JP2530785B2 - Method for manufacturing electric fusion joint - Google Patents

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, which is suitable for use in a liquid transportation line, particularly in a water or ultrapure water transportation line for producing foods, medicines and the like. It is a thing.

[0002]

2. Description of the Related Art Conventionally, as an electric fusion joint used for joining a thermoplastic resin pipe of polyethylene, polypropylene or the like, welding means composed of an electric heating element is buried in the inner peripheral portion of the pipe receiving port. After inserting the thermoplastic resin tube into the pipe receiving port, energize the current-carrying heating element to generate heat, and melt the resin on the inner peripheral part of the pipe receiving port and the outer peripheral part of the thermoplastic resin pipe in contact with it.
A "sleeve joint" is used in which a thermoplastic resin tube and an electric fusion joint are fused to each other.

In order to manufacture such an electric fusion joint,
Basically, a linear mandrel (core) with a linear electric heating element directly wound around the outer periphery of the mold is inserted into the outer mold of the mold, and the molten resin is inserted into the cavity formed between them. Injection-filling and removing the mandrel (JP-A-63-
No. 71323), a molded body (bobbin) forming the inner surface of the electric fusion joint is preliminarily molded, and a linear electric heating element is spirally wound around the outer peripheral surface of the bobbin, and then the bobbin is set on the mandrel. And injection molding in the same manner as described above (Japanese Patent Application Laid-Open No. 59-13180).
(Refer to the official gazette), and two methods are used.

In the above manufacturing method, the step of winding the electric heating element around the mandrel or bobbin has a simple structure in which the electric heating element is spirally embedded only in the inner peripheral portion of the cylindrical pipe receiving port. Therefore, the object can be easily achieved by moving the mandrel or the bobbin or the drum of the winding machine in the axial direction while rotating the mandrel or the bobbin.

[0005]

However, in the above-mentioned conventional electric fusion joint, since the electric heating element is provided only on the cylindrical inner peripheral portion of the pipe receptacle of the electric fusion joint, a thermoplastic resin pipe is provided. Even if the end surface of the electric fusion joint is in contact with the stopper of the electric fusion joint, the resin at the end surface portion of the thermoplastic resin pipe or the electric fusion joint is not melted enough to cause fusion, and the so-called " The butt joint (butt joint) is performed in an incomplete state. As a result, a gap is formed in the abutting portion due to poor melting of the resin, water is retained, and the water quality is deteriorated due to putrefaction and inhabitation / proliferation of bacteria. For this reason, it has been impossible to use the above-described conventional electric fusion splicing joints in applications such as production lines for foods, pharmaceuticals, semiconductors, etc., where extremely high quality water is required.

Therefore, the inventor has proposed an electric fusion splicing joint which can be used for handling such extremely high-purity water (Japanese Patent Application No. 250647 in 1991). In this new electric fusion joint, the electric heating element is embedded not only in the inner peripheral portion of the pipe receiving port but also in the stopper, and not only the sleeve joining but also the butt joining at the abutting surface is completely performed. It is a feature.

However, in the case of this new electric fusion-bonding joint, since the electric heating element is buried in the stopper,
Unlike the conventional electric fusion joint, it is necessary to wind the energization heating element in a spiral shape in the plane perpendicular to the axis of the electric fusion joint at the stopper portion, but this is not possible with the conventional manufacturing method. It was

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing the above-mentioned novel electric fusion joint.

[0009]

In order to achieve the above object, in the method for manufacturing an electric fusion joint of the present invention, an electric heating element is embedded in an inner peripheral portion of a pipe receiving port made of a thermoplastic resin and a stopper. A method for manufacturing an electric fusion-bonded joint, wherein an electric heating element covered with an electric insulating layer of a thermoplastic resin is formed in a stopper portion molding annular groove formed by a pair of axially divided mandrels, A step of winding from the bottom of the annular groove to the height of the outer peripheral surface of the mandrel, a step of spirally winding the electric heating element on the outer peripheral surface of the mandrel, and fixing the mandrel wound with the electric heating element in a mold. , A step of injecting and filling a molten thermoplastic resin into the cavity formed by the mandrel and the outer mold, a step of opening the mold to take out the electric fusion joint of the product, and pulling out the mandrel are summarized. It is intended to.

Further, as a method of winding the electric heating element along the side wall of the stopper portion forming annular groove formed by the pair of mandrels, a support ring is attached to the stopper portion forming annular groove formed by the pair of mandrels. In the annular gap formed by the support ring and the mandrel,
The gist of the present invention is to wind up the above-mentioned energization heating element.

Further, the gist of the present invention is to heat and fuse the surface of the electrically insulating layer above its melting temperature prior to the thermoplastic resin injection filling step. As the thermoplastic resin used in the present invention, polyethylene,
General-purpose thermoplastic resin such as polypropylene, polyvinyl chloride, ABS, polyamide, polyvinylidene fluoride, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polysulfide, polyether sulfone, polyether ether ketone, crystalline or non-crystalline such as polyimide A crystalline thermoplastic engineering resin or the like is used, but it is preferably the same as the thermoplastic resin pipe to be joined or a resin having a good compatibility with this.

An electric heating element coated with an electrically insulating layer of a thermoplastic resin used in the present invention (hereinafter referred to as "coated electric heating element").
Refers to a heating wire such as a nichrome wire, a monofilament of carbon fiber or a twisted wire thereof, which is covered with an electrically insulating layer made of the above-mentioned thermoplastic resin, and has a circular or square cross section. It may be rectangular or the like, and can be manufactured by a method such as extrusion molding (electric wire coating molding) or passing through a molten resin.

The electric fusion joint manufactured by the method of the present invention may be one in which the electric heating element is exposed and embedded in the side surface of the stopper (the contact surface of the ends of the thermoplastic resin tube). Further, it may be embedded in the meat near the center of the width of the stopper.

Details will be described below in the embodiments.

[0015]

Function: Assembling the mandrel into two parts to form an annular groove for forming the stopper portion of the electric fusion joint, and in the annular groove, in the direction perpendicular to the axis of the electric fusion joint, from the bottom of the annular groove to the outer peripheral surface of the mandrel. By winding the coated electric heating element in a spiral shape up to the height of, the electric heating element embedded in the stopper portion of the electric fusion joint can be arranged. Since the heating wire is wrapped around the energized heating element covered with an electrically insulating layer of thermoplastic resin, a bare heating wire does not come into contact with the heating wire to cause a short circuit.

Further, since the support ring is mounted in the annular groove, an annular gap is provided between the side wall of the annular groove and the support ring, and the coated electric heating element is spirally wound in the annular gap. The annular gap width for winding can be appropriately maintained according to the width of the coated electric heating element, and the winding operation can be easily performed.

Prior to the thermoplastic resin injection filling step, the electrically insulating layer is heated to a temperature above its melting temperature to melt and fuse the surface, whereby the coated electric heating element is kept in a constant shape on the mandrel. Also, it does not move or lose its shape due to the injection pressure at the time of thermoplastic resin injection filling.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings by embodiments. FIG. 1 is a cross-sectional view showing an embodiment of an electric fusion joint manufactured according to the present invention, in which a substantially cylindrical electric fusion joint is provided with inner peripheral portions of tube receiving ports 2a and 2b on both sides and stoppers. An energization heating element 4 is embedded in both side surfaces of 3, that is, in the vicinity of the contact surfaces of the ends of the thermoplastic resin tube, and both ends thereof are connected to terminals 5 and 5. More specifically, the electric heating element 4 is spirally wound in the opposite direction on the left pipe receiving port 2a side and the right pipe receiving port 2b side, and in the vicinity of both side faces of the stopper 3, along the both side faces. Spirally wound from the vicinity of the inner surface of the stopper 3 to the inner peripheral portions of the pipe receiving ports 2a and 2b. Then, the crossover portion 41 of the electric heating element 4 crosses one portion of the stopper 3 and the left pipe receiving port 2
The structure is continuous from the a side to the right pipe receiving port 2b side.

Next, the main manufacturing equipment used in the present invention will be described. FIG. 2 is an explanatory view of an assembly of a mandrel and a support ring used in the method for manufacturing the electric fusion joint 1 of FIG. 1, and FIG. 3 is an explanatory view of the support ring.

In FIG. 2, a pair of steel mandrels 6 are provided.
Is the mandrel half 6 divided into left and right in the axial direction.
It is assembled by connecting a and 6b. The mandrel halves 6a and 6b are provided with connecting means such as bolts and nuts for connecting and disassembling them and positioning means such as guide pins, but they are omitted in the figure.

The outer peripheral surfaces 6s of the mandrel halves 6a, 6b,
6s is formed in a substantially cylindrical shape in order to form the tube receiving ports 2a, 2b of the electric fusion joint 1. In addition, since the mandrel halves 6a and 6b are butt-connected,
A stopper portion forming annular groove 7 for forming the stopper 3 of the electric fusion joint 1 shown in FIG. 1 is formed, and a support ring is formed on the bottom portion 7c of the stopper portion forming annular groove 7, that is, the minimum outer diameter portion of the mandrel half 6a. 8 is fixed (although only the upper half of the support ring 8 is shown in FIG. 2).

The support ring 8 is made of a metal such as steel or brass, and as shown in FIG. 3, it is composed of support ring halves 8a and 8b which are diametrically divided into two parts. It is formed so that they can be connected to each other and disassembled by other suitable connecting means and can be fixed to the bottom portion 7c of the stopper-forming annular groove 7 of the mandrel half 6a. Further, when the support ring halves 8a and 8b are connected, a gap 9 through which the coated electric heating element 10 can pass is formed over the entire length of one mating surface. Further, when the support ring 8 is fixed to the mandrel 6, the coating energization heating element is present in the two annular gaps Ha, Hb formed by the side walls 7a, 7b of the stopper portion forming annular groove 7 and both side surfaces of the support ring 8. It can be accommodated, and furthermore, the coated electric heating element and the annular gaps Ha, Hb
It is essential that there is not much "play" between the two. Therefore, the width r of the support ring 8 is determined by the stopper portion forming annular groove 7
Where h is the width and m is the width of the cross-section of the energized heating element, h
-It is formed in a size slightly smaller than -2 m.

Thus, the two annular gaps Ha and Hb are formed by the side walls 7a and 7b of the stopper-forming annular groove 7, the bottom portion 7c and both side surfaces of the support ring 8, and the support ring 8 is formed.
They are communicated by the gap 9.

Next, a method of winding the coated electric heating element will be described. FIG. 4 is an explanatory view showing a state in which the coated electric heating element 10 is wound around the assembly of the mandrel 6 and the support ring 8.

The assembly of the mandrel 6 and the support ring 8 assembled as described above is mounted on the winding machine M, and the coated electric heating element 10 is provided between the two drums on the left and right of the winding machine M. When the central portion of the above is inserted into the gap 9 of the support ring 8 and the assembly of the mandrel 6 and the support ring 8 is rotated by 1/2 by the winding machine, the coated energization heat generating element 10 has a stopper portion inside the gap 9. The crossover portion 41 is formed by reaching the bottom portion 7c of the molding annular groove 7. When the assembly of the mandrel 6 and the support ring 8 is subsequently rotated, the coated electric heating element 10
In the two annular gaps Ha, Hb along the side walls 7a, 7b of the stopper forming annular groove 7 from the bottom 7c.
Is wound up to the height of the outer peripheral surfaces 6s, 6s.

The coated electric heating element 10 has annular gaps Ha, Hb.
When it reaches the height of the outer peripheral surfaces 6s, 6s after being wound inside, the two drums of the winding machine are moved along the outer peripheral surfaces 6s, 6s at both ends (left and right) at a constant speed to cover. The energization heating element 10 is wound around the outer peripheral surfaces 6s, 6s in a predetermined number of turns in a spiral shape, after which the winding operation is stopped, and the terminals are connected and fixed.

The coated electric heating element 10 wound as described above injects a thermoplastic resin for molding the electric fusion joint 1 so that it does not move or lose its shape due to the injection pressure of the molten resin. Prior to the step of filling, it is extremely preferable to heat the electric insulating layer of the coated electric heating element 10 to a melting temperature or higher to melt and fuse the surface, and the mandrel 6 after the coated electric heating element 10 has been wound. And preferably before removing the support ring 8 from the support ring 8 assembly.

As a method for this, at a temperature not lower than the melting temperature of the thermoplastic resin forming the electric insulating layer of the coated electric heating element 10,
The surface of the mandrel 6, in particular, the surfaces of the side walls 7a and 7b of the stopper-forming annular groove 7 are preheated and wound, and wound while heating, and the surface of the coated electric heating element 10 is wound while heating with hot air or the like. Alternatively, it is possible to energize the coated energization heating element 10 to heat it after the coated energization heating element 10 has been wound (before charging into the mold).

Then, in this manner, the coated electric heating element 1
The support ring 8 is removed from the assembly of the mandrel 6 and the support ring 8 in which the surface of the electrical insulation layer is melted and fused, and the metal having a structure divided into two in the plane including the shaft is formed as shown in FIG. The molten thermoplastic resin is injected into the cavity C formed by the mandrel 6 around which the energization heating element 10 is wound around and the outer mold 11 from the injection hole 12 and then solidified by cooling. Then, the outer mold 11 is opened to take out the electric fusion splicing joint 1 in which the mandrel 6 is still inserted, and then the mandrel 6 is disassembled into mandrel halves 6a and 6b and removed to obtain a product. Outer mold 1
1, sleeves 13, 13 for molding the terminals 5, 5
Is attached, but is removed after injection filling the resin.

In the above embodiment, the support ring 8 is made of metal. However, the support ring 8 is made of the same thermoplastic resin as the electric fusion joint 1 or a thermoplastic resin having good compatibility therewith.
The molten resin may be injected and filled without being removed while being fixed to the mandrel 6 and embedded in the electric fusion joint 1.

Further, the boss 81a is made of a thermoplastic resin and is not a two-divided structure as shown in FIG. 3, but is slightly longer than the width h of the stopper portion forming annular groove 7 as shown in FIG.
And a gap 9a may be formed as an integral structure. With such a structure, the boss 81a can be sandwiched and fixed by the mandrel halves 6a and 6b, and the widths of the annular gaps Ha and Hb can be set uniformly and easily.

The mandrel of FIG. 2 has a cylindrical shape with a smooth outer surface, but it facilitates winding of the energized coating heating element 10 or the energization heating of the coating by injection pressure of the molten resin during injection filling. In order to prevent the body 10 from moving,
A spiral groove having a predetermined pitch may be provided on the cylindrical surface.

In the above embodiment, the electric heating element is buried in the vicinity of both side surfaces of the stopper (contact surfaces of the ends of the thermoplastic resin tube), but the electric heating element is The same manufacturing method can be applied to the case of the electric fusion joint embedded in the meat near the center of the stopper.

[0034]

As is apparent from the above description, according to the method of manufacturing the electric fusion joint of the present invention, the electric fusion member in which the electric heating element is embedded not only in the inner peripheral portion of the pipe receiving port but also in the stopper is provided. It is possible to easily manufacture a fusion splicing joint, and it can be used for manufacturing an electric fusion splicing joint suitable for use in handling extremely high-purity water.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of an electric fusion joint manufactured according to the present invention.

FIG. 2 is an explanatory view of an assembly of a mandrel and a support ring.

FIG. 3 is an explanatory diagram of a support ring.

FIG. 4 is an explanatory view showing a state in which a coated electric heating element is wound around an assembly of a mandrel and a support ring.

FIG. 5 is an explanatory view showing a state in which an assembly of a mandrel wound with a coated electric heating element and a support ring is mounted on an injection molding die.

FIG. 6 is an explanatory view showing another embodiment of the support ring.
(A) is a front view. (B) is a sectional view taken along line XX of (A).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrofusion joint 2a, 2b Pipe socket 3 Stopper 4 Electric heating element 41 Crossover part 6 Mandrel 6a, 6b Mandrel half 6s Outer peripheral surface 7 Stopper molding annular groove 7a, 7b Side wall 7c Bottom 8,81 Support ring 8a , 8b Support ring half body 81a Boss 9,9a Gap 10 Coated electric heating element 11 Outer type Ha, Hb Annular gap

Claims (3)

(57) [Claims] 1. A method of manufacturing an electric fusion joint in which an electric heating element is embedded in an inner peripheral portion of a pipe receiving port made of a thermoplastic resin and a stopper, which is coated with an electric insulating layer of a thermoplastic resin. A step of winding the energization heating element in a stopper portion forming annular groove formed by a pair of mandrels divided in the axial direction from the bottom of the annular groove to the height of the outer peripheral surface of the mandrel, Spirally winding the outer peripheral surface, fixing the mandrel wound with the electric heating element in a mold, and injecting a molten thermoplastic resin into a cavity formed by the mandrel and the outer mold by injection, A method for producing an electric fusion joint, comprising the steps of opening the mold, taking out the electric fusion joint of the product, and pulling out the mandrel. 2. A support ring is mounted in an annular groove for forming a stopper portion formed by a pair of mandrels, and an annular gap formed by the support ring and the mandrel is coated with an electrically insulating layer of thermoplastic resin to generate heat. The method for producing an electric fusion joint according to claim 1, wherein the body is rolled up. 3. The electricity according to claim 1, wherein the electric insulating layer is heated to a temperature equal to or higher than its melting temperature to melt and fuse the surface prior to the thermoplastic resin injection filling step. Manufacturing method of fusion spliced joint.