JP2003287186A - Welding joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of bad welding in a welding joint using a pipe joint having a heating element embedded in a cylindrical body formed of the thermoplastic resin, having synthetic resin tubes made of the thermoplastic resin inserted in both sides of the pipe joint, and having the pipe joint and the synthetic resin pipe heated by the heating element to weld and integrate both by performing welding under a condition of equalizing clearance between the pipe and the pipe joint around the whole circumference and preventing movement of the pipe with a simple structure. <P>SOLUTION: A wedge ring made of wedge section shape thin plate of which thickness gradually changes in width direction is inserted in a clearance part between the synthetic resin pipe and an opening part of the pipe joint by pressing in a thin side of the wedge ring. The synthetic resin pipe and the pipe joint are heated and welded under condition that centers thereof are aligned and coming off is prevented by wedge action of the wedge ring. The wedge ring has preferably one slit structure. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding joint used for joining gas pipes, water pipes and the like made of thermoplastic resin.

[0002]

2. Description of the Related Art Synthetic resin pipes are widely used for pipes of water, gas, etc. because they have advantages such as light weight and excellent water resistance. As a method for joining the synthetic resin pipes,
Electric welding joints are often used. This welded joint is a thick part of a pipe joint made of thermoplastic synthetic resin.
The heating element (heating wire) is embedded along the inner peripheral surface thereof, and the heating wire is attached in a state where pipes made of thermoplastic synthetic resin are fitted and fixed in the openings on both sides of the pipe joint. Is energized to heat and weld.

When a synthetic resin pipe is joined by using the above-mentioned welding joint, if there is variation in the clearance between the synthetic resin pipe and the pipe joint, or the synthetic resin pipe moves during heat welding, the entire circumference is covered. It is not possible to perform uniform welding, resulting in poor joints, and problems such as water leakage when used in water pipes. Therefore, in welding, centering of the pipe joint and the pipe is important, and moreover, it is necessary to fix the pipe so that the pipe does not move in the pull-out direction during welding.

[0004]

As a method for solving the above problems in a welded joint, for example, an inclined annular position fixing member having a plurality of slits open to the inner peripheral side is attached to the inside of the pipe joint. A method for centering and retaining a synthetic resin pipe with a member (JP-A-4-191592), and attaching a shape memory alloy retaining member to the inner end of the pipe joint or the tip of the pipe to perform welding. Method (JP-A-4-3371)
No. 90), a method in which a locking member is interposed in the gap between the inner peripheral surface of the receiving port of the joint and the outer peripheral surface of the end portion of the synthetic resin pipe to weld the synthetic resin pipe while preventing the synthetic resin pipe from slipping out (JP-A-5-302).
694) and various other types have been proposed.

However, each of the above-mentioned conventional methods has a problem that the inner peripheral portion of the pipe joint needs to be machined or another member having a complicated shape is required. Therefore, it is an object of the present invention to make it possible to perform centering and retaining of a pipe in an electric welding joint without using special processing for the pipe joint and using a simple member. There is.

[0006]

In order to solve the above problems, the present invention employs the following configurations. That is, the welding joint according to the present invention uses a pipe joint formed by embedding a heating element inside a tubular body formed of a thermoplastic resin, and is made of a thermoplastic resin in openings on both sides of the pipe joint. In a welding joint in which a synthetic resin pipe is inserted and the pipe joint and the synthetic resin pipe are heated by the heating element, and both are welded and integrated, in the clearance portion between the synthetic resin pipe and the opening of the pipe joint,
A wedge ring consisting of a thin plate with a wedge-shaped cross section whose thickness gradually changes in the width direction is pushed in from the thin side, and heat welding is performed with the wedge action of the wedge ring performing centering and retaining of the synthetic resin pipe and pipe joint. It is characterized by doing.

As the wedge ring, it is convenient to use an elongated thin plate-like member having an appropriate length and ring-shaped to divide it into one. In addition, the material for this wedge ring is formed into a strip-shaped long body, which is wound into a roll and carried into a site, and cut into a required length at the site for use. This is preferable because it can be appropriately used for a plurality of joints having different diameters.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below. FIG. 1 shows an example of an electric welding joint according to the present invention. The welding joint 1 includes a pipe joint 2 and
It is composed of pipes 3 and 3 to be joined.

The pipe joint 2 is composed of a tubular body made of a thermoplastic resin such as polyethylene, and has openings 4 and 4 formed at both ends thereof, and a pipe to be joined at the central portion in the longitudinal direction thereof. An annular projection 7 for positioning is provided. Further, in the thick portion of the pipe joint 2, a coil-shaped heating wire 9 is embedded as a heating element along the inner peripheral surface thereof. The heating wire is, for example, a nichrome wire. A pair of left and right tubular bosses 10, 10 are provided on the outer peripheral portion of the pipe joint 2, and terminals 11, 11 are provided therein. Both ends of the heating wire 9 are connected to these terminals 11, 11.

In the openings 4 and 4 on both sides of the pipe joint 2,
Similarly to the above, the tubes 3 and 3 made of a thermoplastic resin such as polyethylene are respectively inserted. At this time, the tip of the inserted tube 3 is positioned by contacting the annular projection 7. Since the inner diameter of the pipe joint 2 is formed to be slightly larger than the outer diameter of the pipe 3, a slight gap (clearance) is formed between the inner surface of the pipe joint 2 and the outer peripheral surface of the pipe 3 when the pipe 3 is inserted. ) C occurs. If there is variation in this clearance c, there will be a portion where welding is not performed well as described above, so it is necessary to make this clearance c uniform over the entire circumference during welding. In addition, if the pipe moves during welding (it does not move in the pushing direction but moves in the pulling direction because of the annular projection 7), defective welding occurs, so this movement must also be prevented.

In the present invention, a wedge ring is used in order to make the clearance c uniform and prevent the pipe from moving in the direction in which the pipe comes out. FIG. 2 shows a specific example of the wedge ring. The wedge ring 20 is formed by rolling a thin thin plate made of a material having appropriate strength and elasticity. Wedge ring 20
As the material of the metal, for example, engineering plastic or metal such as steel can be used.

The wedge ring 20 is formed in a wedge-shaped cross section in which the wall thickness changes along the width w direction, and the thickest part thereof has a wall thickness t of, for example, 1.5 to 2.5 mm and a width w of 10 to 10. Two
It is about 0 mm. These dimensions may be optimal according to the diameter of the pipe, the size of the clearance c, and the like.

The welding method using the wedge ring 20 will be described. First, the pipes 3 to be joined are provided in the openings 4 and 4 on both sides of the pipe joint 2, respectively, and the tips thereof are the annular projections 7 of the pipe joint 2. Insert until it touches. After that, the wedge ring 20 is fitted onto the pipe 3 and tapped into the clearance c. Since the wedge ring 20 has a split structure and has elasticity, it can be easily fitted into the pipe 3 by opening the split 21. Further, since the wedge ring 20 has a wedge-shaped triangular cross section, the clearance c is provided from the thin side.
By inserting and tapping into the portion, it is possible to firmly fix the pipe 3 and the pipe joint 2 with the cores aligned.

After the centering and fixing (removal) of the pipe 3 and the pipe joint 2 are performed by the wedge ring 20, the power cord is connected to the terminals 11 and 11 and the heating wire 9 is energized. By this energization, the heating wire 9 generates heat to heat and weld the pipe joint 2 and the pipe 3. In this case, the clearance between the pipe joint 2 and the pipe 3 is uniform over the entire circumference, and moreover, since the pipe 3 is firmly fixed to the pipe joint 2, welding defects do not occur and good joining is performed.

FIG. 3 shows an embodiment different from the above, and in this example, minute projections 22, are formed on the surface of the wedge ring 20.
... is formed. It is preferable that the protrusions are formed as convex stripes along the longitudinal direction, but simple protrusions may be dispersed and provided. Such a protrusion 22
The provision of is advantageous in that the slip-out does not easily occur when hitting into the clearance. The cross-sectional shape of the protrusion 22 is not limited to the triangular shape as shown in the drawing, but may be a rectangular shape or any other suitable shape.

The wedge ring 20 is not limited to the one-piece structure as shown in the above-described example, but may be a complete ring shape without cracks. In this case, it is necessary to prepare a plurality of types so as to adapt to different outer diameters of the pipe 3. The thin and thin wedge-shaped material 25 forming the wedge ring is formed as a strip-shaped long body, and as shown in FIG. 4, it is provided by winding it in a roll shape convenient for transportation and storage. Then, it is convenient because the wedge ring 20 having a desired diameter can be easily obtained by cutting and rolling it to an appropriate length on site.

[0017]

As is apparent from the above description, in the welding joint according to the present invention, a wedge ring made of a thin plate having a wedge-shaped cross section is fitted in a clearance portion between the pipe joint and the pipe to prevent the centering and the pipe from moving. Since it is performed, it is possible to perform good welding / joining without needing to perform complicated processing on the pipe joint and without requiring complicated members. The wedge ring is economical because it has a simple shape and can be made of inexpensive material. In addition, if the material of this wedge ring is manufactured as a strip-shaped elongated body having a wedge-shaped cross section, and a ring with a split structure is adopted by cutting and rolling the material from the material to the required size, It is extremely convenient for practical use.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a welding joint illustrating an embodiment of the present invention.

FIG. 2 is a front view (a) and a sectional side view (b) of the wedge ring.
Is.

FIG. 3 is a cross-sectional view of a wedge ring showing a different embodiment.

FIG. 4 is an explanatory diagram of a wedge ring material.

[Explanation of symbols]

1 Welding joint 2 pipe fittings 3 tubes 7 protrusions 9 Heating wire (heating element) 20 wedge ring

Claims (3)

[Claims] 1. A pipe joint in which a heating element is embedded in a tubular body formed of a thermoplastic resin is used, and synthetic resin pipes made of the thermoplastic resin are inserted into openings on both sides of the pipe joint. Then, in the welding joint in which the pipe joint and the synthetic resin pipe are heated by the heating element, and the both are welded and integrated, in the clearance portion between the synthetic resin pipe and the opening of the pipe joint, the thickness gradually increases in the width direction. It is characterized in that a wedge ring made of a thin plate having a changing wedge-shaped cross section is pushed in from the thin side, and heat welding is performed in a state where the synthetic resin pipe and the pipe joint are aligned and prevented from coming off by the wedge action of the wedge ring. Welded joint. 2. The welded joint according to claim 1, wherein the wedge ring has a split structure. 3. The welding joint according to claim 2, wherein the wedge ring is formed by using a strip-shaped elongated body having a wedge-shaped cross-section as a material and cutting the material cut to a desired length and rolling the material.