Toothbrush

Abstract

To provide a toothbrush that can effectively prevent the occurrence of the over-brushing state by allowing the toothbrush to smoothly oscillate and be displaced in a reverse direction to a protruding direction of bristle bundles while suppressing wobbling of a head portion during brushing in a state where the toothbrush is firmly gripped.SOLUTION: There is provided a toothbrush in which a handle portion 3 includes a core material 4 made of a first hard resin and a coating material 5 made of a second hard resin having low adhesion properties relative to the first hard resin, the core material 4 includes a core material body 6 embedded in the coating material 5 and a movable portion 7 that oscillates and is displaced in a reverse direction B to a protruding direction A of the bristle bundles 10, a through groove 52 is provided in the tip-side portion of the coating material 5, and a region at least including a facing region where a connecting portion 53 is formed in a coating manner on the outer circumferential surface on the ventral side of the movable portion 7 is formed by a surface in the substantially arch shape in the cross-sectional view including a pair of flat inclined surfaces 71 that is inclined inward from respective left and right edge positions and extends linearly toward the ventral side by a predetermined length, and a convex surface 72 in the substantially arcuate shape in the cross-sectional view connecting the extended ends of the pair of flat inclined surfaces.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to a toothbrush including a head portion on which tufts of bristles are implanted, a neck portion connected to the head portion, and a handle portion serving as a grip.

Background Art

[0002] Conventionally, as shown in Patent Document 1 for example, in order to gently contact the teeth and gums to give a comfortable cleaning feeling and to easily suppress overbrushing, a head portion having a bristle-implanted surface provided on the tip side in the major axis direction, a gripping portion (handle portion) disposed on the rear end side of the head portion, a neck portion disposed between the bristle-implanted surface and the gripping portion, a hard portion disposed on the rear end side of the bristle-implanted surface and formed of a hard resin, and a soft portion formed of a soft resin and covering at least a part of the hard portion are included. A toothbrush is known that includes a deformed portion that deforms by an external force in a first direction orthogonal to the bristle-implanted surface, and the hard portion sandwiches and compresses the soft portion in the major axis direction.

[0003] However, when configured to deform the deformed portion provided on the gripping portion in this way, while the user can sense that the toothbrush is in an overbrushing state in response to this deformation, the gripability of the toothbrush may be reduced, which may hinder the brushing operation. In addition, since the hard portion is covered with a soft resin made of an elastomer or the like that is more expensive than the hard resin, there is a problem that the manufacturing cost of the toothbrush is high. Furthermore, when the deformed portion deforms according to the external force acting during brushing, there is a possibility that the hard portion and the soft portion constituting the deformed portion may peel off according to the difference in rigidity between the two.

[0004] In contrast, the present inventor has already proposed a toothbrush comprising a head portion in which tufts of hair are implanted, a neck portion connected to the head portion, and a handle portion serving as a grip, wherein the handle portion is composed of a core material made of a first rigid resin integrally formed with the neck portion, and a coating material formed to cover the core material with a second rigid resin having a property of low adhesion to the first rigid resin. The core material has a core body embedded in the coating material, and a movable portion provided on the tip end side thereof that swings and displaces in a direction opposite to the protruding direction of the tufts of hair in response to a brushing pressure acting in a direction perpendicular to the hair-implanting surface of the head portion. A space portion that allows the swinging displacement of the movable portion is provided in the tip end side portion of the coating material (Patent Document 2).

[0005] According to the toothbrush of Patent Document 2, when the user brushes their teeth, it is allowed to swing and displace a movable portion provided on the tip end side portion of the core body made of the first rigid resin within the space portion of the coating material without deforming the coating material made of the second rigid resin. Therefore, the user of the toothbrush can appropriately bring the tufts of hair of the head portion into contact with the teeth while gripping the coating material of the handle portion, and can swing and displace the movable portion of the core material in response to the brushing pressure. Thus, without causing problems such as deterioration of grip as in the toothbrush disclosed in Patent Document 1, it is possible to effectively clean the teeth by preventing an excessive brushing pressure from acting by deforming the head portion and the neck portion of the toothbrush.

[0006] In the toothbrush of Patent Document 2, in order to enable smooth swinging displacement of the movable portion located in the tip end side portion of the handle portion and to prevent water from accumulating in the space portion of the coating material, it is desirable to provide a certain gap between the coating material and the movable portion. However, in a toothbrush provided with such a gap, the movable portion is likely to sway or twist within the space portion of the coating material during brushing, so there is a possibility that the head portion will wobble and the operability of the toothbrush will deteriorate.

Prior Art Documents

Patent Documents

[0007] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2021-7471 Patent Document 2 Japanese Unexamined Patent Application Publication No. 2023-29268 Summary of the Invention Problems to be Solved by the Invention

[0008] Therefore, in view of the above situation, the problem to be solved by the present invention is to provide a toothbrush that can effectively prevent the occurrence of an overbrushing state by smoothly swinging and displacing in the direction opposite to the protruding direction of the tuft while suppressing the wobbling of the head part during brushing in a state where the toothbrush is firmly gripped. Means for Solving the Problems

[0009] That is, the present invention includes the following inventions.

[0010] (1) A toothbrush comprising a head portion where tufts are implanted, a neck portion connected to the head portion, and a handle portion serving as a grip. The handle portion has a core material made of a first rigid resin integrally formed with the neck portion, and a coating material formed to coat the core material with a second rigid resin having a property of low adhesion to the first rigid resin. The core material has a core body embedded in the coating material, and a movable portion provided on the tip end side thereof, which bends and swings in the dorsal direction opposite to the protruding direction of the tufts in response to a brushing pressure acting in a direction perpendicular to the tuft-implanting surface of the head portion. The tip end side portion of the coating material has a pair of branched arms, and a through groove is formed between the arms to penetrate the coating material from the dorsal side to the ventral side and allow the swinging displacement of the movable portion. A connecting portion is provided between the ventral tip ends of the arms to cover the movable portion and hold the ventral portion of the movable portion. The toothbrush is characterized in that a region including at least a facing region held by the connecting portion on the outer peripheral surface of the ventral side of the movable portion is composed of a pair of flat inclined surfaces that are inclined inward from the positions of the widest left and right skirts respectively and extend linearly in the ventral direction for a predetermined length, and a convex curved surface that is substantially arc-shaped in cross-section connecting the extending ends thereof, forming a substantially arch-shaped surface in cross-section.

[0011] (2) The toothbrush according to (1), wherein the region includes a region exposed in the through groove.

[0012] (3) The toothbrush according to (2), wherein the inward inclination angle of the inclined surface is 3° or more.

[0013] (4) The toothbrush according to (2), wherein the predetermined length of the inclined surface is 2 mm or less.

[0014] (5) The toothbrush according to (1), wherein the outer peripheral surface of the dorsal side of the movable portion also has a region composed of a pair of flat inclined surfaces that are inclined inward from the positions of the widest left and right skirts respectively and extend linearly in the dorsal direction for a predetermined length, and a convex curved surface that is substantially arc-shaped in cross-section connecting the extending ends thereof, forming a substantially arch-shaped surface in cross-section.

[0015] The toothbrush according to (1), wherein the axial length of the connecting portion is within the range of 1 mm to 7 mm.

Advantages of the Invention

[0016] According to the present invention configured as described above, in a state where the toothbrush is firmly gripped, it is possible to effectively prevent the occurrence of an overbrushing state by smoothly swinging and displacing in the direction opposite to the protruding direction of the tuft while suppressing the wobbling of the head portion during brushing.

Brief Description of the Drawings

[0017]

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Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, components denoted by the same reference numerals are the same components, and the description thereof will be omitted.

[0019] As shown in FIGS. 1 to 8, the toothbrush H according to the present invention includes a head portion 1 in which a tuft 10 is implanted, a substantially rod-shaped neck portion 2 connected to the rear end portion of the head portion 1, and a handle portion 3 serving as a grip. The head portion 1 and the neck portion 2 are formed of a first hard resin such as polyacetal resin (POM). The handle portion 3 has a shaft-shaped core material 4 integrally formed with the head portion 1 and the neck portion 2 by the first hard resin, and a covering material 5 formed so as to cover the core material 4.

[0020] The covering material 5 is made of a hard resin that has the property of low adhesion to the first hard resin, that is, it has the property (low weldability) of not mixing with the first hard resin during molding and separating from each other after molding. For example, a crystallized resin made of polyacetal resin (POM), polyamide resin (PA), polybutylene terephthalate (PBT), or polypropylene resin (PP), etc., has the property of low adhesion (low welding) to each other when the other is a crystallized resin (except for PP to PP) or a non-crystallized resin. Therefore, if either the first hard resin constituting the core material 4 or the second hard resin constituting the covering material 5 is a crystallized resin such as polyacetal resin (POM), and the other is a non-crystallized resin made of, for example, acrylonitrile-butadiene-styrene resin (ABS), polycarbonate (PC), or acrylic resin (PMMA), etc., the first hard resin and the second hard resin will not mix during molding, and the core material 4 and the covering material 5 will be in a separated state from each other after molding.

[0021] In addition, when both the first hard resin and the second hard resin are crystallized resins, it is possible to prevent the core material 4 and the covering material 5 from fusing with each other in principle. For example, if either the first hard resin constituting the core material 4 or the second hard resin constituting the covering material 5 is a crystallized resin such as polyacetal resin (POM), and the other is a crystallized resin made of polyacetal resin (POM), polyamide resin (PA), or polypropylene resin (PP), etc., it is possible to prevent the first hard resin and the second hard resin from mixing during molding and keep the core material 4 and the covering material 5 separated from each other after molding. However, among the crystallized resins, polypropylene resins (PP) have high adhesion to each other, so those with both the first hard resin and the second hard resin being polypropylene resin (PP) are excluded.

[0022] As the second hard resin constituting the covering material 5, it is preferable to use a transparent material. This "transparent" means that visible light can be transmitted. Also, even a resin in which a small amount of a substance that does not transmit visible light (for example, lame, pigment, etc.) is mixed is considered a transparent material as long as it can transmit visible light. As the resin, it is particularly preferable to use a resin whose value measured by the test method of JIS K 7105 is 80% or more. When the covering material 5 is formed of such a transparent material as the second hard resin, the pattern or coloring applied to the core material 4 can be visually recognized from the outside, and the designability of the toothbrush H can be improved.

[0023] As shown in FIG. 1, the core material 4 has a substantially rod-shaped core material body 6 embedded in the covering material 5, and a movable portion 7 provided on the tip side of the core material body 6 that bends and swings in the reverse direction B to the protruding direction A of the tuft 10 in response to the brushing pressure. Further, as shown in FIG. 3, columnar convex portions 61 and 62 are formed at predetermined positions in the longitudinal direction on the ventral side of the core material body 6, that is, on the protruding direction A side of the tuft 10. Further, a substantially circular plate-shaped portion 63 is provided at the rear end portion of the core material body 6.

[0024] In the cross-sectional view shown in FIG. 5, the movable portion 7 is formed in a vertically long, substantially oval shape in which the width V in the front-rear direction from the back to the belly is larger than the width W in the lateral direction. Further, the outer peripheral surface of the movable portion 7 is composed of a pair of flat inclined surfaces 71, 71 that are inclined inward from the position of the widest hem, which is the central position 70 in the front-rear direction in this embodiment, and extend linearly toward the ventral side and the dorsal side by a predetermined length L, and a convex curved surface 72 that is substantially arc-shaped in cross-sectional view connecting the extended ends thereof.

[0025] As shown in FIGS. 6 and 7, the tip-side portion of the covering member 5 has a pair of arms 51, 51 branched to the left and right, and a through groove 52 is formed between the arms 51, 51 that penetrates the covering member 5 from the back side to the front side to allow the swing displacement of the movable portion 7. Further, as shown in FIGS. 7 to 10, a connecting portion 53 that holds the ventral portion of the movable portion 7 is provided between the ventral tips of the arms 51, 51. The outer surface formed by the ventral surface of the connecting portion 53 is formed as a tapered surface having a predetermined length that is inclined so as to be closer to the core material 4 toward the tip end (see FIG. 8).

[0026] As shown in FIG. 6, gaps 55, 55 are provided between the inner surfaces of the arms 51, 51 provided at the tip-side portion of the covering member 5 that face each other and the left and right side surfaces of the movable portion 7 to prevent the movable portion 7 from interfering with the inner surfaces of the arms 51, 51 during the swing displacement of the movable portion 7. Further, as shown in FIG. 7, a gap 56 is provided between the base end surface of the neck portion 2 and the tip end surface of the covering member 5 to prevent the base end surface of the neck portion 2 from interfering with the covering member 5 during the swing displacement of the movable portion 7.

[0027] Further, as shown in FIG. 9, the connecting portion 53 is formed with a recessed hole 59 having inclined surfaces 57, 57 and a concave curved surface 58 corresponding to the inclined surfaces 71, 71 and the convex curved surface 72 of the movable portion 7. Then, as shown in FIG. 10, the ventral portion of the movable portion 7 is fitted and held in the recessed hole 59 of the connecting portion 53, so that the swing displacement of the movable portion 7 in the ventral direction (A direction), the lateral shake of the movable portion 7 displaced in the lateral direction C, and the twist of the movable portion 7 rotating are respectively regulated.

[0028] The manufacturing method of the toothbrush H having the above-described configuration will be described below. First, as shown in FIG. 11, with the first split mold 81 and the second split mold 82 of the first molding die 8 clamped, a first hard resin made of a crystallized resin such as polyacetal resin (POM) is injected into the molding space 80 of the first molding die 8 from the injection gate 83, whereby, as shown in FIG. 3, a primary molded product 11 in which the head portion 1, the neck portion 2, and the core material 4 of the handle portion 3 are integrally connected is molded.

[0029] Next, after opening the first mold 8 and taking out the primary molded product 11, as shown in FIG. 12, with the primary molded product 11 set in the second mold 9 having a space for installing the primary molded product 11 and a molding space 90 for the coating material 5, the first split mold (movable mold) 91 and the second split mold (fixed mold) 92 are clamped. Then, a hard resin having a property of low adhesion (low welding) to the first hard resin, for example, an acrylonitrile-butadiene-styrene resin (ABS), a polycarbonate (PC), or an acrylic resin (PMMA) and other non-crystallizing resins, or a second hard resin made of a crystallizing resin such as a polyacetal resin (POM), a polyamide resin (PA), a polybutylene terephthalate (PBT), or a polypropylene resin (PP) is injected into the molding space 90 of the second mold 9 from the injection gate 93 formed in the first split mold 91 or the like to mold the coating material 5. In this way, a toothbrush H is manufactured in which the core material 4 of the primary molded product 11 made of the first hard resin is coated with the coating material 5 made of the second hard resin.

[0030] In FIG. 12, reference numerals 94 to 97 are ejector pins for detaching the molded toothbrush H from the second split mold 92. The ejector pin 94 on the tip side is disposed at a position corresponding to the outer surface of the connecting portion 53 of the coating material 5. The ejector pins 95 and 96 in the middle portion are disposed at positions corresponding to the columnar convex portions 61 and 62 provided on the abdominal side of the core material body 6, respectively. The ejector pin 97 on the base end side is disposed at a position corresponding to the plate-like portion 63 of the core material body 6. Further, in FIGS. 13 and 14, reference numerals 98 and 99 are concave-shaped protrusions provided on the first split mold 91 and the second split mold 92 for forming a through groove 52 in the tip-side portion of the coating material 5.

[0031] When taking out the toothbrush H formed from the second mold 9 as described above, a plurality of ventral positions on the outer surface of the coating material 5 or the core material 4 are pushed out by the ejector pins 94 to 97 for extraction. When one ejector pin 94 is disposed at a position corresponding to the outer surface of the connecting portion 53 provided at the ventral tip of the coating material 5, the toothbrush H according to the present invention can be easily taken out from the second mold 9 without impairing its commercial value.

[0032] That is, by pressing the outer surface of the connecting portion 53 located at the tip side portion of the coating material 5, which has a tendency to stick to the molding surface of the second mold 9 due to a smaller filling amount of the second hard resin compared to the rear side portion of the coating material 5, with the ejector pin 94, the tip side portion of the coating material 5 can be surely detached from the second mold 9. Therefore, it is possible to smoothly take out the toothbrush H from the second mold 9 using a robot hand or the like (not shown), and mass production of the toothbrush H can be achieved. Moreover, unlike the case where the rear end side portion of the neck portion 2 made of the first hard resin is configured to be pushed by an ejector pin, no recessed trace corresponding to the installation portion of the ejector pin is formed at a prominent position of the toothbrush H, so that it is possible to prevent the commercial value of the toothbrush H from being impaired.

[0033] The toothbrush H according to the present invention has, as described above, a handle portion 3 serving as a grip, which is composed of a core material 4 made of a first hard resin integrally formed with the head portion 1 and the neck portion 2, and a coating material 5 formed by molding to cover the core material 4 with a second hard resin having a property of low adhesion (low welding) to the first hard resin. A movable portion 7 that swings and displaces ventrally according to the brushing pressure is provided on the tip end side of the core material 4, and a through groove 52 that allows the swinging displacement of the movable portion 7 is formed between a pair of left and right arm portions 51 provided at the tip side portion of the coating material 5. For this reason, it is possible to prevent the movable portion 7 made of the primary molded product 11 and the coating material 5 covering the same from being fused to each other. When the user brushes their teeth, the movable portion 7 made of the first hard resin provided at the tip end side of the core material body 6 can be swung and displaced within the through groove 52 of the coating material 5 without deforming the coating material 5 made of the second hard resin.

[0034] Therefore, the user of the toothbrush H can effectively clean the teeth by operating the tuft 10 of the head portion 1 while stably gripping the covering material 5 located on the outer peripheral portion of the handle portion 3, and at the same time, according to the brushing pressure at that time, the movable portion 7 of the core material 4 can be easily bent and swing-displaced in the back side direction B opposite to the protruding direction A of the tuft 10. As a result, unlike the prior art in which the gripping portion of the toothbrush is covered with a soft synthetic resin, problems such as the gripping portion being deformed and the gripping property of the toothbrush deteriorating do not occur, and by smoothly swing-displacing the movable portion 7 of the core material 4, it is possible to prevent an excessive brushing pressure from acting. Moreover, it is possible to reduce the manufacturing cost of the toothbrush H at low cost by using an inexpensive hard resin without using a soft resin made of an expensive elastomer or the like as in Patent Document 1.

[0035] In addition, since the through groove 52 provided in the tip side portion of the covering material 5 functions as a drainage hole, the moisture accumulated in the through groove 52 after use of the toothbrush H can be quickly discharged to the outside, preventing stickiness of the toothbrush H and ensuring its cleanliness. Moreover, when brushing the teeth with the tip side portion of the handle portion 3 gripped by the pen grip method, the pair of arm portions 51, 51 provided on the left and right of the through groove 52 function as a gripping portion, so that the teeth can be effectively cleaned while firmly gripping the toothbrush H. For example, as shown in FIG. 15, when gripping the toothbrush H by the pen grip method, the thumb o of the user can be pressed against the ventral surface of the handle portion 3 located on the rear side of the through groove 52, and the index finger h and the middle finger n can be placed on the outer surfaces of the arm portions 51, 51, respectively. Therefore, despite the through groove 52 having a predetermined width provided at the ventral tip portion of the covering material 5, the teeth can be effectively cleaned while firmly gripping the handle portion 3 of the toothbrush H.

[0036] Then, as shown in FIGS. 7 to 10, between the tip ends of the arm portions 51, 51 provided on the covering material 5, a connecting portion 53 is provided to cover and hold the ventral portion of the movable portion 7. As shown in FIG. 5, on the ventral side of the movable portion 7 held by the connecting portion 53, from the positions of the left and right widest hems (the central position 70 in the front-rear direction in this embodiment), a pair of flat inclined surfaces 71, 71 that are inclined inward and extend linearly toward the ventral side by a predetermined length L, and a convex curved surface 72 that is substantially arc-shaped in cross section and connects the extending ends thereof are provided, forming a surface that is substantially arch-shaped in cross section. Therefore, during brushing, the movable portion 7 does not sway or twist, and it is possible to effectively suppress the head portion 1 from wobbling during brushing.

[0037] For example, when the movable portions 7a, 7b shown in FIGS. 16 and 17 do not have flat inclined surfaces, such as the circular cross-section movable portion 7a shown in FIG. 16 and the elliptical cross-section movable portion 7b shown in FIG. 17, it is difficult to restrict the rotational displacement of the movable portions 7a, 7b, and torsion is likely to occur at the base end portion of the neck portion 2. Also, as shown by the broken lines in FIGS. 16 and 17, when the movable portions 7a, 7b swing and displace in the direction B opposite to the protruding direction A of the tuft of bristles 10 in response to the brushing pressure, a large gap is formed between the outer peripheral surface of the movable portions 7a, 7b and the inner peripheral surface of the connecting portions 53a, 53b, making it inevitable that the movable portions 7a, 7b wobble in the lateral direction C and the operability during brushing deteriorates.

[0038] In contrast, in the present invention, as shown in FIG. 10, by bringing the inclined surfaces 71, 71 of the movable portion 7 into contact with the inclined surfaces 57, 57 (see FIG. 9) of the connecting portion 53 to restrict the rotational displacement of the movable portion 7, it is possible to effectively prevent torsion from occurring at the base end portion of the neck portion 2. Also, as shown by the broken line in FIG. 10, even when the movable portion 7 swings and displaces in the direction B opposite to the protruding direction A of the tuft of bristles 10 in response to the brushing pressure, a large gap is not formed between the outer peripheral surface of the movable portion 7 and the inner peripheral surface of the connecting portion, and there is an advantage that the movable portions 7a, 7b are effectively suppressed from wobbling in the lateral direction C and stable operability is obtained.

[0039] Incidentally, when flat surfaces extending in the vertical direction of the figure are provided on the movable parts 7c and 7d, such as the movable part 7c having an elliptical cross-section shown in Fig. 18 and the movable part 7d having a rectangular cross-section shown in Fig. 19, it is possible to suppress the rotational displacement and the lateral wobbling in the direction C of the movable parts 7c and 7d. However, in this configuration, when the movable parts 7c and 7d swing and displace in the direction B opposite to the protruding direction A of the tuft 10 in response to the brushing pressure, the flat surfaces of the movable parts 7c and 7d may rub against the recessed holes of the connecting parts 53c and 53d, generating abnormal noises, or the smooth swinging displacement of the movable parts 7c and 7d may be inhibited. Further, in the case of the movable part 7d having a rectangular cross-section shown in Fig. 19, after the bent state is released, when the movable part 7d returns to its original shape, the corner part of the movable part 7d may be caught by the recessed hole of the connecting part 53d, making it difficult to fit properly and possibly causing a sense of discomfort during tooth cleaning.

[0040] On the other hand, as in the present invention, when flat inclined surfaces 71, 71 that are inclined inward from the positions of the skirts of the movable part 7 and extend linearly toward the ventral side are provided, the movable part 7 can be smoothly swung and displaced without rubbing against the recessed holes 59 of the connecting part 53 during the swinging displacement of the movable part 7. Moreover, since a convex curved surface 72 that is substantially arc-shaped in cross-section and connects the extending ends of the inclined surfaces 71, 71 is provided on the movable part 7, when the movable part 7 returns to its original shape after the bent state of the movable part 7d is released, the peripheral surface of the movable part 7 will not be caught by the recessed hole 59 of the connecting part 53, and the ventral side portion of the movable part 7 can be neatly accommodated in the recessed hole 59.

[0041] The cross-sectional shape of the movable part 7 does not need to be uniform in the length direction. For example, it is also possible to gradually change the cross-sectional shape of the movable part 7. However, by making the cross-sectional shape of the movable part 7 uniform in the length direction, etc., including the holding part by the connecting part 53 and the region exposed in the through groove 52, when a cross-sectionally substantially arch-shaped surface composed of a pair of flat inclined surfaces 71, 71 and a convex curved surface 72 that is substantially arc-shaped in cross-section and connects the extending ends thereof is provided on the ventral side of the movable part 7, as shown in Fig. 13, there is an advantage that the toothbrush H formed in the molding space 90 of the second molding die 9 can be easily taken out.

[0042] That is, as shown in FIG. 14, the second mold 9 is provided with concave-shaped protrusions 98 and 99 for forming a through groove 52 in the tip side portion of the coating material 5. When the second hard resin is injected into the molding space 90 of the second mold 9, the movable portion 7 of the primary molded product 11, which is heated by this and becomes in a softened state, is likely to stick to the concave-shaped surface of the protrusion 99, and there may be a case where it is difficult to push out the molded toothbrush H by the ejector pins 94 to 97. However, as described above, when a cross-sectionally substantially arch-shaped surface composed of inclined surfaces 71, 71 inclined inward from the hem portion and a convex curved surface 72 having a substantially arc shape in cross-section connecting the extending ends thereof is provided on the ventral side portion of the movable portion 7, by pressing the handle portion 3 of the toothbrush H with a slight force by the ejector pins 94 to 97, the toothbrush H can be easily released from the second split mold 92 of the second mold 9.

[0043] In addition, when the inclination angle θ of the inclined surfaces 71, 71 shown in FIG. 5 is small, there may be a case where the effect of promoting the release of the toothbrush H cannot be sufficiently obtained. Therefore, it is preferable that the inclination angle θ is 3° or more. Also, the predetermined length L of the inclined surfaces 71, 71 is preferably 0.2 mm or more. However, if the length L becomes longer than necessary, the inclined surfaces 71, 71 of the movable portion 7 are likely to stick to the concave-shaped protrusion 99 provided on the second split mold 92, and conversely, the releasability may decrease. Therefore, it is preferable that the predetermined length L of the inclined surfaces 71, 71 is 2 mm or less.

[0044] Further, in the above-described embodiment, since a cross-sectionally substantially arch-shaped surface composed of a pair of flat inclined surfaces 71, 71 extending toward the back side and a convex curved surface 72 having a substantially arc shape in cross-section connecting the extending ends thereof is also provided on the outer peripheral surface on the back side of the movable portion 7, as shown in FIG. 13, after injecting the second curable resin into the second mold 9 to mold the toothbrush H, when separating the first split mold 91 from the second split mold 92, it is possible to prevent the inclined surfaces 71, 71 of the movable portion 7 from sticking to the concave-shaped surface of the protrusion 98 provided on the first split mold 91, and the toothbrush H can be easily released from the first split mold 91.

[0045] When the axial length X (see Fig. 7) of the connecting portion 53 provided at the tip of the covering material 5 is short, the through groove 52 becomes large, and fingers are likely to be caught in the through groove 52, such as when the tip side portion of the handle portion 3 is gripped by the palm grip method. Conversely, if the axial length X of the connecting portion 53 is too long, water is likely to accumulate at the tip of the covering material 5, which is not hygienic, and the contact area between the movable portion 7 and the covering material 5 increases, resulting in an excessive load when the movable portion 7 is swing-displaced. Therefore, the axial length X of the connecting portion 53 is preferably in the range of 1 mm to 7 mm.

[0046] As shown in Figs. 5 and 6, instead of the above-described embodiment in which the movable portion 7 provided on the core material 4 of the toothbrush H has a vertically long shape in which the width V in the front-rear direction is larger than the width W in the lateral direction in cross-sectional view, the movable portion 7 may have a horizontally long shape in which the width V in the front-rear direction is smaller than the width W in the lateral direction, or the width V in the front-rear direction and the width W in the lateral direction of the movable portion 7 may be made equal. However, in this case, depending on the width W in the lateral direction of the movable portion 7, the lateral width of the covering material 5 may become too large, and the gripability of the toothbrush H may deteriorate. Therefore, it is preferable that the movable portion 7 has a vertically long shape as shown in Figs. 5 and 6.

[0047] Also, as shown in Fig. 1, when the core body 6 of the primary molded product 11 is provided with cylindrical convex portions 61 and 62, the setting state of the primary molded product 11 can be stabilized by making the convex portions 61 and 62 function as spacers when the primary molded product 11 is set in the second mold 9. Moreover, after the toothbrush H is molded, the convex portions 61 and 62 can function as locking pieces that prevent the covering material 5 from moving relative to the core body 6. Further, when a circular plate-like portion 63 is provided at the rear end portion of the core body 6 and is configured to be covered by the covering material 5 around it, the coupling state between the core material 4 and the covering material 5 can be stabilized by making the plate-like portion 63 function as a retaining portion for the covering material 5.

[0048] Furthermore, when removing the toothbrush H formed from the second molding die 9, ejector pins 95 to 97 that press positions other than the outer surface of the connecting portion 53 are exposed from the covering material 5 at the positions of the core material 4, specifically, as shown in FIGS. 12 and 13, at the positions pressing the columnar convex portions 61 and 62 provided on the abdominal side of the core material body 6 and the plate-like portion 63 provided at the rear end portion of the core material body 6, there is an advantage that conspicuous dent marks can be prevented from being formed on the covering material 5. That is, immediately after the covering material 5 is molded from the second hard resin, if an ejector pin is pressed against its surface before the covering material 5 is sufficiently hardened, ejector pin pressing marks will be prominently formed on the covering material 5 made of a transparent material or the like. On the other hand, as shown in the above-described embodiment, when ejector pins 95 to 97 are respectively disposed at positions corresponding to the columnar convex portions 61 and 62 and the plate-like portion 63 of the primary molded product 11, it is possible to prevent conspicuous pressing marks from being formed on the outer surface of the covering material 5.

Explanation of Signs

[0049] 1 Head portion 2 Neck portion 3 Handle portion 4 Core material 5 Covering material 6 Core material body 7 Movable portion 10 Bristle bundle 11 Primary molded product 51 Arm portion 52 Through groove 53 Connecting portion 57 Inclined surface 58 Concave curved surface 59 Recessed hole 71 Inclined surface 72 Convex curved surface H Toothbrush

Claims

1. A toothbrush comprising a head portion implanted with tufts of bristles, a neck portion connected to the head portion, and a handle portion serving as a grip, wherein the handle portion has a core material made of a first rigid resin integrally formed with the neck portion, and a coating material formed to coat the core material with a second rigid resin having a property of low adhesion to the first rigid resin, the core material has a core body embedded in the coating material, and a movable portion provided on the tip end side thereof, which bends and swings in the reverse direction of the protruding direction of the tufts of bristles in response to a brushing pressure acting in a direction orthogonal to the implanting surface of the head portion, the tip end side portion of the coating material has a pair of arm portions branched left and right, and a through groove is formed between the arm portions to penetrate the coating material from the back side to the front side to allow the swinging displacement of the movable portion, a toothbrush in which a connecting portion is provided to be covered on the movable portion and hold the ventral side portion of the movable portion between the ventral side tip ends of the arm portions, a toothbrush characterized in that a region including at least a facing region held by the connecting portion on the outer peripheral surface of the ventral side of the movable portion is composed of a pair of flat inclined surfaces that are inclined inward from the positions of the widest left and right skirts and extend linearly toward the ventral side by a predetermined length, and a convex curved surface that is substantially arc-shaped in cross section connecting the extending ends thereof, forming a surface that is substantially arch-shaped in cross section.

2. The region includes a region exposed in the through groove, The toothbrush according to Claim 1.

3. The inward inclination angle of the inclined surface is 3° or more, The toothbrush according to Claim 2.

4. The predetermined length of the inclined surface is 2 mm or less, The toothbrush according to Claim 2.

5. The outer peripheral surface of the dorsal side of the movable portion also has a region composed of a pair of flat inclined surfaces that are inclined inward from the positions of the widest left and right skirts and extend linearly toward the dorsal side by a predetermined length, and a convex curved surface that is substantially arc-shaped in cross section connecting the extending ends thereof, forming a surface that is substantially arch-shaped in cross section. The toothbrush according to Claim 1.

6. The axial length of the connecting portion is within the range of 1 mm to 7 mm, The toothbrush according to Claim 1.

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