Brush molded body

Abstract

To provide a brush molded body with excellent cleaning power. [Solution] The brush comprises a head base made of soft resin, a plurality of brush portions protruding to the front from a support surface located on the front side in the thickness direction of the head base, and an undercut portion formed by a recess located on the front side of the support surface and in a position that is in shadow when viewed from the front.

Description

Technical Field

[0001] The present invention relates to a brush molded body.

Background Art

[0002] An integrally molded toothbrush that manufactures a toothbrush only with an injection molding machine has been proposed (for example, Patent Document 1). Since the integrally molded toothbrush integrally molds the filaments and the head base portion (or the head portion), it does not require the procurement of filament materials and a hair implanting machine, and has the advantage of being able to be manufactured at a lower cost than a hair-implanted toothbrush.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Injection molding involves injecting resin into a mold and removing the molded product from the mold to obtain a molded object. Many brush molded bodies and toothbrushes having a brush portion made of a soft resin molded by injection molding have already been disclosed, and the shape of the brush portion has been widely studied.

[0005] On the other hand, in injection molding, there are cases where the molded product has a structure called an undercut that cannot be demolded in the mold opening and closing direction. In this case, since it is difficult to obtain a molded object, it is necessary to incorporate a special mechanism into the mold, and since the manufacturing cost of the mold increases, there are many brush portion shapes assuming a structure without an undercut. Therefore, brush molded bodies and toothbrushes with brush portion shapes that are not necessarily excellent in cleaning power have been provided.

[0006] The present invention has been made in consideration of the above points, and an object thereof is to provide a brush molded body excellent in cleaning power. [Means for solving the problem]

[0007] The present invention has the following aspects. [1] A head base made of soft resin, Multiple brush portions protruding toward the front from a support surface located on the front side in the thickness direction of the head base portion, An undercut portion formed by a recess located on the front side of the support surface and in a position that is in shadow when viewed from the front side, A brush molded body having a brush. [2] The brush molded body according to [1], wherein the undercut portion is formed on the surface of the brush portion. [3] The brush molded body according to [1] or [2], wherein the undercut portion is formed inside the brush portion. [4] The brush molded body according to any one of the claims [1] to [3], wherein the undercut portion is formed at a position that supports the brush portion with respect to the support surface. [Effects of the Invention]

[0008] The present invention provides a brush molded body with excellent cleaning power. [Brief explanation of the drawing]

[0009] [Figure 1] This is a front view of a brush molded body 20 and a toothbrush 1 according to an embodiment of the present invention. [Figure 2] This is a side view of the brush molded body 20 and the toothbrush 1. [Figure 3] This is a front view of the handle body 10. [Figure 4] This is an enlarged front view of the fitting projection 12. [Figure 5] This is a side view of the brush molded body 20. [Figure 6] This is a cross-sectional view of AA in Figure 5. [Figure 7]It is a view of the brush molded body 20 in Form 2 seen from the tip side. [Figure 8] It is a view of the bristle part 23 in Form 2 partially seen from the front side. [Figure 9] It is a view of the brush molded body 20 in Form 3 seen from the tip side. [Figure 10] It is a partial B - B cross - sectional view in FIG. 9. [Figure 11] It is a view of the brush molded body 20 in Form 4 seen from the tip side. [Figure 12] It is a view of the brush molded body 20 in Form 4 seen from the front side. [Figure 13] It is a partial enlarged view showing a modified example of the protrusion 23k. [Figure 14] It is a perspective view of the brush molded body 20 in Form 5. [Figure 15] It is a perspective view of the brush molded body 20 in Form 6. [Figure 16] It is a front view of the brush molded body 20 in Form 6. [Figure 17] It is a perspective view of the brush molded body 20 in Form 7. [Figure 18] It is a cross - sectional view of the brush molded body 20 in Form 7. [Figure 19] It is a perspective view of the brush molded body 20 in Form 7.

Embodiments for Carrying out the Invention

[0010] Hereinafter, embodiments of the brush molded body of the present invention will be described with reference to FIGS. 1 to 19. The following embodiments show one aspect of the present invention, do not limit this invention, and can be arbitrarily changed within the scope of the technical idea of the present invention. Also, in the following drawings, for the sake of clarity of each configuration, the actual structure and the scales, numbers, etc., in each structure are made different.

[0011] Figure 1 is a front view of the brush molded body 20 and toothbrush 1 according to this embodiment. Figure 2 is a side view of the brush molded body 20 and toothbrush 1. The toothbrush 1 comprises a rod-shaped handle body 10 and a brush molded body 20. The handle body 10 and the brush molded body 20 are separate components. The brush molded body 20 can be detachably attached (inserted) into the handle body 10. The brush molded body 20 is made of a soft resin. The handle body 10 is made of a hard resin.

[0012] In this embodiment, the front side refers to the side (upper side in Figure 2) on which the brush portion 23, described later, protrudes in the thickness direction (hereinafter simply referred to as the thickness direction), which is the normal direction of the support surface 21a (details described later) of the brush molded body 20. In the thickness direction of the brush molded body 20, the side opposite to the front side is appropriately referred to as the back side. In addition, the length direction (hereinafter simply referred to as the length direction) of the handle body 10, in which the handle body 10 is inserted into the brush molded body 20 (hereinafter simply referred to as the insertion direction), is perpendicular to the above-mentioned normal direction. In the length direction, the side on which the handle body 10 is attached to the brush molded body 20 is referred to as the rear end side (one side in the length direction), and the side opposite to the rear end side is appropriately referred to as the front end side (the other side in the length direction). In addition, the direction perpendicular to the above-mentioned normal direction and the insertion direction is the width direction (hereinafter simply referred to as the width direction) of the brush molded body 20. In this embodiment, the long axis direction is the direction in which the brush portion 23 extends, and is parallel to the normal direction described above.

[0013] Figure 3 is a front view of the handle body 10. As shown in Figure 3, the handle body 10 comprises a rod-shaped gripping portion 11 and a fitting projection 12 that protrudes from the longitudinal end of the gripping portion 11. In the toothbrush 1, the fitting projection 12 of the handle body 10 is inserted into the brush molded body 20, which will be described later, thereby attaching the brush molded body 20 to the fitting projection 12.

[0014] The handle body 10 is made of a rigid resin. As an example of a rigid resin, a resin with a flexural modulus (JIS K7171) of 1500 MPa or more and 3000 MPa or less can be used. Specifically, examples include polypropylene resin (PP), polyacetal resin (POM), polybutylene terephthalate (PBT), polyester resin (PCTA), polyethylene terephthalate copolymer (PETG), and high-density polyethylene (HDPE). Among these, PP is preferred as a general-purpose resin considering cost, and POM and PBT are even more preferred in order to ensure the strength of the fitting projection 12.

[0015] In this embodiment, the front view shape of the gripping portion 11 is, for example, curved, such that the width gradually narrows from the front end to the rear end, then extends to a constant width, and then gradually widens before narrowing again. The rear end of the gripping portion 11 has a roughly semi-circular shape when viewed from the front.

[0016] As shown in Figure 2, the side view shape of the gripping portion 11 extends from the front end to the rear end with a constant width, and then gradually widens to the maximum thickness that forms the finger rest portion. The side view shape of the gripping portion 11 changes curvilinearly so that the width gradually narrows from the finger rest portion, which is the maximum thickness, towards the rear end. The rear end of the gripping portion 11 has a roughly semi-circular shape.

[0017] In this invention, the shape of the gripping portion 11 is not limited to the shape shown in this example, and can be appropriately set considering strength, operability, design, etc. The dimensions of the gripping portion 11 are not particularly limited and can be set as appropriate. For example, the length of the gripping portion 11 can be 100 mm or more. For example, the length of the gripping portion 11 can be 200 mm or less.

[0018] The fitting projection 12 is the portion that is covered by the brush molded body 20 when the brush molded body 20 is attached to the handle body 10. The rear end of the fitting projection 12 is the rear end position of the brush molded body 20 when the brush molded body 20 is attached to the handle body 10.

[0019] Figure 4 is an enlarged front view of the fitting projection 12. As shown in Figure 4, the fitting projection 12 is rectangular in shape and extends in the longitudinal direction. The fitting projection 12 extends in the longitudinal direction with a constant thickness. The fitting projection 12 has a base portion 13 connected to the tip side of the gripping portion 11, a tip portion 14 provided at the tip of the base portion 13, and a recess 15. The tip portion 14 is located closer to the tip than the recess 15.

[0020] The recesses 15 are provided on both sides in the width direction. The two recesses 15 on both sides in the width direction are in the same position in the length direction. The recesses 15 have an arc shape with the arc center on the outside in the width direction and a concave shape on the inside. The recesses 15 are provided symmetrically with respect to the width direction.

[0021] The base portion 13 and the tip portion 14 have steps on both sides in the width direction relative to the gripping portion 11. In other words, the width dimension of the base portion 13 and the tip portion 14 is smaller than the tip of the gripping portion 11. The base portion 13 has a constant width dimension on the rear end side of the recess 15. The tip portion 14 has a constant width dimension on the tip side of the recess 15. The tip portion 14 has a smaller width dimension than the base portion 13. The front view shape and side view shape of the fitting projection 12 are substantially the same as the fitting hole 22 in the brush molded body 20 (details will be described later).

[0022] Figure 5 is a side view of the brush molded body 20. Figure 6 is a cross-sectional view of AA in Figure 5. As shown in Figures 5 and 6, the brush molded body 20 comprises a head base portion 21 with a substantially rectangular shape in front view, and a plurality of brush portions 23 provided on the front surface of the head base portion 21.

[0023] 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 fitting portion 35. The fitting hole 22 extends in the insertion direction and opens at the rear end face 21b. The fitting hole 22 has a first portion 33 that opens at the end face 21b and a second portion 34 that is located closer to the front than the first portion 33. The first portion 33 and the second portion 34 are spaced apart in the thickness direction from the support surface 21a and the back surface 21c of the head base portion 21, respectively.

[0024] The first part 33 is located at the rear end of the fitting portion 35 in the longitudinal direction. The first part 33 has a constant width dimension. The base 13 of the fitting projection 12 is fitted into the first part 33.

[0025] The second part 34 is located towards the tip of the fitting portion 35. The second part 34 has a constant width dimension. The width dimension of the second part 34 is shorter than the width dimension of the first part 33. The tip 14 of the fitting projection 12 is fitted into the second part 34. The front view and side view shapes of the fitting hole 22 are substantially the same as those of the fitting projection 12 on the handle body 10.

[0026] The side walls 25 are located on both sides of the fitting hole 22 in the width direction. The side walls 25 are arranged at regular intervals in the width direction. The side walls 25 extend from both ends of the base 24 in the width direction 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 ends of the side walls 25. The bottom wall 26 is arranged at a regular distance from the base 24 in the thickness direction.

[0027] 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, the tip of the bottom wall 26, and the tips of the side walls 25. The fitting hole 22 is formed by being surrounded by the base 24, the side walls 25, the bottom wall 26, and the tip wall 27.

[0028] The fitting portions 35 are provided on both sides in the width direction. The two fitting portions 35 on both sides in the width direction are at the same position in the length direction. The fitting portions 35 have an arc shape with the arc center on the outside in the width direction and convex on the inside. The fitting portions 35 are provided symmetrically with respect to the width direction. The recesses 15 of the fitting projections 12 are fitted into the fitting portions 35.

[0029] The handle body 10 is attached to and integrated with the brush molded body 20 by fitting the base 13, tip 14, and recess 15 of the fitting projection 12 into the first part 33, second part 34, and fitting part 35 of the fitting hole 22, respectively.

[0030] As shown in Figure 5, the base 24 is located on the front side of the fitting hole 22. The base 24 has a support surface 21a from which the brush portion 23 protrudes. The support surface 21a is planar and perpendicular to the thickness direction.

[0031] The brush portion 23 is substantially columnar in shape, protruding from the support surface 21a of the head base portion 21 toward the front along the long axis. As shown in Figure 1, for example, the brush portions 23 are arranged in a grid pattern with 13 rows of 6 brushes spaced apart in the width direction and spaced apart in the length direction. The arrangement of the brush portions 23 is not limited to a grid pattern; for example, they may be arranged in a staggered pattern in which the brush portions 23 of adjacent rows in the length direction are offset by half a pitch in the width direction.

[0032] [Form 1: An undercut portion is formed on the surface of the brush portion 23] Each brush portion 23 of Embodiment 1 has a cylindrical portion 23a and a frustoconical portion 23b. Multiple cylindrical portions 23a and frustoconical portions 23b are arranged alternately along the long axis. The cylindrical portions 23a are provided at both ends of the brush portion 23 in the long axis direction. The outer diameters of the multiple cylindrical portions 23a are the same. The frustoconical portions 23b taper towards the back side from the end on the back side (support surface 21a side) of the cylindrical portion 23a and connect to the adjacent back side cylindrical portion 23a. The outer diameter of the frustoconical portion 23b at the position where it connects to the adjacent back side cylindrical portion 23a is smaller than the outer diameter of the cylindrical portion 23a.

[0033] The outer circumferential surface of the frustoconical portion 23b faces the support surface 21a. Therefore, the outer circumferential surface of the frustoconical portion 23b is in shadow when the brush portion 23 is viewed from the front side facing the support surface 21a in the longitudinal direction. In other words, a recess 40a is provided on the support surface 21a side of the outer circumferential surface of the frustoconical portion 23b, which is in shadow when the brush portion 23 is viewed from the front side. The recess 40a is located on the front side of the support surface 21a. The recess 40a is formed in the area of ​​the surface of the brush portion 23 enclosed by the outer circumferential surface of the frustoconical portion 23b, a virtual cylindrical surface extending in the longitudinal direction including the outer circumferential surface of the cylindrical portion 23a, and the front end face of the cylindrical portion 23a adjacent to the frustoconical portion 23b on the support surface 21a side.

[0034] If the brush portion 23 and the head base portion 21 are molded by injection molding using a pair of molds, one of the molds that molds the brush portion 23 has a core portion that molds the recess 40a. When the molded brush portion 23 is released from one of the molds, it moves relative to the support surface 21a side of the other mold. As the brush portion 23 moves relative to the support surface 21a side, the core portion located on the support surface 21a side of the outer circumferential surface of the frustoconical portion 23b becomes an obstacle to release. In other words, the core portion located on the support surface 21a side of the outer circumferential surface of the frustoconical portion 23b becomes an undercut when the brush portion 23 is released.

[0035] In other words, the brush molded body 20 has an undercut portion 41a formed by a recess 40a located on the front side of the support surface 21a and in a position that is in shadow when viewed from the front. The undercut portion 41a is provided on the support surface 21a side of the outer surface of a plurality of frustoconical portions 23b in each brush portion 23. The undercut portion 41a is provided intermittently along the long axis in each brush portion 23.

[0036] The undercut portion 41a creates a thicker portion formed by the cylindrical portion 23a and a thinner portion formed by the frustoconical portion 23b of the brush portion 23. The presence of the thinner portion of the brush portion 23 creates a flexible flex that allows it to conform more easily to the tooth surface. In addition, the presence of the thicker portion of the brush portion 23 generates a repulsive force based on the high rigidity of the thicker portion, making it easier to remove plaque. Furthermore, the presence of the undercut portion 41a creates a continuous uneven surface along the long axis of the brush portion 23. This uneven surface traps plaque present on the tooth surface, further enhancing the plaque removal effect and resulting in a brush molded body 20 with superior cleaning power.

[0037] The thickness of the base of the brush portion 23 (cylindrical portion 23a) (diameter of the circumscribed circle on the support surface 21a) is preferably 0.4 mm or more and 1.3 mm or less, more preferably 0.6 mm or more and 1.2 mm or less, and even more preferably 0.7 mm or more and 1.1 mm or less. If the diameter of the base of the brush portion 23 is less than 0.4 mm, the rigidity of the brush portion 23 may decrease, resulting in insufficient cleaning power. If the diameter of the base of the brush portion 23 exceeds 1.3 mm, the flexibility may be insufficient, reducing its ability to conform to the dentition and potentially decreasing cleaning power. By setting the base thickness of the brush portion 23 to 0.4 mm or more and 1.3 mm or less, the rigidity of the brush portion 23 is increased, improving cleaning power, and the ability to follow the alignment of teeth is improved by the appropriate flexibility, thereby enhancing cleaning power.

[0038] In the brush portion 23 of Form 1 shown in Figure 5, for example, the cylindrical portions 23a located at both ends in the longitudinal direction have a diameter of 1.0 mm and a height of 0.75 mm, while the other cylindrical portions 23a have a diameter of 1.0 mm and a height of 0.5 mm. The frustoconical portion 23b has a maximum diameter of 1.0 mm, a minimum diameter of 0.5 mm, and a height of 0.5 mm. The brush portions 23 of Form 1 are arranged at a pitch of 1.5 mm in both the longitudinal and width directions. For example, the brush portion 23 of Form 1 has a bristle length of 10 mm.

[0039] The brush portion 23 described above is preferably positioned at the tip of the head base portion 21 or in the center in the longitudinal direction, from the viewpoint of improving cleaning efficiency and making it easier to feel that cleaning is being done. The number of pairs of cylindrical portions 23a and frustoconical portions 23b arranged in the longitudinal direction is preferably 2 to 19, more preferably 3 to 18, and particularly preferably 4 to 17. The spacing between pairs of cylindrical portions 23a and frustoconical portions 23b may be equal or not.

[0040] [Form 2: An undercut portion is formed on the surface of the brush portion 23] Figure 7 shows the brush molded body 20 of form 2 as seen from the tip side. Figure 8 shows a partial view of the brush portion 23 from the front side.

[0041] As shown in Figure 7, each brush portion 23 of the morphology 2 is formed in a Y-shape, having a cylindrical portion 23c and an extended portion 23d that branches out from the tip of the cylindrical portion 23c toward the front, moving away from each other along the width direction. The cylindrical portion 23c is either cylindrical with the same diameter extending in the longitudinal direction or tapered towards the tip.

[0042] The extension portion 23d is formed in a semi-circular shape that opens to the front side. The tip of the extension portion 23d protrudes further than the cylindrical portion 23c in the width direction. As shown in Figure 8, the tip of the extension portion 23d is elliptical in shape when viewed from the front side, extending in the length direction.

[0043] On the support surface 21a side of the curved surface 23e, which is located on the outer diameter side of the semi-circular extension 23d when viewed from the tip side, a recess 40b is provided that is in shadow when the brush portion 23 is viewed from the front side. The curved surface 23e is formed facing the back side. The recess 40b is located on the back side of the curved surface 23e and on the front side of the support surface 21a.

[0044] As described above, if the brush portion 23 and the head base portion 21 are molded by injection molding using a pair of molds, the core portion that forms the recess 40b is located on the support surface 21a side of the curved surface 23e, resulting in an undercut when the brush portion 23 is demolded. In other words, the brush molded body 20 has an undercut portion 41b formed by the recess 40b, which is located on the front side of the support surface 21a and is in a position that is in shadow when viewed from the front.

[0045] The undercut portion 41b creates a thicker portion formed by the cylindrical portion 23c and a thinner portion formed by the extended portion 23d in the brush portion 23. As a result, the thinner portion allows for flexible bending, making it easier to follow the tooth surface, while the thicker portion generates a rebound force based on its high rigidity, making it easier to remove plaque. In addition, the undercut portion 41b traps plaque present on the tooth surface, further enhancing the plaque removal effect and resulting in a brush molded body 20 with superior cleaning power.

[0046] The thickness of the base of the brush portion 23 (cylindrical portion 23c) (diameter of the circumscribed circle on the support surface 21a) is preferably 0.4 mm or more and 1.3 mm or less, more preferably 0.6 mm or more and 1.2 mm or less, and even more preferably 0.7 mm or more and 1.1 mm or less. If the diameter of the base of the brush portion 23 is less than 0.4 mm, the rigidity of the brush portion 23 may decrease, resulting in insufficient cleaning power. If the diameter of the base of the brush portion 23 exceeds 1.3 mm, the flexibility may be insufficient, reducing its ability to conform to the dentition and potentially decreasing cleaning power. By setting the base thickness of the brush portion 23 to 0.4 mm or more and 1.3 mm or less, the rigidity of the brush portion 23 is increased, improving cleaning power, and the ability to follow the alignment of teeth is improved by the appropriate flexibility, thereby enhancing cleaning power.

[0047] The number of branches in the extension portion 23d is preferably two or more and six or less. If the number of branches in the extension portion 23d is greater than or equal to the lower limit above, a plaque removal effect can be obtained by increasing the contact area with the tooth surface. If it is less than or equal to the upper limit, the thickness of one branch (one side of the Y-shape) becomes sufficient, the rigidity of the extension portion 23d increases, and the plaque removal effect tends to improve. The tip diameter of the extension portion 23d is preferably 0.02 mm or more and 1.00 mm or less, and more preferably 0.05 mm or more and 0.90 mm or less. If the tip diameter is above the lower limit, rigidity increases, making it easier to remove plaque. If it is below the upper limit, flexibility increases, making it easier to adhere to the tooth surface, thus also making it easier to remove plaque. The tip shape of the extension portion 23d is not particularly limited, but examples include a cone, a triangular pyramid, and a square pyramid, and it may also be tapered. Preferably, the branching position of the extension portion 23d is provided from 20% of the total length of the brush portion 23 towards the tip. For example, the cylindrical portion 23c is cylindrical with a diameter of 1.0 mm. For example, the extension portion 23d has a curved surface 23e on the outer diameter side with a diameter of 1.5 mm and a curved surface on the inner diameter side with a diameter of 0.5 mm. Preferably, the branching position of the extension portion 23d is provided from 20% of the total length of the brush portion 23 towards the tip. By providing it from 20% towards the tip, the thin portion formed by the extension portion 23d does not become too thin, maintaining sufficient rigidity, and the effect of trapping plaque in the undercut portion 41b is enhanced.

[0048] [Form 3: An undercut portion is formed on the surface of the brush portion 23] Figure 9 is a view of the brush molded body 20 of form 3 from the tip side. Figure 10 is a partial cross-sectional view of the BB in Figure 9.

[0049] Each brush portion 23 of Embodiment 3 has a cylindrical portion 23f and an annular portion 23g provided at the tip of the cylindrical portion 23f, as shown in Figure 9. The cylindrical portion 23f is either cylindrical with the same diameter extending in the direction of the long axis or tapered towards the tip.

[0050] The annular portion 23g has a through hole 23h that penetrates in the longitudinal direction. The annular portion 23g is an annular shape centered on an axis that extends in the longitudinal direction. The annular portion 23g protrudes more than the cylindrical portion 23c on both sides in the width direction. As shown in Figure 10, the cross-section of the annular portion 23g is elliptical in shape that extends in the longitudinal direction.

[0051] On the outer surface of the ring-shaped annular portion 23g, as viewed from the tip side, a recess 40c is provided on the support surface 21a side of the outer surface that protrudes more than the cylindrical portion 23f on both sides in the width direction, and is in shadow when the brush portion 23 is viewed from the front. The recess 40c is located on the back side of the outer surface of the annular portion 23g and on the front side of the support surface 21a. The through hole 23h is also in shadow when the brush portion 23 is viewed from the front. In other words, the through hole 23h becomes a recess 40d that is in shadow when the brush portion 23 is viewed from the front. The recess 40d is located on the support surface 21a side of a part of the front side of the annular portion 23g and is on the front side of the support surface 21a.

[0052] As described above, if the brush portion 23 and the head base portion 21 are molded by injection molding using a pair of molds, the core portion that molds the recess 40c is located on the support surface 21a side of the outer circumferential surface of the annular portion 23g, resulting in an undercut when the brush portion 23 is demolded. Similarly, the core portion that molds the recess 40d is also located on the support surface 21a side of a portion of the front side of the annular portion 23g, resulting in an undercut when the brush portion 23 is demolded.

[0053] In other words, the brush molded body 20 has an undercut portion 41c formed by a recess 40c located on the front side of the support surface 21a and in a position that is in shadow when viewed from the front, and an undercut portion 41d formed by a recess 40d located in a position that is in shadow when viewed from the front.

[0054] The undercut portions 41c and 41d create a thicker portion formed by the cylindrical portion 23f and a thinner portion formed by the annular portion 23g in the brush portion 23. As a result, the thinner portion allows for flexible bending, making it easier to follow the tooth surface, while the thicker portion generates a rebound force based on its high rigidity, making it easier to remove plaque. Furthermore, the presence of a through-hole 23h in the annular portion 23g creates a flexible ring shape that allows the annular portion 23g itself to bend flexibly. This allows the through-hole 23h to retain plaque when brushing the tooth surface, thus enhancing the plaque removal effect. In addition, the undercut portions 41c and 41d trap plaque present on the tooth surface, further enhancing the plaque removal effect and resulting in a brush molded body 20 with superior cleaning power.

[0055] The thickness of the base of the brush portion 23 (cylindrical portion 23f) (diameter of the circumscribed circle on the support surface 21a) is preferably 0.4 mm or more and 1.3 mm or less, more preferably 0.6 mm or more and 1.2 mm or less, and even more preferably 0.7 mm or more and 1.1 mm or less. If the diameter of the base of the brush portion 23 is less than 0.4 mm, the rigidity of the brush portion 23 may decrease, resulting in insufficient cleaning power. If the diameter of the base of the brush portion 23 exceeds 1.3 mm, the flexibility may be insufficient, reducing its ability to conform to the dentition and potentially decreasing cleaning power. By setting the base thickness of the brush portion 23 to 0.4 mm or more and 1.3 mm or less, the rigidity of the brush portion 23 is increased, improving cleaning power, and the ability to follow the alignment of teeth is improved by the appropriate flexibility, thereby enhancing cleaning power.

[0056] The shape of the annular portion 23g is not particularly limited, but may be circular, elliptical, or the like in addition to an annular shape. The width of the annular portion 23g is preferably 2.0 mm or less, more preferably 1.8 mm or less, and particularly preferably 1.6 mm or less.

[0057] The cylindrical portion 23f is, for example, cylindrical with a diameter of 1.0 mm. The longitudinal dimensions of the annular portion 23g are, for example, an outer diameter of 1.5 mm and a through hole 23h diameter of 0.5 mm. The longitudinal dimension of the annular portion 23g is, for example, 1.0 mm.

[0058] [Form 4 in which an undercut portion is formed on the surface of the brush portion 23] Figure 11 is a view of the brush molded body 20 of form 4 from the tip side. Figure 12 is a view of the brush molded body 20 of form 4 from the front side.

[0059] Each brush portion 23 of Embodiment 4 has a cylindrical portion 23j and a projection 23k that protrudes radially outward from the cylindrical portion 23j, as shown in Figure 11. The cylindrical portion 23j is cylindrical with the same diameter and extending in the longitudinal direction, or tapered towards the tip. The projection 23k is cylindrical with the same diameter and extending radially, or tapered towards the tip.

[0060] Multiple projections 23k are arranged at regular intervals in the thickness direction (9 in Figure 11). As shown in Figure 12, multiple projections 23k are arranged at intervals in the circumferential direction relative to the cylindrical portion 23j (4 in Figure 12 at 90° intervals). As an example, the brush portion 23 is arranged in a grid pattern with 8 rows of 4 brushes spaced apart in the width direction and 8 rows spaced apart in the length direction. The arrangement of the brush portion 23 is not limited to a grid pattern; for example, it may be arranged in a staggered pattern where the brush portions 23 of adjacent rows in the length direction are offset by half a pitch in the width direction.

[0061] When viewed from the tip side, a recess 40e is provided on the support surface 21a side of the projection 23k, which is in shadow when the brush portion 23 is viewed from the front side. The recess 40e is located on the front side of the support surface 21a. The recess 40e is provided between adjacent projections 23k in the thickness direction, among the multiple projections 23k arranged in the thickness direction. In other words, the recesses 40e are formed continuously along the thickness direction.

[0062] As described above, if the brush portion 23 and the head base portion 21 are molded by injection molding using a pair of molds, the core portion that forms the recess 40e is located on the support surface 21a side of the projection 23k, resulting in an undercut when the brush portion 23 is demolded. In other words, the brush molded body 20 has an undercut portion 41e formed by a recess 40e located on the front side of the support surface 21a, in a position that is in shadow when viewed from the front.

[0063] The undercut portion 41e creates a thicker portion formed by the cylindrical portion 23j and a thinner portion formed by the projection portion 23k on the brush portion 23. As a result, the thinner portion allows for flexible bending, making it easier to follow the tooth surface, while the thicker portion generates a rebound force based on its high rigidity, making it easier to remove plaque. Furthermore, the presence of the undercut portion 41e creates a continuous uneven surface along the long axis of the brush portion 23. This uneven surface traps plaque present on the tooth surface, further enhancing the plaque removal effect and resulting in a brush molded body 20 with superior cleaning power.

[0064] The thickness of the base of the brush portion 23 (cylindrical portion 23j) (diameter of the circumscribed circle on the support surface 21a) is preferably 0.4 mm or more and 1.3 mm or less, more preferably 0.6 mm or more and 1.2 mm or less, and even more preferably 0.7 mm or more and 1.1 mm or less. If the diameter of the base of the brush portion 23 is less than 0.4 mm, the rigidity of the brush portion 23 may decrease, resulting in insufficient cleaning power. If the diameter of the base of the brush portion 23 exceeds 1.3 mm, the flexibility may be insufficient, reducing its ability to conform to the dentition and potentially decreasing cleaning power. By setting the base thickness of the brush portion 23 to 0.4 mm or more and 1.3 mm or less, the rigidity of the brush portion 23 is increased, improving cleaning power, and the ability to follow the alignment of teeth is improved by the appropriate flexibility, thereby enhancing cleaning power.

[0065] The number of protrusions 23k aligned along the long axis of a single brush portion 23 is, for example, 2 or more and 20 or less. The total number of protrusions 23k on a single brush portion 23 is preferably 4 to 60, more preferably 8 to 56, and particularly preferably 16 to 52. The length of the projection 23k protruding from the cylindrical portion 23j is preferably 0.1 mm or more and 1.5 mm or less from the surface of the brush portion, more preferably 0.2 mm or more and 1.2 mm or less, and particularly preferably 0.3 mm or more and 1.0 mm or less. The shape of the projection 23k is not particularly limited, but in addition to being cylindrical, it may be conical, triangular pyramidal, square pyramidal, or tapered.

[0066] Figure 13 is a partially enlarged view showing a modified example of the projection 23k. The projection 23k may be provided on the support surface 21a side, as shown in Figure 13, and may have a bulging portion 23m that extends toward the support surface 21a side as it approaches the cylindrical portion 23j from the tip side. Having a bulging portion 23m on the support surface 21a side of the brush portion 23 increases the bending rigidity in the thickness direction and improves durability.

[0067] [Form 5 in which an undercut portion is formed inside the brush portion 23] Figure 14 is a perspective view of the brush molded body 20 of form 5. Each brush portion 23 of the form 5 has a frustoconical portion 23n and a cavity 23p, as shown in Figure 14.

[0068] The frustum of the cone 23n is a trumpet-shaped frustum of cone whose diameter gradually increases from the support surface 21a toward the front. The cavity 23p opens at the center of the tip surface of the frustum of the cone 23n and extends in the longitudinal direction toward the support surface 21a. The cavity 23p has a circular cross-section and extends toward the support surface 21a with a constant diameter or a decreasing diameter.

[0069] The outer circumferential surface of the frustoconical portion 23n faces the support surface 21a. Therefore, the outer circumferential surface of the frustoconical portion 23n is in shadow when the brush portion 23 is viewed from the front. In other words, a recess 40f is provided on the support surface 21a side of the outer circumferential surface of the frustoconical portion 23n, which is in shadow when the brush portion 23 is viewed from the front. The recess 40f is located on the front side of the support surface 21a. The recess 40f is formed in the region enclosed by the outer circumferential surface of the frustoconical portion 23n, a virtual cylindrical surface extending in the longitudinal direction including the outer circumferential surface of the tip surface of the frustoconical portion 23n, and the support surface 21a.

[0070] As described above, if the brush portion 23 and the head base portion 21 are molded by injection molding using a pair of molds, the core portion that forms the recess 40f is located on the support surface 21a side of the outer circumferential surface of the frustoconical portion 23n, resulting in an undercut when the brush portion 23 is demolded. In other words, the brush molded body 20 has an undercut portion 41f formed by a recess 40f located on the front side of the support surface 21a, in a position that is in shadow when viewed from the front. The undercut portion 41f is provided continuously along the long axis in each brush portion 23.

[0071] Because the frustoconical portion 23n described above has a cavity 23p inside, the wall thickness at a specific position in the longitudinal direction is thinner compared to the case where there is no cavity 23p. Therefore, in each brush portion 23, the outer surface of the frustoconical portion 23n is compressed and elastically deformed by contact with the tooth surface during brushing, which increases the contact area with the tooth and improves the wiping and scraping force.

[0072] The thickness of the base of the brush portion 23 (frustoconical portion 23n) (diameter of the circumscribed circle on the support surface 21a) is preferably 0.3 mm or more and 1.2 mm or less, more preferably 0.4 mm or more and 1.1 mm or less, and even more preferably 0.5 mm or more and 1.0 mm or less. If the diameter of the base of the brush portion 23 is less than 0.3 mm, the rigidity of the brush portion 23 may decrease, resulting in insufficient cleaning power. If the diameter of the base of the brush portion 23 exceeds 1.2 mm, the flexibility may be insufficient, reducing its ability to conform to the dentition and potentially decreasing cleaning power. By setting the base thickness of the brush portion 23 to 0.3 mm or more and 1.2 mm or less, the rigidity of the brush portion 23 is increased, improving cleaning power, and the ability to follow the alignment of teeth is improved by the appropriate flexibility, thereby enhancing cleaning power.

[0073] The frustum of the cone 23n may be frustum of a pyramidal shape or a pyramidal shape, as long as its diameter increases from the support surface 21a toward the front side. Furthermore, if the cavity 23p decreases in diameter toward the support surface 21a, the wall thickness on the front side of the frustum of the cone 23n becomes thinner, and the outer surface is more easily compressed and elastically deformed by contact with the tooth surface, which is preferable.

[0074] [Form 6: An undercut portion is formed inside the brush portion 23] Figure 15 is a perspective view of the brush molded body 20 of form 6. Figure 16 is a front view of the brush molded body 20 of form 6. Each brush portion 23 of the form 6 has a spiral portion 23q and a cavity 23r, as shown in Figures 15 and 16.

[0075] The helical portion 23q is axial in shape with a circular cross-section. The helical portion 23q is a spiral that extends with a constant diameter in the circumferential direction around an axis extending in the longitudinal direction as it moves from the support surface 21a toward the front side. The cavity 23r is located in the center of the brush portion 23 and extends in the longitudinal direction. The helical portion 23q orbits around the cavity 23r as it moves from the support surface 21a toward the front side.

[0076] The revolving spiral sections 23q are adjacent in the longitudinal direction, separated by a recess 40g at the same circumferential position. The outer circumferential surface of the spiral section 23q located on the front side of the recess 40g faces the support surface 21a. Therefore, the outer circumferential surface of the spiral section 23q facing the support surface 21a is in shadow when the brush section 23 is viewed from the front. In other words, a recess 40g is provided on the support surface 21a side of the outer circumferential surface of the spiral section 23q, which is in shadow when the brush section 23 is viewed from the front. The recess 40g is located on the front side of the support surface 21a.

[0077] As described above, if the brush portion 23 and the head base portion 21 are molded by injection molding using a pair of molds, the core portion that forms the recess 40g is located on the support surface 21a side of the outer circumferential surface of the helical portion 23q, resulting in an undercut when the brush portion 23 is demolded. In other words, the brush molded body 20 has an undercut portion 41g formed by a recess 40g located on the front side of the support surface 21a, in a position that is in shadow when viewed from the front. The undercut portion 41g is continuously provided in a helical shape along the long axis in each brush portion 23.

[0078] Because the spiral portion 23q described above has a cavity 23r inside, in each brush portion 23, the spiral portion 23q collapses and elastically deforms upon contact with the tooth surface during brushing, thereby increasing the contact area with the tooth and improving the wiping and scraping power.

[0079] The number of turns of the helical portion 23q is preferably 1.5 to 10 times, more preferably 2 to 6 times, and even more preferably 2.5 to 4 times.

[0080] The thickness of the base of the brush portion 23 (spiral portion 23q) (diameter of the circumscribed circle on the support surface 21a) is preferably 1.0 mm or more and 3.0 mm or less, more preferably 1.2 mm or more and 2.9 mm or less, and even more preferably 1.5 mm or more and 2.8 mm or less. If the diameter of the base of the brush portion 23 is less than 1.0 mm, the rigidity of the brush portion 23 may decrease, potentially resulting in insufficient cleaning power. If the diameter of the base of the brush portion 23 exceeds 3.0 mm, insufficient flexibility may reduce its ability to conform to the dentition, potentially leading to reduced cleaning power. By setting the base thickness of the brush portion 23 to 1.0 mm or more and 3.0 mm or less, the rigidity of the brush portion 23 is increased, improving cleaning power, and the ability to follow the alignment of teeth is improved by the appropriate flexibility, thereby enhancing cleaning power.

[0081] [A configuration 7 in which an undercut portion is formed at a position that supports the brush portion relative to the support surface] Figure 17 is a perspective view of the brush molded body 20 of form 7. Figure 18 is a cross-sectional view of the brush molded body 20 of form 7. Each brush section 23 of the form 7 has a brush body 23s and a support section 23t, as shown in Figure 17.

[0082] The brush body 23s is a columnar shape with a circular cross-section that extends in the longitudinal direction from the support surface 21a toward the front. The tip of the brush body 23s is conical, pointed toward the front. The support part 23t supports the brush body 23s relative to the support surface 21a. The support part 23t connects the support surface 21a to the outer circumferential surface of the brush body 23s. The number of support parts 23t is preferably two or more and four or less. In form 7, four support parts 23t are provided on the outer circumferential surface of the brush body 23s at 90° intervals. The support parts 23t are connected to the outer circumferential surface of the brush body 23s at a position closer to the front than the support surface 21a.

[0083] A recess 40h is formed through each support portion 23t connected to the outer circumferential surface of the brush body 23s and the support surface 21a. The outer circumferential surface of the support portion 23t located on the front side of the recess 40g faces the support surface 21a. Therefore, the outer circumferential surface of the support portion 23t facing the support surface 21a is in shadow when the brush portion 23 is viewed from the front. In other words, a recess 40h is provided on the support surface 21a side of the outer circumferential surface of the support portion 23t, which is in shadow when the brush portion 23 is viewed from the front. The recess 40h is located on the front side of the support surface 21a.

[0084] As described above, if the brush portion 23 and the head base portion 21 are molded by injection molding using a pair of molds, the core portion that forms the recess 40h is located on the support surface 21a side of the outer peripheral surface of the support portion 23t, resulting in an undercut when the brush portion 23 is demolded. In other words, the brush molded body 20 has an undercut portion 41h formed by the recess 40h located on the front side of the support surface 21a, in a position that is in shadow when viewed from the front. An undercut portion 41h is provided for each support portion 23t in each brush portion 23. That is, in embodiment 7, the undercut portion 41h is formed at the position that supports the brush portion 23 (brush body 23s) relative to the support surface 21a.

[0085] Since the brush body 23s described above has a support portion 23t that supports the brush body 23s with respect to the support surface 21a, each brush portion 23 has improved conformability to the tooth arrangement due to appropriate flexure, and improved wiping and scraping power due to improved rigidity.

[0086] The thickness of the base of the brush portion 23 (brush body 23s) (diameter of the circumscribed circle on the support surface 21a) is preferably 0.4 mm or more and 1.3 mm or less, more preferably 0.6 mm or more and 1.2 mm or less, and even more preferably 0.7 mm or more and 1.1 mm or less. If the diameter of the base of the brush portion 23 is less than 0.4 mm, the rigidity of the brush portion 23 may decrease, resulting in insufficient cleaning power. If the diameter of the base of the brush portion 23 exceeds 1.3 mm, the flexibility may be insufficient, reducing its ability to conform to the dentition and potentially decreasing cleaning power. By setting the base thickness of the brush portion 23 to 0.4 mm or more and 1.3 mm or less, the rigidity of the brush portion 23 is increased, improving cleaning power, and the ability to follow the alignment of teeth is improved by the appropriate flexibility, thereby enhancing cleaning power.

[0087] [A configuration 8 in which an undercut portion is formed at a position that supports the brush portion relative to the support surface] Figure 19 is a perspective view of the brush molded body 20 of form 8. Each brush portion 23 of the form 8 has a beam portion 23v and a support portion 23w, as shown in Figure 19.

[0088] The beam section 23v extends in the width direction at a position away from the support surface 21a towards the front. The support sections 23w extend in the longitudinal direction from the support surface 21a. The support sections 23w are provided in pairs and are connected to both sides of the beam section 23v in the width direction, supporting the beam section 23v from the support surface 21a side. In other words, the support sections 23w support the beam section 23v relative to the support surface 21a. The beam section 23v and the support sections 23w are axial in shape and are formed in a U-shape that protrudes towards the front from the support surface 21a. Both ends of the beam section 23v that connect to the support sections 23w are formed in an arc shape.

[0089] A recess 40j is formed, extending longitudinally through a U-shaped beam portion 23v and support portion 23w. The outer circumferential surface of the beam portion 23v, located on the front side of the recess 40j, faces the support surface 21a. Therefore, the outer circumferential surface of the beam portion 23v facing the support surface 21a is in shadow when the brush portion 23 is viewed from the front. In other words, a recess 40j is provided on the support surface 21a side of the outer circumferential surface of the beam portion 23v, which is in shadow when the brush portion 23 is viewed from the front. The recess 40j is located on the front side of the support surface 21a.

[0090] As described above, if the brush portion 23 and the head base portion 21 are molded by injection molding using a pair of molds, the core portion that forms the recess 40j is located on the support surface 21a side of the outer circumferential surface of the beam portion 23v, resulting in an undercut when the brush portion 23 is demolded. In other words, the brush molded body 20 has an undercut portion 41j formed by the recess 40j located on the front side of the support surface 21a, in a position that is in shadow when viewed from the front. An undercut portion 41j is provided for each beam portion 23v in each brush portion 23. That is, in embodiment 8, the undercut portion 41j is formed at a position that supports the brush portion 23 (beam portion 23v) relative to the support surface 21a.

[0091] Since the beam portion 23v has a support portion 23w that supports the beam portion 23v with respect to the support surface 21a, each brush portion 23 has improved conformability to the tooth arrangement due to appropriate deflection, and improved wiping and scraping power due to improved rigidity.

[0092] The thickness of the base of the brush portion 23 (support portion 23w) (diameter of the circumscribed circle on the support surface 21a) is preferably 0.4 mm or more and 1.3 mm or less, more preferably 0.6 mm or more and 1.2 mm or less, and even more preferably 0.7 mm or more and 1.1 mm or less. If the diameter of the base of the brush portion 23 is less than 0.4 mm, the rigidity of the brush portion 23 may decrease, resulting in insufficient cleaning power. If the diameter of the base of the brush portion 23 exceeds 1.3 mm, the flexibility may be insufficient, reducing its ability to conform to the dentition and potentially decreasing cleaning power. By setting the base thickness of the brush portion 23 to 0.4 mm or more and 1.3 mm or less, the rigidity of the brush portion 23 is increased, improving cleaning power, and the ability to follow the alignment of teeth is improved by the appropriate flexibility, thereby enhancing cleaning power.

[0093] The shaft diameter of the beam section 23v and the support section 23w is, for example, 0.5 mm. The maximum width dimension of the brush section 23 is, for example, 2.5 mm. The width dimension of the recess 40j (undercut section 41j) is, for example, 1.5 mm.

[0094] [Manufacturing method for the brush part 23] The method for manufacturing the brush portion 23 described above is not particularly limited. For example, the brush portion 23 may be manufactured separately from the head base portion 21 using a well-known manufacturing method, and the brush portion 23 may be fixed to the support surface 21a of the head base portion 21 by welding or adhesive.

[0095] Furthermore, it is also possible to manufacture the brush part 23 as an additively manufactured body by repeatedly curing the liquid resin layer by layer and stacking the cured resin bodies in multiple layers along the long axis on the support surface 21a. When manufacturing the brush part 23 as an additively manufactured body, a 3D printer can be used that has a stage that can move in the vertical direction and a light irradiation unit that irradiates the material placed on the stage with energy light to cure it. When manufacturing the brush part 23 using a 3D printer, for example, stereolithography, inkjet printing (multi-jet printing), or powder bed deposition can be selected.

[0096] The stereolithography method involves irradiating a liquid resin placed on a stage with energy light, such as ultraviolet light, to cure each layer of the liquid resin, and then moving the stage vertically before irradiating the next layer of liquid resin with ultraviolet light to cure it and form a cured body. This process is repeated to create a layered body that is stacked along the long axis, forming the brush part 23.

[0097] By manufacturing the brush portion 23 as an additively fabricated body, the brush portion 23 can flex appropriately, improving its ability to conform to the tooth surface and enhancing cleaning power.

[0098] The inkjet method involves repeatedly ejecting droplets of ultraviolet-curable resin onto a stage and irradiating the impacted droplets with ultraviolet light to form a cured body, thereby creating the brush part 23 as a layered structure stacked along the normal direction.

[0099] The powder bed deposition method is a method of fabricating a brush part 23 as a laminated body stacked along the long axis by repeatedly irradiating a powdered material placed on a stage with energy light, such as laser light, to sinter the material and form a hardened body, and then moving the stage vertically and irradiating the next layer of powdered material with laser light to harden it and form a hardened body.

[0100] If the brush portion 23 is linear and there is only one, it is also possible to create the brush portion 23 using a material extrusion deposition method in which a linear resin material extruded from a nozzle and heated to a molten state is cured while moving the stage and nozzle, or the nozzle.

[0101] When manufacturing the resin brush part 23 using the above manufacturing method, the material of the brush part 23 is not particularly limited, and examples include synthetic resin materials such as polyamide (6-12 nylon, 6-10 nylon, 12-nylon, etc.), polyester (polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, etc.), polyolefin (polypropylene, etc.), and elastomer (olefin-based, styrene-based, etc.), as well as natural materials.

[0102] When manufacturing the brush portion 23 as an additively fabricated body, the material of the brush portion 23 is not particularly limited, and examples include materials polymerized from (A) a component having an acrylic acid skeleton and (B) a component having a terminal amine of divalent or higher. Preferred components of (A) are trimethylolpropane trimethacrylate, dodecyl methacrylate, diethylene glycol monomethyl ether methacrylate urethane dimethacrylate, polyethylene glycol dimethacrylate, 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane, tricyclo[5.2.1.02,6]decanedimethanol diacrylate, methoxydiethylene glycol methacrylate, and polydimethylsiloxane acrylate. (B) Preferably, the component is 4,4'-methylenebis(2-methylcyclohexylamine, polyetheramine, trimethylolpropanepoly(oxypropylene)triamine, poly(propylene glycol)triamine, 4,4'-diaminodiphenyl sulfone, or 3,3'-diaminodiphenyl sulfone.

[0103] The brush portion 23 can be made of a material having a Shore A hardness of 70 or higher according to JIS K 6253. More preferably, the Shore A hardness is 75 or higher and 100 or lower, and the Shore D hardness is 70 or lower and 40 or higher. "Shore A hardness" refers to the Durometer A hardness of plastics measured according to JIS K 7215 or JIS K 6253. "Shore D hardness" refers to the hardness of Durometer Type D as defined in JIS K 6253. By setting the hardness of the brush portion 23 within the above range, a comfortable feel, good resilience, appropriate flexibility, and appropriate rigidity can be obtained.

[0104] The maximum length of the bristles in the longitudinal direction of the brush portion 23 is preferably 7 mm or more and 15 mm or less, more preferably 7.5 mm or more and 14 mm or less, and even more preferably 8 mm or more and 13 mm or less. If the bristle length of the brush section 23 is less than 7 mm, the bristles will be too rigid and will not bend sufficiently, potentially resulting in a less comfortable feel against the gums. If the bristle length of the brush section 23 exceeds 15 mm, the bristles may bend too much, potentially reducing cleaning power and the feeling of cleanliness. By setting the bristle length of the brush section 23 to between 7mm and 15mm, the bristles become less flexible and their rigidity increases, improving cleaning power and the feeling of cleaning. Furthermore, the bristle rigidity becomes appropriate, resulting in a better feel against the gums. Additionally, the ability to conform to the tooth surface is improved, further enhancing cleaning power.

[0105] As described above, the brush molded body 20 and toothbrush 1 of this embodiment have various types of undercut portions, resulting in superior cleaning power compared to the brush molded body 20 and toothbrush 1 molded by injection molding.

[0106] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but it goes without saying that the present invention is not limited to these examples. The shapes and combinations of the constituent members shown in the above examples are merely examples, and can be modified in various ways based on design requirements, etc., without departing from the spirit of the present invention.

[0107] For example, in the above embodiment, a configuration in which various forms of brush parts 23 are provided in one type is illustrated, but the configuration is not limited to this, and a configuration in which two or more types of brush parts 23 are used in combination may also be used.

[0108] Furthermore, in Embodiment 5 of the above embodiments, a configuration in which a cavity 23p is provided in the frustoconical portion 23n is illustrated, but the configuration is not limited to this, and a configuration in which a cavity 23p is not provided in the frustoconical portion 23n is also possible. Furthermore, in Embodiment 5, a configuration is shown in which the cavity 23p is provided from the front end face of the frustoconical portion 23n to the position of the support surface 21a, but the configuration is not limited to this. For example, the position of the bottom of the cavity 23p in the longitudinal direction may be set to a position on the front side of the support surface 21a. In this configuration, the rigidity of the frustoconical portion 23n can be improved by increasing the wall thickness at the base of the frustoconical portion 23n. Alternatively, the position of the bottom of the cavity 23p can be varied according to the position of the frustoconical portion 23n on the support surface 21a, thereby adjusting the rigidity of the frustoconical portion 23n according to its position on the support surface 21a.

[0109] Furthermore, in the above embodiment, the toothbrush 1 is composed of a separately molded brush body 20 and a handle body 10, and the brush body 20 is attached to the handle body 10 by fitting the fitting projection 12 of the handle body 10 into the fitting hole 22 of the brush body 20. However, the configuration is not limited to this. For example, the handle body 10 may be formed by primary molding using a first mold, and then the brush molded body 20 may be insert-molded by secondary molding using a second mold in which the fitting projection 12 of the handle body 10 is installed inside. Through this insert molding, the fitting projection 12 fits into the fitting hole 22, and a toothbrush 1 can be obtained as a molded body in which the brush molded body 20 and the handle body 10 are integrally molded.

[0110] Furthermore, although the above embodiment illustrates a configuration in which the handle body 10 is formed of a hard resin, the configuration is not limited to this, and for example, a part of the handle body 10 (such as the gripping portion 11) may be covered with a soft resin. Adopting this configuration can improve decorative appeal and grip. [Explanation of Symbols]

[0111] 1...Toothbrush, 10...Handle body, 12...Matching projection, 20...Brush molded body, 21...Head base, 21a...Support surface, 22...Matching hole, 23...Brush part, 35...Matching part, 40a, 40b, 40c, 40d, 40e, 40f, 40g, 40h, 40j...Recess, 41a, 41b, 41c, 41d, 41e, 41f, 41g, 41h, 41j...Undercut part

Claims

1. A head base made of soft resin, Multiple brush portions protruding toward the front from a support surface located on the front side in the thickness direction of the head base portion, An undercut portion formed by a recess located on the front side of the support surface and in a position that is in shadow when viewed from the front side, A brush molded body having a brush.

2. The undercut portion is formed on the surface of the brush portion. The brush molded body according to claim 1.

3. The undercut portion is formed inside the brush portion. The brush molded body according to claim 1.

4. The undercut portion is formed at a position that supports the brush portion relative to the support surface. The brush molded body according to claim 1.

Images