A rotary system includes a retention member and a flexible yoke having an opening forming a bridge. The rotary system is further provided with two bearing assemblies, a first bearing assembly extending through the opening of the yoke and configured to secure a rotor blade to the retention member and a second bearing assembly extending through the opening of the flexible yoke and configured to secure the rotor blade to the bridge. The second bearing element includes a bearing element having a first surface forming a spherical contouring and an opposing integral second surface forming a conical contouring.

BACKGROUND

1. Field of the Invention

The present application relates generally to rotary systems, and more particularly, to a rotary system having one or more bearing assemblies. The present application is well suited for use in the field of aircraft, for example, helicopters, tiltrotor, and other rotary wing aircraft.

2. Description of Related Art

Conventional rotary systems are well known in the art for effectively reacting movement of an aircraft during flight. The rotary systems utilize a hub retention assembly as the primary structural for driving torque to and reacting loads created by a plurality of rotor blades rotatably attached thereto. In some embodiments, the rotary system employs one or more bearing assemblies to react blade forces exerted on the retention member, for example, lead/lag, coning, feathering, and centrifugal blade forces.

The above bearing assemblies typically include an arrangement of elastomeric material for reacting to the rotor blade forces. In one known embodiment, the bearing assembly is provided with an axisymmetric spherical bearing element disposed between layers of elastomeric material to facilitate stability and to further control the bearing assembly. U.S. Pat. No. 5,601,408 illustrates an articulated rotor system of the type described above and is generally indicative of the current state-of-the art rotary system with a bearing assembly having an axisymmetric bearing element.

Although great strides have been made in rotary assemblies, many shortcomings remain.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The system of the present application overcomes common disadvantages associated with conventional rotary systems. Specifically, the rotary system provides effective means for reacting rotor blade forces exerted on the retention member, namely, centrifugal, flapping, feathering, lead/lag, coning, and/or other blade forces. To achieve these features, the rotary system comprises at least one bearing assembly having a bearing element disposed between elastomeric materials. In the preferred embodiment, the bearing element is manufactured with two different opposing surface contouring: a spherical surface and a conical surface. The rotary system is further provided with a flexible yoke, which in turn provides further reaction of the blade forces.

Referring now to the drawings wherein like reference characters identify corresponding or similar elements throughout the several views,FIGS. 1 and 2show two different rotary aircraft utilizing the rotary system of the present application.FIG. 1depicts a side view of a helicopter101, whileFIG. 2depicts an oblique view of a tiltrotor aircraft201.

Helicopter101comprises a rotary system103carried by a fuselage105. One or more rotor blades107operably associated with rotary system103provide flight for helicopter101and are controlled with a plurality of controllers within fuselage105. For example, during flight a pilot can manipulate the cyclic controller109for changing the pitch angle of rotor blades107and/or manipulate pedals111, thus providing vertical, horizontal, and yaw flight movement.

Tiltrotor aircraft201includes two or more rotary systems203having a plurality of proprotors205and carried by rotatable nacelles. The rotatable nacelles provide means for allowing aircraft201to takeoff and land like a conventional helicopter and for horizontal flight like a conventional fixed wing aircraft. It should be understood that, like helicopter101, tiltrotor aircraft201is provided with controls, e.g., cyclic controllers and pedals, carried within the cockpit of fuselage207, for reacting movement of the aircraft.

Referring next toFIGS. 3 and 4in the drawings, a rotary system301according to the preferred embodiment of the present application is shown.FIG. 3depicts a top view of rotary system301, whileFIG. 4depicts a cross-sectional view of rotary system301taken at IV-IV ofFIG. 3.

It will be appreciated that rotary system301efficiently reduces, if not eliminates, the adverse effects of the rotor blade forces exerted against the rotary system during flight. It should be understood the both rotary system103and203include the features of rotary system301. Thus, the features of rotary system301discussed herein are utilized in rotary systems for helicopters, tilt rotor aircraft, and other types of rotary aircraft.

Rotary system301includes a plurality of rotor blades303operably associated with a retention member305. Retention member305is driven by an aircraft engine rotatably coupled to a rotor mast (not shown) and is manipulated via a swashplate (not shown) during flight. In the illustrative embodiment, rotary system301is shown having four rotor blades303; however, the present application contemplates more or less rotor blades in an alternative embodiment.

For ease of description, not all of the required systems and devices operably associated with rotary system301are shown and discussed. Examples of such system include, but are not limited to, sensors, connectors, power sources, mounting supports, circuitry, software, control systems, and the like, which are not all shown in order to clearly depict the novel features of the rotary system of the present application. However, it should be understood that the rotary system disclosed herein is operably associated with these and other required systems and devices for operation, as conventionally known in the art, although not discussed in detail nor depicted in the drawings.

Retention member305includes a flexible yoke307for securing the rotor blades303thereto. For ease of description, only a portion of yoke307, rotor blade303, and operably associated components of system301are depicted and discussed in detail. However, it should be understood that the yoke members, rotor blades, and other components of rotary system301are substantially similar in form and function, and include the features discussed herein.

It will be appreciated that yoke307is preferably manufactured with flexible material, e.g., laminate and/or fiberglass material, that allows for flexure as blade forces are exerted thereagainst. One of the unique features of Yoke307is an opening309extending the thickness therethrough. Opening309forms a bridge311that receives the root of the rotor blade and a bearing assembly. More specifically, a blade grip313is utilized to attach a root portion315of rotor blade303to bridge311. In the preferred embodiment, a first bearing assembly317elastically couples grip313to retention member305, while a second bearing319elastically couples grip313to bridge311. Further discussion of these bearing assemblies is provided below. It should be understood that the combination of a flexible yoke and the bearing assemblies provides efficient means for reacting the blade forces exerted against the retention member during flight.

Referring specifically toFIG. 4, bearing assembly317is selectively positioned between a top spoke arm401and a bottom spoke arm403of retention member305. Bearing assembly317comprises one or more of a bearing405securely bonded to a housing407that in turn is rigidly attached to both spoke arms401and403. Bearing405securely receives and attaches to a grip support member409secured to a base portion411of grip313. In the preferred embodiment, bearing405is a radial shear bearing formed with layers of elastomeric material. An optional feature would include a plurality of rigid shims layered within the elastomeric material for providing a desired shear resistance.

Grip313comprises a top plate413, a bottom plate415, and a pitch horn417, which all integrally attach to base portion411. Both plates413and415provide efficient means for attaching blade root315therebetween in any convenient manner, for example with bolts. Disposed between plates413and415, and positioned within opening309, is bearing assembly319.

In the exemplary embodiment, bearing assembly319is provided with a housing419and a support member421. InFIGS. 5A-5B, various views of bearing assembly319are illustrated. Bearing assembly319further comprises a bearing501securely held in positioned with housing419and support421. Bearing501includes a bearing element503, a first elastomeric material505, and a second elastomeric material507. As is depicted, first elastomeric material505is sandwiched between a first surface509of bearing element503and a surface511of housing419, while the second elastomeric material507is sandwiched between a second surface513of bearing element503and a surface515of support421. The elastomeric material is preferably bonded through a vulcanization process; however, alternative bonding means could easily be employed in different embodiments. It will be appreciated that the elastomeric materials505and507take the form of the surfaces being bonded thereto. An optional feature would include a plurality of rigid shims517and519layered within respective elastomeric material505and507for adding additional support and rigidity.

InFIG. 5B, bearing element503is shown comprising a first section521having a spherical profile and a second section523having a conical section, wherein the conical contouring includes a larger diameter near section521and gradually decreases away therefrom. It will be appreciated that the selective contouring of bearing element503allows compensation for lead/lag, flapping, and one-half of the feathering blade forces relative to the spherical contouring, while allowing for a single moment of freedom relative to the conical contouring to react for one-half of the remaining feathering blade forces.

InFIGS. 6A-6C, various view of an alternative embodiment of bearing assembly317is shown. Bearing assembly601is similar to bearing assembly319, wherein both bearing assemblies utilize a bearing element disposed between elastomeric material for reacting blade loads during flight. In this exemplary embodiment, bearing assembly601includes an anti-symmetrical bearing element603having two opposing contoured surfaces605and607.

InFIG. 6B, surface605is formed of a curved profile having a center focal point C1, while surface607is formed of a curved profile having a center focal point C2. In the illustrative embodiment, center focal point C1is offset from center focal point C2; thus, forming an anti-symmetrical bearing element. It will be appreciated that one of the unique features of bearing element603is that the bearing element takes less space than conventional spherical elements.

Referring toFIG. 6B, element603is shown securely bonded to a housing609and a support member611. Disposed between element603and housing609is a first elastomeric material613bonded to the outer surface615of element603and an inner surface617of housing609. A second elastomeric material619is disposed between outer surface615and an inner surface621of member611. In the preferred embodiment, bonding of elastomeric material613and619is achieved through a vulcanization process; however, it should be appreciated that other bonding process could be utilized in lieu of the preferred embodiment. An optional feature would include layering a plurality of rigid shims within the elastomeric material for adding additional support and rigidity.

Referring next toFIG. 7in the drawings, a flowchart701depicting the preferred process is shown. Box703comprises the first step, which includes providing a rotary system having a retention member with a flexible yoke forming an opening. The next step includes attaching the blade grip to the flexible yoke with a first and a second bearing assembly, as depicted in box705. The bearing assemblies are selective attached to the bridge, as depicted in box707. Finally, the first and second bearing assemblies are adapted to control the blades forces exerted on the retention member, namely, centrifugal, feathering, coning, and lead/lag blade forces, as depicted in boxes709and711.