JP2002295779A - Electrofusion joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable electrofusion joint capable of preventing the generation of fluid leakage from a plastic pipe at a part connected by the electrofusion joint. SOLUTION: In this electrofusion joint 20 in which a plastic pipe 1 to be connected is inserted in a plastic joint body 8 with an electric heating body 9 built therein, the electric heating body 9 is heated, an inner circumferential surface of the joint body 8 in which the plastic pipe body 2 is inserted and an outer circumferential surface of the plastic pipe 1 which are a joining surface of the joint body 8 with the plastic pipe 1 are heated and melted, heat-welded and joined with each other, a metal or ceramic reinforcing layer 21 is provided on the outer circumferential surface of the joint body 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrofusion joint used for connecting plastic pipes for transporting a fluid such as gas, oil, water or the like, or for connecting the plastic pipes to another member.

[0002]

2. Description of the Related Art Plastic pipes are widely used and widely used in place of conventional iron pipes because gas pipes and water pipes are easy to construct and have excellent earthquake resistance. When used at a small fluid pressure of about 0.1 to 0.3 MPa, the plastic tube has a single-layer or two-layer structure and is not particularly reinforced. However, when used at a higher fluid pressure, particularly at a higher pressure of 1 MPa or more, for example,
As shown in FIG. 2, a plastic tube 1 reinforced with a steel strip or the like or reinforced with a high-strength fiber such as an aramid fiber is used. That is, a thin tape of normal steel such as mild steel or stainless steel is fixed on the outer periphery of a plastic pipe main body 2 made of polyethylene or the like having an inner diameter of about 50 to 500 mm via a cushion layer 3 formed by winding a cloth tape around. And a protective layer 6 made of a plastic such as polyethylene is provided on the outer periphery of the metal tape wound layer 4 via a holding tape wound layer 5 formed by the wrapping of a cloth tape. Is used.

[0003] On the other hand, when connecting a plastic pipe, an electrofusion joint 7 as shown in FIG. 3 is used, for example, because the pipe connection operation is easy, the workability on site is excellent, and the fluid leakage after connection is small. (Electrical fusion joints, abbreviated EF joints) are widely used and widely used.

The electrofusion joint 7 has a plastic tube 1 to be connected to a plastic joint body 8 having a built-in current-generating heating element 9 such as a heating wire, and is energized to energize the current-generating heating element 9 to generate heat. The inner peripheral surface of the joint body 8 and the outer peripheral surface of the plastic tube 1 which are the joining surfaces of the joint body 8 and the plastic pipe 1 are heated and melted, and are thermally fused and joined. Reference numeral 10 denotes a terminal which is electrically connected to both ends of the current-carrying heating element 9 via lead wires 11 and protrudes from outer peripheral surfaces near both ends of the joint body 8, 12 denotes a connector connected to the terminal 10, 13 Is a controller for turning on / off, switching, and controlling the current value of the current supplied to the current-carrying heating element 9; 14 is an output cord for electrically connecting the connector 12 to the controller 13; A power source 16 such as a battery for heating the base is attached to the connector 12 at the base end, and the front end is inserted into the vicinity of the current-carrying heating element 9 built in the joint body 8 to be thermally fused near the joint surface. This is a temperature sensor for detecting and monitoring the temperature of the plastic resin.

When the plastic tubes 1 are connected to each other by using the electrofusion joint 7 as shown in FIG. 3, for example, first, the protective layer 6 at the terminal portion of the plastic tube 1 to be connected, the holding tape, The winding layer 5, the metal tape winding layer 4, and the cushion layer 3 are peeled off and the plastic pipe main body 2 is exposed. The exposed plastic pipe main body 2 is inserted into the joint main body 8 of the electrofusion joint 7, and the electric heating is performed. The body 9 is energized to generate heat, and the joint surface between the joint body 8 and the plastic pipe body 2, that is, the inner peripheral surface of the joint body 8 where the plastic tube 1 is inserted and the outer peripheral surface of the plastic tube 1 are maintained at a predetermined temperature. Heat until And the said joining surface heat-fuses and heat-fuses,
When the joint body and the plastic pipe body 2 have been joined,
The controller 13 stops energization of the energizing heating element 9, confirms the thermal fusion state of the joining surface, that is, the joining state, visually and by touching the finger, and removes the connector 12 of the output cord 14 from the terminal 10.

[0006]

When the connection of the plastic tube 1 is performed by the electrofusion joint 7 as described above, the plastic tube 1 is reinforced by the metal tape winding layer 4 at locations other than the electrofusion joint 7. ,
Since the portion connected by the electrofusion joint 7 is not reinforced by the metal tape winding layer 4, the mechanical strength is reduced. Further, since the joint body 8 of the electrofusion joint 7 is made of plastic, it generally has low mechanical strength.

For this reason, the strength of the portion of the plastic tube 1 connected by the electrofusion joint 7 is insufficient. If the strength of the part is insufficient, an unexpected situation occurs, and if the internal pressure of the pipe greatly increases, the pipe of the part expands and deforms, or if a large external pressure or external force is applied to the joint 7, Buckling deformation of the tube, a crack is generated in the heat fusion bonded portion of the electrofusion joint, and the joint body is easily damaged. When cracks or breakage occur, there is a problem that a fluid leaks from a plastic tube at a portion connected by the electrofusion joint, and the reliability of the electrofusion joint is reduced.

An object of the present invention is to solve the above problems and to provide a highly reliable electrofusion joint that prevents fluid leakage from a plastic pipe at a portion connected by an electrofusion joint.

[0009]

In order to achieve the above object, an electrofusion joint according to the present invention is characterized in that a plastic tube to be connected is inserted into a plastic joint body having a built-in energizing heating element, and the energizing heating element is inserted. Is heated, the joint surface between the joint body and the plastic pipe is heated and melted, and the joint is formed by heat-sealing, wherein a reinforcing layer is provided on the outer periphery of the joint body. Further, the reinforcing layer may be a metal or ceramic reinforcing layer.

As described above, the reinforcing layer is provided on the outer periphery of the plastic joint body to mechanically reinforce the joint body. Therefore, even if the internal pressure of the pipe is greatly increased, the pipe at that portion does not expand and deform. Alternatively, even when a large external pressure or external force is applied to the joint 7, the tube at that portion does not buckle and a crack is generated at the heat fusion bonded portion of the electrofusion joint, or the joint body is damaged. It becomes difficult to do. Therefore, fluid leakage does not occur from the plastic tube at the portion connected by the electrofusion joint, and the reliability of the electrofusion joint can be improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to an embodiment shown in the drawings. Note that the same reference numerals are used for components having the same configuration as the conventional technology. FIG. 1 is a cross-sectional view of an electrofusion joint 20 used for connecting the plastic tubes 1 to each other, for example. The electrofusion joint 20 is a straight pipe joint including a plastic cylindrical joint body 8 having a built-in electric heating element 9.

The joint body 8 is formed by molding a thermoplastic plastic material such as a polyvinyl chloride resin, a polyethylene resin, and a polybutene resin. Also, the current-carrying heating element 9
Is composed of a heating wire such as a nichrome wire. The energizing heating element 9 is spirally wound and buried in the joint body 8 near the inner peripheral surface of the joint body 8 which is a joint surface between the joint body 8 and the plastic pipe 1 to be connected to be connected thereto. Is done. In order to incorporate the current-carrying heating element 9 in the joint body 8 as described above, for example, a core is disposed in advance in the center of the molding die of the joint body 8, and a coil-shaped core is surrounded so as to surround the core. The energization heating element 9 is inserted and inserted, and the resin material is injected into the mold to form the joint body 8 and embedded integrally in the joint body 8. After the injection molding, the mold is disassembled and removed. Together with the core. The heating element 9 may be made of, for example, carbon black, graphite particles, metal particles (powder of copper, iron, nickel, or the like), or conductive particles such as a mixture thereof, in addition to the heating wires. And a current-carrying layer mixed in a thermoplastic material such as polypropylene.

Reference numeral 10 denotes a lead wire 11 at both ends of the heating element 9.
A terminal electrically connected to the joint body 8
Are protruded from the outer periphery near both ends. The terminal 10 is also provided integrally with the molding of the joint body 8. 12 is a connector connected to the terminal 10, 13 is a controller for turning on / off, switching, and controlling the current value of the current supplied to the energizing heating element 9, 14 is an output cord for electrically connecting the connector 12 and the controller 13, Reference numeral 15 denotes a power source such as a battery for supplying a current to the heating element 9 to heat the heating element 9. Temperature sensor for detecting and monitoring the temperature of the heat-sealed plastic resin near the joint surface. Then, the controller 13 is operated to supply electric power from the power supply 15 to the energizing heating element 9, thereby energizing the heating element 9 to generate heat, and the joint body 8 is a joint surface between the joint body 8 and the plastic pipe 1 to be connected. The inner peripheral surface of the plastic tube 8 and the outer peripheral surface of the plastic tube 1 are heated and melted, and are thermally fused and joined.

The above configuration is the same as the conventional one. The electrofusion joint 20 of the present invention is characterized in that a reinforcing layer 21 is provided on the outer periphery of the joint main body 8.
What is illustrated as the reinforcing layer 21 is a metal reinforcing layer,
For example, it is constituted by a metal tube. The thickness of the metal pipe is determined by the magnitude of the fluid pressure flowing through the plastic pipe 1, and is generally about 0.5 to 5 mm. Also,
The material of the metal tube is generally and desirably made of ordinary steel such as mild steel, carbon steel, and stainless steel having high mechanical strength, low cost, and good formability, but is not limited thereto. Instead, metal materials such as titanium, copper, copper alloy, aluminum, and aluminum alloy can also be applied.

Although the reinforcing layer 21 has some problems in cost and moldability, it may be formed of a ceramic reinforcing layer, for example, a ceramic tube (not shown). As the material of the ceramic tube, one or a mixture of aluminum oxide, magnesium oxide, calcium oxide, silicon nitride, and the like is used.

If the metal pipe or the ceramic pipe constituting the reinforcing layer 21 has, for example, an integral pipe structure which cannot be divided into two, the terminal 10 can be protruded from the outer periphery near both ends of the joint body 8 through these pipes. As described above, a terminal insertion hole is provided in advance in a place where the terminal 10 of these tubes is inserted. When the reinforcing layer 21 composed of these pipes is attached to the outer periphery of the joint body 8, the reinforcing layer 21 is previously stored and positioned and fixed in a molding die of the joint body 8. It is desirable to inject a predetermined molding plastic material into the joint body 8 to mold the joint body 8 and, at the same time, to integrally fix and attach to the joint body 8.

In the case of the reinforcing layer 21 made of metal, a steel tape or a stainless steel tape is usually wound around the outer periphery of the joint main body 8 formed in advance by injection molding or the like into a plurality of layers, and the end face of the tape is wound. It may be formed by joining by welding or the like.

When the reinforcing layer 21 is formed of such a tape winding layer or formed of a splittable tubular body, the plastic pipe 1 is inserted into the joint main body 8 and heat is applied. After the body 9 is heated and the joint surface between the joint body 8 and the plastic pipe 1 is thermally fused and joined, the reinforcing layer 21 may be provided on the outer periphery of the joint body 8.
The time of providing the reinforcing layer 21 does not matter before or after the time of inserting the plastic pipe 1 into the joint body 1.

Further, in the electrofusion joint 20 of the above embodiment, the location of the terminal 10 is not reinforced by the reinforcing layer 21, but since the area occupied by the terminal portion is relatively small, an excessive internal / external pressure or external force acts thereon. Even so, the plastic thickness of the joint body 8 can sufficiently withstand the problem, and there is no practical problem. Terminal 10 as needed
In the case of reinforcing the portion, the terminal 10 may be cut off after the plastic tube 1 is heat-sealed, and a metal tape or a metal wire may be wound around the terminal 10 for reinforcement.

When connecting the plastic pipes 1 using the electrofusion joint 20, first,
Protective layer 6, terminal tape winding layer 5, metal tape winding layer 4, and cushion layer 3 at the end of plastic pipe 1 to be connected
The plastic tube body 2 is exposed by peeling off the plastic tube body 2. The exposed plastic tube body 2 is inserted into the joint body 8 of the electrofusion joint 7, and the electric heating element 9 is energized to generate heat. The joint surface of the pipe main body 2, that is, the inner peripheral surface of the joint main body 8 into which the plastic pipe main body 2 is fitted and the outer peripheral surface of the plastic pipe main body 2 are heated to a predetermined temperature. Then, when the joint surface is heated and melted and heat-fused, and the joint between the joint body and the plastic pipe body 2 is completed, the controller 13 stops supplying electricity to the energizing heating element 9 and the heat-fused state of the joint surface, That is, the joining state is confirmed visually and by a finger, and the output code 14
The connector 12 is removed.

In the above embodiment, the method of connecting the plastic tubes 1 with each other using the electrofusion joint 20 has been described. However, the case where the plastic tubes 1 are branched and connected, or the members are connected to another member, for example, a device or the like. It is also possible to apply the case. Depending on these applications, electrofusion joints will also be replaced with straight pipe joints,
A Y-branch joint, a T-branch joint, an elbow joint, a saddle joint, a reducer, and the like can be used.

[0022]

As described above, according to the electrofusion joint of the present invention, a reinforcing layer is provided on the outer periphery of the joint main body to mechanically reinforce the joint main body. Even if the pipe in that part does not expand and deform, or even if a large external pressure or external force is applied to the joint 7, the pipe in that part does not buckle and a crack may occur in the heat-fusion joint of the electrofusion joint. Also, the joint body is less likely to be damaged. Therefore, fluid leakage does not occur from the plastic tube at the portion connected by the electrofusion joint, and the reliability of the electrofusion joint can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of an electrofusion joint according to the present invention.

FIG. 2 is a cross-sectional view showing an example of a plastic tube to be connected by an electrofusion joint.

FIG. 3 is a sectional view showing a conventional electrofusion joint.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plastic pipe 2 Plastic pipe main body 3 Cushion layer 4 Metal tape winding layer 5 Pressing tape winding layer 6 Protective layer 7 Electrofusion joint 8 Joint body 9 Electric heating element 10 Terminal 11 Lead wire 12 Connector 13 Controller 14 Output cord 15 Power supply 16 Temperature Sensor 20 Electrofusion joint 21 Reinforcing layer

Claims (2)

[Claims] 1. A plastic pipe to be connected is inserted into a plastic joint body having a built-in electric heating element, the electric heating element is heated, and the joint surface between the joint body and the plastic pipe is heated and melted, and heat fusion is performed. An electrofusion joint, wherein a reinforcing layer is provided on an outer periphery of the joint body. 2. The electrofusion joint according to claim 1, wherein the reinforcing layer is a reinforcing layer made of metal or ceramic.