| abstract |
The shoe sole incorporating spring apparatus comprises a shoe sole with a cavity in its upper side, the planform of the cavity being essentially that of the foot of a wearer of a shoe incorporating the sole. Two elliptical springs are situated entirely in the cavity, one spring located under the heel of the user, termed the heel spring, the other under the ball of the user's foot, termed the toe spring. The springs are contoured in planform to fit snugly but freely in the cavity. A flexible bridge piece fits over the springs. The planform of the bridge conforms closely to that of the cavity, allowing free motion of the bridge to the cavity. The springs and bridge are made of acetal plastic. The spring rates of the springs are attuned to the weight of the wearer, reaching full deflection under forces which are a factor times the weight of the wearer. The factor ranges from 1 to 4 with 3 being a preferred factor for the heel spring and 1.5 being a preferred factor for the toe spring in a walking shoe and 3 in a shoe intended for more vigorous use. |