GB2220532A - Branch of clip for heat-shrink sleeve - Google Patents

Abstract

In forming a sealed enclosure around a cable branch-off, a generally U-shaped clip 1 is applied to an end of a heat-shrinkable sleeve 20 positioned around the branch-off, and heat is applied to shrink the sleeve. The clip 1 is formed of an electrically insulating material resistant to the high temperatures of a torch used to apply heat to shrink the sleeve, e.g. a thermally resistant aromatic polymer such as aramid, polybenzimidazole or polyether ether ketone. The inner walls 14 of the clip may taper to minimise milk-off. <IMAGE>

Description

FORMING BRANCH-OFF ENCLOSURES This invention relates to a method of forming an enclosure around jointed substrates such as power or telecommunications cables. This invention further relates to kit for use in carrying out the method and also to a clip used in the method.

United Kingdom patent spoecification No. 1 604 98 discloses a method of forming a sealed enclosure around a branch-off in e.g. an electricity supply line. The method comprises placing a heat-shrinkable sleeve around the branch-off, applying a U-shape clip to an end of the sleeve between two branching cables extending from t at end of the sleeve, the clip serving to pinch together opposite portions of the sleeve between the two branches, and then applying heat to the sleeve causing it to shrink and seal around the two branches at the end of the sleeve.

United Kingdom patent specification 1 604 98 teaches the use of a metal U-shape clip, so that it will facilitate the application of heat to the adjacent regions of the heat-shrinkable sleeve and thus ensure that an adhesive lining of the sleeve will be fully melted in order to form an effective seal with the cable branches. Specification 63-98@ acknewledges Belgian patent No. 833 916 as disclesing the use of U-shaped clips made from polycarbonate, acrylonitrile butadiene styrene copolymer, styrene acrylonitrile resins or filled polymers (preferably glass-filled polyamide), but specification 1 604 981 further teaches that clips of such materials would not be suitable for use in the method to which it relates.

However, the use of metal clips in underground cable joints is found to be undesirable because of potential electrical conduction and corrosion problems. These risks are reduced if the metal clip is coated with epoxy resins but this coating is prone to damage, for example if the joint is pulled through a duct.

In accordance with this invention as seen from one aspect, there is provided a method of forming a sealed enclosure around a branch-off, comprising disposing a heatshrinkable sleeve around the branch-off, applying a generally U-shaped clip to an end of the sleeve between two branching elements emerging from. that end of the sleeve, the clip serving to pinch together the opposite portions of the sleeve between the two branches, and applying heat to the sleeve causing It to shrink and seal around the two branches at said end of the sleeve, the clip comprising an electrically insulating material resistant to high temperatures suon as those to which the clip would be subjected by a torch which may be used to apply the heat to the sleeve In accerdance with this invention as seen from a second aspect, there 5 provided a kit for carryIng out the above-defined method, comprising a heat-shrinkable sleeve and at least one generally U-shaped clip comprising an electrically insulating material resistant to high temperatures such as those to which the clip would be subjec- ted by a torch which may be used to apply heat to the sleeve to cause it to shrink.

In accordance with this invention as seen from a third aspect, there is provided a generally U-shaped oli for use In the above-defined method, the 0li comprising an electrically insulating material resistant to temperatures such as those to which the clip would be subjected by a torch which may be used to apply heat to the sleeve to cause it to shrink.

Preferably the material of the clip is able to resist a temperature of at least 2500C for a period of at least 5 minutes.

The clip may be formed of wood treated with fire retardant. Preferably, however, the material of the clip comprises a thermally resistant aromatic polymer. The latter is typically a linear polymer containing aromatic nuclei (such as benzene rings) in the back- bone thereof, with, preferably, no aliphatic hydrocarbon groups in the backbone. Any carbon In the backbone is preferably in the aromatic nuclei mentioned above; any further carbon atoms are preferably present in carbon groups. Examples of suitable such thermally resistant polymers are polyphenylene sulphide and polyphenylene oxide. Such a thermoplastic material may, if desired, contain reinforcing filler, which again should be thermally resistant.Other possible materials are aromatic polyamldes (aramids), polybenzimidazole, and polyether ether ketones (the latter being known as "PEEK" polymers.

Clips of thermoplastics materials can be formed by standard manufacturing techniques such as injection moulding or compression moulding. The clips can therefore be made more cheaply than the prior art metal clips, which must be made by diecasting or pressing. In carrying out the method of enclosing the branch-off, the clip may be applied to the end of the heat-shrinkable sleeve between the two branching elements so as to pinch together opposite portions of the sleeve, then heat may be applied to the sleeve from a propane gas torch to cause the sleeve recover. The clip is however able to resist the heat t which it is subjected by the torch.In an alternative embodiment of the method, the clip may be applied after the heat has been applied to the sleeve, although in th case preferably the opposite portions of toe sleeve are pinched together between the two branches using a pair of tongs before the heat is applied.

further because the OliPs may be ermed by moulding, design restristions which apply to metal castings and press ings are removed. Preferably, the inner end of the clip slot is radiused to reduce the risk of the end of the heatshrinkable sleeve splitting. Preferably alse, the clip tapers in thickness from the outer edge to the inner edge of each of its two prongs : this allows the two adjacent branch elements to rest closer together.

A further problem with the use of U-shaped clips for holding together opposite portions of the heat-shrink sleeve between the two branches concerns the tendency for the clip to progressively slip off, or "milk off".

In accordance with this invention as seen from a fourth aspect, there is provided a method of forming a sealed enclosure around a branch-off, comprising disposing a heat-shrinkable sleeve around the branch-off, applying a generally U-shaped clip to an end of the sleeve between two branching elements emerging from that end of the sleeve, the clip serving to pinch together the opposite portions of the sleeve between the two branches, and applying heat to the sleeve causing It to shrink and seal around the two branches at said end of the sleeve, the clip having the facing inner edges of its two prongs tapering towards each other towards their free ends so that the clip once applied is resistant to slipping off.

In accordance with this invention as seen from a fifth aspect, there is provided a kit for crying out the method defined In the last preceding paragraph, comprising a heat-shrInkable sleeve and at least one generally Ushaped clip, the facIng inner edges of the two prongs of the clip tapering towards each other towards their free ends.

In accordance with this invention as seen from a sixth aspect, there is provided a generally U-shaped clip for use in the method defined above, the facing inner edges of the two prongs of the clip tapering towards each other towards their free ends.

EmbodIments of this invention ili now be des cr ber b; way of example only and with reference to the accompanying drwings, in which : FIGURE is a side elevation of a generally y U- shapped clip; FIGURE 2 is a longitudinal section through the clip on the line II-II of Figure 1; FIGURE 3 is a cross-section through the clip on the line III-III of Figure 1; FIGURE LI is an end view of the clip in the direction of arrow A in Figure 1; FIGURE 5 is a side elevation of a clip of modified shape; and FIGURE 6 is a view of a sealed enclosure being formed around a branch-off using a cli as shown in Figures 1 to 24.

Referring to Figures to 24 4 of the drawings. there is shown a generally U-shaped clip formed of electrically insulating thermo-plasties materials as mentioned previously, and formed by injection mou@ding or compression moulding.

The clip is generally flat but as shown in Figure 3 eaon of its two prongs 1,2 tapers in thickness from its outer edge 3 to Its inner edge . Also, each prong tapers from its inner end to its free enc, and the facing inner edges 4 of the two prongs , 2 taper towards each other towards the free ends of the prongs. At the web-end of the U- shaped clip, the clip is formed with portion 5 projecting away from the prongs and this portion 5 is formed with an aperture 6 for use in removing the olip from the joing sleeve should this prove necessary.This aperture c is thus outside the load bearing areas of the clip. The inner end of the slot between the two prongs is radluse-, as shown at 7 in Figure 2, and all the other edges cf clip are radiused so that the clip is free of any sharp edges.

accorcance With tis invention, a kit for use in a method of encicsing a branch-off comprises a heatshrinkable sleeve together with at least one clip such as snow n Figures to r. In carrying out an embedimnt of this method, the sleeve 20 is disposed around the branchoff and the clip is applied to one end of the sleeve between two branching elements 22, 24 (e.g. cables) emerging from that end of the sleeve, the clip serving to pinch opposite portions of the sleeve together between those elements (Figure 6). Then a propane gas torch is used to apply heat to the sleeve, causing it to shrink and embrace the point, sealing around the two branch cables at the end of the sleeve from which these emerge.Preferably the sleeve has an adhesive coating on its inner surface, which coating is melted by the application of heat to flow and complete the seal between the sleeve and the cables, the adhesive setting as the sleeve is allowed to cool.

As explaIned previously, the material of the clip is resistant to the temperatures to which it is subjected by use of the torch. however, in an alternative method, the clip may be applied after the heat is applied to the sleeve, preferably in this case the opposite portions r of the sleeve at its end being pinched together between the two cables using a pair of tongs, before the heat is applied.Further as expalined above, because of the tapering shape of the slot between the two prongs ,2 of the olip, the olip is resistant to slipping off or "mi ing off" once 10 15 applied to the end of the sleeve.

In addition to the advantages of the clip as referred to already in this specification, there is a further advantage as follows. It It becomes necessary to repair a joint, the current practice is to cut it open leaving the clip(s) in position, repair the joint then reseal the joint by recovering a tubular sleeve about This tubular sleeve covers the whole jeing includIng the eringinal clips and is lined with an adhesive seaman which is required to bond to the clip (s) to provide an effective moisture barrier.Such adhesive are found to adhere to a limited extent to the coatings provided on the metal clips used hitherto, but we have gound that they bond better to the thermoplastics materials specified above for the clips in accordance with this invention.

Referring to Figure 5, a modified clip is shown, again being generally U-shaped and flat but with its two prongs 11, 12 tapering in thickness from its outer edge 13 to its inner edge 14 and with each prong tapering from its inner end to its free end. The facing inner edges 14 of the two prongs 1, 2 taper towards each other, from the inner end towards the free ends, but then diverge at a substantially greater angle over portions 15 adjacent the free ends of the prongs. The clip has a generally rec- angular outline with the outer edges is of the two prongs divergIng at a small angle over portions 6 adjacent the free ends of the prongs. The free ends of the prongs - -, 12 are rouncec as shown. Because this clip presents a wide entry to the slot between the two prongs, the is easy to pusn onto the end of the heat-shrink sleeve.

The clip shown In Figure 5 may be formed of any of one electrically insulating materials mentioned previus

Claims (1)

1. CLAIMS 1) A method of forming a sealed enclosure around a branch-off, comprising disposing a heat-shrinkable sleeve around the branch-off, applying a generally U-shaped clip to an end of the sleeve between two branching elements emerging from that end of the sleeve, the clip serving to pinch together the opposite portions of the sleeve between the two branches, and applying heat to the sleeve causing it to shrink and seal around the two branches at said end of the sleeve, the clip comprising an electrically insulating material resistant to high temperatures such as those to which the clip would be subjected by a torch which may be used to apply the heat to the sleeve.

   2) A method as claimed In claim 1, in which the material of the clip is able to resist a temperature of at least 25000 for a period of at least 5 mnutes.

   3) A kit for carrying out the method claimed in cam 1, the kit comprising a heat-shrinkable sleeve and at least one U-shaped clip comprising an electrically insulating material resistant to high temperatures such as those to which the clip would be subjected by a torch which may be sued to app heat to the sleeve to cause It to shrink.

   kit r. kit as claimed in claim 3, in which tne material of the clip is able to resist a temperature of at least 250 c for a period of at least 5 minutes.

   5) A kit as claimed in claim 4, in which the material of the clip comprises a thermally resistant aromatic polymer.

   6) A generally U-shaped clip for use in the method claimed in claim 1, the clip comprising an electrIcally insulating material resistant to high temperatures such as those to which the clip would be sutjected by a torch which may be used to apply heat to the sleeve to cause it to shrink.

   7) A clip as claimed in claim 6, in which said electrically insulating material is able to resist a temperature of at least 250 c for a period of at least 5 minutes.

   8) A clip as claimed in claim 7, in which the material of the clip comprises a thermally resistant aromatic polymer.

   9) A method of forming a sealed enclosure around a branch-off, comprising disposing a heat-shrinkable sleeve around the branch-off, applying a generally U-shaped clip to an end of the sleeve between two branching elements emergIng from that end of the sleeve, the clip serving to pinch together the opposite portions of the sleeve between the two branches, and applying heat to the sleeve causing it to shrink and seal around the two branches at said end of the sleeve, the clip navl ng the facing inner edges of its two prongs tapering towards each other towards their free ends so that the clip once applied is resistant to slipping off.

   10) A kIt for carrying out the method claimed in claim 9, comprising a heat-shrinkable sleeve and at least one generally U-shaped clip, the facing inner edges of the two prongs of the clip tapering towards each other towards their free ends.

   11) A generally U-shaped clip for use in the method claimed in claim 9, the facing inner edges of the two prongs of the clip tapering towards eahc other towards their free ends.

   12) A method of forming a sealed enclosure around a branch-off. the method being substantially as ere cescrloec with reference to the accompanying drawings, 13) A kit for carrying out the method claimed in claim 12, the kit being substantially as herein described with reference to the accompanying drawings.

   14) A generally U-shaped clip substantially as herein described with reference to Figures 1 to LI or Figure 5 of the accompanying drawings.