toothbrush

Abstract

To provide a toothbrush having excellent design by suppressing molding failure even when a design having a closed space or a substantially closed space is applied to both surfaces of a handle body.SOLUTION: A toothbrush comprises a handle body 10 including a head part and a grip part, and a brush part on a front of the head part, where at least a part of a handle main body 30 of the handle body 10 is covered with a covering part 40. When being viewed from a direction perpendicular to a long axis direction of the handle body 10, the handle main body 30 includes a first space 50 on one side thereof, and a second space 60 on the other side, where the first space 50 and a second space 60 are connected by a first through passage 31. The toothbrush is configured to make a second resin reach from the first space 50 through the first through passage 31 to the second space 60, and the first space 50, first through passage 31 and second space 60 are filled with the second resin.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] This invention relates to a toothbrush. [Background technology]

[0002] Toothbrushes equipped with a handle body made of hard resin, where the gripping portion and other parts are covered with soft resin, offer excellent grip and provide a sense of security during use (for example, Patent Documents 1 and 2). Such toothbrushes are manufactured using a method known as two-color molding, in which the handle body, obtained by injection molding using a primary mold, is placed in a secondary mold, and soft resin is injected and filled into the secondary mold to form the handle body.

[0003] In addition to the functionality mentioned above, two-color molding allows for creative design of the handle shape and color, and the inclusion of logos and motifs on the surface enhances the toothbrush's aesthetic appeal and increases its overall attractiveness. The most common methods for adding logos or motifs are to use different colors for the handle body and the covering, leaving a portion of the handle body exposed and outlined, or to apply them using hot stamping or transfer decals. Of these methods, the one requiring the most ingenuity in manufacturing is the aforementioned method of partially exposing the handle body and then framing it. For example, when forming a logo or motif such as an "O" that has a closed space inside, with a hollow interior surrounded by walls, a conventional technique is known in which a through hole is provided in the handle body that leads to the side with the closed space and the opposite side, and soft resin is poured into the closed space through the through hole from the opposite side of the closed space where the logo or motif such as "O" is not provided. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2001-299450 [Patent Document 2] Japanese Patent Publication No. 2002-336049 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, with conventional technology, when a letter or pattern (logo or motif) with a hollow interior and enclosed space surrounded by walls, such as "O", or a partially enclosed space surrounded by walls except for a part, such as "V", is placed on one side of the handle body, and a similar logo or motif is also placed on the opposite side, conventional technology presents difficulties in molding. Specifically, compared to when a logo is on only one side, when logos are on both sides, the placement of through-holes connecting both sides is restricted by the logos. If not properly positioned, the injection pressure during molding is dispersed, preventing the resin from flowing properly towards the through-holes. As a result, it becomes difficult to adequately distribute the soft resin throughout these enclosed or partially enclosed spaces, which can lead to molding defects. Therefore, conventionally, characters and patterns (logos and motifs) that have enclosed or nearly enclosed spaces were only placed on either the front (the surface of the head with the flocked surface) or the back of the handle, which limited the design freedom. Given these circumstances, the inventors diligently studied to solve the above problems and found that controlling the position and arrangement of the logos and through holes, thereby preventing a reduction in the injection pressure of the secondary resin, is effective in realizing a two-color molded toothbrush having logos on both sides, leading to the present invention.

[0006] The present invention aims to provide a toothbrush with excellent design that suppresses molding defects even when the handle body is designed to have closed or nearly closed spaces on both sides. [Means for solving the problem]

[0007] The present invention includes the following configuration. [1] A toothbrush comprising a handle body having a head portion and a gripping portion, and having a brush portion on the front of the head portion, The handle body comprises a handle body including a core rod and a covering portion that covers at least a part of the handle body. The handle body is made of a first resin, and the covering portion is made of a second resin. Viewed from a direction perpendicular to the long axis of the handle body, the handle body has a first space on one side consisting of a closed space surrounded entirely by walls, or a substantially closed space surrounded by walls except for a portion of its perimeter, and a second space on the other side consisting of a closed space surrounded entirely by walls, or a substantially closed space surrounded by walls except for a portion of its perimeter. Both the first space and the second space are open to the surface of the handle body. The first space and the second space are connected by at least one first through passage that penetrates the handle body, and the second resin reaches the second space from the first space through the first through passage. A toothbrush in which the second resin is filled throughout the first space, the first passage, and the second space. [2] The first passage is located inside the wall surrounding the first space and inside the wall surrounding the second space, A second through-passage is formed in the handle body, connecting the area outside the wall surrounding the second space with the first space, and the second resin enters the first space through the second through-passage and further reaches the second space through the first through-passage. The toothbrush according to [1], wherein the second resin is filled throughout the second passage, the first space, the first passage and the second space. [3] The toothbrush according to [1] or [2], wherein the first space is a closed space. [4] The toothbrush according to [1] or [2], wherein the first space is a closed space and the second space is a closed space. [5] When the first space is viewed from the front side from the opening side, the opening area is S A1 (mm 2 ), the sum of the cross-sectional areas of the passages of the first through-passage connected to the first space is S B1 (mm 2 When S is set to ), A1 / S B1 A toothbrush as described in [1] or [2], wherein the ratio is between 1.0 and 60.0. [6] The toothbrush according to [2], wherein the wall surrounding the first space and the wall surrounding the second space are provided on the mandrel, and the first through passage and the second through passage penetrate the mandrel. [7] The toothbrush according to [1] or [2], wherein in a cross-section perpendicular to the longitudinal axis direction of the handle body, the wall surrounding the first space is disposed outside the mandrel, and the first through passage penetrates the mandrel. [8] When the opening area of the first space is viewed from the front in the opening side is S A1 (mm 2 ), and when the opening area of the second space is viewed from the front in the opening side is S A2 (mm 2 ), the toothbrush according to [1] or [2], which satisfies S A1 ≧S A2 .

Advantages of the Invention

[0008] According to the present invention, even when a design having a closed space or a substantially closed space is applied to both surfaces of the handle body, it is possible to provide a toothbrush with excellent design properties in which molding defects are suppressed.

Brief Description of the Drawings

[0009] [Figure 1] It is a side view showing a schematic configuration of a toothbrush of an example of an embodiment. [Figure 2] It is a front view of the toothbrush of FIG. 1. [Figure 3] It is a rear view of the toothbrush of FIG. 1. [Figure 4] It is a front view showing a schematic configuration of a handle body in the toothbrush of FIG. 1. [Figure 5] It is a side view of the handle body of FIG. 4. [Figure 6] It is a cross-sectional view taken along line A-A of the toothbrush of FIG. 3. [Figure 7] It is a cross-sectional view taken along line B-B of the toothbrush of FIG. 3. [Figure 8] It is a cross-sectional view taken along line C-C of the toothbrush of FIG. 3. [Figure 9]This is an explanatory diagram illustrating the definitions of closed spaces and partially closed spaces. [Modes for carrying out the invention]

[0010] The toothbrush of the present invention will be described below with reference to an example shown in the drawings. Note that the dimensions and other specifications shown in the following description are examples only, and the present invention is not necessarily limited to them. It can be modified as appropriate without altering its essence.

[0011] Figure 1 is a side view showing a schematic configuration of a toothbrush 1, which is an example of an embodiment. Figure 2 is a front view of toothbrush 1, and Figure 3 is a rear view of toothbrush 1. The toothbrush 1 of this embodiment includes a handle body 10 having a head portion 12, a gripping portion 14, and a neck portion 16 connecting the head portion 12 and the gripping portion 14. A brush portion 20 is planted on the bristle surface 12a on the front side of the head portion 12 of the handle body 10.

[0012] Hereinafter, the direction from the tip of the head portion 12 to the rear end of the gripping portion 14 in the handle body 10 will be referred to as the "long axis direction". Furthermore, the direction parallel to the bristle surface 12a of the head portion 12 and perpendicular to the longitudinal axis is defined as the "short axis direction". Furthermore, the direction perpendicular to the bristle surface 12a of the head portion 12 is defined as the "thickness direction".

[0013] The handle body 10 includes a handle body 30 made of a first resin and a covering portion 40 made of a second resin that covers at least a part of the handle body 30.

[0014] The first resin is preferably a hard resin, but is not limited to it. However, in this invention, "hard resin" means a resin with a Shore A hardness of more than 90. Examples of hard resins include polypropylene resin, polyacetal resin, polybutylene terephthalate resin, and polyester resin. The second resin is preferably a soft resin, but is not limited to it. However, "soft resin" means a resin with a lower Shore A hardness than a hard resin, i.e., a resin with a Shore A hardness of 90 or less. Examples of soft resins include elastomers such as olefin-based elastomers, styrene-based elastomers, polyester-based elastomers, and polyurethane-based thermoplastic elastomers. "Shore A hardness" refers to the Dirometer A hardness of plastics measured according to JIS K 7215.

[0015] As shown in Figures 4 and 5, the handle body 30 in this example comprises a core rod 32, a projection 34 protruding from the front side (fuzzy surface 12a side) of the portion of the core rod 32 corresponding to the gripping portion 14, a projection 36 protruding from the back side of the portion of the core rod 32 corresponding to the gripping portion 14, and a projection 38 protruding from the side side of the portion of the core rod 32 corresponding to the gripping portion 14. In the present invention, "core rod" refers to the portion that mainly forms the rod-shaped handle body, as shown in Figures 4 and 5. As shown in Figures 1-3 and 6-8, the covering portion 40 is formed by covering the outer peripheral edge and back side portion of the head portion 12, the outer peripheral portion of the neck portion 16, and the portion of the gripping portion 14 other than the protruding portions 34, 36, and 38 with the second resin. In this embodiment, the gate position 80 of the second resin during molding (Figure 3) is located near the center of the handle body 10 in the longitudinal direction and on the back side of the handle body 10. Furthermore, since the neck portion 16 has a concave groove connected to the head portion 12, the second resin injected from the gate position 80 covers the portion of the gripping portion 14 other than the protruding portions 34, 36, and 38, and at the same time covers the outer peripheral edge and back side portion of the head portion 12 and the outer peripheral portion of the neck portion 16, forming a covering portion 40.

[0016] The tip surfaces of the protrusions 34, 36, and 38 are exposed surfaces 34a, 36a, and 38a, respectively, on the surface of the handle body 10. In addition, the handle body 30 and the covering part 40 are different colors, and letters or patterns are formed on the surface of the gripping part 14 of the handle body 10, bordered by the exposed surfaces 34a, 36a, and 38a of the protrusions 34, 36, and 38. The positional relationship between the exposed surfaces 34a, 36a, 38a of the protruding portions 34, 36, 38 and the surface of the covering portion 40 is not particularly limited. The exposed surfaces 34a, 36a, 38a may be flush with the surface of the covering portion 40, may protrude outward, or may be recessed inward.

[0017] In this example of toothbrush 1, the exposed surface 34a of the protruding portion 34 forms the letters "KODOMO", an animal character, and its footprints on the front surface of the gripping portion 14. Furthermore, the letters "KODOMO" and footprints are formed on the back surface of the gripping portion 14 by the exposed surface 36a of the protruding portion 36. Furthermore, a circular mark is formed on the side surface of the gripping portion 14 by the exposed surface 38a of the protruding portion 38. Note that the letters, patterns, etc., formed on the surface of the handle body 10 are not limited to those in this example.

[0018] As shown in Figures 2-4, the handle body 30 is On the front side, there is a first space 50 consisting of a closed space surrounded entirely by walls, or a substantially closed space surrounded by walls except for a portion of the surrounding area, On the rear side, there is a second space 60 which consists of a closed space surrounded entirely by walls, or a partially closed space surrounded by walls except for a portion of the surrounding area. Both the first space 50 and the second space 60 are open to the surface of the handle body 10.

[0019] However, "closed space" means a space that is completely surrounded by continuous walls, as viewed from the exposed side of the handle body, and where the length L of the walls is 5.0 mm or more. Furthermore, the length L of the walls forming the closed space means the length of the entire circumference of the edge of the inner wall surface on the exposed side of the wall, as viewed from the exposed side of the handle body. For example, as shown in Figure 9(A), in a front view from the exposed side of the handle body, a space 72 enclosed by a wall 71 having an arc-shaped inner wall surface 71a and an inwardly convex, bent inner wall surface 71b, the sum of the length of the arc of the exposed-side edge of the inner wall surface 71a and the lengths of the two straight lines of the exposed-side edge of the inner wall surface 71b is the length of the wall, and a space 72 is considered a closed space when the length of the wall L is 5.0 mm or more.

[0020] The length L of the wall surrounding the enclosed space is 5.0 mm or more, and may be 5.5 mm or more, 6.0 mm or more, 6.5 mm or more, or 7.0 mm or more. The upper limit of the length L of the wall surrounding the enclosed space may be 60.0 mm or less, 55.0 mm or less, 50.0 mm or less, or 45.0 mm or less. The lower and upper limits of the length L of the wall surrounding the enclosed space can be any combination.

[0021] In this example of toothbrush 1, as shown in Figure 2, the first space 50 on the front of the handle body 10, specifically the space inside the letters "D" and "O," and the face and belly of the animal character, is a closed space completely surrounded by the wall 52 that constitutes the protruding part 34. Also, as shown in Figure 3, the second space 60 on the back of the handle body 10, specifically the space inside the letters "D" and "O," is a closed space completely surrounded by the wall 62 that constitutes the protruding part 36.

[0022] Furthermore, "approximately enclosed space" refers to a space in the handle body where, when the exposed surface of the handle body is viewed from the front, the surrounding area is enclosed by walls that are continuous for 3.0 mm or more, with some exceptions, and where the proportion P represented by the following formula (1) is 70.0% or more. P = {L / (L+D)} × 100 ... (1) However, the symbols in equation (1) have the following meanings. P: Percentage of walls surrounding a roughly enclosed space (%) L: Length of the wall surrounding the roughly enclosed space (mm) D: The shortest distance (mm) between open sections of walls surrounding a nearly enclosed space.

[0023] "The shortest distance between open parts of the walls surrounding a nearly enclosed space" means the following (i) to (iii) when viewed from the exposed side of the handle body in a front view of a nearly enclosed space that is surrounded by walls except for a small portion. (i) When there is an open area without surrounding walls in a nearly enclosed space, and the ends of the walls enclosing the nearly enclosed space are present on both sides of that open area, this means the shortest distance between those ends. (ii) If the end of a wall enclosing a substantially enclosed space exists only on one side of an open portion where there are no surrounding walls, this means the shortest distance between that end and the wall surface opposite that end. (iii) When there are no walls surrounding a nearly enclosed space and there are no ends of walls enclosing the nearly enclosed space on either side of the open portion, this means the shortest distance between the opposing inner wall surfaces on both sides. Furthermore, in a front view from the exposed side of the handle body, the length L of the wall forming the substantially enclosed space is defined as the length obtained by connecting the points that are the shortest distances on both sides of the open portion in the wall surrounding the substantially enclosed space, along the edge of the exposed side of the inner wall surface of the wall.

[0024] For example, as shown in Figure 9(B), if a space 72 is surrounded by walls 71 except for a portion of it, and viewed from the exposed side of the handle body, and there are ends 74 and 75 of the walls 71 on both sides of the open portion 73, then the shortest distance D is defined as the distance between the closest points of those ends 74 and 75 (points a and b in Figure 9(B)). Furthermore, in a front view from the exposed side of the handle body, the length from point a to point b along the edge of the exposed side of the inner wall surface 71a of the wall 71 is defined as the length L of the wall that forms a substantially enclosed space.

[0025] As an example of a case that fits the definition in (ii) above, as shown in Figure 9(C), when viewing a space 72 surrounded by walls 71 except for a portion of it from the exposed side of the handle body, and an end 74 of the wall 71 exists on only one side of the open portion 73, the shortest distance D is defined as the distance between that end 74 and the closest points (points a and b in Figure 9(C)) on the inner wall surface 71a facing that end 74. Furthermore, in a front view from the exposed side of the handle body, the length from point a to point b along the edge of the exposed side of the inner wall surface 71a of the wall 71 is defined as the length L of the wall that forms a substantially enclosed space.

[0026] Furthermore, as shown in Figure 9(D), if a space 72 surrounded by walls 71 except for a portion of it is viewed from the exposed side of the handle body in a front view, and there are no ends of walls 71 on either side of the open portion 73, then the distance between the inner wall surfaces 71a on both sides of the open portion 73 is defined as the shortest distance D. In this case, if the exposed side edge shape of the inner wall surfaces 71a on both sides of the open portion 73 is curved when viewed from the exposed side of the handle body in a front view, then the position where the curvature of that curve changes from the inside to the outside of the open portion 73 (inflection point) is defined as the reference point for the distance between the inner wall surfaces 71a on both sides (point a in Figure 9(D)), and the distance to the nearest point b of the inner wall surface 71a opposite to that reference point is defined as the shortest distance D. Furthermore, in a front view from the exposed side of the handle body, the length from point a to point b along the edge of the exposed side of the inner wall surface 71a of the wall 71 is defined as the length L of the wall that forms a substantially enclosed space.

[0027] The percentage P is 70.0% or higher, preferably 75.0% or higher, 80.0% or higher, 85.0% or higher, or 90.0% or higher. The upper limit of the percentage P is less than 100.0%, preferably 99.0% or lower, 98.0% or lower, 97.0% or lower, or 95.0% or lower. The lower and upper limits of the percentage P can be any combination.

[0028] The length L of the wall surrounding the nearly enclosed space is 3.0 mm or more, preferably 4.0 mm or more, 5.0 mm or more, 7.0 mm or more, or 10.0 mm or more. The upper limit of the length L of the wall surrounding the nearly enclosed space is preferably 20.0 mm or less, 18.0 mm or less, 15.0 mm or less, or 12.0 mm or less. The lower and upper limits of the length L of the wall surrounding the enclosed space can be any combination.

[0029] In this example of toothbrush 1, to give a typical example, as shown in Figure 2, the inner space of the first space 50 on the front of the handle body 10, except for a part enclosed by the tip of the animal character's tail, is a substantially closed space enclosed by the wall 52 that constitutes the protruding part 34.

[0030] The opening shape of the first space 50 is not particularly limited and can be designed as appropriate depending on the desired logo or motif. Similarly, the opening shape of the second space 60 is not particularly limited and can be designed as appropriate depending on the desired logo or motif. As shown in Figures 2, 4, and 7, the first space 50B may have protrusions 34 (such as the eyes of a character) that do not constitute the wall 52 on the inside of the wall 52 surrounding the first space 50. The same applies to the second space 60.

[0031] (1st passage) As shown in Figure 6, the handle body 30 has a first through passage 31 that penetrates the handle body 30 and connects the first space 50A and the second space 60A, which are located in positions where the front and back of the handle body 30 overlap when viewed from the thickness direction. Similarly, as shown in Figure 7, the first space 50B(50) and the second space 60B(60) are connected by the first passageway 31, and as shown in Figure 8, the first space 50C(50) and the second space 60C(60) are connected by the first passageway 31. The first space 50 and the second space 60, connected by the first passage 31, may completely overlap or partially overlap when viewed from the thickness direction.

[0032] In this way, during injection filling, the second resin reaches the second space 60 from the first space 50 through the first passage 31, and the second resin fills the entire first space 50, the first passage 31, and the second space 60. This makes it easier for the second resin to fill every corner of the second space 60 during injection filling, and reduces the likelihood of molding defects. This is because the second resin heading towards the second space 60 is temporarily trapped in the first space 50, which is surrounded by the wall 52 in front of it. As a result, the resin spreads throughout the first space 50, and the injection pressure increases within the first space 50. This suppresses the decrease in injection pressure, and ensures sufficient pressure to flow the second resin towards the second space 60.

[0033] It is preferable for the first space 50 to be a closed space rather than a nearly closed space, as this has a high effect in suppressing the decrease in injection pressure, makes it easier to distribute the second resin to every corner of the second space 60, and reduces the likelihood of molding defects. If the first space 50 is a closed space, even if the second space 60 is a closed space, it is easier to secure sufficient pressure to flow the second resin towards the second space 60, and thus reduces the likelihood of molding defects.

[0034] The number of first passageways 31 connected to one first space 50 is not limited to one, but may be two or more, for example, 1 to 3. The number of first passageways 31 connected to one second space 60 is not limited to one, but may be two or more, for example, 1 to 3. The first through passage 31 may connect multiple first spaces 50 to one second space 60, or one first space 50 may connect multiple second spaces 60.

[0035] The number of second spaces 60 connected by one first space 50 and a first through passage 31 is preferably three or less, and more preferably one. If the number of second spaces 60 is below the upper limit, the injection pressure necessary to flow resin into the second spaces 60 can be secured.

[0036] (2nd passageway) As shown in Figures 6 and 7, it is preferable that the handle body 30 has a second through passage 33 that connects the area outside the wall 62 surrounding the second space 60 on the back side of the handle body 10 with the first space 50. In this case, the second resin enters the first space 50 from the second through passage 33 and then reaches the second space 60 through the first through passage 31, thereby filling the entire second through passage 33, the first space 50, the first through passage 31, and the second space 60 with the second resin.

[0037] By forming the second through passage 33, the excess amount of resin and injection pressure during inflow can be limited, making it easier to flow the second resin into the first space 50 and further suppressing the decrease in injection pressure within the first space 50. Then, by being trapped in the first space 50 surrounded by the wall 52, the resin spreads throughout the first space 50 and the injection pressure within the first space 50 increases. As a result, the effect of securing the pressure to flow the second resin towards the second space 60 is further enhanced, and molding defects become even less likely to occur. The number of second passageways 33 connected to one first space 50 is not limited to one, but may be two or more, for example, 1 to 5.

[0038] As shown in Figure 6, in the toothbrush 1, it is preferable that a wall 52 surrounding the first space 50A (50) and a wall 62 surrounding the second space 60A (60) are provided on the core rod 32, and that the first through passage 31 and the second through passage 33 penetrate the core rod 32. In particular, when the "first space 50, first through passage 31, second through passage 33, and second space 60" are located away from the gate position, as shown in Figures 3 and 6, the injection pressure may be reduced compared to when they are located near the gate position. Therefore, this configuration is preferable when they are located away from the gate position. As a result, the distance over which the resin flows through the first space 50, the first through passage 31, the second through passage 33, and the second space 60 can be shortened, making it less likely for the injection pressure of the second resin to decrease further within the first space 50, and making it easier to fill the second space 60 completely with the second resin.

[0039] Furthermore, as shown in Figure 7, it is also preferable that, in a cross-section perpendicular to the long axis of the handle body 30, the wall 52 surrounding the first space 50B(50) is located outside the core rod 32, and the first through passage 31 penetrates the core rod 32. In particular, when the "first space 50, first through passage 31, second through passage 33, and second space 60" are located close to the gate position, as shown in Figures 3 and 7, it is possible to take advantage of the fact that they are more susceptible to the high temperature resin and high injection pressure immediately after injection from the gate compared to when they are far from the gate position. Therefore, this configuration is preferable when they are located close to the gate position. This makes it easier to secure a second through passage 33 with a larger passage cross-sectional area, making it easier to inject the second resin at a higher temperature into the first space 50 while maintaining a higher injection pressure. As a result, the decrease in injection pressure within the first space 50 is further suppressed, making it even easier to fill the second space 60 completely with the second resin. In addition, the configuration in which the wall 52 of the first space 50 is located outside the core rod 32 offers greater design flexibility compared to the configuration in which the wall 52 of the first space 50 is located on the core rod 32. In this embodiment, since the wall 52 is located outside the core rod 32, there is a risk that the handle will become too thick, so it is preferable that the wall 52 has a curved shape (mortar-like) that follows the edge of the handle, as shown in the cheek area of ​​the character's face in Figure 5. This not only improves the handle from becoming too thick, but also has the advantage that the curved surface makes it easier to stock the resin flowing into the first space without gaps.

[0040] In this case, the distance at the position where the distance from the center point of the first through passage 31 to the wall 52 of the first space 50 in the short axis direction is longest (longest distance) is preferably longer than the distance from the center point of the first through passage 31 to the side edge of the core rod 32 at that position, preferably 15.0 mm or less, and more preferably 10.0 mm or less.

[0041] When the first space 50 is viewed from the front side (exposed surface side), the opening area is S. A1 (mm 2 ), The opening area when the second space 60 is viewed from the front side is S. A2 (mm 2 ), The sum of the cross-sectional areas of the passages of the first through-passage 31 that connects to the first space 50 and the second space 60 is S. B1 (mm 2 ), The sum of the cross-sectional areas of the passages of the second passageway 33 connected to the first space 50 is S. B2 (mm 2 ) However, the opening area of ​​a substantially enclosed space shall mean the area of ​​the opening when a straight line is assumed to be part of the opening edge, connecting the open parts without walls surrounding the substantially enclosed space by the shortest distance D. Furthermore, the opening area S of the first space 50 A1 and the opening area S of the second space 60 A2 The sum of the total opening area S A Let's assume that.

[0042] As the amount of the second resin flowing into the first space 50 increases, the second resin is less likely to cool within the first space 50, and the second resin flows more easily into the second space 60, S A1 / S B1 S is preferably 1.0 or higher, more preferably 5.0 or higher, even more preferably 10.0 or higher, and particularly preferably 20.0 or higher. Also, the distance from the first passage 31 to the wall 52 does not become too far, and the decrease in injection pressure within the first space 50 is easily suppressed, A1 / S B1 The value is preferably 60.0 or less, more preferably 55.0 or less, even more preferably 50.0 or less, and particularly preferably 40.0 or less. A1 / S B1 The preferred lower and upper limits can be combined in any way, for example, 1.0 or more and 60.0 or less is preferred.

[0043] Opening area S of the first space 50 A1 The opening area S of the second space 60 is A2 Being equal to or greater in size than S A1 ≥S A2 It is preferable that this condition is met. This increases the flow velocity of the second resin from the first space 50 to the second space 60, making it easier for the second resin to reach every corner of the second space 60. Furthermore, if multiple first spaces 50 are connected to the same second space 60, the sum of the opening areas of those multiple first spaces 50 is S A1 In addition, if one first space 50 is connected to multiple second spaces 60, the sum of the opening areas of those multiple second spaces 60 is S. A2 Let's assume that.

[0044] S A1 / S A2 A value of 1.0 or higher is preferred, 3.0 or higher is more preferred, 5.0 or higher is even more preferred, and 10.0 or higher is particularly preferred. Also, S A1 / S A2 The value is preferably 30.0 or less, more preferably 25.0 or less, even more preferably 20.0 or less, and particularly preferably 15.0 or less. A1 / S A2 The preferred lower and upper limits can be combined in any way, for example, 1.0 or more and 30.0 or less is preferred.

[0045] S A / S B1 A value of 1.0 or higher is preferred, and a value of 20.0 or higher is more preferred. A / S B1 If the value is above the lower limit, the resin is more likely to flow into the second space 60 before it cools and hardens. A / S B1 It is preferably 60.0 or less, and more preferably 40.0 or less. A / S B1 If it is below the upper limit, it is easier to secure a sufficient flow rate to fill the second space 60 with resin. A / S B1 The preferred lower and upper limits can be combined in any way, for example, 1.0 or more and 60.0 or less is preferred.

[0046] Opening area S of the first space 50 A1 5.0mm 2 The above is preferable, 20.0 mm 2 The above is more preferable. Opening area S A1 If the value is above the lower limit, it is easier to secure a sufficient flow rate to fill the second space 60 with resin. Opening area S A1 60.0mm2 The following is preferable: 50.0 mm 2 The following is more preferable: Opening area S A1 If the opening area S is below the upper limit, it is easier to secure the injection pressure necessary to flow the resin into the second space 60. A1 The preferred lower and upper limits can be combined in any way, for example, 5.0 mm 2 60.0mm 2 The following are preferable.

[0047] Opening area S of the second space 60 A2 It is 1.0 mm 2 The above is preferable, 2.0 mm 2 The above is more preferable. Opening area S A2 If the opening area S is above the lower limit, the injection pressure required to flow the resin into the second space 60 will not become too high. A2 40.0mm 2 The following is preferable: 10.0 mm 2 The following is more preferable: Opening area S A2 If the opening area S is below the upper limit, the time required to flow the resin into the second space 60 will not become too long. A2 The preferred lower and upper limits can be combined in any way, for example, 1.0 mm 2 40.0 mm 2 The following are preferable.

[0048] The sum of the cross-sectional areas of the passages in the first passageway 31, S B1 0.5mm 2 The above is preferable, 1.0 mm 2 The above is more preferable. Total S B1 If it is above the lower limit, it is easier to secure a sufficient flow rate to fill the second space 60 with resin. Total S B1 5.0mm 2 The following is preferable: 3.0 mm 2 The following is preferable: Sum S B1 If it is below the upper limit, it is easier to secure the injection pressure necessary to flow the resin into the second space 60. Total S B1 The preferred lower and upper limits can be combined in any way, for example, 0.5 mm 2 5.0mm or more 2The following is preferable.

[0049] The total cross-sectional area S of the second through-passage 33 B2 is preferably 1.0 mm 2 or more, and more preferably 2.0 mm 2 or more. If the total S B2 is at least the lower limit value, it is easy to secure a sufficient flow rate for resin supply to the first space 50. The total S B2 is preferably 20.0 mm 2 or less, and more preferably 15.0 mm 2 or less. If the total S B2 is at most the upper limit value, it is easy to secure the injection pressure necessary for flowing the resin into the second space 60. The total S B2 The preferable lower and upper limits can be arbitrarily combined. For example, 1.0 mm 2 or more and 20.0 mm 2 or less are preferable.

[0050] The total cross-sectional area S of the first through-passage 31 B1 is larger than the total cross-sectional area S of the second through-passage 33 B2 , that is, it is preferable to satisfy S B2 > S B1 . Thereby, it is easy to secure the amount of resin for flowing the resin into the second space 60. S B2 / S B1 is preferably 1.5 or more, more preferably 3.0 or more, further preferably 4.5 or more, and particularly preferably 6.0 or more. Also, S B2 / S B1 is preferably 20.0 or less, more preferably 18.5 or less, further preferably 17.0 or less, and particularly preferably 15.5 or less. S B2 / S B1 The preferable lower and upper limits can be arbitrarily combined. For example, 1.5 or more and 20.0 or less are preferable.

[0051] The minimum thickness of the wall 52 of the first space 50 is preferably 0.5 mm or more, and more preferably 1.0 mm or more. If the minimum thickness of the wall 52 is equal to or greater than the lower limit, it becomes easier to dam up the second resin that flows into the first space 50 and send it to the second space 60. The minimum thickness of the wall 52 is preferably 10.0 mm or less, and more preferably 5.0 mm or less. If the minimum thickness of the wall 52 is equal to or less than the upper limit, it becomes easier to dam up the second resin that flows into the first space 50 and send it to the second space 60. The preferred lower and upper limits for the minimum thickness of the wall 52 can be arbitrarily combined, for example, 0.5 mm or more and 10.0 mm or less is preferred.

[0052] The minimum thickness of the wall 62 of the second space 60 is preferably 0.5 mm or more, and more preferably 1.0 mm or more. If the minimum thickness of the wall 62 is equal to or greater than the lower limit, molding defects (burrs) are less likely to occur. The thickness of the wall 62 is preferably 10.0 mm or less, and more preferably 5.0 mm or less. If the minimum thickness of the wall 62 is equal to or less than the upper limit, molding defects (short shots) are less likely to occur. The preferred lower and upper limits for the minimum thickness of the wall 62 can be arbitrarily combined; for example, 0.5 mm or more and 10.0 mm or less is preferred.

[0053] The brush section 20 is not particularly limited, and the number of bristle bundles, cross-sectional shape, bristle length, bristle bundle diameter, and arrangement pattern of bristle bundles on the bristle surface 12a can be appropriately set according to the application. Examples of materials for the bristles that make up the bristle bundle include polyamide, polyester such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate, and polyolefins such as polypropylene.

[0054] The method for manufacturing the toothbrush 1 is not particularly limited, and known methods can be employed. For example, a so-called two-color molding method can be used, in which the handle body 30 is molded from a first resin by injection molding using a primary mold, and then the handle body 10 is molded by injecting and filling a second resin while the handle body 30 is placed in a secondary mold.

[0055] As described above, in the toothbrush of the present invention, when viewed from a direction perpendicular to the long axis of the handle body, a first space is provided on one side of the handle body and a second space on the other side, and these are connected by a first through passage. As a result, when the second resin enters the first space during injection filling, the decrease in injection pressure is suppressed, and the resin can flow to the second space while maintaining sufficient injection pressure, so that the second resin can fill every corner of the second space. As a result, molding defects are sufficiently suppressed, the degree of design freedom is increased, and it is possible to make a toothbrush with excellent design, such as having complex logos or motifs on both sides. Furthermore, while the difficulty of molding increases as the distance between the first and second spaces and the gate position increases, the toothbrush of the present invention can sufficiently suppress molding defects even when the gate position of the secondary mold and the positions of the first and second spaces are 10.0 mm or more apart.

[0056] Furthermore, the toothbrush of the present invention is not limited to the toothbrush 1 described above. For example, the first space and the second space may be located on one side and the other side of the handle body in the direction of its short axis. In Figures 2 and 3, "one side" and "the other side" are exemplified as the front and back sides, but they are not limited to these; they could also be the side sides (right side and left side) as in Figure 1. Furthermore, "one side" and "the other side" do not have to be on opposite sides of the same line; for example, they could be the front side and the right side. The handle body may have a protruding portion that extends from the core rod, the tip of which is not exposed to the surface of the handle body. In the handle body, protrusions that are exposed on the surface of the handle body and form logos or motifs are preferably provided on the gripping portion, but they may also be provided on the head portion or neck portion.

[0057] Furthermore, without departing from the spirit of the present invention, the components in the above embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate. [Explanation of Symbols]

[0058] 1...toothbrush, 10...handle body, 12...head part, 14...grip part, 16...neck part, 20...brush part, 30...handle body, 31...first passage, 32...core rod, 33...second passage, 34,36,38...protruding parts, 34a,36a,38a...exposed surfaces, 40...covered parts, 50,50A~50C...first space, 52...wall, 60,60A~60C...second space, 62...wall, 71...wall, 71a,71b...inner wall surface, 72...space, 73...open part, 74,75...ends.

Claims

1. A toothbrush comprising a handle body having a head portion and a gripping portion, and having a brush portion on the front of the head portion, The handle body comprises a handle body including a core rod and a covering portion that covers at least a part of the handle body. The handle body is made of a first resin, and the covering portion is made of a second resin. When viewed from a direction perpendicular to the long axis of the handle body, the handle body has a first space on one side which is a closed space surrounded entirely by walls, or a substantially closed space surrounded by walls except for a portion of its perimeter, and a second space on the other side which is a closed space surrounded entirely by walls, or a substantially closed space surrounded by walls except for a portion of its perimeter. Both the first space and the second space are open to the surface of the handle body. The first space and the second space are connected by at least one first through passage that penetrates the handle body, and the second resin reaches the second space from the first space through the first through passage. The first passage is located inside the wall surrounding the first space and inside the wall surrounding the second space. A second through passage is formed in the handle body, connecting the area outside the wall surrounding the second space with the first space. The second resin enters the first space through the second passage and then reaches the second space through the first passage. A toothbrush in which the second penetration, the first space, the first penetration, and the second space are filled with the second resin.

2. The toothbrush according to claim 1, wherein the first space is a closed space.

3. The toothbrush according to claim 1, wherein the first space is a closed space and the second space is a closed space.

4. The opening area when the first space is viewed from the front side is S. Ａ１ (mm ２ ), the sum of the cross-sectional areas of the passages of the first through-passage connected to the first space is S Ｂ１ (mm ２ ) When that is the case, S Ａ１ / S Ｂ１ The toothbrush according to claim 1 or 2, wherein the coefficient of the toothbrush is 1.0 or more and 60.0 or less.

5. The toothbrush according to claim 1 or 2, wherein the wall surrounding the first space and the wall surrounding the second space are provided on the core rod, and the first through passage and the second through passage penetrate the core rod.

6. The toothbrush according to claim 1 or 2, wherein in a cross section perpendicular to the long axis of the handle body, the wall surrounding the first space is located outside the core rod, and the first through passage penetrates the core rod.

7. Let the opening area when the first space is viewed from the front in the opening direction be S Ａ１ (mm ２ ), and let the opening area when the second space is viewed from the front in the opening direction be S Ａ２ (mm ２ ). When this is the case, the toothbrush according to claim 1 or 2 satisfies S Ａ１ ≧ S Ａ２ .

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