Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Reexamination Certificate
1999-06-16
2001-06-12
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
C174S093000
Reexamination Certificate
active
06245999
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an arrangement for and method of enclosing an elongate substrate. The substrate may comprise a cable, for example an electrical power or telecommunications cable, and in particular a cable connection. The cable connection may comprise a joint between two, or more, cables, or a termination of a cable, for example on to a terminating lug or bushing connected to electrical equipment such as switchgear or a transformer. The termination may comprise an adapter, for example an elbow.
The invention will be further particularly described with reference to an in-line joint between two electric power cables, but it is to be understood that this is by way of example only and not by way of limitation.
Joints between two power cables, whether either or both are polymeric or paper insulated cables, need to be enclosed within an outer protective arrangement that includes an electrically insulating layer. Heat shrink technology has been applied for this purpose for many years, with products available from Raychem and others. However, technologies that do not require heat are also employed. Push-on sleeves and elbows are available but unlike heat shrinkable products, these have severe range-taking limitations that necessitate a large inventory. Other so-called cold applied solutions require a tubular elastomeric sleeve to be radially expanded and mounted on a rigid holdout member, the internal diameter of which is larger than the maximum outer diameter of the cable joint to be enclosed. One example of the latter is the PST sleeve available from 3M, as exemplified in U.S. Pat. No. 3,515,798. Such a sleeve has an inner holdout member that consists of a continuous narrow strip of tough flexible material in the form of a rigid closed helix having adjacent coils interconnected. The held out sleeve is mounted over the cable joint and the helical strip is then unwound, thus allowing the insulating stretched elastic cover to shrink down onto the joint. However, it is inconvenient having to unwind the holdout strip helically around the extended cable, especially if the work has to be done in the confined space of a trench or manhole. Another example of a cold applied arrangement is disclosed in U.S. Pat. No. 3,824,331, in which a resilient tubular cover is supported in a stretched condition by an easily removable external one piece support member, each end of the cover being rolled back over the outside of the support. The cover and support member are mounted on an internal sleeve in the form of a longitudinally slit tube held in a state of increased diameter by a dividing strip in the shape of an I-beam. When in position over the cable joint, removal of the dividing strip longitudinally from the slit allows the inner tube to be squeezed and then freely withdrawn from the cover. The cover ends are then unrolled onto the adjacent cable sections and the external support member is removed. It will be appreciated that such an arrangement requires an inner and an outer holdout member, each of which has to be removed.
EP-B-0 530 952 discloses a cover assembly in which an elastomeric tube is held out in a stretched condition on an inner support core. The core is frangible such that application thereto of a force beyond that produced by the tube causes breakage of the core so as to allow contraction of the elastomeric tube onto the substrate. The fragments of the collapsed core remain within the tube and must therefore be as small as possible to facilitate accommodation therewithin.
It is an object of the present invention to provide an arrangement for and method of enclosing an elongate substrate that overcome disadvantages of the known arrangements, facilitates enclosure of the substrate and that can also provide further useful functions.
SUMMARY OF THE INVENTION
Thus, in accordance with one aspect of the present invention, there is provided an arrangement for enclosing an elongate substrate, comprising an outer resilient sleeve held in a radially-expanded configuration by being mounted on an inner holdout member, wherein the holdout member comprises a generally tubular member that has a slit extending longitudinally thereof such that application of a force radially thereof causes the holdout member to reduce in circumference and to collapse around the substrate under the action of the recovery force of the outer resilient sleeve.
In contrast with the known arrangements, therefore, the enclosing arrangement of the present invention is such that the holdout member is not discarded, but remains in place around the substrate, and does so in its integral state. In this manner, the rigidity of the holdout member can be selected to provide mechanical protection for the substrate. Furthermore, by appropriate selection of the electrical properties of the holdout member, it can also perform an electrical function if required.
A substrate is usually regarded as being elongate if its longitudinal dimension exceeds its lateral dimension, but this need not necessarily be the case.
It will be appreciated that in collapsing around the substrate, it will depend on the size of the substrate and the rigidity of the holdout member as to whether or not contact is made between the holdout member and the substrate. In some applications it is preferred to arrange for such contact to be made.
Preferably, the radial force causes one edge of the slit to slide beneath the other edge, thereby to allow the holdout member to curl upon itself.
Arrangements of the invention are thus capable of a large amount of range-taking, that is to say, of being usable with substrates of a large range of lateral dimensions, usually diameters.
The holdout member may be cylindrical, and especially right cylindrical, but it is envisaged that it may have a polygonal cross section.
Preferably, the longitudinal slit of the holdout member extends along the entire length thereof, preferably substantially axially thereof., and may extend radially completely through the wall thereof. Alternatively, the slit may define a weakened line of the holdout member, which is broken or displaced when it is required to collapse the arrangement, for example to bring it into conformity with the substrate.
The holdout member may have two or more slits so as to allow the collapsing, preferably curling, around the substrate, and one or more of the slits may act as a hinge. In one embodiment, the member has three slits, one of which may be arranged to sever such that one edge of the member can curl beneath another edge thereof. The slit that is arranged to sever may alternatively be completely severed initially and may be temporarily held together by a bridging member of flexible material, for example an adhesive tape.
An insert may be provided in the slit that is arranged to allow the collapsing, as opposed to the hinging, action of the holdout member, the insert being secured to one of the edges of the slit and being arranged to deflect the other edge, preferably under the first, to effect the collapse of the holdout member.
The collapsing of the holdout member may be facilitated by the slit being arranged at an angle that is inclined to a radius of the holdout member.
In preferred embodiments, safety features are preferably included, substantially to prevent premature collapses of the holdout member. In some instances, it is therefore desirable to provide temporary retaining means for the holdout member so as to prevent its premature collapse, during storage or transport, for example. Such retaining means may comprise a pin secured through an overlap of the slit tube, or an insert at one or both ends of the tube. Removal of the retaining means may then be arranged to cause collapse of the tube under the action of the recovery force of the resilient sleeve, or may allow collapse upon application of an external radial force. In another embodiment, the insert may be of noncircular, for example oval, shape inside a circular holdout, whereby rotation of the insert may cause or allow collapsing of the holdout.
In one embodiment
Borrill Christopher
Costigan Philip
Wakenshaw Jonathan
Winfield Philip Roland
Myers Bigel & Sibley & Sajovec
Nguyen Chau N.
Raychem Limited
Reichard Dean A.
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