The stairway's length may vary as a multiple of standard sections by securely locking unused sections in an annular bayonet device attached to the load- bearing structure and arranged round the top part of the stairway.

Over the years a number of different kinds of rescue devices have been developed in order to permit evacuation, e. g., of offshore platforms as well as houses in an emergency situation. One type of such rescue devices, which has been specially developed for use in connection with houses, consists of stairway devices with platforms which can be lowered from a special structure which is built into the house or which can be folded out from the wall of the house. Another type of such rescue devices consists of stocking- like or casing-or sheath-like devices which can be lowered from a stand at a window or a balcony and where a person can be passed down through the stocking or sheath in some suitable way or another.

In the latter category, e. g., can be found the rescue stocking which is described in Norwegian patent no. 149 760 where there is provided in a net stocking a zigzag line across forwardly and backwardly extending net surfaces along which a person can move or climb at his own pace down to the water or to the ground from a house. This type of rescue stocking has proved to be very successful in practice and a number of different variants have been developed with a view to facilitating the access to the rescue stocking as well as the possibility of emerging into safety at the lower end.

This type of stocking also has the advantage that, e. g. in connection with a house, the stocking can be entered at several different levels through openings in the wall.

Even though the latter rescue device has proved to be highly suitable as an evacuation device from offshore platforms and houses, there has nevertheless been a need for rescue equipment which has more in common with a stairway, thus also making it very easy to ascend in a building or on a platform and not only descend. There has therefore been a need for a stairway which may to a certain extent be compared with a ladder, but

avoiding the elements of uncertainty generated by the movement of a ladder, i. e. the risk and fear of losing one's grip and falling down.

In the publication"Offshore Engineer", October 1987, pages 36-38, there is a survey of various evacuation solutions for offshore platforms. Described here are stocking-shaped evacuation devices, slides and folding stairways. The above-mentioned rescue stocking according to NO patent no. 149 760 is also mentioned in this article, but the device is not very suitable if one wishes to climb up, since it has no step function. There is indeed a description of a steps solution in the article, but in this case it involves a relatively heavy and voluminous solution without safety means which would be able to prevent people from falling off the edge of the steps.

In SU-A-1216916 and SU-A-1283151 there are described evacuation solutions from an offshore structure to rafts where stocking solutions are employed which are held taut via stabilising lines to underlying weights.

In DE-A1-2360666 there is described a foldable compact spiral-shaped stairway, but it is only suitable for transfer between relatively small differences in level, e. g. between two floors, and therefore has clear technical and practical limitations with regard to height differences. The stairway is built up by means of telescopic cylinders and with distance elements between the steps.

Thus none of these devices is suitable for use as rescue equipment which will make it easy to move in both directions, i. e. both up and down from a building or a platform.

The above-mentioned drawbacks have partly been solved in Norwegian patent no. 180032 which describes a foldable stairway characterized in that the stairway's steps are suspended in internal and external suspension ropes with a predetermined step distance, that the whole stairway is surrounded by a foldable net stocking and that at least two external suspension ropes are connected to each step and that the front edge of a step is attached to the same rope as the back edge of the following step.

The disadvantage of the above-mentioned patent is that the stairway has to be manufactured in a predetermined length, since it is not easy to alter the total

length without further ado when, e. g., ships of different sizes dock at an oil installation.

The present invention constitutes a foldable stairway where the steps are placed in a spiral round a central guide wire, with the result that they are radially controlled thereby, but can slide in the wire's longitudinal direction, where the steps are supported by a number of tension release devices independent of the guide wire, and where the guide wire under the bottom step is terminated in or radially controls a platform or a floating body, with the result that the stairway can be folded in a controlled manner on top of it when the guide wire is kept taut and the tension release device is relieved, e. g. when a winch pulls in the wire and lifts the platform or floating body relative to the tension release device's upper termination points, characterized in that the stairway is divided up into a number of stairway sections where each stair section consists of a section ring and a smaller number of steps, where each section ring is radially controlled by the same guide wire in the same way as the steps, and where during folding of the stairway, each section ring supports the steps between this section ring and the overlying section ring, and where during folding, each section ring simultaneously rests on the underlying section ring without loading or disturbing the stacking of the underlying step.

At the bottom the stairway has a flexible zone where each step is attached to the central wire by a wire lead-through which consists of a plate 3, rollers and a holder, also attached to one another as above.

A funnel-shaped bayonet device is attached to the load-bearing structure by a plurality of flexible coupling elements which may be varied in length. The stair sections can be winched up to the top position, thereafter ascending into the funnel-shaped bayonet device. Securing means in the form of radial lock bolts on the outside of the stair section will grip on to corresponding grooves on the inside of the funnel-shaped locking device, which communicates with transverse grooves. By twisting a stair section it can be locked on to the bayonet device and only the underlying stair sections can then be lowered.

This is expedient when, e. g., boats of different sizes and height come alongside, offering the possibility of altering the length of the stairway in a simple manner.

In addition to the central guide wire there may be several approximately synchronously extending support wires which are preferably passed through the section rings and at least through the floating body, which is terminated in smaller weights dependent on the heavier weight which holds the central guide wire taut, with the result that when they are hoisted up alone or together with the central weight, the said smaller weights support the floating body, and that at least the smaller weights'support points for the floating body are located higher than the floating body's centre of gravity, with the result that the floating body is suspended in a rotationally stable manner and approximately horizontal during hoisting, and any lockable rings are stabilised against rotation during hoisting, safely attaining the correct position in the locking mechanism.

The invention will now be described in more detail with reference to the figures, in which fig. 1A illustrates a section ring viewed from above; and fig. 1B is a section in line A-A; figs. 2A, B and C illustrate the bayonet device; figs. 3 and 4 illustrate individual steps in the flexible zone; fig. 5 illustrates a wire lead-through with plate 3, rollers and holder; and fig. 6 is a layout view with the stairway winched out (A) and stored (B); fig. 7 illustrates tension release devices with (A) and without (B) protecting cover.

The system consists of the following main components: 1. Storage container.

2. Deployment arrangement.

3. Bayonet for attachment of lockable standard stair sections.

4. Standard stair sections.

5. Flexible zone.

6. Floating body.

7. Stabilising weight.

8. Net wall

The stairway may be used in houses, towers, ships, oil platforms, helicopters, etc., hereinafter called structures. The stairway is designed with a view to taking up little space, being light in weight, offering protection from the wind while at the same time being functional in use. It is used as an ordinary stairway for getting up and down from different installations. It may also be used as an escape route in the event of accidents, and especially form part of a complete evacuation system, e. g. for evacuation from ships and platforms, where inflatable life rafts are also integrated with the stairway.

1. Storage container The flexible stairway is attached up to a load-bearing part of the structure.

Around the stairway there will be protection means, which may be anything from a simple tarpaulin to a large mustering/waiting room for evacuation. It will also be able to be protected from fire and to contain necessary equipment for evacuation, first aid, fire extinguishing, etc. This storage container may be mounted in such a manner that there is free space under it for deployment of the flexible stairway or it may be a separate arrangement which pushes, swivels or tips it out (fig. 6).

2. Deployment arrangement The stairway is lowered by means of a winch, where a central wire passes through central guides in the stairway and is terminated in a stabilising weight right at the bottom of the system. The winch has a centrifugal brake, which enables the lowering to be performed in a controlled manner and at a given rate. The entire deployment may be remotely controlled, whether it be from a control room on the structure, from an adjacent ship or from another location. In addition to the central guide wire there are several approximately synchronously extending support wires which are preferably passed through section rings and at least through the floating body, which is terminated in smaller weights independent of the heavier weight which holds the central guide wire taut, with the result that during hoisting the said smaller weights alone or together with the central weight support the floating body, and that at least the smaller weights'support points for the floating body are located higher than the floating body's centre of gravity, with the result that the floating body is suspended in a rotationally stable manner and approximately horizontally during lifting and any lockable rings are stabilised against

rotation during lifting, safely attaining the correct position in the locking mechanism.

3. Bayonet for attachment of lockable standard stair sections The bayonet device is described in figs. 2A, B and C. Attachment of the stairway to the load-bearing structure is implemented by means of a bayonet device. This has the object of enabling the length of the stairway to be adjusted by simple means. The stairway is constructed in such a manner that there is a flexible zone at the bottom. When employed, e. g., on an oil platform, this flexible zone will cover the wave height. However, in cases where the ebb and flow of the tide is high, or where people have to be lowered on to a ship at a certain height above the sea, it will be possible to adjust the length of the stairway by simple means by suspending the necessary number of standard stair sections in the bayonet.

The bayonet is an annular funnel which is attached to the structure by means of several flexible coupling elements which may be varied in length. When the stairway is winched up, in its top position it will ascend into the bayonet, thus causing externally provided bolts on the stair section rings to grip on to longitudinal grooves on the inside of the bayonet device, these grooves being formed in such a manner that by twisting the stair section slightly it will be possible to terminate the desired section ring in the bayonet. When the stairway is then lowered, those sections which are above the section ring which was inserted into the bayonet will remain located in the bayonet. In this manner the length of the stairway is adjusted so that the exit is always in the flexible zone. This is very important where there is a variable distance between entering and leaving, e. g. due to wave motion.

4. Standard stair sections A stair section is the distance between two subsequent section rings. Within a standard stair section the following components can be found: * A section ring (fig. 1), which is an external stacking box for the foldable stairway. It is constructed in such a manner that within the height of each section ring all the steps in this section will be stored. This is implemented by means of a very special design of the steps, which causes them to be located side by side. At the same time it forms termination points

for tension release devices and a spiral (distance element) along the periphery of the stairway. To the section rings there is securely mounted a landing slab and a central wire lead-through with rollers, where all the internal tension release devices are also terminated.

* A certain number of steps (figs. 3,4) and a landing slab (in order to adapt the number of steps to circumference and height). These are designed so as to lie neatly side by side. Each step has 3 termination points for tension release devices (two in each corner on the periphery and one at the top in towards the centre of the stairway) and a wire lead-through in towards the centre of the stairway, with the result that each step is controlled by the central winch wire and is suspended in the three tension release devices.

Along the periphery of the steps there is also an attachment point for a distance element which goes in a spiral from step to step along the outer edge of the stairway.

* Tension release devices. There are the same number in the centre as along the periphery where they are arranged in such a fashion that each tension release device is terminated in two steps. The tension release devices are terminated at the top and bottom of the section rings. All the tension release devices (fig. 7) in a stair section are exactly the same length and extend from one section ring to the next between specially-produced bolts, where each tension release device is made in the form of a circular sling of a tension-rigid material, e. g. aramide fibre, that the two parts of the circular sling are taped together at a suitable distance from each other at the steps' attachment points, that a bolt hole is made in a template in an exact position through the said tape, that the tape is of a friction-promoting material, that the steps are securely screwed to the tension release device through the said hole by means of a disc which covers both the sections of the circular sling, and that the screw connections are so firmly tightened that the step is supported by friction independently of the tape's strength, thus enabling the steps to be mounted and dismantled in an exact position while the stairway is suspended at full length and without knots or the like affecting the tightening of the tension release devices.

* The distance element is a special element or wire which goes in a spiral along the periphery of the stairway, from one section ring down to the next. Each step is attached to this and its function is to ensure that the steps

are located in the correct position when the stairway is folded up. The wire lead-throughs for steps outside the flexible zone may be designed as thinner U-shaped hoops which are screwed to the steps in such a manner that the U encloses a slide and wear disc which ensures suitable radial clearance in the wire lead-through after mounting.

5. Flexible zone Between the bottom section ring and a floating body there is provided a flexible bottom section which is substantially higher than a man's height, with the result that over a large area in this section, which approximately corresponds to the area of movement of the floating body in the water, a person can walk upright out of the stairs between the tension release devices in the external circuit without coming into conflict with a section ring.

The flexible zone of the stairway is especially for use at sea, in order to compensate for the wave motion. The height of the flexible zone can therefore vary from installation to installation. In this part there are no section rings. The flexible zone consists of the following parts: * On each step (figs. 3,4) there are attachment points for 3 tension release devices, one in each corner. At the same time there is a centre wire guide, which holds the step in position from the centre of the stairway. This consists of three parts; a wire guide plate, a certain number of rollers, e. g. 3, and a wire guide holder. This is arranged in such a manner that it should be able to be dismantled and replaced without removing the wire (fig. 5).

* The tension release devices are terminated in the bottom section ring in a standard stair section, passing through several steps, depending on the height of the flexible zone.

* A distance element which goes in a spiral along the periphery of the stairway, where each step is terminated therein, will help to brace and stabilise this part of the stairway and ensure that, when the floating body moves on the waves, the steps will lie neatly down in the bottom of the wave.

These distance elements are sufficiently tension-rigid to stabilise the stairway in the tangential direction when it is extended and in use, and simultaneously sufficiently tension-rigid to keep the steps away from one another during hoisting of the stairway, with the result that the steps lie in layers beside one

another for each winding or each section, possibly in a marked location partly under or on top of a landing slab.

* A wire lead-through (fig. 5) which sits on each step, is composed of three parts; a plate, three rollers and a holder, thus enabling it to be dismantled and replaced without taking down the whole stairway. This is important since this is a part which will be subject to a great deal of wear and tear.

The flexible bottom section can have as many steps as to constitute more than one winding of the spiral formed by the stairway, that the steps in underlying windings of the spiral are attached to the same tension release devices as the steps in the above winding, that the tension release devices are terminated in the bottom steps in each position along the circumference, that the floating body has a recess which supports and protects the steps in the flexible zone, and that the floating body's recess is not larger than that outside the recess there is a support for the stairway's lowest section ring.

6. The floating body This is a buoyancy body, which when used in marine evacuation will act as a reference point at sea level. The stair system's guide wire passes through the floating body, thus enabling it to move freely up and down on this guide wire. The surplus part of the stairway will fold up in the bottom of this floating body. It will also act as a reception platform at sea level for personnel. The floating body may be a solid structure with a given buoyancy, or an inflatable raft. For marine evacuation other rafts may be integrated with this floating body. Reference is made to figs. 1 and 3 in Norwegian patent no.

180032. A fixed floating body of this kind is designed in such a manner that the steps in the flexible zone lie in position in a recess therein. The stabilising weight stays below the floating body, and together they form the bottom of the storage container.

7. Stabilisation weight This is a weight which is as pointed as possible with a weight determined by the need for stabilising the individual stocking. It is directly connected to the stabilising wire and during marine evacuation will be located well below the level at which the floating body will move. For coupling directly to the deck

of a ship, a standard heave compensation system (constant tension) can be used on the stabilising wire.

8. Net wall The whole stairway is surrounded by a net wall which is attached to the tension release devices and the section rings. This provides good ventilation in the stairway and a limited field of view. Openings are made therein at points where it is appropriate to leave the stairway. The entire flexible zone can be without this net wall.