Spring devices – Resilient shock or vibration absorber
Reexamination Certificate
1999-12-10
2001-06-19
Schwartz, Christopher P. (Department: 3613)
Spring devices
Resilient shock or vibration absorber
C244S017270
Reexamination Certificate
active
06247684
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antivibration device intended to reduce the transmission of vibration between two bodies, and to applications of said antivibration device.
Although said antivibration device can be used in all situations in which transmission of vibration between two bodies needs to be reduced, it is more specifically applicable to improving a device for the suspension of a transmission gearbox of a rotary-wing aircraft and, in particular, of the main transmission gearbox of a helicopter.
2. Description of the Related Art
It is known that a helicopter main transmission gearbox of this type, mounted between propulsion means and a lift rotor of said helicopter so that it is roughly longitudinal with respect to the axis of said rotor and which is suspended from the fuselage of said helicopter, is subjected to significant vibration generated by said lift rotor. This vibration is particularly troublesome because, in the absence of any system to filter the vibration, such as a transmission gearbox suspension device for example, it is transmitted to the structure of the fuselage of the helicopter and in particular is likely to limit the maximum speed of the helicopter, structurally weaken it and have an adverse effect on the comfort of the occupants of the helicopter. It is therefore necessary for said suspension device to be as effective as possible in opposing the transmission of such vibration and the associated forces from the main transmission gearbox toward the fuselage of the helicopter so as to avoid premature wear of the elements subjected to this vibration and make the pilot cockpit and passenger cabin as comfortable as possible.
Patents FR-2 499 505 and FR-2 669 982 in the name of the Applicant Company, disclose helicopter main transmission gearbox suspension devices which allow a particularly efficient reduction in the vibration generated by the lift rotor.
To this end, the suspension devices described in these prior-art documents are of the type comprising:
support or attachment pieces or bars, distributed radially around said transmission gearbox, the upper ends of which pieces or bars are connected to the upper part of the transmission gearbox and the lower ends of which pieces or bars are articulated on suspension leaves or on the fuselage;
possibly a suspension system connecting the lower part of the transmission gearbox to the aircraft fuselage and comprising, in particular, said suspension leaves which are distributed radially around said transmission gearbox in a plane which is roughly orthogonal to the axis of the rotor, the radially inner ends of which are fixed to the lower part of said transmission gearbox and the radially outer ends of which are articulated on the fuselage; and
resonator means associated respectively with said support pieces, either at their lower ends (FR-2 499 505), or at their upper ends (FR-2 669 982). Each of said resonator means comprises a mass support which is secured by one of its ends either to the suspension leaf connected to the associated support piece or directly to this support piece, and which is equipped at its other end with a beating mass. Said resonator means are essentially intended to reduce the vibration of the rotor transmitted by said support pieces.
Although particularly effective, said known uspension device does have certain drawbacks, particularly:
its accessibility is limited and its size is large, particularly as a -result of the presence of the aforementioned resonator means; and
its cost is high, particularly because of the existence of elastomer articulations, particularly to allow an effective arrangement and effective operation of the suspension leaves and of the mass supports.
Document U.S. Pat. No. 4,781,363 discloses an antivibration device which can be mounted between the main transmission gearbox and the fuselage of a helicopter, to reduce the transmission of vibration between the two.
To this end, this known antivibration device comprises:
a first cylindrical chamber and a second cylindrical chamber which communicate, which are filled with a fluid and which are deformable in the direction of the vibrational movement. The second chamber has a cross section of smaller area than the first chamber so that this second chamber is deformed to a greater extent than the first and its fluid is accelerated when there is deformation; and
an inertial mass which is connected to a piston arranged in said second chamber and which is moved when the vibration is generated, the movement of this inertial mass leading to a change in the pressure of the fluid in said second chamber so as to generate an effect which opposes the vibration.
In addition, when the rigidity of the deformable chambers is not great enough to withstand the effects of the vibration, said known device may additionally comprise a resistant elastic element of circular shape, made of a glass-fiber reinforced plastic.
This known device thus allows certain drawbacks of the aforementioned suspension device to be overcome, and in particular makes it possible to reduce the size.
However, this known antivibration device also has a great many drawbacks, and in particular:
its operation is limited by the freezing point of the fluid used;
there are risks of leakage of said fluid, liable in particular to reduce the effectiveness of said device;
it is difficult to completely fill the device with fluid, because of the risk of the appearance of air pockets, without providing complex and expensive bleed means; and
particularly because of the high number of parts of which it is made, it is particularly complicated and difficult to produce.
SUMMARY OF THE INVENTION
The object of the present invention is to overcome these drawbacks. The invention relates to an antivibration device of low cost and size, which is particularly simple and reliable and allows the transmission of vibration between two bodies, and particularly between two sections of a bar, for example a bar connecting two vibrating elements to be reduced effectively, said antivibration device being able in particular to be used to improve a rotary-wing aircraft transmission gearbox suspension device.
To this end, according to the invention, said device is noteworthy in that it comprises:
an elastic annular element which is connected to said two bodies so as to serve as a connection between them and which is capable of being deformed under the action of vibration generated in at least one of said bodies; and
a resonator means connected, via at least two leaves which are flexible in terms of bending and rigid in terms of tension and in terms of compression, to the internal face of said annular element so as to be set in oscillating rotation when said annular element is deformed, by the action of said vibration so that, by this oscillating rotation, said resonator means generates an antivibration inertia force which opposes said vibration and thus reduces its transmission from one body to the other.
Thus, when vibration is generated, the annular element deforms and makes the resonator means rotate, he angular deformation of the latter being compensated or by the deformation in bending of the leaves. Through this rotation, said resonator means generates an antivibration inertia force which is transmitted to the annular element and to the vibrating body, by means of the compression or tension of the leaves, which makes it possible effectively to reduce the transmission of vibration from one vibrating body to another body.
Furthermore, as will be seen in greater detail hereinbelow from a number of different embodiments, said antivibration device is simple, small in size, inexpensive and highly reliable.
Furthermore, even in the improbable scenarios:
of breakage of one or more leaves, the only consequence is a drop in the reduction of vibration and therefore an increase in its transmission from one body to the other; and
of breakage of the annular element, the resonator means comes into abutment between said bodies, and this maintains a conne
Eurocopter
Schwartz Christopher P.
Stevens Davis Miller & Mosher L.L.P.
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