JP2002225087A - Injection mold and method for manufacturing membrane circular body using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection mold generating no weld line. SOLUTION: The injection mold comprises at least a fixed mold 11 and a movable mold 12 and a membrane circular cavity 16 is formed between the fixed mold 11 and the movable mold 12 by clamping both molds 11 and 12. A gate port 14 is provided to the fixed mold 11 at the almost center of the surface facing to the cavity 16 thereof and a projection 15 is provided to the movable mold 12 at the almost center of the surface facing to the cavity 16 thereof to protrude up to the gate port 14 when the fixed mold 11 and the movable mold 12 are clamped. In the method for manufacturing the membrane circular body using the injection mold, the fixed mold 11 and the movable mold 12 are clamped and a molten metal is injected in the cavity 16 through the gate port 14 and, after the molten metal is cooled, the movable mold 12 and the fixed mold 11 are opened to take out a molded object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for injection molding and a method for producing a thin film circular body using the same.

[0002]

2. Description of the Related Art Heat-fused resin is injected into a mold.
The injection molding method of cooling and solidifying to obtain a resin molded product has advantages such as excellent mass productivity because once a mold is manufactured, even a complicated three-dimensional molded product can be easily mass-produced. It is widely used as a method for producing various molded articles in various fields.

However, in the conventional injection molding method using an injection mold (hereinafter sometimes simply referred to as a "mold"), a thin film circular molded article having a through hole at the center is molded. If so, there is a problem that a weld line is likely to occur.

FIG. 6 is a cross-sectional view of a conventional mold used for molding a thin film circular molded body having a through hole at the center. As shown in FIG. 6, the conventional mold mainly includes a fixed mold 61 and a movable mold 62.
By clamping both, a thin film circular cavity 63 is formed. Cavity 6 in movable mold 62
On the surface facing 3, a pin 64 for forming a through hole is provided. Further, the fixed die 61 is provided with a pin gate 65 for injecting resin into a place other than the place corresponding to the through hole.

Conventionally, using such a mold, a pin gate 65 is used.
Injected molten resin (molten metal) from the above, a thin film circular molded body provided with a through hole was manufactured. When a mold as shown in FIG. 6 is used, the injected molten metal is
The flow is divided into right and left at the position, and the pins 64 are fused again on the side opposite to the pin gate 65, and the cavity 63 is filled. Therefore, in the fusion portion of the molten metal, the temperature distribution becomes non-uniform or the properties of both are strictly different, so that the fusion cannot be completed completely, so that a weld line having a line pattern is likely to occur.

[0006] The occurrence of such weld lines not only causes the appearance of the molded product to deteriorate or lowers the strength, but also causes the molded product to be used as a material requiring high sealing properties such as packing. This is not preferable because it causes leakage.

When a mold as shown in FIG. 6 is used, a molded body obtained when the fixed mold 61 and the movable mold 62 are opened after molding corresponds to the resin injection port of the pin gate 65. There is also a problem that a gate mark remains in a portion.
Again, no satisfactory and effective solution has been found.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a mold for injection molding which does not generate a weld line and a method for manufacturing a thin film circular body using the same. Another object of the present invention is to provide a mold for injection molding that does not cause gate marks and a method for manufacturing a thin film circular body using the same.

[0009]

The above object is achieved by the present invention described below. That is, the first present invention comprises at least a fixed type having a gate port and a runner portion communicating with the gate port, and a movable type provided with a columnar projection, and the fixed type and the movable type An injection molding die in which a thin-film circular cavity is formed between the two by closing the mold, wherein the gate port is provided substantially at the center of a surface of the fixed die facing the cavity. And wherein the projection is provided substantially at the center of a surface of the movable mold facing the cavity, and projects to the gate opening when the fixed mold and the movable mold are clamped. It is a mold for injection molding.

According to the first aspect of the present invention, when the molten metal is injected from the runner portion into the cavity through the gate port provided substantially at the center of the cavity with the fixed mold and the movable mold clamped, Is supplied to the top of the protrusion,
The molten metal is uniformly filled up to the peripheral edge of the cavity since the metal is uniformly spread radially around the projection. Therefore, there is no portion where the molten metal is fused in the cavity, and the generation of a weld line can be prevented.

According to a second aspect of the present invention, there is provided a fixed type having at least a gate port and a runner portion communicating with the gate port;
A movable mold provided with a columnar projection, and wherein the fixed mold and the movable mold are mold-clamped to form a thin-film circular cavity between the molds. The gate port is provided at substantially the center of the surface of the fixed mold facing the cavity, and the projection is provided at substantially the center of the face of the movable mold facing the cavity, Is configured to move up and down independently of the mold, and when the fixed mold and the movable mold are mold-clamped and the projections are raised to the uppermost part, they are projected to the gate opening. It is a mold for injection molding characterized by the following.

The second aspect of the present invention is different from the first aspect of the present invention in that the projection is configured to move up and down independently of the movable mold. By raising the protrusion to the opposed fixed gate port, a through hole is provided at the center of the thin film circular molten metal filled in the cavity. Since the through-hole is provided in the molten metal by raising the protrusion to the gate opening, the molten metal is effectively cut near the gate opening in addition to the same operation and effect as the first aspect of the present invention. Can be prevented.

In the first and second aspects of the present invention, it is preferable that a portion from the fixed runner portion to the gate port be a hot runner. By using a hot runner, runnerless molding becomes possible, and molding costs are reduced. In addition, since there is no waste, environmentally friendly production becomes possible.

A third aspect of the present invention is a method of manufacturing a thin film circular body using the injection mold according to the first aspect of the present invention, wherein a fixed mold and a movable mold are clamped, and the fixed mold runner portion is provided. A molten metal is injected into the cavity through a gate opening, and after cooling, the movable mold and the fixed mold are opened to take out a thin-film circular molded body.

According to the third method of manufacturing the thin film circular body of the present invention, the molten metal is supplied from the runner portion to the cavity through the gate port provided substantially at the center of the cavity while the fixed mold and the movable mold are clamped. When the molten metal is injected into the inside, the molten metal is supplied to the upper portion of the projection and spreads radially around the projection, so that the molten metal is uniformly filled up to the peripheral edge of the cavity. Therefore, there is no portion where the molten metal is fused in the cavity, and the generation of a weld line can be prevented.

A fourth aspect of the present invention is a method for manufacturing a thin-film circular body using the injection mold of the second aspect of the present invention, wherein a fixed mold and a movable mold are clamped and provided on the movable mold. With the protrusions lowered, the molten metal is injected into the cavity from the fixed type runner portion through a gate port, the protrusions are raised to the gate port, and after cooling, the movable mold and the fixed mold are opened to form a thin film. This is a method for producing a thin-film circular body, which comprises taking out a circular molded body.

According to the method of manufacturing a thin film circular body of the fourth aspect of the present invention, it is possible to efficiently prevent the occurrence of weld lines as in the method of manufacturing a thin film circular body of the third aspect of the present invention. By raising the protrusion to the gate opening, the occurrence of gate marks can be prevented.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments. << First Embodiment >> FIG. 1 is a schematic cross-sectional view of an injection mold according to a first embodiment of the present invention. The injection molding die according to the present embodiment includes a fixed die 11 having a gate port 14 and a runner portion 13 communicating with the gate port 14, and a movable die 12 provided with a columnar projection 15.
By clamping the fixed mold 11 and the movable mold 12,
A thin film circular cavity 16 is formed between the two.

As shown in FIG. 1, the fixed mold 11 according to the present embodiment has a runner portion 13 and a gate port 14. The gate port 14 is provided substantially at the center of the surface of the fixed mold 11 that faces the cavity 16. The molten metal is supplied to the runner section 13 and injected into the cavity 16 through the gate port 14. In the present invention, the “substantially center” as used herein means within a range of 10% (preferably 5%) of the diameter of the cavity in the radial direction from the center of the surface of the fixed mold facing the cavity. In the fixed type, if the gate port is provided in such a range, the distance from the gate port to the peripheral edge of the cavity does not substantially differ depending on the location, and the behavior that the molten metal fuses in the cavity. Never show.

The diameter of the gate port 14 needs to be larger than the diameter of the projection 15 at the height h from the root of the movable die 12, and specifically, at least 0.02 mm from the diameter.
The diameter is preferably 0.06 mm or more (more preferably 0.1 mm or more) larger than the diameter. The upper limit of the diameter of the gate port 14 is preferably set to 1.0 mm. On the other hand, the diameter of the entrance 13a of the runner section 13 is preferably larger than the gate port 14 so that the molten metal can be easily charged.

The fixed mold 11 is made of iron and its alloys (stainless steel, stainless steel, etc.) from the viewpoints of heat resistance, durability, solvent stability and the like.
Carbon steel, chromium molybdenum steel, etc.). The surface of the fixed mold 11 is preferably subjected to a heat treatment such as a nitriding treatment or a carbonization treatment. By performing such a heat treatment, the durability can be improved.

It is preferable that a portion from the runner portion 13 of the fixed die 11 to the gate port 14 is a hot runner. By using a hot runner, runnerless molding becomes possible, and molding costs are reduced. In addition, since there is no waste, environmentally friendly production becomes possible. here,
The "hot runner" refers to a runner method in which the resin in the runner is constantly melted by heating the runner portion so that only a molded product is formed or a runner portion molded product is not formed as much as possible.

As shown in FIG. 1, the movable mold 12 according to the present embodiment has a projection 15, and the projection 15 is
Is provided substantially at the center of the surface facing the cavity 16 and projects to the gate opening 14 when the fixed mold 11 and the movable mold 12 are clamped. In the present invention, the “substantially center” as used herein means that the center of the surface of the movable mold facing the cavity is radially equal to one of the diameter of the cavity.
0% (preferably 5%). By providing the projection in such a range, a through hole can be provided substantially at the center of the obtained thin film circular body. Further, in the present invention, “projecting to the gate opening 14” means a state where the thickness from the root of the projection 15 to the top of the cylindrical portion is equal to or more than the thickness h of the cavity 16.

The protrusions 15 are fixed type 11 and movable type 12
Is projected to the gate opening 14 when the mold is clamped. The preferred projection height of the projection 15 is the cavity 16
Is not less than the thickness h. If it is not more than h, it is impossible to form a through hole in the thin film circular body.

The projection 15 has a columnar shape because it is necessary to provide a through hole in the thin film circular body. Here, the “columnar shape” means that at least a portion corresponding to the through hole of the thin film circular body to be molded has a cylindrical shape. Therefore, a part that finally forms a through hole in the thin film circular body,
That is, a portion of the projection 15 from the base of the movable mold 12 to the thickness h of the cavity 16 or more may be formed in a shape such as a truncated cone, a cone, a hemisphere, and a wedge. By adopting any of the above shapes, the molten metal injected from the gate port 14 is less likely to stay at the upper portion of the projection 15, and the molten metal is more quickly and uniformly spread radially in the cavity 16. growing.

In the range of the height of the projection 15 from the base of the movable mold 12 to the height of less than the thickness h of the cavity 16, the diameter of the projection 15 becomes the diameter of the through hole of the thin film circular body as it is. May be set to a desired size as the diameter of the through-hole. However, in the range of the height of h or more from the base of the movable die 12 of the projection 15, the diameter of the gate port 14 (from the viewpoint of ease of molten metal injection) (Diameter) is desired. Therefore, the movable mold 1 of the projection 15
In the range from the base of No. 2 to a height of h or more, the diameter of the projection 15 is preferably 20% or less, more preferably 10% or less of the diameter of the gate port 14.

The center axis of the gate port 14 and the center axis of the projection 15 are, of course, most preferably coincident with each other.
It is difficult to make a perfect match. Therefore, the center axis of the projection 15 is radially shifted from the center of the gate port 14 to the gate port 1.
In a range of 20% of the difference (R−r) between the radius R of the projection 4 and the radius r at the height h from the base of the movable mold 12 of the projection 15,
Preferably, it is in the range of 10%. If the projection 15 exists outside this range, the gate port 1
It becomes difficult for the molten metal injected from 4 to be evenly supplied to the projections 15, and finally, a portion to be fused in the cavity 16 may be generated. In addition, gate marks may be formed on the obtained thin film circular body.

The movable mold 12 and the projection 15 are
It is preferable that the surface thereof is subjected to the same surface treatment as that of the fixed mold 11.
Is required to be more durable than other members, and is therefore preferably subjected to a surface treatment. The projection 15 may be formed by providing a concave portion at the center of the movable mold 12 and fitting and fixing a cylindrical member in the concave portion, or the cylindrical member may be fixed by a heat-resistant adhesive. Further, the movable mold 12 and the projection 15 may be molded at the same time, and both may be formed by one member.

The cavity 16 refers to a space formed between the fixed mold 11 and the movable mold 12 by clamping the mold, as shown in FIG. I have. The thickness h and the diameter of the cavity 16 can be appropriately changed in accordance with the size of the product to be molded.
2-3 mm, diameter 5-100 mm. The shape of the obtained thin film circular body can be changed to a desired shape by making various changes such as making the upper surface and / or the bottom surface of the cavity 16 a stepped shape and chamfering the circumferential end. it can.

In the method for manufacturing a thin film circular body using the injection mold of the present embodiment (third invention), the fixed mold 11 is used.
Then, the movable mold 12 is clamped, the molten metal is injected into the cavity 16 from the runner portion 13 of the fixed mold 11 through the gate port 14, and after cooling, the movable mold 12 and the fixed mold 11 are opened to take out the thin film circular body. . Hereinafter, a specific description will be given.

First, the fixed mold 11 and the movable mold 12 are clamped. Thereafter, a molten metal such as a thermoplastic resin is poured into the runner section 13 of the fixed mold 11 and injected into the cavity 16 through the gate port 14. The temperature of the molten metal at this time depends on the type of the molten metal, but is preferably from 120 to 300 ° C, more preferably from 150 to 230 ° C.

The injected molten metal is supplied to the upper part of the protrusion 15 of the movable mold 12, descends to the base of the protrusion, and fills the cavity 16 radially and uniformly with the protrusion 15 as a center. Therefore, generation of a resin fusion part is prevented, and generation of a weld line can be prevented.

After the cavity 16 is filled with the molten metal, it is cooled by air cooling or the like. After cooling, the fixed mold 11 and the movable mold 12 are opened by moving the movable mold 12 in the direction of arrow A as shown in FIG. 2, and the molded product is taken out of the movable mold 12 by an ejector (not shown). here,
The ejector generally refers to an apparatus including an ejector plate and an ejector pin, and the ejector pin provided on the ejector plate includes a surface of the movable mold 12 facing the cavity 16, It is configured such that it can protrude from a location other than the location where the projection 15 is provided. When the ejector pins mechanically protrude from the movable mold 12 by the mechanism of the molding machine, the molded product protrudes from the movable mold 12 and is taken out. As described above, a thin film circular body 40 having a through hole 41 at the center as shown in FIG. 3 is obtained. The obtained thin film circular body 40 has no weld line and has good quality.

<< Second Embodiment >> FIG. 4 is a schematic sectional view of an injection mold according to a second embodiment of the present invention. The injection mold according to the present embodiment includes a fixed die 11 having a gate port 14 ′ and a runner 13 communicating with the gate port 14 ′, and a movable die 12 ′ having a columnar projection 15 ′. Become. By clamping the fixed mold 11 and the movable mold 12 ′, a thin film circular cavity 16 is formed therebetween. The injection mold according to the present embodiment includes:
The difference is that the protrusion 15 ′ can be moved up and down independently of the movable mold 12 ′.
This is the same as in the first embodiment. FIG.
1 and the members having the same reference numerals in FIG. 1 showing the first embodiment mean members having the same functions. Hereinafter, a description will be specifically given focusing on points different from the first embodiment.

As shown in FIG. 4, the projection 15 'is connected to the driving device 27 and can move up and down independently of the movable mold 12'. The protrusion 15 'is a member for providing a through hole substantially at the center of the thin film circular body, similarly to the protrusion 15 of the first embodiment.

The molten metal supplied from the runner section 13 is injected into the cavity 16 through the gate port 14 '. If the projections 15 'are raised in a state in which the cavity 16 is filled with the molten metal by the injection, the portions where the projections 15' have passed finally become through holes of the thin film circular body. Protrusion 1
5 'is configured to be able to ascend to the gate opening 14'. As a result, the protrusion 15 'penetrates the molten metal and the molten metal is effectively cut in the vicinity of the gate port 14'.
The occurrence of gate marks can be prevented. In order to more effectively prevent the occurrence of gate marks, it is preferable that the diameter of the gate opening 14 ′ be equal to or smaller than the diameter of the projection 15 ′, or that the projection 15 ′ be inserted as completely as possible. Further, the projection 15 'may be formed in a columnar shape as in the first embodiment, and the tip portion may be formed in a frustoconical shape, a conical shape, a hemispherical shape, a wedge shape, or the like.

In the present invention, "gate port 1"
"Projecting to 4 '" means a state in which the uppermost end of the projection 15' is higher than the joint surface of the fixed mold 11.

In the method for manufacturing a thin film circular body using the injection mold of the present embodiment (fourth invention), the fixed mold 11 is used.
Then, the movable mold 12 ′ is clamped, and the protrusion 16 ′ provided on the movable mold 12 ′ is lowered, and the cavity 16 is passed through the gate port 14 ′ from the runner portion 13 of the fixed mold 11.
The molten metal is injected into the inside, the protrusion 15 'is raised to the gate port 14', and after cooling, the movable mold 12 'and the fixed mold 11 are opened to take out the thin film circular body. Hereinafter, a specific description will be given.

First, the fixed mold 11 and the movable mold 12 'are clamped. At this time, as shown in FIG. 5 (a), the projection 15 'may be slightly protruded into the cavity 16, and the surface of the movable mold 12' facing the cavity 16 and the projection 15 ' It is good also as a state where the height with an end face matches. Thereafter, a molten metal such as a thermoplastic resin is poured into the runner portion 13 of the fixed mold 11 and injected into the cavity 16 through the gate port 14 '. The temperature of the molten metal to be poured is preferably the same as in the first embodiment.

The injected molten metal is the protrusion 1 of the movable mold 12 '.
Flowing to 5 'and filling the cavity 16 uniformly in the radial direction with the protrusion 15' as the center, as in the first embodiment, the occurrence of a resin fusion portion is prevented, and the weld line is reduced. Never happen.

After the cavity 16 is filled with the molten metal, the projection 15 'is connected to the gate port 1 as shown in FIG.
Raise to 4 '. Thereafter, the inside of the cavity 16 is cooled by air cooling or the like. After cooling, the product is taken out in the same manner as in the first embodiment. As described above, a thin film circular body 40 having a through hole 41 at the center as shown in FIG. 3 is obtained. The obtained thin film circular body 40 has no weld line. Further, the protrusion 15 'rises to the gate opening 14', and the molten metal is effectively cut in the vicinity of the gate opening 14 ', so that no gate mark is generated.

Although the present invention has been described with reference to the embodiments, the present invention is not limited to the above-described embodiments, and various modifications may be made based on known knowledge. Can be added.

The injection mold and the method for producing a thin-film circular body according to the present invention can be applied without particular limitation as long as the molten resin is a thermoplastic resin containing an elastomer. Preferably, an elastomer is applied. The thin-film circular body obtained by the present invention does not generate weld lines or gate marks and has excellent sealing properties, and thus can be used for packing, gaskets, and the like.

[0044]

According to the injection mold of the present invention, since the gate port and the projection are provided at substantially the center of the cavity,
The occurrence of a weld line, which has been a problem, can be prevented. In addition, by allowing the protrusion to move up and down, the occurrence of gate marks can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an injection mold according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a state in which the injection mold according to the first embodiment of the present invention is opened.

FIG. 3 is a diagram showing an example of a manufactured thin film circular body.

FIG. 4 is a schematic sectional view showing an injection mold according to a second embodiment of the present invention.

FIGS. 5A and 5B are explanatory diagrams illustrating a method of manufacturing a thin-film circular body using an injection mold according to a second embodiment of the present invention. FIG. (B) shows a state in which the protrusion has risen to the gate opening.

FIG. 6 is a schematic cross-sectional view showing an example of a conventional injection mold.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Fixed type 12 ... Movable type 13 ... Runner part 13a ... Entrance of a runner part 14 ... Gate port 15 ... Projection 16 ... Cavity h ... height

Claims (5)

[Claims] 1. A fixed mold having at least a gate port and a runner portion communicating with the gate port, and a movable mold having a columnar projection, wherein the fixed mold and the movable mold are clamped. A mold for injection molding in which a thin-film circular cavity is formed between the two, wherein the gate port is provided substantially at the center of a surface of the fixed mold facing the cavity; Is provided substantially at the center of a surface of the movable mold facing the cavity, and projects to the gate port when the fixed mold and the movable mold are clamped. Type. 2. A fixed mold having at least a gate port and a runner portion communicating with the gate port, and a movable mold having a columnar projection, wherein the fixed mold and the movable mold are clamped. A mold for injection molding in which a thin-film circular cavity is formed between the two, wherein the gate port is provided substantially at the center of a surface of the fixed mold facing the cavity; Is provided substantially at the center of the surface of the movable mold facing the cavity, is configured to move up and down independently of the movable mold, and clamps the fixed mold and the movable mold. When the protrusion is raised to the uppermost part, the protrusion is projected to the gate opening. 3. The injection mold according to claim 1, wherein a portion from the fixed runner portion to the gate port is a hot runner. 4. A method for manufacturing a thin film circular body using an injection mold according to claim 1, wherein a fixed mold and a movable mold are clamped, and a cavity is formed from a runner portion of the fixed mold through a gate port. A method for manufacturing a thin-film circular body, comprising: injecting a molten metal into a tee, cooling, opening the movable mold and the fixed mold, and taking out a thin-film circular molded body. 5. A method of manufacturing a thin film circular body using the injection mold according to claim 2, wherein the fixed mold and the movable mold are clamped, and the projection provided on the movable mold is lowered. In this state, the molten metal is injected into the cavity through the gate port from the fixed-type runner section, the protrusion is raised to the gate port, and after cooling, the movable mold and the fixed mold are opened to form a thin-film circular molded body. A method for producing a thin film circular body, comprising: