Patent Publication Number: US-7214411-B2

Title: Coating spray apparatus and method of using same

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a manufacturing line for gypsum boards, and in particular to a coating spray apparatus and method of using for a manufacturing line for gypsum boards. 
   2. Discussion of Related Art 
   In a conventional gypsum board manufacturing process, a slurry of gypsum is sandwiched between two layers of facing sheets. After the gypsum core sets, the core, together with the facing sheets, is cut into board lengths. The cut boards are then sent through a dryer to substantially dry the gypsum core. 
   According to WO 02/12144, it is known to apply a coating to one side of the board. WO 02/058902 teaches applying a coating to a wet gypsum board prior to drying the gypsum board. In addition, U.S. Pat. No. 6,663,979 teaches applying a coating to a gypsum board either before or after drying of the board. 
   However, the gypsum board manufacturing line may be used for making different types of boards. Some of the boards may be coated with coating equipment as discussed above, and some boards may not be coated. 
   OBJECTS AND SUMMARY 
   Accordingly, it is an object of one embodiment of the present invention to provide a coating spray apparatus which can be pivoted from an operative position, wherein the spray apparatus is over the gypsum board manufacturing line to an inoperative position, wherein the spray apparatus is remote from the line and does not interfere with regular operations. 
   It is a further object of the present invention to provide a coating spray apparatus for a gypsum board manufacturing line that is able to apply the spray in a fine, easily controlled manner. 
   According to a first embodiment of the present invention, a manufacturing line for gypsum boards includes a conveyor for moving gypsum boards in a line; a spray arm having a pivot at one end thereof for supporting a spray arm in a pivotable manner; a base frame mounted adjacent the convey; a support for the pivot mounted on the base frame so that the spray arm can be pivoted from an operative position wherein the spray arm extends over the conveyor to an inoperative position; a plurality of spray nozzles arranged on the spray arm for spraying a coating on the gypsum boards on the conveyor; and a pump system on the base frame to deliver the coating to the plurality of spray nozzles. 
   According to another embodiment of the present invention, a spray arm for a manufacturing line for gypsum boards includes a support beam; a pivot at one end thereof for supporting the spray arm in a pivotable manner so that the spray arm can be pivoted at least about 90 degrees from an operative position to an inoperative position; and a plurality of spray nozzles arranged on the support beam for spraying a coating on gypsum boards, the plurality of nozzles arranged in clusters and the nozzles in each cluster are staggered so that at least some of the nozzles in each cluster are at different distances from the support beam with respect to each other. 
   According to another embodiment, a method according to the present invention of spraying a coating on a gypsum board on a gypsum board manufacturing line includes providing a spray arm having a plurality of nozzles attached thereto over the gypsum board manufacturing line; the plurality of nozzles are arranged in clusters and the nozzles in each cluster are staggered so that at least some of the nozzles in each cluster are at different distances from the spray arm with respect to each other, and the nozzles are further arranged such that the spray from each nozzle covers less than an entire width of the gypsum board on the line; emitting a coating from the spray nozzles such that a plurality of overlapping sprays are sprayed onto the gypsum board in succession; and wherein the nozzles are arranged such that a substantially uniform coating is applied to the board. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  discloses a schematic view of a portion of a gypsum board manufacturing line including an embodiment of the present invention. 
       FIG. 2  discloses a side view of a portion of an embodiment of the present invention. 
       FIG. 3  is a side view of a pumping system in an embodiment of the present invention. 
       FIGS. 4A and 4B  illustrate details of a spray arm of an embodiment of the present invention. 
       FIG. 5  illustrates the application of a plurality of layers of coating according to an embodiment of the present invention. 
       FIG. 6  illustrates a plumbing schematic of an embodiment of the present invention. 
       FIG. 7  illustrates another plumbing schematic of a different portion of the embodiment of  FIG. 6 . 
       FIG. 8  illustrates yet another portion of an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1–8  illustrate a preferred embodiment of the present invention. The preferred embodiment includes an apparatus for spraying a coating onto gypsum boards, after the gypsum has set, but before the boards have been sent through a dryer. The coating is intended to provide a finish on the gypsum boards which facilitates providing a finished surface on the boards. In a preferred embodiment, the coating includes a mineral filler and is designed to match a joint compound used to finish joints between adjacent boards. 
   Turning attention to  FIG. 1 , an overview of a portion of a line on which the gypsum boards are dried is shown, with the preferred embodiment of the present invention in place. The line includes a conveyor assembly  42  for conveying the set, but wet, gypsum boards  44 ,  46 ,  48 ,  50  through the dryer. 
   In this embodiment, a spray arm  10  of the present invention is arranged above the conveyor assembly  42 , prior to the boards  44 ,  46 ,  48 ,  50  reaching the dryer. The spray arm  10  is mounted to a skid or frame  14  in a pivotable manner so that the spray arm  10  can be pivoted at least 90 to 180 degrees from an inoperative position illustrated in solid lines to an operative position illustrated in dashed lines. As best seen in  FIG. 2 , the spray arm  10  is arranged downstream of a hood  40 , both of which are suspended above the conveyor  42 . The spray arm  10  and the hood  40  are preferably arranged such that particles emitted from the spray arm  10  that reflect off of the boards  44 ,  46 ,  48   50  are picked up by the hood  40 , which includes conventional exhaust and/or filtering equipment. 
   The coating apparatus includes several components. For example, the skid  14  ( FIG. 3 ) is provided for supporting pumps and related equipment. As illustrated in  FIG. 3 , the skid  14  may be provided on wheels  52  so that the skid can be rolled into and out of place, as needed. At one end of the skid  14  is a pivot  12  which rotatably supports the spray arm  10  so that the spray arm  10  can be rotated into a working or operative position over the conveyor  42  or away from the conveyor  42 , as illustrated in  FIG. 1 . 
   The skid  14  includes a plurality of pumps  28 , each of which is driven by a respective pump motor  26 . In the preferred embodiment, the pump motors  26  are air driven motors such that the speed of the output thereof can be controlled by the air pressure that is delivered to the pump motors  26 . In the preferred embodiment, five pumps and pump motors are provided on the skid. However, only four are actually used for applying the coating. The fifth pump and pump motor are provided to serve as a back-up in the event that one of the four pumps fails. In a preferred embodiment, the pumps are manufactured by Graco. 
   A suction header  24  delivers a coating formula to each of the pumps  28  via respective hoses  34 . The coating formula is delivered to the suction header  24  from pipe  80  ( FIGS. 6 and 7 ) which is described in greater detail below. At the discharge end of each of the pumps  28 , a hose  18  delivers the coating formula under high pressure to a spray feed header  16 . In the preferred embodiment, the coating formula is output from the pumps at a pressure of about 2250 psi. The higher the pressure, the more coating formula is delivered to the boards. Thus, the delivery pressure of the coating formula may be varied depending upon the desired application. In general, the output pressure of the coating formula will typically be within the range of 1200 to 4500 psi. To achieve this range, the pump motors are supplied with air at a pressure of about 30–40 psi. However, the present invention is not limited to the pressure ranges set forth herein. 
   A control air manifold  20  is also present on the skid  14  adjacent the pump motors  26 . Separate hoses  30  connect the control air manifold  20  to the respective pump motors  26  to provide the motive force for the pump motors  26 . 
     FIGS. 4A and 4B  illustrate the spray arm  10 . As can be seen at the right side of  FIG. 4A , the spray arm  10  is connected to a pivot  12 , which is fixed to the skid  14 . The spray arm  10  includes a support beam  62  which supports sixteen nozzles ( 54 A,  56 A,  58 A,  60 A,  54 B,  56 B,  58 B,  60 B,  54 C,  56 C,  58 C,  60 C,  54 D,  56 D,  58 D,  60 D) and at least three conduits. A first conduit  64  delivers the high pressure coating formula from the spray feed header  16  to each of the nozzles  54 ,  56 ,  58 ,  60 . A second conduit  66  delivers atomizing air to each of the nozzles  54 ,  56 ,  58 ,  60  via hoses  72  so that the coating formula can be uniformly sprayed onto the boards  44 ,  46 ,  48 ,  50 . A third conduit  68 , which is also attached to the support beam  62 , delivers air under pressure through respective hoses  70  to control each of the nozzles  54 ,  56 ,  58 ,  60 . 
   As can be best seen in  FIGS. 4A and 5 , the sixteen nozzles are arranged in four clusters of four nozzles in each cluster. The nozzles in each cluster are staggered such that the spray from nozzle  60 A, for example, reaches the board prior to the spray from nozzle  58 A, which reaches the board prior to the spray from nozzle  56 A, and which reaches the board prior to that from nozzle  54 A. As a result, the board receives essentially four layers of coating in short succession. By applying the coating in four successive layers, better control over the spray can be achieved. In the preferred embodiment, the layers are applied in such short order that the layers of coating formula essential commingle and become one uniform layer on the board. In other words, the layers do not form four separate layers on the board when dried. Although the preferred embodiment uses four clusters of four nozzles, the present invention could be practiced with other combinations of nozzles. Furthermore, it is also not necessary to use all of the nozzles provided on the support beam  62 . For example, one or more nozzles in each cluster could be turned off. 
     FIG. 5  illustrates the overlapping nature of the spray from the nozzles. As can be seen in  FIG. 5 , the left margin  44   a  of the board  44  receives only three layers of coating, i.e., from nozzles  54 A,  56 A, and  58 A. The spray from nozzle  60 A does not reach the far left edge  44   a  of the board  44 . However, the remaining portions of the board are coated with substantially four layers. In other words, the nozzles are arranged such that the spray from nozzle  54 A does not substantially overlap with the spray from nozzle  54 B, nor is there any significant spacing therebetween. Similarly, the spray from nozzle  56 A does not overlap with the spray from nozzle  56 B, nor is there any significant space therebetween, etc. By using this spacing with the nozzles, a substantially uniform coat from four nozzles is applied to each portion of the board, except for the left margin  44   a  of the board  44 . 
   In a preferred embodiment, the nozzles or spray heads are manufactured by Graco. Various size nozzles have been tried, including #25, 27, 29, 31, 33, and 35. However, the #31 nozzle provides a spray with a width of about twelve inches, as it contacts the board, when the pump motor pressure is about 40 psi and the system pressure is about 2250 psi. At these parameters, about four gallons of coating per 1000 square feet is applied at the rate of about 2.25 gallons per minute. However, the present invention can be practiced with other combinations of nozzles, pressures, and spray widths. 
     FIG. 6  illustrates a schematic “plumbing” diagram of the preferred embodiment of the present invention. Most of the components illustrated in  FIG. 6  are arranged on the skid  14 . For example, the control air manifold  20 , the pump motors  26 , the pumps  28 , the spray feed header  16 , and the suction header  24  are all located on the skid  14 . 
   At the right side of  FIG. 6  is illustrated a bypass circuit  110  which is connected to a filter  108 . If desired, valve  109  can be closed and valves  111 ,  113  can be opened to divert the coating formula through the filter  108  prior to delivery to the nozzles  54 ,  56 ,  58 ,  60  on the spray arm  10 . 
   Hose  80  delivers the coating formula from a storage tank  133  located off of the skid  14  to a low pressure pump  82 , which pumps the coating formula to the suction header  24 . The coating formula may be delivered directly to the suction header  24  through pipes  84  and  90 . Alternatively, by the manipulation of the valve  85 , pipe  84  may be shut off, and the coating formula may be delivered to pipe  90  through a filter  88  and pipe  86 . Thus, by controlling the valves in and about the filter  88 , the coating formula may be delivered either directly to the suction header  24  or may be filtered through filter  88  prior to delivery to the suction header  24 . The pump  82  is driven by compressed air received from the control air manifold  20 . 
   Another hose  78  is connected to pipe  90  and can be used to deliver unused coating formula back to the storage tank  133 , which is illustrated in  FIG. 7 . 
   At the top of  FIG. 6  is illustrated a pump  92 , which provides pressurized air to an atomizing air receiving tank  96  through pipe  94 . Also extending from pipe  94  is a pipe  102  which delivers pressurized air to the control air manifold  20 . Preferably, the pump  92  maintains the pressure in the control air manifold at approximately 100 psi. From the atomizing air receiving tank  96 , a pipe  98  delivers atomizing air to the atomizing air delivery pipe  66 , which is connected to the support beam  62  of the spray arm  10 . See  FIG. 4B . In addition, a pipe  100  connects the atomizing air receiving tank  96  to the control air delivery pipe  68 , which is also mounted to the support beam  62  of the spray arm  10 . 
   The control air from the control air delivery pipe  68  is used to turn the nozzles  54 ,  56 ,  58 ,  60  on and off. The air is controlled by a solenoid (not illustrated). The solenoid is controlled by a timer that is coordinated with the drive mechanism for rollers associated with the conveyor  42 . Preferably, the timer controls the solenoid and nozzles such that the coating is only sprayed from the nozzles while there is a board below the nozzles, so as to avoid wasting the coating. However, during normal continuous runs, the pumps  28  continue to operate and pressure is maintained in the conduit  64  even when the nozzles are turned off between boards. 
   The nozzles  54 ,  56 ,  58 ,  60  are air-actuated spray heads. When pressurized air is delivered by the conduit  68  to the nozzles, the nozzles are opened allowing the coating formula and atomizing air to flow through the nozzles. When the pressure in the conduit  68  is dropped, e.g., to atmospheric pressure, the nozzles are closed. 
   In the lower right corner of  FIG. 6  is illustrated a double diaphragm pump  106  which is used to clean out a drip/overspray pan  74 , which is illustrated in  FIG. 8 , and described later herein. 
     FIG. 7  illustrates a storage tank  112 . The storage tank  112  is filled with the coating formula by a pipe  126  that is connectable to a tanker truck. Alternatively the tank  112  can be filled with the coating formula delivered in drums or barrels  114 . A tank  116  is also provided for clean-out. 
   The coating formula in the tank  112  may be circulated or stirred by a propellor blade  127  located within the tank  112 . In addition, a drain  125  at the bottom of the tank can be used to recirculate the coating formula by means of a pump  118  and plumbing  124  so that the coating formula can be removed from the bottom of the tank  112  and redelivered to the top of the tank  112  to recirculate or stir the coating formula. 
   In addition, bypass plumbing  122  can be provided so that the coating formula can be bypassed through a filter  120  during the recirculation process so that the coating formula may be filtered, while it is being recirculated. In addition, pipe  129  can be used to drain off or remove coating formula from the system. 
   Pipe  131 , which is connected to the pump  118  via plumbing  124 , is used to deliver the coating formula from the tank  112  to an intermediate tank  133  illustrated schematically. The intermediate tank  133  can be located adjacent the skid  14 , or in any convenient location, preferably near the skid. 
   During the operation of the spray apparatus, the operating pressure from the air control manifold  20  to the pump motors  26  is preferably in the range of 30–40 psi. However, higher or lower pressures may be used, as desired. 
   Because the spray arm  10  is connected to the skid  14  with a pivot  12 , the spray arm  10  can be moved into position over the board conveyor  42 , or can be pivoted so that it is no longer over the board conveyor  42 . 
   In addition, as set forth above, the skid  14  can be mounted on wheels  52 . However, in an alternative embodiment, the skid  14  may be permanently fixed to the plant floor. 
   As illustrated in  FIG. 8 , a drip/overspray pan  74  is provided with four cutouts  76 . The drip/overspray pan  74  and cutouts  76  are arranged such that the drip/overspray pan  74  can be secured to the support beam  62  of the spray arm  10  so that the drip/overspray pan  74  is located with the cutouts  76  in alignment with the four clusters of nozzles. The drip/overspray pan  74  can be used for rinsing or flushing the nozzles  54 ,  56 ,  58 ,  60  with water. 
   Although only preferred embodiments are specifically illustrated and described herein, it will be appreciated that many modifications and variations of the present invention are possible in light of the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.