Note: Descriptions are shown in the official language in which they were submitted.
2036 1 44
The present invention relates to a blanking cutter for
punching out a dumbbell-shaped test piece from a sheet of
rubber, plastic, vinyl, polyethylene, paper, or the like.
Aspects of the prior art and present invention will be
described by reference to the accompanying drawings in which:
FIG. 1 is an exploded perspective view of a blanking
cutter according to the present invention;
FIG. 2 is a front elevational view of the blanking
cutter according to the present invention;
FIG. 3 is a bottom view of the blanking cutter shown in
FIG. 2;
FIG. 4 is a cross-sectional view taken along line IV -
IV of FIG. 3;
FIG. 5 is a plan view of a base of the blanking cutter
according to the present invention;
FIG. 6 is a plan view of a presser plate of the blanking
cutter according to the present invention;
FIG. 7 is a plan view of a dumbbell-shaped test piece;
FIG. 8 is a front elevational view of a conventional
blanking cutter;
FIG. 9 is a bottom view of the conventional blanking
cutter shown in FIG. 8;
FIG. 10 is a cross-sectional view taken along line X - X
of FIG. 9; and
FIG. 11 is a perspective view of another conventional
blanking cutter.
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203 ~ 1 44
Various materials such as rubber, plastic, vinyl,
polyethylene, paper, etc. are tested for mechanical strength
using a dumbbell-shaped test piece of such a material, as
shown in FIG. 7 of the accompanying drawings. The dumbbell-
shaped test piece has widened opposite ends 2 each having awidth B1 and an intermediate narrower strip portion 3 having
a width B2. The opposite ends 2 have lateral sides smoothly
joined along sine curves to the lateral sides of the
intermediate strip portion 3 via convex curves 4a having a
radius of curvature rl and concave curves 4b having a radius
of curvature r2. The shape and dimensions of such a
dumbbell-shaped test piece are specified in detail according
to various industrial standards including JIS (Japan), DIN
(Germany), and ASTM (U.S.A.).
Heretofore, dumbbell-shaped test pieces are cut out of a
sheet by a forged blanking cutter 5 as shown in FIG. 11. The
blanking cutter 5 has an upper edge 6 forged to a shape
complementary to the shape of a dumbbell-shaped test piece to
be blanked. The upper edge 6 is sharpened by a grinder or
the like into a shearing blade, which is subse-
- la -
~t, ~
quently heat-treated for deslred hardness. The shearing
blade is howeveL relatively low in dimensional accuracy
because it is sharpened manually by the grind~r. If the
shearing blade is b~oken or damaged, it is necessary to
replace the entire blanking cutter 5, which iS not
economical.
In view of the above drawback, the applicant has
proposed a blanklng cutter 100 with replaceable shearing
blades, as shown in FIGS. 8 through 10 (see Japanese
Laid-Open Patent Publication No. 54(1949)-60389).
The blanking cutter 100 comprlses a base 101 having
a shape complementary to the shape of a dumbbell-shaped test
piece to be blanked, four presser plates 102a, 102b, 103a,
103b fastened intimately to the respective four sides of the
base 101, four shearing blades 105a, 105b, 106a, 106b
clamped between the base 101 and the respective presser
plates 102a, lG2b, 103a, 103b, and a grlp boss 107 joined to
an upper surface of the base 101. Each of the shearing
blades 105a, 105b, 106a, 106b is in the form of a thin plate
having a thickness of 0.3 mm, for example, and is so flexi-
ble that the shearing blades 105a, 105b can intimately be
held against the curved lateral sides of the base 101 by the
presser plates 102a, ~02b. The shearing blades 105a, 105b,
106a, 106b have lengths equal to the exten~ed lengths of the
corresponding four sides of the base 101. The shearing
blades 105a, 105b, 106a, 106b pressed by the respective
~ 2036 1 4~
presser plates 102a, 102b, 106a, 106b and fastened to the
base 1 have respective cutting edges pro;ecting downwardly
of the base 101 and the presser plates 102a, 102b, 103a,
103b.
The blanking cutter 100 is attached to a press by
the grip boss 107. Then, the blanking cutter 100 is held
against a sheet, and forced into the sheet by the press,
thereby cutting out a dumbbell-shaped test pLece from the
sheet.
It has been found that the cutting edges of the
shearing blades 105a, 105b for defining the curved sides of
a dumbbell-shaped test piece tend to be deflected inwardly
as indicated by the two-dot-and-dash lines A in FIG. 9. The
deflected shearing blades 105a, 105b are shown exaggerated
for illustrative purpose, and the actual amount of deflec-
tion of the shearing blades 105a, 105b ls smaller. Since
dumbbell-shaped test pieces are required to have high dimen-
sional accuracy, if the shearing blades 105a, 105~ are
deflected as shown in FIG. 9, it is difficult to produce
dumbbell-shaped test pieces which meet desired accuracy
requirements. If a dumbbell-shaped test piece 1 (FIG. 1)
were produced hy the blanking cutter 100 with deflected
shearing blades, then the width s2 of the intermediate strip
portion 3 and the shape of the curves 4a, 4b would be sub-
jected to error. Any material test using such a dumbbell-
shaped test piece 1 with dimensional errors would be unable
to achieve proper results.
2036 1 44
The present invention provides a blanking cutter with
replaceable shearing blades, which is capable of cutting out
dumbbell-shaped test pieces with high dimensional accuracy.
The present invention also provides a blanking cutter
which includes shearing blades for defining curved sides of a
dumbbell-shaped test piece, the shearing blades being
prevented from being deflected inwardly.
More particularly, in one aspect, the invention provides
a blanking cutter for cutting out, from a sheet, a dumbbell-
shaped blank test piece having wider opposite end portionsand a narrower, substantially straight-sided, intermediate
strip portion joined thereto along convexly and concavely
curved side portions, and comprising: a base with wider
opposite end portions and a narrower intermediate strip
portion providing an outer profile corresponding in shape to
the dumbbell-shaped test piece and formed by opposite
longitudinal sides and opposite lateral sides, the
longitudinal sides having intermediate, substantially
straight portions joining convexly and concavely curved
portions; a plurality of thin, flat flexible shearing blades
having respective lengths at least equal to perimetrical
lengths of opposite sides of said base; a plurality of
presser plates having side portions of complementary shapes
to the respective sides of the base and held intimately
against the respective sides of the base with the shearing
blades clamped therebetween, thereby attaching said shearing
-- 4
d.
2036 1 44
blades to the sides of said base; said shearing blades
surrounding fully the outer profile of said base and having
respective cutting edges projecting beyond said base and said
presser plates; wherein the improvement resides in that the
intermediate substantially straight portions of the
longitudinal sides of said base which correspond to the
substantially straight sided intermediate strip portion of
the dumbbell-shaped test piece, and portions of the sides of
said presser plates which are of complementary shape to the
intermediate portions of the longitudinal sides of the base
and which are held intimately thereagainst with the
corresponding shearing blades clamped therebetween, comprise
concave and convex surfaces having respective large radii of
curvature so as to prevent the projecting cutting edges of
said blades from being deflected inwardly, towards each
other, out of alignment with the outer profile formed by the
intermediate portions of the longitudinal sides of said base.
`t~
2036 ~ 44
FIG. 1 shows a blanking cutter in exploded perspective,
the blanking cutter being shown upside down. The blanking
cutter comprises a support plate 10, a base 20 joined to the
support plate 10, four shearing blades 50, 55 attached
respectively to four sides of the base 20, four presser
plates 30, 40 for pressing the shearing blades 50, 55 to the
respective sides of the base 20, and a knockout plate 11 for
pushing out a blanked test piece. The shearing blades 50,
55, and the presser plates 30, 40 are fastened to the base 20
by bolts 36, 37, 49 and nuts 38, as shown in FIGS. 2 through
4.
As shown in FIG. 5, the base 20 is complementary in
shape to a dumbbell-shaped test piece to be blanked by the
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blanking cutter, and comprises two wider opposite ends 21
and an intermediate narrower strip portion 22. The base 22
is joined to the lower surface of the support plate 10. A
grip boss 15 is ~oined to the upper surface of the support
plate 10. The support plate 10 and the base 20 ~ointly have
two vertical through lloles 26 positioned in the respective
ends 21. Studs 12 with lower ends joined to the knockout
plate 11 are inserted, from below, into the respective
through holes 26. Nuts 12a are threaded over respective
upper ends of the studs 12, such that the knockout plate 11
is attached for vertical movement with respect to the sup-
port plate 10 and the base 20. The base 20 also has two
spring holes 25 defined therein. Before the knockout plate
11 is attached, knockouk springs 13 are placed respectively
in the spring holes 25 and held against the knockout plate
11. As shown in FIG. 4, the knockout plate 11 is pushed
downwardly under the bias of the knockout springs 13 with
the nuts 12 on the upper ends of the studs 12 being held in
abutment against the upper surface of the support plate 10.
The base 20 has an outer profile including two lon-
gitudinal opposite sides 24 having flat surfaces at the
respective wider ends 21. The shearing blades 55, which are
shorter than the shearing blades 50, are of the same length
as the sides 24. The shearing blades 55 are clamped against
the respective sides 24 by the presser plates 40. Each of
the presser plates 40 has two positioning pins 41 and a bolt
2036 1 44
hole 42 defined between the positioning pins 41. Each of
t~le shorter shearing blades 55 has three holes 56 for inser-
tion of the positioning pins 41 and a bolt 49. The posi-
tioning pins 41 are inserted through the holes 56 into holes
29a in the sides 24 of the base 20, and the shorter shearing
blades 55 are held against the respective sides of the base
20 by the presser plates 40. Then, the bolts 49 are
threaded through the holes 42, 56 into threaded holes 29b
defined in the sides 24 of the base 20, thereby fastening
the shorter shearing blades 55 to the respective sides 24.
Each of the shorter shearing blades 55 is in the form of a
stainless steel plate having a thickness of 0.3 mm, and has
a cutting edge 55a directed downwardly and pro;ecting below
the lower surfaces of the base 20 and the pLesser plates 40.
The outer profile of the base 20 also includes two
transverse opposite sides each composed of a first flat sur-
face 21a servi~lg as a lateral side of one of the wider ends
21, a second surface 22a serving as a lateral side of the
intermediate strip portion 22, two convex surfaces 23a and
two curved surfaces 23b which join the first and second sur-
faces 21a, 22a. The convex surfaces 23a have a radius of
curvature Rl and the concave surfaces 23b have a radius of
curvature R2. The second side surfaces 22a correspond to
the lateral sides of the intermediate strip portion of a
dumbbell-shaped test piece. The second side surfaces 22a
comprise concave surfaces having a very large radius of cur-
vature R3.
-- 8 --
~ 20361 44
The longer shearing blades 55, which are in the
form of thin flexible plates, have the same length as the
ex~ended transverse opposite sides of the base 20, and are
intimately attached respectively to the transverse opposite
sides of the base 20 by the respective presser plates 30.
As shown in FIG. 6, each of the presser plates 30 is of a
complementary shape for holding the longer shearing blade 50
intimately against the transverse side of the base 20. Each
presser plate 30 comprlses two first side surfaces 31 for
mating with the first side surfaces 21a, respectively, of
the base 20, a second side surface 32 for mating with the
second side surface 22a of the base 20, two concave surfaces
33a for mating with the respective convex surfaces 23a of
-the base 20, and two convex surfaces 33b for mating with the
respective concave surfaces 23b of the base 20. The concave
surfaces 33a have a radius of curvature R4 and the convex
surfaces 33b have a radius of curvature R5. The second side
surface 32 corresponds to the second side surface 22a of
the base 20, and comprises a convex surface having a very
large radius of curvature R6 which is substantially the same
as the radius of curvature R3.
The presser plates 30 are held against the lateral
sides of the base 20 with the longer shearing blades 50
clamped therebetween, and fastened in place by the bolts 36,
37 and the nuts 38. The presser plates 30 and the longer
shearing blades 50 have bolt holes 35, 51, 52 through which
2036 1 44
the bolts 36, 37 are inserted, and the base 20 has through
holes 37 -through which the bolts 37 extend and threaded
holes 28 into which the bolts 36 are threaded.
Each of the longer shearing blades 50 comprises a
stainless steel plate having a thickness of 0.2 mm. Since
the longer shearing blades 50 are flexible, they are
elastically deformed and intimately held against the lateral
sides of the base 20 when pressed by the presser plates 30.
Since the second side surfaces 22a of the base 20 are con-
cave surfaces with the radius of curvature R3 and the second
side surfaces 32 of the presser plates 30 are convex sur-
faces with the radius of curvature R6, the cutting edges 50a
of the shearing blades 50 clamped between these second side
surfaces 22a, 32 are prevented from belng deflected
inwardly, unlike the conventional arrangement shown in FIG.
9.
The radii of curvature R3, R6 are selected to pre-
vent the cutting edges 50a from being deflected inwardly.
The radii of curvature R3, R6 are affected by the radius of
curvature rl of the convex surfaces 4a and the radius of
curvature r2 of the concave surfaces 4b of the dumbbell-
shaped test piece 1, the thickness of the longer shearing
blades 50, the difference between the width Bl of the wider
ends 2 and the width B2 of the intermediate portion 3 of the
dumbbell-shaped test piece 1, and the length L of the
intermediate portion 3 thereof. Therefore, the radii of
-- 10 --
20361 44
curvature R3, R6 are experimentally established for each
blanking cutter design.
Specific examples will be described below.
Example 1:
If the thickness of the longer shearing blades 50
is 0.2 mm, the radius of curvature rl of the convex surfaces
4a of the dumbbell-shaped test piece 1 is 25 mm, the radius
of curvature r2 of the concave surfaces 4b thereof is 14 mm,
the width B1 of the wider ends 2 is 25 mm, the width B2 of
the intermediate por~ion 3 is 12 mm, and the length Ll
thereof is 60 mm, then the rad~us of curvature R3 of the
concave second side surfaces 22a of the base 20 is 3600 mm,
and the radius of curvature R6 of the convex second side
surfaces 32 of the presser plates 30 is 3599.8 mm.
Example 2:
If the thickness of the longer shearing blades 50
is 0.3 mm, the radius of curvature rl of the convex surfaces
4a of the dumbbell-shaped test piece 1 is 25 mm, the radius
of curvature r2 of the concave surfaces 4b thereof is 14 mm,
the width Bl of the wider ends 2 is 19 mm, the width s2 of
the intermediate portion 3 is 6 mm, and the length Ll
thereof is 33 mm, then the radius of curvature R3 of the
concave second side surfaces 22a of the base 20 is 1360 mm,
and the radius of curvature R6 of the convex second side
surfaces 32 of the presser plates 30 is 1359.8 mm.
Because the radii of curvature R3, R6 are governed
by the other dimensions described above, they cannot
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~ 20361 4~
uniquely he establis~led in advance, but have to be deter-
mined for each blanking cutter design. Generally, however,
the radii o~ curvature R3, R6 tend to become ~reater as the
radii of curvature rl, r2 of the convex and concave surfaces
4a, 4b are greater, the difference between thc widths sl, s2
is smaller, and the length Ll is larger.
The blanking cutter thus constructed is used as
follows: The blanking cutter is attached to a press by the
grip boss 15. Then, the blanking cutter is held against a
sheet of rubber, plastic, vinyl, polyethylene, paper, or the
like, and forced into the sheet by the press, thereby caus-
ing the cutting edges of the shearing blades 50, 55 to cut
out a dumbbell-shaped test piece from the sheet. At this
time, the knockout plate 11 which is vertically movable is
pushed upwardly beyond the cutting edges. When the blanking
cutter is subsequen-tly lifted, the knockout plate 11 is
pressed downwardly by the knockout springs 13, pushing the
blanked test piece off shearing blades 50, 55.
Although a certain preferred embodiment has been
shown and described, it should be understood that many
changes and modifications may be made therein without
departing from the scope of the appended claims.
