JPH11325367A - Indicator of electric fusion joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent fusion integration of a recessed hole and a pin, even if injection molding cycle time is shortened, by making a clearance between the recessed hole and the pin in a specific dimension or more, in an indicator of an electric fusion joint in which the pin is erected at the bottom part of the recessed hole provided on the outside surface of a joint body. SOLUTION: An electric fusion joint is constituted of a polyethylene resin joint body 11, heating wire buried within a fusion boundary face on the inner periphery except both the end parts of the joint body 11 and an exothermic body 12 such as a conducting sheet. Both the end parts of the exothermic body 12 are connected with terminal pins for energizing which stands on the outside surface of the joint body 11. In the joint body 11, bosses are erected around both the terminal pins. In an electric fusion joint, a pin 17 is stood at the bottom part of the recessed hole 16 provided on the outside surface of the joint body 11, as an indicator 15 to be a standard of a good or bad decision for fusion of a pipe to be joined to the joint body 11. At this time, a clearance between the recessed hole 16 and the pin 17 is set to 1 mm or more, as compared with a conventional clearance of 0.5 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an indicator for an electrofusion joint (electrofusion joint) used for joining water and sewer pipes, gas pipes, deformed pipes and the like made of a thermoplastic resin.

[0002]

2. Description of the Related Art Conventionally, as described in JP-A-64-74381, a heating wire is embedded in the inner surface of a joint body as an electric fusion joint for joining polyethylene (PE) pipes and the like. There is a type in which a pipe to be joined is inserted into a main body, the fitting contact surface (fusion interface) between the joint main body and the pipe to be joined is heated and melted by the heat generated by the heating wire, and the pipe to be joined is fused to the joint body.

As a method for embedding a heating wire in a joint body of an electric fusion joint, a coating heating wire in which a heating wire is concentrically covered with a coating portion made of a thermoplastic resin is prepared. Is spirally wound around a core (core material) of an injection molding die, the core is inserted into the die, and a thermoplastic resin is injection-molded into the die to form a joint body ( JP-A-64-74281).

However, in the prior art, a pin is set up at the bottom of a recessed hole provided on the outer surface of the joint body as an indicator for judging the quality of fusion of the pipe to be joined to the joint body in the electrofusion joint. (Japanese Patent Laid-Open No. 61-62696). With this indicator,
The pressure of expansion of the resin that melts at the fusion interface of the joint body due to the current generated by the electric heating wire in the electric fusion joint causes the pins implanted in the joint body to rise outward from the recessed holes, and the pin It is possible to judge the end of the proper fusion and, consequently, the good fusion of the pipe to be joined to the joint body by the amount of protrusion.

In FIG. 6, 1 is a joint body, 2 is a heating wire, 3 is a recessed hole, and 4 is a pin.

[0006]

However, if the injection molding cycle time of the joint main body is shortened and the timing of removing the joint main body from the mold is shortened in order to improve the production yield of the electrofusion joint, the hollow of the joint main body is reduced. The inner peripheral surface of the hole expands so as to reduce the diameter of the hole even after being taken out without reaching the cooling and solidifying state yet. Then, the recessed hole and the pin are welded and integrated, and the indicator function is not fulfilled in the subsequent use stage.

An object of the present invention is to provide an electro-fusion joint,
Even if the injection molding cycle time of the joint body is shortened, it is an object to prevent fusion integration of the recessed hole and the pin.

[0008]

According to the present invention, a heating element is buried in a fusion interface of a joint body made of a thermoplastic resin, and a pin is provided at a bottom of a concave hole provided on an outer surface of the joint body. The clearance between the recessed hole and the pin is set to 1 mm or more in the indicator of the electrofusion joint in which the upright is raised.

According to a second aspect of the present invention, there is provided an electric machine comprising a heating element buried in a fusion interface of a thermoplastic resin joint body and a pin set up on the bottom of a recessed hole provided on an outer surface of the joint body. In the indicator of the fusion joint, the inner peripheral surface of the recessed hole and / or the outer peripheral surface of the pin are made uneven.

[0010]

According to the first aspect of the present invention, the following operations are provided. In the electric fusion joint, the clearance between the recessed hole and the pin provided in the joint body is as large as 1 mm or more. Therefore, in order to improve the production output of the electro-fusion joint, when the injection molding cycle time of the joint body is shortened and the timing of taking out the joint body from the mold is accelerated, the inner peripheral surface of the recessed hole of the joint body is reduced. Even after being removed, even if the hole is expanded so as to reduce the hole diameter before reaching the cooling and solidification state, the recessed hole and the pin are not welded and integrated due to the presence of the large clearance described above.

According to the second aspect of the present invention, the following operations are provided. In the electrofusion joint, the inner peripheral surface of the recessed hole and / or the outer peripheral surface of the pin were made uneven. Therefore, in order to improve the production output of the electro-fusion joint, even if the injection molding cycle time of the joint body is shortened and the timing of removing the joint body from the mold is accelerated, the inner peripheral surface of the recessed hole and / or the pin is not required. The outer peripheral surface is cooled and solidified by the cooling fin effect of the above-mentioned uneven surface, and welding and integration of the recessed hole and the pin can be prevented.

[0012]

FIG. 1 is a schematic view showing an example of an electro-fusion joint, FIG. 2 is a schematic view showing a first embodiment, and FIG.
FIG. 4 is a schematic diagram showing a specific implementation result of the embodiment, FIG. 4 is a schematic diagram showing a second embodiment, FIG. 5 is a schematic diagram showing a third embodiment, and FIG. 6 is a schematic diagram showing a conventional example.

(First Embodiment) (FIGS. 1 to 3) As shown in FIG. 1, an electric fusion joint 10 has a joint body 11 made of PE resin and an inner periphery of the joint body 11 excluding both ends. It comprises a heating element 12 such as a heating wire or a conductive sheet embedded in the fusion interface. At both ends of the heating element 12, terminal pins 13, 13 for energization, which are erected on the outer surface of the joint body 11.
Is connected. In the joint body 11, bosses 11A, 11A are erected around both terminal pins 13, 13.

In the case of the electric fusion joint 10, FIG.
As shown in the figure, the pipe to be joined to the joint body 11 (PE pipe) 2
As an indicator 15 as a guide for judging the quality of fusion of the joints 1 and 21, a concave hole 16 provided on the outer surface of the joint body 11 is used.
The pin 17 is erected on the bottom of the. At this time, in the present invention, the clearance between the recessed hole 16 and the pin 17 is set to 1 mm or more, compared to the conventional 0.5 mm or less.

Accordingly, the electrofusion joint 10 is manufactured as follows. That is, the heating element 12 is wound around a core of an injection molding die, this core is inserted into the die, and PE is
The joint body 11 is formed by injection molding a resin. At this time, the recessed hole 1 of the indicator 15 is
6. The pins 17 are also formed. This is cooled and removed from the mold to obtain the electrofusion joint 10.

The electrofusion joint 10 is used as follows. That is, the to-be-joined pipes 21, 21 are inserted into the sockets at both ends of the joint body 11 of the electric fusion joint 10, and the terminal pins 1
Electricity is supplied through the power cords connected to 3,13. As a result, the heating element 12 generates heat and the surrounding joint body 11
The PE resin and the outer surface layers of both joined pipes 21 and 21 are in a molten state, and the electric fusion joint 10 and both joined pipes 21 and 21 are melted.
Are fused.

At the stage of using the electrofusion joint 10, the indicator 15 causes the joint body 1
The pressure of expansion of the resin melted at the fusion interface causes the pin 17 implanted in the joint body 11 to protrude outward from the recessed hole 16, and the amount of the pin 17 to protrude allows proper fusion. It is possible to determine the end, and thus the goodness of fusion of the pipe 21 to be joined to the joint body 11.

Therefore, according to the present embodiment, the following operations are provided. That is, in the electric fusion joint 10, the joint body 1
1 the clearance between the recessed hole 16 and the pin 17
As large as 1 mm or more. Therefore, in order to improve the production output of the electro-fusion joint, when the injection molding cycle time of the joint body is shortened and the timing of taking out the joint body from the mold is accelerated, the inner peripheral surface of the recessed hole of the joint body is reduced. Even after being removed, even if the hole is expanded so as to reduce the hole diameter before reaching the cooling and solidification state, the recessed hole and the pin are not welded and integrated due to the presence of the large clearance described above.

FIG. 3 shows the specific results of the first embodiment. In the electrofusion joint 10 having a nominal diameter of 100, the clearance between the recessed hole 16 and the pin 17 is set to 1.15 mm at the minimum. In addition, the productivity of the injection molding of the joint body 11 was improved 2.8 times that of the conventional one, and the function of the indicator 15 was secured.

(Second Embodiment) (FIG. 4) In an indicator 15 according to a second embodiment, an inner peripheral surface of a concave hole 16 formed by injection molding of a joint body 11 has an uneven surface 16A.

According to this, cooling and solidification of the inner peripheral surface of the recessed hole 16 is promoted by the cooling fin effect of the concave and convex surface 16A, and welding and integration of the recessed hole 16 and the pin 17 can be prevented.

(Third Embodiment) (FIG. 5) In the indicator 15 of the third embodiment, the joint body 11
In this case, the outer peripheral surface of the pin 17 formed by the injection molding is an uneven surface 17A.

According to this, the cooling effect of the outer peripheral surface of the pin 17 is promoted by the cooling fin effect of the uneven surface 17A, and welding and integration of the recessed hole 16 and the pin 17 can be prevented.

In the second and third embodiments, the concave portions 16 and the convex portions of the uneven surfaces 16A and 17A of the pin 17 are preferably not flat but pointed to improve the cooling effect. .

In the second embodiment and the third embodiment, when the pin 17 is raised in the use stage of the electrofusion joint 10, the pin 17 is bent or the like so that the inner peripheral surface of the recessed hole 16 is formed. Even if they contact, the contact area between the recessed hole 16 and the pin 17 becomes smaller due to the uneven surfaces 16A and 17A, so that friction can be reduced and the amount of protrusion of the pin 17 can be stabilized.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and the design can be changed without departing from the scope of the present invention. The present invention is also included in the present invention.

[0027]

As described above, according to the present invention, in the electric fusion joint, even if the injection molding cycle time of the joint body is shortened, the fusion of the recessed hole and the pin can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an electric fusion joint.

FIG. 2 is a schematic diagram showing a first embodiment.

FIG. 3 is a schematic diagram showing a specific implementation result of the first embodiment.

FIG. 4 is a schematic diagram showing a second embodiment.

FIG. 5 is a schematic diagram showing a third embodiment.

FIG. 6 is a schematic diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Electric fusion joint 11 Joint main body 12 Heating element 15 Indicator 16 Recessed hole 17 Pin 16A, 17A Uneven surface

Claims (2)

[Claims] 1. An indicator for an electric fusion joint, wherein a heating element is buried in a fusion interface of a thermoplastic resin joint body and a pin is erected at a bottom of a concave hole provided on an outer surface of the joint body. An indicator for an electrofusion joint, wherein the clearance between a hole and a pin is 1 mm or more. 2. An indicator for an electric fusion joint, wherein a heating element is buried in a fusion interface of a thermoplastic resin joint body and a pin is erected at a bottom of a concave hole provided on an outer surface of the joint body. An indicator for an electro-fusion joint, wherein an inner peripheral surface of a hole and / or an outer peripheral surface of a pin are made uneven.