JP2001200981A - Method of manufacturing electrically fusible branch connection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of inexpensively manufacturing an electrically fusible branch connection having a branch joining part and a boring part of various shapes having the same saddle part shape and nonproblematic in strength. SOLUTION: In this manufacturing method of the electrically fusible branch connection for integrally injection molding a saddle part 1 and the branch joining part 2, the electrically fusible branch connection is molded by installing an attachable metal mold 5 at injection molding time by attaching the metal mold part 5 for injection molding the branch joining part 2 from a main fixed metal mold 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrofusion type branch joint having a saddle portion and a branch joint used for connecting a resin pipe such as a polyethylene pipe.

[0002]

2. Description of the Related Art In recent years, resin pipes made of thermoplastic resins such as polyethylene and polybutene, which are lightweight, have excellent corrosion resistance, and are flexible and resistant to earthquakes, have been produced in large numbers in gas pipes and water pipes. It is being used.

When connecting a branch pipe to a main pipe made of such a resin pipe, an electric fusion type branch joint made of the same kind of resin as the main pipe and the branch pipe and having a saddle portion and a branch joint is used. There are two types of electrofusion type branch joints: a type in which a branch joint is directly provided in a saddle portion, and a type in which a branch joint is provided through a perforated portion in a saddle portion. While pressing the concave side of the buried saddle against the main pipe, electricity is supplied to the heating wire to melt the resin on the contact surface, which is fused to the main pipe and inserted into the opening at the tip of the branch joint. A branch pipe is connected via a fusion joint. Then, the welded portion between the saddle portion and the main pipe portion is perforated by a cutter inserted from the branch joint portion or a cutter built in the upper portion of the perforated portion so that gas and water can flow from the main pipe to the branch pipe. After the perforation, the head of the perforated portion is closed with a cap to prevent gas and water from leaking therefrom.

In order to manufacture such an electrofusion type branch joint, usually, a saddle portion and a branch joint portion or a perforated portion are integrally formed by injection molding. Therefore, even if the saddle part has the same shape, if the size and shape of the branch joint part and the perforated part are different, it is necessary to use a mold suitable for each, and the mold cost will increase for products with low production volume and the product cost will increase significantly. The problem of pushing up arises.

Therefore, recently, Japanese Patent Application Laid-Open No. 7-208677 discloses that a saddle portion and a branch joint portion are separately formed, and then the branch joint portion is integrated with the saddle portion by fusion, so that a product having a small production amount is used. There has been proposed a method of manufacturing an electrofusion type branch joint which does not require a metal mold and reduces costs.

[0006]

SUMMARY OF THE INVENTION
In the method described in JP-A-7-208677, the fusion strength is weaker than that of the integral injection molding, and when bending stress is applied to the fusion portion due to ground subsidence, stress concentration occurs in the fusion bead and breakage occurs. May happen. Further, this method cannot be applied to a joint having a threaded groove for covering the head with a cap or a perforated portion requiring a branch joint on the side wall.

The present invention has been made in order to solve such a problem, and has a saddle portion of the same shape, and has a branch joint portion and a perforated portion of various shapes, and is an electrofusion type having no problem in strength. It is an object of the present invention to provide a method for manufacturing a branch joint at low cost.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to provide a method for manufacturing an electro-fusion type branch joint in which a saddle portion and a branch joint are integrally formed by injection molding. The problem is solved by a method of manufacturing an electro-fusion type branch joint which is detachable from a fixed mold and is mounted and molded at the time of injection molding.

If the mold part for injection molding of the branch joint is made detachable from the main fixed mold, and this detachable mold is attached and molded at the time of injection molding, not only the whole mold but also various branches are formed. It is inexpensive because an electric fusion type branch joint having the same saddle shape and different branch joint shapes can be formed only by preparing a partial mold corresponding to the joint. Further, since the saddle portion and the branch joint portion are integrally formed by injection molding, there is no problem in strength.

[0010] In a method for manufacturing an electrofusion type branch joint in which a saddle portion, a branch joint portion and a perforated portion are integrally injection-molded,
If the mold part for injection-molding the branch joint and the perforated part is made detachable from the main fixed mold, for the same reason as above, there are branch joints and perforated parts having the same saddle part shape and various shapes. In addition, an electrofusion type branch joint having no problem in strength can be manufactured at low cost.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a method for manufacturing an electrofusion type branch joint according to the present invention. FIG. 1 shows a mold cross-section having a saddle portion cavity 1, a branch joint portion cavity 2, and a perforated portion cavity 3 for injection-molding an electrofusion type branch joint including a saddle portion, a branch joint portion, and a perforated portion. The main fixed mold 4 has a detachable mold 5 corresponding to the shape of the branch joint and the hole, a core 6 corresponding to the shape of the branch joint, and a core corresponding to the shape of the hole. 7
Is set. In addition, a screw groove 8 for a cap is formed at a position corresponding to the head of the perforated portion of the mold 5.

[0012] The mold 5 according to the shape of the branch joint and the perforated portion.
By changing the shape of the core 6 and the core 7 for the branch joint and the core 7 for the perforated part, without changing the whole mold, the saddle shape is the same, and the electric having the branch joint and the perforated part of various shapes is the same. The fusion spliced joint can be integrally injection molded. for that reason,
Mold costs can be reduced, and there is no problem with strength.

[0013]

Since the present invention is constructed as described above, it has the same saddle portion shape, and has various shapes of branch joints and perforations, so that there is no problem in the strength of the electrofusion type branch. It is possible to provide a method for manufacturing a joint at low cost.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a method for manufacturing an electrofusion type branch joint according to the present invention.

[Explanation of symbols]

 1 Saddle cavity 2 Branch joint cavity 3 Perforated cavity 4 Fixed mold 5 Removable mold 6 Core for branch joint 7 Core for punch 8 Screw groove

Claims (2)

[Claims] 1. A method of manufacturing an electro-fusion type branch joint in which a saddle portion and a branch joint are integrally injection-molded, wherein a mold portion for injection-molding the branch joint is detachable from a main fixed mold, A method for manufacturing an electrofusion type branch joint, wherein the detachable mold is mounted and molded at the time of injection molding. 2. A method of manufacturing an electrofusion type branch joint in which a saddle portion, a branch joint portion, and a perforated portion are integrally injection-molded, wherein a die portion for injection-molding the branch joint portion and the perforated portion is mainly fixed. A method for manufacturing an electrofusion type branch joint which is detachable from a mold and is mounted and molded at the time of injection molding.