US Patent 6896230 Equipoise arm assembly

An equipoise arm assembly for supporting an article in equipoise with a support arm, a proximal arm joint, a distal arm joint for supporting an article either directly or through a second support arm, a spring arrangement including a spring member with a distal end coupled to a body portion of the support arm and a proximal end pivotally retained to pivot about an effective pivot axis to create a spring force moment arm of a given length whereby the spring arrangement will tend to provide a resistive torque in support to the support arm, and an arrangement for altering the effective pivot axis of the spring arrangement to change the length of the spring force moment arm.