Note: Descriptions are shown in the official language in which they were submitted.
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KNIFE SHARPENER
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a knife sharpener.
Description of the Related Art
As a knife sharpener of this type, Unexamined Japanese
Patent Publication No. 2004-90169, for example, discloses a
device having a V-shaped sharpening groove for the blade
edge of a knife to be pressed and slid against it. More
specifically, the knife sharpener disclosed in the document
has a plurality of sharpening strips arranged to intersect
with each other in the shape of the letter V. These
sharpening strips compose the V-shaped sharpening groove
between abrasive surfaces formed in one of the sides of
each strip. According to the knife sharpener described in
the document, since the sharpening strips each have
elasticity, the burr of the blade edge is pressed by the
abrasive surfaces and the blade edge is straightened when
the knife is being sharpened. Therefore the knife can be
sharpened in a short time.
In the process of sharpening the blade edge of a knife,
there is formed in the tip end portion of the knife a
portion called a final bevel having the shape of an
isosceles triangle in section. It is preferable that the
final bevel be so finished that each side face is shaped
into a rounded convex surface. This is because if both
side faces of the final bevel are sharpened into flat
surfaces, the separability of an object to be cut is
degraded at the time of the cutting, and this makes
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difficult the handling of the knife. Furthermore, since
the final bevel is thin, a nick is easily made in the knife,
and the sharpness of the knife is deteriorated in a short
period. Consequently, the knife requires frequent
sharpening.
SUNIIHARY OF THE INVENTION
It is an object of the present invention to provide a
knife sharpener with a simple structure, which sharpens a
knife so that the knife has excellent handling and lasts in
sharpness for a long period.
In order to achieve the above object, the knife
sharpener of the present invention has at least two
sharpening strips arranged to adjoin each other in a width
direction thereof and intersect with each other at an
intersection point, the sharpening strips each being
elastically deformable and including spread portions, the
spread portions stretching from the intersecting point to
one ends of the sharpening strips and being splayed to form
a V-shaped groove having a vertex angle; abrasive surfaces
formed on one surfaces of the spread portions, respectively,
the abrasive surfaces forming side faces of said groove;
and bending means for bending the abrasive surfaces to
increase the vertex angle when a blade edge of a knife is
sharpened in said groove.
According to the knife sharpener of the present
invention, when the blade edge of the knife is pressed
against the groove, the sharpening strips are elastically
deformed and each of the abrasive surfaces is bent into a
concave shape so that the vertex angle increases. When the
knife is relatively moved in the groove with the increased
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vertex angle, a final bevel produced in a tip end of the
blade edge is so formed that both side faces thereof each
have a convex shape matching the concave shape of the
abrasive surfaces, which increases an angle of the final
bevel.
The knife sharpened with the knife sharpener of the
present invention in this manner enhances separability of
an object to be cut and enables excellent handling thereof
because both side faces of the final bevel formed in the
tip end of the blade edge are each sharpened into the
convex shape. Such a knife allows the final bevel to be
thick, so that a nick is hard to be made in the knife, and
the sharpness of the knife lasts for a long time.
In a preferred aspect, the bending means includes
fixing member fixing the other ends of the sharpening
strips, and stoppers brought into contact with the
sharpening strips to limit the maximum opening width of the
groove.
In a preferred aspect, the knife sharpener further has
a case accommodating the sharpening strips and having a
slot stretching in the width direction of the sharpening
strips. The slot receives the blade edge of the knife
movably in a direction of blade length of the knife when
the blade edge is sharpened.
In a preferred aspect, the case is formed into a box-
like shape and has a wall with the slot in shape of a
straight line formed therein and inner wall surfaces
serving as the stoppers.
In a preferred aspect, four or more the sharpening
strips are alternately arranged along the width direction
thereof.
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In a preferred aspect, the knife sharpener further
has an outer case that accommodates the case as an inner
case such that the inner case is protrudable therefrom and
serves as a holding portion during the sharpening of the
knife.
In a preferred aspect, a plurality of said grooves
are radially arranged around a rotary shaft to be rotatable
integrally with the rotary shaft, and the spread portions of
the sharpening strips are splayed in a radial outward
direction of the rotary shaft, and the knife sharpener
further has a motor for rotating the rotary shaft.
In a preferred aspect, the case is disposed to be
rotatable integrally with the rotary shaft and formed into a
cylinder-like shape. The case has a circumferential wall
with the slot in a ring shape formed therein and inner wall
surfaces serving as the stoppers.
According to one aspect of the present invention,
there is provided a knife sharpener comprising: at least two
sharpening strips arranged to adjoin each other in a width
direction thereof and intersect with each other at an
intersecting point, said sharpening strips each being
elastically deformable and including spread portions, the
spread portions stretching from the intersecting point to
one ends of said sharpening strips and being splayed to form
a V-shaped groove having a vertex angle; abrasive surfaces
formed on one surfaces of the spread portions, respectively,
said abrasive surfaces forming side faces of said groove;
and bending means for bending said abrasive surfaces to
increase the vertex angle when a blade edge of a knife is
sharpened in said groove, said bending means including a
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fixing member fixing the other ends of said sharpening
strips and stoppers brought into contact with said
sharpening strips to limit maximum opening width of said
groove.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully
understood from the detailed description given hereinbelow
and the accompanying drawings which are given by way of
illustration only, and thus, are not limitative of the
present invention, and wherein:
FIG. 1 is a perspective view showing a knife
sharpener of a first embodiment with an outer case and an
inner case thereof being partially cut away;
FIG. 2 is a plan view showing the knife sharpener
of FIG. 1 with the inner case being partially cut away;
FIGS. 3A and 3B are sectional views taken along
line III-III in FIG. 2, showing a state where an inner case
is accommodated in the outer case and a state where the
inner
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case protrudes from the outer case, respectively;
FIG. 4 is a developed view showing a sharpening member
applied to the knife sharpener of FIG. 1;
FIGS. 5A and 5B are diagrams for explaining a function
5 of stoppers in the knife sharpener of FIG. 1, and showing a
sharpening groove with and without the stoppers,
respectively;
FIG. 6 is a view showing a knife sharpened with the
knife sharpener of FIG. 1, and an enlarged sectional view
showing a blade edge and its vicinity in a circle;
FIG. 7 is a side view showing a knife sharpener of a
modification example, partially illustrated in section;
FIG. 8 is an exploded view showing the knife sharpener
of FIG. 7; and
FIG. 9 is an elevation view showing a sharpening
member applied to the knife sharpener of FIG. 7 with one
disc thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 through FIGS. 3A and 3B show a knife sharpener
of a first embodiment. The knife sharpener has an outer
case 2. The outer case 2 is formed into a box-like shape
of a rectangular parallelepiped, and yet an entire one end
face and an entire one side face of the outer case 2 are
open.
An inner case 4 is accommodated in the outer case 2 in
an embedded state and is protrudable from the open side
face of the outer case 2. The inner case 4 is formed by
bending a band plate into the shape of the letter U and has
two side wall portions 6 and one curved portion 8. The
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side wall portions 6 stretch parallel to each other along a
longitudinal direction of the outer case 2. When the inner
case 4 is accommodated in the outer case 2, one of the side
wall portions 6 is so positioned as to close the open side
face of the outer case 2. Base ends of the side wall
portions 6 are joined together with the semicircular curved
portion 8. The curved portion 8 is disposed on the other
end face side of the outer case 2.
When the inner case 4 is accommodated in the outer
case 2, tip ends of the side wall portions 6 are positioned
on the open end face side of the outer case 2. At the tip
ends of the side wall portions 6, there are formed
projections 10 and 10 projecting toward each other. A gap
formed between the projections 10 and 10 defines a slot 12.
When the inner case 4 protrudes from the outer case 2, the
slot 12 receives a knife to be sharpened such that the
knife is movable in a direction of blade length. The blade
length direction matches a width direction of the side wall
portions 6, or a longitudinal direction of the slot 12.
Disposed in the inner case 4 is a sharpening member 14,
which is formed by bending a plate material 16 shown in FIG.
4. The plate material 16 has a rectangular base portion 18
in the middle thereof, and two strip portions 20 extend
from each end of the base portion 18. A gap between the
strip portions 20 on each end of the base portion 18 is
virtually equal to the width of the strip portion 20. The
four strip portions 20 have axes parallel to each other.
The strip portions 20 are formed alternately in both the
ends of the base portion 18 with respect to the width
direction thereof.
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Each of the strip portions 20 has elasticity. There
is formed an abrasive surface 22 in one face of each of the
strip portions 20. Abrasive grains having a proper grain
diameter dispersedly adhere onto the abrasive surface 22
such that surface roughness thereof conforms to for example
a 300 grit whetstone, that is, a coarse grit whetstone.
Although a material of the abrasive grains is not
particularly limited, it is preferably diamond or titanium
nitride in consideration of its high strength.
Referring to FIG. 1 and FIGS. 3A and 3B again, in
order to make the sharpening member 14 out of the plate
material 16, the plate material 16 is bent at its
longitudinally middle portion.
To be more specific, the base portion 18 of the plate
material 16 is so bent that the abrasive surfaces 22 faces
outside, and is molded into a semicircle that is
inscribable to the curved portion 8 of the inner case 4.
Roots of the strip portions 20, which continue to the base
portion 18, are bent in the same direction as a bending
direction of the base portion 18 such that the strip
portions 20 extending from both the ends of the base
portion 18 intersect with each other as if engaged with
each other.
The sharpening member 14 made out of the plate
material 16 is accommodated in the inner case 4 in a state
where the base portion 18 is inscribed to the curved
portion 8 of the inner case 4. The strip portions 20
crossly extend between the side wall portions 6 of the
inner case 4, and tip ends of the strip portions 20 come
into contact with inner wall surfaces of the side wall
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portions 6 near roots of the projections 10. Since the
four strip portions 20 intersect with each other as if
engaged with each other, they are arranged alternately in
the width direction of the side wall portions 6, or in the
longitudinal direction of the slot 12, and positioned
adjacently to each other.
In the sharpening member 14, portions (hereinafter
referred to as spread portions) included in the strip
portions 20, which stretch from an intersecting point to
the tip ends of the strip portions 20, form a V-shaped
sharpening groove 24. The spread portions are splayed
toward the slot 12, and an opening of the sharpening groove
24 is positioned near the slot 12. The sharpening groove
24 stretches along the slot 12, and the abrasive surfaces
22 form both side faces of the sharpening groove 24.
Since the tip ends of the strip portions 20 are in
contact with inner wall surfaces of the inner case 4, the
maximum width of the opening of the sharpening groove 24 is
determined by distance between the inner wall surfaces and
is greater than the width of the slot 12. When the
sharpener is out of operation, an intersection angle
(hereinafter also referred to as a preset intersection
angle) between the strip portions 20 is determined by the
distance between the inner wall surfaces of the inner case
4.
In the outer case 2, a block 26 made of resin is
disposed on the other end face side thereof. The block 26
supports the inner case 4 and the sharpening member 14 such
that they are turnable.
To be concrete, the block 26 has a columnar shape, and
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the bent base portion 18 of the sharpening member 14 and
the bent roots of the strip portions 20 are in sliding
contact with an outer circumferential surface of the block
26. As illustrated in FIG. 2, the block 26 is fastened to
one side wall of the outer case 2 with a screw 28 and has a
flange portion 30 in one end on the screw 28 side. The
flange portion 30 is positioned between the inner case 4
and the one side wall of the outer case 2, thereby securing
a space therebetween. Disposed in this space is a leaf
spring 32, which presses the inner case 4 against a side
wall of the outer case 2, opposite to the one side wall.
In FIG. 3, reference numeral 34 represents a
collapsible stopper rod. The stopper rod 34 is disposed
between the outer case 2 and the inner case 4. Both ends
of the stopper rod 34 are hinge-jointed to the outer case 2
and the inner case 4.
A knife-sharpening method using the above-mentioned
knife sharpener will be described below.
To use the knife sharpener, the inner case 4 is first
rotated to protrude from the outer case 2. As illustrated
in FIG. 3B, the inner case 4 is brought into an upright
position such that the slot 12 is positioned on an upper
side. At this point, the inner case 4 is supported by the
stopper rod 34, which prevents undesired falling of the
inner case 4. Subsequently, the user holds down the outer
case 2 with one hand, and grasps the knife with the other.
Subsequently, while pressing a blade edge of the knife
against the sharpening groove 24 through the slot 12, the
user moves the knife back and forth several times in the
blade length direction, to thereby sharpen the blade edge.
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When the strip portions 20 are pressed by the blade
edge of the knife during the sharpening, as
diagrammatically shown in FIG. 5A, the strip portions 20
are elastically deformed and bent outward into a concave
5 shape in relation to the blade edge of the knife. In other
words, due to the pressure of the knife, an intersection
angle 0 between the strip portions 20, which corresponds to
a vertex angle of the sharpening groove, is increased
beyond the preset intersection angle determined by the
10 inner wall surfaces of the inner case 4. This is because
the roots of the strip portions 20 are fixed in the inner
case 4, and moreover the tip ends of the strip portions 20
are in contact with the inner wall surfaces of the inner
case 4.
If the blade edge is moved in the sharpening groove 24
in the state where the intersection angle 0 is beyond the
preset intersection.angle as described, a final bevel
having convex side faces is formed in the blade edge
correspondingly to the bending of the strip portions 20,
and the convex faces have a virtually involute shape. FIG.
5B diagrammatically shows the deformation of the strip
portions 20 when the knife is pressed against the
sharpening groove 24 on the assumption that the tip ends of
the strip portions 20 are not restrained by the inner wall
surfaces of the case 4. It is apparent from FIG. 5B that
if the ends of the strip portions 20 are not restrained, it
is impossible to gain the final bevel having convex side
faces.
FIG. 6 shows a knife 40 sharpened with the above-
mentioned knife sharpener. As shown in a circle of the
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figure, a final bevel 44 is formed within an area
stretching about 0.02 to 0.2 mm from a tip end of a blade
edge 42 of the knife 40. In the sharpener, according to a
preferred aspect, the preset intersection angle, elasticity
characteristic, and the like of the strip portions 20 are
so selected that an angle a of the blade edge 42 of the
knife 40 sharpened falls in a range between about 18 and 22
degrees, and that an angle (3 of the final bevel 44 between
about 28 and 32 degrees.
In case that the knife 40 is used, since both faces of
the final bevel 44 created in the blade edge 42 is formed
into the convex shape, the knife is easily separated from
an object to be cut and moreover cuts well at the time of
the cutting, compared to a knife in which both the faces of
the final bevel 44 are shaped into flat surfaces.
Furthermore, since the sharpening groove 24 splays
beyond the preset intersection angle during the sharpening,
the angle (3 of the final bevel 44 is greater than the angle
a of the blade edge 42. As a result, a nick attributable
to omission of carbide grains or the like is hard to be
made, and the sharpness of the knife is retained for a long
period. Consequently, it is not necessary to sharpen the
knife frequently.
The present invention is not limited to the first
embodiment, and various modifications can be made. For
example, the outer case 2 may be molded from resin to have
such a shape that is easily held down. It is also possible
to integrally form a holding portion in the inner case 4
without providing the outer case 2.
In the first embodiment, the inner wall surfaces of
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the inner case 4 function as the stoppers that determine
the maximum opening width of the sharpening groove 24 and
the preset intersection angle between the strip portions 20.
As stoppers, however, it is possible to provide for example
pins that can contact somewhere in the spread portions of
the strip portions 20 from the outside.
In addition, the tip ends of the strip portions 20 are
in contact with the inner wall surfaces of the inner case 4
even in the unused state, and the intersection angle 0 in
the unused state equals the preset intersection angle.
However, the preset intersection angle may be set greater
than the intersection angle 0 in the unused state by
providing an allowance between the tip ends of the strip
portions 20 and the inner wall surfaces of the inner case 4.
Although in the first embodiment, the sharpening
member 14 has the four strip portions 20 intersecting with
each other, the number of the strip portions 20 is
sufficient if there are at least two or more so that the
strip portions 20 may intersect with each other. It is
preferable, however, that the number of the strip portions
20 be four or more in order to retain the proper elasticity
characteristic in the strip portions 20 and prevent the
knife from wobbling during the sharpening at the same time.
Additionally, although the sharpening member 14 is
made of metal, a sharpening member made of resin or a
vegetable fiber may be utilized. In this case, the strip
portions and the abrasive surfaces may be integrally formed
by molding a mixture of a resin fiber or a vegetable fiber
and abrasive grains to have thickness by using a method of
manufacturing paper, self welding or an adhesive agent.
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Furthermore, it is possible to form the strip portions
in which the abrasive surfaces are integrally formed by
rolling a plurality of, for example, 400-mesh or 600-mesh
metal nets in which abrasive grains are studded on the
surfaces of wires, in a piled state to be integrated. In
this case, the thickness of the gained strip portions may
be adjusted by inserting released paper between the metal
nets.
FIGS. 7 and 8 show the knife sharpener of a second
embodiment. The knife sharpener has a motor 54 to which a
case 50 and a sharpening member 52 are integrally and
rotatably attached.
More specifically, the case 50 of the knife sharpener
has two discs 56. The discs 56 are fixed to a rotary shaft
58 of the motor 54 and are separated away from each other.
Formed in the rims of the discs 56, rim-shaped projections
60 protruding toward each other, and a gap between the
projections 60 defines the width of a slot 62. The slot 62
extends in a circumferential direction of the discs 56, or
the case 50, to have a ring-like shape.
The sharpening member 52 of the knife sharpener has a
first member 64 and a second member 66 combined together as
if engaged with each other, and a columnar spacer 68
interposed between centers of the first and second members
64 and 66. The first and second members 64 and 66 have
equilateral octagonal base portions 64a and 66a,
respectively, for sandwiching the spacer 68. Strip
portions 64b and 66b radially extend from each side of the
base portions 64a and 66a as shown in FIG. 9. Abrasive
surfaces 64c and 66c are formed in one face of each of the
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strip portions 64b and 66b, respectively.
The width of each of the strip portions 64b and 66b
corresponds to half the length of each side of the base
portions 64a and 66a. Roots of the strip portions 64b and
66b are arranged on one side of each side of the base
portions 64a and 66a so as to allow the strip portions 64b
and 66b to intersect with each other as if engaged with
each other. The roots of the strip portions 64b and 66b
are so bent that the strip portions 64b and 66b intersect
with each other. Tip ends of the strip portions 64b and
66b are in contact with inner wall surfaces of the discs 56
near roots of the projections 60.
Again in this case, spread portions of the strip
portions 64b and 66b, which stretch from the intersecting
points to the tip ends of the strip portions 64b and 66b,
form V-shaped sharpening grooves 70. The spread portions
are splayed toward the slot 62, and openings of the
sharpening grooves 70 are positioned near the projections
60. The sharpening grooves 70 are disposed at regular
intervals in a circumferential direction of the slot 62.
The abrasive surfaces 64c and 66c of the strip portions 64b
and 66b form both side faces of the sharpening grooves 70.
Again, since the tip ends of the strip portions 64b
and 66b are in contact with inner wall surfaces of the
discs 56, or inner end faces of the case 50, the maximum
width of the opening of each of the sharpening grooves 70
is determined by distance between the inner wall surfaces,
and is greater than the width of the slot 62. When the
sharpener is not in use, the preset intersection angle
between the strip portions 64b and 66b is determined by the
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distance between the inner wall surfaces of the case 50.
The discs 56, the first and second members 64 and 66,
and the spacer 68 each have a fixing hole in which the
rotary shaft 58 of the motor 54 is inserted such that they
5 cannot relatively rotated.
Reference numeral 72 denotes a protective cover, which
encloses the rotating case 50. Formed in the protective
cover 72 is an opening 74 that matches an upper half
peripheral portion of the slot 62.
10 In case that the knife sharpener of the above
modification example is used, the blade edge of the knife
is first pressed against the sharpening grooves 70 splaying
upward through the opening 74 of the protective cover 72
and the slot 62. If the motor 54 is operated with the
15 knife grasped in this state, the first and second members
64 and 66 are integrally rotation-activated together with
the case 50. The rotation causes the rotation of the
sharpening grooves 70, that is, relative movement between
the sharpening grooves 70 and the knife in the blade length
direction, which sharpens the blade edge. Accordingly, the
knife sharpener enables not only the formation of the final
bevel 44 in the blade edge but also the rapid sharpening.
The rotation speed of the motor 54 can be properly changed
using a controller which is not shown.
The invention thus described, it will be obvious that
the same may be varied in many ways. Such variations are
not to be regarded as a departure from the spirit and scope
of the invention, and all such modifications as would be
obvious to one skilled in the art are intended to be
included within the scope of the following claims.
