Device for pressing sheets of a multicolor sheet-fed rotary printing press onto an impression cylinder

摘要

Sheet pressing means for a multi-color sheet-fed press adapted for both first-side printing and perfecting printing wherein the press includes a press frame and first and second impression cylinders with a sheet-turning cylinder therebetween. The sheet pressing means includes a plurality of hollow air-blowing fingers disposed after the printing zone of the first impression cylinder for directing blown air to press a sheet onto the surface of the first impression cylinder, with the fingers being disposed in substantially equidistant relationship to one another on a support tube which is disposed above the first impression cylinder and substantially parallel to the axis thereof along substantially the entire length of the first impression cylinder. Preferably, the fingers each have at the downstream end thereof an air exit surface with air exit orifices formed therein, and the exit surfaces are formed to conform generally to the convex external contour of the first impression cylinder and have a downstream tip end adapted to be positioned closely adjacent the point of tangency between the first impression cylinder and the sheet-turning cylinder. In the preferred embodiment, an articulated linkage is mounted on the press frame for selectively moving the support tube, the fingers and the tip ends thereof toward said point of tangency for perfecting printing and away from said point of tangency for first-side printing and a valve is provided for controlling the air flow through the fingers.