Patent Publication Number: US-9850880-B2

Title: System for servicing wind turbine rotor

Description:
FIELD OF THE INVENTION 
     The present subject matter relates generally to wind turbines and, more particularly, to an improved method and system for enabling servicing of the rotor of the wind turbine without completely removing the rotor from the wind turbine. 
     BACKGROUND OF THE INVENTION 
     Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of the wind using known foil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy. A power converter typically regulates the flow of electrical power between the generator and a grid. 
     Typically, to initially install a rotor blade onto the wind turbine hub and/or to remove or lower one of the existing rotor blades from the hub, a significantly large crane must be transported to the wind turbine site in order to provide a means for raising and/or lowering the rotor blade relative to the hub. Unfortunately, it is often extremely expensive to both transport the crane to the wind turbine site and operate the crane for the amount of time necessary to install and/or remove/lower the rotor blade(s). As a result, the costs of employing such large cranes currently accounts for a significant portion of the overall costs associated with initial wind turbine installations and rotor maintenance or service operations. 
     Accordingly, an improved method and related system for lowering wind turbine rotor blades to enable rotor service that do not require the use of a significantly large crane would be welcomed in the technology, and the improved method and related system would make wind power more economically competitive with other forms of power generation. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In one aspect of the invention, a system is provided for enabling servicing of a rotor of a wind turbine. The system includes a rotor servicing fixture configured to attach to and be supported by a first rotor blade and a second rotor blade. The rotor servicing fixture is configured to contact a tower of the wind turbine. A clamp assembly is connected to the rotor servicing fixture. The clamp assembly is configured to clamp onto a third rotor blade. The clamp assembly is configured to lower the third rotor blade from a hub, and to raise the third lower blade back to the hub. A lifting assembly is connected to the rotor servicing fixture and the clamp assembly. The lifting assembly is configured for raising and lowering the third rotor blade via the clamp assembly. A slide assembly is connected to the rotor servicing fixture. The slide assembly is configured to support the rotor part and to slidably move the rotor part away from and/or towards the wind turbine. The system enables the rotor part to be removed and/or replaced without requiring the rotor to be removed from the wind turbine. 
     In another aspect, a method is provided for servicing a rotor of a wind turbine. An attaching step attaches a rotor servicing fixture to the rotor of the wind turbine. The rotor servicing fixture is configured to attach to and be supported by a first rotor blade and a second rotor blade. The rotor servicing fixture is configured to contact a tower of the wind turbine. A second attaching step attaches a clamp assembly onto a third rotor blade. The clamp assembly is connected to the rotor servicing fixture. The clamp assembly is configured to clamp onto the third rotor blade. A lowering step lowers the third rotor blade by a predetermined amount with the clamp assembly and a lifting assembly. The clamp assembly is configured to lower the third rotor blade from a hub and to raise the third lower blade back to the hub. The lifting assembly is connected to the rotor servicing fixture and the clamp assembly. The lifting assembly is configured for raising and lowering the third rotor blade via the clamp assembly. A servicing step services the rotor part, and the servicing step is performed without removing the rotor from the wind turbine. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  illustrates a perspective view of one embodiment of a wind turbine; 
         FIG. 2  illustrates a perspective view of one of the rotor blades of the wind turbine shown in  FIG. 1 ; 
         FIG. 3  illustrates another perspective view of the wind turbine shown in  FIG. 1 , particularly illustrating a rotor blade to be removed from the wind turbine positioned in a generally vertical orientation relative to a support surface of the wind turbine and a blade sock installed onto the rotor blade; 
         FIG. 4  illustrates a close-up, partial perspective view of the rotor blade and the blade sock shown in  FIG. 3 ; 
         FIG. 5  illustrates a cross-sectional view of the rotor blade and blade sock shown in  FIG. 4  taken about line  5 - 5 ; 
         FIG. 6  illustrates a top-down view of the cross-section shown in  FIG. 5  relative to a support surface of the wind turbine, particularly illustrating sock cables extending from the blade sock to corresponding winches supported on and/or adjacent to the support surface; 
         FIG. 7  illustrates a similar cross-sectional view to that shown in  FIG. 5 , particularly illustrating another embodiment of a blade sock in accordance with aspects of the present invention; 
         FIG. 8  illustrates a similar cross-sectional view to that shown in  FIG. 5 , particularly illustrating a further embodiment of a blade sock in accordance with aspects of the present invention; 
         FIG. 9  illustrates a side view of a system for enabling servicing of the rotor, according to an aspect of the present invention; 
         FIG. 10  illustrates a side view of the rotor servicing fixture, according to an aspect of the present invention; 
         FIG. 11  illustrates a top view of the system and rotor servicing fixture, according to an aspect of the present invention; 
         FIG. 12  illustrates a top view of one example of a clamp assembly, according to an aspect of the present invention; 
         FIG. 13  illustrates a partial side view of the lifting assembly, according to an aspect of the present invention; 
         FIG. 14  illustrates a partial, cross-sectional view of the slide assembly, according to an aspect of the present invention; 
         FIG. 15  is a close-up, partial perspective view of a rotor blade and the hub, particularly illustrating another embodiment of a lifting/lowering system including support cables/chains secured to the rotor blade and corresponding cable translation devices positioned within the hub; 
         FIG. 16  illustrates a close-up, partial perspective view of the interface between the rotor blade and the pitch bearing shown in  FIG. 15  prior to the rotor blade being lowered from the hub, particularly illustrating a support cable coupled between a support nut installed within the blade root and a corresponding cable translation device positioned within the hub; 
         FIG. 17  illustrates a perspective view of the support nut shown in  FIG. 15 ; 
         FIG. 18  is a flow chart of a method for servicing a rotor, according to an aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     In general, the present subject matter is directed to a method and system for lowering a rotor blade from a hub and removing or installing a rotor part without having to use a crane to lower the entire rotor or blade to the ground. Specifically, as will become apparent from the description provided below, the disclosed method and system avoids the use of a large, expensive crane capable of raising or lowering the entire rotor, thereby significantly reducing the costs associated with blade lowering and re-installation. 
     Referring now to the drawings,  FIG. 1  illustrates a side view of one embodiment of a wind turbine  10 . As shown, the wind turbine  10  generally includes a tower  12  extending from a support surface  14  (e.g., the ground, a concrete pad or any other suitable support surface). In addition, the wind turbine  10  may also include a nacelle  16  mounted on the tower  12  and a rotor  18  coupled to the nacelle  16 . The rotor  18  includes a rotatable hub  20  and at least one rotor blade  22  coupled to and extending outwardly from the hub  20 . For example, in the illustrated embodiment, the rotor  18  includes three rotor blades  22 . However, in an alternative embodiment, the rotor  18  may include more or less than three rotor blades  22 . Each rotor blade  22  may be spaced about the hub  20  to facilitate rotating the rotor  18  to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. For instance, the hub  20  may be rotatably coupled to an electric generator (not shown) positioned within the nacelle  16  to permit electrical energy to be produced. 
     Referring now to  FIG. 2 , a perspective view of one of the rotor blades  22  shown in  FIG. 1  is illustrated in accordance with aspects of the present subject matter. As shown, the rotor blade  22  includes a blade root  24  configured for mounting the rotor blade  22  to the hub  20  of a wind turbine  10  and a blade tip  26  disposed opposite the blade root  24 . A body  28  of the rotor blade  22  may extend lengthwise between the blade root  24  and the blade tip  26  and may generally serve as the outer shell of the rotor blade  22 . As is generally understood, the body  28  may define an aerodynamic profile (e.g., by defining an airfoil shaped cross-section, such as a symmetrical or cambered airfoil-shaped cross-section) to enable the rotor blade  22  to capture kinetic energy from the wind using known aerodynamic principles. Thus, the body  28  may generally include a pressure side  30  and a suction side  32  extending between a leading edge  34  and a trailing edge  36 . Additionally, the rotor blade  22  may have a span  38  defining the total length of the body  28  between the blade root  24  and the blade tip  26  and a chord  40  defining the total length of the body  28  between the leading edge  34  and the trailing edge  36 . As is generally understood, the chord  40  may vary in length with respect to the span  38  as the body  28  extends from the blade root  24  to the blade tip  26 . 
     Moreover, as shown in  FIG. 2 , the rotor blade  22  may also include a plurality of T-bolts or root attachment assemblies  42  for coupling the blade root  24  to the hub  20  of the wind turbine  10 . In general, each root attachment assembly  42  may include a barrel nut  44  mounted within a portion of the blade root  24  and a root bolt  46  coupled to and extending from the barrel nut  44  so as to project outwardly from a root end  48  of the blade root  24 . By projecting outwardly from the root end  48 , the root bolts  46  may generally be used to couple the blade root  24  to the hub  20  via a pitch bearing  150  of the wind turbine  10 . For example, the pitch bearing  150  may define a plurality of bolt holes  151  configured to receive the root bolts  46 . Additionally, as will be described below, a portion of such root bolts  46  may also be utilized when the rotor blade  22  is being lowered or removed from and/or re-installed onto the hub  20 . 
     It should be appreciated that, although the methods will generally be described with reference to lowering a rotor blade  22  from the hub  20  of wind turbine  10 , the various method steps and system components disclosed herein may similarly be used to re-install the rotor blade  22  onto the hub  20  by simply reversing the order in which the method is performed. It should also be appreciated that, although the methods will be described herein as being performed in a particular order, the methods may generally be performed in any suitable order that is consistent with the disclosure provided herein. 
     Referring particularly to  FIG. 3 , the rotor blade  22  to be lowered may be initially rotated to a vertically downward position (e.g., a 6 o&#39;clock position) such that the blade  22  has a generally vertical orientation relative to the support surface  14  of the wind turbine  10 . The other two blades  22  will be at the 10 o&#39;clock and 2 o&#39;clock positions. For example, as shown in  FIG. 3 , one rotor blade  22  is extending vertically downward from the hub  20  such that the blade tip  26  is pointing towards the support surface  14 . It should be appreciated that, due to a tilt angle and/or cone angle of the wind turbine  10 , the rotor blade  22  may be angled slightly away from the tower  12  when moved to the vertically downward position. 
     In several embodiments, once the rotor blade  22  is rotated to the vertically downward position, a blade sock  100  may be installed onto the blade  22  at an intermediate location  102  defined between the blade root  24  and the blade tip  26 . In one embodiment, the intermediate location  102  may correspond to a location defined along an outboard section of the rotor blade  22 , such as at a location spaced apart from the blade root  24  by a distance  104  that is greater that about 50% of the blade span  38 . For example, the distance  104  may range from about 50% of the span  38  to about 95% of the span  38 , such as from about 65% of the span  38  to about 95% of the span  38  or from about 75% of the span  38  to about 90% of the span  38  and any other subranges therebetween. 
     As shown in  FIG. 3 , to install the blade sock  100  onto the rotor blade  22 , one or more lift cables  106  may be secured to the blade sock  100  and may extend upward to an up-tower location, such as at a location on and/or within the hub  20  or the nacelle  16 . For instance, in one embodiment, the lift cable(s)  106  may extend upward from the blade sock  102  to personnel located within and/or on top of the hub  20  or the nacelle  16 . Regardless, the lift cable(s)  106  may be used to lift the blade sock  100  vertically upwards relative to the support surface  14  to allow the sock  100  to be installed around the rotor blade  22  at the intermediate location  102 . For instance, as will be described below, the blade sock  100  may define a closed shape configured to extend around the entire outer perimeter of the rotor blade  22 . Thus, when lifting the blade sock  100  via the lift cable(s)  102 , the sock  100  may be carefully aligned with the rotor blade  22  such that the blade tip  26  is received within the sock  100 . 
     Additionally, one or more sock cables  108 ,  110  may also be coupled to the blade sock  100  and may extend downward to a location adjacent to the support surface  14 . For instance, in the illustrated embodiment, the system includes a first sock cable  108  and a second sock cable  110  coupled between the blade sock  100  and corresponding winches  112  disposed on and/or adjacent to the support surface  14 . The sock cables  108 ,  110  may, for example, be utilized to assist in aligning the blade sock  100  with the rotor blade  22  as the sock  100  is being lifted up onto the blade  22  via the lift cables  106 . In addition, as will be described below, the sock cable(s)  108 ,  110  may also be used as a means for tightening the blade sock  100  around the rotor blade  22  at the intermediate location  102  and/or for applying a force through the blade sock  100  in order to adjust and/or control the orientation of the rotor blade  22  as it is being lowered below the hub  20 . In alternative embodiments, the cables  108 ,  110  may be replaced by ropes so that they function as tag lines. 
     Referring now to  FIGS. 4-6 , differing views of one embodiment of the blade sock  100  described above are illustrated in accordance with aspects of the present subject matter. Specifically,  FIG. 4  illustrates a close-up, perspective view of the blade sock  100  installed onto the rotor blade  22  at the intermediate location  102  with the lift cables  106  being removed and  FIG. 5  illustrates a cross-sectional view of the blade sock  100  shown in  FIG. 4  taken about line  5 - 5 . Additionally,  FIG. 6  illustrates top-down view of the cross-section shown in  FIG. 5 , particularly illustrating the sock cables  108 ,  110  extending from the blade sock  100  to corresponding winches  112  disposed on and/or adjacent to the support surface  14 . 
     As particularly shown in  FIGS. 4 and 5 , the blade sock  100  may include a sock strap  114  generally defining a closed shape configured to extend around the outer perimeter of the rotor blade  22 . In addition, the blade sock  100  may include one or more edge supports  116 ,  118  positioned between the sock strap  114  and the rotor blade  22 . For example, as shown in the illustrated embodiment, the blade sock  100  includes both a leading edge support  116  positioned between the sock strap  114  and the rotor blade  22  around the location of the leading edge  34  of the blade  22  and a trailing edge support  118  positioned between the sock strap  114  and the rotor blade  22  around the location of the trailing edge  36  of the blade  22 . 
     In general, the sock strap  114  may be configured to be tightened around the outer perimeter of the rotor blade  22  in order to secure the blade sock  100  to the blade  22  at the intermediate location  102 . In several embodiments, the sock strap  114  may be configured to be self-tightening. For example, as shown in  FIG. 5 , the sock strap  114  may extend lengthwise between a first end  120  and a second end  122 . In addition, the sock strap  114  may include suitable coupling mechanisms (e.g., mount rings or hooks or any other suitable coupling device) positioned at the ends  120 ,  122  of the strap  114  for coupling each end  120 ,  122  to one of the sock cables  108 ,  110 . Specifically, as shown in  FIG. 5 , a first mount ring  124  may be secured to the first end  120  of the sock strap  114  and a second mount ring  126  may be secured to the second end  122  of the sock strap  114 . In such an embodiment, the sock strap  114  may be configured to be looped around the outer perimeter of the rotor blade  22  in a partially overlapping manner such that the first mount ring  124  is disposed on one side of the rotor blade  22  (e.g., the pressure side  30 ) and the second mount ring  126  is disposed on the opposite side of the rotor blade  22  (e.g., the suction side  32 ). As such, when the sock cables  108 ,  110  are coupled to the mount rings  124 ,  126  and subsequently pulled or otherwise tensioned (e.g., via the winches  112 ) so as to apply a tightening force at each end  120 ,  122  of the sock strap  114  (indicated by arrows  128  in  FIG. 5 ), the strap  114  may be configured to tighten around the outer perimeter of the rotor blade  22 , thereby securing the blade sock  100  to the rotor blade  22 . 
     The edge supports  116 ,  118  of the blade sock  100  may generally correspond to any suitable rigid support-type members configured to prevent damage to the leading and trailing edges  34 ,  36  of the rotor blade  22  as the sock strap  114  is tightened around the blade  22  and/or as the blade sock  100  is used to at least partially support the weight of the rotor blade  22  (as will be described below). For example, as shown in  FIG. 5 , the leading edge support  116  may include side portions  134  configured to extend along portions of the pressure and suction sides  30 ,  32  of the rotor blade  22  and may also include an edge portion (indicated by bracket  136 ) extending between the side portions  134  around leading edge  34 . Specifically, the edge portion  136  may be configured to define a curved profile generally corresponding to the curved profile of the leading edge  34  of the blade  22  such that the edge portion  136  wraps around and provides a nesting configuration for the leading edge  34 . Similarly, the trailing edge support  118  may include side portions  138  configured to extend along portions of the pressure and suction sides  30 ,  32  of the rotor blade  22  and may also include an edge portion (indicated by bracket  140 ) extending between the side portions  138  around the trailing edge  36 . However, unlike the edge portion  136  of the leading edge support  116 , the edge portion  140  may be configured to extend around the trailing edge  36  such that a gap is defined between the trailing edge  36  and the corresponding support  116 , thereby providing a buffer to prevent compression forces applied via the tightened sock strap  114  from being directed through the trailing edge  36 . 
     It should be appreciated that the edge supports  116 ,  118  may generally be configured to be formed from any suitable rigid material. For instance, in one embodiment, the edge supports  116 ,  118  may be formed from a fiber-reinforced laminate composite, such as a carbon and/or glass fiber-reinforced laminate. Alternatively, the edge supports  116 ,  118  may be formed from any other suitable rigid material, such as any suitable metal and/or any suitable rigid polymer-containing material. Additionally, in several embodiments, for the portions of the edge supports  116 ,  118  configured to contact the outer surface of the rotor blade  22 , the edge supports  116 ,  118  may include an inner layer (not shown) formed from a suitable cushioning material in order to protect the blade&#39;s outer surface. For instance, the inner layer may be formed from a foamed material or any other suitable soft and/or cushioning material. 
     It should also be appreciated that, although the edge supports  116 ,  118  are shown in the illustrated embodiments as two separate components, the edge supports  116 ,  118  may, instead, be configured as a single component configured to extend around the entire outer perimeter of the rotor blade  22 . Additionally, in alternative embodiments, the blade sock  100  may only include one of the edge supports  116 ,  118 , such as by only including the trailing edge support  118 . 
     Referring to  FIG. 6 , as indicated above, the sock cables  108 ,  110  may, in one embodiment, be configured to be coupled between the blade sock  100  and corresponding winches  112  disposed on and/or adjacent to the wind turbine&#39;s support surface  14 . In such an embodiment, the positioning of the winches  112  relative to the position of the rotor blade  22  (as mounted on the hub  20 ) may be selected to ensure that the winches  112  are spaced sufficiently apart from the rotor blade  22  to allow for the orientation of the blade  22  to be adjusted and/or controlled as it is lowered from the hub  20 . For example, as shown in  FIG. 6 , the winches  112  may be positioned a horizontal distance  142  from the rotor blade  22 , which may vary depending on the overall length of the blade&#39;s span  38 . In addition, the winches  112  may be spaced apart from one another in a cross-wise direction such that each sock cable  108 ,  110  extends from the blade sock  100  at a given cable angle. For instance, in one embodiment, the cable angle  144  may range from about 30 degrees to about 60 degrees, such as from about 35 degrees to about 55 degrees or from about 42 degrees to about 48 degrees and any other subranges therebetween. 
     It should be appreciated that, as an alternative to the winches  112 , the sock cables  108 ,  110  (which may also be referred to as tag lines) may be coupled to and/or held in position by any other suitable device, object and/or person positioned on and/or adjacent to the support surface  13 . For instance, in one embodiment, sock cables  108 ,  110  may simply be held by personnel standing on the support surface  14 . 
     It should be appreciated that, in alternative embodiments, the sock strap  114  may have any other suitable configuration that allows it to be tightened around the rotor blade  22  using the sock cables  108 ,  110 . For instance, instead of being looped around the rotor blade  22  in the partially overlapping manner shown in  FIG. 5 , the sock strap  114  may be configured similar to a choker-type lifting sling. An example of such a configuration is illustrated, for example, in  FIG. 7 . As shown in  FIG. 7 , the sock strap  114  may be configured to be looped around the rotor blade  22  once, with the first end  120  of the sock strap  114  being received through the mount ring  126  secured to the second end  122  of the strap  114 . In such an embodiment, by coupling one of the sock cables (e.g., the first sock cable  108 ) to the first end  120  of the strap  114 , the sock cable  108  may be used to apply a tightening force through the sock strap (as indicated by arrow  128 ) in order to tighten the sock strap  114  around the rotor blade  22 . 
     Alternatively,  FIG. 8  illustrates yet another example of a choker-type configuration that may be utilized to allow the sock strap  114  to be self-tightening. As shown, the sock strap is formed from two separate strap portions  114 A,  114 B. Specifically, the first strap portion  114 A may be configured to extend partially around the outer perimeter of the rotor blade  22  between first and second mount rings  124 ,  126 . In addition, the second strap portion  114 B may be configured to extend around the remainder of the outer perimeter of the rotor blade  22 . In such an embodiment, each end of the second strap portion  114 B may be received through one of the mount rings  124 ,  126  of the first strap portion  114 A and coupled to one of the sock cables  108 ,  110 . Thus, each sock cable  108 ,  110  may be used to apply a tightening force (as indicated by arrows  128 ) through the first and second strap portions  114 A,  114 B that allows the sock strap to be tightened around the rotor blade  22 . 
     It should be appreciated that the sock strap  114  (including strap portions  114 A,  114 B) may generally be formed from any suitable material(s) that allow the strap  114  to function as described herein. For instance, in several embodiments, the sock strap  114  may be formed from a relative strong and/or durable material, such as nylon, Kevlar or any other suitable material typically utilized to form lifting straps and/or slings. 
       FIG. 9  illustrates a side view of a system  901  for enabling servicing of the rotor  18 , according to an aspect of the present invention. The system  901  includes a rotor servicing fixture  900  that is used to slightly lower a rotor blade  22  so that a rotor part (e.g., a rotor bearing) can be removed or replaced without having to remove the entire rotor  18  from the wind turbine. In  FIG. 1 , the upper two (e.g., first and second) rotor blades are shown in the 10 o&#39;clock and 2 o&#39;clock positions. The third rotor blade  22  is shown pointing generally downwardly and is in the 6 o&#39;clock position. The rotor servicing fixture  900  is configured to attach to a rotor in this general position, so that the rotor servicing fixture  900  is supported by both the first and second (i.e., the upward pointing) rotor blades. The rotor servicing fixture is also supported by the tower  12 . 
     The system  901  includes the rotor servicing fixture  900 , a clamp assembly  910 , a lifting assembly  920  and a slide assembly  930 .  FIG. 10  illustrates a side view of the rotor servicing fixture  900 . The rotor servicing fixture  900  includes a first leg  1002  and a second leg  1004  (shown in  FIG. 11 ), and both legs are configured to contact the tower  12 . An adjustable extension section  1003 ,  1005  can be linearly adjusted in or out to contact the outer wall of the tower  12 . The adjustable extension sections may include padded feet  1006 ,  1007  to protect the tower. The adjustable extension sections may also lock in place (e.g., with suitable fasteners or stops) to provide a secure base mount for the rotor servicing fixture. As examples only, the legs  1002 ,  1003  and adjustable extension sections  1003 ,  1005  could be hydraulic rams or telescoping members that lock in place by the use of pins or bolts. 
     A main body  1010  includes a vertical support section  1020  that is connected to both the first and second legs  1002 ,  1003 . The vertical support section  1020  is connected to a top section  1030  that includes a lifting member  1035  configured for attachment to a crane (not shown). The lifting member  1035  could be comprised of a reinforced bracket having a through-hole and/or or a shackle or other suitable connector attached to the top section  1030 . The top section  1030  is connected to two rotor blade clamp assemblies  1040  (only one shown in  FIG. 10 ), that are configured to attach to the first rotor blade and the second rotor blade (i.e., the rotor blades oriented generally in the 10 o&#39;clock and 2 o&#39;clock positions, respectively). Both the first and second rotor blades remain attached to rotor  18 . The rotor blade clamp assemblies  1040  may have a hinged connection  1041  to the top section  1030 , and a rotor blade clamp  1042  comprised of a top member  1043  and a lower sling or strap  1044 . The strap  1044  may be a ratcheting type of strap to securely lock onto the root section of the first and second rotor blade. There is a rotor blade clamp  1042  for each of the upper rotor blades. When the rotor servicing fixture  900  is securely mounted to the rotor, by attaching the rotor blade clamps  1042  to each of the first and second rotor blades, and by adjusting the lower legs  1002 ,  1003  to contact the tower  12 , the rotor servicing fixture  900  is properly configured to support the third (i.e., 6 o&#39;clock) rotor blade. 
       FIG. 11  illustrates a top view of the system  901  and rotor servicing fixture  900 , according to an aspect of the present invention. The clamp assembly  910  is connected to the rotor servicing fixture  900 , so that the weight of the downwardly pointing rotor blade  22  is transferred to the rotor servicing fixture  900 . The clamp assembly  910  is configured to clamp onto rotor blade  22  so that it may be lowered from and raised back to hub  20 . In the example shown, the third rotor blade  22  is oriented generally in the 6 o&#39;clock position, or in other words rotor blade  22  points generally downward towards the ground or other supporting surface. The clamp assembly  910  is comprised of a generally C-shaped clamp having articulated arms  912 . The arms  912  are configured to open to pass over the root section of the third rotor blade  22  and to close and clamp onto the root section. For example, a hinge  914  may be used to pivot a distal end of arm  912  so that it can open and close. The arms  912  may be opened and closed (i.e., activated) manually or by electric, hydraulic or pneumatic systems. Alternatively, the distal ends of arms  912  can be tightened (clamped) around the root section of blade  22  by means of a cable, ratcheting strap or chain. One example of a hydraulically activated clamp will be discussed hereinafter, and in conjunction with  FIG. 12 . The clamp assembly  910  is attached to the lifting assembly  920 , and configured so that the rotor blade  22  may be lowered from the hub  20  (or rotor  18 ). The blade  22  can be lowered so that a rotor part  1100 , such as a blade bearing, can be removed from the blade  22  or installed on blade  22 . Alternatively, any suitable hub or rotor part can be removed, replaced or installed by using system  901 , such as control boxes, pitch motors, pitch bearings or any other heavy or cumbersome part that would be difficult to bring up through the tower. 
       FIG. 12  illustrates a top view of one example of a clamp assembly  1200 , according to an aspect of the present invention. In general, the clamp assembly  1200  (which may be used in place of clamp assembly  910 ) may include a plurality of curved clamp members  1202  configured to be engaged around the outer circumference of the rotor blade  22 . Specifically, each clamp member  1202  may be configured to extend circumferentially around a portion of the blade root  24  of the rotor blade  22 . In several embodiments, each clamp member  1202  may be configured to be coupled to any adjacent clamp member(s)  1202  via a pivotal connection. For example, as particularly shown in  FIG. 12 , a hinge pin  1204  may be configured to extend through the ends of each pair of adjacent clamp members  1202 , thereby allowing such clamp members to be pivoted or rotated relative to one another. As such, when the clamp assembly  1200  is properly positioned along the blade root  24  at its desired installation location, the clamp members  1202  may be pivoted relative to one another to allow the clamp assembly  1200  to be tightened and/or engaged around the blade root  24 . 
     It should be appreciated that, in general, the clamp members  1202  may be configured to be actuated or otherwise rotated relative to one another using any suitable actuating means known in the art. For example, in several embodiments, a suitable actuating cylinder  1206  (e.g., an electric cylinder, pneumatic cylinder or a fluid-driven or hydraulic cylinder) may be coupled between each pair of adjacent clamp members  1202  so that the cylinder  1206  extends across the joint formed between the clamp members  1202  via the hinge pin  1204 . As particularly shown in  FIG. 12 , each actuating cylinder  1206  may include a piston cylinder  1208  coupled to one of the adjacent clamp members  1202  and a piston rod  1210  coupled to the other adjacent clamp member  1202 . As such, when the piston rod  1210  is actuated relative to piston cylinder  1208 , the adjacent clamp members  1202  may be rotated relative to one another, thereby allowing the clamp members  1202  to be engaged around and/or disengaged from the rotor blade  22 . 
     It should be appreciated that, in several embodiments, one or more clamp pads  1216  may be secured to one or more of the clamp members  1202  such that the clamp pads  1216  are positioned directly between the clamp member(s)  1202  and the rotor blade  22  when the clamp assembly  1200  is installed around the blade root  24 . In one embodiment, the clamp pads  1216  may have a friction coating or surface that allows for improved gripping of the rotor blade surface when the clamp members  1202  are engaged around the blade root  24 . Alternatively, the clamp pads  1216  may be formed from a foamed material or other suitable cushioning material so as to provide a layer of protection for the outer surface of the rotor blade  22 . 
       FIG. 13  illustrates a partial side view of the lifting assembly  920 , according to an aspect of the present invention. The lifting assembly  920  is connected to the rotor servicing fixture  900  and the clamp assembly  910 , and is configured to raise and lower the rotor blade  22  via the clamp assembly  910 . The lifting assembly includes a plurality of cylinders  922  that are configured to raise and lower. For example, the plurality of cylinders  922  may be hydraulically activated, pneumatically activated, electrically activated or mechanically activated. In the example shown, four cylinders  922  are used to raise and lower the third rotor blade  22 . To remove a blade or pitch bearing, the clamp assembly  910  is clamped around the root section  24 , and then the lifting assembly can lower the blade  22  enough to allow the pitch bearing  1100  to be removed. The old pitch bearing can be transferred over to slide assembly  930  and picked up and removed by a crane. A new pitch bearing can be brought up and installed. After installation, the blade  22  can be raised back up to the hub  20  by the lifting assembly  920  and the rotor blade  22  can be re-attached to the rotor  18 /hub  20 . 
       FIG. 14  illustrates a partial, cross-sectional view of the slide assembly  930 . The slide assembly  930  has at least two sliding rails  932  that are configured to slide back and forth (i.e., linearly) along frame rails  931 . The rotor part  1100  can be rested upon (or attached to) the sliding rails  932 , so that the rotor part  1100  can be moved away from or towards the wind turbine  10 . The sliding rails  932  may ride on a plurality of bearings  934  to aid in linear translation of the rails  932 . In addition, one or more threaded holes  936  may be provided for attachment of the rotor part, if desired. The slide assembly  930  can be attached to the rotor servicing fixture by a plurality of support members  938 . 
     Referring now to  FIGS. 15-17 , another embodiment of suitable components that may be included within a lowering system to initially lower the rotor blade  22  from the hub  20  is illustrated in accordance with aspects of the present subject matter. Specifically,  FIG. 15  illustrates a partial perspective view of the hub  20 , the rotor blade  22  and the pitch bearing  1100  of the wind turbine  10  after the blade  22  has been lowered from the hub  20  by an initial vertical distance  1501 .  FIG. 16  illustrates a partial, perspective view of the interior of the hub  20  at the interface between the rotor blade  22  and the pitch bearing  1100  prior to the blade  22  being lowered relative to the hub  20 . Additionally,  FIG. 17  illustrates a perspective view of one embodiment of a modified barrel-type support nut  1700  configured for use in the illustrated lowered system in accordance with aspects of the present invention. 
     As particularly shown in  FIGS. 15 and 16 , to allow the rotor blade  22  to be initially lowered, several of the root bolts  46  extending through the bolt holes  49  defined in the pitch bearing  1100  may be removed. The existing barrel nuts  44  associated with such bolts  46  may then be replaced with cylindrically-shaped support nuts  1700 , with each support nut  1700  being configured to allow a corresponding support cable  1502  to be coupled to the blade root  24 . For example, as shown in  FIG. 15 , in one embodiment, four of the existing barrel nuts  44  may be removed and replaced with suitable support nuts  1700 . In doing so, the remainder of the root bolts  46  may be initially maintained in engagement with the pitch bearing  1100  (e.g., via suitable attachment nuts  1602  to allow the rotor blade  22  to continue to be supported by the hub  20  until the rotor blade  22  is ready to be lowered. 
     It should be appreciated that the support nuts  1700  may generally have any suitable configuration that allows each support nut  1700  to be inserted through the blade root  24  in place of one of the existing barrel nuts  44  as well as to provide a means for coupling each support cable  1502  to the rotor blade  22 . For example, in one embodiment, each support nut  1700  may be configured as a modified barrel nut. For instance, as shown in  FIG. 17 , each support nut  1700  may include a threaded opening  1706  extending vertically through the support nut  1700  to allow a corresponding root bolt  46  or other suitable threaded member to be coupled to the nut  1700  and extend vertically therefrom. In addition, each support nut  1700  may include a laterally extending threaded opening  1708  defined through one of the sides of the nut  1700 . The opening  1708  may allow for a suitable coupling device  1710  (e.g., a swivel eye, mount ring, mount hook or any other suitable attachment mechanism) to be secured to the support nut  1700  for coupling each support cable  1502  to the rotor blade  22 . 
     As indicated above, in one embodiment, four support nuts  1700  may be installed through the blade root  24  in place of the existing barrel nuts  44  to allow four corresponding support cables  1502  to be coupled to the rotor blade  22 . However, in other embodiments, any other suitable number of support nuts  1700  may be secured within the blade root  24  to provide a means for coupling a corresponding number of support cables  1502  to the rotor blade  22 , such as by installing less than four support nuts  1700  within the blade root  24  (e.g., two or three support nuts) or greater than four support nuts  1700  within the blade root  24  (e.g., five, six or more support nuts). 
     Additionally, it should be appreciated that the support nuts  1700  may be configured to be maintained in position relative to the rotor blade  22  using any suitable attachment means. For instance, in one embodiment, once a given support nut  1700  is inserted within the blade root  24 , a corresponding root bolt  46  may be inserted through the pitch bearing  1100  and screwed into the vertically extending opening  1706  of the support nut  1700  in order to secure the nut  1700  within the blade root  24 . Alternatively, as shown in  FIG. 16 , an alignment pin  1512  may be configured to be inserted through the pitch bearing  1100  and screwed into the vertically extending opening  1706  of each support nut  1700 . In such an embodiment, each alignment pin  1512  may generally be configured for attachment within the corresponding support nut  1700  in a manner similar to the existing root bolts  46  and, thus, may include a threaded end  1514  for engaging the threaded opening  1706  of the support nut  1700 . Each alignment pin  1512  may define a vertical height or length  1616  that is greater than the length of the root bolts  46 . Accordingly, the alignment pins  1512  may also be utilized to align the rotor blade with the pitch bearing as the rotor blade (or a different rotor blade with the alignment pins installed therein) is being lifted up onto the hub. 
     Each support cable  1502  may be configured to extend from one of the support nuts  1700  to a corresponding cable translation device  1510  positioned within the hub  20 . As shown and in one embodiment, the cable translation device  1510  may correspond to cable hoists (including chain hoists) configured to be mounted to and/or supported by any suitable wind turbine component(s) positioned within the hub  20  (e.g., the hub gusset(s), joist(s) and/or any other suitable component(s)). As is generally understood, cable hoists may be configured to allow suitable cables to be passed therethrough in a controlled manner. Thus, in the present application, such cable hoists may be utilized to safely and effectively lower the rotor blade  22  relative to the hub  20 . 
     It should be appreciated that, in alternative embodiments, the cable translation devices  1510  may correspond to any other suitable devices and/or mechanisms that allow for the rotor blade  22  to be lowered relative to the hub  20  via the corresponding support cables  1502 . For instance, in another embodiment, the cable translation devices  1510  may correspond to winches positioned within the hub  20 . 
     It should also be appreciated that, similar to the support cables described above, each support cable  1502  may generally correspond to any suitable elongated cable-like object that has a rated load capacity sufficient to handle the weight of the rotor blade  22 . For instance, as shown in the illustrated embodiment, the support cables  1502  are configured as metal chains. However, in other embodiments, the support cables  1502  may correspond to steel cables or any other suitable wire ropes. Moreover, it should be appreciated that each support cable  1502  may generally be configured to define any suitable length that permits the cables  1502  to be utilized to lower the rotor blade  22  away from the hub  20  by the initial vertical distance  1501 . The support cables  1502  may also be connected to blade  22  by cutting a hole into the blade root  24  to install an attachment to the root bolts  46 . 
       FIG. 18  is a flowchart of a method  1800  for servicing a rotor  18  of a wind turbine  10 , according to an aspect of the present invention. The method  1800  includes the steps of, attaching  1810  a rotor servicing fixture  900  to the rotor  18 , attaching  1820  a clamp assembly  910  onto a rotor blade  22 , lowering  930  the rotor blade  22  by a predetermined amount and servicing  940  a rotor part  1100 . For the attaching step  1810 , the rotor servicing fixture may be brought to the rotor  18 /hub  20  with a crane (not shown). An advantage of the present invention is that a smaller and cheaper crane may be used for this operation, as the crane need only lift and transport the rotor servicing fixture  900  and not the entire rotor  18 . The rotor  18  is much heavier than the rotor servicing fixture. The rotor servicing fixture  900  is attached to and supported by a first rotor blade and a second rotor blade. The first and second rotor blades would preferably be oriented in the 10 o&#39;clock and 2 o&#39;clock positions. In addition, a lower part of the rotor servicing fixture contact the tower  12  of the wind turbine  10 . 
     In the attaching step  1820 , the clamp assembly  910  is attached to a third rotor blade  22 . The third rotor blade would be oriented in the 6 o&#39;clock position (or pointing generally downwardly). The clamp assembly  910  is now clamped onto the third rotor blade by a pair of articulated arms. The clamp assembly can now support the weight of the third rotor blade via the lifting assembly and rotor servicing fixture. The lowering step  1830  lowers the third rotor blade by a predetermined amount with the clamp assembly  910  and the lifting assembly  920 . The predetermined amount may be about 3 to about 6 feet, or any suitable amount as desired in the specific application. As one example only, if the pitch bearing is being replaced, then the predetermined amount would have to be large enough to allow for the pitch bearing to be removed and a new pitch bearing to be installed. Both the clamp assembly and the lifting assembly are configured to lower the third rotor blade from the hub and to raise the third lower blade back to the hub. When servicing is complete the third rotor blade can be lifted up and re-installed/attached back onto the hub. 
     In the servicing step  1840 , the rotor part is serviced. This could include, removing, replacing repairing or installing the rotor part. The rotor part may be a pitch bearing, pitch motor, pitch controller or any other part or system that is in the blades or hub. The servicing is performed without removing the rotor from the wind turbine. As mentioned before, this is a very big advantage as the entire rotor does not have to be removed from the wind turbine to service the rotor part. A transporting step, transports the rotor part with a slide assembly. The slide assembly supports the rotor part and is configured to slidably move the rotor part away from or towards the wind turbine. For example, a pitch bearing can be removed from the blade/hub and slid outwards so that it can be picked up and moved away with a crane. A new pitch bearing can be brought up, placed on the slide assembly and slid into place for installation. When the rotor is re-assembled (and all desired servicing is complete), the rotor servicing fixture and its associated parts can be detached from the rotor and carried away from the rotor using a crane (not shown). 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.