JP2000254971A - Production of synthetic resin lining pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a lining pipe in which productivity is excellent and a nonconformity of low bonding strength and overexpansion is not caused. SOLUTION: In the method for producing the synthetic resin lining pipe, the inner surface of a metallic pipe is covered by expanding a heating expandable synthetic resin pipe successively in the axial direction of the pipe in the direction of diameter while being carried in the inside of a heating device in such a state that the heating expandable synthetic resin pipe is inserted on the inner surface of the metallic pipe through an adhesive. The position of a boundary between such a part that the heating expandable synthetic resin pipe C adheres to the metallic pipe A and unadhering part is detected. The setting temperature of the heating device 2 is corrected so that displacement from the standard position of the preset boundary is made small.

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 synthetic resin-lined pipe in which the inner surface of a metal pipe is coated with a synthetic resin or the like, which can be suitably used for water supply, hot water supply, drainage, and the like.

[0002]

2. Description of the Related Art Conventionally, a composite pipe having an inner peripheral surface of a metal pipe lined with a synthetic resin having excellent corrosion resistance has been used. As a method for manufacturing such a composite pipe, for example, a metal pipe shown in FIG. A heat-expandable synthetic resin pipe C having an outer diameter smaller than the inner diameter of the metal pipe is inserted into the inner peripheral surface of A via an adhesive b, and is heated by a heating device to expand the diameter of the synthetic resin pipe. Thus, there is known a method of obtaining a synthetic resin lining pipe (see FIG. 2) in which a resin pipe C is bonded and integrated with an inner surface of a metal pipe A.

For example, Japanese Unexamined Patent Publication No. 3-120029 discloses that a heating device having a V-shape as a whole is used to prevent the formation of air pockets between a metal pipe and a synthetic resin pipe. A method is disclosed in which a synthetic resin tube is sequentially expanded from a central portion toward the tube end by heating sequentially from the center to the tube end to bond and integrate with the inner surface of the metal tube (see FIG. 3).

In the heating device disclosed in this publication, a hot air outlet and a suction port are formed, and a metal tube having a heat-expandable synthetic resin tube inserted into an inner surface thereof is conveyed between the hot tube and the hot air. When the heating temperature is too low, the adhesive strength between the synthetic resin tube and the metal tube on the inner surface may be weak and peeled off. Conversely, if the heating temperature is too high, the inner synthetic resin tube may expand too much and buckle inside as shown in FIG. Therefore, it is necessary to set an appropriate temperature.

However, for example, when hot air is used as a heat medium,
It is very difficult to uniformly set the amount of hot air in the entire device if the heating device is to be prevented from becoming too large, and the pressure inside the hot air duct will change slightly depending on the set temperature. Conditions have become narrow, and there has been a problem that it is very susceptible to changes in the outside air temperature, variations in the material temperature of the initial metal tube and the synthetic resin tube, and the like. In fact, when peeling or buckling occurs due to the above-described failure in the set temperature, several tens of wires existing in the heating furnace are used.
The in-process products of several hundred synthetic resin lining pipes are also rejected at the same time, resulting in a very large loss, which is a serious problem in practical use.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned problems of the conventional method of manufacturing a synthetic resin-lined pipe, and has a high productivity, a low adhesive strength and a problem of overexpansion which do not occur. It is an object of the present invention to provide a method for producing the same.

[0007]

In order to achieve the above object, the present invention according to the first aspect of the present invention provides a heating apparatus in which a heat-expandable synthetic resin tube is inserted into an inner surface of a metal tube via an adhesive. A method of manufacturing a synthetic resin-lined pipe by radially expanding a heat-expandable synthetic resin pipe in the pipe axis direction while transporting the inside to cover a metal pipe inner surface, wherein a predetermined position of a heating device is provided. In, the boundary position of the portion where the metal tube and the heat-expandable synthetic resin tube are in close contact and the portion that is not in close contact is detected, and the displacement of the predetermined boundary from the standard position is reduced, so that the heating device is Provided is a method for manufacturing a synthetic resin-lined pipe that corrects a set temperature. According to a second aspect of the present invention, there is provided the method of manufacturing a synthetic resin-lined pipe according to the first aspect, wherein the method for detecting the position of the boundary is a method based on image processing from a pipe end. Hereinafter, the present invention will be described in more detail.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 5, 1 is a conveyor, 2 is a V-shaped heating device, A is a metal tube, b is an adhesive,
C indicates a synthetic resin tube. The metal tube A into which the synthetic resin tube C is inserted is conveyed in the heating device in the direction of the arrow by the conveyor, and heating is started from the center in the tube axis direction. Since the synthetic resin tube C is heat-expandable and slightly shrinks in the axial direction while expanding in the radial direction, a tube slightly longer than the metal tube A is usually used.

The synthetic resin tube C is inserted into the inner surface of the metal tube A. At this time, an adhesive is applied to the outer surface of the synthetic resin tube in advance, or an adhesive is applied to the inner surface of the metal tube,
When the synthetic resin tube C is heated and expanded, for example, by applying an adhesive to both of them, or by coating the outer surface of the synthetic resin tube with a hot-melt adhesive, the inner surface of the metal tube A The coating layer of the synthetic resin tube C is formed in close contact with water. As the metal pipe A, a steel pipe is generally used, but a galvanized steel pipe for water supply, a copper pipe, an aluminum pipe, and the like can be used similarly.

As the synthetic resin pipe C, vinyl chloride resin,
Examples include chlorinated vinyl chloride resins, olefin resins such as polybutene and polyethylene, and nylon. As the adhesive b, a solvent-based, hot-melt-based adhesive such as SBS copolymer, or a reactive adhesive is used. If necessary,
The adhesive may be applied after the primer is applied.

The thermal expansion characteristics of the synthetic resin tube C are set, for example, such that, at the time of extrusion molding of the synthetic resin tube, the outer shape at a high temperature immediately after being discharged from the mold is made larger than the inner diameter of the metal tube.
By making the outer shape at the time of cooling and solidification smaller than the inner diameter of the metal tube, a characteristic that can be restored to almost the original outer diameter at the time of reheating is provided.

The hot air temperature of the heating device 2 is generally 150 ° C.
To 300 ° C, the residence time of each part in the heating furnace is 5
Set to about 15 to 15 minutes. (A) and (b) of FIG.
Is an explanatory diagram of the heating device 2 which is usually provided to face each other up and down, is composed of a plurality of sets of hot air generators, and is capable of controlling the temperature in each part such as the first half and the second half. It is a schematic plan view in the state where the upper hot air generator was removed. In some cases, the heating device 2 may include one hot air generator. At a certain point in the expansion process, the synthetic resin tube gradually heats and expands to reach and contact the metal tube. For example, it has been empirically confirmed that, when any part is ideally and uniformly heated, the part reaches the heating furnace wall 21 at a certain position as shown by a broken line in FIG.

It was also confirmed that when the heating temperature was too high, the one-dot chain line shifted to the inlet side, that is, to the left in FIG. 5, and conversely when the heating temperature was too low, the one-dot chain line shifted to the outlet side. Therefore, in advance, for example, after grasping the expansion characteristics derived from the material and manufacturing method of the synthetic resin tube, the position where the metal tube has actually reached is managed and detected, and the portion where the metal tube and the heat-expandable synthetic resin tube are in close contact with each other The degree of heating is always optimized by correcting the set temperature of the heating device so that the deviation from the standard position of the boundary of the part that is not in close contact with the ideal position, that is, the ideal arrival position represented by the dashed line, is reduced. It became possible to keep it.

For example, as shown in FIG. 6, at a certain position in the heating furnace, an optical camera constantly photographs from the end of the tube,
Manage reached position L ₁ by the image processing, if farther than the distance the optimum position of the pipe end portion to reach position, the manner to increase the temperature setting is determined that the amount of heating is less than optimum position in the opposite If they are close to each other, it is determined that the heating is too high, and the sequence is electrically set so as to lower the set temperature. The reaching position can be determined by the shade because the inner surface of the synthetic resin pipe is bent. The mechanism at the time of image processing is as shown in FIG.
Two lines (e1, e2) are observed between the line (c1, c2) and both pipe ends. Geometrically, the ratio between the distance between e1 and e2 and the distance between the distance c1 and e1 to the near-side expansion reaching line is calculated so as to be a constant value.

[0015]

According to the first aspect of the present invention, at a predetermined position of the heating device, a position of a boundary between a portion where the metal tube and the heat-expandable synthetic resin tube are in close contact and a portion where the metal tube and the heat-expandable synthetic resin tube are not in close contact is detected. Since the set temperature of the heating device is corrected so that the displacement of the preset boundary from the standard position is reduced, according to the present invention, even if there is a sudden change in the outside air temperature or the material temperature, heating is performed. Since the temperature is always kept at an optimal level, it is possible to produce synthetic resin-lined pipes with low adhesive strength and overexpansion without causing peeling or buckling with high productivity. is there. According to the second aspect of the present invention, as the method of detecting the position of the boundary, a method based on image processing from a pipe end is employed, so that the above-described effect can be further ensured without using a large-scale apparatus. be able to.

[Brief description of the drawings]

FIG. 1 is a side view of a synthetic resin lining pipe before lining.

FIG. 2 is a side view of the synthetic resin-lined pipe after lining.

FIG. 3 is a diagram for explaining an example of sequential heating from the center.

FIG. 4 is a cross-sectional view showing a problem due to overexpansion.

5A and 5B are diagrams for explaining a method for manufacturing a synthetic resin lining tube of the present invention, wherein FIG. 5A is a schematic plan view of an apparatus suitable for application to the present invention, and FIG. It is a front view.

FIG. 6 is a side view of the lining tube while the synthetic resin tube is expanding.

FIG. 7 is a diagram illustrating a positional relationship between a camera and a pipe when capturing an expansion reaching position from a pipe end.

[Explanation of symbols]

 1. Conveyor 2. Heating device 9. Ideal position of expansion line A. Metal tube b. Adhesive C. Synthetic resin tube c1, c2.・ Synthetic resin pipe end

Claims (2)

[Claims] In a state where the heat-expandable synthetic resin tube is inserted into the inner surface of the metal tube via an adhesive, the heat-expandable synthetic resin tube is sequentially moved in the tube axial direction while being conveyed in the heating device. A method for producing a synthetic resin lining tube by expanding and covering an inner surface of a metal tube, wherein a predetermined portion of a heating device is in close contact with a portion where the metal tube and the heat-expandable synthetic resin tube are in close contact with each other. A method for manufacturing a synthetic resin-lined pipe, comprising detecting a boundary position of a non-existing portion and correcting a set temperature of a heating device so that a displacement from a preset standard position of the boundary is reduced. 2. The method for manufacturing a synthetic resin-lined pipe according to claim 1, wherein the method for detecting the position of the boundary is a method based on image processing from a pipe end.