JPH0716864A - Production of molded product and injection molding apparatus - Google Patents

Abstract

PURPOSE:To easily control the wall thickness of a molded product and the forming position of a reinforcing rib by a method wherein a thermoplastic resin is injected into a mold cavity as a raw material in a molten state and the volume of the mold cavity is expanded while or after compressed gas is introduced into the injected molten resin under pressure to provide a large hollow part. CONSTITUTION:An injection molding apparatus is set to a clamping state to form a mold cavity 9. A molten resin is injected into the mold cavity 9 and compressed gas is introduced into the molten resin under pressure from a compressed gas inlet 4. The volume of the mold cavity 9 is expanded after or while the compressed gas is introduced into the molten resin under pressure. At the time of the expansion of the volume of the mold cavity 9, a movable core 3 is allowed to retreat by the resin injection pressure remaining in the molten resin injected into the mold cavity 9, the pressure of the compressed gas and the operation of the low oil pressure supply means provided to the movable plate moving hydraulic mechanism C of a molding machine. By this constitution, a hollow molded product uniform in thickness and excellent in strength and appearance can be efficiently produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a molded article having a hollow structure by an injection molding method, and an injection molding apparatus suitable for carrying out this method. More specifically, a thermoplastic resin is used as a raw material and is injected into the mold cavity in a molten state. While the pressurized gas is being injected into the injected molten resin, or after the injection, the volume of the mold cavity is increased. Thus, the present invention relates to a method for producing a molded product having a large hollow portion, and an injection molding apparatus suitable for carrying out this method.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a molded article having a hollow structure by an injection molding method, after injecting an insufficient amount of molten resin into the mold cavity of a mold, or by injecting On the other hand, a method of pressurizing a pressurized gas to press the molten resin against the outer peripheral portion of the mold cavity to obtain an object has been proposed (for example, JP-B-57-14968 and JP-B-61-53208). JP-A-3-98
No. 20, JP-A-4-35709, etc.).

By the way, conventionally, a technique for expanding the volume of a mold cavity when a molded product having a hollow structure is manufactured by an injection molding method is disclosed in JP-A-3-9820 and JP-A-4-9820.
No. 3,570,091 and the like. In particular, a molded product having a large hollow structure has a problem that the strength of the outer wall surface of the molded product is weakened. To solve this problem, JP-A-4-35709 discloses a molded product having a reinforcing rib in the hollow portion. An injection mold having a special structure suitable for manufacturing a product and a molding method using the same have been proposed.
However, in the case of these conventionally proposed techniques, there is still some uncertainties about the strength of the outer wall of the molded product, the strength of the reinforcing ribs formed in the hollow part, and the appearance of the molded product is poor. There was a problem such as doing.

[0004]

The inventors of the present invention, when manufacturing a molded product having a hollow structure by an injection molding method, have uniform wall thickness of the molded product and strength in reinforcing ribs formed in the hollow portion. As a result of intensive studies aimed at obtaining a molded product with excellent appearance without any anxiety, it was found that the above-mentioned drawbacks of the prior art depend on the volume expansion technology of the mold cavity, and based on this finding, The invention has been completed.

[0005]

SUMMARY OF THE INVENTION The gist of the present invention is, however, that a sprue and a pressurized gas inlet are provided and a concave shape is formed when a molded product having a hollow portion inside is manufactured by an injection molding method. A fixed mold having a mold cavity forming surface, a movable mold capable of forming a parting surface with the fixed mold, and a fixed mold slidably disposed through substantially the center hole of the movable mold. A step of forming a mold cavity of a molded product at the forward position of the movable insert by means of a movable insert capable of moving forward and backward, injecting a molten resin into the mold cavity, and adding the molten resin into the molten resin. While pressurizing the pressurized gas from the pressurized gas inlet, or after pressing it,
While maintaining the state in which the movable die is pressed to the fixed die side by the elastic force of the spring, the movable insert is set to the elastic force of the spring, the resin pressure of the molten resin injected in the die cavity,
The process of expanding the volume of the mold cavity by retracting it by the action of the gas pressure of the pressurized gas pressed into the molten resin and the operation of the low hydraulic pressure supply means provided in the movable platen moving hydraulic mechanism of the molding machine. After the product is cooled, it is moved by the low hydraulic pressure supply means provided in the movable platen moving hydraulic mechanism of the molding machine through the movable insert and the connecting metal fitting that connects the movable insert and the outside of the movable die. The mold is set back and separated from the fixed mold, and a method for producing a molded product, comprising a step of releasing the molded product from the mold cavity and taking it out, and a sprue and a pressurized gas inlet are provided, and
A fixed die having a concave die cavity forming surface, a movable die capable of forming a parting surface with the fixed die, and a movable die which is slidably disposed so as to penetrate substantially the center hole of the movable die. With a movable insert that can move forward and backward with respect to the mold,
In an injection molding apparatus in which a mold cavity of a molded product is formed at the forward position of the movable insert, and the volume of the mold cavity can be expanded by retracting the movable insert, a movable plate of the movable insert is mounted on a movable platen. A base plate is formed in the contacting portion, one surface of the movable die forms the parting surface of the fixed die and the injection molding die, and the surface opposite to the surface forming the parting surface of the movable die is formed. A plurality of pairs of holes having a shaft parallel to the moving axis of the movable insert are formed on the surface, facing the surface of the base plate portion of the movable insert and facing each other. A spring is inserted into the formed hole, and the movable die and the base plate portion are connected by a connecting metal fitting installed on the outside of both, and when the die is clamped, the hydraulic mechanism of the molding machine resists the repulsive force of the spring. The mold is clamped and the volume of the mold cavity is increased. Repulsive force, the resin pressure of the molten resin injected in the mold cavity, the action of the gas pressure of the pressurized gas injected into the molten resin, and the low hydraulic pressure supply means provided in the movable platen moving hydraulic mechanism of the molding machine. When the molded product is released from the mold, the movable insert and the outside of the movable insert and the movable mold are connected by the low hydraulic pressure supply means provided in the movable plate moving hydraulic mechanism of the molding machine. The injection molding apparatus is characterized in that the movable mold can be retracted through a connecting fitting.

The present invention will be described below in detail with reference to the drawings. The drawings conceptually show one embodiment of the present invention. FIG. 1 shows a state before the mold cavity volume of an injection molding die is expanded, and FIG. 2 shows a state after the mold cavity volume is expanded. FIG. 2 is a schematic side view in vertical section showing each state. Figure 3
[Fig. 10] Fig. 10 shows another embodiment, and is a schematic vertical cross-sectional side view showing a state after the mold cavity volume has been expanded. FIG. 4 is a partially enlarged side view of the connecting fitting that acts when the injection molding die is opened.

In the drawing, A is a molding machine fixed plate, B is a molding machine movable plate, C is a movable platen moving mechanism, D is a molding machine tie bar,
1 is a fixed type, 2 and 52 are movable types, 3 and 53 are movable inserts,
3a, 3a 'is a base plate part, 3b, 3b' is a base part, 4 is a pressurized gas inlet, 5 is a sprue, 5a is a runner, 6 is a pressurized gas injection nozzle, 7 is a small hole, 8 is a check valve. , 9 is a mold cavity, 10 and 40 are hollow parts of a molded product, 11 and 11 'are springs, 12, 12', 13 and 13 'are spring holes, 14 is a hydraulic ram, 15 is a hydraulic cylinder, and 15a.
Is the rear chamber of the hydraulic cylinder, 15b is the front chamber of the hydraulic cylinder,
16 and 17 are directional valves, 18, 19 and 20 are pressure regulating valves, 21 is a speed control valve, 22 is a pump, 23 is an oil tank, 24, 25, 26, 27, 28, 29 and 30.
Is a conducting tube, 44 is a convex portion formed on the mold cavity surface at the tip of the movable insert, 45 is a reinforcing rib of the hollow portion of the molded product, 50,
50 'is a connecting tool, 51 is a connecting rod, 52a is a movable outer surface, 53a is a movable insert outer surface, 54 is a fixing metal fitting, 55 is a connecting rod guide metal fitting, and x and y are ends of the connecting rod.

Hereinafter, a method of manufacturing a molded product and an injection molding apparatus according to the present invention will be described with reference to FIGS. 1 and 2.
The present invention is not limited to the following examples. The fixed mold 1 fixed to the molding machine fixing plate A is provided with a sprue 5 and a pressurized gas inlet 6, and has a concave mold cavity forming surface. In FIG. 1, the sprue 5 and the pressurized gas inlet 6 are provided separately, but they do not necessarily have to be provided separately, but they may be provided at the same place. When they are provided at the same place, a molten resin nozzle with a pressurized gas inlet may be used.

The movable die fixed to the movable platen B of the molding machine at the base plate portions 3a and 3a 'is composed of a movable insert 3 and a movable die 2. The movable mold 2 has a movable insert 3 at the center thereof.
Has a through hole formed so that the outer surface of the can slides on the inner surface thereof. The movable mold 2 normally moves when the mold is opened along with the movement of the movable platen B of the molding machine, but as will be described later,
When the volume of the mold cavity 9 is expanded, when the mold is opened, and when the mold is clamped, different movements from the movable insert 3 are possible.

The movable insert 3 is controlled by the movement of the movable platen B of the molding machine and slides in the hole formed in the movable die 2,
The fixed mold 1 can be moved forward and backward. The mold cavity 9 for resin molding is formed by the concave mold cavity forming surface of the fixed mold 1, the extension surface of the parting surface forming surface of the movable mold 2, and the mold cavity forming surface of the movable insert.

When a convex portion 44 is provided at the tip of the movable insert 3 which constitutes the mold cavity 9 as shown in FIG. 3, a reinforcing rib 45 is formed in the hollow portion, so that the wall surface of the molded product can be reinforced. It is preferable because it is possible. The convex portion 4 is provided at the tip of the movable insert 3.
4 is used, the molten resin between the convex portions and the mold cavity surface of the fixed mold 1 facing the convex portions is cooled earlier than the molten resin in the cavity portion having no convex portion, so that the molten resin is melted. When the pressurized gas is pressed into the resin and the movable insert 3 is retracted to expand the volume of the mold cavity, the pressurized gas easily enters the high temperature resin portion and hardly enters the cooled resin portion. The reinforcing rib 45 remains in the hollow portion of the molded product, and acts to reinforce the wall surface of the molded product.

The shape of the convex portion 34 is preferably a trapezoidal cross section at the tip, but is not limited to this, and the cross section may be a mountain shape, a circular shape or the like. Depending on the design of the reinforcing ribs to be provided in the molded product, this convex portion may be formed by forming a plurality of straight lines at regular intervals, arbitrarily forming a plurality of curved lines or forming concentric circles, or combining straight lines and curved lines. Can be The shape, size, arrangement density, etc. of the convex portions can be appropriately determined depending on the shape, size, structure, application, etc. of the molded product.

The movable die 2 allows the movable insert 3 to slide through a through hole, forms a die cavity 9, and forms a parting surface between the stationary die 1 and the injection molding die, and further forms a parting surface. Forming surface and base 3 of movable insert 3
It has a function of holding the springs 11 and 11 'between b and 3b'. The springs 11 and 11 'are movable nests 3
The base parts 3b and 3b 'of the movable die 2 and the surface opposite to the surface forming the parting surface of the movable die 2 are opposed to each other, and both surfaces opposed to each other are parallel to the movement axis of the movable insert 3. A plurality of pairs of holes 12, 12 ', 13, 1 drilled to have an axis
It is inserted in 3 '. The springs 11 and 11 ′ inserted into these holes are clamped against the repulsive force of the spring by the movement of the molding machine movable platen moving mechanism C during mold clamping, and when the volume of the mold cavity is expanded, The repulsive force of the springs 11 and 11 ′ presses the movable die 2 against the fixed die 1 to prevent the parting surface from opening.

The volume expansion of the mold cavity is effected not only by the repulsive force of the springs 11 and 11 ', but also by the resin pressure of the molten resin injected into the mold cavity 9 and the gas pressure of the pressurized gas injected into the molten resin. , And by operating the low hydraulic pressure supply means provided in the movable platen moving hydraulic mechanism C of the molding machine, the mold opening is achieved by operating the movable platen moving hydraulic mechanism C, respectively.

The movable plate moving hydraulic mechanism C of the molding machine has a hydraulic ram 14 as shown in the schematic vertical sectional side views of FIGS.
And a drive unit comprising a hydraulic cylinder 15; a pump 2
2, a pressure adjusting valve 20 and a speed control valve 21, a high hydraulic pressure supply means for transmitting a high hydraulic pressure into the hydraulic cylinder rear chamber 15a, a pump 22 and a pressure adjusting valve 19, and a low pressure inside the hydraulic cylinder front chamber 15b. A drive unit for the hydraulic ram 14, which includes a low hydraulic pressure supply unit for transmitting hydraulic pressure, a pressure adjusting valve 18, and a hydraulic release unit for discharging oil in the hydraulic cylinder front chamber 15b and the hydraulic cylinder rear chamber 15a;
Consists of.

When the volume of the mold cavity is expanded, the movable platen B of the molding machine is moved backward and the movable insert 3 fixed to the movable platen B is adjusted. The retracted distance and the retracted speed at this time are accurately adjusted. Although necessary, this adjustment can be performed by operating the movable platen moving hydraulic mechanism C. In order to retreat the molding machine movable plate B in order to expand the volume of the mold cavity, the pump 22 of the low hydraulic pressure supply means shown in FIG. Regulator valve 19, directional switching valve 17, conducting pipe 25, directional switching valve 16, conducting pipe 2
6 into the hydraulic cylinder front chamber 15b, and at the same time, the oil in the hydraulic cylinder rear chamber 15a is passed through the passage pipe 27 of the hydraulic pressure releasing means to the direction switching valve 16, the passage pipe 26, and the pressure adjusting valve 18, and then the passage. The oil is discharged from the pipe 29 to the oil tank 23. As a result, the hydraulic ram 14 of the molding machine movable plate B drive unit is retracted. The backward speed of the movable platen B of the molding machine is adjusted by the hydraulic cylinder front chamber 15b and the hydraulic cylinder rear chamber 1
By properly adjusting the balance of internal pressure with 5a,
It is possible. Further, the retreat distance of the molding machine movable platen B can be set and adjusted by using the retreat distance of the hydraulic ram 14 by using a positioning means such as a limit switch (not shown).

After the volume of the mold cavity is expanded, the molded product is cooled while keeping the volume of the mold cavity, and after cooling is completed, the mold is opened and the molded product is taken out. Mold opening is a movable insert 3
Is further retracted from the position where the mold cavity volume is enlarged by the movable platen moving hydraulic mechanism C, and the movable mold is parted through the coupling tools 50 and 50 'which connect the outside of the movable insert and the movable mold. Achieved by moving away from the surface. Then, the molded product is released from the mold cavity and taken out. The coupling tools 50 and 50 'are composed of a fixing metal fitting 54 fixed to the movable outer surface 52a, a connecting rod guide metal fitting 55 fixed to the movable insert outer surface 53a, and connecting rods 51 and 51'. A nut or the like is attached to both ends of the connecting rods 51 and 51 ', and one end x is fixed through a hole provided through the fixing metal fitting 54. The connecting rod itself is the connecting rod guide metal fitting 5.
5 is slidably passed through a hole penetrating 5 and the other end y is arranged without being fixed (see FIG. 4A).

When the mold is opened, the movable insert 53 is moved to the left side in FIG. 4, and the connecting rod end y contacts the connecting rod guide fitting 55 fixed to the movable insert outer side surface 53a to move to the left side. The movement is transmitted to the movable die 52 via the connecting rod 51 and the fixing metal fitting 54 (see FIG. 4B), and the movable die 52 is moved.
Is separated from the parting surface, and a space sufficient for dropping the molded product is formed between the fixed mold and the movable mold. When opening the mold for taking out the molded product, the hydraulic ram 14 is also used.
The retreat distance can be set and adjusted by using a means other than the positioning means such as the limit switch for expanding the mold cavity volume.

When the movable platen B of the molding machine is advanced and the mold is clamped, oil of a constant pressure is supplied from the pump 22 of the high-pressure supply means shown in FIG. It is sent into the hydraulic cylinder rear chamber 15a through the valve 20, the speed control valve 21, the direction switching valve 17, the communication pipe 25, the direction switching valve 16, and the communication pipe 27, and at the same time, the oil in the hydraulic cylinder front chamber 15b is released into the hydraulic pressure releasing means. Through the conduit 26 of
The oil is discharged to the oil tank 23 through the direction switching valve 16, the conduit pipe 28, the pressure adjusting valve 18, and then the conduit pipe 29. by this,
The hydraulic ram 14 of the molding machine movable plate B drive unit moves forward.

Next, a method for producing a molded article having a hollow structure by using the injection molding apparatus according to the present invention will be described. First, as shown in FIG. 1, the injection molding apparatus is clamped to form the mold cavity 9. Next, the molten resin is injected into the mold cavity 9, and the pressurized gas is injected into the molten resin through the pressurized gas inlet 4. Examples of the resin that can be used at this time include thermoplastic resins used for injection molding, and various resin additives may be blended therein as necessary. Examples of the pressurized gas that can be used at this time include air, helium gas, carbon dioxide gas, nitrogen gas and the like, among which air and nitrogen gas are preferable.

After pressurizing the pressurized gas into the molten resin, or while pressurizing it, the volume of the mold cavity 9 is expanded. The volume expansion of the mold cavity 9 is movable by the resin injection pressure remaining in the molten resin injected into the mold cavity 9, the pressure of the pressurized gas, and the operation of the low hydraulic pressure supply means provided in the movable plate moving hydraulic mechanism C of the molding machine. This is achieved by retracting the nest 3. The retreat speed, retreat distance, retreat timing, etc. of the movable insert 3 will vary depending on the shape, size, structure, application of the molded product, but several shots of test molding are carried out for each molded product, and suitable conditions are set appropriately I can decide. In addition,
While expanding the volume of the mold cavity 9 and while cooling the molded product, the movable mold 2 is pressed toward the fixed mold 1 by the biasing force of the springs 11 and 11 'so that the parting surface does not open. Need to be maintained.

A molded product having a hollow structure is cooled, the mold is opened, the mold is released, and the mold is taken out while the volume of the mold cavity 9 is still expanded. After cooling the molded product, the movable insert 3 is further retracted from the position where the mold cavity volume is expanded by the operation of the low hydraulic pressure supply means provided in the movable platen moving hydraulic mechanism C of the molding machine, and the movable mold 2 is As described above, the mold 50 is separated from the fixed mold 1 and the molded product is separated from the mold cavity via the coupling tools 50 and 50 ′ arranged outside the movable mold 2 and the movable insert 3 as already described. . After taking out the molded product, the mold can be clamped and the next shot can be molded.

According to the method of the present invention, the field of home electric appliances such as outer boxes such as radios and televisions, televisions, and mounting bases for electrical equipment; personal computers,
Office computers, copiers, printer housings, and other office automation equipment products; various shelves, toilet seats, toilet lids, etc.

[0024]

INDUSTRIAL APPLICABILITY The present invention has the following particularly remarkable effects, and its industrial utility value is extremely large. (1) According to the method of the present invention, it is easy to control the wall thickness of the molded product, the formation position of the reinforcing ribs, etc., and the molded product having a hollow structure with a uniform wall thickness and excellent strength and excellent appearance is efficiently used. Can be manufactured in a simple manner. (2) Since the injection molding apparatus according to the present invention is provided with the movable insert that can move forward and backward with respect to the fixed mold, and the volume of the mold cavity can be expanded, a molded product having a large hollow portion can be manufactured. . (3) In the injection molding apparatus according to the present invention, since the movable insert is moved forward and backward by the low hydraulic pressure supply means provided in the movable platen moving hydraulic mechanism C of the molding machine, the volume expansion timing of the mold cavity, the volume expansion speed, The amount of enlargement and the like can be easily adjusted.

[Brief description of drawings]

FIG. 1 is a conceptual view showing an embodiment of the present invention, and is a schematic vertical cross-sectional side view showing a state before the mold cavity volume of an injection molding mold is enlarged.

FIG. 2 is a conceptual diagram showing an embodiment of the present invention, and is a schematic vertical cross-sectional side view showing a state after the volume of the mold cavity of the injection molding mold is enlarged.

FIG. 3 is a conceptual view showing another embodiment of the present invention, and is a schematic vertical cross-sectional side view showing a state after the volume of the mold cavity of the injection molding mold is enlarged.

FIG. 4 is a conceptual view showing an embodiment of the present invention, and is a partially enlarged side view schematically showing a connecting metal fitting that acts when the injection mold is opened.

[Explanation of symbols]

 A: Molding machine fixed plate B: Molding machine movable plate C: Movable platen moving mechanism D: Molding machine tie bar 1: Fixed mold 2, 52: Movable mold 3, 53: Movable insert 3a, 3a ': Base plate part 3b, 3b ': base part 4: pressurized gas inlet 5: sprue 5a: runner 6: pressurized gas injection nozzle 7: fine hole 8: check valve 9: mold cavity 10, 40: hollow part of molded product 11 and 11' : Spring 12, 12 ', 13, 13': Spring hole 14: Hydraulic ram 15: Hydraulic cylinder 15a: Hydraulic cylinder rear chamber 15b: Hydraulic cylinder front chamber 16, 17: Direction switching valve 18, 19, 20: Pressure adjustment Valve 21: Speed control valve 22: Pump 23: Oil tank 24, 25, 26, 27, 28, 29, 30: Conducting pipe, 44: Convex part, 45: Reinforcing rib of hollow part of molded product 50, 50 ': Connector 51: connecting rod 52 : Mobile outer surface 53a: movable insert outer surface 54: fixing bracket 55: connecting rod guide bracket x, y: end of the connecting rod

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[Procedure amendment]

[Submission date] May 20, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction content]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a molded article having a hollow structure by an injection molding method, and an injection molding apparatus suitable for carrying out this method. More specifically, a thermoplastic resin is used as a raw material, and this is injected into a mold cavity in a molten state, and a volume of the mold cavity is expanded while or while pressurizing a pressurized gas into the injected molten resin. And a method for producing a molded product having a large hollow portion, and an injection molding apparatus suitable for carrying out this method.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

[0004]

The inventors of the present invention, when manufacturing a molded product having a hollow structure by an injection molding method, have uniform wall thickness of the molded product and strength in reinforcing ribs formed in the hollow portion. As a result of intensive studies for the purpose of obtaining a molded product having an excellent appearance without any anxiety, it was found that the drawback of the above-mentioned conventional technique is the technique for expanding the volume of the mold cavity, and based on this finding, the present invention Is completed.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

In the drawing, A is a molding machine fixed plate, B is a molding machine movable plate, C is a movable platen moving mechanism, D is a molding machine tie bar,
1 is a fixed type, 2 and 52 are movable types, 3 and 53 are movable inserts,
3a, 3a 'is a base plate part, 3b, 3b' is a base part, 4 is a pressurized gas inlet, 5 is a sprue, 5a is a runner, 6 is a pressurized gas injection nozzle, 7 is a small hole, 8 is a check valve. , 9 is a mold cavity, 10 and 40 are hollow parts of a molded product, 11 and 11 'are springs, 12, 12', 13 and 13 'are spring holes, 14 is a hydraulic ram, 15 is a hydraulic cylinder, and 15a.
Is the rear chamber of the hydraulic cylinder, 15b is the front chamber of the hydraulic cylinder,
16 and 17 are directional valves, 18, 19 and 20 are pressure regulating valves, 21 is a speed control valve, 22 is a pump, 23 is an oil tank, 24, 25, 26, 27, 28, 29 and 30.
Is a conducting tube, 44 is a convex portion formed on the mold cavity surface at the tip of the movable insert, 45 is a reinforcing rib in the hollow portion of the molded product, 50, 5
0'is a connecting tool, 51 is a connecting rod, 52a is a movable outer surface,
53a is an outer surface of the movable insert, 54 is a fixed metal fitting, 55 is a connecting rod guide metal fitting, and x and y are end portions of the connecting rod.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

Hereinafter, a method of manufacturing a molded product and an injection molding apparatus according to the present invention will be described with reference to FIGS. 1 and 2.
The present invention is not limited to the following examples. The fixed mold 1 fixed to the molding machine fixing plate A is provided with a sprue 5 and a pressurized gas inlet 6, and has a concave mold cavity forming surface. In FIG. 1, the sprue 5 and the pressurized gas inlet 6 are provided separately, but they need not necessarily be provided separately and may be provided at the same place. When they are provided at the same place, a molten resin nozzle with a pressurized gas inlet may be used.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

The shape of the convex portion 44 is preferably a trapezoidal cross section at the tip, but is not limited to this, and the cross section may be a mountain shape, a circular shape, or the like. The protrusions may be arranged such that a plurality of straight lines are formed at regular intervals, a plurality of curved lines are formed arbitrarily or concentric circles are formed, depending on the design of the reinforcing rib to be provided in the molded product, or It is possible to use a combination of a linear shape and a curved shape. The shape, size, arrangement density, etc. of the convex portions can be appropriately determined depending on the shape, size, structure, application, etc. of the molded product.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

When expanding the volume of the mold cavity, the movable platen B of the molding machine is moved backward, and the movable insert 3 fixed to the movable platen B is moved backward. At this time, the retracted distance and the retracted speed are accurately adjusted. However, this adjustment can be performed by operating the movable platen moving hydraulic mechanism C. In order to retreat the molding machine movable plate B in order to expand the volume of the mold cavity, the pump 22 of the low hydraulic pressure supply means shown in FIG. Regulator 1
9, through the direction switching valve 17, the conduit 25, the direction switching valve 16, and the conduit 28, it is sent into the hydraulic cylinder front chamber 15b, and at the same time, the oil in the hydraulic cylinder rear chamber 15a is passed through the conduit 27 of the hydraulic releasing means. , Direction switching valve 16, conduit 2
6 and the pressure regulating valve 18 and then the conduit 29 to discharge the oil to the oil tank 23. As a result, the hydraulic ram 14 of the molding machine movable plate B drive unit is retracted. The backward speed of the movable platen B of the molding machine can be adjusted by appropriately adjusting the balance of the internal pressures of the hydraulic cylinder front chamber 15b and the hydraulic cylinder rear chamber 15a. Further, the retreat distance of the molding machine movable platen B is determined by using the retreat distance of the hydraulic ram 14 by using a positioning means such as a limit switch (not shown).
It can be set and adjusted.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

After the volume of the mold cavity is expanded, the molded product is cooled while keeping the volume of the mold cavity, and after cooling is completed, the mold is opened and the molded product is taken out. Mold opening is a movable insert 3
Is further retracted from the position where the mold cavity volume is enlarged by the movable platen moving hydraulic mechanism C, and the movable mold is parted through the coupling tools 50 and 50 'which connect the outside of the movable insert and the movable mold. Achieved by moving away from the surface. The coupling tools 50 and 50 ′ are composed of a fixing metal fitting 54 fixed to the movable outer surface 52 a, a connecting rod guide metal fitting 55 fixed to the movable insert outer surface 53 a, and a connecting rod 51. A nut or the like is attached to both ends of the connecting rod 51, one end x is fixed through a hole formed through the fixing metal fitting 54, and the rod itself of the connecting rod is installed through the connecting rod guide metal fitting 55. The other end y is arranged so as not to be fixed (see FIG. 4A).

[Procedure Amendment 8]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

According to the method or apparatus according to the present invention, the field of home electric appliances such as outer boxes such as radios and televisions, televisions, mounting bases for electric appliances, personal computers, office computers, copying machines, printer housings, etc. OA equipment product field; various sundries such as various kinds of shelves, toilet seats and toilet lids; automotive fields such as automobile knobs; and various hollow structure molded articles can be easily manufactured.

[Procedure Amendment 9]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

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Claims (4)

[Claims] 1. When manufacturing a molded product having a hollow portion inside by an injection molding method, a fixed mold provided with a sprue and a pressurized gas inlet and having a concave mold cavity forming surface, and this fixed mold. The movable die that can form a parting surface and the movable insert that is slidably disposed through the substantially central hole of the movable die and that can move forward and backward with respect to the fixed die A step of forming a mold cavity of a molded product at the forward position of the nest, injecting a molten resin into the mold cavity, and pressurizing or injecting a pressurized gas into the molten resin from the pressurized gas inlet. rear,
While maintaining the state in which the movable die is pressed to the fixed die side by the elastic force of the spring, the movable insert is set to the elastic force of the spring, the resin pressure of the molten resin injected in the die cavity,
The process of expanding the volume of the mold cavity by retracting it by the action of the gas pressure of the pressurized gas pressed into the molten resin and the operation of the low hydraulic pressure supply means provided in the movable platen moving hydraulic mechanism of the molding machine. After the product is cooled, it is moved by the low hydraulic pressure supply means provided in the movable platen moving hydraulic mechanism of the molding machine through the movable insert and the connecting metal fitting that connects the movable insert and the outside of the movable die. A method for producing a molded product, which comprises the steps of retracting the mold to separate it from the fixed mold, releasing the molded product from the mold cavity, and taking it out. 2. The method for producing a molded article according to claim 1, wherein the volume expansion speed of the mold cavity is adjusted by a low hydraulic pressure supply means provided in the movable platen moving hydraulic mechanism. 3. A fixed mold provided with a sprue and a pressurized gas inlet and having a concave mold cavity forming surface, a movable mold capable of forming the fixed mold and a parting surface, and substantially the center of the movable mold. A mold cavity of a molded product is formed at a forward position of the movable insert by a movable insert that is slidably disposed through the hole and is movable forward and backward with respect to the fixed mold; In an injection molding device in which the volume of the mold cavity can be expanded by retracting the movable insert, a base plate is formed in the portion of the movable insert that contacts the movable plate of the molding machine, and one surface of the movable mold is formed. Forms the parting surface of the fixed mold and the injection molding die, and the surface opposite to the surface forming the parting surface of the movable die faces the surface of the base plate part of the movable insert. Flatten the moving axis of the movable insert on both surfaces facing each other. A plurality of pairs of holes having a row axis are drilled, and springs are fitted and inserted into the holes forming these pairs,
In addition, the movable die and the base plate are connected by connecting metal fittings installed on the outside of both, and at the time of mold clamping, the hydraulic mechanism of the molding machine clamps the mold against the repulsive force of the spring, increasing the volume of the mold cavity. Is the repulsive force of the spring, the resin pressure of the molten resin injected in the mold cavity, the action of the gas pressure of the pressurized gas injected into the molten resin, and the low hydraulic pressure provided in the movable plate moving hydraulic mechanism of the molding machine. It is achieved by the operation of the supply means, and when the molded product is released from the mold, the low hydraulic pressure supply means provided in the movable platen moving hydraulic mechanism of the molding machine connects the movable insert and the outside of the movable insert and the movable die. The injection molding apparatus is characterized in that the movable mold can be retracted through a connecting metal fitting. 4. The injection molding apparatus according to claim 3, wherein a convex portion protruding toward the mold cavity surface of the fixed mold is formed on a surface of the movable insert that forms the mold cavity.