Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1091881
This invention relates to a heat-recoverable article,
more e~pecially to such an article for use in covering a
splice in an electric cable.
The u~e of heat-recoverable articleY for covering
junction~ or splice~ in electric cables i~ known. The article
is usually a heat-skrinkable sleeve, which may either be
tubular or in ~heet form 80 that the sleeve may be wrapped
around the cable splice after it has been made. The sleeve
usually ha~ a layer of sealan~ or adhe~ive, e.g., a ma~tic
or hot melt adhesive, applied to its inner surface. Such
sleeve3 are described in U.S. Patent No. 3,297,819 granted
on 10th January, 1967 to J.D. Wetmore and suitable means
for joining opposite edges of a wrap-around sleeve are
described in U.S. Patent ~o. 3,455,336 granted 15th July,
t96g to R.H. Ellis.
Such articles may be rendered heat-recoverable by
heating to or above a certain temperature, expansion, and
cooling while retaining an expanded fonm: one method for
achieving this ie described in U.SO Patent No. 3,086,242
to P.M. Cook et al, issued 29th March, 1966.
Many electrical cables are nowadays maintained under
internal pressure, to reduce the pos~ibility of moisture
penetrating the cable jacket, especially at splices, and
damaging the materials or cau~ing short-circuits. The
excess pressure inside the cable may be achieved and
maintained by pump~, which are connected to the cables
through a valve. It would be convenient to position the
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valve in the wall of a heat-recoverable sleeve which may
be in-~talled e.g., over an aperture in the jacket of the
~leeve, 80 that the site of the sleeve could be used to
pre~surize the cable. Further, such a valved sleeve may
be used as a site for te~ting the pressure inside a cable.
It has been found, however, that despite the use of many
different valve mountings, inadequate sealing between the
valve and the sleeve ha3 caused leakage, and this problem
has inhibited the use of valved sleeves in pressurized
cable splicing.
It is also possible to instal a valve in a sleeve
over a splice, as an example of a splice in electrical
conduits which it would be desirable to pressurize, there
may be mentioned that described in ~.V. Raychem S.A.'s
British Patent No. 1,431,167.
The pre3ent intention provides a heat-recoverable,
preferably a heat-shrinkable, sleeve having an appendage,
preferably a valve mounted therein in a portion of the
sleeve that is dimensionally heat stable, or i~ subject
to significantly les~ dimensional change than elsewhere
in the ~leeve on recovery.
The sleeve may have one or two open ends, and is
preferably tubular. If the sleeve has one closed end, it
is to be understood that the valve is not mounted in the
end wall, but is mounted in the circumferential wall, i.e.,
in the ca~e of a tubular sleeve closed at one end, in the
tubular wall.
Although the description will refer more especially
to a valve installation, the invention i~ applicable to
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all sleeves having devices mounted in their circumferential
wall, or having aperture~ in the wall to allow, for example,
an elongate ~tructure to be po~itioned therethrough. A~
examples, there may be mentioned an applicator for injection
of foamable material into the ~pace enclosed by the sleeve,
a pres~ure indicating or sensing device or an electrical
conductor or conductors leading to, for example, a piezo
electric device, for ~en~ing pre~sure or other chan~e~, or
leading to mean~ for measuring temperature at point~ within
the space enclo~.ed by the sleeve, e.g., the interface between
the internal wall of the sleeve and a substrate enclosed
thereby.
The portion of the Rleeve may be of a small area,
e.g., a disk in the sleeve, it may extend the whole length
of the sleeve as a longitudinal band, or it may be, although
le~ de~irably, a circumferential band, the shape and size
of the portion depending on the intended use of the ~.leeve
and o~ the processes u~ed in its manufacture.
The portion may result from expansion of the whole
sleeve and controlled re-shrinkage in the desired area, but
advantageously result3 from expan~ion of the remainder of
the sleeve only, and prevention or control of expan~ion
of the portion during manufacture.
For example, if a tube i~ expanded by pas~ing through
a heating mean~ while it i~ subjected to exces~ internal
pre~ure heat may be prevented from reaching a portion of
the circumference of the tube by an in~ulating or blocking
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device, resulting in a longitudinal band of non-shrinkable
or less ~hrinkable material extending the length of the
tube, the band appearing a~ a portion of greater wall
thickness. The tube may then be cut into ~leeves of
appropriate length, an aperture made in the band, and a
valve mounted in the aperture. Another possible method
compri~es positioning a ~uitably ~haped member, e.g., a
disk or rectangle of suitable material, e.g., aluminium,
at intervals on a tube to be expanded, whereby heat may
be prevented from reaching the tube at the regions under
the member, and expansion restricted, for example becau~e
the member acts as a heat sink.
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As a further method, the tube may be ~ubjected to
uniform heating superimpo~ed on which i~ a ~elective
cooling of one position to prevent or reduce expansion.
It will be apparent as indicated above that the
invention may be employed where other appendages, e.g.,
device~ other than valves, are to be incorporated into
heat-recoverable articles and i8 useful in all in~tances
where proper functioning is dependent to some extent on
proper attachment of the device to the article.
Two forms of article constructed in accordance with
the invention will now be described in greater detail by
way of example with reference to the accompanying drawings,
in which
FIG. 1 is a perspective view of a valved heat-
shrinkable sleeve having a longitudinal
band of non-8hrinkable màterial, and
FIG. 2 i~ a cro~s-section through a valved heat-
shrinkable sleeve having a valve mounted
in a non-shrinkable zone.
Referring to Fig. 1., a sleeve indicated generally by
the reference numeral 1 is generally heat-shrinkable with a
longitudinal band 2 being les~ shrinkable or dimensionally
heat ~table. Mounted in the band 2 i8 a valve 3. On
recovery of the sleeve, the wall thicknes~ of the band 2
will remain substantially constant, while the remainder of
the ~leeve will contract radially with re~ulting wall
thickne~ increase.
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Figure 2 illustrate~ a cross-section of sleeve 1
having a diqk 4 of unexpanded material, the valve 3 being
centered in the disk.
