Abstract:
A rotor assembly for use with rotor blades and a drive shaft includes a one-piece molded rotor hub having a central hub and a plurality of hollow spindles integrally molded with and extending radially outwardly of the central hub to which rotor blades are attachable. The central hub includes a hollow interior that is receptive to a drive shaft configured to rotate the one-piece molded rotor hub.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to U.S. Provisional Application No. 62/298,217, filed on Feb. 22, 2016, the contents of which are incorporated by reference herein in its entirety. 
     
    
     STATEMENT OF FEDERAL SUPPORT 
       [0002]    This invention was made with Government support under Agreement No. W911W6-13-2-0003 for the Joint Multi-Role Technology Demonstrator Phase I-Air Vehicle Development program. The Government has certain rights in the invention. 
     
    
     BACKGROUND 
       [0003]    Exemplary embodiments pertain to the art of aircraft and, more particularly, to a one-piece molded rotor hub for an aircraft. 
         [0004]    A fixed wing aircraft may include one or more propellers that provide energy for forward movement. Rotary wing aircraft include one or more rotors that provide lift, yaw control, and/or forward movement. More specifically, rotary wing aircraft include a main rotor assembly that provides lift and a tail rotor assembly that provides yaw control or, in the case of a propulsor, energy for forward movement. In some cases, both the main rotor assembly and the propulsor include dual rotor assemblies. The dual rotor assemblies may represent counter rotating rotors or co-rotating rotors. 
       BRIEF DESCRIPTION 
       [0005]    Disclosed is a rotor assembly for use with rotor blades and a drive shaft includes a one-piece molded rotor hub having a central hub and a plurality of hollow spindles integrally molded with and extending radially outwardly of the central hub to which rotor blades are attachable. The central hub includes a hollow interior that is receptive to a drive shaft configured to rotate the one-piece molded rotor hub. 
         [0006]    In addition to one or more of the features described above or below, or as an alternative, further embodiments could include a tension torsion strap extending through each of the plurality of hollow spindles, the tension torsion strap including a first end operatively connected to the central hub and a second end projecting proudly of the corresponding one of the plurality of hollow spindles. 
         [0007]    In addition to one or more of the features described above or below, or as an alternative, further embodiments could include a plurality of openings extending through the central hub, each of the plurality of openings being arranged along a central axis of a corresponding one of the plurality of hollow spindles. 
         [0008]    In addition to one or more of the features described above or below, or as an alternative, further embodiments could include a pin member extending through each of the plurality of openings and operatively connected to the first end of the tension strap arranged in the corresponding one of the plurality of hollow spindles. 
         [0009]    In addition to one or more of the features described above or below, or as an alternative, further embodiments could include wherein the rotor blade is operatively coupled to the second end of the tension torsion strap. 
         [0010]    In addition to one or more of the features described above or below, or as an alternative, further embodiments could include at least one sleeve installed over each of the plurality of hollow spindles. 
         [0011]    In addition to one or more of the features described above or below, or as an alternative, further embodiments could include wherein the at least one sleeve is formed from a different material from that which forms the one-piece molded rotor hub. 
         [0012]    In addition to one or more of the features described above or below, or as an alternative, further embodiments could include a clam shell connected to the one-piece molded rotor hub and having openings through each the plurality of hollow spindles extend, the clam shell having a fastening system which connects the one-piece molded rotor hub to the drive shaft. 
         [0013]    In addition to one or more of the features described above or below, or as an alternative, further embodiments could include wherein the one-piece molded rotor hub assembly is produced using formed from a resin composite. 
         [0014]    In addition to one or more of the features described above or below, or as an alternative, further embodiments could include wherein the resin composite includes one of graphite and an epoxy, and the one-piece molded rotor hub and plurality of hollow spindles are formed as a single molded rotor assembly using a resin transfer molding process. 
         [0015]    In addition to one or more of the features described above or below, or as an alternative, further embodiments could include wherein the one-piece molded rotor hub and spindles are produced using a process which produces an integrally formed rotor hub. 
         [0016]    Also disclosed is an aircraft including an airframe, a power source, a drive member operatively connected to the power source, and a rotor assembly operatively connected to the drive member. The rotor assembly a one-piece molded rotor hub having a central hub and a plurality of hollow spindles integrally molded with and extending radially outwardly of the central hub to which rotor blades are attachable. The central hub includes a hollow interior that is receptive to a drive shaft coupled to the drive member. 
         [0017]    In addition to one or more of the features described above or below, or as an alternative, further embodiments could include a tension torsion strap extending through each of the plurality of hollow spindles, the tension torsion strap including a first end operatively connected to the central hub and a second end projecting proudly of the corresponding one of the plurality of hollow spindles. 
         [0018]    In addition to one or more of the features described above or below, or as an alternative, further embodiments could include a plurality of openings extending through the central hub, each of the plurality of openings being arranged along a central axis of a corresponding one of the plurality of hollow spindles, a pin member extending through each of the plurality of openings and operatively connected to the first end of the tension strap arranged in the corresponding one of the plurality of hollow spindles, and a rotor blade operatively connected to the second end of the tension torsion strap. 
         [0019]    In addition to one or more of the features described above or below, or as an alternative, further embodiments could include a clam shell connected to the one-piece molded rotor hub and having openings through each the spindles extend, the clam shell having a fastening system which connects the rotor hub to the drive shaft. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0021]      FIG. 1  depicts a rotary wing aircraft including a rotor assembly having a one-piece molded hub, in accordance with an exemplary embodiment; 
           [0022]      FIG. 2  is a perspective view of a rotary wing aircraft of  FIG. 1 , in accordance with an exemplary embodiment; 
           [0023]      FIG. 3  is a partial perspective view of the rotor assembly, in accordance with an aspect of an exemplary embodiment; 
           [0024]      FIG. 4  is a perspective view of the one-piece molded rotor hub, in accordance with an aspect of an exemplary embodiment, and 
           [0025]      FIG. 5  is a partial cross-sectional view of the rotor assembly, in accordance with an aspect of an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
         [0027]      FIGS. 1 and 2  depict an exemplary embodiment of a rotary wing, vertical takeoff and landing (VTOL) aircraft  10 . Aircraft  10  includes an airframe or fuselage  12  having a plurality of surfaces (not separately labeled) with an extending tail  14 . A coaxial main rotor assembly  18  is located at the fuselage  12  and rotates about a main rotor axis, A. In an exemplary embodiment, the fuselage  12  includes a cockpit  20  having two seats for flight crew (e.g., pilot and co-pilot) and six seats for passengers (not shown). Main rotor assembly  18  is driven by a power source, for example, one or more engines  24 , via a gearbox  26 . Main rotor assembly  18  includes an upper rotor assembly  28  that may be driven in a first direction (e.g., counter-clockwise) about the main rotor axis, A, and a lower rotor assembly  32  that may be driven in a second direction (e.g., clockwise) about the main rotor axis, A, opposite to the first direction (i.e., counter rotating rotors). Of course, it should be understood that upper and lower rotor assemblies  28  and  32  may be driven in the same direction. 
         [0028]    In accordance with an exemplary embodiment, upper rotor assembly  28  includes a first plurality of rotor blades  34  supported by a first or upper rotor hub  36 . Lower rotor assembly  32  includes a second plurality of rotor blades  38  supported by a second, or lower rotor hub  39 . In some embodiments, aircraft  10  may include a translational thrust system or propulsor  40  having a rotor or propeller assembly  42  located at extending tail  14  to provide translational thrust (forward or rearward) for aircraft  10 . Propeller assembly  42  includes a plurality of blades  43 . 
         [0029]    Main rotor assembly  18  also includes a shaft fairing  44  generally located between and around the upper and lower rotor assemblies  28  and  32  such that lower rotor hub  39  may be at least partially contained therein. Shaft fairing  44  extends about a rotor shaft  46  operatively connecting upper rotor assembly  28  and engine(s)  24 . Shaft fairing  44  extends between lower hub  39  and an upper hub member  47  arranged inwardly of upper rotor assembly  28  and operates to reduce drag which might otherwise exist at rotor shaft  46 . First plurality of rotor blades  34  may be connected to upper rotor hub  36  in a hingeless manner, also referred to as a rigid rotor system. Similarly, second plurality of rotor blades  38  may be connected to lower rotor hub  39  in a hingeless manner. Although a particular aircraft configuration is illustrated in this non-limiting embodiment, other rotary wing aircraft will also benefit from embodiments of the invention. Although, the dual rotor system is depicted as coaxial, embodiments include dual rotor aircraft having non-coaxial rotors. Further, while a particular aircraft configuration is illustrated in this non-limiting embodiment, other rotary wing aircraft will also benefit from embodiments of the invention, such as those not including a fairing. Moreover, aspects can be used in non-rotary wing aircraft, including fixed wing aircraft and tilt wing aircraft using rotor blades and/or propellers, and can be used in maritime propulsion systems, wind turbines and the like. 
         [0030]    Propeller assembly  42 , or translational thrust system  40 , is connected to, and driven by, the engine  24  via the gearbox  26 . Translational thrust system  40  may be mounted to the rear of the fuselage  12  with a translational thrust axis, T, oriented substantially horizontal and parallel to the aircraft longitudinal axis, L, to provide thrust for high-speed flight. The term “parallel” should be understood to include a translational thrust axis that is coincident with the longitudinal axis. Translational thrust axis, T, corresponds to the axis of rotation of propeller assembly  42 . While shown in the context of a pusher-prop configuration, it is understood that the propeller assembly  42  could also be a more conventional puller prop or could be variably facing so as to provide yaw control in addition to, or instead of, translational thrust. It should be further understood that any such system or other translational thrust systems may alternatively or additionally be utilized. Alternative translational thrust systems may include different propulsion forms, such as a jet engine. 
         [0031]    In accordance with an aspect of an exemplary embodiment, propeller assembly  42  may include propeller blades  43  having a variable pitch. More specifically, the pitch of propeller blades  43  may be altered to change the direction of thrust (e.g., forward or rearward). In accordance with another aspect of an exemplary embodiment, extended tail  14  includes a tail section  50  including starboard and port horizontal stabilizers  51  and  52 . Tail section  50  also includes a vertical stabilizer  53  that extends downward from extending tail  14 . Starboard horizontal stabilizer  51  includes a starboard active elevator  54  and a starboard active rudder  56 . Similarly, port horizontal stabilizer  52  includes a port active elevator  58  and a port active rudder  60 . Elevators  54  and  58  and rudders  56  and  60  act as controllable surfaces, e.g., surfaces that alter a flight path/characteristics of aircraft  10 . 
         [0032]    In accordance with an exemplary embodiment illustrated in  FIGS. 3-5 , propeller assembly  42  includes a one-piece molded rotor hub  80  including a central hub  82  and a plurality of hollow spindles, one of which is indicated at  84 . Central hub  82  includes a hollow interior portion  86  ( FIG. 5 ) and is mounted to a drive member  90  which, in turn, is operatively connected to engines  24 . Drive member  90  includes a plurality of recesses, one of which is indicated at  92 , which receive corresponding ones of hollow spindles  84 . One-piece molded rotor hub  80  is secured to drive member  90  by a clamshell member  96  having a plurality of recessed portions  98 . Recessed portions  98  align with recesses  92  to encircle each of hollow spindles  84 . Clamshell member  96  may be secured to drive member  90  through a variety of techniques known in the art. 
         [0033]    Each hollow spindle  84  includes a first end portion  104 , a second end portion  105  and an intermediate section  106  extending therebetween. A central passage  108  extends from hollow interior  86 , through intermediate section  106  to second end portion  105 . Central passage  108  includes a longitudinal axis “w”. A tension torsion strap  120  extends through central passage  108  along longitudinal axis “w”. Tension torsion strap may be similar to the tension torsion strap described in corresponding U.S. Patent Application 62/174,275 entitled “Tension Torsion Strap” filed on Jun. 11, 2015, the disclosure of which is incorporated by reference. In accordance with an aspect of an exemplary embodiment, one or more sleeves  122  may extend over hollow spindle  84  along central passage  108  to improve wear resistance of one-piece molded rotor hub  80 . In accordance with an aspect of an exemplary embodiment, metal sleeves  122  may be formed from steel. Of course, it should be understood that other materials may also be employed. 
         [0034]    Tension torsion strap  120  includes a first end  124 , a second end  125  and an intermediate portion  128  extending therebetween. Second end  125  includes a blade attachment member  130  that operatively connects with one of blades  43 . First end  124  is secured within hollow interior  86  of central hub  82 . More specifically, a plurality of openings, one of which is indicated at  140 , extends through central hub  82 . Openings  140  may extend axially through central hub  82  or at an angle relative thereto and are aligned with longitudinal axis “w” of each hollow spindle  84 . A pin  144  extends through each opening  140  and engages with first end  124  of each tension torsion strap  120 . As such, even while the propeller assembly  42  rotates, each rotor blade  43  is retained by the corresponding tension torsion strap  120 . 
         [0035]    In accordance with an aspect of an exemplary embodiment, one-piece molded rotor hub  80  is formed from a composite resin. In accordance with another aspect of an exemplary embodiment, one-piece molded rotor hub  80  is formed from a composite resin including a graphite constituent and an epoxy constituent. The particular constituents of the composite resin may vary depending upon various design, operational envelope and other considerations. One-piece molded rotor hub  80  may be formed by a resin transfer mold (RTM) process. However, one of ordinary skill in the art would recognize that there exist various processes for forming one-piece molded rotor hub  80 . 
         [0036]    At this point, it should be understood that exemplary embodiments describe a one-piece molded rotor hub for an aircraft. The one-piece molded rotor hub is formed from a lightweight, structural material capable of supporting loads associated with rotating blades at a reduced weight over that of previous designs. Further, the use of the clamshell member to secure the propeller assembly to the aircraft reduces installation time, complexity and maintenance issues. Further, exemplary embodiments provide a one-piece molded rotor hub that is easy to manufacture that reacts to system centrifugal forces and blade-to-blade loads while only transmitting thrust, torque and head moment to the drive member. 
         [0037]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof. 
         [0038]    While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.