JP2833608B2 - Blow 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 blow mold, and more particularly to an improvement of a blow mold in which the shape and thickness of a molded product can be arbitrarily set.

[0002]

2. Description of the Related Art In a blow molding machine, a molten resin supplied from an extruder is formed into a cylindrical molten resin cylinder called a parison by a die having a ring-shaped resin discharge port, and this is sandwiched between molds. Thereafter, a gas such as air is blown into the parison and cooled to form a hollow product.

In such a blow molding machine, the parison injection die has a cylindrical resin passage formed therein and a ring-shaped resin discharge port formed at a lower end surface thereof to inject a hollow parison. . The thickness of the parison is controlled by adjusting the amount of the die lip in and out of the opening gap of the resin discharge port, thereby controlling the thickness of the molded product.

The injected parison is usually sandwiched between a pair of molding dies, and is expanded by air blow to form a desired hollow molded product in a shape following the cavity formed in the mold. I'm trying to get. In this case, the cavity has a predetermined shape in advance, and is usually set to a predetermined shape by clamping a metal mold with a hydraulic drive.

[0005] By the way, if the product shape to be molded is 3
If the mold is bent in two dimensions, a split mold that simply opens the mold to the left and right will not allow the parison to follow the cavity. The parison is placed by moving it three-dimensionally, and then the molds are clamped to form a mold, or the mold is inclined at 45 degrees and the lower mold is slid upward to place the parison and then clamped. The way you do it is done. Further, a method has been proposed in which the parison is moved by suction by an air flow so as to follow the cavity.

[0006]

However, in the conventional blow molding machine, a large moving space of the mold is required to perform mold clamping at the time of molding, and a hydraulic device for driving is required. Therefore, there is a problem that the equipment becomes complicated and large. Further, the thickness of the molded product is controlled only by adjusting the thickness at the time of injection of the parison, and this is usually performed as a measure against drawdown. Therefore, there is a problem that the thickness of the molded product cannot be directly adjusted in the mold.

Further, in order to obtain a three-dimensional molded article by a conventional apparatus, a structure for moving a die, a structure for moving a die three-dimensionally, or a suction air flow device so as to conform to the cavity shape are used. And a complicated structure accompanied by the above, which is very problematic in terms of structure and controllability. In particular, the conventional one has a disadvantage that the cavity shape once determined cannot be changed without changing the mold itself.

The present invention has been made in view of the above-mentioned conventional problems. A first object of the present invention is to perform mold clamping and mold opening with a simple structure and to control the thickness of a molded product by a parison. An object of the present invention is to provide a blow mold that can be performed inside a mold after injection. A second object of the present invention is to provide a blow mold capable of forming a three-dimensional molded product extremely easily and changing the shape of the cavity arbitrarily.

[0009]

In order to achieve the above-mentioned object, a blow mold according to the present invention comprises a parison mold injected from a die, wherein a cavity forming portion is formed by a flexible cavity film. An airtight chamber divided by partitions is formed inside the membrane, and a gas supply / discharge means is connected to each airtight chamber so that the cavity forming surface can be expanded and contracted. In this case, the flexible cavity film has a structure in which a woven fabric is coated with a resin,
This may be formed in a bag shape to form an airtight expansion / contraction container. Then, the inside of the airtight container is divided by a partition wall of a similar coated woven fabric to form a multi-stage room. The hermetic container may be housed in a metal cylindrical container, the inner surface of the hermetic container may be used as a cavity surface, and one inner surface formed by combining split molds may be used as a cavity. At this time, the bag-shaped airtight container may be configured as a split mold and housed in a cylindrical container so that the airtight container properly adheres when inflated to form a cavity.

[0010]

According to the above arrangement, the cavity surface formed by the flexible cavity film can be expanded and contracted by supplying and discharging gas. Therefore, when injecting the parison, the internal pressure of the cavity film is reduced to widen the cavity shape to form a so-called mold opening, causing the parison to hang down, and then blowing air or other gas into the cavity film to expand and close the mold. Is performed to obtain a predetermined cavity shape. At the same time, air is blown into the parison, and it is molded in close contact with the cavity surface. Since clamping and opening of the mold are performed only by supplying and discharging gas, the structure becomes very simple, and there is no need to secure a large space for opening the mold.

The internal pressure of the cavity and the internal pressure of the parison can be arbitrarily set by adjusting the pressure of the blown gas. Since the thickness of the molded product is determined by the pressure sandwiching the molded product, the thickness of the molded product can be controlled while being confined in the molding die by appropriately adjusting the pressure inside the cavity and the blow pressure inside the parison.

Further, an airtight chamber partitioned by partitions is formed inside the cavity film, and gas can be supplied to and discharged from each of the airtight chambers. The shape can be bent three-dimensionally. Therefore, by adjusting the amount of gas into the cavity, it is possible to easily form a cavity having a complicated curve and manufacture a molded product having an arbitrary curve. In this molding die, there is no need to perform complicated operations such as driving the die or driving the die in clamping.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a blow mold according to the present invention.

FIG. 1 shows a longitudinal sectional view and a transverse sectional view of a blow mold in an open state according to an embodiment. First, a parison injection die 12 is provided at an upper position of a molding die for injecting a parison 10 as a molding material. This is pressurized by a ring piston 16 containing a molten resin supplied from an extruder 14, The injection is performed downward from the ring nozzle 18 opened at the lower end. The parison 10 has a cylindrical shape and hangs down so as to penetrate the center of the blow mold 20 according to the embodiment.

The blow mold of the embodiment has a metallic cylindrical container 22 constituting an outer shell of the mold.
Inward flanges 24 and 26 are integrally provided at the upper edge and the lower edge of the second member. An expansion / contraction container 28 for forming a cavity is accommodated in the internal space of such a metal container 22. The expansion / contraction container 28 is formed by forming a flexible film in which a heat-resistant resin or aluminum is coated on a heat-resistant woven fabric in a cylindrical bag container. The surface constitutes a cavity film portion 30 which becomes a mold for molding. In this case, the flexible film itself is configured to be incapable of expansion and contraction, that is, not elastically deformed. The expansion / contraction container 28 is adhered and integrated with the inner wall surface of the metal container 22 as a container, but the cavity film portion 30 and a part connected to the cavity film portion 30 project inward from the inner peripheral edges of the flanges 24 and 26. The inner diameter of the cavity film part 30 can be reduced. A pair of notches 32 are formed in the inner peripheral surface of the cavity film portion 30 at positions opposed to each other by 180 degrees so that the inner diameter of the cavity can be expanded and contracted. When the diameter is reduced, the notch 32 is closed to form a perfect circle.

In the inside of the expansion / contraction container 28, partitions 33 are provided at regular intervals along the direction in which the parison 10 hangs, and partitions are provided therein.
A, 34B and 34C are formed. Furthermore, it is divided also in the circumferential direction, and the notch 3
A partition 36 for the circumferential direction is formed corresponding to the portion 2, thereby dividing the airtight chambers 34A, 34B, 34C in the circumferential direction.

Each airtight chamber 34 of such an expansion / contraction container 28
Nozzles 38A, 38B, 38C are opened in A, 34B, 34C through the metal container 22. An air supply pipe 40 connected to a compressed air pump (not shown) and an exhaust pipe 42 connected to a vacuum pump (not shown) are connected to the respective nozzles 38A, 38B, 38C. And each nozzle 38A, 38B, 38 in the air supply pipe 40
An expansion valve 44 is attached to a connection to C, and a vacuum valve 46 is attached to a connection to each nozzle 38A, 38B, 38C in the exhaust pipe 42. Therefore, by opening the expansion valve 44, compressed air is supplied to the inside of the expansion container 28 to expand it, and by opening the vacuum valve 46, air is sucked and exhausted from the inside of the expansion container 28, and the expansion container 28 is opened. Contracts. At this time,
Valve 44 for each nozzle 38A, 38B, 38C,
46, each airtight chamber 34A, 34B, 3
4C can be individually expanded and contracted.

In the above-mentioned mold, an upper pinch 48 is attached to the upper and lower flanges 24 and 26 of the metal cylindrical container 22.
A lower pinch 50 is attached. These pinch 4
Reference numerals 8 and 50 respectively denote that the semi-disc is opened and closed by the cylinder mechanisms 52 and 54 so that the parison 10 can be pinched up and down during molding.

In the drawing, reference numeral 56 denotes a blow nozzle provided on the parison injection die 12.

The operation of the blow mold having the above configuration is as follows. When the hollow cylindrical container is formed, the mold is first opened. This is performed by sucking and discharging the internal air from the inside of the expansion / contraction container 28 by the action of a vacuum pump. That is, the vacuum valve 46 is opened, and the pressure in each of the hermetic chambers 34A, 34B, 34C is reduced. Thereby, the cavity film portion 30 is expanded by the action of the notch portion 32, and the inner diameter is widened. In this expanded state, the vacuum valve 46
Is closed.

Next, the parison 10 is injected from the die 12 placed above the mold, and is suspended to a predetermined length. After the injection of the parison 10 is completed, the expansion / contraction container 2
8 is blown with compressed air. This is expansion valve 4
4 is opened, each airtight chamber 34A, 34B, 34C is connected to a compression pump, and air is supplied at a predetermined pressure (5 to 8 kg / cm ² ). By this air blowing, the expansion / contraction container 28 expands, and the cavity film portion 30 closes the cutout portion 32 to form a regular cavity shape. As shown in FIG.
0 is closed to pinch off, and the built-in parison 10 is air blown by the blow nozzle 56 to expand the parison 10. At this time, each airtight chamber 34 of the expansion / contraction container 28
The adjustment may be made while observing the state of the molded article in consideration of the balance between the internal pressures P ₁ P ₂ P _{3 of} A, 34B, 34C and the pressure P ₄ inside the parison 10. After the molding, the inner pressure of the parison 10 is reduced, and the expansion and contraction container 28 is reduced.
The user opens the 50 and takes out the molded product.

According to such an embodiment, the mold clamping, the gas supply / discharge operation to the expansion / contraction container 28 is simply performed without using the conventional large hydraulic cylinder unit.
Since the mold is opened and the mold is clamped and opened inside the metal cylindrical container 22, the space used is small and the structure is extremely simple. Moreover, the parison 10 is placed inside the mold.
Are sealed, each airtight chamber 34A of the expansion / contraction container 28,
The internal pressures P ₁ P ₂ P _{3 of} 34B and 34C and the pressure P ₄ inside the parison 10 can be adjusted, whereby the thickness of the molded product can be adjusted. Moreover, since the expansion / contraction container 28 is divided into a plurality of airtight chambers, operations such as partially increasing the thickness of the molded product can be performed, and a versatile use method can be realized.

Next, a method for performing three-dimensional blow molding will be described with reference to FIG. This is a multi-stage (upper and lower 4 in this example)
Airtight chambers 34A, 34B, 34C, 34 formed in
D is provided, and each of the hermetic chambers 34A, 34B, and 34C uses the expansion / contraction container 28 which is divided into right and left.
In particular, the length of the internal partition wall 33 may be adjusted so that the cavity film section 30 forms a cavity that is bent in a predetermined three-dimensional manner with the container 28 expanded. Thereby, the cavity shape determined when the container 28 expands can be ensured.

First, the parison 10 is ejected. At this time, as shown in FIG. 3A, suction and exhaust are performed mainly on the airtight chamber of the part of the expansion / contraction container 28 which protrudes into the hanging area of the parison 10 in advance. To prevent the parison 10 from becoming an injection obstacle. Next, the parison 10 is ejected from the die 12 as shown in FIG. Parison 1
When 0 reaches the lower end of the mold, compressed air is supplied to each of the airtight chambers 34A, 34B, 34C, and 34D to expand them, as shown in FIG. Thereby, the cavity film 3
0 constitutes a predetermined cavity shape. At this time, a bottom plate 62 having a blow nozzle 60 for blowing air into the parison 10 is provided on the lower surface of the mold so that air is blown from below the parison 10. After molding in this manner, each of the airtight chambers 34A, 34B, 34C, 34
The internal gas may be sucked and exhausted from D, and the product 64 may be taken out by opening the mold.

According to such a three-dimensional blow molding method,
In particular, each airtight chamber 34A, 34B, 34 of the expansion / contraction container 28
By adjusting the internal pressures of C and 34D, mold clamping and mold opening can be performed in a space-saving manner, and a three-dimensional bent product can be easily formed without performing complicated movements on a die or a mold. The bending shape can be arbitrarily changed by adjusting the internal pressure, and the cavity shape can be changed without changing the mold itself. Therefore, a highly versatile mold can be obtained.

In the above embodiment, by forming the partition wall 33 by using a material that can expand and contract, there is an effect that the degree of change in the cavity shape can be increased.

In the above embodiment, the expansion / contraction container 28 is divided into two parts in the circumferential direction by the partition wall 36. However, it is also possible to adopt a configuration in which the container is not divided in the circumferential direction if necessary, or it is divided into two or more parts. It can also be configured.

[0028]

As described above, according to the present invention,
The cavity forming part in the parison mold injected from the die is formed by a flexible cavity film, and an airtight chamber divided by a partition is formed inside the cavity film, and gas supply / discharge means is connected to each airtight chamber. And the cavity forming surface can be expanded and contracted,
The mold can be opened, the wall thickness of the molded product can be controlled inside the molding die after the parison injection, the three-dimensional molded product can be molded extremely easily, and the cavity shape can be arbitrarily changed. Excellent effects can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view and a transverse sectional view of a blow mold according to an embodiment in an open state.

FIG. 2 is a longitudinal sectional view and a transverse sectional view of a blow-molding die according to an example in a mold-clamped state.

FIG. 3 is a process diagram of three-dimensional blow molding using a blow mold according to an example.

[Explanation of symbols]

 Reference Signs List 10 parison 12 parison injection die 20 blow molding die 22 metal cylindrical container 28 expansion / contraction container 30 cavity film part 32 notch part 33, 36 partition wall 34A, 34B, 34C airtight chamber 38A, 38B, 38C nozzle 40 air supply pipe 42 exhaust pipe 44 Expansion valve 46 Vacuum valve 48, 50 Parison pinch 56 Blow nozzle

──────────────────────────────────────────────────続 き Continuing from the front page (72) Yoshiaki Kano, inventor 1980, Kogushi-ji, Obe-shi, Ube-shi, Ube-shi, Yamaguchi Ube Industries, Ltd. Ube Resin Processing Machine Research Laboratory (56) References JP-A-57-207026 (JP) , A) JP-A-63-312111 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B29C 49/00-49/80 B29C 33/38-33/42 B29L 22:00

Claims (1)

(57) [Claims] 1. A cavity forming part in a parison mold injected from a die is formed by a flexible cavity film, and an airtight chamber divided by a partition is formed inside the cavity film, and gas is supplied to each airtight chamber. A blow molding die, characterized in that a cavity forming surface can be expanded and contracted by connecting a supply / discharge means.