Wheel with folding segments

1. A folding wheel having a rolling shape substantially corresponding to a circle with a wheel diameter and a center, the folding wheel comprising:

a center wheel section encompassing the center and adapted to be mounted to an axle at the center, and having a first side substantially corresponding to a first chord of the circle and a second side opposite the first side and substantially corresponding to a second chord of the circle;

a first wheel segment pivotally attached to the center wheel section about a first pivot axis extending along the first side of the center wheel section;

a second wheel segment pivotally attached to the center wheel section about a second pivot axis extending along the second side of the center wheel section;

wherein the first and second wheel segments are movable from a rolling orientation, where outer edges of the first and second wheel segments are aligned with an outer edge of the center wheel section such that the folding wheel takes the rolling shape, to a folded orientation where the first and second wheel segments extend laterally away from the respective first and second pivot axes.

2. The folding wheel of claim 1 wherein the first and second wheel segments extend laterally away from the respective first and second pivot axes in the same direction.

3. The folding wheel of claim 1 wherein the first and second wheel segments extend laterally away from the respective first and second pivot axes in opposite directions.

4. The folding wheel of claim 1 wherein the first and second chords are substantially parallel and substantially the same length.

5. The folding wheel of claim 1 comprising at least one gripping lug extending from an end of one of the first and second sides of the center wheel section when the first and second wheel segments are in the folded orientation.

6. The folding wheel of claim 5 comprising a gripping lug extending from each end of each side of the center wheel section when the first and second wheel segments are in the folded orientation.

7. A robot apparatus, the robot apparatus comprising:

a robot body, and an axle mounted to the robot body;

right and left folding wheels according to claim 1 , the center wheel sections thereof attached to corresponding right and left outer ends of the axle;

a control mechanism operative to move the first and second wheel segments of the right and left folding wheels between the rolling orientation and the folded orientation; and

a drive operative to rotate the right and left folding wheels.

8. The robot apparatus of claim 7 wherein the control mechanism for at least the right folding wheel comprises a right linkage mounted to the center wheel section of the right folding wheel, the linkage connected to the first and second wheel segments of the right folding wheel, and a push member connected at an outer end thereof to the linkage and extending through the axle.

9. The robot apparatus of claim 8 wherein an inner end of the push member is connected to an actuator operative to move the push member in and out along the axle.

10. The robot apparatus of claim 8 comprising a tail section attached to the robot body and configured to rest on a surface behind the robot body when the robot apparatus travels along the surface in a forward operating travel direction, and wherein when the wheels are in the folded orientation the tail section can be moved to a substantially vertical orientation.

11. The robot apparatus of claim 10 wherein an extendable arm is attached at a lower end thereof to a rear portion of the tail section about an arm axis, and an arm drive is operative to rotate the extendable arm about the arm axis, and wherein when the wheels are in the folded orientation the tail section and extendable arm can be moved to an aligned substantially vertical orientation.

12. The robot apparatus of claim 7 wherein the robot body is configured to float on water, and wherein when the wheels are in the folded orientation, rotating the wheels propels the robot body.

13. The robot apparatus of claim 12 wherein the first and second wheel segments of at least the right folding wheel extend laterally away from the respective first and second pivot axes in opposite directions.

14. The robot apparatus of claim 13 wherein the first and second wheel segments of the left folding wheel extend laterally away from the respective first and second pivot axes in opposite directions.

15. The robot apparatus of claim 12 wherein the axle is above the water when the robot body is floating.

16. A folding wheel having a rolling shape substantially corresponding to a circle with a wheel diameter and a center, the folding wheel comprising:

a center wheel section encompassing the center and adapted to be mounted to an axle at the center, and having a side substantially corresponding to a chord of the circle;

a wheel segment pivotally attached to the center wheel section about a pivot axis extending along the side of the center wheel section;

wherein the wheel segment is movable from a rolling orientation, where an outer edge of the wheel segment is aligned with an outer edge of the center wheel section such that the folding wheel takes the rolling shape, to a folded orientation where the wheel segment extends laterally away from the pivot axis.

17. The folding wheel of claim 16 wherein the center wheel section has a first side that substantially corresponds to a first chord of the circle and second side opposite the first side that substantially corresponds to a second chord of the circle, and comprising first and second wheel segments pivotally attached to the center wheel section about respective first and second pivot axes extending along the corresponding first and second sides of the center wheel section; and

wherein the wheel segments are movable from a rolling orientation, where outer edges of the wheel segments are aligned with the outer edge of the center wheel section such that the folding wheel takes the rolling shape, to a folded orientation where the wheel segments extend laterally away from the pivot axes.

18. The folding wheel of claim 16 wherein the center wheel section has a first side that substantially corresponds to a first chord of the circle, a, second side that substantially corresponds to a second chord of the circle, and a third side that substantially corresponds to a third chord of the circle, and comprising first, second, and third wheel segments pivotally attached to the center wheel section about respective first, second, and third pivot axes extending along the corresponding first, second, and third sides of the center wheel section; and

wherein the wheel segments are movable from a rolling orientation, where outer edges of the wheel segments are aligned with the outer edge of the center wheel section such that the folding wheel takes the rolling shape, to a folded orientation where the wheel segments extend laterally away from the pivot axes.

19. The folding wheel of claim 16 comprising at least one gripping lug extending from an end of the side of the center wheel section when the wheel segment is in the folded orientation.

20. A robot apparatus comprising:

a robot body, and an axle mounted to the robot body;

right and left folding wheels according to claim 16 , the center wheel sections thereof attached to corresponding right and left outer ends of the axle;

a control mechanism operative to move the wheel segments of the right and left folding wheels between the rolling orientation and the folded orientation; and

a drive operative to rotate the right and left folding wheels.