JP2018027645A - Method for production of synthetic resin-made pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain occurrence or remaining of weld flash at a branch part in injection molding of a synthetic resin-made pipe having a branch duct.SOLUTION: There is provided an injection molding method for a synthetic resin-made pipe 1 comprising a main duct and a branch duct branching from the main duct. A core mold of an injection mold is configured by the first and second core molds C1, C2 forming a main duct and a third core mold C3 forming the branch duct. The end e3 of the third core mold C3 faces the portion at which the ends of the first and second core molds C1 and C2 contact each other. The first core mold contacts the second one in a mold-closing state, and the end of the third core mold departs from the first and second core molds. By injection of a synthetic resin, a resin film 1d is formed between the first/second core molds C1, C2 and the end e6 of the third core mold together with the pipe 1. After that, the resin film 1d is cut off from the pipe 1 by retracting the first/second core molds C1, C2 and advancing the third core mold C3 at a prescribed distance.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for producing a synthetic resin pipe. In particular, the present invention relates to a method for manufacturing a synthetic resin pipe having a branch pipe using injection molding.

Synthetic resin pipes are used for various purposes. Synthetic resin pipes are also used for connector members for hoses and tubes. If a synthetic resin pipe is manufactured using injection molding, the manufacturing efficiency is high and economical. In particular, it is preferable that the pipe shape of the pipe is formed by injection molding because a process such as cutting is unnecessary.

Further, when a synthetic resin pipe having a branch pipe is integrally formed by injection molding, it is convenient that a pipe such as a tube can be branched by the synthetic resin pipe.
When injection molding a synthetic resin pipe having a branch pipe, the core mold is divided at the branch portion, and when the mold is clamped, the tips of the core mold are brought into contact with each other. Injection molding is performed so that a branched pipe line is formed.

For example, Patent Document 1 discloses a technique for injection-molding a branch pipe having a pipe branching into a Y-shape, and providing three core molds corresponding to each pipe, A technique is disclosed in which a mold is formed so that the end portions of the core molds can come into contact with each other, and a branch pipe is manufactured by injecting resin in a state in which these three core molds are in contact. According to the technique, even if burrs or the like occur, a branch pipe with a small pressure loss can be obtained.

JP-A-11-153283

However, in the technique disclosed in Patent Document 1, it is necessary to manufacture a mold so that the tip portions of the three core molds are brought into close contact with each other, and it is not easy to manufacture such a mold. There wasn't. The three core molds are arranged so that the axis of each core mold does not become one straight line, and it is necessary to abut the tip portion in a state where they are strongly pressed against each other. This is because the pressing force becomes a force that tilts the other core molds, and the alignment of the core molds is likely to go wrong. For this reason, in the technique disclosed in Patent Document 1, it is difficult to adjust the contact of the core mold tip, and burrs are likely to occur. Therefore, it is difficult to adopt such a manufacturing method in applications of branch pipes where burrs are not allowed.

In addition, as a technique for bringing the tip portions of the three core molds into contact with each other more precisely, a so-called “touch structure”, “guide structure”, and the like are known. The “touch structure” means that the end surfaces of the core molds 91 and 92 that constitute the main pipes of the bent tubular shape are brought into contact with each other as shown in FIG. 7 in which the cavity mold 99 and the core molds 91, 92, and 93 are configured. In this mold structure, the branch pipe core mold 93 whose end face shape is adjusted to a shape that matches the corners of the butted portions of the core molds 91 and 92 is brought into contact. In addition, the “guidance structure” means that the end surfaces of the core molds 94 and 95 that constitute the main pipes of the bent tubular shape are butted together, as shown in FIG. 8 in the configuration of the cavity mold 99 and the core molds 94, 95, and 96. In addition, the die structure is such that a hole is formed in the abutting portion in the extending direction of the branch pipe core mold 96, and the end of the branch pipe core mold 96 is tightly inserted into the hole.

If a mold having such a touch structure or a guiding structure is employed, the branch pipe (9) can be injection-molded while reducing the occurrence of burrs. However, even if such a structure is adopted, it is difficult to completely prevent the generation of burrs because the structure of the mold becomes complicated and the mating surface also has a complicated shape. In addition, the complexity of the mold structure tends to adversely affect the strength and durability of mold parts, and burrs tend to occur as molding is repeated.

Further, in a synthetic resin pipe having a branch pipe, there is a problem that if a burr occurs at a branch portion of the pipe, it is difficult to remove the burr and it is difficult to inspect whether there is a burr. Further, burrs that could not be removed at the time of manufacture may fall off during use and be mixed into the fluid.

An object of the present invention is to suppress the generation and remaining of burrs at a branch portion when a synthetic resin pipe having a branch pipe is injection-molded.

As a result of intensive studies, the inventor applied the end face of the third core type that forms the inner peripheral surface of the branch pipe to the contact portion of the first core type and the second core type that forms the inner peripheral surface of the main pipe line. The resin is injected in a state of being separated so as not to contact, and a resin film is formed between the end face of the third core mold and the first core mold and the second core mold, and then the third core mold is advanced. Thus, it has been found that if the resin film is separated from the molded synthetic resin pipe, the occurrence of burrs at the branch portion can be suppressed, and the present invention has been completed.

The present invention is a method for manufacturing a synthetic resin pipe having a main pipe line and a branch pipe branching from the main pipe line by using injection molding, and includes a step of preparing an injection mold. The injection mold has a cavity mold that defines the outer surface shape of the synthetic resin pipe and a core mold that defines the inner surface shape of the synthetic resin pipe, and the core mold is an inner peripheral surface of a main pipe line. Are divided into a first core type and a second core type that form the inner periphery, and a third core type that forms the inner peripheral surface of the branch pipe, and ends of the first core type and the second core type The end portion of the third core mold is opposed to the portion where they abut each other, and has a step of closing the injection mold following the mold preparation step, and the first core is in a closed state. The end of the third core mold is in contact with the first core mold and the second core mold while the mold and the second core mold abut. After the mold closing process, the mold core has an injection process for injecting and filling synthetic resin into the mold cavity. In the injection process, the end of the third core mold is integrated with the synthetic resin pipe. And a resin film is formed between the first core mold and the second core mold, and following the injection process, the first core mold and the second core mold are at least partially opposed to the end of the third core mold. Retreating to a position where it does not occur, and with the first core mold and the second core mold retracted, the third core mold is advanced by a predetermined distance, and the resin film is separated from the synthetic resin pipe, It is a manufacturing method of the synthetic resin pipe which has the process of taking out the synthetic resin pipe from which the resin film was removed from a metal mold | die after a cutting process (1st invention).

In the first invention, it is preferable that the main pipeline has a bent shape, and the branch pipeline is branched from the bent portion of the main pipeline (second invention). In the first invention, it is preferable that the cross section of the main pipeline is changed to a stepped tube, and the branch pipeline is branched from the stepped portion (third invention).

According to the method for producing a synthetic resin pipe of the present invention, when a synthetic resin pipe having a branch pipe is injection-molded, the generation and remaining of burrs at the branch portion can be suppressed.
Further, according to the second and third inventions, even if the main pipeline is bent or the main pipeline is a stepped tube, it is effective to generate and remain burrs at the branch portion. Can be suppressed.

It is an external view which shows the shape of the synthetic resin pipes of 1st Embodiment. It is sectional drawing which shows the shape of the synthetic resin pipes of 1st Embodiment. It is a schematic diagram which shows the injection mold for shape | molding the synthetic resin pipe of 1st Embodiment. It is a schematic diagram which shows the process of a series of injection molding which shape | molds the synthetic resin pipes of 1st Embodiment. It is sectional drawing which shows the shape of the synthetic resin pipes of 2nd Embodiment. It is a schematic diagram which shows the injection mold for shape | molding the synthetic resin pipe of 2nd Embodiment. It is a schematic diagram which shows the example of the form which core type | molds mutually contact in a prior art. It is a schematic diagram which shows the other example of the form which core type | molds mutually contact in a prior art.

Embodiments of the invention will be described below with reference to the drawings, taking as an example a synthetic resin pipe that can be used as a connector member for a rubber tube or a synthetic resin tube. Note that the present invention is not limited to the individual embodiments described below, and the embodiments can be changed and implemented.

1 and 2 show an external appearance and a cross-sectional view of a synthetic resin pipe 1 according to a first embodiment manufactured by the synthetic resin pipe manufacturing method of the present invention. In this embodiment, the synthetic resin pipe 1 can be used as a connector member such as a rubber tube. The synthetic resin pipe 1 has a shape in which three straight tubular portions 11, 12, 13 having through holes (pipes) are integrally connected, and has a so-called three crotch shape. That is, the synthetic resin pipe 1 has main pipe lines 1a and 1b formed by the tubular parts 11 and 12, and a branch pipe line 1c formed by the tubular part 13, and the branch pipe line 1c is the main pipe line 1c. The pipes 1a and 1b branch off from the connected portion, and the pipes 1a, 1b and 1c communicate with each other. Moreover, in the synthetic resin pipe 1 of this embodiment, the 1st tubular part 11, the 2nd tubular part 12, and the 3rd tubular part 13 have a cylindrical outer peripheral surface and a cylindrical inner peripheral surface, respectively.

Furthermore, although not essential, in the synthetic resin pipe 1 of the present embodiment, the main pipes 1a and 1b have a bent pipe shape. That is, the synthetic resin pipe 1 is formed so as to be a bent pipe in which the first tubular portion 11 and the second tubular portion 12 that are straight tubular are connected at an angle of about 90 degrees, Main pipes 1a and 1b are provided in an L shape.

The synthetic resin pipe 1 can be used as a connector member for piping by covering a rubber tube on the end of each tubular portion 11, 12, 13 or the like. By using the synthetic resin pipe 1 having a branch pipe, it is possible to easily pipe a tube having a branched branch. Moreover, it can also be used by inserting the end of each tubular portion of the synthetic resin pipe 1 into the connection hole of the connection partner member. The synthetic resin pipe 1 may be provided with an annular protrusion for preventing the tube from coming off at the end as necessary. Further, the synthetic resin pipe 1 may be provided with a stay for attachment, a screw hole, or the like.

It does not specifically limit as a synthetic resin material which comprises the synthetic resin pipe 1, Various synthetic resins which can be injection-molded can be used. Preferably, an olefin resin such as a polypropylene resin, a thermoplastic resin such as a polyamide resin or an acrylonitrile butadiene styrene resin, a thermosetting resin such as a melamine resin, rubber, a thermoplastic elastomer, or the like can be used. The synthetic resin pipe 1 of this embodiment is formed of a polyamide resin. The synthetic resin pipe 1 is formed by injection molding as will be described later, but other molding methods such as cutting and welding may be used in combination as necessary.

A method for manufacturing the synthetic resin pipe 1 will be described. The synthetic resin pipe 1 is formed by using synthetic resin injection molding. FIG. 3 is a schematic cross-sectional view of an injection mold used for molding the synthetic resin pipe 1. The injection mold includes a cavity mold D that defines the outer surface shape of the synthetic resin pipe 1 and core molds C1, C2, and C3 that define the inner surface shape of the synthetic resin pipe 1. In the present embodiment, the cavity mold D is configured so that the mold can be opened in the depth direction of the drawing. The core molds C1, C2, and C3 are attached to the cavity mold D, and are configured to be able to perform operations such as sliding and rotation as appropriate. A so-called cavity C is defined by the inner peripheral surface of the cavity mold D and the outer peripheral surfaces of the core molds C1, C2, and C3. The resin is filled in the cavity C and solidified to form the synthetic resin pipe 1. Is done.

The core molds C1, C2, and C3 are divided into a first core mold C1, a second core mold C2, and a third core mold C3 so as to have a shape corresponding to the shape of the pipe of the synthetic resin pipe 1. Has been. In the present embodiment, the core molds C1, C2, and C3 are provided in a columnar shape. It does not have to be a strict cylinder and may have a draft angle or the like.

The first core type C1 and the second core type C2 are provided so as to be able to advance and retreat along the extending direction of the main pipelines 1a and 1b, respectively, and correspond to the main pipeline 1a. C1 is provided, and the second core mold C2 is provided so as to correspond to the main pipeline 1b. When the mold is closed, the first core mold C1 and the second core mold C2 are in contact with the tip portions e1 and e2 of both core molds, and when the resin is injected, The core type C1 and the second core type C2 are configured so that the main pipelines 1a and 1b are obtained in a continuous form.

In the present embodiment, the first core mold C1 and the second core mold C2 are in contact with each other at the bent portions of the L-shaped main pipes 1a and 1b. A surface AS on which the first core mold C1 and the second core mold C2 abut is a plane inclined with respect to the central axis m of the first core mold C1. When they are brought into contact with each other in a plane, the end portions can be brought into close contact with each other, and the occurrence of burrs at the contact portions of the first core mold C1 and the second core mold C2 can be effectively suppressed.

The third core mold C3 is provided so as to be able to advance and retreat along the direction in which the branch pipe 1c extends, and a portion where the end portions e1 and e2 of the first core mold C1 and the second core mold C2 are in contact with each other. The end e3 of the third core mold C3 is configured to face each other.

When the mold is closed, a predetermined gap is generated between the portion where the ends of the first core mold and the second core mold are in contact with each other and the end e3 of the third core mold C3. The mold is configured to do so. Due to the existence of this gap, a resin film is formed between the end portion e3 of the third core mold C3 and the first core mold C1 and the second core mold C2 when the resin is injected. The The gap is preferably adjusted so that the thickness of the film is preferably 0.1 mm to 1.5 mm, more preferably 0.2 mm to 1 mm.

Although detailed description is omitted, the injection mold is a cavity mold D and core molds C1, C2, C3, as well as a configuration necessary for a series of injection molding, such as a sprue, a gate, an opening / closing mechanism, a guide pin, a slide It has a mechanism, a drive mechanism, a protruding pin, and the like. In particular, the injection mold of this embodiment has a slide mechanism that moves the core molds C1, C2, and C3 in the axial direction. These mechanisms are preferably configured to move to a predetermined position at a predetermined timing in conjunction with the opening / closing operation of the mold.

A series of steps in which the synthetic resin pipe 1 is injection molded will be described with reference to FIG.
First, an injection mold as described above is prepared.
(Mold closing process)
Next, the prepared mold is closed. A cavity C is formed by the cavity mold D and the core molds C1, C2, and C3 (FIG. 4A). Here, as described above, while the mold is closed, the first core mold C1 and the second core mold C2 are in contact with each other, while the end e3 of the third core mold C3 is the first core mold and the second core mold. The mold is closed so as to be spaced apart from each other.

(Injection process)
A liquid resin is injected into the cavity C to solidify the resin, and the synthetic resin pipe 1 can be formed inside the mold. The injection and solidification of the resin may be performed by a known technique according to the type of resin. At this time, simultaneously with the molding of the synthetic resin pipe 1, the injected resin enters between the end portion e3 of the third core mold C3 and the first core mold C1 and the second core mold C2, and the resin film 1d Is formed integrally with the synthetic resin pipe 1 (FIG. 4B).

(Separation process)
After the resin is injected and the synthetic resin pipe 1 is formed, first, the core molds C1 and C2 are retracted. The retraction is performed at least until the portion facing the end portion e3 of the third core mold C3 does not occur so that the third core mold C3 can be advanced and retracted without interfering with other core molds. The core mold C1 and the second core mold C2 are retracted (retracted) (FIG. 4C).

With the first core mold C1 and the second core mold C2 retracted, the third core mold C3 is advanced by a predetermined distance toward the resin film 1d. Then, the resin film 1d formed integrally with the synthetic resin pipe 1 is separated from the synthetic resin pipe 1 (FIG. 4D). The resin film 1d is separated from the inner peripheral surface of the synthetic resin pipe 1 by the corner of the end portion e3 of the third core mold C3.
The third core mold C3 is advanced to at least the thickness of the resin film 1d, and preferably the end e3 of the third core mold C3 is exposed in the main pipes 1a and 1b, so that the entire resin film 1d is synthesized. It is cut off from the resin pipe 1.

In addition, it is preferable that the retraction / separation operation of the core mold is performed in a state where the cavity mold D is not yet opened. Since the cavity mold D is closed, it is possible to prevent the molded synthetic resin pipe 1 from being deformed with advance of the third core mold C3 and separation of the resin film 1d. This is because a synthetic resin molded product can be obtained. If the deformation of the synthetic resin pipe 1 can be prevented, the third core mold C3 may be advanced after the cavity mold D is opened, and the resin film 1d may be separated.

(Removal process)
After separating the resin film 1d, the injection mold is completely opened. At this time, the first core mold C1, the second core mold C2, and the third core mold C3 are retracted to a position that does not hinder the removal of the molded body, if necessary. When the mold is opened, the synthetic resin pipe 1 from which the resin film 1d has been removed is taken out of the mold (FIG. 4E). It is preferable to blow away the removed resin film 1d with air or the like so that it does not remain inside the synthetic resin pipe 1 or inside the mold.
By the above manufacturing method, while the molded body (synthetic resin pipe 1) is still inside the mold, the resin film 1d can be removed from the molded body to obtain the synthetic resin pipe 1 having a branch pipe. .

The operation and effect of the present invention will be described.
As described above, according to the synthetic resin pipe manufacturing method of the above embodiment, the end e3 of the third core mold C3 is separated from the first core mold C1 and the second core mold C2 when the mold is closed, The resin film 1d is formed from the resin injected into the part, and then the third core mold is advanced so that the resin film 1d is separated from the synthetic resin pipe 1. Therefore, the synthetic resin pipe having the branch pipe is injected. When molding, the generation and remaining of burrs at the branch portion can be suppressed.

In the prior art, when the branch pipe is injection-molded, the ends of the three core molds must be brought into close and precise contact with each other, which increases the difficulty of mold manufacture and causes burrs. It was easy. In the prior art, it is also possible to move the core mold forward / backward so as to remove the generated burrs. However, if the generated burrs are small, the burrs may fall down and the burrs may be removed. Insufficient burrs were likely to remain on the molded body.

In the synthetic resin pipe manufacturing method of the above embodiment, the resin film 1d is once formed in the vicinity of the end e3 of the third core mold C3, and then the resin film 1d is removed. Can be suppressed. Since the resin film 1d is formed at the tip of the end portion e3 of the third core mold C3 and no small burrs are generated, it is possible to suppress the small burrs from remaining in this portion. The thickness of the resin film 1d is preferably so that the resin film 1d is reliably formed and the resin film 1d is integrally removed from the synthetic resin pipe without being decomposed by the advancement of the third core mold C3. It is preferable to determine the amount of separation of the end portion e3 of the third core mold C3 so as to be 0.1 mm to 1.5 mm, more preferably 0.2 mm to 1 mm.

Further, since the end e3 of the third core mold C3 is separated from the first core mold C1 and the second core mold C2 when the mold is closed, the first core mold C1 and the second core mold C2 are separated. The contact between the first core mold C1 and the second core mold C2 can be reduced by reducing the difficulty of manufacturing the mold by using a technique of contacting two normal core molds. It is also possible to suppress the occurrence of.

In addition, if the synthetic resin pipe manufacturing method of the present invention is applied to a synthetic resin pipe in which a branch pipe is integrated with a bent pipe as in this embodiment, the main pipe line is bent with high manufacturing difficulty. Even if it is a synthetic resin pipe having a shape and a branch pipe branching from a bent part of the main pipe, the generation and remaining of burrs at the branch of the pipe can be suppressed.

The invention is not limited to the embodiment described above, and can be implemented with various modifications. Although other embodiments of the invention will be described below, in the following description, portions different from the above-described embodiment will be mainly described, and detailed descriptions of the same portions will be omitted. Moreover, these embodiments can be implemented by combining some of them or replacing some of them.

FIG. 5 shows a synthetic resin pipe 2 having a stepped straight pipe shape as a main pipe shape as a second embodiment. In the synthetic resin pipe 2, the main pipe lines 2 a and 2 b have cross sections changed to a stepped tube, and the branch pipe line 2 c is branched from the stepped portion. The synthetic resin pipe 2 can also be used as a connector member for connecting a rubber tube or the like.

The synthetic resin pipe 2 of the second embodiment is also manufactured by injection molding. As shown in FIG. 6, a first core mold C4 corresponding to the main pipe line 2a and a second core mold C5 corresponding to the main pipe line 2b are arranged with respect to the cavity mold D, and the first core mold C4 and The second core mold C5 is configured such that the ends abut against each other when the mold is closed. Further, the third core type C6 corresponding to the branch pipe 2c is provided so that the end part e6 of the third core type faces the portion where the first core type C4 and the second core type C5 abut. In addition, the mold is configured so that the end e6 of the third core mold is separated from the first core mold C4 and the second core mold C5 when the mold is closed.

Even in such an embodiment, as in the first embodiment, it is possible to suppress the occurrence or remaining of burrs at the branching portion. That is, when injection molding is performed using the mold of the present embodiment, the portion where the end portion e6 of the third core mold faces the first core mold C4 and the second core mold C5 integrally with the synthetic resin pipe 2 Thus, a resin film is formed. After the resin is solidified, the first core mold C4 and the second core mold C5 are retracted, and the third core mold C6 is advanced to the inside of the main pipelines 2a and 2b, whereby the resin film is made of a synthetic resin pipe. 2 and the occurrence of burrs at the portion is suppressed.

As in the present embodiment, the extending direction of the third core mold C6 (on the resin film formed between the end e6 of the third core mold and the first core mold C4 and the second core mold C5 ( When there is a portion extending substantially parallel to the (sliding direction), the resin film is separated by combining the advancement and rotation of the third core mold C6 so that the resin film is separated efficiently and cleanly. You may do it.

Although the specific form of the contact portion of the first core type and the second core type provided so that the end portions come into contact with each other when the mold is closed is not particularly limited, the viewpoint of preventing the contact portion from being burred From this, it is preferable that the contact portion is a flat surface. Alternatively, when the main pipe is a stepped pipe, as in the case of the synthetic resin pipe 2 of the second embodiment, the first core type and the second core type are used as a so-called lead-in structure in the form of a stamp. By making contact, the occurrence of burrs at the contact portion can be more effectively suppressed.

The cross-sectional shape of each core type, that is, the cross-sectional shape of each pipeline (1a, 1b, 1c) is not particularly limited. The first core type and the second core type can be in the form of a cylinder or a prism. Further, the third core mold can be formed in a columnar shape, a prismatic shape, or the like as long as the core mold can be slidably attached to the cavity mold. Of the three pipes, which pipe is the main pipe and which pipe is the branch pipe is not particularly limited, but the narrowest pipe among the three pipes. Is preferably selected as the branch pipe because the step of advancing the third core mold and separating the resin film is facilitated.

In the above embodiment, various mechanisms and the like can be used for advancement / retraction of the first core type, the second core type, and the third core type, and the means for advancement / retraction is not particularly limited. For example, the first core type and the second core type may be moved forward / backward by a mechanism combining a motor and a gear, and the motor may be an electric motor or a hydraulic motor. The advance / retreat mechanism may be configured by combining an electromagnet, an air cylinder, a hydraulic cylinder, or the like with a slider mechanism or a gear mechanism. In addition, using a cam, guide groove, spiral groove, slide mechanism, gear, etc., a mechanism that converts the opening / closing operation of the mold and the operation of other slide mechanisms into a core type advance / retreat operation is used. The mold may be advanced or retracted.

In the above embodiment, the example in which the outer peripheral surface of each tubular portion (11, 12, 13) constituting the synthetic resin pipe is a simple cylindrical shape has been described. However, the shape of the outer peripheral surface of the synthetic resin pipe is The present invention is not limited to this, and other forms may be used. For example, a seal groove for mounting an O-ring may be provided at the end of the tubular portion. Alternatively, the end portion of the tubular portion may be enlarged in diameter so as to prevent the inserted rubber tube from coming off. Or the edge part of a tubular part may be formed in the shape which can be connected and latched with another connector member.

The synthetic resin pipe according to the present invention is not limited to a pipe made of only pipes. You may have a flange on the outer periphery of a pipe. In addition, the synthetic resin pipe of the present invention has an annular protrusion formed on one end of a pipe portion formed in a bent tube shape, and a cap is integrally formed on the other end of the pipe portion. It may be a thing. The cap can be a bottle or a container lid. Thus, other members may be integrally formed with the synthetic resin pipe.

The specific use of the synthetic resin pipe is not particularly limited. The synthetic resin pipe can be used as a connector member for connecting a rubber tube or a synthetic resin tube, and the synthetic resin pipe can also be used as a hose connection member. Alternatively, a synthetic resin pipe can be used as a connector member of a pressure transmission circuit such as a hydraulic circuit or a pneumatic circuit. In these applications, a seal groove may be provided in the synthetic resin pipe, or the seal member may be integrally formed.

According to the method for producing a synthetic resin pipe, a synthetic resin pipe having a branch pipe can be efficiently produced by using injection molding, and the industrial utility value is high.

DESCRIPTION OF SYMBOLS 1 Synthetic resin pipe 11, 12, 13 Tubular part 1a, 1b, 1c Pipe line D Cavity type C1 1st core type C2 2nd core type C3 3rd core type AS Contact surface C Cavity 1d Resin film

Claims (3)

A method of manufacturing a synthetic resin pipe having a main pipe line and a branch pipe branching from the main pipe line using injection molding,
Having a step of preparing an injection mold,
The injection mold has a cavity mold that defines the outer surface shape of the synthetic resin pipe and a core mold that defines the inner surface shape of the synthetic resin pipe,
The core type is divided into a first core type and a second core type that form the inner peripheral surface of the main pipeline, and a third core type that forms the inner peripheral surface of the branch pipeline,
The first core mold and the second core mold are configured such that the ends of the third core mold face each other at the portion where the ends of the second core mold contact each other.
Following the mold preparation process, it has the process of closing the injection mold,
While the mold is closed, the first core mold and the second core mold abut, while the end of the third core mold is separated from the first core mold and the second core mold,
Following the mold closing process, it has an injection process of injecting and filling synthetic resin into the mold cavity,
In the injection process, a resin film is formed between the end portion of the third core mold and the first core mold and the second core mold integrally with the synthetic resin pipe,
Subsequent to the injection step, the first core mold and the second core mold are retracted to a position where at least a portion facing the end of the third core mold does not occur,
With the first core mold and the second core mold retracted, the third core mold is advanced by a predetermined distance, and the resin film is separated from the synthetic resin pipe,
Subsequent to the separation step, the step of removing the synthetic resin pipe from which the resin film has been removed from the mold,
A method for manufacturing synthetic resin pipes. The method for producing a synthetic resin pipe according to claim 1, wherein the main pipe has a bent shape, and the branch pipe is branched from a bent portion of the main pipe. The method for producing a synthetic resin pipe according to claim 1, wherein a cross section of the main pipe line is changed to a stepped tubular shape, and the branch pipe line branches from the stepped portion.

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