Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Patent
1994-08-16
1996-06-18
Ryan, Patrick J.
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
428257, 428259, 428913, B29D 2200, B29D 2300, B32B 108
Patent
active
055275753
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to a heat recoverable fabric sleeve for enclosing an elongate object such as a pipe or cable, or a joint between pipes or cables. In particular the invention relates to such a sleeve for covering an object which varies in cross-sectional area along its length.
INTRODUCTION TO THE INVENTION
Heat recoverable artides are well known. They are artides whose dimensional configuration may be made to change when subjected to an appropriate treatment. Typically heat recoverable articles comprise a heat shrinkable sleeve made from a polymeric material that exhibits the property of elastic or plastic memory as described, for example in U.S. Pat. Nos. 2,027,962, 3,086,242 and 3,597,372. More recently heat recoverable articles comprising fabrics have become known, as described for example in EP-A-0116393, EP-A-0117026, EP-B-0115905 and EP-A-0116392. These comprise a recoverable fabric in conjunction with a polymeric matrix formed by laminating a polymeric material to one or both sides of the fabric to render it impervious.
SUMMARY OF THE INVENTION
Recoverable fabrics have found many applications. EP-A-0115905 describes a polymeric-laminated, heat recoverable fabric having a recovery ratio of at least 40%, preferably at least 50 or 60%, that may be used for example to cover substrates with varying or discontinuous contours to provide mechanical protection or protection from the environment. The entire disclosure of EP-B-0115905 is incorporated herein by reference.
Within the scope of the invention described in U.S. Pat. No. 4,624,720 (issued Nov. 25, 1986), the counterpart of European Patent Publication No. 0115905 we have discovered a spedtic heat recoverable fabric configuration that provides a high recovery ratio and particularly advantageous properties.
A first aspect of the invention provides a heat recoverable sleeve having a recovery ratio of at least 60% preferably at least 70%, and comprising: in one direction, woven in a twill, preferably a broken twill, configuration with 1 to 10 heat stable fibers per cm in the other weave direction, and 1 to 4 heat recoverable fibers per cm in the said other weave direction, and
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 and 2 are schematic drawings of a fabric design according to the invention; recovery; and
DETAILED DESCRIPTION OF THE INVENTION
The recovery ratio in the present invention is defined in terms of percentages. The ratio represents a change in a dimension as a percentage of the same dimension before recovery. The recovery ratio of the present invention is preferably at least 60%, more preferably at least 70%. Ratios as high as 75% or even 78 or 80% may even be achieved. This large recovery ratio allows the sleeve to be used inter alia in applications where the elongate object exhibits large transitions in cross-sectional area.
The heat recoverable sleeve is preferably heat-shrinkable, preferably radially.
As examples of applications, the sleeve may be used to cover pipes or cables or joints therebetween. Particular applications include (i) end caps for district heating pipes where one end of the sleeve needs to recover onto the outer thick insulation, and the other end needs to recover onto the much smaller diameter steel pipe, (ii) covers for mechanical or flange couplers for pipes, and (iii) covers for bell and spigot joints between pipes. In such applications the maximum cross-sectional dimension of the object to be covered may be as much as 3.5 times, or even 4.5 times the minimum dimension of the object to be covered. A sleeve of the present invention that is initially of uniform cross-sectional size along its length can advantageously be made to shrink around these substrates exhibiting large changes in dimensions along their length.
We have found that the fabric design is an important parameter in achieving a high recovery ratio fabric. In particular we have found a broken twill 2/4 design is the most effective. The configuration of a broken twill 2/4 design is desc
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Overbergh Noel
Ros Firmin
Van Loo Robert H.
Vansant Jan
Burkard Herbert G.
Gerstner Marguerite E.
Gray J. M.
NV Raychem SA
Ryan Patrick J.
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