JP2001295978A - Electric fusion pipe fittings - Google Patents

Abstract

(57) [Problem] To provide an electrofusion pipe joint which does not cause internal fluid leakage even if a slight gap is generated between layers. SOLUTION: An innermost layer (inner member layer) 3 made of a heat-sealable material and an outermost layer (outer member layer) 2 formed along the outer periphery of the innermost layer 3 are formed in a radial direction. The boundary surface 9 between the innermost layer 3 and the outer peripheral layer 2 is formed by a multilayer pipe of a thermoplastic resin laminated over the entire surface, so that the pipe joint inner peripheral surface 8 is formed.
In the innermost layer 3 near at least one of the receptacles 12, there is buried an energized heating element 4 that generates heat when energized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrofusion pipe joint for joining thermoplastic resin pipes used for gas, water distribution, vacuum pipes and the like.

[0002]

2. Description of the Related Art Conventionally, polyethylene, polypropylene, and the like have been used for piping such as gas pipes, water pipes, sewer pipes, and hot water pipes.
Thermoplastic resin pipes such as polyvinyl chloride and polyvinylidene fluoride are used. In the piping work of these thermoplastic resin pipes, an electric fusion pipe joint in which a heating wire is embedded in a joint for joining the thermoplastic resin pipes has been developed. The inner surface of the fusion-pipe joint is fusion-bonded to the thermoplastic resin tube by heating the heated heating wire with electric current.

[0003] As such, for example, an electrofusion pipe joint 1 as shown in FIG. 3 is known. The electrofusion pipe joint 1 includes an outer member layer 2 constituting a pipe joint body and an inner member layer 3 formed on the inner peripheral surface thereof. The heating wire 4 is buried in the wire, and the heating wire 4 is connected to a terminal 5.

In the electrofusion pipe joint 1 having such a configuration, the inner member layer 3 previously injection-molded is attached to the cavity of the outer member layer 2, and the outer member layer 2 is formed by injection molding. 4, a heating wire 4 obtained by coating a heating resin 4 with a thermoplastic resin 4 is attached to a cavity of the outer member layer 2 to form the outer member layer 2 by injection molding. When the outer member layer 2 is formed by such injection molding, the inner member layer 3 and the coated heating wire 7 are made of thermoplastic resin in order to minimize the generation of distortion due to cooling and solidification of the thermoplastic resin. Since it has a great effect on the cooling and solidification of the resin, it was made compact to minimize distortion.

[0005]

However, in such an electrofused pipe joint 1, water leakage may be observed in an internal pressure test. This is because the contraction of the thermoplastic resin is different due to the difference in the thickness of the inner member layer 3 and the outer member layer 2 in the conventional structure, as shown in the schematic diagram partially enlarged in the circle of FIG. Interface 9 between inner member layer 3 and outer member layer 2
May form a small gap Δ due to separation or the like. When this gap Δ is exposed on the inner peripheral surface 8 of the pipe joint, the boundary surface 9
In some cases, the internal fluid may enter from the small gap Δ of a and leak out to the outside as indicated by the arrow.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrofusion pipe joint which does not cause internal fluid leakage even if a gap is formed at a boundary surface between layers.

[0007]

According to a first aspect of the present invention, there is provided an innermost layer made of a heat-sealable material and formed along the outer periphery of the innermost layer. An outer layer is formed of a thermoplastic multi-layer pipe laminated on the entire surface in the radial direction, and at least one innermost layer in the vicinity of the receiving port is buried with an energized heating element that generates heat when energized. It is an electrofusion pipe joint characterized by being performed.

With this configuration, since the current-carrying heating element is buried in the innermost layer near the receptacle, electric fusion can be performed by supplying current to the current-carrying heating element. In addition, since the innermost layer and the outer peripheral layer are formed of a multilayer pipe of a thermoplastic resin laminated on the entire surface in the radial direction, the boundary surface between the innermost layer and the outer peripheral layer is exposed on the inner peripheral surface of the tube. Absent. Thereby, even if a gap is generated at the boundary surface due to a difference in thickness between the inner peripheral layer and the outer peripheral layer and a difference in heat shrinkage, since the boundary surface is not exposed to the inner peripheral portion of the pipe, The fluid inside the tube does not leak.

According to a second aspect of the present invention, there is provided the electrofusion tube according to the first aspect, wherein the receiving hole at at least one end of the multi-layer tube is not embedded with the current-carrying heating element so as to be capable of performing butt fusion. It is a joint.

According to this structure, in addition to the function of the first aspect, the receptacle at one end can connect the pipe joined by butt fusion to the pipe made of another thermoplastic resin by electric fusion.

The invention according to claim 3 is characterized in that the innermost layer is formed from a groove provided on the outer periphery around which the linear body of the energized heating element is wound. It is a joint.

According to this structure, in addition to the function of the first aspect, the outer peripheral layer is formed on the innermost layer in which the linear body is wound around the outer peripheral groove, so that the outer peripheral groove of the innermost layer and the linear body are formed. The outer peripheral layer is formed on the uneven surface formed by the above, and the area of the boundary surface between the innermost layer and the outer peripheral layer is increased as compared with a case where the boundary surface is a flat surface. Less likely to happen.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. In addition, the same or equivalent parts as those of the prior art will be described with the same reference numerals.

First, the structure of the electrofusion pipe joint 10 of this embodiment is a socket type having receiving ports 11 and 12 at both ends as shown in FIG. An outer member layer (outer layer) 2 and an inner member layer (innermost layer) 3 made of a heat-sealable material are provided on the inner surface thereof in the radial direction (reception ports 11 and 12 at both ends).
) Is generally constituted by a multi-layer pipe laminated on the entire surface over the entire period. As a result, the boundary surface 9 between the inner member layer 3 and the outer member layer 2 is exposed at both ends, but the pipe joint inner peripheral surface 8 is exposed.
Not exposed to. In the inner member layer 3 near the receptacle 12, a heating wire 4 as an energizing heating element that generates heat when energized is embedded.

The material forming the electrofusion pipe joint is appropriately selected from, for example, thermoplastic resins and the like having high fusing properties and high adhesiveness. For example, polyethylene (high density, medium density, low density may be any), polypropylene,
Examples thereof include, but are not limited to, olefin resins such as polybutene, polyamide, polyester, polyetherimide, polyether polyether ketone, polyether sulfone, polyphenylene sulfide, polyoxymethylene, ABS, and AES.

The innermost layer and the outermost layer may each be further multilayered depending on the intended use of the tube material (required performance, etc.), and a resin forming the innermost layer and an outermost layer may be used. It may be different from the resin to be formed. When the resins are different, the resin forming the outer layer is selected from those having a higher heat distortion temperature than the resin forming the innermost layer.

The material of the electric heating element is not particularly limited, and examples thereof include nickel (nickel) chromium (alloy), stainless steel, copper nickel alloy, iron chromium alloy and the like, and these can be obtained as a heating wire. .

The method for forming the electrofusion pipe joint 10 having such a configuration is not limited. For example, an inner layer member 14 having a groove 13 for winding the heating wire 4 around the outer periphery as shown in FIG. 2 is formed in advance by injection molding or the like, and the heating wire 4 is spirally wound around the groove 13. Alternatively, after attaching the inner layer member 14 to the cavity of the outer member layer 2, the heating wire 4 is spirally wound, and then the outer member layer 2 is formed by injection molding. The pipe fitting 10 can be manufactured.

The thus formed electrofusion pipe joint 1
0 is the outer member layer 2 and the inner member layer 3
Peeling off hardly occurs. Also, in this case, the size (depth, width, etc.) of the concave groove 13 may be such that irregularities are formed on the outer surface of the inner layer member 14 even after the heating wire 4 is wound.
It may be larger or smaller than the diameter of the heating wire 4.

Alternatively, the outer member layer 2 can be formed by attaching the inner member layer 3 previously injection-molded to the cavity of the outer member layer 2 and forming the outer member layer 2 by injection molding. The outer member layer 2 may be joined to the inner layer member 14 by butt fusion to form an electric fusion joint.

In such an electro-fused pipe joint 10, the receiving port 11 at one end is butt-fused, and an integral conduit is formed by butt-fusing with a pipe (not shown) having the same outer diameter and thickness. be able to.

Further, a plug of an electric fusion machine (not shown) is connected to the terminal 5 of the other receiving port 12, and a predetermined amount of electricity is supplied, so that the heating wire 4 generates heat. Can be melted by heating and electrofused with another tube (not shown).

According to such an electrofusion pipe joint 10,
Even if a gap Δ is generated at the boundary surface 9 due to a difference in thickness between the inner member layer 3 and the outer member layer 2 and a difference in thermal shrinkage, the gap Δ does not communicate with the internal fluid ( Since there is no boundary surface 9a exposed on the pipe joint inner peripheral surface 8 shown in FIG. 3), it is possible to prevent the internal fluid from leaking from the gap Δ. As a result, the boundary surface 9 between the inner member layer (innermost layer) 3 and the outer member layer (outer peripheral layer) 2 is not exposed on the pipe joint inner peripheral surface 8, so that the internal fluid may leak. Even if the internal pressure test, which is one of the evaluation items of the electrofusion pipe joint, is performed, the electrofusion pipe joint 10 that does not cause water leakage or leakage can be obtained.

In addition, since the internal fluid does not come into direct contact with the outer member layer 2, when the corrosive fluid is held in the pipe, only the material of the inner member layer 3 is made resistant to corrosion. In some cases, the cost of the electrofusion pipe joint may be reduced, for example, the material may be selected from the above materials.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration of the present invention is not limited to this embodiment, and a design change or the like may be made without departing from the gist of the present invention. Even if present, it is included in the present invention.

For example, the heating wire 4 may be embedded in the inner periphery of the receiving ports 11 and 12 at both ends.
The electric fusion pipe joint 10 is not limited to the socket type, but may be an elbow type, a three-way or more T pipe joint, a cross pipe joint, or the like.

[0027]

As described above, according to the first aspect of the present invention, a gap is formed at the boundary between the innermost layer in which the energizing heating element is buried near the receptacle and the outer peripheral layer forming the outer periphery thereof. Even if this occurs, the boundary surface is not exposed to the inner circumference of the pipe, so that the fluid inside the pipe does not leak from this gap, and even if there is a slight gap between the layers, there is no electricity leakage inside the pipe. A fusion splice can be provided.

According to the second aspect of the present invention, in addition to the effect of the first aspect, the receiving port at one end can connect a pipe joined by butt fusion to a pipe made of another thermoplastic resin by electric fusion. An electrofusion fitting can be provided.

According to the third aspect of the present invention, in addition to the effect of the first aspect, the boundary surface between the innermost layer and the outer peripheral layer becomes uneven, and the bonding area is increased as compared with the case where it is flat. In addition, the present invention has a practically useful effect that an electro-fused pipe joint in which delamination of a boundary surface does not easily occur can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a main part of an electrofusion pipe joint according to the present invention.

FIG. 2 is a partial vertical cross-sectional view illustrating a structure of an inner layer member 14 which is a member used when manufacturing the electrofusion pipe joint of FIG.

FIG. 3 is a vertical cross-sectional view schematically illustrating the structure of a conventional electrofusion pipe joint and the principle of water leakage.

FIG. 4 is a cross-sectional view illustrating a coated heating wire.

[Explanation of symbols]

 2 Outer layer (outer member layer) 3 Innermost layer (inner member layer) 4 Electric heating element (heating wire) 5 Terminal 9 Boundary surface 10 Electrofusion pipe joint 11, 12 Receptacle 13 Groove (groove) 14 Inward Layer members

Claims (3)

[Claims] 1. A multi-layer thermoplastic resin tube in which an innermost layer made of a heat-sealable material and an outer peripheral layer formed along the outer periphery of the innermost layer are laminated over the entire surface in a radial direction. And a current-carrying heating element that generates heat when energized is buried in the innermost layer near at least one receiving port. 2. A joint according to claim 1, wherein said electric heating element is not buried in at least one end of said multi-layer tube so as to be capable of butt fusion. 3. The electrofusion pipe joint according to claim 1, wherein the innermost layer is formed of a groove provided around an outer periphery of the linear body of the electric heating element.