Link device of controllable variable length

1. A controllable variable length link device comprising:

a first half-link including a first end connected to a driving system and a second end;

a second half-link including a first end connected to a driven system and a second end;

a rotary displacement member including a rotator shaft and a rotary head cooperating with said second ends of said half-links to bring about opposite movement of said half-links;

a bearing unit in which said rotator shaft is mounted;

first and second guiding units which guide said first and second half-links, respectively, in translation in at least two parallel directions, said guiding units being mechanically connected to said bearing unit; and

a driving unit which drives said shaft in rotation in both directions in accordance with a predetermined relationship, by which the length of the link may be varied based on the rotation of said shaft, when said link device is operating.

2. A link device according to claim 1 , wherein each of said guiding units comprises a portion close to the second end of the respective half-link which includes a cylindrical external surface that is parallel to the axis of said half-link and a guide member mechanically connected to said bearing unit including a passage conjugate with said cylindrical surface.

3. A link device according to claim 2 , further comprising a casing in which said bearing unit and said two guide members of said guiding units are formed.

4. A link device according to claim 2 , wherein said rotary head of said rotary member is a yoke comprising two arms extending radially relative to said shaft, each arm being connected to the second end of one half-link.

5. A link device according to claim 4 , wherein said passages in said guide members are aligned.

6. A link device according to claim 2 , wherein each half-link has near its second end a rack portion and said head of said rotary member is a pinion meshing with said racks.

7. A link device according to claim 6 , wherein said passages in said guide members have parallel axes.

8. A link device according to claim 6 , wherein said guiding units further comprise two rings forming cams in which said half-links are slidably mounted, said rings being disposed on respective opposite sides of said rack portion.

9. A link device according to claim 8 , wherein said guiding units further comprise means for immobilizing said rings against rotation and against movement in translation in a direction parallel to the axis of the half-link.

10. A link device according to claim 1 , wherein said driving unit includes a motor with an output shaft that is mechanically connected to said shaft of said rotary member.

11. A link device according to claim 1 , wherein said driving unit includes an arm orthogonal to said drive shaft and one end of which is fastened to said drive shaft and the other end of which is slidably mounted in a bearing attached to a pivot fixed relative to a casing.

12. A link device according to claim 1 , wherein said driving unit includes an arm orthogonal to said drive shaft and a first end of which is fastened to said shaft and the other end of which is fastened to a roller constrained to move in a fixed slot.

13. A variable pitch guide vane control device comprising a link device comprising:

a first half-link including a first end connected to a driving system and a second end;

a second half-link including a first end connected to a driven system and a second end;

a rotary displacement member including a rotator shaft and a rotary head cooperating with said second ends of said half-links to bring about opposite movement of said half-links;

bearing means in which said rotator shaft is mounted

respective means for guiding said two half-links in translation in at least two parallel directions, said guiding means being mechanically connected to said bearing means; and

means for driving said shaft in rotation in both directions in accordance with a predetermined relationship.

14. A turbomachine compressor comprising a link device comprising:

a first half-link including a first end connected to a driving system and a second end;

a second half-link including a first end connected to a driven system and a second end;

a rotary displacement member including a rotator shaft and a rotary head cooperating with said second ends of said half-links to bring about opposite movement of said half-links;

bearing means in which said rotator shaft is mounted;

respective means for guiding said two half-links in translation in at least two parallel directions, said guiding means being mechanically connected to said bearing means; and

means for driving said shaft in rotation in both directions in accordance with a predetermined relationship.

15. A turbomachine comprising a link device comprising:

a first half-link including a first end connected to a driving system and a second end;

a second half-link including a first end connected to a driven system and a second end;

a rotary displacement member including a rotator shaft and a rotary head cooperating with said second ends of said half-links to bring about opposite movement of said half-links;

bearing means in which said rotator shaft is mounted;

respective means for guiding said two half-links in translation in at least two parallel directions, said guiding means being mechanically connected to said bearing means; and

means for driving said shaft in rotation in both directions in accordance with a predetermined relationship.