Paint spray booth with flooded floor
INTRODUCTION 
     This invention relates to paint spray booths and more particularly to a paint spray booth incorporating a flooded sub-floor for the extraction of paint overspray. 
     BACKGROUND OF THE INVENTION 
     It is customary to spraypaint automobiles and other mass-produced articles in a spray booth having the physical characteristics of an elongated corridor or chamber through which the automobiles are longitudinally conveyed and within which a human operator or mechanical robot or a combination of same actuate paint spraying equipment. It is essential in the operation of a paint spray booth to maintain a proper supply of fresh air and to remove paint overspray by means of an air exhaust system. 
     Paint overspray is conventionally removed from the air by drawing the air through water flooded cylinders which are disposed along the center line of a sub-floor within the booth at longitudinally spaced intervals. The sub-floor is made up of two longitudinally continuous planes which slope toward the center line and which are flooded with a thin sheet of water which catches some of the paint overspray. A mixing action between air and water takes place within the spaced cylinders to catch the remaining paint overspray. Water flowing down through the cylinders drops into a relatively static pond which flows outwardly into a disposal sluice which runs from the paint spray booth to a treatment center. Such a paint spray booth is disclosed in the U.S. patent to Halls U.S. Pat. No. 3,421,293. 
     BRIEF SUMMARY OF THE INVENTION 
     The principal objective of the present invention is to improve upon the prior art paint spray booth which exhibits the sloping sub-floor system above described. More particularly, an objective of the invention is to provide a paint spray booth having a relatively flat flooded sub-floor which is more effective in handling both paint overspray and heavy chunks of accumulated paint from the perforated work floor, which simplifies the periodic sludge removal process, which reduces the amount of water required per lineal foot of paint spray booth, which reduces noise within the paint spray booth, which eliminates the possibility of dry spots and non-uniform water flow and which otherwise simplifies the water distribution function. 
     In general, the objectives set forth above are accomplished by providing a paint spray booth having a perforated working floor and a flat sub-floor which is relatively deeply flooded with water and which includes a plurality of longitudinally spaced cylindrical or tubular outlet structures, preferably spaced along the center line thereof, with the walls of said cylindrical structures being spaced above the sub-floor level quite substantially, i.e., on the order of three inches, so as to create the substantial depth of sub-floor flooding and to produce a weir effect. 
     Other features of the invention include a simplified water delivery system comprising inlet conduits which extend upwardly through the sub-floor from a supply conduit. Other features and advantages of the invention will be more fully set forth hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified perspective drawing of a section of a paint spray booth incorporating the features of the present invention; and 
     FIG. 2 is a detailed cross-sectional drawing through a paint spray booth incorporating the features of the invention. 
    
    
     DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENT 
     Referring to FIG. 1, there is shown a paint spray booth for automobiles or other mass-produced articles and comprising an elongate housing structure 10 defining a large open interior area through which automobiles are towed by means of a conveyor and around which a human operator may move to spray paint on the automobile bodies as they pass longitudinally through the structure 10. Above the main working area is an air supply plenum 12 having adjustable baffles 14 and a diffusion ceiling 16 made of porous urethane foam. Lights 18 are disposed continuously along the spray booth structure 10 to illuminate the working area. Windows 20 may be disposed in the sidewalls of the structure 10 to permit the interior operations to be viewed and to create an open airy atmosphere within the spray booth. 
     The working floor is defined by a full width grating 22 which, as shown in FIG. 2, typically includes a conveyor structure 37 for towing automobiles or other articles longitudinally through the booth. Disposed approximately 18 inches beneath the grating 22 is a sub-floor 24 in the form of a deep pan which is substantially flat, i.e., does not slope from the outside edges toward the center as is common to the prior art. Centrally of the sub-floor pan 24 are a plurality of longitudinally spaced cylinders 26. The cylinders are preferably fabricated from thin gage metal, galvanized or plated for corrosion resistance, and welded or otherwise secured in place within the sub-floor 24. Although dimensions are given by way of example rather than by way of limitation, a preferred arrangement includes cylinders 26 of approximately 18-inch diameters spaced longitudinally along the sub-floor at a spacing of 30 inches between centers. 
     As noted in FIG. 1 the cylinder sidewalls extend above the floor 24 by approximately three inches thereby creating a pool of approximately three inches in depth when the sub-floor is supplied with water as hereinafter described. In addition, the three-inch rise above the sub-floor 24 creates a weir effect which increases the speed of flow in the immediate vicinity of the cylinders 26, also as hereinafter defined. Cylinders 26 extend approximately two feet below the sub-floor 24 and preferably contain baffles, helical vanes, watersprays, or such other mechanisms as will create a mixing action of air and water within the cylinders for the effective removal of fine paint overspray as hereinafter described. 
     Cylinders 24 are spaced above a trough-shaped flooded base floor 28 which slopes laterally upwardly to both sides toward drain sluices 30. The sluices 30 on opposite sides of the base floor 28 convey paint laden water to a treatment plant not shown. 
     Water is supplied to the sub-floor 24 by means of longitudinally extending conduit 32 having spaced vertically extending distributor legs 34 which extend upwardly through the sub-floor as best shown in the left side of FIG. 1 and again in FIG. 2. A large volume of water may be supplied to the sub-floor 24 by means of the distributor pipes 34 on a substantially continuous basis. Air which is pulled down through the cylinders 26 in the sub-floor 24 is exhausted from the spacing between the sub-floor 24 and the base floor 28 by means of longitudinally spaced exhaust plenum 36. Because of the extremely effective paint removal action of the subject booth, the air emitted from the exhaust plenum 36 tends to be very clean and bearing a minimum paint overspray. 
     In operation, air is forced by turbines or other suitable means to flow into the supply plenum 12 downwardly through the diffusion ceiling 16, around the automobile or other object being spraypainted in the working area, through the grating 22, thence downwardly through the cylinders 26 in the sub-floor 24 and thence back to the atmosphere through exhaust plenum 36. Paint overspray which is picked up in the working area tends to be exchanged into the water system by direct contact with the three-inch deep quantity of water on the sub-floor 24, and again at the mixing sites provided by the cylinders 26. The paint-laden water flowing downwardly through the cylinders 26 impacts the surface of the pond on the sub-floor 28 and flows outwardly to the sluices 30 where it flows toward the treatment center. Treated water may be recirculated into the supply conduit 32 where it is again used to maintain the flooding action of the flat sub-floor 24. Paint overspray which adheres to and accumulates on the grating 22 may eventually form relatively large deposits. After a time these deposits fall through the grating 22 into the three-inch deep pond of water on the sub-floor 24. Because of the depth of the water pond on the sub-floor 24 such paint deposits tend to be completely submerged and lay on the bottom of the sub-floor where they are kept wet, thus facilitating later removal by manual scraping and/or high-pressure water guns at the cleaning interval. Moreover, the substantial depth of the water pond on the sub-floor 24 tends to permit surface water to flow easily over and around the large paint deposits which fall from the grating 22, thereby maintaining the effectiveness of the water surface to catching and removing the fine paint overspray which is carried down into the sub-floor area by the forced air flow. 
     Referring now to FIG. 2, the details of an actual paint spray booth structure will be disclosed in such full and complete detail as to permit persons skilled in the art to actually fabricate a spray booth therefrom. As stated above, the drawing of FIG. 2 is a full section through an actual spray booth at a location which reveals all of the essential details of both the air and water systems. 
     In FIG. 2 structure corresponding to that shown in FIG. 1 has been identified with like reference characters. Accordingly, the main spray booth structure 10 is again shown to define the overhead air supply plenum 12, the adjustable perforated baffles 14 and the diffusion ceiling 16 for supplying air uniformly to the interior working space of the paint spray booth. The bar grating 22 is interrupted at the center by a conventional conveyor unit 37 for towing automobiles through the paint spray area. As shown in the drawing, the interior dimension of the booth is approximately 20 feet, thus permitting substantial working room for a human operator to move around an automotive vehicle. 
     Sub-floor 24 is formed beneath the grating 22 and spaced therefrom by means of tubular supports 40 to define a spacing of approximately 18 inches. The cylindrical tubes or cylinders 26 rise above the sub-floor 24 by approximately three inches. Each cylinder 26 is fitted with a set of interior vanes 42 of the type disclosed in the Halls patent so as to create a flushing or mixing action of air and water for the effective removal of paint overspray. Alternatives exist; for example, the mixing structure of U.S. Pat. No. 3,934,495 may be used, the objective being to create an effective transfer of paint overspray from air to water in the vicinity of the tubes 26. The sub-floor 24 is supported relative to the base floor 28 by means of tubular supports 44 so as to create a spacing of just over three feet. Sub-floor 28 is defined by a large metal plate which slopes upwardly toward the right and left lateral extremes as shown in FIG. 2. At the left and right extremes, the sub-floor abuts the sidewall 46 of a longitudinally extending water disposal sluice 30, the main tube of which extends to the treatment center as previously described. 
     The water for the flooded floor is provided by means of supply conduit 32 having spaced upstanding feeder pipes 34. Balancing valves 48 are disposed within the feeder pipes 34. The feeder pipes extend through the sub-floor and to a point approximately four inches above the sub-floor. A deflection plate 50 is disposed above and spaced from the outlet end of each feeder pipe 34 so as to prevent water from spraying up through the grating 22. 
     The air exhaust plenum 36 is connected by suitable ducting to the laterally opposite sides of the spaced between the sub-floor 24 and the base floor 28 as shown. Access doors 52 may be provided for periodic clean-out. 
     Sludge removal from the sub-floor 24 may be facilitated by longitudinally spaced covers 54 in the sub-floor connecting with cylindrical pipes 56 spaced immediately over the water sluice 30. Clean-out may thus be achieved by shutting off the flooded floor water supply, opening the cover 54 in the floor hatch and discharging accumulated paint deposits through the pipes 56 directly into the sluice 30. Additionally or alternately, a door 58 may be placed in the lateral end wall of the booth structure such that a disposal box might be placed beneath the door on the concrete floor 60, the door opened and semi-dry accumulated sludge simply scraped or pushed out through the door and into the trash container. As mentioned above, the fact that the accumulated heavy paint deposits are kept under water until removed tends to substantially facilitate the removal operation as well as to promote the effective removal of paint overspray by contact with the flooded floor surface as previously described. 
     Although not intended by way of limitation, it has been found that the sidewall 46 of the sluice structure should extend approximately 11/2 inches above the inner section with the sub-floor 28 so as to provide an adequate depth water pond over and along the base floor 28; the water supply or feeder pipes 34 as well as the discharge sluice structures may be spaced approximately ten feet apart, the depth of the pond immediately beneath the discharge end of the tubes 26 should be approximately ten inches (this depth will be depressed somewhat in the center due to the force of the airflow). The disposal caps 54 may be placed approximately every 40 feet. Various other dimensional relationships will be apparent from the drawing of FIG. 2 which is substantially to scale.