Chipper saw

A circular saw adapted to produce chip-size material when cutting wood. The saw comprises a saw blade with teeth distributed about the circumference of the blade. The teeth are separated from each other in such a manner that in cutting a kerf, wood material is chiseled away in relatively large chip size, and such material is permitted to fall away from the kerf with minimal tendency of crushing or fracturing which would reduce the chip size.

The present invention relates to saws, and more particularly to a circular 
saw having a novel construction which enables the saw to cut, when making 
a kerf in lumber or wood, relatively large, chip-size material, rather 
than the finely chopped up sawdust which normally is produced by a saw. 
The chip material produced may be converted, for instance, into paper, and 
under normal economic times has greater value and more varied uses than 
sawdust. As a consequence, use of the saw tends to minimize waste and 
maximize profits for an operator. 
In the usual circular saw, the region between adjacent saw teeth is 
referred to as a gullet. Generally, circular saws have a large number of 
teeth, and the gullet is small and presents a narrow space between teeth. 
Thus, when the teeth pass through lumber fed into the saw, wood loosened 
by the teeth in the making of a kerf lodges in the gullets, with such 
tending to become jammed or crushed therein. Further, the cutting action 
of the teeth is such that relatively fine-sized material is cut from the 
wood, rather than relatively large pieces. In modern saw equipment, 
circular saws are usually run at relatively high speeds, and this has 
further tended to promote the production of finely sized, sawdust 
material. 
As contemplated by this invention, a circular saw is provided which is 
devoid of the usual gullets found in conventional saws separating one 
tooth from another. A saw constructed according to the invention has 
substantially less teeth than the usual saw with the angular spacing 
between adjacent teeth ordinarily being 40.degree. or more. Furthermore, 
the edge of the saw, extending between a tooth and the next tooth which 
precedes it, extends in a curved reach which initially curves at a 
negative angle inwardly toward the center of the saw, the thence joins 
smoothly with a substantially lineal expanse which expanse extends to 
substantially where the preceding tooth is defined. Describing the saw, 
progressing from one tooth to the tooth that follows it on the saw, the 
edge of the blade curves convexly in defining the first tooth and thence 
joins smoothly with this lineal reach described, the spacing of the 
various teeth being such that this lineal reach, when extended as an 
imaginary line rearwardly on the saw, subtends the following tooth and 
meets with the edge of the saw blade where such extends rearwardly from 
the following tooth toward the tooth next following. 
It is further contemplated according to a preferred embodiment of the 
invention that the saw be provided with cutting tips or bits on the teeth 
thereof, such tips being set at a negative angle on the teeth and serving, 
in effect, to chisel wood material from the lumber being cut in the 
production of a kerf. 
When using the saw under normal conditions, only one tooth at a time passes 
through the lumber being cut. On a tooth chiseling wood material from the 
lumber, such wood material is provided with a relatively wide, smoothly 
contoured void space where such may collect. And, by reason of the fact 
that when one tooth is making a cut there is no tooth preceding it passing 
through the kerf which in a manner of speaking would block passage of 
material away from the kerf, cut material is permitted to fall away with 
minimal fracturing and breaking. 
The saw contemplated may be operated at conventional speeds and still 
produce chip material of considerable size. In addition to the advantage 
of the type of material cut, use of the saw results in several other 
advantages. For instance, it has been noted that the power requirements to 
use the saw generally is substantially less than normal power 
requirements. Furthermore, maintenance of the saw, including tooth 
sharpening, is simplified, producing resultant economies. 
A general object of the invention, therefore, is to provide an improved 
circular saw which makes possible the production of relatively large, 
chip-size material when the saw is operated to cut a kerf. 
Another object is to provide a circular saw which can be run at speeds 
characterizing modern saw equipment, with the production of relatively 
large, chip-size material, instead of conventional sawdust. 
Yet another object is to provide a circular saw which, in operation, tends 
to chisel material from the lumber being cut, and which is constructed in 
such a manner that there is minimal tendency to fracture or break such 
material as such is cut away from the wood. 
Yet a further object of the invention is to provide a novel method of 
cutting lumber with the production of chip-size material as the debris 
that is cut away in making the kerf.

Turning now to the drawings, and referring initially to FIG. 1, a circular 
saw as contemplated herein is shown generally at 10. Such comprises a saw 
blade having a central eye or opening 14 adapted to receive the usual 
arbor which mounts the saw. Distributed about the circumference of the saw 
blade, in a substantially circular zone extending about the perimeter of 
the blade, are cutting teeth 12. 
The saw illustrated in FIG. 1 has six cutting teeth, so the teeth are 
angularly spaced one from another at 60.degree.. In the usual instance, a 
saw constructed as contemplated by the invention will have no more than 
about nine teeth, or an angular spacing between successive teeth of 
40.degree.. Because of this spacing, and considering normal operation of 
the saw, as probably is most clearly illustrated in FIG. 1, during the 
cutting of a kerf in lumber (as exemplified by lumber 16), no more than 
one tooth is moving through the wood at any time. Put in another, with 
rotation of the saw when such is cutting lumber, successive teeth in the 
saw move through the lumber, with one tooth moving into and across and 
then beyond the side-to-side dimension of the lumber before the next 
following tooth on the saw partakes of such movement. 
It will be further noted, and with reference to FIG. 1, that each of the 
teeth in the saw is provided with a cutting portion, in the particular 
embodiment of the invention shown a carbide tip or bit 15. Each tip is 
sharpened along the outer edge thereof and along opposite side edges. The 
plane occupied by a tip occupies what is referred to herein as a negative 
angle, which is to say that with respect to a radius on the saw which 
passes through the outermost extremity of the tip, an acute angle is 
defined by the plane of the tip and such radius, which acute angle faces 
inwardly on the saw and is on the trailing side of such radius. 
With further reference to FIG. 1, the edge of the saw blade, extending from 
the cutting portion of a tooth (and reference is made to tooth 12) to the 
next tooth preceding it on the saw (which in FIG. 1 is tooth 12'), extends 
in a curved reach 13a which initially curves at a negative angle inwardly 
toward the center of the saw. The curvature thence joins smoothly with a 
substantially lineal expanse or reach shown at 13b, and progressing from 
this lineal reach joins smoothly with a convexly curved reach 13c which 
curves convexly over a smaller radius than the radius of the saw to form 
the back of the next preceding tooth. It will further be noted that lineal 
reach 13c intersects and is normal to a radius R1 in the saw at a location 
which is in advance of tooth 12 but which is closer to tooth 12 than to 
tooth 12' which precedes it. In this way, a void region of substantial 
size is provided in front of tooth 12, and behind the preceding tooth, 
which is bounded by smoothly contoured portions of the saw blade, and 
which is adapted to receive material cut off by the tooth enabling such 
material free passage from the cutting zone and without tending to induce 
fracture or breaking of such material. 
It should also be noted, and with reference to FIG. 1, that the edge of the 
saw blade (and considering such as extending from the tip of the cutting 
portion of a tooth to the next tooth that follows it, i.e., considering 
the edge as it extends rearwardly from tooth 12' in FIG. 1) initially 
curves convexly about a radius which is less than the radius of the saw 
and thence joins smoothly with a substantially lineal reach 13c. This 
lineal reach joins with a concavely curved expanse (expanse 13a) which 
meets with a cutting portion of the following tooth. The lineal reach, 
when extended as an imaginary line as indicated at 13b' rearwardly on the 
saw, subtends the following tooth, and meets at 17 with the edge of the 
saw where such extends rearwardly of the following tooth toward the next 
following tooth. This relationship is another characteristic of providing 
the contour indicated between successive widely spaced teeth in the saw 
which is not found in conventional saw construction. 
Referring to FIGS. 2 and 3, when saw 10 is utilized to cut a kerf in wood, 
when such is rotated in a clockwise direction in the figures, tooth 12 
chisels out chips 20 from the wood of the lumber. These chips tend to curl 
around curved expanse 13a onto lineal expanse 13b, and on separating fully 
tend to fall unimpeded into the void which is presented in front of each 
tooth and thence out of the kerf. With the top arbor saw which is shown in 
the figures, these chips move downwardly and without striking a preceding 
tooth to fall to the underside of the lumber, whence they may be collected 
in a convenient manner. 
Describing the operation of a typical embodiment of the saw, a 30 inch 
diameter saw was prepared having a gauge of 0.120 inch and six teeth 
equally distributed about the periphery thereof, i.e., the tooth spacing 
was 60.degree.. Tips or bits on the saw had a side-to-side dimension of 
0.190 inch. The saw was mounted on an arbor run at 1350 rpm and 4 inch 
wide lumber cut with a rip cut made along the length of the lumber, using 
a feed speed for the lumber of 120 feet per minute. Operation of the saw 
as described produced chips having a side-to-side dimension corresponding 
to the side-to-side dimension of the bits or tips of 0.190 inch, i.e., 
approximately 3/16 inch (the dimension "w" indicated in FIG. 4). The 
fiber length dimension of the chip, i.e., the dimension indicated at "t" 
in FIG. 4, was about 0.18 inch. The length dimension corresponding to the 
dimension "l" in FIG. 4, in the preponderance of the chips produced 
exceeded the thickness and width dimensions, and with most chips was 
within the range of 3/8 to 3/4 inch. The residue produced by the saw when 
screened was found to be 70% chip material. 
Various feed speeds can be used for the lumber, ranging typically from 85 
to 150 feet per minute. Arbor speeds are also variable, of course, with 
the arbor speed indicated typifying modern saw operation. 
While the invention has been particularly shown and described with 
reference to the foregoing preferred embodiment, it will be understood by 
those skilled in the art that changes in form and detail may be made 
therein without departing from the spirit and scope of the invention as 
defined in the appended claims.