The present invention relates to the formation of an environmental seal around objects such as telecommunications and other cables.

Splicing of cables requires removal of cable jackets in order to expose the underlying conductors for connection. Once the conductors have been connected some sort of seal must be built up across the splice, effectively replacing the removed jacket, in order to protect the otherwise exposed conductors from the environment. The resulting seal, known as a splice case, should have a life-time comparable to that of the cables themselves, commonly twenty or so years. In addition to protecting the conductors from moisture and other environmental contaminants, the splice case must provide some mechanical protection such as axial pull strength, so that any stresses on the cables are not taken up by the conductor connections. Cables may be pressurized in order to prevent ingress of moisture or to provide a means for detecting and locating leaks and a splice case in a pressurized cable will, in general, need to be able to resist pressure-induced creep over its desired life-time. Splice case must often be installed under unfavourable outdoor conditions and installation must therefore be simple and quick.

It can be seen from these requirements that design of a splice case is not a trivial matter. In recent years heat-shrinkable sleeves, internally coated with a hot-melt adhesive, have become widely used for protecting cable splices. They are quick and easy to install and provide the desired environmental and mechanical protection. However, they generally require the use of an open-flame torch or other special tool for installation which, in some locations, can be inconvenient or danserous.

Whilst the use of a special tool for initial installation of a cable splice case might present no problems, it is desirable that subsequent access to the cable splice be possible without special tools.

For convenience of installation it is desirable that at least some of the components of the splice case be of the so-called wraparound type. This term is well known in the art and means simply that the article concerned can be installed around an intermediate portion of a cable without access to a free end.

We have now designed a sealing device that can be used with two sleeves, one to make a permanent seal to a cable and one to provide a removable cover over a cable splice. A butt splice case can be made with a dome-shaped or otherwise blind removable sleeve, and an in-line splice case can be made with a removable wraparound sleeve sealed at each end thereof to cables at either side of a splice.

The sealing device is preferably of the wraparound type and preferably comprises a split support.

Thus, the present invention provides a device for forming an environmental seal around an elongate object such as a cable, which comprises :

(a) first and second sleeves that can be positioned around the object substantially end-to-end;

( b) a split support for the sleeves that can be positioned ^" within the sleeves and bridging their mutually facing ends :

the support having a reservoir for a sealing material which breaks through the split along a length thereof sufficient to bridge the mutually facing ends of the sleeves.

The sealing material blocks a leak path that might otherwise run from between the end-to-end sleeves along the split in the support and into the splice case. The invention therefore allows separate sleeves to be provided for permanent fixture to the cables and for removable covering of the cable splice.

The invention differs from a superficially similar technique for sealing disclosed in US 4845314 (Siemens). In that patent only one sleeve is employed, and it is in the sleeve rather than in an underlying support that a reservoir for a sealing material is provided. A cable seal is disclosed having a sleeve engaging a pair of end members which carry ring seals around their periphery. The sleeve is of the wraparound type and it has a longitudinal sealing element to seal its longitudinal split. The sealing element lies in a groove along one longitudinal edge of the split sleeve, and an inner wall of the groove in the region of the ring seals has a lateral opening or window through which a portion of the longitudinal sealing member can extend to contact the ring seals.

In the present invention the reservoir may break an outer surface of the support at a first location for sealing to the first sleeve and at a second location, separated from the first location, for sealing to the second sleeve.

The sleeve which is preferably removable to provide access to an installed splice will be referred to herein as the first sleeve, and the sleeve or sleeves which preferably become permanently attached to the cables either side of the splice will be referred to as second sleeves.

Since heat-shrinkable sleeves are ideal for making permanent seals, we prefer that the second sleeves be heat-shrinkable. Where use of an open-flame torch is undesirable the heat-shrinkable sleeves may be designed to shrink at low temperatures and require small quantities of heat in order that they be shrinkable by means of, for example, a hot-air gun. Suitable sleeves include composite materials, such as those including heat-shrinkable fibres, and they may conveniently comprise linear low density polyethylene. The sleeves are preferably internally coated with a hot-melt adhesive.

Where a heat-shrinkable sleeve is used the support preferably has a substantially cylindrical outer surface onto which the sleeve can shrink, and therefore the second location at which the reservoir breaks an outer surface of the support is preferably substantially cylindrical.

The first sleeve is preferably removable without special tools, and in preferred embodiments this precludes heat-shrinkage and hot-melt adhesives. ^• We prefer that the support have an O-ring or other circular seal around its periphery over which the first sleeve can be_ installed. Such a circular seal will generally be truly circular (since the housing around which it is to seal will generally be truly circular), but it can have other shapes and by "circular" we simply mean that in use the seal forms a closed loop. The seal may, however, be supplied in "wraparound" form and therefore comprise a link of sealing material whose ends can be brought together. The seal is preferably an O-ring of oval or substantially truly circular cross-section. Where such a circular seal is used the reservoir may break through an outer surface of the support at a seat for the circular seal. Such ^" _a seat may serve to locate the circular seal, and it may comprise a circumferentially-extenαing recess around the support.

The reservoir preferably has means for applying pressure to a sealing material therein, which means preferably comprises a spring- loaded moveable surface such as a piston or diaphragm, defining a boundary of the reservoir. A screw thread may be provided for biasing the spring.

The sealing material preferably has a cohesive strength greater than its adhesive strength to the reservoir and it preferably has a hardness at room temperature using a Stevens-Volland texture analyser greater than 45 g, preferably greater than 60g, and an ultimate elongation at room temperature greater than 60%, preferably greater than 100%, as determined by by ASTM D638.

Preferred sealing materials comprise gels such as those based on silicone, polyurethane or block copolymers such as those known by the trademarks Kraton and Septon. Gels may be produced from these base polymers by extending them with a mineral or other oil.

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

Figures 1A and I B show a prior art solution to the triple point problem;

Figures 2A and 2B show a device and split support parts for the present invention;

Figures 3 A, 3B and 3C show a reservoir in a split support part;

Figure -J- shows a reservoir in cross-section;

Figure 5 shows split edges of support parts;

Figures 6A and 6B show a support before and after pressurization of a sealing material in a reservoir;

Figure 7 shows installation of a support around a cable;

Figure 8 shows a further step during installation;

Figure 9 shows installation of a split casing between two supports; and

Figure 10 shows a completed splice case.

A solution to the trip point problem as disclosed in US 4845314 is illustrated in figures 1A and I B. A splice case is formed around a cable 1 (partially drawn) and comprises split end plates 2, the split 3 allowing the plates to be ^" wrapped around" the cables. A wraparound casing 4 is then installed around the end plate and the longitudinal .edges 5 fastened together. A longitudinal seal 6 provides a seal between edges 5. The sleeve 4 can be seen in figure 1A to have a window 7 breaking through its internal surface such that longitudinal seal 6 is able to contact an O-ring 8 that surrounds each end plate 2.

Figure 2A shows a device 9 of the invention for forming an environmental seal around an elongate object such as cables 10. The device 9 comprises:

(a) first and second sleeves 1 1 , 12 that can be positioned around the cables 10 substantially end-to-end, the sleeves -being shown in dotted outline; and

( b) a split support 13 comprising support parts 14 for the sleeves 1 1 , 12 that can be positioned within the sleeves and bridging their mutually facing ends, the support 13

preferably having a crowned end 15 the fingers of which can be bent inwardly to produce a frusto-conical end to the support allowing a gentle taper of sleeve 12 down to the cables 10;

the support 13 having a reservoir 16 for a sealing material breaking through the split 17 along a length thereof sufficient to bridge the mutually facing ends of the sleeves 1 1 , 12.

Figure 2B shows the two support parts 14 separated from one another. The reservoir 16 can be seen to be partly formed in each split 17, although one of the split surfaces 17 could be planar with the sealing material retained in a reservoir wholly within the other split surface. We prefer that the support parts 14 be identical for ease of manufacture.

We prefer that the reservoir 16 breaks an outer surface of the support at a first location 18 for sealing to the first sleeve 1 1 and at the second location 19, separated from the first location 18, for sealing to the second sleeve 12.

The reservoir 16 may break through an outer surface of the support at a seat 20 for an O-ring or other circular seal. The first sleeve 11 may then seal to the circular seal, rather than directly to the support 13. We prefer that the reservoir also breaks through to an outer cylindrical surface 21 of the support 13, such that second sleeve 12 can be sealed directly to the support 13. Pressure can be applied to sealing material in the reservoir by means of a suitable pressurization device such as a bolt 22 which is explained in more detail below.

The reason why two different types of sealing arrangement are preferred is that this allows two different types of sleeve 1 1 , 12 to be used. Thus, a heat-shrinkable sleeve 12, which seals best to a

substantially cylindrical surface, can be used to make a permanent seal from the support 13 to the cables 10; and a dimensionally-stable (ie non heat-shrinkable) sleeve which for optimum sealing requires a circular seal can be used to form a removable covering over a cable splice to the left of the support 13 as drawn in figure 2A.

Figure 3 A shows in perspective view a split support part 14 similar to that illustrated in figure 2B . A split support may be provided at each end of the splice case and the two supports joined together by tie bars 24. A catch 25 is provided at the top surface as drawn of cylindrical surface 21 to help retain an end of a heat- shrinkable sleeve on cylindrical surface 21 during heat-shrinkage.

A section through plane alpha-alpha of figure 3A is shown in figure 3B, and a section along plane beta-beta is shown in figure 3C. Figure 3B therefore shows sealing material 23 in the reservoir emerging at second location 19 on the cylindrical surface 21. Figure 3C shows the sealing material 23 emerging at first location 18, being the seat 20 for a cylindrical seal 26, and also at the second location 19 on cylindrical surface 21.

In figure 4 a part of a support 13 is shown with first and second sleeves 11 and 12 overlying it. The sleeves are shown slightly separated from the support for clarity. As before, the support carries fingers forming a crowned end 15 to provide a gentle transition of the sleeve 12 from the cylindrical surface 21 of a support down to the cables (not shown) that it carries. A sealing material 23 is shown in reservoir 16, the sealing material breaking through along the cylindrical surface 21 and the seat 20 for a cylindrical seal 26. ^" _ The reservoir has means for applying pressure to sealing material 23 comprising a spring-loaded moveable surface 27 defining a boundary of the reservoir 16. Spring-loading may be by means of a coil spring 28 having a bolt or other screw thread 22 to bias the spring. The sealing material 23 can therefore be maintained

under compression by means of the spring 28 in spite of some creep or compression set. Pressure is preferably applied to the sealing material after sleeve 12 has been shrunk or otherwise installed.

Figure 5 shows two support parts, again carrying crowned ends 15. Sealing material 23 can be seen at the edge of each split part 14. The moveable surface 27, spring 28 (hidden in figure 5 but shown in figure 4) and the bolt 22 can be seen to be provided wholly in one of the split parts 14. A second moveable surface 27, spring 28 and bolt 22 may however be provided in the other part 14 at an opposite split. Thus, the two split parts 14 may be identical as illustrated in figure 2B.

Figures 6 A and 6B show the split support 13 before and after the sealing material 23 has been pressurized by rotating the bolt 22. In figure 6B the sealing material can be seen to have exuded through the windows that break through the slit 17 at the cylindrical surface 21 and the seat 20 for the circular seal.

In figure 7 a tape 29 is being wrapped around the crowned ends 15 of the support 13 in order to form the desired frusto-conical transition to the cable 10.

A dimensionally heat-shrinkable sleeve may then be shrunk over the end of the support 13 to provide a seal from the cylindrical surface 21 down to the cable 10. Such a sleeve is shown installed in figure 8. The sleeve here is a wraparound sleeve, its longitudinal edges having been held together by a channel 30. We prefer that a two piece sleeve be used, each piece extending around substantially 180° of the cylindrical surface 21 , since this allows two sleeve closure mechanisms to be employed diametrically opposed to one another. This closure mechanism can latch onto some part of the support for example by means of catch 25 shown in figure 3A. This reduces any chance of the sleeve 12 slipping off the circumferential

surface 21 during shrinkage and/or mitigates the effect of any longitudinal shrinkage of the sleeve. Figure 8 also shows positioning of an O-ring 26 in the seat 20.

A splice case is being completed in figure 9, and it consists of two supports 13 one at each end of the splice and sealed to the ingoing cables by means of second sleeves 12. A first, non- shrinkable, sleeve 1 1 is shown being installed around the two supports 13 and extending from one O-ring 26 to the other. The sleeve 1 1 has wedge-shaped rails 31 along opposing longitudinal edges thereof which are brought together as the sleeve is installed around the support. Figure 10 shows the completed splice case where wedge-shaped channels 32 have been positioned over the wedge-shaped rails shown in figure 9. A seal between opposing longitudinal edges of the sleeve 1 1 , and between that seal and the underlying circular seal may be provided using a window of the general type disclosed in US 4845314 referred to above. Access to the cable splice between the supports 13 can readily be had simply by removing wedge-shaped channels 32 and removing sleeve 1 1. The seals to the cables 10 provided by the sleeve 12 are, however, intended to be substantially permanent.