WO1992021173A1

WO1992021173A1 - Support member

Info

Publication number: WO1992021173A1
Application number: PCT/GB1992/000855
Authority: WO
Inventors: Jean-Marie Etienne Nolf
Original assignee: N.V. Raychem S.A.; Raychem Limited
Priority date: 1991-05-23
Filing date: 1992-05-13
Publication date: 1992-11-26
Also published as: BR9206043A; AU1745292A; EP0585284A1; GB9111110D0

Abstract

A method of enclosing a cable which comprises: (a) positioning around the cable a liner having a socket for receipt of a valve; (b) positioning around the liner a heat-shrinkable sleeve such that the socket is covered by the overlying sleeve; and (c) heating the sleeve to cause it to shrink into engagement with the liner.

Description

SUPPORT MEMBER

The present invention relates to a support member, in particular to a liner for use for example with a heat-shrinkable sleeve in the formation of a cable splice case or other enclosure.

Heat-shrinkable sleeves are now widely used in the cable accessories and pipe protection and other industries for environmental protection. A shrinkable sleeve can be installed with ease around a cable or other substrate to be protected, and then heated to cause it to shrink into tight, sealing engagement with the cable. In this way close tolerances in manufacture of the sleeve are avoided. Such sleeves may be of tubular or wrap¬ around design. Wraparound sleeves are often preferred since access to a free end of the cable is not required for their installation. Wraparound sleeves are disclosed in GB 1155470 (Raychem). Sleeves may be internally-coated with a sealing material such as a hot-melt adhesive.

In many instances, particularly where a cable splice case is to be constructed, the sleeve is shrunk down over a liner which is previously installed around the splice. Such a liner provides the splice case with a regular, neat, shape, reduces heating of the conductors of the splice by the descending sleeve, provides impact and other mechanical strength and may provide a moisture vapour barrier.

Such liners, which often comprise a larger central section and smaller end sections corresponding to the shape of a cable splice, may be made in many ways. A canister comprising aluminium or other half-shells having shaped ends can be provided with hinges or interlocking edges for wraparound installation. This type of canister may be made of sheet material, or may have the appearance of a cage and comprise supporting rings and a series of longitudinal struts joining them. Such a liner is disclosed in GB 1431167. An alternative liner may be made from a roll of rather stiff material which is wrapped around the splice with a degree of overlap. The material used may comprise a laminate of cardboard and/or plastics material together with layers for reducing heat or moisture vapour transfer. Such liners may therefore include a support layer (preferably cardboard or plastics material), optionally a foam layer as heat barrier, a metal foil layer as a moisture vapour barrier, and optionally one or more thin films of polymeric material (optionally perforated) for further protection. A liner based on cardboard is described in GB 2059873, and one based on a thermoplastics material is disclosed in GB 2069773.

The structure just described may constitute merely the central or larger part of the liner, the ends that provide transitions down to the cables being provided by separate end pieces. A liner may however comprise a sheet of rather stiff material having crowned or slotted ends that allow formation of substantially frusto-conical ends when the liner is wrapped around a cable splice.

Splice cases in general must be able to withstand a certain internal pressure. They may be used around splices between pressurized cables, where the need to withstand pressure is self- evident, and they may be used around non-pressurized cables where pressure-resistance is necessary in order that temporary pressurization tests can be carried out to check for leaks.

In each case, some pressure access point may be required either to cause pressurization or to test for pressure. As a result splice cases have been designed to incorporate valves.

US 4320252 (Western Electric) discloses a pressurizable closure for a telecommunications cable. The closure has a metallic air valve extending through a closure, to each end of which electrical couplers are secured for use in grounding the cable sheath. The use of a valve in connection with a heat-shrinkable splice case is disclosed in DE 3616535 (Siemens), US 4783353 (Raychem), GB 2135836 (Raychem) and GB 2112224 (Raychem). Mention may also be made of EP 0045239 (SILEC).

GB 2112224 discloses an assembly suitable for enclosing a substrate (such as a cable splice) which comprises: an inner support such as a canister provided with an outwardly extending appendage such as a valve; an outer recoverable sleeve having a hole therein for co¬ operation with the appendage; and means for sealing the sleeve to the substrate; the appendage providing communication from the support to the outside of the assembly.

GB 2135836 discloses a cable splice case including a recoverable fabric-based sleeve. The sleeve may be used with a liner that carries a valve. The valve preferably has a screw- threaded body and is sealed to the liner by means of sealing washers and a nut. The use of a fabric rather than a continuous material as the sleeve has a particular advantage here; it is possible to force a hole through the fabric without any split propagating later during recovery. The valve may be passed through the liner and then through the hole in the fabric sleeve so that its base abuts against the inside of the liner. Various sealing washers are installed and tightened down by means of a nut. Improved sealing can be achieved if the washer which overlies the fabric has a larger hole than the hole in the fabric since in this arrangement an annular portion of fabric becomes pinched between the top washer and the valve body.

In US 4783353 a valve is preferably secured to a fabric- based sleeve, although it could be secured to an apertured liner within the sleeve. The valve is secured via a socket in the form of a rivet which is clamped around the edges of a hole through the sleeve or liner.

Whilst the above arrangements are ideal in most cases they do, of course, require the use of a special sleeve, namely one that has a preformed hole in the correct position relative to the valve in the liner. Furthermore, care has to be taken during installation to ensure that the valve on the liner correctly mates with the hole in the sleeve.

We have considered that a true requirement is that each splice case be merely capable of pressure access during its service life; and that this does not mean that every splice case will in fact be accessed. As a result we have designed a liner which can be used with a regular non-punctured sleeve, to form a splice case that can be accessed after installation. The liner carries a socket for a valve which is initially covered by the overlying sleeve. A hole is later made in the sleeve only when access is required.

Thus, the invention provides a method of enclosing a cable which comprises:

(a) positioning around the cable a liner having a socket for receipt of a valve;

(b) positioning around the liner a heat-shrinkable sleeve such that the socket is covered by the overlying sleeve; and

(c) heating the sleeve to cause it to shrink into engagement with the liner.

The invention also provides a kit of parts for carrying out a method according to the invention, which comprises:

(a) a liner for supporting a heat-shrinkable sleeve, the liner having a socket therein capable of receiving a valve; and

(b) said sleeve which can be heat-shrunk around the liner, the sleeve having a portion that will cover the socket when so shrunk (and preferably having an uninterrupted surface, ie one with no holes in it).

The invention further provides a liner for supporting a heat- shrinkable sleeve, the liner having a socket capable of receiving a valve, and means for providing between the sleeve and the liner a seal along at least a continuous line around the socket.

If during the service life of the product which may be 10 or 20 years or more, it becomes necessary to access the cable enclosure, a hole may be cut in the shrunk sleeve immediately above the socket, and a valve inserted in the socket. This can usually be done without heating the sleeve, and as a result the sleeve will not split. In the case of a reinforced sleeve heat may be applied to ease cutting without any danger of splitting. After pressure testing or pressurization the valve may be left in place.

This technique not only avoids the provision of specially punctured sleeves, but avoids the expense of provision of valves for every cable enclosure, and those that are required need not be purchased until they are needed. Nonetheless, it may be noted that the present invention does not preclude the provision of a valve in the liner before the sleeve is shrunk over it. In general, that would of course require a low profile valve.

We prefer that the liner be supplied with a plug that is inserted into the socket before the sleeve is shrunk around the liner. This prevents the socket being contaminated with adhesive or other matter, and ensures that the mechanical protection provided by the liner is complete.

The socket preferably comprises a female screw thread into which a valve and. where provided, a plug can be screwed. The female screw threads or other fixing means may be provided directly into the material of the liner proper, or a further screw threaded or otherwise shaped part, such as a collar, may be fitted into a hole in the liner proper. Such filling may be an interference fit, by riveting or by means of a nut and bolt. For example, the socket may have an external screw thread and extend through the material of the liner, the liner being sandwiched between nuts that are screwed onto the socket. Instead of nuts, other radially- extending parts of the socket could be provided.

In general after the sleeve has been cut the valve will be simply inserted into the socket, for example by screwing. A seal may therefore be obtained between the valve and the socket for example by means of a sealing washer on the valve or in the socket or merely by the valve bottoming-out on a shoulder of the socket. Also, the socket may be sealed to (or integral with) the remainder of the liner. That, however leaves a potential leak path through the hole formed in the sleeve, down beside the valve and then between the sleeve and liner. Such a leak path can be avoided if the valve is sealed to the sleeve, for example by having a radially-extending flange that covers the hole in the sleeve. On screwing the valve into the socket this flange would engage the outer surface of the sleeve. The flange could comprise a resilient material, ensuring a good seal. We prefer, though, that the liner and/or the sleeve has means for providing between the sleeve and the liner a seal along at least a continuous line around the socket Such a seal can be made before, during or after heat- shrinkage of the sleeve. It is preferably made during heat- shrinkage, perhaps completed or reinforced by some so-called post-heating, and it preferably has the shape of an anulus around the socket.

The means for providing the seal is preferably part of the liner, and more preferably comprises a washer of sealing material that surrounds the socket. Such a washer may comprise a heat- activatable material such as a hot-melt adhesive and it may be secured on a threaded support between two nuts, between which may also be sandwiched the material of the liner proper. The threaded support will in general be the socket itself. In the case of a liner comprising a sheet of material intended to be wrapped around a splice, the socket is preferably about half-way along its length and 1.5-5, particularly 2-3 cms from a longitudinal edge. When such a liner wrapped around a splice the longitudinal edges will usually be made to overlap, and this can be done such that one edge underlies the socket. This ensures that the underlying spliced conductors are covered by at least one thickness of liner, even over the area of the socket.

When the time comes for access to a completed splice case, it is clearly necessary that the position of the (now covered) socket be ascertainable. Its position may be uncertain because the liner can be installed at any rotational position with respect to the overlying sleeve. Installation instructions could direct that the valve always be positioned at, for example, 180° to the position of the rails when a rail and channel wrap-around sleeve is used. That is however likely to be an unreliable way of ensuring that the valve be found and the hole in the sleeve made at the correct place. We prefer therefore that the liner have a guide means for indicating through a sleeve heat-shrunk thereover the position of the socket. This means for indicating may comprise a raised or sunken relief . of the socket, or adjacent the socket.

The invention is further illustrated with reference to the accompanying drawings, in which

Figure 1 shows a prior art cable splice case employing a valve;

Figure 2 shows a liner of the invention;

Figure 3 shows a sleeve installed over a liner of the invention.

Figure 4 shows the sleeve of figure 3 after a hole has been made in it;

Figure 5 shows pressure testing of a splice case via a valve in the socket of a liner of the invention. Figure 1 shows a prior art splice case disclosed in GB-A- 2135836 (Raychem). A splice 1 between two telecommunications cables 2 is enclosed in a liner 3 that has frusto-conical ends to correspond to the diameter change from splice down to cables. The liner 3 carries a valve 4. A sleeve 5 having a hole for the valve is shrunk around the liner and into engagement with the cables 2 either side of the splice, thus forming an environmentally sealed enclosure. The sleeve was provided with an internal coating of a hot-melt adhesive that, on heat-shrinkage of the sleeve, became molten and flowed to form the seal 6. The valve 4 is secured and sealed to the sleeve by means of a nut 7 and washers 8.

A new liner is shown in figure 2. The liner 3 comprises a sheet of stiff cardboard or other material that can be wrapped around a cable splice. It is shown in its partially wrapped form. It has crowned ends (or other means for rendering its ends frusto-conical), the fingers of which will be bent radially inwardly to form frusto-conical ends. The liner carries a socket 9 for a valve, that is shown temporarily blocked by means of a plug 10 that may be screwed into it. The liner is provided with means for forming a seal around the socket end between the liner and an overlying sleeve. Such a seal should be formed along at least a continuous line around the socket in order to prevent contaminants such as moisture passing from the valve area and along the surface of the liner, between it and the sleeve. Such means for forming a seal preferably comprises a hot-melt adhesive or other sealing material in the form of a washer. That washer may be secured to the socket in a similar way in which the regular washer 8 of figure 1 was sealed to the valve 4. The socket is preferably positioned about 2.5 cm from longitudinal edge 12. and that edge is preferably positioned over the other edge when the liner is wrapped around a splice. Figure 3 shows a splice case formed by shrinking a sleeve 5 around a liner of figure 2. The sleeve is a wraparound sleeve, the closure rails and channel being shown at 13. The position of the socket is apparent because its raised relief causes a corresponding raised relief 14 in the sleeve. The liner can be seen to have been positioned such that the socket is at 180° relative to the rails and channel 13. A knife 15 is about to be used to make a hole in the sleeve 5 to gain access to the underlying socket.

The result of making a hole 16 in the sleeve is shown in figure 4. The socket is now visible. Plug 10 is then removed, and a valve 17 is screwed into . the socket in its place. That is shown in figure 5 where a pressure test head 18 is about to be used to pressurize the splice case. A meter 19 may then be used to measure the internal pressure. A soap solution 20 can be brushed around the splice case ends, or along its closure, or around the valve etc to determine whether any leaks exists. The valve 17 may incorporate or be used with some means such as a flange or washer around it to cover the hole in the sleeve. Such a flange or washer may comprise a sealing material such as a gel or an adhesive.

Claims

1. A method of enclosing a cable which comprises:

(c) heating the sleeve to cause it to shrink into engagement with the liner.

2. A method according to claim 1, in which the liner has guide means for indicating through a sleeve heat-shrunk thereover the position of the socket.

3. A method according to claim 1 or 2, in which a cable splice is enclosed, the liner having frusto-conical end portions at least when positioned around the splice.

4. A method according to any preceding claim, in which the socket is closed by a removable plug.

5. A method according to any preceding claim, in which the liner and/or the sleeve has means for providing between the sleeve and the liner a seal along at least a continuous line around the socket, said seal being made before during or after heat-shrinkage of the sleeve.

6. A method according to any preceding claim, in which said means for indicating comprises a raised or sunken relief of the socket or adjacent the socket, and in which the sleeve is heat-shrunk such that the relief is apparent at an outer surface of the shrunk sleeve.

7. A kit of pans for carrying out a method according to any preceding claim, which comprises:

(b) said sleeve which can be heat-shrunk around the liner, the sleeve having a portion that will cover the socket when so shrunk.

8. A kit according to claim 7, in which the sleeve is a wrap¬ around sleeve.

9. A kit according to claim 7 or 8, in which the sleeve comprises a fibre-reinforced composite.

10. A kit according to claim 7, 8 or 9, in which the liner is a wrap-around liner.

1 1. A kit according to any of claims 7, 8, 9 or 10, in which the liner at least when installed around a cable has frusto- conical end portions or means for rendering its ends frusto- conical.

12. A kit according to any of claims 7-11 , which additionally comprises means for providing between the sleeve and the liner a seal along at least a continuous line around the socket.

13. A kit according to claim 12, in which said means for providing is provided as part of the liner.

14. A kit according to claim 13, in which said means for providing comprises a layer of sealing material surrounding the socket.

15. A kit according to claim 14, in which said means for providing comprises a sealing material in the form of a washer.

16. A kit according to any of claims 7-15, in which the socket extends through material of the liner, the liner being sandwiched between radially extending parts of the socket.

17. A kit according to claim 16, in which the socket comprises a hollow bolt and nuts, between which nuts the liner is sandwiched.

18. A liner for supporting a heat-shrinkable sleeve, the liner having a socket capable of receiving a valve, and means for providing between the sleeve and the liner a seal along at least a continuous line around the socket.

19. A liner according to claim 18, that comprises a sheet that can be wrapped around a cable, the sheet having crowned ends that allow formation of substantially frusto-conical ends to the liner when it is so wrapped.

20. A liner according to claim 18 or 19, in which said means for providing comprises a layer of sealing material surrounding the socket.

21. A liner according to claim 17, 18 or 19, in which the socket comprises a hollow bolt that can be positioned through a hole in the liner, the bolt having nuts between which the liner can be sandwiched.

22. A liner according to claim 21, in which the means for providing comprises sealing material in the form of a washer that can be positioned over the hollow bolt and sandwiched between a nut and the liner.

23. A liner according to any of claims 18-23, in which the socket when in use or a portion of the liner adjacent the socket when in use has raised or sunken relief.