toothbrush

Abstract

The present invention provides a toothbrush that provides excellent handleability within the oral cavity even when a brush molding having a fitting structure is in use. This toothbrush is equipped with: a handle body which is formed of a hard resin; and a brush molding (20) which is formed of a soft resin and provided to the leading end side of the handle body. The handle body has an insertion part provided so as to protrude on the leading end side thereof. The brush molding includes a head base body (21) and filaments (23) that protrude from the front face side of the head base body. The head base body has formed therein an insertion hole (22) in which the insertion part is inserted and fitted. The brush molding is configured such that: the maximum distance between the base end of the filaments and the back-side surface (21c) of the head base body is 2.0-4.5 mm; and, when the maximum length of the head base body in the insertion direction is defined as L1, and when the maximum length of the insertion hole in the insertion direction is defined as L2, the proportion, represented by L2 / L1, of the maximum length of the insertion hole to the maximum length of the head base body is 0.30-0.70.

Description

[Technical field]

[0001] The present invention relates to a toothbrush. This application claims priority based on Japanese Patent Application No. 2019-231982, filed on December 23, 2019, the contents of which are incorporated herein by reference. [Background technology]

[0002] An integrally molded toothbrush has been proposed, which is manufactured using only an injection molding machine (for example, Patent Document 1). Since the filament and head base (or head) are molded as a single unit, an integrally molded toothbrush does not require the procurement of filament material or a bristle implantation machine, and has the advantage of being cheaper to manufacture than bristle implanted toothbrushes.

[0003] As an integrally molded toothbrush for cleaning, it has been proposed to separately mold a head part (brush molded body) having a filament and an insertion hole, and a handle part having an insertion part at one end, and then fit them together to provide an integrally molded toothbrush (for example, Patent Documents 2 and 3). In the toothbrushes described in Patent Documents 2 and 3, the head part is replaceable by the user, so it is expected to save resources by allowing only the head part to be discarded and the handle to be reused. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 61-207233 [Patent Document 2] China Utility Model No. 204561298 [Patent Document 3] China Patent Publication No. 107041792 Summary of the Invention [Problem to be solved by the invention]

[0005] From the viewpoint of maneuverability within the oral cavity, particularly maneuverability for the back teeth, it is desirable for the toothbrush head to be thin. However, in the conventional toothbrushes described above, it is necessary to form an insertion hole, which inevitably reduces the ratio of the resin to the thickness of the head. Therefore, when the brush molded body is made thinner, the thickness formed by the resin becomes even thinner, and as a result, the resin fluidity during molding decreases. If the resin fluidity during molding decreases, the moldability of the filament decreases. Therefore, it is possible to make the insertion part of the handle thinner, but in this case, the resin strength of the insertion part and the strength of the mold for molding the insertion part cannot be ensured.

[0006] The present invention has been made in consideration of the above points, and has an object to provide a toothbrush that is excellent in intraoral operability even when a brush molding with a fitting structure is used. [Means for solving the problem]

[0007] According to a first aspect of the present invention, there is provided a toothbrush comprising a handle body formed of a hard resin and a brush molding formed of a soft resin and provided on the tip side of the handle body, wherein the handle body has an insertion portion protruding toward the tip side, the brush molding has a head base portion and a filament protruding toward the front side of the head base, the head base portion has an insertion hole into which the insertion portion is inserted and fitted, and the brush molding has a maximum distance between the base end of the filament and the back surface of the head base portion of 2.0 mm or more and 4.5 mm or less, and wherein, when the maximum length of the head base portion in the insertion direction is L1 and the maximum length of the insertion hole in the insertion direction is L2, the ratio of the maximum length of the insertion hole to the maximum length of the head base portion, expressed as L2 / L1, is 0.30 or more and 0.70 or less.

[0008] In addition, in the toothbrush according to one embodiment of the present invention, the distance between the tip end of the insertion hole and the tip end of the head base, represented by L1-L2, is characterized in that it is 5 mm or more and 15 mm or less.

[0009] Furthermore, in the toothbrush according to one aspect of the present invention described above, the head base portion has a thin-walled region in which the tip side of the back surface gradually slopes toward the front side and becomes gradually thinner as it approaches the tip side, and the maximum length of the thin-walled region in the insertion direction is 40% or more of the maximum length of the head base portion in the insertion direction.

[0010] Furthermore, in the toothbrush according to one aspect of the present invention described above, the insertion portion has one or more inwardly concave recesses on an edge in a direction perpendicular to the protruding direction of the filament, and the head base portion has a protrusion at a position that fits into the recess when the insertion portion is inserted into the insertion hole.

[0011] Furthermore, in the toothbrush according to one embodiment of the present invention described above, the recess is provided on the widthwise edge perpendicular to the protruding direction of the filament and the insertion direction, and is located on the rear end side within a range of 30% to 70% of the maximum length of the insertion part in the insertion direction, starting from the tip of the insertion part in the insertion direction.

[0012] In the toothbrush according to the above aspect of the present invention, the soft resin is polyurethane.

[0013] In addition, in the toothbrush according to one aspect of the present invention described above, the position of the base end of the filament in the protruding direction of the filament is the same as the position of the parting surface of the brush molding. Effect of the Invention

[0014] According to the present invention, even when a brush molded body having an interlocking structure is used, a toothbrush that is excellent in intraoral operability can be provided. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a front view of a toothbrush according to an embodiment of the present invention. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. 2 is an enlarged front view of the insertion section 12. [Diagram 5] FIG. 2 is an enlarged side view of the insertion portion 12. [Figure 6] FIG. 2 is a front view of the brush molding 20. [Figure 7] 7 is a cross-sectional view taken along the line AA in FIG. 6. [Figure 8] FIG. 2 is a view of the brush molding 20 as viewed from the rear end side. [Figure 9] 2 is a cross-sectional view taken along a plane parallel to the upper surface 21a and including the insertion hole 22. FIG. [Figure 10] 1 is a cross-sectional view showing a simplified example of a mold MD for molding a brush molded body 20. FIG. [Figure 11] FIG. 2 is a cross-sectional view showing a simplified view of the mold MD before clamping. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of a toothbrush of the present invention will be described with reference to Figs. 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 idea of ​​the present invention. In addition, in the following drawings, the scale and number of each structure are different from the actual structure in order to make each configuration easier to understand.

[0017] Fig. 1 is a front view of a toothbrush 1 according to this embodiment. Fig. 2 is a side view of the toothbrush 1. The toothbrush 1 comprises a rod-shaped handle body 10 and a brush molding 20. The handle body 10 and the brush molding 20 are separate members. The brush molding 20 can be detachably attached (inserted) to the handle body 10.

[0018] In this embodiment, the front side is the side from which a filament 23, which will be described later, protrudes in the normal direction (hereinafter simply referred to as the normal direction) of the upper surface 21a (details of which will be described later) of the brush molding 20. The front side is the length direction of the handle portion 11, and the direction in which the handle body 10 is inserted into the brush molding 20 (hereinafter simply referred to as the insertion direction) is perpendicular to the normal direction. The direction perpendicular to the normal direction and the insertion direction is the width direction of the brush molding 20 (hereinafter simply referred to as the width direction).

[0019] FIG. 3 is a front view of the handle body 10. FIG. 3, the handle body 10 includes a rod-shaped handle portion 11 and an insertion portion 12 provided at the tip of the handle portion 11 and protruding toward the tip side in the longitudinal direction of the handle portion 11. In the toothbrush 1, the insertion portion 12 of the handle body 10 is inserted into a brush molding 20, which will be described later, so that the brush molding 20 is attached by covering the insertion portion 12.

[0020] In this embodiment, the handle portion 11 has a front view shape that gradually narrows from the tip side to the rear end, then extends at a constant width, then gradually widens, and then narrows again in a curved manner. The front view shape of the handle portion 11 has a substantially semicircular rear end.

[0021] As shown in Fig. 2, the handle portion 11 has a side view shape that extends from the tip side to the rear end side with a constant width, and then gradually widens to a maximum thickness that becomes a finger rest. The side view shape of the handle portion 11 changes in a curved shape so that the width gradually narrows from the finger rest part of maximum thickness toward the rear end side. The side view shape of the handle portion 11 has a substantially semicircular rear end.

[0022] In the present invention, the shape of the handle portion is not limited to the shape in this example, and can be set appropriately taking into consideration strength, operability, design, and the like. The dimensions of the handle portion 11 are not particularly limited and can be set appropriately. For example, the length of the handle portion 11 can be 100 to 200 mm.

[0023] The insertion part 12 is the part covered by the brush molded body 20 when the brush molded body 20 is attached to the handle body 10. The rear end of the insertion part 12 is the rear end position of the brush molded body 20 when the brush molded body 20 is attached to the handle body 10.

[0024] FIG. 4 is an enlarged front view of the insertion part 12. FIG. 5 is an enlarged side view of the insertion part 12. As shown in FIG. 4, the insertion part 12 has a base part 13 provided on the tip side of the handle part 11 and a tip part 14 provided at the tip of the base part 13. As shown in FIG. 5, the base part 13 and the tip part 14 have steps with respect to the handle part 11 on both the front side and the back side, and are formed with the same thickness that is thinner than the handle part 11.

[0025] The base part 13 is substantially rectangular in plan view. The base part 13 has steps with respect to the handle part 11 on both sides in the width direction, and is formed with a width L13 that is narrower than the maximum width L11 on the tip side of the handle part 11 (L13 < L11). The tip part 14 is substantially elliptical in plan view with the width direction as the major axis direction. The tip part 14 has a shape in which the side edges are notched with a straight line parallel to the insertion direction of the insertion part 12 on both sides in the width direction of the substantially elliptical shape. The tip part 14 has steps with respect to the base part 13 on both sides in the width direction, and is formed with a width L14 that is narrower than the width L13 of the base part 13.

[0026] The insertion part 12 has a depression 15 at substantially the center in the insertion direction, between the base part 13 and the tip part 14. The depressions 15 are provided on both sides in the width direction. The depression 15 has an arc shape with the center of the arc on the outer side in the width direction and concave on the inner side. The shortest distance L15 between the depressions 15 is shorter than the width L13 of the base part 13 and the width L14 of the tip part 14. As an example, the amount of depression of the depression 15 with respect to the edge defining the width L14 at the tip part 14 is 1 mm.

[0027] The position of the apex of the inwardly recessed recess 15 is preferably located in a range of 30% to 70% of the maximum length L12 of the insertion direction of the insertion portion 12 on the rear end side, starting from the tip end in the insertion direction of the insertion portion 12, and more preferably in a range of 40% to 60%. Furthermore, the entire area forming the recess 15 is preferably located in a range of 30% to 70% of the maximum length L12, and more preferably in a range of 40% to 60% (details will be described later). The maximum depth of the recess 15 in the width direction (the recess amount relative to the edge that defines the width L13 in the base 13) is preferably 0.5 mm to 1.8 mm, and more preferably 0.8 mm to 1.5 mm (details will be described later).

[0028] By devising a shape for the recess 15, it is possible to strengthen the fit between the brush molding 20 and the handle body 10. Although an arc shape is exemplified as the shape of the recess 15, it may be substantially rectangular, and a so-called barb may be provided on the tip side of the insertion part of the recess 15. A barb is a shape in which the recess direction of the recess 15 is not perpendicular toward the inside in the width direction, but is recessed obliquely toward the handle part 11 side. Further, the recesses 15 are exemplified as having an inwardly concave shape on both sides in the width direction of the insertion portion 12, but may have an outwardly convex shape.

[0029] The handle body 10 is made of a hard resin. As an example of the hard resin, a resin having a flexural modulus (JIS K7171) of 1500 MPa or more and 3000 MPa or less can be exemplified. Specific examples include polypropylene resin (PP), polyacetal resin (POM), polyester resin (PCTA), polyethylene terephthalate copolymer (PETG), and high density polyethylene (HDPE). Among these, PP, which is a general-purpose resin, is preferable in terms of cost.

[0030] Fig. 6 is a front view of the brush molded body 20. Fig. 7 is a cross-sectional view taken along line AA in Fig. 6. As shown in Fig. 6 and Fig. 7, the brush molded body 20 includes a head base part 21 having a substantially rectangular shape when viewed from the front, and a plurality of filaments 23 provided on the front surface of the head base part 21.

[0031] The filament 23 has a generally columnar shape protruding toward the front side from the upper surface 21a of the head base portion 21. The base end side of the filament 23 has a generally triangular prism shape with a generally triangular cross section, and the tip side extends from the generally triangular prism and tapers into a triangular pyramid shape.

[0032] The tapered shape of the filament 23 may have one or more change points of the taper angle, with change points provided at two locations, 0 to 2 mm and 4 to 8 mm from the tip, being examples of such a shape. The filament 23 may also be in a quadrangular pyramid shape. Even if the filament 23 is in a quadrangular pyramid shape, it may have one or more change points of the taper angle, and may have two change points at 0 to 2 mm and 4 to 8 mm from the tip. By adopting this configuration, it is possible to improve the cleaning property while ensuring the moldability.

[0033] The filaments 23 are arranged in a plurality of rows along the width direction of the brush molding 20 such that adjacent rows in the insertion direction are shifted by half a pitch. That is, the filaments 23 are arranged in a staggered manner.

[0034] FIG. 8 is a view of the brush molding 20 as viewed from the rear end side. As shown in FIG. 8, the filament 23 is high in the center in the width direction and low on the outer sides in the width direction. The filament 23 may be flat with no height difference in the width direction, or may be low at the center and high at the outside in the width direction, but a dome shape with a high center in the width direction can improve the cleaning ability of the oral cavity. The height difference of the filament is preferably 0.5 to 3.0 mm, and more preferably 0.5 to 2.0 mm. The region in which the central filament 23 is located (the width across the width of the filament base end (the maximum width of the width-wise region in which the filament base end is located)) is preferably 20 to 45% of the width-wise length occupied by the entire filament, and more preferably 25 to 40%. The arrangement pitch of the filaments is preferably 0.5 to 1.5 mm in both the length direction and the width direction, and more preferably 0.8 to 1.2 mm.

[0035] The maximum length of the filament 23 is preferably 7 mm or more and 15 mm or less, and more preferably 9 mm or more and 13 mm or less. If the maximum length of the filament 23 is less than 7 mm, the ability to clean the oral cavity may decrease. If the maximum length of the filament 23 exceeds 15 mm, the releasability when the brush molded body 20 is molded by injection molding decreases. By setting the maximum length of the filament 23 to 7 mm or more and 15 mm or less, the ability to clean the oral cavity and the releasability during molding can be ensured.

[0036] The cross-sectional area of ​​the base end of the filament 23 is 0.8 mm 2 Preferably, it is less than 0.6 mm. 2 More preferably, it is 0.4 mm or less. 2 It is even more preferable that: The cross-sectional area of ​​the base end of the filament 23 is 0.8 mm 2 If the cross-sectional area of ​​the base end of the filament 23 exceeds 0.8 mm, the filament 23 becomes difficult to bend, and the cleaning performance of the gaps between teeth and the neck of the teeth may decrease. 2 By satisfying the following conditions, it is possible to ensure the ability to clean gaps between teeth, around the neck of teeth, etc.

[0037] The ratio of the total cross-sectional area of ​​the base ends of the multiple filaments 23 to the area of ​​the top surface 21a of the head base portion 21 is preferably 10% or more and 50% or less. If the ratio of the total cross-sectional area of ​​the base ends of the filaments 23 is less than 10%, the ability to clean the oral cavity may decrease. If the ratio of the total cross-sectional area of ​​the base ends of the filaments 23 exceeds 50%, the releasability when molding the brush molded body 20 by injection molding decreases. By setting the ratio of the total cross-sectional area of ​​the base ends of the filaments 23 to 10% or more and 50% or less, it is possible to ensure the ability to clean the oral cavity and the releasability during molding.

[0038] The cross-sectional shape of the filament 23 can be selected from a substantially triangular shape, a substantially polygonal shape such as a substantially square shape, a substantially circular shape, a substantially star shape, a substantially spatula shape, etc. In addition to a tapered shape tapered from the tip, the filament 23 may be configured to extend straight or may be tapered from the base end.

[0039] The top surface 21a of the head base portion 21 is a plane parallel to the width direction and the insertion direction. The top surface 21a is flush with the base end of the filament 23 in the protruding direction of the filament 23. As shown in Fig. 6 and Fig. 8, the top surface 21a forms the outer contour (outermost periphery) of the head base portion 21. In other words, the top surface 21a is a parting surface when the brush molded body 20 is injection molded.

[0040] The head base 21 has an insertion hole 22 that extends in the insertion direction and opens to an end face 21b on the rear end side. Fig. 9 is a cross-sectional view of a plane parallel to the top face 21a including the insertion hole 22. As shown in Fig. 9, the insertion hole 22 has a first portion 33 that opens to the end face 21b and a second portion 34 that is located deeper than the first portion 33. As shown in Fig. 7, the first portion 33 and the second portion 34 are formed to have the same thickness that is thinner than the head base 21.

[0041] The head base portion 21 has a protrusion 35 located approximately in the center of the insertion hole 22 in the insertion direction, between the first portion 33 and the second portion 34. The protrusions 35 are provided on both sides in the width direction of the insertion hole 22. The protrusions 35 are provided at positions that will fit into the recesses 15 when the insertion part 12 is inserted into the insertion hole 22. The protrusions 35 are in an arc shape that has an arc center on the outside in the width direction and is convex inward.

[0042] The maximum width L21 of the rear end side (end face 21b) of the head base portion 21 is approximately the same as the maximum width L11 of the handle portion 11 on the tip side. The shape of the insertion hole 22 in a front view is substantially the same as the shape of the insertion portion 12 in a front view. The width L33 of the first portion 33 is a length into which the base portion 13 of the insertion portion 12 can be inserted, and is substantially the same as the maximum width L13 of the base portion 13. The width L34 of the second portion 34 is a length into which the tip portion 14 of the insertion portion 12 can be inserted, and is substantially the same as the maximum width L14 of the tip portion 14.

[0043] The shortest distance L35 between the protrusions 35 is shorter than the width L33 of the first portion 33 and the width L34 of the second portion 34. The shortest distance L35 between the protrusions 35 is a length that allows the tip portion 14 and the recess 15 of the insertion portion 12 to be inserted, and is approximately the same as the shortest distance L15 between the recesses 15. The amount by which the protrusions 35 protrude inward in the width direction from the second portion 34 is, for example, 1 mm. The amount by which the protrusions 35 protrude from the second portion 34 is the amount of undercut when the mold (slide core) that molds the insertion hole 22 is pulled toward the rear end during injection molding of the brush molded body 20. If the handle body 10 has a barb on the tip side of the insertion portion of the recess 15, the engagement between the brush molding 20 and the handle body 10 can be made even stronger.

[0044] Returning to FIG. 7, the maximum distance (maximum thickness) T between the upper surface 21a of the head base 21 and the second surface 21c on the back side is preferably 2.0 mm or more and 4.5 mm or less. If the maximum distance T is less than 2.0 mm, the gap between the upper surface 21a and the surface of the insertion hole 22 on the upper surface 21a side, or the gap between the second surface 21c and the surface of the insertion hole 22 on the second surface 21c side, becomes small, and the fluidity of the molten resin decreases during molding, so that there is a possibility that the resin will not be filled. If the maximum distance T exceeds 4.5 mm, there is a possibility that the operability when the brush molding body 20 is inserted into the oral cavity will decrease. By setting the maximum distance T to 2.0 mm or more and 4.5 mm or less, it is possible to ensure the filling property of the resin and the operability when the brush molding body 20 is inserted into the oral cavity.

[0045] The widthwise distance (maximum length) of the head base 21 is not particularly limited, but is, for example, 10 to 16 mm. In particular, when the maximum widthwise length of the head base 21 is 13 to 16 mm, the head portion can be made thin to ensure intraoral operability while still providing a wide head.

[0046] The height t1 of the insertion hole 22 is preferably 1.0 mm or more and 2.5 mm or less. The thickness (distance) t2 of the head base portion 21 between the upper surface 21a and the surface of the insertion hole 22 on the upper surface 21a side is preferably 0.5 mm or more and 2.0 mm or less. The thickness (distance) t3 of the head base portion 21 between the second surface 21c on the rear side of the head base portion 21 and the surface of the insertion hole 22 on the second surface 21c side is preferably 0.5 mm or more and 2.0 mm or less.

[0047] Furthermore, if the maximum length of the head base portion 21 in the insertion direction is L1 and the maximum length of the insertion hole 22 in the insertion direction is L2, the ratio of the maximum length L2 of the insertion hole 22 to the maximum length L1 of the head base portion 21, expressed as L2 / L1, is preferably 0.30 or more and 0.70 or less, more preferably 0.40 or more and 0.60 or less, and even more preferably 0.45 or more and 0.55 or less.

[0048] If the value represented by L2 / L1 is less than 0.30, the area where the insertion portion 12 made of hard resin does not exist becomes large, which may cause the front of the brush molding 20 to bend more easily and reduce the usability of the toothbrush 1. If L2 / L1 exceeds 0.70, the volume occupied by the mold (slide core) that forms the insertion hole 22 during molding becomes large and the resin flow is restricted, which reduces the moldability of the filament 23. By setting the value represented by L2 / L1 to be 0.30 or more and 0.70 or less, it is possible to suppress a decrease in the moldability of the filament 23 while suppressing a decrease in the usability of the toothbrush 1.

[0049] In addition, the distance between the tip end of the insertion hole 22 and the tip end of the head base 21, represented by L1-L2, is preferably 5 mm or more and 15 mm or less, and more preferably 8 mm or more and 12 mm or less. If the value represented by L1-L2 is less than 5 mm, the resin flow is restricted, and the moldability of the filament 23 is reduced. If the value represented by L1-L2 exceeds 15 mm, the region where the insertion part 12 formed of the hard resin does not exist becomes large, so that the front of the brush molding body 20 is easily bent, and usability may be reduced. By setting the value represented by L1-L2 to 5 mm or more and 15 mm or less, it is possible to suppress the deterioration of the moldability of the filament 23 while suppressing the deterioration of the usability of the toothbrush 1.

[0050] When the maximum thickness T of the head base part 21 in the brush molding body 20 is reduced, it is possible to reduce the height t1, thickness t2, and t3 described above. However, when the thicknesses t2 and t3 are reduced, it is necessary to consider the fluidity of the soft resin during molding. In particular, when the thickness t2 is reduced, it has a large effect on the moldability of the filament 23. Specifically, when the thickness t2 is reduced, the cross-sectional area perpendicular to the insertion direction of the flow path of the soft resin toward the filament 23 in the mold for molding the brush molding body 20 becomes smaller, and molding defects such as shorts are more likely to occur, and the moldability of the filament 23 decreases. Therefore, the minimum distance S between the base end of the filament 23 located at the most distal end side and the back surface of the head base part 21 is preferably 1.5 mm or more and 3.0 mm or less.

[0051] The minimum thickness of the head base part 21 is preferably 1.0 to 2.5 mm. By setting the minimum thickness of the head base part 21 within this range, it is possible to improve intraoral operability while reducing the discomfort felt when the tip of the head part comes into contact with intraoral tissue.

[0052] Therefore, in this embodiment, in order to improve the fluidity of the soft resin even when the thickness t2 is small, a certain region is provided on the tip side of the insertion hole 22 in the brush molding body 20 where the insertion hole 22 (i.e., the mold (slide core) for molding the insertion hole 22) is not present. This allows the resin to flow into the region in the mold where the slide core for molding the insertion hole 22 is not present during molding, thereby suppressing the impairment of resin fluidity caused by the presence of the slide core and improving the moldability of the filament 23. Note that the gate position for filling the resin into the mold can be selected, for example, at the tip of the head base portion 21, but is not particularly limited. The gate position can be, for example, disposed on the back surface or rear end of the head base portion 21, which can avoid problems such as the gate mark leaving behind after cutting the gate damaging oral tissue.

[0053] Furthermore, as described above, by providing the depression 15 in the insertion part 12, the slide core is formed with a recess 35M (see FIG. 10) in the normal direction for molding the protrusion 35 that fits into the recess 15. This recess 35M constitutes a flow path for resin flow connecting the back side to the front side of the slide core where the insertion hole 22 is formed in the mold during molding. Normally, the resin flow is restricted in the area occupied by the slide core, but by ensuring the recess 35M for molding the protrusion 35 as a flow path for resin flow, the moldability of the filament 23 is improved.

[0054] As described above, the depression 15 (protrusion 35) is located in a range of 30% to 70%, preferably 40% to 60%, of the maximum length L12 of the insertion direction of the insertion part 12 from the tip of the insertion part 12 in the insertion direction toward the rear end side, starting from the tip of the insertion part 12 in the insertion direction, so that the recess 35M of the slide core for molding the protrusion 35 is located near the center of the insertion direction of the insertion hole 22. If the position of the protrusion 35 is outside the above range in the insertion direction of the insertion part 12, there is a possibility that the resin flow during molding will be biased and the filament 23 will not be molded uniformly. By positioning the protrusion 35 within the above range in the insertion direction of the insertion part 12, the bias of the resin flow is suppressed and the filament 23 can be molded uniformly.

[0055] In addition, the maximum depth of the recess 15 (protrusion 35) in the width direction (recess amount relative to the base 13) is preferably 0.5 mm or more and 1.8 mm or less (more preferably 0.8 mm or more and 1.5 mm or less). If the maximum depth of the recess 15 in the width direction is less than 0.5 mm, the recess 35M is formed only on the edge of the slide core, so that a significant improvement in resin fluidity cannot be expected, and the engagement with the protrusion 35 is weak, and the brush molding 20 may fall off when the toothbrush 1 is used. If the maximum depth of the recess 15 in the width direction exceeds 1.8 mm, the engagement with the protrusion 35 (amount of undercut) becomes large, and the insertion part 12 may break when demolded. By setting the maximum depth of the recess 15 in the width direction to 0.5 mm or more and 1.8 mm or less, it is possible to improve the resin fluidity, prevent the brush molding 20 from falling off, and prevent the insertion part 12 from breaking. If the handle body 10 has a barb on the tip side of the insertion portion of the recess 15, the engagement between the brush molding 20 and the handle body 10 can be made even stronger.

[0056] The head base 21 has a thin region 21d that gradually becomes thinner at the tip side of the back surface 21c and gradually slopes toward the front side as it approaches the tip side. As shown in Fig. 7, the maximum length L3 of the thin region 21d in the insertion direction is preferably 40% or more, and more preferably 50% or more, of the maximum length L1 of the head base 21 in the insertion direction.

[0057] By making the maximum length L3 of the thin region 21d 40% or more of the maximum length L1 of the head base 21, the volume of the back side of the brush molding 20 can be reduced, so that the molten resin can flow preferentially toward the upper surface 21a during molding, improving the moldability of the filament 23. This effect is more prominent when the gate position is disposed at the tip of the head base 21. If the maximum length L3 of the thin region 21d is less than 40% of the maximum length L1 of the head base 21, the improvement in moldability may be weak. In addition, in order to prevent damage to the soft resin when the insertion part 12 is fitted into the insertion hole 22 and when the toothbrush 1 is used, the distance t3 from the back surface 21c of the head base 21 to the back surface of the insertion part 12 needs to be 0.5 mm or more.

[0058] As the soft resin constituting the brush molded body 20, various elastomers can be used, but polyurethane is preferable. Since polyurethane tends to have a higher tensile strength than other elastomers such as styrene-based or polyester-based elastomers, by using polyurethane as a soft resin, mechanical strength can be ensured even if the material is thin, and breakage can be suppressed when the insertion portion 12 is engaged with the insertion hole 22 and when the toothbrush 1 is in use.

[0059] Polyurethane contains 0.01 to 1.0 wt% (mass%) of any one of saturated / unsaturated hydrocarbons with C10 or more, higher alcohols, fatty acid amides, fatty acid esters, low molecular weight polyethylene, polyethylene glycol (PEG), fatty acid metal salts, long-chain fatty acids, fatty acid glycerin, and silicone, or a combination of these, and functions as a lubricant and release agent.

[0060] Moreover, compared to the other elastomers listed above, polyurethane has a wider range of hardness options, and it is possible to select the resin hardness taking into consideration its usability (for example, bending of the tip of the brush molded body) according to the thickness of the brush molded body 20. The hardness of polyurethane is preferably shore 90A or more and 70D or less. If the polyurethane has a hardness softer than Shore 90A, it will be easily deformed when formed with a thin wall, and the fitting will be weak, making the brush molding 20 more likely to fall off when the toothbrush 1 is used. If the polyurethane has a hardness harder than Shore 70D, there is a possibility that pain will be caused when the tip of the head base part 21 hits oral tissue if the back surface of the head base part 21 is inclined. By setting the hardness of the polyurethane to Shore 90A or more and 70D or less, it is possible to prevent the brush molding 20 from falling off when the toothbrush 1 is used, or to prevent pain from being caused when the tip of the head base part 21 hits oral tissue.

[0061] As the polyurethane, it is preferable to use an ether-based polyurethane from the viewpoint of ensuring water resistance and antibacterial properties.

[0062] Fig. 10 is a cross-sectional view showing, in a simplified manner, an example of a mold MD for molding the brush molded body 20. Fig. 11 is a cross-sectional view showing, in a simplified manner, the mold MD before clamping. The mold MD includes a first mold MD1 and a second mold MD2 that move relatively in the opening / closing direction (the up-down direction in FIG. 10). The first mold MD1 and the second mold MD2 are clamped together with a parting surface PL, which is flush with the upper surface 21a, as a joining surface.

[0063] The first mold MD1 is attached to, for example, the fixed side of an injection molding machine, and is filled with molten resin from the injection molding machine. The second mold MD2 is attached to, for example, the movable side of the injection molding machine, and is moved in the opening and closing direction relative to the first mold MD1, whereby the mold MD is also opened and closed.

[0064] The first mold MD1 has a molding surface 21aM where the upper surface 21a is molded when the first mold MD1 is clamped and joined to the second mold MD2, and a cavity 23M where the filament 23 is molded.

[0065] The second mold MD2 has a cavity 21M in which the head base 21 is molded when the second mold MD2 is clamped and joined to the first mold MD1, a gate portion G that opens at the tip end of the cavity 21M and introduces molten resin into the cavity 21M, and an abutment surface 21eM that is provided at the end face 21b in the insertion direction and perpendicular to the insertion direction. For example, a side gate method is used as the gate portion G, but a pinpoint gate method or a tunnel gate method may also be used. The abutment surface 21eM extends in the second mold MD2 in a direction away from the PL surface from a position where the back surface of the head base 21 is molded.

[0066] The second mold MD is provided with a slide core SL. The slide core SL has a core portion 22M in which the insertion hole 22 is formed, and a molding surface 21bM perpendicular to the direction in which the core portion 22M protrudes and is inserted. As shown in FIG. 11, the molding surface 21bM is separated from the abutment surface 21eM before the mold is clamped. When the first mold MD1 and the second mold MD2 are clamped, the slide core SL is positioned at a position where a part of the molding surface 21bM abuts against the abutment surface 21eM and the core portion 22M is inserted into the cavity 21M, as shown in FIG. 10. Of the molding surface 21bM, a region facing the cavity 21M without abutting against the abutment surface 21eM is a region for molding the end surface 21b. Furthermore, when the first mold MD1 and the second mold MD2 are opened, the slide core SL moves in a direction in which the core portion 22M separates from the cavity 21M so that the core portion 22M does not interfere with the release of the molded brush molding body 20. The movement direction of the slide core SL is preferably horizontal to avoid unexpected movement due to its own weight.

[0067] The above-mentioned configuration of the mold MD has been exemplified by forming the insertion hole 22 for the brush molding 20 by the slide core SL, but it is also possible to select a manufacturing method in which the handle body 10 is inserted into the mold MD and the brush molding 20 is secondarily molded. In that case, it is disadvantageous to make the brush molding 20 and the handle body 10 detachable, but the post-process of fitting the handle body 10 and the brush molding 20 together after molding can be omitted.

[0068] Since the rear surface on the tip side of the slide core SL comes close to the inclined rear surface of the head base part 21, by performing R chamfering or C chamfering, it becomes possible to prevent damage to the head base part 21 (resin tearing) when the slide core SL is removed or fitted into the insertion part 12 of the handle body 10. The dimension of the R chamfering or C chamfering is preferably 1.5 mm or more, and more preferably 3.0 mm or more.

[0069] In the above-mentioned mold MD, when the first mold MD1 and the second mold MD2 are clamped together, the molten resin introduced into the cavity 21M from the gate portion G can be made to flow preferentially toward the upper surface 21a due to the fact that a sufficient volume is secured toward the tip side of the core portion 22M of the cavity 21M and that the back side of the cavity 21M is inclined and thin at the tip side, and the molten resin introduced into the tip side of the cavity 21M can be made to flow preferentially toward the upper surface 21a side, and the molten resin can be filled into the cavity 23M with sufficient filling pressure.

[0070] In addition, in the cavity 21M, the molten resin introduced to the back side of the core portion 22M can flow to the front side using the recess 35M formed near the center of the core portion 22M in the insertion direction as a flow path, so that the filament 23 can be uniformly molded while suppressing bias in the resin flow in the insertion direction.

[0071] As described above, in the toothbrush 1 of this embodiment, even if the thickness of the head base portion 21 is reduced to 2.0 mm or more and 4.5 mm or less by using the brush molding 20 with an interlocking structure, it is possible to mold the brush molding 20 without reducing the resin fluidity, thereby providing a toothbrush 1 with excellent intraoral operability.

[0072] [Example] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following examples and can be modified appropriately without departing from the gist of the present invention.

[0073] (Examples 1 to 7, Comparative Examples 1 to 2) According to the specifications shown in [Table 1], the toothbrushes differed in at least one of the following: maximum distance T between the base end of the filament and the back surface of the head base, minimum distance S between the base end of the filament and the back surface of the head base, height t1 of the insertion hole, maximum length L1 of the head base, maximum length L2 of the insertion hole, ratio L2 / L1 of maximum length L2 of the insertion hole to maximum length L1 of the head base, difference L1-L2 between maximum length L1 of the head base and maximum length L2 of the insertion hole, maximum length L3 of the thin region, ratio L3 / L1 of maximum length L3 to maximum length L1, presence or absence of a recess, position LC of the recess with respect to the tip of the insertion portion as the base point, and ratio LC / L12 (LC / L2) of the position of the recess to maximum length L12 (maximum length L2 of the insertion hole) of the insertion portion 12 in the insertion direction. The resin constituting each sample was polyurethane.

[0074] [Evaluation method] Each sample of Examples 1 to 7 and Comparative Examples 1 and 2 was evaluated in terms of moldability of the filaments, resistance to bending of the brush molded body, and ease of brushing the entire oral cavity.

[0075] (1) Evaluation method for filament formability Five brush moldings molded under the same conditions were evaluated according to the following criteria. 5 points: No defects in appearance were observed. 4 points: The tip of the filament is deformed when released from the mold (because sufficient pressure was not applied, it bends due to external force when releasing from the mold). 3 points: The thickness of the filament tip is thinner than the design value. 2 points: The filament length is shorter than the design value (all filaments are more than half the total length). 1 point: The filament length is shorter than the design value (some filaments are less than half the total length). The five evaluation points were then averaged and rated on the following four-point scale. ◎(double circle mark): 4.5 or higher, 5.0 or lower. ○ (circle mark): 3.5 or more, but less than 4.5 points. △ (triangle mark): 2.5 or more, less than 3.5 points. ×(cross mark): Less than 2.5 points.

[0076] (2) Method for evaluating the bending resistance of brush moldings A sensory evaluation was conducted by 10 expert panelists, and the difficulty of bending the brush body forward when brushing was evaluated according to the following criteria. 5 points: Very difficult to bend. 4 points: Somewhat difficult to bend. 3 points: Neither. 2 points: Slightly easy to bend. 1: Very easy to bend. The evaluation scores of the 10 expert panelists were then averaged and rated on the following four-point scale. ◎: 4.5 or higher, 5.0 or lower. ○: 3.5 or more, but less than 4.5 points. △: 2.5 or more, but less than 3.5 points. ×: Less than 2.5 points.

[0077] (3) Method for evaluating ease of brushing the entire oral cavity A sensory evaluation was conducted by 10 expert panelists who rated the ease of brushing the entire oral cavity (with particular emphasis on the ease of brushing the molars) using the following criteria. 5 points: Very easy to polish. 4 points: Somewhat easy to polish. 3 points: Neither. 2 points: Somewhat difficult to polish. 1 point: Very difficult to polish. The evaluation scores of the 10 expert panelists were then averaged and rated on the following four-point scale. ◎: 4.5 or higher, 5.0 or lower. ○: 3.5 or more, but less than 4.5 points. △: 2.5 or more, but less than 3.5 points. ×: Less than 2.5 points.

[0078] [Table 1]

[0079] As shown in Table 1, for Examples 1 to 7 in which the maximum distance T between the base end of the filament and the back of the head base was 2.0 mm or more and 4.5 mm or less, and the ratio L2 / L1, which is the ratio of the maximum length L2 of the insertion hole to the maximum length L1 of the head base, was 0.30 or more and 0.70 or less, good results were obtained in terms of the moldability of the filament, the resistance to bending of the brush molded body, and the ease of brushing the entire oral cavity.

[0080] In contrast, in Comparative Example 1, in which the ratio L2 / L1 of the maximum length L2 of the insertion hole to the maximum length L1 of the head base was less than 0.30, good results were not obtained in terms of the resistance to bending of the brush molding. Also, in Comparative Example 2, in which the ratio L2 / L1 of the maximum length L2 of the insertion hole to the maximum length L1 of the head base exceeded 0.70, good results were not obtained in terms of the moldability of the filament.

[0081] Furthermore, in Examples 4 and 5, in which the ratio L3 / L1, which is the ratio of the maximum length L3 of the thin-walled region to the maximum length L1 of the head base portion, was less than 40%, results in terms of the formability of the filament and the ease of brushing the entire oral cavity were not as good as those in Example 1.

[0082] In addition, in Example 6, in which the center position LC of the depression based on the tip of the insertion portion was less than 3 mm and the ratio LC / L12 (LC / L2), which is the ratio of the position LC of the depression to the maximum length L12 of the insertion portion 12 in the insertion direction (maximum length L2 of the insertion hole), was less than 30%, and in Example 7, in which the center position LC of the depression based on the tip of the insertion portion was more than 7 mm and the ratio LC / L12 (LC / L2), which is the ratio of the position LC of the depression to the maximum length L12 of the insertion portion 12 in the insertion direction (maximum length L2 of the insertion hole), was 70% or more, the results in terms of filament moldability were not as good as those in Example 1.

[0083] In addition, for comparison example 1, in which the difference between the maximum length L1 of the head base and the maximum length L2 of the insertion hole, represented by L1-L2, exceeds 15 mm, not only were good results not obtained in terms of the resistance of the brush molding to bending, but also results as good as those for example 1 were not obtained in terms of the ease of brushing the entire oral cavity.

[0084] Although the preferred embodiment of the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to the 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.

[0085] For example, in the above embodiment, a configuration was exemplified in which the upper surface 21a forming the outer contour (outermost circumference) of the head base portion 21 and the base end of the filament 23 are flush with each other, and the filament 23 protrudes from the upper surface 21a, but this configuration is not limited to this. For example, a base portion may be provided on the upper surface 21a, which is located inside the outer contour of the head base portion 21 and protrudes from the upper surface 21a with a certain thickness, and the filament 23 may protrude from the upper surface of the base portion instead of the upper surface 21a (the upper surface of the base portion and the base end of the filament 23 are flush with each other). In this case, the brush molding body 20 becomes thicker by the thickness of the base portion, so it is preferable that the upper surface 21a, which becomes the parting surface PL, and the base end of the filament 23 are flush with each other. When a base portion is not provided, the fluidity of the resin is lower than when a base portion is provided, and the effect of the present invention becomes more pronounced.

[0086] In the above embodiment, the handle body 10 is formed from a hard resin, but the present invention is not limited to this configuration, and may be configured such that, for example, a part of the handle body 10 (handle portion 10, etc.) is covered with a soft resin. When this configuration is adopted, the decorativeness and gripping properties can be improved. [Industrial Applicability]

[0087] The present invention is applicable to toothbrushes. [Explanation of symbols]

[0088] REFERENCE SIGNS LIST 1...toothbrush, 10...handle body, 11...handle portion, 12...insertion portion, 15...recess, 20...brush molding body, 21...head base portion, 21a...upper surface (parting surface), 21c...rear surface, 21d...thin region, 22...insertion hole, 23...filament, 35...projection

Claims

1. A handle body formed of hard resin; a brush body formed of soft resin and provided on a tip side of the handle body, The handle body has an insertion portion protruding from a tip end side, The brush molding has a head base and a filament protruding from a front side of the head base, the head base portion has an insertion hole into which the insertion portion is inserted and fitted, The brush molding has a maximum distance between the base end of the filament and the back surface of the head base portion of 2.0 mm or more and 4.5 mm or less, The maximum length of the head base portion in the insertion direction is L1, If the maximum length of the insertion hole in the insertion direction is L2, a ratio of a maximum length of the insertion hole to a maximum length of the head base portion, represented by L2 / L1, is 0.30 or more; the head base portion has a thin-walled region inclined toward the front side and gradually thinner as the tip side of the back surface approaches the tip side, a maximum length L3 of the thin-walled region in the insertion direction is 40% or more of a maximum length L1 of the head base portion in the insertion direction, a minimum distance S between the base end of the filament located at the most distal end side and the back surface of the head base portion is 1.5 mm or more and 3.0 mm or less; A toothbrush characterized in that a gate mark is formed on the front end of the tip of the head base.

2. The distance between the tip end of the insertion hole and the tip end of the head base, represented by L1-L2, is 5 mm or more and 15 mm or less.

2. The toothbrush of claim 1.

3. The insertion portion has at least one recess that is recessed inward on an edge in a direction perpendicular to a protruding direction of the filament, the head base portion has a protrusion at a position where the protrusion fits into the recess when the insertion portion is inserted into the insertion hole; 3. The toothbrush according to claim 1 or 2.

4. The recess is provided on an edge in a width direction perpendicular to a protruding direction of the filament and the insertion direction, and is located on a rear end side in a range of 30% to 70% of a maximum length of the insertion part in the insertion direction, starting from a tip end of the insertion part in the insertion direction.

4. The toothbrush of claim 3.

5. The soft resin is polyurethane.

5. A toothbrush according to any one of claims 1 to 4.

6. With respect to the protruding direction of the filament, the position of the base end of the filament is the same as the position of the parting surface of the brush molding.

6. A toothbrush according to any one of claims 1 to 5.

7. The minimum thickness of the head base is 1.0 to 2.5 mm.

7. A toothbrush according to any one of claims 1 to 6.

8. A thickness t2 of the head base portion between the upper surface of the front side of the head base portion and the surface of the front side of the insertion hole is 0.5 mm or more and 2.0 mm or less.

8. A toothbrush according to any one of claims 1 to 7.

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