JPH0247028A - Manufacture of composite tube - Google Patents

Abstract

PURPOSE:To enable covering the title tube with a substantially uniform thickness by locally heating melted resin adhering to the inner peripheral face of a metal tube. CONSTITUTION:A metal sheet 70 is shaped in a circularly tubular state during passage of a gap between a resin flowing tube 12 and an outer die 30, the side edges of the sheet 70 adhere by a welding machine 40 thereby to form a metal tube 71. Melted resin flows in a gap between the inner peripheral face of the tube 12 and the outer peripheral face of a core 13, and is extruded while extending outward. The extruded resin is into contact with the inner peripheral face of the tube 71, formed in a predetermined thickness between the end 13a of the core 13 and the inner peripheral face of the tube 71, strongly brought into pressure contact with the inner peripheral face of the tube 71 at the end 13a of the core 13 to adhere to the inner peripheral face of the tube 71. When a synthetic resin layer is in an irregularly thick state, a heater 51 opposed through the tube 71 in a heating device 50 to the thick part is operated to heat the thick part, thereby forming a circumferentially and substantially uniform thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a composite tube in which the inner peripheral surface of a metal tube is coated with a synthetic resin layer.

(Conventional technology) Recently, it has been used as a piping material for hot water supply, hot water heating, etc.

Composite tubes are used in which the inner peripheral surface of a metal tube is coated with a synthetic resin layer. Such composite tubes are made by forming a band-shaped metal sheet into a circular tube shape, and extruding molten resin from the inner circumferential side of the formed metal tube in a cylindrical shape using a metal tube inner circumferential surface coating device to coat the inner circumferential surface of the metal tube. It is manufactured by covering with a synthetic resin layer.

2 For example, when forming a metal sheet into a metal tube, the apparatus for coating the inner peripheral surface of a metal tube positions the tip of a resin flow tube through which molten resin flows inside the formed metal tube, and the molten resin is passed from the tip. By extruding into a cylindrical shape and adhering the resin to the inner circumferential surface of the metal tube, the inner circumferential surface of the metal tube is covered with a synthetic resin layer.

Since the resin flow tube needs to extrude the molten resin onto the inner circumferential surface of the formed metal tube, its tip must be located within the metal tube formed by forming a metal sheet into a circular tube shape. On the contrary, the base end of the resin flow tube needs to be positioned on a metal sheet that is not shaped into a circular tube because it is necessary to flow the molten resin through the tube. For this reason, the resin flow tube becomes long, and since its tip is located within the metal tube, there is no way to support the tip, and the resin flow tube is supported in one piece. As a result, the resin flow pipe may bend due to its own weight or due to the flow of resin. A core base or the like is supported at the tip of the resin flow tube so as to be concentric with the tip in order to extrude the molten resin into a cylindrical shape with uniform thickness. As the tube bends, the tip of the resin flow tube and the core cap become eccentric,
It becomes impossible to extrude the molten resin into a cylindrical shape with uniform thickness.

In addition, it is very difficult to extrude molten resin with uniform pressure in the circumferential direction, so even if the core mouthpiece is concentric with the metal tube, the parts where the extrusion pressure is high will be thicker and the synthetic resin will become thicker. Unable to achieve uniform thickness.

In order to make the thickness of the synthetic resin layer covering the inner circumferential surface of the metal tube uniform, it is necessary to adjust the thickness while coating the inner circumferential surface of the metal tube by actually extruding the molten resin toward the inner circumferential surface of the metal tube. . However, since the core cap is located inside the metal tube, there is no way to adjust it from the outside.In the past, the core cap was fixed to the resin flow pipe so that it could be adjusted with a ring. , the coating work had to be temporarily stopped and adjustments had to be made again.

This adjustment work could not be completed in one go, and was a troublesome work.

In order to solve such problems, for example,
Publication No. 198447 discloses an apparatus for adjusting the uneven thickness of one synthetic resin layer by moving a metal tube whose inner peripheral surface is coated with a synthetic resin layer in a two-dimensional direction perpendicular to the II feeding direction. There is.

(Problems to be Solved by the Invention) With the device disclosed in the publication, if the metal tube is relatively thin and flexible, it is possible to move the metal tube in a two-dimensional direction perpendicular to its conveyance direction. If the metal tube has high rigidity, it will be very difficult to move it in this way, and there is a possibility that it will not be possible to adjust the uneven thickness of the synthetic resin layer covering the inner peripheral surface of the metal tube.

The present invention solves the above-mentioned conventional problems.

The purpose is to provide a method for manufacturing a composite tube that can easily adjust the uneven thickness of a synthetic resin layer coated on the inner circumferential surface of a metal tube, even if the metal tube has high rigidity.

(Means for Solving the Problems) The present invention is a method for manufacturing a composite tube in which the inner circumferential surface of a metal tube is coated with a synthetic resin layer, in which a metal tube is manufactured by sequentially forming a band-shaped metal sheet into a circular tube shape. a step of extruding the volume resin radially (from inside the manufactured metal tube), and a step of extruding the volume resin radially from the inside of the manufactured metal tube, and extruding the molten resin in the circumferential direction in order to adjust the uneven thickness of the molten resin extruded radially inside the metal tube. heating a predetermined portion of the wafer, thereby achieving the above object.

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

The method for manufacturing a composite pipe of the present invention is carried out using, for example, a composite pipe manufacturing apparatus shown in FIG. The composite pipe manufacturing apparatus uses, for example, a metal sheet 70 which is bent by an outer die (not shown) so that its side edges are positioned upward, and is conveyed in the direction indicated by arrow A in FIG.

It has an outer mold 30 that is continuously molded into a cylindrical shape, and a resin coating mold 10 that coats a synthetic resin layer on the inner peripheral surface of a metal sheet 70 that is molded into a 9-cylindrical shape.

The resin coating mold 10 has a main body 11 located on a curved metal sheet 70 immediately before being molded into a bicylindrical shape, and a resin flow pipe 12 supported on one side by the main body 11. The resin flow pipe 12 extends horizontally from the main body 11 toward the downstream side in the conveyance direction of the metal sheet 11, and communicates with a resin flow path 11a formed vertically within the main body 11. Then, molten resin is fed into the resin flow pipe 12 through the resin flow path 11a.

An outer mold 30 is fitted in the middle of the resin flow pipe 12 with a predetermined gap, and a metal sheet 70 is inserted into the core outer mold 30.
By passing through the metal sheet 70, the metal sheet 70 is formed into a circular tube shape. Note that in order to form the metal sheet 70 into a circular tube shape, a roll may be used instead of such an outer mold 30.

A welding machine 40 is disposed between the outer mold 30 and the tip of the resin flow pipe 12. The welding machine 40 welds side edges of a metal sheet 70 formed into a circular tube shape using nine outer molds 30 to manufacture a metal tube 71.

The metal pipe of the welding machine 40? 11 The distal end of the resin flow pipe 12 located on the downstream side in the feeding direction is a tapered surface 12a whose diameter gradually increases as the inner circumferential surface approaches the distal end side.

A core portion 13 is fitted inside the resin flow pipe 12 .

The base end portion of the core portion 13 is supported on one side by the main body portion 11 so as to be concentric with the resin flow pipe 12 with a predetermined gap therebetween. The tip portion 13a of the core portion 13 extends from the resin flow tube 12 via a tapered surface that is parallel to the tapered surface 12a of the inner peripheral surface of the tip portion of the resin flow tube 12. The distal end portion 13a of 13 is connected to the resin flow pipe 2.
It has a cylindrical shape with an outer diameter approximately equal to the outer diameter of 0.

Tapered surface 12 of the inner peripheral surface of the tip of the resin flow pipe 124
The molten resin flowing through the resin flow pipe 12 is extruded into a cylindrical shape from the cylindrical gap formed by the tapered surface of the core portion 13a extending from the resin flow pipe 12. The molten resin extruded from the tip of the resin flow tube 12 is pressed by the outer circumferential surface of the tip 13a of the core portion 13 against the inner circular surface of the metal tube 71 formed before reaching the tip of the resin flow tube 12.
The inner peripheral surface of the metal tube 71 is coated. Therefore, the thickness of the synthetic resin layer covering the inner peripheral surface of the metal tube 71 is determined by the gap between the outer peripheral surface of the tip 13a of the core section 13 and the inner peripheral surface of the metal tube 71.

Tip portion 13a of core portion 13 extending from resin flow pipe 12
A cylindrical heating device 50 is fitted onto the outside.

The end of the heating device 50 is also fitted onto the tip of the resin flow tube 12, and heats the molten resin extruded from the tip of the resin flow tube 12 via the metal tube 71. The heating device 5
0 has a tubular shape with a plurality of heaters arranged in parallel in the circumferential direction, and each heater is independently controlled. The circumferential length of the heating area of each heater is equal.

As the heater constituting the heating device 50, one that utilizes radiant heat from far infrared rays is preferably used. An example of such a heater is shown in FIG.

The heater 51 includes a pair of supports 51b and 51b on the mirror surface of an arcuate reflecting plate 51a having a mirror surface.

Each terminal portion 51d is supported at each end of a ceramic-coated far-infrared heating element 51c by each support 51b, which is erected at appropriate intervals in the axial direction with respect to the arc of the reflector 51a. . The heating element 51c is installed between the side skin holders 51c, and each terminal portion 51d is fixed to each support 51b by a stopper 51e. Then, the case 51f covers the reflector 51 so as to cover the 1 heating element 51C.
It is installed on a.

The plurality of heaters 51 having such a configuration are arranged in a tubular shape so that the radiation surface of the case 51f faces inward.
0 is configured. 5. The heating device 50 is fitted concentrically to a metal tube 71 on which a molten resin is pressed against the inner circumferential surface of the metal tube 71. Heater 5 facing each other via pipe 71
1 is activated to heat the area.

As shown in FIG. 3, the heater 51 includes a plurality of nichrome wire heating elements 51
You may use the one accommodated in y. Also in this case, the heaters 51 are arranged in a tubular shape so that the radiation surface of the case 51y faces inward.

The operation of the composite pipe manufacturing apparatus having such a configuration is as follows. The metal sheet 70 is formed into a circular tube shape while passing through the gap between the resin flow pipe 12 and the outer mold 30. Then, the side edges of the metal sheet 70 are bonded together by the welding machine 40 to form the metal tube 71.

On the other hand, molten resin is passed through the resin flow path 11a of the main body 11 in the resin-coated mold 10, and the resin flow pipe 12
will be sent to Then, the molten resin is transferred to the resin flow pipe 12.
The flow passes through the gap between the inner circumferential surface and the outer circumferential surface of the core part 13, passes through the gap between the tapered surface 12a at the tip of the resin flow tube 12, and the tapered surface of the core part 13, and is extruded while expanding outward. be done. The extruded molten resin.

It contacts the inner circumferential surface of the metal tube 71 which is fitted onto the distal end of the resin flow pipe 12 and the distal end portion 13a of the core portion 13 and is conveyed downstream, and then contacts the distal end portion 13a of the core portion 13 and the inner circumferential surface of the metal tube 71. The tip portion 13a of the core portion 13 has a predetermined thickness between
The metal tube 71 is strongly pressed against the inner circumferential surface of the metal tube 71 and bonded to the inner circumferential surface of the metal tube 71.

After the composite pipe is manufactured in this way, it is checked whether the synthetic resin layer covering the inner peripheral surface of the metal pipe 71 has a uniform thickness, and if the synthetic resin layer has an uneven thickness, The heater 51 in the heating device 50, which faces the thick portion via the metal tube 71, is operated to heat the thick portion. The molten resin extruded from the resin flow pipe 12 toward the inner peripheral surface of the metal tube 71 begins to solidify when it is adhered to the inner peripheral surface of the metal tube 71. At this time, when the thick portion of the resin is heated, the viscosity of the thick portion decreases and solidification of that portion is delayed. Therefore, the molten resin on the inner circumferential surface of the metal tube 71 begins to solidify from the thin portion that is not heated. Then, when the thin-walled portion undergoes thermal contraction when solidifying, the resin in the thick-walled portion that has not yet reached the solidification temperature due to heating may have a reduced viscosity.
It is pulled by the thermal contraction of the thin walled portion. The result + aA
The thickness of the j'+i wall portion becomes thicker, and on the contrary, the wall thickness of the thicker wall portion becomes thinner, so that the synthetic resin layer bonded to the inner peripheral surface of the metal tube has a substantially uniform radius in the circumferential direction.

In this embodiment, since the heater 51 of the heating device 50 is one that emits far infrared rays, it is possible to efficiently heat the molten resin portion of the inner circumferential surface of the metal tube 71 whose length in the axial direction is relatively short.

Next, a specific example of the method of the present invention will be described.

1 As a heating device for one operation, a device in which six heaters shown in FIG. 2 were arranged in a tubular shape was used. Each heater has a capacity of 1 kty, and each heater is arranged such that the distance between each radiation surface and the metal tube surface is 5 mm. On the other hand, as 5 metal sheets, aluminum alloy (5052) with a thickness of 1,5 mm
adhesive polystyrene (MI) was used as the molten resin.
=0.4g/10mln) was used. Then, the metal sheet was generally fed once at a speed of 0.5 m/min.

A composite tube was manufactured using the apparatus shown in FIG. In the obtained composite tube, the synthetic resin layer coated on the inner circumferential surface of the metal tube has an uneven thickness, with a thickness of 2.3 mm in the thick part and 1 mm in the thin part.
It was 8 mm thick. Therefore, by operating three heaters facing the thick wall part and its surroundings, the area was heated to 3K.
It was heated with w. At this time, the aluminum alloy metal tube had a temperature of 250''C. The synthetic resin layer of the obtained composite tube had a maximum thickness of 2.1 mm.

The minimum thickness was 2.9 mm.

As a heating device, six heaters arranged in a tubular shape as shown in FIG. 3 were used. The total heating capacity of the heating device was 7.2-. The gap between the heat radiation surface of each heater and the metal tube is 5
It is n+m. On the other hand, as a metal sheet, the thickness is 1,5
The iron was transported at a speed of 0.8 m/min. Then, as the molten resin, adhesive polystyrene (M
+=0.4g/10mln) was produced. The synthetic resin layer of the obtained composite pipe has a maximum thickness of 2.4 mm.
The minimum thickness was 1.8 mm. Therefore, when the maximum thickness portion was heated to 2.4°C using two heaters, the surface temperature of the iron pipe became 240'C.

The maximum thickness of the synthetic resin layer of the obtained composite tube was 2.2 mm.

The minimum thickness was 2.0 mm.

(Effects of the Invention) In this way, the method for manufacturing a composite pipe of the present invention locally heats the molten resin bonded to the inner circumferential surface of the metal tube to adjust the uneven thickness state. A composite pipe coated with a synthetic resin layer having a substantially uniform thickness can be easily manufactured.

A-114■ An audience at a 11 m2 turn - Figure 1 is a cross-sectional view of a composite pipe manufacturing apparatus used to carry out the method of the present invention. Figure 2 (a) is a partial cross-sectional view showing an example of a heating device. , FIG. 2(b) is a front view of the heater, FIG. 3(a) is a partial sectional view showing another example of the heating device, and FIG. 3(b) is a partial sectional view showing another example of the heating device.
is a front view of the heater.

10...Resin coated mold, 12...Resin flow pipe, 13
... core part, 30 ... outer mold, 40 ... welding machine, 5
0... Heating device.

that's all

Claims (1)

[Claims] 1. A method for manufacturing a composite tube in which the inner circumferential surface of a metal tube is coated with a synthetic resin layer, comprising: manufacturing a metal tube by successively forming a band-shaped metal sheet into a circular tube shape; A step of extruding molten resin radially from inside the manufactured metal tube, and heating a predetermined portion of the molten resin in the circumferential direction in order to adjust the uneven thickness of the molten resin extruded radially inside the metal tube. A method for manufacturing a composite pipe, comprising: