Abstract:
A rotor blade assembly includes a rotor blade including one or more pockets and a housing located on the rotor blade within one or more pockets. The housing is secured to the rotor blade via one or more dovetail joints. A drive mechanism for a control surface of a rotor blade includes an actuator and a rocker operably connected to the actuator. At least one hinge rod is operably connected to the rocker and operably connected to a control surface at a control surface pivot. The drive mechanism translates substantially linear motion of the actuator into rotational motion of the control surface about the control surface pivot.

Description:
GOVERNMENT RIGHTS STATEMENT 
     This invention was made with Government support under Agreement No. W911W6-08-2-0002 for the Operations Support and Sustainment Technology (OSST) Advanced Technology Development (6.2) program. The Government has certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to rotary wing aircraft. More specifically, the subject disclosure relates to control devices for rotor blades of rotary wing aircraft. 
     Rotary-wing aircraft typically include passive blades which are controlled using a swashplate assembly that transfers motion of non-rotating control members to rotating control members. The transfer of motion occurs once per blade revolution (1/rev) and affects all blades in a similar fashion. On-blade control overcomes this limitation and allows for both the potential to control blades on an individual bases, and to transfer motion more than once per blade revolution. In order to perform on-blade control, blades can be equipped with one or more devices to control trim flaps, trailing edge effectors, and the like. These devices include actuators, etc, which are installed at or on the rotor blades. Installation of such devices can involve cutting holes in the rotor blade spar for routing of mechanical connections, hydraulic lines, electrical lines, etc. These holes compromise the baseline structural properties of the rotor blade, often resulting in redesign and additional strengthening of the blade to return it to baseline structural integrity. Further, the typical attachment of such structures to the blade can increase drag, noise, vibration, weight, and be intensive in maintenance time required to service, repair, or replace such devices. Finally, installation of such devices can require a complete redesign of the entire blade and limit the blade to only one particular active device. The art would well receive an improved control device and installation method thereof for control of rotor blades. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one aspect of the invention, a rotor blade assembly includes a rotor blade including one or more pockets and a housing secured to the rotor blade within one or more of the pockets. The housing is secured to the rotor blade via one or more dovetail joints. 
     According to another aspect of the invention, a drive mechanism for a control surface of a rotor blade includes an actuator and a rocker operably connected to the actuator. At least one hinge rod is operably connected to the rocker and operably connected to a control surface at a control surface pivot. The drive mechanism translates substantially linear motion of the actuator into rotational motion of the control surface about the control surface pivot. 
     According to yet another aspect of the invention, a control system for a rotor blade includes a housing secured to a rotor blade within one or more pockets of the rotor blade. The housing is secured to the rotor blade via one or more dovetail joints. A drive mechanism is secured in the housing including an actuator and a rocker operably connected to the actuator. At least one hinge rod is operably connected to the rocker and operably connected to a control surface at a control surface pivot. The drive mechanism translates substantially linear motion of the actuator into rotational motion of the control surface about the control surface pivot. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic of an embodiment of a helicopter; 
         FIG. 2  is an exploded view of an embodiment of a control system of a rotor blade; and 
         FIG. 3  is a cross-sectional view of an embodiment of a drive mechanism. 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Shown in  FIG. 1  is a schematic illustration of a rotary wing aircraft  10  having a main rotor assembly  12 . The aircraft  10  includes an airframe  14  having an extending tail  16  at which is mounted an anti-torque rotor  18 . Although the configuration illustrated is a helicopter, it is to be appreciated that other machines such as turbo-props and tilt-rotor aircraft will also benefit from the system of the present disclosure. The main rotor assembly  12  includes a plurality of rotor blades  20  located about a rotor shaft  22 . One or more of the rotor blades  20  includes a control surface such as a trim tab  24  located at a trailing edge  26  of the rotor blade  20 . While the control surface shown in  FIG. 1  is a trim tab  24 , it is to be appreciated that other types of on-blade control surfaces, such as conformal flaps, active flow control devices, unsteady and/or steady blowing devices, flaps, mass displacement devices, etc., are contemplated within the scope of the present disclosure. Further, while the trim tab  24  is shown located at the trailing edge  26  of the rotor blade  20 , it is to be appreciated that the control surface may be disposed in other locations, for example, a leading edge  28  of the rotor blade  20 . 
     Referring now to  FIG. 2 , the trim tab  24  is installed at the rotor blade  20  via a modular installation unit  30 . The unit  30  is installed within the pocket  32  of the rotor blade  20 , without penetrating holes, or otherwise compromising the spar  68  therefore preserving structural integrity of the rotor blade  20 . To facilitate installation of the unit  30 , portions of the rotor blade  20  pocket  32  are removed, leaving an opening  36 . One or more interface pieces  34  are installed in the rotor blade  20 . As shown in  FIG. 2 , two interface pieces  34  may be utilized, one interface piece  34  at each lateral end of the rotor opening  36 . The interface pieces  34  are secured to the rotor blade  20  via any preferable means, such as mechanical fasteners or adhesives. 
     Each interface piece  34  includes an interface dovetail  38  to receive a corresponding housing dovetail  40  of a housing  42 . The housing  42  is installed in the rotor opening  36  between the two interface pieces  34 , with the interface dovetail  38  meshing with the housing dovetail  40  to align and secure the housing  42  therein. In some embodiments a dampening material, for example, an elastomer or foam (not shown), may be inserted between the interface dovetail  38  and the housing dovetail  40 . 
     The dovetail arrangement connecting the interface pieces  34  with the housing  42  and the location of the housing  42  within the pocket  32  reduces the reduction of structural integrity of the rotor blade  20  compared to the installations of the prior art. Further, the dovetail connection can be tuned by, for example, modifying a shape of the dovetails to further reduce undesirable effects such as noise and/or vibration. 
     A drive mechanism  44  is installed in the housing  42 , and may be secured therein by any conventional means. The drive mechanism  44  is connected to the trim tab  24  extending from the trailing edge  26  of the rotor blade  20 . Referring to  FIG. 3 , the trim tab  24  is pivotably located at the trailing edge  26 , specifically at a tab pivot  46 . The drive mechanism  44  includes a hinge rod  48  connected to the trim tab  24 , such that movement of the hinge rod  48  about the tab pivot  46  results in pivot of the trim tab  24  about the tab pivot  46 . The drive mechanism  44  also includes a rocker  50  secured in the housing at a rocker pivot  52 . The rocker  50  is connected to the hinge rod  48  via a slider  54 . The slider  54  connection to the hinge rod  48  translates rotation of the rocker  50  about the rocker pivot  52  into rotation of the hinge rod  48  and thus the trim tab  24  about the tab pivot  46 , via the sliding motion of the slider  54  along a length of the hinge rod  48 . As is best shown in  FIG. 2 , more than one hinge rod  48  may connect the rocker  50  to the trim tab  24 . For example, two hinge rods  48  are shown in  FIG. 2 . Each hinge rod  48  is connected to a unique slider  54  which is connected to the rocker  50 . 
     The rocker  50  is in turn connected to an actuator  56  which may be, for example, a linear actuator, worm drive or the like. The actuator  56  acts to rotate the rocker  50  about the rocker pivot  52  to drive rotation of the trim tab  24  about the tab pivot  46 . In some embodiments, an intermediate arm  58  is located between and connected to the actuator  56  and the rocker  50  via an actuator pivot  60 , which allows relative rotation between the actuator  56  and the rocker  50 . The drive mechanism  44  described herein is low-profile, thus fitting into existing space in the interior of the rotor blade  20 , yet can deliver a relatively large amount of movement of the trim tab  24  about the tab pivot  46 . In some embodiments, the rotation of the trim tab  24  about the tab pivot  46  is about +/− 5 degrees. 
     In some embodiments, a wireless controller  62  is located in the housing  42  to transmit commands from, for example, a flight control system (not shown), to the actuator  56 . Further, in some embodiments, the actuator  56  may be powered by a power source located in the housing  42 , for example, a battery pack  64 . Finally, a cover plate  66  (shown in  FIG. 2 ) is secured over the housing  42  to contain the drive mechanism  44  and preserve the aerodynamic shape of the rotor blade  20 . 
     It is to be appreciated that while one drive mechanism  44  is illustrated and described herein, in some embodiments, more than one drive mechanism  44  may be contained in more than one housing  42  per rotor blade  20 . Further, in some embodiments, more than one drive mechanism  44  may be contained in a housing  42 . 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.