Aircraft pitch change mechanism

• US 5,242,265 A
• Filed: 07/23/1990
• Issued: 09/07/1993
• Est. Priority Date: 07/23/1990
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Bulman, David E., Joyce, David L., Wakeman, Thomas G., Miller, Edwin K., Hora, Petr, Hermans, Thomas C.
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): LARSON, JAMES
• Application Number:
  US07/556,242
• Time in Patent Office: 1,142 Days
• Field of Search: 416/26, 416/32, 416/46, 416/128, 416/129, 416/130, 416/152, 416/160, 416/162, 416/170 R, 416/169 R, 416/153
• US Class Current: 416/26
• CPC Class Codes: B64C 11/32 mechanical
• CPC Class Codes: B64D 2027/005 Aircraft with an unducted turbofan comprising contra-rotating rotors, e.g. contra-rotating open rotors [CROR]
• CPC Class Codes: F01D 7/00 Rotors with blades adjustable in operation; Control thereof for reversing F01D1/30
• CPC Class Codes: F05D 2260/74 by turning around an axis perpendicular the rotor centre line
• CPC Class Codes: F05D 2260/76 the adjusting mechanism using auxiliary power sources
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft

Abstract

A system for changing pitch in aircraft propfans is disclosed, in which a motor, located at a stationary position, changes pitch of the blades by of a gear train. Three features of the system are that a feather brake can override the motor and drive the blades toward feather; a unison brake can prevent pitch from undergoing excursions toward fine pitch when propeller speed exceeds a limit; and the motor is non-rotating in the absence of pitch change. A pair of such systems can be used in a counterrotating propfan system, in order to independently change pitch of the propfans.

Claims

1. An aircraft propulsion system, comprising:

a) an array of propeller blades of the variable-pitch type;

b) pitch-change means for changing blade pitch, wherein said pitch-change means comprises,

i) a plurality of reduction gear sets, each one associated with one of said propeller blades,

ii) a pair of common ring gears driving all of said reduction gear sets,

iii) a sun gear and a plurality of planet gears driving said pair of common ring gears, and a third ring gear which is fixed with respect to the propeller blades and is used to react an overturning moment on said planet gears, and

iv) a driving means for driving said sun gear wherein said driving means includes a rotating shaft;

c) unison brake means for overriding the pitch-change means and impeding excursions toward fine pitch, wherein said unison brake means comprises a mono-directional centrifugal brake which,

i) is inoperative when said pitch-change means is driving said propeller blades toward coarse pitch,

ii) applies a retarding drag to said sun gear when said pitch-change means is driving said propeller blades toward fine pitch,

iii) maintains pitch in a constant position, by locking said sun gear to said fixed ring gear when said rotating shaft breaks,

iv) includes a ratchet-like overrunning device, and

v) does not interfere with the pitch-change operation in either direction for pitch adjustments within an engagement band of said ratchet-like overrunning device;

d) feather brake means for overriding the pitch-change means and driving the blades toward coarse pitch; and

e) pitch-limit means for limiting pitch attainable in both forward and reverse pitch modes.

2. An aircraft propulsion system, comprising:

a) an annular carrier supporting a plurality of propeller blades;

b) a ring gear driving a plurality of quill-shafts, one quill-shaft for each propeller blade;

c) a torque multiplier connected between each quill-shaft and a respective propeller blade; and

d) means for changing the speed of the ring gear relative to that of the annular carrier for changing blade pitch.

3. A pitch-change mechanism for an array of aircraft propeller blades carried by an annular carrier, comprising:

a) a stationary hydraulic motor;

b) a drive gear driven by the motor;

c) differential means for driving two pinion gears at speeds having a difference which is proportional to the algebraic speed of the drive gear; and

d) a gear train connecting the differential means with the propeller blades for changing blade pitch in accordance with the algebraic speed difference.

4. A propulsion system for an aircraft, comprising:

a) first and second counterrotating turbines;

b) a gas generator for providing a gas stream for driving both turbines;

c) first and second propellers of the pitch-changeable type driven by the respective first and second turbines;

d) first and second gear trains for changing pitch of the respective first and second propellers;

e) first feathering means for slowing rotation of the first propeller while the gas generator remains running; and

f) second feathering means for slowing rotation of the second propeller while the gas generator remains running.

5. A system according to claim 4 in which the first and second feathering means are operable independently of each other.

6. An aircraft propulsion system, comprising:

a) first and second annular carriers which

i) are counterrotating and coaxial, and

ii) carry respective first and second propeller blade arrays;

b) a first gear train connecting between a first motor, which is mounted to a stationary support, and the first array of propeller blades for changing pitch of the first array, wherein said first gear train comprises a planetary system which includes

i) first and second bevel ring gears which drive shafts which change blade pitch,

ii) first and second ring gears connected to the first and second bevel gears, and driven by a compound planet gear which

A) engages the first and second ring gears at first and second, different, ratios, and

B) engages a third ring gear which is synchronous with the first annular carrier, at a third ratio, different from the first and second ratios, and

iii) a sun gear which drives the compound planet gear and causes opposite relative rotation of the first and second bevel ring gears; and

c) a second gear train connecting between a second motor, which is mounted to a stationary support, and the second array of propeller blades for changing pitch of the second array, independent of the pitch of the first array.

7. An aircraft propulsion system, comprising:

a) first and second annular carriers which

i) are counterrotating and coaxial, and

ii) carry respective first and second propeller blade arrays;

b) a first gear train connecting between a first motor, which is mounted to a stationary support, and the first array of propeller blades for changing pitch of the first array, wherein said first gear train comprises a planetary system which includes

i) first and second bevel ring gears which drive shafts which change blade pitch,

ii) first and second ring gears connected to the first and second bevel gears, and driven by a compound planet gear which

A) engages the first and second ring gears at first and second, different, ratios, and

B) engages a third ring gear which is synchronous with the first annular carrier, at a third ratio, different from the first and second ratios, and

iii) a sun gear which drives the compound planet gear and causes opposite relative rotation of the first and second bevel ring gears; and

c) a second gear train connecting between a second motor, which is mounted to a stationary support, and the second array of propeller blades for changing pitch of the second array, independent of the pitch of the first array, wherein said second gear train comprises a planetary system which includes;

i) first and second bevel ring gears which drive shafts which change blade pitch;

ii) first and second ring gears connected to the first and second bevel gears, and driven by a compound planet gear which

A) engages the first and second ring gears at first and second, different, ratios, and

B) engages a third ring gear which is synchronous with the first annular carrier, at a third ratio, different from the first and second ratios, and

iii) a sun gear which drives the compound planet gear and causes opposite relative rotation of the first and second bevel ring gears.

8. An aircraft propulsion system, comprising:

a) first and second annular carriers which

i) are counterrotating and coaxial, and

ii) carry respective first and second propeller blade arrays;

b) a first gear train connecting between a first motor, which is mounted to a stationary support, and the first array of propeller blades for changing pitch of the first array, wherein said first gear train comprises a planetary system which includes

i) first and second bevel ring gears which drive shafts which change blade pitch,

ii) first and second ring gears connected to the first and second bevel gears, and driven by a compound planet gear which

A) engages the first and second ring gears at first and second, different, ratios, and

B) engages a third ring gear which is synchronous with the first annular carrier, at a third ratio, different from the first and second ratios, and

iii) a sun gear which drives the compound planet gear and causes opposite relative rotation of the first and second bevel ring gears; and

c) a second gear train connecting between a second motor, which is mounted to a stationary support, and the second array of propeller blades for changing pitch of the second array, independent of the pitch of the first array, wherein said second gear train comprises a planetary system which includes;

i) first and second bevel ring gears which drive shafts which change blade pitch;

ii) first and second ring gears connected to the first and second bevel gears, and driven by a compound planet gear which

A) engages the first and second ring gears at first and second, different, ratios, and

B) engages a third ring gear which is synchronous with the first annular carrier, at a third ratio, different from the first and second ratios, and

iii) a sun gear which drives the compound planet gear and causes opposite relative rotation of the first and second bevel ring gears; and

d) wherein said first and second stationary motors independently drive the respective sun gears in the first and second gear trains.

9. An aircraft propulsion system, comprising:

a) first and second annular carriers which

i) are counterrotating and coaxial, and

ii) carry respective first and second propeller blade arrays;

b) a first gear train connecting between a first motor, which is mounted to a stationary support, and the first array of propeller blades for changing pitch of the first array, wherein said first gear train comprises a planetary system which includes

i) first and second bevel ring gears which drive shafts which change blade pitch,

ii) first and second ring gears connected to the first and second bevel gears, and driven by a compound planet gear which

A) engages the first and second ring gears at first and second, different, ratios, and

B) engages a third ring gear which is synchronous with the first annular carrier, at a third ratio, different from the first and second ratios, and

iii) a sun gear which drives the compound planet gear and causes opposite relative rotation of the first and second bevel ring gears;

c) a second gear train connecting between a second motor, which is mounted to a stationary support, and the second array of propeller blades for changing pitch of the second array, independent of the pitch of the first array, wherein said second gear train comprises a planetary system which includes;

i) first and second bevel ring gears which drive shafts which change blade pitch;

ii) first and second ring gears connected to the first and second bevel gears, and driven by a compound planet gear which

A) engages the first and second ring gears at first and second, different, ratios, and

B) engages a third ring gear which is synchronous with the first annular carrier, at a third ratio, different from the first and second ratios, and

iii) a sun gear which drives the compound planet gear and causes opposite relative rotation of the first and second bevel ring gears; and

d) wherein said first and second stationary motors independently drive the respective sun gears in the first and second gear trains.

e) differential means in each gear train for allowing each motor to remain non-rotating when pitch-change is not occurring in the motor'"'"'s respective propeller; and

f) wherein each gear train changes pitch of the respective array of propeller blades in a direction which depends upon the direction of rotation of the respective motor.

10. A system according to claim 9 and further comprising:

g) a first plurality of hub gear sets, each

i) located near the blade root of a respective propeller blade in the first array; and

ii) interconnected with the first gear train for amplifying torque provided by the first gear train; and

h) a second plurality of hub gear sets, each

i) located near the blade root of a respective propeller blade in the second array; and

ii) interconnected with the second gear train for amplifying torque provided by the second gear train.

11. An aircraft propulsion system, comprising:

a) a rotatable turbine having an annular flowpath;

b) an array of propeller blades mounted on an annular carrier surrounding the turbine;

c) a sun gear located radially inside the annular flowpath, and coaxial with, the turbine;

d) a radial array of shafts, all

i) commonly driven by a drive means, which includes said sun gear, located radially inside the turbine flow path; and

ii) extending through the turbine flowpath;

e) a plurality of reduction gears, each interconnected between one shaft and a respective propeller blade, for providing each shaft with a torque advantage over its blade; and

f) means for providing power to the drive means for changing blade pitch.

12. An aircraft propeller system having defined therein a pitch axis for each propeller blade and an axis of rotation for the propeller, comprising:

a) first and second ring gears (250,

     253) which are coaxial with the axis of rotation (67);

b) a gear train connecting between the first and second ring gears and propeller blades (6), such that relative rotation between the first and second ring gears causes a change in pitch of the propeller blades;

c) a sun gear (220) coaxial with the axis of rotation (67);

d) a plurality of planet gears (240) engaging the first and second ring gears at different gear ratios, and engaging the sun gear;

e) a third ring gear (210) fastened to the sun gear;

f) a first stationary gear (200) driving the third ring gear;

g) a second stationary gear (365); and

h) differential means connecting between the first and second stationary gears for allowing positive and negative rotation of an input shaft (410) to respectively accelerate and decelerate the second stationary gear with respect to the first stationary gear.

13. A pitch-change mechanism for an array of aircraft propeller blades carried by an annular carrier, comprising:

a) a stationary hydraulic motor;

b) a sun gear driven by the motor;

c) first and second pinion gears;

d) differential means for

i) driving the first pinion gear faster than the second pinion gear when the sun gear rotates in one direction; and

i) driving the first pinion gear slower than the second pinion gear when the sun gear rotates in the opposite direction; and

e) a gear system including

i) a first ring gear (360) which is synchronous with the annular carrier and which drives the second pinion gear at a fixed speed with respect to the annular carrier;

ii) a second ring gear (210) which is movable with respect to the annular carrier and which engages the first pinion gear;

iii) a sun gear (220) affixed to the second ring gear;

iv) a plurality of planet gears (240) driven by the sun gear;

v) a third ring gear (253) which is synchronous with the rotatable carrier and planet gears;

vi) a fourth ring gear (eg,

     250) which is movable with respect to the annular carrier and engaging the planet gears at a gear ratio different than that between the third ring gear and the planet gears, such that rotation of the planet gears causes relative movement of the third and fourth ring gears;

vii) an annular bevel gear (eg,

     265) affixed to the fourth ring gear; and

viii) a blade bevel gear (270) engaging the annular bevel gear and affixed to a shaft (275) which changes blade pitch when rotated.

14. An aircraft propulsion system, comprising:

a) first and second pinion gears;

b) an array of propeller blades carried by an annular carrier;

c) gear means connecting between the first and second pinion gears and the propeller blades such that, during normal operation;

i) a speed difference between the first and second pinion gears is sufficient, by itself, to cause pitch change;

ii) the magnitude of the speed difference controls the rate of the pitch change;

iii) the algebraic sign of the speed difference controls the direction of pitch change; and

iv) in the absence of pitch change, the first and second pinion gears rotate at equal speeds.

15. An aircraft propulsion system, comprising:

a) first and second pinion gears;

b) an array of propeller blades carried by an annular carrier;

c) gear means connecting between the first and second pinion gears and the propeller blades such that, during normal operation;

i) a speed difference between the first and second pinion gears is sufficient, by itself, to cause pitch change;

ii) the magnitude of the speed difference controls the rate of the pitch change;

iii) the algebraic sign of the speed difference controls the direction of pitch change; and

iv) in the absence of pitch change, the first and second pinion gears rotate at equal speeds; and

d) wherein said gear means comprises a planetary reduction gear system which includes;

i) three ring gears which cooperate with a common planet gear, a first of the ring gears being synchronous with the annular carrier, and the second and third ring gears being driven in opposite relative directions by relative movement between the planet gear and the first ring gear; and

ii) a bevel gear driven by the second and third ring gears and driving a shaft which causes pitch change when rotated.

16. An aircraft propulsion system, comprising:

a) first and second counterrotating propellers;

b) first and second gear trains for changing the respective pitches of the first and second propellers; and

c) unison brake means in each gear train which, when activated,

i) impedes pitch change toward fine pitch and

ii) presents no impediment to pitch change toward a coarser position; and

d) wherein each of said unison brake means comprises a mono-directional centrifugal brake.