CA2126901A1 - Disc knife - Google Patents

Abstract

DISC KNIFE
Abstract of the Disclosure 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 edge for cutting off strips of wood fiber cut longitudinally from the passing log by a knife blade.

Description

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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 212690~
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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21269~1 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 2~2~901 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 212690~
- 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 212~90~
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.
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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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- 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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Claims (10)

1. A disc knife for a log canter, wherein said knife is mountable on a rotatable disc, to cut smooth a planed surface of a log after initial rough cutting of said log to form said planed surface, comprises a relief surface having first and second opposed relief surface edges, a bottom surface having first and second opposed bottom surface edges, first opposed faces extending from said first opposed relief surface edges to said first opposed bottom surface edges so as to form first opposed cutting edges along said first opposed relief surface edges, second opposed faces, contiguous to said first opposed faces, extending from said second opposed relief surface edges, said first opposed faces sloping inwards from said first opposed relief surface edges, said second opposed faces sloping outwards from said second opposed relief surface edges, said second opposed faces intersecting said first opposed faces so as to form corner cutting edges along said intersection between said first and second faces, whereby when said disc knife is mounted on said rotatable disc, wood fibre on said planed surface may be cut by rotation of said disc.

2. The device of Claim 1 wherein said first opposed cutting edges are linear and said corner cutting edges are linear.

3. The device of Claim 2 wherein said relief surface and said bottom surface are rectangular.

4. The device of Claim 3 wherein said relief surface and said bottom surface are planar and parallel.

5. The device of Claim 4 wherein said disc knife is removably mountable on said rotatable disc and may be mounted in a first position or mounted in a second position rotated 180 degrees from said first position, said rotation in a plane parallel to a plane contain-ing said disc.

6. The device of Claim 1 wherein said second opposed faces extending from said second opposed relief surface edges extend to said second opposed bottom surface edges so as to form second opposed cutting edges along said second opposed bottom surface edges.

7. The device of Claim 6 wherein said first and second opposed cutting edges are linear and said corner cutting edges are linear.

8. The device of Claim 7 wherein said relief surface and said bottom surface have a rectangular shape.

9. The device of Claim 8 wherein said relief surface and said bottom surface are planar and parallel.

10. The device of Claim 9 wherein said knife is removably mountable on said rotatable disc and said knife may be rotated 180 degrees in a plane parallel to a plane containing said disc so as to be mountable on said disc in a first position or in a second position rotated 180 degrees from said first position relative to said disc, and said knife is also, when removed from said rotatable disc, rotatable 180 degrees about an axis bisecting said knife, so as to reverse said bottom surface for said relief surface and said relief surface for said bottom surface relative to said disc, and remountable on said disc.