Offshore lifting crane

Abstract

Described is an offshore lifting crane, as for a vessel or platform, that includes a support structure, a crane boom connected to the support structure, a winch drum rotatable around its longitudinal axis, a winch drum drive means, and an elongated hoisting member. The hoisting member includes a first end connected to the winch drum and a second end connectable to a load. The hoisting member extends over at least a part of the crane boom, and the winch drum is arranged such that its longitudinal axis is substantially vertical.

Claims

1. Offshore lifting crane comprising: a support structure; a crane boom connected to said support structure; a winch drum surrounding a crane king of the support structure, wherein the winch drum is rotatable around a longitudinal axis of the winch drum and wherein the crane king extends through the winch drum; a winch drum drive means; and an elongated hoisting member having a first end connected to said winch drum and a second end connectable to a load, said elongated hoisting member extending over at least a part of said crane boom, wherein said winch drum is arranged such that said longitudinal axis is substantially vertical, wherein said winch drum is integrated with said support structure.

2. The offshore lifting crane according to claim 1, wherein said winch drum is connected to and rotatable around a portion of the crane support structure.

3. The offshore lifting crane according to claim 2, wherein said crane support structure comprises a slew bearing provided below said winch drum, said slew bearing enabling an upper portion of said crane support structure to rotate relative to a lower portion of said crane support structure around an axis substantially coinciding with said longitudinal axis of the winch drum.

4. The offshore lifting crane according to claim 3, wherein said winch drum drive means is provided inside said crane support structure.

5. The offshore lifting crane according to claim 4 wherein said winch drum drive means is provided inside the crane king of the crane support structure.

6. The offshore lifting crane according to claim 2 wherein said winch drum is connected to and rotatable around the crane king.

7. The offshore lifting crane according to claim 1, wherein said offshore lifting crane comprises a spooling assembly for spooling said elongated hoisting member onto and/or from said winch drum.

8. The offshore lifting crane according to claim 7, wherein the spooling assembly comprises one or more sheaves for directing said elongated hosting member substantially perpendicularly onto the winch drum.

9. The offshore lifting crane according to claim 8, wherein said spooling assembly further comprises a second sheave, and wherein a first sheave is displaceable substantially in parallel with said longitudinal axis of said winch drum.

10. The offshore lifting crane according to claim 1, wherein said elongated hoisting member comprises fibre rope.

11. The offshore lifting crane according to claim 1, wherein the lifting crane is provided with a heave compensation means.

12. The offshore lifting crane according to claim 1, wherein said winch drum is provided in a material comprising a steel and concrete composite.

13. A vessel comprising an offshore lifting crane according to claim 1.

14. Offshore lifting crane comprising: a support structure; a crane boom connected to said support structure; a winch drum rotatable around a longitudinal axis of the winch drum; a winch drum drive means; and an elongated hoisting member having a first end connected to said winch drum and a second end connectable to a load, said elongated hoisting member extending over at least a part of said crane boom, wherein said winch drum is arranged such that said longitudinal axis is substantially vertical, wherein said winch drum is integrated with and surrounds an outer portion of said support structure; wherein said crane support structure comprises a slew bearing configured to enable the crane boom to rotate about the longitudinal axis of the winch drum.

15. The offshore lifting crane according to claim 14, wherein said winch drum is connected to and rotatable around a portion of the crane support structure.

16. The offshore lifting crane according to claim 14, wherein said winch drum drive means is provided inside said crane support structure.

17. The offshore lifting crane according to claim 14, wherein said offshore lifting crane comprises a spooling assembly for spooling said elongated hoisting member onto and/or from said winch drum.

18. The offshore lifting crane according to claim 17, wherein the spooling assembly comprises one or more sheaves for directing said elongated hosting member substantially perpendicularly onto the winch drum.

19. The offshore lifting crane according to claim 18, wherein said spooling assembly further comprises a second sheave, and wherein a first sheave is displaceable substantially in parallel with said longitudinal axis of said winch drum.

20. The offshore lifting crane according to claim 14 wherein said winch drum is connected to and rotatable around a crane king of the crane support structure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments described herein are illustrated in the accompanying drawings, wherein:

(2) FIG. 1 shows, in a side view, an offshore lifting crane according to the present disclosure;

(3) FIG. 2 shows, in a cross-sectional view, the offshore lifting crane as seen through the line A-A in FIG. 1;

(4) FIG. 3 shows, in a side view, an offshore lifting crane according to the present disclosure;

(5) FIG. 4 shows, in a rear view, the offshore lifting crane of FIG. 3;

(6) FIG. 5 shows, in a rear view, an enlarged detail of the lifting crane of FIG. 4;

(7) FIG. 6 shows, in a top view, a vessel provided with an offshore lifting crane according to the present disclosure; and

(8) FIG. 7 shows, in a top view, a vessel provided with another embodiment of an offshore lifting crane according to the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSED EXEMPLARY EMBODIMENTS

(9) In the following, the reference numeral 1 will indicate an offshore lifting crane according to the present disclosure, whereas the reference numeral 30 indicates a vessel provided with such an offshore lifting crane. Identical reference numerals refer to identical or similar features in the figures. The figures are simplified and schematic, and the various features in the figures are not necessarily drawn to scale.

(10) Reference is first made to FIGS. 1 and 2 showing a first embodiment of an offshore lifting crane 1 according to the present disclosure in the form of a knuckle-boom crane. The knuckle-boom crane 1 comprises a support structure 2, the support structure 2 including a lower portion including a pedestal 12 and an upper portion including a crane king 14 and a housing 16. The crane 1 comprises two crane booms; a main boom 4 and a knuckle-boom 41, the main boom 4 being pivotally connected to the housing 16 and the knuckle-boom 41 being pivotally connected to the distal end of the main boom 4. The general luffing motion of the main boom 4 and the knuckle-boom 41 will be known to a person skilled in the art, and will therefore not be described in detail herein. In the shown embodiment, a winch drum 6 is rotatably connected to the crane support structure 2, around the crane king 14, thus providing a very compact lifting crane. Compared to a not shown knuckle-boom crane according to the prior art, the skilled person will recognize that the king 14 has been made longer so that it extends all the way down from the housing 16 and to a lowered pedestal slew bearing 18, enabling the rest of the knuckle-boom crane 1 to rotate relative to the pedestal 12 around and axis substantially parallel to a longitudinal axis L of the winch drum 6. The winch drum 6 is rotatably connected around the crane king 14 by means of an upper slew bearing 32 and a lower slew bearing 34, thus enabling the winch drum 6 to rotate around the crane king 14 independently from the crane king's 14 rotation relative to the pedestal around the pedestal slew bearing 18.

(11) In the exemplary embodiment shown in FIGS. 1-2, the winch drum 6 is adapted to be rotated by means of winch drum drive means 8 provided inside the crane support structure 2 in the pedestal 12 as can be seen in the cross-sectional view in FIG. 2. The drive means 8 comprises a plurality of electric motors and gears, each of which is provided with a rotatable shaft with a gear pinion 40 at its end, each gear pinions 40 engaging with gear teeth 38 integrated with the inner race of the lower slew bearing 34. The lower slew bearing 34 in turn being connected to the winch drum 6 by being connected/bolted to a winch drum flange 36. In FIGS. 1-2, the winch drum 6 is shown only driven by electric motors at its lower end. The details of the winch drum flange 36, the lower winch drum slew bearing 34, and the drive means 8 are not easily seen in FIGS. 1 and 2 due to the scale of the drawings. Reference is therefore made to FIG. 5 for a detailed view of an equivalent embodiment, though with the drive means 8 provided on the outside of the crane support structure.

(12) An elongated hoisting member 10 in the form of a fibre rope extends from the winch drum 6 along the crane king 14 and housing 16 and over the main boom 4 and knuckle-boom 41, where a free end of the fibre rope is connectable to a load, typically by means of a hook or the like. In order to direct the fibre rope 10 onto/from the winch drum 6 and to reduce the fleet angle, the knuckle-boom crane 1 is provided with a spooling means 20, in the shown embodiment comprising a displaceable sheave 22, a fixed sheave 24 and a drive means 26 for the displaceable sheave, where the drive means 26 is only shown with reference to FIGS. 3 and 4 as discussed below. The two sheaves 22, 24 change the direction of the fibre rope 10 by approximately 90 each. The displaceable sheave 22 is linearly displaceable in rails/arms 42 substantially parallel to the longitudinal axis L of the winch drum 6, so as to direct the fibre rope 10 onto/from the winch drum 6 while substantially minimizing the fleet angle so as to position the fibre rope 10 in a helical groove on the winch drum 6.

(13) FIGS. 3-5 show another exemplary embodiment of an offshore lifting crane 1 according to the present disclosure. Only a small portion of the fibre rope 10 is shown in these figures. In this second embodiment, the winch drum drive means 8 is provided on the outside of the pedestal 12, the gear pinions 40 of the electric motors engaging with gear teeth 38 integrated with an outer race of the lower winch drum slew bearing 34, as can be best seen in the enlarged view in FIG. 5. Further, the spooling device 20 is shown in some more detail, where the displaceable sheave 22 is displaceable by means of hydraulic actuators 26 adapted to displace the sheave 22 in parallel with the longitudinal axis L of the winch drum 6 as indicated in FIG. 2. In other embodiments, other drive means, such as electric of pneumatic actuators, may be used to move the displaceable sheave 22. In the shown embodiment, the displaceable sheave 22 is also tiltable around an axis substantially coinciding with the axis along which the sheave 22 is displaceable, though not strictly necessary when used with fibre ropes 10 stored in no more than two layers on the winch drum 6.

(14) FIG. 5 is an enlarged view of the lower part of the knuckle-boom crane 1 of FIG. 4. The figure shows a lower part of the winch drum 6 with the drum flange 36, the drum flange 36 being connected to the lower winch drum slew bearing 34. The lower winch drum slew bearing 34 having gear teeth 38 integrated with its outer race. Gear pinions 40 rotatable by means of the electric motors 8 engage with the gear teeth. The pedestal slew bearing 18 is shown below and partially behind the electric motors 8. The pedestal slew bearing 18, and the rotation of the rest of the offshore lifting crane 1 relative to the pedestal 12 will be known to a person skilled in the art, and will not be discussed in further detail herein.

(15) FIG. 6 shows a vessel 30 provided with an offshore lifting crane 1 according to the present disclosure. As discussed above, the offshore lifting crane 1 according to the present disclosure, and in particular according to the above-described embodiments, when used on a vessel 30 offers the advantages of compactness, reduced tail swing and lower centre of gravity and the possibility of hoisting larger loads into deeper waters as compared to offshore lifting cranes according to the prior art. FIG. 7 shows another embodiment, where the winch drum 6 is provided at a distance from the rest of the offshore lifting crane 1. The winch drum 6 may be provided on deck, below deck or as extending through deck, while its vertical arrangement still reduces the footprint compared to winch drums according to the prior art.

(16) It should be noted that the above-mentioned embodiments illustrate rather than limit the present disclosure, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb comprise and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article a or an preceding an element does not exclude the presence of a plurality of such elements.

(17) The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.