Print density control

Claim 1

In a printer having a plurality of print hammers with firing means disposed to be energized from a source of electrical energy and a type carrier with a plurality of type characters movable past said print hammers, means for storing data to be printed in each of a plurality of print positions corresponding to said print hammers, means for determining the character at a particular hammer position, and means for addressing said storage means and comparing the data in storage for the particular hammer position with the character on the carrier at said particular position and generating a print compare signal when they are the same to effect operation of a selected one of said print hammers, the improvement in hammer timing logic comprising: means including a variable speed motor driving said type carrier to move said type characters past said print hammers, motor contrOl means connected to run said motor at a speed dependent on the voltage of said source, and pulse means including a transducer connected in operating relation with said type carrier to produce subscan pulses which vary in duration in response to changes in the speed of said type carrier and connected to address said storage means and effect energization of said print hammers in response to said print compare signal said variable duration subscan pulses thus controlling the duration of energization of said print hammer firing means in response to variations in the voltage of said source.