JPH0751296B2 - Manufacturing method of welded joint - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a welding joint for welding a synthetic resin gas pipe or a water pipe by welding.

(Prior Art) Conventionally, as a method for manufacturing a welded joint in which a joint body is formed in a cylindrical shape and conductive wires are embedded in a spiral shape in an inner peripheral portion of the joint body, for example, JP-A-59-13180 is known. The manufacturing method as described in the gazette etc. is known.

In this conventional method, a tubular body formed of a thermoplastic resin is installed on the outer circumference of a mandrel, and a conductive wire is further wound around the outer circumference of the tubular body while heating. In this method, a mandrel provided with is installed in a mold and injection molding is performed.

(Problems to be Solved by the Invention) By the way, in such a conventional manufacturing method, by winding the conductive wire around the outer periphery of the cylindrical body while heating the conductive wire, Since the conductive wire is sealed in the outer peripheral portion, the winding tension of the conductive wire is set so that the conductive wire has an optimum sealed depth. Then, when the pipe is inserted into the welding joint and the welding is performed, the conductive wire linearly expands so that the winding tension of the conductive wire is generally insufficient, and as a result, the resin around the conductive wire is melted. There is a problem that the conductive wire is likely to cause a short circuit when moving.

The present invention focuses on the above problems, by winding a conductive wire around the mandrel with a sufficient winding tension, to provide a method for manufacturing a welded joint in which short-circuiting of the conductive wire is less likely to occur during welding. Is.

(Means for Solving the Problem) The present invention has been made for the purpose of solving the above-mentioned problems, and in order to achieve this object, the method for producing a fusion-bonded joint according to the present invention is A method for manufacturing a welded joint formed in a cylindrical shape, in which conductive wires are embedded in a spiral shape in an inner peripheral portion of the joint body, wherein the outer periphery of a mandrel formed in a cylindrical shape is coated with a thermoplastic resin. The method includes a winding step of winding the coated conductive wire, and a molding step of performing injection molding by installing a mandrel around which the coated conductive wire is wound in a mold, and winding tension of the coated conductive wire in the winding step. This is a method of setting P to the strength calculated based on the following arithmetic expression.

P = aΔt (EwAw + EpAp) a: Linear expansion coefficient of conductive wire Δt: Temperature of conductive wire during welding −23 Ew: Young's modulus of conductive wire Aw: Cross section of conductive wire Ep: Young's modulus of coating resin Ap: Coating resin In the method for manufacturing a fusion-bonded joint according to the present invention, the winding tension P of the coated conductive wire in the winding step is set to the strength calculated based on the above-mentioned arithmetic expression, so that the energization is performed. At times, the conductive wire is heated and linearly expands, and the winding tension around the mandrel does not loosen due to the linear expansion.Therefore, when the pipe is inserted into the welding joint and the welding is performed, the conductive wire is expanded and Even if the surrounding resin melts and moves, the conductive wire is unlikely to cause a short circuit.

(Examples) Examples of the present invention will be described in detail below with reference to the drawings.

First, the configurations of the mold 1 and the tension adjusting device 2 used in the method for manufacturing the welded joint of the present embodiment will be described.

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

The tension adjusting device 2 includes three drums 21, 22, and 23. The rotary shaft 211, is located at the center of each drum 21, 22, 23.
221, 231 are provided, and the drums 21, 22, 23 are provided so as to be rotatable about their rotation shafts 211, 221, 231. One drum (hereinafter referred to as the first drum) 21
Is capable of adjusting the rotation pressure, and the other two drums (hereinafter referred to as the second drum and the third drum) 22,2
3 is provided in the state of being close to the first drum 21.

That is, when the covering conductive wire 3 is wired so as to pass between the first drum 21 and the second drum 22 and between the first drum 21 and the third drum 23, the covering conductive wire 3 is covered according to the rotation pressure of the first drum 21. The tension required when pulling out the conductive wire 3 can be adjusted.

Next, a method for manufacturing the welded joint of this embodiment will be described.

First, as shown in FIG. 1, the coated conductive wire 3 supplied from the bobbin 4 is passed through the tension adjusting device 2, and the tension adjusting device 2
Wind it around the mandrel 12 of the mold 1 while pulling it out (winding step). At this time, the tension adjusting device 2 determines that the winding tension P when the coated conductive wire 3 is wound around the mandrel 12 is
Set so that the strength is calculated based on the following formula.

_{P = aΔt (E W A W} + E P A P) a: linear expansion coefficient of the conductive wire Delta] t: temperature -23 E _W of the welding time of conductive lines: Young's modulus of the conductive wire A _W: cross-sectional area of the conductive wire E _P : Young's modulus of the coating resin A _P : Cross-sectional area of the coating resin This arithmetic expression assumes that the coated conductive wire 3 is heated and linearly expands during energization, and that the linear expansion causes the winding tension around the mandrel 12 to relax. The winding tension when winding the coated conductive wire 3 around the mandrel 12 is calculated in consideration of the amount in advance.

When it is necessary to increase the winding tension of the coated conductive wire 3 extremely, the winding tension can be increased not only by the tension adjusting device 2 but also by giving a resistance to the rotation of the bobbin 4.

Further, when the coated conductive wire 3 is wound around the mandrel 12, the conductive wire is wound around the mandrel 12 at equal intervals, so that the coated conductive wire 3 is not exposed from between the coated conductive wires 3. It is necessary to wind it without any gap.

The coated conductive wire 3 is a conductive wire coated with a thermoplastic resin, and the conductive wire is, for example, a dichrome wire, a copper wire.
Nickel alloy wire, Angan / nickel alloy wire, Angan / nickel alloy wire, chromel wire, wire for general resistance such as iron chrome are preferable, and the thermoplastic resin is, for example, polyethylene resin, polypropylene resin, polyvinyl chloride resin, Polybutene and the like are preferable.

Next, as shown in FIG. 2, the mandrel 12 is fitted into the outer mold 11, the cavity 13 formed in the outer mold 11 is filled with a thermoplastic resin, and injection molding is performed (molding step). Before fitting the mandrel 12 to the outer mold 11, the terminals 5 are connected to both ends of the covered conductive wire 3 and the terminals 5 are supported by the fixing jig 6.

The thermoplastic resin with which the cavity 13 is filled includes polypropylene resin, polyethylene resin, vinyl chloride resin, polybutene resin and the like. Also, this cavity 13
The thermoplastic resin to be filled in 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 coated conductive wire 3.

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

When welding the thermoplastic resin pipes P1 and P2 to the welding joint 7, first, the thermoplastic resin pipes P1 and P2 are respectively inserted from the open ends of the joint body. Then, a constant voltage is applied between the terminals 5 and 5 to energize the conductive wire 72 to generate heat. Then, the heat causes the inner peripheral portion of the joint body 71 and the outer peripheral portions of the synthetic resin pipes P1 and P2 to be melted, and the welding joint 7 and the synthetic resin pipes P1 and P2 are welded and joined to each other.

Therefore, in the manufacturing method of the present embodiment, the winding tension P of the coated conductive wire 3 in the winding step is set to the strength calculated based on the above arithmetic expression, and therefore the joint body of the welding joint 7 is set.
When the synthetic resin pipe P is inserted into 71 to be 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 is unlikely to cause a short circuit.

That is, in the manufacturing method of this embodiment, the synthetic resin pipe P
It is possible to manufacture the welding joint 7 with high accuracy in which the conductive wire 72 does not short-circuit during the welding and joining with 1, P2.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and the present invention can be applied even if there is a design change or the like within a range not departing from the gist of the present invention. included.

For example, in the embodiment, the example applied to the method for manufacturing a socket-shaped welded joint is shown, but it can also be applied to the manufacture of welded joints having different shapes, such as an elbow, a cheese, and a reducer whose joint body is cylindrical. .

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

(Effects of the Invention) As described above, in the method for manufacturing a welded joint of the present invention, it is possible to manufacture a highly accurate welded joint in which a conductive wire does not cause a short circuit during welding. Is obtained.

[Brief description of drawings]

FIG. 1 is a perspective view for explaining a winding step of a method for manufacturing a welded joint according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view for explaining joint forming in the method for the first embodiment, and FIG. 3 is this embodiment. It is a longitudinal section showing a welding joint manufactured by a method. 1 ... Mold 12 ... Mandrel 3 ... Coated conductive wire 7 ... Welded joint 71 ... Joint body

Claims (1)

[Claims] 1. A method for producing a welded joint in which a joint body is formed in a cylindrical shape and conductive wires are embedded in a spiral shape in an inner peripheral portion of the joint body, the method comprising: The outer periphery is provided with a winding step of winding a coated conductive wire coated with a thermoplastic resin, and a molding step of performing injection molding by installing a mandrel wound with the coated conductive wire in a mold, and the winding step. Winding tension P of coated conductive wire at
Is set to a strength calculated based on the following arithmetic expression, a method for manufacturing a welded joint. P = aΔt (EwAw + EpAp) a: Linear expansion coefficient of conductive wire Δt: Temperature of conductive wire during welding −23 Ew: Young's modulus of conductive wire Aw: Cross section of conductive wire Ep: Young's modulus of coating resin Ap: Coating resin Cross section of