Vacuum cylinder for printing presses

Abstract

The disclosure relates to an improved form of vacuum-operated printing cylinder for a printing press, providing a practical means for holding the printing plate on the cylinder by vacuum alone, without requiring separate adhesive means and/or supplementary mechanical devices for clamping the plate. In the preferred form, the cylinder includes a supporting shaft mounting, between its bearing portions, a plurality of cylinder supporting rings. A cylinder sleeve is supported by the rings and forms, together with the rings and the supporting shaft, a hollow cylinder structure having a plurality of vacuum chambers. The interior of the cylinder can be evacuated from one end of the shaft, and independently controllable valve means are built into the cylinder, to enable the several chambers thereof to be independently evacuated. In one form of the invention, the cylinder sleeve is provided with a large number of radial passages, providing communication to the outside surface of the cylinder. In another form, the sleeve is provided with a plurality of axially spaced, continuous annular grooves, which communicate at one or more places with the interior of the cylinder. The continuous grooves are blocked off at one or more places around the circumference of the cylinder to avoid leakage at the end-to-end discontinuity in a printing plate supported on the cylinder.

Dependencies are inferred from the claim text.