LV10699B

LV10699B - Branch-off seal

Info

Publication number: LV10699B
Application number: LVP-93-201A
Authority: LV
Inventors: Wambeke Alain; Van-Hentenrijk Robert
Original assignee: Raychem Ltd
Priority date: 1991-01-18
Filing date: 1993-03-19
Publication date: 1995-12-20
Also published as: MX9200234A; WO1992012843A1; GB9101159D0; LV10699A

Description

LV 10699

BRANCH-OFF SEAL

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

Because čabies 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 bv 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 ardcles 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 othenvise treated to cause them to shrink etc into tight engagement with the čabies. A good environmental seal can therefore be obtained. A heat-shrinkable sleeve can be made in wrap-around form, ailowing 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 čabies etc. are to be seaied 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 seai between a heat-shrinkable sleeve and at least two substrates. such as telecommunication or other čabies. which comprises the steps of: (a) positioning the substrates vvithin the heat-shrinkable sleeve, (b) forming at least two heat-shrinkable termiņai 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 extemally of the sleeve, and the substrates are within the termiņai 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 centra! 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 recoverv 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 exampie, where the branching čabies 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 čabies have more than one jacket, a large gap may exist that has to be filled bv seaiing material. LV 10699 - j -

Some proposals have been made to deal with these situations.

For exampie GB 1604984 discloses a fork-like member through the prongs of which can be threaded the double thickness of sleeve between branching čabies. Where the čabies are separated by a significant, fixed, distance this threading can hold together the two thicknesses of sleeve* ailowing 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 čabies. Such a design may be useful where the čabies 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 čabies. When the sleeve is heat-shrunk, the reservoir shrinks away causing the now-softened adhesive it contains to be displaced into the branch-region. Unfortunateiy, 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 čabies or other substrates, which comprises: (a) positioning the substrates within the sleeve; (b) positioning at an end of the sleeve means such as a d . clip or clamp or a filling piece which comprises a sealing material (preferably a hot-meit 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 termiņai conduits in the sleeve, and it may do this for exampie 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 mouided-on or othervvise affixed block thereof. Also, the sleeve may have an internai 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 materiāls comprise hot-melt adhesives - 3 - LV 10699 such as those based on polvamides or on ethvlene vinvlacetate copolymers.

The means for displacing the seaiing material mav be operated manuaily or otherwise by the person carrying out the method of the invention. Altematively, 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-acdvatable adhesive to become activated. Thus heat may aiso cause or allow release of some resiliently biased means which on relaxation causes displacement of the seaiing material. A spring could be held in a biased configuration by the seaiing material itself, such that when the material is heat-softened it aliows the spring to displace it. (It may be noted that a temperature indicator operadng 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 generallv parallel to and between the branching čabies, and a displacement axial or radial with respect to it will be desired to fill a gap between the čabies.

In one embodiment the means for displacing displaces seaiing 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 substandally frasto-conical, the apex of the cone preferably pointing away from the end of the sleeve. This helps - 6 - the means dispiace the adhesive. The flanges may, however. be substantiallv planar.

This displacement of sealing material to the end of the sieeve may be useful when the cross-sectional size of the substrate decreases from that at a first position immediately within the sieeve to that at a second position further within the sieeve. The means for displacing may then dispiace sealing material from the first position (where it may be easily initiallv positioned) to the second position (where it is desired). This situation may exist where čabies 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 sieeve.

In another embodiment, the means for displacing can be altered from a substantiaily 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 reiease 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 čabies. That can be done if desired by introducing a fluid, such as air, or a foaming or LV 10699 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:

Figurē 1 shows a prior art cable branch-off;

Figurē 2 shows a splice between muiti-jacketed čabies where the present invention may be useful;

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

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

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

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

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

Figurē 8 shows a variation on the mechanism of figurē 7;

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

Figurē 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 - δ - coated with a hot-melt adhesive positioned inside the sleeve. The sleeve is used to seal a spiice between branching čabies that are omitted from the drawing for claritv. The spiice wouid be positioned within the sleeve, with respective čabies entering through respective conduits 3.

Figurē 2 shows a cable spiice 6 between čabies having two jackets, one, 7, of which may be an armouring giving mechanicai 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 eiiminated since the outer jackets prevent the čabies being positioned much closer together. A simiiar problem exists for any cable type where the čabies 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 an clip disclosed above.

Figurē 3 illustrates a branch-off clip 2 to be positioned on an end of a heat-shrinkable sleeve as iliustrated in figurē 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 aiso the seaiing material 10. The means 9 may be activated by pulling (or pushing or rotating or otherwise moving) pan 11. In the embodiment iliustrated means 9 includes substantially frusto-conicai 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 figurē 2 to position A and/or position C. Thus a large volume of, originally solid, sealing material mav be positioned between the čabies, and displaced when softened during or after shrinkage of the sleeve to the desired position.

Figurē 4 shows a clip 2, having a mechanism 13 for displacing sealing material. When part 11 is pulled (or pushed LV 10699 . ο . etc) the mechanism 13 is made. or made more oblate, thus displacing sealing material radiallv with respect to the Central leg 5 of the clip 2. The mechanism 13 has end plates 14 and 15 vvhich, by pulling part 11 vvhich, 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 shovvn in figurē 5a or 5b. In figurē 5a casing 17 has ruptured and due to its inherent springiness, or due to an internai spring, has sprung outwards.

This may occur automatically or may be caused by the installer.

In figurē 5b the means 17 has mereiy become oblate and remained so. In each case surrounding adhesive will have been displaced.

In figurē 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 figurē 6b. Movement of these plates deforms a casing 17 similar to that illustrated in figurē 5.

In figurē 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 reiax when surrounding sealing material 10 has softened. In this case, therefore, the sealing material 10 can be automatically displaced when the clip etc on vvhich it is carried has reached the desired temperature. A similar arrangement is shown in figurē 8, except that there a coil spring 21 is allovved to unvvind when the restraint of its surrounding sealing material 10 is removed by heating. - 10 -

Figurē 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

Formula 1: A method of forming a hermetic seal between a sleeve and at least two branching branches comprises the following steps: (a) the branches are inserted into the sleeve; (b) a means comprising a sealing material and a means for displacing the sealing material is placed at the end of the sleeve; and (c) actuating the sealant transfer means so as to form an airtight seal between the sleeve and at least one branch.

2. A method according to claim 1, characterized in that the means to be applied at the end of the sleeve is a clamp or clamp.

Method according to claim 1 or 2, characterized in that the means for transporting the sealing material comprises a sealing material.

Method according to claim 2, characterized in that the clip is formed by at least two elements on the outside of the sleeve and one inside the sleeve forming means for displacing the sealing material.

5. The method of claim 2, wherein the clamp compresses the peripheral areas of the sleeve.

A method according to any preceding claim, wherein the sleeve is heat-shrinkable.

A method according to any preceding claim, wherein the sealing material is inserted into the sleeve between the two tines. 1

8. A method according to any one of the preceding claims, characterized in that the means for moving the sealing material is hand-operated.

9. The method of any one of claims 1-7. , characterized in that the means for moving the sealing material starts to operate automatically under certain conditions.

10. The method of claim 9, wherein said conditions are the temperature of a particular sealant and / or a sealant.

Method according to claim 10, characterized in that the means for moving the sealing material is a resilient member held by a thermoplastic sealing material in a tensioned state.

Method according to any of the preceding claims, characterized in that the sealing material is a hot-melt adhesive.

13. A method according to claim 6, characterized in that during the sleeve thermal shrinkage the sealing material transfer means is inserted at the end of the sleeve.

Method according to any of the preceding claims, characterized in that the sealing material transfer means pushes the sealing material to the end of the sleeve.

Method according to claim 14, characterized in that the sealing material displacement means comprises one or more sockets which, at least partially, extend at right angles to the branches.

Method according to claim 14 or 15, characterized in that the cross-section of the branch is reduced in the direction from the end of the sleeve to the middle and the means for moving the sealing material from the end of the sleeve sealing material to the middle.

Method according to any of the preceding claims, characterized in that the sealing material transfer means having a generally conical or truncated cone shape can be increased in cross-section, thereby achieving radial displacement of the sealing material.

Method according to any of the preceding claims, characterized in that the sealing material displacement means having a substantially cylindrical shape can reduce the length, thereby achieving radial displacement of the sealing material.

19. A method according to claim 18, wherein said reduction of the length of said cylindrical shape results in a barrel or an increase in its barrel capacity. 2 LV 10699

A method according to any of the preceding claims, characterized in that the displacement means can be loaded until it breaks down and the removal of the load causes the sealing material to move.

A method according to any one of the preceding claims, characterized in that the displacement means is a resilient hollow body which can extend perpendicularly to the branches.

22. The method of claim 21, wherein the hollow body is expanded by injecting fluid therein.

23. The method of claim 21, wherein the hollow body comprises a spring.

24. The method of any one of claims 21-23. characterized in that a sealing material is present on the outside of the hollow body.

25. A method according to any one of the preceding claims, wherein said branches are cable branches.

26. A method according to any one of the preceding claims, wherein said branches are spaced apart from one another.

27. A method according to claim 25, characterized in that each cable has at least two sheaths which are removed at different lengths before the sleeve location.

28. Airtight seal if it is formed by any of the methods described in any of the preceding claims.

29. A clamp or clamp or accessory for sealing a branching method according to any one of claims 1 to 27, comprising a sealing material and a means for moving it. 3