JP3981852B2 - Method for forming undercut of molded product, and surface fastener and composite molded product using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for 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 method.
[0002]
[Prior art]
The conventional hook-and-loop fastener has an undercut part that becomes an engaging part, so that the tip of a rod-like protrusion standing on the surface is melted into a spherical shape, 2 is curled into a fishhook shape, 3 ▼ There was a rubber die forcibly with a spherical tip removed, and {circle around (4)} an undercut 1 provided by pressing the die as shown in a sectional view in FIG.
[0003]
In addition, in order to form a composite molded product, two different materials (for example, when a hard material and a soft material are joined) are bonded by adhesion or heat fusion.
[0004]
[Problems to be solved by the invention]
However, the above (1) requires post-processing such as melting the tip of the rod-shaped protrusion, (2) curling, etc., and (3) requires a special mold and material, and the mold life However, (4) has a drawback that the mold structure is complicated and a core back is required when making a composite molded product as a primary molded product.
[0005]
In addition, when obtaining the above composite molded product, it is difficult to recycle because the material that can be bonded or the material that can be heat-sealed is limited, or when the material is bonded or heat-sealed, it is difficult to separate the materials. There was a problem. For example, gears and racks having sliding surfaces are often molded with polyacetal, but polyacetal is difficult to bond and cannot be molded.
[0006]
The present invention has been made to solve the above-described problems. A method of forming an undercut portion of a molded product by merely opening and closing the mold without complicating post-processing and the mold, and It aims at providing the composite molded product which can be isolate | separated regardless of the used surface fastener and material.
[0007]
[Means for Solving the Problems]
The present invention adopts the following configuration in order to achieve the object.
[0008]
The undercut forming method for a molded product according to the present invention is such that a resin is injected into a space formed between a fixed mold and a movable mold, and elastic deformation occurs when the movable mold is opened. After forming a molded product with an undercut to the extent that it can be restored, immediately after opening the movable mold, the molded mold is closed and the movable mold is closed and the undercut is crushed and spread while the molded product is still attached to the fixed mold It is what has.
[0009]
The hook-and-loop fastener of the present invention is formed by forming a plurality of undercuts having the above molding process on a base.
[0010]
The composite molded product of the present invention is formed by adhering a resin having a material different from that of the primary mold molded body to the primary mold molded body having the molding step.
[0011]
In the undercut forming method for a molded product according to the present invention, the undercut that is elastically deformed when the movable mold is opened and the elastic deformation is restored includes a plurality of columnar bodies or cylindrical bodies erected from the base. The top of the columnar body or cylindrical body is provided with a recess, the tip is formed in a shape where the diameter of the tip is opened from the root of the columnar body or the cylindrical body, and the tip of the divided body is the root. It is formed to taper from the tip to the tip, or it is formed by inclining a columnar body or cylindrical body standing from the base toward the tip and tapering the tip from the root to the tip. Is desirable.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of an undercut forming method according to the present invention (hereinafter referred to as “example”) will be described with reference to the accompanying drawings.
[0013]
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 when the resin is injected, and FIG. 2 shows a state in which the movable mold is opened. FIG. 3 shows a state in which the movable mold is closed. 4 is an enlarged view of the molded product in the state of FIG. 1, and FIG. 5 is an end view of the tip of the divided body of the molded product in the state of FIG.
[0014]
As shown in FIG. 1, the mold is composed of a normal mold of this type including a fixed mold 11 and a movable mold 12, and the fixed mold 11 and the movable mold 12 are closed (in close contact). In this state, a resin is injected into a space formed between the fixed mold 11 and the movable mold 12 to form a molded product 13 having a slight undercut 14 that can be forcibly removed. As shown in FIG. 4, the undercut 14 divides a columnar body or cylindrical body 16 erected from the base 15 into a plurality of parts, and provides a recess 17 at the center of the distal end of the columnar body or cylindrical body 16, The tip diameter (D) is formed in a shape that is wider than the diameter (d) of the base of the columnar body or the cylindrical body 13, and the tip of the divided body 18 is tapered from the root to the tip. It is designed so that it can be forcibly removed. The movable mold 12 is divided into molds 12a and 12b in order to provide a space portion having the shape of the undercut 14.
[0015]
After the molded product 13 is obtained, when the movable mold 12 is forcibly removed (the divided body is contracted and removed from the mold) and opened from the length of the columnar body or cylindrical body 16 as shown in FIG. Is elastically restored after being elastically deformed (shrinked), so that D> d is maintained. Immediately thereafter, as shown in FIG. 3, the movable mold 12 is closed and the divided body 18 is crushed and spread while the molded product 13 is left on the fixed mold 11. After the divided body 18 is crushed and expanded, the movable mold 12 is opened again to obtain a large undercut 19 of the molded product 13.
[0016]
When the divided body is crushed, the total thickness including the base 15 can be adjusted by closing and adjusting the mold, so that it can be varied according to the degree of undercut and the thickness of the secondary side at the time of 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 retained. However, in the case of a material that can be cold-caulked, such as polyacetal and polycarbonate, the shape is sufficiently retained even after the resin is hardened.
[0017]
As shown in the end view in FIG. 5, the number of divisions of the tip is appropriately selected according to the material shape such as (a) two-divided 18a, (b) three-divided 18b, (c) four-divided 18c, In the case of a material having relatively good elongation (for example, polyamide, polyethylene, polypropylene, etc.), it is not necessary to divide as long as there is a recess 17 at the center of the tip. In this case, a strong undercut with a rivet head shape can be formed.
[0018]
Further, in the above embodiment, the concave portion 17 or the divided body 18 is formed at the tip portion. However, the present invention is not limited to the above embodiment. For example, as shown in FIGS. There should be as little undercut as possible. 6 to 8 are sectional views of a mold showing another embodiment of the present invention. FIG. 6 shows a state in which the mold is closed when the resin is injected, and FIG. 7 shows the movable mold. FIG. 8 shows the opened state and FIG. 8 shows the closed state of the movable mold. As shown in FIG. 6, the mold includes a fixed mold 21 and a movable mold 22, and the fixed mold 21 and the movable mold 22 are closed (in close contact) with the fixed mold 21 and the movable mold 22. In the same manner as in the above embodiment, resin is injected into the space formed between the movable molds 22 to form a molded product 23 having a slight undercut portion 24 that can be forcibly removed. As shown in FIG. 7, the undercut 24 is formed by inclining a columnar body or a cylindrical body 26 erected from the base 25 toward the tip, and by tapering the tip from the root to the tip. It is something that can be done.
[0019]
After obtaining the molded product 23, as shown in FIG. 7, when the movable mold 22 is forcibly removed (the divided body is contracted and removed from the mold) and opened from the length of the columnar body or cylindrical body 26, the columnar body or The cylindrical body 26 is elastically restored after being elastically deformed (vibrated in a direction perpendicular to the base 25). Immediately after that, as shown in FIG. 8, the movable mold 22 is closed while the molded product 23 is left on the fixed mold 21, and the columnar body or the cylindrical body 26 is crushed and widened. After the columnar body or cylindrical body 26 is crushed and expanded, the movable mold 22 is opened again to obtain a large undercut 29 of the molded product 23.
[0020]
Further, according to the above method, as shown in FIG. 9 as a cross-sectional view of a molded product, a large undercut 19 can be formed in a recessed portion 30 or a recessed portion 30 which is impossible with a conventional rubber mold.
[0021]
A hook-and-loop fastener can be formed by forming a plurality of large undercuts formed by the above steps on the base.
[0022]
The above-mentioned undercut and hook-and-loop fastener can form the undercut part only by opening and closing the mold without complicating the mold, so that post-processing, which is a drawback of the prior art, is unnecessary and high productivity. In addition, the mold structure is simple, the mold has high durability, and the mold cost can be reduced.
[0023]
In addition, the mold is formed by processing only on one side (the surface of the base), and the flexibility of the back surface of the bases 15 and 25 is high. For example, the snap on the back surface of the bases 15 and 25 is impossible with a conventional core back. And other shapes can be formed.
[0024]
The large undercut formed by the process of the embodiment of the present invention can be used as a primary molded product of a composite molded product. As shown in a cross-sectional view in FIG. 10, a primary mold molded body 32 provided with a plurality of large undercuts 33 is formed on a base 35 by the above process, and resins of different materials are applied to the primary mold molded body 32. The composite molded product 31 can be formed by applying 36 by insert molding, two-color molding, urethane injection molding, or the like. That is, it is possible to join even a combination of difficult-to-adhere materials such as a composite molded product of a gear or rack using polyacetal or the like and another part. Further, since the joining of the composite molded product 31 of the embodiment of the present invention is a physical joining, it can be easily separated after being recycled. In addition, when a conventional molded product shown in FIG. 11 is obtained as a primary molded product by a core-back method, the number of corners increases. According to the embodiment of the present invention, the undercut portion has elasticity and can be separated cleanly at the time of separation. The composite molded product 31 of the embodiment of the present invention can be used as a heat insulating case and an instrument panel of an automobile by applying a soft foamed resin such as urethane-based elastomer. Moreover, since the height of the undercut can be changed depending on the crushing method, the thickness of the secondary side can be reduced by reducing the height of the undercut, which also saves material.
[0025]
The engagement strength of the hook-and-loop fastener and the joint strength of the composite molded product according to the embodiment of the present invention can be varied by increasing or decreasing the number of undercuts or changing the manner of crushing. That is, it is only necessary to increase the number of undercuts or increase the amount of crushing wherever strength is desired.
[0026]
【The invention's effect】
Since this invention is comprised as mentioned above, there exists an effect described below.
[0027]
According to the first aspect of the present invention, since the undercut portion can be formed only by opening and closing the mold without complicating the mold, post-processing is unnecessary and productivity is high. It is possible to provide an undercut forming method for a molded product that is simple and can reduce the mold cost.
[0028]
According to the invention of claim 2, 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.
[0029]
According to invention of Claim 3, since it can join also with the combination of the material which cannot adhere | attach, it can couple | bond with dissimilar materials regardless of a material, and can provide the composite molded product which can isolate | separate easily.
[0030]
According to the invention of claim 4 or claim 5, it is possible to form an undercut that is easy to forcibly remove the movable mold in the undercut forming method.
[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.
2 shows a state where the movable mold in FIG. 1 is opened.
3 shows a state in which the movable mold is closed immediately after the state of FIG.
FIG. 4 is an enlarged view of a molded product in the state of FIG.
FIG. 5 is an end view of the tip of the molded product divided body in the state of FIG. 1. FIG. 6 is a cross-sectional view of a mold showing another embodiment of the present invention. The mold is shown closed.
7 shows a state in which the movable mold in FIG. 6 is opened.
FIG. 8 shows a state in which the movable mold is closed immediately after the state of FIG.
FIG. 9 is a cross-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 cross-sectional view showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Fixed mold 12 Movable mold 13 Molded product 14 Some undercut 15 Base 16 Columnar body or cylindrical body 17 Recess 18 Divided body 19 Large undercut 21 Fixed mold 22 Movable mold 23 Molded product 24 Some under Cut 25 Base 31 Composite molded product 32 Primary mold molded body 33 Large undercut 35 Base 36 Adhesion

Claims (5)

Injecting resin into the space formed between the stationary mold and the movable mold, and elastically deforming when the movable mold is opened. A method of forming an undercut of a molded product, comprising: a molding step of closing the movable mold and expanding the undercut by closing the movable mold with the molded product attached to the fixed mold immediately after opening the movable mold. A hook-and-loop fastener in which a plurality of undercuts having the molding step according to claim 1 are formed on a base. A composite molded article obtained by adhering a resin having a material different from that of the primary mold molded body to the primary mold molded body having the molding process according to claim 1. The undercut that is elastically deformed when the movable mold is opened and the elastic deformation is restored is divided into a columnar body or a cylindrical body standing upright from the base, and the columnar body or the cylindrical body A concave portion is provided in the center of the tip, the tip is formed in a shape in which the tip diameter is opened 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. A method for forming an undercut of a molded product according to claim 1. The undercut, which is elastically deformed when the movable mold is opened and the elastic deformation is restored, inclines the columnar body or cylindrical body erected from the base toward the tip, and the tip is from the root to the tip. The undercut forming method for a molded product according to claim 1, wherein the undercut forming method is formed so as to be tapered over the portion.

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