Toothbrush and toothbrush manufacturing method

Abstract

To provide a toothbrush that can maintain a good weight balance while increasing gripping performance, can brush teeth easily and maintain quality and appearance at a good level, and can prevent an increase in cost and an increase in an amount of used plastic.SOLUTION: A handle body H is composed of: a handle base material part 4 composed by combining a plurality of resin moldings 41 and 42 having recessed parts 410 and 420 constituting an inner wall of a hollow part S1 on an inner surface side in a state that openings of the recessed parts face each other; and a joint covering part 51 covering joint parts of the resin moldings of the handle base material part 4, which is composed of secondary resin or elastomer.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a toothbrush having a head portion in which tufts of bristles are attached and a handle body connected to the head portion. [Background technology]

[0002] Conventionally, toothbrush handles are designed to be thick to improve grip. For people with reduced grip strength, it is desirable for the handle to be thicker than usual. However, especially in the case of toothbrushes with thin heads and thin necks, the weight balance tends to be biased toward the handle since the head and neck are light, and if the handle is made even thicker, the weight balance will be excessively biased toward the handle. As a result, there is a problem that the head becomes unstable, making it difficult to brush. Also, the thicker the handle, the more plastic is used.

[0003] In response to this, toothbrushes have been proposed in which the handle is made by blow molding (see, for example, Patent Documents 1 and 2). According to these toothbrushes, a hollow portion is formed in the handle, which makes it possible to increase the outer diameter of the handle and improve grip while suppressing an increase in weight.

[0004] However, this type of blow molding has problems in that it is difficult to control the thickness of the handle, and it is difficult to maintain strength and other qualities. Other methods of forming a hollow part in the handle like this include molding separate parts that form the hollow part with resin, and then joining them by ultrasonic welding, or assembling them. However, it is difficult to finish the joint neatly, and post-processing is required, which increases costs. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2015 / 137180 Brochure [Patent Document 2] JP 2016-179011 A Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above-mentioned circumstances, the present invention seeks to provide a toothbrush that is easy to hold while maintaining a good weight balance, is easy to brush, maintains good quality and appearance, and prevents increases in costs and plastic usage. [Means for solving the problem]

[0007] In view of this current situation, the inventors conducted extensive research and discovered that by combining multiple resin molded bodies to form a hollow section, it is possible to construct a basic part of a handle body having a set thickness compared to blow molding, and by providing a secondary resin or elastomer bonding coating at the joint, a clean joint can be formed without post-processing and additional costs can be avoided, thereby completing the present invention.

[0008] That is, the present invention includes the following inventions. (1) A toothbrush comprising a head portion in which bristles are implanted and a handle body having a hollow portion therein, characterized in that the handle body comprises a handle base portion formed by combining a plurality of resin moldings having recesses on their inner surface that form the inner wall of the hollow portion with the openings of each recess facing each other, and a bonding covering portion made of a secondary resin or elastomer that covers the joints between the resin moldings in the handle base portion.

[0009] (2) A toothbrush as described in (1), in which a fitting piece is protrudingly provided on the opening edge of the recess of the resin molding and fits inwardly and outwardly with the opening edge of a mating resin molding whose openings face each other, thereby forming the joint.

[0010] (3) The toothbrush described in (2) above, in which a groove is provided along the joint portion on the outer peripheral surface of the handle base material portion, with the outer mating piece of the overlapping inner and outer mating pieces serving as a base, and the joint covering portion covers the groove so as to fill it.

[0011] (4) The toothbrush described in (1), further comprising a grip covering portion made of a secondary resin or elastomer, which has a circumferentially extending groove formed in a predetermined region on the outer surface of the resin molding, which is formed continuous with the joint covering portion of the handle base material, and which covers and fills the grooves of each of the resin moldings to form a grip portion.

[0012] (5) The toothbrush according to (4), wherein a reinforcing rib extending laterally perpendicular to the axial direction is provided on the inner surface side of the specified region of the resin molding.

[0013] (6) A toothbrush as described in (4), in which a protrusion is provided on the inner surface of the specified area of ​​one of the resin moldings facing each other, and a cylindrical protrusion into which the protrusion is inserted is provided on the inner surface of the specified area of ​​the other resin molding.

[0014] (7) A method for manufacturing a toothbrush having a head portion in which bristles are implanted and a handle body having a hollow portion therein, wherein the handle body is formed by molding a plurality of resin moldings having recesses on their inner surfaces that form the inner walls of the hollow portion, and assembling the plurality of resin moldings with the openings of each recess facing each other to form a handle base portion, and coating the joints between the resin moldings in the handle base portion with a secondary resin or elastomer by injection molding to form a joint coating portion, thereby configuring the handle body consisting of the handle base portion and the joint coating portion.

[0015] (8) A toothbrush as described in (7), in which a mating piece is protrudingly provided on the opening edge of the recess of the resin molding, the mating piece fitting so as to overlap inside and outside with the opening edge of a mating resin molding whose opening faces each other to form the joint, and a recess is provided along the joint on the outer peripheral surface of the handle base material, with the outer mating piece of the overlapping inside and outside as its base, and the secondary resin or elastomer is coated by the injection molding so as to fill the recess.

[0016] (9) A method for manufacturing a toothbrush as described in (8), in which a circumferentially extending groove is formed in a predetermined area on the outer surface of the resin molding, and the secondary resin or elastomer is coated by the injection molding so as to fill the groove as well as the groove, thereby forming a grip coating portion that is continuous with the joint coating portion.

[0017] (10) A method for manufacturing a toothbrush as described in (9), wherein a reinforcing rib extending laterally perpendicular to the axial direction is provided on the inner surface side of the specified region of the resin molding, and the secondary resin or elastomer is injected from an injection gate provided in a position facing the reinforcing rib in an injection molding die. Effect of the Invention

[0018] According to the present invention as described above, it is possible to increase the outer diameter of the handle while reducing the amount of plastic used, thereby improving gripping ability, and a good weight balance can be maintained, providing a toothbrush that is easy to brush. At the same time, the thickness and dimensions can be made as designed, providing a toothbrush of stable quality. Furthermore, a good appearance can be obtained without post-processing of the joints, and costs can be prevented from increasing. [Brief description of the drawings]

[0019] [Figure 1] 1 is a perspective view of a toothbrush according to an exemplary embodiment of the present invention. [Diagram 2] This is a plan view of the toothbrush from the bristled side (ventral side). [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] 4. (a) is a lateral end view of the toothbrush at the position AA in FIG. 4, and (b) is a lateral end view of the toothbrush at the position BB in FIG. 4. [Figure 6] 4. (a) is a lateral end view of the toothbrush at position CC in FIG. 4, and (b) is a lateral end view of the toothbrush at position DD in FIG. 4. [Figure 7] FIG. 4 is an exploded perspective view of the handle base and head portion of the toothbrush. [Figure 8] FIG. 4 is a perspective view showing the handle base member and the head portion. [Figure 9] FIG. 9 is a lateral end view taken along the line A'-A' of FIG. 8 . [Figure 10] FIG. 4 is an explanatory diagram showing a state in which a primary molded product is set in a secondary molding die. [Figure 11] An enlarged view of the gate area after it has been set (part of the primary molded product has been broken away to show the internal structure). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0021] As shown in Figures 1 to 6, the toothbrush T according to the present invention is a manual toothbrush including a head portion 1 at the tip end side in which a bristle bundle 6 is implanted, and a handle body H having a hollow portion S1 inside at the base end side. The handle body H is composed of a neck portion 2 and a handle portion 3, and the neck portion 2 is connected to the rear end side of the head portion 1. In this example, the hollow portion S1 is formed only in the handle portion 3 of the handle body H, but the present invention is not limited to this, and also includes toothbrushes in which the hollow portion S1 extends to the neck portion 2.

[0022] The toothbrush T of the present invention is particularly characterized in that the handle body H is composed of a handle substrate 4 which is formed by combining a plurality of resin moldings 41, 42 having recesses 410, 420 on their inner surfaces which form the inner walls of the hollow portion S1, with the openings of each recess facing each other, and a joint coating portion 51 made of a secondary resin or elastomer which covers the joints between the resin moldings of the handle substrate 4.

[0023] By having this hollow portion S1, the amount of plastic used can be reduced while the handle body H, particularly the handle portion 3, can be enlarged to improve gripping ability and maintain a good weight balance. Furthermore, since the handle body H is realized from the handle base material portion 4 which is a combination of multiple resin molded bodies 41, 42, it can be made to have the designed thickness and dimensions, and since the bonded state is maintained by the bonded covering portion 51, no post-processing is required, which reduces costs and provides a good appearance.

[0024] As shown in Figures 3 and 4, the head part 1 is formed into a thin head having a substantially flat bristle base 11 with a thickness t1 of 4 mm or less, and a plurality of bristle bundles 6 are planted on a bristle planting surface 12 located on the ventral side of the bristle base 11. The bristle bundles 6 may be planted by driving them together with a flat wire into bristle planting holes formed in the bristle base 11, or may be planted by erecting the bristle bundles 6 using a fusion method or an in-mold method without using a flat wire.

[0025] The material of each filament constituting the bristle bundle 6 is not particularly limited, and may be artificial hair made of a resin material such as nylon, polyester, or polyolefin, or natural hair such as pig hair. In addition, the cross-sectional shape and cross-sectional size of the bristle bundle 6 may be widely selected from known shapes. The number and arrangement of the bristle bundles 6 are also not particularly limited.

[0026] A toothbrush equipped with a thin head as described above has improved maneuverability in the oral cavity, and the head portion 1 can reach the fine parts of the molars, making it possible to more reliably and firmly brush the entire oral cavity, including the molars, with light pressure. The thickness t1 of the bristle base 11 is preferably set to 4.0 mm or less, more preferably 3.0 mm or less, and even more preferably 2.5 mm or less.

[0027] As shown in Figures 2 to 4, the neck portion 2 is configured as a thin neck with a thickness dimension t2 in the front-rear direction and a width dimension w2 in the left-right direction of 5.5 mm or less in the portion closer to the tip than the center position. By configuring the neck as a thin neck in this way, the head portion 1 can reach the small parts of the back teeth, and the entire oral cavity including the back teeth can be brushed more reliably and thoroughly. The remaining portion on the base end side of the neck portion 2 has a diameter dimension that expands from the tip to the base end, and has a flared shape (trumpet shape) with the expansion rate increasing toward the base end.

[0028] As shown in Figures 4, 7 and 8, in this example, the handle substrate 4 is constructed by combining two resin molded bodies 41, 42: a resin molded body 41 located on the ventral side, which is the direction in which the bristle bundle 6 protrudes, and a resin molded body 42 located on the opposite dorsal side. The ventral resin molded body 41 constitutes the ventral portion of the handle portion 3, and is also integrally formed with the neck portion 2 and head portion 1. In other words, the resin molded body 41 has the head portion 1 and a ventral portion that includes the entire circumference of the tip portion 81 of the handle body H including the neck portion 2.

[0029] In this example, the tip side portion 81 constituted by the resin molded body 41 over the entire circumference is a portion constituted by the entire neck portion 2 and the tip portion 30 of the handle portion 3. However, the resin molded body 42 may be extended to a position midway through the neck portion 2, in which case the "tip side portion" constituted by the resin molded body 41 over the entire circumference is a portion on the tip side of the midway position of the neck portion 2.

[0030] On the other hand, the rear-side resin molded body 42 is molded from a primary resin separately from the resin molded body 41, and is a molded body that constitutes only the rear-side portion of the handle body H. The rear-side resin molded body 42 is assembled in a state in which its tip portion 42a abuts against a step wall 81b formed at the base end of the tip portion 81 constituted by the ventral resin molded body 41. As a result, when the head portion 1 and the neck portion 2 are bent toward the rear side by pressing the bristle bundle 6 against the teeth during use of the toothbrush T, the step wall 81b is supported by the tip portion 42a of the resin molded body 42, and since the head portion 1 and the neck portion 2 are integral with the ventral resin molded body 41, the head portion 1 and the neck portion 2 are prevented from bending more than necessary.

[0031] If the dorsal resin molded body 42 was molded integrally with the head portion 1 at the same time, and the other ventral resin molded body 41 was molded separately from the dorsal resin molded body using a primary resin to form a molded body constituting only the ventral portion of the handle body H, when the head portion 1 and the neck portion 2 bend toward the rear side, a gap would be generated at the tip of the ventral resin molded body, or the gap would become larger, which could allow dirt to get into the gap and cause hygiene problems, or the amount of movement due to the bending of the head portion 1 and the neck portion 2 toward the rear side would also increase, resulting in a slight decrease in operability during use, etc. The above-mentioned configuration of this embodiment is a configuration that can avoid such problems.

[0032] In this embodiment, the resin molded bodies constituting the handle body H are the above-mentioned two resin molded bodies 41 and 42, but it is also possible to combine three or more resin molded bodies to constitute the handle body H. In this case as well, it is preferable that the head portion 1 is molded integrally with the resin molded body located on the ventral side.

[0033] The bottom surfaces 41c, 42c of the recesses 410, 420 of the resin molded bodies 41, 42 are curved in an arc shape in cross section as seen from the axial direction, as shown in Figures 5 and 6. This maintains strength against external forces such as the injection pressure of the secondary resin or elastomer and the gripping force during use. The recesses 410, 420 are composed of the bottom surfaces 41c, 42c, which are curved in an arc shape, and flat left and right side surfaces 41b, 42b that extend from the left and right ends of the bottom surface toward the opening.

[0034] 4 to 7 and 9, fitting pieces 71, 72 are provided protrudingly around the entire periphery of each opening edge of the recesses 410, 420 of the resin molded bodies 41, 42, and these fitting pieces 71, 72 form the joint by fitting so as to overlap inside and outside with the opening edge of the opposing resin molded body. By fitting these fitting pieces 71, 72 together, the resin molded bodies 41, 42 are firmly combined to maintain their overall strength, and by injecting a secondary resin or elastomer into the joint, the fitting pieces 71, 72 are thermally welded to each other, further improving the joint strength.

[0035] However, if the overlap of the fitting pieces 71, 72 is designed to be precisely abutted, assembly and automation would be difficult, so the fitting is set loosely so that they overlap with a minute gap s2 of preferably 0.1 to 0.5 mm, as shown in Fig. 9. After assembly, as shown in Figs. 5 and 6, the outer fitting piece 72 bends inward due to the injection pressure of the secondary resin or elastomer, and they are configured to withstand the injection pressure while in contact with each other.

[0036] In this example, the fitting pieces 71, 72 are formed around the entire periphery of the opening edge of the recesses 410, 420, but one or both of the fitting pieces may be provided partially rather than around the entire periphery. In particular, it is preferable to provide the inner fitting piece 71, which does not directly receive the secondary resin or elastomer, partially.

[0037] 4 to 6 and 8, in the assembled body 7 in which these resin molded bodies 41, 42 are assembled, a groove 70 is formed along the joint portion on the outer peripheral surface of the handle base material 4, with the outer mating piece 72 of the inner and outer overlapping mating pieces 71, 72 as the bottom surface, and the joint covering part 51 covers so as to fill the inside of the groove 70. In this example, the groove 70 is formed by setting it so that a gap is formed between the outer edge part 411 of the resin molded body 41 that is outer than the mating piece 71 and the outer edge part 421 of the resin molded body 42 that faces the outer edge part 411 that is outer than the mating piece 72 when assembled (in the assembled body 7 state).

[0038] Further, the outer edge portion 411 is provided with an engagement groove 73 into which the tip portion of the engagement piece 72 of the opposing resin molded body 42 engages. This allows the engagement pieces 71, 72 to be more securely engaged with each other, thereby maintaining strength.

[0039] 4, 7 and 8, grooves 41d, 42d extending in the circumferential direction are formed in predetermined regions R1, R2 (predetermined regions on the tip side forming the handle portion 3) on the outer surface side of each resin molded body 41, 42. Grip covering portions 52 made of a secondary resin or elastomer constituting the grip portion 31 are provided on each resin molded body 41, 42 side, respectively, so as to fill in the grooves 41d, 42d and continue from the joint covering portion 51. The grooves 41d, 42d are grooves that open into the outer edge portions 411, 421 of each resin molded body 41, 42, and the left and right central portions of the grip portion 31 are formed by the joint covering portion 51.

[0040] The grooves 41d, 42d are provided with a plurality of protrusions 74 that are not covered by the grip covering portion 52 and are exposed flush with the outer surface of the grip portion 31, improving the design and preventing the grip covering portion 52 from moving axially or rotating when pressed by the user's fingers, and improving the degree of adhesion by increasing the contact area with the handle base material portion 4. The protrusions 74 also have the effect of stably supporting the assembly 7 within the secondary mold.

[0041] 4 and 7, one or more reinforcing ribs (75a, 75b, 75c / 76a, 76b, 76c) extending laterally perpendicular to the axial direction are provided on the inner surface of each resin molded body 41 / 42 so as to axially divide the inside of the recessed portion 410 / 420. In this example, the secondary resin or elastomer forming the bonding coating portion 51 and the grip coating portion 52 is injected from the approximate axial center position of the grip portion 31 and the position of the groove 70, from which the secondary resin or elastomer flows inside the groove 70 toward the tip end and base end to form the bonding coating portion 51, and enters the grooves 41d and 42d to flow circumferentially on the outer surface of each resin molded body to form the grip coating portion 52.

[0042] Therefore, the reinforcing ribs (75a, 75b, 75c / 76a, 76b, 76c) of the resin molded bodies 41 / 42 are provided mainly at the positions of the predetermined regions R1 / R2 that form the grip portion 31, and are configured so that the resin molded bodies 41, 42 can withstand the injection pressure of the secondary resin or elastomer. If the resin molded bodies 41, 42 are deformed by the injection pressure, the secondary resin or elastomer may enter the hollow portion S1 inside the handle base material portion 4 or leak out onto the outer surface, which may result in molding defects or damage to the aesthetic appearance, but the provision of the reinforcing ribs more reliably prevents such problems.

[0043] In addition to the reinforcing ribs (75a, 75b, 75c / 76a, 76b, 76c) described above, on the inner surface of each resin molded body 41 / 42, as shown in Fig. 4, Fig. 5(b), and Fig. 7, one or more protrusions 77a, 77b are provided on the inner surface of the predetermined region R2 of one of the resin molded bodies 42 facing each other, and cylindrical protrusions 78a, 78b into which the protrusions 77a, 77b are inserted are provided on the inner surface of the predetermined region R1 of the other resin molded body 41. The protrusions 77a, 77b and the cylindrical protrusions 78a, 78b align the resin molded bodies 41, 42 when they are combined to form the assembly 7, making it possible to easily and reliably perform the assembling work, and also preventing the resin molded bodies 41, 42 of the assembly 7 from being displaced from each other due to the injection pressure of the secondary resin or elastomer, and functioning to maintain the assembled state with each other.

[0044] In particular, since this injection pressure acts in multiple directions on the grip portion 31, it is preferable that at least one pair of the projections 77a, 77b and the cylindrical projections 78a, 78b are provided in the regions R1, R2 covered by the grip covering portion 52. It is preferable that the projections 77a, 77b and the cylindrical projections 78a, 78b are configured to abut against each other in the front-rear direction when the resin molded bodies 41, 42 are assembled to form the handle base material portion 4. This allows the injection pressure to be received not only in the left-right direction where the joint portion exists, but also in the front-rear direction when the ventral side is the front side and the dorsal side is the rear side, and more reliably prevents resin leakage into the cavity portion S1.

[0045] Examples of the primary resin that can be used to form the resin molded bodies 41 and 42 include olefin resin, polyamide resin, polyester resin, polymethylmethacrylate, cellulose propionate, thermoplastic polyurethane, polycarbonate, polyacetal, and ABS (Acrylonitrile Butadiene Styrene) resin. In particular, it is preferable to use olefin resin or polyester resin because they have excellent compatibility with elastomers and form a hollow space with sufficient airtightness.

[0046] It is also preferable to use light-transmitting polyester resin or polyamide resin as the primary resin. This can improve the design. As the polyester resin, a hard resin such as polyethylene terephthalate (PET) is preferable. As the polyamide resin, 6-nylon, 6,6-nylon, etc. are preferable. Here, "light-transmitting" means that visible light can be transmitted. Even if a translucent resin is mixed with a substance that does not transmit visible light (e.g., glitter, pigment, etc.), it is considered to be light-transmitting as long as it can transmit visible light.

[0047] The degree of light transmittance is preferably a resin with a total light transmittance of 40% or more. The total light transmittance can be measured by the method described in JIS K7375:2008. More preferably, the total light transmittance is 85% or more. Specifically, for example, a material made of polycarbonate (PC), acrylonitrile butadiene styrene (ABS), acrylonitrile styrene copolymer (AS resin), polystyrene (PS), polyethylene (PE), polypropylene (PP), or the like and having light transmittance is preferable. Also, resins that do not have a melting point, such as PC and ABS, can be used.

[0048] In addition, polystyrene-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, 1,2-polybutadiene-based thermoplastic elastomers, ethylene-vinyl acetate-based thermoplastic elastomers, polyvinyl chloride-based thermoplastic elastomers, natural elastomer-based thermoplastic elastomers, fluorine-based thermoplastic elastomers, trans-polyisoprene-based thermoplastic elastomers, and chlorinated polyethylene-based thermoplastic elastomers can be suitably used as the secondary resin or elastomer forming the joint coating portion 51 and the grip coating portion 52. In particular, the use of olefin-based and polyester-based elastomers is preferred in terms of excellent compatibility with the primary resin and forming a hollow airtightness.

[0049] The difference in melting point between these primary resins and the secondary resin or elastomer is preferably within 10 to 50° C. This is because the joints between the resin molded bodies 41, 42 made of the primary resins are partially softened or melted by the heat generated during injection of the secondary resin or elastomer, and are fused together.

[0050] As a combination of a primary resin and a secondary resin or an elastomer, a combination in which the primary resin is an olefin resin and the secondary resin or the elastomer is an olefin elastomer, or a combination in which the primary resin is a saturated polyester resin and the secondary resin or the elastomer is a polyester elastomer is particularly preferable in terms of the properties of the material combination and forming the airtightness of the hollow part.

[0051] Hereinafter, the manufacturing procedure of the toothbrush T according to the present embodiment will be described. First, the resin molded bodies 41 and 42 are molded using the primary resin in a primary mold (not shown). Next, as shown in FIG. 7, by combining the resin molded bodies 41 and 42 with the openings of the respective recesses 410 and 420 facing each other, an assembly 7 including the handle base part 4 and the head part 1 is formed.

[0052] Next, as shown in FIGS. 10(a) and 10(b), the assembly 7 is set in the molding space 90 of the secondary mold 9, and a secondary resin or an elastomer is injection molded onto the concave strip 70 formed at the joint portion between the resin molded bodies 41 and 42 to form a joint coating portion. As can be seen from the partial enlarged view of FIG. 11, the secondary resin or the elastomer is injected from an injection gate 91 provided at a position corresponding to the positions of the reinforcing ribs 75b and 76b among the positions facing the concave strip 70 in the injection molding die (secondary mold 9).

[0053] The secondary resin or the elastomer injected by the injection molding flows through the concave strip 70 and is filled to form the joint coating portion 51, and also flows into the concave grooves 41d and 42d of the respective resin molded bodies 41 and 42 and is filled to form the grip coating portion 52. When the joint coating portion 51 is formed, the fitting piece 72 constituting the bottom surface of the concave strip 70 falls to the inner fitting piece 71 side and is pressed by the injection pressure, and the heat of the injected secondary resin or elastomer is transferred, so that the fitting piece 72 and the fitting piece 71 are heat-fused to each other and firmly joined.

[0054] Although the embodiments of the present invention have been described above, the present invention is not limited to these examples, and it is of course possible to implement the present invention in various forms without departing from the spirit of the present invention. [Explanation of symbols]

[0055] 1 Head section 2 Neck 3 Handle 4. Handle base material 6 Hair bundle 7 Assembled 9 Secondary mold 11 Hair transplantation table 12 Flocked surface 30 Tip part 31 Grip section 41, 42 Resin molding 41b, 42b side 41c, 42c bottom 41d, 42d groove 42a Tip 51 Joint covering part 52 Grip covering part 70 Concave 71, 72 Mating piece 72 Mating piece 73 Engagement groove 74 Protrusion 75a, 75b, 75c Reinforcing ribs 76a, 76b, 76c Reinforcing ribs 77a,77b protrusion 78a, 78b Cylindrical protrusion 81 Tip side part 81b Step wall 90 Molding space 91 Ejection Gate 410, 420 Recess 411, 421 Outer edge H Handle body R1, R2 area S1 cavity s2 Gap T Toothbrush

Claims

1. A toothbrush comprising a head portion in which bristles are attached and a handle body having a hollow portion therein, The handle body is A handle base material portion formed by combining a plurality of resin molded bodies having recesses on the inner surface side that constitute the inner wall of the hollow portion with the openings of the recesses facing each other; A toothbrush characterized by comprising a joint covering portion made of a secondary resin or elastomer that covers the joint portions between the resin molded bodies of the handle base material portion.

2. The toothbrush of claim 1, wherein a fitting piece is protrudingly provided on the opening edge of the recess of the resin molding, the fitting piece fitting inwardly and outwardly with the opening edge of a mating resin molding whose openings face each other, thereby forming the joint.

3. A recess is provided along the joint portion on the outer circumferential surface of the handle base member, the recess having a bottom surface on an outer mating piece of the inner and outer overlapping mating pieces, 3. The toothbrush according to claim 2, wherein the bonding covering portion covers the grooves so as to fill them.

4. A groove extending in a circumferential direction is formed in a predetermined region on an outer surface side of the resin molded body, The toothbrush of claim 1, further comprising a grip covering portion made of a secondary resin or elastomer that is formed continuously with the bonded covering portion of the handle base material portion and that covers and fills the grooves of each of the resin moldings to form a grip portion.

5. 5. The toothbrush according to claim 4, wherein a reinforcing rib is provided on an inner surface side of the predetermined region of the resin molded body, the reinforcing rib extending in a lateral direction perpendicular to the axial direction.

6. The toothbrush of claim 4, wherein a protrusion is provided on an inner surface of the specified region of one of the resin moldings facing each other, and a cylindrical protrusion into which the protrusion is inserted is provided on an inner surface of the specified region of the other resin molding.

7. A method for manufacturing a toothbrush having a head portion in which bristles are attached and a handle body having a hollow portion therein, comprising the steps of: The handle body is molding a plurality of resin molded bodies each having a recess on an inner surface side thereof that constitutes an inner wall of the hollow portion; The plurality of resin molded bodies are assembled in a state in which the openings of the respective recesses face each other to form a handle base portion; A joint coating portion is formed by coating a secondary resin or an elastomer by injection molding on the joint portion between the resin molded bodies of the handle base material portion; This results in a method for manufacturing a toothbrush in which the handle body is formed from the handle base material portion and the bonded covering portion.

8. A fitting piece is provided on the opening edge of the recess of the resin molded body so as to fit between the opening edge of the opposing resin molded body and the recess so as to overlap with the opening edge of the opposing resin molded body, thereby forming the joint. Also, a recess is provided along the joint on the outer circumferential surface of the handle base material, the bottom surface being an outer fitting piece of the fitting pieces that overlap with the inside and outside. The method for manufacturing a toothbrush according to claim 7, wherein the secondary resin or elastomer is coated by the injection molding so as to fill the inside of the grooves.

9. A groove extending in a circumferential direction is formed in a predetermined region on an outer surface side of the resin molded body, The secondary resin or elastomer is coated by the injection molding so as to fill the grooves as well as the grooves, thereby forming a grip coating portion continuous with the bonding coating portion. A method for manufacturing the toothbrush according to claim 8.

10. A reinforcing rib is provided on the inner surface side of the predetermined region of the resin molded body, the reinforcing rib extending in a lateral direction perpendicular to the axial direction, 10. The method for manufacturing a toothbrush according to claim 9, wherein the secondary resin or elastomer is injected from an injection gate provided in an injection mold at a position facing the reinforcing rib.

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