toothbrush

Abstract

To provide a toothbrush suppressed in cost of manufacture, having a stable quality, reducing loads of a maker side, facilitating design change, facilitating separate processing at household, and capable of preventing contamination at a handle part side to be recycled, and promoting environmental load reduction.SOLUTION: A toothbrush comprises a first molding 11 at a head part side comprising a first rigid resin, and a second molding 12 at a handle part side comprising a second rigid resin having a low adhesive quality to the first rigid resin. There is formed an engaging structure 10 in a junction part thereof, inhibiting relative displacement along an axial direction (a0), permitting relative tilting in a predetermined one direction (d1) orthogonal to the axial direction (a0), and permitting separation due to that an engagement state is released in an inclined posture in which an angle made by axis (a1, a2) thereof becomes a predetermined angle (θ1) or more by tilting.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a toothbrush having a head portion in which tufts of bristles are attached, a neck portion, and a handle portion that serves as a handle, and in particular to a toothbrush that does not require cutting of the head portion during sorting. [Background technology]

[0002] In recent years, as part of efforts to promote the 3Rs (Reduce, Reuse, Recycle) for plastic products, there has been a demand for toothbrushes to be developed as products that promote recycling and reduce environmental impact. Toothbrushes are usually disposed of as combustible waste because the heads become contaminated with use and because there is a flat wire (metal) that is driven into the head along with the bristles. When recycling these, specialized companies are required to collect them and equipment is required to cut off the heads and separate them.

[0003] As a toothbrush that does not require cutting of the head, a toothbrush with replaceable brushes has been proposed in which the brush portion (unit) of the head is detachably fitted to the head body (see, for example, Patent Documents 1 and 2). With such toothbrushes with replaceable brushes, when discarded, the brush portion can be removed at home and disposed of as incinerated waste, while the rest of the toothbrush can be recycled and separated for disposal.

[0004] However, these toothbrush replacements have a large burden on manufacturers, as they have issues with the increased number of parts, the increased number of molds and processes (assortment), and the increased manufacturing costs, as well as quality issues related to ensuring the fit of the brush parts. Furthermore, they require manufacturers to maintain inventory for a certain period of time even after the product is discontinued, and there is little freedom to change the design. Another problem is that the gaps in the fitting structure can become contaminated. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-165641 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-255112 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above-mentioned situation, the present invention aims to solve the problem of providing a toothbrush that reduces manufacturing costs, has stable quality, places little burden on the manufacturer, allows for easy design changes, can be easily separated and disposed of at home, and prevents contamination of the handle when recycled, thereby promoting a reduction in environmental impact. [Means for solving the problem]

[0007] The present invention includes the following inventions. (1) A toothbrush characterized in that a first molded body made of a first hard resin on the head side, on which bristle bundles are implanted, and a second molded body made of a second hard resin having low adhesive properties with respect to the first hard resin on the handle side, which serves as a handle, are joined coaxially in the longitudinal direction at the position of the neck, and an engagement structure is formed at the joint between the first molded body and the second molded body, which, in their normal coaxial positions, prevents relative movement along the axial direction, but allows relative tilting in a predetermined direction perpendicular to the axial direction, and, in an inclined position where the angle between the axes becomes equal to or greater than a predetermined angle due to the tilting, disengages and allows separation.

[0008] (2) The toothbrush described in (1), wherein the predetermined direction in which the engagement structure allows relative tilting is the forward direction in the front-to-back direction with the bristle surface of the head portion as the front side and the back side as the rear side, or either the left-to-right direction in the left-to-right direction and the axial direction.

[0009] (3) A toothbrush as described in (1) or (2), in which the engagement structure is formed so that the joining portion of one of the first molded body and the second molded body is covered by the joining portion of the other, except for at least a portion of the area on the specified side.

[0010] (4) The toothbrush according to (3), wherein the synthetic resin that is the material of the other of the first molded body and the second molded body is a synthetic resin that has a lower molding temperature than the synthetic resin that is the material of one of the first molded body and the second molded body.

[0011] (5) The toothbrush according to any one of (1) to (4), wherein the engagement structure has a partially arcuate guide surface that guides the relative tilting movement in the predetermined direction.

[0012] (6) A toothbrush as described in (5), in which the engagement structure is such that the joining portion of one of the first molded body and the second molded body is composed of a plate-like piece having a partially arc-shaped outer peripheral surface centered on the central axis of rotation as the relative tilting movement, and the joining portion of the other is composed of a pair of clamping walls that clamp the plate-like piece from the front and back or left and right in the direction of the central axis, and a support wall that has a similarly partially arc-shaped inner peripheral surface that covers the partially arc-shaped outer peripheral surface except for the side in the left and right or front and back directions perpendicular to the central axis.

[0013] (7) A toothbrush as described in (6), in which the radius of the partial arc of the plate-like piece is set to a value equal to or greater than half the width of the neck portion in a direction perpendicular to both the central axis and the axial direction of the toothbrush. [Effects of the Invention]

[0014] The toothbrush of the present invention, constructed as described above, uses a first hard resin and a second hard resin with low adhesive properties. The first and second molded bodies can be easily and inexpensively manufactured using a two-piece mold, similar to that of a conventional toothbrush, by two-color molding or insert molding, for example. This allows for stable quality and a high degree of freedom in design modifications. Furthermore, the head and handle can be easily separated at home without the use of tools by simply tilting them relative to one another in a predetermined direction to release the adhesive (separation) and then pulling them out in the tilted direction. Furthermore, because the head and handle remain attached to each other until separation, problems such as contamination of gaps, which are common in conventional toothbrushes with detachable designs, are eliminated, preventing contamination of the handle for recycling.

[0015] Here, if the specified direction in which the engagement structure allows relative tilting is the forward direction in the front-to-back direction with the bristle surface of the head portion as the front and the back side as the rear, or either the left or right direction in the left or right lateral direction perpendicular to the front-to-back direction and the axial direction, these directions are not the direction of the force applied when brushing, and accidental relative tilting when brushing can be more reliably prevented.

[0016] Furthermore, if the engagement structure is formed so that the joint portion of one of the first molded body and the second molded body is covered by the joint portion of the other body, except for at least a portion of the area on the specified side in one direction, the above-mentioned unexpected relative tilting during brushing can be prevented even more reliably.

[0017] Furthermore, if the synthetic resin that is the other material of the first molded body and the second molded body is a synthetic resin that has a lower molding temperature than the synthetic resin that is one of the materials, two-color molding can be easily performed without melting the molded part that was molded first.

[0018] Furthermore, if the engagement structure has a partially arcuate guide surface that guides the relative tilting movement in the predetermined direction, the tilting movement during the sorting process can be carried out more smoothly.

[0019] In particular, the engagement structure may be such that the joint portion of one of the first and second molded bodies is composed of a plate-like piece having a partially arc-shaped outer peripheral surface centered on the central axis of rotation as the relative tilting, and the joint portion of the other body is composed of a pair of clamping walls that clamp the plate-like piece from the front-to-back or left-to-right directions in the direction of the central axis, and a support wall having a similarly partially arc-shaped inner peripheral surface that covers the partially arc-shaped outer peripheral surface except for the specified side of the left-to-right or front-to-back directions perpendicular to the central axis.In this case, the toothbrush can tilt only in the specified front-to-back direction where no force is applied when brushing, and movement in other directions is firmly restricted by the clamping walls and support walls, thereby more reliably preventing unexpected relative tilting when brushing.

[0020] Furthermore, if the arc (radius) of the partial arc of the plate-like piece is set to a value equal to or greater than half the width of the neck portion in a direction perpendicular to both the central axis and the axial direction of the toothbrush, when the previously molded first molded body is inserted to mold the second molded body, the plate-like piece of the first molded body can be firmly supported from the front and back directions without moving due to resin pressure, and a high-quality product can be manufactured. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a plan view of a toothbrush according to a representative embodiment of the present invention, viewed from the front. [Figure 2] (a) is a right side view of the toothbrush, and (b) is a left side view. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] (a) is a cross-sectional view taken along the line AA in Fig. 4, and (b) is a cross-sectional view taken along the line BB. [Figure 6] FIG. 10 is an explanatory view showing the toothbrush in a tilted state after the first molded body is tilted relative to the second molded body. [Figure 7] FIG. 10 is an explanatory diagram showing the steps for sorting toothbrushes. [Figure 8] 10A and 10B are explanatory views showing a modified example of the engagement structure of the toothbrush, in which (a) is a plan view seen from the front, and (b) is a cross-sectional view taken along the line CC of (a). [Figure 9] 10A and 10B are explanatory views showing another modified example of the engagement structure, in which (a) is a plan view seen from the front, and (b) is a DD cross-sectional view of (a). [Figure 10] 10A and 10B are explanatory views showing still another modified example of the engagement structure, in which (a) is a plan view seen from the front, and (b) is an E-E cross-sectional view of (a). [Figure 11] FIG. 10 is an explanatory view showing still another modified example of the engagement structure. [Figure 12] 10A and 10B are explanatory views showing still another modified example of the engagement structure, in which (a) is a plan view seen from the front, (b) is a side view, and (c) is an FF cross-sectional view of (a). [Figure 13] FIG. 10 is an explanatory view showing still another modified example of the engagement structure. [Figure 14] 14A is a side view of the modified example shown in FIG. 13, FIG. 14B is a rear view, and FIG. 14C is a cross-sectional view taken along the line GG. [Figure 15] 14 is an explanatory diagram showing the inclined state of the toothbrush of the modified example shown in FIG. 13 due to relative tilting. FIG. [Figure 16] FIG. 10 is an explanatory diagram showing yet another modified example of the engagement structure. [Figure 17] FIG. 10 is an explanatory diagram showing yet another modified example of the engagement structure. [Figure 18] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0022] Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0023] 1 and 2, the toothbrush 1 of the present invention is constructed by joining a first molded body 11 on the head portion 2 side, where bristle bundles 20 are implanted, and a second molded body 12 on the handle portion 4 side, which serves as a handle, coaxially in the longitudinal direction, with the neck portion 3 as the boundary. The first molded body 11 is constructed of a first hard resin such as polyethylene terephthalate resin (PET). The second molded body 12 is constructed of a second hard resin that has low adhesive properties with respect to the first hard resin, such as polypropylene resin (PP) if the first hard resin is polyethylene terephthalate resin (PET).

[0024] At the joint between the first molded body 11 and the second molded body 12, an engagement structure 10 is formed which, in a normal position where they are coaxial (axis a0), prevents relative movement along the axial direction (a0) and allows relative tilting (rotation) in a predetermined direction (d1) perpendicular to the axial direction (a0), and, as shown in Figures 6 and 7, disengages and allows separation when the tilted position causes the angle between the axes (a1, a2) to be equal to or greater than a predetermined angle (θ1).

[0025] Furthermore, by simply tilting the head and handle in one direction to release the bond (peel) and then pulling them out in the tilted direction, the head and handle can be easily separated at home without the use of tools. Furthermore, because they are joined together until separation, problems such as contamination of the gaps that occur with conventional detachable devices do not occur, and contamination of the handle can be prevented.

[0026] In this example, the predetermined direction (d1) in which relative tilting is permitted is the front-to-back direction with the tufted surface 2a of the head portion 2 as the front and the back side as the rear, and either the left or right direction of the left or right sides perpendicular to the axial direction a0 (in this example, the right direction (upward on the paper in Figure 1)). However, the present invention is not limited to this, and it is also preferable to set the direction to the front of the front-to-back direction, as in the examples of Figures 13 to 15 described below.

[0027] 1 to 3, the engagement structure 10 is formed so that the joining portion of one of the first molded body 11 and the second molded body 12, that is, joining portion 5 provided on the base end side (handle side) of the first molded body 11 in this example, is covered by joining portion 6 provided on the tip end side (head side) of the other (second molded body 12 in this example) except for at least a partial region R1 on the side of the predetermined direction d1. More specifically, it has partially arc-shaped guide surfaces 5a and 6b that guide the relative tilting in the predetermined direction d1.

[0028] More specifically, as shown in FIG. 4, the joint 5 of the first molded body 11 is composed of a plate-like piece 50 having a partially arcuate outer peripheral surface (guide surface 5a) centered on a central axis a3 of rotation as a relative tilt. The plate-like piece 50 is formed thin to the extent that it is covered by the joint 6, and a substantially circular plate portion 502 having the partially arcuate outer peripheral surface (guide surface 5a) is formed on the base end side (handle portion side) of the toothbrush. The specific thickness of the plate-like piece 50 is configured as a thin plate that is 10 to 90% of the neck thickness on the distal end side (head portion side). The arc (radius) of the partially arcuate outer peripheral surface (guide surface 5a) of the plate-like piece 50 (substantially circular plate portion 502) is set to be equal to or greater than half the width w1 of the neck portion in a direction perpendicular to both the central axis a3 of the arc and the axial direction a0 of the toothbrush. Here, in this example, the central axis a3 is located on the axis a0 of the toothbrush, but the present invention is not limited to this in any way, and the central axis a3 may of course be located at a position offset from the axis a0, or may be located outside the molded body, as in the examples of Figures 17 and 18 described below.

[0029] 4 and 5, the joint 6 of the second molded body 12 is composed of a pair of clamping walls 60A, 60B that clamp the plate-like piece 50 from the front-to-rear direction, which is the direction of the central axis a3 of rotation as the relative tilting, and a support wall 61 having a partially arcuate inner peripheral surface (guide surface 6b) that covers the partially arcuate outer peripheral surface (guide surface 5a), except for a partial region R1 on the side of at least the predetermined direction d1 (upward in the paper in FIG. 1 in this example) in the left-right direction perpendicular to the central axis a3. The partial region R1 is a region that allows the joint 5 to tilt in the direction d1 relative to the joint 6 when the first molded body 11 tilts relative to the joint 6.

[0030] Furthermore, the radius (radius) of the partial arc of the outer peripheral surface (guide surface 5a) of the plate-like piece 50 (approximately circular plate portion 502) is set to a value equal to or greater than half the width w1 of the neck portion, specifically, greater than half the value of w1, and a portion of region R2 is exposed from the support wall 61 in the direction opposite to d1, that is, on the left side in this example. That is, the support wall 61 of the joint 6 is separated by region R2 into a support wall 611 on the tip side of region R2, and a support wall 612 on the base side that supports the area from region R2 to region R1.

[0031] As shown in FIGS. 1 and 4, in the normal position where they are coaxial (axis a0), the plate-shaped piece 50 (approximately circular plate portion 502) is engaged with the base end portion 611a of the support wall 611 on the tip side and cannot be separated along the axial direction (a0). The support wall 612 also partially supports the region of the outer peripheral surface (guide surface 5a) of the plate-shaped piece 50 (approximately circular plate portion 502) in the direction d1 (right side). That is, the support wall 612 extends to the position of the end portion 612a. This allows the above-mentioned relative tilting to be performed stably.

[0032] The front and rear positions of the plate-like piece 50 at the joint 5 of the first molded body 11 form step portions 51A, 51B into which the clamping walls 60A, 60B fit to clamp the plate-like piece 50. The clamping walls 60A, 60B are configured so that, when they are in the step portions 51A, 51B, their outer surfaces are continuous and flush with the outer surface of the neck portion 3 on the head portion 2 side. The tip end surfaces 601 of the clamping walls 60A, 60B and the opposing step surfaces 510 on the step portions 51A, 51B sides are also partially arc-shaped guide surfaces having the same central axis as the arcs of the guide surfaces 5a, 6b.

[0033] In this way, the first molded body 11 and the second molded body 12 are structured so that the partially arcuate guide surface 5a is guided by the guide surface 6b, and the tip surface 601 is guided by the stepped surface 510, respectively, allowing for smooth relative tilting in a predetermined direction (d1). Therefore, by applying a force exceeding the adhesive strength of the resins in the predetermined direction d1, the bonded state is released (peeled off), allowing for smooth relative tilting in the predetermined direction d1 as shown in Figures 6 and 7. In order to appropriately set the adhesive strength against the force in the d1 direction, it is preferable to set the width w5 of the clamping walls 60A, 60B, which clamp the region 501 of the plate-like piece 50 closer to the toothbrush tip than the approximately circular plate portion 502, to a value in the range of 20 to 95% of the width of the neck portion at the corresponding position. In order to reduce this ratio, as shown in Figure 16, the portion 501 of the plate-like piece 50 may be located in an area extending from a position a certain distance inside the end 11a of the molded body 11 in one direction d1 to the end 11b in the opposite direction, and a structure may be adopted in which the width of the clamping walls 60A, 60B is made smaller.

[0034] The distance w2 (see FIG. 6) between the base end 611a of the tip-side support wall 611 and the tip end 612a of the base-side support wall 612 facing the region R1 is set to be approximately the same as or larger than the width in the left-right direction of the plate-like piece 50 (approximately circular plate portion 502) of the first molded body 11, i.e., the width w1 (see FIGS. 1 and 4) of the neck portion in this example. As a result, as shown in FIG. 6, the first molded body 11 and the second molded body 12 are configured to be able to move apart in the inclined direction in an inclined posture in which the inclination angle due to relative tilting is the predetermined angle (θ1).

[0035] Modified examples of the engagement structure 10 will be described below. As shown in Figures 8(a) and (b), it is also preferable that fillets 52, 52 are formed on both end edges of the plate-like piece 50 of the first molded body 11 in the direction of the central axis a3 (front-rear direction) along the region R1, and that covering pieces 602, 602 bent inward to cover the fillets 52 are formed on the front and rear sandwiching walls 60A, 60B of the joint 6 of the second molded body 12 in portions corresponding to the fillets 52, 52. In this way, the force that deforms the joint 6 so as to widen it restricts the tilting movement as shown in Figure 8(c), and thereby the joint strength when a force is applied in the direction d1 can be adjusted.

[0036] 9, instead of the fillet portion 52, it is also preferable to form a predetermined region or the entire region of one or both of the two side surfaces of the plate-like piece 50 in the direction of the central axis a3 (front-rear direction) closer to the region R1 as an inclined surface 53 whose thickness decreases toward the region R1, and to configure the inner surface of one or both of the front and rear sandwiching walls 60A, 60B of the joint 6 of the second molded body 12 as an inclined surface 603 facing the inclined surface 53. This also serves to restrict the tilting movement of the joint 6 due to the force that deforms the joint 6 so as to widen it, thereby making it possible to adjust the joint strength when a force is applied in the direction d1.

[0037] 10, it is also preferable to provide a recess or protrusion (groove 54 in this example) on one or both of the two side surfaces of the plate-like piece 50 in the direction of the central axis a3 (front-rear direction), and to provide a protrusion or recess (ridge 604 in this example) that engages with the recess or protrusion (54) on the inner surface of one or both of the front and rear sandwiching walls 60A, 60B of the joint 6 of the second molded body 12. This also restricts the tilting movement by the force that disengages the protrusion and recess and deforms the joint 6 so that it widens, thereby making it possible to adjust the joint strength when a force is applied in the direction d1.

[0038] 11, it is also preferable that the tip surfaces 601 of the sandwiching walls 60A, 60B of the second molded body 12 and the opposing step surfaces 510 of the first molded body 11 are configured as flat surfaces extending straight to the left and right sides, rather than as the partially arcuate guide surfaces described above. In this way, when a force is applied in the d1 direction, the step surfaces 510 of the first molded body 11 press against the tip surfaces 601 of the sandwiching walls 60A, 60B, and the force of the deformation that widens the joint 6 restricts the tilting movement, thereby making it possible to adjust the joint strength when a force is applied in the d1 direction.

[0039] As shown in FIG. 12, the approximately circular plate portion 502 at the base end (handle side) of the plate-like piece 50 of the first molded body 11, which has a partially arcuate outer peripheral surface (guide surface 5a), may have a larger width in the front-to-rear direction than the other portions, and one or both of the clamping walls 60A and 60B that clamp the plate-like piece 50 may be correspondingly thinner. This structure prevents the joint 6 from being easily disengaged when the plate-like piece 50 is tilted toward the tilting direction d1 and then released in the tilting direction due to the force that expands and deforms the joint 6. For the same purpose, it is also preferable to form the approximately circular plate portion 502 into a convex lens-like approximately circular plate with one or both bulging sides, rather than a flat approximately circular plate. As shown in FIGS. 17 and 18, it is also preferable to position the central axis a3 of the relative tilting motion at an outer position on the tilting direction (d1) side of the molded body 11 / 12 that constitutes the toothbrush 1, thereby increasing the radius of the relative tilting motion and making it easier to apply the peeling force during tilting. In this case, to prevent the applied force from becoming too large, in this example, fillets 52, 52 are formed on both front and rear end edges along region R1 of plate-like piece 50 of first molded body 11, as in the example of Fig. 8 described above, and covering pieces 602, 602 bent inward to cover fillets 52, 52 are formed on front and rear sandwiching walls 60A, 60B of joint 6 of second molded body 12 at portions corresponding to fillets 52, 52, but this does not have to be done if the adhesive strength is sufficient. Alternatively, inclined surfaces, recessed grooves, etc., as shown in the examples of Figs. 9 to 11 described above may be formed.

[0040] In the toothbrush 1 of this example, first, a primary mold for molding the first molded body 11 (see also FIG. 3) on the head portion 2 side is closed, and a first hard resin is injected into this primary mold to mold the first molded body 11. A mold with an efficient upper-lower split structure can be used for the primary mold. Next, after the primary mold is opened, the first molded body 11 is set in a secondary mold for molding the second molded body 12, and the mold is closed. A second hard resin having low adhesion to the first hard resin is injected into the secondary mold, and the second molded body 12 is two-color molded. A mold with an efficient upper-lower split structure can also be used for the secondary mold.

[0041] In this way, toothbrush 1 can be molded by two-color molding, comprising head portion 2 with bristle bundles 20 implanted therein, neck portion 3 connected to head portion 2, and handle portion 4 serving as a handle, with engagement structure 10 formed at the neck portion 3. Therefore, like ordinary toothbrushes, toothbrushes can be manufactured easily and inexpensively using a two-part mold, with consistent quality and a high degree of freedom in design changes.

[0042] Here, the radius (arc) of the partial arc of the outer peripheral surface (guide surface 5a) of the plate-shaped piece 50 (approximately circular portion 502) of the first molded body 11 is set to a value equal to or greater than half the width w1 of the neck portion in a direction perpendicular to both the central axis a3 of the arc and the axial direction a0 of the toothbrush, resulting in a structure in which the above-mentioned region R2 is exposed, so that when set in the second mold, the approximately circular portion 502 of the plate-shaped piece 50 can be firmly held in the mold so as to be sandwiched.

[0043] The second hard resin injected into the secondary mold is preferably a synthetic resin with a lower molding temperature than the first hard resin, since this allows for stable two-color molding. Specifically, polyethylene terephthalate resin (PET) or polybutylene terephthalate resin (PBT) is preferably used as the first hard resin. Furthermore, polypropylene resin (PP) or polyethylene resin (PE) is preferably used as the second hard resin.

[0044] That is, the first hard resin and the second hard resin can be a combination of hard resins with low adhesiveness (low adhesive strength). Specifically, the adhesive strength should preferably be 0.5N to 50N, more preferably 10N to 30N (rotation direction (d1)) so that they do not peel off when subjected to force from any direction during normal brushing. Furthermore, because separating the waste becomes impossible if the neck portion bends too much during separation, the adhesive strength should preferably be 90% or less, more preferably 70% or less, of the bending strength of the neck portion (bending strength in the direction d1).

[0045] For example, crystallizable resins such as polyacetal resin (POM), polyamide resin (PA), polybutylene terephthalate (PBT), or polypropylene resin (PP) have low adhesion to each other when paired with a crystallizable resin (excluding PP-PP pairs) or an amorphous resin. Therefore, low adhesion can be achieved by using a crystallizable resin such as polyacetal resin (POM) for one of the first and second hard resins and an amorphous resin such as acrylonitrile butadiene styrene resin (ABS), polycarbonate (PC), or acrylic resin (PMMA). Furthermore, among the crystallizable resins, polypropylene resin (PP) has high adhesion to each other. Therefore, even when both the first and second hard resins are crystallizable resins, they have low adhesion to each other, except when both the first and second hard resins are made of polypropylene resin (PP). Therefore, for example, low adhesion can be achieved by making one of the first hard resin and the second hard resin a crystallizable resin such as polyacetal resin (POM) and the other a crystallizable resin made of polyacetal resin (POM), polyamide resin (PA), polybutylene terephthalate (PBT), polypropylene resin (PP), or the like.

[0046] 13 to 15 show a modified example in which the predetermined direction in which relative tilting is permitted is the front direction (d2) in the front-to-rear direction with the tufted surface 2a of the head portion 2 as the front surface and the back surface as the rear surface.

[0047] The engagement structure 10 of this modified example is formed so that the joint 5 provided on the base end side (handle side) of the first molded body 11 is covered by the joint 6 provided on the tip side (head side) of the other side (the second molded body 12 in this example) except for a partial region R1 on the side of the specified direction d2 and a region R2 on the opposite side, and has partial arc-shaped guide surfaces 5a, 6b that guide relative tilting in the specified direction d2.

[0048] The joint 5 of the first molded body 11 is composed of a plate-like piece 50 having a partially arcuate outer peripheral surface (guide surface 5a) centered on the central axis a3 of rotation as the relative tilting movement. The plate-like piece 50 is formed in a thin plate shape to the extent that it is covered by the joint 6, and has the partially arcuate outer peripheral surface (guide surface 5a) on the base end side (handle side) of the toothbrush.

[0049] The joint 6 of the second molded body 12 on the other hand is composed of a pair of clamping walls 60A, 60B that clamp the plate-like piece 50 from the left and right directions, which is the direction of the central axis a3 of the relative tilting, and a support wall 61 having a partially arcuate inner peripheral surface (guide surface 6b) that covers the partially arcuate outer peripheral surface (guide surface 5a). Regions R1 and R2 are regions that allow the joint 5 to tilt in the direction d2 with respect to the joint 6 when the first molded body 11 tilts relative to the first molded body 11.

[0050] Furthermore, the radius (radius) of the partial arcs of the outer peripheral surface (guide surface 5a) of plate-like piece 50 is such that two partial arcs of different radiuses, with the radius on the front side being larger than the radius on the rear side, are connected via step portion 5c on the base end side (handle side) of the toothbrush. This allows tilting in the direction d2 but prevents tilting in the opposite direction because step portion 5c abuts against step portion 6c of corresponding guide surface 6b, and also increases the bonding area between joints 5, 6, making it easy to maintain bonding strength.

[0051] The support wall 61 is divided into a support wall 611 on the toothbrush tip side of the region R2, and a support wall 612 on the toothbrush base side that supports the area from the region R2 to the region R1.

[0052] 13 and 14, in the normal position where the plates are coaxial with each other, the plate-shaped piece 50 is engaged with the base end 611a of the support wall 611 on the tip side, and is configured so as not to be able to separate along the axial direction. The support wall 612 also partially supports the region in the direction d2 (front side) of the outer peripheral surface (guide surface 5a) of the plate-shaped piece 50. In other words, the support wall 612 extends to the position of the end 612a. This allows the above-mentioned relative tilting to be performed stably.

[0053] In this way, the first molded body 11 and the second molded body 12 are structured so that the partially arcuate guide surface 5a is guided by the guide surface 6b, allowing smooth relative tilting in a predetermined direction (d2). Therefore, by applying a force in the predetermined direction d2 that exceeds the adhesive strength of the resins, the bonded state is released (peeled off), and smooth relative tilting in the predetermined direction d2 is possible, as shown in Figures 6 and 7.

[0054] The distance w4 (see FIG. 15) between the base end 611a of the tip-side support wall 611 and the tip end 612a of the base-end support wall 612 facing the region R1 is set to be approximately the same as the front-to-rear width of the plate-like piece 50 of the first molded body 11, in this example the front-to-rear width w3 (see FIG. 14) of the neck portion, or to a value larger than this width w3. As a result, as shown in FIG. 15, the first molded body 11 and the second molded body 12 are configured to be able to move apart in the inclined direction in an inclined posture in which the inclination angle due to relative tilting is equal to or greater than the predetermined angle.

[0055] The above describes embodiments of the present invention, but the present invention is not limited to these examples. For example, in the embodiments, an example has been described in which a joint 5 is provided on the base end side (handle side) of the first molded body 11 and a joint 6 covering joint 5 is provided on the tip end side (head side) of the second molded body 12. However, it is of course also possible to provide the opposite, that is, a joint 5 is provided on the tip end side (head side) of the second molded body 12 and a joint 6 covering joint 5 is provided on the base end side (handle side) of the first molded body 11 (in this case, too, the selection of resins for the primary and secondary sides when performing two-color molding, etc., can be made in accordance with the representative embodiments described above). It is of course possible to implement the present invention in various forms as long as they do not deviate from the gist of the present invention. [Explanation of symbols]

[0056] 1 toothbrush 2 Head 2a Flocked surface 3 Neck 4 Handle 5 Joint 5a Guide surface 5c Step 6 Joint 6b Guide surface 6c Step 10 Engagement structure 11 First molded body 12 Second molded body 20 hair bundles 50 slabs 51A,51B Stepped section 52 Fillet 53 Slope 54 Groove 502 Disc part 510 Step surface 60A, 60B clamping wall 61 Supporting wall 601 Tip surface 602, 602 Covering piece 603 Slope 604 Convex strip 611 Supporting wall 611a Proximal end 612 Supporting wall 612a end

Claims

1. a first molded body on the head side, made of a first hard resin, into which tufts of bristles are attached, and a second molded body on the handle side, made of a second hard resin having low adhesive properties with respect to the first hard resin, which serves as a handle, are joined coaxially in the longitudinal direction with the neck portion as the boundary; At the joining portion of the first molded body and the second molded body, In a normal posture where they are coaxial with each other, relative movement along the axial direction is inhibited, and relative tilting in one predetermined direction perpendicular to the axial direction is permitted; When the tilting movement causes the angle between the axes to be equal to or greater than a predetermined angle, the engagement state is released and an engagement structure is formed that allows separation, the engagement structure has a partially arcuate guide surface that guides the relative tilting movement in the predetermined direction, the joint portion of one of the first molded body and the second molded body is composed of a plate-like piece having a partially arcuate outer peripheral surface centered on a central axis of rotation as the relative tilting movement, The other joint portion is configured by a support wall having a partially arcuate inner peripheral surface that covers the partially arcuate outer peripheral surface, except for a partial region on the side of the predetermined direction in the left-right or front-rear direction perpendicular to the central axis. A toothbrush characterized by:

2. The predetermined direction in which the engagement structure allows relative tilting is 2. The toothbrush of claim 1, wherein the direction of the bristle movement is either the front direction in the front-to-back direction with the bristle-implanted surface of the head portion as the front side and the back side as the rear side, or the left-to-right direction perpendicular to the front-to-back direction and the axial direction.

3. The toothbrush of claim 1 or 2, wherein the engagement structure is formed so that the joint portion of one of the first molded body and the second molded body is covered by the joint portion of the other, except for at least a portion of the area on the specified side.

4. 4. The toothbrush according to claim 3, wherein the synthetic resin that is the material of the other of the first and second molded bodies has a molding temperature lower than that of the synthetic resin that is the material of the other of the first and second molded bodies.

5. A toothbrush as described in claim 1, wherein the other joint part is composed of a pair of clamping walls that clamp the plate-like piece from the front, back, or left and right in the direction of the central axis.

6. 6. The toothbrush of claim 5, wherein the radius of the partial arc of the plate-shaped piece is set to a value equal to or greater than half the width of the neck portion in a direction perpendicular to both the central axis and the axial direction of the toothbrush.

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