JP7464776B2 - Interdental brushes - Google Patents

Description

The present invention relates to an interdental brush used to clean between teeth.

The interdental brush includes a handle portion including a grip portion for a user to grip, a core material joined to the handle portion, and a filament bundle implanted in the core material. The core material and the handle portion are joined by, for example, insert molding. Patent Document 1 discloses an example of a conventional interdental brush.

JP 2016-104382 A

In the insert molding of interdental brushes, for example, the force applied to the core material when the resin material is fed into the mold may cause the core material placed in the mold to shift from its specified position. Interdental brushes manufactured in such a state of deviation may not have a sufficient bond between the handle and the core material, for example.
An object of the present invention is to provide an interdental brush that allows easy visual confirmation that the handle portion and the core material are properly joined by insert molding.

One form of interdental brush related to the present invention comprises a handle portion made of resin and a brush portion joined to the handle portion so as to be able to clean between the teeth, the brush portion including a core material and a filament bundle attached to the core material, the core material including a covering portion which covers the handle portion, and the handle portion including an opening which allows a portion of the covering portion to be visually observed.
Because the handle portion includes an opening, it is easy to visually confirm through the opening that the core and the handle portion are properly joined.

In one example of the interdental brush, the handle portion includes a first front surface and a second front surface extending in the longitudinal direction of the handle portion and arranged on either side of a central axis along the longitudinal direction of the handle portion, and the opening includes a first opening that opens in the first front surface and a second opening that opens in the second front surface.
It is easy to see from both the first front surface and the second front surface that the core material and the handle portion are properly joined.

In one example of the interdental brush, the handle portion further includes a partition wall formed to separate the first opening and the second opening, and the covering portion is joined to the partition wall.
This allows the handle portion and the core material to be bonded more strongly.

In one example of the interdental brush, the thickness of the partition wall is in the range of 0.3 to 0.7 mm.
It has been confirmed by tests that when the thickness of the partition wall is in the range of 0.3 mm or more, the handle portion and the core material are more strongly joined, and when the thickness of the partition wall is in the range of 0.7 mm or less, the visibility of the covering portion through the opening is improved.

According to one example of the interdental brush, the handle portion includes a grip portion and a neck portion, the covering portion covers at least the neck portion, and the opening is provided in the neck portion.
Since the opening is provided in the neck portion, the user's fingers are less likely to get caught in the opening when using the interdental brush.

According to one example of the interdental brush, the opening is provided at an end of the neck portion on the grip portion side.
Since the opening is provided at a position away from the filament bundle, plaque and the like adhering to the filament bundle is less likely to infiltrate into the opening.

With the above interdental brush, it is easy to see that the handle and core are properly joined by insert molding.

FIG. 2 is a perspective view of a first front side of the interdental brush according to the embodiment. FIG. 2 is a second front perspective view of the interdental brush of FIG. 1 . FIG. 2 is a front view of the interdental brush of FIG. 1 . FIG. 2 is a side view of the interdental brush of FIG. 1 . FIG. 2 is an enlarged view of the neck portion and its surroundings in FIG. 1 . FIG. 6 is a cross-sectional view taken along line D6-D6 in FIG. 7 is a cross-sectional view taken along line D7-D7 in FIG. 4. FIG. 8 is an enlarged view of the second portion of FIG. 7 . FIG. 7 is an enlarged view of the second portion of FIG. 6 . FIG. 2 is a side view of the interdental brush of FIG. 1 in a first mode of use. FIG. 2 is a side view showing a second usage mode of the interdental brush of FIG. 1 . FIG. 2 is a side view of the interdental brush of FIG. 1 in a third mode of use. FIG. 2 is a side view showing a fourth mode of use of the interdental brush of FIG. 1 . Cross-sectional view of a clamped mold. FIG. 4 is a cross-sectional view showing a state in which a resin material is injected into a mold. 1 is a table showing test conditions and measurement results for a first test. 13 is a table showing test conditions and measurement results for the second test. 18 is a graph showing the relationship between the first deformation ratio and maximum torque shown in FIG. 17 . 18 is a graph showing the relationship between the second deformation ratio and maximum torque shown in FIG. 17 . 13 is a table showing test conditions and measurement results for the third test. 13 is a table showing test conditions and measurement results for the fourth test.

(Embodiment)
The structure of an interdental brush 1 will be described with reference to FIGS.
The interdental brush 1 includes a handle portion 10 and a brush portion 100. The handle portion 10 constitutes the main body of the interdental brush 1. The brush portion 100 is joined to the handle portion 10 so as to be able to clean between the teeth. The interdental brush 1 can be defined in an axial direction, a width direction, and a thickness direction. The axial direction of the interdental brush 1 is a direction along the central axis C of the interdental brush 1. The width direction of the interdental brush 1 is a direction perpendicular to the axial direction of the interdental brush 1 when viewed from the front of the interdental brush 1. The thickness direction of the interdental brush 1 is a direction perpendicular to the axial direction of the interdental brush 1 when viewed from the side of the interdental brush 1. The structure of the interdental brush 1 is plane-symmetrical with respect to a central plane D (see FIG. 4) that is parallel to the axial direction and width direction of the interdental brush 1. The central axis C of the interdental brush 1 is included in the central plane D.

The handle portion 10 includes a first front surface 10A (see FIG. 1), a second front surface 10B (see FIG. 2), a first end portion 10C, and a second end portion 10D. The first front surface 10A and the second front surface 10B are surfaces arranged to sandwich the central axis C and the central plane D (see FIG. 4) of the interdental brush 1. The first end portion 10C is one end portion of the handle portion 10 in the axial direction of the interdental brush 1. The second end portion 10D is the other end portion of the handle portion 10 in the axial direction of the interdental brush 1. The shape of the first end portion 10C is approximately spherical. Therefore, when the first end portion 10C comes into contact with tissue in the mouth, it is possible to soften the impact. The shape of the second end portion 10D is approximately hemispherical.

The handle portion 10 further includes a neck portion 20, a grip portion 30, and a portion to be folded 40. The grip portion 30 is configured to allow the user to grip it firmly with his/her fingers. The neck portion 20 is configured to be relatively thinner than the grip portion 30 so as to be less likely to come into contact with tissue in the mouth. The neck portion 20 includes a first end portion 10C of the handle portion 10. The grip portion 30 includes a second end portion 10D of the handle portion 10. The grip portion 30 is configured to allow the user to grip it. The portion to be folded 40 includes a first portion to be folded 41 and a second portion to be folded 42.

The first intended folding portion 41 is provided on the neck portion 20. The second intended folding portion 42 is provided on the grip portion 30. Each intended folding portion 41, 42 is configured to be bent in order to adjust the insertability of the brush portion 100 between the teeth. Because the first intended folding portion 41 is provided on the neck portion 20, the neck portion 20 can be easily folded. Because the second intended folding portion 42 is provided on the grip portion 30, the posture of the brush portion 100 can be adjusted in a more diverse manner.

The brush unit 100 includes a core material 110, a filament bundle 200, and a cleaning unit 140. The core material 110 holds the filament bundle 200. The cleaning unit 140 is the part of the brush unit 100 that is directly involved in cleaning between teeth. The cleaning unit 140 is composed of the part of the core material 110 to which the filament bundle 200 is implanted (hereinafter referred to as the "holding unit 121"), and the filament bundle 200. The filament bundle 200 is composed of multiple filaments so that plaque and food residue can be removed from between teeth. Examples of materials that make up the filaments are nylon resin and polybutylene terephthalate resin. The filament bundle 200 is implanted in the core material 110 so as to protrude radially from the core material 110.

The interdental brush 1 can be used in multiple ways. In each way, the handle portion 10 has a shape that corresponds to the area between the teeth to be cleaned. In one example, the multiple ways of using the interdental brush 1 include first to fourth ways of using.

Figure 10 is a side view of the interdental brush 1 in the first usage configuration. The first usage configuration is suitable for cleaning between the front teeth. In the first usage configuration, the bendable portion 40 is not bent, and the handle portion 10 is straight.

Figure 11 is an example of a side view of the interdental brush 1 in the second usage configuration. The second usage configuration is suitable for cleaning between premolars. In the second usage configuration, the handle portion 10 is bent at the first intended bending portion 41 so that the brush portion 100 can be folded down.

Figure 12 is an example of a side view of the interdental brush 1 in the third usage configuration. The third usage configuration is a configuration that is primarily suitable for cleaning between molar teeth. In the third usage configuration, the handle portion 10 is bent at the second intended bending portion 42 so that the brush portion 100 can be folded over.

Figure 13 is an example of a side view of the interdental brush 1 in the fourth usage configuration. The fourth usage configuration is a configuration that is primarily suitable for cleaning between molar teeth. In the fourth usage configuration, the handle portion 10 is bent at each of the intended bending portions 41, 42 so that the brush portion 100 can be tilted.

As shown in FIG. 3, the handle portion 10 further includes an opening 50 and a partition wall 60. The opening 50 and the partition wall 60 are provided in the neck portion 20. The opening 50 is a hole formed in the handle portion 10 and a portion including a resin portion of the handle portion 10 that forms the hole. In one example, the opening 50 includes a first opening 51 and a second opening 52 (see FIG. 2). The first opening 51 opens in the first front surface 10A. The second opening 52 opens in the second front surface 10B. The partition wall 60 separates the first opening 51 from the second opening 52.

Because the handle portion 10 includes the opening 50, it is easy to confirm that the handle portion 10 and the core material 110 are properly joined. Because the opening 50 includes the first opening 51 and the second opening 52, it is easy to confirm the joining state between the handle portion 10 and the core material 110 from both the first front surface 10A side and the second front surface 10B side of the handle portion 10. Because the opening 50 is provided in the neck portion 20, it is difficult for the user's fingers to get caught in the opening 50 when using the interdental brush 1.

The handle portion 10 is made of a resin material. This allows the entire handle portion 10 to be molded as a single piece, allowing the interdental brush 1 to be manufactured efficiently. The type of resin material that makes up the handle portion 10 and its physical properties are preferably determined, for example, from the relationship between the strength of the handle portion 10 against fatigue and the ease with which the handle portion 10 can be bent. The physical properties of the resin material that affect these factors include at least density, melting point, and elastic modulus. The strength of the handle portion 10 against fatigue is preferably determined so that fatigue does not occur during the typical period of use of the interdental brush 1.

An example of a preferred resin material is a crystalline resin material. An example of a preferred crystalline resin material is a polyolefin resin. An example of a preferred polyolefin resin is a polyethylene resin or a polypropylene resin (PP). An example of a preferred polyethylene resin is a linear low-density polyethylene resin (LLDPE), a high-density polyethylene resin (HDPE), or a branched low-density polyethylene resin (LDPE). The preferred physical properties of the handle portion 10 made of a polyolefin resin are shown below.

An example of a preferred upper density limit is 930 kg/m3. An example of a more preferred upper density limit is 928 kg/m3. An example of a preferred lower density limit is 920 kg/m3. An example of a more preferred lower density limit is 923 kg/m3. An example of a preferred range for density is 920 to 930 kg/m3. An example of a more preferred range for density is 923 to 928 kg/m3. An example of a preferred density is 925 kg/m3.

An example of a preferred upper limit of the melting point is 126°C. An example of a more preferred upper limit of the melting point is 124°C. An example of a preferred lower limit of the melting point is 120°C. An example of a more preferred lower limit of the melting point is 121°C. An example of a preferred range of the melting point is 120 to 126°C. An example of a more preferred range of the melting point is 121 to 124°C. An example of a preferred melting point is 123°C.

An example of a preferred upper limit of the elastic modulus is 300 MPa. An example of a more preferred upper limit of the elastic modulus is 230 MPa. An example of a preferred lower limit of the elastic modulus is 200 MPa. An example of a more preferred lower limit of the elastic modulus is 210 MPa. An example of a preferred range for the elastic modulus is 200 to 300 MPa. An example of a more preferred range for the elastic modulus is 210 to 230 MPa. An example of a preferred elastic modulus is 230 MPa.

3 and 4, the neck portion 20 will now be described in greater detail.
The neck portion 20 includes a base portion 21, an intermediate portion 22, and a tip portion 23. The base portion 21 is a portion that is connected to the grip portion 30. The opening 50 is provided in the base portion 21. The intermediate portion 22 has a flat shape. The first intended folding portion 41 is provided in the base portion 21 and the intermediate portion 22. The tip portion 23 is a portion that includes a first end portion 10C of the handle portion 10.

3 and 4, the width and thickness of the neck portion 20 vary depending on the location of the neck portion 20. The width of the neck portion 20 is the dimension of the neck portion 20 in the width direction of the interdental brush 1. The thickness of the neck portion 20 is the dimension of the neck portion 20 in the thickness direction of the interdental brush 1. The width LA and thickness LB of the base 21 narrow from the grip portion 30 side toward the intermediate portion 22 side. In a cross section of the neck portion 20 perpendicular to the central axis C of the interdental brush 1, the width LA is greater than the thickness LB. The width LC and thickness LD of the intermediate portion 22 are constant. In a cross section of the neck portion 20 perpendicular to the central axis C of the interdental brush 1, the width LC is greater than the thickness LD.

5, the first bendable portion 41 includes one or more first grooves 41A. In the illustrated example, the first bendable portion 41 includes eight first grooves 41A. The first grooves 41A are formed so that the neck portion 20 can be bent in the direction in which the protruding portion 120 of the brush portion 100 falls. Each first groove 41A is provided on each of the first front surface 10A and the second front surface 10B. Each first groove 41A is aligned in the axial direction of the interdental brush 1. Each first groove 41A is provided over approximately the entire neck portion 20 in the width direction of the interdental brush 1. Since the first bendable portion 41 includes at least one first groove 41A, the first bendable portion 41 can be easily bent. In the following description, in order to distinguish each first groove 41A, the first grooves 41A are numbered in order from the first groove 41A formed closest to the grip portion 30.

The width XA and depth HA (see FIG. 6) of the first groove 41A are preferably determined, for example, from the relationship between the ease of bending the first intended bending portion 41 and the strength of the neck portion 20 against bending. The width XA of the first groove 41A is the dimension of the first groove 41A in the axial direction of the interdental brush 1. The depth HA of the first groove 41A is the dimension of the first groove 41A in the thickness direction of the interdental brush 1, and is determined, for example, on a cross section of the handle portion 10 (see FIG. 6) perpendicular to the center plane D of the interdental brush 1.

The width XA1 of the first first groove 41A is the widest among the widths XA of the first grooves 41A. The width XA2 of the second first groove 41A is the second widest among the widths XA of the first grooves 41A. The width XA3 of the third first groove 41A is the third widest among the widths XA of the first grooves 41A. The widths XA4 of the fourth to eighth first grooves 41A are equal to each other and are the narrowest among the widths XA of the first grooves 41A.

A preferred upper limit for width XA is 1.2 mm. A more preferred upper limit for width XA is 1.0 mm. A preferred lower limit for width XA is 0.3 mm. A more preferred lower limit for width XA is 0.4 mm. A preferred range for width XA is 0.3 to 1.2 mm. A more preferred range for width XA is 0.4 to 1.0 mm. A preferred width XA1 is 1.01 mm. A preferred width XA2 is 0.8 mm. A preferred width XA3 is 0.6 mm. A preferred width XA4 is 0.4 mm.

The depth HA of each first groove 41A is the same. An example of a preferred upper limit of the depth HA is 0.7 mm. An example of a more preferred upper limit of the depth HA is 0.6 mm. An example of a preferred lower limit of the depth HA is 0.05 mm. An example of a more preferred lower limit of the depth HA is 0.1 mm. An example of a preferred range for the depth HA is 0.05 to 0.7 mm. An example of a more preferred range for the depth HA is 0.1 to 0.6 mm. An example of a preferred depth HA is 0.1 mm.

The grip portion 30 will now be described in detail with reference to FIGS.
The grip portion 30 includes an upper portion 31, a middle portion 32, and a lower portion 33. The grip portion 30 has a flat shape. The upper portion 31 is a portion that is connected to the base portion 21 of the neck portion 20. The lower portion 33 is a portion that includes the second end portion 10D of the handle portion 10. The middle portion 32 is a portion between the upper portion 31 and the lower portion 33. The second intended folding portion 42 is provided in the middle portion 32. The grip portion 30 is narrowed so that the middle portion 32 is narrower than the upper portion 31 and the lower portion 33 when viewed from the front of the interdental brush 1.

3, the second intended folding portion 42 includes one or more second grooves 42A. In the illustrated example, the second intended folding portion 42 includes six second grooves 42A. The second grooves 42A are formed so that the grip portion 30 can be folded in the direction in which the protruding portion 120 of the brush portion 100 falls. The second grooves 42A are provided on each of the first front surface 10A and the second front surface 10B. The second grooves 42A are aligned in the axial direction of the interdental brush 1. The second grooves 42A are provided so as to go around the grip portion 30 around the central axis C of the interdental brush 1. Since the second intended folding portion 42 includes at least one second groove 42A, the second intended folding portion 42 can be easily folded.

The width XB and depth HB (see FIG. 6) of the second groove 42A are preferably determined, for example, from the relationship between the ease of bending the second intended bending portion 42 and the strength of the grip portion 30 against bending. The width XB of the second groove 42A is the dimension of the second groove 42A in the axial direction of the interdental brush 1. The depth HB of the second groove 42A is the dimension of the second groove 42A in the thickness direction of the interdental brush 1, and is determined, for example, on a cross section of the handle portion 10 perpendicular to the center plane D of the interdental brush 1 (see FIG. 6).

The width XB of each second groove 42A is the same. An example of a preferred upper limit of the width XB is 0.7 mm. An example of a more preferred upper limit of the width XB is 0.6 mm. An example of a preferred lower limit of the width XB is 0.3 mm. An example of a more preferred lower limit of the width XB is 0.4 mm. An example of a preferred range for the width XB is 0.3 to 0.7 mm. An example of a more preferred range for the width XB is 0.4 to 0.6 mm. An example of a preferred width XB is 0.5 mm.

The depth HB of each second groove 42A is the same. An example of a preferred upper limit of the depth HB is 1.2 mm. An example of a more preferred upper limit of the depth HB is 1.0 mm. An example of a preferred lower limit of the depth HB is 0.2 mm. An example of a more preferred lower limit of the depth HB is 0.3 mm. An example of a preferred range for the depth HB is 0.2 to 1.2 mm. An example of a more preferred range for the depth HB is 0.3 to 1.0 mm. An example of a preferred depth HB is 0.5 mm.

The brush unit 100 will now be described in detail with reference to FIG.
The core material 110 is made of a wire. Examples of materials that may be used to form the wire include stainless steel, ferritic stainless steel, austenitic stainless steel, austenitic-ferritic stainless steel, martensitic stainless steel, precipitation hardening stainless steel, nickel-based alloy, cobalt-based alloy, and titanium-nickel alloy.

The core material 110 is twisted so that it can hold the filament bundle 200. In one example, the brush part 100 is configured as follows. First, a single wire that is the material for the core material 110 is bent to form a bent portion of the wire (hereinafter, "bent portion 110P of the core material 110"). This divides the wire into one portion (hereinafter, "first folded portion 110A of the core material 110") relative to the folded portion 110P and the other portion (hereinafter, "second folded portion 110B of the core material 110").

Next, the first folded portion 110A and the second folded portion 110B of the core material 110 are overlapped so that they are parallel to each other. Next, the filament bundle 200 is inserted between the first folded portion 110A and the second folded portion 110B so that it is sandwiched between the overlapped first folded portion 110A and the second folded portion 110B. Next, the first folded portion 110A and the second folded portion 110B are twisted together so that the filament bundle 200 is firmly held by the first folded portion 110A and the second folded portion 110B.

After the first folded portion 110A and the second folded portion 110B are twisted, the filament bundle 200 is cut, for example, into a conical shape to form the brush portion 100. The twisted first folded portion 110A and the second folded portion 110B form a single wire. The tip portion 110C of the core material 110 includes a bent portion 110P. The coated end portion 110D, which is the end of the core material 110 opposite the tip portion 110C, includes the tip of the first folded portion 110A and the tip of the second folded portion 110B. The thickness of the core material 110 varies in the direction along the central axis of the core material 110. In one example, the maximum thickness of the core material 110 represents the thickness of the core material 110. The maximum thickness of the core material 110 is approximately twice the diameter of the wire.

The core material 110 includes a protruding portion 120 and a covering portion 130. The protruding portion 120 includes a retaining portion 121 and a non-retaining portion 122. The retaining portion 121 includes the bent portion 110P of the core material 110, and is the portion in which the filament bundle 200 is implanted. The non-retaining portion 122 is the portion between the retaining portion 121 and the tip portion 23 of the neck portion 20, and is the portion in which the filament bundle 200 is not implanted.

The thickness of the protrusion 120 is preferably determined, for example, in relation to the strength of the protrusion 120 against bending. The thickness of the protrusion 120 is, for example, the same as the thickness of the core material 110. An example of a preferred upper limit of the thickness of the protrusion 120 is 0.7 mm. An example of a more preferred upper limit of the thickness of the protrusion 120 is 0.6 mm. An example of a preferred lower limit of the thickness of the protrusion 120 is 0.3 mm. An example of a more preferred lower limit of the thickness of the protrusion 120 is 0.4 mm. An example of a preferred range for the thickness of the protrusion 120 is 0.3 to 0.7 mm. An example of a more preferred range for the thickness of the protrusion 120 is 0.4 to 0.6 mm. An example of a preferred thickness of the protrusion 120 is 0.4 mm.

The covering portion 130 is a portion covered by the handle portion 10, and includes a first portion 131 and a second portion 132. The first portion 131 is a portion that has not been subjected to plastic processing. The second portion 132 is a portion that has been subjected to plastic processing. An example of the plastic processing applied to the second portion 132 is press processing. The second portion 132 is formed by pressing a part of the core material 110 in which the first folded portion 110A and the second folded portion 110B are twisted. The shape of the second portion 132 is a flattened approximately rectangular shape. The shape of the second portion 132 can be changed arbitrarily. Other examples of the shape of the second portion 132 are a flattened approximately square shape, a flattened approximately circular shape, a flattened approximately oval shape, or a flattened approximately triangular shape. The second portion 132 is provided at any position of the covering portion 130 of the core material 110. In a preferred example, the second portion 132 is provided in a range including the covered end portion 110D of the core material 110. A portion of the covering portion 130 (hereinafter referred to as the "visible portion 133") is visible through the opening 50. In one example, the visible portion 133 is included in the first portion 131.

The thickness MA of the first portion 131 is preferably determined, for example, from the relationship between the ease of bending the first intended bending portion 41, the ability of the neck portion 20 to retain its shape in the bent state, and the strength of the neck portion 20 against fatigue. In the illustrated example, the thickness of the first portion 131 is the same as the thickness of the core material 110.

A preferred example of the upper limit of the thickness of the first portion 131 is 0.7 mm. A more preferred example of the upper limit of the thickness of the first portion 131 is 0.6 mm. A preferred example of the lower limit of the thickness of the first portion 131 is 0.3 mm. A more preferred example of the lower limit of the thickness of the first portion 131 is 0.4 mm. A preferred example of the range for the thickness MA of the first portion 131 is 0.3 to 0.7 mm. A more preferred example of the range for the thickness MA of the first portion 131 is 0.4 to 0.6 mm. A preferred example of the thickness MA of the first portion 131 is 0.4 mm. It is preferred that the thickness MA of the first portion 131 is greater than the thickness of the partition wall 60.

The ease of bending the first intended folding portion 41 and the ability of the neck portion 20 to retain its shape are related not only to the thickness MA of the first portion 131 itself, but also to the core material occupancy PX. The core material occupancy PX is the ratio of the thickness MA of the first portion 131 to the thickness of the thinnest part of the neck portion 20 (hereinafter referred to as the "minimum dimension PM"). In one example, the minimum dimension PM is defined on a cross section of the handle portion 10 perpendicular to the center plane D of the interdental brush 1 (see FIG. 6), and is the distance between the bottom surface of the first groove 41A formed on the first front surface 10A and the bottom surface of the first groove 41A formed on the second front surface 10B. The formula for calculating the core material occupancy PX is "PX=MA/PM×100(%)".

A preferred upper limit for the core material occupancy rate PX is 45%. A more preferred upper limit for the core material occupancy rate PX is 40%. A preferred lower limit for the core material occupancy rate PX is 15%. A more preferred lower limit for the core material occupancy rate PX is 20%. A preferred range for the core material occupancy rate PX is 15-45%. A more preferred range for the core material occupancy rate PX is 20-40%. A preferred core material occupancy rate PX is 20%. When the core material occupancy rate PX is in the range of 20% or more, the neck portion 20 is likely to maintain the bent state. When the core material occupancy rate PX is in the range of 40% or less, the first intended folding portion 41 is likely to be folded.

The degree of deformation of the covering portion 130 due to plastic processing can be determined, for example, by at least one of the first deformation rate PA and the second deformation rate PB. The first deformation rate PA is the ratio of the maximum width MB of the second portion 132 (see FIG. 9) to the thickness MA of the first portion 131. The maximum width MB of the second portion 132 is the dimension of the second portion 132 in the width direction of the interdental brush 1. The formula for calculating the first deformation rate PA is "PA = MB/MA x 100 (%)". The second deformation rate PB is the ratio of the thickness MA of the first portion 131 to the thickness MC of the second portion 132 (see FIG. 8). The thickness MC of the second portion 132 is the dimension of the second portion 132 in the thickness direction of the interdental brush 1. The formula for calculating the second deformation rate PB is "PB = MA/MC x 100 (%)".

The first deformation rate PA is preferably determined, for example, from the bond strength between the handle portion 10 and the covering portion 130 against twisting, and the strength of the second portion 132 of the covering portion 130. A preferred upper limit for the first deformation rate PA is 150%. A more preferred upper limit for the first deformation rate PA is 145%. A preferred lower limit for the first deformation rate PA is 130%. A more preferred lower limit for the first deformation rate PA is 135%. A preferred range for the first deformation rate PA is 130% to 150%. A more preferred range for the first deformation rate PA is 135% to 145%. A preferred range for the first deformation rate PA is 140%.

When the first deformation rate PA is in the range of 130% or more, the connection between the handle portion 10 and the covering portion 130 is unlikely to come loose when a force twisting the handle portion 10 and the protruding portion 120 is applied to the interdental brush 1. When the first deformation rate PA is in the range of 150% or less, high strength is ensured for the second portion 132. In addition, when the interdental brush 1 is manufactured by insert molding, the position of the brush portion 100 relative to the mold is unlikely to deviate from the specified position.

The second deformation rate PB is preferably determined, for example, from the bond strength between the handle portion 10 and the covering portion 130 against twisting, and the strength of the second portion 132. A preferred upper limit for the second deformation rate PB is 260%. A more preferred upper limit for the second deformation rate PB is 250%. A preferred lower limit for the second deformation rate PB is 200%. A more preferred lower limit for the second deformation rate PB is 210%. A preferred range for the second deformation rate PB is 200-260%. A more preferred range for the second deformation rate PB is 210-250%. A preferred range for the second deformation rate PB is 240%.

When the second deformation rate PB is in the range of 200% or more, the connection between the handle portion 10 and the covering portion 130 is unlikely to come loose when a force is applied to twist the handle portion 10 and the protruding portion 120. When the second deformation rate PB is in the range of 260% or less, high strength is ensured for the second portion 132. In addition, when the interdental brush 1 is manufactured by insert molding, the position of the brush portion 100 relative to the mold is unlikely to deviate from the specified position.

Factors other than the first deformation rate PA and the second deformation rate PB are also related to the joint strength between the handle portion 10 and the covering portion 130 against twisting. One example is the separation rate PC and the covering rate PD. The separation rate PC and the covering rate PD affect the joint strength individually, and also affect the joint strength independently of the first deformation rate PA and the second deformation rate PB.

The separation ratio PC is the ratio of the separation distance HY of the second portion 132 to the length HX of the covered portion 130 shown in Figures 6 and 7. The length HX of the covered portion 130 is the dimension of the covered portion 130 in the axial direction of the interdental brush 1. The separation distance HY of the second portion 132 is the distance between the covered end portion 110D of the core material 110 and the center point 132A of the second portion 132. The formula for calculating the separation ratio PC is "PC = HY/HX x 100 (%)".

An example of a preferred range for the separation ratio PC is 55% or less. An example of a more preferred range for the separation ratio PC is 30% or less. An example of a preferred separation ratio PC is 7%. When the separation ratio PC is within the range of 55% or less, the connection between the handle portion 10 and the covering portion 130 is unlikely to come off when a force twisting the handle portion 10 and the protruding portion 120 is applied to the interdental brush 1.

The coverage ratio PD is the ratio of the length HX of the covering portion 130 to the length ZA of the core material 110. The length ZA of the core material 110 is the overall dimension of the core material 110 in the axial direction of the interdental brush 1. The length HX of the covering portion 130 is the overall dimension of the covering portion 130 in the axial direction of the interdental brush 1. The formula for calculating the coverage ratio PD is "PD = HX/ZA x 100 (%)".

An example of a preferred range for the coverage ratio PD is 40% or more. An example of a more preferred range for the coverage ratio PD is 55% or more. An example of a preferred coverage ratio PD is 60%. When the coverage ratio PD is in the range of 40% or more, the connection between the handle portion 10 and the covering portion 130 is unlikely to come off when a force twisting the handle portion 10 and the protruding portion 120 is applied to the interdental brush 1.

An example of a factor related to the operability of the interdental brush 1 is the protrusion ratio PE. The protrusion ratio PE is the ratio of the length NA of the neck portion 20 to the length SA of the protrusion 120. The length SA of the protrusion 120 is the dimension of the protrusion 120 in the axial direction of the interdental brush 1. The length NA of the neck portion 20 is the dimension of the neck portion 20 in the axial direction of the interdental brush 1. The formula for calculating the protrusion ratio PE is "PE = NA / SA x 100 (%)". The protrusion ratio PE is preferably determined from the relationship between the ease of inserting the cleaning portion 140 between the teeth and the distance between the cleaning portion 140 and the grip portion 30 in the axial direction of the interdental brush 1.

A preferred upper limit for the protrusion rate PE is 150%. A more preferred upper limit for the protrusion rate PE is 140%. A preferred lower limit for the protrusion rate PE is 30%. A more preferred lower limit for the protrusion rate PE is 40%. A preferred range for the protrusion rate PE is 30-150%. A more preferred range for the protrusion rate PE is 40-140%. A preferred range for the protrusion rate PE is 125%.

When the protrusion rate PE is in the range of 30% or more, the distance between the grip portion 30 and the cleaning portion 140 in the axial direction of the interdental brush 1 is long, so that plaque, food residue, etc. adhering to the cleaning portion 140 are less likely to adhere to the user's hands. In addition, the distance between the opening 50 and the cleaning portion 140 is long, so that plaque, etc. adhering to the cleaning portion 140 are less likely to penetrate into the opening 50. When the protrusion rate PE is in the range of 170% or less, the cleaning portion 140 is easy to insert between the teeth.

The opening 50 and the partition wall 60 will be described in detail with reference to FIG.
The opening 50 includes a hole that allows the visible portion 133 of the covering portion 130 to be visible from the outside of the handle portion 10. Therefore, it is possible to visually check through the opening 50 whether the partition wall 60 and the covering portion 130 are properly joined. Examples of a state in which the partition wall 60 and the covering portion 130 are not properly joined include a state in which the core material 110 cannot be seen through the opening 50, and a state in which the core material 110 seen through the opening 50 is significantly biased with respect to the central axis C of the interdental brush 1. When such a state is confirmed, the corresponding interdental brush 1 can be excluded from being shipped. The first opening 51 includes a hole that opens at the base 21 of the neck portion 20 of the first front surface 10A. The second opening 52 (see FIG. 2) includes a hole that opens at the base 21 of the neck portion 20 of the second front surface 10B. The opening area of the hole included in each opening 51, 52 becomes narrower from the opening of the hole toward the partition wall 60.

The minimum opening area of the opening 50 is preferably determined, for example, in relation to the visibility of the covering portion 130. In one example, the portion of the first opening 51 closest to the partition wall 60 (hereinafter referred to as the "bottom 51A of the first opening 51") has the minimum opening area. The shape of the bottom 51A of the first opening 51 is rectangular. The minimum opening area is determined by the dimension YA of the bottom 51A in the axial direction of the interdental brush 1 and the dimension YB of the bottom 51A in the width direction of the interdental brush 1.

An example of a preferred upper limit of the minimum opening area is 2.0 ^mm2 . An example of a more preferred upper limit of the minimum opening area is 1.8 ^mm2 . An example of a preferred lower limit of the minimum opening area is 1.0 ^mm2 . An example of a more preferred lower limit of the minimum opening area is ^1.2 mm2. An example of a preferred range for the minimum opening area is 1.0 to 1.2 ^mm2 . An example of a more preferred range for the minimum opening area is 1.2 to 1.8 ^mm2 . An example of a preferred minimum opening area is 1.8 ^mm2 . The minimum opening area of the second opening 52 is determined in the same manner as that of the first opening 51.

The partition wall 60 is joined to the covering portion 130. This provides a stronger bond between the handle portion 10 and the covering portion 130. The thickness of the partition wall 60 is preferably determined, for example, based on the relationship between the visibility of the covering portion 130 through the opening 50 and the bonding strength between the handle portion 10 and the covering portion 130 against twisting. The thickness of the partition wall 60 is the dimension of the partition wall 60 in the thickness direction of the interdental brush 1.

A preferred upper limit of the thickness of the partition wall 60 is 0.7 mm. A more preferred upper limit of the thickness of the partition wall 60 is 0.6 mm. A preferred lower limit of the thickness of the partition wall 60 is 0.3 mm. A more preferred lower limit of the thickness of the partition wall 60 is 0.4 mm. A preferred range of the thickness of the partition wall 60 is 0.3 to 0.7 mm. A more preferred range of the thickness of the partition wall 60 is 0.4 to 0.6 mm. A preferred thickness of the partition wall 60 is 0.4 mm. When the thickness of the partition wall 60 is in the range of 0.3 mm or more, the handle portion 10 and the covering portion 130 are bonded more strongly. When the thickness of the partition wall 60 is in the range of 0.7 mm or less, the visibility of the covering portion 130 through the opening 50 is improved.

11 to 13, second to fourth usage patterns of the interdental brush 1 will be described.
In the second usage form shown in FIG. 11, the first bent portion 41 is bent. Therefore, the angle (hereinafter, "first angle θA") between the central axis C of the handle portion 10 and the central axis CA of the portion of the neck portion 20 closer to the tip portion 23 than the first bent portion 41 is greater than 0 degrees. For example, the first angle θA is preferably within a range in which the shape of the handle portion 10 allows the cleaning portion 140 to be easily inserted and removed between the molar teeth. An example of a preferred range for the first angle θA is greater than 0 degrees and less than or equal to 90 degrees. An example of a more preferred range for the first angle θA is 40 to 60 degrees. An example of a preferred range for the first angle θA is 40 degrees.

In the third usage form shown in FIG. 12, the second intended fold portion 42 is folded. Therefore, the angle (hereinafter "second angle θB") between the central axis C of the handle portion 10 and the central axis CB of the portion of the grip portion 30 closer to the neck portion 20 than the second intended fold portion 42 is greater than 0 degrees. For example, it is preferable that the second angle θB is within a range in which the shape of the handle portion 10 has high gripping and operability. One example of a preferred range for the second angle θB is greater than 0 degrees and less than or equal to 40°. One example of a more preferred range for the second angle θB is 25 to 35°. One preferred example of the second angle θB is 30°.

In the fourth usage form shown in FIG. 13, each of the intended bending portions 41, 42 is bent. Therefore, the angle (hereinafter referred to as the "third angle θC") between the central axis C of the handle portion 10 and the central axis CC of the portion of the neck portion 20 closer to the tip portion 23 than the first intended bending portion 41 is greater than 0 degrees. For example, it is preferable that the third angle θC is within a range in which the shape of the handle portion 10 is such that the cleaning portion 140 can be easily inserted and removed when cleaning between molar teeth. One example of a preferred range for the third angle θC is greater than 0 degrees and less than or equal to 80°. One example of a more preferred range for the third angle θC is 50 to 60°. One preferred example of the third angle θC is 55°.

The angle (hereinafter "fourth angle θD") between the central axis C of the handle portion 10 and the central axis CD of the portion of the grip portion 30 closer to the neck portion 20 than the second intended bend portion 42 is greater than 0 degrees. For example, it is preferable that the fourth angle θD is within a range in which the shape of the handle portion 10 has high gripping and operability. One example of a preferred range for the fourth angle θD is greater than 0 degrees and less than or equal to 30°. One example of a more preferred range for the fourth angle θD is 10 to 20°. One preferred example of the fourth angle θD is 15°.

A method for manufacturing the interdental brush 1 will now be described with reference to FIGS.
In one example, the interdental brush 1 is manufactured by insert molding. In a first step, the brush part 100 is manufactured. In a second step, the brush part 100 is placed at a specified position in a mold 300, as shown in Fig. 14. The mold 300 includes a holding mold 310 and a molding mold 340. The holding mold 310 is a mold for holding the brush part 100. The molding mold 340 is a mold for molding the handle part 10.

The retaining type 310 includes a fixed retaining type 320 and a movable retaining type 330. The fixed retaining type 320 includes a first retaining portion 321 and a first storage portion 322. The first retaining portion 321 includes a groove in which the non-retaining portion 122 of the core material 110 can be arranged. The first storage portion 322 includes a recess in which half of the brush part 100 can be arranged relative to the center surface D (see FIG. 4) of the interdental brush 1. The movable retaining type 330 includes a second retaining portion 331 and a second storage portion 332. The second retaining portion 331 includes a groove in which the non-retaining portion 122 of the core material 110 can be arranged. The second storage portion 332 includes a recess in which half of the brush part 100 can be arranged relative to the center surface D (see FIG. 4) of the interdental brush 1.

The mold 340 includes a fixed mold 350 and a movable mold 360. The fixed mold 350 includes a first mold portion 351, a first gate portion 352, a first seal portion 353, and a first protrusion portion 354. The first mold portion 351 includes a recess for molding one of the portions on the first front surface 10A side and the second front surface 10B side of the handle portion 10, which are divided by the center plane D (see FIG. 4) of the interdental brush 1. The first gate portion 352 includes a groove that constitutes a part of the gate 342 of the mold 340. The first seal portion 353 constitutes a part of the seal portion 343 of the mold 340. The first protrusion portion 354 is a protrusion for molding one of the first opening 51 and the second opening 52 in the handle portion 10.

The movable mold 360 includes a second molding portion 361, a second gate portion 362, a second seal portion 363, and a second protrusion portion 364. The second molding portion 361 includes a recess for molding the other of the portion on the first front face 10A side and the portion on the second front face 10B side of the handle portion 10, which are separated by the center plane D (see FIG. 4) of the interdental brush 1. The second gate portion 362 includes a groove that constitutes a part of the gate 342 of the mold 340. The second seal portion 363 constitutes a part of the seal portion 343 of the mold 340. The second protrusion portion 364 is a protrusion for molding the other of the first opening 51 and the second opening 52 in the handle portion 10.

In the second step, the brush part 100 is placed at a specified position in the retaining mold 310 as follows: First, the brush part 100 is placed in the open fixed retaining mold 320. At this time, the non-retaining part 122 of the core material 110 is placed in the first retaining part 321. Next, the movable retaining mold 330 is aligned with the fixed retaining mold 320 so that the closed retaining mold 310 is formed. When the closed retaining mold 310 is formed, the first retaining part 321 and the second retaining part 331 sandwich the non-retaining part 122 of the core material 110. Therefore, the position of the brush part 100 relative to the retaining mold 310 is determined.

Next, the holding mold 310 is placed in a position where it contacts the fixed mold 350 so that the covering part 130 of the brush part 100 held by the holding mold 310 is placed on the fixed mold 350. At this time, the visible part 133 of the covering part 130 is placed on the first convex part 354. Next, the movable mold 360 is aligned with the fixed mold 350 so that the closed mold 340 is formed. The closed mold 340 includes a molding space 341, a gate 342, and a seal part 343. The molding space 341 is composed of a first molding part 351 and a second molding part 361. The gate 342 is composed of a first gate part 352 and a second gate part 362 so that the molten resin can be supplied to the molding space 341. The seal part 343 is composed of a first seal part 353 and a second seal part 363 so that the resin supplied to the molding space 341 does not flow into the holding mold 310.

When the closed molding die 340 is constructed, the second convex portion 364 is disposed on the visible portion 133 of the covering portion 130, and the first convex portion 354 and the second convex portion 364 face each other with a predetermined distance (hereinafter "convex portion distance TA"). The convex portion distance TA is the distance between the end face 354A of the first convex portion 354 and the end face 364A of the second convex portion 364 in the closed molding die 340. The end face 354A of the first convex portion 354 and the end face 364A of the second convex portion 364 include an area (hereinafter "first area") that faces the visible portion 133 in a direction perpendicular to each end face 354A, 364A, and an area (hereinafter "second area") that does not face the visible portion 133 in the same direction. The partition wall 60 (see FIG. 5) is formed by the resin supplied between each end face 354A, 364A.

The state of each of the convex portions 354, 364 relative to the visible portion 133 (hereinafter, "opposing state") is classified into first to third opposing states according to the convex portion interval TA. Any of the first to third opposing states can be selected by setting the height of each of the convex portions 354, 364. The first opposing state is a state in which the convex portion interval TA is substantially equal to the thickness of the visible portion 133, and each end face 354A, 364A and the visible portion 133 are in contact without being pressed. The second opposing state is a state in which the convex portion interval TA is substantially equal to the thickness of the visible portion 133, and each end face 354A, 364A and the visible portion 133 are in pressure contact. The third opposing state is a state in which the convex portion interval TA is wider than the thickness of the visible portion 133, and each end face 354A, 364A and the visible portion 133 are not in contact.

In the example shown in FIG. 14, the opposing state of each of the protrusions 354, 364 is the second opposing state. Each of the protrusions 354, 364 holds the visible portion 133 of the covering portion 130, which is a portion closer to the second portion 132 than the center of the covering portion 130 in the axial direction of the interdental brush 1. In this way, when the portion of the covering portion 130 closer to the gate 342 is held by each of the protrusions 354, 364, the covering portion 130 becomes even less likely to bend when resin is injected into the molding space 341.

In the third step shown in FIG. 15, molten resin is injected into the molding space 341 (see FIG. 14) through the gate 342. The resin supplied around each of the protrusions 354, 364 forms the opening 50 (see FIG. 5) of the handle portion 10. When the first region of each of the end faces 354A, 364A is in contact with the visible portion 133, resin is not supplied between the part of the visible portion 133 that contacts the first region and the first region of each of the end faces 354A, 364A, but resin is supplied between the second region of the end face 354A and the second region of the end face 364A. When the first region of each of the end faces 354A, 364A is not in contact with the visible portion 133, resin is supplied between the visible portion 133 and the first region of each of the end faces 354A, 364A, and between the second region of the end face 354A and the second region of the end face 364A. The resin supplied between the end faces 354A, 364A forms a partition wall 60 (see FIG. 5). The partition wall 60 (see FIG. 5) formed in the example shown in FIG. 15 does not cover the portion of the visible portion 133 that comes into contact with the first region. In the fourth step, the handle portion 10 is cooled until the injected resin hardens. In the fifth step, the holding mold 310 and the molding mold 340 are opened, the interdental brush 1 is removed from the metal mold 300, and the resin portion corresponding to the gate 342 is cut from the handle portion 10.

The opposing state of the protrusions 354, 364 will now be described in detail.
In the first opposing state, the first region of each end face 354A, 364A contacts the visible portion 133 so as not to substantially deform the visible portion 133, and the second region of each end face 354A, 364A faces the visible portion 133 via a gap. Therefore, each protrusion 354, 364 holds the covering portion 130 by the frictional force between the first region and the visible portion 133. In the second opposing state, the first region of each end face 354A, 364A is pressed against the visible portion 133, and the second region of each end face 354A, 364A faces the visible portion 133 via a gap. Therefore, each protrusion 354, 364 holds the covering portion 130 by a frictional force stronger than that in the first opposing state.

According to the first and second opposing states, the covering portion 130, which is the portion of the brush portion 100 on the gate 342 side, is held by the respective convex portions 354 and 364, so that the covering portion 130 is less likely to bend when the resin is injected into the molding space 341. This improves the moldability of the handle portion 10. According to the second opposing state, the frictional force between the respective convex portions 354 and 364 and the visible portion 133 is large, so that the covering portion 130 is even less likely to bend, and the moldability of the handle portion 10 is even more improved. In addition, when the first or second opposing state is formed in the molding die 340, the non-holding portion 122 is held by the respective holding portions 321 and 331, and the visible portion 133 is held by the respective convex portions 354 and 364, so that the position and posture of the brush portion 100 relative to the mold 300 are stable when the resin is injected into the molding space 341. This also contributes to improving the moldability of the handle portion 10. Furthermore, in the first and second opposing states, the portions of the visible portion 133 that come into contact with the first regions of the end faces 354A and 364A are not covered by the partition wall 60 (see FIG. 5), further increasing the visibility of the visible portion 133.

In the third opposing state, the first region of each end face 354A, 364A faces the visible portion 133 without contacting the visible portion 133, and the second region of each end face 354A, 364A faces the visible portion 133 through a gap. According to the third opposing state, the range in which the covering portion 130 bends is limited by each end face 354A, 364A, so that the covering portion 130 is prevented from bending significantly when the resin is injected into the molding space 341. This improves the moldability of the handle portion 10. The narrower the convex interval TA, the narrower the range in which the covering portion 130 bends when the resin is injected. When the handle portion 10 is molded in the third opposing state, the entire visible portion 133 is covered by the partition wall 60 (see FIG. 5). Even in this case, the visibility of the visible portion 133 can be improved by reducing the thickness of the partition wall 60. When the resin material forming the partition wall 60 is a resin material with high transmittance such as a transparent material or a translucent material, the visible portion 133 is ensured to have substantially the same degree of visibility in both cases where a part of the visible portion 133 is not covered by the partition wall 60 and where the entire visible portion 133 is covered by the partition wall 60. In addition, when the handle portion 10 is molded in the third opposing state, the partition wall 60 is thicker than when the handle portion 10 is molded in the first opposing state and the second opposing state, so that the bond strength between the handle portion 10 and the covering portion 130 is high.

As described above, the convex portion spacing TA is related to the moldability of the handle portion 10, the visibility of the visible portion 133, and the bonding strength between the handle portion 10 and the covering portion 130 against twisting. For this reason, it is preferable to determine the convex portion spacing TA in relation to these factors. One example of a preferable convex portion spacing TA determined from the standpoint of moldability is the spacing at which each end face 354A, 364A is crimped against the visible portion 133.

(Example)
First to fourth tests conducted to evaluate the performance of the interdental brush 1 will be described. In each test, a sample of an example was used. The sample of the example is a sample related to the interdental brush 1 of the embodiment. The molding method of the handle portion 10 of each sample was the same as the molding method exemplified in the embodiment. In the third test, a transparent resin material was used to manufacture each sample in order to visually inspect the condition of the covering portion 130.

The first test will now be described. In the first test, the type of resin material constituting the handle portion 10, its physical properties, and the relationship between the strength of the handle portion 10 against fatigue were confirmed using the samples of Examples 1 to 8. The test conditions were the type of resin material, the density of the resin material, the melting point of the resin material, the elastic modulus of the resin material, and the diameter of the material of the core material 110. Specific test conditions are shown in Figure 16. The elastic modulus of the samples of Examples 1 to 5 and 7 is the flexural modulus of elasticity. The elastic modulus of the samples of Examples 6 and 8 is the tensile modulus of elasticity.

In the first test, in order to evaluate the strength of the neck portion 20 against fatigue, the first intended bending portion 41 was repeatedly bent so that the first angle θA (see FIG. 11) was approximately 90°, and the number of times the first intended bending portion 41 was bent when it broke due to fatigue (hereinafter referred to as the "maximum number of times of bending") was measured. The process of changing the usage form of the handle portion 10 from the first usage form to the second usage form and then changing it back to the first usage form was counted as one bending.

As shown in FIG. 16, it was confirmed that the samples of Examples 1 to 4 had a greater maximum number of bending cycles than the samples of Examples 5 to 8. This indicates that when the type of resin material and its physical property values fall within the conditions exemplified in the embodiment, the strength of the neck portion 20 against fatigue is increased.

The second test will be described. In the second test, the relationship between the degree of plastic processing of the covering portion 130 and the joint strength between the handle portion 10 and the covering portion 130 against twisting was confirmed using the samples of Examples 9 to 14. The samples of Examples 9 to 12 differ in the first deformation rate PA and the second deformation rate PB. The samples of Examples 9 to 12 differ from the samples of Examples 13 and 14 in the shape of the core material 110. The core material 110 of the sample of Example 13 has a linear shape. The core material 110 of the sample of Example 14 includes a second portion 132 formed by bending. This second portion 132 is a portion of the covering portion 130 that is bent so that a part of the covering portion 130 protrudes in the radial direction of the covering portion 130. Specific test conditions are shown in Figure 17.

In the second test, in order to evaluate the joint strength between the handle portion 10 and the covering portion 130 against twisting, the torque (hereinafter "maximum torque") at which the joint between the handle portion 10 and the covering portion 130 came loose was measured. The method for measuring the maximum torque is as follows. First, the cleaning portion 140 of the core material 110 is fixed to a torque gauge. Next, a torque that rotates the handle portion 10 around the central axis C of the interdental brush 1 is applied to the handle portion 10, and the torque is gradually increased until the maximum torque is measured when the handle portion 10 rotates relative to the core material 110.

As shown in FIG. 17, it was confirmed that the samples of Examples 9 to 12 and Example 14 had a higher maximum torque than the sample of Example 13. This shows that when the second portion 132 is formed in the covering portion 130, the maximum torque is increased by joining the handle portion 10 and the second portion 132. FIG. 18 is a graph showing the relationship between the first deformation rate PA and the maximum torque for the samples of Examples 9 to 12. FIG. 19 is a graph showing the relationship between the second deformation rate PB and the maximum torque for the samples of Examples 9 to 12. The maximum torque of the samples of Examples 9 to 12 is 3.1 times or more that of the sample of Example 13. This shows that when the second portion 132 is formed so that at least one of the first deformation rate PA and the second deformation rate PB is within the numerical range exemplified in the embodiment, a high maximum torque can be obtained even if the second portion 132 is not a portion formed by bending processing like the sample of Example 14.

The third test will be described. In the third test, the relationship between the degree of plastic processing of the covering portion 130 and the formability of the handle portion 10 was confirmed using the same samples as in the second test. To evaluate the formability of the handle portion 10, N pieces of each sample were molded, and the number N1 of the first type samples, the number N2 of the second type samples, and the number N3 of the third type samples contained in the N samples were measured by visual inspection. From the results, the ratio of the number N1 of the first type samples to N (hereinafter "first molding rate P1"), the ratio of the number N2 of the second type samples to N (hereinafter "second molding rate P2"), and the ratio of the number N3 of the third type samples to N (hereinafter "third molding rate P3") were calculated.

The first type of sample is a sample that satisfies the first evaluation condition. The first evaluation condition is that the covering portion 130 is covered by the handle portion 10 in a straight state. When the covering portion 130 is in a straight state, the central axis C of the interdental brush 1 and the entire central axis of the covering portion 130 are substantially coaxial. In the first type of sample, a straight visible portion 133 can be observed through the opening 50. Therefore, it can be confirmed that the first evaluation condition is met even when the grip portion 30 is made of an opaque resin.

The second type of sample is a sample that satisfies the second evaluation condition. The second evaluation condition is that the covering end 110D of the covering portion 130 is offset in a direction perpendicular to the central axis C of the interdental brush 1, and the covering portion 130 is bent with the non-retaining portion 122 as a fulcrum. During molding of the handle portion 10, the visible portion 133 is disengaged from between the first convex portion 354 and the second convex portion 364 by the force of the resin supplied to the molding space 341, and the resin hardens in this state, forming the second type of sample. If the amount of bending of the covering portion 130 in the second type of sample is large, the covering portion 130 is not exposed to the opening 50. If the amount of bending of the covering portion 130 in the second type of sample is small, a curved state of a part of the covering portion 130 can be observed through the opening 50.

The third type of sample is a sample that satisfies the third evaluation condition. The third evaluation condition is that the portion of the covering part 130 between the visible part 133 and the non-retained part 122 is warped when the visible part 133 is not offset in a direction perpendicular to the central axis C of the interdental brush 1. When the handle part 10 is molded, the visible part 133 is maintained in a state of being held by each of the protrusions 354, 364 even when resin is supplied to the molding space 341, and the covering part 130 is warped with the non-retained part 122 and the visible part 133 as fulcrums due to the force of the supplied resin, and the resin hardens in this state, forming a third type of sample. In the third type of sample, the visible part 133 tilted with respect to the central axis C of the interdental brush 1 can be observed through the opening 50.

Figure 20 is an example of the measurement results under the test conditions of N = 100. The sample of Example 14 has a lower first molding rate P1 than the samples of Examples 9 to 13. The reason for this is considered as follows. Since the second portion 132 in the sample of Example 14 is a bent portion, it provides a large resistance to the flow of resin supplied to the molding space 341, and the second portion 132 receives a large force from the resin. When the component of the force that the second portion 132 receives from the resin in the direction perpendicular to the central axis of the core material 110 is strong, the visible portion 133 is removed from between the first convex portion 354 and the second convex portion 364, and a second type of sample is formed. When the component of the force that the second portion 132 receives from the resin in the direction along the axial direction of the core material 110 is strong, the second portion 132 is pushed toward the non-retained portion 122, and the portion between the visible portion 133 and the non-retained portion 122 sandwiched between the convex portions 354 and 364 bends, and a third type of sample is formed.

The samples of Examples 9 to 12 also contain the second portion 132, but it is believed that the resistance it provides to the flow of resin is smaller than that of the second portion 132 in the sample of Example 14, which is why relatively favorable results were obtained with respect to the first molding rate P1. The sample of Example 13 does not contain the second portion 132, so relatively favorable results were obtained with respect to the first molding rate P1.

The fourth test will be described. In the fourth test, the relationship between the position of the second portion 132 in the axial direction of the covering portion 130 and the bond strength between the handle portion 10 and the covering portion 130 against torsion was confirmed using the samples of Examples 15 to 24. The samples of Examples 15 to 22 are samples related to the interdental brush 1 of the embodiment. The samples of Examples 23 and 24 include a linear core material 110, similar to the sample of Example 13. The test conditions are the type of resin material, the density of the resin material, the melting point of the resin material, the elastic modulus of the resin material, the diameter of the material of the core material 110, the length ZA of the core material 110, the length HX of the covering portion 130, the first deformation rate PA, the second deformation rate PB, and the separation rate PC. Specific test conditions are shown in Figure 21.

As shown in the measurement results for the samples of Examples 15 to 17 and Examples 19 to 21, it was confirmed that the smaller the separation ratio PC, the higher the maximum torque. This is thought to be due to the fact that the force transmission distance from when the torque applied to the cleaning portion 140 of the core material 110 is transmitted to the second portion 132 is long, and the torque applied to the core material 110 can be received over a wider range of the core material 110. However, as shown in the measurement results for the samples of Examples 18 and 22, it was confirmed that when the length ZA of the core material 110 is a predetermined length or longer, the maximum torque is strongly dependent on the length ZA of the core material 110, not on the separation ratio PC. This is thought to be because the length ZA of the core material 110 is long, the transmission distance of the force is long, and the torque applied to the core material 110 can be received over a wider range of the core material 110. In addition, as shown in the measurement results for the groups of Examples in which the type, density, melting point, and elastic modulus of the resin material are different and other test conditions are the same, it was confirmed that the higher the elastic modulus of the resin material, the higher the maximum torque. The corresponding pairs of examples are Example 15 and Example 19, Example 16 and Example 20, Example 17 and Example 21, and Example 18 and Example 22.

(Modification)
The above-described embodiments are merely examples of possible forms of the interdental brush according to the present invention, and are not intended to limit the forms thereof. For example, the interdental brush according to the present invention may take the following modified forms of the above-described embodiments, or a combination of at least two mutually non-inconsistent modified forms.

The configuration of the handle portion 10 can be changed as desired. In the first example, the handle portion 10 does not include the first intended folding portion 41. Even in this case, the use form of the interdental brush 1 can be changed in the same manner as in the embodiment by folding the neck portion 20. Since the neck portion 20 includes the flattened intermediate portion 22, the neck portion 20 can be easily folded even in the handle portion 10 in which the first intended folding portion 41 is omitted. In the second example, the handle portion 10 does not include the second intended folding portion 42. Even in this case, the use form of the interdental brush 1 can be changed in the same manner as in the embodiment by folding the grip portion 30. In the third example, the handle portion 10 does not include the intended folding portion 40. Even in this case, the use form of the interdental brush 1 can be changed in the same manner as in the embodiment by folding at least one of the neck portion 20 and the grip portion 30. In the fourth example, the handle portion 10 has a structure in which the neck portion 20 and the grip portion 30 are not distinguished. One example of this structure is one in which the shape of the grip portion 30 is uniform or similar in the axial direction of the interdental brush 1 at each cross section of the grip portion 30 perpendicular to the central axis C of the interdental brush 1.

The configuration of the opening 50 can be changed arbitrarily. In a first example, the opening 50 includes only one of the first opening 51 and the second opening 52. In a second example, one of the first opening 51 and the second opening 52 included in the opening 50 in the first example is provided in the grip portion 30. In this case, the length of the covering portion 130 is determined so that the visible portion 133 is located in the grip portion 30. In a third example, at least one of the first opening 51 and the second opening 52 is provided in the grip portion 30. In this case, the length of the covering portion 130 is determined in the same manner as in the second example. In a fourth example, the shape of the hole formed in the opening 50 is a shape other than a rectangle. Examples are a square, a circle, an ellipse, and a triangle.

The configuration of the core material 110 can be changed as desired. In a first example, the core material 110 includes a plurality of second portions 132. In a second example, the shape of at least one of the plurality of second portions 132 in the first example is different from the shape of the other second portions 132.

The manufacturing method of the interdental brush 1 can be changed as desired. In one example, the interdental brush 1 is manufactured by a manufacturing method using thermal welding as disclosed in JP 09-117324 A. According to this manufacturing method, the handle portion 10 and the brush portion 100 are first formed separately. Next, the covering portion 130 of the core material 110 is heated, and in this state, the covering portion 130 is inserted into the handle portion 10. As a result, the handle portion 10 and the covering portion 130 are welded together.

1: Interdental brush 10: Handle portion 10A: First front surface 10B: Second front surface 20: Neck portion 30: Grip portion 50: Opening 51: First opening 52: Second opening 60: Partition wall 100: Brush portion 110: Core material 200: Filament bundle

Claims (11)

A handle portion made of a resin material;
a brush portion connected to the handle portion so as to be capable of cleaning between teeth,
The brush portion includes a core material and a filament bundle provided on the core material,
The core material includes a covering portion that covers the handle portion,
the handle portion includes an opening that is opened so that a part of the covering portion can be visually confirmed, and a first front surface and a second front surface that extend in a longitudinal direction of the handle portion and are provided so as to sandwich a central axis along the longitudinal direction of the handle portion;
The opening includes a first opening that opens on the first front surface and a second opening that opens on the second front surface,
An interdental brush, wherein the shape of the first opening and the shape of the second opening are symmetrical with respect to a central plane parallel to an axial direction and a width direction of the interdental brush. the handle portion further includes a partition wall formed to partition the first opening and the second opening,
The interdental brush according to claim 1 , wherein the covering portion is joined to the partition wall. A handle portion made of a resin material;
a brush portion connected to the handle portion so as to be capable of cleaning between teeth,
The brush portion includes a core material and a filament bundle provided on the core material,
The core material includes a covering portion that covers the handle portion,
The handle portion includes a neck portion and a grip portion,
The neck portion includes a folding portion and an opening,
The opening is provided between the intended bending portion and the grip portion in the axial direction of the interdental brush, and opens to allow a part of the covering portion to be visually observed. A handle portion made of a resin material;
a brush portion connected to the handle portion so as to be capable of cleaning between teeth,
The brush portion includes a core material and a filament bundle provided on the core material,
The core material includes a covering portion that covers the handle portion,
The handle portion includes a neck portion and a grip portion,
the neck portion includes a tip and an opening;
The opening is opened so that a part of the covering portion can be visually confirmed,
An interdental brush, wherein a distance between the opening and the grip portion in an axial direction of the interdental brush is shorter than a distance between the opening and the tip portion. A handle portion made of a resin material;
a brush portion connected to the handle portion so as to be capable of cleaning between teeth,
The brush portion includes a core material and a filament bundle provided on the core material,
The core material includes a covering portion that covers the handle portion,
the handle portion includes an opening including a hole through which a portion of the covering portion can be viewed;
An interdental brush, wherein an opening area of the hole narrows from the opening of the hole toward the covering portion in a thickness direction of the interdental brush. A handle portion made of a resin material;
a brush portion connected to the handle portion so as to be capable of cleaning between teeth,
The brush portion includes a core material and a filament bundle provided on the core material,
The core material includes a covering portion that covers the handle portion,
the handle portion includes an opening including a hole through which a visible portion that is a part of the covering portion can be visually observed ;
The visible portion is provided in the opening along the longitudinal direction of the handle portion.
Interdental brush. The handle portion includes a first front surface and a second front surface extending in a longitudinal direction of the handle portion and disposed on either side of a central axis along the longitudinal direction of the handle portion,
The interdental brush according to claim 3 , wherein the openings include a first opening that opens on the first front surface, and a second opening that opens on the second front surface. the handle portion further includes a partition wall formed to partition the first opening and the second opening,
The interdental brush according to claim 7 , wherein the covering portion is joined to the partition wall. The interdental brush according to claim 8, wherein the thickness of the partition wall is in the range of 0.3 to 0.7 mm. The handle portion includes a grip portion and a neck portion,
The covering portion covers at least the neck portion,
The interdental brush according to any one of claims 1 to 9, wherein the opening is provided in the neck portion. The interdental brush according to claim 10, wherein the opening is provided at an end of the neck portion on the grip portion side.