PRINTER SYSTEM RIBBON DRIVE HAVING CONSTANT RIBBON SPEED AND TENSION

摘要

An impact printer ribbon drive of the reel-to-reel type in which a length of ink ribbon extending between and wound around opposite reels is disposed between a reciprocating hammer bank and print paper on a platen drives the ribbon at substantially constant speed and tension independent of varying ribbon pack on the two reels. Each one of the reels is driven by a different one of a pair of DC permanent magnet motors. The motors are energized by a circuit which maintains the sum of the currents through the two motors substantially constant and which also maintains the voltage at the leading or take-up motor substantially constant. The sum of the currents and the voltage are maintained substantially constant by a pair of servo circuits associated with different ones of the motors and coupled to be alternately actuated in response to external direction commands. Also included is circuitry responsive to voltages in different parts of the circuit for signalling unwanted conditions such as a run-away ribbon, a jammed ribbon or a loose hub at one of the reels.