Lithographisches Bildaufzeichnungssystem für austauschbare Plattenzylinder

摘要

A plate-imaging system and a plate-cylinder support structure are coupled in a manner that achieves precise spacing between a writing head and the surface of a lithographic plate. The imaging unit (48) is designed to permit the writing head to undergo controlled advancement toward the plate cylinder (25), and includes a pair of rollers fixed with respect to the writing head and spaced so as to facilitate rolling contact with peripheral segments of the cylinder. When the imaging unit is brought into contact with the structure containing the plate cylinder, the writing head is advanced toward the cylinder until the rollers make contact with the peripheral segments (30b). The alignment between the rollers and the writing head is fixed such that rolling contact between the rollers and the peripheral cylinder segments ensures proper spacing between the writing head and a plate mounted to the plate cylinder. To ensure a constant tangential (linear) rotation velocity of the plate cylinder regardless of its diameter, the plate cylinder is driven with a fixed-diameter drive gear (107). In this way, the tangential velocity of the plate cylinder is constant and determined by the the pitch diameter of the drive gear.