JP7617835B2 - Brush molded body and toothbrush - Google Patents

Description

The present invention relates to a brush molded body and a toothbrush.

One-piece molded toothbrushes have been proposed, which are manufactured using only an injection molding machine (for example, Patent Document 1). One-piece molded toothbrushes have the advantage that they can be manufactured more cheaply than bristle toothbrushes, since the filament and head base (or head) are molded as a single unit, eliminating the need to procure filament material or use a bristle implantation machine.

One-piece toothbrushes have been proposed in which a head portion (brush molded body) having a filament and fitting holes and a handle portion having a fitting portion at one end are molded separately and then fitted together (for example, Patent Document 2). Because the brush molded body can be attached and detached by the user, it is expected that resources will be saved by replacing it with a new one when the quality deteriorates due to the bristles opening up due to repeated use, while the handle portion can be reused.

In integrally molded toothbrushes, the contact area between the filaments and the mold is large during molding. In addition, when polyurethane is used as the molding material, the integrally molded toothbrush adheres strongly to the mold. As a result, the filaments of integrally molded toothbrushes are difficult to release from the mold during molding, and the brush part tends to be prone to quality defects due to deformation. In particular, because cap-type integrally molded toothbrushes have fitting holes, the base that supports the filaments (the area from the base end of the filaments to the top surface of the fitting holes) must be made thin to a certain level, making the brush part even more susceptible to deformation during mold release.

Patent Document 2 discloses that the bristles of the filament group are all the same length, thereby making the release resistance on the brush part uniform. Deformation of the brush part is suppressed even when the bristles arranged in the short axis direction of the head part are all the same length, without making the bristles of the filament group all the same length.

In addition, if the thickness of the base supporting the brush part (the area from the base end of the filament to the top surface of the fitting hole) falls below 2 to 3 mm, the brush part is likely to deform, so in Patent Document 2, the thickness of the base is increased to counteract the mold release resistance. Furthermore, when molding with a gate placed on the tip side of the brush molded body, the resin is preferentially filled on the rear end side of the brush molded body, so that pressure is likely to be applied to that part. In this case, the rear end side of the brush molded body is likely to become overpacked. Therefore, in Patent Document 2, in order to prevent poor mold release due to the filament on the rear end side of the brush from affecting the entire brush, a configuration is adopted in which no filament is placed on the rear end side of the brush molded body, leaving a margin.

Furthermore, in Patent Document 2, a step is provided on the base, which makes it possible to release the brush molded body from the mold while pressing the outer edge of the base. In this case, the mold is equipped with a pressing mechanism. Deformation of the brush is suppressed by releasing the brush molded body from the mold while pressing the outer edge of the base.

On the other hand, in the above-mentioned Patent Document 2, the filament shape is a triangular pyramid. When the filament shape is a triangular pyramid, one of the side faces is positioned parallel to the mold release direction from the viewpoint of mold processing, which results in poor mold releasability and easy deformation of the brush part. For this reason, there is a method of improving mold releasability by making the filament shape a pyramid shape with a draft angle on the entire filament side face, for example a square pyramid shape.

Japanese Utility Model Application Publication No. 61-207233 Chinese Utility Model No. 204561298

The above-mentioned methods for improving releasability have a significant impact on appearance and usability, and reduce design freedom, so they often act as constraints in product development. Therefore, a solution that allows for more flexible design was needed.

The present invention was made in consideration of the above points, and aims to provide a brush molding and toothbrush that have a high degree of design freedom.

According to a first aspect of the present invention, there is provided a brush molding having a head base portion formed of a soft resin, and a plurality of filaments extending from a support surface located on the front side of the thickness direction of the head base portion to the front side, the head base portion having a base having a fitting hole extending in a lengthwise direction perpendicular to the thickness direction and opening to one side in the lengthwise direction, a holding surface located on the front side of the fitting hole facing the fitting hole and the support surface, and one or more structures protruding from the holding surface of the base toward the rear side opposite the front side in the thickness direction.

According to a second aspect of the present invention, there is provided a toothbrush comprising the brush molded body of the first aspect and a handle body formed of a hard resin and having a fitting protrusion that can be attached and detached to the fitting hole of the brush molded body.

According to a third aspect of the present invention, there is provided a toothbrush comprising the brush molded body of the first aspect and a handle body having a fitting protrusion that fits into the fitting hole of the brush molded body, the brush molded body and the handle body being an integrally molded body.

The present invention provides a brush molded body and toothbrush with high design freedom.

FIG. 1 is a front view of a brush molded body 20 and a toothbrush 1 according to an embodiment of the present invention. FIG. 2 is a side view of the brush molding 20 and the toothbrush 1. FIG. 2 is an enlarged front view of a fitting protrusion 12. FIG. FIG. 2 is a front view of the brush molded body 20 according to the first embodiment. This is a cross-sectional view taken along line AA in FIG. 5. This is a cross-sectional view taken along the line B-B in FIG. This is a cross-sectional view taken along the line CC in FIG. 2 is a cross-sectional view showing a simplified example of a mold MD for molding the brush body 20. FIG. FIG. 13 is an external perspective view of a core block SL2. 10 is a cross-sectional view showing the initial state of mold opening when the brush molding 20 does not have a structure 31. FIG. 2 is a cross-sectional view of the head base portion 21. FIG. FIG. 4 is a cross-sectional view of a brush molded body 20 according to a second embodiment. FIG. 11 is a cross-sectional view of a head base 21 according to a second embodiment. 11 is a cross-sectional view of a head base 21 according to a third embodiment, taken along a line perpendicular to the thickness direction at a position including a structure 31. FIG. 13 is a cross-sectional view perpendicular to the width direction of a head base portion 21 according to a fourth embodiment. FIG. 13 is a cross-sectional view perpendicular to the width direction of a head base portion 21 according to a fifth embodiment. FIG. 13 is a cross-sectional view perpendicular to the length direction of a head base portion 21 according to a sixth embodiment. FIG. 13 is a cross-sectional view perpendicular to the length direction of a head base portion 21 according to a seventh embodiment. FIG. FIG. 23 is an external perspective view of a core block SL2 according to the seventh embodiment. FIG. 13 is a cross-sectional view showing a modified example of the structure 31B according to the seventh embodiment. FIG. 13 is a cross-sectional view showing a modified example of the structure 31B according to the seventh embodiment. FIG. 13 is a cross-sectional view showing a modified example of the structure 31B according to the seventh embodiment.

Embodiments of the brush molded body and toothbrush of the present invention will be described below with reference to Figures 1 to 23. In this embodiment, an example of a toothbrush in which the brush molded body is detachably attached to the handle body will be used.

The following embodiment shows one aspect of the present invention, does not limit the present invention, and can be modified as desired within the scope of the technical concept of the present invention. In addition, in the following drawings, the scale and number of each structure are different from the actual structure to make each configuration easier to understand.

Figure 1 is a front view of the brush molding 20 and toothbrush 1 according to this embodiment. Figure 2 is a side view of the brush molding 20 and toothbrush 1. The toothbrush 1 comprises a rod-shaped handle body 10 and a brush molding 20. The handle body 10 and the brush molding 20 are separate members. The brush molding 20 can be detachably attached (inserted) to the handle body 10. The brush molding 20 is made of a soft resin. The handle body 10 is made of a hard resin.

In this embodiment, the front side is the side from which the filament 23 (described later) protrudes (upper side in FIG. 2) in the thickness direction (hereinafter simply referred to as the thickness direction), which is the normal direction of the support surface 21a (details will be described later) of the brush molding 20. In the thickness direction of the brush molding 20, the side opposite the front side is appropriately referred to as the back side. In addition, the length direction of the handle body 10 (hereinafter simply referred to as the length direction), and the direction in which the handle body 10 is inserted into the brush molding 20 (hereinafter simply referred to as the insertion direction) are perpendicular to the normal direction. In the length direction, the side where the handle body 10 is attached to the brush molding 20 is the rear end side (one side in the length direction), and the side opposite the rear end side is appropriately referred to as the tip side (the other side in the length direction). In addition, the direction perpendicular to the normal direction and the insertion direction is the width direction of the brush molding 20 (hereinafter simply referred to as the width direction). In this embodiment, the long axis direction is the direction in which the filament 23 extends, which is parallel to the normal direction.

FIG. 3 is a front view of the handle body 10. FIG.
3, the handle body 10 includes a rod-shaped handle portion 11 and a fitting protrusion 12 that protrudes from the longitudinal tip side of the handle portion 11. In the toothbrush 1, the fitting protrusion 12 of the handle body 10 is inserted into a brush molding 20 (described later), whereby the brush molding 20 is attached by covering the fitting protrusion 12.

The handle body 10 is formed of a hard resin. An example of a hard resin is a resin with a flexural modulus (JIS K7171) of 1500 MPa or more and 3000 MPa or less. Specific examples include polypropylene resin (PP), polyacetal resin (POM), polyester resin (PCTA), polyethylene terephthalate copolymer (PETG), and high density polyethylene (HDPE). Among these, PP, which is a general-purpose resin, is preferable in terms of cost, and POM is even more preferable in order to ensure the strength of the fitting protrusion 12.

In this embodiment, the shape of the handle portion 11 in a front view gradually narrows from the tip side to the rear end, then extends at a constant width, then gradually widens and then narrows in a curved manner. The shape of the handle portion 11 in a front view is approximately semicircular at the rear end.

As shown in FIG. 2, the handle portion 11 has a side view shape that extends from the tip end toward the rear end with a constant width, and then gradually widens until it reaches its maximum thickness, which is the finger rest area. The handle portion 11 has a side view shape that curves so that the width gradually narrows from the finger rest area of maximum thickness toward the rear end. The handle portion 11 has a side view shape with a roughly semicircular rear end.

In the present invention, the shape of the handle portion 11 is not limited to the shape in this example, and can be set appropriately taking into consideration strength, operability, design, and the like.
The dimensions of the handle portion 11 are not particularly limited and can be set appropriately. For example, the length of the handle portion 11 can be 100 mm or more. For example, the length of the handle portion 11 can be 200 mm or less.

The fitting protrusion 12 is the portion that is covered by the brush molding 20 when the brush molding 20 is attached to the handle body 10. The rear end of the fitting protrusion 12 is the rear end position of the brush molding 20 when the brush molding 20 is attached to the handle body 10.

Figure 4 is an enlarged front view of the fitting protrusion 12. As shown in Figure 4, the fitting protrusion 12 has a base 13 provided on the tip side of the handle portion 11, a tip portion 14 provided at the tip of the base 13, a recess 15, and a groove portion 16. Although not shown, the base 13 and the tip portion 14 are formed with a step in the thickness direction with respect to the handle portion 11 on both the front side and the back side, and are formed with the same thickness that is thinner than the handle portion 11. The recess 15 is provided on both sides in the width direction. The recess 15 has an arc shape with an arc center on the outside in the width direction and a concave inward. The groove portion 16 is provided on the front side of the fitting protrusion 12. The groove portion 16 is located in the center of the fitting protrusion 12 in the width direction and extends in the length direction.

[First embodiment of brush molded body 20]
Fig. 5 is a front view of the brush molded body 20 according to the first embodiment. Fig. 6 is a cross-sectional view taken along line AA in Fig. 5. Fig. 7 is a cross-sectional view taken along line BB in Fig. 5.
As shown in FIGS. 5 to 7 , the brush molded body 20 includes a head base portion 21 having a substantially rectangular shape when viewed from the front, and a plurality of filaments 23 provided on the front surface of the head base portion 21 .

As the soft resin constituting the brush molded body 20, various elastomers can be used, but polyurethane is preferable.
Since polyurethane tends to have a higher tensile strength than other elastomers such as styrene-based or polyester-based elastomers, by using polyurethane as a soft resin, mechanical strength can be ensured even if the material is thin, and damage can be reduced when the handle body 10 is engaged with the engaging hole 22 and when the toothbrush 1 is in use.

Polyurethane contains 0.01 to 1.0 wt% (mass%) of any of the following: saturated/unsaturated hydrocarbons with C10 or more, higher alcohols, fatty acid amides, fatty acid esters, low molecular weight polyethylene, polyethylene glycol (PEG), fatty acid metal salts, long-chain fatty acids, fatty acid glycerin, liquid paraffin, and silicone, or a combination of these, and functions as a lubricant and release agent.

In addition, polyurethane has a wider range of hardness options than the other elastomers, and the resin hardness can be selected in consideration of usability (e.g., bending of the tip of the brush molded body) according to the thickness of the brush molded body 20. The hardness of polyurethane is preferably shore 90A or more and 70D or less.
If the polyurethane has a hardness softer than Shore 90A, it becomes easily deformed when formed with a thin wall, and the fitting becomes weak, so that the brush molding 20 becomes easily detached when the toothbrush 1 is used. If the polyurethane has a hardness harder than Shore 70D, there is a possibility that pain will occur when the tip of the head base part 21 hits oral tissue if the back surface of the head base part 21 is inclined. By setting the hardness of the polyurethane to Shore 90A or more and 70D or less, it is possible to prevent the brush molding 20 from falling off when the toothbrush 1 is used, and to prevent pain from occurring when the tip of the head base part 21 hits oral tissue.

In addition, it is preferable to use ether-based polyurethane as the polyurethane, in order to ensure water resistance and antibacterial properties.

The filaments 23 are generally columnar and protrude from the support surface 21a of the head base 21 to the front side. The base end of the filaments 23 is generally triangular prism-shaped with a generally triangular cross section, and the tip end is generally triangular pyramid-shaped extending from the generally triangular prism. The filaments 23 are arranged in multiple rows along the insertion direction such that the rows aligned along the width direction of the brush molding 20 are shifted by half a pitch in the width direction from adjacent rows in the insertion direction. In other words, the filaments 23 are arranged in a staggered pattern.

As shown in Fig. 7, the filaments 23 have a long bristle length in the group at the center in the width direction and a short bristle length in the group on the outside in the width direction. The maximum bristle length of the filaments 23 is preferably 7 mm or more, and more preferably 9 mm or more. The maximum bristle length of the filaments 23 is preferably 15 mm or less, and more preferably 13 mm or less. If the maximum length of the filaments 23 is less than 7 mm, the cleaning ability of the oral cavity may decrease. If the maximum length of the filaments 23 exceeds 15 mm, the releasability when the brush molding 20 is molded by injection molding decreases.
By setting the maximum length of the filament 23 to 7 mm or more, the ability to clean the oral cavity can be ensured. By setting the maximum length of the filament 23 to 15 mm or less, the releasability during molding can be ensured.
By setting the maximum length of the filament 23 to be 7 mm or more and 15 mm or less, it is possible to ensure the ability to clean the oral cavity and the ability to be easily released during molding.

The cross-sectional area of the base end of the filament 23 is preferably 0.8 ^mm2 or less, and more preferably 0.6 ^mm2 or less. If the cross-sectional area of the base end of the filament 23 exceeds 0.8 ^mm2 , the filament 23 becomes difficult to bend, and the ability to clean gaps between teeth, at the neck of teeth, etc. may decrease. By setting the cross-sectional area of the base end of the filament 23 to 0.8 ^mm2 or less, the ability to clean gaps between teeth, at the neck of teeth, etc. can be ensured.

The ratio of the total cross-sectional area of the base ends of the filaments 23 to the area of the support surface 21a of the head base 21 is preferably 10% or more. The ratio of the total cross-sectional area of the base ends of the filaments 23 to the area of the support surface 21a of the head base 21 is preferably 50% or less, and more preferably 30% or less.
If the ratio of the total cross-sectional area of the base ends of the filaments 23 is less than 10%, the oral cavity cleaning performance may decrease. If the ratio of the total cross-sectional area of the base ends of the filaments 23 is more than 50%, the releasability when the brush molded body 20 is molded by injection molding decreases.
By making the ratio of the base end of the filament 23 to the total cross-sectional area 50% or less, releasability during molding can be ensured.
By making the ratio of the total cross-sectional area of the base end of the filament 23 to 10% or more and 50% or less, it is possible to ensure the ease of cleaning the oral cavity and the ease of releasability during molding.

The cross-sectional shape of the filament 23 can be selected from a substantially triangular shape, a substantially polygonal shape such as a substantially square shape, a substantially circular shape, a substantially star shape, a substantially spatula shape, and the like. In addition to a tapered shape with a tapered tip, the filament 23 may be configured to extend straight, or may be tapered from the base end. A triangular pyramid has one side parallel to the demolding direction (thickness direction), and the apex is away from directly above the center of the base end. Using this shape can reduce the number of steps required for cutting the mold, and production costs can be reduced.

The head base portion 21 has a fitting hole 22 , a base 24 , a side wall 25 , a bottom wall 26 , a tip wall 27 , and a structure 31 .
The fitting hole 22 extends in the insertion direction and opens at the end face 21b on the rear end side (one side). Fig. 8 is a cross-sectional view taken along CC in Fig. 7. As shown in Fig. 8, the fitting hole 22 has a first portion 33 that opens at the end face 21b and a second portion 34 that is located further back than the first portion 33. As shown in Fig. 6, the first portion 33 and the second portion 34 are disposed spaced apart from the support surface 21a and the back surface 21c of the head base portion 21, respectively.

The head base 21 has a protrusion 35 located between the first portion 33 and the second portion 34 in the insertion direction of the fitting hole 22. The protrusions 35 are provided on both sides of the fitting hole 22 in the width direction. The protrusions 35 are provided at positions that will fit into the recesses 15 when the fitting protrusion 12 of the handle body 10 is inserted into the fitting hole 22. The protrusions 35 are arc-shaped with an arc center on the outside in the width direction and a convex shape on the inside.

When the fitting protrusion 12 of the handle body 10 is inserted into the fitting hole 22 of the head base part 21, the base part 13 fits into the first part 33, the tip part 14 fits into the second part 34, and the protrusion 35 fits into the recess 15. As a result, the handle body 10 and the head base part 21 are integrated.

As shown in FIG. 7, the base 24 is located on the front side of the fitting hole 22. The base 24 has a support surface 21a and a holding surface 24a. The holding surface 24a is located on the rear side of the base 24 and faces the fitting hole 22. The support surface 21a and the holding surface 24a are planar and perpendicular to the thickness direction. The side walls 25 are located on both sides in the width direction of the fitting hole 22. The side walls 25 extend from both ends in the width direction of the base 24 to the rear side.

The bottom wall 26 is located on the rear side of the fitting hole 22. The bottom wall 26 connects the rear side ends of the side walls 25. As shown in Fig. 6, the bottom wall 26 gradually extends in a direction toward the front side as it approaches the tip side. The distance between the base end of the filament 23 located at the most tip side and the rear surface 21c is preferably 1.5 mm or more. The distance between the base end of the filament 23 located at the most tip side and the rear surface 21c is preferably 3.0 mm or less.
The smaller the distance between the base end of the filament 23 and the back surface 21c, the more the operability in the oral cavity improves. On the other hand, if the distance between the base end of the filament 23 and the back surface 21c is large, the operability decreases.

The tip wall 27 is located on the tip side of the fitting hole 22. The tip wall 27 connects the tip of the base 24 and the tip of the bottom wall 26. The fitting hole 22 is surrounded by the base 24, the side wall 25, the bottom wall 26, and the tip wall 27.

The structure 31 protrudes from the holding surface 24a of the base 24 toward the rear side. The structure 31 protrudes toward the rear side with a constant width dimension. The widthwise distance of the structure 31 is, for example, 0.5 mm or more. The widthwise distance of the structure 31 is, for example, 5.0 mm or less. As shown in Figures 5 and 6, the structure 31 is located at the center in the width direction and extends in the length direction with a constant width dimension. The structure 31 is rectangular. The tip side of the structure 31 is connected to the bottom wall 26 and the tip wall 27. The end of the structure 31 on the rear side is connected to the bottom wall 26. That is, the structure 31 is connected to the base 24 and the bottom wall 26 in the thickness direction. In this embodiment, a configuration in which one structure 31 is provided is illustrated, but a configuration in which two or more structures 31 are provided at intervals in the width direction may also be used.

FIG. 9 is a cross-sectional view showing a simplified example of a mold MD for molding the brush molded body 20. As shown in FIG.
The mold MD includes a first mold MD1 and a second mold MD2 that move relatively in the opening/closing direction (the up-down direction in FIG. 9). The first mold MD1 and the second mold MD2 are clamped together with a parting surface PL, which is flush with the support surface 21a, as a joining surface.

The first mold MD1 is attached to, for example, the fixed side of an injection molding machine, and molten resin is filled in from the injection molding machine. The second mold MD2 is attached to, for example, the movable side of the injection molding machine, and the mold MD is opened and closed by moving in the opening and closing direction (thickness direction of the brush molding body 20) relative to the first mold MD1.

The first mold MD1 has a molding surface 21aM where the support surface 21a is molded and a cavity 23M where the filament 23 is molded when the first mold MD1 is clamped and joined to the second mold MD2.

The second mold MD2 has a cavity 21M in which the head base portion 21 is molded when the second mold MD2 is clamped and joined to the first mold MD1, a gate portion G that opens to the tip side of the cavity 21M and introduces molten resin into the cavity 21M, and an abutment surface 21eM that is provided at the end face 21b in the insertion direction and is perpendicular to the insertion direction. For example, a side gate method is used as the gate portion G, but a pinpoint gate method or a tunnel gate method may also be used. The abutment surface 21eM extends in the second mold MD2 in a direction away from the PL surface from the position where the back surface of the head base portion 21 is molded.

The second mold MD2 is provided with a slide core SL. The slide core SL has a main body portion SL1 and a core block SL2. The core block SL2 is fixed to the parting surface PL side of the main body portion SL1. The core block SL2 has a core portion 22M in which the fitting hole 22 is formed, and a molding surface 21bM perpendicular to the direction in which the core portion 22M protrudes and is inserted. The area of the main body portion SL1 that faces the cavity 21M without abutting the abutment surface 21eM constitutes the molding surface 21bM. Before clamping, the molding surface 21bM is separated from the abutment surface 21eM.

FIG. 10 is an external perspective view of the core block SL2.
10, the core portion 22M has a first core portion 33M for molding the first portion 33, a second core portion 34M for molding the second portion 34, a third core portion 35M for molding the protrusion 35, and a through groove 31M for molding the structure 31. The through groove 31M penetrates the core portion 22M in the opening/closing direction of the mold MD. The through groove 31M opens at a tip end in the insertion direction.

When the first mold MD1 and the second mold MD2 are clamped, as shown in FIG. 9, a part of the molding surface 21bM abuts against the abutment surface 21eM, and the slide core SL is positioned at a position where the core portion 22M is inserted into the cavity 21M. The area of the molding surface 21bM that does not abut against the abutment surface 21eM and faces the cavity 21M is the area where the end surface 21b is molded. In addition, when the first mold MD1 and the second mold MD2 are opened, the slide core SL moves in a direction in which the core portion 22M leaves the cavity 21M (to the right in FIG. 9) so that the core portion 22M does not interfere with the release of the molded brush molding body 20. The movement direction of the slide core SL is preferably horizontal to avoid unexpected movement due to its own weight.

In the above-mentioned mold MD, when the first mold MD1 and the second mold MD2 are clamped, the molten resin is introduced from the gate G into the cavity 21M, and fills the cavity 21M and also the cavity 23M. The molten resin filled into the cavity 21M and the cavity 23M is cooled for a predetermined time inside the mold MD and solidifies, forming the brush molding body 20.

Then, the second mold MD2 moves relative to the first mold MD1 to open the mold. In the initial stage of mold opening, the first mold MD1 and the second mold MD2 separate without the slide core SL moving. When the first mold MD1 and the second mold MD2 separate without the slide core SL moving, the filament 23 is released from the first mold MD1.

The mold release resistance when the filament 23 is released from the first mold MD1 acts as a tensile force toward the front side on the base 24 of the brush molding body 20 held in the second mold MD2.

FIG. 11 is a cross-sectional view showing an initial state of mold opening when the brush molding 20 does not have the structure 31.
As shown in Figure 11, the core portion 22M is fitted into the fitting hole 22 in the molded brush molding 20, so that the bottom wall 26 of the head base portion 21, which contacts the front side of the core portion 22M, and the side wall 25 and tip wall 27 connected to the bottom wall 26, are held by the core portion 22M in the second mold MD2.

On the other hand, in the head base part 21, the base 24 is not held by the core part 22M inside the side wall 25 in the width direction in addition to the filament 23 being provided. Furthermore, the aggregate of the filaments 23 has a large surface area, and the polyurethane, which is the molding material, has the property of easily adhering to the mold. Therefore, the release resistance is increased in the central region in the width direction, where the surface area is large and the bristles of the filaments 23 are long, compared to the outer regions in the width direction, where the bristles of the filaments 23 are short. From the above two points, if the filaments 23 are arranged in a dome profile in which the bristles of the group in the width direction are long and the bristles of the group on the outer sides of the width direction are short, as shown in FIG. 7, the release resistance is likely to be uneven throughout the brush, and the difference between the regions tends to be large. Therefore, when the release resistance of the filaments 23 is large compared to the bending strength of the base 24, the tensile force caused by the release resistance may cause the base 24 to deform into a curved shape that bulges toward the front side.

Since the filament 23 is molded along the normal direction of the support surface 21a of the base 24, if the support surface 21a is curved and deformed, the base end of the filament 23 is subjected to a force in a direction intersecting the mold opening direction, as shown by the arrow in Figure 11. When the mold opening of the first mold MD1 and the second mold MD2 proceeds in this state, the filament 23 may be released while being handled by the first mold MD1, causing deformation.

On the other hand, as shown in FIG. 7, in the brush molding 20 of this embodiment, the structure 31 connects the base 24 and the bottom wall 26. Therefore, the base 24 is held in the core portion 22M via the bottom wall 26 and the structure 31. The base 24 is prevented from deforming toward the front side at the center of the width where the structure 31 is located. Therefore, deformation of the filament 23 during demolding is prevented.

Fig. 12 is a cross-sectional view of the head base 21. In Fig. 12, the filament 23 is omitted.
12, the distance in the thickness direction between the support surface 21a and the holding surface 24a (the thickness of the base 24) is t1 (mm), the maximum width of the head base part 21 is W1 (mm), the maximum width of the fitting hole 22 is W2 (mm), the maximum distance in the width direction of the structure 31 (the width dimension of the structure 31) is V, and the width of the fitting hole 22 located between the structure 31 and the side wall 25 in the width direction of the head base part 21 is W3 (mm). It is assumed that a tensile force caused by the release resistance acts as an evenly distributed load P on the base 24 supported at both ends by the side wall 25, and the Young's modulus of the head base part 21 is E and the second moment of area is I.

In the head base portion 21 not having the structure 31 shown in Figure 11, when the side wall 25 and bottom wall 26 held by the core portion 22M are treated as rigid bodies, the base 24 deforms with a maximum width W2, and the maximum deflection δ1 is expressed by the following equation (1).
δ1=(5×P×W2 ⁴ )/(384×E×I) (1).

On the other hand, in the head base portion 21 having the structure 31 shown in Figure 7, when the side wall 25, bottom wall 26 and structure 31 held by the core portion 22M are treated as rigid bodies, the base 24 deforms with a maximum width W3, and the maximum deflection δ2 is expressed by the following equation (2).
δ2=(5×P×W3 ⁴ )/(384×E×I) (2).
Therefore, the ratio of the maximum deflection δ2 in the head base 21 having the structure 31 to the maximum deflection δ1 in the head base 21 not having the structure 31 is expressed by the following formula (3) using formulas (1) and (2).
δ2/δ1=(W3/W2) ⁴ ...(3)

For example, if the distance t1 is 0.4 mm, the maximum width W2 is 8.4 mm, and the width dimension V of the structure 31 is 0.3 mm, then the maximum width W3 is 4.05 mm, and δ2/δ1 is approximately 0.05. In other words, by having the structure 31, the head base 21 can reduce deformation caused by release resistance to approximately 1/20.

The preferred maximum thickness T of the head base 21 is 2.0 mm or more. The preferred maximum thickness T of the head base 21 is 5.5 mm or less, and more preferably 4.5 mm or less. By setting the preferred maximum thickness T of the head base 21 within the above range, operability in the oral cavity can be improved.
The maximum thickness t2 (mm) of the fitting hole 22 (i.e., the maximum height t4 of the structure 31) is preferably 1.0 mm or more. The maximum thickness t2 (mm) is preferably 2.5 mm or less.
The maximum thickness t3 (mm) of the bottom wall 26 is preferably 0.5 mm or more. The maximum thickness t3 (mm) of the bottom wall 26 is preferably 2.0 mm or less.

The distance t1 is preferably 0.4 mm or more, more preferably 0.5 mm or more, and even more preferably 0.8 mm or more. The distance t1 is preferably 2.0 mm or less, more preferably 1.5 mm or less, and even more preferably 1.2 mm or less.
If the distance t1 is less than 0.4 mm, the fluidity of the resin may decrease, which may result in molding defects such as non-filling of the filament 23. If the distance t1 is more than 2.0 mm, the head base portion 21 becomes large, which may result in poor operability in the oral cavity.
By setting the distance t1 to 0.4 mm or more, it is possible to suppress molding defects in the filament 23. By setting the distance t1 to 2.0 mm or less, it is possible to ensure good intraoral operability.
By setting the distance t1 to be 0.4 mm or more and 2.0 mm or less, molding defects in the filament 23 can be suppressed while ensuring good intraoral operability.

As described above, in the brush molding 20 of this embodiment, the structure 31 that protrudes from the holding surface 24a of the base 24 to the rear side is provided, thereby reducing deformation of the base 24. Therefore, in the brush molding 20 of this embodiment, it is no longer necessary to take specification measures that have a significant impact on the appearance and usability in order to suppress deformation of the filament 23, and design freedom is possible.

[Second embodiment of brush molded body 20]
Next, a second embodiment of the brush molding 20 will be described with reference to FIGS.
In these figures, the same elements as those in the first embodiment shown in FIGS. 1 to 12 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 13 is a cross-sectional view of a brush molded body 20 according to the second embodiment.
As shown in FIG. 13, the brush molding 20 of this embodiment has a structure 31A.
The structure 31A protrudes toward the rear side from the holding surface 24a of the base 24. The structure 31A protrudes toward the rear side with a constant width dimension. The structure 31A is located at the center in the width direction and extends in the length direction with a constant width dimension. The end of the structure 31A on the rear side is separated from the bottom wall 26. In the core portion 22M of the core block SL2, a groove portion extending in the insertion direction and recessed from the front side to the rear side is provided in order to mold the structure 31A.
The other configurations are similar to those of the first embodiment.

In the brush molding 20 of this embodiment, the structure 31A functions as a beam connected to the bottom wall 26 and the tip wall 27 at the tip side of the base 24, and compared to a case in which the structure 31A is not included, it is possible to suppress deformation of the base 24 caused by the tensile force resulting from the release resistance of the filament 23, and thus suppress deformation of the filament 23. Therefore, with the brush molding 20 of this embodiment, the same action and effect as in the first embodiment can be obtained.

In the brush molding 20 of this embodiment, the cross section of the structure 31A is added to the cross section of the base 24. Therefore, the second moment of area corresponding to the T-shaped cross section of the base 24 and the structure 31A when the structure 31A is present is larger than the rectangular cross section of the base 24 when the structure 31A is not present.

Fig. 14 is a cross-sectional view of the head base 21 according to the second embodiment. In Fig. 14, the filament 23 is omitted.
As shown in FIG. 14, for example, the distance t1 of the base 24 to the base 24 is 0.4 mm, the maximum width W2 is 8.4 mm, the width dimension V of the structure 31A is 3.0 mm, the height of the structure 31A (the amount of protrusion from the holding surface 24a to the back side) t4 is 0.3 mm, the second moment of area in the base 24 is I1, and the second moment of area in the base 24 and the structure 31A is I2. In this case, the second moment of area I1 of the rectangular cross section is about 0.0448, and the second moment of area I2 of the T-shaped cross section is about 0.1385. Therefore, the ratio (I2/I1) of the second moment of area I2 of the head base part 21 having the structure 31 to the second moment of area I1 of the head base part 21 not having the structure 31 is about 3.1. That is, by having the structure 31A, the head base part 21 can reduce the deformation caused by the mold release resistance to about 1/3.

If the area of the structure 31A on the same plane as the holding surface 24a is S1 ( ^mm2 ) and the area of the fitting hole 22 including the intersection with the structure 31A is S2 ( ^mm2 ), then the value expressed by (S1/S2) x 100(%) is preferably 10% or more. The value expressed by (S1/S2) x 100(%) is preferably 40% or less, more preferably 30% or less, and even more preferably 20% or less.

When the value expressed by (S1/S2)×100(%) is less than 10%, the width or length of the structures 31A becomes shorter, and therefore there is a possibility that suppressing the deformation of the base 24 will not be sufficient to suppress the deformation of the filament 23. When the value expressed by (S1/S2)×100(%) exceeds 40%, the resin will not be cooled and solidified uniformly between the portions of the base 24 that intersect with the structures 31A and the portions that do not intersect with the base 24, and molding defects known as sink marks will easily occur at the portions of the base 24 that intersect with the structures 31A.
By setting the value expressed by (S1/S2)×100(%) to 10% or more, it is possible to ensure a sufficient force for suppressing deformation of the base 24. By setting the value expressed by (S1/S2)×100(%) to 40% or less, it is possible to suppress molding defects.
By setting the value represented by (S1/S2)×100(%) to be 10% or more and 40% or less, it is possible to suppress molding defects while ensuring a sufficient force for suppressing deformation of the base 24.

The area S1 of the structures 31A is preferably 10 mm ² or more. The area S1 of the structures 31A is preferably 70 mm ² or less.
The area S2 of the holding surface 24a is preferably 60 ^mm2 or more. The area S2 of the holding surface 24a is preferably 200 ^mm2 or less. Furthermore, if the area of the support surface 21a is S5 ( ^mm2 ), the value expressed by (S1/S5) x 100 (%) is preferably 5% or more. The value expressed by (S1/S5) x 100 (%) is preferably 30% or less, more preferably 20% or less, and even more preferably 15% or less.

If the cross-sectional area of the structure 31A perpendicular to the length direction is S3 (mm ² ) and the cross-sectional area of the fitting hole 22 perpendicular to the length direction is S4 (mm ² ), the value expressed by (S3/S4)×100(%) is preferably 5% or more. The value expressed by (S3/S4)×100(%) is preferably 30% or less, more preferably 25% or less, and even more preferably 20% or less.
However, in the case where the structure 31A is tapered in the width direction and narrows toward the tip side in the longitudinal direction, it is sufficient that the value expressed by (S3/S4)×100(%) is within the above range in an area of 80% or more of the total length of the structure 31A in the longitudinal direction.

When the value expressed by (S3/S4)×100(%) is less than 5%, the width or height of the structure 31A is shortened, so that the force of suppressing the deformation of the filament 23 by suppressing the deformation of the base 24 may not be sufficient. When the value expressed by (S3/S4)×100(%) exceeds 30%, the cross-sectional area of the core portion 22M in the slide core SL is greatly reduced, so that it becomes difficult to ensure the strength of the steel material forming the core portion 22M. In addition, when the value expressed by (S3/S4)×100(%) exceeds 30% and the width of the structure 31A is long, the resin is cooled and solidified non-uniformly between the portion of the base 24 that intersects with the structure 31A and the portion that does not intersect with the structure 31A, so that molding defects called sink marks are likely to occur at the portion of the base 24 that intersects with the structure 31A.
Setting the value represented by (S3/S4)×100(%) to 5% or more ensures a sufficient force to suppress deformation of the base 24. Setting the value represented by (S3/S4)×100(%) to 30% or less makes it possible to suppress molding defects while sufficiently ensuring the strength of the steel material forming the core portion 22M.
By setting the value represented by (S3/S4) x 100 (%) to be greater than 5% and less than 30%, it is possible to suppress molding defects while sufficiently ensuring the force suppressing deformation of the base 24 and the strength of the steel material forming the core portion 22M.

The cross-sectional area S3 of the structure 31A is preferably 0.5 mm ² or more. The cross-sectional area S3 of the structure 31A is preferably 10 mm ² or less.
The cross-sectional area S4 of the fitting hole 22 is preferably 8 ^mm2 or more. The cross-sectional area S4 of the fitting hole 22 is preferably 24 ^mm2 or less.
The height of the structures 31A is preferably 0.5 mm or more, and 2.5 mm or less.

In the first and second embodiments, the width of the structures 31 and 31A is constant in the length direction, but the present invention is not limited to this. The width of the structures 31 and 31A may be gradually increased toward the tip end in the length direction.
When this configuration is adopted, the grooves of the core parts 22M in the slide core SL for molding the structures 31, 31A are inclined as a draft angle with respect to the sliding direction of the slide core SL, thereby improving the slidability of the slide core SL.

Furthermore, when this configuration is adopted, the opening at the tip side where the gate portion G is located becomes larger, and the filling property of the resin introduced from the tip side through the gate portion G can be improved. By improving the filling property of the resin, the molding conditions can be relaxed, and overfilling of the resin can be suppressed, which also contributes to improving the releasability of the filament 23.

[Third embodiment of brush molded body 20]
Next, a third embodiment of the brush molding 20 will be described with reference to FIG.
In this figure, the same elements as those in the first embodiment shown in FIGS. 1 to 12 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 15 is a cross-sectional view in the thickness direction at a position including the structure 31.
As shown in FIG. 15, the width of the head base portion 21 located outside the fitting hole 22 in the width direction gradually increases from the rear end side to the front end side.
The other configurations are similar to those of the first embodiment.

In this embodiment, in addition to obtaining the same effects and advantages as the first embodiment, the volume of the space at the tip end of the cavity 21M in which the head base portion 21 is molded can be made larger than the volume of the space at the rear end. Therefore, when the gate portion G is disposed at the tip end, the resin fluidity is improved, making it possible to fill and mold the resin at low speed and low pressure. As a result, deformation of the filament 23 can be suppressed in the brush molding body 20, particularly at the rear end where overfilling is likely to occur.

[Fourth embodiment of brush molded body 20]
Next, a fourth embodiment of the brush molding 20 will be described with reference to FIG.
In this figure, the same elements as those in the first embodiment shown in FIGS. 1 to 12 are designated by the same reference numerals, and the description thereof will be omitted.

Fig. 16 is a cross-sectional view perpendicular to the width direction of the head base 21 according to the fourth embodiment. As shown in Fig. 16, the thickness dimension of the base 24 gradually increases from the tip end side to the rear end side.
The other configurations are similar to those of the first embodiment.

When the gate portion G is located at the tip side, the resin is introduced into the cavity 21M from the tip side during molding, so the pressure due to the resin flow tends to concentrate at the end portion on the rear end side located on the opposite side of the gate portion G in the longitudinal direction. As a result, overfilling is likely to be induced at the end portion on the rear end side, and the releasability of the filament 23 tends to decrease. In this embodiment, in addition to obtaining the same action and effect as the first embodiment, the thickness dimension of the base 24 gradually increases from the tip side to the rear end side, so that the releasability of the filament 23 can be improved by reducing the pressure at the end portion on the rear end side.

On the other hand, if the thickness dimension of the head base 21 is increased, the maneuverability in the oral cavity decreases when the toothbrush is used to reach areas with narrow spaces, such as the back teeth. Therefore, by gradually increasing the thickness dimension of the base 24 from the tip side to the rear end side, it is possible to suppress deformation of the filament 23 while suppressing the decrease in maneuverability in the oral cavity.

[Fifth embodiment of brush molded body 20]
Next, a fifth embodiment of the brush molding 20 will be described with reference to FIG.
In this figure, the same elements as those in the first embodiment shown in FIGS. 1 to 12 are designated by the same reference numerals, and the description thereof will be omitted.

Figure 17 is a cross-sectional view perpendicular to the width direction of the head base 21 according to the fifth embodiment. As shown in Figure 17, the head base 21 has a second structure 32. The second structure 32 protrudes from the support surface 21a to the front side. The height of the second structure 32 is preferably 0.5 mm or more. The height of the second structure 32 is preferably 3.0 mm or less. The second structure 32 is disposed on the rear end side of the multiple filaments 23. The shape of the second structure 32 when viewed from the rear end side is not particularly limited, and a rectangular shape, a trapezoidal shape, a semicircular shape, etc. can be selected. The shape of the second structure 32 when viewed in the width direction is not limited to the rectangular shape shown in Figure 17, and a trapezoidal shape, a semicircular shape, etc. can be selected.

In this embodiment, the second structure 32 is positioned further rearward than the multiple filaments 23, so by making the head base 21 thicker only at the rear end, which is a region where deformation is likely to occur, it is possible to resist the tensile force at the region where deformation is likely to occur, and to prevent deformation of the brush part without affecting operability in the oral cavity.

[Sixth embodiment of brush molded body 20]
Next, a sixth embodiment of the brush molding 20 will be described with reference to FIG.
In this figure, the same elements as those in the first embodiment shown in FIGS. 1 to 12 are designated by the same reference numerals, and the description thereof will be omitted.

Figure 18 is a cross-sectional view perpendicular to the length direction of the head base 21 according to the sixth embodiment. As shown in Figure 18, the holding surface 24a facing the fitting hole 22 gradually curves and extends in a direction toward the rear side as it moves outward in the width direction from the structure 31.

In this embodiment, the thickness dimension of the base 24 in the head base portion 21 increases from the structure 31 toward the outside in the width direction, so the second moment of area of the base 24 outside the structure 31 in the width direction becomes large. Therefore, in this embodiment, it is possible to reduce deformation of the base 24 due to tensile force caused by release resistance without increasing the thickness dimension of the head base portion 21. As a result, in this embodiment, it is possible to improve the releasability of the filament 23 while suppressing deterioration of intraoral operability.

[Seventh embodiment of brush molded body 20]
Next, a seventh embodiment of the brush molding 20 will be described with reference to FIG.
In this figure, the same elements as those in the first embodiment shown in FIGS. 1 to 12 are designated by the same reference numerals, and the description thereof will be omitted.

Figure 19 is a cross-sectional view perpendicular to the length direction of the head base portion 21 according to the seventh embodiment. As shown in Figure 19, the brush molding 20 of this embodiment has a structure 31B. The structure 31B protrudes from the holding surface 24a of the base 24 toward the rear side. The end of the structure 31B on the rear side is separated from the bottom wall 26.

With respect to the cross-sectional area perpendicular to the thickness direction, structure 31B has a first region 31C having a first cross-sectional area, and a second region 31D located closer to the rear side than first region 31C and having a second cross-sectional area larger than the first cross-sectional area. The width dimension of structure 31B gradually increases toward the rear side. The cross-sectional shape of structure 31B is a trapezoid with an inclined surface 30 that extends in a direction toward the outside in the width direction toward the rear side.

If the width dimension of the structure 31B on the same plane as the holding surface 24a is V1 (mm) and the width dimension of the structure 31B at the end on the rear side is V2 (mm), the second region 31D having the width dimension V2 is located closer to the rear side than the first region 31C having the width dimension V1.

Therefore, in structure 31B, if an arbitrary position located closer to the front side than the rear end is defined as first region 31C, then the region located closer to the rear side than first region 31C is defined as second region 31D. For example, in structure 31B, if the position of holding surface 24a in the thickness direction is defined as first region 31C, then the region located closer to the rear side than holding surface 24a in the thickness direction is defined as second region 31D.

FIG. 20 is an external perspective view of a core block SL2 according to the seventh embodiment.
As shown in FIG. 20, the core portion 22M has a through groove 31BM that forms the structure 31B.
In the core portion 22M of the core block SL2, a groove portion 31BM extending in the insertion direction and recessed from the front side to the back side is provided to form the structure 31B. The core portion 22M has inclined surfaces 30M facing the groove portion 31BM on both sides in the width direction. The inclined surfaces 30M form the inclined surfaces 30. The inclined surfaces 30M extend in a direction toward the outside in the width direction as they approach the back side.

In this embodiment, immediately after the brush molding body 20 is molded, the inclined surface 30M of the core portion 22M contacts the inclined surface 30 from the front side, as shown in FIG. 19. When the mold is opened and the filament 23 is released from the first mold MD1, a tensile force caused by the mold release resistance is applied to the base 24. At this time, the inclined surface 30 of the structure 31B protruding from the base 24 to the rear side is restricted from moving toward the front side by contacting the inclined surface 30M of the core portion 22M from the front side. Therefore, the structure 31B is considered to be a rigid body with respect to the tensile force caused by the mold release resistance.

Therefore, deformation of the base 24 is suppressed at the point where it intersects with the structure 31B in the width direction, and similar to the base 24 shown in FIG. 12, it deforms at the maximum width W3 located between the structure 31B and the side wall 25 in the width direction and facing the fitting hole 22. Therefore, in this embodiment, the maximum deflection against the tensile force caused by the mold release resistance can be significantly reduced compared to when the base 24 deforms at the maximum width W1 in the width direction. Therefore, in the brush molding 20 of this embodiment, it is no longer necessary to take specification measures that have a significant impact on the appearance and usability in order to suppress deformation of the filament 23, and design with a high degree of freedom is possible.

Furthermore, in the brush molding 20 of this embodiment, the position in the thickness direction where the structure 31B contacts the core portion 22M is immediately adjacent to the base 24, so that the stretching of the structure 31B itself due to the tensile force caused by the mold release resistance is also minimized. As a result, in the brush molding 20 of this embodiment, there is no need to take specification measures that have a significant impact on the appearance and usability in order to more effectively suppress deformation of the filament 23, and design freedom is possible.

The configuration of the structure 31B having the second region with the second cross-sectional area larger than the first cross-sectional area in the first region is not limited to the trapezoidal cross-sectional shape described above.
For example, as shown in FIG. 21, a structure 31E may be used in which the end portion on the rear side is connected to the bottom wall 26.
In this configuration, even at the rear end of the structure 31E, the core portion 22M can restrict movement toward the front side due to a tensile force caused by mold release resistance via the bottom wall 26.

Also, for example, as shown in FIG. 22, a first region 31C having a constant width dimension is arranged on the front side, a second region 31D having a width dimension that increases toward the rear side is arranged on the rear side, and a structure 31F is provided in which the end of the second region 31D is connected to the bottom wall 26.
With this configuration as well, the same actions and effects as those of the structure 31E shown in FIG. 21 can be obtained.

Also, for example, as shown in FIG. 23, a structure 31G may be provided in which a first region 31C whose width dimension increases linearly toward the rear side is arranged on the front side, and a second region 31D which forms a curved surface whose width dimension increases curvedly toward the rear side is arranged closer to the rear side than the first region 31C.
In this configuration, the direction of the normal force on the curved surface of the second region 31D is closer to the opposite side to the direction of the tensile force caused by the release resistance applied to the structure 31G, so that the thickness-wise position of the structure 31G can be more firmly maintained.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples and can be modified as appropriate without departing from the spirit of the invention.

(Examples 1 to 6, Comparative Example 1)
According to the specifications shown in Table 1, toothbrush samples having a brush molded body were prepared. As shown in the cross-sectional shape item of Table 1, the toothbrush having the structure of the seventh embodiment shown in FIG. 21 was used as the sample of Example 1. The toothbrush having the structure of the first embodiment shown in FIG. 7 was used as the sample of Examples 2, 4 to 6. The toothbrush having the structure of the second embodiment shown in FIG. 13 was used as the sample of Example 3. The toothbrush having no structure was used as the sample of Comparative Example 1. In each sample, the maximum length dimension of the head base was 20.3 mm, and the maximum length dimension of the fitting hole was 18.3 mm. Of the resins constituting each sample, the resin of the brush molded body was thermoplastic polyurethane (TPU), and the handle portion was polyacetal resin (POM).

[Evaluation method]
Each sample of Examples 1 to 6 and Comparative Example 1 was evaluated for "filament deformation due to mold release resistance" and "intraoral operability."

(1) Evaluation Method for Filament Deformation Due to Release Resistance Ten brush molded bodies molded under the same conditions were visually evaluated according to the following criteria.
5 points: No defects in appearance were observed.
4 points: Deformation occurred within a range of 0.5 to 3 mm from the tip of the filament.
3 points: The entire filament is deformed, but no deformation of the base is observed.
2 points: The entire filament and base are deformed.
1 point: The entire brush part and base are significantly deformed, and some of the filaments are broken at the base end.
The average of the 10 evaluation points was calculated and rated according to the following four levels.
◎(double circle mark): 4.5 or above, 5.0 or below.
○ (circle mark): 3.5 or more, less than 4.5 points.
△ (triangle mark): 2.5 or more, less than 3.5 points.
× (cross mark): Less than 2.5 points.

(2) Method for evaluating intraoral operability A sensory evaluation was conducted by 10 expert panelists, who evaluated the ease of brushing the entire oral cavity when brushing (with particular emphasis on the ease of brushing the molars) according to the following criteria.
5 points: Very easy to polish.
4 points: Somewhat easy to polish.
3 points: Neither.
2 points: A little difficult to polish.
1 point: Very difficult to polish.
The evaluation scores of the 10 expert panelists were then averaged and rated on the following four-point scale.
◎: 4.5 or more, 5.0 or less points.
○: 3.5 or more and less than 4.5 points.
△: 2.5 or more and less than 3.5 points.
×: Less than 2.5 points.

As shown in Table 1, the samples of Examples 1 to 6 having the structure were given good evaluations for both "filament deformation due to release resistance" and "intraoral operability". The samples of Examples 1 to 5, in which the maximum thickness T of the head base is 4.0 mm or less, were given particularly good evaluations for "intraoral operability". Furthermore, the samples of Examples 1, 5 to 6, in which the distance (base thickness) t1 from the filament base end to the fitting hole holding surface is 1.0 mm or more, were given particularly good evaluations for "filament deformation due to release resistance". The sample of Example 1, in which the position in the thickness direction where the structure contacts the core is closest to the base, received the highest score in the evaluation of "filament deformation due to release resistance".

In contrast, the sample of Comparative Example 1, which does not have a structure, did not receive a good evaluation for "filament deformation due to release resistance."

Although the preferred embodiment of the present invention has been described above with reference to the attached drawings, it goes without saying that the present invention is not limited to the examples. The shapes and combinations of the components shown in the above examples are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention.

For example, in the above embodiment, the toothbrush 1 is composed of the brush molding 20 and the handle body 10 which are molded separately, and the brush molding 20 is attached to the handle body 10 by fitting the fitting protrusion 12 of the handle body 10 into the fitting hole 22 of the brush molding 20, but this configuration is not limited to the above. For example, the handle body 10 may be molded by primary molding using a first mold, and then the brush molding 20 may be insert molded by secondary molding using a second mold in which the fitting protrusion 12 of the handle body 10 is installed. This insert molding allows the toothbrush 1 to be obtained as a molded body in which the fitting protrusion 12 fits into the fitting hole 22 and the brush molding 20 and the handle body 10 are molded integrally.

In addition, in the above embodiment, the handle body 10 is formed from a hard resin, but this is not limited to this configuration. For example, a part of the handle body 10 (handle portion 11, etc.) may be coated with a soft resin. When this configuration is adopted, the decorativeness and gripping properties can be improved.

1...toothbrush, 10...handle body, 20...brush molded body, 21...head base, 21a...support surface, 21b...end surface, 22...fitting hole, 23...filament, 24...base, 24a...holding surface, 31, 31A, 31B, 31E, 31F, 31G...structure, 31C...first region, 31D...second region

Claims (11)

A head base portion formed of a soft resin;
A plurality of filaments extending from a support surface located on a front side in a thickness direction of the head base portion to the front side;
having
The head base portion is
A fitting hole extending in a length direction perpendicular to the thickness direction and opening to one side in the length direction;
a base having a holding surface located on the front side of the fitting hole and facing the fitting hole and the support surface;
a bottom wall located on a rear side opposite to the front side in the thickness direction of the fitting hole;
one or more structures protruding from the holding surface of the base toward the rear surface side and connected to the base and the bottom wall ;
The brush molding is characterized in that the structure is located at the center in a width direction perpendicular to both the thickness direction and the length direction . The area of the structure on the same plane as the holding surface is S1,
If the area of the holding surface is S2,
The value represented by (S1/S2) x 100 (%) is 10% or more and 40% or less.
The brush molding according to claim 1 . A cross-sectional area of the structure perpendicular to the longitudinal direction is S3,
If the cross-sectional area of the fitting hole perpendicular to the longitudinal direction is S4,
The value represented by (S3/S4) x 100 (%) is 5% or more and 30% or less.
The brush molding according to claim 1 or 2. The distance from the base end of the filament to the holding surface is 0.4 mm or more and 2.0 mm or less.
The brush molding according to any one of claims 1 to 3. The structure comprises:
a first region having a first cross-sectional area with respect to a cross-sectional area of the structure perpendicular to the thickness direction;
a second region located closer to the rear surface than the first region and having a second cross-sectional area larger than the first cross-sectional area;
having
The brush molding according to any one of claims 1 to 4. a width dimension of the head base portion located outside the fitting hole in a width direction perpendicular to the thickness direction and the length direction gradually increases from the one side to the other side in the length direction;
The brush molding according to any one of claims 1 to 5. a thickness dimension of the base in the thickness direction gradually increases from the other side toward the one side in the length direction;
The brush molding according to any one of claims 1 to 6. a second structure disposed on the one side of the filaments in the length direction and protruding from the support surface to the front side;
The brush molding according to any one of claims 1 to 7. the holding surface facing the fitting hole gradually extends in a direction toward the rear side as it moves outward from the structure in a width direction perpendicular to the thickness direction and the length direction;
The brush molding according to any one of claims 1 to 8. A brush molding according to any one of claims 1 to 9,
a handle body formed of a hard resin and having a fitting protrusion that is detachably attached to the fitting hole of the brush molded body. A brush molding according to any one of claims 1 to 9,
a handle body having a fitting protrusion that fits into the fitting hole of the brush molded body,
The toothbrush is characterized in that the brush body and the handle body are an integrally molded body.

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