Patent ID: 12246826

DETAILED DESCRIPTION

The advent of electric vertical takeoff and landing (eVTOL) presents a new challenge in aircraft actuation. Tilt actuators have conventionally been very heavy and required supporting systems—such as hydraulic systems. The high weight penalty of conventional tilt actuators has been tolerated in turbine driven aircraft. EVTOL aircraft however—due to the limited energy reserves—may be especially weight sensitive. As such, hydraulic based tilt actuation systems may leave much to be desired for eVTOL tilt actuation applications. Furthermore, conventional linear actuator systems require a large, heavy linear actuator to achieve large tilt angle ranges. An additional problem—seen in some conventional tilt actuator systems—is a non-uniform mechanical advantage throughout the tilt travel range.

In one aspect, the subject matter herein presents a tilt actuation device that utilizes a plurality of cables and a linear actuator. Such a device may address several problems for eVTOL tilt actuation applications including: the desire for consistent effective mechanical advantage throughout the travel; the desire for an actuator that does not require a hydraulic support systems; the desire to package the tilt-actuator in space confined areas; the need for a light weight system; and, the desire for a large angular range of tilt actuation.

In one aspect—the subject matter herein describes a cable tilt-actuator—the actuator is configured to tilt a propulsion unit between vertical takeoff and landing (VTOL) mode and airplane mode.

In one aspect—the subject matter herein describes a tilt actuator that addresses many issues faced by vertical takeoff and landing (VTOL)—and especially (eVTOL) electric propulsion unit tilting systems. In one aspect, a tilt actuator described herein addresses a desire for a lightweight, easy to package, tilt actuator. Furthermore, in one aspect the subject matter herein addresses the need for a large amount of angular travel—for example upwards of one-hundred degrees—for example one-hundred and five degrees—with consistent mechanical advantage throughout the travel.

In one aspect, the subject matter herein—as shown inFIG.1andFIG.2—describes a tilt actuator that is configured to convert linear actuation to rotary actuation using a first cable section107b. A first cable section107bis fixed—at a first end of the first cable section—relative to a cable spool104; a second cable section107ais fixed—at a first end of the second cable section—relative to a cable spool. The second end of the first cable section107bis fixed relative to a first end of compression beam109. The second end of the second cable section107ais fixed relative to a second end of compression beam109, wherein the second end of the compression beam109is opposite the first end of the compression beam109. A linear actuator111is configured to drive the compression beam. Linear actuation of the linear actuator111is transformed to rotational actuation using the first cable section107b. In the embodiments ofFIG.1andFIG.2, there are a plurality of cable sections107that share the load in each direction.

In one aspect—the subject matter herein describes a cable tilt-actuator for a tiltrotor aircraft. One or more linear actuators are configured to actuate a tiltrotor nacelle about a nacelle tilt axis. The linear actuator actuates the nacelle by sliding a compression beam107fore and aft relative to the nacelle. As the compression beam slides fore and aft, the nacelle is driven to rotate about the nacelle tilt axis.

Force is transferred from a spool104—to the compression beam109, by way of a plurality of cables107. The cable spool104is fixed rigidly to the wing structural member105—shown inFIG.1. In some embodiments, wing structural member105may comprise a wing spar section. Opposing cables107wind around the spool104and attach to opposite ends of the compression beam109—as the compression beam109moves fore and aft, the nacelle102is caused to tilt about the nacelle tilt axis “A”.

Shown inFIG.1is one embodiment of a cable tilt actuator. Tilt actuator system101is shown. Nacelle102is attached to wing103with an axial degree of freedom about nacelle tilt axis “A”. Spool104is fixed relative to wing structural member105.

FIG.2shows a detailed view of some aspects of the embodiment ofFIG.1. Aft Cables107aare held fixed relative to spool104at a first end using cable ends108a. The cable ends may be pulled tight against a locating feature—such as locating feature113. Cable ends may comprise swaged ends or any suitable cable ends.

Linear actuator111drives compression beam109fore and aft relative to nacelle102. Linear actuator111is attached to the nacelle102at linear actuator nacelle attachment pivot112; in the embodiment ofFIG.1, the attachment pivot allows an axial degree of freedom. The forward shaft of linear actuator111—in the embodiment ofFIG.1—is fixed to compression beam109. Thus—in the embodiment ofFIG.1—the linear actuator109is moment carrying. Attachment pivot112may comprise a pin joint, ball joint or any suitable connection.

In the embodiment ofFIG.1, the compression beam109and linear actuator111behave as one light-moment resisting assembly with column stability in the extended direction.

As the compression beam109is driven forwards—by linear actuator111, a tension force is applied to aft cables107aand a reaction force is applied to the compression beam—through cable ends108b—causing the nacelle to rotate. As compression beam109is driven forward, tension force on cables107bis reduced—thus driving the compression beam109and the nacelle102, to rotate.

The embodiment ofFIG.1comprises eight cables107. Eight cables—four fore cables107band four aft cables107aprovide strength to the embodiment. However, any other number of cables may be used. Furthermore, inFIG.2, the illustrated embodiment is shown with the fore cables107bon the inner four stations of the spool104and compression beam109. While the aft cables107aare illustrated on the outer stations of the spool104and compression beam109. Such an arrangement allows for offsetting torques about an axis perpendicular to the compression beam—axis “B”—during nominal operating condition. Axis “B” is shown inFIG.2. Other configurations such as alternating fore and aft cables may address instability caused by failure of one or more cables.

In the embodiment ofFIG.1, the compression beam109comprises a neutral plane in line with linear actuator111and cable attachment points114. The cable attachment points114being co-planar with the centerline of the linear actuator111may address problems resulting from both external forces and cable tension forces acting on compression beam109. The compression beam comprises rigid compression beam edges115. The compression beam may comprise composite material such as carbon fiber.

In an alternative embodiment, the compression beam comprises a top hat structure—which addresses the desire for the cable attachment points114to be in a plane with the center of the linear actuator111.

Any suitable type of linear actuator may be used including: a ball-screw linear actuator or a threaded rod linear actuator, or any other suitable linear actuator. Some embodiments may comprise an electric linear actuator. Some embodiments may comprise a linear actuator that comprises an anti-rotation device which may address twisting of the compression beam in some embodiments.

The embodiment ofFIG.1comprises cable tensioners110aand110b—shown inFIG.2. The cable tensioners may comprise a nut configured to thread onto the respective cable ends108b. The cable tensioners1010aand1010bmay be used to load preload into the system. Cable tensioners110aand110bmay be tightened to preload the system. Preloading addresses the problem of backlash. The embodiment ofFIG.1comprises one preload feature per cable—such a configuration allows for preload to be ideally balanced between the different cables107.

Some embodiments may have additional features for loading preload into the system—for example, some embodiments may comprise springs, washers, flexure devices, or any suitable device for loading preload into the system. Addressing backlash in a propulsion unit tilt actuator may be desired because backlash and lack of rigidity in a propulsion unit tilt actuator system may affect aircraft dynamics. In some embodiments, the cable ends, compression beam, or other aspect of the tilt actuator system may address the problem of pre-load. Likewise, in some embodiments the cable tensioner may also address the problem of fixing the cables107relative to the compression beam109.

FIG.3illustrates the same embodiment ofFIG.1—FIG.3merely illustrates the embodiment at a different position in the tilt travel range.FIG.3corresponds to a nacelle angle that may occur during aircraft transition between VTOL mode and wingborne mode. Linear actuator111drives compression beam109towards the front of the nacelle102. The reaction force—to the resulting cable loading—applies a torque to the nacelle102. The nacelle is driven to rotate from the angular position shown inFIG.1to the angular position shown inFIG.3.

FIG.4illustrates the same embodiment ofFIGS.1,2, and3—FIG.4merely illustrates the embodiment at a different position in the tilt travel range.FIG.4corresponds to a nacelle-to-wing angle that may occur during wingborne flight mode.

FIG.5illustrates an aircraft501that may comprise aspects of the subject matter described herein. The embodiment ofFIG.5comprises two cable tilt actuator systems503—one configured to tilt each nacelle502. Other embodiments may comprise any number of cable tilt actuators.

FIGS.6A and6Billustrate an embodiment of a spool104. Spool104comprises cable guide grooves601.

FIG.7Aillustrates an embodiment of a compression beam. Compression beam109comprises cable guide grooves701and cable end locating features702.

FIG.7Billustrates a section view of an embodiment of a compression beam—FIG.7Billustrates the same embodiment as shown inFIG.7A.

In one aspect, the subject matter herein describes a tilt actuator system that tilts a propulsion unit. Some embodiments may be configured to tilt substantially a whole nacelle along with the propulsion unit, while other embodiment may be configured to tilt only a portion of the nacelle. Furthermore, other embodiments may be configured to tilt any portion of the aircraft.

In a second aspect, the subject matter herein describes a scalable aircraft actuator.FIG.8illustrates a rotor system800. Rotor system800comprises an embodiment configured to actuate blade pitch. Rotor hub801comprises actuators802. The actuators comprise compression beams803. Rotor system800comprises rotor blades805. Rotor blades805comprise rotor blade spars806.

Motors802drive ball-screws809. As the compression beams are driven by motor802—through ball screws809—the tension on either cables808aor cables808bis increased. The cable set with the increased tension causes the blade to rotate about the blade pitch axis (also known as the feather axis). In the embodiment ofFIG.8, rotor blade spar806comprises a spool. In other embodiments, the rotor system may comprise a separate spool—the spool would be fixed relative to the blade spar. The blade spar is located—with a rotational degree of freedom—by rotor blade pitch bearings810.

Alternative to the actuator orientation shown inFIG.8, the actuator system could be oriented at any angle about the rotor blade pitch axis—for example, the actuator could be oriented such that the motor was coming out of the page.

While the term rotor blade is used in the preceding example—it should be understood that concepts described herein may be applicable to any propulsion blade pitch actuation system including: rotors, propellers, prop-rotors, etc.

FIG.9Aillustrates an embodiment of a cable tilt actuator with redundant motors. Threaded shaft912ais configured to be driven optionally by either motor911aor911b. The redundant motors address the desire for high levels of safety and redundancy in many aerospace applications. Shown also is cable spool904and compression beam909.

FIG.9Billustrates an alternative embodiment of a cable tilt actuator with redundant motors911. The embodiment ofFIG.9bcomprises a first and a second threaded shaft912aand912b. If one motor911fails, the operational motor911can drive the compression beam909.

In one aspect, the subject matter herein describes a jam tolerant cable actuator. The embodiment illustrated inFIG.10illustrates an embodiment of a jam tolerant cable tilt actuator. The embodiment comprises a compression beam1009and housing1010.

The motor1011bmay lock itself in place using the motor or a locking mechanism which may be part of the motor or may be a separate unit. Motor1011amay be commanded—under nominal operating conditions—to drive tray1009longitudinally in order to actuate tilt. Under normal operating conditions, the embodiment ofFIG.10operates similar to the embodiment ofFIG.1since housing1010remains fixed relative to motor1011b—motor1011bis attached at a pivot point to the nacelle. However, in the event of a jam in motor1011a, motor1012bmay unlock and drive housing1010longitudinally to actuate tilt. There may be a lock that locks cable tray1009fixed to housing1010during fail—operation mode—addressing the problem of motor1011abecoming unjammed during fail-operation mode. Motor1011bis fixed relative to the nacelle1005. Spool1004is fixed relative to wing structural member1016.

Shown inFIG.11is a color-coded illustration of an embodiment. The green components correspond to components that may remain fixed relative to the wing. The red aspects correspond to aspects that may rotate with the nacelle. The yellowish-orange aspects correspond to aspects that may rotate with the nacelle but may have additional components of motion as well. The cables are illustrated as gray.

FIG.12shows a cutaway view of the embodiment ofFIG.1as viewed from towards the front of the nacelle. Cable ends108aand cable tensioners110bare shown.

FIG.13Aillustrates a side view of a compression beam of one embodiment.

FIG.13Billustrates an end view of an alternative embodiment of a compression beam1301. The compression beam embodiment illustrated inFIG.13Bcomprises an “I” beam structure to increase rigidity. High rigidity in the compression beam may address a challenge of high bending loads created by the cable tension. High compression beam rigidity addresses the desire for a very rigid tilt actuation system. Other rigidity increasing beam structures may be used including “C” channel beam shape or any other suitable design that addresses rigidity.

FIG.13Cillustrates a side view of another alternative embodiment of a compression beam1302. The compression beam embodiment ofFIG.13Cmay comprise a cable truss1303. Compression beam1302may comprise truss cables1304, truss support1305, cable straps1306. The cable straps1306may comprise a device for pre-loading the cable1304. The cable truss1303may address bending introduced into the compression beam by the cables connected to the spool.

FIG.14illustrates an alternative embodiment of a cable tilt actuator. The embodiment ofFIG.14comprises spool1404, compression beam1409, and compression beam sliders1410. The linear actuator1411is attached to compression beam1409at a compression beam pivot attachment1412. The linear actuator1411is attached to nacelle1414at nacelle pivot attachment1413. The embodiment ofFIG.14transfers moment to the nacelle through compression beam sliders1410aand1410b.

FIG.15illustrates an embodiment of a linear actuator1403. The linear actuator may comprise motor1402.

In one aspect, the subject matter herein describes a tilt actuator comprising end stops1601—illustrated inFIG.16. The end stops may be fixed relative to the cable spool904. End stops1601may address the desire for actuator rigidity at either end of travel.

Aspects of the subject matter described herein may comprise any suitable material or combination thereof, including: metal, composite, plastics, resin, rubber, fiber, or any other suitable material.

It should be understood that the number of cables as well as the type and size of cables used may be selected to address desired system characteristics. Furthermore, the dimensions of various aspects may be selected to address desired characteristics, including the dimensions of an embodiment of a spool. In some embodiments a high ratio of spool diameter to cable diameter may address longevity problems.

In one aspect of the subject matter herein describes tilt actuators comprising four cables that apply tension in a first direction and four cables that apply tension in a second direction. However, it should be understood that any number of cables may be configured to apply tension in each direction—for example 1, or 2, or 3. Furthermore, one or more cables could be divided into cable sections—the cable sections being configured to carry loads as independent cables.

In one aspect, the subject matter herein describes actuator embodiments using cables. However, it should be understood that other embodiments may comprise: chain; chord; rope; belt; or, any other suitable material. Such embodiments may comprise components configured for use with the selected material.

While some aspects described herein describe examples of the subject matter, it should be understood aspects described herein could have very broad application, especially in aircraft dynamics controls.