FR2868007A1 - Insert, for electric welding of joints and pipes, has a thermo-fusible insulating film substrate covering an electrical conductive circuit at least partially - Google Patents

Abstract

The insert (1), especially for a junction or pipe of a material which can be welded electrically, has a thermo-fusible substrate (2) with two fitted connections (10) at the end tabs (16,17) of an electrical circuit formed by a conductor (3) around a center opening (15). The substrate forms a flexible and insulating film over at least a part of one conductor surface. An independent claim is included for a process of making the insert.

Description

Electrofusion insert, method for obtaining such an insert and connection

  The present invention relates to electrofusion plastic fittings. More particularly, the present invention relates to an electrofusion insert for such fittings, a method for obtaining such an insert and a connector incorporating such an insert.

  The technical field of the invention is that of the manufacture of fluid transport conduits and fittings for such conduits, and more particularly conduit and conduit fittings of hot melt plastic material.

  Electrofusion fittings made by injecting a thermoplastic material and incorporating an electrically conductive yarn serving to cause the welding of the connection to a duct or to another connection to cause softening and / or softening are known in the prior art. melting the thermoplastic material surrounding the conductive wire. In this respect, several techniques have been proposed to incorporate a conductive wire within such a connection.

  No. 5,096,632 discloses methods in which the wire is wrapped around a preform; in one method the wire is heated and stretched so that it penetrates inside the superficial part of the preform which it melts or softens; in an alternative embodiment, the heated wire is pressed against the preform to promote its insertion into it; in other processes, the wire is covered with a layer of thermoplastic material provided and deposited thereon under the effect of the heating of the material by a weld bead, or by a layer of molten thermoplastic material projected on the wire and the preform; in other variants, it is proposed to replace the preform with a rotating mandrel which is separated from the wire after solidification of the melt covering the wire; in all cases the connection is obtained by overmolding the preform; although this patent mentions the possibility of making connections of various shapes (tubular sleeves or tees in particular), the described methods do not allow for saddle-shaped branch connections as described in particular in patents US 4,455,482 and US 5 , 708,251.

  No. 4,455,482 discloses an insert in the form of a thin wafer pierced with an opening in its center and hollowed out on one of its two main faces with a groove whose path extends in a spiral and opens out at the periphery. the wafer; this insert is injection molded, then is equipped with a section of conductive wire that is inserted into the groove and whose two ends are respectively wound around electrical connection terminals of the wire to a source of electrical energy for welding the connection to a conduit.

  The insert thus produced is introduced into a mold delimiting a cavity having the shape of the connection to be obtained, is then bent and then embedded in the thermoplastic material injected into the cavity of the mold to form the coupling. This method has the disadvantage of requiring the insertion of the conductive wire into the spiral groove requiring a cautious manual operation representing a time and cost important for industrial production.

  In the method described in US Pat. No. 5,708,251, a groove is hot-dug on the surface of a coupling already made in the form of a saddle; a head moving along four axes and a laser source delivering a laser beam to the head for digging the groove in which the conductive wire is then inserted under pressure are used for this purpose; the manufacturing device is complex; in addition, when a defect occurs during the digging of the groove or the insertion of the wire, the entire part must be discarded.

  These known methods also generally have the disadvantage that the pattern of the groove receiving the conductive wire is in the form of a spiral, which is not always the optimal configuration with regard to the heating of the coupling for the purpose of its welding to a conduit.

  It has also been proposed in US Pat. No. 5,229,581 to replace this wire with a doped polymer insert or with an insert made of a plastic material comprising a powder or metal fibers or carbon black; the insert incorporates a thermoregulator element which, depending on its dimensions and when a determined energy has been dissipated by the insert, is destroyed and therefore interrupts the welding of the fitting to which it was integrated. This idea comes up against various practical difficulties: long research seems necessary to select among the doped polymers known for their low resistivity properties, those usable in this application; the use of these conductive polymers to form an insert configuration adapted to that of a specific connection, which is not described in this document, is at least as expensive as that of the non-conductive plastics (due to the price a mold); Moreover, the presence of a heat-regulating element integrated into the insert in the form of a hot-melt part can be restrictive insofar as the welding energy of a connection to be welded can vary in significant proportions depending on the welding conditions; depending on these, this hot melt may be destroyed before the weld is made, or on the contrary too late, after degradation of the weld fitting or the conduit receiving it.

  An object of the invention is to provide an electro-weldable connection and its manufacturing process, which are improved or at least partially overcome the disadvantages of known connectors and their known manufacturing processes.

  The invention aims in particular to provide an electrofusion insert that is very simple and inexpensive to produce fully automatically, without manual operations, which can be integrated into all types of connections regardless of the shape and material of those ci, and that adapts to all types of surfaces and shapes of parts to be welded.

  According to a first aspect, the invention proposes to provide an insert, in particular for an electrofusion pipe connection or element, comprising a hot-melt substrate and at least two connection terminals, integral with said substrate at the ends of an electrically conductive circuit, characterized in that said substrate forms a flexible sheet of electrically insulative material coated on or near at least a portion of a surface with a flexible conductive track or strip forming said conductive circuit.

  Here, a conductive strip or strip is understood to mean a continuous path of electrically conductive and resistive material connecting the two so-called electrical connection terminals, of a width greater than its thickness, and deposited directly on the surface of said substrate or embedded therein. at least partially in said substrate.

  A conductive track embedded in the substrate material is particularly advantageous for improving the quality and homogeneity of the welds.

  Indeed, the presence of substrate material covering the track increases the amount of material to be melted and therefore the surface of the welding area. In addition, this additional material melts first when circulating an electric current and to fill any games at the welding interface and thus improve the homogeneity of said welding.

  Such an insert has the advantage of being very easily produced by automated means and according to known techniques for forming conductive circuits. In particular, it is possible, in the same automated production line, to continuously cut substrates according to various determined formats, for example in rolls of an electrically insulating hot-melt material, and then to deposit on these substrates a conductive track following a mask (a layout) programmed for each said format of substrate, and finally place said electrical connection terminals at the ends of said track, said ends being easily identifiable on the layout of said track.

  In addition, the insert according to the invention is, by the flexibility and flexibility of the substrate and the conductive track, very easily deformable which facilitates its overmolding and integration into electroweldable connections or duct elements that can be of variable shapes and sizes. complex to fit all types of duct surfaces or ductwork elements to be connected.

  The use of a conductive strip or strip also has the advantage of dissipating the heat energy produced by the Joule effect when the strip or strip is traversed by an electric current over a larger area, compared with a conductive thread of the same section. Indeed, the track is bonded to the substrate, in permanent direct contact therewith.

  Such a connection is mechanically more efficient than a wire overmolded or wound on the surface of the substrate which avoids the movements that can cause short circuits during the softening of the substrate material; As a result, a faster and more homogeneous fusion of the plastic material surrounding the track or web can be achieved. In particular, this makes it possible to simultaneously melt a portion of said substrate and of the external surface of the main duct at the point where the connection is to be made, which allows a homogenization of the melt of the substrate and the main duct and thus a improved welding, with a perfect seal.

  The use of a conducting track also facilitates the realization, at the ends of the track in particular, equipotential electrical connections with pads or electrical connection terminals of the track of the insert with an electrical generator providing the energy required for welding fitting; commercially available terminals which extend through an orifice provided in the track and in the substrate may be used.

  This also makes it possible to produce an insert of very small thickness since it is not necessary to form a groove in the substrate for depositing or embedding a resistive conductive wire.

  According to a preferred embodiment, the insert according to the invention is such that in which the ratio of the thickness of the insulating substrate to the thickness of the track or conductive strip is greater than 1, in particular situated in a range of from 1 to 200.

  These values correspond to the extreme values of ratio of respective thicknesses of substrate and track to control the flexibility of the insert and its welding properties.

  In particular, a substrate thickness of preferably between 0.3 and 2 mm makes it possible to control the amount of substrate material to be melted while at the same time retaining a certain flexibility during overmoulding and a certain rigidity for maintaining the assembly and his manipulation.

  Similarly, a track thickness of between 0.01 and 0.2 mm makes it possible to vary the resistance of the conductive track as a function of the power to be obtained while keeping a certain flexibility of the track during the overmolding of the insert. without having an electrical break.

  Advantageously, the ratio of the width of the track or conductive strip to its thickness is also greater than 1, in particular in a range from 5 to 300.

  The width of the conductive track, preferably between 1 and 3 mm, makes it possible to vary the resistance as a function of the welding power to be obtained as a function of the thickness of said track.

  It is thus possible to vary the resistance of the track, for an applied voltage of 40 volts, between 5 and 10 ohms, thereby releasing by Joule effect energy between 15000 and 25000 Joules. Advantageously, it is also possible to make inserts for controlling the stopping of the welding cycle.

  Indeed, it is possible, knowing the power required to perform the welding with a substantially constant input voltage and the desired duration of the welding cycle, to determine the resistance of the track, and therefore the width / thickness ratio of this track to ensure the welding in the desired time and the rupture of said track at the end of the same period. The track thus advantageously acts as a fuse to instantly stop welding.

  According to another characteristic of the invention, the substrate forms a sheet of an insulating thermoplastic material consisting essentially of at least one polymer of polyolefinic, vinyl or other type, in particular polyethylene (PE).

  The use of an insulating sheet substrate does not require a mold for the manufacture of the substrate. Such a substrate advantageously allows better incorporation in fittings or elements of electrofusion conduits themselves essentially composed of polymers of polyolefinic type, vinyl or other.

  The incorporation of the substrate into the connector is facilitated by a better mechanical connection between the substrate and the track than the substrate with a wire which tends to block the movement of one relative to the other. This also allows improved weldability on aforementioned type polymer conduits by melting and homogenous mixing of the substrate material and that of the surface of said conduit at the weld point under the effect of the heat generated by the conductive track.

  In order to allow a Joule heating that is sufficient to melt the substrate and the material of the conduit to be connected while having a minimum thickness on said substrate, the conductive strip or strip is constituted by a resistive ink (or paste) comprising less a precious metal selected from the group gold, silver, palladium, platinum.

  Such materials have the important advantage of being good electrical and thermal conductors, which makes it possible, when a current is passed through them, to obtain a significant release of heat by the Joule effect, while also being metals. ductile and malleable which gives them, at very low thickness, good flexibility with good wear resistance.

  However, each insert being intended for a single use, other less expensive materials can be used to make the conductive track such as copper for example.

  According to a preferred embodiment of the insert according to the invention, the conductive strip or strip has a substantially constant width.

  This allows a heating of the track and a diffusion of heat produced by Joule effect that are homogeneous at any point of said track.

  According to another preferred embodiment of the insert according to the invention, the conductive strip or strip has a variable width.

  It is thus possible to obtain an insert having variable heat diffusion along said conductive track, thus making it possible to adapt the heat diffusion zones in the track as a function of the geometry of the surface of the parts to which the insert is applied.

  In another preferred embodiment, the conductive strip or strip is branched. This advantageously makes it possible to produce tracks of varied geometry determined as a function of the thickness and the width of said track and the heat flux necessary to transmit to achieve the weld, as well as the surface of the desired weld point.

  The variation of the geometry of the track allows the zone cutting of the surface to be welded and the control of the power to be applied in these different zones.

  According to a preferred feature of the invention, the thickness of the substrate of the insert is in a range from 0.1 to 2 mm, and wherein the thickness of the track or conductive strip is in a range of from 0.01 to 0.2 mm.

  According to another preferred embodiment, the conductive track of the insert extends along a labyrinthine curvilinear path on the surface of the insulating substrate.

  Such a layout advantageously allows homogeneous diffusion of the heat flux over the entire weld surface covered by the insert with a minimum thickness and a minimum conductive track width. In addition, such a geometry of the track avoids any possibility of passage of the melt from the inside to the outside of the welding zone when a fitting fitted with such an insert is applied to a pipe to be connected. In this configuration, the resistive conductive track of the insert prevents the effusion of the melt out of the welding zone.

  According to another preferred embodiment, the insert according to the invention comprises several independent conductive tracks or strips.

  It is thus possible to multiply the number of positions of the weld spot or to perform successive or simultaneous welds of a coupling incorporating such an insert to one or more conduits.

  According to a second aspect, the invention proposes an electrofusion pipe connection or element characterized in that it comprises an insert of the type described above.

  Such a connection or duct element has this advantage over the known electroweldable duct fittings or duct elements of the prior art that it is much simpler to produce insofar as it is no longer necessary to make a groove. in the connection for tediously inserting a conductive wire to perform the electrowelding.

  In addition, by the flexibility of the insert, made independently of the fitting or the element to have it, we can now adapt indefinitely the geometry of the fitting and the weld surface thereof as needed by adapting the shape the substrate of the insert and the track deposited on this substrate.

  Finally, the improved diffusion properties of heat, produced by the Joule effect, allowed by the largest surface of the conductive track of the inserts according to the invention compared to the spiral electric wires of the prior art give the connections and electrofusion elements including such inserts increased weldability and better controlled.

  According to the third aspect, the invention relates to a method of manufacturing an insert, in particular for a connection or element of electroweldable conduit on a fluid transport conduit, according to which a layer of an electrically conductive material is deposited along a path continuous and narrow continuous to form a track or conductive strip on at least a portion of a surface of a substrate of a second electrically insulating material, said substrate and said conductive track or strip being flexible.

  The formation of the conductive strip by deposition of a conductive material on an insulating substrate makes it possible to obtain at a lower cost a conductive strip or strip having various configurations without requiring expensive tools.

  According to a first embodiment, the method of manufacturing the insert is characterized in that said track or conductive strip is formed by screen printing.

  According to a second embodiment, said conductive strip or strip is formed by etching.

  These two embodiments are particularly advantageous in that they allow complete automation of the process of deposition of the track using robots programmed to reproduce track masks determined according to the different formats of substrates used.

  These embodiments are moreover particularly flexible, which is advantageous in terms of the industrial production of inserts; it is thus possible to produce a just-in-time production of inserts according to the demand and the desired formats.

  The configurations of the track or conductive strip may also be calculated and designed to cause, depending on the needs, the geometry of the duct on which the connection is to be welded, and / or the nature of the plastic material, a disparity of the 1.2 heat flow along the conductive strip; for this purpose for example, there may be a first section of the strip having a first width and a second section of the strip having a second width greater than the first width; the heat flow (per unit area) dissipated along said second section will then be less than the heat flux (per unit area) dissipated along said first section.

  Conversely, the configuration of the track or strip may be provided to cause a homogeneous heat dissipation along the track and / or on the surface of the insulating substrate; for this purpose, the width of the band can be kept constant over a substantial part of its length. The optimization of the distribution of the thermal flux at the surface of the substrate can in particular be obtained by providing a track or branched band, that is to say comprising at least two track elements or strip connected in parallel.

  According to another aspect, the invention consists in proposing a method of manufacturing a coupling or a duct element incorporating an said insert in which: an insert is disposed in a mold cavity of a said coupling or electrofusion conduit element; and casting in said cavity a thermoplastic material of identical or similar nature to that of the substrate of said insert, so as to integrate the insert into the fitting by overmolding.

  In the manufacture of electrofusion fittings, the manufacturing process essentially consists of an injection of thermoplastic material into a cavity of a mold where the insert has been previously introduced and held in place, for example as described in US Pat. No. 4,455,482. ; the substrate of said insert 25 being preferably made of a thermoplastic material identical or similar to that injected to form the coupling, in order to promote the production of a substantially homogeneous piece and to promote the securing of the insert to the injected material to form the fitting.

  For the manufacture of a pipe-shaped connector or duct-shaped duct element, for the connection of, for example, two ducts, it is also possible to wind and hold an said insert on a cylindrical preform and to overmold said fitting by casting or spraying thermoplastic material. on said insert.

  The invention makes it possible to produce electro-welded injected pieces by melting the contact surface in which said conductive track of said insert is incorporated, and in which said contact surface can conform to various shapes; the invention particularly allows the realization of welding fittings in the form of sleeve, tee, y, or derivation whose body has a saddle-shaped portion.

  Said thermoplastic material of the connectors is preferably based on polymers of the polyolefin, vinyl or other type, in particular polyethylene, for the production of connections to be welded on transport conduits of all types of fluids, such as, for example, water or combustible gas.

  The invention allows the realization of a connection in which the conductive track is flush or prominent on the contact surface of the connector to be welded to a conduit, or located close to said contact surface; this advantageously results that the fusion of the portion of the pipe to be welded can be achieved more quickly, using less energy, and / or more precisely; the invention allows the realization of welds of better quality.

  Other features and advantages of the invention appear in the following description, which refers to the accompanying drawings, and which illustrates without any limiting nature of the preferred embodiments of the invention.

  Unless otherwise indicated, identical or similar references are used to designate identical or similar elements.

  Figures 1, 2 and 3 illustrate an embodiment of an insert according to the invention in the form of a straight strip; Figure 2 is a top view of the insert with a connection terminal; Figure 1 is a longitudinal sectional view - according to I - I - of the insert of Figure 2; FIG. 3 is a cross-sectional view on III-III of the insert of FIG.

  Figure 4 is a perspective view of a second embodiment of an insert according to the invention.

  Figure 5 is a schematic perspective view of a tubular sleeve blank of circular section equipped with a conductive strip according to the invention.

  Figures 6a and 6b respectively show front and right views of a branch fitting incorporating a flexible insert 20 according to the invention.

  With reference to FIGS. 1, 2 and 3, the insert 1 essentially comprises an electrically insulating substrate formed by a sheet 2 of a polymer of polyolefinic, vinylic or other type, in particular of polyethylene (PE), the thickness of which is is close to 1 millimeter, on an upper face 4 of which is deposited a conductive track 3 made of an electrically conductive material.

  The track 3 covering a portion of the surface 4 has a thickness ep ranging from 0.01 to 0.2 mm; depending on the applications and the materials used, the dimensions of the strip 2 and the conductive strip 3 may vary in large proportions; however, the ratio of the width 1p of the track 3 to the thickness ep of this track will be greater than 1, in particular situated in a range from 5 to 300, so as to promote a homogeneous distribution of the heat flow dissipated by the track when connected to a power source; for the same purpose, the ratio of the width lr, a first portion of the track to the gap i separating (see Figure 3) this portion of a track of an adjacent portion of the track, will be greater than 1, too.

  In addition, the ratio of the thickness of the insulating substrate 2 to the thickness ep of the conductive track 3 will also be greater than 1., in particular in a range from 1 to 200; this facilitates in particular the realization of a conductive track having sufficient flexibility to be bent or wound so as to match the shape of the skin of the fitting to which the insert is intended to be integrated.

  In the embodiment illustrated in Figures 1, 2 and 3, the insulating substrate 2 and the conductive strip 3 extend along a longitudinal axis 5 common to these two strips; an orifice 6, 7 (with axis 8, 9) is respectively provided at each longitudinal end of the conductive strip 3, and extends therethrough as well as the substrate.

  In the embodiment described here, a generally screw-shaped electrical connection terminal 10 which extends along the axis 8 through the orifice 6 and is extended by a rod 12; a nut 13 being screwed on the rod 12 to bear on the upper surface 14 of the conductive strip 3, for securing the terminal 10 to the insert1. However, this embodiment of the connection terminals is not limiting. It is also possible to envisage, for example, a mounting of said terminals by riveting or by interlocking in force a male piece extending through the orifice 6, 7 in a female part pinching the conductive strip 3 and the substrate. 2 so as to secure the terminal to said substrate.

  For the realization of this circuit, the conductive material may be first applied over the entire upper face 4 of the substrate 2, and then removed from specific portions of this face 4 which must not be electrically conductive.

  This removal can be obtained mechanically or chemically, in particular by using a mask.

  Alternatively, the conductive material may be selectively deposited on the face 4, only in the portions of this face to be covered with the track 3, including not known screen printing techniques or etching.

  Preferably, the conductive material consists of a resistive ink (or paste) comprising at least one precious metal selected from the group consisting of gold, silver, palladium and platinum; which makes it possible, when a current is passed through the resistive track 3, to obtain a significant release of heat by the Joule effect, since these metals are good electrical and thermal conductors.

  However, each insert being intended for a single use, other less expensive materials can be used to make the conductive track such as copper for example.

  FIG. 2 illustrates a track 3 presenting, in a central part 3a of the track, a width lpa less than the width lp of the longitudinal ends of the track.

  In the embodiment illustrated in FIG. 4, the insulating substrate 2 is in the form of a thin disk pierced with a central orifice 15 and provided with two diametrically opposite appendages 16, 17; each appendix comprises one end of the conductive track 3, is pierced with an orifice (such as 6, 7, FIG. 1) and is equipped with a terminal 10 for electrically connecting the track with which it is in contact (mechanical and electrical ); the track 3 of substantially constant width extends over a substantial portion of the upper face of the support disc 2, in a sinuous labyrinthine pattern.

  In the embodiment illustrated in FIGS. 5, 5a and 5b, the insert comprises an insulating substrate 2 cut in a substantially rectangular shape on the surface of which is deposited, by screen printing or etching, a conductive track 3. The conductive track 3 is preferably deposited on the substrate 2 so that it forms meanders directed along the length L of the substrate 2 so as to improve the flexibility of the insert 1 and especially the track in this direction. The insert can thus be easily rolled, for example on a preform, to form a cylinder whose inner wall is covered with the track 3, said cylinder being then overmolded with plastic, for example polyethylene, to form a sleeve tubular 18 electrofusion as shown in Figure 5.

  In this embodiment, each end of the track 3 is at diagonally opposite angles of the rectangle formed by the substrate 2 when the insert is flat. At each of these ends of the track is pierced an orifice 6, 7 through which there is a connection terminal 10 whose rod 12 has a length at least equal to three times the thickness es of the substrate 2. Such a length of the rod 12 of the terminals is provided so that these terminals 10 can pass through the wall of the tubular sleeve 18 and that the track can be connected to a source of electrical energy.

  It is thus very easy to produce an electrofusion tubular sleeve 18 by overmoulding an insert 1 rolled on a preform.

  The insert illustrated in FIG. 3 is in turn particularly suitable for fitting into the constitution of the electrofusion device for connecting two conduits, for example a branch connection 19 for connecting a bypass line D to a fluid transport pipe designated in FIG. its set by reference C and as illustrated in Figures 6a and 6b.

  For this purpose, the insert 1 is introduced into a cavity of a mold (not shown) whose shape corresponds to that of the connection to be obtained.

  The insert is arranged in the mold so that, on the one hand, during the injection of material into the mold to form the coupling, the central orifice 15 pierced in the insulating substrate is in correspondence with the barrel 20 of the mold. 19, so as to allow the passage of a perforating member (not shown) to establish the communication between the connector and a pipe C, and secondly, that the substrate 2 of the insert 1 forms the inner surface 22 (skin surface) of the saddle 21 of the fitting 19 on either side of the opening portion 23 of the barrel 20.

  Advantageously, the cores (not shown) are arranged around the connection terminals 10 connected to the conductive track 3 of the insert so as to provide, during molding, two opposite openings 24a, 24b in the saddle 21 of the connection to allow connection to the connections. two said terminals 1. 0 and provide the electrical energy required to perform the electrofusion of the connector 19 on the pipe C through the track 3 of the insert.

  Thus, during the injection of molten material into the mold, the insert is molded and integrated into the connector 19, the track 3 perfectly following the molding form of the seat 21 of the connector 19 by its flexibility and that of the substrate the insert and being on or slightly below the skin surface 22 of said seat 21, and the two connecting terminals 10 opening freely through the openings 24a, 24b of the seat 21 of the connector.

  Line C comprises a wall 25, cylindrical in the example shown, and is used to transport a fluid under pressure, liquid or gaseous, in a distribution network of this fluid between a supply station of this fluid and one or more stations users of this fluid.

  The wall 25 consists of a thickness ec of nonmetallic fuse material such as a plastic such as polyolefin polymers, vinyl or other, adapted to the nature of the fluid to be transported and the pressure to which this fluid is subjected.

  To make a bypass on this pipe C using the connector 19 described in Figure 6, said fitting is placed astride the pipe where it is desired to conduct a bypass and the latter is held securely, for example by means of a flange connecting the two lugs 26 of the saddle 21 and passing around the pipe C. It is then sufficient to connect an electrical source to the two terminals 10 of the insert molded in the connection 19 to heating the track 3 on the skin surface of the saddle 21 so as to partially melt the fusible outer wall 25 of the pipe C and the substrate 2 in the interstices of the conductive track 3 and achieve a homogeneous weld of said fitting 19 on the duct C. Advantageously, the resistance of the track 3 of the fitting insert is such that said track automatically breaks when it reaches its melting temperature after a certain heating period. fage, usually between 50 and 100 seconds, at the end of which the welding is carried out. This automatically stops the welding cycle and avoids overheating the fuse material of the substrate and the pipe C, which could be detrimental to the mechanical strength and tightness of the junction made.

  In a variant embodiment not shown, the conductive track 3 may also have branches extending from a regular main band deposited on the surface of the substrate 2. Such a layout of the conductive track advantageously makes it possible, among other things, to increase the surface area of the contact of the track of an insert intended to be incorporated in a complex electrofusion fitting track, requiring a welding surface, therefore a large track, but for which there exists despite the flexibility of the track a risk of rupture due to the complexity shape of the fitting.

  The main strip of the conductive track is then formed in a pattern that makes it possible to obtain a minimum weld without breaking the track, and at the ends of this strip there are the electrical connection terminals. The branches of the track are then made from this main band to extend the surface of the conductive track. Thus, even if a branch breaks when the insert is overmolded in the connection or during welding, this does not cause an opening of the electrical circuit between the terminals and the soldering can be carried out without incident.

  The present invention has been described in preferred but not limiting embodiments. In particular, a person skilled in the art can easily modify the shape of the substrate or the conductive track deposited on it, or use inserts according to those of the present invention in other technical fields without departing from the scope of the present invention.

Claims (18)

  1. Insert (1), in particular for a connection or electroweldable conduit element, comprising a hot-melt substrate (2) and at least two connection terminals (10), integral with said substrate at the ends of an electrically conductive circuit (3), characterized in that said substrate forms a flexible sheet of electrically insulating material coated on at least a portion of a surface (3), or in proximity thereto, of a flexible conductive strip or strip (3) forming said conductive circuit.   2. Insert according to claim 1, wherein the ratio of the thickness (es) of the insulating substrate (2) to the thickness (ep) of the conductive strip or strip (3) is greater than 1, in particular located in a range from 1 to 200.   3. Insert (1) according to any one of claims 1 or 2, wherein the ratio of the width (lp, lpa) of the track or conductive strip (3) to its thickness (ep) is greater than 1, in particular in a range from 5 to 300.   4. Insert according to any one of claims 1 to 3, wherein the substrate (2) forms a sheet of an insulating thermoplastic material consisting essentially of at least one polyolefin polymer, vinyl or other.   An insert as claimed in any one of claims 1 to 4, wherein said conductive strip or strip comprises at least one material selected from the group consisting of gold, silver, palladium, platinum or copper.   6. Insert according to any one of claims 1 to 5, wherein said track or conductive strip (3) has a width (1p) substantially constant.   7. Insert according to any one of claims 1 to 5, wherein the track or conductive strip (3) has a variable width (1p).   An insert according to any one of claims 1 to 7, wherein the conductive track or strip (3) is branched.   9. Insert according to any one of claims 1 to 8, wherein the thickness (es) of the insulating substrate (2) is in a range from 0.3 to 2mm, and wherein the thickness of the track or conductive strip is in the range of 0.01 to 0.2 mm An insert according to any one of claims 1 to 9, wherein the conductive track (3) extends along a labyrinthine curvilinear path.   11. Insert according to any one of claims 1 to 10, characterized in that it comprises several tracks or conductive strips (3) independent.   Electrofusible connection or duct element (18, 19), characterized in that it comprises an insert (1) according to one of claims 1 to 11.   Electrofusible connection or duct element (18, 19) according to claim 12, characterized in that the track (3) of the insert is flush with the contact surface of the connection or duct element, or located at near said contact surface.   14. A method of manufacturing an insert (1) according to one of claims 1 to 11, characterized in that a layer of an electrically conductive material is deposited in a long and narrow continuous pattern to form a track or conductive strip (3) on at least a portion of a surface (4) of a substrate (2) of a second electrically insulating material, said substrate and said conductive track or strip being flexible.   15. The method of claim 14, characterized in that said track or conductive strip (3) is formed by screen printing.   16. The method of claim 14, characterized in that said track or conductive strip (3) is formed by etching.   17. A method of manufacturing an electrofusion coupling or duct element (18, 19) according to one of claims 12 or 13, characterized in that: an insert (1) according to one of claims 1 to 11 is provided. in a mold cavity of said electrofusion conduit or conduit member; and injected into said cavity a thermoplastic material of identical or similar nature to that of the substrate (2) of said insert (1), so as to integrate the insert to the fitting (18, 19) by overmoulding.   18. A method of manufacturing an electrofusion coupling or duct element (18) according to one of claims 12 or 13, characterized in that an insert (1) is wound and maintained according to one of claims 1 to 11 on a preform and overmold said fitting by injection of thermoplastic material around said insert.