Field of the Invention

This invention relates to improved access to structures, especially for use with wind turbines.

Background to the Invention

Due to the increasing desire for renewable energy sources to be employed, there is an increase in the number of near-shore (within 10km of land) and off-shore (more than

10km from land) wind turbines, and especially wind turbine fields. The size of such wind turbines can be considerably larger than those used on land for various reasons, notably, noise pollution and access - ships can carry larger turbine blades than can be carried on road as they do not need to go round corners. Off-shore wind turbine towers are often between 50 metres and 80 metres, but wind turbines may have a height of over 100 metres.

When repairs and/or maintenance are required within a wind turbine nacelle, which is the unit attached to the top of the wind turbine tower that carries the blades and can be rotated so that the blades face into the wind, the operator enters the tower through a small door at the lower end of the tower and proceeds to climb a ladder attached to the internal wall of the tower. Considering the height of such towers, the operator is usually tired by time he reaches the top of the tower. Furthermore, there is limited space and lifting means for transporting tools and materials to the nacelle. With near-shore and off-shore turbines, a Wind Turbine Support Vessel (WTSV) is manoeuvred to the outside of the tower and the operator climbs a 10 metre to 15 metre ladder to a platform around the outside of the tower. From the platform the operator can enter the wind turbine tower and then climb the ladder attached to the inside of the tower wall, again of a considerable distance. A ladder on the outside of such a structure would be dangerous and restrictive as to what can be carried, due to, inter alia, the wind experienced in such situations. Occasionally, the tower is supplied with an internal lift mechanism inside the tower structure to transport personnel and equipment to the nacelle. However, such a mechanism is reliant upon power from the turbine. If the turbine has failed, such a lift is likely to be without power and is thus redundant. A further problem with existing near- shore and off-shore structures is getting personnel and equipment onto the wind turbine quickly in difficult weather, especially where a large quantity of materials and/or tools is required.

Similar disadvantages occur with access to existing oil and gas platforms. Summary of the Invention

Accordingly, the present invention is directed to an access system for transporting people and/or materials in a generally vertically direction on a substantially vertical tower structure surrounded by or adjacent to water, the tower structure comprising a

substantially vertical external rail mechanism and a docking unit adapted to engage the rail mechanism and to receive and releasably engage with a supply carrier, or capsule, wherein, when engaged with the carrier, the docking unit and carrier can be raised and/or lowered on the rail mechanism, relative to the base of the tower and on the outside thereof, and wherein the carrier is adapted to be releasably connected to a ship-borne lifting arm.

By having an external mechanism, the amount of people and /or materials that can be transported is not limited by the internal diameter of the structure. Furthermore, the use of a capsule that can be docked onto the external mechanism allows for quicker loading and unloading of people and/or materials than having to transport the same through a doorway in the side of the tower. Preferably, the ascending and descending of the docking unit and capsule is controlled by a motorised mechanism, and the power supply for the said mechanism is contained within the capsule. By having the power supply in the capsule, the capsule can be operated when the tower is without power, either during construction of the wind turbine or if the turbine has failed. The power supply may be in the form of an electric or hydraulic motor, or a combustion engine using, for example, diesel. For electric and hydraulic motors, the energy may be stored in batteries or pressurised hydraulic accumulators. Further methods of powering the mechanism may be possible.

Preferably, the external rail mechanism comprises a geared rack, and the capsule comprises a pinion. A rack and pinion mechanism allows for a compact and reliable system, which can have built in safety mechanisms, such as an emergency brake. Further more, the rack and pinion system may be manually operated, using a reduction gearbox to transmit torque from a hand- wheel or ratcheted lever. Manual operation would normally be used in emergencies or in locations where automation is not possible or impractical.

For off-shore and near-shore applications, ships are the most convenient and cost- effective method of transporting bulk materials to a wind-turbine or gas platform.

Therefore, by providing the capsule with a connection for connecting to ship-borne lifting apparatus, the capsule can be loaded with the required goods before the ship sets sail, and the capsule can be easily lifted from the deck of the ship to the docking unit of the access system.

It is preferable that the lifting arm comprises a stabilisation mechanism to reduce the movement of the capsule due to the wave motion of the ship. The capsule needs to be kept substantially horizontal to allow it to be docked on the docking unit. A stabilised ship-born mechanism, for example, as disclosed in GB2336828 in the name of Oceantech PLC, keeps the capsule sufficiently steady for it to be located on the docking unit when the ship is being affected by wave-motions. Advantageously, the docking unit comprises pins and the capsule comprises recesses and latches, and wherein the recesses accept the pins and the latches lock the docking unit and capsule together. By using a pin and latch mechanism, the capsule can be releasably attached to the docking unit in a reliable and firm way. The recesses engaging the pins prevent lateral movement of the capsule, especially when combined with other engaging mechanisms. The weight of the capsule in the chassis of the docking unit prevents vertical movement of the capsule with respect to the docking unit. It is advantageous if the tower structure is part of a wind turbine or a gas platform. These structures are especially difficult to access with large amounts of people and/or materials.

Brief Description of the Drawings

An embodiment of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 is a diagram showing a perspective view of an embodiment of the present invention;

Figure 2 is a diagram showing the docking unit of Figure 1 located on the rail assembly of Figure 1; and

Figure 3 is a diagram showing the docking unit of Figure 2 engaged with the capsule of Figure 1.

Detailed Description of Exemplary Embodiments Figures 1-3 show an access system 10 comprising a tower portion 12, being a tower portion of a wind turbine or a stationary platform, having a rail assembly 14 positioned in a substantially vertical orientation with respect to the tower 12 and extending up the outside of the tower 12. A safety platform 15 is provided at the lower end of the tower 12. The rail assembly 14 comprises an outer engaging flange 16A and 16B extending from the edges of the rail assembly along the full height of the rail assembly 14. The rail assembly 14 further comprises a central geared rack 18 in the form of a substantially vertical strip extending along the full height of the rail assembly 14 and equidistant between the two engaging flanges 16A and 16B. The geared rack 18 has teeth extending along its length.

The access system 10 further comprises a docking unit 20, in the form of a trolley. The trolley comprises a square-shaped chassis 22 that lays flat against the rail assembly 14. The intended upper part of the chassis 22 has an upwardly- extending lip portion 23 positioned so that there is a gap between the rail assembly 14 and the lip portion 23 of the chassis 22, when the trolley 20 is in position on the rail assembly 14. The chassis 22 has two pairs of wheels 24A and 24B at opposite sides thereof, the wheels 24A and 24B engage the underside of flanges 16A and 16B, that is to say, the side of the rail assembly facing the tower, so that the rail assembly 14 is between the wheels and the chassis 22, thereby engaging the docking unit 20 in such a way that docking unit 20 cannot be detached from the rail assembly 14. The chassis 22 further comprises a rectangular base section 26, which extends

perpendicularly to the chassis 22 at the intended base thereof. Support members 28 are provided to reinforce the joint between the chassis 22 and the base section 26.

The base section 26 is provided with stabbing pins 30 extending perpendicularly from the base section 26 along the side most distant from the rail assembly 14 and in an intended upward direction.

The access system further comprises a capsule 40, in the form of a substantially cubic carriage 42. Attached to the intended upper surface, or roof, 44 is a connection member 46. The top portion is also provided with a lip-engaging portion 48, in the form of a plate extending along the plane of the roof 44 and beyond the side wall 50 of the carriage, having a downwardly extending lip 52.

A geared pinion 54 extends from wall 50 of the capsule, which is powered by a drive mechanism within the capsule (not shown), the power source being part of the capsule 20.

The capsule 40 is provided with recesses (not shown) in its base, which are themselves provided with securing latches (not shown). In order to transport people and/or materials up an off-shore tower 12, the capsule is taken to the location aboard a ship (not shown). A lifting arm (not shown) is then attached to the connection member 46 and the capsule 40 is then lifted from the deck of the ship. Using a stabilised transfer system, the capsule 40 is manoeuvred onto the docking unit 20, with the lip-engaging portion 48 engaging lip portion 23, and the stabbing pins 30 received in the recesses in the base of the capsule 40. The latch mechanism of the capsule 40 can then be operated in order to lock the capsule 40 to the stabbing pins 30 and prevent the capsule 40 and trolley 20 from disengaging. The latches maybe be operated either from within the capsule 40, from aboard the ship or by way of radio telemetry signals. The lifting arm is released from the capsule and retracted once the latches are secured to the stabbing pins 30. With the capsule 40 in place, the teeth of the pinion 54 engage the teeth of the geared rack 18 of the rail assembly 14. The pinion 54 is then rotated in order to move the trolley 20 and capsule 40 vertically along the rail assembly 14. A brake mechanism (not shown) is provided within the capsule to allow for a controlled decent and for use in emergency situations. The wheels 24 A and 24B keep contact with the rail assembly 14 allow the docking unit to ascend and descend the rail assembly 14 in a smooth fashion.

A door may be provided in the tower 12 of the structure at a desired entry point.

Alternatively, the rail mechanism 14 may extend into the nacelle of a wind turbine and a platform provided within the nacelle onto which the contents of the capsule 40 can be unloaded provided the nacelle can be rotated and positioned so that rails in the nacelle are accurately aligned with those in the tower and form an extension of them.

When the work/inspection of the tower is complete, the capsule 40 is lowered to a position near close to sea-level. The ship is then moved sufficiently close to the tower for the lifting arm to be connected to the connection member 46. The arm is extended and securely connected to the capsule 40. The latches are then released from the stabbing pins 30 and the capsule 40 is removed from the docking unit 20 and positioned on the deck of the ship. The capsule 40 may be provided with transparent walls and/or inspection equipment so that the tower can be inspected whilst ascending and/or descending. The inspection equipment may comprise optical fibres extending outwardly and being controllable to see around the circumference of the tower.

Variations and modifications to the illustrated construction are possible without taking the device outside the scope of the present invention. For example, although it is preferable that the lifting arm is attached to a delivery vehicle, it may be part of the tower structure. Although such an arm requires power to be supplied from the tower structure, the present invention encompasses such a design.

Alternatively, the capsule may not need to be stabilised and therefore a regular lifting mechanism could be used, for example on land-based wind turbines. Also, the capsule may be in the form of a platform with connecting means, rather than a capsule.

Furthermore, when connected to the trolley, the capsule may be raised and lowered by way of other mechanisms, for example, a winch system wherein at least one winch drum is connected to the capsule and a wire is connected to a point on the upper end of the tower. The winch then 'climbs' the wire to reach the top of the tower.

The rail assembly may be fitted with a plurality of racks and the capsule supplied with a plurality of pinions. This would allow a back-up system to be installed in case the primary mechanism failed.

Although it is preferable for the pinion to be connected to the capsule, it may be connected to the docking unit, with the power supply being provided by the capsule via a suitable connection.