JPH0480817B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a plastic tube (hereinafter referred to as a "porous plastic tube") having a large number of through holes in the tube wall in the tube axis direction.
Regarding the method of forming an enlarged diameter socket at the end of the
The present invention relates to a molding method that provides a socket with a good appearance and excellent flatness resistance.

(Prior art) This type of porous plastic pipe has holes in the pipe wall, which allows for the saving of plastic materials and reduces the weight of the pipe, and by increasing the thickness of the pipe wall. It has the advantage of increasing the rigidity of the

Therefore, in recent years, porous plastic pipes have been used as underground pipes.

In general, this connection between porous plastic pipes is similar to the conventional connection between pipes without holes, in which an enlarged socket is provided at the end of one pipe, and the end of the other pipe is connected to the socket. The method used is to insert and connect sequentially.

When molding a socket at the end of a porous plastic tube, conventionally the tube end 1 is heated and softened, and an inner mold 3' is press-fitted into the tube end, as shown in a half-sectional view in FIG. It was molded.

However, in this molding method, when the inner mold 3' is press-fitted into the tube end and the diameter is expanded at the enlarged part 31',
Buckling deformation occurred, and unevenness occurred on the outer and inner circumferential surfaces of the tube, resulting in poor appearance.

One of the causes of this buckling deformation is that when the tube end of a porous plastic tube is heated, the outer circumferential wall 11', inner circumferential wall 12', and partition wall 14' cannot be heated and softened to a substantially uniform temperature. There are many things that can be mentioned.

That is, in the conventional heating method, the tube end was inserted into the heating device and the outer circumferential wall 11' and the inner circumferential wall 12' were simply heated. It was not possible to heat and soften up to the partition wall 14'.

Therefore, if an attempt is made to sufficiently soften the partition wall 14', the outer circumferential wall 11' and the inner circumferential wall 12' will become softer than necessary, resulting in loss of stiffness and buckling when the inner mold 3' is press-fitted.

Furthermore, if the outer circumferential wall 11' and the inner circumferential wall 12' are heated and softened to an appropriate temperature, the partition wall 14' will not be sufficiently softened, and when the inner mold 3' is press-fitted and expanded in diameter, the partition wall 14' will not be sufficiently softened.
In some cases, cracks or the like were generated on the 4', or unevenness was formed on the outer peripheral surface and inner peripheral surface, resulting in a poor appearance.

Furthermore, the partition wall 14' that joins the outer circumferential wall 11' and the inner circumferential wall 12' is folded down in one direction as shown in FIG. 5B by diameter expansion molding from the state shown in FIG.
This caused a fatal problem of reduced impact resistance and flatness resistance.

(Object of the Invention) The present invention solves the problems of the conventional forming method, and when the tube end is inserted into a heating device and heated, hot air is forced into the through hole opened in the tube end surface. The partition wall is heated and softened to approximately the same temperature as the outer circumferential wall and the inner circumferential wall, and then the through hole opened at the end of the tube is closed, and a pressurized fluid is introduced into the through hole to apply internal pressure to the through hole. This molding method is characterized by press-fitting an inner mold into the end of the pipe while the pipe is still hanging, and produces a socket with a smooth outer and inner peripheral surface, a good appearance, and excellent flatness resistance. It provides:

(Structure of the Invention) Hereinafter, a specific structure of the present invention will be explained in detail with reference to drawings shown in examples.

Figure 1 is a sectional view showing the heating process of the present invention, Figure 2 is a sectional view showing the heating process of the present invention.
The figure is a partial front view of a porous plastic tube, and FIG. 3 is a half cross-sectional view showing the diameter expansion process using an inner mold.
3 is an inner mold, 4 is an outer mold divided into a plurality of pieces, and 5 is a suction device.

The porous plastic tube 1 is a synthetic resin tube made of vinyl chloride resin or the like having a perfect circular, elliptical, oval, or other appropriate cross-sectional shape, and has an outer circumferential wall 11 and an inner circumferential wall 12 joined by a partition wall 14. A large number of through holes 13 communicating in the axial direction are provided inside.

In the present invention, the end of the porous plastic tube 1 is first inserted into the heating device 2, and the tube end is heated to a substantially uniform temperature.

Heaters 21 and 22 are arranged in the heating device 2, and the heater 2 is heated while slowly rotating the tube 1.
1 heats the outer peripheral wall 11, and a heater 22 heats the inner peripheral wall 12. Then, the hot air in the heating device 2 is blown into the through hole 13 opened at the end surface of the tube to heat the partition wall 14.

As a means for blowing hot air into the through hole 13, for example, as shown in FIG. 1, a suction device 5 is connected to the other end of the porous plastic tube 1, and a vacuum device (not shown) is connected to the suction device 5. It is preferable to connect the heating device 2 and introduce the hot air into the through hole 13, but in addition to this, a fan or the like may be provided in the heating device 2 to blow hot air into the through hole 13.

After the tube end is heated and softened to a uniform temperature in this manner, the through hole 13 opened in the tube end is closed. This hole can be closed by embedding a sealant such as silicone rubber into the hole 13, or by pressing a crushing mold 6 against the tip of the tube to crush the hole 13, as shown by the dashed line in FIG. You can do it like this.

After that, relatively low pressure pressurized fluid (0.3 to 1
Kg/cm ² ) is introduced, and the inner mold 3 is press-fitted into the tube end while applying internal pressure to the through hole 13, thereby expanding the diameter of the tube end as shown by the broken line in FIG.

In the present invention, during this diameter expansion process, the outer peripheral wall 11,
The inner circumferential wall 12 and the partition wall 14 are heated and softened to a substantially uniform temperature, and the internal pressure acts on the through hole 13 to maintain the tension between the outer circumferential wall 11 and the inner circumferential wall 12, so that the end of the tube is heated and softened. Press fit the inner mold 3 to expand the enlarged part 3
1, buckling deformation does not occur even when the diameter is expanded.

Moreover, this diameter expansion molding prevents unevenness from occurring on the outer peripheral surface and the inner peripheral surface, and prevents the partition wall 14 from collapsing in one direction as shown in FIG. 5B, thereby preventing a decrease in flat strength.

Next, move the slide member 33 in the axial direction,
The core member 32 is expanded in the outer circumferential direction to form a groove for attaching a rubber ring.

After forming the enlarged diameter socket having the rubber ring mounting groove through the above molding process, the outer mold 4 is applied to the outer circumferential surface of the socket, and the high pressure pressurized fluid (2 to 5
Kg/cm ² ), the outer peripheral wall 11 and the inner peripheral wall 12
is brought into close contact with the outer mold 4 and the inner mold 3.

In this way, the outer peripheral surface and the inner peripheral surface are made smooth,
A socket with good appearance and excellent flatness resistance can be obtained.

In the above-mentioned embodiments, a method for molding a socket having a rubber ring mounting groove has been described, but it goes without saying that the present invention can also be applied to an adhesive type socket that does not have a rubber ring mounting groove.

(Effects of the Invention) As detailed above, the socket forming method of the present invention heats and softens the outer circumferential wall, inner circumferential wall, and partition wall of the tube end to a substantially uniform temperature, and then opens the through hole in the tube end surface. After that, pressurized fluid is introduced into the through hole, and an inner mold is press-fitted into the end of the tube while applying internal pressure to the through hole to expand the diameter. This prevents buckling deformation during diameter expansion molding. A receptacle with an excellent appearance can be obtained by making the outer circumferential surface and the inner circumferential surface smooth without causing damage to the flatness resistance due to the collapse of the partition wall or the collapse of the partition wall.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the heating process of the present invention, Figure 2 is a sectional view showing the heating process of the present invention.
The figure is a partial front view of a porous plastic tube, Figure 3 is a half-sectional view showing the forming process of the expanded diameter socket, Figure 4 is a half-sectional view showing the conventional forming process, and Figures 5 A and B are FIG. 4 is a cross-sectional view taken along the E-I line and the Ro-RO line in FIG. 4; 1...Porous plastic pipe, 11...Outer peripheral wall,
12... Inner peripheral wall, 13... Through hole, 14... Partition wall,
2...Heating device, 3...Inner mold, 4...Outer mold, 5...
...Suction device, 6...Crushing type.

Claims (1)

[Claims] 1. When forming an enlarged diameter socket by press-fitting an inner mold into the end of a plastic tube that has a large number of axial holes in the tube wall in which the outer circumferential wall and the inner circumferential wall are joined by a partition,
The end of the tube is inserted into a heating device to heat and soften the outer peripheral wall and the inner peripheral wall, and hot air is introduced into the through hole to heat and soften the partition wall, and then the inside of the through hole opened in the end surface of the tube is closed. Thereafter, a pressure fluid is introduced into the through hole from the other end of the tube, and an inner mold is press-fitted into the tube end while applying internal pressure to the through hole. .