JPH06155502A - Production of resin tubular body - Google Patents

Abstract

PURPOSE:To integrally mold a resin tubular body having an inner surface of an end part of high accuracy in shape and dimension in a simple manner. CONSTITUTION:Split molds 10A, 10B provided with a cavity 11 for regulating an outer surface of a resin tubular body and a resin relief recess 16 connected to the cavity 11 are parted at a bent parting surface 13. A tip end of a core 12 is inserted to an insertion port 17 of the closed split molds 10A, 10B. A melt resin of a predetermined amount is injected into the cavity 11 through a nozzle hole 12A. After that, the core 12 is further projected into the cavity 11, thereby being inserted into the melt resin 15 for forming an inner surface of an end part with a high accuracy in shape and dimension. During or after the insertion of the core 12, a pressurized fluid is injected into the melt resin 15 through an introducing tube 14. A hollow part is formed by the pressure of the pressurized fluid. Thus, a molded piece is integrally molded with a hollow along the cavity 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a resin-made tubular body having a highly accurate shape and size of the inner surface of an end portion.

[0002]

2. Description of the Related Art Conventionally, as a method for manufacturing a resin tubular body of this type, there are the following methods (a) and (b).

(A) According to an extrusion blow molding method, a molten parison is extruded and arranged by an extrusion die between split molds which are then opened, and then the split mold is closed to sandwich the parison. Then, a pressurized fluid is introduced into the parison to blow-mold the tubular body, and then the core mold is inserted into the opening of the tubular body.

(B) According to the injection molding method,
The split mold is closed with the core mold inserted, and a molten resin is injected and filled into the cavity formed between the core mold and the split mold to form a tubular body, and the split mold is cooled. Open the mold and pull out the core mold.

[0005]

Among the above-mentioned conventional techniques, in the method (a), after the split mold is closed to sandwich the parison, a cutting mechanism and an outer surface holding mechanism for cutting the parison are provided. This results in a problem that the manufacturing apparatus becomes complicated and the number of manufacturing steps increases, resulting in low productivity.

In the method (b), since it is necessary to pull out the core mold which is in contact with the entire length of the injection-molded tubular body, a long tubular body or a tubular body having a bent portion is manufactured. There is a problem that is difficult.

The present invention has been made in view of the above problems of the prior art, and a resin tubular body having a highly accurate shape and size of the inner surface of the end can be easily integrally formed. It is intended to realize a method for manufacturing a resin tubular body.

[0008]

In order to achieve the above object, the first method for manufacturing a resin tubular body according to the present invention is a split type mold having a cavity for regulating the outer peripheral surface of the resin tubular body. , Projecting the tip of the core mold into the cavity and closing the mold, and then injecting a molten resin into the cavity, and pressurizing fluid through the core mold during or after completion of the injection injection. Is injected into the molten resin to form a hollow portion to integrally form a hollow molded article, and then the molded article is cooled in a mold.

The second method for manufacturing a resin tubular body is as follows.
After the mold of a split type having a cavity for regulating the outer peripheral surface of the resin tubular body is closed, injection injection of the molten resin is started into the cavity, and then the tip of the core die is inserted into the molten resin. Then, during or after the insertion of the core mold, after forming a hollow portion by injecting a pressurized fluid into the molten resin through the core mold to integrally mold a hollow molded article, It is characterized in that the molded product is cooled in a mold.

[0010]

The molten resin injected into the cavity is restricted in shape and size by the tip of the core die projecting into the cavity and the inner surface of the end of the tubular body being restricted. It will be accurate.

Since the portion other than the inner surface of the end portion is a hollow portion formed by the pressure of the pressurized fluid injected into the molten resin, the core mold contacts only the inner surface of the end portion of the tubular body. It's easy to pull out the core mold.

[0012]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a resin tubular body manufactured according to an embodiment of the present invention.

As shown in FIG. 1, the resin tubular body is released from a cylinder body 1 having a bent portion, and one end portion 2 having a highly precise shape and size of the end face 3 and the end inner face 5. The other end 7 is provided, and the end outer surface 6 has a pair of flanges 4 </ b> A and 4 </ b> B protrudingly provided at intervals.

Next, an embodiment of the present invention for producing the resin tubular body shown in FIG. 1 will be described.

As shown in FIG. 2, split molds 10A and 10B, which are split molds, have a cavity 11 for restricting the outer surface of a resin tubular body having a bent portion, and an anti-core mold for the cavity 11. The split molds 10A, 1 are provided with a resin escape recess 16 communicating with the front end on the side, an insertion opening 17 for the core mold 12, and a pair of grooves 11A, 11B for forming the flange.
The mating surface 13 of 0B is bent.

First, as shown in FIG. 2, split molds 10A, 1
The tip end of the core mold 12 is fitted into the insertion opening 17 of 0B and the mold is closed, and a predetermined amount of the molten resin 15 is injected and injected into the cavity 11 through the nozzle hole 12A of the core mold 12. The injection injection of the molten resin may start at any time during or after completion of the mold closing, and the injection injection is completed before the injection of the pressurized fluid.

Next, as shown in FIG. 3, the core mold 12 is further projected into the cavity 11 to melt the molten resin 1.
5 to form an inner end surface 5, an outer end surface 6 and flanges 4A and 4B of the resin tubular body.
During or after the insertion of 2, the pressurized fluid is injected into the molten resin 15 through the introduction pipe 14 provided inside the core mold 12, and the hollow portion 18A is formed by the pressure of the pressurized fluid. A hollow molded product 18 is integrally molded along the cavity 11.

At this time, the excess molten resin 18B flows toward the side opposite to the core mold of the cavity 11 and the resin escape recess 1 is formed.
6 and the hollow ratio of the hollow portion 18A is improved.

After that, the molded product 18 is cooled in a mold, then the mold is opened and taken out, and burrs are removed by cutting at the cutting portion A.

Incidentally, instead of the core type of this embodiment, the injection nozzle and the core type as in the second embodiment described later may be separate bodies.

Next, another embodiment of the present invention will be described.

As shown in FIG. 4, split molds 20A and 20B, which are split molds, have a bellows portion forming portion 21A at a part thereof.
A cavity 21 for restricting the outer surface of a resin tubular body having a groove, a resin escape recess 26 communicating with the cavity 21, an insertion opening 27 for inserting the core die 22, and an injection nozzle 28. An injection nozzle insertion port 29,
The split molds 20A and 20B are provided with a pair of grooves 21A and 21B for flange formation, the mating surfaces 23 of the split molds 20A and 20B are bent, and the injection nozzle insertion port 29 is connected to the cavity 21 by a passage 29A.

First, as shown in FIG. 4, split molds 20A, 2
The cavity 22 is inserted by inserting the core mold 22 into the insertion opening 27 of 0B.
1, the mold is closed, and a predetermined amount of molten resin is injected and injected from the injection nozzle 30 fitted into the injection nozzle insertion port 29. The injection injection of the molten resin may be started at any time during the progress of mold closing or after completion thereof.

During or after the injection of the molten resin is completed or completed, a pressurized fluid is injected into the molten resin 25 through an introduction hole 24 provided in the core mold 22, and as shown in FIG. A portion that forms the hollow portion 28A by the pressure of the pressurized fluid and becomes the cylinder main body along the remaining portion of the cavity 21,
Hollow molded article 2 having a bellows portion and an open end portion
8 is integrally molded.

At this time, the surplus molten resin 28B flows toward the side opposite to the core mold of the cavity 21 and the resin escape recess 26 is formed.
And the hollowness of the molded product 28 is improved.

After that, the molded product 28 is cooled in a mold, opened, taken out, and cut at a cutting portion B to form a resin tubular body having both ends open and a bellows portion. To manufacture.

It should be noted that the injection nozzle and the core mold of this embodiment may be replaced by separate bodies, and the injection nozzle and the core mold as in the first embodiment may be integrated.

In each of the above-mentioned embodiments, a resin escape recess is provided as a means for improving the hollow ratio of the tubular body so as to allow the excess molten resin to escape, but instead of this, (1)
A slide core type that can slide freely is arranged in the split mold,
When the pressurized fluid is injected, the slide core mold is slid to increase the volume of the cavity. (2) Use the pressurized fluid that is a liquid before being injected into the molten resin but becomes a gas after the injection. Means such as increasing the pressure of the injected pressurized fluid may be used.

When the molded product is cooled, a hole is made in the hollow portion of the molded product, or a pressurized fluid is guided to the outside of the molded product by using an introduction hole or the like to introduce the pressurized fluid into the molded product. By circulating the product, the molding time of the molded product can be shortened.

The resin tubular body produced according to the present invention is
Polyethylene, polypropylene, polyamide, modified polyphenylene oxide, polybutylene terephthalate,
In addition, it is made of a thermoplastic synthetic resin material having an elastomeric property such as EPDM, and is used as a duct, hose, or tube in the fields of automobiles, electric appliances and the like.

The thermoplastic synthetic resin material may be used by blending known reinforcing fillers, flame retardants, pigments, foaming agents and the like, if necessary.

[0033]

Since the present invention is configured as described above, it has the following effects.

A resin tubular body having a highly accurate shape and size of the inner surface of the end can be easily produced by integral molding, and even a resin tubular body having a long length or a bent portion can be easily integrally molded. be able to.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a resin tubular body manufactured by the method of the present invention.

FIG. 2 is a schematic cross-sectional view showing an embodiment of a method for producing a resin tubular body of the present invention, showing a step of injecting and injecting a molten resin into a split mold that is closed.

3 is a schematic cross-sectional view showing a step of injecting a pressurized fluid into the molten resin to form a hollow portion after the step shown in FIG.

FIG. 4 is a schematic cross-sectional view showing another embodiment of the method for producing a resin tubular body of the present invention, showing a step of injecting and injecting a molten resin into a split mold that is closed.

5 is a schematic cross-sectional view showing a step of injecting a pressurized fluid into the molten resin to form a hollow portion after the step shown in FIG.

[Explanation of symbols]

 1 Cylinder Main Body 2 One End 3 End Faces 4A, 4B Flange 5 End Inner Face 6 End Outer Surface 7 Other End 10A, 10B, 20A, 20B Split Mold 11,21 Cavity 12,22 Core Mold 13,23 Mating Surface 14 introduction pipe 15,25 molten resin 16,26 resin escape recess 17,27 insertion opening 18,28 molded product 18A, 28A hollow portion 18B, 28B excess molten resin 21A bellows portion forming portion 24 introduction hole 29 injection nozzle insertion opening 29A passage 30 injection nozzle

Claims (2)

[Claims] 1. A split type mold having a cavity for restricting an outer peripheral surface of a resin tubular body is closed by projecting a tip of a core mold into the cavity, and then melted into the cavity. After injecting and injecting, the pressurized fluid is injected into the inside of the molten resin through the core mold to form a hollow portion to integrally form a hollow molded product. A method for producing a resin tubular body, characterized in that the molded article is cooled in a mold. 2. A mold of a split type having a cavity for restricting the outer peripheral surface of the tubular body is closed, injection of molten resin is started into the cavity, and then the tip of the core die is inserted into the molten resin. Part, and while the insertion of the core mold is in progress or after completion, a hollow part is formed by injecting a pressurized fluid into the molten resin through the core mold to integrally mold a hollow molded product. Then, the method for producing a resin tubular body, characterized in that the molded article is cooled in a mold.