Toothbrush

Abstract

To provide a toothbrush capable of being restrained from becoming unsanitary even when the toothbrush is repeatedly used and capable of effectively preventing the occurrence of an overbrushing state, and a method of manufacturing the same.SOLUTION: A tip-side part 41 with a predetermined length in an axial direction, which is connected to a neck part 3 of a handle part 4, has a handle base material part 42 that is made of a synthetic resin molded integrally with another part, and a handle flexible part 43 that is made of elastomer for coating the handle base material part. A small-diameter neck shaft-like part 32 continuing into the handle base material part 42 is protrusively provided on a base end-side part 31, which is connected to the handle part 4, of the neck part 3. A clearance is formed between the neck part 3 and the handle flexible part 43 around the neck shaft-like part 32.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to 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 give an operation feeling that is gentle on teeth and gums and to easily suppress overbrushing, a head portion provided on the tip side in the long axis direction and having a hair implanting surface, a gripping portion (handle portion) disposed on the rear end side of the head portion, a neck portion disposed between the hair implanting surface and the gripping portion, a hard portion disposed on the rear end side of the hair implanting surface and formed of a hard resin, and a soft portion formed of a soft resin and covering the hard portion are included, and a deformation portion that is deformed by an external force in a first direction orthogonal to the hair implanting surface and in which the hard portion sandwiches and compresses the soft portion in the long axis direction is provided. There is known a toothbrush provided with.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the embodiment of the toothbrush disclosed in Patent Document 1, a hard portion made of a hard resin and a soft portion made of a soft resin that covers the entire hard portion without a gap are included, and a deformation portion in which the hard portion sandwiches and compresses the soft portion in the long axis direction is disposed between the head portion and the gripping portion, and is configured such that the deformation portion deforms in response to an external force in a first direction orthogonal to the hair implanting surface of the tufts of hair. And it is said that it is possible to sufficiently feel the deformation of the deformation part that occurs when the user brushes teeth while gripping the gripping part of the toothbrush, and it is possible to prevent an overbrushing state.

[0005] When the deformation part as described above is provided, when the deformation part deforms according to the external force acting during toothbrushing, it is considered that the user can perceive that the toothbrush is in an overbrushing state according to this deformation. However, there is a concern that the hard part and the soft part constituting the deformation part may peel off according to the difference in rigidity between the two. In particular, on the tip side near the neck part of the deformation part, when the deformation part bends, the amount of bending increases, and at the interface between the axial front end surface of the soft part formed of the soft resin of the deformation part and the axial base end surface of the hard part which is the neck part, peeling is likely to occur due to the repeated loading of tensile stress during brushing. When such peeling occurs, the slurry during toothbrushing enters, but it is not easy to completely remove it, so there is a high possibility that germs will multiply and it is feared that it will become unhygienic.

[0006] Therefore, in view of the above situation, the problem to be solved by the present invention is to provide a toothbrush and a method for manufacturing the same that can suppress the toothbrush from becoming unhygienic even after repeated use and can effectively prevent the occurrence of an overbrushing state.

Means for Solving the Problems

[0007] As a result of intensive studies in view of such a situation, the present inventor made the tip side portion of the handle portion have a handle base material portion made of a synthetic resin integrally formed with other portions and a handle soft portion covering the handle base material portion, and made a small-diameter neck shaft portion continuous with the handle base material portion project from the base end side portion of the neck portion, and formed a gap between the handle soft portion around the neck shaft portion and the neck portion. By doing so, it was found that even when the toothbrush is repeatedly used, the occurrence of an overbrushing state can be effectively prevented, peeling on the tip side between the handle base material portion and the handle soft portion is suppressed, cleaning of the gap is easy, and the toothbrush can be prevented from becoming unhygienic. Further, when the handle base portion of the toothbrush has a pair of left and right support pieces in the width direction, by providing the filling gate of the secondary mold for forming the handle soft portion to open in the front-rear direction orthogonal to the width direction of the handle base portion in the space for forming the handle soft portion, it is possible to prevent deformation of the support pieces and the like, and it has been found that a toothbrush capable of uniformly suppressing deformation in the width direction can be easily and inexpensively provided. Based on the above findings, the inventor has completed the present invention.

[0008] That is, the present invention includes the following inventions. (1) A toothbrush comprising a head portion in which a tuft is implanted, a neck portion connected to the head portion, and a handle portion connected to the neck portion, wherein a tip-side portion having a predetermined axial length connected to the neck portion of the handle portion is made of a synthetic resin integrally molded with other portions, a handle base portion, and a handle soft portion made of an elastomer covering the handle base portion, and a thin-diameter neck shaft portion continuous with the handle base portion projects from a base-end side portion of the neck portion connected to the handle portion, and a gap is formed between the handle soft portion around the neck shaft portion and the neck portion.

[0009] (2) The toothbrush according to (1), wherein the handle base portion has a handle shaft portion extending axially at the center of the handle portion and continuous with the neck shaft portion of the neck portion, and a pair of left and right support pieces extending in a cantilever shape substantially parallel to the handle shaft portion along the left and right side edges in the width direction of the tip-side portion, and the handle soft portion is filled between the handle shaft portion and each support piece.

[0010] (3) The toothbrush according to (2), wherein at least left and right side portions in the width direction in a tip region continuous with the neck shaft portion of the handle shaft portion, or at least left and right inner surface portions in the width direction facing the tip region of the handle shaft portion in the tip regions of the left and right support pieces in the width direction are provided with bulging portions that partially reduce the distance between them.

[0011] (4) The at least left and right side portions in the width direction in the tip region continuous with the neck shaft portion of the handle shaft portion, and at least the left and right inner surface portions in the width direction facing the tip region of the handle shaft portion or the left and right side edges in the width direction of the handle shaft portion in the tip regions of the left and right support pieces in the width direction, wherein the shortest distance in the width direction therebetween is 3.5 mm or less. The toothbrush according to claim 2 or 3.

[0012] (5) A toothbrush comprising a head portion in which tufts are implanted, a neck portion connected to the head portion, and a handle portion connected to the neck portion, wherein a tip-side portion having a predetermined axial length connected to the neck portion of the handle portion is composed of a handle base material portion made of a synthetic resin integrally formed with other portions, and a handle soft portion made of an elastomer covering the handle base material portion, and a thin-diameter neck shaft portion continuous with the handle base material portion protrudes from a base-end side portion of the neck portion connected to the handle portion, and a gap is formed between the handle soft portion around the neck shaft portion and the neck portion, the handle base material portion extends in the axial direction through the center portion of the handle portion, and has a handle shaft portion continuous with the neck shaft portion of the neck portion, and a pair of left and right support pieces extending in a cantilever shape substantially parallel to the handle shaft portion along the left and right side edges in the width direction of the tip-side portion, and a method for manufacturing a toothbrush in which the handle soft portion is filled between the handle shaft portion and each support piece, wherein a filling gate of a secondary mold for forming the handle soft portion is opened in a space for forming the handle soft portion so as to be in a front-rear direction perpendicular to the width direction of the handle base material portion inserted into the secondary mold, and the elastomer is injected from the filling gate to mold the handle soft portion. [Advantages of the Invention]

[0013] The toothbrush according to the present invention thus configured can effectively prevent the occurrence of overbrushing even when the toothbrush is repeatedly used, suppress peeling between the handle base material portion and the handle soft portion, facilitate cleaning of the gap, and suppress the toothbrush from becoming unhygienic.

[0014] That is, the distal end side portion of the handle portion is provided with a handle base portion made of a synthetic resin integrally formed with other portions and a handle soft portion covering the handle base portion, and a small-diameter neck shaft portion continuous with the handle base portion is provided protruding from the proximal end side portion of the neck portion, so that it is possible to effectively prevent the occurrence of an overbrushing state even when the toothbrush is repeatedly used. Further, since a gap is formed in advance between the handle soft portion around the small-diameter neck shaft portion protruding from the proximal end side portion of the neck portion and continuous with the handle base portion and the neck portion, the gap is easy to clean, and since the handle base portion and the handle soft portion are joined in the axial direction in the portion close to the gap, the followability with respect to bending is good, so that peeling between the joint surfaces of the two is suppressed. As a result, even if the slurry enters the gap, it does not enter the joint portion between the handle base portion and the handle soft portion, so that it is possible to suppress the toothbrush from becoming unhygienic by washing the slurry away from the gap.

[0015] Further, in the deformed portion where the hard portion having the structure as in the embodiment described in Patent Document 1 sandwiches and compresses the soft portion in the long axis direction, the deformed portion deforms in response to an external force in the first direction (front-rear direction) orthogonal to the tuft implantation surface of the bristle tufts, but it is also likely to deform in the width direction (left-right direction) in the plane direction parallel to the implantation surface orthogonal to the axial direction of the toothbrush during normal use. This is also a factor that peeling is likely to occur at the interface between the axially distal end surface of the soft portion and the axially proximal end surface of the hard portion during brushing. Further, when deformed in the width direction in this way, it may be difficult to brush the teeth, and the cleanability and the feeling of use may be deteriorated.

[0016] In contrast, the tip-side portion of the handle part has a handle base part made of synthetic resin integrally formed with other parts, and a handle soft part covering the handle base part. A neck shaft-shaped part with a small diameter continuous with the handle base part protrudes from the base-end side portion of the neck part. In addition to forming a gap between the handle soft part around the neck shaft-shaped part and the neck part, the handle base part has a handle shaft-shaped part extending in the axial direction at the center part of the handle part and continuous with the neck shaft-shaped part of the neck part, and a pair of left and right support pieces extending in a cantilever shape substantially parallel to the handle shaft-shaped part along the left and right side edges in the width direction of the tip-side portion. By filling the space between the handle shaft-shaped part and each support piece with the handle soft part, the occurrence of overbrushing can be effectively prevented, the peeling between the handle base part and the handle soft part can be further suppressed, the cleaning of the gap is easy, and the toothbrush can be prevented from becoming unhygienic. Furthermore, since the deformation in the width direction can be suppressed, the difficulty of brushing teeth and the deterioration of cleanability and usability can be suppressed.

[0017] Also, when bulging parts that partially reduce the distance between them are provided at least on the left and right side parts in the width direction in the tip region of the handle shaft-shaped part continuous with the neck shaft-shaped part, or at least on the left and right inner surfaces in the width direction facing the tip region of the handle shaft-shaped part in the tip regions of the left and right support pieces in the width direction, the deformation in the width direction can be more effectively suppressed. Also, when the shortest distance in the width direction between at least the left and right side parts in the width direction in the tip region of the handle shaft-shaped part continuous with the neck shaft-shaped part and at least the left and right inner surfaces in the width direction facing the tip region of the handle shaft-shaped part in the tip regions of the left and right support pieces in the width direction or the left and right side edges in the width direction of the handle soft part is 3.5 mm or less, the deformation in the width direction can be further effectively suppressed.

[0018] Moreover, in the manufacturing method of the toothbrush according to the present invention thus configured, when the toothbrush has a pair of left and right support pieces in the width direction in its handle base part, it is possible to easily and inexpensively manufacture a toothbrush capable of preventing the deformation of the support pieces and uniformly suppressing the deformation in the width direction.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Embodiments for Carrying Out the Invention

[0020] Hereinafter, a toothbrush according to an embodiment of the present invention will be described with reference to the accompanying drawings. As shown in FIGS. 1 and 2, a toothbrush 1 according to an embodiment of the present invention includes a head portion 2 in which tufts 20 are implanted, a neck portion 3 connected to the head portion 2, and a handle portion 4 connected to the neck portion 3. A distal end side portion 41 having a predetermined axial length connected to the neck portion 3 of the handle portion 4 has a handle base portion 42 made of a synthetic resin integrally formed with other portions, and a handle soft portion 43 made of an elastomer covering the handle base portion 42. A neck shaft-like portion 32 having a small diameter continuous with the handle base portion 42 protrudes from a proximal end side portion 31 of the neck portion 3 connected to the handle portion 4. A gap S is formed between the handle soft portion 43 around the neck shaft-like portion 32 and the neck portion 3. In the present embodiment, as shown in FIG. 3, the toothbrush 1 is composed of a primary molded product 11 made of a synthetic resin in which the head portion 2, the neck portion 3 connected to the head portion 2, and the handle portion 4 connected to the neck portion 3 are integrally formed, and a handle soft portion 43 made of an elastomer.

[0021] In the present embodiment, the gap S has an annular space surrounding the rod-shaped neck shaft-like portion 32 extending in the axial direction between the base end surface 33 of the proximal end side portion 31 of the neck portion 3 and the tip end surface 41a formed by the handle soft portion 43 of the distal end side portion 41 of the handle portion 4. Therefore, even if slurry or the like during toothbrushing enters the gap S, water for cleaning can easily pass through from the outside, and the slurry can be easily removed by the cleaning water.

[0022] The neck portion 3 provided on the tip side of the gap S has a frustum of a cone shape that flares from the tip side toward the base side. This has the effect of making it difficult for toothpaste or saliva to slide down into the gap S during use. Further, the tip-side portion 41 of the handle portion 4 provided on the base side of the gap S has a frustum of a cone shape where the width and the size in the front-rear direction gradually increase from the tip toward the base side, and a portion that is continuous with the said portion and has an inverted frustum of a cone shape where the width and the size in the front-rear direction gradually decrease from the tip side toward the base side. And, the outer peripheral surface of the base-side portion 31 of the neck portion 3 and the outer peripheral surface of the frustum of a cone-shaped portion of the tip-side portion 41 of the handle portion 4 form a smoothly continuous outer peripheral surface with the gap S therebetween, having few catches during use and ensuring a good aesthetic appearance.

[0023] The base end surface 33 of the base-side portion 31 of the neck portion 3 that forms the gap S may have an annular surface perpendicular to the axial direction, or may have an annular surface having a convex or concave inclined surface toward the neck shaft portion 32 protruding from the base end surface 33, or may be an annular concave surface or convex surface curved toward the tip side or the base side in the axial direction. Also, similarly, the tip end surface 41a of the tip-side portion 41 of the handle portion 4 that forms the gap S may have an annular surface having a convex or concave inclined surface toward the neck shaft portion 32, or may be an annular concave surface or convex surface curved toward the tip side or the base side in the axial direction. The axial length of the gap S can be appropriately set in consideration of the degree of deflection in the front-rear direction and the width direction orthogonal to the hair implanting surface of the hair bundle 20 and the like.

[0024] The neck shaft portion 32 is continuous from the base-side portion 31 of the neck portion 3, extends from its base end surface 33 toward the base side, and has a thin rod-like shape with a smaller thickness than the base-side portion 31 of the neck portion 3 and the handle portion 4. The shape of the cross section in the width direction of the neck shaft portion 32 can be appropriately determined in consideration of the degree of suppression of overbrushing and the suppression of bending in the width direction. In the present embodiment, it has a cross-sectional shape such as an oval shape or a bow shape where the front-rear direction is larger than the width direction. Here, "thin diameter" means that the thickness of the neck shaft portion 32 is relatively smaller than other portions, and is not intended to be limited to a circular cross section.

[0025] As shown in FIGS. 2 and 3, the neck shaft portion 32 is continuous with the handle base material portion 42 of the tip side portion 41 of the handle portion 4 on the proximal end side. In the present embodiment, the handle base material portion 42 of the tip side portion 41 has a handle shaft portion 44 extending in the axial direction at the center of the handle portion 4, and the proximal end and the distal end of the handle shaft portion 44 are smoothly continuous with the proximal end of the neck shaft portion 32, and the two together form a shaft portion with a small diameter. That is, the neck portion 3 and the handle portion 4 are integrally formed via the neck shaft portion 32 and the handle shaft portion 44. In this way, the shaft portions (32, 44) with a small diameter continuously connect the neck portion 3 and the handle portion 4 integrally, so that when a load is applied in the front-rear direction during brushing, it can be elastically deformed and bent appropriately at this portion without breaking, and the brushing pressure can be reduced. And the handle shaft portion 44 is covered with a handle soft portion 43 made of an elastomer, and by reinforcing the outer peripheral portion of the handle shaft portion 44 with the handle soft portion 43, the thickness of the handle shaft portion 44 is reduced and the entire tip side portion 41 of the handle portion 4 is deflected, so that the displacement angle in the front-rear direction of the head portion 2 during brushing can be reduced, and it is possible to suppress a decrease in cleaning performance and usability. This point will be described in detail as follows.

[0026] If an attempt is made to control the brushing pressure only by the handle shaft-like portion 44 and the neck shaft-like portion 32 without reinforcement by the handle soft portion 43, it becomes necessary to increase its thickness in relation to the strength, the degree of bending at the shaft-like portions (32, 44) is small, and as a result, there is a tendency to bend with the vicinity of the proximal end side portion of the neck portion 3 as a fulcrum. As a result, the bending radius during brushing is small, the inclination of the head portion 2 in the front-rear direction becomes large, it becomes difficult for the entire tuft 20 to come into contact with the tooth row uniformly, the cleaning performance deteriorates, and the usability also deteriorates. However, by covering and reinforcing with the handle soft portion 43, it becomes possible to make the shaft-like portions (32, 44) have a small diameter without increasing their thickness. Therefore, the distal end side portion 41 of the handle portion 4 can be bent as a whole. As a result, the bending radius becomes large, the inclination of the head portion 2 in the front-rear direction during brushing can be reduced, it becomes easier for the entire tuft 20 to come into contact with the tooth row in the axial direction, and the deterioration of the cleaning performance and usability can be suppressed.

[0027] The thicknesses of the handle shaft-like portion 44 and the neck shaft-like portion 32 can be appropriately determined in consideration of the degree of suppressing the brushing pressure and the like. Regarding the axial thickness of the handle shaft-like portion 44, it is preferable that a thicker portion is formed in the distal end side portion than in the proximal end side portion. Thereby, while making the fulcrum of bending the proximal end side, the entire distal end side portion 41 of the handle portion 4 can be bent, making it easier to bend, and thereby making it easier to control the brushing pressure. In addition, the inclination of the head portion 2 in the front-rear direction during brushing can be reduced, and the deterioration of the cleaning performance and usability can be suppressed.

[0028] In the present embodiment, as shown in FIGS. 2 to 5, the handle base portion 42 of the distal end side portion 41 of the handle portion 4 further has a pair of left and right support pieces 45 in the width direction. The pair of support pieces 45 are provided to extend in a cantilevered manner substantially parallel to the handle shaft-like portion 44 along the left and right side edges in the width direction of the distal end side portion 41. And a handle soft portion 43 is filled between the handle shaft-like portion 44 and each support piece 45. By extending the pair of left and right support pieces 45 in the width direction substantially parallel to the handle shaft-like portion 44 in this way, the load on the handle shaft-like portion 44 of the handle portion 4 with respect to the stress in the front-rear direction orthogonal to the width direction during brushing is dispersed, and the stress is concentrated on the handle soft portion 43 made of an elastomer close to the handle shaft-like portion 44. By suppressing this, it becomes possible to more effectively suppress the peeling at the tip portions of the handle shaft-like portion 44 and the handle soft portion 43. Furthermore, since the deformation in the width direction during brushing can also be suppressed, the concentration of stress on the handle soft portion 43 close to the handle shaft-like portion 44 can be further suppressed. Therefore, the deterioration of hygiene due to peeling is further suppressed, and the deterioration of cleanability and usability due to the deformation in the width direction during brushing is further suppressed.

[0029] It is preferable that the structure of the pair of support pieces 45 has a structure that is symmetric in the width direction from the viewpoint of suppressing deformation in the width direction evenly on both the left and right sides. In the present embodiment, as shown in FIGS. 2 to 4, the support piece 45 protrudes from the handle main body 46 on the base end side rather than the tip end side portion 41 of the handle portion 4 toward the tip end side, and the outer peripheral side is not covered by the handle soft portion 43, and has a base end portion 45b and a tip end portion 45a having a portion that extends from the base end portion 45b toward the tip end side and whose outer peripheral side is covered by the handle soft portion 43. The outer shape of the outer side in the width direction of the tip end portion 45a of the support piece 45 has a shape corresponding to the shape of the outer peripheral surface of the tip end side portion 41, and the outer shape of the side facing the handle shaft-like portion 44 of the tip end portion 45a has a plane parallel to the axial direction. In the present embodiment, the tip end portion 45a becomes wider in each direction from the base end side toward the tip end side in the width direction and the front-rear direction, and then becomes smaller from the base end side toward the tip end side. In this way, by adjusting the shape of the tip end portion 45a of the support piece 45 by adjusting the sizes in the front-rear direction and the width direction in the axial direction, the degree of deformation of the handle soft portion 43 can be adjusted, and the control of the brushing pressure, the suppression of deformation in the width direction, and the suppression of peeling of the handle soft portion 43 can be performed more effectively. In the present embodiment, it has a substantially plate-like structure that extends along the axial direction with a smaller size in the width direction than in the front-rear direction, increases the contact area with the handle soft portion 43 in the width direction, and improves the reinforcing effect against deformation in the width direction, but it is not limited to such a shape.

[0030] In the present embodiment, a protrusion 47 is formed on the outer peripheral surface of the tip end side of the tip end portion 45a. The outer peripheral surface of this protrusion 47 is a portion not covered by the handle soft portion 43 and forms the outer peripheral surface of the tip end side portion 41. By providing such a protrusion 47, the outer peripheral surface of the protrusion 47 is brought into contact with the inner wall of the secondary mold to support the support piece 45 from the outside in the width direction, so that it is possible to prevent the support piece 45 from deforming or being displaced due to the molding pressure when injecting the elastomer. Further, the entire tip end side of the tip end portion 45a is covered by the handle soft portion 43.

[0031] In an embodiment of the present invention, a pair of bulging portions 48 are provided on the left and right side portions in the width direction of the tip-side region continuous with the neck shaft portion 32 of the handle shaft portion 44. By providing the bulging portions 48, the interval a of the gap formed between the outer surface of the bulging portion 48 and the inner surface on the handle shaft portion 44 side of the support piece 45 can be partially reduced. The size of this interval a is the shortest distance in the width direction between the left and right side portions in the width direction of the tip region continuous with the neck shaft portion 32 of the handle shaft portion 44 and the left and right inner surface portions in the width direction facing the tip region of the handle shaft portion 44 in the tip regions of the support pieces 45 on the left and right in the width direction. And, in this way, by reducing the interval a in the width direction between the support piece 45 and the handle shaft portion 44 (that is, the shortest distance which is its size) in the tip-side region of the neck shaft portion 32, the thickness in the width direction of the handle soft portion 43 made of an elastomer filled in the portion where the bulging portion 48 is provided in the said region becomes small. During brushing, since the base end of the handle shaft portion 44 is used as a fulcrum and it bends in the width direction, the degree of bending deformation (displacement angle) becomes the largest in the tip-side region. In the portion where the displacement angle becomes large in this way, the elastomer also deforms relatively largely, but by providing the bulging portion 48 and reducing the thickness of the elastomer, its deformation can be suppressed. In this way, by providing the bulging portion 48 in the width direction in the tip-side region, the deformation in the width direction can be more suppressed. On the other hand, since the support piece 45 does not exist in the front-rear direction, there is no influence on the bending in the front-rear direction, and the bulging portion 48 has substantially no influence on the control of the brushing pressure.

[0032] The interval a of the gap can be determined in consideration of the shapes, structures of the handle shaft portion 44 and the pair of support pieces 45, the type of the elastomer of the handle soft portion 43, etc. From the viewpoint of controlling the brushing pressure well and suppressing the deformation in the width direction well, it is preferably 3.5 mm or less, and more preferably less than 2.0 mm. Further, the bulging portion 48 preferably has a structure capable of continuously forming a predetermined interval a in the axial direction.

[0033] In the embodiment shown in FIGS. 1 to 4, the bulge portion 48 is provided at the left and right side portions in the width direction of the handle shaft portion 44, thereby reducing the interval a between the handle shaft portion 44 and the support piece 45. However, as in the modification shown in FIG. 6, the bulge portion 48 may be provided on the entire outer periphery of the tip end side region of the handle shaft portion 44 and the neck shaft portion 32 continuous from the region. Alternatively, as in the modification shown in FIG. 7, the bulge portion 48 may be provided on the left and right inner surface portions in the width direction facing at least the tip end region of the handle shaft portion in the tip end regions of the pair of support pieces 45, thereby reducing the interval a. In the modifications shown in FIGS. 6 and 7, different from the embodiment shown in FIGS. 1 to 4, the protrusion 47 is not provided on the outer peripheral surface on the tip end side of the tip end portion 45a of the support piece 45. Further, the tip end of the tip end portion 45a is not covered with the handle soft portion 43, and the tip end surface 41a of the tip end side portion 41 is formed. That is, in the case of the modifications shown in FIGS. 6 and 7, in the secondary mold, by bringing the tip end of the tip end portion 45a into contact with the inner wall of the secondary mold and supporting the support piece 45 from the tip end side in the axial direction, it is possible to prevent the support piece 45 from being deformed or displaced due to the molding pressure when injecting the elastomer.

[0034] Further, in the modification shown in FIG. 8, the tip end portion 45a of the support piece 45 in the embodiment shown in FIGS. 1 to 4 does not exist, and it is constituted only by the base end portion 45b. In this case, in the tip end region where the handle shaft portion 44 is continuous with the neck shaft portion 32, since the support piece 45 does not exist, referring to the shortest distance in the width direction (reference numeral a in the figure) between the left and right side edges in the width direction of the handle soft portion 43 and the left and right side portions in the width direction of the handle shaft portion 44, it is advisable to adjust the thickness in the width direction of the handle soft portion 43.

[0035] In addition, the modified example shown in FIG. 9 does not have the bulging portion 48 in the embodiments shown in FIGS. 1 to 4, FIG. 6, and FIG. 7. In this case, in the tip region continuous with the neck shaft portion 32 of the handle shaft portion 44, although the support piece 45 exists, since the bulging portion 48 does not exist, the left and right side portions in the width direction of the handle shaft portion 44 in the tip region, and the left and right inner surface portions in the width direction facing the tip region of the handle shaft portion 44 in the tip regions of the left and right support pieces 45 in the width direction, refer to the shortest distance in the width direction (reference sign a in the figure), and the thickness in the width direction of the handle soft portion 43 may be adjusted.

[0036] The synthetic resin constituting the primary molded product 11 in which the head portion 2, the neck portion 3 connected to the head portion 2, and the handle portion 4 connected to the neck portion 3 are integrally molded can be one generally used in the technical field. For example, crystalline resins such as polyacetal resin (POM), polyamide resin (PA), polybutylene terephthalate (PBT), polypropylene resin (PP), etc., non-crystalline resins such as acrylonitrile-butadiene-styrene resin (ABS), polycarbonate (PC), polymethyl methacrylate resin (PMMA), etc. can be mentioned. Among these, from the viewpoint of strength, crystalline resins are preferable, and POM and PBT are more preferable. Also, for the elastomer constituting the handle soft portion 43, one generally used in the technical field can be used. From the viewpoint of deforming during brushing and simultaneously reinforcing the handle shaft portion 44, it is preferably 40 to 90 in Shore A hardness. Examples of such an elastomer include thermoplastic elastomers (TPE) such as polystyrene-based (SBC), polyolefin-based (TPO), polyvinyl chloride-based (TPVC), polyurethane-based (PU), polyester-based (TPEE), polyamide-based (TPAE), and silicone. Incidentally, although the primary molded product 11 is integrally molded with a synthetic resin as described above, for example, a portion coated with an elastomer may be formed on the surface of a portion on the base end side rather than the base end of the tip side portion 41 of the handle portion 4.

[0037] Next, a method for manufacturing a toothbrush according to an embodiment of the present invention will be described with reference to the accompanying drawings. First, a method for manufacturing a toothbrush according to a representative embodiment shown in FIGS. 1 to 4 will be described. First, with the primary mold for molding the primary molded product 11 in which the head portion 2, the neck portion 3, and the handle portion 4 of the toothbrush are integrally connected, for example, a synthetic resin as described above is filled into the primary mold in a state where the primary mold is clamped, and the primary molded product 11 is molded. The primary mold can adopt an efficient upper and lower split structure mold.

[0038] Next, after the primary mold is opened, with the secondary mold for molding the secondary molded product composed of the handle soft portion 43 in a state where the secondary mold is clamped, an elastomer is injected into the secondary mold to mold the secondary molded product. The secondary mold can also use an efficient upper and lower split structure mold. Hereinafter, a state in which the primary molded product 11 is attached to the secondary mold and the secondary mold is clamped will be described with reference to the drawings.

[0039] As shown in FIG. 14, the primary molded product 11 is attached to the secondary mold 5 so that the handle base portion 42 of the primary molded product 11 is located within the cavity 51 of the secondary mold 5. The primary molded product 11 is held and fixed between the upper mold 5a and the lower mold 5b of the secondary mold 5 that are vertically split in the front-rear direction orthogonal to the width direction of the handle base portion 42. In the present embodiment, an annular convex portion 53 that forms a gap between the portion that becomes the handle soft portion 43 around the neck shaft portion 32 and the neck portion 3 and seals the injected elastomer is provided on the upper mold 5a and the lower mold 5b. By this convex portion 53, at least the neck shaft portion 32 is supported and fixed, and the neck portion 3 side of the primary molded product 11 is supported. Further, the base end side of the primary molded product 11 is supported at a portion including the base end portion 45b of the support piece 45 of the handle base portion 42. Further, although not shown in the figure, the outer surface of the protrusion 47 formed on the outer peripheral surface of the tip end side of the tip end portion 45a of the pair of support pieces 45 abuts against the inner wall surface of the secondary mold 5, and each support piece 45 is supported by the wall surface in the width direction.

[0040] The filling gate 52 of the elastomer is provided to open into a space (cavity 51) that forms the handle soft portion 43 of the lower mold 5b of the secondary mold 5 so as to be in the front-rear direction orthogonal to the width direction of the handle base portion 42 (toothbrush 1).

[0041] As described above, with the primary molded product 11 mounted on the secondary mold 5 and the secondary mold 5 clamped, a desired elastomer is filled from the filling gate 52 using a molding machine to mold the handle soft portion 43. The elastomer injected from the filling gate 52 flows in the front-rear direction of the handle base portion 42 and further easily flows into the space between the handle shaft portion 44 and the pair of support pieces 45. Therefore, by reducing the stress load on the support piece 45 due to the flow of the elastomer, displacement and deformation can be prevented. Further, in the present embodiment, since the protruding portions 47 of the pair of support pieces 45 are in contact with the inner wall surface of the secondary mold 5 and are supported by the wall surface, displacement and deformation can be more effectively prevented.

[0042] The molding conditions can be appropriately determined according to the characteristics of the elastomer and the like.

[0043] By demolding after cooling, a secondary molded product (toothbrush 1) having a handle soft portion 43 formed so as to cover a predetermined range of the handle base portion 42 is obtained.

[0044] In this way, a toothbrush including a head portion 2 in which the tuft 20 is implanted, a neck portion 3 connected to the head portion 2, and a handle portion 4 connected to the neck portion 3, having a handle base portion 42 made of a synthetic resin in which the tip-side portion 41 of the handle portion 4 is integrally molded with other portions, and a handle soft portion 43 made of an elastomer covering the handle base portion 42, with a gap formed between the handle soft portion 43 around the neck shaft portion 32 protruding from the base end of the neck portion 3 and the neck portion 3, and a pair of left and right support pieces 45 extending along the left and right side edges in the width direction of the tip-side portion 41 substantially parallel to the handle shaft portion 44 continuous with the neck shaft portion 32, and the handle soft portion 43 filled between the handle shaft portion 44 can be easily and inexpensively manufactured by two-color molding.

[0045] By using a toothbrush as described above, it is possible to effectively prevent the occurrence of overbrushing. Also, it is possible to suppress the toothbrush from becoming unhygienic even with repeated use. Furthermore, since the handle base portion 42 has a pair of support pieces 45, these effects can be further improved.

[0046] As described above, the embodiments of the present invention have been explained. However, the present invention is not limited to such examples, and it goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention.

Example

[0047] Hereinafter, for the purpose of confirming the influence on the deformation in the width direction due to the difference in the magnitude of the shortest distance (a value) in the width direction between at least the left and right side portions in the width direction in the tip region continuous with the neck shaft portion 32 of the handle shaft portion 44 and the left and right inner surface portions in the width direction facing the tip region of the handle shaft portion 44 in the tip regions of the support pieces 45 on the left and right in the width direction or the left and right side edges in the width direction of the handle shaft portion 44, the following test samples were produced and evaluated. The test samples were based on the basic structure of the toothbrush 1 of the embodiment shown in FIGS. 1 and 2, and the structure of the handle base portion 42 was changed to each structure shown in FIGS. 8 to 13, and the structure of the handle soft portion 43 was also changed accordingly, but otherwise had the same structure as the basic structure.

[0048] (Example 1) After molding a primary molded product 11 having the structure shown in FIGS. 3, 4, and 7 using a synthetic resin (PBT), a toothbrush a which is a secondary molded product having the structure shown in FIGS. 1 and 2 and having a handle soft portion 43 made of an elastomer (PEE (polyester type)) was produced using the secondary mold shown in FIG. 14. The structure of the handle base portion 42 of the toothbrush a is as shown in FIG. 5. The thickness in the width direction of the handle shaft portion 44 is 3.0 mm, and the shortest distance (the distance indicated by the symbol a in FIG. 5) is the shortest distance (0.8 mm) in the width direction between the left and right side portions in the axial direction of the bulging portion 48 and the left and right inner surface portions in the axial direction of the support piece 45.

[0049] (Example 2) As shown in Fig. 8 for the structure of the handle base portion 42, a toothbrush b was produced in the same manner as in Example 1, except that the tip portions 45a of the pair of support pieces 45 were eliminated from the structure shown in Fig. 5, and only the base end portions 45b were retained. The shortest distance in the toothbrush b (the distance indicated by reference sign a in Fig. 8) is the shortest distance in the width direction (3.1 mm) between the left and right side portions in the width direction of the bulging portion 48 and the left and right side edges in the width direction of the handle soft portion 43.

[0050] (Example 3) As shown in Fig. 9 for the structure of the handle base portion 42, in the structure shown in Fig. 5, (i) the bulging portion 48 of the handle shaft portion 44 was eliminated, and the left and right sides in the width direction were each uniformly narrowed by 0.6 mm along the axial direction so that the width direction thickness was 1.8 mm, and (ii) the protruding portions 47 provided on the outer peripheral surfaces of the tip end sides of the tip portions 45a of the pair of support pieces 45 were eliminated, and the tip ends of the support pieces 45 were made capable of forming the tip end surface 41a of the tip end side portion 41, and a toothbrush c was produced in the same manner as in Example 1, except that the axial length of the support pieces 45 was increased. The shortest distance in the toothbrush c (the distance indicated by reference sign a in Fig. 9) is the shortest distance in the width direction (2.0 mm) between the tip end of the handle shaft portion 44 and the left and right inner surface portions in the axial direction of the tip ends of the support pieces 45.

[0051] (Example 4) As shown in Fig. 10 for the structure of the handle base portion 42, in the structure shown in Fig. 5, (i) the bulging portion 48 was eliminated, and the left and right inner surface portions in the axial direction of the pair of support pieces 45 were each uniformly cut by 0.5 mm along the axial direction to reduce the thickness in the width direction, and (ii) the protruding portions 47 provided on the outer peripheral surfaces of the tip end sides of the tip portions 45a of the pair of support pieces 45 were eliminated, and the tip ends of the support pieces 45 were made capable of forming the tip end surface 41a of the tip end side portion 41, and a toothbrush d was produced in the same manner as in Example 1, except that the axial length of the support pieces 45 was increased. The shortest distance in the toothbrush d (the distance indicated by reference sign a in Fig. 10) is the shortest distance in the width direction (1.9 mm) between the left and right side portions in the width direction of the tip end of the handle shaft portion 44 and the left and right inner surface portions in the axial direction of the tip ends of the support pieces 45.

[0052] (Example 5) As shown in Fig. 11 for the structure of the handle base part 42, in the structure shown in Fig. 5, (i) the bulging part 48 of the handle shaft-like part 44 is eliminated, and both the left and right sides in the width direction are uniformly thinned by 0.3 mm along the axial direction, and the width direction thickness is made 2.4 mm, (ii) the protruding part 47 provided on the outer peripheral surface on the tip side of the tip parts 45a of the pair of support pieces 45 is eliminated so that the tips of the support pieces 45 can form the tip surface 41a of the tip side part 41, and a toothbrush e was produced in the same manner as in Example 1 except that the axial length of the support piece 45 was increased. The shortest distance (the distance indicated by reference sign a in Fig. 11) in the toothbrush e is the shortest distance (1.7 mm) in the width direction between the left and right side parts in the width direction at the tip of the handle shaft-like part 44 and the left and right inner surface parts in the axial direction at the tip of the support piece 45.

[0053] (Example 6) As shown in Fig. 12 for the structure of the handle base part 42, in the structure shown in Fig. 5, (i) both the left and right inner surface parts in the width direction of the pair of support pieces 45 are uniformly cut by 0.5 mm along the axial direction to reduce the thickness in the width direction, (ii) the protruding part 47 provided on the outer peripheral surface on the tip side of the tip parts 45a of the pair of support pieces 45 is eliminated so that the tips of the support pieces 45 can form the tip surface 41a of the tip side part 41, and a toothbrush f was produced in the same manner as in Example 1 except that the axial length of the support piece 45 was increased. The shortest distance (the distance indicated by reference sign a in Fig. 12) in the toothbrush f is the shortest distance (1.3 mm) in the width direction between the left and right side parts in the width direction of the bulging part 48 of the handle shaft-like part 44 and the left and right inner surface parts in the axial direction at the tip of the support piece 45.

[0054] (Example 7) As shown in Fig. 13 for the structure of the handle base part 42, in the structure shown in Fig. 5, a toothbrush g was produced in the same manner as in Example 1 except that the left and right side parts in the width direction of the pair of bulging parts 48 of the handle shaft-like part 44 were uniformly cut by 0.3 mm along the axial direction to reduce the length in the width direction of the bulging part 48. The shortest distance (the distance indicated by reference sign a in Fig. 13) in the toothbrush g is the shortest distance (1.1 mm) in the width direction between the left and right side parts in the axial direction of the bulging part 48 and the left and right inner surface parts in the axial direction of the support piece 45.

[0055] (Evaluation) <Bending test> Regarding the toothbrushes a to f manufactured in Examples 1 to 7, the head was made horizontal so that the width direction became the load direction, and the position of the handle portion 4 at a horizontal distance of 110 mm from the center of the tufted portion toward the proximal end side was fixed, and it was supported in a cantilever state. A 200 g weight corresponding to the recommended brushing pressure was hung at the position of the center of the tufted portion of the head portion 2 and held for 10 seconds, and the amount of deflection (displacement) of the head portion 2 before and after hanging the weight was measured. The results are shown in Table 1.

[0056] <Friction force test> For the friction force test, a jig simulating the upper right molar as shown in FIGS. 15 and 16 was prepared. Regarding the toothbrushes a to f manufactured in Examples 1 to 7, as shown in FIG. 16, they were supported on a fixed table having a toothbrushing pressure detector, and fixed to the above jig of a tactile sensation measuring device (Tribogear TYPE33 manufactured by Shinto Kagaku Co., Ltd.) with a built-in three-axis force sensor. With the hairs being applied vertically (in the Z direction), after setting the pushing-in amount so that the Z load becomes the maximum value of 100 gf, it was slid in the X direction in the figure from the molar to the premolar, and the load in the Y direction (width direction) during the sliding was measured by the three-axis force sensors of the above tactile sensation measuring device. The results are shown in Table 1.

[0057]

Table 1

[0058] As shown in Table 1, when the a value is 3.5 mm or less, the deflection in the width direction during brushing is suppressed to 17.5 mm or less, and the friction force in the width direction is reduced to 11.49 gf or less. It can be seen that while suppressing the brushing pressure, the brushing pressure is appropriately transmitted in the axial direction (X direction). Further, in the case of the toothbrushes of Examples 1 and 4 to 7 where the a value is less than 2.0 mm, the deflection in the width direction and the friction force are further reduced. By adjusting the a value, it is possible to reduce the brushing pressure favorably and at the same time suppress the deformation in the width direction and maintain good cleanability.

Explanation of symbols

[0059] 1 Toothbrush 2 Head part 3 Neck part 4 Handle part 5 Secondary mold 5a Upper mold 5b Lower mold 11 Primary molded product 20 Bristle bundle 31 Base end side part 32 Neck shaft part 33 Base end face 41 Tip end side part 41a Tip end face 42 Handle base material part 43 Handle soft part 44 Handle shaft part 45 Support piece 45a Tip end part 45b Base end part 46 Handle body 47 Protrusion 48 Bulge 51 Cavity 52 Filling gate 53 Convex part S Gap

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 connected to the neck portion, wherein a tip-side portion having a predetermined axial length connected to the neck portion of the handle portion is composed of a handle base portion made of a synthetic resin integrally formed with other portions, and a handle soft portion made of an elastomer covering the handle base portion, a neck shaft-like portion having a small diameter continuous with the handle base portion protrudes from a base-end side portion of the neck portion connected to the handle portion, and a gap is formed between the handle soft portion around the neck shaft-like portion and the neck portion.

2. The handle base portion has a handle shaft-like portion extending axially through the center of the handle portion and continuous with the neck shaft-like portion of the neck portion, and a pair of left and right support pieces extending in a cantilevered manner substantially parallel to the handle shaft-like portion along left and right side edges in the width direction of the tip-side portion, wherein the handle soft portion is filled between the handle shaft-like portion and each support piece. The toothbrush according to claim 1.

3. At least left and right side portions in the width direction in a tip region of the handle shaft-like portion continuous with the neck shaft-like portion, or at least left and right inner surface portions in the width direction facing the tip region of the handle shaft-like portion in tip regions of the left and right support pieces in the width direction are provided with bulging portions that partially reduce the distance between them. The toothbrush according to claim 2.

4. The shortest distance in the width direction between at least left and right side portions in the width direction in a tip region of the handle shaft-like portion continuous with the neck shaft-like portion and at least left and right inner surface portions in the width direction facing the tip region of the handle shaft-like portion in tip regions of the left and right support pieces in the width direction or left and right side edges in the width direction of the handle shaft-like portion is 3.5 mm or less. The toothbrush according to claim 2 or 3.

5. A toothbrush comprising a head portion in which tufts are implanted, a neck portion connected to the head portion, and a handle portion connected to the neck portion, wherein a tip-side portion having a predetermined axial length connected to the neck portion of the handle portion is composed of a handle base portion made of a synthetic resin integrally formed with other portions, and a handle soft portion made of an elastomer covering the handle base portion, a neck shaft-like portion having a small diameter continuous with the handle base portion protrudes from a base-end side portion of the neck portion connected to the handle portion, a gap is formed between the handle soft portion around the neck shaft-like portion and the neck portion, and the handle base portion A handle shaft portion that extends axially at the center of the handle portion and is continuous with the neck shaft portion of the neck portion, and a pair of left and right support pieces extending in a cantilevered manner substantially parallel to the handle shaft portion along the left and right side edges in the width direction of the tip-side portion. A method for manufacturing a toothbrush in which a handle soft portion is filled between the handle shaft portion and each support piece, wherein a filling gate of a secondary mold for forming the handle soft portion is opened in a space for forming the handle soft portion so as to be in a front-rear direction orthogonal to the width direction of the handle base portion inserted into the secondary mold. A method for manufacturing a toothbrush, wherein the elastomer is injected from the filling gate to mold the handle soft portion.

Images