JPH0953763A - Manufacture of compound pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To join a corgate pipe and a straight pipe with each other easily and manufacture a large aperture compound pipe at low cost by interposing a layer containing a material heated by a high frequency inducing heat in resin, between the corgate pipe made of a thermoplastic resin and the straight pipe inserted therein. SOLUTION: In case where a compound pipe is manufactured by inserting and joining the same kind of resin made straight pipe 2 as a corgate pipe 1 on the inner surface of a thermoplastic resin made corgate pipe 2 such as polyethylene, a tape 3 which is formed by mixing a material heated by high frequency inducing heat with resin between the joining surfaces of the corgate pipe 1 and the straight pipe 2. The tape 3 is heating fused by heat inducing super heating so as to join both pipes 1, 2. Preferably ferromagnetic metal is used in a material mixed with resin and used in the tape 3, and a material formed in a fiber shape or in a particle shape is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention inserts a straight pipe made of resin of the same kind as the corrugated pipe, which has an outer diameter close to the minimum inner diameter of the corrugated pipe, on the inner surface of the thermoplastic resin corrugated pipe. The present invention relates to a method for manufacturing a composite pipe in which both pipes are joined, and particularly to a method for manufacturing a large-diameter composite pipe.

[0002]

2. Description of the Related Art Conventionally, concrete or iron has been used as a pipe for conducting a liquid buried in the ground.
With the invention of corrugated pipe manufacturing method of thermoplastic resin,
An alternative is a corrugated pipe made of vinyl chloride resin. In the case of a buried pipe used for drainage of spring water or the like, since sand is mixed with water, the inner surface of the pipe is required to be smooth. That is, if the inner surface of the pipe is wavy, dirt or the like may be accumulated and the pipe may be clogged. Therefore, in order to make the inner surface of the pipe smooth, a composite pipe in which a straight pipe is provided on the inner surface of the corrugated pipe is used.

When the diameter of the composite pipe is less than 1 m, a method has been adopted in which the outer corrugated pipe and the inner straight pipe are integrally molded at the same time by a composite pipe die using a single screw extruder. . On the other hand, when the diameter is 1 m or more, an extruder having a discharge capacity required for integral molding and a die for a composite pipe are expensive, and a large amount of investment is required for manufacturing, so integral molding has been postponed. Therefore, in the case of a large-diameter pipe, a method of arranging a straight pipe on the inner surface of a separately prepared corrugated pipe to bond the joint surface has been studied.

On the other hand, in recent years, in order to cope with earthquakes and cold regions, the use of composite pipes made of polyethylene resin, for example, has become more and more widespread, because it is more flexible and resistant to cold than vinyl chloride resin, is less likely to break and is less likely to be damaged. is there. However, in the case of a composite pipe made of polyethylene resin, since it is difficult to bond it with a general adhesive, it is necessary to rely on the heat welding method.

In addition, if the minimum inner diameter of the corrugated pipe and the outer diameter of the straight pipe are not equal to each other for bonding, it is difficult to bond since the joining surfaces do not contact each other, but If the outer diameter of the straight pipe is the same, it was impossible to insert the straight pipe into the inner surface of the corrugated pipe.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a composite pipe made by joining a corrugated pipe made of a thermoplastic resin, particularly polyethylene, and a straight pipe, which has been difficult to join with an adhesive in the past. In particular, it is to provide a large-diameter composite pipe at low cost.

[0007]

According to a first aspect of the present invention, a thermoplastic resin corrugated pipe has an inner surface having an outer diameter close to the minimum inner diameter of the corrugated pipe and is made of the same kind of resin as the corrugated pipe. A method for producing a composite pipe in which both pipes are joined by inserting a pipe, wherein a layer containing a substance that generates heat by high frequency induction heating in a resin is interposed between the corrugated pipe and the straight pipe joining surface, It is a composite pipe manufacturing method in which both pipes are joined by melting the layer by induction heating. A second invention is the first invention, wherein the inner surface of the thermoplastic resin corrugated pipe has an outer diameter close to the minimum inner diameter of the corrugated pipe and is made of the same kind of resin as the corrugated pipe. In the method for manufacturing a composite pipe, when the pipe is inserted, the cross section of the straight pipe is deformed and then restored after the insertion.
A third invention is the composite pipe manufacturing method according to any one of the first to second inventions, wherein the substance that generates heat by high-frequency induction heating is a fiber or particles.
A fourth invention is the composite pipe manufacturing method according to any one of the first to third inventions, characterized in that the resin-containing layer containing a substance that generates heat by high-frequency induction heating is a tape. . A fifth invention is the composite pipe manufacturing method according to any one of the first to fourth inventions, wherein the thermoplastic resin is polyethylene.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a sectional view showing an embodiment of a method for joining a corrugated pipe and a straight pipe according to the present invention. As shown in the drawing, a tape 3 in which a substance that generates heat by high frequency induction heating is kneaded with a resin is interposed between the joining surfaces of the corrugated pipe 1 and the straight pipe 2 to be joined.

The width of the tape 3 may cover the circumference of the minimum inner diameter portion of the corrugated pipe which is in contact with the straight pipe,
Therefore, the length is at least equal to the circumference of the minimum inner diameter of the corrugated pipe. The thickness of the tape 3 is usually 0.2 mm
It is 1.0 mm, preferably 0.3 mm to 0.5 mm. The resin used for the tape 3 may be any resin as long as it contributes to the adhesion between the corrugated pipe 1 and the straight pipe 2 by being heated and melted.
The same material for the corrugated pipe 1 and the straight 2 is preferable. The substance used for the tape 3 and kneaded with the resin is
Any material capable of generating heat by high-frequency induction heating can be selected, and it can be selected from ferromagnetic metals (for example, Fe, Ni and alloys thereof), and is preferably fibrous or particulate (hereinafter abbreviated as metal fiber or particle). Metal fibers or particles
Needle-like or rod-like, thicker is better in heat efficiency, but from the viewpoint of tape workability (to avoid difficulty in cutting, to avoid noticeable appearance of fibers, etc.), the thickness is usually 100 μm or less, preferably Is 30 μm to 60 μm. The length is usually 3 mm or less, preferably 2 mm or less from the viewpoint of workability of the tape and the feedability of the raw material to the molding machine. The substance that generates heat by high-frequency induction heating is preferably contained in an amount of 30 to 80% by weight, and more preferably 40 to 60% by weight, based on the entire tape. It is preferable to knead the substance that generates heat by high frequency induction heating so that it is dispersed in the resin as uniformly as possible.

A tape 3 is interposed between the joining surfaces,
When the work coil 4 is set through the openings of the corrugated pipe 1 and the straight pipe 2 and a high frequency magnetic field is generated by the work coil 4 using the high frequency oscillator 5, the metal fibers or particles in the tape 3 generate heat by electromagnetic induction. Begins. This heat causes the resin in the tape 3 to melt,
The corrugated pipe 1 and the straight pipe 2 are joined via the melted tape. At this time, the molten portion is pressurized and cooled for several tens of seconds from the outer peripheral side of the corrugated pipe 1 by using semicircular pressing jigs 6A and 6B, and one cycle of the welding process is completed. This pressurizing and cooling process may be performed simultaneously with the generation of the high frequency magnetic field by the work coil 4 and the melting of the tape 3, or may be performed with a slight delay. In order to make one composite pipe, a welding cycle of the number of pitches of the corrugated pipe 1 is required.

The second aspect of the present invention, as shown in FIG. 2, deforms the cross section of the straight pipe 2 and inserts it into the corrugated pipe 1. In the minimum inner diameter portion of the corrugated pipe 1, a tape 3 in which a substance that generates heat by high frequency induction is kneaded with resin is arranged in advance. The straight pipe 2 is set so as to come into contact with the tape 3. If the tape 3 and the straight pipe 2 do not come into contact with each other even if they are set, even if the tape 3 is welded by the high frequency induction heating as described above, the corrugated pipe 1 and the straight pipe 2
Can not be joined. Therefore, corrugated pipe 1
Assuming that the minimum inner diameter of R is R, the outer diameter of the straight pipe 2 is preferably R-2 mm to R + 10 mm, more preferably R-1 mm to R + 5 mm. Since the minimum inner diameter of the corrugated pipe 1 and the outer diameter of the straight pipe 2 are substantially equal to each other, it is difficult to insert the corrugated pipe 1 into the inner surface of the corrugated pipe 1 while keeping the shape of the cross section of the straight pipe, but as shown in FIG. It can be easily inserted by deforming the cross section of the straight pipe 2. Therefore, the straight pipe 1 has an appropriate flexibility, for example, a bending elastic modulus (ASTMD-790) of 1000 to 8000 kg / cm.
² is preferable, and further 3000 to 6000 kg /
cm ² is preferred.

[0012]

[Example] Maximum outer diameter 1200 mm, minimum inner diameter 1000 mm,
Corrugated part length 5,000 mm, pitch 150 mm (pitch number 33), thickness 20 mm high density polyethylene corrugated pipe tape high frequency induction heating adhesive material (composition; iron needle filler 60 wt%, straight chain) Low density polyethylene (40% by weight) is temporarily welded with a soldering iron, and then a straight pipe made of linear low density polyethylene having an outer diameter of 1000 mm and a thickness of 10 mm is deformed and inserted.
A work coil with an outer diameter of 975 mm is set on the inner surface of a straight pipe, with an oscillation frequency of 400 KHz and an output of 10 KW.
Immediately after applying the high frequency current for 40 seconds, the outer peripheral surface of the corrugated pipe was pressed for 20 seconds by the pressing jig. It took 30 seconds to set the work coil on the next pitch. The time required for joining one composite pipe was about 50 minutes.

[0013]

By using the high-frequency induction heating bonding method, it is possible to manufacture a corrugated pipe and a straight pipe separately and then bond them together to produce a composite pipe, which is inexpensive, lightweight, and easy to handle. It is now possible to provide a pipe for burial drainage of a caliber.

[0014]

[Brief description of drawings]

FIG. 1 is a sectional view showing a method of joining a corrugated pipe and a straight pipe.

FIG. 2 is a sectional view when a straight pipe is deformed and is inserted into a corrugated pipe.

[Explanation of symbols]

1: Corrugated pipe 2: Straight pipe 3: Tape in which a substance that generates heat by high frequency induction is kneaded with resin 4: Work coil 5: High frequency oscillator 6A, 6B: Pressing jig

Claims (5)

[Claims] 1. An inner diameter of a corrugated pipe made of a thermoplastic resin has an outer diameter close to the minimum inner diameter of the corrugated pipe,
And a method for producing a composite pipe in which a straight pipe made of the same kind of resin as the corrugated pipe is inserted to join the two pipes together, and a substance that generates heat by high frequency induction heating is provided between the corrugated pipe and the straight pipe joint surface. A method for producing a composite pipe, characterized in that a layer impregnated in a resin is interposed and the layers are melted by high frequency induction heating to join the two pipes. 2. The thermoplastic resin corrugated pipe has an inner surface having an outer diameter close to the minimum inner diameter of the corrugated pipe,
The method for producing a composite pipe according to claim 1, wherein, when the straight pipe made of the same kind of resin as the corrugated pipe is inserted, the cross section of the straight pipe is deformed and restored after the insertion. 3. The method for producing a composite pipe according to claim 1, wherein the substance that generates heat by high-frequency induction heating is a fiber or particles. 4. The method for producing a composite pipe according to claim 1, wherein the resin-containing layer containing a substance that generates heat by high-frequency induction heating is a tape. 5. The method for producing a composite pipe according to claim 1, wherein the thermoplastic resin is polyethylene.