Davit crane

Abstract

A davit crane (2), comprising: - a pedestal (6); - a boom (4) that extends from a proximal end to a distal end, the proximal end being connected to the pedestal and the distal end being provided with a roller element (22); - a drive comprising a rotating shaft (14), wherein the rotating shaft is provided with a first drive roller (16) and a second drive roller (18); and - a chain (30) that extends between a drive end and a lift end, wherein, seen from the drive end to the lift end, the chain is subsequently arranged over the first drive roller, the roller element, the second drive roller and the roller element.

Description

[0001] DAVIT CRANE

[0002] The present invention relates to a davit crane, an offshore wind structure comprising the davit crane, a wind turbine comprising the davit crane, a method of lifting a load, and a method of driving a davit crane.

[0003] Different davit cranes are known from practice. Two types of known davit cranes are of the chain type and of the cable type. Chain davit cranes are provided with a chain and a drive. The drive system is positioned close to the top of the boom of the davit crane in order to ensure that the hook that is provided on the chain will lower in synchronization with the drive.

[0004] A disadvantage of the drive being positioned close to the top of the boom is that the drive is open to the outside weather conditions. Especially in offshore structures this is disadvantageous, as in offshore structures the amount of wind together with the salty water causes a lot of erosion on the drive.

[0005] Cable davit cranes are provided with a cable and a drive. The drive can be positioned in the pedestal of the crane. In general, the hook has an additional weight added to it to ensure that the hook lowers when the drive unwinds the cable. A disadvantage of the cable davit cranes is that due to the added weight on the hook, there is a chance that due to winds the hook starts to sway. This is highly dangerous for the personnel working in the proximity of the crane, as they can take a hit of the hook.

[0006] It is an object for the present invention to obviate or at least reduce the abovementioned problems. In particular, it is an object of the present invention to provide a davit crane that has a longer lifespan and is more secure.

[0007] This object is achieved by a davit crane, comprising: a pedestal; a boom that extends from a proximal end to a distal end, the proximal end being connected to the pedestal and the distal end being provided with a roller element; a drive comprising a rotating shaft, wherein the rotating shaft is provided with a first drive roller and a second drive roller; and a chain that extends between a drive end and a lift end, wherein, seen from the drive end to the lift end, the chain is subsequently arranged over the first drive roller, the roller element, the second drive roller and the roller element.

[0008] An advantage of chain being subsequently arranged over the first drive roller, the roller element, the second rive roller and the roller element is that the lift end of the chain moves synchronously with the rotation of the rotating shaft of the drive. This ensures an effective lifting operation of the crane. This is especially advantageous if the crane is used for lifting loads on ships that move vertically due to waves, as the lift end of the chain has to move synchronously with the vertical movement of the ship, for example when the crane is arranged on a platform of a wind turbine. This synchronous movement can be easily achieved with the crane according to the present invention.

[0009] Another advantage of the extra loop, i.e. the part of the chain that is arranged between the roller element, the second drive roller, and the roller element, is that the drive can be positioned in the pedestal of the crane. This positioning of the drive in the pedestal has the advantage that the drive is less susceptible to the weather conditions, which reduces the chance of corrosion. This increases the lifespan of the crane according to the invention.

[0010] Synchronous movement between the rotating shaft and the lift end must in the context of the present invention be understood as the lift end moving directly, i.e. without delay, upon rotation of the rotating shaft of the drive.

[0011] The lift end of the chain is the end which is configured to be attached to a load that is to be lifted. The lift end normally is provided with a hook that can be attached to the load.

[0012] The first and second drive roller are corotating due to their connection with the joint rotating shaft.

[0013] It is clear for the skilled person that the davit crane can be positioned on any structure. Examples of structures can be wind turbines, buildings, or even on the ground. Additionally, the davit crane can be a standalone crane.

[0014] In an embodiment according to the invention the rotating shaft of the drive is configured to rotate such that the lift end of the chain moves synchronously with the rotating shaft of the drive.

[0015] The rotating shaft can rotate around a rotation axis. The rotation axis extends in a direction that is substantially perpendicular to the vertical lifting direction. The vertical lifting direction is the direction in which the lift end of the chain moves during lifting.

[0016] In an embodiment according to the invention the first and second drive roller are positioned adjacently.

[0017] Due to the adjacent positioning of the first and second drive roller the angel between the parts of the chain which are extending towards and away from the drive are minimized. The advantage of the minimal angle between the parts of the chain is that friction is reduced. Another advantage is that a higher speed of the chain is possible.

[0018] A different wording would be that the adjacent positioning of the first and second drive roller minimizes the angle between the loop parts of the chain.

[0019] A loop part is in the context of the present invention defined as a chain part that extends from the roller element to a drive roller, or from a drive roller to the roller element. Optionally, there is a predetermined distance provided between the first and the second drive roller. The predetermined distance may be less than 20 centimetres, is preferably less than 10 centimetres, and most preferably is less than 5 centimetres.

[0020] In an embodiment according to the invention the roller element comprises a roller element shaft that is provided with a first roller element and a second roller element.

[0021] The first and second roller element are corotating due to their connection with the roller element shaft. The roller element shaft is a joint roller shaft for the first roller element and the second roller element. The first roller element and / or second roller element may be separate rollers that are attached to the roller element shaft. The first roller and / or second roller element may be guides provided on or in the roller element shaft. Due to the first and second roller element the chain is securely guided over the roller element. This ensures a correct movement of the chain, such that jamming of the crane is minimized.

[0022] Optionally, the crane comprises a third roller element and a third drive roller. This embodiment may comprise an extra loop of the chain that extends from the second roller element to the third drive roller and back to the third roller element.

[0023] In an embodiment according to the invention the davit crane further comprises a rotation sensor that is configured to measure the number of rotations of the rotation shaft and / or roller element, and a processor that is configured to receive the number of rotations from the rotation sensor and calculate the position of the chain based on the number of rotations.

[0024] Due to the measurement of the number of rotations, the controller can effectively determine the exact position of the chain. The controller can for example determine that that one full rotation equals a movement of the chain of 20 centimeters if the circumference of the rotation shaft is 20 centimeters. An advantage of this determination of the position of the chain is that no end stop is needed to determine the end of the chain when winding the chain. This removes the possibility of breaking the chain and / or drive in case of a dysfunctional end stop.

[0025] In an embodiment according to the invention the davit crane further comprises a closed housing, wherein the pedestal and the boom are closed off by the closed housing such that an inner space is formed inside the pedestal and the boom.

[0026] The closed housing may be an external wall or casing of the pedestal and boom. An advantage of the closed housing is that the inside of the pedestal and the boom, namely the inner space, is protected from outside conditions. Especially when the crane is positioned on an off shore structure, this is advantageous as the crane is then subject to harsh winds and salty seawater.

[0027] In an embodiment according to the invention the drive is positioned in the pedestal, preferably in the inner space of the pedestal. Due to the drive being positioned in the pedestal, the drive is effectively protected from outside conditions. This is especially the case when the pedestal comprises an outside housing. This improves the lifespan of the crane according to the invention.

[0028] In an embodiment according to the invention the chain is at least partly positioned in the inner space of the pedestal and boom.

[0029] Due to the chain being positioned in the inner space of the pedestal and the boom, the chain is effectively protected from outside conditions. This improves the lifespan of the crane according to the invention.

[0030] In an embodiment according to the invention the lift end comprises a hook that is configured to lift a load.

[0031] With the hook the crane can easily pick up loads, for example from a vessel.

[0032] In an embodiment according to the invention the drive comprises an electric drive.

[0033] An advantage of the electric drive is that the number of emissions of the drive at the working site is reduced. This improves the working conditions for the people working in the vicinity of the crane.

[0034] In an embodiment according to the invention an angle between the pedestal and the boom is in the range of 170-100 degrees, preferably in the range of 150-120 degrees, most preferably in the range of 140-130 degrees.

[0035] The abovementioned ranges provide a crane that has a sufficient horizontal reach away from the pedestal. This facilitates an easy lifting with the crane.

[0036] The invention further relates to an offshore structure that is provided with a davit crane according to any one of the foregoing embodiments.

[0037] The offshore structure provides similar effects and advantages as described for the davit crane.

[0038] The invention further relates to a wind turbine that is provided with a davit crane according to any one of the foregoing embodiments.

[0039] The wind turbine provides similar effects and advantages as described for the davit crane and the offshore structure. The davit crane is preferably arranged on the platform that is attached to the wind turbine, e.g. a working platform for maintenance.

[0040] The invention further relates to a method of lifting a load, comprising: providing a davit crane according to the invention, an offshore structure according to the invention or a wind turbine according to the invention; rotating the rotating shaft of the drive; and lifting the load that is attached to the lifting end of the chain. The method provides similar effects and advantages as described for the davit crane, the offshore structure and the wind turbine.

[0041] The invention further relates to a method of driving a davit crane, comprising: providing a davit crane according to the invention; and jointly rotating the rotating shaft and the roller element by the drive driving the rotating shaft such that the chain rotates the roller element.

[0042] The method provides similar effects and advantages as described for the davit crane, the offshore structure and the wind turbine.

[0043] Further advantages, features and details are elucidated based on preferred embodiments thereof, wherein reference is made to the accompanying drawings, wherein: figure 1, a perspective view of a davit crane according to the invention; figure 2, a perspective view of a drive; figure 3, a perspective view of a roller element; and figure 4, a side view of a crane according to the invention on a wind turbine.

[0044] Davit crane 2 (figure 1) comprises boom 4 and pedestal 6. Boom 4 and pedestal 6 are provided with inner space 8 that is arranged inside outside housing 10. Outside housing 10 comprises an external wall is arranged at substantially the complete outside of boom 4 and pedestal 6. In inner space 8 of pedestal 6 drive 12 is provided. Due to drive 12 being provided in inner space 8 of pedestal 6, drive 12 is shielded by outside housing 10 from the wind and / or rain. This improves the lifespan of drive 12. Drive 12 comprises rotation shaft 14. On rotation shaft 14 first drive roller 16 and second drive roller 18 are arranged. First drive roller 16 and second drive roller 18 are fixed on joint rotation shaft 14, such that first drive roller 16 and second drive roller 18 are configured to corotate. Rotation shaft 14 is configured to rotate around rotation axis A. On lift end 20 of boom 4 roller element 22 is arranged. Roller element 22 is configured to rotate around rotation axis B. Rotation axis B is substantially parallel with rotation axis A. Roller element 22 comprises roller shaft 24 whereon first roller element 26 and second roller element 28 are provided. First roller element 26 and second roller element 28 are fixed on joint roller shaft 24, such that first roller element 26 and second roller element 28 are configured to corotate.

[0045] Chain 30 extends from drive end 32 to lift end 34. Lift end 34 is provided with hook 36. Hook 36 is configured to be attached to a load that is to be lifted. Chain 30 is arranged subsequently, as seen from drive end 32 to lift end 34, on first drive roller 16, first roller element 26, second drive roller 18 and second roller element 28. Chain 30 is, as seen from drive end 32 to lift end 34, subsequently arranged on top of first drive roller 16, below first roller element 26, on top of second drive roller 18, and below second roller element 28. Although chain 30 is partially shown as a cable, this is only for illustrative purposes. Chain 30 of davit crane 2 is substantially completely made of chain links. First chain part 35a extends from first drive roller 16 to first roller element 26. Second chain part 35b extends from first roller element 26 to second drive roller 18. Third chain part 35c extends from second drive roller 18 to second roller element 28.

[0046] Drive 12 (figure 2) is provided with rotation shaft 14 which rotates around rotation axis A. Arranged on rotation shaft 14 is first drive roller 16 and second drive roller 18. First drive roller 16 and second drive roller 18 are both arranged at first side 33 of drive 12. The first drive roller 16 comprises two substantially parallel positioned disc-shaped elements 15 that are connected by connecting shaft 13. On connecting shaft 13 chain 30 can be rolled on and off. Similarly, second drive roller 18 comprises two substantially parallel positioned disc-shaped elements 19 which are connected by connecting shaft 17. Chain 30 comprises chain links 30e, 30f, 30g. Chain part 31 is depicted as a cable but comprises chain links similar to chain links 30e, 30f, 30g. Further provided on drive 12 is rotation sensor 52. Rotation sensor 52 is configured to measure the rotation of rotation shaft 14. Rotation sensor 52 is operatively connected to controller 54. Controller 54 can determine, based on the information received from rotation sensor 52, the amount of rotation of rotation shaft 14. With the amount of rotation, controller 54 can subsequently determine the distance travelled by chain 30 during rotation of rotation shaft 14. Controller 54 can for example determine based on a multiplication of the amount of rotation with the diameter of connecting shaft 17 how much chain 30 travelled.

[0047] Roller element 22 (figure 3) is provided on lift end 20 of boom 4. Roller element 22 comprises roller element shaft 24 that rotates around rotation axis B. Arranged on roller element shaft 24 is first roller roller 26 and second roller element 28. First roller element 26 comprises two substantially parallel positioned disc-shaped elements 25 that are connected by connecting shaft 27. On connecting shaft 27 chain 30 can be rolled on and off. Second roller element 28 comprises two substantially parallel positioned disc-shaped elements 29 which are connected by connecting shaft 23. Chain 30 comprises chain links 30a, 30b, 30c, 30d. Chain part 31 is depicted as a cable but comprises chain links similar to chain links 30a, 30b, 30c, 30d.

[0048] Davit crane 2 (figure 4) is arranged on platform 42. Platform 42 is attached to wind turbine 44 which comprises wind turbine blades 46. Hook 36 on lift end 34 of chain 30 is attached to load 48. Load 48 is picked up from vessel 50 that transports loads to wind turbine 44. In this way, davit crane 2 can effectively bring load 48 from vessel 50 towards wind turbine 46. Angle a between central axis 38 of boom 4 and central axis 40 of pedestal 6 is in the illustrated embodiment 130 degrees. It is clear for the skilled person that davit crane 2 can also be positioned on any other structure, or even on the ground.

[0049] In an embodiment according to the invention hook 36 is provided near lift end 20 of boom 4. Vessel 50 moves towards wind turbine 44 in order to bring load 48 towards platform 42 of wind turbine 44. Load 48 may comprise equipment that is necessary for maintenance of wind turbine 44. Rotation shaft 14 of drive 12 rotates in direction D such that chain 30 unwinds from first drive roller 16 and second drive roller 18. Due to chain 30 extending from first drive roller 16 towards first roller element 26 and back to second drive roller 18, chain 30 rotates roller element 22. In this way, it is ensured that hook 36 lowers simultaneously with the rotation of rotation shaft 14 of drive

[0050] 12 even if hook 36 is positioned near lift end 20 of boom 4. After unwinding chain 30 from second roller element 28 hook 36 is attached to load 48.

[0051] After attachment of hook 36 to load 48, rotation shaft 14 of drive 12 rotates in direction C.

[0052] This rotates first drive roller 16 and second drive roller 18 in direction C, thereby winding up chain 30 and thus lifting hook 36. In this way load 48 can be brought on level with platform 42.

[0053] The present invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following clauses within the scope of which many modifications can be envisaged.

Claims

CLAIMS1. Davit crane, comprising: a pedestal; a boom that extends from a proximal end to a distal end, the proximal end being connected to the pedestal and the distal end being provided with a roller element; a drive comprising a rotating shaft, wherein the rotating shaft is provided with a first drive roller and a second drive roller; and a chain that extends between a drive end and a lift end, wherein, seen from the drive end to the lift end, the chain is subsequently arranged over the first drive roller, the roller element, the second drive roller and the roller element.

2. Davit crane according to claim 1, wherein the rotating shaft of the drive is configured to rotate such that the lift end of the chain moves synchronously with the rotating shaft of the drive.

3. Davit crane according to claim 1 or 2, wherein the first and second drive roller are positioned adjacently.

4. Davit crane according to claim 1, 2 or 3, wherein the roller element comprises a roller element shaft that is provided with a first roller element and a second roller element.

5. Davit crane according to any one of the foregoing claims, further comprising a rotation sensor that is configured to measure the number of rotations of the rotation shaft and / or roller element, and a processor that is configured to receive the number of rotations from the rotation sensor and calculate the position of the chain based on the number of rotations.

6. Davit crane according to any one of the foregoing claims, wherein the drive is positioned in the pedestal.

7. Davit crane according to any one of the foregoing claims, further comprising a closed housing, wherein the pedestal and the boom are closed off by the closed housing such that an inner space is formed inside the pedestal and the boom.

8. Davit crane according to claim 7, wherein the chain is at least partly positioned in the inner space of the pedestal and boom.

9. Davit crane according to any one of the foregoing claims, wherein the lift end comprises a hook that is configured to lift a load.

10. Davit crane according to any one of the foregoing claims, wherein the drive comprises an electric drive.

11. Davit crane according to any one of the foregoing claims, wherein an angle between the pedestal and the boom is in the range of 170-100 degrees, preferably in the range of 150- 120 degrees, most preferably in the range of 140-130 degrees.

12. Offshore structure that is provided with a davit crane according to any one of the foregoing claims.

13. Wind turbine that is provided with a davit crane according to any one of the claims 1-11.

14. Method of lifting a load, comprising: providing a davit crane according to any one of the claims 1-11, an offshore structure according to claim 12 or a wind turbine according to claim 13; rotating the rotating shaft of the drive; and lifting the load that is attached to the lifting end of the chain.

15. Method of driving a davit crane, comprising: providing a davit crane according to any one of the claims 1-11; and jointly rotating the rotating shaft and the roller element due to the drive driving the rotating shaft such that the chain rotates the roller element.

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