JPH11287383A - Coil for electrofusion and joint and bulb - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate covering a heating wire by resin by surrounding the inner periphery or the outer periphery of the coil part of the heating wire wound in a coil shape used to join piping by thermal fusion with a cylindrical body composed of a thermoplastic film forming a large number of holes, and integrally forming the film and a coil by heating. SOLUTION: A large number of holes 2a are bored in a cylindrical body 2 formed of a thin resin film, the outer periphery of a heating wire 1 wound in a coil shape is surrounded by this cylindrical body 2, and the inner periphery of the cylindrical body 2 is melted by carrying an electric current to the heating wire 1 to form a coil for electrofusion by integrally fixing the cylindrical body 2 and the heating wire 1. When molding an electrically fusible pipe joint and a bulb body, injection molding is performed by installing the heating wire 1 integrally formed with the cylindrical body 2 in a core in a metal mold for molding the connecting part of the joint and the bulb body. At this time, an electric current can be carried to the heating wire 1 by connecting an electric power source to this connector pin after fixing the connector pin to both ends of the heating wire 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrofusing coil used for joining pipes by heat fusion, and a joint and a valve using the same.

[0002]

2. Description of the Related Art Conventionally, when manufacturing an electrofusion joint, as disclosed in Japanese Patent Application Laid-Open No. 3-244896, a heating wire coated with a resin is wound around a mold core, and the heating wire is wound around the mold core. The company manufactures resin joints with built-in heating wires by injecting synthetic resin.

[0003] In addition, there has been proposed a method of manufacturing a joint or the like by mounting a fixed heating wire wound in a coil shape in a mold. For example, in JP-A-5-157189, a spiral groove is formed in the outer periphery of a resin bobbin along the axial direction, and a heating wire is wound in a coil shape along the groove to fix the heating wire. doing.

In Japanese Patent Application Laid-Open No. Hei 3-30931,
A resin-made linear member that covers the heating wire is formed in an uneven shape, and when wound in a coil shape, the uneven portions of adjacent linear members are connected and fixed.

Further, in Japanese Patent Application Laid-Open No. 1-164889, a heating wire covered with a resin is wound in a coil shape around a cylindrical body, the cylindrical body or the coating resin is heated, and the adjacent coated resins are melted and integrated. And fix it.
In Japanese Patent No. 51997, a heating wire coated with a resin is wound in a coil shape, and adjacent coated resins are partially fused at one or more locations on the outer periphery and fixed so as not to separate.

[0006]

However, the above-mentioned prior art has the following problems. That is, JP-A-3-
The method described in Japanese Patent No. 244896 has a small cost burden, but it is very difficult to accurately embed the heating element at a desired position due to the pressure and speed during injection molding.

In the method described in Japanese Patent Application Laid-Open No. 5-157189, it is necessary to manufacture a bobbin molding die when molding a main body such as a joint. At the time of integral molding, there has been a problem that poor fusion is likely to occur due to the outer surface of the bobbin being oxidized.

The method described in Japanese Patent Application Laid-Open No. 3-30931 has a large shape in consideration of rigidity due to injection pressure and speed, and has no product value including cost.

Japanese Patent Application Laid-Open No. 1-164889 and Japanese Patent Publication No.
In the method described in Japanese Patent No. 51997, when only the coating resin is heat-sealed, it is necessary to pay sufficient attention to the management based on the fusing temperature and time, and since the once fused portion of the coating resin is oxidized, There is a high possibility that adhesion to the resin for molding the body of the joint or the like becomes insufficient, and there is a problem that the mold slide core is easily damaged when mounted.

The present invention has been developed in view of the conventional problems, and its object is to not only reduce the cost with a simple structure, but also to reduce the cost when molding joints and valves. An object of the present invention is to provide an electrofusion coil that does not hinder the flow of resin, and to provide a joint and a valve using the coil.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a tube made of a thermoplastic film having a number of holes formed on an inner or outer periphery of a coil portion of a heating wire wound in a coil shape. It is surrounded by a body, and the film and the coil are integrated by heating.

The thus formed electrofusion coil is integrally formed on the inner or outer periphery of the connection portion of the thermoplastic resin joint, or is integrally formed on the inner or outer periphery of the connection portion of the thermoplastic resin valve. Furthermore,
It is preferable that the melting point of the thermoplastic film is higher than that of the thermoplastic resin at the joint of the joint or the valve.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an electrofusion coil of the present invention, and a joint and a valve using the same will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a heating wire wound in a coil shape, 2 denotes a cylindrical body formed of a thin resin film,
A large number of holes 2a are formed in the cylindrical body 2. Then, the outer periphery of the heating wire 1 wound in a coil shape by the cylinder 2 is surrounded, and the cylinder 2 and the heating wire 1 are fixedly integrated by heating. In this step, for example, the heating wire 1 is wound around a rod-shaped jig (not shown) in a coil shape, and the outer periphery thereof is
And heat is applied to the heating wire 1 to melt the inner periphery of the cylindrical body 2 so that the heating wire 1 is fixedly integrated. Alternatively, the tubular body 2 is heated to be integrated with the heating wire 1. This integration is for the purpose of maintaining the shape, and may be in a temporarily fixed state.

Further, as shown in FIG. 5, the heating wire 1 may be integrated with the outer periphery of the cylindrical body 2. In this case, a rod-shaped jig (not shown) is inserted into the cylindrical body 2 and the heating wire 1 is wound around the outer periphery of the cylindrical body 2 with a predetermined tension to heat the heating wire 1 or to heat the cylindrical body 2. Thereby, the heating wire 1 and the cylindrical body 2 are integrated.

As a method of winding the heating wire 1, a method of winding a single wire as shown in FIG. 3 and a method of winding a coil in a parallel state in which the heating wire 1 is double bent at the center as shown in FIG. There is. When the heating wire 1 is wound as in the latter case, the connector pins 22 and 23 fixed to the ends of the heating wire 1 can be projected in the same direction when a joint or the like is formed (see FIGS. 4 and 5). .

[0017] The electrofusion type pipe joint 10, shown in Figs.
When molding the valve body 20 shown in FIG.
Connections 11 and 12 of joints 10 and 30 and valve body 20
The heating wire 1 integrated with the cylindrical body 2 is attached to a core in a mold for forming the first and 31 and injection molding is performed. At this time, connector pins 12, 22, and 32 are fixed to both ends of the heating wire 1. By connecting a power source to the connector pins 12, 22, and 32, the heating wire 1 can be energized.

FIG. 3 is a partial sectional view of an embodiment of a joint made of a thermoplastic resin. In the case of this joint 10, a heating wire 1 integrated with a cylindrical body 2 is provided on the inner periphery of a connecting portion 11 on both sides. Are provided, and connector pins 12 for connecting a power source are provided at upper portions on both sides of each connection portion 11.

FIG. 4 is a sectional view of one embodiment of the valve body. In the case of this valve body 20 as well, the heating wire 1 is integrated with the inner circumference of the connecting portion 21 and the inner circumference of the cylindrical body 2. The power supply side connector is inserted into the outer peripheral portion of the heating wire 1 and two connector pins 22 fixed to both ends of the heating wire 1 are projected into the fitting cylindrical portion 23. Has been established. The heating wire 1 is, like the heating wire 1 shown in FIG. 5, double-folded at the center and wound around the outer periphery of the cylindrical body 2 in a parallel state. The valve body 20
In the above, the connecting portion 22 is formed of a thermoplastic resin, and the other portion 24 is formed of metal. That is, as long as the connecting portion 22 in which the heating wire 1 is embedded is formed of at least resin, the entire body does not need to be formed of resin.

FIG. 5 is a partial cross-sectional view of another embodiment of a joint made of a thermoplastic resin.
The heat generating wire 1 integrated with the outer periphery of the cylindrical body 2 is connected to the connecting portion 31.
And two connector pins 32 projecting from a central portion of the connection portion 31 for connecting a power source. Also in this case, the heating wire 1 is double-folded at the center and wound around the outer periphery of the cylindrical body 2 in a parallel state.

When a resin joint or a connecting portion of a valve body (hereinafter referred to as a joint) is formed as described above, the resin of the cylinder 2 is a resin having a melting point slightly higher than that of the joint. Is preferred. By increasing the melting point, the cylindrical body 2 is not melted at the time of forming the joints, so that the heating wire 1 fixed in a coil shape can be prevented from being deformed. Moreover, breakage, deformation, and the like at the time of mounting the mold core can be prevented.

Further, since a large number of holes 2a are provided in the cylindrical body 2, the molten resin can pass through the holes 2a and spread evenly to the side of the heating wire at the time of forming joints, thereby preventing poor filling. Heating wire 1 located on inner or outer circumference of cylindrical body 2
The molten resin can smoothly flow around the surroundings. As described above, since the joints can be formed in a state where the resin is wrapped around the heating wire 1, the joints and the resin pipe and the like can be reliably fused.

The resin used for the cylinder 2 and the joints is a thermoplastic resin, for example, a polyolefin resin such as polybutene, polyethylene, or polypropylene;
Polyvinyl chloride, polystyrene, or polyolefin is converted to an unsaturated carboxylic acid or its anhydride (maleic anhydride,
Benzoyl peroxide, acrylic acid, methacrylic acid, etc.). The heating wire used in the present invention may be either a bare wire or a resin-coated wire. In the latter case, the wires may be close to each other.

[0024]

As is evident from the above, according to the present invention, the heating wire is not covered with the resin, so that the cost can be significantly reduced, and the melting temperature can be reduced when forming the joints such as joints and valves. Since the resin flows between the heating wires and through the holes of the cylinder, the resin has good fixation to the heating wires and the cylinder, and can suppress molding defects. Further, the heating wire can be easily formed into a coil shape, and can also be fixed in a highly accurate position when being fixed in the mold, and the fixing operation can be easily performed, so that the operation time can be reduced.

[0025] Even when molding joints such as joints and valves, molding can be performed with a specially formed slide core, so that capital investment can be suppressed.

[Brief description of the drawings]

FIG. 1 is an exploded view of an electrofusion coil according to the present invention.

FIG. 2 is a cross-sectional view showing one embodiment of an electrofusion coil according to the present invention.

FIG. 3 is a partial cross-sectional view showing an embodiment of a joint using the electrofusion coil.

FIG. 4 is a cross-sectional view showing one embodiment of a valve body using another embodiment of the electrofusion coil according to the present invention.

FIG. 5 is a partial cross-sectional view showing one embodiment of a joint using another embodiment of the electrofusion coil according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating wire 2 Cylindrical body 2a Hole 10, 30 Joint 12, 22, 32 Connection part 20 Valve body

Claims (4)

[Claims] An inner or outer periphery of a coil portion of a heating wire wound in a coil shape is surrounded by a cylindrical body made of a thermoplastic film having a large number of holes, and the film and the coil are integrated by heating. Electrofusion coil. 2. A thermoplastic resin joint in which the electrofusion coil is integrally formed on the inner periphery or outer periphery of a connecting portion. 3. A thermoplastic resin valve in which the electrofusion coil is integrally formed on the inner periphery or outer periphery of a connecting portion. 4. A thermoplastic resin joint or valve in which the melting point of the thermoplastic film is higher than that of the thermoplastic resin according to claim 2.