Abstract:
An improved apparatus and method for drying materials. A hot surface in a strong electrostatic field is used to ionize a stream of heated gasses passing over the surface, which assists in directing the stream against the object to be dried, and ionizes the vapors and gasses emitted from surface of the material being dried, which assists in their separation and removal.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to the drying and setting of materials, and more particularly, but not limited to, the drying ink and paint coatings.  
           [0002]    A variety of industrial, commercial and consumer goods require a solidification process, either removal of liquids contained in the structure of the goods, or a coating applied thereon, or by catalysis of the goods themselves or their coatings. Some materials require a curing process that may is usually initiated by the addition of some form of energy. In the case of many inks and coatings, the removal of some or all of the liquid portion to initiate solidification releases a large perfusion of fumes and vapors, many having known health risks. Commonly, a large volume of high-velocity heated air is directed at the surface, even though only a fraction of the air actually comes even near the surface, due to the difficulty in penetrating through the “boundary layer effect” of vapors and gasses near the surface. The countercurrent of fumes and vapors clinging to the surface also create a barrier against convective heating as well as preventing radiation from reaching the surface of the material to be dried.  
           [0003]    Electrostatic precipitators generally will not remove gasses, so an odor would remain. Large high-pressure fans are required to even partially penetrate the boundary layer near the surface of the material, and once the blast of hot air, fume and vapors has left the surface it is not usually reused, but is “cleaned up” and exhausted into the atmosphere. Due to the huge volumes of air contaminated with vapors and fumes produced by this process, removal of the contaminants through incineration or high-temperature catalysis is expensive and wasteful, often doubling the energy expenditure of the initial drying operation. Water based coating drying systems, while not requiring as much “clean-up” of the effluent, still require substantial amounts of energy and process time due to the high latent h at of vaporization of water, thus slowing production rat s.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention discloses a drying system comprising: a blower that passes air over flames electrically charged to a high-voltage source, ionizing rods containing rows of pins, some of which are connected to ground and some to a high-voltage DC supply, and insulated strands of wire in the effluent stream for collecting the ionized fumes and solvents. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 shows a semi diagrammatic view of the system for drying one side of a continuous web using the concepts of this invention.  
         [0006]    [0006]FIG. 2 shows a pictorial view of the invention showing an overall external view.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0007]    Referring now specifically to the drawings, FIG. 1 shows diagrammatically a drying system in accordance with the present invention. The purpose of the illustrated system is to rapidly dry and cure printing inks or coatings applied upstream on the web by a printing press or coater of common design and construction which is located upstream (not shown). Although the illustrations depict a paper web with uncured or wet printing ink applied thereto, the present method and apparatus will be understood to apply to objects of various shapes and compositions. These objects may themselves be solidified, dried of cured, or they may have a surface or internal coating to be altered. Inks, coatings, films and plastics may be formulated which are particularly susceptible to being selectively altered by the ultraviolet radiation and ozone produced by this system.  
         [0008]    As illustrated in FIG. 1, the web enters from the right and passes under the outlet from duct  2  that encloses preheated air  1  descending past heated tubes  4  that are maintained at a high voltage negative potential by wire  5  connected from DC power supply to said tubes thereby causing an electrostatic field  8  between the flames  7  in serrated channel  6  to the web  10  and the ink image  9  applied thereto, and thence to charge bars  11  connected to the power supply ground by wire  12 .  
         [0009]    These heated tubes are referred to hereinafter as “charge tubes” and may or may not have flames emitting therefrom. “Charge bars” are elongated, insulated structures have exposed conductive surfaces from which an electrostatic charge emanates, usually in the form of a row of oxidation-resistant pins usually internally electrically interconnected. There are commercially available variations, some having the individual pins connected to a common bus by resistors, which serves to even out the electrostatic field and reduce arcing. They are usually constructed of an insulating material, and have an internal electrical connection from the conducting surfaces to a connection plug or terminal.  
         [0010]    The flow of electrical current through said electrostatic field and web to the charge bars  11  creates additional heating added to the convective heat from the airstream  1 , and said heating impinging on the web and the ink applied thereon, causes vaporization and oxidizing of some of the ink components. With sufficiently high voltage, a corona may be caused to occur on the surfaces being treated, which may solidify certain inks. Ozone may also be produced which may rapidly oxidize certain inks and coatings. The vapors and fumes  16  emanating from said web and ink into the electrostatic field acquire a charge. Convective movement away from the web by said fumes and vapors  16  is assisted by said acquisition of a negative charge  15 , said charge causing them to be repelled from the surface of the web that now passes over negatively charged bars  14 . Said fumes and vapors move into up into duct  20  by a combination of suction airstream  21  and repulsion from a negative charge on the plurality of charge bars  14 , said bars being connected to the power supply by wire  13 . The ionized vapors and fumes  16  are attracted to wires  18  that are at a positive high-voltage potential, said vapors and fumes adhering to said wires in the form of liquid and solids  19  that runs down said wires into receptacles  17  for removal and recycling. Special inks may be formulated that are particularly sensitive to exposure to electrons in the electrostatic field, said inks adhering to said web undergoing a reaction so disposed as to cause curing and solidification. Removal of the fumes and vapors attracted to wires  18  may be facilitated by wires that are formed into an endless belt, whereby said wires may be continuously cleaned by moving past a cleaning means such as a brush or scraper.  
         [0011]    Although drying of only one side of a web is depicted, it is understood that by inverting or re-orienting the structures of the present invention, drying or curing my be effected on opposing sides of any object, the top and bottom of a web printed or coated on both sides in this instance.  
         [0012]    [0012]FIG. 2 shows the present invention in an overall view of the preferred embodiment for drying or curing the top of a web. Blower  25  driven by motor  26  draws environmental air into adjustable aperture  1  and expels said air through preheater  27 , into duct  2  where it moves across ionizing bars  4  and impinges against the top of web  10  which enters housing  7  through elongated aperture  28 . High-voltage supply  29  is connected by ground wire  12  to the housing. Insulated negative high-voltage wires  5  and  13  connect to the ionizing bars  4  and  14  respectively. Collector wires  18  (shown in FIG. 1) are connected to the positive high-voltage terminal of said power supply by insulated wire  24 . Liquid captured from the airstream  21  is conveyed by drain tube  30  into an appropriate container. Remaining contaminants in the airstream  21  are removed by conventional filtering means  22 . A potion of the air exiting from said filtering means is recycled into the inlet of blower  26  by duct  23 .