Aeronautics and astronautics – Aircraft – heavier-than-air – Helicopter or auto-rotating wing sustained – i.e. – gyroplanes
Reexamination Certificate
2000-02-22
2001-12-04
Poon, Peter M. (Department: 3644)
Aeronautics and astronautics
Aircraft, heavier-than-air
Helicopter or auto-rotating wing sustained, i.e., gyroplanes
C416S114000
Reexamination Certificate
active
06325326
ABSTRACT:
The present invention relates to a cyclic and collective pitch control device for a helicopter rotor.
BACKGROUND OF THE INVENTION
Cyclic and collective pitch control of known helicopter rotors is normally effected by rocking-plate control devices substantially comprising two concentric rings, the outer one of which is supported for rotation, by means of bearings, by the inner ring, and is connected angularly to a drive shaft to rotate a number of pitch-change rods, each hinged eccentrically to a respective blade.
In such rotors, the inner ring is carried coaxially by a substantially sleeve-shaped movable element in turn fitted in axially-sliding manner to a fixed pylon, through which the drive shaft extends in axially-fixed, angularly-free manner.
The movable element is defined by a spherical annular outer surface mating with a spherical seat on the inner ring; and the inner ring is normally secured to the movable element by two bolts fitted through respective radial holes in the inner ring and each engaging a respective key in turn engaging in sliding manner a respective substantially vertical slot formed on the outside of the movable element, so that the inner ring is locked angularly to the spherical annular surface of the movable element and, by virtue of the key and slot, is permitted to rock in any direction, with respect to the movable element, about the center of the spherical annular surface.
Known control devices also comprise a number of hydraulic actuators equally spaced about and extending substantially parallel to the drive shaft, and which cooperate with and exert thrust on the inner ring to move the inner and outer rings and the movable element axially and jointly with respect to the pylon, and to rock the inner and outer rings, with respect to the movable element, about axes substantially perpendicular to the axis of the drive shaft.
Finally, the inner and outer rings are secured respectively to the drive shaft and pylon by a first and second compass-type connecting mechanism, each defined, as is known, by two connecting rods secured to each other by a cylindrical hinge. The first connecting mechanism is designed to prevent angular displacement of the inner ring and the movable element about the drive shaft axis and with respect to the pylon, and the second connecting mechanism to transmit rotary motion from the drive shaft to the outer ring.
Though valid in terms of performance, compass-type connecting mechanisms of the above type are relatively heavy and expensive, and, being subjected, in use, to reciprocating loads which tend to increase the clearance between the connecting rods, need to be lubricated and checked continually. Moreover, to conform with constraint redundancy requirements typical of aircraft applications, the number of connecting mechanisms must be doubled, thus compounding the aforementioned drawbacks.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a cyclic and collective pitch control device for a helicopter rotor, which is cheap to produce, reliable, lightweight and, in particular, features a small number of compass-type connecting mechanisms as compared with the aforementioned known devices.
According to the present invention, there is provided a cyclic and collective pitch control device for a helicopter rotor fitted to a drive shaft having a longitudinal axis; said device being carried by a fixed supporting element coaxial with said longitudinal axis, and comprising:
a movable element coaxial with said longitudinal axis and fitted in axially-sliding manner to said supporting element;
a rocking-plate assembly coaxial with said longitudinal axis, fitted to said movable element so as to rock, with respect to the movable element, about transverse axes substantially perpendicular to said longitudinal axis, and in turn comprising an angularly-fixed first annular element, and a second annular element rotating on said first annular element together with said drive shaft;
supporting and actuating means cooperating with said first annular element to move said rocking-plate assembly and said movable element jointly along said longitudinal axis with respect to said supporting element, and to rock said assembly, with respect to said movable element, about said transverse axes; and
constraint means for preventing angular displacement of said movable element, with respect to said supporting element, about said longitudinal axis;
characterized in that said constraint means comprise prismatic connecting means between said movable element and said supporting element.
REFERENCES:
patent: 3841586 (1974-10-01), Broadley et al.
patent: 3972491 (1976-08-01), Ferris et al.
patent: 4361415 (1982-11-01), Aubry
patent: 4375940 (1983-03-01), Lovera et al.
patent: 6033182 (2000-03-01), Rampal
patent: 2 771 708 (1999-06-01), None
English Translation of Abstract from France Patent Document 2 771 708 dated Jun. 4, 1999 (see above).
European Search Report for European Application No. EP 00 10 3643, completed Nov. 17, 2000.
Agusta S.P.A.
Dinh Tien
Pitney Hardin Kipp & Szuch LLP
Poon Peter M.
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