Note: Descriptions are shown in the official language in which they were submitted.
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~a
The present invention relates to a seal, and in particular to a ring seal. The seal may
generally be used to seal between any two surfaces, but it has particular utility in electrical or
telecommul ~ic~lions cable splice closures.
United States Patent No. 45~8174 (AT&T Bell Laboratories) .::,,.loses a closure for a
cable splice which has two mating covers and two end plate asser"blies. A peripheral channel
in each end plate is filled with a circu" ~r~r~ntial gasket which seals between the periphery of
each end plate and the surrounding covers. The ends of each circumferential gasket are
connected together. This is accol I ~,GIished by forming each circumferential gasket with a pair
of longitudinally extending passageways. At the junction of the ends of the gasket, pins are
positioned in the passageways such that they extend from one end. The other end is brought
into juxtaposition with the one end and the extending pins are caused to be positioned in the
passageways of the other end.
Ring seals for cable splice closures, which col I ,prise a single ela:,lul I ,eric tube, the
ends of which are joined together by means of a solid connection pin, are also known.
An object of the present invention is to provide an elongate compressible seal in which
two ends can be joined together firmly, yet substantially without detriment to the
col"pl~ssibilily of the seal at the join. Another object of the invention is to provide an
improved seal which is col"pr~ssible, prer~,dbly subsldn" "y uniformly compressible, along
substantially its entire length. Where the seal is, in use, a ring seal, the seal is consequently
preferably co~"plessil~le around sub:,ldnl;a:ly the entire ring.
According to the invention, there is provided an elongate compressible seal in which,
in use, two ends are joined together by means of at least one connection pin located in, and
extending between, at least one opening in each end, wherein the or each connection pin is
hollow and con ,~ !e and the seal is therefore co" ",rt:ssiL,le at the join between the two
ends. Pl~r~rdbly, the seal is hollow, i.e. hollow in addition to being hollow at each end by
virtue of the or each opening.
The invention has the advantage that, because the connection pin is hollow and
compressible, the seal is compressible at the join between the two ends. This is in contrast
with the known tubular ring seals mentioned above, in which the ends are joined together by
means of a solid connection pin, and consequently the seal is substantially incompressible at
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the join, or at least is significantly less col "I~r~ssible at the join than around the remainder of
the seal. This generally means that with these known ring seals, there is a region of the seal
which has significantly poorer sealing cha~ d~Lt::l islics than the remainder of the seal. In
addition, with tnese known ring seals it is generally necessary, when installing the cable splice
closure, to orientate the ring seal such that the join (which has poor sealing c hdl d~ ristiCs) is
not located at the so-called triple point (i.e. the point of i"l~r~e~,Lion of the ring seal and the
longitudinal seal of the splice closure casing). This is because the triple point is generally the
location which needs the greatest degree of reliability from the seals if the environmental
sealing of the splice closure is to be ~ai,lldined. The seal of the invention can
advantageously be used as a circu",rt:r~r,Lial seal and/or a longitudinal seal in a cable splice
closure in which such seals meet at a triple point.
Preferably, the seal according to the invention is "c ~ licnLly co~"~,r~s~ t 1~ and/or the or
each connection pin is resiliently col"pr~s ' !e, and advantageously the seal is therefore
resiliently compressible at the join between the two ends. This normally has the advantage of
making the seal particularly reliable, since when the seal is col"pr~ssed between two
surfaces, for example, its resilience normally causes it to press against the surfaces.
The seal according to the invention may advantageously be substantially uniformly
compr~ssiLJle, in use, along suL,~Ldntially its entire length. Even more advantageously, the
seal may, along substantially its entire length, be suL,:,LdnLidlly uniformly resilient to
compression, in use. The or each join in the seal, when cor,Ldi"i"g the hollow co"")ressible
connection pin(s), therefore preferably has sL~ Ldll' 'Iy the same, or at least approximately
the same, degree of resilient col",ur~s~ .y as does the remainder of the seal. In some
embodiments of the invention, this may advantageously be achieved by using one or more
hollow col"pl~ssiL,le connection pins which have very little resilience upon being col"~,r~:ssed,
e.g. subsLdn" 'Iy negligible resilience cor,~pa~t:d to the resilience exhibited by the remainder of
the seal.
The outer diameter of the connection pin(s) is preferably greater than the diameter of
the openings in the ends of the seal in which the connection pin is, or the connection pins are,
located. This can have the advantage of enabling a tight grip to be formed between the
connection pin(s) and the ends of the seal.
The connection pin is, or pins are, prts~rdbly an interference fit in the openings in the
ends of the seal. Ad,liLionally or alternatively, however, the pin(s) and/or openings may be
profiled to interlock with each other.
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The seal is preferably a ring seal, e.g. an O-ring seal, and preferably has a
suiJsld~Lic.''y annular shape in use. The seal may, for example, extend around an end block of
a cable splice closure, to form a seal between the end block and the casing of the closure
which surrounds the end block. The two ends in the seal which are joined together by means
of the or each connection pin are preferably opposite ends of the same discrete elongate
article. The seal is therefore preferably an elongdLe seal the two ends of which are joined
together to form a closed loop. Additionally or alternatively, however, the two ends in the seal
which are joined together by means of at least one connection pin according to the invention
may be the ends of different discrete elongate articles. The seal acco, ii"g to the invention
may therefore comprise two or more discrete seals which are joined end-to-end by means of
at least one connection pin according to the invention. The seal may, for example, be a linear
seal, e.g. a longitudinal seal of a cable splice closure, and/or the seal may be a ring seal
formed from two or more discrete seals joined together.
It was mentioned above that the seal and the connection pin(s) are hollow. The seal
and the connection pin may advantageously be hollow by virtue of any suitable internal
structure. The seal itself and the connection pin(s) may, in some er"bodi",er,l~, have different
types of internal structure, but preferably they have slJb:,ldlllially the same type of internal
structure. The seal and/or the connection pin(s) may, for exdl",~,le, comprise polymeric foam,
either closed-cell foam or open-cell foam. in most preferred e",bo ii",enls however, the seal
and/or the connection pin(s) are not formed from polymeric foam.
The seal and/or the or each conne~;lion pin may advantageously be tubular. When
the or each connection pin is tubular it may, for exd"., Ir, be closed at one or both ends, but
preferably it is open at both ends. The connection pin(s) may, in some embodiments,
advantageously have a longitudinal slit. In this way the or each pin can often have very little
resilience to CO~ JreSSiOll (the advantage of which was explained above) and/or the or each
pin can grip the ends of the seal firmly. The longitudinal edges of the slit may, for exdr"~ie,
overlap.
The seal of the invention may advant~geously have at least one cavity extending
along sub.~ildi~tially its entire length, and the openings in which, in use, the or each connection
pin is located are preferably ends of the or each cavity. As mentioned above, the seal may,
for example, be tubular. Preferably, the cross-sectional didlllelér of the or each cavity is
sui sldr,l 'Iy uniform along suiJ:,ldntidlly the entire length of the seal.
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In certain preferred embodiments, the seal may be formed from sealing material,
and/or it may have sealing material as at least part of an external surface thereof. A preferred
sealing material is gel. The gel may, for example, co",prise silicone gel, urea gel, urethane
gel, thermoplastic gel, or any suitable gel or gelloid sealing material. Preferred gels cor"prise
an oil - extended polymer co",posiLion. P~ rdbly the gel has a hd,d"ess at room
temperature as determined using a Stevens-Volland Texture Analyser of greater than 459,
particularly greater than 509, especially greater than 559, e.g. between 559 and 609. It
preferably has a stress-relaxation of less than 12%, particularly less than 10% and especi-"y
less than 8%. Tensile modulus at 100% strain is pr~f~rdbly at least 1.8 MPa more preferably
at least 2.2 MPa. In general co",prt:ssion set is preferably less than 35%, especially less than
25%. Preferably, the gel has a cone peneL,dLion as measured by ASTM D217 of at least 50
(10-1mm), more preferably at least 100 (10~1mm), even more plt rt rdbly at least 200 (10-
1mm) and preferably no greaterthan 400 (10~1mm), especially no greaterthan 350 (10~1mm).
The polymer COI "posiLion of the gel may for example cor"~rise an elastc " ,er, or a block
copolymer having relatively hard blocks and relatively ela:,Lur, ,eric blocks. Examples of such
copolymers include styrene-diene block copolymers, for exd",,: '~ styrene-butadiene or
styrene-isoprene diblock or triblock copolymers, or styrene-ethylene-butylene-styrene triblock
copolymers as disclosed in intell,alional patent puLI - ' -n numberWO88/00603. Preferably,
however, the polymer co" "~osiLion 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 p~rt7~dbly comprise oils. The oils may be
hydrocarbon oils, for example pardrri"ic or naphthenic oils, synthectic oils for example
polybutene Ol polypropene oils, and mixtures thereof. The preferred oils are mixtures of non-
arul"dlic paldrri,ls and naphthenic hyd~uudlbon oils. The gel may contain additives, e.g. such
as moisture scavengers (eg. Benzoyl chloride), dnlioxidal,L~, pi~",el,L~ and fungicides.
.
The seal is preferably formed, at least in part, from elask,l"eric material. Forexample, the seal may be formed from natural or synthetic rubber, or a rubber-like plastics
material. Neoprene is an example of a prt~ "~d material.
As stated above, the seal accord;"g to the invention has particular utility in an
electrical or telecommunications cable splice closure. P,~rerdbly, therefore, the seal
comprises part of a cable splice closure. The seal may, for example, cor"pl ise a ring seal
which, in use, extends around an end block of the cable splice closure, e.g. between the end
block and an outer casing of the closure. The splice closure may, for example, have only one
such end block, but preferably it has two such end blocks, one at each end of the casing.
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According to a second aspect of the invention, there is provided a cabie splice closure
which includes one or more seals according to the invention. Any or all of the preferred
features of the seal acco~ di~ lg to the first aspect of the invention may advantageously be
present in the seal(s) included in the cable splice closure according to the second aspect of
the invention.
The invention will now be described, by way of example, with l~:r~r~nce to the
acco",panying drawings, of which:
Figure 1 shows a join region of a seal according to the invention, and details of
a preferred form of connection pin for forming the join; and
Figure 2 shows a join region of a similar seal according to the invention, and
details of another preferred form of connection pin for forming the
join.
Figure 1 shows a tubular seal 1, in which two ends 3 are about to be joined together
by means of a tubular connection pin 5. The connection pin 5 con Ipl ises an open-ended tube
which has been inserted into one of the open ends 3 in the tubular seal 1. To join together the
two ends 3 of the seal 1 to form a closed ring seal, the tubular connection pin may be inserted
into the other open end 3 of the seal. Pl ~r~ dLly, the outer diar"eler of the connection pin 5 is
greater than the didll ~t:ter of the openings in the ends 3 of the seal 1, causing the seal 1 to grip
the connection pin 5 firmly and thereby form a firm join.
Figure 2 shows a tubular seal 1 similar to that shown in Figure 1, with a modified form
of hollow connection pin 7. This connection pin 7, although tubular (at least in use), has a
longitudinal slit 9, the longitudinal edges of which overlap. This type of connection pin 7 can
often be more co"")ressil,le (i.e. it can often be cG",prt:ssed more easily than that shown in
Figure 1 ) and/or it can often have an increased grip on the ends of the seal 1. In this
embodiment too, the outer dianleier of the connection pin 7 is pl ~ r~, dbly greater than the
diameter of the openings in the ends 3 in the seal 1.
