JPS63154328A - Blow molding method - Google Patents

Abstract

PURPOSE:To constitute the title method so that it does not happen that crush of the inside diameter and an uneven thickness are generated at the time of blow molding of a molded product having a contracted diameter part, by a method wherein the diameter of a parison is made somewhat large by adjusting it to the maximum diameter part of the molded product which is to be molded, and blow molding of an expanded diameter part is performed with air through an air feed nozzle. CONSTITUTION:A parison 27 is supplied between molds 23, 25 through an extrusion die 26. The parison which is on a position corresponding to a small diameter cavity part 22C is pressurized and molded from the inside and outside with a male screw part 32 of an insert member 30 and female screw part 22D formed on the small diameter cavity part 22C of the mold. When air is fed within the parison 27 through an air feed nozzle 28, the air is fed within the parison positioned on large diameter cavity parts 22A, 22B through a small hole 34 of the insert member 30, and molding is performed with this air pressure. With this construction, a thickness at expanded parts 10A, 10B is secured sufficiently and a molded product free of uneven thickness as a whole without having pile up inwardly in a contracted diameter bellows part 10C.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a blow molding method in which a parison is pinched between a pair of molds having a cavity shaped like a molded product, and air is supplied into the parison to form the parison. In particular, the present invention relates to a blow molding method suitable for producing a molded product having a reduced diameter portion such as a constriction.

[Conventional technology]

As shown in FIG. 8, a conventional blow molding machine for molding a resin container (molded product) 1 having a reduced diameter part IC in the middle is used to form cavities 2 and 4 as shown in FIG. A pair of molds 3 and 5 are arranged to face each other on the left and right, and an extrusion die 6 is opened from above toward between the molds 3 and 5, and an extrusion die 6 is opened from above toward between the molds 3 and 5. It has a structure in which the air supply nozzle 8 protrudes. When the parison 7 supplied from the extrusion die 6 reaches the lower end position of the molds 3 and 5, the molds 3 and 5 move toward the parison 7, and as shown in FIG. Pinch. At the same time, air is supplied from the air supply nozzle 8 into the parison 7, and as shown in FIG.
is pressed against the inner peripheral surface of cavity 2゜4, is cooled and becomes the first
A core 6A is provided in an extrusion die 6 in which a molded product 1 as shown in FIG. 1 is molded.

[Problem to be solved by the invention]

In the conventional blow molding method described above, when the parison 7 has a small diameter, particularly when the diameter is approximately the same as or smaller than the reduced diameter part IC of the molded product 1, the enlarged diameter part IA is formed as shown in FIG.
In (IB), the material is stretched and becomes significantly thinner than the thickness of the reduced diameter section IC.

There was a problem when using it as a part that required strength. Although it is possible to adjust the wall thickness of the molded product by adjusting the gap (slit) of the extrusion die 6, it is difficult to actually adjust the wall thickness, and there are limits to the wall thickness adjustment.

On the other hand, if the parison 7 has a large diameter close to the enlarged diameter parts LA and IB, the enlarged diameter parts IA and IB can have sufficient wall thickness, but as shown in FIG. In this step, the material moves from the pinch portion 7A into the cavity, forming a bulge 7B along the pinch portion 7A. Therefore, especially when the inner diameter is small, there is a problem in that the necessary inner diameter is crushed by this bulge 7B.

In addition, if the reduced diameter part has a bellows structure, the finished molded product will be bent in the direction of the raised part (vertical direction in Figure 12), and the flexibility will vary depending on the direction of the force acting on the molded product. There was a problem.

As described above, when molding a container with a reduced diameter IC as shown in Fig. 11, the conventional blow molding method tends to cause collapse of the inner diameter and uneven thickness, so it is difficult to meet the requirements for thin walls and high durability. Currently, it is only used for molding molded products that are not processed.

The present invention was made in view of the problems of the prior art described above, and is a blow molding method that does not cause collapse of the inner diameter or uneven thickness when blow molding a molded product that has a reduced diameter part such as a constriction part in the middle. is intended to provide.

[Means for solving problems]

Next, the present invention will be explained with reference to FIGS. 1 to 4, which show an embodiment of an apparatus for carrying out the present invention.

The present invention is a method for blow molding a molded product having a reduced diameter (bellows) portion 10C such as a constriction that may bulge inward and cause uneven thickness when blow molded. The enlarged diameter part 10A, which is the maximum diameter part of IO
B, and the reduced diameter (bellows) part 10c is pressure molded using the insert member 30 and the mold 23.25, while the enlarged diameter part 10A and IOB are blow molded using air from the air supply nozzle 28. I decided to do so.

[Effect]

The parison corresponding to the reduced diameter (bellows) part 10C, such as the constriction of the molded product, is pinched on both sides with the molds 23 and 25, and is pressure-formed with the insert member 3o and the small diameter hollow part 22C of the cavity 22. Ru. On the other hand, the enlarged diameter part 10A
, the parison corresponding to the IOB position is pinched on both sides, or even if it is not pinched, the size is close to the size of the large diameter cavities 22A and 22B of the cavity 22, and the parison is expanded by supplying air. The ratio is relatively small to ensure sufficient wall thickness.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing an embodiment of an apparatus for carrying out the blow molding method according to the present invention. As shown in FIG. 4, a molded product ( container)
10 is a vertical cross-sectional view of a blow molding machine for blow molding.

In FIG. 1, the blow molding machine 20 includes a pair of molds 23 and 25 that are arranged opposite to each other in the left and right direction and are slidable in six directions of arrows.
The molds 23 and 25 are arranged at an upper position between the molds 23 and 25.
an extrusion die 26 that supplies the parison 27 between the parisons 25 and 25; an air supply nozzle 28 that is disposed with its tip protruding from below the molds 23 and 25 between the molds 23 and 25 and supplies air into the parison 27; 27, and the mold 2
3.25 and an insert member 30 that press-forms a part of the molded product 10 in cooperation with the insert member 3.25.

A cavity 22 having a shape that matches the outer peripheral surface shape of the molded product 10 is formed on the opposing surfaces of the molds 23 and 25, respectively.
It consists of large diameter hollow parts 22A and 22B corresponding to B, respectively, and a small diameter hollow part 22G corresponding to the reduced diameter bellows part 10C. A female screw portion 22D is formed in the small diameter hollow portion 22C to match the shape of the outer peripheral surface of the reduced diameter bellows portion 10C of the molded product.

The tip of the extrusion die 26 is adjusted so that the parison 27 supplied between the molds 23 and 25 has a size close to the diameter of the enlarged diameter portion 10A and IOB, and the parison is pinched at the peripheral edge 21 of the cavity 22. It is now possible to do so. Note that the reference numeral 26A is a core disposed within the extrusion die 2.6.

A cylindrical insert member 3 is located directly below the extrusion die 26.
0 is arranged to protrude from below the molds 23 and 25 to the large diameter cavity 22A position, and an air supply nozzle 28 is inserted and arranged in this insert member 30.

A male threaded portion 32 having an outer circumferential surface shape matching the inner circumferential surface shape of the reduced diameter bellows portion 10C of the molded product 1o is formed on the outer circumferential surface of the approximately central portion in the longitudinal direction of the insert member 30.
The reduced diameter bellows portion 10G is press-formed in cooperation with the small diameter hollow portion 22G. A large number of small holes 34 are bored in the tip and rear ends of the insert member 30, and air supplied from the air supply nozzle 28 is directed through the small holes 34 to the large diameter cavities 22A and 22B. It is designed to be able to be supplied within the parison. The root portion 31 of the insert member 30 has a diameter larger than the outer diameter of the male threaded portion 32, and after molding, the insert member 3o can be removed by twisting from the opening side of the molded product (bottom direction in Figure 3). It looks like this.

Furthermore, it is desirable that the mold 23, 25 and the member 30 for the insert 1 be made of a metal with good thermal conductivity, such as iron, in order to enhance the cooling effect during molding.

Next, the blow molding method according to the present invention will be carried out using this blow molding machine 20, and the procedure for molding the molded product 10 shown in FIG. 4 will be explained.

First, the parison 27 is fed from the extrusion die 26 between the molds 23° and 25°. And as shown in Figure 1, parison 2
When the tips of the parisons 7 fully reach the lower ends of the molds 23 and 25, the supply of the parison 27 from the extrusion die 26 is stopped. At the same time, the molds 23 and 25 are brought close to each other so that they are in close contact with each other as shown in FIG. The parison protruding from the cavities of the molds 23 and 25 is pinched by the cavity peripheral portion 21, while the parison located at a position corresponding to the small diameter cavity 22G is pinched by the male threaded portion 32 of the insert member 3o.
and the female screw portion 2 formed in the small diameter cavity 22G of the mold.
2D pressure molding from the inside and outside. While bringing the cavity peripheral parts 21 into close contact with each other, the air supply nozzle 2
8 supplies air into the parison 27. Air enters the large diameter cavities 22A, 2 through the small holes 34 of the insert member 30.
It is fed into the parison located at 2B, and the parison is shaped by air pressure, as shown in FIG. This state is maintained until the parison is cooled and solidified, and when the parison is cooled and solidified, the insert member 30 is twisted and pulled out from the lower opening of the molded product, and then the molds 23 and 25 are separated and the molded product is taken out. Note that the insert member 30 may be removed by twisting the sides of the molds 23 and 25;
25 may be extracted after being separated. Then, if necessary, Paris is removed from the molded product.

As described above, according to the blow molding method using the blow molding machine 2o according to this embodiment, the enlarged diameter portion 10A.

A molded product can be obtained in which a sufficient wall thickness is ensured at 10B, and there is no inward bulge in the diameter-reduced bellows section 10C, and there is no uneven thickness throughout.

In the first embodiment, blow molding of a molded product having a bellows-shaped constriction has been described, but it goes without saying that the present invention can also be applied to a molded product having a simply flat constriction.

5 and 6 are views showing other embodiments of the apparatus for carrying out the blow molding method according to the present invention. As shown in FIG. A vertical cross-sectional view of a blow molding machine for blow molding a molded product 4o in which a portion 42 is formed is shown.

In these figures, a cavity 52 that matches the shape of the outer peripheral surface of the molded product 4o is formed on the opposing surfaces of a pair of opposing molds 53 and 55, and the cavity 52 has an inclined surface 5.
2B, a large diameter cavity 52A, and a small diameter cavity 5 with a uniform diameter.
2C and a medium diameter cavity 52D. An insert member 58 is disposed directly below the extrusion die 26 for pressure-forming the constriction 41 and flange 44 of the molded product 40 in cooperation with the small diameter cavity 52C and the medium diameter cavity 52D of the cavity 52. There is.

The molded product 40 is disposed on the upper end surface 59 of the insert member 58.
A male threaded portion 60 having a shape that matches the shape of the female threaded portion 42 formed on the inner peripheral surface of the constricted portion 41 is formed protrudingly, and cooperates with the small diameter hollow portion 52C5 and the medium diameter hollow portion 52D to form the female thread. Part 42. The flange portion 44 is formed by pressure molding. A gap 61 between the medium-diameter cavity 52D and the insert member 58 is set to be sufficiently smaller than the thickness of the parison 57, and during molding, the material within this gap 61 flows toward the flange 44, causing the flange to collapse. The thickness of the parison 44 is made to be sufficiently thicker than the thickness of the parison 57. Further, the insert member 58 has a hollow shape, and the air supply nozzle 28 is inserted therein. The size of the parison 57 supplied from the extrusion die 26 is close to that of the large diameter cavity 52A, and the size of the parison 57 is close to that of the large diameter cavity 52A.
A sufficient wall thickness is ensured.

In this way, in this embodiment, as in the first embodiment described above, it is possible to mold a molded product with sufficient wall thickness and no uneven thickness. Furthermore, in this embodiment, the upper end surface of the flange portion 44 of the molded product 40, the constricted portion 41, the internal threaded portion 42
Since these parts are pressure-molded, it is possible to precisely mold these parts, and it is possible to omit work such as finishing of these parts after molding.

In this second embodiment, the insert member 58 is fixed to the molds 53 and 55, but in the case of a molded product that does not need to be formed into a female thread shape, the insert member 58 may be moved upward by a force such as hydraulic pressure. It is also possible to press-form the flange portion 44 more effectively by molding it while pushing it up.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to mold a highly accurate molded product without uneven thickness.

In particular, according to the present invention, products with complex shapes such as constrictions, which could not be manufactured by blow molding in the past, or products with threaded joints that can be tightly attached, which required finishing processing, can be manufactured. This has the very advantageous effect of being able to manufacture products that require such precision.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view showing one embodiment of a blow molding machine for carrying out the method according to the present invention, Figs. FIG. 5 is a vertical sectional view showing a second embodiment of a blow molding machine for carrying out the method according to the present invention, FIG. 6 is an explanatory diagram illustrating its operating state, and FIG. Figure 8 is a perspective view of a molded product, Figures 8 to 12 are explanatory diagrams explaining the conventional blow molding method, Figure 8 is a vertical cross-sectional view of a conventional blow molding machine, and Figures 9 and 12 are explanatory views for explaining the conventional blow molding method. Fig. 10 is an explanatory diagram explaining its operating state, Fig. 11 is a perspective view of the molded product, Fig. 12 is a sectional view taken along the line X-X shown in Fig. 10, and Fig. 13 is the molded product. It is a cross-sectional view of the main part of the product. 10.40... Molded product, IOA, IOB, 40A...
・Enlarged diameter part, IOC...Reduced diameter bellows part, 20...Blow molding machine, 22.52...Cavity, 22A, 22B
...Large diameter cavity, 22C, 52C...Small diameter cavity,
22D... Female thread part, 23, 25, 53.55...
Mold, 26... Extrusion die, 27.57... Parison, 28... Air supply nozzle, 30.58... Insert member, 32.60... Male thread part, 34... Air Small hole for ejection, 41...reduced diameter part, 52D... medium diameter cavity part. Figure 1 Figure 2 Figure 3 Figure 5 Figure 6 Figure 9 Figure 10 Figure 1I Figure 12 Figure 13

Claims (1)

[Claims] (1) The parison supplied between a pair of opposing molds is pinched from both sides by the pair of molds, and air is supplied into the parison from an air supply nozzle protruding into the parison to form the mold. A blow molding method characterized in that an insert member is inserted into the parison, and a predetermined portion of the molded product is pressure-molded by the mold and the insert member.