Apparatus and method for oscillating the form rollers in a printing press

Abstract

An apparatus and method for oscillating the ink form rollers and dampening form roller in a lithographic printing press to apply a smooth, relatively uniform coating of ink to the ink-receptive areas of a lithographic printing plate and to prevent ink from being transferred from the dampening form roller to the ink-rejecting areas of the printing plate. The ink form rollers and the dampening form roller are each comprised of a hollow cylindrical metal core surrounded by a rubber covering. First and second bronze bushings are partially inserted into the hollow core at respective opposite ends of the roller. Each roller is mounted on a shaft rotatable about its own axis. The shaft has first and second shaft keys for mating with complementary first and second keyways formed in the respective first and second bushings to allow the bushings to engage the shaft for common rotation while allowing the roller and bushings to slide axially with respect to the shaft. First and second collar members are disposed at respective predetermined locations on the shaft for limiting the axial movement of the roller on the shaft between selected limits. The ink form rollers and dampening form roller are each rotated and moved axially substantially in unison with the rotation and axial movement of the corresponding vibrating rollers, thereby substantially eliminating 'ghosting' and 'tracking'.