Patent Description:
The availability of excess lift is most essential during take-off and landing evolutions of an unmanned aerial vehicle. Precision control of altitude is critical when an unmanned aerial vehicle attempts to take off from or land at a given location, in order to enable the unmanned aerial vehicle to avoid any surrounding objects, structures, animals (e.g., humans) or other unmanned aerial vehicles that may be located nearby. Accordingly, multi-rotor unmanned aerial vehicles are commonly equipped with greater lift capacity than is commonly utilized or required during most transiting operations, in order to ensure that sufficient lift is available when needed, primarily in take-offs or landings.

In order to conserve onboard electrical power when excess lift is not desired, the powered rotation of one or more propellers of a unmanned aerial vehicle may be shut down when the unmanned aerial vehicle is transiting, or in a thrust mode, such as after the unmanned aerial vehicle has successfully taken off, and recommenced when the unmanned aerial vehicle prepares to land at a given location. For example, an unmanned aerial vehicle may feature sets of thrust propellers and lift propellers. When a maximum amount of lift is desired, both the thrust propellers and the lift propellers may be operated. When the maximum amount of lift is no longer desired, however, the operation of the lift propellers may be stopped, thereby reducing the amount of electrical power consumed during operations. A propeller that is provided on an operating unmanned aerial vehicle and is at rest may create undesirable drag, however, and restrict the stability of the unmanned aerial vehicle during transiting operations.

<CIT> discloses a brake system and tooth clutch for disengaging a propeller from an aircraft engine. <CIT> discloses a retractable drive for powered gliders.

As is set forth in greater detail below, the present disclosure is directed to propeller clutch mechanisms. A propeller system is disclosed as specified in claim <NUM>, and a method to operate an aerial vehicle is disclosed as specified in claim <NUM>. More specifically, the systems and methods disclosed herein are directed to spring-biased mechanisms that are mounted in association with propeller blades, e.g., to an attachment plate provided on an underside of a propeller blade. In some embodiments, an aerial vehicle, e.g., an unmanned aerial vehicle, includes a motor having a shaft for rotating a propeller. The shaft extends through a base having one or more posts (or shoulders) that define an axis along which the propeller is to be substantially aligned when the rotation of the propeller is no longer desired. A spring-biased clutch mechanism having a pair of feathering arms (or locking arms) that are rotatably mounted to the propeller and linked by tension springs or other biasing elements is mounted to a planar surface of the propeller, and surrounds a point at which the propeller is joined to the shaft.

When the propeller is not rotating, the feathering arms contract around the shaft, and form a narrow channel within which the posts of the base are received. Thus, when the posts of the base are received within the narrow channel, and the motor is off, the propeller remains substantially aligned along the axis defined by the posts. When the motor is started, and the propeller begins to rotate, the feathering arms are forced open by contact between such arms and the posts until the propeller reaches a sufficiently high angular velocity, e.g., when the angular velocity of the propeller exceeds a predetermined threshold. When the propeller is spinning under power at an angular velocity consistent with normal operations, the biasing force provided by the biasing element is fully overcome by centrifugal forces acting on the feathering arms, and the feathering arms eventually remain open, free of contact with the posts. When the motor is stopped, and the angular velocity of the propeller falls below a predetermined threshold, the feathering arms will begin to contract again before coming into contact with the posts, and the propeller will eventually come to a stop, aligned along the axis defined by the posts.

Therefore, in accordance with the present disclosure, a spring-biased clutch mechanism may have a closed position in which feathering arms narrowly surround one or more posts mounted to a base, and cause the propeller to remain in an axial orientation defined by the posts, and an open position in which the feathering arms extend beyond the posts, enabling the propeller to rotate freely about a shaft at a sufficiently high rotational velocity. The spring-biased clutch mechanisms may therefore cause a propeller to be aligned in a predefined orientation (e.g., along a predefined axis) when a motor to which the propeller is joined is not operating, without the use of any further electrical or mechanical devices or components. The predefined orientation may be selected on any basis, including but not limited to drag, acoustic or other operational considerations.

Referring to <FIG>, portions of an aerial vehicle <NUM> are shown. The aerial vehicle <NUM> includes a propeller <NUM>, a clutch mechanism <NUM>, a base <NUM>, a motor <NUM> and a motor mount <NUM>. The propeller <NUM> is rigidly joined to the motor <NUM> by a shaft <NUM> that causes the propeller <NUM> to rotate in response to a motive force provided by the motor <NUM>. The clutch mechanism <NUM> is mounted to an attachment plate <NUM>, which is itself mounted to one side (e.g., an underside) of the propeller <NUM>. The propeller <NUM> and the attachment plate <NUM> are shown in broken lines.

As is shown in <FIG>, the clutch mechanism <NUM> includes a pair of tension springs <NUM> and a pair of feathering arms <NUM>. Each of the feathering arms <NUM> shown in <FIG> has an angled or tapered shape, e.g., similar to that of a traditional hockey stick, defining an obtuse angle of approximately one hundred thirtyfive degrees (<NUM>°). As is shown in <FIG>, each of the feathering arms <NUM> includes a tapered end <NUM> and a weighted end <NUM>. The feathering arms <NUM> are rotatably or pivotably mounted to the attachment plate <NUM> using a fastener <NUM> of any kind, e.g., threaded screws, nuts, bolts, brads, or any other suitable component by which the feathering arms <NUM> may be rotatably joined to the attachment plate <NUM>.

The feathering arms <NUM> may be formed from any suitable materials. In some embodiments, the feathering arms <NUM> may be formed of lightweight metals such as aluminum, metals of heavier weights including alloys of steel, composites, or any other combinations of materials. In some other embodiments, the feathering arms <NUM> may be formed from one or more plastics (e.g., thermosetting plastics such as epoxy or phenolic resins, polyurethanes or polyesters, as well as polyethylenes, polypropylenes or polyvinyl chlorides) or woods (e.g., woods with sufficient strength properties such as ash). In still other embodiments, the feathering arms <NUM> may be formed from other materials including but not limited to carbon fiber, graphite, machined aluminum, titanium, or fiberglass.

Moreover, portions of the feathering arms <NUM>, including but not limited to the tapered end <NUM> or the weighted end <NUM>, may have any suitable dimensions. For example, as is shown in <FIG>, the weighted ends <NUM> of the feathering arms <NUM> may have lengths, widths and/or cross-sectional areas that are larger than the tapered ends <NUM> of the feathering arms <NUM>. The weighted ends <NUM> may be subjected to greater centrifugal forces than the tapered ends <NUM> when the feathering arms <NUM> are rotated at a sufficiently high angular velocity. In some embodiments, the weighted ends <NUM> may include further components such as screws or other fasteners that increase the masses at the corresponding ends of the feathering arms <NUM>. Alternatively, in some other embodiments, the weighted ends <NUM> may be formed from a material having a greater density than a material from which the tapered ends <NUM> are formed, and the weighted ends <NUM> may have the same lengths, widths and/or cross-sectional areas as the tapered ends <NUM>, thereby also causing the weighted ends <NUM> to be subjected to greater centrifugal forces when the feathering arms <NUM> rotate at a significantly high angular velocity. The material composition and/or dimensions of the feathering arms <NUM> may be manipulated in any manner in order to cause one or more of the operations or effects described herein when the propeller <NUM> is rotating or stationary.

Each of the tension springs <NUM> may be any type or form of spring or other biasing element to provide a biasing force for urging one of the respective tensioning arms <NUM> into a contracted position about the shaft <NUM>. As is shown in <FIG>, each of the tensioning springs <NUM> is joined at a first end to the fastener <NUM> rotatably mounting one of the feathering arms <NUM> to the attachment plate <NUM> and at a second end to the weighted end <NUM> of the other of the feathering arms <NUM>. In some implementations, the tension springs <NUM> may comprise wires having a cross-sectional area of any size or shape (e.g., round, rectangular or square) that is tightly coiled between the fasteners <NUM> or other portions of one of the feathering arms <NUM> and the weighted ends <NUM> of another of the feathering arms <NUM>. The tension spring <NUM> may thus expand in length, and contract in coil diameter, in response to tensile stresses created by the rotation of the feathering arms <NUM> about the fasteners <NUM>.

Although the clutch mechanism <NUM> of <FIG> includes a pair of tensioning springs <NUM> for biasing the respective feathering arms <NUM>, those of ordinary skill in the pertinent arts will recognize that any number of biasing elements, and any biasing elements other than tensioning springs, may be utilized to provide a biasing force to the respective feathering arms <NUM> in accordance with the present disclosure, including but not limited to compression springs, extension springs, torsion springs, leaf springs, constant force springs or like elements. For example, in some embodiments, the feathering arms <NUM> may be leaf springs that are self-biased into closed positions about a shaft, and may be urged into an open position due to centrifugal forces acting thereon that exceed the biasing forces provided by the leaf springs.

The attachment plate <NUM> is mounted beneath the propeller <NUM>, and is provided to rigidly join the clutch mechanism <NUM> to the propeller <NUM>, thereby ensuring that the propeller <NUM> and the clutch mechanism <NUM> rotate in tandem. As is shown in <FIG>, the attachment plate <NUM> further includes a pair of mechanical stops <NUM>, each of which is aligned to come into contact with one of the tapered ends <NUM> when one of the feathering arms <NUM> has rotated about an axis defined by the fastener <NUM> to a maximum extent, thereby resisting further rotation of the feathering arms <NUM>. The mechanical stops <NUM> may include or comprise one or more posts, screws, nuts, bolts, brads or any other suitable components that may extend from the attachment plate <NUM> and/or the propeller <NUM> and be aligned to resist rotation of the feathering arms <NUM>.

The attachment plate <NUM> may be joined to the propeller <NUM> via one or more of the fasteners <NUM> and/or the mechanical stops <NUM>, which may extend through the respective feathering arms <NUM> and the attachment plate <NUM>, and into the propeller <NUM>. Alternatively, the attachment plate <NUM> may be joined to the propeller <NUM> by any other component or substance, including but not limited to one or more additional fasteners (not shown) or glues or other adhesives. In some embodiments, the clutch mechanism <NUM> may be joined to the propeller <NUM> directly, and the attachment plate <NUM> need not be included as a separate, discrete component.

The base <NUM> includes a pair of raised posts (or shoulders) <NUM> extending radially outward from a cylindrical platform <NUM> provided about an opening <NUM>. The base <NUM> is mounted to the motor mount <NUM> by a plurality of stanchions or other supports, and extends over the motor <NUM>. As is shown in <FIG>, the posts <NUM> are formed on the base <NUM> and commonly aligned with respect to the opening <NUM> in order to define an axis that is substantially parallel to the motor mount <NUM>. The shaft <NUM> extends between the motor <NUM> and the propeller <NUM> through the opening <NUM>, thereby enabling the posts <NUM> to remain fixed in position along the axis with respect to the propeller <NUM>.

The motor <NUM> is mounted to the motor mount <NUM> and includes a shaft <NUM> that extends through the opening <NUM> and is rigidly joined to the propeller <NUM>. In some embodiments, the motor <NUM> may be a brushless direct current (DC) motor. In other embodiments, the motor <NUM> may be any other type or form of motor, including but not limited to one or more other electric motors, e.g., alternating current (AC) or DC powered motors, as well as any gasoline-powered motors, or motors operating based on any other power or fuel source. In some embodiments, the motor mount <NUM> may include all or a portion of a frame of the aerial vehicle <NUM>, e.g., a fuselage, one or more wings, or any other component thereof to which the base <NUM> and/or the motor <NUM> are mounted. In some embodiments, the base <NUM> and/or one or more of the posts <NUM> may be mounted directly to a non-rotating portion of the motor <NUM>, or in any other location.

The operation of the clutch mechanism <NUM> is shown with regard to <FIG>, <FIG>, and <FIG>. Referring to <FIG>, the motor <NUM> is stopped, and the propeller <NUM> is stationary. As is shown in <FIG>, the tension springs <NUM> of the clutch mechanism <NUM> urge the feathering arms <NUM> into a closed position, e.g., with the feathering arms <NUM> spaced narrowly apart from one another and defining a window therein, which encompasses the posts <NUM>. Thus, when the aerial vehicle <NUM> is in flight, but the motor <NUM> is stopped, the tension springs <NUM> will prevent the propeller <NUM> from rotating in response to varying wind flows over and around the aerial vehicle, by maintaining the feathering arms <NUM> in the closed position shown in <FIG>, and the propeller <NUM> will remain aligned in the axis defined by the posts <NUM>.

Referring to <FIG>, the propeller <NUM> is shown as the motor <NUM> is started, and the propeller <NUM> begins to rotate. Because the clutch mechanism <NUM> is joined to the propeller <NUM> via the attachment plate <NUM>, the clutch mechanism <NUM> begins to rotate with the propeller <NUM>, causing the posts <NUM> to come into contact with inner faces of each of the feathering arms <NUM> with each half-cycle rotation of the propeller <NUM>. The contact between the posts <NUM> and the inner faces of the feathering arms <NUM>, and centrifugal force acting on the feathering arms <NUM>, e.g., the weighted ends <NUM>, forces the feathering arms <NUM> to begin to open from the closed position of <FIG> as the angular velocity of the propeller <NUM> begins to increase.

Referring to <FIG>, the motor <NUM> is shown as causing the propeller <NUM> to rotate at an angular velocity above a predetermined threshold. The centrifugal force acting on the weighted ends <NUM> causes the feathering arms <NUM> to remain in a fully open position, such that the feathering arms <NUM> do not come into contact with either of the posts <NUM> as the propeller <NUM> is rotating. Conversely, when the motor <NUM> is brought to a stop, and the angular velocity of the propeller <NUM> begins to decrease, the feathering arms <NUM> are drawn inward from the fully open position of <FIG> due to the biasing force provided by the tension springs <NUM>, until the feathering arms <NUM> begin to contact the posts <NUM>, such as is shown in <FIG>. Once the propeller <NUM> comes to a complete stop, the feathering arms <NUM> are biased into the closed position shown in <FIG> by the tension springs <NUM>, with the posts <NUM> received therein, and the propeller <NUM> will remain aligned along the axis defined by the posts <NUM>.

The movement of the feathering arms of one embodiment of a clutch mechanism in accordance with the present disclosure is shown in <FIG>. Referring to <FIG>, views of aspects of a propeller clutch mechanism <NUM> in accordance with embodiments of the present disclosure are shown. Except where otherwise noted, reference numerals preceded by the number "<NUM>" shown in <FIG> indicate components or features that are similar to components or features having reference numerals preceded by the number "<NUM>" shown in <FIG>.

As is shown in <FIG>, the clutch mechanism <NUM> includes a pair of tension springs <NUM> and a pair of feathering arms <NUM> rotatably or pivotably mounted to an attachment plate <NUM> by fasteners <NUM>. Each of the feathering arms <NUM> includes a tapered end <NUM> and a weighted end <NUM>. The attachment plate <NUM> further includes a pair of mechanical stops <NUM>, each of which is aligned to stop the rotation of the feathering arms <NUM>, and an opening <NUM> adapted to receive a shaft (not shown) therein. Each of the tension springs <NUM> is connected at a first end to the fastener <NUM> that mounts one of the feathering arms <NUM> to the attachment plate <NUM> and at a second end to the weighted end <NUM> of another of the feathering arms <NUM>.

As is shown in <FIG>, the feathering arms <NUM> are in a closed position, e.g., wherein a propeller (not shown) to which the attachment plate <NUM> is mounted is stationary, and the tension springs <NUM> bias the feathering arms <NUM> toward one another, and around a shaft of the propeller. When the feathering arms <NUM> are in the closed position of <FIG>, a window for encompassing one or more posts (not shown) that are aligned along a predefined axis is defined between the feathering arms <NUM>, such that the propeller remains aligned along the predefined axis until a motor causes the propeller to rotate when the one or more posts are received therein.

As is shown in <FIG>, the feathering arms <NUM> are in a fully open position, e.g., wherein a propeller (not shown) to which the attachment plate <NUM> is mounted rotates at a sufficient angular velocity, such that centrifugal forces acting on the weighted ends <NUM> of the feathering arms <NUM> exceed the biasing forces applied to the feathering arms <NUM> by the tensioning springs <NUM>. When the feathering arms <NUM> are in the fully open position of <FIG>, the feathering arms <NUM> are sufficiently separated, such that the feathering arms <NUM> rotate freely of the one or more posts (not shown) between the feathering arms <NUM>, and the tapered ends <NUM> of the feathering arms <NUM> come into contact with the corresponding mechanical stops <NUM>.

Those of ordinary skill in the pertinent arts will recognize that the components of the clutch mechanisms of the present disclosure may take any shape or form, and are not limited to the orientations or shapes of the components of the clutch mechanism <NUM> shown in <FIG>. For example, springs or other elements for providing biasing forces to feathering arms and mechanical stops for inhibiting rotation of the feathering arms may be provided as separate or discrete components of the feathering arms or, alternatively, integral to or within such feathering arms. Referring to <FIG>, views of aspects of a propeller clutch mechanism <NUM> in accordance with embodiments of the present disclosure are shown. Except where otherwise noted, reference numerals preceded by the number "<NUM>" shown in <FIG> indicate components or features that are similar to components or features having reference numerals preceded by the number "<NUM>" shown in <FIG> or by the number "<NUM>" shown in <FIG>.

As is shown in <FIG>, the clutch mechanism <NUM> includes a pair of feathering arms <NUM> rotatably or pivotably mounted to an attachment plate <NUM> via fasteners <NUM>. Each of the feathering arms <NUM> includes a torsion spring <NUM> embedded within a rotatable canister-type housing <NUM> mounted about one of the fasteners <NUM>. Each of the feathering arms <NUM> further includes a slot <NUM> provided within and extending through the housing <NUM> and a weighted end <NUM>. The attachment plate <NUM> further includes a pair of mechanical stops <NUM> in the form of pegs or posts. As is shown in <FIG>, one of the mechanical stops <NUM> is extended into each of the slots <NUM>. As is also shown in <FIG>, each of the weighted ends <NUM> of the feathering arms <NUM> has a rounded (e.g., concave) surface that conforms to a rounded (e.g., convex) surface of the housing <NUM> of another of the feathering arms <NUM>.

As is shown in <FIG>, the feathering arms <NUM> are in a closed position, e.g., wherein a propeller (not shown) to which the attachment plate <NUM> is mounted is stationary, and the torsion springs <NUM> bias the feathering arms <NUM> toward one another, and around a shaft of the propeller. When the feathering arms <NUM> are in the closed position of <FIG>, one or more posts (not shown) that are aligned along a predefined axis may be received between the feathering arms <NUM>, such that the propeller remains aligned along the predefined axis until a motor causes the propeller to rotate. When the feathering arms <NUM> are in the closed position of <FIG>, a window for encompassing one or more posts (not shown) that are aligned along a predefined axis is defined between the feathering arms <NUM>, and the rounded surfaces of the weighted ends <NUM> and the housings <NUM> of opposing arms smoothly mate with one another.

As is shown in <FIG>, the feathering arms <NUM> are in a fully open position, e.g., wherein a propeller (not shown) to which the attachment plate <NUM> is mounted rotates at a sufficient angular velocity, such that centrifugal forces acting on the weighted ends <NUM> of the feathering arms <NUM> exceed the biasing forces applied to the feathering arms <NUM> by the tensioning springs <NUM>. When the feathering arms <NUM> are in the fully open position of <FIG>, the feathering arms <NUM> are sufficiently separated, such that the feathering arms <NUM> rotate freely of the one or more posts (not shown) between the feathering arms <NUM>.

As is shown in <FIG>, the rotation of the feathering arms <NUM> of the clutch mechanism <NUM> is limited by the extent to which the mechanical stops <NUM> may rotate within the slots <NUM>, which have arcuate shapes corresponding to the shapes of the housings <NUM>. For example, each of the feathering arms <NUM> may rotate between the closed position of <FIG> and the open position of <FIG>, each of which is defined by the extent and length of the corresponding slots <NUM> within the respective feathering arms <NUM>. Rotation of the feathering arms <NUM> beyond the open position of <FIG> or the closed position of <FIG> is inhibited by contact between the mechanical stops <NUM> and internal surfaces of the slots <NUM>.

As is discussed above, the clutch mechanisms of the present disclosure may include any type or form of feathering arm (or locking arm) provided in a rotatable or pivotable manner that may defining a window or opening for accommodating posts or shoulders that are aligned along a predefined axis when the feathering arms are in a closed position, and for permitting a propeller to rotate free of contact with such posts when the feathering arms are in a closed position. Those of ordinary skill in the pertinent arts will recognize that the clutch mechanisms of the present disclosure are not limited to the feathering arms <NUM> of <FIG>, or the feathering arms <NUM> of <FIG>, or any particular arrangement or orientation thereof.

As is discussed above, one or more posts may be provided in a predetermined alignment such that when the posts are received between feathering arms of a clutch mechanism of the present disclosure, and a propeller to which the clutch mechanism is joined falls below a predetermined threshold angular velocity, the feathering arms are biased to positions surrounding the posts, and the propeller comes to a stop in an orientation consistent with the predetermined alignment of the posts. Referring to <FIG>, a view of aspects of a propeller clutch mechanism in accordance with embodiments of the present disclosure is shown. Except where otherwise noted, reference numerals preceded by the number "<NUM>" shown in <FIG> indicate components or features that are similar to components or features having reference numerals preceded by the number "<NUM>" shown in <FIG>, by the number "<NUM>" shown in <FIG> or by the number "<NUM>" shown in <FIG>.

As is shown in <FIG>, a base <NUM> includes a pair of raised posts <NUM> extending radially outward from a cylindrical platform <NUM> provided about an opening <NUM>. The base <NUM> is mounted to the motor mount <NUM> by a plurality of stanchions <NUM> or other supports. As is discussed above, the base <NUM> is formed in a substantially trapezoidal shape, and may be mounted above a motor (not shown) in a manner that enables a shaft (not shown) of the motor to extend between the motor and a propeller (not shown) through the opening <NUM>, thereby enabling the posts <NUM> to remain fixed in position with respect to the propeller.

As is also shown in <FIG>, the posts <NUM> are formed on the base <NUM> and commonly aligned with the opening <NUM> to define an axis. Thus, in some embodiments, when the base <NUM> of <FIG> is provided in an aerial vehicle (not shown) having a propeller mounted to a shaft (or other propeller mounting structure) extending through the opening <NUM>, and the propeller is stationary, the posts <NUM> may be received within or between feathering arms of a clutch mechanism (not shown) joined to the propeller that are in a closed position, such that the propeller remains in an orientation consistent with the axis defined by the posts <NUM>.

The clutch mechanisms of the present disclosure may be configured to cause a stationary propeller to remain aligned in any orientation or along any axis, and such orientations or axes may be selected on any basis. For example, referring again to <FIG>, the posts <NUM> of the base <NUM> may be aligned in a selected axis that is consistent with or parallel to a direction of travel of an aerial vehicle, such that a stationary propeller having a clutch mechanism of the present disclosure is biased into an alignment along the axis. In this regard, the clutch mechanisms of the present disclosure may be used to reduce the drag of an aerial vehicle operating in a thrust mode, e.g., where fewer than all of the propellers provided on the aerial vehicle are required for lift, by aligning propellers that are not required in order to operate in the thrust mode in a direction of travel, thereby reducing drag associated with allowing such propellers to rotate freely. The clutch mechanisms of the present disclosure operate based on biasing forces provided by springs or other biasing elements, and centrifugal forces generated by a rotating propeller, thereby enabling a propeller to be placed in a predetermined alignment without any electrical or powered mechanical components.

As is discussed above, the clutch mechanisms of the present disclosure are rotatable components mounted to or otherwise associated with propellers and are configured to receive one or more stationary components, e.g., posts or shoulders provided on a base or other structural feature, therein. Spatial relationships of the various components of an aerial vehicle including one of the clutch mechanisms of the present disclosure are shown in FIG. Referring to <FIG>, an exploded view of aspects of an aerial vehicle <NUM> including a propeller clutch mechanism <NUM> in accordance with embodiments of the present disclosure is shown. Except where otherwise noted, reference numerals preceded by the number "<NUM>" shown in <FIG> indicate components or features that are similar to components or features having reference numerals preceded by the number "<NUM>" shown in <FIG>, by the number "<NUM>" shown in <FIG>, by the number "<NUM>" shown in <FIG> or by the number "<NUM>" shown in <FIG>.

As is shown in <FIG>, the aerial vehicle <NUM> includes a propeller <NUM>, a clutch mechanism <NUM>, a base <NUM>, and a motor <NUM>. The propeller <NUM> is rigidly joined to the motor <NUM> by a shaft <NUM>, which may cause the propeller <NUM> to rotate in response to a rotating motive force provided by the motor <NUM>. The clutch mechanism <NUM> is mounted to an underside of the propeller <NUM> by an attachment plate <NUM>, and includes a pair of tension springs <NUM> and a pair of feathering arms <NUM>. The base <NUM> is mounted to a motor mount <NUM> above the motor <NUM>, e.g., by one or more stanchions, and includes a pair of raised posts <NUM> extending upwardly above the base <NUM> and into an opening defined by the pair of feathering arms <NUM>. As is shown in <FIG>, the posts <NUM> are formed on the base <NUM> and define an axis that is substantially parallel to the motor mount <NUM>. The shaft <NUM> extends between the motor <NUM> and the propeller <NUM> through the opening <NUM>, thereby enabling the posts <NUM> to remain fixed in position with respect to the propeller <NUM>.

Therefore, as is shown in <FIG>, the aerial vehicle <NUM> includes a plurality of rotatable components, including but not limited to the propeller <NUM> and the clutch mechanism <NUM>, which may be caused to rotate by the motor <NUM>, and a plurality of stationary components, including but not limited to the base <NUM>, the motor <NUM> and the motor mount <NUM>, which remain fixed in position without regard to the rotation or position of the propeller <NUM> or the clutch mechanism <NUM>. One or more of the stationary components, e.g., the posts <NUM> provided on the base <NUM>, may extend into a window or other opening defined by the feathering arms <NUM> of the clutch mechanism <NUM>, which are biased into a closed position by the tension springs <NUM>. When the motor <NUM> is stopped, an angle of orientation of the rotatable components may be defined by the stationary components, e.g., the posts <NUM>, extending into the window or opening of the rotatable clutch mechanism <NUM>. When the motor <NUM> is started, however, the propeller <NUM> and the clutch mechanism <NUM> begin to rotate, and centrifugal forces cause the feathering arms <NUM> to open around the posts <NUM>.

As is discussed above, the systems and methods of the present disclosure may be utilized to place a propeller in a preferred alignment when rotation of the propeller is neither desired nor required. The alignment of the propeller may be selected on any basis, including but not limited to drag, acoustic or other operational considerations. For example, a clutch mechanism may be used to cause a propeller to align in a direction of travel of an aerial vehicle when the propeller is not operating. Referring to <FIG> and <FIG>, views of aspects of an aerial vehicle <NUM> including a plurality of propeller clutch mechanisms 610A, 610B, 610C, 610D in accordance with embodiments of the present disclosure are shown. Except where otherwise noted, reference numerals preceded by the number "<NUM>" shown in <FIG> or <FIG> indicate components or features that are similar to components or features having reference numerals preceded by the number "<NUM>" shown in <FIG>, by the number "<NUM>" shown in <FIG>, by the number "<NUM>" shown in <FIG>, by the number "<NUM>" shown in <FIG> or by the number "<NUM>" shown in <FIG>.

As is shown in <FIG> and <FIG>, the aerial vehicle <NUM> includes a fuselage <NUM>, four propellers 605A, 605B, 605C, 605D, four clutch mechanisms 610A, 610B, 610C, 610D and four motors 660A, 660B, 660C, 660D. The propellers 605A, 605B, 605C, 605D, the clutch mechanisms 610A, 610B, 610C, 610D and the motors 610A, 610B, 610C, 610D are joined to the fuselage <NUM> by mounts 670A, 670B, 670C, 670D.

Referring to <FIG>, the aerial vehicle <NUM> is shown during lift operations, e.g., where each of the propellers 605A, 605B, 605C, 605D and the clutch mechanisms 610A, 610B, 610C, 610D are rotated by the motors 660A, 660B, 660C, 660D. When the motors 660A, 660B, 660C, 660D cause the propellers 605A, 605B, 605C, 605D to rotate at a sufficiently high angular velocity, the clutch mechanisms 610A, 610B, 610C, 610D are in a fully open position, and the rotation of the propellers 605A, 605B, 605C, 605D occurs in an unimpeded fashion during the lift operations shown in <FIG>.

Referring to <FIG>, the aerial vehicle <NUM> is shown during thrust operations, e.g., where only the propellers 605A, 605B and the clutch mechanisms 610A, 610B are rotated by the motors 660A, 660B, and where the motors 660C, 660D are stopped. Thus, while the rotation of the propellers 605A, 605B occurs in an unimpeded fashion, without contact between the clutch mechanisms 610A, 610B and the bases 650A, 650B, the propellers 605C, 605D are aligned along axes defined by the bases 650C, 650D, e.g., by one or more posts or shoulders extending upwardly and into windows or openings defined by the clutch mechanisms 610A, 610B. More specifically, as is shown with regard to the clutch mechanism 610D of <FIG>, feathering arms 630D-<NUM>, <NUM>-D-<NUM> are biased into a closed position around the base 650D by the tension springs 620D-<NUM>, 620D-<NUM>. Thus, because the bases 650C, 650D define axes that are parallel to or consistent with the direction of travel, the propellers 605C, 605D aligned along such axes, thereby reducing or minimizing drag or other adverse acoustic conditions that may result if the propellers 605C, 605D were permitted to drift or freely rotate during thrust operations of the aerial vehicle <NUM>.

An axis along which a propeller may be aligned when the rotation of the propeller is no longer desired may be defined or selected on any basis using one or more of the clutch mechanisms of the present disclosure. Additionally, the clutch mechanisms of the present disclosure are not limited for use in helicopter-type aerial vehicles, or unmanned aerial vehicles. Referring to <FIG>, views of aspects of an aerial vehicle <NUM> including a propeller clutch mechanism <NUM> in accordance with embodiments of the present disclosure are shown. Except where otherwise noted, reference numerals preceded by the number "<NUM>" shown in <FIG> indicate components or features that are similar to components or features having reference numerals preceded by the number "<NUM>" shown in <FIG> or <FIG>, by the number "<NUM>" shown in <FIG>, by the number "<NUM>" shown in <FIG>, by the number "<NUM>" shown in <FIG>, by the number "<NUM>" shown in <FIG> or by the number "<NUM>" shown in <FIG>.

As is shown in <FIG>, the aerial vehicle <NUM> is a fixed-wing aircraft having a fuselage <NUM>, a pair of wings <NUM>-<NUM>, <NUM>-<NUM> and four propellers 705A, 705B, 705C, 705D that may be caused to rotate about shafts driven by one or more motors (not shown) mounted to the wings <NUM>-<NUM>, <NUM>-<NUM>. Each of the propellers 705A, 705B, 705C, 705D may have a clutch mechanism 710A, 710B, 710C, 710D configured to rotate about bases 750A, 750B, 750C, 750D that are aligned along predefined axes corresponding to the wings <NUM>-<NUM>, <NUM>-<NUM>. Thus, when each of the propellers 705A, 705B, 705C, 705D are required for operation of the aerial vehicle <NUM>, e.g., in a high-speed or maximum-power evolution, such as is shown in <FIG>, each of the clutch mechanisms 710A, 710B, 710C, 710D are in a fully open position, and the propellers 705A, 705B, 705C, 705D may rotate about the bases 750A, 750B, 750C, 750D in an unimpeded fashion.

When the operation of one or more of the propellers 705A, 705B, 705C, 705D is neither desired nor required, however, the motors coupled to such propellers 705A, 705B, 705C, 705D may be stopped, and the rotation of the corresponding propellers 705A, 705B, 705C, 705D is permitted to slow to below a threshold angular velocity. When an angular velocity of one or more of the propellers 705A, 705B, 705C, 705D falls below the threshold, the clutch mechanisms 710A, 710B, 710C, 710D of such propellers 705A, 705B, 705C, 705D contract around their respective shafts and cause such propellers 705A, 705B, 705C, 705D to be aligned along axes defined by their respective bases 750A, 750B, 750C, 750D. For example, referring to <FIG>, motors corresponding to propellers 705A, 705D are stopped, and the clutch mechanisms 710A, 710B mounted to propellers 705A, 705B cause the propellers 705A, 705D to remain fixed in alignment along axes defined by the bases 750A, 750D, e.g., corresponding to the angles of orientation of the respective wings <NUM>-<NUM>, <NUM>-<NUM>.

Those of ordinary skill in the pertinent arts will recognize that the clutch mechanisms of the present disclosure may be utilized to align propellers along a predefined axis in any manner, on any basis, and for any purpose. For example, referring again to <FIG>, the bases 750A, 750D may be aligned in an axis substantially perpendicular to the respective wings <NUM>-<NUM>, <NUM>-<NUM>, so as to minimize any reductions in lift caused by drag due to the non-rotating propellers 705A, 705D, to enable easier access to motors (not shown) to which such propellers 705A, 705D are mounted during maintenance evolutions, or for any other purpose.

For example, those of ordinary skill in the pertinent arts will recognize that the clutch mechanisms of the present disclosure are not limited to combinations of two feathering arms (or locking arms) and two tension members. Some embodiments of clutch mechanisms provided in association with propellers may include a single feathering arm, e.g., a crescent-shaped feathering arm, having a single tensioning member that enables the single feathering arm to rotate or pivot away from one or more stationary posts or shoulders provided on a base at sufficiently high angular velocities yet causes the single feathering arm to contract around such posts or shoulders at sufficiently low angular velocities, or when a propeller is no longer rotating. Other embodiments of clutch mechanisms of the present disclosure may include three or more feathering arms, each of which may be configured to rotate or pivot away from posts or shoulders, or contract around such posts or shoulders, depending on an angular velocity of a propeller with which such clutch mechanisms are associated. For example, the three or more feathering arms may define a polygonal or continuous shape (e.g., an equilateral triangle or a circle) when such arms are in a closed position, and may contract around one or more stationary posts or shoulders that are arranged in a similar or corresponding shape. Furthermore, tensioning members for biasing such arms may be mounted to any portion of a propeller, an attachment plate, or other rotating component in accordance with the present disclosure.

Furthermore, those of ordinary skill in the pertinent arts will also recognize that the clutch mechanisms disclosed herein may be utilized in connection with propellers having any number of blades, and are not limited to two-bladed propellers. Such propellers may be caused to align along a predefined axis selected on any basis. Additionally, the clutch mechanisms of the present disclosure are also not limited for use on aerial vehicles. For example, a clutch mechanism may be mounted in association with a propeller on a seagoing vessel, and may cause the propeller to align in a preferred orientation, e.g., co-aligned with a rudder or other appurtenance, when rotation of the propeller is no longer desired, thereby reducing not only drag or other adverse flow effects but also a risk of damage to the propeller during slow or abnormal operations, e.g., departing from port, returning to port, or entering a dry-dock. Moreover, the clutch mechanisms may be utilized in connection with one or more other systems for managing flow conditions or reducing drag or acoustic effects caused thereby.

Furthermore, although some of the embodiments disclosed herein reference the use of unmanned aerial vehicles, those of ordinary skill in the pertinent arts will recognize that uses of one or more of the clutch mechanisms disclosed herein are not so limited, and may be utilized in connection with any type or form of aerial vehicle (e.g., manned or unmanned) for which the rotation of a propeller may be desired on a temporary basis, or for less than an entire duration of flight or related operations.

It should be understood that, unless otherwise explicitly or implicitly indicated herein, any of the features, characteristics, alternatives or modifications described regarding a particular embodiment herein may also be applied, used, or incorporated with any other embodiment described herein, and that the drawings and detailed description of the present disclosure are intended to cover all modifications, equivalents and alternatives to the various embodiments as defined by the appended claims. Moreover, with respect to the one or more methods or processes of the present disclosure described herein, orders in which such methods or processes are presented are not intended to be construed as any limitation on the claimed inventions, and any number of the method or process steps or boxes described herein can be combined in any order and/or in parallel to implement the methods or processes described herein. Further, the drawings herein are not drawn to scale.

Conditional language, such as, among others, "can," "could," "might," or "may," unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey in a permissive manner that certain embodiments could include, or have the potential to include, but do not mandate or require, certain features, elements and/or steps. In a similar manner, terms such as "include," "including" and "includes" are generally intended to mean "including, but not limited to. " Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular embodiment.

Disjunctive language such as the phrase "at least one of X, Y, or Z," or "at least one of X, Y and Z," unless specifically stated otherwise, is otherwise understood with the context as used in general to present that an item, term, etc., may be either X, Y, or Z, or any combination thereof (e.g., X, Y, and/or Z). Thus, such disjunctive language is not generally intended to, and should not, imply that certain embodiments require at least one of X, at least one of Y, or at least one of Z to each be present.

Unless otherwise explicitly stated, articles such as "a" or "an" should generally be interpreted to include one or more described items. Accordingly, phrases such as "a device configured to" are intended to include one or more recited devices. Such one or more recited devices can also be collectively configured to carry out the stated recitations. For example, "a processor configured to carry out recitations A, B and C" can include a first processor configured to carry out recitation A working in conjunction with a second processor configured to carry out recitations B and C.

Language of degree used herein, such as the terms "about," "approximately," "generally," "nearly" or "substantially" as used herein, represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms "about," "approximately," "generally," "nearly" or "substantially" may refer to an amount that is within less than <NUM>% of, within less than <NUM>% of, within less than <NUM>% of, within less than <NUM>% of, and within less than <NUM>% of the stated amount.

Claim 1:
A propeller system comprising:
a propeller (<NUM>, <NUM>, <NUM>, <NUM>);
a shaft (<NUM>, <NUM>) for rotating the propeller;
a clutch mechanism (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) provided around the shaft,
wherein the clutch mechanism further comprises:
at least one arm (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) pivotably mounted to a first surface of the propeller, wherein the at least one arm is configured to pivot between a first position proximate the shaft and a second position remote from the shaft;
at least one biasing element (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) applying a biasing force urging the at least one arm into the first position, the propeller system further comprising:
a base (<NUM>, <NUM>, <NUM>, <NUM>) through which the shaft extends, the propeller and clutch mechanism configured to rotate together relative to the base; and
a first and a second post (<NUM>, <NUM>, <NUM>) formed on the base which define an axis along which the propeller is to be substantially aligned when the rotation of the propeller is no longer desired;
wherein the at least one arm of the clutch mechanism is configured to contact the first post or the second post when the at least one arm is in the first position so as to align the propeller along the axis when the at least one arm is in the first position, and
wherein the clutch mechanism is configured to rotate relative to the base, without contacting the first post or the second post when the at least one arm is in the second position.