toothbrush

Abstract

The present invention provides a toothbrush having a handle body composed of a core material formed from a primary resin and a covering part formed on the core material from a secondary resin, wherein the core material does not deform and the toothbrush is excellent in terms of design and decorative qualities. [Solution] A toothbrush comprising a head portion and a handle body connected to the head portion, wherein at least a part of the handle body is composed of a core material portion 4 molded from a primary resin and a covering portion 5 molded on the core material portion from a secondary resin, and an exposed portion is formed at the base end of the handle body, extending from the base end in the longitudinal direction of the core material portion toward the tip, exposing the core material portion, the exposed portion has a rib 42 extending from a part of the base end of the core material portion toward the tip in the longitudinal direction so as to form a cross section continuous in a direction perpendicular to the longitudinal direction of the core material portion, and the covering portion has a gate mark 5g of secondary resin provided on the opposite side of the rib at the base end of the handle body.

Description

Technical Field

[0005]

[0001] The present invention relates to a toothbrush.

Background Art

[0002] A toothbrush includes a head portion where bristles are implanted and a handle body connected to the head portion. This head portion is required to have high physical properties and chemical resistance, such as no cracking when implanting the bristles, withstanding the influence of chemicals such as dentifrices, and withstanding various stresses during toothbrushing. For this reason, the head portion tends to be limited to resin materials suitable for use, such as polyolefin-based resins. On the other hand, the handle body is not required to have the same high physical properties and chemical resistance as the head portion or the neck portion, and the material selection is relatively free.

[0003] Therefore, a two-color molded toothbrush has been proposed in which the handle body is composed of a core material portion integrally formed with the head portion by a primary resin and a coating portion formed on the core material portion by a secondary resin, and for the secondary resin of the coating portion, a material (for example, a highly transparent resin, etc.) that can impart functions other than physical properties and chemical resistance, such as designability and decorativeness, is selected (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The toothbrush described in Patent Document 1 has a structure in which a resin with good light transmittance is embedded in a shaft-shaped core material and exposed on the surface of the handle body. Therefore, during secondary molding, the core material is reliably supported in the axial direction by the secondary mold. For this reason, it is considered that the core material will not deform due to the injection pressure of the secondary resin during secondary molding. On the other hand, for example, if the outer circumference of the core material in the longitudinal direction is to be covered with secondary resin over its entire circumference, the core material in the area where the covered portion is formed may deform due to the injection pressure of the secondary resin. For this reason, it is considered necessary to provide multiple ribs protruding from the intermediate portion of the core material in the longitudinal direction in the area where the covered portion is formed, in particular, to contact the secondary mold and support the core material in order to prevent deformation of the core material. If such ribs are provided in the intermediate portion of the core material in the longitudinal direction, these ribs will be exposed on the surface of the handle body, reducing the freedom of design and decorative aspects.

[0006] Therefore, the object of the present invention is to provide a toothbrush with excellent design and decorative properties in a two-color molded toothbrush in which at least a part of the handle body is composed of a shaft-shaped core material part molded from a primary resin and a covering part molded on the core material part from a secondary resin, wherein the shaft-shaped core material part does not deform. [Means for solving the problem]

[0007] The inventors diligently conducted research to solve the aforementioned problems. As a result, they found that by providing a rib extending from a part of the base end of the axial core material towards the tip in the long axis direction, so as to form a cross section that is continuous in a direction perpendicular to the long axis direction of the core material, the core material is supported at its base end within the secondary mold, and the injection gate of the secondary mold is opened on the opposite side of the rib so as to form a gate mark of the secondary resin of the coating portion at the base end of the handle body, it is possible to provide the coating portion on the core material without deformation of the core material, even without providing any other ribs.

[0008] In other words, the present invention encompasses the inventions related to (1) to (9) below. (1) A toothbrush comprising a head portion on which a bundle of bristles is planted, and a handle body connected to the head portion, At least a portion of the handle body is composed of a shaft-shaped core material portion molded from a primary resin and a covering portion molded on the core material portion from a secondary resin, and an exposed portion is formed at the base end of the handle body, extending from the base end in the longitudinal direction of the core material portion toward the tip, in which the core material portion is exposed. The exposed portion has ribs extending from a part of the base end of the core material toward the tip in the longitudinal direction, so as to form a cross section that is continuous in a direction perpendicular to the longitudinal direction of the core material. The toothbrush has a secondary resin gate mark on the covering portion, located on the side opposite the rib at the base end of the handle body. (2) The toothbrush according to (1), wherein the center of the gate mark is located on the tip side of the tip of the rib. (3) The toothbrush according to (1) or (2), wherein a recess is formed on the side opposite the rib at the base end of the core material portion, the thickness of the core material portion decreases toward the base end. (4) The toothbrush according to any one of (1) to (3), wherein the exposed portion comprises the rib and a plate-shaped piece that forms the end of the handle body in a continuous manner at the base end of the rib. (5) The toothbrush according to any one of (1) to (4), wherein the gate mark is formed on the side opposite to the side on which the bristle bundle of the head is planted. (6) The handle body has a neck portion connected to the base end of the head portion and a handle portion connected to the base end of the neck portion, The handle portion is composed of the core material portion and the covering portion. The toothbrush according to any one of (1) to (5), wherein the covering portion is formed on the core material portion extending from the tip of the handle portion to the tip of the rib. (7) A toothbrush according to any of (1) to (6), wherein the center of the gate mark is located on the central axis in the longitudinal direction of the core material when the head portion is viewed in plan from the surface opposite to the surface on which the bristle bundle is planted. (8) A toothbrush according to any one of (1) to (7), wherein the secondary resin is light-transmitting. (9) A method for manufacturing a toothbrush as described in any of (1) to (8), A process of integrally molding a primary molded product consisting of a head portion and a core material portion constituting the handle body, with the rib formed at the base end of the core material portion, by injecting primary resin into the molding space of a primary mold, and The process includes mounting the primary molded product into a secondary mold and injecting a secondary resin into the molding space of the secondary mold to form a covering portion constituting the handle body on the core material portion, and molding the exposed portion at the end of the core material portion, A method for manufacturing a toothbrush, wherein the injection gate of the secondary mold is opened in a position facing the core material such that the center of the injection gate is located on the opposite side of the rib at the base end of the core material, and on the tip side of the tip of the rib. [Effects of the Invention]

[0009] According to the present invention, in a two-color molded toothbrush in which at least a part of the handle body is composed of a shaft-shaped core material portion molded from a primary resin and a covering portion molded on the core material portion from a secondary resin, it is possible to provide a toothbrush with excellent design and decorative properties without deformation of the shaft-shaped core material portion. [Brief explanation of the drawing]

[0010] [Figure 1] A plan view of a toothbrush according to a representative embodiment of the present invention, viewed from the bristle-planted (ventral) side. [Figure 2] (a) is a rear view showing the toothbrush, and (b) is a close-up view of the main part. [Figure 3] A side view showing a toothbrush. [Figure 4] A side view of the primary molded toothbrush, shown with solid lines. [Figure 5] (a) is a side view showing the main parts of the primary molded toothbrush with solid lines, (b) is a top view showing the main parts of the primary molded toothbrush with solid lines, and (c) is a rear view showing the main parts of the primary molded toothbrush with solid lines. [Figure 6] A longitudinal sectional view showing the main part of the toothbrush (secondary molded product) as well. [Figure 7] (a) is a side view showing the main part of the primary molded product of the toothbrush according to the first modification of the representative embodiment of the present invention in solid lines, (b) is a plan view showing the main part of the primary molded product of the toothbrush in solid lines, and (c) is a rear view showing the main part of the primary molded product of the toothbrush in solid lines. [Figure 8] A longitudinal sectional view showing the main part of the toothbrush (secondary molded product) according to the first modification as well. [Figure 9] (a) is a side view showing the main part of the primary molded product of the toothbrush according to the second modification of the representative embodiment of the present invention in solid lines, (b) is a plan view showing the main part of the primary molded product of the toothbrush in solid lines, and (c) is a rear view showing the main part of the primary molded product of the toothbrush in solid lines. [Figure 10] A longitudinal sectional view showing the main part of the toothbrush (secondary molded product) according to the second modification as well. [Figure 11] (a) is a side view showing the main part of the primary molded product of the toothbrush according to the third modification of the representative embodiment of the present invention in solid lines, (b) is a plan view showing the main part of the primary molded product of the toothbrush in solid lines, and (c) is a rear view showing the main part of the primary molded product of the toothbrush in solid lines. [Figure 12] A longitudinal sectional view showing the main part of the toothbrush (secondary molded product) according to the third modification as well. [Figure 13] (a) is a side view showing the main part of the primary molded product of the toothbrush according to the fourth modification of the representative embodiment of the present invention in solid lines, (b) is a plan view showing the main part of the primary molded product of the toothbrush in solid lines, and (c) is a rear view showing the main part of the primary molded product of the toothbrush in solid lines. [Figure 14] A longitudinal sectional view showing the main part of the toothbrush (secondary molded product) according to the fourth modification as well. [Figure 15] (a) is a side view showing the main part of the primary molded product of the toothbrush according to the fifth modification of the representative embodiment of the present invention in solid lines, (b) is a plan view showing the main part of the primary molded product of the toothbrush in solid lines, and (c) is a rear view showing the main part of the primary molded product of the toothbrush in solid lines. [Figure 16]A longitudinal cross-sectional view showing the main part of a toothbrush (secondary molded product) related to the fifth modified example. [Figure 17] A longitudinal cross-sectional view showing a primary mold for forming a toothbrush according to a typical embodiment of the present invention. [Figure 18] This is a vertical cross-sectional view showing the primary molded product set in the secondary mold used to form the toothbrush. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0012] (toothbrush) As shown in Figures 1 to 3, the toothbrush T1 according to an embodiment of the present invention is a manual toothbrush comprising a head portion 1 at the tip and a handle body H at the base. The handle body H is composed of a neck portion 2 and a handle portion 3, with the neck portion 2 being connected to the base end of the head portion 1. The handle portion 3 is composed of a shaft-shaped core material portion 4 integrally molded with the head portion 1 and the neck portion 2 from a primary resin, and a covering portion 5 molded on the core material portion 4 from a secondary resin.

[0013] As shown in Figure 3, the head portion 1 is formed as a thin head having a substantially flat bristle base 11 with a thickness t1 of 4 mm or less, and multiple bristle bundles 10 are implanted on the bristle surface 12 located on the ventral side of the bristle base 11. The bristle bundles 10 may be implanted by driving them into the bristle holes formed in the bristle base 11 together with a flat wire, or they may be erected upright by fusion or in-mold methods without using a flat wire.

[0014] The material of each filament constituting the hair bundle 10 is not particularly limited; it may be artificial hair made of resin materials such as nylon, polyester, or polyolefin, or natural hair such as pig bristles. In addition, the cross-sectional shape and size of the hair bundle 10 can also be widely adopted from known forms. The number and arrangement of the hair bundles 10 are also not particularly limited.

[0015] Toothbrushes equipped with the thin head described above offer improved maneuverability in the oral cavity, allowing the head 1 to reach even the smallest areas of the molars, and enabling more thorough and effective cleaning of the entire oral cavity, including the molars, with less force. Furthermore, by making the plate thickness t1 of the bristle base 11 4 mm or less, the contact of the bristle base 11 with the oral cavity is reduced, and it also appears thinner and slimmer than it actually is, offering the advantage of less resistance when inserting it into the molars. The thickness t1 of the bristle base 11 is preferably 3.0 mm or less, more preferably 2.5 mm or less.

[0016] As shown in Figures 1 and 3, the neck portion 2 has a slender neck with a thickness dimension t2 in the front-to-back direction and a width dimension w2 in the left-to-right direction of 5.5 mm or less, more preferably 3.5 mm or more and 4.5 mm or less, in the portion closer to the tip than the center. By forming the thickness and width of the portion closer to the tip than the center to 5.5 mm or less to match the thin head, the head portion 1 can reach even the finer areas of the molars, making it possible to more reliably and thoroughly clean the entire oral cavity, including the molars. The remaining portion of the neck portion 2 at the proximal end has a flared shape (trumpet shape) in which the thickness and width dimensions increase from the tip to the proximal end, with the rate of increase being greater towards the proximal end.

[0017] As shown in Figures 4-6, the core material portion 4 of the handle portion 3 has a rod-shaped portion 41 to which the covering portion 5 is covered, a rib 42 projecting from the front (ventral) side of the rod-shaped portion 41 so as to extend a predetermined length from the base end of the core material portion 4 toward the tip in the longitudinal direction, and a substantially disc-shaped plate-like piece 44 provided at the base end of the rod-shaped portion 41 and continuous with the base end of the rib 42. The exposed portion E is formed by the outer surfaces of the rib 42 and the plate-like piece 44 that are not covered by the covering portion 5. The rib 42 functions as a support base to prevent the core material portion 4 from bending in the mold when the secondary resin is injected from the gate on the back side, and further functions as a locking piece to prevent the covering portion 5, which has low adhesion (welding properties, bonding properties), from moving relative to the core material portion 4 after molding. Furthermore, since the covering portion 5 is formed around the entire circumference of the rod-shaped portion 41 from the tip 43 of the rib 42 toward the tip, and there are no other ribs to serve as support bases, the design freedom of the outer surface of the covering portion 5 and the surface of the rod-shaped portion 41 that is visible through the covering portion 5 when the covering portion 5 is light-transmitting can be improved.

[0018] In this embodiment, the rib 42 is provided on the front (ventral) side of the rod-shaped portion 41 and extends in the longitudinal direction with the same width dimension as the rod-shaped portion 41. A cross-section is formed along the entire length of the rib 42 in the longitudinal direction, perpendicular to the longitudinal direction of the core material portion 4, and is integrated with the rod-shaped portion 41. In this way, because the rib 42 is provided protruding from the front (ventral) side of the rod-shaped portion 41 at the base end of the core material portion 4, deformation due to the heat and injection pressure of the molten secondary resin injected from the injection gate provided on the opposite side of the rib 42 during secondary molding can be prevented. The distance parallel to the longitudinal direction between the base end of the core material portion 4 and the tip 43 of the rib 42 can be set considering design and moldability, and is preferably 4 to 13.5 mm. Here, the tip 43 of the rib 42 is composed of a point, line, or surface located at the furthest tip of the rib 42 in the longitudinal direction of the core material portion 4, depending on its shape.

[0019] In this embodiment, a recess 45 is provided on the back side of the core material portion 4, that is, on the side opposite to the rib 42. The recess 45 is provided along the entire width dimension of the rod-shaped portion 41, and is formed so that the thickness of the rod-shaped portion 41 decreases toward the base end side of the core material portion 4. In this embodiment, the recess 45 is formed by creating an inclined surface that gradually slopes toward the central axis in the long axis direction from a position closer to the tip 43 of the rib 42 to the continuous portion between the plate-shaped piece 44 and the rod-shaped portion 41. With the recess 45 provided in this way, the molten secondary resin injected from the injection gate on the side opposite to the rib 42 during secondary molding flows more easily, and deformation due to heat and injection pressure can be further prevented.

[0020] The primary resin used for molding the core material portion 4 of the integrally molded head portion 1, neck portion 2, and handle portion 3 is a resin with a higher melting point than the secondary resin used for molding the coating portion 5. In the case of a resin that does not have a melting point, the glass transition point (glass transition temperature) is used as an indicator. For the primary resin, polyester resins and polyamide resins are preferred. Considering the selection of the secondary resin, the primary resin is preferably a resin with a melting point of 225 to 265°C. As polyester resins, rigid resins such as polybutylene terephthalate (PBT) and polyethylene terephthalate (PET) are preferred. As polyamide resins, nylon 6 and nylon 6,6 are preferred.

[0021] If the covering portion 5 is made of a light-transmitting secondary resin as described later, the surface of the core material portion 4 can be seen through the covering portion 5. Therefore, by providing a pattern with irregularities on the surface of the colored core material portion 4, it is possible to create a toothbrush with excellent design and decorative qualities (sometimes collectively referred to as "design"). Examples of patterns include geometric patterns, twill patterns, checkerboard patterns, and houndstooth patterns. There are no particular limitations on the color.

[0022] The secondary resin constituting the coating portion 5 is a resin with a lower melting point than the primary resin. The secondary resin may be a soft resin such as an elastomer or a hard resin. Examples of soft resins include thermoplastic elastomers (TPE) such as polystyrene (SBC), polyolefin (TPO), polyvinyl chloride (TPVC), polyurethane (PU), polyester (TPEE), and polyamide (TPAE). Examples of hard resins include polycarbonate (PC), acrylonitrile butadiene styrene copolymer (ABS), acrylonitrile styrene copolymer (AS resin), polystyrene (PS), polyethylene (PE), and polypropylene (PP). Furthermore, when using resins without a melting point, such as PC and ABS, it is sufficient that the glass transition point of the resin is lower than the melting point of the primary resin.

[0023] From the viewpoint of design in combination with the surface pattern of the core material 4, it is preferable to use a light-transmitting resin for the secondary resin, more preferably a resin with a total light transmittance of 40% or more, and even more preferably 85% or more. The total light transmittance can be measured in accordance with JIS K7375:2008. Examples of such resins include the hard resins mentioned above. Here, "light transmittance" 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 considered light-transmitting if it can transmit visible light.

[0024] The covering portion 5 is preferably composed of a solidified secondary resin melted at a molding temperature of 200 to 300°C. Using a secondary resin melted within this temperature range efficiently suppresses the melting of the primary resin during two-color molding. Furthermore, if the secondary resin is a light-transmitting resin, there is the advantage of easily forming a light-transmitting covering portion 5 with excellent transparency. In the embodiments shown in Figures 1 to 6, the core material portion 4 and the covering portion 5 are provided only on the handle portion 3, but for example, the core material portion and the covering portion may also be provided in a part or the entire area of ​​the neck portion 2. In such modified examples, the combination of secondary resins constituting the covering portions of the neck portion and the handle portion may be the same or different.

[0025] It is preferable that both the primary and secondary resins be rigid resins. In particular, it is preferable to use a combination of rigid synthetic resins that have low welding (low adhesion) properties to each other, that is, rigid resins that do not mix during molding and remain separated from each other after molding.

[0026] The gate mark 5g formed at the base end of the covering portion 5 is formed at the bottom of an inverted frustoconical recessed hole 51, as shown in Figures 2, 5, and 6. By forming it at the bottom of such a recessed hole 51, even if burrs remain on the gate mark 5g, they will not come into contact with the user's hands, thus avoiding discomfort and enhancing safety. Furthermore, the center 46 of the gate mark 5g is located on the tip side of the tip 43 of the rib 42. By positioning the center of the gate mark 5g in this way, the rib 42 can more easily function as a support during secondary molding, allowing the molten secondary resin to flow well to the tip and base sides of the core material portion 4, thus suppressing deformation along the entire length of the rod-shaped portion 41. The distance L parallel to the central axis X in the long axis direction between the center 46 of the gate mark 5g and the tip 43 of the rib 42 can be set considering the shape, moldability, and design of the rib 42. In the embodiments shown in Figures 1 to 6, the distance L can be 0.3 to 5 mm. Preferably, the center 46 of the gate mark 5g lies on the central axis X in the long axis direction when viewed in plan on the back side of the covering portion 5. In this case, during secondary molding, the molten secondary resin flows evenly to the left and right of the central axis X of the core material portion 4, making it easier for the secondary resin to fill well. As a result, the adhesion with the core material portion 4 is good, and if the secondary resin is light-transmitting, the visibility of the surface of the core material portion 4 through the covering portion 5 is further improved, and the design of the handle portion 3 can be improved by the pattern applied to the surface of the core material portion 4.

[0027] Furthermore, the distance t3 in the longitudinal cross-section between the surface of the core material portion 4 (the surface of the portion where the depression 45 is formed in this embodiment) and the center 46 of the gate mark 5g of the covering portion 5 is preferably set to 1 mm or more. If it is less than 1 mm, depending on the material and molding conditions (injection pressure and temperature of the secondary resin), there is a risk that the core material portion 4 may become concave or deformed by the injection pressure, or melt and whiten due to the heat.

[0028] As shown in Figures 1 and 2, the tip of the handle portion 3 is provided with a radially bulging finger rest portion 31. The tip of this finger rest portion 31 is provided with a tapered portion 30 that narrows towards the connection point with the neck portion 2, with the radial dimension gradually decreasing. This tapered portion 30 is composed of the tip portion 4a of the core material portion 4 and a covering portion 5 that covers it. The covering portion 5 that constitutes the tapered portion 30 is inclined to narrow towards the tip, and its outer circumferential surface is continuously connected to the flared outer circumferential surface of the base end of the neck portion 2.

[0029] Furthermore, a plurality of grooves 50 extending in the width direction are formed on the front side (ventral side) of the finger rest portion 31, thereby forming a non-slip surface for the fingers and enabling the user to clearly recognize the position of the finger rest portion 31. The finger rest portion 31 and its base end portion are configured such that the width gradually decreases toward the central position 32 in the long axis direction of the handle portion 3. In addition, the portion toward the base end from the central position 32 in the long axis direction is provided with an enlarged diameter portion 33 configured such that the width gradually increases toward the base end of the handle portion 3, and a terminal portion 34 that is continuous from the base end of the enlarged diameter portion 33 and is configured such that the width gradually decreases toward the base end of the handle portion 3.

[0030] The finger rest portion 31 has a shape in which its thickness and width are approximately the same. With this shape, the handle portion 3 can be properly gripped in either the pen grip or palm grip grip position, allowing for precise operation of the head portion 1 and resulting in excellent cleaning performance. The reduction in width between the finger rest portion 31 and the central position 32 in the long axis direction of the handle portion 3 is set to 10-40%. This allows the center of gravity of the entire toothbrush to be positioned within a predetermined area including the finger rest portion 31, which is located towards the tip of the axial center of the handle portion 3.

[0031] Furthermore, the rear side of the handle portion 3 is provided with a long, flat surface 35 that extends over approximately the entire axial length of the handle portion 3. This effectively improves the grip strength when holding the handle portion 3. Moreover, it offers advantages such as providing a stable resting position when the back side (flat surface 35) of the toothbrush is placed on a table or the like.

[0032] Next, toothbrushes T2 to T6 relating to modified examples 1 to 5 will be described with reference to Figures 7 to 16. These modified examples are variations in the form of the ribs 42 provided on the core material portion 4 of toothbrush T1. Therefore, the explanation will focus on the changes, and the same reference numerals will be used for parts common to toothbrush T1.

[0033] The toothbrush T2 according to the modified example 1 shown in Figures 7 and 8 also comprises a head portion 1 at the tip and a handle body H at the base. The handle body H consists of a neck portion 2 connected to the base end of the head portion 1 and a handle portion 3 connected to the base end of the neck portion 2. The handle portion 3 consists of a shaft-shaped core material portion 4 integrally molded with the head portion 1 and neck portion 2 from primary resin, and a covering portion 5 molded on the core material portion 4 from secondary resin.

[0034] The core material portion 4 of the handle portion 3 has a rod-shaped portion 41 that is covered by the covering portion 5, a rib 42a that protrudes from the front (ventral) side of the rod-shaped portion 41 so as to extend a predetermined length from the base end of the core material portion 4 toward the tip in the longitudinal direction, and a substantially disc-shaped plate-like piece 44 provided at the base end of the rod-shaped portion 41 and continuous with the base end of the rib 42a. An exposed portion Ea is formed by the outer surfaces of the rib 42a and the plate-like piece 44 that are not covered by the covering portion 5. Due to the exposed portion Ea, a substantially semicircular pattern is formed on the outer surface of the ventral side of the base end of the handle portion 3 when viewed from the ventral side in plan view.

[0035] The rib 42a has a roughly semi-cylindrical protrusion that extends along the rod-shaped portion 41 on the front (ventral) side of the rod-shaped portion 41, forming an arc-shaped curved surface that is continuous with the plate-shaped piece 44 and convex toward the tip in the longitudinal direction. The maximum width of this protrusion in the width direction is greater than that of the rod-shaped portion 41 but smaller than that of the plate-shaped piece 44, ensuring design aesthetics and maintaining its function as a support base by ensuring sufficient contact area with the secondary mold during secondary molding. The tip 43a of the rib 42a is formed as a line on the longitudinal cross section along the central axis in a plan view from the ventral side (Figure 8). A gate mark 5g is formed on the back side of the covering portion 5, toward the tip in the longitudinal direction from the tip 43a. The center 46 of the gate mark 5g is located at a distance L parallel to the longitudinal direction from the tip 43a. A recess 45 is formed on the back side of the core material portion 4, opposite to the rib 42a, and the center 46 of the gate mark 5g is formed at the location where the recess 45 is formed.

[0036] By having the ribs 42a described above, it is possible to prevent deformation of the core material portion 4 during secondary molding, similar to the toothbrush T1, and improve the design of the toothbrush. In addition, the exposed portion Ea, which has a roughly semicircular shape visible on the ventral side of the handle portion 3, can be used to add variation to the design of the toothbrush.

[0037] The toothbrush T3 according to the modified example 2 shown in Figures 9 and 10 also comprises a head portion 1 at the tip and a handle body H at the base. The handle body H consists of a neck portion 2 connected to the base end of the head portion 1 and a handle portion 3 connected to the base end of the neck portion 2. The handle portion 3 consists of a shaft-shaped core material portion 4 integrally molded with the head portion 1 and neck portion 2 from primary resin, and a covering portion 5 molded on the core material portion 4 from secondary resin.

[0038] The core material portion 4 of the handle portion 3 has a rod-shaped portion 41 that is covered by the covering portion 5, a rib 42b that protrudes from the front (ventral) side of the rod-shaped portion 41 so as to extend a predetermined length from the base end of the core material portion 4 toward the tip in the longitudinal direction, and a substantially disc-shaped plate-like piece 44 provided at the base end of the rod-shaped portion 41 and continuous with the base end of the rib 42b. The exposed portion Eb is formed by the outer surfaces of the rib 42b and the plate-like piece 44 that are not covered by the covering portion 5.

[0039] The rib 42b has a first protrusion 47, which is approximately semi-cylindrical in shape, extending along the rod-shaped portion 41 on the front (ventral) side of the rod-shaped portion 41, continuous with the plate-shaped piece 44, and forming an arc-shaped curved surface that is convex toward the tip in the longitudinal direction (front-side plan view). It also has a second protrusion 48, which is approximately cylindrical or semi-cylindrical in shape, extending along the rod-shaped portion 41, projecting toward the tip in the longitudinal direction from the arc-shaped surface of the first protrusion 47, and forming two arc-shaped surfaces that are relatively smaller than the first protrusion 47. In this embodiment, the two second protrusions 48 are provided at symmetrical positions on the central axis in the front-side plan view. The exposed portion Eb of the rib 42b, including both protrusions 47 and 48, is formed such that, in the front-side plan view, the first protrusion 47 forms the outline of a face and the second protrusion 48 forms the outline of an ear, including a caricatured silhouette of, for example, the face of an animal, which is suitable for improving the design variations of toothbrushes. Patterns may also be applied to the surfaces of both protrusions 47 and 48.

[0040] The maximum width of the first protrusion 47 in the width direction is greater than that of the rod-shaped portion 41 and less than that of the plate-shaped piece 44. Each second protrusion 48 is provided to protrude outward from the rod-shaped portion 41 in a plan view from the front (ventral) side, ensuring aesthetic appeal and maintaining its function as a support base by securing the contact area with the secondary mold during secondary molding. The tip 43b of the rib 42b is located at the furthest end of the two second protrusions 48 in the longitudinal direction. A gate mark 5g is formed on the back side of the covering portion 5, beyond the tip 43b in the longitudinal direction. The center 46 of the gate mark 5g is located at a distance L parallel to the longitudinal direction from the tip 43b. A recess 45 is formed on the back side of the core material portion 4 opposite to the rib 42b, and the center 46 of the gate mark 5g is formed at the location where the recess 45 is formed.

[0041] Having the ribs 42b described above makes it possible to prevent deformation of the core material portion 4 during secondary molding, similar to the toothbrush T1, and improves the design of the toothbrush. In addition, the exposed portion Eb visible on the ventral side of the handle portion 3, which can form, for example, the face of a caricatured animal, is suitable for improving the variety of toothbrush designs.

[0042] The toothbrush T4 according to the modified example 3 shown in Figures 11 and 12 also comprises a head portion 1 at the tip and a handle body H at the base. The handle body H consists of a neck portion 2 connected to the base end of the head portion 1 and a handle portion 3 connected to the base end of the neck portion 2. The handle portion 3 consists of a shaft-shaped core material portion 4 integrally molded with the head portion 1 and neck portion 2 from primary resin, and a covering portion 5 molded on the core material portion 4 from secondary resin.

[0043] The core material portion 4 of the handle portion 3 has a rod-shaped portion 41 to which the covering portion 5 is covered, a rib 42c projecting from the front (ventral) side of the rod-shaped portion 41 so as to extend a predetermined length from the base end of the core material portion 4 toward the tip in the longitudinal direction, and a substantially semicircular plate-shaped plate-like piece 44c provided at the base end of the rod-shaped portion 41 and continuous with the base end of the rib 42c. The exposed portion Ec is formed by the outer surfaces of the rib 42c and the plate-like piece 44c that are not covered by the covering portion 5.

[0044] The rib 42c is provided on the front (ventral) side of the rod-shaped portion 41, and is provided to constitute the entire front (ventral) half of the end portion 34 of the handle portion 3, and a portion that extends almost the entire length in the longitudinal direction of the end portion 34. This increases the contact area with the inner wall of the secondary mold, improving the function of supporting the core material portion 4, and improving the function of preventing deformation of the rod-shaped portion 41 due to the heat and injection pressure of the molten secondary resin injected from the injection gate provided on the opposite side of the rib 42 during secondary molding. In addition, the area of ​​the exposed portion Ec of the outer surface of the rib 42c is increased, making it suitable for improving the design by applying a pattern to this portion and combining it with the surface pattern of the covering portion 5 itself, or the surface pattern of the rod-shaped portion 41 that is visible through the covering portion 5 if the covering portion 5 is light-transmitting. It is also possible to make it easier for the user to apply a pattern or mark to this portion for a desired purpose.

[0045] The tip 43c of the rib 42c is located at the very tip in the longitudinal direction and is composed of a plane perpendicular to the longitudinal direction. A gate mark 5g is formed on the back side of the covering portion 5, further towards the tip in the longitudinal direction from the tip 43c. The center 46 of the gate mark 5g is located at a distance L parallel to the longitudinal direction from the tip 43c. A recess 45 is formed on the back side of the core material portion 4, opposite to the rib 42c, and the center 46 of the gate mark 5g is formed further towards the tip in the longitudinal direction from the position where the recess 45 is formed. The formation of such a recess 45 makes it easier for the molten secondary resin to flow during secondary molding, preventing the occurrence of sink marks and other defects.

[0046] Having the ribs 42c described above makes it possible to prevent deformation of the core material portion 4 during secondary molding, similar to the toothbrush T1, and improves the design of the toothbrush. In addition, the exposed portion Eb, which is visible on the ventral side of the handle portion 3 and forms almost the entire end portion 34 of the handle portion 3, is suitable for improving the variety of toothbrush designs.

[0047] The toothbrush T5 according to Modification 4 shown in Figures 13 and 14 is a modification of the toothbrush T4 of Modification 3. In Modification 4, an inclined surface 49 is provided at the tip of the rib 42d in the longitudinal direction, where the height in the thickness direction of the outer surface decreases toward the tip in the longitudinal direction. The tip 43d of the rib 42d is continuous with the tip of the inclined surface 49, located at the very tip in the longitudinal direction, and is composed of a plane perpendicular to the longitudinal direction. This plane is formed to be axially symmetric in a plan view from the ventral side. A covering portion 5 is also formed on the inclined surface 49, and an exposed portion Ed is formed on the outer surface of the remaining part on the ventral side and on the outer surface of the plate-like piece 44c. The inclined surface 49 is a plane, but it may be a convex or concave curved surface. In particular, if the covering portion 5 is light-transmitting, and a pattern is provided on the inclined surface 49, a visual effect can be obtained by changing the pattern visible through the covering portion 5 by varying the thickness of the covering portion 5 along the longitudinal direction of the inclined surface 49, which is suitable for improving design variations. Since Modification 4 has the same configuration as Modification 3 except for this point, it also has the same effects and functions as Modification 3.

[0048] The toothbrush T6 according to Modification 5 shown in Figures 15 and 16 is a modification of the toothbrush T4 of Modification 3. In Modification 5, an inclined surface 49a is provided at the tip portion of the rib 42e in the longitudinal direction, where the height in the thickness direction decreases toward the tip side in the longitudinal direction, opposite to the outer surface side. In other words, the inclined surface 49a is provided so as to face the rod-shaped portion 41, and the portion where the inclined surface 49 is formed is separated from the rod-shaped portion 41 in a cross section perpendicular to the longitudinal direction, and the core material portion 4 becomes discontinuous. Even if such a discontinuous portion is formed, the portion of the rib 42e other than where the inclined surface 49a is formed functions sufficiently as a support base during secondary molding, so the portion where the inclined surface 49a is formed does not deform. The inclined surface 49 is a plane, but it may be a concave or convex surface. The tip 43e of the rib 42e is formed by the ridge of the tip side of the inclined surface 49a.

[0049] In Modification 5, the exposed portion Ee is formed by the outer surface of the rib 42e and the plate-like piece 44c that is not covered by the covering portion 5. By providing such an inclined surface 49a, the surface area of ​​the exposed portion Ee can be made larger than in Modification 3 while ensuring moldability. As a result, the degree of freedom of the pattern of the exposed portion Ee visible from the ventral side is improved, which is suitable for improving the degree of freedom of the design of the handle portion 3.

[0050] (How to manufacture toothbrushes) Next, the manufacturing method according to the embodiment of the present invention will be explained using the toothbrush T1 shown in Figures 1 to 6 as an example.

[0051] As shown in Figure 17, primary resin is injected into the molding space 70 of primary molds 71 ​​and 72 through the injection gate 73 to integrally mold a primary molded product M1 consisting of a head portion 1 and a neck portion 2 and core material portion 4 that constitute the handle body H. The injection gate 73 opens at a predetermined position overlooking the space in which the core material portion 4 is molded.

[0052] Next, as shown in Figure 18, the primary molded product M1 formed in primary molds 71 ​​and 72 is placed in the molding space 80 of the secondary molds 81 and 82, and secondary resin is injected into the molding space 80 through the injection gate 83 to form the covering portion 5 that constitutes the handle body H on the core material portion 4. The injection gate 83 opens on the opposite side of the rib 42 at the base end of the core material portion 4 of the primary molded product M1, and the center of the injection gate 83 is located further forward than the tip 43 of the rib 42, so as to face the core material portion 4. That is, the central axis Y of the injection gate 83 is located further forward than the tip 43 of the rib 42 in the longitudinal section. The center of the opening of the gate 83 is on the central axis Y of the gate 83, and this center corresponds to the center 46 of the gate mark 5g of the covering portion 5. Therefore, the injection gate 83 is opened so that the distance parallel to the long axis direction between the central axis Y and the tip 43 of the rib 42 corresponds to the aforementioned distance L. Furthermore, the injection gate 83 opens at the tip of a frustoconical protrusion 84 that protrudes into the molding space 80.

[0053] The thickness d1 of the molding space below the opening of the injection gate 83 of the secondary mold is set to 1 mm or more in order to prevent dents, deformation, and heat-induced whitening of the primary resin (core material) due to injection pressure. Furthermore, the opening diameter of the injection gate 83 is preferably set to 0.3 mm or more and 3.0 mm or less in order to prevent filling defects.

[0054] When the toothbrush, which is a secondary molded product, is removed from the secondary molds 81 and 82, a gate portion that has hardened within the injection gate 83 protrudes from the outer surface of the coating portion 5. By cutting and removing this gate portion from its base, a gate mark 5g is formed on the outer surface.

[0055] Although embodiments of the present invention have been described above, the present invention is not limited in any way to these examples, and can be implemented in various forms without departing from the spirit of the invention. [Explanation of symbols]

[0056] T1, T2, T3, T4, T5, T6 toothbrushes E, Ea, Eb, Ec, Ed, Ee Exposed part H Handle Body M1 Primary molded product X, Y center axis 1. Head section 2. Neck section 3. Handle section 4. Core material section 4a Tip 5 Covering part 5g gate marks 10 strands of hair 11. Hair implantation stand 12 Hair transplant surface 30 Tapered section 31 Finger rest area 32 Long axis center position 33 Expanded diameter part 34 Terminal section 35 Flat surface 41 Rod-shaped part 42, 42a, 42b, 42c, 42d, 42e Ribs 43, 43a, 43b, 43c, 43d, 43e tip 44, 44c plate-like piece 45. Indentation 46 center 47 First protrusion 48 Second protrusion 49, 49a Slope 50 grooves 51 Hole 70 Molding space 71, 72 Primary mold 73 Injection Gate 80 Molding space 81, 82 Secondary mold 83 Injection Gate 84 Convex part d1 thickness t1 Thickness (plate thickness) t2 Thickness dimension t3,L distance w2 width dimension

Claims

1. A toothbrush comprising a head portion into which a bundle of bristles is planted, and a handle body connected to the head portion, At least a portion of the handle body is composed of a shaft-shaped core material portion molded from a primary resin and a covering portion molded on the core material portion from a secondary resin, and an exposed portion is formed at the base end of the handle body, extending from the base end in the longitudinal direction of the core material portion toward the tip, in which the core material portion is exposed. The exposed portion has ribs extending from a part of the base end of the core material toward the tip in the longitudinal direction, so as to form a cross section that is continuous in a direction perpendicular to the longitudinal direction of the core material. The toothbrush has a secondary resin gate mark on the covering portion, located on the side opposite the rib at the base end of the handle body.

2. The toothbrush according to claim 1, wherein the center of the gate mark is located on the tip side of the tip of the rib.

3. The toothbrush according to claim 1 or 2, wherein a recess is formed on the side opposite the rib at the base end of the core material portion, such that the thickness of the core material portion decreases toward the base end.

4. The toothbrush according to claim 1 or 2, wherein the exposed portion comprises the rib and a plate-shaped piece that forms the end of the handle body, continuous with the base end of the rib.

5. The toothbrush according to claim 1 or 2, wherein the gate mark is formed on the side opposite to the side on which the bristle bundle of the head portion is planted.

6. The handle body has a neck portion connected to the base end of the head portion and a handle portion connected to the base end of the neck portion. The handle portion is composed of the core material portion and the covering portion. The toothbrush according to claim 1 or 2, wherein the covering portion is formed on the core material portion extending from the tip of the handle portion to the tip of the rib.

7. The toothbrush according to claim 1 or 2, wherein the center of the gate mark is located on the central axis in the longitudinal direction of the core material when the head portion is viewed in plan from the surface opposite to the surface on which the bristle bundle is planted.

8. The toothbrush according to claim 1 or 2, wherein the secondary resin is light-transmitting.

9. A method for manufacturing a toothbrush according to claim 1, A process of integrally molding a primary molded product consisting of a head portion and a core material portion constituting the handle body, with the rib formed at the base end of the core material portion, by injecting primary resin into the molding space of a primary mold, and The process includes mounting the primary molded product into a secondary mold and injecting a secondary resin into the molding space of the secondary mold to form a covering portion constituting the handle body on the core material portion, and molding the exposed portion at the end of the core material portion, A method for manufacturing a toothbrush, wherein the injection gate of the secondary mold is opened in a position facing the core material such that the center of the injection gate is located on the opposite side of the rib at the base end of the core material, and on the tip side of the tip of the rib.

Images