Twisted string transmission

1. A twisted string actuator that converts rotational motion to linear motion, comprising:

a motor that generates the rotational motion; and

a string having threads that are substantially parallel and twist about each other between the motor and a load, the string having different thread diameters at different portions of the string along its length between the motor and the load, wherein the string connects to the motor at a first end thereof and the load at a second end thereof, and the actuator is without a split between the motor and the load that engages the threads and separates the threads in a direction transverse to a longitudinal axis of the string.

2. The twisted string actuator according to claim 1 , wherein the string has a larger diameter at least at the first end connected to the motor.

3. The twisted string actuator according to claim 1 , wherein the string has a larger diameter at least at the second end connected to the load than at another portion of the string.

4. The twisted string actuator according to claim 1 , wherein at least one of the threads is braided, spun, monofilament or made up of parallel filaments.

5. The twisted string actuator according to claim 4 , wherein at least two of the threads are parallel to each other.

6. The twisted string actuator according to claim 1 , wherein a portion of the string has at least a 10% larger diameter than a smaller diameter portion.

7. The twisted string actuator according to any claim 1 , wherein the variable diameter of the string is provided by of at least two of the threads having different diameters that are united into the string.

8. The twisted string actuator according to claim 7 , wherein the at least two different diameter threads are united by the threads being loops and that they are interconnected by one of the loops passing through the other loop.

9. The twisted string actuator according to claim 7 , wherein the at least two different diameter threads are united by a knot, melting, braiding, adhesive or original fabrication.

10. The twisted string actuator according to claim 1 , wherein the diameter of one of the threads varies along the length of that thread.

11. A twisted string actuator for converting rotational motion to linear motion, comprising:

a motor that generates the rotational motion; and

a string that comprises three looped sections, including a first section adjacent the motor, a second section adjacent a load, and a third section between the first and second sections, and wherein each of the first section and the second section comprise more than one loop of threads, respectively.

12. The twisted string actuator according to claim 11 , wherein the third section comprises one loop of the threads.

13. The twisted string actuator according to claim 11 , wherein the first section and the second section have larger diameters that the third section.

14. The twisted string actuator according to claim 1 , wherein a portion of the string has at least a 30% larger diameter than a smaller diameter portion.

15. A twisted string actuator that converts rotational motion to linear motion for moving a load, comprising:

a motor that generates the rotational motion;

a split; and

a string having threads that are substantially parallel and twist around each other between the motor and the split, the split located between the threads of the string and precludes twisting of the threads around each other between the split and the load, and wherein the string has different thread diameters at different portions of the string along its length between the motor and the split.

16. The twisted string actuator according to claim 15 , wherein the string has a larger diameter at a connection of the string to the motor than at another portion of the string.

17. The twisted string actuator according to claim 15 , wherein the string has a larger diameter at a portion of the string that engages the split.

18. The twisted string actuator according to any claim 15 , wherein the variable diameter of the string is provided by at least two of the threads having different diameters that are united into the string.

19. The twisted string actuator according to claim 18 , wherein the at least two different diameter threads are united by the threads being loops and that they are interconnected by one of the loops passing through the other loop.