JPH04236892A - Spiral composite pipe - Google Patents

Abstract

PURPOSE:To provide a composite pipe having a resin layer forming structure where peeling is extremely difficult to occur and improves durability by partially forming a given gap in a weld part to form a plurality of non-weld parts, and causing resin to leak in a hole formed by the non-weld parts. CONSTITUTION:A composite pipe is formed such that, in a state that a beltform metallic sheet 10 is spirally wound, adjoining side edges are welded together to form a metallic pipe 1 the inner peripheral surface of which is covered with resin. A plurality of non-weld parts 12 are partially formed in a weld part 11 of the metallic pipe 1 at intervals of a given gap, and covering resin is caused to lead in a hole formed by the non-weld part 12. An anchor effect is produced as a result of resin entering the non-weld parts 12 formed in the middle of the weld part 11. Anchor parts produced by leakage of the resin are scattered throughout the overall length of the pipe and in a peripheral direction. Even when partial peel of resin occurs, there is entirely no fear of expansion enough for closing of a pipe occurring, contraction of a resin pipe hardly occurs, and slip off of the resin pipe is also prevented from occurring.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The present invention relates to pipe materials used for water supply and drainage pipes, hot water supply pipes for air conditioning, etc., and more particularly to a highly durable composite pipe in which the inner surface of a metal pipe is coated with a resin.

0002

[Prior Art] Traditionally, steel pipes have been mainly used as pipe materials for drainage pipes, air conditioning piping, etc. However, due to problems such as water leakage due to corrosion and pipe blockage due to rust lumps, steel pipes have been used in recent years. Composite pipes whose inner surfaces are lined with resin are attracting attention. Manufacturing methods for such composite pipes include inserting a resin pipe inside a metal pipe and fixing it to each other using adhesive, or rolling or spiral forming a strip-shaped metal plate while simultaneously forming the inner surface of the pipe. A method is known in which a resin is extruded and coated (for example, JP-A-62-198447 to JP-A-50-73963).

0003

[Problems to be Solved by the Invention] However, in composite pipes manufactured using the conventional manufacturing method as described above, even if the adhesive strength between the metal and the resin is high, the metal-resin may deteriorate after long-term use.
A small amount of rust on the metal at the resin interface inhibits the adhesion of the resin, causing peeling or blistering of the resin, which can lead to pipe blockage. In addition, in a structure in which the tube end comes into contact with the fluid flowing inside the tube, the internal fluid tends to enter the interface between the resin and the metal, causing the resin to peel over the entire length of the tube and sometimes causing the entire lining resin to fall off.

[0004] To prevent the internal fluid from entering from the end of the pipe, measures such as sealing the end of the pipe with a packing structure have been conventionally adopted; however, repeated changes in temperature and residual strain during resin molding For these reasons, the resin pipe may shrink significantly, and in such cases, the end of the pipe cannot be sufficiently sealed, making it impossible to prevent the above-mentioned lining resin from peeling over its entire length.

An object of the present invention is to solve these problems and provide a more durable composite pipe.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the composite pipe of the present invention is made by welding adjacent side edges of a strip metal plate wound in a spiral shape. In a composite pipe in which the inner surface of a metal pipe is coated with resin, a plurality of non-welded parts are partially formed at a predetermined gap at the welded part of the metal pipe, and the coating is applied to the hole created by the non-welded part. Characterized by resin leakage.

[0007]

[Function] An anchor effect is produced by the resin entering the hole formed by the non-welded part provided in the middle of the welded part formed in a spiral shape on the metal tube. The anchor parts due to this resin leakage will extend over the entire length of the pipe and will also be scattered in the circumferential direction, so even if the resin peels off partially, there is a risk of blistering leading to pipe blockage. There is no shrinkage of the resin tube at all, and the resin tube does not fall out.

[0008]

Embodiment FIG. 1 is an external view of an embodiment of the present invention, and FIG. 2 is an enlarged sectional view showing the vicinity of the non-welded portion 12 cut along the welded portion 11. A resin 2 is uniformly coated on the inner surface of a spiral metal tube 1 in which a band-shaped metal plate 10 is spirally wound and the abutting portions of the spiral metal tube 1 are welded to each other. Welded portion 11 formed in a spiral shape on metal tube 1
are not formed continuously, but are partially provided with a plurality of non-welded parts 12 at predetermined intervals, and these non-welded parts 12 are made of metal pipes as shown in FIG. A through hole reaching from the inner surface to the outer surface of 1 is formed. The resin 2 covering the inner surface of the metal tube 1 leaks into the non-welded portion 12.

A plurality of non-welded portions 12 are provided while the welded portion 11 travels 360° on the metal tube 1, so that the metal tube 1 has a large number of non-welded portions 12 in the circumferential direction over its entire length. are scattered uniformly, and the resin 2 leaks into each non-welded part 12. The resin 2 that coats the inner surface of the tube prevents the tube from clogging even if it partially peels off from the metal tube 1 due to the anchoring effect caused by the leakage to the non-welded portions 12 that are scattered circumferentially along the entire length of the tube. The resin tube does not swell to the extent that it causes it, and the resin tube does not shrink or fall off.

Next, an example of the manufacturing method of the embodiment of the present invention as described above will be described. FIG. 3 is an overall configuration diagram showing an example of the manufacturing apparatus. The strip-shaped metal plate 10 is continuously supplied to a surface treatment device 31, and is treated to have a surface condition suitable for applying a resin layer. The surface-treated metal plate 10 is then supplied to a tube making device 33 by a drive roll device 32.

The pipe making device 33 has a plurality of forced rolls 331 and
・331 are arranged in the circumferential direction of the spiral tube to be formed so that each roll axis is approximately along the longitudinal direction of the spiral tube, and the drive roll device 32 is used to roll a strip metal plate inside the forced rolls 331...331. The metal plate 10 has a mechanism for forcing the metal plate 10 into a tubular shape by pressing the metal plate 10 in such a manner that the outer side of the metal plate 10 is restricted and the side edges of the metal plate 10 are brought into contact with each other.

As shown in FIG. 4, the band-shaped metal plate 10 formed into a tubular shape is welded at the butt portion with a torch 341 connected to a welding machine 34 to form the metal tube 1, but this welding is performed continuously. As a result, a spiral weld 1 is formed in the metal tube 1.
1, a plurality of non-welded parts 12 are scattered at predetermined intervals.

After this welding, the force roll 331
...Metal pipe 1 in a concentric positional relationship with the installation circumference of 331
The resin 2 is extruded onto the inner surface of the metal tube 1 by the mold 351 inserted therein, and the inner peripheral surface of the tube is coated with a resin layer. That is, an extruder 35 is disposed on the front side of the tube manufacturing device 31, and a mold 351 connected to the extruder 35 is inserted into the metal tube 1. A resin discharge port provided near the tip of the mold 351 is located downstream of the welding point, and extrudes the molten resin in a cylindrical shape into the metal tube 1 after welding.

The molten resin discharged from the mold 351 leaks into the non-welded parts 12 scattered around the metal tube 1, resulting in a composite tube having the structure shown in FIGS. 1 and 2. Note that the composite pipe whose inner surface is coated with resin is then discharged from the pipe manufacturing apparatus 33 by a drive device 37 for stably transporting the pipe.
It is cut into a predetermined length by a cutting device 38. Also,
In order to adhesively coat the inner surface of the metal tube 1 with resin, the heating device 36 may be placed upstream of the tip of the mold 351, if necessary.

Furthermore, if the resin leaking into the non-welded portion 12 extends to the outside of the tube, a cutter is provided to cut off the resin beyond the outer circumferential surface of the tube, or a cutter is provided to cut off the resin beyond the outer peripheral surface of the tube, or a cutter is provided to cut off the resin beyond the outer circumferential surface of the tube. A cooling core may be placed in substantially contact with the outer surface to prevent excessive resin leakage. Here, as the welding machine 34, it is sufficient to use an optimal welding machine according to the material of the band-shaped metal plate 10 to be used, but for example, when using mild steel, high frequency resistance welding, TIG welding, etc. can be used. be. Methods for temporarily stopping welding to perform intermittent welding include, for example, electrical methods such as lowering the current value or lowering the high frequency frequency, separating the torch 341, or using high frequency Mechanical methods such as separating the contacts can be used.

[0016] By the above manufacturing method, a width of 50 mm is obtained.
A spiral composite tube with an inner diameter of 100 mm was manufactured using the metal strip plate. At this time, while the spiral tube rotates 360 degrees, five non-welded parts, that is, resin leak holes, are provided.
At the same time, silane-modified polyethylene was extruded and coated inside the tube. Using this composite pipe, 80°C hot water and 20°C water were repeatedly passed in a 3-minute cycle, but no abnormality occurred even after 8000 cycles.

[0017] As a comparative example, a spiral composite pipe that was completely the same except that there was no non-welded part, and therefore no resin leakage part, was manufactured, and it was also subjected to a 3-minute cycle of 80°C hot water and 20°C water. As a result of repeatedly passing water through the tube, shrinkage of the tube end was observed after 8,000 cycles. Steel, copper and its alloys, titanium alloys, aluminum and its alloys can be used as the band-shaped metal plate in the present invention.

[0018] As the resin, acid-modified polyethylene, silane-modified polyethylene, etc. are suitable. Furthermore, the length of the non-welded part should be 0.5 mm to 3 m because if it is too small, the anchor effect will be small, and if it is too large, the pipe strength will be weak.
m is appropriate. In addition, the interval is the width of the strip metal plate,
Although it depends on the diameter of the pipe, it is preferable to arrange three or more per axial length corresponding to the diameter of the pipe. The non-welded portions are preferably arranged evenly in the circumferential direction so as not to be linearly biased in the axial direction.

Furthermore, the manufacturing method of the present invention is not limited to the above-mentioned example, and any method can be adopted. However, while forming the spiral pipe as described above, the molten resin is transferred to a mold having a long land portion. An efficient method is to extrude from the rear. In addition to the structure shown in FIGS. 1 and 2, the structure of the present invention is such that the outer surface of the tube is also coated with resin, and the resin on the inner and outer surfaces is bonded through the through hole made by the non-welded part. According to this structure, durability over time is further improved.

[0020]

[Effects of the Invention] As explained above, according to the present invention, a plurality of non-welded parts are formed partially at predetermined intervals in the welded part of a spiral composite pipe, and the non-welded parts Since the structure is such that the inner layer resin leaks into the hole, the inner layer resin is extremely difficult to peel off due to the anchor effect of the resin leakage portion. Moreover, since these resin leakage parts are scattered in a spiral pattern along the entire length of the composite pipe, there will be no blockage or resin pipe falling out even after long-term use, making it possible to obtain a highly durable composite pipe. .

Furthermore, since the holes for resin leakage are formed in the non-welded portions, there is no need to separately form holes mechanically by punching or the like, and no chips or the like are generated.

[Brief explanation of the drawing]

[Figure 1] External view of the embodiment of the present invention

[Figure 2] An enlarged cross-sectional view of the vicinity of the non-welded part 12 in Figure 1 taken along the welded part

[Fig. 3] Overall configuration diagram showing an example of an apparatus for manufacturing the embodiment of the present invention

[Figure 4] Cross-sectional view at the welding point in Figure 3

[Explanation of symbols]

1...Metal tube 2...Resin 10... Band-shaped metal plate 11...Welding part 12...Non-welded part

Claims (1)

[Claims] Claim 1: A composite tube in which the inner surface of a metal tube is formed by welding adjacent side edges of strip-shaped metal plates wound in a spiral shape to each other and coated with a resin, wherein the welded portion is coated with a resin. A spiral composite pipe characterized in that a plurality of non-welded portions are partially formed with predetermined gaps, and the resin leaks into holes formed by each of the non-welded portions.