Modified parallel eccentric rotary actuator

1. A rotary actuator, comprising:

an internal gear;

first and second parallel eccentric gears which mesh with said internal gear;

a crankshaft equipped with first and second eccentrics which are 180° out-of-phase and which drive said first and second parallel eccentric gears, respectively;

a prime mover which drives said crankshaft;

first and second crosslinks which prevent the rotation of said first and second parallel eccentric gears, respectively; and

first and second sets of splines which engage said first and second parallel eccentric gears, respectively;

wherein said first and second parallel eccentric gears have circular arc gear teeth.

2. The rotary actuator of claim 1 , further comprising an internal ring gear, wherein said first parallel eccentric gear is equipped with a first mesh, wherein said second parallel eccentric gear is equipped with a second mesh, and wherein said first and second parallel eccentric gears mesh with said internal ring gear such that said first and second meshes are 180° out-of-phase.

3. The rotary actuator of claim 1 , wherein each of said first and second splines has a longitudinal axis, and wherein all of the moving masses in said rotary actuator move in a direction parallel to the longitudinal axis of the first or second spline.

4. The rotary actuator of claim 1 , further comprising set of roller bearings that constrain the motion of the output ring gear relative to the stationary gear cage.

5. The rotary actuator of claim 1 , wherein said first and second parallel eccentric gears are oscillating gears.

6. The rotary actuator of claim 5 , wherein said first and second parallel eccentric gears are supported by a plurality of roller element bearings.

7. The rotary actuator of claim 1 , wherein said circular arc gear teeth move in a hypocyclic motion when the rotary actuator is activated.

8. The rotary actuator of claim 1 , wherein said circular arc gear teeth have a pressure angle in the range of 6° to 8°.

9. The rotary actuator of claim 1 , wherein said circular arc gear teeth have a pressure angle of about 7°.

10. The rotary actuator of claim 1 , wherein said internal gear is a single output internal gear.

11. The rotary actuator of claim 1 , wherein said crankshaft is a central crankshaft.

12. The rotary actuator of claim 1 , wherein said first and second eccentrics drive said first and second parallel eccentric gears without rotation.

13. The rotary actuator of claim 12 , wherein rotation of the first and second parallel eccentric gears is prevented by first and second crosslinks.

14. The rotary actuator of claim 1 , wherein said first and second parallel eccentric gears are external gears.

15. The rotary actuator of claim 1 , wherein said first crosslink has a first set of surface features on a surface thereof which engage a second set of surface features on said first eccentric gear.

16. The rotary actuator of claim 15 , wherein each member of said first and second sets of surface features is a protrusion or a depression.

17. The rotary actuator of claim 15 , wherein each member of said first set of surface features is a tongue, and wherein each member of said second set of surface features is a groove.

18. The rotary actuator of claim 17 , wherein, and wherein said first and second sets of features form a tongue and groove spline.

19. The rotary actuator of claim 1 , wherein said first eccentric gear is disposed on a first end of said crankshaft, and wherein said second eccentric gear is disposed on a second end of said crankshaft.

20. The rotary actuator of claim 1 , wherein said actuator has a torque density within the range of about 40 ft-lbf/lbf to about 80 ft-lbf/lbf.