Note: Descriptions are shown in the official language in which they were submitted.
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Flexible Collar Tee
This invention relates to recoverable, preferably
heat-recoverable, articles. In particular, the invention
relates to articles for producing T-shaped branch-offs from
conduit 5 .
Recoverable articles are articles the dimensional
configuration of which may be made substantially to change
on suitable treatment, and heat-recoverable articles are one
which change on heat treatment. Usually 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 article
which, 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 US Patents 2,027,962; 4,086,242
and 3,957,372. As is made clear in, for example, US 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
dimensionally 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 the production of heat recoverable articles, the
polymeric material may be cross-linked at any stage in the
production of the article that will enhance the desired
dimensional recoverability. One manner of producing a
heat-recoverable article comprises shaping the polymeric
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material into the desired heat-stable form, subsequently cross-linking the poly-
meric material, heating the article to a temperature above the crystalline melt-
ing point or, for amorphous materials the softening point, as the case may be, of
the polymer, deforming the article and cooling the article whilst in the deformed
state so that the deformed state of the article is retained. In use, sinoe the
deformed state of the article is heat-unstable, application of heat will cause
the article to assume its original heat-stable shape.
In other articles, as described, for example, in British Patent
1,440,524, an elastomeric member such as an outer tubular member is held in a
streched state by a second member, such as an inner tubular member, which, upon
heating, weakens and thus allows the elastomeric mem~er to recover.
me use of recoverable articles, for mechanical protection and elec-
trical insulation where appropriate, in covering articles, for example pipes and
cables, has been disclosed in, for example, US Patent Nos. 2,027,962 to Currie
and 3,297,819 to Wetmore. mese articles are designed primarily for covering a
single pipe or a butt-junction between tWD pipes. In US Patent No. 3,445,336 to
Ellis there is disclosed a heat-shrinkable sleeve which can be wrapped around an
article or two butt-joined articles, which is suitable for use, for example, when
no free end of the pipe or pipes is available. In the Ellis patent, there is dis-
closed a heat-recoverable closure member, usually of sheet form, two opposite
edges of which have protuberances along their length which, when the sheet is
wrapped around an article to be covered, are in abutting relationship and can be
held in such relationship during and after recovery by a fastening means, for
example
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a metal channel. By the use of suitably moulded closure
members, and using two or more sets of abutting protuberances,
the closure member can be used for covering T or Y junctions
on existing pipes and cables. Such mouldings are, however,
relatively expensive.
UK Patent 1447048 discloses a heat-recoverable article
that is adapted to cover a conduit junction having at least
three arms, which comprises a radially heat-shrinkable
tubular member or a member in sheet form of which opposing
edge regions can be brought and held together to form a
radially heat-shrinkable tubular member, the member having
at least one heat-shrinkable aperture with an upstanding
wall around its periphery, preferably outwardly extending
from the member, the wall being such that, on heating, its
height and periphery are reduced. A further method of
sealing a branch-off to a main conduit is to wrap tapes,
generally heat-recoverable tapes, around the crutch region
between the main conduit and the branch-off conduit. This is
not satisfactory in some instances since it can be difficult
to obtain a good seal with certainty, and the wrapping
operation is time consuming and craft sensitive.
Branch-offs are often connected after the main conduit
has been installed, and therefore the sleeve must be
a wraparound. Existing systems have many parts or use
tape, which is craft sensitive. It is difficult therefore to
get a good seal especially on large diameter pipes. We
have now discovered a means of sealing a branch-off conduit
to a main conduit which is particularly applicable to
~-shaped branch-offs, but which is also suitable where the
branch-off conduit is not perpendicular to the main conduit.
When we use the term "main conduit" we do not indicate that
it is necessarily larger that the branch conduit, but merely
to differentiate between the conduit which branches off and
the conduit from which the branching off occurs.
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Thus, the present invention provides a recoverable
sheet material for forming a conduit which has been differ-
entially expanded, the change in extent of expansion across
its surface being accommodated by pleats which increase in
depth or number in the direction of increasing expansion.
It is to be understood that the word pleats as used in
the specification and claims has a broad meaning including
but not limited to folds or creases which are doubled upon
themselves, or which have any particular geometric form; the
word is intended to encompass any series of corrugations
folds, creases or undulations by which a sheet may be
compacted into a smaller area than the surface area of its
material.
The present invention in particular provides `a recover-
able sheet material for providing a sealed branch-off from a
main conduit, comprising: a first portion which can define
or enclose a branch-off conduit, and a second portion having
been expanded differentially and which thus can splay out to
form a collar around a hole in the main conduit. Preferably
the whole of the sheet is first expanded and the differential
expansion of the second portion is superimposed.
The sheet material can be used to join an independent
branch-off conduit to a main conduit, or said first
portion can itself constitute the branch-off conduit. The
invention is particularly useful for larger conduits such as
those used for carrying oil or gas.
The invention also provides a method of forming a
branch-off, in which the sheet material of the invention is
placed on a conduit with the collar around a hole in the
conduit, the collar is secured to the conduit, and the
; sheet material recovered. The collar is secured to the
conduit by means of an overlying recoverable wrap-around
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sleeve which has a hole through which said first portion
can pass, or by two patches or wrap-around or tubular
sleeves one either side of the branch-off conduit, where
the conduits are large it will generally be necessary to
use two patches or sleeves, rather than a single item with
a hole.
The sheet material of the invention can be provided as
a wrap-around closure member, in which case means will
generally be required to secure it in the closed configuration.
Such means can be adhesive or the provision of a rail and
channel closure, such as that described in our US Patent
3455336, modifications to this idea are disclosed in UK
Patent 1529351 and in applications 80~8703 and 8005501.
Alternatively the sheet material can be provided as a closed
tube. In either case some sort of sealant (such a hot-melt
adhesive or mastic) will generally be employed when the
branch-off is made. It is preferred, none-the-less, that the
sheet material be provided plain, a sealant being added by
the craftsman on site where required. The alternative is to
provide a coating of sealant on the inner surface of the
sheet material; this however makes production of the material
more expensive. The sheet material of the invention may be
held in the closed configuration, and it may be sealed to
the main conduit by a pressure sensitive or heat-activated
closure patch, such as that sold by Raychem under the trade
mark WPCP.
The method of producing the sheet material in wrap-around
form is as follows. A sheet of a suitable plastics material
is subjected to the usual cross-linking (by chemical means
or by radiation) and heating/cooling operations, but the
expansion is a two part process. The sheet is longitudinally
expanded as a whole, and the part which is to become the
second portion is further expanded. This further expansion
increases in extent throughout the width of the second
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portion in a direction away from the first portion. The
differential expansion of the second portion allows the
second portion to splay out to form a collar which can
overly a hole in the main conduit. It is to be understood
that the expansion of the whole and the further expansion
need not be done sequentially, but may be part of the same
process. After this expansion, and before the material is
closed to form a tube, the second portion preferably will
have a generally pleated configuration. The size of such
pleats can vary over a wide range, but a typical size could
bre regarded as 50mp pitch and 50mp depth.However, the
precise configuration will depend on the method employed in
the expansion. A continuous in line process can be employed,
in which convolutes are produced in the second portion
simply simply by pressing.
Where the sheet material is to be in the form of a
closed tube, it may be made as above and then welded closed,
or it may be moulded as a tube, and then radially expanded
in a way corresponding to that described above.
The extent of expansion, and therefore the recovery
ratio, is not critical, but for some materials we prefer
that the greatest expansion of the second portion is by a
factor of 2-3. Any suitable polymeric material having
elastic memory imparted thereto can be used in the present
invention, for example polyolefins such as polyethylene or
polypropylene or copolymers of these polymers with other
ethylenically unsaturated monomers, other polymers that are
suitable include PVC, polyvinylidene fluoride, polytetra-
fluoroethylene and polyvinyl fluoride/hexafluoropropylene.
Additional features can also be provided such as a coating
of thermochromic paint to indicate when sufficient heat has
been applied for recovery. Other additives of often used in
conjunction with polymeric materials in this context include
fillers, pigments, antioxidants and flame retardants.
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The invention is particularly applicable for use in
conjunction with large conduits, for example those having a
diameter or from l/2-3m but larger or smaller branch-offs
can be made. In general, the branch-off conduit will of
course have a smaller diameter than the main conduit,
although the relative sizes of the two conduits is not
critical. We expect the invention to be particularly applicable
to conduits for carrying oil and gas, but it can also be
used at joints in conduits carrying supply cables.
The invention can also provide a pipe bend. In this case the
sheet material would be provided with a region of differential
expansion which increases in extent of expansion and then
decreases again across the sheet. The sheet would then be
wrapped around to form a closed tube which would naturally
form a bend; the region of maximum expansion would become
the outer radius and the regions of minimum expansion (now
joined) would become the inner radius. The whole of the
sheet is preferably expanded uniformly (in one direction),
and the region of differential expansion superimposed
leaving two edge strips not expanded differentially. These
edge strips would be used to form the inner radius of the
bend, and could be provided with closure rails, or other
closure means. Alternatively, the sheet material could be
formed as a tube and then expanded.
The invention will now be further described, by way of
example, with reference to the accompanying drawings, in
which:
Figure 1 shows a sheet of recoverable material before
use;
Figures 2 and 3 show a branch-off formed using the
sheet of Figure l; and
Figures 4-6 shows how a double region of differential
expansion can be used to form a pipe bend.
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g
The sheet of recoverable material A has a first portion
1, which has been expanded to a certain extent, and a second
portion 2 which has been expanded to a greater extent. The
second portion 2 has a pleated configuration because it has
been differentially expanded, the extent of expansion
increasing in a direction away from the first portion.
Although the pleats here are regular and produced by
sharp folds, when we use the term pleats we intend to
cover configurations which are irregular and which are
produced by gentler folding or curving.
This differential expansion allows the second portion 2
to splay out to form a collar 5 which can overly a main
conduit 3. This is shown in Figures 2a and 2b. In these
figures the first portion 1 is used to secure a separate
branch-off conduit 4, although the first portion 1 could
itself extend a considerable distance thus forming an
integral branch-off conduit.
The collar 5 can be secured to the main conduit 3 in
many ways, one of which is illustrated in Figure 3. In this
figure a recoverable wrap-around sleeve 6 is provided which
has a hole 7 through which passes the first portion 1 of the
sheet material. The wrap-around 6 is then secured in its
closed configuration and then recovered. It is not critical
whether the sheet material is recovered before, after or
simultaneously with the wrap-around sleeve 6.
The sheet material can be used to cover irregular main
conduits. Although the main conduit 3 is of constant cross-
section, it may in some cases be stepped at the point where
the branch-off occurs, due to the reduced volume that it has
to carry after the branch-off.
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Figures 4-6m show the production of a pipe bend using a
recoverable sheet A having a double region of differential
expansion 2a,2b. Firstly, the sheet A is uniformly expanded
in the direction shown by the arrow in Figure 4. Then (or
simultaneously) further expansion is carried out to produce
two regions of pleats 2a and 2b, where the extent of expansion
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increases towards the centre. The~ could be reversed'so that
~J maximum expansion occurred a the two edges, but this is not
preferred. The sheet is then wrapped-around so that the
rails 7 meet. A closure channel 10 or other means is then
used to maintain the tubular shape 9. Recovery is then
carried out. Preferably the outer regions 11 of the sheet
are not subjected to the differential expansion. One of the
rails to provide a flap 12 which will underly the rails when
the tube 9 is formed. This flap 12 serves to enhance the
join and to protect any substrate within the tube.
