Cable seal

A seal for sealing between a cable and a casing enclosing part of the cable includes a wall member having a plurality of substantially concentric removable portions which may selectively removed to provide a cable aperture of required diameter through the wall member. The seal also includes sealing material retained by the wall member, which seals, in use, around a cable extending through the cable aperture in the wall member. When a removable portion of the wall member is removed, a corresponding portion of the sealing material is also removed, thereby providing a cable aperture of the required diameter through the sealing material.

FIELD OF THE INVENTION 
The present invention relates to cable seal for sealing between a cable and 
a casing enclosing part of the cable. The casing may comprise a cable 
slice closure casing, and consequently the invention further relates a 
cable splice closure including one or more cable seals. The casing may 
alternatively be for attaching to, and sealing, an end of a duct, and 
consequently the invention additionally relates to a duct sealing 
apparatus including one or more such cable seals. The term cable is meant 
to include a telecommunications cable (either conductive or optical 
fiber), an electrical cable or other conductive cable, a wire or an 
optical fiber. 
BACKGROUND OF THE INVENTION 
U.S. Pat. Nos. 4,857,672 and 4,822,954 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. 
SUMMARY OF THE INVENTION 
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 of the wall member is removed, a 
corresponding portion of the sealing material is also removed, preferably 
automatically, thereby providing a cable aperture of the required diameter 
through the sealing material. 
The seal according to the invention has the advantage that, in addition to 
each wall member, it includes sealing material retained by the wall 
member, and when a removable portion of the wall member is removed, a 
corresponding portion of the sealing material is also removed, preferably 
automatically, thereby providing a cable aperture of the 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 of 
the sealing material. It has the further advantage that the seal is 
provided with a sufficient amount of sealing material for sealing any of a 
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 of the 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 of the 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 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. 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 of the sealing material also displaces some of 
the 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 of the removable portions of the seal is preferably achieved by 
cutting, tearing or pulling the portions away from the remainder of the 
seal. Advantageously, between the removable portions of the wall member(s) 
are portions of the wall member(s) of reduced thickness and/or strength 
which may, for example, be cut, and/or which is frangible. Alternatively, 
the removable portions of the 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 of the 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 of the invention, each removable portion of 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 of the sealing material and a cable extending through the seal. More 
preferably, each retaining portion preferably extends generally, or 
substantially, parallel to such a cable or axially inwardly. The retaining 
portions may, for example, project from a major surface of each wall 
member which faces towards the sealing material. Each retaining portions 
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 from 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 each retaining portion 
closest to a cable extending through the seal to be flexed against the 
cable. This has the advantage that the compression of the sealing 
material, which might otherwise result in exudation of the sealing 
material out of the 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. 
Each retaining portion may advantageously have substantially the same 
cross-sectional shape as the remainder of the removable portion of which 
it comprises a part. For example, 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 removable portion of sealing material is preferably separated from an 
adjacent removable portion of the wall member by a gap. This gap may 
facilitate the removal of the 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 of the 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, of the wall member. Advantageously, if, in use, the sealing 
material of the seal is compressed, some of the sealing material is forced 
into each such gap. 
The seal according to the invention is preferably split to allow side-entry 
of a cable into 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 of 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 of the seal to each cable aperture, so that 
each cable aperture may be opened-out to receive a cable by side-entry. 
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 plastic material, e.g. 
polypropylene, and/or from an elastic material, e.g. an elastomer, 
especially natural or synthetic rubber. The sealing material ray, 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) of no 
more than 80 g, more preferably no more than 70 g, especially no more than 
60 g. A particularly preferred hardness range is 45 g to 60 g. 
Additionally or alternatively, the sealing material preferably has a cone 
penetration as measured by ASTM D217 of at least 50 (10.sup.-1 mm), more 
preferably at least 100 (10.sup.-1 mm), even more preferably at least 200 
(10.sup.-1 mm), and preferably no greater than 400 (10.sup.-1 mm), 
especially no greater than 350 (10.sup.-1 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 of the gel may for example comprise an elastomer, 
or a block copolymer having relatively hard blocks and relatively 
elastomeric blocks. Examples of such copolymer include styrenediene 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 
napthenic 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 of a cable splice closure. Accordingly, 
a second aspect of the invention provides a cable splice closure, 
comprising a casing to enclose the cable splice, and one or more seals 
according to the first aspect of the invention, to seal an end of the 
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 of the invention 
provides a duct sealing apparatus, comprising a casing for attaching to, 
and sealing, an end of a duct, and one or more seals according to the 
first aspect of the invention, to seal between the casing and one or more 
cables extending through the casing and the duct.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1a and 1b show 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 of the 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. As shown in FIG. 1b, the seal 1 is split into two separate 
pieces through the cable aperture 7, each piece having part of the 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. 
FIG. 2 shows the cable aperture region of one of the pieces of the seal 1, 
in greater detail. The piece has half of the cable aperture 7 in the form 
of a semi-cylindrical recess. The diameter of the cable aperture without 
any of the removable portions 5 removed is advantageously of the 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 of a 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 of the wall 
member projecting, substantially co-axially with the cable aperture 7, 
from the major surface of the 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 FIG. 2. To 
facilitate this flexing of the 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 of the sealing material 
next to the cable in the cable aperture. 
It can also be seen from FIG. 2 that each removable portion 5 of the wall 
members 3 has a corresponding portion of sealing material 9 which is 
removed when, in use, the removable portions 5 are removed. Each portion 
of sealing material 9 which is so removed is separated from each adjacent 
removable portion 5 of the wall members by a gap 15. The cuttable portions 
11 if 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 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 
of the 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 of the 
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. 
FIGS. 3a-3c show a preferred cable splice closure utilizing 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 of the base 17, and the 
cover 19 is closed on top of them. The seals 1 shown in FIG. 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.