JPH07251456A - Welding of electric welding joint - Google Patents

Abstract

PURPOSE:To enable the axes of pipes composed of a thermoplastic resin to coincide with the axis of an electric welding joint connecting both pipes before welding the pipes. CONSTITUTION:When pipes 1 composed of a thermoplastic resin are welded and connected using an electric welding joint, wedges 5 are inserted in the gaps generated between the pipes 1 and the electric welding joint 2. By this method, the axes of the pipes 1 are allowed to coincide each other to weld the pipes 1. Welding deficiencies, the outflow of a molten resin, the short-circuit of an electric wire or the like can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for fusing a gas pipe or the like made of a thermoplastic resin and an electric fusion joint for connecting the same.

[0002]

2. Description of the Related Art An electric fusion splicing joint is a joint for connecting a gas pipe made of a thermoplastic resin and has been rapidly popularized in recent years. The fusion of the pipe and the joint is performed by passing a current through a heating wire embedded in the inner peripheral surface of the joint to heat and melt the interface between the pipe and the joint.

[0003]

However, when a large-diameter pipe having a nominal diameter of 100 A or more is fusion-bonded, the gap between the pipe and the joint is large, so that as shown in FIG. It is difficult to fuse the joints 2 by aligning the axes of the joints 2, and the pipes 1 are often fused in a certain direction. As a result, defective fusion may occur, or the heating wire may move along with the resin flow in a large space, causing a serious trouble of short-circuiting the heating wire. Reference numeral 4 is a connector portion.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for fusing a pipe and an electric fusion joint by aligning the axes of the fusion splicing joint.

[0005]

Means for Solving the Problems The above problem is that when a pipe made of a thermoplastic resin is fusion-bonded using an electric fusion joint, a wedge is inserted into a gap formed between the pipe and the electric fusion joint. It is solved by performing fusion bonding. At this time, if the core layer is made of a material having high rigidity and the surface layer is made of a material having low rigidity or a wedge made of wood, the wedges can be fused without falling off.

[0006]

[Operation] A plurality of wedges are inserted into the gap between the pipe and the opening of the joint. Since the wedge has a taper shape, the axial centers of the pipe and the joint can be matched by adjusting the amount of driving the wedge. When the axes of the pipe and the joint coincide with each other, the voids are evenly distributed in the circumferential direction, and uniform fusion-bonding performance is obtained in the circumferential direction. In addition, since an extremely large space cannot be formed in the void, uneven flow of the molten resin does not occur, and a short circuit of the heating wire can be prevented.

When a wedge whose core layer is made of a material having a high rigidity and whose surface layer is made of a material having a low rigidity is used, the surface layer is elastically deformed to an appropriate degree, so that the wedge is prevented from falling off due to thermal expansion of the joint during fusion. be able to. Although the reason is not clear, a wedge made of wood such as cypress has the same effect as the wedge of the composite material.

[0008]

EXAMPLE In order to match the shaft center of a polyethylene pipe having a nominal diameter of 150 A with an electric fusion joint made of polyethylene, a wedge having various shapes shown in FIG. 3 was inserted into a gap between the pipe and the joint. . An example thereof is shown in FIGS. In the figure, 1 is a tube, 2 is an electric fusion joint, 3
Is a heating wire, 4 is a connector portion, and 5 is a wedge. In this example, the wedges 5 were inserted into the four gaps between the pipe 1 and the joint 2, and the connector portion 4 was energized for 220 seconds with an electric power of 1200 W for fusion.

The wedges used are of three types: polyethylene, a core layer made of polyethylene, a surface layer made of a composite material made of urethane elastomer, and a wood made of cypress. For comparison, fusion was also performed by a conventional method without using a wedge. Under each condition, four samples were prepared and tested. The compression peeling test method described in JIS K6775 was used as the fusion performance evaluation method. In addition, the presence or absence of molten resin flowing out of the joint opening and short-circuiting of the heating wire was also examined.

The compression peel test method described in JIS K6775 will be briefly described below. As shown in FIG. 5, a test piece is cut out from the sample after fusion of the pipe 1 and the joint 2, and the distance L between the heating wires of the fusion-bonded portion of the test piece is measured as shown in FIG. As shown, the test piece is attached to the holding jig 6 and held for 10 minutes until the inner surface of the tube comes into contact. Then, the peeling length of the heating wire is measured, and the ratio (peeling length ratio) to the distance L between the heating wires is obtained to evaluate the fusion performance. According to JIS, if this ratio is 15% or less, there is no problem with the fusion performance.

Table 1 shows the test results. According to the method of the present invention in which the pipe and the shaft center of the joint are aligned and fused using a wedge,
No matter which wedge was used, a fusion-bonding performance that did not pose any problem in practical use was obtained, and neither the molten resin flowed out nor the heating wire short-circuited.

On the other hand, in the conventional method of fusion bonding without using a wedge, the peeling length ratio is out of the range specified by JIS, a sample having a problem with fusion bonding performance is produced, and the molten resin flows out or the heating wire is short-circuited. Happened.

From the above results, it can be seen that the method of the present invention is a remarkably excellent method for fusing an electric fusion joint as compared with the conventional method. Also, the difference between the types of wedges is that the fusion rate evaluated by the peeling length ratio was higher than that of the polyethylene wedge when the core layer was made of polyethylene and the surface layer was made of a composite material made of urethane elastomer or a wooden wedge made of cypress was used. It was slightly superior in performance.

In addition to the polyethylene shown in the examples, a polymeric material such as epoxy, a metal material such as mild steel or aluminum, copper or brass, or an elastomer such as hard rubber may be used as the constituent material of the wedge. The effect of is obtained. In addition to the urethane elastomer shown in the examples, a material such as vulcanized rubber or foamed resin may be used for the surface layer portion of the wedge made of the composite material.

The number and shape of the wedges to be used are not particularly limited as long as the axes of the pipe and the joint can be matched.
For example, even if one cylindrical wedge with slits is used, the effect of the present invention is not lost.

[0016]

[Table 1]

[0017]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it is possible to fuse the pipe and the joint by aligning the axes of the joints with each other, resulting in poor fusion, outflow of molten resin, short circuit of heating wire, etc. The problem of can be avoided.

[Brief description of drawings]

FIG. 1 is a diagram showing a method for aligning the pipe and the axis of a joint by using a wedge according to an embodiment of the present invention.

FIG. 2 is a view of FIG. 1 viewed from the axial direction.

FIG. 3 is a diagram showing an example of a wedge shape which is not necessary for the present invention.

FIG. 4 is a diagram showing an example of a positional relationship between a pipe and a joint according to a conventional method.

FIG. 5 is a view showing a test piece described in JISK6775.

FIG. 6 is a diagram showing a definition of a distance L between heating wires described in JISK6775.

FIG. 7 is a diagram showing a method of compressing a test piece described in JISK6775.

[Explanation of symbols]

 1 tube 2 electric fusion joint 5 wedge

Claims (3)

[Claims] 1. A fusion welding of a pipe made of a thermoplastic resin by using an electrofusion joint, wherein a wedge is inserted into a gap formed between the pipe and the electrofusion joint. Fusing method. 2. The method for fusing an electric fusion joint according to claim 1, wherein the core layer is made of a material having high rigidity, and the surface layer is made of a wedge made of a material having low rigidity. 3. The method for fusing an electric fusion joint according to claim 1, wherein a wedge made of wood is used.