Footwear heel spring device

1. A device for easing foot entry into an article of footwear and configured to surround a portion of a foot-receiving cavity at a heel region of the article of footwear, the device comprising:

a control bar having:

a center segment;

a medial side arm extending downwardly and forwardly from the center segment, wherein the medial side arm is wider in a longitudinal direction at a terminal end of the medial side arm than at the center segment; and

a lateral side arm extending downwardly and forwardly from the center segment, wherein the lateral side arm is wider in a longitudinal direction at a terminal end of the lateral side arm than at the center segment;

wherein the device includes a medial terminal end and a lateral terminal end, and the device defines a gap between the medial terminal end and the lateral terminal end;

wherein the medial side arm and the lateral side arm bend and the center segment pivots downward and rearward relative to the terminal end of the medial side arm and the terminal end of the lateral side arm under an applied force to a loaded position, storing potential energy that returns the center segment to an unstressed position upon removal of the applied force; and

wherein the center segment extends downwardly and forwardly to the medial side arm more steeply than the medial side arm extends downwardly and forwardly from the center segment.

2. The device of claim 1 , wherein the device is a single, unitary, one-piece component.

3. The device of claim 1 , wherein the medial terminal end of the device includes an anterior extremity and a posterior extremity; and

wherein a lower portion of a rear edge of the medial side arm extends downwardly and rearwardly to the posterior extremity.

4. The device of claim 1 , wherein the lateral terminal end of the device includes an anterior extremity and a posterior extremity; and

wherein a lower portion of a rear edge of the lateral side arm extends downwardly and rearwardly to the posterior extremity.

5. An article of footwear comprising:

a footwear upper defining an ankle opening;

a sole structure secured to and underlying the footwear upper; the footwear upper defining a foot-receiving void over the sole structure, with the ankle opening permitting foot entry into the foot-receiving void;

a heel spring device comprising a control bar having:

a center segment secured to the footwear upper rearward of the ankle opening;

a medial side arm extending downwardly and forwardly from the center segment along a medial side of the footwear upper; and

a lateral side arm extending downwardly and forwardly from the center segment along a lateral side of the footwear upper;

a medial terminal end of the heel spring device terminating on and secured to a medial side wall of the sole structure, a lateral terminal end of the heel spring device terminating on and secured to a lateral side wall of the sole structure, and the heel spring device defining a gap between the medial terminal end of the heel spring device and the lateral terminal end of the heel spring device;

wherein the control bar pivots rearward under an applied force to a loaded position, storing potential energy that returns the control bar to an unstressed position upon removal of the applied force, the footwear upper moving with the control bar; and

wherein the footwear upper is an elastically stretchable material that bows inward under the center segment when the control bar is in the unstressed position prior to foot entry in the foot-receiving void.

6. The article of footwear of claim 5 , wherein the heel spring device is entirely exterior to the footwear upper and the sole structure.

7. The article of footwear of claim 5 , wherein the medial side arm is secured to the medial side of the footwear upper and the lateral side arm is secured to the lateral side of the footwear upper.

8. The article of footwear of claim 5 , wherein the heel spring device extends along the footwear upper and not along the sole structure at a rear of the article of footwear between the medial side arm and the lateral side arm.

9. The article of footwear of claim 5 , wherein the heel spring device is wider in a longitudinal direction of the article of footwear at the medial side wall of the sole structure than at the medial side of the footwear upper, and the heel spring device is wider in the longitudinal direction of the article of footwear at the lateral side wall of the sole structure than at the lateral side of the footwear upper.

10. The article of footwear of claim 5 , wherein the sole structure has a recess at the medial side wall, and the medial terminal end of the heel spring device is nested in the recess at the medial side wall.

11. The article of footwear of claim 5 , wherein:

the sole structure and the footwear upper meet at and define a biteline;

the medial terminal end of the heel spring device includes an anterior extremity and a posterior extremity; and

both the anterior extremity and the posterior extremity are below the biteline on the medial side wall of the sole structure.

12. The article of footwear of claim 11 , wherein a rear edge of the medial side arm extends downwardly and rearwardly to the posterior extremity.

13. The article of footwear of claim 11 , wherein the sole structure has a recess at the medial side wall, and both the anterior extremity and the posterior extremity are nested in the recess at the medial side wall.

14. The article of footwear of claim 5 , wherein:

the sole structure and the footwear upper meet at and define a biteline;

the lateral terminal end of the heel spring device includes an anterior extremity and a posterior extremity; and

both the anterior extremity and the posterior extremity are below the biteline on the lateral side wall of the sole structure.

15. The article of footwear of claim 14 , wherein a rear edge of the lateral side arm extends downwardly and rearwardly to the posterior extremity.

16. The article of footwear of claim 14 , wherein the sole structure has a recess at the lateral side wall, and both the anterior extremity and the posterior extremity are nested in the recess at the lateral side wall.

17. The article of footwear of claim 5 , wherein the article of footwear is characterized by the absence of a heel counter between the control bar and the sole structure at a rear of the article of footwear between the medial side arm and the lateral side arm.

18. The article of footwear of claim 5 , wherein the center segment extends downwardly and forwardly to the medial side arm more steeply than the medial side arm extends downwardly and forwardly from the center segment.

19. An article of footwear comprising:

a footwear upper defining an ankle opening;

a sole structure secured to and underlying the footwear upper;

a heel spring device comprising a control bar having:

a center segment secured to the footwear upper rearward of the ankle opening;

a medial side arm extending downwardly and forwardly from the center segment along a medial side of the footwear upper; and

a lateral side arm extending downwardly and forwardly from the center segment along a lateral side of the footwear upper;

a medial terminal end of the heel spring device terminating on and secured to a medial side wall of the sole structure, a lateral terminal end of the heel spring device terminating on and secured to a lateral side wall of the sole structure, and the heel spring device defining a gap between the medial terminal end of the heel spring device and the lateral terminal end of the heel spring device;

wherein the control bar pivots rearward under an applied force to a loaded position, storing potential energy that returns the control bar to an unstressed position upon removal of the applied force, the footwear upper moving with the control bar; and

a fastening system including:

loops secured to the medial side arm; and

a cable extending over the footwear upper and anchored by the loops.