Patent Publication Number: US-2023137714-A1

Title: Articulated Electric Propulsion System And Lightweight Vertical Take-Off And Landing Aircraft Using Same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/436,812 to Bevirt et al., filed Jun. 10, 2019, which is a continuation of U.S. patent application Ser. No. 14/660,838 to Bevirt et al., filed Mar. 17, 2015, which is a continuation-in-part of U.S. patent application Ser. No. 14/218,845 to Bevirt et al., filed Mar. 18, 2014, now U.S. Pat. No. 9,694,911, which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     Field of the Invention 
     This invention relates to powered flight, and more specifically to a vertical take-off and flight control aircraft and flight method. 
     Description of Related Art 
     There are generally three types of vertical takeoff and landing (VTOL) configurations: wing type configurations having a fuselage with rotatable wings and engines or fixed wings with vectored thrust engines for vertical and horizontal translational flight; helicopter type configuration having a fuselage with a rotor mounted above which provides lift and thrust; and ducted type configurations having a fuselage with a ducted rotor system which provides translational flight as well as vertical takeoff and landing capabilities. 
     With VTOL aircraft, significantly more thrust may be required for takeoff and landing operations than during regular forward flight. This extra thrust may also be required during the transitions between vertical and horizontal flight. In the case of propeller driven aircraft, for example, with a plurality of pivoting thrust units using propellers for takeoff, some or many of these thrust units may be idled during regular, horizontal forward flight. 
     What is called for is a thrust unit utilizing a propeller which allows for rotation of the thrust unit from a position of vertical thrust to a position wherein the thrust unit provides horizontal thrust. What is also called for is a thrust unit which is capable of stowing the propeller blades completely, into a nested configuration. 
     SUMMARY 
     An aerial vehicle adapted for vertical takeoff and landing using pivoting thrust producing elements for takeoff and landing. An aerial vehicle which is adapted to takeoff with thrust units providing vertical thrust and then transitioning to a horizontal flight path. An aerial vehicle with pivoting thrust units with propellers, wherein some or all of the propellers are able to be stowed and fully nested during forward flight. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of an aerial vehicle in a takeoff configuration according to some embodiments of the present invention. 
         FIG.  2    is a perspective view of an aerial vehicle in a forward flight configuration according to some embodiments of the present invention. 
         FIG.  3    is a view of a stowing blade system in a deployed forward flight configuration according to some embodiments of the present invention. 
         FIG.  4    is a perspective view of a stowing blade system in a stowed configuration according to some embodiments of the present invention. 
         FIG.  5    is a front view of a stowing blade system in a stowed configuration according to some embodiments of the present invention. 
         FIG.  6    is a partial view of a stowing blade system in a stowed configuration according to some embodiments of the present invention. 
         FIG.  7    is a front partial view of a stowing blade system in a stowed forward flight configuration according to some embodiments of the present invention. 
         FIG.  8    is a partial view of a stowing blade system in a stowed configuration according to some embodiments of the present invention. 
         FIG.  8 A  is an illustration of a fin mount according to some embodiments of the present invention. 
         FIG.  9    is a partial view of a stowing blade system in a stowed configuration according to some embodiments of the present invention. 
         FIG.  10    is a side view of an exemplary blade stowed according to some embodiments of the present invention. 
         FIG.  11    is a side view of an articulated mounting system in a forward flight configuration according to some embodiments of the present invention. 
         FIG.  12    is a side view of an articulated mounting system in a take off configuration according to some embodiments of the present invention. 
         FIG.  13    is a side view of an articulated mounting system in a transitioning configuration according to some embodiments of the present invention. 
         FIG.  14    is a top view of an articulated mounting system in a transitioning configuration according to some embodiments of the present invention. 
         FIG.  15    is a perspective view of an articulated mounting system in a transitioning configuration according to some embodiments of the present invention. 
         FIG.  16    is a partial side view of an articulating mounting system with its blades deployed according to some embodiments of the present invention. 
         FIG.  17    is a rear perspective view of an articulated mounting system according to some embodiments of the present invention. 
         FIG.  18    is a partial view of the underside of a rotor hub according to some embodiments of the present invention. 
         FIG.  19    is a partial side cutaway view of the stowing mechanics according to some embodiments of the present invention. 
         FIG.  20    is a bottom perspective view of the rotor stowing mechanics according to some embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Although vertical takeoff and landing (VTOL) aircraft have always been desired, compromises in the realization of these aircraft have limited their usefulness and adoption to certain niches. The thrust needed for VTOL is significantly higher than the thrust needed to maintain horizontal flight. The vertical take-off thrust may also be needed during the transition to forward flight. Once moving in forward flight, the wings of the aircraft provide lift, supplanting a function delivered by motors during VTOL and during transition. Thrust producing elements needed during take-off, but not during forward flight, may be altered during forward flight such that they impart less drag onto the flying system. 
     In some aspects, an aerial vehicle may use bladed propellers powered by electric motors to provide thrust during take-off. The propeller/motor units may be referred to as rotor assemblies. In some aspects, the motor driven propeller units on the wings may rotate relative to a fixed wing, such that the propellers provide vertical thrust for take-off and landing. The rotation of the motor driven propeller units may allow for directional change of thrust by rotating both the propeller and the electric motor, thus not requiring any gimbaling, or other method, of torque drive around or through a rotating joint. The motor driven propeller units may be referred to herein as motor driven rotor units. 
     In some aspects, some or all of the wing mounted motor driven rotors are adapted to have the rotor blades fold back into a stowed position wherein the blades nest in recesses in the adjoining nacelle body after a transition to horizontal flight. The nested blades may result in a significantly lower drag of the aerial vehicle, while also allowing a significantly reduced power usage with only some of the rotors providing forward thrust. 
     In some aspects, extended nacelles with two coaxial propellers are used such that one of the propellers is used during forward flight, and another during vertical take-off and landing. The VTOL propeller may be adapted to nest its blades during forward flight. In some aspects, the extended nacelle may reside at the tip of a wing, or at the end of a rear V-tail element. In some aspects, each of the coaxial propellers has its own electric motor. In some aspects, the coaxial propellers are driven by the same electric motor. In some aspects, the electric motor has directional clutches such that one propeller is driven while the motor rotates in a first direction, and the other propeller is driven while the motor rotates in a second direction. 
     In some aspects, the mass balance of the aerial vehicle may be altered by movement of masses such as the battery mass. In some aspects, the battery mass may be adjusted to retain balance when a different number of occupants are supported. In some aspects, mass balance may be adjusted in automatic response to sensors within the aerial vehicle. In some aspects, the battery mass may be distributed between a two or more battery packs. The battery packs may be mounted such that their position may be changed during flight in response to changes in the balance of the aerial vehicle. In some aspects, the flight control system of the aerial vehicle may sense differential thrust requirements during vertical take-off and landing, and may move the battery mass in order to achieve a more balanced thrust distribution across the rotor assemblies. In some aspects, the battery mass may be moved should there be a failure of a rotor assembly during transition or vertical take-off and landing, again to balance the thrust demands of the various remaining functioning rotors. 
     In some embodiments of the present invention, as seen in  FIG.  1   , an aerial vehicle  100  is seen in take off configuration. The aircraft body  101  supports a left wing  102  and a right wing  103 . Motor driven rotor units  140  include propellers  107  which may stow and nest into the nacelle body  106 . The aircraft body  101  extends rearward is also attached to raised rear stabilizers  104 . The rear stabilizers have rear motors  105  attached thereto. Portions of the rotor unit have been omitted in  FIG.  1    for illustrative clarity. 
       FIG.  1    illustrates the aerial vehicle  100  in a vertical take-off and landing configuration such that the thrust of the rotors is directed upward. The propellers  107  have been rotated relative to the nacelle bodies  106  using articulated linkages. In this vertical take-off and landing configuration, the aerial vehicle  100  is able to utilize six propellers providing thrust in a vertical direction. The propellers  107  are adapted to raise the vehicle  100 . After the initial vertical take-off, the vehicle transitions to forward horizontal flight. The transition is facilitated by the articulation of the propellers from a vertical thrust configuration to positions off of vertical, transitioning to a horizontal thrust configuration.  FIG.  3    is illustrative of the motor driven rotor unit in a powered forward flight configuration. 
     As the aerial vehicle  100  transitions to a forward, horizontal, flight configuration, the wings  102 ,  103  begin to provide lift. Once traveling in a horizontal attitude, with speed, significantly less thrust is needed to propel the aerial vehicle  100  forward than was needed as vertical thrust during take-off.  FIG.  2    illustrates a forward flight configuration of an aerial vehicle  100  wherein the blades  108  of the propellers  107  have been stowed into recesses  110  on the nacelle bodies  106 . With the blades stowed during forward flight, a low drag profile may be attained. In some aspects, some of the main propellers  107  may be used for forward flight. In some aspects, all of the main propellers  107  may be stowed, and alternate forward flight propellers  111  may be used in forward flight. 
     In an exemplary configuration of the first embodiment, the aerial vehicle has 6 rotors and weighs 900 kg. The rotor diameters are 2.1 meters, with a thrust per rotor of 1500 N in hover. The continuous rpm of the motor at sea level is 1030 rpm, with a maximum of 1500 rpm. The wingspan is 7.5 meters. The battery mass is 360 kg, and the mass per motor is 9 kg. The cruise speed is 320 km/h. The continuous hover shaft power per motor is 25 kW at standard sea level conditions. 
       FIGS.  3  and  4    illustrate the deployed and stowed configurations, respectively, of the main propellers  107  of the motor driven rotor units  140 . In the deployed configuration, the propeller blades  108  of the propeller  107  are deployed to a position approximately perpendicular to the rotation axis of the motor driven rotor unit  140 . The actual blade angle may vary as a function of motor rpm and other factors, as discussed below. A spinner  109  presents a leading surface for the motor driven rotor unit  140 . 
     In the stowed configuration, the blades  108  reside within recesses  110  in the nacelle body  106 . As seen in front view in  FIG.  5   , in the stowed configuration the outer surface of the forward portion of the nacelle is composed of the surfaces of the blades  108  of the propeller  107 . The outer surface of the nacelle with the blades in the stowed configuration is a composite of the five blades&#39; surfaces. The blades and the nacelles may be designed in concert such that the nacelle aerodynamic requirements and those of the propeller fit into each other into a complementary design. The recesses  110  may be adapted to provide a very snug fit for the blades  108  in the stowed configuration. 
       FIGS.  6  and  7    illustrate a perspective view and a front view, respectively, of a motor driven rotor unit with the spinner removed to help the viewer visualize a design according to some aspects of the present invention. The main hub  122  is seen as a mounting point for each of the five propeller blades  108 . The main hub  122  provides the main support of the propeller blades, which are each pivotally connected to the main hub. The main hub  122  also provides the drive torque to the blades  108  of the propeller  107 . As discussed further below, the main hub  122  is coupled to the outboard bracket of the rotor deployment mechanism via a rotary bearing, or bearing assembly. 
       FIG.  8    illustrates a perspective view of a motor driven rotor unit with further portions removed for clarity of illustration. The propeller blade  108  is illustrated solely as a partial blade  142 , allowing for observation of the fin mount  121 . The fin mount  121  is bonded within the (missing in this view) inner portion of the propeller blade. In some aspects, the propeller blade is formed from a number of pre-formed pieces which are then bonded together, with the fin mount affixed therein. The fin mount  121  may be metal, and constructed such that it is adapted to allow for mounting to the main hub  122  with a hinge pin  123 , for example. In some embodiments, as seen in  FIG.  8 A , the fin mount  121  may be a plurality of independent pieces. These pieces may be fixtured during assembly of the propeller blade  108  such that the finished component is adapted to mount to the main hub  122  with a hinge pin. A stowing tab  143  may be affixed to the fin mount  121  to allow for moving the blade into a stowed configuration into the recess and against the nacelle body. In some aspects, the propeller blade  108  may be of a composite material. The propeller blade  108  may be assembled from pieces such that the blade is a hollow shell assembled from pre-manufactured individual pieces. A deploy spring  141  allows for the blades of the propeller to achieve a deployed configuration in the absence of centrifugal forces. The deploy spring allows for full deployment of the propeller blades even when the rotors are not turning. To achieve full stowage, the stowing tabs  143  on the propeller blades  108  of the propeller  107  are pushed on by a stowing mechanism, until the blades are fit within the recesses  110  of the nacelle bodies. 
       FIG.  9    illustrates another perspective view of a motor driven rotor unit with even further portions removed for clarity of illustration. The main hub  122  is seen supporting the fin mount  121 . The fin mount  121  is adapted to pivot relative to the main hub  122  using a hinge pin  123 . In some recesses, the partial blades  142  are seen, and other recesses  110  no blade is seen, for purpose of visual clarity only. As the further portions have been removed for illustrative effect, the rotor deployment mechanism, the motor, and other components come into view. 
       FIG.  10    illustrates a side view of portions of a rotor according to some embodiments of the present invention. The propeller blade  108  is seen in a stowed position. The propeller blade  108  is hinged with a hinge pin  123  to the main hub  122 . The main hub is seen mounted within a bearing assembly  125 . The bearing assembly  125  is mounted to the outboard bracket  124  of the rotor deployment mechanism. In some aspects, the main hub  122  is mounted to the inner race or races of the bearing assembly  125 , and the outer race of the bearing assembly  125  is mounted within the outboard bracket  124  of the rotor deployment mechanism. 
       FIG.  11    is a side view of portions of a rotor deployment mechanism of a deployable motor driven rotor assembly in a forward flight configuration according to some embodiments of the present invention. The main mounting points  127 ,  128  are the structural attachment points for the rotor deployment mechanism  143 , and by extension, for the motor driven rotor unit, to the aerial vehicle. The drive motor  126  is adapted to drive the rotor main hub  122 , and by extension, the propeller of the rotor unit. In this forward flight configuration, the rotor thrust vector is oriented facing with regard to the aerial vehicle, and is horizontal. In some aspects, with the use of rotor deployment mechanisms as described herein, the nacelle may be seen as being split during the rotor deployment such that the rear portion of the nacelle stays with the wing in a fixed positional relationship. The rotor deployment may then be able to occur from a nacelle along the wing, or along a rear horizontal stabilizer element. The rotor deployment mechanisms may be mounted at a position that is not the end of the wing, or other horizontal element. 
       FIG.  12    illustrates rotor deployment mechanism  143  in a deployed, vertical take-off, configuration. The rotor deployment mechanism has both rotated and displaced the rotor. The deployment has pushed the rotor hub forward, and away, from the main mounting points  127 ,  128 , as well as upward vertically relative to the main mounting points. In this vertical take-off configuration, the rotor axis is vertical. 
     The outboard bracket  124  is attached to the deployment linkages at the bracket attach points  134 ,  135 . The bracket arms  129 ,  130 ,  131  link via pivot points  132 ,  133 . With the use of multi-arm linkages the rotor may be moved to preferred positions in both the deployed and stowed configurations.  FIGS.  13 - 16    illustrate the rotor with its linkages in a partially deployed configuration, which is seen during transitions from vertical to horizontal thrusting, or from horizontal to vertical thrusting. 
     The electric motor/propeller combination being on the outboard side of the articulating joint allows for a rigid mounting of the propeller to the motor, which is maintained even as the propeller is moved through various attitudes relative to the rear nacelle portion. With such a configuration the rotating power from the motor need not be gimbaled or otherwise transferred across a rotating joint. 
       FIG.  17    illustrates a deployment drive system for a deployment mechanism according to some embodiments of the present invention. A drive unit  151  may be coupled to the aerial vehicle, within the wing in an area adjacent to the mounting points for the main mounting points  127 ,  128 . Drive screws  150  may be driven such that the deployment linkage is driven from a stowed configuration to a deployed configuration, and from a deployed configuration to a stowed configuration. 
       FIG.  18    is a partial view of the underside of a main rotor hub  122  mounted into an outboard bracket  124  of a rotor deployment mechanism according to some embodiments of the present invention. A stowing rod  153  is adapted to drive the stowing levers  152  against the stowing tabs  143 . The stowing tabs  143  then drive the propeller blades into a nested position onto the nacelle body. The deploy springs  141  are adapted to deploy the propeller blades  108  from a stowed position to a deployed position.  FIG.  19    is a partial side cutaway view of the stowing rod  153  coupled to a plurality of stowing levers  152 . The stowing rod  153  may be driven by a linear actuator to engage the stowing tabs  143  in order to deploy the propeller blades from their stowed, nested, configuration. When fully deployed, the propeller blades will not reside on the stowing levers.  FIG.  20    is a bottom perspective view of the stowing rod  153  and its coupling to the stowing levers  152 , and ultimately to the fin mounts  121  of the propeller blades  108 . Position indicators may be used to properly line up the propeller relative to the recesses in the nacelle. 
     In an exemplary embodiment of a method for flying an aerial vehicle with an articulated electric propulsion system and fully stowing blades, an aerial vehicle may be on the ground. The aerial vehicle may have a plurality of wing and tail mounted motor driven rotor units. The motor driven rotor units may begin with propeller blades that are stowed such that the stowed propeller blades comprise all or most of the effective wetted area of portions of the nacelles of which they form a part. The nacelles may have recesses adapted to receive the stowed blades. 
     The stowed blades may be held in the stowed position with the assistance of stowing mechanisms. In preparation for vertical take-off, the stowed blades may deploy to a deployed configuration. The blades may utilize deployment springs which assist with the deployment of the blades upon the release of stowing levers. The stowing levers may be adapted to pivot the propeller blades from a deployed to a stowed configuration. 
     Once the propeller blades are in a deployed position, the entire motor driven rotor assembly may be itself deployed from a forward flight position to a vertical take-off and landing position with the use of an articulating rotor deployment mechanism. The deployment mechanism is adapted to position the propellers in front of and above the wings, or otherwise clear of other aerial vehicle structure. With the propeller blades now deployed, and with the motor driven rotor units now articulated into a vertical take-off configuration, the aerial vehicle is able to begin a vertical take-off. The rotors are spun up and the vehicle rises from the ground. 
     After take-off, the aerial vehicle will begin a transition to forward flight by articulating the rotors from a vertical thrust orientation to a position which includes a horizontal thrust element. As the aerial vehicle begins to move forward with speed, lift will be generated by the wings, thus requiring less vertical thrust form the rotors. As the rotors are articulated further towards the forward flight, horizontal thrust, configuration, the aerial vehicle gains more speed. 
     Once the aerial vehicle is engaged in regular forward flight, the rotors in use during take-off may no longer be necessary. The thrust requirement for forward flight may be significantly less than that required during vertical take-off and landing. The forward flight may be maintained by just a subset of the rotor used for take-off, or by different rotors than those used during take-off. The unused rotors may have their propeller blades stowed in to recesses on the nacelles supporting the rotors. The stowed propeller blades may form the exterior surface of portions of the nacelle. 
     As evident from the above description, a wide variety of embodiments may be configured from the description given herein and additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader aspects is, therefore, not limited to the specific details and illustrative examples shown and described. Accordingly, departures from such details may be made without departing from the spirit or scope of the applicant&#39;s general invention.