JP2018079626A - Method for producing tubular resin molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an indentation that may occur in a cut-off part of a gate from becoming a weak point in terms of a quality and strength of a tubular molded body 1.SOLUTION: The tubular resin molded body 1 having a hollow tubular part 11 is produced by injection molding of a thermoplastic resin. In injection molding, a mold having a cavity 31 having a pressurizing port 32 at one end and a discharge port 33 at the other end is prepared, the thermoplastic resin is injected into the cavity through a gate, and then the hollow tubular part 11 is formed by press fitting a pressurized fluid from the pressurizing port 32 into the cavity. The tubular resin molded body 1 has a protrusion 12 in the hollow tubular part 11. The protrusion 12 is provided with a concave portion 13 in a thickness-stealing shape, and a cross-sectional shape of a portion where the protrusion 12 and the hollow tubular part 11 are connected is, for example, an U-shaped cross section. A gate 35 of an injection mold is provided radially outside a partial cavity 311 forming the protrusion 12.SELECTED DRAWING: Figure 5

Description

The present invention relates to a method for producing a tubular resin molded body integrally molded with a synthetic resin. In particular, the present invention relates to a method for manufacturing a tubular resin molded body using injection molding.

Tubular resin moldings integrally molded with synthetic resin are used in various applications such as various pipes, connector members, and pipe joints. In particular, if the tubular resin molded body is integrally formed by using synthetic resin injection molding, the tube end seal structure and the mounting member can be integrally formed, which is convenient.

A technique for manufacturing a tubular resin molded body using injection molding is known. If the hollow tubular portion is a short tubular resin molded body, the tubular resin molded body can be injection molded using a mold having a core mold that defines the inner peripheral surface shape of the tube.
Also, in recent years, a technology that forms a hollow tubular part by introducing a pressurized gas or liquid into the central part of the resin and eliminating the resin at the central part of the resin once injected into the cavity has been put into practical use. Has been. As such a technique, a gas-assisted injection technology (Gas-assisted Injection Technology: GIT method), a water-assisted injection technology (Water-assisted Injection Technology: WIT method), and the like are known. For example, Patent Document 1 discloses a tubular resin molded body formed by a water assist injection molding technique.

In addition, as a technique for forming a hollow tubular portion by introducing a gas or liquid pressurized during injection molding, a technique using a so-called floating core is also known. For example, in Patent Document 2, after injecting molten resin into a cavity, a floating core having a size that can pass through the cavity is pushed from the pressurized port of the cavity with a pressurized fluid and injected into the cavity. An injection molding technique is disclosed in which a hollow tubular portion is formed by advancing the molten resin along the mold cavity to the discharge port. According to the manufacturing method, it is disclosed that a hollow product having a complicated shape with a uniform hollow part size can be injection-molded.

JP2015-139879A Japanese Patent Laid-Open No. 04-208425

When these tubular resin moldings are formed by the GIT method, the WIT method, or the molding method using a floating core, the gate separation part may cause a quality problem. That is, when a gate for injecting the resin into the cavity in these methods is provided on the outer periphery of the hollow tubular portion, when the gate is cut, a depression is generated in the gate cut portion (so-called gate mark) of the tubular resin molded body, It may be a problem in appearance quality. In addition, such a depression may be a weak point in strength when the hollow tubular portion is used as a pressure-resistant tube.

In particular, when a tubular resin molded body is molded from a thermoplastic resin containing reinforcing fibers, the indentation that occurs in the portion where the gate is separated tends to increase, and the above problem tends to become apparent.

The objective of this invention is providing the manufacturing method of a tubular resin molding which can suppress that the hollow which may arise in the isolation | separation part of a gate becomes a weak point on the quality and strength of a tubular molded body. .

As a result of intensive studies, the inventor has found that the above problem can be solved by providing a projection of a specific form in the hollow tubular part of the tubular molded body and providing a gate at a position on the radially outer side of the projection, The present invention has been completed.

The present invention is a method for producing a tubular resin molded body having a hollow tubular portion by using injection molding of a thermoplastic resin, and the injection molding includes a pressurized port capable of injecting a pressurized fluid at one end. A mold having a cavity having a discharge port at the other end is prepared, the outer surface shape of the tubular resin molded body is defined by the cavity, and a molten thermoplastic resin is injected into the cavity through a gate and filled. The pressurized fluid is press-fitted into the cavity from the pressurized port, and a part of the resin in the cavity is discharged from the discharge port to form a hollow tubular part. Adjacent to the tube, and has a protruding portion that is formed to protrude outward in the radial direction of the tube, and the protruding portion is provided with a recess in a stealing shape, and the protruding portion and the hollow tubular portion are connected to each other The cross-sectional shape of the part is It has a cross-section of a letter shape, a letter H shape, a letter C shape, a letter U shape, a letter L shape, a letter shape, or a letter T shape. It is a manufacturing method of the tubular resin molding provided in the radial direction outer side of the pipe | tube of the partial cavity to form (1st invention).

In the first invention, preferably, prior to injection of the thermoplastic resin, the floating core is provided in the pressurized port, the floating core is moved to the discharge port side by pressurization of the pressurized fluid, and the hollow tubular is moved by the movement of the floating core. Part is formed (second invention). In the first invention, preferably, the thermoplastic resin contains reinforcing fibers (third invention).

According to the method for manufacturing a tubular resin molded body of the present invention (first invention), even if a dent is generated due to the separation of the gate, problems in quality and strength of the hollow tubular portion hardly occur. Moreover, it can also suppress that the problem on quality or an intensity | strength arises in a hollow tubular part by providing a protrusion part. In the second invention, in particular, the shape of the inner peripheral surface of the hollow tubular portion can be stably and accurately formed, and the effect of suppressing the occurrence of problems in quality and strength of the hollow tubular portion is high. In the third invention, even when the thermoplastic resin contains reinforcing fibers, it is possible to suppress the occurrence of problems in quality and strength of the hollow tubular portion.

It is a partial cross section figure which shows the shape of the tubular resin molding manufactured by the manufacturing method of this invention. The perspective view which shows the shape of the protrusion part of the tubular resin molding manufactured by the manufacturing method of this invention It is a figure which shows the cross-sectional shape of the connection part vicinity of the protrusion part of a tubular resin molding. It is a figure which shows the other example of the cross-sectional shape of the connection part vicinity of the protrusion part of a tubular resin molding. It is a schematic diagram which shows the structure of the injection mold used for the manufacturing method of this invention. It is a schematic diagram which shows a part of process of the manufacturing method of this invention. It is a schematic diagram which shows a part of process of the manufacturing method of this invention. It is a schematic diagram which shows a part of process of the manufacturing method of this invention. It is sectional drawing which shows the shape of the resin molding taken out from the metal mold | die in the process of the manufacturing method of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, taking as an example a tubular resin molded body used for liquid transfer piping. The invention is not limited to the individual embodiments shown below, and can be carried out by changing the form.

FIG. 1 is a diagram showing the shape of a tubular resin molded body 1 manufactured by a manufacturing method to be described later. In the drawing, lower and left portions of the tube center line are shown in cross section, and other portions. Is shown in appearance. The tubular resin molded body 1 has a hollow tubular portion 11 that is shaped to be a hollow tube. The hollow tubular portion 11 may be a straight tubular shape or a curved tubular shape. According to the manufacturing method described later, the hollow tubular portion 11 can be formed even in a bent tube shape, particularly a bent tube shape in which it is difficult to remove a normal core type.

The tubular resin molded body 1 has a projecting portion 12 that is formed adjacent to the hollow tubular portion 11 so as to project from the outer periphery of the hollow tubular portion 11 to the radially outer side of the tube. In the present embodiment, the overall shape of the projecting portion 12 is a rectangular parallelepiped shape that is long in the direction along the center line of the tube, but is not limited to this, and is not limited to this, but a triangular prism shape, a cylindrical shape, a pyramid shape, a kamaboko shape. Other protruding shapes such as a shape may be used.

The protrusion 12 is provided with a recess 13 in the form of stealing. That is, the projecting portion 12 is formed in a stealed shape so that a concave portion 13 is formed in an overall shape of, for example, a rectangular parallelepiped shape, and is integrally formed on the outer periphery of the hollow tubular portion. And the cross-sectional shape (cross-sectional shape in the XX cross section of FIG. 1) of the part which the protrusion part 12 and the hollow tubular part 11 connect is a U-shaped cross section, as shown in FIG. The thickness t of the protruding portion in the cross section of the connecting portion, that is, the width dimension t of the line in the cross section of the connecting portion (the dimension indicated by t in FIG. 3) of the hollow tubular portion 11 at the position where the protruding portion is to be formed. It is preferable that t <T with respect to the wall thickness T.

The cross-sectional shape of the portion where the projecting portion 12 and the hollow tubular portion 11 are connected is not limited to the U-shape as shown in the above embodiment, but as shown in FIG. , H-shape (a), C-shape (b), U-shape (c), L-shape (d), self-shape or T-shape (e), (f), etc. It can be a cross section.

The protrusion 12 has a gate mark 15. The gate mark 15 is provided at a position on the outer side in the radial direction of the pipe in the protrusion 12.

The tubular resin molded body 1 may include other portions of the hollow tubular portion 11 and the protruding portion 12. For example, the tubular resin molded body 1 includes a flange 16 in the vicinity of the end of the hollow tubular portion 11, and can improve the attachment property and sealing property of the tube. Similarly, a seal groove, a protrusion or the like may be provided near the end of the hollow tubular portion 11. The tubular resin molded body 1 may be integrally formed with stays, fixing portions, bosses, and the like for attachment and connection. Further, the tubular resin molded body 1 may be provided with a branch pipe branched from the hollow tubular portion.

As the resin material constituting the tubular resin molded body 1, various thermoplastic resins capable of injection molding can be used. As the thermoplastic resin, typically, general-purpose resins such as olefin resins, engineering plastics such as polyamide resins and polyacetal resins, and super engineering plastics such as polyphenyl sulfide resins and polyether ether ketone resins can be used. . Various kinds of reinforcing materials (such as talc) and reinforcing fibers may be blended in the thermoplastic resin. Examples of the reinforcing fiber include glass fiber, aramid fiber, and carbon fiber. You may mix | blend various fillers, additives, a coloring agent, etc. with a thermoplastic resin.

The tubular resin molded body 1 can be used, for example, as a constituent member such as a hydraulic pipe of an automatic transmission of an automobile or a water-cooled pipe of a cooling mechanism. In addition, the use of the tubular resin molded body 1 is not limited to this, and can be used as a tube used for transferring gas and fluid and transmitting pressure, and also as a tube used for transferring powder and granules. Can be used.

Hereinafter, the manufacturing method of the said tubular resin molding 1 is demonstrated. First, the resin molded body 5 (FIG. 9) is integrally molded using injection molding, and unnecessary portions are cut out from the resin molded body 5 to obtain the tubular resin molded body 1. FIG. 9 is a sectional view showing the shape of the resin molded body 5. In this example, the tubular resin molded body 1 as shown in FIG. 1 is obtained by cutting both ends of the hollow tubular portion at positions indicated by AA and BB in FIG. 9 and cutting the gate and the runner. .

The process of injection molding the resin molded body 5 will be described. A mold used for injection molding of the resin molded body 5 has a gate and a cavity, and a molten thermoplastic resin is injected into the cavity through the gate. When the cavity is filled with resin, the cavity 31 defines the outer surface shape of the resin molded body 5 (that is, the tubular resin molded body 1). The cavity is provided with a pressurized port through which pressurized fluid can be injected at one end side of the portion forming the hollow tubular portion. Furthermore, the cavity has a discharge port on the other end side.

In the injection molding process, molten thermoplastic resin is injected and filled into the cavity through the gate. After the resin is filled, while the resin in the cavity is not completely solidified, a pressurized fluid is pressed into the cavity from the pressurized port, and a part of the resin in the cavity, particularly the part of the cavity that forms the hollow tubular part is formed. The resin at the center is discharged from the discharge port to form a hollow tubular portion. After the hollow tubular portion is formed, cooling is further performed, and after the shape of the resin molded body 5 is fixed, the resin molded body 5 is taken out from the mold.

For the injection molding of the hollow tubular portion using such a pressurized fluid, the above-described GIT method, WIT method, or molding method using a floating core can be used. Hereinafter, the injection molding process will be described in detail by taking a molding method using a floating core as an example with reference to FIGS. 5 to 8, but the invention is not limited to the molding method using a floating core.

FIG. 5 is a schematic sectional view of a mold used in the injection molding process. The mold 3 is configured to be openable and closable in a direction perpendicular to the paper surface so that the molded product can be taken out. The mold 3 is provided with a cavity 31 and a gate 35. By injecting and filling molten thermoplastic resin from the runner 36 into the cavity through the gate 35, the inner peripheral surface shape of the cavity 31 is transferred and the outer surface shape of the resin molded body 5 is defined.

The cavity 31 includes a partial cavity 311 corresponding to the protrusion 12 of the tubular resin molded body 1, and the shape of the inner peripheral surface of the partial cavity 311 defines the shape of the protrusion 12 and the shape of the recess 13. The gate 35 is provided at a radially outer position of the pipe of the partial cavity 311.

A pressurizing port 32 is provided at one end of the cavity 31 corresponding to the hollow tubular portion 11. The pressurized port 32 is connected to a pressurized fluid system (not shown) for pressurizing and discharging pressurized fluid. Further, a portion for temporarily supporting the floating core is provided in a portion where the pressurization port communicates with the cavity, and the floating core 2 is disposed in this portion prior to the injection of the resin.

The floating core 2 may be made of metal or resin. In the case of resin, it may be the same type of resin as the thermoplastic resin used for injection molding or a different type of resin. The shape of the floating core 2 is a shape having a cross-sectional shape of the inner peripheral surface to be formed, such as a cylindrical shape, a conical shape, a bullet shape, and the like in addition to the illustrated spherical shape.

A discharge port 33 is provided at the other end of the portion of the cavity 31 corresponding to the hollow tubular portion 11. A waste cavity 34 is connected to the discharge port 33. An opening / closing means 37 that can be opened and closed is provided between the discharge port 33 and the disposal cavity 34.

6 to 8 are diagrams showing each stage of the injection molding process.
First, the mold 3 is closed with the floating core 2 disposed on the pressure port 32 side. At this time, the opening / closing means 37 is closed. As shown in FIG. 6, molten resin is injected and filled into the cavity 31 through the runner 36 and the gate 35. At this time, the resin injected from the gate 35 fills the cavity 31 via the partial cavity 311 that forms the protruding portion 12. It is not necessary to completely fill the cavity 31 of the mold with resin at this stage. If the filling of the resin into the cavity 31 is completed by the press-fitting of the pressurized fluid described later, the filling of the resin at this stage is an incomplete filling so that the resin does not reach a part of the cavity 31. There may be.

After the injection of the resin from the gate 35 is completed, the opening / closing means 37 provided at the discharge port 33 is opened, and pressurized fluid is press-fitted into the cavity 31 from the pressurized port 32. The pressurized fluid may be a gas such as nitrogen gas, carbon dioxide gas, or air, or may be a liquid such as glycerin, liquid paraffin, or water. The pressurized fluid is preferably a fluid that does not react with or be compatible with the injected resin, and an inert gas such as nitrogen gas is particularly preferable. The pressurization of the pressurized fluid may be performed by a known pressurized fluid system.

When the pressurized fluid is injected, as shown in FIG. 7, the floating core 2 is pushed by the pressurized fluid and moves in the resin in the cavity. At this time, the floating core 2 moves forward toward the discharge port 33 while leaving the resin near the outer periphery of the cavity 31 that has started to be cooled and solidified, throwing out the molten resin at the center that is delayed in cooling from the discharge port 33 to the cavity 34. To do. And after the floating core 2 passes, the hollow tubular part 11 which has an internal diameter substantially equal to the diameter of the floating core 2 will be formed. Further, the resin of the portion that becomes the hollow tubular portion 11 is pressed against the inner peripheral surface of the cavity of the mold by the pressure of the pressurized fluid, and is cooled in a state where the shape of the tube is maintained.

When the pressurization of the pressurized fluid is further advanced, the floating core 2 reaches the position of the discharge port 33 as shown in FIG. 8, and the entire hollow tubular portion 11 is formed. By holding the pressurized fluid pressure inside the hollow tubular portion 11 formed in this state, the resin and the peripheral wall surface of the cavity 31 can be sufficiently pressed together, and the outer shape of the molded body is accurate. Is preferable.

In this embodiment, the floating core 2 is configured to stop on the front side of the discharge port 33, but the diameter of the discharge port is increased so that the floating core 2 reaches the disposal cavity 34 beyond the discharge port 33. You may make it do.

In the state shown in FIG. 8, when the resin in the cavity of the mold 3 was sufficiently solidified, the pressurization of the pressurized fluid was released, and then the mold 3 was opened and molded. The resin molded body 5 is taken out.

As shown in AA and BB in FIG. 9, unnecessary portions of the tubular resin molded body 1 in FIG. Further, the gate and runner portions are separated from the resin molded body 5. Thereby, the tubular resin molding 1 is obtained. In addition, when obtaining the tubular resin molding 1 from the resin molding 5, you may perform drilling by drilling, the assembly | attachment of another member, etc. as needed.

Hereafter, the effect | action and effect of the said tubular resin molding 1 and the said manufacturing method are demonstrated.
In the tubular resin molded body 1 manufactured by the above manufacturing method, since the gate 35 is connected to the radially outer side of the pipe of the partial cavity 311 that forms the protruding portion 12, the gate or Even if the runner part is excised, the gate mark 15 remaining in the excised part is generated at a position separated from the hollow tubular part 11. Therefore, even if a defect or a dent is generated in the gate mark 15 due to the separation of the gate, it is difficult to cause a problem in quality and strength of the hollow tubular portion 11.

When the thermoplastic resin used for injection molding contains reinforcing fibers, the defects and dents generated in the gate mark 15 due to the separation of the gate often become larger, but even in this case, the manufacturing method is used. In the tubular resin molded body 1 to be formed, the gate marks 15 are formed on the outer side in the radial direction of the protruding portion 12 so as to be separated from the hollow tubular portion 11.

From the viewpoint of more reliably suppressing problems in quality and strength of the hollow tubular portion 11, the distance from the outer peripheral surface of the hollow tubular portion 11 to the location where the gate is connected, that is, the protrusion of the protrusion 12. It is preferable that the amount be 1 or more times, more preferably 2 or more times the thickness dimension of the gate.

In addition, as described below, when the tubular resin molded body 1 is manufactured by the above manufacturing method, the protruding portion is provided with a concave portion in a stealing shape, and the protruding portion and the hollow tubular portion are connected to each other. The cross-sectional shape is a U-shaped, H-shaped, C-shaped, U-shaped, L-shaped, self-shaped or T-shaped cross-section. It contributes to suppressing the problem on the quality of the hollow tubular part 11 which tends to arise by providing in a protrusion part, and the intensity | strength.

During the investigation, in the injection molding of the hollow tube using pressurized fluid, if a gate is provided on the outer peripheral side of the protruding part that does not have a meat steal-shaped recess, the gate trace is kept away from the hollow tubular part. Nevertheless, the inventors have discovered that quality problems and strength problems such as a decrease in the pressure resistance of the tubular portion or a defective molding due to a failure of the injection molding process may occur.

The manufacturing method includes a step of press-fitting a pressurized fluid into the cavity after the resin is injected, and discharging a part of the resin in the cavity from the discharge port to form a hollow tubular portion. In this resin discharge process using pressurized fluid, the inner peripheral surface shape of the tube is not clearly defined by the mold, and is formed by discharging the portion where resin cooling or solidification is delayed. There is a problem in that it is difficult to form a hollow tubular portion having a uniform cross section with a high degree of freedom in which position and shape the inner peripheral surface of the tube is formed.

For this reason, if a protrusion without a stealing-shaped recess is provided and a gate is provided there, the temperature in the vicinity of the protrusion is high. The inventors speculated that the uniformity of the temperature distribution in the circumferential direction and the axial direction in the portion that should become the hollow tubular portion would be impaired. As a result, the hollow tubular portion becomes uneven, resulting in a thin tube wall, resulting in a decrease in pressure resistance, or a portion with a high resin temperature being unevenly distributed, resulting in molding failure at the press-fitting stage of pressurized fluid. The inventors have speculated that this may be a problem in terms of quality and strength.

In the tubular resin molded body 1 according to the present invention, the protruding portion 12 (partial cavity 311) provided with a gate at the time of injection molding is provided with a concave portion in the shape of a stealer, the protruding portion and the hollow tubular portion. The cross-sectional shape of the portion to which is connected is a U-shaped, H-shaped, C-shaped, U-shaped, L-shaped, self-shaped or T-shaped cross-section, Thereby, the location where the protruding portion 12 and the hollow tubular portion 11 are connected is connected with an elongated linear cross section, and the capacity of the protruding portion 12 (partial cavity 311) is reduced. For this reason, the resin present in the protruding portion 12 (partial cavity 311) is difficult to prevent the cooling of the resin to be the hollow tubular portion, and the quality and strength problems are less likely to occur.

From this point of view, the width t of the cross-sectional line in the cross-sectional shape of the portion where the protruding portion 12 and the hollow tubular portion 11 are connected (the dimension indicated by t in FIGS. 3 and 4) is that the protruding portion should be formed. It is preferable that t <T with respect to the thickness T of the hollow tubular portion 11 at the position. By making the width dimension t of the cross section smaller than the thickness T of the hollow tubular portion, the cooling of the resin in the cavity portion forming the hollow tubular portion 11 is less affected by the resin forming the protruding portion 12. Because. Note that the width dimension t does not need to be a constant width over the entire cross section, and may be a width dimension that varies depending on a portion in the cross section.

In particular, prior to the injection of the thermoplastic resin, the floating core is provided in the pressurized port, the floating core is moved to the discharge port side by pressurization of the pressurized fluid, and the hollow tubular portion is formed by the movement of the floating core. That is, when the hollow tubular part is formed by press-fitting a pressurized fluid in combination with a floating core, the hollow tubular part can be easily formed thinner than the GIT method or the WIT method. The shape of the inner peripheral surface of the hollow tubular portion can be stably and accurately molded, and the effect of suppressing the occurrence of problems in quality and strength of the hollow tubular portion is high.

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

In the detailed description of the above embodiment, the method of forming the hollow tubular portion by press-fitting a pressurized fluid using a floating core has been described in detail. However, in other methods that do not use a floating core, such as the GIT method and the WIT method. Similarly, the gate mark 15 is formed by the protrusion 12 so as to be separated from the hollow tubular portion 11, and the protrusion 12 having the recess 13 has a specific cross-sectional shape (for example, a U-shape). 11, the cooling of the resin in the hollow tubular portion is suppressed from becoming uneven, and the occurrence of problems in terms of quality and strength of the hollow tubular portion 11 in the tubular resin molded body 1 is suppressed. Can be suppressed.

Moreover, although the hollow tubular part demonstrated the example which does not have a branch pipe in the tubular resin molding 1 in the said embodiment, the branch pipe may be provided in the hollow tubular part. Such a branch pipe may be formed at the same time as the hollow tubular portion serving as the main pipe by using press-fitting of a pressurized fluid. Alternatively, the hollow tubular portion serving as the main tube is formed by using press-fitting of a pressurized fluid, and the branch pipe portion is formed by drilling by a drilling process or the like to form the branch pipe portion by other methods. Also good. In the description of the above embodiment, an example in which the hollow tubular portion 11 is formed in a cylindrical shape has been described. However, the hollow tubular portion 11 may be formed in another shape, for example, a rectangular tube shape. If a square tubular hollow tubular part is to be formed, a floating core having, for example, a rectangular cross-sectional shape may be used.

In the description of the above embodiment, an example of a mold in which the discharge port 33, the opening / closing mechanism 37, and the discard cavity 34 are sequentially arranged is shown, but the specific shape of the discharge port and the discard cavity is not particularly limited, For example, both may have the same cross-sectional shape in a cross section perpendicular to the resin flow direction. Further, the opening / closing mechanism 37 may be omitted if a series of injection processes and a pressurizing process of pressurized fluid can be performed.

According to the said manufacturing method, the tubular resin molding excellent in quality can be manufactured efficiently, and industrial utility value is high.

DESCRIPTION OF SYMBOLS 1 Tubular resin molding 11 Hollow tubular part 12 Projection part 13 Recess 15 Gate mark 16 Flange 2 Floating core 3 Injection mold 31 Cavity 311 Partial cavity 32 Pressurization port 33 Discharge port 34 Disposal cavity 35 Gate 36 Runner 37 Opening / closing means 5 resin moldings

Claims (3)

A method for producing a tubular resin molded body having a hollow tubular portion using injection molding of a thermoplastic resin,
The injection molding is
A mold having a cavity having a pressurized port capable of injecting pressurized fluid at one end and a discharge port at the other end is prepared, and the outer surface shape of the tubular resin molded body is defined by the cavity,
Molten thermoplastic resin is injected into the cavity through the gate and filled,
A pressurized fluid is pressed into the cavity from the pressurized port, and a part of the resin in the cavity is discharged from the discharge port to form a hollow tubular part,
The tubular resin molded body is
Adjacent to the hollow tubular portion, it has a protruding portion that is formed to protrude outward in the radial direction of the tube, and the protruding portion is provided with a concave portion in a stealing shape, and the protruding portion and the hollow tubular portion The cross-sectional shape of the portion to which is connected is a U-shaped, H-shaped, C-shaped, U-shaped, L-shaped, self-shaped or T-shaped cross-section,
In the mold, the gate is provided on the radially outer side of the tube of the partial cavity that forms the protrusion.
Manufacturing method of tubular resin molding. Prior to injection of thermoplastic resin, a floating core is provided in the pressure port,
The method for producing a tubular resin molded body according to claim 1, wherein the floating core is moved to the outlet side by pressurization of the pressurized fluid, and the hollow tubular portion is formed by the movement of the floating core. The manufacturing method of the tubular resin molding of Claim 1 in which a thermoplastic resin contains a reinforced fiber.

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