JPH1158473A - Die for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the cooling time of a core in the cooling process of a die for injection molding. SOLUTION: The tip of a core of the die for injection molding is formed from a cap support block 3, which is not deformed even if a resin injection pressure is applied to the block 3 at the time of injection, and a core tip cap 1, which is attached to the outer periphery of the block 3 and formed from an extremely thin material so that the cap 1 itself is deformed by a resin pressure. And a cooling medium is passed through gaps formed by bringing the inner periphery of the cap 1 into close contact with the outer periphery of the block 3, on which spiral grooves are formed, to cool the core.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold, and more particularly to an injection mold capable of cooling a core.

[0002]

2. Description of the Related Art As an injection molding die, for example, an injection molding die for molding a pipe joint made of a thermoplastic resin is shown in FIG.
The guide 1 is provided between the movable mold 10 and the fixed mold 11 as shown in FIG.
Slide plates 16, 17 that can move forward and backward along 8, 19
And cores 14 and 15 for forming an inner surface shape. Outer dies 12, 13 for forming the outer shape of the molded product
Are mounted on a movable mold and a fixed mold, respectively, and a cavity 21 is formed by outer molds 12 and 13 and cores 14 and 15. The heat of the molten thermoplastic resin filled in the mold from the runner 11 is absorbed by heat conduction from the contact surface with the mold during the cooling process. During the cooling step, if the cooling is not performed sufficiently, the molded product will be deformed or distorted.Therefore, for the purpose of increasing the cooling efficiency of the mold, a cooling hole is provided inside the mold, and a cooling medium such as water is provided. Often passed.

By the way, the molten resin filled in the cavity of the mold is cooled and shrunk by the outer molds 12 and 13 and the cores 14 and 15 until the mold is released. Also, the volume may be reduced, a gap may be formed between the outer dies 12, 13 and the molded product, and the contact area for cooling may be reduced to make it difficult to cool the molded product. Therefore, in order to efficiently cool the molten resin, the core 1 which cools from the inner surface of the molded product is particularly used.
Cooling from the 4 and 15 sides must be performed efficiently.

On the other hand, in the cooling step, since the cores 14 and 15 are always surrounded by the molten resin until the mold is released, heat is easily accumulated and tends to be high.

In order to suppress the temperature rise of the cores 14 and 15, the core is composed of a cooling bush 6 having a cooling hole 2 provided at a central portion and an outer peripheral surface, and a core outer block 7, as shown in FIG. It has a double structure. The cooling medium is passed through the cooling holes 2 to cool the core.

[0006]

However, when the resin is filled with the resin, the inflow pressure of the resin in the oblique direction from the injection nozzle to the outer peripheral surface of the core at the time of filling the resin, or the resin in the cavity in the inner direction of the core applied to the outer peripheral surface of the core after filling. Pressure (hereinafter simply referred to as “resin pressure”). Therefore, the pressure resistance must be secured by increasing the thickness of the core outer block 7 covering the cooling bush 6.

However, if the thickness of the core outer block 7 is increased, the distance between the cooling hole 2 and the outer peripheral surface of the core that is in contact with the molten resin is naturally increased, and the temperature gradient in the thickness direction of the core outer block 7 is increased. There was a problem that the cooling efficiency deteriorated. Accordingly, an object of the present invention is to provide an injection molding die capable of efficiently cooling a core having the above-described double structure.

[0008]

According to a first aspect of the present invention, there is provided an injection mold having an outer mold and a core, wherein a cavity is formed between the outer mold and the core when the mold is closed. And a core tip cap attached in close contact with the outer peripheral surface of the cap support block, a gap is provided in a part of a contact surface between the cap support block and the core tip cap, and a cooling medium is passed through the gap to form a core. This is a mold for injection molding characterized by cooling.

Incidentally, the core tip cap referred to here is deformed by resin pressure by itself because the thickness is reduced.

According to a second aspect of the present invention, there is provided the injection molding die according to the first aspect, wherein the gap comprises a cooling groove provided on an outer peripheral surface of the cap support block and a core tip cap.

According to a third aspect of the present invention, the gap comprises a cooling groove provided on the outer peripheral surface of the cap support block and a cooling groove provided on the inner peripheral surface of the core tip cap. Injection molding die.

(Operation) As shown in FIG. 1, the resin pressure applied to the mold tries to deform the core tip cap 1 formed with a thickness much smaller than that of the conventional core outer block, but adheres to the inner peripheral surface. The cap support block 3 supports the resin pressure and maintains the core shape.

As a result, the heat of the molten resin filled in the mold and covering the periphery of the core tip cap 1 is efficiently absorbed from the outer peripheral surface of the core tip cap 1, and is further transferred to the cooling holes 2 of the cap support block. The supplied cooling medium wastes heat from the mold to the outside.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an example of the injection mold of the present invention. Core is cap support block 3
And a core tip cap 1 attached so as to be in close contact with the cap support block 3. Since the core tip cap 1 is formed with a very small thickness, the core tip cap 1 itself is deformed by the resin pressure applied to the core tip.

Therefore, the cap support block 3 has a structure in which the cap pressure is supported by closely contacting the inner peripheral surface of the core tip cap 1. The gap is formed when the outer peripheral surface of the cap support block 3 having the cooling groove for allowing the cooling medium to flow therethrough and the inner peripheral surface of the core tip cap 1 are tightly adhered to each other in a state where the resin pressure is applied. Constitutes a part of the cooling hole 2.

Here, the thickness of the core tip cap 1 is
The thickness is designed to be the minimum necessary thickness calculated by a computer based on the resin pressure applied to the core and the width of the gap. That is, if the thickness of the core tip cap 1 in the gap is too thin, the strength is weakened, and as shown in FIG. 6, when the resin pressure is increased, the core is severely bent and then broken. Further, if extreme bending occurs without breaking, the surface of the molded product will have irregularities.

The cap support block 3 directly supports the resin pressure applied to the core tip while maintaining the shape of the core tip cap 1. The material of the cap support block 3 is desirably a high-strength metal that does not cause deformation or distortion.
For example, S55C material can be used. Resin pressure is applied to the core tip having such a structure, and the core tip cap 1 is pushed inward of the core. Due to this pressure, the dimensional accuracy of the cap support block 3 and the core tip cap 1 is less than a predetermined value (for example, a resin pressure of 300).
If the error is 0.01 mm or less and 0.05 mm or less in kg / cm ² ), they are in close contact with each other.

Although the core tip is fixed to the core body with a fastening bolt, the core body and the core tip may be integrated to eliminate the fastening bolt. FIG.
A cooling hole 2 is provided at an outer peripheral surface and a central portion of the core support block 3 at the core distal end, and heat of the molten resin passes through the cooling hole 2 so that heat of the molten resin passes through the outer peripheral surface of the core distal end cap 1. Endothermic. If the core tip cap 1 is made of a metal having high strength and high thermal conductivity, the cooling efficiency is better, so that a copper alloy, beryllium copper, an aluminum alloy or the like is suitable.

Further, since the thickness of the core tip cap 1 can be reduced, even if the core tip cap 1 is changed to a metal having low thermal conductivity, the cooling efficiency can be improved as compared with a mold having a conventional structure. Therefore, a metal having a low thermal conductivity but a high corrosion resistance may be used.
A corrosion-resistant metal layer may be further provided on the surface. For example, stainless steel can be used.

The size of the space through which the cooling solvent passes does not need to be constant, and a portion where the cooling capacity is desired to be increased may be made thicker, and a portion where the strength is desired to be secured may be made thinner.

The cooling medium is supplied from the outside of the core body and enters the gap through the cooling hole 2 at the center of the cap support block. Then, the cooling medium is drained again through the cooling holes 2 at the center of the core block through the voids. Note that the supply path of the cooling medium does not necessarily have to be formed in a spiral shape, and an optimal path may be set according to the shape of the molded product and the resin used.

FIG. 2 shows a more specific embodiment of an injection mold having a cooling hole 2 on the outer peripheral surface of a cap support block. The gap that forms a part of the cooling hole 2 includes an outer peripheral surface of a cap support block 3 provided with a cooling groove for allowing a cooling medium to pass therethrough, and a core tip cap 1.
It is formed by closely contacting the inner peripheral surface with no gap in a state where the resin pressure is applied. The core tip is 100m in diameter
A core tip cap 1 made of S55C material having a thickness of 5.5 mm and having a thickness of 5.5 mm is attached so as to be in close contact with the outer peripheral surface of the cap support block, and a gap having a width of 7 mm and a depth of 8 mm is spirally provided.

In FIG. 3, a gap formed by a cooling groove provided on the outer peripheral surface of the cap support block 3 and a cooling groove provided on the inner peripheral surface of the core tip cap 1 forms a part of the cooling hole 2. 1 shows an embodiment of an injection mold. The core tip is attached so that the core tip cap 1 of S55C material having a diameter of 100 mm and the thinnest portion having a thickness of 4.5 mm is in close contact with the outer peripheral surface of the cap support block 3, and a gap of 7 mm in diameter is spirally provided. ing.

The time required for cooling when the injection mold of the present invention was used for a 75 mm diameter vinyl chloride joint tube was simulated using a computer. When the material of the mold for injection molding is calculated based on the material of S55C, in the conventional structure, the core outer block thickness is 15 mm and
Cooling was completed in seconds. Therefore, using the injection mold of the present invention, the material S55C material, the core tip cap thickness 5 m
When the calculation was performed with m, the result showed that the cooling time was 20 seconds and the time could be reduced by about 17%.

[0025]

According to the mold of the present invention, the thickness of the core tip cap can be reduced, so that the cooling medium can be passed to a portion close to the core surface, and the temperature of the core tip cap can always be kept low. Further, since it is no longer necessary to ensure the pressure resistance, the material of the core tip cap can be changed to a metal having better thermal conductivity. Thereby, the cooling time in the cooling step of injection molding can be shortened.

[Brief description of the drawings]

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

FIG. 2 is a sectional view showing a schematic shape of a core in which a cooling groove is provided in a cap support block.

FIG. 3 is a sectional view showing a schematic shape of a core in which cooling grooves are provided in both a cap support block and a core tip cap.

FIG. 4 is a sectional view showing a schematic shape of an injection mold for a pipe joint.

FIG. 5 is a cross-sectional view showing a schematic shape of a core of a conventional injection molding die.

FIG. 6 is a conceptual diagram of deformation of a core tip cap due to resin pressure applied to the core.

[Explanation of symbols]

 Reference Signs List 1 core tip cap 2 cooling hole 3 cap support block 6 cooling bush 7 core outer block 12, 13 outer mold 14, 15 core

Claims (3)

[Claims] 1. An injection mold comprising an outer mold and a core, wherein a cavity is formed between the outer mold and the core when the mold is closed.
The core tip is composed of a cap support block and a core tip cap attached so as to be in close contact with the outer peripheral surface of the cap support block, and a gap is provided in a part of a contact surface between the cap support block and the core tip cap,
A mold for injection molding, wherein the core is cooled by passing a cooling medium through the gap. 2. The injection molding die according to claim 1, wherein said gap comprises a cooling groove provided on the outer peripheral surface of the cap support block and a core tip cap. 3. The injection molding metal according to claim 1, wherein said gap comprises a cooling groove provided on the outer peripheral surface of the cap support block and a cooling groove provided on the inner peripheral surface of the core tip cap. Type.