives thin
is due, at
least in part, to the security of the clamping force provided by the screw 34
as well as the
indexing provided by the deflector ridges.
The knives 30 and the gibs 32 need not extend the entire (axial) length of the
hub
28. For example, two knives 30 and/or two associated gibs 32, axially butted
against one
another, are preferably used in each pocket 31, each pair of a knife and
associated gib
extending about half the axial length "1" of the hub. Two axially disposed
knives and/or
two axially disposed gibs, or more than two axially disposed knives and/or
more than two
axially disposed gibs may be provided in each pocket without departing from
the
principles of the invention.
The just described planer head 26 corresponds to two of the four planer heads
16a
- 16d of Figures 1A and 1B. Turning to Figure 8A, a generalized cross-section
of a
length of unfinished construction lumber 45UF is shown. Two of the planer
heads 26 are
arranged in correspondence to the heads 16a and 16b of Figures 1A and 1B and
cut,
respectively, top and bottom faces F~ and Fb of the lumber 45,x. After this
cutting the
lumber has a finished thickness "tF," and an unfinished width "w"f."
Figure 8B shows a cross-section of the article of lumber shown in Figure 7A in
a
finished condition 45F as a result of cutting two side faces FS, along with
four respective
radiused corners "r," with planer heads corresponding to 16c and 16d of
Figures 1A and
1 B. Accordingly, each of the side-cutting planer heads has corner-cutting
adaptations for
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cutting two radiused corners "r" in addition to an adaptation for face-cutting
a flat side
face FS.
Turning to Figures 9A and 9B, a side-cutting planer head 46 is shown having
the
corner and face-cutting adaptations just indicated. Particularly, the side-
cutting planer
head 46 has a face-cutting center portion 47 and two corner-cutting end
portions 49a and
49b, on either side of the center portion 47, for cutting respective radiused
corners "r."
The portions may be attached to a shaft for rotating the portions as is known
in the art or
may be formed integrally with the shaft.
Turning to Figure 10, the face-cutting center portion 47 includes a hub 48
carrying
a plurality of circumferentially spaced apart knives 50. Each knife 50 is
disposed in an
associated pocket 51 and has an associated gib 52. A screw 54 is threadably
received
through the hub 48. The screw 54 preferably has the same features as the screw
34 for
wedging against the gib 52, and in turn for wedging the knife against a
supporting wall
S lc of the pocket 51. As the center portion 47 is used to cut a flat face
like the planer
head 26 described above, the center portion is preferably provided with all of
the features
of the planer head 26.
With reference to Figures 10 and 1 l, each corner-cutting end portion 49
includes a
hub 58 (58a, 58b in Figure 10) carrying a plurality of circumferentially
spaced apart
knives 60. Each knife 60 is disposed in an associated pocket 61 and has an
associated gib
62. A screw 64 is threa.dably received through the hub. The screw 64
preferably has a
ramping shoulder portion 64b that is the same as or similar to the ramping
shoulder
portion 34b of the screw 34, for wedging against the gib 62, and in turn for
wedging the
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knife against a supporting wall 61 c of the pocket 61. The screw 64 is shown
with a
female tightening member 64c; however, as mentioned above, either female or
male
tightening member may be used.
As best seen in Figure 9B, the corner-cutting end portions 49 are adapted to
cut
two of the radiused corners "r"shown in Figure 8B. Turning to Figures 12A and
12B,
showing the knife 60 in more detail, the knife has at least one corner-cutting
edge "CE,"
for this purpose. It is advantageous, however, to provide the knife 60 with
four corner-
cutting edges "CEO," "CEZ," "CE3," and "CE4," so that the knife carries a
multitude of
replacement edges and so that a symmetry is provided in the knife so that the
knife is
suitable for use in either end portion 49. However, any number of corner-
cutting edges
(or cutting edges) may be provided. Preferably, the four corner-cutting edges
are
disposed with respect to one another with 90 degree rotational symmetry as
shown;
generally, it is preferable to provide "n" cutting edges with 360/n degree
rotational
symmetry.
1 S The knife 60 has a front side 60a (Figure 12A) and a back side 60b (Figure
12B).
Taking the end portion 49a for example and with reference to Figure 9, to
expose the
corner-cutting edge "CE"" the knife is indexed to the pocket 61 by seating a
first outer
edge "OE," against a bottom supporting wall 61b in the hub 58a. A second outer
edge
"0E2" is index to a sidewall 53a (see also Figures 9A and 9B) of a pocket 53
in the
adjacent hub 48 of the center portion 47. Similar considerations apply in
mirror image
for the end portion 49b.
With particular reference to Figure 12B, the cutting edge "CE" is a portion of
a
CA 02525900 2005-02-04
concavely circular arc for cutting a round (radiused) corner "r," though other
shapes could
be used for forming corners having different configurations. A full 90 degree
arc,
necessary for cutting a complete 1/4 round corner "r,"is shown superimposed on
the
cutting edge "CE," in dotted line. The 90 degree arc terminates at end-points
P3
(corresponding to P,) and P4 (corresponding to PZ). Tangent lines "LT3" and
"LT4" that
are tangent to the end-points P3 and P4 are spaced apart 90 degrees.
By contrast, the cutting edge "CE," is preferably less than a full 90 degree
arc and
terminates at end-points P1 and P2. Tangent lines "LT," and "LTZ" that are
tangent to the
end-points P~ and PZ are spaced apart greater than 90 degrees. Particularly,
respective
alignment relief areas "RA," and "RAZ" are defined between the respective
tangent lines
"LT," and "LTZ" and the corresponding respective tangent lines "LT3" and"LT4."
These
alignment relief areas (or "alignment reliefs") are preferably formed by
employing,
preferably though not necessarily, straight outer perimeter sections "OP"
flanking, on
each side, the cutting edge "CEO." An alignment relief angle 83 corresponding
to the
alignment relief area "RA," and an alignment relief angle 84 corresponding to
the
alignment relief area "RAZ" are preferably equal to each other and are
preferably about 20
degrees; however, the angles can vary depending on need according to the
following
considerations.
The alignment reliefs are provided to ensure that the knife does not extend
into
space in which it is not desired as a result of misalignment of the knives.
Even if the
knives are originally perfectly aligned, such misalignment can subsequently
occur, for
example, as a result of the process known in the art as "jointing," which is
used to
16
A
CA 02525900 2005-02-04
sharpen the knives in a planer head with a stone, while the knives remain
clamped to the
apparatus. Referring to Figures 9A and 9B for context, the stone (not shown)
contacts the
cutting edges of the knife 50 of the center portion 47 and the cutting edges
of the knives
60 of the end portions 49 at the same time, and it is highly desirable that
the stone be
applied to the same thickness of metal for all cutting edges, to provide for
even
sharpening. However, if the outer perimeter sections of the knives 60 extended
along the
lines "LT3" and "LT4," and if the knives 60 were not perfectly aligned or
oriented with
respect to the knives 50, portions of the knives 60 would project into space
adjacent to
that occupied by portions of the knives 50, "doubling-up" on the amount of
metal
confronted by the stone at such locations.
As another consideration, the alignment reliefs prevent potential interference
between the corner-cutting knife 60 and an adjacent face-cutting knife. An
example is
shown in Figures 13A and 13B. Figure 13A shows a corner portion (in cross-
section) of
an article of lumber 45c. A top face "FT" is cut with a face-cutting planer
head (not
shown) such as the planer head 26, while a side face "FS" is cut with the face-
cutting
center portion 47 of planer head (also not shown) adapted for corner cutting
such as the
planer head 46. A corner-cutting end-portion 49 (also not shown) of the planer
head
carries a knife 60 having a cutting edge "CE." As shown, the cutting edge "CE"
is a full
1/4 round and is perfectly aligned with respect to the top face "FT;" however,
this is not a
practical circumstance.
Turning to Figure 13B, if the knife 60 is misaligned by any angle 0 that is
greater
than zero, the cutting edge CE will cut into the top face "FT" regardless of
whether the top
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CA 02525900 2005-02-04
face is cut before or after the side face "FS." If the knife is misaligned in
the opposite
direction, a similar interference will occur with the side face "FS."
The knives 50 and screws 54 of the center portion 47 of the planer head 46 are
preferably oriented as shown in Figure 10. The gib 62 associated with the
pocket wall
61 c defines an orientation of an axis "TAa" in the plane of the back surface
60a (Figure
12A) of the knife 60 as installed in the hub 58. This orientation can be
specified as an
angle 8~a relative to a radial line "RLa" extending through the axis of
rotation "R" of the
head. The angle 8~a establishes the axis "TAa." The angle 8~a is optimized to
provide a
desired angle of attack for the knife and is preferably in the range of 10 -
30 degrees.
A hole 65 for receiving the threaded portion of the screw 34 has an elongate
axis
"EAa" that makes an angle 82a relative to the radial line "RLa." The angle 82a
is
optimized to direct the clamping force against the knife. The angle 62a is
preferably in the
range of 0 - 20 degrees and is determined without regard to the angle 8,a,
i.e., the axes
"EAa"and "TAa" rotate together as the angle 8~a is varied.
The prior art typically provided a single knife having a straight cutting edge
integrally formed with one (or two) curved cutting edges, to cut both the side
face FS and
one (or two) of the corners r of the article of lumber 45F in Figure 8B. The
novel
construction of the present invention provides a number of outstanding
advantages over
the prior art. For example, to change the radius of the finished lumber, all
that is required
. according to the invention is to change the relatively small and inexpensive
corner-cutting
knives 60, while in the prior art, the entire cutting surface needed to be
changed.
Moreover, the prior art planer head was adapted for a particular knife.
Turning
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CA 02525900 2005-02-04
back to Figure 10, the center and end portions according to the present
invention are
preferably provided as separate units that are bolted together as shown.
Although this
feature is not essential and the end portions may be manufactured integrally,
the feature
provides for changing the width of the finished lumber simply by changing out
the center
portion 47, while in the prior art, the entire planer head would need to be
changed.
According to another aspect of the invention, and taking advantage of the
preferred "bolt-together" construction of the planer head 46 shown in Figure
10, the
planer head can be adjusted from being adapted to cut dry lumber to being
adapted to cut
green lumber, and the reverse, simply by changing the knives 60 and the end
portions 49.
Figure 14A shows the outline of a representative knife 6OoRY, corresponding to
the
configuration shown in Figure 12A, for cutting an article of lumber of nominal
size from
stock that has been kiln dried. The cutting edges CF,~RY have respective radii
RDRY
Shown in dotted line is the outline of a corresponding knife 6Oc~EN having
larger
respective radii RG~EN adapted for cutting the same article of lumber from
green stock.
Figure 14B shows an of a finished 2 X 4 70DRY finished from dry stock,
corresponding to the outline shown for the article 45F in Figure 9B, along
with the
corresponding outline of a 2 X 4 70c~EN finished from green stock shown in
dotted line.
The widths of the two articles differ slightly, typically by the dimensions
indicated, and
the radii of the respective corners RDRY and R.c~EN differ as shown Figure
14A.
With additional reference to Figure 10, it is recognized that to leave the
outer
edges OE (Figure 14A) of the knives 60 available for indexing to the center
portion 47
(particularly, the sidewall 53a) as described above, the end portions 49 the
knives 60DRv
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CA 02525900 2005-02-04
and 6Oc~EN can be shifted relative to one another as shown in Figure 14C
(compare with
Figure 14A). Outer edges OE of both knives remain positioned to contact the
sidewall
53a (Figure 10) of the center portion 47, so that the same center portion can
be used.
Outer edges OEDRY and OEG~~,, are shifted relative to one another, and this
shift can be
accommodated by modification of the end portions 49.
For example, to cut 2 X 4's from dry stock, the knife 6ODRy has the position
shown
in Figure 14C: A cutting edge CEflRY merges or aligns with the face side FS of
the 2 X 4;
the knife 60DRY is indexed to the sidewall 53a of the center portion 47 at the
outer edge
OED ; the knife 60DRY is indexed to the bottom supporting wall 61b of the
pocket 61 of the
end portion 49 (49a in Figures 9B and 10) at the outer edge OEDRy. Similarly,
to cut 2 X
4's from green stock, the knife 6Oc~EN has the position shown in Figure 14C. A
cutting
edge CEG~EN merges or aligns with the face side FS of the 2 X 4, the knife
60G,~EN 1S
indexed to the sidewall 53a at the outer edge OED, and is indexed to the
bottom
supporting wall 61b at the outer edge OEc~.EN. The outer edges OEDRY and
OEG~EN ~e
displaced an amount 0 from one another that is equal to %i the difference in
the widths
shown in Figure 14B, and the respective depths of the pockets 61 of end
portions 49
corresponding to the two knives are provided accordingly.
Preferably, the pockets 61 are identical for end portions adapted for the two
types
of wood stock, and the depths of the pockets are adjusted simply by changing
the outer
diameter "D" of the end portion (see Figure 10), though this is not essential.
In any event,
to change from cutting green lumber to dry lumber or the reverse, or to change
the width
of the article of lumber a small amount fox any other reason, only the knives
60 and the
CA 02525900 2005-02-04
end portions 49 need to be changed; the more expensive center portion 47 may
be used
for either purpose and therefore may remain in the cutting apparatus.
Turning to Figure 15A, the knife 60 has a distinct configuration that can be
defined with reference to lines "BL" that bisect the cutting edges CE of the
knife. Each
cutting edge CE is preferably semi-circular as described above and, therefore,
has a radius
of curvature Rc that is constant. The radii of curvature extend from
respective focal
points Pf that lie on the lines BL. The lines BL intersect the cutting edges
at respective
points PI , and vectors extending along the lines BL in the direction from the
points PI to
the points Pf diverge from another as shown, i.e., they do not cross one
another. Figure
15B provides a comparison with a prior art knife having two curvilinear
cutting edges.
The same principles can apply to distinguish knives 60 having more complex
curvilinear
shapes for the cutting edges.
Figures 16A - 16C illustrate another aspect of the knife 60 according to the
present invention. As seen in Figure 16A, a number of line segments "LS" are
shown on a
beveled face "Fb" that includes the cutting edge CE4 shown in Figure 12B. The
line
segments "LS" are lines perpendicular to both an outer peripheral contour
"OCa" that
defines a periphery of the front surface 60a of the knife (not visible in
Figure 16A-see
Figure 12A) that includes the cutting edge "CE4"and a corresponding, parallel
outer
peripheral contour "OCb" that defines a periphery of the back surface 60b of
the knife.
The line segments "LS" are therefore of minimum length for connecting the two
outer
contours. As the line segments "LS" are geometric constructions rather than
distinct
21
CA 02525900 2005-02-04
physical features, there are an infinite number of the line segments "LS"
defining the
beveled face "Fb."
Figures 16B - 16D are cross-sections of the knife 60. Each cross-section is
taken
in a plane perpendicular to (a) the front surface 60a, (b) the parallel back
surface 60b, and
(c) the respective outer contours "OCa" and "OCb," and includes one of the
Iine segments
"LS." Particularly, Figure 16B illustrates the cross-section indicated in
Figure 16A that
includes the line segment "LS,sB," Figure 16C illustrates the cross-section
indicated in
Figure 16A that includes the line segment "LS,SC," and Figure 16D illustrates
the cross-
section indicated in Figure 16A that includes the line segment "LS,SD."
Each of these line segments are angled, as are all of the line segments "LS,"
with
respect to the plane of the front side 60a of the knife, by a substantially
fixed angle ~y that
is preferably in the range of 25 - 40 degrees. The angle Y is referred to
herein as an
"attack relief angle" to distinguish it from the alignment relief angle
described earlier.
The attack relief angle is often referred to in the art simply as "relief."
The attack relief angle can be better understood with reference to Figures 17A
and
17B. Referring to Figure 17A, a schematic drawing of an elongate article of
lumber 45 is
shown being cut or chipped by a knife 75 rotating in the direction indicated
and defining a
cutting arc "Rc." The knife 75 corresponds to the face-cutting knife 50 of the
center
portion 47 of the planer head 46 shown in Figure 10. The article 45 extends
along an
elongate axis "EA~U,",BER" An attack relief angle yL with respect to the
elongate axis
having some nonzero magnitude must be provided to avoid hammering the wood
with an
22
CA 02525900 2005-02-04
undersurface "US" of the knife 75. Such hammering deleteriously affects the
surface
finish provided by the knife.
Figure 17B views the article of wood shown in Figure 17A from'a direction
perpendicular to the axis "EAL~gER." The knife 75 is omitted, but a corner-
cutting knife
77 according to the present invention is shown. The knife 77 has a front side
60a and two
outer contours OCa and OCb as described above. The line segment "LSL "in
Figure 17B
corresponds to the line segment "LS,6B" in Figure 16B and, therefore, provides
an attack
relief angle y as shown in Figure 16B. Thence, attack relief in the
longitudinal direction,
i.e., the direction of "EALUMaER,"is provided by the knife 77.
An outstanding advantage of the knife 77 is that the knife 77 also provides
attack
relief in the transverse direction "TLUMBER~" P~icularly, the line segment
"LST" shown in
Figure 17B corresponds to the line segment "LS,6D" in Figure 16D and,
therefore,
provides an attack relief angle 'y as shown in Figure 16D. Moreover, according
to the
present invention, the knife 77 provides an attack relief angle of 'y in every
and all
intermediate directions. In the preferred embodiment of the invention the
attack relief
angle is constant over the surface "Fb" (Figure 16A) as mentioned above;
however, this is
not essential.
The curvilinear knife 77 according to the present invention is provided
independent of the corresponding face-cutting, linear knife and it is
therefore relatively
easy to provide an optimally configured surface Fb. For example, it is
relatively easy to
manufacture the knife 77 with a constant attack angle of relief over the
entire surface Fb.
Moreover, because the curvilinear knives are staggered with respect to the
corresponding
23
a
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face-cutting knives so that their cutting surfaces overlap, jointing the
knives does not
increase the width of the cut or cause surface imperfections such as lines at
the apparent
points of joinder of the respective cutting surfaces.
It is to be recognized that, while a particular high speed planer head has
been
shown and described as preferred, other configurations and methods could be
utilized, in
addition to those already mentioned, without departing from the principles of
the
invention.
The terms and expressions which have been employed in the foregoing
specification are used therein as terms of description and not of limitation,
and there is no
intention in the use of such terms and expressions to exclude equivalents of
the features
shown and described or portions thereof, it being recognized that the scope of
the
invention is defined and limited only by the claims which follow.
24
