JP2002018910A - Structure of valve gate of mold for injection molding and molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure of a valve gate of a mold for injection molding capable of preventing an undesired protrusion shape at a gate irrespective of a type of a resin material. SOLUTION: The structure of the valve gate of the mold for injection molding comprises a valve pin 6 for opening/closing the valve gate 4 in such a manner that a distal end part for molding a part of the molding of the pin 6 is formed in a conical surface shape or a spherical surface shape in a direction for projecting to a cavity side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve gate structure of an injection mold.

[0002]

2. Description of the Related Art In recent years, many plastic injection molding dies have a hot runner structure for the purpose of saving a resin material, shortening a molding cycle, etc., and particularly have a valve gate system. The proportion of things is increasing.

A valve gate type mold has a mechanism in which a valve pin closes or opens a gate portion of the mold by hydraulic pressure or air pressure of an injection molding machine in accordance with timing at which molten resin is supplied to a cavity space. ing. Due to the provision of such a mechanism, a mold having a valve gate system is more desirable than a mold having a hot runner mechanism of other systems and a mold of a cold runner in that a gate cutting portion is clean and has burrs and the like. It is characterized in that it is possible to comparatively reduce the occurrence of no projection shape.

FIGS. 4 and 5 show a tip portion of a conventional valve gate structure. FIG. 4 shows a state in which the valve gate is closed by the valve pin, and FIG. 5 shows a state before the valve gate is closed by the valve pin. As shown in this figure, in the conventional valve gate structure, the tip shape of the valve pin 6 that closes or opens the gate portion 4 of the mold, that is, the portion that forms a part of the molded product, has a flat shape. The gate portion is set to be flush with the surrounding surface. 4 and 5, 1
Is a fixed mold member, 2 is a movable mold member, 3 is a cavity,
5 is a resin flow path, and 8 is a gate nozzle.

[0005]

However, when a part of the resin material is injection-molded by using the mold having the conventional valve gate structure, the gate cut portion which is an essential feature of the valve gate system is clean. However, there is a case where an undesired projection shape such as a burr is formed. According to the experience of the inventor of the present application, this phenomenon often occurs when a styrene-based resin is injection-molded, and the cause is presumed as follows.

When the filling of the molten resin into the cavity space 3 is completed and the valve pin 6 starts to enter the cavity side to close the gate 4, the resistance of the molten resin in the cavity filled with a high molding pressure is high. Receive. Further, the molten resin has started to be cooled and solidified by receiving a cooling effect of a mold for solidifying the molten resin, and has a higher viscosity than at the time of starting the filling. This also increases the resistance when the valve pin 6 enters the gate portion 4 to close the gate. The resistance of the resin generated when the valve pin penetrates into the gate prevents the valve pin from reaching a predetermined position when the gate is closed, thereby generating an undesired projection shape at the gate portion of the molded product. This causes the problem described above.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a valve gate structure and a molded product of an injection mold capable of preventing generation of an undesired projection at a gate portion. It is to provide.

[0008]

Means for Solving the Problems The above-mentioned problems are solved,
In order to achieve the object, a valve gate structure of an injection mold according to the present invention has a valve pin for opening and closing a valve gate in the valve gate structure of an injection mold, and a molded product of the valve pin. Is formed in a conical surface shape or a spherical shape in a direction protruding toward the cavity side.

A molded product according to the present invention is characterized in that a conical or spherical concave portion is formed in a portion corresponding to a valve gate of an injection mold.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described.

In this embodiment, a conical surface or a spherical shape in the direction protruding toward the cavity is provided at the tip of a valve pin which forms a part of a molded product. That is,
When the tip portion of the valve pin has a conical surface or a spherical shape in the direction protruding toward the cavity side, when the filling of the molten resin into the cavity is completed and the valve pin enters the cavity side to close the gate, The purpose is to reduce the resistance received from the molten resin in the cavity and the resin that has started to solidify, so that the valve pin can easily enter the predetermined position when the gate is closed.

Hereinafter, description will be made with reference to the drawings.

FIGS. 1 to 3 show one embodiment of the valve gate structure of the present invention.

1 to 3, reference numeral 1 denotes a fixed mold member, and 2 denotes a movable mold member, both of which form a cavity 3 serving as a product shape portion. 1 and 2 show a state in which the mold is closed, and the movable mold member 2 has a structure capable of moving in a direction indicated by an arrow A in FIG. The fixed mold member 1 is mounted on a fixed platen of an injection molding machine via a fixed mounting plate 9. The movable mold member 2 is attached to a movable platen of an injection molding machine via a spacer block and a movable mounting plate, not shown.

Reference numeral 4 denotes a gate, which serves as an entrance for filling the cavity 3 with the molten resin injected from the nozzle of the molding machine through the fixed mold member 1 of the mold. . Reference numeral 5 denotes a flow path of the molten resin from the fixed side mold member 1 to the gate 4. Reference numeral 6 denotes a valve pin, which opens or closes the gate 4 by moving the valve pin 6 vertically in the figure by the driving force of a driving device (not shown). Reference numeral 7 denotes a manifold which is located between the fixed mold member 1 and the fixed mounting plate 9, and is used for heating the molten resin injected from the nozzle of the injection molding machine to each gate while maintaining a predetermined temperature. Built-in heater. 8 is a gate nozzle,
This is a member that is incorporated in the fixed mold member 1 and guides the molten resin supplied from the manifold 7 to the gate 4 through the resin flow path 5. At the center thereof, a valve pin 6 is configured to be slidable in the vertical direction in the figure.

Next, the operation will be described with reference to FIGS.

The molten resin injected from the nozzle of the injection molding machine is temporarily accumulated in the manifold 7. The molten resin maintained at a predetermined temperature by a heater built in the manifold 7 is guided to the gate 4 through the resin flow path 5.
At this time, the valve pin 6 is moved upward in the figure by the driving force of a driving device (not shown), and the gate 4 is provided with a gap through which the molten resin can pass.

The molten resin passes through the gate 4 and fills the cavity 3 of the mold. When a predetermined amount of the molten resin is charged, the valve pin 6 moves downward in the figure by the driving force of a driving device (not shown), the gate 4 is closed, and the supply of the molten resin is stopped.

Here, the operation when the filling is completed and the valve pin 6 moves downward in the figure will be described in detail as follows.

First, when the molten resin is filled in the cavity 3, the fixed mold member 1 and the movable mold member 2 forming the cavity 3 perform temperature control within an appropriate range to cool and solidify the molten resin. Have been. Since the management method and the appropriate range depart from the gist of the present invention, the description is omitted here. When the valve pin 6 starts to move downward in the figure, the molten resin in the cavity 3
Solidification has begun under the influence of the temperature of the movable mold member 2, and the tip of the valve pin 6 receives a resistance force in the moving direction from the resin that has started to solidify in the moving direction. At this time, the tip shape of the valve pin 6 is
By forming the conical surface or the spherical shape in the direction protruding to the side, the resistance force received from the resin that has started to solidify can be reduced, and the valve pin 6 can be moved to a predetermined position for closing the gate 4. It will be easier. As a result, the occurrence of undesired projections such as burrs around the gate 4 is reduced, and the defect occurrence rate can be reduced.

In the molded product molded by the mold having the valve gate structure described above, a conical or spherical concave portion corresponding to the tip shape of the valve pin 6 is formed at a portion corresponding to the valve gate. You.

[0022]

As described above, according to the present invention,
It is possible to prevent generation of an undesired projection shape such as a burr at a gate portion of a molded product, and it is possible to reduce defects in injection molding.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a valve gate structure of the present invention, and is a view showing a state where a gate is closed.

FIG. 2 is a view showing the entire valve gate structure of one embodiment.

FIG. 3 is a diagram showing a state before the gate is closed in the valve gate structure of one embodiment.

FIG. 4 is a view showing a state in which a gate is closed in a conventional valve gate structure.

FIG. 5 is a view showing a state before a gate is closed in a conventional valve gate structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed-side mold member 2 Movable-side mold member 3 Cavity 4 Gate 5 Resin channel 6 Valve pin 7 Manifold 8 Gate nozzle 9 Fixed side mounting plate

Claims (2)

[Claims] 1. A valve gate structure for an injection molding die, comprising: a valve pin for opening and closing a valve gate, wherein a tip of a part of a molded product of the valve pin is formed in a direction protruding toward a cavity. A valve gate structure for an injection molding die, which is formed in a conical surface shape or a spherical shape. 2. A molded product characterized in that a conical or spherical concave portion is formed in a portion corresponding to a valve gate of an injection molding die.