Patent ID: 6242841
Filing Date: 2001-06-05
Classification: H02N

Abstract:
A stepper motor comprising:a rotatable hub;a first shaped memory alloy (abbreviated to SMA) rotary-driver, which when heated undergoes a shape change to rotationally couple with said hub and rotate said hub in a predetermined direction, and which can be deformed to reverse the shape change to rotationally uncouple from said hub;a first return spring connected with said first SMA rotary-driver for deforming said first SMA rotary-driver, when no longer heated, to reverse the shape change of said first SMA rotary-driver and rotationally uncouple said first SMA rotary driver from said hub;a second SMA rotary-driver, which when heated undergoes a shape change to rotationally couple with said hub and rotate said hub in the predetermined direction, and which can be deformed to reverse the shape change to rotationally uncouple from said hub;a second return spring connected with said second SMA rotary-driver for deforming said second SMA rotary-driver, when no longer heated, to reverse the shape change of said second SMA rotary-driver and rotationally uncouple said second SMA rotary-driver from said hub; anda control device for heating said first and second SMA rotary-drivers in succession and only one at a time, whereby said first and second SMA rotary-drivers can take turns to stepwise rotate said hub in the predetermined direction.