Abstract: A printing apparatus employs a rotatable cam having an enclosed cam slot for controlling the rocking motion of an inking roll without the need for a cam follower spring. The apparatus also includes an articulated printing member support assembly which executes a complex curvilinear movement under the control of a fixed cam slot without the use of linear bearings. Complementary cam profiles are used on both cam surfaces in order to maintain tangency between the inking roll and printing element during inking. A yieldable connecting link is used to prevent excessive printing pressures from being applied, and a movable filler plate closes off a slot in a front cover of the printing apparatus through which a portion of the movable printing member protrudes.