Aeronautics and astronautics – Aircraft – heavier-than-air – Helicopter or auto-rotating wing sustained – i.e. – gyroplanes
Reexamination Certificate
1999-12-21
2001-09-04
Jordan, Charles T. (Department: 3644)
Aeronautics and astronautics
Aircraft, heavier-than-air
Helicopter or auto-rotating wing sustained, i.e., gyroplanes
C244S054000
Reexamination Certificate
active
06283408
ABSTRACT:
The invention relates to an anti-vibration or anti-resonance suspension device for a main helicopter rotor comprising a rotor shaft driven in rotation by a main gearbox about the axis of the shaft, which is the rotation axis of rotor.
An anti-vibration suspension device of this type is designed to be mounted on a helicopter, the structure of which supports, in general, on a mechanical floor on top of the fuselage, an engine assembly, the main rotor and the main gearbox, acting as a reducing gear and located between the engine assembly and the main rotor in order to drive the latter in rotation. An anti-vibration suspension device of this type is therefore inserted between the main gearbox and the helicopter structure, on the one hand to transmit static forces and torques, acting on the rotor, between the rotor and the structure and, on the other hand, to provide an effective damping or filtering action against the dynamic components of the forces and torques acting on the rotor and in particular the dynamic component of the force directed along the rotor shaft (pumping) and the forces and torques excited in the plane of the rotor.
The invention relates more specifically to an anti-vibration suspension device of the type comprising a set of at least three oblique and rigid bars for supporting the gearbox on the structure of the helicopter, these oblique bars being distributed around the gearbox and inclined relative to the rotor axis so as to converge with one another substantially at a point on the rotor axis, generally at their top ends, and such that the point of convergence is located between the hub, at the centre of the rotor, and the upper part of the gearbox, these oblique bars being articulated, on the one hand to the gearbox by means of their top ends, and on the other to the helicopter structure by their bottom ends and by means of rigid levers, a same number of these being provided as there are oblique bars, each lever supporting at least one oscillating weight at one end and being articulated to the structure by its opposite end part, in the vicinity of which the bottom end of a corresponding oblique bar is articulated on the corresponding lever, the articulated joints linking each lever to the structure and to the corresponding oblique bar being articulated joints which pivot at least about axes substantially perpendicular to a corresponding radial plane containing the axis of the rotor and the longitudinal axis of the corresponding oblique bar.
Suspension devices of this type are known from U.S. Pat. No. 4,458,862 and U.S. Pat. No. 4,431,148, in which each oblique bar is articulated at its top end directly on the upper part of the gearbox and at its bottom end on the external radial end, relative to the rotor axis, of one respectively of arms, equal in number to the number of oblique bars, and arranged radially around the base of the gearbox to which these arms are linked. Each arm is articulated on the structure in the region of its external radial end, which is rigid, and to which the corresponding rigid lever is attached or joined by its end opposite that supporting the corresponding oscillating weight.
In U.S. Pat. No. 4,458,862, the arms are radial extensions and substantially coplanar with the central part of a suspension plate, for suspending the gearbox on the structure, this central part being joined to the base of the gearbox and the arms, arranged in a star design around this central part, being rigid in their plane but flexible in a direction perpendicular to this plane, i.e. in the direction of the rotor axis. Accordingly, each arm constitutes a flexible blade between the central part of the plate fixed to the gearbox and the rigid, external radial end part of the arm which is articulated on the structure and on the bottom end of the corresponding oblique bar, and to which is attached or with which is joined the end of the lever on the side opposite the oscillating weight, the lever being oriented substantially radially either towards the interior (towards the rotor axis) or towards the exterior. The articulated joints of each arm permit deflections thereof by deformation in a direction perpendicular to the plane of the part thereof forming a flexible blade, and the unit comprising the corresponding lever and its oscillating weight form an anti-resonance or oscillating system, acting by inertia, and building up inertial forces which counter-balance the reactions at the linkage points to the structure corresponding to the deformations of the flexible blades of the plate.
U.S. Pat. No. 4,431,148 proposes an anti-resonant suspension device of this type which is simplified due to the fact that the suspension plate is independent of radial arms and comprises a thin membrane, which deforms by bending when subjected to forces exerted perpendicularly to its plane or pivot moments exerted around its centre by the gearbox but is rigid under the effect of traction/compression when subjected to forces and torques is exerted in its plane, such as the reaction torque occurring when the rotor is driven, this membrane being integrated in the upper structure of the fuselage.
As a result, each radial arm is directly linked to the base of the gearbox by means of a support bearing, which not only provides a pivot axis perpendicular to the radial plane containing this arm but also a flexible link which imparts a certain freedom of movement to the arm, both angularly and longitudinally, for example a laminated bearing with combined support, spherically and in translation.
Each radial arm may be made from a single piece having a flexible part on the one hand and, on the other hand, a rigid part at points of which the arm is articulated on the corresponding oblique bar, and on a corresponding structural support, and to which the rigid lever comprising the support for the corresponding oscillating weight is attached. In a preferred embodiment of the above-mentioned patent, however, each radial arm is formed by a flexible radial blade and by a part of a rigid lever, the other part of which constitutes the support for the corresponding oscillating weight, the outer radial end (relative to the rotor axis) of the blade being joined to the rigid lever in the region where the latter is articulated on the structural support of the fuselage.
This design involves using a complex laminated support bearing to provide the link between the inner radial end of each flexible blade to the gearbox, which fulfils a ball joint function and permits parasitic movement of the inner end of the flexible blade along its longitudinal axis when the blade is deformed due to bending.
This arrangement also involves using flexible blades which are difficult to design in terms of dimension and manufacture. Furthermore, the mounting between the rigid lever and the corresponding radial arm can cause problems due to fretting.
The underlying problem of the invention is to simplify an anti-vibration suspension device of this type, in particular by dispensing with blades which flex under bending and preferably also their complex support bearing on the base of the gearbox, thereby achieving very substantial savings on manufacturing, fiting and maintenance costs.
Another objective of the invention is to propose a simplified antivibration suspension device which is still compatible with the use of a membrane as proposed in U.S. Pat No. 4,431,148 in order to absorb the reaction to the driving torque and the forces acting on the base of the gearbox whilst securing the requisite degree of freedom in terms of pumping and rotation, the simplied device proposed by the invention simultaneously and advantageously being compatible with mono- or bi-directional suspensions comprising a pair of identical and parallel rod linkages articulated between the base of the gearbox and the structure, as described in U.S. Pat. No. 5,782,430 and U.S. Pat. No. 5,788,182, bringing additional savings compared with using a membrane.
To this end, the invention proposes an anti-vibration suspension device of the type outlined above, which is
Bietenhader Claude
Ferullo David
Best Christian M.
Eurocopter
Jordan Charles T.
Piper Marbury Rudnick & Wolfe
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