JP3512820B2 - Winding core and method of manufacturing electrofusion joint using the core - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in piping work using plastic pipes, and is an electro-conductive wire in which a heating wire consisting of a covered wire or a bare wire is buried in a coil shape inside a socket joint, an elbow joint, a cheese joint or a cap joint. The present invention relates to a metal wound wire core used in a method for manufacturing a fusion joint and a method for manufacturing the joint using the core.

[0002]

2. Description of the Related Art An electrofusion joint has been recently developed as a joint for a plastic pipe that has been widely used in plumbing works such as water and sewerage and gas pipes. There are various types of joints such as socket joints, elbow joints, cheese joints, and cap joints.For fusion with a pipe, after inserting the plastic pipe end into the joint, power is supplied to the plastic pipe. This is done by heating and melting the contact surface of.

Taking a socket joint as an example, a method for manufacturing such a joint is conventionally known in which a metal wound wire core wound with a heating wire is set in an injection molding die and then injection molded. The metal wound wire core is designed so that the molded product taken out from the mold is cooled and then taken out. The metal wound wire core used in this method usually has a stepped stopper 2 at its end in order to prevent the wound heating wire 1 from being washed away by the resin during injection molding as shown in FIG. Has been formed. The higher this stopper is,
Although the flow of the heating wire can be prevented, the diameter of the frontage of the product 3 is increased, and the molten resin is more likely to leak from the gap formed between the product 3 and the plastic tube inserted during fusion bonding.

In order to prevent resin leakage at the time of fusion bonding, a groove 5 is formed adjacent to the stopper 4 as shown in FIG. 2, and a protrusion for eliminating a gap between the product 6 and the plastic pipe. There is also a type that is provided with.

[0005]

The higher the height of the stopper for preventing the flow of the heating wire is, the more effective it is in preventing the flow of the wire. However, the product obtained by using the core as shown in FIG. As described above, the diameter of the opening becomes large, and the resin leakage is likely to occur at the time of fusion, and a short circuit may occur due to the flow of the heating wire.

Also, when a core as shown in FIG. 2 is used, the core is forcibly removed, so that the higher the stopper, the more corrugated scratches are generated in the opening (cold zone), and the appearance is reduced. Will be damaged. It is an object of the present invention to provide a wound wire core and a method for manufacturing an electrofusion joint using the core, which can solve the above problems.

[0007]

The wound wire core of the present invention is used in a method for producing an electrofusion joint in which a metal wound wire core wound with a covered wire is set in a mold and then injection-molded. Depending on the resin when the wire is injection molded
The stepped wound wire core provided with a stopper for preventing it from flowing, the surface roughness of a portion around which the covered wire is wound is defined by JIS B 0659, which is a classification value of 1.6-
The roughness is S or more, and the stopper for preventing the flow of the wire is eliminated or lowered.

The present invention can be used for manufacturing socket joints, elbow joints, cheese joints, cap joints, etc.
As the wound wire core, a standard type shown in FIG. 1 in which the stopper has a stepped shape, or a forceless type shown in FIG. 2 in which a groove is provided adjacent to the stopper can be used.

[0009]

In the metal wound core, the prevention of the wound wire flow has conventionally depended on the height of the stopper. However, according to the experiments conducted by the present inventors, the surface roughness of the core is selected so that It has been found that the height can be reduced or eliminated. Table 1 shows the relationship between the surface roughness obtained by the experiment and the height of the stopper. As shown in the table, when the surface roughness becomes large, the stopper is not needed, and conversely the surface roughness becomes small. Then, it was found that the height of the stopper needs to be equal to or larger than the diameter of the covered wire.

[0010]

[Table 1]

[0011]

EXAMPLE A metallic wound wire core for a cap joint having a surface roughness of 25-S and a stopper height of 0.3 mm was used, and a coated wire having a diameter d of 2.4φ was wound around the core. As a result of injection molding, the wound wire was not set and was set in an injection molding die. Injection molding conditions at this time, using a medium-density polyethylene as a raw material,
The temperature was 230 ° C., the injection pressure was 90 kg / cm ² G, and the injection speed was 50%.

[0012]

[Comparative Example] A cap joint was injection-molded under the same injection-molding conditions as in the example, using the same metal wound core as in the example except that the surface roughness was set to 0.8-S. , The covered wire has moved beyond the stopper and has been greatly displaced.

[0013]

As described above, according to the wound wire core of the present invention, the stopper can be lowered or eliminated by increasing the surface roughness, and thus the standard type product obtained by using the stopper can be obtained. Since the frontage can be made smaller, it is possible to eliminate resin leakage at the time of fusion bonding, and in the type of product in which the core is forcibly removed, it is possible to prevent wavy scratches when removing the core. Will be able to.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a standard type wound core.

FIG. 2 is a cross-sectional view of a forced winding type wound core.

[Explanation of symbols]

1 ... Heating wire 2, 4 ... Stopper 3, 6 ... Product 5 ... Groove

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) F16L 47/02 B29C 45/14 B29C 65/36 B29L 31:24

Claims (2)

(57) [Claims] 1. A metal Maki wire core with plated coating lines used in the production process of the electro-fusion fitting injection molding After set in a mold, coating lines are in the end
A stopper that prevents the resin from being washed away during molding
In the above wound wire core, the surface roughness of a portion around which the covered wire is wound is set to a roughness of a classification value of 1.6-S or more specified in JIS B 0659 and a stopper for preventing wire flow is eliminated. A wound wire core characterized by being thin or low. 2. A method of manufacturing an electrofusion joint using the wound wire core according to claim 1.