JP2000102930A - Method for forming undercut of molded product and composite molded product using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming the undercut of a molded product only by opening and closing a mold without performing post-processing or complicating the mold and a surface fastener and a composite molded product using the same. SOLUTION: A resin is injected into the space part formed between a fixed mold 11 and a movable mold 12 to be elastically deformed when the movable mold 12 is opened to form a molded product 13 provided with an undercut 14 of a degree such that the deformation is elastically restored and, thereafter, the movable mold 12 is closed while the molded product 13 attached to the fixed mold 11 immediately after the mold 12 is opened to collapse the undercut 14 to expand the same. A surface fastener is formed by this molding method. Further, a resin of different material quality is applied to the primary molded product formed by this method to form a composite molded product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming an undercut of a molded product for forming an undercut used as an engaging portion of a surface fastener, for example, and a surface fastener and a composite molded product using the same. .

[0002]

2. Description of the Related Art A conventional hook-and-loop fastener is formed by melting a tip of a bar-shaped projection formed on a surface into a spherical shape, curling into a hook shape, or a rubber mold to form an undercut portion serving as an engaging portion. There were ones in which a spherical tip was forcibly removed and one in which an undercut 1 was provided by pressing and cutting a mold as shown in a sectional view in FIG.

In order to form a composite molded article, 2
The bonding of two different materials (for example, when joining a hard material and a soft material) is performed by bonding or heat fusion.

[0004]

However, the above method requires post-processing such as melting or curling the tip of the rod-shaped projection, or requires a special mold or material, and requires a long mold life. Is short, the mold structure is complicated and
When a composite molded article is produced as a primary molded article, there is a disadvantage that a core back is required.

[0005] Further, when obtaining the above-mentioned composite molded article, there is a problem that the materials that can be bonded and the materials that can be heat-fused are limited. There was a problem that it was difficult to do. For example, gears and racks having a sliding surface are often formed of polyacetal, but polyacetal is difficult to form due to poor adhesion.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a method for forming an undercut portion of a molded product only by opening and closing the mold without post-processing or complicating the mold. It is another object of the present invention to provide a composite molded product which can be separated from any surface fastener and material using the same.

[0007]

The present invention employs the following structure to achieve the object.

According to the method of forming an undercut of a molded article of the present invention, a resin is injected into a space formed between a fixed mold and a movable mold, and elastically deforms when the movable mold is opened. After forming a molded article provided with an undercut such that the deformation is elastically restored, immediately after opening the movable mold, the movable mold is closed with the molded article attached to the fixed mold, and the undercut is crushed. It has a molding step of expanding.

The surface fastener of the present invention is formed by forming a plurality of undercuts having the above-mentioned forming step on a base.

[0010] The composite molded article of the present invention is obtained by applying a resin of a material different from that of the primary molded article to the primary molded article having the molding step.

In the method for forming an undercut of a molded article according to the present invention, the undercut that is elastically deformed when the movable mold is opened and the elastic deformation is restored is a columnar or cylindrical member that stands upright from the base. The body is divided into a plurality, a concave portion is provided at the center of the tip of the columnar body or the cylindrical body, and the tip is formed in a shape in which the diameter of the tip is open from the base of the columnar body or the cylindrical body, and the divided body of the divided body That the tip is tapered from the root to the tip, or that a column or cylinder erected from the base is inclined toward the tip and the tip is tapered from the root to the tip It is desirable that

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment (hereinafter referred to as an "embodiment") of an undercut forming method according to the present invention will be described with reference to the accompanying drawings.

FIGS. 1 to 3 are sectional views of a mold showing an embodiment of the present invention. FIG. 1 shows a state in which the mold is closed and the resin is injected when the resin is injected, and FIG. 2 shows a movable mold. FIG. 3 shows a state in which the movable mold is closed. FIG. 4 is an enlarged view of the molded article in the state of FIG. 1, and FIG. 5 is an end view of the tip of the divided body of the molded article in the state of FIG.

As shown in FIG. 1, the mold is a normal mold of this kind comprising a fixed mold 11 and a movable mold 12, and the fixed mold 11 and the movable mold 12 are closed ( In this state, the resin is injected into the space formed between the fixed mold 11 and the movable mold 12 to form a molded article 13 having a slight undercut 14 that can be forcibly removed. As shown in FIG. 4, the undercut 14 divides a columnar or cylindrical body 16 erected from a base 15 into a plurality of parts, provides a concave portion 17 at the center of the distal end of the columnar or cylindrical body 16, The diameter (D) of the tip is formed so as to be wider than the diameter (d) of the column or the cylindrical body 13 and the tip of the divided body 18 is formed to be tapered from the root to the tip, thereby facilitating easy operation. It is designed to be able to be forcibly removed. The movable mold 12 is divided into 12a and 12b in order to provide a space having the shape of the undercut 14.

After obtaining the molded product 13, the movable mold 12 is forcibly removed as shown in FIG.
When the length of the columnar or cylindrical body 16 is larger than the length, the divided body 18 elastically deforms (shrinks) and then recovers elastically, so that D> d is maintained. Immediately thereafter, as shown in FIG. 3, the movable mold 12 is closed while the molded article 13 is placed on the fixed mold 11, and the divided body 18 is crushed and expanded. After crushing and expanding the divided body 18, the movable mold 12 is opened again to
A large undercut 19 of 3 is obtained.

When the divided body is crushed, the entire thickness including the base 15 can be adjusted by closing and adjusting the mold so that the thickness can be changed according to the degree of undercut and the thickness of the secondary side during composite molding described later. . Since the crushing is performed immediately after molding (resin injection) and the resin is not yet solidified, the shape is sufficiently maintained. However, in a material such as polyacetal or polycarbonate capable of being cold-crimped, the shape is sufficiently maintained even after the resin has hardened.

As shown in the end view of FIG. 5, the number of divisions of the tip is (a) divided by 18a, (b) divided by 1
8b, (c) is appropriately selected depending on the material shape such as a quarter 18c. However, if the material has relatively good elongation (eg, polyamide, polyethylene, polypropylene, etc.), it is not necessary to divide the material if the recess 17 is provided at the center of the tip. In this case, a strong undercut like a rivet head can be formed.

Further, in the above embodiment, the concave portion 17 is formed at the tip end and the divided body 18 is formed. However, the present invention is not limited to the above embodiment.
It is sufficient if there is a slight undercut that can be forcibly removed as shown in FIG. 6 to 8 are cross-sectional views of a mold showing another embodiment of the present invention. FIG. 6 shows a state in which the mold is closed and the resin is injected when the resin is injected, and FIG. 7 shows a movable mold. FIG. 8 shows an opened state, and FIG. 8 shows a state in which the movable mold is closed. As shown in FIG. 6, the mold includes a fixed mold 21 and a movable mold 22. In a state where the fixed mold 21 and the movable mold 22 are closed (closely contacted), the fixed mold 21 and the movable mold 22 are closed. A molded product 2 having a slight undercut portion 24 that can be forcibly removed by injecting a resin into a space formed between the movable molds 22.
Forming 3 is the same as in the above embodiment. As shown in FIG. 7, the undercut 24 is formed by inclining a columnar or cylindrical body 26 erected from the base 25 toward the tip and tapering the tip from the root to the tip so that the undercut 24 can be easily forcibly removed. It is made possible.

After obtaining the molded product 23, the movable mold 22 is forcibly removed as shown in FIG.
When the column or the cylindrical body 26 is opened beyond the length of the column or the cylindrical body 26, the column or the cylindrical body 26 is elastically deformed (oscillates in a direction perpendicular to the base 25) and then elastically restored. Immediately after that, as shown in FIG. 8, the movable mold 22 is closed while the molded article 23 is placed on the fixed mold 21, and the columnar or tubular body 26 is crushed and expanded. After crushing and expanding the columnar or cylindrical body 26, the movable mold 22 is opened again to obtain a large undercut 29 of the molded product 23.

Further, according to the above method, as shown in the sectional view of the molded product in FIG.
9 can be formed.

The surface fastener can be formed by forming a plurality of large undercuts formed in the above steps on the base.

The above undercuts and hook-and-loop fasteners are
Since the undercut portion can be formed only by opening and closing the mold without complicating the mold, post-processing which is a drawback of the conventional technology is unnecessary, productivity is high, and the mold structure is simple, The durability of the mold is high, and the cost of the mold can be reduced.

The mold is formed by processing only one side (the front surface of the base), and the back surface of the bases 15 and 25 has a high degree of freedom. Possible snaps and other shapes can be formed.

The large undercut formed by the steps of the embodiment of the present invention can be used as a primary molded article of a composite molded article. As shown in FIG. 10 as a cross-sectional view, a primary molded body 32 having a plurality of large undercuts 33 provided on a base 35 by the above process.
The composite molded article 31 can be formed by applying a resin of a different material to the primary molded body 32 by insert molding, two-color molding, urethane injection molding or the like. That is, it is possible to join even a combination of hardly adherent materials such as a composite molded product of a gear or a rack using polyacetal or the like and another component. Further, since the joining of the composite molded article 31 of the embodiment of the present invention is a physical connection, it can be easily peeled and separated during recycling. In the case where the conventional molded product shown in FIG. 11 is used as a primary molded product to obtain a composite molded product by the core back method, the number of corners increases.
In some cases, the undercut portion is elastic and the undercut portion can be separated neatly during separation. The composite molded article 31 of the embodiment of the present invention can be used as a heat insulating case or an instrument panel of a car by applying a soft foamed resin such as a urethane elastomer. In addition, since the height of the undercut can be changed depending on the crushing method, the thickness of the secondary side can be reduced by lowering the height of the undercut, thereby saving material.

The engaging strength of the surface fastener of the embodiment of the present invention and the joining strength of the composite molded product can be varied by increasing or decreasing the number of undercuts or changing the method of crushing.
In other words, the number of undercuts may be increased only where the strength is desired, or the method of crushing may be increased.

[0026]

Since the present invention is configured as described above, the following effects can be obtained.

According to the first aspect of the present invention, the undercut portion can be formed only by opening and closing the mold without complicating the mold. It is possible to provide a method for forming an undercut of a molded product, which has a simple mold structure and can reduce a mold cost.

According to the second aspect of the present invention, it is possible to provide a hook-and-loop fastener that does not require post-processing, has a simple mold structure, and can reduce costs.

According to the third aspect of the present invention, it is possible to provide a composite molded article which can be joined even with a combination of materials which cannot be adhered to each other, regardless of the material, and which can be easily separated for recycling. Can be.

According to the invention of claim 4 or 5, the undercut forming method can form an undercut in which the movable mold is easily forcibly removed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a mold showing an embodiment of the present invention, showing a state in which the mold is closed when resin is injected.

FIG. 2 shows a state where the movable mold of FIG. 1 is opened.

FIG. 3 shows a state in which the movable mold is closed immediately after the state of FIG. 2;

FIG. 4 is an enlarged view of a molded product in the state of FIG.

FIG. 5 is an end view of a tip end of a divided body of the molded product in the state of FIG. 1;

FIG. 6 is a cross-sectional view of a mold showing another embodiment of the present invention, showing a state in which the mold is closed when resin is injected.

FIG. 7 shows a state where the movable mold of FIG. 6 is opened.

FIG. 8 shows a state in which the movable mold is closed immediately after the state of FIG. 7;

FIG. 9 is a sectional view showing an example of use of the embodiment of the present invention.

FIG. 10 is a cross-sectional view showing composite molding according to an embodiment of the present invention.

FIG. 11 is a sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Fixed mold 12 Movable mold 13 Molded article 14 Slight undercut 15 Base 16 Columnar or cylindrical body 17 Depression 18 Split body 19 Large undercut 21 Fixed mold 22 Movable mold 23 Molded article 24 Slight undercut Cut 25 Base 31 Composite molded product 32 Primary molded body 33 Large undercut 35 Base 36 Adhesion

Claims (5)

[Claims] A resin is injected into a space formed between a fixed mold and a movable mold, and is elastically deformed when the movable mold is opened, and an undercut is formed to such an extent that the deformation is elastically restored. Immediately after opening the movable mold after forming the provided molded article, the undercut of the molded article having a molding step of closing the movable mold with the molded article attached to the fixed mold and crushing and expanding the undercut Forming method. 2. A surface fastener having a plurality of undercuts having the molding step according to claim 1 formed on a base. 3. A composite molded article comprising a primary molded article having the molding step according to claim 1 and a resin made of a material different from that of the primary molded article. 4. An elastic deformation when the movable mold is opened,
The undercut to the extent that the elastic deformation is restored is to divide the columnar or cylindrical body erected from the base into a plurality of parts, provide a concave portion in the center of the distal end of the columnar or cylindrical body, and set the distal end to the diameter of the distal end. 2. The undercut formation of a molded product according to claim 1, wherein the shape is formed so as to be open from the root of the columnar body or the cylindrical body, and the tip of the divided body is tapered from the root to the tip. Method. 5. An elastic deformation when the movable mold is opened,
The undercut to the extent that the elastic deformation is restored is characterized in that the column or the cylindrical body erected from the base is inclined toward the tip and the tip is tapered from the root to the tip. 2. The method for forming an undercut of a molded article according to claim 1.