JPH07265131A - Manufacture of brush by insert molding and die for brush manufacture by insert molding - Google Patents

Abstract

PURPOSE: To manufacture a brush by one process of insert forming. CONSTITUTION: When a brush comprising a bristle part and a base made of a resin is to be manufactured, A bristle 4 is inserted into each plural through holes 11 of a mold for injection molding with a core pattern with plural through holes and a cavity pattern with cavities on positions facing to the plural through holes, the bristle is engaged at a position the tip end of the bristle reached into the cavity, a resin is filled in the cavity and a base id injection molded to fix the bristle to the base on completion of injection molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a brush such as a toothbrush having a bristle portion and a resin base by insert molding, and a die used for the method for producing the brush.

[0002]

2. Description of the Related Art Conventionally, a brush consisting of a bristle portion and a resin base has been manufactured by a method of implanting bristol in the base. That is, after manufacturing a base having holes for inserting the bristles by injection molding, the bristles 41 bundled as shown in FIG. 4 (A) are folded in two, and the holes for the base 43 are provided together with the locking plates 42 such as brass. It is manufactured by a method of press-fitting into 44 and fixing as shown in FIG.

However, the conventional method has a problem that the work efficiency is poor because it requires two steps of injection molding of the base and locking of the bristles to the base.

[0004]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for manufacturing a brush in one step by insert molding.

[0005]

According to the present invention for achieving the above object, in a method of manufacturing a brush comprising a bristle portion and a resin base, a core mold having a plurality of through holes and a plurality of through holes facing each other are provided. A mold for injection molding having a cavity mold having a cavity at a position, a bristol is inserted into each of the plurality of through holes, and the bristol is locked at a position where the tip of the bristle reaches the cavity, A brush manufacturing method is characterized in that the bristles are fixed to the base when the injection molding is completed by filling the cavity with resin and injection-molding the base.

The bristles used in the present invention are conventionally used bristles, and have a material, shape, hardness and thickness suitable for the application of the brush.
For example, when a toothbrush is manufactured by the manufacturing method of the present invention, resins such as polypropylene and polyamide and natural materials such as pig hair can be used.

The base of the present invention is manufactured by using a resin having a mechanical property such as a flexural modulus suitable for the use of the brush as a material. If both the material of the bristles and the material of the base are the same material such as nylon, the brush can be easily recycled, and if the type (composition) is the same, for example, nylon 612, it is more suitable for recycling.

The injection mold used in the manufacturing method of the present invention has a plurality of through holes for penetrating the bristles and a cutter for cutting the bristles inserted into each of the plurality of through holes. And a cavity mold having a cavity for molding the base portion of the brush for fixing the bristles at a position facing the plurality of through holes.

The cavity mold and the core mold are made of a metal material having a predetermined thickness and good thermal conductivity.

[0010]

In the present invention, first, the bristles are inserted into the through holes provided in the core mold in order to penetrate the bristles from the core mold to the cavity for molding the base portion of the brush. More specifically, the bristle tip is made to project into the cavity provided in the cavity mold a sufficient length so that the bristle is fixed by the resin injected in the base of the brush. For that purpose, the bristles may be moved by a predetermined length, or after the tips of the bristles reach the bottom of the cavity mold, the bristles may be retracted by a predetermined length.

The size of the through hole provided in the core mold is determined according to the thickness and the number of the bristles to be inserted,
The number of through holes is determined according to the size of the brush and the like.
In the case of an ordinary brush, dozens of bristles are bundled and each bundle is inserted into the through hole. A tubular guide may be provided for each bundle so that the bundle of bristles can be easily inserted into the through hole.

The bristles penetrating the core die and protruding into the cavity are cut into a predetermined length by inserting a cutter through a cutter insertion port provided in the core die. The cutter insertion port is a portion through which the core-type bristles penetrate, and is provided at a position in consideration of the length of the bristles according to the material and application of the brush.

Insert the cutter from the cutter insertion port,
After cutting the bristles, the mold is closed and the resin material is injected into the cavity through the sprue, runner and gate. The cut bristles are held in the through holes during resin injection by friction with the through hole wall and the cutter surface. The resin filled in the cavity is cooled by the core mold and the cavity mold, and the resin material is solidified. When the resin material has solidified, pull out the inserted cutter. After that, the mold is opened from the parting line, and the sprue, runner, and molded product move with respect to the core mold. After the mold has been fully opened, the ejector pin will move to the sprue, runner,
The molded product is ejected, and at this time, the bristles for the next shot are inserted into the through holes provided in the core mold. For the next shot of Bristol, a molded product is ejected together with an ejector pin, and a brush in which the tip of the Bristol is fixed to the base is manufactured.

If the bristles can be locked by other means regardless of the cutter surface, the bristles may be cut after the resin has been solidified, and the bristles may be inserted into the through holes provided in the core mold and the cutter may be cut. The cutter may be inserted into and removed from the insertion opening automatically.

In this way, according to the present invention, the bristles are locked to the base by insert molding, so that the brush can be manufactured in one step.

[0016]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

FIG. 1 is a perspective view of an embodiment of a mold for manufacturing a brush according to the present invention. The mold is a core mold 1 and a cavity mold 2.
The core mold 1 is integrally assembled with a bristle supply guide tool 12 having a plurality of through holes 11. A cutter insertion opening 13 for inserting a cutter 3 for cutting the bristle is provided between the bristle supply guide tool 12 and the main body of the core die 1. A projecting plate 15 is provided on the core mold 1 side. The cavity mold 2 is formed with a cavity 21 for injecting resin to mold the base, and the guide pin 14 and the guide hole 22 close or open the core mold 1 and the cavity mold 2. The core mold 1 and the cavity mold 2 respectively include a movable side mounting plate 16 and a fixed side mounting plate 23.
Attached to the injection molding machine. The bristles 4 are gripped by a bristle gripping / supplying tool (not shown), are passed through the through holes 11, and are transferred and supplied so that their tips reach a predetermined position in the cavity 21.

FIG. 2 (A) is a sectional view of the main part of the mold in the closed state, and FIG. 2 (B) is a top view of the cavity mold. The cavity 21 is a base part 2 for fixing the bristles.
1A, a handle portion 21B and a connecting portion 21C between the base portion and the handle portion. The base portion 21A of the cavity is located so as to face the core-type bristle supply guide tool 12, more specifically, the region where the plurality of through holes 11 provided in the guide tool 12 are present.

Using such a die, a toothbrush having a bristle portion of 10 mm was manufactured by the manufacturing method of the present invention.

The mold is made of structural carbon steel, and the cavity of the mold has a base portion for fixing the bristles of 22 m.
It was formed to have a size of m × 12 mm and a thickness of 3.5 mm. The core of the mold has 34 holes with a diameter of 1.7 mm for inserting the bristles, and the part where the bristles of the core penetrate is 1 part from the parting line of the mold.
A cutter insertion port was provided at a position of 2 mm.

Nylon 612 (DuPont Zitel) was used as the base material. Bristol is 0.2m thick
m nylon 612 filaments (Tynex DuPont) were used, and 40 filaments each were used as a bundle.

After inserting the bristles into the through holes of the core mold, the mold was closed, and the above-mentioned base material was injected and injected into the cavity to manufacture a toothbrush in which the base and the bristles were integrally molded. FIG. 3 shows a partial sectional view of the manufactured toothbrush. Bristol was held firmly in the base.

[0023]

As described above, in the brush manufacturing method of the present invention, since the bristles are locked to the base by insert molding, the brush can be manufactured in one step.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of a mold according to the present invention.

2A and 2B show an embodiment of a mold according to the present invention, FIG. 2A is a sectional view of a main part, and FIG. 2B is a top view of a cavity mold.

FIG. 3 is a partial cross-sectional view of a toothbrush manufactured according to the present invention.

FIG. 4 is a cross-sectional view showing a conventional toothbrush manufacturing method, (A) showing a press-fitting step, and (B) showing a manufacturing state.

[Explanation of symbols]

 1 Core type 2 Cavity type 3 Cutter 4 Bristol 11 Through hole 12 Bristol supply guide tool 13 Cutter insertion port 14 Guide pin 21 Cavity 21A Base part 21B Handle part 21C Connecting part 22 Guide hole 41 Bristol 42 Locking plate 43 Base 44 hole

Claims (2)

[Claims] 1. A method for manufacturing a brush comprising a bristle portion and a resin base, the injection molding comprising a core mold having a plurality of through holes and a cavity mold having a cavity at a position facing the plurality of through holes. Inserting a bristle into each of the plurality of through holes of the metal mold, locking the bristol at a position where the tip of the bristle reaches the cavity, filling the cavity with resin, and injection-molding the base. According to the method of manufacturing a brush, the bristles are fixed to the base upon completion of injection molding. 2. A core mold having a plurality of through-holes for penetrating the bristles and a cutter insertion opening for inserting a cutter for cutting the bristles inserted in each of the plurality of through-holes, and the plurality of penetrating holes. A mold for manufacturing a brush, comprising: a cavity mold having a cavity for molding a base portion of the brush that fixes the bristles at a position facing the hole.