Selection controlled print impression control for single element impact

Abstract

The impact velocity with which a single element printer prints is determined by the velocity with which the printing element is propelled toward the record sheet. The mechanism disclosed herein is capable of adjusting the velocity with which a print element is projected toward the page such that the impact velocity and, thus the impact forces which are related to the velocity, are controlled and varied to provide a minimum of compromise with respect to printing forces and, thus, print quality. The control of the velocity with which the print element is propelled against the record sheet is accomplished by a cam which rotates with the print element during character selection and has thereon a plurality of rises corresponding to a displacement of a cam follower engaged with a print cam. The print cam is formed to present, in a plurality of different planes perpendicular to its axis, a like plurality of cam profiles and rises. By shifting the print cam follower from one plane to another along the axis of the print cam, the velocity may be selected and controlled. This velocity selection is a direct result of the amount of rise in the cam attached to the shaft which rotates the print element. Thus, print element position, in response to conventional keyboard selection, directly controls the velocity of the print element derived from the rotation of the print cam and therefore, controls impact force.