Abstract:
An apparatus and method for spraying an atomized liquid compound onto a sheet material traveling along a material coating process line. The apparatus and method heats and mixes a liquid compound then atomizes and sprays the atomized liquid compound to coat the sheet material. The apparatus and method selectively provide an atomized liquid compound which improves coating, dries quickly on the sheet material, and increases process line productivity.

Description:
FIELD OF THE INVENTION  
         [0001]    The present apparatus and method relates to spray coating sheet materials and, more particularly, to an apparatus and method for spray coating sheet material with a heated and atomized liquid compound to decrease coating drying time, improve coating quality and increase production efficiency.  
         BACKGROUND OF THE INVENTION  
         [0002]    Application of spray coatings to sheet materials, such as forming lubricants sprayed onto sheet metal or coiled steel, that undergo drawing operations exposing the sheet and lubricant to extreme pressures are known in the art. The application of lubricants suitable for sheet metals varies on the forming process used, material to be coated and the properties of the lubricant itself. It has long been known to apply common oils and greases to lubricate the sheet to facilitate drawing or forming and to prevent unwanted thinning or tearing of the material. In the case of ferrous materials, the greases and oils further acted to prevent premature corrosion.  
           [0003]    These common greases or oils, however, were difficult to remove since such solvents required special handling and storage.  
           [0004]    During World War II, oils and greases became difficult to obtain, and it was discovered that borax or soap-based lubricants provided the necessary lubrication without having to remove the lubricant prior to subsequent coating of the sheet material with primer or paint. Such soap-based lubricants were dissolvable in water, rolled or sprayed on the sheet material, and eventually dried on the sheet once the water evaporated. The soap-based lubricants, although applied mixed with water, became known as “dry” lubricants as the lubricant is dry at the time of forming the sheet metal. Progression of the sheet metal along the processing line was dependent on the typically lengthy drying time of the lubricant which required reduced line speeds. Due to the need to keep the process line moving, a significant length of floor space was needed to ensure drying of the lubricant prior to further processing.  
           [0005]    Prior methods for applying dry lubricants were typically conducted by spraying an excessive amount of a lubricant/water mixture onto the sheet material. In order to obtain the recommended or desired coating weight per square foot of material, prior roll coating processes used rubber rollers on the top and bottom surfaces of the sheet metal to squeeze or press the undesired quantity and weight of the sprayed-on lubricant from the sheet material. Such prior art processes provided full coverage of the sheet metal but had numerous disadvantages.  
           [0006]    The prior roll coating processes are problematic in that dry lubricants are very costly, and the prior art methods used excessive amounts of dry lubricant, much of which was wasted through the spraying and squeezing process and often producing uneven coating weight on the material. The prior art processes were further problematic in that the rubber rollers used to squeeze off excess lubricant were subject to wear requiring reconditioning or replacement and added to uneven coating weight of the dry lubricant. The prior art processes were further problematic in that they slowed the process line speed requiring significant space in the process line and time for the water to sufficiently evaporate from the sheet material. The prior art processes were further subject to significant down time of the process line due to replacement of worn rollers and the necessity to change the rollers between coating production runs.  
           [0007]    Consequently, it would be desirable to provide a spray coating apparatus and method that improved the problematic conditions in the prior art, that is efficient in applying a desired coating weight, that improves the consistency of the coating, that reduces clogging of the apparatus, that facilitates an increase in productivity through an increase in process line speed, that reduces the space required for the apparatus in the process line and space needed for drying the coating, and that is simple and relatively inexpensive to produce and operate.  
         SUMMARY OF THE INVENTION  
         [0008]    The spray coating apparatus of the present invention includes a base having a batch tank positioned thereon which is used to contain and mix water with a water soluble material to form a liquid compound. The apparatus includes at least one spray control valve in fluid communication with the batch tank to selectively dispense the liquid compound from the batch tank to at least one spray nozzle. The apparatus further includes at least one spray nozzle which is adapted to receive the liquid compound from the control valve and receive a supply of heated gas which is mixed with the liquid compound in the nozzle to heat and begin atomizing the compound and spray the atomized compound onto the sheet material.  
           [0009]    In another embodiment of the invention, the apparatus further includes a spray header positioned along the coating line for the sheet material in spaced relation to the base. The spray header includes a plurality of spray nozzles adapted to receive and communicate with the liquid compound and the heated gas.  
           [0010]    In another embodiment of the invention, steam is used as the heated gas that is placed in communication with the liquid compound.  
           [0011]    In yet another embodiment of the invention, a process tank is positioned on the base in fluid communication with the batch tank to hold a reserve of mixed liquid lubrication compound to be sent to the spray control valve.  
           [0012]    In an additional embodiment, a user control terminal is positioned on the base for monitoring and controlling the mixing of the liquid lubrication compound and the spraying of the atomized lubricant on the sheet material.  
           [0013]    The present invention also provides a method for applying a spray coating to sheet material including the steps of adding a water soluble material to a quantity of water in a batch tank and mixing the material with water in the batch tank to form a liquid compound. The liquid compound is selectively dispensed under pressure to at least one spray nozzle. The liquid compound is then atomized and sprayed onto the sheet material traveling along a coating line.  
           [0014]    In another embodiment of the inventive method, the water and liquid compound in the batch tank are heated in the batch tank.  
           [0015]    In another embodiment, the spray nozzles are adapted to receive and communicate the liquid compound and a heated gas to further heat the liquid compound and begin atomizing the liquid compound.  
           [0016]    In yet another embodiment of the inventive method, a process tank is provided in fluid communication with the batch tank to store a reserve of liquid lubrication compound to be selectively dispensed to the spray nozzle.  
           [0017]    In an additional embodiment of the inventive method, a plurality of spray control valves and spray nozzles are provided for dispensing the liquid lubrication compound through selected valves to selected nozzles to coat the material sheet.  
           [0018]    In even another embodiment of the inventive method, a heated gas is supplied to a jacket in the spray nozzle to heat and deter clogging of the nozzle.  
           [0019]    In a further embodiment of the inventive method, a user control terminal is provided to control and monitor the mixing and spraying of the atomized lubrication compound to the sheet material along the coating line.  
           [0020]    Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:  
         [0022]    [0022]FIG. 1 is a partial schematic view of the apparatus and method including the batch mixing assembly including the batch tank recirculation components;  
         [0023]    [0023]FIG. 2 is a partial schematic view of the apparatus and method including the process mixing assembly including the process tank recirculation components and monitoring sensors;  
         [0024]    [0024]FIG. 3 is a partial schematic of the apparatus and method including the flow control valves for the spray header device;  
         [0025]    [0025]FIG. 4 is a partial front elevational view of the spray header;  
         [0026]    [0026]FIG. 5 is a side elevational view of the spray header device shown in FIG. 4;  
         [0027]    [0027]FIG. 6 is a partial plan view of the spray header device shown in FIG. 4;  
         [0028]    [0028]FIG. 7 is a sectional view taken along line A-A in FIG. 4;  
         [0029]    [0029]FIG. 8 is an enlarged view of an area circled in FIG. 4;  
         [0030]    [0030]FIG. 9 is a partial schematic of the apparatus and method of the present invention showing the base, batch mixing and process mixing assemblies, user control terminal and spray control valves; and  
         [0031]    [0031]FIG. 10 is a partial, cut-away schematic of the apparatus and method showing the spray header, coating line and material sheet. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0032]    Referring to FIGS.  1 - 10 , an apparatus and method  10  for applying a spray coating to sheet material is illustrated. Referring specifically to FIGS. 1 and 9, the apparatus  10  includes a batch mixing assembly  12  including a batch tank  14  positioned on a rigid base  15  as shown in FIG. 9. Batch tank  14  is a cylindrically-shaped, vertically oriented holding tank having a capacity of approximately 200 gallons and base  15  is a rectangularly-shaped rigid steel plate suitable for moving by a forklift or overhead crane.  
         [0033]    Batch mixing assembly  12  includes a first mixer  16  positioned above batch tank  14  and includes a shaft  17  and first impeller  18  extending downwardly into batch tank  14  as best seen in FIG. 1. Batch mixing assembly  12  further includes a batch liquid level sensor  20  which extends downwardly into batch tank  14 .  
         [0034]    Batch mixing assembly  12  further includes a batch pump  26  which is in fluid communication with the batch tank  14  through batch recirculation line  27 .  
         [0035]    As best seen in FIG. 1, a supply of water is provided under pressure to batch tank  14  through water line  28 . The flow of water is controlled by an inlet water valve  30 . Inlet water valve  30  is a pneumatically operated control valve receiving air under pressure through air line  32  from an air header  128  shown in FIG. 3. Inlet water valve  30  is operated and monitored by signals sent to and received from a user control terminal  22  as seen in FIG. 9 through control signal input line  23  and control signal output line  24 . Control terminal  22  is a personal computer, not shown, having software adapted to the apparatus and process and a touch-screen user interface as described below.  
         [0036]    Batch mixing assembly  12  further includes a heating element  40  positioned inside batch tank  14  as seen in FIG. 1. The apparatus includes a heating element  40  which is a coil heated by a heated gas, most preferably steam, supplied under pressure through batch steam lines  36  and  37 . The heating element  40  is positioned at the 45 gallon point in the 200 gallon capacity batch tank  14 . Steam for heating element  40  is controlled by a batch steam control valve  38  which is pneumatically operated through connection to the pressurized air line  32 . Steam control valve  38  is controlled and operated by the user control terminal  22  through signal input  23  and signal output  24  lines as previously described. Batch steam control valve  38  is electronically connected to a batch tank temperature sensor  42  which protrudes into batch tank  14  to monitor the temperature of the liquid contents in batch tank  14  and to transmit the temperature to the user control terminal  22  which in turn signals steam control valve  38  to open and close as needed. In an alternate aspect, the heated gas is heated air instead of steam.  
         [0037]    Batch mixing assembly  12  further includes a three-way batch solenoid valve  50  positioned between batch tank  14  and batch pump  26  in batch recirculation line  27  as best seen in FIG. 1. Pneumatically operated batch solenoid valve  50  is controlled and operated by user control terminal  22 . Batch mixing assembly  12  also includes an inlet port  52  in batch tank  14  for adding a water soluble material in the form of liquid, powder, pellets or other form of media to the batch tank  14  to be mixed with the water to form a liquid compound.  
         [0038]    The spray coating apparatus and method preferably further includes a process mixing assembly  60  as best seen in FIGS. 2 and 9. The process mixing assembly  60  stores a reserve of heated and mixed liquid compound that stands ready for disbursement while a new batch of liquid compound is heated and mixed. The reserve of liquid compound provides a continuous or almost continuous supply of liquid compound to support the needs of the coating line. Where such continuous supply of compound is not needed or downtime is not critical, the batch tank assembly  12  may be employed without the need for process mixing assembly  60 .  
         [0039]    Process mixing assembly  60  includes a process tank  62  similar in configuration and capacity as batch tank  14 . Process mixing assembly  60  further includes a second mixer  64  extending downwardly into process tank  62  and includes a second impeller  66  for mixing the contents of the process tank  62 . Process mixing assembly  60  further includes a process tank level sensor  68  extending downwardly into process tank  62  for monitoring the level of liquid in the tank. Process mixing assembly  60  further includes a process pump  74  in fluid communication with process tank  62  through process recirculation line  76 . Process mixing assembly  60  also includes a process tank inlet line  78  which is in fluid communication with batch solenoid control valve  50  to permit flow of fluid from batch tank  14  to process tank  62  through opening of batch solenoid valve  50  on signal from the user control terminal  22 .  
         [0040]    The preferred process mixing assembly  60  further includes a heating element  88  positioned inside process tank  62  similar in construction, position and function as heating element  40  in batch tank  14 . Heating element  88  is preferably heated by steam provided under pressure from steam line  36  through process steam inlet line  82  and process tank steam control valve  84 . Process tank steam control valve  84  is pneumatically operated and controlled by user terminal  22  and is electronically connected to process tank temperature sensor  92  as previously described for valve  38  and sensor  42  in batch tank  14 .  
         [0041]    Process mixing assembly  60  further includes a process recirculation valve  98  positioned between process tank  62  and process pump  74  and is pneumatically controlled and operated by user control terminal  22  to permit the flow of fluid from process tank  62  through recirculation line  76 .  
         [0042]    Process mixing assembly  60  further includes a first steam purge line  102  in gaseous communication with steam line  32 . A first steam purge solenoid valve  104  is positioned in steam purge line  102  to selectively permit the passage of steam to and through process tank inlet line  78  to flush the line with steam to disperse sedimentation and prevent clogging as further described below. In an alternate aspect, heated air is used instead of steam.  
         [0043]    Process mixing assembly  60  further includes a process tank outlet  110  and a process three-way solenoid control valve  112  in fluid communication with process recirculation line  76 . The solenoid valve  112  is pneumatically operated and controlled by user terminal  22  in a similar fashion as batch solenoid control valve  50  as previously described. Solenoid valve  112  selectively permits the passage of fluid from process tank  62  to the remainder of the system as described immediately below.  
         [0044]    The spray coating apparatus and method  10  further includes at least one spray control valve  124 , and most preferably nine spray control valves  124 ( a )-( i ) as best seen in FIG. 3. In a preferred aspect of the invention, spray control valves  124  are positioned in adjacent proximity to spray header  150  discussed below. For simplicity of illustration, in an alternate aspect, spray control valves  124  are positioned on base  15  as shown in FIG. 9. Spray control valves  124  are positioned in fluid communication with process tank outlet  110  through process tank solenoid control valve  112  and through spray valve inlet line  136 . Spray valve inlet line  136  permits the selective passage of fluid to the spray control valves  124  through a spray valve manifold  126 . The spray control valves  124  are pneumatically operated and controlled by user control terminal  22  through the pressurized air header  128  and air line  32 . Spray control valves  124  further include spray control valve outlet lines  144  having one outlet line  144  for each spray control valve  124 ( a )-( i ).  
         [0045]    The spray coating apparatus and method  10  further include a spray header  150  as best seen in FIGS. 4 through 8 and  10 . Spray header  150  includes an upper header frame  154  and a lower header frame  156  as best seen in FIG. 4.  
         [0046]    Upper frame  154  includes upper support columns  158  and an upper beam  162 .  
         [0047]    Lower frame  156  includes lower support columns  160  and a lower beam  164 . Upper  158  and lower  160  support columns are vertically adjustable through elbows  161  to accommodate different heights of the coating line  234  and sheet material to be coated. Upper and lower beams  162 ,  164 , respectively, include a cover  166  to close the open surface of the beams. In a preferred aspect, 3×3 inch square steel tubing is used for the lower portion and 2½×2½ inch square steel tubing for the telescoping upper portion of upper  158  and lower  160  column supports. Upper  162  and lower  164  beams are made from thin gage steel in a C-shaped section having a corrosion resistant coating. Spray header  150  is positioned in spaced, but adjacent, relationship to base  15  while remaining in fluid and gaseous communication with process mixing assembly  60  and steam line  32 . It is contemplated that to aid in space reduction and further portability, spray header  150  may be attached to base  15 .  
         [0048]    Spray header  150  further includes a spray manifold  170  attached to one of the upper support columns  158  as best seen in FIGS. 4 and 5. Spray manifold  170  includes nine manifold steam inlet receptacles  172  and  18  manifold steam outlet lines  174 . Steam inlet receptacles  172  receive a heated gas, most preferably steam, under pressure from nine steam lines, not shown, in gaseous communication with steam line  36 . In an alternate aspect, heated air is used instead of steam for the heated gas. Spray manifold  170  further includes nine liquid compound fluid inlet receptacles  176  and  18  manifold liquid lubrication outlet lines  178 , nine of the fluid outlet lines  178  being routed to upper beam  162  and nine fluid lines  178  routed to lower beam  164 . In similar fashion, nine of the manifold steam outlet lines  174  are routed to upper beam  162  and nine are routed to lower beam  164 . Manifold  170  further includes a nozzle jacket steam inlet receptacle  192  and two nozzle jacket steam outlet lines  194 , one line  194  being routed to upper beam  162  and one routed to lower beam  164  as seen in FIG. 4. Nozzle jacket steam inlet receptacle  192  is most preferably in gaseous communication with steam line  36 . In an alternate aspect, heated air is used instead of steam as the heated gas.  
         [0049]    Spray header  150  further includes at least one spray nozzle  184  and most preferably a total of 18 spray nozzles  184  spaced in relation to one another as best seen in FIGS.  4 - 6 . Nine nozzles  184  are spaced in longitudinal and lateral orientation from one another across upper beam  162  and lower beam  164  as best seen in FIGS. 4 and 6. A row of five nozzles placed at a distance  250  apart are separated by a distance  252  from a second row of four nozzles spaced at a distance  250  apart from one another for spray coating sheet material  228 . The distance  250  between nozzles  184  is approximately 16 inches apart on center of each nozzle and the distance  252  between rows is approximately two inches.  
         [0050]    In a most preferred embodiment, each nozzle  184  is adapted to receive a steam outlet line  174  and a liquid compound outlet line  178  from the manifold  170 . Each nozzle  184  also includes a spray nozzle jacket which is adapted to receive a steam outlet line  194  from manifold  170  as best seen in FIGS. 4, 7 and  8 . Each nozzle  184  is adapted to place liquid from manifold liquid outlet lines  178  in direct communication with a heated gas, most preferably steam, from manifold steam outlet lines  174  to further heat and begin atomizing the liquid compound. In an alternate aspect, heated air is used instead of steam for the heated gas for either or both atomizing the liquid compound and heating the nozzle jacket. The at least partially atomized lubrication compound is forced to exit nozzle  184  under pressure as an atomized spray  200  having a spray width  202  and length  204  as best seen in FIG. 8.  
         [0051]    Spray header  150  is positioned along the sheet material coating line  234  and is adapted to receive sheet material  228  between the upper beam  162  and lower beam  164  passing between the spray nozzles  184  placing an upper and a lower surface of the sheet material, not shown, in spray communication with spray nozzles  184  suitable to provide a desired coating weight on the upper and lower surface of sheet material  228 . Sheet material  228  is supported by a conveyor, not shown, traveling along coating line  234  and is interrupted for a brief length prior to and through spray header  150  and recommences to support and carry the sheeting material for drying and subsequent processing.  
         [0052]    Referring to FIG. 2, spray coating apparatus and method  10  further includes a second steam purge line  212  in gaseous communication with steam line  36  to flush the lines or path the liquid lubrication compound follows between the process solenoid valve  112  and spray nozzles  184 . The passage of steam through second purge line  212  into spray inlet line  136  is controlled by a second steam purge solenoid valve  214  in gaseous communication with spray valve inlet line  136 . Steam purge solenoid valve  214  is pneumatically operated from pressurized air from air line  32  and controlled by signals from user control terminal  22 . Spray coating system  10  further includes a third steam purge valve  218  in gaseous communication with steam line  36  to selectively permit the flow of steam from steam line  36  to the steam manifold inlet receptacles  172  through steam purge line  220 . Valve  218  is pneumatically controlled through pressurized air from air line  32  and controlled by signals from user control terminal  22 . Steam purge line  220  further includes a steam flow sensor  222  and pressure sensor  226  which monitors and signals user control terminal  22  for display to the user. In an alternate aspect, heated air is used instead of steam.  
         [0053]    Referring to FIGS. 1 through 10, the inventive method of the present invention is illustrated. Prior to filling and initiating spraying by the spray coating apparatus  10 , several operator inputs or variables must be defined. The user control terminal  22  includes a computer display monitor, not shown, having an operator interface touch screen (HMI). The operator interface includes an initial Setup Screen or mode programmed in the user control terminal  22  computer software, not shown, for input of the linear speed of the mill line which is the speed the sheet material  228  will be traveling along the coating line  234 . At this Setup Screen, the width of the mill strip or sheet material  228  is also manually entered. It is contemplated that additional sensors, not shown, could operate to automatically detect and monitor the width of sheet  228  and monitor the linear speed of the sheet material  28  traveling along coating line  234  and provide representative signals to user control terminal  22  versus manually entering the speed and width as described above. In the event sensors are available and are automatically monitoring line speed and material width, an Automatic feature or mode on the operator interface screen could be employed versus a manual feature or mode whereby the operator manually inputs the information as described above.  
         [0054]    In order to initiate the filling of the spray coating apparatus  10 , a Tank Setup feature or mode is accessed by a user on the user interface. At the Tank Setup screen, the user can manually set a high liquid level and low liquid level for the batch tank  14 . Using a 200 gallon batch tank, a high level set point of 150 gallons and a low level set point of 45 gallons is input or established as a default in the control terminal  22  program.  
         [0055]    On input of the information under the Tank Setup screen, the user proceeds to a Batch Mixing Tank screen displayed on the user interface. On the Batch Mixing Tank screen, an option to select a Fill To 50% button is pushed or activated to initiate the flow of water under pressure through water line  28 . The user control terminal provides a signal to automatically open pneumatically operated water inlet valve  30  which permits flow of water into batch tank  14 . Once the level of water in batch tank  14  achieves the low liquid level amount of 45 gallons, user control terminal  22  sends a signal to open batch steam inlet valve  38  permitting a heated gas, most preferably steam, to flow into batch heating element  40  to heat the water while the water continues to rise. In an alternate aspect, heated air is used instead of steam for the heated gas. At approximately this point, user control terminal  22  will signal and start the first mixer  16  and place the batch pump  26  in a recirculation mode. In this mode, batch pump  26  will draw water from a lower portion of batch tank  14  and force the water through batch recirculation line  27  for deposit of the warming water into an upper portion of batch tank  14  as seen in FIG. 1. The mixer  16  will provide agitation to mix and uniformly heat the water.  
         [0056]    Once the batch tank  14  is filled to one-half of the desired high liquid level point of 150 gallons and reaches a temperature of approximately 180° F. as measured by batch temperature sensor  92 , an indicator visible on the interface screen of the user control terminal  22  to Add Powder will be enabled permitting the operator to add a necessary amount of water soluble material to the heated water. In one embodiment, the material is a water soluble forming lubricant for sheet metal. In a preferred embodiment, a borax-based “dry” sheet metal drawing lubricant, as previously described, is added to the heated water in powdered form through inlet  52  in batch tank  14  to form a liquid lubrication compound. For exemplary purposes only, a suitable borax-based, water-soluble dry drawing lubricant is T.C.  1800 - 3  manufactured by Tru-Chem Co., Inc. of Columbus, Ohio. It is contemplated that other borax-based, water-soluble dry lubricants and other water soluble materials, in powdered, liquid, flaked, pelletized, granular, or other forms, may be used without departing from the present invention.  
         [0057]    The amount of water soluble material added to the heated water in batch tank  14  is dependent on several factors including: the width of the sheet material  228 , the line or linear process speed of sheet material  28  that passes spray header  150  in a given period of time and the desired weight of the coating to be applied to the sheet material. It has been determined that 24.5 oz. of T.C. 1800-3 to one gallon of water will achieve a coating weight of approximately 300 mg/sq. ft. Once the water soluble material is automatically or manually added to batch tank  14 , the user acknowledges that the powder has been added by pressing the Add Powder acknowledgment button or prompt on the user interface of user control terminal  22 .  
         [0058]    To continue the process, the operator next activates a Fill To 100% button visible on the Batch Mixing Tank screen on the user interface which signals and re-opens water inlet valve  30  permitting additional water to enter the batch tank  14 . Once sufficient water is added to batch tank  14  to reach the desired high liquid level set point of 150 gallons, the user control terminal signals and closes water inlet valve  30  preventing additional water from entering the batch tank.  
         [0059]    In one embodiment, when batch tank  14  is filled to 150 gallons, first mixer  16  will continue mixing the liquid lubrication compound for 30 minutes while batch heating element  40  maintains the liquid lubrication compound at approximately 180° F. Throughout this time, batch pump  74  remains in a recirculation mode to recirculate the liquid lubrication compound through recirculation line  76  to deter sedimentation and clogging in the pump and recirculation line. Following the preferred 30 thirty minutes mixing time period at 180° F., a Batch Ready prompt will be displaced on the user interface on the user control terminal  22 . The liquid lubrication compound is now ready for distribution from the batch tank to the spray control valves  124 .  
         [0060]    In another embodiment of the inventive method, a process mixing assembly  60  is placed on base  15  in liquid communication between the batch tank  14  and the spray control valves  124 . The process mixing assembly  60  permits a reserve of heated and mixed liquid lubrication compound to be stored while the batch tank  14  is refilled, the water is heated, and the lubrication is mixed while the process mixing assembly  60  stands ready or supports active spraying. The reserve of prepared liquid lubrication provides for a near constant flow of liquid lubrication compound to the spray header  150  to support the coating line. As explained, if a reserve is not required, the liquid lubrication compound may be dispensed directly from the batch tank  14 .  
         [0061]    In yet another embodiment of the inventive method, batch pump  26  is taken off the recirculation mode by the user control terminal  22  and the three way batch solenoid control valve  50  is opened to permit batch pump  26  to force liquid lubrication compound from batch tank  14  along process tank inlet  78  to an upper portion of process tank  62  to begin filling the process tank as seen in FIG. 2. Once the liquid lubrication compound reaches the predetermined lower liquid level of 45 gallons as measured by the process liquid level sensor  68 , process tank heating element  88  will be heated through the opening of process steam control valve  84  by the user control terminal  22 . The contents of batch tank  14  will be pumped into process tank  62  until the liquid level in batch tank  14  reaches the predetermined low level point of 45 gallons effectively transferring 105 gallons to the process tank. It is desired that the contents of batch tank  14  not fall below the 45 gallon liquid low level mark which would fall below the position of batch heating element  40  and allow the liquid lubrication compound in batch tank  14  to begin to cool. In a similar fashion, it is understood that subsequent batches of liquid lubrication compound from batch tank  14  to batch tank  62  will raise the contents of process tank  62  to the desired predetermined high liquid level mark of 150 gallons as the transfer of 105 gallons will be added to the 45 gallons already in process tank  62  left from the prior batch.  
         [0062]    Once the transfer to batch tank  14  to process tank  62  has been made and batch tank  14  is at the low liquid level of 45 gallons, the user control terminal  22  will signal and close the batch solenoid valve  50  and place batch pump  26  and process pump  74  in a recirculation mode to deter sedimentation and clogging of the liquid lubrication compound. While batch solenoid valve  50  is closed preventing additional liquid lubrication compound from passing to the process tank  62 , the process tank inlet line  78  is flushed with heated gas, most preferably steam, to clear the line and prevent sedimentation and clogging of the line. This accomplished through opening of the first steam purge solenoid valve  104  as best seen in FIG. 2 to allow the steam under pressure to pass through first steam purge line  102  into process tank inlet line  78  purging the steam and residual liquid lubrication compound into process tank  62 . Flushing of process inlet line  78  continues for approximately 15 minutes. In an alternate aspect, heated air is used instead of steam for the heated gas.  
         [0063]    If additional liquid lubrication compound is required to support the coating line  234  beyond the reserve in process tank  62 , the operator can again initiate filling and mixing of the batch tank through the Batch Tank screen through the method previously described. Upon depleting the liquid lubrication compound in process tank  62  to the predetermined low liquid level line of 45 gallons, user control terminal  22  halts recirculation mode of batch pump  26 , opens batch solenoid valve  50  and batch pump  26  again transfers the 105 gallons of heated and mixed liquid lubrication compound from batch tank  14  to process tank  62  as previously described.  
         [0064]    On achieving the predetermined high liquid level mark of 150 gallons in process tank  62  and the preferred temperature of 180° F. is achieved through monitoring by process tank temperature sensor  92 , dispensing of the liquid lubrication compound to the spray control valves  124  is initiated by either of two ways: Automatic or Manual Mode. In the Automatic Mode, once the system prerequisites of liquid level and temperature are met, user control terminal  22  halts recirculation mode of process pump  74 , opens process recirculation valve  98  and opens three-way process solenoid valve  112 . User control terminal  22  automatically activates the process pump  74  to begin pumping the heated liquid lubrication compound to the spray control valves  124 . A visual indicator will be displayed on the user interface indicating the sprays are On. In the Manual Mode, the user will receive a prompt through the user interface that the system is ready to initiate spraying. The user then activates a Spray On prompt or button. Once the sprayers are placed in an On position by either automatic or manual mode, the liquid lubrication compound will be permitted to pass from the process tank  62  to the spray control valves  124 .  
         [0065]    The liquid lubrication compound will be supplied under pressure by process pump  74  to at least one, and most preferably nine, pneumatically controlled spray control valves  124 ( a )-( i ) through spray valve inlet line  136  to a spray valve manifold  126  as best seen in FIG. 3. In order to maximize the efficiency of spraying the-sheet material  228  and thereby minimizing waste of the liquid lubrication compound, spray control valves  124 ( a )-( i ) will be selectively opened depending on the width of the sheet material  228  that is either automatically determined on the coating line  234  or manually input by the user at the Setup Screen as previously described. Referring to FIG. 3, the following valves are selectively opened to provide adequate coating to a sheet  228  based on standard sheet metal roll widths noted below.  
         [0066]    Sheet material  228  in a 24 inch width: open spray control valves  124 ( g )-( i );  
         [0067]    Sheet material  228  in a 34 or 40 inch width: open spray control valves  124 ( e )-( i );  
         [0068]    Sheet material  228  in a 48 inch width: open spray control valves  124 ( c )-( i ); and  
         [0069]    Sheet material  228  in a 62 or 72 inch width: open spray control valves  124 ( a )-( i ).  
         [0070]    Referring to FIGS.  3 - 5 , each spray control valve  124  through spray manifold  170  provides liquid lubrication compound to two spray nozzles  184 , one nozzle on upper beam  162  and one nozzle on lower beam  164 . For example, for sheet material  228  in a 24 inch width, three spray control valves are opened providing liquid lubrication compound to a total of six spray nozzles  184 , three spray nozzles on the upper beam  162  and three nozzles to the lower beam  164 .  
         [0071]    In order to provide or support the required spray nozzles  184  to apply the desired coating weight, the process tank valve  98  is opened and adjusted to a position to provide the necessary volume of liquid lubrication compound to the spray control valves. As explained above, the proper volume of liquid lubrication compound depends on the width of sheet material  228 , the linear speed sheet metal  228  is traveling along the coating line  234 , and the desired coating weight. To achieve active monitoring of the flow and pressure of liquid lubrication compound in spray valve inlet line  136 , a flow sensor  138  and pressure sensor  140  are positioned in line  136  as seen in FIG. 2. Signals from sensors  136  and  138  to control terminal  22  through control signal input  23  and output 24 lines are compared against acceptable figures stored in user terminal  22  software and the flow of liquid lubrication compound is adjusted through valve  98  to maintain acceptable volume passing to the spray control valves  124 .  
         [0072]    On passage of the liquid lubrication compound through the selected spray control valves  124 , the liquid lubrication compound passes to the spray manifold  170  and into fluid inlet receptacles  176  depending on which spray control valves  124  are open. For each control valve outlet line  144  providing fluid to a particular fluid inlet receptacle  176 , the fluid is divided in manifold  170  to provide fluid to two nozzles  184 , one nozzle on the upper beam  162  and one nozzle on the lower beam  164 . Manifold fluid outlet lines  178  provide the liquid lubrication compound for the particular control valves to the respective spray nozzles  184 .  
         [0073]    Simultaneously, a heated gas, most preferably steam, under pressure from steam line  36  is provided to the spray manifold  170  and into steam inlet receptacles  172  as shown in FIG. 5. Steam will be supplied to all 18 of the nozzles  184  compared with only the selected nozzles  184  receiving liquid lubrication compound. Supply of steam to all of the nozzles aids in the atomization of the liquid lubrication compound sprayed from the activated nozzles  184  and aids in controlling and confining the spray pattern to the desired area. To initiate supply of steam to manifold  170  and spray nozzles  184 , user control terminal  22  opens the pneumatically operated steam control valve  218  as best seen in FIG. 2. To monitor and control the flow and pressure of steam provided to spray header  150  in a similar fashion to liquid lubrication compound to the spray control valves  124 , a steam flow sensor  222  and pressure sensor  226  are positioned along spray header steam line  220  and along with user control monitor  22 , steam control valve  218  is adjusted to ensure an adequate supply of steam is available to support spray header  150 . In an alternate aspect, heated air may be used instead of steam as the heated gas.  
         [0074]    Referring to FIGS. 4, 6 and  8 , as described above, most preferably nine nozzles  184  are placed in spaced relationship to one another on the upper beam  162  and nine nozzles  184  on the lower beam  164  as best seen in FIGS. 5 and 6. Each nozzle  184  is adapted to receive a single and dedicated liquid lubrication outlet line  178  from manifold  170  and a single, dedicated steam outlet line  174  from manifold  170 . Each nozzle  184  is adapted to place the in-flowing liquid lubrication compound under pressure and incoming steam under pressure in direct fluid and gaseous communication with one another to further heat and atomize the liquid lubrication compound. Through a spray aperture in each of nozzles  184 , atomized spray coating  200  having a width of spray  202  and length of spray  204  is produced as best seen in FIGS. 4 and 8. The heated and atomized spray  200  is directed toward the adjacent upper or lower surface of sheet material  228  to completely coat the material sheet with the desired weight of coating. Spray  200  has a width  202  of approximately 9 inches when the depth of spray  204  is approximately 7½ inches. In a preferred aspect of the invention, the distance  256  between opposing nozzles  184  on upper beam  162  and lower beam  164  is approximately 15⅛ inches as seen in FIG. 4.  
         [0075]    Referring to FIGS. 4 and 8, each nozzle  184  preferably includes a nozzle jacket  188  which is adapted to receive an independent supply of a heated gas, most preferably steam, to the nozzle jacket  188  for the purpose of heating the nozzle  184  and further deterring clogging of the nozzle  184 . Steam is supplied to the nozzle jackets  188  from steam line  36  through spray header steam line  220  which supplies manifold  170  with steam in receptacle  192  as seen in FIG. 5. Manifold  170  provides two steam outlet lines  194 , one for passage of steam to the nozzle jackets  188  on upper beam  162  and one line  194  to the nozzle jackets  188  on lower beam  164  as best seen in FIGS. 4, 5 and  6 . Only one steam outlet line  194  is used to service all of the nozzle jackets  188  on the upper beam  162  and one line  194  to service all of the nozzle jackets  188  on the lower beam  164  as best seen in FIGS. 4 and 6. A suitable connection of steam lines  194  to spray header  150  is shown through section A-A taken from FIG. 4 as shown in FIG. 7. In an alternate aspect, heated air is used instead of steam for the heated gas.  
         [0076]    Control of pressurized steam to the nozzle jackets  188  as described is controlled by user control terminal  22  which, when spray control valves  124  are open and providing liquid lubrication compound to the spray header  150 , steam flow control valve  218  is equally opened providing steam to atomize the liquid lubrication compound and simultaneously, providing steam to the nozzle jackets  188  as described. The total flow and pressure of steam provided to atomize the liquid lubrication compound and supplied to the nozzle jackets  188  is monitored by steam flow sensor  222  and pressure sensor  226  as previously described.  
         [0077]    In operation, the atomized lubrication compound  200  is applied to both upper and lower surfaces of sheet material  228  to completely coat the sheet material with the desired weight of coating. The heating and atomizing of the liquid lubrication compound provides a very consistent coating of sheet material  28  without the use of secondary rollers to squeeze or press excess coating from sheet material  228 . Through selective use of spray nozzles  184  tailored to the width of material sheet  228 , a significant reduction in the amount of spray lubricant that is wasted is achieved.  
         [0078]    On reaching the trailing end of sheet material  228  traveling along coating line  234 , or when the level of liquid lubrication compound and process tank  62  reaches the predetermined lower liquid level of 45 gallons, spraying of the material sheet is halted. Cessation of spraying may be achieved automatically by sensors, not shown, detecting the end of the sheet  228  or manually through a button or prompt on the user interface. Regarding the former occurrence, if it is anticipated that a short time period will lapse until spraying is recommenced, process mixing assembly  60  will be placed in a recirculation mode by closing a process solenoid control valve  112  thereby circulating the liquid lubrication compound in recirculation line  76  by process pump  74  as previously described. If a longer period is anticipated, the path of the liquid lubrication compound downstream of process solenoid valve  112  is flushed with a heated gas, most preferably steam, or in an alternate aspect heated air, as previously described. This is achieved by the user control terminal  22  opening steam flow control valve  218  which, as described, provides pressurized steam to the spray control valves  124 , manifold  170 , nozzles  184  and nozzle jackets  188  to flush the system of any lubricant residue. This flushing takes place for approximately 15 minutes.  
         [0079]    Where the level of liquid lubrication compound in process tank  62  reaches the predetermined lower liquid level line of 45 gallons as monitored by process tank level sensor  68 , transfer of a pre-prepared, heated and mixed batch of liquid lubrication compound in batch tank  14  may be simultaneously transferred to the process tank  62  as previously described providing for a continuous flow of liquid lubrication compound to spray header  150  without stopping the coating line  234 .  
         [0080]    The atomization of the heated liquid lubrication compound through spray  200  provides for quick evaporation of the water in the atomized spray  200  providing for rapid drying of the sprayed-on lubricant on sheet material  228 . Advantages of fast drying the lubricant are two-fold. First, higher line speeds may be used. Second, it greatly reduces the distance required for drying along the coating line  234  once the sheet material passes through spray header  150 . The length required for drying of the sheet material under the present inventive method is up to 90% less than prior art processes. Due to the reduction of space required for drying along the process line and relatively small space required for the spray header  150  along the process line, coating apparatus  10  may be readily installed and positioned to suit the demanding needs of the coating facility.  
         [0081]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.