Device for controlling the pitch of the blades of a convertible aircraft rotor

• US 20030183722A1
• Filed: 03/20/2003
• Published: 10/02/2003
• Est. Priority Date: 03/29/2002
• Status: Active Grant

• Current Assignee: Airbus Helicopters
• Original Assignee: Eurocopter
• Inventors: Zoppitelli, Elio, Cornille, Eric, Rampal, Etienne
• Granted Patent: US 6,824,096 B2
• Time in Patent Office: Days
• US Class Current: 244/7A
• CPC Class Codes: B64C 27/28 with forward-propulsion propellers pivotable to act as lifting rotors
• CPC Class Codes: B64C 27/41 with flapping hinge or universal joint, common to the blades
• CPC Class Codes: B64C 27/605 including swash plate, spider or cam mechanisms
• CPC Class Codes: B64C 29/0033 the propellers being tiltable relative to the fuselage

Abstract

A pitch control device is provided for a blade of a tilting rotor of a convertible aircraft. The pitch control device is external to a rotor hub which is driven in rotation by a mast and connected to the latter by means for tilting the hub as a whole, and each blade of which is connected to the hub by a coupling for retaining and hingeing the blade in pitch about its pitch change axis. The pitch control device comprises a pitch change lever, integral in rotation with its blade root about its axis and projecting towards the base of the mast, a pitch control rod, which can be moved in the direction of the mast, a bellcrank pivoting about a pin on a drive plate integral in rotation with the mast, and to which the pitch control rod is hinged at a point offset radially towards the outside of the pivot pin relative to the axis of the mast, the bellcrank being also hinged to a link rod connected to the pitch change lever and slightly inclined to any radial plane relative to the axis of the mast, and the slope of which relative to this plane corresponds to the desired pitch-flap relation of the rotor.

Claims

1. A pitch control device for controlling pitch of blades of a rotor of a convertible aircraft, where the rotor comprises:

a rotor mast having a base and a longitudinal axis, the rotor mast being designed to be driven in rotation by said base about said longitudinal axis,

a hub, driven in rotation by the mast, and connected to the mast by a tilting arrangement allowing the hub as a whole to tilt about any flapping axis passing through the axis of the mast and perpendicular to the axis of the mast,

at least two blades, each of which is connected to the hub by a coupling retaining and hingeing said blade in pitch about a longitudinal pitch change axis of said blade, which pitch change axis extends it a plane of rotation of the rotor,

wherein the pitch control device is external to the hub and comprises, for each blade of the rotor;

a pitch change lever integral in rotation with a root of said blade about said pitch change axis, and projecting on a side of a plane of rotation of the rotor which faces towards the base of the mast,

a pitch control rod, which is movable in a direction substantially parallel to the longitudinal axis of rotation of the mast,

a bellcrank, mounted so as to pivot, about a pivot pin substantially contained in a radial plane relative to the longitudinal axis of rotation of the mast, on a fixed point of a drive plate, integral in rotation with the mast, said pitch control rod being hinged to said bellcrank at least so as to pivot about a pin substantially parallel to the pivot pin of the bellcrank on the drive plate and at a point offset radially outwardly of said pivot pin relative to the longitudinal axis of rotation of the mast, and

a link rod, hinged at least so as to pivot at one end on said pitch change lever, about a pin substantially parallel to said pitch change axis, and at an other end of said link rod, to the bellcrank, at a fixed point on the bellcrank situated between said plane of rotation of the rotor and the point at which the bellcrank is hinged to the drive plate, so that said link rod is slightly inclined to any radial plane relative to the longitudinal axis of rotation of the mast, and that the bellcrank converts any movement of the pitch control rod into movement of the link rod in a direction substantially transverse to the direction of the longitudinal axis of the mast.

2. A pitch control device according to claim 1, wherein said link rod remains one of substantially parallel and slightly inclined to any radial plane relative to the longitudinal axis of rotation of the mast when said blade performs angular deflection movements within a pitch range of said blade.

3. A pitch control device according to claim 1, wherein an angle of inclination of said link rod to any radial plane relative to the axis of the mast corresponds to a pitch-flap relation (delta-3 relation) desired for the corresponding blade.

4. A pitch control device according to claim 1, wherein an angle of inclination of said link rod to any radial plane, perpendicular to the longitudinal axis of the mast, varies so as to obtain pitch-flap coupling (delta-3 relation) according to a law determined as a function of pitch angle of said blade, when the blade performs angular deflection movements in flapping.

5. A pitch control device according to claim 1, wherein the bellcrank is substantially L-shaped, hinged at an elbow to the pitch change rod, at one end of one of its arms to the drive plate, and at one end of another arm to the link rod.

6. A pitch control device according to claim 1, wherein the pins pivoting the bellcrank respectively to the drive plate, to the pitch control rod, and to the link rod are substantially parallel with each other, and with the pitch change axis of its blade, in a neutral position of the hub.

7. A pitch control device according to claim 6, wherein said bellcrank and said link rod move substantially in a plane parallel to the longitudinal axis of the mast and perpendicular to the pin pivoting the bellcrank to the drive plate and substantially perpendicular to the pitch change axis of said blade.

8. A pitch control device according to claim 1, wherein said pitch change lever projects towards the base of the mast at a radially inner end, relative to the axis of the mast, of a blade cuff, rigid in torsion and connected in torsion to the root of said blade about the pitch change axis, and surrounding said coupling for retaining and hingeing said blade in pitch.

9. A pitch control device according to claim 1, wherein said bellcrank is mounted so as to pivot in a yoke projecting outwardly on the drive plate.

10. A pitch control device according to claim 1, wherein said link rod is hinged to said pitch change lever and to said bellcrank by ball joint connections.

11. A pitch control device according to claim 1, wherein said bellcrank is connected to said pitch control rod by a ball joint connection.

12. A convertible aircraft comprising at least one tilting rotor movable from a first position in which the at least one tilting rotor operates as am aeroplane propeller to a second position in which the at least one tilting rotor operates as a helicopter main lifting rotor, the at least one rotor comprising:

a rotor mast having a base and a longitudinal axis, the rotor mast being designed to be driven in rotation by said base about said longitudinal axis,

a hub, driven in rotation by the mast, and connected to the mast by a tilting arrangement allowing the hub as a whole to tilt about any flapping axis passing through the axis of the mast and perpendicular to the axis of the mast,

at least two blades, each of which is connected to the hub by a coupling retaining and hingeing its blade in pitch about its longitudinal pitch change axis, which extends it a plane of rotation of the rotor,

a pitch control device for each blade of the rotor, each pitch control device being external to the hub and comprising;

a pitch change lever integral in rotation with a root of said blade about its pitch change axis, and projecting on a side of a plane of rotation of the rotor which faces towards the base of the mast,

a pitch control rod, which is movable in a direction substantially parallel to the longitudinal axis of rotation of the mast,

a bellcrank, mounted so as to pivot, about a pivot pin substantially contained in a radial plane relative to the axis of rotation of the mast, on a fixed point of a drive plate, integral in rotation with the mast, said pitch control rod being hinged to said bellcrank at least so as to pivot about a pin substantially parallel to the pivot pin of the bellcrank on the drive plate and at a point offset radially outwardly of said pivot pin relative to the longitudinal axis of rotation of the mast, and

a link rod, hinged at least so as to pivot at one end on said pitch change lever, about a pin substantially parallel to said pitch change axis, and at its other end, to the bellcrank, at a fixed point on the bellcrank situated between said plane of rotation of the rotor and the point at which the bellcrank is hinged to the drive plate, so that said link rod is slightly inclined to any radial plane relative to the longitudinal axis of rotation of the mast, and that the bellcrank converts any movement of the pitch control rod into movement of the link rod in a direction substantially transverse to that of the longitudinal axis of the mast.