Application of Pressure and Vacuum to Lithographic Presses.

Air pressure and vacuum used for controlling sheets through lithographic presses generally is produced by pumps of the rotary vane type. Lines leading from these pumps should be of optimum size and contain a minimum of constrictions caused by fittings and valves. A consideration of the factors affecting volume of air delivered at given pressures is dependent upon the configuration of the line and elements it contains. Factors affecting the vacuum at a given point are similar. The size of terminal openings in air and vacuum lines determines the effectiveness with which sheets are controlled in feeders and deliveries. The relationship of these openings bears a direct relationship to the pump and line. The force exerted by air jets is proportional to pressure and size. The ability of a vacuum sucker to attract a sheet is more dependent upon line size than upon degree of vacuum.