Apparatus and method for controlling print ribbon feed

Abstract

A printing system includes print ribbon wound on first and second rotatable reels and a rotatable capstan for moving the ribbon between the first and second reels, such that ribbon is supplied from the first reel and is collected after use on the second reel. A microprocessor controls both the reel and capstan movements and computes the quantity of ribbon wound on each reel based on a known diameter of the capstan and the relationship between the number of rotational steps moved by the capstan and the number of rotational steps moved by the corresponding reel during a given time period. The microprocessor includes a random access memory in which a plurality of ramp tables are stored for controlling the movements of the reels. Each ramp table includes a speed parameter representing a particular rotational speed and an acceleration parameter representing a number of rotational steps for ramping up to and down from the particular speed, for a discrete range of ribbon diameters. The diameter of ribbon wound on each reel is determined periodically by comparing the number of steps moved by the corresponding reel to a plurality of reference values representing respective predetermined ribbon diameters, to determine the particular discrete range of ribbon diameters applicable to each reel. The particular discrete range of ribbon diameters determines the particular ramp table used to control the movements of the corresponding reel.

Dependencies are inferred from the claim text.