JP2000213683A - Manufacturing method of electrically fused coupling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrically fused coupling capable of manufacturing the electrically fused coupling of a large aperture not causing inner failure. SOLUTION: This manufacturing method is constituted of a process to injection mold two pieces of end part inners 2 for installation of a connector pin 5 and a central part inner 3 of a part equivalent to a coupling central part not to be fused on a resin pipe, a process to install the connector pin 5 on each of the two end part inners 2, a process to fix a bare heating wire 4 on one of the connector pins 5, to directly wind spirally around a part of the core 1 equivalent to a part to be fused with one of the resin pipes, to directly wind spirally around a part equivalent to a part to be fused with the other resin pipe and to fix on the other connector pin 5 and a process to injection mold an outer 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an electric fusion joint for connecting resin pipes made of a thermoplastic resin such as polyethylene or polybutene, and more particularly to a preform called an inner (hereinafter simply referred to as an inner). ).

[0002]

2. Description of the Related Art In an electric fusion joint, an outer surface of a resin tube to be connected is brought close to an inner surface of the joint, and a heating wire provided on an inner surface of the joint is energized to fuse the joint and the resin tube to each other. And various types of sockets, elbows, cheeses, service tees, saddles, and the like.

One of the methods for manufacturing a socket or an elbow-type electrofusion joint is a method for manufacturing the same by using an inner as described in Japanese Patent Publication No. 3-75795 by the following steps. .

(1) A tubular inner is molded by injection molding using the same kind of resin as the resin tube to be connected.

(2) Attach connector pins for supplying current to the heating wire at both ends of the outer surface of the inner.

(3) The naked heating wire is fixed to one of the connector pins, spirally wound around the portion of the inner tube that is to be fused with the resin tube, passed over the center of the inner tube, and wound on the other portion of the inner tube that is fused to the resin tube. Wrap spirally and secure to the other connector pin.

(4) A connector pin is attached, a core is inserted into an inner wire on which a naked heating wire is wound, and the core is set in a mold, and the same type of resin is used to form an outer cover (hereinafter simply referred to as an outer material). Injection molding).

[0008]

However, when manufacturing a large-diameter electrofusion joint by such a method using the inner, it is necessary to manufacture the large-diameter inner by injection molding. Since the inner wall thickness of the part that is rolled up and fused to the resin tube is extremely thin, less than 1 mm due to the fusion efficiency, the resin flow in the cavity corresponding to this thin part does not go smoothly and an inner defect occurs There is a problem that it is easy to do.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a method of manufacturing an electro-fusion joint which can manufacture a large-diameter electro-fusion joint without causing inner defects. .

[0010]

SUMMARY OF THE INVENTION The above-mentioned problem is solved on a core by:
A step of injection-molding two end inners for attaching a connector pin and a central inner part corresponding to a joint central part which is not fused to the resin pipe; and attaching a connector pin to each of the two end inners Fixing the bare heating wire to the one connector pin, directly helically winding the core portion corresponding to a portion to be fused with one resin tube, and passing over the center inner, An electric fusion joint comprising: a step of directly spirally winding around the core portion corresponding to a portion to be fused with the resin tube, and fixing the other to the other connector pin, and a step of injection molding an outer. Is solved.

By removing the thinner part of the conventional inner part that is fused with the resin tube and extruding the inner part consisting of only two relatively thicker inner and inner parts, the cavity itself can be formed. Since the volume of the resin can be reduced, the flow of the resin in the cavity can be made smooth and the inner defect does not occur.

At this time, the inner end portion is necessary for facilitating attachment of the connector pin and for preventing a short circuit due to contact between the naked heating wires at the time of fusion with the resin tube. Also, if the naked heating wire is exposed on the inner surface of the joint,
When passing high-pressure water or gas, water or gas may enter the gap between the naked heating wire and the resin, causing water leakage or gas leakage. Necessary to prevent exposure and to prevent leakage.

[0013] After injection molding the two end inner and the center inner, without removing them from the core, connector pins are attached to each of the two end inners, and a bare heating wire is fixed to one of the connector pins. Spirally wound directly around the core part corresponding to the part to be fused with one resin tube, passed over the center inner, and spiraled directly to the core part corresponding to the part fused to the other resin tube. By wrapping, fixing to the other connector pin and injection molding the outer, an electrofusion joint can be manufactured.

[0014] In this case, since the outer can be injection-molded without removing it from the core after the end inner and the center inner are injection-molded, the electrofusion joint can be manufactured by one injection molding machine.

Further, the inner end portion and the inner central portion are separately molded by injection molding or extrusion molding, set on a core, installed with a connector pin or a bare heating wire, set on a mold, and injection-molded on an outer. However, the electrofusion joint can be manufactured without causing the inner defect described above.

In any of the manufacturing methods, the end inner and the center inner do not necessarily have to be annular.
The connector pin may be attached and the joint may be formed in an arc shape having such a size that the bare heating wire is not exposed at the center.

[0017] When the surface temperature of the end inner part and the central part inner part is heated to 70 ° C or more and the outer is injection molded, the adhesion between the inner and the outer is improved.

In the case of a large-diameter and thick electrofusion joint, if the outer is injection-molded at a high injection pressure at one time, the inner or bare heating wire is displaced, causing water leakage or gas leakage, or short-circuiting when energizing. Therefore, it is desirable to perform injection molding in several times. In addition, by performing the steps several times, the thickness per layer can be reduced, which is effective in increasing productivity and preventing the occurrence of sink marks.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows one embodiment of the invention of a method for manufacturing an electrofusion joint according to the present invention. In FIG. 1, (a) shows a state in which an annular end inner and a center inner are injection-molded on a core, (b) shows a state in which a connector pin is attached, and a bare heating wire is wound, and (c) shows an outer injection. Indicates the state after molding.

(A) First, in consideration of the shape of the joint to be manufactured, a resin such as polyethylene or polybutene is used on the core 1 and two annular inner ends 2 for attaching the connector pins 5 to the resin. The central inner 3 corresponding to the central portion of the joint that is not fused to the pipe is injection-molded.

(B): Next, without removing the end inner 2 and the center inner 3 from the core 1,
Attach the connector pin 5 to 2, fix the naked heating wire 4 to one connector pin 5, wind directly spirally around the core 1 corresponding to the part to be fused with one resin tube, and attach the center inner 3 The wire is spirally wound directly around a portion of the core 1 corresponding to a portion to be fused with the other resin tube, and fixed to the other connector pin 5.

(C): Finally, if the outer 6 is injection-molded, an electrofusion joint can be manufactured. As described above, in the method of the present invention, only the relatively thick end portion inner 2 and the central portion inner 3 need to be injection-molded. Therefore, the flow of the resin in the cavity becomes smooth, and the electrofusion joint can be manufactured without causing the inner defect.

[0023]

Since the present invention is configured as described above, it is possible to provide a method for manufacturing an electro-fusion joint that can manufacture a large-diameter electro-fusion joint without causing an inner defect.

[Brief description of the drawings]

FIG. 1 is a view schematically showing one embodiment of the invention of a method for manufacturing an electro-fusion joint according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core 2 End inner 3 Central inner 4 Bare heating wire 5 Connector pin 6 Outer

Claims (4)

[Claims] 1. A connector for mounting a connector pin on a core.
A step of injection molding two inner end parts, a central inner part corresponding to a central part of the joint which is not fused with the resin pipe, a step of attaching connector pins to each of the two inner end parts, A heat wire is fixed to the one connector pin, directly helically wound around a portion of the core corresponding to a portion to be fused with one resin tube, passed over the center inner, and fused with the other resin tube. A method for manufacturing an electro-fusion joint, comprising: a step of directly spirally winding around a portion of the core corresponding to a portion to be attached and fixing the core to the other connector pin; and a step of injection-molding an outer. 2. A step of molding two end inner parts for attaching a connector pin, and forming a center inner part of a part corresponding to a center part of a joint which is not fused to the resin pipe; Setting the inner part to the core, attaching a connector pin to each of the two end inner parts, fixing the naked heating wire to the one connector pin, and fusing the one with the one resin tube. Directly spirally wound around the corresponding core portion, passed over the center inner, directly spirally wound around the core core portion corresponding to the portion to be fused with the other resin tube, and wound on the other side. A method for producing an electro-fusion joint, comprising: a step of fixing to a connector pin; and a step of setting a core after winding the bare heating wire in a mold and injection molding an outer. 3. The outer molding is heated by heating the surface temperatures of the inner end portion and the inner central portion to 70 ° C. or more.
3. The method for producing an electrofusion joint according to claim 1 or 2. 4. The method for producing an electro-fusion joint according to claim 1, wherein the outer injection molding is performed in several steps.