Note: Descriptions are shown in the official language in which they were submitted.
l ~ 7762~
This invention relates to heat~recoverable
articleA and their use in the insulation and protection
of substrates such as supply lines.
Heat-recoverable articles, especially heat-
shrinkable articles, are now widely used in many areaswhere insulation, sealing and encapsulation are
required. Usual~y these articles recover, on heating,
towards an original shape from which they have
previously been deformed, but the term "heat-
recoverable", as used herein, also includes an articlewhich, on heating, adopts a new configuration, even if
it has not been previously deformed.
In their most common form, such articles comprise
a heat-shrinkable sleeve made from a polymeric
material exhibiting the property of elastic or plastic
memory as described, for example, in U S. P~tents
2,027,962, 3,086,242 and 3,597,372. As is made clear
in, for example, U,S. Patent 2,027,962,the original
dimensionally heat-stable form may be a transient form
in a continuous process in which, for example, an
extruded tube is expanded, whilst hot, to a dimen-
sionally heat-unstable form but, in other applications,
a preformed dimensionally heat stable article is
deformed to a dimensionally heat unstable form in a
separate stage.
In other articles, as described, for example, in
British Patent 1,440,524, an elastomeric member such
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1 177~27
as an outer tubular member is held in a stretched
state by a second member, such as an inner tubular
member, which, upon heating, weakens and thus allows
the elastomeric member to recover.
Heat-shrinkable sleeves find many applications,
especially in the connection and termination of wires,
cables and pipes. However, there are other applica-
tions where it is desirable to provide a connecting,
insulating or protective heat-recoverable member
for enlongated objects such as cables and pipes
where the ends are not accessible or, if they are
accessible, where it is undesirable to disconnect
: or otherwise displace them. For such applications
: so-called "wrap-around" sleeves have been developed.
Basically these are heat-recoverable sheets which
can be wrapped round the substrate to form a generally
tubular shape and which, in general, are provided
with fastening means for holding them in the wrapped-
up configuration during recovery. Typically such
fastening means are mechanical in nature and comprise,
for example, rigid clamps, pins or channel members
which co-operate with suitably shaped moulded or
extruded protuberances adjacent to the overlapping
edges of the heat-recoverable sheet. Various types
of fastening means are described, for example, in
.S. Patents 3,379,218 and British Patents 1,155,47Q;
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1,221,988 and 1,346,~79. In other applications,
however, the sheet may be held in the wrapped-up
configuration during recovery by means of an adhesive
which may, in some cases, be applied on site.
Heat-recoverable sleeves and wrap-around sleeves
have been successfully employed in many fields of
application. However, problems may arise when two
or more substrates such as supply lines, for example
cable or pipes, have to be sealed at one position.
This problem, which is known as "branch-off" may
occur, for example, at the outlet of a heat-recoverable
part. Amongst areas in which this problem is typically
; encountered there may especially be mentioned the
outlets of the splice cases described and claimed
in British Patent 1,431,167, the feed-through devices
described and claimed in British Patent 1,245,119
and the duct seal devices described and claimed
in Canadian Patent No. 1,100,156.
One effective solution for tubular sleeves
has been to use moulded heat-shrinkable parts pro-
vided with preformed outlets for the individual
supply lines. However, in general such moulded
; parts have to be made to suit a specific application.
Their versatility has been improved by the use of
end caps which seal outlets which are not needed
in a specific operation, as described and claimed
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1 177~2'7
in German Offenlegungsschrift 2,748,383, but they
are nonetheless expensive and thus their use becomes
economically lnfeasible in many routine applications.
Another, less expensive, solution which has
frequently been employed is to use mastic tape to
seal the gap between the supply lines so that, on
recovery, a proper encapsulation is formed at the
end of the heat-recoverable part. However, the
use of such tape requires skill on the part of the
installer and the method is not applicable to large
arts. In addition, the mastic may degrade the
overall performance of products which are provided
with an inner lining or coating of a hot-melt adhesive.
The present invention is based on the surprising
discovery that an effective branch-off at the end
of a heat-recoverable part can be obtained by forming
the individual outlets by means of a suitably shaped
clip made from a relatively rigid material.
Accordingly, the present invention provides a
method of forming a branch-off seal between a heat-
shrinkable sleeve
- 4a -
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and at least two substrates such as supply lines ~-hich
comprises the steps of
(a) positioning a clip having at least two elongate legs
on the heat-shrinkable sleeve at an open end thereof
with at least one of said legs inside the sleeve so
as to form at least two terminal conduits,
(b) positioning the substrate within the conduits: and
; (c) applying heat so as to effect shrinkage and to form
the desired seal.
It will be appreciated that step (a) and (b) ~ay be
effected in any order or simultaneously, For exam~le in
~; many cases the clip will be pushed into place afte~ the
sleeve has been positioned about the substrates.
The present invention also provides an assem~ly
15 resulting from the above method, which comprises a sleeve
having at least two substrates emerging from an end therof
's and a clip having at least two elongate legs positioned on
,~ the sleeve so as to form two conduits for the subs~rates, one
of the legs being positioned within the sleeve,
Whilst it has been proposed to use clips and other
clamping devices in connection with heat-shrinkable products
. "
it has never before been proposed to use a clip, as in the
present invention, to form two or more outlets frcm a
heat-shrinkable sleeve and maintain them agains~ the recovery
forces of the sleeve. Thus, whilst Belgian Paten'. 833,916
proposes to provide clips between the outlets of 2 spl ice case
it specifically states that heat-recoverable surfaces sho~ld
~, not come into contact with each other and for th~s reason
in preferred embodiments, forms the operative part of the
splice case from a heat-recoverable upper part positioned
,
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1 ~77~27
on a non-heat-recoverable lower part which is provided
with a ridge or ~inger to prevent contact of the
heat-recoverable material with itself as it passes
round a cable. In addition, the material of the
heat-recoverable upper part is not deformed, except
around the cables, so that the clips, which are
;~ positioned between the cables, do not enclose any
heat-recoverable material and thus are not subjected
to any recovery forces which might tend to deform
them; this is stated to be an advantage.
Similarly, whilst German Offenlegungsschrift
2,413,623 proposed to use a U-shaped clip in con-
junction with a heat-recoverable branch-off, the
clip is not employed until after shrinkage and is
designed to be positioned inside the heat-recoverable
sleeve between adjacent cables.
The methods using clips in the prior art are,
therefore, completely different from the method
using them in the present invention.
In its simplest form the clip used in the present
invention is U-shaped and its two legs are slid
over the surface of the heat-recoverable sleeve
or wrap-around sleeve and another co-operating surface,
which may itself be part of another heat-recoverable
component, to form the conduits at one end of the
sleeve. It is surprising that such a clip does
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not "milk-off" during xecovery. Of course, the
clip must be sufficiently long, especially if the
substrates are large,but a suitable length can readily
be ascertained by simple tests, and resistance against
milk-off can be increased, if desired, by providing
saw-tooth or sinusoidal surfaces on the legs of
the clip but, in general, this will not be necessary.
Another way in which milk-off can be avoided
is to apply heat to the clip and the heat-recoverable
material in the vicinity thereof before effecting
total recovery. This local heating step results
in a local increase in thickness of the heat-
recoverable material and enhances the gripping action
of the clip. In addition if, as in preferred embodi-
ments, the sleeve or wrap-around sleeve is provided
with an inner coating of an adhesive, the adhesive
flows and thus ensures that a satisfactory bond
is formed in the vicinity of the clip prior to recovery
about the substrates. Such a local heating step
may advantageously be employed with all forms of
clip used in the present invention.
In further preferred embodiments of the present
invention, as described in more detail hereinafter,
the clip itself is constructed so as to obviate
the problem of milk-off and may, for this purpose,
be adjustable so as to conform to the requirements
of any situation.
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1 177627
This clip used in the present invention is
advantage~usly made from a thermally conductive
material and/or is so constructed that it facilitates
the application of heat to the heat-recoverable
material in its vicinity (for example, it may be
constructed as described and claimed in German
Offenlegungsschrift 2,756,021). However, in other
instances, the heat-recoverable sleeve may be pro-
vided with internal or self-contained heating means
in which case the clip may be made from a non-
~hermally conductive material.
For this and other reasons the clip is preferably
made from a metal including, for example, steel,
copper, brass, beryllium copper, and, especially,
aluminium. An aluminium clip may be made, for example,
by mould injection possibly followed by a deburring
operation to remove sharp edges; a steel clip may
be made by stamping followed, if necessary, by a
similar deburring operation. In many applications
it will be desirable to protect the clip agalnst
corrosion, for example, an aluminium clip is preferably
given a black anodization treatment or is provided
against mechanical damage by, for example an epoxy
; resin coating. Such a coating may further provide
electrical insulation, for example where two lead-
jacketed cables are involved.
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~ 177~27
The significance of the function of the clip
in the transference of heat to and away from the
heat-recoverable material and adhesive in its vicinity
is another factor not appreciated in the prior art.
Thus, whilst Belgian Patent 833,016 mentions that
; a clip may be made from metal, it also mentions
many other non-thermally conductive materials, such
as plastics which would not, in general, be suitable
in the present invention, its preferred material
being a glass filled polyamide. German OS 2,413,623
does not mention the material from which the clip
is made.
In certain applications, the metal of the clip
may be a memory alloy, for example one of the nickel-
titanium alloys described in U.S. Paterts 3,174,851;
3,351,463; 3,753,700 and 3,759,552 or a beta-brass
alloy as described in U.S. Patents 3,783,037 and
4,019,925. In such instances the clip itself may
be heat-recoverable so that the legs of the clip
move towards each other when the assembly is heated
to effect shrinkage of the sleeve. (Alternatively,
the clip may be heat-recovered before or after said
step.) Preconditioned memory alloys, especially
beta-brass alloys, are preferred for use in this
aspect of the present invention. Such alloys and
methods for preconditioning them are described and
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1 1~762~
claimed in U.S. Patents 4,036,669; 4,067,752 and
4,095,999.
In other embodiments the clip may be made from
a resilient metal such as spring steel or beryllium
copper and may exert resilient forces to enhance
the seal formed. Thus resiliently deformed outer
legs may be "held out" for example by hot melt adhesive
so that they spring together on heating.
Whilst the simplest form of clip used in the
present invention is generally U-shaped, it will
be appreciated that its configuration may be varied
from application to application. For example, in
some applications it may be necessary to form more
than two outlets at the end of the heat-recoverable
component. This may be done by providing two or
more simple U-shaped clips between the outlets or,
in another arrangement, a single clip may be employed,
such as having three or more legs so that each adjacent
pair of arms acts as a simple U-shaped clip. These,
and other configurations, fall within the scope
of the present invention.
In one especially preferred embodiment of the
present invention the clip is formed as a trident
and the central leg of the trident passes into the
heat-recoverable sleeve whilst at least one of the
outer legs passes outside it. In this way a layer
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1 177~27
of heat-recoverable material is pinched between
the central leg and the outer leg. In such a clip
the inner surfaces of the outer legs preferably
taper inwardly, so that the gap between the outer
legs is greater at the open end of the clip than
at the base of the gap. The surfaces of the central
legs are also preferably tapered so that they run
substantially parallel with the inner surfaces of
the outer legs. Such an arrangement facilitates
the positioning of the clip on the sleeve, which
is especially useful for large diameter sleeves,
and, once the clip is positioned in the heat-
recoverable sleeve, milkir.g-off becomes practically
impossible, especially after recovery. It will
be appreciated that with such a clip the inner surfaces
of the heat-recoverable sleeve do not come into
contact in the vicinity of the clip and the central
leg of the clip acts to separate the two conduits
which are formed. For this reason the central leg
is preferably provided on each side with a layer
of a hot-melt adhesive or another heat-activatable
sealant, which flows during recovery to seal the
gap between the conduits and thus ensures that the
substrates within the conduits do not come into
; 25 contact.
The sides of the central leg are, therefore,
preferably roughened or contoured to facilitate
1 1
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1 17762~
adhesion and, also, to ensure the adhesive remains
in the area of the clip on heatin~. An especially
preferred clip has a waffled pattern on the surfaces
of the central leg.
The outer legs of the clip are preferably pro-
vided with a thermochromic indicator. The reason
for this is that when heat is applied to the clip,
there may be a temperature difference of as much
as 20C between the outer legs and the central leg.
The use of a thermochromic indicator (such as, for
example, a system using the melting of white poly-
propylene powder in a suitable binder) ensures that
the operator applies sufficient heat to cause the
hot-melt adhesive on the central leg to melt and
flow.
The clip may, of course, be provided with other
means for indicating that a desired temperature
has been reached. For example, a resilient member
such as a spring having an indicator element attached
thereto, may be held in a biased position by a hot-
melt adhesive so that, when the adhesive melts,
the spring resiliently recovers causing the indicator
element to move and thus signify that the desired
temperature has been achieved.
Similarly, the clip may be provided with means
for indicating that pressure seal has been safely
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1 ~7762~
achieved. In one pre~erred embodiment means are
provided for indicating both that the desired tem-
perature has been achieved and that there are no
leaks in the seal at the outlet(s) of, for example,
a pressurized splice case. In such an embodiment
an indicator element may be held in a fixed position
by a hot-melt adhesive but may be caused to move
when the adhesive melts by the pressure built up
~ inside the sealed joint; if the indicator does not
; 10 move, either the adhesive has failed to melt, i.e.
.he required temperature has not been reached, or else
the pressure has failed to reach the required level
because of a leak in the seal formed on recovery.
-In a simple device of this sort, the hot-melt adhesive
(or another thermofusible material) may itself act
as the indicator, being extruded from the clip when
the pressure builds up inside the joint.
A clip for use in the method described above
advantageously comprises two or more outer elongate
legs and at least one central leg, the inner edges
of the outer legs and the edges of the central leg
forming channels for the insertion of heat-recoverable
sheet material between the outer legs and the central
leg and at least part of the surfaces on both sides
of the central leg being provided with a heat-
activatable adhesive or sealant and, as described
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1 177~2~
above, these surfaces of the central leg being pre-
ferably roughened or contoured.
In certain applications, especially in the
formation of branch-offs from pressurized splice
cases and/or with cables of 30 mm diameter or more
~e.g. from 35 to 80 mm), it may be advantageous
for the inner edges of both outer legs and the edges
of the central leg to lie in a mutually parallel
arrangement.
However, in many applications, as described
before, it will be preferable for the inner edges
of the outer legs and the edges of the central leg
to taper inwardly towards the closed base of the
clip. Such a clip has certain advantages. First
of all, the tapering of the inner edges of the outer
legs and the edges of the central legs provides
two sloping channels, so that when the clip is slipped
on to the sleeve it is virtually locked in position.
It will be appreciated, however, that once again,
on shrinkage the heat-recoverable material thickens
and further tightens the clip to the sleeve. Another
advantage is that by correct choice of the angle
defined by the outer legs and correct choice of
the maximum width of the central leg, it is possible
to tailor the clip to conform with the substrates.
In this respect it may also be preferable for the
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1 177~2~
central leg to be longer than the outer legs. Inthis way the required seal between the branch conduits
formed is facilitated.
Other ways in which the clip may be shaped
to conform with the substrates and thus, for example,
to reduce the risk of adhesion failure are to provide
concave outer surfaces on the central leg of the
clip to accommodate small sized cables (e.g. of
from about 8 mm to 35 mm diameter) and to provide
a central leg of lesser thickness, at least over
part of its lensth, to accommodate large size cables
(e.g. of diameter greater than about 30 mm, typically
from 35 to 80 mm).
Once the hot-melt adhesive has flowed to fill
the gap between the conduits, it will not be possible
to remove the clip without causing the sleeve to
become disbonded from the substrates. Thus there
is no danger of the clip slipping off and leaving
the branch-off division liable to failure by peel.
It will be appreciated that the trident clip
may be adapted to multi-outlet branch-off arrange-
ments in the same way as the simple U-clip and,
in some instances, it is even possible to construct
a clip which is adjustable according to the direction
required by the conduits. In some multi-outlet
clips it may be appropriate to form the central
- 15 -
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1 17762~
leg as a solid or hollow generally conical memberco-operating with a plurality of outer legs.
Similarly, as in the simple U-clips, the base of
the gaps in the trident clip may be cut away to
provide extra strength, in which case the thickness
of the adhesive coating must be such as to provide
sufficient material to fill these gaps on recovery.
A typical range of hot-melt adhesive thickness on
each side of the central leg is from 2 to 5 mm,
but the thickness may, if desired, be varied along
the length of the leg, it being greater at the open
end of the clip than at the base. As mentioned
above, the surface of the central leg is preferably
rough or is corrugated or waffled to provide a seat
for the adhesive and also to ensure that, on recovery,
adhesive is not forced away from the central leg
but, rather, ls forced into the surface irregularities.
In these and other embodiments of the present invention
it may be advantageous to pigment the hot-melt adhesive
so that its diffusion into and coalescence with
the clear hot-melt lining of the sleeve may be noted
to indicate that sufficient heating has occurred.
A further design modification concerning the
provision of a hot-melt adhesive layer on the central
leg is to provide it with one or more upper and/or
lower longitudinal ridges over at least part of
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1 1776~
the length of the central leg to enhance the initial
push-fit force of the clip on a sleeve and thereby
to facilitate secure positioning of the clip on
relatively thin expanded coated sleeves.
The strength of the clips used in the present
invention is enhanced when they are made from flat
stock, that is to say, when the width of the legs
extending above and below the heat-recoverable
sleeve is greater than their thickness in contact
with the sleeve. Typically, the width will be from
1.5 to 3 times the thickness.
In some especially preferred embodiments of
the present invention, one or more of the legs of
the clip, especially the central leg, may be used
to fulfil a secondary function. For example,
the central leg may be hollow and act as an inlet
or outlet for compressed air, as in a pressurized
splice case, or for jelly, epoxy resins or foam
materials, etc. The leg may, of course, be provided
with a valve for such a purpose. In some of these
embodiments the leg may itself act as a substrate.
For example, a branch-off may be made from a single
cable using such a clip specifically to provide
an inlet valve.
In other embodiments, the clip may be provided
` with means for ensuring that electrical continuity
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l l7762~
is maintained between, for example,shielded cables
positioned within the condutis. Such means may
comprise, for example, jaws or similar members posi-
tioned on one or more of the legs of the clip and
adapted to receive and grip tags cut from or attached
to the shielding of the cables.
Whilst, in general, it is not contemplated
that the clips will be used in conjunction with
other members it is possible that in some cases
it may be advantageous to provide a co-operating
insert member and/or to use the method of the present
invention in conjunction with other methods including,
for example, the mastic tape method referred to
above. In certain instances it may also be advan-
tageous to use the clip to connect the heat-recoverable
sheet material to another component. For example,
a plurality of clips may be used to form branch-offs
around a distribution box or to form a large number
of branch-offs from a single splice case by using
a further heat-recoverable component such as a cap
positioned internally of the heat-shrinkable sleeve.
Such embodiments are explained in more detail here-
inafter.
It will be appreciated that the heat-recoverable
sleeve may be a wrap-around sleeve and/or may comprise
a closed end, i.e. it may be an end cap, or may
- 18 -
1 ~7762~
be part of a larger article, for example a largerheat-recoverable article, and that, in any case,
the present invention is not in any wa~ limited
to the size or configuration of the heat-recoverable
component. For example, the heat-shrinkable sleeve
may be formed from two (or more) sheets of heat-
recoverable material. All that is necessary for
the purposes of the present invention is that the
heat-shrinkable component has a hollow terminal
portion within which the substrates are positioned.
When the clips are used in conjunction with
a wrap-around sleeve it may be advantageous to form
the clip so that it can co-operate with the fastening
means of the wrap-around device. In some instances
it may even be possible to form the clip as part
of said fastening means.
Whilst, the clip will be held securely in posi-
tion by the heat-recoverable sleeve anc, in some
embodiments, may be made adjustable so that the
2~ gap between the legs can be altered according to
the thickness of the sleeve so as furt~er to facilitate
the formation of a secure grip upon recovery, it
may, in certain applications, be advantageous to
provide the clip with one or more members which
co-operate with the substrates externally of the
heat-recoverable sleeve so as to facilitate the
- 19 -
1 177~2~
correct positioning of the clip. For example a clipmay be provided with a ring member which is adapted
to surround a pressure transducer externally of a
heat-shrinkable splice case joint. In another embodi-
ment a clip may be provided with metal straps whichcan be fastened around heavy cables as they leave
a joint so as to provide strain relief for the joint.
The heat-recoverable material may be of any
of the polymers known from the art to be useful for
the production of heat-recoverable articles. Generally
the sheet material will be of constant composition
throughout; however laminates of two different polymers
bonded or fused together may be used in certain
instances. Amongst suitable polymers there may be
mentioned, for example, polyolefins, especially
polyethylene, copolymers of ethylene and vinyl acetate,
copolymers of ethylene and ethyl acrylate, chlorinated
and fluorinated polymers, especially polyvinyl chloride,
polyvinylidene fluoride and polymers incorporating
units from vinylidene fluoride, hexafluoroethylene
and chlorotrifluoroethylene; and rubbers such as
ethylene/propylene rubber, chlorinated rubbers, e.g.
Neoprene, and silicone rubbers which may be used
in a blend with a crystalline or glassy polymer such
as an olefin polymer. All of the above materials
- 19a -
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1 17762~
may, if desired, be cross linked for example byirradiation and/or chemical means.
As mentioned above, the internal surface of
the heat-recoverable component will, in general,
be provided with a coating of an adhesive or a sealant
such as a hot-melt adhesive or a mastic. Especially
suitable hot-melt adhesives include, for example,
polyamides, ethylene/vinyl acetate copolymers and
terpolymers (with or without incorporated waxes)
and polyesters. Such materials are described, for
example, in British Patent 1,440,810 and German
OS 2,709,717. Also suitable are curable adhesives
which melt and flow on heating but which will not
afterwards be ho;t-meltable. There may also be
mentioned epoxy resins and conventional mastics
such, for example, as those based on butyl and
isobutylene rubbers modified with suitable materials
known in the art. Obviously the use or otherwise
of such materials and their type, if chosen, will
depend upon the particular requirements in any given
case.
In most applications the force exerted on the
clip will lie in the range of from 5 to 15 kg, depend-
ing on the diameter of the substrate and the wall
thickness and the degree of unresolved recovery
~; of the sleeve. It will be appreciated in this latter
- 19b -
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1 177~2~
respect that, as compared with the mastic tape method,
the heat-recoverable sleeve will be required to
shrink less and, therefore, have a smaller expansion
ratio, because the clip forces the sleeve to conform
to the circumstances of the cables in the central
region, whereas in the mastic tape method the sleeve
does not come into contact with the cables in this
region. Of course, the degree of expansion required
for the sleeve is lower when a trident clip is used
than when a simple U-clip is employed.
It will be appreciated that the present invention
provides a very simple method of making a satisfactory
branch-off, thus removing any need for skillful
installation and providing a consequent decrease
in cost. The elongate legs of the clip ensure that
a seal is formed from the edge of the heat-recoverable
materials to the ends of said legs, thereby satisfac-
torily separating the substrates throughout that
region.
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1 17762~
Various embodiments of the present invention ~ill now
be described by way of example only, with reference to the
accompanying drawings, in which:
Figures la and lb illustrate a clip suitable for use
in the present invention
Figures 2, 3, 4 and 6 show the use of the clip of
Figures 1 and 5 in accordance with an invention which is
the subject-matter of our co-pending Application No.319,306,
although these Figures do not directly illustrate the inven-
tion they are included since they do so indirectly by show-
ing the type of use to which the trident clip used in the
method of the present invention may be put.
Figure 5 shows a second form of clip,
. Figure 7 shows a preferred form of trident clip for
use in the present invention;
Figure 8 shows the use of the trident clip in
forming a branch-off,
Figures 9a and 9b show a modified trident clip
designed to form a 3-way branch-off,
Figure 10 illustrates a further modification for
forming an asymmetric branch-off,
Figure 11 illustrates a clip for forming a ~-~ay
branch-off,
Figure 12 illustrates a clip forming an 8-way
. 25 branch-off,
Figures 13a and 13b illustrate an adaptable clip
for forming a 3-way branch-off,
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1 177~2~
Figures 14a and 14b illustrate a clip which
can act as an inlet valve;
Figures 15a and 1Sb illustrate the use of a
clip to provide a branch-off for an inlet or outlet
valve;
Figures 16a and 16b show a preferred form of
trident clip;
Figures 17a to 17e show the use of a further
. form of clip in conjunction with a heat-recoverable
sleeve and a distribution box to form a multi-outlet
termination;
Figures 18a to 18c show a somewhat similar
multi-outlet termination;
Figure 19 shows a clip provided with a temperature
indication device;
Figures 20a to 20c show a clip provided with
a combined pressure and temperature indication device;
Figures 21a to 21c illustrate the use of a
: clip provided with means for facilitating electrical
continuity;
Figures 22a and 22b show a clip suitable for
use with a pressure transducer;
, Figures 23a and 23b show a clip designed to
provide strain relief to a formed joint;
25Figures 24a and 24b show a self-adjusting clip
,.~
for use in the present invention;
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Figure 25 shows a further form of clip for
use with a pressurized splice case joint;
Figures 26a and 26b show a clip for use with
small diameter cables; and
Figure 27a to 27c show a clip for use with
larger diameter cables.
Referring now to the drawings, Figures 1a and
1b show aluminium clip 1 for use in the present
invention. It will be seen that the width of the
legs 2 and 3 is greater than their thickness. In
addition, the base of the gap between the legs 2
and 3 has been cut away at 4 for added strength.
Typical deimensions for the clip are as follows:
, length 64 mm; width 24 mm; length of legs 52 mm;
width of arms 10 mm; thickness of arms 5 mm; gap
between arms 4 mm.
F'igure 2 shows how the clip 1 may be used to
- form a branch-off for two telecommunication cables
5 and 6 passing into a splice case 7 of the XAGA-type
20 2S described and claimed in British Patent 1,431,167.
The assembly is shown after recovery.
Figure 3 (which is a section), shows the use
of two such clips to form a 3-way branch-off on
a similar product. The clips 1 operate to space
the cables 8, 9, 10 apart and at the same time,
ensure that the cables are separated by hot-melt
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adhesive. This is most important if the cables areto be kept separate during subsequent flexing and
bending. This has been a problem with the mastic
tape method, where the mastic has beco~.e squeezed
out and created leakage paths between the cable surfaces.
Figure 4 shows the application of a single clip
1 to a duct seal 11 of the type described and claimed
in German Offenlegungsschrift 2,748,894. As can be
seen, the duct seal is arranged to conduct multi-wire
cables 12 and 13 through a duct (not shown) and is
provided with external flanges 14 for the sealant
15 positioned between them. On heating these flanges
14 to deform and the sealant 15 melts and flows so
as to seal the device within the duct.
In Figure 5 there is shown an alu~inium clip 16,
which is provided with three legs 17, 18 and 19, which
are arranged symmetrically about the longitudinal
access of the clip. The legs are in other respects
similar to those of the clip 1 of Figure 1 and, once
again, a portion of the clip has been cut away at
the base of the gaps between the arms for added strength.
Figure 6 shows how the clip 16 may be used to
form a 3-way branch-off at the end of 2 XAGA splice
case 20. As can be seen, one of the b-anch-off conduits
21 so formed has been caused partially to shrink about
a reinforcing coil and has been provided with an end
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cap 23 in accordance with German Offenlegungsschrift2,748,383. The end cap 23 can be removed when it
becomes necessary to use the feed-through device 22.
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In Figure 7 there i9 shown a trident clip 31
according to the present invention. The inner surfaces
of the outer legs 32 and 33 and the surfaces of the
central leg 34 are tapered so as to define an angle ~.
The surfaces of the outer legs and the central leg run
substantially parallel to form two sloping channels 35
and 36, each of which is cut away at the bottom for
increased strength by stress distribution.
The central leg 34 is provided on each side with
a hot-melt coating 37 and the surfaces of the outer
legs are provided with a coating 38 of a thermochromic
indicator.
Typical dimensions for the clip are as follows:
thickness, 5 mm, width of central leg, 11 mm decreasing
to 5.5 mm' gap between legs, 1 to 2 mm according to
sleeve material wall thickness.
Figure 8 shows the clip 31 in position on a heat-
shrinkable sleeve 39 to fGrm two branch-off conduits
40 and 41. As can be seen, in the recovered position,
the central leg 34 forms a separating barrier between
the conduits.
Figures 9a and 9b show an adapted trident clip 42
designed to form a three-way branch-off, the central
leg 43 being formed as a part of Y-shaped cross-section.
Figures 10, 11 and 12 show various clips 4 , 45
and 46, respectively, for forming other multi-outlet
branch-offs
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Figures 13a and 13b show an adjustable three-way
branch-of~ clip, In this clip two of the outer legs 47
and 48 are rotatably mountable on an extended part of
the inner leg 49, whereas outer leg 50 is fixed to said
;5 inner leg 49. Such a clip can be adjusted according to
the nature of the branch-off required.
In Figure 14a there is shown the use of a trident
clip 51 to provide an inlet for pressurised air within
;- a cable splice 52. In this embodiment, as shown in
Figure 14b, the central leg 53 of the trident clip 51
is hollow and is provided with a valve 54 and an
inlet duct 55. The central leg 53 of the clip 51 acts
as a substrate in the branch-off from cable 56.
In Figure 15a there is shown how two trident clips
57 and 58 may be employed with a wrap-around splice 59
to form a branch-off inlet and outlet at the ends
,thereof. In this case the inlet and outlet are
provided with separate devices 60 and 61 (as shown in
,Figure 15b) which form the substrates in the branch-
off from cables 62 and 63, respectively.
;Figures 16a and 16b show a further form of
preferred trident clip 64 in accordance with the
~^present invention. This clip 64 has the preferred
features that the central leg 65 extends ~eyond the
ends of the outer legs 66 and 67 and that the side
surfaces of the central leg 65 are waffled to provide
a suitable base for adhesive, as discussed previously.
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Finally, in Figures 17a to 17e there is shown how
the present invention may be employed .o form branch
outlets from a heat-recoverable sleeve and a further
co-operating component.
In Figure 17a there is shown a distribution box
68 provided on its external surfaces with hot-melt
adhesive 69. This distribution box is designed to
distribute pairs of cables from a large incoming
cable to a large number of outgoing smaller cables.
In accordance with the present invention the
adhesive coatings 69 are pre-cut to remove strips
which are slightly wider than the thickness of the
clips 70 (as shown in Figure 17b). The box 68 is
then inserted within a large diameter heat-
recoverable sleeve 71 and the outgoing cables 72
are arranged around the surface of the distribution
box 68. As is shown in Figures 17c and 17d the
clips 70 are then positioned between the cables 72
and over the external surface of the heat-recover-
able sleeve 71 and the internal surface of thedistribution box 68. The assembly so produced may
then be heated to cause recovery of sleeve 71 and
flow of the adhesive 69 to produce the completed
distribution box shown in Figure 17e. As indicated,
some of the branch-offs may be occupied by devices
73 provided with caps 74 for future use.
The distribution box 68, preferably made from
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a strong thermally conductive metal, may be provided
with grooves on its internal surface to assist
location of the clips. The heat-recoverable sleeve 71
may, of course, be a wrap-around sleeve and ~ay be
internally coated to reduce water vapour penetration.
At its other end it is shrunk about the large
incoming cable 75.
The box 68 may have different geometries such as
circular, elliptical, star-shape etc. and various
different forms of clip 70 may be used.
Figures 18a to 18c show a somewhat similar
multi-outlet branch-off arrangement for use with a
pressurized splice case. As shown in Figure 18a the
splice case 80, which may be formed from two metal
half shells, is protected and insulated by a wrap-
around heat-shrinkable sleeve 81 provided with a
conventional fastening means 82. Ingoing cable 83
is to be spliced to form four outlet cables 84 and,
in accordance with the invention, a seal is formed
at the inlet using a trident clip 85 which provides
a conduit for a pressure valve 86. The seal at the
inlet is formed as described previously. At the
outlet there is provided a heat-shrinkable cap 87
which has a hot melt adhesive coating on its
external surface. As shown, the cap is provided
with four trident clips 88 in accordance with the
present invention. The cap 87 and the clips 88
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co-operate with the outlet end of heat-shrinkable
sleeve 81 and the arrangement before recovery is shown
in ~igure 18b. It will be seen that the cap, the
sleeves and the clips between them form four conduits
for ~he outgoing cables 84. When the assembly qhown
in Figure 18b is complete the heat-recoverable sleeve
, 81 is caused to shrink by using a conventional torch
; and the heat-shrinkable cap 87 is preferably caused
'; to shrink by means of a so-called "hot pack", i.e. a
`` 10 pyrotechnic type heating device, which is pre-
installed within it. Ishe recovered assembly is shown
in Figure 18c.
Such an arrangement is especially useful in the
~; formation of multi-outlet branch-offs from pressurized
splice cases where the expansion rate of the heat-
recoverable sleeve is kept as low as possible, usually
at about 1.3 in order to keep the wall thickness of
the sleeve to a maximum and to reduce unresolved
recovery to a minimum, thereby obviating the rupture
s:~
of the sleeve under pressure.
In ~igure 19 there is shown a trident clip, the
central leg 91 of which is provided with a temperature
indication device which comprises an indicator rod 92
positioned within the leg 91 and a load spring 93
,~ 25 which is held in compression within chamber 94 by
being embedded in a thermofusiblç material (not shown).
When the desired temperature is reached the
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thermofusible material melts and the spring gl recovers
resiliently to move the rod 92 to the position shown by
the dotted lines, thus indicating that the desired
temperature has been reached.
Figures 20a to 20c show a clip 100 which is
provided with means for indicating that both a desired
temperature and a desired pressure have been attained
within heat-shrinkable sleeve 101. As shown in Figure
20b the central leg 102 of clip 100 is provided with
a chamber 103 in which is positioned a ball valve 104.
Also positioned within chamber 103 and in a channel
105 which connects the chamber to the closed end of
the clip 100 is a thermofusible material 106.
The positioning of the clip 100 within a
pressurized splice case joint 107 is shown in Figure
20c. When the desired temperature is reached the
thermofusible material 106 melts and, provided that
a correct seal is achieved, the pressure within the
joint 107 causes the ball valve 104 to move along the
chamber 103 thereby forcing a volume of molten thermo-
fusible material out from the end of the clip, the
volume extruded being approximately equal to the
volume originally positioned in chamber 103. The
~- operator can thus be sure not only that has the
correct temperature been reached but also that there
are no leaks in the seal formed at the joint.
Figures 21a to 21c show a trident clip 110, the
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central le~ of which is provided on each side with
jaw members 111. These are designed to accommodate and
grip strips 112 cut from the aluminium shielding foil
of telecommunication cables 113, as shown in Figure 21c,
S and thus ensure electrical continuity between the
cables 113 and electrical bond line 114 which is
attached to the central leg of the clip 110.
Figures 22a and 22b show a further form of clip
116 and its use in the ~ormation of a joint at the end
of a pressurized splice case provided with a pressure
transducer. As shown, the clip 116 is provided with
a locating ring 117 which is designed to fit around
the pressure transducer container 118. If desired,
the ring 117 could be formed as a cap for the
container 118.
Figures 23a and 23b show trident clip 1~0 which
is provided with two straps 121 and 122 which are
designed to be fastened around cables 123 and 124,
respectively, as they leave a splice joint 125. This
arrangement not only serves properly to locate the
cables and the clip at the joint, but also provides-
strain relief to the system and ensures that movement
of the cables externally of the joint does not cause
damage. It is, therefore, especially appropriate for
use with heavy duty cables or service pipes, etc.
In Figures 24a and 24b there is shown clip 130
which is designed so as to be self-adjusting in that
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1 177~27
the gaps between the central leg 131 of the externallegs 132 and 133 may vary according to the thickness
of the heat-recoverable sleeve. For this purpose
the central leg 131 is constructed from two parts,
5 a U-shaped member 135 being slidably mounted on a
- central member 136 and, initially, held in an extended
position against the force of a tension spring 137,
the whole assembly being embedded in a hot-melt adhesive
138 to prevent recovery of the tension spring. When,
in operation, clip 130 is heated the hot-melt adhesive
138 fuses and the tension spring recovers causing
the U-shaped member 135 to move along the central
member 136 towards the base of the clip, as shown
by the dotted lines. ~n doing so the gap between
the legs is reduced, thereby ensuring that the heat-
recoverable sleeve material positioned therein is
firmly gripped.
Figure 25 shows a further form of clip 140 for
use with pressurized splice cases. As shown this
- 20 clip 140 has three legs of equal length which will,
in general, be longer than the clip shown, for example,
Figure 5. In addition, the width of the central leg
141 is constant throughout its length and is kept
as small as practicable, e.g. at about S }nm, in order
to facilitate the formation of a good seal between
the heat-recoverable sleeve and the cables in the
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vicinity of the clip. ~oth sides of central leg
141 are provided with a layer of a hot~melt adhesive.
Finally, in Figures 26 and 27 there are shown
two other advantageous clips for use in the present
invention. The clip shown in Figure 26 is designed
for use with cables of outside diameter from about
8 to about 35 mm. As can be seen most clearly from
Figure 26c, which is a section taken near the open
of the clip, the sides of central leg 151 are concave
in nature to accommodate the cables. In addition
the upper and lower surfaces of the hot-melt adhesive
layer 152 are each provided with two longitudinally
extending ribs 153. As mentioned earlier, the provision
of these ribs enhances the push-fit of the clip
over the sleeve prior to shrinkage.
The clip shown in Figure 27 is designed for
larger cables of outside diameter greater than about
30 mm. In this clip the central leg 161 decreases
in thickness from the closed end to the open end
of the clip in order to accommodate the cables.
Once again, hot-melt adhesive layer 162 is provided
with longitudinal ribs 163 to enhance the positioning
of the clip prior to recovery but in this case the
ribs 163 extend over only a part of the length of
central leg 161 in order to allow facile initial
installation of the clip.
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Other modifications and variations falling within
the scope of the present invention will be apparent
to those skilled in the art.
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