JP5794851B2 - Cutting blade - Google Patents

Description

  The present invention relates to a cutting blade, and more particularly to a metal cutting blade that cuts in contact with a food wrap film laid in a plane so as to be substantially orthogonal to the cutting blade.

  FIG. 6 is a perspective view of a state in which a lid of a wrap case to which a conventional cutting blade is attached is opened, and FIG. 7 is a view of a state in which a roll-shaped wrap film is accommodated in the wrap case shown in FIG. 6 is a cross-sectional view of the VII-VII line shown in FIG. 6, FIG. 8 is an enlarged view of the cutting edge of the cutting blade shown in FIG. 6 viewed from the plate thickness direction, and FIG. 10 is an end view of the IX line, FIG. 10 is a view seen from the XX line shown in FIG. 8, and FIG. 11 is a sectional view of the lap case shown in FIG. FIG. 8 is a diagram corresponding to FIG. 7.

  First, referring to FIGS. 6 and 7, the wrap case 40 is made of synthetic resin, and the storage case portion 50 and the lid portion 60 are rotatably connected to each other via a hinge portion 45. .

  The storage case portion 50 has a substantially rectangular shape in plan view and a substantially U-shaped cross-sectional shape. At the upper end of the front wall 51 of the storage case 50, there is provided a cutting blade storage 52 for storing a cutting blade 80, which will be described later, made up of cutting blade storage walls 53a and 53b erected in parallel in the front-rear direction. . A wrap made of a sheet made of a laminate of an elastic ABS resin on a synthetic rubber core containing carbon ceramic is attached to the upper surface portion, front side surface portion, and rear side surface portion of the cutting blade storage wall portion 53a. An anti-slip portion 54 is formed. The distance between the rear side surface of the cutting blade storage wall portion 53a and the front side surface portion of the cutting blade storage wall portion 53b is set to 9 mm.

  Inside the storage case 50, a wrap film roll is formed by winding a wrap film 71 formed as a belt-like sheet made of a synthetic resin such as polyethylene around the surface of a cylindrical core 72 having both ends open. 70 is rotatably held via a wrap locking member 56 inserted inside the winding core 72.

  The lid part 60 has a substantially rectangular shape in plan view and has a substantially inverted U-shaped cross section, and is formed so as to cover the upper side of the storage case part 50. A cutting blade 80 is attached to the lid portion 60 between a front wall portion 61 of the lid portion 60 and a back plate 62 formed inside the lid portion 60. The distance between the front wall 61 and the back plate 62 is set to 12 mm, and the distance between the front wall 61 and the cutting blade 80 is set to 7 mm.

  The cutting blade 80 is made of stainless steel and includes a body 81 having a strip shape and a plurality of cutting edges 82 formed in one end portion of the body 81 and formed in a sawtooth shape.

  Next, referring to FIGS. 8, 9, and 10, each of the cutting edges 82 has an acute angle shape in the shape of the distal end portion 84 as viewed from the plate thickness direction and the cross-sectional shape at the distal end position 86. .

In use, referring to FIG. 7, first, with the lid 60 opened, the end of the wrap film 71 is pulled to draw out an appropriate amount of the wrap film 71, and the wrap film 71 is cut according to the cutting position of the wrap film 71. The wrap film 71 is pushed downward in a state where it is placed on the upper ends of the blade housing walls 53a and 53b. Then, since the wrap film 71 is fixed by the wrap slip prevention portion 54, the wrap film 71 is stretched without sagging between the cutting blade storage wall portions 53a and 53b.
Referring to FIG. 11, when the lid 60 is closed from the state of FIG. 7, the wrap film 71 stretched between the cutting blade storage wall portions 53 a and 53 b is pressed against the wrap film 71 by the back plate 62. The cutting blade 80 is inserted between the cutting blade storage wall portions 53a and 53b from above the cutting blade storage portion 52 so as to be substantially orthogonal. Then, since the blade edge 82 of the cutting blade 80 is configured as described above, the blade edge 82 easily penetrates the wrap film 71 and wraps through each of the openings formed in the wrap film 71 by the penetration of the blade edge 82. The film 71 is cut in the width direction.

2005-88991

  The conventional cutting blade as described above is housed between the front wall portion of the lid and the back plate, but because the blade edge is sharp, it inadvertently injures fingers etc. when cutting the wrap film There was a fear.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a cutting blade with improved safety and durability.

In order to achieve the above-mentioned object, the invention according to claim 1 is a metal cutting blade that cuts in contact with a food wrap film laid in a plane so as to be substantially perpendicular to the food wrap film. And a plurality of cutting edges formed on one end edge of the fuselage and formed in a sawtooth shape, each of the cutting edges having a flat surface whose outer edge is parallel to the thickness direction of the fuselage, It consists of a tip part having an arc shape when viewed from the direction and a transition part connected to the tip part and increasing in thickness toward the inside, and the cutting blade is made of stainless steel or iron material and has an arc-shaped curvature. The radius is not less than 0.10 mm and not more than 0.35 mm, and one surface of the transition portion is inclined outward with respect to a first imaginary plane orthogonal to the flat surface from a position connected to the flat surface, and the tip portion The ridge line on one side and the first virtual plane at the tip position of The angle formed theta, and 10 ° or 25 ° or more or less, the other surface of the transition section is perpendicular to the planar surface, the thickness of the flat surface is 0.05mm or 0.20mm or less.
If comprised in this way, there will be no sharp part in a blade edge | tip and thickness will increase inward.

The invention according to claim 2 is a metal cutting blade that cuts in contact with a food wrap film laid in a plane so as to be substantially orthogonal to the body, and has a body having a strip shape and one end edge of the body And each of the blade edges has a flat surface whose outer edge is parallel to the plate thickness direction of the body and has an arc shape when viewed from the plate thickness direction. Part and a transition part connected to the tip part and increasing its thickness inward, the cutting blade is made of stainless steel or iron material, and the radius of curvature of the arc shape is 0.10 mm or more and 0.00. 35 mm or less, and one surface of the transition portion is inclined outward with respect to the first imaginary plane orthogonal to the flat surface from a position connecting to the flat surface, and the other surface of the transition portion is connected to the flat surface. The second virtual plane perpendicular to the flat surface Write the inclined, at the tip position of the distal end portion, one side of the ridge and the angle theta ₁ which forms a first virtual plane ridge of the other side and the second angle plus the angle theta ₂ formed between a virtual plane theta is The flat surface has a thickness of 0.05 mm or more and 0.20 mm or less.
If comprised in this way, there will be no sharp part in a blade edge | tip and thickness will increase inward.

  As described above, the invention according to claim 1 does not have a sharp portion on the blade edge, and the thickness increases inward, so that safety and durability are improved, and cutting performance is improved. .

  In the invention according to the second aspect, since there is no sharp portion on the blade edge and the thickness increases inward, safety and durability are improved, and cutting performance is improved.

It is an enlarged view of the blade edge | tip of the cutting blade by 1st Embodiment of this invention, Comprising: It is a figure corresponding to FIG. 8 of the conventional cutting blade. It is an end elevation of the II-II line shown in Drawing 1, and is a figure corresponding to Drawing 9 of the conventional cutting blade. It is the figure seen from the III-III line shown in FIG. 1, Comprising: It is a figure corresponding to FIG. 10 of the conventional cutting blade. It is the schematic diagram which showed the cutting process of the wrap film by the cutting blade shown in FIG. It is an end elevation of the cutting edge of the cutting blade by 2nd Embodiment of this invention, Comprising: It is a figure corresponding to FIG. 2 of previous 1st Embodiment. It is a perspective view of the state which opened the cover part of the lap case to which the conventional cutting blade was attached. It is sectional drawing of the VII-VII line shown in FIG. 6 in the state which accommodated the roll-shaped wrap film in the wrap case shown in FIG. It is the enlarged view seen from the plate | board thickness direction of the blade edge | tip of the cutting blade shown in FIG. FIG. 9 is an end view of the IX-IX line illustrated in FIG. 8. It is the figure seen from the XX line shown in FIG. It is sectional drawing of the state which closed the cover part of the lap case shown in FIG. 6, Comprising: It is a figure corresponding to FIG.

  FIG. 1 is an enlarged view of a cutting edge of a cutting blade according to the first embodiment of the present invention, corresponding to FIG. 8 of a conventional cutting blade, and FIG. FIG. 11 is an end view of the II line corresponding to FIG. 9 of the conventional cutting blade, and FIG. 3 is a view of the conventional cutting blade as viewed from the III-III line shown in FIG. 10 corresponds to FIG.

  First, referring to FIG. 1 and again to FIGS. 6, 7, and 8, the cutting blade 10 is replaced with a cutting blade 80 in which a cutting edge 82 is configured by the cutting edge 12. That is, the cutting blade 10 is made of stainless steel (SUS304) and includes a body 11 having a strip shape and a plurality of cutting edges 12 formed at one end of the body 11 and formed in a sawtooth shape.

  Next, referring to FIGS. 1, 2, and 3, each blade edge 12 has a flat surface 13 whose outer edge is parallel to the plate thickness direction of the body 11 and has an arc shape when viewed from the plate thickness direction. And a transition portion 15 that is connected to the distal end portion 14 and increases in thickness toward the inside of the cutting blade 10. Note that one surface 18 of the transition portion 15 is inclined outwardly from the position connecting to the flat surface 13 with respect to the first virtual plane 21 orthogonal to the flat surface 13, and the other surface 19 is relative to the flat surface 13. Orthogonal.

  If comprised in this way, there will be no sharp part in the blade edge | tip 12, and since thickness will increase inward, safety | security and durability will improve.

  The cutting blade 10 is subjected to a polishing process on a saw-toothed pre-molded body (plate thickness t: 0.4 mm) formed by stamping of a press (not shown), and the cutting edge 12 is processed as shown in FIGS. Made up of. The other surface 19 is a flat surface.

  The radius of curvature R of the tip portion 14 having an arc shape is 0.15 mm, the straight ridge line 28 (shown by a two-dot chain line in FIG. 1) of the one surface 18 at the tip position 16 of the tip portion 14 and the first virtual plane 21. Is set to 15 °, and the thickness h of the flat surface 13 is set to 0.10 mm. If comprised in this way, not only safety | security and durability but cutting property will also improve.

The distance D ₁ between the blade edges 12 is 2 mm, the distance L ₁ from the front end position 16 to the rear end position 17 of the front end portion 14 is 2.5 mm, and the distance L ₂ from the rear end position 17 to the body 11 is 1 mm. Respectively.

  FIG. 4 is a schematic view showing a process of cutting the wrap film by the cutting blade shown in FIG.

Referring to the drawing, from the position indicated by the two-dot chain line in the figure so that an appropriate amount is drawn and substantially orthogonal to the wrap film 71 stretched without sagging between the cutting blade storage walls 53a and 53b. The cutting blade 10 is inserted into a position indicated by a solid line in the figure between the cutting blade storage wall portions 53a and 53b. At this time, the distance W between the front side surface of the cutting blade storage wall portion 53a (including the wrap slip prevention portion 54) and the rear side surface portion of the cutting blade storage wall portion 53b is 5 mm, and the cutting blade storage wall portion 53b the distance _{L 3} is 3.5mm and the cutting blade 10 and the rear side surface portion, the distance between the cutting blade housing walls 53a and 53b wrap film 71 stretched between the flat surface 13 of the cutting blade 10 during insertion D ₂ is set to 6.5 mm.

  Then, as shown in FIG. 1, the radius of curvature R of the tip 14 of the cutting edge 12 of the cutting blade 10 is as small as 0.15 mm, and as shown in FIG. 2, the flat surface of the cutting edge 12 of the cutting blade 10. Since the thickness of 13 is set as thin as 0.10 mm, the cutting edge 12 easily penetrates the wrap film 71 even though there is no sharp point. And the wrap film 71 is cut | disconnected through each of the opening formed in the wrap film 71 by penetration of the blade edge | tip 12. FIG.

  FIG. 5 is an end view of the cutting edge of the cutting blade according to the second embodiment of the present invention, and corresponds to FIG. 2 of the first embodiment.

  Referring to the drawing, the cutting blade is a first virtual plane in which the transition portion 15 of the cutting edge 12 according to the first embodiment is orthogonal to the flat surface 13 from the position where the one surface 18 is connected to the flat surface 13. The other surface 19 is configured to be inclined outward with respect to the second virtual plane 22 orthogonal to the flat surface 13 from a position where the other surface 19 is connected to the flat surface 13. Has been replaced by something. The other constituent elements of the cutting blade are the same as those according to the first embodiment, and the description thereof will not be repeated here.

Here, referring to FIG. 1 again, the radius of curvature R of the arcuate tip 14 is set to 0.15 mm. Referring to FIG. 5, the thickness h of the flat surface 13 is 0.10 mm, and the angle θ ₁ formed by the straight ridge line 28 of the one surface 18 at the tip position 16 of the tip and the first virtual plane 21. Is set to 10 °, and the angle θ ₂ formed by the straight ridge line 29 of the other surface 19 and the second virtual plane 22 is set to 5 °, respectively, and the angle θ obtained by adding θ ₁ and θ ₂ is 15 It is °. If comprised in this way, not only safety | security and durability but cutting property will also improve.

  In each of the above embodiments, the cutting blade is made of stainless steel, but may be made of other metals.

  Further, in each of the above embodiments, the cutting blade is formed by subjecting a saw-toothed pre-molded body molded by stamping molding to a polishing process, but other mold molding or the like. You may shape | mold by a manufacturing method.

  Further, in each of the above embodiments, the ridge line on one surface at the tip position of the tip portion and the ridge line on the other surface in the second embodiment are both linear, but may be curved. Good.

  Further, in each of the above-described embodiments, the radius of curvature of the tip and the thickness of the flat surface are set to specific values, but may be set to other values as long as safety and durability can be maintained.

  Furthermore, in the first embodiment described above, the angle formed by the ridge line of one surface at the tip position of the tip portion and the first virtual plane is set to a specific numerical value. However, if safety and cutting performance can be maintained. Other numerical values may be set.

  Furthermore, in the second embodiment, the angle formed by the ridge line on one surface and the first virtual plane at the tip position of the tip and the angle formed by the ridge line on the other surface and the second virtual plane are set to specific numerical values. However, it may be set to other numerical values as long as safety and cutting performance can be maintained.

  As described above, the cutting blade 10 includes a tip portion 14 in which each of the blade edges 12 has a flat surface 13 whose outer edge is parallel to the plate thickness direction of the body 11 and has an arc shape when viewed from the plate thickness direction. If it is comprised from the transition part 15 which is connected to 14 and the thickness increases toward inward, safety | security and durability will improve.

  However, even with the cutting blade 10 having such a configuration, if the radius of curvature is too large, the cutting edge 12 is difficult to penetrate the wrap film and the cutting performance is degraded. It becomes weaker and durability is lowered.

  Further, if the angle of the blade edge including the angle formed by the one surface 18 and the first virtual plane 21 and the angle formed by the other surface 19 and the second virtual plane 22 is too small, the blade edge 12 becomes too sharp and safety is improved. On the other hand, if the blade edge angle is too large, the blade edge 12 is difficult to penetrate the wrap film and the cutting performance is lowered.

  Furthermore, if the thickness of the flat surface 13 is too small, the cutting edge 12 becomes too sharp and the thickness of the transition portion 15 on the tip portion 14 side becomes thin, so that safety and durability are lowered, while the thickness of the flat surface 13 is reduced. If the thickness is too large, the cutting edge 12 will not easily penetrate the wrap film, and the cutting performance will deteriorate.

  Therefore, an experiment was conducted to examine the degree of influence on the quality of the cutting blade 10 by the radius of curvature, the blade edge angle, and the thickness of the flat surface 13.

First, in the experiment, in the cutting blade according to the first embodiment shown in FIGS. 1 and 2, samples in which the radius of curvature, the edge angle, and the thickness of the flat surface are set to specific values are shown in Table 1 to be described later. To determine whether cutting, safety, and durability are good or bad.
1. Experiments on cutting performance (1) Measurement conditions In the following products, etc., with the lid of the wrap case with the sample attached open, grasp the end of the wrap film with one hand and pull it out about 40 cm. Tension is applied between the cutting blade storage units. Thereafter, the wrap film is cut by closing the lid of the wrap case.
Lap Case: Lap Cutter Saving Master (Life Toe Co., Ltd.)
Wrap film: NEW poly wrap regular (polyethylene): width 30cm, length 50m (manufactured by Ube Film Co., Ltd.)
(2) Measurement Criteria The case where the cutting of the wrap film in the width direction was completely performed by the cutting blade was normal, the result of performing the above-described cutting operation 50 times was determined to be acceptable, and 50 times In cutting, even a part of the wrap film having a defective cutting area that was not cut by the cutting blade is rejected.
2. Experiments on safety (1) Measurement conditions During the experiment on cutting performance, the pain felt when the fingers of both hands touch the sample and the same person as the one who performed the experiment have the following curvature radius, cutting edge angle, flatness The pain to be felt when contacting the cutting blade for judgment reference according to the first embodiment set to the thickness of the surface is compared.
Curvature radius: 0.05mm
Cutting edge angle: 17 °
Flat surface thickness: 0.01mm
(2) Measurement criteria Acceptance is less than the pain felt on the cutting blade for the judgment criterion, and rejected if the pain felt on the cutting blade for the judgment criterion is equal to or higher than that felt. To do.
3. Experiment for durability (1) Measurement conditions In the following products and the like, the aluminum foil is cut in the same procedure as the cutting test using a roll-shaped aluminum foil instead of the wrap film.
Aluminum foil: width 30cm, thickness 11μm
(2) Measurement criteria The case where the cutting in the width direction of the aluminum foil was completely performed with the cutting blade was normal, and the result of performing the cutting operation 100 times was regarded as normal, and in 100 times cutting Any part of the aluminum foil that had a defective cutting area that was not cut by the cutting blade is rejected.

  The following table shows the determination results of each experiment for each sample.

４．切断性に対する実験の測定結果
上記の表の「切断性」の列を参照して、切断動作を５０回行った結果全てが正常であったものには○印を、５０回の切断において、ラップフィルムの一部でも切断刃により切断されなかった切断不良の領域があったものには×印を付けている。

4). Measurement result of experiment on cutting performance Referring to the column of “cutting performance” in the above table, a circle mark is given to those in which all the cutting operations were normal 50 times, and wrapping was performed in 50 cuttings. Even if a part of the film had a defective cutting area that was not cut by the cutting blade, a cross was marked.

  The following contents were found from the measurement results.

  In the cutting blade according to the first embodiment, the one with the radius of curvature set to 0.40 mm, the edge angle of 15 °, and the flat surface thickness set to 0.10 mm (Comparative Example 1) has poor cutting performance. Yes. This seems to be due to the dispersion of the force applied from the blade edge to the wrap film as the radius of curvature increases.

  In addition, in the case where the radius of curvature is set to 0.15 mm, the edge angle is set to 30 °, and the thickness of the flat surface is set to 0.10 mm (Comparative Example 4), the cutting performance is lowered. This seems to be due to the fact that the cutting edge becomes difficult to penetrate the wrap film as the cutting edge angle increases.

  Furthermore, the cutting ability is lowered in the case where the radius of curvature is set to 0.15 mm, the edge angle is set to 10 °, and the thickness of the flat surface is set to 0.30 mm (Comparative Example 6). This seems to be due to the fact that the force applied from the cutting edge to the wrap film is dispersed with the increase in the thickness of the flat surface.

The maximum value of the radius of curvature of the cutting blade is 0.35 mm, the maximum value of the blade edge angle is 25 °, and the maximum value of the thickness of the flat surface is 0.20 mm when the cutting properties in all samples are not deteriorated. It is.
5. Measured results of experiment on safety Referring to the column of “Safety” in the table above, ○ is marked for those whose pain is less than the pain felt for the judgment standard cutting blade, and the judgment standard cutting blade Those who felt pain equal to or greater than the pain felt in are marked with a cross.

  The following contents were found from the measurement results.

  In the cutting blade according to the first embodiment, the one with the radius of curvature set to 0.15 mm, the edge angle of 8 °, and the flat surface thickness set to 0.10 mm (Comparative Example 3) has reduced safety. Yes. This seems to be caused by the sharpness of the blade edge in the thickness direction as the blade edge angle decreases.

  In addition, the safety (Comparative Example 5) in which the radius of curvature is set to 0.15 mm, the edge angle is set to 25 °, and the thickness of the flat surface is set to 0.03 mm is deteriorated. This also seems to be due to the force concentrating on the cutting edge as the thickness of the flat surface decreases.

The minimum value of the cutting edge angle of the cutting blade when the safety of all the samples is not lowered is 10 °, and the minimum value of the thickness of the flat surface is 0.05 mm.
6). Measured results of experiments on durability Referring to the column of “Durability” in the table above, the result of performing the cutting operation 100 times was all normal. An x mark is given to a part of the foil where there was a defective cutting area that was not cut by the cutting blade.

  The following contents were found from the measurement results.

  In the cutting blade according to the first embodiment, the one in which the radius of curvature is set to 0.05 mm, the blade edge angle is set to 15 °, and the thickness of the flat surface is set to 0.10 mm (Comparative Example 2) is deteriorated in durability. Yes. This seems to be due to the fact that the cutting edge becomes weak against external force as the radius of curvature decreases.

  Moreover, the durability is lowered in the case where the curvature radius is set to 0.15 mm and the blade edge angle is set to 25 ° and the thickness of the flat surface is set to 0.03 mm (Comparative Example 5). This seems to be due to the fact that the thickness on the tip side of the transition portion becomes thinner as the thickness of the flat surface decreases.

The minimum value of the radius of curvature of the cutting blade when the durability of all the samples did not decrease is 0.10 mm, and the minimum value of the thickness of the flat surface is 0.05 mm.
7). Summary With reference to Table 1, all the samples that cleared all the above three experiments had a radius of curvature of 0.10 mm to 0.35 mm, a cutting edge angle of 10 ° to 25 °, and a flat surface thickness. Falls within the range of 0.05 mm to 0.20 mm.

  Therefore, a cutting blade having no quality problem has a radius of curvature of 0.10 mm to 0.35 mm, a cutting edge angle of 10 ° to 25 °, and a flat surface thickness of 0.05 mm to 0.20 mm. It can be said that the cutting blade falls within the following range.

  From the above, it can be said that the curvature radius of the cutting blade, the edge angle and the thickness of the flat surface are factors that greatly affect the cutting performance, safety and durability at the time of cutting the wrap film, and there are appropriate selections. The existence becomes meaningful.

  In the above experiment, the cutting blade according to the first embodiment was used, but the same result was obtained even when the cutting blade according to the second embodiment was used.

  In the above experiment, the cutting blade made of stainless steel was used, but the same result was obtained even when a cutting blade made of iron material was used.

  Further, in the above experiment, the cutting blade made of stainless steel was used. However, when the cutting blade made of aluminum alloy was used, the same result was obtained except for the durability.

DESCRIPTION OF SYMBOLS 10 ... Cutting blade 11 ... Body 12 ... Blade tip 13 ... Flat surface 14 ... Tip part 15 ... Transition part 16 ... Tip position 18 ... One side 19 ... Other side 21 ... 1st virtual plane 22 ... 2nd virtual plane 71 ... Wrap film In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

A cutting blade made of metal that cuts in contact with a food wrap film laid in a plane so as to be substantially orthogonal,
A fuselage having a strip shape;
A plurality of cutting edges formed in one end edge of the body and formed in a sawtooth shape;
Each of the cutting edges is
The outer edge has a flat surface parallel to the plate thickness direction of the body, and a tip portion having an arc shape when viewed from the plate thickness direction;
It consists of a transition part connected to the tip and increasing in thickness towards the inside,
The cutting blade is made of stainless steel or iron material,
The radius of curvature of the arc shape is 0.10 mm or more and 0.35 mm or less,
One surface of the transition portion is inclined outwardly from a position connected to the flat surface with respect to a first virtual plane orthogonal to the flat surface, and the ridge line of the one surface at the tip position of the tip portion And the first imaginary plane is at an angle θ between 10 ° and 25 °, and the other surface of the transition portion is orthogonal to the flat surface,
The thickness of the said flat surface is a cutting blade which is 0.05 mm or more and 0.20 mm or less. A cutting blade made of metal that cuts in contact with a food wrap film laid in a plane so as to be substantially orthogonal,
A fuselage having a strip shape;
A plurality of cutting edges formed in one end edge of the body and formed in a sawtooth shape;
Each of the cutting edges is
The outer edge has a flat surface parallel to the plate thickness direction of the body, and a tip portion having an arc shape when viewed from the plate thickness direction;
It consists of a transition part connected to the tip and increasing in thickness towards the inside,
The cutting blade is made of stainless steel or iron material,
The radius of curvature of the arc shape is 0.10 mm or more and 0.35 mm or less,
One surface of the transition portion is inclined outward from a position connecting to the flat surface with respect to a first virtual plane orthogonal to the flat surface, and the other surface of the transition portion is connected to the flat surface. An angle θ ₁ formed by the ridge line of the one surface and the first imaginary plane at the tip position of the tip portion, which is inclined outward from a position where the imaginary line is perpendicular to the second imaginary plane perpendicular to the flat surface. An angle θ obtained by adding an angle θ ₂ formed by the ridge line of the other surface and the second virtual plane is 10 ° or more and 25 ° or less,
The thickness of the said flat surface is a cutting blade which is 0.05 mm or more and 0.20 mm or less.

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