Fluid reaction surfaces (i.e. – impellers) – Sustained ancillary movement of rotary working member – Responsive to fixed actuator
Reexamination Certificate
1998-09-21
2001-08-28
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Sustained ancillary movement of rotary working member
Responsive to fixed actuator
C416S13400R, C416S141000, C416S1700HM
Reexamination Certificate
active
06280141
ABSTRACT:
The invention concerns control systems for the pitch of the blades of a gyroplane, in particular a helicopter main rotor, the rotor being of the type for which each blade is, on the one hand, rotated about a rotational axis of a rotor shaft, or rotor axis, by means of a hub fixed to rotate with the shaft, and, on the other hand, fixed to rotate, around a longitudinal change of pitch axis of the blade, with at least a pitch lever controlled by a corresponding pitch rod.
The invention relates more precisely to a pitch control system of the type including an assembly of swash-plates, and such that each pitch rod is connected to a plate rotating with the rotor and belonging to the swash-plates assembly, in which the rotating plate is mounted to rotate on a non-rotating plate, held by at least a non-rotating connecting part connecting the non-rotating plate with the gyroplane structure, the two plates being annular, surrounding the rotor axis and being able to be axially translated, that is to say parallel to the rotor axis, and inclined in every direction around the rotor axis, under the action of control actuators connecting the non-rotating plate to the structure, in order to control respectively the collective pitch and the cyclic pitch of the blades.
Generally, the two plates surround the rotor shaft and the control actuators are three servo controlled jacks or similar actuators placed between the cylindrical plates and the gyroplane structure, and articulated by ball joints at their lower and upper ends respectively on this structure and in devises of the non-rotating plate, whereas the pitch rods extend between the swash-plates and the pitch levers of the rotor blades, and are articulated by ball joints at their upper and lower ends respectively on the pitch levers and in devises distributed along the periphery of the rotating plate.
Most often, the swash-plates are translatable axially and able to be inclined by an axial translation and tipping guiding assembly which includes a central ball joint, centred on the rotor axis, and on which the non-rotating plate, and therefore the swash-plates, are mounted to oscillate, the ball joint being itself mounted axially sliding (parallel to the rotor axis) around a cylindrical guide coaxial with the rotor axis and non-rotating around this rotor axis, and generally fixed in relation to the gyroplane structure. When the swash-plates surround the rotor shaft, which is most often the case, the cylindrical guide is tubular, surrounds the rotor shaft, and is fixed to a casing secured to the gyroplane structure and surrounding the connection of the base of the rotor shaft to the main gear box.
Also most often, one or several of the upper and rotating connecting part(s), or lower and non-rotating connecting part(s) which connect respectively the rotor to the rotating plate in order to rotate this latter, and the structure to the non-rotating plate, in order to hold this latter, is or are one or both of compasses with two arms articulated as scissors and connected together by a pivot or a hinge, which enables the two arms of each compass to separate or approach one another in order to enable the displacements in the direction of the rotor axis, since the upper and lower arms of a rotating compass are moreover articulated respectively on the shaft or the rotor hub and on the rotating plate, and that the lower and upper arms of a non-rotating compass are moreover articulated on the gyroplane structure and on the non-rotating plate.
These rotating and non-rotating compasses have the disadvantage that their articulations comprise traditional bearings, little reliable, or, on the most recent helicopters, ball joints and self-lubricating bearings including numerous shafts and carbide rings, which are heavy and expensive.
Moreover, a certain height or axial (parallel to the rotor axis) size and width is necessary for efficient operation of the compasses. Now, in order to facilitate their loading, for example in the hold of a transport aircraft, and to improve their capability of being housed in the hangar, for example of a ship, modern helicopters must have a vertical or axial compactness as good as possible for the shaft and the main rotor assembly and the swash-plates assembly which surround it. But the reduction of height or axial dimension of such an assembly is limited by interferences between the two arms of a compass in the closing of this latter as well as by the maximum ball joint angles permitted by construction of the compasses' articulation ball joints.
The axial size of a swash-plates control system with compasses being principally determined by the clearances of the compasses, because of the closing and ball jointing angles necessary for their operation, it has already been proposed, in order to reduce the height of such an assembly, to remove either the rotating compass or compasses, or the non-rotating compass or compasses, and to use two guide columns, parallel to each other and to the rotor axis on either side of this axis in a same radial plane passing through the rotor axis, of an axial translation and tipping guide system of the cylindrical plates which includes also a universal connecting joint, with an intermediate ring sliding axially with the aid of the columns, and articulated by pivoting on these columns around a diametral axis of the ring, which is an axis remaining perpendicular to the rotor axis, whereas the ring is articulated by pivoting on one of the swash-plates around another diametral axis of the ring, which is perpendicular to the first diametral axis, as proposed by DE-A-36 03 -400 and DE-A-36 20 794. In this way, the axial displacements of the swash-plates and the ring are guided by the two columns, whereas the tipping of the swash-plates in every direction around the rotor axis is obtained by pivoting the swash-plates relative to the ring about one of the two diametral and perpendicular axes of the ring, and by pivoting the ring on the columns about the other of these two perpendicular diametral axes.
The guide columns can be rotating (rotating with the rotor), and therefore consequently the ring installed in this case between the rotating columns, on the one hand, and, on the other hand, the rotating plate in this way rotated by the columns and the ring which replace one or both rotating compasses. But the guide columns can also be non-rotating, that is to say held against all rotation around the rotor axis by a support fixed to the gyroplane structure, in which case the ring is also non-rotating and installed between, on the one hand, the non-rotating columns, and, on the other hand, the non-rotating plate, thus held in rotation by the non-rotating columns and the non-rotating ring, which replace one or both non-rotating compasses.
If the column systems have the advantage of giving a gain in (axial) height compared with the compass systems, the fact remains that the column systems have the inconveniences of a greater transverse size, as a result of a greater diameter of the swash-plates assembly in order to house the intermediate ring between the swash-plates and the columns, as well as a low resistance and a bad handling of the vibrations, which leads to avoiding the use of rotating columns. Finally, the use of rotating or non-rotating guide columns does not prevent the simultaneous use of one or more compasses respectively non-rotating or rotating, because it is to exclude a system comprising at the same time non-rotating columns and rotating columns insofar as it does not enable all the tipping demanded by the cyclic pitch controls and assured by the universal joint ring.
The problem at the base of the invention is to propose a swash-plates pitch control system which does not comprise a rotating compass for rotating the rotating plate, and which comprises instead means which enable the reduction of the axial size of the pitch control system, and therefore the mast-hub assembly of a main rotor.
Another aim of the invention is to propose a pitch control system in which one or both rotating compasses o
Garcin Sylvie
Rampal Etienne Jean
Eurocopter
Look Edward K.
Piper Marbury Rudnick & Wolfe
Woo Richard
LandOfFree
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