Abstract:
A paint system containing at least one pump  150  and at least one paint mixing vessel  160 . At least one return line  46  functions to route paint from the paint system back into the paint mixing vessel from whence it was drawn. At least one eductor  522  fluidly communicates with a respective paint mixing vessel  160  and a respective return line  46  whereby during operation of the paint system, as paint traverses through return line  46  and into eductor  522 , paint is drawn from the respective paint mixing vessel  160  thereby mixing the paint drawn from the vessel with the paint in the return line  46.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation-in-part application of co-pending and co-owned U.S. application Ser. No. 11/349,501 having a filing date of Feb. 6, 2006, and claims priority thereto. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    In large paint finishing facilities, paint materials are delivered to application points through a network of distribution pipes. The paint is generally pumped through the pipes from a central location (paint mix room or paint kitchen) designed for handling and storage of flammable and combustible liquids (e.g., solvent-based paints and/or water-based paints.) Various types of pumps are used for this purpose. The paint materials are adjusted to proper viscosity for application and contained in tanks connected to the pumps. 
         [0003]    The paint is continually circulated between the mix room and the application points to prevent settling of pigments and metallic particles or similar appearance enhancers (mica, etc.) in the distribution pipes, which would result in sub-standard finish appearance on the painted product. Paint tank agitation methods commonly used to maintain mixing of the paint within the paint mixing vessel may employ a series of paddles, propeller, or serrated disks ( FIGS. 2-5 ) connected to a drive shaft which, in turn, is connected to a gear motor or to a gear reducer and motor. In high volume production facilities such as automotive or similar production, electric motors ranging in horsepower from ½ to ten HP, depending on the mix tank size and paint properties are used to drive the agitators at the required speed. 
         [0004]    The components of conventional paint agitation systems are generally bulky and expensive, and frequent, complex, and expensive maintenance procedures may be required to maintain these components in working order. Furthermore, the drive mechanism or motor for each agitator increases the cost of operating the paint system as well as increasing the maintenance requirements for the overall system. In particular, systems with multiple paint colors require an agitation means for each paint pot of the system. As the number of paint pots increase within a given system, the operating cost increases accordingly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a schematic view of a paint circulating system in accordance with the present invention; 
           [0006]      FIG. 2  is a cross-sectional view of a mix tank and an associated paint agitation system in  FIG. 2  is a cross-sectional view of a mix tank and an associated paint agitation system in accordance with the present invention; and 
           [0007]      FIG. 2A  is a cross-sectional plan view of the mix tank shown in  FIG. 2 ; 
           [0008]      FIG. 3  is a cross-sectional view of an alternative embodiment of the mix tank and associated paint agitation system shown in  FIG. 2 ; and 
           [0009]      FIG. 3A  is a cross-sectional plan view of the mix tank shown in  FIG. 3 . 
           [0010]      FIGS. 4 and 5 , when combined, disclose an exemplary paint system in accordance with the present invention. 
           [0011]      FIG. 6  is a view of the system of  FIGS. 4 and 5  in the paint recovery mode. 
           [0012]      FIG. 7  is a view of the system of  FIGS. 4 and 5  in the line flush mode; 
           [0013]      FIG. 8  is a view of the spray gun line flush fluid circuit; and 
           [0014]      FIG. 9  is a view of the pump flush fluid circuit. 
           [0015]      FIGS. 10 and 11 , when combined, is a view of a second paint line within a paint system of the present invention, thereby illustrating a plurality of paint lines within a paint system, particularly when combined with  FIGS. 4 and 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 1  shows a schematic of a paint circulating system  510  incorporating a paint agitation system  520  in accordance with the present invention. 
         [0017]    Paint circulating system  510  includes a paint mix tank  518  for storing and mixing of the paint, a paint application area  512  (for example, a paint spray booth), at least one paint supply line  514  for conveying paint from mix tank  518  to paint application area  512 , and at least one paint recovery or return line  516  for conveying paint from application area  512  to mix tank  518 . Circulation of paint between mix tank  518  and application area  512  is provided and managed by a paint flow regulation system, generally designated  515 . 
         [0018]    Paint flow regulation system  515  comprises an arrangement of known elements, such as pumps, valves, pressure regulators, compressed air lines, and other components necessary for regulating flow of the paint between a paint reservoir (such as mix tank  518  of the present invention) and paint application area  512 , in accordance with design requirements of the paint system. One example of such a flow regulation system is disclosed in U.S. Pat. No. 5,389,149, incorporated herein by reference. Numerous other known configurations of flow regulation system are possible and would be suitable for regulating paint flow in the paint circulating system described herein, depending on design requirements. 
         [0019]    Paint recovery line  516  provides a conduit for conveying unused paint from paint application area  512  back to mix tank  518 . In the embodiment shown in  FIGS. 2 and 2A , one or more flexible branch lines  516   b  extend from a main line  516   a . Branch lines  516   b  are fluidly coupled, via suitable piping or tubing, to eductors  522 , described in greater detail below. The use of multiple branch lines  516   b  extending from main recovery line  516   a  enables multiple associated eductors  522  to be supplied with paint from the main return line. Because eductors  522  are fluidly coupled to paint recovery line  516 , the pumps in paint flow regulation system  515  used to circulate the paint through the paint system can also be used to supply paint to the eductors. 
         [0020]      FIG. 2  shows a cross-sectional view of a mix tank and an associated paint agitation system in accordance with the present invention. Mix tank  518  is provided for storing and mixing paint compounds. Mix tank may include one or more baffles  519  for disrupting paint flow patterns within tank  518 , thereby increasing turbulence within the stored paint, in a manner known in the art. 
         [0021]    The present invention uses the circulated paint returning to mix tank  518  to agitate the tank contents, using Coanda or Venturi effect eductors to amplify the volume of the returning paint to maintain required agitation of the tank contents, thereby eliminating or reducing the need for separate agitation devices. Referring again to  FIG. 2 , one or more eductors  522  are positioned proximate the bottom of mix tank  518  where settling of the paint constituents is most likely to occur. However, eductors  522  may alternatively be positioned at any suitable level within mix tank  518 . In addition, multiple eductors  522  may be positioned at different levels within mix tank  518 , depending upon such factors as the tank geometry and the mixing requirements of a particular paint composition. 
         [0022]    The design and positioning of eductors  522  are optimized to produce a high turbulence in mixing tank  518  to prevent settling of pigments and metallic particles or similar appearance enhancers. Eductors  522  are known liquid eductors for agitating chemicals in tanks. One example of a suitable liquid eductor is manufactured by Fox Valve Development Corp. of Dover, N.J. In a Venturi-type eductor, for example, the paint is forced through a narrow or restricted area in the eductor, resulting in an increase in the speed of paint flow. The increased speed results in a reduction in pressure adjacent the accelerated fluid flow. This causes additional paint to flow through the eductor  522  thereby increasing the total paint volume through the eductor  522  and thus creating a high degree of agitation. Depending on the paint volume and pressure entering the eductor  522 , the total paint volume through the eductor  522  may be amplified or increased by varying volumes of ten to possibly twenty times the volume entering the eductor  522 , again leading to optimized agitation of the paint. 
         [0023]    In certain applications, a paint mixture having highly pigmented constituents and dense settling characteristics may need supplemental agitation to overcome settling. Also, because of variable production requirements and variables that exist in the operation of paint mix facilities, including scheduled shutdowns, it may be necessary to provide additional, mechanical agitation of select tanks. Thus, in an alternative embodiment of the paint circulating system (shown in  FIGS. 3 and 3A ), a conventional agitation system may be incorporated into paint agitation system  520  to augment the mixing effects of eductors  522 . The conventional agitation system may include an agitator drive unit  524  suspended from a load balancer  530 , and an associated mechanical agitator  526  including a mixing paddle  526   a . Agitator  526  and drive unit  524  may be fitted with complementary quick-disconnect features to enable drive unit  524  to be quickly disconnected from a first mix tank and reconnected to another mix tank having a similar design, as the need arises. It should be appreciated that the agitator drive unit  524 , the load balancer  530 , the agitator  526 , and the agitator paddle  526   a  are optional, removable, and temporary, and only used to stir up the paint vessels after prolonged periods of inactivity, over shutdown periods for example. 
         [0024]    Stated another way, the present invention counter-intuitively incorporates eductor mixers during steady state operation of the paint system as an exclusive means for mixing the paint, or after start-up of the system has been completed as explained below. Contrary to accepted belief, mechanical agitators are not necessary for the relatively thick and viscous paints, and in fact, homogeneous mixtures of the paint may be achieved through mixing exclusively accomplished by the eductor(s)  522 . In the past, it has been widely accepted that paddles or mechanical agitators had to be incorporated in the paint vessels to achieve and maintain homogeneous mixtures of the paint during steady state operation of the paint system. As such, the overall energy requirements to run the paint system were substantially increased due to operating costs associated with the mechanical agitators. It will be appreciated that the term “mechanical agitator” in general means any mixing article that operates independently of the paint circulating pumps. As stated above, the eductors  522  are inventively combined with the recirculation pumps to achieve homogeneous mixing at a fraction of the electric costs generally absorbed during the paint process. The reduction in electric costs offers a substantial benefit not heretofore realized in paint systems developed to date. Accordingly, the present invention incorporates a paint system that is absent any mechanical agitation during steady state operation of the paint system. It will be appreciated that “steady state” in this context means operation of the paint system after all start-up procedures and accommodation have been satisfied. 
         [0025]    The apparatus and principles set forth above may be applied to any suitable paint reservoir to provide needed agitation of the paint mixture. 
         [0026]    The present invention offers several advantages. Use of eductors as set forth herein may obviate the need for conventional agitation systems. Thus, the present invention may enable the elimination (or a substantial reduction in the number) of expensive conventional agitation system components, such as explosion-proof electric agitator motors, explosion-proof wiring, and agitator motor starters and controls. Elimination or reduction of these components reduces agitation system maintenance time and associated costs, system power consumption, and system power feeds. 
       Exemplary Paint System 
       [0027]    Various paint systems are known in the art. In accordance with the present invention, and for example only, a description of a paint system incorporating the agitation means or mechanism of the present invention is described below. 
         [0028]    Referring to  FIGS. 4 and 5  of the drawings, a paint system  20 , in accordance with an exemplary constructed embodiment of the present invention, comprises a paint booth  22  that accommodates one or more vehicle bodies  24 . Conventionally, the vehicle body  24  moves through the paint booth  22  on a skid  26 . The essence of the instant invention is a paint system  20  that enables the vehicle  24  to be painted with a custom color in an economical manner from the standpoint of both time and paint utilization. 
         [0029]    The paint system  20  comprises a plurality of color changers  30  through  44  that are connected, in series relationship, by, for example, fourteen (14) discrete paint lines  46  through  59 . A paint line is provided for each color accommodated by the system. Thus, in the disclosed and constructed embodiment of the invention, fourteen (14) colors can be accommodated by the system  20 . However, for purposes of clarity, only one line  46  is shown connecting the color changers  30  through  44  in series. 
         [0030]    The color changers  30  through  44  are provided with solenoid valve panels  60  through  74 , respectively, located exteriorly of the spray booth  22  which, in turn, are controlled by push buttons on a like plurality of push button panels  76  through  90 , respectively, located internally of the spray booth  22 . 
         [0031]    Each of the color changers  30  through  44  services a spray gun  100  through  114 , respectively, through discrete flexible paint supply lines  120  through  134 , respectively. 
         [0032]    Paint is supplied to the system  20  through, for example, the line  46  from a pump  150 . It is to be understood that each of the paint lines  46  through  59  is supplied by a separate pump. Only the pump  150 , paint line  46  and their associated supply and control system is discussed herein for purposes of clarity. 
         [0033]    The pump  150  is energized by compressed air supplied thereto from a line  152  through a solenoid valve  154 , pressure regulator  156 , and flexible air line  158 . Paint is supplied to the pump  150  from a paint pot  160  of, for example, 10 gallon capacity, through a ball valve  162  and flexible line  164 . The pump  150  supplies paint under pressure to the line  46  through a check valve  166 , flexible paint line  168 , ball valve  170 , and solenoid valve  172 . 
         [0034]    Paint is returned through a return portion of line  46  from the color changers  30  through  44 , through a ball valve  180 , back pressure regulator  182 , flow meter  184 , flexible paint return line  186 , and ball valve  188  to the paint pot  160 . The diaphragm of the back pressure regulator  182  is loaded by air pressure from the air line  152  through a regulator  190  and solenoid valve  192 . 
         [0035]    The system  20  is flushed by aerated solvent or foam produced in a turbulator  200 . Aerated solvent flows from the turbulator  200  under the control of solenoid valves  230  and  232  for the solvent, and solenoid valves  234  and  236  for the air. The solvent flows through a line  238  to a bank of solenoid valves  240  through  266  and through a line  270  to a bank of solenoid valves  272  through  296 , the function of which will be described hereinafter. 
       Operation 
       [0036]    The paint system  20  is conditioned for painting of a given color by connecting the paint supply hose  164  between the pump  150  and the paint supply solenoid  162  of a paint pot  160 , containing a desired color. The paint return hose  186  is then connected from the flow meter  184  to the paint return ball valve  188  on the paint pot  160 . The paint pot valves  162  and  188  are then opened. 
         [0037]    The system  20  is electronically conditioned for start by entering a vehicle number, a paint code number, and paint line number into a conventional process control computer (PC). As a vehicle  24  enters the spray booth  22  a conventional encoder (EC) transmits vehicle position to the control computer. The computer will search its memory for the appropriate paint which has previously been loaded into a specific paint pot  160  of the paint system  20 . When the paint number is found, the computer (PC) energizes the pump  150  and appropriate push button lights at each of the paint station push button consoles  76  through  90 . Paint circulates continuously in line  46  through the color changers  30  through  44 . In the example illustrated in the drawings, the push buttons at each console  76  through  90  would be lit that control the paint line  46 . When the operator pushes any lighted push button at any console  76  through  90 , paint flows from the associated color changer  30  through  44 , respectively, to its associated spray gun. It is to be noted that in the example, only the lighted push buttons controlling line  46  can be activated. 
         [0038]    After a predetermined spraying interval, the painter can either energize stop buttons on his associated control console  76  through  90  or the tracking logic in the encoder (EC) and computer (PC) shuts off the color valves controlling line  46  in the color changers  30  and  44 . 
       Spray Gun Line Flush 
       [0039]    As best seen in  FIG. 8 , after a vehicle  24  passes a particular color changer  30  through  44 , its associated spray gun line  120  through  134 , respectively, is flushed. Flushing is initiated by first closing the color valve in a color changer  30  through  44  by pushing an appropriate push button on the corresponding color console  76  through  90 . The painter then disengages an associated spray gun  100  through  114  from a gun line  120  through  134  and attaches the line  120  through  134  to an associated solvent flush connector  300  through  314 , respectively. All of the connectors  300  through  314  are connected to a common solvent return line  316  thence to a solvent collection tank  318 . 
         [0040]    As shown in  FIG. 8 , the spray gun  100  has been detached from the spray gun line  120  and the line  120  has been reattached to the connector  300  of the solvent return line  316 . The operator then presses a purge push button on the console  76  which automatically initiates a cleaning cycle of the color changer  30  and spray gun hose  120  by alternately opening the solvent and air solenoids of the color changers. The opening, closing and time duration sequence is controlled by the control computer. Solvent and air flows through the color changer  30  and line  120  for return to the tank  318 . The lines  120  through  134  are flushed successively as the vehicle  24  moves through the spray booth  22 . 
       Paint Recovery 
       [0041]    As best seen in  FIG. 5  and in  FIG. 6 , after a vehicle  24  has passed through the booth  22  and there is no future requirement for the color, as dictated by the control computer (not shown), the paint line, for example paint line  46 , is purged of paint. The control computer terminates the flow of paint by shutting off the pump  150  and then opening a paint blowdown valve  400  in air line  152  and closing valve  192  which fully opens the back pressure valve  182  so as to blow the paint through the line  46  back to the paint pot  160 . 
       Line Flushing 
       [0042]    After the paint line has been cleared of paint, and as seen in  FIG. 5  and in  FIG. 7 , the operator disconnects the paint inlet hose  186  from the paint pot  160  and connects it to a solvent connection  410 . He then opens solvent and air line valves  236  and  232  so as to initiate foamed solvent flow through line  238 , valve  252 , lines  46  and  186  to tank  220 . After a predetermined period the solvent valve  232  is closed to initiate flow of compressed air only to affect compressed air blowdown. 
       Pump Flushing 
       [0043]    As seen in  FIG. 5  and  FIG. 9 , flushing of the pump  150  is initiated by disconnecting the pump inlet hose  164  from the paint pot  160  and connecting it to a solvent connection  404 . A pump flush control is then energized opening the air and solvent valves  234  and  230 , respectively, in the turbulator  200  and starting the pump  150 . Solvent is pumped through the line  270 , valve  284 , line  164 , pump  150 , and line  168  to the tank  220 . The solvent valve  230  is closed after a set period and compressed air only flows through the pump  150  effecting final blowdown. 
         [0044]    In accordance with the present invention, at least one eductor  522  is positioned in line with the paint return line  46 , and also in fluid communication with the paint mixing vessel  160 . As paint fluid flows through line  46  it necessarily draws paint from the paint pot  160  and then directs the fluid into the paint pot  160  as determined by design criteria. For example, the fluid flowing through paint return line  46  may be directed to the bottom of the paint pot  160  thereby providing an aggressive agitation of the paint within paint pot  160 . It will be appreciated that each paint return line associated with a given color may contain an eductor/mixer  522  if desired thereby decreasing the overall energy requirements of the paint system. Stated another way, in operation, a paint system of the present invention contains at least one paint pot, at least one pump circulating at least one paint stream drawn from the at least one paint pot, and at least one eductor in fluid communication with both the at least one pump and the at least one paint pot. It will be further appreciated that  FIGS. 10 and 11  illustrate a second paint stream line  47  being circulated to a second paint pot  160 B, whereby a second pump  150 B circulates the second paint stream  47  thereby establishing fluid communication between a second eductor  522 B and the second paint pot  160 B. 
         [0045]    In further accordance with the present invention and with the description given above, a method of mixing paint within a paint vessel is characterized by first providing a paint source within a mixing vessel, then circulating or pumping a paint stream, then returning the paint stream through an eductor in fluid communication with the mixing vessel to draw paint from the mixing vessel, then returning the paint stream and the drawn paint to the mixing vessel. It should be appreciated that a paint system and a method of mixing a plurality of paint streams within the paint system is defined as containing a plurality of paint streams may be independently pumped from a corresponding plurality of paint mixing vessels, whereby each of said plurality of paint streams is routed through one of a corresponding plurality of eductors by pumping said paint stream through one of a corresponding plurality of pumps. Accordingly, a plurality of paint lines is provided wherein each paint line incorporates at least one eductor fluidly communicating with a paint pump, a paint mixing vessel, and a paint return line, thereby providing an improved method of mixing paint. 
         [0046]    It should be understood that the preceding is merely a detailed description of various embodiments of this invention and that numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit or scope of the invention. The preceding description, therefore, exemplifies but should not be construed to limit the scope of the invention.