Adhesive bonding and miscellaneous chemical manufacture – Methods – Making electrical conductors of indefinite length
Patent
1991-04-15
1993-06-01
Simmons, David A.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Making electrical conductors of indefinite length
156 49, 156 86, 156248, 29868, 174 92, 174DIG8, 428 351, H01B 1300
Patent
active
052156079
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a technique for re-entry and reclosure of a cable splice case, particularly formed from a heat-shrinkable wrap-around sleeve
Where cables, such as multicore telecommunications cables are spliced a protective covering known as a splice case, has to be built up around the splice and extending from the intact cable jacket on one side of the splice to the intact cable jacket on the other side of the splice. In this way the missing cable jacket is replaced, providing environmental protection for the otherwise exposed conductors, and the resulting splice case is generally expected to have a life-time comparable to that of the cables themselves, typically at least twenty years.
In recent years, heat-shrinkable plastics materials have been used in the form of sleeves that are positioned around cable splices and shrunk down into engagement with the cables to either side of the splice. Heat-shrinkability allows such sleeves to be supplied over-sized, providing easy installation, and afterwards caused to engage tightly against the cables, providing excellent environmental sealing, by the simple step of heating, generally by means of a gas torch.
In order to provide improved mechanical strength, and often to provide an enhanced barrier to transmission of water vapour, such sleeves may be used with a liner. A liner comprises a central cylindrical part and frusto-conical end pieces and is positioned around a cable splice, the central part overlying the bulky splice itself and the end pieces providing smooth tapers down to the cables to either side of the splice. A liner may comprise, for example two semi-cylindrical half shells or a sheet of material that is rolled around the splice. In either case, end portions of the liner may comprise tapered fingers (giving ends of the liner the appearance of a crown) which can be bent inwards to provide the frusto-conical end portions. The sleeve is shrunk around the liner, giving the resulting splice case the shape of a cylinder with frusto-conical ends.
It is often desirable that the sleeve be installable around a cable splice without access to a free cable end, in which case a sleeve supplied in tubular form (of closed cross-section) cannot of course be used. The solution is to use a wrap-around sleeve, a most successful design of which is disclosed in GB 1155470 (Raychem). Such a sleeve is supplied as a sheet of heat-shrinkable material having upstanding protuberances (known as rails, although no particular shape is implied by the term) at, and generally running continuously along, opposing edge portions of the sheet. The sleeve is wrapped around the splice by bringing together opposing rails which are then secured together to maintain the sleeve in the wrapped-around configuration. They may be secured together by, for example, an elongate channel C-shaped in cross-section that is slid over them. The sleeve is then heated to cause it to shrink. One of the rails may be positioned a short distance (a few centimeters being typical) from an extreme edge, the portion of sleeve between that rail and that extreme edge being known as a flap. The flap will underlie the two rails when they are brought together on installation of the sleeve, and may form a seal or help improve sealing between the rails.
The sleeve may be internally coated with a sealing material to enhance the environmental seal provided. Preferably the sealing material is heat-activatable, for example a hot-melt adhesive, such that a single heating step causes shrinkage of the sleeve and activation of the sealing material.
It may be necessary to re-enter a splice case in order to gain access to the conductors within. This may be necessary in order to repair a fault, to reorganize the spliced conductors or to make new connections. After the splice has been attended to a new splice case has to be built. A special technique of re-entry and reclosure has been developed for splice cases formed from heat-shrinkable sleeves and the present invention is a modification of that technique.
The known techni
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Read Michael R.
Verhoeven Henri
Burkard Herbert G.
N.V. Raychem S.A.
Osele Mark A.
Simmons David A.
Zavell A. Stephen
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