Printing press using shiftable inking means

Abstract

An ejection-type inking assembly for use in printing presses is provided which gives precise, readily alterable ink application to an inking roll train and eliminates conventional ink fountains and associated adjustable ink keys. The inking assembly preferably includes a shuttle-mounted reciprocal inking unit having an ink ejector nozzle, a supply of ink and a feed pump for pressurizing successive charges of high viscosity ink and delivering the charges at a constant flow rate to the nozzle. The preferred pump is a twin screw, counter rotating positive displacement device driven by means of a stepper motor. As the inking unit traverses an ink-receiving roller, the stepper motor is activated for precise periods of time correlated with the position of the unit, so as to deliver measured, variable quantitites of ink for each respective increment of distance traveled by the inking unit. In practice, the copy plate is electronically scanned to ascertain the amount of ink needed for each strip zone on the copy, and this information is employed with appropriate microprocessor control to operate the pump stepper motor as required to deliver the proper variable quantitites of ink to the ink train during translation of the inking unit along the length of the ink-receiving roller. Use of a shiftable inking unit including the ink supply, pump and motor eliminates long, high pressure ink feed lines and minimizes ink wastage, particularly in short printing runs.