Abstract: A multiple spray nozzle, offset press dampening system of the type having individual metering pumps for the respective nozzles utilizes a device for opening the pump output valves while maintaining dampening liquid feed pressure substantially elevated, thereby purging feed lines, pump passageways and pump chambers of bubbles and particles which would interfere with accurate metering. Constant recirculation and filtering of the feed liquid under pressure maintains purging liquid substantially bubble and particle free.

Abstract: Dampening rolls receive spray from a multi-nozzle spray member having a spray path extending beyond the ends of the rolls. Overspray preventing shields are mounted at opposite ends of the spray path and have free dripping lower portions positioned over the dampening rolls. An oscillating roll runs against a dampening roll to spread the moisture film and a wet form roll provides contact between the oscillating roll and the plate cylinder. Preferably, the spray member oscillates transversely along the dampening rolls and separate shields are mounted on the spray member and fixed with respect to the press frame.

Abstract: A multiple spray nozzle, offset press dampening system of the type having individual metering pumps for the respective nozzles achieves improved control and reliability by substantially increasing feed water pressure entering the metering pumps, thereby reducing the formation of bubbles. The pump output valve flow-through pressure is also increased to retain accurate metering conditions.