WO2020039867A1

WO2020039867A1 - Rotating shaver and inner blade of same

Info

Publication number: WO2020039867A1
Application number: PCT/JP2019/030017
Authority: WO
Inventors: 政秀 ▲徳▼田
Original assignee: 株式会社Ｔｏｋｕｄａ－Ａｒｄ
Priority date: 2018-08-23
Filing date: 2019-07-31
Publication date: 2020-02-27
Also published as: JP6482149B1; JP2020028500A

Abstract

[Problem] To provide a rotating shaver in which the shave quality is improved, and an inner blade of the rotating shaver. [Solution] This rotating shaver (1) comprises a discoid outer blade (10) having a plurality of slits (11) provided in the surface thereof, and an inner blade (20) configured to be capable of rotating relative to the outer blade (10) about the central axis of the outer blade (10). The outer blade (10) has a blade edge at a lower end of inner walls of each of the plurality of slits (11). The inner blade (20) has a discoid base (21), and a plurality of small blades (22) that project from the base (21) toward the outer blade (10). Each of the plurality of small blades (22) has a primary blade (23a) and a secondary blade (23b) that are provided so as to be set apart from each other. The secondary blades (23b) are provided at rotational-direction R2 distal ends of upper surfaces (22a) of the corresponding small blades (22). The primary blades (23a) are provided at positions that are closer to the base (21) and farther forward in the rotational direction R2 than the secondary blades (23b).

Description

Rotary shaver and its inner blade

The present invention relates to a rotary shaver and its inner blade.

In a rotary shaver, a disk-shaped outer blade provided with a plurality of slits on the surface and an inner blade provided inside the outer blade relatively rotate to cut a beard that has entered the slit. Some are configured as follows. The inner blade has a disk-shaped base and a plurality of small blades protruding from the base toward the inner surface of the outer blade, and each of the small blades and the inner edge of the slit are like scissors. , The beard is cut off.

Patent Documents

1 and 2 disclose examples of such a rotary shaver.

回転 In this type of rotary shaver, as shown in, for example, FIG. 8 of Patent Document 1, an acute-angled cutting edge is provided at an upper surface end of each small blade. As described in Patent Literature 1, conventionally, it is considered that the angle of the cutting edge is preferably as small as possible. Patent Literature 1 discloses that the angle of the cutting edge is reduced as much as possible while maintaining the rigidity of the small blade. The invention has been disclosed.

JP-A-2005-071002 US Patent Application Publication No. 2013/0145627

回転 By the way, there is a problem in the rotary shaver according to the background art that it is difficult to provide a sufficient shaving taste. Hereinafter, this problem will be described in detail with reference to the drawings.

FIG. 6A is a diagram showing a cross section of the rotary shaver 100 according to the background art of the present invention. As shown in FIG. 1, the rotary shaver 100 includes an outer blade 101 having a slit 102 and an inner blade 110 having a base 111 and a small blade 112. The outer blade 101 and the base 111 are each formed in a disk shape and share a central axis. The small blade 112 is formed so as to protrude upward (toward the outer blade 101) from the base 111. FIG. 6A also shows a beard H to be cut.

FIG. 6B is an enlarged view of FIG. 6A near the slit 102. As shown in the figure, the outer blade 101 has a blade edge 103 at the lower end of the inner wall of the slit 102. The small blade 112 has a cutting edge 114 having an angle α at the tip of the upper surface 113 in the rotation direction R.

スプリング A spring (not shown) is provided between the inner blade 110 and the housing of the rotary shaver 100. This spring serves to press the upper surface 113 of the small blade 112 against the lower surface of the outer blade 101 by urging the inner blade 110 in the direction A (upward) shown in FIG. However, if the pressing force is too strong, the rotation of the inner blade 110 is hindered. Therefore, the biasing force of the spring is set to be weak.

The inner blade 110 is configured to perform a rotational movement about the center axis of the outer blade 101 relative to the outer blade 101. The rotation direction R shown in FIG. 6A indicates the direction of this rotational movement. When the inner blade 110 rotates relative to the outer blade 101, the cutting edge 114 and the cutting edge 103 engage like two blades forming scissors. The beard H that has entered the slit 102 is cut by the blade edge 114 and the blade edge 103 thus engaged.

とき When the beard H is sandwiched between the

blade edges

103 and 114, a force in the illustrated direction B (downward) is applied to the inner blade 110. Since the biasing force of the above-described spring is not strong enough to cancel the force in the direction B, when the force in the direction B is applied, as shown in FIG. A gap G is formed between the lower surface and the lower surface. Further, with the rotation of the inner blade 110, the beard is pulled in the rotating direction and falls down. As a result, the force for cutting the beard H is weakened, and the user perceives that the shaving taste is low.

Therefore, one of the objects of the present invention is to provide a rotary shaver with improved shaving taste and an inner blade thereof.

The rotary shaver according to the present invention includes a disk-shaped outer blade provided with a plurality of slits on a surface thereof, and an inner blade configured to be relatively rotatable with respect to the outer blade about a center axis of the outer blade as a rotation axis. The outer blade has a cutting edge at a lower end of the inner wall of each of the plurality of slits, and the inner blade has a disk-shaped base and a plurality of blades protruding from the base toward the outer blade. Each of the plurality of small blades has first and second cutting edges provided separately from each other, and the second cutting edge is provided on an upper surface of the corresponding small blade. The first shaving edge is a rotary shaver that is provided at a tip in a rotating direction and is provided closer to the base than the second cutting edge and at a position forward in the rotating direction.

Further, the inner blade of the rotary shaver according to the present invention has a center axis of a disk-shaped outer blade having a blade edge at a lower end of each of a plurality of slits provided on the surface, and the center axis of the outer blade is relatively to the outer blade. An inner blade of a rotary shaver configured to be rotatable, comprising a disk-shaped base, and a plurality of small blades protruding from the base toward the outer blade, wherein the plurality of small blades are Each has a first and a second cutting edge provided separately from each other, the second cutting edge is provided at the tip of the upper surface of the corresponding small blade in the rotation direction, and the first cutting edge is An inner blade of a rotary shaver provided closer to the base than the second blade edge and at a position forward in the rotation direction.

According to the present invention, first, the first blade bites into the beard and pulls the beard downward. Next, when the blades of the second blade and the outer blade start cutting the beard, the inner blade and the outer blade come into close contact with each other due to the force of the skin to return the beard once lowered. In addition, the beard can be prevented from falling by sufficiently shortening the distance in the rotation direction between the first blade edge and the second blade edge. Therefore, it is possible to provide a rotary shaver having improved shaving taste and an inner blade thereof.

In the rotary shaver or the inner blade thereof, the first cutting edge may be formed at 90 degrees, and the second cutting edge may be formed at an angle smaller than the first cutting edge. According to this, the lowering of the beard by the first blade and the cutting of the beard by the second blade can be suitably performed.

In the rotary shaver or the inner blade thereof, the first and second cutting edges may be formed by forming an integral stainless steel by forging and then smoothing the corresponding upper surface. According to this, since the distance in the rotation direction between the first blade and the second blade can be reduced, it is possible to prevent the first blade from pulling the beard too much. Therefore, it is possible to prevent the user from feeling pain. In addition, since one piece of stainless steel is used, high durability can be obtained. Preferably, the smoothing is specifically performed by polishing or transferring the shape of the lower surface of the outer cutter to the upper surface by electric discharge machining.

In the above-mentioned rotary shaver or the inner blade thereof, the shaping is performed by forging two adjacent regions of a surface of the corresponding small blade positioned forward in the rotation direction at different depths by forging. It may be executed. According to this, the first cutting edge formed between the two regions can be formed with high accuracy.

According to the present invention, first, the first blade bites into the beard and pulls the beard downward. Next, when the second cutting edge starts cutting the beard, the inner blade and the outer blade come into close contact with each other due to the force of the skin that attempts to return the beard once lowered. In addition, the beard can be prevented from falling by sufficiently shortening the distance in the rotation direction between the first blade edge and the second blade edge. Therefore, it is possible to provide a rotary shaver having improved shaving taste and an inner blade thereof.

It is a figure showing appearance of rotary type shaver 1 by an embodiment of the invention. FIG. 2 is an exploded perspective view showing an outer blade 10 and an inner blade 20 arranged in a head unit 3 shown in FIG. 1. (A) is a top view of the inner cutter 20 shown in FIG. 2, and (b) is a side view of the inner cutter 20 shown in FIG. FIG. 3 is a diagram schematically showing a result of observing a slit 11a shown in FIG. 2 from above with a microscope. (A) is a figure which shows the cross section of the rotary shaver 1 shown in FIG. 1, (b) is a figure which expands (a) in the vicinity of the slit 11. FIG. (A) is a figure which shows the cross section of the rotary shaver 100 by a background art, (b) is the figure which expanded (a) in the vicinity of the slit 102.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a view showing an appearance of a rotary shaver 1 according to an embodiment of the present invention. As shown in FIG. 1, the rotary shaver 1 includes a substantially cylindrical main body 2 and a head unit 3 installed at an upper end of the main body 2.

The main body 2 is formed of, for example, a resin and has a shape that can be easily held by a user with one hand. The user normally uses the rotary shaver 1 while holding the main unit 2 with one hand and holding the head unit 3 against the chin. Although not shown, inside the main body 2, a motor for rotating the outer blade 10 and the inner blade 20 (see FIG. 2) in the head portion 3, a battery for supplying power to the motor, And a circuit board including a control circuit for controlling the operation of the motor. A power button 4 is disposed on a side surface of the main body 2, and the control circuit starts driving the motor when the user presses the power button 4 while the motor is stopped. When the user presses the power button 4, the motor stops driving.

The head portion 3 is a member having a structure in which a disk-shaped outer blade 10 is disposed at each of the three vertices of a triangle, and is connected to the main body 2 via a connection member (not shown). The connection member serves to connect the main body 2 and the head 3 so that the head 3 can swing and move up and down with respect to the main body 2. Further, the connection member is configured to enable the user to replace the head unit 3. The housing of the head unit 3 is formed of, for example, a resin, similarly to the main body 2.

FIG. 2 is an exploded perspective view showing the outer cutter 10 and the inner cutter 20 arranged in the head unit 3. FIG. Although FIG. 1 shows only one outer blade 10 and the inner blade 20 formed inside the outer blade 10, the same applies to the other two outer blades 10 and the corresponding inner blades 20. As shown in the figure, the outer blade 10 is a disk-shaped (more specifically, a cylindrical shape with a bottom), and the inner blade 20 is a member formed by connecting a cylindrical member below a disk-shaped member. It is a member. Each member of the outer blade 10 and the inner blade 20 is arranged so as to share a central axis. The outer cutter 10 and the inner cutter 20 are both formed of a rigid body such as stainless steel (more specifically, for example, a martensitic stainless steel represented by SUS420J2, for example).

The inner cutter 20 is configured to be rotatable relative to the outer cutter 10 around the shared central axis as a rotation axis by driving the above-described motor. More specifically, the inner blade 20 is configured to rotate in the illustrated rotation direction R2, and the outer blade 10 is configured to rotate in the illustrated rotation direction R1 (the direction opposite to the rotation direction R2) with the shared central axis as the rotation axis. You. Therefore, the rotation speed of the inner cutter 20 with respect to the outer cutter 10 is a speed obtained by adding these rotation speeds (the rotation speed with respect to the main body 2).

The shape of the outer cutter 10 will be specifically described. The surface of the outer cutter 10 corresponding to the bottom of the bottomed cylinder (hereinafter referred to as the “upper surface” of the outer cutter 10) includes a plurality of slits 11a to 11d. Are provided. Each of the plurality of slits 11a to 11d penetrates the upper surface of the outer blade 10, and although not shown, has a cutting edge at the lower end (inner edge) of each inner wall. The angle of the cutting edge is, for example, 90 °. The upper surface of the outer cutter 10 is divided into three regions by two concentric circles centered on the center axis of the outer cutter 10, and the outermost region (hereinafter, referred to as “outer annular region”) has a slit. Slits 11c and 11d are formed in the second region from the outside (hereinafter referred to as "inner annular region") 11a and 11b.

The plurality of slits 11a are substantially linear grooves formed to be slightly inclined with respect to the radial direction from the side surface of the outer cutter 10 to the inner periphery of the outer annular region, and are provided at equal intervals along the circumferential direction. Can be Specifically, when viewed in the rotation direction R1, the end on the side surface of the outer cutter 10 is located behind the end on the inner peripheral side of the outer annular region. Each slit 11a is not strictly a straight line, but is formed so as to be curved so that the central portion slightly swells forward in the rotation direction R1. The specific number of the slits 11a is, for example, 45, and in this case, the installation interval between the slits is 8 °.

The plurality of slits 11b are substantially linear grooves provided one by one between two adjacent slits 11b. Each slit 11b is provided along the adjacent slit 11a, and therefore has the same inclined and curved shape as the slit 11a. However, the end of the slit 11b located on the inner peripheral side of the outer annular region is located slightly outside (the position close to the side surface of the outer cutter 10) that of the slit 11a. It is shorter than the entire length of the slit 11a.

The plurality of slits 11c are substantially linear grooves formed slightly inclining with respect to the radial direction from the outer periphery of the inner annular region to the inner periphery of the inner annular region. The plurality of slits 11c are arranged, for example, in units of sets each including four, and each set is provided at equal intervals along the circumferential direction. The specific number of sets of the slits 11c is, for example, five, and in this case, the installation interval of each set is 72 °. Each slit 11c has the same inclined and curved shape as the slit 11a, and is arranged in each set at equal intervals along the circumferential direction.

The plurality of slits 11d are a plurality of circular holes arranged between sets of the slits 11c, and are arranged in a zigzag manner in a circumferential direction between two sets adjacent to each other.

Next, the shape of the inner blade 20 will be specifically described. The inner blade 20 has a disk-shaped base 21 and a plurality of small blades 22 protruding from the base 21 toward the outer blade 10. Be composed. Each of the small blades 22 has an upper surface 22a which is smoothed so as to be parallel to the base 21.

スプリング A spring (not shown) is provided between the inner blade 20 and the housing of the head unit 3 (see FIG. 1). The spring urges the inner blade 20 in an upward direction (a direction toward the outer blade 10; a direction A shown in FIG. 5A described later) so that the upper surface 22a of the small blade 22 is moved to the lower surface of the outer blade 10. Plays a pressing role. However, if the pressing force is too strong, the rotation of the inner blade 20 is hindered, so that the biasing force of the spring is set to be weak.

FIG. 3A is a top view of the inner cutter 20, and FIG. 3B is a side view of the inner cutter 20. As shown in these figures, the plurality of small blades 22 are arranged in two rows along the circumference of the base 21. The inner row corresponds to the slits 11c and 11d of the outer blade 10, and has a configuration in which seven small blades 22 are arranged at equal intervals. The outer row corresponds to the

slits

11a and 11b of the outer blade 10, and has a configuration in which 14 small blades 22 are arranged at equal intervals. Each of the small blades 22 is formed so as to project obliquely at an angle θ from the surface of the base 21. θ is the angle between the rotation direction R2 and the direction in which the small blade 22 projects, and is, for example, 65 °.

Each of the small blades 22 forms a substantially U-shaped groove in a circular stainless steel, and uses a forging process and a smoothing process on a tip formed as a result thereof to form a cutting edge (a primary blade 23a and a secondary blade 23b described later). Is formed, a portion corresponding to the root of the small blade 22 is bent to an angle θ. The method of forming the primary blade 23a and the secondary blade 23b will be described later in more detail. As understood from FIGS. 3A and 3B, the primary blade 23a and the secondary blade 23b are each formed in a straight line orthogonal to the rotation direction R2.

FIG. 4 is a view schematically showing the result of observing the slit 11a from above with a microscope. As described above, since the slit 11a is inclined with respect to the radial direction and has a curved shape, when viewed with a microscope, the inner wall of the slit 11a (and the cutting edge formed at the lower end thereof) and the small blade 22 are formed. The cutting edge is not parallel, but is oblique as shown in FIG. Thus, when the outer blade 10 rotates in the rotation direction R1 and the inner blade 20 rotates in the rotation direction R2, the cutting edge of the small blade 22 (specifically, the secondary blade 23b) and the cutting edge formed at the lower end of the slit 11a. (A cutting edge 12 shown in FIG. 5B described later) gradually overlaps from the end near the shared central axis, and as a result, cutting like scissors is realized. The same applies to the slits 11b to 11d.

FIG. 5A is a diagram showing a cross section of the rotary shaver 1. FIG. 2 also shows a beard H of the user to be cut. FIG. 5B is an enlarged view of FIG. 5A near the slit 11. In these figures, only one blade 22 and slit 11 are shown. In the following, the description will be continued focusing on the illustrated blade 22 and slit 11, but the other blade 22 and slit 11 will be described. The same is true.

小 As shown in FIG. 5A, the small blade 22 includes a primary blade 23a (first blade) and a secondary blade 23b (second blade) provided separately from each other. The secondary blade 23b is formed at an angle θ at the tip of the upper surface 22a of the small blade 22 in the rotation direction R2, as shown in FIG. 5B. On the other hand, the primary blade 23a is formed at a position closer to the base 21 and at a position 90 degrees ahead of the secondary blade 23b when viewed in the rotation direction R2. The position forward in the rotation direction R2 means that the position Ta in the circumferential direction of the illustrated primary blade 23a is ahead of the position Tb in the circumferential direction of the secondary blade 23b in the rotation direction R2. Means

形成 A method for forming the primary blade 23a and the secondary blade 23b will be described in detail. The primary blade 23a and the secondary blade 23b are formed by forming an integral stainless steel by forging and then smoothing the upper surface 22a of the small blade 22. Forming by forging is performed by forging two adjacent areas A1 and A2 of the surface 22b located forward in the rotation direction R2 of the small blade 22 at different depths by forging.

More specifically, the region A2 is a rectangular region having the upper edge of the surface 22b before forging / smoothing as one side. The area A1 is a rectangular area having one side on the lower side of the rectangular area A2 (one side opposed to the above-described upper edge). In the forging process, the region A2 is pressed into the depth D2 and the region A1 is pressed at a depth D1 shallower than the depth D2 perpendicularly to the surface 22b. By doing so, first, the primary blade 23a is formed at the boundary between the region A1 and the region A2.

At this stage, an edge 23c that appears to have a shape similar to the primary blade 23a at first glance is formed below the region A1, but it is difficult to form the edge 23c sharply in an actual forging process. The edge 23c cannot be expected to function as a cutting edge. Stated another way, in order to form the primary blade 23a, forging using the two-step depth as described above is essential.

位置 The position of the primary blade 23a in the rotation direction R2 is set ahead of the edge 23c. That is, the formation of the primary blade 23a is performed such that the circumferential position Ta of the illustrated primary blade 23a is ahead of the circumferential position Tc of the edge 23c when viewed in the rotation direction R2. This is because the primary blade 23a is brought into contact with the beard H before the edge 23c whose shape is not determined comes into contact with the beard H.

After the forging process, the upper surface 22a of the small blade 22 is smoothed. At this time, the upper surface 22a is smoothed so that the upper surface 22a and the surface 22b of the small blade 22 form an angle θ. Thereby, the secondary blade 23b having the angle θ is formed, and finally (after the root of the small blade 22 is bent to the angle θ), the upper surface 22a is parallel to the base 21 and the lower surface of the outer blade 10. . Note that the smoothing step may be performed after the root of the small blade 22 is bent.

Here, in the smoothing, the shape of the upper surface 22a of the small blade 22 is formed along the lower surface of the outer blade 10 (that is, the clearance between the upper surface 22a of the small blade 22 and the lower surface of the outer blade 10 is constant). And is typically performed by polishing. However, when the lower surface of the outer cutter 10 is a curved surface or the like, electric discharge machining may be used instead of polishing. That is, a shape electrode having a shape corresponding to the shape of the lower surface of the outer blade 10 is formed, and the shape of the lower surface of the outer blade 10 is transferred to the upper surface 22a of the small blade 22 by performing electric discharge machining using the shape electrode. You may do it.

Hereinafter, the effects provided by the rotary shaver 1 and the inner blade 20 thereof according to the present invention will be described in detail with reference to FIGS. 5 (a) and 5 (b).

When the user uses the rotary shaver 1, the user's beard H enters the slit 11 as shown in FIG. In this state, when each of the inner blade 20 and the outer blade 10 rotates under the control of the control circuit described above, the primary blade 23a first bites into the beard H, and pulls down the beard H in the illustrated direction C (downward). Next, when the secondary blade 23b and the blade edge 12 of the outer blade 10 start cutting the beard H, the inner blade 20 is lifted in the illustrated direction D (upward) by the force of the skin to return the beard H once lowered. As a result, the inner cutter 20 and the outer cutter 10 come into close contact with each other. Therefore, according to the rotary shaver 1 of the present invention, a gap as shown in FIG. 6 does not occur between the inner cutter 20 and the outer cutter 10.

In addition, according to the rotary shaver 1 of the present invention, since the primary blade 23a and the secondary blade 23b are formed by forging and smoothing, the distance in the rotational direction between the primary blade 23a and the secondary blade 23b. (= Ta−Tb) can be reduced. As a result, it is possible to prevent the primary blade 23a from pulling the beard too much and the beard from falling down, so that it is possible to provide a rotary shaver with improved shaving taste and an inner blade thereof. Also, it is possible to prevent the user from feeling pain.

According to the rotary shaver 1 of the present invention, since the small blades 22 are formed using integral stainless steel, high durability can be obtained.

Furthermore, according to the rotary shaver 1 according to the present invention, two adjacent areas A1 and A2 of the front surface 22b positioned forward in the rotation direction R2 of each of the small blades 22 are forged to different depths D1 and D1. Since the primary blade 23a is formed by pushing in with D2, the primary blade 23a can be formed with higher precision than when the edge 23c shown in FIG. 5B is used as the primary blade.

As described above, the preferred embodiments of the present invention have been described, but the present invention is not limited to these embodiments at all, and the present invention can be implemented in various modes without departing from the gist thereof. Of course.

DESCRIPTION OF SYMBOLS 1 Rotary shaver 2 Main body 3 Head part 4 Power button 10

Outer blade

11, 11a-11d Slit 12 Blade edge 20 of outer blade 10 Inner blade 21 Base 22 Small blade 22a Upper surface 22b of small blade 22 Surface 23a of small blade 22 Primary Blade 23b Secondary blade 23c Edge H User's beard

Claims

A disk-shaped outer blade having a plurality of slits on its surface,
An inner blade configured to be rotatable relative to the outer blade with the center axis of the outer blade as a rotation axis,
The outer blade has a cutting edge at the lower end of the inner wall of each of the plurality of slits,
The inner blade has a disk-shaped base, and a plurality of small blades projecting obliquely from the base toward the outer blade,
Each of the plurality of small blades has first and second cutting edges provided separately from each other,
The second cutting edge is provided at a tip in the rotational direction of the upper surface of the corresponding small blade,
The first cutting edge is provided closer to the base than the second cutting edge, and is provided at a position forward in the rotation direction.
The first and second cutting edges are formed by forming an integral stainless steel by forging and then smoothing the corresponding upper surface,
The molding is a rectangular region in the first surface having one side as an upper edge of the first surface positioned forward in the rotation direction of the blade before forging / smoothing. A region is pressed into the region at a second depth perpendicular to the first surface by forging, and a rectangular region in the first surface having a lower side as one side. By forging, by forging, at a first depth shallower than said second depth, perpendicular to said first surface,
The first cutting edge is formed at a boundary between the first region and the second region.
Rotary shaver.
The first cutting edge is formed at 90 degrees,
The second cutting edge is formed at an angle smaller than the first cutting edge;
The rotary shaver according to claim 1.
The smoothing is performed by polishing, or transferring the shape of the lower surface of the outer blade to the upper surface by electric discharge machining,
The rotary shaver according to claim 1.
An inner blade of a rotary shaver configured to be rotatable relative to the outer blade around a central axis of a disk-shaped outer blade having a blade edge at a lower end of each of a plurality of slits provided on the surface. And
A disk-shaped base,
A plurality of small blades projecting obliquely from the base toward the outer blade,
Each of the plurality of small blades has first and second cutting edges provided separately from each other,
The second cutting edge is provided at a tip in the rotational direction of the upper surface of the corresponding small blade,
The first cutting edge is provided closer to the base than the second cutting edge, and is provided at a position forward in the rotation direction.
The first and second cutting edges are formed by forming an integral stainless steel by forging and then smoothing the corresponding upper surface,
The molding is a rectangular region in the first surface having one side as an upper edge of the first surface positioned forward in the rotation direction of the blade before forging / smoothing. A region is pressed into the region at a second depth perpendicular to the first surface by forging, and a rectangular region in the first surface having a lower side as one side. By forging, by forging, at a first depth shallower than said second depth, perpendicular to said first surface,
The first cutting edge is formed at a boundary between the first region and the second region.
Inner blade of rotary shaver.