Note: Descriptions are shown in the official language in which they were submitted.
wo 95/06347 2 1 6 9 9 2 C P~ llv~ 1/01839
Sealin,~ Member
The invention relates to a sealing system comprising an
elastomeric or other seal preferably in block or strip form, and
preferably for sealing a cable splice case.
..
Providing casings, containers etc., more particularly cable
sleeves, or other splice cases the internal space of which must be
protected as durably as possible against environmental influences,
especially dampness, is f~mili~r. Examples exist where casing
closing elements, such as doors and lids are present or where
elements enter the c~Rings, such as ingoing cables in the case of
cable sleeves. In the older solutions it was known to apply an
ins~ *ng mastic etc. in excessive quantities to the cable input area,
between two separate casing halves. When the casing halves were
closed around the cable splice the mastic was deformed around the
ingoing cables to form a seal. One problem of such mastics, for
example, those based on butyl rubber, is that they creep under
temperature cycling. As a result, therefore, of different thermal
eYp~nRion coefficients and different heat transfer values between the
sealing surfaces and the mastic, leakages occur. In order to avoid
such problems, heat-shrinkable sleeves were used around cable
inlets which shrink when heat is applied and thereby seal tightly to
the casing inlet and to the cable passing through it. Hot-melt
adhesive coatings on the heat-shrink sleeves ensured the necessary
~iheRion. Although this technology has considerable advantages,
one of its disadvantages is that a flame always has to be used for
shrinking, which often leads to local problems on site.
The aim of the invention is to ovelcome the problems of the
prior art, and in particular to provide a seal that is simple to use and
can acco.~ odate the varying forces that result from temperature
and pressure cycling.
To this end we have devised a seal of a particular shape and
preferably having a first element having an adhesive external
surface and a springy or elastic second element which can store
w0 ssto6347 2 1 6 9 9 ?~ ~- 2 ~ J5 1/01839
energy thus maint~ining the first element in contact with a surface
(such as a cable and/or a splice case) to be sealed.
Thus, the invention provides a seal shaped to have one or more
of the following characteristics:
(a) a cable and/or housing mating surface is tapered and/or
frustoconical thus allowing cables of different sizes to be sealed
within a housing of given inlet size;
(b) a seal has a subst~ntiA11y convex outer surface, such as
circular (which term includes semi- or other part circular) or
polygonal such as pentagonal, hexagonal, heptagonal or octagonal
such that externally applied compressive forces (resulting for
example from closure of a housing in an inlet of which the seal is
provided) are concentrated or focused on a cable within the seal; and
(c) the seal comprises two parts, each having first and
second partial cavities therein, such that the parts can be ~semhled
with the two first parts or the two second parts mutually aligned, the
two first partial cavities together defining an inlet of L~erellt size or
shape than the two second partial cavities together.
The seal preferably has an adhesive outer surface provided by a
first element (which may be a layer that is Att~che-l to the remAin-ler
of the seal, or that is integral with it) and springy or elastomeric
second element that can in general store energy thereby m~int~ining
the first element in contact with the cable or splice case inlet etc. In
this way it is possible to ~cco.~...lodate expansion and contracting of
the various parts of the splice case, due for ~mp1e to tempe~alule
or pressure cycling. Adhesion to the various surfaces can therefore
be maintained. The elasticity on the one hand and adhesiveness on
the other can also result in the seal being pressed into uneven areas,
thus increasing the sealing effect even further.
The level of adhesiveness will be chosen depending on the
particular end use, and it need not be high. The surface may be
merely slightly tacky or may merely "wet" the surface to which it is to
WO 95/06347 21 6 9 ~ 2 ~ P~ ~b~ 1/01839
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be sealed. Furthermore, adhesiveness may become manifest only on
the application of a certain pressure. We prefer, nonetheless, that
the desired adhesiveness be menifest at ambient temperture.
Due to the preferred dual nature of the system it is also possible
to adapt it easily to the appropriate application, both in terms of
dimensioning and also special material properties and geometric
features. Thus, a single design of seal can be used in a variety of
splice cases and for a variety of cable sizes.
In the design it is envisaged that the springy and/or elastic
second element is subst~nti~lly completely ~ullo~ ded by the first
element with the adhesive surface. A further layer, or surface
treatment, may be provided to give the seal protection against
petroleum or other fluids.
The complete surrounding of the elastic and/or springy
elemçnts means that the restoring forces can act in subst~nti~lly all
directions.
The springy element may comprise a mechanical spring, a
pneumatic chamber or an elastomer, by means of which energy can
be stored.
The seal preferably comprises a cross-linked elastomer, more
particularly an ATV or other silicon rubber, and the first and second
elements may each comprise such materials, but cross-linked to
di~elent e~tentq to produce the di~erellt properties desired.
In the case of such seals various applications are known. An
elastomer and/or synthetic rubber often has very favourable
properties, whereby a silicon rubber vlllc~ni~ed at high temperature,
e.g. type MVQ, is frequently used here. In order to achieve complete
cross-linking of such a material, a peroxide quota and silicic acid
content of the raw material, various hartln~sses of elastomers can be
obtained. We have found that these materials are useful as seals,
since they can exhibit low creep and low compression-set. As a
result mechanical deformation is highly reversible, thus
WO95/06347 2,~699~ PCT/GB94/01839
m~int~ining the sealing effect over time. Usually such deformability
is measured in accordance with German standard DIM 53517, i.e. a
pressure deformation residue is given as a yardstick after contact
deformation.
In addition to the crocslinked sealing materials there are other
sealing materials such as non-cross-linked systems with very high
viscosity and a&esiveness based on butyl rubber for instance. In the
case of these materials the sealing effect maybe achieved less as a
result of deformation, and more due to the surface adhesion to
n~?ighhouring surfaces, such sealing material exhibiting a restoring
capability. Such sealing systems may have the disadvantage that
they are less useful on components subject to great temperature
variations. Nonetheless, seals having the designs required by the
present invention can produce useful results with these less
preferred materials.
In further embo~imçnts the invention provides a seal, which is
characterised by incomplete cross-linking to give an adhesive.
Preferably such a seal comprises a silicone rubber or other elastomer
or other suitable material having a pero~cide content of 1% or less by
*eight, based on the weight of cross-link~hle material.
In such an incompletely cross-linked elastomer seal a
sufficient restoring c~p~hility rem~in.C guaranteed on the one hand,
and on the other att~hmçnt of the material to the surface through
the residue adhesiveness is possible.
Expediently the peroxide quota lies under 0.5% by weight. For
e~mple, silicon rubber of type MVQ having various levels of
peroxide was cross-linked, and we have shown that even with a
pero2~ide quota of 0.2% adequate mechanical properties can be
achieved. In particular, the required restoring force was achieved as
well as an adhesiveness which allows for adequate surface adhesion
to the nPighbouring surfaces bordering on the seal.
21 6 9 9 2 6 PCI/GB94/01839
WO 95/06347
-5 -
At this point is should be noted that not only chemical cross-
linkinÉ is possible, but also physical cross-linking, e.g. through high-
energy radiation.
In another embodi_ent the invention also provides for the seal
being formed of at lest two differently cross-linked layers. In this way
at least one of the layers, irrespective of the type of cross-linking, be it
chemical or physical, can be more, and preferably substantially
completely, cross-linked.
Various layer structures can be realised here or half-shells
and/or other forms produced, the different layers being cross-linked
to different extents. For P~m~le a partially cross-linked sealing
material can be provided on the inside of a hollow seal (to seal for
example to a cable p~csin~ through it) and/or on the outside (to seal to
a splice case around it). The core of the material of the seal can be
cross-linked to a greater extent to increase its resilience, reducing
creep and allowing greater storage of energy.
Further embotliments according to the invention consist in
seals formed of at least two layers co.~t~;..;ng cross-link~ble material,
which are connected to each other and subsequently subjected to
cross-linking. The seal may be formed of at least two connected
layers with a varying peroxide content, whereby the overall composite
is subjected to cross-linking. Alternatively, the seal maybe formed of
an under-cross-linked first section and an as yet non-cross-lin_ed
second section which are connecte-l to each other and then subjected
to joint cross-linking.
The invention is described below in more detail with the aid of
the accomr~nying d~awillgs, in which:
Figure 1 shows a cable splice case with a seal of the invention;
Figures 2-7 show various designs of seals;
Figure 8 shows several seals, sealed to each other;
WO 95/06347 216 9 9 6 - PCI/GB94101839
Figure 9 shows a splice case with an additional sealing strip;
and
Figures 10-14 show embodiments of the sealing strip.
Figure 1 shows a cable splice case 1 suitable for sealing splices
between various types of cables (not shown). The splice case 1
comprises a base or other first part 2 and a lid or other second part 3
(each preferably moulded from a plastics material) that can be
brought together by hinging etc. to form a substantially closed space
around a cable splice (not shown). The cables may be for ~ mrle
multi-con~llctor copper cables, co~ l cables or optical fibre cables.
The splice case may therefore ~ccommodate conductor splice
bundles, CATV splitters or taps or optical fibre splices, splitters or
organiser trays. Means 4 are provided to located the splice bundles,
splitters or trays etc. For ~mple, means 4 may comprise quides
within which a stack of trays may be suitably received. The splice
case is shown with three inlets 5 at each end, although other
configurations are possible. Each inlet may cont~in a seal 6 of the
invention and a strain relief device 7, so that stresses on the cables
are not trans_itted to the seals 6 or to the conn~ctions within the
splice case. The seal 6 can be seen to have a cable mating surface
that is frusto-conical, thus allowing cables of different sizes to be
sealed. The frusto-conical internal surface is shown ribbed, thus
giving it greater fl~ibility. The ribs may become deformed as a cable
is sealed between the seal 6 shown and a second seal (not shown) that
could be secured to the lid 3 or otherwise positioned above seal 6.
The seal 6 of Figure 1 is shown in greater detail in Figure 2.
The seal is in the form of a complete block, the inner part of which
may co~lise one or more softer or tacky layers 10 preferably
embedded, or provided between, harder elastomeric layers 11. The
surface of the block that is to contact the cable and/or splice case
housing may be coated with a gel, petroleum jelly or other suitable
sealing material, or such sealing material may be an integral part of
the seal. At least in the parting plane of the block, the softer layer or
layers 10 preferably extend proud of the harder layer or layers 11 in
order to ensure good cable sealing. This feature may be provided in
WO 95/06347 21 69 9 26 PCTIGB94/01839
the absence of other aspects of shape, and is independently inventive
and useful.
The block of Figure 3 is shown with its front walls removed to
reveal cavities 4 that may be air-filled and may give pneumatic
resilience to the seal. Even if such cavities are open (as shown), they
may be a-lv~ntageous in altering the resilient behaviour of the block.
Figure 4 shows block parts 8, 9 which together have a convex
outer surface, in this case, hexagonal, such that an externally
applied compressive force (indicated by the alll.)W:~) iS conrPntrated or
focused onto a cable 15 therein. This co~ressive force could result
from the seal being closed in an inlet 5 between the base 2 and lid 3 of
a splice case such as that shown in Figure 1. Another layer of the
block parts 8, 9 is preferably tacky, and the core 10 of the parts is
preferably more resilient.
The seal of Figure 5 co.~l;ses two parts 8, 9, each having first,
16, and second 17, cavities therein, such that the parts can be
assembled with the two first partial cavities, 16, mutually ~ ne~l, as
shown, or with the two second partial cavities, 17, aligned. This can
allow inlets of different size to be produced from a single pair of block
parts;
Figure 6 shows a ~e~ling block having an insert 18 that can be
removed for use with large cables. Each of the inserts 18, and the
rem~in~ier of the block may have the dual, adhesive and elastomeric,
construction refel,ed to above.
The seal of Figure 7 co.,.l lises a split hollow cylinder, such
that the split 20 can be opened to allow a cable to be slid laterally into
hole 21. Such a split seal can of course have the overall shape shown
in Figures 2 and 4 etc.
In Figure 8 shows three seals sealed to each other. Each seal
has a COllvt:~, 22, and a concave, 23, surface such that ~imil~r seals
can be juxtaposed with the concave surface 22 of one engaging the
convex surface 21 of another.
WO 95/06347 2 ~ 6 9 9 ~ PCT/GB94/01839
- 8 -
Figures 10 to 14 show sealing strips 27 suitable for use around
the periphery of a splice case, such as that of Figure 9. These seals
may allow a sealing force applied to a splice case cover to act
indepen-lent.ly upon the cables 28 and upon the base 2 and cover 3.
Preferably the sealing strips shown are substantially completely
oullded by material of the base or cover of the splice case.
Sealing strips 27 may co~lise a silicone rubber or other elastomer,
and may be cross-linked. Alternative materials comprise gels and
mastics. The dual, adhesive and elastomeric, construction described
above for seal 6 may be used. The sealing strip may have a hollow
core 29 such that the desired re.qilien~e is provided at least in part
pnellm~ticAlly. In Figure 12 a soft material 30 is located by a harder
material to one side which is useful in the embo-lim~nt of Figure 11
where the sealing strip 27 abuts an inclined surface. Figures 13A
and 13B show two ways in which a sealing strip 27 is retained in a
recess in lid 3. Here a harder fet~;ll;llg core 31 is provided, with
di~erent m~teri~lq 32 and 33 at its surface. Figures 14A and 14B
show a sealing strip before its co~l,ression against a surface 2 to be
sealed.
Figure 9 shows a splice case having sli~ing catches 24 for
holding the base 2 and the lid 3 closed. The catches 24 may have a
tapered recess by means of which wedge shaped ridges on the base
and lid may be forced towards one another thereby putting seals
(such as seal 6 of the invention) under compression. Other means
may be provided for urging first and second parts of a splice case
together, thereby putting a seal under compression.
The splice case is shown housing optical fibre organiser trays
25 (three are visible). The trays are located on hinges 26 by means of
which they can be moved to expose the fibres on any one thereof.
An elongate sealing strip 27 is provided extending
substantially around the periphery of the base 2 of the splice case, to
form a seal between the base 2 and the lid 3 when they are brought
together. Such a sealing strip 27 may in general be provided on first
and/or second parts of a splice case, and may be preinstalled in a
W095/06347 21 69926 PCI'IGB94/01839
_- g
recess for example, or may be applied when the splice case is
installed. The sealing strip 27 may become sealed to the seal 6 when
the first and second parts of the splice case are brought together.
A seal may also, or alternatively be shaped to have one or more
of the following characteristics:
1. the seal is provided in subst~nti~lly block or strip form
and has one or more cavities, preferably air (or other gas) filled and
preferably to give pneumatic resilience to the seal;
2. the seal comprises a split hollow cylinder; and
3. the seal has a collve~ and a covcave surface such that
simil~r seals can be juxtaposed with the convex surface of one
engaging the concave surface of another.
For the avoidance of doubt it is noted that the invention
provides various shapes, constrllc*on.~, materials, uses, and other
aspects of ~cignc for se~ling cables and other substrates. Any one or
more of the rlesign~ described or illustrated may be used in the
presence or ~hs~nce of any of the others, and any one or more of them
may be used in a cable splice case particularly as at least part of a
cable inlet.
