Patent Description:
Aircraft typically employ nose-wheel steering systems to steer the aircraft while taxiing on the ground. A typical nose-wheel steering system includes a collar gear provided upon a strut associated with the nose-wheel. Various actuators and gear trains may be associated with rotating the collar gear, and hence the strut, thereby adjusting the orientation of the nose-wheel to affect steering (i.e., the direction of the taxiing aircraft). Current actuator and gear train arrangements typically include a rack and pinion type mechanism that converts linear movement of a rack into to rotary movement. These arrangements are relatively large and, therefore, add weight and space claim to the landing gear and are not always easy to accommodate with other landing gear components. Further, these larger actuator and gear train arrangements may not be aesthetically pleasing.

<CIT> discloses an actuator comprising: two motors; an output member; and a harmonic gear comprising: an elliptical wave generator component; a flexible spline component which is coupled to the wave generator by a bearing and flexes to conform to the elliptical shape of the wave generator; and a circular spline component which surrounds and meshes with the flexible spline component.

<CIT> discloses a steering device for the landing gear of an aircraft, said steering device being characterised in that it comprises at least one means which is used to rotate the wheels of the landing gear and is arranged along the strut of the landing gear.

According to an aspect, a nose-wheel steering system as recited in claim <NUM> is disclosed herein.

Further, optional features are recited in each of claims <NUM> to <NUM>.

According to an aspect, a shock strut assembly for an aircraft landing gear assembly as recited in claim <NUM> is also disclosed herein.

Further, optional features are recited in claim <NUM>.

According to an aspect, a nose landing gear assembly as recited in claim <NUM> is also disclosed herein.

Further, optional features are recited in claims <NUM> and <NUM>.

The features and elements as well as the operation of the disclosed embodiments will become more apparent in light of the following description and accompanying drawings.

The accompanying drawings illustrate various embodiments employing the principles described herein and are a part of the specification. The illustrated embodiments are meant for description and not to limit the scope of the claims.

It should also be understood that unless specifically stated otherwise, references to "a," "an," or "the" may include one or more than one and that reference to an item in the singular may also include the item in the plural.

With reference to <FIG>, an aircraft <NUM> is illustrated. In accordance with various embodiments, aircraft <NUM> may include one or more landing gear assemblies, such as, for example, a left landing gear assembly <NUM> (or port-side landing gear assembly), a right landing gear assembly <NUM> (or starboard-side landing gear assembly) and a nose landing gear assembly <NUM>. Each of left landing gear assembly <NUM>, right landing gear assembly <NUM>, and nose landing gear assembly <NUM> may support aircraft <NUM> when not flying, allowing aircraft <NUM> to taxi, takeoff, and land safely and without damage to aircraft <NUM>. In various embodiments, left landing gear assembly <NUM> may include a left shock strut assembly <NUM> and a left wheel assembly <NUM>, right landing gear assembly <NUM> may include a right shock strut assembly <NUM> and a right wheel assembly <NUM>, and nose landing gear assembly <NUM> may include a nose shock strut assembly <NUM> and a nose wheel assembly <NUM>. One or more pilot steering input(s) <NUM> (e.g., steering wheels, pedals, knobs, or the like) may be located in a cockpit of aircraft <NUM>.

Referring now to <FIG>, nose landing gear assembly <NUM> is illustrated. In accordance with various embodiments, shock strut assembly <NUM> of nose landing gear assembly <NUM> includes a strut cylinder <NUM> and a strut piston <NUM>. Strut piston <NUM> may be operatively coupled to strut cylinder <NUM>. Strut cylinder <NUM> may be configured to receive strut piston <NUM> in a manner that allows the two components to telescope with respect to one another. Strut piston <NUM> may translate into and out strut cylinder <NUM>, thereby absorbing and damping loads imposed on nose landing gear assembly <NUM>. An axle <NUM> of nose wheel assembly <NUM> may be coupled to an end of strut piston <NUM> that is opposite strut cylinder <NUM>. The nose wheels have been removed from nose wheel assembly <NUM> in <FIG> to more clearly illustrate the features of shock strut assembly <NUM>.

In various embodiments, nose landing gear assembly <NUM> may include a torque link <NUM> coupled to shock strut assembly <NUM> and/or to axle <NUM>. Torque link <NUM> includes a first (or upper) arm <NUM> and a second (or lower) arm <NUM>. First arm <NUM> is pivotably coupled to second arm <NUM>. Strut cylinder <NUM> is coupled to an attachment linkage <NUM> configured to secure shock strut assembly <NUM> to the aircraft <NUM> and to translate nose landing gear assembly <NUM> between the landing gear up and landing gear down positions. Nose landing gear assembly <NUM> may include one or more drag brace(s) such as drag brace <NUM>. In various embodiments, drag brace <NUM> may be located proximate an aft side of shock strut assembly <NUM>. Nose landing gear assembly <NUM> may include one or more hydraulic fluid lines (i.e. conduits), such as hydraulic fluid line <NUM>.

In accordance with various embodiments, nose landing gear assembly <NUM> includes a nose-wheel steering system <NUM>. Nose-wheel steering system <NUM> is operably coupled to nose wheel assembly <NUM> via shock strut assembly <NUM>. In this regard, and as described in further detail below, nose-wheel steering system <NUM> is configured to rotate strut piston <NUM> about a piston axis of rotation A (also reference to as "axis A"), thereby adjusting the orientation of the nose wheel assembly <NUM> and the taxiing direction of the aircraft <NUM>. Axis of rotation A may be parallel to the direction of translation of strut piston <NUM> relative to strut cylinder <NUM>. In various embodiments, axis of rotation A may be generally perpendicular to the axis of rotation W of nose wheel assembly <NUM>. As used in the previous context only, "generally perpendicular" means ±<NUM>° from perpendicular.

Nose-wheel steering system <NUM> includes a steering collar housing <NUM>, a gear assembly housing <NUM>, and an actuator housing <NUM>. In various embodiments, gear assembly housing <NUM> and actuator housing <NUM> may include a generally cylindrical shape. For example, a cross-section of gear assembly housing <NUM> and actuator housing <NUM>, taken in a plane parallel to axis of rotation A, may be generally circular. While gear assembly housing <NUM> and actuator housing <NUM> are illustrated as located on an aft-side of steering collar housing <NUM>, the size and/or shape of gear assembly housing <NUM> and actuator housing <NUM>, along with the orientation of the rotating components located in steering collar housing <NUM>, gear assembly housing <NUM>, and actuator housing <NUM> (described in further detail below), allow gear assembly housing <NUM> and actuator housing <NUM> to be located in other locations about axis of rotation A. For example, gear assembly housing <NUM> and actuator housing <NUM> may be located on the forward-side, the port-side, or the starboard-side of steering collar housing <NUM>. In this regard, a location of gear assembly housing <NUM> and actuator housing <NUM> may be selected based not only on available space, but also based on aesthetics.

Referring now to <FIG> and <FIG>, a perspective view and a cross-section view, respectively, of nose-wheel steering system <NUM>, not falling within the scope of the claims, are illustrated. The nose-wheel steering system <NUM> includes a collar gear <NUM>. Collar rear may be located in steering collar housing <NUM>. Collar gear <NUM> is coupled to strut piston <NUM> such that rotation of collar gear <NUM> about axis of rotation A is transferred to strut piston <NUM>. In this regard, rotation of collar gear <NUM> about axis of rotation A causes rotation of strut piston <NUM> about axis of rotation A.

Nose-wheel steering system <NUM> further includes a bevel gear <NUM>. Bevel gear may be located in gear assembly housing <NUM>. Bevel gear <NUM> engages (i.e. is intermeshed with) collar gear <NUM>. Bevel gear <NUM> rotates about a bevel gear axis of rotation B (also referred to as "axis B"). Axis of rotation B is non-parallel to axis of rotation A. In various embodiments, axis of rotation B is generally perpendicular to axis of rotation A of collar gear <NUM>. As used in the previous context only, "generally perpendicular" means ±<NUM>°.

Bevel gear <NUM> is operably coupled to an actuator <NUM>. Actuator <NUM> is configured to drive rotation of bevel gear <NUM> about axis of rotation B. Actuator <NUM> includes a drive shaft <NUM> rotationally coupled to bevel gear <NUM>. In this regard, rotation of drive shaft <NUM> about axis of rotation B drives rotation of bevel gear <NUM> about axis of rotation B, which in turn drives rotation of collar gear <NUM> about axis of rotation A.

In various embodiments, actuator <NUM> comprises a single vane hydraulic rotary actuator. In this regard, and with additional reference to <FIG>, actuator <NUM> includes a rotating vane <NUM> and a stationary vane <NUM>. Stationary vane <NUM> is attached to, and/or may be integral with, actuator housing <NUM>. Rotating vane <NUM> rotates relative to stationary vane <NUM> and about axis of rotation B. Drive shaft <NUM> is coupled to, and/or may be integral with, rotating vane <NUM>. In this regard, rotation of rotating vane <NUM> drives rotation of drive shaft <NUM>.

In accordance with various embodiments, rotation of rotating vane <NUM> is controlled via hydraulic pressure. In various embodiments, actuator <NUM> includes a first hydraulic chamber <NUM> and a second hydraulic chamber <NUM>. First hydraulic chamber <NUM> is defined, at least partially, by an inner circumferential surface 258a of actuator housing <NUM>, a first radially extending surface 254a of rotating vane <NUM>, and a first radially extending surface 256a of stationary vane <NUM>. Second hydraulic chamber <NUM> is defined, at least partially, by inner circumferential surface 258a of vane housing <NUM>, a second radially extending surface 254b of rotating vane <NUM>, and a second radially extending surface 256b of stationary vane <NUM>. First radially extending surface 254a of rotating vane <NUM> is opposite (i.e., oriented away from) second radially extending surface 254b of rotating vane <NUM>. First radially extending surface 256a of stationary vane <NUM> is opposite (i.e., oriented away from) second radially extending surface 256b of stationary vane <NUM>.

First hydraulic chamber <NUM> is fluidly connected to a first conduit <NUM>. Second hydraulic chamber <NUM> is fluidly connected to a second conduit <NUM>. A control valve assembly <NUM> is operably connected to first and second conduits <NUM>, <NUM>. Control valve assembly <NUM> is configured to control the flow of hydraulic fluid to and from each of first hydraulic chamber <NUM> and second hydraulic chamber <NUM>. Control valve assembly <NUM> may include a servo valve, one or more solenoid valve(s), or any valve or combination of valves suitable for controlling the flow volume and direction of flow to and from first chamber <NUM> and second hydraulic chamber <NUM>. Control valve assembly <NUM> is operably coupled to a steering controller <NUM>. Actuation of control valve assembly <NUM> may be controlled via steering controller <NUM>. Stated differently, steering controller <NUM> is configured to control the opening and closing (i.e., actuation) of control valve assembly <NUM>, thereby controlling the flow of hydraulic fluid to and from each of first hydraulic chamber <NUM> and second hydraulic chamber <NUM>. Steering controller <NUM> is operably coupled to pilot steering input <NUM>. Steering controller <NUM> may send actuation commands to control valve assembly <NUM> based on signals received from pilot steering input <NUM>.

In operation, and with additional reference to <FIG>, first hydraulic chamber <NUM> is pressurized with hydraulic fluid, which forces rotating vane <NUM> to rotate in a first circumferential direction (e.g., counterclockwise) away from first radially extending surface 256a and toward second radially extending surface 256b of stationary vane <NUM>. Rotation of rotating vane <NUM> drives rotation of drive shaft <NUM>, which in turn drives rotation of bevel gear <NUM> in the first circumferential direction. Rotation of the bevel gear <NUM>, which has gear teeth configured to engage gear teeth on collar gear <NUM>, causes the collar gear <NUM> to rotate in a first direction (e.g., a counterclockwise direction) with respect to the axis of rotation A. Rotation of the collar gear <NUM> in the first direction causes strut piston <NUM> to likewise rotate in the first direction, thereby enabling the aircraft <NUM> to turn, for example toward its left (or port-side).

With additional reference to <FIG>, the process is reversed to enable turning the aircraft <NUM> to the right (or starboard-side). That is, the first hydraulic chamber <NUM> is depressurized while the second hydraulic chamber <NUM> is pressurized with hydraulic fluid, which forces rotating vane <NUM> to rotate in a second circumferential direction (e.g., clockwise) away from second radially extending surface 256b and toward first radially extending surface 256a of stationary vane <NUM>, thereby causing drive shaft <NUM> and bevel gear <NUM> to rotate in the second circumferential direction about axis of rotation B, which in turn causes collar gear <NUM> to rotate in a second direction that is opposite the first direction about axis of rotation A.

Employing a single vane actuator tends to reduce the torque associated with the actuator. For example, collar gear <NUM> may be associated with a rotation of ±<NUM>° about axis A. Rotating vane <NUM> may be associated with a rotation of between ±<NUM>° and ±<NUM>° about axis B, between ± <NUM>° and ±<NUM>° about axis B, and/or between ±<NUM>° and between ±<NUM>° about axis A. The greater the difference between the number of degrees rotating vane <NUM> may rotate to produce <NUM> degrees of rotation in collar gear <NUM> decreases the torque requirement of actuator <NUM>. A decreased torque requirement allows for smaller and lighter actuators.

Referring now to <FIG>, a nose-wheel steering system <NUM>, similar to the nose-wheel steering system <NUM> described above with reference to <FIG> and <FIG>, is illustrated. Nose-wheel steering system <NUM> includes a gear train <NUM> operably coupled between drive shaft <NUM> of actuator <NUM> and bevel gear <NUM>. Gear train <NUM> is a planetary (or epicyclic) gear system with drive shaft <NUM> forming the sun gear (or input gear) of the planetary gear system. For example, gear train <NUM> may include one or more planet gear(s) <NUM> engaged (i.e., intermeshed) with drive shaft <NUM> and with a ring gear <NUM> of gear train <NUM>.

Ring gear <NUM> of gear train <NUM> is configured to be a stationary, non-rotating component. Ring gear <NUM> may be coupled to, or otherwise supported by, gear assembly housing <NUM> and/or actuator housing <NUM>. Each planet gear <NUM> is coupled to a carrier <NUM> of gear train <NUM> via a pin <NUM>. In various embodiments, a bearing may be located between the planet gear <NUM> and the pin <NUM>. Pins <NUM> are configured to rotationally couple planet gears <NUM> to carrier <NUM> such that the torque generated by rotation of planet gears <NUM> about an inner circumference of ring gear <NUM> is transferred to carrier <NUM>. Carrier <NUM> is rotationally coupled to bevel gear <NUM> such that rotation of carrier <NUM> is transferred to bevel gear <NUM>. In various embodiments, bevel gear <NUM> may be integral with <NUM>, such that a sloped outer circumferential surface of carrier <NUM> defines the gear teeth of bevel gear <NUM>.

In operation, and with combined reference to <FIG> and <FIG>, first hydraulic chamber <NUM> is pressurized with hydraulic fluid, which forces rotating vane <NUM> to rotate in the first circumferential direction (e.g., counterclockwise) away from first radially extending surface 256a and toward second radially extending surface 256b of stationary vane <NUM>. Rotation of rotating vane <NUM> drives rotation of drive shaft <NUM>, which in turn drives rotation of planet gears <NUM>, which drives rotation of carrier <NUM> and bevel gear <NUM> above axis of rotation B. Rotation of bevel gear <NUM>, which has gear teeth configured to engage gear teeth on collar gear <NUM>, causes the collar gear <NUM> to rotate in a first direction (e.g., a counterclockwise direction) with respect to the axis of rotation A. Rotation of the collar gear <NUM> in the first direction causes strut piston <NUM> to likewise rotate in the first direction, thereby enabling the aircraft <NUM> to turn, for example toward its left (or port-side).

With combined reference to <FIG> and <FIG>, the process is reversed to enable turning the aircraft <NUM> to the right (or starboard-side). That is, the first hydraulic chamber <NUM> is depressurized while the second hydraulic chamber <NUM> is pressurized with hydraulic fluid, which forces rotating vane <NUM> to rotate in a second circumferential direction (e.g., clockwise) away from second radially extending surface 256b and toward first radially extending surface 256a of stationary vane <NUM>, thereby causing drive shaft <NUM>, planet gears <NUM>, carrier <NUM>, and bevel gear <NUM> to rotate in the second circumferential direction about axis of rotation B, which in turn causes collar gear <NUM> to rotate in a second direction opposite direction about axis of rotation A.

Coupling gear train <NUM> between bevel gear <NUM> and actuator <NUM> may further decrease the torque associated with actuator <NUM> rotating strut piston <NUM> about axis A. Decreasing the torque reequipment of actuator <NUM> allows for smaller and lighter actuators.

While actuator <NUM> is illustrated as a single vane hydraulic rotary actuator, in various embodiments, nose-wheel steering system <NUM> in <FIG> and <FIG> or nose-wheel steering system <NUM> in <FIG> may include a dual vane hydraulic rotary actuator <NUM> as illustrated in <FIG> in place of actuator <NUM>. Dual vane hydraulic rotary actuator <NUM> includes a first rotating vane <NUM>, a second rotating vane <NUM>, a first stationary vane <NUM>, and a second stationary vane <NUM>. First and second stationary vanes <NUM>, <NUM> are coupled to, and may be integral with, an actuator housing <NUM> of dual vane hydraulic rotary actuator <NUM>. First and second rotating vanes <NUM>, <NUM> are rotationally coupled to drive shaft <NUM>. In this regard, rotation of First and second rotating vanes <NUM>, <NUM> drives rotation of drive shaft <NUM> about axis of rotation B. A dual vane hydraulic rotary actuator generates approximately double the torque output relative to a single vane hydraulic rotary actuator, assuming pressure and area are constant. However, the range of rotation (e.g., the maximum angular rotation) of a dual vane hydraulic rotary actuator is approximately half the range of rotation of the single vane hydraulic rotary actuator. For example, a single vane hydraulic rotary actuator may have a ±<NUM>° range of rotation, while a dual vane hydraulic rotary actuator may have a ±<NUM>° range of rotation. In this regard, a dual vane actuator may tend to be used more often in steering systems that are associated with a smaller rotation range of the nose wheel assembly <NUM> (e.g., steering systems that are associated with less than or equal to approximately ±<NUM>° of rotation).

Rotation of first and second rotating vanes <NUM>, <NUM> is controlled via hydraulic pressure in manner similar to rotating vane <NUM> in <FIG>. In this regard, a first hydraulic chamber <NUM> and a second hydraulic chamber <NUM> are pressurized with hydraulic fluid, which forces first and second rotating vanes <NUM>, <NUM> to rotate in the first circumferential direction (e.g., counterclockwise), thereby enabling the aircraft <NUM> to turn in a first direction (e.g., to the left or port-side). The process is reversed to enable the aircraft <NUM> to turn in a second opposite direction (i.e., to the right or starboard-side). That is, the first hydraulic chamber <NUM> and second hydraulic chamber <NUM> are depressurized while a third hydraulic chamber <NUM> and a fourth hydraulic chamber <NUM> are pressurized with hydraulic fluid, which forces first and second rotating vanes <NUM>, <NUM> to rotate in the second circumferential direction (e.g., clockwise).

Systems, methods, and apparatus are provided herein.

Numbers, percentages, or other values stated herein are intended to include that value, and also other values that are about or approximately equal to the stated value, as would be appreciated by one of ordinary skill in the art encompassed by various embodiments of the present disclosure. A stated value should therefore be interpreted broadly enough to encompass values that are at least close enough to the stated value to perform a desired function or achieve a desired result. The stated values include at least the variation to be expected in a suitable industrial process, and may include values that are within <NUM>%, within <NUM>%, within <NUM>%, within <NUM>%, or within <NUM>% of a stated value. Additionally, the terms "substantially," "about" or "approximately" as used herein represent an amount close to the stated amount that still performs a desired function or achieves a desired result. For example, the term "substantially," "about" or "approximately" may refer to an amount that is within <NUM>% of, within <NUM>% of, within <NUM>% of, within <NUM>% of, and within <NUM>% of a stated amount or value.

In various embodiments, system program instructions or controller instructions may be loaded onto a tangible, non-transitory, computer-readable medium (also referred to herein as a tangible, non-transitory, memory) having instructions stored thereon that, in response to execution by a controller, cause the controller to perform various operations. The term "non-transitory" is to be understood to remove only propagating transitory signals per se from the claim scope and does not relinquish rights to all standard computer-readable media that are not only propagating transitory signals per se.

Claim 1:
A nose-wheel steering system (<NUM>), comprising:
an actuator (<NUM>) including a drive shaft (<NUM>) configured to rotate about a first axis (B);
a bevel gear (<NUM>) rotationally coupled to the drive shaft (<NUM>) of the actuator (<NUM>) and configured to rotate about the first axis (B);
a collar gear (<NUM>) intermeshed with the bevel gear (<NUM>) and configured to rotate about a second axis (A), the second axis (A) being generally perpendicular to the first axis (B); and
a gear train (<NUM>) rotationally coupled between the drive shaft (<NUM>) of the actuator (<NUM>) and the bevel gear (<NUM>), wherein the gear train (<NUM>) includes a planetary gear system, the planetary gear system comprising:
a non-rotating ring gear (<NUM>);
a planet gear (<NUM>) configured to rotate about an inner circumferential surface of the non-rotating ring gear (<NUM>), wherein rotation of the planet gear (<NUM>) is driven by rotation of the drive shaft (<NUM>) about the first axis (B);
a carrier (<NUM>) coupled to the planet gear (<NUM>) and configured to rotate the bevel gear (<NUM>),
characterised in that an outer circumferential surface of the carrier (<NUM>) defines a toothed surface of the bevel gear (<NUM>), the toothed surface of the bevel gear (<NUM>) being intermeshed with the collar gear (<NUM>), and
wherein the actuator (<NUM>) includes a rotating vane (<NUM>) and a stationary vane (<NUM>), and wherein the rotating vane (<NUM>) is rotationally coupled to the drive shaft (<NUM>).