JP2024005548A - toothbrush - Google Patents

Abstract

PROBLEM TO BE SOLVED: 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

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a toothbrush.

A toothbrush equipped with a handle body made of a hard resin whose gripping portion is coated with a soft resin has a high grip and provides a sense of security during use (for example, Patent Documents 1 and 2).
Such toothbrushes are manufactured by placing a handle body obtained by injection molding using a primary mold into a secondary mold, and molding the handle body by injecting and filling a soft resin into the secondary mold. Manufactured by color molding.

In addition to the functionality mentioned above, two-color molding improves the design of the toothbrush by changing the shape and color of the handle body, and adding logos and motifs to the surface, thereby increasing the product's appeal.
The most common ways to add a logo or motif are to paint the handle body and the cover in different colors, leave a portion of the handle body exposed and frame it, or apply a hot stamp or transfer sticker.
Among these methods, the method that requires the most ingenuity in manufacturing is the method described above in which a portion of the handle body is exposed and bordered.
For example, when forming a logo or motif such as "O" with a closed space inside by being hollow on the inside and surrounded by walls, the side with the closed space on the handle body and the opposite side. A method known in the prior art is to provide a communicating through hole and pour soft resin into the closed space through the through hole from the opposite side of the closed space where a logo or motif such as "O" is not provided.

Japanese Patent Application Publication No. 2001-299450 Japanese Patent Application Publication No. 2002-336049

However, with conventional technology, characters and patterns such as "O" which are hollow inside and surrounded by walls, or characters and patterns such as "V" which have a substantially closed space surrounded by walls except for a part, such as "V", etc. In the case where a logo or motif (logo or motif) is provided on one side of the handle body and a similar logo or motif is provided on the opposite side, molding is difficult in the conventional technology. Specifically, compared to when there is a logo, etc. on one side, if there is a logo, etc. on both sides, the installation position of the through hole that leads to both sides will be restricted by the logo, etc., and it will be necessary to install it properly. , the injection pressure during molding is dispersed, and the resin does not flow properly toward the through holes. As a result, it is difficult to sufficiently spread the soft resin throughout these closed spaces or almost closed spaces, resulting in molding defects. This may occur.
For this reason, conventionally, characters and patterns (logos and motifs) with closed spaces or nearly closed spaces were placed only on either the front (the surface on the flocked side of the head) or the back of the handle body, and the design The design freedom was limited.
In light of these circumstances, the inventors of the present invention made extensive studies to solve the above problems, and found that in order to realize a two-color molded toothbrush that has a logo etc. on both sides, it is necessary to control the position and arrangement of the logo etc. and through-holes. Therefore, it was discovered that it is effective not to reduce the injection pressure of the secondary resin, leading to the present invention.

An object of the present invention is to provide a toothbrush with an excellent design that suppresses molding defects even when a handle body is designed to have a closed space or a substantially closed space on both sides.

The present invention includes the following configurations.
[1] A toothbrush comprising a handle body having a head portion and a gripping portion, and having a brush portion in front of the head portion,
The handle body includes a handle body including a core rod, and a covering portion that covers at least a portion of the handle body,
The handle body is made of a first resin, the covering part is made of a second resin,
When viewed from a direction perpendicular to the longitudinal axis of the handle body, the handle body has a closed space on one side that is entirely surrounded by walls, or a substantially closed space that is surrounded by walls except for a part of the periphery. A first space consisting of a closed space, and on the other side, a second space consisting of a closed space whose periphery is entirely surrounded by walls, or a substantially closed space whose periphery is surrounded by walls except for a part. has
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 passage passing through the handle body, and the second resin reaches the second space from the first space through the first passage. It looks like this,
The toothbrush, wherein the first space, the first through path, and the second space are entirely filled with the second resin.
[2] The first through path is located inside a wall surrounding the first space and inside a wall surrounding the second space,
A second through-path is formed in the handle body, and the second through-path connects the first space with an area outside the wall surrounding the second space, and the second resin is transferred from the second through-path to the first space. and further reaches the second space through the first through path,
The toothbrush according to [1], wherein the second through path, the first space, the first through path, and the second space are entirely filled with the second resin.
[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] S _A1 (mm ² ) is the opening area when the first space is viewed from the front from the opening side, and S _B1 (mm ² ) is the sum of the passage cross-sectional areas of the first through passages that connect to the first space. The toothbrush according to [1] or [2], wherein S _A1 /S _B1 is 1.0 or more and 60.0 or less.
[6] A wall surrounding the first space and a wall surrounding the second space are provided on the core rod, and the first through path and the second through path penetrate the core rod, The toothbrush according to [2].
[7] In a cross section perpendicular to the longitudinal direction of the handle body, a wall surrounding the first space is disposed outside the core rod, and the first through path passes through the core rod. The toothbrush according to [1] or [2].
[8] The opening area when the first space is viewed from the opening side is S _A1 (mm ² ), and the opening area when the second space is viewed from the opening side is S _A2 (mm ² ). The toothbrush according to [1] or [2], wherein S _A1 ≧ S _A2 is satisfied.

According to the present invention, it is possible to provide a toothbrush with excellent design, in which molding defects are suppressed even when a handle body is designed to have a closed space or a substantially closed space on both sides.

BRIEF DESCRIPTION OF THE DRAWINGS It is a side view which showed the schematic structure of the toothbrush of an example of embodiment. FIG. 2 is a front view of the toothbrush of FIG. 1; FIG. 2 is a rear view of the toothbrush of FIG. 1; FIG. 2 is a front view showing a schematic configuration of a handle body of the toothbrush shown in FIG. 1. FIG. FIG. 5 is a side view of the handle body of FIG. 4; 4 is a sectional view taken along line AA of the toothbrush shown in FIG. 3. FIG. FIG. 4 is a cross-sectional view taken along line BB of the toothbrush shown in FIG. 3. 4 is a cross-sectional view taken along the line CC of the toothbrush shown in FIG. 3. FIG. FIG. 2 is an explanatory diagram illustrating definitions of a closed space and a substantially closed space.

Hereinafter, an example of the toothbrush of the present invention will be shown and explained based on the drawings. Note that the dimensions of the figures illustrated in the following description are merely examples, and the present invention is not necessarily limited thereto, and can be practiced with appropriate changes within the scope of the gist thereof. .

FIG. 1 is a side view showing a schematic configuration of a toothbrush 1 according to an example of an embodiment.
2 is a front view of the toothbrush 1, and FIG. 3 is a rear view of the toothbrush 1.
The toothbrush 1 of this embodiment includes a handle body 10 having a head portion 12, a grip portion 14, and a neck portion 16 connecting the head portion 12 and the grip portion 14. A brush portion 20 is implanted on the front side bristle surface 12a of the head portion 12 of the handle body 10.

Hereinafter, the direction from the tip of the head portion 12 of the handle body 10 toward the rear end of the grip portion 14 will be referred to as the “long axis direction”.
Further, a direction parallel to the flocked surface 12a of the head portion 12 and perpendicular to the long axis direction is defined as a "short axis direction".
Further, the direction perpendicular to the flocked surface 12a of the head portion 12 is defined as the "thickness direction."

The handle body 10 includes a handle body 30 made of a first resin, and a covering portion 40 made of a second resin and covering at least a portion of the handle body 30.

The first resin is preferably a hard resin, but is not limited thereto. However, in the present invention, "hard resin" means a resin having a Shore A hardness of over 90. Examples of the hard resin include polypropylene resin, polyacetal resin, polybutylene terephthalate resin, and polyester resin.
The second resin is preferably a soft resin, but is not limited thereto. However, "soft resin" means a resin having a Shore A hardness lower than that of a hard resin, that is, a resin having a Shore A hardness of 90 or less. Examples of the soft resin include elastomers such as olefin elastomers, styrene elastomers, polyester elastomers, and polyurethane thermoplastic elastomers.
"Shore A hardness" means the derometer A hardness of plastics measured according to JIS K 7215.

As shown in FIGS. 4 and 5, the handle body 30 of this example includes a core rod 32 and a protrusion 34 that protrudes toward the front side (toward the flocked surface 12a side) of a portion of the core rod 32 that corresponds to the gripping portion 14. , a protrusion 36 that protrudes toward the back side of a portion of the core rod 32 that corresponds to the grip portion 14, and a protrusion portion 38 that protrudes toward the side surface of a portion of the core rod 32 that corresponds to the grip portion 14. In the present invention, the "core rod" means a rod that mainly forms the rod-shaped handle body, as shown in FIGS. 4 and 5.
As shown in FIGS. 1 to 3 and 6 to 8, the outer circumferential edge portion and back side portion of the head portion 12 in the handle body 30, the outer circumferential portion of the neck portion 16, and the protruding portions 34, 36 of the grip portion 14, A covering portion 40 is formed by covering portions other than 38 with the second resin.
In this embodiment, the gate position 80 (FIG. 3) of the second resin during molding is located near the center of the handle body 10 in the longitudinal direction and on the back side of the handle body 10. Further, since the neck portion 16 has a concave groove connected to the head portion 12, the second resin injected from the gate position 80 of the second resin is transferred to the protruding portions 34, 36 of the gripping portion 14, The covering part 40 is formed by covering the parts other than 38 and at the same time covering the outer peripheral edge part and the back side part of the head part 12 and the outer peripheral part of the neck part 16.

The tip surfaces of the protrusions 34, 36, and 38 are exposed surfaces 34a, 36a, and 38a exposed on the surface of the handle body 10, respectively. Moreover, the handle body 30 and the covering part 40 are different colors, and the surface of the grip part 14 of the handle body 10 has letters and letters bordered by the exposed surfaces 34a, 36a, 38a of the protrusions 34, 36, 38. A pattern is formed.
The positional relationship between the exposed surfaces 34a, 36a, 38a of the protrusions 34, 36, 38 and the surface of the covering section 40 is not particularly limited, and the exposed surfaces 34a, 36a, 38a are flush with the surface of the covering section 40. It may be curved, protrude outward, or be concave inward.

In the toothbrush 1 of this example, the letters "KODOMO", animal characters, and their footprints are formed on the front surface of the grip part 14 by the exposed surface 34a of the protrusion 34.
Further, on the back surface of the gripping part 14, the letters "KODOMO" and footprints are formed by the exposed surface 36a of the protruding part 36.
Furthermore, a circle is formed on the side surface of the gripping portion 14 by the exposed surface 38a of the protruding portion 38.
Note that the characters and patterns formed on the surface of the handle body 10 are not limited to those in this example.

As shown in FIGS. 2 to 4, the handle body 30 is
On the front side, there is a first space 50 consisting of a closed space whose periphery is entirely surrounded by walls, or a substantially closed space whose periphery is surrounded by walls except for a part, and
On the back side, there is a second space 60 consisting of a closed space whose periphery is entirely surrounded by walls, or a substantially closed space whose periphery is surrounded by walls except for a part.
Both the first space 50 and the second space 60 are open to the surface of the handle body 10.

However, a "closed space" is a space that is completely surrounded by continuous walls when viewed from the front from the exposed surface side of the handle body, and the wall length L is 5.0 mm or more. means a space surrounded by Further, the length L of the wall forming the closed space means the length of the entire circumference of the edge of the inner wall surface of the wall on the exposed surface side when viewed from the front side from the exposed surface side of the handle body.
For example, as shown in FIG. 9A, when viewed from the front from the exposed surface side of the handle body, the handle body is surrounded by a wall 71 having an arcuate inner wall surface 71a and an inwardly convex bent inner wall surface 71b. In the case of the space 72, the sum of the arc length of the edge of the exposed surface side of the inner wall surface 71a and the length of two straight lines of the edge of the inner wall surface 71b on the exposed surface side is the wall length L, The space 72 where the length L is 5.0 mm or more is defined as a closed space.

The length L of the wall surrounding the closed 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 closed 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 closed space can be arbitrarily combined.

In the toothbrush 1 of this example, as shown in FIG. 2, in the first space 50 on the front of the handle body 10, the letters "D" and "O" and the space inside the animal character's face and stomach are located. , is a closed space entirely surrounded by walls 52 that constitute the protrusion 34. Further, as shown in FIG. 3, the space inside the letters "D" and "O" in the second space 60 on the back surface of the handle body 10 is entirely surrounded by the wall 62 that constitutes the protrusion 36. It is a closed space.

Furthermore, a "substantially closed space" is a space that is surrounded except for a part by a continuous wall of 3.0 mm or more when the surface of the handle body where the handle body is exposed is viewed from the front. , means a space surrounded by walls in which the ratio P expressed by the following formula (1) is 70.0% or more.
P={L/(L+D)}×100...(1)
However, the symbols in formula (1) have the following meanings.
P: Ratio of walls surrounding a nearly closed space (%)
L: Length of wall surrounding a nearly closed space (mm)
D: Shortest distance of the open part of the wall surrounding the nearly closed space (mm)

"The shortest distance between the open parts of a wall surrounding a substantially closed space" refers to the following (i ) to (iii).
(i) If there are edges of walls surrounding a substantially closed space on both sides of an open portion that does not have walls surrounding the substantially closed space, it means the shortest distance between those ends.
(ii) If there is an edge of a wall surrounding a substantially closed space on only one side of an open part where there is no wall surrounding the substantially closed space, the relationship between that end and the wall facing the end is means the shortest distance.
(iii) In the case where there are no ends of walls surrounding a substantially closed space on both sides of an open portion where there are no walls surrounding the substantially closed space, it means the shortest distance between the opposing inner wall surfaces on both sides.
In addition, when viewed from the front from the exposed surface side of the handle body, connect the shortest distance points on both sides of the open part of the wall that surrounds the nearly closed space along the edge of the exposed surface side of the inner wall surface of the wall. Let the length at that time be the length L of the wall forming the substantially closed space.

For example, as shown in FIG. 9(B), a space 72 surrounded by a wall 71 except for a part is viewed from the exposed surface side of the handle body as shown in the above definition (i). When the ends 74 and 75 of the wall 71 exist on both sides of the open portion 73, the points closest to the ends 74 and 75 (points a and b in FIG. 9(B)) Let the distance between them be the shortest distance D.
In addition, when viewed from the front from the exposed surface side of the handle body, the length from point a to point b along the edge of the exposed surface side of the inner wall surface 71a of the wall 71 is the length of the wall forming the substantially closed space. Let it be L.

As shown in FIG. 9(C), the above definition (ii) is applied when a space 72 surrounded by a wall 71 except for a part is viewed from the front from the exposed side of the handle body. , when the end 74 of the wall 71 exists only on one side of the open portion 73, the closest point between the end 74 and the inner wall surface 71a facing the end 74 (in FIG. 9(C) Let the distance between points a and b) be the shortest distance D.
In addition, when viewed from the front from the exposed surface side of the handle body, the length from point a to point b along the edge of the exposed surface side of the inner wall surface 71a of the wall 71 is the length of the wall forming the substantially closed space. Let it be L.

In addition, as shown in FIG. 9(D), a space 72 surrounded by a wall 71 except for a part is viewed from the exposed surface side of the handle body as shown in FIG. 9(D). When the ends of the wall 71 are not present on either side of the open portion 73, the distance between the inner wall surfaces 71a on both sides of the open portion 73 is defined as the shortest distance D. At this time, when the edge shape on the exposed surface side of the inner wall surfaces 71a on both sides of the open portion 73 is curved in a front view from the exposed surface side of the handle body, the curvature of the curve is the inner side of the open portion 73. The position (inflection point) at which the distance changes outward from the point is set as the reference point for the distance between the inner wall surfaces 71a on both sides (point a in FIG. Let the distance be the shortest distance D.
In addition, when viewed from the front from the exposed surface side of the handle body, the length from point a to point b along the edge of the exposed surface side of the inner wall surface 71a of the wall 71 is the length of the wall forming the substantially closed space. Let it be L.

The ratio P is 70.0% or more, preferably 75.0% or more, 80.0% or more, 85.0% or more, or 90.0% or more. The upper limit of the ratio P is less than 100.0%, preferably 99.0% or less, 98.0% or less, 97.0% or less, or 95.0% or less. The lower limit and upper limit of the ratio P can be arbitrarily combined.

The length L of the wall surrounding the substantially closed 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 substantially closed 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 closed space can be arbitrarily combined.

In the toothbrush 1 of this example, to take a typical example, as shown in FIG. The inner space surrounded by the projection 34 is a substantially closed space surrounded by the wall 52 that constitutes the protrusion 34 .

The opening shape of the first space 50 is not particularly limited, and can be appropriately designed depending on a desired logo or motif. Similarly, the opening shape of the second space 60 is not particularly limited, and can be appropriately designed depending on a desired logo or motif.
As in the first space 50B shown in FIGS. 2, 4, and 7, a protrusion 34 (such as a character's eye) that does not form the wall 52 is provided inside the wall 52 surrounding the first space 50. Good too. The same applies to the second space 60.

(1st penetration path)
As shown in FIG. 6, the handle body 30 has a first space 50A (50) and a second space 60A (60) arranged at overlapping positions on the front and back sides when the handle body 30 is viewed from the thickness direction. A first through passage 31 is formed between the handle body 30 and the first space 50A and the second space 60A.
Similarly, as shown in FIG. 7, the first space 50B (50) and the second space 60B (60) are connected by the first through path 31, and as shown in FIG. ) and the second space 60C (60) are connected by the first through path 31.
The first space 50 and the second space 60 connected by the first through path 31 may completely overlap when viewed from the thickness direction, or may partially overlap.

In this way, the second resin during injection and filling reaches the second space 60 from the first space 50 through the first through path 31, and fills the entire first space 50, first through path 31, and second space 60. The second resin is filled. This makes it easier to fill every corner of the second space 60 with the second resin during injection filling, making it difficult for molding defects to occur.
This is because the second resin heading towards the second space 60 is once trapped in the first space 50 surrounded by the wall 52 that exists in front of it, so that the resin spreads throughout the first space 50 and the second resin flows into the first space 50. This is because the injection pressure is increased within the first space 50, so a drop in the injection pressure is suppressed, and a sufficient pressure to flow the second resin toward the second space 60 is ensured.

The first space 50 is a closed space rather than a substantially closed space in that it is more effective in suppressing a drop in injection pressure, the second resin can easily spread to every corner of the second space 60, and molding defects are less likely to occur. It is preferable that If the first space 50 is a closed space, even if the second space 60 is a closed space, it is easy to ensure sufficient pressure to flow the second resin toward the second space 60, and molding defects are less likely to occur. .

The number of first through passages 31 connected to one first space 50 is not limited to one, and may be two or more, for example, one to three.
The number of first through passages 31 connected to one second space 60 is not limited to one, and may be two or more, for example, one to three.
A plurality of first spaces 50 may be connected to one second space 60 by the first through path 31, and one first space 50 may be connected to a plurality of second spaces 60.

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

(Second penetration path)
As shown in FIGS. 6 and 7, the handle body 30 has a second through passage 33 that connects the first space 50 with an area outside the wall 62 surrounding the second space 60 on the back side of the handle body 10. It is preferable that it is formed. In this case, the second resin enters the first space 50 from the second through path 33 and further reaches the second space 60 through the first through path 31, so that the second resin enters the second through path 33, the first space 50, The first through path 31 and the second space 60 are entirely filled with the second resin.

By forming the second through passage 33, it is possible to limit the excessive amount of resin and the injection pressure when it flows in, so it becomes easy to flow the second resin into the first space 50, and the second resin flows into the first space 50. It is possible to further suppress a decrease in the injection pressure inside the cylinder. Once the resin is trapped in the first space 50 surrounded by the wall 52, the resin is spread throughout the first space 50 and the injection pressure increases within the first space 50. As a result, the effect of securing the pressure that causes the second resin to flow toward the second space 60 is further increased, and molding defects are less likely to occur.
The number of second through passages 33 connected to one first space 50 is not limited to one, and may be two or more, for example, from one to five.

As shown in FIG. 6, in the toothbrush 1, 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 the first through path is 31 and the second through passage 33 preferably pass through the core rod 32. In particular, when "the first space 50, the first through path 31, the second through path 33, and the second space 60" exist in a place far from the gate position as shown in FIGS. 3 and 6, This configuration is preferable in an embodiment in which the injection pressure is located at a location far from the gate position, since the injection pressure may be lower than that in the case where the injection pressure is lowered.
As a result, the distance of the resin flowing through the first space 50, the first through path 31, the second through path 33, and the second space 60 can be shortened, so that the injection pressure of the second resin within the first space 50 is further reduced. This makes it easier to fill the second space 60 with the second resin to every corner.

Further, as shown in FIG. 7, in a cross section perpendicular to the long axis direction of the handle body 30, a wall 52 surrounding the first space 50B (50) is disposed outside the core rod 32, and the first through path 31 It is also preferable that the core rod 32 be penetrated through the core rod 32. In particular, when "the first space 50, the first through path 31, the second through path 33, and the second space 60" exist in a place close to the gate position as shown in FIGS. 3 and 7, when it is far from the gate position, In comparison, this configuration is preferable in an embodiment where the resin is located close to the gate position because it can take advantage of the fact that the resin is easily subjected to high temperature resin and high injection pressure immediately after injection from the gate.
This makes it easier to secure the second through passage 33 with a larger passage cross-sectional area, making it easier to pour the second resin at a higher temperature into the first space 50 while maintaining a higher injection pressure. As a result, the drop in the injection pressure within the first space 50 is further suppressed, so it becomes easier to fill every corner of the second space 60 with the second resin. Further, the configuration in which the wall 52 of the first space 50 is provided outside the core rod 32 has a higher degree of design freedom than the configuration in which the wall 52 of the first space 50 is provided on the core rod 32. In this case, since the wall 52 is placed outside the core rod 32, the thickness of the handle may become too thick. A curved shape (mortar-like shape) along the edge is preferred. This not only improves the problem of making the handle too thick, but also has the advantage that the curved surface makes it easier to stock the resin flowing into the first space without any gaps.

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

The opening area when the first space 50 is viewed from the front from the opening side (exposed surface side) is S _A1 (mm ² ),
The opening area when the second space 60 is viewed from the opening side is S _A2 (mm ² ),
The sum of the passage cross-sectional areas of the first through passages 31 connected to the first space 50 and the second space 60 is S _B1 (mm ² ),
The sum total of the passage cross-sectional areas of the second through passages 33 connected to the first space 50 is S _B2 (mm ² ).
However, the opening area of a substantially closed space means the area of the opening when the straight line connecting the wall-less surrounding open parts of the substantially closed space at the shortest distance D is assumed to be part of the opening edge. shall be.
Further, the sum of the opening area _SA1 of the first space 50 and the opening area _SA2 of the second space 60 is defined as the total opening area _SA .

Since the amount of the second resin flowing into the first space 50 increases, the second resin is difficult to be cooled in the first space 50, and the second resin easily flows into the second space 60, S _A1 /S _B1 is preferably 1.0 or more, more preferably 5.0 or more, even more preferably 10.0 or more, and particularly preferably 20.0 or more. Furthermore, S _A1 /S _B1 is preferably 60.0 or less, since the distance from the first through passage 31 to the wall 52 is not too long and it is easy to suppress a drop in the injection pressure within the first space 50. It is more preferably 55.0 or less, even more preferably 50.0 or less, and particularly preferably 40.0 or less. The preferable lower limit and upper limit of S _A1 /S _B1 can be arbitrarily combined, and for example, 1.0 or more and 60.0 or less are preferable.

It is preferable that the opening area _SA1 of the first space 50 be equal to or larger than the opening area _SA2 of the second space 60, that is, satisfy _SA1 ≧ _SA2 . As a result, the flow velocity of the second resin from the first space 50 to the second space 60 becomes higher, and the second resin easily spreads to every corner of the second space 60.
Note that when a plurality of first spaces 50 are connected to the same second space 60, the total opening area of the plurality of first spaces 50 is set as S _A1 . Further, when one first space 50 is connected to a plurality of second spaces 60, the total opening area of the plurality of second spaces 60 is set as S _A2 .

S _A1 /S _A2 is preferably 1.0 or more, more preferably 3.0 or more, even more preferably 5.0 or more, and particularly preferably 10.0 or more. Moreover, S _A1 /S _A2 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. The preferable lower and upper limits of S _A1 /S _A2 can be arbitrarily combined, and are preferably 1.0 or more and 30.0 or less, for example.

S _A /S _B1 is preferably 1.0 or more, more preferably 20.0 or more. If S _A /S _B1 is equal to or greater than the lower limit value, the resin can easily flow into the second space 60 before the resin cools and hardens. S _A /S _B1 is preferably 60.0 or less, more preferably 40.0 or less. If S _A /S _B1 is below the upper limit value, it is easy to ensure a sufficient flow rate to fill the second space 60 with resin. The preferable lower limit and upper limit of S _A /S _B1 can be arbitrarily combined, for example, preferably 1.0 or more and 60.0 or less.

The opening area S _A1 of the first space 50 is preferably 5.0 mm ² or more, more preferably 20.0 mm ² or more. If the opening area S _A1 is equal to or larger than the lower limit value, it is easy to ensure a sufficient flow rate to fill the second space 60 with resin. The opening area S _A1 is preferably 60.0 mm ² or less, more preferably 50.0 mm ² or less. If the opening area S _A1 is less than or equal to the upper limit value, it is easy to ensure the injection pressure necessary to flow the resin into the second space 60. The preferable lower limit and upper limit of the opening area S _A1 can be arbitrarily combined, for example, preferably 5.0 mm ² or more and 60.0 mm ² or less.

The opening area S _A2 of the second space 60 is preferably 1.0 mm ² or more, more preferably 2.0 mm ² or more. If the opening area S _A2 is equal to or greater than the lower limit value, the injection pressure required to flow the resin into the second space 60 will not become too high. The opening area S _A2 is preferably 40.0 mm ² or less, more preferably 10.0 mm ² or less. If the opening area S _A2 is below the upper limit value, the time required to flow the resin into the second space 60 will not be too long. The preferable lower limit and upper limit of the opening area S _A2 can be arbitrarily combined, and are preferably 1.0 mm ² or more and 40.0 mm ² or less, for example.

The total passage cross-sectional area S _B1 of the first through passage 31 is preferably 0.5 mm ² or more, and more preferably 1.0 mm ² or more. If the sum S _B1 is equal to or greater than the lower limit value, it is easy to ensure a sufficient flow rate to fill the second space 60 with resin. The total sum S _B1 is preferably 5.0 mm ² or less, more preferably 3.0 mm ² or less. If the sum S _B1 is less than or equal to the upper limit value, it is easy to ensure the injection pressure necessary to flow the resin into the second space 60. The preferable lower limit and upper limit of the sum S _B1 can be arbitrarily combined, for example, preferably 0.5 mm ² or more and 5.0 mm ² or less.

The total cross-sectional area S _B2 of the second through passage 33 is preferably 1.0 mm ² or more, more preferably 2.0 mm ² or more. If the total sum S _B2 is equal to or greater than the lower limit value, it is easy to ensure a sufficient flow rate for resin supply to the first space 50. The total sum S _B2 is preferably 20.0 mm ² or less, more preferably 15.0 mm ² or less. If the total sum S _B2 is below the upper limit value, it is easy to ensure the injection pressure necessary to flow the resin into the second space 60. The preferable lower and upper limits of the sum S _B2 can be arbitrarily combined, and are preferably 1.0 mm ² or more and 20.0 mm ² or less, for example.

It is preferable that the sum S _B1 of the passage cross-sectional areas of the first through passages 31 be larger than the sum S _B2 of passage cross sectional areas of the second through passages 33, that is, satisfy S _B2 > S _B1 . Thereby, it is easy to ensure 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, even more preferably 4.5 or more, and particularly preferably 6.0 or more. Further, S _B2 /S _B1 is preferably 20.0 or less, more preferably 18.5 or less, even more preferably 17.0 or less, and particularly preferably 15.5 or less. The preferable lower limit and upper limit of S _B2 /S _B1 can be arbitrarily combined, and for example, 1.5 or more and 20.0 or less are preferable.

The minimum thickness of the wall 52 of the first space 50 is preferably 0.5 mm or more, more preferably 1.0 mm or more. If the minimum thickness of the wall 52 is equal to or greater than the lower limit value, it becomes easy to dam up the second resin flowing 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, more preferably 5.0 mm or less. If the minimum thickness of the wall 52 is less than or equal to the upper limit value, the second resin flowing into the first space 50 can be dammed up and easily sent to the second space 60. The preferable lower and upper limits of the minimum thickness of the wall 52 can be arbitrarily combined, and are preferably, for example, 0.5 mm or more and 10.0 mm or less.

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

The brush section 20 is not particularly limited, and can be appropriately set according to the purpose, such as the number of hair bundles, cross-sectional shape, hair length, hair bundle diameter, and arrangement pattern of the hair bundles on the flocking surface 12a.
Examples of the material of the bristles constituting the bristles include polyesters such as polyamide, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate, and polyolefins such as polypropylene.

The method for manufacturing the toothbrush 1 is not particularly limited, and any known method can be used. For example, after molding the handle body 30 with a first resin by injection molding using a primary mold, the handle body 30 is injected and filled with a second resin while the handle body 30 is placed in the secondary mold. 10, so-called two-color molding can be adopted.

As explained above, in the toothbrush of the present invention, the first space is provided on one side of the handle body and the second space is provided on the other side, when viewed from a direction perpendicular to the long axis direction of the handle body. are connected by the first through path. This suppresses the drop in injection pressure when the second resin enters the first space during injection and filling, and allows the resin to flow to the second space while maintaining sufficient injection pressure. Every corner can be filled with the second resin. As a result, since molding defects are sufficiently suppressed, the degree of freedom in design is increased, and a toothbrush with excellent design features, such as a complex logo or motif on both sides, can be obtained.
Further, the difficulty of molding the first space and the second space increases as the distance from the gate position increases, but in the toothbrush of the present invention, the gate position of the secondary mold and the positions of the first space and the second space are 10.0 mm. Even if the distance is greater than that, molding defects can be sufficiently suppressed.

Note that 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 arranged on one side and the other side in the short axis direction of the handle body.
In FIGS. 2 and 3, "one side" and "the other side" are exemplified as the front side and the back side, but are not limited to this. ). Further, "one side" and "the other side" may not be opposite sides on the same straight line, and may be, for example, the front side and the right side.
The handle body may have a protrusion that protrudes from the core rod and whose distal end surface is not exposed to the surface of the handle body.
In the handle body, a protrusion that forms a logo, motif, etc. and is exposed on the surface of the handle body is preferably provided on the grip portion, but may be provided on the head portion or neck portion.

In addition, without departing from the spirit of the present invention, the components in the embodiments described above may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate.

DESCRIPTION OF SYMBOLS 1... Toothbrush, 10... Handle body, 12... Head part, 14... Grip part, 16... Neck part, 20... Brush part, 30... Handle body, 31... First penetration path, 32... Core rod, 33... Second Penetration path, 34, 36, 38... Projection, 34a, 36a, 38a... Exposed surface, 40... Covering part, 50, 50A to 50C... First space, 52... Wall, 60, 60A to 60C... Second space, 62... Wall, 71... Wall, 71a, 71b... Inner wall surface, 72... Space, 73... Open portion, 74, 75... End.

Claims (8)

A toothbrush comprising a handle body having a head part and a grip part, and having a brush part in front of the head part,
The handle body includes a handle body including a core rod, and a covering portion that covers at least a portion of the handle body,
The handle body is made of a first resin, the covering part is made of a second resin,
When viewed from a direction perpendicular to the longitudinal axis of the handle body, the handle body has a closed space on one side that is entirely surrounded by walls, or a substantially closed space that is surrounded by walls except for a part of the periphery. A first space consisting of a closed space, and on the other side, a second space consisting of a closed space whose periphery is entirely surrounded by walls, or a substantially closed space whose periphery is surrounded by walls except for a part. has
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 passage passing through the handle body, and the second resin reaches the second space from the first space through the first passage. It looks like this,
The toothbrush, wherein the first space, the first through path, and the second space are filled with the second resin. The first through path is located inside a wall surrounding the first space and inside a wall surrounding the second space,
A second through-path is formed in the handle body, and the second through-path connects the first space with an area outside the wall surrounding the second space, and the second resin is transferred from the second through-path to the first space. and further reaches the second space through the first through path,
The toothbrush according to claim 1, wherein the second through path, the first space, the first through path, and the second space are filled with the second resin. The toothbrush according to claim 1 or 2, wherein the first space is a closed space. The toothbrush according to claim 1 or 2, wherein the first space is a closed space and the second space is a closed space. When the opening area when the first space is viewed from the opening side is S _A1 (mm ² ), and the sum of the passage cross-sectional areas of the first through passages connected to the first space is S _B1 (mm ² ). ,
The toothbrush according to claim 1 or 2, wherein S _A1 /S _B1 is 1.0 or more and 60.0 or less. 2. A wall surrounding the first space and a wall surrounding the second space are provided on the core rod, and the first through path and the second through path pass through the core rod. The toothbrush described in. Claim 1: In a cross section perpendicular to the longitudinal direction of the handle body, a wall surrounding the first space is disposed outside the core rod, and the first through path passes through the core rod. Or the toothbrush according to 2. When the opening area when the first space is viewed from the front from the opening side is S _A1 (mm ² ), and the opening area when the second space is viewed from the opening side from the front is S _A2 (mm ² ), S The toothbrush according to claim 1 or 2, which satisfies _A1 ≧S _A2 .

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