Patent Description:
An escape system, such as an evacuation system is used for evacuating people from a structure at sea in the event of an emergency. Such a structure may be an oil rig or a ship.

One form of evacuation system includes an inflatable craft into which the people are evacuated. Since, when inflatable crafts are deployed on water, there is usually a significant difference in height (freeboard) between the point on the structure from which the people are evacuated and the inflatable crafts on the water, it is necessary to provide some form of passage between the two.

It is known to provide an angled or vertical passage, which may be formed from inflatable members, extending between the evacuation point and the inflatable crafts. The angled or vertical passage can extend either direct to the inflatable crafts or to an inflatable floating structure or platform to which the inflatable crafts are attached. In some vessels, the freeboard may be <NUM>-<NUM> metres and so the angled or vertical passage is of significant length.

Evacuation systems should preferably be able to operate in force six weather which will include a <NUM> metre swell.

An angled or vertical passage is not readily able to meet such a requirement as the angled or vertical passage projects from the side of a vessel and is subjected to significant lateral movements in heavy weather which may make evacuation hazardous.

<CIT>) discloses a marine escape system having a chute in the form of a flexible helical tube which extends between an evacuation point on a vessel and an inflatable liferaft. The helical tube has stiffening bands and is further supported by a plurality of rigid hoops which are connected to surround the chute by cords and resilient elastomeric members. The connection between the evacuation point and one of the hoops is by non-elastic flexible members, with further connection from the hoop to the liferaft by means of flexible elastic members held in tension so that, as the liferaft moves on the swell, the tube extends and retracts.

<CIT>, our ref: <NUM>) discloses a marine escape system for evacuating a marine structure comprising a chute, a buoyant non-inflatable platform and at least one inflatable life raft. These parts are deployable from a packed disposition on the structure to a disposition in which the chute leads from the structure to the platform floating on the water and the platform leads to the inflated life raft so providing a passage for people from the structure to the life raft. In an alternative embodiment, the platform may be either inflatable or non-inflatable and be formed by inner and outer parts that are relatively rotatable to allow, on deployment, the life raft to swing relative to the chute.

<CIT>) discloses an inflatable escape chute consists of inflatable tubes, and a connecting piece and inflatable liferafts connected to it by painters, through the intermediary of an inflatable platform. The apparatus is stowed on the deck of a ship, preferably under a hinged ramp which pivots overboard when the chute is inflated, and may act to support the upper part of the chute. The platform may be attached to the chute, or its inflatable surround may be integral with the chute tubes. The chute may be divided into two parallel chutes by a central longitudinal tube. The floor of the platform is preferably formed of inflatable tubes. The platform may be stabilized by means of drogues or water pockets.

<CIT> discloses a system that has a group of inflatable life rafts, including a reception raft and evacuation rafts, and a chute in the form of a stocking for transferring people from a ship to the life rafts. The life rafts are held deflated on a frame that can be lowered from a ship into the water where the life rafts inflate on the water and the frame continues beneath the water to stabilise the reception raft and the stocking via wires that pass from the frame to the ship through the reception raft and the stocking. The stocking leads to the reception raft so providing a pathway for people from the ship to the reception raft and thence to the life rafts.

<CIT> discloses an escape system having a slide that comprises a helical inflatable member. A chute is fixed to the upper surface of the inflatable member.

It would be desirable to provide an improved evacuation system able to be operated safely in heavy weather.

A first aspect of the present invention provides an escape system as defined in claim <NUM>.

The structure may a ship or other vessel, or an oil rig, for example.

The or each helical inflatable path may be configured to extend generally vertically between the structure and the water. This may make the slide safer to use in adverse weather conditions.

The slide may comprise a plurality of helical inflatable paths. This may increase the evacuation rate from the structure.

A first of said helical inflatable paths and a second of said helical inflatable paths may have a common central axis. A first of said helical inflatable paths and a second of said helical inflatable paths may have a double helix configuration. The first of said helical inflatable paths and the second of said helical inflatable paths may be interlaced or intertwined.

Two or more of said helical inflatable paths may be arranged side by side with spaced apart and substantially parallel central axes.

The slide comprises spacing means for controlling the pitch between helix turns of the or each of the helical inflatable paths.

The spacing means may be operable to set a minimum distance between two adjacent helix turns of the or each of the helical inflatable paths. This may prevent a slide path being blocked when the freeboard is reduced.

The spacing means comprise a plurality of tubular parts attached to the slide, the gap between adjacent ones of the tubular parts varying with the pitch between the helix turns, and the abutment of adjacent tubular parts (when the gap closes) preventing the distance between two adjacent helix turns falling below said minimum distance.

The spacing means are operable to maintain a substantially equal distance between adjacent helix turns of the or each of the helical inflatable paths. This may reduce the likelihood of a part of a slide path being blocked when the freeboard is reduced.

The spacing means may comprise a plurality of elastically deformable cables extending along the slide, the cables being attached to the slide at spaced apart locations along the length of the slide and being held in tension.

The spacing means comprises a winch or pulley system.

The slide may include a plurality of bowsing attachment parts spaced apart along the slide between an entrance to the slide at the structure and the water.

The slide may include at least one exit configured to allow evacuees from the structure to transfer directly from the slide to at least one craft (e.g. inflatable liferaft).

The escape system may include a platform for floating on the water, the platform being attached to the slide. The platform may be configured to secure thereto the or each craft during boarding of the evacuees. The platform may be inflatable.

The or each helical path may be formed by a plurality of partially overlapping sections. Each of said sections may have an upper surface having an exposed portion and an overlapped portion that is overlapped by the one of the sections above, the exposed portions of the upper surfaces of the sections being arranged to define the helical path.

The slide may include a linear path portion that extends from the helical inflatable path. The linear path portion may extend obliquely to a central axis of the helical inflatable path. An exit of the slide may be formed at an end of the linear portion.

The slide comprises inflatable drop stitch material. This may provide high strength and maintain the desired shape when inflated to high pressures. The platform may comprise inflatable drop stitch material. This may provide high strength and maintain the desired shape when inflated to high pressures.

The dimensions of the slide may be so chosen that evacuees from the structure travel along the helical path at a speed of between <NUM> and <NUM> kph. One of the dimensions may be a diameter of a substantially cylindrical space around which the or each helical path extends. One of the dimensions may be a pitch of the or each helical path. One of the dimensions may be a length of the slide.

The slide may include a substantially cylindrical outer wall extending around an outer periphery of the or at least one of the helical paths, the outer wall being longitudinally elastically deformable to accommodate changes in distance between an entrance to the or each slide at the structure and the water.

The slide includes a substantially cylindrical inner wall extending around an inner periphery of the or at least one of the helical paths, the inner wall being longitudinally elastically deformable to accommodate changes in distance between an entrance to the or each slide at the structure and the water.

A second aspect of the present invention provides an escape system comprising a slide for facilitating evacuation of from a structure to water, wherein the slide comprises at least one helical path, wherein the or each helical path is formed by a plurality of partially overlapping sections. Some or all of the sections may be inflatable. Some or all of the sections may be non-inflatable. Each of said sections may have an upper surface having an exposed portion and an overlapped portion that is overlapped by the one of the sections above, the exposed portions of the upper surfaces of the sections being arranged to define the helical path.

A third aspect of the present invention provides a marine escape system comprising the escape system as mentioned above, further including at least one craft coupleable to said slide for receiving evacuees from the structure. The or each craft may be inflatable. The or each craft may be a liferaft.

A bowsing arrangement for an escape system is also disclosed that has a slide for facilitating evacuation of from a structure to water, the bowsing arrangement including a plurality of retractable or removable bowsing attachment parts for being mounted spaced apart to the structure and for attachment to corresponding attachment parts spaced along the slide between an entrance to the slide at the structure and the water.

The bowsing attachment parts may be configured to be magnetically coupled to the structure. The bowsing attachment parts may include an inflatable portion. The bowsing attachment parts comprise a plurality of sections moveable between a deployed configuration and a retracted configuration, e.g., the bowsing attachment part sections being configured foldable or mounted for telescopic relative movement. The bowsing attachment parts may be configured to be coupled to the structure by suction.

For a better understanding of the present invention embodiments will now be described by way of example, with reference to the accompanying drawings, in which:.

In the drawings, like elements are generally designated with the same reference sign.

<FIG> shows a ship or other vessel <NUM> that has an escape system <NUM> provided on board and which is shown in a deployed state.

The escape system <NUM> includes a slide <NUM> that provides one or more passages from an entry platform <NUM> on the ship <NUM> to one or more exits <NUM>. The entry platform <NUM> includes one or more entrances <NUM> to the slide <NUM>. The slide <NUM> may be inflatable.

When it is desired to evacuate the ship <NUM>, passengers enter the slide <NUM> via the entrance or entrances <NUM> and travel down the slide <NUM> until they reach the exit or exits <NUM> at or near the sea level, and from where they can board one or more life rafts (or other type of crafts) <NUM>.

Crafts <NUM> may be inflatable. The crafts <NUM> may be of the type disclosed in our co-pending patent application number <CIT> (publication number <CIT> (our ref: <NUM>).

The escape system may comprise a floating sea platform <NUM> that is generally T-shaped and defines two recesses for accommodating the life rafts <NUM> during boarding of the evacuated passengers. The sea platform <NUM> may be inflatable.

The slide <NUM>, life rafts <NUM> and sea platform <NUM> may be stored in a deflated state in storage unit <NUM> fixed to the ship <NUM>. The escape system <NUM> advantageously occupies a small area on the ship <NUM>, so freeing up space for passenger accommodation and windows. The storage unit <NUM> is closed by doors <NUM> in order to control the environment in which the deflated escape system is stored.

When it is desired to deploy the escape system <NUM>, it is inflated by a supply of compressed gas on the ship <NUM>. The doors <NUM> are opened and the slide <NUM>, life rafts <NUM> and sea platform <NUM> are lowered to the surface of the sea.

The slide <NUM> extends generally vertically. The slide extends generally parallel to the side of the ship <NUM>.

<FIG> shows one embodiment of the slide <NUM> in more detail. In this embodiment the slide <NUM> comprises two slide assemblies 21a and 21b. Each of the slide assemblies 21a and 21b provides two helical paths 23a and 23b, each having a plurality of helix turns (a helix turn being a <NUM>° turn of the path). One of the slide assemblies 21a will now be described in detail. The other of the slide assemblies 21b is of the same configuration.

The slide assembly 21a is of generally cylindrical or tubular form, and has an exit end <NUM> attached to the sea platform <NUM> and an entry end <NUM> attached to the entry platform <NUM>. The slide assembly 21a includes a substantially cylindrical outer wall <NUM> and substantially cylindrical inner wall <NUM>. The outer wall <NUM> and inner wall <NUM> are formed from elastically deformable sheet material. The inner wall <NUM> defines a central substantially cylindrical space <NUM> along which the central axes of the helical paths 23a and 23b extend.

Between the outer wall <NUM> and the inner wall <NUM> an annular space is defined that accommodates the helical paths 23a and 23b. The helical paths 23a and 23b are connected (or fixed) to the outer wall <NUM> and inner wall <NUM>. This enables the pitch of the helix turns to vary without imparting a twisting movement on the slide.

The helical paths 23a and 23b may have a double helix configuration. The helical paths 23a and 23b are interlaced. Each of the helical paths 23a and 23b turn in the same sense (clockwise/anticlockwise) about the cylindrical space <NUM>.

The entrance 37a to the helical path 23a is spaced on the entry platform <NUM> from the entrance 37b to the helical path 23b, thereby allowing passengers to enter each of the helical paths 23a and 23b simultaneously.

The helical path 23a has an exit 39a directly into a first of the lifeboats <NUM>, and the other helical path 23b has an exit 39b directly into the same life raft <NUM>.

Although two helical paths 23a and 23b are described, it should be appreciated that one, three or more helical paths may be provided.

The pitch or distance between adjacent helix turns of the helical paths 23a and 23b will vary as the distance between the entry platform <NUM> and the surface of the water (freeboard) changes, and also due to the effect of evacuee passengers travelling along the helical paths 23a and 23b and distorting the slide due to their weight. This movement can be referred to as concertinaing of the slide assembly <NUM>. The main deck height (where the entry platform <NUM> is mounted) from waterline may be, e.g., <NUM> metres. The sea conditions may be such that this distance may vary vertically +/- <NUM> metres.

Various different arrangements for controlling the spacing between the helix turns will now be described.

<FIG> show alternative arrangements in which a series of spaced apart annular plates <NUM> are provided that are fixed to the outer wall <NUM>. The annular plates <NUM> each include a plurality of circumferentially distributed apertures or eyes (four are shown in the examples) through which a corresponding plurality of wires or lines <NUM> are slidably mounted, in order to maintain the cylindrical shape of the slide while allowing the length to vary. The wires/lines <NUM> are fixed at the top of the slide <NUM> and run through eyes in each annular plate <NUM> and have a weight <NUM> below the water surface to keep them taut.

Opposite facing surfaces of the adjacent annular plates <NUM> have fixed thereto opposite ends of a plurality of elastically deformable members <NUM>. In the embodiments these elastically deformable member are elastic cords or ropes. The uppermost annular plate <NUM> is fixed to the entry platform <NUM>. The weight <NUM> may comprise a heavy ballast weight to prevent the elasticity of the members <NUM> lifting the sea platform <NUM> from the water.

The elastically deformable members <NUM> may be configured in a linear or diagonal truss bungee arrangement, as shown in <FIG>, respectively. In <FIG> the elastically deformable members <NUM> extend parallel to one another and to the central axis of the helical paths 23a and 23b. In <FIG> the elastically deformable members <NUM> extend obliquely to the central axis of the helical paths 23a and 23b in two different directions, the elastically deformable members <NUM> crossing one another between the annular plates <NUM>.

The elastically deformable members <NUM> are held in tension in normal sea conditions by weight <NUM>.

Because the elastically deformable members <NUM> have substantially identical elasticity, this tends to maintain a constant pitch along the helical paths 23a and 23b, so that the space <NUM> between adjacent helix turns remains equal as the slide is longitudinally extended and contacted due to movement of the ship <NUM> in the water.

An alternative approach to controlling the pitch of the helical paths 23a and 23b is shown in <FIG>, B and C. In this arrangement spaced annular plates <NUM>, like those described with reference to <FIG> are again provided. For the sake of clarity <FIG>, B and C do not show the helical paths, other than schematically in <FIG>.

A series of pulleys <NUM> and lines <NUM> are provided that are attached to the annular plates <NUM> to maintain the annular plates <NUM> equidistant. The lines <NUM> are all attached to the weight <NUM>. Each of the lines <NUM> is of the same length and is attached to one of the plates <NUM>. Each line passes around one or more pulleys <NUM> before being attached to a plate <NUM> in order to control the longitudinal position of that plate <NUM>. As in <FIG>, a weight <NUM> is provided in order to keep the lines <NUM> in tension.

<FIG>, B and C show a further alternative arrangement for maintaining an equal pitch between the helix turns of the helical paths 23a and 23b. In this arrangement spaced annular plates <NUM>, like those described with reference to <FIG> are again provided. For the sake of clarity <FIG>, B and C do not show the helical paths, other than schematically in <FIG>.

In this embodiment one or more constant tension winches <NUM> are provided with multiple drum diameter sections, around each of which a respective line <NUM> is wound, the distal end of each of the lines <NUM> being attached to a respective one of the annular plates <NUM>. The platform mount <NUM> is weighted in this embodiment in order to keep the lines <NUM> in tension. This arrangement requires a source of power for the winch <NUM> and a feedback system. The arrangement of <FIG>, B and C may be combined with the arrangement of <FIG>, B and C.

<FIG>, <FIG> show an arrangement for maintaining a minimum pitch or spacing between adjacent helix turns of the helical paths 23a and 23b. In this embodiment, as in <FIG>, <FIG> wires/lines <NUM> are provided. However, in this arrangement, rather than annular plates <NUM>, a series of hollow cylinders or tubes <NUM> are provided to which the wires/lines <NUM> are slidably coupled. The cylinders <NUM> may be coupled to each other by elastically deformable members <NUM> (not shown) as in <FIG>.

According to this embodiment, when the distance (freeboard) between the entry platform <NUM> and the surface of the sea reduces significantly, and the elastically deformable members <NUM> are no longer held in tension, and so the tendency of the elastically deformable members <NUM> to maintain the equal pitch is no longer effective, the cylinders <NUM> will prevent the pitch reducing below a minimum value by adjacent cylinders <NUM> sliding along the wires/lines <NUM> until they abut (as shown in <FIG>), whereafter no further reduction in pitch in the region of the cylinders <NUM> is possible.

The cylinders <NUM> may be inflatable. They may each be a unitary inflatable structure, or may comprise a series of connected inflatable linear tubes or tubular rings which may allow for easier integration with other parts of the slide. The cylinders <NUM> may be formed of drop stitch (or drop thread) material, having a form as shown in <FIG>. In such drop stitch a material, thousands of (e.g. nylon) threads connect the opposite faces to keep the panels in the desired shape when inflated and to provide rigidity. By having the cylinders <NUM> inflatable, this allows for the slide to be stored in a compact deflated state. The cylinders <NUM> when deflated do not prevent the pitch reducing below the minimum value mentioned above - thereby facilitating compact storage.

<FIG> shows an alternative arrangement of slide <NUM> to that of <FIG>, in which a single slide assembly <NUM> is provided.

The slide assembly <NUM> provides two helical paths 23a and 23b, each having a plurality of helix turns.

The slide assembly <NUM> is of generally cylindrical form, and has an exit end <NUM> attached to the sea platform <NUM> and an entry end <NUM> attached to the entry platform <NUM>. The slide assembly <NUM> includes a substantially cylindrical outer wall <NUM> and substantially cylindrical inner wall <NUM>. The outer wall <NUM> and inner wall <NUM> are formed from elastically deformable sheet material. The inner wall <NUM> defines a central substantially cylindrical space <NUM> along which the central axes of the helical paths 23a and 23b extend.

Between the outer wall <NUM> and the inner wall <NUM> an annular space is defined that accommodates the helical paths 23a and 23b. The helical paths 23a and 23b are preferably fixed to the outer wall <NUM> and inner wall <NUM>. The helical paths 23a and 23b may have a double helix configuration. The helical paths 23a and 23b are interlaced. Each of the helical paths 23a and 23b turn in the same sense about the cylindrical space <NUM>.

In contrast to <FIG>, where each helical path 23a and 23b provides a single track along which an evacuating passenger can slide, the <FIG> arrangement provides each of the helical paths 23a and 23b with twin tracks 61a and 61b arranged side by side. A dividing wall may be provided between the tracks 61a and 61b. The dividing wall may be formed of drop stitch material of the type shown in <FIG>.

At each entrance 37a and 37b the two tracks 61a and 61b are available, so two passengers can enter each of the helical paths 23a and 23b simultaneously. The entrance 37a to the helical path 23a is spaced on the entry platform <NUM> from the entrance 37b to the helical path 23b, thereby allowing passengers to enter each of the helical paths 23a and 23b (each having two tracks) simultaneously.

The helical path 23a has an exit 39a directly into a first of the life rafts <NUM>, and the other helical path 23b has an exit 39b directly into a second of the life rafts <NUM>.

Although each of the helical paths 23a and 23b is described with twin tracks 61a and 61b arranged side by side, it should be understood that tree or more tracks (arranged side by side, or otherwise) may be provided.

Although two helical paths 23a and 23b are described, it should be understood that one, three or more helical paths (each with one, two, three or more tracks) may be provided.

According to the <FIG> embodiment, although only a single slide assembly <NUM> is provided, the evacuation rate is generally the same as the slide of <FIG> due to the twin tracks 61a and 61b.

<FIG> shows a further arrangement of the slide <NUM>, which includes a slide assembly <NUM> of the same general configuration as in <FIG>, having two helical paths 23a and 23b, each with twin tracks 61a and 61b. The helical paths extend from the entry platform <NUM> but not all the way to the sea platform <NUM>. Instead, a liner (non-helical) slide assembly <NUM> extends from the lowermost helix turn of each other helical paths 23a and 23b to the upper surface of the sea platform <NUM>. In this embodiment the slide assembly <NUM> having the helical paths 23a and 23b may have a fixed vertical length (rather than concertinaing in the manner of the previously described embodiments). Variations in distance between the entry platform <NUM> and the surface of the sea are accommodated by variations in the angle of inclination of the linear slide assembly <NUM> to the upper surface of the sea platform <NUM>.

In any of the embodiments it is advantageous for the slide <NUM> to be attached to the ship <NUM>, not only where it connects to the entry platform <NUM>, but also at one or more positions closer to the surface of the sea.

<FIG> shows one example of a bowsing line fixture point <NUM> that is fixed to the hull of the ship <NUM> and to which the slide <NUM> is attached by a bowsing line (not shown). The bowsing line fixture point <NUM> in shown more clearly on <FIG>, and comprises a plurality of reinforced high pressure inflatable tubes <NUM>. The tubes <NUM> may be mounted to the hull of the ship <NUM> by the storage unit <NUM> or entry platform <NUM>. The tubes <NUM> may provide a bowsing line fixing location close to the waterline that the storage unit <NUM> or entry platform <NUM> - e.g. <NUM> meters closer to the waterline that the storage unit <NUM> or entry platform <NUM>. Advantageously, the inflatable tubes <NUM> may be deflated when not in use. The tubes may be formed of drop stitch material of the type shown in <FIG>.

A plurality of retractable or removable bowsing line fixture points <NUM> may be mounted spaced apart to the vessel <NUM> and for attachment to corresponding attachment parts spaced along the slide <NUM> between an entrance <NUM> to the slide at the vessel <NUM> and the water.

The bowsing line fixture points <NUM> may be configured to be magnetically coupled to the structure.

The bowsing line fixture points <NUM> may comprise a plurality of sections moveable between a deployed configuration and a retracted configuration. The bowsing line attachment part sections may be configured foldable or mounted for telescopic relative movement.

The bowsing line fixture points <NUM> may be configured to be coupled to the vessel <NUM> by suction.

One or more bowsing line fixture points <NUM> may be used with any embodiment of the invention, including those shown in <FIG> and <FIG>.

<FIG> show an example of a suitable arrangement of bowsing lines <NUM> for bowsing the sea platform <NUM> to the ship <NUM>.

A first pair 71a of bowsing lines extend from the entry platform <NUM> to opposite ends of the top bar <NUM> of the T-shaped sea platform <NUM>. These lines 71a may pass through channels in the sea platform <NUM> to a first pair of submerged weights 75a.

A second pair 71b of bowsing lines extend from mounting points <NUM> on the hull of the ship, spaced along the hull from the entry platform <NUM>, to the opposite ends of the top bar of the T-shaped platform <NUM>. These lines 71b may pass through the channels in the sea platform <NUM> to the first pair of submerged weights 75a.

A third pair 71c of bowsing lines extend from the mounting points <NUM> on the hull of the ship <NUM> to the distal end of a central bar <NUM> of the T-shaped sea platform <NUM>. As best shown in <FIG>, these lines 71c may pass through a channel in the sea platform <NUM> to the first pair of submerged weights 75a.

As best shown in <FIG>, the wires/lines <NUM> described above extend through channels in the sea platform to the submerged weight <NUM>.

In <FIG> the slide <NUM> is of the form shown in the <FIG> embodiment, although the bowsing arrangement is applicable to other forms of slide described above.

<FIG> show a slide <NUM> of the type of the <FIG> embodiment, where two side-by-side parallel slide assemblies 21A and 21B are provided and extend between the entry platform <NUM> and the sea platform <NUM>.

In any of the embodiments the helical paths 23A and 23B may each be formed of a continuous helical member (as shown in <FIG> and <FIG>) that extends from the entry platform <NUM> to the sea platform <NUM>. The continuous members may be inflatable. The continuous members may be formed of drop stitch material of the type shown in <FIG>.

As an alternative to continuous members, the helical paths 23a and 23b may be formed of a series of discrete parts.

<FIG>, B and C show an arrangement of the helical paths 23A and 23B, where the paths are formed by a plurality of partially overlapping slide sections 83A and 83B. Each section 83A and 83B has an upper surface having an exposed portion <NUM> and overlapped portion <NUM> that is overlapped by the section immediately above. The exposed portion <NUM> are arranged to define a helical path and are the surfaces along which evacuating passengers slide. The sections 83A and 83B may be tapered from the overlapped portion <NUM> to the distal end of the exposed portion <NUM> to provide an inclined surface along which the evacuating passengers slide. The gap between the sections 83A and 83B may vary in some embodiments as the distance between the entry platform <NUM> and the surface of the sea varies.

The sections 83A and 83B may be inflatable, and may be formed of drop stich material of the type shown in <FIG>. However, it should be understood that the sections 83A and 83B (and any other parts shown in <FIG>, B and C) may be non-inflatable - e.g. they may be solid or hollow and rigid or flexible.

In any of the embodiments dividing walls <NUM> may be provided between the helical paths 23A and 23B, between the helical path 23A and the outer wall <NUM>, and between the helical path 23B and the inner wall <NUM>. The dividing walls <NUM> may be formed of a series of cylindrical sections. The sections may be inflatable, and may be formed of drop stich material of the type shown in <FIG>.

In any of the embodiments, as shown in <FIG>, a plurality of transverse horizontal supports <NUM> may be provided underneath the helical paths 23A and 23B, and which are attached at opposite ends to the outer wall <NUM> and the inner wall <NUM>, respectively. The supports <NUM> may be inflatable. The supports may be formed of drop stitch material of the type shown in <FIG>.

The helical paths 23A and 23B may alternatively, or additionally, be suspended by supports <NUM> from above, as shown in <FIG>. The supports <NUM> are attached at opposite ends to the outer wall <NUM> and the inner wall <NUM>. The supports <NUM> are attached to the helical paths 23a and 23b by cables <NUM>.

<FIG> shows in detail an example configuration of the sea platform <NUM>. The sea platform <NUM> may be inflatable. The sea platform <NUM> may be formed from drop stitch material of the type shown in <FIG>.

The edges of the central bar <NUM> of the sea platform <NUM> (that extends from the top bar <NUM> of the sea platform <NUM>) include vertical walls <NUM> that extend above the flat upper surface of the platform <NUM> along all or part of the central bar <NUM>.

Additionally, or alternatively, longitudinal stiffening beams <NUM> may be provided along the central bar <NUM>.

Claim 1:
An escape system comprising a slide (<NUM>) for facilitating evacuation from a structure (<NUM>) to water, wherein the slide (<NUM>) comprises at least one helical inflatable path (23A, 23B), wherein the slide (<NUM>) comprises spacing means for controlling the pitch between helix turns of the or each of the helical inflatable paths (23A,23B); wherein the spacing means is operable to set a minimum distance between two adjacent helix turns of the or each of the helical inflatable paths (23A, 23B); and characterised in that the spacing means comprises a plurality of hollow cylinders (<NUM>) formed of drop stitch material and attached to the slide (<NUM>), the gap between adjacent ones of the hollow cylinders (<NUM>) varying with the pitch between the helix turns, and the abutment of adjacent hollow cylinders (<NUM>) preventing the distance between two adjacent helix turns falling below said minimum distance.