CABLE ENCLOSURE

Abstract: An enclosure for mounting on a substrate, comprising a rigid tubular support member (4) and revolvable elastic sleeve (6) having a double wall enclosing lubricant (14) sealed therein, wherein the sleeve is mounted on the support member in an expanded state with a portion of the inner wall of the sleeve secured (16) to the support member so that the sleeve can be revolved over the end of the support member to contract elastically to a less expanded state while retaining a portion of the sleeve on the support.

Description: Cable Enclosure This invention relates to an enclosure, and particularly though not exclusively to one for use with a cable, for example a cable joint or termination. The enclosure of the invention finds particular application to electric, and especially power, cables, but is also applicable to other cables, for example telecommunications cables. For convenience only and not by way of limitation, the invention will be discussed with reference to an electric power cable joint. When two power cables are to be jointed, the outer layers thereof are successfully stripped back to expose the conductors. The electrical connection between the conductors is then effected in any convenient manner. The outer layers of the cables then need to be replaced by fresh components in order to restore electrical and mechanical integrity, and this may be effected in various ways, using various technologies, including tape wrapping. Heat shrink technology, for example using heat recoverable polymeric sleeves and kits from Tyco Electronics Raychem GmbH, has been known and used successfully for many years, often in preference to the traditional filling of a casing with hot bitumen or epoxy resin. As an alternative to heat-shrinkable sleeves, elastic sleeves that are recoverable around a cable joint without the application of heat thereto have been available for some time. One example of such a sleeve is that sold by 3M under the tradename PST, which consists of an elastomeric cylindrical sleeve that is held out in an expanded configuration by a rigid inner spiral member. These sleeves, mounted on their hold-outs, are positioned over the cable joint, and the hold-out is then removed from inside the sleeve. Other elastic sleeves are known which are held out in an expanded configuration on a rigid support member with an end of the sleeve folded back on top of the portion of the sleeve which is in direct contact with the tubular support, as described by 3M in EP-A-0767523. When the tubular hold-out is positioned over the cable joint, the folded-back portion of the sleeve may be rolled over the end of the hold-out to form a bridge that contracts elastically down onto the cable. It is observed in EP-A-0767523 that the removal of the spiral holdouts is problematic and that physical stress relief adaptations are necessary for the folded-back sleeves. WO-A-9113756 describes a revolvable double-wall elastomeric sleeve, available from Tyco Electronics Raychem GmbH under the tradename RAYVOLVE, that has a lubricant enclosed by the double wall of the sleeve. This sleeve, which is not previously expanded, can be rolled onto a cable to one side of the jointing area, which usually involves having to increase the sleeve diameter by up to a factor of two or more, and subsequently can be revolved back across the formed joint. The lubricant facilitates the revolving of the two, inner and outer, walls of the sleeve over one another. The lubricant remains within the sealed double wall of the sleeve, allowing the sleeve to be revolved away and re-used, if the joint needs to be re- entered. A RAYVOLVE sleeve is usually employed to provide at least some of the insulation over the cable joint, and may, for example, functionally replace the outer jacket of the cable at the cable joint. It is an object of the present invention to provide an improved enclosure for a substrate. In accordance with one aspect of the present invention, there is provided an enclosure for mounting on a substrate, comprising a rigid tubular support member and a revolvable elastic sleeve having a double wall enclosing lubricant sealed therein, wherein the sleeve is mounted on the support member in an expanded state with a portion of the inner wall of the sleeve secured to the support member so that the sleeve can be revolved over the end of the support member to contract elastically to a less expanded state while retaining a portion of the sleeve on the support. Thus, the revolvable sleeve is retained attached to the support member but is able to be revolved off the member so as to be recovered to a smaller size around the underlying substrate, in conformity therewith. The retention of the sleeve at one end on the support member allows the positioning of the other end of the sleeve on the substrate after deployment to be controlled, thus ensuring, for a given enclosure and substrate, not only that sufficient overlap onto the substrate is achieved, but also that the sleeve does not roll too far off the support member. The revolvable nature of the sleeve inherently facilitates re-entry of the substrate, for example a cable joint, if required. The provision of the support member provides for storage of the sleeve prior to initial installation and also during any re-entry of the substrate. It has been found that the support member may be economically manufactured, for example by simply cutting and de-burring suitable lengths from an extruded plastics tube, advantageously omitting any special stress relief adaptations. This advantage may possibly result from the self-reinforcing effect of the double-wall sleeve, which resists damage at the end regions of the support member more effectively that single- wall folded-back sleeves. The sleeve may be secured to the support member by any suitable means. It is envisaged that this may be by bonding, for example using an interposed adhesive, and/or by mechanical compression around the outside of the sleeve, for example using a hose clamp or roll spring, and/or by being compressed onto the inner surface of the support member by an inner expandable means. The sleeve may thus conveniently be sealed to the support member. Typically, the support member is of substantially elongate cylindrical shape, with the sleeve being secured to or adjacent one end thereof. A. further sleeve, similar to the aforementioned sleeve, may be mounted on and secured to the support member, typically providing an arrangement whereby the sleeves can be revolved down off respective ends of the support member onto the substrate, for example a cable each side of a joint, whilst remaining secured on to the support member by the said portions. The or each sleeve is preferably a RAYVOLVE sleeve. Such sleeves are disclosed in European Patent Application Publication Nos. 0209 399, 0210 061, 0 210807 and 0212 851, the entire disclosures of which are incorporated herein by this reference, A sealant such as a mastic, may be provided, advantageously on the substrate or on the sleeve, to seal the sleeve or sleeves to the substrate. The rigid support member can thus provide mechanical protection for the substrate. Advantageously, it is made from a plastics material. The support member may also provide an electrical function, especially when the enclosure surrounds an electric cable. For example, it may provide an electrically insulating layer. The support member may be made of metal, or otherwise be metallic, for example being metallised, and thus may provide electrical continuity or earthing over the substrate, or electrical screening thereof. Storing the double-walled lubricated elastic sleeve in an expanded configuration, on the rigid support member, avoids the need to urge it into an expanded condition as it is revolved up onto a substrate, such as a cable joint. Unlike known single layer expanded elastic sleeves, the lubricant stays in place, it does not dry out, and it is not exuded from the interface between the sleeve and the support member, so that removal of the sleeve from the tubular hold-out member is facilitated. The sleeve may be expanded to between, say, two and four times its original diameter, thus providing an enclosure, having a suitably sized rigid support member, with a good range-taking capability. The sleeve can thus be revolved off the support member onto the substrate with the application of little force, even though its rubber wall has been stored in a stretched configuration for some time, with the enclosed lubricant having been subjected to high pressure. The enclosure has a comparatively small overall length, since the sleeve (or sleeves) can be stored thereon within its overall length. Embodiments of an enclosure, each in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a section through a first embodiment of enclosure prior to its installation over a power cable joint; Figure 2 is a simplified partial section through the installed enclosure of Figure 1; Figure 3 is a section through a detail of a second enclosure prior to deployment; Figure 4 is a section through the second enclosure in its deployed configuration; Figure 5 is section through a detail of a third enclosure prior to deployment; and Figure 6 is section through the third enclosure in its deployed configuration. Referring to Figures 1 and 2, an enclosure 2 comprises a tubular right-cylindrical rigid elongate plastics tube 4. A revolvable RAYVOLVE sleeve 6, which has been expanded to three times its original diameter is mounted on one end 8 of the tube 4. The sleeve 6 has an inner wall 10 that lays along the outer surface of the tube 4 and, contiguous therewith, an outer wall 12. A liquid lubricant 14 is trapped between the walls 10 and 12 of the sleeve 4 so as to allow free revolving movement of the sleeve. A strip of adhesive 16 extends around the outer circumference of the tube 4 adjacent its end 8 and serves to secure the inner wall 10 of the sleeve 6 to the tube 4. A further RAYVOLVE sleeve 18, substantially identical with the sleeve 6, is similarly secured at the other end 20 of the tube 4. Components of the sleeve 6 corresponding to those of the sleeve 4 are identified with the addition of the reference "a". Figure 1 shows the enclosure 2 in its configuration after manufacture, with the two RAYVOLVE sleeves 6 and 18 expanded and secured thereto, prior to the mounting of the enclosure 2 on to a substrate. Figure 2 shows the enclosure 2 of Figure 1 subsequent to its mounting on a substrate, which in this embodiment is exemplified as an electrical power cable joint. Thus, the enclosure 2 is shown in Figure 2 after it has been mounted so as to encompass a joint region 30 between two electrical power cables 32 and 34. It will be appreciated that the particular enclosure 2 will have been selected such that the tube 4 has a diameter that allows it easily to include the joint region 30. Also, the enclosure 2 will have been selected such that the length of the tube 4 extends sufficiently beyond the joint region 30. Prior to forming the joint between the cables 32 and 34, the enclosure 2 is parked to one side over one of the cables. The joint between the conductors of the two cables is made in a convenient manner, for example by means of a crimp, primary insulation is provided around the jointed conductors, and additional insulation and screening as required in dependence upon the power rating and structure of the cables 32 and 34 is applied. The enclosure 2 is then removed from its parked position and centralised over the joint region 30. The RAYVOLVE sleeves 6 and 18 are revolved off their respective ends 8 and 20 of the tube 4 and allowed to contract down to the outer jackets 36 and 38 respectively of the cables 32 and 34. It will be appreciated that the sleeves 6 and 18 will be retained on the tube 4 by means of the respective adhesive strips 16 and 16a. Furthermore, a sealant 40, 42, is provided so as to lie between the respective sleeves 6 and 18 and the underlying outer jacket 36, 38 of the cables 32 and 34, so as to seal the sleeve 6, 18 on to the respective cable 32, 34. Thus, the enclosure 2 in its recovered position, as shown in Figure 2, provides mechanical protection by means of its rigid tube 4 around the joint region 30 of the cables, and provides sealing on to the cable jackets 36 and 38 at each side thereof. It will be appreciated that should there be a need to re-enter the joint region 30, this may be easily accomplished by rolling the sleeves 6 and 18 back up onto the tube 4 and moving the released enclosure 2 to one side, thereby leaving the enclosure 2 available for re-use. The enclosure of the first embodiment has been described with the revolvable sleeves 6 and 18 secured to the plastics tube 4 by being bonded thereto, using an adhesive 16, 16a respectively. It is envisaged, however, that the or each revolvable sleeve may be secured to the support member alternatively, or additionally, by a mechanical clamping means, which need not require the formation of a bond. Arrangements of such enclosures are shown in Figures 3 to 6, which show a detail only of the securement of the revolvable sleeve to the support member, other features of these enclosures may correspond to those disclosed above. Referring to Figures 3 and 4, a generally circular hose clamp 50 is located around one end 52 of a revolvable sleeve 54, adjacent one end 56 of a rigid cylindrical plastics tube 58. As with the enclosure of the first embodiment, the enclosure formed thereby is mounted over a substrate and the sleeve 54 is revolved over the end 56 of the tube 58 into the deployed position as shown in Figure 4, with the sleeve end 52 clamped around its outer surface to the tube 58 by the hose 50. It will thus be appreciated that the inwardly-directed compression of the hose clamp 50 retains the sleeve 54 on the tube 58 at all times. In a further embodiment of a clamping means shown in Figures 5 and 6, one end 70 of a revolvable sleeve 72 is folded inwardly over one end 74 of a cylindrical rigid plastics tube 76 and is held in place by a spiral spring 78 located around the inner circumference thereof. It will be appreciated that the spring 78 has a tendency to uncoil outwards and thereby compresses the end 70 of the sleeve 72 against the inner circumference of the end 74 of the tube 76. The remaining length 80 of the sleeve 72 lies along the outer surface of the tube 76. To prevent any tendency of the sleeve portion 80 to revolve off the tube 76 of its own accord, an outer circumferential fixing device 82 is located therearound at the opposing end 84 of the sleeve 72. The fixing device 82 may conveniently be breakable by hand, whereby the sleeve portion 80 may be revolved over the outer surface of the tube 76 and deployed down onto the substrate, as can be seen from Figure 6. Advantageously, breaking of the fixing device 82 may trigger self-deployment of the sleeve 72 down onto the substrate.

Claims: Claims 1. An enclosure for mounting on a substrate, comprising a rigid tubular support member and a revolvable elastic sleeve having a double wall enclosing lubricant sealed therein, wherein the sleeve is mounted on the support member in an expanded state with a portion of the inner wall of the sleeve secured to the support member so that the sleeve can be revolved over the end of the support member to contract elastically to a less expanded state while retaining a portion of the sleeve on the support. 2. An enclosure according to claim 1, wherein the support member is of substantially elongate cylindrical shape, and the sleeve is secured thereto in the region of one end thereof. 3. An enclosure according to claim 2, comprising a further double- alled elastic sleeve having lubricant sealed therein, the further sleeve being mounted on the support member in an expanded configuration with a portion of its inner wall secured to the support member in the region of the other end thereof. 4. An enclosure according to any one of the preceding claims, wherein the or each sleeve is secured to the support member by adhesive. 5. An enclosure according to any one of the preceding claims, wherein the or each sleeve is secured to the support member by a clamping means. 6. An enclosure according to any one of the preceding claims, wherein the support member is made of a plastics material. 7. An arrangement comprising a substrate located within an enclosure according to any one of the preceding claims, wherein the or each sleeve has been revolved along the support member and contracted onto the substrate. 8. An arrangement according to claim 7, wherein a further portion of the inner wall of the or each sleeve is sealed on to the substrate. . An arrangement according to claim 7 or 8, wherein the substrate comprises an electric cable, preferably a cable joint or cable termination. 10. An arrangement according to claim 9, wherein the support member provides electrical screening of the cable.

Inventors: HOFMANN JENS, SCHUMACHER HERBERT, HOFMANN, JENS, SCHUMACHER, HERBERT
Applicants: HOFMANN JENS, SCHUMACHER HERBERT, TYCO ELECTRONICS LTD UK, TYCO ELECTRONICS RAYCHEM GMBH, HOFMANN, JENS, SCHUMACHER, HERBERT, TYCO ELECTRONICS UK LIMITED
Application year: 2001
Main classification: H02G15
IPC codes: H02G15