FR2533360A1 - Heat-recovery article made from polymer material. - Google Patents

Abstract

This article is characterised in that it comprises an incorporated cutting member 20 intended for opening the article after its heat recovery. Application in particular to the protection of electrical cable splices.

Description

The present invention relates to heat recovery objects, in particular to heat shrinkable objects for use in the protection and isolation of supply lines such as electric cables.
Heat recovery objects, in particular heat shrinkable objects, are at present widely used in many fields where insulation, sealing and encapsulation are necessary. Usually these objects take up, by application of heat, a initial form from which they were previously deformed, but the term "heat recovery", as used herein, also includes an object which, by application of.

heat, adopts a new configuration, even if it does not.

was previously distorted.

In their most common form, these objects include a heat-shrinkable sleeve made of a polymer material having the property of elastic or plastic memory as described, for example, in American patents Nos.
2,027,962; 3,086,042 and 3,957 3,720 As clearly shown, for example, in US Patent No. 2,027,962, the initial thermally stable form may be a transient form in a continuous process in which, for example, an extruded tube is expanded, while still hot, in a dimensionally thermally unstable form but, in other applications, a dimensionally stable thermally preformed object is deformed into a dimensionally thermally unstable configuration during a separate operation.

In other objects, as described, for example, in British Patent No. 1,440,524, an elastomeric element such as an outer tubular element is maintained in an expanded state by a second element, such as a internal tubular element, which, by application of heat, weakens - and allows
thus the recovery of the elastomer element.

Heat shrink sleeves find many applications, particularly in the connection and termination of wires, cables and pipes. However, there are other applications in which it is desirable to provide an element of connection, isolation or protection with thermal recovery for elongated objects such as cables and pipes whose ends are not accessible or, If they are, where it is undesirable to disconnect them or to move them in another way. For such applications, so-called rolled sleeves "have been developed. Basically, they are heat-recovery sheets which can be wrapped around the substrate to take a substantially tubular shape and which, generally, are provided with fixing members for # keeping it in the wound configuration during recovery ~ Ty pique, these fixing members are mechanical in nature and include, for example, rigid staples, dowels or barrels cooperating with molded or extruded protuberances of suitable shape adjacent to the overlapping edges of the sheet Different types of fasteners are described, for example, in US Patent No. 3,379,2 and in British Patents Nos. 1,155,470 I,211,988 and 1,346,479. In other applications, the sheet can be kept in its rolled up configuration during recovery using an adhesive that can, in some cases, be applied in situ: 0
A particular area of application for thermal recovery objects of the type described above is isolation and pro.

detection of fittings behind supply lines, in particular electrical cables. When making such connections, for example, between telephone or power cables, many problems arise in meeting the required requirements for continuity, isolation and grounding, sealing the joint against the irruption of contaminants such as humidity and insects and to provide the necessary resistance to tension, compression, bending and impact. British patent No. 1,155,470 proposes using tubes or sleeves made of heat-shrinkable material to protect and insulate electrical cable fittings0 However, since the cables are frequently pressurized and must be watertight, it is necessary to coat the inner wall of the heat-shrinkable sleeve with a sealant such as glue hot fuse or putty. When the sleeve is heated, the sealant melts and forms a water-tight, pressure-resistant seal between the sleeve and the cable.

This has the disadvantage that, in certain cases, the sleeves cannot be opened easily later for repair or modification of the connection without requiring the complete renewal of the connection and the process is also inappropriate when the anointed or the electric coastituaats going to the Seal have delicate or breakable elements.

 It has therefore been proposed to produce modified heat-shrinkable articles in which a central part does not have the recovery property or in which reinforcing members are provided to prevent recovery in the central region, for example, the British patent NO I 248908 describes a heat-shrinkable object containing a bridging sleeve of non-shrinkable material and end sleeves of non-shrinkable material and end sleeves of heat-shrinkable material, the sleeves being interconnected, for example, by? screw connections. However, such an arrangement requires relatively tight manufacturing tolerances to ensure that the threads and threads of the parts can cooperate easily.

 A proposal which has been more successful is that of British patent NO 1 431 167 in which a heat-shrinkable sleeve, which may be a rolled sleeve, is provided with a central reinforcement comprising a longitudinally relatively rigid split tube typically, such a tube is produced. from a pair of semi-circular half-shells, for example aluminum. Such objects have the advantage that they can be easily reopened to repair or modify a cable connection, but have been found to be rather expensive.

The present invention provides an object with thermal recovery comprising a heat-shrinkable sleeve, preferably tubular, having an internal lining in a continuous metal sheet and equipped with a central reinforcement member comprising one or more longitudinally compressible coils.
The present invention is based on the surprising observation that the combination of the doubling of thin metal sheet and of the coil (s) located in the center provides an inexpensive, but high-efficiency means (a) for ensuring, after recovery, a cable connection. is effectively sealed against penetration of water vapor and (b) to ensure that the object after recovery has the desired mechanically resistant tubular structure in its central region.

The use of reinforcing means in thermal recovery devices is described in British patent N 1 245 119 and a proposed reinforcing means is a coil, but the use of a coil in these devices is mainly intended to produce an external surface similar to a screw on the object after recovery in order to facilitate the introduction of the crossing device inside and the withdrawal of the latter from a wall which it passes through an important characteristic of the coil (s) used in the present invention is that, while being sufficiently resistant to ensure the desired mechanical properties of the central region (which, during a test, must be able to withstand, without deformation, the force of a 0.5 kg steel cylinder with a spherical end which is dropped on the ob-
Jet of a height of 1 meter), they are, moreover, compressible long: "tudiralement, that is to say that they can etle compressed manually or using a simple hand tool.

Thus, when it is desired to repair or modify the cable junction, the heat-shrinkable sleeve can be cut and removed and the coils can be compressed longitudinally so as to allow access to the connector. After the repair or modification has been carried out, the coils can return to their previous configuration. It is therefore preferable that the coils are elastic so as to facilitate this procedure, In one embodiment, for example, a single coil spring can be used which can be pulled from one end to allow access0 However, when only one coil is used, problems may arise in accommodating the coil in the fully compressed state and, in addition, it may it is not possible in some cases to compress the coil sufficiently to allow access to all the components of the cable splice.

 In a particularly preferred embodiment, therefore, the reinforcement is provided by two coils arranged end to end, so that after recovery, they ensure the effective replacement of a single coil. One or both coils can be equipped with members to position them correctly before recovery. For example, one of the coils can be fitted with a short tubular accessory in or around which another coil can be placed. When, as in the preferred embodiments, the coils are elastic, staples can be provided to keep them in the compressed state when it is desired to access the connector again.

 Objects according to the present invention may advantageously be provided with support members to ensure that the splice remains correctly positioned inside the central region during and after recovery. Such members can, for example, be small. metal bands placed at the ends of the coils. Preferably, however, the members are "crowns" or 'combs as described and shown, for example, in British Patent No. 1,431,167.

These generally include a metal strip having a set of deformable teeth or protrusion extending therefrom. the projections are preferably more deformable near their ends and their presence ensures a regular progression of the diameter of the heat-shrinkable sleeve from the reinforced central part to the point where it grasps the cable, thus minimizing a stress on the sleeve material and protrusions reinforce this region of diameter change 0 Of course, the crowns can be used in conjunction with other support members, but this is generally not necessary.

 The heat-shrinkable tubular sleeve may have a closed cross section or may be a rolled sleeve as described in the aforementioned patents. The term "tubular" as used herein is not limited to straight cylindrical configurations, but includes elements of irregular and / or variable cross-section as well as Y-shaped elements of 2 and a.

 The sleeve can, of course, be made from any of the heat-shrinkable materials known in the art, but among the particularly preferred materials, there may be mentioned, for example, polyolefins, in particular polyethylene, ethylene copolymers and vinyl acetate copolymers of ethylene and ethyl acrylate; chlorinated and fluorinated polymers, in particular polyvinyl chlorlae, polyvinylidene fluoride and polymers suitable for vinylidene fluoride, hexafluorethylene and chlorofluorethylene; and rubbers such as ethylene / propylene rubber, chlorinated rubbers, for example neoprene, and silicone rubbers which can be used in a mixture with a crystalline or glassy polymer such as an olefin polymer. All of the above materials can, if desired, be crosslinked, for example by irradiation and / or by chemical means. The sleeve will generally be provided at least at its ends with an internal coating. With a sealing agent such as a hot-melt adhesive or a mastic although, in certain applications, these may be applied in situ. Particularly suitable hot melt adhesives include, for example, polyamides, copolymers of ethylene and vinyl acetate and terpolymers (with or without incorporated waxes) and polyesters. Such materials are described, for example, in British Patent No. 1,440,810 and in German Patent Application DOS 2 709 7170 Also vulcanizable adhesives which melt and flow under the application of heat are suitable, but which are not not then hot fuses.

 Mention may also be made of epoxy resins and sealants class ques such as, for example, those based on rubbers and isobutylene modified with suitable materials known in the art. Obviously, the use or other of such materials and their type, if they are chosen, will depend on the requirements of these particulars in each case.

As mentioned above # a particularly important aspect of the present invention is the realization of the continuous metal sheet lining to provide protection against penetration of water vapor. In the heat recovery objects described in British Patent No. 1,431,167, the risk of water penetration between the teeth of the crowns at both ends and, in any case, the permeability to water vapor of the polymer material typically used for the heat recovery sleeve is high and thus requires the use of silica gel bags inside the splice case during installation. In preferred objects of the present invention, however, the foil metal covers the splice between the teeth of the crown after recovery and extends to the end of the heat-shrinkable tubular sleeve Comparative tests of permeability to water vapor indicate that the arrangement according to the invention ensures a reduction of water vapor permeability by a factor of about 8 compared to the previously proposed product using aluminum half-shells. Not only was this surprising improvement obtained, but it was also é found that by correctly choosing the thickness of the metal sheet, which will generally be an aluminum sheet, it is possible to obtain a heat-shrinkable product which will shrink to give a uniform surface configuration, but in which the sheet of metal doesn't tear me apart. That is to say that it is sufficiently thin without flaming or adopting a shape having ridges and hollows which could, for example, cause a deterioration of the heat-shrinkable sleeve or create a path for the introduction of contaminantsh D ' on the other hand, the thickness of the sheet is sufficient to prevent its deterioration, for example its tearing, during recovery, even around irregularly shaped substrates
When using aluminum foil, it has been found that a desirable thickness range is from 10 to 25 microns in particular from 12 to 15 microns. Other metal sheets which can be used according to similar thicknesses are copper foil, soft iron foil (for example when magnetic shielding is required) and some foils of metallized plastic such as a biaxially oriented polyester sheet coated with commercially available gold.

 In one of its aspects, therefore, the present invention also provides a heat recovery object comprising a heat shrink tubular sleeve provided with an internal lining of a continuous metal sheet having an appropriate thickness as described above, in especially aluminum foil having a thickness of 10 to 25 microns, preferably 12 to 15 microns. In a particularly preferred embodiment of this aspect of the invention, - a heat-shrinkable tube provided with an internal layer of hot-melt adhesive is provided with an internal lining of a metallic foil of appropriate thickness which is itself provided with an internal coating of a hot melt adhesive. Such a product has proved to be particularly useful for encapsulating cable splices, in wound products and for carrying out transitions between outlets of cable bottle and incoming cables.

 In accordance with this aspect of the present invention, a tubular sleeve may be of closed cross section or may be a coiled sleeve. In the case of a rolled up sleeve, the metal sheet can easily be applied either during or after the realization of the sleeve. For example, the sleeves are typically coated with a hot-melt adhesive at a certain stage of their manufacture, and the metal sheet, if desired, with its previously applied layer of hot-melt adhesive, can be applied to the sleeve while the hot-melt adhesive on the sleeve is still pasty. The application of an internal sheet on tubular products of cross-closed section is more difficult but, in the case of tubes of large diameter, it can be applied according to a co-extrusion process and in the case of larger diameter tubes, it can be applied using a deformable mandrel. For example, a mandrel can consist of two cylindrical half-shells articulated internally to each other, for example by a piano hinge, one of the shells having a slightly smaller diameter so as to fit inside of the antrum to deform the mandrel. Such a mandrel can be coated with a removable plastic material and covered for example with aluminum foil with or without a layer of hot-melt adhesive, and a heat-shrinkable tubular sleeve coated with an internal layer of hot-melt adhesive can then be partially shrunk around the mandrel and allowed to cool, After cooling, the mandrel can be deformed as described above and removed to leave the desired laminated product. coils must also be incorporated, these can be placed above the tear-off plastic (which can be, for example, a mixture of polyethylene and a silicone-based polymer) before applying the aluminum foil In this aspect, it has surprisingly been observed that the aluminum foil itself rests in an orderly fashion on the spool after removal without tearing.

 It has previously been proposed to provide heat-shrinkable objects with internal metallic linings for electrical and structural purposes in 9 for example, the British patent N0 1,482,918 and in the American patent 1f 3,312,772e Meanwhile, the metallic lining proposed in British Patent 1,482,918 is corrugated longitudinally and can only compress in a direction permitted by the corrugation. In addition, the corrugations can cause deterioration of the sleeve with thermal recovery or of a substrate, a danger which is particularly mentioned Wans the British patent, and it is not suggested that a simple uniform doubling of a metal sheet as proposed by the present invention could lead to the aforementioned surprising properties. Nor is it suggested a laminated object in three or four parts comprising one or two layers of hot-melt adhesive or of ~ fixing the metal lining to the shrinkable sleeve by means of such an adhesive .

 The added metal sheet proposed in US Patent 3,312,772 plays a protective role and obviously could not retract uniformly with the recovery sleeve. In any case, it is not provided in the form of a continuous internal lining linked or closely fitting to the interior of the resumed element. These last remarks also apply to the corrugated sheath described in the patent. British 1,482,918 where it is indicated in particular that the heat-shrinkable sleeve is preferably longer than the corrugated sheath in order to provide the necessary barrier at the ends against the penetration of contaminants. According to the present invention, the metal lining extends con ueaent all over the retractable sleeve Up to the ends thereof. Not only has it been found that such an arrangement can provide the necessary hermetic seal at the ends after recovery, but also the fact that the coating extends to the ends of the heat-shrinkable sleeve has significant advantages in particular in electrical applications where a shielding continuity may be necessary. In summary, therefore, under this aspect of the present invention, there is provided a heat-shrinkable laminated product consisting of a re-heat-shrinkable polymer sheet having a lining of a metallized sheet only on at least substantially the whole of its surface, the metallic lining being arranged so as to be in the direction of the recovery of the material with thermal recovery, and having a thickness such that it allows a uniform recovery without deterioration neither to itself # meAme, nor to the recovery material.

 Finally, a preferred characteristic of the objects according to the present invention is the provision of an incorporated cutting member so as to facilitate the removal of at least the central part of the object when it is desired to gain access to the interior again. this one. Due to the arrangement comprising a reel, the use of a knife to cut the laminating formed by the heat recovery sleeve and the metal sheet is rather difficult since there is no coati nate surface. to support the end of the knife, which could entager mage the splice, and the turns of the coil prevent a displacement of regular cutter. In a preferred embodiment, therefore, the object is provided with a thin metal wire, for example a piano wire with a diameter of about 0.6 mm which is placed beforehand longitudinally between the or the coils and the sheet. In particular, when the object is preheated, it has been found that a regular longitudinal cut through the lamination can be obtained simply by spreading the thread of the spool (s). Circular cuts beyond the ends of the central part can, of course, be carried out in the usual manner with a knife if metal support rings are provided, but it is possible to wind the wire so that it can also play this role.

The wire is preferably equipped with a small terminal ring which is placed outside the object with thermal recovery and which; can be cut after localized heating or removed differently and # pulled to make the desired cut-O
Different embodiments of the present invention will now be described by way of example only with reference to the appended drawings, in which:
- Figure I shows a reinforcing member :.

 - Figure 2 shows the reinforcement member of Figure 1 in the longitudinally compressed state.

 - Figure 3a is a longitudinal section of a reinforcing member equipped with rings and dezoouronnes at each of its ends.

 - Figure 3b is a longitudinal section of a somewhat similar reinforcing member.

FIG. 4 is a longitudinal section of a device comprising the reinforcement member of FIG. 3a placed inside one of a heat-shrinkable sleeve,
Figure 5 is an end view of the heat-transferable sleeve of Figure 40
FIG. 6 is a partially enlarged longitudinal section of the device shown in FIG. 4.

 - Figure 7 is a view of the device shown in Figure 4.

 FIG. 8 is a longitudinal section of an encapsulated connector produced using the device of FIG. 4.

 FIG. 9 represents an incorporated cutting member suitable for use with the device of FIG. 4.

 - Figure 10a shows a heat-shrinkable sleeve equipped with an internal lining of metal foil.

 - Figure lOb is an end view of the sleeve of Figure Iota.

 . - Figure 10c is a longitudinal section of the sleeve shown in 12 Figure lova.

We now refer to the drawings; in Figure 1 is shown a reinforcing member suitable for use in the present invention. Of reinforcement member cQ has two coils 1 and 2 placed end-to-endO As shown in, Figure 2, the coils I and 2 are elastically compressible longitudinally and can be maintained in the compressed state longitudinally by means of clips 3 and 4, respectively, when you want to access the connection
FIG. 3a represents a reinforcing member comprising: a single elastically longitudinally compressible coil 5 # fitted at each of its ends with support rings 6 and 7, as described in British patent 1 431 167. In FIG. 2b is shown a somewhat similar reinforcement member in which two elastically longitudinally compressible coils 8 and 9 are arranged end to end, the coil 8 being provided with a short copper tube 10 in which the coil 9 penetrates for correct positioning.

 ~ Figure 4 shows an object with thermal recovery according to the present invention in which the reinforcement member of 1- Figure 3a is positioned inside a heat-shrink sleeve table It which has been partially retracted around the reinforcement member in the central part.

As shown in FIGS. 5 and 6, the sleeve 11 which is made of crosslinked polyethylene having a thickness of approximately 2.3 mm, is equipped with an internal lining 12 of aluminum foil with a thickness of approximately 15 microns, A layer of hot-melt adhesive 13 is provided between the lining and the sheet which is # meAme coated on its internal surface with another layer of hot-melt adhesive 14o
As shown in Figure 6, the thermal recovery sleeve II and the lining 12 conform to the shape of the coil, but the sheet lining does not tear.

Another view of the device of FIG. 4 is shown in FIG. 7 in which the teeth 15 of the terminal crown 7 are more clearly visible.
FIG. 8 represents the device of FIG. 4 after it has been positioned and retracted around a connector 16 between two cables 17 and 18. As can be seen, the forecasting of the rings ensures a regular variation in diameter from the central region Up to the terminal part thus ensuring that no excessive stress occurs on the material with thermal recovery at the ends of the central region.

 FIG. 9 represents how a section of piano wire can be wound inside the sleeve with thermal recovery and its lining in metallic foil so that the desired cutting action can be easily obtained when it is desired to access new to the fitting0 As shown, the wire 20 is wound around two supports 21 and 22 which may be provided on the reinforcing member and is anchored at one end 23. At the other end, it has a ring 24 which is accessible from the outside of the heat-shrinkable sleeve which can be pulled to produce the desired circular and longitudinal cuts through the sleeve and its lining.

In FIG. ICa is shown a simple heat-shrinkable sleeve 30 made, for example, of crosslinked high density polyethylene. According to the present invention, the sleeve 30 is provided with a continuous internal lining 31 of aluminum foil having a thickness of 10 to 25 microns, preferably from 12 to 15 microns, the thickness of the heat-shrinkable sleeve being typically from 1 to 5 core As shown more clearly #:: in FIGS. 10b and 10c, two layers of hot-melt adhesive 32 and 33 are provided between the sleeve 30 and the sheet 31, and on the internal surface of the sheet 31, respectively.
Although the invention has been particularly described with reference to the production of connections between electric cables, it goes without saying that the objects with thermal recovery which it offers will have many other useful applications, in particular those in which a screen continuous against water vapor, radiation or a magnetic field is # required,

Claims (9)

 1) Object with thermal recovery in polymer material, characterized in that it comprises an incorporated -pored cutting member provided to open the object after its thermal recovery.  2) Heat recovery object according to claim 1, characterized in that the cutting member comprises a thin wire.  3) thermal recovery object according to claim 2, characterized in that the wire is carried on an inner surface of the object.  4) object with thermal recovery according to claim 2 or 3, characterized in that one end of the wire is anchored in the object and the other end of the wire comprises a member to facilitate its traction to achieve the cutting of the object .  5) Object with thermal recovery according to claim 2 or 3, characterized in that one end of the wire is arranged outside the object and comprises a member to facilitate its traction.  6) Object with thermal recovery according to one of claims 1 to 5, characterized in that it is a heat-shrinkable tubular sleeve.  7) thermal recovery object according to claim 6, characterized in that the tubular sleeve has a closed end.  8) thermal recovery object according to claim 6, characterized in that the tubular sleeve is a rolled sleeve.  9) thermal recovery object according to one of claims 1 to 8, characterized in that the polymeric material is provided with a metal foil lining.