Metered spray dampening system

For use in combination with an offset printing press, a lithographic dampener system, said dampener system comprising:

• a. a spray member having a plurality of dampening liquid atomizing spray nozzles, individual dampening liquid output conduit means connected at one end thereof to said nozzles,
• b. a pump member having a plurality of individual, bubble and particle sensitive, reciprocal metering pumps respectively including an input portion containing a loaded input valve and an output portion containing a loaded output valve which periodically opens as a result of metering pump operation, said output valve being loaded to a substantially greater opening pressure than said input valve and a pump pathway extending between said input and output valves,
• c. said output conduit means being respectively individually connected at the other end thereof to one of said metering pump output portions whereby each spray nozzle is connected to a separate metering pump, said metering pumps respectively having reciprocating pump means communicating with said pump pathways between said input and output valves and alternately increasing and decreasing the dampening liquid volume of the respective pump pathway,
• d. a source of dampening liquid susceptible to bubble formation and particle inclusion therein, input conduit means connected between said liquid source and said respective input portions, a feed pump operably located in said input conduit means,
• e. pressure regulator means associated with said feed pump and together controlling the feed pressure of said dampening liquid into said respective input portions to a point above atmospheric pressure an amount sufficient to suppress the formation of bubbles and greater than that required to open said loaded input valve but less than the sum of the opening pressures of said input plus output valve, thereby causing said dampening liquid to be maintained substantially above atmospheric pressure during flow from said feed pump and through said metering pumps, whereby bubbles tending to form in said dampening liquid are urged to remain in solution permitting accurate metering by said respective metering pumps, and
• f. means selectively maintaining said loaded output valves simultaneously in an open position independently of pump function and without blocking said output portions, whereby bubbles and particulate matter in said dampening liquid are driven by said feed pressure through said pump pathways and past said output valves.