Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Reexamination Certificate
2001-01-04
2002-05-28
Nguyen, Chau N. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
C174S093000
Reexamination Certificate
active
06395988
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the enclosing and sealing of elongate substrates, for example electrical or telecommunications cables, and especially joints between such cables.
BACKGROUND OF THE INVENTION
WO 91/00601 (Raychem) discloses a joint closure for an electrical cable. The closure comprises a heat-recoverable fabric sleeve wrapped around a sealing mastic, the ends of the sleeve being secured with a closure member. Two scaling materials may be used in such a closure, one material acting as a blocking material having both a higher viscosity at room temperature and a melt viscosity which is higher than the viscosity of the other material.
SUMMARY OF THE INVENTION
According to a first aspect, the invention provides an article for enclosing an elongate substrate, the article comprising a container at least in use, a first sealing material and a second scaling material, such that the first scaling material is located between the second sealing material and an end of the container, characterised in that both sealing materials are polymeric and in that the first sealing material has a higher softening point and a higher melt viscosity at a defined temperature than the second sealing material.
According to a first aspect, the invention provides an article for enclosing an elongate substrate, the article comprising a container containing, at least in use, a first sealing material and a second scaling material, such that the first sealing material is located between the second sealing material and an end of the container, characterised in that both sealing materials are polymeric and in that the first sealing material has a higher softening point and a higher melt viscosity at a defined temperature than the second sealing material.
According to a second aspect, the invention provides a method of enclosing an elongate substrate, the method comprising the steps of:
a) placing first and second sealing material on the substrate; and
b) placing a container around the first and second scaling material and around the substrate, such that the first sealing material is located between the second polymeric sealing material and an end of the container;
which method is characterised in that both sealing materials are polymeric and in that the first sealing material has a higher softening point and a higher melt viscosity at a defined temperature than the second sealing material.
Preferably, there are at least two portions of the first polymeric sealing material. At least in use, at least one portion of the first polymeric sealing material is preferably placed on each opposite side of the second polymeric scaling material, on the elongate substrate.
According to a third aspect, the invention provides an article for enclosing an elongate substrate, comprising:
(a) a container; and
(b) a polymeric sealing material;
at least in use, the polymeric sealing material being located within the container.
According to a fourth aspect, the invention provides a method of enclosing an elongate substrate, comprising:
(a) placing a polymeric sealing material on the substrate; and
(b) placing a container around the polymeric sealing material and the substrate.
In use, the polymeric sealing material is preferably heated, preferably to above 100° C., to cause it to melt and to flow, and to conform closely to the substrate.
In some embodiments, the polymeric sealing material may be curable. In such embodiments, the invention preferably further comprises a curing agent for curing the polymeric sealing material. The curing agent may be part of the polymeric sealing material, or intimately mixed with the sealing material, or it may be separate from the sealing material. The curing agent may, for example, be present in the form of pellets, contained in microcapsules, provided as a layer on the sealing material or be provided in or on another component, e.g. a sheet, a bag, or a mesh. If the curing agent is not provided as part of, or intimately mixed with, the sealing material, it preferably becomes mixed with the sealing material during heating.
The polymeric sealing material may be separate from the container, e.g. in the form of a layer. The sealing material, or at least a portion of it, may however be provided on an inner surface of the container, e.g. as a layer. In this case, steps (a) and (b) of the methods according to the invention may be one and the same step, i.e. placing on the substrate a container which has polymeric sealing material (e.g. a layer of polymeric sealing material) on an inner surface thereof.
For the avoidance of doubt, it should be understood that any or all features of each aspect of the invention may be combined with any or all features of any or all other aspects of the invention.
The container is preferably dimensionally-recoverable, e.g. dimensionally-shrinkable. It is especially preferred for the container to be dimensionally heat-recoverable. The container may, for example, be in the form of a tube or a sleeve. It may be in the form of a sheet or the like which may be wrapped around the elongate substrate, e.g. it may be a so-called wraparound sleeve. The wraparound sleeve preferably has closure rails along opposite longitudinal edges, and a separate channel component by means of which the wrapped sleeve is retained in a closed configuration during use.
Once the container has been placed (e.g. wrapped) around the elongate substrate, it is preferably then heated (e.g. by means of a torch flame or by hot air) in order to cause it to recover around the substrate. This heating preferably causes the or each polymeric sealing material to melt and to flow, and to conform closely to the substrate. Once the container has been recovered, the polymeric sealing material preferably substantially fills the volume between the container and the substrate, leaving substantially no gaps.
According to the first and second aspects of the invention, there is a first polymeric sealing material which has a relatively high softening point and/or a relatively high melt viscosity at a defined temperature, and there is a second polymeric sealing material which has a relatively low softening point and/or a relatively low melt viscosity at said defined temperature. (These physical characteristics of each material are “high” or “low” relative to the corresponding values of the other material.) The softening point of the first polymeric sealing material is preferably at least 80° C., more preferably at least 85° C., e.g. at least 88° C. The softening point of the second polymeric sealing material is preferably lower than 80° C., more preferably lower than 78° C., e.g. lower than 76° C. The relative melt viscosity of each sealing material is preferably as measured at 100° C., and at this temperature the melt viscosity of the first polymeric sealing material is preferably at least 100 Pas (Pascal seconds), more preferably at least 150 Pas. At the same temperature, the viscosity of the second polymeric sealing material is preferably lower than 60 Pas, more preferably lower than 50 Pas.
The softening points of the sealing materials are preferably as measured in accordance with ASTM standard test method E28-97 (“Softening Point of Resins by Ring-and-Ball Apparatus”). The melt viscosities of the sealing materials are preferably as measured in accordance with ASTM standard test method D-3236-88, using a Brookfield model HBT viscometer, and spindle SC-27.
The use of two polymeric sealing materials with different softening points and/or different melt viscosities has the advantage that two conflicting requirements can be met, namely that the sealing material should flow and conform closely to the substrate during the heating operation, but that it should not escape from the container before it has solidified. The first polymeric sealing material preferably acts as a dam to prevent the more fluid molten second polymeric sealing material from flowing out of the container. Preferably each longitudinal end of the container (e.g. sleeve) has a quantity of the first sealing material to block the esc
Lietzke Ralf
Nolf Jean-Marie Etienne
Overbergh Noel
Van Meeuwen Bart
Van Overmeir Peter
Myers Bigel Sibley & Sajovec P.A.
Nguyen Chau N.
Tyco Electronics Raychem NV
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