Dual output variable pitch turbofan actuation system
AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration
InventorsRobert H. Griswold, Jr., Carl L. Broman
Life of this patent
Estimating the term…
Abstract
An improved actuating mechanism is provided for a gas turbine engine incorporating fan blades of the variable pitch variety, the actuator adapted to rotate the individual fan blades within apertures in an associated fan disc. The actuator includes means such as a pair of synchronizing ring gears, one on each side of the blade shanks, and adapted to engage pinions disposed thereon. Means are provided to impart rotation to the ring gears in opposite directions to effect rotation of the blade shanks in response to a predetermined input signal. In the event of system failure, a run-away actuator is prevented by an improved braking device which arrests the mechanism.
Claims23
In a turbofan engine of the variety including an annular fan duct, a core engine disposed internally of the fan duct and comprising a compressor, a combustion chamber and a turbine, a variable pitch fan comprising:
- a fan disc, generally circular in peripheral shape, rotatable about its axis and having a plurality of apertures in its periphery;
- a fan blade disposed within said duct and including a shank adapted to penetrate one of said apertures;
- bearing means interconnecting said shank and said one aperture and permitting relative rotation therebetween;
- and
- pitch varying means for rotating said shank comprising:
- a shaft coaxial and rotatable with said disc, the shaft secured in a predetermined axial relationship with the disc;
- a first sleeve telescopically receiving the shaft, said first sleeve being axially translatable with respect to and rotatable about the shaft;
- a second sleeve telescopically received in the first sleeve, said second sleeve being rotatable within said first sleeve and about said shaft;
- a casing telescopically receiving the shaft, the first sleeve and the second sleeve, the casing being rotatable about the shaft;
- first means carried by the casing for rotating said blade shank in response to rotation of the casing about the shaft;
- second means carried by the second sleeve and cooperating with said first means for rotating said blade shank in response to rotation of said second sleeve with respect to said first sleeve;
- third means cooperating with the first sleeve and the shaft for causing rotation and translation of the first sleeve in response to differential rotation of the shaft with respect to the disc;
- first mating means disposed between the first sleeve and the casing and having a predetermined first helix angle for permitting said first sleeve to translate with respect to the casing and the casing to rotate about the shaft;
- thrust bearing means carried between the shaft and second sleeve;
- and
- second mating means operatively connecting the first sleeve and the second sleeve and having a predetermined second helix angle for permitting said rotation about the first sleeve and the shaft, and wherein the shaft, the first and second sleeves, the second mating means, and the thrust bearing means are interconnected to form a closed axial thrust loop.
An actuator for changing the pitch of a fan blade carried by a rotatable disc comprising:
- a shaft coaxial with the disc and secured in a constant axial spacial relationship therewith;
- motor means driving said shaft at a differential rotational speed with respect to the disc;
- a sleeve telescopically receiving the shaft and operatively connected to a ring gear which engages a sector gear connected to the blade to effect the pitch change thereof;
- a recirculating ball actuator to drive the sleeve linearly and rotationally with respect to the shaft, thereby imparting rotational motion to the ring gear;
- brake means connected to the shaft for limiting the rotational travel of the sleeve with respect to the shaft, wherein said brake means is of the disc variety, comprising a first plurality of radially extending, axially spaced discs fixedly connected to the shaft, a second plurality of radially extending, axially spaced discs in alternating frictional engagement with the first plurality of discs;
- and means for engaging the sleeve with the second plurality of discs to impart rotation thereto when the sleeve has substantially reached its limit of linear travel.
Dependencies are inferred from the claim text.