Patent Abstract:
A method of and apparatus for extending the life of fountain solutions used in commercial printing presses comprises withdrawing fountain solution from the dampener recirculation system of a printing press and directing the withdrawn fountain solution through a sediment prefilter, a separation filter, and a posttreatment filter. The sediment prefilter preferably comprises a melt blown polypropylene filter; the separation filter preferably comprises a diatomaceous earth filter; and the post-treatment filter preferably comprises a zeolite filter.

Full Description:
TECHNICAL FIELD 
     This invention relates generally to improvements in commercial printing systems and more particularly to a system for removing contaminants from and thereby extending the life of fountain solutions utilized in commercial printing plants. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     A typical offset lithographic printing press has a plate cylinder upon which the negative of the text and illustrations to be printed are etched by a photographic and/or an electronic process. Dampening rollers apply a fountain solution to the plate cylinder which adheres to the plate cylinder except in the areas in which the text and illustrations are located. 
     Next, a series of form rollers, also known in the art as inking rollers, apply a layer of ink to the plate cylinder. The ink adheres to the plate cylinder only in the etched areas comprising the text and illustrations. 
     The plate cylinder then presses the inked text and illustrations onto a rubber blanket cylinder. An impression cylinder then presses a sheet of paper or other substrate to be printed against the blanket cylinder as the paper or other substrate passes between the blanket cylinder and the impression cylinder. The inked text and illustrations on the blanket cylinder are transferred onto the paper or other substrate to effect printing thereof. 
     Over time, ink, paper fiber, spray powder, and other contaminants build up in the fountain solution. These contaminants negatively impact print quality. Additionally, as the fountain solution degrades water, adjustments are required. Eventually the fountain solution becomes so contaminated that it needs to be replaced. The present invention comprises a system for minimizing fountain solution contamination thereby extending the useful life of the fountain solution by a substantial period of time. 
     The fountain solution recycling system of the present invention utilizes a unique multi-stage separation technology and a recirculation pump to clean and restore the fountain solution. Removal of contaminants is achieved by processing the solution through three separate treatment stages resulting in a reusable, stabilized fountain solution. Components of the fountain solution which are consumed due to carry-off by the printing substrate and evaporation are replaced in the conventional manner. 
     Use of the fountain solution recycling system of the present invention easily and reliably reduces costs and improves productivity in an aspect of the commercial printing business that has traditionally been neglected. Simply extending the life of the fountain solution typically adds 1-2 hours of productivity per week per printing press because changing the fountain solution and cleaning the system are no longer required. 
     Additionally, by extending the life of the fountain solution waste, disposal costs associated with fountain solution replacement are dramatically reduced. In those instances in which spent fountain solution is drained, use of the present invention greatly reduces the copper, zinc, ink, glycols, phosphates and suspended solids going into the drain thereby lessening the impact on the environment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention may be had by reference to the following Detailed Description when taken in connection with the accompanying Drawings, wherein: 
         FIG. 1  is a perspective view of a fountain solution recycling system for commercial printers incorporating the invention; and 
         FIG. 2  is a schematic illustration of the fountain solution recycling system of FIG.  1  and the interaction thereof with a commercial printing press. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the Drawings, and particularly to  FIG. 1  thereof, there is shown a fountain solution recycling system  10  incorporating the present invention. The system  10  includes a pump  12  which receives fountain solution from a commercial printing press through a line  14 . The output of the pump  12  is directed to a sediment prefilter  16  through a line  18 . The sediment prefilter  16  comprises a housing  20  which contains a strainer or filter formed from melt blown polypropylene and having a consistency generally similar to that of a fibrous web. The function of the sediment prefilter  16  is to remove relatively large particles from the flowing fountain solution. 
     From the sediment prefilter  16  the fountain solution is directed to a separation cartridge  22  through a line  24 . The separation cartridge  22  comprises a housing which contains a diatomaceous earth filter and functions to remove sub-micron sized particles from the flowing fountain solution. Thus, having passed through the sediment prefilter  16  and the separation cartridge  22  the fountain solution is substantially free of particulate and colloidal contaminants. 
     From the separation cartridge  22  the fountain solution is directed to a post treatment cartridge  26  through a line  28 . The post treatment cartridge  26  comprises a housing which contains a natural zeolite filter material which removes copper ions, zinc ions, and other ions from the flowing fountain solution thereby substantially removing metal ion contaminants from the fountain solution. After flowing through the post treatment cartridge  26  the fountain solution is returned to the dampener recirculating device of the commercial pressing press through a line  30 . 
     The sediment prefilter  16 , the separation cartridge  22 , and the post treatment cartridge  26  comprise a three stage treatment system in which each stage has a symbiotic relationship with the former stage. The use of the combined system comprising the prefilter  16 , the separation cartridge  22 , and the post treatment cartridge  26  affords two highly beneficial results. First, the use of the combined system substantially extends the life of fountain solution flowing therethrough. Second, the combined system renders the fountain solution much more environmentally friendly upon ultimately disposal. 
       FIG. 2  illustrates the use of the fountain solution recycling system  10  in conjunction with a commercial printing press  32 . A recirculation pump  34  withdraws fountain solution from a fountain solution recirculation tank  36  and directs the fountain solution to one or more printing press dampener pans  38  as indicated by the arrows  40  and  42 . From the printing press dampener pans  38  the fountain solution is applied to dampening rollers which in turn apply the fountain solution to the plate cylinder of the printing press  32 . In the operation of the printing press  32  fountain solution is continuously withdrawn from the printing press dampener pans  38  and returned to the tank  36  as indicated by the arrows  44  and  46 . 
     The fountain solution recycling system  10  of the present invention withdraws fountain solution from the tank  36  through the line  14  and returns the fountain solution to the tank  36  through the line  30 . Thus, the system  10  of the present invention functions to maintain the fountain solution within the tank  36  in a substantially clean condition characterized both by a lack of particulate contamination and a reduction of metal ion contamination. 
     As is best shown in  FIG. 1 , the components of the fountain solution recycling system of the present invention may be mounted on a pallet. By mounting all of the components of the system on a pallet, installation of the system at a convenient location within a commercial printing plant is readily accomplished. All that remains to be done is the connection of the lines  14  and  30  to one or more printing presses within the plant, whereupon operation of the system can be commenced. 
     EXAMPLE 
     A typical eight-color 40″ 0  printing press requires the disposal of about 40 gallons of fountain solution per week, or about 2100 gallons per year. 2100 gallons equals about 40 barrels of spent fountain solution that must be disposed of annually. At a typical disposal cost of about $250/barrel the annual fountain solution disposal cost is about $10,000 per year per printing press. Conversely, when the present invention is used the annual fountain solution disposal requirement is about 2 barrels or about $500 per year per press. Elimination of press downtime for fountain solution change out is another benefit resulting from the use of the present invention. At just one hour of eliminated downtime per week the use of the present invention saves over $15,000 per year per press. When down time savings are combined with disposal cost savings use of the present invention results in about $25,000 in annual savings per press. 
     Although preferred embodiments of the invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions of parts and elements without departing from the spirit of the invention.

Technology Classification (CPC): 1