Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1066469
It has long been known that recoverable articles
are uaeful for covering, protecting and/or encapsulating
other articles. For example, elastomer sleeves have often
been used to cover cylindrical articles merely by choosing
a sleeve which, in its relaxed cDndition, has a diameter
less than that of the article to be covered. The tendency
of the sleeve to retract when it has been expanded and
placed over the article results in a covering for the article
which, for some few purposes, is satisfactory. Heat-
recoverable articles have been used in a somewhat similar
manner and generally found superior to elastomer covers in
many applications. However, many of the previously proposed
heat-recoverable encapsulating articles have not been com-
pletely satisfactory, particularly under circum~tances where
a strong and impervious bond between the recoverable article
and the workpiece which i8 to be covered is desired. For
example, it iB common practice to install insulating coverings
over electrical components such as conductors. The insulat-
ing material must, of course, be securely bonded to the con-
ductor in order to protect the conductor from water or air or
other media with which it may come into contact. Furthermore,
it is also highly important that there be no air spaces
between the covering and the conductor. The occurrence of
air spaces is particularly troublesome where the insulating
material is applied to a substrate having an irregular surface,
for example a plurality of wires which have been twistea
together to form a cable or braided structure. Thus, as
is well-known to those skilled in the art, there has been a
long standing need for heat-recoverable coverings-which are
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~066~6~1
easy to apply, and yet are capable of forming a secure,
intimate, impervious bond with the article which is covered.
U.S. Patents Nos. 3,243,211 and 3,396,460 disclose
heat-recoverable articles capable of being applied to sub-
strates in such a manner that a secure, intimate and
impervious bond was formed. Furthermore, Belgian Patent
No. 781,546 describes the use of heat-recoverable sleeves
to repair breaks in m`ine cables. These specifications
disclose, inter alia, a heat-recoverable, hollow article
provided with a fusible insert or liner. If the liner is
positîoned in abutting relationship with both the recoverable
member and the substrate to which the recoverable member
i8 to be applied, a heat-induced change, i.e., recovery,
of the recoverable member will urge the fusible member
toward the substrate and bring it into compressive abutment
therewith.
In order, however,-to obtain a secure, intimate
and impervious bond between the recoverable member and the
substrate, the interposed fusible mem~er must become "fluid~,
that is it must be reduced in viscosity to an extent
sufficient for it to flow and "wet" the adjacent surfaces
of the substrate and of the recoverable memker and thereby
form a bond therebetween. With polymeric substances, the
term "flow temperature" may be used to denote the
temperature at which the polymer has a sufficiently low
viscosity to "wet" surfaces it contacts. With substantially
crystalline polymers the flow temperature approximately
corresponds to the melting point of the polymer and the
melting point is taken herein as the flow temperature of
)66 ~6~
both crystalline ~d non-cryst~llir.e polymers. ~hus to achieve
a good bond sufficient heat should always be applied to the
fusible insert or liner to raise it above its melting point.
Under circumstances where the recoverable member i8 thin and
lts heat-recovery temperature substantially greater than the
melting point of the fusible liner this iB readily achieved.
When, however, thick recoverable members and/or comparatively
high melting fusible inserts are used, an uns~illed worker
irequently will not apply su~iicient heat completely to melt
the iusible liner. ~his is, of course, highly undesirable since
the liner will then not fully wet the suriaces oi both the sub-
strate and the heat-recoverable member, and a sufficiently
secure, intimate and imprevious bo~d may not be iormed there-
between.
The present invention provides a method oi covering
a substrate, which method comprises 80 positioning the sub-
strate, an insert, and a iirst, heat-recoverable,member that the
substrate is i~ the direction of recovery oi the heat-recover-
able member and, on recovery oi the heat-recoverable member, at
lesst part oi the insert will be urged towards the 3ubstrate,
(~
the i~sert eitherlbeing corrugated and comprising a material
that i8 fusible or a material that becomes less vi~cous on
being heated to a temperature above the storage temperature
(~)
orLcomprising a second member having at least one protuberance
on a sur~ace thereof, the second member comprising a material
that i8 fusible or a material that becom~s less viscous on
being heated to a temperature abo~e the storage temperatuL~e,
the protuberance or corrugation being-of such a size and shape
that it can be detected through the heat-recoverable member
; 30 after recovery of the heat-reco~èrable member and be~ore
.
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,~;
`- lO~;G469
application o~ a qu~ntity of heat which is su~ficient to cause
the ~aid material or the second member to ~low and being capable
o~ indicating when su~icient heat h~s been applied to cau~e the
eaid material or the second member, and/or the protuberance or
corrugation, to flow, recovering the heat-recoverable member,
and applying heat until the protuberance or corrugation detec-
able through the heat-reco~erable member indicates that the
said material or the second member has flowed and/or indic2tes
that the protuberance or corrugation has flowed.
o~
The insert, or a second member~f the~ protuberance
forming part o~ the insert, may comprise a material which is
strictly fusible, that is, which shows a sharp drop in vis-
008i~y at a particular temperature on heating to a temperature
above the storage temperature (that is, a material ~ith a
definite melting point in the temperature range in question) or
a material which is not strictly fusible, that is, does not
~how a sharp drop in ~iscosity at a particular temperature
~that is, a material without a de~inite melting point in the
temperature range in question) but does become less vi~cous
(that is more ilo~able) on heating to a temperature above the
storage temperature.
In thiS description-the insert is sometime~ referred
a
to as/"liner". It is to be understood that the terms "insert"
and "liner`' include all members which can be positioned such
that they will be interposed between a heat-recoverabie member
and a ~ubstrate. Thus, ~or esample, i~ the heat-recoverable
member iB a heat-expansible tube, the insert or liner mUBt be
such that it can be positioned around the tube.
~he invention also provides an assembly suitable for
~Q use in the method of the invention, which a~sembly comprises
,. ,i
..
1 oti~ 9
a first,heat-recoverable,membsr and ~n insert positioned in
abutting relation to, and in the direction o~recovery of, the
heat-recoverable member so that, on recovery of the heat-
recoverable member, at least par~ of the insert will be urged
towards a substrate po3itioned, in use, in the direction of
recovery of the heat-recoverable member, the insert either (A)
being corrugated and comprising a material that i9 fusible or a
material that becomes less viscous on being heated to a tem-
perature above the ~torage temperature or(~comprising a second
member having at least one protuberance on a surface thereoi,
the second member comprising a material that is fusible or a
material that becomes less viscous on being heated to a tem-
perature above the storage temperature, the protuberance orcorrugation being of such a size and shape that it can be
detected through the heat-recoverable member after recovery of
. the heat-recoverable member but before application of an amount
o~ heat which i~ ~ufficient to csuse the said material or the
seoond member to flow, and being capable of indicating when
suificient heat has been applied to cause the said material or
~econd member, and/or the protuberance or corrugation, to flow.
~ he invention further provides an assembly which
comprises a iirst, heat-reco~erable, member and an insert
poQitioned in abutting relation to and in the direction of
recovery of, the heat-recoverable member 80 that, on recovery
as of the heat-recoverable member, at least part of the insert
will be urged toward~ a substrate positioned, in use, in the
direction of reco~ery of the heat-reco~erable member, the
insert ~ither/being corrugated and comprising a material that
i8 fusible or a material that becomes le~s vi~cous on being
heated to a temperature above the storage temperature or ~)
comprising a second member having at least one protuber~nce on
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1C~6~69
a surface thereof, the ~econd member comprising a material
that is fusible or a material that becomes leæs viscous on
being heated to a temperature above the storage tem~erature,
the protuberance or corrugation being capable of indicating -
when sufficient heat has been applied to cause the saidmaterial or the second member, and/or the protuberance or
corrugation, to ilow, and the protuberances or corrugation
being detectable through the heat-recoverable member, and
al80 provides a method of covering a substrate, which
comprises so positioning the substrate, an insert, and a heat-
recoverable member that the substrate is in the direction of
recovery of the heat-recoverable member and, on recovery oi
the recoverable member, at least part o~ the insert will be
urged towards the substrate, the insert comprising a ~usible
member and a plurality oi protuberances on the suriace of the
~usible member iacing the heat-recoverable member, the pro-
tuberances being of such a size and shape that they can be de-
tected through the heat-recoverable member aiter recovery o~
the heat-recoverable member and before application of a
quantity oi heat which is suf~icient to cause the ~usible
member to flow, and applying heat until the protuberances
detectable through the heat-recoverable member disappear and
indicate that the ~usible member has ~lowed.
~hus, in accordance with the invention, a member
having protuberances on at least one sur~ace may be dispo~ed
between a heat-recoverable sleeve and a substrate over which
the sleeve is to be recovered. When the sleeve has been
recovered but insufficient heat applied to make the member
ilowable, the protuberances iorm detectable bump~ on the
outer surface oi the sleeve indicating that more heat should
be added to render the member flowable.
In this s~eci~ication, a material is said to ~low
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.... . .. ~
1066~69
or to be flowable if it has substantially no stability of
form under the pressure exerted on it by the recoverable
member.
The invention makes it possible to provide a
composite structure comprising a hollow heat-recoverable
sleeve and a liner and a method of using same whereby even
the most unskilled workman will be certain that sufficient
heat has been applied to render the liner completely flow-
able and thereby bond said recoverable sleeve to any work-
p~ece t~1~scope within same. The invention also makes itpossible to provide a means whereby simple visual and/or
tactile examination of the workpiece after heating of the
aforementioned composite structure to encapsulate said
workplece will be sufficient to determine if sufficient
heat has been applied to render the liner flowable.
Although the following discussion will be directed
primarily towards heat-recoverable members of tubular form
(sometimes for convenience referred to as "sleeves" or
"jackets"), it should be understooa that the present
invention is equally applicable to and therefore encompasses
structures wherein the heat-recoverable member is in the
form of an end cap (for example, a cup), a T, X or Y, a ring
or any other hollow configuration having at least one open
end which can receive a substrate workpiece. Furthermore,
the heat-recoverable member may be either heat-shrinkable
or heat-expansible.
According to the present invention, the surface
of a second member or liner is provided with a protuberance,
or a plurality ~ separate upstanding protuberances, which may
be formed fram either the same material as the second member
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1066~69
or other compatible material (as hereinafter defined).
These protuberances may be present on either the surface of
the second member aisposed towards the substrate or the
surface disposed towards the heat-recoverable member, or
both. If the heat applied to effect recovery of the heat-
recoverable member is sufficient to also render the second
member flowable, then the protuberances will melt and the
recovered composite structure will have a smooth outer
surface (for example, the outer surface of an encapsulating
sleeve will be smooth). eonversely, if the amount of heat
supplied is sufficient to effect reeovery of the heat-
recoverable member, but insufficient to render the second
member completely flowable, then the protuberances on the
member will not melt and will form corresponding bulges
showing on the surface of the recovered member. Even under
conditions of poor visibility, such bulges can readily be
felt by running the hand over the recovered member. The
heating referred to in this specification as being required
to effect recovery of the heat-recoverable member and
flowing of the second member may be by any positive
application of heat, for example, radiation heating, in-
duction heating, electric resistance heating or heat
generated by an exothermic reaction.
~he number, form and manner of disposition of the
protuberances on the second member according to the in-
vention is not critical provided the basic objective of the
invention is adhered to. With respect to number, obviously
if only a very limited number of protuberances are present,
the operator a~ter recovery will be less certain that all
the $usible liner, including the areas thereof which are
~66~69
furthest from any protuberance, has been sufficiently
heated. It i8 therefore apparent that sufficient protu-
berances should preferably be present so that their
disappearance on heating i8 a clear indication that all of
the second member has been rendered flowable. Likewise,
to achieve this objective the protuberances are preferably
distributed over substantially the entire surface of the
second member. Such distribution can be random or in any
conceivable geometric pattern. With respect to the form of
the protuberances, they can be, for example, discrete (for
example bumps or pimples) or in the form of continuous or
discontinuous lines (for example, ridges). Preferably such
bump~ or ridges will be sharp sided and relatively high in
proportion to their cross-sectional area so that if they
?5 are not fully melted they will form readily apparent
corresponding bumps or ridges on the surface of the recover-
able memker. Thus it is preferable that the height of the
protuberances be equal to at least about the diameter or-.
width, as the case may be, of the base of the protuberance.
It is further preferred that the height of the protuberances
be at least about equal to the thickness of the-recovered
member with which they are associated. Obviously, the most
appropriate nu~ber and form of the protuberances will vary
with the thickness and shape of the recoverable member and
the contemplated heating means and for any given type of
heat-recoverable member can readily be determined by simple
routine experiment.
The inserts can be functionally combined with the
heat-recoverable member in any suitable manner. For
example, the insert material may be applied to either the
_ g _
1066~69
heat-recoverable member or to the substrate as a coating
thereon with the protuberances being disposed on either or
both surfaces of the insert. For example, the insert can
be coated on the inner surface of the heat-recoverable
member, i.e., the surface which is disposed towards a
substrate telescoped therewithin, the outer surface or
both. Normally, the protuberances will be present on the
surface of the fusible insert which i8 not bonded to the heat-
recoverable member and will therefore be disposed towards
the substrate. Conversely, if the insert is applied to
the outer surface of the substrate the protuberances will
typically be on the other surface of the insert, being
thereby disposed towards the inner surface of the enveloping
heat-recoverable member. However, if desired, the side
containing the protuberance(s) may readily be bonded to
the substrate or sleeve, for example, by bonding the liner
at points between the protuberances. Alternatively, the
- insert in sheet form can first be wrapped around the
substrate followed by telescoping the encased substrate
within the sleeve. Or, a separate integral tube of insert
can be interposed between the substrate and the heat-
recoverable member. Under these circumstanees the insert
can have protuberances present on either or on both of its
surfaces, that is, the surface disposed towards the
substrate and/or on the surface disposed towards the heat-
recoverable member.
If the insert is to be positioned on the inner
surface of the heat-recoverable member this would, of course,
be done subsequent to the deformation of said member to its
heat-recoverable condition. -If desired, although this is
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1066~69
not preferred, the insert need not coat or envelop the
entire surface of the substrate or coat the entire surface
of the heat-recoverable member but can be deposited on
either the substrate or heat-recoverable member in the form
of rings, strips or other discontinuous areas of material
on the substrate outer surface or jacket inner surface,
respectively.
In general, the protuberances will be of the same
material as the second member and will have the same melting
point as the second member. However, in some cases, it may
be desirable for the protuberances to melt or flow at a
temperature different from that of the rest of the liner.
For example, the protuberances may melt or flow at a
temperature higher than the temperature at which the rest
of the liner melts or flows. In such a case, there would
be a heat margin, thus insuring that the rest of the liner
had melted or flowed when the protuberances di~appeared.
Further, if the protuberances melt at a temperature higher
than the melting temperature of the rest of the liner, they
may dig into either the substrate or the sleeve thus
providing for maintenance of good gripping between the
liner and substrate, liner and sleeve or all three prior
to fusing of the liner. Indeed, the protuberances may be
infusible at the heating temperatures so that they remain
in contact with the substrate and/or sleeve after the rest
of the liner has melted. For this purpose, pieces of,
for example, metal, ceramic or a thermosetting plastics
material, which may be applied, for example, by sprinkling
them onto the insert, m~y be used as protuberances,
protuberances which mechanically engage the sleeve and/or
106G~6~
the substrate may increase the mechanical strength of the
joint. In particular, when the substrate comprises two
articles having a joint or splice therein, such protuber-
ances may provide mechanical reinforcement of the joint
or splice against stress in use and may assist in
preventing, for example, ~ngitudinal or torsional slippage.
Alternatively, the protuberances may melt or flow
at a temperature lower than the melting or flowing
temperature of the second member. Use of such lower melting
or flowing protuberances may be desirable where timed heating
is to occur. For example, when applying sleeves with
fusible liners to cold pipelines, it is desirable to heat
the sleeve covering the pipeline for a set period of time
after a predetermined temperature has been reached. Thus,
if the protuberances are set to melt at the predetermined
temperature, timing can be started from that point.
The protuberances may be used for purposes other
than indicating whether fusing of the second member has
occurred. ~hus, it is sometimes desirable to have a layer
of foamed material as a liner for imparting desir~ dielectric
properties. The protuberance~ may be fusible or hollow
and fusible so that they allow sufficient volume for
controlled foaming of the balance of the liner. Thus,
foaming agents placed in the liner could result in the
production of a foam which would occupy, in part, the
space originally occupied by the hollow protuberances.
The protuberances on the second member can be
formed in a wide variety of ways, the choice being
primarily dependent upon whether the insert is to be used
as a separate sheet or tube or on the recovèrable member
6~
or substrate, as described above. Where the insert is used
in the form of a separate sheet or tube, such a sheet or tube
may be prepared by extrusion. Thus, the sheet or tube may
be extruded using a die shaped to extrude a sheet or tube
profile with ridges integrally formed thereon. Alternatively,
a transfer coating apparatus can be used to embo~s any
desired pattern of protuberances on either or both of the
sheet surfaces. A tube, sheet or a coating of material
can be provided with protuberances by sprinkling pellets,
preferably of the insert material, onto the surface of the
tube, sheet or coating which will preferably be warmed
sufficiently to ensure adherence of the pellets. A tube
interiorly coated, that is, lined, with a suitable material
can be provided with internal ridges, either longitudinal
or helical, by passing the lined tube over a vertical spray
head which i8 received within the tube and sprays molten
material onto the interior surface of the second member.
If the lined tube is simultaneously rotated as it traverses
the spray, helical ridges are formed. Alternatively, an
internal rotating spray head can be used to provide a
series of ridges on the inside surface of the second member
where the tube is stationary and the head rotates and then
either the tube or the head is displaced in stages
longitudinally. Another method is to partly heat-recover
a heat-recoverable tube with a liner onto an engraved
mandrel which will thereby emboss any desired pattern of
ridges or bumps on the liner inner surface.
Under some circumstances, it may be desirable to
_ bring the insert to a temperature somewhat higher than its
flowing or melting point or range. In these cases, the
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1066~69
protuberances may be made by sprinkling or otherwise app~ying,
as described above, onto the surface of the second member
protuberances of a material with a melt or flow temperature
higher than that of the second member,the material being
compatible with the second member. In some cases, the
desired temperature corresponds to the softenlng temperature
of a cable upon which the heat-shrinkable jacket is being
applied. The term "compatible", as used herein, merely in-
dicates that at the melting or flow temperature of the
higher melting protuberance material, said material will
become dissolved or otherwise dispersed into the material
of the second member when the latter is flowable. In many
instances the melting point or flow temperature of the
protuberances is substantially the same as that of the
second member so that flowing and elimination of the
protuberances indicates flowing of the second member. In
other instances (see above) the melting point or flow
temperature of protuberances may advantageously be sub-
stantially above or below that of the second member.
The heat-recoverable member used according to the
invention may be extruded or moulded in the desired shape.
Where a simple tubular shape is desired, it may also be
fabricated from a flat sheet of material simply by rolling
it into a tube and suitably sealing the seam. Preferably,
the heat-recoverable member comprises a material having the
property of elastic memory, for example those materials
disclosed in United States Specification No. 3,086,242.
As is well-known to those skilled in the art, materials
having the property of elastic memory are dimen~ionally
heat-unstable and may be caused to change shape and/or
- 14 -
1~66~69
dimension simply by the application of heat. Elastic
memory may be imparted to polymeric materials by first
extruding or otherwise moulding the polymer into a
desired shape. The polymer is then crosslinked by
exposure to high energy radiation, for example, a high
energy electron beam, exposure to ultra-violet irradiation,
or by chemical means, for example, incorporation of peroxides
when polyolefins are used. The crosslinked polymeric
material is then heated and deformed and then locked in that
deformed condition by quenching or other suitable cooling
or, alternatively, the same process can be carried out at
room temperature by using greater force to deform the
polymer. The deformed material will retain its shape almost
indefinitely until exposed to an elevated temperature
sufficient to cause recovery, for example, approximately
250F in the case of polyethylene. Among the polymers which
can be processed in this way are polyolefins (for example,
polyethylene and polypropylene), polyamides, polyurethanes,
polyvinylchloride, polytetrafluoroethylene and polyvinyl-
idene fluoride. The property of elastic memory can also be
imparted without actual crosslinking to materials having
the properties of crosslinked polymers (for example poly-
tetrafluoroethylene, polyolefins, or vinyl polymers) which
have a sufficiently high molecular weight to give the
polymer appreciable strength at temperatures above the
crystalline melting point.
Suitable materials for the insert include inorganic
fusible materials, for example, solder, and conventional
thermoplastics materials, for example polyolefins (for
example, polyethylene and polypropylene), polyamides (for
106~i~69
example, Nylon 6 and Nylon 66), polyesters (for example
polyethylene terephthalate), and polyether sulphones (for
example, 4,4'-phenylene ether sulphone). Particularly
preferred are hot melt adhesives, for example those
disclosed in German Offenlegungsschrift No. 2,347,799
filed in the name of Raychem Corporation and published
25th April, 1974. It is to be understood, however, that
the present invention is not limited to the use of
conventional thermoplastics as the fusible material and
initially flowable thermosetting materials are also
suitable. Materials such as epoxy resins, polyurethane
resins, phenolformaldehyde resins and the like may, therefore,
also be used either alone or in combination with a thermo-
plastic material to form the insert.
The invention will now be described, by way of
example only, with reference to the accompanying drawings,
in which:
Figure~ 1 and 2 are enlarged, fragmentary v~iews
of two different liners according to the
invention,
Figure 3 is a view of a heat-recoverable sleeve,
liner and substrate,
Figure 4 is a view of a substrate having
positioned around it a liner and a heat-
recoverable sleeve;
Figure 5 is a view illustrating bumps visible
through the sleeve when the liner has
not been heated sufficiently to flow:
Figure 6 is a view illustrating a method of
making a liner,
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106~;~69
Figure 7 is a cross-section through a sleeve and
liner illustrating embossing of the
liner; and
Fîgure 8 is a view, partly in cross-section,
illustrating the formation of a liner
having helical rid.g s.
Referring now to the drawings, Figure 1 shows a
liner 1 which includes protuberances 2 in the form of bumps
or pimples. m e liner is in the form of a sheet which
could be wrapped around a substrate, but it should be
understood that the liner could be in the form of a tube or
could have any other desired shape. It can be seen that
the pimples 2 are sharp and relatively high in relation
to their cross-sectional area. Normally, when the lincr
is placed in the direction of.recovery of a heat-recover-
able member, the pimples are disposed away from the
. member. If desired, however, the liner could be positioned
with the pimples 2 disposed toward the.recoverable member
Also, although only one side of the liner 1 is provided
with protuberances, it could have protuberances on both
sides.
Figure 2 shows a liner 1 which includes ridges~
These ridges may be discontinuous ridges 3 or continuous
ridges 4. The ridges may also be placed on both sides of
~5 the liner and should be relatively high in relation to
their cross-sectional area.
The use of the liner which includes protuber~nces
is illustrated in Figure 3. A substrate 5 is inserted into
a heat-rccoverable slceve 6 having an inner liner which
comprises a fusiblc mcmber 7 with protuberanccs 8 illustrat~d
1066~6~
here as bumps. In this Figure, the liner is attached to the
recoverable sleeve 6 and the protuberances are disposed
toward the substrate 5 as illustrated, they could, however,
be on the sleeve 3ide of the liner if desired.
In Figure 4, a substrate 9 is covered with a
liner which includes a second member in the form of a tube
10. This liner includes protuberances 11 again illustrated
as bumps. A recoverable sleeve 12 is then placed over the
liner and heat-recovered. In this case, the protuberances
are preferably disposed toward sleeve 12.
When either sleeve 6 or sleeve 12 is heat-
recovered, the sleeve may recover before enough heat has
been applied to cause the 3econd member to flow. In that
case, the protuberances will be visible on the outer
surface of the sleeve. This condition is illustrated in
Figure 5. As can be seen, a substrate 13 is covered by a
heat-recoverable sleeve 14. A second member 15 has not yet
become flowable and, as a result, the protuberances are
visible at 16 on the outer surface of heat-recoverable
sleeve 14. When this condition exists, it can be seen and
the workman applying the sleeve can thus readily determine,
either visually or by feel, that insufficient heat has been
applied and that more heat should be applied. When the
outer surface of sleeve 14 becomes smooth, this indicates
that the second member has reached a flowable condition,
and that sufficient heat has been applied.
Figure 6 illustrates a method of manufacturing a
liner. A sheet of fusible material 17 is warmed and then
pellets of fusible material 18 are sprinkled onto the
surface to form protuberances 19. The pellets should be
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i9
compatible with the material 17 so that they adhere thereto
when material 17 is warmed.
A~ illustrated in Figure 7, protuberances can also
be formed while using an engraved mandrel. A tube of heat-
recoverable material 20 is provided with an inner sleeve 21
of insert material. The tube is then placed over a mandrel
22 having grooves or indentations 23 therein. The heat-
recoverable sleeve is then partially heat-recovered over
the mandrel. q~he heat causes the inner sleeve 21 to flow
into the indentation 23 thus forming protuberances on the
inner surface of the sleeve 21. The sleeves 20 and 21 are
then removed from the mandrel, and a heat-recoverable tube
20 having an inner liner with protuberances on the inner
surface is obtained.
A method for forming protuberance~3 in the form of
ridges on the second member is illustrated in Figure 8. A
heat-recoverable tube is indicated generally at 24. It
comprises an outer heat-recoverable sleeve 25 and an inner
member 26. The member 26 has protuberances in the form of
ridges 27. These ridges are applied by spraying fusible
material through a spray head 28. The ridges 27 are formed
helically by rotating tube 24 and at the same time moving
it laterally. Alternatively, the spray head 28 ~uld-be
rotated as tube 24 moves laterally.
In addition to the embodiments specifically
disclosed in the Figures above, it should be understood
that this invention is applicable to any type of pro-
tuberance on the liner and any method of forming such a
protuberance. Thus, protuberances in any form may be
employed, the only restriction being that the protuberances
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1~66~
be discernible by sight or feel when the heat-recoverable sleeve is re-
covered without causing the second member to become flowable. Further, any
method of forming the protuberances which is desired may be employed.
It should be understood that in the method and assembly of the
invention the insert may be a fusible corrugated article which may have one
or more corrugations.
It will also be appreciated that the invention is applicable to
recovery over any type of substrate which may be in the form of one or more
articles.
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