Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
This invention rela*es to an air vent assembly for
use in conjunction with heat-recoverable closures when used to
seal, repair and/or protect pressurized cables. The air
vent assembly, in conjunction with a heat recoverable closure,
can also be used to pro-vide access to pressurized air in the
cable.
Heat-recoverable closures, such as, tubular sleeves~
wraparound sleeves and tape are used to form a protective
cove~ing around elongate substra.tes such as cables, including
pressurized and non-pressurized telephone cables, The heat-
recoverable sleeve or tape is generally coated with a layer
of mastic or an adhesive, preferably a hot melt adhesive.
Alternatively the adhesive may be applied in the form of a
tape, sheet or sleeve positioned aro~md the cable, or other
substrate before placing the heat-recoverable closure around
the substrate. Heating of the closure causes the closure to
recover and the adhesive to melt and flow. Upon cooling~ a
pressure and watertight seal results. It has been found that
when such a protective system is used with pressurized cables,
ZO pressurized air escaping from the cable forces its way
through the molten adhesive, resulting in leakage pathways
and inadequate ssaling between the heat-recovered sleeve or
tape and the cable. To avoid this result~ it is often
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necessar~ or desirable to depressurize the cable prior to
and during the heat-recovery step. To avoid depressurizing the
cable, a pressure access flange is sometimes used. However,
this requires making a hole or slit in the hea-t-recoverable
cl~sure to accomodatc the outlet of the pressure access 1ange.
This hole in the closure can cause splitting along the leng~h
of the closure during the heat-recovery step.
This present invention provides a means for forming
a pressure and watertight seal between a pressurized cable
and a heat-recoverable closure without the need for making
a hole in the closure or for depressurization of the cable.
One aspect of this invention comprises an air vent assembly
comprising:
(a) a tubular fitting;
~b) an elongate semi-flexible, non-collapsible
hollow tube3 one end of which is connected
to said fittlng; and
(c) deflection means, secured at the other end
of said hollow tube, for deflecting pressur-
2n ized air into the tube while preventing
ingress of viscous material.
Another aspect of this invention comprises a
method of protecting a pressurized cable (or other conduit)
having an outer protective jacket, which jacket has an opening
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therein permitting air to escape from the cable, which comprises:
(a) placing an air vent assembly against the cable,
said air vent assembly comprising:
(i) a tubular fitting;
(ii) an elongate, semi-flexible, non-collapsible
hollow tube, one end of which is connected
to said fitting; and
(iii) a deElec-tion means secured at the other
end of said hollow tube;
said assembly being positioned so that the end
of the hollow tube remote from the air is placed
against said opening in said jacket;
(b) positioning said deflection means to prevent the
Elow of viscous material into said tube and to
deflect air from said opening into said tube;
(c) positioning a heat-recoverable closure over said
cable and vent assembly such that the fitting ex-
tends beyond the closure; and
(d) heating the closure to cause it to recover.
Yet another aspect of this invention comprises:
a method for providing access to a pressurized
cable (or other conduit), said cable having an outer
jacket which prevents air from escaping from said cable,
which method comprises
(a) forming a hole in the outer cable jacke-t of said
pressurized cable;
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~b) pla.cing an air ven-t assembly against the cable,
said vent assembly comprising:
(i) a tubular fitting;
(ii) an elongate, semi-flexible, non-collapsible
hollow tube, one end of which is connec-ted
-to said fitting; and
(lii) a deflection means secured at the other en~
of said hollow tube;
said assembly being positioned so that the end
of the hollow tube remote from said fitting is
placed against said opening in said jacket;
(c) positioning said deflection means to prevent -the
flow of viscous material into said tube and to
deflect air from said opening into said tube;
~d) positioning a heat-recoverable closure over said
cable and vent assembly such that the fi-tting ex-
tends beyond the closure; and
(e) heating the closure to cause i.t to recover.
A further aspect of the invention is an analo~ous method
for enclosing a cable (or other conduit).
The invention will now be described in grea-ter de-tail
with reference -to the accompanying drawings, in which:
Figure 1 illustrates a typical vent assembly of -this
invent:ion wherein the hollow -tube is a metal spring encompassed
by a polymeric sheath.
Figure 2 il:Lustrates the deflection means of -the vent
assembly of Figure 1
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Figure 3 demonstrates the use of a vent assembly of
this invention for the repair of a pressurized cable
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using a heat-shrinkable tape spirally wrapped around the pressurized
cable.
FIGURE 4 illustrates a typical vent assembly o:E this inven-
tion wherein the hollow tube is a flattened metal tube.
FIGURE 5 illustrates an end view of the vent assembly
similar to tha~ of Figure 4 with a .shape retention means within the
hollow tube.
FIGURE 6 illustrates a typical vent assembly oE this inven-
tion wherein the hollow tube is of nylon.
DETAILED DESCRIPTION OF T~IE INVENTION
The air vent assembly is used in conjunction with a heat-
recoverable closure used to enclose a pressurized cable. The heat-
recoverable closure can be a heat-shrinkable tubular sleeve, wrap-
around sleeve or tape which can be spirally wound around a cable.
Such heat-recoverable closures are well known in the art. Descrip-
tions of such closures can be found, for example in U.S. Patents Nos.
3,455,336, 4,035,534, 4,142,592, 4,163,117, and 4,177,376 and U.~.
Patent No. 1,562,086. The inner surface of the closure is generally
coated with a layer o~ a mastic or an adhesive, preferably a hot melt
adhesive, to provide a pressure and waterti.ght seal between the cable
and the closure. The heat-recoverable closure can be used to protect,
repair and seal an opening in the cable outer protective jacket. The
hole or opening, can
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be the result of damage to the cable, a gap between the
jacket cable and a splice case, or any other source of
leakage of air from the cable.
- The vent assembly of this invention can also be
used to provide access to the pressurized air in the
cable. In this case a hole is deliberately made in the
outer jacket of the cable for installation of the air
vent. The heat-recoverable closure provides a protective
seal around the vent assembl~. The vent assembly can be
installed at any point along the pressurized cable and can
be used as an outlet for measuring pressure at that point.
The air vent can also be used to provide access to the
pressurized air of the cable for use as a source of
pressurized air~ For example, a tube can be connected to
the fitting of the ~ent assembly and to the air inlet
valve of an apparatus case for pressurizing the apparatus
case.
The air vent assembly can also be used with
unpressurized cables to provide for flash testing of the
installed heat-recovered closure to establish that an
environmental seal has been formed~
The air vent assembly is installed by placing
the assembly on the cable with the elongate hollow tube
extending along the length of the cable. The open end of
the hollow tube is plared next to the hole or o~enin,~ in
the cable jacket with the deflection means being positioned
around the opening to direct the air flow from the
cable opening into the tube. The deflection means also
functions to prevent other material, in particular viscous
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material such as molten adhesive, from flowing into the
tube. The heat-recoverable closure is then placed over
the cable and vent assembly leaving the fitting extending
so that it remains accessible~ The heat-recoverable
closure is then heated causing it to shrink down into
intimate contact with the cable and air vent. During the
heat-recovery step, the adhesive of the heat-recoverable
closure melts and flows. The deflection means is positioned
to prevent the viscous molten adhesive from flowing into the
hollow tube~ The deflection means thus serves a dual
function, i.e. deflecting air from the opening in the
cable to the tube while preventing the flow of molten
adhesive into the tube.
At one end of the air vent assembly is a tubular
fitting. The tubular fitting is of a solid materlal, prefer-
ably metal. The fitting can be adapted to receive a cap or
connector, such as a tube or tube and valve combination to
conduct air from the cableO Preferably the end portion of
the fitting has a threaded outer surface for this purpose.
The internal surface of the fitting preferably also is
threaded to accommodate a valve core~ A valve core can be
placed within the fitting immediately after installation1
if desired. Generally, a valve core will be added if the
air vent is to remain unconnected to another piece of
equipment, such as an apparatus case as mentioned above.
The valve core prevents pressurized air ~rom escaping
through the air vent and can be u~ed to test the pressure
in the system. After the valve core has been installed r a
cap can be attached to the fitting to protect the fitting
and valve from corrosion and/or mechanical damage.
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An elongate, semi-flexible non-collapsible
hollow tube is attached to one end of the tubular fitting~
The hollow tube allows air to flow from an opening in the
pressurized cable when a heat-recoverable closure is being
installed. The tube must be sufficiently non-collapsible
so that it is capable of withstanding the forces and
temperatures developed during the heat-recovery step. The
tube can be of metal r plastic, or reinforced plastic. The
tube should be sufficiently flexible to conform to the
shape of the cable. If the tube is of metal, it should be
a relatively thin-walled tube or of a tube of convoluted
shape.
In a preferred embodiment of the inven~ion~ the
tube is of a relatively high melting plastic such as
nylon, polyethylene terephthalate, polytetrafluoroethylene,
or the like.
In another preferred embodiment, the tube
comprises a metal spring encompassed by a polymeric
sheath. Such a tube can readily be formed by placing a
heat-recoverable sleeve over the metal spring, then
heating to cause the sleeve to shrink to encompass the
spring. The spring can be circular, or can be flattened
into an eliptical shape, if desiredO Preferably the
spring is attached to the end of the fitting before the
sleeve is applied. The heat-recoverable sleeve is posi-
tioned so that it covers the end of the fitting 25 Wel 1 as
the rest of the spring. A watertight seal is formed
between the sleeve and the fitting by applying a strip of
hot melt adhesive to the fitting or by use of 2 heat-
recoverable sleeve coated on the inside thereof with hot
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melt adhesive. It has been Eound advantageous to add
grooves to the outside of the fitting to accommodate the
hot melt adhesive and assure a watertight seal~
As discussed above, the air vent assembly of
this invention is used in conjunction with a heat-recover-
able closure. Such heat-recoverable closures are generally
coated on the lnside with a layer of mastic or adhesive,
preferably a hot melt adhesive. To assure that a pressure
and watertight seal is formed between the heat-recoverable
closure, the air vent assembly and the cable, it has been
found to be advantageous to use additional hot melt
adhesive. The additional adhesive is preferably added
along the length of the elongate hollow tube of the air
vent. The adhesive can be molded around the hollow tube
or placed around the hollow tube in the form of a sheet or
sleeve. When heat is applied to recover the heat-recover-
able closure, this additional hot melt adhesive will melt
and flow to fill completely the space between the cable
and closure Adequate heating of ~he hot melt adhesive
under the tube is facilitated i the adhesive is rendered
thermally conductive. This can be accomplished by adding
metal flakes or wires to the adhesive. A preferred method
is to form a laminate of two layers of hot melt adhesive
with an intermediate layer oE a metal mesh r screen or
foil.
It has been found that the adhesive used around
the air vent should have certain desired flow characteristics,
depending on the ultimate system with which it is used.
For use with a pressurized telecommunication cable the
adhesive should be adequate to form a seal around the air
EAR 62/B ~ MP0757-CA
vent and maintain that seal over fluctuating environmental
temperatures. Typically, the adhesive should maintain a
seal at temperatures from -40C to +60C.
The deflection means is attached to the end of
the hollow tube of the air vent assembly. The deflection
means is shaped such that when the end of the hollow tube
is placed adjacent an opening in the cable jacket, the
deflection means makes contact with the jacket surrounding
the opening~ A layer of pressure sensitive adhesive on
the inner surface of the deflection means holds it in
place during installation of the air vent assembly and
heat-recoverable closure. ~he deflection means preferably
is sufficiently flexible to be molded to con~orm to the
shape of the cable~ In a preferred embodiment, the
deflection means comprises a layer of flexible polymeric
foamr for example, a foam of ethylene-propylene-diene
rubberl neoprene, silicone rubber or the like, and a layer
of a solid material to provide structural integrity for
the foam. This layer can be of, for example, a polymer
such as polypropylene, a laminate of paper or aluminum and
polyethylene terephthalate, and the like.
The invention is further illustrated in the
accompanying drawings. Figure 1 shows a typical valve
assembly of this invention. In Figure 1, a brass fitting,
1, is connected to a hollow tube, 2~ The tube is
prndl~ced ~v th~eading a metal spring (not shown directly
in the drawings) onto the end portion of the fitting and
then installing a polymeric sheath over the spring. The
polymeric sheath is applied in this case by positioning
a heat-shrinkable sleeve over the fitting and then heating
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to shrink the tube down onto the outer surface of the
spring forming the convoluted tube, 2, shown in Figure 1.
In this case, the heat~shrinkable sleeve used is of
cross-linked polyethylene and the inner surface thereof
was coated with a hot melt adhesive to provide a watertight
seal between the sleeve and the fittingO As mentioned
above, a strip of hot melt adhesive applied to the fitting
can be used to achieve this result. The hollow tube, 2,
is provided with a layer of hot melt adhesive, 3. This
layer of hot melt adhesive preferably extends along the
length of the hollow tube. The holt melt adhesive is of
the same type known in the art for use in installing
heat-recoverable closures. For example, a description of
suitable hot melt adhesives can be found in U.S. Patent
No. 4,018,733 of Lopez et al. A layer of mastic or other
adhesive can be used in place of the hot melt adhesive,
although hot melt adhesive is preferred. It is also
possible to add a layer of hot melt to the hollow tube, 2,
of the vent assembly after it has been positioned against
the cable but prior to application of the heat-recoverable
closure. A deflection means, 4, is attached to the open
end of the hollow tube, 2.
In Figure 2, the deflection means of the vent
assembly of Figure 1 is illustrated in greater detail~
E`igure 2 shows the laminate structure of the deflection
meansO An outer layer, 5, of relatively rigid material
extends completely across the deflection means. In this
particular embodiment, this layer, 5, is of polypropylene.
A foam layer, 6, adheres to the outer layer, 5. The foam
layer is cut out in a shape to accommodate the open end of
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the hollow tube, 7, and to deflect air from an opening in
the cable over which it is placed into the hollo~ tube.
The inner surface, 8, of the foam is coated with a pressure
sensitive adhesive to be applled o t]-,e ca'.,le sllr,aue
sur~ di~J ~l~ opening.
Figure 3 illustrates the use of the vent assembly
of Figure 1. In Figure 3, the fitting, 1, of the vent
-assembly and a portion of the hollow tube, 2, extend from
a heat-recoverable tape, 9, which is spirlly wrapped
around a pressurized cable, 10. The heat-recoverable tape
used in this particular embodiment is an electrically self-
heating heat-shrinkable tape commercially available from
Raychem Corporation as "AutoWrap#". The adhesive layer, 3,
and deflection means, 4, are shown by dotted lines as they
are positioned between the cablel 10, and heat-recoverable
closure, 9. The deflection means, 4, is positioned over
an opening in the cable, 10, so that air rom the cable
flows into the hollow tube, 2, of the air vent. A valve
core can be placed within the fitting, 1, and a protective
cap placed over the fitting, if desired.
Figures 4 and 5 show another typical air vent
assembly of this invention. In this embodiment~ a fitting,
11, is connected to a hollow metal tube! 12. The metal
tube is flattened along a portion thereof so that it will
lie flat when positioned against a cable. A sheet of hot
melt adhesive~ is provided aro~nd the flattened
portion of the hollow tube. A deflection means, 14, is
provided at the end of the hollow tube. In this embodiment
the deflection means, 14, is a metal shield bent to
accommodate the hollow tube, 12l and a cable. That portion
EAR 62/B MP0757-CA
of the hollow tube which extends beyond the adhesive is
coated with a protective coating~ In the embodiment
shown, this part of the hollow tube is covered with a
polymeric sheath, applied in the form of a tubular heat-
shrinkable polymér sleeve heated to shrinX into intimate
contact with the tube and preferably coated on the inside
with a hot melt adhesive so that a watertight seal is
created. Figure 5 is an end view of the assembly of
Figure 4 showing shape retention means~ 15, positioned
with the flattened portion of the hollow tube, 12. The
shape retention means, 15, is a metal rod which extends
the length of the flattened portion of the tube, preventing
its collapse if it is bent longitudinally to conform to
the cable.
Figure 6 shows another preferred embodiment of
this invention. In Figure 6, the air vent comprises
hollow tube, 22, of nylon, deflection means, 24, and
fittinq, 21. A strip of hot melt adhesive, 23, containing
a metal mesh, 25, is placed around that portion of the hollow
tube which will be positioned within a heat-recoverable
closure. The hot melt adhesive used in this embodiment is
an ethylene-vinyl acetate based polymer which has been
subjected to irradiation at a dose of about 1 megarad.
The air vent assembly can be used on a pressurized cable
adjacent an apparatus case. The hollow tube is sufficiently
long to enable it to be connected to the apparatus case to
conduct air under pressure from the cable into the apparatus
case (not shown).
The present invention has been set forth in the
form of several preferred embodiments. It is nevertheless
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understood that modifications may be made by those skilledin the ar~ without departing from the spirit and scope of
the present invention. Moreover, such modifications are
considered to be within the purview of the appended
claims.
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