toothbrush

Abstract

This invention provides a transparent toothbrush with a wide, thin head and a slender neck, and excellent moldability. [Solution] The brush body comprises a head portion located at the tip and having a bristle-planted surface, a gripping portion located at the rear end of the head portion, and a neck portion located between the head portion and the gripping portion. The brush body is made of a transparent saturated polyester resin, the head portion has a maximum thickness of 2 mm or more and 4 mm or less in the thickness direction perpendicular to the bristle-planted surface, the maximum width in the width direction perpendicular to both the long axis direction and the thickness direction of the brush body is 12 mm or more and 18 mm or less, the neck portion has a maximum dimension of 3.0 mm or more and 5.5 mm or less perpendicular to the long axis direction, the head portion has a plurality of bristle-planted holes arranged on the bristle-planted surface, and in the row of bristle-planted holes located at the rear end in the long axis direction and arranged in the width direction, the sum of the distances in the width direction between the edge of the bristle-planted holes at both ends in the width direction and the side edge of the head portion is greater than the sum of the diameters of the bristle-planted holes.

Description

Technical Field

[0001] The present invention relates to a toothbrush.

Background Art

[0002] There are many toothbrushes on the market that have a wide-head type, a thin head portion, and a thin neck portion (for example, Patent Document 1). Since many of this type of toothbrush are made of opaque resins such as PP (polypropylene), PBT (polybutylene terephthalate), and POM (polyacetal), widening, thinning of the head portion, and thinning of the neck portion using a transparent (transparent or translucent) resin are desired from the viewpoint of appearance discrimination. )。

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, polyester resins have been mainly used as transparent resins for toothbrushes, but these resins generally have low fluidity during injection molding. Therefore, it is necessary to set a high molding temperature. The resin is often filled into the mold from the rear end of the gripping portion, and the filling of the head portion is the last. In this case, since the resin filled in the mold is quickly cooled and solidification progresses, it is difficult to apply injection pressure and holding pressure when filling the resin into the widened and thinned head portion through the thinned neck portion.

[0005] As a result, molding defects such as sink marks and voids are likely to occur in the head portion. When a transparent resin is used, since the above-mentioned molding defects are easily visible, there is a problem of poor appearance.

[0006] This invention has been made in consideration of the above points, and aims to provide a transparent toothbrush with a wide head, a thin head portion and a slender neck portion, and excellent moldability. [Means for solving the problem]

[0007] The present invention has the following aspects. [1] A head portion located at the tip and having a bristle surface, a gripping portion positioned at the rear end of the head portion, and a neck portion positioned between the head portion and the gripping portion, Equipped with a brush body having, The brush body is made of a transparent saturated polyester resin. The head portion is, The maximum thickness in the thickness direction perpendicular to the aforementioned flocked surface is 2 mm or more and 4 mm or less. The maximum width in the width direction perpendicular to both the long axis direction in which the brush body extends and the thickness direction is 12 mm or more and 18 mm or less. The neck portion has a maximum dimension perpendicular to the long axis direction of 3.0 mm or more and 5.5 mm or less. The head portion has a plurality of bristle-planting holes arranged on the bristle-planting surface, A toothbrush in which, in the row of bristle holes located furthest towards the rear end along the longitudinal axis and arranged in the width direction, the sum of the distances in the width direction between the edge of the bristle holes at both ends of the bristle holes and the side edge of the head portion is greater than the sum of the diameters of the bristle holes. [2] In the cross-section perpendicular to the longitudinal axis in the row, the cross-sectional area of ​​the head portion is larger than the total area of ​​the hair implantation holes. The toothbrush described in [1] above. [3] In a cross-section perpendicular to the longitudinal axis at the position in the longitudinal axis where the head portion has its maximum width and the sum of the diameters of the hair implantation holes arranged in the width direction is maximum, the cross-sectional area of ​​the head portion is smaller than the total area of ​​the hair implantation holes. The toothbrush described in [1] or [2] above. [Effects of the Invention]

[0008] In the present invention, it is possible to provide a transparent toothbrush having a wide-head type, a thin head portion, and a thin neck portion, and excellent in formability.

Brief Description of the Drawings

[0009] [Figure 1] It is a view showing an embodiment of the present invention and is a front view of the toothbrush 1. [Figure 2] It is a side view of the toothbrush 1. [Figure 3] It is an enlarged front view of the head portion 3. [Figure 4] It is a cross-sectional view orthogonal to the major axis direction in row G1. [Figure 5] It is a cross-sectional view orthogonal to the major axis direction of row G3 in FIG. 4.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the toothbrush of the present invention will be described with reference to FIGS. 1 to 5. Note that the following embodiments show one aspect of the present invention, do not limit this invention, and can be arbitrarily changed within the scope of the technical idea of the present invention. In addition, in the following drawings, in order to make each configuration easy to understand, the actual structure, the scale, the number, etc. in each structure are made different.

[0011] In addition, in the following description, the side where the bristle planting surface 3a of the head portion 3 described later is provided (bristle planting surface side) is defined as the front side of the toothbrush 1, and the side opposite to the side facing the bristle planting surface 3a of the head portion 3 is defined as the back side of the toothbrush 1. In addition, the direction orthogonal to the bristle planting surface 3a will be described as the thickness direction of the toothbrush 1. Further, the direction in which the brush body 2 extends is defined as the major axis direction, and the direction orthogonal to both the major axis direction and the thickness direction is defined as the width direction of the toothbrush 1. In addition, the side where the head portion 3 is provided (head portion side) will be described as the tip side, and the side where the gripping portion 5 is provided (gripping portion side) will be described as the rear end side.

[0012] FIG. 1 is a front view of the toothbrush 1 as seen from the side of the tufted surface 3a. FIG. 2 is a side view of the toothbrush 1 as seen in the width direction. In FIG. 1, the illustration of the brush 40 is omitted.

[0013] As shown in FIGS. 1 and 2, the toothbrush 1 of the present embodiment includes a brush body 2 made of a resin molded body formed in an elongated shape as a whole and a brush 40.

[0014] The brush body 2 has a head portion 3 located on the tip side and having a tufted surface 3a, a gripping portion 5 disposed on the rear end side of the head portion 3, and a neck portion 4 disposed between the head portion 3 and the gripping portion 5. The toothbrush 1 can clean the oral cavity with a brush 40 having a plurality of tufts (not shown) implanted on the tufted surface 3a of the head portion 3.

[0015] The resin constituting the brush body 2 is formed of a transparent or translucent transparent amorphous hard resin. Note that even crystalline resins can be molded in an amorphous state by suppressing crystallization between polymer chains depending on the molding conditions to achieve transparency or translucency. The brush body 2 of the present embodiment uses a PCTG resin (glycol-modified polycyclohexylene dimethylene terephthalate), which is one of the saturated polyester resins, as the amorphous hard resin. Examples of the amorphous saturated polyester resin include a PCT resin composed of a dicarboxylic acid component mainly containing terephthalic acid (TA) and a diol component mainly containing 1,4-cyclohexanedimethanol diol (CHDM), a PCTA resin composed of a dicarboxylic acid component mainly containing terephthalic acid (TA) and isophthalic acid (IPA) and a diol component mainly containing 1,4-cyclohexanedimethanol diol (CHDM), or polybutylene terephthalate (PBT), polyethylene terephthalate (PET), glycol-modified polyethylene terephthalate (PETG), and polyarylate resin. Examples of amorphous resins other than polyester resins include polystyrene resin, polyarylate resin, polycarbonate resin, and acrylonitrile styrene resin. Even if the above-mentioned resin contains fillers such as glass fibers or cellulose fibers, the problem addressed in this application remains the same, and therefore, it falls under the scope of the present invention.

[0016] (Outline contour shape of the front side of the brush body) In this embodiment, when the brush body 2 is viewed from the side, the outer contour line on the front side of the brush body 2 has a first straight region L1 that extends linearly from the bristle surface 3a of the head portion 3 toward the grip portion 5, continuous with the rear end; a first curved region E1 that has a center of curvature on the front side and extends in an arc shape from the rear end of the first straight region L1 toward the rear end; a second curved region E2 that has a center of curvature on the back side and extends in an arc shape from the rear end of the first curved region E1 toward the rear end; a third curved region E3 that has a center of curvature on the front side and extends in an arc shape from the rear end of the second curved region E2 toward the rear end; and a fourth curved region E4 that has a center of curvature on the back side and extends in an arc shape from the rear end of the third curved region E3 toward the rear end.

[0017] (Outline contour shape on the back of the brush body) In this embodiment, when the toothbrush 1 is viewed from the side, the outer contour line on the back side of the brush body 2 has a second linear region L2 that extends linearly from the back of the head portion 3 toward the grip portion 5, continuous with the back of the head portion 3 toward the rear end, a fifth curved region E5 that has its center of curvature on the back side and extends in an arc shape from the middle of the rear end of the second linear region L2 toward the rear end, and a third linear region that extends linearly from the rear end of the fifth curved region E5 toward the rear end parallel to the long axis. It comprises region L3, a sixth curved region E6 having its center of curvature on the back side and extending in an arc from the rear end of the third straight region L3 toward the rear end, a seventh curved region E7 having its center of curvature on the front side and extending in an arc from the rear end of the sixth curved region E6 toward the rear end, an eighth curved region E8 having its center of curvature on the back side and extending in an arc from the rear end of the seventh curved region E7 toward the rear end, and a ninth curved region E9 having its center of curvature on the front side and extending in an arc from the rear end of the eighth curved region E8 toward the rear end.

[0018] (Outer contour shape of both sides in the width direction of the brush body) In this embodiment, when the toothbrush 1 is viewed from the front, the outer contour lines on both sides of the brush body 2 in the width direction are formed symmetrically with respect to a center line that is located at the center in the width direction and extends in the direction of the long axis. Therefore, in the following description, we will describe the outer contour line on one side in the width direction (the lower side in Figure 1). Furthermore, regarding the position of the center of curvature of the curved region extending in an arc shape, the case where it is on the side of the center in the width direction relative to the outer contour line is referred to as the inside, and the case where it is on the opposite side of the center in the width direction is referred to as the outside.

[0019] In this embodiment, when the toothbrush 1 is viewed from the front, the outer contour line of the brush body 2 in the width direction includes a fourth linear region L4 that extends linearly from the boundary between the head portion 3 and the neck portion 4 (details will be described later) toward the rear end, a tenth curved region E10 that has its center of curvature on the outside and extends in an arc shape from the rear end of the fourth linear region L4 toward the rear end, and an eleventh curved region E11 that has its center of curvature on the inside and extends in an arc shape from the rear end of the tenth curved region E10 toward the rear end.

[0020] (Head section) Figure 3 is an enlarged front view of the head section 3. As shown in Figure 3, the head portion 3 is the part that brushes the inside of the mouth with multiple bundles of bristles, and has a roughly rectangular parallelepiped shape with rounded corners. In a front view, the head portion 3 has a roughly rectangular, flat plate shape with four vertices that are rounded at the corners.

[0021] In this embodiment, the boundary between the head portion 3 and the neck portion 4 is the endpoint of the curve that forms the corner cut on the neck portion 4 side in the front view shape of the head portion 3, that is, the position P1 (see Figure 1) where the curvature direction of the curve that forms the corner cut changes.

[0022] The head portion 3 is not limited to any particular shape or size that facilitates cleaning the inside of the mouth; for example, it may have a shape in which the width gradually narrows from the base to the tip. The head portion 3 may also have a tapered shape in which the thickness gradually decreases from the base to the tip, or it may have a rounded shape with a raised central part on the back side of the head portion 3.

[0023] The maximum thickness of the head portion 3 across its entire area is preferably 2 mm or more and 4 mm or less. If the maximum thickness of the head portion 3 is less than 2 mm, durability may be reduced. If the maximum thickness of the head portion 3 exceeds 4 mm, insertion into molars and maneuverability may be reduced. By setting the maximum thickness of the head portion 3 to 2 mm or more and 4 mm or less, insertion into molars and maneuverability can be improved without reducing durability.

[0024] The maximum width of the head portion 3 in the width direction is preferably 12 mm or more and 18 mm or less. If the maximum width of the head portion 3 is less than 12 mm, the contact area with each part of the tooth will decrease as it becomes a wide-head type, and it will be difficult to thoroughly clean multiple teeth. If the maximum width of the head portion 3 exceeds 18 mm, the ease of insertion into the back teeth and the ease of operation may decrease. By setting the maximum width of the head portion 3 to 12 mm or more and 18 mm or less, the contact area with each part of the tooth can be increased, allowing multiple teeth to be cleaned efficiently, and the ease of insertion into the back teeth and the ease of operation can be improved.

[0025] The head portion 3 has a flocked surface 3a on its front side. Multiple flocked holes 6 of the same diameter are arranged side by side on the flocked surface 3a. The diameter of the flocked holes 6 is not limited to the same diameter, and multiple different hole diameters may be mixed. Multiple rows of flocked holes 6 are arranged in the width direction, with spacing in the width direction corresponding to the width direction of the head portion 3 (3 to 6 holes in Figure 3), and these rows are spaced apart in the longitudinal direction (8 rows in Figure 3). The flocked holes 6 are arranged in a grid pattern. The grid pattern arrangement of the flocked holes 6 makes it easier for the resin injected into the area where the head portion 3 is molded during injection molding to flow through in a single continuous motion along the longitudinal direction. Hereinafter, the "area in the mold where the head portion 3 is molded during injection molding" may be referred to as the "head portion 3 area." The same applies to the neck portion 4 and the gripping portion 5.

[0026] Each bristle hole 6 is insulated with a bundle of bristles that make up the brush 40. The bristle bundles are insulated by bundling multiple brush bristles (filaments), folding them in half, inserting a metal retaining clip called a flat wire (not shown) between them, and then driving them into the bristle holes 6. The head portion 3 has a front bristle surface 3a and a back surface that are flat and parallel to each other.

[0027] In row G1 of the flocked holes 6 located furthest to the rear in the longitudinal direction and aligned in the width direction, the sum of the edge widths D1 and D2, defined by the length of the line segment extending in the width direction that connects the widest point of the hole edges of the flocked holes 6 at both ends in the width direction to the side edge of the head portion 3, and the shortest distance between the hole edge and the side edge, is greater than the sum of the hole diameters of the flocked holes 6 in row G1. In other words, in this embodiment, if the sum of the hole diameters of the flocked holes 6 in row G1 is HT, then the relationship (D1+D2)>HT is satisfied.

[0028] By satisfying the relationship (D1+D2)>HT, the flow resistance increases on the central side in the width direction where the bristles 6 are located at the point where the neck 4 region flows into the head 3 region, while the flow resistance on both sides in the width direction decreases relatively. Therefore, a portion of the resin flowing from the narrow neck 4 region to the central side in the width direction of the head 3 region and flowing towards the tip can be efficiently branched to both sides in the width direction. As a result, the resin that flows into the head 3 region can be smoothly diffused throughout the entire width direction. This makes it possible to apply sufficient injection pressure and holding pressure to the entire three areas of the head, suppressing molding defects such as sink marks and voids during molding.

[0029] The edge width forming distance D1 or the edge width forming distance D2 is preferably large enough to accommodate additional hair implantation holes 6, and it is even more preferable that both the edge width forming distance D1 and the edge width forming distance D2 are large enough to accommodate hair implantation holes 6. As a result, because distance D1 or distance D2 is sufficiently large, the flow resistance is reduced on the outer side in the width direction, allowing the resin that flows into the head section 3 to flow smoothly while being diffused throughout the entire width direction.

[0030] It is preferable that the sum of the distances D1 and D2 is 40% or more of the width D3 of the head portion 3 in row G1. As a result, the sum of distances D1 and D2 is sufficiently large, reducing flow resistance on both sides in the width direction, allowing the resin that flows into the three head regions to flow smoothly while being diffused throughout the entire width direction.

[0031] Furthermore, as shown in Figure 3, it is preferable that the sum of the distances D1 and D2, which are the edge widths in row G1, is 30% or more of the maximum width D4 of the head portion 3. As a result, even with respect to the maximum width D4 of the head section 3, the distances D1 and D2 between the edges of row G1 at the rearmost end of the flocked section are sufficiently large, reducing the flow resistance on both sides in the width direction. This allows the resin that flows into the head section 3 region to flow smoothly while being diffused throughout the entire width direction.

[0032] The number of hair flocking holes 6 in row G1 is preferably two or more fewer than the number of hair flocking holes 6 in row G2, which are located in the second row from the rear end in the longitudinal direction and are aligned in the width direction. In this embodiment, the number of hair flocking holes 6 in row G1 is two fewer than the number of hair flocking holes 6 in row G2. More preferably, the flocking holes 6 in rows G1 and G2 are arranged in a grid pattern, and the flocking holes 6 in row G1 are located towards the center rather than at the ends in the width direction. As a result, the distances D1 and D2 of the edge widths in row G1 are sufficiently large, reducing flow resistance on both sides in the width direction, allowing the resin that flows into the head section 3 to flow smoothly while being diffused throughout the entire width direction.

[0033] It is preferable that the region 4A, which extends from the finest part of the neck portion 4 to the head portion 3, overlaps with at least a portion of all the hair implantation holes 6 of row G1. This allows a portion of the resin that flows from the four neck regions to the central side in the width direction of the three head regions to be more efficiently branched to both sides in the width direction.

[0034] Figure 4 is a cross-sectional view perpendicular to the longitudinal axis in row G1. As shown in Figure 4, the maximum depth in the thickness direction of the bristle-planting hole 6 is shallower than the maximum thickness of the head portion 3. The distance D5 between the bottom of the bristle-planting hole 6 and the back surface of the head portion 3 is preferably 0.3 mm or more and 0.6 mm or less. If the distance D5 is less than 0.3 mm, it may be difficult to fill the space between the flocked hole 6 area and the back surface area with resin during injection molding, potentially resulting in unfilled areas. If the distance D5 exceeds 0.6 mm, it becomes difficult to increase the momentum of the resin flow by intentionally creating areas with narrower flow channels. By setting the distance D5 to between 0.3 mm and 0.6 mm, it is possible to increase the momentum of the resin flow while suppressing unfilled areas.

[0035] Furthermore, in the cross-section shown in Figure 4, it is preferable that the cross-sectional area of ​​the head portion 3 is larger than the total area of ​​the hair implantation holes 6. As a result, the resin flow path is large in three dimensions at the point where the four areas of the neck section meet the three areas of the head section, allowing for efficient and smooth flow of resin even in a wide-head type, with the resin diffused across the entire width. Therefore, it becomes possible to apply sufficient injection pressure and holding pressure to the entire three areas of the head, suppressing molding defects such as sink marks and voids during molding.

[0036] Furthermore, in the cross-section shown in Figure 4, it is preferable that the ratio of the cross-sectional area of ​​the pitch portion 3b of the head portion 3 located between adjacent bristles 6 to the cross-sectional area of ​​the bristles 6 is 0.8 or less. This makes it possible to further increase the momentum of the resin flow by deliberately creating areas where the flow path is locally narrow. The cross-sectional area of ​​the pitch section 3b is calculated using the bottom surface of the adjacent flocking holes 6 at the lower end as the reference.

[0037] Furthermore, in the cross-section at row G1, it is preferable that the cross-sectional area of ​​the head portion 3 is larger than the cross-sectional area of ​​the finest part of the neck portion 4. As a result, the edge width in row G1 is increased, making it possible to apply sufficient injection pressure and holding pressure to the entire head portion 3 area even with a narrow neck portion 4, thereby suppressing molding defects such as sink marks and voids during molding.

[0038] Figure 5 is a cross-sectional view perpendicular to the major axis of row G3 in Figure 4. Row G3 is the row in which the head portion 3 has the maximum width, the number of bristles 6 arranged in the width direction is the largest, and the sum of the hole diameters is the largest. In the cross-section shown in Figure 5, it is preferable that the cross-sectional area of ​​the head portion 3 is smaller than the total area of ​​the bristles 6.

[0039] In the early to middle stages of injection molding, when the flow path is wide and the resin has not yet completely filled the three head regions, the direction of resin flow disperses, causing the flow velocity to decrease. As a result, the resin solidifies before it reaches the tip of the three head regions, making it difficult to apply the injection pressure and subsequent holding pressure necessary to fill the tip of the three head regions with resin.

[0040] Therefore, in the initial to mid-stages of injection molding, the widest region near the center along the long axis is narrowed to control the direction of resin flow along the long axis, thereby utilizing the propulsive force of the resin in that direction. This allows the resin to be accelerated before solidification progresses and reach the tip of the three head regions. As a result, it becomes easier to apply sufficient injection pressure and holding pressure to the entire three head regions, including the tip, enabling molding while suppressing the occurrence of molding defects such as sink marks and voids.

[0041] In the mid-to-late stages of injection molding, when the resin is almost completely filled into the three head regions and holding pressure is applied, the area where sufficient pressure is applied to the resin gradually increases from the tip to the center of the three head regions. Therefore, by narrowing the edge width, the reaction force generated by damming up the resin being filled during holding pressure makes it easier to apply further pressure to both the resin already filled at the tip and the resin newly filled during holding pressure.

[0042] As described above, the cross-sectional area of ​​the head portion 3 is larger than the total area of ​​the hair implantation holes 6 in row G1, and smaller than the total area of ​​the hair implantation holes 6 in row G3. In this way, by increasing the area for resin flow at the rear end of the head section 3 and narrowing the flow path in the center of the widest section where flow is most difficult to achieve, thereby accelerating the flow velocity, it becomes easier to apply sufficient injection pressure and holding pressure to the entire head section 3 region, allowing for molding while suppressing the occurrence of molding defects such as sink marks and voids.

[0043] The sum of the distances D6 and D7, which are the edge widths in row G3, is preferably 18% or less of the maximum width D4 of the head portion 3. As a result, the central side in the longitudinal direction where the head portion 3 is at its widest point has a narrower flow path at the edge width. This allows the resin to be accelerated to reach the tip of the head portion 3 area before solidification progresses during the initial to middle stages of injection molding, and during the middle to final stages of injection molding, the reaction force generated by damming the resin being filled during holding pressure makes it easier to apply further pressure to both the resin already filled at the tip and the resin newly filled during holding pressure.

[0044] In row G4 of the bristles 6 located furthest towards the tip in the longitudinal direction and aligned in the width direction, it is preferable that at least one of the edge widths D8 and D9, defined by the length of the line segment extending in the width direction connecting the edge of the bristles 6 at both ends in the width direction to the side edge of the head portion 3, is large enough to accommodate additional bristles 6. As a result, the edge width widens at the tip of the head section 3, which is the end point of resin filling. This allows the resin to flow all the way to the tip of the head section 3 while maintaining the momentum of the resin gained at the rear end of the head section 3, ensuring thorough resin filling and making it easier to apply pressure. Consequently, it becomes possible to apply sufficient injection pressure and holding pressure to the entire head section 3 area, suppressing molding defects such as sink marks and voids during molding.

[0045] In order to produce the effects described above in rows G1, G4, and row G3 where the head portion 3 has its maximum width, it is preferable that the border width narrows abruptly from row G1 to row G3 where it has its maximum width. It is also preferable that the border width narrows abruptly from row G4 to row G3 where it has its maximum width. "Abruptly" means, for example, that the border width becomes half.

[0046] In a front view, the head portion 3 has an arc-shaped side edge 3c extending from the neck portion 4 to row G1. The side edge 3c is an arc shape with its center of curvature on the outside in the width direction. If the radius of curvature of the side edge 3c is small, the increase in the width of the head portion 3 per unit length in the long axis direction becomes large, and the width widens rapidly. This rapid widening causes the momentum of the resin flowing into the head portion 3 area to be lost in the width direction. Therefore, it is preferable that the radius of curvature of the side edge 3c be large, for example, 13 mm or more. The radius of curvature of the side edge 3c is larger than, for example, the radius of curvature of the arc-shaped side edge 3d extending from row G3 to row G4.

[0047] The side edge 3d has an arc shape with its center of curvature on the inside in the width direction. The radius of curvature of the side edge 3d is preferably small. For example, the radius of curvature of the side edge 3d is preferably 9 mm or less. By rapidly narrowing the width of the head section 3 from the center, where it is at its widest point, to the tip, the resin can be smoothly distributed to the tip and is easier to contain. This makes it easier to apply pressure, and allows for molding while suppressing molding defects such as sink marks and voids.

[0048] In a front view, the head portion 3 has a side edge 3e connecting the side edge 3c and the widest portion. The side edge 3e is an arc shape with its center of curvature on the inside in the width direction. Preferably, the radius of curvature of the side edge 3e is larger than the radius of curvature of the side edge 3d. This allows the width to gradually widen at the point where the resin flows into the head section 3, enabling efficient resin flow across the entire width despite the wide head design. Furthermore, by making the radius of curvature of the side edge 3d smaller than that of the side edge 3e, the width of the head section 3 can be abruptly narrowed from the center, where it is widest, to the tip. This allows the resin to spread smoothly to the tip and makes it easier to block it. As a result, it becomes easier to apply pressure, suppressing molding defects such as sink marks and voids during molding.

[0049] (Neck area) The neck portion 4 is positioned between the gripping portion 5 and the head portion 3 and connects the gripping portion 5 and the head portion 3. In this embodiment, the outer contour of the neck portion 4 and the gripping portion 5 in front view and side view is a shape in which multiple straight lines and gentle curves are connected from the boundary between the head portion 3 and the neck portion 4 toward the gripping portion 5 side. In the front view, the boundary between the neck portion 4 and the gripping portion 5 is defined as the position P2, which is the intersection of the 10th curve region E10 and the 11th curve region E11 shown in Figure 1 and where the curvature changes.

[0050] In a front view, the neck portion 4, from the boundary position P1 with the head portion 3 toward the gripping portion 5, has a constant minimum width in the region where the outer contour line is formed by the fourth straight region L4, and the width gradually increases from the minimum width in the region where the outer contour line is formed by the tenth curved region E10. In a side view, the neck portion 4, from the boundary with the head portion 3 toward the gripping portion 5, has a constant minimum thickness in the region where the outer contour line is formed by the first straight region L1 and the third straight region L3, and the thickness gradually increases from the minimum thickness in the region where the outer contour line is formed by the curved region E1 and the sixth curved region E6.

[0051] The neck portion 4 preferably has a maximum dimension perpendicular to the long axis of the tooth between 3.0 mm and 5.5 mm. If the maximum dimension of the neck portion 4 is less than 3.0 mm, the strength may be insufficient. If the maximum dimension of the neck portion 4 exceeds 5.5 mm, the ease of insertion into molars and the ease of operation may be reduced. By setting the maximum dimension of the neck portion 4 to 3.0 mm or more and 5.5 mm or less, sufficient strength can be ensured while improving ease of insertion into the molars and maneuverability. The cross-sectional shape of the neck portion 4 is preferably approximately square, approximately polygonal, perfectly circular, or elliptical.

[0052] (gripping part) The gripping portion 5 is the part that the user grips and is formed in a long columnar shape. To ensure sufficient length for gripping and using the gripping portion 5, it is preferable that the length from position W in a front view to the rear end of the gripping portion 5 be 100 to 200 mm.

[0053] The gripping portion 5 gradually widens in width from the boundary position P2 with the neck portion 4 toward the rear end, up to the position where the outer contour line shows the maximum value of the 11th curve region E11 in a front view. From the position where the 11th curve region E11 shows the maximum value in a front view toward the rear end, the outer contour line gradually narrows in width until it reaches the rear end.

[0054] The gripping portion 5 gradually increases in thickness from the boundary position P2 with the neck portion 4 toward the rear end until the first curved region E1 on the front side intersects with the second curved region E2 in a side view, and the sixth curved region E6 on the back side intersects with the seventh curved region E7. After that, the gripping portion 5 gradually decreases in thickness toward the rear end until the third curved region E3 shows a minimum value and the eighth curved region E8 shows a minimum value in a side view. After that, the gripping portion 5 gradually increases in thickness toward the rear end until the fourth curved region E4 shows a maximum value and the ninth curved region E9 shows a maximum value in a side view, and then gradually decreases in thickness toward the rear end.

[0055] The change in the cross-sectional area of ​​the tip of the gripping portion 5 from the position where the fourth curve region E4 and the ninth curve region E9, which are the thickest parts of the gripping portion 5 in a side view, show their maximum values, is, for example, for every 1 mm toward the tip, the change in cross-sectional area is 1 mm. 2 The following is preferable: When resin flows towards a narrow region during injection molding, a large change in cross-sectional area impairs the resin flow velocity due to shear force against the mold. Therefore, the change in cross-sectional area should be limited to 1 mm. 2By doing the following, it becomes possible to mold the resin smoothly with minimal resistance between the resin and the mold. As a result, the gripping part 5 can be molded while suppressing the occurrence of molding defects such as sink marks and voids.

[0056] The change in cross-sectional area from the rear end to the thickest part of the gripping portion 5 is, for example, for every 1 mm toward the tip, the change in cross-sectional area is 1 mm 2 The following is preferable: The rear end of the gripping portion 5 is the position of the rear end of the 11th curved region E11. The change in cross-sectional area from the rear end to the thickest part of the gripping portion 5 is 1 mm. 2 By doing the following, the resin flow path becomes linear when the resin flows during injection molding, allowing the resin to flow without reducing its flow velocity, and enabling the gripping portion 5 to be molded while suppressing the occurrence of molding defects such as sink marks and voids.

[0057] Preferably, the absolute value of the change in cross-sectional area from the rear end to the thickest part of the gripping portion 5 is greater than the absolute value of the change in cross-sectional area from the thickest part to the tip. This allows the resin to flow smoothly and maintain its flow velocity when moving towards a narrow area (from the thickest part of the gripping section 5 towards the tip) without resistance from shear force with the mold, and when moving towards a wider area (from the rear end of the gripping section 5 towards the thickest part). As a result, the resin can flow all the way to the tip of the head section 3, enabling molding while suppressing the occurrence of molding defects such as sink marks and voids.

[0058] It is preferable that the change in cross-sectional area from the tip of the gripping portion 5 to the finest part of the neck portion 4 is small. For example, the change in cross-sectional area should be 1 mm for every 1 mm increase toward the tip. 2 The following applies, and the smallest part of the neck section 4 has a diameter of 5 mm or less. When moving towards a narrow area, if the change in cross-sectional area is large, the resin flow velocity will be impaired by the shear force with the mold. Therefore, the change in cross-sectional area from the tip of the gripping part 5 to the narrowest part of the neck part 4 should be reduced by 1 mm for every 1 mm increase towards the tip. 2By doing the following, the resin can flow smoothly through the neck section 4 and maintain its flow rate. As a result, the resin can flow all the way to the tip of the head section 3, allowing for molding while suppressing the occurrence of molding defects such as sink marks and voids.

[0059] The gripping portion 5 has a substantially straight shape extending in the longitudinal direction, and it is preferable that the increase or decrease in thickness from the gripping portion 5 to the neck portion 4 is small. The difference between the maximum thickness of the gripping portion 5 and the minimum thickness of the neck portion 4 is preferably 2 mm or more and 8 mm or less. Similarly, it is preferable that the increase or decrease in width from the gripping portion 5 to the neck portion 4 is small. The difference between the maximum width of the gripping portion 5 and the minimum width of the neck portion 4 is preferably 2 mm or more and 8 mm or less. This prevents the opening from narrowing, allowing the flow of the resin to maintain its momentum.

[0060] The brush body 2 has a neck portion 4 and a gripping portion 5 that are both approximately straight in shape. The thickness and width of the brush body 2 change only slightly from the rear end of the gripping portion 5 to the tip of the neck portion 4. The cross-sectional area of ​​the brush body 2 perpendicular to the long axis gradually increases from the rear end of the gripping portion 5 towards the tip, up to the point where the thickness and width are maximum, and then gradually decreases towards the tip of the neck portion 4. From the point where the cross-sectional area is maximum (the thickest part of the gripping portion 5) to the point where it is minimum (the narrowest part of the neck portion 4), the rate of increase in thickness relative to length is, for example, less than 0.1.

[0061] When the brush body 2 is formed by injection molding using the rear end of the gripping portion 5 as a gate, that is, when a gate mark is provided at the rear end of the gripping portion 5, the fact that the neck portion 4 and the gripping portion 5 are in a substantially straight shape results in a linear flow path for the resin in the mold, allowing the injected resin to be transmitted to the position where the head portion 3 is formed while suppressing a decrease in momentum. In addition, the flow path for the resin in the mold does not narrow from the position where the gripping portion 5 is formed to the position where the neck portion 4 is formed, thus maintaining the momentum of the resin flow.

[0062] Those skilled in the art would typically attempt to secure a flow path by increasing the thickness of the gripping portion 5 when the head portion 3 is thin. However, if the increase or decrease in thickness (cross-sectional area) from the gripping portion 5 to the neck portion 4 is large, the mold narrows from the position where the gripping portion 5 is formed to the position where the neck portion 4 is formed, increasing the frictional resistance between the mold surface and the resin, and suppressing the momentum of the resin flow before it reaches the position where the head portion 3 is formed. In this embodiment, since the increase or decrease in thickness (cross-sectional area) from the gripping portion 5 to the neck portion 4 is gradual, the momentum of the resin flow can be maintained.

[0063] As described above, in the toothbrush 1 of this embodiment, in row G1 of the bristle holes 6 located at the rearmost end in the long axis direction and arranged in the width direction, the sum of the widthwise distances between the hole edges of the bristle holes 6 at both ends in the width direction and the side edges of the head portion 3 is greater than the sum of the hole diameters of the bristle holes 6. Therefore, the flow resistance is reduced on the outside in the width direction, and the resin that flows into the head portion 3 area can be smoothly flowed while being diffused throughout the entire width direction. As a result, in the toothbrush 1 of this embodiment, it is possible to apply sufficient injection pressure and holding pressure to the entire head portion 3 area, and molding defects such as sink marks and voids can be suppressed during molding. As a result, a transparent toothbrush 1 with a wide head type, a thin head portion and a slender neck portion, and excellent moldability can be provided.

[0064] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but it goes without saying that the present invention is not limited to these examples. The shapes and combinations of the constituent members shown in the above examples are merely examples, and can be modified in various ways based on design requirements, etc., without departing from the spirit of the present invention.

[0065] For example, in the above embodiment, a configuration in which the hair flocking holes 6 are arranged in a grid pattern was illustrated, but the configuration is not limited to this. By setting the edge width as described above, a configuration in which the hair flocking holes 6 are arranged in a staggered pattern is also possible. [Explanation of Symbols]

[0066] 1...Toothbrush, 2...Brush body, 3...Head, 3a...Bristle surface, 4...Neck, 5...Holding part, 6...Bristle holes, G1...Row

Claims

1. A head portion located at the tip and having a bristle surface, a gripping portion positioned at the rear end of the head portion, and a neck portion positioned between the head portion and the gripping portion, Equipped with a brush body having, The brush body is made of a transparent saturated polyester resin. The head portion is, The maximum thickness in the thickness direction perpendicular to the aforementioned flocked surface is 2 mm or more and 4 mm or less. The maximum width in the width direction perpendicular to both the long axis direction in which the brush body extends and the thickness direction is 12 mm or more and 18 mm or less. The neck portion has a maximum dimension perpendicular to the long axis direction of 3.0 mm or more and 5.5 mm or less. The head portion has a plurality of bristle-planting holes arranged on the bristle-planting surface, A toothbrush in which, in the row of bristle holes located furthest towards the rear end along the longitudinal axis and arranged in the width direction, the sum of the distances in the width direction between the edge of the bristle holes at both ends of the bristle holes and the side edge of the head portion is greater than the sum of the diameters of the bristle holes.

2. In the cross-section perpendicular to the longitudinal axis in the row, the cross-sectional area of ​​the head portion is larger than the total area of ​​the hair implantation holes. The toothbrush according to claim 1.

3. In a cross-section perpendicular to the longitudinal axis at the position in the longitudinal axis where the head portion has its maximum width and the sum of the diameters of the hair implantation holes arranged in the width direction is maximum, the cross-sectional area of ​​the head portion is smaller than the total area of ​​the hair implantation holes. The toothbrush according to claim 1 or 2.

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