Abstract
Telescopic lattice type crane boom for a crane, further comprising a locking system configured to lock at least one telescopic boom section with respect to a base boom section in at least an extended position, wherein said locking system includes a plurality of pins, each pin being configured to extend, in at least the extended position of the boom, at least partly through a corresponding pin receiving aperture provided in one of the base boom section and the at least one telescopic boom section.
Claims
1. An extendable lattice type crane boom for a crane, the crane boom comprising a lattice type base boom section and at least one lattice type telescopic boom section, wherein the at least one telescopic boom section is adjustable with respect to the base boom section between a retracted position and an extended position, in which, in the extended position, the telescopic boom section is outside of the base boom section to a greater extent than in the retracted position, further comprising a locking system configured to lock the at least one telescopic boom section with respect to the base boom section in at least the extended position, wherein said locking system includes a plurality of pins that include at least one primary pin configured to extend, in at least the extended position of the boom, at least partly through a corresponding primary pin receiving aperture provided in one of the base boom section and the at least one telescopic boom section, wherein the primary pin can be received at a wider part of the corresponding primary pin receiving aperture and then, to provide further locking, can move to a narrower part of the corresponding primary pin receiving aperture to align and lock the primary pin in the corresponding primary pin receiving aperture, wherein the wider part of said corresponding primary pin receiving aperture is larger than a cross-sectional dimension of said primary pin for engaging said primary pin in said corresponding primary pin receiving aperture and allowing movement of said primary pin in said corresponding primary pin receiving aperture, wherein the plurality of pins further include at least one secondary pin configured to extend at least partly through a corresponding secondary pin receiving aperture, wherein the secondary pin can be received in the corresponding secondary pin receiving aperture only after the at least one primary pin has moved to the narrower part of the corresponding primary pin receiving aperture.
2. The extendable lattice type crane boom according to claim 1, wherein said locking system comprises a support structure from which the plurality of pins extend.
3. The extendable lattice type crane boom according to claim 2, wherein said support structure is provided at a distal end of the base boom section.
4. The extendable lattice type crane boom according to claim 1, wherein the corresponding primary pin receiving aperture is provided at a chord of the telescopic boom section.
5. The extendable lattice type crane boom according to claim 4, wherein the chord is at a proximal end of the telescopic boom section.
6. The extendable lattice type crane boom according to claim 4, wherein said at least one primary pin and said corresponding primary pin receiving aperture are a plurality of primary pins and corresponding primary pin receiving apertures, said plurality of primary pins and corresponding primary pin receiving apertures being provided at every chord of the telescopic boom section.
7. The extendable lattice type crane boom according to claim 1, wherein said at least one secondary pin and said corresponding secondary pin receiving aperture are a plurality of secondary pins and corresponding secondary pin receiving apertures, said plurality of secondary pins and corresponding secondary pin receiving apertures being provided at a lower side of the base boom section and of the telescopic boom section.
8. The extendable lattice type crane boom according to claim 1, comprising a guiding system configured to guide a movement of the telescopic boom section along the base boom section, wherein said guiding system is provided on a chord of the base boom section and/or the telescopic boom section under an angle of 45° with respect to an upper or a lower side of the boom.
9. The extendable lattice type crane boom according to claim 1, further comprising a measurement system that detects a position of the telescopic boom section with respect to the base boom section.
10. The extendable lattice type crane boom according to claim 1, further comprising a telescopic system arranged to adjust the at least one telescopic boom section between said retracted position and said extended position, wherein the telescopic system comprises two reeving systems, each provided on an opposite side of the base boom section.
11. The extendable lattice type crane boom according to claim 10, wherein the two reeving systems are provided on opposite, lateral sides of the base boom section.
12. The extendable lattice type crane boom according to claim 1, wherein the at least one telescopic boom section is a plurality of telescopic boom sections, wherein each of said plurality of telescopic boom sections is lockable with a contiguous telescopic boom section via the locking system.
13. A crane comprising the extendable lattice type crane boom according to claim 1, wherein said telescopic boom section is movable between a transit position, in which said telescopic boom section is in the retracted position and substantially horizontal, and a working position, in which the telescopic boom section is in the extended position; a crane base to which said extendable lattice type crane boom is pivotably connected; a boom hoisting system arranged to move the telescopic boom section between said transit position and said working position; a load hoisting system configured to hoist a load.
14. The crane according to claim 13, wherein the boom hoisting system is connected to a distal end of the base boom section as well as to a distal end of the telescopic boom section.
15. The crane according to claim 13, wherein the crane base is mountable around a leg of a jack up platform.
16. A jack up platform including the crane according to claim 13.
17. The extendable lattice type crane boom according to claim 1, wherein the corresponding secondary pin receiving aperture has a size which is larger than a cross-sectional dimension of the at least one secondary pin configured to extend at least partly there through.
18. A method of operating a crane including an extendable lattice type crane boom, wherein the extendable lattice type boom comprises a lattice type base boom section and at least one lattice type telescopic boom section, the method comprising the steps of: operating a boom hoisting system to bring the extendable lattice type crane boom from a transit position to a working position; operating a telescopic system to adjust the at least one lattice type telescopic boom section with respect to the lattice type base boom section from a retracted position to an extended position, in which the lattice type telescopic boom section is outside of the lattice type base boom section to a greater extent than in the retracted position; inserting at least one primary pin least partly through a corresponding primary pin receiving aperture to substantially determine a position of the lattice type telescopic boom section with respect to the lattice type base boom section, wherein a size of the corresponding primary pin receiving aperture is larger than a cross-sectional dimension of the at least one primary pin to allow movement of the primary pin in the corresponding primary pin receiving aperture; adapting an angular position of the lattice type telescopic boom section with respect to the lattice type base boom section until a secondary pin receiving aperture corresponds with a secondary pin; inserting the secondary pin in the secondary pin receiving aperture.
19. The method according to claim 18, wherein during operation of the telescopic system to extend or retract the lattice type telescopic boom section with respect to the lattice type base boom section, the boom hoisting system is controlled to follow the telescopic system to facilitate the movement of the lattice type telescopic boom section.
20. The method according to claim 18, wherein during operation of the telescopic system, a crane boom angle is approximately 80 degrees.
21. The method according to claim 18, wherein during operation of the telescopic system, a measurement system determines an actual position of the lattice type telescopic boom section with respect to the lattice type base boom section, wherein the measurement system provides output of a determined actual position to an output module.
22. The method according to claim 21, wherein, upon approaching a desired extended position, the measurement system controls a speed reduction of the telescopic system.
23. The method according to claim 22, wherein upon reaching the desired extended position, the at least one primary pin is inserted in the at least one corresponding primary pin receiving aperture.
Description
(1) The disclosure will further be elucidated on the basis of exemplary embodiments given by way of non-limitative description and illustration. It is noted that the figures are only schematic representations of embodiments of the disclosure that are given by way of non-limiting example. Various modifications, variations, and alternatives are possible, as well as various combinations of the features described. The specifications, drawings and examples are, accordingly, to be regarded in an illustrative sense rather than in a restrictive sense. Embodiments according to the disclosure will, by way of non-limiting example be described in detail with reference to the accompanying drawings. In the drawings:
(2) FIGS. 1a and 1b show a perspective view of a crane including an extendable crane boom according to an embodiment of the invention in a retracted and an extended position respectively;
(3) FIGS. 2a and 2b show a side view on the crane of FIG. 1 in a retracted and an extended position respectively;
(4) FIG. 3a shows a perspective view on an upper side of a telescopic boom section of the extendable boom in the crane of FIG. 1;
(5) FIG. 3b shows a cross-sectional view of a base boom section and the telescopic boom section of the extendable boom in the crane of FIG. 1;
(6) FIG. 4 shows a perspective view on part of the extendable boom in an extended position of the crane of FIG. 1;
(7) FIGS. 5a-5e show a side view on part of the extendable boom of FIG. 1, illustrating a method operating said extendable crane boom;
(8) FIG. 6a shows a side view of a crane arrangement according to another embodiment of the invention comprising an extendable boom with a telescopic boom section in a retracted position;
(9) FIG. 6b shows the crane arrangement of FIG. 6a with the telescopic boom section in an extended position;
(10) FIG. 7 is a perspective view of a locking system of the crane arrangement of FIG. 6;
(11) FIG. 8 shows a side view of the crane arrangement of FIG. 6a with the guiding contacts during extension or retraction.
(12) FIG. 9 show a side view of a locking system illustrating the sequence of steps required to lock the telescopic boom section of the crane arrangement of FIG. 6 in an extended position, with:
(13) FIG. 9a showing step 1: Insertion of the upper pin;
(14) FIG. 9b showing Step 2: Alignment of the telescopic part;
(15) FIG. 9c showing Step 3: Insertion of the lower pin;
(16) FIG. 10 shows a third embodiment of a crane arrangement comprising an extendable boom with a telescopic part in extended position and the boom hoist wires connected to the pivoting part of the extendable boom;
(17) FIG. 11 show a side view of a locking system illustrating the sequence of steps required to lock the telescopic boom section of the crane arrangement of FIG. 10 in an extended position, with:
(18) FIG. 11a Step 1: Insertion of the lower pin
(19) FIG. 11b Step 2: Alignment of the telescopic part
(20) FIG. 11c Step 3: Insertion of the upper pin
(21) FIG. 12 shows a fourth embodiment of a crane arrangement with the main hoist at the top of the pivoting part of the extendable boom integrated with the locking-pin box structure, and an auxiliary hoist at the boom tip.
(22) FIGS. 1a and 1b show a perspective view on a crane 1 including an extendable crane boom 2 according to an embodiment of the invention in a retracted and an extended position respectively. The crane 1 comprises a crane base 3 to which said extendable lattice type boom 2 is rotatably connected. The crane base 3 may be mounted around a leg 4 of a jack up platform, but may also be mounted differently, for example on a standard pedestal with slewing bearing, on a jack up platform or on any other structure where this type of crane is needed. The crane base 3 may be configured such as to be mounted around a leg 4 of a jack up platform. The lattice type boom 2 is movable between a transit position (not shown), in which said lattice type boom 2 is in a substantially retracted and substantially horizontal position, and a working position, in which the lattice type boom is extendable. To perform said movement of the crane boom, the crane 1 also includes a boom hoisting system 5 arranged to move the extendable boom 2 between said transit position and said working position. Said boom hoisting system includes at least one, preferably two, boom hoist winches 11 mounted on the crane base. The boom hoisting system 5 may include two parallel wire rope and sheaves systems both connected to a distal end of the extendable boom, and/or to a distal end of the base boom section 2a. The crane 1 is further equipped with a load hoisting system 6 configured to hoist a load. Said load hoisting system 6 may include at least one main hoist winch 10, a head assembly 7 mounted on a distal end of the extendable crane boom 2, as well as an optional secondary hoisting system 8 including an auxiliary hoist winch, which may be configured to hoist smaller loads, to a greater height and more quickly than the main load hoisting system. The main hoisting system may for example be configured to hoist loads of up to approximately 2500 tons to a height of approximately 115 m above ground/deck, or a load of up to approximately 1250 tons to a height of approximately 156 m above ground/deck. Such a configuration allows installation of off-shore wind turbines of up to approximately 16 MW. It is understood that this is just an example, and that smaller or larger configurations are possible. The extendable boom 2 comprises a lattice type base boom section 2a and at least one lattice type telescopic boom section 2b. The lattice type base boom section 2a, as well as the lattice type telescopic boom section 2b, each include longitudinal chords 15, in particular four chords 15, at each corner of the boom section 2a, 2b, which are interconnected with trusses 16. A diameter of the chords 15a of the base boom section 2a is typically larger than a diameter of the chords 15b of the telescopic boom section 2b. The telescopic boom section 2b is adjustable with respect to the base boom section 2a between a retracted position (FIG. 1a), in which the telescopic boom section 2b is substantially inside of the base boom section 2a, and an extended position (FIG. 1b), in which the telescopic boom section 2b is at least partly outside of the base boom section 2a. In the above-mentioned example of a hoisting system configured for hoisting loads up to 2500 tons, the total boom length may for example be around 95 m in a retracted position, whereas the total boom length in a most extended position may for example be as long as approximately 135 m, or longer or shorter.
(23) FIGS. 2a and 2b show a side view on the crane of FIG. 1 in a retracted and an extended position respectively. The boom hoisting system 5 is connected to a distal end of the base boom section 2a as well as to a distal end of the telescopic boom section 2b, more in particular, to the head assembly 7 on the telescopic boom section 2b and to a support structure 9 on a distal end of the base boom section 2a. In a working position, as shown, when the extendable boom 2 can be extended, the crane boom 2 makes an angle α with a substantially horizontal transit position of the crane boom 2 in a range of approximately 75°-85°, preferably an angle of approximately 80° with a tolerance of approximately 2°. Said position allows to decrease as much as possible loads on a guiding system (see FIG. 3) of the extendable boom 2. The transit and working positions also allow to define an upper side 17 and a lower side 18 of the extendable boom 2, the lower side 18 being the side of the extendable boom 2 turned downwards in a transit position, and the upper side 17 of the extendable boom 2 being the opposite side of the lower side 18. The boom hoisting system 5 is at least partly mounted on the upper side 17 of the extendable boom 2, whereas loads are hoisted along the lower side 18 of the extendable boom 2. The extendable crane boom 2 also comprises a telescopic system 12 arranged to adjust the at least one telescopic boom section 2b between said retracted position and said extended position. Said telescopic system 12 comprises at least one reeving system, preferably two reeving systems, each provided on an opposite side of the base boom section 2a, preferably on lateral sides of the base boom section 2a (see FIG. 4). The telescopic system 12 can be configured to extend the extendable boom 2 from a retracted position (FIG. 2a) to an extended position (FIG. 2b) in relatively swiftly. The telescopic system 12 also includes at least one telescopic winch 13. The reeving system may be configured such that pulling a wire rope 14 in with the winch 13 can for example result in the telescopic boom section 2b being pulled out of the base boom section 2a, thus extending the boom, while moving along a guiding system. During retraction of a telescopic boom section 2b, the winch 13 can be operated to release the wire rope 14 allowing the telescopic boom section to move inside of the base boom section, typically moving down as a result of gravity.
(24) FIG. 3a shows a perspective view on an upper side of a telescopic boom section 2b of the extendable boom 2 in the crane 1 of FIG. 1, whereas FIG. 3b shows a cross-sectional view of a base boom section 2a and a telescopic boom section 2b of the extendable boom 2 in the crane 1 of FIG. 1. In order to improve a smooth extension and/or retraction of the telescopic boom section 2b in and out the base boom section 2a, the extendable boom comprises a guiding system including guide rails and guiding elements configured to be guided along the guide rails. The telescopic boom section 2b can for example be provided with at least one upper guide rail 19, which is preferably positioned on a chord 15b on an upper side 17 of the telescopic boom section 2b, more preferably on each of the two chords 15b on the upper side 17 of the telescopic boom section 2b. The upper guide rails 19 are preferably positioned making an angle with the upper side 17 of the extendable boom 2 of approximately 45°. The upper guiding element 20 configured to be guided on the upper guide rails 19 may for example be a sliding pad mounted on the base boom section 2a, preferably on a distal end of the base boom section 2a, for example on a support structure 9 on the distal end of the base boom section 2a. The upper guiding element 20 may be configured to engage the guide rail 19 on an upper surface of the guide rail 19, which upper surface is substantially in parallel with an upper side 17 of the extendable boom 2. The upper guide rail 19 may be configured to be engaged by a secondary upper guiding element (not shown) along a side of the upper surface of the guide rail 19, which side is at a substantially right angle with said upper surface. The base boom section 2a is further provided with at least one lower guide rail 21, preferably with two lower guide rails 21, each provided on a chord 15a on the lower side 18 of the extendable boom 2, preferably radially extending inwardly making an angle of 45° with said lower side 18. Lower guiding elements 22 configured to be guided on the lower guide rails 21 may for example be a sliding pad mounted on the telescopic boom section 2b, preferably radially extending on a proximal end of the chords 15b on a lower side 18 of the telescopic boom section 2b. The lower guiding elements 22 engage the lower guide rails 21 on an engagement surface of the guide rail 21, which surface is tilted under an angle of approximately 45° with the lower side of the extendable boom 2, providing a lower radial guiding engagement in contrast to an upper angles guiding engagement. In summary, the base boom section 2a is provided with lower guide rails 21 and upper guiding elements 20, whereas the telescopic boom section 2b is provided with upper guide rails 19 and lower guiding elements 22. It will be clear to the person skilled in the art that an opposite installation of the guiding system, or a different guiding system, is possible as well. All guide rails 19, 21 can for example be made of steel, preferably greased steel. The upper and lower guide rails 19, 21 can for example extend over a length of approximately 45-50 m along the chords of the telescopic boom section 2b or the base boom section 2a respectively, depending on a total length of the extendable boom and on a length of the telescopic boom section.
(25) FIG. 4 shows a perspective view on part of the extendable boom in an extended position of the crane of FIG. 1. The extendable boom 2 further comprises a locking system 23 configured to lock the at least one telescopic boom section 2b with respect to the base boom section 2a in at least an extended position. Said locking system 23 includes a plurality of pins 24, each pin 24 being configured to extend, in at least the extended position of the boom, at least partly through a corresponding pin receiving aperture 25 provided in one of the base boom section 2a and the at least one telescopic boom section 2b. A size of at least one of said pin receiving apertures 25 is substantially larger than a cross-sectional dimension of a corresponding one of said plurality of pins 24 for engaging in the pin receiving aperture 25. In the embodiment shown in FIG. 4, the locking system 23 comprises a support structure 9 from which the plurality of pins 24 extend. Said support structure 9 is provided at a distal end of the base boom section 2a. The corresponding pin receiving apertures 25 are provided at a chord 15b of the telescopic boom section 2b, in particular at a proximal end of the telescopic boom section 2b, more in particular of every chord 15b of the telescopic boom section 2b. The locking system of the embodiment of FIG. 4 includes four primary pins, each extending into a corresponding aperture 25 in the telescopic boom section 2b. The locking system 23 also comprises a secondary set of pins 26 and corresponding pin receiving apertures, which are provided in the chords 15b on the lower side 18 of the extendable boom 2. Preferably at least one of the pin receiving apertures has a size which is substantially larger than a cross-sectional dimension of the corresponding pin to be received. The pins 24 are applied to obtain a direct connection between the chords 15b of the telescopic boom section 2b and the chords 15a of the base boom section 2a. The telescopic boom section 2b can include a locally forged or welded structure 27 at the location of the pin receiving apertures 25.
(26) FIGS. 5a-5e show a side view on part of the extendable boom 2 of FIG. 1, illustrating a method of operating said crane 1. The method comprises a first step (not shown) of operating a boom hoisting system 5 to bring the extendable lattice type boom 2 from a transit position to a working position, so from a substantially horizontal and retracted position to a position in which the extendable crane boom 2 includes a crane boom angle of approximately 80° with the substantially horizontal transit position. As a next step, illustrated in FIG. 5a, a telescopic system 12 is operated to adjust the telescopic boom section 2b with respect to the base boom section 2a from a retracted position, in which the telescopic boom section 2b is substantially inside of the base boom section 2a, to an extended position, in which the telescopic boom section 2b is substantially outside of the base boom section 2a. During operation of the telescopic system 12 to extend or retract the telescopic boom section 2b with respect to the base boom section 2a, the boom hoist system 5 may be operated to facilitate the movement of the telescopic boom section 2b. An separate alignment system is not needed in this embodiment. During operation of the telescopic system 12, a measurement system 28 can determine an actual position of the telescopic crane boom section 2b with respect to the base boom section 2a. The measurement system can provide output of a determined actual position to an output module, which can for example automatically control the telescopic system. Upon approaching a desired extended position, i.e. a locking position in which the pins 24 are facing the corresponding pin receiving apertures 25, the measurement system 28 may control a speed reduction of the telescopic system 12, for example a speed reduction to approximately 10% of the previous speed, so for example to a speed of 5 mm per second from 0.5 m before said locking position. The telescopic system 12 may be configured to stop automatically when the telescopic boom section 2b reaches the desired locking position. The exact position of the telescopic boom section 2b can then be checked again, for example visually by an operator using for example a closed circuit TV system. The operator can then give a signal for pin insertion, which is the next step of the method, as illustrated in FIG. 5b. At least one, but preferably all four primary pins 24, are inserted through a corresponding pin receiving aperture 25 to substantially determine a position of the telescopic boom section 2b with respect to the base boom section 2a. The pins can for example be hydraulically actuated, or actuated in any other known way. As can be seen in FIG. 5b, the pin receiving apertures 25 are substantially larger than a cross-sectional dimension of a corresponding one of said plurality of pins 24 for engaging in the pin receiving aperture 25, i.e. the space around the pins 24 during insertion into the apertures 25 is at least 10 mm, and preferably a lot more in a longitudinal direction of the chords, so that insertion can be done freely and the pins 24 cannot get stuck. The primary pins 24 to be inserted into a corresponding aperture in a chord 15b on the upper side 17 of the extendable boom 2 are preferably pins having a substantially round cross-section, whereas the pins to be inserted into a corresponding aperture in a chord 15b on the lower side 18 of the extendable boom 2 are preferably pins having a substantially rectangular cross-section. The pin receiving apertures 25 may for example also be droplet-shaped. In a next step, illustrated in FIG. 5c, an angular position of the telescopic boom section 2b with respect to the base boom section 2a is adapted until a secondary pin receiving aperture 25b corresponds with a secondary pin 26. The secondary pin receiving aperture 25b may be separated from the primary pin receiving aperture 25, as illustrated here, but may also be part of a larger single pin receiving aperture, of which an upper section is configured to receive a primary pin 24 and a lower section is configured to receive a secondary pin 26. This adapting of an angular position can be done by operating the telescopic system 12, lowering the telescopic boom section 2b until the primary pins 24 on the upper side 17 of the boom 2 make contact with an edge of the corresponding pin receiving aperture 25. The guiding system, in particular the upper guide rail 19, on the upper side 17 of the boom 2 is now free and load is now transferred through said pins, while the guiding system, in particular the lower guide rails 21, on the lower side 18 of the boom 2 still makes contact and is loaded. As illustrated in FIG. 5d, the telescopic boom section 2b is then lowered still further until the primary pins 24 on the lower side 18 of the crane boom 2 make contact with an upper edge of the corresponding pin receiving aperture 25. Now both the upper guide rails 19 as well as the lower guide rails 21 are unloaded. The pins 24 on the upper side 17 take shear and axial load, whereas the pins 24 on the lower side 18 of the crane boom 2 only take axial load. Finally, at least one, and preferably two secondary pins 26 are inserted into corresponding pin receiving apertures, preferably only on the lower side 18 of the crane boom 2. The secondary pins 26 make contact with a lower edge of the corresponding pin receiving aperture 25b, such as to stably lock the telescopic boom section 2b with respect to the base boom section 2a.
(27) In FIGS. 6a and 6b a second embodiment of an extendable crane 1′ with a base boom section 2a, also known as the fixed boom part, and one telescopic boom section 2b is presented in the retracted and the extended position respectively. The boom hoist wires or luffing wires of the boom hoisting system 5 are connected to the top of the telescopic part. Note that ‘wire’ can also mean ‘wire rope’, ‘rope’ or ‘cable’. The extendable boom is shown as part of a pedestal crane, but this can be any type of crane with boom hoist wires.
(28) The boom 2 is in retracted position when the distal telescopic boom sections 2b are stored in the base boom section 2a. In the retracted position the boom 2 can be upended by means of the boom hoist system 5. For normal lifting purposes, the crane 1′ can be used in the retracted position, as the crane is then stronger (more capacity) and/or more flexible and/or easier to use than with an extended boom 2. In the upended or working position the boom 2 can be extended when large lifting height is required, for example when installing a wind turbine on top of a tower.
(29) FIG. 7 shows a perspective view of the locking system 23′. The lattice structure has in this embodiment a rectangular shape with four chords 15. The chords 15 at the side where boom hoisting elements are provided, are denoted as ‘upper chords’. The chords at the opposite side thereof, are denoted as ‘lower chords’. The telescopic boom section 2b may fit into the base boom section 2a. For the telescopic system 12 a multi-falls reeving system is provided that is mounted in between the telescopic boom section 2b and the base boom section 2a. The hauling part is going to a winch located on the slewing platform.
(30) Guide rails 19′ are connected on the chords 15 of the telescopic boom section 2b. In the base boom section 2a the lower and upper guides 20′ are mounted. The guide system can be arranged vice versa as well, for example with the guide rails 19′ on the base boom section 2a and the guides 20′ on the telescopic boom section 2b.
(31) The locking system 23′ comprises a support structure 9′ that is provided in the head of the base boom section 2a. The support structure 9′ is embodied here as a reinforced ‘box-like’ structure, of which the sides are provided as plate structure to which the locking pins are mounted. For reasons of simplicity, the side plates are not shown in FIG. 7. The box structure has additional reinforcements to transfer the load of the locking pins locally. The support structure 9′ is designed in such a way that the pin load, when the boom is in extended and locked position, does not lead to additional moments in the chords of the fixed part. So the chords of the fixed part are advantageously only loaded in compression (or tension).
(32) In FIG. 8 an extendable boom crane 1′ with luffing wires (boom hoist wires) of the boom hoist system 5 connected to the telescopic boom section 2b of the boom 2 is shown. The locations where the telescopic guides have contact are indicated by arrows 30. This is the situation when the boom 2 is fully extended and with no load in the hook. Because of the own weight of the boom and the position of the luffing wires the boom is subject to a bending moment and slightly bends downwards. In FIG. 8 the bending of the boom is exaggerated. In practice there is only a relatively small play between the guiding of the base boom section 2a and the telescopic boom section 2b. Basically the upper chords 15 are likely to remain under compression. Thereto a slotted-hole connection can be applied for easy insertion of the locking pin 24 in the upper chord 15, as shown in FIG. 9a. After alignment of the telescopic boom section 2b with respect to the base boom section 2a, the locking pin 26 can also be inserted into the aperture 25b of the lower chord, which preferably is a fitting aperture. Since the lower chords can be loaded under tension, as well as under compression, with load in the hook, the locking pin connection at the lower chord is preferably a fitting connection, contrary to the slotted connection of the upper chord.
(33) The procedure for operating the extendable boom with boom hoist wires connected to the boom top is shown in FIGS. 9a-9c.
(34) Step 1: With the winch of the telescopic system the telescopic boom section 2b can be extended. The telescopic boom section 2b can be extended a little bit “too” far. The upper pin 24 can be easily inserted in the slotted hole 25. The own weight bending moment in the boom can still be transferred by the guiding system. After the upper pin insertion the telescopic system 12 can lower the telescopic boom section 2b a little bit until the upper pin 24 is in contact with the corresponding slotted aperture 25 of the telescopic boom section 2b. The telescopic system 12 does not need to be actuated anymore, and the actuator can be decoupled and/or unloaded from the telescopic system, so the telescopic system does not transfer load in the extended position. The slotted hole dimensions will be designed in such a way that it can take over the compression load but it also allow alignment of the telescopic boom section and can unload the upper guides, after alignment.
(35) Step 2: With the hydraulic jacks 31 of the alignment system the telescopic boom section 2b can be rotated over a small angle with respect to the upper pin connection to undo the contact of the lower guide 20′ from its corresponding guide rail 19′. The telescopic boom section 2b can now be accurately aligned with the base boom section 2a. When both the telescopic boom section 2b and the base boom section 2a are in line, the locking pin 26 and aperture 25b of the lower part will be in line as well and the lower pin 26 can be inserted.
(36) Step 3: The final step can be to insert the lower locking pin 26 and to release the hydraulic jacks 31 of the alignment system. All the guides 20′ are retrieved now and not in load transferring contact anymore with the respective guide rail. The boom loads can be transferred through the locking pins. When the locking pins are engaged the winch of the telescopic system may be unloaded to be sure that all the load transfer is via these locking pins.
(37) In FIG. 10 an extendable boom crane 1″ with luffing wires (boom hoist wires) of a boom hoist system 5 connected to the base boom section 2a is shown. The locations where the telescopic guides have contact are again indicated by arrows 30. The loads act in the opposite direction when compared to the situation shown in FIG. 8. This is the situation when the crane is fully extended and with no load in the hook. Because of the own weight of the boom and the position of the luffing wires the boom is subject to a bending moment and bends upwards. In FIG. 10 the bending of the boom is exaggerated. In practice there is only a relatively small play between the guiding of the base boom section and the telescopic boom section. The load moment in the telescopic boom section is in this case always in the same direction. The upper chords are loaded under tension and the lower chords are loaded under compression. So there is no change of load direction. Both upper and lower holes can therefore be provided as slotted holes. The locking procedure is less critical but the pin load is in this execution much higher because of the additional load moment due to the overturning of the telescopic boom section. A fitting pin and aperture connection is not required but can be applied in the upper chord.
(38) The procedure for operating the extendable boom crane 1″ with boom hoist wires (luffing wires) connected to the top of the base boom section is shown in FIGS. 11a-11c.
(39) Step 1: With the winch of the telescoping system the telescopic boom section 2b can be extended. The telescopic boom section 2b will be extended a little bit “too” far. The lower pin can 24 be easily inserted in the slotted hole 25. The own weight moment in the boom will still be transferred by the guiding system. After the lower pin insertion the telescopic system 12 may lower the telescopic boom section 2b a little bit until the upper pin 24 is in contact with the corresponding aperture 25 of the telescopic boom section 2b. The actuator of the telescopic system can be unloaded, so to relieve the telescopic system from load transfer. The slotted hole dimensions are preferably designed in such a way that it can take over the compression load but it also may also allow alignment of the telescopic boom section.
(40) Step 2: With the hydraulic jacks of the alignment system the telescopic boom section 2b can be rotated over a small angle with respect to the lower pin connection to undo the load transferring connection between the upper guide and the corresponding guide rail. The telescopic boom section 2b can now be accurately aligned with the base boom section 2a. When both the telescopic boom section 2b and the base boom section 2a are in line, the pin 26 and aperture 25b of the upper part may be in line as well and the upper pin 26 can be inserted.
(41) Step 3: The final step may be to insert the upper locking pin 26 and to release the hydraulic jacks of the alignment system. All the guides are free from their corresponding guide rail, so load transfer between the guide and the guide rail may be obviated. Preferably, the guide and the guide rail are not in contact anymore. The boom loads may be transferred through the locking pins. When the locking pins are engaged the actuator of the telescopic system can be unloaded as well to ensure that all the load transfer is via these locking pins and not via the telescopic system.
(42) FIG. 12 shows an alternative embodiment of a crane 1′″ around a leg 4, such as frequently utilized on an offshore jack up platform 100, with extendable boom 2. The support structure 9 at the top of the base boom section 2a, in which the locking pins 24 are mounted, now has an integrated main hoist 32. In normal operation, the telescoping section 2b will be retracted and the main hoist 32 at the base boom section 2a will be used. When large lifting height is required, such as when a wind turbine is installed on top of a tower, or blades are attached to the wind turbine, the crane 1′″ will be extended and the auxiliary hoist 8 will be used.
(43) A crane 1 with extendable boom 2, comprising of lattice type sections, has several advantages when utilized on offshore installation jack-up platforms. The crane boom 2 may be retracted when in transit positions which means that the boom, capable of large lifting height as required for installing wind turbines, may not protrude from the boom rest, which obviates the problems that occur when utilizing a longer fixed boom.
(44) It is to be noted that the figures are only schematic representations of embodiments of the invention that are given by way of non-limiting examples. For the purpose of clarity and a concise description, features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described. The word ‘comprising’ does not exclude the presence of other features or steps than those listed in a claim. Furthermore, the words ‘a’ and ‘an’ shall not be construed as limited to ‘only one’, but instead are used to mean ‘at least one’, and do not exclude a plurality. The mere fact that certain features are recited does not indicate that a combination of these features cannot be used to an advantage. Many variants will be apparent to the person skilled in the art. All variants are understood to be comprised within the scope of the invention.
