JP3121643B2 - How to join tubes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining pipes which can be used for clean pipes for transporting ultrapure water and the like.

[0002]

2. Description of the Related Art When butt-welding pipes, a weld bead is generated on the inner and outer surfaces of the joint during welding. Complex irregularities are formed on the inner surface of the tubular body due to the weld bead generated on the inner surface of the weld bead, particularly on the inner surface of the joint. This complicated uneven surface becomes a liquid pool portion, and there is a problem that live bacteria inhabit the liquid pool portion and lower the cleanliness (purity) of the fluid.

[0003] In order not to lower the cleanliness of the fluid, a method for preventing the occurrence of weld beads on the inner surface of the joint has been disclosed (Japanese Patent Laid-Open No. 1-110127).
In this method, an expandable inner peripheral support device is inserted into a tube body, and when the tubular members are butt-welded, the inner peripheral support device is mechanically expanded or the inner peripheral support device is pressurized by using a pressure medium such as pressurized air. By expanding the device, the welding bead surface on the inner periphery of the tubular member in the butt welding region is pressed, so that the welding bead does not flow out of the joint inner surface in the butt welding region, so as to form a smooth inner wall. I have.

[0004]

However, the method using the expandable inner peripheral support device requires a complicated device such as mechanical expansion or expansion of a pressure medium such as pressurized air.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a method of joining a tubular body in which a complicated uneven weld bead is not formed on an inner surface of a joint without requiring a complicated device.

[0006]

According to the method of joining tubes of the present invention, two tubes are arranged at positions where their end faces face each other.
A core made of shape memory alloy is placed on the inner surface of the facing part
The core is heated and the end face of the tube is heated and melted.
After welding, the end faces of the pipes are butt-welded together.
It is a sign.

In the present invention, the pipe means a pipe or a pipe joint. Examples of the material of the tube used in the present invention include polyetheretherketone resin (PEEK), polyphenylenesulfide resin (PPS), polyethersulfone resin (PES), polyethyleneterephthalate resin (PET), and polybutyleneterephthalate resin (PBT). ), A thermoplastic engineering resin such as a polyimide resin (PI) and a polysulfone resin (PSF).

Further, vinyl chloride resin (PVC), polypropylene resin (PP), polyethylene resin (PE), A
A general-purpose thermoplastic resin such as a BS resin (ABS), or a composite material or a polymer alloy obtained by filling the general-purpose thermoplastic resin with a filler or the like can also be used.

It is desirable that a core made of a shape memory alloy is coated with a non-adhesive fluorine resin or the like so that the molten resin does not adhere.

The core may have a solid shape or a hollow shape. It is desirable that the core is formed in a cylindrical shape. The gap between the outer diameter of the core body and the inner diameter of the tube body may be such that the core body can be separated from the tube body after butt welding.

As a material of the shape memory alloy, nickel-
Titanium alloys are preferred, other copper-aluminum alloys,
Alternatively, a copper-zinc alloy or the like may be used. Also, the core body made of a shape memory alloy is formed so that the shape is memorized so as to have substantially the same outer diameter as the inner diameter of the tube at a high temperature, and smaller than the inner diameter of the tube at a low temperature. It is desirable to keep.

[0012]

The two pipes are arranged at positions where their end faces are opposed to each other, and are made of a shape memory alloy disposed on the inner surface of the opposed portion.
The core is restored to its shape before plastic working by heating the core
The restoring force causes the core to press against the inner surface of the tube.
And the resulting weld bead during butt welding
Does not flow out of the inner surface of the pipe,
No complicated irregularities of the weld bead are formed.

Further, since the core body made of the shape memory alloy presses the inner surface of the tube, no step is formed on the inner surface of the tube. After the butt welding of the core body made of the shape memory alloy, the pipe body is cooled and the core body made of the shape memory alloy is also cooled, so that the core body is transformed into a cylindrical body having a smaller diameter than the pipe body. The core can be easily detached from the tube.

[0014]

Embodiments will be described below with reference to the drawings.

[0015] Figures 1-3 are sectional views illustrating the sequence of steps of an embodiment of the present invention. FIG. 1 is a cross-sectional view showing a heated state of an end face of a tube and a core, FIG. 2 is a cross-sectional view showing a state of butt welding of a tube, and FIG. 3 is cooling of the core after butt welding . It is sectional drawing which shows a state.

Reference numeral 10 denotes a core made of a shape memory alloy,
The core body 10 is disposed on the inner surfaces of the facing portions 8 and 9 of the tubes 1 and 2. The joining of the tubes is performed as follows.

The two tubes 1 and 2 are arranged at positions where their end faces 6 and 7 face each other, and a core 10 made of a shape memory alloy is provided on the inner surfaces of the opposing portions 8 and 9. After the body 10 is heated and the end faces 6, 7 of the tubes 1, 2 are melted by heating, the end faces 6, 7 of the tubes 1, 2 are butt-welded. At this time, the outer peripheral surface of the core body 10 is pressed against the inner surfaces of the tubular bodies 1 and 2 by the restoring force of the core body 10 so that the weld bead generated on the inner surface flows out of the welded beads to the inner surfaces of the tubular bodies 1 and 2. Is suppressed. As a result, smooth inner wall surfaces without irregularities are formed on the tubular bodies 1 and 2. After butt welding, the core 10
Is removed from the inner surfaces of the tubes 1 and 2.

The end surfaces 6 and 7 of the tube 2 is heated and melted by contact with the heating member 3. The heating of the core body 10 is performed by radiant heat from the heating body 3 for heating the end surface. After the end surfaces 6 and 7 are heated and melted and the core body 10 is heated, the heating body 3 is removed. The heating of the core body 10 may be performed by providing a heater inside the core body 10 and controlling the temperature of the core body 10 separately from the heating body that heats the end surface.

Temperature of [0019] Note that core 10, the melting temperature of the synthetic resin below, being controlled in transformation temperature above the temperature of the shape memory alloy is preferable. The core body 10 is heated and restored, and presses the inner surfaces of the tubular bodies 1 and 2 by this restoring force. Further, the core body 10 is cooled and contracted, and a gap is generated between the core body 10 and the inner surfaces of the pipe bodies 1 and 2. The formation of the gap facilitates removal of the core body 10.

[0020]

According to the present invention, since no complicated unevenness of the weld bead is formed on the inner surface of the joint of the pipe, viable bacteria do not inhabit the liquid pool portion of the complicated uneven surface, and the cleanliness (purity) of the fluid is reduced. The problem of lowering is eliminated.

[0021] By using a substrate made of a shape memory alloy, mechanically expandable or a pressure medium such as pressurized air without the need for complex apparatus, such as inflating, the junction the inner surface of the tubular body The tube can be easily joined without forming complicated irregularities of the weld bead.

A core made of a shape memory alloy has the advantage that no step is formed on the inner surface of the tube.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a method of joining a tubular body of the present invention, showing a heated state of an end face of the tubular body and a core body.

FIG. 2 is a cross-sectional view illustrating a butt-welded state of a pipe body according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a cooled state of a core after butt welding.

[Explanation of symbols]

1, 2 tube 3 heating body 10 core body 6, 7 end face 8.9 facing part

Claims (1)

(57) [Claims] 1. Two cores are disposed at positions where their end faces face each other, and a core made of a shape memory alloy is disposed on the inner surface of the opposing portion. A method for joining pipes, wherein the end faces of the pipes are butt-welded after heating and melting the end faces.