Patent Description:
This application relates to lift systems, especially to a lifting appliance mountable on wind turbines.

Wind turbines require periodic maintenance to remain operable. Due to the extreme height at which many wind turbines operate, maintaining and/or replacing turbine parts (e.g. a rotor, blade, main bearing, main shaft, intermediate shaft, gearbox, etc.) becomes problematic. For reasons of safety and practicality, turbine parts are generally lowered to ground level for maintenance and/or replacement. Typically, a crane is used to lower (and then re-raise) the parts to be maintained or replaced.

There have been a number of cranes developed in the prior art specifically adapted for maintenance of various parts of the wind turbine. For example, the cranes disclosed in copending <CIT> and <CIT> and are capable of lifting various turbine as well as lifting part of other cranes that can be mounted on the wind turbine.

<CIT> discloses the preamble of claim <NUM> with a lift system mountable in a nacelle of a wind turbine, the lift system comprising:a boom comprising a proximal end and a distal end, the proximal end of the boom mountable in the nacelle, the distal end of the boom extending over a hub of a rotor of the wind turbine when the lift system is mounted in the nacelle; a frame structure for mounting the proximal end of the boom in the nacelle; a winch mounted to the boom; a fastener situated below the boom and operatively connected to the winch by at least one cable.

<CIT> discloses a crane with a trolley movably mounted to the boom to permit translation of the trolley longitudinally along the boom. The crane makes use of at least one cable reeved through at least one trolley sheave mounted on and moveable with the trolley thereby permitting longitudinal movement of the fastener with respect to the boom when the trolley translates longitudinally along the boom.

None of the documents <CIT> nor <CIT> discloses a system which is suitable for lifting heavy turbine components, such as an entire fully assembled rotor.

Accordingly, there still remains a need for a turbine-mounted crane that is capable of lifting, moving and lowering heavy turbine components, such as a fully-assembled rotor and/or a fully-assembled main shaft assembly.

According to the invention, there is provided a lift system mountable in a nacelle of a wind turbine, the lift system comprising: a boom comprising a proximal end and a distal end, the proximal end of the boom mountable in the nacelle, the distal end of the boom extending over a hub of a rotor of the wind turbine when the lift system is mounted in the nacelle; a frame structure for mounting the proximal end of the boom in the nacelle; a winch mounted to the boom; a fastener situated below the boom and operatively connected to the winch by at least one cable; and, a trolley movably mounted to the boom to permit translation of the trolley longitudinally along the boom thereby permitting longitudinal movement of the fastener with respect to the boom, wherein the at least one cable comprises first and second cables (<NUM>, <NUM>), and the first and second cables between the winch (<NUM>) and the fastener (<NUM>) pass, respectively, on first and second transverse sides of the boom (<NUM>) so that the cables (<NUM>, <NUM>) do not interfere with longitudinal translation of the trolley (<NUM>) on the boom.

In some embodiments, the boom may be a beam or a truss structure. The boom may extend longitudinally with respect to a major axis of the nacelle when the lift system is mounted in the nacelle. To extend longitudinally, the boom does not need to be exactly parallel to the longitudinal axis of the nacelle, but can be angled by an amount, for example about <NUM>° or less, preferably about <NUM>° or less, horizontally and/or vertically with respect to the longitudinal axis of the nacelle. Preferably, the boom is substantially not angled horizontally with respect to the longitudinal axis of the nacelle. Preferably, the boom is angled vertically with respect to the longitudinal axis of the nacelle by an amount of about <NUM>° or less.

In one embodiment, the frame structure comprises a mounting base mountable on a structure capable of supporting all forces imparted to the nacelle by the lift system including the weight of the lift system, for example pillow blocks of a gearbox of the wind turbine, a bedplate, a generator, etc. In one embodiment, the frame structure comprises a plurality of upwardly extending support struts. In one embodiment, at least one of the support struts is supportable on the mounting base. In one embodiment, at least one of the support struts is mountable at a position in the nacelle proximate a main bearing of the wind turbine, for example on a yaw drive mount. In one embodiment, the plurality of upwardly extending support struts comprises a first strut mountable on the mounting base over a first gearbox pillow block of the nacelle, a second strut mountable on the mounting base over a second gearbox pillow block of the nacelle, a third strut mountable at a first position in the nacelle proximate the main bearing, for example on a first yaw drive mount of the nacelle, and a fourth strut mountable at a second position in the nacelle proximate the main bearing, for example on a second yaw drive mount of the nacelle.

In one embodiment, the winch is mounted on an upper surface of the boom. In one embodiment, the winch is mounted underneath the boom. In one embodiment, lengths of the first and second cables are independently adjustable to permit steering a load connected to the fastener. In one embodiment, the first cable is linked to a first hydraulic cylinder mounted on the first side of the boom and the second cable is linked to a second hydraulic cylinder mounted on the second side of the boom. In one embodiment, the links are direct connections of the cables to the hydraulic cylinders, although in other embodiments the links may be formed with linking structures between the cables and the hydraulic cylinders. The first and second hydraulic cylinders may be independently actuatable to independently adjust the lengths of the first and second cables.

In one embodiment, the wind turbine further comprises a main drive shaft mounted in the nacelle, the main drive shaft having a longitudinal axis oriented at a non-zero angle away from horizontal. In one embodiment, the boom has a longitudinal axis substantially parallel to the longitudinal axis of the main drive shaft. In one embodiment, the trolley translates longitudinally along a path substantially parallel to the longitudinal axis of the main drive shaft.

In one embodiment, the trolley extends transversely beyond the transverse sides of the boom. In one embodiment, the trolley comprises a first trolley sheave on a first transverse side of the boom and a second trolley sheave on a second transverse side of the boom, and the cables are reeved through the first and second trolley sheaves. Each of the first and second trolley sheaves may comprise one sheave or more than one sheave disposed side-by-side. In one embodiment, the winch is mounted on the trolley and moves with the trolley.

In one embodiment, the trolley comprises two or more movably connected pieces, for example two movably connected pieces, which can move relative to each other, for example in directions transverse to the direction of travel of the trolley, to permit yawing the load on the lift system. The two or more pieces may be movably connected, for example, by linkages, actuators or a combination thereof. For example, if the first and second hydraulic cylinders are independently actuatable and one or more linear bearings bridge the two or more pieces, a suitable arrangement would be provided.

The lift system of the present invention is safer, less costly and more reliable than existing cranes for lifting very heavy components (e.g. a fully-assembled rotor, a fully assembled main shaft assembly) of wind turbines. The lift system of the present invention reduces or eliminates the need for large ground-based cranes to making corrective repairs to such wind turbine components. The lift system of the present invention is a nacelle-mountable system having a lifting capacity of up to at least <NUM> tonnes, and which can perform the same lifting work as a <NUM>-ton conventional ground-based crane, while being easily mobilized to a site in fewer standard ISO containers.

The present lift system has all required rigging at the top of the wind turbine when mounted in the nacelle and does not require ground-based rigging or support cables running down to the ground, although a power cable may still be required in some cases to run from the generator to the ground. Therefore, the present lift system permits the rotor of the wind turbine to be turned into the wind when the lift system is installed and used, which reduces undesirable wind shear on the nacelle during erection and de-erection of wind turbine components. The present lift system also permits placing the rotor blades in the required position relative to the ground.

Further features will be described or will become apparent in the course of the following detailed description. It should be understood that each feature described herein may be utilized in any combination.

For clearer understanding, preferred embodiments will now be described in detail by way of example, with reference to the accompanying drawings, in which:.

With reference to the Figures, a lift system <NUM> mountable on a nacelle <NUM> of a wind turbine <NUM> comprises a cantilevered beam <NUM>, a frame structure <NUM> on which the beam <NUM> is supported and a winch <NUM> mounted on the beam <NUM>.

The frame structure <NUM> comprises first, second, third and fourth upwardly extending struts <NUM>, <NUM>, <NUM>, <NUM>, respectively, connected to a proximal end <NUM> of the beam <NUM>. The first and second struts <NUM>, <NUM>, respectively, are connected at the very end of the proximal end <NUM> while the third and fourth struts <NUM>, <NUM>, respectively, are connected to the proximal end <NUM> at a position longitudinally forward, with respect to the beam <NUM>, of first and second struts <NUM>, <NUM>. The frame structure <NUM> comprises a base <NUM> on which the first and second struts <NUM>, <NUM> are mounted. The base <NUM> is mountable on first and second front gearbox pillow blocks <NUM>, <NUM>, respectively, of the nacelle <NUM> (see <FIG>), although the base <NUM> may be mountable on any structure in the nacelle <NUM> capable of supporting the weight of the lift system. The third and fourth struts <NUM>, <NUM> are mountable on first and second yaw drive mounts <NUM>, <NUM>, respectively, of the nacelle <NUM> (see <FIG>). The frame structure <NUM> further comprises a plurality of cross-braces <NUM> between the struts <NUM>, <NUM>, <NUM>, <NUM> to provide structural rigidity to the frame structure <NUM>. While the proximal end <NUM> of the beam <NUM> is supported on the frame structure <NUM>, a distal end <NUM> of the beam <NUM> extends longitudinally forwardly, with respect to a major axis of the nacelle <NUM>, which is laterally forward with respect to a vertical axis of the wind turbine <NUM> The distal end <NUM> of the beam <NUM> extends over a hub <NUM> of a rotor <NUM> of the wind turbine <NUM>.

The winch <NUM> comprises a spool with two spool halves <NUM>, <NUM> mounted atop the beam <NUM> at the proximal end <NUM> of the beam <NUM> so that the weight of the winch <NUM> is borne by the frame structure <NUM>. A trolley <NUM> is mounted on trolley skidding track <NUM> on an upper surface of the beam <NUM>. The trolley <NUM> is movable by sliding longitudinally along the beam <NUM> on the trolley skidding track <NUM>. In one embodiment, the trolley <NUM> may comprise a bracket that engages the upper and side surfaces of the beam <NUM> and the trolley skidding track <NUM> may comprise one or more hydraulic cylinders, with the trolley <NUM> mounted to one or more cylinder rods of the one or more hydraulic cylinders, whereby actuation of the one or more hydraulic cylinders to extend and retract the cylinder rods causes the trolley <NUM> to move longitudinally on the beam <NUM>. The trolley <NUM> may ride or slide on bearings between the bracket and the beam <NUM>, if desired.

Cables <NUM>, <NUM> wound around the spool halves <NUM>, <NUM>, respectively, connect the winch <NUM> to a fastener block <NUM> situated below the beam <NUM>. The spool is driven by a motor so that the two spool halves <NUM>, <NUM> are driven simultaneously at the same speed. The cables <NUM>, <NUM> are isolated on to their respective spool halves <NUM>, <NUM> by a divider. The cables <NUM>, <NUM> are reeved from the spool halves <NUM>, <NUM> through forward sheaves <NUM>, <NUM>, respectively, mounted on the distal end <NUM> of the beam <NUM>. From the forward sheaves <NUM>, <NUM>, the cables <NUM>, <NUM> are reeved through trolley sheaves <NUM>, <NUM>, respectively, mounted and moveable with the trolley <NUM>. From the trolley sheaves <NUM>, <NUM>, the cables <NUM>, <NUM> are reeved through fastener block sheaves <NUM>, <NUM>, respectively, mounted on the fastener block <NUM>. From the through fastener block sheaves <NUM>, <NUM>, the cables <NUM>, <NUM> are reeved back through the trolley sheaves <NUM>, <NUM>, respectively. From the trolley sheaves <NUM>, <NUM>, the cables <NUM>, <NUM> are reeved through rearward sheaves <NUM>, <NUM>, respectively, to end terminations on the proximal end <NUM> of the beam <NUM>. The cables <NUM>, <NUM> are on opposite sides of the beam <NUM> so that the cables <NUM>, <NUM> do not interfere with movement of the trolley <NUM> on the beam <NUM>. A hook <NUM>, or other fastener such as a lifting lug, is attached to the fastener block <NUM>, the hook <NUM> depending downwardly to be able to fasten to a convenient part of a turbine component, for example the rotor <NUM> (see <FIG>) or a main drive shaft assembly <NUM> (see <FIG>).

The rearward sheaves <NUM>, <NUM>, are mounted on ends of hydraulic cylinders <NUM>, <NUM>, respectively. The opposite ends of the hydraulic cylinders <NUM>, <NUM> are fixedly mounted on the beam <NUM>. Actuation of the hydraulic cylinders <NUM>, <NUM> adjusts the lengths of the cables <NUM>, <NUM>. The hydraulic cylinders <NUM>, <NUM> are independently actuatable to so that the lengths of the cables <NUM>, <NUM> can be independently and differentially adjusted. Differential adjustments of the cables <NUM>, <NUM> causes the rotor <NUM> to move slightly to the left or right to allow alignment of the rotor <NUM> with the main drive shaft assembly <NUM> to be able to mount the rotor <NUM> on the drive shaft even when there is a side-wind that causes the rotor <NUM> to drift. Differential adjustments of the cables <NUM>, <NUM> may also assist aligning the main drive shaft assembly <NUM> with the bearings and other components mounted in the nacelle <NUM> so that the main drive shaft assembly <NUM> may be smoothly withdrawn from the nacelle <NUM>. Sequential operation of the hydraulic cylinders <NUM>, <NUM> effectively permits steering the main drive shaft assembly <NUM> when necessary to smoothly remove the main drive shaft assembly <NUM> from the nacelle <NUM> by keeping a longitudinal axis of the main drive shaft assembly <NUM> aligned with a path required to remove the main drive shaft assembly <NUM> from the nacelle <NUM>.

As illustrated in <FIG>, the lift system <NUM> may be used to lower the fully-assembled rotor <NUM> from atop the wind turbine <NUM> to the ground. The hook <NUM> is attached to the hub <NUM> with blades <NUM> of the rotor <NUM> still attached to the hub <NUM>, bolts securing the hub <NUM> to the nacelle <NUM> are loosened and the trolley <NUM> is moved to the distal end <NUM> of the beam <NUM>. The hub <NUM> is then dismounted from the nacelle <NUM> as seen in <FIG>, and the winch <NUM> operated to lower the rotor <NUM> as seen in <FIG>. Because all of the rigging for the lift system <NUM> is located on the wind turbine <NUM>, the rotor <NUM> can be turned into the wind for lowering to prevent wind loading on the rotor <NUM>. Further, the cables <NUM>, <NUM> are situated forward of the nacelle <NUM> so the nacelle <NUM> does not interfere with lowering the rotor <NUM>. As seen in <FIG>, a small mobile ground-based crane <NUM> may be attached to an end of one of the blades <NUM> simply to help stabilize and guide the rotor <NUM> while the rotor <NUM> is being lowered. Tag lines (not shown) may also be used on upwardly extending blades <NUM> to prevent rotation of the rotor <NUM> around an axis perpendicular to a plane of the blades <NUM>. Reversing the procedure can be done to re-install the rotor <NUM>.

As illustrated in <FIG>, the lift system <NUM> may be used to lower the fully-assembled main drive shaft assembly <NUM> from atop the wind turbine <NUM> to the ground. The trolley <NUM> is moved closer to the proximal end <NUM> of the beam <NUM> to a position over the main shaft assembly <NUM> where the hook <NUM> can be attached to the main shaft assembly <NUM>, for example with the assistance of a lifting tool <NUM>. The lifting tool <NUM> may comprise an adjustment tool <NUM> (e.g. a manual or a hydraulic tool) to change the angle of the main drive shaft assembly <NUM>. The main drive shaft assembly <NUM> is slightly angled when mounted in the nacelle <NUM> relative to the horizontal to account for wind loading on the rotor blades <NUM> to prevent interference between the rotor blades <NUM> and a tower <NUM> of the wind turbine <NUM> when the wind is blowing. The angle of the main drive shaft assembly <NUM> is generally in a range of about <NUM>-<NUM>° with respect to the horizontal, preferably about <NUM>-<NUM>°, for example about <NUM>°. In order to remove the rotor <NUM> from the nacelle <NUM>, the rotor <NUM> must be drawn out at this angle relative to the horizontal. In order to remove the main drive shaft assembly <NUM> from the gearbox, the main drive shaft assembly <NUM> may need to be drawn out at a steeper angle relative to the horizontal, for example about <NUM>°, to be able to clear some stud bolts. Further changing of the angle of the main drive shaft assembly <NUM> is accomplished with the adjustment tool <NUM>. The angles are different for different makes of wind turbine, hence a need for a way of adjusting the angle of the lifting tool <NUM>.

Alternatively to, or in addition to, using the adjustment tool <NUM>, the beam <NUM> is mounted on the frame structure <NUM> at an angle to the horizontal, the angle of the beam <NUM> matching the angle of the main drive shaft assembly <NUM> so that the trolley <NUM> moves along the beam <NUM> along a line parallel to the longitudinal axis of the main drive shaft assembly <NUM>, thereby permitting drawing of the rotor <NUM> off the main drive shaft assembly <NUM> without the need to use the adjustment tool <NUM>. The angle of the beam <NUM> may be adjusted by using third and fourth struts <NUM>, <NUM> of different length to match the main drive shaft assembly angle for the particular make of wind turbine. The adjustment tool <NUM> may be used to further adjust the angle of the main drive shaft assembly <NUM> after the rotor <NUM> has been drawn off the main drive shaft assembly <NUM> so that the main drive shaft assembly <NUM> can be drawn out of the nacelle <NUM> without the main drive shaft assembly <NUM> jamming on or otherwise striking the nacelle <NUM>.

Once the lift system <NUM> is connected to the main shaft assembly <NUM>, the main drive shaft assembly <NUM> is disconnected from the nacelle <NUM>. With the main drive shaft assembly <NUM> disconnected from the nacelle <NUM>, the trolley <NUM> is moved longitudinally forward to the distal end <NUM> of the beam <NUM> as seen in <FIG> so that the main drive shaft assembly <NUM> clears a front <NUM> of the nacelle <NUM>. The lifting tool <NUM> or the hook <NUM> may also have a swivel to allow rotation of the main drive shaft assembly <NUM> to create more clearance for the main drive shaft assembly <NUM> once the main drive shaft assembly <NUM> clears the front <NUM> of the nacelle <NUM>. The main shaft drive assembly <NUM> can then be lowered to the ground by the winch <NUM>. Reversing the procedure can be done to re-install the main drive shaft assembly <NUM>.

The lift system <NUM> is very large. To mount the lift system <NUM> on the nacelle <NUM>, a first auxiliary crane <NUM> may be used to lift the parts of the lift system <NUM> up to the nacelle <NUM> of the wind turbine <NUM> where the lift system <NUM> is assembled. The first auxiliary crane <NUM> is also a large crane, though not as large as the lift system <NUM>. A second auxiliary crane <NUM> may be used to lift the parts of the first auxiliary crane <NUM> up to the nacelle <NUM> where the first auxiliary crane <NUM> is assembled. The second auxiliary crane <NUM> is also a large crane, though not as large as the first auxiliary crane <NUM>. A third auxiliary crane <NUM> may be used to lift the parts of the second auxiliary crane <NUM> up to the nacelle <NUM> where the second auxiliary crane <NUM> is assembled. The third auxiliary crane <NUM> may be an existing nacelle-mounted service crane that is included with the wind turbine <NUM> when the turbine <NUM> is built.

Claim 1:
A lift system (<NUM>) mountable in a nacelle (<NUM>) of a wind turbine (<NUM>), the lift system (<NUM>) comprising:
a boom (<NUM>) comprising a proximal end (<NUM>) and a distal end (<NUM>), the proximal end of the boom mountable in the nacelle (<NUM>), the distal end of the boom extending over a hub (<NUM>) of a rotor (<NUM>) of the wind turbine (<NUM>) when the lift system (<NUM>) is mounted in the nacelle;
a frame structure (<NUM>) for mounting the proximal end (<NUM>) of the boom (<NUM>) in the nacelle;
a winch (<NUM>) mounted to the boom;
a fastener (<NUM>) situated below the boom and operatively connected to the winch (<NUM>) by at least one cable (<NUM>, <NUM>), characterised in
a trolley (<NUM>) is movably mounted to the boom (<NUM>) to permit translation of the trolley longitudinally along the boom, thereby permitting longitudinal movement of the fastener (<NUM>) with respect to the boom;
wherein the at least one cable comprises first and second cables (<NUM>, <NUM>), and the first and second cables between the winch (<NUM>) and the fastener (<NUM>) pass, respectively, on first and second transverse sides of the boom (<NUM>) so that the cables (<NUM>, <NUM>) do not interfere with longitudinal translation of the trolley (<NUM>) on the boom.