Patent Description:
Angle of attack sensors with rotatable vanes are installed on the exterior of an aircraft to measure the aircraft angle of attack, the angle between oncoming airflow and the aircraft zero line (a reference line of the aircraft, such as a chord of a wing of the aircraft). The angle of attack sensor is mounted to the aircraft such that the rotatable vane protrudes outside the aircraft and is exposed to oncoming airflow. Aerodynamic forces acting on the rotatable vane cause the vane to align with the direction of the oncoming airflow. Rotational position of the vane is sensed and used to determine the aircraft angle of attack.

Dampers are utilized in angle of attack sensors to assist with proper functioning of the angle of attack sensor. Tolerances among components within the damper result in implicit variation among dampers. Such variation results in variations in the angle of attack sensor's dynamic response, or the vane's response to the removal of deflecting forces.

<CIT> describes a rotary viscous damper that provides damping force constancy over the operating temperature range of a viscous working fluid includes a damper housing defining a stationary conical damping surface, a shaft member rotatably mounted in the damper housing, a rotor member having a rotating conical damping surface, a temperature compensation mechanism, and a bias spring.

According to a first aspect of the invention, a damper assembly for an angle of attack sensor includes a rotor including a conical portion, a damper housing in which the rotor is positioned, the damper housing being axially adjustable with respect to the rotor and including a tapered interior surface that matches a profile of the conical portion and interior housing threading on an interior surface of the damper housing, a body having a portion positioned in the damper housing, the body connected to the damper housing to form a chamber between the body and the damper housing, wherein the rotor is located within the chamber, and wherein the body includes exterior threading, and a locking mechanism adjacent the damper housing to fix the damper housing with respect to the rotor.

The damper assembly of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:.

In general, the present disclosure describes an angle of attack sensor that has a damper assembly including a rotor having a conical portion and a damper housing having a tapered interior surface matching the profile of the conical portion, the damper housing being movable with respect to the rotor to adjust the gap between the rotor and the damper housing. The damper assembly also includes a locking mechanism to fix the damper housing with respect to the rotor once the desired gap width is achieved. As a result, the damper assembly can be adjusted to account for implicit variation that results from mechanical tolerances and tolerance in damper fluid viscosity, or to change the dynamic performance characteristics of the damper.

<FIG> is a partial cross-sectional view of angle of attack sensor <NUM>. Angle of attack sensor <NUM> includes faceplate <NUM>, housing <NUM>, vane <NUM>, vane shaft <NUM>, counterweight <NUM>, damper assembly <NUM>, which includes sensor <NUM>, and connector <NUM>.

Faceplate <NUM> of angle of attack sensor <NUM> is about flush with the surface, or skin, of an aircraft when angle of attack sensor <NUM> is installed on an aircraft. Faceplate <NUM> is positioned on housing <NUM>. Housing <NUM> is cylindrical with an annular sidewall between an open first end and a closed second end. Faceplate <NUM> is positioned on the open first end of housing <NUM>. Vane <NUM> is rotatable and extends through faceplate <NUM> into external airflow. Vane <NUM> may be wedge-shaped, airfoil-shaped, or any other suitable shape. Vane <NUM> is part of a vane assembly attached to vane shaft <NUM>. A first end of vane shaft <NUM> is connected to vane <NUM>. Vane shaft <NUM> extends into housing <NUM>. Counterweight <NUM> is mounted on vane shaft <NUM> within housing <NUM>. As such, vane <NUM>, vane shaft <NUM>, and counterweight <NUM> are configured to rotate together. A second end of vane shaft <NUM> is connected to damper assembly <NUM>. In this embodiment, damper assembly <NUM> is aligned with vane shaft <NUM>, or the center axis of rotation of vane <NUM>. In alternate embodiments, damper assembly <NUM> may be offset from vane shaft <NUM>. Damper assembly <NUM> is a mechanical damper. In this embodiment, damper assembly <NUM> includes sensor <NUM> aligned with vane shaft <NUM>. Vane shaft <NUM> is coupled to sensor <NUM>. Sensor <NUM> may be a resolver, an RVDT, or any other suitable sensor. Sensor <NUM> is electrically connected to connector <NUM> via wiring (not shown). Connector <NUM> is connected to a flight computer (not shown).

Angle of attack sensor <NUM> is installed on the exterior of an aircraft and mounted to the aircraft via fasteners, such as screws or bolts, and mounting holes on faceplate <NUM>. As a result, an exterior surface of faceplate <NUM> is about flush or just below flush with the skin of the aircraft, and housing <NUM> extends within an interior of the aircraft. Vane <NUM> extends out from the exterior of the aircraft and is exposed to oncoming airflow, causing vane <NUM> to rotate with respect to faceplate <NUM> via a series of bearings within angle of attack sensor <NUM>. Vane <NUM> rotates based on the angle the aircraft is flying at relative to the oncoming airflow. More specifically, vane <NUM> rotates to be parallel with oncoming airflow. Vane <NUM> causes rotation of vane shaft <NUM>, which is coupled to sensor <NUM> to measure the local angle of attack or angle of the airflow relative to the fixed aircraft structure. Counterweight <NUM> is mounted on vane shaft <NUM> to counterbalance vane <NUM>. Damper assembly <NUM> controls how vane <NUM> responds to oncoming airflow. Damper assembly <NUM> minimizes oscillation of vane <NUM> that can result from an impulse load or impulse deflection to vane <NUM>, thus providing damping to angle of attack sensor <NUM>. Connector <NUM> communicates the angle of attack measurement to a flight computer so that angle of attack measurements may be utilized.

<FIG> is a cross-sectional view of damper assembly <NUM> of angle of attack sensor <NUM>. Damper assembly <NUM> includes sensor <NUM>, damper shaft <NUM>, body <NUM>, rotor <NUM>, damper housing <NUM>, chamber <NUM>, gap <NUM>, fill fluid <NUM>, fill port <NUM>, fill screw <NUM>, seal <NUM>, spring <NUM>, and locking mechanism <NUM>. Body <NUM> includes exterior threading <NUM>. Rotor <NUM> includes cylindrical portion <NUM> and conical portion <NUM>. Damper housing <NUM> includes tapered interior surface <NUM>, interior housing threading <NUM>, and exterior housing threading <NUM>. Locking mechanism <NUM> includes threaded ring portion <NUM> and teeth <NUM>.

A first end of damper shaft <NUM> is connected to vane shaft <NUM> (shown in <FIG>), which is connected to vane <NUM> (shown in <FIG>). Damper shaft <NUM> extends through body <NUM>. In this embodiment, body <NUM> is a body of sensor <NUM>. In alternate embodiments, body <NUM> is a housing separate from sensor <NUM>. A second end of damper shaft <NUM> is connected to rotor <NUM>. Rotor <NUM> may be affixed to damper shaft <NUM> or may be integral to damper shaft <NUM>. Rotation of rotor <NUM> is coupled with rotation of vane <NUM>. A portion of body <NUM> and rotor <NUM> are positioned in damper housing <NUM>. Damper housing <NUM> is connected to body <NUM> to form chamber <NUM> between body <NUM> and damper housing <NUM>. Chamber <NUM> is a cavity in damper assembly <NUM>. Rotor <NUM> is located within chamber <NUM>. Damper housing <NUM> and rotor <NUM> also form gap <NUM>, which is part of chamber <NUM>, between rotor <NUM> and damper housing <NUM>. Fill fluid <NUM> fills, or is located within, chamber <NUM>. As such, fill fluid <NUM> also fills gap <NUM>. Fill fluid <NUM> is a viscous damping fluid. Fill port <NUM> is an opening in damper housing <NUM>. Fill port <NUM> extends from an exterior surface of damper housing <NUM> to an interior surface of damper housing <NUM> at chamber <NUM>. Fill screw <NUM> is positionable in fill port <NUM>. Seal <NUM> is located between damper housing <NUM> and body <NUM>. Spring <NUM> is also positioned between damper housing <NUM>, near a first end of damper housing <NUM>, and body <NUM>. Spring <NUM> is an annular wave spring. Locking mechanism <NUM> is adjacent damper housing <NUM> and body <NUM>. In this embodiment, locking mechanism <NUM> is a locking ring positioned around damper housing <NUM> and body <NUM>. In alternate embodiments, locking mechanism <NUM> may be a locking patch, a fastener, a lock washer, staking, or any other suitable locking mechanism.

Body <NUM> has exterior threading <NUM> on an exterior surface of body <NUM>. In this embodiment, exterior threading <NUM> is threading on an annular surface of body <NUM> between a first end and a second end of body <NUM>. Rotor <NUM> has cylindrical portion <NUM> connected to conical portion <NUM>. Cylindrical portion <NUM> is also connected to damper shaft <NUM>. As such, a first end of cylindrical portion is connected to damper shaft <NUM>, and a second end of cylindrical portion <NUM> is connected to a first end of conical portion <NUM>. Conical portion <NUM> has a tapered profile, such that conical portion <NUM> has an angled sidewall between the first end and a second end of conical portion <NUM>. Conical portion <NUM> is adjacent tapered interior surface <NUM> of damper housing <NUM>. Tapered interior surface <NUM> is a tapered, or angled, surface of a wall of damper housing <NUM> near a second end of damper housing <NUM>. Tapered interior surface <NUM> matches the profile of conical portion <NUM>. As such, tapered interior surface <NUM> is annular and adjacent the sidewall of conical portion <NUM>. Gap <NUM> is the space between the angled sidewall of conical portion <NUM> and the angled surface of tapered interior surface <NUM>. Gap <NUM> is sized to be small enough to develop a shear gradient.

Interior housing threading <NUM> is threading on an interior surface of damper housing <NUM> near the first end of damper housing <NUM>. Interior housing threading <NUM> couples, or engages, with exterior threading <NUM> of body <NUM>. Spring <NUM> is positioned between damper housing <NUM> and body <NUM> adjacent interior housing threading <NUM> of damper housing <NUM> and threading <NUM> of body <NUM>. Exterior housing threading <NUM> is threading on an exterior surface of damper housing <NUM> near the first end of damper housing <NUM>. Exterior housing threading <NUM> couples, or engages, with threaded ring portion <NUM> of locking mechanism <NUM>. Threaded ring portion <NUM> is a ring-shaped portion of a locking ring defining locking mechanism <NUM> with threading on an inner diameter of threaded ring portion <NUM>. Teeth <NUM> extend out of a top of threaded ring portion <NUM> and contact spring <NUM> and body <NUM> when threaded ring portion <NUM> is threaded onto damper housing <NUM>. Locking mechanism <NUM> may have any number of teeth <NUM>.

Damper shaft <NUM> rotates as vane shaft <NUM> rotates along with rotation of vane <NUM>. Rotor <NUM> rotates as damper shaft <NUM> rotates. As such, rotor <NUM> rotates in chamber <NUM> as vane <NUM> rotates in response to oncoming airflow. Fill fluid <NUM> in chamber <NUM> exerts a shear force on spinning rotor <NUM> at gap <NUM> to cause damping. Fill screw <NUM> is removable to expose fill port <NUM>, which is used to add fill fluid <NUM> and evacuate entrapped air from chamber <NUM>. Seals <NUM> prevent leakage of fill fluid <NUM> outside damper assembly <NUM>.

Damper housing <NUM> can be moved, or adjusted, relative to rotor <NUM> to vary the width of gap <NUM>. Damper housing <NUM> is adjusted axially using the threaded interface between interior housing threading <NUM> of damper housing <NUM> and exterior threading <NUM> of body <NUM>. Damper housing <NUM> is moved axially via threading or unthreading damper housing <NUM> onto or from body <NUM> to vary the width of gap <NUM>, which affects damping performance. For example, if vane <NUM> is underdamped, or vane <NUM> excessively overshoots the home position of <NUM> degrees after an impulse force or deflection is applied, damper housing <NUM> can be tightened, or further threaded, to body <NUM> to decrease the width of gap <NUM>. As a result, damping characteristics are adjusted, causing vane <NUM> to overshoot <NUM> degrees to a lesser extent. Therefore, damper housing <NUM> is adjusted with respect to rotor <NUM> to achieve the desired width of gap <NUM>, or the width of gap <NUM> that results in the desired damping characteristics.

Once the desired width of gap <NUM> is achieved, locking mechanism <NUM> is utilized. Locking mechanism <NUM> fixes damper housing <NUM> to body <NUM>, and thus fixes damper housing <NUM> with respect to rotor <NUM>, after adjustment. In this embodiment, locking mechanism <NUM> is a locking ring and threaded ring portion <NUM> of the locking ring is threaded onto exterior housing threading <NUM>. As threaded ring portion <NUM> is threaded onto damper housing <NUM>, teeth <NUM> are forced into engagement with spring <NUM> and lock onto body <NUM>. Spring <NUM> biases damper housing <NUM> axially to one side of exterior threading <NUM> of body <NUM> for consistency, minimizing variation of gap <NUM>, and fixes rotation of damper housing <NUM> with respect to body <NUM> while tightening, or threading, locking mechanism <NUM> onto damper assembly <NUM>.

When vane <NUM> (shown in <FIG>) is released after being displaced by oncoming airflow or other environmental inputs, vane <NUM> needs to return to near <NUM> degrees within a certain time (the time constant), without oscillating too much, in order for angle of attack sensor <NUM> to provide accurate angle of attack readings to the aircraft's flight computer. A properly functioning damper assembly <NUM> causes vane <NUM> to return to near <NUM> degrees within an appropriate amount of time without excessively overshooting <NUM> degrees, or without overshooting <NUM> degrees at all.

Traditionally, damper assemblies have a fixed gap between the damper housing and a cylindrical rotor. Damping precision is affected by the viscosity of the fill fluid and the width of the gap between the rotor and the damper housing. The viscosity of the fill fluid is generally fixed but can vary with temperature. The width of the gap varies due to mechanical part tolerances, such as the tolerance of the rotor and the tolerance of the damper housing. Thus, implicit variation exists in fluid viscosity and gap width that directly impacts the overall damper tolerance. As a result, a traditional damper assembly having a fixed gap has a limited ability to achieve a precise damping performance.

Damper assembly <NUM> allows for more control over damping performance by allowing for variation in the width of gap <NUM>, which changes, or fine tunes, the damping performance. Width of gap <NUM> can be adjusted to account for implicit design characteristics in damper assembly <NUM>, such as variation in the viscosity of fill fluid <NUM> and the tolerances of damper housing <NUM> and rotor <NUM>. Once the desired and precise damping performance characteristics (optimal time constant and overshoot) have been achieved, gap <NUM> is fixed and damper assembly <NUM> has the optimal dynamic response. Damper assembly <NUM> may be customized and interchangeable, as a single set of parts is able to achieve different damping profiles. As a result, damper assembly <NUM> is also more cost-effective, allows for easy replacement, and increases design cycle efficiency.

<FIG> is a cross-sectional view of offset damper assembly 22A. Damper assembly 22A includes damper shaft 28A, body 30A, rotor 32A, damper housing 34A, chamber 36A, gap 38A, fill fluid 40A, fill port 42A, fill screw 44A, seal 46A, and locking mechanism 50A. Body 30A includes exterior threading 52A. Rotor 32A includes cylindrical portion 54A and conical portion 56A. Damper housing 34A includes tapered interior surface 58A, interior housing threading 60A.

Damper assembly 22A is offset from, or not directly connected to, vane shaft <NUM> (shown in <FIG>), or the center axis of rotation of vane <NUM> (shown in <FIG>). As such, damper assembly 22A is connected to vane shaft <NUM> and sensor <NUM> by gears, pulleys, or any other suitable connection. Damper shaft <NUM> extends through body 30A, which is a housing separate from sensor <NUM> (shown in <FIG>), and is connected to rotor 32A. Damper assembly 22A is not directly connected to sensor <NUM>. A portion of body 30A and rotor 32A are positioned in damper housing 34A, which is connected to body 30A to form chamber 36A. Rotor 28A is located within chamber 36A. Rotor 32A rotates in chamber 36A as vane <NUM> rotates in response to oncoming airflow. Gap <NUM> is between rotor 32A and damper housing 34A. Fill fluid 40A fills chamber 36A and gap 38A exerts a shear force on spinning rotor 32A at gap 38A to cause damping. Fill port 42A is an opening in damper housing 34A used to add fill fluid 40A and evacuate entrapped air from chamber 36A, and fill screw 44A is positionable in fill port 42A. Seal 46A is located between damper housing 34A and body 30A to prevent leakage of fill fluid <NUM>. Locking mechanism 50A is adjacent damper housing 34A and body 30A. In this embodiment, locking mechanism 50A is a locking patch, such as Loctite, positioned between exterior threading 52A of body 30A and interior housing threading 60A on an interior surface of damper housing 34A. In alternate embodiments, locking mechanism <NUM> may be a locking ring, a fastener, a lock washer, staking, or any other suitable locking mechanism.

Rotor <NUM> has cylindrical portion 54A connected to conical portion 56A. Cylindrical portion 54A is also connected to damper shaft 28A. Conical portion 56A has a tapered profile, such that conical portion 56A has an angled sidewall between the first end and a second end of conical portion 56A. Conical portion 56A is adjacent tapered interior surface 58A of damper housing 34A. Tapered interior surface 58A is a tapered, or angled, surface of a wall of damper housing 34A. Tapered interior surface 58A matches the profile of conical portion 56A. Gap 38A is the space between the angled sidewall of conical portion 56A and the angled surface of tapered interior surface 58A. Gap 38A is sized to be small enough to develop a shear gradient.

Interior housing threading 60A couples, or engages, with exterior threading 52A of body 30A. Damper housing 34A can be moved, or adjusted, relative to rotor <NUM> to vary the width of gap 38A. Damper housing 34A is adjusted axially using the threaded interface between interior housing threading 60A of damper housing 34A and exterior threading 52A of body 30A, such as by threading or unthreading damper housing 34A onto or from body 30A. Therefore, damper housing 34A is adjusted with respect to rotor 32A to achieve the desired width of gap 38A, or the width of gap 38A that results in the desired damping characteristics. Subsequently, locking mechanism <NUM> is used to fix damper housing 34A to body 30A, fixing damper housing 34A with respect to rotor 32A.

Damper assembly 22A allows for more control over damping performance by allowing for variation in the width of gap 38A, which changes, or fine tunes, the damping performance. Width of gap 38A can be adjusted to account for implicit design characteristics in damper assembly 22A, such as variation in the viscosity of fill fluid 40A and the tolerances of damper housing 34A and rotor 32A. Once the desired and precise damping performance characteristics (optimal time constant and overshoot) have been achieved, gap 38A is fixed and damper assembly 22A has the optimal dynamic response. Damper assembly <NUM> may be customized and interchangeable, resulting in cost-effectiveness, easier replacement, and increased design cycle efficiency. Further, because damper assembly 22A is not directly connected to a vane shaft and a sensor, damper assembly 22A is more adaptable and can be installed in a greater amount of applications.

A damper assembly for an angle of attack sensor includes a rotor including a conical portion; a damper housing in which the rotor is positioned, the damper housing being configured to be adjusted axially with respect to the rotor and including a tapered interior surface that matches a profile of the conical portion; and a locking mechanism adjacent the damper housing.

The damper assembly of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
The locking mechanism is configured to fix the damper housing with respect to the rotor.

The locking mechanism is a locking ring.

An adjustable gap between the tapered interior surface and the conical portion of the rotor.

The adjustable gap is adjusted by axially adjusting the damper housing with respect to the rotor.

The damper housing includes interior housing threading on an interior surface of the damper housing.

The damper assembly is connectable to a vane shaft of the angle of attack sensor.

The damper assembly is directly connectable to the vane shaft of the angle of attack sensor.

The damper assembly is indirectly connectable to the vane shaft of the angle of attack sensor.

Rotation of the rotor is coupled with rotation of a vane of the angle of attack sensor.

A damper assembly for an angle of attack sensor includes a shaft; a body surrounding the shaft and including exterior threading on an exterior surface of the body; a damper housing including: interior housing threading engageable with the exterior threading of the body; and a tapered interior surface; and a rotor connected to an end of the shaft and located between the body and the tapered interior surface of the damper housing, the rotor including a conical portion adjacent the tapered interior surface of the damper housing.

The damper assembly of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
The tapered interior surface of the damper housing matches a profile of the conical portion.

The adjustable gap is adjusted by threading or unthreading the damper housing and the body.

A locking mechanism adjacent the body and the damper housing.

The locking mechanism is configured to fix the damper housing with respect to the rotor.

A spring located between the damper housing and the body.

The damper shaft is directly connectable to a vane shaft of an angle of attack sensor.

The damper assembly is indirectly connectable to a vane shaft of the angle of attack sensor.

A method of adjusting a damper assembly of an angle of attack sensor includes moving a damper housing axially with respect to a rotor to adjust a width of a gap between the damper housing and the rotor of a damper assembly; and fixing the damper housing with respect to the rotor using a locking mechanism.

The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
Moving the damper housing axially to adjust a width of the gap between the damper housing and a rotor of the damper assembly includes threading or unthreading the damper housing from a body adjacent the damper housing.

Fixing the damper housing with respect to the rotor includes threading a locking ring onto the damper housing.

The gap is formed between a conical portion of the rotor and a tapered interior surface of the damper housing.

Claim 1:
A damper assembly (<NUM>; 22A) for an angle of attack sensor (<NUM>), the damper assembly (<NUM>; 22A) comprising:
a rotor (<NUM>; 32A) including a conical portion (<NUM>; 56A);
a damper housing (<NUM>; 34A) in which the rotor (<NUM>; 32A) is positioned, the damper housing (<NUM>; 34A) being axially adjustable with respect to the rotor (<NUM>; 32A) and including a tapered interior surface (<NUM>; 58A) that matches a profile of the conical portion (<NUM>; 56A) and interior housing threading (<NUM>; 60A) on the interior surface (<NUM>; 58A) of the damper housing (<NUM>; 34A);
a body (<NUM>; 30A) having a portion positioned in the damper housing (<NUM>; 34A), the body (<NUM>; 30A) connected to the damper housing (<NUM>; 34A) to form a chamber (<NUM>; 36A) between the body (<NUM>; 30A) and the damper housing (<NUM>; 34A), wherein the rotor (<NUM>; 32A) is located within the chamber (<NUM>; 36A), wherein the damper housing and the rotor form a gap (<NUM>), wherein the gap (<NUM>) is part of the chamber (<NUM>; 36A) and is between the rotor (<NUM>; 32A) and the damper housing (<NUM>; 34A) and wherein the body (<NUM>; 30A) includes exterior threading; and
a locking mechanism (<NUM>) adjacent the damper housing (<NUM>; 34A) to fix the damper housing (<NUM>; 34A) with respect to the rotor (<NUM>; 32A).