Footwear heel spring device
A device configured to surround a portion of a foot-receiving cavity at a heel region of an article of footwear comprises a control bar having a center segment, a first side arm extending from the center segment, and a second side arm spaced from the first side arm and extending from the center segment. The control bar may include a series of slats. A base supports the control bar and is connected to the first side arm and the second side arm. The control bar is biased to an unstressed position with the center segment a first distance from the base, and elastically bends under an applied force to a loaded position with the center segment a second distance from the base less than the first distance. The device stores potential energy that returns the control bar to the unloaded position upon removal of the applied load.
1. An article of footwear comprising:
a footwear upper defining an ankle opening and a foot-receiving cavity;
a sole structure secured to and underlying the footwear upper; and
a device configured to surround a portion of the foot-receiving cavity at a heel region of the article of footwear, the device comprising:
a control bar including:
a center segment defining a posterior extremity of the device;
a medial side arm extending downwardly and forwardly from the center segment; and
a lateral side arm extending downwardly and forwardly from the center segment;
a medial base arm extending rearwardly from the medial side arm to a medial terminal end, the device including a medial anterior extremity at the medial base arm and a medial posterior extremity at the medial terminal end; and
a lateral base arm extending rearwardly from the lateral side arm to a lateral terminal end, the device including a lateral anterior extremity at the lateral base arm and a lateral posterior extremity at the lateral terminal end;
wherein:
the center segment is disposed at the footwear upper rearward of the ankle opening;
the sole structure and the footwear upper meet at and define a biteline;
both the medial anterior extremity and the medial posterior extremity of the medial base arm are below the biteline at the sole structure;
the device defines a gap between the medial terminal end and the lateral terminal end; and
a distance in a posterior direction from the medial anterior extremity to the medial terminal end is greater than a distance in the posterior direction from the medial terminal end to the posterior extremity of the center segment.
2. The article of footwear of claim 1 , 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.
3. The article of footwear of claim 2 , wherein the medial side arm and the lateral side arm bend and the center segment pivots downward and rearward relative to the medial terminal end and the lateral terminal end under the applied force to the loaded position, storing potential energy that returns the center segment to the unstressed position upon removal of the applied force.
4. The article of footwear of claim 1 , wherein the device is a single, unitary, one-piece component.
5. The article of footwear of claim 1 , wherein the medial side arm extends downwardly and forwardly from the center segment at a medial side of the footwear upper.
6. The article of footwear of claim 1 , wherein the lateral side arm extends downwardly and forwardly from the center segment at a lateral side of the footwear upper.
7. The article of footwear of claim 1 , wherein a lower edge of the medial base arm rests along the sole structure.
8. The article of footwear of claim 1 , wherein a lower edge of the lateral base arm rests along the sole structure.
9. The article of footwear of claim 1 , wherein a junction of the medial base arm and the medial side arm is wider in a fore-aft direction of the article of footwear than the medial side arm.
10. The article of footwear of claim 1 , wherein the sole structure has a recess, and the medial base arm is nested in the recess.
11. The article of footwear of claim 1 , 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.
12. The article of footwear of claim 11 , wherein the center segment has an elongated tip extending rearward to the posterior extremity of the center segment.
13. The article of footwear of claim 1 , wherein an upward-facing surface of the elongated tip slopes forward and inward toward the foot-receiving cavity.
14. The article of footwear of claim 13 , wherein the center segment extends along the ankle opening.
15. An article of footwear comprising:
a footwear upper defining an ankle opening and a foot-receiving cavity;
a sole structure secured to and underlying the footwear upper; and
a device configured to surround a portion of the foot-receiving cavity at a heel region of the article of footwear, the device comprising:
a control bar including:
a center segment;
a medial side arm extending downwardly and forwardly from the center segment; and
a lateral side arm extending downwardly and forwardly from the center segment;
a medial base arm extending rearwardly from the medial side arm to a medial terminal end, the device including a medial anterior extremity at the medial base arm and a medial posterior extremity at the medial terminal end; and
a lateral base arm extending rearwardly from the lateral side arm to a lateral terminal end, the device including a lateral anterior extremity at the lateral base arm and a lateral posterior extremity at the lateral terminal end;
wherein:
the center segment is disposed at the footwear upper rearward of the ankle opening and extends along the ankle opening;
the sole structure and the footwear upper meet at and define a biteline;
both the medial anterior extremity and the medial posterior extremity of the medial base arm are below the biteline at the sole structure; and
the device defines a gap between the medial terminal end and the lateral terminal end.
16. The article of footwear of claim 15 , wherein a junction of the medial base arm and the medial side arm is wider in a fore-aft direction of the article of footwear than the medial side arm.
17. The article of footwear of claim 15 , wherein the center segment has an elongated tip extending rearward to a posterior extremity of the center segment.
18. The article of footwear of claim 17 , wherein an upward-facing surface of the elongated tip slopes forward and inward toward the foot-receiving cavity.
19. The article of footwear of claim 15 , wherein a lower edge of the medial base arm rests along the sole structure.
20. The article of footwear of claim 15 , wherein a lower edge of the lateral base arm rests along the sole structure.