JPH11325373A - Electrically fusing joint and coated heating wire thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity and dimensional accuracy of coated heating wire when energizing energy to heating wire is effectively utilized by making coated thickness on the side of a fusion boundary face nipping heating wire and coated thickness on the side of a non-fusion boundary face substantially equal each other and thin in a coating part and providing projection parts on both the sides of the surface on the side of the non-fusion boundary face. SOLUTION: This electrically fusing joint is constituted of a polyethylene(PE) resin joint body and coated electric wire 12 buried on a fusion boundary face on an inner periphery except the both the end parts. In the coated electric wire 12, heating wire 13 is coated with PE resin coating part 14 and both the end parts are connected with terminal pins for energizing which stands on the outside face of the joint body. Bosses are erected around both the terminal pins. At this time, in the coating part 14 of coated wire 12, coated thickness t1 on the side of a fusion boundary face nipping heating wire 13 and coated thickness t2 on the side of a non-fusion boundary face are made equal each other and thin, and projection parts 14A, 14A are provided on both the sides of the surface on the side of the non-fusion boundary face. As the shape, an edged shape and a rounded shape are allowed, but it is desirable that the width is smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric fusion joint (electrofusion joint) used for joining water and sewage pipes, gas pipes, deformed pipes and the like made of a thermoplastic resin, and a coated heating wire thereof.

[0002]

2. Description of the Related Art Conventionally, as described in JP-A-64-74381, a heating wire is embedded in the inner surface of a joint body as an electric fusion joint for joining polyethylene (PE) pipes and the like. There is a type in which a pipe to be joined is inserted into a main body, the fitting contact surface (fusion interface) between the joint main body and the pipe to be joined is heated and melted by the heat generated by the heating wire, and the pipe to be joined is fused to the joint body.

As a method for embedding a heating wire in a joint body of an electric fusion joint, a coating heating wire in which a heating wire is concentrically covered with a coating portion made of a thermoplastic resin is prepared. Is spirally wound around a core (core material) of an injection molding die, the core is inserted into the die, and a thermoplastic resin is injection-molded into the die to form a joint body ( JP-A-64-74281).

[0004]

However, the prior art has the following problems. That is, when the covering portion of the coated heating wire embedded in the joint body is made concentric with the heating wire (FIG. 4), when the diameter of the joint is increased and the wire diameter of the heating wire is increased, the heating wire is increased. As a result, the distance (pitch) between the heating wire and the heating wire is maintained at a constant ratio to the wire diameter of the heating wire, so that the distance between the fusion interface of the joint body and the heating wire increases. For this reason, the energization energy supplied to the heating wire is not effectively used for fusion with the pipe to be joined.

In order to reduce the distance between the heating wire of the coated heating wire and the fusion interface of the joint body, the coating portion is rectangular, and the coating thickness on the fusion interface side sandwiching the heating wire and the anti-fusion It is conceivable to make the coating thickness on the interface side equal to each other (FIG. 5). However, in this coating structure, after the coated heating wire is spirally wound around the above-mentioned core, the heating plate or the like is prevented from flowing by the injection pressure of the thermoplastic resin injected into the mold. In the step of melting and fixing the coated heating wires with each other, if the coating thickness on the anti-fusion interface side of the coating portion is thin, there is no melting allowance, and the coated heating wires cannot be fixed properly.

Further, in order to secure a melting margin of the coating portion on the anti-fusing interface side of the coating heating wire, the surface of the coating portion on the fusion interface side is flattened, and the surface on the anti-fusing interface side with respect to the heating wire. Concentricity is also conceivable (FIG. 6). However, in this coating structure, when the coating thickness on the fusion interface side and the coating thickness on the anti-fusion interface side are significantly different, in the resin coating process on the heating wire, the amount of resin extruded from the crosshead increases around the heating wire. As a result, high-speed extrusion cannot be performed and productivity is lowered. In addition, the coating portion on the thin side is not uniformly coated, or an extremely sink shape is generated.

In FIGS. 4 to 6, reference numeral 1 denotes a heating wire;
Is a covering part.

An object of the present invention is to provide an electric fusion joint,
When reducing the distance that the heating wire of the coated heating wire makes to the fusion interface to make effective use of the energizing energy to the heating wire,
It is an object of the present invention to improve the productivity and dimensional accuracy of a coated heating wire, and to make it possible to satisfactorily fuse and fix the coated heating wires in a joint forming step.

[0009]

According to the present invention, there is provided an electrofusion method comprising burying a heating wire coated with a thermoplastic resin in a fusion interface of a joint body made of a thermoplastic resin. In the joint, the coating portion of the coated heating wire is formed such that the coating thickness on the fusion interface side and the coating thickness on the anti-fusion interface side sandwiching the heating wire are substantially equal to each other and thinner. It is provided with a projection.

According to a second aspect of the present invention, there is provided a coated heating wire covered with a thermoplastic resin, which is used by being embedded in a fusion interface of a thermoplastic resin joint body. The thickness of the coating on the fusion interface side and the thickness of the coating on the anti-fusion interface side are substantially equal to each other and thinner, and projections are provided at both ends of the surface on the anti-fusion interface side.

[0011]

According to the first and second aspects of the present invention, the following effects are obtained. The coating thickness on the fusion interface side of the coating heating wire was reduced similarly to the coating thickness on the anti-fusion interface side. Therefore, the distance between the heating wire of the coating heating wire and the fusion interface can be reduced, and the energy supplied to the heating wire can be effectively used.

The coating thickness of the coated heating wire on the fusion interface side and the coating thickness on the anti-fusion interface side are made equal to each other with the heating wire interposed therebetween. Therefore, in the step of coating the heating wire with the resin, the resin extruded from the crosshead flows almost uniformly between the fusion interface side and the anti-fusion interface side of the heating wire, and high-speed extrusion molding becomes possible. Can be improved.

The coating thickness of the coating heating wire on the fusion interface side and the coating thickness on the anti-fusion interface side were made equal to each other with the heating wire interposed therebetween. Therefore, the shrinkage of the coating resin is constant at the fusion interface side and the anti-fusion interface side across the heating wire, and high dimensional accuracy can be obtained.

In the joint forming step, after the coated heating wire is spirally wound around the core, when the coated heating wire is melted and fixed with a hot plate or the like, the protrusions at both ends of the adjacent coated heating wire are fixed. Because they are in contact with each other, the projections pressed by a hot plate or the like serve as a melting margin, and the coated heating wires can be reliably and easily fixed.

[0015]

FIG. 1 is a schematic view showing an example of an electric fusion joint, FIG. 2 is a cross-sectional view showing a coated heating wire, FIG. 3 is a cross-sectional view showing a state where the coated heating wire is spirally wound, 4 is a cross-sectional view showing a coated heating wire having a circular cross section, FIG. 5 is a cross-sectional view showing a coated heating wire having a rectangular cross section, and FIG. 6 is a cross-sectional view showing a coated heating wire having a modified cross section.

As shown in FIG. 1, the electric fusion joint 10
It is composed of a joint body 11 made of E resin, and a coated heating wire 12 buried in a fusion interface on the inner periphery excluding both end portions of the joint body 11. As shown in FIG. 2, the coated heating wire 12 is obtained by covering a heating wire 13 with a coating portion 14 made of a PE resin. Terminal pins 15 and 15 are connected. In the joint body 11, both terminal pins 15, 1
Bosses 11A, 11A are erected around the periphery of the boss 5.

At this time, the coating portion 14 of the coating heating wire 12
As shown in FIG. 2, the coating thickness t ₁ on the fusion interface side sandwiching the heating wire 13 and the coating thickness t ₂ on the anti-fusion interface side are made equal and thin to each other. Protrusions 1 on both ends
4A and 14A are provided. The shape of the protruding portion 14A may be a shape with an edge or a radius, but it is preferable that the width is small. The preferable range of the above-mentioned thin coating thicknesses t ₁ and t ₂ is determined based on the wire diameter d _{1 of the} heating wire.
It is preferable that t ₁ = t ₂ = 0.2 d ₁ to 0.5 d ₁ . d ₁
When t = 1.5 mm, t ₁ = t ₂ = 0.3 to 0.75 mm.

The electric fusion joint 10 is manufactured as follows. That is, the coated heating wire 12 is used as the core of the injection mold as shown in FIG.
And spirally wound as shown in FIG. In the state of being wound around this core, as shown in FIG. 3, there is a melting allowance at both end protrusions 14A of the coating portion 14 of the adjacent coating heating wire 12, and this protrusion 14A is easily melted by a hot plate or the like. Can be integrated.
At this time, since the hot plate does not directly hit the coating portions 14 having the coating thicknesses t ₁ and t ₂ on both sides of the heating wire 13, no load is applied to the heating wire 13 by pressing the hot plate. The core is inserted into a mold, and a PE resin is injection-molded into the mold to form the joint body 11. This is cooled and removed from the mold to obtain the electrofusion joint 10.

The electrofusion joint 10 is used as follows. That is, the PE pipes are inserted into the sockets at both ends of the joint body 11 of the electrofusion joint 10, and the power is supplied through the power cord connected to the terminal pins 15. As a result, the heating wire 13 of the coated heating wire 12 generates heat, the surrounding PE resin of the joint body 11 and the outer surface layer of both PE pipes become molten, and the electrofusion joint 10 and both PE pipes are fused. Will do.

Therefore, according to the present embodiment, the following operations are provided. The coating thickness of the coating heating wire 12 on the fusion interface side was reduced similarly to the coating thickness on the anti-fusion interface side. Accordingly, the distance between the heating wire 13 of the coated heating wire 12 and the fusion interface can be reduced, and the energy supplied to the heating wire 13 can be effectively used.

The coating thickness of the coating heating wire 12 on the fusion interface side and the coating thickness on the anti-fusion interface side were made equal to each other with the heating wire 13 interposed therebetween. Therefore, in the step of coating the heating wire 13 with the resin, the resin extruded from the crosshead flows almost evenly on the fusion interface side and the anti-fusion interface side of the heating wire 13, and high-speed extrusion molding becomes possible. Productivity can be improved.

The coating thickness of the coating heating wire 12 on the fusion interface side and the coating thickness on the anti-fusion interface side were made equal to each other with the heating wire 13 interposed therebetween. Therefore, the shrinkage of the coating resin is constant on the fusion interface side and the anti-fusion interface side sandwiching the heating wire 13, and high dimensional accuracy can be obtained.

In the joint forming step, the coated heating wire 12
When the coated heating wires 12 are melted and fixed with a hot plate or the like after being spirally wound, the protruding portions 14A of both ends of the adjacent coated heating wires 12 are in contact with each other, so that the heating wires 12 are pressed together. The projected portions 14A serve as a melting margin, and the coated heating wires 12 can be reliably and easily fixed.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and the design may be changed without departing from the scope of the present invention. The present invention is also included in the present invention.

[0025]

As described above, according to the present invention, in the electric fusion joint, the distance between the heating wire of the coated heating wire and the fusion interface is reduced so that the energy supplied to the heating wire is effectively used. In this case, the productivity and dimensional accuracy of the coated heating wires can be improved, and the coated heating wires can be satisfactorily fused and fixed in the joint forming step.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an electric fusion joint.

FIG. 2 is a sectional view showing a coated heating wire.

FIG. 3 is a cross-sectional view of a state in which a coating heating wire is spirally wound.

FIG. 4 is a cross-sectional view showing a coated heating wire having a circular cross section.

FIG. 5 is a sectional view showing a coated heating wire having a rectangular section.

FIG. 6 is a cross-sectional view showing a coated heating wire having a modified cross section.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Electric fusion joint 11 Joint main body 12 Coating heating wire 13 Heating wire 14 Coating part 14A Projection

Claims (2)

[Claims] 1. An electric fusion joint comprising a thermoplastic resin-coated joint body and a coated heating wire covered with a thermoplastic resin embedded in a fusion interface of the joint body. The thickness of the coating on the fusion interface side and the thickness of the coating on the anti-fusion interface side are made substantially equal to each other and thinned, and projections are provided at both ends of the surface on the anti-fusion interface side. Fittings. 2. A coated heating wire covered with a thermoplastic resin, which is used by being embedded in a fusion interface of a thermoplastic resin joint body, wherein a coating portion has a coating thickness on a fusion interface side sandwiching the heating wire. And a coating thickness on the anti-fusing interface side which is substantially equal to and thinner than each other, and wherein projections are provided at both ends of the surface on the anti-fusing interface side.