CRANE AND METHOD FOR POSITIONING AN OBJECT

Description

[0001] The invention relates to the field of cranes. For example very tall cranes are nowadays envisaged for use in offshore windfarms, e.g. in view of handling wind turbine components. For example, the nacelle of a wind turbine may comprise components like a gearbox and / or generator, etc., that may need replacement in case of malfunctioning. The same holds for the blades of a wind turbine.

[0002] Nowadays windfarm installation and maintenance is often done from jack-up vessels, wherein the lifted hull provides a stable base for the one or more cranes on such a jack-up vessel. Nonetheless, influences like wind, bending of the main boom of the crane under the load, etc., entail that lifting jobs are often restricted or difficult to perform. Even more demanding in this regard is the use of a non-jack-up vessel, or a jack-up vessel in floating condition, with a tall crane thereon to perform such activities.

[0003] A known crane used to transfer objects from and to a vessel comprises a revolving superstructure, a boom, e.g. lattice boom, pivotally mounted to the revolving superstructure, e.g. to a foot portion thereof, a luffing assembly, and a hoist assembly. Therein the boom comprises a main boom and a jib.

[0004] The main boom comprises firstly a main boom member, e.g. a latticed main boom member, the lower end of which is pivotally mounted about a first pivot axis to the superstructure. It may secondly comprise a main boom strut, an end of which is mounted to an upper end of the main boom member and extending essentially perpendicular to the main boom member, and may thirdly comprise a boom stay extending between the main boom strut and a lower portion of the main boom member.

[0005] The jib is pivotally mounted about a second pivot axis to the main boom. It comprises firstly a jib member, e.g. a latticed jib member, an inner end of which is pivotally mounted to the upper end of the main boom member. It may secondly comprise a jib strut, an end of which is mounted to an inner end of the jib member and extending essentially perpendicular to the jib member, and may thirdly comprise a jib stay extending between the jib strut and the jib member.

[0006] In embodiments comprising the struts and stays, the boom further comprises a variable length stay mechanism, which is provided between the main boom strut and the jib strut. In these embodiments the luffing assembly comprises a luffing winch mounted to the superstructure, and a luffing cable extending between the luffing winch and the main boom. The hoist assembly comprises firstly a hoist winch, and secondly a hoist cable, extending from the hoist winch along the main boom and the jib via a jib departure sheave, e.g. on or close to the free end of the jib member, to an object suspension device. The hoist winch is provided with heave compensation, e.g. by embodying the hoist winch as an AHC winch or by means of heave compensating cylinders operating on the unwound section of the hoist cable. The object suspension device is with an upper part thereof connected to the hoist cable and with a lower part to an object to be transferred by the crane.

[0007] When transferring an object using the crane, wave-induced motion of the vessel and / or wind may force an object to be hoisted into a pendulous action, causing it to swing unchecked. A prior art solution to this problem is to compensate the wave-induced motion of the vessel by operating the crane accordingly - i.e. the crane motions normally used to position an object suspension device / object are then used for wave-induced motion compensation. Thereto the hoist cable is commonly provided with heave compensation functionality, e.g. by embodying the hoist winch as an AHC (active heave compensated) winch or by means of one or more heave compensating cylinders operating on a section of the hoist cable. Motion compensation may also involve the slew and luffing system of the crane. The compensation hereby achieved is however not capable prevent the load from swinging.

[0008] In positioning of objects handled by a crane, it is common to attach tugger cables to the hoisted object, or the object suspension device, for rotating it around the load bearing cable of the crane and / or translate it in the horizontal plane thereof, e.g. to compensate and / or correct unwanted motions thereof in the horizontal plane. For this purpose, the tugger cables run generally horizontally to the boom, e.g. via main boom departure sheaves, to one or more tugger winches. The capacity of the tugger winches is generally low compared to that of the main hoist winch of the crane as the tuggers do not carry the weight of the load. Examples are disclosed by JP2507856, JPH0631156, EP2490975 and US2008216301. Therein, the tugger cable sheaves are movable along the main boom member, so to maintain the horizontal orientation of the tugger cables. Document WO 2015 105414 A1 describes a crane with the features of the preamble of claim 1.

[0009] The present invention aims to propose an improved crane, e.g. for use on a vessel, e.g. on a jack-up vessel, according to claim 1. Herein the crane comprises a hoisting system, which hoisting system comprises one or more hoist winches, and both a main boom hoist assembly and a jib hoist assembly.

[0010] The main boom hoist assembly comprises two main boom departure sheaves, and two main boom hoist cables. The two main boom hoist cables are configured to extend from the, or one or two of the, hoist winches along the main boom member via the main boom departure sheaves to the object suspension device. This may be accomplished through a single-fall arrangement of these hoist cables, or through a multiple-fall arrangement.

[0011] In a particular embodiment, the main boom hoist cables may be arranged in a double-fall arrangement. Herein the main boom hoist assembly comprises two pairs of main boom departure sheaves. Each pair of main boom departure sheaves is therein mounted to an upper end of the main boom member at opposite lateral sides thereof. The main boom hoist assembly therein further comprises two main boom spreader sheaves, each connected to the object suspension device, e.g. via a respective spreader cable or e.g. by means of a respective spreader beam.

[0012] The main boom hoist cables are each configured to extend from one of the hoist winches along the main boom member successively via one main boom departure sheave of a respective pair of main boom departure sheaves, a respective one of the two main boom spreader sheaves, the other main boom departure sheave of the respective pair of main boom departure sheaves to the one of the hoist winches.

[0013] Furthermore the jib hoist cable may be arranged in a double-fall arrangement. Therein the jib hoist assembly comprises a pair of jib hoist sheaves, mounted to the jib member, e.g. to the free end thereof. The jib hoist assembly therein further comprises a jib spreader sheave, connected to the object suspension device, e.g. via a spreader cable or e.g. by means of a spreader beam.

[0014] The jib hoist cable is configured to extend from one of the hoist winches along the main boom and the jib successively via one jib departure sheave of the pair of jib hoist sheaves, the jib spreader sheave, the other jib hoist sheave of the pair of jib hoist sheaves to the one of the hoist winches.

[0015] The main boom hoist assembly further comprises a main boom hoist heave compensation mechanism. Herein, e.g., the hoist winch(es) from which the main boom hoist cables extend are embodied as AHC (active heave compensated) winches, or, e.g., the main boom hoist heave compensation mechanism comprises a heave compensating cylinder operating on a section of the main boom hoist cable.

[0016] The jib hoist assembly comprises a jib hoist departure sheave, and a jib hoist cable. The jib hoist cable is configured to extend from the, or one of the, one or more hoist winches along the main boom member and the jib member via the jib departure sheave(s) to the object suspension device, e.g. in a single-fall arrangement or in a multiple-fall arrangement. The jib hoist assembly further comprises a jib hoist heave compensation mechanism, e.g. wherein the hoist winch from which the jib hoist cable extends is embodied as an AHC winch, or wherein the jib hoist heave compensation mechanism comprises a heave compensating cylinder operating on a section, e.g. the unwound section, of the jib hoist cable.

[0017] The object suspension device is supported by the jib hoist cable and by the two main boom hoist cables, e.g. with an upper part thereof connected or connectable to the main boom hoist cables and the jib hoist cable, and with a lower part to an object to be transferred by the crane.

[0018] The two main boom departure sheaves are connected to the upper end of the main boom member at opposite lateral sides thereof.

[0019] In an embodiment the main boom departure sheaves are mounted to lateral ends of a transverse beam. Therein the transverse beam is at a center portion thereof mounted to the upper end of the main boom member, e.g. substantially at the height of the second pivot axis, e.g. directly below the second pivot axis. Therein, the length of the transverse beam, e.g. substantially corresponding to the lateral distance between the two main boom departure sheaves, is e.g. in the range of 8 - 30 meter, e.g. 12 meter.

[0020] In an embodiment the crane further comprises two boom extensions, e.g. forming an additional jib strut in addition to the already provided jib strut, each provided with a separate cable running over the upper end thereof. Lower ends of the two boom extensions are therein connected to the upper end of the main boom member. The boom extensions extend from said upper end at equal upward angles, e.g. between 60 and 90°, relative to the horizontal. The boom extensions diverge from each other and from the jib, e.g. at a mutual angle of between 40 and 80°, e.g. preferably around 60°, when seen in a top view of the crane. Therein each of the main boom departure sheaves are mounted to a respective upper end of the boom extensions.

[0021] As enabled by the mounting of the two main boom departure sheaves to the upper end of the main boom member at opposite lateral sides thereof, the main boom hoist assembly is adapted to, together with the jib hoist assembly, hoist the object suspension device with an object connected thereto, up to the height of the main boom departure sheaves while the jib hoist cable and the main boom hoist cables together define a reverse pyramid diverging upwards from the object suspension device.

[0022] This inventive arrangement of the main boom hoist assembly having hoisting capability in cooperation with the jib hoist assembly, enables that up to the height of the main boom departure sheaves, by controlling the paying out and / or drawing in of the jib hoist cable and two main boom hoist cables in coordination with one another, e.g. software-based, the position of the object may be more effectively controlled, and over a larger range of horizontal positions for a certain height, than in prior art tugger systems without this hoisting capability of the tugger cables. Therein the earlier mentioned rotations and translations of the object, in the prior art established by the main boom hoist assembly generally independently of the vertical motions established by the jib hoist assembly, are now established by the main boom hoist assembly and the jib hoist assembly together, in cooperation with each other, and in dependence of the vertical motions of the object established by these same assemblies together.

[0023] The jib hoist cable and the two main boom hoist cables define a reverse pyramid having a triangular base which reduces, e.g. substantially avoids, swinging of the load, which allows for a more accurate positioning by adjusting the length of the paid out section of the respective cables.

[0024] For instance, in practical use of the crane, the horizontal distance between the object and a stationary object outside the vessel, e.g. a wind turbine, and / or between the object and the vessel itself, e.g. the main boom of the crane, may be altered without pivoting the jib - namely by merely adjusting the ratio between the length of the main boom hoist cables being paid out or drawn in and the length of the jib hoist cable being paid out or drawn in. Therein, by furthermore dependently controlling this ratio in dependence of the height of the object suspension device during hoisting, this distance may be kept constant, so to e.g. hoist the object over a vertical line.

[0025] By adjusting the jib relative to the main boom, e.g. using a variable length stay mechanism between a main boom strut and a jib strut, the shape of the inverted pyramid may be adjusted in favour of optimization of the hoisting job.

[0026] In embodiments the jib hoist is embodied and operable as a truly independent jib hoist system when disconnected from the two cables from the main hoist assembly. This may allow for the jib hoist to be operated in stand-alone mode. This allows for maximum hoisting height.

[0027] According to the invention the vertical load of the object is distributed over the three hoist cables, which may e.g. be advantageous in terms of efficiency and / or speed while hoisting up to this height, in particular when hoisting heavy objects.

[0028] Preferably, the main boom hoist assembly is furthermore adapted to for controlling horizontal components of movements of the object suspension device with an object connected thereto up to a height of the object suspension device directly below the jib departure sheave. Therein, when the jib is at an upward angle relative to the horizontal and the object suspension device is at a height in between the main boom departure sheaves and the jib departure sheave, the main boom hoist cables cannot be used for hoisting as these then extend upwardly to the object suspension device. However, at this height paying out and / or drawing in the main boom hoist cables may still effectuate substantially horizontal movements of the object suspension device and the object. Therein these function alike the prior art tugger cables.

[0029] In a practical use of the crane, heavier objects may be hoisted or lowered over the same height with the same bending moment around the first pivot axis, e.g. twice as heavy, as with prior art systems employing tugger assemblies without hoisting capabilities and heave compensation.

[0030] The inventive arrangement of the main boom hoist assembly and the jib hoist assembly according to the invention enables that the object is hoisted and / or lowered along a trajectory which has a smaller horizontal distance from the first pivot axis than the departure sheave, e.g. below a center portion of the jib, e.g. below the middle of the jib, instead of substantially below the main boom departure sheave such as in prior art systems. This applies when the object is at a height up to substantially the height of the main boom departure sheaves, wherein the main boom hoist cables and the jib hoist cables together, as well as a height above the main boom departure sheaves in which the jib is at an upwards angle relative to the horizontal.

[0031] The inventive arrangement of the main boom hoist assembly and the jib hoist assembly enables that for the same weight of the object, the crane is advantageously subjected to less bending stresses. Correspondingly, a heavier weight may advantageously be hoisted or lowered by the crane without increasing, e.g. while even decreasing, the bending stress the crane is subjected to.

[0032] In an embodiment of the crane, the one or more hoist winches consist of one single hoist winch, e.g. wherein the jib hoist heave compensation mechanism and the main boom hoist heave compensation mechanism comprise cylinders operating on the unwound section of the jib hoist cable and the main hoist cables, respectively.

[0033] In another embodiment, the one or more hoist winches comprise one jib hoist winch and one main boom hoist winch, the jib hoist cable extending from the jib hoist winch, and the two main boom hoist cables from the one main boom hoist winch.

[0034] In a still other embodiment, the one or more hoist winches consist of one jib hoist winch and two main boom hoist winches, the jib hoist cable extending from the jib hoist winch, and the two main boom hoist cables each from a respective one of the two main boom hoist winches.

[0035] In embodiments in which one or two main boom hoist winches are present, at least these winches may be embodied as AHC winches, e.g. comprised by the main boom hoist heave compensation system. Alternatively any hoist cable may be heave compensated by means of heave compensating cylinders operating on the unwound section of the hoist cable.

[0036] Preferably, the crane is provided with a control device, e.g. configured to control operation of the luffing assembly and / or any variable length say mechanism when present.

[0037] In a practical embodiment the length of the main boom can be at least 50 meters.

[0038] In embodiments in which one or two main boom hoist winches and a jib hoist winch are present, the control device is preferably programmed to operate the main boom hoist winches and jib hoist winches, e.g. embodied as AHC (active heave compensated) winches, so as to control the position and / or velocity of the object by simultaneously paying out and / or drawing in of the jib hoist cable and the main boom hoist cables in dependence of one another, e.g. in a (pre)determined constant or dynamic ratio.

[0039] The operation of the hoist winches may, furthermore or alternatively, also be so as to control the position and / or velocity of the object e.g. based on a predetermined trajectory and / or reference positions, and / or e.g. in dependence of the actual vertical and / or horizontal position and / or orientation and / or motions of the object and / or the object suspension device and / or the vessel and / or the crane, e.g. by feedback and / or feedforward control based on live measurements by sensors providing actual data on the position and / or orientation and / or motions of the object to the control device.

[0040] The crane also allows to deal with any motion of the crane itself, e.g. periodic bending of the boom due to wind effects, etc.

[0041] In an embodiment the winches are operated to provide damping effects on any pendulous motion of the object suspension device and object suspended therefrom.

[0042] In an embodiment the object suspension device is provided with a sensor, e.g. radar, adapted to determine the position thereof relative to one or more beacons. For example a beacon is mounted on a nacelle or top of the mast of a wind turbine, so that the object suspension device is directly correlated as to its position relative to the nacelle and / or top of the mast. Hereby any motions of the mast and / or nacelle are directly accounted for in the control of the crane during lifting or lowering of a wind turbine component. It will be appreciated that this provision of sensor and one or more beacons may also be applied for other types of offshore windfarm cranes.

[0043] The control device is preferably also programmed to operate the main boom hoist winches and jib hoist winches separately and / or independently, e.g. to separately and / or independently control horizontal and vertical movement components of the object.

[0044] In an embodiment, the object suspension device is provided, preferably at its outer side surface above the connection of the object suspension device with the object, with at least two cable connectors to which each of the main boom hoist cables and the jib hoist cable are respectively connected or connectable, preferably provided with three cable connectors of which each is connected to a respective one of the main boom hoist cables and jib hoist cable. These cable connectors form the points of application for the hoisting and / or tugging forces exerted thereon by the cables. Therein the cable connectors are preferably provided at equal mutual angles around a central vertical axis of the object suspension device, preferably three cable connectors being provided at a mutual angle of 60° around said central vertical axis. Furthermore therein the cable connectors e.g. comprise eyelets, directed outwards in a vertical plane.

[0045] In an embodiment, the main boom hoist assembly comprises two main boom hoist winches, from each of which a respective one of the two main boom hoist cables extends. In this embodiment, the main boom hoist winches are operable separately, e.g. by the control device which is therein programmed to do so, such as to have a different length of main boom hoist cable unwounded, so that the object is positioned in a position which, and / or hoisted and / or lowered along a trajectory which, in a top view of the crane, at least partly, extends laterally of the jib.

[0046] Preferably, the cable connectors are pivotable around a vertical pivot axis. This enables to align the cable connectors such that the cables point to a center axis of the object suspension device, so as to ensure that the load remains suspended directly below the object suspension device.

[0047] Preferably, a lower part of the object suspension device connected to the object is rotatable relative to an upper part of the object suspension device connected to the jib hoist cable and / or the main boom hoist cables, so that the object is rotatable around the central vertical axis of the object suspension device. Therein preferably, in case the control device is present, the rotation of said lower part relative to said upper part is controllable by means of the control device, so that the angular position of the object in its horizontal plane is controllable thereby.

[0048] Preferably, the main boom hoist cable(s) and / or jib hoist cable are connected to the object suspension device with respective terminal ends thereof.

[0049] In an embodiment, the connection between the main boom hoist cables and the object and / or the object suspension device is releasable, e.g. by means of the control device. This enables that the main boom hoist cables are disconnected from the object and / or the object suspension device, so that the jib hoist assembly is usable as a second hoist, wherein the object connector device is solely connected to the jib hoist cable, and the main boom hoist cable is usable as a first hoist. The first hoist is capable of hoisting and / or lowering objects between a lower position and a position at a height up to the height of the main boom departure sheaves. The second hoist is capable of, e.g. simultaneously, hoisting and / or lowering objects between a lower position and a position at a height up to the height of the main boom departure sheaves.

[0050] In an embodiment, the connection between the jib hoist cable and the object and / or the object suspension device, is releasable, e.g. by means of the control device. Based on the hoisting capability of the main boom hoist assembly this enables that the jib hoist cable is disconnected from the object and / or the object suspension device, so that the main boom hoist assembly is usable as a first hoist, wherein the object connector device is solely connected to the main boom hoist cables, and the jib hoist assembly is usable as a second hoist. The first hoist is capable of hoisting and / or lowering objects between a lower position and a position at a height up to the height of the main boom departure sheaves. The second hoist is capable of, e.g. simultaneously, hoisting and / or lowering objects between a lower position and a position at a height up to the height of the main boom departure sheaves. Therein, the connection between one or both of the main boom hoist cables and the object and / or the object suspension device may also be releasable, so that the object suspension device may be disconnected from one of the main boom hoist cables so as to be suspended from a single main boom hoist cable only, e.g. wherein each main boom hoist cable extends from a separate main boom hoist winch.

[0051] In an embodiment, the connection between the jib hoist cable and the object and / or the object suspension device, as well as the connection between the jib hoist cable and the object and / or the object suspension device, is releasable, e.g. by means of the control device.

[0052] According to any embodiment of the invention in which the connection between the jib hoist cable and the object and / or the object suspension device, and / or the connection between the jib hoist cable and the object and / or the object suspension device, is releasable, advantageously three fully valuable hoists are provided which are controllable to cooperate with each other for precisely and controllably positioning the object suspension device and the attached object, and controllable to be used in other configurations, e.g. in which the hoists operate separately or wherein one of the main boom hoist assembly and the jib hoist cable fulfils the function of hoisting, and the other one that of tuggering.

[0053] The invention will now be described with reference to the drawings. In the drawings: - fig. 1shows a first embodiment of a crane according to the invention, - fig. 2shows a second embodiment of a crane according to the invention, - fig. 3schematically shows a possible arrangement of the hoist assembly of a crane according to the invention, - figs. 4A-Hschematically show a crane according to the invention in different possible working positions; - fig. 5shows an object suspension device according to either embodiment.

[0054] Fig.1 shows an embodiment of a motion compensating crane according to the invention in perspective view.

[0055] The crane comprises a revolving superstructure 2. It further comprises a boom 3 pivotally mounted to the revolving superstructure 2, e.g. to a foot portion 21 thereof.

[0056] The boom comprises a main boom 30, comprising firstly a main boom member 31, the lower end 31a of which is pivotally mounted about a first pivot axis 11 to the superstructure 2. It secondly comprises a main boom strut 32, an end 32a of which is mounted to an upper end of the main boom member 31 and extending essentially perpendicular to the main boom member 31. It thirdly comprises a boom stay 33 extending between the main boom strut 32 and a lower portion 31b of the main boom member 31.

[0057] The boom further comprises a jib 34, pivotally mounted about a second pivot axis 12 to the main boom 30. The jib comprises firstly a jib member 35, an inner end 35a of which is pivotally mounted to the upper end of the main boom member. It secondly comprises a jib strut 36 an end 36a of which is mounted to the inner end 35a of the jib member 35 and extending essentially perpendicular to the jib member 35. It thirdly comprises a jib stay 37 extending between the jib strut 35 and the jib member 36.

[0058] The boom further comprises a variable length stay mechanism 38 provided between the main boom strut 32 and the jib strut 36.

[0059] The crane further comprises a luffing assembly 4 comprising a luffing winch, mounted to the superstructure 2, and a luffing cable 42, extending between the luffing winch and the main boom 30.

[0060] The crane further comprises an object suspension device 13, to which an object is connected or connectable underneath the object suspension device 13.

[0061] As shown in Figs. 1 and 3, the crane further comprises a jib hoist assembly 5, which firstly comprises a jib hoist winch 51 and secondly a jib departure sheave 52, e.g. mounted on the free end of the jib member 35. It thirdly comprises a jib hoist cable 53, extending from the jib hoist winch 51 along the main boom 30 and the jib 34 via the jib departure sheave 52 to the object suspension device 13. It fourthly comprises a jib hoist heave compensation mechanism 66. Therein, the jib hoist heave compensation mechanism 54 comprises heave compensating cylinders operating on the unwound section of the jib hoist cable 5. In alternative, not shown embodiments, the one or two main boom hoist winches are embodied as AHC winches.

[0062] The crane further comprises a main boom hoist assembly 6, comprising, firstly one or two main boom hoist winches 61, secondly two main boom departure sheaves 62. It thirdly comprises two main boom hoist cables 63, configured to extend from either of the one or two main boom hoist winches along the main boom member 31 via the main boom departure sheaves 62 to the object suspension device 13. It fourthly comprises a main boom hoist heave compensation mechanism 66, wherein the main boom hoist heave compensation mechanism comprises heave compensating cylinders operating on the unwound section of the main boom hoist cable 63.

[0063] As shown in Fig.1, and schematically in Fig.4H, the two main boom departure sheaves 62 of the crane 1 are mounted to an upper end 31c of the main boom member 31 at opposite lateral sides thereof.

[0064] The object suspension device 13 is supported by the jib hoist cable 53 and the two main boom hoist cables 63, as visible from Figs. 1 and 3 and Figs. 4A-H.

[0065] As most clearly visible from Fig.1, the main boom hoist assembly 6 is adapted to, together with the jib hoist assembly 5 hoist and / or lower the object suspension device 13 with an object 7 connected thereto, between a lower position and a position at a height up to substantially the height of the main boom departure sheaves 62 while the jib hoist cables 53 and the main boom hoist cables 63 together define a reverse pyramid diverging upwards from the object suspension device 13.

[0066] Fig.2 shows a second embodiment of the crane according to the invention. The features discussed up to now for the embodiment shown in Fig.1, are present as well in this embodiment shown in Fig. 2, wherein the reference numerals thereof correspond to those of the first embodiment, increased by 100.

[0067] Correspondingly, the arrangement of the jib hoist assembly 5 and the main boom hoist assembly 6 shown in Fig.3, is applicable to the second embodiment as well. The same applies to the object suspension device shown in Fig.5.

[0068] The crane 1 according to the first embodiment, shown in Fig. 1, has its main boom departure sheaves 62 mounted to lateral ends of a transverse beam 64, which transverse beam 64 is at a center portion thereof mounted to the upper end 31c of the main boom member 31.

[0069] The crane 101 according to the second embodiment, shown in Fig. 2, comprises two boom extensions 165, each having a lower end 165a thereof connected to the upper end 131c of the main boom member 131. The boom extensions 165 extend from the upper end 131c at equal upward angles relative to the horizontal and diverging from each other and from the jib 134 when seen in a top view of the crane 101. Therein each of the main boom departure sheaves 162 are mounted to a respective upper end 165b of the boom extensions 165.

[0070] As shown in Fig. 3 and Fig.5, in embodiments the object suspension device 13 is provided, preferably at its outer side surface 13a above the connection of the object suspension device 13 with the object 7, with cable connectors 13c, namely with three cable connectors 13c, to which each of the main boom hoist cables 63 and the jib hoist cable 53 are respectively connected or connectable. As is preferred, these are herein provided at equal mutual angles around a central vertical axis 13b of the object suspension device 13. The cable connectors 13c are pivotable around a respective vertical pivot axis 13b.

[0071] A lower part of the object suspension device 13 connected to the object 7 is rotatable relative to an upper part of the object suspension device 13 connected to the jib hoist cable and / or the main boom hoist cables, so that the object 7 is rotatable around the central vertical axis 13b of the object suspension device 13, wherein preferably the rotation of said lower part relative to said upper part is controllable by means of the control device, so that the angular position of the object 7 in its horizontal plane is controllable thereby.

[0072] Not shown in the figures is that the crane is furthermore provided with a control device, programmed to operate the variable length stay mechanism and the luffing assembly automatically.

[0073] Therein the control device is programmed to operate the one or two main boom hoist winches and jib hoist winch, so as to control the position of the object by simultaneously paying out and / or drawing in of the jib hoist cable and the main boom hoist cables in dependence of one another.

[0074] Therein the control device is furthermore programmed to operate the one or two main boom hoist winches and the jib hoist winch based on a predetermined trajectory and / or one or more reference positions of the object.

[0075] Therein the control device is furthermore programmed to operate the main boom hoist winches and jib hoist winch in dependence of the vertical and / or horizontal position and / or motions of the object.

[0076] Therein the control device is furthermore programmed to operate the main boom hoist winches and jib hoist winch by feedback control and / or feedforward control based on live measurements by sensors providing actual data on the position and / or orientation and / or motions of the object and / or the jib hoist cable and / or the main boom hoist cables to the control device.

[0077] Therein the control device is furthermore programmed to operate the main boom hoist winches and jib hoist winch independently.

[0078] In the embodiment shown in Fig.3 the main boom hoist assembly 6 comprises one main boom hoist winch 61, from which both of the two main boom hoist cables 63 extend.

[0079] In embodiments other than that shown in Fig.3 wherein furthermore the control device is provided, and the main boom hoist assembly comprises two main boom hoist winches 61, from each of which a respective one of the two main boom hoist cables 63 extends, the control device is programmed to operate each of the main boom hoist winches 61 separately.

[0080] In the shown embodiments the connection between the jib hoist cable and the object and / or the object suspension device and / or the connection between the jib hoist cable and the object and / or the object suspension device is releasable.

[0081] Furthermore the main boom hoist cables and / or jib hoist cable are connected to the object suspension device with respective terminal ends, in the first embodiment terminal ends 53a and 63a, and in the second embodiment terminal ends 153a and 163a thereof.

[0082] The following is a discussion of a method wherein a crane according to the invention is used, in relation to the figures.

[0083] In particular, the discussed embodiments of the crane are suitable for use in a method for positioning an object suspended therefrom. Figs. 4A-H show the first embodiment in different working positions in a side view of the crane. It may be understood that these positions are attainable as well with other embodiments. For the second embodiment as discussed, the following discussion in referral to the figures is correspondingly applicable as well, with the reference numerals changed by 100.

[0084] The method comprises the operation of the main boom hoist assembly 6 and the jib hoist assembly 5 such as to, synchronously, hoist and / or lower the object suspension device 13 with an object 7 connected thereto between a lower position, e.g. as shown in Fig. 4A to a position at a height up to substantially the height of the main boom departure sheaves 62 as shown e.g. in Fig. 4B, while the jib hoist cable 53 and the main boom hoist cables 63 together define a reverse pyramid that diverges upwards from the object suspension device 13.

[0085] Therein the method may comprise paying out and / or drawing in of the jib hoist cable 53 and the main boom hoist cables 63 in dependence of one another, in hoisting and / or lowering the object 7 in between a lower position e.g. as shown in Fig. 4A and a position at a height up to the height of the main boom departure sheaves 62 e.g. as shown in Fig. 4B.

[0086] The advancement from Fig. 4A to Fig.4D illustrate the method comprising the positioning of the object in a position with, and / or hoist and / or lower the object 7 along a trajectory with, a smaller horizontal distance to the first pivot axis 11 than the horizontal distance between the jib departure sheave 52 and the first pivot axis 11.

[0087] Respectively in alphabetic or reverse order these figures illustrate the object 7 being hoisted and lowered along a trajectory with a smaller horizontal distance to the first pivot axis 11 than the horizontal distance between the departure sheave 52 and the first pivot axis 11, wherein the trajectory is an straight vertical imaginary line 14.

[0088] Fig.4E and 4F show two example positions of the imaginary straight vertical line 14 along which hoisting and / or lowering is possible according to embodiments. The position of Fig. 4E is closer to the main boom departure sheave 62 than to the departure sheave 52, and that of Fig. 4F is closer to the departure sheave 52 than to the main boom departure sheave.

[0089] Not illustrated is an embodiment in which the operation of the one or two main boom hoist winches and the jib hoist winch such as to hoist and / or lower the object 7 while the angle of the jib hoist cable with respect to the plane defined by the main boom hoist cables remains constant.

[0090] As illustrated by the advancement from Fig.4A to 4B and from Fig.4E to 4F, in an embodiment of the method the jib 34 remains at the same angle with the main boom member 31 during said hoisting and / or lowering of the object 7.

[0091] Not illustrated in the figures is an embodiment in which the main boom hoist assembly 6 comprises two main boom hoist winches 61 from each of which a respective one of the two main boom hoist cables 63 extends. In this embodiment the method comprises an operation of the main boom hoist winches 61 such as to have a different length of main boom hoist cable 63 unwounded, so to position the object 7 in a position which, and / or hoist and / or lower the position along a trajectory which, in a top view of the crane 1, at least partly, extends laterally of the jib 34.

[0092] A particular option in the method is illustrated by the advancement from Fig.4A to Fig.4D. It comprises the following steps. a) suspending the object 7 in a lower position underneath the middle of the jib 34, so as to arrive at the position shown in Fig. 4A, b) operating the one or two main boom hoist winches 61 and the jib hoist winch 51 such as to draw in the main boom hoist cable 63 and the jib hoist cable 63 at a ratio such that the object 7 is hoisted along a substantially straight vertical imaginary line 14 underneath the middle of the jib 34, from the lower position and a position up to substantially the height of main boom departure sheaves 62, e.g. up to a height just below the main boom departure sheaves 62, while maintaining the jib 34 at the same angle with the main boom member 31, so as to arrive at the position shown in Fig. 4B, c) pivoting the jib 34 upwards to lift the object 7 to a height above the main boom departure sheaves 62, so that substantially the whole weight of the object 7 is therein transferred from the main boom hoist cables 63 and the jib hoist cable 53 to the jib hoist cable 53 only, wherein the one or two main boom hoist winches 61 are operated such as to pay out the main boom hoist cables 63 at a rate such that the object 7 is hoisted in line with said substantially straight vertical imaginary line 14, so as to arrive at the position shown in Fig. 4C, and d) operating the jib hoist winch 61 so as to hoist the object 7 upwards in line with said straight vertical imaginary line 14, while optionally operating the main boom hoist winches 61 to control the horizontal position and / or orientation of the object 7, so as to arrive at the position shown in Fig. 4D.

[0093] Therein the bending moment on the crane 1 around the second pivot axis 12 caused by the weight of the object 7 remains constant during steps a, b, c, and d. In this embodiment, the jib 34 has a substantially horizontal position during steps a and b, and the main boom member has a substantially vertical position during steps a, b, c and d.

[0094] As illustrated in Figs.3 and 5, in an embodiment the object suspension device 13 is provided, preferably at its outer side surface above the connection of the object suspension device 13 with the object 7, with cable connectors 13c, namely three cable connectors 13c, to which each of the main boom hoist cables 63 and the jib hoist cable 53 are respectively connected. These are provided at equal mutual angles around the central vertical axis 13b of the object suspension device. Therein the method comprises an adjustment, e.g. a corrective adjustment, of the angular position of the object 7 in its horizontal plane by pivoting the cable connectors around their vertical pivot axes.

[0095] In a not illustrated embodiment a lower part of the object suspension device 13 connected to the object 7 is rotated relative to an upper part of the object suspension device 13 connected to the jib hoist cable 53 and / or the main boom hoist cables 63, so that the object 7 is rotated around the central vertical axis 13b of the object suspension device 13. Therein preferably the rotation of said lower part relative to said upper part is controlled by means of the control device, so that said rotation and thereby the angular position of the object 7 in its horizontal plane is controlled thereby.

[0096] A particular option in the method is that it comprises the steps of: e1) paying out the main boom hoist cables 63 until the object 7 is substantially underneath the departure sheave 52, and substantially the whole weight of the object 7 is supported by the jib hoist cable 53, e.g. to arrive at the position of Fig. 4C, and g1) hoisting and / or lowering the object 7 by operating the jib hoist winch 51, wherein optionally the main boom hoist winches 61 are operated to adjust the horizontal position and / or orientation of the object by the main boom hoist cables.

[0097] A particular option in the method is that it comprises the steps of: e2) paying out the jib hoist cable 53 until the object 7 is substantially underneath the main boom departure sheaves 62, and substantially the whole weight of the object 7 is supported by the main boom hoist cables 63, e.g. so as to arrive at the position of Fig. 4G, and g2) hoisting and / or lowering the object 7 by operating the one or two main boom hoist winches 61, wherein optionally the jib hoist winch 51 is operated to adjust the horizontal position and / or orientation of the object 7 by the jib hoist cable 53.

[0098] Not illustrated in the figures is an option in the method wherein where the connection between the main boom hoist cables 63 and the object 7 and / or the object suspension device 13 is releasable, and the main boom hoist cables 63 and the jib hoist cable 53 are connected to the object suspension device 13, the method comprises the steps of: e3) paying out the main boom hoist cables 63 until the object 7 is substantially underneath the departure sheave 62, and substantially the whole weight of the object 7 is supported by the jib hoist cable 53, f3) releasing the connection between the main boom hoist cables 63 and the object 7 and / or the object suspension device 13, g3) hoisting and / or lowering the object 7 by operating the jib hoist winch 51, wherein optionally the main boom hoist winches 61 are operated to adjust the horizontal position and / or orientation of the object 7 by the main boom hoist cables.

[0099] Not illustrated in the figures is an option in the method wherein where the connection between the jib hoist cable 53 and the object 7 and / or the object suspension device 13 is releasable, and the main boom hoist cables 63 and the jib hoist cable 53 are connected to the object suspension device 13, the method comprises the steps of: e4) paying out the jib hoist cable 53 until the object 7 is substantially underneath the main boom departure sheaves 62, and substantially the whole weight of the object 7 is supported by the main boom hoist cables 63, f4) releasing the connection between the jib hoist cable 53 and the object 7 and / or the object suspension device 13, g4) hoisting and / or lowering the object 7 by operating the one or two main boom hoist winches 61.

Claims

1. A crane (1; 101), e.g. for use on a floating vessel, said crane (1; 101) comprising: • a revolving superstructure (2; 102), • a boom (3; 103), pivotally mounted to the revolving superstructure (2; 102), e.g. to a foot portion (21; 121) thereof, comprising: ∘ a main boom (30; 130), comprising a main boom member (31; 131), the lower end (31a; 131a) of which is pivotally mounted about a first pivot axis (11; 111) to the superstructure (2; 102), ∘ a jib (34; 134), pivotally mounted about a second pivot axis (12; 112) to the main boom (30; 131), comprising a jib member (35; 135), an inner end (35a; 135a) of which is pivotally mounted to the upper end of the main boom member, • a luffing assembly (4; 104) configured for luffing of the main boom, • a jib angle adjustment mechanism (32,36, 38) configured to adjust the pivot angle of the jib relative to the main boom, and • an object suspension device (13; 113) configured to be connected to an object underneath the object suspension device (13; 113), wherein the crane (1; 101) comprises a hoisting system, comprising: • one or more hoist winches (51, 61; 151, 161), • a jib hoist assembly (5; 105), comprising: ∘ a jib departure sheave (52; 152), mounted to the jib member (35; 135), e.g. to the free end (35b; 135b) thereof, and ∘ a jib hoist cable (53; 153), configured to extend from the, or one of the, one or more hoist winches (51; 151) along the main boom (30; 130) and the jib (34; 134) via the jib departure sheave (52; 152) to the object suspension device (13; 113), ∘ a jib hoist heave compensation mechanism (54), e.g. wherein the hoist winch (51; 151) from which the jib hoist cable extends is embodied as an AHC (active heave compensated) winch, or, e.g., wherein the jib hoist heave compensation mechanism comprises a heave compensating cylinder operating on the unwound section of the jib hoist cable (53; 153), characterized in that the hoisting system further comprises: • a main boom hoist assembly (6; 106) comprising: ∘ two main boom departure sheaves (62; 162), mounted to an upper end (31c; 131c) of the main boom member (31; 131) at opposite lateral sides thereof, and ∘ two main boom hoist cables (63; 163), configured to extend from the, or one or two of the, one or more hoist winches along the main boom member (31; 131) via the main boom departure sheaves (62; 162) to the object suspension device (13; 113), ∘ a main boom hoist heave compensation mechanism (66), e.g. wherein the hoist winch(es) (61; 161) from which the main boom hoist cables extend is / are embodied as AHC (active heave compensated) winch(es), or wherein the main boom hoist heave compensation mechanism comprises a heave compensating cylinder operating on a section of the main boom hoist cable (63; 163), in that the object suspension device (13; 113) is supported by the jib hoist cable (53; 153) and by the two main boom hoist cables (63; 163), and in that the main boom hoist assembly (6; 106) is adapted to, together with the jib hoist assembly (5; 105), hoist and / or lower the object suspension device (13; 113) with an object (7; 107) connected thereto, between a lower position and a position at a height up to substantially the height of the main boom departure sheaves (62; 162) while the jib hoist cable (53; 153) and the two main boom hoist cables (63; 163) together define a reverse pyramid diverging upwards from the object suspension device (13; 113).

2. Crane (1; 101) according to claim 1, wherein the main boom departure sheaves (62; 162) are mounted to lateral ends of a transverse beam (64), which transverse beam (64) is at a center portion thereof mounted to the upper end (31c; 131c) of the main boom member (31; 131).

3. Crane (1; 101) according to claim 1, wherein the crane (1; 101) further comprises two boom extensions (165), each having a lower end (165a) thereof connected to the upper end (31c; 131c) of the main boom member (31; 131), the boom extensions (165) extending from said upper end (31c; 131c) at equal upward angles relative to the horizontal and diverging from each other and from the jib (34; 134) when seen in a top view of the crane (1; 101), wherein each of the main boom departure sheaves (62; 162) are mounted to a respective upper end (165b) of the boom extensions.

4. Crane (1; 101) according to any of claims 1 - 3, wherein the one or more hoist winches (51, 61; 151, 161) consist of: • one jib hoist winch (51; 151) and one main boom hoist winch (61; 161), the jib hoist cable (53; 153) extending from the jib hoist winch (51; 151), and the two main boom hoist cables (63; 163) from the one main boom hoist winch, or • one jib hoist winch (51; 151) and two main boom hoist winches (61; 161), the jib hoist cable (53; 153) extending from the jib hoist winch (51; 151), and the two main boom hoist cables (63; 163) each from a respective one of the two main boom hoist winches (61; 161), wherein, optionally, at least the one or two main boom hoist winches (61; 161) are embodied as AHC (active heave compensating) winches, or wherein at least the main boom hoist cables (63; 163) are heave compensated by means of heave compensating cylinders operating on the unwound section of each hoist cable (53, 63; 153, 163).

5. Crane (1; 101) according to any of the preceding claims, wherein the crane (1; 101) is furthermore provided with a control device, which is programmed, • preferably, to operate a variable length stay mechanism (38; 138), when present, and the luffing assembly (4; 104) automatically, and / or • to operate the one or two main boom hoist winches (61; 161) and jib hoist winch (51; 151), so as to control the position and / or velocity of the object (7; 107) by simultaneously paying out and / or drawing in of the jib hoist cable (53; 153)) and the main boom hoist cables (63; 163) in dependence of one another, e.g. in a (pre)determined constant or dynamic ratio, and / or • when the crane (1; 101) corresponds to claim 4, to operate the main boom hoist winch(es) (61; 161) and jib hoist winch (51; 151) separately and / or independently, e.g. to separately and / or independently control horizontal and vertical movement components of the object, and / or • to operate the one or two main boom hoist winch(es) (61; 161) and the jib hoist winch (51; 151) based on a predetermined trajectory and / or one or more reference positions of the object (7; 107), and / or • to operate the main boom hoist winches (61; 161) and jib hoist winch (51; 151) in dependence of the vertical and / or horizontal position and / or motion of the object (7; 107) and / or the object suspension device and / or the vessel and / or the crane, and / or • to operate the main boom hoist winches (61; 161) and jib hoist winch (51; 151) by feedback control and / or feedforward control based on live measurements by sensors providing actual data on the position and / or orientation and / or motions of the object (7; 107) and / or the jib hoist cable (53; 153) and / or the main boom hoist cables (63; 163) to the control device.

6. Crane (1;101) according to any of the preceding claims, wherein the object suspension device is provided with a sensor, e.g. radar, adapted to determine the position thereof relative to one or more beacons, e.g. a beacon mounted on a nacelle or top of the mast of a wind turbine, so that the object suspension device is directly correlated as to its position relative to the nacelle and / or top of the mast, wherein any motions of the mast and / or nacelle are directly accounted for in the control of the crane during lifting or lowering of a wind turbine component.

7. Crane (1; 101) according to any of the preceding claims, wherein the jib (34; 134) of the crane further comprises: • a jib strut (36; 136), an end (36a; 136a) of which is mounted to the inner end of the jib member (35; 135) and extending essentially perpendicular to the jib member (35; 135), and • a jib stay (37; 137) extending between the jib strut (36; 136) and the jib member (35; 135), and wherein the main boom (30; 130) further comprises: • a main boom strut (32; 132), an end (32a; 132a) of which is mounted to an upper end of the main boom member (31; 131) and extending essentially perpendicular to the main boom member (31; 131), and • a boom stay (33; 133) extending between the main boom strut (32; 132) and a lower portion (31b; 131b) of the main boom member (31; 131), and the boom (3; 103) further comprises a variable length stay mechanism (38; 138) provided between the main boom strut (32; 132) and the jib strut (36; 136), wherein, preferably, the luffing assembly (4; 104) of the crane further comprises: • a luffing winch, mounted to the superstructure (2; 102), and • a luffing cable (42; 142) extending between the luffing winch and the main boom (30; 130).

8. Crane (1; 101) according to any of the preceding claims, wherein the main boom hoist cables (63; 163) are each arranged in a double-fall arrangement, wherein the main boom hoist assembly (6; 106) comprises two pairs of main boom departure sheaves (62; 162), each pair of main boom departure sheaves being mounted to an upper end (31c; 131c) of the main boom member (31; 131) at opposite lateral sides thereof, and further comprises two main boom spreader sheaves, each connected to the object suspension device (13; 113), e.g. via a respective spreader cable or e.g. by means of a respective spreader beam, and wherein the main boom hoist cables (63; 163) are each configured to extend from one of the hoist winches along the main boom member (31; 131) successively via one main boom departure sheave (62; 162) of a respective pair of main boom departure sheaves, a respective one of the two main boom spreader sheaves, and the other main boom departure sheave (62; 162) of the respective pair of main boom departure sheaves to the one of the hoist winches, and / or wherein the jib hoist cable (53; 153) is arranged in a double-fall arrangement, wherein the jib hoist assembly (5; 105) comprises a pair of jib hoist sheaves (52; 152), mounted to the jib member (35; 135), e.g. to the free end (35b; 135b) thereof, and further comprises a jib spreader sheave, connected to the object suspension device (13; 113), e.g. via a spreader cable or e.g. by means of a spreader beam, and wherein the jib hoist cable (53; 153) is configured to extend from one of the hoist winches along the main boom (30; 130) and the jib (34; 134) successively via one jib departure sheave (52; 152) of the pair of jib hoist sheaves, the jib spreader sheave, and the other jib departure sheave (52; 152) of the pair of jib hoist sheaves to the one of the hoist winches.

9. Crane according to any of the preceding claims, wherein the object suspension device (13; 113) is provided, preferably at its outer side surface (13a; 113a) above the connection of the object suspension device (13; 113) with the object (7; 107), with cable connectors (13c; 113c), preferably three cable connectors (13c; 113c), to each of which a respective hoist cable (53, 63; 83a, 83b, 83c; 153, 163) is connectable or connected, preferably provided at equal mutual angles around a central vertical axis (13b; 113b) of the object suspension device (13; 113), wherein the cable connectors (13c; 113c) are preferably pivotable around a respective vertical pivot axis.

10. Crane (1; 101) according to any of the preceding claims, wherein a lower part of the object suspension device (13; 113) connected to the object (7; 107) is rotatable relative to an upper part of the object suspension device (13; 113) connected to the hoist cables, so that the object (7; 107) is rotatable around a central vertical axis (13b; 113b) of the object suspension device (13; 113), wherein the rotation of said lower part relative to said upper part is preferably controllable by means of the control device, if present, so that the angular position of the object (7; 107) in its horizontal plane is controllable thereby.