Note: Descriptions are shown in the official language in which they were submitted.
323
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This invention relate~ to heat-recoverable article~,
especially heat-shrinkable articles for use in the prstection
and insulation of suppl~ lines such as elactric cables.
Heat-recoverable articles, e3pecially heat-shrinkable
articles, are now widely used in many areas where insulation,
sealing and encap~ulation are required. Usually these articles
reco~er, on heati~g, towards an original shape ~rom which they have
previously been deformed, but the term "heat-recoverable", as
used herein, also includes an article ~hich, on heating, adopts a
10 new con~iguration, even if it has not been previou~ly deformed.
In their mo3t common form, such articles compri~e a heat-
~hrinkable eleeve made from a polymeric material exhibiting the
property of ela~tic or plastic memory aæ de~cribed, for e~ample,
in ~.S. Patents 2,027,962; 3,086,242 and 3,957,372. ~s is made
clear in, for e~ample, ~.S. Patent 2,027,962, the original
dimensionally heat-stable form may be a transient form in a
continuou~ process in which, for example, an extruded tube is
expanded, whilst hot 9 to a dimensionally heat-unætable form but,
in other application~, a preformed dimen~ionally heat stable
article is de~ormed to a dimensionally heat unstable ~orm in a
separate stage.
In other articles, as described, for e~ample, in British
Patent 1,44C,524, an elastomeric member such as an outer tubular
member is held in a stretched state by a second member, such a~ an
inner tubular member, which, upon heating, weakens and thus
allows the elastomeric member to recover.
Heat-~hrinkable sleeve~ find many applications, especially
in the connection and termination o~ wires, cables and pipe~.
However, there are other applications where it is desirable to~
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pro~ide a connecting, insulating or protective heat-recoverable
member for elongated objects such as cables and pipe9 where the
end~ are not acces~ible or, if they are acce~sible9 where it i8
unde~irable to disconnect or otherwise di~place them. For ~uch
S applications so-called "wrap~around" ~leeves have been developed.
Basically these are heat-recoverable sheet~ which can be wrapped
round th~ sub~trate to form a generally tubular shape and which,
in general, are pro~ided with ~astening mean~ for holding them ln
the wrapped-up configuration during recovery. Typically such
fa~tening means are mechanical in nature and compri e, for e~ample,
rigid clampQ, pins or channel members which co-operate with ~uitably
shaped moulded or extruded protuberances adjacent to the over-
lapping edge~ of the heat-recoverable sheet. ~arious types of
~astening means are described, for example, in U.S. Patents
3,~79,218 and Briti~h Patents 1,155,470; 1,2119988 and 1,346,479.
In other applications the ~heet may be held in the wrapped-up
configuration durin~ recovery by means of an adhesi~e which may, in
! ~ome cases, be applied on site.
One particular area of application of heat-reco~erable
article~ of the type described above i~ i~ the in~ulation and
protectio~ of junc$ions between ~upply line~, especially electric
cables. In making such junctione, for example, between telephone
or power cable~, many problem~ ari~e in meeting the necessary
requirement~ of continuity o~ ineulation and earthing, of ~ealing
the joint against the ingress of contaminants such as moisture and
insects and in providi~g the neces~ary strength of resi~tance to
ten~ion, compression, flexing and impact. British Patent
No. 1,155,470 propo~e~to use tubes or slee~es of heat-shrinkable
material to protect and insulate joi~t~ in the electric cable~
3~Z3
However, because the cable~ are ~requently pres~uri~ed and must
be waterproof it is necessary to coa~ the inner wall o~ the heat-
~hrinkable ~leeve with a ~ealant such a~ a hot-melt adhe~ive or a
mastic. When the ~leeve i~ heated the sealant melt~ and form~ a
water-tight and pres~ure-tight seal betwee~ the sleeve and the cable.
~his has the disadvantage that, ~ n certain ca~e~, the sleeves
cannot ~ub~equently easily b~ ope~ed for repair or modification of
the joint without necessitating the complete renewal of the
junction and the method is al~o unsuitable where the joint or the
electric component~ leading to the aoint comprise component~ which
are delicate or frangible,
It has, there~ore, been proposed to provide modified heat-
shrinkable article~ in which a central portion does not recover or
in which rein~orcement means are provided to prevent recovery in
the central region. For example~ Briti~h Patent No. 1,248,908
di~closes a heat-~hrinkablc article containing a bridging sleeve o~
non-recoverable material and terminal æleeves of heat-shrinkable
; material, the sleeve~ being connected to one another, for example,
by ~crew connections. Ho~ever, such an arrangement requires relati-
- 20 vely close tolerances in manufacture to ensure that the male and
female screw threacl~ of the parts are readily engageable.
A more ~ucce~qful propo~al i8 that of Briti~h Patent
1,431,167 in which a heat-shrinkable ~l~e~e, which may be a wrap-
around sleevQ i~ provided with central rein~orcement ¢emprising
a relatively rigid longitudinally ~plit tube. ~ypically ~uch a
tube i~ made ~rom a pair o~ ~emi-cylindrical hal~ ~hell~, for egample
made from aluminium. Such article~ ha~e the ad~antage that they
may ea~ily be re-opened for repair ~ork or modi~ication o~ a cable
ioint but they have pro~ed rather e~pensive~
- 5 -
The present invention prsvides a heat-recoverable article
o~ polymeric materi~l, whLch compri~es ~elf-contained cutting means
arranged to cut open the article a~ter heat-recovery therso~0
The heat-recoverable article is preferably a heat-~hrinkable
tubular sleeve, which may have a clo~ed cro~s-~ection or may be a
wrap-around 31eeve as described in the patent specif ications referred
to above. ~he term "tubul~r" as u~ed herei~ is not limited bo
member~ of right cylindrical configuration,but i~clude~ members
o~ irregular andJor varying cro s-section as well a3 ~-~haped, ~-
shaped and ~-shaped members.
The 31eeve may, o~ course, be made from any of the heat-
recoverable material~ known in the art, but amon~t especially
pre~erred materials there may be mentioned, for example, polyole~in3,
eepecially polyeth~/lene, copolymers o~ ethylene a~d vinyl acetate,
copolymerg of ethylene and ethyl acrylate; chlorinated and ~luori-
nated polymers, e~pecially polyvinyl chloride, polyvinylidene
fluoride he~afluoroethylene and chlorotri~luoroethylene; and rubbers
~uch as ethylene~propylene rubber~ ohlorinated rubbers, e.g.
Neoprene, and silicone rubber~ which may be u~ed in a blend with a
cry~talline or gla~sy polymer such as an ole~in polymer. ~11 of the
above materials may, lf desired, be cros~-linked for e~ample by
lrradiation and/or chemical means. ~he eleeve will generally be pro-
vided at at least it~ end with an inner ¢oating of a sealant such a~
a hot-melt adhe~ive or a ma~tic although, in certain application3,
2S these may be applied on ~ite. E~pecially suitable hot-melt adhesive~
include, for example, polyamides, ethylene/vinyl acetate copolymers
and terpolymer~ (with or without incorporated wa~es) and polyester~0
Such materials are de~cribed~ for example, i~ British Patent 1,440,810
and German OS 2,709,717. Alqo suitable are curable adhesives which
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melt and flow on heating but which will not afterward~ be hot-
meltabl~. There may al~o be mentioned epoxy resin~ and con~entional
mastics ~uch, for example, a~ those based on butyl and isobutylene
rubbers modified with suitable material~ known in the artO
Obviously the use or otherwise o~ such materials and their type,
i~ chosen will depend upon the partic~lar requirements in any
given casec
The present invention i3 e~pecially applicable to the
heat-recoverable articles described and claimed in co-pending
Canadian Patent Application Serial No. 315,985 (~rom which this
application ha~ been dlvided) which compri~e a heat-shrinkable,
pre~erably tubular, sleeve which has an inner lining oY a contin-
uous metal io~l and which is preferably provided with central
reinforcing meane compri~i~g one or more longitudinally compre3sible
coil~.
The combination of the th.in metal ~oil lining and the
centrally positioned coil(q) provides an inexp~n~ive, but highly
ef~icient, means (a) for ensuring that, a~ter recovery, a cable
joint is e~fecti~ely ~ealed again~t inward water vapour tran3mission
and tb) ~or en~urirlg that the recovered article has the desired
mechanically stron~ tubular con3truction in its central region.
An e~pecially important aspect of the invention described
and claimed in Application ~o. 315,985 i~ the provision o~ the
continuous metal ~oil lining to pro~ide protection against inward
water vapour transmission. For e~ampleJ in the heat-shrinkable
articles pre~iously described in British Patent Specifieation
1,431,167 the water vapour permeability o~ the polymeric material
typically employed for the heat recoverable sleeve i~ high and thus
leads to the need for the use of ~ilica gel bags within the splice
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case at installation. However, comparative tests sug~e~t that in
the pre~erred articles described and claimed in Application No.
315,985 the metal ~oil lining leads to a reduction in water vapour
permeability by a ~actor of about 8 a~ compared with the previously
proposed product u~ing aluminium hal~ ~hells. Not o~ly i~ th~
surprising improvement obtained, but also it has been ~ound that
by choosing the correct thickness o~ the metal ~oil, which in
general ~ill be an aluminium foil, it is possible to obtain a heat
~hrinkable product which will recover to give an even surface
configuration, but in which there is no teariDg of the metal foil.
~hat is to ~ay, the metal foil i~ 3uf~iciently thin that it doe~ not
buckle and adopt a ~hape exhibiting such peaks and valleys which
might, for example, lead to damage to the heat shrinkable ~leeve or
provide a path for the ingress of contaminant~. Qn the other
hand, the metal foil i~ not ~o thin that it is damaged, e.g. torn,
during recover~v, even about sub~trate~ of irregular ~hape.
U~ing aluminium ~oil it has been found that a desirable range
of thickne~s is ~rom 10 to 25 microns~ e~pecially from 12 t~ 15
microna. Other metal ~oils which may be employed at similar thickne-
s6es include copper foil, soft iron foil (e.g. where magneticshielding l~ required) and certain metallised plastic~ ~oils such a~
the commercially availabla biaxially oriented polyester foil coated
with gold.
In one e~pecially preferred embodiment, a heat-~hrinkable
tube provided with an inner layer o~ a hot-melt adhesive i~ provided
with an inner lining o~ a metal foil of the appropriate thicknes~
which is itself provided with an internal coating of a hot-melt
adhesive. Such a product has been ~ound to be e~pecially u~eful in
encapsulating cable splice~, in wrap-around products and in making
~ ~3~23
transition~ Irom cable bo~ outlets to incoming cables.
The tubular sleeve may be one of closed cross-~ection,
i.e. w~th o~e clo~ed end, or may be a wrap-around sleeve. In the
case of a wrap-around ~leeve the metal foil may readily be applied
either during or after the manufacture of the sleeve. ~or example,
the 31eeves are typically coated with a hot-melt adhe~ive at
some stage of their manufacture, and the metal ~oil, if desired,
with its pre-applied layer of hot-melt adhesive on the sleeve is
still taoky. ~he provi3ion of an inner foil on tubular product~
o~ closed cros3-section is more difficult, but in the case of tubes
o~ small diameter it may be provided by a co-e~trusion process and
- in the case of tubes of larger diameter, it may be applied by using
a collap~ible mandrel. ~or e~ample, a mandrel may be formed from
two cylindrical hal~ sh211s which are internally hinged together,
for example by a piano hinge, one of the shells having a ~lightly
smaller diameter BO that it fitted inside the other to collapsa
the mandrel. Such a mandrel may be coated with a relea~e pla~tic
and covered with, for e~ample, aluminium foil with or withou~ a hot-
melt adhesive layer, and a heat-~hrinkable tubular ~leeve provided
with an inner layer of a hot-melt adhesive may then be partially
shrunk do~n about the mandrel and then allowed to cool. ~fter
cooli~g the mandrel may be collapsed a~ described abuve and removed
to leave the de~ired laminated product. When one or more coils is
al~o to be incorporated these may be positioned over the relea~e
pla~tic (which may, ~or e~ample, be a blend o~ a polyethylene with
a silicon based polymer) prior to application of the aluminium ~oil.
In this resp~ct, it has ~urpri~ingly been observed that the aluminium
foil lays itsel~ neatly sn the coil after shrinkaæe without tearing.
In accordance with the present invention, the articles
_ g _
described and claimed in Application No. 315,985 are provided with
a self-contained cutting means so as to facilitate rsmoval of at
least the central part o~ the article when re-entr~ is desired~
Because of the coil arrangement the use of a knife to cut the
heat-recoverable sleeve/metal foil laminate is rather difficult
becau~e there i~ no continuous surface to support the tip o~ the
knife, which could damage the splice, and tha windings of the
coil prevent a ~mooth cutting moYement. In a preferred embodiment,
therefore, the article i9 provided with a thin metal wire e.g~
a piano steel wire of a diameter of about 0.6mm which is pre-
installed longitudinally between the coil(~ and the ~oil. Especially
when the article i~ preheated it ha3 been found that a smooth longi-
tudinal cut through the laminate may be obtained merely by putting
the wire away from the coil(s). Sircular cut~ beyo~d the ends of
the central ~ection can, of course, be per~ormed in the usual way
with a kni~e if metal support rings are provided, but it is possible
~o to wind the wire that it can al~o per~orm this function. The
wire is preferably provided with a ~mall terminal ring which is
lccated o~ the outside of the heat-recoverable article and which may
be cut out a~ter local heating or otherwise removed and pulled to
effect the deeired cutting.
One embodiment of the present invention will now be
described, by way oi example only, with reference to the accompany-
ing drawing~ in whioh;
Figure 1 i8 a longitudinal section through a h~at-recoverable
article comprising the reinforcing means positioned within a heat-
shrinkable sleeve;
Figure 2 is an end view o~ the heat-shrinkable sleeve of
Figure l;
~ 3~3
-- 10 _
Figure 3 i8 a magni~ied partiall~ longitudin~l ection
of the device shown in Figure l;
Figure 4 i~ a v~ew of the device shown in Figure l;
Figure 5 is a longitudinal section through an encapsulated
joint made using the device of Figure 1; and
Figure 6 illustrates self-contained cutting means for uæe
with the device of Figure 1.
Figure 1 shows a heat-recoverable article in which a rein-
forcin~ means compri~ing a single resiliently longitudinally com-
pressible coil 5 provided at each of its end with support crowns6 and 7, as described in Briti~h Patent 1,431,167, is positioned
within a heat-shrinkable ~leeve 11 which has been partially
shrunk down about the reinforcing means in the central region.
As shown in ~igure~ 2 and 3, the sleeve 11, ~hich is made
~rom cros~-linked polyethylene having a thickness of about 2.3 mm,
is provided with an inner lining 12 of ~luminium foil of a thickness
of about 15 microns. A layer of hot-melt adhesive 13 is provided
between the lining and the foil which is it~elf coat~d on its inner
surface with a ~urther layer of hot-melt adhesive 14.
As shown in ~igure 3, the heat recoverable sleeve 11 and the
lining 12 conform to the ~hape of the coil, but the foil lining
does not tear.
Another view o~ the device of Figure 1 is shown in Figure 4
in which the prongs 15 of the terminal crown 7 are more clearly
vi~bleO
Figure 5 shows the device of Figure 1 after it has been
positioned about and shrunk over a ~unction 16 between two cables 17
and 18. As can be ~een, the provision of the crowns ensures a smooth
q'~3
change in diameter from the central region to the end region thus
ensuring that no undue stre3s on the heat-recoverable material
occurs at the end of the central region.
Figure 6 shows how ln accordance with the present in~ention
a length of piano steel wire may be wound inside the heat-recoverable
sleeve and its metal foil lining so that the desired cutting action
can be readily obtained when it is desired to re-enter the junction.
As shown, the wire 20 is wound about two supports 21 and 22 which
may be provided on the reinforcing mean~ and iæ anchored at one end
23. At the other end it is provided with a ring 24 which is acce-
ssible from the outside of the heat-~hrinkable sleeve and which
may be pulled to produce the required circular and longitudinal
cuts through the sleeve and its lining~
Whilst the present invention has been especially described
with reference to the formation of joints between electric ¢ables
it will, of course, be appreciated that the heat-reco~erable
article~ which it provides will ha~e many othex u~eful application.
