JP2002018911A - Method for molding resin tube and mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for molding a resin tube capable of molding the tube accurately at an end of each tube as one component in the case of molding the tube of a tubular shape having at least one bent tube part. SOLUTION: The method for molding the resin tube comprises the step of slidably inserting three slide cores 23, 24 and 25 to a position in the drawing in a cavity C of a branched tube shape of a main mold 21. The method further comprises the step of then injecting a molten resin from a resin gate 26. The method also comprises the step of pouring a high pressure water from a check valve 30 to the molten resin filled in a slide core insertion impossible region A via a water channel 24a of the core 24. Thus, a tubular hollow wall as shown by a chain dotted line in the drawing is formed at the region A by pouring the high pressure water, excess molten resin urged by the water is drained together with the high pressure water from a communication passage 25b of the core 25 by drawing a piston 28, and a branch tube is molded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a resin tube, and more particularly to a method and a device for molding a resin tube having a bent tube portion extending along at least one bending path.

[0002]

2. Description of the Related Art Conventionally, when a branch pipe is formed by resin molding, a resin injection molding method using a slide die (slide core) has been used. That is, after injecting the molten resin into the cavity of the main mold corresponding to the outer surface shape of the molded product, the slide core is inserted to form the branch pipe. However, in the case of a branch pipe having a bent pipe portion extending in at least one bent path, it is difficult to form the pipe in one piece. Therefore, like the branch pipe 81 shown in FIG. 8, two parts, one straight pipe 82 extending straight and a bent pipe 83, are formed, and the two parts 82, 83 are assembled to manufacture the branch pipe 81. Was.

[0003] If a blow molding method is used, a branch pipe of this kind can be formed in one piece. That is, a hollow pipe having a desired branch shape is blow-molded, and each branched end of the hollow body is cut and opened to form a branch pipe.

[0004]

However, when the branch pipe is formed by blow molding, the thickness of the pipe tends to be uneven at the end of the pipe. For example, as shown in FIG. A constricted portion 85a is formed on the peripheral surface, and a locally thin portion is formed. Since the end of the branch pipe is a connection to a hose or pipe, this connection requires a certain degree of shape (such as the shape of the inner peripheral surface) and dimensions (such as the inner diameter and thickness). Strength is also needed. For this reason,
Such a constricted portion 85a reduces the accuracy of the shape and dimensions,
As a result, the strength is reduced, so that a method of assembling two parts as shown in FIG. 8 has to be adopted. Further, Japanese Patent Application Laid-Open No. 7-88897 discloses a gas injection molding method for molding an S-shaped tube. However, this gas injection molding method also suffers from the problem that it is difficult to obtain sufficient accuracy in the shape and dimensions, for example, a constriction is formed on the inner peripheral surface of the tube end.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to form a tubular resin tube having at least one bent tube portion with high precision at the end of each tube portion. Another object of the present invention is to provide a molding method and a mold apparatus capable of molding a resin tube as one part.

[0006]

According to a first aspect of the present invention, there is provided a tube having a bent tube portion extending in at least one bent path and having a tube end open at all ends. A method for molding a resin tube, comprising: an injection step of injecting molten resin into a cavity of a main mold for molding an outer surface of the resin tube; and a slide mold insertion for slidingly inserting a plurality of slide molds to a predetermined position in the cavity. By the process, while forming the inner peripheral surface of the end portion of all the tube portion, for the molten resin in the region including a part of the bent tube portion where the slide mold is not inserted, a plurality of the slide molds sandwiching the region The assist fluid is injected through at least one of the above, and the excess molten resin displaced by the injection of the assist fluid through another slide mold is supplied to the area. The point is to remove it from the area.

According to the present invention, the injection step of injecting the molten resin into the cavity of the main die and the slide die insertion step of slidingly inserting a plurality of slide dies into the cavity to a predetermined position are performed in any order regardless of the order. Then, the inner peripheral surfaces of the ends of all the tube portions are formed. Next, the assist fluid is injected into the molten resin in a region including a part of the bent tube portion into which the slide mold is not inserted, via at least one of a plurality of slide molds sandwiching this region. The excess molten resin displaced by the injection of the assist fluid is removed from the area via another slide mold. By the injection of the assist fluid, the inner peripheral surface of the bent tube portion is formed to form the tube wall. The inner peripheral surface of the end of the tube is formed with high precision by a slide die. Therefore, by using this molding method, it is possible to mold a resin pipe having at least one bent pipe part with high accuracy at the end of each pipe part and as one part.

According to a second aspect of the present invention, in the method for molding a resin pipe according to the first aspect, the tip of the slide die for molding the inner peripheral surface at the end of the bent tube is bent. The gist is to form a surface shape corresponding to the inner surface, and to form the bent inner surface of the bent tube portion at the distal end surface when the slide mold is slid and inserted.

According to this invention, in addition to the operation of the second aspect of the present invention, the bent inner surface of the bent tube portion is formed by the tip of the slide die inserted to form the inner circumferential surface of the end portion of the bent tube portion. Molded. Therefore, the thickness of the bent portion of the bent tube portion is formed uniformly.

[0010] The invention described in claim 3 is the invention according to claim 1 or 2.
Wherein the assist fluid is an incompressible fluid. According to this invention, in addition to the effect of the first or second aspect of the invention, since the assist fluid injected into the molten resin in the region is an incompressible fluid (for example, a liquid), the compressible fluid (for example, a gas) is used. The bent tube portion can be formed to have a more uniform wall thickness as compared with the case where it is used.

According to a fourth aspect of the present invention, in the method for molding a resin pipe according to any one of the first to third aspects, the resin pipe is a branch pipe. ADVANTAGE OF THE INVENTION According to this invention, the branch pipe | tube which has at least one bending pipe | tube part can shape | mold the end part of each pipe | tube part accurately, and also as one part.

According to a fifth aspect of the present invention, there is provided a mold apparatus for molding a resin tube having a tube shape having a bent tube portion extending in at least one bending path and having all ends of the tube portion open. A main mold having a cavity having an inner surface shape for molding the outer surface of the resin tube, a slide mold that is slid into the cavity to mold an end inner peripheral surface of the tube, and the slide mold. In order to inject an assist fluid through at least one of the plurality of slide dies sandwiching the region, the molten resin in the region including a part of the bent tube portion that is not inserted is provided in the slide die. A fluid injection means is provided on the other slide mold for removing excess molten resin displaced by the injection of the assist fluid from the area via the other slide mold. And summarized in that and a fat discharging means.

According to the present invention, the molten resin is injected into the cavity of the main mold, the slide mold is slid into the cavity to a predetermined position, and the inner peripheral surfaces of the ends of all the pipes are formed. Next, an assist fluid is injected into the molten resin in a region including a part of the bent tube portion into which the slide die is not inserted by the fluid injection means via at least one of a plurality of slide dies sandwiching this region. You. Then, the excess molten resin displaced by the injection of the assist fluid is removed to the outside of the area by the resin discharging means via another slide mold. By the injection of the assist fluid, the inner peripheral surface of the bent tube portion is formed to form the tube wall. The inner peripheral surface of the end of the tube is formed with high precision by a slide die. Therefore, by using this molding method, a resin tube having at least one bent tube portion, the end portion of the tube portion with high accuracy,
Moreover, it can be molded as one part.

According to a sixth aspect of the present invention, in the mold apparatus according to the fifth aspect, the slide die for forming the inner peripheral surface of the end portion of the bent tube portion has a distal end surface formed of the bent tube portion. The gist is to have a surface shape corresponding to the bent inner surface.

According to this invention, in addition to the function of the invention of claim 5, the bent inner surface of the bent tube portion is formed by the tip of the slide die which is slid and inserted to form the inner circumferential surface of the end portion of the bent tube portion. Molded. Therefore, the thickness of the bent portion of the bent tube portion is formed uniformly.

The invention according to claim 7 is the invention according to claim 5 or 6.
Wherein the assist fluid is an incompressible fluid. According to this invention, in addition to the effect of the invention of claim 5 or 6, since the assist fluid injected into the molten resin in the region is an incompressible fluid, the bending pipe is in comparison with the case of using a compressible fluid. The portion can be formed to have a more uniform thickness.

According to an eighth aspect of the present invention, in the mold apparatus according to any one of the fifth to seventh aspects, the fluid injection means includes a flow path formed inside the slide die, The gist of the present invention is to include a valve mechanism that prevents fluid from flowing into the flow channel from a region and allows the assist fluid to flow from the flow channel to the region.

According to the present invention, the assist fluid is injected into the molten resin in the area via the valve mechanism through the flow path formed inside the slide mold. Further, the valve mechanism prevents fluid such as molten resin from flowing (backflow) into the flow path in the slide mold. For this reason, the assist fluid can be skillfully injected into the molten resin in the region, and the slide-type assist fluid injection mechanism is less likely to cause a problem.

According to a ninth aspect of the present invention, in the mold apparatus according to any one of the fifth to seventh aspects, the resin discharging means has an opening facing the area in the slide die. The gist of the present invention is a piston mechanism including a formed communication passage and a piston that moves in the communication passage.

According to the present invention, the injected resin is blocked by the piston so as not to reach the inside of the slide-type communication passage. Thereafter, an assist fluid is injected. At the time of this injection, for example, there are a method of removing the piston and a method of not removing the piston. In the former case, the excess molten resin that has been injected and driven away by the assist fluid is discharged together with the assist fluid from the slide-type communication passage without pulling the piston.
In the latter case, the excess molten resin injected and driven away by the assist fluid is discharged into the communication passage while pushing out the piston. At this time, by pushing the piston to the original position, the resin in the communication passage is removed from the slide mold.
Therefore, no matter which method is adopted, excess molten resin can be skillfully removed from the area to the slide mold, and further, the subsequent cleaning of the slide mold is not required, and the cleaning for removing the resin from the slide-type communication path can be performed. Easier to do.

According to the tenth aspect, in the fifth aspect,
The gist of the die apparatus according to any one of aspects 9 is to form a branch pipe as the resin pipe. ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to shape | mold the branch pipe which has at least one bending pipe part with high precision at the end part of each pipe part, and as one part.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 3, a branch pipe 10 as a resin pipe is a three-branch pipe, and has three pipe parts 11, 12, and 13 branching in three directions. The tube portion 11 and the tube portion 12 extend straight and coaxially, and a bent tube portion 13 extending in a direction substantially orthogonal to the tube portion is bent at a substantially right angle in the middle. The end of each of the pipes 11, 12, 13 is connected to a connecting portion 11a for connecting a hose or a pipe.
12a, 13a, and the connecting portions 11a, 12a,
13a has a cylindrical shape having openings 14, 15, 16 at its ends, and is threaded on the outer peripheral surface of each.

As shown in FIG. 1, the mold apparatus 20 includes a main mold 21 composed of a fixed mold 22 and a movable mold (only the fixed mold is shown), and a state in which the fixed mold 22 and the movable mold are joined. And three slide dies (hereinafter referred to as slide cores) which are slid into the cavity C formed in the main die 21.
23, 24, and 25. The main mold 21 is a branch pipe 10
Is formed so as to be formed by the cavity C. Therefore, the outer shape of the branch pipe 10 is formed by the main mold 21.

The three slide cores 23, 24, 25
Each connection part 11a, 12 is inserted into the cavity C from a position corresponding to the opening 14, 15, 16 of each pipe part 11, 12, 13.
It is provided so as to be movable so that it can be slid and inserted along the axial direction of a and 13a. Each slide core 23, 2
4 and 25 have the same outer diameter as the inner diameter of each of the pipe portions 11, 12 and 13. FIG. 1 shows the slide cores 23, 24, 25.
Shows a state in which the slide insertion has been completed to the predetermined position. The two slide cores 23 and 24 arranged coaxially each have a flat end surface, and in the state of FIG. 1, the end surfaces of the two slide cores 23 and 24 are in close contact with each other to form one cylindrical shape. The two slide cores 23 and 24 form the inner peripheral surfaces of the pipe portions 11 and 12. The contact position of the two slide cores 23, 24 is
It is displaced from the root of the bent tube portion 13 in the axial direction of the tube portion 11 (12).

The slide core 25 to be slid and inserted from the position corresponding to the opening 16 of the bent tube portion 13 has a tip surface 25a formed in the same surface shape as the bent inner surface of the bent tube portion 13. The slide core 25 is inserted up to a position where the distal end surface 25a coincides with the bent inner surface of the bent tube portion 13,
The connecting portion 1 of the bent tube portion 13 by the slide core 25
An inner peripheral surface (including a bent inner surface) of a portion extending along the axial direction of 3a is formed.

In a state where the three slide cores 23, 24, and 25 are inserted at predetermined positions in FIG.
A region A in which the slide core cannot be inserted is formed near the branching point. This area A is surrounded by the cavity inner peripheral surface of the main mold 21 and the two slide cores 24 and 25,
It is in a state of being sandwiched between two slide cores 24 and 25. Further, a resin gate 26 for injecting the molten resin into the cavity C is provided in the main mold 21 at a position slightly above the root of the bent tube portion 13. However, resin gate 2
The position of 6 can be changed as appropriate.

In the present embodiment, the two slide cores 24 and 25 have a special structure in order to form the portion of the region A, that is, the inner peripheral surface of the bent pipe portion 13 near the branch point. A water path 24 as a flow path for supplying water (high-pressure water) as an assist fluid to the slide core 24.
a is formed inside, and a check valve 30 as a valve mechanism is embedded in a portion facing the region A. Check valve 3
0 indicates that when the water pressure in the water passage 24a exceeds a certain value, the valve is opened to enable injection of high-pressure water into the region A, and to prevent inflow or backflow of fluid from the region A into the water passage 24a. . The opening 30a of the check valve 30 arranged on the outer wall surface of the slide core 24 has a diverging diameter substantially equal to the lightening diameter indicated by a chain line in FIG. The fluid channel 24a and the check valve 30 constitute a fluid injection unit.

On the other hand, the slide core 25 is formed with a communication passage 25b which is opened on the lower surface of the distal end as shown in FIG. A piston 28 is inserted into the communication passage 25b,
The piston 28 is movable in the communication passage 25b. The position of the piston 28 shown in FIG. 1 is an initial position where the piston 28 is set before the start of molding. In a step subsequent to the molding step (slide core insertion + resin injection) in FIG. 1, water assist in which high-pressure water is injected from the check valve 30 into the molten resin in the area A is performed, and the water assist causes the inside of the molten resin to be injected. During the process of expanding the hollow (high-pressure water) formed in the slide core, excess molten resin is discharged through the communication passage 25b of the slide core 25. The reason why the piston 28 is inserted into the communication passage 25b is to block and prevent the injected molten resin from going to the inside of the communication passage 25b of the slide core 25. The communication passage 25b and the piston 28
This constitutes a resin discharging means and a piston mechanism.

As the assist fluid, a compressive fluid such as a gas may be used. However, when it is required to control the bent tube portion 13 to have a more uniform thickness, an incompressible fluid such as a liquid is used. It is better to use. In the present embodiment, the bent tube portion 1
In order to control 3 to a more uniform thickness, an incompressible fluid is used, and particularly, inexpensive and easy-to-handle water is used as the assist fluid.

The check valve 30 is a poppet valve. Its structure is as shown in FIG.
Is composed of a body 31, a movable body 32, a spring 33, and a poppet (valve element). The lower end of the poppet 34 is fixed integrally with the movable body 32 in a state of being inserted through the body 31 and the movable body 32, and the poppet 34 is integrated with the movable body 32 with respect to the body 31 fixed to the slide core 24. Displaces up and down. The movable body 32 is urged away from the body 31 by the elastic force of the spring 33, and the urging force causes the valve portion 34 a formed at the upper end of the poppet 34 to abut on the valve seat 31 a of the body 31. Then, the check valve 30 is closed. Also, when the water pressure of the high-pressure water supplied into the water channel 24a is received, the movable body 32
And the poppet 34 is also subjected to an upward force.
Is displaced upward together with the movable body 32 against the urging force of the spring 33, and the valve portion 34a is separated from the valve seat 31a, whereby the check valve 30 is opened. In forming the tubular hollow wall to a predetermined thickness by the water assist method, the pressure of the high-pressure water has an appropriate range, and the valve opening pressure of the check valve 30 is adjusted so that the valve opens at the appropriate range of water pressure. Has been adjusted. The injection amount of the high-pressure water is adjusted to an appropriate value by controlling the solenoid valve on the high-pressure water source side.

Next, a method of forming the branch pipe 10 using the above-configured mold apparatus will be described with reference to FIG. First, the movable mold of the main mold 21 is moved and joined to the fixed mold 22, and the main mold 2 is moved.
The cavity C is formed in the inside of the device 1. Next, FIG.
As shown in (2), the slide cores 23, 24 and 25 are slid and inserted to a predetermined position (slide type insertion step). The respective distal end surfaces of the slide cores 23 and 24 are in close contact with each other so as to form a columnar shape. At this time, the piston 28 is located at the initial position shown in FIG.

Then, as shown in FIG. 4B, a predetermined amount of molten resin MP is injected from the resin gate 26 into the cavity C (injection step). As a result, the molten resin spreads over the space between the inner peripheral surface of the cavity of the main mold 21 and the slide cores 23, 24, 25, and a part of the inner periphery corresponding to the area A near the branching point of the bent tube portion 13. The outer peripheral surface and the inner peripheral surface of the branch pipe 10 are formed while leaving the surface. Two slide cores 24,
The region A sandwiched between the upper and lower sides by the molten resin 25 is almost filled with the molten resin. At this time, the piston 28 disposed at the initial position
As a result, the injected molten resin is blocked so as not to reach the inside of the communication passage 25b of the slide core 25.

The order of the slide-type insertion step and the injection step shown in FIGS. 4A and 4B may be reversed, and each of the small steps constituting each step may be performed in chronological order until both steps are completed. It may be performed intricately. For example, the slide core 23,
First, a slide-type pre-insertion step of slidingly inserting the slide core 25 to the final position (predetermined position) is performed while the slide insert 24 is inserted halfway. And the resin gate 26
Then, a predetermined amount of molten resin MP is injected into the cavity C by a short shot (injection step). Next, slide core 2
3 and 24 are slid into the predetermined positions where the respective end faces come into contact with each other.
The molten resin is spread in the space between 3, 4, and 25 (slide type insertion step). Thus, it is sufficient if the two steps of the slide type insertion step and the injection step are performed anyway so as to obtain the state of FIG. 4B.

After the above-described slide-type insertion step and injection step are completed, high-pressure water is then supplied to the water channel 24a of the slide core 24. Then, as shown in FIG. 4 (c), the molten resin MP in the region A from the check valve 30 opened by the water pressure.
High-pressure water is injected into the molten resin MP in the region A, and a hollow (high-pressure water) created by water assist expands inside the molten resin MP in the area A, while the excess molten resin MP displaced by the high-pressure water is spread.
Is discharged together with the assist fluid (water) from the communication passage 25b of the slide core 25 as it is after the piston 28 is pulled out. Because the pressure and injection volume of high pressure water are adjusted,
As shown by the chain line in FIG. 4C and FIG. 1, the inner peripheral surface of the bent tube portion 13 is also formed in the region A, and a tubular hollow wall is formed at this portion with a desired thickness. Note that the piston 28 can be positively pulled out when the assist fluid is injected.

Thereafter, the slide cores 23, 24, 25 are removed, and the water in the area A is eliminated. And the main mold 21
Moving mold is separated from the fixed mold 22 and the formed branch pipe 10
Is taken out. The piston 28 of the slide core 25
Is returned to the initial position. By repeating the above cycle, the branch pipe 10 is continuously formed by the mold device 20.

Therefore, according to the present embodiment, the following effects can be obtained. (1) The inner peripheral surfaces of the connecting portions 11a, 12a, 13a are formed by three slide cores 23, 24, 25,
A portion of the bending tube portion 13 where the slide core cannot be inserted is bent by injecting an assist fluid (high-pressure water) from one slide core 24 sandwiching the region A and removing excess molten resin from the other slide core 25. The tube 13 was formed. Therefore, the branch pipe 10 can be formed as one part, and the connecting portions 11a, 12a, and 13a can be formed with good shape and dimensional accuracy. For this reason, the strength of the connection parts 11a, 12a, and 13a connected to other pipes and high sealing performance (airtightness and watertightness) at the time of connection can be ensured.

(2) Tip surface 25a of slide core 25
Has a surface shape corresponding to the bent inner surface of the bent tube portion 13 and a method of forming the bent portion of the bent tube portion 13 by the slide core 25 is employed, so that the thickness of the bent portion of the bent tube portion 13 is made uniform. Can be.

(3) When water (liquid), which is an incompressible fluid, is used as the assist fluid, the thickness of the bent tube portion 13 is larger than in the gas assist system in which gas, which is a compressible fluid, is used as the assist fluid. Can be made more uniform.

(4) Since the check valve 30 is provided on the slide core 24, high-pressure water can be skillfully injected into the region A, and at the same time, the inflow of the molten resin from the region A into the water passage 24a and the backflow of water can be prevented. Therefore, the channel 24 of the slide core 24
Problems such as abnormality of the check valve 30 and clogging of the water channel 24a due to the inflow of the resin into the water passage a are unlikely to occur.

(5) The communication passage 25b of the slide core 25
Since the piston mechanism in which the piston 28 is inserted is adopted, the molten resin injected during the resin injection is
The fifth communication passage 25b can be blocked so as not to go deeper. When the assist fluid is injected, the piston 28
The pressure of the high-pressure water injected into the molten resin MP in the region A does not need to be reduced so much by the resistance of the region A, so that the thickness of the bent tube portion 13 can be formed uniformly. In addition, since the excess molten resin is discharged from the communication passage 25b together with the assist fluid by pulling out the piston 28, the slide core 2
5 can be unnecessary or simply cleaned.

It should be noted that the embodiment is not limited to the above description, but can be implemented as follows. -The bent pipe section is not limited to only one branch pipe. For example, as shown in FIG. 5 and FIG. 6, it may have two or more bent tube portions. Further, the number of pipe portions of the branch pipe is not limited to three, and may be four or more.

The branch pipe 40 shown in FIG. 5 is a three-branch pipe, and all three branches form bent pipe portions 41, 42, and 43.
Three slide types (slide cores) 44 and 4 that are slid and inserted from locations corresponding to the openings of the respective tube portions 41 to 43.
The region A sandwiched between 5, 46 has a three-branch shape,
For example, one slide core 44 has a water passage 44a therein.
A check valve 30 that opens by the pressure of the high-pressure water supplied to the other is provided, and the other two slide cores 45, 46 incorporate a piston 28 that is slidably inserted into each of the communication passages 45a, 46a therein. . Conversely, a combination of two slide cores with a check valve and one slide core with a piston is also possible. In short, it suffices that at least one high-pressure water injection port and at least one resin discharge port are provided at each slide core facing the region sandwiched by the plurality of slide cores.

The branch pipe 50 shown in FIG. 6 is a four-branch pipe.
It has a tube shape in which two bent pipe portions 53 and 54 extend from two pipe lines 51 and 52 extending straight and coaxially. Two slide types (slide cores) 55 and 56 inserted from positions corresponding to the openings of the tube portions 51 and 52 until they come into contact with each other, and a slide type inserted from positions corresponding to the openings of the bent tube portions 53 and 54. (Slide core) 5
7 and 58, two regions A are respectively formed. The pair of slide cores 55 and 56 have an area A.
A check valve 30 for opening water passages 55a, 56a is provided at a position facing the area A, and communication passages 57b, 58b communicating with the piston 28 are provided at a position facing the area A in the other pair of slide cores 57, 58. Open. And each slide core 5
By injecting high-pressure water into the region A through the valves 30 of 5, 56, excess molten resin is repelled to the communication passages 57b, 58b, and is hollowed into a tube near the branching point of the bent pipes 53, 54 by water assist. A wall is formed.

The slide die does not always have to be used to form the inner bent surface of the bent tube portion. For example, as shown in FIG. 7, a method in which only the connection portion 13 a of the bent tube portion 13 is formed using the slide core 25 may be used. The open end of the slide core 25 has a tapered shape extending to the bent portion and expanding to the branch pipe diameter. Even in this case, if an incompressible fluid such as high-pressure water is used as the assist fluid, a tubular hollow wall formed by injecting the assist fluid as shown by a chain line in FIG. It can be formed into a fairly uniform wall thickness. For example, the excess molten resin displaced from the region A at the time of injection of the assist fluid is supplied to the communication passage 25b of the slide core 25.
Is discharged. In this case, after the slide core 25 is pulled out, the piston 28 is pushed into the communication passage 25b (to the left in FIG. 7) to push out the resin so that the slide core 2 is pushed out.
Clean 5

When an incompressible fluid is used as the assist fluid, the incompressible fluid is not limited to water. For example, it may be an oily liquid. Even when a liquid other than water is used, the thickness of the bent portion of the bent tube portion can be made more uniform than when a compressible fluid such as a gas is used as the assist fluid. When a compressive fluid is used as the assist fluid, a gas such as air, nitrogen, or argon can be used. When using a gas assist method that uses gas, it is difficult to obtain a uniform wall thickness compared to when using a liquid such as water (an uncompressed fluid), but at least the end part (connection part) of each pipe is accurately formed. You can.

The resin discharging means is not limited to the piston mechanism. In short, it is only necessary that excess molten resin can be removed from the region A via the slide mold. For example, only a communication passage having an opening for resin discharge in a portion facing the region A of the slide core is formed in the slide core, and a throttle (pore) for preventing the water pressure of the high-pressure water from dropping in the middle of the communication passage. May be provided. Further, a shutter may be provided at an opening for discharging the resin of the slide core.

The fluid injection means is not limited to a structure using a valve mechanism such as a check valve. For example, a slide type shutter that opens when the assist fluid is injected may be provided. The valve mechanism is not limited to a check valve, but may be an electromagnetic valve. For example, a method may be employed in which high-pressure water (assist fluid) is constantly supplied to the water passage in the slide core, and the electromagnetic valve is opened by electric control when the high-pressure water is injected into the region A.

The resin pipe is not limited to a branch pipe. For example, the above-described molding method and mold apparatus can be used for molding a U-shaped tube or an S-shaped tube. In short, as long as the tube shape has an area where the slide die cannot be inserted into the slide, that is, a tube shape having at least one bent tube portion and all ends of each tube portion being open, the molding method and the mold apparatus described above are used for the molding. Can be applied. In the case of the above-mentioned resin tube, the resin tube can be molded as one part by using the molding method and the mold device, and the end of each tube can be molded with high precision.

[0049]

As described in detail above, claims 1 to 1 are provided.
According to the invention, when molding a tubular resin tube having at least one bent tube portion, the end portion of each tube portion can be molded with high precision and as a single component.

According to the second to fourth and sixth to tenth aspects of the present invention, the bent inner surface of the bent tube is formed at the tip end surface of the slide mold, so that the bent portion of the bent tube is formed to have a uniform thickness. can do.

According to the third, fourth and seventh to tenth aspects of the present invention, since the assist fluid is an incompressible fluid, the bent tube portion can be formed to have a substantially uniform thickness.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a main part of a mold apparatus according to an embodiment.

FIG. 2 is a side sectional view of a check valve provided on a slide core.

FIG. 3 is a perspective view of a branch pipe.

FIG. 4 is a schematic cross-sectional view illustrating a forming process of a branch pipe.

FIG. 5 is a schematic cross-sectional view of a main part showing a mold apparatus used for molding another example of a branch pipe.

FIG. 6 is a schematic cross-sectional view of a main part showing another example of a mold apparatus different from FIG. 5;

FIG. 7 is a schematic cross-sectional view of a main part showing another example of a mold apparatus different from FIG. 6;

FIG. 8 is a side sectional view showing the structure of a conventional branch pipe.

FIG. 9 is a schematic cross-sectional view showing an end of a conventional blow-molded branch pipe.

[Explanation of symbols]

10 ... branch pipes as resin pipes, 11, 12, 51, 52
... pipe part, 13, 41, 42, 43, 53, 54 ... bent pipe part, 20 ... mold device, 21 ... main mold, 23, 24, 2
5, 44, 45, 46, 55, 56, 57, 58: a slide core as a slide type; 24a, a fluid passage as well as a water passage as a flow passage; and 25b, a resin passage as a resin discharge means and a piston mechanism. Passage 28, piston constituting resin discharge means and piston mechanism, 30
... A check valve which constitutes a fluid injection means and serves as a valve mechanism.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H019 BA02 BD03 3H111 AA01 BA15 CB02 EA05 4F202 AG08 AG12 AG28 CA11 CB01 CK42 CK54

Claims (10)

[Claims] 1. A method for molding a resin tube having a bent tube portion extending in at least one bending path and having a tube shape in which all ends of the tube portion are opened, wherein a main mold for molding an outer surface of the resin tube is provided. An injection step of injecting the molten resin into the cavity of the mold, and a slide mold insertion step of slidingly inserting a plurality of slide molds into the cavity to a predetermined position, thereby forming the inner peripheral surfaces of the ends of all the pipe portions, For the molten resin in the region including a part of the bent tube portion where the mold is not inserted, the assist fluid is injected via at least one of the plurality of slide molds sandwiching the region, and another slide is inserted. A method for forming a resin tube, comprising: removing excess molten resin displaced by injection of the assist fluid through a mold from the region. 2. The method of molding a resin pipe according to claim 1, wherein a tip end surface of a slide die for forming an inner peripheral surface of an end portion of the bent tube portion has a surface shape corresponding to the bent inner surface of the bent tube portion. And forming a bent inner surface of the bent tube portion at a tip end surface when the slide die is slid and inserted. 3. The method of molding a resin tube according to claim 1, wherein the assist fluid is an incompressible fluid. 4. The method for forming a resin tube according to claim 1, wherein the resin tube is a branch tube. 5. A mold apparatus for molding a resin tube having a tube shape that has a bent tube portion extending in at least one bending path and that is open at all ends of the tube portion, wherein an outer surface of the resin tube is formed. A main mold having a cavity having an inner surface shape, a slide mold inserted into the cavity to form an inner peripheral surface of an end of the tube portion, and a bent tube portion into which the slide mold is not inserted. A fluid injection means provided in the slide mold for injecting an assist fluid into the molten resin in an area including a part via at least one of the plurality of slide molds sandwiching the area; Resin removing means provided on the other slide mold for removing excess molten resin displaced by the injection of the fluid from the area via another slide mold. Mold apparatus, characterized in that there. 6. The mold apparatus according to claim 5, wherein the slide mold for forming the inner peripheral surface of the end portion of the bent tube portion has a front end surface corresponding to the bent inner surface of the bent tube portion. A mold apparatus comprising: 7. The mold apparatus according to claim 5, wherein the assist fluid is an incompressible fluid. 8. The mold device according to claim 5, wherein the fluid injection unit includes a flow path formed inside the slide mold and a flow path from the region to the flow path. A mold device comprising: a valve mechanism for preventing inflow of a fluid and allowing outflow of the assist fluid from the flow path to the region. 9. The mold device according to claim 5, wherein the resin discharging means includes a communication passage formed in the slide mold so as to have an opening facing the area, A piston mechanism comprising: a piston moving in the communication passage. 10. The mold apparatus according to claim 5, wherein a branch pipe is formed as the resin pipe.