CN210123061U

CN210123061U - Electric melting pipe fitting with built-in accommodating groove

Info

Publication number: CN210123061U
Application number: CN201920576288.5U
Authority: CN
Inventors: 刘向东; 聂辉
Original assignee: Youjiete Environmental Technology Co Ltd
Current assignee: Youjiete Environmental Technology Co Ltd
Priority date: 2019-04-25
Filing date: 2019-04-25
Publication date: 2020-03-03
Anticipated expiration: 2029-04-25

Abstract

The utility model provides a pair of built-in slot type electric smelting pipe fitting that holds, include: the pipe body comprises a plurality of end heads, and the end face wall of at least one end head is inwards sunken to form a plurality of annular accommodating grooves; at least two connector lugs arranged on the tube body; the first hot-melt material layer is at least partially fixed on the outer layer surface of the accommodating tank and/or the inner layer surface of the accommodating tank; one of the first heating wires is fixed on the first hot-melt material layer on the outer layer surface of the accommodating groove; the two ends of the first electric heating wire are respectively and electrically connected with the connector lug. First aspect, the utility model discloses a holding tank melting connecting tube, it has a plurality of connection faces, and its firmness is higher than current product greatly.

Description

Electric melting pipe fitting with built-in accommodating groove

Technical Field

The utility model relates to an electric smelting pipe fitting field, concretely relates to it holds slot type electric smelting pipe fitting to embed.

Background

At present, electric smelting pipe fitting means that the high temperature that utilizes the electric current to produce makes the pipe fitting of a plurality of polyethylene materials of mutual contact link together after melting, compare in traditional pipe connection mode, like threaded connection, bayonet connection, owing to need rotate or exert the effort to the pipe fitting in the connection process, to some large-scale pipe fittings, the site operation is very difficult, the electric smelting connection mode advantage is outstanding in the construction engineering, to polyethylene material pipe fitting, utilize the electric fusion welding technique, can easily be connected two pipe fittings.

In recent years, the electric melting pipe fittings are widely applied in the fields of urban water pipe networks, urban gas pipe networks, petroleum, chemical industry, sewage discharge and the like, and the electric melting pipe fittings used in different fields are greatly different in specification and structure, for example, an electric melting pipe fitting elbow disclosed in patent CN202708443U, wherein an electric heating wire and a wiring terminal are arranged on a pipe body, and in the construction process, only an external power supply is required to be connected with the wiring terminal, and after the electric heating pipe fittings are electrified, the two pipe fittings are melted and then connected into a whole under the action of current; the specifications and structures do not match for the two butt-jointed fittings. The site construction operation of the electric melting pipe fittings is simple and the application is wide, but the success rate of the connection of the electric melting pipe fittings is not a hundred percent, the electric melting pipe fittings are connected by single-side melting, the connection surface is only one side, and the firmness is poor.

Disclosure of Invention

Technical problem to be solved

The utility model aims at providing a built-in containing groove type electric melting pipe fitting, which adopts the end face wall of the end head to be sunken inwards to form a plurality of containing grooves, and the containing grooves are provided with a plurality of connecting faces and have high firmness; the defects that the existing electric melting pipe fittings are connected by single-side melting, the connection surface is only one side, and the firmness is poor are overcome.

(II) technical scheme

In order to solve the technical problem, the utility model provides a pair of built-in slot type electric smelting pipe fitting that holds, include: the pipe body comprises a plurality of end heads, and the end face wall of at least one end head is inwards sunken to form a plurality of accommodating grooves; at least two connector lugs arranged on the tube body; the first hot-melt material layer is at least partially fixed on the outer-layer ring surface of the accommodating groove and/or the inner-layer ring surface of the accommodating groove; the first heating wire is fixed in the first hot-melt material layer; the two ends of the first electric heating wire are respectively and electrically connected with the connector lug. First aspect, the utility model discloses a holding tank melting connecting tube, it has a plurality of connection faces, and its firmness is higher than current product greatly. In a second aspect, gaps are often formed between the fused electrofusion pipe and the insert in the prior art due to poor flow of the molten liquid or generation of bubbles, so that the liquid can permeate and escape along the gaps. The utility model discloses be equipped with a plurality of holding tank on the section wall of end, the insertion head of being convenient for insert the pipe fitting inserts, liquid after its melting in its holding tank fills up the holding tank, can not the overflow outflow, the infiltration route of its liquid is crooked U type, greatly increased the resistance of liquid infiltration, and the liquid gap infiltration escape between the melting of liquid follow electric smelting pipe fitting and insert that has significantly reduced, the grafting mode of its structure simultaneously, it is fixed to conveniently aim at, the melting has been guaranteed to the difference at the melting in-process needs the support equipment to support insert and electric smelting body.

Preferably, the receiving groove is a plurality of grooves distributed on the periphery of the pipe orifice located at the innermost side of the pipe fitting. The utility model discloses be equipped with a plurality of holding tanks to distribute in the orificial periphery that is located the pipe fitting inboard, it is further, more convenient aim at fixedly, and the difference needs the support equipment to support insert and electric smelting body and has guaranteed the melting at the molten process, is difficult to rotate.

Preferably, the number of the accommodating grooves is 1. The utility model discloses an annular holding tank, its simple structure, its single integral holding tank, it does not have the interval between a plurality of holding tanks, has the melting liquid material easily and can't fill up the interval between the holding tank, has avoided liquid to have the inhomogeneous condition of interval distribution of melting liquid material between a plurality of holding tanks easily, has guaranteed the homogeneity of whole course of working.

Preferably, a second hot-melt material layer is at least partially fixed on the surface of the inner side wall of the pipe body, a second heating wire is fixed on the second hot-melt material layer, and the second heating wire is externally connected with a connector lug. The utility model discloses an inside wall of body is equipped with the second heating wire, and its permission inside wall that can step forward can be in the same place with the insert melting, combines the first aspect, and both play dual fail-safe's leak protection function.

Preferably, the connector lugs are two pairs, wherein two ends of the first heating wire are connected with one pair of connector lugs, and the second heating wire is connected with the other pair of connector lugs. The utility model discloses what first heating wire and second heating wire connect two pairs of connector lugs respectively, can separately carry out electric smelting butt joint operation like this independently.

Preferably, a third hot-melt material layer is fixed on at least a part of the surface of the outer side wall of the tube body, a third heating wire is fixed on the second hot-melt material layer, and the third heating wire is externally connected with a connector lug. The utility model discloses the lateral wall surface of body is fixed with third hot melt type material layer and third heating wire at least locally, and it allows the lateral wall can combine the first aspect together with the insert melting, and both play dual fail-safe's leak protection function. Preferably, a second hot-melt material layer is at least partially fixed on the surface of the inner side wall of the tube body, a second heating wire is fixed on the second hot-melt material layer, and the second heating wire is externally connected with a connector lug. The utility model discloses a three-layer hot melt type material layer and three group's heating wires, it can regard as a standard component, can satisfy different inserts or the assembly of outer sleeve spare, and it only can satisfy different inserts on the market simultaneously with a mould or production line, and the change has reduced the cost of generation mutually.

Preferably, the connector lug is arranged on the outer side wall of the pipe body. The utility model discloses a connector lug is installed on the lateral wall, and its simple structure processing is convenient.

Preferably, the terminal block is disposed on an outer side edge of the end face wall of the pipe body. The radial connector lug is arranged, the connector lug ring shaft is required to be radially arranged, and the occupied space of the whole electric melting pipe body is increased. The utility model discloses an outside edge of terminal surface wall of connector lug installation body, its connector lug can insert and play butt joint location and fixed effect in the insert, the biggest external diameter of electric smelting body is littleer (the height of the connector lug of radially arranging has not been had), has reduced the shared space of whole electric smelting body, more connector lugs are allowed to arrange of its axial connector lug, its syntropy connecting wire is more convenient regular and operation, and not the electric wire of different orientations, easy confusion.

Preferably, the connector lug is provided with a terminal far away from one end of the pipe orifice. The second aspect, the utility model discloses the connector lug is all installed the end and is kept away from mouth of pipe one end, and its minimize has mouth of pipe one end external diameter, and it concentrates on the middle part end, and the trompil is established to its mould only one end, and its mould is more simple, and it is more convenient to produce. Meanwhile, if the connector lug is separately arranged, the resistance at the joint between the connector lug and the electric heating wire at the two ends of the connector lug is small, so that the heating effect at the two ends of the connector lug is poor; the connector lug is positioned at the same end, so that the area with poor heating effect at one end is reduced, and the heating effect is improved; the distance between the connector lugs is the axial length of the bent heating wire, the connector lugs can occupy a certain length (the connector lugs can be thickened and enlarged due to high current passing power), and the arrangement of shorter heating wires is greatly limited; and a connector lug is arranged on one side of the pipe orifice, which can influence the opening of the pipe orifice into other fastening and butt joint structures such as threads and the like, and particularly the structure that the electric heating wire is arranged on the outer side wall of the pipe fitting again.

Preferably, the tube body has two ends, and the included angle between the center lines of the ends is 90 °, 120 °, 135 °, 150 ° or 180 °. The included angle between the central lines of the end heads adopted by the utility model is 90 degrees, 120 degrees, 135 degrees, 150 degrees or 180 degrees; as a common standard component, different use environments can be used.

Preferably, only one of the ends is provided with an annular receiving groove. The utility model discloses an annular holding tank is convenient for connect one of them side pipeline.

Preferably, both ends are provided with annular receiving grooves. Utility model adopts an annular holding tank, is convenient for connect wherein both sides pipeline.

Preferably, the tube has three ends, two of the ends having the same center line, and the center line of the third end is perpendicular to the common center line of the two ends. The utility model discloses a structure of three-way pipe, it is as common standard component, can use different service environment.

Preferably, the outer diameters of the two ends of the pipe body are larger than that of the middle part of the pipe body. The utility model discloses the external diameter that sets up the body both ends is greater than the external diameter at middle part, is convenient for increase end portion, and reduces non-welded part's size, has reduced manufacturing cost.

Preferably, the outer diameters of the two ends of the pipe body are smaller than the outer diameter of the middle part of the pipe body. The utility model discloses the external diameter that sets up the body both ends is less than the external diameter at middle part, is convenient for strengthen the intensity at middle part.

(III) advantageous effects

The utility model provides a pair of built-in slot type electric smelting pipe fitting that holds, it has following advantage:

1. first aspect, the utility model discloses a holding tank melting connecting tube, it has a plurality of connection faces, and its firmness is higher than current product greatly. In a second aspect, gaps are often formed between the fused electrofusion pipe and the insert in the prior art due to poor flow of the molten liquid or generation of bubbles, so that the liquid can permeate and escape along the gaps. The utility model discloses be equipped with a plurality of holding tank on the section wall of end, the insertion head of being convenient for insert the pipe fitting inserts, liquid after its melting in its holding tank fills up the holding tank, can not the overflow outflow, the infiltration route of its liquid is crooked U type, greatly increased the resistance of liquid infiltration, and the liquid gap infiltration escape between the melting of liquid follow electric smelting pipe fitting and insert that has significantly reduced, the grafting mode of its structure simultaneously, it is fixed to conveniently aim at, the melting has been guaranteed to the difference at the melting in-process needs the support equipment to support insert and electric smelting body.

2. The utility model discloses the connector lug is all installed the end and is kept away from mouth of pipe one end, and its minimize has mouth of pipe one end external diameter, and it concentrates on the middle part end, and the trompil is established to its mould only one end, and its mould is more simple, and it is more convenient to produce. Meanwhile, if the connector lug is separately arranged, the resistance at the joint between the connector lug and the electric heating wire at the two ends of the connector lug is small, so that the heating effect at the two ends of the connector lug is poor; the connector lug is positioned at the same end, so that the area with poor heating effect at one end is reduced, and the heating effect is improved; the distance between the connector lugs is the axial length of the bent heating wire, the connector lugs can occupy a certain length (the connector lugs can be thickened and enlarged due to high current passing power), and the arrangement of shorter heating wires is greatly limited; and a connector lug is arranged on one side of the pipe orifice, which can influence the opening of the pipe orifice into other fastening and butt joint structures such as threads and the like, and particularly the structure that the electric heating wire is arranged on the outer side wall of the pipe fitting again.

Drawings

Fig. 1 is an external view of an embodiment 1 of the electric melting pipe fitting with a built-in accommodating groove of the present invention;

fig. 2 is a sectional view of an embodiment 1 of the electric melting pipe fitting with a built-in containing groove of the present invention;

fig. 3 is a structure view of a first heating wire of an electric melting pipe fitting with a built-in receiving groove of the present invention in example 1;

fig. 4 is a sectional view of an embodiment 2 of the electric melting pipe fitting with a built-in containing groove of the present invention;

fig. 5 is an external view of an embodiment 2 of the electric melting pipe fitting with a built-in containing groove of the present invention;

fig. 6 is an external view of an embodiment 3 of the electric melting pipe fitting with a built-in containing groove of the present invention;

fig. 7 is a side view of an embodiment 3 of the electric melting pipe fitting with a built-in receiving groove of the present invention;

fig. 8 is a sectional view of an embodiment 3 of the electric melting pipe fitting with a built-in containing groove of the present invention;

fig. 9 is an external view of an embodiment 4 of the electric melting pipe fitting with a built-in containing groove of the present invention;

fig. 10 is a sectional view of an embodiment 4 of the electric melting pipe fitting with a built-in receiving groove of the present invention;

fig. 11 is a view showing an assembly structure of embodiment 1 of the electric melting pipe fitting with a built-in accommodating groove of the present invention and a pipeline;

fig. 12 is an external view of an embodiment 5 of the electric smelting pipe fitting with a built-in containing groove of the present invention;

fig. 13 is an external view of an embodiment 6 of the electric melting pipe fitting with a built-in receiving groove of the present invention;

fig. 14 is an external view of an embodiment 7 of the electric smelting pipe fitting with a built-in containing groove of the present invention;

fig. 15 is an external view of an embodiment 8 of the electric melting pipe fitting with a built-in accommodating groove of the present invention.

1. The heating wire comprises a pipe body, 2, a connector lug, 3, a first heating wire, 4, an accommodating groove, 5, a first hot-melt material layer, 6, a second hot-melt material layer, 7, a second heating wire, 8, a third hot-melt material layer, 9, a third heating wire, 10 and an end socket.

In addition, A, B, C refers to ports (e.g., three ports) of the pipe fitting, respectively, and AC 1/AC 2, BC1/BC2, CC1/CC2 refers to three port inner ring inner walls and three port outer ring inner walls, respectively;

jxda 1/jxda 2 refers to two terminals on the surface of the annular groove on the port a that connect the inner annular groove wall AC1 first heating wire;

jxdb 1/jxdb 2 refers to two terminals on the annular groove surface on the A port, which are connected with the first heating wire of the outer annular groove wall AC 2;

jxdc 1/jxdc 2 refers to two terminals on the ring groove surface on the B port, which are connected with the first heating wire of the inner ring groove wall BC 1;

jxdd 1/jxdd 2 refers to two terminals on the ring groove surface on the B port, which are connected with the first heating wire of the outer ring groove wall BC 2;

jxde 1/jxde 2 refers to two terminals on the annular groove surface on the port B, which are connected with the first electric heating wire of the inner annular groove wall CC 1;

jxdf 1/jxdf 2 refers to two terminals on the ring groove surface on the B port that connect the first heating wire of the outer ring groove wall CC 2.

Detailed Description

The following detailed description of the embodiments of the present invention is provided with reference to the accompanying drawings and examples. The following examples are intended to illustrate the invention, but are not intended to limit the scope of the invention.

In the description of the present invention, "a plurality" means two or more unless otherwise specified; the terms "upper", "lower", "left", "right", "inner", "outer", "front", "rear", "head", "tail", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are merely for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "connected" and "connected" are to be interpreted broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; may be mechanically coupled, directly coupled, or indirectly coupled through an intermediary. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example 1

As shown in fig. 1 and 2, the utility model discloses a built-in containing groove type electric melting pipe fitting, which comprises a pipe body 1 and eight connector lugs 2 arranged on the pipe body, wherein the pipe body comprises two end heads 10 and a first heating wire 3, and the end surface walls of the end heads at the two ends are inwards sunken to form an integral annular containing groove 4; the included angle between the center lines of the two end heads is 180 degrees. The first hot-melt material layer 5 is fixed on the outer-layer ring surface of the holding tank and the inner-layer ring surface of the holding tank; the first heating wire is fixed in the first hot-melt material layer; the two ends of the first electric heating wire are respectively and electrically connected with the connector lug. The connector lug sets up on the lateral wall of body end, and all installs the end and keeps away from mouth of pipe one end. The outer diameters of the two ends of the pipe body are smaller than the outer diameter of the middle part of the pipe body.

The electric heating wire is shown in fig. 3, the electric heating wire comprises two parallel cylindrical spiral electric heating wires which are spiral in the same direction, and the wire ends of the two cylindrical spiral electric heating wires which are positioned on the same side are connected; the two cylindrical surface spiral heating wires are positioned at the other side, and the wire ends of the two cylindrical surface spiral heating wires are connected with two different wire connectors. The electric heating wires comprise two parallel cylindrical spiral electric heating wires which are spirally arranged in the same direction, and the wire ends of the two cylindrical spiral electric heating wires which are positioned on the same side are connected; the two cylindrical spiral electric heating wires are positioned at the other side, and the two spiral electric heating wire ends are connected with two different connector posts. The outer side generatrix of the spiral line of the cylindrical spiral electric heating wire is a straight line.

In the practice of this embodiment, as shown in fig. 11, when the two sets of two terminals, all in plastic material, are all connected together, only one set, i.e., two terminals, may be on the outer surface. The pipeline is inserted into the annular groove at one end of the pipe fitting, the inner wall of the pipeline corresponds to the inner ring inner wall of the annular groove at the corresponding end of the pipe fitting, a part of outer ring inner wall of the local area of the annular groove of the pipe fitting corresponds to a part of outer wall of the corresponding local area of the pipeline, and the inner ring inner wall of the annular groove surface corresponding to the pipe fitting can be simultaneously subjected to plastic deformation melting under the condition that the two connector lugs are electrified, after the electrification is finished for a certain time, the softened and melted plastic material is re-solidified after the re-cooling, at the moment, the pipe fitting and the pipeline are firmly connected together in a plastic deformation electric melting welding mode at the end with the annular groove surface.

Example 2

As shown in fig. 4 and 5; embodiment 2 differs from embodiment 1 in that a built-in accommodating groove type electrofusion pipe fitting comprises a pipe body and eight connector lugs arranged on the pipe body, wherein the pipe body comprises two ends and a first heating wire 3, and end face walls of the two ends are inwards sunken to form an integral annular accommodating groove 4; the first hot-melt material layer 5 is fixed on the outer-layer ring surface of the holding tank and the inner-layer ring surface of the holding tank; the first heating wire is fixed in the first hot-melt material layer; the two ends of the first electric heating wire are respectively and electrically connected with the connector lug. And a second hot-melt material layer 6 is fixed on the surface of the inner side wall of the pipe body, a second heating wire 7 is fixed on the second hot-melt material layer, and the second heating wire is externally connected with a connector lug. The connector lug is two pairs, wherein one pair of connector lug is connected at first heating wire both ends, and the second heating wire is connected another pair of connector lug. And a third hot-melt material layer 8 is fixed on the surface of the outer side wall of the pipe body, a third heating wire 9 is fixed on the third hot-melt material layer, and the third heating wire is externally connected with a connector lug.

Example 3

As shown in fig. 6, 7 and 8, the embodiment 2 is different from the embodiment 1 in that the outer diameters of both ends of the pipe body are larger than that of the middle portion. The included angle between the center lines of the two end heads is 180 degrees. And annular accommodating grooves are formed in the two end heads.

Example 4

As shown in fig. 9 and 10, embodiment 4 differs from embodiment 1 in that the outer diameters of both ends of the pipe body are smaller than the outer diameter of the middle portion. The included angle between the center lines of the two end heads is 180 degrees. And annular accommodating grooves are formed in the two end heads. The first heating wire is positioned on the inner side surface and the outer side surface of the ring groove.

Example 5

As shown in fig. 12, embodiment 5 is different from embodiment 1 in that the outer diameters of both ends of the pipe body are smaller than the outer diameter of the middle portion. The included angle between the center lines of the two ends is 120 degrees. And annular accommodating grooves are formed in the two end heads.

Example 6

As shown in fig. 13, embodiment 6 is different from embodiment 1 in that the outer diameters of both ends of the pipe body are smaller than the outer diameter of the middle portion. The included angle between the center lines of the two ends is 135 degrees. And annular accommodating grooves are formed in the two end heads.

Example 7

As shown in fig. 14, embodiment 6 is different from embodiment 1 in that the outer diameters of both ends of the pipe body are smaller than the outer diameter of the middle portion. The included angle between the center lines of the two ends is 90 degrees. And annular accommodating grooves are formed in the two end heads.

Example 8

As shown in fig. 15, embodiment 6 is different from embodiment 1 in that the tube body has three ends, two of which have the same center line, and the center line of the third end is perpendicular to the common center line of the two ends.

It should be noted that, at the same time, only one end of the pipe fitting with three ends has the ring groove, and the other two ends do not have the ring grooves, or, in the pipe fitting with three ends, three ends all have the ring grooves or in the pipe fitting with three ends, only two ends have the ring grooves, and the other end does not have the ring groove (the ring groove is a connecting structure on one end of the pipe fitting).

The above-mentioned embodiments are only used for explaining the present invention, wherein the structure, connection mode, etc. of each component can be changed, all the equivalent transformation and improvement performed on the basis of the technical solution of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. A built-in groove formula electric smelting pipe fitting that holds, its characterized in that includes:

the pipe body comprises a plurality of ends, and the end face wall of at least one end is inwards sunken to form a plurality of annular accommodating grooves;

at least two connector lugs arranged on the tube body;

the first hot-melt material layer is at least partially fixed on the outer-layer ring surface of the accommodating groove and/or the inner-layer ring surface of the accommodating groove; and

at least two first electric heating wires, wherein one first electric heating wire is fixed on the first hot-melt material layer of the outer ring surface of the accommodating groove; the two ends of the first electric heating wire are respectively and electrically connected with the connector lug.

2. An electrofusion tube member of the built-in receiving channel type as defined in claim 1, characterised in that said receiving channel is plural and distributed over the periphery of the mouth of the tube which is located innermost of the tube member.

3. An electrofusion tube member having a built-in receiving channel as claimed in claim 1, characterised in that the receiving channel is 1.

4. An electric smelting pipe fitting with a built-in containing groove according to claim 1, 2 or 3, wherein a second hot-melt material layer is fixed on at least a part of the inner side wall surface of the pipe body, and a second heating wire is fixed on the second hot-melt material layer and is externally connected with a connector lug.

5. An electrofusion tube assembly with a built-in receiving channel as recited in claim 1, wherein the terminals are provided in two pairs, wherein the first heating wire is connected at both ends to one of the pairs of terminals and the second heating wire is connected to the other pair of terminals.

6. An electric smelting pipe fitting with a built-in containing slot according to claim 1, 2 or 3, wherein a third layer of hot melt type material is fixed on at least a part of the outer side wall surface of the pipe body, and a third heating wire is fixed on the third layer of hot melt type material and is externally connected with a connector lug.

7. An electrofusion tube assembly of the built-in receiving channel type as recited in claim 1, characterised in that the lug is provided on an outer side wall of the body.

8. An internally-housed channel electrofusion tube member as claimed in claim 1, wherein said lug is provided on the outside edge of the end face wall of the tube body.

9. An electrofusion tube member of the built-in receiving channel type as claimed in claim 7 or 8, characterised in that the terminals are each mounted at the end of the stub remote from the nozzle.

10. A built-in receiving channel electrofusion tube unit as claimed in claim 1, 2 or 3, characterised in that the tube body has two ends, the centre line of which is at an angle of 90 °, 120 °, 135 °, 150 ° or 180 °.

11. An electrofusion tube member with an internally received channel as recited in claim 10, wherein only one of the terminations is provided with an annular receiving channel.

12. An electrofusion tube member with a built-in receiving channel as claimed in claim 10, characterised in that both ends are provided with an annular receiving channel.

13. A pipe member according to claim 1, 2 or 3, wherein the body has three ends, two of which have the same centre line, and the centre line of the third end is perpendicular to the common centre line of the two ends.

14. An electrofusion tube member of the built-in receiving channel type as defined in claim 1, 2 or 3, characterised in that the external diameter of the tube body at both ends is greater than the external diameter of the central portion.

15. An electrofusion tube member of the built-in receiving channel type as defined in claim 1, 2 or 3, characterised in that the external diameter of the ends of the tube body is smaller than the external diameter of the central portion.