CABLE SEAL

Abstract: A seal for sealing between a cable and a casing enclosing part of the cable, comprising: (a) a wall member (3) having a plurality of substantially concentric removable portions (5) which may be selectively removed to provide a cable aperture of required diameter through the wall member (3); and (b) sealing material (9) retained by the wall member (3), which seals, in use, around a cable extending through the cable aperture in the wall member (3); wherein, in use, when a removable portion (5) of the wall member (3) is removed, a corresponding portion of the sealing material (9) is also removed, thereby providing a cable aperture of the required diameter through the sealing material (9).

Description: Cable Seal The present invention relates to a cable seal for sealing between a cable and a casing enclosing part ofthe cable. The casing may comprise a cable splice closure casing, and consequently the invention further relates a cable splice closure including one or more such cable seals. The casing may alternatively be for attaching to, and sealing, an end of a duct, and consequently the invention additionally relates to duct sealing apparatus including one or more such cable seals. By a cable is meant a telecommunications cable (either conductive or optical fibre), an electrical cable or other conductive cable, a wire or an optical fibre. United States Patents 4857672 and 4822954 each disclose a cable closure end cap which may be adapted to accommodate more than one cable extending into an end of a cable closure. The end cap comprises first and second end cap members positioned against one another and forming a wall member which has at least one longitudinal cable bore. Each cable bore is defined by a plurality of substantially concentric substantially cylindrical ring members spaced from one another by transverse wall sections. The concentric ring members can be selectively cut out to accommodate a range of sizes of cable. According to a first aspect of the present invention. there is provided a seal for sealing between a cable and a casing enclosing part of the cable, comprising: (a) a wall member having a plurality of substantially concentric removable portions which may be selectively removed to provide a cable aperture of required diameter through the wall member; and (b) sealing material retained by the wall member, which seals, in use, around a cable extending through the cable aperture in the wall member; wherein, in use, when a removable portion ofthe wall member is removed, a corresponding portion ofthe sealing material is also removed, preferably automatically, thereby providing a cable aperture ofthe required diameter through the sealing material. The seal according to the invention has the advantage that, in addition to the or each wall member, it includes sealing material retained by the wall member, and when a removable portion ofthe wall member is removed, corresponding a portion ofthe sealing material is also removed, preferably automatically, thereby providing a cable aperture ofthe required diameter through the sealing material. This is advantageous because it provides a seal which is able to accommodate a range of sizes of cable while providing a substantially watertight seal around the cables by virtue ofthe sealing material. It has the further advantage that the seal is provided with a sufficient amount of sealing material for sealing any ofa range of sizes of cable, and in order to adapt the seal to fit a particular size of cable, the installer merely needs to remove the appropriate amount of sealing material. The seal may have one or a plurality of cable apertures extending through it. If two or more such apertures are present, preferably each aperture has its own series of substantially concentric removable portions. The seal according to the invention may or may not be supplied with one or more cable apertures already extending through it, i.e. the installer may or may not have to remove a portion ofthe seal in order to obtain an aperture. If the seal is supplied with one or more cable apertures already extending through it, it is preferably also provided with a plug for each aperture, in case one or more ofthe apertures will not contain a cable. Preferably the seal further comprises a second wall member substantially parallel to the first wall member and having a plurality of substantially concentric removable portions corresponding to those ofthe first wall member and which may be selectively removed to provide a corresponding cable aperture of required diameter through the second wall member, the sealing material being retained between the two wall members. Advantageously, in use the wall members may be forced towards each other, thereby applying compression to the sealing material and displacing some of it laterally inwards against a cable extending therethrough. Preferably such longitudinal compression ofthe sealing material also displaces some ofthe sealing material laterally outwards against the casing. In this way, a tight seal between the cable and the casing can preferably be achieved. The removal ofthe removable portions ofthe seal is preferably achieved by cutting, tearing or pulling the portions away from the remainder ofthe seal. Advantageously, between the removable portions ofthe wall member(s) are portions ofthe wall member(s) of reduced thickness and/or strength which may, for example, be cut, and/or which is frangible. Alternatively, the removable portions ofthe wall member(s) may comprise interlocking portions for example, which may be separated. The removable portions are preferably substantially annular or semi-annular, thereby to conform to a cable that has a generally circular cross-section. However, a wide variety of shapes are possible, depending on the particular requirements ofthe seal. A single cable aperture may, for example, be required to accommodate two or more cables, in which case the removable portions may, for example, be oval or semi- oval in cross-section. In preferred embodiments ofthe invention, each removable portion ofthe or each wall member further comprises at least one retaining portion, such that for each diameter of cable aperture which may be selected, there is at least one retaining portion which, in use. substantially prevents exudation of the sealing material next to the cable through the cable aperture in the wall member. This has the advantage that no matter which diameter of cable needs to be sealed, and consequently no matter how many (if any) removable portions need to be removed from the seal, the retention of the sealing material is normally equally good. Each retaining portion (where present) preferably extends, in use, between part ofthe sealing material and a cable extending through the seal. More preferably, each retaining portion preferably extends generally, or substantially, parallel to such a cable. The retaining portions may, for example, project from a major surface ofthe or each wall member which faces towards the sealing material. Each retaining portion is preferably separated by a gap from an adjacent retaining portion, i.e. from a retaining portion which comprises part of an adjacent removable portion. There may be sealing material and/or air between each adjacent retaining portion. In embodiments in which the seal comprises a pair of wall members having sealing material between them, preferably each wall member has a series of retaining portions, and more preferably the retaining portions of each series are spaced apart form each other, at least before the wall members are forced towards each other to compress the sealing material. Advantageously, each retaining portion (where present) may be flexible, e.g. so that it can conform to a cable. More advantageously, in use the sealing material is compressed, thereby causing the or each retaining portion closest to a cable extending through the seal to be flexed against the cable. This has the advantage that the compression ofthe sealing material, which might otherwise result in exudation ofthe sealing material out ofthe cable aperture, actually enhances, or at least does not worsen, its retention, since by causing the retaining portion to be flexed against the cable, it normally substantially closes a gap between the wall member and the cable through which the sealing material might otherwise have escaped. The or each retaining portion may advantageously have substantially the same cross-sectional shape as the remainder ofthe removable portion of which it comprises a part. For example, the or each retaining portion may be circular, semi-circular, oval, or semi-oval in cross-section, e.g. being generally cylindrical or semi-cylindrical in shape. Additionally or alternatively each retaining portion may comprise one or more flaps or the like. Each portion of sealing material which is removed, in use, when a removable portion ofthe or each wall member is removed, is preferably separated from the or each adjacent removable portion ofthe or each wall member by a gap. This gap may facilitate the removal ofthe wall member and sealing material portions, for example by providing a region free from sealing material for a knife or other cutting tool to cut. This region where there is a gap between some ofthe sealing material and a portion of the wall member may be spanned by a frangible portion, or a portion of reduced thickness and/or strength, ofthe wall member. Advantageously, if, in use, the sealing material ofthe seal is compressed, some ofthe sealing material is forced into the or each such gap. The seal according to the invention is preferably split to allow side-entry ofa cable into the or each cable aperture. The seal may, for example, be split into two or more separate or separable pieces, e.g. half pieces, each piece having part ofthe or each cable aperture, which pieces may be brought together to form the one or more cable apertures. Alternatively, the seal may not be completely split, i.e. the split may comprise a slit or a slot extending from the periphery ofthe seal to the or each cable aperture, so that the or each cable aperture may be opened-out to receive a cable by side-entry. The or each wall member is preferably harder (e.g. as measured by a Stevens- Volland texture analyser) than the sealing material. The wall member(s) is/are preferably formed from a plastics material, e.g. polypropylene, and/or from an elastic material, e.g. an elastomer, especially natural or synthetic rubber. The sealing material may, for example, comprise gel (described in more detail below), polymeric foam, elastomeric material and/or mastic or the like. It may additionally or alternatively comprise adhesive material, especially pressure-sensitive adhesive. It is preferred that the sealing material have a Stevens- Volland hardness (i.e. a hardness as measured by a Stevens- Volland texture analyser) ofno more than 80g, more preferably no more than 70g, especially no more than 60g. A particularly preferred hardness range is 45g to 60g. Additionally or alternatively, the sealing material preferably has a cone penetration as measured by ASTM D217 of at least 50 (10 " 'mm), more preferably at least 100 (10 ' 'mm), even more preferably at least 200 (10 ' 'mm), and preferably no greater than 400 (10 " 'mm), especially no greater than 350 (lO-'mm). As mentioned above, a particularly preferred sealing material comprises gel. The gel may, for example, comprise silicone gel, urea gel, urethane gel, thermoplastic gel, or any suitable gel or gelloid sealing material. Preferred gels comprise liquid (e.g. oil)-extended polymer compositions. The polymer composition ofthe gel may for example comprise an elastomer, or a block copolymer having relatively hard blocks and relatively elastomeric blocks. Examples of such copolymers include styrene- diene block copolymers, for example styrene-butadiene or styrene-isoprene diblock or triblock copolymers e.g. as disclosed in international patent publication number WO 88/00603. Preferably, however, the polymer composition comprises one or more styrene-ethylene-propylene-styrene block copolymers, for example as sold under the Trade Mark 'Septon' by Kuraray of Japan. The extender liquids employed in the gel preferably comprise oils. The oils may be hydrocarbon oils, for example paraffinic or napthenic oils, synthetic oils for example polybutene or polypropene oils, and mixtures thereof. The preferred oils are mixtures of non-aromatic paraffins and naphthenic hydrocarbon oils. The gel may contain additives, e.g. such as moisture scavengers (e.g. Benzoyl chloride), antioxidants, pigments and fungicides. As indicated above, a preferred use for the seal according to the first aspect of the invention is as part ofa cable splice closure. Accordingly, a second aspect ofthe invention provides a cable splice closure, comprising a casing to enclose the cable splice, and one or more seals according to the first aspect ofthe invention, to seal an end ofthe casing. Another preferred use for the seal is to seal a duct which has one or more cables extending through it. Accordingly, a third aspect ofthe invention provides a duct sealing apparatus, comprising a casing for attaching to, and sealing, an end ofa duct, and one or more seals according to the first aspect ofthe invention, to seal between the casing and one or more cables extending through the casing and the duct. The invention will now be described, by way of example, with reference to the accompanying drawings, of which: Figure 1 shows a seal according to the invention; Figure 2 shows a detail ofthe seal shown in Figure 1 ; and Figure 3 shows a cable splice closure including two seals according to the invention Figure 1 shows a seal 1 according to the invention, comprising a pair of wall members 3 having a plurality of substantially concentric removable portions 5 which may be selectively removed to provide a cable aperture 7 of required diameter through the wall members. Between the wall members 3 is sealing material 9 (preferably gel). In use, the wall members 3 are forced closer together, causing some ofthe sealing material between them to be displaced laterally inwards into the cable aperture 7, thereby sealing against a cable in the aperture, and laterally outwards around the periphery of the seal, thereby sealing against a casing in which the seal is placed. A shown in Figure lb, the seal 1 is split into two separate pieces through the cable aperture 7, each piece having part ofthe cable aperture, to allow side-entry of a cable into the aperture. The sealing material in each piece advantageously seals the split when the two pieces are brought together. Figure 2 shows the cable aperture region of one ofthe pieces ofthe seal 1, in greater detail. The piece has half of the cable aperture 1 in the form ofa semi¬ cylindrical recess. The diameter ofthe cable aperture without any ofthe removable portions 5 removed is advantageously ofthe correct size for the smallest diameter cable to be sealed by the seal. The seal may, alternatively, have no cable aperture initially, an aperture only being provided upon the removal ofa central removable portion. The concentric removable portions 5 of each wall member are separated from each other by concentric portions 11 of reduced thickness which can be cut with a cutting tool (e.g. a knife). An integral part of each removable portion 5 of each wall member is a retaining portion 13 for retaining sealing material next to a cable in the cable aperture, which comprises a semi-cylindrical portion ofthe wall member projecting, substantially co¬ axially with the cable aperture 7, from the major surface ofthe wall member which faces towards the sealing material. Each retaining portion 13 is advantageously flexible, and when the sealing material 9 is put under compression (e.g. by forcing the wall members 3 closer together), the sealing material preferably forces the retaining portions closest to a cable in the cable aperture to be flexed against the cable, e.g. as shown in dotted outline in Figure 2. To facilitate this flexing ofthe retaining portions, they may be slit so that they each comprise two or more flaps or the like. Because each removable portion 5 has its own retaining portion 13, for each diameter of cable aperture which may be selected there is at least one retaining portion which substantially prevents exudation ofthe sealing material next to the cable in the cable aperture. It can also be seen from Figure 2 that each removable portion 5 ofthe wall members 3 has a corresponding portion of sealing material 9 which is removed when, in use, the removable portions 5 are moved. Each portion of sealing material 9 which is so removed is separated from the or each adjacent removable portion 5 ofthe wall members by a gap 15. The cuttable portions 11 of reduced thickness in the wall members span these gaps 15, and the fact that these gaps are present means that the removal of each corresponding portion of sealing material is made easier than would otherwise be the case. It is preferred that the sealing material have a high degree of cohesiveness to facilitate the production ofthe gaps 15, and for this purpose gel is an ideal sealing material. It is particularly preferred that the gaps 15 extend from one wall member 3 to the other, so that each corresponding portion of sealing material is entirely separated from its adjacent portion(s). However, this may not always be possible, and it is generally sufficient for the gaps 15 to be between the sealing material 9 and each adjacent retaining portion 13 immediately adjacent to the inwardly-facing major surface of each wall member 3. When the sealing material is compressed in use, some ofthe sealing material may advantageously substantially fill the gaps 15. Preferably, therefore, there is sufficient sealing material to fill the gaps 15 and to seal against a cable in the aperture. Figure 3 (a to c) shows a preferred cable splice closure utilising cable seals according to the invention. The closure comprises a casing having a base 17 and a cover 19, and an o-ring seal 21 sealing between the base and the cover. The seals 1 are inserted into the ends ofthe base 17, and the cover 19 is closed on top of them. The seals 1 shown in Figure 3 each have four cable apertures 7. Plugs 23 may be provided to block-off any unused cable apertures. Also shown are fastening devices 25 to fasten the cables 27 to the casing.

Claims: Claims 1. A seal for sealing between a cable and a casing enclosing part ofthe cable, comprising: (a) a wall member having a plurality of substantially concentric removable portions which may be selectively removed to provide a cable aperture of required diameter through the wall member; and (b) sealing material retained by the wall member, which seals, in use, around a cable extending through the cable aperture in the wall member; wherein, in use, when a removable portion ofthe wall member is removed, a corresponding portion ofthe sealing material is also removed, thereby providing a cable aperture ofthe required diameter through the sealing material. 2. A seal according to claim 1, further comprising a second wall member substantially parallel to the first wall member and having a plurality of substantially concentric removable portions corresponding to those of the first wall member and which may be selectively removed to provide a corresponding cable aperture of required diameter through the second wall member, the sealing material being retained between the two wall members. 3. A seal according to claim 2, in which, in use, the wall members are forced towards each other, thereby applying compression to the sealing material and displacing some of it laterally against a cable extending therethrough. 4. A seal according to any preceding claim, in which each removable portion of the or each wall member further comprises at least one retaining portion, such that for each diameter of cable aperture which may be selected, there is at least one retaining portion which, in use, substantially prevents exudation ofthe sealing material next to the cable through the cable aperture in the wall member. 5. A seal according to claim 4, in which each retaining portion extends, in use, between part ofthe sealing material and a cable extending through the seal. 6. A seal according to claim 4 or claim 5, in which each retaining portion is flexible. 7. A seal according to claim 6 when dependent on claim 5, in which, in use, the sealing material is compressed, thereby causing the or each retaining portion closest to a cable extending through the seal to be flexed against the cable. 8. A seal according to any preceding claim, in which each portion of sealing material which is removed, in use, when a removable portion ofthe or each wall member is removed, is separated from the or each adjacent removable portion ofthe or each wall member by a gap. 9. A seal according to claim 8, in which, in use, the sealing material is compressed, thereby forcing some ofthe sealing material into the or each said gap. 10. A seal according to any preceding claim, which is split to allow side-entry ofa cable into the cable aperture. 11. A seal according to any preceding claim, in which, at least in use, the or each wall member and the sealing material have a plurality of said cable apertures extending therethrough. 12. A cable splice closure, comprising a casing to enclose the cable splice, and one or more seals according to any preceding claim, to seal an end ofthe casing. 13. Duct sealing apparatus, comprising a casing for attaching to, and sealing, an end ofa duct, and one or more seals according to any preceding claim, to seal between the casing and one or more cables extending through the casing and the duct.

Inventors: DAMM JESPER, DAMM, JESPER
Applicants: DAMM JESPER, RAYCHEM LTD, RAYCHEM SA NV, DAMM, JESPER, N.V. RAYCHEM S.A., RAYCHEM LIMITED
Application year: 1996
Main classification: H02G15
IPC codes: H02G15