Suspended load rotation device

Abstract

Suspended object rotation device (1) that is arranged to be suspended from a lifting device and for rotating a lifted object that is coupled to the suspended object rotation device; the suspended object rotation device comprising: • - an inner frame (10) and an outer frame (20), wherein said outer frame comprises a through opening (21) and wherein said inner frame is arranged in said through opening; • - wherein said inner frame is rotatable with respect to the outer frame around a primary axis (I); • - wherein said outer frame is arranged to be held stationary around said primary axis; • - wherein the inner frame comprises a upper surface (113, 123, 133) and an opposing lower surface that can both be engaged from the outside of the suspended object rotation device; • - wherein said inner frame comprises, on the upper surface, a plurality of lifting cable receiving sections (131) for receiving and engaging a plurality of lifting cables (51-53) that are suspended from the lifting device, such as a crane; • - wherein, on its lower surface, said inner frame is arranged for coupling to the object that is to be lifted by the lifting device; such that, when the object is lifted, the suspended object rotation device is arranged in between the lifting device and the object and enables to rotate the object by rotating the inner frame with respect to outer frame that is held stationary.

Description

[0001] Suspended load rotation device

[0002] The present invention relates to a suspended object rotation device that is arranged to be suspended from a lifting device and for rotating a lifted object that is coupled to the device and to a method of rotating a suspended object using the suspended object rotation device.

[0003] The ongoing energy transition, from a fossil fuel based economy to a renewable energy based economy, requires installing vast amounts of offshore wind turbines. These turbines are formed from a number of separate components, such as an offshore foundation, a tower, a nacelle and a rotor, that are typically assembled offshore using specialized installation vessels, such as heavy lift vessels and / or jack-up vessels, comprising cranes and / or other lifting devices. Transition time, i.e. the sum of periods that the installation vessels are not installing, but, for instance, sailing between the offshore installation site and the harbour and loading the components onto the deck of installation vessels, is effectively lost time. Hence, transition time is to be minimized, for instance by optimizing, when docked at a quay site in the harbour, the loading sequence of said vessel, such that as many components as possible can be loaded in the least amount of time as possible. These requirement are often conflicting, as loading as many components as possible requires an exact positioning and orienting of the components and auxiliary tools required for installing the components, such as lifting frames, onto the deck of the vessel. This exact positioning and orienting simply takes more time, when compared to loading less components in a way that uses the deck of the vessel in a less optimal manner.

[0004] The components and auxiliary tools (i.e. objects) are typically large and heavy components that need to be rotated around a vertical axis (that is substantially parallel to the direction of gravity), such that any extremities extending outwardly are positioned and oriented such that they do not interfere with the other components, auxiliary tools and / or parts of the vessel itself. In order to be able to orient the various objects, tugger lines (which are, in the context of this disclosure, deemed equivalent to taglines) often need to be connected to the objects, whereby a number of riggers (i.e. personnel) is needed for handling the tugger lines, such that the object can be exactly positioned and oriented, after which the tugger lines are disconnected, taken to the next object, manually connected to the next object to be lifted, following by lifting and manually manipulating the orientation of the next object, and so on. This procedure takes, due to all the manual actions required, typically too much time.

[0005] Also, in recent times, monopiles not requiring a transition piece, so-called “TP-less monopiles” have become more popular. A TP-less monopile is provided, at its upper outer end, with a connecting section, typically a bolted-flange connection, for connecting to a bottom section of the wind turbine tower. As the auxiliary structures, such as corrosion protection systems, boat landings, external ladders, cable entry systems and / or support systems, internal platforms and external platforms, will not survive the monopile hammer driving installation process, they need to be mounted to the monopile after installation. Typically, a number of mounting sections are prepared on the monopile for mounting these auxiliary structures after installation of the monopile. Nonetheless, subsequently mounting the various auxiliary structures requires a lot of installation time, which can thereby prove to be a bottleneck in the overall installation process for an offshore wind turbine.

[0006] Recently, a number of lifting and installation tools (i.e. auxiliary tools) have been introduced that aid in the mounting of these auxiliary structures. However, installing the various auxiliary structures requires a number of custom-made installation tools that are typically only usable for a single project only. Also, as the these installation tools need to be movable in various degrees of freedom, among which a rotation around the vertical axis is common, they are typically fitted with a number of driving devices, rendering the tools expensive and relatively complex.

[0007] There is thus a need for a device that is able to manipulate the orientation (i.e. by rotating the object around the vertical axis) that does not require the above described time consuming steps and thus reduces the overall transition time of an installation vessel. Additionally, a device that would lead to the use of simpler and less expensive installation tools would also be beneficial.

[0008] Published patent publications CN111661766A and US4883184 describe different devices that are able to rotate a therefrom suspended load, but still come with a number of downsides.

[0009] Hence, it is the goal of the present disclosure to provide for an improved suspended object rotation device, i.e. a device that is arranged to be suspended from a lifting device (e.g. arranged to be lifted by a crane) and arranged for rotating a lifted object that is coupled to the device, wherein some of the downsides of devices according to the prior art are overcome, or at least partly relieved, as will be described in more detail below.

[0010] In a first aspect, the present disclosure relates to a suspended object rotation device that is arranged to be suspended from a lifting device, such as a crane, and for rotating a lifted object that is coupled to the suspended object rotation device; the suspended object rotation device comprising: an inner frame and an outer frame, wherein said outer frame comprises a through opening, wherein said through opening is preferably substantially centrally arranged in said outer frame, and wherein said inner frame is arranged in said through opening, preferably such that through opening and the inner frame are arranged substantially coaxially; wherein said inner frame is rotatable with respect to the outer frame around a primary axis; preferably the inner frame and outer frame are restraint with respect to each other in all other degrees of freedom, such that the inner frame is only rotatable along the primary axis with respect to the outer frame; wherein said outer frame is arranged to be held stationary around said primary axis; wherein the inner frame comprises a upper surface and an opposing lower surface that can both be engaged from the outside of the suspended object rotation device; preferably wherein, when lifted by the lifting device, said upper surface faces substantially upwards and said lower surface faces substantially downwards; wherein said inner frame comprises, on the upper surface, a plurality of lifting cable receiving sections for receiving and engaging a plurality of lifting cables that are suspended from the lifting device, such as a crane; preferably wherein the lifting cable receiving sections are spaced apart, in the radial direction, from said primary axis, and preferably wherein said lifting cable receiving sections are arranged at different angular coordinates around the primary axis; wherein, on its lower surface, said inner frame is arranged for coupling to the object that is to be lifted by the lifting device; such that, when the object is lifted, the suspended object rotation device is arranged in between the lifting device and the object and enables to rotate the object by rotating the inner frame with respect to outer frame that is held stationary.

[0011] The rotation devices according to the prior art comprise an upper frame that is connected (i.e. lifted) by the crane, typically through a plurality of lifting cables, and a lower frame that is connected to the lifted object. It is noted that with a lifting cable the full range of synonyms or equivalent slings, ropes and like is meant, such as hoisting cables, lifting slings, hoisting slings, lifting ropes, lifting chains, etc. The upper and lower frames are interconnected by means of a bearing arrangement allowing the upper and lower frames to rotate with respect to each other in order to rotate the object that is connected to the lower frame. In this arrangement, the full weight of the object is to be transferred through the bearing arrangement, which is thereby relatively heavily loaded. In order to allow the prior art devices to function, relatively complex and expensive bearings are required. Additionally, a failure of the bearing structure could cause the object to fall, thereby posing an additional safety risk.

[0012] In the suspended object rotation device according to the current disclosure, the crane, in particular lifting cables therefrom, are received on the upper surface (i.e. a first side) of the inner , and the object is operatively coupled to the lower surface (i.e. a an opposing second side) of the inner frame. The outer frame is arranged around the inner frame, such that the rational interface (e.g. a bearing structure) between the inner and outer frame only needs to carry the weight of the outer frame, as the weight of the object is directly transferred through the first frame, to the (lifting cables ol) the crane. The arrangement further allows to rotate the inner frame with respect to the outer frame for more than a full rotation (i.e. more than 360°); preferably it allows to rotate the inner frame with respect to the outer frame for a plurality of full rotations (in theory an infinite amount of rotations). The suspended object rotation device is preferably substantially axi-, and / or mirror-symmetric, such that a centre of gravity of the suspended object rotation device is preferably located on the primary axis. In one embodiment, the lifting cable receiving sections may be means for only coupling the lifting cables in the plane of the inner frame, such that the inner frame may be left free to move along the longitudinal directions of the cables. This may be obtained by providing cable through holes through the inner frame through which the lifting cables may extend, while being (fully) enclosed by the outer circumference of the cable through holes. Alternatively, shackles, rings, pad-eyes, carabiners may be arranged for receiving the lifting cables therethrough. In such a way, the lifting cables run directly from the crane, for instance directly from the crane hook thereof, to the object, while extending through the lifting cable receiving sections. The gravitational force, that is due to the weight, of the lifted object is thereby not even transferred through said inner frame, such that the inner frame only has to withstand the rotational torque that is used for rotating the lifted object. The inner and outer frame can thereby be constructed in a lightweight manner. As the lifting cables have a tendency to straighten under the applied tension, the inner frame may automatically be moved up, or down, under the influence of the cables, such that an arrangement is obtained wherein the cables run straight between the crane hook and the lifted object, and the inner frame simply sits “on top” of the tensioned cables.

[0013] Upon rotating the inner frame with respect to the outer frame, the induced (rotational) movement of a respective lifting cable receiving section will exert a traverse force onto a respective lifting cable that is received therein. This will cause a rotational movement of the lifted object around the primary axis (which is preferably arranged to be parallel to the vertical axis). In particular, when the lifting cable receiving sections are arranged at substantially equal angular distances (around the primary axis) in the inner frame, the sum of the traverse forces will substantially be self-equilibrating, such that substantially only a torque around the primary axis will remain, causing the rotation of the object around the primary axis.

[0014] In a preferred embodiment, the plurality of lifting cable receiving sections are arranged as a plurality of, in particular three, hook-on points that are arranged to the upper surface of the inner frame and are arranged for connecting to respective lifting cables. By arranging the hook on points on the upper surface of the inner frame, the suspended object rotation device can simply be connected to an arrangement of three lifting cables, such as a three leg wire rope sling comprising a central ring-shaped member whereto three lifting cables are connected having connecting eyes and / or eye-hooks at the respective free outer ends.

[0015] Preferably, the lower surface is arranged with a plurality, in particular three, connection members that are arranged for connecting to the suspended object. These connection members may comprise lifting cable connection points for connecting further lifting cables that extend between the lifted object and the inner frame. The connection member may also comprise clamping means, means for arranging a locking pin therein and / or may be a customized interface that is arranged to connect to a therewith cooperating connecting section that is arranged on the object, such as an auxiliary installation tool. Hence, in a preferred embodiment, the object is an installation tool for installing an auxiliary structure to a monopile, wherein the object is coupled to the suspended object rotation device.

[0016] It is further preferred that the number of lifting cable receiving sections is equal to the number of connection members; and wherein each respective lifting cable receiving section is paired with a respective connection member, such that the respective lifting cable receiving section and the respective connection member are arranged at positions having substantially the same angular coordinate, as determined in a cylindrical coordinate system around the primary axis. Thereby, the respective lifting cable receiving section and the respective connection member are arranged at a short distance from each other, such that the internal bending moment in the inner frame due to the gravitational forces of the lifted object are minimized, enabling a relative light-weight construction of the inner frame and overall device.

[0017] In a preferred embodiment, the inner frame is formed from a central section through which the primary axis extends and a plurality of arm members that extend from the central section in different substantially radial directions; preferably wherein said arm members are evenly spaced apart along the angular direction. This allows for a relatively open, and thereby light-weight construction of the inner frame, in particular in case the lifting cable receiving section and the connection member forming a pair, as described above, are arranged onto the same arm member. This can, for instance, be arranged in an embodiment wherein the number of arm members are equal to the number of lifting cable receiving sections, and wherein each lifting cable receiving section is arranged on a different arm member. At the same time, it enables to arrange the lifting cable receiving section(s) and / or connection member(s) at a radial position along the arm members, such that the centre of gravity of the lifted object may be positioned with respect to the primary axis, as is described in more detail below.

[0018] Preferably, the through opening of the outer frame is substantially circular, such that the inner frame is surrounded by the substantially circular through opening and wherein the inner frame engages the substantially circular through opening, as this enables a setup wherein the inner frame is effectively arranged in the outer frame in such a manner that both the upper and lower surfaces can be engaged from the outside of the device, thereby enabling the associated advantages.

[0019] It is preferred that a radial outer end section of the inner frame, in particular the radial outer ends of the arm members, and the through opening of the outer frame are arranged to mutually cooperate for forming a bearing structure, in particular wherein the inner frame is retained in the through opening in at least one of the radial direction for forming a radial bearing structure and the axial direction for forming an axial bearing structure. This allows to obtain an inner frame that is only movable (i.e. rotatable) with respect to the outer frame around the primary axis. Again, as noted before, the interface between the inner and outer frame transfers only a very limited load (when compared to the devices according to the prior art). In a preferred embodiment, the suspended object rotation device comprises a slew drive mechanism for rotating the inner frame with respect to the outer frame; preferably a spur slew drive mechanism comprising a pinion and ring gear. The ring gear may be an external ring gear (i.e. wherein the teeth of the gear extend in a radially outward direction with respect to the ring-shaped main body of the ring gear) that is connected to the inner frame, whereby coopering a drive, in particular comprising a motor (e.g. an electrical or hydraulic motor), a pinion gear and a gearbox arranged therebetween, is arranged onto the outer frame. It is however preferred that the ring gear is an internal ring gear (i.e. wherein the teeth of the gear extend in a radially inward direction with respect to the ring-shaped main body of the ring gear) that is arranged in the through opening of the outer frame. The inner frame is then provided with the drive (as described above). The slew drive mechanism thereby enables to form an endless drive that allows for, in theory, infinitely rotating the inner frame with respect to the outer frame around the primary axis.

[0020] In order to hold the outer frame stationary with around the primary axis, the outer frame is preferably retained by coupling it to the lifting device, in particular to a boom of the crane and / or a base of the crane (wherein it is noted that the base is preferably rotatable). In one embodiment, this is obtained by that the outer frame comprises, at each of the longitudinal end sections thereof, tugger line connection points for coupling the outer frame to the lifting device, in particular to a boom, and / or base, of the lifting device, by using tugger lines, such that the outer frame is arranged to be held stationary around said primary axis. Not only does this provide a very simple and robust system, that does not require further active control, is also allows to automatically orient the outer frame in a manner corresponding to the crane, in particular the boom, and / or the base, thereof, leading to a simple control of the suspended object rotation device. Alternatively, the outer frame may be provided with a gyroscopic stabilization system, in particular wherein a gyroscopic stabilizers are arranged at the longitudinal end sections of the outer frame.

[0021] It is then preferred that a distance, as determined along the longitudinal axis of the outer frame, between the through opening and a tugger line connection point (or a gyroscopic stabilizer) is no less than l / 4th of the width of the inner frame, in particular no less than 1 / 4th of the diameter of the through opening. Hereby, a sufficient long arm is obtained to counteract the torque required for rotating the suspended object with limited reaction forces from the tugger lines (or gyroscopic stabilizers).

[0022] In a preferred embodiment, the suspended object rotation device further comprises a secondary rotation drive system for rotating the suspended object rotation device around at least a secondary axis, wherein said secondary axis is substantially perpendicular to the primary axis and parallel to a horizontal plane. In cases where the centre of gravity of the lifted object is not exactly centre with the primary axis of the device, the device might tilt around a secondary axis that is substantially parallel to the horizontal plane and perpendicular to an auxiliary axis extending from the centre of gravity of the lifted object through the primary axis. This, in turn, causes the primary axis to tilt around said secondary axis. As the primary axis is thereby no longer substantially parallel to the direction of gravity (i.e. the vertical axis), a rotation of the primary axis will also lead to a displacement of the centre of gravity of the lifted object, leading to increased torque requirements that a rotational drive (e.g. slew drive) needs to generate, but also to an increased loading of the interface between the inner and outer frame. The main issue is however that this leads to a undesired tilting of the object and an uneven distribution of forces over the lifting cables, rendering such a lift unsafe. By arranging a secondary rotation drive system for rotating the suspended object rotation device around at least the secondary axis, the primary axis can be set parallel to the vertical axis again, thereby overcoming the directly hereabove described issues. In particular, the secondary rotation device is arranged for moving the centre of gravity of the lifted object, such that the lifted object can moved towards, and in line with, the primary axis, such that the lifted object will automatically be oriented in the right orientation, thereby leading to an even distribution of forces through the lifting cables again.

[0023] The secondary rotation system is thus preferably a drive system that enables to displace the centre of gravity of the object with respect to the inner frame, to bring the centre of gravity of the object in line with the primary axis. This is for instance achieved by an embodiment, wherein the secondary rotation system is arranged for moving at least one, preferably all, of the lifting cable receiving sections and / or at least one, preferably all, of the connection members from, and towards, the primary axis along at least the radial direction such that, when in use, the centre of gravity of the object may be displaced away from, and towards, the primary axis for causing a rotation around the secondary axis; and preferably wherein the secondary rotation system comprises at least one linear drive, such as an hydraulic cylinder or electrical linear actuator for moving the at least one of the lifting cable receiving sections or the at least one of the connection members, more preferably wherein a linear drive is provided for each lifting cable receiving section that is movable and for each connection member that is movable.

[0024] In a preferred embodiment, said suspended object rotation device, in particular the connection members thereof, comprises coupling and decoupling drive system for coupling and decoupling the object from the suspended object rotation device; preferably by use of a, or a plurality of, linear actuator(s), such as hydraulic cylinder(s) or electrical linear actuator(s). This enables to couple and decouple objects without requiring a rigger (i.e. personnel) to physically access the coupling points, as this can be mechanically performed, preferably remotely, thereby saving time and requiring less personnel.

[0025] This is, for instance, also enabled by an embodiment of the suspended object rotation device comprising a power source for providing power to the respective drive systems of the suspended object rotation device; and / or comprises a control device, preferably comprising a receiver, allowing the suspended object rotation device to be remotely operated. Preferably, when all the drive systems of the suspended object rotation device are arranged on the inner frame, the power source is also arranged on the inner frame, and vice versa in case the drive systems are arranged on the outer frame, as rotary joints / unions (such as hydraulic and / or electrical slip rings) are not required for allowing a transfer of power between the inner and outer frames, while enabling the full rotational capabilities of the device. In a preferred embodiment, the power source is arranged on the central section of the inner frame, such that a substantially axi- symmetric setup of the inner frame and a substantially mirror symmetric setup of the suspended object rotation device is obtained. By making the suspended object rotation device substantially remotely operable, all the actions required for orienting the lifted object can be executed from a distance, such as from the cabin of the crane by a crane operator. Thereby, the need for riggers on the deck is minimized, which leads to a reduction in spend time and an increase in safety.

[0026] In a second aspect, the present disclosure relates to a lifting system comprising a lifting device, such as a crane, and a thereto connected suspended object rotation device according to any of the preceding claims that is arranged to be lifted by the lifting device, wherein the outer frame is connected to the lifting device for maintaining the outer frame in the same orientation, with respect to the direction of gravity, as the lifting device; in particular, wherein the lifting system comprises a pair of tugger lines that extend between the lifting device, in particular the boom of the crane and / or the base of the crane, and the outer frame. Thereby, the above described advantages can be obtained.

[0027] In a third aspect, the present disclosure relates to a method of rotating a suspended object using a suspended object rotation device according to any of the preceding claims, comprising the steps of: providing the suspended object rotation device; receiving the plurality of lifting cables that are suspended from the lifting device in the plurality of lifting cable receiving sections, such that the inner frame is engaged with the plurality of lifting cables; coupling the suspended object rotation device to the object that is to be lifted by the lifting device; lifting the object using the lifting device; rotating the object around a vertical axis that is substantially parallel to the direction of gravity by causing the outer frame to remain stationary with respect to the lifting device and by causing the inner frame to rotate around the primary axis with respect to the outer frame. Thereby, the above described advantages can be obtained.

[0028] The present invention is further illustrated by the following figures, which show preferred embodiments of the different aspects of the present disclosure, and are not intended to limit the scope of the invention in any way, wherein:

[0029] - Figure 1 schematically shows, in a three-dimensional perspective view, an embodiment of the suspended object rotation device.

[0030] - Figure 2 schematically shows, in a top-down view, the suspended object rotation device of figure 1.

[0031] - Figure 3 schematically shows, in a frontal view, the suspended object rotation device of figure 1 .

[0032] - Figure 4 schematically shows, a detailed view of a part of secondary rotation drive system as comprised in the suspended object rotation device of figure 1. - Figure 5 schematically shows, a detailed view of a part of the slew drive mechanism as comprised in the suspended object rotation device of figure 1.

[0033] - Figure 6 schematically shows, in a frontal view, a sequence of steps of the process of loading a boat landing, that is to be installed onto a monopile, onto a jack-up installation vessel using the suspended object rotation device.

[0034] - Figure 7 schematically shows, in a top-down view, a number of the steps of the process as shown in figure 6.

[0035] Figure 1 shows an embodiment of the suspended object rotation device 1 (hereafter also referred to as rotation device 1) that is arranged to be suspended from a lifting device and for rotating a lifted object that is coupled to the suspended object rotation device (as is shown in figures 6 and 7). The rotation device 1 comprises an outer frame 20 comprising a substantially centrally arranged circular through opening 21, wherein the inner frame 10 is arranged, such that through opening 21 and the inner frame 10 are arranged substantially coaxially with respect to the primary axis I.

[0036] The outer frame 20 comprises a substantially ring-shaped main body 22 comprising protruding outer frame sections 23 that extend from the ring-shaped main body 22 from two opposing sides along a longitudinal axis II of the outer frame 20. The outer frame sections 23 are formed as triangular trusses, wherein the main legs of the triangular trusses intersect at the outer most point of the outer frame 20 (as seen along the longitudinal axis II), where the tugger line connection points 24 are arranged that are connected to tugger lines 59 that extend towards the crane, in particular the boom of the crane and / or the base of the crane (as is seen in figures 6 and 7). The tugger lines thereby keep the outer frame 20 stationary. A relatively light-weight and stiff outer frame 20 is hereby obtained.

[0037] The inner frame 10 is formed from a central section 14 from which three arm members 11, 12, 13 extend in substantially radial directions (with respect to the primary axis I). The central section 14 is arranged with a hydraulic power pack 40, comprising a hydraulic pump that is driven by a motor, for powering the different drives found on the device 1. Each arm member 11, 12, 13 is arranged with a lifting cable receiving sections 111, 121, 131, which are formed with pad-eye members 112, 122, 132 that extend upwardly from the respective upper surfaces 113, 123, 133 of the respective arm members 11, 12 13. These upper surfaces 113, 123, 133 thereby effective form the upper surface of the inner frame 10. A lifting cable arrangement 50 comprising three legs 51, 52, 53 that extend downwards and radially outwards from a central lifting ring 55 is seen to be connected to the respective pad-eye members 112, 122, 132 by use of the cable coupling members 54 that are arranged at the free ends of the respective legs 51, 52, 53 of the lifting cable arrangement 50.

[0038] The opposing lower surfaces of the respective arm members 11, 12, 13 are arranged for coupling to the object that is to be lifted. Hence, from the respective lower surfaces of the arm members 11, 12, 13 connection members 31, 32, 33 that are arranged for connecting to the suspended object, extend in a downward direction, as is described in more detail in relation to figure 3. By arranging the connection members 31, 32, 33 directly on the arm with, at a close distance from, the lifting cable receiving sections 111, 121, 131, the induced internal bending moments in the arm members 11, 12, 13 can be limited, such that a more slender and light-weight inner frame 10 may be used.

[0039] The connection members 31, 32, 33 all comprise a downward extending coupling bar 36 having a connector 37 that is arranged at the distal end thereof. The connector comprises a pair of spaced apart pad-eye shaped members 34 having a central hole therethrough wherein a locking pin 35 is movable by a, or a pair of, linear actuators, in particular hydraulic cylinders 42, which are powered by the hydraulic power pack. The object may be arranged with a cooperating pad-eye shaped member that is received in between pair of spaced apart pad-eye shaped members 34, when the locking pin 35 is retracted from the connector 37. Once the cooperating pad-eye shaped member is received therein, the locking pin 37 is inserted through said pair of spaced apart pad-eye shaped members 34 and the cooperating pad-eye shaped member for coupling and locking the object to the rotation device 1.

[0040] The outer radial ends 114, 124, 134 of the respective arm members 11, 12 ,13 are substantially C-shaped to receive the inner circumference 25 of the outer frame 20 therein. Rolling and / or gliding elements may be provided in between the respective outer radial ends 114, 124, 134 and the inner circumference 25 for providing a smooth movement between them. The mutually cooperating outer radial ends 114, 124, 134 and the inner circumference 25 thereby effectively lock the inner frame 10 withing the outer frame 20 is such a way that the inner frame 10 is only allowed to rotate with respect to the outer frame 20 around the primary axis I. As was described above, the gravitational force of the lifted object need not to be transferred through this interface, such that the interface can be made relatively simple and robust. Some, or all, outer radial ends 114, 124, 134 of the respective arm members 11, 12, 13 may be arranged with rotational drives 41 for driving the relative rotational movement between the inner and outer frames 10, 20 as is explained in more detail below.

[0041] Figure 4 shows arm member 13 in more detail, as it comprises a part of secondary rotation drive system. The secondary rotation drive system is a drive system that enables to displace the centre of gravity of the object with respect to the inner frame 10, to bring the centre of gravity of the object in line with the primary axis I. For this, at least one (although two, or three may also be possible) of the lifting cable receiving sections 111, 121, 131 is movable from, and towards, the primary axis I along at least the radial direction III. The lifting cable receiving sections 131 is slidably arranged on top of the upper surface 133 and along the side surfaces 135 of the arm member 13. A sliding bearing arrangement, comprising low friction plates 136 may be arranged on these surfaces 133, 135 for this. The lifting cable receiving sections 131 is then moved back and forth by use of a linear actuator, in particular by hydraulic cylinder 43 that is powered by the hydraulic power pack 40. Figure 5 shows a part of the rotational drive for driving the rotation of the inner frame 10 with respect to the outer frame 20 around the primary axis I in more detail. The rotational drive, which is a spur slew drive mechanism in the current embodiment, comprises a motor 41, typically comprising an integrated (planetary) gearbox and a thereby driven output pinion 45 that engages a cooperating internal ring gear 26. The motor 41 is connected to the arm member 11, at the outer radial end thereof, using a suitable bracket 115, whereas the internal ring gear 26 is fixed to the inner circumference 25 of the outer frame 20. Hence, by driving the output pinion 45 using the motor 41, the outer and inner frame 10, 20 are rotated with respect to each other around the primary axis I. Again, the motor 41 is powered by the power pack 40 that is provided onto the inner frame. As all the motors and actuators are provided on the inner frame with the power pack, no complex hydraulic slip rings and the like are required.

[0042] Figure 6 schematically shows a sequence of steps A - C of the process of loading a boat landing, that is to be installed onto a monopile, onto a jack-up installation vessel using the suspended object rotation device 1. A jack-up vessel 1000 is positioned on its legs 1001 which penetrate into the harbour subsurface in a body of water 3 adjacent to a quayside 2 in a harbour area and ready to be loaded by, for instance, boat landing parts 201, 202 that need to be installed offshore onto a recently installed monopile. The jack-up vessel 1000 comprises a crane 1100 having a rotatable base section 1101 whereon a boom 1102 is arranged over which the lifting cable 1103 runs. The lifting cable is provided with a lifting hook 1104 at its free end. The suspended object rotation device 1 is suspended from the lifting hook 1104 by use of the lifting cable arrangement 50. The orientation of the outer frame 20 is fixed to the boom 1103 and / or the base of the crane by means of the tugger lines 59.

[0043] In step A, the boat landing parts 201, 202 are mounted to an installation tool 203, or sea fastening structure 203, for forming a temporary assembly 200 that is at a storage location 204 at the quayside 2. In step B, the temporary assembly 200 is to be coupled to the suspended object rotation device 1 for lifting the temporary assembly 200, after which the temporary assembly 200 is lifted and translocated to just above a sea fastening structure 1003 that is connected to the deck 1002 of the jack-up vessel 1000.

[0044] In step C, which is best seen in figure 7, the temporary assembly 200 needs to be rotated in order to be able to be mounted to the sea fastening 1003 in the right orientation. The initial orientation (as indicated in grey) does not satisfy the fastening requirement, as the outwardly protruding boat landing parts 201, 202 would not fit. Hence, the inner frame 10 is rotated, for instance by remote control performed by the crane operator, with respect to the outer frame 20, thereby rotating the temporary assembly (i.e. the object) 200 that is coupled to the underside of the inner frame 10. The outer frame 20, whose orientation is fixed with respect to the boom 1102 of the crane, and / or the base of the crane, is able to absorb the reaction moment, such that the inner frame 10 and the thereto connected temporary assembly 200 are rotated until correct orientation is obtained. After which the temporary assembly 200 is lowered onto sea fastening 1003, connected thereto, such that the suspended object rotation device 1 can be disconnected from the temporary assembly 200 and directly moved to the next object to be lifted and placed. There is thus no need for riggers on the deck that, by manually pulling tugger lines connected to the temporary assembly 200, try to pull it in the right orientation. The speed and safety of the process is thereby significantly improved.

[0045] The present invention is not limited to the embodiments shown, but also extends to other embodiments falling within the scope of the appended claims.

Claims

Claims1. Suspended object rotation device that is arranged to be suspended from a lifting device and for rotating a lifted object that is coupled to the suspended object rotation device; the suspended object rotation device comprising: an inner frame and an outer frame, wherein said outer frame comprises a through opening and wherein said inner frame is arranged in said through opening; wherein said inner frame is rotatable with respect to the outer frame around a primary axis; wherein said outer frame is arranged to be held stationary around said primary axis; characterized in that the inner frame is formed from a central section through which the primary axis extends and a plurality of arm members that extend from the central section in different substantially radial directions; and wherein the inner frame comprises an upper surface and an opposing lower surface that can both be engaged from the outside of the suspended object rotation device; wherein said inner frame comprises, on the upper surface, a plurality of lifting cable receiving sections for receiving and engaging a plurality of lifting cables that are suspended from the lifting device, such as a crane; wherein, on its lower surface, said inner frame is arranged for coupling to the object that is to be lifted by the lifting device; such that, when the object is lifted, the suspended object rotation device is arranged in between the lifting device and the object and enables to rotate the object by rotating the inner frame with respect to outer frame that is held stationary.

2. Suspended object rotation device according to claim 1, wherein the plurality of lifting cable receiving sections are arranged as a plurality of, in particular three, hook-on points that are arranged to the upper surface of the inner frame and are arranged for connecting to respective lifting cables.

3. Suspended object rotation device according to claim 1 or 2, wherein the lower surface of the inner frame is arranged with a plurality, in particular three, connection members that are arranged for connecting to the suspended object.

4. Suspended object rotation device according to claim 3, wherein the number of lifting cable receiving sections is equal to the number of connection members; and wherein each respective lifting cable receiving section is paired with a respective connection member, such that the respective lifting cable receiving section and the respective connection member are arranged at positions having substantially the same angular coordinate, as determined in a cylindrical coordinate system around the primary axis.

5. Suspended object rotation device according to any of the preceding claims, wherein said arm members are evenly spaced apart along the angular direction.

6. Suspended object rotation device according to any of the preceding claims, wherein the number of arm members are equal to the number of lifting cable receiving sections, and wherein each lifting cable receiving section is arranged on a different arm member.

7. Suspended object rotation device according to any of the preceding claims, wherein the through opening is substantially circular, such that the inner frame is surrounded by the substantially circular through opening, and wherein the inner frame engages the substantially circular through opening.

8. Suspended object rotation device according to any of the preceding claims, wherein a radial outer end section of the inner frame, in particular the radial outer ends of the arm members, and the through opening of the outer frame are arranged to mutually cooperate for forming a bearing structure, in particular wherein the inner frame is retained in the through opening in at least one of the radial direction for forming a radial bearing structure and the axial direction for forming an axial bearing structure.

9. Suspended object rotation device according to any of the preceding claims, wherein the suspended object rotation device comprises a slew drive mechanism for rotating the inner frame with respect to the outer frame; preferably a spur slew drive mechanism comprising a pinion and ring gear.

10. Suspended object rotation device according to any of the preceding claims, wherein the outer frame comprises, at each of the longitudinal end sections thereof, tugger line connection points for coupling the outer frame to the lifting device, in particular to a boom, and / or a rotatable base, of the lifting device, by using tugger lines, such that the outer frame is arranged to be held stationary around said primary axis.

11. Suspended object rotation device according to claim 10, wherein a distance, as determined along the longitudinal axis of the outer frame, between the through opening and a tugger line connection point is no less than 10%, preferably no less than !thof the width of the inner frame, in particular no less than 10%, preferably no less than !thof the diameter of the through opening.

12. Suspended object rotation device according to any of the preceding claims, wherein the suspended object rotation device further comprises a secondary rotation system for rotating thesuspended object rotation device around at least a secondary axis, wherein said secondary axis is substantially perpendicular to the primary axis and parallel to a horizontal plane.

13. Suspended object rotation device according to claim 12, wherein the secondary rotation system is arranged for moving at least one, preferably all, of the lifting cable receiving sections and / or at least one, preferably all, of the connection members from, and towards, the primary axis along at least the radial direction, such that, when in use, the centre of gravity of the object may be displaced away from, and towards, the primary axis for causing a rotation around the secondary axis; and preferably, wherein the secondary rotation system comprises at least one linear drive, such as an hydraulic cylinder or electrical linear actuator for moving the at least one of the lifting cable receiving section or the at least one of the connection member, more preferably wherein a linear drive is provided for each lifting cable receiving section that is movable and for each connection member that is movable.

14. Suspended object rotation device according to any of the preceding claims, wherein said suspended object rotation device, in particular the connection members thereof, comprises coupling and decoupling drive system for coupling and decoupling the object from the suspended object rotation device; preferably by use of a, or a plurality of, linear actuator(s), such as hydraulic cylinder(s) or electrical linear actuator(s).

15. Suspended object rotation device according to any of the preceding claims, wherein said suspended object rotation device comprises a power source for providing power to the respective drive systems of the suspended object rotation device; and / or comprises a control device, preferably comprising a receiver, allowing the suspended object rotation device to be remotely operated.

16. Lifting system comprising a lifting device, such as a crane, and a thereto connected suspended object rotation device according to any of the preceding claims that is arranged to be lifted by the lifting device, wherein the outer frame is connected to the lifting device for maintaining the outer frame in the same orientation, with respect to the direction of gravity, as the lifting device; in particular, wherein the lifting system comprises a pair of tugger lines that extend between the lifting device, in particular the boom of the crane and / or a base of the crane, and the outer frame.

17. Method of rotating a suspended object using a suspended object rotation device according to any of the preceding claims, comprising the steps of: providing the suspended object rotation device;receiving the plurality of lifting cables that are suspended from the lifting device in the plurality of lifting cable receiving sections, such that the inner frame is engaged with the plurality of lifting cables; coupling the suspended object rotation device to the object that is to be lifted by the lifting device; lifting the object using the lifting device; rotating the object around a vertical axis that is substantially parallel to the direction of gravity by causing the outer frame to remain stationary with respect to the lifting device and by causing the inner frame to rotate around the primary axis with respect to the outer frame.

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