Abstract:
A gimbal lock mechanism for a rotor hub can include a cam member having a cuff lock lobe and a gimbal lock lobe. The cam member is configured so that rotation can cause the first cuff lobe to become adjacent to the root end of the rotor blade and at the same time causes the gimbal lock lobe to become adjacent to a gimbal so as to inhibit gimbaling of the gimbal. A first moveable pin can be located on the root end portion of the rotor blade and inserted into the cuff lock lobe to prevent pitch change of the rotor blade.

Description:
DESCRIPTION OF THE DRAWINGS 
       [0001]    The novel features believed characteristic of the system and method of the present disclosure are set forth in the appended claims. However, the system and method itself, as well as a preferred mode of use, and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein: 
         [0002]      FIG. 1  is a perspective view of a tiltrotor aircraft in helicopter mode, according to one example embodiment; 
         [0003]      FIG. 2  is a perspective view of a tiltrotor aircraft in airplane mode, according to one example embodiment; 
         [0004]      FIG. 3A  is an isometric view of a proprotor with the rotor blades in normal pitch, according to one example embodiment; 
         [0005]      FIG. 3B  is an isometric view of a proprotor with the rotor blades feathered, according to one example embodiment; 
         [0006]      FIG. 3C  is an isometric view of a proprotor with the rotor blades being folded, according to one example embodiment; 
         [0007]      FIG. 3D  is an isometric view of a blade lock mechanism in normal proprotor mode, according to one example embodiment; 
         [0008]      FIG. 3E  is an isometric view of a blade lock with the rotor blade pitch locked out, according to one example embodiment; 
         [0009]      FIG. 4A  is an isometric, detail isometric, and top view of a gimbal lock mechanism with the gimbal being allowed to flap, according to one example embodiment; 
         [0010]      FIG. 4B  is an isometric, detail isometric, and top view of a gimbal lock mechanism with the gimbal being prevented from flapping, according to one example embodiment; 
         [0011]      FIG. 5A  is a top view of a gimbal lock mechanism with the gimbal being allowed to flap, according to one example embodiment; 
         [0012]      FIG. 5B  is an isometric view of a gimbal lock mechanism with the gimbal being allowed to flap, according to one example embodiment; 
         [0013]      FIG. 5C  is a top view of a gimbal lock mechanism during transition, according to one example embodiment; 
         [0014]      FIG. 5D  is an isometric view of a gimbal lock mechanism during transition, according to one example embodiment; 
         [0015]      FIG. 5E  is a top view of a gimbal lock mechanism with the gimbal being locked and prevented from flapping, according to one example embodiment; and 
         [0016]      FIG. 5F  is an isometric view of a gimbal lock mechanism with the gimbal being locked and prevented from flapping, according to one example embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    Illustrative embodiments of the system and method of the present disclosure are described below. In the interest of clarity, all features of an actual implementation may not be described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer&#39;s specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
         [0018]    In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present disclosure, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction. 
         [0019]    Referring to  FIGS. 1 and 2  in the drawings, a tiltrotor aircraft  101  is illustrated. Tiltrotor aircraft  101  can include a fuselage  103 , a tail member  107 , a wing  109 , engines  111 , and proprotors  113 . Each proprotor  113  includes a plurality of rotor blades  119 , associated therewith. The position of proprotors  113 , as well as the pitch of rotor blades  119 , can be selectively controlled in order to selectively control direction, thrust, and lift of tiltrotor aircraft  101 . 
         [0020]    Tiltrotor aircraft can fly in at least three modes, including helicopter mode, proprotor mode, and airplane mode.  FIG. 1  illustrates tiltrotor aircraft  101  in helicopter mode, in which proprotors  113  are positioned substantially vertical to provide a lifting thrust.  FIG. 2  illustrates tiltrotor aircraft  101  in an airplane mode, in which proprotors  113  are positioned substantially horizontal with rotor blades  119  folded backwards, the forward thrust being provided by engines  111 , the lifting force being supplied by wing  109 . Further, tiltrotor  101  can fly in proprotor mode (not shown), in which forward thrust is provide by proprotors  113  oriented substantially horizontally. It should be appreciated that tiltrotor aircraft can be operated such that proprotors  113  are selectively positioned between proprotor mode and helicopter mode, which can be referred to as a conversion mode. Engines  111  are convertible engines that can selectively provide shaft power to proprotors  113  and provide thrust power as a turbo fan engine. 
         [0021]    Further, proprotors  113  are illustrated in the context of tiltrotor aircraft  101 ; however, proprotors  113  can be implemented on other tiltrotor aircraft. For example, an alternative embodiment may include a quad tiltrotor that has an additional wing member aft of wing  109 ; the additional wing member can have additional proprotors similar to proprotors  113 . In another embodiment, proprotors  113  can be used with an unmanned version of tiltrotor aircraft  101 . Further, proprotors  113  can be integrated into a variety of tiltrotor aircraft configurations. 
         [0022]    A tiltrotor aircraft that uses only proprotors  113  for forward propulsion in proprotor mode is fundamentally limited in forward speed by the proprotor propulsion efficiency due to compressibility (Mach) effects. Higher speeds can be obtained by stopping the rotors and folding them in combination with using an alternative propulsion method, such as a turbofan engine  111 . When proprotor  113  is a gimbaled (flapping) proprotor, the proprotor  113  becomes subject to high flapping angles when the proprotor speed (RPM) is slowed to a stop since the centrifugal forces are lower at lower proprotor speeds. In order to prevent the proprotor  113  from from gimbaling too much under large loads and damaging itself, i.e. mast bumping, a locking mechanism locks out the flapping degree of freedom. 
         [0023]    Referring to  FIGS. 3A-3E , the embodiments of the present disclosure provide a mechanism to ‘lock’ the gimbal degree of freedom to prevent flapping at lower proprotor RPMs, but allow flapping at higher RPMs. The embodiments of the present disclosure also provides a means to lock the blade feather or pitching motion out, when the gimbal is locked, by providing a rigid connection point in proximity to a cuff  321  of the rotor blade  119 , but moves the rigid connection away from the cuff  321  of the rotor blade  119  to allow sufficient clearance when the gimbal is unlocked and allowed to flap. 
         [0024]    Still referring to  FIGS. 3A-3E , a folding proprotor transition sequence is illustrated. A pitch horn  301  functions to not only change the pitch of the rotor blade  119  while in proprotor mode, but also as the blade fold mechanism when folding the rotor blades  119  to convert into airplane mode. During proprotor mode, a pin  303  couples pitch horn  301  to a portion  307  on a cuff  321  of the rotor blade  119  so that up/down movements of a swashplate  313  change the pitch of the rotor blade  119  via a plurality of pitch links  323 . However, when actuator  305  is actuated, pin  303  decouples the pitch horn  301  from the portion  307  of the rotor blade  119  and simultaneously engages a pin  309  to a cuff lock lobe  311 , which prevents a pitch change in rotor blade  119 . Next, an upward movement of the swashplate  313  causes the rotor blades  119  to fold backwards about a crank axis of rotation  315 , thus allowing the pitch horn  301  to be used for both rotor blade pitch change during proprotor mode, as well as for folding the rotor blades  119  when converting to airplane mode. Pitch horn  301  is rotatably coupled to rotor blade  119  with a spindle  327  that defines the crank axis of rotation  315 . 
         [0025]    In the illustrated embodiment, pin  303  and pin  309  are part of a single lock device  319  that is coupled to actuator  305  such that actuation of lock device  319  simultaneously locks out pitch change motion by insertion of pin  309  into cuff lock lobe  311 , and unlocks a fold crank  317  by removal of pin  303  from pitch horn  301 , which allows the rotor blades  119  to fold for high speed flight configuration in airplane mode. Conversely, when the rotor blades  119  unfold into proprotor mode, the translation of lock device  319  removes pin  309  from cuff lock lobe  311  so as to un-lock the pitch degree of freedom, and simultaneously inserts pin  303  into a hole  325  in pitch horn  301  so as to lock out the fold degree of freedom. The lock device  319  is shaped to allow lock engagement in different locations on the blade root. The lock device  319  is affected by the actuator  305  located on the cuff portion  321  on the root end of rotor blade  119 . Each rotor blade  119  and cuff  321  has an actuator  305  and lock device  319 . 
         [0026]    Referring also to  FIGS. 4A, 4B, and 5A-5F , a gimbal lock mechanism  401  is illustrated. Gimbal lock mechanism  401  includes a plurality of cams  405  each having the cuff lock lobe  311  and a gimbal lock lobe  407  that can selectively rotate about a hinge  409  when selectively actuated by an actuator  411 . Cams  405  are rotatably coupled to a housing  419 . Housing  419  is coupled to the rotor mast  421  so as to concentrically rotate with the rotor mast  421 . Each cam  405  is also coupled together by a ring  413  and linkages  415  such that only a single actuator  411  can rotate all the cams  405  by rotating ring  413 . Actuator  411  is secured to housing  419 . 
         [0027]    Each gimbal lock lobe  407  can be selectively rotated into close proximity with the gimbal  403  to physically restrain the gimbal  403  so as to prevent the gimbal  403  from tilting. In the illustrated embodiment, three gimbal lock lobes  407  are used to secure gimbal  403  and prevent gimbal  403  from flapping. The cams  405  are configured to allow gimbal flapping when the cams  405  are in one rotational position, and prevent or constrain the gimbal hub  403  in another rotational position. One advantageous feature of the gimbal lock mechanism  401  is that the cuff lock lobe  311  is integral to the gimbal lock lobes  407  of the cams  405  such that the cuff lock lobes  311  are only in close proximity with the root ends of the rotor blades  119  when the gimbal  403  is locked and prevented from tilting. This prevents undesired interference between rotor blades  119  and the cuff lock lobes  311  during proprotor operation which involves gimbaling (flapping). 
         [0028]    The cams  405  can have a shape with a feature (a ‘lock lobe’) that rotates in proximity to the blade/cuff root, when the cams  405  are in the locked position, to allow the blade pitch to be locked out by the insertion of pin  309  into a mating aperture  417 . Pitch lock-out is important in order to fold the blades with the swashplate actuators. 
         [0029]    In the illustrated embodiment, the gimbal lock lobe  407  is illustrated with an arcuate geometry that is configured to mate with a similar mating geometry of the gimbal  403  to prevent flapping. It should be appreciated that the exact mating geometries of gimbal  403  and gimbal lock lobe  407  is implementation specific and not limited to an arcuate geometry. Gimbal lock lobe  407  will contact gimbal  403  if gimbal  403  attempts to gimbal or flap, therefore a compliant layer, such as an elastomer, can be used therebetween. 
         [0030]    The particular embodiments disclosed herein are illustrative only, as the system and method may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Modifications, additions, or omissions may be made to the system described herein without departing from the scope of the invention. The components of the system may be integrated or separated. Moreover, the operations of the system may be performed by more, fewer, or other components. 
         [0031]    Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the disclosure. 
         [0032]    To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims to invoke paragraph 6 of 35 U.S.C. §112 as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.