MXPA99008529A - Recoverable article - Google Patents

Abstract

A recoverable article comprising an inner resilient tubular member (2) that is held out in a laterally expanded configuration by engagement with outer holdout means (6, 8), wherein the outer surface of the inner member (2) is provided with a plurality of cavities, and wherein the holdout means (6, 8) occupies the cavities so as to provide the holdout engagement, wherein the holdout means comprises at least one initiating portion (6) that is structurally different from the remaining portion that engages at least one associated cavity, whereby release of the initiating portion (6) from its cavity facilitates subsequent release of the remaining portion (8) of the holdout means.

Description

RECOVERABLE ARTICLE This invention relates to a recoverable article for, and method for, enclosing an elongate substrate. The substrate can comprise, for example, a cable, which can be a power or telecommunications cable, and in particular a cable connection. The cable connection may comprise a connection, or splice, between two, or more, cables, or a termination of a cable, for example on a terminal insulator pin or sleeve connected to electrical equipment such as a distribution device or a transformer. The termination may comprise an adapter, for example an elbow. The invention will be further described in particular with reference to an in-line seal between two electrical power cables, but it should be understood that this is by way of example only and not by way of limitation. The joints between two power cables, whether one or the other or both are insulated cables with polymer or paper, 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 used. Sleeves and push-on elbows are available but unlike heat shrinkable products, these have severe range limitations that require a large inventory. Other so-called cold-applied solutions require a tubular elastomeric sleeve to be expanded and mounted radially on a rigid retainer member, whose internal diameter is larger than the maximum external diameter of the cable seal to be enclosed. An example of the latter is the available PST manga of 3M, as exemplified in EU-A-3615798. Such sleeve has an internal retaining member consisting of a continuous narrow strip of hard flexible material in the form of a rigid closed spiral having adjacent interconnected curls. The sustained sleeve is mounted on the cable joint and the helical strip is then unwound, thus allowing the stretched insulating elastic cover to shrink on the joint. However, it is inconvenient to have to unwind the support strip helically around the extended cable, especially if the work has to be done in the confined space of a manhole or ditch. Another example of a cold-applied arrangement is described in EU-A-3824331 (AMP), in which an elastic tubular cover is supported in a stretched condition by an easily removable outer support member, each end of the cover being rolled back on the outer side of the support. The cover and the support member are mounted on an inner sleeve in the form of a longitudinally split pipe maintained in a state of increased diameter by a dividing strip in the shape of a beam I. When in position on the cable joint, the removal of the dividing strip longitudinally from the cut allows the inner tube to be constricted and then freely removed from the cover. The ends of the cover are then unrolled on the cable sections adjacent and the external support member is removed. It will be appreciated that such an arrangement requires an internal withholding member and an external withholding member, each of which must be removed. EP-B-O 530 952 (3M) discloses a cover assembly in which an elastomeric tube is held in a stretched condition in an internal support core. The core is fragile so that the application thereto of a force beyond that produced by the tube causes rupture of the core to allow the contraction of the elastomeric tube on the substrate. The fragments of the collapsed core remain inside the tube and should therefore be as small as possible to facilitate their accommodation within it. With each of these arrangements, the retaining member is disposed internally of the sleeve to be applied to the substrate cable. Thus, the sleeve can not conveniently have an internal coating, gel, putty or adhesive for example, applied thereto. This problem is avoided by the recoverable sleeve assembly described in EU-A-4410009 (Sigmaform), in which an inner elastomeric tube is maintained in a radially stretched condition having an external rigid tube surrounding and secured to the outer surface thereof. . The outer tube is a rigid thermoset adhesive polyurethane, so the outer tube is sufficiently adhesive to keep the inner tube in its stretched condition, but it will detach from the inner tube by force impact. EU-A-4070746 (Raychem) describes a recoverable tubular article in which an elastomeric sleeve is retained in a condition radially expanded by a external coercion that is attached to it. The coercion is strong enough to retain the sleeve in its expanded form under ordinary storage conditions, but is susceptible to attack by solvents that weaken the bond sufficiently to allow the elastomeric sleeve to detach from the constraint and recover to its original state. EU-A-4233731 (Raychem) describes a dimensionally recoverable article comprising a hollow elastic member which has been expanded to a dimensionally unstable configuration in which it is retained by a latch placed between and separating two parts of the hollow member away from the recovery path of it. The insurance is made of a matepal that weakens or changes its shape by heating and / or chemical treatment, for example that is chemically degradable when subjected to a solvent. In one embodiment, a simple wedge of fusible material is interposed in the break in the circumference of a divided beryllium copper alloy tube. In another embodiment a tubular member made of an engineering plastic has dovetail protrusions on its outer surface between which strips of a polycarbonate are inserted to maintain the expanded configuration. EP-A-0590469 (Kabelmetal) discloses a recoverable tubular elastomeric article which is maintained in its expanded state by thermoplastic clamp means in the form of a profile helically applied 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 in its expanded configuration by an advantageous external retaining means so as not to interfere with any internal layer, of gel material, adhesive or putty for example, which may be applied internally thereto as a coating or which may be placed around the substrate to be locked up Thus, according to one aspect of the present invention, a recoverable article is provided comprising an internal elastic tubular member that is maintained in a laterally expanded configuration by engagement with an external retainer means, wherein the outer surface of the inner member is provided. with a plurality of cavities, and wherein the retainer means occupies the cavities to provide the retainer coupling, wherein the retainer means comprises at least one initiation portion that is structurally different from the remaining portion that engages at least one cavity. associated, thereby releasing the initiation portion of its cavity facilitates the subsequent release of the remaining portion of the retainer means. The forces generated within an expanded elastic member that tend to cause it to recover may be large, the larger the thicker the wall of the material. Thus, although such a cavity member can be expanded and maintained in its expanded configuration by maintaining the elongated size of the cavities, in some cases it can be found that it is extremely difficult, due to high friction forces, to remove the retainer 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 the interface between the retaining means and the member, such as for example where the retaining means comprises a strip that fills a cavity in the shape of a long channel. It can be almost impossible to remove such strip from the channel. By providing the retainer means with an initiation portion, or trigger, which is structurally different from the remaining portion, the initiator portion can be arranged to be released more easily, and advantageously by hand, thereby reducing the frictional forces that retain the remaining portion of the retainer in place, which can then be manually removed as well. Preferably, the or each initiating portion comprises two parts such that (a) when the two parts are coupled, the integrity of the retaining means is maintained, and (b) when one of the two parts is released from the other part that is in coupling with the cavity, the other part is removable from the inner member. In such an article, the release of the two parts from each other may allow the other part to be expelled from the cavity by the recovery force of the elastic member. In one embodiment, the retainer, trigger, or other means may comprise at least one strip of high modulus material that engages respective channels of the crenellated outer surface of the inner member, each strip being embedded within a modulus sheath minor that retains a lubricant. The release of the retainer can be effected by cutting the outer sheath from one end to the other so that the lubricant facilitates the strength of the member's recovery.

Internal push the strips out of the channels. The cut can be effected by an annular ring with cutting surfaces projecting inwardly to couple more than one retaining strip. Advantageously, the release of a part of the initiating portion may result in the other part undergoing a change in shape, for example by a pivoting or hinge movement, which facilitates its removal from the cavity. The two parts can inter-close, be hinged together, and can be integrally formed. The fracture of, for example by cutting through, one of the parts may allow a change in shape so that the other part can be removed from the cavity. Alternatively, one part can be inserted into the other to maintain the shape of the other part to prevent collapse, or recovery, of the cavity. In the latter mode, the removal of the insert may result in the recovery force of the limb collapsing and ejecting the other part. The retainer means may comprise a plurality of initiator portions positioned symmetrically on the outer surface of the elastic member, whereby the remaining portion of the retainer member is easily releasable relatively subsequent to the removal of all the initiator portions, however, it is more preferred. currently for this to be a simple initiating portion. Advantageously, the cavities comprise a plurality of channels extending longitudinally of the article, preferably parallel to each other, and preferably parallel to the longitudinal axis of the tubular member. Alternatively, the channels may extend helically wound around and along the elastic member. The channels may be of substantially rectangular configuration, but may be re-entrants to increase the retention of the retainer means therein. Preferably, the channels are provided by the elastic member having an outer crenellated surface. The or each initiator portion and / or the remaining portion of the retainer means may comprise a plurality of strips that are retained within one of the respective channels. The strips are preferably removable by a detachment action from one end of the strip to the other. In a particularly preferred embodiment the initiator portion comprises a single strip (which may comprise two or more parts), and the remaining portion of the retainer means comprises a plurality of other strips. The recovery of the elastic tubular member is carried out by removing the starter strip and subsequent removal of the other strips, preferably sequentially around the circumference of the tubular member. This method of recovery (shrinkage) of the tubular member has the advantage that it helps to prevent entrapment of air below the limb when it recovers. In embodiments in which the retainer means comprises a plurality of strips, the article may include one or more (preferably two) supports, for example in the form of rings, for retaining the tubular member (preferably via the retainer strips), in a configuration of substantially circular cross section. The or each support is preferably positioned radially inwardly of the retaining strips and / or the tubular member. The or each support may be positioned adjacent one end of the tubular member, preferably exterior to the tubular member. A portion of the retainer means may be applied in a flowable form, such as sand or other granular material, and held in place by a wrapper, of polymeric material or other suitable material. The flowable material can be a hardenable, or curable material, such as gypsum, cement, a curable epoxy resin system or another thermoset, which may or may not require a wrap. In general, however, whether or not the retainer means is flowable, it may be desirable to enclose the article of the invention within an outer sheath to increase the retention of the retainer means during storage and transportation. A portion of the retainer means may comprise foam, preferably high density foam, which can be formed into strips to fit into the channels on the external surface of the inner member for example, or which can be foamed in situ to fill the expanded cavities. In one embodiment, the retainer may be formed by a layer extending around the entire circumference of the inner member and joined thereto to extend over the top of the cavities. In its retainer configuration, the layer can be diverted to the cavities, and can be removed towards outside, for example prog resively from one end of the article to the other, to rotate to a configuration that allows the recovery of the article. A portion of the retainer means may be formed, especially when it comes to the configuration of strips, of material exhibiting good compressive strength in the transverse direction, while exhibiting more flexibility, or brittleness, in the longitudinal direction of the inner member, for facilitate with this the controlled removal of the same, and thus the controlled recovery of the internal member. It has been found that the cardboard is a suitable material, for example a material comprising layers composed of Kraft cardboard approximately 0.9 mm thick. Also suitable materials are wooden slats, fibreboard or plasterboard. In the latter case, it has been found suitable, a cardboard comprising a 9 mm thick gypsum layer laminated between layers of cardboard giving a total thickness of approximately 10 mm. Such retaining means are cheap comparatively and are also biodegradable. It is also thought, however, that the retaining means of the article of the invention can be polymeric, preferably biodegradable. The retaining means can be extruded on the outer surface of the internal tubular member. Advantageously, the cavities, for example the longitudinal channels, on the external surface of the inner member are re-entrants to increase the retention of the retaining means.

It will be appreciated that the formation of the cavities must be such as to ensure that the internal member is retained in its expanded configuration under expected conditions of storage and transport to its place of application and then released without the need for excessive force, preferably manually, when the article is going to be applied to a substrate. The shape of the interface between the inner member and the retaining means will thus depend on factors such as (i) the material of the inner tubular member and the retaining means, in particular the relative hardness, and (ii) the force within the expanded tubular member. which tends to cause its recovery, which will depend only on the material, the expansion ratio of the member, and its thickness. Thus, for example, a thick-walled inner member made of material with relatively high, highly expanded modulus will require a relatively greater amount of mechanical interlock through the retainer means due to its relatively high recovery forces. The inner member is preferably made of polymeric material, preferably elastomeric. One or both ends of the internal tubular member may advantageously have a beveled inner surface (especially chamfered). This can help prevent the end of the tubular member from getting into a substrate (e.g., a cable) around which it recovers. The inner member can be part of an enclosure for a termination, splicing of electric cables, or the like, and can be formed from electrically conductive material, for example for form electrical continuity through, and / or electrical protection of, the junction. The inner tubular member may have one, or more, additional layers on its inner surface, which may be co-extruded therewith. For example, an electrically insulating layer and / or a polymeric voltage rating layer electrically can be co-extruded internally with the inner member. Such an additional layer may have different mechanical properties to those of the inner member, for example by being more elastic to increase the conformation with the substrate, for example a cable splice. There may also be an electrically conductive layer the innermost one, for example that extends along only part of the length of the other layer (s), to provide a Faraday cage. An inner layer of gel, putty or adhesive can be provided to increase conformation and sealing, for example to exclude air and / or humidity, with the substrate. It is also thought that such a sealant layer can be applied separately to the substrate. According to another aspect of the present invention, there is provided a substrate, for example an electrical component, which includes a junction, termination or elbow of electric cables, enclosed by an article recovered in accordance with said one aspect of the present invention. According to a further aspect of the present invention, there is provided a method for recovering a recoverable article according to the one aspect on a substrate, by the steps of releasing the, or each, initiating portion of the retaining means from its cavity, and break free subsequently the remaining portion of the retainer means, preferably in a sequential manner around the circumference of the article. When it is in the form of strips, the retaining means is preferably released by stripping (peeling) from one end thereof to the other. Preferably, there is a simple initiator portion which is released, followed by the sequential release of the strips from the remaining portion of the retainer means. The embodiments of recoverable article, its methods of manufacture and application, each in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an end view of an article in its expanded configuration; Figure 2 is an isometric view of the article of Figure 1 showing the first step in its recovery; Figure 3 is an isometric view showing part of the length of the article of Figure 2 in its recovered form; Figures 4 and 5 show partial end views of alternative recoverable items; Figure 6 shows a release member for use with the articles of Figures 4 and 5; and Figure 7 is an isometric view of a recovered article that is part of an inline power cable splice. With reference to Figures 1, 2 and 3, the recoverable article comprises a sleeve 2 the innermost cylindrical insulating electrically elastomeric and, externally attached thereto, an electrically elastomeric conductive member 4 having an outer crenellated surface. An external retainer arrangement consists of twelve relatively rigid polymer strips that fill the twelve valleys of crenellated member 4 from one end thereof to the other. Retaining strips are of two types. The first type of retainer strips consists of four firing strips 6 that are equidistant circumferentially around the tubular member 4, and these are interspaced with the remaining eight strips 8 that are of a different structure. Each strip is of two parts, an internal part 10 generally of H-shape that couples with the valley of the expanded tubular member 4, and a snap-on cover 12. Each strip 8 consists of a hollow strip of rectangular section that fits within its valley. The composite recoverable member 2, 4, which may have been formed by molding or extrusion, is expanded such that the valleys on its outer surface open. The retaining strips 6, 8 are then pushed into position and the expansion means, which may be an internal mandrel, is removed. The slight relaxation of the elastic recoverable member then firmly retains the strips 6, 8 in position, and they, which are relatively stiff, prevent subsequent retrieval of the article 2, 4. The removal of the strips 8 is particularly difficult, if not impossible manually , due to the highly frictional forces that exist over the extensive surface area between them and the valleys or crenellated channels. The shot strips 6, however, are structurally designed differently to be relatively easy to manually remove, and then, releasing some of the recovery forces on the strips 8, to facilitate manual removal of the remaining strips 8. The generally H-shape of the internal component 10 of the strips 6 allows them to act as a hinge when the outer retention cover 12 is removed. Thus, the removal of the cover 12, by the stripping (peeling) action shown in Figure 2, results in the circumferential restoring force within the elastic member 4 exerting pressure on the internal legs radially of the H-shaped component 10 which then rotates about its transverse member such that the component 10 is forced out of its channel. It is conceivable that the cover 12 could be completely removed, end to end, of each strip 6 in turn, resulting in expulsion, or removal, of all four strips 6. This results in partial recovery of composite article 2, 4, and thus an associated reduction in the stored recovery force. Consequently, the forces retaining the rigid tubular strips 8 in position are reduced, such that the strips 8 can now be removed, thereby allowing full recovery of article 2, 4. It will be appreciated that under free recovery, i.e. in the absence of a substrate, the article will tend to return to the size at which it was originally formed. However, in practice, the article will be recovered in a substrate of such transverse dimension, usually diameter, that there is still some unresolved recovery within the article to thereby improve its retention in, and sealing to, the substrate.

Figure 3 shows an alternative way of recovering the article, in an intermediate stage. In this mode, the four trigger strips 6 are initially released but only a part of the section along the length of the article. The strips 8 are then released at 5 along the same length. This alternate release of the two types of strips is then continued throughout the article until it has been recovered along its entire length. Figure 4 shows an end view of a segment of one more mode of the recoverable article in which a channel 80 between adjacent flat portions 82 of the outer surface of an elastic inner member is filled with an elongated two-part retainer strip 84. A central support portion 86 of the strip 84 is generally H-shaped with the narrow intermediate connection portion forming a hinge. The other part of the retainer strip 84 consists of a pair of side strips which act to provide a lower friction angle with the central portion 86 than would the part 86 with the sides of the flat portions 82. Removal of the retainer 84 is achieved by means of the firing ring 100 of the Figure 6. Ring 100 is formed of a rigid plastic material and has an annular portion 102 that is large enough to pass around the exterior of the article of Figure 4, and a set of twelve tapered fingers 104 that are axially directed and placed in a "-" * circle of radius such that when the ring 100 is placed axially at one end of the article of Figure 4, the fingers 104 engage with the respective 5 openings formed between the central support portions 86 and the background of the associated channels 80. Thus, as the ring 102 moves along the length of the recoverable article, the central support portions 86 are triggered to be pulled out of the channels, allowing the article to recover. The side strips 88 can be removed separately, or they can be left in place as long as they do not interfere with the recovery of the article and the subsequent reduction in the transverse dimension of the channels 80. Figure 5 shows a modification of the article of the Figure 4, because the central support portion 90 is generally hollow rectangular in shape with external corners with spokes, and wedge-shaped side strips 92 to conform to the correspondingly formed side walls of the castellated internal member channel, and increase retention of the part 90 retainer in it. The trigger ring 100 of Figure 6 will be arranged to mate with the recess of the central portion 90, and the radio portions of its internal corners will aid in its ejection. In a further embodiment, the reduction in friction achieved by employing side pieces of a retainer, such as the side strips 88 or 92, can alternatively be achieved by spray coating the sides of the channels of the inner member or the retaining portion 84, 90 with a low friction material, or applying grease to them. In the latter mentioned embodiments of the invention, a retention sheath may be necessary to retain the retainer strips in position until their release is required. In such instances, ring 1 00 of Figure 6 may not be required.

Figure 7 shows an article 140, which may be in accordance with any one of the preceding modes, in its recovered condition on a splice of electric power cables in line. Article 140 consists of an electrically conductive crenellated elastic member 142, and an innermost layer 144 of electrically insulating polymeric material. Each cable has an external polymeric sheath 146, ground shield wire 148 bent back, and primary dielectric 150. Prior to the recovery of article 140, the region around the connector of the cable conductors (not shown) has been enclosed within a layer 152 of tension control material, which has been compressed to conform to the underlying components by the recovery of article 140, thereby excluding air from the splice region. Although not shown, it will be understood that an outer protective liner is to be applied to the splice as shown in Figure 7 to encompass article 140 and to seal each cable liner 146. The electrical continuity through the joint, via the conductive layer 142, between the wire wires 148 will also be made. Advantageously, the external protective liner is as described in British Patent Application No. 9626364.5, the entire contents of which are hereby incorporated by reference. It will be appreciated that it may be advantageous to place the firing portion (s) of the retaining means of the invention about symmetrically of the inner tubular member, but this need not be the case. In addition, the number of firing portions with respect to the number of remaining portions may be varied to suit the particular article. He Recovery mode may be different from the examples given, with, for example, some of the remaining portion that is removed before the entire shot portion has been removed. As a further alternative, the entire firing portion, for example all four firing strips 6, can be simultaneously removed substantially, followed by substantially simultaneous removal of the remaining retainer portion, for example strip 8. In the latter mode , a release means functionally corresponding to that shown in Figure 6 can be thought of to remove the covers 12 from the strips 6 and then remove the strips 8.

Claims (34)

1 . A recoverable article comprising an internal elastic tubular member that is maintained in a laterally expanded configuration by engagement with external retainer means, wherein the outer surface of the internal member is provided with a plurality of cavities, and wherein the retainer means occupies the cavities to provide the retainer coupling, wherein the retainer means comprises at least one initiator portion that is structurally different from the remaining portion that engages at least one associated cavity, whereby the release of the initiator portion of its cavity facilitates the Subsequent release of the remaining portion of the retainer medium. An article according to claim 1, wherein the or each initiating portion comprises two parts such that (a) when the two parts mate with each other, the integrity of the retaining means is maintained, and (b) when one of the two parts is released from the other part that is in engagement with the cavity, the other part is removable from the internal member.

3. An arrangement according to claim 2, wherein the release of the two parts of the initiating member allows the other part to be expelled from the cavity by the recovery force of the internal member.

4. An article according to claim 2 or claim 3, wherein by the release of a part of the initiating portion, the other part undergoes a change in shape that facilitates its removal from the cavity.

An article according to claim 4, wherein the change of shape is effected by a pivoting movement of the other part of the initiating portion.

6. An article according to any one of claims 2 to 5, e, n wherein said part of the initiating portion comprises an inter-closing cover for the other part.

7. An article according to any one of claims 2 to 6, wherein the two parts of the initiating portion are integral with each other.

8. An article according to any one of claims 2 to 7, wherein the two parts are hinged together.

9. An article according to any one of claims 2 to 7, wherein the fracture of the one part allows the removal of the other part.

10. An article according to any one of claims 2 to 5, wherein said part is inserted into the other part, thereby preventing the change of form thereof. eleven .

An article according to any one of the preceding claims, wherein the remaining portion of the retaining means is retained by the internal member until at least one initiating portion has been removed therefrom.

12. An article according to any one of the preceding claims, wherein the cavities comprise a plurality of channels extending longitudinally of the article, preferably parallel therebetween.

An article according to claim 12, wherein the or each initiator portion and / or the remaining portion of the retainer means comprises a plurality of strips that are retained within the respective channels.

14. An article according to claim 13, wherein at least the strips of the remaining portion of the retaining means are rigid with respect to the material of the inner member.

15. An article according to claim 13 or claim 14, wherein there is a simple initiator portion, comprising a single strip.

16. An article according to any one of claims 12 to 14, further comprising one or more supports positioned radially inwardly of the retaining strips for retaining the tubular member in a substantially circular cross section configuration.

An article according to any one of claims 13 to 16, wherein each strip comprises a plurality of longitudinally spaced retainer members that substantially fill a cavity in discrete positions along its length, successive retaining members of each strip that they are articulated together.

18. An article according to any one of the preceding claims, wherein the external surface of the inner member is crenellated.

19. An article according to any one of the preceding claims, wherein at least a portion of the retainer means comprises: (a) a particulate material; or (b) a cured material; or (c) a high density foam material; or (d) compacted fibrous material; said material being held in place by a wraparound cover, if required.

20. An article according to any one of the preceding claims, wherein the retaining means comprises material stably, preferably biodegradable. twenty-one .

An article according to claim 20, wherein the retainer material is polymeric.

22. An article according to any one of the preceding claims, wherein the inner tubular member is electrically conductive.

23. An article according to any one of the preceding claims, wherein the inner tubular member is made of polymeric material, preferably elastomeric.

24. An article according to any one of the preceding claims, comprising a tubular arrangement

elastic, radially internal, additional in which the internal tubular member is mounted, preferably integrally therewith.

25. An article according to claim 24, wherein the additional tubular arrangement comprises at least one tubular member that is more elastic than the internal elastic tubular member.

26. An article according to claim 24 or claim 25, wherein the additional tubular array comprises an electrically insulative tubular member and / or a tubular electrically tension controlling member.

27. An article according to any one of claims 24 to 26, which comprises an innermost layer electrically radially inwardly of the additional tubular array, and preferably positioned only in a longitudinally central region of the article to provide a cage of Faraday.

28. An article according to any one of claims 24 to 27, wherein the additional tubular arrangement is made of polymeric material.

29. An article according to any preceding claim, wherein at least one end, preferably each end, of the inner tubular member has a beveled inner surface.

30. An article according to any one of the preceding claims, of substantially cylindrical configuration.

31 An article recoverable substantially as described hereinabove with reference to the accompanying drawings.

32. An electrical component, including a splice, termination or elbow of electric cables, enclosed by a recovered article according to any one of the preceding claims.

A method for recovering a recoverable article according to any preceding claim, by the steps of releasing the, or each initiating portion of the retaining means from its cavity, and subsequently releasing the remaining portion of the retaining means.

34. A method according to claim 33, wherein the remaining portion of the retainer means comprises a plurality of strips, and the strips are released in a sequential manner around the circumference of the article.