Abstract:
A brake comprising a caliper assembly; brake linings associated with the caliper assembly; and one of an electromechanical actuator module or a hydraulic actuator module. The body of the caliper assembly has a mounting wherein the module(s) can be removably mounted to the caliper without requiring modification to the caliper assembly. The mounting enables the actuator modules to be quickly changed out with a new actuator in the case of repair or maintenance; as well as facilitates initial assembly and upgrades to the brake.

Description:
CROSS-REFERENCE TO RELATED CASES 
       [0001]    The present application claims the benefit of the filing date of U.S. Provisional Application Ser. No. 61/089,066; filed Aug. 15, 2008, the disclosure of which is expressly incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to braking systems for wind turbines, and in particular, to a modular actuator for a wind turbine brake. 
       BACKGROUND 
       [0003]    The primary braking system for most modem wind turbines is the aerodynamic braking system, which essentially consists in turning the rotor blades about 90 degrees along their longitudinal axis to the wind direction (in the case of a pitch controlled turbine or an active stall controlled turbine ), or in turning the rotor blade tips 90 degrees (in the case of a stall controlled turbine) to the wind. A mechanical brake is used as a backup system for the aerodynamic braking system; and as a parking brake, once the turbine is stopped in the case of a stall-controlled turbine. In the case an emergency where immediate braking of the wind turbine is needed, the mechanical brake can be activated simultaneously with the aerodynamic brakes. The mechanical brake typically comprises two hydraulically actuated calipers that engage a disk on the shaft that connects the gearbox and generator. It is also known to provide electromechanical actuators to control the movement of the calipers. 
         [0004]    Current hydraulic wind turbine brakes require the brake to be removed from the wind turbine and disassembled in order to replace worn seals and other components in the actuator. The brake weight and mounting location can make changing out the components difficult and costly. Each brake weighs between 200-500 lbs and can be located in a tower in excess of 300 feet above the ground. 
       SUMMARY 
       [0005]    At least one embodiment of the invention provides a brake comprising a caliper assembly; brake linings associated with the caliper assembly; and one of an electromechanical actuator module or a hydraulic actuator module; the caliper assembly having a mounting wherein the module(s) can be easily and simply removably mounted to the caliper assembly without requiring modification to the caliper assembly. 
         [0006]    The body of the caliper assembly includes a circular mounting opening into a central cavity of the body. An annular flat mounting surface surrounds the opening, and an annular sidewall bounds the mouth of the opening and projects from the opening into the central cavity. The mounting surface of the module is mounted flush against the mounting surface of the caliper body, and an actuator of the module projects into the mounting opening and engages and moves one of the brake linings during use. 
         [0007]    The mounting enables the actuator module to be quickly changed out with a new actuator in the case of repair or maintenance; as well as facilitates initial assembly and upgrades to the brake. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0008]    Embodiments of this invention will now be described in further detail with reference to the accompanying drawing, in which: 
           [0009]      FIG. 1  is a perspective view of a brake for a wind turbine application constructed according to the principles of the present invention, including a caliper assembly and a hydraulic actuator; 
           [0010]      FIG. 2  is a perspective view of the caliper assembly of  FIG. 1 , shown with the actuator removed; 
           [0011]      FIG. 3  is a front plan view of the brake of  FIG. 1 ; 
           [0012]      FIG. 4  is a cross-sectional side view of the brake of  FIG. 3 , taken substantially along the plane defined by the lines  4 - 4  of  FIG. 3 ; 
           [0013]      FIG. 5  is a cross-sectional side view of the brake of  FIG. 3 , taken substantially along the plane defined by the lines  5 - 5  of  FIG. 3 ; 
           [0014]      FIG. 6  is a perspective view of the brake of  FIG. 1 , shown with an electromechanical actuator module mounted to the caliper assembly; and 
           [0015]      FIG. 7  is a sectional perspective view of the electromechanical actuator brake showing the interior of the actuator in  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]    Referring initially to  FIGS. 1 and 2 , a brake constructed according to the principles of the present invention is indicated generally at  10 , and includes a caliper assembly indicated generally at  11 , having a mounting, indicated generally at  12 , for an actuator, indicated generally at  14 . As will be described in greater detail below, the actuator  14  in a first embodiment described herein is a hydraulic actuator; while in another embodiment illustrated in  FIGS. 6 and 7 , the actuator (indicated generally at  140 ) can be an electromechanical actuator. It should be appreciated that in a general sense, any appropriate actuator may be used with the caliper assembly for controlling the brake, and the present invention is not limited to the particular hydraulic and electromechanical actuators described herein, as should be appreciated by those skilled in the art. 
         [0017]    Referring to  FIGS. 1-5 , the caliper assembly  11  includes a body  15  supporting a pair of calipers blades or plates  16 ,  17 , in parallel relation to each other, and each of which includes a friction lining  18 ,  19 , respectively, fixed to its inner surface. The linings  18 ,  19  are configured to engage and disengage a rotating disk  20  ( FIG. 7 ) centrally located between the linings to slow or stop the rotation of the disk. Disk  20  is associated with a shaft that connects a gearbox and generator in a wind turbine, such as shown and described for example, in U.S. Pat. Nos. 4,423,333; 7,436,083; and 7,075,192, which are incorporated herein by reference. 
         [0018]    The body  15  for the caliper assembly has a generally C-shaped configuration, with generally parallel and spaced-apart first and second sidewalls  23 ,  24  and an end wall portion  25  defining a central cavity, indicated generally at  26 . A pair of end brackets or stops  27  are mounted via bolts  28  to opposite ends of sidewall  23 ; while a pair of end brackets or stops  29  are likewise mounted via bolts  30  to opposite ends of sidewall  24 . Stops  27  and  29  locate and guide the caliper blades with respect to the respective sidewalls  23 ,  24  of the caliper body, and absorb the reaction load of the friction linings during use. 
         [0019]    The caliper blade  16  and associated brake lining  18  are supported and held against sidewall  23  via a pair of return bolts  31  ( FIG. 4 ) projecting through lateral apertures  32  in the sidewall and into blind-end threaded bores in the outer surface of caliper blade  16 . A return spring  33  is located around each bolt  31  and compresses between an inner shoulder of the aperture and an enlarged head of the bolt, to urge the caliper blade  16  against the inner surface of the sidewall  23 —but to also allow the caliper blade to move inwardly away from the sidewall under the influence of the actuator, as will be describe below. The caliper blade can also float somewhat if necessary to match the surface geometry and orientation of the brake disk during use. 
         [0020]    Caliper blade  17  and associated brake lining  19  are likewise supported and held against sidewall  24  via a pair of return bolts  35  ( FIG. 4 ) projecting through lateral apertures  36  in the sidewall and into blind-end threaded bores in the outer surface of caliper blade  17 . A spring  36  is located around each bolt  35  and compresses between an inner shoulder of the aperture and an enlarged head of the bolt, to force the caliper blade  17  against the inner surface of the sidewall  24 —but again, to also allow the caliper to float somewhat if necessary to match the surface geometry and orientation of the brake disk. 
         [0021]    A pair of bushings  38  are provided in caliper body  15 , which receive torque pins (for example as shown at  39  in  FIG. 6 ) to mount the caliper assembly on an appropriate support surface in the turbine cowl. A “floating” mount can be used, where the brake includes spherical bearings which are supported for axial and angular movement on the torque pins, such as shown and described in U.S. patent application Ser. No. ______, to Culbertson for “Floating Yaw Brake for Wind Turbine”, filed concurrently herewith, and which is incorporated herein by reference. 
         [0022]    Referring now to  FIG. 2 , mounting  12  includes a circular opening, indicated generally at  40 , with a flat, mostly annular mounting surface  42 , surrounding the opening and being slightly raised from the surface of the body. A series of threaded bolts holes  44  are arranged around the mounting surface and extend into the caliper body for mounting the actuator, as will be described below in more detail. An annular sidewall  46  inwardly bounds the opening  40 , and extends inwardly from the mounting surface  42  into the cavity  26  of the caliper body. Opening  40  is located centrally in the caliper body  15 , and extends laterally through the body, with a return bolt  31  located on opposite sides of the opening. 
         [0023]    As shown in FIGS.  1  and  3 - 5 , hydraulic actuator module  14  fits closely within opening  40  and is fixed, e.g., bolted to the caliper body  15 . To this end, module  14  includes a cylinder body  47  having an annular sleeve  48  and an end wall or plate  49 , together which form a chamber  50 . A cylindrical piston  51  is closely and slidingly received within sleeve  48  of cylinder body  47 . The sleeve  48  of the cylinder body has an outer diameter that fits closely within the circular opening  46  in the caliper body  15 . Plate  49  has an inner annular and flat mounting surface  59  that fits flush against the outer flat mounting surface  42  of the mounting for the caliper body when the actuator is assembled within the opening  40 . Plate  56  also includes holes corresponding to threaded holes  44  in the mounting surface of the caliper body, and in which bolts  60  are received to mount actuator  14  to caliper body  15 . Mounting bolts  60  are spaced around the plate  49  to ensure a close, rigid attachment of the actuator to the mount  12  of the caliper body. 
         [0024]    Annular seals  62  are carried within channels formed in the inner surface of sleeve  48  and provide a seal against the outer diameter of piston  51 . Piston  51  has a length such that it essentially fills chamber  50  and normally engages against the inside surface of caliper blade  16  when the cylinder body is mounted to the caliper body. The close fit of the cylinder body within the opening  46  ensures that the piston is properly located with respect to the caliper blade, and ensures standard assembly and repeatable operation. A high pressure inlet port  64  is formed at one appropriate location in the end plate  47  of the cylinder body, while a high pressure outlet port  66  is formed at another appropriate location. Each of the inlet and outlet ports are attached to appropriate tubing and direct hydraulic fluid into and out of the inner end of piston chamber  50  to appropriately move the piston  51 . Directing hydraulic fluid through inlet port  64  into the chamber  50  increases the pressure against the inside end of the piston and moves piston  51  against caliper plate  16 ; to move plate  16 , and hence friction lining  18 , inwardly away from sidewall  23  and against the disk. Directing fluid out of outlet port  66  reduces pressure against the inside end of piston, which allows the return spring  33  to move the caliper plate away from the disk and toward the sidewall  23 . Systems for controlling the flow of fluid into and out of the ports  64 ,  66  under pressure are well known to those skilled in the art and will not be described herein for sake of brevity. Again, seals  62 , in conjunction with the close fit of piston  51  within sleeve  48 , ensure the hydraulic fluid is contained, and does not leak during actuator mounting or removal from the caliper body. All components of the module are removed together as a unit when the module is removed from the mounting on the caliper assembly. 
         [0025]    As described above, the hydraulic module is a compact, self-contained component that can be easily assembled and mounted to the caliper body in a rigid manner, using only a few standard bolts and standard tools. Likewise, if servicing of the hydraulic actuator module is needed, standard tools can be used to remove the bolts  60  and hydraulic actuator module  14  can be simply and easily removed from the caliper body  15 —while the caliper assembly otherwise remains installed on the wind turbine. This allows seal repair and/or replacement, or complete hydraulic module replacement, on-site, if needed. 
         [0026]    Referring now to  FIGS. 6 and 7 , a further embodiment of an actuator for a wind turbine brake is shown. In this embodiment, the brake  10  includes an electromechanical actuator module, indicated generally at  140 , mounted to the caliper assembly  11 . The electromechanical actuator module  140  is attached to the caliper assembly  110  by bolts  60 , as in the first embodiment described above. To this end, actuator module  140  includes a body  141  having an annular, radially-projecting base  142  with a flat annular mounting surface  143 . Bolts  60  are received through openings in annular base  142  of the actuator module, and are received in the threaded apertures  44  ( FIG. 2 ) in the caliper body to attach the mounting surface  143  of the actuator in a rigid manner against the mounting surface  42  ( FIG. 2 ) of the caliper body. As in the first embodiment, the inner end  144  of actuator body  141  has an annular configuration which is closely received within the sidewall  46  of the caliper body  15 . 
         [0027]    As shown primarily in  FIG. 7 , the electromechanical actuator  140  comprises a motor  145  coupled to a gear system  146 , with the gear system  146  directly coupled to a ball screw  147 . Ball bearing bushings  148  support the rotational movement of ball screw  147  within actuator body  141 . The ball screw  147  can be a high efficiency ball screw, which allows the use of inexpensive dowel pins to be used to prevent rotation of the pusher piston  150  instead of expensive splines. Rotation of the ball screw  147  causes a ball screw nut  149  to move a pusher piston  150  toward or away from caliper plate  16 . The gear system  146  can be a two-stage 25:1 planetary gear which, along with the high efficiency ball screw, allows for smaller motor torque requirement. The pusher piston  150  has an end plate  151  the rear surface of which is acted upon by at least one, and preferably eight evenly-spaced apart compression springs  160  laterally supported within body  141 . Compression springs  160  cause the pusher piston  150  to move evenly toward the disk  20  to engage the brake  10  by creating a clamping load on the linings  18 ,  19  and the disk  20 . 
         [0028]    During operation, the brake  100  is disengaged by the electromechanical actuator  140  which retracts the pusher piston  150  away from the disc  20  and compresses the springs  160 . In a stopping situation, the actuator  140  can move the pusher piston  150  toward the disc  20  to allow the compression springs  160  to extend and provide a clamping force to stop or slow the disk  20 . If additional clamping force is required, the actuator  140  can provide additional force against the pusher piston  150  to assist the springs  160 . 
         [0029]    Accordingly, the brake  10  provides a hybrid passive and active brake system by providing the “fail safe” of the spring  160  and using the electromechanical force of the actuator  140  to increase the clamping force beyond the spring force. In the same manner, the clamping force can be controlled by incrementing the motor and using an encoder or strain gauge to provide a closed loop control of the braking. Use of an encoder also allows the brake  10  to compensate for the decrease in spring force caused by lining wear and provides the actual wear and lining thickness. 
         [0030]    In the embodiment shown in  FIG. 7 , the spring force provided by the compression spring(s)  160  is adjustable. The end of the spring  160  is held in place by a disc  162  in the spring cylinder that is held in place by a set screw  164 . The spring force can be reduced by adding washers underneath one or more of the set screw heads which will also provide a visual indication for spring force setting by means of washers. In the embodiment shown, the spring force can be modified down to 50% of nominal torque. 
         [0031]    As with actuator  14  in the first embodiment, actuator  140  is also self-contained, that is, actuator body  140  encloses all the major components of the actuator (except motor  144  which is mounted to the body), and all components of the module are removed together as a unit when the module is removed from the mounting on the caliper assembly. 
         [0032]    In any of the embodiments describe above, the modular mounting technique of the actuator to the caliper assembly provides multiple choices for brake actuation, depending on the specific need (e.g. electrical versus hydraulic power supply, safety considerations, etc.). This modular approach allows a single casting, which comprises the heavy structural portion of the brake, to be used for multiple types of brakes. This can improve the economy of scale for the casting and brake structure, which is one of the higher cost components of the brake assembly. 
         [0033]    As should be appreciate from the above, the brake assembly of the present invention provides numerous improvements such as: i) maintenance—the brake can remain mounted on the wind turbine when the seals are replaced and the cylinder sleeve eliminates potential piston wear against the structural portion of the brake assembly, to maximize the life of the costly/heavy brake structure; ii) modularity of the actuator—the brake structure remains the same for different actuator types and the modular actuator can be mounted on the same brake structure and bolt hole pattern; iii) economy of scale—multiple actuator types can be used on the same brake structure which allows lower unit cost due to of higher quantities; and iv) lower machine cost—the opening for the modular actuator allows the machining of the opposite face which eliminates one machine setup cost. 
         [0034]    Although the principles, embodiments and operation of the present invention have been described in detail herein, this is not to be construed as being limited to the particular illustrative forms disclosed. They will thus become apparent to those skilled in the art that various modifications of the embodiments herein can be made without departing from the spirit or scope of the invention. Accordingly, the scope and content of the present invention are to be defined only by the terms of the appended claims.