Downhole torque-generating and generator combination apparatus

1. A combination of a torque-generating apparatus and an alternator/generator positioned axially adjacent to one another on a common shaft ( 8 ), the torque-generating apparatus comprising: a first assembly ( 10 , 25 ) including a generally cylindrical member of magnetically soft material and having a longitudinal axis, a second assembly ( 2 ) arranged coaxially within the first assembly and including an electromagnetic winding ( 4 ), the first assembly ( 10 , 25 ) and the second assembly ( 2 ) being rotatable relative to each other about the axis; the alternator/generator incorporating a permanent magnent rotor; the combination further including rectifications means ( 31 ) for converting alternating current electrical output from the alternator/generator ( 22 ) to provide direct current to the electromagnetic winding ( 4 ) of the torque-generating apparatus, the voltage of which direct current is dependent upon the speed of rotation of the alternator/generator, whereby relative rotation between the first ( 10 , 25 ) and second ( 2 ) assemblies of the torque-generating apparatus induces a magnetic field which generates rotational torque between the first and second assemblies to generate a progessive braking effect dependent on the voltage applied to the electromagnetic winding ( 4 ).

2. A combination as claimed in claim 1 , wherein the first assembly is a rotor assembly ( 10 , 25 ) of the torque generating apparatus for producing rotational torque and the second assembly ( 2 ) is a stator assembly of the torque generating apparatus.

3. A combination as claimed in claim 1 , wherein the second assembly ( 2 ) comprises a magnetically soft steel.

4. A combination as claimed in claim 1 , wherein the first ( 10 , 25 ) and second assemblies ( 2 ) are separated by a narrow gap.

5. A combination as claimed in claim 1 , wherein the first assembly ( 10 , 25 ) is disposed so as to substantially surround the second assembly ( 2 ).

6. A combination as claimed in claim 1 , wherein the first assembly is of a form selected from substantially solid ( 10 ) or is formed from a plurality of laminations ( 25 ).

7. A combination as claimed in claim 1 , wherein the second assembly ( 2 ) is of a form selected from substantially solid or is formed from a plurality of laminations.

8. A combination as claimed in claim 1 , wherein a number of generally longitudinal grooves ( 20 ) are provided to the inside surface of the cylindrical member of the first assembly ( 10 ).

9. A combination as claimed in claim 8 , wherein the grooves ( 20 ) are substantially parallel to the longitudinal axis of the first assembly ( 10 ).

10. A combination as claimed in claim 8 , wherein the grooves ( 20 ) are provided so as to form at least a partial helix around the longitudinal axis of the first assembly ( 10 ).

11. A combination as claimed in claim 1 , wherein the second assembly ( 2 ) is provided with a number of pole pieces extending generally radially from the longitudinal axis thereof.

12. A combination as claimed in claim 11 , wherein the pole pieces of the second assembly are provided with an electromagnetic winding, adjacent poles being magnetisable in opposite directions.

13. A combination as claimed in claim 11 , wherein means is provided to control the degree of the magnetisation.

14. A combination as claimed in claim 11 , wherein gaps between the pole pieces are filled with a potting material.

15. A combination as claimed in claim 11 , wherein a surface of the second assembly ( 2 ) is covered with a layer selected from soft magnetic and non-magnetic material ( 21 ).

16. A combination as claimed in claim 1 , wherein the first assembly ( 10 , 25 ) is provided with external rotation means ( 12 ) adapted to rotate the first assembly ( 10 , 25 ).

17. A combination as claimed in claim 16 , wherein the external rotation means comprises an impeller ( 12 ).

18. A combination as claimed in claim 17 , wherein the impeller ( 12 ) is adapted to be disposed in use within a moving fluid, the motion of the fluid acting upon the impeller so as to rotate the first assembly.

19. A combination as claimed in claim 1 , wherein the alternator/generator ( 22 ) is provided with external rotation means ( 12 ).

20. A combination as claimed in claim 19 , wherein the external rotation means comprises an impeller ( 12 ) adapted to rotate the alternator/generator ( 22 ).

21. A combination as claimed in claim 20 , wherein the impeller ( 12 ) is adapted to be disposed in use within a moving fluid, the motion of the fluid acting upon the impeller ( 12 ) so as to rotate the alternator/generator ( 22 ).

22. A combination as claimed in claim 20 , wherein the impeller ( 12 ) is an integral part of a magnet carrier of the alternator/generator ( 22 ).

23. A combination as claimed in claim 1 , wherein the rectified electrical output of the alternator/generator ( 22 ) is connected directly to the electromagnetic winding ( 4 ) of the torque-generating apparatus to create the electromagnetic braking effect.

24. A combination as claimed in claim 23 , wherein the electromagnetic braking effect can be modified by varying the resistance of the electromagnetic winding ( 4 ).

25. A combination as claimed in claim 24 wherein the resistance of the electromagnetic winding ( 4 ) can be modified by varying the resistance of the electromagnetic winding ( 4 ) with at least one external resistance.

26. A combination as claimed in claim 24 wherein the resistance of the electromagnetic winding ( 4 ) can be modified by changing the gauge of the winding wire.

27. A combination as claimed in claim 23 wherein in the electromagnetic braking effect can be modified by varying the gap between the first ( 10 , 25 ) and second ( 2 ) assemblies of the torque-generating apparatus.

28. A combination as claimed in claim 1 , wherein the rectified electrical output of the alternator/generator ( 22 ) is connected indirectly to the electromagnetic winding ( 4 ) of the torque-generating apparatus by way of alternator voltage regulation means to create the electromagnetic braking effect.

29. A combination as claimed in claim 1 , wherein the progressive braking effect is activated at a predetermined set point.

30. A combination as claimed in claim 29 , wherein the predetermined set point is determined by the voltage output of the alternator/generator ( 22 ).

31. A combination as claimed in claim 30 wherein the predetermined set point is variable.

32. A method of generating an electromagnetic braking effect in a combination of a torque-generating apparatus and an alternator/generator positioned axially adjacent to one another on a common shaft ( 8 ), the torque-generating apparatus comprising: a first assembly ( 10 , 25 ) including a generally cylindrical member of magnetically soft material and having a longitudinal axis, a second assembly ( 2 ) arranged coaxially within the first assembly and including an electromagnetic winding ( 4 ), the first assembly ( 10 , 25 ) and the second assembly ( 2 ) being rotable relative to each other about the axis; the alternator/generator incorporating a permanent magnet rotor; the combination further including rectification means ( 31 ) for converting alternating current electrical output from the alternator/generator ( 22 ) to provide a direct current voltage which is dependent upon the speed of rotation of the alternator/generator, the method including the step of applying the voltage to the electromagnetic winding ( 4 ) of the torque-generating apparatus whereby relative rotation between the first ( 10 , 25 ) and second ( 2 ) assemblies of the torque-generating apparatus induces a magnetic field which generates rotational torque between the first and second assemblies to generate a progessive braking effect dependent on the voltage applied to the electromagnetic winding ( 4 ).

33. A method according to claim 32 and including the step of connecting the electrical output of the alternator/generator ( 22 ) directly to the electromagnetic winding ( 4 ) of the torque-generating apparatus to create the electromagnetic braking effect.

34. A method according to claim 33 and including the step of varying the resistance of the electromagnetic winding ( 4 ) to modify the electromagnetic braking effect.

35. A method according to claim 34 , wherein the resistance of the electromagnetic winding ( 4 ) is modified with a least one external resistance.

36. A method according to claim 34 , wherein the resistance of the electromagnetic winding ( 4 ) is modified by changing the gauge of the winding wire.

37. A method according to claim 33 and including the step of varying the gap between the first ( 10 , 25 ) and second ( 2 ) assemblies of the torque-generating apparatus to modify the electromagnetic braking effect.

38. A method according to claim 32 and including the step of connecting the rectified electrical output of the alternator/generator ( 22 ) indirectly to the electromagnetic winding ( 4 ) of the torque-generating apparatus by way of alternator voltage regulation means to create the electromagnetic braking effect.

39. A method according to claim 38 and including the step of activating the progressive braking effect at a predetermined set point.

40. A method according to claim 39 wherein the predetermined set point is determined by the voltage output of the alternator/generator ( 22 ).

41. A method according to claim 40 , wherein the predetermined set point is variable.