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 finger rest formed on the surface of the covering part is easily visible and cracks in the finger rest can be prevented even after repeated use. [Solution] A toothbrush comprising a head portion and a handle body connected to the head portion, wherein 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 a core material portion molded from a primary resin and a covering portion molded on the core material portion from a secondary resin, the core material portion together with the covering portion constitutes the gripping portion of the handle body, and the gripping portion has a recess 45 at a position corresponding to the finger rest portion for recognizing the position of the finger rest portion through the covering portion, and the opening periphery of the recess is formed in an R shape.

Description

Technical Field

[0001] The present invention relates to a toothbrush.

Background Art

[0002] A toothbrush includes a head portion where a tuft of bristles is 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 not cracking when implanting the tuft of bristles, withstanding the effects of chemicals such as dentifrices, and withstanding various stresses during toothbrushing. Therefore, the head portion tends to be limited to resin materials suitable for use, such as polyolefin-based resins. On the other hand, for the handle body, high physical properties and chemical resistance like those of the head portion and neck portion are not required, and the selection of materials is relatively free.

[0003] For this reason, a two-color molded toothbrush has been proposed in which the handle body is composed of a core material portion integrally molded with the head portion using a primary resin and a covering portion molded on top of the core material portion using a secondary resin, and for the secondary resin of the covering portion, a material that can impart functions other than physical properties and chemical resistance, such as designability and decorativeness (for example, a highly transparent resin, etc.) is selected (see, for example, Patent Document 1). Also, the applicant of the present application has used a light-transmissive resin as the secondary resin for the covering portion of such a handle body, and by overlapping the gate trace of the secondary resin formed on the covering portion with the position of the gate trace of the primary resin formed on the core material portion, a toothbrush has been proposed that is less conspicuous from the outside for the gate trace of the core material portion, has excellent designability and decorativeness, and can be provided efficiently (Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

[0005] As with conventional technology, it is possible to provide a toothbrush with excellent design and decorative qualities by providing a light-transmitting coating on a core material molded from a primary resin. However, when a light-transmitting coating is provided, it can be difficult to visually perceive the surface shape of the coating. For example, the gripping part of a toothbrush has bumps or grooves on the finger rest to serve as an indicator for proper gripping. By visually recognizing these bumps on the outer surface of the finger rest and gripping it appropriately, more effective cleaning can be achieved. However, as mentioned above, the bumps and grooves on the light-transmitting coating are not always sufficiently visible, raising concerns that the toothbrush may not be gripped in the correct position.

[0006] Therefore, the inventor conceived of forming a marker on the surface of the core material portion that can be recognized through a light-transmitting coating portion at a position corresponding to the finger rest portion of the gripping portion, making it easier to visually confirm the position of the irregularities provided on the finger rest portion. Then, when molding the primary molded product, which includes the head portion and core material portion integrally molded from the primary resin, the inventor considered forming a corresponding protrusion on the inner wall surface of the mold in order to form a recess that can serve as a marker at a predetermined position on the core material portion, and then molding the primary molded product.

[0007] Incidentally, primary molded products, including the head portion and core portion which are integrally molded from the primary resin, are generally molded by injection molding. In this case, a movable pin (movable pin) that can move toward the molding space side of the mold (primary molded product side) may be used to demold the molded product. When demolding, it is necessary to provide the movable pin at an appropriate position according to the shape of the primary molded product in order to prevent deformation of the primary molded product. The inventors focused on the fact that the position corresponding to the aforementioned finger rest portion is located approximately in the center of the long axis direction of the primary molded product and is suitable as an extrusion position when demolding the primary molded product. Therefore, they conceived and investigated a molding method in which a convex portion is formed at the tip of the movable pin, a recess with a shape corresponding to the convex portion is provided at a predetermined position on the core portion, and the movable pin is moved toward the primary molded product side when demolding the primary molded product from the mold.

[0008] Based on the above findings, a secondary molded product was fabricated using a primary molded product in which the aforementioned recess was formed at a predetermined position in the core material, with a covering portion provided on top of the core material. However, it was found that when a toothbrush made using this secondary molded product was used several times, cracks sometimes appeared in the covering portion of the core material where the recess was provided.

[0009] In view of the above findings, the object of the present invention is to provide a 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 light-transmitting coating part molded on the core material part from a secondary resin, wherein the finger rest formed on the surface of the coating part is easily visible and cracks in the finger rest part can be prevented even after repeated use. [Means for solving the problem]

[0010] The inventors diligently conducted research to solve the aforementioned problems. As a result, they found that by constructing the gripping portion of the handle body with a core material portion and a covering portion, providing a recess at a position corresponding to the finger rest portion of the gripping portion to allow the position of the finger rest portion to be recognized through the covering portion, and forming the opening periphery of this recess in an R shape, it is possible to prevent cracks from occurring in the finger rest portion even when the toothbrush is used repeatedly.

[0011] In other words, the present invention encompasses the inventions described in (1) to (5) 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, 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 a shaft-shaped core portion molded from a primary resin and a light-transmitting covering portion molded on the core portion from a secondary resin. The core portion, together with the covering portion, constitutes a gripping portion that serves as the handle of the handle body, and the gripping portion has a recess at a position corresponding to the finger rest portion, which allows the position of the finger rest portion to be recognized through the covering portion, and the opening periphery of the recess is formed in an R shape, a toothbrush. (2) The toothbrush according to (1), wherein the bottom surface of the recess has irregularities formed thereon. (3) The recess includes a bottom surface and a peripheral wall surface that is continuous with the peripheral edge of the bottom surface, The toothbrush according to (1) or (2), wherein the continuous portion between the bottom surface and the peripheral wall surface is formed in an R shape. (4) The toothbrush according to any one of (1) to (3), wherein the finger rest is provided at a predetermined distance from the tip of the covering portion. (5) A method for manufacturing a toothbrush as described in any of (1) to (4), A process of integrally molding a primary molded product consisting of the head portion and the core portion in which recesses based on the shapes of the neck portion and the tip portion of the movable pin are formed at predetermined positions, by injecting primary resin into the molding space of a primary mold provided with a movable pin having a tip shape corresponding to the shape of the recess, A step of moving the movable pin toward the primary molded product and demolding the primary molded product from the primary mold, A method for manufacturing a toothbrush, comprising the step of mounting a primary molded product having the recess formed thereon into a secondary mold, and then injecting a secondary resin into the molding space of the secondary mold to form a light-transmitting coating portion constituting the handle body on the core material portion. [Effects of the Invention]

[0012] 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 part molded from a primary resin and a light-transmitting coating part molded on the core material part from a secondary resin, it is possible to provide a toothbrush in which the finger rest part formed on the surface of the coating part is easily visible and cracks can be prevented from occurring in the finger rest part even when used repeatedly. [Brief explanation of the drawing]

[0013] [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 rear view showing a toothbrush. [Figure 3] A side view showing a toothbrush. [Figure 4] (a) is a side view showing the primary molded product of a toothbrush, indicated by solid lines. [Figure 5] (a) is an enlarged perspective view of the main part of the primary molded product that constitutes a toothbrush, (b) is an enlarged plan view of the main part of the primary molded product that constitutes a toothbrush, viewed from the bristle side, and (c) is a longitudinal cross-sectional view of the main part of the primary molded product of the toothbrush, with the solid lines showing the main part. [Figure 6](a) is an enlarged perspective view of the main part of a primary molded product constituting a toothbrush according to a first modification of a representative embodiment of the present invention, (b) is an enlarged plan view of the main part as viewed from the side of the bristle-implanted surface of the primary molded product constituting the toothbrush, and (c) is a longitudinal sectional view of the main part showing the primary molded product of the toothbrush with a solid line. [Figure 7] (a) is an enlarged perspective view of the main part of a primary molded product constituting a toothbrush according to a second modification of a representative embodiment of the present invention, (b) is an enlarged plan view of the main part as viewed from the side of the bristle-implanted surface of the primary molded product constituting the toothbrush, and (c) is a longitudinal sectional view of the main part showing the primary molded product of the toothbrush with a solid line. [Figure 8] (a) is an enlarged perspective view of the main part of a primary molded product constituting a toothbrush according to a third modification of a representative embodiment of the present invention, (b) is an enlarged plan view of the main part as viewed from the side of the bristle-implanted surface of the primary molded product constituting the toothbrush, and (c) is a longitudinal sectional view of the main part showing the primary molded product of the toothbrush with a solid line. [Figure 9] (a) is an enlarged perspective view of the main part of a primary molded product constituting a toothbrush according to a fourth modification of a representative embodiment of the present invention, (b) is an enlarged plan view of the main part as viewed from the side of the bristle-implanted surface of the primary molded product constituting the toothbrush, and (c) is a longitudinal sectional view of the main part showing the primary molded product of the toothbrush with a solid line. [Figure 10] (a) is an enlarged perspective view of the main part of a primary molded product constituting a toothbrush according to a fifth modification of a representative embodiment of the present invention, (b) is an enlarged plan view of the main part as viewed from the side of the bristle-implanted surface of the primary molded product constituting the toothbrush, and (c) is a longitudinal sectional view of the main part showing the primary molded product of the toothbrush with a solid line. [Figure 11] A longitudinal sectional view showing a primary mold for molding a toothbrush according to a representative embodiment of the present invention. [Figure 12] A longitudinal sectional view showing a state in which a primary molded product is set in a secondary mold for molding a toothbrush.

Mode for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings.

[0015] (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 neck portion 2 from a primary resin, and a light-transmitting coating portion 5 molded on the core material portion 4 from a secondary resin. Here, "light transmittance" means that visible light can be transmitted. Even a translucent resin mixed with a substance that does not transmit visible light (for example, glitter, pigment, etc.) is considered light-transmitting if it can transmit visible light.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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 on the proximal end side has a flared shape (trumpet shape) in which the diameter increases from the tip to the proximal end, and the rate of increase is greater towards the proximal end.

[0020] As shown in Figure 4, the core material portion 4 of the handle portion 3 has a rod-shaped portion 41 over which the covering portion 5 is covered, one or more cylindrical protrusions 42, 43 projecting from the front (ventral) side of the rod-shaped portion 41 at axial intervals, a recess 45 provided on the front side of the rod-shaped portion 41 at a position corresponding to the finger rest portion 31 in the approximate center of the primary molded product described later, and a disc-shaped plate portion 44 provided at the base end of the rod-shaped portion 41. The protrusions 42, 43 function as spacers when setting in the secondary mold, and as support bases 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. Furthermore, after molding, they function as locking pieces to prevent the covering portion 5, which has low adhesion (welding properties, bonding properties), from moving relative to the core material portion 4. The recess 45 functions as a marker to make the position of the finger rest portion 31 easily recognizable by sight through the light-transmitting covering portion 5.

[0021] As shown in Figures 4 and 5, the recess 45 has a cylindrical space, and its opening periphery 46 is formed in an R shape. By making the opening periphery 46 R-shaped, there are no edges on the opening periphery 46, which suppresses stress concentration at the contact point with the coating 5 when used as a toothbrush, and prevents the occurrence of cracks during repeated use. In addition, it is easier to fill the recess 45 with secondary resin during secondary molding, and the generation of air bubbles in the recess 45 and the surrounding coating 5 can be prevented. In this embodiment, the recess 45 has a bottom surface 47 and a periphery wall surface 48 that is continuous with the bottom surface 47, and this continuous portion is also formed in an R shape. Furthermore, a convex portion 49 is formed on the bottom surface 47, projecting in a straight line in a direction perpendicular to the long axis when viewed from the ventral side in plan view, thereby creating an uneven surface on the bottom surface 47. The height of the convex portion 49 from the bottom surface 47 is set lower than the opening periphery 46. The continuous portion between the convex portion 49 and the bottom surface 47 and periphery wall surface 48 is also formed in an R shape. Furthermore, the ventral side of the protrusion 49 is formed with a flat surface 49a. This flat surface 49a is also continuous with the peripheral wall surface 48 and the side surface 49b of the protrusion 49 facing the peripheral wall surface 48 by an R shape. The formation of the protrusion 49 can further improve the visibility of the recess 45 through the covering portion 5. In addition, when demolding from the primary mold, the holding ability of the tip of the movable pin (see Figure 11, reference numeral 74) which has a shape corresponding to the recess 45 is improved, and rotation of the movable pin relative to the axis in the direction of movement can be prevented. As a result, for example, when manufacturing toothbrushes by automation, the primary molded product can be stably moved to the secondary mold by various means. Furthermore, by applying an R shape not only to the opening periphery 46 of the recess 45, but also to the bottom surface 47 that forms the recess and the continuous portion with the peripheral wall surface 48, the filling of the recess 45 with the secondary resin becomes easier, preventing the generation of air bubbles in the covering portion 5 and improving moldability.

[0022] 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 light-transmitting 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 or polyamide resins are more preferable. Considering the selection of a light-transmitting secondary resin, the primary resin is preferably a resin with a melting point of 225 to 265°C, and suitable polyester resins include hard resins such as polybutylene terephthalate (PBT) and polyethylene terephthalate (PET). Suitable polyamide resins include nylon 6 and nylon 6,6.

[0023] Since the surface of the core material 4 can be seen through the light-transmitting coating 5, it is possible to create a toothbrush with a superior design by providing a pattern with irregularities on the surface of the colored core material 4. Examples of patterns include geometric patterns, twill patterns, checkerboard patterns, and houndstooth patterns. There are no particular limitations on the color.

[0024] The secondary resin constituting the coating portion 5 can be a resin with a lower melting point than the primary resin and is light-transmitting. It is preferable to use 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. It is more preferable to have a transmittance of 85% or more. It is preferable that both the core material portion 4 and the coating portion 5 be molded from a hard resin. In particular, it is preferable to use a combination of hard synthetic resins that have low welding (low adhesion) properties to each other, that is, hard resins that do not mix during molding and remain separated from each other after molding.

[0025] Specifically, the secondary resin is preferably a rigid synthetic resin with a lower heat resistance temperature than the primary resin, such as polycarbonate (PC), acrylonitrile butadiene styrene (ABS), acrylonitrile styrene copolymer (AS resin), polystyrene (PS), polyethylene (PE), or polypropylene (PP), and is also preferably a light-transmitting material. Alternatively, resins without a melting point, such as PC or ABS, can also be used. Such resins only need to have a glass transition temperature lower than the melting point of the primary resin.

[0026] Furthermore, it is preferable that the covering portion 5 is composed of a solidified secondary resin melted at a molding temperature of 200 to 300°C. By using a secondary resin melted within this temperature range, the melting of the primary resin can be efficiently suppressed during two-color molding, which has the advantage of making it easier to form a light-transmitting covering portion 5 with excellent transparency. In Figures 1 and 2, the core material portion 4 and the light-transmitting covering portion 5 are provided only on the handle portion 3, but for example, the core material portion and the light-transmitting covering portion may also be provided in a part or the entire area of ​​the neck portion 2.

[0027] As shown in Figures 2 and 3, the gate marks 5g formed on the covering portion 5 are formed at the bottom of the inverted frustoconical recessed hole 51. By forming the gate marks 5g at the bottom of the recessed hole 51 in this way, even if burrs remain on the gate marks 5g, they will not come into contact with the user's hands, thus avoiding discomfort and enhancing safety.

[0028] As shown in Figure 1, 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 towards the connection point. 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. Thus, the finger rest portion 31 is provided at a predetermined distance from the tip of the covering portion 5, and the covering portion 5 is also formed on the tip side of the finger rest portion 31. Furthermore, the thickness of the covering portion 5 in the longitudinal cross-section of the tapered portion 30 is set to be greater than the thickness of the groove 50 of the finger rest portion 31. Furthermore, by providing such a covering portion 5 on the tip side of the finger rest portion 31, when a recess 45 is provided at a position that overlaps with the finger rest portion 31 in a plan view from the abdominal side, it is possible to more effectively suppress the occurrence of cracks in the finger rest portion 31 of the covering portion 5.

[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 portion for the finger. In addition, a recess 45 is provided on the ventral side of the rod-shaped portion 41 corresponding to the portion where the non-slip portion is formed. The recess 45 is visible through the covering portion 5, overlapping with at least one of the grooves 50 of the non-slip portion in a plan view from the ventral side, so that the position of the finger rest portion 31 can be clearly recognized by the user. The finger rest portion 31 and its base end portion are configured such that the width dimension gradually decreases toward the axial center position 32 of the handle portion 3. Furthermore, the portion toward the base end from the axial center position 32 is provided with an enlarged diameter portion 33 configured such that the width dimension gradually increases toward the base end of the handle portion 3, and a terminal portion 34 configured such that the width dimension 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 axial center position 32 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 according to modified examples 1 to 5 will be described with reference to Figures 6 to 10. These modified examples are variations in the form of the recess 45 provided in the core material portion 4 of toothbrush T1, and the external shape is the same as in Figures 1 and 2. In other words, toothbrushes T2 to T6 according to modified examples 1 to 5 also consist of a head portion 1 at the tip and a handle body H at the base end, and 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 an axial core material portion 4 integrally molded with the head portion 1 and the neck portion 2 from primary resin, and a covering portion 5 molded on the core material portion 4 from secondary resin.

[0033] In the toothbrush T2 according to Modification 1, as shown in Figure 6, the toothbrush T1 is formed from a primary molded product M2 having a recess 45a instead of the recess 45, but the other configurations are the same as the toothbrush T1. In the primary molded product M2, the recess 45a is formed as an annular groove in a plan view from the ventral side. The inner and outer surfaces of the annular opening periphery 46a of the recess 45a are formed in an R shape. The recess 45a has an annular bottom surface 47a, and inner and outer periphery walls 48a that are continuously opposed to the inner and outer circumferences of the bottom surface 47a and the inner and outer circumferences of the opening periphery 46a, respectively, and the continuous portion between the bottom surface 47a and the periphery walls 48a is formed in an R shape. In this case, when the recess 45a is annular, it is easy to obtain holding force with the movable pin during primary molding, which has a tip shape corresponding to the recess 45a, and the movable pin can be held stably when demolding the primary molded product M2, allowing for stable operation from demolding from the primary mold to mounting the primary molded product M2 onto the secondary mold.

[0034] Furthermore, the recess 45a is formed at the tip portion 4a of the core material portion 4 and is positioned to correspond to the finger rest portion 31 of the handle portion 3. Here, the position corresponding to the finger rest portion 31 is not limited to a position that overlaps with the finger rest portion 3 in a plan view of the ventral side of the handle portion 3, but also includes a position that is slightly offset from the finger rest portion 31 in the longitudinal direction in the same plan view. However, from the viewpoint of visibility of the finger rest portion 31 through the covering portion 5, it is preferable that the positional relationship between the recess 45a and the finger rest portion 31 overlaps in a plan view of the ventral side of the handle portion 3. In addition, the depth of the groove of the recess 45a in the longitudinal cross-sectional direction is made to be approximately the same as the inclination of the ventral surface of the tip portion 4a, so that the entire piece detaches almost simultaneously when it detaches from the movable pin.

[0035] In the toothbrush T2 according to Modified Example 1, a recess 45a is formed at the tip a of the core material part 4 corresponding to the tapered portion 30. The thickness of the covering portion 5 of the tapered portion 30 in the longitudinal cross-section is set to be greater than the thickness of the part of the finger rest 31 where the groove 50 is provided, so the strength of the secondary resin is relatively greater, improving durability during repeated use. Furthermore, by making the structure of the recess 45a an annular groove, the contact area between the core material part 4 and the covering portion 5 is secured, which increases the holding force of the covering portion 5 by the core material part 4 during brushing at the boundary between the base end of the neck portion 2 and the tip of the covering portion 5, and suppresses the occurrence of gaps at that boundary. Thus, Modified Example 1 has the advantage that by providing a recess 45a at the tip 4a, durability during repeated use is improved, suppressing the occurrence of cracks and suppressing the occurrence of gaps at the boundary between the neck portion 2 and the covering portion 5.

[0036] In the toothbrush T3 according to Modification 2, as shown in Figure 7, the toothbrush T3 is formed from a primary molded product M3 having a recess 45b instead of the recess 45 of the toothbrush T1, but the other configurations are the same as the toothbrush T1. In the primary molded product M3, the recess 45b has a cylindrical space that is circular in a plan view from the ventral side, and its opening periphery 46b is formed in an R shape. The bottom surface 47b of the recess 45b is made of a circular flat surface. The peripheral wall surface 48b of the recess 45b is formed in a cylindrical shape, and the continuous portion with the periphery of the bottom surface 47b is formed in an R shape. The depth of the opening periphery 46b in the thickness direction changes according to the outer shape of the rod-shaped part 41. In the recess 45b of the toothbrush T3 of Modification 2, the diameter of the circle in a plan view from the ventral side is larger than that of the recess 45 of the toothbrush T1, and the depth in the longitudinal cross-sectional (thickness) direction is larger. This makes it easier for the secondary resin to fill and further suppresses the generation of air bubbles. Therefore, by suppressing stress concentration caused by repeated use, the occurrence of cracks can be further suppressed.

[0037] Furthermore, the recess 45b is provided at a position corresponding to the finger rest portion 31, but is formed at a position corresponding to the base end in a plan view of the ventral side, from the position where the anti-slip portion, which is formed by the groove 50 provided on the ventral side of the finger rest portion 31, is provided. Since the recess 45b provided at such a position is far from the head portion 2, which is the point of action during brushing, and the finger rest portion 31, which is the fulcrum, based on the lever principle, the load on the recess 45b during brushing can be reduced. As a result, stress concentration in the recess 45b during repeated use is suppressed, and the occurrence of cracks can be further suppressed.

[0038] As described above, Modification 2 improves the filling of the recess 45b with secondary resin, further suppresses stress concentration during repeated use, and can be said to be an effective form from the viewpoint of suppressing the occurrence of cracks during repeated use.

[0039] In the toothbrush T4 according to Modification 3, as shown in Figure 8, the toothbrush T4 is formed by a primary molded product M4 having a recess 45c instead of the recess 45 of the toothbrush T1, but the other configurations are the same as the toothbrush T1. In the primary molded product M4, the recess 45c has a columnar space that is an elliptical or oblong shape with a large width in a plan view from the ventral side, and its opening periphery 46c is formed in an R shape. The bottom surface 47c of the recess 45c is composed of an elliptical or oblong flat surface. The peripheral wall surface 48c of the recess 45c is formed in a cylindrical shape, and the continuous portion with the periphery of the bottom surface 47c is formed in an R shape. The depth of the opening periphery 46c changes in the thickness direction according to the outer shape of the rod-shaped part 41. Because the recess 45c has different shapes in the width direction and the long axis direction, when demolding the primary molded product M4, it does not rotate with respect to the axis of movement of the movable pin having the shape of the tip corresponding to the recess 45c, so that various operations afterward are stable and mounting to the secondary mold can be done more smoothly.

[0040] Furthermore, the recess 45c is provided at a position corresponding to the finger rest portion 31 and is formed at a position corresponding to the groove 50 on the ventral side of the finger rest portion 31. Therefore, as with the toothbrush T1, the position of the anti-slip portion is easily visible through the covering portion 5.

[0041] In the toothbrush T5 according to Modification 4, as shown in Figure 9, the toothbrush T5 is formed from a primary molded product M5 having a recess 45d instead of the recess 45 of the toothbrush T1, but the other configurations are the same as the toothbrush T1. In the primary molded product M5, the recess 45d has a columnar space that forms a star shape when viewed from the ventral side in plan view, and its opening periphery 46d is formed in an R shape. The bottom surface 47d of the recess 45d is composed of a star-shaped flat surface corresponding to the opening periphery 46d when viewed from the ventral side in plan view. The peripheral wall surface 48d of the recess 45d is formed in a cylindrical shape with a continuous curved surface that forms a star shape when viewed from the ventral side in plan view, and the continuous portion with the periphery of the bottom surface 47d is formed in an R shape. Because the recess 45d is star-shaped in this way, when demolding the primary molded product M4, the contact area with the movable pin having the shape of the tip corresponding to the recess 45c is increased, the holding force is increased, and since it does not rotate with respect to the axis of the movable direction of the movable pin, various subsequent operations are stabilized and mounting to the secondary mold can be done more smoothly. Furthermore, the star-shaped recess 45d, which is visible through the covering portion 5, can improve the design and decorative qualities of the toothbrush T5.

[0042] Furthermore, the recess 45d is provided at a position corresponding to the finger rest portion 31 and is formed at a position corresponding to the groove 50 on the ventral side of the finger rest portion 31. Therefore, as with the toothbrush T1, the position of the anti-slip portion is easily visible through the covering portion 5.

[0043] In the toothbrush T6 according to Modification 5, as shown in Figure 10, the toothbrush T6 is formed by a primary molded product M6 having a recess 45e instead of the recess 45 of the toothbrush T1, but the other configurations are the same as the toothbrush T1. In the primary molded product M6, the recess 45e has a rectangular prism-shaped space that is a rectangle with a large width in a plan view from the ventral side, and its opening periphery 46e is formed in an R shape. The bottom surface 47e of the recess 45e is composed of a rectangular flat surface corresponding to the opening periphery 46e in a plan view from the ventral side. The peripheral wall surface 48e of the recess 45e is formed in a cylindrical shape with a continuous curved surface such that the plan view from the ventral side is rectangular, and the continuous portion with the periphery of the bottom surface 47e is formed in an R shape. Because the recess 45e has a rectangular shape in this way, when demolding the primary molded product M4, it does not rotate with respect to the axis of the direction of movement of the movable pin having the shape of the tip corresponding to the recess 45e, so that various operations afterward are stable and mounting to the secondary mold can be done more smoothly.

[0044] Furthermore, the recess 45e is provided at a position corresponding to the finger rest portion 31 and is formed at a position corresponding to the groove 50 on the ventral side of the finger rest portion 31. Therefore, as with the toothbrush T1, the position of the anti-slip portion is easily visible through the covering portion 5.

[0045] (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 5 as an example.

[0046] As shown in Figure 11, 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 is integrally molded by injecting primary resin through an injection gate 73 into the molding space 70 of primary molds 71 ​​and 72. The injection gate 73 opens at a predetermined position overlooking the space in which the core material portion 4 is molded. Of the primary molds 71 ​​and 72, the primary mold 72 that forms the molding space 70 on the ventral side of the primary molded product M1 is provided with a movable pin 74 that has a tip portion 75 shaped to correspond to a recess 45 formed in the core material portion 4 and a rod-shaped base portion 76 continuous with the tip portion 75, and operates when demolding the primary molded product M1. The movable pin 74 is movable relative to the primary mold 72 along the long axis direction of the base portion 76. The tip portion 75 of the movable pin 74 protrudes into the molding space 70, forming the molding space 70. The tip portion 75 has a cylindrical protrusion 77, and a linearly extending groove 79 is provided on the tip surface 78 of the protrusion 77. The continuous portion between the protrusion 77 and the base portion 76 is rounded in shape, and this continuous portion forms the opening periphery 46 of the recess 45 of the primary molded product M1. The tip surface 78 of the pin 74 corresponds to the bottom surface 47 of the recess 45 of the primary molded product M1, and the groove 79 of the pin 74 forms the protrusion 49 of the primary molded product M1. In addition, the outer surface of the protrusion 77 is rounded in shape so that no edge portion is formed. Note that, if necessary, other movable pins may be provided in the primary molds 71 ​​and 72 at desired positions in addition to the movable pin 74.

[0047] Next, the primary molds 71 ​​and 72 and the movable pin 74 are moved relative to each other, and the primary molded product M1 is demolded from the primary molds 71 ​​and 72 while the tip 75 of the movable pin 74 holds the primary molded product M1. Then, by a desired means, as shown in Figure 12, the primary molded product M1 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 light-transmitting coating portion 5 that constitutes the handle body H on the core material portion 4. Since the primary molded product M1 is held at the tip 75 when demolding from the primary mold, for example, when automating the operation after demolding from the primary mold, various operations up to mounting to the secondary mold can be performed stably and reliably.

[0048] 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.

[0049] 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]

[0050] T1, T2, T3, T4, T5, T6 toothbrushes H Handle Body M1, M2, M3, M4, M5, M6 primary molded products 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, 43 Protrusions 44 Plate-like part 45, 45a, 45b, 45c, 45d, 45e recess 46, 46a, 46b, 46c, 46d, 46e Opening periphery 47, 47a, 47b, 47c, 47d, 47e Base 48, 48a, 48b, 48c, 48d, 48e surrounding wall surface 49 Convex part 49a flat surface 49b Side view 50 grooves 51 Hole 70 Molding space 71, 72 Primary mold 73 Injection Gate 74 Movable pins 75 Tip 76 Proximal end 77 Convex part 78 Tip surface 79. Grooves 79a Bottom 80 Molding space 81, 82 Secondary mold 83 Injection Gate 84 Convex part t1 Thickness (plate thickness) t2 Thickness dimension 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, 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 a shaft-shaped core portion molded from a primary resin and a light-transmitting covering portion molded on the core portion from a secondary resin. The core portion, together with the covering portion, constitutes a gripping portion that serves as the handle of the handle body, and the gripping portion has a recess at a position corresponding to the finger rest portion, which allows the position of the finger rest portion to be recognized through the covering portion, and the opening periphery of the recess is formed in an R shape, a toothbrush.

2. The toothbrush according to claim 1, wherein the bottom surface of the recess has irregularities formed on it.

3. The recess includes a bottom surface and a peripheral wall surface that is continuous with the peripheral edge of the bottom surface. The toothbrush according to claim 1 or 2, wherein the continuous portion between the bottom surface and the peripheral wall surface is formed in an R shape.

4. The toothbrush according to claim 1 or 2, wherein the finger rest portion is provided at a predetermined distance from the tip of the covering portion.

5. A method for manufacturing a toothbrush according to claim 1 or 2, A process of integrally molding a primary molded product consisting of the head portion and the core portion in which recesses based on the shapes of the neck portion and the tip portion of the movable pin are formed at predetermined positions, by injecting primary resin into the molding space of a primary mold provided with a movable pin having a tip shape corresponding to the shape of the recess, A step of moving the movable pin toward the primary molded product and demolding the primary molded product from the primary mold, A method for manufacturing a toothbrush, comprising the step of mounting a primary molded product having the recess formed thereon into a secondary mold, and then injecting a secondary resin into the molding space of the secondary mold to form a light-transmitting coating portion constituting the handle body on the core material portion.

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