Abstract:
A method of making wallboard including the steps of providing an unfinished length of wallboard that has a recess along its longitudinal edges by conveying it upon a conveyor in a first direction in a step, forming recesses in the unfinished length of wallboard at both lateral edges thereof, selecting an apparatus for forming the recess from a plurality of device for forming the recess, forming the recess with the selected apparatus, and separating the unfinished length of wallboard at a location of the recess to form finished lengths of wallboard, such that the finished lengths of wallboard have recessed lateral edges. Also disclosed is a system for performing the method.

Description:
RELATED APPLICATIONS  
       [0001]     The present application claims priority to U.S. Provisional Patent Application No. 60/736,123, filed Nov. 9, 2005, the contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates generally to gypsum board, and more specifically to a method and apparatus for providing recessed portions on the lateral edges of wallboard.  
       BACKGROUND OF THE INVENTION  
       [0003]     Conventional gypsum wallboard or drywall is typically manufactured from a gypsum plaster slurry which is put between two layers of paper. More specifically, in the conventional method, a wet slurry of gypsum is poured on a conveyor between two layers of paper, and the slurry is allowed a certain amount of time to set. In gypsum wallboard, the two layers of paper contain the slurry and provide the tensile strength required in installation and use.  
         [0004]     In at least some known fabrication methods, the conveyor is a closed loop conveyor that can travel at speeds of four hundred feet per minute or faster. The conveyor enables the wallboard to be fabricated using rolls of paper and accordingly, includes at least a longitudinal edge forming system, a cutting system, and a drying system. The edge forming system uses wedge shaped raised edges along the conveyor that create recessed areas along the longitudinal edges in the face of the wallboard prior to the wallboard being fully cured. When the wallboard is later cut to size and installed, the recesses are filled with wallboard compound, taped over, and finished to produce a smooth joint.  
         [0005]     The cutting system enables the wallboard to be cut into predetermined discrete lengths such that substantially rectangular wallboard members are formed. The cutting system is adjustable to allow different lengths of wallboard to be cut without substantial interruption of the manufacturing operation.  
         [0006]     After being cut, the wallboard members are moved away from the cutting station to a loading area where they are loaded into a drying system to dry the cut wallboard members.  
         [0007]     Known wallboard includes recessed areas that extend along both of the opposed longitudinal edges of the wallboard. The recessed areas are formed by the raised edges on the conveyor. The recessed areas are in the shape of inclined planes that taper from the face of the wallboard to the longitudinal edges and have a maximum depth at the side edges of about 0.090″ below the face of the wallboard.  
         [0008]     When the wallboard is cut by the cutting system, panels of conventional wallboard are formed which are bordered by the opposed recessed longitudinal edges and by a pair of lateral non-recessed edges that connect the longitudinal edges. More specifically, the wallboard is typically cut such that the panels are fabricated with a longitudinal length that is commonly eight feet, ten feet, twelve feet, fourteen feet, and sixteen feet or longer. Additionally, wallboard panels are made in thicknesses that are commonly ¼″, ⅜″, ½″ and ⅝″ thick. For maximum efficiency and conservation of plant space, the same line must have the capability of fabricating all of the different lengths of wallboard without a major shutdown of the line.  
         [0009]     During installation, depending on the length of the wall being formed by the wallboard, wallboard panels are typically positioned for installation such that the longitudinal edges are parallel to the floor, an installation known as a “horizontal orientation”. In this installation, a longitudinal recess of a first panel is adjacent to a longitudinal recess of the adjacent panel. This forms a longitudinal recessed joint. A wallboard compound fill material and tape are then used to seal the recessed joint formed by the recessed longitudinal edges of the panels. Specifically, the recessed areas of the joints are filled with the wallboard compound, taped and smoothed across the joint, such that the joint is covered without the compound creating an unsightly bulge extending outwardly between the panels. Installing the wallboard panels such that the longitudinal length extends horizontally along a wall parallel to the floor, rather than vertically and substantially perpendicularly to the floor, facilitates faster installation time of the wallboard panels, and faster finishing time of the installed wallboard panels. In addition, when wallboard is installed in a vertical orientation, installation and labor costs may be increased as the installers and tapers must use ladders for installation and finishing.  
         [0010]     When wallboard panels are installed on longer walls and ceilings, because the recessed areas only extend along two longitudinal edges of each panel, a butt joint may be formed between the lateral edges of two adjacent panels. Such joints must still be covered with tape and compound, but because the lateral edges do not include a recessed area, the joint compound must be spread over a wider area than those of the longitudinal joints to facilitate blending the butt joints into the wall surface without creating unsightly bulges.  
         [0011]     Adding to the difficulty of creating recessed area in lateral edges of wallboard panels is that the panels are made in continuous lengths, which are then cut to size after the wallboard panel has fully cured. It is very difficult to create the recessed areas in the wallboard panel after the gypsum is fully cured and a particular problem has been delamination of the paper from the gypsum core.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention comprises a method of making wallboard comprising the steps of a) providing an unfinished length of wallboard that has a recess along its longitudinal edges by conveying it upon a conveyor in a first direction in a step, b) forming recesses in the unfinished length of wallboard at both lateral edges thereof, c) selecting an apparatus for forming the recess from a plurality of devices for forming the recess, d) forming the recess with the selected apparatus, and e) separating the unfinished length of wallboard at a location of the recess to form finished lengths of wallboard, such that the finished lengths of wallboard have recessed lateral edges.  
         [0013]     The present invention provides a device for forming the recesses in an unfinished length of wallboard. The device comprises a first press located at a first lateral edge of the unfinished length of wallboard, and a second press located at a second lateral edge of the unfinished length of wallboard opposite the first lateral edge. A third press is located between the first and second press. As unfinished lengths of wallboard are fed into the first, second and third presses, the first press forms a recess along the first lateral edge, the second press forms a recess along the second lateral edge and the third press forms a recess in the wallboard generally parallel to the first recess and between the first and second lateral edges. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is plan view of gantry having a plurality of drywall presses according to an embodiment of the present invention;  
         [0015]      FIG. 2  is perspective view of a drywall press according to an embodiment of the present invention;  
         [0016]      FIG. 3  is perspective view of an upper press assembly according to an embodiment of the present invention;  
         [0017]      FIG. 4  is perspective view of a lower press assembly according to an embodiment of the present invention;  
         [0018]      FIG. 5  is perspective view of an upper shoe assembly according to an embodiment of the present invention in an extended position;  
         [0019]      FIGS. 6A-6F  are views of an upper shoe according to an embodiment of the present invention;  
         [0020]      FIG. 7  is perspective view of an upper shoe assembly according to an embodiment of the present invention in a retracted position;  
         [0021]      FIGS. 8A-8D  are views of a lower shoe according to an embodiment of the present invention;  
         [0022]      FIG. 9  is perspective view of a lower shoe assembly according to an embodiment of the present invention;  
         [0023]      FIGS. 10A-10C  are views of a pin according to an embodiment of the present invention;  
         [0024]      FIG. 11  is a partial side view of a length of wallboard passing through an upper and lower press assembly according to an embodiment of the present invention; and  
         [0025]      FIG. 12  is a side view of a length of wallboard passing through an upper and lower press assembly according to an embodiment of the present invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]     While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated.  
         [0027]     Referring to  FIG. 1 , a preferred embodiment of the present invention comprises a press  20  for forming of one or more recessed lengths in partially cured gypsum wallboard such that when the partially cured wallboard is cut into finished lengths, the lateral edges of the finished lengths have recessed edges on all four edges of the board. For the purposes of the present invention, a recess can be a tapered or non-tapered recess. The invention preferably performs this press function in partially cured gypsum wallboard panels after gypsum slurry has been applied to paper backing but before the wallboard is sent to ovens to fully cure. However, it is within the scope of the present invention to form recesses along cured gypsum before it is cut into finished lengths or to sheets of cured gypsum wallboard that has already been cut to finished lengths.  
         [0028]     In the preferred aspect, where the gypsum is only partially cured and the wallboard not cut to finished lengths, the recessed areas are formed along the lateral edges of the uncut wallboard and also in several locations along the length of the uncut wallboard. The locations of the recesses on the length of the uncut wallboard will vary depending upon whether eight foot lengths, nine foot lengths, ten foot lengths, etc. of wallboard, or combinations of length thereof, are being produced. Typically, the length of uncut and partially cured wallboard that is sent to ovens to be fully cured is 32′, although other lengths may be produced in various gypsum wallboard plants. The 32′ foot length, or other appropriate length, is referred to as the unfinished length. In the event of 32′ lengths, it is preferably to have presses located at 0′ (i.e. the lateral edge), 8′, 9′ 10′, 12′, 14′, 16′, 18′, 20′, 22′, 23′, 24′, 27′ and 32′ (i.e. the opposite lateral edge). The present invention accomplishes this by providing presses at each location indicated. Alternatively, a smaller number of presses are provided that are positionable on the support system to the various required locations. Additionally, the presses are easily removable so that a press may be removed for repair and maintenance. By feeding the  32 ′ length into the press and forming recesses in the ends and at one or more locations along the length of the wallboard, recesses running the width are formed therein such that every common length of wallboard can be manufactured with lateral edge tapers at the finished wallboard lengths.  
         [0029]     The presses  20  each comprise an upper press assembly  22  and a lower press assembly  24 . Wallboard  26  passes between the upper and lower press assemblies  22  and  24 . The upper press assemblies  22  are moveable from an upper position where the upper press assemblies  22  do not contact the uncut wallboard and a lower position where the upper press assemblies  22  come into contact with the uncut wallboard. Because the recesses are most preferably only about 0.090″ deep, the upper press assemblies  22  are infinitely adjustable in the vertical direction such that fine adjustment can be made to adjust for tolerances in the thickness of the wallboard and also to accommodate wallboard of different nominal thicknesses. The proper adjustment of the height of the upper press assembly may be detected by either a laser measure or by physically contacting the wallboard, for example with a roller that measures the precise thickness of the wallboard. The upper presses  22  are all individually adjustable to properly control recess depth as the wallboard moves through the presses. As can been seen in  FIG. 1 , four upper press assemblies  22  have been lowered in position at 0′, 12′, 22′ and 32′ to make wallboard of 10′ and 12′ lengths.  
         [0030]      FIG. 2  shows the upper press assembly  22 , the lower press assembly  24  and a takeout conveyor  28  to remove the wallboard from the press. An upper surface of the takeout conveyor  28  is preferably in a plane lower than the upper surface of the lower press assembly  24  so that the wallboard  26  will move away from the upper press assembly  22  as it exits the lower press assembly  24 . Lengths of wallboard  26  are shown between the upper and lower press assemblies  22  and  24 , and the press assemblies  22  and  24  and takeout conveyor  28  move the wallboard in a direction indicated by arrow A.  
         [0031]     As shown in  FIG. 3 , the upper press assembly  22  comprises two spaced apart plates  30  and  32  attached to one another to form an upper plate assembly  34 . Riding upon the upper plate assembly  34  are a plurality of upper shoe assemblies  36 . The upper shoe assemblies  36  are attached to one another end-to-end and form a loop around the upper plate assembly  34 . A large sprocket  38  is located at a first end  40  of the plate assembly  36 , and a small sprocket  42  is located at an opposite, second end  44  of the plate assembly  36 . The sprockets are located between the plates  30  and  32 . One or both of the sprockets  38  and  42  are powered to cause the upper shoe assemblies  36  to rotate about the upper plate assembly  34  in the direction shown by the arrows B. Also provided is a shoe support bar  46  that maintains the upper shoe assemblies  36  adjacent the upper plate assembly  34  as the upper shoe assemblies  36  travel along the bottom portion of the upper plate assembly  34  until the upper shoe assemblies  36  are out of contact with the wallboard as they extend around the large sprocket  38 , as further described below.  
         [0032]     The lower press assembly  24  is shown in  FIG. 4  and comprises first and second plates  48  and  50  attached to one another and spaced apart from one another to form a lower plate assembly  52  having a first end  56  and a second end  60 . Mounted upon the lower plate assembly  52  are a plurality of lower shoe assemblies  54 . The lower shoe assemblies  54  extend around the lower plate assembly  52  to form a loop. The lower shoe assemblies  54  are further driven by one or both of a first sprocket  58  at the first end  56  and a second sprocket (not shown) at a second end  60 .  
         [0033]     Referring to  FIGS. 5 and 6 A- 6 F, the upper shoe assemblies  36  of the upper press assembly  22  comprise a forming plate  64 . The forming plate  64  comprises two upstanding outer walls  66  and  67 . Between the walls  66  and  67  are located two support blocks  68 . Each support block  68  defines a bore  70  that is in line with bores  72  defined in each outer wall  66  and  67 . The support blocks  68  each further define an arcuate stop portion  74 . Mounted within the bores  70  and  72  is a pin  76 . The pin  76  captures three roller bearings  78  as well as two chain side plates  80 . Another pin  82  captures three more roller bearings  84  and an opposite end of the chain side plate  80 . The pin  82  is associated with the upper shoe assembly  36  by virtue of the pin  82  extending into two slots  85  that are formed within the side walls  66  and  67  of the forming plate  64 . The bearings  84  are spaced apart by collars  75  placed over the pin  82  and between the bearings  84 .  
         [0034]     As a result of pin  82  being located within the slots  84 , the forming plate  64  is allowed to pivotally move about the pin  76  move from a first, open position as shown in  FIG. 6  to a second, closed position as shown in  FIG. 7 , making the distance between the bearing  82  and a bottom surface  90  of the forming plate  64  variable.  
         [0035]     The upper shoe assembly  36  further comprises a pair of shoe alignment bearings  86  mounted on the support blocks  68 . Additionally, shoe pivot bearings  88  are attached to each wall  66  and  67 .  
         [0036]     In the most preferred embodiment, the bottom surface  90  of the forming plate  64  is 6½″ wide as viewed from  FIG. 6D  and  FIG. 6F . A flat pad  92  is centered on the bottom surface  90  of the forming plate  64  is approximately 1¼″ wide. First tapered portions  94  taper at about a three degree angle from the flat pad  92  for about 1¼″ from the center of the bottom surface  90 . Second tapered portions  96  taper at about a one degree angle from the flat pad  92  from the first tapered portion  94  to either edge of the forming plate  64 . The multiple tapered surfaces prevent bulging of the wallboard it the edge of the forming plate  64 .  
         [0037]     Multiple upper shoe assemblies  36  are attached to one another through the use of additional chain side plates  80  which extend from the pin  82  to a pin  76  of an adjacent, trailing upper shoe assembly  36  and a chain side plate  80  that extends from a pin  76  of the upper shoe assembly  36  to the pin  82  of an adjacent, preceding upper shoe assembly  36 . The forming plates  64  further comprise a front support surface  69  and a rear support surface  71 . The point where the support surface  69  meets the bottom surface  90  is located at or behind an imaginary line Z—Z which passes though the center of the aligned bores  70  and  72  and perpendicular to the surface  90 . When the upper shoe assemblies  36  are attached to one another with the chain side plates  80 , the front support surface  69  of one upper shoe assembly  36  rests upon the rear support surface  71  of an adjacent upper shoe assembly  36 . In this manner the bottom surfaces  90  of each shoe provide a consistent surface in which the flat pads  92 , first tapered portions  94  and second tapered portions  96  of the attached upper shoe assemblies  36  align and are coplanar to form a consistent surface even with significant force applied to the surface  90  of each forming plate  64 .  
         [0038]     Referring to FIGS.  8 A-D and  9 , the lower shoe assemblies  54  comprise a support plate  98 . The support plate  98  has a flat lower surface  100  and two upwardly extending sidewalls  102  and  103 . The support plate  98  also comprises a pair of support blocks  104  each having aligned bores  106  defined therein which align with bores  108  defined within the sidewalls  102  and  103 . Inserted within the aligned bores  106  and  108  is a pin  110 . The pin  110  retains three roller bearings  120  and two chain side plates  202  to the support plate  98 . Also attached to the two support blocks  104  are alignment bearings  106 . The chain side plates  202  each attach to a pin  110  of a preceding, adjacent support plate  98  and the chain side plates  202  of a following, adjacent support plate  98  attach to the pin  110  of the present support plate  98 , and so on, to create a chain.  
         [0039]     The forming plate  98  further defines an arcuate surface  204  and a rear support shelf  206 . When multiple lower shoe assemblies  54  are placed are attached to one another by the chain side plates  80  the arcuate surface  204  of a lower shoe assembly  54  rests upon the rear support shelf  206  of an adjacent lower shoe assembly  54 . As a result, lower surfaces  100  of the lower shoe assemblies  54  form a flat surface upon which a sheet of partially cured wallboard  26  may rest without deformation of the wallboard  26 .  
         [0040]     Referring to FIGS.  10 A-C, the pins  76 ,  82  and  110  are preferably identical and are described with respect to representative pin  76 . The pin  76  has central bore  130  that is threaded at either end. The pin  76  further has annular grooves  132  at the locations that correspond to the mounting of bearings thereon. Connecting bores  134  extend through the pin  76  at the location of the annular grooves  132  to provide a path from the annular grooves  132  to the central bore  130 . In this manner, grease fittings may be threaded into the pin  76  at the central bore  130  to provide grease through the central bore  130  to the connecting bores  134  to the annular grooves  132  and to lubricate the bearings mounted on the pin  76 . Annular grooves  136  are sized to accept retainer clips to retain the pins  76  in the forming plate  64  or support plate  98 , as the case may be.  
         [0041]     The upper shoe assemblies  36  of the upper press assembly  22  are maintained and aligned on the plates  30  and  32  by the shoe alignment bearings  86 . The shoe alignment bearings  86  contact inner surfaces  120  and  122  of the plates  30  and  32 , respectively, of the upper press assembly  22 . Likewise, the lower shoe assemblies  54  of the lower press assembly  24  are maintained and aligned on the plates  48  and  50  by the alignment bearings  106 . The alignment bearings  106  contact inner surfaces  124  and  128  of the plates  48  and  50  of the lower press assembly  24 .  
         [0042]      FIG. 12  shows a simplified view of the interaction of the upper shoe assemblies  36  and the lower shoe assemblies  54  as they are moved about the perimeter of the plates  30  and  32  and the plates  48  and  50 , respectively. The upper shoe assemblies  36 , as they pass the around the second end  44  of the upper press assembly  22 , pivot outwardly. In this manner, the surfaces  90  of the upper shoe assemblies  36  become parallel to the wallboard  26  at the point where the surfaces  90  first make contact with the wallboard. The upper shoe assemblies  36  initially make contact with the wallboard  26  and compress it an initial 0.010″. In this manner, the upper shoe assemblies  36  to not dig into or put divots in the wallboard  26  with a leading edge of the upper shoe assembly  36 .  
         [0043]     The lower shoes assemblies  54 , as they pass around the second end  41  of the lower press assembly  24 , as viewed in  FIG. 12 , are brought into parallel relationship with the wallboard  26  and contact wallboard  26  prior to the upper shoe assemblies  36  contacting the wallboard  26 . In this manner, the lower shoe assemblies  54  provides support for the wallboard  26  and an opposing force for the upper shoe assembly  36  when it makes initial contact with the wallboard  26  and begins compressing the wallboard  26 . Additionally, in order to prevent a preceding lower shoe assembly  54 , labeled M in  FIG. 12 , from being forced into the wallboard  26  by the support surface  204  (if the support surface were not arcuate) a trailing lower shoe assembly  54 , labeled N in  FIG. 12 , the support surface  204  is made arcuate such that the center of the arc formed by the surface  204  is the center of the bore  108 .  
         [0044]     Referring to  FIG. 12 , as the wallboard  26  traverses from right to left, the upper shoe assemblies  36  are moved from an initial impression of 0.010″ near a point X to a final impression of 0.0102″ near a point Y with the horizontal length between points X and Y preferably being about 67″. This is accomplished by a taper along the bottom plates  30  and  32  which force the upper shoe assemblies  36  into the wallboard by virtue of contact with the bearings  78  and  84 . After point Y, the plates  30  and  32  provide a taper that brings the upper shoe assemblies  36  out of contact with the wallboard  26 . A takeout conveyor  28  removes the wallboard  26  from the press  20 .  
         [0045]     In a further preferred aspect of the invention, the lateral edges of finished lengths of wallboard are wrapped with paper to further strengthen the edge of the wallboard.  
         [0046]     While the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention, and the scope of protection is only limited by the scope of the accompanying claims.