Abstract:
A wind turbine includes a tower; a blade for rotating on the tower; a rotor shaft, connected to the blade, having an axial hole; a line, arranged in the hole, for carrying a signal; a support, wrapped around the line inside the hole, for spacing the line from the rotor shaft inside the hole; where the support expands radially to at least partially fill an annular space between the line and an inside wall of the axial hole.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The subject matter described here generally relates to wind turbines, structures, and, more particularly, to expandable cable supports for wind turbines. 
     2. Related Art 
     A wind turbine is a machine for converting the kinetic energy in wind into mechanical energy. If the mechanical energy is used directly by the machinery, such as to pump water or to grind wheat, then the wind turbine may be referred to as a windmill. Similarly, if the mechanical energy is converted to electricity, then the machine may also be referred to as a wind generator or wind power plant. 
     Wind turbines are typically categorized according to the vertical or horizontal axis about which the blades rotate. One so-called horizontal-axis wind generator is schematically illustrated in  FIG. 1 . This particular configuration for a wind turbine  2  includes a tower  4  supporting a nacelle  6  enclosing a drive train  8 . The blades  10  are arranged on a hub to form a ‘rotor’ at one end of the drive train  8  outside of the nacelle  6 . The rotating blades  10  drive a gearbox  12  connected to an electrical generator  14  at the other end of the drive train  8  arranged inside the nacelle  6  along with a control system  16  that may receive input from an anemometer  18 . 
     The blades  10  generate lift and capture momentum from moving air that is them imparted to a rotor as the blades spin in the “rotor plane.” Each blade is typically secured at its “root” end, and then “spans” radially “outboard” to a free, “tip” end. The front, or “leading edge,” of the blade connects the forward-most points of the blade that first contact the air. The rear, or “trailing edge,” of the blade is where airflow that has been separated by the leading edge rejoins after passing over the suction and pressure surfaces of the blade. A “chord line” connects the leading and trailing edges of the blade in the direction of the typical airflow across the blade. The length of the chord fine is simply the “chord.” 
     “Angle of attack” is a term that is used in to describe the angle between the chord line of the blade  10  and the vector representing the relative motion between the blade and the air. “Pitching” refers to rotating the angle of attack of the entire blade  10  into or out of the wind in order to control the rotational speed and/or absorption of power from the wind. For example, pitching the blade “towards feather” rotates of the leading edge of the blade  10  into the wind, while pitching the blades “towards stall” rotates the leading edge of the blade out of the wind. 
     For so-called “pitch controlled” wind turbines, the pitch may be adjusted each time the wind changes in order to maintain the rotor blades at the optimum angle and maximize power output for all wind speeds. For example, the control system  16  may check the power output of the turbine  2  several times per second. When the power output becomes too high, the control system  16  then sends a signal to the blade pitch mechanism (not shown in  FIG. 1 ) which causes the blades  10  to be pitched slightly out of the wind. The blades  10  are then turned back into the wind when the wind speed slows down. 
     Commonly-assigned U.S. Pat. No. 7,126,236 entitled “Methods and Apparatus for Pitch Control Power Conversion” is incorporated by reference here and partially reproduced in  FIG. 2 . The control system  16  (from  FIG. 1 ) includes one or more controllers within control panel  112  for overall system monitoring and control including pitch and speed regulation, high-speed shaft and yaw brake application, yaw and pump motor application and fault monitoring. 
     The control system  16  provides control signals to the variable blade pitch drive or actuator  114  to control the pitch of blades  10  ( FIG. 1 ) that drive hub  110 . The drive train  8  ( FIG. 1 ) of the wind turbine  2  includes a main rotor shaft  116  (also referred to as a “low speed shaft”) connected to hub  110  and a gear box  12 . A high speed shaft from the opposite end of the gear box is used to drive a first generator  120 . In some configurations, torque is transmitted via a coupling  122 . 
     The blade pitch control signals are typically provided in the form of electrical impulses signals from the control system  16  that are carried along cables extending through a hole at the center of the shaft  116  from a slip ring attached to the back of the gearbox  12 . However, the rotating shaft  116  can damage the external protective coating of the cables which can short circuit or otherwise interfere with the transmission of those control signals. 
     BRIEF DESCRIPTION OF THE INVENTION 
     These and other drawbacks associated with such conventional approaches are addressed here in by providing, in various embodiments, a wind turbine, including a tower; a blade for rotating on the tower; a rotor shaft, connected to the blade, having an axial hole; a line, arranged in the hole, for carrying a signal; and a support for spacing the line from the rotor shaft inside the hole. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this technology will now be described with reference to the following figures (“FIGs.”) which are not necessarily drawn to scale, but use the same reference numerals to designate corresponding pails throughout each of the several views. 
         FIG. 1  is a schematic side view of a conventional wind generator. 
         FIG. 2  is a cut-away orthographic view of the nacelle and hub of the conventional wind generator shown in  FIG. 1 . 
         FIG. 3  is a schematic, partial cross-section of the rotor shaft and gearbox shown in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view taken along section line IV-IV in  FIG. 3 . 
         FIG. 5  is an alternative cross-sectional view taken along section line IV-IV in  FIG. 3 . 
         FIG. 6  is a plan view of the mat shown in  FIG. 5  in an unrolled configuration; 
         FIG. 7  is cross-sectional view taken along section line VII-VII in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 3  is a schematic, partial cross-section of the gearbox  12  and rotor shaft  116  from  FIG. 2 . The rotor shaft  116  includes an axial hole  200  containing one or more lines  202  for carrying signals between, for example, the slip ring  204  to the blade pitch actuator  114  shown in  FIG. 2 . The term “lines” is used here broadly to include electrical leads, conductors, wires, cables, cords, pneumatic and hydraulic carriers, waveguides, and fibers such as optical fibers. The term “signals” is not limited to communication signals and may also include power and/or power signals. For example, the lines may carry electrical power. 
       FIG. 4  is a cross-sectional view of the rotor shaft  116  taken along section line IV-IV in  FIG. 3  including one example of a line support  206  for spacing one or more of the fines  202  from the rotor shaft  206  inside the hole  200 . However, the line support may also be used in other holes, such as ductwork, and/or to support other members such as pipes. A portion of the line support  206  may also extend beyond the end of the axial hole  200 . 
     In  FIG. 4 , the illustrated line support  206  is provided with one or more optional fingers  208  for positioning the support  206  in the hole  200 . In this example, seven fingers  208  extend radially from the lines  202  arranged on the axis of the shaft and the fingers extend along a length of the mat substantially parallel to the lines  202 . However, any other number of fingers  208  and/or orientation may be provided. For example, the fingers may be arranged substantially perpendicular to the lines  202 , in a spiral configuration around the lines, and/or may extend only partially or intermittently across the width ad/or length of the line support  202 . Each of the fingers  208  may also be filled with a resilient and/or compressible material, such as foam rubber, for providing additional structural rigidity to the fingers. As illustrated in  FIG. 5 , the line support  206  may be alternatively provided without fingers  208  so that the line support  206  has a substantially uniform thickness. 
       FIG. 6  illustrates a plan view of the line support  206  shown in  FIG. 5  in an unrolled configuration, while  FIG. 7  illustrates a cross-section taken along section line VII-VII.  FIG. 6  illustrates one way in which the line support  206  may be configured as a mat. The lines  202  are placed on one side of the line support  206  which is then wrapped around the lines  202  so as to enclose or partially-enclose the lines  202 . A fastener  210  may be provided on the line support  206  for securing the line support around the lines  202 . For example, the fastener may include a hook and loop fastener, batten, bolt, screw, cap screw, stud, buckle, button, clamp, clasp, clip, grommet, peg, pin, ring, band, snap, strap, staple, tack, tie, toggle, wedge anchor, and/or zipper. The fastener  210  may be arranged on one or more sides of the mat, such as for better fixation. 
     The line support  206  may also be expandable in order to fill or partially fill the hole  200  in the rotor shaft  116 . For example, the line support  206  may be provided with a valve  212 , stopper, or other closure for allowing fluid to be added or removed from the inside of the support. In this configuration, after rolling, compressing, and fastening the line support  206  mat around the lines, the line support may be further compressed such as by extracting air using a vacuum pump attached to the valve  212 . The further compressed line support  206  and lines  202  may then be easily inserted into the hole  200 . Once inside the hole  200 , the line support  206  may then be pressurized in order to fill or partially-fill the hole  200 . Alternatively, or in addition, the line support  206  may be filled with a resilient material  214  ( FIG. 7 ), such as foam rubber, so that the valve  212  may simply be reopened in order to allow that resilient material in fingers to expand. In this configuration, line support  206  is self-inflating. Although  FIG. 7  illustrates the line support  206  in an expanded configuration prior to being wrapped around the fines  202 , the fine support may also be maintained in a compressed or partially compressed configuration with the valve  212  closed in order to facilitate wrapping of the compressed line support around the lines before the line support and lines are inserted into the hole  200  and the line support is expanded by opening the valve. 
     The line support  206  offers various advantages over conventional approaches. For example, the device avoids the need for spacing and/or securing cables and other fines  202  in ductwork with messy and noxious polyurethane foam that can otherwise require significant time to cure and then still be easily damaged by vibration and/or other movement once it has set. When expanded, the cable support  206  also provides a level of vibration damping that stiffer supports, such as conventional cable conduits, do not provide. The cable support  206  also allows lines  202  to be easily inserted into tight spaces and then helps to protect the entire length of those lines once they are inside the hole  200  or other spaces. For example, the support  206  helps to minimize dynamic stress on cables or other lines inside the hole  200 . The lines  202  can also be pre-packaged in the line support  206  in order to simplify field installation. Installation and maintenance of the lines  202  and surrounding equipment is also facilitated by the capacity of the support  206  to be easily removed from the hole  200  when depressurized and then just as easily reinserted when re-pressurized. 
     It should be emphasized that the embodiments described above, and particularly any “preferred” embodiments, are merely examples of various implementations that have been set forth here to provide a clear understanding of various aspects of this technology. One of ordinary skill will be able to alter many of these embodiments without substantially departing from scope of protection defined solely by the proper construction of the following claims.