Brakes – Inertia of damping mass dissipates motion
Reexamination Certificate
1999-09-28
2001-08-28
Butler, Douglas C. (Department: 3613)
Brakes
Inertia of damping mass dissipates motion
C267S136000
Reexamination Certificate
active
06279704
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for reducing the vibration generated on the structure of a rotary-wing aircraft, particularly a helicopter.
Although not exclusively, the present invention applies more particularly to reducing the vibration generated by the aerodynamic flow through the main rotor which provides the helicopter with lift and forward drive.
It is known that said main motor, as it turns, sucks in air situated above it and drives it downward, accelerating it, in such a way as to create a stream of moving air. The pressure and speed of the air vary thoughout this air stream. The flow of this air over the structure of the helicopter generates vibration which is particularly noticeable in the cockpit region.
The vibration thus generated is due mainly to the excitation by the aforementioned aerodynamic flow of the characteristic modes of the helicopter structure, and particularly the first lateral or vertical bending mode of the helicopter tail boom, and is generally known as tail shake in the aeronautical field. The vibrations due to the excitation of this bending mode generally have a frequency of a few hertz and are extremely troublesome.
The various vibrations generated on the structure of a helicopter exhibit numerous drawbacks, particularly:
in terms of the comfort of the crew and of the passengers,
in terms of the fatigue of the parts and equipment items, and
in terms of the operation of the weapon systems when the helicopter is equipped therewith.
SUMMARY OF THE INVENTION
The object of the present invention is to remedy these drawbacks. The invention relates to a simple and low-cost device that makes it possible, simply and effectively, to reduce the vibrations generated on the structure of a rotary-wing aircraft, and particularly the vibrations generated by the aerodynamic flow through the main rotor which provides said aircraft with lift and forward drive.
To this end, according to the invention, said device is noteworthy in that it comprises:
at least one flapping mass connected to said structure;
at least one controllable actuating means capable of causing said flapping mass to flap; and
a control unit intended to control said actuating means in such a way that it causes said flapping mass to flap at a frequency and at an amplitude that allow said vibrations to be reduced and minimized.
Thus, by virtue of the invention, said device is an active device, whose vibration-reduction action, generated by the flapping mass, can be adjusted and optimized, thus allowing said vibrations to be effectively reduced.
Furthermore:
because of the low number of components, said device is simple, compact and inexpensive; and
because of the absence of moving parts, the operating cost of this device is very low.
Furthermore, advantageously, said device additionally comprises:
a flexible blade connecting said flapping mass to said structure, which, in particular, makes the flapping of the flapping mass easier; and/or
a position sensor capable of measuring values which represent the position of said flapping mass, said values being transmitted to said control unit and used by the latter to determine, refine and/or control the commands for controlling said actuating means, which makes it possible to increase the effectiveness of said device.
Although said actuating means can be of various types, particularly mechanical or hydraulic, it is preferably formed in such a way as to exert an electromagnetic force to cause said flapping mass to flap, and comprises at least one electromagnet.
According to the invention, said damping means may be produced in various ways.
By way of alternative forms, it may, in particular, comprise:
a single electromagnet which is secured to the structure and acts on the flexible blade fixed to the structure, near to the attachment region, which makes it possible to obtain a simplified embodiment; a static load is constantly applied, and the dynamic load is applied around this static load;
two electromagnets arranged one on each side of said flexible blade, which makes it possible to increase the amplitude of the flapping; or
a single electromagnet which is secured to the flexible blade and exerts an electromagnetic force on said structure, which makes it possible to save weight.
Furthermore, in another embodiment, said actuating means comprises an iron bar arranged on said flapping mass and a coil surrounding said iron bar and dissipating energy into an electric resistor via a unit controlling the current or the voltage or alternatively the resistance of the dissipating resistor.
The vibration-reduction device obtained is therefore very lightweight and consumes little energy.
REFERENCES:
patent: 5086564 (1992-02-01), Schalz
patent: 5456341 (1995-10-01), Garnjost et al.
patent: 5814963 (1998-09-01), Girard et al.
patent: 5883447 (1999-03-01), Clausin
patent: 394 180 A2 (1990-10-01), None
patent: 2 730 288 (1996-08-01), None
French Search Report dated Jun. 17, 1999, 3 pages.
Butler Douglas C.
Eurocopter
Marshall O'Toole Gerstein Murray & Borun
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