SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide an athletic shoe that optimizes the conflicting concerns of shock absorption and stability, while also maximizing comfort and durability.
It is a more specific object of the present invention to construct an athletic shoe having a sole unit which provides differential cushioning properties at different regions of the sole, so as to attenuate impact forces at heel strike without introducing instability to the subsequent motion in the running gait cycle.
It is another object of the present invention to provide an athletic shoe sole that adopts a mechanical cushioning system, which is designed to absorb impact forces with a specific configuration of an elastic and durable material, eliminating the need for relying heavily on the less durable foam material for impact absorption.
It is a further object of the present invention to provide an athletic shoe sole having a mechanical cushioning system which can be easily customized for the specific application and individual wearing the shoe by slightly modifying its configuration.
These and other objects are achieved by the midsole for an article of footwear in accordance with the present invention. Such midsole comprises a midsole element comprising: (a) a medial element comprising a top medial plate, a bottom medial plate, and a plurality of medial strut members disposed between the top and bottom medial plates for supporting the top medial plate a distance away from the bottom medial plate; and (b) a lateral element comprising a top lateral plate, a bottom lateral plate, and a plurality of lateral strut members disposed between the top and bottom lateral plates for supporting the top lateral plate a distance away from the bottom lateral plate; wherein at least a portion of the plurality of lateral strut members are arranged at an angle to at least a portion of the plurality of medial strut members. The angle between the lateral strut members and the medial strut members is greater than 0 degrees to less than 180 degrees, preferably about 5 to 120 degrees, more preferably about 10 to about 90 degrees, and most preferably about 15 to about 75 degrees.
In accordance with a further aspect of the present invention, the medial and lateral strut members in the midsole element described above have a C shaped cross-section when intersected by an imaginary plane that intersects the respective top and bottom medial and lateral plates at approximate right angles. Preferably at least two adjacent C shaped strut members face in the same direction.
In accordance with another aspect of the present invention, there is provided a midsole for an article of footwear comprising a midsole element, which comprises a top plate; a bottom plate; and a plurality of strut members disposed between the top and bottom plates for supporting the top plate a distance away from the bottom plate; at least two of the strut members being adjacent to each other and having a C shaped cross-section facing in the same direction when intersected by an imaginary plane that intersects the top and bottom plates at approximate right angles.
In accordance with a further aspect of the present invention, the midsole element described above further comprises a heel cleft which is medial to the point of heel strike at the midsole element. The heel cleft provides flexibility to the midsole and allows the midsole to bend at impact thereby decreasing the amount and velocity of pronation. The heel cleft is about 0 to about 180 degrees, preferably about 0 to about 120 degrees, more preferably about 0 to about 90 degrees, offset from the transverse axis of the midsole. For shoes intended for linear movement activities such as walking and running, the heel cleft is preferably about 15 to about 75 degrees, and more preferably about 17 and about 65 degrees, offset from the transverse axis of the midsole. For shoes intended for lateral movement activities such as basketball, the heel cleft may be about 65 to about 90 degrees, preferably about 75 to about 90 degrees, offset from the transverse axis of the midsole.
In accordance with a still further aspect of the present invention, there is provided an article of footwear which comprises an upper, a midsole of the present invention as described above, and an outsole.
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