JPH0459319A - Manufacture of welding joint - Google Patents

Abstract

PURPOSE:To constitute the above method so that an electric conducting wire is not short-circuited, by a method wherein winding tension of a coated electric conducting wire in a winding process is set up to a strength calculated based on the coefficient of linear expansion of the electric conducting wire. CONSTITUTION:A coated electric conducting wire 3 to be fed through a bobbin 4 is passed through a tension adjusting device 2 and wound round a mandrel 12 of a mold 1 while pulling out through the tension adjusting device 2. At this time, the tension adjusting device 2 sets up winding tension P at the time of winding of the coated electric conducting wire 3 round the mandrel 12 so that the same becomes strength calculated based on a formula. Thermoplastic resin pipes P1, P2 are inserted respectively into a joint main body through opening ends. Fixed voltage is applied to a space between terminals 5, 5 for electrification and an electric conducting wire 72 is heated. Then an internal circumferential part of a joint main body 71 and external circumferential parts of synthetic resin pipes P1, P2 are molten by heat and a welding joint 7 and the synthetic resin pipes P1, P2 are welded and joined to each other. With this construction, the electric conducting wire 72 is expanded and even if resin on the circumference of the electric conducting wire 72 is molten and moved, short circuit of the electric conducting wire 72 is hard to occur.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a welded joint for welding and joining synthetic resin gas pipes and water pipes.

(Prior Art) Conventionally, as a manufacturing method of a welded joint in which a joint body is formed in a cylindrical shape and a conductive wire is embedded in a spiral shape in the inner circumference of the joint body, for example, Japanese Patent Application Laid-Open No. 59-13180 is known. Manufacturing methods such as those described in publications are known.

In this conventional method, a cylindrical body molded from thermoplastic resin is placed around the outer periphery of a mandrel, and a conductive wire is then wound around the cylindrical body while heating. This is a method of injection molding by placing a mandrel provided with a mold in a mold.

(Problem to be Solved by the Invention) By the way, in such a conventional manufacturing method, by wrapping a conductive wire around the outer periphery of a cylindrical body while heating it, the conductive wire heats up the cylindrical body by its own heat. Since the conductive wire was encapsulated at the outer periphery, the winding tension of the conductive wire was set so that the conductive wire was encapsulated at an optimum depth. In this case, when the pipe is inserted into the welding joint and welded and joined, the conductive wire undergoes linear expansion, so generally the winding tension of the conductive wire is insufficient, and as a result, the resin around the conductive wire melts. There was a problem in that the conductive wires were prone to short circuits during movement.

The present invention focuses on the above-mentioned problems and provides a method for manufacturing a welded joint in which short-circuiting of the conductive wire is unlikely to occur during welding and joining by winding the conductive wire around a mandrel with sufficient winding tension. It is.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and in order to achieve this purpose, the method for manufacturing a welded joint of the present invention is such that the joint body is A method for manufacturing a welded joint formed in a cylindrical shape and having a conductive wire embedded in a spiral shape in the inner circumference of the joint body, the method comprising coating the outer periphery of a mandrel formed in a cylindrical shape with a thermoplastic resin. a winding process in which the coated conductive wire is wound, and a molding process in which a mandrel wrapped with the coated conductive wire is placed in a mold and injection molded, and the winding tension of the coated conductive wire in the winding process is is set to a strength calculated based on the linear expansion coefficient of the conductive wire.

(Function) In the method for manufacturing a welded joint of the present invention, the winding tension of the coated conductive wire in the winding step is set to a strength calculated based on the coefficient of linear expansion of the conductive wire, so that the welded joint Even if the conductive wire linearly expands and the resin around the conductive wire melts and moves when the tube is inserted into the pipe and welded and joined, the conductive wire is unlikely to cause a short circuit.

(Example) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, the configurations of the mold 1 and tension adjustment device 2 used in the method for manufacturing a welded joint of this embodiment will be explained.

The mold 1 has a mandrel 12 fitted inside an outer mold 11. The mandrel 12 has a cavity 13 formed inside the outer mold 11, has a cylindrical shape, and has a structure that can be divided into two in the axial direction.

The tension adjustment device 2 includes three drums 21, 22, 23.
It is equipped with Rotating shafts 211, 221, 231 are provided at the center of each drum 21, 22.23;
It is rotatably provided around 21 and 231. In addition, one drum (hereinafter referred to as the first drum) 21 can adjust the rotational pressure, and the other two drums (hereinafter referred to as the second drum and the third drum) 22.23
is provided in close proximity to the first drum 21.

That is, between the first drum 21 and the second drum 22 and the first
When the coated conductive wire 3 is wired so as to pass between the drum 21 and the third drum 23, the tension required when drawing out the coated conductive wire 3 can be adjusted according to the rotational pressure of the first drum 21. There is.

Next, a method for manufacturing the welded joint of this example will be explained.

First, as shown in FIG. 1, the coated conductive wire 3 supplied from the bobbin 4 is passed through the tension adjustment device 2.
While pulling it out, it is wound around the mandrel 12 of the mold 1 (wrapping process). At this time, the tension adjustment device 2 adjusts the winding tension P when winding the coated conductive wire 3 around the mandrel 12.
is set so that the strength is calculated based on the following calculation formula.

P=aΔt (Ew Aw + Ep Ap) Q: Coefficient of linear expansion of the conductive wire Δt: Temperature of the conductive wire during welding -23 Ew: Young's modulus of the conductive wire Aw: Cross-sectional area of the conductive wire EP: Young's modulus of the coating resin AP : Cross-sectional area of coated resin This calculation formula assumes that the coated conductive wire 3 is heated and linearly expands when energized, and that linear expansion loosens the tension around the mandrel 12, and takes this into consideration in advance. The winding tension when winding the coated conductive wire 3 around the mandrel 12 is calculated.

Note that if it is necessary to make the winding tension of the coated conductive wire 3 extremely strong, the winding tension can be made strong not only by the tension adjusting device 2 but also by providing resistance to the rotation of the bobbin 4.

Furthermore, when winding the coated conductive wire 3 around the mandrel 12, in order to ensure that the conductive wires are wound around the mandrel 12 at equal intervals, the coated conductive wire 3 is wrapped so that the mandrel 12 is not exposed between the coated conductive wires 3. It needs to be wrapped without any gaps.

The coated conductive wire 3 is a conductive wire coated with a thermoplastic resin, and the conductive wire is made of, for example, nichrome wire, copper wire, etc.
General resistance wires such as nickel alloy wire, angane-nickel alloy wire, chromel wire, and iron-chromium wire are preferred, and as the thermoplastic resin, for example, polyethylene resin, polypropylene resin, polyvinyl chloride resin, polybutene, etc. are preferred.

Next, as shown in FIG.
The cavity 13 formed in the outer mold 11 is filled with thermoplastic resin, and injection molding is performed (molding process).

Note that before fitting the mandrel 12 to the outer mold 11, terminals 5 are connected to both ends of the covered conductive wire 3, and the terminals 5 are supported by a fixing jig 6.

The thermoplastic resin to be filled into the cavity 13 is as follows:
Examples include polypropylene resin, polyethylene resin, vinyl chloride resin, polybutene resin, etc.

The thermoplastic resin filled in the cavity 13 is preferably the same as the thermoplastic resin used for the coated conductive wire 3, but different materials may be combined as long as they are compatible with each other.

The filled thermoplastic resin is compatible with and integrated with the thermoplastic resin of the covered conductive wire 3.

FIG. 3 is a longitudinal sectional view showing a welded joint manufactured by the above manufacturing method, in which a joint main body 71 is formed in a cylindrical shape, and a conductive wire 72 is embedded in a spiral shape in the inner peripheral part of the joint main body 71. There is.

When welding and joining the thermoplastic resin pipes PI and P2 to the welding joint 7, the thermoplastic resin pipes P1 and P2 are first inserted from the open end of the joint body, respectively. And terminals 5, 5
A constant voltage is applied between them to energize and generate heat in the conductive wire γ2. Then, the heat causes the inner peripheral part of the joint body Y1 and the synthetic resin pipe P1. The outer periphery of P2 is melted to weld and join the welding joint 7 and the synthetic resin pipes Pi and P2 to each other.

Therefore, in the manufacturing method of this embodiment, the winding tension of the covered conductive wire 3 in the winding step is set to a strength calculated based on the linear expansion coefficient of the conductive wire 72, so that the welded joint 7
When the synthetic resin pipe P is inserted into the joint body 71 and welded and joined, the conductive wire 72 linearly expands and even if the resin around the conductive wire 72 melts and moves, the conductive wire 72 will not cause a short circuit. hard.

In other words, in the manufacturing method of this embodiment, the synthetic resin pipe P
1. It is possible to manufacture a highly accurate welded joint 7 in which the conductive wire 72 does not cause a short circuit when welded and joined to P2.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention may be modified without departing from the gist of the present invention. included.

For example, in the example, an example was shown in which the method was applied to the manufacturing method of a socket-shaped welded joint, but it can also be applied to the manufacture of welded joints of different shapes, such as elbows, cheeses, reducers, etc. whose joint bodies are cylindrical. .

Further, the means for adjusting the winding tension of the covered conductive wire is not limited to the structure shown in the embodiment.

(Effects of the Invention) As explained above, the method for manufacturing a welded joint of the present invention has the advantage that a highly accurate welded joint that does not cause a short circuit in the conductive wire during welding and joining can be manufactured. is obtained.

[Brief explanation of drawings]

Fig. 1 is a perspective view illustrating the winding process of the method for manufacturing a welded joint according to the embodiment of the present invention, Fig. 2 is a longitudinal sectional view illustrating the joint forming in the method of the first embodiment, and Fig. 3 is the present embodiment. FIG. 3 is a longitudinal cross-sectional view showing a welded joint manufactured by the method. 1...Mold 12...Mandrel 3--Coated conductive wire 7...Welded joint 71...Joint body

Claims (1)

[Scope of Claims] 1) A method for manufacturing a welded joint in which the joint body is formed in a cylindrical shape and a conductive wire is embedded in a spiral shape in the inner circumference of the joint body, the method comprising: a winding step of winding a coated conductive wire coated with a thermoplastic resin around the outer periphery of a mandrel, and a molding step of placing the mandrel wrapped with the coated conductive wire in a mold and performing injection molding; A method for manufacturing a welded joint, characterized in that the winding tension of the coated conductive wire in the winding step is set to a strength calculated based on the linear expansion coefficient of the conductive wire.