Scissoring propeller with centripetally actuated centering lever lock

A propeller assembly including a shaft having a rotational axis; a plurality of propellers connected to the shaft; means for deploying the plurality of propellers using a centrifugal force generated from a rotation of the shaft, so as to provide vertical thrust during a vertical take-off and landing of the aircraft; and means for restoring the propellers into a stowed configuration.

BACKGROUND

The present disclosure relates to propeller assemblies, aircraft including the same, and associated methods.

2. Description of the Related Art

Aircraft such as rotorcraft utilize propellers to generate a vertical thrust for lifting the aircraft. In some such examples, the propellers are utilized primarily during take-off and landing of the aircraft (and/or for other altitude adjustments), and the aircraft further includes a forward thrust generator for propelling the aircraft forward. However, the propellers generating the vertical thrust also output considerable noise when operating at high revolutions per minute. In such examples, it is desirable to configure the propellers for maximum vertical thrust production at low rotational velocities and with reduced noise, which may be accomplished by increasing the number of propellers and/or the number of propeller blades of each propeller. However, in such examples, it also is desirable to configure the propellers to generate a low drag force when not in use, such as when the aircraft is propelled forward through air. The present disclosure satisfies this need.

SUMMARY

Propeller assemblies, aircraft including the same, and associated methods are disclosed herein.

a shaft having a rotational axis;

a first propeller coaxially connected to the shaft;

a second propeller;

a bearing rotatably and coaxially connecting the second propeller to the shaft;

a mechanism comprising a mass connected to the first propeller and the second propeller, the mechanism configured to deploy the second propeller away from a stowed configuration in response to a centrifugal force acting on the mass and generated by a rotation of the shaft about the rotational axis; and

at least one spring connecting the mechanism to the first propeller or the second propeller, the spring having a bias force configured to bias the second propeller in the stowed configuration.

A2. The propeller assembly of paragraph A1, wherein:

the first propeller comprises a first hub coaxially connected to the shaft;

the second propeller comprises a second hub and the bearing rotatably and coaxially connects the second hub to the shaft,

the mechanism comprises a connector assembly connecting the mass to the first hub and pivotally connecting the mass to the second hub, so as to pivot the second hub about the rotational axis and deploy the second propeller in response to the centrifugal force.

A3. The propeller assembly of paragraph A2, wherein the mass comprises a first mass and a second mass and the mechanism comprises a connector assembly including:

a first lever connecting the first mass to a first position on the first hub and a second lever connecting the second mass to a second position on the first hub, the second position diametrically opposed to the first position;

a third lever connected at a third position on the second hub and the third lever pivotably connected to the first lever, so that a first motion of the first mass in response to the centrifugal force causes the first lever to move the third lever and the second hub; and

a fourth lever connected at a fourth position on the second hub diametrically opposed to the third position and the fourth lever pivotably connected to the second lever, so that a second motion of the second mass in response to the centrifugal force causes the second lever to move the fourth lever and the second hub, in coordination with the first motion, to deploy the second propeller.

A4. The propeller assembly of paragraph A3, wherein:

the third lever is pivotally connected to the first lever at a fifth position between the first hub and the first mass, and

the fourth lever is pivotably connected to the second lever at a sixth position between the first hub and the second mass.

A5. The propeller assembly of paragraph A3, wherein the at least one spring comprises a first spring connecting the first lever to the first propeller and a second spring connecting the second lever to the first propeller.

A6. The propeller assembly of paragraph A1, wherein the second propeller is deployed in response to the centrifugal force overcoming the bias force.

A7. An aircraft comprising the propeller assembly of paragraph A1, further comprising:a fuselage;the propeller assembly operatively connected to the fuselage;a motor connected to the shaft to rotate the shaft; and

a computer coupled to the motor, wherein the computer is configurable to command the motor to:

rotate the shaft with an angular velocity generating the centrifugal force deploying the second propeller into a deployed configuration, so that the propeller assembly generates a thrust during a vertical flight of the aircraft, and

decrease the angular velocity so that the centrifugal force is reduced below the bias force so that the second propeller returns to the stowed configuration when the aircraft is cruising or moving in a forward direction.

A8. The aircraft of paragraph A7, wherein:

the first propeller comprises first propeller blades having a first longitudinal axis and the second propeller comprises second propeller blades having a second longitudinal axis, and

the first longitudinal axis and the second longitudinal axis in the stowed configuration are substantially aligned along a forward direction so as to reduce a drag of the first propeller and the second propeller when the aircraft is moving in the forward direction.

A9. The aircraft of paragraph A7, further comprising an additional propulsor operationally connected to the fuselage for providing the aircraft with the thrust comprising forward thrust.

A10. A method of controlling a propeller assembly, comprising:

controlling a propeller assembly comprising:

a shaft having a rotational axis;

a first propeller coaxially connected to the shaft;

a second propeller;

a bearing rotatably and coaxially connecting the second propeller to the shaft;

a mechanism comprising a mass connected to the first propeller and the second propeller, the mechanism configured to deploy the second propeller away from a stowed configuration in response to a centrifugal force acting on the mass and generated by a rotation of the shaft about the rotational axis; and

at least one spring connecting the mechanism to the first propeller, the spring having a bias force configured to bias the second propeller in the stowed configuration; and

deploying the second propeller away from the stowed configuration, comprising rotating the shaft at an angular velocity to generate the centrifugal force that exceeds the bias force.

A11. The method of paragraph A10, wherein the angular velocity is more than 1000 revolutions per minute.

A12. The method of paragraph A10, wherein:

the first propeller comprises a first hub coaxially connected to the shaft;

the second propeller comprises a second hub and the bearing rotatably and coaxially connects the second hub to the shaft,

the mechanism comprises a connector assembly connecting the mass to the first hub and pivotally connecting the mass to the second hub, so as to pivot the second hub about the rotational axis and deploy the second propeller in response to the centrifugal force.

A13. The method of paragraph A12, wherein

wherein the mass comprises a first mass and a second mass and the mechanism comprises a connector assembly including:

a first lever connecting the first mass to a first position on the first hub and a second lever connecting the second mass to a second position on the first hub, the second position diametrically opposed to the first position;

a third lever connected at a third position on the second hub and the third lever pivotably connected to the first lever, so that a first motion of the first mass in response to the centrifugal force causes the first lever to move the third lever and the second hub; and

a fourth lever connected at a fourth position on the second hub diametrically opposed to the third position and the fourth lever pivotably connected to the second lever, so that a second motion of the second mass in response to the centrifugal force causes the second lever to move the fourth lever and the second hub, in coordination with the first motion, to deploy the second propeller.

A14. The method of paragraph A13, wherein:

the third lever is pivotally connected to the first lever at a fifth position between the first hub and the first mass, and

the fourth lever is pivotably connected to the second lever at a sixth position between the first hub and the second mass.

A15. The method of paragraph A14, wherein the at least one spring comprises a first spring connecting the first lever to the first propeller and a second spring connecting the second lever to the first propeller.

A16. The method of paragraph A10, wherein

the first propeller comprises first propeller blades having a first longitudinal axis and the second propeller comprises second propeller blades having a second longitudinal axis, and

the first longitudinal axis and the second longitudinal axis in the stowed configuration have are substantially aligned along the forward direction so as to reduce a drag of the first propeller and the second propeller when the aircraft is moving in the forward direction.

A17. The method of paragraph A11, further comprising retracting the second propeller into the stowed configuration, comprising reducing the angular velocity so that the bias force exceeds the centrifugal force.

A18. The method of paragraph A17, wherein:

the first propeller comprises first propeller blades having a first longitudinal axis and the second propeller comprises second propeller blades having a second longitudinal axis, and

the retracting comprises stopping the rotating so that the bias force biases the second propeller in the stowed configuration including the first longitudinal axis and the second longitudinal axis substantially aligned along a forward direction so as to reduce a drag of the first propeller and the second propeller when the aircraft is moving in the forward direction.

A19. An aircraft comprising a propeller assembly, the propeller assembly comprising:a shaft having a rotational axis;a plurality of propellers connected to the shaft;

means for deploying the plurality of propellers using a centrifugal force generated from a rotation of the shaft, so as to provide vertical thrust during a vertical take-off and landing of the aircraft; and

means for restoring the propellers into a stowed configuration when the centrifugal force is below a threshold level.

A20. The propeller assembly of paragraph A19, wherein the means for deploying comprises a plurality of levers connecting a mass to the propellers and the means for restoring comprises a spring connecting the mass to one of the propellers.

DESCRIPTION

In the following description, reference is made to the accompanying drawings which form a part hereof, and which is shown, by way of illustration, several examples. It is understood that other examples may be utilized and structural changes may be made without departing from the scope of the present disclosure.

Technical Description

FIGS.1A-1I,2A,2B,3A, and3Bprovide illustrative, non-exclusive examples of propeller assemblies100, of aircraft incorporating propeller assemblies, and/or of methods of operating propeller assemblies, according to the present disclosure. In propeller-driven aircraft (such as rotorcraft), it is generally desirable that each propeller generate a high amount of thrust (e.g., a vertical thrust) at a low rotational velocity, such as to minimize a noise level produced by the propeller. Accordingly, many aircraft utilize propellers that include a plurality of propeller blades that spin at least substantially in unison to generate increased thrust at a given rotational velocity relative to propellers with fewer propeller blades. In some circumstances, however, such multi-bladed propellers may generate an undesirable drag force, such as when the propellers are selectively disabled from producing vertical thrust and the aircraft moves in a forward (e.g., horizontal) direction under the power of a separate thrust source. Accordingly, and as described herein, the present disclosure is directed to propeller assemblies that include a plurality of stacked propellers that are configured to transition between a thrust-generating mode of operation and a low-drag mode of operation.

As used herein, two or more components may be described as being coupled or connected to one another. The desired definition is that element A coupled to/connected to B is defined as either A directly or indirectly connected to B, including coupled or connected through one or more intervening elements.

Example Propeller Assemblies and Deployment

FIG.1A-1Iillustrate example propeller assemblies100, comprising a shaft102having a rotational axis104; a first propeller106coaxially connected to the shaft102; a second propeller108; a bearing110rotatably and coaxially connecting the second propeller108to the shaft102; and a mechanism112comprising a mass114connected to the first propeller106and the second propeller108. The mechanism112is configured to deploy116the second propeller108away from the stowed configuration118(FIG.1A,FIG.1E) into the deployed configuration116a(FIG.1C,FIG.1G) and in response to a centrifugal force117acting on the mass114and generated by a rotation104aof the shaft102about the rotational axis104. The propeller assembly100further comprises at least one spring120connecting the mechanism112to the first propeller106or the second propeller108, the spring120having a bias force119configured to bias the second propeller108in the stowed configuration118.

FIG.1A-1Gillustrate a propeller assembly according to a first example, wherein the first propeller106comprises a first hub122(or first propeller carrier) and first blades123extending from the first hub122, and the second propeller108comprises a second hub124(or second propeller carrier) and second blades125extending from the second hub124. The first hub122is coaxially attached and fixed to the shaft102so that the first hub122and the first propeller106rotates in unison with the shaft102. The bearing110rotatably and coaxially connects the second hub124to the shaft102so that the second hub124and the second propeller can freely rotate about the rotational axis104independently from the first propeller106. An example bearing110includes, but are not limited to, roller bearings including ball bearings or slide bearings with shaft nuts to control play.

WhileFIG.1A-1Gillustrate the mechanism112directly connected to the first hub122and the second hub124, in other examples the mechanism112is directly connected to any part of the first propeller106or the second propeller108. In other examples, the mechanism112is directly connected to the shaft102and thereby is connected to the first propeller106through the intervening shaft102.

Example mechanisms112include, but are not limited to, a connector assembly126pivotally connecting the mass114to the first hub122and pivotally connecting the mass114to the second hub124, so as to pivot the second hub124about the rotational axis104and deploy116the second propeller108in response to the centrifugal force.

Examples of connector assemblies126include, but are not limited to, various configurations or linkages comprising connectors, connecting pieces, connecting members, levers, or arms connecting the mass114to the first propeller106and the second propeller108.

InFIGS.1A-1G, the mass114comprises a first mass114aand a second mass114band the connector assembly126comprises:a first lever128connecting the first mass114ato a first position130on the first hub122;a second lever132connecting the second mass114bto a second position134on the first hub122so that the second position134is diametrically opposed to the first position130;a third lever136connected at a third position138on the second hub124, wherein the third lever136is pivotably connected to the first lever128so that a first motion140of the first mass114ain response to the centrifugal force117causes the first lever128to move the third lever136and the second hub124; anda fourth lever142connected at a fourth position144on the second hub124diametrically opposed to the third position138, wherein the fourth lever142is pivotably connected to the second lever132so that a second motion146of the second mass114bin response to the centrifugal force117causes the second lever132to move the fourth lever142and the second hub124, in coordination with the first motion140, to deploy the second propeller.

As illustrated, the third lever136is pivotally connected to the first lever128at a fifth position148between the first hub122and the first mass114a, and the fourth lever142is pivotably connected to the second lever132at a sixth position150between the first hub122and the second mass114b. The at least one spring120comprises a first spring120aconnecting the first lever128to the first propeller106and a second spring120bconnecting the second lever132to the first propeller106.

As illustrated inFIG.1A-1G, the motion140,146of the mass114, in response to the centrifugal force117, actuates the deployment of the second propeller108, moving the second propeller108from a stowed configuration118(shown inFIG.1A) to a transition configuration (FIG.1B) and then to a deployed configuration116a(shown inFIG.1C).FIG.1Gshows the extent of deployment or deployment angle160between a first longitudinal axis162of the first blades123and a second longitudinal axis164of the second blades125(when the first longitudinal axis162and the second longitudinal axis164intersect at a vertex on the rotational axis104), is determined or limited by the geometry of the levers128,132,136,142(e.g., dimensions such as length), a stop mechanism (e.g., comprising the shaft102, the first hub,122or the second hub124), the weight of the mass114, or the centrifugal force117itself.FIG.1Cillustrates the levers128,132,136,142are connected and dimensioned so that a stop mechanism (in this case, physical contact155between the first lever128and the first hub122and physical contact between the second lever132and the first hub rigidly locks the levers128,132,136,142when the first position130, the third position138, and the fifth position148are aligned, and the second position134, the fourth position144, and the sixth position150are aligned, thereby preventing any further movement of the second propeller108around the rotational axis104and rigidly fixing the propeller assembly100in the deployed configuration118having the deployment angle160(e.g., but not limited to, in a range of 30-80 degrees, e.g., 60 degrees). In the stowed configuration, as illustrated inFIG.1A, the first longitudinal axis162and the second longitudinal axis164are substantially aligned (i.e., the deployment angle160is zero degrees or within 5 degrees).

As illustrated inFIG.1D, the first lever128pivotally connecting the first mass114ato a first position130on the first hub122comprises the first lever128pivoting with respect to the first hub122about a first pivot axis165passing through first position130of the joint connecting the first lever128to the first hub122. The second lever132pivotally connecting the second mass114bto a second position134on the first hub122comprises the second lever132pivoting with respect to the first hub122about a second pivot axis168passing through second position134at the joint connecting the second lever132to the first hub122. The third lever136pivotally connected at a third position138on the second hub124comprises the third lever136pivoting with respect to the second hub124about a third pivot axis167passing through the third position138at the joint connecting the third lever136to the second hub124. The third lever136pivotally connected to the first lever128comprises the third lever136being able to pivot with respect to the first lever128about a fourth pivot axis166passing through the fifth position148at the joint connecting the first lever128and the third lever136. The fourth lever142pivotally connected at a fourth position144on the second hub124comprises the fourth lever142being able to pivot with respect to the second hub124about a fifth pivot axis passing through the fourth position144at the joint connecting the fourth lever142to the second hub124. The fourth lever142pivotally connected to the second lever132comprises the fourth lever142being able to pivot about a sixth pivot axis169passing through sixth position150at the joint connecting the fourth lever142and the second lever132.

FIGS.1H and1Iillustrate a propeller assembly100according to a second example. In this example, the first lever128and the second lever132each comprise a primary arm170including a first section172and a second section174at an angle with respect to the first section172. The third lever136and the fourth lever142each comprise a secondary arm176. The first section172of the first lever128pivotally connects the first mass114ato the shaft102at a first joint178aand the first section172of the second lever132pivotally connects the second mass114bto the shaft102at a second joint178b. The second section174of the first lever128pivotally connects to the secondary arm176of the third lever136at a third joint180and the second section174of the second lever132pivotally connects to the secondary arm176of the fourth lever142at a fourth joint182. A first spring120acomprising a first elastic material184connects the first section172of the first lever128to the second propeller108and a second spring120bcomprising a second elastic material186connects the first section172of the second lever132to the second propeller108. The first spring120aand the second spring120bare connected to the second propeller108on diametrically opposite sides of the first hub1224.

The levers128,132,136,142or connector assembly126arrangements illustrated herein are merely provided as non-limiting examples of how parts are linked to actuate deployment of the second propellers108using a centrifugal force117. Other designs consistent with the descriptions herein are also possible. For example, more generally, the present disclosure discloses a propeller assembly100comprising: a shaft102having a rotational axis; a plurality of propellers106,108connected to the shaft102; means for deploying190the plurality of propellers using a centrifugal force117generated from a rotation104aof the shaft102; and means for restoring192the propellers106,108into a stowed configuration118. Examples of the means for deploying190include the mechanism112and examples of the means for restoring192include the spring120, as illustrated inFIG.1I.

The propeller assembly100has been discussed in terms of the top two propellers inFIGS.1A-1I. However, similar mechanisms112and springs are connected between the central propeller and the lowest (bottom propeller) inFIGS.1A-1Ito deploy all the propellers. For example, as illustrated inFIG.1B, the at least one spring120further includes a third spring120cand a fourth spring120dconnecting the first propeller106to the mechanism112between the lowest second propeller108and the first propeller106, as discussed in the next section.

Example Propeller Assembly Configurations

A propeller assembly100according to examples described herein includes any number of propellers106,108that can be stacked in a variety of configurations.

FIG.2Aillustrates an example propeller assembly100,200including a stack of three propellers including the first propeller106, comprising a central propeller202, and a plurality of the second propellers108, comprising a top propeller204and a bottom propeller206. The central propeller202is fixed to the shaft102, the top propeller204is mounted via a coaxial or axial bearing110to the shaft102at a location above the central propeller202, and the bottom propeller206is mounted via a coaxial or axial bearing110to the shaft102at a location below the central propeller202. As described herein, one of the mechanisms112connects the central propeller202to the top propeller204and another of the mechanisms112connects the central propeller202to the bottom propeller206.

FIG.2Billustrates another example propeller assembly208wherein the first propeller106fixed to the shaft102is the bottom propeller206and the plurality of second propellers108comprise the central propeller202and top propeller204. The central propeller202is mounted via coaxial or axial bearing110to the shaft102at a location above the bottom propeller206and the top propeller204is mounted via coaxial or axial bearing110to the shaft102a location above the central propeller202. One of the mechanisms112connects the bottom propeller206to the central propeller202and another of the mechanisms112connects the central propeller202to the top propeller204.

AlthoughFIGS.2A and2Billustrate propeller assemblies including three propellers202,204,206, the propeller assembly100,200,208may include any number of propellers comprising one or more first propellers106and one or more second propellers108as described herein. In one example, the first propeller106fixed to the shaft102is between second propellers108(a parallel connection). In the parallel connection illustrated inFIG.2A, the first propeller106pulls or acts on each of the second propellers108(comprising top propeller204and bottom propeller206) individually. In another example, the first propeller106fixed to the shaft102is below two adjacent second propellers108(a series connection). In the series connection illustrated inFIG.2B, the first propeller106(bottom propeller206) pulls or acts on the adjacent second propeller (in this case the central propeller202) and the remaining second propeller108(in this case top propeller204) follows the motion of the first propeller106though connection with the other second propeller108(central propeller202). A mechanism112is between the first propeller106and the second propeller108and/or between two adjacent second propellers108.

As illustrated herein, the propeller assembly100comprising multiple propellers (e.g., 3 two-bladed propellers) unfold at a variety of angles in between the individual blades.FIG.1Gshows the deployment angle160between a first longitudinal axis162of the first blades123of the first propeller106and a second longitudinal axis164of the second blades125of the second propellers108. In the example ofFIG.2A, the second blades125of the second propellers108(the top propeller204and the bottom propeller206) deploy at the deployment angle160with respect to the first blades123of the first propeller106(central propeller202). In the example ofFIG.2B, the second blades125of the second propellers108(the central propeller202and the top propeller204) deploy at the deployment angle160with respect to the first blades123of the first propeller106(the bottom propeller206). Example deployment angles160include, but are not limited to, deployment angles160in a range of 30-80 degrees, e.g., 60 degrees.

FIG.2AandFIG.2Bfurther illustrate a motor210operably coupled to the shaft102so as to drive or power rotation of the shaft102and the propeller assembly100.

Fourth Example: Aircraft Including a Propeller Assembly

FIG.3AandFIG.3Billustrate an aircraft300comprising a fuselage302; a wing304connected to the fuselage302; and the propeller assembly100operatively connected to the wing304. The aircraft300further includes a computer306coupled to the motor210.FIG.3Aillustrates the computer306is configurable to command the motor210to rotate the shaft102with an angular velocity generating the centrifugal force117deploying the second propeller108into a deployed configuration116a, so that the propeller assembly100generates a vertical thrust308during a vertical flight or take-off of the aircraft300.FIG.3Billustrates the computer306is further configurable to command the motor210to decrease the angular velocity so that the centrifugal force117is reduced below the bias force119of the spring120and the second propeller108returns to the stowed configuration118when the aircraft300is cruising or moving in a forward direction310.FIG.3Bfurther illustrates an example wherein the first blades123and the second blades125in the stowed configuration118have their longitudinal axes (first longitudinal axis162and second longitudinal axis164) substantially aligned along the forward direction310so as to reduce a drag of the propeller assembly100when the aircraft300is moving in the forward direction310. As illustrated inFIG.3, substantially aligned is defined as the first longitudinal axis162, the second longitudinal axis164, and the forward direction310being parallel or the first longitudinal axis162and/or the second longitudinal axis164being oriented at an angle within 5 degrees of the forward direction310.

FIG.3Bfurther illustrates the aircraft300comprises an additional propulsor316operationally connected to the fuselage302for providing the aircraft300with the thrust comprising forward thrust318propelling the aircraft in the forward direction310.

Fifth Example: Process Steps

Method of Making

FIG.4is a flowchart illustrating a method of making a propeller assembly according to one or more examples (referring also toFIGS.1A-1I,2A-2B,3A, and3B)

Block400represents providing a shaft102having a rotational axis104.

Block402represents coaxially attaching a first propeller106to the shaft102so that the first propeller is fixed to the shaft102and rotates in unison with the shaft102.

Block404represents coaxially attaching a second propeller108to the shaft using a bearing110rotatably and coaxially connecting the second propeller108to the shaft102, e.g., so that the second propeller108interacts with the first propeller106or the shaft102through the bearing110and can rotates freely and independently about the rotational axis104independently of the first propeller106.

Block406represents connecting a mechanism112comprising a mass114to the first propeller106and the second propeller108, the mechanism112configured to deploy116the second propeller108away from a stowed configuration118in response to a centrifugal force117acting on the mass114and generated by a rotation104aof the shaft102about the rotational axis104.

Block408represents connecting at least one spring120to the mechanism112and the first propeller106or the second propeller108, the spring having a bias force119configured to bias the second propeller108in the stowed configuration118.

Block410represents the end result, a propeller assembly100. Illustrative, non-exclusive examples of inventive subject matter according to the present disclosure are described in the following enumerated paragraphs:

A1. A propeller assembly100, comprising a shaft102having a rotational axis104; a first propeller106coaxially connected to the shaft102; a second propeller108; a bearing110rotatably and coaxially connecting the second propeller108to the shaft102; a mechanism112comprising a mass114connected to the first propeller106and the second propeller108, the mechanism112configured to deploy116the second propeller108away from a stowed configuration118in response to a centrifugal force117acting on the mass114and generated by a rotation104aof the shaft102about the rotational axis104; and at least one spring120connecting the mechanism112to the first propeller106or the first propeller106, the spring120having a bias force119configured to bias the second propeller108in the stowed configuration118.

A2. The propeller assembly100of paragraph A1, wherein the first propeller106comprises a first hub122coaxially connected to the shaft; the second propeller comprises a second hub124and the bearing rotatably and coaxially connects the second hub124to the shaft, the mechanism112comprises a connector assembly126connecting the mass114to the first hub122and pivotally connecting the mass114to the second hub124, so as to pivot the second hub124about the rotational axis104and deploy116the second propeller108in response to the centrifugal force117.

A3. The propeller assembly of paragraph A1, wherein the mass114comprises a first mass114aand a second mass114band the mechanism112comprises a connector assembly126including:

a first lever128connecting the first mass114ato a first position130on the first hub122and a second lever132connecting the second mass114bto a second position134on the first hub, the second position134diametrically opposed to the first position130;

a third lever136connected at a third position138on the second hub124and the third lever136pivotably connected to the first lever128, so that a first motion140of the first mass114ain response to the centrifugal force117causes the first lever128to move the third lever136and the second hub124; and

a fourth lever142connected at a fourth position144on the second hub124diametrically opposed to the third position138and the fourth lever142pivotably connected to the second lever132, so that a second motion146of the second mass114bin response to the centrifugal force117causes the second lever132to move the fourth lever142and the second hub124, in coordination with the first motion140, to deploy the second propeller108.

the third lever136is pivotally connected to the first lever128at a fifth position148between the first hub122and the first mass114a, and

the fourth lever142is pivotably connected to the second lever132at a sixth position150between the first hub122and the second mass114b.

A5. The propeller assembly100of paragraph A3 or A4, wherein the at least one spring120comprises a first spring120aconnecting the first lever128to the first propeller106and a second spring120bconnecting the second lever132to the first propeller106.

A6. The propeller assembly of any of the paragraphs A3-A5, wherein rotating, spooling up, or spinning the shaft102and the propeller assembly100generates the centripetal force forcing the first mass114aand the second mass114boutwards against the at least one spring120, and the first lever128holding the first mass114aand the second lever132holding the second mass114bforce, through the third lever136and fourth lever142, respectively, the first propeller106and the second propeller108to unfold.

A7. The propeller assembly100of any of the paragraphs A3-A6, wherein rotating, spooling up, or spinning of the first propeller106generates the centrifugal force117moving the first mass114aand the second mass114bsuch that the first position130, the third position138, and the fifth position148are aligned, and the second position134, the fourth position144, and the sixth position150are aligned.

A8. The propeller assembly100of paragraph of any of the paragraphs A3-A7, further comprising a stop mechanism or the arrangement of the levers128,132,136,142preventing the masses114a,114bfrom moving further in response to the centrifugal force117above a threshold level.

A9. The propeller assembly100of paragraphs A7 and A8, further comprising a stop mechanism rigidly fixing or rigidly connecting the first lever128and the third lever136when the first position130, the third position138, and the fifth position148are in alignment and rigidly fixing or rigidly connecting the second lever132and the fourth lever142when the second position134, the fourth position144, and the sixth position150are in alignment, thereby preventing any further movement of the second propeller108around the rotational axis104and locking the propeller assembly100in the deployed configuration118.

A10. The propeller assembly100of any of the paragraphs A1-A9, further comprising a stop mechanism rigidly fixing the connector assembly126, thereby locking the first propeller106and the second propeller108at a desired deployment angle160.

A11. The propeller assembly100of any of the paragraphs A1-10, wherein the mechanism112directly connects the mass114to the shaft102so that the mechanism and the shaft are in physical contact.

A12. The propeller assembly100of any of the paragraphs A1-A11, wherein the mechanism112is configured so that the mass114swings against and with the rotation104aof the shaft102about the rotational axis104.

A13. The propeller assembly100of any of the paragraphs A1-A12, wherein the first propeller106and the second propeller108swing in opposite directions about the rotational axis104in response to the centrifugal force117deploying the second propeller108.

A14. The propeller assembly100of any of the paragraphs A1-A13, further comprising the at least one spring120connected to a damping mechanism.

A15. The propeller assembly100of any of the paragraphs A1-A14, wherein the second propeller108is deployed in response to the centrifugal force overcoming the bias force119.

A16. The propeller assembly100of paragraph A15 configured so that when the angular velocity of the shaft102drops below a certain threshold (e.g. less than 1000 revolutions per minute), the at least one spring120applies the biasing force that is greater than the centripetal force and pulls the second propeller108back into the stowed configuration118.

A17. The propeller assembly100of any of the paragraphs A1-A16, wherein the first propeller106has a first propeller blades123having a first longitudinal axis162, the second propeller108has second propeller blades125having a second longitudinal axis164, the propeller blades123,125in the stowed configuration having their longitudinal axes162,164substantially aligned along the forward direction310so as to reduce a drag of the first propeller106and second propeller108when the aircraft300is moving in the forward direction310.

A18. A propeller assembly100comprising: a shaft102having a rotational axis; a plurality of propellers106,108connected to the shaft102; means for deploying190the plurality of propellers (e.g., to an unfolded state) using a centrifugal force generated from a rotation104aof the shaft102, so as to provide vertical thrust308during a vertical take-off and landing of the aircraft300; and means for restoring192the propellers106,108into a stowed configuration118(e.g., folded state) when the centrifugal force is below a threshold level.

A19. The propeller assembly100of paragraph A18, wherein the means for deploying190comprises a mass114(or weight) that actuates the deployment of the propeller108by a centripetal force.

A20. The propeller assembly of paragraph A19, wherein the means for deploying190comprises the mechanism112of any of the paragraphs A1-A18.

A21. The propeller assembly of paragraphs A1-A20, wherein the means for deploying190or the mechanism112comprises a linkage, connector assembly126, plurality of levers, arms, or connectors, connecting a mass114to the propellers106,108and the means for restoring192comprises a spring120, connecting the mass114to one of the propellers106, the spring120biasing the propellers108to the stowed configuration118when the angular velocity (e.g., revolutions per minute) falls below a threshold level.

A22. The propeller assembly100of paragraph A21, wherein mass114actuates two levers comprising a primary arm170and a secondary arm176, wherein the primary arm170connects the mass114and the shaft102and the secondary arm176connects the primary arm170with one of the propellers108.

A23. The propeller assembly100of any of the paragraphs A1-A21, wherein the connector assembly126comprises a first member and a second member each comprising a lever, a connector, or an arm, wherein the mass114is fixed to the first member at a certain position, and the members are fixed at one end to each other and at the other end to the first propeller106and the second propeller108, respectively.

A24. The propeller assembly100of any of the paragraphs A1-A23, wherein the deployed configuration comprises the propellers in an open or unfolded state and the stowed configuration comprises the propellers in a folded or closed state.

Block412represents optionally mounting one or more propeller assemblies100on an aircraft300.

A25. An aircraft300comprising the propeller assembly100of any of the paragraphs A1-23, comprising:a fuselage302;the propeller assembly100operatively connected to the fuselage302;a motor210connected to the shaft102to rotate the shaft102; and

a computer306coupled to the motor210, wherein the computer306is configurable to command the motor210to:

rotate the shaft102with an angular velocity generating the centrifugal force deploying the second propeller108into a deployed configuration116a, so that the propeller assembly100generates a vertical thrust308during a vertical flight of the aircraft300, and

decrease the angular velocity so that the centrifugal force is reduced below the bias force119so that the second propeller108returns to the stowed configuration118when the aircraft300is cruising or moving in a forward direction310.

A26. The aircraft of paragraph A25, further comprising an additional propulsor316operationally connected to the fuselage302for providing the aircraft with the thrust comprising forward thrust318.

Method of Operating

FIG.5represents a method of controlling thrust.

Block502represents obtaining or providing a propeller assembly as described herein including any of the paragraphs A1-A26.

Block502represents rotating, spooling up, or spinning the propeller assembly100at an angular velocity to generate the centrifugal force used to deploy504the propeller assembly. In one example, the angular velocity generates the centrifugal force that exceeds the bias force119needed to retract the propeller assembly100into the stowed configuration118. In one example, the angular velocity is more than 1000 revolutions per minute.

Block506represents retracting or stowing the second propeller into the stowed configuration. The step comprises reducing or decreasing the angular velocity so that the centrifugal force is reduced below the bias force119so that the second propeller108automatically returns to the stowed configuration118when the aircraft is cruising or moving in a forward direction310. In one or more examples, the retracting comprises stopping the rotating so that the bias force119biases the second propeller in the stowed configuration including the first longitudinal axis and the second longitudinal axis substantially aligned along a forward direction so as to reduce a drag of the first propeller and the second propeller when the aircraft is moving in the forward direction.

Processing Environment

FIG.6illustrates an exemplary system600used to implement processing elements needed to control the propeller assembly100. In other examples, the system600is a flight control system used to control deployment and retraction of the propeller assembly as described herein.

The computer602,306comprises a processor604(general purpose processor606A and special purpose processor606B) and a memory606, such as random access memory (RAM). Generally, the computer602operates under control of an operating system608stored in the memory606, and interfaces with the user/other computers to accept inputs and commands (e.g., analog or digital signals from the crew or flight control system) and to present results through an input/output (I/O) module610. The computer program application612accesses and manipulates data stored in the memory806of the computer602. The operating system608and the computer program612are comprised of instructions which, when read and executed by the computer602, cause the computer602,306to perform the operations and/or methods herein described, controlling the motor210to control angular velocity of the shaft102and thereby opening/deploying and closing/stowing of the propeller assembly100. In one embodiment, instructions implementing the operating system608and the computer program612are tangibly embodied in the memory606, thereby making one or more computer program products or articles of manufacture capable of controlling the propeller assembly as described herein. As such, the terms “article of manufacture,” “program storage device” and “computer program product” as used herein are intended to encompass a computer program accessible from any computer readable device or media. Also shown is a source of power616for the computer.

Those skilled in the art will recognize many modifications may be made to this configuration without departing from the scope of the present disclosure. For example, those skilled in the art will recognize that any combination of the above components, or any number of different components, peripherals, and other devices, may be used.

CONCLUSION

This concludes the description of the examples of the present disclosure. The foregoing description of the examples has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of rights be limited not by this detailed description, but rather by the claims appended hereto.