"Closures" This invention relates to closures, and relates more particularly but not exclusively to closures for tubular articles composed of non-rigid sheet material.

Various forms of marine flotation systems are known in which inflatable bags are utilised to provide buoyancy to vessels or articles which are partly or wholly immersed in water. For larger scale flotation systems, the inflatable bags can be dimensionally extended until they are transformed to tubes, which may have a length substantially greater than their circumference when inflated. Fabrication of such flotation tubes from sheet material which is flexible but substantially inextensible allows the flotation tube to be collapsed to a substantially flat condition when not in use which minimises storage volume. Sheet material which is flexible, substantially non-extensible, and substantially impervious to gases and water can (for example) be a

fabric-reinforced polymer or a polymer-impregnated or coated fabric.

While the use of such flexible flotation tubes has advantages over other forms of flotation system, there exists the problem of providing end closures which are economic, practicable, and can reliably withstand the inflation-induced force tending to detach the closure from the tubes. Since the detachment force increases with the square of the tube diameter (for a given inflation pressure), the problems of closure attachment become particularly acute in larger sizes of flotation tubes e. g. in flotation tubes having inflated diameters above 1 meter.

Some embodiments of the present invention allows the effective reduction in the area of the closure exposed to pressure within a flotation tube or other inflatable article to which the closure is functionally attached.

In its first aspect, the present invention comprises a closure for an inflatable article, the closure comprising a plug means having a plurality of grooves to receive portions of the inflatable article, the closure also having clamp means which can retain portions of the inflatable article against the plug means.

Typically the article is a tubular article.

Typically the article is composed of non-rigid sheet material, and has a given circumference when fully inflated and fully distended that is substantially greater than the peripheral extent of the plug means.

Typically the plug means has an inner end face intended to face the interior of the inflatable article when the closure is installed and in use, and an outer end face opposite the inner end face.

Typically the grooves are formed on at least the outer end face of the plug means, extending inwards from its periphery and mutually spaced apart.

The grooves can adapt the relatively larger circumference of the inflatable article to the relatively lesser peripheral extent of the plug means.

The grooves may optionally be formed solely in the outer end face of the plug means, or the grooves may longitudinally extend between the outer end face and the inner end face. The grooves may extend substantially radially inwardly from the periphery of the plug means, or the grooves may extend inwardly from the periphery along respective directions comprising a radial component and a circumferential component, the circumferential components optionally having a common or similar angular bias so that the grooves each extend from the periphery inwards at the same or a similar angle across the radius. Typically

the clamp means is clamped against the plug means by screw thread means drawing the clamp means towards the plug means by relative rotation in a given rotational direction, and the angular bias of the grooves is preferably in same or a similar given rotational direction so that the relative rotation of the clamp means with respect to the plug means to clamp the clamp means against the plug means tends to drag the trapped folded portions of the inflatable article radially inwards across the outer end face of the plug means.

The plug means is preferably cylindrical, but the cross-section through its long axis can have any suitable shape. The generally circular periphery may be formed with one or more circumferential recesses adapted to accept circumferential clamp means such as bands which extend around portions of the inflatable tubular article when the closure is installed so as to enhance retention of the closure on the inflatable article.

The plug means may additionally comprise a conduit extending between the outer and inner end faces for the transport of air or other fluid to inflate the inflatable article when the closure is installed and in use.

A second aspect of the present invention comprises a method of fabricating a closure according to the first aspect of the present invention, the method

comprising the steps of providing a core of the plug means in the form of a substantially rigid central member having at least one radially extending flange, moulding the remainder of the plug means around the core, forming the grooves in the moulded portion of the plug means, and providing a clamp means clampable onto the outer end face of the plug means.

The grooves are preferably formed as part of the moulding process by incorporating groove-shaping means into the mould utilised for moulding the remainder of the plug means around the core of the plug means, but the grooves may alternatively be formed as a separate step by moulding the remainder of the plug means around the core without grooves, and subsequently sawing, milling or otherwise forming the grooves in the moulded portion of the plug means.

The core of the plug means can be formed of any suitable material, for example of plastics, or a metal which may be steel. The central member of the core may be a hollow tube to serve as the transport conduit for air or other inflation fluid. The central member preferably extends longitudinally from the outer end face of the moulded portion of the plug means, and is preferably externally screw-threaded so that the clamp means may be either directly screw- threaded onto it or alternatively so that the clamp means may be provided with a clearance hose to fit over the screw-threaded portion of the central member and be retained thereon by a nut or other suitable

screw-thread engaging member. The clamp means may conveniently be shaped as a flange member and formed of any suitable material, for example of a metal such as steel.

The moulded portion of the plug means may be formed of any suitable mouldable material, for example, of a thermoplastic polymer of an elastomer such as a hard rubber.

According to a third aspect of the present invention there is provided a flotation assembly comprising an inflatable member being closed by a closure according to the first aspect of the present invention.

Preferably each end of the inflatable tube is closed by a respective closure according to the first aspect of the present invention, at least one of these closures preferably incorporating a conduit for the transport of air or other fluid for inflating the flotation assembly. When fully inflated and fully distended, the inflatable tube may have any suitable dimensions, and any suitable ratio of length to circumference; for example the tube may have a circumference of about 3.15 metres (i. e. a diameter of about 1 metre if circular) and a length of 28 metres, the or each closure for such a tube having a peripheral extent of about 942 millimetres (i. e. a diameter of about 300 millimetres if circular), and therefore having an inner end area exposed to inflation pressure of less than one-tenth of the

cross-sectional area of the inflatable tube, with a proportional reduction in detachment force compared to a prior art closure having a diameter equal to the diameter of the inflatable tube. A larger form of such tube may have a circumference of about 4 meters.

If one end of the inflatable tube is self-closed (e. g. by in-turning, overlapping and mutually adhering portions of the tube material at that end), then the tube may effectively be considered as equivalent to a bag, i. e. an inflatable article having a single opening (and therefore requiring only a single closure in accordance with the first aspect of the present invention).

In a preferred aspect, the pleats of material inserted into the grooves are generally uniform in size and overlaps in the pleats are minimised, so that excess folds are avoided, and the grooves and circumference of the plug match the inner circumference of the tube as closely as possible avoiding rucks and surplus fabric.

The non-rigid material of which the inflatable tube is optionally composed preferably has the form of a flexible fabric material which is substantially impermeable to gases and liquids, and which is preferably substantially non-extensible. Such a flexible sheet material may comprise a fabric- reinforced polymer, or a polymer-impregnated fabric, or any other suitable material.

Preferred uses of the flotation tubes include fenders, water filled test bags or"water weights", containers for hazardous or toxic contents, and inflatable barriers to prevent escape of oilslicks etc, coastal erosion, for use in harbours, and for use in positioning subsea structures such as caissons.

The flotation assembly in accordance with the third aspect of the present invention may comprise a plurality of such inflatable tubes, each tube having at least one end closed by a respective closure according to the first aspect of the present invention, the plurality of tubes preferably being aggregated into a composite bundle (for example, a symmetric group of seven individual tubes of substantially identical dimensions) which bundle may be provided with a shroud or harness by which the flotation assembly can be attached to a vessel or article whose buoyancy is to be increased by the flotation assembly.

A flotation assembly can be coupled to a vessel or submerged/subsea structure or pipeline in a buoyancy- assisting manner at a location which places at least an effective fraction of the volume of the or each flotation assembly, and preferably substantially all of the or each flotation assembly, below the waterline of the vessel when fully floated with the assistance of the flotation assembly or assemblies,

but with minimal extension below the maximum depth of the keel (or keels or hull bottom (s) ) of the vessel when so floated.

According to the fourth aspect of the present invention there is provided a method of assisting a vessel to navigate a body of water whose depth is less than the minimum draft of the vessel alone, the method comprising the step of increasing the buoyancy of the vessel by the application to the vessel of at least one flotation assembly in accordance with the third aspect of the present invention, the or each flotation assembly being applied to the vessel in a manner which increases the buoyancy of the vessel but which substantially avoids increasing the minimum draft of the vessel.

As an example of practical application of the fourth aspect of the present invention, consider the case where a ship is constructed or modified within a dry- dock having a dockgate sill whose submersion even at the highest tide is less than the minimum draft of the ship (i. e. the greatest depth of the keel or hull bottom when the ship is unladen and deballasted).

The ship will then be unable to leave the dock when completed owing to the minimum depth of water (at the sill of the dockgate) being less than the irreducible minimum depth of water required to float the vessel.

Despite such restrictions, the ship can nevertheless be floated out of the dock if a suitable number of flotation assemblies according to the third aspect of

the present invention are harnessed to the ship and inflated such as to increase the ship's buoyancy to an extent that the ship's keel or hull bottom now clears the dockgate sill. The flotation assemblies can be coupled to the sides of the ship's hull in the manner of submerged sponsons so as to be immersed to the maximum extent practicable but without significantly extending below the previous maximum depth of the keel or hull bottom (thus avoiding any increase in the depth of water necessary to float the ship). The flotation assemblies can uplift against brackets attached to the sides of the ship's hull, and/or uplift the ship by means of straps passing under the hull between flotation assemblies on opposite sides of the hull (the straps being thin enough to cause only a negligible increase the draft of the ship, this increase being more than offset by the increased buoyancy of the ship when the flotation assemblies are inflated.

The invention also provides a method of sealing a flotation member, the method comprising providing a closure for the flotation member, the closure having a plug with grooves to receive portions of the member at an opening thereof, and a clamp to retain the portions in contact with the plug, the method also including the step of inserting folded portions of the member into the grooves, and clamping the member against the plug.

Embodiments of the invention will now be described by way of example, with reference to the accompanying drawings wherein:- Fig. 1 is an elevation of a plug forming part of a first embodiment of a closure; Fig. 2 is an elevation of an end clamp forming another part of the first embodiment; Fig. 3 is a sectional elevation of the first embodiment of closure as assembled; Fig. 4 is a plan view of the assembled first embodiment; Fig. 5 is a sectional elevation of the core of the plug of Fig. 1; Fig. 6 is a plan view of the core of Fig. 5; Fig. 7 is a plan view of the plug of Fig. 1, showing details of grooves formed therein; Fig. 8 is a fragmentary view, to an enlarged scale, of part of Fig. 7; Fig. 9a, b, c and d show end, side and end sectional views of a flotation tube closed by the first embodiment;

Fig. 10 is a plan view of a modified form of end clamp; Fig. 11 is a sectional elevation of the modified form of end clamp shown in Fig. 10; Fig. 12a, b, c and d show end, side and end sectional views of a further embodiment; Fig. 13a and b show plan and side view of a further embodiment; and Fig. 14a, b, c and d show end, side and end sectional views of a further embodiment.

Referring first to Fig. 1, this is an elevation of a plug 100 forming part of a closure (shown complete in Figs 3 and 4) constituting a first embodiment of the present invention. The plug 100 comprises a steel core member 102, (shown in more detail in Figs. 3,5 and 6) around which a generally cylindrical plug body 104 is moulded.

The core member 102 has one end 106 protruding from an end face 108 of the plug 100 (the end 106 being the only part of the core 102 visible in Fig. 1).

The core member end 106 is externally screw-threaded for a purpose to be subsequently detailed with reference to Fig. 3. The plug end face 108 will constitute an outer end face when the plug 100 forms part of a closure which is installed and in use. The

opposite end face 110 of the plug 100 (the lower end face as viewed in Fig. 1) will constitute an inner end face when the plug 100 forms part of a closure which is installed and in use.

As will be noted from Fig. 4, the transverse cross- section of the plug body 104 is circular such that the plug periphery 112 is cylindrical (apart from two circumferential recesses 114 provided for a purpose to be detailed hereafter).

The plug body 104 is moulded from a suitable polymer or elastomer, e. g. from NBR or NMBR rubber with a Shore hardness of A70. The moulded plug body 104 is solid other than for grooves (not visible in Figs. 1 or 3) which will subsequently be detailed with reference to Figs. 5 and 6.

Referring now to Fig. 2, this is an elevation of an end clamp or nut 120 forming part of the closure shown complete in Figs. 3 and 4. The clamp 120 has a hollow tubular centre member 122 with a bore which is dimensioned to be a clearance fit over the externally screw-threaded end 106 of the core member 102 of the plug 100 (Fig. 1). A circular flange 124 is welded to and extends radially from one end of the centre member 122 (the lower end of the centre member 122 as viewed in Fig. 2) The centre member 122 is buttressed to the flange 124 by a circumferentially distributed array of twelve radially and axially extending ribs 126 (all of which are shown in Fig. 4

but only two of which are depicted in Fig. 2 for the sake of simplicity). The centre member 122 and the ends of the ribs 126 axially opposite the flange 124 are capped by a small circular flange 128 having a central hole (not visible in Fig. 2 but depicted in Fig. 4) which dimensionally matches-the bore of the centre member 122 to allow the clamp 120 to be fitted over the end 106 of the core member 102 of the plug 100 (as shown in Fig. 4). The outer face of the small flange 128 serves to accept and distribute clamping force applied by a nut in the assembled closure, as will subsequently be detailed with reference to Fig. 4.

The various components 122,124, 126 and 128 of the end clamp 120 are formed of any suitable material, e. g. of steel, and are assembled by any suitable method, e. g. by welding.

Referring now to Figs. 3 and 4, these respectively depict a sectional elevation and a plan view of an assembled closure 200, formed by fitting an end clamp 120 over the protruding core end 106 of a plug 100, and then forcing the clamp flange 124 against the upper end face 108 of the plug 100 by means of a nut 130 (shown only in Fig. 3 and omitted from Fig. 4) screwed onto the externally screw-threaded core end 106. As an alternative to utilising the nut 130 for the application of clamping forces, the centre member 122 of the end clamp 120 can be internally screw- threaded for direct attachment to the externally

screw-threaded end 106 of the core member 102 of the plug 100 with relative rotation of the end clamp 120 and the plug 100 causing the application of clamping force between the clamp flange 124 and the plug face 108, any subsequent installation of a nut primarily serving merely as a lock-nut.

As may be seen from Figs. 3,5 and 6, the generally circular core member 102 of the plug 100 is a hollow cylindrical tube 140 from which two circular flanges 142 and 144 radially extend. The lower flange 142 (visible only in Figs. 3 and 5; obscured in Fig. 6) is secured to the end of the tube 140 axially opposite the externally screw-threaded end 106, while the upper flange 144 (visible in each of Figs. 3,5 and 6) is located axially closer to the upper face 108 than to the lower face 110 (with which the lower flange 142 is contiguous). Within the plug 100, the flanges 142 and 144 serve to assist adherence of the moulded body 104 to the core member 102 as well as generally providing internal reinforcement.

Referring now to Figs. 7 and 8, these respectively show a plan view of the upper face 108 of the plug 100, and a view, to an enlarged scale, of the fragment of Fig. 7 denoted"XIII". Figs. 7 and 8 detail the provision in the plug 100 of an array of twenty four grooves 150 extending radially inwards from the plug periphery 112. The grooves 150 are equiangularly spaced around the plug 100 (though alternative numbers, spacings or angular positions of

grooves could be adopted as necessary or desirable), and as well as each groove 150 extending radially inwardly from the plug periphery 112, each groove 150 is circumferentially offset from the intersection of the groove with the periphery, the circumferential offset increasing with increasing displacement radially inwards of the periphery such that each groove 150 lies at an angle to any radius intersecting the groove. Each of the grooves 150 extends axially between the opposite end faces 108 and 110 of the plug 100 with the radially outer and inner edges of each groove 150 lying parallel to the longitudinal axis of the generally circularly symmetrical plug 100. While the above-described form of the grooves 150 is preferred, other arrangements are possible, for example the grooves 150 could extend inwardly of the plug periphery 112 by an extent which varies as a function of the axial distance between inner and outer plug faces 110,108, and the grooves 150 may not axially extend all the way from the outer face 108 to the inner face 110, i. e. the inner face 110 may be free of grooves in an arrangement where grooves are present only in the outer face 108 and run out to zero depth at some predetermined extent axially inboard of the outer face 108. Equally the grooves need not be straight and could be arcuate or"zig-zag".

The purpose of the grooves 150 is to accommodate folded portions of a flotation tube (not shown in Figs 1-8) composed of a flexible sheet material and

having a total peripheral extent substantially greater than the circumference of the plug periphery 112 (e. g. from 2-5 times greater), so as to adapt the end region of the tube to the circumferentially smaller plug 100 of the closure 200 in a manner which ideally leaves a single thickness of tube material wrapping the plug periphery without folded-over portions of the tube end lying externally of the closure. For this purpose, the end region of the location tube is prepared for coupling to the closure by gathering and inwardly folding twenty four pleats in the tube material (by manual manipulation or by use of a suitable tool), locating a plug 100 (minus clamp 120) inwardly of the pleated tube end such that the plug end face 110 faces along the interior of the tube and the plug end face 108, together with the protruding core end 106, is directed towards the open end of the tube, and inserting pleats into successive grooves 150. The placement of the pleats in the grooves 150 preferably leaves a suitable portion of the tube overhanging the outer end face 108 (for a purpose shortly to be explained), and the pleats are uniformly driven into their respective grooves until ideally only a single thickness of tube material is exposed on the plug periphery 112, around which the tube material is tightly wrapped in a wrinkle-free manner. Next, the end clamp 120 to be associated with the plug 100 is coaxially located over the protruding core end 106 with the clamp flange 124 facing the plug end face 108, the overhanging portions of the pleated tube end are tucked into the

gap between the flange 124 and the face 108, and the end clamp 120 is pushed axially against the plug end face 108 to compress the tube end between the clamp 120 and the plug 100. This clamping process is assisted by rotating the clamp 120 around the axis of the plug 100 such that the clamp 120 rotates in a clockwise direction relative to a static plug 100 when viewed in a direction facing the outer end face 108; as may be seen from the rake or angular alignment of the groove 150 as viewed in Fig. 7, such clockwise rotation of the clamp 120 not only tends to spread the tube end against the plug face 108 but also tends to pull each pleat of tube material more deeply into its respective groove 150 to enhance the integrity of attachment of the tube to its end closure. Finally, the tube closure is completed by tightening of the nut 130, followed by tightening of a ring clamp 250 in each of the recesses 114 to trap and clamp the underlying tube material wrapping the plug periphery 118. The combination of flotation tube 260 and end closure is illustrated in Fig. 9.

The other end of the flotation tube 260 may be closed in any suitable manner, for example by a further closure similar or identical to the closure 200 described above.

When the flotation tube 260 is closed at both ends and then inflated with a suitable fluid (e. g. compressed air or nitrogen), only the inner end face 110 of the plug 100 forming parts of the closure 200

is exposed to the inflation pressure and hence subject to a force tending to eject the closure 200 from the end of the flotation tube. Since the total area of the plug end face 110 is typically less than the cross-sectional area of the fully inflated and distended flotation tube, the closure 200 of the invention is subjected to an ejection force which is correspondingly less than the ejection force than would be applied to a closure occupying the full cross-sectional area of the flotation tube.

An air hose (not shown) can be screwed on to the plug end 106 using the same screw-thread as that which holds the nut 130 to serve as a supply of compressed air for inflation of the flotation tube. A valve (not shown) can be incorporated to seal the air passage down the tube 140 when the floatation tube is not being inflated or deflated. Where a closure according to the invention is not required to pass inflation fluids, the hollow tube 140 (or its equivalent in another embodiment of the invention) may be omitted or substituted by a solid rod.

When closed at both ends and suitably inflated, a flotation tube of the kind depicted in Fig. 9 having a circumference of 4 metres and a length of 28 metres will have a volume of about 350 cubic metres. A harnessed bundle of seven such flotation tubes will have a flotation capacity in excess of two kilotonnes. The attachment of a suitable number of such bundles of flotation tubes to a ship therefore

makes it possible to increase the buoyancy of the ship to such an extent that the ship can navigate waterways significantly shallower than those navigable without such buoyancy enhancement; e. g. a ship trapped in a dock by an excessively shallow dock exit can have its buoyancy increased and its draft correspondingly reduced by the use of flotation tubes in accordance with the invention, to an extent that the assisted ship can navigate the dock exit.

Figs. 10 and 11 show a form of end clamp 220 which is a modified form of the end clamp 120 previously described. Those parts of the clamp 220 which are identical or analogous to corresponding parts of the claps 120 are given the same reference numerals, but with the leading"1"substituted by a leading"2".

The principal difference in the clamp 220 with respect to the clamp 120 lies in the use of six ribs 226 (in place of twelve ribs 126), and the keying of the ribs 226 into radial slots in the flange 224. In other respects, the clamp 220 is essentially the same as the clamp 120, to the description of which reference should be made for details of identical or analogous parts not otherwise detailed in this paragraph.

Referring now to Figs 12 and 13, a further embodiment has a plug 300 having a slotted ring 310 of rubber (or other material) having slots 315 extending radially from the inside of the ring part way to the periphery and at an angle to the radius. The ring

310 receives within its bore 310b a plug 320 with a radially extending flange 320f that abuts against the inner surface of the ring 310, and an axially extending wall 320w that fits snugly into the bore 310b against the inner surface of the ring 310.

Bolts 325 secure the ring 310 between a top plate 312 and the plug 320.

The plug 320 is inserted into the opening of the flotation tube 260 so that the fabric of the flotation tube 260 passes over the wall 320w and flange 320f of the plug 320. The fabric of the tube 260 is then inserted into the bore of the ring 310b, which is then fitted over the wall 320w of the plug.

The pleats of fabric are then inserted into the slots 315 in the ring, and the ring is then secured between the top plate 312 and the plug 320 by the bolts 325 so that the fabric of the tube 260 is clamped between the plug 320 and the ring 310.

A compression seal can be used at the bolts 325.

The above embodiment 300 can easily be fitted and removed from the outside of the tube 260.

Fig. 14 shows a modified form of the above embodiment 300 used in a textile flotation tube 265 supported by webbing straps 267.

While certain modifications and variations have been described above, the invention is not restricted

thereto, and other modifications and variations can be adopted without departing from the scope of the invention.