Knife with improved cutting edge for producing novel wood flake

An improved cutter knife for wood chip and flake producing apparatus includes shallow grooves in either the heel face or the gullet face of the knife intersecting the cutting edge and extending away from the cutting edge. The depth of the grooves is less than the depth of cut of the knife, and the grooves and corners formed by the grooves with the cutting edge provide an aggressive serrated cutting edge which penetrates into the wood and remains sharp longer than conventional cutting edges. Also disclosed is a novel wood flake material in which flake members have a larger area of exposured grain than of exposed side grain, thereby providing a short fiber length flake which can absorb moisture quickly by means of the exposed end grains, and can also dry quickly. The flake material is particularly useful as a bedding material for animals.

TECHNICAL FIELD 
The present invention relates to the processing of wood, usually in the 
form of logs, into chips or flakes, and more particularly relates to an 
improved knife for wood processing systems and a novel wood flake produced 
using the knife. 
BACKGROUND ART 
In known wood processing machines used to convert logs into chips or 
flakes, it has been common for the machines to include one or more knives 
mounted either on the face of a rotary disc or on the circumferential 
surface of a rotating drum. The logs are guided or urged into the disc or 
drum so that the knives cut away chips or flakes of wood as the log is 
consumed by the knives. It is preferable to orient the log at an angle of 
38 degrees with respect to the path of travel of the knives through the 
wood in order to minimize the power required to drive the knives across 
the grain of the wood. 
The knives conventionally utilized in such known wood processing machines 
generally have a linear cutting edge formed by double grinding a metal 
blank to form a sharp edge between the back surface of the knife and an 
end (gullet) face. The cutting edges of such knives are typically two 
inches or more in length, and also can include wings as shown in U.S. Pat. 
No. 3,219,076 and No. 3,559,705. As the sharp cutting edge of a knife 
dulls, the knife loses the heal clearance provided between the back 
surface of the knife and the surface of the wood. In order to permit 
penetration of the sharp edge into the wood, a heel clearance angle of 
about two to eight degrees between the back surface of the knife and the 
wood should be provided. When the knife edge dulls, the heel clearance 
adjacent to the cutting edge disappears, and the knife tends to drag along 
the wood rather than penetrating into the wood. This causes the knife to 
dull even more quickly. More power is then required to drive the dull 
knife through the wood and significant resources must be utilized to 
change the knives and to resharpen the dull knives. Downtime of the wood 
processing machine is directly related to the frequency of the intervals 
at which the knives must be changed. Also, good penetration is required in 
order to cut thin flakes of wood, and therefore conventional knives that 
dull quickly cannot be used for continuous cutting of thin flakes. 
In some known wood processing knives, a single elongated metal blank is 
formed into sections, as is shown in U.S. Pat. No. 2,997,082. In such 
patent, sharpened working edge sections which are about 11/8" in length 
are separated by 7/8" non-cutting recesses. Adjacent rows of such multiple 
knives are staggered on a drum so that the working segments overlap as the 
drum rotates. In U.S. Pat. No. 2,951,518, a wood processing knife is shown 
in which grooves have been machined in the end (gullet) face of the knife 
to at least the depth of cut in order to divide the wood flake being 
removed from the log into separate narrow ribbons. U.S. Pat. No. 2,349,034 
shows a shreading cutter which includes triangular teeth formed by grooves 
in the back surface of the cutter. The cutter is drawn with the grain of 
the wood to scratch out "wood wool" shreads or filaments. U.S. Pat. No. 
2,813,557 shows a knife including a plurality of spaced forward blade 
edges and a plurality of integral rear wood blade edges disposed between 
the forward blade portions. The serrated forward blade edge is formed by 
grooves in the gullet face of the knife such that the size of chips is 
determined by the spacing between the forward teeth. It appears that the 
depth of cut is less than the depth of the grooves. In U.S. Pat. No. 
2,825,371, chip breaking teeth 32 are spaced apart along the gullet 
surface of the cutting knife, the edge of which is a conventional 
continuous linear cutting edge. Other knife configurations in various 
types of wood processing machines are shown in U.S. Pat. Nos. 3,732,907; 
3,304,970; 242,138; 3,011,535; 2,964,079; 4,077,450; 3,327,746; 3,907,016; 
3,421,561; 3,262,476; 3,162,222; 3,059,676; 2,997,082; 2,710,635; 
3,219,076; 3,559,705; and 3,195,592. 
A need has existed in the wood processing art for a knife that can retain 
its sharpness for longer periods of time and thereby be capable of 
precision cutting very thin flakes from the ends of logs. 
SUMMARY OF THE INVENTION 
The present invention provides an improved wood processing knife that 
remains sharp longer than prior knives, requires less power to cut through 
logs, and is capable of producing a novel wood flake product, which itself 
is also a part of the present invention. Small, shallow grooves cut into 
the heel or gullet surface of the knife parallel to the direction of 
travel of the knife create a serrated cutting edge having sharp corners 
which aggressively penetrate into the wood and prevent the cutting edge 
from becoming rapidly dulled by dragging along the wood. 
Generally described, the knife of the present invention for removing 
material from a wooden member is of the type having a heel face which 
extends, during cutting, adjacent to the wooden member, and a gullet face 
forming an acute angle with the heel face, the heel face and gullet face 
defining at the intersection thereof a transverse primary cutting edge. 
The invention comprises the improvement in the cutting edge comprising at 
least one shallow groove defined in one of the heel face and the gullet 
face, extending at right angles from the primary cutting edge, the groove 
having a depth of less than the thickness of material being removed from 
the wooden member, forming corners at the intersection of the groove with 
the primary cutting edge, and forming a secondary cutting edge at the 
intersection of the groove with the other of the heel face and gullet 
face. 
In a preferred embodiment, the knife includes a plurality of rectangular 
shallow grooves, each including a pair of sidewalls defining the corners 
with the primary cutting edge, and a bottom surface parallel to the 
primary cutting edge to form the secondary cutting edge. The longitudinal 
shallow grooves in the knife are preferably spaced from one another by no 
more than 1/2", and are preferably no more than 1/2" wide. In the 
preferred embodiment disclosed herein, the grooves are 0.01" deep, 1/8" 
wide and are separated by 1/8". 
Thus, in place of the continuous cutting edge provided in the prior art, a 
knife emboding the present invention provides a serrated cutting edge 
which includes a series of sharp corners which tend to guide and stabilize 
the penetration of the knife into the wood, and then pull the blade behind 
them. As a result, knives embodying the invention last approximately 
30-150 percent longer between resharpenings than conventional knives. The 
efficient penetration of the serrated knife also permits even cutting of 
very thin flakes from the end of logs. A knife emboding the invention is 
also simple to sharpen since one grinding pass along the front end face of 
the knife sharpens both the primary and secondary cutting edges and 
redefines the penetrating corners. 
Although a knife embodying the present invention can be used advantageously 
in any wood processing operation, such a knife is particularly useful in 
the production of a novel wood flake material which also forms a part of 
the present invention. The wood flake material comprises flake members 
having a larger area of exposed end grain than of exposed side grain, 
therby providing a short fiber length flake which can absorb moisture 
quickly by means of the exposed end grains, and can also dry quickly. 
These features make the wood flake material according to the invention 
ideal for use as a bedding material for chickens and the like. Production 
of a wood flake material is made possible by the ability of a knife 
embodying the present invention to cut thin slices off the end of a log 
for significant periods without dulling. 
The flake produced is sheet-like in nature, having two large parallel 
planar end grain surfaces connected by narrow end and side surfaces which 
expose the side grain. Each flake is preferably about 1" wide and less 
than 1/4" thick. The preferred thickness is about 0.04", which provides a 
very high ratio of end grain surface area to side grain surface area. The 
action of the knife in cutting the flake material imparts a curve to each 
flake, which tends to open the grain on the convex planar surface of the 
flake. This facilitates absorbtion and drying. In order to efficiently 
produce wood flake material embodying the invention, an elongate knife can 
be constructed having short serrated knife sections embodying the 
invention at alternating levels separated by about 0.05". The flakes 
produced by the knife sections at each level are separated from one 
another, to form separate flakes having a width equal to the width of the 
knife sections, which is preferably about 1". 
Thus, it is an object of the present invention to provide an improved wood 
processing knife. 
It is a further object of the present invention to provide an improved wood 
flake material suitable for animal bedding and the like. 
It is a further object of the invention to provide a wood processing knife 
that penetrates easily into the wood and resist dulling. 
It is a further object of the present invention to provide a wood 
processing knife that is capable of sustained production of thin wood 
flake material cut from the end of a log. 
It is a further object of the present invention to provide a wood flake 
material having improved rates of absorbency and drying, and which is 
light weight and piles loosely.

DETAILED DESCRIPTION 
Referring now in more detail to the drawing, in which like numerals 
represent like parts throughout the several views, FIG. 1 shows knife 10 
embodying the present invention. The knife 10 is machined from a metal 
blank, and includes a back or top surface 12 and an end face 13 which meet 
to form a transverse primary cutting edge 14. The acute angle formed 
between the back or heel surface 12 and the end or gullet face 13 is 
preferably 38 degrees. 
A plurality of longitudinal shallow grooves 16 are machined into the back 
surface 12 of the knife 10. The parallel grooves 16 intersect the end face 
13, and therefore interrupt the primary cutting edge 14. Each longitudinal 
groove 16 includes a bottom surface 17 and a pair of sidewalls 18. The 
sidewalls 18 are preferably perpendicular to the back surface 12, forming 
a pair of square edges or shoulders 20 at the intersection of the 
sidewalls 18 and the back surface 12. Where the bottom surfaces 17 of the 
grooves 16 intersect the end face 13, a plurality of secondary transverse 
cutting edges 19 are formed, and the primary cutting edge 14 is 
interrupted and divided into segments. Where the shoulders 20 intersect 
the end face 13, a plurality of sharp points or corners 21 are formed. The 
points 21 penetrate into the wood when the cutting edges 14, 19 meet the 
wood, and draw the sharp edges into the wood. 
The depth of the grooves 16, shown as dimension A in FIG. 2, is less than 
the depth of cut into the wood, and is preferably 0.01," although such 
depth can be as small as "0.001." The width of the grooves 16, shown as 
dimension B, should be 2" or less to provide a sufficient number of 
penetrating corners 21. In the preferred embodiment shown, the width B is 
1/8". The spacing between the grooves 16, shown as dimension C, should 
also be 2" or less, and preferably is 1/8." 
The knife 10 also includes a wing 23 which, in a conventional manner, 
assists in the shaping of wood chips for the pulp industry. Shallow 
grooves can be machined into one of the faces of the wing if desired. The 
knife 10 is mounted in a manner (not shown) known to those skilled in the 
art in a recess in the surface of the drum or in the flat side of a disc 
with the cutting edge protruding beyond the surface of the drum or disc. 
The knife is angled to provide the proper heel clearance between the back 
surface 12 of the knife and the surface of the wood. 
As a result of the better penetration and sharpness of the knife 10, less 
power is required to drive the knife through a log, so that energy 
requirements for producing wood chips or flakes can be reduced. For 
example, a drum carrying a plurality of knives 10 would be effective at a 
rotational speed of only 100-250 RPM. Also, the knife 10 makes a precision 
cut and produces less sawdust waste than conventional knives. 
FIG. 4 shows a second embodiment of a knife 25 constructed according to the 
present invention. The knife 25 has a much longer cutting edge than the 
knife 10, and is particularly useful in the production of wood flake 
material embodying the present invention. The knife 25 includes a knife 
portion 26 and a clamp-receiving portion 27 integrally formed from a 
single blank. The knife portion 26 has a back surface 28 which defines, at 
regular intervals across the width of the knife 25, a plurality of major 
grooves 30, as shown in FIGS. 4, 5 and 6. The major grooves 30 are 
preferably about 1" wide and 0.05 to 0.11" deep (dimension D in FIG. 7), 
and are separated by about 1". A pair of sidewalls 31 connect the major 
grooves 30 to the back surface 28 of the knife portion 26. A plurality of 
minor grooves 32, identical to the shallow grooves 16 described above, are 
machined into the knife portion 26 both at the bottom of the major grooves 
30 and in the raised portions between the major grooves 30. The knife 
portion 26 also defines an end face surface 33 which meets the back 
surface 28 at an angle to define a serrated transverse cutting edge 34 
which is intersected by both the major and minor grooves. The angle shown 
in FIG. 7, between the transverse plane of the knife 25 and the end face 
33 is preferably 38 degrees. 
The clamp-receiving portion 27 of the knife 25 comprises a flat plate into 
which a plurality of U-shaped clamping slots 36 have been cut, extending 
perpendicular to the cutting edge of the knife. The mounting of the knife 
25 in a drum-type wood processing apparatus is shown in FIG. 8. The drum 
38 is provided with a plurality of recesses 39 which receives the knife 
and clamping assembly. At the front of each recess 39, a stop 41 is 
provided in the plane of the desired orientation of the end face 33 of the 
knife 25. An L-shaped knife holder 42 rests on the bottom of the recess 
39. The knife holder 42 defines an outwardly extending projection 43 and, 
at the opposite end of the knife holder 42, a slanting surface 45 which 
abuts the stop 41. The knife 25 rests on the knife holder 42 with the end 
face 33 abutting the stop 41 and the clamp-receiving portion 27 adjacent 
to the projection 43 of the knife holder 42. The clamping slots 36 of the 
knife 25 are aligned with openings in the knife holder 42 through which 
are passed clamping bolts 47. The clamping bolts 47 are flared at their 
upper ends to be matingly received by openings in corresponding clamp 
members 46, which bear down upon the clamp-receiving portion 27 of the 
knife 25. A nut 48 is threaded onto each clamping bolt 47 to secure the 
knife 25 against the knife holder 42 and the stop 41. The knife holder 42 
is oriented such that the angle .theta. between the back surface of the 
knife and a tangent to the drum 38 taken at the point of the cutting edge 
34 is between 2 degrees and 8 degrees. The angle provides heel clearance 
between the knife and the log which is necessary to permit the cutting 
edge to penetrate into the wood. 
A plurality of knives 25 can be mounted axially in a parallel sequence (not 
shown) around the circumferential surface of the drum 38. The drum 38 
rotates counter clockwise, causing the cutting edges of the knives 25 to 
cut wood flake material from the end of a log 51 that is urged into the 
drum 38 by a conventional log-handling apparatus (not shown) at an angle 
of approximately 38 degrees. As best shown in FIG. 8, the cutting edge 34 
of the knife 25 protrudes beyond the periphery of the drum 38 by a 
distance E which is less than 1/4" and is preferably only 0.03 to 0.09." 
This distance E defines the depth of cut of the knife 25 into the log. 
Preferably, they are spaced apart by a distance that causes two knives to 
be engaging the log at all times. 
As the cutting edge 34 of the knife 25 enters the end of the log 51, the 
plurality of sharp corners formed at the intersection of both the major 
and minor grooves with the end face 33 penetrate into the wood and cause 
the knife 25 to make a precision cut through the end grain of the log, 
leaving behind grooves in the end of the log corresponding to the raised 
portions of the knife 25 between the major grooves 30. The next knife 25 
on the drum is aligned with the path of the preceding knife, with a groove 
30 following a raised portion. As the following knife following a groove 
30, and a raised portion engages the log 51, a similar cut is made in the 
log. Since the grooves 30 are deeper (dimension D) than the depth of cut 
E, no bridging material will connect the individual flakes formed by the 
alternating grooves and raised portions. Thus, the knives 25 will form 
individual flakes of the type shown in FIG. 9. The flake material being 
separated from the log tends to fracture transversely at intervals of 
about 1" more or less as the result of the pressure of the knife 25 
moving through the log. The length can be controlled somewhat by varying 
the speed of rotation of the drum 38. The action of the knife 25 tends to 
curl the wood flake away from the log, imparting a curve to the wood flake 
material. The presence of the minor grooves 32 of the knife give the wood 
flake material a ribbed texture. 
FIGS. 9 and 10 show a wood flake 53 embodying the present invention, 
produced by the knife 25 described above. The wood flake 53 includes a top 
surface 54 and a bottom surface 55, both of which comprise end grain 
surface area. The flake also includes two parallel ends 56 and two 
parallel sides 57, all of which comprise side grain surface area. The 
predominance of end grain surface area over side grain surface area is the 
result of the shallow depth of cut of the knife 25 across the end grain of 
the log being processed. 
The length and width of the wood flake 53 are determined by the 
characteristics of the knife 25, and the thickness of the wood flake 53 is 
determined by the depth of cut, as noted above. The dimensions of a wood 
flake embodying the invention are selected to make the area of the 
surfaces 54 and 55 exceed the area of the surfaces 56 and 57. The 
preferred wood flake 53 is about 1" wide by 1" long or more by less than 
0.09" thick, resulting in a ratio of end grain surface area to side grain 
surface area of more than 5:1. Because the end grain surface area of the 
flake is larger than the side grain surface area, the wood fibers of the 
flake are relatively short. The flake is highly absorbent as the result of 
presenting the wick-like end grains for contact with the liquid to be 
absorbed. By the same token, liquid can escape more readily from the short 
fibers of the wood flake, permitting efficient drying. 
The precision action of the knife 25 cutting across the end grains of a log 
leaves grooves 58 separated by ribs 59, running the length of the wood 
flake 53. Such grooves and ribs are the result of the minor grooves 32 of 
the knife 25. The action of the knife 25 also imparts a curved shape to 
the flake, as best seen in FIG. 10. The curving of the flake 53 tends to 
thin out the grain of the flake, resulting in slight openings 60 of the 
grain of the flake at intervals along the top or convex surface 54 of the 
flake 53. The openings 60 further increase the absorbtion and drying 
efficiency of the flake. Also, the curvature of the flake and the grooves 
58 and ribs 59 result in loose or fluffy packing of significant volumes of 
the flakes. This permits air circulation through the flakes which promotes 
freshness and dryness of a volume of the flakes when used in applications 
such as animal bedding material. 
The wood flakes 53 are cut to a precision thickness by the knife 25, and 
the presence of the major grooves 30 in the knife 25 result in wood flakes 
having a reasonably consistent width approximately equal to the width of 
the major grooves and the raised portions between the major grooves, as a 
result of the fracturing described above. However, the length of the wood 
flakes 53, that is, the length of the side surfaces 57, can vary from 
approximately 1/8" to 1". As the knife 25 passes through the log, as shown 
in FIG. 8, the mechanical force of the knife on the thin flake material 
being separated from the log causes the flake material to fracture and to 
break away from the material being separated from the log. Depending on 
the strength of the wood, the angle between the path of travel of the 
cutting edge and the grain of the wood, the depth of cut and other 
factors, the wood flake material may fracture at various lengths. However, 
because the wood flake is so thin, the area of exposed end grain surface 
is larger than the exposed side grain surface, even if the length of the 
sides 57 is relatively short. Of course, the length of the flakes may also 
be reduced by breakage during physical handling of the flakes subsequent 
to production. 
The wood flake 53 also makes a good fuel which burns efficiently and 
completely as a result of the size and shape of the flakes and the 
capability of good air circulation through the wood flake material. 
Production of the flakes from waste wood material is efficient using the 
knife 25 embodying the invention because of the low power requirements for 
driving the knife 25 through the logs. Furthermore, several logs can be 
processed at once when knives 10 or 25 are mounted on a drum of sufficient 
length. 
FIGS. 11 and 12 show a third embodiment of the invention in a knife 62 
primarily intended for use in a chipper disc. The intersection of a heel 
face 63 and a gullet face 64 form a primary cutting edge 65. Shallow 
grooves 66 of the type formed in the knife 10 of FIG. 1 are machined into 
the gullet face 64 at right angles from the cutting edge 65. 
The knife 62 is shown mounted in a chipper disc 68 in FIG. 12. The disc 68 
defines a recess which receives a knife holder 70, the knife 62, and a 
clamp 71. A bolt 72 is countersunk into the clamp 71 and passes through 
the knife holder and the disc and is fitted with a nut 73. Force is 
exerted by the bolt 72 on the clamp 71 to hold the knife 62 at a proper 
angle so that the heel face 63 provides proper heel clearance with respect 
to the log (not shown). The cutting edge 65 extends partially over a 
gullet 74 which passes through the disc 68 to allow chips removed from the 
log to pass through the disc for collection. The grooves 66 perform the 
same function as the grooves shown in the other embodiments, although they 
are machined in the gullet face of the knife rather than in the heel face. 
As in prior embodiments, the depth of the groove 66 is less than the depth 
of cut into the log, and thereby function to improve the cutting edge 
rather than to separate or define the size of chips being removed from the 
log. 
FIG. 13 shows a fourth embodiment of the invention in a saw tooth 76. The 
saw tooth 76 includes a cutting edge 77. A heel face 78 of the saw tooth 
includes a shallow groove 79 extending at right angles from the cutting 
edge 77. The tooth 76 also includes a shank 80 for attachment to a saw 
blade in a manner well known to those skilled in the art. Although more 
than one shallow groove 79 can be machined into a saw tooth, the 
embodiment shown in FIG. 13 demonstrates that the advantages of the 
invention can be incorporated into small cutting elements, and the 
improvement provided by the invention will be noticeable even if only a 
single groove is provided. 
While this invention has been described in detail with reference to 
preferred embodiments thereof, it will be understood that variations and 
modifications can be made within the spirit and scope of the invention as 
described here and above and as defined in the appended claims.