JP3099094B2 - Spiral knife - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blade used for a pencil sharpener or a pill remover, and more particularly to a blade having a spiral cutting edge line.

[0002]

2. Description of the Related Art The same applicant has previously proposed a spiral blade similar to the spiral blade shown in FIG. 3 by the same applicant (Japanese Patent Application No. 2-125178). This is obtained by insert-molding a spiral small blade 2 made of a stainless steel sheet along the peripheral surface of a cylindrical base 1. According to this, the productivity can be improved and the cost can be advantageously reduced as compared with conventional spiral blades in which a spiral blade is cut out of a tubular or rod-shaped blade material using a hobbing machine.

[0003]

However, in the above-mentioned spiral blade, the sharpness of the spiral blade is easily reduced due to bending deformation of the spiral blade. For example, when a spiral blade is applied to the inner blade of a rotary electric razor, the spiral blade has a tendency to bend and deform in the circumferential direction due to the shear resistance of the whiskers, and further, a radial external force applied via a mesh-shaped fixed outer blade Accordingly, the spiral blade tends to be deformed so as to fall to the side where the rake angle increases.

In order to eliminate such a tendency of deformation, it is preferable to increase the thickness of the spiral small blade and increase its deformation strength. However, when the plate thickness of the spiral small blade is increased, the sliding contact area between the spiral small blade and the outer blade is increased, and the sliding resistance is increased. Therefore, a large-sized, high-output motor is required to drive the blade. Furthermore, the spiral small blade is twisted and deformed in a spiral shape, and insert molding is performed on the base.In this case, the larger the spiral small blade, the greater the stress during torsional deformation, and the more difficult it is to maintain the posture of the spiral small blade. Processing becomes difficult as a whole, including subsequent grinding. The deformation tendency can also be eliminated by reducing the length of the spiral blade from the base. However, in this case, when the spiral blade is applied to an electric razor, problems such as the inability to introduce long beards and the tendency of cut shavings to easily blow out from the hair introduction hole of the outer blade are unavoidable, which is a practical problem. is there.

The present invention solves such a problem, and a spiral blade having a structure in which a spiral small blade made of a plurality of thin metal plates is embedded in the peripheral surface of a cylindrical base with a twist angle as described above. In the above, by improving the cross-sectional shape of the spiral small blade, the mechanical strength of the spiral small blade itself is improved without increasing the sliding contact resistance with respect to the outer blade, so that stable and excellent sharpness can be exhibited. The purpose is to:

[0006]

As shown in FIG. 1, a spiral blade according to the present invention has a blade wall 4 of a spiral small blade 2 protruding from a peripheral surface of a base 1 and an embedded blade 1 in the base 1. The boundary line with the base wall 5 is formed by bending the right side wall 7 having a predetermined length sequentially from one end to the other end in the spiral direction so as to form a multi-stage folded line, and the blade wall is formed. The cutting edge 6 of 4 is formed in a spiral curve shape that changes smoothly and continuously.

In order to bend the boundary between the blade wall 4 of the spiral small blade 2 and the embedding base wall 5 into a multi-step folding line, for example, a multi-step folding line is inserted into the base forming die during insert molding. A blade holding groove may be provided, and the spiral small blade 2 may be inserted into this groove to be bent, or may be bent in advance by a press.

[0008]

The boundary between the blade wall 4 of the spiral small blade 2 and the embedment base wall 5 is formed in a multi-step folding line, and the cutting edge 6 of the blade wall 4 is formed in a spiral curve that changes smoothly and continuously. As a result, the cross section at the boundary line is formed in a multi-stage folded line shape, and the cross section changes to a smooth curved shape as it reaches the cutting edge 6, that is, the blade wall 4 becomes a right side wall on the boundary line. 7 is formed as a continuum of the reinforcing three-dimensional surface wall 8 having the refraction point 9 as a deformation concentration point. The reinforcing three-dimensional surface wall 8 varies in the direction of the surface wall depending on the position and can increase the second moment of area,
Therefore, as compared with the conventional spiral small blade composed of a continuum having only a simple twisted surface wall, a large deformation stress is exerted against a buckling load and a bending load in a plate thickness direction.

[0009]

According to the spiral blade of the present invention, the blade edge 6 of the blade portion wall 4 of the spiral small blade 2 is formed in a spiral curve shape that changes smoothly and continuously like the conventional spiral blade edge. Since the boundary line with the embedded base wall 5 of 4 is bent into a multi-stage folded line to have rigidity,
Even when the spiral small blade 2 is formed of a thin plate, the spiral small blade 2 can stably exhibit good sharpness without bending and deformation against shear resistance and external force in the radial direction during cutting.

[0010]

1 to 4 show an embodiment of a spiral cutting tool according to the present invention. In FIG. 3, this spiral blade is formed by insert-molding a plurality of spiral blades 2 with a predetermined twist angle on the peripheral surface of a plastic cylindrical base 1. The blade wall 4 projects from the peripheral surface of the base 1, and an embedded base wall 5 is embedded in the base 1. The embedding base wall 5 is provided with holes 10 at a predetermined pitch in the entire length or a part thereof so as not to get out of the base 1. The rotating shaft 3 projects from the center of both end surfaces of the base 1, and this shaft 3 is also insert-molded at the same time as the spiral small blade 2.

At the time of insert molding, the spiral small blade 2 is formed by punching a thin stainless steel plate into a partial arc shape in advance. Then, the spiral small blade 2 inserts the blade portion wall 4 into the multi-stage folded linear groove provided along the inner surface of the cavity of the base forming die, exposing the embedded base wall 5 into the cavity. To hold. At this time,
The spiral small blade 2 is subjected to bending deformation by being passed through a spiral groove having a multi-stage folding line in a mold, and a boundary between the blade portion wall 4 and the embedding base wall 5 has a right side having a predetermined length. The section wall 7 is bent in a multi-stage folded line shape that sequentially connects the section walls 7 from one end of the spiral direction to the other end in a “<” shape, and as shown in FIG. The refraction angle θ formed by the inner wall 7 and the right side wall 7 is minimized, and the refraction angle θ increases as the cutting edge 6 is reached, so that the cutting edge 6 can be smoothly bent into a continuously changing spiral curve. I have to.

When all the spiral small blades 2 are loaded into the base forming die, the rotating shaft 3 is held in the cavity, and then the molten resin is injected into the cavity to fill it, thereby forming the base 1. At the same time, the spiral blade 2 and the rotating shaft 3 are embedded and formed, so that the spiral blade 2 having a predetermined rake angle α (see FIG. 4) and a twist angle β can be obtained. The rake angle α is set to a predetermined angle when the spiral small blade 2 is mounted on a molding die in a state of being elastically deformed by torsion, and is restored by its own deformation stress after the die is removed. The twist angle β is defined by the spiral groove of the mold.

After molding, a desired cutting edge angle is obtained only by forming a clearance angle on the cutting edge 6 of the spiral small blade 2 having a rake angle α by cylindrical polishing. In other words, after forming, the blade can be sharpened only by cylindrical polishing.

The above spiral blade is used, for example, as an inner blade of an electric razor. In this case, when the diameter of the cutting edge is 10 mm and the length of the base 1 in the axial direction is 40 mm,
The length of the right side wall 7 (the interval between the refraction points 9) was 2 mm, and the protruding length of the blade wall 4 was 1.2 mm. The thickness of the spiral blade 2 was 0.1 mm. The spiral blade 2 has a twist angle β of 1
0 to 20 °, preferably 18 °, rake angle α is 3 to 10
°, preferably 5 °. Here, the right side wall 7
The central portion between the refraction points 9.9 may be curvedly projecting with respect to a straight line connecting the refraction points 9.9 (see a broken line E shown in FIG. 5), and the extension amount is For example, when the plate thickness of the spiral small blade 2 is 0.1 mm, the amount may be smaller (60 μm) than the plate thickness. In this case, each refraction point 9 is refracted with a force of about 150 g · cm.

Further, the refraction point 9 is not limited to a point-like shape, but has a width or a surface such as a weight or a bulging shape as shown in FIG. A straight line can be formed between the refraction points 9.9 using the difference in length due to the contraction between the refraction points 9.9 due to the shape.

Further, as shown in FIG. 7, a straight rib can be bent into a multi-stage folded line by pressing the straight side wall 7 in the same manner.

As described above, the entire blade portion wall 4 of the spiral small blade 2 is torsionally deformed, and the boundary line with the embedded base wall 5 is bent into a multi-step folding line, so that the secondary moment of area is reduced. Can increase. Therefore, not only can a large deformation stress be exerted against the shear resistance (bending load) acting on the cutting edge 6, but also a large deformation stress can be exerted against an external force (buckling load) acting on the cutting edge 6 in the centripetal direction. .

In the above embodiment, the spiral small blade 2 is held in the molding die at the time of insert molding, so that the boundary line is subjected to bending deformation in a multi-stage folded line.
Instead of this, for example, a spiral small blade 2 punched from a plate material can be bent into a multi-stage folded line shape by press working.

When the spiral small blade 2 is insert-molded on the base 1 as in the above embodiment, instead of injection molding with plastic, die casting with a molten metal such as zinc or aluminum alloy can also be performed.

[Brief description of the drawings]

FIG. 1 is a perspective view in which a part of a spiral blade is cut away.

FIG. 2 is an explanatory diagram showing a cross-sectional shape of a part of a spiral small blade.

FIG. 3 is a front view of a spiral blade.

FIG. 4 is a sectional view taken along line BB in FIG. 3;

FIG. 5 is a sectional view of a right side wall portion of the spiral blade.

FIG. 6 is a perspective view of a part of a spiral small blade showing another embodiment.

FIG. 7 is a perspective view of a part of a spiral small blade showing still another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 2 Spiral small blade 4 Blade wall 5 Embedded base wall 6 Cutting edge 7 Right side wall 9 Refraction point

Claims (1)

(57) [Claims] A spiral blade in which a plurality of spiral small blades are embedded with a twist angle on a peripheral surface of a cylindrical base. , The blade wall 4 protruding from the base 1 and the embedded base wall 5
Is formed in a multi-stage fold line obtained by sequentially connecting right-side wall portions 7 having a predetermined length from one end in the spiral direction to the other end, and the cutting edge 6 of the blade portion wall 4 is smooth. A spiral cutting tool characterized by being formed in a spiral curve shape that continuously changes.