Brush-shaped body and toothbrush

Abstract

This invention provides a brush-shaped body that can simultaneously suppress molding defects and maintain fit strength even when the Shore hardness is A90 or higher. The brush-shaped body includes: a brush head base portion formed of soft resin; and a plurality of monofilaments protruding from the front side of the head base portion in the thickness direction. The head base portion includes: a fitting hole extending in the length direction and opening on one side in the length direction; and fitting portions formed by a protrusion protruding into the fitting hole in the width direction or a recess recessing from the fitting hole in the width direction, disposed on both sides in the width direction. The thickness dimension of the brush head base is 3.0 mm or more and 4.5 mm or less; the Shore hardness of the soft resin is A90 or more and A100 or less, or D40 or more and D70 or less; and the distance between the front end and the position where the width dimension of the fitting hole begins to decrease from the front end on the other side of the length direction is 50% or more relative to the length dimension of the fitting hole.

Description

Technical Field

[0001] This utility model relates to a brush-shaped body and a toothbrush.

[0002] This application claims priority based on Japanese Patent Application No. 2022-209664, filed in Japan on December 27, 2022, the contents of which are incorporated herein by reference. Background Technology

[0003] A one-piece toothbrush is proposed, which can be manufactured using only an injection molding machine. The one-piece toothbrush integrally forms the monofilament with the brush head base (or brush head), thus eliminating the need for monofilament material ordering and tufting machines, and has the advantage of being cheaper to manufacture compared to tufted toothbrushes.

[0004] In toothbrushes with monofilaments formed of soft resin, a method is often used to fix the handle and brush body together by providing a recess on one side and a protrusion on the other side, both of which are made of hard resin. Methods for manufacturing toothbrushes combining materials with such different properties include integral molding, gluing, and assembly. However, from the viewpoint of productivity and cost, most toothbrushes use a method of separately manufacturing the handle and brush body and then assembling them (back-fitting toothbrush). Patent Document 1 discloses a shape in which a protrusion protruding towards the brush head is provided in a form that allows the brush head to be inserted into the brush body, thereby fixing the handle and brush body together.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2020-62196

[0008] Technical problem to be solved by the utility model

[0009] In a back-fitting toothbrush, the brush body is first shaped using a sliding core mold, and then the handle is inserted into the inside of the brush body to fit it in. Therefore, a recess is usually provided in the handle, and a protrusion is provided on the inner wall of the brush body.

[0010] Therefore, during the forming of brush molded parts, the resulting undercut shape, which requires forced demolding using a sliding mold core, often leads to poor forming (curling) on ​​the front side of the protrusion. This poor forming results in the following problems: reduced fit between the brush molded part and the shank, and an increased risk of the brush molded part detaching during use.

[0011] The brush-molded body disclosed in Patent Document 1 has a shape that generates forced demolding, but the above-mentioned problem is solved by making the resin forming the brush-molded body have a low hardness of A20 to A80 on the Shore hardness scale. In other words, in the technology disclosed in Patent Document 1, when the Shore hardness is A90 or higher, it is impossible to solve the molding defects caused by forced demolding. Utility Model Content

[0012] This invention was made with the above considerations in mind, and its purpose is to provide a brush-shaped body and a toothbrush that can simultaneously suppress poor forming and maintain fitting strength when the Shore hardness is A90 or higher.

[0013] Technical means for solving technical problems

[0014] The present invention has the following technical solution.

[0015] [1] A brush-shaped body, characterized in that the brush-shaped body comprises: a brush head base portion, the brush head base portion being formed of a soft resin, and

[0016] Multiple monofilaments protrude from the support surface located on the front side in the thickness direction of the head base portion.

[0017] The brush head base portion has: a fitting hole extending in a length direction orthogonal to the thickness direction and opening on one side of that length direction; and

[0018] The fitting portion is formed by a protrusion that protrudes into the fitting hole in the width direction orthogonal to the thickness direction and the length direction, or a recess that is recessed from the fitting hole in the width direction, and is provided on both sides of the width direction;

[0019] The maximum dimension in the thickness direction of the brush head base portion is 3.0 mm or more and 4.5 mm or less; the Shore hardness of the soft resin is A90 or more and A100 or less, or D40 or more and D70 or less; the distance between the width direction dimension of the fitting hole and the front end of the position where the width direction dimension begins to decrease from the front end on the other side of the length direction is 50% or more relative to the maximum dimension in the length direction of the fitting hole.

[0020] [2] According to the brush-shaped body described in [1], the total length of the fitting portion in the front view is more than 10% and less than 30% of the length of the entire circumference of the fitting hole.

[0021] [3] According to the brush-shaped body described in [1] or [2], the maximum dimension in the thickness direction of the fitting portion is 2.5 mm or less.

[0022] [4] According to any one of [1] to [3], in the region where the fitting portion is located in the length direction, the thickness of the brush head base portion on the front side in the thickness direction relative to the fitting hole, and the thickness of the brush head base portion on the back side in the thickness direction opposite to the front side relative to the fitting hole are 0.5 mm or more and 1.5 mm or less, respectively.

[0023] [5] According to any one of [1] to [4], the dimension in the width direction of the fitting hole located on the front end side relative to the fitting portion gradually decreases as it moves toward the front end side, and the maximum dimension in the width direction of the fitting hole located on the front end side relative to the fitting portion is at least 2.0 mm different from the dimension in the width direction at a position 1 mm away from the front end on one side in the length direction.

[0024] [6] According to any one of [1] to [5], the dimension in the thickness direction of the fitting hole located on the front end side relative to the fitting portion gradually decreases as it moves toward the front end side, and the maximum dimension in the thickness direction of the fitting hole located on the front end side relative to the fitting portion is 0.5 mm or more different from the dimension in the thickness direction at a position 1 mm away from the front end on one side in the length direction from the front end.

[0025] [7] According to any one of [1] to [6], the fitting portion is formed by the protrusion, and in a frontal view, the fitting portion has: a first curved portion, curved into an arc shape that connects with the fitting hole at the front end side, and

[0026] The second curved portion is curved into an arc shape that connects to the fitting hole on one side of the length direction, and the radius of the first curved portion is greater than the radius of the second curved portion.

[0027] [8] According to any one of [1] to [7], the brush head base has a gate mark on the front end side, the fitting portion is formed by the protrusion, and if in the region where the fitting portion is located in the length direction, the cross-sectional area of ​​the head base containing the fitting hole at the first position in the length direction with the smallest dimension in the width direction of the fitting hole is set as A1, and the cross-sectional area of ​​the fitting hole at the first position is set as A2, and in the region closer to the front end side than the fitting portion, the cross-sectional area of ​​the head base containing the head base at the first position with the smallest dimension in the width direction of the fitting hole is set as A2, and the cross-sectional area of ​​the head base containing the head base at the first position with the smallest dimension in the width direction of the fitting hole is set as A2, then in the region closer to the front end side of the head base, the cross-sectional area of ​​the head base containing the head base with the largest dimension in the width direction of the fitting hole is set as A2, then the cross-sectional area of ​​the head base containing the head base at the first position in the length direction with the smallest dimension in the width direction of the fitting hole is set as A2, then the cross-sectional area of ​​the head base containing ... If the cross-sectional area of ​​the head base portion containing the fitting hole at the second position in the degree direction is set as B1, and the cross-sectional area of ​​the fitting hole at the second position is set as B2, and if, in the region closer to the front end side than the fitting portion, the cross-sectional area of ​​the head base portion containing the fitting hole at the third position in the length direction where the width dimension of the fitting hole is the smallest is set as C1, and the cross-sectional area of ​​the fitting hole at the third position is set as C2, then the value represented by B1 / B2-A1 / A2 is 0.15 or less, and the value represented by B1 / B2-C1 / C2 is 0.10 or more.

[0028] [9] A toothbrush, characterized in that it comprises: a brush-shaped body as described in any one of [1] to [8], and a handle body formed of hard resin, having a fitting protrusion that can be attached to or detached from the fitting hole of the brush-shaped body.

[0029]

[10] A toothbrush, characterized in that it comprises: a brush-shaped body as described in any one of [1] to [8], and a handle body having a fitting protrusion that fits into the fitting hole of the brush-shaped body, wherein the brush-shaped body and the handle body are integrally formed.

[0030] Effects of the utility model

[0031] In this invention, even when the Shore hardness is A90 or higher, it is possible to both suppress poor forming and maintain fitting strength. Attached Figure Description

[0032] Figure 1 This is a front view of the brush-shaped body 20 and the toothbrush 1 according to an embodiment of the present invention.

[0033] Figure 2 This is a side view of the brush-shaped body 20 and the toothbrush 1.

[0034] Figure 3 This is the front view of the handle 10.

[0035] Figure 4 This is a magnified front view of the fitting protrusion 12.

[0036] Figure 5 This is a magnified side view of the fitting protrusion 12.

[0037] Figure 6 This is the main view of the brush-shaped body 20.

[0038] Figure 7 yes Figure 6 AA section diagram.

[0039] Figure 8 yes Figure 6 BB cross-section diagram.

[0040] Figure 9 yes Figure 8 CC section diagram.

[0041] Figure 10 This is a simplified cross-sectional view of an example of a mold MD that forms a brush-shaped body 20.

[0042] Figure 11 This is an external 3D view of the SL2 chip. Detailed Implementation

[0043] The following is for reference Figures 1 to 11 The embodiments of the brush-shaped body and the toothbrush of this utility model will be described.

[0044] Furthermore, the following embodiments represent one aspect of the present invention and do not limit the present invention; modifications can be made arbitrarily within the scope of the technical concept of the present invention. Additionally, in the following drawings, for ease of understanding of the structures, the scale, quantity, etc., of each construction differ from the actual construction.

[0045] Figure 1 This is a front view of the brush-shaped body 20 and the toothbrush 1 of this embodiment. Figure 2 This is a side view of the brush-shaped body 20 and the toothbrush 1. The toothbrush 1 has a rod-shaped handle 10 and a brush-shaped body 20. The handle 10 and the brush-shaped body 20 are separate parts. The brush-shaped body 20 can be detachably installed (inserted) into the handle 10. The brush-shaped body 20 is made of soft resin. The handle 10 is made of hard resin.

[0046] Furthermore, in this embodiment, the front side refers to the side where the monofilament 23 protrudes in the thickness direction (hereinafter simply referred to as the thickness direction) of the support surface 21a (described in detail later) of the brush forming body 20. Figure 2(The upper side of the brush forming body 20). In the thickness direction of the brush forming body 20, the side opposite to the front side is appropriately referred to as the back side. In addition, the length direction of the handle 10 (hereinafter simply referred to as the length direction) and the direction in which the brush forming body 20 is inserted into the handle 10 (hereinafter simply referred to as the insertion direction) are orthogonal to the above-mentioned normal direction. In the length direction, the side on which the handle 10 is mounted on the brush forming body 20 is referred to as the rear end side (one side in the length direction), and the side opposite to the rear end side is appropriately referred to as the front end side (the other side in the length direction). In addition, the direction orthogonal to the above-mentioned normal direction and insertion direction is the width direction of the brush forming body 20 (hereinafter simply referred to as the width direction). In this embodiment, the long axis direction refers to the direction in which the monofilament 23 extends, which is a direction parallel to the above-mentioned normal direction.

[0047] Figure 3 This is the front view of the handle 10.

[0048] like Figure 3 As shown, the handle 10 has a rod-shaped grip portion 11 and a fitting protrusion 12 protruding from the front end of the grip portion 11 in the longitudinal direction. In the toothbrush 1, the brush forming body 20 is covered and mounted on the fitting protrusion 12 by inserting the fitting protrusion 12 of the handle 10 into the brush forming body 20 described later.

[0049] The handle 10 is formed of a rigid resin. As an example of a rigid resin, a resin with a flexural modulus (JISK7171) of 1500 MPa or more and 3000 MPa or less can be cited. Specifically, examples include polypropylene resin (PP), polyacetal resin (POM), polybutylene terephthalate (PBT), polyester resin (PCTA), polyethylene terephthalate copolymer (PETG), and high-density polyethylene (HDPE). Among these, PP, as a general-purpose resin, is preferred considering cost, while POM and PBT are more preferred to ensure the strength of the interlocking protrusion 12.

[0050] The shape of the handle portion 11 in this embodiment changes in a curved manner from the front view, gradually narrowing in width from the front end to the rear end, then extending at a constant width, and then gradually widening in width before narrowing again. The rear end of the handle portion 11 in the front view is approximately semi-circular.

[0051] like Figure 2 As shown, the side view shape of the grip portion 11 extends with a constant width from the front end to the rear end, and then gradually widens until it reaches its maximum thickness, which is the finger contact portion. The side view shape of the grip portion 11 changes in a curved manner, with its width gradually narrowing from the finger contact portion with the maximum thickness towards the rear end. The rear end of the side view shape of the grip portion 11 is approximately semi-circular.

[0052] Furthermore, in this invention, the shape of the handle portion 11 is not limited to the shape in this example, and can be appropriately set considering strength, operability, appearance design, etc.

[0053] The size of the grip portion 11 is not particularly limited and can be set appropriately. For example, the length of the grip portion 11 can be 100 mm or more. For example, the length of the grip portion 11 can be 200 mm or less.

[0054] The fitting protrusion 12 is the portion covered by the brush forming body 20 when the brush forming body 20 is mounted on the handle body 10. The rear end of the fitting protrusion 12 is the rear end position of the brush forming body 20 when the brush forming body 20 is mounted on the handle body 10.

[0055] Figure 4 This is a magnified front view of the fitting protrusion 12. Figure 5 This is a magnified side view of the fitting protrusion 12.

[0056] like Figure 4 and Figure 5 As shown, the fitting protrusion 12 has a base 13 provided on the front end side of the handle portion 11, a front end portion 14 provided at the front end of the base 13, and a recess 15. The front end portion 14 is located on the front end side compared to the recess 15.

[0057] Recesses 15 are provided on both sides in the width direction. The two recesses 15 on both sides in the width direction are at the same position in the length direction. The recesses 15 are arc-shaped with an arc center on the outer side in the width direction and concave inward. The recesses 15 are symmetrically arranged with respect to the width direction line.

[0058] The base 13 and the front end portion 14 have steps on both sides of the front and back sides relative to the handle portion 11 in the thickness direction. That is, the thickness dimension of the base 13 and the front end portion 14 is smaller than the front end of the handle portion 11. The base 13 and the front end portion 14 also have steps on both sides of the width direction relative to the handle portion 11. That is, the width dimension of the base 13 and the front end portion 14 is smaller than the front end of the handle portion 11.

[0059] The width dimension of the base 13 is constant at the position relative to the rear end of the recess 15. The base 13 also includes the position where the recess 15 is formed, and is formed with a constant thickness that is thinner than the grip portion 11.

[0060] The width dimension of the front end portion 14 gradually decreases towards the front end side. The width profile of the front end portion 14 is formed by a curve bent into an arc shape. The thickness dimension of the front end portion 14 gradually decreases towards the front end side. The front face side surface of the front end portion 14 is coplanar with the front face side surface of the base 13. The back face side surface of the front end portion 14 curves towards the front end side from a position coplanar with the back face side surface of the base 13 towards the front end side.

[0061] The front and side view shapes of the fitting protrusion 12 are roughly the same as those of the fitting hole 22 in the brush-formed body 20 (details will be described later).

[0062] Figure 6 This is the main view of the brush-shaped body 20. Figure 7 yes Figure 6 AA section diagram. Figure 8 yes Figure 6 The BB cross-section diagram in the image is the cross-section diagram at the first position.

[0063] like Figures 6 to 8 As shown, the brush-shaped body 20 has a brush head base portion 21 with a generally rectangular shape from the front view, and a plurality of monofilaments 23 disposed on the front side of the brush head base portion 21.

[0064] The monofilament 23 is a generally columnar shape protruding from the support surface 21a of the brush head base portion 21 towards the front side. The base end of the monofilament 23 is a generally triangular prism with a generally triangular cross-section, and the front end is a triangular pyramid extending from the generally triangular prism and gradually tapering. The monofilament 23 is configured to have a mixture of staggered and lattice arrangements. The staggered arrangement is that columns arranged along the width direction of the brush forming body 20 are staggered by half a spacing in the width direction between adjacent columns in the insertion direction, and multiple columns are arranged along the insertion direction. The lattice arrangement is that columns arranged along the width direction are spaced at the same distance between adjacent columns in the insertion direction.

[0065] The cross-sectional shape of the monofilament 23 can be approximately triangular, or it can be approximately quadrilateral, polygonal, circular, star-shaped, or shovel-shaped. Besides a tapered shape that tapers towards the front, the monofilament 23 can also be a straight-lined structure or a tapered shape that tapers towards the base. The triangular pyramid is a shape with its sides parallel to the demolding direction (thickness direction) and its apex directly above the center of the base. By adopting this shape, the machining time for the mold can be reduced, thus lowering manufacturing costs.

[0066] The brush head base 21 has a fitting hole 22, a base 24, a side wall 25, a bottom wall 26, a front end wall 27, and a fitting part 35.

[0067] The maximum thickness dimension of the brush head base portion 21 is preferably 3.0 mm or more and 4.5 mm or less. The lower limit is preferably 3.0 mm or more, more preferably 3.5 mm or more. The upper limit is preferably 4.5 mm or less, more preferably 4.0 mm or less.

[0068] By setting the preferred maximum size of the brush head base portion 21 within the range described above, the operability within the oral cavity can be improved.

[0069] The fitting hole 22 extends along the insertion direction and opens on the end face 21b on the rear end side (one side in the length direction). Figure 9 yes Figure 8 The CC section diagram in the image. Figure 9 As shown, the fitting hole 22 has a first portion 33 that opens at the end face 21b, and a second portion 34 located on the front end side relative to the first portion 33. Figure 7 As shown, the first part 33 and the second part 34 are configured to be spaced apart from the support surface 21a and the back surface 21c of the brush head base 21, respectively.

[0070] The first part 33, in its length direction, is located at the rear end side relative to the boundary (position K) between the second part 34 and the fitting portion 35. Position K is the position where the width direction, starting from the front end of the fitting hole 22 towards the rear end side, begins to decrease. The width direction dimension of the first part 33 relative to the fitting portion 35 on the rear end side remains constant. Figure 7 As shown, the thickness dimension of the first part 33 is constant.

[0071] The second part 34 is located on the front side relative to position K. The width dimension of the second part 34 gradually decreases as it moves towards the front side. The contours on both sides of the width direction of the second part 34 are formed by curves that are bent into arc shapes.

[0072] The thickness dimension of the second part 34 gradually decreases towards the front end. The front side surface of the second part 34 is coplanar with the front side surface of the first part 33. The back side surface of the second part 34 bends from a position coplanar with the back side surface of the first part 33 towards the front end and then towards the front side.

[0073] The shape of the fitting hole 22 from the front view and the shape of the fitting protrusion 12 in the handle 10 are roughly the same.

[0074] like Figure 8 As shown, the base 24 is located on the front side of the fitting hole 22. The base 24 has a support surface 21a with a protruding monofilament 23. The support surface 21a is a plane orthogonal to the thickness direction.

[0075] Sidewalls 25 are located on both sides of the fitting hole 22 in the width direction. Sidewalls 25 extend from both ends of the base 24 in the width direction toward the rear side. The sidewalls 25 are arranged at a constant interval in the width direction relative to the rear end side of position K. The interval in the width direction of the sidewalls 25 gradually decreases towards the front end side relative to position K.

[0076] The bottom wall 26 is located on the back side of the fitting hole 22. The bottom wall 26 connects the back-side ends of the side walls 25 to each other. The bottom wall 26 is disposed at a constant interval in the thickness direction from the base 24 on the rear-side relative to position K. The bottom wall 26 gradually extends towards the front side from the front-side relative to position K.

[0077] The front end wall 27 is located on the front end side of the fitting hole 22. The front end wall 27 connects the front end of the base 24, the front end of the bottom wall 26, and the front end of the side wall 25 to each other. The fitting hole 22 is formed by the base 24, the side wall 25, the bottom wall 26, and the front end wall 27.

[0078] like Figure 9 As shown, the fitting portion 35 is provided on both sides of the fitting hole 22 in the width direction. The fitting portion 35 is formed by a protrusion protruding in the width direction within the fitting hole 22. The fitting portion 35 has an arcuate shape that has an arcuate center on the outer side in the width direction in a frontal view and protrudes inward in the width direction. The fitting portion 35 has a first curved portion 35a and a second curved portion 35b.

[0079] The first curved portion 35a is curved into an arc shape that connects with the fitting hole 22 located on the front end side and formed by the inner surface of the sidewall 25. The first curved portion 35a is an arc shape that protrudes outward in the width direction. The second portion 34 of the fitting hole 22 intersects with the first curved portion 35a at position K.

[0080] If the maximum length dimension of the fitting hole 22 is set as L1, and the distance from the front end of the fitting hole 22 to position K facing the rear end is set as L2, then the ratio of distance L2 to the maximum dimension L1 is more than 50%. That is, position K is located at the center of the fitting hole 22 in the length direction or at the rear end side relative to the center.

[0081] The second curved portion 35b is curved into an arc shape that connects with the fitting hole 22 formed by the inner surface of the sidewall 25 on the rear end side. The second curved portion 35b is an arc shape that protrudes outward in the width direction. The radius of the first curved portion 35a is larger than the radius of the second curved portion 35b.

[0082] The fitting portion 35 is an arc shape that protrudes inward in the width direction when viewed from the front. Therefore, the tangent at the center of the length direction in the fitting portion 35 is parallel to the length direction. As it moves away from the center in the length direction, the angle of intersection of the tangent with respect to the length direction increases.

[0083] On the other hand, as the tangents connecting to the first bend 35a and the second bend 35b move further away from the center in the length direction, the angle of intersection of the tangents with respect to the length direction decreases. The radius of the first bend 35a is larger than the radius of the second bend 35b, therefore the perimeter of the first bend 35a is greater than the perimeter of the second bend 35b.

[0084] Therefore, compared with the second bending portion 35b, the area where the tangent crosses at a smaller angle relative to the length direction is larger in the first bending portion 35a.

[0085] When the fitting protrusion 12 in the handle 10 is inserted into the fitting hole 22 in the brush head base portion 21, the base portion 13 fits into the first portion 33, the front end portion 14 fits into the second portion 34, and the fitting portion 35 fits into the recess 15. Thus, the handle 10 and the brush head base portion 21 are integrated.

[0086] Various elastomers can be used as the soft resin constituting the brush-shaped body 20, but polyurethane is preferred.

[0087] Compared with other elastomers such as styrene-based and polyester-based elastomers, polyurethane tends to have high tensile strength. Therefore, by using polyurethane as a soft resin, mechanical strength can be ensured even if the wall is thin, and damage can be suppressed when the fitting protrusion 12 in the handle 10 fits into the fitting hole 22 and when the toothbrush 1 is used.

[0088] In polyurethane, 0.01 to 1.0 wt% (mass %) of any one or a combination of saturated / unsaturated hydrocarbons with C10 or higher, 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 glycerol, liquid paraffin, and organosilicon can be used as lubricants and release agents.

[0089] Figure 10 This is a simplified cross-sectional view of an example of a mold MD that forms a brush-shaped body 20.

[0090] Mold MD has opening and closing directions (in Figure 10 The first mold MD1 and the second mold MD2 move relative to each other in the vertical direction. The first mold MD1 and the second mold MD2 close together with the parting surface PL, which is coplanar with the support surface 21a, as the mating surface.

[0091] The first mold MD1 is installed on, for example, the fixed side of the injection molding machine, and molten resin is filled from the injection molding machine. The second mold MD2 is installed on, for example, the movable side of the injection molding machine, and the mold MD is opened and closed by moving relative to the first mold MD1 in the aforementioned opening and closing direction (the thickness direction of the brush-shaped body 20).

[0092] The first mold MD1 has a forming surface 21aM and a cavity 23M. The forming surface 21aM provides support surface 21a for forming when the mold is closed and engaged with the second mold MD2, and the cavity 23M provides monofilament 23 for forming.

[0093] The second mold MD2 has a cavity 21M, a gate G, and an abutment surface 21eM. The cavity 21M forms the brush head base portion 21 when the mold is closed and engaged with the first mold MD1. The gate G is open at the front end of the cavity 21M to allow molten resin to enter the cavity 21M. The abutment surface 21eM is positioned at the end face 21b in the insertion direction and is orthogonal to the insertion direction. The gate G can be a side gate, but a pin gate or tunnel gate can also be used. The abutment surface 21eM extends in the second mold MD2 from the back side of the formed brush head base portion 21 in a direction away from the PL surface.

[0094] A sliding mold core SL is provided in the second mold MD2. The sliding mold core SL has a main body SL1 and a core block SL2. The core block SL2 is fixed to the parting surface PL side of the main body SL1. The core block SL2 has a core 22M and a forming surface 21bM, the core 22M being formed for the fitting hole 22, and the forming surface 21bM protruding from the core 22M and orthogonal to the insertion direction. The area of ​​the main body SL1 that does not abut against the abutment surface 21eM but faces the cavity 21M constitutes the forming surface 21bM. Before mold closing, the forming surface 21bM separates from the abutment surface 21eM.

[0095] Figure 11 This is a 3D view of the SL2 chip.

[0096] like Figure 11 As shown, the core 22M has: a first core 33M forming a first portion 33, a second core 34M forming a second portion 34, and a third core 35M forming a fitting portion 35, wherein the third core 35M has a recessed portion.

[0097] When closing the first mold MD1 and the second mold MD2, as follows Figure 10As shown, the sliding mold core SL is positioned where a portion of the forming surface 21bM abuts against the abutment surface 21eM and the core 22M is inserted into the cavity 21M. The area of ​​the forming surface 21bM that does not abut against the abutment surface 21eM but faces the cavity 21M is the area of ​​the forming end face 21b. Furthermore, when the first mold MD1 and the second mold MD2 open, the core 22M of the sliding mold core SL moves in the direction of disengagement from the cavity 21M. Figure 10 The sliding core SL moves to the right side (hereinafter referred to as the release direction) so that the core 22M does not obstruct the demolding of the formed brush molded body 20. To avoid accidental movement due to its own weight, the movement direction of the sliding core SL is preferably horizontal.

[0098] In the aforementioned mold MD, molten resin introduced from the gate G into the cavity 21M while the first mold MD1 and the second mold MD2 are closed fill the cavity 21M and the cavity 23M simultaneously. The molten resin filling the cavities 21M and 23M solidifies by cooling inside the mold MD for a specified time, forming a brush molded body 20.

[0099] Then, the mold is opened by moving the second mold MD2 relative to the first mold MD1. In the initial stage of mold opening, the first mold MD1 and the second mold MD2 separate when the sliding mold core SL is not moving. When the first mold MD1 and the second mold MD2 separate when the sliding mold core SL is not moving, the monofilament 23 is demolded from the first mold MD1.

[0100] The first mold MD1 is demolded by the monofilament 23, and the second mold MD2 moves relative to the first mold MD1, thereby causing the core 22M of the sliding mold core SL to move from the cavity 21M in the disengagement direction.

[0101] At this time, the mating portion 35, which is undercut in the separation direction, is formed in the third core portion 35M with a recess. Therefore, for the core portion 22M, which is located on the front end side and overlaps with the mating portion 35 in the separation direction, so-called forced demolding is performed, which compresses the mating portion 35 and causes it to elastically deform while moving in the separation direction.

[0102] This forced demolding is performed by the core 22M during injection molding, and also when the fitting protrusion 12 inserted into the fitting hole 22 of the brush head base 21 is pulled out.

[0103] After the core 22M is detached by forced demolding, the brush-formed body 20 is demolded from the second mold MD2, and the gate on the front end side is cut off, thereby manufacturing a molded article with a gate mark on the front end.

[0104] When the hardness of the soft resin constituting the above-mentioned brush molded body 20 is low, the softness of the brush molded body 20 increases, thus making it easy to undergo reversible deformation and reducing the load during forced demolding.

[0105] From the viewpoint of reducing the load on the core block SL2 and the interlocking protrusion 12 in the handle 10 during forced demolding, the soft resin constituting the brush-shaped body 20 preferably has a Shore hardness of A90 or higher and A100 or lower, or a Shore hardness of D40 or higher and D70 or lower, more preferably a Shore hardness of A95 or higher and A100 or lower, or a Shore hardness of D50 or higher and D66 or lower.

[0106] If the Shore hardness of the soft resin is lower than the lower limit of the above range, the brush-formed body 20 may detach from the handle 10 inserted into the fitting protrusion 12 in the fitting hole 22 during brushing. If the Shore hardness of the soft resin is higher than the upper limit of the above range, the softness is insufficient, and the load during forced demolding increases.

[0107] By keeping the Shore hardness of the soft resin within the above-mentioned range, it is possible to suppress the brush-molded body 20 from detaching during brushing and reduce the load during forced demolding.

[0108] Furthermore, by ensuring that the distance L2 between the position K where the width of the fitting hole 22 begins to decrease from the front end to the rear end in the length direction is more than 50% relative to the maximum dimension L1 in the length direction of the fitting hole 22, the load during forced demolding can be reduced.

[0109] In this embodiment, the front end of the fitting hole 22 of the brush-shaped body 20 is blocked by the front end wall 27, while the rear end of the fitting hole 22 is open and has a flexible shape.

[0110] Therefore, when the ratio of distance L2 to the maximum size L1 is less than 50%, the load during forced demolding increases due to insufficient flexibility caused by proximity to the obscured front end.

[0111] In contrast, by positioning the forced demolding position K at the rear end where the opening of the fitting hole 22 is located, the brushed body 20 is made soft and easily reversibly deformed, thereby reducing the load during forced demolding.

[0112] Furthermore, when the fitting protrusion 12 of the handle 10, which is inserted into the fitting hole 22 in the brush head base 21, is inserted, the fitting protrusion 12 has a front end wall 27 made only of soft resin on the front end side. Therefore, during brushing, the brush head base 21 is prone to flexing in the thickness direction starting from the front end wall 27. Thus, if position K is located on the front end side, the fitting of the fitting part 35 and the recess 15 is easily disengaged and detached.

[0113] In this embodiment, for position K, which becomes the starting position for forced demolding, by setting the ratio of distance L2 to the maximum size L1 to 50% or more, preferably 60% or more, it is possible to suppress the brush-shaped body 20 from detaching from the handle 10 during brushing.

[0114] Furthermore, the larger the width of the brush head base portion 21, the softer the brush-shaped body 20 becomes and the easier it is to undergo reversible deformation, which can reduce the load during forced demolding. Therefore, the maximum width dimension of the brush head base portion 21 is preferably 9.0 mm or more, and more preferably 13 mm or more.

[0115] In a frontal view, the total length of the fitting portion 35, including the first curved portion 35a and the second curved portion 35b, is preferably 10% or more and 30% or less of the length of the entire circumference of the fitting hole 22, more preferably 15% or more and 25% or less.

[0116] If the total length of the fitting portion 35 is greater than 30% of the total circumference of the fitting hole 22, the proportion occupied by the fitting portion 35 increases, thus increasing the load during forced demolding. If the total length of the fitting portion 35 is less than 10% of the total circumference of the fitting hole 22, the brush-formed body 20 is prone to detachment during brushing.

[0117] Furthermore, in a frontal view, the total length of the fitting portion 35, including the first curved portion 35a and the second curved portion 35b, is preferably 70% or less of the maximum size L1 of the fitting hole 22, more preferably 40% or more and 60% or less.

[0118] If the total length of the fitting portion 35 is greater than 70% of the maximum size L1 of the fitting hole 22, the proportion occupied by the fitting portion 35 increases, thus increasing the load during forced demolding. If the total length of the fitting portion 35 is less than 40% of the maximum size L1 of the fitting hole 22, the brush-formed body 20 is prone to detachment during brushing.

[0119] Furthermore, the surface of the core 22M is typically not ground, thus tending to increase friction. Therefore, if the overall circumference length or maximum dimension L1 of the fitting hole 22 is too long, the load during forced demolding caused by friction between the brush-formed body 20 and the core 22M increases; if it is too short, trajectory jitter may occur when the core 22M is moved in the release direction, increasing the load during forced demolding. Therefore, the overall circumference length and maximum dimension L1 of the fitting hole 22 are preferably set considering the load caused by friction and the trajectory jitter of the core 22M.

[0120] The maximum dimension in the thickness direction of the fitting portion 35 is preferably 2.5 mm or less, more preferably 1.5 mm or more and 2.5 mm or less.

[0121] If the maximum dimension in the thickness direction of the fitting part 35 is greater than 2.5 mm, the load during forced demolding will increase.

[0122] If the maximum dimension in the thickness direction of the fitting part 35 is less than 1.5 mm, the brush-shaped body 20 may detach during brushing.

[0123] By setting the maximum dimension in the thickness direction of the fitting portion 35 to be more than 1.5 mm and less than 2.5 mm, it is possible to suppress the brush-formed body 20 from detaching during brushing and reduce the load during forced demolding.

[0124] In the region where the fitting portion 35 is located in the longitudinal direction, the thickness of the base 24, which is the thickness of the head base portion on the front side in the thickness direction compared to the fitting hole 22, and the thickness of the bottom wall 26, which is the thickness of the brush head base portion 21 on the back side compared to the fitting hole 22, are preferably 0.5 mm or more and 1.5 mm or less, respectively.

[0125] If the thickness exceeds 1.5mm, the flexibility will be insufficient, and the load during forced demolding will increase. If the thickness is less than 0.5mm, the molded body 20 may detach during brushing.

[0126] By setting the thicknesses to 0.5 mm or more and 1.5 mm or less respectively, it is possible to suppress the detachment of the brush-formed body 20 during brushing and reduce the load during forced demolding.

[0127] Compared to the fitting part 35, the width of the fitting hole 22 located on the front end side gradually decreases as it moves towards the front end side.

[0128] The width dimension of the fitting hole 22 gradually decreases towards the front end, thereby creating a shape with a draft angle that extends relative to the disengagement direction of the core 22M on both sides of the fitting hole 22 in the width direction. Therefore, even when the fitting hole 22 is longer than the fitting portion 35 located on the front end side, the core 22M can quickly separate from the brush head base portion 21 with a draft angle relative to the fitting portion 35 when moving towards the disengagement direction, reducing the demolding resistance of the core 22M.

[0129] Compared to the maximum dimension in the width direction of the fitting hole 22 located on the front end side of the fitting part 35, the difference between the dimension in the width direction at a position 1 mm away from the front end on one side in the length direction is preferably 2.0 mm or more, more preferably 2.5 mm or more, and even more preferably 3.0 mm or more.

[0130] If the difference in the above dimensions is less than 2.0 mm, the load during forced demolding will increase.

[0131] By setting the difference between the above dimensions to 2.0 mm or more, the load during forced demolding can be reduced.

[0132] Compared to the fitting part 35, the thickness dimension of the fitting hole 22 located on the front end side gradually decreases as it moves towards the front end side.

[0133] The thickness dimension of the fitting hole 22 gradually decreases as it moves toward the front end, so that the profile of the back side in the thickness direction of the fitting hole 22 becomes a shape with a draft angle that extends relative to the release direction of the core 22M.

[0134] Therefore, even when the fitting hole 22 is longer than that of the fitting part 35 located at the front end, the core 22M can quickly separate from the brush head base part 21 with a demolding slope that is located at the front end of the fitting part 35 when moving in the disengagement direction of the core 22M, thereby reducing the demolding resistance of the core 22M.

[0135] Compared to the maximum dimension in the thickness direction of the fitting hole 22 located on the front end side of the fitting portion 35, the difference between the dimension in the thickness direction at a position 1 mm away from the front end on one side in the length direction is preferably 0.5 mm or more, more preferably 0.75 mm or more, and even more preferably 1.0 mm or more.

[0136] If the difference in the above dimensions is less than 0.5mm, the load during forced demolding will increase.

[0137] As described above, when using the brush, the base portion 21 of the brush head is prone to flexing in the thickness direction starting from the front end wall 27, and the engagement between the fitting portion 35 and the recess 15 is easily disengaged and detached.

[0138] By setting the difference in the above dimensions to 0.5 mm or more, the front end of the fitting hole 22 is made thinner with the deflection starting point as the front end side, thereby preventing the brush-shaped body 20 from detaching from the handle body 10 during brushing.

[0139] Furthermore, it is preferable that, compared to the fitting portion 35, the area on the front end side having at least a fitting hole 22 with a thickness of 1.5 mm or less, or at least a brush head base portion 21 with a thickness of 3.5 mm or less.

[0140] Furthermore, as mentioned above, the radius of the first curved portion 35a is larger than the radius of the second curved portion 35b. Therefore, compared to the second curved portion 35b, the area where the tangent of the first curved portion 35a intersects the longitudinal direction at a smaller angle is larger. The longitudinal direction is the direction in which the core 22M disengages. Therefore, during forced demolding, the force applied by the core 22M to the first curved portion 35a generates vertical resistance in the first curved portion 35a, which becomes the resistance during forced demolding. The longitudinal (disengagement direction) component of the vertical resistance is greatest at the point where the tangent of the curved fitting portion 35 intersects the longitudinal direction at a 90° angle, and decreases as the angle decreases.

[0141] Therefore, in the first bend 35a, where the tangent has a smaller intersection angle with the length direction than the radius of the second bend 35b, the resistance of the fitting portion 35 caused by vertical resistance is reduced, which can reduce the load during forced demolding.

[0142] In the region where the fitting portion 35 is located along the length direction, the cross-sectional area of ​​the brush head base portion 21 containing the fitting hole 22 at the first position along the length direction, where the width dimension of the fitting hole 22 is the smallest, is set as A1. The cross-sectional area of ​​the fitting hole 22 at the first position is set as A2. The first position is the position along the length direction of the center of the arc in the protruding arc-shaped fitting portion 35.

[0143] In the region closer to the front end of the fitting portion 35, the cross-sectional area of ​​the brush head base portion 21 containing the fitting hole 22 at the second position in the length direction, where the width dimension of the fitting hole 22 is the largest, is set as B1. The cross-sectional area of ​​the fitting hole 22 at the second position is set as B2. The second position is position K.

[0144] In the region closer to the front end than the fitting portion 35, the cross-sectional area of ​​the brush head base portion 21 containing the fitting hole 22 at the third position in the length direction where the width dimension of the fitting hole 22 is the smallest is set as C1. The cross-sectional area of ​​the fitting hole 22 at the third position is set as C2. The third position is the position in the length direction 1 mm away from the front end from the front end of the fitting hole 22 towards the rear end.

[0145] Regarding the aforementioned cross-sectional areas A1, A2, B1, B2, C1, and C2, the value represented by B1 / B2-A1 / A2 is less than 0.15, and the value represented by B1 / B2-C1 / C2 is greater than 0.10.

[0146] If the value represented by B1 / B2-A1 / A2 is higher than 0.15, it means that the amount of the fitting part 35 protruding into the fitting hole 22 is too much, and the load during forced demolding is increased.

[0147] If the value represented by B1 / B2-C1 / C2 is less than 0.10, it means that the change in the fitting hole 22 from the second position to the first position is small, and the load during forced demolding is large.

[0148] Therefore, by setting the value represented by B1 / B2-A1 / A2 to below 0.15 and the value represented by B1 / B2-C1 / C2 to above 0.10, the load during forced demolding can be reduced.

[0149] Regarding the measurement of the fitting hole 22 of the brush-shaped body 20 described above, the desired shape is exposed by using a cutting tool such as a cutter or pliers from the front or back side while the handle body 10 is in the fitted state. Alternatively, X-ray CT or similar methods can be used for measurement. Furthermore, the front and side view shapes of the fitting hole 22 are approximately the same as the fitting protrusion 12 in the handle body 10, so the shape of the fitting protrusion 12 can also be used instead.

[0150] As explained above, in the brush-shaped body 20 and toothbrush 1 of this embodiment, when the Shore hardness is A90 or higher, the load during forced demolding can be reduced. Therefore, it can suppress molding defects such as curling and maintain the fitting strength by preventing the brush-shaped body 20 from detaching during brushing.

[0151] Example

[0152] The present invention will now be described in detail with reference to the embodiments shown, but the present invention is not limited to the embodiments shown below and can be implemented with appropriate modifications without departing from its spirit.

[0153] (Examples 1-11, Comparative Examples 1-3)

[0154] According to the specifications shown in [Table 1] and [Table 2], samples of brush-shaped bodies were fabricated using polyurethane resin. Regarding the samples of brush-shaped bodies, the head base and the fitting hole were both designed as rectangles in a frontal view. That is, samples of brush-shaped bodies were fabricated having a cubic head base and fitting hole with constant dimensions in both the width and thickness directions.

[0155] In the sample of the brush-formed body, one convex fitting part is arranged on each side in the width direction.

[0156] The toothbrush sample is formed by inserting the fitting protrusion of the handle into the sample of the brush-shaped body. The sample of the handle is made of polyacetal resin (POM).

[0157] For the sample of the brush-formed body, set the maximum dimension in the thickness direction to 4.0 mm and the maximum dimension in the width direction to 12.0 mm.

[0158] The width dimension of the fitting hole and the fitting protrusion is set to 8.0 mm.

[0159] The thickness dimension of the fitting hole and the fitting protrusion in the fitting part is set to 2.0 mm.

[0160] The maximum thickness dimensions of the base and the bottom wall are set to 1.0 mm.

[0161] Regarding the monofilament, the cross-section is set to a triangular pyramid shape, the filament height is set to 10.0mm, and in a frontal view, 10 filaments are arranged in a grid pattern in the width direction and 17 filaments in the length direction.

[0162] [Evaluation Method]

[0163] For each sample of Examples 1 to 11 and Comparative Examples 1 to 3, the evaluation was carried out according to the "formability of the fitting part" and the "ease of detachment of the brush-shaped body during use".

[0164] (1) Evaluation method of the formability of the fitting part

[0165] The cut surfaces of the interlocking portions in 100 samples of brush-formed bodies formed under the same forming conditions were evaluated according to the following criteria.

[0166] The presence or absence of defects in appearance is evaluated by visual observation, and the probability of occurrence of defects is calculated. The evaluation is carried out in the following 5 stages.

[0167] Regarding the evaluation results, ★, ◎, ○, and △ are marked as qualified (OK), and × is marked as unqualified (NG).

[0168] ★(star mark): 0%.

[0169] ◎(double circle mark): 1-4%.

[0170] ○ (circle mark): 5-6%.

[0171] △ (triangle mark): 7-10%.

[0172] × (cross mark): 11-100%.

[0173] (2) Evaluation method for the ease of detachment of brush-shaped objects during use

[0174] A panel of 10 experts conducted a sensory evaluation, visually observing the gap between the brush body and the fitting protrusions on the handle during use, and evaluating the feeling of the gap according to the following criteria.

[0175] 5 points: I can't feel it at all.

[0176] 4 points: Almost imperceptible.

[0177] 3 points: Cannot be determined.

[0178] 2 points: I can feel it slightly.

[0179] 1 point: I can feel it very strongly.

[0180] Furthermore, the average score of the 10 expert panel members was calculated, and the evaluation was carried out in the following 5 levels.

[0181] Regarding the evaluation results, ★, ◎, ○, and △ are marked as qualified (OK), and × is marked as unqualified (NG).

[0182] ★ (star mark): 5.0 points.

[0183] ◎(double circle mark): 4.5 points or higher but less than 5.0 points.

[0184] ○ (circle mark): 4.0 points or higher but less than 4.5 points.

[0185] △ (triangle mark): 3.5 points or higher but less than 4.0 points.

[0186] × (cross mark): less than 3.5 points.

[0187] [Table 1]

[0188]

[0189] [Table 2]

[0190]

[0191] As shown in Table 1-2, the samples of Examples 1 to 11, which have a Shore hardness of A90 or higher and A100 or lower, or a Shore hardness of D40 or higher and D70 or lower, and whose distance from the front end of the fitting hole to the front end of the fitting part is 50% or higher relative to the maximum size of the fitting hole, received good evaluations in both aspects of "formability of the fitting part" and "ease of removal of the brush-shaped body during use".

[0192] Furthermore, in the samples of Examples 9 to 11, where the total length of the fitting portion is 14% to 30% of the total circumference of the fitting hole, better evaluations were obtained for both the "formability of the fitting portion" and the "ease of detachment of the brush-shaped body during use".

[0193] In contrast, in Comparative Example 1, where the distance from the front end of the fitting hole to the front end of the fitting part was less than 50% of the maximum size of the fitting hole, neither aspect of "formability of the fitting part" nor "ease of removal of the brush-shaped body during use" was well evaluated.

[0194] Furthermore, in Comparative Example 2 samples that did not meet the requirements of a Shore hardness of A90 or higher and A100 or lower, or a Shore hardness of D40 or higher and D70 or lower, the "formability of the mating part" was not well evaluated.

[0195] Furthermore, in Comparative Example 3, which did not meet the requirements of a Shore hardness of A90 or higher and A100 or lower, or a Shore hardness of D40 or higher and D70 or lower, the "ease of detachment of the brush-formed body during use" was not well evaluated.

[0196] Based on these results, it can be confirmed that by applying this utility model, the effects of this utility model can be achieved.

[0197] The above is with reference to the appendix. Figure 1 The preferred embodiments of this utility model will be described below, but this utility model is by no means limited to these examples. The shapes and combinations of the constituent components shown in the above examples are just one example, and various modifications can be made based on design requirements, etc., without departing from the spirit of this utility model.

[0198] For example, in the above embodiment, the fitting portion 35 is illustrated by a structure formed by a protrusion protruding in the width direction within the fitting hole 22, but the structure is not limited to this.

[0199] The fitting portion 35 may also be a structure formed by a recess that is recessed outward from the fitting hole 22 in the width direction.

[0200] When this structure is adopted, in the fitting protrusion 12 of the handle 10, the protrusion that fits into the fitting part, i.e. the recess, when inserted into the fitting hole 22 is provided on both sides in the width direction.

[0201] When the fitting portion 35 is located at a position where the distance from L2 to the maximum dimension L1 is less than 50%, there is insufficient flexibility in this area, but the distance along the long axis of the load applied during forced demolding is shorter, thus reducing the load based on forced demolding. However, when it is only located at a position where the distance from L2 is less than 50%, as described above, during brushing use, the brush head base portion 21 tends to flex in the thickness direction starting from the front end wall 27, and the fitting of the fitting portion 35 and the recess 15 easily disengages and separates. Therefore, at least one fitting portion 35 must satisfy 50% or more, but it can also be located at a position less than 50%.

[0202] When the engagement hole 22 is positioned at less than 50%, it is preferable that the width of the engagement hole 22 located on the front end side of the engagement portion 35 gradually decreases towards the front end. In this case, the undercut portion becomes smaller, which further reduces the load during forced demolding. Additionally, it is preferable that the thickness of the engagement hole 22 located on the front end side of the engagement portion 35 gradually decreases towards the front end. In this case, the advantage of a smaller undercut portion is also obtained as described above. Furthermore, for disengagement, even when the engagement portion 35 is used at a position of less than 50%, it does not become disadvantageous.

[0203] Furthermore, in the above embodiment, a structure is illustrated in which one fitting portion 35 is provided on each side in the width direction and one in the length direction, but the structure is not limited to this.

[0204] The fitting portion 35 may also be a structure in which multiple portions are provided on both sides in the width direction and in the length direction.

[0205] When this structure is adopted, at least one fitting portion 35 only needs to satisfy that the distance from the front end of the fitting hole 22 to the front end of the fitting portion 35 is more than 50% of the maximum size of the fitting hole 22.

[0206] In addition, in the above embodiment, a toothbrush 1 is constructed by separately formed brush body 20 and handle 10, and the brush body 20 is installed on the handle 10 by fitting the fitting protrusion 12 of the handle 10 with the fitting hole 22 of the brush body 20, but the structure is not limited to this.

[0207] For example, the brush body 20 can be formed by insert molding after the handle 10 is formed by a first molding process using a first mold, and then by insert molding of the brush body 20 by a second molding process using a second mold in which the fitting protrusion 12 of the handle 10 is provided inside. Through this insert molding, a toothbrush 1 can be obtained, which is a molded body in which the fitting protrusion 12 fits into the fitting hole 22 and the brush body 20 is integrally formed with the handle 10.

[0208] Furthermore, in the above embodiment, a structure in which the handle 10 is formed of hard resin is illustrated, but the embodiment is not limited to this structure. For example, a portion of the handle 10 (grip portion 11, etc.) may be covered with soft resin. Using this structure improves both aesthetics and grip.

[0209] Industrial availability

[0210] This invention can be applied to brush-shaped bodies and toothbrushes.

[0211] Symbol Explanation

[0212] 1. Toothbrush

[0213] 10 Handle

[0214] 12. Fitting protrusions

[0215] 20 Brush-shaped bodies

[0216] 21 Brush head base

[0217] 21a Support surface

[0218] 22 fitting holes

[0219] 23 Monofilament

[0220] 35 chimeric part

[0221] 35a First Bend

[0222] 35b Second bend

Claims

1. A brush-shaped article, characterized in that, The brush-shaped body has: a brush head base portion, which is formed of soft resin, and Multiple monofilaments protrude from the support surface located on the front side in the thickness direction of the brush head base portion; The brush head base portion has: A fitting hole that extends in a length direction orthogonal to the thickness direction and opens on one side of that length direction; as well as The fitting portion is formed by a protrusion protruding into the fitting hole in a width direction orthogonal to the thickness direction and the length direction, or a recessed portion recessed from the fitting hole in the width direction, and is provided on both sides in the width direction. The maximum dimension in the thickness direction of the brush head base portion is 3.0 mm or more and 4.5 mm or less. The soft resin has a Shore hardness of A90 or higher and A100 or lower, or a Shore hardness of D40 or higher and D70 or lower. The distance between the position where the width dimension of the fitting hole begins to decrease from the front end on the other side of the length direction and the front end, and the position relative to the maximum dimension in the length direction of the fitting hole, is more than 50%.

2. The brush-forming body according to claim 1, characterized by The distance between the position where the width dimension of the fitting hole begins to decrease from the front end on the other side of the length direction and the front end, and the position relative to the maximum dimension in the length direction of the fitting hole, is 60.0% or less.

3. The brush-formed article according to claim 1, characterized in that, In a frontal view, the total length of the fitting portion accounts for more than 10% and less than 30% of the total length of the circumference of the fitting hole.

4. The brush-formed article according to claim 1 or 3, characterized in that, The maximum dimension in the thickness direction of the fitting portion is 2.5 mm or less.

5. The brush-formed article according to claim 1 or 3, characterized in that, In the region where the fitting portion is located along the length direction, the thickness of the brush head base portion on the front side in the thickness direction relative to the fitting hole and the thickness of the brush head base portion on the back side in the thickness direction relative to the fitting hole are 0.5 mm or more and 1.5 mm or less, respectively, and the back side is the side opposite to the front side.

6. The brush-formed article according to claim 1 or 3, characterized in that, The width dimension of the fitting hole located on the front end side of the fitting portion gradually decreases as it moves towards the front end side. The maximum dimension in the width direction of the fitting hole located on the front end side of the fitting portion is 2.0 mm or more different from the dimension in the width direction at a position 1 mm away from the front end on one side from the front end in the length direction.

7. The brush-formed article according to claim 1 or 3, characterized in that, The thickness dimension of the fitting hole located on the front end side of the fitting portion gradually decreases as it moves towards the front end side. The maximum dimension in the thickness direction of the fitting hole located on the front end side of the fitting portion is 0.5 mm or more different from the dimension in the thickness direction at a position 1 mm away from the front end on one side from the front end in the length direction.

8. The brush-formed article according to claim 1 or 3, characterized in that, The fitting portion is formed by the protrusion. In a frontal view, the fitting portion has: The first curved portion is curved into an arc shape that connects with the fitting hole on the front end side; as well as The second curved portion is curved into an arc shape that connects with the fitting hole on one side along the length direction. The radius of the first bend is greater than the radius of the second bend.

9. The brush-formed article according to claim 1 or 3, characterized in that, The brush head base has a gate mark on the front end side. The fitting portion is formed by the protrusion. In the region where the fitting portion is located along the length direction. Let A1 be the cross-sectional area of ​​the brush head base portion containing the fitting hole at the first position in the length direction where the dimension in the width direction of the fitting hole is the smallest. Let the cross-sectional area of ​​the fitting hole at the first position be A2. If in the region closer to the front end than the fitting portion, Let B1 be the cross-sectional area of ​​the brush head base portion containing the fitting hole at the second position in the length direction, where the fitting hole has the largest dimension in the width direction. Let the cross-sectional area of ​​the fitting hole at the second position be B2. If in the region closer to the front end than the fitting portion, Let C1 be the cross-sectional area of ​​the brush head base portion containing the fitting hole at the third position in the length direction, where the dimension in the width direction of the fitting hole is the smallest. Let the cross-sectional area of ​​the fitting hole at the third position be C2. The value represented by B1 / B2-A1 / A2 is below 0.

15. The value represented by B1 / B2-C1 / C2 is 0.10 or higher.

10. A toothbrush characterized by have: The brush-shaped article as described in claim 1 or 3, and The handle body, formed of hard resin, has a fitting protrusion that can be attached to and detached from the fitting hole of the brush body.

11. A toothbrush characterized by have: The brush-shaped article as described in claim 1 or 3; and The handle body has a fitting protrusion that fits into the fitting hole of the brush-shaped body. The brush body and the handle body are integrally formed.

Images