Aeronautics and astronautics – Aircraft – heavier-than-air – Airplane and helicopter sustained
Reexamination Certificate
1999-08-06
2001-06-19
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Aircraft, heavier-than-air
Airplane and helicopter sustained
C244S056000
Reexamination Certificate
active
06247667
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates in general to tiltrotor aircraft and, in particular, to an actuator for moving a pylon on a tiltrotor aircraft between a generally vertical position for take off and landing and a generally horizontal position for level flight.
BACKGROUND OF THE INVENTION
Without limiting the scope of the invention, the background will describe tiltrotor aircraft, as an example.
In aircraft design, many actuators are required to move certain movable elements of the craft relative to other reaction elements. One example of such a use is in the actuation of flaps on a conventional fixed wing aircraft. As in any aircraft environment, the actuator would ideally be extremely reliable, lightweight, compact and require a minimum energy input for actuation, among other requirements.
One commonly used actuator is the ball screw actuator. Generally, a ball screw actuator includes a nut with internal threads and a screw with external threads. A plurality of spherical balls are captured within the threads of the nut and engage the threads on the screw. Rotation of the nut about its center axis while resisting similar rotation of the screw will cause the screw to move axially through the nut. When the nut is mounted on a reaction element and the screw on a moving element in an aircraft, the ball screw operates as an actuator.
One type of aircraft that utilizes a ball screw actuator is the tiltrotor aircraft. Such aircraft include one or more engines that may be operated in a position that is normal for propeller driven aircraft and in a position that is normal for the rotor of a helicopter. As such, the tiltrotor aircraft can take off and land vertically, hover when desired, fly more like an airplane in level flight, and obtain speeds greater than normally possible with helicopters. The term “proprotor” is utilized herein to describe the tiltrotor airscrew since the airscrew provides the attributes of a propeller when in the level flight position and the attributes of a helicopter rotor when in the vertical position.
To achieve dual functionality, the proprotor and its associated power plant, is mounted on a pylon which can pivot on the aircraft between a conventional flight mode and a helicopter mode. In the conventional flight mode, the proprotor rotates in a vertical plane to drive the aircraft forward as in a conventional prop driven aircraft. The pylon and proprotor can then be converted or pivoted to position the proprotor in essentially a horizontal plane, where it can act as a helicopter rotor and the aircraft operated as a helicopter for vertical takeoff and landing. In such an environment, a highly reliable and efficient actuator is necessary for the proper operation of the pylon in converting between the aircraft mode and the helicopter mode.
Therefore, a need has arisen for a highly reliable system for operating the pylon between helicopter mode for take off to aircraft mode for conventional flight and back to helicopter mode for landing. A need has also arisen for such a system that includes redundant mechanical and hydraulic systems that operate in the event of partial system failures.
SUMMARY OF THE INVENTION
The present invention disclosed herein comprises highly reliable pylon conversion system for operating the pylon of a tiltrotor aircraft between helicopter mode for take off and landing to aircraft mode for conventional flight. The pylon conversion system includes redundant mechanical and hydraulic systems that operate in the event of partial system failures.
The pylon conversion system comprises first and second pylon conversion actuators each having a retracted position and an extended position that corresponds to the aircraft mode and the helicopter mode of the tiltrotor aircraft. A first gearing system is operably coupled to the first pylon conversion actuator and to a first primary power unit, a first backup power unit and a first clutch. A second gearing system is operably coupled to the second pylon conversion actuator and to a second primary power unit, a second backup power unit and a second clutch operably coupled to the second gearing system. An interconnect drive train is operably coupled between the first and second clutches such that the first and second pylon conversion actuators are operable between the extended position and the retracted position.
The first and second pylon conversion actuators of the pylon conversion system may be ball screws and are preferably two stage ball screws. The first and second gearing systems may each include a planetary differential and an anti-jam gear. The planetary differentials may be a floating differentials that allow for operation by either the corresponding primary power unit, the corresponding backup power unit or both. A pair of bevel gears may be used to couple the first and second clutches to the interconnect drive train.
The pylon conversion system of the present invention has a plurality of redundant mechanical operation modes. For example, the first and second pylon conversion actuators may be operated between the retracted position and the extended position using the first and second primary power units. Alternatively, the first and second pylon conversion actuators may be operated using the first and second backup power units. As another alternative, the first and second pylon conversion actuators may be operated using the first primary power unit and the second backup power unit. In addition, the first and second pylon conversion actuators may be operated using the first primary power unit, the first backup power unit and the interconnect drive train. In another alternative, the first and second pylon conversion actuators may be operated using only the first primary power unit and the interconnect drive train. Likewise, the first and second pylon conversion actuators may be operated using only the first backup power unit and the interconnect drive train.
REFERENCES:
patent: 1846992 (1932-02-01), Decker
patent: 1867963 (1932-07-01), Blahnik
patent: 3360217 (1967-12-01), Trotter
patent: 3766790 (1973-10-01), Weir
patent: 4088284 (1978-05-01), Caswell
patent: 5054716 (1991-10-01), Wilson
patent: 5092539 (1992-03-01), Caero
patent: 5214972 (1993-06-01), Larson et al.
“V-22 Nacelle Conversion Actuator,” G. White, Lucal Western Inc., California, USA—Proc Instn Mech Engrs. vol. 207—ImechE 1993.
Fenny Carlos Alexander
Short Arthur G.
Short Linda Louise
Barefoot Galen L.
Bell Helicopter Textron Inc.
Emanuelson Kenneth T.
Gardere Wynne & Sewell LLP
Short Linda Louise
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