Toothbrush

Abstract

The present invention provides an anchorless toothbrush having sufficient bristle-implanted strength. The present invention comprises: bristle bundles in which a plurality of filaments are bundled; and a head part which has bristle implanting holes formed so as to be recessed toward the back surface side on a bristle implanting surface positioned on the front surface side in the thickness direction, and in which the bristle bundles are implanted. When one or more bristle implanting holes having the same shape and the same size in a front view are defined as one group, the bristle bundle in at least one group has a solidified part in which a plurality of filaments are melted and solidified on one end side in the length direction, and the head part has a fixing part that protrudes from the inner surface of the bristle implanting hole and is positioned on the front side of the solidified part. The solidified part has a flat shape in which the maximum dimension in the width direction is larger than the maximum dimension in the thickness direction in a cross section in which the direction with a shorter distance is the width direction between the distance in the long axis direction of the bristle implanting hole at the center position in the range in which the bristle implanting hole has the maximum dimension in the short axis direction parallel to the bristle implanting surface and orthogonal to the long axis direction, and the distance in the short axis direction of the bristle implanting hole at the center position in the range in which the bristle implanting hole is the maximum dimension in the long axis direction.

Description

toothbrush

[0001] This application claims priority from Japanese Patent Application No. 2023-206816, filed December 7, 2023, the contents of which are incorporated herein by reference.

[0002] In recent years, toothbrushes with a wide variety of specifications have been offered with the introduction of anchorless toothbrushes, which do not use flat wires, instead of the method of attaching folded bristles to the head with flat wires. These types of toothbrushes aim to secure a competitive advantage by creating differentiation through the feel and appearance that take advantage of the anchorless bristle and brush shapes.

[0003] A known anchorless toothbrush is a PTt (Pressure Temperature Time) toothbrush, which melts one longitudinal side of a bristle bundle with heat to create a hot bulb, inserts the hot bulb into a bristle implantation hole formed in the head, and then applies heat and pressure to the head to fix the bristle bundle to the head (see, for example, Patent Document 1).

[0004] International Publication No. 2018 / 177594

[0005] In the toothbrush disclosed in Patent Document 1, the bulb is spherical, and therefore when the bulb is inserted into the bristle implantation hole, the cross-sectional shape near the inner wall of the bristle implantation hole has a tangent line that is oriented in a vertical direction, making it difficult to ensure sufficient bristle implantation strength.

[0006] The present invention has been made in consideration of the above points, and an object of the present invention is to provide an anchorless toothbrush having sufficient bristle strength.

[0007] The present invention has the following aspects. [1] A toothbrush comprising: a bristle bundle formed by bundling a plurality of filaments; and a head portion having bristle bundles, the bristle bundles being provided at the tip of a handle portion extending in the longitudinal direction, recessed into the rear side of the bristle implantation surface located on the front side in the thickness direction, and having bristle implantation holes into which the bristle bundles are implanted; when one or more bristle implantation holes of the same shape and size when viewed from the front are grouped, the bristle bundles in at least one of the groups have a solidified portion at one end in the longitudinal direction where the plurality of filaments have melted and solidified, the head portion having a fixing portion protruding from the inner surface of the bristle implantation hole and located on the front side of the solidified portion; and when the width direction is the shorter of the distance in the longitudinal direction of the bristle implantation hole at the center position of the range where the bristle implantation hole has its maximum dimension in the minor axis direction that is parallel to the bristle implantation surface and perpendicular to the longitudinal axis direction, and the distance in the minor axis direction of the bristle implantation hole at the center position of the range where the bristle implantation hole has its maximum dimension in the major axis direction, the solidified portion having a flat shape in which the maximum dimension in the width direction is greater than the maximum dimension in the thickness direction. [2] The toothbrush according to [1], wherein the cross-sectional shape of the solidified portion is a substantially semicircular shape that bulges toward the rear side. [3] The toothbrush according to [1] or [2], wherein the toothbrush has a protrusion provided on the front side of the fixing portion, extending toward the front side as it approaches the inside of the bristle implantation hole, and whose tip contacts the filament at a position closer to the front side than the bristle implantation surface. [4] The toothbrush according to any one of [1] to [3], wherein the distance from the thickness direction position of the solidified portion at its maximum dimension in the width direction to the bristle implantation surface is shorter than the distance from the thickness direction position of the solidified portion at its maximum dimension in the width direction to the surface of the head portion opposite the bristle implantation surface in the thickness direction. [5] The toothbrush according to any one of [1] to [4], wherein the thickness direction position of the bottom of the bristle implantation hole varies depending on the maximum dimension in the width direction of the solidified portion. [6] A toothbrush described in any one of [1] to [5], wherein the head portion has a maximum dimension in the thickness direction of 1.4 mm or more and 3.0 mm or less.[7] A toothbrush described in any one of [1] to [6], wherein the ratio of the total area of ​​the tufting holes to the head area from the tip of the head portion to the position of the hole edge of the tufting hole located at the rearmost end in the longitudinal direction is 55% or more.

[0008] The present invention can provide an anchorless toothbrush with sufficient bristle strength.

[0009] Fig. 1 is a diagram showing an embodiment of the present invention, and is a partial front view of the toothbrush 1 according to the first embodiment. Fig. 1 is a cross-sectional view taken along line II-II in Fig. 1. Fig. 1 is a cross-sectional view showing the head portion 3 before heat compression treatment along the width direction. Fig. 2 is a partial cross-sectional view showing the head portion 3 in which the cross-section of the solidified portion is spherical. Fig. 3 is a partial cross-sectional view showing the head portion 3 in which the cross-section of the solidified portion is flat. Fig. 4 is a partial cross-sectional view showing the head portion 3 after heat compression treatment along the width direction. Fig. 5 is a cross-sectional view showing the head portion 3 of the toothbrush 1 according to a second embodiment.

[0010] An embodiment of the toothbrush of the present invention will be described below with reference to Figures 1 to 7. Note that the following embodiment shows one aspect of the present invention, does not limit the present invention, and can be modified as desired within the scope of the technical concept of the present invention. In addition, in the following drawings, the scale and number of each structure are different from the actual structure to make each component easier to understand.

[0011] [First embodiment] Fig. 1 is a partial front view of a toothbrush 1 according to a first embodiment. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1.

[0012] As shown in Figure 1, toothbrush 1 has a head portion 3 and a handle portion 4 connected to head portion 3. Head portion 3 is located at the tip side of handle portion 4, which extends in the longitudinal direction (left-right direction in Figure 1). Bristle bundles 12, 22 are implanted in head portion 3.

[0013] The material of the head portion 3 and the handle portion 4 is not particularly limited, and it is preferable to use, for example, polypropylene (PP) resin, polyacetal (POM) resin, polybutylene terephthalate (PBT) resin, polyethylene terephthalate (PET) resin, etc.

[0014] In the following description, the direction normal to the flocked surface 2 (the direction perpendicular to the paper in Fig. 1, the vertical direction in Figs. 2 and 3) is referred to as the thickness direction, and the direction parallel to the flocked surface 2 and perpendicular to the major axis direction (the vertical direction in Fig. 1, the horizontal direction in Fig. 3) is referred to as the minor axis direction. The side opposite the flocked surface 2 in the thickness direction is referred to as the front side, and the side opposite the front side is referred to as the back side.

[0015] The head portion 3 has a rectangular shape extending in the longitudinal direction when viewed from the front. The head portion 3 has a bristle implantation surface 2, bristle implantation holes 3A and 3B, and fixing portions 5A and 5B. The head portion 3 has a first bristle implantation portion 11 and a second bristle implantation portion 21.

[0016] The tufting hole 3A is located in the first tufting section 11. The tufting hole 3A is recessed from the tufting surface 2 toward the back side in the thickness direction. The tufting hole 3A is formed in a shape that corresponds to the shape of the first tufting section 11 when viewed from the front. The tufting hole 3B is located in the second tufting section 21. The tufting hole 3B is recessed from the tufting surface 2 toward the back side in the thickness direction. The tufting hole 3B is formed in a shape that corresponds to the shape of the second tufting section 21 when viewed from the front.

[0017] The front view shapes of the first bristle-implanted portion 11 and the second bristle-implanted portion 21 are not particularly limited, and may each be provided in one or more shapes, such as a circle, an ellipse, an arc, a ring, a straight line, a polygon, or a polygonal frame shape, and in one or more types.

[0018] As shown in FIG. 1, the first bristle-implanting portion 11 and the second bristle-implanting portion 21 have a circular shape when viewed from the front, and therefore the bristle-implanting holes 3A and 3B also have a circular shape when viewed from the front.

[0019] In the anchorless toothbrush 1, the bristle implantation holes 3A, 3B can be made to have different shapes in the cross section along the long axis direction and the cross section along the short axis direction, and depending on the cross-sectional position, the way in which they are affected by forces, for example, caused by brushing, will differ.

[0020] Therefore, for the tufting holes 3A in the head 3, where the tufts are implanted, the width direction will be defined as the direction in which the shorter distance is between the distance in the long axis direction of the tufting hole 3A at the center position of the range in which the tufting hole 3A has its maximum dimension in the short axis direction and the distance in the short axis direction of the tufting hole 3A at the center position of the range in which the tufting hole 3A has its maximum dimension in the long axis direction. The same concept applies to the tufting hole 3B. Furthermore, if the shape of the tufting holes 3A and 3B in a front view is a perfect circle, for example, and the distance in the long axis direction is the same as the distance in the short axis direction, the short axis direction will be defined as the width direction.

[0021] In this case, the direction with the shorter distance in the width direction (the direction with the shorter distance) is more susceptible to the force of brushing, etc., and this is important when considering the crimping structure. Also, the solidified portions 14 and 24, which are hot bulbs and will be described later, tend to be thickest and have the widest width at the center of the tufting holes 3A and 3B in the width direction. Therefore, the setting of the width direction is important when considering the crimping structure.

[0022] Since the tufting holes 3A and 3B of this embodiment have a circular shape when viewed from the front, the maximum distance in the cross section along the major axis direction is the same as the maximum distance in the cross section along the minor axis direction.

[0023] Figure 3 is a cross-sectional view of the head portion 3 taken along the width direction. The head portion 3 shown in Figure 3 is a pre-molded body prior to the heat compression treatment described below. That is, as shown in Figure 3, the head portion 3 is molded in advance, for example, by injection molding. The tufting holes 3A in the head portion 3 of the pre-molded body extend toward the back side with a constant diameter. Note that the second tufted portion 21 differs only in size from the first tufted portion 11, and therefore has the same cross-sectional shape. Therefore, only the appropriate reference numerals are shown in the drawings, and the description of the second tufted portion 21 may be omitted or simplified.

[0024] The first bristle portions 11 are arranged on both outer sides in the short axis direction. Adjacent first bristle portions 11 in each row in the long axis direction are at the same position in the short axis direction, and a plurality of first bristle portions 11 (four in each row in FIG. 1 ) are arranged at intervals in the long axis direction.

[0025] The second bristle sections 21 are arranged closer to the center in the short axis direction than the first bristle sections 11. A plurality of second bristle sections 21 (14 in FIG. 1 ) are arranged at intervals in the long axis direction. The rows of the second bristle sections 21 are arranged alternately along the long axis direction, with two bristle sections 21 at the same position in the long axis direction and spaced apart in the short axis direction, and one bristle section 21 adjacent to the long axis direction but at a different position in the short axis direction.

[0026] In this embodiment, when one or more tufting holes 3A, 3B having the same shape and size when viewed from the front are defined as one group, the tufts in at least one group will be described.

[0027] As shown in Fig. 2, the first bristle implantation section 11 has a bristle bundle 12. The bristle bundle 12 has a plurality of bundled filaments 13 and a solidified section 14. The plurality of filaments 13 are bundled in a predetermined shape when viewed from the front. In this embodiment, the plurality of filaments 13 are bundled in a circular shape when viewed from the front.

[0028] The second bristle implantation section 21 has a bristle bundle 22. The bristle bundle 22 has a plurality of bundled filaments 23 and a solidified section 24. The plurality of filaments 23 are bundled in a predetermined shape when viewed from the front. In this embodiment, the plurality of filaments 23 are bundled in a circular shape when viewed from the front.

[0029] The material of the filaments 13 and 23 is not particularly limited, but examples thereof include polyamide (e.g., 6-12 nylon, 6-10 nylon), polyester (e.g., polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate), polyolefin (e.g., polypropylene), etc.

[0030] The solidified portion 14 is provided on the back side, which is one end side of the bristle bundle 12 in the longitudinal direction. The solidified portion 14 is formed into a ball shape by melting and solidifying the back side of the bristle bundle 12 in the longitudinal direction by heating it with a heater or the like. The end of the solidified portion 14 on the back side contacts the bottom 3C of the tufting hole 3A. As shown in FIG. 3, the solidified portion 14 has a flat shape in which the maximum dimension L11 in the width direction is greater than the maximum dimension L12 in the thickness direction. The cross-sectional shape of the solidified portion 14 in the width direction is approximately semicircular, bulging toward the back side. The above shape of the solidified portion 14 is maintained even after the heating and compression process described below.

[0031] An approximately semicircular shape is defined as a shape where the value expressed by L2 / L1 is 0.5 or less, where L1 is the distance from the thickness direction position in the solidified portion 14 where the widthwise distance is the maximum dimension L11 to the end on the back side where the widthwise distance is the smallest on the back side, and L2 is the distance from the thickness direction position where the widthwise distance is the maximum dimension L11 to the end on the front side where the widthwise distance is the smallest on the front side.

[0032] 3, the maximum widthwise dimension L11 of the solidified portion 14 is smaller than the diameter D1 of the tufting hole 3A in the head portion 3 of the pre-molded body. The rear side ends of the solidified portion 14 and the plurality of filaments 13 are inserted into the tufting hole 3A in the head portion 3 of the pre-molded body from the front side and come into contact with the bottom portion 3C.

[0033] The solidified portion 24 is provided on the rear side, which is one end side of the bristle bundle 22 in the longitudinal direction. The solidified portion 24 is formed into a ball shape by melting and solidifying the rear side of the bristle bundle 22 in the longitudinal direction by heating it with a heater or the like. The end of the solidified portion 24 on the rear side contacts the bottom 3D of the tufting hole 3B. The solidified portion 24 has a flat shape in which the maximum dimension L21 in the width direction is greater than the maximum dimension L22 in the thickness direction. The cross-sectional shape of the solidified portion 24 in the width direction is approximately semicircular, bulging toward the rear side. The above shape of the solidified portion 24 is maintained even after the heating and compression process described below.

[0034] The maximum widthwise dimension L21 of the solidified portion 24 is smaller than the diameter D2 of the tufting hole 3A in the head portion 3 of the pre-molded body. The rear-side ends of the solidified portion 24 and the plurality of filaments 23 are inserted from the front side into the tufting hole 3B in the head portion 3 of the pre-molded body and come into contact with the bottom portion 3D.

[0035] Furthermore, since the solidified portions 14 and 24 have a generally semicircular cross section that bulges out toward the rear side, it is possible to make the solidified portions 14 and 24 thinner in the thickness direction compared to when the solidified portions 14 and 24 are generally circular, which contributes to making the head portion 3 thinner. Furthermore, by making the head portion 3 thinner, it is possible to crimp the head portion 3 at a position close to the implanted surface 2 in the heat compression process described below, and it is possible to effectively ensure the implanted strength.

[0036] Furthermore, since the cross-sectional shape of the solidified portions 14 and 24 is an approximately semicircular shape that bulges toward the back side, the amount of protrusion of the solidified portions 14 and 24 outward in the width direction from the filaments 13 and 23 tends to be large, thereby strengthening the fixation of the hair bundles 12 and 22 by the fixing portions 5A and 5B.

[0037] From the viewpoint of preventing hair loss during brushing, it is preferable that the diameter of the bristle implantation holes 3A, 3B be 1.5 mm or more, as this increases the contact area with the solidified portions 14 and 24. Furthermore, it is preferable that the distance L1 be 0.5 mm or more and 1.8 mm or less, from the viewpoint of ensuring the implant strength of the solidified portions 14 and 24. Furthermore, since the bristle bundles 12, 22 located at the outermost part of the head part 3 are subjected to a relatively large physical load due to hair loss during brushing, it is preferable that the cross-sectional shape of the solidified portions 14, 24 at the outermost bristle implantation holes 3A, 3B be a roughly semicircular shape that bulges toward the back side.

[0038] The fixing portion 5A protrudes from the inner surface of the implantation hole 3A and is located on the front side of the solidified portion 14. The fixing portion 5A protrudes from the inner surface around the entire circumference of the implantation hole 3A and is located on the front side of the solidified portion 14. By positioning the fixing portion 5A on the front side of the solidified portion 14, the solidified portion 14, whose rear end is in contact with the bottom 3C of the implantation hole 3A, can be held in the thickness direction, thereby preventing unnecessary movement of the hair bundle 12 in the thickness direction and contributing to ensuring and stabilizing the implantation strength.

[0039] The fixing portion 5B protrudes from the inner surface of the implantation hole 3B and is located on the front side of the solidified portion 24. The fixing portion 5B protrudes from the inner surface around the entire periphery of the implantation hole 3B and is located on the front side of the solidified portion 24. By positioning the fixing portion 5B on the front side of the solidified portion 24, the solidified portion 24, whose rear end is in contact with the bottom 3D of the implantation hole 3B, can be held in the thickness direction, thereby preventing unnecessary movement of the hair bundle 22 in the thickness direction and contributing to ensuring and stabilizing the implantation strength.

[0040] The toothbrush 1 having the above configuration is manufactured by subjecting the head portion 3 of the pre-molded body to a heat compression process in the thickness direction using, for example, metal press members P1 and P2, which are heated by a heater, as shown in Figure 3.

[0041] The press member P1 is positioned on the front side of the head portion 3 of the preform. The press member P1 is joined from the front side to the surface of the head portion 3 of the preform that faces the front. The press member P1 has a retaining hole 91 and a retaining hole 92 that penetrate in the thickness direction. The retaining hole 91 is formed in a position that faces the tufting hole 3A in the thickness direction when the press member P1 is positioned on the front side of the head portion 3 of the preform. Multiple bundled filaments 13 are pierced through the retaining hole 91 from the back side. The retaining hole 91 holds the multiple bundled filaments 13 from the radially outer side. The retaining hole 92 is formed in a position that faces the tufting hole 3B in the thickness direction when the press member P1 is positioned on the front side of the head portion 3 of the preform. Multiple bundled filaments 23 are pierced through the retaining hole 92 from the back side. The retaining hole 92 holds the multiple bundled filaments 23 from the radially outer side.

[0042] The pressing member P2 is disposed on the rear surface side of the head portion 3 of the preliminary compact. The pressing member P2 is joined to the surface of the head portion 3 of the preliminary compact facing the rear surface side from the rear surface side.

[0043] When the head portion 3 of the preform is heat-compressed in the thickness direction, the head portion 3 of the preform, press member P1, and press member P2 are arranged with the front side facing down and the back side facing up. The press member P1 is joined from the front side to the surface of the head portion 3 of the preform that faces the front side with the multiple bundled filaments 13 pierced through the holding holes 91, so that the solidified portion 14 is inserted into the tufting hole 3A and the solidified portion 24 is inserted into the tufting hole 3B.

[0044] Then, by applying pressure to the heated press members P1 and P2 in a direction that brings them closer to each other while they are heated, the resin that has been heated and compressed in the head portion 3 of the pre-molded body and melted flows into the tufting holes 3A and 3B, which have a low flow pressure, and is crimped.

[0045] As a result, as shown in Figure 2, in the tufting hole 3A, the fixing portion 5A is formed on the front side of the solidified portion 14. In the tufting hole 3B, the fixing portion 5B is formed on the front side of the solidified portion 24. By forming the fixing portion 5A in the tufting hole 3A and the fixing portion 5B in the tufting hole 3B, the toothbrush 1 is manufactured in which the bristle bundles 12, 22 are fixed to the head portion 3.

[0046] Fig. 4 (comparative example) is a partial cross-sectional view showing the head unit 3 in which the cross sections of the solidified portions 14, 24 are spherical. Fig. 5 is a partial cross-sectional view showing the head unit 3 in which the cross sections of the solidified portions 14, 24 are flattened. As shown in Fig. 4, when the cross sections of the solidified portions 14, 24 are spherical, a tangent line at the position where the front end of the solidified portion 14, 24 contacts the fixing portions 5A, 5B intersects with the inner surface of the fixing portions 5A, 5B at an angle θ1. On the other hand, as shown in Fig. 5, when the cross sections of the solidified portions 14, 24 are flattened, a tangent line at the position where the front end of the solidified portion 14, 24 contacts the fixing portions 5A, 5B intersects with the inner surface of the fixing portions 5A, 5B at an angle θ2.

[0047] When the cross section of the solidified portions 14, 24 is spherical, the angle θ1 is smaller than the angle θ2, so when a force acts on the hair bundles 12, 22 toward the front, slippage may occur at the interface between the back surface of the fixing portions 5A, 5B and the surface of the solidified portions 14, 24, reducing the hair implant strength.

[0048] In contrast, when the cross section is flat, the angle θ2 is larger than the angle θ1, so when a force acts on the front side of the hair bundles 12, 22, slippage is less likely to occur at the interface between the back side surface of the fixing parts 5A, 5B and the surface of the solidification parts 14, 24, making it easier to ensure the strength of the hair implantation.

[0049] 6 is a partial cross-sectional view of the head portion 3 after the thermal compression process along the width direction. As shown in Fig. 6, the solidified portion 14 after the thermal compression process has a flat shape with a maximum width dimension L11 greater than a maximum thickness dimension L12, as shown in Fig. 3, and the cross-sectional shape in the width direction is a substantially semicircular shape that bulges toward the rear side.

[0050] In the solidified portion 14, the distance from the thickness direction position where the widthwise distance is the maximum dimension L11 to the implanted surface 2 is defined as L31, and the distance from the thickness direction position where the maximum dimension L11 is defined as L32 to the surface 6 on the opposite side of the head portion 3 in the thickness direction from the implanted surface 2. If the distance L31 is longer than the distance L32, the solidified portion 14 will contact the inner surface of the implantation hole 3A on the back side of the central position in the thickness direction of the head portion 3. In this case, the distance from the thickness direction position where the maximum dimension L11 is defined as the maximum dimension L11 to the fixing portion 5A of the bristle bundle 12 will be longer, which may cause unstable fixation in the solidified portion 14.

[0051] Therefore, by making the distance L31 shorter than the distance L32, the distance from the thickness direction position where the hair bundle 12 has the maximum dimension L11 to the fixed portion 5A is shortened, thereby stabilizing the fixation in the solidification portion 14.

[0052] Similarly, as shown in Figure 3, the solidified portion 24 after the heating and compression process has a flat shape in which the maximum dimension L21 in the width direction is greater than the maximum dimension L22 in the thickness direction, and the cross-sectional shape in the width direction is an approximately semicircular shape that bulges toward the back side.

[0053] In the solidifying section 24, the distance from the thickness direction position where the widthwise distance is the maximum dimension L21 to the bristle implantation surface 2 is defined as L41, and the distance from the thickness direction position where this distance L41 is to the back surface 6 of the head section 3 is defined as L42. By making the distance L41 shorter than the distance L42, the distance from the thickness direction position where the widthwise distance is the maximum dimension L21 to the fixing section 5B of the bristle bundle 22 is shorter, and fixing in the solidifying section 24 can be stabilized.

[0054] Furthermore, if the distance from the position where the widthwise distance is maximum dimension L11 in the thickness direction of the solidified portion 14 to the position of the front end of the solidified portion 14 is defined as L51, and the distance from the position of the front end of the solidified portion 14 to the implantation surface 2 is defined as L52, it is preferable that the distance L52 is longer than the distance L51. By making the distance L52 longer than the distance L51, the position where the widthwise distance of the bristle bundle 12 is maximum dimension L11 is closer to the fixing portion 5A, and the resin crimped by the heat compression process can more easily come into contact with the solidified portion 14 from the front side. This increases the stability of the solidified portion 14 inside the implantation hole 3A, further stabilizing the implantation strength.

[0055] Similarly, if the distance from the position where the widthwise distance is maximum dimension L21 in the thickness direction of the solidified portion 24 to the position of the front end of the solidified portion 24 is L61, and the distance from the position of the front end of the solidified portion 24 to the implantation surface 2 is L62, it is preferable that the distance L62 is longer than the distance L61. By making the distance L62 longer than the distance L61, the position where the widthwise distance of the bristle bundle 22 is maximum dimension L21 is closer to the fixing portion 5B, and the resin crimped by the heat compression process can more easily come into contact with the solidified portion 24 from the front side. This increases the stability of the solidified portion 24 inside the implantation hole 3B, further stabilizing the implantation strength.

[0056] Furthermore, in the solidified portion 14, if the distance from the end position on the back side in the thickness direction to the surface 6 is L71, it is preferable that the distance L71 is longer than the distance L52. By making the distance L71 longer than the distance L52, the position of the bristle bundle 12 where the distance in the width direction is the maximum dimension L11 can be brought even closer to the fixed portion 5A.

[0057] Similarly, in the solidified portion 24, if the distance from the end position on the back side in the thickness direction to the surface 6 is L81, it is preferable that the distance L81 is longer than the distance L62. By making the distance L81 longer than the distance L62, the position of the bristle bundle 22 where the distance in the width direction is the maximum dimension L21 can be brought even closer to the fixed portion 5B.

[0058] The distances L51 and L61 are preferably 0 mm or more and 1.0 mm or less. The distances L32 and L42 are preferably 0.6 mm or more and 2.6 mm or less. The distances L52 and L62 are preferably 0.2 mm or more and 1.0 mm or less.

[0059] 2, in order to ensure the thicknesswise position of the solidified portions 14, 24, it is preferable that the thicknesswise positions of the bottom portions 3C, 3D in the implantation holes 3A, 3B differ depending on the maximum widthwise dimensions L11, L21 of the solidified portions 14, 24. Specifically, since a solidified portion 24 having a smaller maximum widthwise dimension L21 may have a smaller thicknesswise dimension than the solidified portion 14, it is preferable that the thicknesswise position of the bottom portion 3D be set closer to the front than the thicknesswise position of the bottom portion 3C depending on the ratio or difference between the maximum widthwise dimensions L11, L21. By setting the thicknesswise positions of the bottom portions 3C, 3D depending on the maximum widthwise dimensions L11, L21, it is possible to optimize the thicknesswise positions of the solidified portions 14, 24 where the widthwise distance is the maximum dimension L11, L21 and the positions of the fixing portions 5A, 5B.

[0060] The maximum dimension in the thickness direction of the head portion 3 is preferably 1.4 mm or more and 3.0 mm or less, and more preferably 1.6 mm or more and 2.7 mm or less. By setting the maximum dimension in the thickness direction of the head portion 3 to 1.4 mm or more and 3.0 mm or less, sufficient bristle implant strength can be ensured.

[0061] In the longitudinal direction, the ratio of the total area of ​​the tufting holes 3A and 3B to the head area from the tip of the head portion 3 to the position of the hole edge of the tufting hole 3B located at the rearmost end, indicated by the two-dot chain line, is preferably 55% or more. If the total area of ​​the tufting holes 3A and 3B to the head area is 55% or more, the amount of surface resin of the head portion 3 that can be used for crimping will be reduced, but even in this case, sufficient tufting strength can be ensured.

[0062] As described above, in the toothbrush 1 of this embodiment, the fixing parts 5A, 5B are provided on the front side of the solidified parts 14, 24 of the bristle bundles 12, 22 inserted into the bristle implantation holes 3A, 3B, and since the solidified parts 14, 24 have a flat shape in the cross section in the width direction, slippage is less likely to occur at the interface with the fixing parts 5A, 5B, and sufficient bristle implantation strength can be ensured.

[0063] Second Embodiment Next, a second embodiment of the toothbrush 1 will be described with reference to Fig. 7. In this figure, elements that are the same as those in the first embodiment shown in Figs. 1 to 6 are designated by the same reference numerals, and their description will be omitted.

[0064] Figure 7 is a cross-sectional view showing the head 3 of the toothbrush 1 according to the second embodiment. As shown in Figure 7, the head 3 has protrusions 7 and 8. Protrusions 7 are provided on the front side of the fixing part 5A. Protrusions 7 are inclined so that they extend toward the front as they move toward the inside of the tufting hole 3A. The tips of protrusions 7 contact the filaments 13 from the outside in the radial direction, at a position closer to the front than the tufting surface 2.

[0065] The protrusions 8 are provided on the front side of the fixing portion 5B. The protrusions 8 are inclined so that they extend toward the front side as they approach the inside of the tufting hole 3B. The tips of the protrusions 8 contact the filaments 23 from the outside in the radial direction at a position closer to the front than the tufting surface 2. The other configurations are the same as those of the first embodiment.

[0066] The above-mentioned protrusions 7 and 8 can be formed, for example, by making the diameters of the retaining holes 91 and 92 in the press member P1 larger than the diameter of the bundled filaments 13 and the diameter of the bundled filaments 23, or by providing recesses (e.g., chamfered shapes) corresponding to the shapes of the protrusions 7 and 8 at the rear side ends of the retaining holes 91 and 92.

[0067] In this embodiment, the protrusions 7 are provided on the front side of the fixing part 5A, and the contact area between the filament 13 and the protrusions 7 increases, thereby increasing the frictional force and making it difficult for the bristle bundle 12 to move in the thickness direction. Furthermore, even when the front end of the solidified part 14 is close to the implanted surface 2, the resin thickness at the time of crimping can be ensured, and therefore the implanted strength can be ensured.

[0068] Similarly, in this embodiment, since the protrusions 8 are provided on the front side of the fixing part 5B, the contact area between the filament 23 and the protrusions 8 increases, which increases the frictional force and makes it difficult for the bristle bundle 22 to move in the thickness direction. Furthermore, even if the front end of the solidified part 24 is close to the implanted surface 2, the resin thickness at the time of crimping can be ensured, so the implanted strength can be ensured.

[0069] If the protrusions 7, 8 protrude too far toward the front side, the movement of the bristle bundles 12, 22 in the brushing direction will be suppressed, affecting the feel of use. Therefore, the distance from the bristle implantation surface 2 to the front end of the protrusions 7, 8 is preferably 0.1 mm or more and 1.0 mm or less, and more preferably 0.2 mm or more and 0.5 mm or less.

[0070] Furthermore, if a large amount of resin flows into the protrusions 7, 8 formed during crimping in the heat compression process, there is a possibility that contact between the back side of the fixing parts 5A, 5B and the solidified parts 14, 24 will be insufficient on the back side of the flocked surface 2. For this reason, it is preferable that the ratio of the cross-sectional area of ​​each protrusion 7, 8 to the cross-sectional area of ​​the resin on the back side of the flocked surface 2, of the resin present inside in the width direction from the top of the width of the fixing parts 5A, 5B on the back side of the flocked surface 2 to the flocked surface 2, is 0.5:9.5 to 5:5.

[0071] In the toothbrush 1 of this embodiment, in addition to achieving the same effects and advantages as the first embodiment, the provision of protrusions 7 and 8 increases the contact area, thereby increasing the frictional force and ensuring better bristle strength.

[0072] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to these examples. The shapes and combinations of the components shown in the above examples are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention.

[0073] The present invention is applicable to toothbrushes.

[0074] REFERENCE SIGNS LIST 1...toothbrush, 2...bristle implantation surface, 3...head portion, 3A, 3B...bristle implantation holes, 4...handle portion, 5A, 5B...fixing portion, 6...surface, 7, 8...projection portion, 12, 22...bristle bundle, 13, 23...filament, 14, 24...solidification portion

Claims

a head portion having a bristle bundle formed by bundling a number of filaments; and a handle portion extending in the longitudinal direction, the head portion having a bristle bundle hole formed on the rear side of the bristle implantation surface located on the front side in the thickness direction, the bristle bundle being implanted therein; wherein when one or more bristle implantation holes having the same shape and size when viewed from the front are grouped together, the bristle bundle in at least one of the groups has a solidified portion at one end in the longitudinal direction where the filaments are melted and solidified, the head portion having a fixing portion protruding from the inner surface of the bristle implantation hole and located on the front side of the solidified portion, and wherein, in a cross section taken along the width direction in the direction in which the shorter distance is taken, the solidified portion has a maximum dimension in the width direction that is greater than the maximum dimension in the thickness direction.

2. The toothbrush according to claim 1, wherein the cross-sectional shape of the solidified portion is a generally semicircular shape that bulges toward the rear side.

3. The toothbrush according to claim 1 or 2, further comprising a protrusion provided on the front side of the fixing part, extending towards the front side as it approaches the inside of the bristle hole, and having a tip that contacts the filament at a position closer to the front side than the bristle implantation surface.

4. A toothbrush as described in claim 1 or 2, wherein the distance from the thickness direction position of the solidified portion which is at its maximum dimension in the width direction to the bristle surface is shorter than the distance from the thickness direction position of the solidified portion which is at its maximum dimension in the width direction to the surface of the head portion opposite the bristle surface in the thickness direction.

5. The toothbrush according to claim 1 or 2, wherein the position of the bottom of the bristle hole in the thickness direction varies depending on the maximum dimension of the solidified portion in the width direction.

6. The toothbrush according to claim 1 or 2, wherein the head portion has a maximum dimension in the thickness direction of 1.4 mm or more and 3.0 mm or less.

7. The toothbrush according to claim 1 or 2, wherein the ratio of the total area of ​​the tufting holes to the head area from the tip of the head portion to the position of the edge of the tufting hole located at the rearmost end in the longitudinal direction is 55% or more.

Images