Replaceable toothbrush and brush for replacement

Abstract

To provide a replaceable toothbrush capable of securing strength while having a slim brush part.SOLUTION: A replaceable toothbrush has a handle part 11 with a shaft part 17 projecting outwardly in a longitudinal direction X and formed in one end part on a replaceable brush part 12 side in the longitudinal direction X. The replaceable brush part 12 has, along the longitudinal direction X, a head part 13 having a bristle planting base 15, and a neck part 14 connected to the head part 13. The neck part 14 has an inserted part 19 into which the shaft part 17 is inserted in an end part on the opposite side of the head part 13. A thickness of the neck part 14 gradually reduces from the inserted part 19 in the longitudinal direction X toward the head part 13. A dimension ratio of a minimum thickness T2 of the neck part 14 to a diameter D1 on the tip side of the shaft part 17 is 1:1.3-1:1.5, a diameter D2 of the base end part of the shaft part 17 is 5.5 mm or more, and the diameter D2 is 2.5 times or less of the minimum thickness T2 of the neck part 14.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a replaceable toothbrush comprising a handle portion and a replaceable brush portion detachably attached to the tip side of the handle portion along the longitudinal direction.

Background Art

[0002] Since a replaceable toothbrush can discard only the worn brush portion and replace only the brush portion with a new one, the amount of waste can be reduced compared to a toothbrush in which the brush portion and the handle portion are integrally formed. As the above-described replaceable toothbrush, for example, Patent Document 1 discloses a toothbrush having a fitting portion on the handle neck side and a fitted portion on the tufted portion side that fits therewith, the fitting portion having a plurality of fitting units each comprising an engaging convex portion and an engaging concave portion continuous thereto, the cross-section perpendicular to the axis of which is a polygon similar to each other. This toothbrush is a replaceable toothbrush characterized in that the fitting is completed by a plurality of engaged convex portions of the fitted portion simultaneously overcoming a plurality of engaging convex portions of the fitting portion.

[0003] Further, Patent Document 2 discloses a replaceable toothbrush comprising a brush main body portion and a replacement brush detachably attached to the tip side of the brush main body portion, wherein a shaft portion extending in the major axis direction from the tip of the handle portion constituting the brush main body portion is inserted into a groove-shaped shaft insertion portion formed in the attachment portion of the replacement brush from an opening on the outer peripheral surface side of the attachment portion into the shaft insertion portion. This replaceable toothbrush is such that, in a state where the replacement brush is attached to the brush main body portion, at least a part of the shaft portion in the shaft insertion portion is shielded by a shielding portion when viewed from the opening on the outer peripheral surface side of the attachment portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of ease of use and reduction in the amount of resin used, it is desirable that the brush part of a replaceable toothbrush has a slender shape. However, when the shape of the brush part is made slender, there is a problem that it is likely to break when stress is concentrated during use. However, the replaceable toothbrushes described in Patent Document 1 and Patent Document 2 had room for improvement in terms of ensuring strength while being slender.

[0006] Therefore, an object of the present invention is to provide a replaceable toothbrush that can ensure strength while the brush part is slender.

Means for Solving the Problems

[0007] The present invention relates to a replaceable toothbrush including a handle part and a replaceable brush part detachably attached to the tip side of the handle part along the longitudinal direction. In one embodiment, it is preferable that the handle part has a shaft part protruding outward in the longitudinal direction at one end on the replaceable brush part side in the longitudinal direction. In one embodiment, the replaceable brush part has, along the longitudinal direction, a head part having a bristle base and a neck part connected to the head part. It is preferable that the neck part has an inserted part into which the shaft part is inserted at an end opposite to the head part. In one embodiment, it is preferable that the thickness of the neck part gradually decreases from the inserted part in the longitudinal direction toward the head part. In one embodiment, it is preferable that the dimensional ratio between the minimum thickness of the neck part and the diameter of the tip of the shaft part is 1:1.3 to 1:1.5. In one embodiment, it is preferable that the diameter of the base end part of the shaft part is 5.5 mm or more and the diameter is 2.5 times or less the minimum thickness of the neck part.

[0008] Moreover, the present invention is a replacement brush that is used for the replaceable toothbrush and consists of the replacement brush part.

Advantages of the Invention

[0009] According to the replaceable toothbrush and the replacement brush of the present invention, while the brush part is slender, the strength of the brush part can be ensured.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Modes for Carrying Out the Invention

[0011] Hereinafter, the detachable toothbrush of the present invention will be described with reference to the drawings based on its preferred embodiments. FIGS. 1 to 8 show a detachable toothbrush 10 according to an embodiment of the present invention. As shown in FIG. 1, the detachable toothbrush 10 of the present embodiment includes a handle portion 11 and a replaceable brush portion 12 detachably attached to the tip side of the handle portion 11.

[0012] The detachable toothbrush 10 has a shape that is long in one direction and has a longitudinal direction X and a width direction Y orthogonal thereto. In the detachable toothbrush 10 of the present embodiment, the longitudinal direction X is a direction along the extending direction of the detachable toothbrush 10. Also, the direction orthogonal to both the longitudinal direction X and the width direction Y is referred to as the "vertical direction Z". In the present embodiment, the longitudinal direction X coincides with the extending direction of the handle portion 11 and the extending direction of the replaceable brush portion 12, respectively. The vertical direction Z coincides with the thickness direction of the bristle base 15 and the normal direction to the bristle surface 15a.

[0013] The replaceable brush portion 12 has a head portion 13 having a bristle base 15 and a neck portion 14 connected to the head portion 13 along the longitudinal direction X. The bristle base 15 in the head portion 13 has a pair of flat main surfaces, and bristle implantation holes 16 in which a plurality of tufts 18 are implanted are formed in one of the main surfaces 15a (see FIGS. 1 and 2). The main surface 15a in which the bristle implantation holes 16 are formed is hereinafter referred to as the "bristle surface 15a". The pair of flat main surfaces in the bristle base 15 face each other in the vertical direction Z. In a plan view seen from above, the plurality of bristle implantation holes 16 are arranged, for example, in an annular shape or a staggered shape. A plurality of tufts 18 formed by bundling a plurality of bristles are implanted in the plurality of bristle implantation holes 16 (see FIGS. 1 and 2).

[0014] In this specification, the side where the tufts 18 of the detachable toothbrush 10 are located, that is, the bristle surface 15a side, is referred to as "upward", and the side opposite to the bristle surface 15a is referred to as "downward".

[0015] The head portion 13 is a flat plate-like portion and has a substantially elliptical shape in plan view as viewed from above. The neck portion 14 is a rod-like portion extending from the head portion 13 toward the handle portion 11 in the longitudinal direction X, and the width and thickness gradually increase toward the handle portion 11. The head portion 13 and the neck portion 14 are connected in the longitudinal direction X. In the replacement brush portion 12 of the present embodiment, the position where the width is most constricted in the longitudinal direction X is defined as the boundary BL between the head portion 13 and the neck portion 14 [see Fig. 3(b)]. Unless otherwise specified in this specification, "width" refers to the length in the width direction Y, and "thickness" refers to the length in the vertical direction Z.

[0016] The neck portion 14 is formed with an insertion portion 19 into which the shaft portion 17 is inserted at an end opposite to the head portion 13 in the longitudinal direction X. The insertion portion 19 is a recess formed at the end of the neck portion 14 on the handle portion 11 side in the longitudinal direction X and has an opening on the handle portion 11 side. The insertion portion 19 has an internal space (recess) corresponding to the three-dimensional shape of the shaft portion 17. In a state where the handle portion 11 is attached to the replacement brush portion 12 (hereinafter, also referred to as "attached state"), the entire length of the shaft portion 17 in the longitudinal direction X is inserted into the insertion portion 19, and the outer peripheral surface of the shaft portion 17 and the inner peripheral surface of the insertion portion 19 are in close contact with each other. Thereby, rattling between the replacement brush portion 12 and the handle portion 11 is suppressed, and a more stable attached state is maintained.

[0017] The thickness of the neck portion 14 is minimum at the end on the boundary BL side with the head portion 13 and maximum at the insertion portion 19 farthest from the head portion 13. Such a neck portion 14 is more likely to bend from the end on the boundary BL side to the insertion portion 19 when an external force acts on the head portion 13 from the vertical direction Z, and breakage of the replacement brush portion 12 is less likely to occur.

[0018] The handle portion 11 is the part that the user grips when brushing teeth using the replaceable toothbrush 10. The handle portion 11 is a substantially cylindrical rod-shaped member extending in the longitudinal direction X. From the viewpoint of facilitating the brushing operation by the replaceable toothbrush 10, as shown in Fig. 3(a), the handle portion 11 of the present embodiment has a shape that gently curves upward in a side view seen from the width direction Y. Thereby, it is easier to grip the handle portion 11. The handle portion 11 of the present embodiment has a substantially rectangular shape in a plan view seen from above (see Fig. 3(b)).

[0019] A shaft portion 17 protruding outward in the longitudinal direction X is formed at one end portion of the handle portion 11 on the side of the replaceable brush portion 12 in the longitudinal direction X. The shaft portion 17 protrudes from the end face portion 11a of the handle portion 11 facing the replaceable brush portion 12 along the same longitudinal direction X toward the replaceable brush portion 12 side. The shaft portion 17 of the present embodiment has a substantially frustum shape and has a solid structure. More specifically, the tip portion of the shaft portion 17 in the longitudinal direction X has a cylindrical shape, and the portion on the base end side from the tip portion has a frustum shape with a diameter increasing toward the handle portion 11 side. The replaceable toothbrush 10 is attached to the handle portion 11 by inserting the shaft portion 17 into the insertion portion 19 of the replaceable brush portion 12 described later. In such a mounted state, the replaceable toothbrush 10 includes the replaceable brush portion 12 and the handle portion 11 along the longitudinal direction X.

[0020] The diameter D1 of the tip portion of the shaft portion 17 of the present embodiment (see Fig. 3(b)) is larger than the minimum thickness T2 of the neck portion 14 (see Fig. 3(a)) (D1 > T2). More specifically, the dimensional ratio between the minimum thickness T2 of the neck portion 14 and the diameter D1 on the tip side of the shaft portion 17 (hereinafter, also simply referred to as "dimensional ratio A") is 1:1.3 to 1:1.5, preferably 1:1.3 to 1:1.45, and more preferably 1:1.35 to 1:1.45.

[0021] The diameter D2 of the base end portion of the shaft portion 17 (see Fig. 3(b)) is larger than the minimum thickness T2 of the neck portion 14 (see Fig. 3(a)) (D2 > T2). More specifically, the diameter D2 (see Fig. 3(b)) of the base end portion of the shaft portion 17 is not more than 2.5 times, preferably not less than 1.5 times, more preferably not less than 1.6 times, also preferably not more than 2.2 times, more preferably not more than 2.0 times, and also preferably in the range of not less than 1.5 times and not more than 2.5 times, more preferably in the range of not less than 1.6 times and not more than 2.2 times of the minimum thickness T2 (see Fig. 3(a)) of the neck portion 14. Hereinafter, the ratio of the diameter D2 to the minimum thickness T2 is also simply referred to as "diameter ratio B".

[0022] The diameter D1 (see Fig. 3(b)) of the tip end portion of the shaft portion 17 is 4.0 mm or more, preferably 4.2 mm or more, more preferably 4.5 mm or more, also preferably 5.2 mm or less, more preferably 5.0 mm or less, and also preferably in the range of 4.0 mm or more and 5.2 mm or less, more preferably in the range of 4.2 mm or more and 5.0 mm or less, and still more preferably in the range of 4.5 mm or more and 5.0 mm or less. The tip end portion of the shaft portion 17 is within a range of 6.0 mm or less from the edge on the replacement brush portion 12 side of the shaft portion 17 in the longitudinal direction X toward the handle portion 11 side, and the maximum diameter within this range is defined as the diameter D1 of the tip end portion. The diameter D2 (see Fig. 3(b)) of the base end portion of the shaft portion 17 is 5.5 mm or more, preferably 6.0 mm or more, also preferably 7.5 mm or less, more preferably 7.0 mm or less, and also preferably in the range of 5.5 mm or more and 7.5 mm or less, more preferably in the range of 6.0 mm or more and 7.0 mm or less. The base end portion of the shaft portion 17 is within a range of 3.0 mm or less from the edge on the handle portion 11 side of the shaft portion 17 in the longitudinal direction X toward the replacement brush portion 12 side, and the maximum diameter within this range is defined as the diameter D2 of the base end portion. For the shaft portion 17, the difference between the diameter D1 of the tip end portion and the diameter D2 of the base end portion is preferably 0.3 mm or more and 3.5 mm or less, more preferably 1.5 mm or more and 2.5 mm or less.

[0023] In the replaceable toothbrush 10 in the mounted state, the replaceable brush part 12 is supported by the handle part 11 in a cantilever beam shape. When brushing teeth using this replaceable toothbrush 10, brushing of the tooth surface is performed with the tip of the tuft 18 in contact with the tooth surface. At this time, an external force along the normal direction with respect to the implanting surface 15a, that is, an external force along the vertical direction Z, easily acts on the head part 13 of the replaceable toothbrush 10. When an external force acts on the head part 13 from the vertical direction Z, the external force is transmitted to the neck part 14 and the connection part between the neck part 14 and the handle part 11 (the inserted part 19 and the shaft part 17), and bending stress may concentrate on the inserted part 19 and the shaft part 17. In the replaceable toothbrush 10 of the present embodiment, since the thickness of the neck part 14 gradually decreases from the inserted part 19 in the longitudinal direction X toward the head part 13, the portion on the boundary BL side of the neck part 14 is easily bent in one direction of the vertical direction Z. For example, when an external force is applied to the head part 13, the neck part 14 is easily bent in the direction of the external force along with the external force. Further, the inventor has found that by setting the above-described dimensional ratio A (T2:D1) to 1:1.3 to 1:1.5, setting the diameter D2 of the base end part of the shaft part 17 to 5.5 mm or more, and further setting the diameter magnification B (D2 / T2) to 2.5 times or less, it is possible to ensure the strength of the replaceable toothbrush 10 while making the replaceable brush part 12 slender. Such an effect is considered to be because when an external force along the vertical direction Z acts on the head part 13, bending occurs from the end part on the boundary BL side between the head part 13 and the neck part 14 to the inserted part 19 of the neck part 14, and the bending stress is dispersed. Thereby, breakage of the replaceable brush part 12 at the boundary BL is suppressed, and the replaceable brush part 12 is less likely to break. Also, the mounting state of the shaft part 17 to the inserted part 19 is stably maintained. Such a slender replaceable brush part 12 can improve the operability and design while reducing the amount of resin used in the neck part 14.

[0024] As shown in FIGS. 4(b) to 4(e), the neck portion 14 of the present embodiment has a cross-sectional shape that gradually expands along the width direction Y from the end portion on the boundary BL side to the inserted portion 19. The cross-sectional shape of the neck portion 14 has a horizontally long shape that is long in the width direction Y at the end portion on the boundary BL side, but continuously changes to a vertically long shape that is long in the vertical direction Z as it approaches the inserted portion 19. That is, the neck portion 14 of the present embodiment has a gradually increasing second moment of cross-section from the end portion on the boundary BL side in the longitudinal direction X to the inserted portion 19. Thereby, in the neck portion 14 of the present embodiment, bending stress is more likely to be dispersed from the end portion on the boundary BL side to the inserted portion 19, and it is more difficult to break when an external force acts on the head portion 13 from the vertical direction Z.

[0025] From the viewpoint of making it easier to disperse bending stress and maintaining the state where the shaft portion 17 is inserted into the inserted portion 19 more stably, it is preferable that the aspect ratio is reversed between the boundary BL and the inserted portion 19 in the cross-sectional shape along the width direction Y of the neck portion 14. From the same viewpoint as above, it is preferable that the cross-sectional shape along the width direction Y of the neck portion 14 has a ratio (vertical / horizontal) of the length in the vertical direction Z (vertical length) to the length in the width direction Y (horizontal length) within the following range. For the cross-section at the end portion on the boundary BL side of the neck portion 14, the ratio (vertical / horizontal) of the length in the vertical direction Z (vertical length) to the length in the width direction Y (horizontal length) is preferably 0.80 or more and 1.00 or less, more preferably 0.85 or more and 0.90 or less. For the cross-section at the inserted portion 19 of the neck portion 14, the ratio (vertical / horizontal) of the length in the vertical direction Z (vertical length) to the length in the width direction Y (horizontal length) is preferably 0.90 or more and 1.10 or less, more preferably 0.95 or more and 1.00 or less.

[0026] From the viewpoint of further suppressing breakage of the replacement brush portion 12, it is preferable that the dimensions and the like of the neck portion 14 are within the following ranges. For the neck portion 14, the difference (T1 - T2) between the maximum thickness T1 [see FIG. 3(a)] and the minimum thickness T2 [see FIG. 3(a)] is preferably 5.5 mm or more and 9.0 mm or less, more preferably 6.0 mm or more and 7.0 mm or less. The minimum thickness T2 of the neck portion 14 (see Fig. 3(a)) is preferably 3.0 mm or more and 5.0 mm or less, more preferably 3.5 mm or more and 4.0 mm or less. The maximum thickness T1 of the neck portion 14 (see Fig. 3(a)) is preferably 8.0 mm or more and 12.0 mm or less, more preferably 9.0 mm or more and 11.0 mm or less. When the inserted portion 19 is provided at the portion where the maximum thickness T1 of the neck portion 14 is obtained, the thickness including the inserted portion 19 is defined as the maximum thickness T1.

[0027] The thickness of the neck portion 14 gradually increases from the boundary BL in the longitudinal direction X toward the handle portion 11. From the viewpoint of making the replacement brush portion 12 more flexible and further suppressing breakage of the replacement brush portion 12, the thickness increase amount per 10 mm in the longitudinal direction X of the neck portion 14 is preferably 1.10 mm / 10 mm or more and 1.25 mm / 10 mm or less, more preferably 1.15 mm / 10 mm or more and 1.20 mm / 10 mm or less. The thickness increase amount per 10 mm in the longitudinal direction X is the change amount of the thickness of the neck portion 14 that increases from the boundary BL in the longitudinal direction X toward the handle portion 11.

[0028] From the viewpoint of further stabilizing the mounting state of the shaft portion 17 to the inserted portion 19, the replaceable toothbrush 10 preferably has dimensions within the following ranges. The length L11 of the shaft portion 17 in the longitudinal direction X is preferably 10% or more and 30% or less, more preferably 15% or more and 20% or less, with respect to the length L12 of the replacement brush portion 12 in the longitudinal direction X. The length L11 of the shaft portion 17 in the longitudinal direction X is preferably 15% or more and 50% or less, more preferably 20% or more and 30% or less, with respect to the length L14 of the neck portion 14 in the longitudinal direction X. The length L11 of the shaft portion 17 in the longitudinal direction X is preferably 7.5 mm or more and 25.0 mm or less, more preferably 10.0 mm or more and 15.0 mm or less. The length L12 of the replacement brush portion 12 in the longitudinal direction X is preferably 60 mm or more and 95 mm or less, more preferably 70 mm or more and 80 mm or less. The length L14 of the neck portion in the longitudinal direction X is preferably 25 mm or more and 70 mm or less, more preferably 35 mm or more and 65 mm or less, and even more preferably 45 mm or more and 55 mm or less. Here, the length L14 of the neck portion 14 is the distance from the inserted portion 19 to the boundary BL in the longitudinal direction X (see Fig. 3(a)).

[0029] As shown in Fig. 5, in the replaceable toothbrush 10 of the present embodiment, the shaft portion 17 has a positioning projection 20 at the proximal end portion and an outer annular engagement portion 21 extending in the circumferential direction on the outer peripheral surface of the proximal end portion. The positioning projection 20 of the present embodiment protrudes radially outward from the outer peripheral surface on the proximal end side of the shaft portion 17, and the positions in the radial direction of the outer surface of the positioning projection 20 and the outer peripheral surface of the handle portion 11 are substantially the same. The end portion of the positioning projection 20 on the handle portion 11 side in the longitudinal direction X enters the handle portion 11 (see Fig. 5). The positioning projection 20 of the present embodiment has an oval shape in a plan view from above. The planar shape of the positioning projection 20 is not limited to this and can be any shape. Note that the positioning projection 20 is preferably located on the side of the bristle planting surface 15a in the circumferential direction of the shaft portion 17 in the mounted state. By being located on the side of the bristle planting surface 15a, the mounted state can be more stabilized, and unintentional detachment can be more suppressed. The outer annular engagement portion 21 of the present embodiment is located away from the end surface portion 11a of the handle portion 11 toward the replaceable brush portion 12 side in the longitudinal direction X. As shown in Fig. 5, the positioning projection 20 and the outer annular engagement portion 21 preferably overlap in the longitudinal direction X. In this case, the outer annular engagement portion 21 is continuous in the circumferential direction of the proximal end portion of the shaft portion 17 via the positioning projection 20.

[0030] The inserted portion 19 of the present embodiment has a positioning notch 22 at the end portion on the insertion port side into which the shaft portion 17 is inserted, and an inner annular engagement portion 23 extending in the circumferential direction on the inner peripheral surface of the end portion. The positioning notch 22 is a portion where a part of the opening peripheral edge forming the insertion port is cut out toward the head portion 13 side. The inner annular engaging portion 23 of the present embodiment is arranged to be spaced apart from the end portion on the insertion port 19a side toward the head portion 13 side in the longitudinal direction X. It is preferable that the inner annular engaging portion 23 and the positioning notch portion 22 overlap in the longitudinal direction X. In this case, the inner annular engaging portion 23 is continuous in the circumferential direction of the inserted portion 19 via the positioning notch portion 22.

[0031] In the mounted state where the shaft portion 17 of the replaceable toothbrush 10 of the present embodiment is inserted into the inserted portion 19, the outer annular engaging portion 21 and the inner annular engaging portion 23 engage with each other, and the positioning projection portion 20 fits into the positioning notch portion 22. Thereby, the outer annular engaging portion 21 and the inner annular engaging portion 23 engage the replacement brush portion 12 and the handle portion 11 in the circumferential direction, and the positioning projection portion 20 fitted in the longitudinal direction X is restricted by the positioning notch portion 22 from moving in the longitudinal direction X and the circumferential direction. As a result, the mounted state can be further stabilized, and it is possible to further suppress the replacement brush portion 12 from unintentionally falling off from the handle portion 11.

[0032] In plan view, the notch shape of the positioning notch portion 22 corresponds to the plan view shape of the end portion of the positioning projection portion 20 on the replacement brush portion 12 side in the longitudinal direction X, and they are substantially the same shape. In the mounted state where the replacement brush portion 12 is mounted on the handle portion 11, the positioning projection portion 20 is made engageable with the positioning notch portion 22. Thereby, the circumferential position when mounting the replacement brush portion 12 on the handle portion 11 can be more accurately adjusted, and it is possible to align the warping direction of the handle portion 11 in side view with the circumferential direction of the bristle surface 15a. As a result, the operability during brushing with the replaceable toothbrush 10 can be further improved.

[0033] In the present embodiment, the separation distance from the end portion on the insertion port 19a side in the inner annular engagement portion 23 is equal to the separation distance from the end face portion 11a of the handle portion 11 in the outer annular engagement portion 21. Thereby, in the mounted state, the insertion port 19a of the replacement brush portion 12 comes into contact with the end face portion 11a of the handle portion 11, and the mounted state can be further stabilized.

[0034] As shown in FIGS. 5 and 6(b), in the replaceable toothbrush 10 of the present embodiment, the outer annular engagement portion 21 is an annular rib 21a, and the inner annular engagement portion 23 is an annular groove 23a that can engage with the annular rib. The annular rib 21a is a substantially annular convex portion protruding radially outward from the outer peripheral surface of the base end portion of the shaft portion 17. The annular groove 23a is a substantially annular concave portion formed on the inner peripheral surface of the insertion portion 19. The cross-sectional shape along the longitudinal direction X of the outer annular engagement portion 21 and the inner annular engagement portion 23 is, for example, a semi-circular shape, a U-shaped shape, a V-shaped shape, but is not limited thereto. From the viewpoint of further achieving both the stabilization of the mounted state between the replacement brush portion 12 and the handle portion 11 and the ease of the attachment / detachment operation of the replacement brush portion 12, the widths of the annular rib 21a and the annular groove 23a are preferably 0.1 mm or more and 2.0 mm or less, more preferably 0.3 mm or more and 1.0 mm or less. The widths of the annular rib 21a and the annular groove 23a are the lengths in the direction orthogonal to the extending direction of these rib and groove. From the same viewpoint as above, the height of the annular rib 21a and the depth of the annular groove 23a are preferably 0.05 mm or more and 0.50 mm or less, more preferably 0.15 mm or more and 0.30 mm or less.

[0035] As shown in FIG. 5, in the replaceable toothbrush 10 of the present embodiment, the positioning projection 20 protrudes radially outward from the outer peripheral surface of the handle portion 11 and has a curved surface portion 20a on the tip side of the shaft portion 17. With such a configuration, when the replacement brush portion 12 is attached to the handle portion 11, it becomes easier to insert the positioning projection 20 into the positioning notch portion 22, and the fitting between the two becomes easier. From the viewpoint of facilitating the fitting between the positioning protrusion 20 and the positioning notch 22, the height h (see Fig. 6(b)) of the positioning protrusion 20 is preferably 0.8 mm or more and 4.0 mm or less, more preferably 1.0 mm or more and 3.0 mm or less. The height h of the positioning protrusion 20 is the protruding height in the radially outward direction from the outer peripheral surface of the shaft portion 17. When the outer diameter of the base end portion of the shaft portion 17 changes as described later, the minimum value of the length in the normal direction with respect to the outer peripheral surface of the shaft portion 17 is taken as the height h of the positioning protrusion 20. Since the positioning protrusion 20 has a curved surface portion 20a on the tip side of the shaft portion 17, the positioning protrusion 20 can be smoothly fitted into the positioning notch 22. From the viewpoint of further improving such an effect, the radius of curvature of the curved surface portion 20a in plan view is preferably 0.5 mm or more and 3.0 mm or less, more preferably 1.0 mm or more and 2.0 mm or less.

[0036] As shown in Figs. 5 and 6(b), the shaft portion 17 of the present embodiment has a straight portion 17a with a constant outer diameter on the tip side in the longitudinal direction X, and a tapered portion 17b that is located on the base end side of the straight portion 17a and whose outer diameter gradually increases toward the base end side. Thereby, it becomes easier to insert the shaft portion 17 into the inserted portion 19, and it is possible to further suppress the dropping off of the inserted portion 19 from the shaft portion 17. From the viewpoint of further achieving both the operability of inserting the shaft portion 17 into the inserted portion 19 and the effect of suppressing the dropping off of the inserted portion 19 from the shaft portion 17, the taper angle of the tapered portion 17b is preferably 1° or more and 6° or less, more preferably 2° or more and 4° or less. The taper angle of the tapered portion 17b is the inclination angle of the outer edge (outline) of the tapered portion 17b with respect to the central axis of the shaft portion 17 in plan view.

[0037] As shown in Figs. 6(a), 7(a) and 7(b), the inserted portion 19 of the present embodiment has a rear inserted portion 19b where the straight portion 17a is arranged in the mounted state where the shaft portion 17 is inserted into the inserted portion 19, and an insertion port side inserted portion 19e whose inner diameter gradually expands toward the handle portion 11 side. The inner peripheral surface of the insertion port side inserted portion 19e corresponds to the outer peripheral surface of the tapered portion 17b. On the inner circumferential surface of the insertion portion 19b on the back side, a plurality of press-fitting ribs 19c along the longitudinal direction X are formed (see Fig. 6(a)). And in the exchangeable toothbrush 10 of the present embodiment, in the mounted state, when the straight portion 17a is inserted into the insertion portion 19b on the back side, the press-fitting ribs 19c are crushed. Thereby, the frictional force between the straight portion 17a and the press-fitting ribs 19c is increased, and it becomes possible to maintain the mounted state more stably. In the present embodiment, four press-fitting ribs are formed at equal intervals in the circumferential direction (see Fig. 7(a)(b)). From the viewpoint of generating an appropriate frictional force between the straight portion 17a and the press-fitting ribs 19c, the dimensions of the straight portion 17a and the press-fitting ribs 19c are preferably within the following ranges. The total length of the straight portion 17a in the longitudinal direction X is preferably 2.0 mm or more and 8.0 mm or less, more preferably 4.0 mm or more and 6.0 mm or less. The number of the press-fitting ribs 19c is preferably 2 or more and 6 or less, more preferably 3 or more and 5 or less. The length of the press-fitting ribs 19c in the longitudinal direction X is preferably 1.0 mm or more and 8.0 mm or less, more preferably 4.0 mm or more and 6.0 mm or less. The width of the press-fitting ribs 19c is preferably 0.5 mm or more and 3.0 mm or less, more preferably 1.0 mm or more and 2.0 mm or less. The width of the press-fitting ribs 19c is the length in the direction orthogonal to the extending direction of the press-fitting ribs 19c. The height of the press-fitting ribs 19c is preferably 0.02 mm or more and 0.2 mm or less, more preferably 0.04 mm or more and 0.1 mm or less. The height of the press-fitting ribs 19c is the protruding height from the inner circumferential surface of the insertion portion 19b on the back side.

[0038] On the outer peripheral surface of the inserted portion 19 of the present embodiment, a recessed portion 19d for gripping with a finger is formed. The recessed portion 19d of the present embodiment is formed on the outer peripheral surface of the inserted portion 19, and is an elliptical recess having a major axis extending from the front surface to the back surface where the positioning notch portion 22 in the inserted portion 19 exists. That is, in side view, the recessed portion 19d has an elliptical shape. The elliptical recessed portions 19d are formed on both sides of the inserted portion 19, and are line-symmetric with respect to the central axis of the neck portion 14 in plan view. When using the replaceable toothbrush 10 of the present embodiment, the replaceable brush portion 12 can be gripped by pinching the recessed portion 19d with the thumb and index finger. Thereby, the ease of attachment and detachment of the replaceable brush portion 12 can be further improved. From the viewpoint of further improving such an effect, the depth of the recessed portion 19d is preferably 0.5 mm or more and 2.0 mm or less, more preferably 0.8 mm or more and 1.5 mm or less.

[0039] The thickness of the bristle base 15 is preferably 2.0 mm or more and 4.0 mm or less, more preferably 2.5 mm or more and 3.5 mm or less. With such a configuration, breakage at the head portion 13 is more suppressed, and a thinner head portion 13 can be obtained, thereby reducing the amount of resin used and improving the operability.

[0040] The forming materials and the like of each part of the replaceable toothbrush 10 in the above-described embodiment will be described. The handle portion 11 and the replaceable brush portion 12 constituting the replaceable toothbrush 10 can be formed using a synthetic resin such as polypropylene (PP), polyacetal (POM), polystyrene (PS), polyethylene terephthalate (PET), acrylonitrile, butadiene, polybutylene terephthalate (PBT), and styrene copolymer. The forming materials of the handle portion 11 and the replaceable brush portion 12 may be the same or different. In the case of the replaceable toothbrush 10, while the replaceable brush part 12 is replaceable, the handle part 11 is continuously used, so each time the replaceable brush part 12 is attached, the shaft part 17 of the handle part 11 and its vicinity tend to wear. From the viewpoint of using the handle part 11 for a longer period, it is preferable that the material of the handle part 11 is harder than the material of the replaceable brush part 12. From the same viewpoint as above, the difference in the flexural modulus (JIS 7171) between the replaceable brush part 12 and the handle part 11 is preferably 300 MPa or more and 2500 MPa or less, more preferably 1000 MPa or more and 1500 MPa or less. The flexural modulus of the handle part 11 is preferably 1000 MPa or more and 3500 MPa or less, more preferably 1300 MPa or more and 2600 MPa or less. The flexural modulus of the replaceable brush part 12 is preferably 800 MPa or more and 3000 MPa or less, more preferably 1300 MPa or more and 2600 MPa or less. The flexural modulus of the materials of the replaceable brush part 12 and the handle part 11 is measured by the following method.

[0041] 〔Method for Measuring Flexural Modulus〕 A 100 g slice is cut out from each of the replaceable brush part 12 or the handle part 11. The 100 g slices may be collected from a plurality of the same type of replaceable toothbrushes 10. Then, it is supplied to a kneader and melt-kneaded at 180 °C for 5 minutes at 30 rpm. For this kneader, a Laboplastmill 28 - 125 type (both manufactured by Toyo Seiki Seisakusho Co., Ltd.) equipped with a roller mixer R - 60 is used. Next, the melt-kneaded material is supplied to a press machine (Labopress P2 - 30T, Toyo Seiki Seisakusho Co., Ltd.) with a spacer having a thickness of 4.0 mm set, and hot-pressed at 180 °C and 200 kg / cm 2 for 5 minutes. Then, it is cooled and pressed at 20 °C and 5 kg / cm 2 for 1 minute to produce a measurement piece having a thickness of 4.0 mm. The measurement pieces are cut out one by one with a size of width 10.0 mm × length 80.0 mm. Next, using a tensilon testing machine (RTC-1150A manufactured by Orientec Co., Ltd.), the flexural modulus is measured in accordance with JIS K7171 (Test Method for Plastics - Flexural Properties).

[0042] Examples of the material of the handle portion 11 include polypropylene (PP), glycol-modified polyethylene terephthalate (PETG), and polybutylene terephthalate (PBT). Examples of the material of the replacement brush portion 12 include polypropylene, polyethylene, polyethylene terephthalate (PET), polyoxymethylene (POM), acrylonitrile, butadiene, and styrene copolymer. A preferred combination of the materials of the handle portion 11 and the replacement brush portion 12 is a combination in which the handle portion 11 is polybutylene terephthalate (PBT) and the replacement brush portion 12 is polypropylene. Each of the replacement brush portion 12 and the handle portion 11 of the present embodiment is a molded product, and is obtained by an injection molding method using the synthetic resin described above.

[0043] In the present embodiment, tufts of bristles 18, each formed by bundling a number of bristles corresponding to the cross-sectional area of the implanting hole 16, are inserted and fixed into the plurality of implanting holes 16 and implanted. The bristles constituting each tuft of bristles 18 are preferably made of a synthetic resin. As the synthetic resin for forming the bristles, various known ones used for bristles can be used without particular limitation. For example, polyamides such as nylon (registered trademark) and nylon 6, polyesters such as polybutylene terephthalate, and polyolefins can be mentioned, and polybutylene terephthalate is preferable.

[0044] The diameter of the bristles is, for example, 75 to 250 μm, preferably 100 to 220 μm, more preferably 140 to 200 μm. When the bristles are tapered bristles, the diameter of the bristles is the diameter of the portion excluding the tapered portion. The tapered portion of the tapered bristles can be easily provided by tapering and sharpening the tip portion of the bristles using a known polishing device, or by immersing the tip portion of the bristles in a known dissolving solvent to a predetermined depth to taper and sharpen it. The tapered bristles are preferably provided by immersing the tip portion of the bristles in a dissolving solvent for processing. The length of the tapered portion in the tapered bristles is preferably 1 to 10 mm, more preferably 3 to 8 mm.

[0045] As a method of implanting the tufts 18 into the plurality of implanting holes 16, various known implanting methods can be adopted. For example, (1) a method of folding the tuft 18 in half with a flat wire and driving it in, (2) a method of heating one end portion of the tuft 18 to form a molten mass, and then injecting a molten resin into a mold in which the molten mass is disposed to injection-mold the implanting base 15, (3) an inserting step of inserting the tuft 18 into the implanting hole 16 of the implanting base having the implanting hole 16 (through hole), a heat processing step of heating one end portion of the tuft 18 protruding from the implanting hole 16 to form a molten mass, and a covering step of covering the molten mass can be used to obtain the implanting base 15 (replacement brush portion 12) in a state where the tuft 18 is implanted.

[0046] The method of implanting the tuft 18 can efficiently implant the tuft into a relatively small-diameter implanting hole, and can reduce the thickness of the implanting base. From the viewpoints of improving the ease of grinding the back teeth, operability, and excellent appearance, it is preferable to adopt fusion implanting including the above-mentioned methods (2) and (3) of forming a molten mass at one end of the tuft, and it is more preferable to adopt the method of (3). Specific examples of the method of (3) can include the methods described in JP-A-9-182632 and JP-A-2003-310353. In the method described in JP-A-2003-310353, one end of the tuft is heated with a non-contact heat source such as a laser beam to form a molten mass and the molten mass is fused with the peripheral edge of the opening of the implanting hole.

[0047] The filling rate of the tuft 18 into the implanting hole 16 is preferably 0.6 to 0.85%, and more preferably 0.65 to 0.85%. The filling rate is "total cross-sectional area of bristles / cross-sectional area of the implanting hole". When the bristles are tapered bristles, the filling rate is "total cross-sectional area of the portion excluding the tapered shape part / cross-sectional area of the implanting hole".

[0048] For the tuft 18 implanted in the implanting hole 16, the height (tuft length) from the implanting surface 15a of the implanting base 15 to the tip of the bristles is preferably, for example, 7 to 16 mm as the average height for each tuft 18.

[0049] The present invention is not limited to the above-described embodiments and can be appropriately changed. Also, the respective configurations of the above-described embodiments may be combined. For example, as shown in FIG. 8, in the replaceable toothbrush 10 according to the present invention, the inner annular engaging portion 23 may be an annular rib 23b, and the outer annular engaging portion 21 may be an annular groove 21b that can engage with the annular rib 23b. In this case, the annular rib 23b is a substantially annular convex portion that protrudes inward from the inner peripheral surface of the inserted portion 19. The annular groove 21b is a substantially annular concave portion formed on the outer peripheral surface of the base end portion of the shaft portion 17. Thereby, even if the annular rib 23b on the replaceable brush portion 12 side wears, the replaceable brush portion 12 itself can be replaced, so that even if the handle portion 11 is used for a long time, the mounting state between the replaceable brush portion 12 and the handle portion 11 can be maintained well.

[0050] Furthermore, in the replaceable toothbrush 10 according to the present invention, the material of the handle portion 11 may have the same hardness as the material of the replaceable brush portion. In this case, the material of the handle portion 11 may be the same as the material of the replaceable brush portion.

[0051] Furthermore, the present invention includes a replacement brush used for the replaceable toothbrush described above. The replacement brush includes a replaceable brush portion 12 attached to the handle portion 11 of the replaceable toothbrush 10. Also, with the replacement brush, similar to the replaceable toothbrush 10, while making the replaceable brush portion 12 slender, the strength of the replaceable toothbrush 10 can be ensured. In addition, such a slender replacement brush can improve the operability and design while reducing the amount of resin used in the neck portion 14.

Example

[0052] Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples.

[0053] 〔Evaluation of Izod impact test by simulation〕 To evaluate the strength of the neck portion 14 of the replaceable toothbrush 10, a simulation of the Izod impact test was conducted. Here, the Izod impact test is a test for measuring the toughness (strength) of a test specimen by measuring the amount of kinetic energy absorbed when a pendulum hammer collides with the test specimen. Toughness represents the degree of resistance of a substance to brittle fracture. The evaluation target models used in the simulation of the Izod impact test were 3D models created based on the dimensional data of Example 1 and Comparative Examples 1 to 3. The physical property values of these 3D models were set based on the stress-strain diagram of polybutylene terephthalate (PBT) (refer to the stress-strain diagram of NOVADURAN (registered trademark) of Mitsubishi Chemical Corporation, URL: https: / / www.mcc-polymers.com / cms / wp-content / themes / mcg / assets / pdf / product / novaduran / physicality.pdf#page=5). For the simulation of the Izod impact test, an analytical model related to damage and fracture in Abaqus / Explicit was used. The pendulum hammer (hereinafter also simply referred to as "hammer") in the simulation of the Izod impact test was set as a rigid body with a cubic shape of 10 3 mm 3 . The Izod impact test using the hammer was performed by simulating the movement of colliding the hammer horizontally from the back surface of the bristle planting surface 15a (replaceable brush portion 12) with the tip of the bristle planting surface 15a of the replaceable toothbrush 10 facing vertically upward and with the handle portion 11 completely fixed. In such a simulation, the amount of kinetic energy of the hammer immediately before colliding with the head portion 13 was set to 2.75 J. The impact test by the above simulation was conducted, and the portion where deformation (strain) occurred in the replaceable brush portion 12 was colored according to the von Mises stress. Then, the location where the von Mises stress higher than the physical property value of PBT occurred was regarded as the damaged location. When there was no such damaged location, it was evaluated as "none", and when there was one or more damaged locations, it was evaluated as "yes".

[0054] 〔Example 1〕 In Example 1, a 3D model of a replaceable toothbrush having the same configuration as the replaceable toothbrush of the embodiment shown in FIGS. 1 to 7 described above was set. Specifically, the forming materials of the replaceable brush part 12 and the handle part 11 were set to polybutylene terephthalate and the dimensions shown in Table 1 below. Further, the thickness of the tuft base 15 was set to 3.1 mm, and the outer diameter of the end of the handle part 11 on the side of the replaceable brush part 12 was set to 9.5 mm. The inserted part 19 was set to have an inner inserted part 19b and an insertion port side inserted part 19e, and the shaft part 17 was set to have a straight part 17a and a tapered part 17b. The inner peripheral surface of the inner inserted part 19b corresponded to the outer peripheral surface of the straight part 17a, and the inner peripheral surface of the insertion port side inserted part 19e was set to correspond to the outer peripheral surface of the tapered part 17b. A 3D model of the replaceable toothbrush was produced with the above settings, and the above-mentioned Izod impact test evaluation was performed by simulation. The results are shown in Table 1.

[0055] 〔Examples 2 and 3〕 In Examples 2 and 3, the forming materials of the replaceable toothbrush were made different, and the simulation of the above-mentioned Izod impact test evaluation was performed. The dimensions were set the same as in Example 1. In Example 2, the physical property values of the 3D model were set with polyoxymethylene (POM) as the forming material of the replaceable toothbrush. The physical property values of this 3D model were set based on the physical property values described in the catalog of Duracon (registered trademark) POM M270-44 manufactured by Polyplastics Co., Ltd. (https: / / www.polyplastics.com / Gidb / GradeListSelectGradeAction.do?id=1773). In Example 3, the physical property values of the 3D model were set with polypropylene (PP) as the forming material of the replaceable toothbrush. The physical property values of this 3D model were set based on the physical property values described in the catalog of Novatec (registered trademark) PP manufactured by Japan Polypropylene Corporation (https: / / www.pochem.co.jp / jpp / product / novatec-pp / novatec-pp_bussei.pdf).

[0056] 〔Comparative Examples 1 to 3〕 A simulation of the Izod impact test evaluation was conducted in the same manner as in Example 1, except that the dimensions were set as shown in Table 1 below. The results are shown in Table 1.

[0057] In Examples 1 to 3 and Comparative Examples 1 to 3, a slender neck portion 14 with a minimum thickness of 3.8 mm or less was provided. In the Izod impact test simulations of each of Example 1 and Comparative Examples 1 to 3, the deformation of the replacement brush portion 12 accompanying the impact of the hammer can be shown in a video. Fig. 9 shows a still image captured from the video. In the simulation of Comparative Example 1, after the replacement brush portion 12 was bent by the impact of the hammer, the inserted portion 19 came off the shaft portion 17. In the simulations of Comparative Examples 2 and 3, after the replacement brush portion 12 was bent by the impact of the hammer, due to the reaction, it bent greatly in the direction opposite to the impact direction of the hammer. In Comparative Examples 2 and 3, as a result, the mounted state in which the shaft portion 17 was inserted into the inserted portion 19 was maintained. In the simulations of Examples 1 to 3, after the replacement brush portion 12 was bent by the impact of the hammer, due to the reaction, it bent in the direction opposite to the impact direction of the hammer, but the reaction was smaller than that in Comparative Examples 2 and 3. Also, in the simulations of Examples 1 to 3, as a result, the mounted state in which the shaft portion 17 was inserted into the inserted portion 19 was maintained.

[0058]

Table 1

[0059] As shown in Table 1, in the replacement toothbrushes of Examples 1 to 3, no damaged portions occurred, whereas in the replacement toothbrushes of Comparative Examples 1 to 3, damaged portions occurred. More specifically, in Comparative Examples 1 to 3, damage occurred on the outer peripheral surface of the shaft portion or in the vicinity of the shaft portion in the handle portion. When damage occurs on the outer peripheral surface of the shaft portion or in the vicinity of the shaft portion, it becomes difficult for the shaft portion to fit into the inserted portion, and repeated use of the handle portion 11 becomes difficult.

[0060] 〔Izod Impact Test Evaluation〕 An actual replacement toothbrush was used as the test specimen, and an Izod impact test was conducted. The test method was carried out in accordance with "JIS K 7110:1999 Plastics - Test Method for Izod Impact Strength". Specifically, the replacement toothbrush of Comparative Example 4 was supported in a cantilever beam shape so that the head part was vertically upward, and a hammer that swung pendulum-like was made to collide with the back surface of the bristle-implanted surface of the replacement toothbrush. At this time, the potential energy before dropping the hammer was set to 2.75 [J], the pendulum length was 0.335 m, and the weight of the pendulum was 13.94 N. Then, the case where there was no damaged part was evaluated as "none", and the case where there was one or more damaged parts was evaluated as "yes". As the replacement toothbrush of the test specimen, Example 4, Comparative Examples 4 and 5 shown below were used.

[0061] [Example 4] A replacement toothbrush having the same dimensions as in Example 1 was manufactured by injection molding. Polybutylene terephthalate was used as the forming material for the replacement brush part 12 and the handle part 11.

[0062] [Comparative Examples 4 and 5] A replacement toothbrush was manufactured in the same manner as in Example 2, except that the dimensions were set as shown in Table 2 below.

[0063] [Table 2]

[0064] In the replacement toothbrushes of Comparative Examples 4 and 5, the connecting portion between the inserted portion and the shaft portion was broken without the neck portion being bent due to the collision of the hammer by the Izod test. On the other hand, in the replacement toothbrush of Example 4, even when the hammer collided, the mounting state between the inserted portion and the shaft portion was maintained, and no damaged parts occurred in the replacement brush part 12 and the handle part 11. From the above results, it was shown that the replacement toothbrush of the present invention can secure strength while the replacement brush part is slender. [Explanation of Signs]

[0065] 10 Interchangeable Toothbrush 11 Handle part 12 Replaceable brush part 13 Head part 14 Neck part 15 Bristle base 15a Bristle surface 16 Bristle hole 17 Shaft part 17a Straight part 17b Tapered part 18 Bristle bundle 19 Inserted part 20 Positioning protrusion 21 Outer annular engagement part 22 Positioning notch 23 Inner annular engagement part X Longitudinal direction Y Width direction Z Vertical direction

Claims

1. An exchangeable toothbrush comprising a handle portion and an exchangeable brush portion detachably attached to the tip side of the handle portion along the longitudinal direction, wherein the handle portion has a shaft portion protruding outward in the longitudinal direction formed at one end on the side of the exchangeable brush portion in the longitudinal direction, the exchangeable brush portion has a head portion having a tuft base and a neck portion connected to the head portion along the longitudinal direction, and the neck portion has an inserted portion into which the shaft portion is inserted formed at an end opposite to the head portion, the thickness of the neck portion gradually decreases from the inserted portion in the longitudinal direction toward the head portion, the dimensional ratio between the minimum thickness of the neck portion and the diameter of the tip end portion of the shaft portion is 1:1.3 to 1:1.5, An exchangeable toothbrush, wherein the diameter of the base end portion of the shaft portion is 5.5 mm or more and the diameter is 2.5 times or less the minimum thickness of the neck portion.

2. The exchangeable toothbrush according to claim 1, wherein the thickness of the tuft base is 2.0 mm or more and 4.0 mm or less.

3. The shaft portion has a positioning protrusion at the base end portion and an outer annular engaging portion extending in the circumferential direction on the outer peripheral surface of the base end portion, the positioning protrusion and the outer annular engaging portion overlap in the longitudinal direction, the inserted portion has a positioning notch at the end on the side of the insertion port into which the shaft portion is inserted and an inner annular engaging portion extending in the circumferential direction on the inner peripheral surface of the end, the positioning notch is formed by cutting a part of the opening peripheral edge forming the insertion port toward the head portion side, the inner annular engaging portion and the positioning notch overlap in the longitudinal direction, The exchangeable toothbrush according to claim 1 or 2, wherein in a mounted state where the shaft portion is inserted into the inserted portion, the outer annular engaging portion and the inner annular engaging portion engage with each other, and the positioning protrusion fits into the positioning notch.

4. The exchangeable toothbrush according to claim 3, wherein the outer annular engaging portion is an annular rib and the inner annular engaging portion is an annular groove capable of engaging with the annular rib.

5. The exchangeable toothbrush according to claim 3, wherein the inner annular engaging portion is an annular rib and the outer annular engaging portion is an annular groove capable of engaging with the annular rib.

6. The exchangeable toothbrush according to claim 4 or 5, wherein the material of the handle portion is harder than the material of the exchangeable brush portion.

7. The positioning protrusion projects radially outward from the outer peripheral surface of the handle portion and has a curved surface portion on the tip side of the shaft portion. The replaceable toothbrush according to any one of claims 3 to 6.

8. A recess for gripping with a finger is formed on the outer peripheral surface of the inserted portion. The replaceable toothbrush according to any one of claims 1 to 7.

9. The shaft portion has a straight portion with a constant outer diameter on the tip side in the longitudinal direction and a tapered portion located on the base end side of the straight portion and having an outer diameter gradually increasing toward the base end side. The inserted portion has an inner inserted portion where the straight portion is arranged in a mounted state where the shaft portion is inserted into the inserted portion, and a plurality of press-fitting ribs along the longitudinal direction are formed on the inner peripheral surface of the inner inserted portion. In the mounted state, the straight portion is press-fitted into the inner inserted portion, so that the press-fitting ribs are crushed. The replaceable toothbrush according to any one of claims 1 to 8.

10. A brush for replacement, which is used for the replaceable toothbrush according to any one of claims 1 to 9 and consists of the replacement brush portion.

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