GB1604380A - Heatrecoverable article with self-contained cutting means raychem sa nv - Google Patents

Description

(54) HEAT-RECOVERABLE ARTICLE WITH SELF-CONTAINED CUTTING MEANS (71) We, N.V. RAYCHEM S.A., a Belgian Company, of B 3200 Kessel-lo, Diestsesteenweg 692, Belgium, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- This invention relates to heat-recoverable articles, especially heat-shrinkable articles for use in the protection and insulation of supply lines such as electric cables.

Heat-recoverable articles, especially heatshrinkable articles, are now widely used in many areas where insulation, sealing and encapsulation are required. Usually these articles recover, on heating, towards an original shape from which they have previously been deformed, but the term "heatrecoverable", as used herein, also includes an article which, on heating, adopts a new configuration, even if it has not been previously deformed.

In their most common form, such articles comprise a heat-shrinkable sleeve made from a polymeric material exhibiting the property of elastic or plastic memory as described, for example, in U.S. Patents 2,027,962; 3,086,242 and 3,957,372. As is made clear in, for example, U.S. Patent 2,027,962, the original dimensionally heatstable form may be a transient form in a continuous process in which, for example, an extruded tube is expanded, whilst hot, to a dimensionally heat-unstable form but, in other applications, a preformed dimensionally heat stable article is deformed to a dimensionally heat unstable form in a separate stage.

fn other articles, as described, for example, in British Patent 1,440,524, an elastomeric member such as an outer tubular member is held in a stretched state by a second member, such as an inner tubular member, which, upon heating, weakens and thus allows the elastomeric member to recover.

Heat-shrinkable sleeves find many applications, especially in the connection and termination of wires, cables and pipes. However, there are other applications where it is desirable to provide a connecting, insulating or protective heat-recoverable member for elongated objects such as cables and pipes where the ends are not accessible or, if they are accessible, where it is undesirable to disconnect or otherwise displace them. For such applications so-called "wraparound" sleeves have been developed. Basically these are heat-recoverable sheets which can be wrapped round the substrate to form a generally tubular shape and which, in general, are provided with fastening means for holding them in the wrapped-up configuration during recovery. Typically such fastening means are mechanical in nature and comprise, for example, rigid clamps, pins or channel members which co-operate with suitably shaped moulded or extruded protuberances adjacent to the overlapping edges of the heat-recoverable sheet. Various types of fastening means are described, for example, in U.S. Patents 3,379,218 and British Patents 1,155A70; 1,211,988 and 1,346,479.

In other applications the sheet may be held in the wrapped-up configuration during recovery by means of an adhesive which may, in some cases, be applied on site.

One particular area of application of heatrecoverable articles of the type described above is in the insulation and protection of junctions between supply lines, especially electric cables. In making such junctions, for example, between telephone or power cables, many problems arise in meeting the necessary requirements of continuity of insulation and earthing, of sealing the joint against the ingress of contaminants such as moisture and insects and in providing the necessary strength of resistance to tension, compression, flexing and impact.

British Patent No. 1,155,470 proposes to use tubes or sleeves of heat-shrinkable material to protect and insulate joints in the electric cables. However, because the cables are frequently pressurised and must be waterproof it is necessary to coat the inner wall of the heat-shrinkable sleeve with a sealant such as a hot-melt adhesive or a mastic. When the sleeve is heated the sealant melts and forms a water-tight and pressure-tight seal between the sleeve and the cable. This has the disadvantage that, in certain cases, the sleeves cannot subsequently easily be opened for repair or modification of the joint without necessitating the complete renewal of the junction and the method is also unsuitable where the joint or the electric components leading to the joint comprise components which are delicate or frangible.

It has, therefore, been proposed to provide modified heat-shrinkable articles in which a central portion does not recover or in which reinforcement means are provided to prevent recovery in the central region.

For example, British Patent No. 1,248,908 discloses a heat-shrinkable article containing a bridging sleeve of non-recoverable material and terminal sleeves of heatshrinkable material, the sleeves being connected to one another, for example, by screw connections. However, such an arrangement requires relatively close tolerances in manufacture to ensure that the male and female screw threads of the parts are readily engageable.

A more successful proposal is that of British Patent 1,431,167 in which a heatshrinkable sleeve, which may be a wraparound sleeve is provided with central reinforcement comprising a relatively rigid longitudinally split tube. Typically such a tube is made from a pair of semicylindrical half shells, for example made from aluminium. Such articles have the advantage that they may easily be re-opened for repair work or modification of a cable joint but they have proved rather expensive.

The present invention provides a heatrecoverable article of oolymeric material, which comprises selfcontained cutting means arranged to cut open the article of polymeric material, which comprises self-contained cutting means arranged to cut open the article after heat-recovery thereof.

The heat-recoverable article is preferably a heat-shrinkable tubular sleeve, which may have a closed cross-section or may be a wrap-around sleeve as described in the patent specifications referred to above. The term "tubular" as used herein is not limited to members of right cylindrical configuration, but includes members of irregular and/or varying crossection as well as Y-shaped T-shaped and Xshaped members.

The sleeve may, of course, be made from any of the heat-recoverable materials known in the art, but amongst especially preferred materials there may be mentioned, for example, polyolefins, especially polyethylene, copolymers of ethylene and vinyl acetate, copolymers of ethylene and ethyl acrylate; chlorinated and fluorinated polymers, especially polyvinyl chloride, polyvinylidene fluoride hexafluoroethylene and chlorotrifluoroethylene; and rubbers such as ethylene/propylene rubbers, chlorinated rubbers, e.g. Neoprene, and silicone rubbers which may be used in a blend with a crystalline or glassy polymer such as an olefin polymer. All of the above materials may, if desired, be cross-linked for example by irradiation and/or chemical means. The sleeve will generally be provided at at least its end with an inner coating of a sealant such as a hot-melt adhesive or a mastic although, in certain applications, these may be applied on site.

Especially suitable hot-melt adhesives include, for example, polyamides, ethylene/ vinyl acetate copolymers and terpolymers (with or without incorporated waxes) and polyesters. Such materials are described, for example, in British Patent 1,440,810 and German OS 2,709,717. Also suitable are curable adhesives which melt and flow on heating but which will not afterwards be hot-meltable. There may also be mentioned epoxy resins and conventional mastics such, for example, as those based on butyl and isobutylene rubbers modified with suitable materials known in the art. Obviously the use or otherwise of such materials and their type, if chosen will depend upon the particular requirements in any given case.

The present invention is especially applicable to the heat-recoverable articles described and claimed in our co-pending application No. 46516/77 (Serial No.

1604379) (from which this application has been divided) which comPrise a heatshrinkable, preferably tubular, sleeve which has an inner lining of a continuous metal foil and which is preferably provided with central reinforcing means comprising one or more longitudinally compressible coils.

The disclosure of Application No. 46516/ 77 (Serial No. 1604379) is incorporated herein by reference.

The combination of the thin metal foil lining and the centrally positioned coil(s) provides an inexpensive, but highly efficient, means (a) for ensuring that, after recovery, a cable joint is effectively sealed against inward water vapour transmission and (b) for ensuring that the recovered article has the desired mechanically strong tubular construction in its central region.

An especially important aspect of the invention described and claimed in Application No. 46516/77 (Serial No. 1604379) is the provision of the continuous metal foil lining to provide protection against inward water vapour transmission. For ex ample, in the heat-shrinkable articles previously described in British Patent Specification 1,431,167 the water vapour permeability of the polymeric material typically employed for the heat-recoverable sleeve is high and thus leads to the need for the use of silica gel bags within the splice case at installation. However, comparative tests suggest that in the preferred articles described and claimed in Application 46516/77 (Serial No. 1604379) the metal foil lining leads to a reduction in water vapour permeability by a factor of about 8 as compared with the previously proposed product using aluminium half shells. Not only is this surprising improvement obtained, but also it has been found that by choosing the correct thickness of the metal foil, which in general will be an aluminium foil, it is possible to obtain a heat-shrinkable product which will recover to give an even surface configuration, but in which there is no tearing of the metal foil. That is to say, the metal foil is sufficiently thin that it does not buckle and adopt a shape exhibiting such peaks and valleys which might, for example, lead to damage to the heat-shrinkable sleeve or provide a path for the ingress of contaminants. On the other hand, the metal foil is not so thin that it is damaged, e.g. torn, during recovery, even about substrates of irregular shape.

Using aluminium foil it has been found that a desirable range of thickness is from 10 to 25 microns, especially from 12 to 15 microns. Other metal foils which may be employed at similar thicknesses include copper foil, soft iron foil (e.g. where magnetic shielding is required) and certain metallised plastics foils such as the commercially available biaxially oriented polyester foil coated with gold.

In one especially preferred embodiment, a heat-shrinkable tube provided with an inner layer of a hot-melt adhesive is provided with an inner lining of a metal foil of the appropriate thickness which is itself provided with an internal coating of a hotmelt adhesive. Such a product has been found to be especially useful in encapsulating cable splices, in wrap-around products and in making transitions from cable box outlets to incoming cables.

The tubular sleeve may be one of closed cross-section, i.e. with one closed end, or may be a wrap-around sleeve. In the case of a wrap-around sleeve the metal foil may readily be applied either during or after the manufacture of the sleeve. For example, the sleeves are typically coated with a hot-melt adhesive at some stage of their manufacture, and the metal foil, if desired, with its pre-applied layer of hot-melt adhesive on the sleeve is still tacky. The provision of an inner foil on tubular products of closed cross-section is more difficult, but in the case of tubes of small diameter it may be provided by a co-extrusion process and in the case of tubes of larger diameter, it may be applied by using a collapsible mandrel. For example, a man- drel may be formed from two cylindricali hailf shells which are internally hinged together, for example by a piano hinge, one of the shells having a slightly smaller diameter so that it fitted inside the other to collapse the mandrel. Such a mandrel may be coated with a release plastic and covered with, for example, aluminium foil with or without a hot-melt adhesive layer, and a heat-shrinkable tubular sleeve pro vided with an inner layer of a hot-melt adhesive may then be partially shrunk down about the mandrel and then allowed to cool. After cooling the mandrel may be collapsed as described above and removed to leave the desired laminated product. When one or more coils is also to be incorporated these may be positioned over the release plastic (which may, for example, be a blend of a polyethylene with a silicon based polymer) prior to application of the aluminium foil. In this re pect, it has surprisingly been observed that the aluminium foil lays itself neatly on the coil after shrinkage without tearing.

In accordance with the present invention, the articles described and claimed in Application 46516/77 (Serial No. 1 604 379) are provided with a selfcontained cutting means so as to facilitate removal of at least the central part of the article when reentry is desired.

Because of the coil arrangement the use of a knife to cut the heat-recoverable sleeve/metal foil laminate is rather difficult because there is no continuous surface to support the tip of the knife, which could damage the splice, and the windings of the coil prevent a smooth cutting movement. In a preferred embodiment, therefore, the article is provided with a thin metal wire e.g. a piano steel wire of a diameter of about 0.6mm which is preinstalled longitudinally between the coil(s) and the foil. Especially when the article is preheated it has been found that a smooth longitudinal cut through the laminate may be obtained merely by putting the wire away from the coil(s). Circular cuts beyond the ends of the central section can, of course, be performed in the usual way with a knife if metal support rings are provided, but it is possible so to wind the wire that it can also Derform this function.

The wire is preferably provided with a small terminal ring which is located on the outside of the heat-recoverable article and which may be cut out after local heat ing or otherwise removed and pulled to effect the desired cutting.

One embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which (Figures 1 to 3 being absent); Figure 4 is a longitudinal section through a heat-recoverable article comprising the reinforcing means positioned within a heat-shrinkable sleeve; Figure 5 is an end view of the heatshrinkable sleeve of Figure 4; Figure 6 is a magnified partially longitudinal section of the device shown in Figure 4.

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

Figure 8 is a longitudinal section through an encapsulated joint made using the device of Figure 4; and Figure 9 illustrates self-contained cutting means for use with the device of Figure 4; Figure 4 shows a heat-recoverable article in which a reinforcing means comprising a single resiliently longitudinally compressible coil 5 provided at each of its ends with support crowns 6 and 7, as described in British Patent 1,431,167, is positioned within a heatshrinkable sleeve 11 which has been patrially shrunk down about the reinforcing means in the central region.

As shown in Figures 5 and 6, the sleeve 11, which is made from cross-linked poly ethylene having a thickness of about 2.3 mm, is provided with an inner lining 12 of aluminium foil of a thickness of about 15 microns. A layer of hot-melt adhesive 13 is provided between the lining and the foil which is itself coated on its inner surface with a further layer of hot-melt adhesive 14.

As shown in Figure 6, the heat-recoverable sleeve 11 and the lining 12 conform to the shape of the coil, but the foil lining does not tear.

Another view of the device of Figure 4 is shown in Figure 7 in which the prongs 15 of the terminal crown 7 are more clearly visible.

Figure 8 shows the device of Figure 4 after it has been positioned about and shrunk over a junction 16 between two cables 17 and 18. As can be seen, the provision of the crowns ensures a smooth change in diameter from the central region to the end region thus ensuring that no undue stress on the heat-recoverable material occurs at the end of the central region.

Figure 9 shows how in accordance with the present invention a length of piano steel wire may be wound inside the heat-recoverable sleeve and its metal foil lining so that the desired cutting action can be readily obtained when it is desired to re-enter the junction. As shown, the wire 20 is wound about two supports 21 and 22 which may be provided on the reinforcing means and is anchored at one end 23. At the other end it is provided with a ring 24 which is accessible from the outside of the heat-shrinkable sleeve and which may be pulled to produce the required circular and longitudinal cuts through the sleeve and its lining.

Whilst the present invention has been especially described with reference to the formation of joints between electric cables it will, of course, be appreciated that the heat-recoverable articles which it provides will have many other useful applications.

WHAT WE CLAIM IS: 1. A heat-recoverable article of polymeric material comprising self-contained cutting means arranged to cut open the article after heat recovery thereof.

2. A heat-recoverable article as claimed in claim 1, wherein the cutting means comprises a thin wire.

3. A heat-recoverable article as claimed in claim 2, wherein the wire is carried on an inner surface of the article.

4. A heat-recoverable article as claimed in claim 2 or claim 3, wherein one end of the wire is anchored in the article and the other end of the wire has means for facilitating pulling to effect cutting of the article.

5. A heat-recoverable article as claimed in any one of claims 1 to 4, which is a heat-shrinkable tubular sleeve.

6. A heat-recoverable article as claimed in claim 5, wherein the tubular sleeve has one closed end.

7. A heat-recoverable article as claimed in claim 5, wherein the tubular sleeve is a wrap-around sleeve.

8. A heat-recoverable article as claimed in any one of claims 1 to 7, wherein the polymeric material is provided with a lining of metal foil.

9. A heat-recoverable article as claimed in claim 8, wherein said metal foil is aluminium foil.

10. A heat-recoverable article as claimed in claim 1, substantially as described herein with reference to, and as illustrated in, the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. ing or otherwise removed and pulled to effect the desired cutting. One embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which (Figures 1 to 3 being absent); Figure 4 is a longitudinal section through a heat-recoverable article comprising the reinforcing means positioned within a heat-shrinkable sleeve; Figure 5 is an end view of the heatshrinkable sleeve of Figure 4; Figure 6 is a magnified partially longitudinal section of the device shown in Figure 4. Figure 7 is a view of the device shown in Figure 4. Figure 8 is a longitudinal section through an encapsulated joint made using the device of Figure 4; and Figure 9 illustrates self-contained cutting means for use with the device of Figure 4; Figure 4 shows a heat-recoverable article in which a reinforcing means comprising a single resiliently longitudinally compressible coil 5 provided at each of its ends with support crowns 6 and 7, as described in British Patent 1,431,167, is positioned within a heatshrinkable sleeve 11 which has been patrially shrunk down about the reinforcing means in the central region. As shown in Figures 5 and 6, the sleeve 11, which is made from cross-linked poly ethylene having a thickness of about 2.3 mm, is provided with an inner lining 12 of aluminium foil of a thickness of about 15 microns. A layer of hot-melt adhesive 13 is provided between the lining and the foil which is itself coated on its inner surface with a further layer of hot-melt adhesive 14. As shown in Figure 6, the heat-recoverable sleeve 11 and the lining 12 conform to the shape of the coil, but the foil lining does not tear. Another view of the device of Figure 4 is shown in Figure 7 in which the prongs 15 of the terminal crown 7 are more clearly visible. Figure 8 shows the device of Figure 4 after it has been positioned about and shrunk over a junction 16 between two cables 17 and 18. As can be seen, the provision of the crowns ensures a smooth change in diameter from the central region to the end region thus ensuring that no undue stress on the heat-recoverable material occurs at the end of the central region. Figure 9 shows how in accordance with the present invention a length of piano steel wire may be wound inside the heat-recoverable sleeve and its metal foil lining so that the desired cutting action can be readily obtained when it is desired to re-enter the junction. As shown, the wire 20 is wound about two supports 21 and 22 which may be provided on the reinforcing means and is anchored at one end 23. At the other end it is provided with a ring 24 which is accessible from the outside of the heat-shrinkable sleeve and which may be pulled to produce the required circular and longitudinal cuts through the sleeve and its lining. Whilst the present invention has been especially described with reference to the formation of joints between electric cables it will, of course, be appreciated that the heat-recoverable articles which it provides will have many other useful applications. WHAT WE CLAIM IS:

1. A heat-recoverable article of polymeric material comprising self-contained cutting means arranged to cut open the article after heat recovery thereof.

2. A heat-recoverable article as claimed in claim 1, wherein the cutting means comprises a thin wire.

3. A heat-recoverable article as claimed in claim 2, wherein the wire is carried on an inner surface of the article.

4. A heat-recoverable article as claimed in claim 2 or claim 3, wherein one end of the wire is anchored in the article and the other end of the wire has means for facilitating pulling to effect cutting of the article.

5. A heat-recoverable article as claimed in any one of claims 1 to 4, which is a heat-shrinkable tubular sleeve.

6. A heat-recoverable article as claimed in claim 5, wherein the tubular sleeve has one closed end.

7. A heat-recoverable article as claimed in claim 5, wherein the tubular sleeve is a wrap-around sleeve.

8. A heat-recoverable article as claimed in any one of claims 1 to 7, wherein the polymeric material is provided with a lining of metal foil.

9. A heat-recoverable article as claimed in claim 8, wherein said metal foil is aluminium foil.

10. A heat-recoverable article as claimed in claim 1, substantially as described herein with reference to, and as illustrated in, the accompanying drawings.