JP2876935B2 - Mold equipment for injection molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold apparatus used for manufacturing an injection molded article having a hollow portion. More specifically, the present invention relates to an injection molding die apparatus suitable for producing a hollow molded article having a reinforcing rib in a hollow portion using a thermoplastic resin as a raw material by an injection molding method.

[0002]

2. Description of the Related Art Heretofore, as a method of molding a hollow molded article by an injection molding method, an insufficient amount of a molten thermoplastic resin to fill a mold cavity of a mold is injected or injected into the mold cavity. A method is known in which a pressurized gas body is pressed into a mold cavity to press a molten resin against the outer periphery of the mold cavity to form a hollow portion (for example, Japanese Patent Publication No. 57-14968, Japanese Patent Publication No. 61-53208). JP, JP-A-3-9820, JP-A-4-35700
No. 9).

[0003] When manufacturing a hollow injection molded article having a large hollow portion, a method of injecting a molten resin into a mold cavity and subsequently injecting a pressurized gas body, followed by enlarging the volume of the mold cavity. Is described in the above-mentioned JP-A-3-98.
No. 20, JP-A-4-35709, and the like.

Further, in the case of a hollow injection molded article having a large hollow portion, a problem in strength occurs due to the presence of the large hollow portion. As a means for solving this problem, a reinforcing rib is formed in the hollow portion. There is also proposed a technique for manufacturing such an injection molded product. Japanese Patent Application Laid-Open No. 4-357,094 discloses that, when manufacturing an injection-molded product in which a reinforcing rib is formed in a hollow portion,
A movable core that can project into the mold cavity and retreat from this position is provided at a position where a reinforcing rib that is integrally connected between surfaces facing each other across the hollow portion of the hollow injection molded product to be molded is formed. There has been proposed a method using an injection mold having the above.

[0005]

However, in the case of these conventional methods, there is a concern about the strength of the formed reinforcing ribs, and only those products whose appearance of the molded product is inferior are produced. I couldn't.
In particular, when the molded article to be manufactured is a thick-walled product, this tendency is remarkable, and a satisfactory product cannot be obtained.
The present inventors have conducted intensive studies with the aim of obtaining a product having a good appearance of a molded product without a fear of strength of the reinforcing ribs. For example, the present inventors have found that the present invention is greatly affected by instability such as the enlargement speed and the enlargement amount, and have completed the present invention based on this finding.

[0006]

SUMMARY OF THE INVENTION Accordingly, the gist of the present invention is to provide a fixed type provided with a runner and a pressurized gas body pressure inlet, and a movable insert capable of moving forward and backward with respect to the fixed type. A mold cavity for a resin molded product to be molded is formed by a movable mold movably provided, and a convex portion toward a fixed mold side mold cavity surface is formed on a mold cavity surface of the movable insert, and A mold apparatus for manufacturing an injection-molded product having a reinforcing rib in a hollow portion, wherein the volume of the mold cavity is made expandable by retreating the movable insert.
The movable nest has a pair of inclined surfaces on the back side of the mold cavity forming surface, and a pair of slides having an inclined surface that is slidable on the back surface of the movable nest in contact with the inclined surface. A block is provided, and the set of slide blocks is capable of retreating or moving forward or away from or close to each other or close to or away from each other.

Hereinafter, the present invention will be described in detail with reference to the drawings. The drawings schematically show an embodiment of the injection mold apparatus according to the present invention, and FIG. 1 shows a state before the volume of the mold cavity of the mold is enlarged.
FIG. 2 shows a state after the volume of the mold cavity of the molding die is enlarged. In the figure, 1 is a fixed type, 2 is a movable type, 3 is a movable insert, 4 and 4 'are slide blocks, 5 is a movable type side wall, 6 is a bar-shaped inversion screw, and 7 and 7' are slide block guides. , 8 is a slide base, 9 is a mounting board, 10 is a driving motor, 11 is a mold cavity, 12
Is a runner, 13 is a sprue, 14 is a pressurized gas body pressure inlet, 15 is a pressurized gas body press-fit nozzle, 16 is a fine hole, 17 is a check valve, 31 and 31 'are movable inclined surfaces, 32 and 32. '
Is a convex portion of the movable insert, 40 is a molded product, 41 and 41 'are reinforcing ribs of the molded product, and 42 is a hollow portion of the molded product.

The injection molding apparatus according to the present invention comprises a fixed mold 1 provided with a runner 12 and a pressurized gas pressure inlet 14, and a movable insert 3 capable of moving forward and backward with respect to the fixed mold 1.
And a movable mold 2 slidably provided to form a mold cavity 11 for a resin molded product to be molded. Although the example shown in the figure is provided at a place different from the runner 12, the pressurized gas body pressure inlet 14 is not necessarily required, and may be provided at the same place as the runner 12. When the pressurized gas body pressure inlet 14 is provided at the same location as the runner 12, a resin injection nozzle having a built-in pressurized gas body pressure inlet may be used.

As shown in the figure, the movable insert 3 slides almost in the center of the movable mold 2 in the same direction as the moving direction of the movable mold 2 so as to face the mold cavity surface of the fixed mold 1. The mold cavity surface on the fixed mold side at a required position on the mold cavity surface, specifically, a position corresponding to the position where the reinforcing rib of the molded product is to be formed. Protrusions 32, 32 'are formed. When the convex portions 32 and 32 'are formed on the mold cavity surface of the movable insert 3, the molten resin sandwiched between these convex portions and the mold cavity surface of the fixed mold 1 opposed to these convex portions is formed. Since the molten resin is cooled earlier than the portion of the molten resin sandwiched between the mold cavity surfaces having no convex portions, the pressurized gas body is pressed into the molten resin, and the movable nest 3 is retracted to increase the volume of the mold cavity. At that time,
The pressurized gas body enters into the higher-temperature molten state without the convex portion to form a hollow portion 42, and the portion which is cooled earlier and hardly enters the pressurized gas body is provided with reinforcing ribs 41, 41 '.
Will remain as.

The shape of the projections 32, 32 'is preferably a trapezoidal shape whose cross section is directed toward the mold cavity surface on the fixed mold side, but is not limited to this, and is similarly a mountain shape, a half shape, and the like. It may be circular or the like. The projections are arranged according to the design of the reinforcing rib to be provided on the molded product. Specifically, for example, a) a plurality of linearly extending projections are arranged at substantially regular intervals at a constant interval; b) a plurality of linearly extending projections are radially arranged; c) an arc extending Any of a plurality of protrusions may be arranged arbitrarily, or d) a combination of these may be arranged. The size, arrangement density, and the like of such protrusions can be appropriately determined depending on the shape, size, structure, application, required strength, and the like of the molded product to be obtained.

In this mold apparatus, the volume of the mold cavity 11 is enlarged by the retreat of the movable insert 3 constituting a part of the movable mold 2, and after one cycle of the molding is completed, the movable insert 3 is closed. Mold cavity 1
1 is configured to be restored to the state before the enlargement. The injection molding die apparatus according to the present invention has a structure in which the speed and distance of the backward movement of the movable insert 3 are precisely controlled by an advance / retreat adjusting mechanism described below.

In the illustrated example, the movable insert 3 is disposed at the center of the movable mold 2, and on the back side of the mold cavity forming surface, the central portion of the movable insert 3 is thick, and the left and right ends are provided. (Peripheral portion) so that the pair of inclined surfaces 31, 31 'are thinned.
Are formed. A pair of slide blocks 4, 4 'having an inclined surface which is slidable in contact with the inclined surface 31, 31' is arranged on the inclined surface 31, 31 '. The movable insert 3 retreats or advances with respect to the fixed mold side cavity surface in accordance with the set of slide blocks 4, 4 'being separated from or approaching each other. In addition,
The illustrated example shows a case where the inclination direction of the inclined surface is convex toward the center of the movable insert 3. In this case,
As the slide blocks 4 and 4 ′ are separated from or approach each other, the two inclined surfaces that are in contact with each other slide,
Although the movable insert 3 is configured to retreat or advance with respect to the fixed mold side cavity surface, the inclination direction of the inclined surface of the movable insert 3 is not limited to the illustrated direction. Conversely, the inclination direction of the inclined surface of the movable insert 3 may be concave toward the center. In this case, the movable nest 3 moves backward or forward as the slide blocks 4, 4 'approach or separate from each other.

The mechanism for moving the slide blocks 4, 4 'apart or close to each other withstands the pressure of the molten resin injected into the mold cavity, the pressure load of the pressurized gas injected into the molten resin, and the like. There is no particular limitation as long as smooth separation and close proximity can be achieved. A preferred mechanism for moving the slide blocks 4, 4 'apart or close to each other is as follows:
Each of the movable molds is screwed to a bar-shaped reversing screw pivotally supported by a pair of moving mold side walls extending from the end of the mold cavity forming surface to the back side, and separated or approached by rotation of the rod-shaped reversing screw. Good to do. With this configuration, the slide block can sufficiently withstand the above-mentioned pressure load, and the slide block can be smoothly separated and approached. Therefore, the retreat speed and the retreat distance of the movable insert can be precisely controlled, which is preferable. A specific example of the above-described mechanism will be described with reference to the drawings.
Is screwed into a bar-shaped inversion screw 6 pivotally supported by a pair of movable mold side walls 5 extending from the end of the movable mold cavity forming surface to the back side, and the rod-shaped inversion screw is rotated by a driving motor 10. Mechanism. In this case, the bar-shaped inversion screw 6 means a screw thread in which directions of engraving are opposite to each other with respect to a middle point of the entire length, for example, one is a right-hand thread and the other is a left-hand thread. Using a bar-shaped reversing screw 6 like this, if it is rotated in one direction by a driving motor 10, preferably a servomotor whose rotational speed can be controlled by a speed controller, a set of screws screwed to this is formed. The slide blocks 4, 4 'are separated by the rotation of the bar-shaped reversing screw 6, and can be brought closer by rotating in the opposite direction.

The pair of slide blocks 4, 4 'are provided with guides on opposite sides of the inclined surfaces to smooth the separation and approach and to support a pressing load on the slide blocks 4, 4'. It is preferable to adopt a structure in which the guides 7 and 7 ′ are fixed and the guide is slid along a slide base 8 fixed on the mounting board 9.

Next, a method of manufacturing a hollow molded product having a reinforcing rib in a hollow portion by an injection molding method using the injection molding die apparatus according to the present invention will be described with reference to FIGS. 1 and 2. I do. First, the movable mold 2 is clamped to the fixed mold 1 by a mold clamping mechanism (not shown), and the position of the movable insert 3 is set to an advanced state. This state is shown in FIG. Next, the molten resin is injected into the mold cavity via the runner 12 from the injection nozzle pressed against the sprue 13. Next, the pressurized gas body is press-fitted from the pressurized gas body pressure inlet 14, and the drive motor 10 is driven to rotate the bar-shaped reversing screw 6 to separate the slide blocks 4, 4 'from each other, whereby the movable insert 3 is moved. By retracting it by a predetermined distance, the volume of the mold cavity is increased. This state is shown in FIG.

The timing of expanding the volume of the mold cavity by retracting the movable nest 3 is during the time when the resin injected into the mold cavity 11 is in a molten state, and before the pressurized gas is injected, or It is preferable that the pressurized gas body is simultaneously injected with the pressurized gas body. When the pressurized gas body is to be press-fitted through the pressurized gas body pressure inlet 14, a pressurized gas body press-fit nozzle 15 having a narrow hole 16 for the gas body and having a check valve 17 at the tip thereof is added. This is carried out by attaching to the pressure gas body pressure inlet 14.

At this time, the volume expansion rate and the volume expansion rate of the mold cavity are controlled by the retreat speed and the retreat distance of the movable insert 3. The retreat speed and the retreat distance of the movable insert 3 can be determined by the separation speed and the separation distance of the slide blocks 4, 4 '. For this purpose, a drive motor is provided by a rotation speed controller (not shown) and positioning means such as a limit switch. This is possible by controlling the driving of the ten.

After the press-fitting of the pressurized gas body and the expansion of the volume of the mold cavity are completed, the molded product 40 having the reinforcing ribs 41, 41 'and the hollow portion 42 is opened and removed according to a conventional method as soon as it is cooled. Thereafter, the mold is clamped again, and the movable insert 3 which has been retracted is advanced to the state shown in FIG. 1, and the next molding step can be performed.

In the present invention, the pressurized gas body includes, for example, nitrogen gas, air, helium gas, carbon dioxide gas and the like. Among them, nitrogen gas, air and the like are preferable. Examples include synthetic resins generally used for extrusion molding and the like, and these resins may contain various additives as necessary.

The use of the injection molding apparatus according to the present invention makes it possible to use a housing for a personal computer, an office computer, a copying machine, a printer, etc. OA equipment products field; daily miscellaneous goods field such as various shelves, toilet seats and toilet lids; and molded articles having various hollow structures such as automobile parts such as automobile doorknobs.

[0021]

The present invention has a particularly remarkable effect as described below, and its industrial value is extremely large. (1) The injection molding die apparatus according to the present invention uses a movable die provided with a movable nest that can move backward with respect to a fixed die, so that a molded product having a large hollow portion can be manufactured. (2) The mold device for injection molding according to the present invention manufactures a molded product in which the convex portion is formed on the mold cavity surface of the movable insert, and the reinforcing rib is formed integrally with a part of the hollow portion. can do. (3) In the injection molding die apparatus according to the present invention, the movable insert can be retracted and advanced using the specific mechanism, so that the volume of the die cavity can be expanded with high accuracy. (4) With the use of the injection molding die apparatus according to the present invention, since the volume of the mold cavity can be accurately increased, it is easy to control the position and thickness of the reinforcing ribs and the thickness of the molded product.

(5) When the injection molding apparatus according to the present invention is used, it is easy to control the position and thickness of the reinforcing rib and to control the thickness of the molded product. It is possible to easily produce a molded product having no uneasiness in strength and having no appearance defect due to sink marks due to uneven thickness. (6) The mold apparatus for injection molding according to the present invention is inexpensive to manufacture because the expansion of the volume of the mold cavity has a simple structure consisting only of the forward / backward movement mechanism of the movable insert.

[0023]

[Brief description of the drawings]

FIG. 1 is a conceptual view showing an embodiment of the present invention, showing a state before the volume of a mold cavity of an injection molding die apparatus is enlarged.

FIG. 2 is a conceptual diagram showing one embodiment of the present invention, and shows a state after the volume of a mold cavity of an injection molding mold device is enlarged.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 fixed type 2 movable type 3 movable type movable insert 4, 4 ′ slide block 5, 5 ′ movable type side wall portion 6 bar-shaped inversion screw 7, 7 ′ guide of slide block 8 slide base 9 mounting board 10 drive motor Reference Signs List 11 mold cavity 12 runner 13 sprue 14 pressurized gas body pressure inlet 15 pressurized gas body press-in nozzle 16 small hole 17 check valve 31, 31 ′ inclined surface of movable insert 32, 32 ′ convex portion of movable insert 40 molding Article 41, 41 'Reinforcing rib of molded article 42 Hollow part of molded article

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-57573 (JP, A) JP-A-5-84764 (JP, A) JP-A-4-257009 (JP, A) JP-A-4,570 212822 (JP, A) Japanese Utility Model Showa 47-38067 (JP, U) Japanese Utility Model Showa 47-38066 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B29C 45/26-45 / 44

Claims (1)

(57) [Claims] 1. A resin mold to be formed by a fixed mold provided with a runner and a pressurized gas pressure inlet, and a movable mold slidably provided with a movable insert capable of moving forward and backward with respect to the fixed mold. A mold cavity for an article is formed, a convex portion is formed on the mold cavity surface of the movable insert toward the mold cavity surface on the fixed mold side, and the volume of the mold cavity can be increased by retreating the movable insert. A mold device for manufacturing an injection molded product having a reinforcing rib in a hollow portion,
The movable nest has a pair of inclined surfaces on the back side of the mold cavity forming surface, and a pair of slides having an inclined surface that is slidable on the back surface of the movable nest in contact with the inclined surface. A block device is provided, and said set of slide blocks is capable of retreating or advancing by being separated or close to each other or by being close to or separated from each other.