Toothbrush

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, can prevent an increase in cost and an increase in an amount of used plastic, and can appeal to users with these excellent features.SOLUTION: A toothbrush T includes a head part 1 on which hair bundles 6 are planted and a handle body H having a hollow part S1 inside. The handle body H includes a light-permeable 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 the hollow part S1 on an inner surface side in a state that openings of the recessed parts 410 and 420 face each other, and a joint covering part 51 composed of secondary resin or elastomer for covering joint parts of the resin moldings 41 and 42 of the handle base material part 4.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. In addition, 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). With this toothbrush, 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, the blow molding method described above has problems in that it is difficult to control the thickness of the handle and to maintain the strength and other qualities. Other methods of forming a hollow part in the handle like this include molding the divided parts that form the hollow part with resin and joining them by ultrasonic welding or assembling them. However, in this case, it is difficult to finish the joint neatly, and post-processing is required, which increases the cost. [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 problem that the present invention seeks to solve is to provide a toothbrush that is easy to grip while maintaining a good weight balance, is easy to brush, maintains good quality and appearance, prevents an increase in costs and plastic usage, and is able to appeal to users by highlighting the presence of these excellent features. [Means for solving the problem]

[0007] In light of this current situation, the inventors conducted extensive research and discovered that by combining a number of resin molded bodies to form a hollow section, it is possible to construct a basic section of a handle body having a set thickness compared to blow molding, and by providing a secondary resin or elastomer bonding coating section at the joint, a clean joint can be formed without the need for post-processing, thereby avoiding increased costs, and by making the basic section of the handle body light-transmitting, it is possible to appeal to users that this is a toothbrush with the excellent features described above, thereby completing the present invention.

[0008] That is, the present invention includes the following inventions.

[0009] (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 light-transmitting handle base material 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 material portion.

[0010] (2) The toothbrush according to (1), wherein the bottom surface of the recess of the resin molding is an arc-shaped curved surface in cross section as viewed from the axial direction.

[0011] (3) The toothbrush according to (2), wherein the recess of the resin molding is composed of a bottom surface which is the arc-shaped curved surface, and flat left and right side surfaces which extend from the left and right ends of the bottom surface toward the opening.

[0012] (4) A toothbrush as described in (1), in which a mating piece is protrudingly provided on the opening edge portion of the left and right side surfaces of the resin molding, and fits inwardly and outwardly with the opening edge portion of the left and right side surfaces of a mating resin molding whose openings face each other, thereby forming the joint.

[0013] (5) The toothbrush described in (4) 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.

[0014] (6) The toothbrush described in (1), in which a reinforcing rib extending vertically is provided in at least a portion of the recess on the inner surface of the resin molding, and an indication portion visible from the outside of the handle body is formed on the surface of the reinforcing rib. Effect of the Invention

[0015] 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 grippability, and also to maintain a good weight balance, thereby providing a toothbrush that is easy to brush. At the same time, the thickness and dimensions can be made as designed, and a product of stable quality can be provided. Furthermore, the joints can have a good appearance without post-processing, preventing cost increases, and the handle has a hollow portion inside, making it possible to promote the toothbrush as having the above-mentioned excellent features. [Brief description of the drawings]

[0016] [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). [Figure 12] FIG. 4 is another longitudinal sectional view of the toothbrush according to the present invention. [Figure 13] FIG. 4 is a perspective view showing another embodiment of a toothbrush according to the present invention. [Figure 14] FIG. 2 is an exploded perspective view of the handle base and head that constitute the toothbrush. [Figure 15] Cross-sectional view of line D'-D' in Figure 13. [Figure 16] FIG. 4 is a cross-sectional view showing yet another embodiment of a toothbrush according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0018] 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 bristle bundles 6 are 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.

[0019] The toothbrush T of the present invention is particularly composed of a handle body H, a handle substrate 4 formed by combining a plurality of resin moldings 41, 42 having recesses 410, 420 on their inner surfaces which form the inner walls of a hollow portion S1, with the openings of each recess 410, 420 facing each other, and a joint coating portion 51 made of a secondary resin or elastomer which covers the joint portions of the resin moldings 41, 42 of the handle substrate 4.

[0020] The primary resin constituting the resin molded bodies 41, 42 is a light-transmitting resin such as an olefin resin, a polyamide resin, a polyester resin, polymethylmethacrylate, cellulose propionate, thermoplastic polyurethane, polycarbonate, or ABS (Acrylonitrile Butadiene Styrene) resin. This enhances the design and allows the user to clearly recognize that the toothbrush T has a high commercial value and has a hollow portion S1 inside the handle body H. In particular, the use of an olefin resin or a polyester resin is preferable in terms of excellent compatibility with elastomers and forming a hollow airtightness. 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 a translucent resin mixed with a substance that does not transmit visible light (e.g., glitter, pigment, etc.) is light-transmitting if it can transmit visible light.

[0021] 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 high light transmittance is preferable. Also, resins that do not have a melting point, such as PC and ABS, can be used.

[0022] 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 combines a number of resin molded bodies 41, 42 formed by injection molding or the like, it can be made to have the designed thickness and dimensions, and since the joined state is maintained by the joint covering portion 51, no post-processing is required, and a good appearance can be obtained while keeping costs down.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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, namely, 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 side, the 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 ventral resin molded body 41 is an integrally molded body having the head portion 1, the entire periphery of the tip portion 81 of the handle body H including the neck portion 2, and the ventral portion of the handle portion 3.

[0028] In this example, the tip side portion 81 constituted by the ventral 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 dorsal resin molded body 42 may be extended to an intermediate position of the neck portion 2, in which case the "tip side portion" constituted by the ventral resin molded body 41 over the entire circumference is a portion on the tip side of the intermediate position of the neck portion 2.

[0029] On the other hand, the rear resin molded body 42 is molded separately from the resin molded body 41 using a primary resin, and is a molded body that constitutes only the rear portion of the handle body H. According to this configuration, the shapes of the resin molded bodies 41 and 42 can be simplified, and these can be easily molded.

[0030] Moreover, the dorsal 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. This has the advantage that it is possible to prevent deterioration of cleaning performance caused by excessive bending of the head portion 1 and neck portion 2, as described below.

[0031] If the dorsal resin molded body 42 is molded integrally with the head portion 1 at the same time, and the other ventral resin molded body 41 is molded separately from the dorsal resin molded body by the primary resin to form a molded body constituting only the ventral portion of the handle body H, if the joining strength of the grip covering portion 52, etc. is insufficient, when the head portion 1 and the neck portion 2 bend toward the rear side, a gap may be generated at the tip of the ventral resin molded body, or the gap may become large, allowing dirt to get into the gap and causing 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 may also become large, 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] That is, as shown in Fig. 4, when the resin molded body 41 located on the ventral side, which is the direction in which the bristle bundle 6 protrudes, is an integrally molded body consisting of the head portion 1, the neck portion 2, and the ventral portion of the handle portion 3, no gap is formed between the neck portion 2 and the handle portion 3 even if the joining strength is not strong, and the above-mentioned problems can be avoided. Moreover, since the brushing pressure acting on the head portion 1 can be efficiently absorbed by the entire resin molded body 41, even if the neck portion 2 and the handle portion 3 are formed to be thin, the connection portion between them can be effectively prevented from breaking.

[0033] In particular, when the ventral resin molded body 41 constitutes the entire tip portion 81 of the handle body H, and the tip portion 42a of the dorsal resin molded body 42 is assembled in a state of abutting against the step wall 81b formed at the base end of the tip portion 81 constituted by the ventral resin molded body 41, when the head portion 1 and neck portion 2 tend to bend toward the dorsal 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. Therefore, the head portion 1 and neck portion 2, which are integral with the ventral resin molded body 41, are prevented from bending more than necessary, excellent cleaning performance can be maintained, and breakage at the connection portion between the neck portion 2 and the handle portion 3 can be more reliably prevented.

[0034] 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.

[0035] The bottom surfaces 41c, 42c of the recesses 410, 420 of the resin molded bodies 41, 42 are formed into an arc-shaped curved surface in a cross section seen from the axial direction, as shown in Figures 5, 6 and 9. The left and right side surfaces 41b, 42b of the recesses 410, 420 are formed into flat surfaces extending from both the left and right ends of the bottom surfaces 41c, 42c toward the openings.

[0036] As described above, by making the bottom surfaces 41c, 42c of the recesses 410, 420 into arc-shaped curved surfaces, it is possible to sufficiently maintain strength against external forces such as the injection pressure when forming the bonding covering portion 51 and the grip covering portion 52 by injecting the secondary resin or elastomer, and the gripping force when using the toothbrush T. As a result, even if the side wall portions of the resin molded bodies 41, 42 are made thin, adverse effects such as inward collapse can be prevented, and transparency can be improved.

[0037] In order to improve the transparency (light transmittance) of the handle substrate 4, it is preferable to reduce the plate thickness of the resin molded bodies 41, 42. In this case, as shown in Fig. 12, if the bottom surfaces 41c', 42c' of the recesses 410', 420' are flat, when an external force Q acts on the side surface of the handle substrate 4', stress concentration occurs at the intersection between the side surfaces 41b', 42b' and 41c', 42c', causing the side walls of the resin molded bodies 41', 42' to collapse inward, causing secondary resin or elastomer to enter the hollow portion S1' or leak out onto the outer surface, which may impair the appearance.

[0038] In contrast, when the bottom surfaces 41c, 42c of the recesses 410, 420 are formed into an arc-shaped curved surface as shown in FIG. 9, even if the plate thickness of the resin moldings 41, 42 is reduced to improve the sagging property, stress concentration due to external forces is unlikely to occur, and the occurrence of the above-mentioned problems caused by the side wall portions of the resin moldings 41, 42 collapsing significantly inward can be effectively suppressed with a simple configuration.

[0039] It is also possible to form the side surfaces 41b, 42b of the recesses 410, 420 into arc-shaped curved surfaces, similar to the bottom surfaces 41c, 42c. However, in this case, the shapes of the fitting pieces 71, 72, etc. described below become distorted, making design difficult. In addition, the thickness of the intersection between the side surfaces 41b, 42b and the bottom surfaces 41c, 42c may become larger than necessary, or the width of the bottom surfaces 41c, 42c may become smaller by the amount that the side surfaces 41b, 42b are formed into arc-shaped curved surfaces, reducing the visibility of the internal hollow portion S1. Therefore, as shown in FIG. 9 and other figures, it is preferable to form the left and right side surfaces 41b, 42b of the recesses 410, 420 into flat surfaces.

[0040] 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, maintaining 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.

[0041] 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.

[0042] 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 71, 72 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.

[0043] 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).

[0044] Further, an engagement groove 73 is provided on the outer edge 411 of the resin molded body 41, 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.

[0045] 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 these grooves 41d, 42d, continuing 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.

[0046] The recessed 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.

[0047] 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 side and the base end side 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.

[0048] 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.

[0049] 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.

[0050] In particular, since this injection pressure acts in multiple directions in 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.

[0051] 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.

[0052] 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.

[0053] As a combination of a primary resin and a secondary resin or elastomer, a combination of an olefin-based resin as the primary resin and an olefin-based elastomer as the secondary resin or elastomer, or a combination of a saturated polyester resin as the primary resin and a polyester-based elastomer as the secondary resin or elastomer, is particularly preferred in terms of the good properties of the material combination and the formation of a hollow airtightness.

[0054] The manufacturing procedure for the toothbrush T according to this embodiment will be described below.

[0055] First, the resin molded bodies 41 and 42 are molded in a primary mold (not shown) using a primary resin. Next, as shown in Fig. 7, the resin molded bodies 41 and 42 are assembled with the openings of the recesses 410 and 420 facing each other to form an assembly 7 consisting of the handle base material 4 and the head portion 1, as shown in Figs. 8 and 9.

[0056] 10(a) and (b), the assembly 7 is set in a molding space 90 of a secondary mold 9, and a secondary resin or elastomer is injection molded into the groove 70 formed in the joint between the resin molded bodies 41, 42 to form the joint covering portion 51. As can be seen from the partially enlarged view of FIG. 11, the secondary resin or elastomer is injected from an injection gate 91 provided at a position facing the groove 70 in the injection molding mold (secondary mold 9) that corresponds to the positions of the reinforcing ribs 75b, 76b.

[0057] The secondary resin or elastomer injected by the injection molding flows and fills the grooves 70 to form the joint coating portion 51, and also flows and fills the grooves 41d, 42d of the resin molded bodies 41, 42 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 groove 70 falls toward the inner fitting piece 71 side and is pressed against it by the injection pressure, as shown in Figures 5(a), (b) and 6(a), (b), and the heat of the injected secondary resin or elastomer is transferred, so that the fitting piece 72 and the fitting piece 71 are thermally fused to each other and firmly joined.

[0058] Next, another embodiment of the toothbrush T according to the present invention will be described. In the toothbrush T of this embodiment, as shown in Figures 13 to 15, some or all of the multiple resin moldings 41, 42 are formed from a light-transmitting resin, and a vertical rib 13 extending in the axial direction is provided in a predetermined region of the handle portion 3, and a display portion 14 such as the toothbrush's brand name, company name, logo, or other patterns is formed on the surface.

[0059] By providing such vertical ribs 13, it is possible to further improve the strength of the handle portion 3 against a compressive load that presses the handle portion 3 in the vertical direction in Fig. 14, a bending load that tries to bend the handle portion 3, and the like. In addition, the display portion 14 provided on the surface of the vertical rib 13 can be seen from the outside through the resin molded bodies 41, 42 made of a light-transmitting resin. Therefore, there is more freedom in the display area and design compared to when a locomotive or the like is formed on the outer surface of the handle portion 3, and it is possible to create an excellent product that arouses the interest of consumers.

[0060] In this embodiment, the vertical rib 13 is provided in a predetermined region located on the base end side of the handle portion 3, but the vertical rib 13 may be provided in substantially the entire region of the handle portion 3 including the tip end side of the handle portion 3. In this embodiment, the vertical rib 13 is provided standing on the ventral side from the bottom surface 42c of the recess 420 provided in the resin molded body 42 located on the dorsal side, but the vertical rib 13 may be provided hanging down on the dorsal side from the bottom surface 41c of the recess 410 provided in the resin molded body 41 located on the ventral side. Furthermore, a plate may be formed separately from the resin molded bodies 41 and 42, and after providing a display portion, the plate may be assembled inside the handle portion 3 by adhesion or the like.

[0061] 16, the vertical rib 13' formed separately from the ventral resin molded body 41 and the dorsal resin molded body 42 may be arranged horizontally between the ventral resin molded body 41 and the dorsal resin molded body 42. This configuration has the advantage that the display unit 14 provided on the upper or lower surface of the vertical rib 13' can be clearly seen from the ventral or dorsal side of the handle portion 3. In the illustrated example, the left and right side edges of the vertical rib 13' are sandwiched between the lower side surface of the resin molded body 41 and the upper side surface of the resin molded body 42. However, instead of this configuration, the left and right side edges of the vertical rib 13' may be bonded to the lower surface of the resin molded body 41 or the side surface of the resin molded body 42.

[0062] 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 gist of the present invention. [Explanation of symbols]

[0063] 1 Head section 2 Neck 3 Handle 4. Handle base material 6 Hair bundle 7 Assembled 11 Hair transplantation table 12 Flocked surface 13 Vertical ribs 14 Display section 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 protrusions 78a, 78b Cylindrical protrusion 81 Tip side part 81b Step wall 130 Vertical ribs 131 First vertical rib 132 Second vertical rib 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 light-transmitting 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 in a state in which the openings of the respective recesses face 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. 2. The toothbrush according to claim 1, wherein a bottom surface of the recess in the resin molding is a curved surface having a circular arc shape in a cross section seen from the axial direction.

3. 3. The toothbrush according to claim 2, wherein the recess of said resin molding is composed of a bottom surface which is the arc-shaped curved surface, and left and right flat side surfaces which extend from the left and right ends of said bottom surface toward said opening.

4. The toothbrush of claim 1, wherein a mating piece is protrudingly provided on the opening edge portion of the left and right side surfaces of the resin molding, the mating piece overlapping inside and outside with the opening edge portion of the left and right side surfaces of a mating resin molding whose openings face each other to form the joint portion.

5. 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, 5. The toothbrush according to claim 4, wherein the bonded covering portion covers the grooves so as to fill them.

6. 2. The toothbrush according to claim 1, wherein a reinforcing rib extending vertically is provided in at least a portion of the recess on the inner surface side of the resin molding, and an indication portion visible from the outside of the handle body is formed on the surface of the reinforcing rib.

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