Directional drilling tool with eccentric coupling

1. A directional drilling tool comprising:

a drive shaft having a longitudinal bore;

a variable position stabilizer, the variable position stabilizer being a sleeve movable radially with respect to a longitudinal axis of the drive shaft;

an inner eccentric sleeve having an eccentric bore, the drive shaft disposed inside the bore of said inner sleeve, the inner sleeve rotatable relative to and concentric with the drive shaft;

an outer eccentric sleeve having an eccentric bore, the inner sleeve disposed inside the bore of said outer sleeve, the outer sleeve rotatable relative to and not concentric with the drive shaft, the outer eccentric sleeve disposed inside the variable position stabilizer,

wherein the radial position of said variable position stabilizer is adjusted by relative rotation of said outer eccentric sleeve and said inner eccentric sleeve; and

an eccentric coupler comprising:

a first coupler sleeve, the first coupler sleeve mechanically coupled with an outer drive sleeve, the outer drive sleeve rotatable by a first motor, the outer drive sleeve concentric with the drive shaft;

a second coupler sleeve;

a first complementary tab and groove set, comprising at least one pair of diametrically opposed tabs and one pair of diametrically opposed grooves configured to transmit torque between said first coupler sleeve and said second coupler sleeve, the tabs slidable within the grooves in a direction transverse to a longitudinal axis of the first coupler sleeve and a longitudinal axis of the second coupler sleeve;

a third coupler sleeve, the third coupler sleeve mechanically coupled to the outer eccentric sleeve; and

a second complementary tab and groove set, comprising at least one pair of diametrically opposed tabs and one pair of diametrically opposed grooves configured to transmit torque between said second coupler sleeve and said third coupler sleeve, the tabs slidable within the grooves in a direction transverse to the longitudinal axis of the second coupler sleeve and a longitudinal axis of the third coupler sleeve, wherein the grooves of said second complementary tab and groove set are orthogonal to the grooves of said first complementary tab and groove set.

2. The directional drilling tool of claim 1 wherein said eccentric coupler transmits torque to said outer eccentric sleeve having an eccentric bore to adjust the position of said variable position stabilizer.

3. The directional drilling tool of claim 1 wherein each tab of said first and second complementary tab and groove sets has a circular lobe portion and a narrow extended neck portion configured such that there is a space between the opposing faces of their associated sleeves permitting each tab to rotate to a limited extent when engaged in its complementary groove.

4. The directional drilling tool of claim 1 , wherein the inner eccentric sleeve is mechanically coupled to an inner drive sleeve rotatable by a second motor, the inner drive sleeve concentric with the drive shaft.

5. The directional drilling tool of claim 1 , wherein the outer drive sleeve is mechanically coupled to the first coupler sleeve by a set of splines.

6. The directional drilling tool of claim 1 , wherein the third coupler sleeve is mechanically coupled to the outer eccentric sleeve by a set of fingers on the third coupler sleeve which engage a set of fingers of the outer eccentric sleeve.

7. The directional drilling tool of claim 1 , wherein the first and second coupler sleeves and the second and third coupler sleeves are free to move relative to each other in a direction transverse to the longitudinal axes of the respective sleeves.

8. The directional drilling tool of claim 1 , further comprising one or more radial bearings positioned between the drive shaft and the inner eccentric sleeve, between the inner eccentric sleeve and the outer eccentric sleeve, between the outer eccentric sleeve and the variable position stabilizer, or combinations thereof.

9. A directional drilling tool comprising:

a drive shaft having a longitudinal bore;

a variable position stabilizer, the variable position stabilizer being a sleeve movable radially with respect to a longitudinal axis of the drive shaft;

an inner eccentric sleeve having an eccentric bore, the drive shaft disposed inside the bore of said inner sleeve, the inner sleeve rotatable relative to and concentric with the drive shaft;

an intermediate outer housing, the intermediate outer housing having a longitudinal axis in common with the drive shaft;

an outer eccentric sleeve having an eccentric bore, the inner sleeve disposed inside the bore of said outer sleeve, the outer sleeve rotatable relative to and not concentric with the drive shaft, the outer eccentric sleeve disposed inside the variable position stabilizer,

wherein the radial position of said variable position stabilizer is adjusted by relative rotation of said outer sleeve and said inner sleeve;

a first eccentric coupler comprising:

a first coupler sleeve, the first coupler sleeve mechanically coupled with an outer drive sleeve, the outer drive sleeve rotatable by a first motor, the outer drive sleeve concentric with the drive shaft;

a second coupler sleeve;

a first complementary tab and groove set, comprising at least one pair of diametrically opposed tabs and one pair of diametrically opposed grooves configured to transmit torque between said first coupler sleeve and said second coupler sleeve, the tabs slidable within the grooves in a direction transverse to a longitudinal axis of the first coupler sleeve and a longitudinal axis of the second coupler sleeve;

a third coupler sleeve, the third coupler sleeve mechanically coupled to the outer eccentric sleeve; and

a second complementary tab and groove set, comprising at least one pair of diametrically opposed tabs and one pair of diametrically opposed grooves configured to transmit torque between said second coupler sleeve and said third coupler sleeve, the tabs slidable within the grooves in a direction transverse to the longitudinal axis of the second coupler sleeve and a longitudinal axis of the third coupler sleeve, wherein the grooves of said second complementary tab and groove set are orthogonal to the grooves of said first complementary tab and groove set; and

a second eccentric coupler comprising:

a fourth coupler sleeve, the fourth coupler sleeve mechanically coupled to the intermediate outer housing;

a fifth coupler sleeve;

a third complementary tab and groove set, comprising at least one pair of diametrically opposed tabs and one pair of diametrically opposed grooves configured to transmit torque between said fourth coupler sleeve and said fifth coupler sleeve, the tabs slidable within the grooves in a direction transverse to a longitudinal axis of the fourth coupler sleeve and a longitudinal axis of the fifth coupler sleeve;

a sixth coupler sleeve, the sixth coupler sleeve coupled to the variable position stabilizer; and

a fourth complementary tab and groove set, comprising at least one pair of diametrically opposed tabs and one pair of diametrically opposed grooves configured to transmit torque between said fifth coupler sleeve and said sixth coupler sleeve, the tabs slidable within the grooves in a direction transverse to the longitudinal axis of the fifth coupler sleeve and a longitudinal axis of the sixth coupler sleeve, wherein the grooves of said fourth complementary tab and groove set are orthogonal to the grooves of said third complementary tab and groove set.

10. The directional drilling tool of claim 9 wherein one of the first and second eccentric coupler transmits torque to said outer eccentric sleeve having an eccentric bore to adjust the position of said variable position stabilizer.

11. The directional drilling tool of claim 9 wherein the tabs of at least one of said complementary tab and groove sets has a circular lobe portion and a narrow extended neck portion configured such that there is a space between the opposing faces of their associated sleeves permitting each tab to rotate to a limited extent when engaged in its complementary groove.

12. The directional drilling tool of claim 9 , wherein the inner eccentric sleeve is mechanically coupled to an inner drive sleeve rotatable by a second motor, the inner drive sleeve concentric with the drive shaft.

13. The directional drilling tool of claim 9 , wherein the outer drive sleeve is mechanically coupled to the first coupler sleeve by a set of splines.

14. The directional drilling tool of claim 9 , wherein the third coupler sleeve is mechanically coupled to the outer eccentric sleeve by a set of fingers on the third coupler sleeve which engage a set of fingers of the outer eccentric sleeve.

15. The directional drilling tool of claim 9 , wherein the fourth coupler sleeve is mechanically coupled to the intermediate outer housing by a set of splines, welding, or a threaded connection.

16. The directional drilling tool of claim 9 , wherein the sixth coupler sleeve is coupled to the variable position stabilizer by a threaded connection or welding.

17. The directional drilling tool of claim 9 , wherein the sixth coupler sleeve is formed as an integral part of the variable position stabilizer.

18. The directional drilling tool of claim 9 , wherein the first, second, fourth, and fifth coupler sleeves are free to move relative to the second, third, fifth, and sixth coupler sleeves respectively in a direction transverse to the longitudinal axes of the respective sleeves.

19. The directional drilling tool of claim 9 , further comprising one or more radial bearings positioned between the drive shaft and the inner eccentric sleeve, between the inner eccentric sleeve and the outer eccentric sleeve, between the outer eccentric sleeve and the variable position stabilizer, or combinations thereof.

20. The directional drilling tool of claim 9 , wherein the variable position stabilizer is movable relative to the intermediate outer housing and is rotationally linked to the intermediate outer housing.