Patent ID: 12221208

DETAILED DESCRIPTION

The figures and the following description relate to preferred embodiments by way of illustration only. It should be noted that from the following discussion, alternative embodiments of the structures disclosed herein will be readily recognized as viable alternatives that may be employed without departing from the principles of what is claimed.

Reference will now be made in detail to several embodiments, examples of which are illustrated in the accompanying figures. It is noted that wherever practicable similar or like reference numbers may be used in the figures and may indicate similar or like functionality. The figures depict embodiments of the disclosed system for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures illustrated herein may be employed without departing from the principles described herein.

The figures use like reference numerals to identify like elements. A letter after a reference numeral, such as “150A,” indicates that the text refers specifically to the element having that particular reference numeral. A reference numeral in the text without a following letter, such as “150,” refers to any or all of the elements in the figures bearing that reference numeral (e.g. “propeller blade150” in the text refers to reference numerals “propeller blade150A” and/or “propeller blade150B” in the figures).

Overview Configuration

Disclosed by way of example embodiments is a propeller assembly that may include propeller blades that self-fold when not in use, thereby minimizing the overall footprint of the propeller assembly. When required, such as during flight conditions (e.g., as the propeller blades rotate), the propeller blades naturally extend to a flight configuration to enable the generation of lift due to centrifugal forces imparted on the propeller blades. Therefore, the propeller assembly can achieve the needed configuration without the need for human intervention. Such a propeller assembly may be attached to an unmanned rotary winged aerial vehicle, e.g., a quadcopter. For ease of discussion, the disclosure will be described with respect to a rotary winged aerial vehicle (or aerial vehicle) configuration that may be a quadcopter, but the principles herein can apply to other rotary winged aerial vehicles, e.g., having two blades, three blades or more than 4 blades.

Example Propeller Assembly

Reference is now made to Figure (FIG.1A, which illustrates a propeller assembly100in a folded state, in accordance with an example embodiment. The propeller assembly100may include a first propeller blade150A, a second propeller blade150B, a first hinge pin120A, a second hinge pin120B, and a central hub110. Furthermore, the propeller assembly100also may include a first and second spring element (not shown inFIG.1A).

Each propeller blade150may be connected to a central hub110. In one example embodiment, the first propeller blade150A includes a connector160A on one end of the first propeller blade150A that couples with the central hub110through the first hinge pin120A. Similarly, the second propeller blade150B includes a connector160B on one end of the second propeller blade150B that couples with the central hub110through the second hinge pin120B. In various example embodiments, the central hub110further includes an attachment point105configured to attach the central hub110to a motor of an aerial vehicle. The attachment point105of the central hub110may be a screw thread, snap-fit, magnetic attachment or any other type of attachment that couples with a motor of the aerial vehicle. Therefore, driving (e.g., spinning) the motor causes a corresponding rotation of the central hub110and the attached propeller blades150.

In various embodiments, each propeller blade150includes a tip155and a root158. Specifically, the connector160of each propeller blade150may be located near the root158of the propeller blade150. Additionally, each propeller blade150may be designed with a leading edge165and a trailing edge170. The leading edge165B of the second propeller blade150B is depicted inFIG.1Awhereas the leading edge165A of the first propeller blade150A is located underneath the second propeller blade150B and is not labeled. Even thoughFIG.1Adepicts two separate propeller blades150A and150B, in some embodiments, the propeller assembly100may include three, four, or more propeller blades150, each coupled to central hub110via a connector160of each propeller blade150.

In various embodiments, the folded state refers to the propeller assembly100at rest (e.g., when no external forces are applied on the propeller assembly100). Each propeller blade150may be placed in this first position (e.g., the folded state) due to the corresponding spring element (not shown inFIG.1A), which is described in further detail below. When the propeller assembly100is in the folded state, as depicted inFIG.1A, the propeller blades150of the propeller assembly100are positioned such that the overall footprint of the propeller assembly100is reduced as compared to the overall footprint of the propeller assembly100when in a flight state. A flight state of the propeller assembly100is described further in regards toFIG.1C.

For example, in the folded state, at least a portion of the first propeller blade150A may be nested underneath a portion of the second propeller blade150B. For example, a portion of the leading edge165A and tip155A of the first propeller blade150A reside underneath the second propeller blade150B. Other example embodiments may involve different configurations such that different portions of the first propeller blade150A are nested underneath a second propeller blade150B or vice versa.

Reference is now made toFIG.1B, which illustrates a sideview of the propeller blades150of the propeller assembly100in the folded state, in accordance with an example embodiment. Each propeller blade150may be designed with a twist along the length of the propeller blade150that enables the generation of lift and furthermore, enables portions of the first propeller blade150A to reside underneath the second propeller blade150B in the folded state. For example, the first propeller blade150A may be designed with a first angle of attack θ1(185) at the tip155A of the first propeller blade150A whereas the second propeller blade150B may be designed with a second angle of attack θ2(190) at the tip155B of the second propeller blade150B. In various embodiments, the first angle of attack θ1(185) may be equal to the second angle of attack θ2(190) at the tip155of each propeller blade150. In various example embodiments, the angle of attack of the first propeller blade150A and second propeller blade150B may vary along the length of each propeller blade150to enable a portion of the first propeller blade150A to nest underneath the second propeller blade150B.

FIG.1Cillustrates a propeller assembly100in a flight state, in accordance with an example embodiment. In various embodiments, the flight state refers to the propeller assembly100during flying conditions (e.g., when the propeller assembly100is driven by an attached motor to rotate). For example, during flying conditions, the propeller blades150of the propeller assembly100rotate and lift is generated on the propeller blades150(and consequently the aerial vehicle that the propeller assembly100is attached to). As displayed inFIG.1C, the propeller blades150in this example configuration rotate in a clockwise fashion such that the leading edge165of each propeller blade150meets the air.

The transition from the folded state, as depicted inFIG.1A, to the flight state, as depicted inFIG.1C, may occur as the propeller assembly100is driven by an attached motor to begin spinning the propeller blades150. To make the transition, the first propeller blade150A may rotate counter-clockwise relative to the central hub110around the first hinge pin120A. The second propeller blade150B may similarly transition by rotating in a clockwise direction relative to the central hub110around the second hinge pin120B. In various example embodiments, the rotation of each propeller blade150relative to the central hub110when transitioning from the folded state to the flight state may be caused by centrifugal forces acting on each propeller blade150as the propeller assembly100is driven by the attached motor. Further details regarding the transitioning of a propeller blade150from a folded state to a flight state, and vice versa, is described in further detail below in regards toFIG.5.

Example Components of the Propeller Assembly

FIG.2illustrates an exploded view of example components in the propeller assembly100, in accordance with an example embodiment. The components in the propeller assembly100may include the first propeller blade150A, second propeller blade150B, the central hub110, a first spring element210A, a second spring element210B, a first hinge pin120A, and a second hinge pin120B. Referring to each component individually, each propeller blade150may include a connector160which may further include a cavity255, a recess260and a hole265. The central hub110may include a top component274, a bottom component270, and a midsection272that connects the top component274to the bottom component270. The central hub110may further include multiple holes250located on the top component274. In various example embodiments, the bottom component270also may include holes substantially aligned with the holes250of the top component274. Each spring element210may further include a first arm215, a second arm220, and a gap218within the spring element210.

Referring specifically now to the elements of the connector160of the propeller blade150, the cavity255of the connector160may be configured to receive the spring element210. For example, the cavity255may be shaped to correspond to the spring element210such that when the spring element210resides in the cavity255, the spring element210is restricted from translational movement due to the elevated walls around the cavity255. For example,FIG.2depicts a cavity255of the connector160that is round in shape. Therefore, the diameter of the cavity255may be slightly larger than the diameter of the spring element210.

Each recess260in the connector160may be in connection with a corresponding cavity255and located proximal to the tip155of the propeller blade150relative to the cavity255. The recess260of the connector160may be configured to receive a first arm215of the spring element210. In various embodiments, the recess260may be shaped to receive the first arm215. For example, the recess260may be a slit in the connector160that corresponds to the shape of the first arm215and may couple with the first arm215through adhesives and/or mechanical connectors. In some example embodiments, the recess260may be directed along the length of the propeller blade150such that centrifugal forces generated on the propeller blade150, when the propeller assembly100rotates, transfer to the first arm215of the spring element210and cause the spring element210to further untwist.

Each hole265of the connector160may reside within the cavity255of the connector160. For example, given that the cavity255is circular, the hole265may be situated at the center of the cavity255. In various example embodiments, the hole265passes from a top surface of the connector160through to a bottom surface of the connector160. Therefore, the hole265may be configured to receive a hinge pin120. Additionally, when the spring element210resides within the cavity255, the hole265of the connector160may substantially align with the gap218of the spring element210.

Referring to the elements of the central hub110, the top component274and the bottom component270may be parallel to one another and connected through a midsection that is perpendicular to both the top274and bottom component270. As such, the top component274and the bottom component270may form a first opening280A and a second opening280B, each opening280located between the top component274and bottom component270. The first opening280A may be configured to receive the connector160A of the first propeller blade150A whereas the second opening280B may be configured to receive the connector160B of the second propeller blade150B. More specifically, each opening280may be designed such that when the connector160of each propeller blade150resides within the opening280, a hole250(e.g.,250A or250B) of the top component274of the central hub110substantially aligns with the hole265(e.g.,265A or265B, respectively) of the connector160of the propeller blade150.

Referring to the first spring element210A and second spring element210B, each spring element210may be a linear spring or may employ alternative stored energy methods to enable the transition of the propeller blades150between the folded and flight state. In an embodiment, each spring element210may be a helical torsion spring element. The first spring element210A and the second spring element210B may be differently wound. For example, as depicted inFIG.2, the first spring element210A is a right-hand wound torsion spring whereas the second spring element210B is a left-hand wound torsion spring. The spring elements210enable each of the propeller blades150to transition between the folded state, as shown inFIG.1A, and the flight state, as shown inFIG.1C. In various embodiments, the spring constant of each spring element210may depend upon the diameter of the corresponding propeller blade150. For example as the diameter of the propeller blade150increases, the corresponding spring element210may have a higher spring constant.

As previously described, the first arm215of each spring element210may be attached to the recess260of the connector160of the propeller blade150. The second arm220of each spring element210may be coupled to the central hub110. Therefore, rotation of the propeller blade150relative to the central hub110may cause a twisting or untwisting of the spring element210.

Reference is now made toFIG.3, which illustrates the assembly of a spring210B with the top component274of the central hub110, in accordance with an example embodiment. More specifically,FIG.3depicts a cross-sectional view of the underside of the top component274of the central hub110that includes a spring element210B located within a cavity310B of the top component274. AlthoughFIG.3only depicts a second spring element210B within a cavity310B, one may appreciate that a first spring element210A may also reside within the corresponding cavity310A.

In various example embodiments, each cavity310of the top component274may be designed to correspond to the shape of the spring element218. For example, the cavity310of the top component274may be circular in shape with a diameter that can receive the diameter of the spring element210. Additionally, the cavity310may further include a portion that is configured to receive the second arm220of the spring element210. For example, the cavity310may include a slot320that couples with the second arm220. The slot320may couple with the second arm220through adhesives and/or mechanical connectors. In various example embodiments, when the spring element210is situated in the cavity320of the top component274of the central hub110, the gap218of the spring element210substantially aligns with the hole250of the top component274of the central hub110.

This is further illustrated inFIG.4, which depicts a cross-sectional view of the hinged joint of the propeller assembly100, in accordance with an example embodiment. For example, the hole250of the top component274of the central hub110may align with the gap218of the spring element210, which further aligns with the hole of the hole265of the connector160. In various embodiments, the bottom component270of the central hub110may also include a hole405, which substantially aligns with a hole250of the top component274, a gap218of the spring element218, and a hole265of the connector160. A hinge pin120may thread through, from top to bottom, the hole250of the top component274, the gap218of the spring element210, the hole265of the connector160, and the hole405of the bottom component270. In various example embodiments, the hinge pin120may be cylindrical in shape to correspond to each hole250/265and gap218that the hinge pin120threads through.

In various example embodiments, the diameters of the hole250of the top component274, the gap218of the spring element210, the hole265of the connector160, and hole405of the bottom component270are each designed such that the hinge pin120rotatably couples the connector160of the propeller blade150to the central hub110. For example, the hole250of the top component274and the hole405of the bottom component may each have a diameter that matches or nearly matches the diameter of the hinge pin120such that the hinge pin120is in contact with the top component274and the bottom component270. Therefore, the central hub110does not rotate relative to the hinge pin120. Alternatively, the diameter of the gap218of the spring element and the diameter of the hole265of the connector may each be larger than the hole250of the top component274and the hole405of the bottom component. As such, the spring element218may twist or untwist while the connector160of the propeller blade150may rotate relative to the hinge pin120and the central hub110.

Transitioning Between the Folded State and the Flight State

FIG.5Adepicts the position of the propeller blades150in a folded state in relation to the central hub110, in accordance with an example embodiment.FIG.5Bdepicts the position of the propeller blades150in a flight state in relation to the central hub110, in accordance with an example embodiment. Further reference will be made to individual components of the propeller assembly100, most notably the first spring element210A and second spring element210B depicted inFIG.3.

In various example embodiments, when in the folded state, the longitudinal axis of each propeller blade150may be perpendicular or near perpendicular (e.g., 90°±10°) relative to the longitudinal axis of the central hub110. The spring element210corresponding to each propeller blade150may be responsible for holding the propeller blade150in a folded state. For example, when each propeller blade150is at rest in the folded state, as depicted inFIG.5A, each spring element210may be in an untwisted state. In this untwisted state, the first spring element210A may provide a clockwise torque to the connector160A of the first propeller150A through the first arm215A of the first spring element210A. Similarly, the second spring element210B may provide a counter-clockwise torque to the connector160B of the second propeller150B through the first arm215B of the second spring element210B. To achieve the rotational configuration of the first propeller blade150A and second propeller blade150B in the folded state, the torque applied by each spring element210may be counteracted by an equal and opposite torque applied by one or more structural detents on the central hub110. For example, the top component274and bottom component270of the central hub110may include a face510A and510B, respectively.

Referring to the first propeller blade150A inFIG.5A, the face510A of the top component274may contact a top structure530A of the connector160A of the first propeller blade150A whereas the face510B of the bottom component274may contact a bottom structure540A of the connector160A of the first propeller blade150A. Although not explicitly shown inFIG.5A, the face510A of the top component274may also contact a top structure530B (not shown) of the connector160B of the second propeller blade150B. Similarly, the face510B of the bottom component270may also contact a bottom structure540B (not shown) of the connector160B of the second propeller blade150B. Therefore, each spring element210and the faces510of the top274and bottom components270apply counteracting forces that hold each propeller blade150in its rotational configuration in the folded state.

FIG.5Aalso depicts the directional rotation of each propeller blade150as they transition from a folded state to the flight state. Namely, the first propeller blade150A rotates in a counterclockwise550direction whereas the second propeller blade150B rotates in a clockwise550B direction. During this transition, each spring element210(located between each connector160and the central hub110) is in tension such that the force applied by each spring element210acts in an opposite direction that each propeller blade150rotates.

Referring now toFIG.5Bwhich depicts the propeller blades150in a flight state, in various embodiments, the longitudinal axis of each propeller blade150may be parallel or nearly parallel (e.g., 0°±10°) relative to the longitudinal axis of the central hub110. In other example embodiments, when in the flight state, the longitudinal axis of each propeller blade150and the longitudinal axis of the central hub110may align. As depicted inFIG.5B, the propeller assembly100may achieve a clockwise spin180. Referring to the spring elements210in the propeller assembly100when in the flight state, the first spring element210A (between first propeller blade150A and central hub110) may be in tension and may apply a torque on the first propeller blade150A that is in the same direction as the clockwise propeller assembly spin180. The second spring element210B (between second propeller blade150B and central hub110) may be in tension and may apply a torque on the second propeller blade150B that is in an opposite direction as the clockwise propeller assembly spin180.

When each propeller blade150is in the flight state, each spring element210may be further untwisted (e.g., in further tension and storing additional potential energy) when in the flight state as compared to when in the folded state. Therefore, each propeller blade150may transition from a folded state to a flight state when a threshold amount of external force overcomes the directional torque applied by each spring element210on the propeller blade150.

In various embodiments, the external force corresponds to the centrifugal force imparted on each propeller blade150as the propeller assembly100begins to spin. Given that centrifugal force is a function of the square of the angular velocity, the centrifugal force imparted on each propeller blade150increases as the propeller assembly100increases in rotational velocity. The centrifugal force may be directed along the length of each propeller blade150outward from the central hub110and as such, is translated to the first arm215(e.g., seeFIG.2) that is attached to the connector160of each propeller blade150. More specifically, the centrifugal force translated to each spring element210may be directed along the length of each first arm215, thereby causing each spring element210to further untwist (e.g., untwist beyond its current untwisted state when in the folded state). The untwisting of the first spring element210A may cause the first propeller blade150A to rotate in a counter-clockwise direction whereas the untwisting of the second spring element210B may cause the second propeller blade150B to rotate in a clockwise direction.

In various example embodiments, the rotational configuration of the propeller blades150in the flight state, as depicted inFIG.5B, is determined by a balance of torques. For example, each spring element210may be designed with a spring constant such that the torque applied by each spring element210onto the first arm215is equal and directionally opposite of the torque applied onto the first arm215by the centrifugal forces. Given that centrifugal forces are a function of the square of angular velocity, each spring element210may be designed with a spring constant such that the rotational configuration of the propeller blades150in the flight state is achieved at a particular angular velocity. Therefore, as the rotational velocity of the propeller assembly100increases from rest (e.g., zero angular velocity) to that particular angular velocity, the rotational configuration of each propeller blade150transitions from the folded state, as depicted inFIG.5Ato the flight state, as depicted inFIG.5B.

In other example embodiments, the rotational configuration of the propeller blades150in the flight state is achieved by employing structural detents that prevent the first propeller blade150A from further rotating in a counter-clockwise direction and that prevent the second propeller blade150B from further rotating in a clockwise direction. The structural detents may be located on the center hub110or on each connector160of the corresponding propeller blade150.

The propeller assembly may also transition from the flight state, as depicted inFIG.5B, back to the folded state, as depicted inFIG.5A, as the propeller assembly100driven by the attached motor slows its spin. As such, the centrifugal forces acting on each propeller blade150reduce as the propeller assembly100slows its rotational spin. Therefore, the directional torque applied by each spring element210may exceed the torque generated by the centrifugal forces, which causes each propeller blade150to rotate from its position in the flight state to the position in the folded state. Thus, when returning to rest, the propeller blades150return to the folded state, thereby achieving a reduced overall footprint.

Additional Embodiment Considerations

The disclosed embodiments of the propeller assembly100provide advantages over conventional propellers. Conventional propeller assemblies are typically configured to remain extended in a flight state so that when rotated, the conventional propeller assembly can generate lift to an attached aerial vehicle. However, when unneeded (e.g., at rest), conventional propeller assemblies require significant storage space as the extended propeller blades may be cumbersome and unwieldy to handle.

Propeller assemblies may be further designed to change the configuration of the propeller blades to conserve space when not in use. However, often times these propeller assemblies require manual input from a human to change the configuration of the propeller blades. Human intervention may result in mechanical error during operation of the propeller assembly.

The current disclosed embodiment enables the propeller blades of a propeller assembly to self-fold into a default configuration that reduces the overall footprint of the propeller assembly without the need for human intervention and/or external forces. When required, the propeller blades can naturally extend into a flight state (e.g., extended state) due to in-flight conditions such that the propeller blades can generate lift for the attached aerial vehicle. Therefore, the process of transitioning from a flight state to a folded state (and vice versa) may occur as required by the external conditions and further does not require human intervention.

Throughout this specification, as used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

In addition, use of the “a” or “an” are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

Finally, as used herein any reference to “one embodiment,” “some embodiments,” or “various embodiments” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.

Upon reading this disclosure, those of skilled in the art will appreciate still additional alternative structural and functional designs for propeller blades as disclosed from the principles herein. Thus, while particular embodiments and applications have been illustrated and described, it is to be understood that the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes and variations, which will be apparent to those skilled in the art, may be made in the arrangement and details of the apparatus disclosed herein without departing from the spirit and scope defined in the appended claims.