Actuator using expansion or contraction to produce linear or rotary motion

1. A motion producing device comprising:

an output member with a contact surface;

a reference member;

an actuator member attached to the reference member, the actuator member having a traction surface and comprising actuator zones, each actuator zone being energizable to move a corresponding portion of the traction surface to change a contact state of the traction surface with the contact surface depending on an energized state of the actuator zone; and

an energy source operatively coupled to the actuator zones for sequentially changing the energized state of the actuator zones;

the actuator member providing a torque transmission path between the reference member and the output member; and

the traction surface being preloaded under compression between the output member and the actuator member.

2. The motion producing device of claim 1 in which, when an actuator zone is energized, the corresponding portion of the traction surface is in contact with the contact surface.

3. The motion producing device of claim 1 in which the output member has an axis, the reference member is concentric to the axis and the actuator zones are spaced circumferentially around the reference member.

4. The motion producing device of claim 1 in which the actuator member comprises an electroactive material that is expandable or contractable in response to an electric current and the actuator zones comprise electrodes.

5. The motion producing device of claim 4 in which the electrodes comprise at least a first array of electrodes and a second array of electrodes with the first array of electrodes disposed closer to the reference member than the second array of electrodes.

6. The motion producing device of claim 4 in which the electrodes comprise at least an inner array of electrodes and an outer array of electrodes.

7. The motion producing device of claim 1 in which the reference member is disposed inwardly of the output member.

8. The motion producing device of claim 1 in which the reference member is disposed outwardly of the output member.

9. The motion producing device of claim 1 in which the contact surface and traction surface each comprise gear teeth.

10. The motion producing device of claim 9 in which the gear teeth are rounded.

11. A motion producing device comprising:

an output member with a contact surface and an axis;

a reference member concentric to the axis;

an actuator member attached to the reference member, the actuator member having a traction surface and comprising actuator zones, each actuator zone being energizable to move a corresponding portion of the traction surface to change a contact state of the traction surface with the contact surface depending on an energized state of the actuator zone;

the actuator zones being spaced circumferentially around the reference member;

an energy source operatively coupled to the actuator zones for sequentially changing the energized state of the actuator zones;

the actuator member providing a torque transmission path between the reference member and the output member; and

reinforcement flexures within and disposed around the actuator member, the reinforcement flexures extending radially outward and being slanted circumferentially through the actuator member.

12. The motion producing device of claim 11 in which the output member is at least partly spherical and the reference member is at least partly spherical to rotate within or outside of the output member.

13. The motion producing device of claim 12 in which the output member and reference member are supported on a shaft.

14. The motion producing device of claim 11 in which the reference member and output member are each cylindrical and axially movable relative to each other under forces generated by the actuator zones.

15. The motion producing device of claim 11 in which the reinforcement flexures are bounded circumferentially by respective inwardly concave and outwardly convex surfaces.

16. The motion producing device of claim 11 in which the contact surface and traction surface each comprise gear teeth.

17. A motion producing device comprising:

an output member with a contact surface and an axis;

a reference member concentric to the axis;

an actuator member attached to the reference member, the actuator member having a traction surface and comprising actuator zones, each actuator zone being energizable to move a corresponding portion of the traction surface to change a contact state of the traction surface with the contact surface depending on an energized state of the actuator zone;

the actuator zones being spaced circumferentially around the reference member;

an energy source operatively coupled to the actuator zones for sequentially changing the energized state of the actuator zones;

the actuator member providing a torque transmission path between the reference member and the output member; and

the actuator member comprising a first actuator segment and a second actuator segment that are spaced apart axially.

18. The motion producing device of claim 17 in which the first actuator segment and the second actuator segment have axially tapered traction surfaces.

19. The motion producing device of claim 18 in which the respective first actuator segment and the second actuator segment taper oppositely.

20. The motion producing device of claim 17 in which the contact surface and traction surface each comprise gear teeth.

21. A motion producing device comprising:

an output member with a contact surface;

a reference member;

an actuator member attached to the reference member, the actuator member having a traction surface and comprising actuator zones, each actuator zone being energizable to move a corresponding portion of the traction surface to change a contact state of the traction surface with the contact surface depending on an energized state of the actuator zone;

an energy source operatively coupled to the actuator zones for sequentially changing the energized state of the actuator zones;

the actuator member providing a torque transmission path between the reference member and the output member; and

each of the reference member, actuator member and output member being linear.

22. The motion producing device of claim 21 in which the contact surface and traction surface each comprise gear teeth.

23. A motion producing device comprising:

an output member with a contact surface;

a reference member;

an actuator member attached to the reference member, the actuator member having a traction surface and comprising actuator zones, each actuator zone being energizable to move a corresponding portion of the traction surface to change a contact state of the traction surface with the contact surface depending on an energized state of the actuator zone;

an energy source operatively coupled to the actuator zones for sequentially changing the energized state of the actuator zones;

the actuator member providing a torque transmission path between the reference member and the output member; and

each actuator zone having an axis and further comprising confining members at respective axial ends of the respective actuator zone.

24. The motion producing device of claim 23 in which the energy source comprises a hydraulic supply, the actuator zones have hollow interiors and the hydraulic supply is coupled by lines to the hollow interiors.

25. The motion producing device of claim 23 in which the confining members comprise electromagnetic coils.

26. The motion producing device of claim 23 in which the contact surface and traction surface each comprise gear teeth.

27. A motion producing device comprising:

an output member with a contact surface;

a reference member;

an actuator member attached to the reference member, the actuator member having a traction surface and being made at least partially of an expandable or contractable material that is expandable or contractable when energized;

the expandable or contractable material being preloaded under compression between the output member and the actuator member;

the contact surface of the output member being in continuous contact with the traction surface of the actuator member; and

an energy source operatively coupled to the actuator member for sequential energization and actuation of spatially separated portions of the actuator member.

28. The motion producing device of claim 27 in which the expandable or contractable material is a polymer that is expandable or contractable in response to an electric current and the energy source comprises electrodes in contact with the expandable or contractable material.

29. The motion producing device of claim 27 in which the output member has an axis, the reference member is concentric to the axis and the spatially separated portions of the actuator member are spaced circumferentially.

30. The motion producing device of claim 29 in which the actuator member is formed of at least two segments that are spaced apart axially.

31. The motion producing device of claim 27 in which the contact surface and traction surface each comprise gear teeth.

32. A motion producing device comprising:

an output member with a contact surface and an axis of rotation;

a reference member concentric to the axis;

an actuator member attached to the reference member, the actuator member having a traction surface and being made at least partially of an expandable or contractable material that is expandable or contractable when energized;

the contact surface of the output member being in continuous contact with the traction surface of the actuator member; and

an energy source operatively coupled to the actuator member for sequential energization and actuation of spatially separated portions of the actuator member;

the spatially separated portions of the actuator member being spaced circumferentially; and

the contact surface of the output member and the traction surface each having cooperating helical shapes to convert rotation of the output member into linear motion.

33. The motion producing device of claim 32 in which the contact surface and traction surface each comprise gear teeth.

34. A motion producing device comprising:

an output member with a contact surface and an axis of rotation;

a reference member concentric about the axis;

an actuator member attached around the reference member, the actuator member having a traction surface and being made at least in part of an expandable or contractable material that is expandable or contractable when energized to press the traction surface against the contact surface or retract the traction surface from the contact surface;

the contact surface of the output member and the traction surface each having cooperating helical shapes to convert rotation of the output member into linear motion; and

an energy source operatively coupled to the actuator member for sequential energization and actuation of circumferentially spaced portions of the actuator member.

35. The motion producing device of claim 34 in which the expandable or contractable material is a polymer that is expandable or contractable in response to an electric current and the energy source comprises electrodes in contact with the expandable or contractable material.

36. The motion producing device of claim 34 in which the actuator member is formed of at least two segments that are spaced apart axially.