JP2024044055A - toothbrush - Google Patents

Abstract

[Problem] To provide a two-color molded toothbrush in which the handle is composed of a core part integrally molded with the head and neck parts from a primary resin, and a covering part molded on the core part from a secondary resin, which can prevent gaps or cracks from occurring at the boundary between the core part and the covering part, which can allow moisture, medicine, etc. to penetrate, or the toothbrush can be damaged. [Solution] The primary resin and the secondary resin are resins that have low adhesion (low adhesion) to each other, and the tip part 4a of the core part 4 has a sloped part 61 in which either or both of the thickness dimension t1 in the front-to-back direction in which the bristle bundle 10 protrudes, and the width dimension w1 in the left-to-right direction perpendicular to the direction in which the bristle bundle 10 protrudes, gradually decrease from the base end side to the position 60 on the tip side where the dimension is smallest. [Selected Figure] Figure 4

Description

The present invention relates to a toothbrush that includes a head portion in which bristles are attached, a neck portion, and a handle portion.

Among the components of a toothbrush, the head and neck parts in particular must be able to withstand the effects of chemicals such as toothpaste, resist the effects of chemicals such as toothpaste, and withstand the various stresses that occur when brushing teeth. Requires advanced physical properties and chemical resistance. For this reason, resin materials suitable for use in the head portion and neck portion, such as polyolefin resin, tend to be limited. On the other hand, the handle part is not required to have the same degree of sophistication, physical properties, and chemical resistance as the head part and the neck part, and the material can be selected relatively freely.

For this reason, two-color molded toothbrushes have been proposed in which the handle is composed of a core part that is molded integrally with the head and neck parts using a primary resin, and a covering part that is molded on top of the core part using a secondary resin, and the secondary resin for the covering part is selected to provide functionality other than physical properties and chemical resistance, such as design or decorativeness (for example, a highly transparent resin) (see, for example, Patent Document 1).

However, in such two-color molded toothbrushes, sink marks occur due to shrinkage in the axial direction when the covering portion hardens. In addition, the head and neck of a toothbrush are subjected to bending stress in various directions when brushing teeth, causing them to bend and deform. A strong peeling force is applied. For this reason, it is necessary to select a secondary resin that has high adhesion (adhesiveness) with the primary resin, which imposes great restrictions on material selection. Furthermore, even if a material with high adhesion is selected, if sink marks or peeling forces greater than expected occur, gaps or minute cracks may occur at the boundary. Such gaps and cracks allow moisture, chemicals, etc. to enter, causing stains and damage.

Japanese Patent Application Publication No. 2007-190439

In light of the above situation, the present invention seeks to solve the problem of providing a toothbrush that is molded using two-color molding, with a handle made of a core part that is molded integrally with the head and neck parts using a primary resin, and a covering part that is molded on top of the core part using a secondary resin, and that can prevent gaps or cracks from occurring at the boundary between the core part and the covering part, which could allow moisture, medicine, etc. to penetrate or cause damage.

In view of the current situation, the inventors of the present invention have conducted extensive studies and believe that increasing the adhesion (adhesiveness) to resist the force of peeling is the cause of cracks. Rather than increasing the adhesion (adhesiveness), on the contrary, the adhesion (adhesiveness) is kept low, and the tip side of the boundary between the core material and the covering part, which is particularly close to the neck where gaps and cracks are likely to occur. However, the present inventors have discovered that by making a new structural innovation, it is possible to prevent the intrusion and damage of moisture, chemicals, etc. without generating gaps or cracks, and have completed the present invention.

That is, the present invention includes the following inventions.
(1) A toothbrush comprising a head portion into which a tuft of hair is implanted, a neck portion, and a handle portion, wherein the handle portion includes a core portion integrally molded with the head portion and the neck portion using a primary resin. and a covering part molded on the core part with a secondary resin, the primary resin and the secondary resin are resins that have low adhesion to each other, and the covering part of the core part is molded. At the tip of the area where the hair bundle is projected, one or both of the thickness dimension in the front-rear direction, which is the protruding direction of the hair bundle, and the width dimension in the left-right direction, which is orthogonal to the protruding direction of the hair bundle, is from the proximal end side. A toothbrush characterized by having an inclined portion that gradually becomes smaller toward a position on the tip side where the dimension is smallest.

(2) The toothbrush described in (1) is formed so that the inclined portion is gradually tapered in thickness in the front-to-rear direction, which is the direction in which the bristle bundles protrude, from the base end toward the tip end.

(3) The toothbrush according to (2), wherein the inclined portion is a tapered surface in which the thickness at the tip end, where the thickness dimension is the smallest, is reduced by 10% or more compared to the thickness at the base end, where the thickness dimension is the largest.

(4) Description in (2), wherein the inclined portion is formed so that the width dimension in the left-right direction perpendicular to the protruding direction of the hair bundle gradually decreases from the base end side to the distal end side position. toothbrush.

(5) The toothbrush according to (4), in which the inclined portion is in the shape of a substantially quadrangular pyramid having a pair of substantially flat inclined surfaces on the front and rear sides and a pair of substantially flat inclined surfaces on the left and right sides.

(6) The sloping portion is a first sloping portion, and the first sloping portion has a first sloping portion whose cross-sectional area gradually increases toward the tip side of the first sloping portion. The toothbrush according to (1), which has two sloped parts.

(7) The toothbrush according to (6), wherein an axial dimension of the second inclined portion is smaller than an axial dimension of the first inclined portion.

The toothbrush of the present invention described above can prevent gaps or cracks from occurring at the boundary between the core and covering, which could allow moisture, medicines, etc. to enter, or cause damage.

FIG. 2 is a plan view of the toothbrush according to the representative embodiment of the present invention, viewed from the ventral side where the bristle bundles are protrudingly provided. FIG. FIG. 2 is a side view showing the primary molded toothbrush product in solid lines. 5A to 5C are explanatory diagrams showing the shape of the tip of the core part of the toothbrush. Similarly, a vertical cross-sectional view showing the main parts of the toothbrush. FIG. (a) is an AA end view of FIG. 6, (b) is a BB end view, (c) is a CC end view, and (d) is a DD end view. FIG. 13 is an explanatory diagram of the main part showing a state in which the covering portion contracts.

Next, an embodiment of the present invention will be described in detail with reference to the attached drawings.

As shown in Figures 1 to 3, the toothbrush T of the present invention comprises a head portion 1 in which bristle bundles 10 are planted, a neck portion 2, and a handle portion 3. The handle portion 3 is composed of a core portion 4 that is integrally molded with the head portion 1 and the neck portion 2 using a primary resin, and a covering portion 5 that is molded on top of the core portion 4 using a secondary resin.

In the present invention, in particular, the primary resin and the secondary resin are resins that have low adhesion (low adhesion, low welding) to each other. In addition, as shown in FIGS. 4(a) to 4(c), a distal end portion 4a (a distal end portion connected to the neck portion 2) near the neck portion 2 in the region where the covering portion 5 of the core material portion 4 is formed is formed. , the thickness dimension t1 in the front-rear direction, which is the protruding direction of the hair bundle 10, and the width dimension w1 in the left and right directions perpendicular to the protruding direction of the hair bundle 10, or both (in this example, both). It is characterized by having an inclined portion 61 whose dimension gradually decreases from the proximal end side to the position 60 where the dimension is the smallest on the distal end side.

In this way, if the primary resin and the secondary resin are resins with low adhesion to each other, even if a large sink occurs in the covering portion 5, no cracks will occur at the boundary with the core portion 4. Furthermore, by having the inclined portion 61, the shrinkage movement in the axial direction (towards the base end) due to sink in the covering portion 5 is restricted by the inclination. This makes it less likely that a gap will occur at the boundary position B1 on the neck portion 2 side, where a gap is likely to occur due to sink in the covering portion 5 or bending when brushing teeth.

In addition, by providing such an inclined portion 61, concentration of bending stress during tooth brushing is suppressed (stress (dispersion), and the generation of gaps at the boundary positions due to bending can be suppressed. That is, by receiving the bending stress on the entire inclined portion 61, stress is prevented from concentrating on the minimum dimension position 60, and as a result, gaps can also be prevented.

As shown in Figs. 1 and 2, the head portion 1 is formed as a thin head having a substantially flat bristle base 11 with a thickness t2 of 4 mm or less, and a plurality of bristle bundles 10 are planted on a bristle surface 12 located on the ventral side of the bristle base 11. The bristle base 11 and neck portion 2 of the head portion 1 are formed of a first hard synthetic resin, preferably polyethylene terephthalate (PET) or the like, which has a relatively high heat resistance temperature (melting point), as the primary resin. The first hard synthetic resin is not limited to polyethylene terephthalate, and polybutylene terephthalate (PBT), 6-nylon, 6,6-nylon, etc. can also be used. In addition, in order to improve the design of the toothbrush, it is preferable that the primary resin is colored in a predetermined color.

The hair bundles 10 may be implanted by driving them together with a flat wire into the implantation hole formed in the hair transplanting table 11, or the hair bundles 10 may be placed upright using a fusion method or an in-mold method without using a flat wire. Of course anything is fine. The material of each filament constituting the hair bundle 10 is not particularly limited either, and may be artificial hair made of a resin material such as nylon, polyester, or polyolefin, or natural hair such as pig hair. In addition, for the cross-sectional shape, cross-sectional size, etc., publicly known forms can be widely adopted. The number and arrangement of the hair bundles 10 are also not particularly limited.

A toothbrush equipped with a thin head as described above has improved operability in the oral cavity, and the head portion 1 can reach even the finer parts of the back teeth, making it possible to more reliably and thoroughly brush the entire oral cavity, including the back teeth, with a light force. It is possible. Moreover, by setting the plate thickness t2 of the bristle implantation table 11 to 4 mm or less, the contact of the bristle implantation table 11 against the inside of the oral cavity is reduced, and it also looks thinner and slimmer than it actually is, and there is less resistance when inserting it into the back teeth. There are advantages. The thickness t2 of the flocking table 11 is preferably 3.0 mm or less, more preferably 2.5 mm or less.

The neck portion 2 is a thin neck with a thickness dimension t3 in the front-to-back direction and a width dimension w3 in the left-to-right direction of 5.5 mm or less, more preferably 3.5 mm or more and 4.5 mm or less, in the portion closer to the tip than the center position. In this way, if the thickness and width of the portion closer to the tip than the center position is formed to 5.5 mm or less to correspond to a thin head, the head portion 1 can reach the fine parts of the back teeth, making it possible to more reliably and thoroughly brush the entire oral cavity, including the back teeth. The remaining portion on the base end side of the neck portion 2 has a diameter dimension that expands from the tip to the base end, and has a flared shape (trumpet shape) with the expansion rate increasing toward the base end.

As shown in FIG. 3, the core part 4 of the handle part 3 has a rod-shaped part 41 embedded in the covering part 5, cylindrical protrusions 42, 43 protruding from the front (ventral surface) side of the rod-shaped part 41, and a circular plate-shaped part 44 provided at the base end of the rod-shaped part 41. The protrusions 42, 43 function as spacers when set in the secondary mold, and also function as locking pieces that prevent the covering part 5 from moving axially relative to the core part 4. As described above, the tip part 4a (the tip part connected to the neck part 2) of the rod-shaped part 41 near the neck part 2 in the region where the covering part 5 of the core part 4 is molded has an inclined part 61 in which both the thickness dimension t1 and the width dimension w1 gradually decrease from the base end side to the position 60 where the dimensions are smallest on the tip side, as shown in FIG. 4(a)-(c), FIG. 5 and FIG. 6.

The inclined portion 61 prevents the covering portion from moving in the axial direction, and this movement can be prevented if either the vertical or horizontal direction of the thickness dimension t1/width dimension w1 has an inclination that gradually decreases as described above. Therefore, if one of the vertical and horizontal directions is tapered, the other may be reversely tapered. However, for stress dispersion during cleaning, the vertical inclination (inclination of the front and rear surfaces) that reduces the thickness dimension t1 is important.

Specifically, as shown in Figs. 4(a) and 5, the inclined portion 61 preferably consists of tapered surfaces 610, 611 around the point where the thickness dimension t1 at the tip end position 60 is the smallest is reduced by 10% or more compared to the thickness at the base end position where the thickness dimension t1 is the largest. A reduction of less than 10% will not be effective in preventing the axial movement of the covering portion. However, a reduction of more than 30%, i.e., a large inclination, will cause problems such as the strength of the core portion 4 not being able to be maintained and the covering portion 5 becoming thicker, resulting in increased costs.

In this example, as shown in Fig. 4(b) and Fig. 6, the width dimension w1 is also configured with left and right tapered surfaces 612, 613 in which the thickness at the smallest point 60 decreases relative to the width at the largest point on the base end side. Thus, as shown in Fig. 7(c), the cross-sectional shape of the inclined portion 61 is configured to be approximately quadrangular with a pair of approximately flat inclined surfaces (610, 611) consisting of a pair of gentle outer convex surfaces on the front and rear, and a pair of approximately flat inclined surfaces (612, 613) consisting of a pair of gentle outer convex surfaces on the left and right. This prevents the occurrence of gaps due to rotational movement around the axis, i.e., twisting of the covering portion 5 relative to the core portion 4.

Further, as shown in FIGS. 4(a) to 5(c), 5 and 6, the tip 4a of the rod-shaped portion 41 is connected to a position 60 where the cross-sectional area is the smallest on the tip side of the inclined portion 61. Further, a second inclined portion 62 whose cross-sectional area gradually increases toward the neck portion 2 on the distal end side is provided. Due to the existence of such an inclined portion 62, even if the covering portion 5 contracts in the axial direction due to sink marks or the like, the end portion 5a can move along the inclined surface of the second inclined portion 62 as shown in FIG. (moves in the direction of the shaded arrow), resulting in a structure that makes it difficult for gaps to form.

It is preferable that the inclined portion 62 is composed of front and rear inclined surfaces such that the thickness at the proximal position 60 where the thickness dimension t1 is the smallest is 30 to 50% smaller than the thickness at the distal side position where the thickness dimension t1 is the largest. When the reduction is greater than 50%, that is, when the slope becomes large, a gap is likely to be formed between the covering portion 5 and the end portion 5a due to sink marks or the like. If it is less than 30%, the tip portion 5a of the covering portion 5 will become too thin and its strength cannot be maintained.

Furthermore, due to the presence of the inclined portion 62, the end portion 5a of the covering portion 5 is formed so as to become gradually thinner toward the connection position with the neck portion 2, so that the amount of shrinkage in the axial direction due to heat shrinkage can be kept as small as possible. This allows the generation of gaps to be suppressed. Furthermore, like the first inclined portion 61, it also has the effect of preventing stress from being concentrated at the position 60. As shown in FIG. 7(b), the second inclined portion 62 has a circular or elliptical shape in cross-section, and has an inner convex shape extending from the position 60 with the smallest cross-sectional area toward the tip side. It has a structure consisting of a complex sloped surface including a rounded surface 620 and a tapered surface 621.

As shown in FIG. 6, the axial dimension L2 of the second inclined portion 62 is set smaller than the axial dimension L1 of the first inclined portion 61. In other words, the dimension L1 of the first inclined portion 61 is set relatively large because a length is required to prevent movement of the covering portion 5 when sink marks or the like occur.

The secondary resin constituting the covering portion 5 is not particularly limited as long as it has low adhesion (low adhesion, low welding) to the primary resin, and may be a resin without light transmittance. If a light-transmitting material is used, for example, a second hard synthetic resin having a lower heat resistance temperature than the first hard synthetic resin, such as polycarbonate (PC), acrylonitrile butadiene styrene (ABS), acrylonitrile, etc. It is made of a styrene copolymer (AS resin), polystyrene (PS), polyethylene (PE), polypropylene (PP), etc., and is also made of a light-transmitting material. Even a translucent resin mixed with a substance that does not transmit visible light (for example, glitter, pigment, etc.) is considered a light-transmissive material if it can transmit visible light. Preferably, a resin having a light transmittance value of 80% or more as measured by the JIS K 7105 test method is used.

As shown in Figures 1 and 2, the tip region of the handle portion 3 is provided with a finger rest 31 that bulges in the radial direction. The tip of this finger rest 31 is provided with a tapered portion 30 that tapers toward the connection position with the neck portion 2, and is configured so that the radial dimension gradually decreases toward the connection position with the neck portion 2. This tapered portion 30 is composed of the tip 4a of the core portion 4 and the covering portion 5 that covers it. The covering portion 5 that constitutes the tapered portion 30 is also tapered toward the tip along the inclined surface of the first inclined portion 61, and its outer circumferential surface is continuously connected to the outer circumferential surface of the base end of the neck portion 2 that is flared toward the tip.

In addition, a number of grooves 50 extending in the width direction are formed on the front side (ventral side) of the finger rest 31, which form a non-slip portion for the fingers and allow the user to clearly recognize the position of the finger rest 31. The finger rest 31 and its base end portion are configured so that the width gradually decreases toward the axial center position 32 of the handle portion 3. In addition, the base end portion of the axial center position 32 is provided with an enlarged diameter portion 33 configured so that the width gradually increases toward the base end side of the handle portion 3, and a terminal portion 34 configured so that the width gradually decreases toward the base end side of the handle portion 3.

The finger rest 31 has a shape in which its thickness and width dimensions are approximately the same. With this shape, the handle 3 can be properly gripped whether using the pen grip method or the palm grip method, allowing the head 1 to be accurately operated and providing excellent cleaning performance. The reduction rate of the width dimension between the finger rest 31 and the axial center position 32 of the handle 3 is set to 10-40%. This allows the center of gravity of the entire toothbrush to be positioned within a specified area including the finger rest 31, which is located toward the tip side of the axial center of the handle 3.

Further, on the back side (rear side) of the handle portion 3, an elongated flat surface 35 that extends over substantially the entire length of the handle portion 3 in the axial direction is provided. Thereby, the grip force when gripping the handle portion 3 can be effectively improved. Furthermore, there is an advantage that a stable placement condition can be obtained when the back surface (flat surface 35) of the toothbrush is placed on a table or the like.

To manufacture the toothbrush of the present embodiment, first, a primary mold is used to form a primary molded product in which the head portion 1, neck portion 2, and core portion 4 of the handle portion 3 of the toothbrush are integrally arranged. With the mold clamped, a first hard synthetic resin is injected as a primary resin into this primary mold to form a primary molded product. Next, the primary molded product is set in a secondary mold, and a second hard synthetic resin is injected as the secondary resin to obtain a secondary molded product (toothbrush) in which the coating portion 5 is covered.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way, and it goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention. For example, regarding the materials, the first hard resin for molding the primary molded product consisting of the core material part 4 etc. and the second hard resin for molding the covering part 5 are a combination of hard resins that have low welding properties to each other. In other words, it is possible to use a second hard resin that does not mix with the first hard resin during molding and has the property of being separated from each other after molding.

As a specific combination, a crystallized resin made of polyacetal resin (POM), polyamide resin (PA), polybutylene terephthalate (PBT), or polypropylene resin (PP) is used when the other party is a crystallized resin (however, (excluding PPs), or in the case of amorphous trees, they have a property of low welding to each other. For this reason, one of the first hard resin constituting the core part 4 and the second hard resin constituting the covering part 5 is made of a crystallized resin such as polyacetal resin (POM), and the other is made of, for example, By using an amorphous resin made of acrylonitrile butadiene styrene resin (ABS), polycarbonate (PC), or acrylic resin (PMMA), the first hard resin and the second hard resin can be mixed during molding. Instead, the core portion 4 and the covering portion 5 can be separated from each other after molding.

In addition, among the crystallized resins, polypropylene resins (PP) have high welding properties, so except for those in which both the first hard resin and the second hard resin are made of polypropylene resin (PP), Even when both the first hard resin and the second hard resin are crystallized resins, it is possible to prevent the core portion 4 and the covering portion 5 from becoming fused to each other. For this reason, for example, one of the first hard resin constituting the core part 4 and the second hard resin constituting the covering part 5 is made of a crystallized resin such as polyacetal resin (POM), and the other is made of a crystallized resin such as polyacetal resin (POM). By using a crystallized resin made of polyacetal resin (POM), polyamide resin (PA), polybutylene terephthalate (PBT), polypropylene resin (PP), etc., as in the above case, the first hard resin is used during molding. It is possible to prevent the core material part 4 and the second hard resin from mixing, and to keep the core part 4 and the covering part 5 separated from each other after molding.

T Toothbrush 1 Head portion 2 Neck portion 3 Handle portion 4 Core portion 4a Tip portion 5 Covering portion 5a End portion 10 Bristle bundle 11 Bristle base 12 Bristle surface 30 Tapered portion 31 Finger rest portion 32 Position 33 Expanded portion 34 Terminal portion 35 Flat surface 41 Rod-shaped portion 42, 43 Protrusion 44 Plate-shaped portion 50 Groove 60 Position 61 Inclined portion 62 Inclined portion 610, 611 Tapered surface 612, 613 Tapered surface 620 R-surface 621 Tapered surface B1 Position

Claims (7)

A toothbrush comprising a head portion on which a tuft of hair is implanted, a neck portion, and a handle portion,
The handle portion includes a core portion integrally molded with the head portion and neck portion using a primary resin, and a covering portion molded on the core portion using a secondary resin,
The primary resin and the secondary resin are resins that have low adhesion to each other,
Either one of the thickness dimension in the front-rear direction, which is the protruding direction of the hair bundle, and the width dimension in the left-right direction orthogonal to the protruding direction of the hair bundle, is attached to the tip of the core material part in the region where the covering part is molded. Alternatively, a toothbrush having an inclined portion in which both dimensions gradually become smaller from the proximal end side to the position where the dimensions are smallest on the distal end side. 2. The toothbrush according to claim 1, wherein the inclined portion is formed so that the thickness in the front-rear direction, which is the protruding direction of the bristle bundle, gradually decreases from the proximal end toward the distal end. 3. The toothbrush according to claim 2, wherein the inclined portion is formed of a tapered surface in which the thickness at the tip side where the thickness is the smallest is reduced by 10% or more compared to the thickness at the proximal side where the thickness is the largest. The toothbrush according to claim 2, wherein the inclined portion is formed so that the width dimension in the left-right direction perpendicular to the protruding direction of the bristle bundle gradually decreases from the proximal end toward the distal end. The toothbrush of claim 4, wherein the inclined portion is substantially in the shape of a quadrangular pyramid having a pair of substantially flat inclined surfaces on the front and rear sides and a pair of substantially flat inclined surfaces on the left and right sides. The inclined part is a first inclined part, and a second inclined part continues from the position where the cross-sectional area is smallest on the distal end side of the first inclined part and gradually increases in cross-sectional area toward the distal end side. The toothbrush according to claim 1, having a portion. 7. The toothbrush of claim 6, wherein the second ramped portion has an axial dimension smaller than the axial dimension of the first ramped portion.

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