JPH11207778A - Manufacture of electrically welded joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an electrically welded joint of good cooling efficiency and superior inner dimension accuracy. SOLUTION: In a manufacturing method for an electrically welded joint with a built-in electric heater wire 2 in which an inner mold 1 and outer molds 4 are used, a structure formed of a thin wall cylindrical core 11 with a core block 12 is used as the inner mold 1 and the core block can be cooled, and a molding layer 5 composed of thermoplastic resin is injection molded between the inner mold 1 on which the electric heater wire 2 is wound and the outer molds 4. Then the molding layer 5 is cooled from inside by the core block 12, and the outer molds 4 and the core block 12 are released, and the cord 11 is released after cooling completely the molding layer 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 electric fusion joint having a built-in heating wire for fusion joining resin pipes for gas, water and sewage.

[0002]

2. Description of the Related Art Conventionally, a method of manufacturing an electric fusion joint having a built-in heating wire is described in, for example, Japanese Patent Application Laid-Open No. 3-244896. As shown in FIG. The heating wire b is wound around, and a synthetic resin is injected around the mold core a to form a cylindrical resin layer c in which the heating wire b is embedded. After the resin layer c is naturally cooled, it is released from the mold. A method has been proposed.

However, according to this method,
Since it takes a long time to cool the injection-molded resin layer c naturally, there is a problem that productivity is poor.

Also, for example, a resin-coated heating wire is wound on the outer peripheral surface of a metal core, and this metal core is mounted in an outer mold,
A molding layer made of a thermoplastic resin is injection-molded between the two, and after a predetermined time has elapsed, the outer mold is released, and the molding layer is cooled in water or air with the metal core attached. The method of molding is adopted.

[0005] However, in the case of the above method, the cooling of the inner surface side of the molded layer cannot be performed quickly, so that
There is a problem that it is not possible to obtain an electrofusion joint having a connection portion having an inner surface with excellent dimensional accuracy. In addition, in the case of a large-diameter electrofusion joint, there is also a problem that the handleability of the core is deteriorated because the weight of the metal core increases.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems and provides an electric fusion joint having good cooling efficiency and excellent inner surface dimensional accuracy. The purpose of the present invention is to provide a manufacturing method.

[0007]

The invention described in claim 1 of the present application (invention 1) is a method for manufacturing an electric fusion joint having a built-in heating wire using an inner mold and an outer mold. As the inner mold, a mold layer made of a thermoplastic resin is used between an inner mold and an outer mold in which a heating core is wound using a thing in which a core block capable of cooling is inserted into a thin cylindrical core. While the injection molding of or after injection molding, the core layer cools the molding layer from the inside, the outer mold and the core block are released, and the cylindrical core is released after the molding layer is completely cooled. It is a manufacturing method of.

The invention described in claim 2 of the present application (Invention 2)
Is a method for manufacturing an electric fusion joint incorporating a heating wire using an inner mold and an outer mold, wherein a coolable core block can be inserted into a thin-walled cylindrical core as an inner mold. A step of winding a heating wire on a cylindrical core, a step of inserting a core block into the cylindrical core to form an inner mold, and a step of heating between the inner mold and the outer mold. Injection molding the molded layer made of the plastic resin, cooling the molded layer from the inside with the core block, removing the outer mold and the core block, removing the cylindrical layer after completely cooling the molded layer. This is a method for producing an electro-fusion joint comprising a step of molding.

The invention described in claim 3 of the present application (the present invention 3)
Is a method for manufacturing an electro-fusion joint having a built-in heating wire using an inner mold and an outer mold, wherein a pair of thin cylindrical cores arranged in series at a predetermined interval as an inner mold. A step of fixing a pair of cylindrical cores to both ends of a fixing jig, a step of winding a heating wire on a pair of cylindrical cores, and A step of inserting the pair of tubular cores into the outer mold while being fixed to both ends of the fixing jig, removing the fixing jig, and then removing the fixing jig into the pair of cylindrical cores arranged in series at a predetermined interval. Injecting a molding layer made of a thermoplastic resin between the step of inserting the block to form the inner mold and the inner mold and the outer mold,
An electrofusion joint comprising a step of cooling the molded layer from the inside with the core block, a step of removing the outer mold and the core block, and a step of removing the pair of cylindrical cores after completely cooling the molded layer. It is a manufacturing method of.

[0010]

According to the method of manufacturing an electric fusion joint of the present invention, an inner mold is used in which a coolable core block is insertable into a thin cylindrical core, and a heating wire is wound. While injection molding or after injection molding a molding layer made of a thermoplastic resin between the mold and the outer mold, the molding layer is cooled from the inside by the core block, the outer mold and the core block are removed, and the molding layer is removed. By completely removing the cylindrical core after complete cooling, the molded layer can be preferentially cooled from the inside, so that the cooling efficiency is excellent, and the so-called sink phenomenon associated with cooling does not appear on the inner surface. Thus, it is possible to obtain an electric fusion joint having excellent inner surface dimensional accuracy.

According to a second aspect of the present invention, there is provided a method for manufacturing an electric fusion joint, wherein an inner mold having a core block which can be cooled is inserted into a thin cylindrical core, and a heating wire is provided on the cylindrical core. And winding the core block into a cylindrical core to form an inner mold, and injection molding a molding layer made of a thermoplastic resin between the inner mold and the outer mold, The step of cooling the molding layer from the inside with the core block, the step of removing the outer mold and the core block, and the step of completely cooling the molding layer and then removing the cylindrical core removes the molding layer. Since the cooling can be preferentially performed from the inside, the cooling efficiency is excellent, and the so-called sink phenomenon due to the cooling does not appear on the inner surface, so that an electro-fusion joint having excellent inner surface dimensional accuracy can be obtained.

According to a third aspect of the present invention, there is provided a method for manufacturing an electrofusion joint, wherein a coolable core block is freely insertable into a pair of thin cylindrical cores arranged in series at predetermined intervals as an inner mold. Fixing a pair of cylindrical cores to both ends of a fixing jig, winding a heating wire on a pair of cylindrical cores, and attaching the pair of cylindrical cores to both ends of the fixing jig. A step of inserting the core block into the pair of cylindrical cores arranged in series at a predetermined interval after removing the fixing jig, and forming an inner mold by removing the fixing jig. And, while injection molding a molding layer made of a thermoplastic resin between the inner mold and the outer mold, a step of cooling the molding layer from the inside with the core block, and a step of removing the outer mold and the core block. And after completely cooling the molded layer, removing the pair of cylindrical cores Thus, the molded layer can be preferentially cooled from the inside, so that the cooling efficiency is excellent, and the so-called sinking phenomenon caused by cooling does not appear on the inner surface. Can be obtained.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an example of an inner mold used in the present invention. As shown in FIG.
Is composed of a thin cylindrical core 11 and a core block 12 which can be inserted into the core.

The cylindrical core 11 is formed of a thin cylindrical body.
The material of the cylindrical core 11 is not particularly limited, but is preferably a lightweight metal material having a high thermal conductivity from the viewpoints of handleability of the insert into the outer mold and cooling efficiency. For example, aluminum is preferably used. .

The thickness of the cylindrical core 11 is such that the resin-coated heating wire is not easily deformed while being wound therearound. It is necessary to have a thickness that can prevent the deformation of the resin layer at the stage of complete cooling, but if it is too thick, it becomes heavy and the handleability deteriorates. It is determined appropriately in consideration of the above.

In the cylindrical core 11, a core block can be inserted. The inner surface of the tubular core 11 is a tapered surface that gradually decreases in diameter from the upper end to the lower end so that the core block can be easily inserted.

The outer surface of the core block 12 is a tapered surface gently inclined toward the tip corresponding to the tapered surface of the inner surface of the cylindrical core 11, and a cooling pipe 121 is provided inside. The refrigerant is circulated in the cooling pipe 121 to be cooled. The material of the core block 12 is not particularly limited, but a metal having high thermal conductivity is preferably used to improve the cooling effect.

Next, an example of a method for manufacturing an electro-fusion joint of the present invention using the inner mold 1 shown in FIG. 1 will be described with reference to FIGS. First, in the first step, as shown in FIG. 2, the resin-coated heating wire 2 is wound on the cylindrical core 11 in a coil shape. At this time, it is preferable that the core die 3 is inserted into the cylindrical core 11 so that the cylindrical core 11 is not deformed by the winding force of the resin-coated heating wire 3.

In the second step, as shown in FIG. 3, the cylindrical core 11 on which the resin-coated heating wire 2 is wound is inserted into the outer mold 4 with the core mold 3 removed.

As a third step, as shown in FIG. 4, a core is wound inside the outer mold 4 in a cylindrical core 11 around which the resin-coated heating wire 2 is wound by an angular pin or the like in accordance with the mold clamping operation. The block 12 is inserted to form the inner mold 1, and the mold is clamped.

In a fourth step, as shown in FIG. 5, a molding layer 5 made of a thermoplastic resin is injection-molded between an inner mold 1 and an outer mold 4 on which a resin-coated heating wire 2 is wound, and a core is formed. The molding layer 5 is cooled from the inside for a predetermined time by circulating the refrigerant in the cooling pipe 121 of the block 12.

In the fifth step, as shown in FIG. 6, after the molding layer 5 has been cooled to some extent, the mold is opened, the outer mold 4 and the core block 12 are released, and then the molding layer 5 is placed inside the cylinder. While the core 11 is inserted, it is allowed to cool, and is completely cooled to near room temperature. In the last step, as shown in FIG. 7, the tubular core 11 is pulled out from the inside of the molding layer 5 to obtain an electrofusion joint 6 having a resin-coated heating wire embedded on the inner surface.

In the above example, when the resin-coated heating wire 2 is wound in a coil shape on the cylindrical core 11, the core mold 3 is inserted into the cylindrical core 11. Without using the mold 3, the core block 12 is inserted into the cylindrical core 11 from the beginning.
May be inserted to form the inner mold 1, and the resin-coated heating wire 2 may be wound on the inner mold 1.

In this case, the inner mold 1 on which the resin-coated heating wire 2 is wound is inserted into the outer mold 4 to perform mold clamping, and the inner mold 1 and the outer mold 4 on which the resin-coated heating wire 2 is wound. The molding layer 5 made of a thermoplastic resin is injection-molded between the above and the cooling medium is circulated in the cooling pipe 121 of the core block 12 to cool the molding layer 5 from the inside for a predetermined time. At this time, the inner side of the molding layer 5 is preferentially cooled.

After the molding layer 5 has been cooled to some extent, the mold is opened, the outer mold 4 is released, the core block 12 is released, and the cylindrical core 11 is inserted into the molding layer 5. In this state, the tubular core 11 is removed from the molded layer 5 and cooled down to near room temperature to obtain an electric fusion joint having a resin-coated heating wire embedded in the inner surface. .

FIG. 8 is a sectional view showing another example of the inner mold used in the present invention. As shown in FIG. 8, the inner mold 7 has a pair of thin cylindrical cores 71, 71 and a core that can be cooled in the pair of thin cylindrical cores 71, 71 arranged in series at a predetermined interval. The block 72 is configured to be freely inserted.

The pair of cylindrical cores 71, 71 are formed of a thin cylindrical body. The material, thickness, inner surface shape, and the like of the tubular cores 71, 71 are the same as those of the tubular core 11 described with reference to FIG. 1, and the structure, material, and the like of the core block 72 are also described with reference to FIG. Since it is the same as the core block 12, only the corresponding figure number is attached in the figure and the detailed description is omitted.

Next, another example of the electrofusion joint of the present invention using the inner mold 7 shown in FIG. 8 will be described with reference to FIGS. First, in the first step, as shown in FIG.
A pair of cylindrical cores 71 are fixed to both ends of the fixing jig 8.

The fixing jig 8 includes a first fixing jig piece 81 provided with a cylindrical core fixing concave portion 811 on one surface and two ribs 812 and 812 on the other surface, and a cylindrical jig on one surface. A core fixing recess 821 is provided, and two ribs 822 and 822 are provided on the other surface.
822 is provided with the second fixing jig piece 82.
The outer method of the ribs 812 and 812 of the first fixing jig piece 81 is as follows.
The inner diameter of the ribs 822 and 822 of the second fixing jig piece 82 is made equal to that of the ribs 822 and 822.

In the fixing jig 8, the first fixing jig piece 81 and the second fixing jig piece 82 are opposed to each other so that the rib surfaces are opposed to each other, and the ribs are spaced apart from each other. 812 and rib 822 can be fixed by bolts 83 and can be reduced when bolts 83 are removed. The cylindrical core 7 is inserted into the cylindrical core fixing recesses 811 and 821 provided at both ends.
The ends of 1, 71 are fixed respectively.

In the second step, as shown in FIG. 10, the resin-coated heating wire 2 is wound in a coil shape on the pair of cylindrical cores 71 in this state. In addition, any of the first step and the second step may be performed first.

In the third step, the resin-coated heating wire 2 is supplied to an outer mold (not shown) in a state where the pair of cylindrical cores 71, 71 are fixed to both ends of the fixing jig 8.

In the fourth step, as shown in FIG.
The fixing jig 8 is removed by removing the bolt 83 so that the distance between the first fixing jig piece 81 and the second fixing jig piece 82 is reduced. As a result, the pair of cylindrical cores 71, 71 are inserted into the outer mold in a state of being arranged in series at a predetermined interval. As shown in FIG. 12, the inner block 7 is formed by inserting a core block 72 into the pair of cylindrical cores 71 in this state.

In the fifth step, as shown in FIG.
After clamping, the inner mold 7 with the resin-coated heating wire 2 wound
The molded layer 9 made of a thermoplastic resin is injection-molded between the outer mold and the outer mold, and the refrigerant is circulated in the cooling pipe 721 of the core block 72 to cool the molded layer 9 from the inside for a predetermined time.

In the sixth step, as shown in FIG.
After the molded layer 9 has been cooled to some extent, the mold is opened, and the outer mold and the core block 72 are removed. In the last step, FIG.
As shown in FIG. 5, the tubular cores 71 are removed from the molded layer 9 to obtain an electro-fusion joint having the resin-coated heating wires 2 embedded in the inner surfaces of both ends.

[0036]

EXAMPLE 1 An electrofusion joint was manufactured by the steps described with reference to FIGS. The resin-coated heating wire 2 was wound in a coil shape on the cylindrical core 11 on which the core mold 3 was inserted. Resin-coated heating wire 2
As a Nichrome wire having a diameter of 0.6 mm, a polyethylene resin (manufactured by Mitsui Petrochemical Co., Ltd., trade name “HIZEX 630”)
0M ") and a diameter of 1.2 mm.

A cylindrical core 11 wound with a resin-coated heating wire 2
Is inserted into the outer mold 4 with the core mold 3 removed, and the core block 12 is inserted in accordance with the mold clamping operation as described with reference to FIG. Forming and clamping were performed. Using an injection molding machine (manufactured by Meiki Seisakusho, model “M # 35011”), a polyethylene resin (manufactured by Mitsui Petrochemical Co., Ltd., trade name “HIZEX 6300
M ”) was injection-molded between the inner mold 1 and the outer mold 4 to form a molded layer 5.

The molding layer 5 was cooled from the inside until the surface temperature of the molded product reached 70 ° C. by circulating the refrigerant in the cooling pipe 121 of the core block 12. Thereafter, the mold is opened, the outer mold 4 is released, and the core block 12 is released.
The molded layer 5 is allowed to cool for 30 minutes while the cylindrical core 11 is inserted therein, and is completely cooled to near room temperature. The cylindrical core 11 is pulled out from the molded layer 5 and the resin is applied to the inner surface. A socket-type electrofusion joint having an inner diameter of 90 mm and a wall thickness of 14 mm in which the coated heating wire was embedded was obtained. When the vertical and horizontal dimensional errors of the inner diameter of the obtained electrofusion joint were measured, it was 0.2 m
m.

A resin-coated heating wire was applied to the inner surface according to the embodiment, except that it was manufactured by the method described with reference to FIG. 16 and that the molded product was cooled in a mold until the surface temperature of the molded product reached 90 ° C. Was embedded, and a socket-type electrofusion joint having an inner diameter of 90 mm and a thickness of 14 mm was obtained. When the vertical and horizontal dimensional errors of the inner diameter of the obtained electrofusion joint were measured, it was 0.5 m
m.

Example 2 An electrofusion joint was manufactured by the steps described with reference to FIGS. The resin-coated heating wire 2 was wound on a pair of cylindrical cores 71 fixed to both ends of the fixing jig 8. As the resin-coated heating wire 2, the same one as in Example 1 was used.

After inserting a pair of cylindrical cores 71, 71 wound with the resin-coated heating wire 2 into the outer mold while being fixed to both ends of the fixing jig 8, the fixing jig 8 is removed, and The inner block 7 was formed by inserting the core block 72. After the mold clamping, a molding layer 9 made of the same polyethylene resin as in Example 1 was injection-molded between the inner mold 7 wound with the resin-coated heating wire 2 and the outer mold.

The molded layer 9 was cooled from the inside until the surface temperature of the molded product reached 70 ° C. by circulating the refrigerant in the cooling pipe 721 of the core block 72. Thereafter, the mold is opened, and the outer mold and the core block 72 are removed from the mold. Then, the molded layer 9 is removed with the cylindrical cores 71 and 71 inserted therein.
After leaving to cool to near room temperature for 0 minutes, the cylindrical cores 71, 71 were pulled out of the molding layer 9, and the resin-coated heating wires 2 were embedded in the inner surfaces of both ends, the inner diameter was 90 mm, and the wall thickness was 14 m.
Thus, a socket-type electrofusion joint having a length of m was obtained. When the vertical and horizontal dimensional errors of the inner diameter of the obtained electrofusion joint were measured, it was found that the inner diameter of the electrofused joint was 0.1 mm.
2 mm.

[0043]

As described above, the method for manufacturing an electro-fusion joint of the present invention has a good cooling efficiency in a mold,
An electro-fusion joint having excellent inner surface dimensional accuracy can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an inner mold used in the present invention.

FIG. 2 is a cross-sectional view illustrating a first step of an example of the method for manufacturing an electro-fusion joint according to the present invention.

FIG. 3 is a second example of an example of the method for producing an electrofusion joint of the present invention.
It is sectional drawing explaining a process.

FIG. 4 shows a third example of the method for producing an electro-fusion joint according to the present invention.
It is sectional drawing explaining a process.

FIG. 5 is a diagram illustrating a fourth example of the method for manufacturing the electro-fusion joint according to the present invention.
It is sectional drawing explaining a process.

FIG. 6 shows a fifth example of the method for producing an electro-fusion joint according to the present invention.
It is sectional drawing explaining a process.

FIG. 7 is a cross-sectional view illustrating the last step of the example of the method for manufacturing an electro-fusion joint according to the present invention.

FIG. 8 is a cross-sectional view showing another example of the inner mold used in the present invention.

FIG. 9 is a cross-sectional view illustrating a first step of another example of the method for manufacturing an electro-fusion joint according to the present invention.

FIG. 10 is a cross-sectional view illustrating a second step and a third step of another example of the method for manufacturing an electro-fusion joint of the present invention.

FIG. 11 is a cross-sectional view illustrating a fourth step of another example of the method for producing an electro-fusion joint of the present invention.

FIG. 12 is a cross-sectional view illustrating a fourth step of another example of the method for manufacturing an electro-fusion joint of the present invention.

FIG. 13 is a cross-sectional view illustrating a fifth step of another example of the method for manufacturing an electro-fusion joint of the present invention.

FIG. 14 is a cross-sectional view illustrating a sixth step of another example of the method for manufacturing an electro-fusion joint of the present invention.

FIG. 15 is a cross-sectional view illustrating the last step of another example of the method for manufacturing an electro-fusion joint according to the present invention.

FIG. 16 is a cross-sectional view illustrating an example of a conventional method for manufacturing an electric fusion joint.

[Explanation of symbols]

 1,7 Inner mold 2 Resin-coated heating wire 5,9 Forming layer 6 Electric fusion joint 8 Fixing jig 11,71 Cylindrical core 12,72 Core block 121,721 Cooling pipe

Claims (3)

[Claims] 1. A method for manufacturing an electro-fusion joint having a built-in heating wire using an inner mold and an outer mold, wherein a coolable core block is inserted into a thin cylindrical core as the inner mold. After injection molding or injection molding a molding layer made of a thermoplastic resin between the inner mold and the outer mold wound with a heating wire, the molding layer was cooled from the inside with a core block. Removing the outer mold and the core block, and after completely cooling the molded layer, removing the cylindrical core. 2. A method for manufacturing an electro-fusion joint having a built-in heating wire using an inner mold and an outer mold, wherein a coolable core block is inserted into a thin cylindrical core as the inner mold. The step of winding a heating wire on a cylindrical core using a flexible one, the step of forming an inner mold by inserting a core block in the cylindrical core, and the step of forming an inner mold and an outer mold Injection molding a molding layer made of a thermoplastic resin between the two, cooling the molding layer from the inside with the core block, removing the outer mold and the core block, and completely cooling the molding layer. Removing the core from the mold. 3. A method of manufacturing an electro-fusion joint having a built-in heating wire using an inner mold and an outer mold, wherein the inner mold includes a pair of thin cylinders arranged in series at a predetermined interval. Fixing a pair of cylindrical cores to both ends of a fixing jig using a core block capable of being inserted into a core block that can be cooled in a cylindrical core,
A step of winding a heating wire on a pair of cylindrical cores, a step of inserting the pair of cylindrical cores into the outer mold while fixing the pair of cylindrical cores at both ends of the fixing jig, and after removing the fixing jig, A step of inserting a core block into a pair of cylindrical cores arranged in series at intervals to form an inner mold, and injecting a molding layer made of a thermoplastic resin between the inner mold and the outer mold. Forming and cooling the molding layer from the inside with the core block, removing the outer mold and the core block, and removing the pair of cylindrical cores after completely cooling the molding layer. What is claimed is: 1. A method for manufacturing an electric fusion joint, comprising: