EP2136678A1

EP2136678A1 - Toothbrush forming method and toothbrush produced through the same

Info

Publication number: EP2136678A1
Application number: EP07834251A
Authority: EP
Inventors: Byong Duk Choi
Original assignee: Individual
Current assignee: CHOI, YONG KEUN; Chungang Interbill
Priority date: 2006-11-24
Filing date: 2007-11-23
Publication date: 2009-12-30
Also published as: WO2008063029A1

Abstract

The present invention relates to a method for forming a toothbrush and a toothbrush manufactured by the same, and more specifically, to a method for forming a toothbrush and a toothbrush manufactured by the same, in which rails with a predetermined structure are injection-molded across the leading end portion, the rear surface, both side surfaces, and portion of the front surface of a toothbrush head and the front surface, the rear surface, and both side surfaces of a connection portion, in order to facilitate the injection molding and to increase a coupling force when a toothbrush is manufactured using materials with a different property and a different melting point. Further, a soft material with a different property and a high melting point is injected into the toothbrush head and the connection portion, thereby forming a soft buffer member which is reliably coupled through thermal adhesion.

Description

TOOTHBRUSH FORMING METHOD AND TOOTHBRUSH PRODUCED THROUGH THE SAME

Technical Field

[1] The present invention relates to a method for forming a toothbrush and a toothbrush manufactured by the same, and more specifically, to a method for forming a toothbrush and a toothbrush manufactured by the same, in which rails with a predetermined structure are injection-molded across the leading end portion, the rear surface, both side surfaces, and portion of the front surface of a toothbrush head and the front surface, the rear surface, and both side surfaces of a connection portion, in order to facilitate the injection molding and to increase a coupling force when a toothbrush is manufactured using materials with a different property and a different melting point. Further, a soft material with a different property and a high melting point is injected into the toothbrush head and the connection portion, thereby forming a soft buffer member which is reliably coupled through thermal adhesion. Background Art

[2] General toothbrushes are composed of a hard material and are formed in various shapes such as a rod shape, a rectangular parallelepiped shape and so on. The toothbrushes have bristles implanted into one surface of the head portion thereof.

[3] When teeth are brushed by such toothbrushes, an impact may be applied to the teeth and gums such that a wound is caused in the mouth, which is not preferable in terms of oral hygiene.

[4] Japanese Unexamined Utility Model Registration Application Publication No.

4-6926 discloses a toothbrush in which a soft elastic member with a large thickness is installed on the top surface of a brush implantation base portion at the leading end of a toothbrush body, and bristles are implanted into the soft elastic member. Japanese Unexamined Utility Model Registration Application Publication No. 57-148332 discloses a toothbrush in which cushion rubber is fixed to the periphery of brush fixed to a toothbrush body.

[5] In Japanese Unexamined Utility Model Registration Application Publication No.

4-6926, it has been described that a buffer operation between the toothbrush body and the bristles implanted into the toothbrush body can be obtained. However, it has not been described that elasticity is provided to the toothbrush body. Further, in Japanese Unexamined Utility Model Registration Application Publication No. 57-148332, a specific means for fixing the cushion rubber to the periphery of the brush has not been described. Therefore, although the cushion rubber and the toothbrush body are bonded to each other through an adhesive, the oral hygiene and an adhesive force therebetween cannot be guaranteed when the toothbrush is inserted into the mouth.

[6] Germany Patent DE3628733 discloses a toothbrush in which the side and front surfaces of a brush head are coated by an injection molding method. However, it has not been described that when the injection molding method is used, materials with a different melting point, a different adhesive force, and a different contraction rate are thermally bonded to each other with reliability. In fact, the toothbrush cannot be manufactured by a typical injection molding method.

[7] To solve the above-described problems, the present applicant has filed Korean

Utility Model Registration No. 1993-15016 and Korean Patent Application No. 1994-25003.

[8] Korean Patent Application No. 1994-25003 ('Apparatus for Manufacturing

Toothbrush Body for Attaching Buffer Member') will be described as follows.

[9] A toothbrush having the following construction is manufactured by the apparatus for manufacturing a toothbrush for attaching a buffer member. In the toothbrush, a plurality of buffer-member connecting projections are formed on the rear surface of a bristle implantation portion of a toothbrush body, and the coupling area between the projections and a buffer member is maximized to prevent the separation from each other when the toothbrush is used. In the apparatus, a backup plate is interposed between a stationary-side fixed plate and a stationary-side main plate such that a plurality of second sprues coincide with a plurality of gates holes of cavities. In the upper cavity of the stationary-side main plate, a gate connected to the second sprues is formed at the entrance to a small- width portion of an upper cavity, and simultaneously, two lock projections are formed. Further, a lower cavity having a small- width portion and a large- width portion, which have the same widths as those of the upper cavity, is formed in the central portion of a core plate which is closely contacted with the stationary-side main plate, with a parting line being set to the boundary therebetween. In this case, a concave portion of which the surface roughness ranges from 0.1 to 0.45 is formed on the bottom surface of the large- width portion. In addition, a toothbrush body molding product for attaching a buffer member is manufactured by the apparatus. In the toothbrush body molding product, an irregularity portion having a plurality of irregularities projecting from the rear surface of the bristle implantation portion having a plurality of bristle insertion holes formed therein is formed to be lower than the thickness of the buffer member including the leading end portion, the left and right side portion, and a buffer member coupling hole. Further, a partial wall of the irregularity portion is formed by the left and right walls so as to guide molding resin and to prevent the molding resin from leaking when the molding resin for buffer member is pressed. [10] In the apparatus for manufacturing a toothbrush for attaching a buffer member, the buffer member molded of elastic materials having a different property can be easily formed on the rear surface of the bristle implantation portion of the primary-molded toothbrush body. The molding range of the buffer member is limited to a portion of the rear surface of the bristle implantation portion of the toothbrush body.

[11] The conventional toothbrush has a connection portion of which the front surface, the rear surface, and both side surfaces are formed of a hard material. Therefore, scratch may occur during tooth brushing, and the teeth and gums may be hurt by the impact.

[12] Further, since a through-hole is provided in the neck portion of the conventional toothbrush, the neck portion becomes weak, and a coupling force between the buffer member and a primary-molded product is reduced. In addition, the concave portion and the external hard material may hurt the teeth and gums during tooth brushing. Since the through-hole is an unnecessary component which serves as a simple guide hole, it may degrade the function of the buffer member.

[13] Recently, as the consciousness of endocrine disrupter in products formed of synthetic resin becomes strong, there is demand for a toothbrush in which a soft buffer member is formed on a connection portion, which is inserted into the mouth, as well as a toothbrush head where a bristle implantation portion of a toothbrush body is formed.

[14] However, when the toothbrush is manufactured using thermoplastic materials with a different property, the thermoplastic materials will not be attached to each other. Further, while the soft buffer member as a secondarily injection-molded product is injected onto the toothbrush body as a primarily injection-molded product with a low melting point, it is difficult to perform the injection molding to solve the above- describe problems. In such a construction of Korean Patent Application No. 1994-25003 where the plurality of irregularities are simply formed, when a buffer member with a different property and a high melting point is molded to the connection portion by an injection molding machine, there are technical difficulties. Therefore, the construction needs to be improved. Disclosure of Invention Technical Problem

[15] An advantage of the present invention is that it provides a method of forming a toothbrush and a toothbrush manufactured by the same, in which a soft buffer member composed of a soft material, which is not harmful to the human body and has a high melting point, is reliably bonded to a toothbrush body through injection molding, and is easily formed on a connection portion connected to a handle as well as the toothbrush head. [16] Another advantage of the invention is that it provides a method of forming a toothbrush and a toothbrush manufactured by the same, in which a soft buffer member is formed to surround the entire rear surface of a toothbrush head and a connection portion of a toothbrush body such that the teeth and gums can be protected even through the toothbrush head and the connection portion hit on the teeth and gums.

[17] A further advantage of the invention is that it provides a method of forming a toothbrush and a toothbrush manufactured by the same, in which only rails are injection-molded on a toothbrush head and a connection portion in order to injection- mold a soft buffer member with a higher melting point that that of a toothbrush body. Then, a mold used for molding a toothbrush is easily formed, which makes it possible to simplify a manufacturing process and cost. Technical Solution

[18] According to an aspect of the invention, a method for forming a toothbrush comprises the steps of: molding a toothbrush body by injecting a thermoplastic material into a predetermined mold, the toothbrush body including a toothbrush head having a plurality of bristle insertion holes into which bristles are inserted, a handle, and a connection portion for integrally connecting the toothbrush head and the handle, wherein rails are injection-molded so as to be connected across the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head having the bristle insertion holes and the front surface, the rear surface, and both side surfaces of the connection portion (primary injection-molding process); and injecting a soft material, which is composed of a different material from the tooth brush body and has a high melting point, into the mold in which the toothbrush body injection-molded by the primary injection molding process is received, so that the soft material is coupled to the rails formed on the toothbrush head and the connection portion through injection molding, thereby molding a soft buffer member, wherein the soft buffer member is integrally molded on the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head and the front surface, the rear surface, and both side surfaces of the connection portion (secondary injection-molding process).

[19] According to another aspect of the invention, a method for forming a toothbrush c omprises the steps of: molding a toothbrush body by injecting a thermoplastic material into a predetermined mold, the toothbrush body including a toothbrush head having a plurality of bristle insertion holes into which bristles are inserted, a handle, and a connection portion for integrally connecting the toothbrush head and the handle, wherein one or more rails are injection-molded so as to be connected across the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head having the bristle insertion holes and the front surface, the rear surface, and both side surfaces of the connection portion, a plurality of irregularities are injection-molded between the rails, each of the rails has one or more rail through- holes formed in a direction perpendicular to the longitudinal direction of the rail along the length of the rail, and each of the irregularities has an irregularity through-hole formed in the same direction as the rail through-hole or in a direction perpendicular to the rail through-hole (primary injection-molding process); and injecting a soft material, which is composed of a different material from the toothbrush body and has a high melting point, into the mold in which the toothbrush body injection-molded by the primary injection molding process is received, so that the soft material is coupled to one or more rails formed on the toothbrush head and the connection portion, the rail through-holes and the irregularities formed on the rail, and the irregularity though- holes formed on the irregularities through injection molding, thereby molding a soft buffer member, wherein the soft buffer member is integrally molded on the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head and the front surface, the rear surface, and both side surfaces of the connection portion (secondary injection-molding process).

[20] According to a further aspect of the invention, a method for forming a toothbrush comprises the steps of: molding a toothbrush body by injecting a thermoplastic material into a predetermined mold, the toothbrush body including a toothbrush head having a plurality of bristle insertion holes into which bristles are inserted, a handle, and a connection portion for integrally connecting the toothbrush head and the handle, wherein a plurality of irregularities are injection-molded on the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head having the bristle insertion holes and the front surface, the rear surface, and both side surfaces of the connection portion, the irregularities having irregularity through- holes formed therein (primary injection-molding process); and injecting a soft material, which is composed of a different material from the toothbrush body and has a high melting point, into the mold in which the toothbrush body injection-molded by the primary injection molding process is received, so that the soft material is coupled to the irregularities formed on the toothbrush head and the connection portion and the irregularity through-holes formed in the respective irregularities through injection molding, thereby molding a soft buffer member, wherein the soft buffer member is integrally molded on the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head and the front surface, the rear surface, and both side surfaces of the connection portion (secondary injection-molding process).

[21] According to a still further aspect of the invention, there is provided a toothbrush manufactured by the method according to any one of the aspects. [22] The toothbrush comprises a toothbrush head having bristles formed thereon; a handle having one or more soft members for preventing slipping; a connection portion that integrally connects the toothbrush head and the handle; and a soft buffer member that is integrally molded so as to surround the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head and the front surface, the rear surface, and both sides surfaces of the connection portion.

Advantageous Effects

[23] According to the invention, the soft buffer member which is a soft material with a different property and a high melting point is easily injection-molded on the toothbrush body, and the coupling force therebetween is increased so that the soft buffer member is not separated even though a strong impact is applied, or sudden heating or cooling is performed.

[24] Further, when the toothbrush is formed with only the rails, a mold cost can be reduced. Since the soft buffer member is quickly rectified, the operation time can be reduced, which makes it possible to enhance productivity.

[25] Further, in the toothbrush manufactured by the method according to the invention, the soft buffer member is molded to surround the leading end portion, both side surfaces, and the rear surface of the toothbrush head and the connection portion of the toothbrush. Therefore, during tooth brushing, the teeth and gums can be protected, and scratch does not occur.

[26] Further, soft materials approved by Korea Environment & Merchandise Testing

Institute may be used as the thermoplastic material used in the invention. Further, soft materials approved by environment & merchandise testing institutes of other countries such as the US, Japan, China, Europe and so on may be used. In some cases, soft materials certified by FDA or UPS in the US may be used. Therefore, the safety thereof is excellent. Brief Description of the Drawings

[27] FIG. 1 is a process diagram for explaining a method for forming a toothbrush according to an embodiment of the invention.

[28] FIGS. 2 to 15 are schematic views for explaining the arrangement structures of various rails formed through a primary injection-molding process in the method for forming a toothbrush according to the invention.

[29] FIGS. 16 to 27 are perspective views and cross-sectional views of various rails molded through the primary injection-molding process in the method for forming a toothbrush according to the invention.

[30] FIGS. 28 A to 28C are schematic diagrams showing an example where a soft buffer member is formed on the toothbrush body, which is formed through the primary injection-molding process, through the secondary injection-molding process.

[31] FIGS. 29 and 30 are rear and front view of a toothbrush body which is primarily injection-molded by a method for forming a toothbrush according to another embodiment of the invention.

[32] FIG. 31 is a schematic view showing the front, side, and rear surfaces of a connection portion of the toothbrush body which is primarily injection-molded by a method for forming a toothbrush according to another embodiment of the invention.

[33] FIG. 32 is a perspective view of the toothbrush body which is primarily injection- molded by the method for forming a toothbrush according to another embodiment of the invention, showing the rails, the irregularities, and the concave grooves of the toothbrush body.

[34]

[35] *FIGS. 33A and 33B are perspective views of a rail formed on the toothbrush head and the connection portion of the toothbrush body which is primarily injection-molded by a method for forming a toothbrush according to another embodiment of the invention.

[36] FIG. 34A and 34B are perspective views of irregularities formed on the toothbrush head and the connection portion of the toothbrush body which is primarily injection- molded by a method for forming a toothbrush according to another embodiment of the invention.

[37] FIG. 35 is a schematic perspective view for explaining the arrangement relationship between the rail and the irregularities which are primarily injection-molded by a method for forming a toothbrush according to another embodiment of the invention.

[38] FIG. 36 is a schematic cross-sectional view of a toothbrush manufactured by the method for forming a toothbrush according to the invention.

[39] FIG. 37 is a perspective view showing an example where irregularities are formed on the toothbrush body which is primarily injection-molded by a method for forming a toothbrush according to another embodiment of the invention.

[40] FIG. 38 is a perspective view of a toothbrush manufactured by the method for forming a toothbrush according to the invention.

[41] FIG. 39 is a front view of the toothbrush according to the invention.

[42] FIG. 40 is a rear view of the toothbrush according to the invention.

[43] FIG. 41 is a partial perspective view for explaining upper and lower caps and a through-hole of a handle in the toothbrush according to the invention.

[44] FIG. 42 is a partial perspective view for explaining the connection relationship between the upper and lower caps and the through hole of the handle of FIG. 41. Best Mode for Carrying Out the Invention

[45] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the respective drawings, like reference numerals will be attached to the same components, although they are illustrated in different drawings.

[46] When it is judged that the specific description of associated known function or constitution can cloud the point of the invention, the description will be omitted.

[47] FIG. 1 is a process diagram for explaining a method for forming a toothbrush according to an embodiment of the invention. FIGS. 2 to 15 are schematic views for explaining the arrangement structures of various rails formed through a primary injection-molding process in the method for forming a toothbrush according to the invention. FIGS. 2 to 8 show examples where concave grooves are formed between the respective rails. FIGS. 9 to 15 show examples where the concave grooves are not formed between the respective rails. FIGS. 16 to 27 are perspective views and cross- sectional views of various rails molded through the primary injection-molding process.

[48] FIGS. 29 and 30 are rear and front views of a toothbrush body which is primarily injection-molded by a method for forming a toothbrush according to another embodiment of the invention. FIG. 31 is a diagram showing the front, side, and rear surfaces of a connection portion of the toothbrush body.

[49] As shown in FIG. 1, the method for forming a toothbrush according to an embodiment of the invention includes a primary injection molding process for injection-molding a toothbrush body and a secondary injection molding process for injection-molding a soft buffer member.

[50] In this case, when a two-tone injection machine is used, a toothbrush body may be molded in a primary injection molding process, a slipping preventing member may be molded in a secondary injection molding process, and a soft buffer member may be formed in a tertiary injection molding process. The primary and secondary injection molding processes may be carried out by one mold.

[51] In the primary injection-molding process, a thermoplastic material is injected into a predetermined mold (not shown) so as to mold a toothbrush body. Preferably, the thermoplastic material is composed of a soft material. However, the thermoplastic material is not limited thereto, and another kind of soft material (including thermosetting material) may be used as the thermoplastic material.

[52] As shown in the accompanying drawings, the toothbrush body includes a toothbrush head 110 having a plurality of bristle insertion holes 112 into which toothbrush bristles 111 are inserted, a handle 150, and a connection portion 130 which integrally connects the toothbrush head 110 and the handle 150. [53] The toothbrush bristles 111 are formed of nylon or silicon. As for the toothbrush bristles 111, bristles made by DuPont (USA) may be used. In addition, the toothbrush bristles 111 may be formed of silicon, thermoplastic elastomer (TPE), or synthetic resin.

[54] FIG. 36 shows a state that the toothbrush bristles 111 are implanted into the bristle insertion holes 112. As shown in FIG. 36, the toothbrush bristles 111 are strongly pressed by a pin (not shown) so as to be reliably stuck into the head 110. Such an implanting process is carried out by an implanting machine (not shown). Since the implanting process corresponds to a well-known technique, the detailed descriptions thereof will be omitted.

[55] In the primary injection molding process, when a thermoplastic material is injected into a predetermined mold so as to mold the toothbrush body, a plurality of rails 113 are injection-molded so as to be connected across the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head 110, where the bristle insertion holes 112 are formed, and the front surface, the rear surface, and both side surfaces of the connection portion 130.

[56] The rails 113 may be formed on the toothbrush head 110 and the connection portion

130, with various arrangement structures. The arrangement structures of the rails 113 can be illustrated as in FIGS. 2 to 15.

[57] The rails 113 of FIG. 2 are formed so as to surround the outside from the lower end of the connection portion 130 to the upper end of the toothbrush head 110, like a screw. To form the rails 113 of FIG. 3, a vertical rail line is formed on the rear surface of the toothbrush head 110 and the connection portion 130 and the front surface of the connection portion 130, respectively. Then, rail lines are formed so as to surround the outside from the lower end of the connection portion 130 to the upper end of the toothbrush head 110.

[58] To form the rails 113 of FIG. 4, a vertical rail line is formed on the rear surfaces and side surfaces of the toothbrush head 110 and the connection portion 130 and the front surface of the connection portion 130, respectively. Then, a plurality of parallel rail lines are formed so as to cross the vertical rail lines at right angles.

[59] To form the rails 113 of FIG. 5, a curved vertical rail line is formed on the rear and side surfaces of the toothbrush head 110 and the connection portion 130 and the front surface of the connection portion 130, respectively. Then, auxiliary rail lines are formed to extend from the respective curved vertical rail lines in the form of blood vessels.

[60] To form the rails 113 of FIG. 6, a vertical rail line is formed on the rear surface of the toothbrush head 110 and the connection portion 130 and the front surface of the connection portion 130, respectively. Then, auxiliary rail lines are formed to extend from the vertical rail line in the form of leaves.

[61] To form the rails 113 of FIG. 7, a vertical rail line is formed on the rear surface of the toothbrush head 110 and the connection portion 130 and the front surface of the connection portion 130, respectively. Then, auxiliary rail lines are formed to obliquely extend upward from the vertical rail line.

[62] To form the rails 113 of FIG. 8, a vertical rail line is formed on the rear surface of the toothbrush bead 110 and the connection portion 130 and the front surface of the connection portion 130, respectively. Then, auxiliary rail lines are formed to extend from the vertical rail line at right angles.

[63] To form the rails 113 of FIG. 9, a vertical rail line is formed on the rear surface of the toothbrush head 110 and the connection portion 130 and the front surface of the connection portion 130, respectively. Then, auxiliary rail lines are formed to obliquely extend downward from the vertical rail line.

[64] To form the rails 113 of FIG. 10, a vertical rail line is formed on the rear surface of the toothbrush head 110 and the connection portion 130 and the front surface of the connection portion 130, respectively. Then, a plurality of auxiliary rail lines are formed to cross the vertical rail line at right angles.

[65] The rails 113 of FIG. 11 are formed in a wave shape which surrounds the outside of the toothbrush head 110 and the connection portion 130. The rails 113 of FIG. 12 are formed in a stair shape which surrounds the outside of the toothbrush head 110 and the connection portion 130. The rails 113 of FIG. 13 are formed in a mesh shape which surrounds the outside of the toothbrush head 110 and the connection portion 130. The rails 113 of FIG. 14 are formed in a brick fence shape which surrounds the outside of the toothbrush head 110 and the connection portion 130. To form the rails 113 of FIG. 15, short auxiliary lines are irregularly formed on the outside of the toothbrush head 110 and the connection portion 130.

[66] As shown in FIGS. 2 to 15, the arrangement structures of the rails 113 can be implemented in various shapes so as to be used for injection molding. In addition to the arrangement structures shown in FIGS. 2 to 15, other arrangement structures may be applied. Further, the arrangement structures of the rails 113 may be injection-molded in a simple or complex manner by a person with a skill in the art. The number of the rails may be selected when a mold for injection-molding the rails 113 is designed.

[67] Further, a plurality of concave grooves 115 may be formed between the respective rails 113 connected across the leading end portion, the rear surface, both the side surfaces, and portion of the front surface of the toothbrush head 110, where the bristle insertion holes 112 are formed, and the front and rear surfaces and both the side surfaces of the connection portion 130. The number of the concave grooves 115 may be adjusted by the mold design of a person with a skill in the art. [68] As shown in FIGS. 9 to 15, only the rails 113 may be formed without the concave grooves.

[69] FIGS. 16 to 27 are perspective and cross-sectional views of various rails formed through the primary injection molding process in the method for forming a toothbrush according to the invention.

[70] FIG. 16 shows a rail 113 formed in an S-shape. FIG. 17 shows a rail 113 formed in an L-shape. FIG. 18 shows a rail 113 formed in '^Λ' shape. FIG. 19 shows a rail 113 formed in a crown shape. FIG. 20 shows a rail 113 formed in a mountain shape with three stubby peaks.

[71] FIG. 21 shows a rail 113 with three protrusions. FIG. 22 shows a rail 113 formed in an 8-shape. FIG. 23 shows a rail 113 formed in such a shape that a crown and a rectangular protrusion are combined. FIG. 24 shows a rail 113 formed in such a shape that stubby protrusions are formed in a groove provided in the center of the rail 113. FIG. 25 shows a rail 113 formed in such a shape that two stubby protrusions are formed in a groove, which is provided in the center of the rail 113 and of which both side surfaces are tapered. FIG. 26 shows a rail 113 formed with two concave grooves. FIG. 27 shows a rail 113 formed in such a shape that two protrusions are formed in a rectangular groove provided in the center of the rail 113.

[72] For convenience of descriptions, the rails 113 shown in FIGS. 16 to 27 have been illustrated in a straight line. Without being limited thereto, the rails 113 may be applied to the various arrangement structures of the rails 113 shown in FIGS. 2 to 15.

[73] As shown in FIG. 24, the rail 113 which is injection-molded with the above- described shape and arrangement structure may have rail irregularities 114 formed therein. That is, various rail irregularities 114 are formed in a groove provided in the center of the rail 113.

[74] As shown in FIGS. 17, 20, 21, and 27, the rail 113 may be formed in such a manner that at least one or more rail through-holes 116 are formed to pass through only the rail 113. In this case, the rail through-holes 116 may be formed in the longitudinal direction of the rail 113 or in a direction perpendicular to the longitudinal direction of the rail 113 along the length of the rail 113.

[75] Further, as shown in FIG. 24, the rail 113 may be formed in such a manner that at least one or more rail irregularity through-holes 118 passes through only the rail irregularities 114 formed in the rail 113. The rail irregularity through-holes 118 may be formed in the longitudinal direction of the rail 113 or in a direction perpendicular to the longitudinal direction of the rail 113.

[76] Further, at least one or more rail through-holes 116 and at least one or more rail irregularity through-holes 118 may be simultaneously formed in the rail 113. In this case, at least one or more of the rail through-holes 116 may be formed in the Ion- gitudinal direction of the rail 113 or in a direction perpendicular to the longitudinal direction of the rail 113 along the length of the rail 113. At least one or more of the rail irregularity through-holes 118 may be formed in the longitudinal direction of the rail 113 or in a direction perpendicular to the longitudinal direction of the rail 113.

[77] The rail 113 may be designed in such a manner that no through-hole is formed therein. In a special case, however, the through-holes are not formed so as to increase a space for the soft buffer member.

[78] In the secondary injection-molding process, a soft material different from that of the toothbrush body is injected into the predetermined mold (not shown) in which the toothbrush body injection-molded through the primary injection-molding process is received. Preferably, the soft material is a thermoplastic material, but is not limited thereto. Another kind of soft material (including a thermosetting material) may be used.

[79] This means that when a thermoplastic material is used in the primary injection- molding process, a thermoplastic material is also used in the secondary injection- molding process. Further, when a thermosetting material is used in the primary injection-molding process, a thermosetting material is also used in the secondary injection-molding process. Although the same thermoplastic or thermosetting materials are used, the melting points thereof are different from each other.

[80] As for a general molding method for thermosetting materials, compression molding, hot air molding, die casting and so on may be used. In a special case, a thermoplastic material which is primarily injection-molded may be coupled to a thermosetting material, which is secondarily injection-molded, by one of the above-described molding methods.

[81] In the secondary injection molding process, a soft material, which is composed of a different material from the toothbrush body and has a high melting point, is injected into the mold in which the toothbrush body injection-molded through the primary injection molding process is received. Then, the soft material is coupled to the rails 113 formed on the toothbrush head 110 and the connection portion 130 through the injection molding, thereby forming a soft buffer member 170. In this case, as shown in FIGS. 36, 38, and 39, the soft buffer member 170 is formed across the leading end portion, the rear surface, both the side surfaces, and portion of the front surface of the toothbrush head 110 and the front and rear surfaces and both the side surfaces of the connection portion 130.

[82] FIGS. 28A to 28C are schematic diagrams showing an example where a soft buffer member is formed on the toothbrush body, which is formed through the primary injection-molding process, through the secondary injection-molding process.

[83] As shown in FIG. 28 A, the rail 113 is formed by the primary injection-molding process such that the rail 113 and the handle 150 are at a different level. Then, when the soft buffer member 170 is formed through the secondary injection molding process, the soft buffer member 170 is on a level with the handle 150.

[84] Preferably, the soft buffer member 170 and the handle 150 are set to be on a level with each other. Without being limited thereto, however, the soft buffer member 170 may be formed to be at a different level with the handle 150, as shown in FIGS. 28B and 28C.

[85] Preferably, the thickness of the soft buffer member 170 is set in such a manner that the soft buffer member 170 can surround the toothbrush head 110 and the connection portion 130 in accordance with the shape of the toothbrush 100.

[86] Meanwhile, the melting point of the soft material for forming the soft buffer member 170, that is, the thermoplastic material is higher than that of the primarily injection-molded product, that is, the toothbrush body. When the soft buffer member 170 is molded, the soft material injected during the secondary injection molding process penetrates into the rails 113 formed on the toothbrush head 110 and the connection portion 130, the rail through-holes 116 formed in the rails 113, and the concave grooves 115 between the respective rails 113. Portions of the rails 113 are melted in such a manner that the thermal adhesion is reliably carried out. Then, the soft buffer member 170 is formed.

[87] When the rail irregularities 114 are formed in each of the rails 113, the thermal adhesion of the soft buffer member 170 is more reliably carried out by the rail irregularities 114. Depending on combination conditions of the rail through-holes 116 and the rail irregularities through-holes 118, which are formed in the rails 113 and the rail irregularities 114, respectively, the thermal adhesion of the soft buffer member 170 is more reliably carried out.

[88] As such, when materials with a different property are coupled to each other through the thermal adhesion, and if a thermal- adhesion area increases, the coupling is more reliably achieved by the fixing action of the rails 113 formed in the toothbrush head 110 and the connection portion 130, the rail irregularities 114 formed in the rails 113, the concave grooves 115, the rail through-holes 116, and the rail irregularity through- holes 118. Further, although the materials have a high melting point, the adhesion is reliably achieved.

[89] Preferably, the shore hardness of the soft buffer member 170, which is integrally molded through the secondary injection molding process, is set in the range of 60 to 72A. When the shore hardness is set to less than 6OA, the soft buffer member 170 becomes so soft that the impact of the handle 150 cannot be absorbed during tooth brushing and the toothbrush head 110 may transmits an impact to the teeth and gums. Further, when the shore hardness is set to more than 72A, a function as the soft buffer member is remarkably degraded, so that the soft buffer member 170 may impact against the teeth and gums.

[90] If the soft buffer member 170 constructed in such a manner is used, the teeth and gums can be protected from the impact occurring when the toothbrush head and the connection portion hit on the teeth and gums during tooth brushing, and scratch hardly occurs. Further, the soft buffer member 170 feels soft to the touch and has high resistance to the external impact.

[91] Preferably, the soft buffer member 170 as a secondarily injection-molded product is injected into a mold, which has been subjected to a heat treatment and a polishing process, so as to be coupled to the toothbrush body. When the soft buffer member 170 is molded by the mold subjected to the polishing process, the surface of the soft buffer member 170 becomes so smooth that the soft buffer member 170 feels smooth during tooth brushing. Further, when the soft buffer member 170 hits on the teeth and gums, noise can be prevented from occurring. In addition, since the soft buffer member 170 is polished, its appearance is improved.

[92] The thermoplastic material used in the primary molding process of the invention may contain a fragrance emitting agent. In this case, 3.0-5.0wt% of the fragrance emitting agent can be input with respect to the entire weight of the toothbrush body as a primarily injection-molded product. It is preferable that 4.3wt% of the fragrance emitting agent is input. When less than 3.0wt% of the fragrance emitting agent is input, the fragrance of the fragrance emitting agent is so weak that the effect is degraded. When more than 5.1wt% of the fragrance emitting agent is input, a problem may occur in forming the toothbrush body as the primarily injection-molded product, and the fragrance of the fragrance emitting agent is so strong that it may give an unpleasant feeling. Further, the fragrance emitting agent may be input into a soft material for injection-molding the soft buffer member 170 or a soft member 152 which is injection- molded on the handle 150 so as to prevent slipping.

[93] As for the fragrance emitting agent, various fragrance emitting agents such as a mint fragrance emitting agent, a lilac fragrance emitting agent, an acacia fragrance emitting agent, a herb fragrance emitting agent, a freesia fragrance emitting agent, a xylitol fragrance emitting agent and so on may be selectively used.

[94] When thermoplastic materials with a different property are to be attached to each other, the melting point of the soft material for molding the soft buffer member 170 should be equal to or higher than that of the toothbrush body as the primarily injection- molded product. When the heat-resistance temperature of the soft material for the soft buffer member 170 is higher as much as 15 degrees than that of the thermoplastic material of the toothbrush body, it can be said that the melting point thereof is high. Further, when the heat-resistance temperature is higher as mush as 23 degrees, it can be said that the melting point thereof is very high.

[95] In a case of vibration welding, when a difference in the resistance temperature is 22 degrees, materials are not attached to each other. Further, it is impossible to apply the vibration welding for soft materials.

[96] FIGS. 29 and 30 are rear and front view of a toothbrush body which is primarily injection-molded by a method for forming a toothbrush according to another embodiment of the invention. FIG. 31 is a schematic view showing the front, side, and rear surfaces of a connection portion of the toothbrush body.

[97] As shown in FIG. 1, the method for forming a toothbrush according to another embodiment of the invention includes a primary injection molding process for injection-molding a toothbrush body and a secondary injection molding process for injection-molding a soft buffer member.

[98] In the primary injection-molding process, a thermoplastic material is injected into a predetermined mold (not shown) so as to mold a toothbrush body.

[99] As shown in FIGS. 29 to 31, the toothbrush body includes a toothbrush head 110 having a plurality of bristle insertion holes 112 into which toothbrush bristles 111 are inserted, a handle 150, and a connection portion 130 which integrally connects the toothbrush head 110 and the handle 150.

[100] The toothbrush bristles 111 may be formed of nylon, silicon, TPE, or synthetic resin. As for the toothbrush bristles 111, nylon bristles made by DuPont (USA) may be used.

[101] FIG. 36 shows a state where the toothbrush bristles 111 are implanted into the bristle insertion holes 112. As shown in FIG. 36, the toothbrush bristles 111 are strongly pressed by a pin (not shown) so as to be reliably stuck into the head 110. Such an implanting process is carried out by an implanting machine (not shown). Since the implanting process corresponds to a well-known technique, the detailed descriptions thereof will be omitted.

[102] FIG. 37 shows an example where only irregularities 131 are formed when the toothbrush body according to the embodiment of the invention is primarily injection- molded. Each of the irregularities 131 has an irregularity through-hole 117 formed therein.

[103] Further, one or more rails 113 are formed on the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head 110 having the bristle insertion holes 112 formed therein, and a plurality of irregularities 131 are formed between the respective rails 113. Each of the rails 113 has one or more rail through-holes 116 formed in a direction perpendicular to the longitudinal direction of the rail 113 along the length of the rail 113. Each of the irregularities 131 has an irregularity through-hole 117 formed in the same direction as the rail through-hole 116 or a direction perpendicular to the rail through-hole 116. Further, the number of irregularities 131 may be adjusted depending on the mold design of a person with a skill in the art.

[104] Further, a plurality of rail irregularity through-holes 118 may be additionally formed in the rail 113. As the soft material is melted and fixed into the respective through-holes, a coupling force increases.

[105] The toothbrush head 110 has one or more rails 113 and a plurality of irregularities

131 formed on the rear surface thereof. As shown in FIGS. 33A and 34B, the rail 113 has a plurality of rail irregularities which are formed integrally with the rail 113 and are composed of rectangular and streamlined irregularities. The irregularities 131 are formed in both sides of the rail 113. In this case, it is preferable that the irregularities 131 facing each other in both sides of the rail 113 have different upper shapes from each other.

[106] This can be checked through the arrangement relationship between the rail 113 and the irregularities 131 shown in FIG. 35.

[107] As described above, the irregularities 131 are formed in both sides of the rail 113.

At the concave portion of the rail 113, the irregularities 131 facing each other in both sides of the rail 113 are formed to have a larger height than the rail 113. At the convex portion of the rail 113, a minute groove 132 is formed on the upper surfaces of the irregularities 131 facing each other in both sides of the rail 113.

[108] Further, the toothbrush head 110 has a plurality of concave grooves 115 formed on the rear surface thereof such that the positions of the concave grooves 115 do not correspond to those of the respective bristle insertion holes 112 into which the bristles 111 are inserted.

[109] As described above, the irregularities 131 are formed on the rear surface of the toothbrush head 110 such that the positions of the irregularities 131 correspond to those of the respective bristle insertion holes 112 where the bristles 111 are implanted. The minute concave grooves 115 are formed on the rear surface of the toothbrush head 110 such that the positions of the concave grooves 115 do not correspond to those of the bristle insertion holes 112. That is, as the irregularities and the concave grooves are formed on the rear surface of the toothbrush head 110, the surface area of the toothbrush is expanded. Therefore, the coupling force increases.

[110] Further, as shown in FIGS. 29 to 31, one or more rails 113 having rail irregularities formed thereon are injection-molded on the front and rear surfaces and both sides surfaces of the connection portion 130, and a plurality of irregularities 131 are injection-molded between the rails 113.

[I l l] That is, one or more rails 113 and the plurality of irregularities 131 are formed on the front and rear surfaces and both side surfaces of the connection portion 130. In this case, as shown in FIG. 33, the rail irregularities formed on each of the rails 113 are composed of rectangular and streamlined irregularities. Further, when the irregularities 131 are formed in both sides of the rail 113, the irregularities 131 facing each other in both sides of the rail 113 have different upper shapes from each other.

[112] As described above, the irregularities 131 are formed in both sides of the rail 113.

At the concave portion of the rail 113, the irregularities 131 facing each other in both sides of the rail 113 are formed to have a larger height than the rail 113. At the convex portion of the rail 113, a minute groove 132 is formed on the upper surfaces of the irregularities 131 facing each other in both sides of the rail 113. Further, the plurality of concave grooves 115 are formed between the respective irregularities 131.

[113] The number of rails 113 installed on the toothbrush head 110 and the connection portion 130 is not limited. Preferably, however, two or three rails 113 are formed on the rear surface of the toothbrush head 110, two or three rails 113 are formed on the r ear surface of the connection portion 130, one rail 113 is formed on the front surface of the connection portion 130, and one rail 113 is formed on the left and right side surfaces of the connection portion 130, respectively.

[114] The irregularities 131, which are shown in FIGS. 34 and 35 and are formed on the toothbrush head 110 and the connection portion 130, are independently constructed in such a manner that the thermal adhesion between different thermoplastic materials is maximized. The rail 113 has the rail irregularities, which are composed of rectangular and streamlined irregularities and are arranged in a line. Therefore, the thermal adhesion area increases, and the thermal adhesion performance between the toothbrush body and other thermoplastic materials is improved two times.

[115] Further, the irregularities 131 may be constructed in various types by reflecting their advantages thereof, and may be constructed in a regular order by reflecting their various functions. If necessary, however, the irregularities 131 may be arranged in a different order, and the number of the irregularities 131 may be increased or reduced. The irregularities 131 serve to improve the thermal adhesion between the toothbrush body and the soft buffer member during the secondary injection-molding process for molding the soft buffer member. Even thermoplastic materials having a different property can be reliably bonded to each other through the thermal adhesion.

[116] In particular, since the rail 113 has the rail irregularities composed of rectangular and streamlined irregularities as shown in FIG. 33, the toothbrush body and the soft buffer member 170 can be more reliably bonded to each other. Even when the melting point of the soft buffer member 170 is very high, the rail 113 serves to reliably attach the toothbrush body to the soft buffer member 170.

[117] FIG. 32 is a perspective view of the toothbrush body which is primarily injection- molded by the method for forming a toothbrush according to the invention, showing the rails, the irregularities, and the concave grooves of the toothbrush body.

[118] As shown in FIG. 32, one rail 113 having a plurality of rail irregularities, which are composed of rectangular and streamlined irregularities, is also formed across the side surface of the tooth brush. Specifically, the rail 113 is continuously formed on one side surface of the connection portion 130, one side surface, the leading end, and the other surface of the toothbrush head 110, and the other side surface of the connection portion 130. Further, irregularities 131 and concave grooves 151 are also formed in both sides of the rail 113.

[119] In this case, only the rail may be formed, and both of the rail and the irregularities may be formed.

[120] The rail 113 shown in FIG. 32 is integrally formed on the side surface of the toothbrush body. Preferably, the rail and the irregularities 113 are formed to have a height of less than 1.78mm. However, the height of the rail and the irregularities 113 may be set to less than 1.83mm. Further, the rail 113 and the irregularities 131 shown in FIG. 32 perform the same function as the rails 113 and the irregularities 131 formed on the front and rear surfaces of the toothbrush head 110 and the connection portion 130.

[121] When the soft buffer member is injected through a nozzle via a cylinder of the injection machine, the rails 113 rectifies the injected soft buffer member such that the soft buffer member is uniformly and quickly distributed. Further, the soft buffer member is guided along the rails 113 so as to be reliably bonded.

[122] Further, when the soft buffer member is injected through the nozzle, the toothbrush body and the soft buffer member are reliably bonded to each other by the rails 113, the irregularities 131, the concave grooves 115, the rail through-holes 116, the irregularity through-holes 117, and the rail irregularity through-holes 118. Further, the toothbrush body and the soft buffer member with a high melting point are reliably fixed to each other by the rails 113, the irregularities 131, the concave grooves 115, the rail through- holes 116, the irregularity through-holes 117, and the rail irregularity through-holes 118. Then, the coupling force therebetween increases. Therefore, although an external impact is applied or the temperature severely changes, the toothbrush body and the soft buffer member are not separated from each other.

[123] In the secondary injection-molding process, a soft buffer member composed of a different material from the toothbrush body is injected into the predetermined mold (not shown) in which the toothbrush body injection-molded through the primary injection-molding process is received. Preferably, the soft buffer member is a thermoplastic material, but is not limited thereto. Another kind of soft material (including a thermosetting material) may be used.

[124] When a thermoplastic material is used in the primary injection-molding process, a thermoplastic material is used as the soft buffer member in the second injection- molding process.

[125] This means that thermoplastic materials are used in the primary and secondary injection-molding processes. In this case, it is preferable that thermoplastic materials having a different property and a different melting point are used.

[126] As for a general molding method for thermosetting materials, compression molding, hot air molding, die casting and so on may be used. In a special case, the toothbrush body (thermoplastic material) which is primarily injection-molded may be coupled to the soft buffer member (thermosetting material), which is secondarily injection- molded, by one of the molding methods.

[127] In the secondary injection molding process, a soft member, which is composed of a different material from the toothbrush body and has a high melting point, is injected into the mold in which the toothbrush body injection-molded through the primary injection molding process is received. Then, the soft member is coupled to one or more rails 113 formed on the toothbrush head 110 and the connection portion 130, the rail through-holes 116 and the irregularities 131 formed in the rails 113, and the rail irregularity through-holes 118 formed on the irregularities 131 through the injection molding, thereby forming a soft buffer member 170.

[128] In this case, as shown in FIGS. 36, 38, and 39, the soft buffer member 170 is formed across the leading end portion, the rear surface, both the side surfaces, and portion of the front surface of the toothbrush head 110 and the front and rear surfaces and both the side surfaces of the connection portion 130.

[129] The soft buffer member 170 may be formed so as to be on a level with the handle

150. Alternately, the soft buffer member 170 may be formed so as to be at a different level with the handle 150.

[130] Meanwhile, the melting point of the soft material for forming the soft buffer member 170 is equal to or higher than that of the primarily injection-molded product, that is, the toothbrush body. When the soft buffer member 170 is molded, portions of the rails 113 and the irregularities 131 formed on the toothbrush head 110 and the connection portion 130 are melted in such a manner that the soft material for forming the soft buffer member 170 and the toothbrush body are melted and bonded to each other. Therefore, the adhesion between the soft buffer member 170 and the toothbrush body are reliably achieved.

[131] Preferably, the soft buffer member 170 is formed across the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head 110 and the front and rear surfaces and both side surfaces of the connection portion 130.

[132] Further, the rails 113, the irregularities 131, the concave grooves 115, the rail through-holes 116, the irregularity through-holes 117, and the rail irregularity through- holes 118, which are formed on the toothbrush head 110 and the connection portion 130, increase the thermal adhesion area such that the soft material injected in the secondary injection-molding process is reliably coupled.

[133] As such, when materials with a different property are coupled to each other through the thermal adhesion, and if a thermal- adhesion area increases, the coupling is more reliably achieved by the fixation action among the rails 113, the irregularities 131, the concave grooves 115, the rail through-holes 116, and the rail irregularity through-holes 118, which are formed in the toothbrush head 110 and the connection portion 130. Further, even the materials having a high melting point are easily injection-molded.

[134] Preferably, the shore hardness of the soft buffer member 170, which is integrally molded through the secondary injection molding process, is set in the range of 60 to 72A. When the shore hardness is set to less than 6OA, the soft buffer member 170 becomes so soft that the impact of the handle 150 cannot be absorbed during tooth brushing and the toothbrush head 110 may transmit an impact to the teeth and gums. Further, when the shore hardness is set to more than 72A, a function as the soft buffer member is remarkably degraded, so that the soft buffer member 170 may impact against the teeth and gums.

[135] If the soft buffer member 170 constructed in such a manner is used, the teeth and gums can be protected from the impact occurring when the toothbrush head and the connection portion hit on the teeth and gums during tooth brushing, and scratch hardly occurs. Further, the soft buffer member 170 feels soft to the touch and has high resistance to the external impact.

[136] Preferably, the soft buffer member 170 as a secondarily injection-molded product is injected into a mold, which has been subjected to a heat treatment and a polishing process, so as to be coupled to the toothbrush body. When the soft buffer member 170 is molded by the mold subjected to the polishing process, the surface of the soft buffer member 170 becomes so smooth that the soft buffer member 170 feels smooth during tooth brushing. Further, when the soft buffer member 170 hits on the teeth and gums, noise can be prevented from occurring. In addition, since the soft buffer member 170 is polished, its appearance is improved.

[137] The thermoplastic material used in the primary molding process of the invention may contain a fragrance emitting agent. In this case, 3.0-5.0wt% of the fragrance emitting agent can be input with respect to the entire weight of the toothbrush body. It is preferable that 4.3wt% of the fragrance emitting agent is input. When less than 3.0wt% of the fragrance emitting agent is input, the fragrance is so weak that the effect is degraded. When more than 5.1wt% of the fragrance emitting agent is input, a problem may occur in forming the toothbrush body as the primary injection-molded product, and the fragrance of the fragrance emitting agent is so strong that it may give an unpleasant feeling. Further, the fragrance emitting agent may be input into a thermoplastic material for injection-molding the soft buffer member 170 or a soft member which is injection-molded on the handle 150 so as to prevent slipping.

[138] As for the fragrance emitting agent, various fragrance emitting agents such as a mint fragrance emitting agent, a lilac fragrance emitting agent, an acacia emitting agent, a herb fragrance emitting agent, a freesia fragrance emitting agent, a xylitol fragrance emitting agent and so on may be selectively used.

[139] When thermoplastic materials with a different property are attached to each other, the melting point of the soft material for molding the soft buffer member 170 should be equal to or higher than that of the primarily injection-molded product, that is, the toothbrush body. When the heat-resistance temperature of the thermoplastic material for the soft buffer member 170 is higher as much as 15 degrees than that of the thermoplastic material of the toothbrush body, it can be said that the melting point is high. Further, when the heat-resistance temperature is higher as mush as 23 degrees, it can be said that the melting point is very high.

[140] The method for forming a toothbrush according to the invention can be applied to a two-tone injection machine including a mold composed of a moving plate and a fixed plate. The two-tone injection machine includes two nozzles such that two injections can be performed at a time. When the two-tone injection machine is used, the injection molding is performed as follows. First, the toothbrush body is primarily injection- molded. Then, the moving plate is moved, and the handle 150 is secondarily injection- molded using a new moving plate in a state where the toothbrush body is held in the mold. After the handle 150 is injection-molded, the toothbrush body is separated from the two-tone injection machine. Then, the toothbrush body is received in a next mold, and a tertiary injection-molding process is performed to injection-mold the soft buffer member 170.

[141] FIG. 38 is a perspective view of a toothbrush manufactured by the method for forming a toothbrush according to the embodiment of the invention. FIGS. 39 and 40 are front and rear views of the toothbrush of FIG. 38. FIGS. 41 and 42 are diagrams for explaining upper and lower caps and a through-hole of the handle in the toothbrush of FIG. 38.

[142] As shown in FIGS. 38 to 42, the toothbrush 100 manufactured by the method for forming a toothbrush according to the invention includes a toothbrush head 110 having bristles 111 formed therein, a handle 150 having one or more soft members 152 for preventing slipping, a connection portion 130 which integrally connects the toothbrush head 110 and the handle 150, and a soft buffer member 170 which is formed to surround the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head 110 and the front and rear surfaces and both side surfaces of the connection portion 130.

[143] The soft members 152 for preventing slipping, which are formed on the handle 150, may be manufactured through a separate injection-molding process. The positions and the number of the soft members 152 are not limited. In the invention, three soft members 152 are used.

[144] Further, as shown in FIG. 39, the soft buffer member 170, which surrounds the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head 110 and the front and rear surfaces and both side surfaces of the connection portion 130, is formed in such a manner that the thickness of the leading end portion thereof is set to 1.34 to 1.93mm, the thickness of the rear surface portion and the side surface portion thereof is set to 0.43 to 0.88mm, and the thickness of the connection portion 130 is set to 0.34 to 0.83mm. As the soft buffer member 170 is formed with an optimal thickness, inconvenience which may be caused by the size of the toothbrush head 110 during tooth brushing can be eliminated. Further , an amount of the expensive soft buffer member can be reduced, which makes it possible to reduce a manufacturing cost.

[145] The handle 150 has a through-hole 154 through which the upper and lower caps 151 are attached and detached to and from each other, the upper and lower caps 151 being coated with a predetermined color of fluorescent material.

[146] The through-hole 154 may be formed through the primary injection-molding process or a separate process. As the upper and lower caps 151 are coated with a predetermined color of fluorescent material (noctilucent material), the toothbrush 100 can be discriminated from other toothbrushes, even through the toothbrushes are stored in one case.

[147] In this case, various colors (for example, seven colors) can be applied in such a manner that toothbrushes can be discriminated from one another, even though they are the same products. In particular, the toothbrushes are more clearly discriminated in a dark place.

[148] Further, the handle 150 may have a logo member 153 on which the name or logo of a company is printed.

[149] The soft buffer member used in the invention is not harmful to the human body. In this case, soft materials (that is, thermoplastic material and thermosetting material) approved by Korea Environment & Merchandise Testing Institute may be used. Further, products approved by environment & merchandise testing institutes of other countries such as the US, Japan, China, Europe and so on may be used. In some cases, products certified by FDA or UPS in the US may be used.

[150] In the invention, TPU UPT Tecoflex EG- 80A may be used as the soft buffer member. This product is the best biomaterial approved by FDA and UPS in the US.

[151] In addition, TPU Estane X 1007 NAT 034 may be used as the soft buffer member.

[152] The toothbrush manufactured by the above-described method has the soft buffer member formed on the toothbrush head and the connection portion of the toothbrush body. Therefore, although the toothbrush head or the connection portion hits on the teeth and gums during tooth brushing, the teeth and gums are not contacted with plastics harmful to the human body, and scratches are prevented. Therefore, the toothbrush can effectively protect the teeth and gums.

[153] In the conventional method for forming a toothbrush, when the toothbrush head and the connection member are covered by the soft buffer member, which has a high melting point and is composed of a thermoplastic material different from the toothbrush head and the connection member, the thermal adhesion therebetween is not reliably achieved. However, the present invention has an advantage of improving the thermal adhesion. The method for forming a toothbrush according to the invention also facilitates the injection molding.

[154] Further, in the conventional toothbrush, since the through-holes are formed in the neck portion thereof, the expensive soft buffer member is used in a useless spot. In the invention, however, the rails and irregularities are used instead of the through holes of the neck portion such that the fixing action is enhanced. Further, since the soft buffer member is formed to surround the neck portion at a small thickness without passing through the neck portion, a material cost is reduced. In addition, it is possible to provide a toothbrush with no weak portion.

[155] While the present invention has been described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications in form and detail may be made therein without departing from the scope of the present invention as defined by the following claims.

Claims

[1] A method for forming a toothbrush, comprising the steps of: molding a toothbrush body by injecting a thermoplastic material into a predetermined mold, the toothbrush body including a toothbrush head having a plurality of bristle insertion holes into which bristles are inserted, a handle, and a connection portion for integrally connecting the toothbrush head and the handle, wherein rails are injection-molded so as to be connected across the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head having the bristle insertion holes and the front surface, the rear surface, and both side surfaces of the connection portion (primary injection- molding process); and injecting a soft material, which is composed of a different material from the tooth brush body and has a high melting point, into the mold in which the toothbrush body injection-molded by the primary injection molding process is received, so that the soft material is coupled to the rails formed on the toothbrush head and the connection portion through injection molding, thereby molding a soft buffer member, wherein the soft buffer member is integrally molded on the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head and the front surface, the rear surface, and both side surfaces of the connection portion (secondary injection-molding process).

[2] The method according to claim 1, wherein each of the rails has rail irregularities formed thereon.

[3] The method according to claim 1 or 2, wherein each of the rails has one or more rail through-holes passing through only the rail, the rail through-holes being formed in the longitudinal direction of the rail or in a direction perpendicular to the longitudinal direction of the rail along the length of the rail.

[4] The method according to claim 2, wherein each of the rails has one or more rail irregularity through-holes passing through only the rail irregularities formed on the rail, the rail irregularity through-holes being formed in the longitudinal direction of the rail or in a direction perpendicular to the longitudinal direction of the rail.

[5] The method according to claim 2, wherein each of the rails has one or more rail through-holes and one or more rail irregularity through-holes formed therein, the rail through-holes are formed in the longitudinal direction of the rail or in a direction perpendicular to the longitudinal direction of the rail along the length of the rail, and the rail irregularity through-holes are formed in the longitudinal direction of the rail or in a direction perpendicular to the longitudinal direction of the rail.

[6] The method according to claim 1, wherein a plurality of concave grooves are formed between the respective irregularities on the rear surface, the leading end portion, both side surfaces, and portion of the front surface of the toothbrush head having the bristle insertion holes formed therein, and the front surface, the rear surface, and both side surfaces of the connection portion.

[7] A method for forming a toothbrush, comprising the steps of: molding a toothbrush body by injecting a thermoplastic material into a predetermined mold, the toothbrush body including a toothbrush head having a plurality of bristle insertion holes into which bristles are inserted, a handle, and a connection portion for integrally connecting the toothbrush head and the handle, wherein one or more rails are injection-molded so as to be connected across the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head having the bristle insertion holes and the front surface, the rear surface, and both side surfaces of the connection portion, a plurality of irregularities are injection-molded between the rails, each of the rails has one or more rail through-holes formed in a direction perpendicular to the longitudinal direction of the rail along the length of the rail, and each of the irregularities has an irregularity through-hole formed in the same direction as the rail through-hole or in a direction perpendicular to the rail through-hole (primary injection-molding process); and injecting a soft material, which is composed of a different material from the toothbrush body and has a high melting point, into the mold in which the toothbrush body injection-molded by the primary injection molding process is received, so that the soft material is coupled to one or more rails formed on the toothbrush head and the connection portion, the rail through-holes and the irregularities formed on the rail, and the irregularity though-holes formed on the irregularities through injection molding, thereby molding a soft buffer member, wherein the soft buffer member is integrally molded on the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head and the front surface, the rear surface, and both side surfaces of the connection portion (secondary injection-molding process).

[8] The method according to claim 7, wherein each of the rails has a plurality of rail irregularities formed thereon, the rail irregularities being composed of rectangular and streamlined irregularities, and the irregularities are formed in both sides of the rail such that the upper shapes of the irregularities facing each other in both sides of the rail are different from each other.

[9] The method according to claim 7 or 8, wherein the irregularities are formed in both sides of the rail such that the height of the irregularities facing each other in both sides of the rail at each concave portion of the rail is set to be larger than that of the rail, and the irregularities facing each other in both sides of the rail at each convex portion of the rail have a minute groove formed thereon.

[10] The method according to claim 7 or 8, wherein a plurality of concave grooves are formed between the respective irregularities on the rear surface, the leading end portion, both side surfaces, and portion of the front surface of the toothbrush head having the bristle insertion holes formed thereon, and the front surface, the rear surface, and both side surfaces of the connection portion.

[11] The method according to claim 1 or 7, wherein the soft material is a thermoplastic or thermosetting material.

[12] The method according to claim 1 or 7, wherein the shore hardness of the soft buffer member, which is integrally molded through the secondary injection- molding process, is set in the range of 60 to 72A, and the soft buffer member, which surrounds the rear surface, the leading end portion, both side surfaces, and portion of the front surface of the toothbrush head, and the front surface, the rear surface, and both side surfaces of the connection portion, is molded in such a manner that the thickness of the leading end portion thereof at the toothbrush head is set to 1.34 to 1.93mm, the thickness of the rear surface portion and the side surface portion thereof at the toothbrush head is set to 0.43 to 0.88mm, and the thickness thereof at the connection portion is set to 0.43 to 0.88mm.

[13] A method for forming a toothbrush, comprising the steps of: molding a toothbrush body by injecting a thermoplastic material into a predetermined mold, the toothbrush body including a toothbrush head having a plurality of bristle insertion holes into which bristles are inserted, a handle, and a connection portion for integrally connecting the toothbrush head and the handle, wherein a plurality of irregularities are injection-molded on the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head having the bristle insertion holes and the front surface, the rear surface, and both side surfaces of the connection portion, the irregularities having irregularity through-holes formed therein (primary injection-molding process); and injecting a soft material, which is composed of a different material from the toothbrush body and has a high melting point, into the mold in which the toothbrush body injection-molded by the primary injection molding process is received, so that the soft material is coupled to the irregularities formed on the toothbrush head and the connection portion and the irregularity through-holes formed in the respective irregularities through injection molding, thereby molding a soft buffer member, wherein the soft buffer member is integrally molded on the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head and the front surface, the rear surface, and both side surfaces of the connection portion (secondary injection- molding process).

[14] A toothbrush manufactured by the method according to any one of claims 1 to

13.

[15] The toothbrush according to claim 14 comprising: a toothbrush head having bristles formed thereon; a handle having one or more soft members for preventing slipping; a connection portion that integrally connects the toothbrush head and the handle; and a soft buffer member that is integrally molded so as to surround the leading end portion, the rear surface, both side surfaces, and portion of the front surface of the toothbrush head and the front surface, the rear surface, and both sides surfaces of the connection portion.

[16] The toothbrush according to claim 15, wherein the shore hardness of the soft buffer member is set to 60 to 72A, and the soft buffer member is molded in such a manner that the thickness of the leading end portion thereof is set to 1.34 to 1.93mm, the thickness of the rear surface portion and the side surface portion thereof at the toothbrush head thereof is set to 0.43 to 0.88mm, and the thickness thereof at the connection portion is set to 0.43 to 0.88mm.

[17] The toothbrush according to claim 15 or 16, wherein the handle has a through- hole through which upper and lower caps are attached and detached to and from each other, the upper and lower caps being coated with a predetermined color of noctilucent material.

[18] The toothbrush according to claim 15 or 16, wherein at least one of the soft buffer member and a toothbrush body composed of the toothbrush head, the connection portion, and the handle contains a fragrance emitting agent.