Method of guiding a blade having a variable pitch angle

1. A guide device for guiding a variable-pitch blade, in particular in a turbomachine compressor, the blade having a pivot formed by a cylindrical axial shank mounted in a cylindrical housing of a casing and pivotally guided about an axis in said housing by bearings, wherein said bearings are abutment bearings with conical rollers, the rollers having rotation axes which are substantially perpendicular to the pivot axis of the blade, each roller abutment bearing comprises two annular rings with the rollers housed between them, each ring being in a plane substantially perpendicular to the pivot axis of the blade, and a first abutment bearing bears via one of its rings against one end of the blade and via its other ring against a shoulder in the housing in the casing, and the other roller abutment bearing has one of its rings bearing against a shoulder in the housing in the casing, and has its other ring bearing against a clamping nut screwed onto the axial shank of the blade.

2. A guide device according to claim 1 , comprising two axially spaced apart abutment bearings with conical rollers, the rollers of each bearing having rotation axes which lie in a common plane substantially perpendicular to the pivot axis of the blade.

3. A guide device according to claim 1 , including means for clamping the conical rollers in each roller abutment bearing between the rings of the abutment bearing, with a clamping direction which is parallel to the pivot axis of the blade.

4. A guide device according to claim 3 , wherein the clamping force on the rollers of the abutment bearings is greater than the forces exerted on said rollers by the aerodynamic forces acting on the blade.

5. A guide device according to claim 1 , wherein the abutment bearings are mounted in the housing of the casing on either side of a collar that projects into the inside of the housing, the radial surfaces of the collar forming the shoulders in the housing in the casing.

6. A guide device according to claim 1 , wherein the first roller abutment bearing is mounted in leaktight manner in the housing of the casing, bearing via its rings against respective radial surfaces at the end of the blade and on a shoulder in the housing in the casing.

7. A guide device according to claim 1 , wherein, in each roller abutment bearing, one annular ring is centered and fixed on the axial shank of the blade, and the other annular ring is centered and fixed in the housing of the casing.

8. A guide device according to claim 7 , wherein the rings of the roller abutment bearings that are centered in the housing of the casing are the rings that are situated closer together, while the rings of the two roller abutment bearings that are centered on the axial shank of the blade are those that are further apart from each other.

9. A guide device according to claim 7 , wherein the rings centered in the casing are prevented from pivoting, and the rings centered on the axial shank are pivotally mounted.

10. A guide device according to claim 1 , wherein the roller abutment bearings are leaktight.

11. A compressor comprising the guide device for guiding a variable-pitch blade according to claim 1 .

12. A turbomachine comprising the guide device for guiding a variable-pitch blade according to claim 1 .

13. A guide device for guiding a variable-pitch blade comprising:

a blade having a pivot formed by a cylindrical axial shank mounted in a cylindrical housing of a casing; and

bearings configured to pivotally guide the blade about a pivot axis in said housing, said bearings being abutment bearings with conical rollers, the rollers having rotation axes which are substantially perpendicular to the pivot axis of the blade,

wherein each roller abutment bearing comprises two annular rings with the rollers housed between them, each ring being in a plane substantially perpendicular to the pivot axis of the blade, and a first abutment bearing bears via one of its rings against one end of the blade and via its other ring against a shoulder in the housing in the casing, and the other roller abutment bearing has one of its rings bearing against a shoulder in the housing in the casing, and has its other ring bearing against a clamping nut screwed onto the axial shank of the blade.

14. A guide device according to claim 13 , wherein the abutment bearings are two axially spaced apart abutment bearings, and the rollers of each bearing have rotation axes which lie in a common plane substantially perpendicular to the pivot axis of the blade.

15. A guide device according to claim 13 , further comprising:

a clamp configured to hold the conical rollers in each roller abutment bearing between the rings of the abutment bearing, with a clamping direction being parallel to the pivot axis of the blade.

16. A guide device according to claim 15 , wherein a clamping force on the rollers of the abutment bearings is greater than forces exerted on said rollers by aerodynamic forces acting on the blade.

17. A guide device according to claim 13 , wherein the abutment bearings are mounted in the housing of the casing on either side of a collar that projects into the inside of the housing, the radial surfaces of the collar forming the shoulders in the housing in the casing.

18. A guide device according to claim 13 , wherein the first roller abutment bearing is mounted in a leaktight manner in the housing of the casing, bearing via its rings against respective radial surfaces at the end of the blade and on a shoulder in the housing in the casing.

19. A guide device according to claim 13 , wherein, in each roller abutment bearing, one annular ring is centered and fixed on the axial shank-of the blade, and an other annular ring is centered and fixed in the housing of the casing.

20. A guide device according to claim 19 , wherein the rings of the roller abutment bearings that are centered in the housing of the casing are the rings that are situated closer together, while the rings of the two roller abutment bearings that are centered on the axial shank of the blade are those that are further apart from each other.

21. A guide device according to claim 19 , wherein the rings centered in the casing are prevented from pivoting, and the rings centered on the axial shank are pivotally mounted.