Lace tightener incorporating sma wire

Abstract

A lace-tightening device for a shoe lace in a shoe comprises a rotating cam within a housing disposed within the shoe. The cam is connected to the opposite ends of the shoe lace and includes an outer surface for receiving the shoe lace as the cam rotates to pull the lace. A driven gear disposed is rotatably coupled to the cam through a one-way clutch configured so that rotation of the driven gear in one direction rotates the cam in the one direction, thereby tightening the shoe lace connected to the rotating cam. A ratchet arm is slidably disposed within the housing and includes linear teeth arranged to engage the teeth of the driven gear as the ratchet arm translates in a linear direction. to rotate the gear in the one direction. The ratchet arm is pulled by at least one shape memory alloy (SMA) wire attached at one end to the ratchet arm and at its opposite end to a controller. The controller is configured to execute a power cycle to energize and deenergize the SMA wire so that the wire sequentially shrinks and returns to its original length to thereby sequentially translate the ratchet arm in the linear direction, and ultimately to incrementally pull and tighten the shoe lace. The controller repeats the cycle a number of times until the lace reaches a tightness desired by the user.