Patent Description:
Electric aircraft typically operate in outdoor environments. Particularly when operating near the ground, as in during takeoff and landing, debris may strike the operating surfaces of the aircraft, including the lift fans and/or other rotors. In flight, birds and other airborne obstacles may strike the lift fans or other rotors.

In addition to needing to be able to withstand contact with foreign objects, lift fans and other rotors must be able to the withstand the forces associated with flight, such as wind, rain, and applying the forces and moments required to control aircraft position and flight.

Electric aircraft lift fans and propellers are powered by onboard batteries. The weight of the aircraft is a significant factor in determining the operating range and other performance parameters of the aircraft. Composite materials may be used to provide a lightweight aircraft, including lightweight lift fan or other rotors, but such materials may be less able than more durable but heavier materials to withstand contact with foreign objects and other stresses of flight.

<CIT> describes a hollow composite airfoil with an integral internal laminated corrugated support structure, which is formed by disposing silicone rubber mandrels in the corrugations of the laminated support structure to form a core assembly having a desired aerodynamic shape, then stacking on both sides of the core assembly laminae of a composite material (of which the support structure may also be formed), with the stacks overlapping adjacent the leading and trailing edges of the core assembly. Heat and pressure being used to bond the airfoil the mandrels being then removed. One open end of the resulting hollow airfoil is plugged and that end is inserted into a recess in a mounting platform with a predetermined substantially uniform clearance space therebetween, an elastomeric material being injected into the clearance space and then cured to bond the platform to the airfoil.

<CIT> describes a dual-skin structure, which comprises a first skin, a second skin and an intermediate structure. The intermediate structure comprises a plurality of first contact portions connected to an interior surface of the first skin, a plurality of second contact portions connected to an interior surface of the second skin and a plurality of interconnecting web portions integral to the first and second contact portions and extending between ones of the first and second contact portions to form an internal supporting structure alternating between the interior surfaces of the first and second skins.

According to an aspect of the present invention, there is provided a rotor according to any of claims <NUM> to <NUM>.

The scope of the invention is limited only by the claims and the invention encompasses numerous alternatives and modifications.

Corrugated rotors are disclosed. In various embodiments, a corrugated rotor as disclosed herein includes a corrugated core encased between an upper rotor skin and a lower rotor skin. The rotor may be used, in some embodiments, to provide a durable but relatively lightweight rotor for aviation applications, such as a lift fan rotor for a vertical (or short) takeoff and landing (VTOL) electric aircraft. In various embodiments, a corrugated rotor as disclosed herein includes a composite corrugated core, a composite upper skin, and a composite lower skin. In some embodiments, the composite corrugated core, a composite upper skin, and a composite lower skin are formed separately and bonded together to form a corrugated rotor.

In various embodiments, the outer skin of a corrugated rotor as disclosed herein comprises a rigid exterior shell, akin to an exoskeleton, and includes a corrugated core that is akin to an endoskeleton. In various embodiments, the corrugated core reinforces the outer shell without adding excessive weight to the rotor.

<FIG> is a diagram illustrating an embodiment of a corrugated lift fan rotor. In the example shown, lift fan rotor <NUM> includes an upper skin <NUM> and a lower skin <NUM>. A corrugated core, not shown in Figure lA, is encased in upper skin <NUM> and lower skin <NUM>.

In some embodiments, upper skin <NUM> and lower skin <NUM> are composite structures, including but not limited to carbon fiber reinforced polymer materials. To fabricate each, layers of prepreg composite precursor fabric are layed up in a mold defining at least in part the shape of the upper skin <NUM> or lower skin <NUM>, as applicable. The laid up prepreg stack is cured, e.g., heat cured under vacuum or other pressure conditions, to form a rigid composite part. In various embodiments, upper skin <NUM> may comprise an at least partially concave down shape, in the orientation a shown, while lower skin <NUM> defines a concave up shape. The corrugated core described above, not shown in Figure lA, in various embodiments at least partly fills a void that would otherwise be defined by bonding the upper skin <NUM> to the lower skin <NUM>, as shown.

The corrugated core extends radially from the bore hole defined in the middle of lift fan rotor <NUM>, to admit a shaft to drive (rotate) the lift fan rotor, and extends longitudinally along at least a part of the respective cores of the left and right rotor blades, as shown.

While a two-bladed rotor is shown in Figure lA, in various embodiments corrugated-core rotors comprising more (e.g., four or more) or fewer (e.g., zero or one) blades are provided. In various embodiments, the central disk or hub portion of a corrugated rotor as disclosed herein may be larger or smaller than in the example shown in <FIG>. Rotors having corrugated cores in one or both of the rotor disk or hub and the rotor blades are contemplated.

<FIG> is a diagram illustrating an embodiment of a corrugated lift fan rotor. Specifically, a top view of the corrugated lift fan rotor <NUM> of <FIG> is shown.

<FIG> is a diagram illustrating an embodiment of a corrugated lift fan rotor. Specifically, a front view of the corrugated lift fan rotor <NUM> of <FIG> is shown.

<FIG> is a diagram illustrating an embodiment of a corrugated lift fan rotor. In the example shown, corrugated lift fan rotor <NUM> of <FIG> is shown to include a corrugated core <NUM> in addition to upper skin <NUM> and lower skin <NUM>.

As indicated by the downward pointing arrows, corrugated core <NUM> is encased between upper skin <NUM> and lower skin <NUM>. Corrugated core <NUM> is shown in <FIG> to be a unitary piece, but in some embodiments the corrugated core may be made up of two or more pieces.

In some embodiments, corrugated core <NUM> is a composite structure. Corrugated core <NUM> is formed in some such embodiments but laying up overlapping strips (or other pieces) of prepreg composite precursor fabric in a mold that at least partly defines the three-dimensional shape of corrugated core <NUM>. The mold includes a plurality of relief features. Prepreg fabric is laid up in the mold, including by draping and layering overlapping pieces of prepreg over the relief features and in the valleys that lie between the relief features, to create a stack of prepreg layers that include portions overlying the relief features to define upper cap portions of the finished composite corrugated core part; portions laid in the lowermost regions of valleys between the relief feature to define lower cap portions of the finished composite corrugated core part; portions between the upper cap and lower cap portions to define web regions of the finished composite corrugated core part. The prepreg layers stacked in the mold are cured, e.g., by heat under vacuum or other pressure, to provide a rigid finished composite corrugated core part.

In various embodiments, a composite corrugated core part fabricated as described above, e.g., corrugated core <NUM> of <FIG>, is bonded (e.g., using paste or other adhesive) to one or both of the upper skin <NUM> and the lower skin <NUM> to provide a lift fan <NUM> with a corrugated core as disclosed herein. For example, in various embodiments, adhesive is applied to the upper cap and lower cap parts of the corrugated core <NUM>, and optionally to one or both of the upper skin <NUM> and lower skin <NUM>, in a pattern corresponding to the upper or lower cap portions of the corrugated core <NUM>, respectively, and the pieces are assembled as indicated by the downward arrows in <FIG> to provide a finished corrugated lift fan rotor <NUM>.

In various embodiments, a substantially cylindrical bearing bore (not shown) is inserted into one or more of the upper skin, the corrugated core, and the lower skin. The bearing bore may be configured to receive a motor shaft to drive (rotate) the rotor.

While the example shown in <FIG> includes a corrugated core <NUM> encased between an exterior skin comprising separate upper and lower skin parts <NUM>, <NUM>, in some alternative embodiments a corrugated core as disclosed herein may be enclosed within an outer rotor skin comprising more or fewer pieces.

<FIG> is a diagram illustrating an embodiment of a corrugated lift fan rotor. In the example shown, the corrugated core <NUM> of <FIG> is shown in conceptual horizontal cross- section. In various embodiments, a corrugated rotor core as disclosed herein, such as corrugated core <NUM>, includes upper cap portions bonded to an inner surface of the upper skin <NUM>, lower cap portions bonded to an inner surface of the lower skin <NUM>, and web portions extending between the upper cap and lower cap portions. As shown in <FIG>, a horizontal cross-section of a corrugated rotor core as disclosed herein includes regions where web portions of the corrugate core are present and voids between them. In various embodiments, increased strength and rigidity are provided by the corrugated core where material comprising the core is present, while leaving voids such as those shown in <FIG> enables a relatively lightweight rotor to be provided.

<FIG> is a diagram illustrating an embodiment of a corrugated lift fan rotor. In the example shown, a portion of corrugated core <NUM> is shown in vertical cross-section. As shown, the illustrated portion of corrugated core <NUM> includes upper cap portions bonded to the inner surface of upper skin <NUM>, lower cap portions bonded to the inner surface of lower skin <NUM>, and web portions running (vertically in this example) between the upper and lower cap portions.

While an "omega" cross-section is shown in <FIG>, in various embodiments and corrugation cross-sectional shape or pattern may be used, including without limitation an "I", an "M", or any other cross-section or combination thereof by which a corrugated core may span between the respective inner surfaces of an upper and lower rotor skin without filling completely the interior space between the upper and lower skin.

<FIG> is a diagram illustrating an embodiment of a corrugated lift fan rotor. Specifically, the portion of corrugated core <NUM> shown in <FIG> is shown without the upper and lower skins <NUM>, <NUM> being shown, to enable parts of the cross-section to be labeled. As shown, the illustrated portion of corrugate core <NUM> includes an upper cap portion <NUM>, lower cap portions <NUM>, and web portions <NUM>.

While composite materials are described herein as being used in various embodiments to provide a corrugated rotor as disclosed herein, in various embodiments other materials may be used to provide one or more of the upper skin, corrugated core, and lower skin. For example, the upper and lower skin may comprise a lightweight metal such as aluminum or titanium. In some embodiments, the corrugated core may be formed from sheet metal and/or by bending or otherwise shaping material that is corrugated, such as honeycombed or otherwise corrugated aluminum or other lightweight metal. In various embodiments, a corrugated core as disclosed herein may be fabricated by extrusion, molding, casting, machining, milling, bending, stamping, or any process and/or combination thereof that defines a corrugation structure as disclosed herein.

<FIG> is a diagram illustrating an embodiment of a corrugated lift fan rotor core. Corrugated core <NUM> includes a central rosette portion associated with a central disk of the lift fan rotor and left/right blade portions. Each of the respective portions include upper cap portions <NUM> that interface with (e.g., contact and may be bonded to) the inner surface of the upper skin (not shown in <FIG>), lower cap portions <NUM>, and web portions <NUM> extending between adjacent upper cap portions <NUM> and lower cap portions <NUM>.

As the example in <FIG> shows, in various embodiments, a corrugated rotor core as disclosed herein may have any arbitrary shape. For example, the upper and lower cap portions <NUM>, <NUM> may have any shape and curvature, e.g., as required to conform to a corresponding shape of an inner surface of a rotor skin to which the corrugated core may be designed to conform. In addition, the height of web portions <NUM> may vary as needed to conform to the height of the space between the respective inner surfaces of the upper and lower skins.

In some embodiments, in assembling a lift fan comprising the corrugated core <NUM> of <FIG>, a bearing bore having tapered teeth on the outer cylinder surface of the bearing bore is inserted in the center of the central rosette portion of corrugated core <NUM>. The tapered teeth engage with and may be bonded to corresponding tapered corrugation structures of the corrugated core <NUM>, specifically the tapered "hat" shaped inner ends of the portions of corrugated core <NUM> that defined the inner hole of the corrugated core <NUM>, to provide strength and rigidity and strong mechanical coupling to the core <NUM>.

<FIG> is a diagram illustrating an embodiment of a corrugated lift fan rotor core. Specifically, the corrugated core <NUM> of <FIG> is shown with dashed tangent lines (instead of solid tangent lines as shown in <FIG>), to further illustrate and highlight features of the corrugated core <NUM>.

<FIG> is a diagram illustrating an embodiment of a bearing bore. In the example shown, bearing bore <NUM> includes a plurality of teeth <NUM> that extend radially from a central bore <NUM>. In various embodiments, the teeth <NUM> are of a size and shape that complements openings in a rosette portion of an associated corrugated lift fan rotor core, such as core <NUM> of <FIG>.

<FIG> is a diagram illustrating an embodiment of a bearing bore and a corrugated lift fan rotor core. In the example shown, vertical dotted lines show how the bearing bore <NUM> mates to the corrugated lift fan rotor core <NUM> of <FIG>.

<FIG> is a diagram illustrating an embodiment of an electric aircraft comprising a plurality of corrugated lift fan rotors. In the example shown, aircraft <NUM> includes a fuselage <NUM> and wings <NUM>. Three underwing mounting booms <NUM> are mounted under each wing <NUM>, and on the forward and aft end of each mounting boom a lift fan <NUM> and associated motor (not shown) is mounted. A pusher type propeller <NUM> provides thrust for forward flight. Aircraft <NUM> includes tail structures <NUM> extending aft from the inboard booms <NUM>. Flight control surfaces <NUM>, <NUM>, and <NUM> provide stability and control during forward flight.

In various embodiments, one or more of the lift fans <NUM> and the propeller <NUM> comprises a corrugated rotor as disclosed herein. For example, in various embodiments, lift fans <NUM> comprise a corrugated lift fan rotor as illustrated in one or more of <FIG>.

Using techniques disclosed herein, a rotor that is durable and lightweight may be provided.

Claim 1:
A rotor (<NUM>), comprising:
an upper skin (<NUM>);
a lower skin (<NUM>); and
an at least partly corrugated core (<NUM>; <NUM>) encased between the upper skin (<NUM>) and the lower skin (<NUM>),
wherein the core (<NUM>; <NUM>) includes a first portion associated with a central disk portion of the rotor and a second portion associated with one or more rotor blade portions of the rotor, and
wherein the first portion comprises a rosette comprising a plurality of corrugated structures that extend radially from a central bore hole of the rotor.