JP2012145139A - Electrical fusion joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrical fusion joint capable of reliably fusing a resin pipe.SOLUTION: In a tubular electrical fusion joint 20A equipped with an inner-layer pipe 21 with bosses 27a, 27b fixed to terminal clamps 28a, 28b and a resistance wire 29 connected to the terminal clamps 28a, 28b and wound around an outer circumferential surface 21a and equipped with an outer-layer pipe 22 formed on the outer circumferential surface 21a of the inner-layer pipe 21, a resin pipe P1 to be connected is inserted into an opening 23 of the inner-layer pipe 21 and the outer-layer pipe 22 to fuse the resin pipe P1, a convex portion 31 is formed on one of the outer circumferential surface 21a of the inner-layer pipe 21 and the inner circumferential surface 22b of the outer-layer pipe 22 and a concave portion 32 that fits to the convex portion 31 is formed on the other thereof in the vicinity of the opening 23.

Description

  The present invention relates to an electric fusion joint for connecting resin pipes.

  In general, for the connection between resin pipes, an electric fusion joint in which a resistance wire such as a nichrome wire is embedded inside the joint and the resistance wire is energized and heated is widely used. This electric fusion joint is to be connected to the connection target resin tube by energizing the terminal fitting to heat and melt the resin near the resistance wire and the end of the connection target resin tube. Conventionally, as such an electric fusion joint, for example, an electric fusion joint described in Patent Document 1 has been proposed.

  As shown in FIG. 5 (c), the electrofusion joint 1 described in Patent Document 1 is manufactured by injection molding of a thermoplastic resin, for example, polyethylene, and an inner layer on which a resistance wire 2 is wound. The tube 3 and an outer layer tube 4 covering the inner layer tube 3 are configured.

Boss 5a, 5b is provided in the outer peripheral surface 3a of the inner layer pipe 3 at intervals. A spiral groove 6 is formed between the two bosses 5 a and 5 b on the outer peripheral surface 3 a of the inner layer tube 3, and the resistance wire 2 is wound around the spiral groove 6. The resistance wire 2 is connected to terminal fittings 7a and 7b fixed to the upper ends of the bosses 5a and 5b, and can be energized from the terminal fittings 7a and 7b.
Since the resistance wire 2 is wound, the wall portion W1 of the inner layer tube 3 and the outer layer tube 4 surrounding the resistance wire 2 is melted when the resistance wire 2 is energized.
Further, the outer peripheral surface of the wall portion W2 of the inner layer tube 3 located on the opening 10 side with respect to the wall portion W1 forms a smooth peripheral surface on which no irregularities are formed.

The above electric fusion joint is manufactured as follows.
First, the inner tube 3 shown in FIG. 5A is injection-molded on the outer surface of the core 8, and one end of the resistance wire 2 is welded to the terminal fitting 7a of one boss 5a as shown in FIG. 5B. Join by caulking. The resistance wire 2 is wound along the spiral groove 6, and the other end of the resistance wire 2 is joined to the terminal fitting 7b of the other boss 5b by welding or caulking. Then, as shown in FIG. 5 (c), the inner layer tube 3 around which the resistance wire 2 is wound is incorporated into the joint molding die 9, and the outer layer tube 4 is melted at a high temperature so that the outer layer tube 4 is firmly adhered to the inner layer tube 3. The outer layer pipe 4 is injection molded to produce the electrofusion joint 1.

JP 2003-287187 A

  By the way, according to the electric fusion joint 1 of Patent Document 1, the resistance wire 2 is wound around the outer peripheral surface 3a of the solidified inner layer tube 3, and the outer layer tube 4 heated and melted is injection molded. Although it is in close contact with the outer tube 4, it is not completely welded and an interface K is formed between them. At this time, in the vicinity of the terminal fitting 7a, the inner layer tube 3 and the outer layer tube 4 are fitted and are difficult to move relative to each other. However, in the peripheral wall portion at a position separated from the terminal fitting 7a, the electric fusion is performed. When a resin tube (not shown) is inserted to fuse with the joint 1 and the electric fusion joint 1 is energized, the resin in the heated wall portion W1 expands, and the resin in the wall portion W1 In some cases, the wall W2 of the inner layer tube 3 near the opening 10 located on the tip side of the wall W1 is peeled from the outer layer tube 4 and pushed outward from the tip of the opening 10.

  At this time, since the resin of the wall portion W1 heated and melted by the resistance wire 2 flows to the tip side of the opening 10, the heat obtained from the resistance wire 2 is concentrated and conducted to the resin tube side to be connected. Therefore, it was assumed that the electric fusion joint 1 and the resin pipe could not be reliably fused.

  Therefore, as described above, when the wall portion W2 of the inner layer tube 3 is pushed out from the opening portion 10 when the electrofusion joint 1 and the resin tube are connected, safety is ensured regardless of the suitability of actual fusion. There was a problem that it had to be handled as a poor fusion for certainty.

  In order to avoid the above problem, in order to make the wall W2 of the inner layer tube 3 in the vicinity of the opening 10 close to the outer layer tube 4 difficult to peel off when the resistance wire 2 is energized, the outer layer tube is formed at an extremely high temperature. 4 has to be injected, it takes time to cool the outer layer pipe 4, and there is a problem that it takes time to complete the production of the electrofusion joint 1.

Therefore, the present invention provides the following means in order to solve the above problems.
The present invention comprises a boss having a terminal fitting fixed thereto, an inner layer tube in which a resistance wire connected to the terminal fitting is wound around the outer peripheral surface, and an outer layer tube formed on the outer peripheral surface of the inner layer tube, In the tubular electric fusion joint in which the resin pipe to be connected is inserted into the inside of the opening of the inner layer pipe and the outer layer pipe and the resin pipe is fused, the outer periphery of the inner layer pipe is in the vicinity of the opening. A convex portion is formed on one of the surface and the inner peripheral surface of the outer layer tube, and a concave portion that fits the convex portion is formed on the other side.
In the present invention, when the resin expands when the resistance wire is energized and the wall portion of the inner layer tube is pressed toward the tip of the opening, the convex portion or the concave portion of the wall portion of the inner layer tube and the concave portion or the convex portion of the outer layer tube are formed. By engaging the portion, the inner layer tube in the vicinity of the opening can be prevented from being separated from the outer layer tube.

According to the electrical fusion joint according to the present invention, the following effects can be obtained by the above-described solving means.
According to the electric fusion joint of the present invention, even if the resin expands when the resistance wire is energized and presses the wall portion of the inner layer tube toward the tip of the opening, the convex portion or the recess portion of the wall portion of the inner layer tube Can be engaged with the concave portion or the convex portion of the outer layer tube so that the inner layer tube in the vicinity of the opening is not separated from the outer layer tube. Therefore, the resin of the inner-layer pipe expanded by heat is intensively conducted to a predetermined portion of the resin pipe to be connected without flowing to the opening side, so that the fusion between the electric fusion joint and the resin pipe is ensured. This is advantageous in that it is possible to eliminate concerns about the occurrence of poor fusion.

  Further, when the inner layer tube is heated and melted, the wall portion of the inner layer tube is separated from the outer layer tube and is not pushed out of the opening portion, so that the wall portion of the inner layer tube protrudes from the opening portion. Since it is not necessary to adjust the prevention by tight adhesion of the outer layer tube to the inner layer tube, the molding temperature of the outer layer tube can be suppressed, the cooling time of the outer layer tube is shortened, and the manufacturing time of the electrofusion joint is shortened There is an effect that can be.

These are principal part sectional drawings of the electrofusion joint shown as the 1st Embodiment of this invention. (A)-(c) is a schematic explanatory drawing which shows the manufacturing process of the electrofusion joint shown as the 1st Embodiment of this invention. These are explanatory drawings which showed the effect | action at the time of the resin pipe fusion | melting of the electric fusion joint shown as the 1st Embodiment of this invention. These are principal part sectional drawings of the modification of the electrofusion joint of the 1st Embodiment of this invention. (A)-(c) is the schematic explanatory drawing which showed the manufacturing process of the conventional electrofusion joint.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a half part of the main part of the electric fusion joint shown as the first embodiment of the present invention, and FIG. 2 is a schematic explanation showing the manufacturing process of the electric fusion joint of FIG. FIG.

The electric fusion joint 20 </ b> A is a single-piece type joint, and is configured such that the outer layer tube 22 is formed on the inner layer tube 21.
The inner layer tube 21 and the outer layer tube 22 have a large diameter portion 24 into which a resin tube P1 to be connected is inserted from an opening 23 formed on one end side thereof, and a tapered portion 25 provided continuously to the large diameter portion 24. And a small diameter portion 26 connected to the taper portion 25, and a resin pipe P <b> 2 is welded to an end portion 26 b of the small diameter portion 26.

  Boss 27a, 27b is formed in both the opening part 23 side and the end part 24b of the taper part 25 side of the large diameter part 24 in the inner layer pipe 21, and the terminal metal fitting 28a is formed at the upper end of these bosses 27a, 27b. , 28b are fixed.

A spiral groove 30 is formed between the bosses 27a and 27b in the outer peripheral surface 21a of the inner layer pipe 21 except for the vicinity of the bosses 27a and 27b, and is not covered with insulation along the spiral groove 30. A resistance wire 29 is wound.
Both ends of the resistance wire 29 are connected to terminal fittings 28a and 28b, respectively.

  When the electric fusion joint 20A is energized, the resistance wire 29 melts the wall portion W3 of the inner layer tube 21 and the outer layer tube 22 around the resistance wire 29, and the end of the resin tube P1 with which the wall portion W3 abuts. The resin W4 on the outer peripheral side of the part is melted.

  Further, on the outer peripheral surface of the wall portion W5 in the vicinity of the opening portion 23 of the inner layer tube 21, a plurality of convex portions 31, 31,... Formed in the circumferential direction are continuously and annularly formed in the axis L direction. . The shape of the convex portion 31 is a cross-sectional mountain shape.

The outer layer tube 22 is formed in close contact with the entire outer peripheral surface 21a surface of the inner layer tube 21 in which the resistance wire 29 is spirally wound, and the inner layer surface 22b in the vicinity of the opening 23 is formed on the inner layer surface 21b. Concave portions 32, 32... Are formed to fit the convex portions 31, 31.
The outer peripheral surface 22a of the outer tube 22 is formed to have a smooth cylindrical shape except for the bosses 33 and 33 having openings for energizing the terminal fittings 28a and 28b.

  The inner layer tube 21 is made of, for example, medium density polyethylene, and the outer layer tube 22 is made of, for example, high density polyethylene.

Next, a manufacturing method of the electrofusion joint 20A having the above-described configuration will be described with reference to FIG.
First, as shown in FIG. 2 (a), an injection molding machine (inside a mold cavity composed of first movable outer dies 41, 41, fixed outer dies 42, and inner dies 43 that can be divided in the vertical direction). The medium density polyethylene melted from the gate portion 44 is filled in by cooling (not shown) and solidified.
After the medium density polyethylene is solidified, the first movable outer molds 41 and 41 are opened in the vertical direction to obtain a thin-walled cylindrical inner tube 21 having a spiral continuous groove 30 around the inner mold 43. .

  Next, as shown in FIG. 2 (b), one end of the resistance wire 29 is joined to one terminal fitting 28a by welding, caulking or the like, and this resistance wire 29 is connected to the inner side using a winding machine (not shown). The resistance wire 29 is wound around the groove 30 of the inner tube 21 with the mold 43 attached, and the other end of the resistance wire 29 is joined to the other terminal fitting 28b by welding, caulking or the like. 28a and 28b are electrically connected.

  Then, as shown in FIG. 2 (c), the second movable outer molds 45, 45 are arranged so that a predetermined space is formed around the inner mold 43 to which the inner layer pipe 21 is attached, and the inner layer pipe 21 is arranged. The outer layer is filled with high-density polyethylene melted from the gate portion 44 by an injection molding machine (not shown) in a cavity formed by the outer peripheral surface 21a of the second moving outer mold 45 and the inner peripheral surface 45a of the second movable outer mold 45. The tube 22 is formed. The temperature of the outer layer tube 22 at the time of injection molding is set to a temperature at which the outer layer tube 22 can be in close contact with the inner layer tube 21 after the outer layer tube 22 is solidified.

  The recesses 32, 32,... In the vicinity of the opening 23 of the outer layer tube 22 are formed in close contact with the projections 31, 31,.

  After cooling and solidifying the outer layer pipe 22, the second movable outer molds 45, 45 and the inner mold 43 are removed, and the resin pipe P2 shown in FIG. 1 is welded to the end 26b on the small diameter part 26 side. An electrofusion joint 20A as shown in FIG. 1 is obtained.

Next, a method and an operation of connecting another resin pipe P1 to the electrofusion joint 20A will be described.
First, as shown in FIG. 3, the end of the resin pipe P1 is inserted from the opening 23 of the electrofusion joint 20A until it abuts against the taper part 25 of the inner layer pipe 21, and the terminal fittings 28a and 28b are energized to resist. The wire 29 is heated.

By heating the resistance wire 29, the wall portion W3 around the resistance wire 29 is heated and melted. When the wall portion W3 melts, the resin of the wall portion W3 expands and presses the resin around the molten resin.
By this compression, the wall portion W5 of the inner layer pipe 21 that is located on the opening portion 23 side of the wall portion W3 and whose end face is exposed is pressed in the direction of the opening portion 23, but the wall portion W5 near the opening portion 23 has Since the convex portions 31, 31... Are formed in the circumferential direction, and the concave portions 32, 32... Of the outer tube 22 are in close contact with each other, the convex portions 31, 31. And the wall portion W5 of the inner layer tube 21 near the opening 23 is not peeled off from the outer layer tube 22, and the resin of the wall portion W3 expanded by melting is held in a fixed place.

  Further, since the resin of the outer layer tube 22 located on the outer peripheral side of the resin of the expanded wall portion W3 and the resin of the tapered portion 25 side of the inner layer tube 21 are not melted, the resin is pressed against the expanded wall portion W3 by the resin. As a result, the resin of the expanded wall portion W3 is held in one place, and the outer peripheral surface of the end portion of the resin pipe P1 is pressed to conduct heat.

The wall portion W4 on the outer peripheral side of the end portion of the resin pipe P1 is gradually melted and expanded by the heat of the resin of the wall portion W3 melted at a high temperature, but the wall portion on the inner peripheral side of the end portion of the resin pipe P1 is Since it has been solidified, it expands toward the inner layer tube 21 side of the electrofusion joint 20A, and is mixed with the molten resin of the inner layer tube 21 to be integrated.
At this time, the energization is stopped, the connecting portion between the electrofusion joint 20A and the resin pipe P1 is cooled, and the solidification is completed, thereby completing the connection between the electrofusion joint 20A and the resin pipe P1.

  According to the electrofusion joint 20A formed as described above, the resin of the wall portion W3 expands when the resistance wire 29 is energized and presses the wall portion W5 of the inner tube 21 toward the opening 23 side. However, since the convex portion 31 of the wall portion W5 of the inner layer tube 21 is engaged with the concave portion 32 of the outer layer tube 22, the resin of the wall portion W3 expanded by heat does not flow toward the opening portion 23 side. The resin of the portion W3 acts intensively on the side of the resin pipe P1 to be connected, effectively transferring heat on the wall W3 side to the wall W4 side, and the electrofusion joint 20A and the resin pipe P1. It is possible to reliably perform fusion with the above, and it is possible to eliminate the concern about the occurrence of poor fusion.

  Further, due to the convex portion 31 of the inner layer tube 21 and the concave portion 32 of the outer layer tube 22, when the inner layer tube 21 is heated and melted, the wall portion W5 of the inner layer tube 21 is peeled from the outer layer tube 22 and pushed outward of the opening 23. Since it is configured so that it does not come out, it can be set while suppressing the injection molding temperature of the outer layer pipe 22 without considering the protrusion of the wall part W5 from the opening 23, and the time required for cooling the outer layer pipe 22 can be set. There is an effect that the electrofusion joint 20A can be manufactured in a shorter time by shortening.

  Further, convex portions 31, 31... Are repeatedly formed in the longitudinal direction on the wall portion W 5 in the vicinity of the opening 23 of the inner layer tube 21, and the outer layer tube 22 is closely fitted to the inner layer tube 21. , 32... Are formed, and there is an effect that the adhesion between the inner layer tube 21 and the outer layer tube 22 can be further strengthened in the vicinity of the opening 23.

  FIG. 4 shows a modified example of the electrofusion joint 20A. The convex portion 31 and the concave portion 32 of the electrofusion joint 20A shown in FIG. Formed. Also by the electrofusion joint 20B according to this modification, the same effects as those of the electrofusion joint 20A described above can be obtained.

  In addition, in the above-mentioned electrofusion joint 20A and electrofusion joint 20B, the convex part 31 or the convex part 34 is repeatedly and continuously formed in the direction of the axis L in the wall part W5 of the inner layer pipe 21. The wall portion W5 is not separated from the outer tube 22 due to the expansion of the wall portion W3 when the electrofusion joints 20A and 20B are energized. Also good.

20A Electric fusion joint 21 Inner layer pipe 21a Inner layer pipe outer peripheral surface 22 Outer layer pipe 22b Outer layer pipe inner peripheral surface 23 Opening 27a, 27b Boss 28a, 28b Terminal fitting 29 Resistance wire 31, 34 Convex part 32, 35 Concave part P1 Resin tube

Claims (1)

An inner layer pipe having a boss to which the terminal fitting is fixed and a resistance wire connected to the terminal fitting is wound around the outer circumferential surface; and an outer layer pipe formed on the outer circumferential surface of the inner layer pipe. In a tubular electric fusion joint for inserting the resin pipe to be connected into the opening of the outer pipe and fusing the resin pipe,
In the vicinity of the opening, a convex portion is formed on one of the outer peripheral surface of the inner layer tube and the inner peripheral surface of the outer layer tube, and a concave portion that fits the convex portion is formed on the other side. An electric fusion joint characterized in that.

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