JPH08174672A - Manufacturing method of composite pipe - Google Patents

Abstract

(57) [Summary] [Purpose] A metal tube with a thermally expandable resin tube coated with an adhesive is carried into a heating furnace, and the resin tube is thermally expanded, and the resin tube is attached to the inner surface of the metal tube. When closely contacting, the resin tube can be closely contacted with the inner surface of the metal tube without air remaining between the metal tube and the resin tube. [Arrangement] An M-shaped cooling zone B is arranged on the upstream side where a metal pipe 1 into which a resin pipe 2 is inserted is carried into a V-shaped heating furnace A. The metal tube 1 is heated from the center to both ends in the heating furnace A, but the surface temperature of the metal tube 1 is maintained at 10 ° C. to 60 ° C. by the cooling zone B until just before being heated. Make sure that the resin pipe 2 does not expand before it is loaded into the container.

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 composite pipe in which a resin pipe is closely attached to the inner surface of a metal pipe and is used as a water supply pipe, a hot water supply pipe or a drainage pipe. The present invention relates to a method for producing a composite pipe, which allows air to be closely attached without remaining.

[0002]

2. Description of the Related Art As water supply pipes and drainage pipes, composite pipes having a metal lined inside with a resin are often used for corrosion protection. To line the resin on the inner surface of the metal tube, apply an adhesive to the outer surface of the thermoplastic resin tube, insert the resin tube into the metal tube, and heat the metal tube from one end to the other end in order. By melting the adhesive layer and simultaneously heating and expanding the resin pipe, the resin pipe is brought into close contact with the inner surface of the metal pipe. However, the thermal conductivity of resin is 1
Since it is as low as about / 7, if the metal pipe is heated from one end to the other end in sequence, the thermal expansion of the resin pipe on the other end side is significantly delayed, and a uniform lining cannot be obtained.

In order to solve such a problem, a method for manufacturing a vinyl chloride lined steel pipe is disclosed in Japanese Patent Laid-Open No. 48-892.
No. 71 publication. The method for manufacturing a vinyl chloride lining steel pipe disclosed in this publication is such that the metal pipe 1 is sequentially heated from the central portion toward both ends by an apparatus as shown in FIGS. 4 and 5. This device is provided on both the upper and lower sides of the forward side of the conveyor 10 that conveys the metal tube 1.
A heating element 20 having a Y-shaped plane is arranged, and both heating elements 20
A kind of heating furnace A is formed by forming a large number of hot air outlets 21 in a V-shape on the opposing surfaces of.

According to the prior art, a resin pipe 2 coated with an adhesive is inserted into a metal pipe 1, and the metal pipe 1 is conveyed by the conveyor 1.
0 conveys the inside of the heating furnace A. Since the heating furnace A has a hot air outlet 21 formed in a V shape, when the metal tube 1 is conveyed in the heating furnace A by the conveyor 10,
The metal tube 1 is heated from the central portion toward both ends in order. Therefore, the resin pipe 2 inserted in the metal pipe 1 also thermally expands from the central portion to both end portions.

[0005]

The outer surface of the metal tube 1 carried into the heating furnace A is heated, and the heat is transferred to the inner surface, whereby the resin tube 2 inserted into the metal tube 1 is heated. And thermally expands to come into close contact with the inner surface of the metal tube 1. Here, it is important that the expansion of the resin pipe 2 is sequentially performed in the longitudinal direction of the pipe, and when the resin pipe 2 expands from a discontinuous portion, an air pocket may be formed between the metal pipe 1 and the resin pipe 2. This causes the inner surface of the resin pipe 2 to swell.

However, since a metal tube having a small wall thickness has good thermal conductivity, the central portion of the metal tube is simply carried into the heating furnace A, so that not only the central portion of the metal tube but also its peripheral portion, and sometimes both ends. Heat is even transmitted to the department. Then, before the both ends of the metal pipe are carried into the heating furnace A, the periphery of the heating portion of the resin pipe 2 and both ends thereof are also heated, and the temperature of the resin pipe 2 rises to near the expansion start temperature. Therefore, the resin tube 2 will start to expand from an irregular site. In such a state, even if both end sides of the metal pipe are carried into the heating furnace A, the resin pipe 2 is not expanded in order from the central portion to both end portions as originally assumed, so that Problems such as air remaining between the resin pipe 2 and the resin pipe 2 swelling toward the inner surface occur.

The above-mentioned problems occur particularly markedly when a thin metal tube is used. Even when a thick metal tube is used, the temperature in the vicinity of the axial direction of the tube entering the heating furnace A is also increased. When the metal tube is put in the heating furnace A with no difference, the same problem occurs. For example, when the metal tube is put in the heating furnace A while the temperature of the atmosphere in the work place is high and the temperature of the entire metal tube is uniformly high as in the summer, a slight heat is generated from the heating furnace A. Since the resin pipe starts to expand just by receiving it, the resin pipe in the peripheral portion expands due to heat conduction from the heating unit.

Therefore, the present invention pays attention to the above-mentioned problems of the prior art, and provides a method for manufacturing a composite pipe in which air can be adhered between a metal pipe and a resin pipe without remaining air. The purpose is to

[0009]

[Means for Solving the Problems] A first means for achieving the above object is to insert a heat-expandable resin pipe coated with an adhesive into a metal pipe, and insert the resin pipe into the center of the metal pipe. Part to both ends, or one end to the other end, are sequentially loaded into a heating furnace, and the resin pipes are sequentially thermally expanded to adhere the resin pipes to the inner surface of the metal pipe. A method for producing a composite pipe, which comprises partially cooling the outer surface of a metal pipe into which a thermally expandable resin pipe coated with the agent has been inserted, until the metal pipe is successively loaded into a heating furnace.

A second means for achieving the above object is to:
Cooling is performed by air, and the outer surface of the metal tube is cooled to 10 ° C-6
The method for producing a composite tube according to the above first means is characterized in that the method is maintained at 0 ° C.

[0011]

According to the first means, after the resin pipe coated with the adhesive is inserted into the metal pipe, the metal pipe is partially heated from the central portion to both end portions or from one end portion to the other end. The portion of the metal pipe that has not been loaded into the heating furnace is the portion of the metal pipe that has been heated in the heating furnace by cooling the outer surface of the metal pipe until it is loaded into the furnace and heated sequentially. It is no longer heated by the heat of. Therefore, the resin pipes inserted into the metal pipes are sequentially heated, and the poor adhesion due to the residual air is eliminated, so that the metal pipes and the resin pipes come into close contact with each other.

According to the second means, by cooling the outer surface of the metal tube by air cooling, the metal tube is transported in the cooling atmosphere and the entire circumference of the metal tube is cooled, so that it is heated. The resin in the part where it adheres surely adheres to the metal pipe. Further, by maintaining the surface of the metal tube at 10 ° C. to 60 ° C. until it is carried into the heating furnace, it is possible to prevent the quality from becoming unstable due to the change in the atmospheric temperature over the year.

[0013]

Embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a plan view of an apparatus for carrying out the present invention. FIG. 2 is also a plan view of the cooling means. FIG. 3 is a cross-sectional view of a state in which a resin pipe is loaded in the metal pipe before entering the apparatus in FIG. It should be noted that the same parts as those of the related art are denoted by the same reference numerals and the description thereof will be omitted.

The method for producing a composite pipe according to the present invention is carried out by an apparatus having a cooling zone B arranged upstream of a heating furnace A as shown in FIG. When the V-shaped furnace as shown in FIG. 1 is arranged, the M-shaped cooling zone B is arranged so as to sandwich the upstream end of the heating furnace A. The cooling zone B is constituted by a cooling body 30 as shown in FIG. 2, for example.
The cooling body 30 is configured such that a pipe 32 meanders in a box body 31 and a refrigerant gas or cooling water is circulated in the pipe 32.

In the method for manufacturing the composite pipe of this embodiment, the metal pipe 1 is moved in parallel by the conveyor 10 and the cooling zone B is used.
And heating furnace A. When passing through the cooling zone B, the metal tube 1 may be moved in a state of being in direct contact with the cooling body 30 or may be moved in a state of being separated. When the metal pipe 1 is moved away from the cooling body 30, the cooling body 30 is arranged so as to face each other with the forward side (conveying side) of the conveyor 10 that conveys the metal pipe 1 sandwiched between the cooling bodies 30. Forced air is blown from behind the body 30 with a fan (not shown). When cooling with air as described above, it is desirable to use a pipe 32 of the cooling body 30 having fins. A method of cooling the metal tube 1 using air is recommended in that the entire circumference of the metal tube 1 can be cooled uniformly.

When the metal tube 1 is moved in direct contact with the cooling body 30 when passing through the cooling zone B,
The cooling body 30 is installed only on the lower surface side, and the metal tube 1 is rolled and moved by the conveyor 10. When the equipment layout is such that the conveyor 10 penetrates the cooling zone B and the heating furnace A as shown in FIG. 1, the height of the lower surface of the metal tube 1 should be such that the lower surface of the metal tube 1 can come into contact with the cooling body 30. In some cases, the cooling body 30 may be provided with a groove or the like through which the chain of the conveyor 10 passes.

In order to manufacture a composite pipe with such an apparatus, as shown in FIG. 3, first, a thermally expandable resin pipe 2 coated with an adhesive 3 is inserted into a metal pipe 1 and the resin pipe 2 is then inserted. The metal tube 1 in which the is inserted is placed on the upstream side of the conveyor 10. The metal tube 1 is conveyed to the conveyor 10. When the metal tube 1 reaches the line C-C in FIG. 1, the metal tube 1 is cooled by the cooling zone B over its entire length. This cooling is performed in order to adjust the work start temperature of the metal tube 1 in case the metal tube 1 is heated by the ambient temperature of the work place. Therefore, when the temperature of the metal tube 1 is low as in winter, cooling may be omitted.

When the conveyor 10 runs and the metal tube 1 reaches the line D-D in FIG. 1, the central portion is heated in the V-shaped heating furnace A. Then, the central portion of the resin pipe 2 is also heated and expanded, and the metal pipe 1 and the resin pipe 2 are brought into close contact with each other by the adhesive 3. At this time, around the heating part of the metal tube 1,
Since it is cooled by the cooling zone B, both sides of the central portion of the resin pipe 2 inserted in the metal pipe 1 are not heated and expanded.

When the metal pipe 1 is conveyed downstream by the conveyor 10 to the vicinity of the E-E line, the portions slightly closer to both ends than the central part are sequentially carried into the heating furnace A and heated.
At this time, since both ends of the metal tube 1 are located in the cooling zone B, they are not heated. Therefore, the resin pipe 2 inserted in the metal pipe 1 is also heated and expanded only on the sides of both ends rather than the central portion, and the metal pipe 1 is expanded by the adhesive 3.
Glue to the inner surface of.

Then, when the metal pipe 1 moves to the periphery of the FF line, the central portion is naturally cooled and only the both end portions are heated, and the resin pipes 2 are expanded in the both end portions of the metal pipe 1 to expand the metal pipe. It adheres to the inner surface of 1. In the present embodiment, the portion where the metal tube 1 is not carried into the heating furnace A is not heated in this way, and the metal tube 1 is carried into the heating furnace A and heated, so that it is inserted into the metal tube 1. The resin pipes 2 are sequentially heated to both ends and expanded, and the air between the metal pipe 1 and the resin pipes 2 is pushed out to both ends. Therefore, the poor adhesion due to the residual air does not occur, and the composite pipe in which the metal pipe 1 and the resin pipe 2 are in close contact is completed.

In the method of manufacturing the composite pipe of this embodiment,
The surface temperature of the metal tube 1 in the cooling zone B is 10 ° C to 60 ° C.
It is desirable to maintain the temperature at ℃, and by setting the surface temperature of the metal tube 1 within the temperature range, it is possible to complete a composite tube in which the metal tube 1 and the resin tube 2 are in close contact with each other, and the annual ambient temperature change. It is also possible to prevent the instability of quality due to. Further, the surface temperature of the metal tube 1 in the cooling zone B, which should be further encouraged, is 20 ° C. ± 10 ° C. If the surface temperature of the metal tube 1 is maintained within the temperature range, a more complete metal tube 1 and a resin tube can be obtained. Bonding with 2 can be performed. The temperature inside the heating furnace A is 1
00 ° C to 150 ° C is desirable. Below this temperature, the resin pipe 2 does not expand, and above this temperature, it overexpands.

The heat-expandable resin tube 2 may be a single layer or multiple layers, and various materials such as polyvinyl chloride, polyethylene, polypropylene, expanded polyvinyl chloride, expanded polyethylene, expanded polypropylene can be used. . As a measure of thermal expansion, there are cases where the resin material itself is expanded by heat, gas in the foam layer is thermally expanded, or a foam material is mixed in the resin to start foaming by heat. As the metal tube 1, a steel tube such as SGP or STK, a copper tube, or an aluminum tube can be used.

(Experiment) An experiment conducted to confirm the effect of the present invention will be described below. The outer diameter of the experiment is 54.6
Hot melt adhesive 3 on the outer surface of the thermally expandable resin tube 2 of mm
Was applied, and this resin pipe 2 was inserted into a STK 41, steel pipe having an inner diameter of 56.5 mm and a wall thickness of 2 mm, and a composite pipe was manufactured by the above apparatus. The cooling zone B was non-contact and air-cooled by a fan. The cooling temperature of the metal tube 1 was set to 20 ° C. The temperature of the heating furnace was 120 ° C. and 140 ° C.

As a comparative experiment, the same composite pipe was manufactured with the cooling zone B removed. Then, the produced composite pipe was used to test the adhesive strength. Further, the close contact state between the metal tube 1 and the resin tube 2 was inspected. The results are shown in Table 1.

[0025]

[Table 1]

As a result of the experiment, it can be understood that the adhesive strength and the adhered state are good according to the method for producing the composite pipe of the present invention.

The present invention is not limited to the above-mentioned embodiments, and the design can be changed within the scope of the present invention. For example, the heating furnace is not limited to the V-shape, and the heating furnace is arranged in an oblique direction with respect to the traveling direction of the metal tube 1 to heat the metal tube 1 from one end side to the other end side. It can be carried out. In this case, the cooling zone needs to be diagonally arranged at least on the upstream side of the heating furnace.

[0028]

According to the present invention, the adhesion is improved over the entire length in the axial direction of the composite pipe, and the resin pipe is uniformly and surely adhered to the metal pipe 1. Therefore, when the composite pipe is actually used. In addition, peeling of the resin pipe from the metal pipe and blister can be prevented, and the durability can be improved.

[Brief description of drawings]

1 is a plan view of an apparatus for practicing the present invention. FIG.

FIG. 2 is a plan view of cooling means for carrying out the present invention.

FIG. 3 is a cross-sectional view showing a state in which a resin pipe has been inserted into the metal pipe before entering the apparatus in FIG.

FIG. 4 is a front view of a conventional composite pipe manufacturing apparatus.

FIG. 5 is a plan view of a conventional composite pipe manufacturing apparatus.

[Explanation of symbols]

 A heating furnace B cooling zone 1 metal tube 2 resin tube 3 adhesive

Claims (2)

[Claims] 1. A heat-expandable resin tube coated with an adhesive is inserted into a metal tube, and the metal tube in which the resin tube is inserted is heated sequentially from the center to both ends or from one end to the other end. In a method of manufacturing a composite pipe in which the resin pipe is brought into a furnace and sequentially thermally expanded to closely adhere the resin pipe to the inner surface of the metal pipe, a metal pipe into which a thermally expandable resin pipe coated with an adhesive is inserted, Sequentially
A method for producing a composite pipe, characterized in that the outer surface is partially cooled until it is carried into a heating furnace. 2. The method for producing a composite pipe according to claim 1, wherein the cooling is performed by air, and the outer surface of the metal pipe is maintained at 10 ° C. to 60 ° C.