The invention is related to a system and method for the safe and comfortable vertical transfer of humans or goods in an offshore environment from one structure to another structure such as a platform of which at least one structure is floating and is moving due to waves.

The key aspects to consider in this operation are in order of priority the safety and comfort of the personnel or other persons involved. Problems may be that the relative motion between structures makes transfer difficult and poses a significant physical danger to personnel.

A marine transfer method may make use of a hoisted basket or cabin as in

EP2123552A1 either with or without some form of impact dampening built into the system to protect the personnel being transferred. Where said impact arises from the relative motions at the instant when the basket or similar structure experiences the first contact with the moving vessel. A big disadvantage of such methods is the potentially harmful impact load upon first contact due to relative motions and the resulting hazard of tipping over and sliding sideways in an uncontrolled manner.

Other marine transfer systems make use of an articulated walkway of some kind as in NL1025923 and NL1027103. Disadvantages of such transfer methods are the required preparations for compatibility and the relative complex controls and actuators required to make the connection between bodies without inflicting damage. Other known disadvantage to such motion controlled walkways is the sudden change in motion at some point on said walkway were the walkway extends and the required adaptations to the structure receiving the walkway.

Other systems make use of a guide wire of some kind either tensioned or not as in US2006/0236912A1 either or not in combination with a passive compensated cabin as in US4395178. Disadvantages of such systems are the initial impact with the receiving vessel or structure and the required preparations of the vessels involved in the transfer of personnel.

Alternatively helicopters are used for marine personnel transfer. A helicopter lands on a specially installed platform on the structure to which personnel is to be transferred. A transfer with a helicopter is however limited due to wind speed, landing structure platform motions and local visibility. Other disadvantages of the helicopter transfers are the high costs and the safety-training and safety preparations required by the personnel being transferred. It is an objective to provide a marine transfer system for the transfer of a human or goods between a first structure (A) to a second structure (B) of which at least one structure is floating and is movable due to waves.

Accordingly there is provided a system for the transfer of a human or goods between a first structure (A) to a second structure (B) of which at least one structure is floating and is movable due to waves, whereby the system comprises a transfer platform for carrying the human or goods, said platform being movable in use from the first structure to the second structure and vice versa, wherein the system is provided with a first and second winch on the first structure, the platform being suspended from the first winch and guided with a guiding wire suspended from the second winch, the guiding wire being connectable to the second structure and the second winch being controllable to keep the guiding wire in use continuously under tension.

The benefit of such a system may be that it enables a smooth transfer between two structures that are in relative motion and at no moment during the transfer there exists the possibility of any type of impact load on the platform and human. The tensioned guiding line provides information from the moving structure to the other structure. This information is used to compensate the motion of the moving platform e.g. a cabin. Both winches are placed on the first structure thereby enabling any type of ship or vessel with steel deck or simple receiving mechanism to receive the cabin and enable transfer of persons or goods.

The platform may be vertically movable in use from the first structure to the second structure and vice versa. The guiding wire may be substantially vertical. By having a substantial vertical guiding wire the platform does not require substantial tensioning of the guide wire as the loads on said wire are minimal and only required for lateral corrections. Further the verticality allows for the platform to travel the normally large vertical distance between the vessel (structure A) and deck of a typical platform of other structure to which transfer is desired. Another key advantage of the vertical connection is the attachment options for the guide wire to the lower, typically floating, structure.

The verticality allows the connection to be made by gravity simply by placing the floating structure below the fixed structure where the lowering winch is placed and simply receive the connection unit by lowering/paying-out of the guide wire winch. To fully optimise this advantage use may be made of a magnetic connection between the guide wire and the lower platform thereby not requiring any presence of personnel during this relatively dangerous operation and also not requiring to connect with any specific receiver of mechanical latch. This in turn greatly reduces the station keeping requirements and vessel position control of the guide-wire receiving vessel. According to a further embodiment the marine transfer system can be designed with the guiding wire connectable to the second structure, by having the guiding wire running over a sheave which is connectable to the second structure, the guiding wire running from the sheave to the platform.

The main benefit of having a sheave connected to the second structure, is that a closed system is defined. The guiding wire runs from the first winch on the first structure over the sheave connected to the second structure, to the second winch on the first structure. This closed loop system enables an inherently safe transfer mechanism due to the fixed mechanical or hydraulically relations between the winch drives. Further it enables the use of a single pretension mechanism tensioning both winches.

The guiding wire may be connected at one end to the first winch and with a second end to the second winch and the transfer platform is rigidly connected at one point on the guiding wire. In this way the platform motion is controlled by the relative rotations between the two winches. The guiding wire may be substantially vertical.

The first and second winch are controllable to keep the guiding wire in use continuously under tension. The main benefit of the pretension is the feedback of structure 2 motion and the ability to use this as input to the passive compensation system. There may exist a gearing or similar connection between the two inches enabling the use of a single pretension device pre-tensioning both winches, thereby creating a closed loop system. The guiding wire may be substantially vertical.

According to an objective the speed of at least one of the winches is controllable to eliminate the relative motions between the transfer platform and the first structure (A) or the second structure (B).

The speed of the winches is made controllable in order to compensate the motions of the moving vessel. This is carried out gradually from the motions of one structure to the other during the transfer. This causes a smooth and safe transfer of a human or goods. When the platform arrives at the structure (B), normally a moving vessel, there exist near to none relative motions between the structure (B) and the platform ensuring a comfortable and safe demounting from the platform onto the structure 2.

The connection of the sheave to the moving structure can be made with a magnetic device. Offshore structures and vessels or ships are predominantly made of steel, enabling fast and flexible connection with a magnetic device. This system can be handled unmanned, disabling the requirement men need to be on deck handling the connection and thus having a safer and simpler system that requires an absolute minimum of adaptation on the structure (B).

This magnet are preferably the semi-permanent or the electric type. Both having their individual advantages in their holding power and control options over the permanent type, thereby enabling a safer and energy efficient system with adequate redundancy.

According to an embodiment the transfer platform is a closed cabin. The human or goods being transferred are then shielded from the sometimes harsh environment encountered offshore and tend to feel more secure and safe. This cabin than also provides adequate buoyancy and stability in case there may be an emergency and the cabin get into the water.

According to an embodiment the guiding wire is connectable with the second structure by an end of the wire being connectable with the second structure. The guiding wire may be substantially vertical.

Instead of having a sheave, the guiding wire can be connected to the moving structure directly from the first winch. The guiding wire is kept under constant tension and information of the winch is used to compensate the motion of the cabin with the second winch. The cabin is not connected to guiding wire, which is only used to transfer information of the motions and restrain excessive sideways movement. This allows for a small amount of components and a relative light guiding wire. The wire can be made connectable to the structure (B) by means of a magnetic device as described above.

The marine transfer system may comprise a synchronous device to synchronize the rotation of the first and second winch. The synchronous device may be an adjustable synchronous device to adjustably synchronize the rotation between the first and second winch. The advantage of synchronizing, with a single ratio or an adjustable ratio, the rotation between the two winches is that this makes the complete system a closed loop system. The closed loop system is straightforward in its control and loss of platform or platform wire control is minimal. It further enables relative simple yet gradually applied passive heave compensation by means of a gradual variation of the synchronising ratio between the two winches.

The system may comprise hydraulic actuators, gears, magnets, pressure vessels, cables, sheaves and winches in such a configuration that a person carrier structure, such as a cabin or cargo platform of some sort, is suspended in a pre-tensioned wire configuration between the two structures such that the relative motions between two structures in which the system is engaged are not being obstructed. The cabin experiences no relative motion with the structure to which it is closely situated. During the travel between the two structures the motions are gradually transformed to adapt from the motions of the departure structure to the motions of the structure to which is being travelled. The invention comprises various hydraulical, pneumatical, mechanical and magnetic subcomponents such that the relative motions between object structure (A), object structure (B) and said personnel or cargo carrying means, object (C), which is preferably a closed cabin, are such that a relation exists between the relative distance (R) along the traveling distance between (A) and (B) that complies with:

R = Distance from A / Distance from A to B

The variables in this relation all vary in time due to wave induced motions of (A) or motions of both (A) and (B). During the transfer shocks can be avoided if no sudden changes in velocity occur and the velocity of the cabin in three directions V1 , V2 and V3 only change gradually in time, where V1 , V2 and V3 represent the three (3) linear degrees of freedom: forward, sideways and vertically. At the start of the transfer motion operation of the carriage (C) from (A) to (B), the velocities of the carriage in three directions is equal to the velocity of the starting point of the transfer which is fixed to structure (A). At the end of the transfer motion operation of the carriage, the velocities of the carriage in three directions is equal to the velocity of the arrival point which is fixed to structure (B). During the lifting or lowering of such operation the motions are gradually changed as a result of the hydraulic and mechanical components. As a result there are at no point or moment sudden changes of motions, thereby preventing any shock experiences.

One such configuration of hydraulic, pneumatic, mechanical and magnetic

components is such that a continuous pre-tension is present in a rope pulley arrangement in combination with hydraulic actuator devices that apply a constant torque to a primary freely- rotating device on which one end of a two-fall cable system is being connected. The other end is connected to a secondary freely rotating device who's axis in turn is connected to the primary freely rotating device by means of a (set of) constant variable transmissions either of mechanical nature as pulley or planetary gear type or of hydraulic nature. The primary and secondary freely rotating devices are fixed to object (A) in translations. A cable sheave is part of said two-fall cable system which is either mechanically or magnetically connected to the object (B). Said cabin is connected to the cable which is guided over the cable sheave. Within both the primary freely rotating device and the secondary freely rotating device are mounted internal motors of either hydraulic or electrical nature that allow a drum to rotate relative to the part of the freely rotating device that is not directly connected to either end of the cable. By rotation in countering directions of said internal motors the system will pass the cable trough the sheave lifting or lowering the cabin. By rotation in equal direction the system will allow to lift or lower said magnetic or mechanically connected sheave attached either or not to abject (B).

In this manner, a transfer system is obtained that enables the gradual change of motions of the object from where the transfer starts to the motions of the object to where the transfer arrives, therefore allowing for safe and easy transfer of humans.

Embodiments of the invention will be described by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figures 1 to 3 show a schematic embodiment where personnel (1) is to be transferred from a vessel (7) to a fixed offshore platform (8);

Figure 4 presents a schematic of the motions of the cabin during the transfer from the position at the platform (8) and the vessel (7);

Figures 5a and 5b show a preferred yet simplified embodiment of a hydraulic control system of the winches (4) and (5);

Figure 6a presents a more mechanical solution in which a set of mechanical constant variable transmissions (25) is used;

Figure 6b presents an embodiment in which two winches (4) and (5) operate relatively independent and the transfer of vessel (7) induced motions is achieved by sliding sheave (28) along a spindle type linear system (29) rotating about some fixed point on the platform (8). The motion of the vessel (7) dictates the motion of the rotating rod (29) through the tensioned wire which is wound onto winch (5);

Figure 7 depicts an embodiment with a purely electrically driven system; and, Figures 8a and b indicate a schematic realization of the cabin.

Figure 1 a shows a schematic embodiment where personnel (1) is to be transferred from a first structure e.g. vessel (7) to a second structure e.g. fixed offshore platform (8) by entering a transform platform e.g. cabin (9) which is lowered on the deck of said vessel. A magnetic or mechanical connection device (2) is lowered by at least one guiding wire (3), whereby said wires (3) are rigidly connected to the cabin (9). The winches (4,5) will pay out the guiding wire (3) and attach the magnetic or mechanical connection component (2) to the deck of the said vessel, after which the guiding wires are tensioned continuously, compensating vertical motions by paying out or taking in wire length in winch (4), while the second winch (5) does not move. The latter situation, in which the wires are tensioned, is presented in figure 1 b.

Figure 1 c depicts the same system in the phase that the cabin (9) has been lowered by the wire(s) (3) onto the deck of the vessel, whereby winch (5) is gradually activated in order to gradually contribute to the compensation of motions, and the action of winch (4) is gradually reduced, thus gradually increasing the vertical motions which follow the vertical wave induced motions of the vessel (7). In this way the cabin (9) is lowered on deck of said vessel while the wave induced motions of the vessel (7) are fully compensated at the moment that winch (4) and winch (5) act at the same speed and all motions are

compensated by the two winches acting together. This is indicated in figure 1 c. In this situation personnel (1) can enter the cabin (9), and said cabin can be lifted from deck according the reversed procedure described above, as indicated in figure 2a and following.

Figure 2a shows the same system at the stage that the personnel (1) has entered the cabin (9), in a situation in which the motions of the cabin (9) are fully compensated for the motions of vessel (7), enabling a safe and smooth transfer. The cabin (9) is gradually raised whilst vertical motions are gradually reduced to be equal to that of platform (8). Figure 2b depicts the stage in which the personnel (1) can safely leave the cabin (9) to enter the platform (8).

The platform may be vertically movable in use from the first structure to the second structure and vice versa and the guiding wire may be substantially vertical. By having a substantial vertical guiding wire the platform does not require substantial tensioning of the guide wire as the loads on said wire are minimal and only required for lateral corrections. Further the verticality allows for the platform to travel the normally large vertical distance between the vessel (structure A) and deck of a typical platform of other structure to which transfer is desired. An advantage of the vertical connection is the attachment options for the guide wire to the lower, typically floating, structure is more easy accomplished. The verticality allows the connection to be made by gravity simply by placing the floating structure below the fixed structure where the lowering winch is placed and simply receive the connection unit by lowering/paying-out of the guide wire winch. To fully optimise this advantage use may be made of a magnetic connection between the guide wire and the lower platform thereby not requiring any presence of personnel during this relatively dangerous operation and also not requiring to connect with any specific receiver of mechanical latch. This in turn greatly reduces the station keeping requirements and vessel position control of the guide-wire receiving vessel.

In figure 3 the magnetic or mechanical connection device (2) is released and lifted by winch (4). Figure 4 presents a schematic of the motions of the cabin during the transfer from the position at the platform (8) and the vessel (7) where dotted line moving about the horizontal axis indicated by numbers (20), (21) and (22) are respectively the vertical motions of the cabin in the conditions that the cabin is at the platform (8), halfway and at the vessel (7). Where the motion (22) is similar to the vertical motion of said vessel (7). The secondary dotted near vertical lines indicate the sideways motion of the vessel (7) and the

consequently sideways motions of said cabin (9) and wire(s) (3).

Figure 5a and 5b show a preferred yet simplified embodiment of a hydraulic control system of the winches (4) and (5). In this embodiment use is made of either traditional hydraulic cylinders or of bladder type systems. The magnetic or hydraulic components (18) in the connection system (2) ensure a safe and secure connection to the vessel (7) and enable the pre-tensioned wire (3) to be controlled by the set of hydraulic actuators (12) which are in turn connected by means of a mechanical or hydraulics constant variable transmission (13). The pre-tension in the system is obtained by means of pressure vessel (16) which in turn is kept at the right operating pressure by actuator (15). The main drive, either hydraulic or mechanic yet here presented as hydraulic (14) ensures that the pressure in (16) is transferred to a constant torque which can be used to maintain pre-tension in wire(s) (3). In addition, as presented in figure 5a, a secondary circuit activated by hydraulic actuator (17) can add or subtract hydraulic fluid from the hydraulic drive of winch (4) thereby lifting or lowering the cabin (9). As an alternative the lifting and lowering motion as well as the compensation motion can be achieved by a typical hydraulic system as presented in figure 5b. Here the drives of the winches (4) and (5) are controlled in a more active manner through the set of swash-plate hydraulic actuators (12), either or not connected by a constant variable gear (13).

As an alternative to the hydraulic solution, figure 6a presents a more mechanical solution in which a set of mechanical constant variable transmissions (25), or CVTs, control the relative pay-in and pay-out of said winches (4) and (5). The CVTs (25) may be pulley, push-band or planetary gear type CVTs that are controlled by a system which relates the ratios of the CVT to the vertical position of the cabin (9). The pretension in this realization of the invention may be obtained by a similar hydraulic system as described before and here indicated as (16). A mechanical or electrical pre-tension system is also envisaged. An alternative mechanical solution is presented in figure 6b, in which the winch-wire connected between the magnet (18) and the magnet-drive winch (5) is fed over a set of sheaves (30) which are being kept at a distance by a hydraulic cylinder (27). The hydraulic cylinder is kept at a constant tension level ensuring that a pre-set amount of tension shall remain in the winch wire running between the magnet-winch (5) and magnet (18). The winch-wire running between the cabin (9) and the cabin winch (4) is fed over a set of sheaves (28) of which one is fixed to the platform (8) and the other is mounted on a pivoted spindle or similar type linear actuator (29). By sliding one of the sheaves of sheave set (28) along the linear actuator (29) the ratio between the movement of the magnet (18) and the cabin (9) is gradually varied thereby resulting in the desired form of compensation. An advantage of this embodiment is that there is no gearing involved and no transfer from mechanical rotational to hydraulic rotational energy and thereby limited loss of energy. This in turn results in a smooth ride and little pretension variation. As an alternative to this embodiment the constant tension cylinder (27), or similar linear actuator, may also be mounted on one end to a spindle or similar type linear actuator (29) and positioned along its length independent from the moving sheave of sheave set (28), thereby enabling a constant pressure in the pressure vessel (31) to control the magnet (18) and cabin (9).

Another alternative solution to obtain the desired motion of cabin (9) is achieved by a purely electrically driven system as indicated in figure 7. Here the set of electrical drives included in control box (26) drives the winches (4) and (5) controlled by an algorithm that uses the wire (3) tension and cabin (9) position as input.

Figure 8a indicates a schematic realization of the cabin (9) as referred to in preceding text. It indicates wire clamps (23) that ensure a fixed position of the cabin (9) relative to the wire (3). This figure also indicates that the cabin (9) will be designed to fit smoothly over the connection unit (2) and be able to land flush on the deck of vessel (7).

Figure 8b indicates the same cabin (9) as before with a key addition on the roof or some other convenient location. Here another winch (24) is present that controls the cabin (9) position relative to the wire (3). This realization enables the lifting and lowering function to be functionally separated from the motion compensating functionality obtained by the various mechanisms described above. This may prove to simplify components and enable a more basic design.

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the invention.

The terms "a" or "an", as used herein, are defined as one or more than one. The term multiple, as used herein, is defined as two or more than two. The terms including and/or having, as used herein, are defined as comprising (i.e., open language, not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention.

It will be apparent to those skilled in the art that various modifications can be made to the system without departing from the scope as defined in the claims.