JPH0369890A - Composite tube and its manufacture - Google Patents

Abstract

PURPOSE:To eliminate possibility of separation of a resin layer from a metal tub so as to be stably usable for a long period by securing a resin layer to a metal tube at a faucet with an expanded diameter. CONSTITUTION:A composite tube 10 has a faucet 10a at one end part of the tube. The faucet 10a is concentrically diameter-expanded to a tube main body part 10b except the faucet 10a, consequently a metal tube 11 and a synthetic resin layer 12 at the faucet 10a are also in a concentrically diameter-expand condition to the metal tube 11 and he synthetic resin layer 12 of the main body part 10b. Many through holes 11a, 11a... are provided at suitable intervals in the periphery and axial directions in the metal tube 11 part in the diameter- expanded condition in the faucet 10a. In this case, a part of a synthetic resin composing the synthetic resin layer 12 is protruded to the outside of the metal tube 11 through each hole 11a, and the protruded part is made larger in diameter than each through hole 11a to be secured on the outer peripheral surface of the metal tube 11.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a composite pipe whose inner peripheral surface is coated with a synthetic resin layer and which is used for purposes such as water supply, hot water supply, drainage, or exhaust. The present invention relates to a manufacturing method, and more specifically, to a composite tube having a socket at one end and a manufacturing method thereof.

(Prior art) Recently, composite pipes in which the inner peripheral surface of metal pipes is coated with a synthetic resin layer have been used as piping materials for hot water supply, hot water heating, etc. After manufacturing, the inner circumferential surface of the metal tube is coated with molten resin.The composite tube is manufactured by, for example, a manufacturing apparatus disclosed in JP-A-62-198447. The composite pipe manufacturing device first forms a metal sheet into a circular tube shape,
After manufacturing a metal tube by welding its side edges together, molten resin is extruded from inside the metal tube to cover the inner peripheral surface of the metal tube.

(Problems to be Solved by the Invention) In the method for manufacturing a composite pipe disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 62-198447, the composite pipe is manufactured sequentially and continuously from metal sheets, so it has excellent manufacturing efficiency. There is. However, the molten resin coated on the inner circumferential surface of the metal tube tends to shrink when it solidifies, but since the resin is bonded and restrained to the metal tube, the inside of the solidified resin has a reduced diameter. tensile stress remains. In this way, when a composite pipe with a synthetic resin layer with residual tensile stress inside is used for hot water supply pipes or drainage pipes, thermal stress is repeatedly applied due to changes in the temperature of the water flowing through the interior, so the thermal stress is There is a risk that cracks may occur in the synthetic resin layer due to fatigue caused by repeated use or stress concentration. Furthermore, due to a decrease in the adhesive strength between the synthetic resin layer and the metal tube, there is a risk that the resin layer will peel off from the metal tube.

Some piping materials for water supply, hot water supply, drainage, etc. are formed with a socket in which one end has a larger diameter than the other part, and the other end of the composite pipe is connected to the socket. The fitting of the tube is inserted and the pair of tubes are joined together. Composite tubes having such a shape are usually manufactured by a method in which a composite tube of a constant diameter is manufactured, and then the diameter of the tube end is enlarged by secondary processing such as bulge processing to form a socket. However, when the socket is formed by secondary processing in this way, the diameter of the metal tube and the synthetic resin layer is expanded and stretched in the formed socket.

In the socket, since the elastic deformation strain of the synthetic resin layer is larger than that of the metal tube, a force that tries to reduce the diameter acts on the synthetic resin layer even more, and the synthetic resin layer peels off from the metal tube even more. It's in easy condition. Therefore, if the initial adhesive force between the synthetic resin layer and the metal tube at the socket is small, or if the adhesive force decreases over time, the synthetic resin layer may easily peel off from the metal tube.

The present invention solves the above-mentioned conventional problems, and its purpose is to provide excellent adhesion between the metal tube and the synthetic resin layer at the socket, and to prevent the resin layer from peeling off from the metal tube even after long-term use. An object of the present invention is to provide a composite pipe in which there is no risk of cracks occurring in the resin layer. Another object of the present invention is to provide a method for easily manufacturing such a composite tube with high efficiency.

(Means for Solving the Problems) The composite tube of the present invention is a composite tube in which the inner circumferential surface of the metal tube is coated with a synthetic resin layer, and a socket is provided at one end of the composite pipe, and the socket is provided with a plurality of sockets. A metal tube with a through hole,
The receptacle is provided with a synthetic resin layer that partially protrudes from each through hole of the metal tube and is locked in each through hole, thereby achieving the above object.

The method for manufacturing a composite tube of the present invention is a method for manufacturing a composite tube in which the inner circumferential surface of the metal tube is coated with a synthetic resin layer and a socket is provided at one end of the composite tube, the method comprising: a step of opening a large number of through holes in each region at a predetermined interval, and a step of sequentially forming the band-shaped metal sheet into a circular tube shape and welding each side edge to each other to manufacture a metal tube, A step of extruding molten resin radially from inside the manufactured metal tube to cover the inner circumferential surface of the metal tube with the resin and leaking the resin from each through hole, and coating the inner circumferential surface with the resin. A process of cutting the metal tube so that the part with many through holes becomes one end, and coating the inner peripheral surface of the part of the cut metal tube with many through holes. The above object is achieved by including the step of expanding the diameter together with the synthetic resin to form a socket.

(Example) The present invention will be described below with reference to Examples.

As shown in FIG. 1, the composite tube of the present invention includes a metal tube 11 and a synthetic resin layer 12 covering the inner peripheral surface of the metal tube 11. The composite tube 10 has a socket 10a at one end thereof. The diameter of the socket 10a is expanded concentrically with respect to the tube main body part 10b excluding the socket 10a. Therefore, the metal pipe 11 and the synthetic resin layer 12 in the socket 10a are also the same as the metal pipe 11 and the synthetic resin layer 12 in the main body part 10b. Synthetic resin layer 1
The diameter is enlarged concentrically with respect to 2.

A large number of through holes 11a, 11a, . . . are opened at appropriate intervals in the circumferential direction and the tube axis direction in the portion of the metal tube 11 in the expanded diameter state in the receiving port 10a.

A part of the synthetic resin constituting the resin layer 12 protrudes from each through hole 11a to the outside of the metal tube 11, and the protruding portion has a larger diameter than each through hole 11a, and the metal tube 1
1. It is locked on the outer peripheral surface.

Such a composite pipe of the present invention is manufactured by the following method of the present invention. FIG. 2 is a schematic diagram of the method for manufacturing the composite pipe 10. In the method of the present invention, first, the metal sheets IF are sequentially pulled out from the uncoiler 110 around which the metal sheets IF are wound.

The metal sheet 1F pulled out from the uncoiler 110 is fed to the punching device 20. The punching device 20 opens a predetermined number of through holes 11a in each predetermined area of the metal sheet 11'. The perforation device 20 is operated every time the metal sheet 11° is moved by a predetermined amount, and a large number of through holes 11a are opened in each area at a predetermined interval in the longitudinal direction of the metal sheet 11°. The region of the metal sheet 11' in which the large number of through holes 11a are opened is set to the length of the composite pipe 10 to be manufactured so as to correspond to the end position of the composite pipe 10 manufactured using the metal sheet 1F. Corresponding spacing is provided.

In this way, the metal sheet 1F in which a large number of through holes 11a are formed in each predetermined area by the perforation device 20 is fed to the surface treatment tank 30. The surface treatment bath 30 performs surface treatments such as degreasing and pickling on the surface of the metal sheet 111 in order to improve the adhesion between the metal sheet 1F and the resin coated on the metal sheet 1F.

The surface-treated metal sheet 1F is formed into a perfect circular cross section by a forming device 40 using a mold or roll, and then formed into a perfect circular cross section with the side edges abutting each other or overlapping each other. molded. Then, the welding machine 50 welds the side edges of the metal sheet IF, which has a perfect circular cross section, to form a metal tube.

A part of the resin coating device 60 is located within the forming device 40 . As shown in FIG. 3, the resin coating device 60 includes a main body portion 61 located within a metal sheet LL′ having a U-shaped cross section immediately before being formed into a perfect circular cross section by the forming device 40; A resin flow pipe 6 is supported on one side by the main body portion 61 and extends from the main body portion 61 in the metal sheet conveyance direction.
2. Molten resin is fed to the resin flow pipe 62.

The resin flow pipe 62 is integrally formed with the main body portion 61, and the inner circumferential surface of the distal end portion thereof is a tapered surface 62a whose diameter gradually increases toward the distal end side. The resin flow pipe 62
A mandrel 63 is inserted concentrically therein with a predetermined gap from the resin flow pipe 62. The mandrel 63 has one end supported by the main body 61,
The distal end portion thereof has a cylindrical core portion 63a extending from the distal end of the resin flow pipe 62. The core portion 63a has a tapered surface 6 whose diameter gradually increases toward the tip, substantially similar to the tapered surface 62a at the inner peripheral portion of the tip of the resin flow tube 62.
3b, and the tapered surface 63b faces the tapered surface 62a of the resin flow pipe 62 with a predetermined gap therebetween. The cylindrical core portion 63a is connected to the forming device 4.
It is located within 11 degrees of the metal sheet formed into a circular tube shape by the welding machine 50, and downstream in the metal sheet conveyance direction from the welding position by the welding machine 50. From the cylindrical gap formed by the tapered surface 63b of the core portion 63a and the tapered surface 62a of the resin flow tube 62, the resin flow tube 6
The molten resin flowing through the gap between the mandrel 2 and the mandrel 63 is extruded into a cylindrical shape. The outer diameter of the core portion 63a is slightly smaller than the inner diameter of the metal tube 11 which is formed into a circular tube shape by a forming device @40 and whose side edges are welded to each other by a welding machine 50, and the gap between the two is the same as the metal tube 11. Corresponds to the thickness of the resin coated on the inner peripheral surface.

Surface treatment if! After the metal notebook 11', which has been subjected to a predetermined surface treatment in step 30, passes through the position where the main body 61 of the resin coating device 60 is disposed, the side edges of the metal notebook 11' are butted against each other or overlapped by a forming device 40. It is molded into a perfect circular cross section. Then, the side edges of the metal sheet lr having a perfect circular cross section are welded and bonded together using a welding machine 50 to form a metal tube.

The inner peripheral surface of the metal tube 11 manufactured in this way is coated with a resin flow pipe 62 and a mandrel 63 in the resin coating device 60.
The molten resin extruded from the gap between the core part 63a and the core part 63a covers the core part 63a. At this time, a portion of the molten resin leaks from each through hole 11a of the metal tube 11.

An outer mold 70 is disposed downstream of the position where the resin coating device 60 coats the inner peripheral surface of the metal tube. The outer mold 70 is concentric with the metal tube 11 manufactured by welding the side edges of the metal sheet IF to each other by a welding machine 50, and has a through hole 71 that is slightly larger than the metal tube 11. ing. The outer mold 70 prevents a large amount of resin from leaking from each through hole 11a when molten resin is deposited on the inner circumferential surface of the area of the metal tube 11 in which a large number of through holes 11a are formed. , the resin leaking from each through hole 11a is smoothed.

As shown in FIG. 2, a cutting device 80 is disposed downstream of the outer mold 70, and the cutting device 80 cuts a metal tube of a constant diameter whose inner peripheral surface is coated with synthetic resin. 11 is cut to a predetermined length so that the area where the many through holes 11a are formed is at the tip on the conveying direction side. The cutting device 8
A diameter expanding device 90 is disposed on the downstream side of the pipe 0, and the diameter expanding device 90 allows the composite pipe 10 cut to a predetermined length to have a large number of through holes 11a opened on the leading end side in the transport direction. The end portion is enlarged in diameter.

In the method of the present invention, various aluminum alloys, various steel plates, various copper alloys, etc. are used as the metal sheet 1F.

The drilling device 20 uses press processing, drilling, etc.
A predetermined number of through holes 11a are opened in the metal sheet 11' at predetermined intervals. The diameter of each through hole 11a is determined by the diameter of the composite pipe 1 to be manufactured.
When the diameter of each through hole 11a is 300 m or less, it is set to 1 to 20 mm, and the number is appropriately set according to the strength of the metal tube 11 to be manufactured, but the diameter and number of each through hole 11a are as follows:
If the total length in the circumferential direction of the metal tube 11 of the space formed by each through hole 11a in the circumferential direction of the metal tube 11 to be manufactured is 1/2 or less of the entire length of the metal tube 11 in the circumferential direction. ,
Deterioration in the strength of the metal tube 11 can be prevented. The size and number of each through hole 11a are such that each through hole 11a is formed so that the resin 12 leaking from each through hole 11a is sufficiently locked to the metal tube 11 in a smoothed state. Metal tube 1 in the space
The total length in one circumferential direction is 1/ of the circumferential length of the metal tube 11.
About 100 liters or more is required. When the diameter of each through hole 11a increases, the portion of the resin layer 12 that covers each through hole 11a becomes thinner, and the strength of the resin layer 12 decreases. When the diameter of each through hole 11a becomes smaller, the amount of resin leaking from each through hole 11a decreases, and the force with which the resin locks onto the metal tube 11 decreases. When the number of each through hole 11a decreases, the locking force of the resin layer 12 to the metal tube 11 decreases, and conversely, each through hole 11
When the number of a increases, the strength of the metal tube 11 decreases, and there is a risk that the metal tube 11 will break when the composite tube diameter is expanded.

It is preferable that the through holes 11a are opened at equal intervals in the circumferential direction of the metal tube 11. The circumferential through hole 11a
The number of rows may be one, or a plurality of rows may be formed in the tube axis direction. When a plurality of rows of through holes 11a opened at equal intervals in the circumferential direction are formed in the tube axis direction, it is preferable that the positions of the through holes 11a in each row are shifted in the tube axis direction. The cross-sectional shape of each through hole may have a constant diameter in the inner and outer directions of the metal tube 11, as shown in FIG. 4, but as shown in FIG. It may also have a tapered shape in which the diameter is gradually reduced.

The surface treatment of the metal sheet IF includes, for example, when the metal pipe 11 is a steel pipe, degreasing treatment such as alkaline degreasing or solvent degreasing treatment, rust removal treatment using hydrochloric acid, etc., in order to improve adhesion with the resin. It will be done.

High frequency welding, resistance welding, arc welding, gas welding, electron beam welding, etc. are used for welding the side edges of the metal sheet IF.

As the resin for coating the inner circumferential surface of the metal tube 11, a modified polyolefin such as water-crosslinkable polyolefin or acid-modified polyethylene, which has good adhesion to a metal sheet that has been subjected to an appropriate surface treatment, is suitable. Furthermore, using these modified polyolefins as an adhesive layer, a resin having excellent chemical resistance and heat resistance, such as high density polyethylene (HDPE), may be laminated on the inner peripheral surface of the modified polyolefin.

In the outer mold 70 into which the metal tube 11 whose inner peripheral surface is coated with the resin layer 12 is inserted, gaps are set so that a large amount of resin does not leak out from each through hole 11a of the metal tube 11.

It is preferable that the resin leaking out of the metal tube 11 from each through hole 11a has a cylindrical shape with a bottom surface having a larger diameter than each through hole 11a, and the bottom surface is made of metal when forming the socket 10a. The diameter is preferably obtained by multiplying the diameter of each through hole 11a by 1.1 to 1.5 times the diameter expansion rate of the tube 11.

The height is preferably about 0.5 to 1.5 m. By expanding the diameter of the metal tube 11 to form the socket 10a, the diameter of each through hole 11a also increases, so that the resin leaking from each through hole 11a is caught in the expanded metal tube 11. , each through hole 1 when the diameter of the metal tube 11 is expanded.
It is necessary to form a cylindrical shape having a bottom surface that is at least 1.1 times the diameter of 1a. Even if the resin leaks into a cylindrical shape having a bottom surface 1.5 times or more the diameter of each through hole Ha when the diameter of the metal tube 11 is expanded, the locking force of the resin to the metal tube 11 cannot be improved. . It is preferable that cooling water be allowed to flow inside the outer mold 70 so that the resin flowing out from each through hole 11a can be cooled.

The diameter expanding device 90 that expands the diameter of the end of a composite pipe cut to a predetermined length to manufacture a socket uses bulge processing, punch processing, expander processing, etc. Bulge processing is preferred since it does not cause any adverse effects such as abrasion on the resin layer I2 to be coated and has excellent moldability.

A composite pipe was manufactured using the method of the present invention, and the peeling state of the resin layer at the socket was examined. The metal sheet is a cold-rolled steel plate (SPC) with a thickness of 1.6 mm and a width of 271.0 mm.
C hoop material), in an area 5.5 m away from the steel plate,
The diameter is 4.0II11 using a punching device using press processing.
Ten through holes having a shape as shown in FIG. 4 were formed in two rows in the tube axis direction, with ten holes arranged in parallel in the circumferential direction. Thereafter, it was formed into a circular tube shape using a roll forming device, and the abutted portions were welded by argon arc welding to produce a steel pipe. Then, the inner peripheral surface of the steel pipe was coated with silane-modified polyethylene to a thickness of 2.0 m using a resin coating device, and the composite pipe was cut into sections every 5.5 m. Furthermore, the end region of each cut composite tube in which a large number of through holes were formed,
The diameter was expanded by rubber bulge processing to form a socket. No peeling of the resin coating the inner peripheral surface of the steel pipe was observed at the socket.

In addition, as shown in Fig. 5, a composite pipe with a socket was manufactured under the same conditions except that a tapered through hole was opened whose diameter gradually decreased toward the inner circumference. No peeling of the resin layer was observed.

(Effects of the Invention) In the composite pipe of the present invention, since the resin layer is locked to the metal pipe at the socket in the enlarged diameter state, there is a risk that the resin layer will peel off from the metal pipe. It can be used stably over a long period of time.

Further, the method for manufacturing a composite pipe of the present invention includes manufacturing a metal pipe from a metal sheet in which a large number of through holes are previously opened at predetermined positions, and coating the inner circumferential surface of the metal pipe with molten resin. After cutting to a predetermined length, the diameter of the end region where each through hole is opened is expanded, so that the tensile stress remaining in the resin layer is alleviated and the resulting composite tube is The resin layer is firmly adhered to the inner peripheral surface of the metal tube. Therefore, the manufactured composite pipe has almost no possibility of cracks occurring in the resin layer, and can be used for a long period of time without peeling or cracking of the resin layer. Moreover, since such a composite pipe can be manufactured continuously, productivity is also excellent.

4. ゛ No.: B Fig. 1 is a partially cutaway side view of the main part of an example of the composite pipe of the present invention, Fig. 2 is a schematic diagram of an example of the implementation state of the method of the present invention, and Fig. 3
The figure is a sectional view showing an example of an apparatus used for carrying out the method of the present invention, and FIGS. 4 and 5 are sectional views each showing an example of each through hole.

lO...Composite pipe, 10a...Socket, 10b...
Main body, 11...metal tube, 11'...metal sheet,
lla...Through hole, 12...Synthetic resin layer, 20...
Perforation device, 30... Surface treatment tank, 40... Forming device, 50... Welding machine, 60... Resin coating device, 6t... Main body, 62... Resin flow pipe, 63 ...
Mandrel, 63a... Core portion, 70... Outer mold, 80... Cutting device, 90... Diameter expansion device.

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Claims (1)

[Scope of Claims] 1. A composite pipe whose inner circumferential surface is covered with a synthetic resin layer and a socket is provided at one end of the metal pipe, the metal pipe having a large number of through holes in the socket. 1. A composite pipe comprising: a pipe; and a synthetic resin layer, a portion of which protrudes from each through hole of the metal tube at the socket and is secured to each through hole. 2. A method for manufacturing a composite pipe in which the inner circumferential surface of the metal pipe is coated with a synthetic resin layer and a socket is provided at one end of the composite pipe, the area being spaced at a predetermined interval in the longitudinal direction of a band-shaped metal sheet. A process of opening a large number of through holes in each metal tube, a process of manufacturing a metal tube by sequentially forming the band-shaped metal sheet into a circular tube shape and welding the side edges together, and a process of manufacturing a metal tube from the inside of the manufactured metal tube. A process of extruding molten resin radially to coat the inner circumferential surface of the metal tube with the resin and leaking the resin from each through hole; The process involves cutting the part with the through holes so that it becomes one end, and expanding the diameter of the part of the cut metal tube with the many through holes, together with the synthetic resin covering the inner circumferential surface, to form a socket. A method of manufacturing a composite pipe comprising: a step of forming a composite pipe;