Uniball bearing with compliant inner member

A spherical bearing which extends from and connects to a deformable component includes an outer member and an inner member. The inner member is pivotable relative to the outer member about an axis. The inner member has an opening formed therein that defines a plurality of coplanar contact surfaces shaped to accommodate and contact the component. The plurality of contact surfaces are movable to accommodate deformation of the component positioned within the opening.

BACKGROUND OF THE INVENTION

Exemplary embodiments of the invention relate to a rotary wing aircraft, and more particularly, to a swashplate for controlling a rotor assembly of a rotary wing aircraft.

Control of a rotary wing aircraft is affected by varying the pitch of the rotor blades individually as the rotor rotates and by varying the pitch of all of the blades together. These are known respectively as cyclic and collective pitch control. Blade pitch control of a rotary wing aircraft is typically achieved through a swashplate assembly which transfers the motion of non-rotating servo-driven control members within to the rotating members.

The swashplate assembly is typically concentrically mounted about a rotor shaft. The swashplate assembly includes two rings connected by a series of bearings with one ring connected to the airframe (stationary), and the other ring connected to the rotor hub (rotating). The rotating ring is connected to the rotor hub through a pivoted link device typically referred to as “scissors”, with the static ring similarly connected to the airframe. The rotating swash plate rotates relative the stationary swash plate. Apart from rotary motion, the stationary and rotating swash plate otherwise move as a unitary component. Collective control is achieved by translating the swash plate assembly up and down with respect to the rotor shaft and cyclic control is achieved by tilting the swash plate relative to the rotor shaft.

The stationary ring is typically mounted about the rotor shaft through a spherical ball joint that allows for tilt of the swash plate assembly, with the rotor shaft allowing translation of the swash plate assembly along the axis. The spherical ball joint requires a running surface to allow for translation along the axis. However, the surface is subject to thermal growth and elastic deformation that may negatively impact operation of the bearing.

BRIEF DESCRIPTION OF THE INVENTION

According to one embodiment of the invention, a spherical bearing which extends from and connects to a deformable component includes an outer member and an inner member. The inner member is pivotable relative to the outer member about an axis. The inner member has an opening formed therein that defines a plurality of coplanar contact surfaces shaped to accommodate and contact the component. The plurality of contact surfaces are movable to accommodate the deformation of the component positioned within the opening.

In addition to one or more of the features described above, or as an alternative, in further embodiments the inner member comprises an elastomeric material.

In addition to one or more of the features described above, or as an alternative, in further embodiments the outer member has a generally concave surface and the inner member has a generally convex surface.

In addition to one or more of the features described above, or as an alternative, in further embodiments a wear liner is disposed on an inner surface of the outer member between the outer member and the inner member.

In addition to one or more of the features described above, or as an alternative, in further embodiments the inner member includes at least one recessed area arranged between adjacent contact surfaces.

In addition to one or more of the features described above, or as an alternative, in further embodiments comprising a liner bonded to at least one of the plurality of contact surfaces of the inner member.

In addition to one or more of the features described above, or as an alternative, in further embodiments the liner comprises a resilient material.

In addition to one or more of the features described above, or as an alternative, in further embodiments the liner comprises a Teflon wear surface.

In addition to one or more of the features described above, or as an alternative, in further embodiments comprising a compressible member positioned within the recessed area between the inner member and the liner.

In addition to one or more of the features described above, or as an alternative, in further embodiments the compressible member biases the liner into contact with a wear surface of the component towards the opening.

According to another embodiment, a rotor system is provided including a rotationally stationary swashplate pivotally mounted about a central pivot point defined along an axis of rotation via a spherical bearing and a rotational swashplate which defines a rotor pitch control point. The rotor pitch control point is defined along an in-line plane which passes through said central pivot point. A bearing system is mounted between said rotationally stationary swashplate and said rotational swashplate. The bearing system includes a spherical bearing for receiving a deformable component. The spherical bearing includes a complementary outer member and an inner member. The inner member is pivotable relative to the outer member about an axis. The inner member has an opening formed therein that defines a plurality of coplanar contact surfaces shaped to accommodate and contact the component. The contact surfaces are movable to accommodate the deformation of the component.

In addition to one or more of the features described above, or as an alternative, in further embodiments the outer member has a generally concave surface and the inner member has a generally convex surface.

In addition to one or more of the features described above, or as an alternative, in further embodiments the inner member comprises an elastomeric material.

In addition to one or more of the features described above, or as an alternative, in further embodiments a wear liner is disposed on an inner surface of the outer member between the outer member and the inner member.

In addition to one or more of the features described above, or as an alternative, in further embodiments comprising a liner bonded to at least one of the plurality of contact surfaces of the inner member.

In addition to one or more of the features described above, or as an alternative, in further embodiments the liner comprises a resilient material.

In addition to one or more of the features described above, or as an alternative, in further embodiments comprising a compressible member positioned within the recessed area between the inner member and the liner.

In addition to one or more of the features described above, or as an alternative, in further embodiments the compressible member biases the liner into contact with a wear surface of the component towards the opening.

In addition to one or more of the features described above, or as an alternative, in further embodiments the rotor system is a portion of an aircraft.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1schematically illustrates an exemplary vertical takeoff and landing (VTOL) rotary-wing aircraft10. The aircraft10in the disclosed, non-limiting embodiment includes a main rotor system12supported by an airframe14having an extending tail which mounts an anti-torque system16such as a tail rotor system. The main rotor system12includes a multiple of rotor blades B mounted to a rotor hub H. The main rotor system12is driven about an axis of rotation A through a main rotor gearbox MRG by one or more engines ENG. The main gearbox MRG may be interposed between the one or more engines ENG, the main rotor system12and the anti-torque system16such that the main rotor system12and the anti-torque system16are both driven by the main gearbox MRG. Although a particular helicopter configuration is illustrated and described in the disclosed embodiment, other configurations and/or machines, such as high speed compound rotary wing aircraft with supplemental translational thrust systems, dual contra-rotating, coaxial rotor system aircraft, turbo-props, tilt-rotors and tilt-wing aircraft, will also benefit from the present invention.

Referring toFIG. 2A, each rotor blade B is mounted to the rotor hub H so as to be flexible about a pitch change axis P. It should be understood that various attachment systems and rotor blade pitch change systems may alternatively or additionally be utilized. Pitch change loads are imparted to each rotor blade B by pitch control rods20. One end section of each pitch control rod20is articulatably connected to the rotor blade B and an opposite end section of the pitch control rod20is articulately connected to a swashplate assembly22. The swashplate assembly22converts control movements in the non-rotating reference frame into the rotating reference frame.

The swashplate assembly22includes a rotationally stationary swashplate24and rotational swashplate26which rotates relative to the rotationally stationary swashplate24through a bearing system25. A stationary scissors assembly28is mounted between the rotationally stationary swashplate24and the airframe14. A rotational scissors assembly30is mounted to the rotational swashplate26and the rotor hub H for rotation therewith (also illustrated inFIG. 2B). The swashplate22receives control inputs through a set of servo control rods32which are each driven by a respective main rotor servo32S. Three main rotor servos32S are typical to allow the swashplate assembly22to move with three degrees of freedom; however, any other number of main rotor servos may alternatively be utilized.

Pitch control commands imparted through the servo control rods32cause tilting of the swashplate assembly22about a uniball34(FIG. 2C) which defines a central pivot point36located along the axis of rotation A. The rotationally stationary swashplate24is mounted to a cylindrical swashplate guide35through the uniball34that permits tilting of the swashplate22about a virtual pivot point36and translation thereof along the axis of rotation A (FIG. 2C). The cylindrical swashplate guide, also referred to herein as “cylindrical guide” is mounted concentrically about, but not in contact with, the rotor shaft37. Tilting of the swashplate assembly22about the central pivot point36imparts pitch change loads to each rotor blade B through the pitch control rods20which are mounted to the rotational swashplate26. Articulation of the swashplate assembly22drives the pitch control rods20which cause the rotor blade B to pitch about the pitch change axis P. Inputs from the servo control rods32cause the swashplate assembly22to axially translate along axis of rotation A to impart pitch control loads to the blades B. When the swash plate assembly22translates along axis A, it imparts a collective pitch change to the blade assemblies and when it tilts about virtual pivot point36, it imparts cyclic pitch change.

Referring now toFIGS. 3 and 4, an example of a uniball or spherical bearing34configured for use with the swashplates22,24is illustrated in more detail. The uniball or spherical bearing34includes an outer race or housing40having an inner surface42configured to accommodate a concave spherical surface. In an embodiment, a wear liner or coating (not shown) may be disposed over the inner surface42of the outer race40to minimize wear and increase the operational life of the bearing34. A generally spherical ball44is positioned within the opening defined by the outer member40. The outer surface46of the spherical ball44is complementary to and dimensioned to contact the inner diameter42of the outer race40. As a result, the inner surface42of the outer member40engages the outer surface46of the spherical ball44. This interface between the spherical ball44and the outer member40serves as the spherical joint and accommodates spherical rotation or pivoting of the spherical bearing34with respect to the cylindrical guide35.

The spherical ball44may be formed from a metallic material and has a generally cylindrical opening48extending from a first end50to a second opposite end52thereof. The opening48defines a translational wear surface of the spherical ball44arranged in sliding contact with a cylindrical guide35positioned within the opening48. In the illustrated, non-limiting embodiment, the portion of the spherical ball44configured to contact the cylindrical guide35is not a continuous surface extending between the first end50and the second end52of the inner member44. Rather, the spherical ball44includes a plurality of contact surfaces56spaced at intervals between the first end50and the second end52of the inner member44.

In an embodiment, at least one pad or liner58is bonded, such as in an overlapping arrangement for example, to one or more of the contact surfaces56of the spherical ball44. For example, as shown inFIGS. 3 and 4, the liner58is positioned over the contact surfaces56closest to the first end50and the second end52of the spherical ball44. Embodiments where a liner58is positioned over one of the intermediary contact surfaces56are also contemplated herein. In an embodiment, the liner58is formed from a resilient material, such as polytetraflourothelyne or other comparable materials for example. The pieces of liner58positioned over the contact surfaces56closest to the first end50and the second end52of the spherical ball44may include a tapered outer edge60configured to facilitate centering of the cylindrical guide35within cylindrical opening48.

One or more recessed areas62are formed in the inner member44between adjacent contact surfaces56. As shown inFIG. 4, the recessed areas62are offset from the plane defined by the contact surfaces56configured to contact cylindrical guide35. Positioned within at least one of the recessed areas62is another liner64. The height of the liner64, measured between the first end50and the second end52of the inner member44, is generally less than the overall height of the recessed area62. In an embodiment, the liner64includes a Teflon wear surface supported on a fiberglass material. A compressible member66, such as formed from an elastomeric or other spring-like material for example, may be positioned between the recessed area62, and the liner64. When the compressible member66is in an uncompressed state, the exposed surface68of the liner64may extend beyond the plane defined by the liner58. As a result, the liner64is biased by the compressible member66into contact with a linear wear surface of the cylindrical guide35disposed within the opening48.

The uniball or spherical bearing34illustrated and described herein provides a means for controlling the fit between the bearing inner member44and the surface of the shaft, while also accommodating deformation of the running surface. Deformation, as used herein may be a result of applied loads and/or thermal growth (i.e. radial expansion and contraction) of the running surface. This adaptability of the spherical bearing34may eliminate the need for traditional swashplate guides and the corresponding hardware, resulting in a more weight efficient design.