JPH09277321A - Equipment and method for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide equipment and a method for injection molding which enable improvement of productivity and the quality of a product by enabling execution of low-pressure molding by increasing the sectional area of a gate. SOLUTION: This equipment is so constructed that a heated and melted material 13 is injected from the fore end part of a nozzle 20A, passed through a runner part 9 provided in a mold 5 and injected into a cavity 6 provided in communication with the runner part 9, so as to mold a product 2. In this construction, the place of the cavity 6 connected to the runner part 9 is provided as a gate part 7 and a gate cut member 22 which is provided movably in correspondence to the gate part 7 and moves toward the gate part 7 side after the material 13 is injected into the cavity 6, so that the material being present in the vicinity of the gate part 7 be let to escape and that the gate part 7 be closed up, is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding apparatus and a molding method for manufacturing a resin molded product or the like.

[0002]

2. Description of the Related Art Generally, in a conventional injection molding apparatus, a gate, which is a sprue, is provided between a tip of a nozzle for injecting a resin material that has been heated and melted and a cavity in a mold. A runner portion is provided which communicates with each cavity when a plurality of molded articles are simultaneously molded. Further, as the gate mechanism, when molding a shell for a disc cassette such as an MD (mini disc), a pinpoint gate or a submarine gate, which can omit post-processing, is often used.

[0003]

However, when the above-mentioned pinpoint gate is applied, the gate portion is often set on the side of the design surface which is visible from the outside of the shell due to the general positional restrictions. . For this reason, traces of the gate part may remain on the design surface to deteriorate the texture, and when printing or labeling on the trace of the gate part, it may be necessary to remove the trace of the gate part. There was a problem in quality and man-hours. In addition, when applying the submarine gate, for example, it is possible to provide a boss in the product in the protruding direction and perform gate cutting in the mold, but the pushing stroke at the time of gate cutting becomes longer and the product There are residual stresses on the gate, and there are restrictions on the gate position. Moreover, in any of the conventional gate structures, it is difficult to increase the gate cross-sectional area and the degree of freedom of injection molding conditions is narrow.

The present invention has been made in view of the above problems, and an object thereof is an injection molding apparatus capable of increasing a gate cross-sectional area to enable low-pressure molding and improving productivity and product quality. To provide a method. Further, other objects will be clarified sequentially in the contents described below.

[0005]

In order to achieve the above object, the present invention is to inject a heated and melted raw material from the tip of a nozzle and pass it through a runner portion provided in a die, In an injection molding device for injecting into a communicating cavity to mold a product, a portion of the cavity connected to the runner portion is provided as a gate portion, and the raw material is provided so as to be movable corresponding to the gate portion. After being injected into the cavity, it moves to the gate portion side to release the raw material existing near the gate portion,
In addition, the main part is to have a gate cut member that closes the gate part.

Further, in order to achieve the above-mentioned object, the present invention ejects a heated and melted raw material from the tip of an injection nozzle, passes a runner portion provided in a mold, and communicates with the cavity. In the injection molding method of injecting into the product to mold the product, if the product has a mating surface that is not visible from the outside in a used state, a portion of the cavity connected to the runner portion is made to correspond to the mating surface of the product. A gate cut member provided as a gate part of the cavity and moved to the mold after the raw material is injected into the cavity so that it exists in the vicinity of the gate part. The main part is to allow the raw material to escape and to close the gate part in the mold to separate the molded product from the runner part side.

According to the above construction, after the raw material is injected into the cavity, the gate cut member is moved to the gate portion to close the gate portion in the mold, so that the width of the gate portion (gate cross-sectional area) is reduced. ) Can be widened, the pressure loss at the gate portion is small, and low pressure molding can be realized. In addition, the product-side or cavity-side gate is provided at a position that cannot be seen from the outside of the product, that is, in correspondence with the mating surface other than the design surface, so that the texture is not impaired and the gate marks do not remain. It can be performed accurately even when printing or labeling.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings. In the explanation of this mode, MD
A case of molding a disc cassette such as a (mini disc) is taken as an example, and FIG. 5 is a schematic external perspective view of the MD disc cassette. The cassette 1 has shells 2 and 2 (A, B) that are abutted against each other with a magneto-optical disk (not shown) inside to form a housing, and an opening / closing shutter 3 is provided on one side. Has been. Further, each shell 2 is formed with a plurality of notched portions 4 having different shapes for positioning the cassette 1 in the device or providing various information to the device.

FIG. 3 is a conceptual view of a mold which is a main part of an injection molding device for molding the shell 2. In FIG.
Reference numeral 5 showing the whole is a mold, and in this mold 5, there are eight cavities 6 corresponding to the shell 2 (1 to 1 in each rectangle).
8), and eight shells 2 are formed at the same time. Reference numeral 7 at the center is a nozzle side gate portion to which the nozzle 20A of the injection cylinder 20 (see FIGS. 1 and 2) is attached, and reference numeral 8 is a product (cavity) provided corresponding to each cavity 6.
A side gate portion, reference numeral 9 is a runner portion connecting the nozzle side gate portion 7 and each product side gate portion 8, and the gate cutting mechanism 1 is provided at a position corresponding to each product side gate portion 8.
0 (see FIGS. 1 and 2) is provided. The product-side gate portion 8 is provided by double hatching in FIG. 4, corresponding to the portion indicated by reference numeral 8a, that is, the mating surface 2a of the shell 2. As a matter of course, the mating surfaces 2a are in contact with each other when the cassette 1 is assembled and are invisible from the outside, that is, a portion other than the design surface.

1 and 2 are schematic cross-sectional views taken along the line AA of FIG. 3, and the main structure of the injection molding apparatus according to the present invention will be described in detail below with reference to FIGS. 1 and 2. The die 5 is composed of a fixed side female die 5A and a moving side male die 5B.
Further, the female die 5A is fixed to the fixed base 11 of the injection molding apparatus, and the male die 5B is also the movable base 1 of the injection molding apparatus.
It is fixed to 2. Then, the male die 5B can be moved to a position (molding position) in which the male die 5B is moved integrally with the movable side base 12 and is in contact with the female die 5A, and a position (product take-out placement) far away from the female die 5A. Has become. This movement is performed by a mold clamping cylinder mechanism (not shown). further,
The mold 5 is provided with a nozzle 20A of the injection cylinder 20 on the female mold 5A side corresponding to the nozzle side gate portion 7, and a raw material, that is, a resin, which is heated and melted in the injection cylinder 20 from the nozzle 20A. The material 13 (portion shown in a satin pattern in FIGS. 1 and 2) is injected, and this is injected into the corresponding cavity 6 through the nozzle side gate portion 7, the runner portion 9, and each product side gate portion 8 at a predetermined pressure. It In addition, such an injection molding apparatus is equipped with a protrusion mechanism for removing the molded product from the mold 5, a cooling mechanism for cooling the mold 5, and the like as other accessory mechanisms as in the conventional case.

Further, the product side gate portion 8 is provided at a portion corresponding to the runner portion 9 of each cavity 6 corresponding to the mating surface 2a of the product (shell 2), and has a rectangular shape in this embodiment. ing. In addition, the gate cutting mechanism 10 corresponds to each product side gate portion 8 and has a male type 5
It is provided on the B side, and is provided with a hydraulic cylinder 21, a piston rod 21A of the hydraulic cylinder 21, and a gate cut punch 22 which is a gate cut member connected via a coupling 23. The tip shape of the gate cut punch 22 is formed to be substantially the same as the sectional shape of the product side gate portion 8. The gate cut punch 22 receives the drive of the hydraulic cylinder 21 via the piston rod 21A and the coupling 23,
When moving forward from the male die 5B side to the product side gate portion 8,
The structure in which the gate portion 8 is closed by the tip of the gate cut punch 22 and the resin material 13 as a raw material existing in the vicinity of the gate portion 8 can be pushed into the runner portion 9 or the cavity 6 side to escape. It has become. 1 and 2, a portion indicated by reference numeral 24 is a guide member also serving as a stopper for guiding the movement of the gate cut punch 22.

The operation of the injection molding apparatus having the above structure will be described below. First, before and after the male die 5B is brought into contact with the female die 5A by a die clamping cylinder mechanism (not shown), as shown in FIG.
Is drawn into the male die 5B by the control of the hydraulic cylinder 21. In this state, the tip of the gate cut punch 22 is controlled so as to be moved to a position where a part of the runner portion 9 is formed as shown in FIGS.

Then, the resin material 13 heated and melted (for example, heated to about 210 ° C. in the case of ABS resin) is heated from the nozzle 20A arranged on the side of the female mold 5A to a predetermined pressure inside the injection cylinder 20. The resin material 13 is injected into the cavities 6 through the nozzle side gate portion 7, the runner portion 9 and the product side gate portion 8. FIG. 1 shows this state.

After the injection of the resin material 13 is completed and the initial pressure holding is performed, the hydraulic cylinder 21 is driven and the gate cut punch 22 is moved forward toward the product side gate portion 8. Then, the tip portion of the gate cut punch 22 moves forward while pushing the semi-molten resin material 13 in the runner portion 9 and in the vicinity of the product side gate portion 8 into the runner portion 9 and the cavity 6 to reach the final position. Then, the gate portion 8 is closed to separate the resin material 13 in the cavity 6 and the resin material in the runner portion 9 so that the products made in the cavity 6 are made independent.

On the other hand, the mold 5 side on which the resin material 13 has been injected is solidified in a short time because it is cooled with water or the like by the cooling mechanism and kept at a temperature of about 40.degree. Then, after that, a mold clamping cylinder mechanism (not shown) is driven, and the male die 5B is separated from the female die 5A. At this time, the gate cut punch 22 is also separated from the gate portion 8 together with the male die 5B. Further, when the male die 5B is returned to a predetermined position, the resin material 13 solidified in the die 5 is taken out via a projecting mechanism or the like. Then, the product (each shell 2) and the portion 9a corresponding to the runner portion 9 can be taken out in a completely separated state. FIG. 7 shows a part of the shell 2 which is a molded product immediately after being taken out from the mold 5, and the shell 2 is completely cut from the part 9a.

Therefore, in the injection molding apparatus according to this embodiment, the product (shell 2) having a substantially complete shape and the portion 9a corresponding to the discarded or unnecessary runner portion 9 can be taken out in a separated form from the beginning. Therefore, in addition to the work for separating the product from the runner, which was performed as a post-work in the conventional method, is unnecessary, the mark 8a of the product-side gate portion 8 cannot be seen from the outside of the product (shell 2), that is, the design. Since it is formed on the mating surface 2a other than the surfaces, the quality is not impaired and the quality can be improved. In addition, since there are no gate marks on the design surface, printing or labeling can be performed without any trouble. Moreover, since the gate cut punch 22 is moved to the product side gate portion 8 and the gate portion 8 is closed in the mold 5, the gate width (cross-sectional area of the gate portion 8) can be widened. Become. Thereby, the pressure loss of the product side gate portion 8 is small, low pressure molding can be realized, and the time for injecting the resin material 13 as the raw material can be shortened, so that the productivity is improved.

Although the product (cavity) side gate portion 8 of the above embodiment is provided corresponding to the flat mating surface 2a of the shell 2, other than this, for example, FIGS. The product (cavity) side gate portion 8 may be provided corresponding to the mating surface as shown. That is, FIGS. 8 and 9 show a mode in which the mating surface of the shell 2 has a notch 4 formed in a part thereof. In FIG. 8, a bottom surface of the cutout portion 4 is formed, and a mating surface 2b that is opposed to and is not closely attached to the mating shell 2 is shown. After molding, a portion corresponding to the product side gate portion 8 is denoted by a reference numeral 8a. Shows. In FIG. 9, there is a case where the notch portion 4 formed in a stepped shape is only partially adhered to the mating shell 2 (only the mating surface excluding the stepped stepped portion 2c is adhered). A portion corresponding to the side gate portion 8 is indicated by reference numeral 8a. In FIG. 10, the protruding wall 25 is provided on the mating surface 2a of the shoulder 2, and the portion corresponding to the product side gate portion 8 after molding is indicated by reference numeral 8a. Thus, in the mating surface of the present invention, when the stepped notch portion 4 as shown in FIG. 9 or the projecting wall 25 as shown in FIG. 10 is provided in a part of the mating surface, the notch portion 4 and the projecting wall The product-side gate portion 8 may be formed corresponding to each surface including each step of 25. Further, although the case where the resin material 13 is used as the raw material has been described, the present invention is not limited to this, and can be widely applied to the case of molding using a material having a property that becomes soft when heated and hardens when cooled.

[0018]

As described above, according to the present invention,
After the heated and melted raw material is injected into the cavity, the gate cut member is moved to the product side (cavity) side gate part, and the gate part is closed in the mold, so the width of the gate part (gate cross-sectional area) Therefore, the pressure loss at the gate portion is small, and low pressure molding can be realized. As a result, the time for injecting the raw material can be shortened without increasing the size of the apparatus, so that effects such as improvement in productivity can be obtained. Further, since the gate portion is provided at a position not visible from the outside of the product, that is, corresponding to a portion other than the design surface, the appearance quality can be improved without impairing the texture, and even when printing or labeling is performed. It can be done without trouble.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a main part of an injection molding apparatus shown as an example of one embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a main part showing the injection molding apparatus in different injection processes.

FIG. 3 is a conceptual diagram of an entire mold which is a main part of the injection molding device.

FIG. 4 is a perspective view of a main part of a product (cassette) made according to the present invention in an exploded manner.

FIG. 5 is an external perspective view showing a cassette that is an example of the product.

FIG. 6 is a cross-sectional view of essential parts taken along the line BB of FIG.

FIG. 7 is a cross-sectional view of a main part for explaining a product molded according to the present invention.

FIG. 8 is a diagram for explaining a modification of the mating surface of the present invention.

FIG. 9 is a diagram for explaining another modification of the mating surface.

FIG. 10 is a diagram for explaining still another modified example of the mating surface.

[Explanation of symbols]

 2 Shell (product) 5 Mold 5A Female mold 5B Male 6 Cavity 7 Nozzle side gate part 8 Product (cavity) side gate part 9 Runner part 10 Gate cut mechanism 13 Resin material (raw material) 20 Injection cylinder 20A Nozzle 22 Gate cut Punch (gate cut member)

Claims (6)

[Claims] 1. Injection for molding a product by injecting a heated and melted raw material from a tip of a nozzle, passing through a runner portion provided in a mold, and injecting into a cavity provided in communication with the runner portion. In the molding apparatus, a portion of the cavity connected to the runner portion is provided as a gate portion, and is provided so as to be movable corresponding to the gate portion, and after the raw material is injected into the cavity, the gate portion side An injection molding apparatus comprising: a gate cut member that moves to a position where the raw material existing in the vicinity of the gate portion escapes and that closes the gate portion. 2. The injection molding apparatus according to claim 1, wherein the product is a shell for a cassette that is assembled by being butted against each other, and the gate portion is provided corresponding to a mating surface of the shells. 3. An injection molding method for molding a product by injecting a heated and melted raw material from a tip portion of an injection nozzle, passing it through a runner portion provided in a mold, and injecting it into a cavity communicating with the runner portion. When the product has a mating surface that cannot be seen from the outside in use, a portion of the cavity that is connected to the runner portion is provided as a mating surface of the product, and is provided as a gate portion of the cavity. After being injected into the cavity, by moving a gate cut member movably provided in the mold to the gate portion,
An injection molding method, characterized in that the raw material existing in the vicinity of the gate part is released, and the gate part is closed in a mold to separate the molded product from the runner part side. 4. The injection molding method according to claim 3, wherein the product is a shell for a cassette assembled by being butted against each other. 5. The method according to claim 4, wherein the gate portion is formed on a part of a mating surface of the shell and provided corresponding to a stepped portion that is opposed to the shell on the mating shell without being in close contact with the mating shell. Injection molding method. 6. The injection molding method according to claim 4, wherein the gate portion is provided corresponding to each surface of a step portion formed in a part of the mating surface of the shell.