Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
This invention relates to a straight saw blade
adapted for rapid reciprocation, as by a motor attached
to one end, the blade being tapered in cross-section
across a substantial part of its width te-g-, more
than half) and being thinnest at or near the points
of the teeth. It is substantially thicker throughout
the portion adjacent the back, the thickness in this
region being preferably uniform and equal to the maxi-
mum thickness of the tapered portion.
This blade is expressly designed for use in a ~-
heavy-duty hydraulically powered saw for splitting :
animal carcasses, wherein the saw blade is about 30" ~-~
long and is driven, from one end, at speeds up to
2200 oscillations per minute.
Reciprocating saw blades have heretofore been
made of flat steel and, in order to have enough rigid-
ity to be practical, the thickness had to be substantial ;
(e.g., at least .065" to .070"). When a beef carcass
was split by such a saw blade an amount of bone and ~;meat corresponding to the blade thickness was removed
and lost. Additionally, a flat blade having only the
thickness named was still relatively flexible and ~
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flexed or "whipped" substantially in use on the
pushing stroke. At high speeds of oscillation this
increased greatly the noise level of the operation,
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raising it beyond the OSHA DBA level rating. Due to
metal fatigue the flat blades have a tendency to break,
1 30 with the danger of serious injury to the operator.
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It is accordingly an object of the invention to
provide a saw blade of tapered cross-section having a thin
cutting edge, whereby the amount of bone and meat lost in the
cutting operation is reduced. ~ ~
It is another object to provide a saw blade with in- -
creased rigidity to resist flexing and thereby reduce the noise
level of the sawing operation.
It is a further object to provide a thin edged rigid
saw blade which can be operated smoothly at high cutting speeds.
It is still a further object to provide a saw blade
having a cutting edge of reduced thickness for easier cutting.
It is yet another object to provide a saw blade
having a thin cutting edge wherein the portion adjacent the
teeth is slightly hollow ground.
The invention accordingly comprises an article of
manufacture possessing the features, properties, and the relation
~of elements which will be exemplified in the article hereinafter
described, and the scope of the invention will be indicated in - :
the claims.
In one aspect of the present invention there is
provided a straight saw blade adapted for reciprocation without
tension in a carcass splitting saw, comprising a back portion
having a back edge and an integral transversely tapering portion
integral with the back portion and having a cutting edge parallel
to the back edge, the back portion having a substantially uni-
form thickness, the tapering portion having its greatest thick-
ness at its line of junction with the back portion and being
~ hollow-ground with its least thickness along a line slightly
-~ spaced from its cutting edge, saw teeth being formed in said
cutting edge, each said tooth being adapted to remove a portion
of the material being sawed, and the width of the back portion
being no greater than about half of the distance from the back
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edge to the base of the teeth.
A practical embodiment of the invention is shown in
the accompanying drawing ~.herein:
FIG. 1 is a somewhat diagrammatic side elevation of
a carcass splitting saw of the type in which the improved saw
blade is intended to be used,
FIG. 2 is a side elevation of the saw blade, part
of its length being cut away'
FIG. 3 is a vertical section on the line III-III .:
10 of FIG. 2.
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FIG. 4 is a side elevation of one end portion
of a modified form of saw blade;
FIG. 5 is a vertical section on an enlarged scale,
taken on the line V-V of FIG. 4; and
FIG. 6 is a detail vertical section on the line
VI-VI of FIG. 4.
Referring to the drawing, and particularly FIGS. 1
to 3, the saw blade 10 comprises a straight strip of
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band saw steel stock having a back portion 11 of uni-
form thickness, greater than that of blades heretofore
in use, and a tapered portion 12 with teeth 13 cut
into the thin edge of the tapered portion. The blade
is tapered on both sides, i.e., the surface planes of
the tapered portion angled symmetrically with respect
to the median plane of the blade. The tips of the
teeth may suitably have a thickness which is about
half the thickness of the back portion 11. The teeth
are straight, not set laterally, symmetrical, and filed
straight across so that their edges lie in planes per-
pendicular to the plane of the blade. Holes 14 are
provided near each end of the blade for mounting the
~ blade in the saw, and the lower corners are preferably
`l beveled as shown at 13'.
A ~orm of carcass splitting saw in which the blade 10
is intended to be used is shown in FIG. 1, by way of
example. This saw includes a hydraulic motor, indicated
generally at 15, driving an eccentric 16 to reciprocate
the link 17 and rock the bell crank 18. The free end
of the bell crank is connected at 19 to one end of the
blade 10, the other end of the blade being engaged at 20 -;;
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with a link 21 housed in the distal end 22 of the saw.
The portion of the blade adjacent to the link 21 is
housed and guided in the downwardly extending portions
23 of the saw casing. About half of the length of the
blade is fully exposed, at 24, between the respective
end portions of the saw. Saw handles, support cable,
hose connection and other details of the saw are not
shown, being conventional.
Upon actuation of the motor 15, the bell crank
is rocked and the saw blade is pushed and pulled along `
a short, almost straight oscillatory path.
The saw blade 10 is typically about 30" long,
as noted above, and is three inches wide, from the
back edge to the tooth points. The back portion 11
has a width of about half the distance from the back
to the base of the teeth (e.g., 1-1/4"). The teeth
are cut at 60 angles between their edges and are
spaced two to the inch. In the tapered portion 12 ;~
the thickness of the blade varies from about .05"
(+ .005") at the points of the teeth to about .109"
at the line of junction between portions 11 and 12.
The blade may suitably be hardened to 40-45 R "c".
Field testing of the tapered saw blade described
above has ~hown that it performs the cutting operation ~i
effectively, with the advantages referred to, but
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that the outward taper from the cutting edge upward
tends to cause a smearing of removed material, such
as fat and the like, across the cut portion of the ;
bone (i.e~, the vertabrae). Some users may consider
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` 30 this to~be objectionable, because of discoloration of
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the bone surfaces, and the expedient shown in FIGS. 4
to 6 may be resorted to in order to overcome the
smearing tendency.
~ In the modified blade 25 of FIGS. 4 to 6 the back
portion 26 has a uniform thickness like the portion
11 in FIGS. 1 to 3, but the tapered portion 27 is
slightly hollow ground, on a long radius 28 (e.g.,
about six feet) centered at a point 29 somewhat above
the base of the teeth (e.g., one inch above). This
creates a zone 30 adjacent the cutting edge and ex-
tending upwardly therefrom, where the blade has a
varying reduced thickness, which may be from .002" to -~
.008" (maximum at 31) less than the thickness at the
points of the teeth. I-t has been found that this
blade cuts more easily and cleaner than the single
tapered blade o~ FIGS. 1 to 3, and elimina~es the
smearing of the bone, while retaining the ability to
stand rapid reciprocation (2200 R.P.M.) with a strong
rigid back portion and teeth having a cutting thick-
ness of only about .050" to .060".
The root portions of the teeth are shown as being
modified by bevel grinding (as with a .25" cutter) -
each side of the blade at its root, as shown at 32,
and the tooth working faces may be joined by a small
radius 33 instead of meeting at a sharp corner. ~`
While a knife blade severs a mass by "disconnec-
tingl' its parts along the blade edge and pushing the
parts aside, the teeth of a saw act to remove and
discard all the material of the mass in their path.
The tapered saw blades described above have a cuttin~ i
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tooth edge which is thinner by about one-third than
the cutting tooth edge of the previously used flat
blade, so that it removes less material, i.e., wastes
less, while requiring less power to cut through a
given distance. The thicker back portions 11 or 26
give the blade substantially greater rigidity so that
flexing is minimized and the narrowness of the teeth
(which move through the material easier than wider
teeth would) contributes to the reduction in flexing.
The bone and meat through which the blade is designed `
to cut, separate as the cutting progresses without
causing the blade to bind.
It will thus be seen that the objects set forth
; above, among those made apparent from the preceding
clescription, are effeciently attained and, since ;
; certain changes may be made in the above article
without departing from the spirit and scope of the
invention, it is intended that all matter contained
in the above description and shown in the accompany-
ing drawing shall be interpreted as illustrative and
not in a limiting sense.
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