JP2717758B2 - Injection molding method and 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 a method of filling a cavity formed between a fixed mold and a movable mold with molten resin, opening the movable mold with respect to the fixed mold, and using a product projecting mechanism. The present invention relates to an injection molding method for removing a molded product and an injection molding die used for performing the method.

[0002]

2. Description of the Related Art An injection molding method for injecting a molten resin from an injection device into a cavity in a mold to obtain a product having a desired shape is well known without mentioning a document name. Both an injection device and an injection molding die used for carrying out this method are well known. The injection mold generally includes a fixed mold, a movable mold driven in a mold closing direction or a mold closing direction with respect to the fixed mold, and a product molded in the mold that is clamped. It is composed of a product projecting mechanism, that is, an ejector device.

[0003] A sprue is formed in the fixed mold, and a runner, a sprue is formed along a parting line between the movable mold and the fixed mold.
A gate is formed. Then, a cavity for forming the product over both the molds is formed. Therefore, when the cavity in the mold is filled with the molten resin from the injection device, a product having a desired shape is formed. When the mold is opened by the mold clamping device after cooling and solidification, the molded product is taken out by the ejector device. When the molded product is obtained as described above, the cavity before filling with the molten resin is filled with air, but this air is generally removed from the mating surface of each part of the mold by the action of the piston of the resin to be filled. You. In this way, the air or gas in the cavity escapes for the time being, but if the gas is not sufficiently removed, it may cause a failure of the molded product. In some cases, a small gap is provided on the bearing surface or the like.

[0004]

When a gap is provided between the parting surfaces of the movable mold and the fixed mold, compared with the case where gas in the cavity is extracted from the mating surface of each part of the mold,
The advantage that it can be reliably removed is recognized. However, there is a problem that it is difficult to adjust the gap. For example, if the gap is relatively wide, it is convenient for degassing. However, depending on the type of resin to be injected, when the cavity is filled with the molten resin, the molten resin enters the wide gap and causes burrs. On the other hand, if the gap is narrowed to prevent the resin from entering, the result is the same as the conventional case in which gas is released from the mating surface of each part of the mold, resulting in poor gas release. If the gas is not sufficiently released, it may cause molding defects such as burns, short shots, and poor appearance. Therefore, according to the present invention, an injection molding method and a molding method capable of inexpensively obtaining a high-quality molded product without generating burrs, short shots, etc., although gas which causes molding failure can be reliably removed. It is intended to provide an injection mold for use in carrying out the method.

[0005]

In order to achieve the above object, the present invention fills a cavity formed between a fixed mold and a movable mold with a molten resin, and fixes the movable mold to the fixed mold. In the injection molding method in which the mold is opened and the molded product is taken out by the product protruding mechanism, in the initial and middle stages of filling the molten resin, an atmosphere communication hole that opens the final filling portion of the cavity to the atmosphere is opened. Fill in the state,
In the final stage of the completion of the filling, the atmosphere communication hole is configured to be closed and filled by the product projecting mechanism. The invention according to the claims comprises a fixed mold, a movable mold, and a product projecting mechanism, wherein the fixed mold and the movable mold are provided with a cavity for molding a molded product, and a final filling portion thereof. Is connected to the atmosphere via an atmosphere communication hole, and the atmosphere communication hole is configured to be opened and closed by the product projecting mechanism 20.

[0006]

The invention described in claim 2 operates as follows. That is, for example, the molten resin is injected into a cavity formed between the fixed mold and the movable mold using an injection machine. At this time, in the initial and middle stages of filling the molten resin, the filling is performed with the air communication hole opened. When the filling progresses and approaches the final stage, the air communication hole is closed by the product projecting mechanism and the filling is performed. After cooling and solidification, the movable mold is opened with respect to the fixed mold, and the molded product is taken out by the product projection mechanism.

[0007]

Embodiments of the present invention will be described below. 1A is an overall view showing a cross section of a part of the first embodiment, FIG. 1B is an enlarged cross-sectional view of a main part, and FIG. 1C is an enlarged cross-section of a main part showing another embodiment. FIG. As is conventionally known, the mold includes a fixed mold 1 attached to a fixed-side mounting plate 34 and a movable mold 10 attached to a movable-side mounting plate 35. And, in the fixed mold 1,
The sprue bush 3 is fitted by the locating ring 2. The sprue bush 3 has a tapered cross section toward the movable mold 10 and communicates with the cavity 5 via a gate not shown in FIG. A runner 4 is formed across the fixed mold 1 and the movable mold 10, and the runner 4 is connected to the cavity 5. The cavity 5 is located far from the sprue bush 3. Therefore, when the molten resin is filled, the runner 4 is filled first, and then the cavity 5 is filled.

[0008] A movable mold 10 that forms a pair with the fixed mold 1 includes:
A plurality of guide holes 11, 12, 13, 14 are formed in the axial direction. And these guide holes 11, 12,
Ejector pins 21 and 22, a return pin 23, a sprue lock pin 24, and the like of an ejector device 20, which will be described later, are inserted through and guided to 13, 14 respectively. In FIG. 1B, the lower left end of the cavity 5 is a filling end portion 5 ', and the upper end of the guide hole 11 is open to the filling end portion 5' of the cavity 5. The movable mold 10 is provided with an air communication hole 15 opened at the upper end of the guide hole 11. As described above, since the guide hole 11 communicates with the filling end portion 5 ′ of the cavity 5, the filling end portion 5 ′ is opened to the atmosphere through the atmosphere communication hole 15. Reference numeral 31 in FIG. 1 indicates a guide bush, and a guide pin 32 is inserted through the guide bush 31 so that the movable mold 10 is guided with respect to the fixed mold 1. Reference numeral 33 denotes a spacer block.

The ejector device 20 has a protruding plate 25. The ejector pins 21 and 22, the return pin 23 and the sprue lock pin 24 are provided on the protruding plate 25. These ejector pins 21, 22, return pin 23, and sprue lock pin 24 are inserted into guide holes 11, 12, 13, 14 of movable mold 10 through holes formed in receiving plate 30. A spring 26 is provided between the lower surface of the receiving plate 30 and the upper surface of the protruding plate 25, and the protruding plate 25 is urged downward in FIG. Therefore, as shown in FIG. 1, when the movable mold 10 is clamped to the fixed mold 1, the upper ends of the ejector pins 21, 22, the return pin 24 and the sprue lock pin 23, and the mold 1 , A gap δ is formed between the parting line P and the lower surface of the cavity 5.

According to the present embodiment, there is a gap δ between the upper end of the ejector pins 21 and the like and the parting lines P of the dies 1 and 10 in the mold-clamped state. A device for filling the gap δ, for example, an ejector device or a hydraulic piston cylinder unit provided in an injection device is provided. However, the hydraulic piston cylinder unit is not shown in the figure. The ejector device and the hydraulic piston cylinder unit provided in the injection device are configured to synchronize with the injection cycle and to supply pressure oil to the cylinder to push the protruding plate 25 when the filling is nearly completed. When the protruding plate 25 is pressed, the upper ends of the ejector pins 21 and 22, the return pin 24 and the sprue lock pin 23 rise to the parting line P, and the air communication hole 15 is closed by the ejector pin 21. I have.

The injection-molded product can be taken out by further driving the protruding plate 25 by an ejector device or a hydraulic piston cylinder unit provided in the above-mentioned injection device. It can also be implemented as is well known in the art. That is, when the filling and cooling are completed and the mold is opened, the movable mold 10 retreats, and when the retreat limit is approached, the protruding lot prevents the receiving plate 30 from retreating. As a result, the ejector pins 21 and 22 relatively move forward. It is also possible to carry out such that the molded product is protruded from the dies 1 and 10.

Next, a description will be given of a forming example using the above-described apparatus. As shown in FIG. 1A, the movable mold 10 is clamped to the fixed mold 1. Then, since the protruding plate 25 is urged downward in the figure by the spring 25, the gap δ is provided between the upper end of the ejector pin 21 and the lower surface of the final filling portion 5 ′ of the cavity 5.
Can be. Of course, there is a gap δ between the upper end portions of the other ejector pins 22, return pins 24 and sprue lock pins 23 and the parting lines P of the dies 1 and 10.

The molten resin is injected and filled toward the cavity 5 by a conventionally well-known injection device including an injection cylinder, a screw driven in the cylinder, and the like. The resin is first filled in the runner 4 and then in the cavity 5. As the resin is filled, the gas filling the runner 4, the cavity 5, and the like is pushed out from the atmosphere communication hole 15 to the outside. As shown in FIG. 2A, when the cavity 5 is filled, that is, when the filling is nearly completed, the projecting plate is provided by the above-described ejector device or hydraulic piston cylinder unit provided in the injection device. 25 is driven upward in the figure. Then, ejector pins 21 and 22 and return pin 2
4 and the sprue lock pin 23 also rise, and the upper end reaches the parting line P. Then, the ejector pins 21 block the atmosphere communication holes 15. The closed state is shown in FIG. Inject further to finish filling. In FIG. 2, the filled resin is shown in black. After cooling and solidification, the movable mold 10 is opened. The protruding plate 25 is driven by an ejector device or a hydraulic piston cylinder unit provided in the injection device to take out the product. Alternatively, it is taken out by a conventionally known method as described above.

As described above, according to the present embodiment, during filling, the air communication hole 15 which is specially provided for degassing is opened, so that gas harmful to molding is almost completely discharged. Can be extruded. When the filling is nearly completed, the sealing is blocked, so that the molten resin does not leak into the air communication hole 15 and burrs do not occur.

In the above embodiment, the air communication hole 15 is provided as a through hole in the movable mold 10, but it may be formed as a groove along the parting line P. For example, as shown in FIG. 1C, an air communication groove 15 ′ having an open top is formed on the parting surface of the movable mold 10, and the air communication groove 15 ′ is formed between the guide hole 11 and the cavity 5. And an air communication hole. In this embodiment, when the ejector pins 21 are lowered, that is, when the filling of the resin is not completed, as shown in FIG. 1C, the air communication groove 15 ′ is connected to the guide hole 11 and the cavity. Since it is in communication with the final filling section 5 'of 5, the gas can be filled while removing gas as described above. In the final stage of filling, the ejector pins 21 are driven to close the atmosphere communication groove 15 ', and the filling is performed. According to the present embodiment, since the air communication groove 15 'is formed as a groove whose upper part is open, an effect that processing is easy and maintenance is easy can be obtained.

FIG. 3 shows a second embodiment of the present invention. According to the present embodiment, in addition to the protruding plate 25, the second protruding plate 25 'is provided so as to be vertically overlapped. The same reference numerals are given to the same elements as those of the above-described embodiment, and the description will not be repeated.
The ejector pin 21 that opens and closes is mounted on the protruding plate 25. The ejector pins 21 penetrate the second protruding plate 25 'loosely, and have no direct relationship with the second protruding plate 25'. Therefore, the second protruding plate 2
When the tip of the return pin abuts the fixed-side member shortly before closing the mold, the tip of the ejector pin 22 ′ provided on 5 ′ becomes the same as the lower surface of the cavity 5. However, since the springs 26, 26 are provided between the protruding plate 25 and the second protruding plate 25 ',
The protruding plate 25 is pushed down, and the upper end of the ejector pin 21 provided on the protruding plate 25 and the partitioning line P
Is formed between them.

It is clear that the present embodiment can be formed in the same manner as the above-described embodiment. According to the present embodiment, the ejector pin 2 located at the filling end 5 ′
1 is driven to open and close in the vertical direction, and the second protruding plate 25 '
The tip of the ejector pin 22 ′ provided on the first hole is the same as the lower surface of the second cavity 5, so that when filling, the molten resin is filled in the guide hole 1 of the ejector pin 22 ′.
It doesn't flow into 4 '. The atmosphere communication hole 1
It is clear that 5 can be formed as an air communication groove 15 'along the parting line P, similarly to the above-described embodiment.

[0018]

As described in detail above, according to the present invention,
In the initial and middle stages of filling the molten resin, filling is performed in a state where the air communication hole that opens the final filling part of the cavity to the atmosphere is open. The effect peculiar to the present invention that the resin to be filled can be reliably pulled out or pushed out through the air communication hole without using a special device is obtained. In addition, in the final stage of the completion of the filling, since the atmosphere communication hole is closed by the product projecting mechanism and the filling is performed, the molten resin does not enter the air communication hole and burrs and the like do not occur. Furthermore, since the atmosphere communication hole communicates with the final filling part of the cavity, there is no gas accumulation compared to the conventional gap provided in the mere parting line. The effect that can be obtained is also obtained.

[Brief description of the drawings]

FIG. 1 is a view showing a first embodiment of the present invention, wherein (a) is a front view showing a part of the cross section, (b) is an enlarged sectional view of a main part, and (c) is another embodiment. It is an expanded sectional view of the important section showing.

FIGS. 2A and 2B are enlarged cross-sectional views of a main part showing the operation of the present embodiment. FIG. 2A is a cross-sectional view schematically showing the state near the end of filling, and FIG.

FIG. 3 is a front view showing a second embodiment of the present invention with a part thereof in section.

[Explanation of symbols]

1 Fixed mold 5
Cavity 5 'Final filling part 10
Movable mold 15 Atmospheric communication hole 15 '
Atmosphere communication groove 20 Ejector device (product projection device) 21 Ejector pin

Claims (2)

(57) [Claims] Cavities (4, 5) formed over a fixed mold (1) and a movable mold (10) are filled with molten resin, and the movable mold (10) is fixed to the fixed mold (1). )
In the injection molding method in which the mold is opened and the molded product is taken out by the product projecting mechanism (20, 21), in the initial and middle stages of filling the molten resin, the final filling part (5 ') of the cavity (5) is removed. The air communication holes (15, 15 ') open to the atmosphere are filled in an open state, and at the final stage of the completion of the filling, the air communication holes (15, 15') are filled.
5 ') is closed and filled by a product projecting mechanism (20, 21). 2. A fixed mold (1) and a movable mold (10).
And a product protruding mechanism (20, 21). The fixed mold (1) and the movable mold (10) are provided with a cavity (5) for molding a molded article, and a final filling portion (5 ') Communicates with the atmosphere through the atmosphere communication holes (15, 15') and the atmosphere communication holes (15, 15 ').
Is opened and closed by said product projection mechanism (20, 21).