Control of variable-pitch blades

1. A device for controlling a pivot of a variable-pitch blade comprising:

a control lever;

a blade pivot with a bottom end and a top end, said top end being connected to the control lever; and

first and second swivel bearings, the first swivel bearing being placed at the bottom end of the pivot and the second swivel bearing being placed at the top end of the pivot,

wherein each of the first and second swivel bearings includes an inner race with a spherical outer surface and an outer race with a spherical inner surface, the spherical outer surface of the inner race cooperating with the spherical inner surface of the outer race to form a swivel connection, wherein the inner race of the swivel bearings and the pivot are prevented from rotating relative to one another.

2. The device for controlling a pivot of a variable-pitch blade as claimed in claim 1 , wherein the pivot comprises at least one flat on its outer surface, the inner surface of the inner race comprising a matching shape.

3. The device for controlling a pivot of a variable-pitch blade as claimed in claim 1 , wherein the pivot has a tenon shape and the inner shape of the inner race has a mortice shape.

4. The device for controlling a pivot of a variable-pitch blade as claimed in claim 1 , wherein the pivot and the inner race of the swivel bearings have matching square-shaped sections.

5. The device for controlling a pivot of a variable-pitch blade as claimed in one of claims 2 to 4 , wherein a plastic film is interposed between the pivot and an inner surface of the inner race of the swivel bearings.

6. A stator comprising a casing with an axis of revolution comprising at least one bore made along a radial axis oriented perpendicularly to said axis of revolution, which also comprises:

at least one control device as claimed in claim 1 , and

at least one blade oriented along the radial axis placed inside the casing, said blade being fixedly attached to the pivot via the bottom end of said pivot,

the swivel bearings being placed inside the bore.

7. The stator as claimed in claim 6 , wherein the bore comprises at least one facing designed to receive a swivel bearing.

8. The stator as claimed in one of claim 6 or 7 , wherein the attachment of a swivel bearing in the bore may be carried out by shrink-fitting, welding or brazing.

9. The stator as claimed in claim 6 , wherein the bottom end of the pivot has an increasing diameter.

10. A compressor comprising:

a stator including:

a casing with an axis of revolution comprising at least one bore made along a radial axis oriented perpendicularly to said axis of revolution;

at least one control device including a control lever; a blade pivot with a bottom end and a top end, said top end being connected to the control lever; and first and second swivel bearings, the first swivel bearing being placed at the bottom end of the pivot and the second swivel bearing being placed at the top end of the pivot; and

at least one blade oriented along the radial axis placed inside the casing, said blade being fixedly attached to the pivot via the bottom end of said pivot,

wherein each of the first and second swivel bearings includes an inner race with a spherical outer surface and an outer race with a spherical inner surface, the spherical outer surface of the inner race cooperating with the spherical inner surface of the outer race to form a swivel connection, and

wherein the swivel bearings being placed inside the bore, pivot are prevented from rotating relative to one another.

11. A turbomachine comprising:

a compressor including a stator, the stator including:

a casing with an axis of revolution comprising at least one bore made along a radial axis oriented perpendicularly to said axis of revolution;

at least one control device including a control lever; a blade pivot with a bottom end and a top end, said top end being connected to the control lever; and first and second swivel bearings, the first swivel bearing being placed at the bottom end of the pivot and the second swivel bearing being placed at the top end of the pivot; and

at least one blade oriented along the radial axis placed inside the casing, said blade being fixedly attached to the pivot via the bottom end of said pivot,

wherein each of the first and second swivel bearings includes an inner race with a spherical outer surface and an outer race with a spherical inner surface, the spherical outer surface of the inner race cooperating with the spherical inner surface of the outer race to form a swivel connection, and wherein the swivel bearings being placed inside the bore, wherein the inner race of the swivel bearings and the pivot are prevented from rotating relative to one another.

12. The device for controlling a pivot of a variable-pitch blade as claimed in claim 1 , wherein the inner race of each of the first and second swivel bearings has a cylindrical inner surface.

13. The device for controlling a pivot of a variable-pitch blade as claimed in claim 12 , wherein the cylindrical inner surface of the inner race of each of the first and second bearings abuts the pivot.

14. The device for controlling a pivot of a variable-pitch blade as claimed in claim 1 , wherein the outer race of each of the first and second swivel bearings has a cylindrical outer surface.

15. The device for controlling a pivot of a variable-pitch blade as claimed in claim 1 , wherein the top end of the blade pivot includes a threaded rod which cooperates with a nut and a washer to connect the top end of the blade pivot to the control lever.