JP3812972B2 - Manufacturing method of electric fusion joint - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an electrofusion joint in which a heating wire is wound around the inner peripheral surface of a joint.
[0002]
[Prior art]
Conventionally, for the connection of a synthetic resin gas pipe, a water supply / hot water supply pipe, and the like, an electric fusion joint in which a heating wire is embedded in a joint surface with the pipe is used. As a manufacturing method of this electric fusion joint, for example, a continuous spiral groove is provided on the outer peripheral surface of a synthetic resin cylindrical body, and then a heating wire is attached to the groove, and the heating wire is wound around the cylindrical body. Has been proposed in which a molten resin is injected into a cavity formed between an outer peripheral surface of a cylindrical body and a mold after the mold is set in the mold.
[0003]
[Problems to be solved by the invention]
However, in the case of this conventional manufacturing method, since the heating wire wound around the outer peripheral surface of the synthetic resin cylindrical body is easy to loosen, the synthetic resin tube is used at the time of manufacturing the joint for injecting the molten resin or by energizing the heating wire. When fusion bonding is performed, adjacent heating wires may be short-circuited, resulting in poor fusion.
[0004]
The present invention solves such a problem, and at the time of manufacturing a joint, or when fusion-bonding a synthetic resin tube, the heating wire does not loosen and short-circuit, and a strong fusion-bonding can be obtained. A method for producing a fusion joint is provided.
[0005]
[Means for Solving the Problems]
The present invention provides a continuous spiral groove on the outer peripheral surface of a synthetic resin cylinder, and a heating wire attached to the spiral groove by providing protrusions across the groove at positions near the start and end of the groove. The cylindrical body is set in the mold after the end portion of the cylinder is locked to the protrusion and the heating wire is not loosened , and the molten resin is placed in the cavity formed between the outer peripheral surface of the cylindrical body and the mold. It is characterized by injecting.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a front view of a main part showing a state in which a heating wire is wound around an outer peripheral surface of a synthetic resin cylindrical body and its end is locked, FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectional view of a state in which a synthetic resin cylinder around which a heating wire is wound is set in a mold, wherein 1 is a synthetic resin cylinder, and 2 is a heating wire such as a nichrome wire.
[0007]
The synthetic resin cylinder 1 is made of a synthetic resin such as polyethylene or polybutene, and a spirally continuous groove 11 is provided on the outer peripheral surface thereof. In addition, a protrusion 12 that crosses the groove 11 is provided at a position near the start end and the end of the groove 11 that is spirally continuous. One end of the protrusion 12 is open, and a relief 110 is provided in the groove 11 corresponding to the opening. In other words, the heating wire 2 can be hidden under the projection 12 while being escaped sideways by the escape 110.
[0008]
In the present invention, the heating wire 2 is wound around the outer peripheral surface of the synthetic resin cylinder 1 while applying tension to the heating wire 2 after the mandrel 4 is inserted into the synthetic resin cylinder 1, and the heating wire along the groove 11. Wear 2 Then, the heating wire 2 is raised after the end of the heating wire 2 is submerged under the starting end of the groove 11 that is spirally continuous and the protrusion 12 provided near the end. Then, since the edge part of the heating wire 2 is latched by the protrusion 12, the terminal pin 3 is fixed to the front-end | tip.
[0009]
Next, the synthetic resin cylinder 1 around which the heating wire 2 is wound is set in the mold 5. At this time, the plug forming die 51 is attached to the terminal pin 3 fixed to the end of the heating wire 2, and the plug forming die 51 is attached to the inside of the mold 5 and then the die is closed. In this way, after setting the synthetic resin cylinder 1 in the mold 5, the molten resin is injected into the cavity formed between the outer peripheral surface of the cylinder 1 and the mold 5. Finally, when the mold 5 is opened and the molded product is taken out, an electric fusion joint in which the heating wire 2 is embedded in the joint surface with the tube is obtained.
[0010]
1 and 2 illustrate an example in which one end of the protrusion 12 is open and a groove 110 is provided in the groove 11, but the present invention is not limited to this. Both ends of the protrusion 12 may be fixed to both sides of the groove 11, and the heating wire 2 may be inserted into and locked in the through hole formed by the protrusion 12 and the groove 11. Further, the protrusion 12 may be detachably mounted across the groove 11.
[0011]
【The invention's effect】
As described in detail above, the present invention provides a starting wire of the spiral groove provided on the outer peripheral surface of the synthetic resin cylindrical body and a protrusion crossing the groove at a position near the terminal end, and the heating wire attached to the spiral groove is provided. Since it is locked to the projection, the heating wire is not loosened and short-circuited when a joint is manufactured by injection molding or when a synthetic resin pipe is fusion bonded.
Therefore, when the electric fusion joint according to the present invention is used, reliable and strong fusion bonding can be obtained.
[Brief description of the drawings]
FIG. 1 is a front view of a main part showing a state in which a heating wire is wound around an outer peripheral surface of a synthetic resin cylinder and its end is locked. FIG. 2 is a cross-sectional view taken along line AA in FIG. It is line sectional drawing.
FIG. 3 is a partial cross-sectional view of a state in which a synthetic resin cylinder around which a heating wire is wound is set in a mold.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Synthetic resin cylinder 2 Heating wire 11 Spiral continuous groove 12 Protrusion

Claims (1)

A continuous spiral groove (11) is provided on the outer peripheral surface of the synthetic resin cylindrical body (1), and a protrusion (12) crossing the groove (11) is provided at a start end of the groove (11) and a position near the end. The end of the heating wire (2) mounted in the spiral groove (11) is locked to the protrusion (12) so that the heating wire (2) does not loosen, and then the cylindrical body (1) is molded. (5) A method for producing an electrofusion joint, characterized in that molten resin is injected into a cavity formed between the outer peripheral surface of the cylindrical body (1) and the mold (5).

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