JPH11173484A - Electro-fusion joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EF joint in a divided cylindrical shape where a joint can be divided as similarly as a joint body can be divided, resin entirely coated over the inner surface of the joint body and the outer surface of a pipe, is continuously and consecutively heated so as to be fused, and a conductive electric wire is buried in the inside of the joint body in such a way that the joint body can properly be fused with the pipe. SOLUTION: This electro fusion joint is equipped with a joint body 2 in a cylindrical shape, in which a part of a circumferential wall made out of thermal plastic synthetic resin is divided in the axial direction, and with an exothermic body 4 in a belt shape in which an electric wire coated with insulating material is multicatively folded so as to be formed into a belt shape, the exothermic body 4 is buried in the inner surface of the joint body 2, and when both the divided end parts 13 and 14 of the joint body are spliced, both the end parts pf the exothermic body 4 are spliced so as to be formed into a ring shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joint for joining pipes made of a thermoplastic synthetic resin, and more specifically, a conductive wire is embedded in a joint made of a thermoplastic synthetic resin to supply electricity to the conductive wire. Accordingly, the present invention relates to an electrofusion joint (hereinafter referred to as an “EF joint”) that heats and melts the resin on the inner surface of the joint and the outer surface of the tube to fuse the joint and the tube.

[0002]

The conductive wire peculiar to the EF joint is spirally wound and embedded in the conventional joint.
The EF joint cannot be provided with a split tube type having this specific structure. For example, the joining of pipes that cannot be joined with an adhesive such as a polyethylene-coated tube having a wire rope passing through inside is performed by hand. There was a problem that the pipes such as the coated tube could not be easily joined together, either directly by welding or manually by using a split tube joint made of polyethylene.

[0003] Therefore, the present invention is capable of breaking the joint body and the pipe properly without breaking the resin on the inner surface of the joint body and the outer surface of the pipe continuously over the entire circumference without breaking the joint body and the pipe. An object of the present invention is to provide a split tube type EF joint by embedding a conductive wire inside the joint main body so as to be able to perform fusion.

[0004]

An EF joint according to the present invention for achieving the above object has a cylindrical joint body made of a thermoplastic synthetic resin and having a part of a peripheral wall divided in an axial direction, and an insulating coating. A heating element in the form of a strip formed by folding one conductive wire into multiple pieces, embedding the heating element in the inner surface of the main body, and joining the split ends of the main body, the ends of the heating elements are joined to form a ring shape. It is configured so that

[0005] In order to minimize the amount of splitting of the main body required when wrapping the ends of the two pipes to be joined by the main body, the end of the heating element should be joined at the same position as the joining position of the split end of the main body. ,
It is advisable to embed a heating element inside the body.

In order to join the end of the heating element at the same position as the split end of the main body, a heating element whose end is joined in one plane like the main body is used. In this case, the conductive wires are arranged in parallel in the longitudinal direction without gaps, and the ends of the conductive wires are
One conductive wire with insulation coating is folded in multiples to form a band-shaped heating element so that the turns are aligned in a horizontal line, and the U-turns at the ends of the heating element are joined together. It is preferable to make a ring shape.

[0007] Unnecessarily increasing the amount of body splitting required when wrapping the two pipe ends to be joined by the main body, and insufficient heating and melting of the resin on the inner surface of the main body and the outer surface of the pipe at the split end of the main body. In order to prevent the fusion failure due to, the end of the heating element is joined at a position different from the joining position of the split end of the main body,
It is preferable to embed a heating element inside the body.

The heating element for joining the end of the heating element at a position different from the joining position of the split end of the main body may be the above-described heating element for joining the ends in one plane. Prevents unnecessarily increasing the amount of main body splitting required when wrapping the tube end, and also causes insufficient heating and melting of the resin on the main body inner surface and the outer tube surface at the main body split end and the end of the heating element. In order to prevent poor fusion, the ends of the heating element are formed in a comb-teeth shape so that the ends of the heating element are joined in an uneven surface, and the end of the heating element is formed at the split end of the main body. It is preferable to embed the heating element in the inner surface of the main body so that the main body is engaged with the center of the joining position or engaged at a position different from the joining position of the main body split end.

In the case of the above-described heating element in which the ends are joined in an uneven surface, the conductive wires are arranged in parallel in the longitudinal direction without any gap,
In addition, a single conductive wire coated with insulation is folded in multiple so that the U-turn portions of the conductive wire are alternately shifted in front and rear in the longitudinal direction at the ends, and the ends are meshed with each other. It is preferable that the heating element is formed in a band-like shape, and each U-turn section at the top of the heating element and each U-turn section at the bottom of the valley are joined to form a ring shape.

In order to join the split ends of the main body and the ends of the heating element without gaps, it is preferable to draw out the end of the conductive wire of the heating element from the outer peripheral surface or the end face of the main body to the outside of the main body.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a front view of a split cylinder type EF joint, and FIG.
FIG. 2 is a cross-sectional view of FIG. 1, wherein the EF joint is made of a thermoplastic synthetic resin and has a cylindrical joint body (2) having one crevice (1) for dividing a part of a peripheral wall in an axial direction; It comprises a heating element (4) embedded in the inner surface of one main body (2) and the inner surface of the other main body (2) from the tube end contact core (3) projecting from the center of the inner surface of (2). .

The molding material of the main body (2) uses a resin of the same material as the thermoplastic synthetic resin tubes (P1) and (P2) to be joined. For example, when the tubes (P1) and (P2) are made of polyethylene, The body (2) is also made of polyethylene.

As shown in FIG. 3, the heating element (4) is an electric resistance wire (5) that generates resistance heat when energized by a nickel wire or the like.
And an insulating layer (6) made of an insulating material such as a glass fiber braid covering the outer surface of the resistance wire (5), and a resin layer (7) made of a thermoplastic synthetic resin covering the outer surface of the insulating layer (6). As shown in FIG. 4, the conductive wires (8) are arranged in parallel in the longitudinal direction without any gap, and the U-turn portion (9) of the conductive wire (8) is provided at the end. One conductive line (8) is folded in multiples to form an end strip so that the same number is arranged in a horizontal line, and the surfaces of the conductive lines (8) are arranged in parallel in the longitudinal direction without gaps. Partially heating the resin layer (7)
Heating element (4) by a plurality of fusion parts (10) to be melted
Is formed in a band shape, and as shown in FIG. 5, the heating element (4) is curved in a circular shape, and the U-turn portions (9) at the end portions are butt-joined in one plane to generate heat. The body (4) is configured to have an endless ring shape.

The molding material for the resin layer (7) is a resin made of the same material as the thermoplastic synthetic resin tubes (P1) and (P2). For example, the tubes (P1) and (P2) are made of polyethylene. In this case, the resin layer (7) is also made of polyethylene.

One end (11) of the conductive wire (8) is located at one end of the heating element (4), and the other end (12) is located at the other end of the heating element (4); When the heating element (4) is formed into a ring shape, the ends of the conductive wires (11) and (12) are raised near the joint of the end of the heating element (4) and radially outward from both sides of the joining section. It is composed.

As shown in FIGS. 1, 2 and 6, the heating element (4) is circumferentially moved from one main body split end (13) to the other main body split end (14). When the main body split ends (13) and (14) are butt-joined to form a circular cross section, each U-turn part (9) at the end of the heating element (4) is connected to the main body split. The inner surface of the main body (2) is joined so as to form an annular shape by joining at the same angular position as the joining position of the end portions (13) and (14), that is, in the same plane as the split (1) of the main body (2). The heat generating element (4) is embedded in the heat generating element (4), and the heat generating element (4) on the inner surface thereof can be split similarly to the main body (2).

The ends (11) and (12) of the conductive wires are located at positions corresponding to the rising position, that is, at the outer peripheral surface near the split (1) of the main body (2) and at the split (1). It is configured to be drawn out of the main body (2) from the conductive wire drawing holes (15) and (16) formed on both sides. In addition, the conductive wire end (11) (1
A conductive wire drawing groove communicating with the end face of the main body (2) from the rising position of 2) is provided, and the conductive wire ends (11) and (12) are connected to the main body (2).
The body (2) may be pulled out from the end face.

The EF joint is constructed as described above.
Two pipes (P1) made of thermoplastic synthetic resin using the EF joint
To join (P2), as shown by the solid line in FIG.
The main body split ends (13) and (14) are butt-joined together, and the ends of the heating element (4) are also butt-joined together with the split ends (1) closed from a free state of a circular cross section. As shown by the imaginary line 1, the body (2) is split into a C-shaped cross section through the crevice (1) by the flexibility of the body, and joined.
After the body (2) is put on the outer surface of the end of the pipe (P1) (P2) from the outer peripheral side, the EF joint is returned to the above free state, and the two pipes (P1) (P2) joined by the body (2) Wrap the ends. At this time, the heating element (4) is also split into a C-shaped section due to its flexibility, and returns to a circular (annular) shape integrally with the main body (2). Wrapping the ends of the two tubes (P1) and (P2). Next, each pipe (P1) (P2) is placed on both sides of the pipe end contact core (3).
After pushing each pipe (P1) (P2) into the main body (2) until the end faces abut, each pipe (P1) (P
Using a metal fusion jig (not shown) for tightly tightening the joint end with 2), preventing the pipes (P1) and (P2) from coming off, holding the butted joints of the main body split ends (13) and (14), and generating heat. The end of the body (4) is butt-jointed, that is, the body (2) is held with the split (1) closed. As a result, the heating element (4) is arranged in a ring shape between the inner surface of the main body (2) and the outer surface of the tubes (P1) and (P2). Next, the ends of the conductive wires (11) and (12) drawn out to the outer surface of the main body (2) are connected to a power supply via a fusion controller (not shown), and the power supply to the conductive wires (8) is started, and the current / voltage and The resin on the inner surface of the main body (2) and the outer surface of the pipe (P1) (P2) is continuously heated and melted without interruption over the entire circumference by the resistance heat generated from the conductive wire (8) while controlling the energization time,
The main body (2) and the tubes (P1) and (P2) are fused to join the tubes (P1) and (P2) together.

The end of the heating element (4) is the split end of the main body (13).
Since the heating element (4) is embedded in the inner surface of the main body (2) so as to be joined at the same position as the joining position of (14), the ends of the two pipes (P1) and (P2) joined by the main body (2) The required amount of body splitting (W) when wrapping the tube is minimized to the minimum tube (P1) (P
2) Only the outer diameter can be used.

The ends (11) and (12) of the conductive wires are connected to the main body (2).
To the outside of the main body (2) from the outer peripheral surface or end surface of the main body (2), the conductive wire ends (11) and (12) from the crease (1) of the main body (2).
Need not be pulled out to the outside of the main body (2).
3) The ends of the heating element (4) and the ends of the heating element (4) can be joined without any gap, and the split ends (13) and (14) of the main body and the inner surface of the main body (2) and the pipe ( P1) (P
2) Poor fusion due to insufficient heating and melting of the resin on the outer surface can be prevented.

In the EF joint, a heating element (4) is inserted into a molding die of the main body (2), and the heating element (4) is embedded in the inner surface when the main body (2) is molded. (4)
After the main body (2) is formed separately, it is provided on the inner surface at the time of molding the main body (2), or the heating element mounting groove (17) provided on the inner surface by cutting in secondary processing after the main body (2) is formed
It can be manufactured by a method of incorporating the heating element (4) into (18).

The above EF joint has a pipe (P1) (P
Since the heating element (4) is embedded in the inner surface of one side of the main body (2) and the inner surface of the other side so that 2) can be joined, the main body split end portion (13) between the respective heating elements (4). (14) cannot be fused, but after the pipes (P1) and (P2) are joined, the main body split ends (13) and (14) between the heating elements (4) are manually fused to form two pipes. (P1) and (P2) can be hermetically bonded and used as joints for water pipes and gas pipes.
The width of each of the two heating elements (4) is increased to the inside of the main body (2), and the inner end of each heating element (4) is joined at the center of the inner surface of the main body (2). Two heating elements (4) are continuously embedded from the one end side to the other end side without any gap, or one heating element (4) continuous from one end side to the other end side is embedded in the inner surface of the main body (2). Also, the two pipes (P1) and (P2) can be hermetically bonded and used as a joint for a water pipe or a gas pipe. In this case, the joint body (2) has a core (3) attached to the pipe end. Without joining, two pipes to be joined (P1)
The end faces of (P2) are directly butt-joined.

As shown in FIG. 7, the main body split end (13)
When the (14) is butt-joined to form a circular cross section, the U-turn portions (9) at the ends of the heating element (4) are located at different neighboring positions from the joining positions of the main body split ends (13) and (14). That is,
The heating element (4) is joined so as to form an annular shape at a corner position slightly shifted in one direction from the split (1) of the main body (2).
Is embedded along the inner surface of the main body (2) to the other main body split end (14) in the circumferential direction from a position retracted by a predetermined dimension (L1) from one main body split end (13), and one main body is cut off. Retracted dimension (L) of the end of the heating element (4) with respect to the split end (13)
The other main body split end (14) having the same dimension (L1) as that of 1)
The body (2) with the end of the heating element (4) protruding from the
The heating element (4) is embedded in the inner surface, and the heating element (4) on the inner surface can be split like the main body (2).

With the above structure, even if the U-turn portions (9) at the ends of the heat generating element (4) are abutted and joined to form a complete ring, a gap (19) is formed therebetween. At the end of the body (4) where the heating efficiency of the resin on the inner surface of the main body (2) and the outer surface of the pipes (P1) and (P2) is the worst, heat conduction is hindered by the crevice (1) and the heating and melting are most difficult Body (2) inner surface and pipe (P1) at body split ends (13) (14)
(P2) When heating / melting of the resin on the outer surface is stopped and the main body split ends (13) and (14) are butt-joined, the longitudinal direction (circumferential direction) of the heating element (4) passing through the inner surface of the joined portion. Each of the conductive wires (8) arranged in parallel with no gap in the main body split end (1
3) The inner surface of the body (2) and the pipe (P1) (P
2) Since the resin on the outer surface is appropriately heated and melted, defective fusion due to insufficient heating and melting of the resin in this portion can be prevented.
On the other hand, at the end of the heating element (4), the heat conduction is performed without being hindered by the crevice (1), and the U-turn portions (9) at the end of the heating element (2) are butt-joined and completely joined. In the case of a ring shape, the resin on the inner surface of the main body (2) and the outer surface of the pipe (P1) (P2) at the end of the heating element (4) is appropriately heated and melted. And the end of the heating element (4) is joined near the joining position of the main body split ends (13) and (14), so that heat is generated from one main body split end (14). The protruding dimension (L1) of the end of the body (4) is short, and the amount of body splitting (W) required when wrapping the ends of the two pipes (P1) and (P2) joined by the main body (2) is unnecessarily enlarged. Can be prevented.

The heating element (4A) shown in FIG. 8 uses the conductive wire (8), the conductive wires (8) are arranged in parallel in the longitudinal direction without gaps, and the end of the conductive wire (8) is Turn part (9
A) One conductive wire (8) is folded in multiples so that the ends are mutually meshed so that (9B) is alternately displaced in the longitudinal direction and aligned in the lateral direction by the same number. The resin layer (7) on the surface of each of the conductive wires (8), which is formed in the formed end-shaped strip shape and is arranged in parallel in the longitudinal direction without any gap, is partially heated.
The heating element (4) is formed by a plurality of fusion parts (10A) to be melted.
A) is kept in a band shape, and as shown in FIG.
A) is curved into a circular shape, and each U-turn part (9A) at the top of the end and each U-turn part (9B) at the bottom of the valley are butt-joined in an uneven surface, so that the heating element (4A) is formed. It is configured to have an endless ring shape.

As shown in FIG. 10, the main body split end (13)
When (14) is butt-joined to form a circular cross section, each U-turn portion (9A) at the top of the heating element (4A) and each U-turn portion (9B) at the bottom of the valley form a main body split end ( 13) (1
Each U-turn portion from the split ends (13) and (14) of the main body to the top of the end of the heating element (4A) so that the ring shape is formed by meshing and joining around the same angular position as the joining position of 4). (9A) is protruded by half the dimension (L2) of the tooth height, and each U-turn portion (9B) at the bottom of the valley at the end of the heating element (4A) from the main body split ends (13, 14). ) To half the tooth height (L
With only 2) retracted, the heating element (4A) is embedded in the inner surface of the main body (2), and the heating element (4A) on this inner surface can be split similarly to the main body (2). .

According to the above configuration, each U-turn part (9A) at the top of the heating element (4A) and each U-turn part (9B) at the bottom of the valley are abutted and joined to form a complete ring shape. ,
In the heating element (4A) in which a gap (20) is formed between the inner surface of the main body (2) and the outer surface of the pipe (P1) (P2), the resin has the worst heating efficiency at the end, and the heat conduction is divided ( Stop heating and melting the resin on the inner surface of the main body (2) and the outer surfaces of the pipes (P1) and (P2) at the main body split ends (13) and (14) which are hindered by 1) and are most difficult to heat and melt. Part (13) (1
4), when the ends of the heating element (4A) passing through the inner surface of the joining portion are connected in parallel with no gap in the longitudinal direction (circumferential direction) of the end of the meshing joint, the main body split end is formed. Department (1
3) The inner surface of the body (2) and the pipe (P1) (P
2) Since the resin on the outer surface is appropriately heated and melted, defective fusion due to insufficient heating and melting of the resin in this portion can be prevented.
On the other hand, at the end of the heating element (4A), heat conduction is divided (1).
The gap (20) between the ends of the heating element (4A) becomes half of the gap (19) between the ends of the heating element (4), and the gap between the body (2) and Due to manufacturing dimensional errors of the heating element (4A) and assembly dimensional errors thereof, each U-turn portion (9) at the top of the end of the heating element (4A).
A) and each U-turn part (9B) at the bottom of the valley do not form a complete ring shape that is butt-joined, but each U-turn part (9A) at the top of the heating element (4A) and each U-turn at the bottom of the valley. Even if a small gap is formed between the portions (9B), the gap is not continuous in a straight line in the axial direction and is interrupted, and the heating element (4
A) Body (2) inner surface and tube (P1) (P2) at end
Since the resin on the outer surface is appropriately heated and melted, it is possible to prevent poor fusion due to insufficient heating and melting of the resin in this portion, and center around the same angular position as the joining position of the main body split ends (13) (14). Since the end of the heating element (4A) is engaged with the main body (4A), the protruding dimension (L2) of the end of the heating element (4A) from the split ends (13) and (14) of the main body is short, and the end is joined by the main body (2). Unnecessary enlargement of the body split amount (W) required when wrapping the ends of the pipes (P1) and (P2) can be prevented.

As shown in FIG. 11, the main body split end (13)
When (14) is butt-joined to form a circular cross section, each U-turn part (9A) at the top of the heating element (4A) and each U-turn part (9B) at the bottom of the valley are divided into main body split ends. (13) (1
Most of the teeth at the end of the heating element (4A) protrude from one of the main body split ends (13) so as to form an annular shape by meshing and joining around a neighboring angular peripheral position different from the joining position of 4). And a heating element (4A) for one of the main body split ends (13).
The heating element (4) is separated from the other main body split end (14) by the same dimension as the retreat dimension of the U-turn section (9B) at the bottom of each valley at the end.
A) The heating element (4A) is embedded in the inner surface of the main body (2) with the teeth at the end protruding, so that the heating element (4A) on the inner surface can be split similarly to the main body (2). With such a configuration, the above-described effects can be obtained.

FIG. 12 shows a split cylinder type EF joint according to the present invention.
As shown in (1), when used for joining tubes that cannot be joined with an adhesive, for example, a polyethylene covering tube (22) for covering a wire rope (21) already stretched inside such as a suspension bridge. The joining of tubes such as the covering tube (22) can be easily performed.

The covering tube (22) is shown in FIGS.
As shown in FIG. 3, one or a plurality of thermoplastic synthetic resin covering sheets (24) are tubed outside the wire rope (21) using a joint (23) made of thermoplastic synthetic resin having an H-shaped cross section. In the joint (23), an electric resistance wire (a bare conductive wire) is formed on two groove surfaces having a U-shaped cross section into which the edges of the covering sheet (24) are inserted. 25) is embedded, and the resistance wire (25)
The joint (23) and the covering sheet (2)
The resin on the bonding surface in 4) is heated and melted to fuse the joint (23) and the covering sheet (24).

[0031]

As is apparent from the above embodiments, the present invention relates to a tubular joint body (2) made of a thermoplastic synthetic resin and having a part of the peripheral wall divided in the axial direction, and a single joint body provided with an insulating coating. And a band-shaped heating element (4A, 4A) formed by folding the conductive wire (8) in multiple layers. The heating element (4, 4A) is embedded in the inner surface of the main body (2), and the main body split end ( 13) (14)
When the ends are joined together, the ends of the heating elements (4) and (4A) are joined together to form a ring shape, so that a split cylindrical E is formed.
An F joint can be obtained.

The end of the heating element (4) is the split end of the main body (13).
The two tubes (P1), (P2), and (22) to be joined by the main body (2) by embedding the heating element (4) in the inner surface of the main body (2) so as to be joined at the same position as the joining position of (14). The amount of main body splitting (W) required for wrapping the end can be minimized.

The end of the heating element (4) is the split end of the main body (13).
By embedding the heating element (4) in the inner surface of the main body (2) so as to join at a position different from the joining position of (14), the two pipes (P1), (P2), (2) joined by the main body (2)
2) Unnecessary enlargement of the main body splitting amount (W) required for wrapping the end portion can be prevented, and the main body split end portion (13) (1)
4) The inner surface of the main body (2) and the pipe (P1) (P2) (2)
2) Poor fusion due to insufficient heating and melting of the resin on the outer surface can be prevented.

The end of the heating element (4A) is formed in a comb-teeth shape that meshes with each other, and the end of the heating element (4A) is divided into the main body split end (13).
The heating element (4A) is attached to the inner surface of the main body (2) so that the main body (2) is meshed and joined around the joint position of (14) or at a position different from the joint position of the main body split ends (13) and (14). 2 pipes (P1) joined by the body (2) by embedding
(P2) (22) Unnecessary enlargement of the main body splitting amount (W) when wrapping the end can be prevented, and the main body split end (13) (14) and the heating element (4A) can be prevented. ) Poor fusion due to insufficient heating and melting of the resin on the inner surface of the main body (2) and the outer surface of the pipe (P1) (P2) (22) at the end can be prevented.

Insulation coating was applied so that the conductive wires (8) were arranged in parallel in the longitudinal direction without any gaps, and the U-turn portions (9) of the conductive wires (8) were aligned in a horizontal line at the ends. One conductive wire (8) is folded in multiples to form a band-shaped heating element (4), and each U-turn portion (9) at the end of the heating element (4) is joined to form a ring shape. This is necessary when the end of the heating element (4) is joined at the same position as the split ends (13) and (14) of the main body, and the end of the heating element (4) is split at the end of the split body (13) (14).
It is possible to obtain a heating element (4) that can be used in a case where the end portions are joined in one plane, which can be used even when the joining is performed at a nearby position different from the joining position.

The conductive wires (8) are arranged in parallel in the longitudinal direction without any gap, and the U-turn portion (9A) of the conductive wire (8) is provided at the end.
A heat generation in which one conductive wire (8) coated with insulation is folded in multiples so that the ends are meshed with each other so that (9B) is alternately displaced in the longitudinal direction. Body (4
A) is formed, and each U-turn part (9A) at the top of the heating element (4A) and each U-turn part (9B) at the bottom of the heating element (4A) are joined to form a ring shape. ) This is necessary when the ends are joined at different positions near the joining positions of the main body split ends (13) and (14), and the end of the heating element (4A) is joined to the main body split ends (13) and (14). The heating element (4A) can be obtained in which the ends are joined in an uneven surface, which can be used also when the joining is performed centering on the center.

The ends (1) of the conductive wires of the heating elements (4) and (4A)
1) By pulling out (12) from the outer peripheral surface or end surface of the main body (2) to the outside of the main body (2), the main body split end portion (13)
(14) The ends of the heating elements (4) and (4A) can be joined to each other without gaps, and the main body (2) the split ends (13) and (14) and the main body at the ends of the heating elements (4) and (4A) (2) Poor fusion due to insufficient heating and melting of the resin on the inner surface and the pipe (P1) (P2) (22) on the outer surface can be prevented.

[Brief description of the drawings]

FIG. 1 is a front view of a split cylinder type EF joint.

FIG. 2 is a sectional view of a split cylinder type EF joint.

FIG. 3 is an explanatory view of a conductive wire.

FIG. 4 is a plan view of a belt-shaped heating element.

FIG. 5 is a plan view of a ring-shaped heating element.

FIG. 6 is an enlarged plan view of a main body split portion.

FIG. 7 is an enlarged plan view of a split portion showing a modified example of a mounting mode of the heating element.

FIG. 8 is a plan view of another heating element in a belt shape.

FIG. 9 is a plan view of another ring-shaped heating element.

FIG. 10 is an enlarged plan view of a main body split portion.

FIG. 11 is an enlarged plan view of a main body split portion.

FIG. 12 is a sectional view of a coated tube.

FIG. 13 is a plan view of a joint portion of the coated tube.

[Explanation of symbols]

 (P1) (P2) Pipe (W) Body split amount (1) Split (2) Joint body (4) (4A) Heating element (8) Conductive wire (9) (9A) (9B) U-turn part ( 11) (12) End of conductive wire (13) (14) Split end of main body (15) (16) Lead hole for conductive wire (19) (20) Gap at junction of heating element

Claims (8)

[Claims] 1. A tubular joint body made of a thermoplastic synthetic resin and having a part of a peripheral wall divided in an axial direction, and a band-shaped heating element formed by folding one conductive wire having an insulating coating over and over. An electrofusion joint characterized in that a heating element is embedded in the inner surface of the main body, and when the split ends of the main body are joined together, the ends of the heating element are joined to form a ring shape. 2. The electrofusion joint according to claim 1, wherein the heating element is embedded in the inner surface of the main body such that the end of the heating element is joined at the same position as the joining position of the split end of the main body. 3. The electrofusion joint according to claim 1, wherein the heating element is embedded in the inner surface of the main body so that the end of the heating element is joined at a position different from the joining position of the split end of the main body. 4. A heating element is embedded in the inner surface of the main body such that the ends of the heating element are formed in a comb-tooth shape that mesh with each other, and the ends of the heating element are engaged with each other around the joining position of the split end of the main body. The electrofusion joint according to claim 1. 5. A heating element is formed on the inner surface of the main body such that the end of the heating element is formed in a comb-teeth shape that meshes with each other, and the end of the heating element is engaged and joined at a position different from the joining position of the split end of the main body. The electrofusion joint according to claim 1, wherein the joint is embedded. 6. A single conductive wire provided with an insulating coating is multiplexed so that conductive wires are arranged in parallel in the longitudinal direction without any gap, and U-turn portions of the conductive wires are aligned in a horizontal line at the end. The electrofusion joint according to claim 1, wherein a band-shaped heating element is formed by folding, and the U-turn portions at the ends of the heating element are joined to form a ring shape. 7. An insulation coating is applied to the conductive wires so that the conductive wires are arranged in parallel in the longitudinal direction without gaps, and the U-turn portions of the conductive wires are arranged at the ends alternately in front and rear in the longitudinal direction. A multi-folded conductive wire is formed to form a comb-shaped heating element having a comb-tooth shape in which the ends are meshed with each other, and each U-turn section at the top of the heating element and each U-turn section at the bottom of the valley. The electrofusion joint according to claim 1, 3, 4, or 5, wherein the joints are joined to form an annular shape. 8. The conductive wire end of the heating element is drawn out from the outer peripheral surface or the end surface of the main body to the outside of the main body.
Or the electrofusion joint according to 5 or 6 or 7.