Abstract:
An electrostatic spraying assembly including a housing and a plurality of elongated electrode elements supported within the housing each defining a respective fluid passageway. An electrode header connectable to a high voltage source is supported within the housing in spaced relation to the electrode elements for charging the electrodes to an electrical potential by induction, and in turn, charging liquid directed through the passageways. The electrode header and a resilient valve element supported thereon are movable between retracted and closing positions for controlling the flow of fluid through the electrode passageways for discharge into an electrical field generated by an induction element supported in spaced relation to the discharge ends of the electrode elements.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    The present application claims the benefit of U.S. Provisional Patent Application No. 60/733,289 filed Nov. 3, 2005, and is a continuation-in-part of application Ser. No. 11/056,703 filed Feb. 11, 2005, which in turn claims the benefit of U.S. Provisional Patent Application No. 60/544,269 filed on Feb. 12, 2004, the disclosures of which are incorporated herein 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 applying oil and other coating and lubricating fluids in various manufacturing processes. Electrostatic spray nozzle assemblies, such as shown in U.S. Pat. No. 4,749,125, discharge a plurality of fluid flow streams which are electrostatically charged and atomized by means of a high voltage electrode with the assistance of a grounded induction bar for disposition onto items to be sprayed or coated, typically as they are conveyed past the spraying apparatus. 
         [0004]    Heretofore, such electrostatic assembly spray nozzle assemblies have suffered from various operating and maintenance problems. For example, imprecise manufacture and assembly of such spray nozzles and charging electrodes can result in high voltage leakage that can significantly affect the operating efficiency of the spray operation. Fluid leakage problems also can adversely affect the spray distribution and lead to waste of costly spray liquids. While it often is desirable to direct a plurality of electro-statically charged flow streams, heretofore it has been difficult to effectively and efficiently control the liquid discharge for cyclic operation and without undesirable dripping and waste of the coating fluid. 
       OBJECTS AND SUMMARY OF THE INVENTION 
       [0005]    It is an object of the present invention to provide an electrostatic spray nozzle assembly that is adapted for more efficient and reliable spraying of oils and other lubricating and coating fluids. 
         [0006]    Another object is to provide an electrostatic spray nozzle assembly which includes electrostatic charging electrodes that are adapted for more precise manufacture and mounting within the nozzle assembly, and hence more efficient operation with reduced power consumption and increased life expectancy. 
         [0007]    A further object is to provide an electrostatic spray nozzle assembly of the foregoing type which is operable for electrostatically charging and controlling the spray discharge of a plurality of fluid flow streams for more uniform coating or lubricating of items that are sprayed. 
         [0008]    Still another object is to provide an electrostatic spray nozzle assembly of the above kind that can be efficiently controlled for repeated cyclic operation without undesirable drippage during shut-off. 
         [0009]    Another object is to provide an electrostatic spray nozzle assembly that has relatively large fluid passages that resist clogging and are easy to clean. 
         [0010]    Yet a further object is to provide such an electrostatic spray nozzle assembly which is relative simple in construction and lends itself to economical manufacture. 
         [0011]    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 
         [0012]      FIG. 1  is a perspective view of an illustrative spray nozzle assembly in accordance with the invention; and 
           [0013]      FIG. 2  is an enlarged vertical section of the illustrated spray nozzle assembly taken in the plane of line  2 - 2  in  FIG. 1 , showing the spray nozzle assembly in an operating condition; 
           [0014]      FIG. 3  is an enlarged longitudinal section, taken in the plane of line  3 - 3  in  FIG. 1 , again showing the spray nozzle assembly in an operating condition; and 
           [0015]      FIG. 4  is an enlarged fragmentary section, showing the spray nozzle assembly in a liquid shut-off condition. 
       
    
    
       [0016]    While the invention is susceptible of various modifications and alternative constructions, a certain illustrated 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. 
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0017]    Referring now more particularly to the drawings, there is shown in an illustrative electrostatic spray nozzle assembly  10  embodying the present invention, which is adapted for directing an elongated spray of oil or other lubricating or coating fluid on items conveyed below the spray assembly  10 . The illustrative spray assembly  10  basically comprises a non-metallic elongated housing  11  having an inlet port connected to a fluid supply pipe  12  that supplies liquid coating or other fluid materials to the spray assembly  10 , an electrode assembly  14  within the spray housing  11  for charging fluid passing through and directed from a lower discharge end of the housing  11 , and an induction bar  15  disposed in parallel spaced relation to the discharge end of the housing  11  for generating an electrical field to enhance liquid particle breakdown. It will be appreciated that the housing  11  may be appropriately supported by support brackets or the like in overlying relation to items to be sprayed. 
         [0018]    In accordance with the invention, the electrode assembly comprises a metallic block or header and a plurality of elongated electrode elements disposed in alignment with respective fluid passageways communicating with the fluid inlet port of the housing for charging fluid as it passes along the length of the elongated electrode elements and is discharged from the spray assembly. To this end, in the illustrated embodiment, the electrode assembly  14  comprises an elongated metallic electrode block  14   a  disposed within a relatively larger sized channel  15  within the housing  11  and a plurality of elongated electrode elements  14   b  supported in a longitudinally spaced array in depending relation to the housing  11 . The rectangular channel  15  of the housing in this case is sized larger than the electrode block  14   a  for defining an elongated generally U-shaped fluid flow passageway  16  ( FIG. 4 ) communicating between the fluid inlet port and each of the elongated electrode elements  14   b . For enclosing the upper end of the elongated channel  15 , the housing  11  has a cover  18  which is secured to the upper end of the housing by appropriate fastening bolts  19  with a sealing gasket  20  interposed there between. The electrode block  14   a  is connected to an appropriate high voltage source, such as 20,000 volt source, by means of a conventional banana coupling  21  coupled to the electrode block  14   a  at a central location through a side wall of the housing  11 . As will become apparent to a person skilled in the art, by reason of the high voltage charged electrode block  14   a , the adjacent row of elongated electrode elements  14   b  will be charged by induction to a sufficiently high electrical potential for charging fluid as it passes along the length of the electrode elements  14   b  and is discharged from the spray assembly. 
         [0019]    In carrying out the invention, the elongated electrode elements are in the form of elongated metallic tubes which each define a respective liquid flow passageway communicating between the internal housing fluid passageway  16  and simultaneously charge the liquid as it is passing through the electrode tubes  14   b . As will be understood by a person skilled in the art, as the fluid passes through the electrode tubes  14   b , it is charged such that when the fluid exits the tubes  14   b  and enters the electrical field between the terminal ends of the tubes  14   b  and the induction bar  15 , fluid is dispersed in a fine particle spray. The use of the electrode tubes  14   b  also provide relatively large flow passages that are more resistant to clogging and are easier to clean. 
         [0020]    The electrode tube receiving body of the housing  11  preferably has a one-piece block construction which facilitates precision concentric mounting of the electrode tubes  14   a  for preventing high voltage leakage. The illustrated housing  11  includes a one-piece body  24 , preferably machined from plastic stock, with electrode tube receiving openings being drilled in the body and the longitudinal channel  15  being milled. It will be understood that by virtue of such one-piece housing body construction, there are no parting planes associated with the liquid flow passageways  16  typical of multi-part housings, nor fasteners for retaining a multi-part housing body in assembled condition at such parting planes. 
         [0021]    The electrode tubes  14   a  preferably each protrude outwardly of the discharge end of the housing  11  a predetermined distance “x,” such as about ¼ inch (see  FIG. 2 ). It has unexpectedly been found that the protruding electrode tubes maximize liquid flow rate through the spray nozzle assembly. Although the theory of operation is not entirely understood, it is believed that the greater surface area of tubes over which the liquid travels facilitates liquid flow and discharge from the spray nozzle assembly. The increased contact with the electrode tubes further enhances charging of the liquid and ultimate atomization. The housing  11  in this case is formed with a generally tapered depending end through which the electrode tubes  14   b  protrude for further preventing the effect of possible surface tension on the liquid as it discharges from the housing. 
         [0022]    To enhance safety, the electrode tubes  14   b  preferably are arranged such that each tube terminates a small distance S ( FIG. 4 ) from the electrode block or header  14   a  which in this case places the upper ends of the tubes  14   b  in slightly recessed relation the upper perimeter of the housing bores within which the tubes are mounted. With this arrangement, the electrode tubes  14   b  will not be charged at such high electrical potential that could pose a safety hazard. Instead, the electrode tubes  14   b  are charged inductively due to their proximity to the electrode header  14   a . The inductive charging of the electrode tubes  14   b  will provide sufficient charging to provide the desired level of added charge to the fluid passing through the tubes  14   b . Accordingly, safety of the spray operation is increased without significant degradation in spray performance. 
         [0023]    The induction bar  15  in this case is mounted for selective positioning relative to the downstream ends of the electrode tubes  14   b  for maximizing the effect of the electrical field therebetween on the discharging liquid, and hence, maximizing liquid particle breakdown. As shown in  FIG. 1 , the induction bar  15 , is supported by elongated arms  26  fixed in depending angled relation to opposite ends of the housing  11 . The induction rod  15  is selectively positionable within elongated slots  28  formed in the supporting arms  26  for effecting the desired spray characteristics. 
         [0024]    In operation of the spray assembly  10 , it will be seen that oil or other lubricating or coating fluid may be supplied through the liquid supply pipe  12  into communication with the longitudinal flow channel  16  and through the plurality of longitudinally spaced depending electrode tubes  14   b , being charged along their entire length of travel. Upon discharge from the electrode tubes into electrical field  23  between the electrode tubes  14   b  and the induction ban  5 , the liquid is dispersed into a fine particle spray with the repelling charges of the particles effecting substantially uniform distribution onto items to be coated positioned as passing below the spray assembly  10 . 
         [0025]    In carrying out a further important aspect of the invention, the spray nozzle assembly  10  is adapted for efficient cyclic operation without undesirable dripping or wastage of liquid. To this end, the underside of the electrode block  14   a  is provided with a valve element in the form of an elongated sealing gasket  30  and the electrode block  14   b  is moveable between a raised operating position that permits the flow of fluid through the housing and to each of the electrode tubes  14   b , as depicted in  FIGS. 2 and 3 , and a lowered closed position in which the elongated sealing gasket  30  simultaneously closes the inlets to each of the electrode tubes  14   b  as depicted in  FIG. 4 . The sealing gasket  30  in this case has a generally cylindrical upper portion  31  which is press fit within to a complimentary recess in the underside of the electrode block  14   a  and a lower generally rectangular portion  32  that defines a flat sealing surface for contacting the flat bottom of the housing channel in overlying relation to the cylindcrical bores that communicates with electrode tubes  14   b . For raising and lowering the electrode block  14   a  and sealing gasket  30  between such operating and closed positions, a pair of air cylinders  35  are mounted in the upper end of the housing cover  18  which each have a respective cylinder rod  35   a  threadedly fixed to the electrode block  14   a . The cylinders may be of a known spring return type, such that upon pressurized air actuation the piston and rod thereof are raised against the biasing force of the return spring and upon deactuation of the pressurized air supply, the cylinder return springs force the piston rods  35   a , electrode block  14   a , and gasket  30  to the lowered position simultaneously interrupting the communication of fluid to the electrode tubes  14   b.    
         [0026]    In carrying out the invention, to permit such raising and lowering of the electrode block  14   a  within the housing channel  15  while maintaining the electrode block in conductive relation to the banana coupling  21 , the electrode block  14   a  is formed with an elongated slot  38 , which receives a conductive rod  39  of the banana coupling  21  ( FIG. 3 ). The slot  38  has a vertical length sufficient to permit movement relative to the conductive rod  39  during raising and lowering movement of the electrode block  14   a  and a width corresponding substantially to the width of the rod  39  for maintaining electrical contact with the conductive rod  39 . 
         [0027]    It has been found that by virtue of the simultaneous opening and shutting of the electrode tubes to the supply of fluid at locations adjacent their inlet ends, the spray nozzle assembly  10  can be efficiently operated with reliable drip-free termination of spraying. The air cylinders further permit easy control and reliable operation. Yet the spray nozzle assembly  10  is relatively simple in construction and lends itself to economical manufacture.