Patent Description:
Landing gear assemblies typically comprise a shock strut assembly coupled to a wheel axle having one or more wheels. Steering systems may include push-pull hydraulic cylinders connected to the steering collar via lugs on a lower strut cylinder. A pilot may provide a steering command signal, which commands a steering system, resulting in axle rotation. <CIT> discloses a steering steering angle adjusting device including a steering rack and a double acting hydraulic cylinder within the rack. <CIT> discloses a steering device for an aircraft wheel comprising a rack and a double acting hydraulic cylinder. <CIT> discloses an aircraft steering system comprising a rack and two cylinders, each comprising a liquid filled chamber and an air filled chamber.

A rack assembly for a rack and pinion gear system according to claim <NUM> is disclosed.

The rack is configured to translate in a first direction in response to receiving hydraulic pressure in the first hydraulic chamber and the fourth hydraulic chamber. The rack may be configured to translate in a second direction in response to receiving hydraulic pressure in the second hydraulic chamber and the third hydraulic chamber. The first direction may be opposite the second direction.

A steering system as defined in claim <NUM> is disclosed herein.

In various embodiments, the rack translates toward the second end of the rack housing in response to pressurizing the first hydraulic chamber and the fourth hydraulic chamber. The rack may translate towards the first end of the rack housing in response to pressurizing the second hydraulic chamber and the third hydraulic chamber. The pinion may rotate in response to the rack translating.

In various embodiments, the steering system further comprises a collar coupled to an outer cylinder, the collar operably coupled to the pinion. The collar and the pinion may form a beveled gear interface, and the rack and the pinion form a rack and pinion interface.

The detailed description of exemplary embodiments herein refers to the accompanying drawings, which show exemplary embodiments by way of illustration.

A steering system is disclosed herein. The steering system comprises an outer cylinder, a pinion, collar, and a rack assembly. The rack assembly may be aligned vertically and/or horizontally. The rack assembly may be operatively coupled to the pinion. The collar may be coupled to the outer cylinder. When the pinion is rotated by a steering input device (e.g., a rack assembly), there may be an angular multiplication of the input resulting a mechanical advantage greater than a <NUM>:<NUM> ratio. In doing so, the steering input device may have shorter travel and/or allow for a smaller steering input device. In various embodiments, the rack assembly may include a steering range and a castor range. The rack and pinion assembly may disengage from interfacing teeth from the collar when the collar is in the castor range.

Referring now to <FIG>, an aircraft <NUM> is illustrated. In accordance with various embodiments, the 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 system <NUM>. Each of the left landing gear assembly <NUM>, the right landing gear assembly <NUM> and the nose landing gear system <NUM> may support the aircraft <NUM> when not flying, allowing the aircraft <NUM> to taxi, takeoff and land, safely and without damage to the aircraft. In various embodiments, the left landing gear assembly <NUM> may include a left shock strut assembly <NUM> and a left wheel assembly <NUM>, the right landing gear assembly <NUM> may include a right shock strut assembly <NUM> and a right wheel assembly <NUM> and the nose landing gear system <NUM> may include a nose shock strut assembly <NUM> and a nose wheel assembly <NUM>.

With reference to <FIG>, an aircraft <NUM> having a nose landing gear system <NUM> is illustrated, in accordance with various embodiments. The nose landing gear system <NUM> includes a steering actuator <NUM>. The steering actuator <NUM> is connected to a steering collar <NUM> that is itself connected to a nose shock strut assembly <NUM> and configured to steer the nose landing gear system <NUM>. In various embodiments, the steering actuator <NUM> comprises a steering power source <NUM> (e.g., hydraulic pump or an electric motor). The steering actuator <NUM> may further comprise a rack assembly <NUM> configured to transmit power provided by the steering power source <NUM> to the steering collar <NUM> in order to steer the aircraft <NUM>. In various embodiments, the combination of the steering power source <NUM> and the rack assembly <NUM> comprise an electro-mechanical actuator assembly, a hydraulic actuator assembly, or the like connected to steering collar <NUM> and the nose shock strut assembly <NUM> and configured to steer the aircraft <NUM>.

Referring now to <FIG> and <FIG>, a steering system <NUM>, in accordance with various embodiments, is illustrated. The steering system <NUM> may be a nose landing gear steering system or the like. The steering system <NUM> comprises a rack assembly <NUM>, a steering housing <NUM>, a gear assembly <NUM>, and an outer cylinder <NUM>.

In various embodiments, the gear assembly <NUM> comprises a pinion <NUM> and a shaft <NUM>. The shaft <NUM> extends through, and is coupled to, the steering housing <NUM>. The pinion is operatively coupled to a rack <NUM> in the rack assembly <NUM>. In this regard, the rack <NUM> and the pinion <NUM> form a rack and pinion gear. Thus, the pinion <NUM> is configured to rotate about a centerline defined by the shaft <NUM> in response to linear actuation of a rack <NUM> in the rack assembly <NUM>. Similarly, the pinion <NUM> is operatively coupled to a collar <NUM>. In this regard, the collar <NUM> is configured to rotate about a centerline defined by the outer cylinder <NUM> in response to rotation of the pinion <NUM> about the centerline of the shaft <NUM>.

In various embodiments, the collar <NUM> is coupled to a radially outer surface of the outer cylinder <NUM>. The collar <NUM> may be fixedly coupled to the outer cylinder <NUM> by bushings, or the like.

In various embodiments, the steering housing <NUM> comprises a manifold <NUM>. The manifold <NUM> may be in fluid communication with a hydraulic pump as described further herein.

Referring now to <FIG> only, a cross-sectional view along section A-A from <FIG> is illustrated, in accordance with various embodiments. The rack assembly <NUM> comprises the rack <NUM>, a rack housing <NUM>, hollow rods <NUM>, <NUM>, and a piston <NUM>. The rack <NUM> extends laterally (i.e., in the - Y-direction) from a first end <NUM> to a second end <NUM>. The rack <NUM> at least partially defines a bore <NUM> extending through the rack <NUM> (i.e., extending from the first end <NUM> to the second end <NUM>. The rack <NUM> further comprises a first end cap <NUM> disposed at the first end <NUM> and a second end cap <NUM> disposed at the second end <NUM>.

The piston <NUM> is disposed axially between the first end cap <NUM> and the second end cap <NUM>. The first hollow rod <NUM> is fixedly coupled to, and extends from (i.e., in a lateral direction, or axial direction, Y-direction), a first end <NUM> of the rack housing <NUM> to the piston <NUM>. Similarly, the second hollow rod <NUM> is fixedly coupled to, and extends from (i.e., in a lateral direction, or axial direction, Y-direction), the piston <NUM> to a second end <NUM> of the rack housing.

The rack assembly <NUM> disclosed herein comprises hydraulic chambers <NUM>, <NUM>, <NUM>, and <NUM>. The hydraulic chamber <NUM> is defined axially between the first end <NUM> of the rack housing and the first end cap <NUM> of the rack and radially between a radially outer surface of the first hollow rod <NUM> and a radially inner surface of the rack housing <NUM>. Similarly, the hydraulic chamber <NUM> is defined axially between the second end cap <NUM> of the rack <NUM> and the second end <NUM> of the rack housing <NUM> and radially between a radially outer surface of the second hollow rod <NUM> and a radially inner surface of the rack housing <NUM>.

The hydraulic chamber <NUM> is defined axially between the first end cap <NUM> and the piston <NUM> and radially between the radially outer surface of the first hollow rod <NUM> and a radially inner surface of the rack <NUM>. Similarly, the hydraulic chamber <NUM> is defined axially between the piston <NUM> and the second end cap <NUM> and radially between the radially outer surface of the second hollow rod <NUM> and the radially inner surface of the rack <NUM>.

In various embodiments, each hydraulic chamber (e.g., hydraulic chambers <NUM>, <NUM>, <NUM>, <NUM>) is fluidly isolated from the other hydraulic chambers. For example, the first end cap <NUM> is fixedly coupled to the rack <NUM> and contains a dynamic seal <NUM> disposed in a groove defined by the first end cap <NUM> and configured to fluidly isolate hydraulic chamber <NUM> from hydraulic chamber <NUM>. Similarly, the second end cap <NUM> is fixedly coupled to the rack <NUM> and contains a dynamic seal <NUM> disposed in a groove defined by the second end cap <NUM> and configured to fluidly isolate the hydraulic chamber <NUM> from the hydraulic chamber <NUM>.

The hydraulic chambers <NUM>, <NUM> are fluidly isolated via the piston <NUM>. For example, with brief reference to <FIG>, a detail view of the piston <NUM> within the rack <NUM> is illustrated, in accordance with various embodiments. In various embodiments, a dynamic seal <NUM> is disposed in a groove extending radially inward from a radially outer surface of the piston <NUM>. The dynamic seal <NUM> is configured to fluidly isolate the hydraulic chamber <NUM> from the hydraulic chamber <NUM>.

Referring now to <FIG> and <FIG>, the first hollow rod <NUM> defines a fluid passage <NUM> configured to be in fluid communication with the hydraulic chamber <NUM> and the manifold <NUM> from <FIG>. Similarly, the second hollow rod <NUM> defines a hollow passage <NUM> configured to be in fluid communication with the hydraulic chamber <NUM> and the manifold <NUM> from <FIG>.

In various embodiments, the first hollow rod <NUM> is coupled to the piston <NUM> in tension in response to hydraulic chamber <NUM> being pressurized. Similarly, the second hollow rod <NUM> is coupled to the piston <NUM> in tension in response to hydraulic chamber <NUM> being pressurized. In this regard, the first hollow rod <NUM> and the second hollow rod <NUM> may be alternately in tension during operation of the rack assembly <NUM> during normal operation. Thus, buckling concerns of the first hollow rod <NUM> and second hollow rod <NUM> may be eliminated, in accordance with various embodiments since some axial play exists between the piston <NUM> and the first and second hollow rods <NUM> and <NUM>. In this regard, a rod outer diameter for the hollow rods <NUM>, <NUM> may be minimized to increase a total working area of the rack assembly <NUM>. In various embodiments, shear ring <NUM> may be disposed radially between the first hollow rod <NUM> and a mating surface of the piston <NUM>. Similarly, shear ring <NUM> may be disposed radially between the second hollow rod <NUM> and the piston <NUM>.

Referring now to <FIG>, in order to steer the collar <NUM> from <FIG> for a right turn (i.e., in the positive Y-direction with respect to <FIG>), the hydraulic chamber <NUM> and the hydraulic chamber <NUM> are pressurized (e.g., via a hydraulic pump). In response to pressurizing the hydraulic chamber <NUM> and the hydraulic chamber <NUM>, the rack <NUM> translates laterally in the positive Y-direction. The rack <NUM> translates laterally relative to the rack housing <NUM>, the piston <NUM>, and the hollow rods <NUM>, <NUM>, which remain stationary during the maneuver. Via a rack and pinion gear system, the pinion <NUM> rotates clockwise in response to translation of the rack <NUM> in the positive Y-direction, which in turn rotates the collar <NUM> of <FIG> about the Z axis.

In order to steer the collar <NUM> from <FIG> for a left turn (i.e., in the negative Y-direction with respect to <FIG>), the hydraulic chamber <NUM> and the hydraulic chamber <NUM> are pressurized (e.g., via a hydraulic pump). In response to pressurizing the hydraulic chamber <NUM> and the hydraulic chamber <NUM>, the rack <NUM> translates laterally in the negative Y-direction. Via the rack and pinion gear system, the pinion <NUM> rotates counterclockwise in response to translation of the rack <NUM> in the negative Y-direction, which in turn rotates the collar <NUM> of <FIG> about the Z axis.

In various embodiments, a total working area for hydraulic pressure may be increased by approximately <NUM>% (e.g., total work area in hydraulic chamber <NUM> + total work area in hydraulic chamber <NUM> is approximately <NUM>% greater than a rack assembly having only solid rack (e.g., only two hydraulic chambers).

A rack assembly is provided herein.

Claim 1:
A rack assembly (<NUM>) for a rack and pinion gear system for a steering system, the rack assembly comprising:
a rack housing (<NUM>) extending from a first end (<NUM>) to a second end (<NUM>);
a rack (<NUM>) disposed in the rack housing;
a first hydraulic chamber (<NUM>) defined axially between the first end and the rack;
a second hydraulic chamber (<NUM>) defined axially between the rack and the second end;
a piston (<NUM>) disposed within the rack;
a third hydraulic chamber (<NUM>) disposed within the rack;
a first hollow rod (<NUM>) extending from the first end (<NUM>) to the piston, the first hollow rod configured to supply a first hydraulic pressure to the third hydraulic chamber (<NUM>);
a fourth hydraulic chamber (<NUM>) disposed within the rack;
a second hollow rod (<NUM>) extending from the piston (<NUM>) to the second end, the second hollow rod configured to supply a second hydraulic pressure to the fourth hydraulic chamber (<NUM>);
a first end cap (<NUM>) coupled to the rack (<NUM>) and at least partially defining the first hydraulic chamber (<NUM>) and the third hydraulic chamber (<NUM>); and
a second end cap (<NUM>) coupled to the rack and at least partially defining the fourth hydraulic chamber (<NUM>) and the second hydraulic chamber (<NUM>), wherein:
the piston (<NUM>) at least partially defines the third hydraulic chamber (<NUM>) and the fourth hydraulic chamber (<NUM>), and
the rack (<NUM>) is configured to translate in a first direction in response to receiving hydraulic pressure in the first hydraulic chamber (<NUM>) and the fourth hydraulic chamber (<NUM>).