WO1992012843A1

WO1992012843A1 - Branch-off seal

Info

Publication number: WO1992012843A1
Application number: PCT/GB1991/002309
Authority: WO
Inventors: Alain Wambeke; Robert Vanhentenrijk
Original assignee: N.V. Raychem S.A.; Raychem Limited
Priority date: 1991-01-18
Filing date: 1991-12-23
Publication date: 1992-08-06
Also published as: GB9101159D0; MX9200234A; LV10699B; LV10699A

Abstract

A method of forming a branch-off seal between a sleeve and at least two substrates, which comprise: a) positioning the substrates within the sleeve; b) positioning at an end of the sleeve means which comprises a sealing material and means for displacing the sealing material; and c) activating the means for displacing so as to form a seal between the sleeve and at least one of the substrates.

Description

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BRANCH-OFF SEAL

The present invention relates to the formation of a branch - off seal, particularly between branching cables for example emerging from a telecommunications or other cable splice.

Because cables are produced in limited lengths and because of the difficulty in handling long lengths, it is of course necessary to splice lengths of them together. Where a splice is made, an outer jacket is stripped back allowing access to the copper or fibre or other conductors that are to be joined. After the splice is made, the protective jacket has to be made good; and this is done by building a so-called splice case around the splice. A splice case is disclosed in GB 1431167.

Splice cases may have many forms, and in recent years dimensionally-recoverable (generally heat-shrinkable) sleeves or other articles have been widely used. Such articles can be supplied over-size, allowing easy installation and avoiding the need for close tolerances. After installation over the cable splice to be protected they are heated or otherwise treated to cause them to shrink etc into tight engagement with the cables. A good environmental seal can therefore be obtained. A heat-shrinkable sleeve can be made in wrap-around form, allowing installation around a splice without access to a free cable end. A wrap-around sleeve is disclosed in GB 1155470.

Problems may, however, arise when two or more cables etc. are to be sealed at one position, eg at one end of a splice case. This problem, which is known as branch-off, was solved for most purposes in the invention disclosed and claimed in GB-B-1604981. That invention provides a method for forming a branch-off seal between a heat-shrinkable sleeve and at least two substrates, such as telecommunication or other cables, which comprises the steps of:

(a) positioning the substrates within the heat-shrinkable sleeve,

(b) forming at least two heat-shrinkable terminal conduits by positioning a clip having at least two elongate legs over the outer surface of the heat-shrinkable sleeve at an open end thereof, wherein at least two of said legs are positioned externally of the sleeve, and the substrates are within the terminal conduits; and

(c) while the clip remains on the outer surface of the heat-shrinkable sleeve applying heat so as to effect shrinkage of the sleeve and to form the desired seal.

Preferably the clip of that earlier patent is formed as a trident and the central leg of the trident passes into the heat- recoverable sleeve while the outer legs pass outside it. In this way a layer of heat-recoverable sleeve is pinched between the central leg and each outer leg. The central leg is preferably provided on each side with a layer of hot-melt adhesive or another heat-activatable sealant which flows during recovery to seal the gap between the conduits.

Such trident clips allow the formation of an excellent seal and have become the world-wide standard for branched heat- shrink telecommunications splice cases.

Nonetheless, under unfavourable conditions some problems may arise. For example, where the branching cables are separated by a fixed, although not necessarily predetermined, distance (as they are in a lead splice case, which may require reinforcing by a surrounding sleeve) or where cables have more than one jacket, a large gap may exist that has to be filled by sealing material. - j -

Some proposals have been made to deal with these situations.

For example GB 1604984 discloses a fork-like member through the prongs of which can be threaded the double thickness of sleeve between branching cables. Where the cables are separated by a significant, fixed, distance this threading can hold together the two thicknesses of sleeve, allowing a seal to be made.

EP 0120603 discloses a branch-off clip having a wide central leg that is coated with adhesive and that is positioned between upper and lower rows of branching cables. Such a design may be useful where the cables have two or more jackets, for example an armour layer and an environmental jacket.

In GB 2109170, a technique is employed to introduce extra adhesive into the branch-off region. Here the sleeve has a small- reservoir in the form of a dimple that is filled with adhesive. A branch-off clip is used to form conduits for the cables. When the sleeve is heat-shrunk, the reservoir shrinks away causing the now-softened adhesive it contains to be displaced into the branch- region. Unfortunately, this idea requires special fabrication of the sleeve, which might be expensive or inconvenient.

I have now discovered that some means for forming conduits in a sleeve may also serve to displace sealing material as required.

Thus, the invention provides a method of forming a branch- off seal between a heat-shrinkable or other sleeve and at least two cables or other substrates, which comprises:

(a) positioning the substrates within the sleeve;

(b) positioning at an end of the sleeve means such as a clip or clamp or a filling piece which comprises a sealing material (preferably a hot-melt adhesive or other heat-activatable material) and means for displacing the sealing material; and (c) activating the means for displacing so as to form a seal between the sleeve and at least one of the substrates.

The invention also provides a branch-off clip or clamp or filling piece for use in the method of the invention, and comprising a sealing material and a means for displacing the sealing material.

The sleeve may be of tubular or wrap-around design, and it may form part of a larger article.

The clip or clamp may additionally have the function of forming terminal conduits in the sleeve, and it may do this for example by forming a partition within the sleeve between the substrates. I prefer, however, that such conduits be formed by the clip or clamp bringing together between the substrates opposing portions of the sleeve. That can reduce the volume of sealing material required. In this case the clip or clamp preferably has at least two legs that are positioned outside the sleeve and a leg (preferably comprising the means for displacing) that is positioned within the sleeve.

The means for displacing the sealing material may carry the sealing material, although in some situations it may be preferable for sealing material to be supplied separately to the branch-off region. The means for displacing may have a coating or a wrap of sealing material, or a moulded-on or otherwise affixed block thereof. Also, the sleeve may have an internal coating of sealing material for bonding to the substrates, and some of that material may be displaced to the branch-off region, especially if the sleeve shrinks. Preferred sealing materials comprise hot-melt adhesives such as those based on polyamides or on ethylene vinylacetate copolymers.

The means for displacing the sealing material may be operated manually or otherwise by the person carrying out the method of the invention. Alternatively, the means for displacing may operate automatically when some condition, such as a chosen temperature, is met. For example, a heat-shrinkable sleeve may be installed by heating it with an open-flame torch to cause the sleeve to shrink and any heat-activatable adhesive to become activated. Thus heat may also cause or allow release of some resiliently biased means which on relaxation causes displacement of the sealing material. A spring could be held in a biased configuration by the sealing material itself, such that when the material is heat-softened it allows the spring to displace it. (It may be noted that a temperature indicator operating on a similar principle, but not causing the displacement now provided, is disclosed in GB 1604981). The heat-shrinkage is therefore preferably carried out while the means for displacing is present at an end of the sleeve.

The means for displacing may have a variety of constructions, and operate in a variety of ways. In general the means will lie generally parallel to and between the branching cables, and a displacement axial or radial with respect to it will be desired to fill a gap between the cables.

In one embodiment the means for displacing displaces sealing material towards the end of the sleeve, generally to form a plug of material at the end of the sleeve to block entry of moisture or other contaminant. The means for displacing may comprise one or more flanges preferably at least a component of whose extension is transverse to the substrate. Thus, the flanges may be substantially frusto-conical, the apex of the cone preferably pointing away from the end of the sleeve. This helps the means displace the adhesive. The flanges may, however, be substantially planar.

This displacement of sealing material to the end of the sleeve may be useful when the cross-sectional size of the substrate decreases from that at a first position immediately within the sleeve to that at a second position further within the sleeve. The means for displacing may then displace sealing material from the first position (where it may be easily initially positioned) to the second position (where it is desired). This situation may exist where cables having two or more jackets are spliced, the outer jacket being stripped back further than the inner jacket.

In another embodiment it can be altered from a substantially conical or frusto-conical form of smaller to one of large cross-sectional size, thereby causing a radial displacement of sealing material. Its action may therefore be like opening an umbrella. This could be done by the installer pulling, or more preferably pushing, on a rod or other means that extends from a clip positioned at an end of the sleeve.

In another embodiment, the means for displacing can be altered from a substantially cylindrical form of greater to lesser length thereby causing a radial displacement of sealing material. This alteration may result in the cylindrical form becoming, or becoming more, oblate.

If desired, the means can be tensioned past a breaking point thereof such that a consequential release of tension causes the displacement.

In a further embodiment the means for displacement comprises a bladder or other resilient hollow member that can be expanded transversely with respect to the cables. That can be done if desired by introducing a fluid, such as air, or a foaming or other liquid, into it. The hollow member may surround a spring, and it may have the sealing material on an outer surface thereof.

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

Figure 1 shows a prior art cable branch-off;

Figure 2 shows a splice between multi-jacketed cables where the present invention may be useful;

Figure 3 shows a branch-off clip useful in the present invention providing axial adhesive displacement;

Figure 4 shows a branch-off clip useful in the present invention providing radial adhesive displacement;

Figures 5a and 5b show two ways in which a clip of the general type shown in figure 4 may displace sealing material;

Figures 6a and 6b show an alternative mechanism for achieving radial adhesive displacement;

Figure 7 shows a mechanism similar to that of figure 6b, but that operates automatically on softening of the sealing material;

Figure 8 shows a variation on the mechanism of figure 7;

Figure 9 shows an air-inflatable means for displacing sealing material.

Figure 1 shows a prior art branch-off as disclosed in GB 1604981. A heat-shrinkable sleeve 1 has positioned at one of its ends a branch-off clip 2. The positioning of the clip has formed two conduits 3 at the end of the sleeve. The clip has two elongate legs 4 positioned outside of the sleeve, and one elongate leg 5 - S -

coated with a hot-melt adhesive positioned inside the sleeve. The sleeve is used to seal a splice between branching cables that are omitted from the drawing for clarity. The splice would be positioned within the sleeve, with respective cables entering through respective conduits 3.

Figure 2 shows a cable splice 6 between cables having two jackets, one, 7, of which may be an armouring giving mechanical strength and one, 8, may provide an environmental barrier. The inner jacket 7 can be seen to have been stripped back less than the outer jacket 8. A gap therefore exists between the inner jackets at region A that cannot be eliminated since the outer jackets prevent the cables being positioned much closer together. A similar problem exists for any cable type where the cables are separated by a fixed distance, as in the case of lead cable splices. It is in these situations that the present invention may be able to improve on the performance of the prior art clip disclosed above.

Figure 3 illustrates a branch-off clip 2 to be positioned on an end of a heat-shrinkable sleeve as illustrated in figure 1. The clip has two outer legs 4 and an inner leg 5, the inner leg comprising means 9 for displacing a sealing material, and also the sealing material 10. The means 9 may be activated by pulling (or pushing or rotating or otherwise moving) part 11. In the embodiment illustrated means 9 includes substantially frusto- conical flanges 12 that may be moved axially with respect to the leg 5 and/or whose shape may be altered. Their shape may be altered, for example, in the way of opening an umbrella. In any one or more of these ways, sealing material 10 may be displaced from position B shown in figure 2 to position A and/or position C. Thus a large volume of, originally solid, sealing material may be positioned between the cables, and displaced when softened during or after shrinkage of the sleeve to the desired position.

Figure 4 shows a clip 2, having a mechanism 13 for displacing sealing material. When part 11 is pulled (or pushed etc) the mechanism 13 is made, or made more oblate, thus displacing sealing material radially with respect to the central leg 5 of the clip 2. The mechanism 13 has end plates 14 and 15 which, by pulling part 11 which, through rod 16, is attached to plate 15, move together due to plate 14 abutting the distal end of leg 5. A similar effect could be made to occur by pushing on part 11 if it bore against plate 14 and if plate 15 were prevented from moving away. Rod 16 is surrounded by casing 17 which is caused to bow outwards.

The effect of this movement could be as shown in figure 5a or 5b. In figure 5a casing 17 has ruptured and due to its inherent springiness, or due to an internal spring, has sprung outwards. This may occur automatically or may be caused by the installer. In figure 5b the means 17 has merely become oblate and remained so. In each case surrounding adhesive will have been displaced.

In figure 6a the inner leg 5 of the clip 2 has a conical member 18 that is connected to the part 11. On pushing part 11 the conical member causes a series of arcuate or other plates 19 to open out radially. See figure 6b. Movement of these plates deforms a casing 17 similar to that illustrated in figure 5.

In figure 7 such plates 19 are carried on a central leg of a clip or as a filling piece and are connected together by a resilient means 20 such as a compressed coil spring, that is able to relax when surrounding sealing material 10 has softened. In this case, therefore, the sealing material 10 can be automatically displaced when the clip etc on which it is carried has reached the desired temperature.

A similar arrangement is shown in figure 8, except that there a coil spring 21 is allowed to unwind when the restraint of its surrounding sealing material 10 is removed by heating. Figure 9 shows an inner leg 5 of a clip (or a filling piece) having an inflatable bladder 22 surrounded by a sealing material 10.

For the avoidance of doubt it is noted that the invention provides a method and article providing improved control of flow or displacement of sealing material in the formation of an environmental seal. Any of the clips, filling pieces, displacement mechanisms and sleeves or closures may be selected.

Claims

1. A method of forming a branch-off seal between a sleeve and at least two substrates, which comprises:

(a) positioning the substrates within the sleeve;

(b) positioning at an end of the sleeve means which comprises a sealing material and means for displacing the sealing material; and

(c) activating the means for displacing so as to form a seal between the sleeve and at least one of the substrates.

2. A method according to claim 1, in which the means that is positioned comprises a clip or clamp.

3. A method according to claim 1 or 2, in which the means for displacing carries the sealing material.

4. A method according to claim 2, in which the clip comprises at least two legs that are positioned outside the sleeve and a leg comprising the means for displacing that is positioned within the sleeve.

5. A method according to claim 2, in which the clip brings together circumferentially-spaced portions of the sleeve.

6. A method according to any preceding claim, in which the sleeve is heat-shrinkable.

7. A method according to any preceding claim, in which the sealing material is positioned within the sleeve between the two substrates.

8. A method according to any preceding claims, in which the means for displacing is operated manually.

9. A method according to any of claims 1-7, in which the means for displacing operates automatically when some condition is met.

10. A method according to claim 9, in which the condition comprises temperature of the sealing material and/or mea for displacing.

11. A method according to claim 10, in which the means for displacing comprises a resilient member held in a biased configuration by the sealing material, the sealing material being heat-softenable.

12. A method according to any preceding claim, in which the sealing material comprises a hot-melt adhesive.

13. A method according to claim 6 in which heat-shrinkage is carried out while the means that is positioned is at the end of the sleeve.

14. A method according to any preceding claim, in which the means for displacing displaces sealing material towards the end of the sleeve.

15. A method according to claim 14, in which the means for displacing comprises one or more flanges at least a component of whose extension is transverse to the substrate.

16. A method according to claim 14 or 15, in which the cross- sectional size of the substrates decreases from that at a first position immediately within the sleeve to that at a second position further within the sleeve; and the means for displacing displaces sealing material from the second position to the first position.

17. A method according to any preceding claim, in which the means for displacing can be altered from a substantially conical or frusto-conical form of smaller to one of larger cross-sectional size, thereby causing a radial displacement of sealing material.

18. A method according to any of preceding claim, in which the means for displacing can be altered from a substantially cylindrical form of greater to lesser length thereby causing radial displacement of sealing material.

19. A method according to claim 18, in which the cylindrical form becomes, or becomes more, oblate on said alteration.

20. A method according to any preceding claim, in which the means for displacing can be tensioned past a breaking point thereof such that a consequential release of tension causes displacement of sealing material.

21. A method according to any preceding claim, in which the means for displacement comprises a resilient hollow member that can be expanded transversely with respect to the substrates.

22. A method according to claim 21, in which the hollow member is expanded by introducing a fluid into it.

23. A method according to claim 21, in which the hollow member contains a spring.

24. A method according to claim 21-23, in which the hollow member has the sealing material on an outer surface thereof.

25. A method according to any preceding claim, in which the substrates comprise cables.

26. A method according to any preceding claim, in which the substrates are separated by a fixed distance.

27. A method according to claim 25, in which each cable has at least two jackets that are stripped back adjacent on end of the sleeve by different amounts.

28. A seal when formed by a method according to any preceding claim.

29. A branch-off clip or clamp or a filling piece, suitable for use in a method according to any of claims 1-27, which comprises a sealing material and means for displacing the sealing material.