JP6657044B2 - Manufacturing method of synthetic resin pipe - Google Patents

Description

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

Synthetic resin pipes are used for various purposes. Synthetic resin pipes are also used for hoses and tube connector members. If a synthetic resin pipe is manufactured using injection molding, the manufacturing efficiency is high and it is economical. In particular, it is preferable that the pipe is formed to have the shape of the pipe by injection molding because a step such as cutting is not required.

In addition, when a synthetic resin pipe having a branch conduit is integrally formed by injection molding, the pipe such as a tube can be conveniently branched by the synthetic resin pipe.
In the case of injection molding a synthetic resin pipe having a branch pipe, the core mold is divided at the branch part, and when the mold is clamped, the tips of the core molds are brought into contact with each other, and the core mold is used. Injection molding is performed so that a branched pipe is formed.

For example, Patent Literature 1 discloses a technique of injection molding a branch pipe having a pipe branching in a Y-shape. In addition to providing three core molds corresponding to each pipe, the three core molds are provided. A technique is disclosed in which a mold is formed so that the ends of the core molds can contact each other, and a resin is injected in a state where the three core molds are in contact with each other to produce a branch pipe. According to this 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 technology disclosed in Patent Document 1, it is necessary to manufacture a mold so that the tip portions of three core molds are brought into close contact with each other and precisely contacted with each other. Did not. The three core molds are arranged such that the axes of the core molds do not become one straight line, and it is necessary to abut the tips 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 tends to be out of order. Therefore, in the technique disclosed in Patent Literature 1, it is difficult to adjust the contact of the core die tip, and burrs are likely to occur. Therefore, such a manufacturing method is difficult to employ in a branch pipe application where burrs are not allowed.

Further, as a technique for bringing the tip portions of the three core types into more accurate contact with each other, a so-called “touch structure” and an “induction structure” are known. As shown in FIG. 7, the “touch structure” refers to a configuration in which the end faces of the core molds 91 and 92 that constitute the main pipe of the bent tube are abutted with each other as shown in the configuration of the cavity mold 99 and the core molds 91, 92, and 93. And a mold structure for abutting a branch conduit core mold 93 whose end face shape is adjusted to a shape that matches the corners of the butting portions of the core molds 91 and 92. In addition, as shown in FIG. 8, the configuration of the cavity mold 99 and the core molds 94, 95, 96 means that the end faces of the core molds 94, 95 constituting the main pipe of the bent tube are abutted with each other. In addition, there is provided a mold structure in which a hole is provided in the abutting portion in the extending direction of the branch pipeline core mold 96, and the end of the branch pipeline 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 generation 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 is complicated and the mating surface is also complicated. Further, when the mold structure is complicated, the strength and durability of the mold parts are likely to be adversely affected, and burrs tend to be easily generated during repeated molding.

Further, in a synthetic resin pipe having a branch pipe, if burrs are formed at a branch portion of the pipe, there is a problem that it is difficult to remove the burrs and it is difficult to inspect whether there is a burr. Further, there is a possibility that burrs that cannot be completely removed at the time of manufacturing may fall off at the time of use and be mixed into the fluid.

SUMMARY OF THE INVENTION An object of the present invention is to suppress the generation and remaining of burrs at a branch portion when injection molding a synthetic resin pipe having a branch conduit.

As a result of intensive studies, the inventor has made the end face of the third core type forming the branch pipe inner peripheral surface into contact with the first core type and the second core type abutment part forming the main pipeline inner peripheral surface. In a state where the resin is separated so as not to be in contact with the resin, resin is injected to form a resin film between the end face of the third core mold and the one core mold and the second core mold, and then the third core mold is advanced. Then, the inventors have found that if the resin film is separated from the molded synthetic resin pipe, it is possible to suppress the occurrence of burrs at the branch portion, and thus completed the present invention.

The present invention is a method for manufacturing a synthetic resin pipe having a main pipe and a branch pipe branched from the main pipe by using injection molding, comprising a step of preparing an injection mold. The injection mold has a cavity mold that defines the outer shape of the synthetic resin pipe, and a core mold that defines the inner shape of the synthetic resin pipe. The core mold has an inner peripheral surface of a main conduit. And a third core type forming the inner peripheral surface of the branch conduit, and an end of the first core type and the second core type. The end portion of the third core mold is configured to face the portion where they abut each other, and has a step of closing the injection molding mold following the mold preparation step. While the mold and the second core mold abut, the end of the third core mold is the first core mold and the second core mold. The mold is separated from the mold, and has an injection step of injecting and filling a synthetic resin into a cavity of the mold following the mold closing step. In the injection step, an 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 after the injection step, the first core mold and the second core mold have at least a portion facing the end of the third core mold. Retracting to a position that does not occur, in a state in which the first core mold and the second core mold are retracted, advancing the third core mold by a predetermined distance, and separating the resin film from the synthetic resin pipe; This is a method of manufacturing a synthetic resin pipe including a step of taking out a synthetic resin pipe from which a resin film has been removed, following a separating step, from a mold (first invention).

In the first invention, it is preferable that the main conduit has a bent shape, and the branch conduit branches off from the bent portion of the main conduit (second invention). Further, in the first invention, it is preferable that the cross section of the main conduit is changed into a stepped tube, and the branch conduit is branched from the stepped portion (third invention).

ADVANTAGE OF THE INVENTION According to the manufacturing method of the synthetic resin pipe of this invention, when injection-molding the synthetic resin pipe which has a branch conduit, generation | occurrence | production of a burr in a branch part and residual can be suppressed.
Further, according to the second and third aspects of the present invention, even if the main conduit has a bent shape or the main conduit has a stepped tubular shape, the generation and remaining of burrs at the branch portion can be effectively prevented. Can be suppressed.

It is an outline view showing the shape of the synthetic resin pipe of a 1st embodiment. It is sectional drawing which shows the shape of the synthetic resin pipe of 1st Embodiment. It is a schematic diagram which shows the injection molding die 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 pipe of 1st Embodiment. It is sectional drawing which shows the shape of the synthetic resin pipe 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 in which a core type | mold contacts each other in a prior art. It is a schematic diagram which shows the other example of the form which a core type contacts mutually in a prior art.

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

1 and 2 show a synthetic resin pipe 1 of a first embodiment manufactured by the synthetic resin pipe manufacturing method of the present invention in an external view and a sectional view. In the present 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, and 13 having through holes (channels) are integrally connected to each other, and is a so-called three crotch shape. That is, the synthetic resin pipe 1 has main pipelines 1a and 1b formed by the tubular portions 11 and 12, and a branch pipeline 1c formed by the tubular portion 13, and the branch pipeline 1c is the main. The pipes 1a, 1b branch off from a connected portion, and the pipes 1a, 1b, 1c communicate with each other. Further, in the synthetic resin pipe 1 of the present embodiment, the first tubular portion 11, the second tubular portion 12, and the third tubular portion 13 have a cylindrical outer peripheral surface and a cylindrical inner peripheral surface, respectively.

Further, although not essential, in the synthetic resin pipe 1 of the present embodiment, the main conduits 1a and 1b have a bent tube shape. That is, the synthetic resin pipe 1 is formed such that the straight tubular first tubular portion 11 and the second tubular portion 12 are bent tubes connected at an angle of about 90 degrees. Main pipelines 1a and 1b are provided in an L shape.

The synthetic resin pipe 1 can be used as a connector member for piping, for example, by covering an end of each of the tubular portions 11, 12, and 13 with a rubber tube. By using the synthetic resin pipe 1 having the branch conduit, it is possible to easily perform the piping of the tube in which the flow path is branched. Further, the end of each tubular portion of the synthetic resin pipe 1 can be used by inserting it into a connection hole of a connection partner member. If necessary, the synthetic resin pipe 1 may have an annular projection at an end to prevent the tube from coming off. Further, the synthetic resin pipe 1 may be provided with a mounting stay or a screw hole.

The synthetic resin material constituting the synthetic resin pipe 1 is not particularly limited, and various synthetic resins that 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, a rubber, a thermoplastic elastomer, or the like can be used. The synthetic resin pipe 1 of the present embodiment is formed of a polyamide resin. The formation of the synthetic resin pipe 1 is performed by injection molding as described later, but if necessary, other molding methods such as cutting and welding may be used together.

A method for manufacturing the synthetic resin pipe 1 will be described. The synthetic resin pipe 1 is formed using injection molding of synthetic resin. FIG. 3 is a schematic cross-sectional view of an injection mold used for molding the synthetic resin pipe 1. The injection mold has a cavity mold D that defines the outer shape of the synthetic resin pipe 1 and core molds C1, C2, and C3 that define the inner shape of the synthetic resin pipe 1. In the present embodiment, the cavity mold D is configured to be openable in the depth direction of the drawing sheet. 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 rotating 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, and the resin is filled into 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 conduit of the synthetic resin pipe 1. Have been. In the present embodiment, these core types C1, C2, and C3 are provided in a columnar shape. It is not necessary that the column is a strict column, and the column 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 direction in which the main pipelines 1a and 1b extend, respectively, and correspond to the first core type 1a. C1 is provided, and is divided so that the second core type C2 is provided corresponding to the main conduit 1b. When the molds are closed, the first core mold C1 and the second core mold C2 are brought into close contact with the tips e1 and e2 of the two core molds, and when the resin is injected, the first core mold C1 and the second core mold C2 are brought into contact with each other. The core type C1 and the second core type C2 are configured so that the main conduits 1a and 1b can be obtained in a continuous form.

In the present embodiment, the first core type C1 and the second core type C2 come into contact with each other at the bent portions of the L-shaped main conduits 1a and 1b. The surface AS where the first core mold C1 and the second core mold C2 come into contact with each other is a plane inclined with respect to the center axis m of the first core mold C1. When they are brought into contact on a flat surface, the ends can be brought into tight contact with each other, and the occurrence of burrs at the contact portions between the first core type C1 and the second core type C2 can be effectively suppressed.

The third core type C3 is provided so as to be able to advance and retreat along the direction in which the branch conduit 1c extends, and is provided at a portion where the end portions e1 and e2 of the first core type C1 and the second core type C2 contact each other. , And the end e3 of the third core die C3 is configured to be opposed.

In a state where the molds are closed, a predetermined gap is formed between a portion where the ends of the first core mold and the second core mold are in contact with each other and an end e3 of the third core mold C3. The mold is configured to perform Due to the existence of this gap, a resin film is formed between the end e3 of the third core die C3 and the first core die C1 and the second core die C2 when the resin is injected. You. 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 a detailed description is omitted, the injection mold includes a cavity mold D, core molds C1, C2, and C3, as well as components necessary for a series of injection molding, such as a sprue, a gate, an opening / closing mechanism, a guide pin, and a slide. It has a mechanism, a drive mechanism, and a protruding pin. In particular, the injection mold of the present embodiment has a slide mechanism for moving the core dies C1, C2, and C3 in the axial direction. It is preferable that these mechanisms be configured to move to a predetermined position at a predetermined timing in conjunction with the opening and closing operation of the mold.

A series of steps for injection molding the synthetic resin pipe 1 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. The 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. Is closed so as to be separated from the mold.

(Injection process)
A liquid resin is injected into the cavity C, and the resin is solidified, so that the synthetic resin pipe 1 is formed inside the mold. Injection and solidification of the resin may be performed by a known technique according to the type of the resin. At this time, simultaneously with the molding of the synthetic resin pipe 1, the resin injected between the end e3 of the third core mold C3 and the first and second core molds C1 and C2 enters the resin film 1d. Are 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 evacuation is performed until at least a position where a portion facing the end e3 of the third core mold C3 does not occur so that the third core mold C3 can be advanced and retracted without causing interference 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 cut off 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 e3 of the third core type C3.
The third core type C3 is advanced at least to the extent of the thickness of the resin film 1d, preferably to such an extent that the end e3 of the third core type C3 is exposed in the main conduits 1a and 1b, and the entire resin film 1d is synthesized. It is to be separated from the resin pipe 1.

It is preferable that the retracting / separating operation of the core mold is performed in a state where the cavity mold D is not yet opened. By closing the cavity mold D, the molded synthetic resin pipe 1 is prevented from being deformed due to the advance of the third core mold C3 and the separation of the resin film 1d, and the accurate shape is obtained. Is obtained. If the deformation of the synthetic resin pipe 1 can be prevented, the third core die C3 may be advanced after the cavity die D is opened to separate the resin film 1d.

(Removal process)
After the separation of the resin film 1d, the injection molding die 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 that the removed resin film 1d is blown off by air or the like so as not to remain inside the synthetic resin pipe 1 or inside the mold.
According to the above manufacturing method, the resin film 1d can be removed from the molded body while the molded body (synthetic resin pipe 1) is still inside the mold, and the synthetic resin pipe 1 provided with the branch conduit can be obtained. .

The operation and effect of the present invention will be described.
As described above, according to the method for manufacturing a synthetic resin pipe 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. A resin film 1d is formed from the resin injected into the portion, and then the third core mold is advanced to separate the resin film 1d from the synthetic resin pipe 1, so that a synthetic resin pipe having a branch conduit is injected. During molding, 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 need to be brought into close and precise contact, which makes the production of the mold more difficult 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, when the generated burrs are small, the burrs fall down and the burrs are removed. It became insufficient, and burrs were likely to remain on the molded body.

In the method of manufacturing a synthetic resin pipe of the above embodiment, the resin film 1d is formed once near the end e3 of the third core mold C3, and then the resin film 1d is removed. Can be suppressed. The resin film 1d is formed at the tip of the end e3 of the third core die C3, and small burrs do not occur. Therefore, it is possible to prevent small burrs from remaining in this portion. The thickness of the resin film 1d is preferably set such that the resin film 1d is reliably formed, and the resin film 1d is removed from the synthetic resin pipe integrally without being decomposed by the advance of the third core mold C3. It is preferable to determine the amount of separation of the end 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.

When the mold is closed, the end e3 of the third core mold C3 is separated from the first core mold C1 and the second core mold C2, so that the first core mold C1 and the second core mold C2 are separated. Can be performed by a normal technique for abutting two core molds, thereby reducing the difficulty in manufacturing a mold, and forming a burr between the first core mold C1 and the second core mold C2. Can also be suppressed.

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

The present invention is not limited to the above embodiment, and can be implemented with various modifications. Hereinafter, other embodiments of the present invention will be described. In the following description, a description will be given mainly of portions different from the above-described embodiment, and detailed description of similar portions will be omitted. Further, these embodiments can be implemented by combining some of them or replacing some of them.

FIG. 5 shows, as a second embodiment, a synthetic resin pipe 2 in which the main conduit has a stepped straight pipe shape. In the synthetic resin pipe 2, the cross sections of the main conduits 2a and 2b are changed into a stepped tubular shape, and a branch conduit 2c 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 die C4 corresponding to the main conduit 2a and a second core die C5 corresponding to the main conduit 2b are arranged with respect to the cavity die D. The second core mold C5 is configured such that the ends contact each other when the mold is closed. The third core type C6 corresponding to the branch conduit 2c is provided such that an end e6 of the third core type is opposed to a portion where the first core type C4 and the second core type C5 are in contact. The mold is configured such 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 generation and remaining of burrs at the branch portion. That is, when injection molding is performed using the mold of the present embodiment, the end e6 of the third core mold is integrally formed with the synthetic resin pipe 2 in a portion facing the first core mold C4 and the second core mold C5. Then, a resin film is formed. After the resin is solidified, the first core type C4 and the second core type C5 are retracted, and the third core type C6 is advanced to the inside of the main conduits 2a and 2b, so that the resin film is formed of a synthetic resin pipe. 2 and the occurrence of burrs at the relevant portion is suppressed.

Note that, as in the present embodiment, the extending direction of the third core type C6 (the direction in which the third core type C6 extends) is applied to the resin film formed between the end portion e6 of the third core type C4 and the second core type C5. If there is a portion extending substantially parallel to (sliding direction), the resin film is separated by combining the advance and rotation of the third core mold C6 so that the resin film is separated efficiently and cleanly. You may do so.

The specific form of the contact portion of the first core type and the second core type provided so that the ends contact each other when the mold is closed is not particularly limited, but a viewpoint of preventing burrs from being generated at the contact portion. For this reason, it is preferable that the contact portion be a flat surface. Alternatively, when the main conduit is a stepped conduit as in the case of the synthetic resin pipe 2 of the second embodiment, the first core type and the second core type are formed in a so-called lure structure, and are shaped like an intaglio. The contact makes it possible to more effectively suppress the generation of burrs at the contact portion.

The cross-sectional shape of each core type, that is, the cross-sectional shape of each conduit (1a, 1b, 1c) is not particularly limited. The first core type and the second core type can be in the form of a column, a prism, or the like. Also, the third core mold may be in the form of a cylinder, a prism, or the like, and it is sufficient that these core molds can be slidably attached to the cavity mold. It is to be noted that, among the three pipelines, which pipeline is the main pipeline and which pipeline is the branch pipeline is not particularly limited, but the narrowest pipeline among the three pipelines. Is preferably selected as a branch conduit because the step of advancing the third core die to separate the resin film can be easily performed.

In the above embodiment, various mechanisms and the like can be used for the advance and retreat of the first core type, the second core type, and the third core type, and the means for advance and retreat 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 forward / backward mechanism may be configured by combining a slider mechanism, a gear mechanism, or the like with an electromagnet, an air cylinder, a hydraulic cylinder, or the like. In addition, using a cam, guide groove, spiral groove, slide mechanism, gear, etc., the core opening / closing operation of the mold and the operation of other slide mechanisms are converted into the core type advance / retreat operation. The mold may be moved back and forth.

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

The synthetic resin pipe according to the present invention is not limited to a pipe made of only a pipe. A flange may be provided on the outer periphery of the pipe. Further, in the synthetic resin pipe of the present invention, an annular projection is formed at one end of the pipe portion formed in a bent tube shape, and a cap is integrally formed at the other end of the pipe portion. It may be a thing. The cap can be a bottle or container lid. As described above, 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 a synthetic resin pipe, or a seal member may be integrally formed.

According to the method of manufacturing a synthetic resin pipe described above, a synthetic resin pipe having a branch conduit can be efficiently manufactured by using injection molding, and has high industrial utility value.

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

Claims (3)

A main pipe, a method of manufacturing a synthetic resin pipe having a branch pipe branched from the main pipe using injection molding,
Having a step of preparing an injection mold,
The injection molding mold has a cavity mold that defines the outer shape of the synthetic resin pipe, and a core mold that defines the inner shape of the synthetic resin pipe,
The core type is configured to be divided into a first core type and a second core type forming an inner peripheral surface of a main conduit, and a third core type forming an inner peripheral surface of a branch conduit,
The first core type and the second core type are configured such that the end of the third core type faces a portion where the ends of the second core type abut against each other,
Following the mold preparation step, there is a step of closing the injection mold,
With the mold closed, the first core mold and the second core mold are in contact with each other, while the end of the third core mold is separated from the first core mold and the second core mold,
Following the mold closing step, there is an injection step of injecting and filling the synthetic resin into the mold cavity,
In the injection step, a resin film is formed integrally with the synthetic resin pipe between the end of the third core mold and the first and second core molds,
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,
A step of advancing the third core mold by a predetermined distance in a state where the first core mold and the second core mold are retracted, and separating the resin film from the synthetic resin pipe;
Following the separating step, having a step of removing the synthetic resin pipe from which the resin film has been removed from the mold,
Manufacturing method of synthetic resin pipe. The method for producing a synthetic resin pipe according to claim 1, wherein the main pipe has a bent shape, and the branch pipe branches 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 conduit is changed into a stepped tubular shape, and the branch conduit is branched from the stepped portion.

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