BACKGROUND TO THE INVENTION

The present invention relates to environmental sealing of substrates, in particular cables splices such as those between telecommunications cables, by articles such as heat-shrinkable tubular or wrap-around sleeves.

When cables are to be spliced together, end portions of respective cable jackets are removed in order to gain access to the conductors within. After the splice has been made, the cable jacket has to be made good across the splice in order to protect the conductors and connectors joining them. The outside environment, in particular moisture, has to be kept at bay, and that is done by constructing around the splice a so-called splice case that overlaps intact cable jacket either side of the splice.

For many years now, the preferred technique for forming a reliable long-lasting splice case has been to shrink a heat-shrinkable sleeve around the splice. A liner may be provided around the splice over which the sleeve is shrunk. The liner serves to provide mechanical protection to the splice, it may provide improved water vapour protection particularly if it is made of metal, and it may provide a gentle, shaped, transition from a bulky splice down to the smaller cables either side of it . This may be achieved using a liner that is substantially cylindrical, but has crowned ends which can be bent inwardly to provide frusto-conical end portions . The use of such a liner together with an adhesive-coated heat-shrinkable sleeve for the formation of a telecommunications splice case is disclosed in GB 1431167 (Raychem) . Such splice cases are marketed by Raychem under the Trade Marks VASM and XAGA.

The seals produced can be so good that difficulty is experienced in removing the splice case when attention to the underlying conductors becomes necessary, for example for installation of new telephone lines or removal of old ones. This activity is called re-entry.

A technique has been developed for re-entering such splice cases that involves making circumferential cuts through the sleeve, one towards each end just inwardly of the frusto-conical portions. A longitudinal cut is then made joining the two circumferential cuts. A central portion of the sleeve can then be removed. A technique is taught in GB 2093402 (Raychem) for carrying out this re¬ entry without damaging the underlying liner. In that specification the liner is provided within a bag which constitutes a release layer. Thus the sleeve comes easily away from the liner, and the liner can then be gently removed from between the remaining butts of the old sleeve. Many liners comprise laminates that would be pulled apart on removal of the sleeve in the absence of the release layer. After attention to the splice, the liner may be replaced and a new sleeve shrunk in place, bridging the butts of the old sleeve.

GB 1604379 (Raychem) discloses the use of a self- contained cutting means to facilitate removal of at least the central part of a sleeve. The sleeve is provided with a thin metal wire, e.g. a piano wire of a diameter of about 0.6 mm, which is pre-installed longitudinally between a liner and the sleeve. An end of the wire is left protruding outside the sleeve which can be pulled causing the wire to cut through the sleeve to produce the desired circumferential and longitudinal cuts. Reference may also be made to GB 2088147 (Rose) .

Recently it has been proposed that heat-shrinkable sleeves comprise a composite material that is recoverable

by virtue of shrinkable fibres that extend circumferentially. The sleeves may be reinforced with non- shrinkable longitudinal fibres, for example glass, which may comprise multifilament bundles. Such sleeves are disclosed in EP 0116393 (Raychem) and EP 0116391 (Raychem) the disclosures of which are incorporated herein by reference.

A problem may, however, arise if such sleeves employ simple multifilament bundles extending longitudinally and are re-entered by the method referred to above, i.e. by removing a central portion, leaving end portions in place on the cables either side, of the splice. A new sleeve, shrunk across the remaining end portions of the old sleeve, will not prevent contaminants passing along interstices between the filaments of the multifilament bundles. In this way contaminants may enter into the newly formed splice case.

This problem may be expressed in general terms. Where a fabric or composite forms only part of an enclosure, such that an edge of one portion of the fabric or composite is exposed to the environment, and an edge of another portion is exposed to the inside of the enclosure, moisture or other contaminants may travel from the outside to the inside of the enclosure by travelling along the thickness of the fabric or composite. It may enter an edge at the first portion and leave at an edge of the second portion.

That problem was recognized in EP 324630 (Raychem) and a solution was proposed, namely to block the multifilament fibres with a material delivered for example as a latex, or as further, heat-softenable, fibres. The disclosure of EP 324630 is incorporated herein by reference.

There may, however, be circumstances in which it is undesirable or unnecessary to provide for such fibre

blocking, and we have now discovered that a block can be made at one end of the fabric or composite (preferably the inwardly facing end in the case of a re-entered splice case) , and that this can be achieved by provision of a sealing member under the original sleeve at a position where a cut is to be made at re-entry.

SUMMARY OF THE INVENTION

Thus, the present invention provides a method of sealing a splice between cables, which comprises:

(a) surrounding the splice with a liner;

(b) positioning a sealing member adjacent an end portion of the liner;

(c) positioning a cutting means, preferably a cutting wire over the sealing member and preferably around the end portion or around one of the cables adjacent the end portion;

(d) positioning a heat-shrinkable sleeve around the liner such that it extends past the end portion, and preferably over the cutting means; and

(e) then heat-shrinking the sleeve.

DESCRIPTION OF THE INVENTION

The sleeve, which may be of wrap-around or tubular form, preferably comprises a composite material particularly one that is recoverable by virtue of recoverable fibres therein. We particularly prefer a sleeve comprising a fabric having shrinkable cross-linked

fibres extending in one direction (generally circumferentially) and reinforcing non-shrinkable fibres extending in a substantially perpendicular direction (generally longitudinally) . The shrinkable fibres preferably comprise high density polyethylene and the non- shrinkable fibres preferably comprise multifilament bundles of glass or high strength polymer. The fibres may be present in a matrix material such as cross-linked low density polyethylene or other suitable polymer. The sleeve may have a sealing material, such as a hot-melt or other adhesive or a mastic on its inner surface.

The liner preferably .has one or more frusto-conical ends, each of which may be formed by bending inwards longitudinally extending, preferably tapered, fingers which give ends of the liner the appearance of a crown. The liner may comprise a sheet of material that can.be rolled- up or otherwise wrapped around the splice, or it may comprise one or more substantially rigid parts. For example it may comprise end pieces (which may comprise the frusto-conical parts) and semi-cylindrical half-shells that can be positioned on and bridging the end parts. More than two such "half-shells" may be provided. The half-shells may engage the end pieces by means of a tongue-and-slot arrangement, or other means. That may allow the half- shells to be removed during re-entry into the splice case, leaving the frusto-conical ends in place within the butts of the old sleeve which remain on the cables .

The sealing member is preferably in tape or other sheet form, and may be wrapped around end portions, such as frusto-conical end portions -of the liner. It may be specially shaped so that, at least when thus wrapped around, it too is frusto-conical. It preferably comprises a backing sheet that does not melt during step (e) , and therefore preferably has a melting point at least 20 or particularly 30 centigrade degrees above the shrinkage

temperature of the sleeve. It may be cross-linked such that it does not melt at all. This backing sheet may be coated, particularly on its outwardly-facing surface, with a sealing material such as a hot-melt or other adhesive, for example a polyamide or an ethylene vinylacetate copolymer.

The cutting means is preferably within the sleeve so that it cuts from the inside out . This avoids damaging any underlying layer (as may happen if an external saw or knife were used) and aids the action of the present sealing member. Furthermore, the cutting means is preferably something, preferably sharp, that itself can cut through the sleeve; it may however be something that facilitates use of some other cutting article for example it may comprise a guide for a knife or some protecting means that limits depth of cut.

Preferably the cutting means comprises a cutting wire which is positioned on the sealing member, such that pulling it to cut through the overlying sleeve will result in a cut edge of the sleeve lying over the sealing member. The sealing member will therefore be correctly positioned to seal the cut edge of the butts of the sleeve that remain when the central portion has been removed. We prefer that the sealing material is localized at the position of the cutting wire and does not extend across the whole of the original sleeve.

Release means may be provided to aid removal of the central portion of the original sleeve, and we prefer to provide a release layer under the sleeve preferably above the cutting wire and sealing member. A further component that may be provided is a creep-resistant layer, and that might be useful where the splice case is to be pressurized in use. Such a creep resistant layer may comprise a high strength, for example biaxially oriented and/or fibre

reinforced, film, and it may be positioned for example over the liner and under the sealing member. The sealing member may comprise at least part of or be affixed to the creep- resistant layer. For example the sealing member may comprise strips that run along opposing longitudinal edges, optionally overlapping them, of a generally rectangular creep-resistant layer.

If the sealing member is initially positioned around an outwardly-facing surface of the liner when the original splice case is constructed, it will in general be in the correct position to block the newly created ends of the old sleeve when the new sleeve is shrunk over them. The heat required to heat-shrink the new sleeve may activate an adhesive component of the sealing member allowing it to flow into the ends of longitudinally-extending multifilament fibre bundles of the old sleeve. It may be noted here that an adhesive coating on the new sleeve is unlikely to be able to perform this function alone.

The sealing member may, however, be positioned elsewhere, and be moved to the desired position at the re¬ entry stage. That may be desirable if one wants to ensure that the heat and pressure resulting from shrinkage of the first sleeve is not to damage the sealing member.

To this end the sealing member may be initially positioned inside the liner. The liner then shields the sealing member from the hot first sleeve as it shrinks down. At re-entry the sealing member may be repositioned around an outwardly-facing surface of an end portion of the liner. One way in which this may be done is to wrap a sealing member around the cable at such a position that the frusto-conical end of the liner will taper down onto the sealing member, say at a position substantially mid-way along it. The cutting wire is positioned around the cable, on top of the sealing member, adjacent the end of the

liner. The sleeve (together with a release layer where appropriate) is then shrunk down over the liner and over a portion of the cable extending out of it. Part of the sealing member will then lie inside the liner and be unaffected by the shrinking of the sleeve, and another part will become trapped under the shrunk sleeve. When the cutting wire is pulled it will make a cut at the base of the liner, allowing sufficient sleeve to be removed for all of the liner also to be removed. The part of the sealing member originally under the sleeve can then be turned inside-out, back over the remaining part of the sleeve. The liner is then replaced, and the turned-back part of the sealing member reinverted if desired, in which case it ends up over the outside of the frusto-conical end of the liner. Whether reinverted or not it will be positioned at the cut end of the old sleeve and will be able to block any multifilament fibre bundles thereof.

The sealing member, or at least that part of it that lies inside the sleeve, may comprise a plurality of layers, say 2-5, one of which is turned inside-out and optionally reinverted at each re-entry and resealing of the splice case.

The cutting wire may be provided within an adhesive or similar strip that is wrapped around the cable or liner.

The original sleeve may be a wrap-around sleeve having upstanding rails or other means which are used to hold it in the wrapped configuration. It may be desirable to provide some sealing means to avoid leak paths at the edges of such rails and under the new sleeve which will overlie them. A shaped block of polymeric material may be positioned over the rails. Such a block may have a recess therein, into which the rails fit, and an outer surface that is gently convex and to which the new sleeve can seal. Such a block, made of adhesive, is disclosed in PCT GB

8900949 (Raychem) . In the present case we prefer that such a block be non-melting, and that it comprise a cross-linked polymeric material such as polyethylene.

Brief Description of the Drawings

The invention is further illustrated by the accompanying drawings in which:

Figures 1A and IB show prior art re-entered and resealed splice cases;

Figures 2A and 2B show a splice sealed by the method of the invention;

Figures 3A and 3B show a modification to the seal of figures 2A and 2B, particularly suitable for pressurized cables;

Figures 4 and 5 show modifications to the seal of figures 2A, 2B 3A or 3B.

Description of the Drawings

Figures 1A and IB show a prior art splice case around a splice 1 between cables 2. A heat-shrinkable sleeve had been shrunk around the splice, overlapping intact portions of cable jacket either side of the splice. A central portion of the original sleeve has been removed leaving in place end portions or butts 3, 4 of the old sleeve. The sleeve can be seen to be of the wrap-around type, having upstanding rails 5 held together by a channel 6.

A new sleeve 7 is shown in dotted outline bridging the butts 3,4. When shrunk down it will engage the butts 3,4 thus resealing the splice.

A problem that can arise with the re-entry and resealing technique of figure 1A is illustrated in figure IB. If the old sleeve (3,4) has longitudinally extending multifilament fibres, the interstices thereof might provide a leak path into the reformed splice case. This potential leak path is shown by the arrow 8. This problem was recognized, and blocked glass as a solution therefor was disclosed, in EP 324630 (Raychem) .

Figure IB also shows a liner 9 having frusto-conical ends 10 tapering down to the cables 2. The liner provides mechanical support, and although it may reduce moisture permeation through the sleeve if the sleeve is bonded to it, it cannot in general deal with the leak path 8. That is simply because moisture etc is likely to be able to pass around its ends.

Sealing techniques according to the invention are illustrated in figures 1A, 2B, 3A, 3B, 4, 5A and 5B.

Figures 2A and 2B show a splice case around a splice between cables 2. Sealing members 12 in strip form are shown positioned around frusto-conical ends of liner 9. Cutting wires 13 are shown underlying shrunk sleeve 11 and positioned such that pulling on the rings at their ends (which rings will lie outside the sleeve) will cause longitudinal and circumferential cuts to be made. (Note GB 1604379, referred to above.) A release layer 14 is shown, enabling a central part of the sleeve to be removed easily from the liner after the cuts have been made. In this way the splice case can be re-entered without the heating that might otherwise be necessary to soften any adhesive coating on the sleeve that bonds it to the cables either side of the splice. Figure 2B shows the situation after a central portion of the sleeve has been removed, leaving butts 3,4 in place. The liner 9 would then be dismantled, or removed, to gain access to the underlying splice.

Figures 3A and 3B show a modification that may be useful if the splice case has to withstand high internal pressures. A creep-resistant layer 15 is provided. Figure 3B shows that the sealing members 12 and the cutting wire 13 may be provided affixed to a creep-resistant sheet.

In figure 4 a sealing member 12 is shown initially partially inside and partially outside the liner 9. The part inside may comprise a plurality of layers 17. The cutting wire 13, provided on an adhesive or other wrap 16, is positioned around the cable 2 on the member 12 adjacent an end of the liner 9. Thus when the wire is pulled, the sleeve is cut adjacent the end of the liner such that the whole of the liner may be easily removed. One or more layers 17 of member 12 may then be turned back, to the right as drawn. The liner is then replaced and if desired the layer 17 is turned back to the left over the end of the liner. A new sleeve is then shrunk down over the liner,

overlapping the end of the old sleeve. The layer 17 that is now outside the liner causes the end of the old sleeve to be blocked. The frusto-conical end 10 of the liner is provided by a plurality of tapered fingers which are bent towards the cable and held there by a tape wrap 18.

A further embodiment is shown in figures 5A and 5B, where the reference numbers have the same meaning as used above. Figure 5A shows the situation before re-entry where the original sleeve 11 is still intact. In figure 5B a new sleeve 7 has been installed to overlap the butt 3 of the old sleeve.

For the avoidance of doubt it is here noted that the invention provides a method of sealing, of re-entering and of resealing, and various components for carrying out these methods. In particular a problem of blocking longitudinal leak paths in an original sleeve is solved. Any one or more of the various sleeves, sealing members, cutters, liners, release layers, creep-resistant layers disclosed may be selected.