VESSEL AND BOOM CONSTRUCTION

Abstract

The invention relates to a vessel provided with a boom construction, especially a gangway construction, for transferring persons and/or cargo from said vessel to an offshore object or vice versa. The boom construction comprises an elongated mast structure extending in a direction substantially upwards from a deck of said vessel. Said mast structure is pivotally mounted with respect to a hull of the vessel in a manner such as to be pivotable with respect to said hull about a single pivot axis only. The boom construction further comprises a boom, especially a gangway, which is connected to the mast structure and which extends from the mast structure in a substantially sideward direction. Furthermore, the boom construction comprises at least one actuator for pivoting the mast structure such as to compensate for at least a part of a roll movement of the hull of the vessel.

Claims

1. A vessel provided with a boom construction for transferring persons and/or cargo from said vessel to an offshore object or vice versa, the boom construction comprising: an elongated mast structure extending in a direction substantially upwards from a deck of said vessel, wherein said mast structure is pivotally mounted with respect to a hull of the vessel in a manner such as to be pivotable with respect to said hull about a single pivot axis only; a boom connected to the mast structure and extending from the mast structure in a substantially sideward direction; and at least one actuator for pivoting the mast structure in order to compensate for at least a part of a roll movement of the hull of the vessel.

2. The vessel according to claim 1, wherein the vessel is an elongated vessel extending in a longitudinal direction and said single pivot axis extends substantially in the longitudinal direction of the vessel.

3. The vessel according to claim 1, wherein the mast structure extends from above the single pivot axis beyond said single pivot axis to a point located below said single pivot axis, wherein said at least one actuator for pivoting the mast structure engages the mast structure at a position located below said single pivot axis.

4. The vessel according to claim 1, wherein the vessel is an elongated vessel extending in a longitudinal direction, and wherein the vessel is arranged to control the at least one actuator in order to allow said at least one actuator to compensate for at least a part of the roll movement of the hull.

5. The vessel according to claim 1, wherein the vessel is arranged to overcompensate and/or undercompensate the mast structure.

6. The vessel according to claim 1, wherein the boom is mounted to an elevation unit being adjustable in height along the elongated mast structure.

7. The vessel according to claim 1, wherein the boom is rotatably connected to the elongated mast structure in order to allow the boom to slew about said elongated mast structure.

8. The vessel according to claim 1, further comprising at least one counterweight for compensating for a moment exerted on the mast structure by the boom at least partly, wherein the at least one counterweight has a center of mass located at a lateral side of the mast structure substantially opposite to a side of the mast structure at which said boom extends from said mast structure.

9. The vessel according to claim 1, further comprising at least one luffing cylinder for tilting the boom with respect to the mast structure, wherein a first end of the luffing cylinder is rotatably connected to the mast structure, and an opposite second end of the luffing cylinder is rotatably connected (a) to a counterweight support lever arm for holding a counterweight or (b) to the boom, in order to tilt the boom when the cylinder is retracted or extended.

10. A boom construction for transferring persons and/or cargo from a vessel to an offshore object or vice versa, the boom construction comprising: an elongated mast structure arranged to be pivotably mounted with respect to a hull of a vessel, the mast structure configured to be pivotable about a single pivot axis only, in a manner in which the mast structure extends in a direction substantially upwards from a deck of said vessel, and a boom arranged for connection to the mast structure and arranged to extend from the mast structure in a substantially sideward direction during use of the boom construction, wherein the boom construction is arranged to be coupled to at least one actuator for pivoting the mast structure during use in order to compensate for at least a part of a roll movement of the hull of the vessel.

11. The boom construction of claim 10, wherein the mast structure comprises a hinge part for pivotally mounting the mast structure to the hull of the vessel, and wherein the mast structure is arranged for connection of the boom to the mast structure at a position located at a first side of the hinge part and wherein the mast structure is further arranged for coupling the at least one actuator to the mast structure at a position located at an opposite side of the mast structure.

12. The vessel according to claim 3, wherein said at least one actuator comprises a piston actuator.

13. The vessel according to claim 12, wherein said piston actuator is a hydraulic piston actuator or a so-called hydraulic cylinder.

14. The vessel according to claim 4, wherein the vessel, arranged to control the at least one actuator in order to allow said at least one actuator to compensate for at least a part of the roll movement of the hull, is arranged such that a center line of the mast structure, during rolling of the vessel, is configured to be kept substantially parallel with a virtual vertical plane extending in the longitudinal direction of the vessel.

15. The vessel according to claim 5, wherein the vessel, arranged to overcompensate and/or undercompensate the mast structure, is arranged in such manner that, during rolling of the vessel, the center line of the mast structure is configured to be tilted with respect to a virtual vertical plane extending in the longitudinal direction of the vessel in a direction opposite to the direction in which the vessel rolls.

16. The vessel according to claim 6, wherein the elevation unit, being adjustable in height along the elongated mast structure, is adjustable in height by means of a motorized rack and pinion system.

17. The vessel according to claim 7, wherein the boom, rotatably connected to the elongated mast structure, is connected to said elongated mast structure by means of a slewing platform rotatably connected to an elevation unit that is adjustable in height along said elongated mast structure.

18. The vessel according to claim 9, wherein the boom is rotatably connected to the elongated mast structure in order to allow the boom to slew about said elongated mast structure by means of a slewing platform rotatably connected to an elevation unit that is adjustable in height along said elongated mast structure, and wherein the first end of the luffing cylinder rotatably connected to the mast structure is rotatably connected to said mast structure via the slewing platform.

19. The boom construction according to claim 10, wherein said boom construction is a gangway construction and said boom forms a gangway.

20. The boom construction according to claim 10, wherein the least one actuator is a piston actuator.

Description

[0039] By way of non-limiting examples only, embodiments of the invention will be described with reference to the accompanying figures in which:

[0040] FIG. 1 shows a schematic perspective view of an exemplary embodiment of boom construction according to the invention;

[0041] FIG. 2 shows schematic, partly cut-away views of an alternative boom construction provided on a vessel, wherein the vessel and the boom construction are shown in three different positions;

[0042] FIG. 3 shows schematic, partly cut-away views of the boom construction and the vessel of FIG. 2 in three different positions;

[0043] FIG. 4 shows a schematic, partly cut-away view of the boom construction of FIG. 1 in three different positions;

[0044] FIG. 5 shows a schematic, partly cut-away view of the boom construction of FIGS. 2 and 3;

[0045] FIG. 6 shows a schematic, partly cut-away view of an alternative boom construction in a mode for transferring persons; and

[0046] FIG. 7 shows a schematic, partly cut-away view of yet a further alternative boom construction in a mode for transferring cargo.

[0047] It is noted that the figures show merely preferred exemplary embodiments according to the invention. In the figures, the same reference numbers refer to equal or corresponding parts.

[0048] FIG. 1 shows a boom construction 2 for a vessel according to an aspect of the present invention and FIGS. 2 and 3 show a vessel 1 provided with an alternative embodiment of the boom construction 2 in different positions. The boom construction 2 is for transferring persons 29 and/or cargo 7 from said vessel 1, especially when in seaway, to an offshore object 8, such as an offshore structure or another vessel, or vice versa. Advantageously, the boom construction 2 is formed as a gangway construction 2 for transferring persons 29. Here, the boom construction 2 comprises an elongated mast structure 3 extending in a direction substantially upwards from a deck 4 of said vessel 1, e.g. the weather deck 4 of said vessel 1. The mast structure 3 can for instance be or comprise a mast or column, e.g. extending substantially transverse to a deck of the vessel 1 during use. Said mast structure 3 is pivotally mounted with respect to a hull 5 of the vessel 1 in a manner such as to be pivotable with respect to said hull 5 about a single pivot axis 6 only. The mast structure 3 can be pivotally mounted with respect to the hull 5 of the vessel 1 by means of a pivot connection 9. For example, said mast structure 3 can comprise a hinge part 9 for pivotally mounting the mast structure 3 to the hull 5 of the vessel 1 and/or the vessel may be provided with a cooperating hinge part 9.

[0049] The mast structure 3 can be mounted to the vessel 1 in such manner that said mast structure 3 cannot pivot with respect to the vessel 1 about another axis, and can then thus substantially not be compensated for the vessel's pitching movements.

[0050] It is noted that the mast structure 3 can extend substantially upright during use and/or in a substantially vertical direction, e.g. in a direction deviating for instance at most 15, at most 10 or at most 5 from a completely vertically upright direction with respect to the horizon.

[0051] Moreover, it is noted that the vessel 1 can advantageously be a ship and/or an elongated vessel, e.g. a mono hull vessel or ship. With respect to said single pivot axis 6 is noted that said pivot axis 6 can preferably extend substantially in line with the longitudinal direction of the vessel 1.

[0052] Further, the boom construction 2, here formed as a gangway construction 2, comprises a boom 10, which preferably can be formed as a gangway 10 or so-called bridge, especially an articulating boom, bridge or ramp, connected to the mast structure 3 and extending from the mast structure 3 in a substantially sideward direction. Additionally or alternatively, such as for instance is the case in the exemplary embodiments of FIGS. 6 and 7, the boom 10, especially when being a cargo boom or a so-called jib, may be provided with a trolley 27 and/or a hoist 28. Said trolley 27 and/or said hoist 28 can be movable along at least a part of said boom 10, and/or said hoist 28 may be arranged for hoisting cargo 7. Alternatively or additionally, the boom 10, especially a cargo boom or a so-called jib, may be arranged to support a conduit and/or may support a conduit, especially an at least partly flexible conduit, which may be used for pumping over gas, liquid, and/or one or more other fluids, including substantially liquid mixtures, such for instance grout.

[0053] Furthermore, the boom construction 2 comprises at least one actuator 11 for pivoting the mast structure 3 such as to compensate for at least a part of a roll movement 12 of the hull 5 of the vessel 1, especially by pivoting said mast structure 3 about said single pivot axis 6.

[0054] Advantageously, said at least one actuator 11 can be a piston actuator or a cylinder actuator, especially a hydraulic cylinder actuator 11. A first end 11a of the cylinder 11 can be attached to the hull 5 of the vessel, e.g. to a middle deck 4 or lower deck, whereas a second end 11b of the cylinder can be attached to the mast structure 3, preferably by means of a pivot connection, more preferably a pivot connection having a pivot axis being substantially parallel to the single pivot axis 6 for pivoting the mast structure 3 with respect to the vessel's hull 5. Since the mast structure 3 can only pivot with respect to vessel's hull 5 about a single axis 6, the pivot connection between the cylinder actuator 11 and the mast structure 3 can be relatively simple in comparison to a connection between a cylinder and a conventional mast structure rotatably about two transverse horizontal pivot axes, which latter for instance may require a spherical bearing.

[0055] Although the boom construction 2 of the present invention comprises at least one actuator 11 for pivoting the mast structure 3 such as to compensate for at least a part of a roll movement 12 of the hull 5 of the vessel 1, said construction 2 may comprise multiple, e.g. two, actuators, preferably multiple actuators each being capable of compensating the mast structure 3 at its own, such that at least one spare mast structure pivoting actuator can be present when one of the actuators fails unexpectedly. Contrary to currently known hexapod type gangway constructions, which have limited redundancy, embodiments of the present boom construction can thus be relatively failproof. For example, two cylinder actuators can be provided substantially parallel, e.g. connected to the same lateral side of the mast structure 3, thereby saving space at the opposite lateral side of the mast structure 3.

[0056] As can be seen in FIG. 1, the mast structure 3 can extend from above the single pivot axis 6 beyond said single pivot axis 6 to a point located below said single pivot axis 6, wherein said at least one actuator 11 for pivoting the mast structure 3 engages the mast structure 3 at a position located below said single pivot axis 6, wherein said at least one actuator 11 can preferably comprises a piston actuator, especially a hydraulic piston actuator or a so-called hydraulic cylinder. By allowing a part of the mast structure 3, e.g. at least 10%, at least 15% or at least 20% or even more of the length of the mast structure 3, to extend or protrude below said single pivot axis 6, the at least one actuator 11 can engage the mast structure at a position relatively far from said pivot axis 6, without being in the way at a position above said pivot axis 6, e.g. without hindering a mechanism 16 for elevating the boom 10 and/or hindering an elevator or stairs for providing access to the boom 10 that preferably can form a gangway 10.

[0057] As for instance can be seen in FIGS. 4 and 5, which show two alternative embodiments, the boom construction 2 can be mounted to a vessel 1 in different manners. For example, the hinge constructing 9 by which the mast structure 3 may be supported may be mounted on a deck 4, e.g. a platform working deck 4 or working deck, as is the case in the embodiments of FIG. 4. Alternatively, the hinge constructing 9 may be attached to or part of a pedestal 17, which can comprise a housing for housing the at least one actuator 11 for compensating the mast structure 3. Preferably, the hinge construction 9 is located at a top side of the pedestal 17.

[0058] It is noted that the vessel 1 and/or the boom construction 2 may be provided with a locking mechanism 18 for locking the mast structure 3, e.g. in a substantially upright position. When the boom construction 2 is not in use, e.g. when the vessel 1 is sailing or when the vessel is moored, the boom construction can be in a parked state, in which the mast structure 3 can be locked, and preferably in which state the boom 10 can be moved down such as to rest with a distal end portion on the deck 4 of the vessel 1. For example, said locking mechanism 18 may comprises a locking pin 18 and a locking hole 18 into which the locking pin 18 can be inserted and/or mechanically locked in order to prevent the mast structure from pivoting about its pivot axis 6. Due to such design, the mast structure 3 can be locked in a relative simple and reliable manner. Although the locking pin 18 may in the shown embodiments be slidably attached to the mast structure 3 and the hole 18 may then be provided at a fixed position with respect to the hull 5, the locking hole may in alternative embodiments be provided at the mast structure 3 while the locking pin 18 may then be slidably mounted to the vessel's hull 5. In embodiments, the locking mechanism can be provided in the pedestal 17.

[0059] Advantageously, the boom construction 2 can be provided with a so-called smit bracket construction for fixedly attaching one or more respective boom construction parts, e.g. its pivot construction 9 and/or its pedestal 17 to the vessel 1. One or more first parts of said smit bracket construction, e.g. one or more smit brackets, can be provided, which can become mounted to the vessel, e.g. to or on a deck 4 of the vessel 1, when the vessel in use, e.g. during sailing. One or more corresponding second parts of the smit bracket construction can be provided at the mast structure 3 and/or at a pedestal 17 of a boom construction 2. For example, the one or more first parts can be welded to the deck while the vessel is not at a dock, but for instance in seaway, and the vessel may subsequently be in a dock or harbor for a relatively short period while the boom construction is fixedly mounted to the pre-installed first parts. Due to the smit bracket construction, the boom construction 2 can be mounted to the vessel 1 in a relatively simple and/or fast manner.

[0060] Besides, it is noted that the vessel 1 and/or the boom construction 2 can be arranged to control the at least one actuator 11 in order to allow said at least one actuator 11 to compensate for at least a part of the roll movement 12 of the hull 5, especially in such manner that the center line of the mast structure 3 can during rolling of the vessel 1 be kept substantially parallel with a virtual or imaginary vertical plane 13 extending in the longitudinal direction of the vessel 1. As can be seen best in FIG. 2, the mast structure 3 can thus be kept substantially straight up with respect to fixed world, even when the vessel 1 is rolling. Since the mast structure 3 can only pivot with respect to the vessel 1 about said single pivot axis 6, the mast structure 3 may thus move along with the pitching movements of the vessel. However, angular rotations of a vessel due to pitching are usually much smaller than angular rotations due to a vessel's rolling. In case of a mast structure fixedly connected to a vessel's hull and/or deck, a mast structure will usually sway far less due to the vessel's pitching than due to the vessel's rolling. By only compensating the mast structure for a vessel's rolling and not for the vessel's pitching, up to 80% or 90% or even more of the swaying of the mast structure 3 can be reduced, whereas the construction can be considerably simplified with respect to a mast structure that can be compensated about two substantially transverse horizontal pivot axes. The present invention may thus result in a relatively simple construction, while the most critical movement of the vessel 1 can still be compensated for substantially. The tilting of the mast structure 3 due to pitching of the vessel 1, which tilting usually is very limited with respect to potential tilting due to the vessel's rolling, may for instance be compensated by slewing the boom 10 about the central axis 15 of the mast structure 3.

[0061] The at least one actuator 11 for compensating the mast structure 3 for the vessel's rolling can be controlled by means of a controller or control unit which get input from one or more motion sensors, e.g. included in a motion reference unit, e.g. a vertical motion reference unit, which may be provided at or in the mast structure 3. The controller may be arranged to drive the at least one actuator 11 to compensate the mast structure 3, e.g. the controller can control the at least one actuator 11 at least partly based on input provided by one or more position sensors, e.g. provided at the vessel 1 and/or at the mast structure 3.

[0062] As is shown in FIG. 3, in embodiments, the vessel 1 may be arranged to overcompensate the mast structure 3, which mast structure 3 due to the rolling of the vessel would have tilted laterally in case the motion of said mast structure would not have be compensated. Especially, a controller may be arranged such as to drive the at least one actuator 11 to overcompensate the mast structure 3 in such manner that, during rolling of the vessel 1, the center line 15 of the mast structure 3 can be tilted with respect to a virtual vertical plane 13 extending in the longitudinal direction of the vessel 1 in a direction opposite to the direction 12 in with the vessel 1 rolls. As a result, a position at which the boom 10 is connected to the mast structure 3 can be kept relatively stationary with respect to a situation in which the mast structure would be compensated, but not overcompensated, as can be seen when comparing FIGS. 2 and 3. Hence, changes in the distance between said connection point at a point at an offshore object temporarily connected by means of the boom 10 can be counteracted or can at least be kept relatively small.

[0063] It is noted that the boom 10 can preferably be an telescopically extendable boom 10, e.g. comprising a first part 10a not laterally movable with respect to the mast structure 3, which can for instance be rotatably connected to said mast structure 3, and a second part 10b laterally movable with respect to said first part 10a and thus laterally movable with respect to the mast structure 3. For example, the second part 10b can be formed as an inner boom, especially an inner bridge, movable within an outer boom 10a, especially an outer bridge 10a, formed by the first boom part 10a.

[0064] In further embodiments, the boom 10 is a telescopically extendable boom 10 with three or more telescoping parts. In an embodiment such a telescopically extendable boom 10 comprises a first telescoping part 10a that is not laterally movable with respect to the mast structure 3, a second telescoping part 10b laterally movable with respect to said first telescoping part 10a and a third telescoping part 10c laterally movable with respect to said second telescoping part 10c. For example, the second and third telescoping part 10b,c can be formed as inner bridges movable within the first and second gangway parts 10a, b respectively. Use of two or more moveable telescoping parts has the advantage that the relative speed of successive telescoping parts with respect to each other can be reduced, making it safer to walk through the bridges.

[0065] The controller can be arranged such as to overcompensate when the stroke of the oscillating motion of the telescopically extendable boom 10 is almost reached during normal compensation of the mast structure 3. For example, the controller may be arranged such as to control that the roll movement of the vessel 1 will be overcompensated in order to relieve the one or more telescoping actuators in extreme cases only, e.g. when the one or more telescoping actuators, e.g. telescoping cylinders, need a predetermined threshold percentage of their maximum stroke to compensate for the elongation or shortening of the distance between the point at which the boom 10 is coupled to the mast structure 3 and a desired point, e.g. a desired of the fixed world, where a distal end of the boom 10 is to be located. In embodiments, said predetermined threshold percentage of the maximum stroke of the one or more telescoping actuators can for instance be at least 70%, 80%, 90% or 95% of the maximum stroke. Instead of telescoping actuators a cable transmission may be used.

[0066] In the shown exemplary embodiments, the boom 10 is mounted to an elevation unit 16 being adjustable in height along the elongated mast structure 3, preferably in a continuously variable manner. For example, the elevation unit 16 can be movable attached to the mast structure 3, and can for instance be adjusted by means of a motorized rack and pinion system 20. For example, the rack 20 can be integrated in the mast structure 3 and the pinion 20 can be positioned on the elevation unit 16. Using an elevation unit 16 for adjusting the height at which the boom 10 engages the mast structure 3 can facilitate that a relatively large range of heights of offshore object landing locations can be reached, as a result of which the boom construction 2 can be a relatively versatile construction. Additionally or alternatively, height elevation by means of the elevation unit 16 can facilitate that the boom 10 can be in a relatively horizontal state during use, as a result of which people to be transferred do not have to substantially climb or to substantially go down an inclined boom, which can make the boom construction 2 relatively safe and/or said height elevation may result in a relatively high workability of the boom construction 2.

[0067] Additionally or alternatively, the boom 10 can be rotatably connected to the elongated mast structure 3 in order to allow the boom 10 to slew 14 about said elongated mast structure 3, e.g. by means of a slewing platform 21, which can be actively rotated by means of one or more slewing actuators 30, which may be controlled by the controller. Advantageously, the slewing platform 21 may be rotatably connected to the elevation unit 16 that is adjustable in height along said elongated mast structure 3.

[0068] Further, the boom construction 2 can preferably comprise at least one counterweight 22 for compensating for a moment exerted on the mast structure 3 by the boom 10 at least partly. The at least one counterweight 22 can have a center of mass located at a lateral side of the mast structure 3 substantially opposite to a side of the mast structure 3 at which said boom 10 extends from said mast structure. Said counterweight 22 can reduce a moment on the mast structure 3, but can also reduce a moment on slew bearings provided for allowing the slewing platform 21 to rotate about the mast structure 3.

[0069] The boom construction 2 can comprise an arm structure 23 for holding the counterweight or a counterweight support lever arm 23 for carrying one or more counterweights 20. Said arm structure or lever arm 23 itself can form a part of the counterweight used for balancing the boom 10 at least partly.

[0070] Advantageously, the boom construction 2 can comprise a main part 10a and at least one second part 10b, said second part 10b and optional further part being telescopically movable with respect to the main part 10a, and if a plurality of moveable parts are used telescopically movable with respect to each other, in order to telescopically extend the length of the boom 10, wherein the boom 10 can then further comprise a movable counterweight 24 for at least partly compensating for a moment exerted on the mast structure 3 by the movable second boom part 10b, wherein the movable counterweight 24 has a center of mass located at a lateral side of the mast structure 3 substantially opposite to a side of the mast structure 3 at which said movable boom part 10b is located.

[0071] Telescoping actuators may be provided to move the counterweight 24 and the moveable telescoping part or parts. Alternatively a cable transmission coupling may be used to transmit movement of the counterweight 24 to the moveable telescoping part or parts in a reciprocal way, with a predetermined transmission ratio. The cable transmission may comprise a winch, one or more cables, wheels and/or blocks. In an embodiment a predetermined ratio between the speeds of relative movements between different pairs of telescoping parts of the beam may be used. But this not necessary. In an embodiment wherein a telescoping boom with two or more moveable telescoping parts is used, computer controlled telescoping actuators may be used, with a computer programmed to distribute the movements needed to move the distal end of the boom in a time dependent way over the moveable telescoping parts. Thus, for example, relative movement between successive telescoping parts where a person walks may be reduced.

[0072] Advantageously, the boom construction 2 can be arranged such that the boom 10 can be tilted with respect to the mast structure 3 in order to alter the angle of inclination of the boom 10. Thereto, the boom 10 can be pivotally connected to the mast structure 3, e.g. by hingedly connecting it, e.g. a first part 10a thereof, directly to said mast structure 3. However, in preferred embodiments, the boom 10 can be hingedly connected to the elevation unit 16, or more preferably hingedly connected to the slewing platform 21. Although a counterweight support lever arm 23 forming and/or carrying one or more counterweights 22, 24 at an opposite side of the mast structure 3 may be substantially fixedly attached to the boom 10, e.g. in order to tilt it 22, 23, 24 together with the boom 10 about a single rotation axis, the counterweight support lever arm 23 may alternatively be connected to the boom 10 by means of a four bar linkage 25, especially a parallelogram linkage 25, as is the case in the exemplary embodiments shown in the figures, which can comprise four bars of fixed length. A change in the inclination angle of the counterweight support lever arm 23 can result in a corresponding, especially equal, change in the inclination of the boom 10. For example, a first one 25a of the four bars of the parallelogram 25 or other four bar linkage 25 may be formed by the slewing platform 21, the elevation unit 16 or the mast structure 3. As a result, a platform, e.g. the slewing platform 21, located at or close to the mast structure 3, may for instance be kept substantially motionless, at least with respect to the mast structure 3, while an angle of inclination between the mast structure 3 and the boom 10 changes. As a result, a platform 21 can be provided which is substantially stabilized during use, as can for instance be understood from FIG. 4.

[0073] It is noted that the boom construction 2 may comprise one or multiple, preferably two, luffing cylinders 26, such as hydraulic cylinder actuators 26, or other actuators for so-called luffing, e.g. tilting the boom 10 with respect to the mast structure 3. For example, a first end 26a of the luffing cylinder 26 can be rotatably connected to the mast structure 3, e.g. by rotatably connecting it to the elevation unit 16 or the slewing platform 21, and an opposite second end 26b of the luffing cylinder 26 can be rotatably connected to another one of the four bars of the four bar linkage 25, such as for instance the counterweight support lever arm 23 or the boom 10. By connecting the second end 26b of a luffing cylinder 26 to the counterweight support lever arm 23 it can be counteracted that the luffing cylinder 26 is in the way, e.g. in the way of persons moving from the slewing platform 21 to the boom 10 or vice versa.

[0074] Although, in the shown exemplary embodiment, said luffing cylinder 26 engage the counterweight support lever arm 23 in order to enable tilting of said support lever arm 23, and hence tilting of the boom 10 cooperatively coupled to said support lever arm 23, e.g. by means of a parallelogram or other four bar linkage 25, it is noted that it is apparent that, in alternative embodiments, one or more luffing cylinders 26 can engage the boom 10 in stead of engaging the counterweight support lever arm 23.

[0075] Furthermore, it is noted that one or more counterweights 22, 24 and/or one or more luffing cylinders 26 can also advantageously be used in other designs, e.g. in case the counterweight support lever arm 23 and the boom 10 are substantially rigidly fixed to each other, e.g. in a manner that they 23, 10 cannot substantially pivot with respect to each other, and are arranged to integrally pivot with respect to the mast structure 3 about a single pivot axis, e.g. a pivot axis extending substantially transverse to the longitudinal direction of the mast structure. Also in such designs, one or more counterweights and/or luffing cylinders can have advantages over conventional mast structure designs having a boom, especially a gangway, suspended by cables attached to a mast structure portion located above the point at which the boom engages the mast structure. For example, they can have the advantage that said one or more counterweights and/or luffing cylinders can facilitate that the mast structure can be relatively short, e.g. because the mast structure does not need to extend above the slewing platform and/or above the boom. Consequently, the mast structure can be kept relatively low and/or light with respect to the maximum working height of the boom. As a result of the relatively low weight of the boom construction 2, the construction may be relatively easy to install and/or may be suitable for relatively small vessel in comparison to both known hexapod type gangway constructions and known crane-like type gangway constructions with mast structures. Moreover, the boom construction 2 may be free of hoisting winches, as result of which such it can be free of hoisting winch fatigue.

[0076] Additionally or alternatively, such as for instance can be seen in the exemplary embodiments of FIGS. 6 and 7, the boom construction 2 can, in preferred embodiments, further comprise a coupler 19 located at or near a distal end of the boom 10 for coupling the boom 10 to an offshore object 8, preferably in a rotatably manner. The offshore object 8 may for example be another vessel, e.g. in seaway, or an offshore structure or so-called offshore construction, such as for instance an offshore platform or a wind turbine. The coupler 19 can for instance comprise a landing foot, such as an electro-magnetic foot. However, many different couplers, e.g. comprising a docking head, are possible.

[0077] As can be seen in the exemplary embodiment shown in FIG. 7, the boom construction 2 may be formed as a gangway construction 2 that may be provided with a trolley 27, which can be movable along at least a portion of the boom 10. Said trolley 27 can preferably be arranged for holding a load, e.g. in order to carry cargo 7 to be moved between an offshore object 8 and the vessel 1 provided with the boom construction 2. The trolley 27 may be a crane trolley and can be provided with a hoist 28 for hoisting cargo 7. The trolley may facilitate that the vessel 1 does not need both a gangway construction for transferring people and a separate system, e.g. a conventional crane system, for transferring cargo.

[0078] During use, embodiments of the present boom construction 2 can be used to provide a temporarily connection between a vessel 1 and an offshore object 8. For example, the vessel 1 can be located close to said offshore object 8, and can be kept substantially in position. The boom 10 can be brought in a substantially horizontal position, can be elevated along the mast structure 3, and/or can be slewed, e.g. towards the offshore object 8. A distal tip or end portion of the boom 10 can be moved towards a location where it is to be coupled to the offshore object 8. The mast structure 3 can be compensated at least partly for the vessel's roll motion, if desired even overcompensated, by means of the at least one mast pivoting actuator 11, the slewing platform 21 can actively be rotated about the mast structure's longitudinal axis 15 in order to compensate for the vessel's pitch motion at least partly by means of the one or more slewing actuators 30, the telescoping boom 10 can be retracted and extended actively, e.g. by means of one or more telescoping actuators, for example in order to compensate at least partly for changes in the distance between the coupling location at the offshore structure 8 and a proximal end of the boom 10 attached to the mast structure 3, and the at least one luffing cylinder 26 can actively adjust the angle between the mast structure 3 and the boom 10, e.g. to keep the boom 10 at a predetermined angle with respect to the horizon. Hence the distal end portion of the boom 10 can be kept substantially motionless with respect to the fixed world and/or can be moved to desired spot, e.g. said coupling location, in a controlled manner. Once the distal end portion of the boom 10 is coupled to the offshore object 8, the one or more slewing actuators 30, the one or more telescoping actuators, and the one or more luffing actuators 26 can be brought into a neutral position, e.g. out of gear. Hence, the extendable boom 10 can be brought into a passive mode of operation or a so-called float mode, in which the position of the mast structure 3 can be compensated for the vessel's roll motion and in which other motions are passively compensated for.

[0079] It is noted that the boom construction 2 can advantageously thus be arranged to bring the one or more slewing actuators 30, preferably formed by one or more radial piston motors 30, the one or more telescoping actuators, preferably formed by one or more radial piston motors, and the one or more luffing actuators 26, preferably formed by one or more hydraulic cylinders of which the chambers can be temporarily fluidly interconnected in order to bring them in a passive mode, into a neutral position, preferably substantially simultaneously. For example, the boom construction 2 and/or its controller may be arranged to bring said slewing, telescoping and luffing actuators into their neutral position when the coupler 19 couples to the offshore object 8. Thereto, the boom construction 2 may for instance comprise one or more sensors for sensing whether the coupler is coupled and/or whether the coupler 19 or a landing foot thereof, e.g. an electro-magnetic foot, is activated.

[0080] Advantageously, the slewing platform 21 can be elevated or lowered while the boom construction 2 is in its passive or neutral mode, e.g. in order to install a crane trolley 27 to the boom 10.

[0081] Moreover, it is noted that advantageous features of the vessel and/or the boom construction, especially forming a gangway construction, disclosed herein can be advantageously employed in other vessels and/or boom constructions. For example, one or more of such features can also be advantageously utilized in a vessel provided with a boom construction, especially a gangway construction, for transferring persons and/or cargo from said vessel to an offshore object or vice versa, wherein the boom construction comprises an elongated mast structure extending in a direction substantially upwards from a deck of said vessel, wherein said mast structure is pivotally mounted with respect to a hull of the vessel in a manner such as to be pivotable with respect to said hull about two pivot axes, preferably two substantially transverse pivot axes, more preferably provided in a two-axes gimbal structure, wherein the boom construction further comprises a boom, especially a gangway, connected to the mast structure and extending from the mast structure in a substantially sideward direction, and wherein the boom construction comprises at least two actuators for pivoting the mast structure such as to compensate for at least a part of a rolling movement of the hull of the vessel and at least a part of the pitching movement of the vessel's hull. It will be apparent that one or more of such features can also be utilized in such boom construction as such. For instance, the feature of overcompensation of the rolling motion of the vessel, the feature of at least partly balancing the boom by means of one or more counterweights, the feature of providing the elevating unit, the feature of locking the mast structure by a mechanical locking mechanism and/or the feature of adapting the angle of inclination of the boom by means of one or multiple luffing cylinders can be advantageously utilized in a boom construction having a motion compensated mast structure mounted to a vessel by means of a two-axes gimbal structure.

[0082] Besides, it is noted that for the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described.

[0083] For example, it is evident to the skilled reader that features disclosed in the context of a vessel provided with a boom construction are also deemed to be with disclosed in the context of a boom construction as such.

[0084] Further, it is noted that the invention is not restricted to the embodiments described herein. It will be understood that many variants are possible.

[0085] For example, the boom construction can comprise an elevator or a stairway, e.g. for allowing one or more persons to move from a deck of the vessel to the slewing platform and/or the boom of the boom construction, or vice versa.

[0086] Such and other variants will be apparent for the person skilled in the art and are considered to lie within in the scope of the invention as formulated in the following claims.