Protective helmet with multiple pseudo-spherical energy management liners

1. A helmet, comprising:

an outer liner having an interior surface defining a first coronal cross-sectional curvature and a first sagittal cross-sectional curvature different from the first coronal cross-sectional curvature, the outer liner comprising a plurality of vents passing through the outer liner wherein each of the plurality of vents is beveled at the interior surface of the outer liner with a curved edge;

an inner liner slidably disposed within the interior surface of the outer liner and slidably coupled thereto, the inner liner having an exterior surface defining a second coronal cross-sectional curvature and a second sagittal cross-sectional curvature different from the second coronal cross-sectional curvature, the inner liner comprising a plurality of channels passing through the inner liner wherein the plurality of channels are in fluid communication with the plurality of vents and each of the plurality of channels is beveled at the exterior surface of the inner liner with a curved edge;

wherein a majority of the interior surface of the outer liner and a majority of the exterior surface of the inner liner are substantially parallel; and

wherein the inner liner is elastically deformable along the interior surface of the outer liner in response to rotation of the outer liner relative to the inner liner caused by an impact to the helmet.

2. The helmet of claim 1 , wherein the majority of the interior surface of the outer liner and the majority of the exterior surface of the inner liner are substantially parallel to a pseudo-spherical surface defining a third coronal cross-sectional curvature and a third sagittal cross-sectional curvature different from the third coronal cross-sectional curvature.

3. The helmet of claim 2 , wherein the third coronal cross-sectional curvature defines a first radius of curvature and the third sagittal cross-section sectional curvature defines a second radius of curvature different from the first radius of curvature.

4. The helmet of claim 3 , wherein the difference between the first radius of curvature and the second radius of curvature is less than about 5 mm.

5. The helmet of claim 1 , wherein the inner liner is coupled to the interior surface of the outer liner through at least one return spring, the at least one return spring comprising an elastomer material.

6. The helmet of claim 1 , wherein at least one of the interior surface of the outer liner and the exterior surface of the inner liner is treated to reduce friction of the exterior surface of the inner liner slidably coupled to the interior surface of the outer liner.

7. The helmet of claim 1 , wherein an air gap exists between a majority of the exterior surface of the inner liner and the interior surface of the outer liner.

8. The helmet of claim 1 , wherein the outer liner has a density greater than the density of the inner liner and the inner liner has a density less than 70 g/L.

9. The helmet of claim 1 , wherein an exterior surface of the outer liner is coupled to an outer shell.

10. A helmet, comprising:

at least one flexible inner energy management liner shaped to interface with an outer liner;

wherein a majority of the interior surface of the outer liner defines a first coronal cross-sectional curvature and a first sagittal cross-sectional curvature different from the first coronal cross-sectional curvature and a majority of the exterior surface of the inner liner defines a second coronal cross-sectional curvature and a second sagittal cross-sectional curvature different from the second coronal sectional curvature;

wherein the interior surface of the outer liner and the exterior surface of the inner liner are substantially parallel;

wherein the inner liner includes an elastically deformable material having a density less than 70 g/L and is slidably coupled to the interior surface of the outer liner; and

a plurality of vents in the outer liner and a plurality of channels in the inner liner that at least partially overlap the plurality of vents in the outer liner;

wherein each of the plurality of vents is beveled at the interior surface of the outer liner with a curved edge; and

wherein each of the plurality of channels is beveled at the exterior surface of the inner liner with a curved edge.

11. The helmet of claim 10 , wherein the majority of the interior surface of the outer liner and the majority of the exterior surface of the inner liner are substantially parallel to a pseudo-spherical surface defining a third coronal cross-sectional curvature and a third sagittal cross-sectional curvature different from the third coronal cross-sectional curvature.

12. The helmet of claim 11 , wherein the third coronal cross-sectional curvature defines a first radius of curvature and the third sagittal cross-sectional curvature defines a second radius of curvature different from the first radius of curvature.

13. The helmet of claim 12 , wherein the difference between the first radius of curvature and the second radius of curvature is less than about 5 mm.

14. The helmet of claim 10 , wherein the inner liner is coupled to the interior surface of the outer liner through at least one return spring, the at least one return spring comprising an elastomer material.

15. The helmet of claim 10 , wherein at least one of the interior surface of the outer liner and the exterior surface of the inner liner is treated to reduce friction of the exterior surface of the inner liner slidably coupled to the interior surface of the outer liner.

16. The helmet of claim 10 , wherein an air gap exists between a majority of the exterior surface of the inner liner and the interior surface of the outer liner.

17. The helmet of claim 10 , wherein the outer liner has a density greater than the density of the inner liner.

18. The helmet of claim 10 , wherein an exterior surface of the outer liner is coupled to an outer shell.