FR2627026A1 - Method of sealing between a cable or similar element and an external duct receiving this cable, and composite tape for implementing this method - Google Patents

Abstract

Method of sealing between a cable or similar element and an external duct receiving this cable. According to the invention, the method consists in using a composite tape, consisting of a layer 12 of heat-shrinkable material prestretched in a preferred direction and including, on at least one of its faces, a layer or coating 13 of a heat-meltable adhesive, in mounting in or around the tape at least one electrical conductor 14, preferably distributed in the thickness of the adhesive layer 13, in winding the tape around the cable 1 with the adhesive layer facing the latter, in the intervening space between this cable and the external duct 4 and then in resistance-heating the composite tape by means of the electrical conductor in such a way that, as a result of the shrinkage of the heat-shrinkable material in the direction of the stretching of the layer, its thickness increases in its winding around the cable, thereby producing the sealing across the intervening space by virtue of the melting of the adhesive forming the binder between the successive facing surfaces. The invention also relates to the composite tapes used for implementing this method.

Description

 The present invention relates to a method for sealing between a catia or similar element of usually cylindrical shape and an external pipe receiving this element. The invention also relates to the means necessary for the implementation of this method.

 In general, the method is known in the art which consists, for sealing the right side of electrical cable splices, for example, in surrounding them with a layer of heat shrinkable material placed in line with these splices, then to heat with a flame or by another similar means of calorie supply, the material which, by shrinking with the sheath, ensures the desired sealing from the outside around the cables, by closely matching the gaps or other irregularities which exist in the location of the connection.

 However, in the case where the target is surrounded by a pipe or an external pipe, in particular buried, it is often difficult to achieve a secure seal between these elements by this conventional process, the retraction of the material previously introduced into the intermediate space between the conduit and the sheath of the target not providing an adequate sealing of this space which must be sealed with a putty or glues which are impractical to use and whose reliability is uncertain.

 Other processes have also been recommended, using foams of the expanded polyurethane type, associated where appropriate with a heat-shrinkable material, with the addition of a complementary intermediate part, bonded to the internal surface of the pipe to ensure the catching up of Game required. This part most of the time protrudes outside the pipe, which is annoying. In addition, once the assembly has been taken in a mass and the seal has been made, it is generally impossible to disassemble the caty with respect to the pipe, which prevents recovery of the latter and change of the catie.

 The present invention relates to a method which makes it possible to overcome these drawbacks by providing a secure and sealed connection, in particular between a catie or a similar element and an external pipe surrounding this catIe, and more generally between two volumes, one of which is included in the 'Other, the cross sections of the inner part and the outer part may be different from each other and each have any profile.

 The invention applies more particularly although not exclusively in the case where the internal element or cable and the external pipe have a circular outline, in particular in the field of electrical or telephone targets placed inside protective pipes, the sealing being in particular to be carried out at the place where the pipe, in urban area, emerges in the basement of a building or other similar construction, in which the cable is extended and then distributed for distribution to users, this sealing being necessary here to avoid water or gas entering the interior of the pipe.

 According to the invention, the process considered consists in using a composite strip, consisting of a layer of heat-shrinkable material previously stretched in a preferential direction and comprising on at least one of its faces a layer or coating of a hot-melt adhesive, to be mounted in or around the strip at least one electrical conductor, preferably distributed in the thickness of the layer of adhesive, to wrap the strip around the cable with the layer of adhesive directed towards it in the intermediate space between this cable and the outer pipe, then to heat by Joule effect the composite strip by means of the electrical conductor so that, as a result of the shrinking of the heat-shrinkable material in the direction of stretching of the layer, an increase in its thickness occurs in its winding around the cable, by sealing it through the intermediate space thanks to the fusion of the adhesive forming binder between the successive surfaces in rega rd.

 The invention also relates to the composite strip used, where the layer of heat-shrinkable material consists for example of a polyolefin crosslinked by irradiation or chemical route.

 According to a particular characteristic of this strip, the layer of heat-shrinkable material is produced by preferential stretching in a direction transverse to the composite strip, the length of the layer remaining practically unchanged during this stretching. The layer thus prepared is then coated with a coating or is associated with a complementary layer of an appropriate hot-melt adhesive, of the kind of glue fusible at higher temperature, the coating of the layer or the deposition of the additional layer taking place. by soaking or by spraying or the like.

 Preferably. the hot-melt adhesive is based on ethyl vinyl acetate.

 The composite strip then being wound on itself around the cable or the internal element, the heating produced by the passage of a current in the electric wire then causes at the same time the fusion of the adhesive, which is distributed homogeneously between the gaps left free by ensuring the connection of the successive windings of the strip, at the same time as the shrinking of the layer of heat-shrinkable material according to its direction of prior stretching This shrinking results in an increase in the thickness of the winding in a radial direction filling the space between the cable and the pipe, to ensure the desired seal.

 According to another characteristic of the composite strip, the electric wire is an insulated wire, in particular an enameled wire, the ends of which extend beyond the strip are joined outside the pipe to an appropriate voltage source.

 In a particular embodiment, the electric wire is wound in a spiral around the composite strip, which has regularly spaced notches in its opposite edges for housing and holding in position the successive turns of the wire. In another embodiment, the electric wire has the shape of a zigzag frieze, embedded in the complementary layer of hot-melt adhesive, the loops of the frieze being preferably oriented in the direction of prior stretching of the strip .

 Advantageously, the composite strip is wound on the cable with the additional layer of adhesive directed towards it and is associated, once the winding is completed, with an external envelope in contact with the internal surface of the pipe. Depending on the case, the external envelope is produced by means of a flexible material of the mastic type, linked to the winding by amalgam or gluing or by an additional thickness of hot-melt adhesive.

 In the previous variants, the wire is continuous and wound or deposited on the strip. In another embodiment, the electrical wire of the composite strip consists of a mesh, the wires of which are electrically insulated.

 In addition, in order to allow the removal of the strip placed around the cable to be carried out if necessary, in particular in order to separate the latter from the external pipe, the winding advantageously incorporates longitudinal hooks, disposed between two consecutive towers of the strip and extending to protrude outside the pipe, allowing, following an increase in temperature causing additional shrinking of the heat-shrinkable material, to release the strip from the cable.

Other characteristics of the method according to the invention and of the means necessary for its implementation will appear from the following description of several examples, given by way of non-limiting example, with reference to the appended drawings in which
- Figure 1 illustrates in perspective and in section with partial cutaway, a first embodiment.

 - Figure 2 is a detail view showing a first variant of the composite strip used.

 - Figures 3 and 4 are views, respectively in perspective and side view, of another variant of the composite strip.

 - Figure 5 is a longitudinal sectional view illustrating the means used to remove the winding after separation of the cable and the pipe.

 - Figure 6 is a sectional view of another variant.

 In the example illustrated in FIG. 1, the reference 1 schematically designates a conventional electric or telephone cable comprising a set of strands 2 mounted inside a sheath 3, these strands possibly being parallel to each other or arranged in twists or other. The cable 1 is designed to be arranged substantially in the axis of an external protective pipe 4, formed of piping 5 of any kind, generally made of a suitable rigid plastic material.

According to the invention, the seal is then produced between the sheath 3 and the piping 5 by housing in the clearance which separates these two elements, a winding of a composite strip 6, the characteristics of which are defined below. Preferably but not exclusively, the strip 6 obtains the obturation of the
Play between target 1 and pipe 4 at the level of the region where this cable leaves the pipe, for example at the outlet of the latter in a basement or the like of a building where the target extends to be then distributed and distributed to different users.

 In the example illustrated in Figure 2, the composite strip 6 forming the sealing winding is formed by means of a layer 7 of a heat-shrinkable material, in particular of the polyolefin type crosslinked by an appropriate treatment, by irradiation or chemical. This strip 6 is previously subjected to a stretching treatment in a preferred direction, in particular oriented in the direction perpendicular to its length, this stretching of the material being able to be variable according to the envisaged applications.

 The composite strip 6 also includes in its lateral edges notches or grooves 8, to maintain and guide around the strip a spiral winding of an electric wire 9, the ends 10 and 11 of which come out of the strip are provided for be connected to an appropriate voltage source (not shown), after winding around the sheath 3 of the cable 1, between the latter and the pipe 4. The wire 9 is surrounded by an insulating sheath, for example enamelled, so to avoid any short circuit on itself during the winding of the strip as described below. The layer 7 of. shrinkable material once surrounded by the wire 9 is then coated on at least one of its faces, in particular on that intended to be directed towards the sheath 3 during the winding of the strip by means of a hot-melt adhesive, by example based on ethyl vinyl acetate.

 In an alternative embodiment, illustrated in Figures 3 and 4, the composite strip 6 consists of two superimposed layers, respectively 12 and 13, the layer 12 being formed of a heat-shrinkable material while the layer 13 is made of adhesive hot melt. In this variant, the electric wire 14, insulated, is embedded in the layer of adhesive 13 and has the shape of a zigzag frieze, the loops of which are preferably oriented, as illustrated in FIG. 3, in the transverse direction of the strip 6, in particular in the direction of the prior stretching direction of the latter. Also in this variant, the ends 15 and 16 of the wire, projecting from the contour of the strip, are again joined to a source of tension.

 Whatever the variant adopted, the composite strip 6 is then wound, with the number of turns necessary, around the sheath 3, the layer 13 of hot-melt adhesive of the strip being directed towards the sheath. Once the winding is completed, with almost complete filling of the clearance leaves free between the sheath 3 and the pipe 4, there is advantageously provided on the strip 6 an additional external layer 17 of hot-melt adhesive or other flexible material, for example a sealant or a plastic foam, which is made to hold on the winding of the strip by gluing or amalgam.

 The assembly thus produced is then slid between the sheath 3 and the pipe 4, the ends 10 and li, or 15 and 16 of the winding of electric wire 9 or 14 being joined to a voltage source allowing, by passage of a suitable current in the wire, gradually heating up the strip.

 This contribution of calories makes it possible on the one hand to melt the layer of hot-melt adhesive 13 while ensuring an effective bond between all the surfaces present, in particular allowing the adhesive to infiltrate into any possible interstices of the winding. . Simultaneously, the layer 7 or 12 of heat-shrinkable material undergoes a shrinkage in its thickness, materializing by a contraction of the strip in the transverse direction against its prior stretching, and correlatively causing an increase in its thickness through the winding. The free play between the sheath 3 and the internal wall 5 of the conduit 4 is thus completely filled, achieving the desired sealed closure, suitable in particular for preventing any subsequent introduction of gas or liquids between the sheath and conduit.

 Thanks in particular to the winding of the electric wire 9 or 14 on the strip and in particular to the transverse direction of the loops formed by this wire, which, once the winding has been carried out, are placed substantially parallel to the longitudinal direction of the cable and the pipe. , it is found that the expansion of the heat-shrinkable material occurs while being guided and controlled by the wire itself which forms the armature in the axial direction, without preventing the material from freely creeping or swelling in the radial direction, which is an advantage particularly important of the process used.

 FIG. 5 illustrates another improvement, consisting in embedding inside the winding of the composite strip 6 substantially longitudinal rods 18, comprising at one end a support head 19 and at the opposite end a hook 20, these rods allowing, after an increase in the temperature created by the electric wire in the winding creating sufficient heating to soften the heat-shrinkable material and the hot-melt adhesive, to easily remove the winding, thereby freeing the cable opposite external pipe screw, for repair, maintenance or replacement.

 In another variant of implementation, illustrated in FIG. 6, two parallel cables 1 are shown here, mounted between two flanges 21 and 22 applied one on the other according to a common transverse plane 23, the clearance between the cables and the bottoms of the housings 24 and 25 receiving them being sealed according to the invention by means of windings of composite strips 6, in a manner analogous to that described with the examples previously represented.

 Whatever the embodiment adopted, it is easily understood that the invention makes it possible to easily adjust the winding thickness necessary for achieving the desired seal in each case or application, by cutting to the appropriate length of the composite strip and in particular of the layer of heat-shrinkable material. Once this cutting has been carried out, the ends of the electrical wires can be easily stripped, for example by partially unwinding the spiral or by tearing off the ends of the wire from the adhesive layer. this results in a very easy and effective implementation, the device requiring no use of flame or other external calorie supply means, the heating necessary for the expansion of the material being obtained by Joule effect in the electric wire exclusively , which can be much easier to perform and offers better safety, especially in a hazardous environment.

 The invention makes it possible to use the composite strip envisaged for any section of the internal and external elements delimiting between them the clearance to be closed, the winding produced being able to be subsequently easily disassembled by reheating the winding, softening the layer of adhesive then promoting the longitudinal sliding of the strip and the separation of the two elements. Finally, we will again mention the advantage which results from the mechanical stiffening structure created by the electric wire associated with the strip, axially rigid but radially flexible, which guides and controls the expansion of the heat-shrinkable material in the necessary direction, by providing a particularly satisfactory result.

 Of course, it goes without saying that the invention is not limited to the embodiments more specifically envisaged above; on the contrary, it embraces all its variants. In particular, no limitation should be envisaged as to the nature of the material capable of constituting the heat-shrinkable layer as well as the layer of hot-melt adhesive. The method of winding the electric wire in the latter can also be variable according to the intended uses. Finally, many variants could be taken into consideration in relation to the shape of the volumes between which the sealing is carried out.

Claims (12)

 1 - Method for sealing between a cable or similar element and an external pipe receiving this cable, characterized in that it consists in using a composite strip (16), consisting of a layer <7-12) of material heat-shrinkable previously stretched in a preferred direction and comprising on at least one of its faces a layer or coating (13> of a hot-melt adhesive, to be mounted in or around the strip at least one electrical conductor (9-14), preferably distributed over the thickness of the adhesive layer (13), wind the strip around the cable (1) with the adhesive layer directed towards it in the intermediate space between this cable and the outer pipe (4 ), then to heat by Joule effect the composite strip by means of the electrical conductor so that, as a result of the shrinking of the heat-shrinkable material in the direction of stretching of the layer, an increase in its thickness occurs in its winding around the cable, e n sealing through the intermediate space by melting the adhesive forming a binder between the successive facing surfaces.  2 - Composite strip for implementing the method according to claim 1, characterized in that the layer of heat-shrinkable material (7-12) consists of a polyolefin crosslinked by irradiation or chemical route.  3 - Composite strip according to claim 2, characterized in that the layer of heat-shrinkable material (7-12) is produced by preferential stretching in a direction transverse to the composite strip, the length of the layer remaining practically unchanged during this stretching.  4 - composite strip according to claim 3, characterized in that the layer is coated with a coating or is associated with a complementary layer (13) of an appropriate hot-melt adhesive, of the kind of hot melt adhesive at higher temperature, the coating of the layer or the deposition of the additional layer being effected by soaking or by spraying with a spray gun or the like.  5 - Composite strip according to claim 4, characterized in that the hot-melt adhesive is based on ethylvinyl acetate.  6 - composite strip according to one of claims 2 to 5, characterized in that the electric wire (9-14) is an insulated wire, in particular an enameled wire, the ends of which extend beyond the band are joined outside of driving to an appropriate voltage source.  7 - composite strip according to one of claims 2 to 5, characterized in that the electric wire (9) is wound in a spiral around the composite strip, which has notches (8) regularly spaced in its opposite edges for housing and maintaining in position the successive turns of the wire.  8 - composite strip according to one of claims 2 to 5, characterized in that the electric wire (14) has the shape of a zigzag frieze, embedded in the additional layer of hot-melt adhesive (13), the loops of the frieze preferably being oriented in the direction of prior stretching of the strip.  9 - composite tape according to any one of claims 2 to 8, characterized in that it is wound on the cable (1) with the additional layer of adhesive directed towards it and is associated once the winding is completed , with an external casing <17) in contact with the internal surface (5) of the pipe (4).  10 - Composite strip according to claim 9, characterized in that the external envelope (17) is produced by means of a flexible material of the putty type, linked to the winding by amalgam or gluing or by an additional thickness of adhesive. hot melt.  11 - Composite strip according to one of claims 2 to 5, characterized in that the electric wire is constituted by a mesh whose wires are electrically insulated.  12 - composite strip according to any one of claims 2 to 11, characterized in that it comprises longitudinal hooks (18), arranged between two successive turns of the strip (6) and extending to protrude to the outside the pipe, by allowing, following an increase in temperature causing a subsequent reheating of the heat-shrinkable material, to release the strip from the cable.