Note: Descriptions are shown in the official language in which they were submitted.
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D~SCRI P'f'.IDN
ROTARY MOWING CUTTER AND PORTABLE POWER MOWER
TECHI~CA L FIELD
The present invention relatesto rotary mowingcutter,
a
and alsoto a portable power mowerusing such mowingcutter.
a
BACKGROUND ,~$T_
As is well known, a typical portable power mower includes
an elongated tubular body connected at its rear end to a small
engine and supporting at its front end a rotary cutter. The
i0 cutter is connected to the engine via a transmission shaft
extending through the tubular body. The cutter may be a
serrated rotating disc, or a circular metal plate provided
with a suitable number of cutting chips regularly arranged
along the edge of the plate. Alternatively, the cutter may
consist of flexible nylon cords or metal wires radially
extending from a drive shaft.
Serrated rotating discs, which are generally inexpensive,
have been widely used in conventional power mowers.
Disadvantageously, however, a serrated disc may be rather
easily broken upon hitting against hard objects such as stones
or metal blocks lying on the ground. Even if the serrated
disc is not broken, hard objects flicked by the rotating
cutter may injure the operator of the mower or people nearby.
Clearly, a circular. metal plate provided with cutting chips is
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apt to suffer from the same problems.
A_s opposed tc> a serrated disc or metal plate with cutting
chips, a cord-type rotary cutter may be free from the problem
of flicking a hard object since the nylon cords or metal wires
are too flexible to thrust the hard object away. However,
when the flexible nylon cords (or metal. wires) hit against
stones for example, they may be broken or permanently
deformed. Further, since these cords are rather small in
weight, they may fail to cut down weeds properly.
nr~~'r.Ogtm~ OF T[~E INVENTION
The present invention has bee proposed under the above
circumstances, and its object is tv provide a rotary mowing
cutter capable of overcoming the above problems.
Specifically, an object of the present invention is to provide
i5 a rotary mowing cutter which is nat easily broken even upon
hitting against a hard object and does not flick the hard
object toward the operator and people nearby.
Another object of the present invention is to provide a
portable power mower using a rotary mowing cutter of the above
type.
According to a first asper_t of the present invention,
there is provided a rotary mowing cutter comprising:
a holder attached to a drive shaft;
a,t least one cutting element fixed to the holder; and
first and second covers between which the cutting element
is arranged;
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wherein the cutting element includes a deformable member
attached to the holder and a cutter member attached to the
deformable member, part of the cutter member being arranged to
protrude from the first and the second covers when the
deformable member extends radially of the drive shaft.
Preferably, part of the cutter member may be caused to
protrude from the first and the second covers when the cutting
elemer.~t is rotated.
In a preferred embodiment, the first .and the second covers
may b~e circular. The first and the second covers may be
integrally rotated with the holder. In this case, the two
covers and the holder may be formed integral with each other.
In another preferred embodiment, the first cover may be
stationary while the holder and the second cover may be
5 integrally rotated.
Preferably, the rotary mowing cutter of the present
invention may fur°ther comprise deformation restricting means
for preventing the cutting element from deforming beyond a
predetermined extent.
Preferably, the cutter member may have a round end.
Further, the cutter member as a whole may be circular.
For facilitating mowing, the cutter member may be provided
with a cutting edr~e of a relatively small thickness.
For protecting an operator from possible injury caused by
the cutter member, the cutter member at rest may be retreated
into a space between the first and the second covers. Only in
operation, the cutter member may be caused to protrude from
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the first and the second covers.
In a preferred embodiment, the cutter member may include
an inner portion having a constant thickness and an outer
portion having a relatively small thickness suitable for
mowing.
Preferably, the inner portion of the cutter member may be
snugly held between the first and the second covers.
Preferably, the holder may be formed with a fixing hole
into which the deformable member. is fitted. In this case, the
fixing hole may include a flaring mouth portion for allowing
movement of the deformable member.
Similarly, the cutter member may be formed with a fixing
hole into which the deformable member is fitted. Again, the
fixing hole may include a flaring mouth portion for allowing
movement of the deformable member.
In a preferred embodiment, the holder may include a body
and a circular piece connected to the deformable member,
wherein the circular piece is pivotably received by the body.
Likewise, the=. cutter member may include a body and a
2p circular piece connected to the deformable member, wherein the
circular piece is pivotably received by the body.
Preferably, the body of the holder may be formed with a
through-hole for receiving the circular piece. The body of
the holder may also be formed with a cutout communicating with
the through-hole for avoiding interference with the deformable
member.
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Preferably, the deformable member may be made of metal
wire.
According to a second aspect of the present invention,
there is provided a portable power mower comprising:
a tubular body:
a transmission shaft extending through the tubular body
to be connected to an engine;
a drive shaft connected to the transmission shaft; and
rotary mewing cutter connected to the engine, the
mowing cutter comprising:
a holder attached to the drive shaft;
at least one cutting element fixed to the holder; and
first and second covers between which the cutting element
is arranged;
wherein the cutting element includes a deformable member
attached to the holder and a cutter member attached to the
deformable member, part of the cutter member being arranged to
protrude from the first and the second covers when the
deformable member extends radially of the drive shaft.
For achieving smooth operation of the mower over the
ground, the second cover may be provided with a downwardly
conve3c portion .
Other features and advantages of the present invention
will become apparent from the detailed description given below
with reference to the accompanying drawings.
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BRIEF DF~C~,j~ION OF DItAWTNCS
Fig. 1 is a side view showing, partly in section,
principal parts of a portable power mower incorporating a
rotary mowing cutter according to a first embodiment of the
present inventions
Fi.g. 2 is a view taken along lines X2-X2 in Fig. 1;
Fi.g. 3 is a side view showing, partly in section,
principal parts of another portable power mower incorporating
a rotary mowing cutter according to a second embodiment of the
present invention;
Fig. 4 is a perspective view showing principal parts of a
rotary mowing cutter according to a third embodiment of the
present invention;
Fp.g. 5 is a plan view showing a rotary mowing cutter
according to a fourth embodiment of the present invention;
Fig. 6 is a plan view showing a rotary mowing cutter
accorciing to a fifth embodiment of the present invention;
Fig. 7 is a plan view showing a rotary mowing cutter
according to a sixth embodiment of the present invention;
F:ig. 8 is a plan view showing a rotary mowing cutter
according to a seventh embodiment of the present invention;
F:ig. 9 is an enlarged view showing a cutter member used in
the rotary cutter' of Fig. 8;
F:ig. 10 is a sectional view taken along lines X10-X10 in
Fig. !~;
Fig. 11 is a sectional view taken along lines X11-X11 in
Fig. !a;
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Fig. 12 is a plan view showing a rotary mowing cutter
according to an eighth embodiment of the present invention;
Fig. 13 is an enlarged view showing a cutter member used
in the rotary cutter of Fig. 12;
Fig. 14 is a sectional view taken along lines X14-X14 in
Fig. 13;
Fig. 15 is a sectional view taken along lines X15-X15 in
Fig. 1:3;
Fig. 16 is a perspective view showing principal parts of
the rotary cutter of the eight embodiment;
Fig. 1? is a side view showing, partly in section, a
portable power mower incorporating a rotary mowing cutter
according to a ninth embodiment of the present invention;
Fig. 18 is a plan view taken along lines X18-X18 in Fig.
17;
Fig. 19 is an enlarged view showing a cutter member used
in the rotary cutter of the ninth embodiment;
Fig. 20 is a sectional view taken along lines X20-X20 in
Fig. 1'9;
Fig. 21 is a sectional view taken along lines X21-X21 in
Fig . 1'9 ;
Fig. 22 is an enlarged view showing a principal part of a
holder used in the rotary cutter of the ninth embodiment;
Fig. 23 is a plan view illustrating the function of the
rotary cutter of the ninth embodiment, with a cutter member
hitting against a hard object;
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~"ig. 24 is an enlarged view illustrating how a cord-like
deformable member is bent relative to the cutter member;
Fig. 25 is a plan view illustrating the function of the
rotaxy cutter of the ninth embodiment, with a cutter member
hitting against a relatively soft object;
Fig. 26 is an enlarged view illustrating how a cord-like
defoxznable member is bent relative to the holder;
Fig. 27 is a plan view showing a rotary mowing cutter
according to a tenth embodiment. of the present invention; and
Fig. 28 illustrates the function of the rotary cutter of
the tenth embodiment, with a cutter member hitting against a
hard object.
BEST MDDF,~ FOR CARR_yT-~~'r OUT THE LNVENTION
Throughout the accompanying drawings, identical or similar
parts are referred to by the same reference numerals and
characters.
Reference is first made to Figs. 1 and 2 illustrating
principal parts of a portable power mower (generally
represented by reference character 1) utilizing a rotary
mowing cutter LO according to a first embodiment of the
present invention. The power mower 1 includes a tubular body
20 connected at its rear end to a small, engine (not shown).
As shown in broken lines, a transmission shaft 21 extends
through the tubular body 20 and is connected at its rear end
to the non-illustrated engine. At its front end, the
transmission shaft 21 is connected to a drive shaft 23 via a
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bevel gear mechanism (not shown) housed in a gear casing 22.
The drive shaft 23 is rotatably supported by the gear casing
22 and formed at its lower end with a bore 23a for receiving a
bolt :15. The rotary mowing cutter 10 is attached to the drive
shaft 23. For preventing weeds from twining around the
rotating drive shaft 23, a guard cover 24 is attached to the
gear .casing 22.
According to the present invention, the non-illustrated
engine may not necessarily be fixed to the rear end of the
tubular body 20. For instance, the engine may be mounted on a
casing carried on the back of an operator. In this case, the
engine may be connected to the transmission shaft 21 via a
flexible shaft.
Pas shown in Figs. 1 and 2, the rotary cutter 10 basically
includes a hold~:r 11 fixed to the drive shaft 23, cutting
elements 12 extending radially from the holder 11, a first
cover 13 arranged above the cutting elements 22, and a second
cover 14 arranged under the cutting elements 12. In the
illustrated embodiment, four cutting elements 12 are provided
(see Fig. 2y. However, the number of the cutting elements 12
is optional, and only one or more than four cutting elements
may be used.
~~s best shown in Fig. 2, the holder 1.1 is in the form of a
disc of a predetermined thickness and formed with a center
hole lla into which the drive shaft 23 is fitted. Further,
the holder 11 is formed with four horizontal fixing holes llb.
These' holes are equally spaced. around the center hole lla and
n
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extend radially of the holder 11 for fixing the inner ends of
the cutting elements 12.
Each cutting element 12 includes a cord-like deformable
member 12a whose inner end is fitted into a respective one of
the fixing holes 11b of the holder 11, and a hard cutter
member 12b fixed to the outer end of the deformable member
12a. The cutter member 12b is formed with a bore 12c into
which the deformable member 12a is inserted. The deformable
member 12a may be a metal wire (or wire strands) made of
stainless steel for example. The cutter, member 12b may be
made of a hard material obtained by quenching structural
carbon steel.
The deformable member 12a may be fixed to the holder 11 by
soldering or calking. Likewise, the cutter member 12b may be
fixed to the deformable member 12a by soldering or calking.
The holder .1 has a thickness of about 6mm, while the
defonnable member 12a has a thickness of about 3mm.
T'he cutter member 12b, which may be about 20-30mm long,
has a generally K:ircular cross section. The cutter member 12b
is divided into two portions, namely, a diametrically larger
inner portion connected to the deformable member 12a and a
diametrically smaller outer portion. The outer diameter of
the inner portioxz of the cutter member 12b may be equal to or
slightly less than Eimm, while the diameter of the outer
portion of the cutter member 12b is rendered small enough to
enable effective mowing of weeds.
in
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Ln the normal state, as shown in Fig. 1, the inner portion
of th.e cutter member 12b is disposed between the first cover
13 ar.~d the second cover 14, while the outer portion of the
cutter member 12b protrudes radially outward of the first and
the second covera 13, 14. In the illustrated embodiment, the
length P of the protruding portion is about 6-l2mm.
The first cover 13 is a circular plate made of e.g.
aluminum and formed with a center hole 13a into which the
drive shaft 23 is fitted. Likewise, the second cover 14,
which has also a circular canfiguration, is made of e.g.
aluminum and formed with a center hole 14a. As shown in Fig.
1, the second cover 14 is provided with a bulging portion 14b
which is downwardly convex. The bulging portion 14b is formed
with a recess 14c: communicating with the center hole 14a. To
5 firmly attach the first cover 13, holder 11 and second cover
14 to the drive shaft 23, the bolt 15 is screwed into the bore
23a. As a result, the first cover 13, the holder 11 and the
second cover 14 are caused to rotate together upon actuation
of the drive shaft 23. It shauld be noted that the head of
the bolt 15 is accommodated in the recess 14c. Thus, the bolt
15 does not protrude downward beyond the bulging portion 14b
of the second cover 14.
As previously stated, the thickness of the holder 11 is
generally the same as the maximum diameter of each cutter
member 12b, while the thickness (or diameter) of each
deformable member 12a is smaller than those of the holder 11
and the cutter members 12b. Thus, as shown in Fig. 1, the
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first and the second covers 13 and 14 are vertically adjacent
to the cutter members 12b, thereby preventing each cutter
member 12b from deviating upward or downward in operation.
The cutter members 12b are snugly held between the first
and the second covers 13, 14 so as to be movable therebetween.
Thus, when an unduly large external force is exerted on any
one of the cutter members 12b, the relevant deformable member
12b wall be bent,, as shown in phantom in Fig. 2, whereby the
entirety of the particular cutter member 12b is retreated into
the space between the first and the second covers 13, 14.
The operations of the portable power mower 1 and the
mowing cutter 10 will now be described.
Though not illustrated, the tubular body 20 of the mower 1
is provided with a throttle lever to control the output of the
engine. Thus, by manipulating the throttle lever, an operator
can increase or decrease the rotational speed of the rotary
cutter 10. The rotational speed may reach 7,000-B,OOOrpm and
the circumferential speed of the cutter 10 may be over
300km/h.
To mow weeds the operator moves the rotating cutter 10
over the ground, holding it close to the ground. In this
manner, the cutter members 12b rotating at: high speed will cut
down the weeds.
An advantage to be enjoyed by the illustrated embodiment
is as follows. When the cutter members 12b hit against hard
but rather small objects such as pebbles or bolts on the
ground, those small objects will not be flicked toward the
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operator or people nearby, even though the cutter members 12b
are rotated at high speed. This is because the kinetic energy
of they cutter members 12b is very small due to a small mass
(10-90 grams) of the cutter members 12b.
Further, upon hitting against small stones or unmovable
concrete blocks, the deformable members 12a are bent as shown
in Fig. 2 (double-dot chain lines), so that the impact of the
hitting is advantageously absorbed, thereby leaving the cutter
members 12b intact.. Further, since the cutter members 12b are
70 not caught by the hard objects thanks to the deflection of the
deflectable members 12a, the rotational speed of the rotary
cutter 10 is advantageously maintained. Once being deformed,
the cleformable member 12a is instantly restored to the
original, straight. shape by the centrifugal force.
According to the illustrated embodiment, the downwardly
convex: portion 14b is formed on the secand cover 14. Thus,
the operator of the power mower 1 is able to move the rotary
cutter 10 smoothly over the ground, with the convex portion
14b held in sliding contact with the ground. Further, due to
the convex portion 14b, the cutter members 12b are prevented
from Gaming too claw to the ground during the mowing
operation. This is advantageous in preventing the cutter
members 12b from ~~oming into direct contact with the ground or
small hard objects lying on the ground.
Since the power mower 1 has the above-described
advantages, the operator can conduct mowing without worrying
about pebbles or bolts hidden in the weeds which would
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othervaise cause damage to the cutter members 12b or injure
people. Thus, the operator can efficiently conduct the mowing
by using the power mower 1. Further, due to the impact-
absorbing function, the power mower 1 can cut down weeds
growing beside a hard wall without damaging the cutter members
12b through contact with the wa7.l.
F;ig. 3 shows a portable power mower lA using a rotary
mowing cutter l0A according to a second embodiment of the
present invention. The power mower lA and the rotary cutter
l0A are substarxtially the same as those of the first
embodiment except that a first cover 13 of the second
embodiment is formed integral with a guard cover 24. Since
the guard cover 24 is fixed to a stationary gear casing 22,
the first cover a3 of this embodiment is not rotated together
with cutting elements 12 and a second cover 14. The
deformable members 12a are functionally similar to those of
the first embodiment.
Fig. 4 shows principal parts of a rotary mowing cutter 10B
according to a third embodiment of the present invention. In
2p this embodiment, as in the previous embodiments, each cutting
element I2 is provided with a deformable member 12a and a
cutter member 12b attached to the deformable member 12a. The
cutter member 12b of the third embodiment differs from that of
the first or second embodiment in the following respects.
Specifically, as shown in Fig. 4, the cutter member 12b is
provided with an inner portion l2ba and an outer portion l2bb
protruding radially outward of first and second covers 13, 14.
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The inner portion l2ba has a rectangular cross section whose
thickness is substantially the same as (or slightly smaller
than) the space between the first cover 13 and the second
cover 14. The protruding outer portion l2bb is provided with
a sharp cutting edge l2bc. Thus, weeds are easily cut down by
the cutting edge l2bc of the cutter member 12b rotating in the
direction indicated by an arrow R.
According to the illustrated arrangement, the rectangular
inner portion l2ba of the cutter member 12b is snugly (but
slidably) disposed between the first and the second covers 13,
14. Thus, the cutter member 12b is prevented from rotating
about the radially extending axis Ax shown in Fig. 4. This is
advantageous because the cutting edge l2bc is held in a
predetermined posture suitable for conducting effective
mowing.
Fig. 5 shows a rotary mowing cutter lOC according to a
fourth embodiment of the present invention. Basically, the
mowing cutter lOC is similar to the mowing cutter 10 of the
first embodiment. Specifically, the mowing cutter 10C
includes a first cover 13, a plurality of cutting elements 12
and a second cover 14 which are all fixed to a common drive
shaft 23 for simultaneous rotation.
Differing from the first embodiment, however, the mowing
cutter lOC of the tourth embodiment is provided with a
plurality of deformation restricting members 16 (only one
shown) disposed between the first and the second covers 13,
14. Each restricting member 16 corresponds to a respective
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one of the cutting elements 12 and is fixed to the inner
surface of the second cover 14, as shown in Fig. 5.
Alternatively, the restricting members 1~ may be fixed to the
first caver 13.
A:~ illustrated, each restricting member 16 comes into
contact with the cutter member 12b of the relevant cutting
element 12 when this particular cutting element 12 is bent, as
shown in phantom. With such an arrangement, it is possible to
prevent the deformable member 12a of each cutting element 12
from being subjer.~ted to bending beyond an acceptable degree.
This is advantageous because, otherwise, the deformable member
12a when unduly bent would be unable to restore to the
original straight form.
F:ig. 6 shows a rotary mowing cutter lOD according to a
fifth embodiment of the present invention. The illustrated
mowing cutter lOD also includes first and second covers 13, 14
and a plurality of cutting elements J.2 (only one shown)
disposed between the two covers 13, 14. Differing from the
previous mowing cutters 10-lOC, the cutting elements 12 of the
mowing cutter lOD are entirely retreated into the space
between the first and the second covers 13 and 14 when the
cutter lOD is not rotated. Fo:r achieving this, each cutting
element 12 at rest is arranged to extend along a line L which
does not pass through the rotational center O. When the
cutter lOD is :rotated, the centrifugal force causes the
retreated cutting element 12 to move to the working position
shown in double-dot chain lines. As a result, the outer
r.
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portion of the cutter member 12b protrudes radially outward of
the f:i.rst and second covers 13 and 14, whereby intended weed
mowing is performed.
According to the fifth embodiment, the cutter members 12b
in nonuse are safely kept between tae first and the second
cover~c 13, 14. Such an arz~angement is advantageous in
protecting an operator from injury by the cutter members 12b.
F:ig. 7 shows a rotary mowing cutter. l0E according to a
sixth embodiment" of the present invention. In this
embodiment, a first cover 13, a second cover 14 and a holder
11 are formed e.g. by die-casting of aluminum, so that these
components are integrally connected to each other. As
illustrated, the mowing cutter 10E includes four radially
elongated partitions 17 between the first and the second
cover~~ 13, 14. Each of the partitions 17,, which may be formed
integral with thc> two covers 13 and 14, is arranged between
two adjacent cutting elements 12. Thus, four generally
sectoz:ial spaces SP are defined by the partitions 17 and the
two covers 13, 14. Each of the cutting elements 12 is movable
within a respective one of the sectorial spaces SP. As in the
fourth embodiment (Fig. 5), the partitions 17 may serve as
defornnation restricting means for the cutting elements 12.
Fig. 8 shows a rotary mowing cutter lOF according to a
seventh embodiment of the present invention. The illustrated
cutter 10F is basically similar to the cutter 10 of the first
embodiment (Fig. 2), except that each cutter member 12b has a
round outer end. The specific configuration of the respective
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cutter members 12b will be described below with reference to
Figs. 9-11.
Fig. 9 is an enlarged plan view showing, partly in
section, one of t:he identical cutter members 12b, while Fig.
10 is a sectional view taken along lines X10-X10 in Fig. 9,
and Fig. 11 is a sectional view taken along lines X11-X11 in
Fig. 9.
As seen from these figures, each cutter member 12b
includes a rectangular inner portion l2ba and an outer portion
l2bb processed suitably for mowing weeds. The outer portion
l2bb extends radially outward from the inner portion l2ba.
The inner portion l2ba has a thickness which is substantially
equal to or slightly smaller than the distance between first
and second covers 13-14, so that the inner portion l2ba is
snugly but slidably held between the two covers 13 and 14.
The protruding amount F~ (Fig. 8) of the outer portion l2bb may
be about 10-20mm.
As best shown in Fig. 10, the outer portion l2bb is
gradually reduced in thickness, as viewed from the center of
the outer portion l2bb toward the respective edges l2bbe
extending in parallel to the axis of the deformable member
12a. Such an arrangement serves to facilitate the mowing of
weeds,
According to the seventh embodiment, the free end l2bc of
the cutter member 12b has a round configuration which is
convex radially outward, as shown in Fig. 9. Upon hitting
against a hard object on the ground, the thus configured
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cutter member 12b is caused to slide over the surface of the
hard object (see Fig. 8) with the deformable member 12a
suitably bent. Thus, advantageausly, the cutter member 12b is
prevented from sticking in the hard object. As a result, the
smooth rotation of the rotary cutter lOF is maintained even
when the cutter 10F encounters hard objects. Further, since
the cutter member 12b does not stick in the hard object, the
deform~able member 12a will not be sharply bent at the portion
where the deformable member 12a is inserted into the cutter
member' 12b .
In view of the above advantages, according to the
illustrated embodiment, use may be made of a small, portable
engine whose displacement volume is about 22-23cc for driving
the rotary cutter lOF. the cutter lOF in operation may attain
a rotation of about 6,OOOrpm, which renders the
circumferential speed of the cutter lOF to be about 150km/h or
more.
F:ig. 12 shows a rotary mowing cutter lOG according to an
eighth embodiment of the present invention. As illustrated,
the rotary cutter lOG includes a circular holder 11 from which
three cutting elements 12 extend radially outward of the
holder 11. The three cutting elements 12 are regularly spaced
around a drive shaft 23. The holder 11 and the cutting
elements 12 are arranged between first and second covers 13,
14.
Each of the cutting elements 12 is provided with a
defornnable member 12a and a cutter member 32b. The deformable
1 ca
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member 12a of this embodiment is identical or similar to that
of the previous embodiments, while the cutter member 32b has a
different configuration. Specifically, as best shown in Fig.
13, each cutter member 32b is in the form of a circle whose
diameter may be about 25mm. The cutter member 32b is divided
into two parts, namely, a flat inner portion 32ba and a
crescent-shaped oaiter portion 32bb. As shown in Fig. 14, the
inner portion 32ba has a predetermined uniform thickness,
while the outer portion 32bb tapers toward its edge 32bc. As
shown in Fig. 15, the inner portion 32bb is gradually reduced
in thickness farther away from the center in the direction
transverse to the axis of the deformable member 12a. Fig. 16
is a perspective view showing the cutter member 32 which is
slidably moved between the firsr_ and the second covers 13 and
14.
According to the eighth embodiment, each cutter member 32b
as a whole is made circular. Thus, it is possible to reliably
prevent the cutter member 32b from sticking in a hard object
on they ground. instead of being caught by e.g. a tree stump,
the i.7Llustrated cutter member 32b is cause to slide over the
surface of the tree stump upon contacting therewith.
In the above embodiment, the three deformable members 12a
have the same Length, thereby equalizing the protruding
amounts of the respective cutter members 32b. The present
invention, however, is not limited to this, and the protruding
amounta may be rendered different. For instance, the
protruding amount: may be l7mm, 15mm and l4mm, respectively.
2('i
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Reference is now made to Fig. 17 showing a portable power
mower incorporating a rotary mowing cutter lOH according to a
ninth embodiment of the present invention. The illustrated
power mower is basically similar to the power mower shown in
Fig. 1 except that the rotary cutter lOH differs in
arrangement from the rotary cutter 10 of the first embodiment.
Referring to Fig. 18, the rotary cutter lOH includes a
holder 11 from which three cutting elements 12 extend radially
outward. The holder 11 is formed with a center hole lla into
which a drive shaft 23 (Fig. 17) is fatted. The cutting
elements 12 are regularly spaced around the center hole 11a
(120° apart). The holder 11 and the cutting elements 12 are
arranged between first and second covers 1.3, 14. Each cutting
element 12 includes a deformable member 12a and a cutter
member 12b fixed to the outer end l2aa of the deformable
member 12a. Opposite to the outer end l2aa, the deformable
member 12a has an inner end l2ab.
Th,e holder 11 is provided with three protrusions extending
radially outward of the holder. As shown in Fig. 18, the
three protrusions are regularly spaced around the center hole
lla (120° apart). Each of the protrusions is formed with a
bore llb into which the inner end l2ab of a corresponding
deformable member 12a is inserted. The holder 11 may have a
thickness of about 6mm and a maximum diameter including the
Protrusions) of about 70mm. The width of each protrusion may
be about l2mm. Each deformable member 12a may have a length
of about 98mm and a diameter of about 3mm. Each cutter member
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12b may have a thickness of about 6mm, a length of about 33mm
and a 'width of about l5mm. The weight of each cutter member
12b may be about 10 grams. The circular first and the second
covers 13-14 made of e.g. aluminum may have a thickness of
about l.5man and an outer diameter of about 230mm.
As seen from Figs. 19-21, each cutter member 12b includes
an inner portion l2ba connected to a de.formable member 12a.
The inner portion l2ba has a constant thickness corresponding
to the spacing between the first cover 13 and the second cover
14. The cutter member 12b also includes an outer portion l2bb
protruding from the inner portion l2ba radially outward of the
first and the second covers 13, 14.
The inner portion l2ba is formed with a bore 12c into
which the outer end l2aa of the deformable member 12a is
75 inserted. The overall depth D1 of the bore 12c may be about
21mm . As shown in Fig . 19 , the bore 12 c has a flaring mouth
portion whose maximum width W1 may be about 6mrn and whose
depth D2 may be about 7mm. The remaining portion of the bore
12c has a depth D3, which may be equal to l4mm, and has a
constant diameter. This remaining portion of the bore 12c
snugly receives t:he outer end l2aa of the deformable member
12a to render the outer end l2aa unmovable. On the other
hand, the deformable member 12a is able to shift Within the
flaring mouth portion (Depth D2), as indicated in double-dot
chain lines (see also Fig. 21).
Aa best shown in Fig. 20, the outer portion l2bb of the
cutter member 12b~ is gradually reduced in thickness away from
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the center of the outer portion toward the respective edges
l2bbe for facilitating the mowing of weeds. It should be
noted that the free end l2bc of the outer portion l2bb is
rendered round. With such an arrangement, it is possible to
reduce: the impact exerted on the outer portion l2bb upon
hitting against a hard object.
Referring now to Fig. 22, each bore llb formed in the
relevant protrusion of the holder 11 has the same
configuration as that of the bore 12c shown in Fig. 19.
Specifically, the total depth dl of the bore llb may be about
2lmm. The flaring mouth portion of the bore llb may have a
maximtun width wl of about 6mm and a depth d2 of about 7mm.
The remaining portion of the bare llb may have a depth d3 of
about 14mm and a constant diameter for snugly receiving the
inner end l2ab of the deformable member 12a. Thus, within
this remaining portion, the deformable member 12a is
unmovable. On the other hand, the deforrnable member 12a is
able to shift w~.thin the flaring mouth portion of the bore
llb, <~s indicated by double-dot chain lines.
According to the ninth embodiment, the rotary cutter lOH
may be rotated at a speed of about S,OOOrpm, which renders the
circutnferential speed of the rotary cutter lOH to be about
2401an/h. For attaining required rotational speeds, an engine
having a displacement volume of about 20cc may be used when
the t;wo covers 13, 14 have a diameter of 9 inches (about
230mm). When the two covers 13, 14 have a diameter of 10
inches (about 2~~4mm), use may be made of an engine whose
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displacement volume is about 30cc.
In addition to the above-described advantages obtainable
by the previous embodiments, the rotary cutter lOH of the
ninth embodiment also enjoys the following advantages.
R~=ferring to Figs.. 23 and 24, when a cutter member 12b
hits capon a rather large stone S1, the deformable member 12a
may seem to be sharply bent at a portion indicated by an arrow
J1. However, as viewed locally, the bent portion J1 of the
defornnable member 12a is not bent sharp, but only gradually
bent due to the flaring mauth portion l2ca of the cutter
member 12b, as shown in Fig. 24. Thus, the bending force
acting on the deformable member. 12a will be distributed so
that the bending force does not: concentrate in a limited part
of the deformable member 12a. In this manner, the deformable
member 12a is prevented from breaking at the bending portion
J1.
When the cutter member 12b hits on a rather soft object
such as a tree slump S2, as shawn in Fig. 25, it may stick in
the soft object while the holder 11 is continued to rotate.
In such an instance, as shown in phantom, the deformable
member 12a is stretched, so that it seems to be sharply bent
at the location shown by an arrow J2. As viewed locally,
however, the defc~rmable member 12a is only gradually bent at
the location J2 due to the flaring mouth portion llba of the
holder 11, as shown in Fig. 26. Thus, in this case again, the
deformable member 12a will not be broken at the bending
portion J2.
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Reference is now made to Figs. 27 and 28 illustrating a
rotary mowing cutter l0I according to a tenth embodiment of
the present invention. In this embodiment, the rotary cutter
l0I includes a holder 30 to which three cutting elements are
attached. The holder 30 is provided With a body 31 and three
pivota'.ble disks 3':'.. The body 3:1 is formed with a center hole
30a inta which a drive shaft knot shown) is fitted. The
pivotable disks 3~' are regularly spaced from each other around
the center hole 30a. The balder 30 is provided with three
1p protrusions corresponding to the pivotable disks 32. Each
protrusion is formed with a through-hole 31a for rotatably
receiving a respective one of the pivotable disks 32.
shown in Fig. 27, each protrusion of the holder 30 is
formed with a cutout for exposing part of the pivotable disk
32 in the radially outward direction of the center hole 30a.
The d~aformable members 12a of the respective cutting elements
are fitted into fixing holes 32a of the pivotable disks 32.
In this manner, as shown in Fig_ 28, each deformable member
12a is pivotable about the center of the relevant pivotable
disk 32 within a predetermined range, which is defined by the
size of the radi.ally outward cutout of the holder 30. The
holder 30 is snugly disposed between first and second covers
13 ar:~d 14. Thus, the pivotable disks 32 are prevented from
being accidentally removed from the through-holes 31a.
As shown in ~'ig. 27, each L.utting member includes a cutter
member 40 provided with a body 41 and a pivotable disk 42.
The body 41 is formed with a through-hole 41a for snugly
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receiving the pivotable disk 42. The body 41 is formed with a
cutout for exposing the pivotable disk 42 in the radially
inward direction ~~f the center hole 30a. The pivotable disk
42 is ,Formed with a fixing hole into which a deformable member
12a is fitted. With such an arrangement, as shown in Fig. 28,
the de~formable member 12a is pivotable with respect to the
body 41 of the cutter member 40 within a predetermined range
defined by the size of the radially inward cutout of the body
41.
According to the tenth embodiment, as seen from Fig. 28,
each deformable member 12a may remain straight even when the
relevant cutter member 40 hits against a hard object S1.
Thus, the deformable member 12a is prevented from breakage due
to otherwise possible stress cancentration. Further, even
when t:he deformable member 12a is bent at a portion indicated
by an arrow J1 or J2 in Fig. 28, the bending may not be severe
due to the cutout. Thus, the deformable member 12a does not
suffer from stress concentration.
A:a described above" the rotary mowing cutters and portable
power mowers according to the present invention are suitable
for mowing weeds, grasses, cereal crops, etc. without damaging
the cutters nor injuring the operator or people nearby.
