Crane and method for positioning an object

Abstract

A wave-induced motion compensating crane includes a hoist assembly. At least two departure sheaves are mounted at opposite lateral sides of the jib. The object suspension device is supported both by two hoist cables extending laterally from the jib and a third hoist cable that runs via another departure sheave. The hoist assembly is adapted to hoist and/or lower the object suspension device with an object connected thereto, between a lower position and a position at a height up to the departure sheaves while the hoist cables together define a reverse pyramid, diverging upwards in between the object suspension device and the departure sheaves.

Claims

1. A crane for use on a floating vessel, said crane comprising: a revolving superstructure; a boom pivotally mounted to the revolving superstructure, the boom comprising: a main boom comprising a main boom member having a lower end pivotally mounted about a first pivot axis to the superstructure; and, a jib comprising a jib member having an inner end pivotally mounted about a second pivot axis to an upper end of the main boom member; a luffing assembly configured for luffing of the main boom; a jib angle adjustment mechanism configured to adjust a pivot angle of the jib relative to the main boom; and an object suspension device configured to be connected to an object underneath the object suspension device, wherein the crane comprises a hoisting system comprising: one or more hoist winches; a jib hoist assembly comprising: a jib departure sheave mounted to the jib member; a jib hoist cable configured to extend from said one or more hoist winches along the main boom and the jib via the jib departure sheave to the object suspension device; and a jib hoist heave compensation mechanism; and a main boom hoist assembly comprising: two main boom departure sheaves mounted to the upper end of the main boom member at opposite lateral sides thereof; two main boom hoist cables configured to extend from said one or more hoist winches along the main boom member via the main boom departure sheaves to the object suspension device; and a main boom hoist heave compensation mechanism, wherein the object suspension device is supported by the jib hoist cable and by the two main boom hoist cables, and wherein the main boom hoist assembly is adapted to, together with the jib hoist assembly, hoist and lower the object suspension device with an object connected thereto between a lower position and a position at a height up to substantially a height of the main boom departure sheaves while the jib hoist cables and the two main boom hoist cables together define a reverse pyramid diverging upwards from the object suspension device.

2. The crane according to claim 1, wherein the main boom departure sheaves are mounted to lateral ends of a transverse beam, the transverse beam being at a center portion thereof mounted to the upper end of the main boom member.

3. The crane according to claim 1, wherein the crane further comprises two boom extensions, each having a lower end thereof connected to the upper end of the main boom member, the boom extensions extending from said upper end at equal upward angles relative to horizontal and diverging from each other and from the jib when seen in a top view of the crane, wherein each of the main boom departure sheaves is mounted to a respective upper end of the boom extension.

4. The crane according to any of claim 1, wherein the one or more hoist winches consist of: one jib hoist winch and one main boom hoist winch, the jib hoist cable extending from the one jib hoist winch, and two main boom hoist cables extending from the one main boom hoist winch, or one jib hoist winch and two main boom hoist winches, the jib hoist cable extending from the one jib hoist winch, and the two main boom hoist cables each extending from a respective one of the two main boom hoist winches.

5. The crane according to claim 1, wherein the jib of the crane further comprises: a jib strut having an end mounted to the inner end of the jib member and extending essentially perpendicular to the jib member; and a jib stay extending between the jib strut and the jib member, wherein the main boom further comprises: a main boom strut having an end mounted to an upper end of the main boom member and extending essentially perpendicular to the main boom member; and a boom stay extending between the main boom strut and a lower portion of the main boom member, wherein the boom further comprises a variable length stay mechanism provided between the main boom strut and the jib strut, wherein the luffing assembly of the crane further comprises: a luffing winch mounted to the superstructure; and a luffing cable extending between the luffing winch and the main boom.

6. The crane according to claim 1, wherein the main boom hoist cables are each arranged in a double-fall arrangement, wherein the main boom hoist assembly comprises two pairs of main boom departure sheaves, each pair of main boom departure sheaves being mounted to the upper end of the main boom member at opposite lateral sides thereof, and further comprises two main boom spreader sheaves, each connected to the object suspension device, and wherein the main boom hoist cables are each configured to extend from one of said 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, and the other main boom departure sheave of the respective pair of main boom departure sheaves to the one of the hoist winches, and wherein the jib hoist cable is arranged in a double-fall arrangement, wherein the jib hoist assembly comprises a pair of jib hoist sheaves, mounted to the jib member, and further comprises a jib spreader sheave, connected to the object suspension device, and wherein 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, and the other jib departure sheave of the pair of jib hoist sheaves to the one of the hoist winches.

7. The crane according to claim 1, wherein the object suspension device is provided with three cable connectors to each of which a respective hoist cable is connected, the three cable connectors being provided at equal mutual angles around a central vertical axis of the object suspension device, wherein the cable connectors are each pivotal around a respective vertical pivot axis relative to the object suspension device.

8. The crane according to claim 1, wherein a lower part of the object suspension device is configured to be connected to the object and is rotatable relative to an upper part of the object suspension device that is connected to the hoist cables, so that the object is rotatable around a central vertical axis of the object suspension device, wherein the rotation of said lower part relative to said upper part is controllable by means of a control device, so that an angular position of the object in a horizontal plane is controllable thereby.

9. A wave-induced motion compensating crane provided with a three-point cable suspension mechanism, said crane being configured for use on a vessel, said crane comprising: a boom comprising: a main boom comprising a main boom member having a lower end pivotally mounted about a first pivot axis to a structure; and a jib comprising a jib member having an inner end pivotally mounted about a second pivot axis to an upper end of the main boom member; a luffing assembly configured for luffing of the main boom; a jib angle adjustment mechanism configured to adjust the pivot angle of the jib relative to the main boom; and an object suspension device configured to connect an object underneath the object suspension device, wherein the three-point cable suspension mechanism comprises: three hoisting systems, each hoisting system comprising a hoist winch, two departure sheaves, a hoist cable, a spreader sheave, and two mobile guide sheaves; and a heave compensation mechanism, wherein the hoisting cable of each hoisting system extends from the hoist winch thereof, successively via one of the two mobile guide sheaves thereof, one of the departure sheaves thereof, the spreader sheave thereof, the other one of the two departure sheaves thereof, and the other one of the two mobile guide sheaves thereof to the hoist winch thereof, wherein each of the two mobile guide sheaves of each hoisting system is connected to a mobile guide sheave of the two other hoisting systems such that a rotational axis thereof is parallel to that of the mobile guide sheave connected thereto, and is mounted to the crane such as to be movable with respect thereto in a direction perpendicular to the rotational axis, and towards or away from an adjacent departure sheave of the respective hoisting system, wherein the departure sheaves are mounted to the jib and/or to the upper end of the main boom, such as to have at least two of the three departure sheaves positioned at opposite lateral sides from the jib, so that the departure sheaves and the mobile guide sheaves define a triangle when seen in a top view of the crane, and wherein the spreader sheaves are each connected to the object suspension device, the spreader sheaves radially surrounding the object suspension device, and wherein the three-point cable suspension mechanism is adapted to hoist and/or lower the object suspension device with an object connected thereto while the three hoist cables together define a reverse pyramid diverging upwards in between the object suspension device and the three departure sheaves, such that any difference in cable tension between the three hoist cables results in a movement of one or more of the interconnected guide sheaves towards or away from the adjacent departure sheaves so as to cancel out said difference in cable tension.

10. The crane according to claim 9, wherein one or more spreaders are provided in between the object suspension device and the spreader sheaves so as to determine a radial distance between a central vertical axis of the object suspension device and each spreader sheave.

11. The crane according to claim 10, wherein two of the three departure sheaves are mounted to lateral ends of a transverse beam, the transverse beam being at a center portion thereof mounted to the upper end of the main boom member or to the jib.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 shows a first embodiment of a crane according to the invention,

(3) FIG. 2 shows a second embodiment of a crane according to the invention,

(4) FIG. 3 schematically shows a possible arrangement of the hoist assembly of a crane according to the invention,

(5) FIGS. 4A-H schematically show a crane according to the invention in different possible working positions;

(6) FIG. 5 shows an object suspension device according to either embodiment; and

(7) FIG. 6 schematically shows the three-point cable suspension mechanism of a crane according to the second aspect of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(8) FIG. 1 shows an embodiment of a wave-induced motion compensating crane according to the invention in perspective view.

(9) 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.

(10) 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.

(11) 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.

(12) The boom further comprises a variable length stay mechanism 38 provided between the main boom strut 32 and the jib strut 36.

(13) 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.

(14) The crane further comprises an object suspension device 13, to which an object is connected or connectable underneath the object suspension device 13.

(15) 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.

(16) 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.

(17) 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.

(18) 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.

(19) 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.

(20) 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.

(21) 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.

(22) 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.

(23) 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.

(24) 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.

(25) 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.

(26) 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.

(27) 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.

(28) 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.

(29) 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.

(30) 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.

(31) Therein the control device is furthermore programmed to operate the main boom hoist winches and jib hoist winch independently.

(32) 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.

(33) 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.

(34) 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.

(35) 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.

(36) It is remarked at this point that even though only the crane according to the first aspect of the invention has been explained in relation to FIGS. 1-5, the illustration of the features apply similarly to a crane according to the second and/or third aspect, even as the explanation thereof and any mentioned effects and/or advantages thereof.

(37) FIG. 6 shows, in a schematic way, the three-point cable suspension mechanism of a crane according to the second aspect of the invention.

(38) This three-point cable suspension mechanism comprises, firstly, three hoisting systems. Each hoisting system comprising a hoist winch 81a, 81b, 81c, two departure sheaves 82a, 82b, 82c, a hoist cable 83a, 83b, 83c, a spreader sheave 84a, 84b, 84c, and two mobile guide sheaves 85a, 85b, 85c.

(39) The three-point cable suspension mechanism comprises secondly a heave compensation mechanism, e.g. wherein one or more of the hoist winches of the hoisting systems are embodied as an AHC winch, or wherein the hoist assembly comprises heave compensating cylinders operating on the unwound section of the hoist cables of the hoisting systems. This heave compensation mechanism is not shown in FIG. 6.

(40) It may be derived that the hoisting cable 83a, 83b, 83c of each hoisting system extends from the hoist winch thereof, successively via one of the two mobile guide sheaves thereof, one of the departure sheaves thereof, the spreader sheave thereof, the other one of the two departure sheaves thereof, and the other one of the two mobile guide sheaves thereof to the hoist winch thereof.

(41) Each of the two mobile guide sheaves 85a, 85b, 85c of each hoisting system being interconnected to a mobile guide sheave of the two other hoisting systems such that its rotational axis is parallel to that of the mobile guide sheave connected thereto, and being mounted to the crane such as to be movable with respect thereto in a direction A, B, C perpendicular to its rotational axis, and towards or away from an adjacent departure sheave of its hoisting system.

(42) It is not shown in FIG. 6 that the departure sheaves 82a, 82b, 82c are mounted to an upper part of the crane, e.g. the jib and/or an upper end of the main boom, such as to have at least two of the three departure sheaves positioned at opposite lateral sides from the jib, so that the departure sheaves and the mobile guide sheaves define a triangle when seen in a top view of the crane.

(43) The spreader sheaves 84a, 84b, 84c are each connected to the object suspension device and therein radially surround the object suspension device.

(44) The three-point cable suspension mechanism is adapted to hoist and/or lower the object suspension device with an object connected thereto between a lower position and a position at a height up to just below the three departure sheaves 82a, 82b, 82c while the three hoist cables 83a, 83b, 83c together define a reverse pyramid diverging upwards in between the object suspension device and the three departure sheaves,

(45) This is done such that any difference in cable tension between the three hoist cables results in a movement of one or more of the interconnected guide sheaves towards or away from the adjacent departure sheaves so as to cancel out said difference in cable tension.

(46) A crane provided with this three-point cable suspension mechanism may furthermore be provided with a control device, programmed to operate the three hoist winches 81a, 81b, 81c so as to control the position and/or velocity of the object by simultaneously paying out and/or drawing in of the three hoist cables 83a, 83b, 83c in dependence of the vertical and/or horizontal position and/or motions of the object and/or the object suspension device and/or the vessel and/or the crane.

(47) Therein the control device may furthermore be programmed to operate the three hoist winches 81a, 81b, 81c so as to simultaneously differently pay out and/or draw in the three hoist cables 83a, 83b, 83c in reaction to, e.g. in dependence of, any difference in cable tension between the three hoist cables, thereby controlling movement of one or more of the interconnected guide sheaves towards or away from the adjacent departure sheaves so as to cancel out said difference in cable tension.

(48) It may be envisaged with the schematic of FIG. 6, e.g. in combination with FIG. 5, that one or more spreaders, e.g. three horizontal beams, may be provided in between the object suspension device and the spreader sheaves 84a, 84b, 84c so as to determine a radial distance between the central vertical axis 13b; 113b of the object suspension device 13; 113 and each spreader sheave.

(49) In embodiments of a method according to the invention that makes use of a crane provided with this three-point cable suspension mechanism, during this hoisting and/or lowering, any difference in cable tension between the three hoist cables is cancelled out by a movement of one or more of the interconnected guide sheaves towards or away from the adjacent departure sheaves.

(50) In embodiments of such a method the three hoist winches 81a, 81b, 81c may be operated by the control device so as to simultaneously differently pay out and/or draw in the three hoist cables 83a, 83b, 83c in reaction to, e.g. in dependence of, any difference in cable tension between the three hoist cables, thereby controlling movement of one or more of the interconnected guide sheaves towards or away from the adjacent departure sheaves so as to cancel out this difference in cable tension.

(51) With regard to the following discussion of embodiments of a method according to the invention in relation to the figures, it is emphasized that even though the explanation relates to a method making use of the crane according to the first aspect of the invention in relation to FIGS. 1-5, the illustration of the features of the method applies similarly to a method making use of a crane according to the second and/or to the third aspect, even as the explanation thereof and any mentioned effects and/or advantages thereof.

(52) 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.

(53) 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.

(54) 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.

(55) 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.

(56) 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.

(57) 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.

(58) 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.

(59) 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.

(60) 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.

(61) A particular embodiment of 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.

(62) 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.

(63) 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.

(64) 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.

(65) A particular embodiment 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.

(66) A particular embodiment 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.

(67) Not illustrated in the figures is an embodiment wherein 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. This embodiment 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.

(68) Not illustrated in the figures is an embodiment wherein 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. This embodiment 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.