Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TILLING SHAFT FOR POWER TILLER
BACKGROUND OF THE INVENTION
Field of the Invention:
The present invention relates to a tilling shaft for
a power tiller which projects from a power transmission
case of a power tiller and is capable of easily and
speedily effecting an operation of replacing wheels and
tilling operation members having a plurality of tilling
blades.
Description of the Related Art:
Conventionally, attachments for traveling, such as
wheels, or attachments for a tilling operation, such as
tilling operation members each having a plurality of
tilling blades, are mounted on a tilling shaft which
projects from both sides of a power transmission case of
a power tiller (including a rotary type), depending on
various operating conditions. The tilling shaft in terms
of its cross section perpendicular to the axial direction
is formed in a polygonal shape, such as a hexagonal shape
or a square shape, and a polygonal shaft-insertion hole
into which the tilling shaft is inserted is provided on
the attachment side. The shaft insertion hole has such a
size that practically no rattling occurs in the tilling
shaft.
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The operation of replacing such attachments from
those designed for traveling to one designed for the
tilling operation and vice versa is effected by a single
operator on a cultivated field. When the wheels are
replaced by the tilling operation members, the operator
inclines the power tiller from one side thereof toward
the other and supports the inclined power tiller by his
or her hand, so that one wheel of the power tiller serves
as a fulcrum, and the other wheel is lifted off the
ground.
Next, the lifted wheel is removed from the tilling
shaft. This operation is effected by one hand of the
operator. Then, the operator holds the tilling operation
member with his or her hand, sets a attachment shaft
having the shaft insertion hole in the tilling operation
member in the same direction as that of the tilling
shaft, and inserts the tilling shaft into the shaft
insertion hole. A fixing pin for coupling is inserted
into the attachment shaft and the tilling shaft inserted
in its shaft insertion hole so as to fix the attachment
shaft. The above-described operation is carried out by
the procedure shown in Figs. 19 to 22.
In the above-described operation, since the operator
Constantly holds the power tiller with his or her one
hand to lift one wheel of the power tiller or the tilling
operation member from the ground, that hand is occupied.
For this reason, the replacement of attachments such as
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the wheels or the tilling operation members must be
carried out with a single hand. During this operation,
the ground is generally unstable. Further, the tilling
operation member is heavy, and imposes an excessively
large burden on the operator. Also, the replacement of
such an attachment in a state in which the power tiller
is inclined forward and the wheels or the tilling
operation members on both sides are lifted up similarly
involves a large burden on the operator.
Furthermore, since the cross sections of the tilling
shaft and the attachment shaft of the attachment are
respectively formed in a polygonal shape, such as a
hexagonal shape or a square shape, to ensure that
rattling will not occur between them, the amount of play
during insertion of the tilling shaft into the attachment
shaft of the attachment is extremely small. Therefore,
unless the shaft and the attachment are accurately
aligned with each other, the tilling shaft cannot be
inserted into the shaft insertion hole. Further, since
it is necessary to take into account the position of the
fixing pin, the attachment replacement operation is even
more difficult and troublesome, imposes physical and
mental fatigue on the operator, and cannot be easily
carried out by one operator alone.
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SUMMARY OF THE INVENTION
In view of the above, it is an object of the present
invention to provide a tilling shaft for a power tiller
which is capable of overcoming the above-described
drawbacks of the conventional art.
In accordance with a first aspect of the present
invention, there is provided a tilling shaft for a power
tiller, comprising: an insertion portion formed on a
distal end of a tilling shaft projecting from a power
transmission case of the power tiller, the insertion
portion having a substantially circular cross section; a
polygonal shaft portion formed on a proximal end of a
tilling shaft in such a manner as to continue from the
insertion portion; and a tapered portion formed at an end
portion of the polygonal shaft portion which continues to
the insertion portion such that a diameter of the tapered
portion is gradually enlarged from a distal end toward a
proximal end of the tapered portion.
In accordance with a second aspect of the present
invention, in the tilling shaft for a power tiller
according to the first aspect of the invention, the
diameter of the insertion portion is identical to the
diameter of an imaginary inscribed circle which fits
within the polygonal shaft portion.
In accordance with a third aspect of the present
invention, in the tilling shaft for a power tiller
according to the first aspect of the invention, the
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diameter of the insertion portion is slightly larger than
the diameter of an imaginary inscribed circle which fits
within the polygonal shaft portion, and a plurality of
ribbon-shaped supporting surfaces are formed on the
insertion portion in such a manner as to be flush with
respective side surfaces of the polygonal shaft portion.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. lA is a perspective view of a tilling shaft of
a type in which a polygonal shaft portion is hexagonal in
cross section, and ribbon-shaped supporting surfaces are
formed on an insertion portion;
Fig. lB is a perspective view of a tilling shaft of
a type in which the polygonal shaft portion is hexagonal
in cross section, but the supporting surface is
cylindrical;
Fig. 2 is a side elevational view of a power tiller;
Fig. 3 is a perspective view illustrating essential
portions of a tilling shaft and an attachment shaft;
Fig. 4A is a plan view of an essential portion of
the tilling shaft;
Fig. 4B is a cross-sectional view taken along line
Pl - Pl in Fig. 4A;
Fig. 4C is an enlarged view of an essential portion
of Fig. 4B;
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Fig. 5A is a plan view, partially in cross-section,
illustrating the attachment shaft as it is about to be
fitted over the tilling shaft;
Fig. 5B is a cross-sectional view taken along line
P2 - P2 in Fig. 5A;
Fig. 5C is an end face view taken along line P3 - P3
in Fig. 5A;
Fig. 6A iS a plan view, partially in cross-section,
illustrating the attachment shaft after it is fitted over
the insertion portion of the tilling shaft;
Fig. 6B is a cross-sectional view taken along line
P4 - P4 in Fig. 6A;
Fig. 7A is a plan view illustrating the attachment
shaft being fitted over the insertion portion of the
tilling shaft, and aligned with the polygonal portion of
the tilling shaft;
Fig. 7B is a cross-sectional view taken along line
P5 - P5 in Fig. 7A;
Fig. 8A is a plan view illustrating the attachment
shaft fitted over the polygonal shaft portion of the
tilling shaft;
Fig. 8B is a cross-sectional view taken along line
P6 - P6 in Fig. 8A;
Fig. 8C is an enlarged cross-sectional view taken in
the direction of arrows along line P7 - P7 in Fig. 8A;
Fig. 8D is an enlarged view of a portion "T"
surrounded by dashed line in FIG. 8C;
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Fig. 9 is a perspective view illustrating the
insertion portion of the tilling shaft inserted in the
attachment shaft;
Fig. 10 is a perspective view illustrating the
insertion portion of the tilling shaft inserted in the
attachment shaft, and the attachment shaft being rotated
in the circumferential direction to align the two shafts
for further engagement;
Fig. 11 is a perspective view illustrating the
polygonal shaft portion of the tilling shaft inserted in
the attachment shaft;
Fig. 12 is a perspective view illustrating a fixing
pin that is about to be inserted into a bore in the
tilling shaft and a bore in the attachment shaft;
Fig. 13A is a perspective view of a tilling shaft of
a type in which the polygonal shaft portion is square in
cross section, and the ribbon-shaped supporting surfaces
are formed on the insertion portion;
Fig. 13B is a perspective view of a tilling shaft of
a type in which the polygonal shaft portion is square in
cross section, but on the insertion portion is
cylindrical;
Fig. 14A is a perspective view of a tilling shaft in
which the polygonal shaft portion is triangular in cross
section;
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Fig. 14B is a perspective view of a tilling shaft in
which the polygonal shaft portion is pentagonal in cross
section;
Fig. 14C is a perspective view of a tilling shaft in
which the polygonal shaft portion is octagonal in cross
section;
Fig. 15 is a perspective view of a second embodiment
of the present invention;
Fig. 16A is a perspective view illustrating a
tilling operation member attachment;
Fig. 16B is a perspective view illustrating another
type of tilling operation member attachment;
Fig. 17 is a side elevational view of a power tiller
provided with a shaft drive-type mechanism;
Fig. 18 is a schematic diagram illustrating the
attachment of the power tiller being replaced;
Fig. 19 is a schematic front elevational view
illustrating the power tiller inclined with one wheel of
the power tiller serving as a fulcrum, and the other
wheel lifted from the ground so that the wheel can be
removed from the tilling shaft;
Fig. 20 is a schematic front elevational view
illustrating a tilling operation member attachment being
mounted on the tilling shaft;
Fig. 21 is a schematic front elevational view
illustrating a tilling operation member attachment
mounted on the tilling shaft; and
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Fig. 22 is a schematic front elevational view
illustrating a tilling operation member attachments
mounted on both sides of the tilling shaft.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the accompanying drawings, a
description will be given of the embodiments of the
present invention. First, an engine 1 is mounted on a
frame 2 (see FIG. 2). The driving force from the engine
1 drives a tilling shaft A located below the frame 2 by
means of a transmission mechanism including a power
transmission case 3 which encases such mechanisms as a
pulley, a belt, a chain, and the like (not illustrated).
There is also a type of power tiller in which the power
from the engine 1 is transmitted to the tilling shaft A
by means of a drive shaft (see Fig. 17).
With this type of power tiller, the axle below the
frame 2 serves as a traveling shaft 16 designed
exclusively for traveling, and tires are mounted thereon.
An operation handle 15 of this power tiller is provided
in such a manner as to be inclined rearwardly upward from
a projection or a casing portion which is provided on the
frame 2 to which the engine 1 is mounted. The angle of
the operation handle 15 can be adjusted to a plurality of
positions. The angle of the handle 15 can be fixed at a
desired position according to the height of an operator
and the operating conditions. The operating handle 15
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can therefore be set to an optimally suited position (see
Fig. 2).
The tilling shaft A is provided on the power
transmission case 3 in such a manner as to project from
each side thereof. An axially central portion of the
tilling shaft A is provided with a chain sprocket, and is
accommodated in the power transmission case 3 (see Fig.
lA). During a cultivating operation, a tilling cylinder
11 having tilling blades 12 is mounted on the tilling
shaft A to perform a tilling operation, but the power
tiller can also travel on a road if wheels are mounted
thereon. As shown in Figs. lA and lB, for example, the
tilling shaft A includes a polygonal shaft portion 4 and
an insertion portion 5 having a substantially circular
cross section.
Portions of the tilling shaft A which project from
each side of the power transmission case 3 will be
referred to as proximal ends. Although the polygonal
shaft portion 4 may be formed in various polygonal
shapes, a hexagonal shape or a square shape is
particularly suitable. A triangular shape (see Fig.
14A), a pentagonal shape (see Fig. 14B), an octagonal
shape (see Fig. 14C), or other similar shapes may also be
used as the cross-sectional shape of the polygonal shaft
portion 4. In this embodiment of the present invention,
a description will be mainly given of the example in
which the cross section of the polygonal shaft portion 4,
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which is perpendicular to the axial direction, is
hexagonal.
The insertion portion 5 is preferably circular in
cross section (see Figs. lA and lB). The insertion
portion 5 and the polygonal shaft portion 4 are of one
piece. The polygonal shaft portion 4 and the insertion
portion 5 may be formed integrally, or the insertion
portion 5 may be formed as a separate member and may be
secured to an end of the polygonal shaft portion 4 by
welding, or the like. At a boundary between the
polygonal shaft portion 4 and the insertion portion 5,
tapered portions 6 are formed in which the diameter of
the shaft is gradually enlarged from the distal end
toward the proximal end. Specifically, the tapered
portions 6 are provided at corner regions between the
polygonal shaft portion 4 and an outer peripheral surface
of the insertion portion 5 (see Figs. lA, lB, and 4A).
The diameter Dl of the insertion portion 5 is
slightly larger than the diameter D20f an imaginary
circle 4d which is inscribed within the cross section
(hexagonal cross section) of the polygonal shaft portion
4 (see Fig. 4B). A plurality of ribbon-shaped supporting
surfaces 5a which are flush with the respective side
surfaces of the polygonal shaft portion 4 are formed on
the insertion portion 5 (see Figs. lB and 4A). An
enlarged view of the ribbon-shaped supporting surfaces 5a
is shown in Fig. 4C. The imaginary inscribed circle 4d
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is indicated by a phantom line (two-dotted dash line),
while the insertion portion 5 is indicated by a solid
line. The drawing shows that the diameter of the phantom
line indicating the imaginary circle 4d is slightly
smaller than the diameter of the insertion portion 5.
The ribbon-shaped supporting surfaces 5a are located
at substantially equal intervals on the peripheral side
surface of the insertion portion 5. In the embodiment in
which the cross section of the polygonal shaft portion 4
is hexagonal, six ribbon-shaped supporting surfaces 5a
are formed on the insertion portion 5. The ribbon-shaped
supporting surfaces 5a support an attachment shaft 10 of
an attachment B, which will be described later. The
attachment shaft 10 has inner peripheral side surfaces
having a polygonal shape in cross section so that
rattling will not occur along the length of the
attachment shaft 10. An attachment bore 4a for an
attachment pin 14, which is inserted after the mounting
of the attachment B, is formed in the polygonal shaft
portion 4. Also, an attachment bore 5b is formed in the
insertion portion 5 as well, and a distal end of the
insertion portion 5 is finished by chamfering. The
ribbon-shaped supporting surfaces 5a need not necessarily
be provided on the insertion portion 5, and it is
possible to shape the insertion point 5 so that the
ribbon-shaped Supporting surfaces 5a are not required
(see Figs. lB and 13B)
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In the tilling shaft A, as for the polygonal shaft
portion 4 and the insertion portion 5 which project from
one side of the power transmission case 3, the length of
the polygonal shaft portion 4 is short and the length of
the insertion portion 5 is long in the examples shown in
Figs. lA, lB, 13A, 13B, and 14A to 14C. Specifically,
the insertion portion 5 is about twice as long as the
polygonal shaft portion 4, and the insertion portion 5 is
about 40 to 50 mm long, and the polygonal shaft portion 4
is about 20 to 25 mm long. In accordance with a second
embodiment, the polygonal shaft portion 4 is longer than
the insertion portion 5, as shown in Fig. 15. In this
case, the length of the insertion portion 5 is much
shorter than the length of the polygonal shaft portion 4.
Wheels B1 and tilling operation members B2are
included as the attachments B. The wheels B1and the
tilling operation member B2are each provided with the
attachment shaft 10 into which the polygonal shaft
portion 4 and the insertion portion 5 of the tilling
shaft A is inserted. The attachment shaft 10 is hollow,
and the inner peripheral cross section of the hollow
portion has a complementary shape to that of the
polygonal shaft portion 4. Namely, when the polygonal
shaft portion 4 is hexagonal, the hollow portion of the
attachment shaft 10 is also hexagonal, and is dimensioned
so that the polygonal shaft portion 4 can be inserted
with practically no occurrence of rattling. The wheel B
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is provided with a tire mounted to the attachment shaft
10 .
As shown in Fig. 16A, the tilling operation member
B2 is provided with the tilling cylinder 11 around the
attachment shaft 10. The cross section of the tilling
cylinder 11, is polygonal. Specifically, just like as
the polygonal shaft portion 4 it may be hexagonal, or
square, triangular, pentagonal, octagonal, or any other
useful shape. The tilling cylinder 11 is provided with
an attachment bore lla, and the attachment bore lla
corresponds to the position of an attachment bore lOa
formed in the attachment shaft 10. Brackets llb (see
FIG. 16A) are provided on the respective outer peripheral
side surfaces of the tilling cylinder 11, and the tilling
blades 12 are respectively received in the brackets llb.
As another type of the tilling operation member B2, as
shown in Fig. 16B, four tilling blades 12 are
respectively secured to corner portions of a
substantially square tilling plate 13. The
aforementioned attachment shaft 10 is secured to a
central portion of the tilling plate 13.
The ribbon-shaped supporting surfaces 5a of the
insertion portion 5 contact with inner peripheral side
surfaces of the attachment shaft 10 of the attachment B.
That is, the contact between the inner peripheral side
surfaces of the attachment shaft 10 and the polygonal
shaft portion 4 is substantially the same as the contact
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with the insertion portion 5. The structure provided is
such that rattling rarely occurs between the attachment
shaft 10 and the polygonal shaft portion 4 or the
insertion portion 5.
Next, a description will be given of the operation
in accordance with the above-described embodiments.
First, the operation of replacing the attachment B
on the tilling shaft A is generally effected by the
procedure shown in Figs. 19 to 22. First, as shown in
Fig. 18, while supporting a side surface of the power
tiller with one hand and elevating one wheel of the power
tiller from the ground while the other wheel serves as a
fulcrum, the operator removes the wheel Bl. Next, the
tilling shaft A is inserted into the attachment shaft 10
of the tilling operation member B2, starting with the
insertion portion 5 (see Figs. 3 and 5A). At this time,
it is not necessary to align the corner portions of the
polygonal shaft portion 4 with the corner portions of the
inner peripheral side surfaces of the attachment shaft
10. This condition is shown in Figs. 5B and 5C as cross
sections of the tilling shaft A and the attachment shaft
10. Figs. 6A, 6B, and 9 show the insertion portion 5 of
the tilling shaft A inserted into the attachment shaft
10. At this stage, the corner portions of the inner
peripheral side surfaces of the attachment shaft 10 and
the corner portions of the polygonal shaft portion 4 are
not aligned with each other (see Fig. 6).
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Next, while rotating the attachment B in an
appropriate manner, the side surface of the attachment
shaft 10 where the attachment bore lOa is located is
positioned to correspond to the side surface of the
tilling shaft A where the attachment bores 4a and 5b are
located, and the corner portions of the inner peripheral
side surfaces of the attachment shaft 10 are aligned with
the corresponding the corner portions of the polygonal
shaft portion 4 (see Figs. 7A, 7B, and 10). Then, the
polygonal shaft portion 4 of the tilling shaft A is
inserted into the attachment shaft 10 such that the
attachment bore lOa and the attachment bore 4a or 5b in
the tilling shaft A are aligned with each other (see
Figs. 8A, 8B, and 11).
Next, the attachment pin 14 is inserted through
attachment B. Namely, the attachment pin 14 is inserted
into the atttachment bore lOa in the attachment shaft 10
and the attachment bore 4a or 5b in the tilling shaft A,
thereby securing the attachment B to the tilling shaft A
(see Fig. 12). During the mounting operation, the inner
end of the attachment shaft 10 contacts the tapered
portions 6 of the tilling shaft A to facilitate the
circumferential rotation of the attachment shaft 10. The
operation of sliding the attachment shaft 10 over the
polygonal shaft portion 4 is then facilitated.
Further, in the case of a single-wheel power tiller,
the tilling shaft A is provided on only one side. In
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this case, the single-wheel power tiller is inclined
forward, and the attachment B is mounted on the tilling
shaft A in the same way as the above-described power
tiller.
Hereafter, a description will be given of the
advantages of the present invention.
As described above, in accordance with a first
aspect of the present invention, the tilling shaft for a
power tiller comprises: an insertion portion 5 formed on
a distal end of the tilling shaft projecting from a power
transmission case of the power tiller, the insertion
portion having a substantially circular cross section; a
polygonal shaft portion 4 formed on a proximal end of the
tilling shaft ad~acent the insertion portion; and a
tapered portion formed between an end region of the
polygonal shaft portion and the insertion portion so that
a diameter of the tapered portion is gradually enlarged
from a distal end toward a proximal end of the tapered
portion. Accordingly, the tilling shaft in accordance
with the present invention offers various advantages.
First of all, the replacement of the attachment B on the
tilling shaft can be effected very efficiently.
Secondly, the structure of the tilling shaft A is simple
despite the fact that the aforementioned operation can be
effected efficiently. Thirdly, the attachment can be
mounted easily and smoothly.
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The tilling shaft A is inserted into the attachment
shaft 10 of the attachment B, starting with the insertion
portion 5 of the tilling shaft A. Therefore, since the
insertion portion 5 has a circular cross section, the
insertion portion 5 can be easily inserted into the
attachment shaft 10. If the attachment B is only rotated
slightly in the circumferential direction when the
attachment B is fitted over the insertion portion 5, the
corner portions of the polygonal shaft portion 4 and the
corner portions of the inner peripheral side surfaces of
the attachment shaft 10 of the attachment B are brought
into alignment with each other. Subsequently, when the
attachment B is rotated to align the attachment bores
with each other, the attachment shaft 10 can be slid over
the polygonal shaft portion 4.
This operation can be effected very easily and
speedily. With a conventional type of tilling shaft,
since the tilling shaft is shaped along its entire length
in a polygonal cross section, the attachment shaft 10 of
the attachment B must be very accurately aligned with the
polygonal shaft portion from the outset of the mounting
operation. While the operator attempts to align the
corners, the operator's hand holding the attachment B
becomes fatigued due to the weight of the attachment B,
and operator becomes physically and mentally fatigued.
In contrast, with the present invention, since the
insertion portion 5 of the tilling shaft A is first
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inserted into the attachment shaft 10 of the attachment
B, the attachment B can readily slide over the distal end
of the tilling shaft A. Therefore, the operator does not
need to hold the attachment B with his or her hand. The
operator's hand engaged in the operation of replacement
of the attachment B has a much higher degree of freedom
in comparison to mounting an attachment to the
conventional type of tilling shaft. Thus, the operator
is able to effect the operation without physical or
mental fatigue.
Furthermore, in the present invention, the tilling
shaft A includes the polygonal shaft portion 4 and the
insertion portion 5, and the structure is such that the
insertion portion 5 with a circular cross section is
provided only at the distal end of the polygonal shaft
portion 4. Therefore, there are advantages in that the
shape and the structure is easy to manufacture, and that
the tilling shaft can be provided at low cost.
In addition, when the attachment shaft 10 is fitted
over the insertion portion 5, the tapered portions 6
provide a smooth transition between the insertion portion
5 and the polygonal shaft portion 4. Therefore, when the
attachment shaft 10 of the attachment B is slid over the
insertion portion 5 and then over the polygonal shaft
portion 4, the operator is able to align the attachment B
very simply and smoothly without a feeling of resistance
or impact.
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218~396
Next, in accordance with a second aspect of the
present invention, in the tilling shaft for a power
tiller in accordance with the first aspect of the
invention, the diameter of the insertion portion 5 is
identical to the diameter of an imaginary circle 4d
inscribed within the polygonal shaft portion 4.
Therefore, the operation of fitting the attachment shaft
10 of the attachment B over the insertion portion 5 of
the tilling shaft A can be effected even more easily.
Since the diameter of the insertion portion 5 is
identical to that of the imaginary inscribed circle of
the polygonal shaft portion 4, the insertion portion 5
can be readily accommodated in the hollow portion of the
attachment shaft 10. Hence, the insertion portion 5 can
be inserted easily into the attachment shaft 10 of the
attachment B, making the operation even more efficient.
Next, in accordance with a third aspect of the
present invention, in the tilling shaft for a power
tiller in accordance with the first aspect of the
invention, the diameter of the insertion portion 5 is
slightly larger than the diameter of the imaginary
inscribed circle 4d of the polygonal shaft portion 4, and
a plurality of ribbon-shaped supporting surfaces 5a are
formed on the insertion portion 5 in such a manner as to
be flush with respective side surfaces of the polygonal
shaft portion 4. Hence, the attachment B can be
supported even more stably.
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The plurality of ribbon-shaped supporting surfaces
5a provided on the periphery the insertion portion are
formed such that the diameter D1of the insertion portion
5 is slightly larger than the diameter D20f the
imaginary circle 4d, and the ribbon-shaped supporting
surfaces 5a are flush with respective side surfaces of
the polygonal shaft portion 4. Accordingly, a contact,
which is similar to that between the inner peripheral
side surfaces of the attachment shaft 10 and the outer
peripheral side surfaces of the polygonal shaft portion
4, can also be achieved between the insertion portion 5
by means of the ribbon-shaped supporting surfaces 5a.
Therefore, rattling is between the inner peripheral side
surfaces of the attachment shaft 10 and the polygonal
shaft portion 4, and the insertion portion 5 of the
tilling shaft A is minimized.
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