Obstacle traversing wheelchair

1. A wheelchair suspension comprising:

a frame;

a front caster pivot arm pivotally connected to the frame;

a front caster coupled to a front end of the front caster pivot arm;

a drive assembly directly pivotally connected to the front caster pivot arm, wherein the drive assembly comprises a drive wheel and a motor that drives the drive wheel;

wherein torquing of the drive wheel by the motor in a forward direction causes the drive assembly to pivot with respect to the front caster pivot arm such that the drive wheel moves forward relatively toward the front caster and a distance between a support surface and said pivotal connection between the drive assembly and the front caster pivot arm increases;

a rear caster coupled to the frame.

2. The wheelchair suspension of claim 1 wherein the front caster pivot arm is pivotally connected to the frame at a first pivot axis and the drive assembly is pivotally connected to the front caster pivot arm at a second pivot axis.

3. The wheelchair suspension of claim 2 wherein the first pivot axis is spaced apart from the second pivot axis.

4. The wheelchair suspension of claim 2 wherein the first pivot axis is not aligned with the second pivot axis.

5. The wheelchair suspension of claim 1 further comprising a spring coupled to the front caster pivot arm, wherein said spring biases the front caster downward into contact with the support surface.

6. The wheelchair suspension of claim 1 further comprising a spring coupled to the drive assembly, wherein said spring biases the drive wheel downward into contact with the support surface.

7. The wheelchair suspension of claim 6 wherein the spring is interposed between the drive assembly and the front caster pivot arm.

8. The wheelchair suspension of claim 1 further comprising a first spring coupled to the front caster pivot arm and a second spring coupled to the drive assembly, wherein said first spring biases the front caster downward into contact with the support surface and said second spring biases the drive wheel downward into contact with the support surface.

9. The wheelchair suspension of claim 8 wherein the second spring is interposed between the drive assembly and the front caster pivot arm.

10. A wheelchair suspension comprising:

a frame;

a front caster pivot arm pivotally connected to the frame;

a front caster coupled to a front end of the front caster pivot arm;

a first spring coupled to the front caster pivot arm, wherein said first spring biases the front caster downward into contact with a support surface;

a drive assembly directly pivotally connected to the front caster pivot arm, wherein the drive assembly comprises a drive wheel and a motor that drives the drive wheel;

a second spring coupled to the drive assembly, wherein said second spring biases the drive wheel downward into contact with the support surface;

a rear caster coupled to the frame.

11. The wheelchair suspension of claim 10 wherein the front caster pivot arm is pivotally connected to the frame at a first pivot axis and the drive assembly is pivotally connected to the front caster pivot arm at a second pivot axis.

12. The wheelchair suspension of claim 11 wherein the first pivot axis is spaced apart from the second pivot axis.

13. The wheelchair suspension of claim 11 wherein the first pivot axis is not aligned with the second pivot axis.

14. The wheelchair suspension of claim 10 wherein the second spring is interposed between the drive assembly and the front caster pivot arm.

15. The wheelchair suspension of claim 10 wherein torquing of the drive wheel by the motor causes the drive assembly to pivot with respect to the front caster pivot arm such that the drive wheel moves forward toward the front caster.

16. The wheelchair suspension of claim 10 wherein torquing of the drive wheel by the motor causes the drive assembly to pivot with respect to the front caster pivot arm such that a distance between the support surface and said pivotal connection between of the drive assembly to the front caster pivot arm increases.

17. A wheelchair suspension comprising:

a frame;

a front caster pivot arm pivotally connected to the frame;

a front caster coupled to a front end of the front caster pivot arm;

a first spring coupled to the front caster pivot arm, wherein said first spring biases the front caster downward into contact with a support surface;

a drive assembly directly pivotally connected to the front caster pivot arm, wherein the drive assembly comprises a drive wheel and a motor that drives the drive wheel;

a second spring coupled to the drive assembly, wherein said second spring biases the drive wheel downward into contact with the support surface;

wherein torquing of the drive wheel by the motor causes the drive assembly to pivot with respect to the front caster pivot arm such that the drive wheel moves forward relatively toward the front caster and a distance between the support surface and said pivotal connection between the drive assembly to the front caster pivot arm increases;

a rear caster coupled to the frame.

18. The wheelchair suspension of claim 17 wherein the front caster pivot arm is pivotally connected to the frame at a first pivot axis and the drive assembly is pivotally connected to the front caster pivot arm at a second pivot axis.

19. The wheelchair suspension of claim 18 wherein the first pivot axis is spaced apart from the second pivot axis.

20. The wheelchair suspension of claim 18 wherein the first pivot axis is not aligned with the second pivot axis.

21. The wheelchair suspension of claim 17 wherein the second spring is interposed between the drive assembly and the front caster pivot arm.