Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM AND METHOD FOR MAKING WALLBOARD
Technical Field
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 Art
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.
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.
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.
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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
thy the cut wallboard members.
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.
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 1/4", 3/8", 1/2" and 5/8"
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.
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
= 30 between the panels. Installing the wallboard panels such that the
longitudinal
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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.
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.
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
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.
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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
Fig. 1 is plan view of gantry having a plurality of drywall presses
according to an embodiment of the present invention;
Fig. 2 is perspective view of a drywall press according to an embodiment
of the present invention;
Fig. 3 is perspective view of an upper press assembly according to an
embodiment of the present invention;
Fig. 4 is perspective view of a lower press assembly according to an
embodiment of the present invention;
Fig. 5 is perspective view of an upper shoe assembly according to an
embodiment of the present invention in an extended position;
Figs. 6A-6F are views of an upper shoe according to an embodiment of
the present invention;
Fig. 7 is perspective view of an upper shoe assembly according to an
embodiment of the present invention in a retracted position;
Figs. 8A-8D are views of a lower shoe according to an embodiment of
the present invention;
Fig. 9 is perspective view of a lower shoe assembly according to an
embodiment of the present invention;
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Figs. 10A-10C are views of a pin according to an embodiment of the
present invention;
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
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.
Best Mode for Carrying Out the Invention
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.
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.
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
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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.
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 .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
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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.
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.
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.
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
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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.
Referring to Figs. 5 and 6A-6F, 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.
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.
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.
In the most preferred embodiment, the bottom surface 90 of the forming
plate 64 is 6-1/2" 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 1-
1/4" wide. First tapered portions 94 taper at about a three degree angle from
the
flat pad 92 for about 1-1/4" 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
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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.
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.
Referring to Figs. 8A-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.
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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.
Referring to Figs. 10A-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.
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.
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
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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.
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.
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.
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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.
The scope of the claims should not be limited by particular
embodiments set forth herein, but should be construed in a manner consistent
with the specification as a whole.
