Abstract:
An air assisted electrostatic liquid spray nozzle assembly having a relatively long elongated nozzle body with a spray tip and surrounding air cap disposed at a downstream end of the nozzle body. The spray nozzle assembly includes an upstream electrode for connection to a high voltage electric source, an elongated feed tube, an electrically enhancing stinger, and the spray tip which are secured and retained by the air cap in electrically conductive relation to each other such that liquid passing through liquid passages of the electrode, feed tube, stinger, and spray tip is discharged in an electrostatically charged pattern of liquid particles. The air cap is removable to permit easy removal and replacement of the spray tip, stinger, and liquid feed tube.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application claims the benefit of U.S. Patent Application No. 61/880,238, filed Sep. 20, 2013, which is incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to spray nozzle assemblies, and more particularly, to electrostatic spray nozzle assemblies that electrostatically charge fluids discharging from spray nozzles to facilitate liquid particle breakdown and distribution. 
       BACKGROUND OF THE INVENTION 
       [0003]    Electrostatic spray nozzle assemblies are utilized for spraying coatings, lubricating fluids and other liquids in various manufacturing processes. To effect adequate liquid particle breakdown for the desired spray application, it often is necessary to further utilize pressurized air. 
         [0004]    In some installations, it is necessary that the spray nozzle assemblies have a relatively long nozzle body with the spray nozzle at the discharge end located a relatively long distance from the liquid inlet, pressurized atomizing air inlet, and high voltage cable connection for the spray nozzle assembly. It can be difficult to properly assemble, install or repair the spray nozzle assemblies in such installations, and improper or imprecise assembly of such spray nozzles and charging electrodes can result in high voltage leakage that can significantly effect the operating efficiency of the spray operation. 
       OBJECTS AND SUMMARY OF THE INVENTION 
       [0005]    It is an object of the invention to provide a pressurized air assisted electrostatic spray nozzle assembly that is adapted for more efficient and reliable operation. 
         [0006]    Another object is to provide a spray nozzle assembly as characterized above which has a relatively long barrel extension or nozzle body and which lends itself to easier assembly, installation and repair. 
         [0007]    A further object is to provide an electrostatic spray nozzle assembly of the above kind that is relatively simple in construction and lends itself to economical manufacture. 
         [0008]    Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a side elevational view of an illustrative spray nozzle assembly in accordance with the invention; 
           [0010]      FIG. 2  is a vertical section of the illustrated spray nozzle assembly taken in the plane of line  2 - 2  in  FIG. 1 ; 
           [0011]      FIG. 3  is an enlarged fragmentary section of the input head of the illustrated spray nozzle assembly; 
           [0012]      FIG. 4  is an enlarged fragmentary section of the discharge end of the illustrated spray nozzle assembly; and 
           [0013]      FIG. 5  is a transverse fragmentary section of the spray nozzle assembly taken in the line of  5 - 5  in  FIG. 4 . 
       
    
    
       [0014]    While the invention is susceptible of various modifications and alternative constructions, a certain illustrative embodiment thereof has been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention. 
       DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]    Referring now more particularly to the drawings, there is shown an illustrative pressurized air atomizing electrostatic spray nozzle assembly  10  in accordance with the invention. The illustrated spray nozzle assembly  10  includes a fluid and high voltage input head  11 , an elongated nozzle barrel or body  12  extending downstream from the input head  11 , and a discharge nozzle assembly  14  at a downstream end of the elongated nozzle body  12 . It will be understood that the nozzle body  12  may be relatively long in length in relation to its diameter for enabling mounting of the spray nozzle assembly  10  in a wall of a processing vessel or the like with the discharge nozzle assembly  14  within the vessel and the input head  11  remotely located outside the vessel. In practice, the elongated nozzle body  12  may have a length of 10 times or more the diameter of the nozzle body  12 , up to 12 inches or more. 
         [0016]    The input head  11  in this case is cylindrical in form, made of plastic or other nonelectrically conducive material, formed with a radial liquid inlet passage  16  that receives and communicates with a liquid inlet fitting  18  connected to a pressurized liquid supply. The input head  11  is formed with a radial pressurized air atomizing inlet passage  19  downstream of said liquid inlet passage  16  that receives and communicates with an air inlet fitting  20  coupled to a suitable pressurized air supply. The input head  11  further has a radial passage  21  upstream of the liquid inlet passage  16  that receives a fitting  22  for securing a high voltage cable  24  connected to a high voltage source and having an end  24   a  extending into the passage  21  in abutting electrically contacting relation to an electrode  28  axially supported within the input hub  11  and extending downstream of the liquid inlet passage  16 . 
         [0017]    For enabling liquid passage through the input hub  11 , the electrode  28  is formed with an internal axial passage  29  communicating with the liquid inlet passage  16  and extending downstream though the electrode  28 . The electrode  28  in this case is formed with a plurality of radial passages  30  communicating between the liquid inlet passage  16  and the internal axial passage  29 . The illustrated electrode  28  has a downstream outwardly extending radial hub  31  fit within a counter bore of the inlet hub  11  with a sealing o-ring  32  interposed there between. 
         [0018]    In carrying out this embodiment, the elongated body  12  includes an outer cylindrical body member  35  made of plastic, such as sold under the trade name Ultem, or other suitable nonconductive material, having an upstream end  35   a  threadedly engaged within a threaded bore of the input hub  11  with a sealing o-ring  36  interposed between the cylindrical body member  35  and the input hub  11 . A liquid feed tube  38 , made of stainless steel or other electrically conductive metal, extends axially through the outer cylindrical body member  35  for defining a liquid flow passage  39  for communicating liquid between the axial electrode liquid passage  29  and the discharge nozzle assembly  14  and for defining an annular atomizing air passage  40  between the liquid feed tube  38  and the outer cylindrical body member  35 . An upstream end of the liquid feed tube  38  which protrudes above the threaded inlet end  35   a  of the outer cylindrical nozzle body  35  fits within a downwardly opening cylindrical bore  45  in the electrode hub  31  in electrical conducting relation. With the electrode  28  charged by the high voltage cable  24 , it will be seen that liquid feed to the inlet passage  16  will be electrically charged during its travel through the electrode passage  29  and liquid feed tube  38  along the entire length of the elongated nozzle body  12 . Pressurized air in this case communicates through the radial pressurized air inlet passage  19  about the upstream end of the liquid feed tube  38  and then into the annular air passage  40  between the liquid feed tube  38  and the outer cylindrical body member  35 . 
         [0019]    In keeping with this embodiment, the liquid feed tube  38  is maintained in precise reliable electrical contacting relation with the electrode  28  for efficiently electrically charging liquid throughout its passage from the input hub  11  and through elongated nozzle body member to the spray nozzle  12 . To this end, the discharge nozzle assembly  14  includes a spray tip  50  having an upstream cylindrical section  51  in surrounding relation to a downstream end of the liquid feed tube  38  with a sealing o-ring  52  interposed therebetween. The spray tip  50  includes an inwardly tapered or conical intermediate section  54  and a downstream cylindrical nose section  56  that defines a cylindrical flow passage  55  and a liquid discharge orifice  58  of the spray tip  50 . The spray tip  50  in this case has a segmented radial retention flange  58  extending outwardly of the upstream cylindrical section  51  which defines a plurality of air passages  57 , as will become apparent. 
         [0020]    For channeling liquid from feed tube  38  into and though the spray tip  50  while continuing to electrostatically charge the liquid as it is directed through the spray tip  50 , an electrically conductive stinger unit  60  is supported within the spray tip  50  in abutting electrically conductive relation to the downstream end of the feed tube  38 . The stinger unit  60  in this case comprises an upstream cylindrical hub section  61  formed with a downstream conical wall section  62  supported within the intermediate conical section  54  of the spray tip  50 . The cylindrical hub section  61  is formed with a plurality of circumferentially spaced radial liquid flow passageways  62  communicating between the liquid feed tube  38  and the spray tip passage section  55 . It will be seen that the electrically conductive stinger unit  60 , when seated within the spray tip  50 , physically supports in abutting relation the downstream end of the liquid feed tube  38 . 
         [0021]    For concentrating the electrical charge on liquid discharging from the spray tip, the stinger unit  60  has a downwardly extending central electrode pin  64  supported in concentric relation to the spray tip passage  55  such that the liquid discharge orifice  58  is annularly disposed about the electrode pin  64 . The electrode pin  64  has a gradually tapered pointed end  64  which extends a distance, such as between about ¼ and ½ inch, beyond the annular spray tip discharge orifice  58 . It will be understood by a person skilled in the art that the increased contact of the liquid about the protruding electrode pin  64  as it exits the spray tip  50  further enhances concentration of the charge on the discharging liquid for enhanced liquid particle breakdown and distribution. 
         [0022]    In further keeping with this embodiment, the discharge nozzle assembly  14  includes an air cap  70  disposed about the spray tip  50  which defines an annular atomizing air passage  71  about the spray tip  50  and which retains the spray tip  50 , stinger unit  60 , and liquid feed tube  38  in assembled conductive relation to each other. The air cap  70  in this instance defines a conical pressurized air flow passage section  71   a  about the downstream end of the spray tip  50  which communicates via the circumferentially spaced air passages  57  in the spray tip retention flange  58  with the annular air passage  40  between the liquid feed tube  38  and the outer cylindrical body member  35  for directing a pressurized air discharge stream through an annular discharge orifice  73  about the spray tip nose  56  and liquid discharging from the spray tip liquid discharge orifice  58 . For retaining the internal components of the spray nozzle in assembled relation, the air cap  70  has an upstream cylindrical end  75  in threaded engagement about a downstream outer threaded end of the outer cylindrical member  35 . The air cap  70  has a counter bore  76  which receives and supports the segmented radial flange  58  of the spray tip  50  for supporting the spray tip  50 , and hence, the stinger unit  60  and liquid feed tube  38  in electrical conducting relation with the upstream electrode  28 . 
         [0023]    It will be understood that with such air cap securement arrangement at the discharge end of the spray nozzle assembly upon disengagement and removal of the air cap  70  from the outer cylindrical body member  35 , the spray tip  50 , stinger unit  60 , and liquid feed tube  38  can easily be assembled and removed without disassembly of the outer annular body member  35  from the input hub  11 . Hence, the air cap  70  not only defines an atomizing air passageway, but supports the liquid feed tube  38  and stinger unit  60  in electrical contacting relation with the electrode  28  in the input unit  11  such that upon unscrewing of the air cap  70  from the outer cylindrical nozzle body  35 , easy access is permitted to internal components of the spray nozzle assembly  10  for repair and/or replacement.