JPH1151280A - Electrofusion joint and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of a trouble such as a disturbance of insertion of a plastic pipe even after a long lapse of time after joint molding by specifying a ratio of a coil diameter of a heating wire buried in the form of coil in a joint to a wire diameter of the heating wide. SOLUTION: In an electrofusion joint 1 provided with a heating wire 2, which is buried in the form of coil on the connection face with a plastic pipe, so as to be electrically fused with the plastic pipe in piping construction using a plastic pipe, a ratio D/d of a coil diameter D of the heating wire 2 buried in the form of coil in the joint 1 to a wire diameter (d) of the heating wire 2 is set to be 145 or less, desirably, 120 or less. When the heating wire 2 in which the ratio D/d is 145 or less is used, an insertion trouble due to shrinkage in a diameter of the plastic pipe can be solved. Although a lower extent of the ratio D/d is not limited, rigidity is increased more as the wire diameter (d) is increased and difficulty in wire winding and increase in costs are caused. In consideration of these points, the lower limit of the ratio D/d is 80 or more, desirably, 90 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for connecting plastic pipes in piping work using plastic pipes. A heating wire is buried in a coil shape at a joint surface with the plastic pipe, and the plastic pipe is fused with the plastic pipe. The present invention relates to an electrofusion joint to be used and a manufacturing method thereof.

[0002]

2. Description of the Related Art Electrofusion joints have recently been developed as joints for plastic pipes used in plumbing works such as water and sewage pipes, hot water supply pipes and gas pipes. This joint consists of a molded product in which a heating wire is embedded in a coil shape on the joint surface with the pipe. Generally, a coated heating wire is wound around a metal core, or a heating wire is wound around a resin bobbin. It is then obtained by inserting it into a core, then mounting it in a mold and injection molding. The size of this molded product changes with time due to post-shrinkage of the resin, and becomes smaller (hereinafter referred to as “diameter reduction”). ).

[0003] On the other hand, plastic pipes are generally obtained by extrusion molding. However, since they are not molded at high pressure and high shearing speed unlike injection molding, internal strain is small and post-shrinkage is extremely small or hardly observed.

[0004]

As described above, the electrofusion joint obtained by injection molding shrinks in diameter with time as described above. If the value is out of the specified range, a trouble that the plastic tube cannot be inserted occurs.

[0005] The present invention provides an electrofusion joint which satisfies the standard value even after a long period of time and does not cause troubles such as inability to insert a plastic tube.
It is intended to provide a manufacturing method thereof.

[0006]

Means for Solving the Problems The present inventors have obtained various experiments,
In an electrofusion joint that can satisfy the JIS standard for a long period of time, there is a correlation between the coil diameter of a heating wire embedded in a coil and the wire diameter of the heating wire. Regardless, it has been found that if a heating wire having a wire diameter larger than the critical wire diameter is selected, an electrofusion joint that can satisfy the JIS standard for a long period of time can be obtained.

The present invention has been made based on this finding, and in the electrofusion joint 1 shown in FIG. 1, the coil diameter D of the heating wire 2 embedded in the joint in a coil shape.
And the ratio D / d of the wire diameter d of the heating wire 2 is 145 or less, preferably 120 or less.
The ratio D / d of the coil diameter D of the heating wire and the wire diameter d of the heating wire embedded in the coil in the joint is 145 or less, preferably 120
It is characterized by using a heating wire as described below.

By using a heating wire having a D / d of 145 or less, it is possible to substantially eliminate the trouble of inserting a plastic tube due to a reduction in diameter. The lower limit does not need to be limited, but as the wire diameter d of the heating wire increases, the rigidity of the heating wire increases, so that the winding becomes difficult and the cost increases. Considering these points, it is not advisable to make the diameter of the heating wire too large, and the lower limit of D / d is preferably 80 or more, more preferably 90 or more.

[0009]

【Example】

Example 1 A heating wire having a wire diameter of 0.55 mmψ and a material coated with a chromium-nickel alloy (hereinafter referred to as “CN alloy”) coated wire (diameter 1.65 mmψ) and having a nominal diameter of 50 was used. A plurality of electrofusion joints shown in No. 1 were produced by injection molding. At this time, the ratio D / d of the coil diameter D at the center of the coated heating wire embedded in the coil to the wire diameter d of the wire was 113, and the coil diameter of the wire of the obtained joint was determined to be one year between immediately after molding and one year. After 2 years and 3 years later, the average value and the minimum value were obtained, and all satisfied the JIS standard value of 60.5 ± 0.20 mm as shown in Table 1 below. Was.

Example 2 A plurality of electrofusion joints having a nominal diameter of 75 were formed by injection molding using a coated heating wire (wire diameter: 1.95 mm) made of a CN alloy having a wire diameter of 0.65 mm #. The D / d at this time was 141, and the coil diameter of the wire of the obtained joint was measured immediately after molding and one year later, and the average value and the minimum value were obtained. JIS standard value 89.7 ±
0.20 mm was satisfied.

Example 3 Injection molding of a plurality of electrofusion joints having a nominal diameter of 75 was performed using the same coated heating wire (wire diameter of 2.55 mm) as in Example 1 except that the wire diameter was 0.85 mm５. Molded by D / d at this time was 109, and the coil diameter of the wire of the obtained joint was measured immediately after molding, and after one year, two years, and three years, respectively, and the average value and the minimum value were obtained. However, as shown in Table 1 below, all of the JIS standard values are 89.7 ± 0.20.
mm was satisfied.

Example 4 A plurality of electrofusion joints having a nominal diameter of 100 were formed by injection molding using a coated heating wire (wire diameter 2.55 mmψ) made of a CN alloy having a wire diameter of 0.85 mmψ. The D / d at this time was 138. The coil diameter of the wire of the obtained joint was measured immediately after molding, one year and two years later, and the average value and the minimum value were obtained. As shown in Table 1 below, the JIS standard value of 114.85 ± 0.25 mm was satisfied.

Experimental Example 5 A plurality of electrofusion joints having a nominal diameter of 100 were formed by injection molding using a coated heating wire (wire diameter: 3.60 mm) made of a CN alloy having a wire diameter of 1.20 mm１．２. The D / d at this time was 99, and the coil diameter of the wire of the obtained joint was measured immediately after molding, one year later, two years later, and 3 days later.
After each year, the average value and the minimum value were determined, and as shown in Table 1 below, J
The value satisfies the IS standard value of 114.85 ± 0.25 mm.

Experimental Example 6 A plurality of electrofusion joints having a nominal diameter of 150 were formed by injection molding using a coated heating wire (wire diameter of 4.05 mm) made of a CN alloy having a wire diameter of 1.35 mm #. The D / d at this time was 126. The coil diameter of the wire of the obtained joint was measured immediately after molding and one year later, and the average value and the minimum value were obtained. JIS standard value 166.1
± 30 mm was satisfied.

EXAMPLE 7 A wire was coated with a nickel-chrome alloy (hereinafter referred to as "NCH alloy") having a wire diameter of 1.45 mmψ (wire diameter: 4.3).
Using 5 mmψ), a plurality of electrofusion joints having a nominal diameter of 150 were formed by injection molding. The D / d at this time was 117, and the inner diameter of the obtained joint was measured immediately after molding and one year later, and the average value and the minimum value were obtained. Both were as shown in Table 1 below. Satisfies the JIS standard value of 166.1 ± 30 mm.

Comparative Example 1 A wire was made of a chromium iron alloy having a wire diameter of 0.36 mm
“FCH alloy” coated heating wire (wire diameter 1.08mm)
Using ψ), a plurality of electrofusion joints having a nominal diameter of 50 were formed by injection molding. D / d at this time
Is 171. The coil diameter of the wire of the obtained joint was measured immediately after molding, 1 year, 2 years, and 3 years later, and the average value and the minimum value were obtained. As shown in the figure, immediately after molding, the JIS standard value of 60.5 ± 0.20 mm was satisfied, but all of the samples after one year or more did not satisfy the JIS standard value.

Comparative Example 2 The same coated heating wire (wire diameter: 1.20 mmψ) as in Comparative Example 1 was used except that the wire diameter was changed to 0.40 mmψ, and a plurality of electrofusion joints having the same nominal diameter as Comparative Example 1 were used. I got one. D / d at this time was 154, and the coil diameter of the wire of the obtained joint was measured immediately after molding, 1 year, 2 years, and 3 years later, and the average value and the minimum value were obtained. As shown in Table 1 below, immediately after molding, the JIS standard value of 60.5 ± 0.20 mm was satisfied, but after one year, the JIS standard value was not satisfied. Some of them did not meet the JIS standard values after 2 years.

Comparative Example 3 A plurality of electrofusion joints having the same nominal diameter as Comparative Example 3 were obtained using a coated heating wire (wire diameter: 1.95 mmψ) made of a CN alloy having a wire diameter of 0.65 mmψ. D / d at this time was 166, and the coil diameter of the wire of the obtained joint was measured immediately after molding, one year, two years, and three years later, and the average value and the minimum value were obtained. ,
As shown in Table 1 below, immediately after molding, the JIS standard value of 60.1 ± 0.20 mm was satisfied, but after one year, it did not satisfy the JIS standard value during one year. All of the samples that had passed two years or more did not meet the JIS standard values.

Comparative Example 4 An electrofusion joint having a nominal diameter of 100 was obtained by injection molding using a coated heating wire (wire diameter: 1.95 mmψ) made of a CN alloy having a wire diameter of 0.65 mmψ. D / d at this time was 180, and the coil diameter of the wire of the obtained joint was measured immediately after molding, one year, two years, and three years later, and the average value and the minimum value were obtained. ,
As shown in Table 1 below, immediately after molding, the JIS standard value of 114.85 ± 0.25 mm was satisfied.
One that has passed one year, some do not satisfy the JIS standard values, and all that have passed two years or more
The standard value was not met. Comparative Example 5 An electrofusion joint having a nominal diameter of 150 was obtained by injection molding using a coated heating wire made of a CN alloy having a wire diameter of 1.10 mmψ (wire diameter of 3.30 mmψ). D / d at this time was 154, and the coil diameter of the wire of the obtained joint was measured immediately after molding, 1 year, 2 years, and 3 years later, and the average value and the minimum value were obtained. ,
As shown in Table 1 below, immediately after molding, the product satisfied the JIS standard value of 166.1 ± 0.30 mm.
Some of the aged ones did not meet the JIS standard values.

Since the electrofusion joint is usually used within one year, each of the above-mentioned examples satisfying the JIS standard values even after one year has been qualified, and has been stored for three years in particular. It is considered that the products of Examples 1, 3 and 5 satisfying the standard value even afterwards have no problem at all.

[0021]

[Table 1] Here, the upper part of the inner diameter shows the average value of the coil diameter, and the lower part shows the minimum value of the coil diameter.

[0022]

The use of a heating wire having a wire diameter satisfying D / d as in the present invention does not cause a trouble that the plastic pipe cannot be inserted even after a long period of time after the joint is formed. When the ratio of D / d is 80 or more, preferably 90 or more, the winding does not become difficult and the cost can be kept relatively low.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electrofusion joint.

[Explanation of symbols]

 1. Electrofusion joint 2. Electric heating wire

Claims (8)

[Claims] 1. An electrofusion joint which is used for connecting a plastic pipe and in which a heating wire is embedded in a coil shape on a joint surface with the plastic pipe and which is electro-fused with the plastic pipe. The ratio D / d of the coil diameter D of the heating wire to the wire diameter d of the heating wire is 14
An electrofusion joint characterized in that the number is 5 or less. 2. The electrofusion joint according to claim 1, wherein D / d is 120 or less. 3. The electrofusion joint according to claim 1, wherein D / d is 80 or more. 4. The electrofusion joint according to claim 1, wherein D / d is 90 or more. 5. A method for manufacturing an electrofusion joint, which is used for connecting a plastic pipe and in which a heating wire is buried in a coil shape on a joint surface with the plastic pipe and is electrically fused to the plastic pipe. Ratio D / d of the coil diameter D of the heating wire buried in the shape and the wire diameter d of the heating wire
A method for producing an electrofusion joint, wherein a heating wire is used so that the value is 145 or less. 6. The method for producing an electrofusion joint according to claim 5, wherein D / d is 120 or less. 7. The method for producing an electrofusion joint according to claim 5, wherein D / d is 80 or more. 8. The method for manufacturing an electrofusion joint according to claim 5, wherein D / d is 90 or more.