JP2940569B2 - Manufacturing method of metal tube / composite tube port - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a metal pipe / composite pipe receiving port, that is, a method for manufacturing a receiving port by expanding the diameter of a metal pipe or a composite pipe by rubber bulging.

[0002]

2. Description of the Related Art For example, in a metal pipe used as a piping material for a building or a composite pipe in which the inner surface of a metal pipe is coated with a corrosion-resistant synthetic resin, a socket for connecting another pipe is provided at an end of the pipe. It is formed. This kind of receiving portion is formed by expanding the diameter of the end of a metal pipe or a composite pipe. As such a method of expanding the end of the pipe, conventionally, for example, Japanese Patent Application Laid-Open No. 2-1233 is disclosed. And a rubber bulge molding method as disclosed in JP-A-2-130126.

As shown in FIG. 6, an end of a tube 101 is set in a mold 100 having an inner surface 100a of a predetermined shape with a predetermined gap from the inner surface, and a bulge is set in the tube. The rubber 102 is fitted, and in this state, the rubber 102 is pressed and compressed by the pressing member 103 in the direction of the arrow a in the axial direction to expand in the radial direction, thereby expanding the diameter of the tube end 101a.

In this case, an inner mold 104 for guiding a molding rubber 102 is arranged on the side of the mold 100 where the tube end 101b is located, and a part of the rubber 102 is placed in the inner mold 104. When the rubber 102 is compressed and expanded in the radial direction in a state in which it is fitted, the end face of the inner mold 104 is designed so that the expanded rubber 102 does not wrap around from the tube end 101b to the outer periphery of the tube. Tube end 101 at 104a
b, and the compression work of the rubber 102 was performed thereafter.

[0005]

However, in the conventional rubber bulge molding method as described above, the pipe end 101
Since the inner mold 104 whose end face 104a facing b is perpendicular to the tube axis direction was used, and the tube end 101a was expanded in a state where the tube end 101b was in close contact with the perpendicular surface (end surface 104a), The following problems occurred.

That is, the pipe end 10 is formed by the method described above.
When the diameter of the pipe end 1a is increased, as shown in FIG.
The outer surface of the tube a is expanded along the inner surface 100a of the mold.
Part of the pipe 101 is used to form the portion 101d reaching 1a, and the pipe end position retreats toward the pipe parallel portion 101c side from the beginning, so that the pipe end at the time of diameter expansion and after the diameter expansion is enlarged. 101b and the end face (orthogonal face) 104a of the inner mold 104
And a gap b is formed between them. However, if there is such a gap b, the rubber 102 enters into the gap b and the pipe end 1
01b, in particular, the rubber 102 is strongly pressed against the inner corner thereof, and as a result, the rubber 102 is scratched in a circumferential shape. The diameter does not expand to the outer diameter.

SUMMARY OF THE INVENTION The present invention addresses the above-described problem in the case where a receiving portion is formed at the end of a metal tube or a composite tube by a rubber bulge molding method. It is an object of the present invention to provide a method capable of remarkably reducing the damage of rubber for bulge molding as compared with the conventional method by using a mold capable of absorbing a retreat of a pipe end position, that is, a contraction of a pipe end.

[0008]

In order to achieve the above-mentioned object, a method for manufacturing a metal tube / composite tube receiving portion according to the present invention comprises the steps of: A composite tube coated with a synthetic resin is set in a predetermined state, rubber for molding a hull is fitted into the tube, and the rubber is compressed in the axial direction and expanded in the radial direction, thereby forming a metal tube or a composite tube. A method for manufacturing a receiving portion by expanding the diameter of a pipe end is characterized in that the diameter of the pipe end is expanded using an inner mold as described below.

That is, the metal tube or the composite tube can be fitted to the mold from one end of the mold so as to face the tube end, and the tube end can be brought into close contact with the surface portion facing the tube end. An inner mold having a tapered surface is used. Then, the bulge molding rubber in the tube is axially compressed and radially expanded in a state where the inner die is fitted to the die and the tube end is brought into close contact with the tapered surface thereof, so that the tube end is formed. To increase the diameter.

Here, the angle of inclination of the tapered surface with respect to the plane perpendicular to the tube axis (hereinafter referred to as the taper angle) depends on the material of the tube to be expanded and the expansion ratio.
The angle may be in the range of 70 °, preferably 20 ° to 60 °
It is. If the angle is too small, the effect of the tapered surface is small. If the angle is too large, the tube end will buckle when the tube end is expanded, and the expanded shape may not be stable.

In consideration of such a point, the dimension of the tube end face retreating due to the diameter expansion is measured in advance for each material and for each diameter expansion ratio, and an inner metal mold having an optimum taper angle for the pipe to be subjected to the diameter expansion processing. Just use the type.

[0012]

According to the above construction, the bulge forming rubber in the metal pipe or the composite pipe is axially mounted in a state where the pipe end of the metal pipe or the composite pipe is in close contact with the tapered surface of the inner die fitted to the die. By being compressed and radially expanded, the tube end is expanded while closely contacting the tapered surface of the inner mold. Therefore, even if the tube end position retreats to the tube parallel part side with the diameter expansion, no gap is formed between the tube end and the inner mold facing the same during and after the diameter expansion, so It is possible to prevent the molding rubber from being damaged when such a gap is present.

[0013]

Embodiments of the present invention will be described below. In this embodiment, the end of a steel pipe having a thickness of 2.0 mm and an outer diameter of 110 mm is expanded, and the outer diameter of the end of the pipe is 132 mm (diameter of expansion of 20 mm).
%) When manufacturing the receiving part.

First, a mold and an inner mold used in this embodiment will be described. As shown in FIG. 1, a mold 1 has an inner surface 1 having a predetermined shape forming a receiving portion at a pipe end 2 a of a steel pipe 2.
a, and one end side thereof is an opening 1b for fitting the inner die. On the other hand, the inner die 3 has a tapered surface 3a which is wide-opened in the die fitting direction on one end surface 3b side as shown in the figure, and further extends from the small diameter end of the tapered surface 3a in the depth direction. Is formed with a rubber guide portion 3c having the same shape as the small diameter end. When the inner mold 3 is fitted to the mold 1, the pipe end 2b of the steel pipe 2 before diameter expansion can be brought into close contact with the tapered surface 3a. The taper angle (θ) of the inner mold 3 used in this embodiment is 30 °.

Next, the method of the present invention performed using such a mold 1 and an inner mold 3 will be described. First, a steel pipe 2 is placed in a mold 1 with a predetermined gap from the inner surface 1a.
Is set, and a bulge forming rubber (urethane rubber in the present embodiment) 4 is fitted inside the steel pipe 2.

Next, one end of the rubber 4 is closed with a pressing member 5, while an inner mold 3 is fitted into the opening 1b of the mold 1 as shown in the figure, and a steel pipe 2 is attached to its tapered surface 3a. Pipe end 2b
Close. In this state, as shown in FIG. 2, the bulge forming rubber 4 is pressed and compressed by a predetermined amount in the direction of arrow A toward the pipe end 2a by the pressing member 5 from the center of the steel pipe 2. By expanding in the radial direction, the diameter of the pipe end 2a is increased to the above-described diameter expansion rate.

According to such a configuration, when the bulge forming rubber 4 fitted in the steel pipe 2 is compressed in the axial direction by the pressing member 5 and expanded in the radial direction, the expansion force of the bulge forming rubber 4 causes the pipe of the steel pipe 2 to expand. The diameter of the end 2a is increased until the end 2a comes into close contact with the inner surface 1a of the mold, and as a result, a socket having a predetermined diameter is formed at the tube end 2a. In this case, the pipe end position of the steel pipe 2 retreats to the pipe parallel part side with the diameter expansion, but the pipe end 2b is closely contacted with the tapered surface 3a of the inner mold 3 fitted to the mold 1. Since there,
In this close state, it retreats while being guided by the tapered surface 3a.
In other words, the pipe end 2a of the steel pipe 2 is always in close contact with the tapered surface 3a of the inner die 3 while the pipe end 2b is being expanded in diameter, and finally expands to a predetermined state shown in FIG. Diameter.

Therefore, even if the end of the steel pipe 2a is retracted toward the pipe parallel side as the diameter of the steel pipe end 2a increases, the retraction is absorbed by the tapered surface 3a. In this case, there is no gap between the tube end 2b and the inner mold 3 opposed thereto as in the conventional case. This prevents a gap between the pipe end and the inner mold end face, which has conventionally been caused by an increase in the diameter of the pipe end, and prevents the rubber from being damaged due to the molding rubber entering the gap. Is avoided or reduced.

With such a method, the diameter of the pipe end 2a of the steel pipe 2 is increased to form a receiving portion. When the number of the receiving portion becomes 500, the molding rubber 4 is examined. The degree of damage was extremely small. Thus, when the method of the present invention is used, the bulge forming rubber 4
It was confirmed that the durability of the steel was remarkably improved. Here, FIGS. 3 to 5 show other examples of the inner mold used in the present invention. 3 shows the inner mold 13 in which a portion 13d located on the side opposite to the tapered surface 13a is closed.
FIG. 4 shows the inner mold 23 in which the small-diameter end side of the tapered surface 23a is closed, and FIG. 5 shows the inner mold 33 in which the tapered surface 33a is formed in a conical shape.

Although the above embodiment relates to the case where the end of the steel pipe is enlarged, the method of the present invention can be applied to a composite pipe in the same manner as in the above embodiment. . As a comparative example, for a steel pipe made of the same material as in the above embodiment, an inner mold having an end face perpendicular to the pipe axis (corresponding to θ = 0 °) was used, and the pipe end was the same. When the receiving portion was formed by expanding the diameter to the diameter expansion ratio, the rubber for forming was torn off when the molding amount reached 200 pieces, and the expanding force against the pipe due to compression did not work. For this reason, further molding was impossible.

[0021]

As described above, according to the present invention, in the case where the pipe end of a metal pipe or a composite pipe is expanded by a rubber bulge forming method to manufacture a receiving portion, the pipe end of the pipe is made of an inner metal. Since the diameter is increased while closely contacting the tapered surface of the mold, even if the tube end position retreats to the tube parallel part side when the diameter is increased, a gap is created between the tube end and the end surface of the inner mold facing this. Disappears. In other words, the amount of contraction in the axial direction of the pipe during the diameter expansion processing is absorbed by the tapered surface. As a result, damage to the bulge molding rubber can be reduced, and the life of the rubber can be prolonged accordingly.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, in which a pipe (steel pipe) is set in a predetermined state in a mold, and a shaft around the pipe end is shown immediately before the pipe end is expanded in diameter. FIG.

FIG. 2 is an axial vertical sectional view of the vicinity of the pipe end, showing a state immediately after the pipe end is expanded in the embodiment.

FIG. 3 is a longitudinal sectional view showing another example of the inner mold used in the present invention.

FIG. 4 is a longitudinal sectional view showing still another example of the inner mold used in the present invention.

FIG. 5 is a longitudinal sectional view showing still another example of the inner mold used in the present invention.

FIG. 6 is a vertical cross-sectional view of the vicinity of a pipe end illustrating a case of manufacturing a receiving portion of a metal pipe or a composite pipe by a conventional general rubber bulge molding method.

FIG. 7 is a vertical cross-sectional view of the vicinity of the end of the pipe at the time of diameter expansion used to show the problems of the conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Die, 1a ... Die inner surface, 2 ... Pipe (steel pipe), 2a ... Pipe end part, 2b ... Pipe end, 3, 13, 23, 33 ... Inner die, 3a, 13a, 23a, 33a: tapered surface; 4, bulge molding rubber (urethane rubber).

Claims (1)

(57) [Claims] 1. A metal pipe or a composite pipe in which a metal pipe is coated with a synthetic resin is set in a predetermined state in a mold having an inner surface of a predetermined shape, and a bulge molding rubber is fitted into the pipe. Then, by compressing the rubber in the axial direction and expanding the rubber in the radial direction, the diameter of the end of the metal tube or the composite tube is increased to produce the receiving portion. An inner mold having a taper surface formed on one side of the mold so as to be able to be fitted to the mold so as to face the end, and having a tapered surface capable of closely contacting the tube end with a surface portion facing the tube end, The bulge molding rubber in the tube is axially compressed and radially expanded in a state where the inner die is fitted to the die and the tapered surface is brought into close contact with the tapered surface, thereby expanding the pipe end. A method for manufacturing a metal tube / composite tube receiving portion, characterized by having a diameter.