Method for manufacturing toothbrush

Abstract

To provide a method for manufacturing a toothbrush that can effectively prevent the occurrence of the over-brushing state without impairing the grip performance of the toothbrush, allows the toothbrush to be easily removed from a second molding die, and also facilitates mass production.SOLUTION: In a method for manufacturing a toothbrush H in which a handle portion 3 includes a core material 4 made of a first hard resin and a coating material 5 made of a second hard resin having low adhesion properties relative to the first hard resin, the core material 4 includes a core material body 6 embedded within the coating material 5 and a movable portion 7 that swings and is displaced in a reverse direction B to a protruding direction A of bristle bundles 10, and a through groove 52 is provided in the tip-side portion of the coating material 5, when removing the toothbrush H molded from a second molding die 9, the toothbrush is removed by pushing out multiple positions on the ventral side of the outer surface of the coating material 5 or the core material 4 using eject pins 94-97, and one eject pin 94 is disposed at the position of the outer surface of a connecting portion 53.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

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

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

[0004] In contrast, the present inventor has already proposed a toothbrush including a head portion in which tufts of bristles are implanted, a neck portion connected to the head portion, and a handle portion serving as a grip, the handle portion including a core material made of a first rigid resin integrally formed with the neck portion, and a coating material formed to cover the core material with a second rigid resin having a property of low adhesion to the first rigid resin, the core material including a core body embedded in the coating material, and a movable portion provided on the tip end side thereof and oscillating and displacing in a direction opposite to the protruding direction of the tufts of bristles in response to a brushing pressure acting in a direction orthogonal to the implanting surface of the head portion, and a space portion allowing the oscillating displacement of the movable portion being provided in a tip end side portion of the coating material (Patent Document 2).

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

[0006] The toothbrush of Patent Document 2 is formed by setting a primary molded article made of a first hard resin molded by a first mold in a molding space of a second mold, and injecting a second hard resin into the molding space so that the core material body of the primary molded article is covered with a covering material to form a toothbrush. Then, the molded toothbrush is taken out of the mold. After the movable mold of the second mold is raised to open the mold, the toothbrush is pushed out by an ejector pin provided on the fixed mold and gripped and taken out by a robot hand or the like. At this time, if the head portion and the neck portion made of the first hard resin are pushed by the ejector pin, a dent mark corresponding to the installation portion of the ejector pin is formed in the delicate portion that enters the oral cavity, which is not preferable. Therefore, the movable portion of the handle portion where the core material is exposed and other exposed portions of the core material are pushed out and taken out by the ejector pin.

[0007] However, when considering mass production and setting the primary molded article in the second mold while it is still soft, the head portion and the neck portion may also adhere to the mold with a small force. As shown in Fig. 15, the phenomenon that the tip side portion of the covering material 5 sticks to the fixed mold 92 of the second mold often occurs. For this reason, the toothbrush H cannot be smoothly taken out from the fixed mold 92, which has been an issue in mass production.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, in view of the above situation, the problem to be solved by the present invention is to effectively prevent the occurrence of overbrushing without impairing the grip of the toothbrush, and to easily remove the molded toothbrush from the second mold without extruding the head portion or the neck portion with an ejector pin, and to provide a toothbrush manufacturing method that facilitates mass production.

Means for Solving the Problems

[0010] In view of such a situation, the present inventor has intensively studied and as a result, a through groove for swinging and displacing the movable part of the primary molded product is formed in the tip side part of the coating material. Therefore, the tip side part has a large contact area with the mold, and the resin filling amount is less than that of others and the shrinkage rate after molding is small, so it is easy to stick to the mold. A connecting part is provided at the tip of this coating material, but this part is located ahead of the part that touches the finger and does not enter the oral cavity, so even if there is a dent mark, there is no problem. In addition, the present inventor has found that if the position of this connecting part is pushed with an ejector pin, the neck part and the head part at the tip thereof can be easily removed, and thus the present invention has been completed.

[0011] That is, the present invention includes the following inventions. (1) A toothbrush comprising a head portion on which tufts are implanted, a neck portion connected to the head portion, and a handle portion serving as a grip. The handle portion has a core material formed by injecting a first hard resin into a first mold and integrally molding it with the neck portion, and a covering material formed by setting the core material in a second mold and injecting a second hard resin having a low adhesion property to the first hard resin to cover the core material. The core material has a core body embedded in the covering material, and a movable portion provided on the tip end side thereof, which bends and swings in the direction opposite to the protruding direction of the tufts in response to a brushing pressure acting in a direction perpendicular to the tuft-implanting surface of the head portion. The tip end side portion of the covering material has a pair of arm portions branched left and right, and a through groove is formed between the arm portions to penetrate the covering material from the back side to the front side to allow the swinging displacement of the movable portion. A connecting portion for restricting the swinging displacement of the movable portion is provided between the front end portions on the front side of the arm portions. In the method for manufacturing a toothbrush, when taking out the toothbrush molded from the second mold, a plurality of ventral positions on the outer surface of the covering material or the core material are pushed out by ejector pins, and one of the plurality of positions is set at the position of the outer surface of the connecting portion.

[0012] (2) The method for manufacturing a toothbrush according to (1), wherein the connecting portion of the toothbrush to be molded has a tapered surface on its outer surface that becomes closer to the core material toward the tip end side.

[0013] (3) The method for manufacturing a toothbrush according to (2), wherein the inclination angle of the tapered surface with respect to the axis is 5 degrees or more.

[0014] (4) The method for manufacturing a toothbrush according to (1), wherein the axial length of the connecting portion is in the range of 1 mm to 7 mm.

[0015] (5) The method for manufacturing a toothbrush according to (1), wherein when taking out the toothbrush molded from the second mold, the head portion and the neck portion are not pushed out by ejector pins, and only the handle portion is pushed out by the ejector pins.

[0016] (6) The manufacturing method of the toothbrush according to (1), wherein, among the plurality of positions, a position other than the outer surface of the connecting portion is defined as the position of the core material exposed from the covering material.

[0017] (7) The second molding die is a die formed by combining a first split die for molding the dorsal half of the covering material and a second split die for molding the ventral half of the covering material. A plurality of ejector pins are provided in the second split die. After injecting the second hard resin and separating the first split die, the ejector pins are projected from the second split die to take out the molded toothbrush. The manufacturing method of the toothbrush according to (1).

[0018] (8) The toothbrush to be molded has gaps respectively provided between the inner surfaces of the left and right arm portions facing each other and the left and right side surfaces of the movable portion. A concave-shaped protrusion forming a through groove including the gaps is provided in the second molding die. The manufacturing method of the toothbrush according to (7).

[0019] (9) In the toothbrush to be molded, the movable portion has a greater width in the front-back direction from the back to the belly than the width in the lateral direction in a cross-sectional view. The manufacturing method of the toothbrush according to (1).

Advantages of the Invention

[0020] According to the present invention configured as described above, without impairing the gripability of the toothbrush, it is possible to effectively prevent the occurrence of an overbrushing state, and the molded toothbrush can be easily taken out from the second molding die without extruding the head portion and the neck portion with an ejector pin, achieving the effect of facilitating mass production.

Brief Description of the Drawings

[0021]

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Figure 18

BEST MODE FOR CARRYING OUT THE INVENTION

[0022] Hereinafter, a method for manufacturing a toothbrush according to the present invention will be described with reference to the drawings. In each figure, components denoted by the same reference numerals are the same components, and the description thereof will be omitted.

[0023] The toothbrush H formed by the manufacturing method of the toothbrush according to the present invention includes, as shown in FIGS. 1 to 7, a head portion 1 in which a tuft 10 is implanted, a substantially rod-shaped neck portion 2 continuously provided at the rear end portion of the head portion 1, and a handle portion 3 serving as a grip. The head portion 1 and the neck portion 2 are formed of a first hard resin such as polyacetal resin (POM). The handle portion 3 has a shaft-shaped core material 4 integrally formed with the head portion 1 and the neck portion 2 by the first hard resin, and a covering material 5 formed so as to cover the core material 4.

[0024] The covering material 5 is formed of a hard resin having a property of low adhesion to the first hard resin, that is, a property (low weldability) of being separated from each other after molding without mixing with the first hard resin during molding. For example, a crystallized resin such as polyacetal resin (POM), polyamide resin (PA), polybutylene terephthalate (PBT), or polypropylene resin (PP) has a property of low adhesion (low welding) to each other when the other is a crystallized resin (except for PP to PP) or a non-crystallized resin. Therefore, if either one of the first hard resin constituting the core material 4 and the second hard resin constituting the covering material 5 is a crystallized resin such as polyacetal resin (POM), and the other is a non-crystallized resin such as acrylonitrile-butadiene-styrene resin (ABS), polycarbonate (PC), or acrylic resin (PMMA), the first hard resin and the second hard resin do not mix with each other during molding, and the core material 4 and the covering material 5 are separated from each other after molding.

[0025] In addition, when both the first hard resin and the second hard resin are crystallization resins, it is possible to prevent the core material 4 and the coating material 5 from being fused to each other in principle. For example, if either the first hard resin constituting the core material 4 or the second hard resin constituting the coating material 5 is a crystallization resin such as polyacetal resin (POM), and the other is a crystallization resin made of polyacetal resin (POM), polyamide resin (PA), or polypropylene resin (PP), etc., it is possible to prevent the first hard resin and the second hard resin from mixing during molding and to keep the core material 4 and the coating material 5 separated from each other after molding. However, among the crystallization resins, polypropylene resins (PP) have high adhesion, so those in which both the first hard resin and the second hard resin are polypropylene resins (PP) are excluded.

[0026] Also, as the second hard resin constituting the coating material 5, it is preferable to use a transparent material. This "transparent" means that it is possible to recognize the transmission of visible light. Also, a resin in which a small amount of a substance that does not transmit visible light (for example, lame, pigment, etc.) is mixed is considered a transparent material as long as it can transmit visible light. As the resin, it is particularly preferable to use a resin whose value measured by the test method of JIS K 7105 is 80% or more. When the coating material 5 is molded with the second hard resin made of such a transparent material, the pattern and coloring applied to the core material 4 can be visually recognized from the outside, improving the design of the toothbrush H.

[0027] As shown in FIG. 1, the core material 4 has a substantially rod-shaped core body 6 embedded in the coating material 5, and a movable part 7 provided on the tip side of the core body 6 that bends and swings in the reverse direction B to the protruding direction A of the tuft 10 in response to the brushing pressure. Also, on the ventral side of the core body 6, that is, on the protruding direction A side of the tuft 10, columnar convex portions 61 and 62 are formed at predetermined positions in the longitudinal direction as shown in FIG. 3. Further, a substantially circular plate-like portion 63 is provided at the rear end portion of the core body 6.

[0028] In the cross-sectional view shown in FIG. 5, the movable part 7 is formed in a vertically long, substantially oval shape where the width V in the front-to-back direction from the back to the front is larger than the width W in the lateral direction. Also, the outer peripheral surface of the movable part 7 is composed of a pair of flat inclined surfaces 71, 71 that are inclined inward from the position of the widest hem, which is the central position 70 in the front-to-back direction in this embodiment, and extend linearly toward the ventral side and the dorsal side by a predetermined length, and a convex curved surface 72 that is substantially arc-shaped in cross-section and connects the extended ends thereof, forming a surface that is substantially arch-shaped in cross-section. The inclination angle θ of the inclined surfaces 71, 71 is 3 degrees or more, and the length of each inclined surface 71 is preferably 0.2 mm or more and 2 mm or less.

[0029] As shown in FIGS. 5 and 6, the tip-side portion of the covering material 5 has a pair of arms 51, 51 that branch to the left and right, and a through groove 52 that penetrates the covering material 5 from the dorsal side to the ventral side and allows the rocking displacement of the movable part 7 is formed between the arms 51, 51. Also, as shown in FIGS. 6 and 7, a connecting portion 53 that restricts the rocking displacement of the movable part 7 is laid between the ventral tip portions of the arms 51, 51. The connecting portion 53 has a tapered surface 54 with a predetermined length L that is inclined so as to be closer to the core material 4 toward the tip end on the outer surface formed by its ventral surface (see FIG. 12).

[0030] As shown in FIG. 5, gaps 55, 55 are provided between the inner surfaces of the arms 51, 51 provided at the tip-side portion of the covering material 5 that face each other and the left and right side surfaces of the movable part 7 to prevent the movable part 7 from interfering with the inner surfaces of the arms 51, 51 during the rocking displacement of the movable part 7. Further, as shown in FIG. 6, a gap 56 is provided between the base end surface of the neck portion 2 and the tip end surface of the covering material 5 to prevent the base end surface of the neck portion 2 from interfering with the covering material 5 during the rocking displacement of the movable part 7.

[0031] As described above, the handle portion 3 serving as a grip is composed of a core material 4 made of a first rigid resin integrally formed with the head portion 1 and the neck portion 2, and a coating material 5 formed so as to coat the core material 4 with a second rigid resin having a property of low adhesion to the first rigid resin. In the toothbrush H configured such that the movable portion 7 provided on the tip end side of the core material 4 can swing and displace within the through groove 52 provided in the coating material 5, there is an advantage that excellent operability can be obtained without impairing the grip of the toothbrush H.

[0032] That is, since the core material 4 of the primary molded product 11 constituting the handle portion 3 of the toothbrush H and the coating material 5 covering the core material 4 are formed of rigid resins having a property of low adhesion to each other, it is possible to prevent the movable portion 7 made of the primary molded product 11 and the arm portion 51 of the coating material 5 covering the side portion thereof from being in a state of being fused to each other. As a result, when the user brushes their teeth, the movable portion 7 made of the first rigid resin provided on the tip end side of the core body 6 can be allowed to swing and displace within the through groove 52 formed between the arm portions 51, 51 of the coating material 5 without deforming the coating material 5 made of the second rigid resin.

[0033] Therefore, the user of the toothbrush H can effectively clean the teeth by operating the tuft 10 of the head portion 1 while stably gripping the coating material 5 located on the outer peripheral portion of the handle portion 3, and can easily bend the movable portion 7 of the core material 4 in the dorsal direction B, which is the direction opposite to the protruding direction A of the tuft 10, according to the brushing pressure at that time, and smoothly swing and displace it. For this reason, problems such as the grip portion deforming and the grip of the toothbrush deteriorating as in the prior art in which the grip portion of the toothbrush is covered with a soft synthetic resin do not occur, and by swinging and displacing the neck portion 2 and the movable portion 7 of the toothbrush H, it is possible to prevent an excessive brushing pressure from acting. Moreover, it is possible to suppress the manufacturing cost of the toothbrush H at a low price by using an inexpensive rigid resin without using an expensive soft resin such as an elastomer as in Patent Document 1.

[0034] In addition, since the through groove 52 provided in the tip-side portion of the covering material 5 functions as a drain hole, the moisture accumulated in the through groove 52 after the use of the toothbrush H can be quickly discharged to the outside, preventing the toothbrush H from becoming sticky and ensuring its cleanliness. Moreover, when brushing teeth while gripping the tip-side portion of the handle 3 by the pen grip method, the pair of arm portions 51, 51 provided on the left and right of the through groove 52 function as a gripping portion, so that the teeth can be effectively cleaned while firmly gripping the toothbrush H. For example, as shown in FIG. 8, when gripping the toothbrush H by the pen grip method, the ventral surface of the handle 3 located on the rear side of the through groove 52 is pressed against by the user's thumb o, and the index finger h and the middle finger n can be placed on the outer surfaces of the arm portions 51, 51, respectively. Therefore, despite forming the through groove 52 with a predetermined width at the ventral tip portion of the covering material 5, the teeth can be effectively cleaned while firmly gripping the handle 3 of the toothbrush H.

[0035] Also, as shown in FIGS. 6 and 7, since a connecting portion 53 that connects the tip portions of the arm portions 51, 51 is provided at the ventral tip portion of the covering material 5, the head portion 1 and the neck portion 2 of the toothbrush H can be restricted from swinging and displacing ventrally in a direction opposite to the acting direction (B direction) of the brushing pressure. Moreover, the connecting portion 53 can prevent deformations such as the expansion of the arm portions 51, 51.

[0036] A method for manufacturing the toothbrush H having the above-described configuration will be described below. First, as shown in FIG. 9, with the first split mold 81 and the second split mold 82 of the first molding die 8 clamped, a first hard resin made of a crystallizable resin such as polyacetal resin (POM) is injected into the molding space 80 of the first molding die 8 from the injection gate 83, thereby molding a primary molded product 11 in which the head portion 1 and the neck portion 2 and the core material 4 of the handle 3 are integrally connected as shown in FIG. 3.

[0037] Next, after opening the first mold 8 and taking out the primary molded product 11, as shown in FIG. 10, with the primary molded product 11 set in the second mold 9 having a space for installing the primary molded product 11 and a molding space 90 for the coating material 5, the first split mold (movable mold) 91 and the second split mold (fixed mold) 92 are clamped. Then, from the injection gate 93 formed in the first split mold 91 etc., into the molding space 90 of the second mold 9, a hard resin having a property of low adhesion to the first hard resin, for example, an amorphous resin made of acrylonitrile-butadiene-styrene resin (ABS), polycarbonate (PC), or acrylic resin (PMMA), or a second hard resin made of a crystallized resin such as polyacetal resin (POM), polyamide resin (PA), polybutylene terephthalate (PBT), or polypropylene resin (PP) is injected to mold the coating material 5. In this way, the toothbrush H is manufactured in which the core material 4 of the primary molded product 11 made of the first hard resin is covered with the coating material 5 made of the second hard resin.

[0038] In FIG. 10, reference numerals 94 to 97 are ejector pins for detaching the molded toothbrush H from the second split mold 92. The ejector pin 94 on the tip side is disposed at a position corresponding to the outer surface of the connecting portion 53 of the coating material 5. The ejector pins 95 and 96 in the middle part are disposed at positions corresponding to the columnar convex portions 61 and 62 provided on the abdominal side of the core material body 6, respectively. The ejector pin 97 on the base end side is disposed at a position corresponding to the plate-like portion 63. Also, in FIGS. 11 and 13, reference numerals 98 and 99 are concave-shaped protrusions provided on the first split mold 91 and the second split mold 92 for forming the through groove 52 in the tip-side portion of the coating material 5.

[0039] In the method for manufacturing the toothbrush H according to the present invention, when taking out the toothbrush H molded from the second molding die 9, a plurality of positions on the ventral side of the outer surface of the coating material 5 or the core material 4 are pushed out by the ejector pins 94 to 97 and taken out. Moreover, since one ejector pin 94 is disposed at a position corresponding to the outer surface of the connecting portion 53 provided at the tip portion on the ventral side of the coating material 5, there is an advantage that the toothbrush H having the above-described configuration can be easily taken out from the second molding die 9 without impairing its commercial value.

[0040] That is, since the filling amount of the second hard resin is smaller than that of the rear side portion of the coating material 5, the outer surface of the connecting portion 53 located at the tip side portion of the coating material 5, which tends to stick to the molding surface of the second molding die 9, is pressed by the ejector pin 94. Thus, the tip side portion of the coating material 5 and the neck portion 2 and the head portion 1 at the tip side thereof can be surely detached from the second molding die 9. Therefore, it is possible to smoothly take out the toothbrush H from the second molding die 9 using a robot hand or the like (not shown), and mass production of the toothbrush H can be achieved.

[0041] Further, in the above-described embodiment, as shown in FIG. 10, the outer surface of the connecting portion 53 provided at the tip portion of the coating material 5 is formed as a tapered surface 54 that becomes closer to the core material 4 toward the tip side, and the tapered surface 54 is pressed by the ejector pin 94. Therefore, according to the biasing force P of the ejector pin 94, a pressing force P1 in a direction orthogonal to the tapered surface 54 and a shearing force P2 in a direction along the tapered surface 54 can be applied to the connecting portion 53. Then, since the ventral surface of the coating material 5 is biased in a direction in which it slides and displaces along the molding surface of the second split die 92 according to the shearing force P2, the adhesion state between the ventral surface of the coating material 5 and the molding surface of the second split die 92 is peeled off. As a result, the molded toothbrush H can be easily detached from the second split die 92 according to the pressing force P1. In order to sufficiently ensure the shearing force P2 and surely peel the ventral surface of the coating material 5 from the molding surface of the second split die 92, it is preferable that the inclination angle α of the tapered surface 54 with respect to the axial center of the handle portion 3 be 5 degrees or more.

[0042] In addition, when the axial length L of the connecting portion 53 is short, it becomes difficult to appropriately push the connecting portion 53 with the ejector pin 94. Conversely, if the axial length L of the connecting portion 53 is too large, water easily accumulates at the tip of the covering material 5, which is not hygienic, and the contact area between the movable portion 7 and the covering material 5 increases, resulting in an increase in the load when the movable portion 7 is swing-displaced. For this reason, the axial length L of the connecting portion 53 is preferably in the range of 1 mm to 7 mm.

[0043] In the above-described embodiment, when taking out the toothbrush H molded from the second mold 9, the head portion 1 and the neck portion 2 made of the first hard resin are not pushed out by the ejector pins, and only the handle portion 3 is pushed out and taken out by the ejector pins 94 to 97. Therefore, there is an advantage that a dent mark corresponding to the installation portion of the ejector pins 94 to 97 is not formed in the delicate portion that enters the oral cavity at a conspicuous position of the toothbrush H, and the commercial value and operability of the toothbrush H can be prevented from being impaired.

[0044] Also, as shown in FIG. 3, when the core body 6 of the primary molded product 11 is provided with cylindrical convex portions 61 and 62, the set state of the primary molded product 11 can be stabilized by making the convex portions 61 and 62 function as spacers when setting the primary molded product 11 in the second mold 9. Moreover, after the toothbrush H is molded, the convex portions 61 and 62 can function as locking pieces that prevent the covering material 5 from moving relative to the core body 6. Further, when a circular plate-like portion 63 is provided at the rear end portion of the core body 6 and the periphery thereof is configured to be covered with the covering material 5, the bonding state between the core material 4 and the covering material 5 can be stabilized by making the plate-like portion 63 function as a retaining portion for the covering material 5.

[0045] When removing the toothbrush H molded from the second mold 9, ejector pins 95 to 97 that press on positions other than the outer surface of the connecting portion 53 are exposed from the coating material 5 at the positions of the core material 4, specifically, as shown in FIGS. 10 and 11, at the positions of the columnar convex portions 61 and 62 provided on the abdominal side of the core material main body 6 and the plate-like portion 63 provided at the rear end portion of the core material main body 6. When disposed, there is an advantage that it is possible to prevent the formation of conspicuous recess marks on the coating material 5. That is, if an ejector pin is pressed against the surface of the coating material 5 immediately after the coating material 5 is molded with the second hard resin and before the coating material 5 is sufficiently hardened, push marks of the ejector pin will be prominently formed on the coating material 5 made of a transparent material or the like. On the other hand, as shown in the above-described embodiment, when the ejector pins 95 to 97 are respectively disposed at positions corresponding to the columnar convex portions 61 and 62 and the plate-like portion 63 of the primary molded product 11, it is possible to prevent the formation of conspicuous push marks on the outer surface of the coating material 5.

[0046] In the above-described embodiment, the second mold 9 is a mold combined with a first split mold 91 that molds the dorsal half of the coating material 5 and a second split mold 92 that molds the ventral half of the coating material 5. A plurality of ejector pins 94 to 97 are provided on the second split mold 92, and the second hard resin is injected into the molding space 90 of the second mold 9. After separating the first split mold 91, the ejector pins 94 to 97 are projected from the second split mold 92 to take out the molded toothbrush H. For this reason, by pushing out the toothbrush H held in the second split mold 92 by the ejector pins 94 to 97, it can be easily taken out from the second split mold 92.

[0047] Also, as shown in Fig. 5, when gaps 55, 55 are provided between the inner surfaces facing each other of both arm portions 51, 51 provided at the tip side portion of the covering material 5 and the left and right side surfaces of the movable portion 7, that is, the wall surfaces of the through groove 52, it is possible to surely prevent the side surface of the movable portion 7 from interfering with the wall surface of the through groove 52 when the movable portion 7 swings. For this reason, when brushing teeth, there is an advantage that it is possible to prevent the movable portion 7 from rubbing against the wall surface of the through groove 52 and generating an unpleasant abnormal noise, or the smooth swing displacement of the movable portion 7 from being inhibited.

[0048] On the other hand, as shown in Fig. 12, it is necessary to provide concave-shaped protrusions 98, 99 for forming the through groove 52 including the gaps 55, 55 in the tip side portion of the covering material 5 in the second mold 9. When the second hard resin is injected into the molding space 90 of the second mold 9, the movable portion 7 of the primary molded product 11 heated and softened thereby tends to stick to the concave-shaped surfaces of the protrusions 98, 99. Therefore, there is a great merit in applying the present invention in which the tip portion of the ejector pin 96 provided in the second mold 9 is pushed out to the outer surface of the connecting portion 53 provided in the covering material 5 to take out the toothbrush H.

[0049] As shown in Fig. 5, when the movable portion 7 provided on the core material 4 of the toothbrush H has a vertically long shape in which the width V in the front-rear direction from the back to the belly is larger than the width W in the lateral direction in a cross-sectional view, while sufficiently ensuring the rigidity of the movable portion 7 in the vertical direction of Fig. 5, that is, the acting direction of the brushing pressure, by suppressing the width W in the lateral direction, it is possible to prevent the gripability of the toothbrush H from decreasing due to the width dimension of the corresponding through groove 52 becoming excessively large. On the other hand, when the movable portion 7 has a vertically long shape, when the second hard resin is injected into the molding space 90 of the second mold 9, the movable portion 7 of the primary molded product 11 heated as described above tends to stick to the concave-shaped protrusions 98, 99, so the merit of applying the present invention is even greater.

[0050] The cross-sectional shape of the movable part 7 is not limited to the above-described embodiments, and various modifications are possible. For example, it may be formed into an oval shape as shown in FIG. 16, or a substantially rectangular shape as shown in FIG. 17, or an elliptical shape as shown in FIG. 18, or a circular shape (not shown). Further, the cross-sectional shape of the movable part 7 does not necessarily have to be uniform in the longitudinal direction. For example, the tip side of the movable part 7 may be formed into a vertically long elliptical shape, and the base end side of the movable part 7 may be formed into a perfect circular shape, or the cross-sectional shape may be configured to gradually change.

Explanation of Signs

[0051] 1 Head part 2 Neck part 3 Handle part 4 Core material 5 Coating material 6 Core material body 7 Movable part 8 First molding die 9 Second molding die 10 Bristle bundle 11 Primary molded product 51 Arm part 52 Through groove 53 Connecting part 54 Tapered surface 55 Gap 56 Gap 80 Molding space 81 First split die 82 Second split die 83 Injection gate 90 Molding space 91 First split die 92 Second split die 94 - 97 Ejector pin H Toothbrush

Claims

1. A toothbrush comprising a head portion in which tufts are implanted, a neck portion connected to the head portion, and a handle portion serving as a grip, wherein the handle portion has a core material formed by injecting a first hard resin into a first mold and integrally formed with the neck portion, and a coating material formed by setting the core material in a second mold and injecting a second hard resin having a low adhesion property to the first hard resin to cover the core material, the core material has a core body embedded in the coating material, and a movable portion provided on the tip end side thereof and bent and swing-displaced in the back side direction opposite to the protruding direction of the tufts in response to a brushing pressure acting in a direction orthogonal to the tuft-implanting surface of the head portion, a pair of arm portions branched left and right are provided at the tip end side portion of the coating material, and a through groove is formed between the arm portions to penetrate the coating material from the back side to the front side and allow the swing displacement of the movable portion, A method for manufacturing a toothbrush in which a connecting portion for restricting the swing displacement of the movable portion is provided between the front end portions on the front side of the arm portions, When taking out the toothbrush formed from the second mold, a plurality of positions on the ventral side of the outer surface of the coating material or the core material are pushed out by ejector pins for taking out, and a method for manufacturing a toothbrush, characterized in that one of the plurality of positions is the position of the outer surface of the connecting portion.

2. The connecting portion of the toothbrush to be formed has a tapered surface on its outer surface that is closer to the core material toward the tip end side, The method for manufacturing a toothbrush according to Claim 1.

3. The inclination angle of the tapered surface with respect to the axis is 5 degrees or more, The method for manufacturing a toothbrush according to Claim 2.

4. The axial length of the connecting portion is in the range of 1 mm to 7 mm, The method for manufacturing a toothbrush according to Claim 1.

5. When taking out the toothbrush formed from the second mold, the head portion and the neck portion are not pushed out by ejector pins, and only the handle portion is pushed out by the ejector pins for taking out, The method for manufacturing a toothbrush according to Claim 1.

6. Among the plurality of positions, a position other than the outer surface of the connecting portion is set as the position of the core material exposed from the coating material, The method for manufacturing a toothbrush according to Claim 1.

7. The second mold is a mold combined with a first split mold for forming the dorsal half of the coating material and a second split mold for forming the ventral half of the coating material, A plurality of ejector pins are provided in the second split mold, After injecting the second hard resin and separating the first split mold, the ejector pin is projected from the second split mold to take out the molded toothbrush. The method for manufacturing a toothbrush according to claim 1.

8. In the toothbrush to be molded, gaps are respectively provided between the inner surfaces of the left and right arm portions facing each other and the left and right side surfaces of the movable portion. A concave-shaped convex portion for forming a through groove including the gap is provided in the second molding die. The method for manufacturing a toothbrush according to claim 7.

9. In the movable portion of the toothbrush to be molded, the width in the front-rear direction from the back to the belly is larger than the width in the lateral direction in a cross-sectional view. The method for manufacturing a toothbrush according to claim 1.

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