Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DISC R~IFE
Field of the Invention
The present invention relates to the field of wood
cutting knives for log canters.
Backaround of the Invention
Log canters or log reducers are commonly in existence
in sawmills and are used to, from a round log, initially form a
cant with two opposite parallel side surfaces before the split
sawing of the cant takes place. As a rule canters are made up
of two opposing conical discs having a truncated conical form.
On the surfaces of the disc are cutting knives installed in
various ways, vis., spiral, combination and long blade types, to
develop a rough cut surface by directly transforming the logs cut
off fiber to chips, for further use as a raw material for pulp
and paper manufacturing.
On the truncated surface of the conical discs are
polishing knives for smoothing of the rough cut surface developed
by the cutting knives. As an example thick saw blades are known
to provide this type of surface finishing.
Swedish Patent No. SE470057 teaches an earlier known
method of finishing the wood for canters which involves a
circular disc with a large number of small flat cutting knives
mounted peripherally thereon. These cutting knives are of the
"turn knife" type and have at least two separate knife edges
which are oriented parallel with the disc's rotation plane, which
during operation splits the wood parallel with the passing log's
fiber direction. By turning the knife, the edges can be put into
position for use. The advantages of such a fini~hing set-up
include the cost of operation and maintenan~e being kept low
through the use of inexpensive knives which can be disposed of
once all the edges are worn out. Therefore it is possible to
mount the knives in fixed holders in the disc without the need
to put time towards fine adjustments of the knives position.
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One disadvantage of such a knife is that the wood is
cut in one plane parallel with the wood fiber without actually
cutting off the wood fiber. The result is the forming of long
strips or shavings of wood fiber which have a tendency to get
stuck in the canter and cause production interruptions. The long
strips also get mixed with coarser chips and have a tendency to
plug holes in chip screen plates.
The present invention is meant to address the above
mentioned problems and disadvantages with earlier knives of known
type and to provide a knife which is simple and cheap to produce
and has the ability to cut off the log's fiber as well as
preparing the finished surface on the canted log.
~5 It is a further object of the present invention to
simply produce a knife in the form of a turn-type knife with at
least two cutting surfaces. It is also an object of the present
invention to produce a knife having a rectangular or square base
to facilitate the mounting of the knife wit~ a positive cutting
angle.
Summary of the Invention
The present invention consists of a wood cutting knife
for a log canter of the kind which is used to cut a log into a
cant having one or more planed faces wherein the log is axially
fed past the log canter and the log canter is mounted in a rotary
disc carrier on the truncated surface of the log canter conical
disc. The log canter knife smooths the corresponding flat cant
face after initial rough surfacing of the log. The knife has an
outside relief surface, an opposed inside bottom surface and
opposed blade surfaces forming an acute angle against the relief
surface. Between the relief surface and the blade surfaces is
a corner cutting edge for cutting off strips of wood fiber cut
longitudinally from the passing log by the knife blade.
Brief Description of the Drawings
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Figure 1 is a perspective view of the relief surface
of an embodiment of the present invention.
Figure 2 is a perspective view of the bottom surface
of the knife of Figure 1.
Figure 3 is a plan view of the relief surface of the
knife of Figure 1.
Figure 4 is a plan view of the bottom surface of the
knife of Figure 1.
Figure 5 is a front elevation view of the knife of
Figure 1.
Figure 6 is a side elevation view of the knife of
Figure 1.
Figure 7 is a partial plan view of a log canter knife
carrier in which the knife of the present invention is mounted.
Figure 8 is a plan view of an alternate embodiment of
the knife of the present invention.
Figure 9 is a side elevation view of the knife of
Figure 8.
Figure 10 is a front elevation view of the knife of
Figure 8.
Figure 11 is a plan view of a further alternate
embodiment of the knife of the present invention.
Figure 12 is, in perspective view, the log canter knife
carrier of Figure 7 and knives of the present invention mounted
to a log canter.
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Detailed Description of a Preferred Embodiment
The log canter disc mountable knife of the present
invention, as illustrated in Figures 1 through 6, has top surface
1, bottom surface 2, two side surfaces 3, 3', and two cutting
surfaces 4, 4'. As illustrated, the knife has a flat, rectangu~
lar form with top surface 1 and bottom surface 2 planar and
parallel to one another. The cutting surfaces 4, 4' are planar
and extend between top surface 1 and bottom surface 2, forming
an angle of about 40 degrees between cutting surfaces 4, 4' and
top surface 1. Two parallel opposed cutting edges 5, 5' are
formed along the intersection of top surface 1 and each of the
two cutting surfaces 4, 4'. Surfaces 6, 6' extend between the
top surface 1 and each of the side surfaces 3, 3' in an obtuse
angle of about 150 degrees with referen~e to top surface 1.
Corner edges 7, 7', 7" and 7"' are thus developed between
surfaces 6, 6' and cutting surfaces 5, 5'. A centrally placed
counter-sunk hole is provided in top surface 1 for releasable
attachment, with a screw or a bolt, of the knife to a knife
carrier as illustrated in Figure 7.
As illustrated in Figures 3 and 4, cutting edges 5, 5'
have corner edges 7, 7', 7" and 7"' extending from the cutting
edges 5, 5' respective ends. Corner edges 7, 7', 7" and 7"' are
linear and form an obtuse angle with reference to the respective
cutting edges 5 or 5'. As illustrated in Figures 5 and 6,
cutting edges 5 and 5' are linear, top surface 1 and bottom
surface 2 are planar, and corner edges 7, 7', 7" and 7"' extend
from cutting edges 5, 5' respective ends downwards towards the
plane of bottom surface 2.
As illustrated in Figures 7 and 12, the knife carrier
may be formed of a disc 9. The disc carries a number of knives
around its periphery, radially spaced apart. For this purpose
the disc has peripheral round cut-outs 10, two of which are shown
in Figure 7. Each cut-out 10 has semicircular sections 11 and
12. Semicircular section 11 is a void forming a semicircular
hole in the disc. Semicircular section 12 is a recessed
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semicircular platform or surface upon which knives may be
mounted. Sections 12 lie in a single plane recessed beneath the
upper surface of disc 9, that is, the exposed disc surface in
Figure 12. Knife holder 13 attaches to section 12 with two
screws 14, 1~'. Knife holder 13 may be semicircular to cover,
when mounted, section 12. Section 11 is left open to enable
passage of wood fiber shavings through disc 9 when in operation.
Knife holder 13 has a support in the form of a bottom
seat 15 and side seat 16. The angle between bottom seat 15 and
side seat 16 corresponds to the angle between bottom surface 2
and cutting surface 4. As illustrated in Figure 7, when a knife
is mounted, the knife's bottom surface 2 and one of cutting
surfaces 4 abut bottom seat 1 and edge seat 16, respectively.
As illustrated in Figure 7, the knife's cutting edge
5 is exposed in the direction of rotation of disc 9, illustrated
as direction "A". Cutting edge 5 is thus positioned for the
dressing of a flat surface on a log which is fed by disc 9
parallel to its rotation plane into the plane of rotating cutting
edges 5.
To assist in preventing heating and unnecessary wear
of "non-working" cutting surface 5', it is preferred to have the
knife mounted so that relief surface 1 is somewhat angled in
relation to the plane of rotation of the upper surface OL disc
9. Thus, cutting edge 5 is situated higher in relation to the
upper surface of disc 9 than the non-working cutting edge 5'.
This, as an example, can be achieved through the forming of
bottom seat 15 somewhat at an angle in relation to the plane of
rotation of the upper surface of disc 9. This angle can in
practice be up to about 4 degrees.
When cutting edge 5 is worn out, the knife may be
turned 180 degrees so that the cutting edge 5' will become the
"working" knife edge.
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Figure 7 also illustrates a notional radial line 17
through the center of rotation of disc 9. As illustrated,
cutting edge 5 is angled relative to radial line 17 to form a
cutting angle. Cutting edge 5 has a positive cutting angle, that
is, relative to the center of rotation of disc 9 the outer
peripheral part of cutting edge 5 is located further forward in
direction "A" than the inner part of cutting edge 5. It has been
found that the cutting angle may be approximately 3 degrees.
In operation, cutting edge 5 surfaces the log face
while outer corner edge 7 cuts off of the wood fiber across its
grain and thus helps avoid the creation of long shavings.
Because the bottom surface of the logs or cants that
are fed through the canter as a rule are situated at the same
level or a short distance below the center of rotation of disc
9, the tangential moving direction of disc 9 will bring the knife
against the log's bottom surface in a direction normal or
approximately normal to the log's bottom surface. It is
therefore advantageous that the knife be mounted with a positive
cutting angle so as to position forward, to first engage the log,
corner edge 7 and the furthest radially outward point of the
cutting edge 5. This may reduce the risk of knot tearouts.
As described above with respect to angling relief
surface 1 relative to the plane of rotation of the surface of
disc 9, surface 6 may also be angled so as to recess corner edge
7"' thereby reducing friction between corner edge 7"' and the log
or cant surface. Reducing friction reduces heating of the knife.
In a preferred design, disc 9 is thinner at its periphery, such
as by the two recessed annular surfaces 17 and 18.
As illustrated in Figures 8 through 10, an alternate
embodiment of the knife of the present invention has four cutting
edges 5, 5', 5", 5"' and four corner edges 7, 7', 7", 7"'. In
this embodiment, the knife, as before, may be rotated or turned
to bring a new cutting edge into position for cutting a log
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- surface, but also may be turned-over for use, whereby the knife
surface which during first usage of the knife served as bottom
2 becomes, at the turning-over of the knife, relief surface 1.
In this embodiment there are no side surfaces per se as all four
sides are formed as potential cutting surfaces such that the
surfaces which during first usage of the knife act as cutting
surfaces 6, 6' will at the knife turnover, become side surfaces.
In this embodiment counter-boring for the screw or bolt head
should be done from both sides of the knife.
The advantages of the knife of the present invention,
as described in two embodiments herein, are that it is possible
to make a knife which includes a main cutting edge as well as a
corner edge at a low cost such that the knife can be thrown out
when all the edges are worn out, eliminating the need to re-
sharpen the knife. This makes it also possible to put knives
into fixed seats in the knife holders, or into separate knife
holders, thereby minimizing the need for measuring the knives to
ensure they are precisely positioned after loosening or replacing
same.
The disc knife's size and its angles between different
knife surfaces can obviously be varied within wide ranges. In
one embodiment the knife has a longest length of 20-35 mm, a
widest width of 15-30 mm and a thickness of 3-10 mm. The angle
between relief surface 1 and the cutting surfaces may be between
30-50 degrees, preferably 35-45 degrees, and the angle between
the relief surface 1 and the cutting surfaces may be between 130-
150 degrees, preferably 135-145 degrees. The knife's maximum
cutting depth can be anywhere from 0.5m-2.5 mm, but preferably
approximately 0.7 mm.
It is understood that the knife of the present
invention can be modified in many ways. It is possible in lieu
of flat cutting surfaces to make them concave or convex. Through
this it is possible to keep the main cutting edge a straight
line, while the corner edge is curved. It would even be possible
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to make the main cutting edge curved in one plane if the knife
~ is mounted so that the plane containing the curve is located
¦ parallel with the plane of rotation of disc 9.
Of course, instead of a "turn-knife" type of knife with
two or more cutting and corner edges the disc knife may have only
one cutting edge and one corner edge. The shape of the knife may
also vary within wide ranges. For example, the knife may have
a triangular shape or a rhombus shape as illustrated in Figure
11. A rhombus shape Aaving angle "a" between the main cutting
edge 5 and the surface 6, may be mounted with a wide positive
cutting angle without the knife's back (with respect to direction
"a") outer (in a radial arm direction on disc 4) corner rubbing
against the edge between tne cut and uncut log surface. The
rhombus angle "a" may be between 75-~0 degrees.
;-:
Instead of attaching several knives of the present
invention in a special knife holder, it is possible to attach
them in seats cut out directly from disc 9. However, there are
certain advantages to use a separate knife holder. If, for some
reason, the knife is dislodged by some foreign object in the log,
for example a nail, bolt or rock, only the knife holder is at
risk of destruction, not the whole of disc 9.
,; ,
If disc 9 has been bent, warped or twisted it is
possible to compensate for this through the placement of spacers
or shims between the recessed surface of section 12 and knife
holder 13. The knives of the present invention may also be
mounted in ways other than using bolts or screws.
The above embodiments of the present invention are made
to be mounted to a canter 20 of the kind illustrated in Figure
12. However, such canters may be made in many different ways.
The knife carrier need not be formed as a disc but could take a
different form. The knife carrier's plane of rotation is in the
normal case oriented vertically, but can be oriented in other
directions also. The knives of the present invention need not
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2126901
- be mounted directly adjacent the rough cutting part of the
canter, but could be completely separate.
As will be apparent to those skilled in the art in the
light of the foregoing disclosure, many alterations and modifica-
tions are possible in the practice of this invention without
departing from the spirit or scope thereof. Accordingly, the
scope of the invention is to be construed in accordance with the
substance defined by the following claims.
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