MARINE KNUCKLE BOOM CRANE

Abstract

A marine knuckle boom crane includes a pedestal and a crane housing rotational relative to the pedestal. A knuckle boom assembly is attached to the crane housing and includes a main boom and a spreader type jib. A hoisting system includes a first departure sheave and a second departure sheave on the jib, and a third departure sheave mounted to the main boom or to the crane housing. One or more winches drive a first, second, and third cable which are each connected to an object suspension device and each pass via the first, second, and third departure sheave, respectively, to the respective winch. The first, the second, and the third cable together define an inverted pyramid which diverges upwards from the object suspension device when handling the object.

Claims

1. A marine knuckle boom crane comprising: a pedestal; a crane housing which is rotational relative to the pedestal about a vertical rotation axis; a knuckle boom assembly attached to the crane housing, the knuckle boom assembly comprising: a main boom having an inner end connected pivotally about a first horizontal pivot axis to the crane housing, an outer end, a topside, a bottom side, and opposed lateral sides; and a jib connected via a pivot structure pivotally to the main boom the jib having a central longitudinal axis; a main boom luffing mechanism configured to pivot the main boom up and down relative to the crane housing; a jib pivoting mechanism configured to pivot the jib relative to the main boom, between a folded position of the knuckle boom assembly, in which the jib is folded back relative to the main boom, and extended positions of the knuckle boom assembly; and a hoisting system, comprising at least one departure sheave mounted on the jib, wherein the jib is a spreader structure jib having a load bearing spreader structure of which a base end connects to the pivot structure, which spreader structure supports remote from said base end a first departure sheave and a second departure sheave of the hoisting system, said first and second departure sheave being laterally spaced from one another at opposed lateral sides of the central longitudinal axis, wherein the hoisting system further comprises: a third departure sheave mounted to the main boom and/or to the crane housing; one or more winches; a first cable driven by one of said one or more winches; a second cable driven by one of said one or more winches; a third cable driven by one of said one or more winches; and an object suspension device configured to be connected to an object to be handled by the crane, wherein the first, the second, and the third cable are each connected to the object suspension device and respectively pass via the first, second, and third departure sheave, to the respective winch of said one or more winches, wherein the first, the second, and the third cable together define an inverted pyramid which diverges upwards from the object suspension device when handling the object.

2. The crane according to claim 1, wherein the position of the third departure sheave is closer to the inner end of the main boom than the position of any of the first and second departure sheaves when the knuckle boom assembly is in the folded position thereof.

3. The crane according to claim 1, wherein the spreader structure of the jib is rigid.

4. The crane according to claim 1, wherein the spreader structure of the jib is collapsible between a collapsed configuration and a spread configuration, wherein the lateral extension of the spreader structure is smaller in the collapsed configuration than in the spread configuration.

5. The crane according to claim 3, wherein the jib is a rigid forked jib, the spreader structure having a jib base connected to the pivot structure and comprising a first and a second jib branch diverging laterally outward from the jib base with a fixed angle between the diverging first and second jib branches.

6. The crane according to claim 4, wherein the jib is a collapsible forked jib, the spreader structure comprising a first and second jib branch that are each pivotally mounted, such that the first and second jib branch are pivotal around respective jib branch pivot axes between the spread configuration of the forked jib in which the jib branches are diverging laterally outward and the collapsed configuration in which the jib branches are closer to the central longitudinal axis.

7. The crane according to claim 6, wherein the collapsible forked jib comprises a jib base that is connected pivotally about a second horizontal pivot axis to the main boom are each pivotally mounted, to the jib base for pivoting between the spread and collapsed configuration.

8. The crane according to claim 6, wherein the first and second jib branch are each at a base end thereof connected via a respective pivot structure to the main boom, so as to be both movable between the folded positions and extended positions of the knuckle boom assembly, as well as between the spread configuration and the collapsed configuration of the collapsible forked jib.

9. The crane according to claim 6, wherein the first and second jib branch are each pivotal between the collapsed position, and one or more spread positions in which the angle between the diverging first jib branch and second jib branch is between 20° and 80°.

10. The crane according to claim 6, wherein the first and second jib branch are each independently pivotal into multiple spread configurations of the jib, allowing for respective jib branch angles relative to the central longitudinal axis of the forked jib to differ from one another.

11. The crane according to claim 6, wherein the first and second jib branch are symmetrically pivotal into one or more spread configurations of the forked jib, so that the respective jib branch angles relative to the central longitudinal axis of the forked jib are equal to one another.

12. The crane according to claim 6, comprising one or more jib branch actuators configured to drive a pivoting of the first and/or of the second jib branch which varies the angle of divergence between them.

13. The crane according to claim 4, wherein the spreader structure is movable into multiple spread configurations to allow for setting of different lateral spacing distances between the first and second departure sheave, the spreader structure comprising one or more actuators to move the spreader structure between the collapsed configuration and the spread configuration, wherein the one or more actuators are configured to vary the lateral spacing between the first and second departure sheave during a hoisting and/or lowering of the object suspension device.

14. The crane according to claim 6, comprising one or more jib branch actuators configured to drive a pivoting of the first and/or of the second jib branch which varies the angle of divergence between them, wherein the spreader structure is movable into multiple spread configurations to allow for setting of different lateral spacing distances between the first and second departure sheave, the spreader structure comprising one or more actuators to move the spreader structure between the collapsed configuration and the spread configuration, wherein the one or more actuators are configured to vary the lateral spacing between the first and second departure sheave during a hoisting and/or lowering of the object suspension device, wherein the one or more jib branch actuators are configured to drive a pivoting of the jib branches during a hoisting and/or lowering of the object suspension device.

15. The crane according to claim 6, wherein the collapsible forked jib comprises a jib branch actuator, configured to extend and contract such as to move a mobile section thereof along the central longitudinal axis, wherein the collapsible forked jib comprises a first and second transverse bar each being pivotally connected to the mobile section with one longitudinal end thereof, and with another longitudinal end thereof to the first and second jib branch, respectively, such that extension and contraction of the jib branch actuator pivots each of the jib branches about the respective jib branch pivot axis via the transverse bars and moves the jib branches between the collapsed configuration and at least one spread configuration.

16. The crane according to claim 1, wherein the one or more winches are mounted on the crane housing, and wherein the first and second cable extend, seen in top view, above the topside of the main boom to a respective cable guide sheave for the first cable and a respective cable guide sheave for the second cable, said cable guide sheaves being mounted on the main boom in proximity to the pivot structure that pivotally connects the jib to the main boom, and wherein the spreader structure is provided with a guide sheave for the first cable and a guide sheave for the second cable that are mounted at the base end of the spreader structure.

17. The crane according to claim 1, wherein the object suspension device is suspended via each of the first, second, and third cable in a multi-fall arrangement, the hoisting system further comprising for the first, second and third hoisting cable a respective first, second, and third return sheave connected to the object suspension device over which the first, second and third hoisting cables are run, respectively.

18. The crane according to claim 1, wherein the hoisting system further comprises a fourth departure sheave and a fifth departure sheave, wherein the fourth departure sheave is mounted to the spreader structure in the plane of the first departure sheave with the first cable running in between the first and fourth departure sheave, such that in the folded position of the knuckle boom assembly the first cable runs over the fourth departure sheave, and in extended positions of the knuckle boom assembly the first cable runs over the first departure sheave, and wherein the fifth departure sheave is mounted to the spreader structure in the plane of the second departure sheave with the second cable running in between the second and fifth departure sheave, such that in the folded position of the knuckle boom assembly the second cable runs over the fifth departure sheave, and in extended positions of the jib the second cable runs over the second departure sheave.

19. The crane according to claim 17, further comprising a twofold actuated active suspension adjustment mechanism which comprises: a first sheave pair and a second sheave pair, each of the sheave pairs comprising a primary sheave and a secondary sheave which are interconnected such as to enable two of the first, second, and third cables to run over the sheaves of the sheave pair in opposite directions; a first adjustment actuator and a second adjustment actuator, each configured for moving respectively the first and second sheave pair in the direction of the two cables running over the sheaves of the respective sheave pair, wherein the first cable is reeved from the respective winch via: the primary sheave of the first sheave pair; the first departure sheave; and the first return sheave, to a location on the crane where a dead end of the first cable is fixed, wherein the second cable is reeved from the respective winch via: the primary sheave of the second sheave pair; the second departure; and the second return sheave, to a location on the crane where a dead end of the second cable is fixed, wherein the third cable is reeved from the respective winch via: the secondary sheave of the second sheave pair; the third departure sheave; the third return sheave; a third guide sheave paired with the third departure sheave on the main boom and/or on the crane housing; and the secondary sheave of the first sheave pair, to a location on the main boom or the crane housing where a dead end of the third cable is fixed, wherein the first adjustment actuator is configured to move the first sheave pair such as to selectively increase or decrease the part of the length of the first cable between the respective winch and the first departure sheave and simultaneously respectively decrease or increase the part of the length of the third cable between the third guide sheave and the dead end of the third cable, wherein the second adjustment actuator is configured to move the second sheave pair such as to selectively increase or decrease the part of the length of the second cable between the respective winch and the second departure sheave and simultaneously respectively decrease or increase the part of the length of the third cable between the respective winch and the third departure sheave.

20. A marine vessel or offshore structure provided with the crane according to claim 1.

21. A method for hoisting an object, comprising using the crane according to claim 1.

22. A method for hoisting an object, comprising using the crane according to claim 19, wherein the two-fold actuated active suspension adjustment mechanism is operated to provide a primarily horizontal controlled motion of the object suspension device, and wherein the one or more winches are operated to provide primarily vertical motion of the object suspension device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0194] The invention will now be described with reference to the appended drawings. In the drawings:

[0195] FIG. 1a shows in a perspective view a first embodiment of the crane according to the invention,

[0196] FIG. 1b shows the first embodiment in another perspective view, along with three magnifications of details,

[0197] FIG. 1c shows the first embodiment in yet another perspective view, along with a magnification of another detail,

[0198] FIG. 2a shows the first embodiment in a front view,

[0199] FIG. 2b shows the first embodiment in a side view,

[0200] FIG. 2c shows the first embodiment in a top view,

[0201] FIG. 2d shows the forked jib of the first embodiment,

[0202] FIG. 3a-c show in a side and two top views the jib of a second embodiment of the crane according to the invention,

[0203] FIG. 4a,b show in a side and top view the second embodiment of the crane according to the invention,

[0204] FIG. 4c shows the second embodiment in a side view in three positions,

[0205] FIG. 5a shows the crane of FIGS. 4a,b on a floating drilling vessel for transfer of objects between said drilling vessel and a supply vessel,

[0206] FIGS. 5b,c show the crane on the drilling vessel in multiple positions,

[0207] FIG. 6a-c schematically show in a two-dimensional visualisation the hoisting system and the active suspension adjustment system according to the invention,

[0208] FIG. 6d schematically shows in a three-dimensional visualisation the hoisting system and the active suspension adjustment system of FIGS. 6a-c,

[0209] FIGS. 6e-f schematically show in a two-dimensional visualisation the hoisting system and another active suspension adjustment system according to the invention,

[0210] FIG. 6g schematically shows in a three-dimensional visualisation the hoisting system and the active suspension adjustment system of FIGS. 6e-f,

[0211] FIGS. 7a-b schematically show in a side and top view a jib of a third embodiment of the crane according to the invention,

[0212] FIG. 7c schematically shows in a perspective view the suspension of the object suspension device from the hoisting cables of the third embodiment,

[0213] FIGS. 8a,b schematically show in a side and top view the jib of a fourth embodiment of the crane according to the invention,

[0214] FIG. 9 shows a schematic comparison of spatial arrangements of departure sheaves in an inverted pyramid configuration of the three cables,

[0215] FIG. 10 shows a fifth embodiment of the crane according to the invention,

[0216] FIG. 11 shows a sixth embodiment of the crane according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0217] The FIGS. 1, 2 and 3 illustrate a first embodiment of the marine knuckle boom crane 1 according to the invention. For example, the crane 1 is embodied to handle ISO shipping containers, e.g. 40 ft. containers, and other objects. For example, crates for transportation of drilling tubulars, e.g. drill pipe, casing pipe, are to be handled by the crane. For example, the object to be handled may have a maximum weight of 50 tons. As explained herein, the inventive concepts may be applied to larger and smaller cranes than illustrated in the drawings.

[0218] The marine knuckle boom crane 1 comprises a pedestal 2a, a crane housing 2b which is rotational relative to the pedestal 2a about a vertical rotation axis 3v, and a knuckle boom assembly 3 attached to the crane housing 2b. A slew bearing 2f is present between the pedestal 2a and the crane housing.

[0219] The pedestal 2a may be a closed contour, hollow box type pedestal, e.g. of a four sided horizontal cross-section as shown. Other embodiments, e.g. as a cylindrical hollow pedestal or as an open framework are also possible, for example.

[0220] The crane housing 2b, in this example, is provided with an operators cabin 2c for accommodating a human crane operator.

[0221] The pedestal 2a is provided with an access platform 2a1 extending about the pedestal 2a and the crane housing 2b is provided with a ladder 2d allowing the crane operator to gain access to the operators cabin 2c via the access platform and the ladder. For example, as here, the pedestal is provided with a stair arrangement 2e to gain access to the elevated access platform 2a1.

[0222] The knuckle boom assembly 3 is composed of a main boom 4 and a spreader type jib 5, here a collapsible forked jib.

[0223] The main boom 4 has an inner end 41 which is connected pivotally about a first horizontal pivot axis 3h1 to the crane housing 2b and has an outer end 43. The main boom 4 is a rigid, unitary structure, e.g. of steel.

[0224] The main boom has a top side 4a, a bottom side 4b, and opposed lateral sides. The cross-section of the main boom may be, e.g. over a major portion of its length, rectangular, as shown, but other cross-sections, e.g. cylindrical, triangular, oval, octagonal, are also possible.

[0225] A main boom luffing mechanism, here comprising a pair of parallel hydraulic cylinders 31, is mounted between the housing 2b and the main boom 4 and is configured to provide luffing motion of the main boom 4 relative to the crane housing 2a.

[0226] In another embodiment of the luffing mechanism, the crane housing 2a is extended upwards, above the luffing pivot axis, and a cable type luffing mechanism extends between an elevated position of the housing, e.g. the top of the housing, and the main boom.

[0227] Being attached to the crane housing 2b, the knuckle boom assembly 3 is, rotational relative to the pedestal 2a about a vertical rotation axis 3v. This is commonly referred to as a slew motion of the crane 1. Preferably, the housing 2b can revolve about 360 degrees, but more limited slew ranges are also possible. A slew drive is provided to effect the slew motion about axis 3v.

[0228] The forked jib 5 comprises: [0229] a jib base 52 that is connected pivotally about a second horizontal pivot axis 3h2 to the main boom 4, here to the outer end 43 thereof as is preferred, [0230] a first jib branch 56 and a second jib branch 57 having a first jib tip 53 and a second jib tip 54, respectively. Herein the first jib branch and second jib branch diverge from the jib base 52 laterally outwardly relative to a central longitudinal axis 5g of the forked jib 5, such that the first jib tip 53 is arranged spaced from the second jib tip 54 in a lateral direction with respect to the central longitudinal axis 5g.

[0231] A forked jib pivoting mechanism 32, here with a single hydraulic cylinder 32, is mounted between the main boom 4 and the jib base 52 and is configured to pivot the forked jib 5 relative to the main boom 4 for folding and extending of the jib 5.

[0232] The cylinder body of cylinder 32 is connected to the underside of the main boom 4 at the gland side of the cylinder body, so where the piston rod extends from the cylinder body. The main boom 4 is provided with a slot 14 in proximity of this cylinder 32 allowing for the cylinder body to move into the slot, e.g. when folding the jib to the most folded position. As preferred, the slot 14 extends from the bottom side to the top side of the main boom 4 allowing the cylinder to protrude above the main boom during folding.

[0233] As explained herein, in alternative designs, pivoting of the main boom and/or of the jib may be effected by a mechanism comprising a winch and a cable. For example, the jib 5 may be embodied with a lever structure opposite from the spreader type structure relative to the pivot about axis 3h2. A cable mechanism can then be employed for extending the jib. If desired, a pull-in cable and winch can be provided to pull the jib into the complexly folded position.

[0234] The crane 1 further comprises a hoisting system 6, which includes: [0235] a first departure sheave 61a on the first jib branch 56, here mounted proximate to the first jib tip 53, [0236] a second departure sheave 62a on the second jib branch 57, here mounted proximate to the second jib tip 54, [0237] a third departure sheave 68 mounted to the main boom 4, [0238] one or more winches, here a first, a second, and a third winch 671, 67b, 67c, said one or more winches here being mounted on the crane housing 2b, [0239] a first cable 63 driven by the first winch 67a, [0240] a second cable 64 driven by the second winch 67b, [0241] a third cable 65 driven by the third winch 67c, [0242] an object suspension device 66 configured to be connected to an object 102 to be handled by the crane 1.

[0243] As can be seen, the first, the second, and the third cable 63, 64, 65 are each connected to the object suspension device 66 and each pass via the first, second, and third departure sheave 61a, 62a, 68, respectively, to the respective winch. The first, the second, and the third cables 63, 64, 65 together define an inverted pyramid which diverges upwards from the object suspension device 66 when handling the object 102.

[0244] In the FIGS. 1, 2, and 3, the object suspension device 66 is suspended via each of the first, second, and third cables 63, 64, 65 in a double-fall, arrangement. The hoisting system 6 further comprises for the first, second and third hoisting cable a respective first, second, and third return sheave 71, 72, 73 connected to the object suspension device 66 over which the first, second and third hoisting cables are run, respectively.

[0245] The forked jib 5 here is a collapsible forked jib, in which the first and second jib branches 56, 57 are each pivotally mounted to the jib base 52 about respective jib branch pivot axes 56v, 57v, such that the first and second jib branches 56,57 are pivotal between a collapsed configuration (FIG. 3b) and a spread configuration of the forked jib 5.

[0246] Each of the first and second jib branches 56,57 is pivotal between: [0247] a collapsed position in which the branch extends parallel to the central longitudinal axis of the forked jib (FIG. 3b), [0248] one or more spread positions in which the angle 55α between the diverging first jib branch 56 and second jib branch 57 is between 20° and 80°, e.g. 40° as shown, e.g. the respective jib branch angles 56α,57α both having an angle of 20° relative to the central longitudinal axis 5g of the forked jib.

[0249] FIG. 5a shows the crane 1, here two cranes 1, being mounted at the side of the deck box a semi-submersible vessel 101, here a drilling vessel 101, to facilitate transfer of objects between the vessel 101 and a supply vessel 105.

[0250] It can be seen in FIG. 5a, that when folded, a rigid forked jib would require considerable space in case the entire jib is to be parked within the contour of the deck of the vessel. The latter is a common requirement. The provision of a collapsible jib allows for the folded knuckle boom assembly to have dimensions similar to prior art knuckle boom cranes. This allows for parking of the folded boom parallel to the side of the vessel.

[0251] In this embodiment of FIG. 1, the first and second jib branches 56, 57 are symmetrically pivotal into one spread configuration of the forked jib, here by a common jib branch actuator 59, so that the respective jib branch angles 56α,57α relative to the central longitudinal axis 5g of the forked jib are equal to one another.

[0252] In this example, the one jib branch actuator 59 is configured to drive a pivoting of the first and of the second jib branch 56,57 to vary the angle 55α of divergence between them. Here, the one jib branch actuator 59 is arranged between the jib base 52 and both of the jib branches 56, 57. In an alternative embodiment, an actuator 59 is arranged between the jib branches 56, 57.

[0253] In more detail, the FIGS. 1,2, and 3 show that the collapsible forked jib 5 comprises a jib branch actuator, e.g. linear jib branch actuator, e.g. a cylinder 59, that is mounted to the jib base 52 and is configured to extend and contract such as to move a mobile section thereof, e.g. a piston rod, along the central longitudinal axis 5g. The collapsible forked jib 5 further comprises a first and second transverse bar 58, each being pivotally connected to the mobile section with one longitudinal end thereof, and with another longitudinal end thereof to the first and second branch 56, 57, respectively, such that extension and contraction of the jib branch actuator 59 pivots each of the jib branches 56, 57 about the respective pivot axis 56v, 57v via the transverse bars 58 and moves the jib branches between the collapsed configuration and the spread configuration.

[0254] It is shown, that the transverse bars 58 and the jib branch actuator 59 form a locking mechanism configured to secure the jib branches 56,57 in a spread configuration, e.g. so as to withstand a collapsing due to the object being handled by the crane and the cables 63, 64 urging the jib branches 56, 57 to the collapsed configuration. Another locking mechanism to avoid uncontrolled collapsing of the jib branches can also be provided.

[0255] For example, as shown here, the first and second transverse bars 58 are pivotal into a locking position, e.g. an overcentre position in which the inner ends of the bars 58 have been moved beyond an imaginary line through the outer ends of the bars 58 so that collapsing of the jib branches is only possible by actuated motion of the inner ends by the actuator 59. This is shown in FIG. 3c, for example.

[0256] The winches 67a, b, c are distinct and independently operable winches. In an embodiment, one or more of the winches 67a,b,c are embodied as AHC-winches.

[0257] The winches 67a, b, c are mounted on the crane housing 2b as is preferred.

[0258] A cable guide sheave 85 for the first cable 63 and a cable guide sheave 86 for the second cable 64 are mounted at the outer end 34 of the main boom 4, here rotatable about an axis coinciding with the second horizontal pivot axis 3h2 as is preferred.

[0259] A further guide sheave 87 for the first cable 63 and a guide sheave 88 for the second cable 64 are mounted to the jib base 51, e.g. each revolving about an axis coinciding with the respective jib branch pivot axis 56v, 57v.

[0260] A cable guide sheave 89 for the third cable 65 is mounted at the outer end of the main boom 4, with the cable 65 passing from the respective winch 67c, along the top side of the main boom, to said sheave. There the cable 65 is guided to the underside of the main boom 4, to extend to the third departure sheave.

[0261] The FIGS. 1, 2, and 3 show that the jib base 52 has a main body 52a that is provided with laterally spaced bracket arms 52b at the inner end, which arms 52b each connect via pivot to the main boom 4 at the outer end 43 thereof. The jib branches 56, 57 are each pivotally connected to the main body 52a of the jib base.

[0262] It is shown that the third departure sheave 68 is attached to the main boom 4. As an alternative the sheave is attached to the crane housing 2b, or to a structure extending between the main boom 4 and the crane housing 2b, e.g. to the pivot mechanism for the main boom.

[0263] The third departure sheave 68 is located between the pair of boom pivoting cylinders 31, so closer to the inner end of the main boom 4 than the points where the boom pivoting cylinders 31 engage on the main boom.

[0264] The position of the third departure sheave 68 is closer to the inner end 41 of the main boom 4 than the position of any of the departure sheaves 61a, 62a on the jib branches 56, 57 when the knuckle boom assembly 3 is in a folded position (FIG. 4a) thereof. This, for example, allows for the enhanced stabilization of the object suspension device 66 irrespective of the angular orientation of the main boom 4 and the jib 5. So, as shown in FIG. 1, even when hoisting is done at relatively closer range to the pedestal 2a, a stabilizing relative wide angle between the cables 63, 64, 65 is obtained.

[0265] For example, the pedestal 2 is configured to be stationary secured, e.g. welded, to a vessel or to another offshore structure. For example, as illustrated, the vessel 101 is a floating drilling vessel, e.g. a semi-submersible type vessel for drilling subsea wellbores. For example, the pedestal is welded on the deck box structure of the vessel at a side thereof.

[0266] For example, as illustrated, the pedestal 2 is secured to the outer side of the deck box structure of a semi-submersible vessel or to the outer side of the hull of another type of vessel.

[0267] For example, the crane 1 is to be used for the transfer of an object 102 between the deck of a supply vessel 105 and the deck of another vessel 101, the crane being mounted on said other vessel.

[0268] For example, the crane 1 is mounted on a vessel having a deck wherein the object is to be lifted that is located higher than the deck of the supply vessel 105. It will be appreciated that a similar transfer of objects is present between a supply vessel 105 and a stationary offshore platform. Commonly, in the situation of a supply vessel 105, the crane 1 will be arranged on the other vessel or offshore platform having the higher deck.

[0269] The objects 102 to be handled are, for example, drilling tubulars, e.g. crates containing drilling tubulars such as drill pipe or casing pipe. Or the objects are shipping containers, or any other object.

[0270] The main boom 4 has a longitudinal main boom axis 4g, an inner end 41, and an outer end 43.

[0271] The inner end 51 of the jib 5 is connected pivotally about a second horizontal pivot axis 3h2 to the outer end 43 of the main boom 4, such as to enable adjustment of the jib angle 5γ of the jib 5.

[0272] As shown in the figures, the jib 5 is pivotal about the second horizontal pivot axis 3h2 at least between extended positions 3e of the knuckle boom assembly 3 and a folded position 3f of the knuckle boom assembly 3 in which the jib 5 is folded back under the main boom 4, e.g. in view of compact parking of the crane when not in use.

[0273] In the folded position, for example, the central longitudinal axis 5g may extend generally parallel along the underside of the main boom 4. Accordingly, in the folded position 3f the jib angle 5γ may approach zero.

[0274] The knuckle boom assembly can be parked in folded position, with the main boom 4 being generally horizontal, with or without the use of a boom rest, as is known in the art.

[0275] It may also be possible to park the knuckle boom assembly in an extended position, e.g. with the jib branches resting on a support, e.g. on a deck of the vessel, e.g. the jib branches being spread in the parked position to provide an extra stable parked position.

[0276] For example, as here, the object suspension device 66 is embodied with a hook.

[0277] For example, the hook is a swivelling hook that can be swivelled about a vertical axis in the device 66. For example, the swivel motion is controlled by a swivel drive of the device 66.

[0278] In an embodiment, the object suspension device 66 includes a lifting frame suspended from the hook, with the lifting frame being connectable to an object to be handled, e.g. an elongated crate or shipping container.

[0279] In an embodiment, the object suspension device 66 and/or any lifting frame to be suspended therefrom for connecting to an object to be handled is provided with a gyroscopic stabilizer.

[0280] It is shown that the third departure sheave 68 is located at a position along the longitudinal axis 4g of the main boom 4 relatively proximate the inner end 41 of the main boom 4, which results in relatively large vertical angles of the cables 63, 64, 65, facilitating the stability and controllability of the object suspension device 66 and the connected object 102.

[0281] The position of the third departure sheave 68 is in a direction along the longitudinal axis 4g of the main boom 4 closer to the inner end 41 than the jib tips 53, 54 and/or sheaves 61a,62a when the knuckle boom assembly 3 is in the completely folded position 3f. This creates stability for the object suspension device in operation of the crane. It also makes that the third cable 65 extends, in the longitudinal direction 4g of the main boom 4, at the side of the object suspension device 66 at which the inner end 41 of the main boom 4 is located, and the first and second cable 63, 64 extend longitudinally at the other side of the object suspension device 66. This may result in a reduced risk for entanglement of the cables 63, 64, 65 and in a more convenient running of the cables over the departure sheaves 61a, 62a, 68.

[0282] The pivoting of the jib 5 around the second horizontal pivot axis 3h2 is driven by controlled extension and contraction of a hydraulic cylinder 32 which is operable between the main boom 4 and the jib 5, being pivotally mounted to the main boom and to the jib base 52.

[0283] FIGS. 1, 2, and 3 show that the jib branches 56, 57 make up the major part of the jib length and the jib base 52 makes up only a minor part, so that the forked jib 5 essentially has the shape of a V when in the spread configuration.

[0284] It is illustrated, that the first and second jib branches 56, 57 are each pivotally mounted to the jib base 52, so that the first and second jib branch are pivotal towards and away from the central longitudinal axis 5g of the jib 5 around respective jib branch pivot axes 56v, 57v. The pivotability of the jib branches 56, 57 results in a changeability of the lateral distance between the departure sheaves 61a, 62a.

[0285] In this embodiment the jib branches 56, 57 are pivotal in unison, the jib branch angles 56α, 57α with respect to the central longitudinal axis 5g of the jib 5 remaining equal to each other.

[0286] FIG. 1a shows the first departure sheave 61a and a first guide sheave 69 being mounted laterally adjacent to one another proximate the first jib tip 53. It shows the reeving of the first cable 63 via the first departure sheave 61a to the first return sheave 71, back to the guide sheave 69 and a dead end fixing location 63c, where it is fixed to the jib branch 56.

[0287] Similarly, the second cable 64 runs via the second departure sheave 62a mounted proximate the second jib tip 54 to the second return sheave 72, back to a second guide sheave 69 mounted laterally adjacent the second departure sheave 62a and to a dead end fixing location 64c, where it is fixed to the jib branch 57.

[0288] The adjacent arrangement of the departure sheaves 61a, 62a and the first and second guide sheaves 69 as well as the fixing locations 63c, 64c are shown in detail.

[0289] It is also shown that the third departure sheave 68 and the third guide sheave 69 over which the third hoist cable 65 runs, are mounted adjacent one another on the boom 4.

[0290] Referring in particular to FIG. 1b, the departure sheaves 61a, 62a, and the first and second guide sheaves 69, are each pivotal about an axis parallel to the longitudinal axis 56g, 57g of the first and second jib branch 56, 57 respectively.

[0291] FIGS. 1,2 show in detail an embodiment of the arrangement of the first, second and third winches 67a,b,c on the crane housing 2, and the extension of respectively the first, second and third hoist cable 63, 64, 65 therefrom.

[0292] Furthermore they show in detail an embodiment of the pivotal mounting of the departure sheave and the associated guide sheave mounted adjacent thereto proximate the jib tip. These are mounted pivotally around the indicated pivot axes, e.g. parallel to the longitudinal axis of the jib branch, the pivot directions also being indicated.

[0293] As best seen, also the third departure sheave 68 and the adjacent third guide sheave 69 may be mounted in the same fashion to the boom 4 to be pivotal. The pivotal mountings enables these sheaves to remain aligned with the hoist cables at different vertical hoist cable departure angles 63γ, 64γ, 65γ thereof.

[0294] FIG. 1b shows a detail of the pivotal mounting of the return sheaves 71, 72, 73 to the object suspension device 66. The return sheaves are pivotal in two perpendicular directions, a first being indicated for the first return sheave 71 and a second for the second return sheave 72. The pivotability facilitates the functioning of the departure sheaves 61a, 62a, 68 as it allows for the alignment thereof with the cables at different vertical departure angles of the cables 63γ, 64γ, 65γ, e.g. which may change during hoisting and lowering of the object and during pivoting of the jib branches 56, 57.

[0295] FIGS. 2a-d indicate the longitudinal axes 4g, 5g, 56g, 57g, of respectively the main boom 4, the jib 5, the first and second jib branch 56, 57, the first and second horizontal pivot axis 3h1, 3h2 and the main boom angle 4γ and 5γ resulting from pivoting the main boom 4 and the jib 5 there around.

[0296] To facilitate the operation of the departure sheaves 61a, 62a, 68, alignment thereof with the cables 63, 64, 65 while respective vertical angles 63γ, 64γ, 65γ change is enabled by the crane 1. The departure sheaves 61a, 62a, are thereto pivotally mounted to the first and second jib tip 53, 54, respectively, such as to allow alignment thereof with the first and second cable 63, 64 while the vertical angles 63γ, 64γ change, including during hoisting and lowering of the object suspension device 66 and pivoting of the boom 4 and/or the jib 5 around the horizontal pivot axes 3h1, 3h2. The third departure sheave 68 is pivotally mounted to the main boom 4 as well in a similar fashion to allow alignment with the third hoist cable 65.

[0297] The FIGS. 1, 2, and 3 also illustrate the provision of a two-fold actuated active suspension adjustment mechanism 7. This mechanism 7 is explained in more detail with reference to FIGS. 6a-d.

[0298] In an embodiment, one or both jib branches are also configured for securing a tool to the jib tip thereof, e.g. a line grabbing tool, e.g. for use in anchor handling operations.

[0299] FIGS. 3a-c, 4a-c show a second embodiment of the crane 1 according to the invention. The crane 1 largely corresponds to the crane according to the first embodiment, so that the above description relating thereto applies to this second embodiment as well.

[0300] The hoisting system 6 of the crane 1 according to the second embodiment comprises, in addition to the first departure sheave 61a, also a fourth departure sheave 61b which is also mounted to the first jib tip 53. The hoisting system 6 also comprises, in addition to the second departure sheave 62a, a fifth departure sheave 62b, mounted to the second jib tip 54. Whether in the second embodiment the first cable 63 extends from the first or fourth departure sheave 61a/b, and whether the second cable 64 extends from the second or fifth departure sheave 62a/b, depends on the position of the jib 5.

[0301] The first and fourth departure sheave 61a, 61b are mounted to the first jib tip 53 such as to extend in the same plane, with the first cable 63 running in between the first departure sheave 61a and fourth departure sheave 61b, such that in more folded positions of the jib 5 the first cable 63 runs over the fourth departure sheave 61b, see FIG. 4a. In more extended positions of the jib 5, shown in FIG. 5b, the first cable 63 runs over the first departure sheave 61a.

[0302] Correspondingly the second and fifth departure sheave 62a, 62b are mounted to the second jib tip 54 such as to extend in the same plane, with the second cable 64 running in between the second departure sheave 62a and fifth departure sheave 62b, such that in some folded positions of the jib 5 the second cable 64 runs over the fifth departure sheave 62b, and in the more extended positions of the jib 5 the second cable 64 runs over the second departure sheave 62a.

[0303] Possibly, in an embodiment, with the jib 5 in a compactly folded position, the crane 1 is capable of hoisting the object 102 with the jib 5 at only a small angle with the main boom 4 so that the jib tips 53, 54 are close to the main boom 4, as shown in FIG. 4a. The upwardly diverging inverted pyramid configuration of the cables 63, 64, 65 is maintained, so that the benefits thereof are also maintained in this position of the jib 5. Furthermore the inverted pyramid configuration is maintained while moving the jib from this folded position to a more extended or forward position, e.g. while hoisting.

[0304] FIG. 3b shows the jib branches 56, 57 in a collapsed configuration and FIG. 3c in a spread configuration. As discussed in relation to the first embodiment, the jib branches 56, 57 are by the operation of the cylinder 59 pivotal with respect to the central longitudinal axis 5g of the jib 5 around respective jib branch pivot axes 56v, 57v. The transverse bars 58 are shown in the locking position in FIG. 3c.

[0305] That the object suspension device 66 is suspended via the cables 63, 64, 65 in a double-fall arrangement, is visible in FIG. 4a, showing the first and third return sheave 71, 73. The double-fall arrangement has been discussed for the first embodiment and is applicable for this embodiment as well.

[0306] The crane 1 comprises, as preferred, an active suspension adjustment mechanism 7. A preferred embodiment thereof is schematically shown in FIGS. 6a-d together with the hoisting system 6. Components of the mechanism 7 are also visible in other illustrations of the crane 1, yet the structure and operation can best be understood with reference to FIGS. 6a-d.

[0307] The FIGS. 6a-d show a twofold actuated active suspension adjustment mechanism 7.

[0308] In general terms the mechanism 7 allows for substantially horizontal motion of the object suspension device 66 while the knuckle boom assembly 3 remains in a constant position, thus maintaining jib angle 5γ and the boom angle 4γ and while the winches 67a-c are stationary. Of course, operation of the mechanism may be combined with motion of the knuckle boom assembly 3 and/or with variation of length of one or more of the cables 63, 64, 65 when desired.

[0309] For understanding the mechanism 7 it is easier, to consider the situation wherein the knuckle boom assembly 3 remains in a constant position and wherein the winches 67a-c are stationary. FIG. 5b illustrates the operation of the mechanism 7. It is shown that the mechanism 7 is used to position the object suspension device 66 in a horizontal plane.

[0310] In more detail, FIG. 5b illustrates that the mechanism 7 is used in the process of positioning the device 66, possibly with an object 102, relative to a supply vessel 105, here a deck 106 thereof. As usual the supply vessel 105 has an accommodation superstructure 107, including a bridge, at the bow of a supply vessel, with the deck 106 aft thereof.

[0311] This positioning is, for example, done as part of the transfer of an object 102 between the supply vessel 105 and another vessel 101, e.g. a drilling vessel. For example, as shown in FIG. 5a, the supply vessel 105 is loaded with objects 102 on the deck 106 thereof that are to be lifted onto the higher deck of the other vessel 101 by the crane 1 arranged on said other vessel 101. For example, as in FIG. 5a, the objects 102 are crates filled with tubulars, e.g. drill pipes, casing pipes, etc.

[0312] In order to connect the device 66 to a selected object 102 on the deck, the positioning of the device 66 at an appropriate location above the object 102 to be lifted from the deck is required. Doing so by slewing of the crane 1 and/or folding/extending of the boom assembly 3 and/or motion of the jib branches 56, 67 (when possible) is difficult, e.g. due to inertia of these rather heavy components. The mechanism 7 allows for a more attractive positioning of the device 66.

[0313] The operation of mechanism 7 is illustrated in FIG. 5b. As preferred, in an embodiment, the crane 1 and the mechanism 7 is such, that merely by operation of the mechanism 7 the device 66 can be horizontally moved and positioned at various locations distributed over the deck 106 of the supply vessel. The FIG. 5c illustrates that in absence of mechanism 7, or without using mechanism 7, significant motion of the boom assembly 3 is necessary to effect the same horizontal displacement of the device 66. As mentioned, a combination of operation of mechanism 7 and motion of the crane, e.g. folding/extending the boom assembly, is also possible.

[0314] FIG. 6a shows schematically and in a two-dimensional view, without regard to the physical structure and locations of the parts of the hoisting system 6 and of the active suspension adjustment mechanism 7 on the crane 1, how these parts interact with each other, in order to give insight in the working principle of the two-fold active adjustment mechanism 7.

[0315] The effect of the operating this adjustment mechanism 7 is shown in a simplified manner in FIGS. 6b and 6c. FIG. 6d shows the arrangement of the parts of the hoisting system 6 and the adjustment mechanism 7 in a three-dimensional view.

[0316] The twofold actuated active suspension adjustment mechanism 7 comprises a first sheave pair 74 and a second sheave pair 75. Each of the sheave pairs 74,75 comprises a primary sheave and a secondary sheave which are interconnected such as to enable a pair of the first, second, and third cables 63, 64, 65 to run over one sheave of the pair in opposite directions.

[0317] The mechanism 7 further comprises a first adjustment actuator 77 and a second adjustment actuator 78, each configured for moving respectively the first and second sheave pair 74,75 in the direction of the pair of cables run over the sheaves. In FIG. 1 the actuators 77, 78 have not been shown. Due to the cables extending in opposite directions, the sheave pair is loaded by the weight of the object in opposed directions and as a result the same load is not placed on the actuator 77, 78. This is beneficial in view of the requirements for these actuators, there connection to the main boom, when present, and for the dynamic control of these sheave pairs 74, 75.

[0318] As preferred, the sheave pairs 74,75 and the adjustment actuators 77, 78 are mounted on the main boom 4, e.g. with the one or more winches 67a-c being mounted on the crane housing 2b. As preferred, the sheave pairs 74,75 and the adjustment actuators 77, 78 are mounted on a topside of the main boom 4. In another embodiment, the sheave pairs are mounted each along one of the lateral sides of the main boom 4. In another, more complex, embodiment, the mechanism 7 is placed on or in the crane housing, or even in the pedestal or below deck.

[0319] As preferred, the sheave pairs 74, 75 are mobile in longitudinal direction of the main boom 4 over a motion range, the motion being governed by the respective adjustment actuator 77, 78.

[0320] The first cable 63 is reeved from the respective winch 67a via: [0321] the primary sheave of the first sheave pair 74, [0322] the first departure sheave 61a, [0323] the first return sheave 71,
to a location on the first jib branch 56 where a dead end 63c of the first cable 63 is fixed.

[0324] The second cable 64 is reeved from the respective winch 67b via: [0325] the primary sheave of the second sheave pair 75, [0326] the second departure sheave 62a, [0327] the second return sheave 72,
to a location on the second jib branch 57 where a dead end 64c of the second cable 64 is fixed.

[0328] The third cable 65 is reeved from the respective winch 67c via: [0329] the secondary sheave of the second sheave pair 75, [0330] the third departure sheave 68, [0331] the third return sheave 73, [0332] a third guide sheave 69 paired with the third return sheave 68 on the main boom or on the crane housing, [0333] the secondary sheave of the first sheave pair 74,
to a location on the main boom or the crane housing where a dead end 65c of the third cable 65 is fixed.

[0334] The first adjustment actuator 77 is configured to move the first sheave pair 74 such as to selectively increase or decrease the part of the length of the first cable 63 between the respective winch 67a and the first departure sheave 61a and simultaneously decrease or increase the part of the length of the third cable 65 between the third guide sheave 69 and the dead end 65c of the third cable.

[0335] The second adjustment actuator 78 is configured to move the second sheave pair 75 such as to selectively increase or decrease the part of the length of the second cable 64 between the respective winch 67b and the second departure sheave 62a and simultaneously decrease or increase the part of the length of the third cable 65 between the winch 67c and the third departure sheave 68.

[0336] As shown here, preferably, the first and second adjustment actuators 77,78 are each embodied as a first and second adjustment cylinder, e.g. hydraulic cylinder, each of which has one longitudinal end thereof fixed to the main boom 4 and another longitudinal end to the associated sheave pair 74,75, respectively, such that a shortening or lengthening of the first and/or second adjustment actuator cylinder 77, 78 respectively moves the first and/or second sheave pair 74, 75 in the directions of the cables run over the sheaves thereof.

[0337] The effect of this mechanism is illustrated in FIGS. 6b-c. Therein the triangular interconnection of the cables 63, 64, 65 is shown in a simplified manner, the dotted imaginary triangle of FIG. 6a being indicated for verification.

[0338] The object suspension device 66 is represented by the same circle as in FIG. 6a, being connected to the three cables 63, 64, 65.

[0339] In the simplified top view of FIG. 6b the curved trajectory 66.1 illustrates the motion of the device 66 as only the sheave pair 74 is moved by the corresponding adjustment actuator 77. The curved trajectory 66.2 illustrates the motion of the device 66 as only the sheave pair 75 is moved by the corresponding adjustment actuator 78. The curved trajectories 66.1, 66.2 over which the device 66 is moved in the horizontal plane is determined by the locations of the departure sheaves 61a, 62a, 68, and the length of the cables between the device 66 and the departure sheaves. This trajectory is curved as a result of the inverted pyramidal arrangement of the cable suspension.

[0340] By purposely combining motions of the sheave pairs 74, 75, e.g. by shortening and/or lengthening of the cylinders 77, 78, components of the two trajectories 66.1, 66.2 are combined allowing to move the object suspension device 66 along other trajectories in the horizontal plane. For example, shortening of both cylinders 77, 78 by the same amount moves the object suspension device 66 over a straight trajectory, in FIGS. 6b-c upwards and in FIG. 5b to the left, so in a forward direction of the crane 1 and along the central longitudinal jib axis 5g. Correspondingly, lengthening of both cylinders 77, 78 by the same amount moves the object suspension device 66 over a straight trajectory downwards in FIGS. 6b-c, so in a backward direction of the crane 1 and to the right in FIG. 5b.

[0341] In FIG. 6c it is illustrated that the object suspension device 66 has been moved substantially horizontally by shifting the sheave pair 74.

[0342] In another embodiment, a threefold actuated suspension adjustment mechanism 7 is provided instead of the twofold actuated suspension adjustment mechanism 7 of FIGS. 6a-d.

[0343] Such a threefold actuated mechanism 7 is illustrated in FIGS. 6e-g in the same fashion as in FIGS. 6a-d. The rest of the components of the crane 1 may for instance be the same as in the first and second embodiment of the crane 1.

[0344] When compared to the twofold actuated mechanism 7, the threefold actuated mechanism comprises in addition a third sheave pair 76 and an associated third adjustment actuator, e.g. a cylinder 79.

[0345] The third adjustment actuator 79 is configured for moving the third sheave pair 76 in the direction of the cables 63, 64 run there through in opposite directions.

[0346] The first cable 63 is reeved from the first winch 67a via: [0347] the primary sheave of the first sheave pair 74, [0348] the first departure sheave 61a, [0349] the first return sheave 71, [0350] a first guide sheave 69 on the first jib branch 56, [0351] the secondary sheave of the third sheave pair 76
back to a dead end 63c of the cable secured to the crane, e.g. to the jib or the main boom.

[0352] The second cable 64 is reeved from the second winch 67b via: [0353] the primary sheave of the third sheave pair 76, [0354] the second departure sheave 62a, [0355] the second return sheave 72, [0356] a second guide sheave 69 on the second jib branch 57, [0357] the secondary sheave of the second sheave pair 75,
back to a dead end 64c of the cable secured to the crane, e.g. to the jib or the main boom.

[0358] The third cable 65 is reeved from the third winch 67c via: [0359] the primary sheave of the second sheave pair 75, [0360] the third departure sheave 68, [0361] the third return sheave 73, [0362] the third guide sheave 69 proximate the third departure sheave 68, [0363] the secondary sheave of the first sheave pair 74,
to a dead end 65c of the cable secured to the crane, e.g. to the main boom 4.

[0364] FIG. 6f, similar to FIG. 6b, illustrates the three respective curved trajectories 66.1, 66.2, 66.3 over each which the object suspension device 66 is moved in the horizontal plane in case just one of the three sheave pairs 74, 75, 76 is moved by the respective adjustment actuator 77, 78, 79.

[0365] By purposely combining operation of the three actuators, e.g. shortening and/or lengthening of the cylinders 77, 78, 79, components of the three movement trajectories 66.1, 66.2 are combined such as to move the object suspension device 66 along other trajectories in the horizontal plane. In particular, contracting and extending just two of the cylinders 77, 78, 79 by the same amount moves the object suspension device 66 over a straight trajectory.

[0366] Extending the first cylinder 77 and contracting the second cylinder 78 by the same amount results in the object suspension device 66 moving upwards in FIG. 6f, e.g. in a forward direction of the crane 1, along the central longitudinal jib axis 5g.

[0367] Straight horizontal movements to a lateral side of the crane can, for example, be obtained by combining components of trajectories 66.1 and 66.3.

[0368] A third embodiment of a crane 1 according to the invention is shown in FIGS. 7a-c. In this embodiment the forked jib 5 is a collapsible forked jib 5.

[0369] The third embodiment differs from the first and second embodiment in that the jib branches 56, 57 are each driven by a respective first and second jib branch actuator 56c, 57c so as to be independently pivotal relative to the jib base 52 about the respective pivot axis. For example, each branch actuator comprises or is embodied as a linear drive actuator, e.g. a hydraulic cylinder, or comprises or is embodied as a motor with rotary output effecting the controlled pivoting of the one associated jib branch. For example, the motor with rotary output is a hydraulic or electric motor. For example, a transmission, e.g. a gear, belt, or chain transmission is connected to the motor with rotary output to effect the pivoting.

[0370] The jib branches 56, 57 are pivotal to provide for a collapsed configuration and multiple spread configurations of the forked jib.

[0371] In spread configurations the angle 55α between the first and second jib branches is larger than 20°. In the spread configuration shown in FIG. 7a the angle 55α of divergence between the first jib branch 56 and the second jib branch 57 is around 40°.

[0372] In the collapsed configuration the angle between branches 56, 57 is small, e.g. as small as possible, e.g. the branches being collapsed into contact with one another.

[0373] In the collapsed configuration the branches 56, 57 extend substantially parallel to each other, see FIG. 7b.

[0374] By operating the jib branch actuators 56c, 57c, the jib branches 56, 57 are independently pivotal. In embodiments, the jib branches 56, 57 are pivoted asymmetrically or symmetrically relative to the central longitudinal axis 5g.

[0375] In embodiment, the independent jib branch actuators 56c, 57c are operable to cause a lateral movement of the object suspension device 66 and the connected object 102 relative to the forked jib 5. For example, the actuators are operable to drive a pivoting of both the first and second jib branch 56, 57 in the direction of one lateral side of the central longitudinal axis 5g of the jib 5, such as to laterally displace the object suspension device 66 and therewith the object 102 connected thereto.

[0376] In embodiment, the independent jib branch actuators 56c, 57c are operable to manipulate the vertical angles 63γ, 64γ of the first and second hoisting cables 63, 64 and therewith the vertical angle 65γ of the third cable 65, e.g. in view of control of the stability of the object suspension device 66 and the connected object 102, as explained herein. For example, the independent jib branch actuators are operable to drive the pivoting such as to decrease the angle 55α between the first and second jib branch 56, 57 during a hoisting of an object 102, and to increase the angle 55α during a lowering of the object.

[0377] FIGS. 7a-c also illustrate an alternative locking mechanism for the spread position of the jib branches. In this embodiment, the collapsible forked jib 5 comprises a transverse bar 58, which is pivotally mounted to the first jib branch 56 and is releasably connectable to the second jib branch 57. In FIG. 7a, the transverse bar 58 is connected to the second jib branch 57 maintaining the first and second jib branch 56, 57 in the spread configuration thereof. In the collapsed configuration shown in FIG. 7b, the transverse bar 58 is pivoted into a position longitudinally aligned with the first jib branch 56.

[0378] FIG. 7c shows schematically the inverted pyramidal configuration of the hoist cables 63, 64, 65 for this second embodiment, which results from the spatial location of the departure sheaves 61a, 62a, and 68. It is visible that the object suspension device 66 here is suspended from the cables 63, 64, 65 in a single-fall arrangement.

[0379] FIGS. 8a, b illustrate the jib of a crane of a fourth embodiment of the invention, in which contrary to the first, second, and third embodiments the forked jib 5 is a rigid forked jib.

[0380] In the rigid forked jib 5 the first and second jib branches 56, 57 are fixed relative to the jib base 52, and form a rigid unit with the jib base 52. Consequently, the angle 55α between the first and second jib branch and the jib branch angles 56α, 57α is fixed.

[0381] The rigid forked jib 5 comprises the jib base 52 and at a bifurcation 55 remote from the inner end of the jib base the first jib branch 56 and the second jib branch are fixed to the base 52. The branches 56, 57 diverge from one another. The first jib branch 56 extends to the first jib tip 53 and a second jib branch 57 extends to the second jib tip 54, so that the second jib tip 54 is arranged spaced from the first jib tip 53 in a lateral direction with respect to the central longitudinal axis 5g of the rigid forked jib 5.

[0382] For example, the angle 55α between the first jib branch 56 and the second jib branch 57 is 40°. The longitudinal axes 56g, 57g of the first and second jib branch 56, 57 depart from the bifurcation 55 at equal jib branch angles 56α, 57α of around 20° with respect to the central longitudinal axis 5g of the jib.

[0383] It is illustrated that the departure sheaves 61a, 62a are each pivotal about an axis that is parallel to the longitudinal axis 56g, 57g of the respective jib branch.

[0384] The FIG. 9 serves to illustrate an advantage of the inventive crane with spreader type jib.

[0385] The FIG. 9 shows schematically, in a top view, two spatial configurations of three cables from which the object suspension device 66 is suspended in an inverted pyramidal configuration, with the triangular base of the pyramid defined by the three departure sheaves.

[0386] In FIG. 9 the crane housing 2b is also identified, all other components are left out for clarity. The right-hand illustration shows the crane with jib according to the invention, wherein the third departure sheave 68 is closest to the crane housing 2b and wherein the departure sheaves 61a, 62a on the jib are further away.

[0387] The left-hand illustrations shows, for sake of comparison, the object suspension device 66 equally far from the crane housing 2b. However, in this arrangement two of the departure sheaves 80, 81 are closest to the crane housing, each laterally from a central vertical plane of the crane boom assembly, and one departure sheave 83 is furthest away from the crane housing. With the triangular base being equal to the right-hand illustration, it can readily be recognized that the sheave 83 is further away from the crane housing 2b in direction of the main boom than with the inventive jib. This illustrates that the inventive spreader type jib knuckle boom crane requires relatively little space for its operation, e.g. avoiding conflict between the crane and accommodation, e.g. at the bow of a supply vessel, adjacent a deck from which an object is to be picked up (normally aft on a supply vessel). Also it can be appreciated that this is beneficial in terms of control and stability, and/or in terms of stresses in the crane resulting from the handling of the object.

[0388] The FIG. 9 also illustrates that the crane 1 is advantageous for mounting at the side of an offshore vessel or structure, e.g. at the side of the hull or deck box structure of an offshore vessel, e.g. of a drilling vessel, e.g. as shown in FIGS. 5a-c, e.g. the crane 1 serving the transfer of objects between a supply vessel and the vessel.

[0389] The features of the different shown embodiments may readily be combined. For instance, the hoisting system 6 and the adjustment mechanism 7 of the third embodiment may readily be applied to the first, second and fourth embodiment, or with other embodiments with other types of forked jibs, knuckle boom assemblies or the other crane parts. Also, the embodiments of the jib may be interchanged between different embodiments of knuckle boom assemblies or the other crane parts.

[0390] FIG. 10 shows a fifth embodiment of the crane according to the invention. Herein components corresponding to earlier described cranes have been denoted with the same reference numeral.

[0391] As in the crane of FIG. 1, the jib 5 is a collapsible forked jib 5. However, instead of the jib branches 56, 57 being mounted to a common jib base, so as to be pivotal with respect to said base, in this fifth embodiment the jib branches 56, 57 are independently mounted to the main boom 4, here the outer end thereof.

[0392] It is shown that each branch 56, 57 at a base end thereof, so an end adjacent the main boom 4, connected via a respective pivot structure 90, 91 to the main boom 4, so as to be both movable between the folded position and extended positions of the knuckle boom assembly, as well as between the spread configuration and the collapsed configuration of the collapsible forked jib 5.

[0393] It is shown that for folding and extending each branch 56, 57 there is an associated actuator, here cylinders 32a, b, that allow for independent control of the pivoting of the branch 56, 57 about a horizontal pivot axis 3h2 relative to the main boom 4.

[0394] For pivoting each branch 56, 57 between collapsed and spread configurations about respective axis 56v, 57v (perpendicular to axis 3h2) there are independently operable first and second jib pivoting actuators 56c, 57c, For example, each actuator 56f, 57f is a cylinder, or a motor, as explained herein.

[0395] The depicted jib 5 of FIG. 10, for example, allows for extending just one jib branch, e.g. when handling a small or light object.

[0396] The depicted jib of FIG. 10, for example, allows to bring the jib branches 56, 57 in different extended positions, e.g. when handling an object with constraints for the spatial location of the jib branches.

[0397] The depicted jib also allows, for example, to pivot both jib branches in the same direction, e.g. both to the left in the FIG. 10, e.g. allowing to shift the object suspension device 66 horizontally relative to a central vertical plane of the knuckle boom assembly.

[0398] The depicted jib also allows, for example, to vary the lateral distance between the first and second departure sheaves 61a, 62a by suitable pivoting of the jib branches 56, 57.

[0399] FIG. 11 shows a sixth embodiment of the crane according to the invention. Herein components corresponding to earlier described cranes have been denoted with the same reference numeral.

[0400] In FIG. 11 the collapsible jib 5 has a collapsible T-shaped spreader structure 150. The central member 151 of the spreader structure is pivotally mounted to the main boom 4, about horizontal axis 3h2, and extends along the longitudinal axis of the jib. Herein the first and second departure sheaves 61a and 62a are mounted on the cross member 152 of the T-shaped spreader structure, e.g. at opposed ends thereof.

[0401] As shown the cross member 152 is embodied so as to be collapsible in order to reduce the lateral extension of the jib 5 when desired, e.g. for storage of the boom assembly. The depicted cross-member is embodied as two swivelling cross-member elements 152a,b, each swivelling relative to the central member about a swivel axis 152c, d between an operative position transverse to the central member (see FIG. 11) and a collapsed position aligned with the central member, e.g. along a lateral side of the central member.

[0402] In conjunction with a collapsible T-shaped spreader structure, the first and second cables may be reeved over guide sheaves 85, 86 at the outer end of the main boom 4, and then pass to the departure sheaves 61a, 62a. For example, the cables 63, 64 first pass to further guide sheaves on the central member 151 and then diagonally to the respective first and second departure sheaves 61a, 62a.