In a miniature printer for printing with dots on printing paper, concentrically mounted driving cams provide both horizontal and vertical motions which synchronize the reciprocating action of the printing head mechanism with the paper feed and ink ribbon feed mechanism. Constant velocity linear motion...http://www.google.fr/patents/US4259026?utm_source=gb-gplus-shareBrevet US4259026 - Dot printer having concentric driving cams
