Field of the Invention
The present invention relates to tipped saws including circular saws
and band saws having tips fixed to saw teeth thereof.
Description of the Related Art
Circular saws are widely known as tipped saws having a cemented
carbide tip fixed to the distal end of each saw tooth thereof. There are
proposed various shapes of tips to be fixed to saw teeth of circular saws
depending on properties of a work piece to be sawn, which include hollow
face tips to be suitably used for sawing or cutting wooden boards and the
like. Since the present invention is proposed in view of difficulties to be
encountered in manufacturing such hollow face tipped saws, details of the
configuration of the hollow face tip will be described first referring to Fig. 19.
Fig. 19 is an explanatory drawing showing schematically a
constitution of a hollow face tip 12 in a tipped saw; in which Fig. 19(1) is a
front view of the tip 12 seen from the backward direction with respect to the
rotational direction of the circular saw 10, Fig. 19(2) is a plan view of the tip
12, and Fig. 19(3) is a left side view of the tip 12. More specifically, while
the tip 12 is brazed to a tip seat 16 formed in each saw tooth 14 in the
circular saw 10, the tip 12 has an arcuate depression formed on its rake face
12a thereof. The tip 12 which has such an arcuate depression (hollow) on
the rake face 12a and equiangular side rake angles on both sides thereof is
referred to as the hollow face tip.
Terms which are frequently used herein are listed below together
with their meanings:
(1) Rake face: The rake face refers to the face of the tip that can be
seen from the backward direction with respect to the rotational direction of
the circular saw and is a front face of the tip as shown in Fig. 19(1); (2) Side back face: The right and left side faces of tip 12 are
referred to as, each having a necessary clearance angle formed in the
backward direction with respect to the rotational direction of the circular
saw, and a left side back face 12b in the tip 12 is shown in Fig. 19(3); (3) Peripheral back face: The peripheral back face is that portion of
the upper end face of a tip where a necessary clearance angle is formed in
the backward direction with respect to the rotational direction of the
circular saw, and a peripheral back face 12c in the tip 12 is shown in Fig.
19(2).
In the hollow face tip 12 described above, positive side rake angles
formed on both sides of the rake face 12a define a pair of side cutting edges
18, 18 correlatively, as shown in Fig. 19(2). Therefore, compared with a
tipped saw having a row of left edged tips and right edged tips arranged
alternately (JIS-B4805, type C), the hollow face tipped saw, having
symmetrical tips provided with side cutting edges on both sides, enjoys
advantages that it can reduce burring and chipping which can occur at the
end of a work piece when it is sawn or cut and that it has a particularly
excellent straight sawing or cutting property. Further, the hollow face
tipped saw may have a small number of teeth compared with other tipped
saws described above so as to exhibit comparable sawing or cutting effect,
advantageously.
The conventional tipped saws use cemented carbide as the material of
the tip to be fixed to each saw tooth. In order to obtain the so-called hollow
face tipped saw by forming an arcuate depression in each tip as described
above, a small-diameter grindstone 19 is set in front of the rake face 12a of a
tip 12 having a tip width W, and the center of the rake face 12a is aligned
with the rotational axis of the grindstone 19. Next, the grindstone 19 is
rotated and is abutted against the rake face 12a under reciprocation of the
grindstone 19 vertically, as shown in Fig. 20(2), to form an arcuate
depression on the rake face 12a. Thus, there is obtained a hollow face
tipped saw having a side rake angle in each side cutting edge. Here,
referring to the size of the gullet present in front of the rake face in the
tipped saw, it should at least be able to admit access of the grindstone 19 to
the rake face.
In the fields of some cutting tools, sintered polycrystalline diamond
(PCD) tips and sintered cubic boron nitride (CBN) tips are used as extra-high
pressure sintered materials which are much harder than the cemented
carbide. These types of tips are cut out into a necessary shape from a
blank of extra-high pressure sintered material prepared by forming a
polycrystalline sintered material layer (a PCD layer or a CBN layer) on a
surface of a cemented carbide substrate.
Since sintered PCD tips and sintered CBN tips are characterized in
that they have higher hardness than cemented carbide, it can be surmised
that an ideal tipped saw for wooden boards and the like can be obtained if
such tips machined into hollow face tips are used. For this purpose, for
example, PCD tips are cut out from a blank of extra-high pressure sintered
material having a PCD layer formed thereon by means of electric discharge
wire cutting, and each PCD tip must be subjected to machining to form an
arcuate depression on the rake face thereof after or before it is fixed to a saw
tooth of the tipped saw. However, the portion of the tip where the arcuate
depression is to be formed is the expensive diamond (PCD) layer which is
harder than the cemented carbide, it is almost impossible technologically to
arcuately grind off such a part of the tip. Even if it should be possible, it
elevates production costs markedly. Accordingly, no hollow face tipped
saws using sintered polycrystalline materials such as of PCD are put into
practical uses under the present circumstances.
Summary of the Invention
The present invention is proposed with a view to appropriately
solving the problems inherent in the conventional tipped saw and is directed
to producing and providing at a reasonable cost a tipped saw, for example, a
hollow face tipped saw having tips of an extra-high pressure sintered
material such as PCD.
In order to solve the problems and attain the intended objective, the
circular tipped saw according to the present invention has tips fixed to saw
teeth thereof respectively, the tips having been cut out into a predetermined
shape from a blank of extra-high pressure sintered material comprising a
cemented carbide substrate and a sintered polycrystalline material layer
formed on a surface thereof; wherein at least two tips of the extra-high
pressure sintered material are designed to be juxtaposed in the thickness
direction of the circular saw and are fixed as such directly to the saw tooth.
Other aspects and advantages of the invention will become apparent
from the following description, taken in conjunction with the accompanying
drawings illustrated by way of examples the principles of the invention.
Brief Description of the Drawings
The features of the present invention that are believed to be novel are
set forth with particularity in the appended claims. The invention together
with the objects and advantages thereof, may best be understood by
reference to the following description of the presently preferred
embodiments together with the accompanying drawings in which:
Fig. 1 shows a front view of a pair of tips juxtaposed in the thickness
direction of a circular saw and is joined together, which is seen from the
backward direction with respect to the rotational direction of the circular
saw; Fig. 2 is a plan view of the tips shown in Fig. 1; Fig. 3 is a left side view of the tips shown in Fig. 1; Fig. 4 shows a front view of the tips fixed directly to a tip seat of a
saw tooth in the hollow face tipped saw; Fig. 5 is a plan view of the tips shown in Fig. 4; Fig. 6 is a left side view of the tips shown in Fig. 4; Fig. 7 shows a front view of the tips juxtaposed such that their rake
faces together define a protuberance; Fig. 8 is a plan view of the tips shown in Fig. 7; Fig. 9 is a left side view of the tips shown in Fig. 7; Fig. 10 shows a front view of the tips in which PCD layers are
designed to serve as peripheral back faces; Fig. 11 is plan view of the tips shown in Fig. 10; Fig. 12 is a left side view of the tips shown in Fig. 10; Fig. 13 shows a front view of the tips shown in Fig. 10, which are
fixed to a tip seat of a saw tooth in a tipped saw; Fig. 14 is a plan view of the tips shown in Fig. 13; Fig. 15 is a left side view of the tips shown in Fig. 13; Fig. 16 shows a front view of the tips juxtaposed such that their
peripheral back faces together define a protuberance; Fig. 17 is a plan view of the tips shown in Fig. 16; Fig. 18 is a left side view of the tips shown in Fig. 16; Figs. 19(1), (2) and (3) are explanatory drawing showing
schematically a constitution of a hollow face tip; in which Fig. 19(1) is a
front view; Fig. 19(2) is a plan view; and Fig. 19(3) is a left side view; and Figs. 20(1) and (2) are drawing explaining means for forming a hollow
face on a cemented carbide tip in a tipped saw; in which Fig. 20(1) is a plan
view of the tip whose rake face is subjected to grinding with a grindstone;
and Fig. 20(2) is a side view of the tip subjected to grinding with the
grindstone.
Detailed Description of the Embodiment
Now, the tipped saw according to the present invention will be
described by way of preferred embodiments referring to the attached
drawings. In the explanation of the following embodiments in this
specification, while sintered polycrystalline diamond (PCD) was selected as
the material of extra-high pressure sintered material tips 12 to be fixed to
saw teeth 14 of the tipped saw, it is of course possible to select sintered cubic
boron nitride (CBN) tips. It should be noted here that the same or like
elements as those explained referring to Figs. 19 and 20 are affixed with the
same reference numbers respectively.
As explained already, the extra-high pressure sintered material tip 12
according to one embodiment of the present invention is obtained by finely
cutting obliquely a blank of extra-high pressure sintered material having a
PCD layer 22 formed as the polycrystalline sintered material layer on a
surface of a cemented carbide substrate 20, for example, by means of electric
discharge wire cutting at an inclination angle such that the tip 12 has a side
rake angle (max 45°), as shown in Fig. 2. If the tip 12 is cut out at an
inclination angle of more than 45°, the resulting sharp edges are likely to
undergo chipping. There are provided a pair of tips 12, 12 cut out obliquely
in such a manner, and they are juxtaposed in the thickness direction of a
saw tooth 14 in a circular saw 10, as shown in Figs. 1 to 4. Here, the tips
are oriented such that they together define a depression on the PCD layer
side, and thus a side rake angle of more than 0° and not more than 45° can
be formed in each tip. The pair of tips 12, 12 is joined together beforehand
by spot welds 13, as shown in Fig. 3. While the spot welds 13 shown in Fig.
3 are typically of circular shape, they may be of other shapes. While two
spots welds 13 are shown in Fig. 3, the number of welds is not limited.
Meanwhile, the tips may be joined together by other means such as laser
welding and brazing in place of spot welding. Figs. 1 to 3 show the state
how the pair of tips 12, 12 juxtaposed in the thickness direction of the
circular saw 10 are joined together; in which Fig. 1 is a front view of the tips
seen from the backward direction with respect to the rotational direction of
the circular saw 10, Fig. 2 is a plan view and Fig. 3 is a left side view.
The pair of tips 12, 12 joined together as described above is directly
fixed, for example, by brazing to a tip seat 16 formed by notching a saw
tooth 14 of the circular saw 10, as shown in Figs. 4 to 6. More specifically,
the portions of the tips 12, 12 present on the left side of the broken line
indicated in Fig. 2 are ground off beforehand to be flattened so that they can
be seated on the tip seat 16 of the saw tooth 14 shown in Fig. 6. Since
these portions are of cemented carbide material, it is also possible to cut off
these portions by means of electric discharge wire cutting and the like. The
grinding or cutting of these portions may be carried out before the above-described
spot welding treatment. If such portions of the tips 12 are not to
be flattened, it is recommended to shape the tip seat 16 conforming to the
fixing faces of the tips 12.
The pair of tips 12, 12 thus obtained is fixed to the tip seat 16 by
known means such as brazing. In the case where brazing is employed as
the means for fixing the tips to the tip seat, a brazing filler metal flows into
a clearance if present between the pair of tips 12 juxtaposed in the thickness
direction of the saw and increases the force of joining the tips together,
advantageously. Meanwhile, in the case where the tips 12, 12 are joined
together by means of brazing and also they are to be fixed to the tip seat 16
by means of brazing, it is desirable to select a brazing filler metal having a
higher melting point for brazing the tips 12 to the tip seat 16 than that used
for joining the tips 12 together.
In this case, the PCD layers (polycrystalline sintered material layers)
22, 22 in the pair of tips 12, 12 serve as rake faces 12a in the circular saw 10,
as shown in Fig. 5. Further, the tips 12 are juxtaposed such that the rake
faces 12a together define a depression to impart a positive side rake angle to
each side cutting edge 18, 18.
A peripheral back face 12c is formed by means of grinding on each tip
12 fixed to the tip seat 16, as shown in Fig. 6. In addition, a pair of side
back faces (right and left) 12b is formed also by grinding, as shown in Fig. 5.
Here again, there is no difficulty in carrying out these grinding treatments,
since the portions to be ground off are substantially of cemented carbide
material. As a result, there is provided easily a circular saw (tipped saw)
10 having hollow face-machined tips 12 with PCD layers 22.
The tipped saw described referring to Figs. 4 to 6 is of the so-called
hollow face type as explained above, in which a pair of tips 12, 12 is
juxtaposed such that the PCD layers 22, 22 thereof serving as the rake faces
together define a depression. Various examples can be proposed for
forming a depression by a pair of tips 12, 12 juxtaposed to each other. For
example, it is possible to interpose an ordinary cemented carbide tip
between a pair of extra-high pressure sintered material tips juxtaposed in
the thickness direction of a saw.
Further, to give some other examples of forming a depression by a
pair of tips 12, 12, the tips 12, 12 may be joined together such that the
position of joining them is not in alignment with the vertical center of a saw
tooth and/or that they are joined together not in alignment with each other:
the position of joining the tips 12, 12 may be deviated to the right or left side
from the center of the saw tooth, and the right tip and the left tip may be
allowed to have different side rake angles respectively; the pair of tips 12, 12
may be joined together not in alignment with each other by shifting them
from each other in the back-and-forth direction (rotational direction) of the
saw and may be allowed to have the same side rake angle; the position of
joining the tips 12, 12 may be deviated to the right or left side from the
vertical center of the saw tooth, and the positions of the right and left side
cutting edges 18, 18 may be shifted from each other in the back-and-forth
direction of the saw, wherein the right and left side rake angles are the
same.
Next, Figs. 7 to 9 show an embodiment where a pair of tips 12, 12 is
juxtaposed such that the rake faces 12a, 12a thereof together define a
protuberance to impart a negative side rake angle to each side cutting edge
18, 18. In the pair of tips 12, 12 juxtaposed such that their rake faces
together define a protuberance as described above, they may have a third tip
interposed between them or may be joined together such that the position of
joining them is not in alignment with the vertical center of a saw tooth
and/or that they are joined not in alignment with each other like the tips of
the embodiment shown in Figs. 1 to 6.
In any of the embodiments or examples described above, a depression
or a protuberance is defined by the rake faces 12a of the tips 12, 12.
However, as shown in Figs. 10 to 15, a depression may be defined by the
peripheral back faces 12c; or as shown in Figs. 16 to 18, a protuberance may
be defined by the peripheral back faces 12c. More specifically, Figs. 10 to
12 show a state where a pair of tips 12, 12 cut out from a blank of extra-high
pressure sintered material is juxtaposed in the thickness direction of a saw
tooth 14 in the circular saw 10. In this case, each tip 12 is cut out from the
blank such that it is inclined by a tip inclination angle η (see Fig. 10) and by
the difference of 90° - edge angle α (see Fig. 12). Accordingly, the PCD
layers 22 in the tips 12 serve as peripheral back faces 12c. The pair of tips
12, 12 is joined together beforehand, for example, by means of spot welding
like in the embodiment shown in Figs. 1 to 3.
The thus joined tips 12, 12 are fixed directly to a tip seat 16 of a saw
tooth 14 by means of brazing and the like, as shown in Figs. 13 to 15. More
specifically, the surfaces of the PCD layers 22 in the pair of tips 12, 12 serve
as peripheral back faces 12c in the circular saw, and the peripheral back
faces 12c, 12c of the juxtaposed tips together define a depression, as shown
in Figs. 13 to 15, that imparts a positive tip inclination angle to each side
cutting edge 18, 18. The pair of tips 12 fixed to the tip seat 16 is subjected
to grinding to form rake faces 12a thereon, as shown in Fig. 15, as well as,
side back faces (right and left) 12b, 12b as shown in Fig. 14.
As described already referring to Figs. 10 to 15, there can be proposed
various examples of forming a depression by the PCD layers 2 serving as
peripheral back faces of the tips 12, 12. For example, an ordinary
cemented carbide tip may be interposed between a pair of extra-high
pressure sintered material tips 12, 12 juxtaposed in the thickness direction
of a circular saw.
To give some other examples of forming a depression by the
peripheral back faces of a pair of tips 12, 12, the tips 12, 12 may be joined
together such that the position of joining them is not in alignment with the
vertical center of a saw tooth and/or that they are joined not in alignment
with each other: the position of joining the tips 12, 12 may be deviated to the
right or left side from the center of the saw tooth, and also the right tip and
the left tip may be allowed to have different tip inclination angles
respectively; and the pair of tips 12, 12 may be joined together not in
alignment with each other by shifting them from each other in the radial
direction of the saw and may be allowed to have an equal tip inclination
angle. What is common to all of these examples is that each pair of tips 12
is juxtaposed such that their peripheral back faces 12 together define a
depression, and thus a positive tip inclination angle is imparted to the right
end and left end of each peripheral cutting edge.
Next, Figs. 16 to 18 show an embodiment where a pair of tips 12, 12 is
juxtaposed such that the peripheral back faces 12c, 12c thereof together
define a protuberance to impart a negative tip inclination angle to each side
cutting edge 18, 18. In the tips 12, 12 juxtaposed such that the peripheral
back faces together define a protuberance as described above, they may have
a third tip interposed between them or may be joined together such that the
position of joining them is not in alignment with the vertical center of a saw
tooth and/or that they are joined not in alignment with each other like the
tips of the embodiment shown in Figs. 4 and 5.
As explained above, it is only an example to use a plurality of (2 or 3)
tips juxtaposed in the thickness direction of the saw, and the present
invention can find wide applications in addition to the formation of a simple
depression or protuberance. Further, it is also possible to use a
combination of different shapes of tips juxtaposed in a saw (circular saw or
band saw) or to arrange alternately known tips and the tips of the present
invention. Incidentally, it is basically preferred that, in the row of tips,
every adjacent two tips are not aligned with each other.
Effect of the Invention
As mentioned above, the tipped saw according to the present
invention has realized manufacturing at a reasonable cost of, for example, a
hollow face tipped saw using extra-high pressure sintered material tips such
as of polycrystalline diamond. Further, the hollow face tipped saw having
a pair of side cutting edges fixed per saw tooth can utilize effectively
expensive extra-high pressure sintered material tips compared with the JIS
C type tipped saw having a single side cutting edge per saw tooth.
Particularly, according to the present invention, there is provided a tipped
saw which is suitable for cutting wooden boards and the like, and which
lasts long and shows excellent qualities in sawing or cutting.
It should be apparent to those skilled in the art that the present
invention may be embodied in many other specific forms without departing
from the spirit or scope of the invention. Therefore, the present examples
and embodiments are to be considered as illustrative and not restrictive,
and the invention is not to be limited to the details given herein, but may be
modified within the scope of the appended claims.
Where technical features mentioned in any claim are followed by reference signs, those reference
signs have been included for the sole purpose of increasing the intelligibility of the claims and
accordingly, such reference signs do not have any limiting effect on the scope of each element
identified by way of example by such reference signs.