Pipes and tubular conduits – Combined – With external support structure
Reexamination Certificate
1999-09-03
2001-02-20
Hook, James (Department: 3752)
Pipes and tubular conduits
Combined
With external support structure
C138S113000, C138S120000, C138S128000, C138S153000, C138S155000, C138S157000, C138S173000
Reexamination Certificate
active
06189575
ABSTRACT:
This invention relates to a recoverable article for, and method of, enclosing an elongate substrate. The substrate may comprise for example a cable, which may be an electrical power or telecommunications cable, and in particular a cable connection. The cable connection may comprise a joint, or splice, 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 a 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 (AMP), 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 (3M) 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.
With each of these arrangements, the holdout member is disposed internally of the sleeve that is to be applied to the substrate cable. Thus, the sleeve cannot conveniently have an internal coating, of gel, mastic or adhesive for example, applied thereto. This problem, is avoided by the recoverable sleeve assembly disclosed in U.S. Pat. No. 4,410,009 (Sigmaform), in which an inner elastomeric tube is maintained in a radially-stretched condition by having an outer rigid tube surrounding and secured to the outer surface thereof. The outer tube is a rigid thermosetting adhesive polyurethane whereby the outer tube is sufficiently adhesive to hold the inner tube in its stretched condition but will peel from the inner tube upon impact of force. U.S. Pat. No. 4,070,746 (Raychem) discloses a recoverable tubular article in which an elastomeric sleeve is retained in a radially expanded condition by an outer constraint that is bonded thereto. The restraint is sufficiently strong to retain the sleeve in its expanded form under ordinary conditions of storage, but is susceptible to attack by solvents that weaken the bond sufficiently to allow the elastomeric sleeve to peel away from the restraint and to recover towards its original state. U.S. Pat. No. 4,233,731 (Raychem) discloses a dimensionally-recoverable article comprising a hollow resilient member which has been expanded to a dimensionally unstable configuration in which it is retained by a keeper positioned between and separating two parts of the hollow member away from the path of recovery thereof. The keeper is made from a material that weakens or changes its shape upon heating and/or chemical treatment, for example by being chemically degradable when subjected to a solvent. In one embodiment a single wedge of fusible material is interposed in the break in the circumference of a split tube of beryllium copper alloy. In another embodiment a tubular member made from an engineering plastics material has dovetailed protuberances on its outer surface between which strips of a polycarbonate are inserted to maintain the expanded configuration. EP-A0590469 (Kabelmetal) discloses a recoverable elastomeric tubular article that is held in its expanded state by thermoplastic bracing means in the form of a profile applied helically to the outer surface of the expanded tube.
It is an object of the present invention to provide a recoverable article and its method of manufacture, in which the article is held out in its expanded configuration by an advantageous external holdout means so as not to interfere with any inner layer, of gel, adhesive or mastic material for example, which may be applied internally thereof as a coating or which may be located around the substrate to be enclosed.
Thus, in accordance with one aspect of the present invention, there is provided a recoverable article comprising an inner resilient tubular member that is held out in a laterally expanded configuration by engagement with outer holdout means, wherein the outer surface of the inner member is provided with a plurality of cavities, and wherein the holdout means occupies the cavities so as to provide the holdout engagement, wherein the holdout means comprises at least one initiating portion that is structurally different from the remaining portion that engages at least one associated cavity, whereby release of the initiating portion from its cavity facilitates subsequent release of the remaining portion of the holdout means.
The forces generated within an expanded resilient member tending to cause it to recover can be large, the more so the thicker is the wall of the material. Thus, although such a cavitied member can be expanded and kept in its expanded configuration by maintaining the enlarged size of the cavities, in some instances it can be found to be extremely difficult, due to high frictional forces, to remove the holdout means in order to allow the member to recover towards, or, in the absence of an underlying substrate, to its original configuration. This difficulty is exacerbated the larger is the interface between the holdout means and the member, such as for example where the holdout means comprises a strip filling a cavity in the form of a long channel. It can be almost impossible to remove such a strip from the channel. By providing the holdout means with an initiating, or trigger, portion that is structurally different from the remaining portion, the initiating portion can be arranged to be released more easily, and advantageously manually, thereb
Costigan Philip
Gansbuehler George
Ions David
Lewington Sean Michael
Toerringer Josef
Hook James
Myers Bigel & Sibley & Sajovec
LandOfFree
Recoverable article does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Recoverable article, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Recoverable article will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2588589