Variable ratio magnetic drive mechanism

A drive mechanism having a first pulley, a second pulley and an endless flexible drive member extending therebetween for transmitting motion from said first pulley to said second pulley wherein at least one of said pulleys is a variable ratio pulley assembly comprising:

• a disk including at least one circular row of apertures, and a drive segment in each of said apertures translatable between a retracted position and an extended position, said drive segments maintained in said retracted or extended position by magnetic force;
• and
• an actuator further comprising:
• a housing at least partially straddling said disk and in a fixed relation thereto;
• a yoke slidably received in said housing and slidable along a radial of said disk, said yoke having a retraction leg extending at least partially along one side of said disk and a retraction cam on an inner face of said retraction leg, said yoke also having an extension leg extending at least partially along an opposite side of said disk and an extension cam on an inner face of said extension leg;
• and
• an inner layer of low friction material positioned between each said leg of said yoke and said disk such that contact of one of said cams with said inner layer selectively causes at least a portion of said layer to sequentially contact said drive segments as said disk rotates.

A variable ratio drive mechanism comprising:

• a first variable ratio pulley comprising a substantially planar disk having first and second faces and further having at least one circular row of apertures through said disk, at least a first fixed magnet affixed to said disk and defining a first magnetic field having a first polarity, a plurality of drive segments in said apertures forming at least one circular row of drive segments, each said drive segment including a second actuating magnet aligned to define a second magnetic field of opposite polarity from said first magnetic field, and further wherein each said drive segment is selectively translatable through its said aperture between an engaged position and a retracted position such that each said drive segment is maintained in either said selected engaged position or said selected retracted position by said first and second magnetic fields;
• an actuator for selectively engaging and retracting individual ones of said drive segments;
• a second pulley spaced apart from said first variable ratio pulley;
• and
• an endless flexible drive member extending from said first variable ratio pulley to said second pulley for transmitting motion between said first variable ratio pulley and said second pulley.