JPH08183109A - Production of synthetic resin coated metal pipe - Google Patents

Abstract

PURPOSE: To produce a synthetic resin coated metal pipe capable of uniformly heating a metal pipe in which a synthetic resin tube is inserted over the whole of the pipe and becoming uniform in the adhesive strength of the metal pipe and the synthetic resin tube over the whole of the pipe. CONSTITUTION: A metal pipe 1 having a synthetic resin tube 2 inserted therein or fitted to the outer surface thereof is moved in the direction crossing the pipe axis thereof at a right angle by a conveyor 3 and an electromagnetic induction heating coil 11 is arranged obliquely with respect to the moving direction of the metal pipe 1 to surround the conveyor 3 and the metal pipe 1 and auxiliary heating devices 4 are arranged so as to cover the end parts of the metal pipe 1. The metal pipe 1 is continuously heated from one end thereof to the other end thereof to closely bond the synthetic resin tube 2 to the metal pipe to produce a synthetic resin coated metal pipe wherein at least one of the inner and outer surfaces of the metal pipe is coated with a synthetic resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a synthetic resin-coated metal tube, and more particularly to a method for coating the outer surface with a heat-shrinkable synthetic resin tube and a method for coating the inner surface with a heat-expandable synthetic resin tube. Regarding the method.

[0002]

2. Description of the Related Art FIG. 9 is a diagram showing a conventional method for manufacturing a synthetic resin-coated metal tube disclosed in Japanese Patent Laid-Open No. 6-64042. In FIG. 9, in order to impart corrosion resistance, chemical resistance, heat insulation, abrasion resistance, designability, etc. to a metal tube, at least one of the inner surface of the tube and the outer surface of the tube is made of synthetic resin. It is for coating, and heats a metal tube in which a synthetic resin tube is inserted into at least one of the inner surface of the tube and the outer surface of the tube by electromagnetic induction to utilize the thermal expansion or heat shrinkability of the synthetic resin tube. Then, the synthetic resin tube is brought into close contact with at least one of the inner surface of the tube and the outer surface of the tube (hereinafter referred to as prior art).

In FIG. 9, reference numeral 11 is an electromagnetic induction heating coil, which is formed in an elliptical shape so as to surround the conveyor 3 and the metal tube 1, and one end 11a of the coil is formed by the conveyor 3 in the tube axis direction. It is located on the upstream side of the metal pipe 1 moving in a direction orthogonal to the other end 11b.
Are arranged obliquely with respect to the moving direction of the metal tube 1 so as to be located on the downstream side of the moving metal tube 1. 12
Is an electromagnetic induction heating generator connected to the electromagnetic induction heating coil 11. The synthetic resin tube 2 is made to have a diameter smaller than a predetermined diameter at the time of molding so as to give it a thermal expansion property, and an adhesive is applied to the outer peripheral surface thereof. The metal tube 1 having the synthetic resin tube 2 inserted inside the tubular body is continuously heated from one end to the other end by the elliptical electromagnetic induction heating coil 11 to expand the synthetic resin tube 2. . Thus, the synthetic resin-coated metal tube in which the synthetic resin tube 2 is in close contact with the inner surface of the metal tube 1 and the inner surface of the tube is covered with the synthetic resin is manufactured.

FIG. 10 is a schematic plan view showing a second example of the prior art described in JP-A-6-64042.
As shown in FIG. 10, two elliptical electromagnetic induction heating coils 14 and 1 surround the conveyor 3 and the metal tube 1.
5 are provided, and one end 14a, 15a of each of them is provided.
Is located at the upstream central portion of the metal pipe 1 that moves in the direction orthogonal to the pipe axis direction, and the other ends 14b, 15
b are radially arranged with respect to the moving direction of the metal tube 1 so that the b is located at both ends on the downstream side of the metal tube 1.

Similarly, FIG. 11 is a schematic view of Japanese Patent Laid-Open No. 6-64042.
It is a schematic plan view which shows the 3rd example of the prior art described in the gazette. As shown in FIG. 11, an electromagnetic induction heating coil 16 having a V-shaped planar shape is provided so as to surround the conveyor 3 and the metal tube 1. This electromagnetic induction heating coil has a V-shaped planar shape. 16, the central portion 16a is
The metal pipe 1 is located on the upstream side of the metal pipe 1 moving in the direction orthogonal to the pipe axis direction, and both ends 16b, 16b thereof are
Are arranged radially in the moving direction of the metal pipe 1 so as to be located at both ends on the downstream side of the.

[0006]

These prior art techniques have the following problems. In any of the heating methods described above, the magnetic flux generated from the electromagnetic induction heating coil causes current to be generated in the metal pipe tube to perform heating, but at the tube end, the magnetic flux from the coil is higher than at the center of the tube. Is more likely to leak and the heat is dissipated more than in the central part of the pipe body, so the temperature tends to be lower than in the central part of the pipe body, and the thermal deformation of the synthetic resin tube will not be completed completely There is a problem that the adhesive strength with the resin tube is lowered.

The present invention has been made in view of the above circumstances, and an object of the present invention is to produce a synthetic resin-coated metal tube in which the bonding strength between the metal tube and the synthetic resin tube is uniform over the entire tubular body.

[0008]

A method for manufacturing a synthetic resin-coated metal pipe according to the present invention is directed to a metal pipe in which a synthetic resin tube is arranged on at least one of the inner surface of the pipe and the outer surface of the pipe, and the direction of the pipe is the same. At least one of the inner surface of the tube and the outer surface of the tube is moved by moving in a direction orthogonal to each other, heating the metal tube by the heating mechanism during the movement, and bringing the synthetic resin tube into close contact with at least one of the inner surface of the tube and the outer surface of the tube. In the method for producing a synthetic resin-coated metal tube, the both ends of the metal tube are each parallel to the moving direction of the metal tube and the outer diameter of the metal tube is A method for producing a synthetic resin-coated metal pipe, characterized in that both ends of the metal pipe are heated by auxiliary heating devices provided so as to cover the pipe end portion having a length corresponding to 6 times or more. is there.

[0009]

According to the present invention, the metal tube has a length parallel to the moving direction of the metal tube immediately after passing through the heating mechanism and a length corresponding to 6 times or more of the outer diameter of the metal tube. Since it is heated by an auxiliary heating device arranged so as to cover the pipe end portion, the temperature of the pipe end portion of the metal pipe in which the synthetic resin tube is inserted does not decrease so much that the temperature of the entire pipe body is kept uniform. Therefore, the thermal deformation of the synthetic resin tube is completely performed, and the adhesive strength between the metal tube and the synthetic resin tube becomes uniform over the entire tubular body. The area where the auxiliary heating device covers the tube end is
If it is not more than 6 times the outer diameter of the metal tube, the effect of suppressing the temperature decrease at the end of the metal tube cannot be sufficiently obtained.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a schematic plan view showing a first example of equipment used in the present invention. As shown in the drawing, a plurality of metal tubes 1 having a synthetic resin tube 2 inserted into the inner surface of the tube are sequentially moved by a conveyor 3 in a direction indicated by an arrow orthogonal to the tube axis direction. Thus conveyor 3
An electromagnetic induction heating coil 11 is arranged as a heating mechanism for heating the metal tube 1 moving by
Is an electromagnetic induction heating generator connected to the electromagnetic induction heating coil 11.

The auxiliary heating device 4 is an electromagnetic induction heating coil 1.
Immediately after passing through 1, the metal pipe 1 is located at the downstream side of the pipe end, parallel to the moving direction of the metal pipe, and both pipe end portions having a length corresponding to 7 times the outer diameter of the metal pipe. It is arranged so as to cover.

FIG. 2 is a schematic process diagram of an embodiment of the present invention. As shown in FIG. 2, in the embodiment of the present invention, the metal tubes 1 are sequentially loaded into the line one by one by the metal tube loading one indexing section 5, and then in the synthetic resin tube insertion section 6. The synthetic resin tube 2 is inserted into the body of each metal tube 1. As shown in the cross-sectional view of the metal tube 1 into which the synthetic resin tube 2 is inserted in FIG. 3, the synthetic resin tube 2 is reduced in diameter from a predetermined diameter at the time of its molding so as to impart thermal expansion property thereto. Then, the adhesive 13 is applied to the outer peripheral surface thereof.

The metal tube 1 into which the synthetic resin tube 2 having the thermal expansion property is inserted is arranged obliquely with respect to the moving direction of the metal tube 1 while moving the heating zone 7. , The elliptical electromagnetic induction heating coil 11 as a heating mechanism, which surrounds the conveyor 3 and the metal tube 1, is continuously heated from one end to the other end to expand the synthetic resin tube 2. Immediately after the electromagnetic induction heating coil 11, as an auxiliary heating mechanism, in parallel with the moving direction of the metal tube 1, both ends of the tube having a length corresponding to 6 times or more of the outer diameter of the metal tube 1 are covered. Metal tube 1 by heating device 4
The heating temperature of the pipe end is made uniform with the entire metal pipe 1, the synthetic resin tube 2 is expanded to the pipe end, and cooled in the cooling zone 8 having a cooling mechanism.

Thus, as shown in FIG. 3, a synthetic resin-coated metal pipe A in which the synthetic resin tube 2 is closely attached to the inner surface of the metal tube 1 and the inner surface of the pipe is covered with a synthetic resin is manufactured. Synthetic resin-coated metal tube A manufactured in this way
Next, the pipe end treatment and marking are performed by the pipe end treatment / marking band 9, and the bundles are bound by the binding band 10.

A steel pipe, a cast iron pipe or the like is used as the metal pipe 1, and a polyester-based, polyolefin-based, polyvinyl chloride-based, polyacrylic-based or polyamide-based tube is used as the synthetic resin tube 2. .

FIG. 4 is a schematic sectional view of a synthetic resin-coated metal tube B in which a synthetic resin tube 2'is in close contact with the outer surface of the metal tube 1 and the outer surface of the tube is covered with a synthetic resin. in this way,
In order to manufacture a synthetic resin-coated metal tube B in which the outer surface of the tubular body is coated with a synthetic resin, a synthetic resin tube 2 ′ having a diameter larger than a predetermined diameter at the time of molding to give heat shrinkability to the synthetic resin tube 2 ′ is provided in advance. The difference from the case of manufacturing the above-mentioned synthetic resin-coated metal pipe A is only that the adhesive 13 is applied to the inner peripheral surface and then inserted into the outer surface of the pipe body.

FIG. 5 is a schematic cross-sectional view of a synthetic resin-coated metal pipe C in which a synthetic resin tube is closely adhered to the inner surface and the outer surface of the metal tube 1 and both the inner surface and the outer surface of the tube are covered with a synthetic resin. Is. As described above, in order to manufacture the synthetic resin-coated metal tube C in which both the inner surface of the tube and the outer surface of the tube are coated with the synthetic resin, the diameter of the metal tube C is made smaller than a predetermined diameter at the time of molding in advance, and the thermal expansion property is increased. The outer peripheral surface of the synthetic resin tube 2 to which the above is applied is coated with the adhesive 13 and is inserted into the inner surface of the pipe, and the diameter is expanded in advance from a predetermined diameter at the time of molding so that the heat shrinkability is increased. The synthetic resin tube 2 ′ that has been imparted is coated with the adhesive 13 on its inner peripheral surface and then inserted into the outer surface of the tubular body only in the above-mentioned synthetic resin-coated metal tube A.
Is different from the case of manufacturing.

FIG. 6 is a schematic plan view showing a second example of equipment used in the present invention. As shown in the drawing, in the second example, the conveyor 3 and the metal pipe 1 are surrounded by 2
This is different from the first example in that two elliptical electromagnetic induction heating coils 14 and 15 are provided.

FIG. 7 is a schematic plan view showing a third example of equipment used in the present invention. As shown in the drawing, in the third example, so as to surround the conveyor 3 and the metal tube 1,
Electromagnetic induction heating coil 16 having a planar V-shape
Is provided, which is different from the first example.

(Examples and Comparative Examples) Examples of the present invention will be described.
This will be described in comparison with a comparative example. The equipment shown in the first example of the present invention (hereinafter referred to as equipment a), the equipment shown in the second example (hereinafter referred to as equipment b) and the equipment shown in the third example (hereinafter referred to as equipment c) are: Under the conditions shown in, the temperature condition of the end of the metal pipe when heating only the metal pipe (hereinafter,
The temperature condition of the present invention) No. 1-3 were investigated. In addition, except that the heating of the metal tube was performed only in the prior art with no electromagnetic induction heating and no auxiliary heating, the temperature condition of the end portion of the metal tube for comparison (hereinafter,
The temperature condition for comparison) No. 1-3 were investigated.

Metal tube: Galvanized steel tube (SGP 20A) Moving speed of metal tube: 0.8 m / min The temperature condition No. of the present invention in which heating was performed by the methods a, b or c of the present invention in this way 1-3 and comparative temperature conditions No. The survey results of 1-3 are shown in FIG. As is clear from FIG. 8, the comparative temperature condition in which only the metal tube is heated without electromagnetic heating of the prior art and without auxiliary heating is equivalent to 7 times the outer diameter from the tube end. There was a large temperature deficiency in the length section. On the other hand, equipment a, b or c
According to the present invention temperature condition No. In all of Nos. 1 to 3, there was no decrease in temperature at the tube end.

(Examples and Comparative Examples Construction Example) A synthetic method in which the inner surface, the outer surface or the inner and outer surfaces of a metal tube was coated with a synthetic resin by using the method of the present invention under the following conditions with the equipment a, b or c. Resin-coated metal pipe (hereinafter referred to as the metal pipe of the present invention)
No. 1-9 were produced.

Metal tube: Galvanized steel tube (SGP 20A), Synthetic resin tube: Hard vinyl chloride, Moving speed of metal tube: 0.8 m / min Metal with synthetic resin tube inserted inside, outside or inside / outside of the tube Under the same conditions as in the present invention, except that the tube was heated only by electromagnetic induction heating of the prior art and no auxiliary heating, a synthetic resin for comparison, in which the inner surface, the outer surface, or the inner and outer surface of the metal tube was coated with a synthetic resin. Coated metal pipe (hereinafter referred to as comparative metal pipe) No. 1-9 were produced.

The metal tube No. of the present invention manufactured by the method of the present invention. 1 to 9 and comparative metal tube No. Table 1 shows the results of examining the product properties and the adhesive strength between the synthetic resin and the metal tube for each of 1 to 9.

As is apparent from Table 1, for comparison, a metal tube in which a synthetic resin tube was inserted into the inner surface, outer surface, or inner / outer surface of the tube was used only with electromagnetic induction heating of the prior art without auxiliary heating. Metal tube No. In Nos. 1 to 9, the properties of the tube end were poor and the adhesive strength was low with respect to the center of the tube, and it was impossible to satisfy the standard value. On the other hand, the metal tube No. of the present invention manufactured by the method of the present invention. All of Nos. 1 to 9 had good product properties, sufficient adhesive strength, and excellent quality.

[0026]

[Table 1]

[0027]

As described above, according to the present invention, since the metal tube is heated by the auxiliary heating device immediately after passing through the heating mechanism, the metal tube in which the synthetic resin tube is inserted. The temperature drop at the end is small and the temperature of the entire tube is kept uniform. Therefore, the thermal deformation of the synthetic resin tube is completely performed, the bonding strength between the metal tube and the synthetic resin tube becomes uniform over the entire tube, and the corrosion resistance, chemical resistance, heat insulation, abrasion resistance, designability, etc. An excellent synthetic resin-coated metal tube can be manufactured with high yield.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing a first example of equipment used for implementing the present invention.

FIG. 2 is a schematic process diagram showing an example of the present invention.

FIG. 3 is an example of a cross-sectional view of a synthetic resin-coated metal tube manufactured by the present invention in which the inner surface of the metal tube is covered with a synthetic resin.

FIG. 4 is an example of a cross-sectional view of a synthetic resin-coated metal tube manufactured by the present invention, in which the outer surface of the metal tube is covered with a synthetic resin.

FIG. 5 is an example of a cross-sectional view of a synthetic resin-coated metal tube produced by the present invention, in which both the inner surface of the metal tube and the outer surface of the metal tube are covered with a synthetic resin.

FIG. 6 is a schematic plan view showing a second example of equipment used for implementing the present invention.

FIG. 7 is a schematic plan view showing a third example of equipment used for implementing the present invention.

FIG. 8 is a graph showing a temperature condition of a tube end portion of a metal tube heated by an example of the present invention and a comparative example.

FIG. 9 is a schematic plan view showing a first example of the prior art.

FIG. 10 is a schematic plan view showing a second example of the prior art.

FIG. 11 is a schematic plan view showing a third example of the prior art.

[Explanation of symbols]

 1 Metal tube 2, 2'Synthetic resin tube 3 Conveyor 4 Auxiliary heating device 5 Metal tube charging 1 indexing section 6 Synthetic resin tube insertion section 7 Heating zone 8 Cooling zone 9 Pipe end treatment / marking zone 10 Bonding zone 11 Electromagnetic induction Heating coil 12 Electromagnetic induction heating generator 13 Adhesive 14 Electromagnetic induction heating coil 15 Electromagnetic induction heating coil 16 V-shaped electromagnetic induction heating coil

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B29L 23:00 (72) Inventor Kunio Todo 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Steel Tube Incorporated (72) Inventor Sadahisa Nakajima 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Tube Co., Ltd.

Claims (1)

[Claims] 1. A metal tube having a synthetic resin tube disposed on at least one of an inner surface of the tube and an outer surface of the tube is moved in a direction orthogonal to an axial direction of the tube, and the metal tube is heated by a heating mechanism during the movement. A synthetic resin tube is adhered to at least one of the inner surface of the pipe and the outer surface of the pipe, and at least one of the inner surface of the pipe and the outer surface of the pipe is covered with a synthetic resin.
In the method for producing a synthetic resin-coated metal pipe, immediately after both ends of the metal pipe have passed through the heating mechanism,
Both ends of the metal tube are provided by an auxiliary heating device that is provided in parallel with the moving direction of the metal tube and covers the tube end portion having a length corresponding to 6 times or more of the outer diameter of the metal tube. A method for producing a synthetic resin-coated metal tube, which comprises heating each of them.