Helicopter

A helicopter having a rotor, a fuselage, and a transmission connected functionally to the rotor; the helicopter has a supporting body supporting at least the transmission, and connecting means having a first connecting member and at least one second connecting member connected to the supporting body and the fuselage respectively; and the connecting means have elastic means interposed between the first and second connecting member.

The present invention relates to a helicopter.

BACKGROUND OF THE INVENTION

The helicopter also comprises at least one engine; a transmission between the engine and the drive shaft; and a connecting device connecting the fuselage to a supporting body supporting the drive shaft and the transmission. In other words, the fuselage is “suspended” from the supporting body by the connecting device.

During normal operation of the helicopter, the engine exerts drive torque on the transmission. By the law of action-reaction, reaction torque is transmitted to the supporting body, and from there to the fuselage by the connecting device, and is balanced by an opposing torque exerted on the fuselage by the tail rotor.

The connecting device inevitably transmits vibration and noise to the fuselage and hence to the cabin, thus impairing the comfort of the crew.

A need is felt within the industry to minimize transmission of this vibration and noise to the cabin, particularly in predetermined frequency ranges.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a helicopter designed to achieve at least one of the above requirements cheaply and easily.

According to the present invention, there is provided a helicopter as claimed in the attached claims.

DETAILED DESCRIPTION OF THE INVENTION

Number1inFIG. 1indicates a helicopter substantially comprising a fuselage2with a nose5; at least one engine6(only shown schematically inFIG. 1); and a main rotor3mounted on top of fuselage2to generate the lift and thrust necessary to lift and move helicopter1forward.

Main rotor3substantially comprises a drive shaft10; a hub11hinged to shaft10; and a number of blades12hinged to hub11and extending in respective directions crosswise to an axis A of shaft10.

Fuselage2defines a cabin8normally occupied by the crew and bounded, on the side facing main rotor3, by a wall15of fuselage2.

Of the stator body,FIG. 1only shows a box14projecting from wall15, on the opposite side to cabin8, and supporting a final stage of transmission7and shaft10in rotary manner about axis A.

Helicopter1also comprises an antitorque tail rotor4projecting from a tail fin of fuselage2at the opposite end to nose5; and connecting means16connecting box14to wall15of fuselage2.

a number of—in the example shown, four—rods17extending, along respective axes sloping with respect to wall15and axis A, between a lateral surface of box14and respective fastening points to wall15; and

a connecting device20connected to a bottom edge of box14and to wall15, and for transmitting reaction torque to fuselage2.

More specifically, the reaction torque is, by the law of action and reaction, equal to and opposite the drive torque transmitted from engine6to shaft10by transmission7, is transmitted to the stator body and hence to box14, and is balanced by an opposing torque generated by tail rotor4.

a cross member21in turn comprising a flange22bolted to the bottom edge of box14and defining a circular opening having an axis B and through which axis A extends; and two V-shaped appendixes23,24converging on opposite sides of axis B and projecting from respective portions of flange22on opposite sides of axis B;

two connecting members25,26located on opposite sides of axis B and each comprising two opposite plates29perpendicular to axis B, and two sidewalls30interposed perpendicularly between plates29;

two members31,32connected to wall15of fuselage2and to respective sidewalls30of member25; and

More specifically, flange22comprises a number of holes35equally spaced about axis B and fitted through with respective bolts (not shown) fixed to the bottom edge of box14. And axis B is inclined with respect to axis A.

Each appendix23,24comprises two sides converging on the opposite side to axis B and extending symmetrically with respect to a respective axis C, D; and a threaded hole36(shown inFIGS. 5-8) extending along respective axis C, D and having an open first axial end located on the opposite side to axis B, and a closed second axial end opposite the first axial end.

With reference toFIGS. 6 and 7, members25,26each comprise a trapezoidal seat27engaged by a respective appendix23,24; and two prismatic, rectangular-section seats28located on either side of seat27and bounded by respective sides30. More specifically, seats28of each member25,26communicate with relative seat27.

Members25,26have respective through holes37with respective axes C, D and aligned axially with holes36of respective appendixes23,24.

Axes C, D are inclined with respect to each other, intersect at the centre O of flange22, and define a plane perpendicular with respect to axis B.

Axes C, D define respective angles β, α with the normal-flight axis of helicopter1extending from tail rotor4to nose5. More specifically, angles β, α are obtuse and equal.

Axis E substantially coincides with the longitudinal axis of fuselage2, and is perpendicular to an axis F shown inFIGS. 3,4,6,7and8.

Sidewalls30of member25are each interposed between a relative member31,32and a relative side of appendix23.

Similarly, sidewalls30of member26are each interposed between a relative member33,34and a relative side of appendix24.

Members31,32,33,34each comprise a main wall38cooperating with a respective sidewall30of respective member25,26; and two parallel lateral walls39projecting from respective opposite end edges of wall38, on the opposite side to relative member25,26.

Each member31,32,33,34is fixed to wall15of fuselage2by a respective bolt19(FIG. 2) having an axis G parallel to axis B. More specifically, each bolt19is fitted through walls39and a central curved portion of wall38of relative member31,32,33,34.

More specifically, connecting device20comprises four damping assemblies40housed in respective seats28and each comprising a number of layers41of elastomeric material, in particular cured rubber, alternating with a number of plates42(FIGS. 4 and 5) of metal connected to layers41by respective layers of adhesive material not shown. In the example shown, layers41and plates42are rectangular, and lie in respective planes parallel to sidewalls30defining respective seats28.

Damping assemblies40are interposed between respective sides of appendixes23,24and respective members31,32,33,34, and so reduce transmission of vibration from cross member21to wall15.

Each damping assembly40also comprises two plates44,43made of metal and connected respectively by adhesive material to the layer41closest to relative axis C, D, and to the layer41closest to relative member31,32,33,34.

Plate43of each damping assembly40has two projections50projecting on the opposite side to relative appendix23,24and engaging respective seats51(FIGS. 5,7,8) defined in wall38of relative member31,32,33,34.

Plate44of each damping assembly40has two projections52projecting towards relative appendix23,24and engaging respective dead seats53(FIGS. 5,6,7) defined in a respective side of relative appendix23,24.

Projections50,52of damping assemblies40engaging seats28in member25extend along respective axes parallel to one another and substantially perpendicular to sidewalls30of member25.

Similarly, projections50,52of damping assemblies40engaging seats28in member26extend along respective axes parallel to one another and substantially perpendicular to sidewalls30of member26.

The connection between projections50,52and respective seats51,53provides for transmitting the torque reaction along axis B from appendixes23,24to respective members31,32,33,34.

two pairs of pins61having respective parallel threaded ends extending along respective axes perpendicular to relative sidewall30of relative member25,26;

two pairs of threaded holes62defined by relative sidewall30of relative member25,26and engaged by respective pins61; and

two pairs of through holes63defined by wall38of relative member31,32,33,34and fitted through with respective pins61.

More specifically, seats51of each member31,32,33,34are interposed between respective holes63, and seat28housing each damping assembly40is interposed between relative holes62.

FIGS. 6 to 8show the assembly sequence of one pair of damping assemblies40of connecting device20.

More specifically,FIGS. 6 to 8show the assembly sequence of damping assemblies40interposed between the opposite sides of appendix23and respective members31,32.

The same also applies to assembly of damping assemblies40interposed between opposite sides of appendix24and respective members33,34, which is therefore not shown in detail.

Damping assemblies40are then inserted inside respective seats28in member25, and members31,32are fixed to respective sidewalls30of member25by pins61, so that projections50,52of each damping assembly40engage respective seats51,53defined by respective members31,32and the relative sides of appendix23.

Damping assemblies40are thus gripped in a predetermined position between respective members31,32and the respective sides of appendix23(FIG. 8).

Shaft10rotates blades12via hub11to produce the lift and thrust required to lift and move helicopter1forward.

The lift and thrust are transmitted to box14and from this, mainly by rods17, to wall15of fuselage2.

By the law of action-reaction, the torque transmitted from the shaft produces a torque reaction on box14equal to and in the opposite direction to the torque on shaft10.

The torque reaction travels through connecting device20and is transmitted to wall15of fuselage2.

More specifically, the torque reaction is transmitted from appendixes23,24to plates44of damping assemblies40by pins52engaging respective seats53, is transmitted from plates43of damping assemblies40to corresponding members31,32,33,34by pins50engaging respective seats51, and is then transmitted by members31,32,33,34to wall15of fuselage2.

Operation of rotor3induces vibration on box14.

The vibration on box14and the relative noise are transmitted from box14to flange22and appendixes23,24of flange22.

Because of layers41of elastomeric material, damping assemblies40oscillate to absorb this vibration and noise in predetermined frequency ranges, and to prevent them from being transmitted to members31,32,33,34and hence to wall15of fuselage2.

In other words, damping assemblies40isolate members31,32,33,34connected to wall15, from appendixes23,24connected to box14.

The preload on layers41is adjustable as a function of a predetermined torque on shaft10and, hence, torque reaction on box14.

More specifically, the preload on layers41is adjusted by tightening pins61more or less inside respective holes62to adjust the gripping force on respective damping assemblies40in a direction substantially parallel to respective axes G.

The advantages of helicopter1according to the present invention will be clear from the above description.

In particular, damping assemblies40transmit the torque reaction from box14to wall15, while reducing transmission of vibration and noise in predetermined frequency ranges to wall15and hence cabin8.

That is, layers41of elastomeric material are interposed between cross member21fixed to box14, and members31,32,33,34fixed to wall15of fuselage2, and are vibrated by the loads transmitted from box14.

In other words, layers41act as respective mechanical filters which isolate wall15from vibration and noise transmitted in predetermined frequency ranges from box14.

The oscillating frequency of layers41of connecting device20can be adjusted by simply altering the material or shape, i.e. adjusting the rigidity, of layers41.

The frequency ranges in which to prevent vibration and noise transmission to fuselage2can thus be selected at the design stage.

In other words, damping assemblies40can be tuned at the design stage to different vibration and noise frequency ranges in which to reduce transmission to fuselage2.

Adjusting means60also allow adjustment of the preload on damping assembly layers41.

This therefore ensures cross member21is balanced when subjected to a predetermined torque reaction by box14and the elastic action of layers41. The predetermined torque reaction exerted by box14corresponds to the torque on shaft10in normal flight conditions of helicopter1.

Clearly, changes may be made to helicopter1as described and illustrated herein without, however, departing from the scope defined in the accompanying Claims.