Abstract:
Apparatus and method for spray coating of a horizontally moving web uses a spray-down unit that sprays downwardly onto the web and a spray-up unit that sprays upwardly onto the web. Each unit has adjustable cut-offs that control the length of the spray pattern by intercepting end portions of the spray pattern. The cut-offs of each unit can be adjusted to block a spray emission opening so as to prevent the entrance of contaminants when the unit is not in operation. Fluid intercepted by the cut-offs is returned for re-use. Both units are supported on a frame, and the spray-down unit can be moved away from the spray-up unit.

Description:
CROSS-REFERENCE TO CO-PENDING APPLICATION  
       [0001]    This application is based upon Provisional Application No. 60/259,515 filed Jan. 4, 2001, incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention is concerned with the application of sprayed fluid to surfaces of an object such as a moving web, and is more particularly concerned with apparatus that includes a pair of vertically separated spray generating units for applying fluid to opposite surfaces of a web that moves horizontally between the units, and with the control of spray patterns.  
           [0003]    Commonly owned U.S. Pat. No. 5,314,119 granted May 24, 1994 (incorporated herein by reference) discloses and claims apparatus for applying thin coatings of fluid droplets to an adjacent surface by the use of a pick-up roll rotating in a supply of fluid and a rotating brush roll. The two rolls counter-rotate with an interference between them, so that bristles of the brush roll are bent as their tips pick up droplets of fluid. After passing out of interference, the bristles snap away from the pick-up roll and project a spray of droplets against a surface of an object to be coated, e.g., a moving web. Coating uniformity is ensured by the use of elements such as a family of windage dams and seals, baffles, blades and mist eliminators, and by the use of a brush roll with a slight spiral. Two fixed shields, one at each end of the spray pattern, isolate the spray pattern from cross currents. The length of the spray pattern laterally of a moving web is controlled by the length of the brush roll and pick-up roll.  
           [0004]    In a specific embodiment disclosed in the aforesaid patent, the spray is directed horizontally for application to one surface of a vertically moving web, but rearrangement of the pick-up roll, the brush roll and accompanying parts would permit the spray to be directed to a non-vertically-moving web, such as a web that is moving horizontally. However, even with such re-arrangement the spray would still be applied to only one surface of the web, and the length of the spray pattern laterally of the web would still be determined by the length of the pick-up and brush rolls.  
         BRIEF DESCRIPTION OF THE INVENTION  
         [0005]    There is a need for applying sprayed fluid simultaneously to opposite surfaces of a moving web, especially a web moving horizontally, and for applying sprayed fluid selectively to a top side or a bottom side of a horizontally moving web. Previous spray generating units, such as the spray generating unit of the aforesaid patent, have applied spray to the full width of a moving web. There is a need for applying sprayed fluid to less than the full width of a moving web and to webs of various widths, such as webs that are narrower than the spray pattern. The present invention satisfies all such needs.  
           [0006]    A preferred embodiment of the invention uses a duplex machine in which two spray generating units are provided, spaced one above the other, with an object to be sprayed, such as horizontally moving web, between the units. An upper unit sprays downwardly onto an upper surface of the web, and a lower unit sprays upwardly onto a lower surface of the web.  
           [0007]    Each spray generating unit has a pair of cut-offs that intercept end portions of the spray pattern from that unit and that are adjustable to control the length of the spray pattern laterally of the web, thereby to accommodate different web widths, for example. The sprayed fluid that is intercepted by the cut-offs is collected in a receptacle, from which it may be re-circulated.  
           [0008]    The spray generating units can be operated at the same time or selectively. The cut-offs of each pair are preferably adjustable toward one another to a position at which a spray emission opening of the associated spray generating unit is blocked, so that when a spray generating unit is not in operation, internal parts are protected from external contaminants. A single spray generating unit can be employed when the ability to spray opposite surfaces of an object is unimportant. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The invention will be further described in conjunction with the accompanying drawings, which illustrate a preferred (best mode) embodiment, and wherein:  
         [0010]    [0010]FIG. 1 is a vertical sectional view of apparatus of the invention;  
         [0011]    [0011]FIGS. 2 and 3 are fragmentary top plan views of cut-offs employed in the invention;  
         [0012]    [0012]FIG. 4 is a contracted bottom plan view of a cut-off plate employed in the invention;  
         [0013]    [0013]FIG. 5 is an end view of the plate of FIG. 4;  
         [0014]    [0014]FIG. 6 is an end view of a cut-off catch pan employed in the invention;  
         [0015]    [0015]FIG. 7 is a contracted transverse sectional view taken along line  7 - 7  in FIG. 6;  
         [0016]    [0016]FIG. 8 is a diagrammatic side elevation view of apparatus of the invention;  
         [0017]    [0017]FIG. 9 is an exploded perspective view showing components of a spray-up unit of the invention;  
         [0018]    [0018]FIG. 10 is a top plan view of a spray-up unit of the invention; and  
         [0019]    [0019]FIG. 11 is a top plan view of a spray-down unit of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    [0020]FIG. 1 shows a duplex machine of the invention that includes a spray-down unit  10  and a spray-up unit  12 . The spray-down unit includes a brush roll  16  and a pick-up roll  18  that transfers fluid to bristles of the brush roll from a trough  20 , connected to a fluid distribution system. The brush roll  16  is partially surrounded by a cylindrical cover or shell  15  having an opening for communicating with a drain pan  17  (for draining fluid to the distribution system) and has an opening at which the brush roll is in interference with the pick-up roll  18 . The drain pan  17  is provided with a series of baffles spaced along its length (described later). A windage gasket  19  blocks air passage between the cover  15  and a wall  21  forming part of a housing  29  of the spray-down unit.  
         [0021]    The spray-up unit includes a brush roll  22  and a pickup roll  24  that transfers fluid from a trough  26  to the brush roll. The spray-up unit has a cylindrical brush roll cover  23  and a brush roll drain pan  25  with internal baffles like the drain pan  17  of the spray-down unit. Drain pan  25  and trough  26  are connected to the fluid distribution system FD, which typically includes fill and drain tubes, a fluid sump and a pump, etc.  
         [0022]    Further details of the above-described components of the two spray generating units can be found in the aforementioned patent.  
         [0023]    The spray-down and spray-up units are mounted, one above the other, on a frame  28 . A web or strip  30  to be coated moves horizontally between the two units. The spray-down unit  10  is supported on tracks  32  by means of rollers  34 , so that the spray-down unit can be rolled end-wise away from the spray-up unit  12 .  
         [0024]    The width of the web or strip  30  (perpendicular to the plane of FIG. 1) can vary over a considerable range, from, for example, 24 inches to 76 inches. Of course, the length of the spray patterns laterally of the web or strip must be sufficient to accommodate the widest web or strip to be processed. In the preferred embodiment the web or strip is centered in the machine so that its longitudinal center line lies in a vertical plane that bisects the brush roll and the pick up roll.  
         [0025]    The spray-down unit  10  has cut-offs  36  in the form of catch pans  38  at opposite ends of the unit. Each catch pan has flanges  40  (see FIG. 6) for slidably mounting the pan in track grooves  42 . Each pan is coupled to a fork  44  that engages a pin  46  on the bottom of the pan. See FIG. 2. The fork is moved by an operator  48  to adjust the position of the pan inwardly and outwardly of the spray-down unit, thereby to determine the length of the applied spray pattern laterally of the web  30 . Each pan  38  intercepts an end portion of the downwardly directed spray generated by the spray-down unit  10 . Fluid picked up by the pan passes via drain tubing  49  into a receptacle  50  extending along the length of the spray-down unit. Fluid in the receptacle passes via drain tubing  51  into one or more funnels  52  to return the fluid to the fluid distribution system.  
         [0026]    The spray-up unit  12  has cut-offs  54  in the form of plates  55  at opposite ends of the unit. Each plate has opposite longitudinal edges  56  (see FIGS. 4 and 5) mounted in track grooves  58  to permit the plate to slide inwardly and outwardly of the spray-up unit. Each plate is coupled to a fork  60  that engages a pin  62  on the top of the plate. See FIG. 3. The fork is moved by an operator  64  to adjust the position of each plate inwardly and outwardly of the spray-up unit laterally of the web  30 .  
         [0027]    The plates  55  intercept end portions of the fluid spray pattern. As shown in FIG. 4, the lower surface of each plate has a series of laterally extending grooves  65 . The laterally extending grooves prevent collected fluid from running the length of each plate and dripping back into the spray generating unit. The plates are tilted, as shown in FIG. 1, so that fluid picked up by the grooves runs into drain holes  67  beneath the lower ends of the grooves for return to the pick-up roll trough  26 .  
         [0028]    As shown in FIGS. 2, 3,  9 ,  10 , and  11 , the cut-offs of each spray generating unit pass through holes in end plates  35  and are stabilized by supports  39  and  41 , such as brackets that extend outwardly from the end plates of the associated spray generating unit. The cut-offs of each pair are preferably movable inwardly of the machine to a position at which they completely block openings through which spray is emitted to the web  30 . By virtue of this arrangement, any contaminants that may be in the air, such as dirt, dust, fiber particles, scale, etc., are blocked from entering the spray generating unit when it is not in use.  
         [0029]    A duplex machine such as that illustrated in FIG. 1 permits simultaneous spray application to opposite surfaces of the web  30  through operation of the spray-down and spray-up generating units concurrently. If it is desired to apply fluid to only one surface of the web, one or the other spray generating unit may be operated selectively. For example, when it is desired to apply fluid to only the lower surface of a web, the spray-up unit is operative and the spray-down unit is inoperative.  
         [0030]    To avoid the possibility of fluid from the spray-down unit dripping onto an upper surface of the web, the spray down unit is mounted on the frame  28  by the rollers  34  and tracks  32  referred to earlier, to permit the spray-down unit to be moved beyond one end of the spray-up unit to an idle position. FIG. 8 illustrates a duplex machine  66  comprising a spray-down unit  10  and a spray-up unit  12 , and shows (in phantom) an alternative position of the spray-down unit when it is moved end-wise away from the spray-up unit.  
         [0031]    [0031]FIGS. 9 and 10 show components of a spray-up unit  12 , including brush roll  22 , pick-up roll  24 , brush roll cover  23 , drain pan  25  with windage control baffles  27  (referred to earlier), fluid trough  26 , frame cross bars  31 ,  33 , end plates  35 , actuators  37  for adjusting the interference between the pick-up roll and the brush roll, cut-off supports  39 , and cut-offs  54 . FIG. 11 shows components of a spray-down unit  10 .  
         [0032]    Typical operators  48  and  64  for moving the cut-offs include hydraulic cylinders, pneumatic cylinders, and electric motor operated screws. The adjustment can be made automatically in response to conventional photoelectric or other edge detectors that detect the width of a web to be coated, or can be made manually.  
         [0033]    By the use of the spray cut-offs, fluid is re-routed back into the fluid distribution system to avoid waste of fluid due to misting or air flow. The grooves  65  on the cut-off plates  55  return fluid to the pick-up roll trough uniformly. This keeps the fluid from causing a disturbance in the trough that would cause a non-uniform application to the pick-up roll.  
         [0034]    Commonly, the fluids to be sprayed must maintain a constant temperature to ensure that a specific viscosity is sustained. If the viscosity changes, the fluid output will change. By trapping unused fluid in the spray cut-offs, the fluid is kept from being cooled down by air and is returned at a more constant temperature. Accordingly, electric heaters used to maintain the fluid temperature need not run as much.  
         [0035]    The spray cut-offs accommodate varying widths of material to be coated. In a duplex machine, the spray cut-offs of the spray-up unit prevent fluid from undesirably spraying into the spray-down unit, and prevent loss of fluid and unintended coating of nearby objects or the upper surface of the web. The spray cut-offs of the spray-down unit prevent fluid from undesirably spraying into the spray-up unit, which could cause the spray-up unit to flood and produce an uneven spray pattern.  
         [0036]    While a preferred embodiment of the invention has been shown and described, it will be apparent to those skilled in the art that changes can be made without departing from the principles and spirit of the invention, the scope of which is defined in the accompanying claims.