Coupling system for a star gear train in a gas turbine engine

1. A star gear train having:

a sun gear rotatable by a shaft;

a ring gear secured to a ring gear shaft;

a plurality of star gears rotatably mounted in a star carrier and meshing with the sun gear and the ring gear; and

a coupling system comprising:

a carrier flexible coupling connecting to a nonrotating mechanical ground;

a torque frame connecting the star carrier to the carrier flexible coupling; and

a deflection limiter comprising a spline that inhibits radial displacement and circumferential rotation of the star carrier, the deflection limiter comprising:

an annular rim of the torque frame forming an outer shoulder;

a plurality of tabs radially extending from the shoulder;

an annular flange extending axially from the carrier flexible coupling; and

a plurality of slots disposed in the annular flange to engage the plurality of tabs.

2. The star gear train of claim 1 wherein the carrier flexible coupling comprises:

a mounting head connected to the ground, wherein the annular flange extends from the mounting head;

a first longitudinal segment extending generally radially inward from the mounting head;

a straight lateral segment extending generally axially from the first longitudinal segment;

a second longitudinal segment extending generally radially inward from the lateral segment; and

a torque head connected to the second longitudinal segment and coupled to the torque frame.

3. The star gear train of claim 2 wherein the coupling system further comprises:

a sun gear flexible coupling connecting the sun gear to the shaft.

4. A star gear train comprising:

a sun gear rotatable by a shaft;

a ring gear secured to a ring gear shaft;

a plurality of star gears rotatably mounted in a star carrier and meshing with the sun gear and the ring gear;

a torque frame extending from the star carrier;

a carrier flexible coupling connecting the torque frame to a non-rotating mechanical ground; and

an annular flange extending from the carrier flexible coupling to engage and limit displacement of the torque frame.

5. The star gear train of claim 4 wherein the annular flange engages the torque frame to inhibit radial displacement and circumferential rotation between the torque frame and the carrier flexible coupling.

6. The star gear train of claim 4 wherein the annular flange is positioned radially between the torque frame and the non-rotating mechanical ground.

7. The star gear train of claim 4 wherein the carrier flexible coupling comprises:

a stationary portion connected to the non-rotating mechanical ground and from which the annular flange extends; and

a radially deflectable portion extending from the stationary portion to connect to the torque frame.

8. The star gear train of claim 4 wherein the torque frame comprises:

a plurality of fingers extending into the torque frame;

an annular rim from which the fingers extend;

a torque disk extending from the annular rim; and

a torque head connected to the torque disk.

9. The star gear train of claim 8 wherein the carrier flexible coupling comprises:

a carrier torque head coupled to the torque head of the torque frame;

a mounting head connected to the non-rotating mechanical ground, wherein the annular flange extends from the mounting head; and

a plurality of segments extending between the torque head and the mounting head.

10. The star gear train of claim 9 wherein the torque frame further comprises:

a shoulder on the annular rim; and

tabs extending from the shoulder to engage slots in the annular flange.

11. The star gear train of claim 9 wherein the plurality of segments are Z-shaped so as to provide radial resiliency and to extend across the annular rim and the torque disk.

12. The star gear train of claim 11 wherein:

the fingers are inserted into an axial aft side of the star carrier;

the torque disk extends axially afterward from the annular rim; and

the plurality of segments extend axially forward from the carrier torque head to the mounting head, such that the annular flange engages the annular rim.

13. A mounting system for an epicyclic gear system, the mounting system comprising:

a non-rotating mechanical ground;

a torque frame comprising:

an annular rim having a first face and a second face;

a plurality of fingers extending from the first face of the annular rim, the plurality of fingers configured to engage the epicyclic gear system;

a torque disk extending radially inward and axially afterward from the second face of the annular rim; and

a torque head connected to the torque disk;

a flexible coupling comprising:

a carrier torque head coupled to the torque head of the torque frame;

a mounting head connected to the non-rotating mechanical ground; and

a plurality of segments extending between the torque head and the mounting head; and

a deflection limiter engaging the torque frame and the flexible coupling to limit relative radial and circumferential movement between the deflection limiter and the torque frame.

14. The mounting system of claim 13 wherein the deflection limiter comprises:

an annular flange extending from the mounting head to engage the torque frame.

15. The mounting system of claim 14 wherein the deflection limiter comprises a spline.

16. The mounting system of claim 14 wherein the annular flange is positioned radially between the annular rim and the non-rotating mechanical ground.

17. The mounting system of claim 14 wherein the plurality of segments extend axially forward from the carrier torque head to the mounting head to extend across the torque disk.

18. The mounting system of claim 14 wherein the flexible coupling comprises:

a first longitudinal segment extending generally radially inward from the mounting head;

a lateral segment extending generally axially from the first longitudinal segment; and

a second longitudinal segment extending generally radially inward from the lateral segment to the second mounting flange;

wherein the lateral segment extends straight between the first longitudinal segment and the second longitudinal segment; and

wherein the lateral segment is flared radially outward from the first longitudinal segment to the second longitudinal segment.

19. The mounting system of claim 14 and further comprising:

a radially opened annular notch disposed in the mounting head of the flexible coupling; and

an O-ring disposed in the notch.

20. The mounting system of claim 14 and further comprising:

a through-bore disposed in the mounting head to permit lubrication fluid to pass through the flexible coupling.