Patent Description:
Linkage assemblies for coupling aircraft wings to an aircraft fuselage include several components. Each of these components is manufactured to a tolerance that is defined by the manufacturing techniques used to manufacture the component. The tolerance represents the expected range of actual dimensions of the component relative to the designed or desired dimensions. For example, a component may be designed to have a length of <NUM> with a tolerance of plus or minus <NUM>. Accordingly, any given part manufactured with such tolerances may be as short as <NUM> or as long as <NUM>.

<CIT> describes an articulated chain with alternating outer chain links and inner chain links, which are connected to one another via chain joints. The outer chain links have two outer plates arranged parallel and at a distance from one another; the outer plates have two bolt openings arranged at a distance from one another in the longitudinal direction of the link (L), in each of which a hinge pin of the chain joints is fixedly arranged. The inner chain links have two inner links arranged parallel and at a distance from one another. Inner plates are arranged in a loose fit on a hinge pin. The outer plates have at least one expansion opening between the pin openings.

<CIT> describes an aircraft including a fuselage, a wing, and a decoupled joint interconnecting the fuselage and the wing. A method of adapting an aircraft to attenuate forces between a main wing and a fuselage thereof includes providing a plurality of sensors upon the aircraft, configured for sensing motion and/or mechanical stress of the main wing and/or the fuselage and producing signals indicative thereof, and providing a plurality of active suspension elements interconnecting the wing and the fuselage, the active suspension elements being configured to move in response to the signals to adjust a position of the wing with respect to the fuselage.

<CIT> describes a wing connection to a fuselage of an airplane, the connection having a plurality of double-jointed coupling members. At least two z-coupling members running substantially parallel to a vertical axis of the airplane and at least two xz-coupling members are arranged in the area of two longitudinal edges of a fuselage recess. The xz-coupling members are constructed parallel to a longitudinal axis of the airplane for a first load maximum of a load in the case of a crash and also of a load during normal flight operation, and are constructed parallel to a vertical axis (z) of the airplane for a second load maximum of a load in the case of a crash and also of a load during normal flight operation. The xz-coupling members are capable of receiving force components parallel to the longitudinal (x-) axis of the airplane, as well as force components which are parallel to the z-axis.

<CIT>discloses a wing-fuselage connection for an aircraft, in which a wing arranged in the upper region of the fuselage is connected to the fuselage by means of a number of connections. The connections are provided for absorbing forces in different directions and each have a maximum load-carrying capacity; the load-carrying capacity of the individual wing connections and their force absorption direction are coordinated with one another in such a way that if one connection is defective, the maximum load-carrying capacity of the remaining connections is sufficient for safe normal flight operations.

As the number of components in the linkage assemblies increases, the tolerances add or stack. As the tolerances stack, the linkage assembly has more clearance between components. This clearance leads to "free play," or the ability of the parts to move relative to each other due to the accumulated tolerances of the components. Joint free play produces audible noise during load reversals as the various components impact each other within the joint.

One solution for reducing the free play is to manufacture the components with tighter tolerances. Manufacturing to tighter tolerances, however, adds cost to the manufactured part and part rejections during quality checks.

Accordingly, it is desirable to provide linkage assemblies that produce less audible noise than is produced by conventional linkage assemblies. In addition, it is desirable to reduce the audible noise without the increased costs associated with tighter tolerances. Furthermore, other desirable features and characteristics will become apparent from the subsequent summary and detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.

An aircraft, an aircraft linkage assembly, and a method of reducing noise in a linkage assembly during operation of an aircraft are disclosed herein.

In a first non-limiting embodiment, an aircraft includes a fuselage, a wing extending out from the fuselage, and a joint coupling the wing to the fuselage. The joint includes a first fitting fixed to the fuselage, a second fitting fixed to the wing, a link assembly pivotably coupled to the first fitting and to the second fitting, and a strap coupled to the link assembly at the first fitting and at the second fitting based on the free play clearance as defined by the manufacturing of the link assembly. The link assembly is configured to support the wing during operation of the aircraft and has a free play clearance defined by a manufacturing of the joint falling within a designed dimensional tolerance of the joint. The strap is further configured to bias the link assembly to restrict movement of the link assembly within the free play clearance during load reversal in the joint.

In another non-limiting embodiment, a joint for a structure subjected to load reversal between a first structure and a second structure includes a first fitting, a second fitting, a link assembly, and a strap. The first fitting is fixed to the first structure. The second fitting is fixed to the second structure. The link assembly is pivotably coupled to the first fitting and to the second fitting. The link assembly has a free play clearance defined by a manufacturing of the joint and falling within a designed dimensional tolerance of the joint. The strap is coupled to the link assembly at the first fitting and at the second fitting based on the free play clearance as defined by the manufacturing of the link assembly and interfacing hardware. The strap is further configured to bias the link assembly to restrict movement of the link assembly within the free play clearance during load reversal in the joint.

In another non-limiting embodiment, a method of reducing noise in a joint during operation of an aircraft includes installing a linkage assembly between a fuselage and a wing of the aircraft to support the wing. The method further includes preloading the linkage assembly. The method further yet includes determining a free play clearance in the linkage assembly due to manufacturing tolerance stacking. The method further yet includes fabricating a strap based on the free play clearance. The method further yet includes installing the strap on the linkage assembly such that the strap biases the linkage assembly to restrict free play movement during pressurized flight of the aircraft.

The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and.

Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

In general, the embodiments described herein include vibration alleviation systems for structural assemblies with free play subjected to load reversals. The embodiments load a joint with free play under pre-load thereby reducing the intensity of vibration during load reversals.

One example of a pre-loading system includes a strap assembly with at least six components. In some embodiments, the six components are two straps and four strap fittings. A conventional link assembly is first installed and held under a certain loading condition. While under the loading condition, the strap assembly is fabricated and installed on the link assembly such that strap assembly is pre-stressed when the pre-load is removed during operation, thereby reducing the intensity of vibration and noise. These embodiments reduce the reliance on tighter tolerance hardware traditionally used to eliminate free play in the joint.

A greater understanding of the embodiments may be obtained through a review of the illustrations accompanying this application together with a review of the detailed description that follows.

<FIG> is an exploded perspective view of an aircraft assembly <NUM>. Aircraft assembly <NUM> may be any type of fixed wing aircraft including, without limitation, a subsonic aircraft, a supersonic aircraft, a propeller driven aircraft, a jet powered aircraft, a commercial airliner, a private business jet, a cargo aircraft, a military aircraft, and any other type of aircraft where wings are supported by a joint between the fuselage and the wing. Additionally, although the joint of the present disclosure is being described and explained in the context of its application for linking aircraft wings to fuselages, it should be understood that the joints of the present disclosure are not limited to connections between fuselages and wings. Rather, the joints of the present disclosure may be used on any type of structure that experiences load reversal during operation. The linkage assemblies are not limited to use in vehicles and may be employed in other applications unrelated to vehicles such as, and without limitation, buildings and bridges.

Aircraft assembly <NUM> includes a fuselage <NUM>, a wing <NUM>, and a joint <NUM>. Fuselage <NUM> and wing <NUM> are similar to conventional components of an aircraft. In the example provided, fuselage <NUM> and wing <NUM> are coupled in a low wing configuration on a transport category aircraft. As will be appreciated by those of ordinary skill in the art, wing <NUM> extends outward from fuselage <NUM> and is supported by fuselage <NUM> through at least one joint <NUM>.

Referring now to <FIG>, and with continued reference to <FIG>, joint <NUM> is illustrated in a cross-section view. Joint <NUM> couples wing <NUM> to fuselage <NUM>. Joint <NUM> includes a first fitting <NUM>, a second fitting <NUM>, a link assembly <NUM>, and straps <NUM>.

First fitting <NUM> is fixed to fuselage <NUM>. As used herein, the term "fixed to" means non-rotatably and non-slidingly connected together to act as a single piece. First fitting <NUM> defines a pair of flanges <NUM> extending out toward second fitting <NUM>. Flanges <NUM> are configured to receive link assembly <NUM>. In the example provided, flanges <NUM> are parallel to each other with a space between flanges <NUM> sized to accommodate link assembly <NUM>. Each of flanges <NUM> defines a fitting aperture <NUM>. Fitting aperture <NUM> is configured to receive components of link assembly <NUM> for pivotably coupling link assembly <NUM> to first fitting <NUM>.

Second fitting <NUM> is fixed to wing <NUM>. Second fitting <NUM> is similar to first fitting <NUM>, where like numbers refer to like components. Second fitting <NUM>, however, is oriented such that flanges <NUM> of second fitting <NUM> extend away from wing <NUM> toward fuselage <NUM>.

Link assembly <NUM> includes a link bar <NUM>, shear pins <NUM>, bolts <NUM>, washers <NUM>, and bushings <NUM>. Link assembly <NUM> pivotably couples to first fitting <NUM> and to second fitting <NUM> to support wing <NUM> during operation of the aircraft. Link assembly <NUM> has a free play clearance defined by a manufacturing of each individual joint <NUM> assembled, as will be shown in <FIG>. The free play clearance falls within a designed dimensional tolerance of joint <NUM> according to the engineered design of joint <NUM>.

Link bar <NUM> has two end portions <NUM> that each accommodate a bearing <NUM>. Each of end portions <NUM> defines a link aperture <NUM> in which bearings <NUM> are disposed. In some embodiments, bearings <NUM> are omitted. Each of end portions <NUM> is located between flanges <NUM> of the respective fitting <NUM> or <NUM> when joint <NUM> is assembled. Bearings <NUM> or link aperture <NUM> are configured to accommodate shear pin <NUM> to secure link bar <NUM> to flanges <NUM> of the respective fitting <NUM> or <NUM>.

Shear pins <NUM> are at least partially disposed within fitting aperture <NUM> and at least partially disposed within link aperture <NUM> and bearing <NUM>. During operation of the aircraft, forces on fuselage <NUM> and wing <NUM> act on fitting <NUM> or <NUM>, respectively. The fitting transfers the forces to shear pin <NUM> at fitting apertures <NUM> of flanges <NUM>. Shear pin <NUM> transfers the forces to bearing <NUM> and link bar <NUM> at link aperture <NUM>. Link bar <NUM> transfers the forces to the other end portion <NUM> where the forces transfer to the other fitting <NUM> or <NUM> through the other shear pin <NUM> in a similar but reversed manner.

Shear pins <NUM> each define a bolt aperture <NUM> that is coaxial with a longitudinal direction of the respective shear pin <NUM>. Bolt aperture <NUM> is configured to receive bolt <NUM>.

Bolt <NUM> restricts disassembly of link joint <NUM> and secures straps <NUM> to link assembly <NUM>. In the example provided, bolt <NUM> directly passes through straps <NUM>, washers <NUM>, and shear pin <NUM>. Bolt <NUM> is secured within joint <NUM> by a nut <NUM>.

Straps <NUM> act as a link coupled in parallel with link assembly <NUM> between first fitting <NUM> and second fitting <NUM>. In the example provided, straps <NUM> are flat metal bars that elastically deform to bias the link assembly during operation of the aircraft.

Straps <NUM> define strap apertures <NUM> through which bolt <NUM> passes. Strap apertures <NUM> are drilled after link assembly <NUM> is coupled to fittings <NUM> and <NUM> and a pre-load is applied between the fittings <NUM> and <NUM>. For example, wing <NUM> may be installed onto fuselage <NUM> using link assembly <NUM>. Wing <NUM> supports fuselage <NUM> through wing mounted landing gear. Accordingly, gravity pulls fuselage <NUM> down toward wing <NUM>, resulting in a compressive load in link assembly <NUM>. The compressive load reverses to a tensile load after pressurization of fuselage <NUM> at cruise altitude of the aircraft.

The compressive load transfers through shear pin <NUM>. Accordingly, bolt <NUM> may be removed if it was already installed during assembly of joint <NUM>. Strap apertures <NUM> are then drilled based on the free play clearance as defined by the manufacturing of the link assembly. For example, the distance between bolt apertures <NUM> may be measured to determine the drilling locations of strap apertures <NUM>. By measuring the distance after assembly, the actual dimensions as manufactured may be accounted for in the strap aperture placement. As loads on joint <NUM> change, straps <NUM> bias link assembly <NUM> to restrict movement of link assembly <NUM> within the free play clearance during load reversal in joint <NUM>.

In the example provided, strap apertures <NUM> have a diameter that is substantially the same as a diameter of bolts <NUM>. Strap apertures <NUM> are also aligned with bolt <NUM> when link assembly <NUM> is loaded by a predetermined pre-load, such as the compressive load on joint <NUM> while the aircraft is stationary on the ground.

Referring now to <FIG>, and with continued reference to <FIG>, operation of a joint <NUM> is illustrated in simplified cross-section views. Joint <NUM> is similar to joint <NUM>, where like numbers refer to like components. Joint <NUM>, however, does not include straps <NUM>.

<FIG> illustrates a joint <NUM> under a compressive load, such as when wings <NUM> are supporting fuselage <NUM> on the ground. The compressive load presses fitting <NUM> against an outer side (fitting side) of shear pin <NUM>. The compressive load also presses link bar <NUM> against an inner side (link bar side) of shear pin <NUM>. A first free play clearance <NUM> is at least partially defined by a difference in dimensions between an inner surface of fitting aperture <NUM> and an outer surface of shear pin <NUM>. A second free play clearance <NUM> is at least partially defined by a difference in dimensions between an inner surface of bearing <NUM> and an outer surface of shear pin <NUM>. Second free play clearance <NUM> may be also partially defined by a difference in dimensions between an outer dimension of bearing <NUM> and an inner dimension of link aperture <NUM>.

In <FIG>, joint <NUM> is in tension. For example, joint <NUM> may be in tension when the aircraft is flying at cruise altitude and pressurization of a cabin of the aircraft causes fuselage shape changes that permit joint <NUM> to go into in tension during load reversals. The tensile load pulls fitting <NUM> against an inner side of shear pin <NUM>. The tensile load also pulls link bar <NUM> against an inner side of shear pin <NUM>. As can be easily seen by comparing <FIG> with <FIG>, the components of joint <NUM> move within the free clearance areas during load reversals between compression and tension.

Referring now to <FIG>, and with continued reference to <FIG>, joint <NUM> is illustrated in operating conditions. In the operating conditions where the load on wing <NUM> is close to zero load (substantially low), straps <NUM> apply tension to joint <NUM> to bias link assembly <NUM> to a limit of the free play clearance <NUM>. Link assembly <NUM> is in compression during operating conditions from tension in straps <NUM>. For example, even when load reversals on wing <NUM> would cause link assembly <NUM> to be in tension, link assembly <NUM> remains in compression from straps <NUM> pulling bolt <NUM> against an inner side of bolt aperture <NUM> and to the inside of link assembly <NUM>. Accordingly, shear pin <NUM> is biased against an inner side of fitting aperture <NUM>.

In the example provided, straps <NUM> are configured to continuously bias link assembly <NUM> to the limit of the free play clearance during predetermined wing loading conditions of joint <NUM> during operation of the aircraft. In other words, the expected loads on wing <NUM> during typical reversals are not sufficient to put the link assembly <NUM> in tension.

It should be appreciated that the location and size of the free clearances may vary without departing from the scope of the present disclosure. Alternative assembly components may be incorporated in some embodiments.

Referring now to <FIG>, and with continued reference to <FIG>, the forces in joint <NUM> and in joint <NUM> alternating between compression and tension during operation are illustrated in graph <NUM>. Line <NUM> represents forces in joint <NUM>. As load reversal occurs about zero load line <NUM>, components of joint <NUM> move within free clearance areas <NUM> and <NUM>, represented by zero load box <NUM>. When the components have traversed to the other side of the free clearance areas, the components forcefully contact each other. This forceful contact results in audible noise for occupants of the aircraft.

Line <NUM> represents forces in joint <NUM>. As load reversal occurs, forces in joint <NUM> remain in compression as shown in <FIG> and biased against one side of the free clearance areas. Accordingly, the forces never reach zero load line <NUM> and the components do not forcefully contact each other and do not traverse the free clearance area.

Referring now to <FIG>, and with continued reference to <FIG>, forces in joint <NUM> are illustrated during a flight of the aircraft. The flight has several phases, including on ground taxi phase <NUM>, climbing phase <NUM>, and cruise phase <NUM>. In ground phase <NUM>, forces <NUM> on link bar <NUM> are compressive, while forces <NUM> on strap <NUM> are substantially zero.

As the aircraft progresses through climb phase <NUM>, the atmospheric pressure decreases and the cabin pressurizes. As pressurization occurs, forces <NUM> become tensile in joint <NUM>. As link assembly <NUM> elongates in elastic deformation, strap <NUM> also elongates and compresses link assembly <NUM> enough to keep link assembly <NUM> in compression, but less than enough to make the typical load in link assembly greater than substantially low relative to the designed load capacity of link assembly <NUM>. During the cruise phase <NUM>, turbulence causes load reversal at wings <NUM>. Because straps <NUM> are biasing link assembly <NUM>, forces <NUM> do not become tensile.

Referring now to <FIG>, and with continued reference to <FIG>, a method <NUM> of reducing noise in a joint during operation of an aircraft is illustrated in flow diagram form. Task <NUM> includes installing a linkage assembly between a fuselage and a wing of the aircraft to support the wing. For example, task <NUM> may include coupling wing <NUM> to fuselage <NUM> with joint <NUM> before installation of straps <NUM>.

Task <NUM> includes preloading the linkage assembly. For example, joint <NUM> is pre-loaded while wings <NUM> support the weight of fuselage <NUM> on the ground.

Task <NUM> includes determining a free play clearance in the linkage assembly due to manufacturing tolerance stacking. In the example provided, determining the free play clearance in the linkage assembly is determining the location of the bolt within the linkage assembly after pre-loading the linkage assembly. For example, strap apertures <NUM> may be marked for drilling based on the locations of bolt apertures <NUM> in the pre-loaded joint <NUM>.

Task <NUM> includes fabricating a strap based on the free play clearance. In the example provided, fabricating the strap further includes drilling bolt apertures in the strap based on a location of a bolt within the linkage assembly after pre-loading the linkage assembly. For example, strap apertures <NUM> may be drilled based on the locations of bolt apertures <NUM> in the pre-loaded joint <NUM>.

Task <NUM> includes installing the strap on the linkage assembly such that the strap biases the linkage assembly to restrict free play movement during pressurized flight of the aircraft. For example, straps <NUM> may be secured to link assembly <NUM> with bolts <NUM>.

Claim 1:
A joint (<NUM>) for a structure subjected to load reversal between a first structure and a second structure, the joint comprising:
said first and second structures;
a first fitting (<NUM>) fixed to the first structure in such a manner that the first fitting and the first structure are non-rotatably and non-slidingly connected together to act as a single piece;
a second fitting (<NUM>) fixed to the second structure in such a manner that the second fitting and the second structure are non-rotatably and non-slidingly connected together to act as a single piece;
a link assembly (<NUM>) pivotably coupled to the first fitting and to the second fitting, the link assembly having a free play clearance defined by a manufacturing of the joint and falling within a designed dimensional tolerance of the joint; and
a strap (<NUM>) coupled to the link assembly (<NUM>) at the first fitting (<NUM>) and at the second fitting (<NUM>) based on the free play clearance as defined by the manufacturing of the link assembly, the strap further configured to bias the link assembly to restrict movement of the link assembly within the free play clearance during load reversal in the joint,
wherein the strap is further configured to bias the link assembly to a limit of the free play clearance an operating state of an aircraft, where the first structure is a fuselage (<NUM>) of an aircraft and the second structure is a wing (<NUM>) of the aircraft.