JPH0970887A - Production of lining pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a resin lining layer without leaving residual stress by applying a twist to a preformed resin pipe having an outer diameter larger than the inner diameter of a metal pipe in a softened state to obtain a resin pipe molded so as to have a diameter smaller than the inner diameter of the metal pipe. SOLUTION: A pereformed resin pipe 2 having an outer diameter larger than the inner diameter of a metal pipe to be lined is extruded from an extrusion mold 1 to be molded. The extruded preformed resin pipe 2 is continuously cooled to the normal temp. in a cooling water tank 3 to be solidified and the obtained resin pipe 4 is taken over by a taking-over machine 5. Therefore, the outer diameter of the preformed resin pipe 2 becomes smaller than the inner diameter of the metal pipe and the resin pipe 4 having an outer diameter smaller than the inner diameter of the metal pipe is continuously obtained. Next, the resin pipe 4 is heater Whereupon, the diameter of the resin pipe 4 expands so that the resin pipe 4 is ready to return to the shape of the preformed resin pipe 4 and the outer surface thereof comes into close contact with the inner surface of the metal pipe 6 to become the resin lining layer 9 integrated with the inner surface of the metal pipe 6 through an adhesive 7 and longitudinal deformation is not also generated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a lining pipe.

[0002]

2. Description of the Related Art Conventionally, a lining pipe provided with a resin lining layer on the inner surface of a metal pipe is disclosed in Japanese Patent Publication No. 1-444 shown below.
It is manufactured by the method as disclosed in Japanese Patent Publication No. 96. (1) A preformed resin pipe (parison) having an outer diameter larger than the inner diameter of the metal pipe is extruded from the extrusion die, and the take-up speed is adjusted to be faster than the extrusion speed to keep the preformed resin pipe in a softened state. The resin pipe is obtained by a so-called drop-molding method in which the final outer diameter is formed to be smaller than the inner diameter of the metal pipe during the heating.

(2) An adhesive is applied to at least one of the outer surface of the resin pipe and the inner surface of the metal pipe obtained as described above, and the adhesive is interposed between the metal pipe and the resin pipe. Insert the resin tube into the metal tube. (3) The metal pipe having the resin pipe inserted therein is introduced into a heating furnace, and the resin pipe is expanded along the inner surface of the metal pipe to form a resin lining layer.

That is, since the resin pipe is obtained by a drop molding method, the resin lining is utilized by utilizing the shape before being dropped by heating and the phenomenon of expanding to return to a large outer diameter (shape memory effect). I am trying to form a layer. In addition, in the step (3), heating is not performed at once in whole, but heating is performed from one end of the pipe to the other end, or from the center of the pipe to both ends. Care is taken to prevent air from intervening at the interface with the resin lining layer.

[0005]

By the way, in the above-mentioned conventional method for manufacturing a lining pipe, when the resin pipe expands by heating, the resin pipe tries to shrink in the lengthwise direction, but between the metal pipe and the resin pipe. Since the adhesive is present, the resin lining may become a resin lining layer in a state where the resin pipe is not sufficiently contracted in the length direction due to the frictional resistance due to the adhesive.

However, if the resin lining layer is formed in such a state that the resin tube is prevented from shrinking in the lengthwise direction, residual stress remains in the resin forming the resin lining layer, If the adhesive strength of the adhesive decreases due to long-term use, the adhesive peels off due to residual stress and the resin that constitutes the resin lining layer shrinks in the longitudinal direction of the pipe, exposing the inner surface of the metal pipe at the pipe end. There is a risk that

In view of such circumstances, the present invention provides a method for manufacturing a lining pipe which can form a resin lining layer without leaving residual stress and can obtain a running pipe having excellent durability. Has an aim.

[0008]

In order to achieve such an object, the method of manufacturing a lining pipe according to the present invention comprises:
A resin pipe is inserted into the metal pipe with an adhesive interposed between the metal pipe and the metal pipe, and the resin pipe is heated to expand along the inner surface of the metal pipe to form a resin lining layer on the inner surface of the metal pipe. In the method for producing a lining pipe, the twisted preformed resin pipe in a softened state, which is preformed to have an outer diameter larger than the inner diameter of the metal pipe as the resin pipe, is formed to have a smaller diameter than the inner diameter of the metal pipe. The resin tube is used.

In the above structure, the resin tube is not particularly limited, but a vinyl chloride resin tube is particularly preferable, and a spiral rib may be formed on the inner surface. As a method for producing a resin pipe, a method is generally used in which a preformed resin pipe is molded by extrusion and twisted while the preformed resin pipe is kept in a softened state. Alternatively, the preformed resin tube may be obtained by a known molding method such as extrusion molding and then reheated to add the twist in a batch manner.

The preformed resin pipe is twisted at a temperature lower than the molding temperature of the preformed resin pipe and higher than the glass transition temperature of the resin. The degree of twist is empirically determined so that the resin tube does not shrink in the longitudinal direction during thermal expansion.

The metal pipe is not particularly limited, but a steel pipe or a galvanized steel pipe is usually used. The adhesive is not particularly limited to hot-melt type or solvent type as long as it has adhesiveness to both resin and metal.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. That is, in the method for manufacturing a lining pipe of the present invention, first, as shown in FIG. 1, a preformed resin pipe 2 having an outer diameter larger than the inner diameter of the metal pipe lined from the extrusion die 1 is extruded.

Then, the preformed resin pipe 2 extruded.
After being continuously cooled and solidified in the cooling water tank 3 to room temperature,
The resin pipe 4 thus obtained is taken by a take-up machine 5. Since the take-up machine 5 is designed to rotate the resin pipe 4 at a predetermined speed in the circumferential direction and take it out at a predetermined speed in the extruding direction of the preformed resin pipe 2, the preformed resin pipe 2 immediately after being extruded. Will be taken while being twisted in the circumferential direction.

Therefore, the preformed resin pipe 2 has an outer diameter smaller than the inner diameter of the metal pipe due to this twisting, and the resin pipe 4 having an outer diameter smaller than the inner diameter of the metal pipe is continuously obtained. Next, as shown in FIG. 2, the resin pipe 4 thus obtained is inserted into the metal pipe 6 with at least one of the inner surface of the metal pipe 6 and the outer surface of the resin pipe 4 being coated with the adhesive 7. Then, as shown in FIG. 3, the metal pipe 6 is gradually introduced into the heating furnace 8 from one end to the other end and heated.

Due to this heating, the diameter of the resin pipe 4 expands so as to return to the shape of the preformed resin pipe 2, and the outer surface of the resin pipe 4 is brought into close contact with the inner surface of the metal pipe 6 and, as shown in FIG. The resin lining layer 9 is integrated with the inner surface of the metal tube 6. The lining pipe 10 thus obtained is obtained by twisting the preformed resin pipe 2 into a smaller diameter by twisting the preformed resin pipe 2. Therefore, when the lining pipe 10 is heated and expanded, the lining pipe 10 is untwisted due to the shape memory effect. Since it expands in the radial direction, there is almost no deformation in the longitudinal direction.

Therefore, even if the residual stress that tends to shrink in the longitudinal direction does not remain and it is used for a long time as in the conventional case, the accident that the inner surface of the metal pipe is exposed at the pipe end is completely eliminated.

[0017]

EXAMPLES Next, more specific examples of the present invention will be described in detail. (Example 1) The outer diameter is 54 mm in the same manner as in the method shown in FIG.
Pre-molded resin pipe made of vinyl chloride resin is extruded at 190 ° C and taken by a take-up machine so that it rotates once every 292 mm.
A resin tube having a wall thickness of 1.5 mm and an outer diameter of 48 mm was obtained.

After applying a hot-melt type adhesive to the outer surface of the resin pipe, the resin pipe is inserted into a steel pipe as a metal pipe having an outer diameter of 60.5 mm and an inner diameter of 49.9 mm which has been subjected to pickling treatment. It was gradually heated toward the end at 160 ° C. to obtain a lining pipe in which the inner surface of the steel pipe was lined with a resin lining layer. In the obtained lining pipe, the resin lining layer was contracted even during long-term use, and the inner surface of the metal pipe was not exposed at the end of the pipe.

[0019]

Since the method for manufacturing a lining pipe according to the present invention is configured as described above, it is possible to form a lining layer on the inner surface of a metal pipe without generating residual stress that tends to shrink in the longitudinal direction. You can Therefore, the lining layer shrinks even after long-term use, and the inner surface of the metal pipe is not exposed at the end of the pipe, and a lining pipe having excellent durability can be provided.

[Brief description of drawings]

FIG. 1 is a schematic view illustrating an example of a resin pipe manufacturing apparatus used in a method for manufacturing a lining pipe according to the present invention.

FIG. 2 is a sectional view showing a state in which a resin pipe is inserted into a metal pipe.

FIG. 3 is a schematic view illustrating a step of heating a metal tube to form a lining layer.

FIG. 4 is a cross-sectional view of a lining pipe obtained by the method for manufacturing a lining pipe according to the present invention.

[Explanation of symbols]

 2 Preformed resin pipe 4 Resin pipe 6 Metal pipe 7 Adhesive 9 Resin lining layer 10 Lining pipe

Claims (1)

[Claims] 1. A resin tube is inserted into the metal tube with an adhesive agent interposed between the metal tube and the metal tube, and the resin tube is heated to expand the resin tube along the inner surface of the metal tube to the inner surface of the metal tube. In a method of manufacturing a lining pipe for forming a resin lining layer, a twist is added to a preformed resin pipe in a softened state which has been preformed as an outer diameter larger than the inner diameter of the metal pipe as the resin pipe, A method of manufacturing a lining pipe, characterized in that a resin pipe molded to have a diameter smaller than the inner diameter is used.