JP2545024B2 - Injection mold - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding die capable of compressing a molten resin injected into a cavity by the pressure of a fluid.

[0002]

2. Description of the Related Art A mold for injection molding comprises a cavity mold and a core mold, which are separately mounted on a fixed plate and a movable plate. In a normal mold, a cavity mold is attached to a fixed plate and a core mold is attached to a movable plate, and both are fixed using a mold mounting plate.

In such a mold, since all are in a fixed state, when pressurizing the molten resin injected into the cavity by the core mold for injection compression molding, it is necessary to move the core mold forward together with the movable plate. There is. Since the movement of the movable platen is performed by controlling the hydraulic pressure, there is no technical difficulty in controlling the movement of the molded product having a large compression allowance,
For molding of molded products that require sufficient compression or partial compression with an extremely small compression allowance, it is difficult to perform fine control due to the influence of the load of each member that makes up the movable plate and core mold. As a result, an excessive compressive force is applied to the molten resin, which causes residual stress to reduce the impact strength of the molded product, and therefore another means is adopted.

As another means, only the core mold located in the cavity is moved to compress the molten resin, or a partial pin is charged with a movable pin. Even in this case, the movement of the movable portion is controlled by controlling the hydraulic pressure.

[0005]

In any of the above compression means, the compression of the molten resin is limited only to the moving direction of the core type or the movable pin, and the compression in the direction perpendicular to the moving direction is impossible. It is in. For this reason, injection compression molding is an extremely effective molding method for disc-shaped molded products such as CDs, precision molded products such as lenses and gears, but overall compression is difficult for molded products having a three-dimensional shape. Therefore, it is difficult to be adopted.

The present invention was conceived in order to solve the above-mentioned conventional problems, and its purpose is to make the wall surface of the cavity movable by the pressure of the fluid even in the case of compression in the perpendicular direction, which has been difficult in the past. It is an object of the present invention to provide a new mold for injection molding that enables not only injection compression molding but also release of a molded product having no draft.

[0007]

The present invention according to the above object comprises a cavity mold for forming a cavity by mold closure and a core mold, and a cap-shaped member made of a material having self-restoring property is inserted into the core mold, The portion of the cap-shaped member facing the cavity is formed as a movable wall inside the cavity that is entirely supported by the core mold, and the movable wall is bulged into the cavity by opening on the side of the core mold inside the movable wall. It has a pressure passage.

Further, according to the present invention, a cavity mold which forms a cavity by mold closing and a core mold are fitted, and an annular member made of a material having a self-restoring property is fitted inside the inner periphery of the recess of the cavity mold. The inner part of the annular member facing the cavity is entirely supported by the nest mold or serves as a movable wall outside the cavity, and the inner side of the nest mold inside the movable wall is opened. Also, a pressurizing path for bulging the movable wall into the cavity is provided.

As the pressurized fluid, hydraulic pressure, compressed air or the like is used, and as the material of the movable wall, a heat resistant and self-restoring material such as a metal plate or silicon rubber is used.

[0010]

[Operation] In the above configuration, since the movable wall is entirely supported by the core type or the nest type, it is not necessary to support the movable wall by an external force for forming the cavity when the molten resin is injected and filled. As in the case of the cavity, when the molten resin is injected and filled, and then external pressure such as hydraulic pressure is applied to the inside of the movable wall, the movable wall swells entirely in the cavity. Due to this bulging, the entire inner surface or outer surface of the molded product, which is in contact with the movable wall, is uniformly pressed, and the molded product is compressed.

When the pressure oil is stopped from being pumped after the molded product is cooled and solidified to release the pressure on the movable wall, the movable wall returns to its original shape due to the self-restoring force, and with the restoration, the cavity outer surface and Clearance occurs with the molded product.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the figure, 1 is a cavity type mounted on the fixed plate side, and 2 is a core type mounted on the movable plate side.

The cavity mold 1 has a nozzle insertion hole 11
Is fixed to a die mounting plate 12 having a central portion, and a cavity 13 is formed in a cavity 13 in the die surface facing the core die 2.
The recess 13 and the nozzle insertion hole 11 are communicated with each other by a sprue bush 14 fitted in a cavity mold so that molten resin can be injected and filled into the cavity 13 through the sprue bush 14. It has become.

The core mold 2 is inserted into a movable mold plate 22 and a stripper plate 23 stacked on the mold mounting plate 21, and is set at the center of the mold mounting plate 21.

In the embodiment shown in FIG. 1, the recess 13 is formed in the insert mold 15, and the protruding end of the core mold 2 is inserted into the recess 13 by closing the mold to form a cavity. In the case where the core mold side of the mold cavity is a movable wall 24 that bulges into the cavity by hydraulic pressure, the movable wall 24 is a cap-shaped member fitted to the core mold 2 and made of a self-restoring material. It is configured with a tip end facing the cavity of 25.

The tip portion of the cap-shaped member 25 which is fitted into the core mold and faces the cavity, that is, the movable wall 24 which is entirely supported by the core mold is formed thinner than the other portions.
Further, inside the core mold 2 which also serves as a support for the movable wall 24, a hydraulic passage 26 that opens to the side of the core mold inside the movable wall and swells the movable wall 24 into the cavity is provided in the mold mounting plate 21.
The movable wall 24 is entirely bulged into the cavity by the pressure oil that is bored from the hydraulic passage 26 and is fed from the hydraulic passage 26 to the inside of the movable wall 24.

The swelling is performed after the molten resin is injected and filled into the cavity through the sprue bush 14, and the swelling presses the entire inner surface of the molded product 3 in contact with the movable wall 24, so that the molded product 3 is pressed. Then, each is subjected to compression in a direction perpendicular to the inner surface, and internal strain due to injection filling is removed.

When the pressure oil is stopped from being pumped after the molded product 3 is cooled and solidified to remove the pressure in the hydraulic passage 26, the movable wall 24 returns to its original shape due to the self-restoring force of the material used therein. Return.

The embodiment shown in FIG. 2 is a case where the side surface of the recess 13 of the cavity mold 1 is formed as a movable wall 24, and the inner periphery of the recess 13 directly formed in the cavity mold 1 is
The inner side of the annular member facing the cavity is formed with a nesting die 16 formed by fitting an annular member made of a material having self-restoring property inside, and the inner side of the annular member facing the cavity is fully supported by the nesting die. It is configured on the wall 24.

A hydraulic passage 26 for bulging the movable wall 24 is provided in the cavity mold 1 to the insert die 16, and the movable wall is opened from the opening of the hydraulic passage 26 formed in the side of the insert die inside the movable wall. The movable wall 24 swells entirely in the cavity by the pressure oil sent inward, and presses the outer surface of the molded product 3.
As a result, the molded product 3 is laterally compressed. In addition, 27 shows a runner.

FIG. 3 shows a long molded product having no draft, for example, a three-plate mold capable of molding a tubular body. The cavity mold 1 is not shown in the drawing, but includes a spring member and a limiting pin. Is provided so as to be able to come into contact with and separate from the mold mounting plate 12, and a runner 27 is provided between the joint surfaces. In addition, the recess 13 of the cavity mold 1 has a long cylindrical shape, and the long core mold 2 integrally formed with the mold mounting plate 21 is located therein to form a tubular cavity.

As for the movable wall 24, a bottomed cylindrical body 28 made of a thin metal plate having the same thickness as a whole is fitted to the core mold 2 having the hydraulic passage 26 formed therein, and a stopper plate 29 is used at its open end. It is watertightly attached to the mold mounting plate 21.

The top end of the movable wall 24 is housed in the step formed at the bottom of the recess 13 together with the tip of the core mold 2 by closing the mold, and acts as the movable wall 24 only on the peripheral side of the core mold 2. is there.

In the above injection mold, after the molten resin is injected and filled in the cavity to form the long tubular molded product 4,
When the movable wall 24 is bulged by hydraulic pressure, the tubular molded product 4
The inner side of the tube is compressed and the tubular molded product 4 contracts. If the tubular molded product 4 in close contact with the movable wall 24 is attracted to the core mold side when it is cooled and solidified in that state and then self-recovered by removing the pressure on the movable wall 24, the cavity outer peripheral surface and the tubular molded product are attracted. A clearance corresponding to the bulge is generated between 4 and 4. As a result, even if there is no draft in the tubular molded product 4, the clearance allows the tubular molded product 4 to be released from the cavity mold 1.

[0025]

As described above, according to the present invention, the inner wall or the outer wall of the cavity is a movable wall made of a self-restoring material which is wholly supported by the core type or the nest type, and the cavity of the movable wall is formed. Since the swelling inside enables compression molding of the molded product, the compression direction of the molded product is not limited to one direction as before, and it is also possible to simultaneously compress in two directions at right angles, which is difficult to achieve in the past. It is possible to perform injection compression molding of a molded product having the three-dimensional shape that has been used.

Moreover, since the movable wall is entirely supported by the core type or the nest type, it is not necessary to support the movable wall by an external force in order to maintain the cavity formation at the time of injection filling of the molten resin, and the cavity of the normal structure is used. Even if the molten resin is injected and filled in the same manner as in the above case, it is not deformed by the injection pressure and the cavity shape is not damaged.

Further, since the movable wall can be constituted by a thin plate capable of bulging by the whole surface support by the core type or the nest type, a large pressing force is not required for the bulging of the movable wall, and most of the pressure applied there is formed. Since it acts as a compressive force for the product,
The compression force can be controlled more easily than in the case of performing compression with a core mold having a load, and as a result of always being able to perform appropriate compression, it is possible to form a molded product without residual stress due to excessive compression.

Furthermore, since the clearance is formed between the molded product and the outer peripheral surface of the cavity due to the restoration of the movable wall after molding, this clearance enables the mold product to be released without the draft required at the time of mold release. As a result, the problem of the wall thickness distribution of the molded product due to the draft can be solved and a molded product with high molding accuracy can be obtained.

Structurally, it suffices to provide a movable wall on the side of the recess of the core mold or the cavity mold by means such as fitting and insertion, and to provide a passage for the pressurized fluid in the support inside the movable wall. Since its main structure is the same as that of the conventional one, it can be applied to conventional dies and can be applied to small dies, which is extremely practical.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an embodiment of an injection molding die according to the present invention in a mold closed state.

FIG. 2 is a schematic sectional view of another embodiment in a mold closed state.

FIG. 3 is a schematic cross-sectional view of an injection-molding die for a molded product having no draft, in a mold closed state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cavity type 2 Core type 3 Molded product 4 Tubular molded product 12 Mold mounting plate 13 Recess for cavity 21 Mold mounting plate 24 Movable wall 25 Cap member 26 Hydraulic path

Claims (2)

(57) [Claims] 1. A cap type member comprising a cavity type and a core type, which form a cavity by mold closing, and a cap-shaped member made of a material having self-restoring property is inserted into the core type, and a portion of the cap-shaped member facing the cavity is a core. It is characterized in that it is formed as a movable wall inside the cavity that is entirely supported by the mold, and that a pressure passage is provided in the core mold so as to open to the side of the core mold inside the movable wall and swell the movable wall into the cavity. Injection mold. 2. A nesting mold comprising a cavity mold for forming a cavity by mold closing and a core mold, and an annular member made of a material having a self-restoring property is fitted inside the inner periphery of the recess of the cavity mold. The inner part of the ring-shaped member facing the cavity is formed as a movable wall outside the cavity that is entirely supported by the insert mold, and the movable wall is opened inside the insert mold to the side of the insert mold. An injection-molding die, characterized in that a pressure passage that bulges out is provided therein.