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BACKGROUND OF INVENTION
There have been developed a wide variety of prefabricated panels or the
like for multiple uses including building structures. One eminently
successful type of prefabricated panel is plywood. There have also been
developed a variety of sandwich structures having, for example, a
honeycomb core.
In the construction of buildings various types of preformed panels have
been employed and in the field of concrete buildings it is known, for
example, to pour large concrete panels which generally have reinforcing
steel therein and may have other materials such as insulation included
therein, for use as walls, floors and the like.
The present invention comprises a panel having an expanded plastic core of
sheet-like configuration with thin reinforcing strips bonded to front and
back surfaces thereof, at least along the edges of the core. This panel
has a variety of uses and may be particularly advantageously employed by
attaching a wire mesh to one surface in spaced relation thereto for
receiving concrete. Panels in accordance with the present invention may be
joined together to form a desired shape or structure and, with the
above-noted wire mesh on the outer surface thereof, concrete may then be
applied to produce a structurally sound building or the like wherein the
panels of the present invention form an integral part thereof.
SUMMARY OF INVENTION
The composite panel of the present invention is comprised as an expanded
plastic core such as expanded polystyrene. The physical configuration of
the core may vary according to the application of the panel and thus, for
example, may be planar, curved in one direction, or curved in two opposite
directions. The core is expanded in a mold so that it is possible to make
substantially any desired panel configuration. The molded sheet of
expanded plastic or core of the panel has thin reinforcing strips bonded
to opposite major surfaces thereof, i.e., the front and back of the panel
have strips thereon. These strips extend along the edges of the surfaces
and additional strips may be provided across the surfaces. The reinforcing
strips preferably extend from two sides of the front surface of each panel
in order to overlap the surfaces of adjacent panels for attachment of
panels together. This attachment may be simply accomplished by the use of
sheet metal screws or the like extending through the overlapping strips of
contiguous panels.
When the panels of the present invention are employed in building
structures, it is advantageous to form the panels with a curvature, and
preferably a double curvature, so that panels of different shapes may be
assembled to form spherical or semi-spherical surfaces to support a
maximum exterior load. For such application the individual panels are
provided with a wire mesh on the exterior surface of each and such mesh is
mounted upon the panel in spaced relation thereto. Such a panel structure,
and particularly a plurality of assembled panel structures, is admirably
adapted to receive and retain a layer of concrete applied to the exterior
surfaces thereof. The wire mesh forms reinforcing rod or wire in the
concrete. Upon hardening of the concrete there is formed an integral wall
structure including the panels of the present invention which may be
treated on the interior surface thereof as desired and such a wall
structure has extremely good insulating property substantially in excess
of that available from conventional construction.
The method of manufacture of the present invention is rapid, efficient and
insures the dimensional stability of the panels. Panel cores are formed by
an expanding plastic, such as polystyrene, in a mold through the
application of heat. It is known that expanded plastic, such as expanded
polystyrene, shrinks upon removal from a mold; however, the present
invention overcomes this difficulty. The expanded plastic core is removed
from the mold and thin reinforcing strips of metal, wood or plastic are
placed on the front and back surfaces of the core and the core returned to
the mold. These strips are placed at least along the edges of the core
surfaces. An adhesive system is employed to bond the strips to the core
through the application of heat and the adhesive may be applied to the
strips prior to their insertion in the mold. Heat is then again applied to
the mold interior to actuate the adhesive system and this also serves to
re-expand the plastic core to the edges of the mold. This re-expanded
plastic bonds to the thin strips which then prevents the expanded plastic
from shrinking when the panel is removed from the mold and cooled.
DESCRIPTION OF FIGURES
The present invention is illustrated as to a particular preferred
embodiment and steps of the method of manufacture in the accompanying
drawings wherein:
FIG. 1 is a perspective view of a panel formed in accordance with the
present invention;
FIG. 2 is a sectional view taken in the plane 2--2 of FIG. 1 and excluding
the wire mesh;
FIG. 3 is a sectional view taken in the plane 3--3 of FIG. 1 and including
the wire mesh attached to the panel;
FIG. 4 is an enlarged partial view illustrating a means of attachment of
wire mesh to the panel in spaced relation thereto;
FIGS. 5, 6 and 7 are perspective illustrations of various panel shapes;
FIGS. 8 and 8A are perspective illustrations of a core mold and mold top,
respectively, as may be employed in carrying out the method of the present
invention;
FIG. 9 is a perspective illustration of a mold core in accordance with the
present invention;
FIG. 10 illustrates a plurality of thin reinforcing strips as employed in
the method hereof to form the panel of this invention;
FIG. 11 is a back elevational view of a panel core with reinforcing strips
arranged thereon;
FIG. 12 is a plan view of an open mold containing a core having reinforcing
strips arranged on front and back surfaces thereof;
FIG. 13 is a plan view of the mold in closed position for bonding the
reinforcing strips to the core;
FIG. 14 is a perspective view of a panel formed in accordance with the
method of the present invention; and
FIG. 15 is a partial sectional view of a panel undergoing degrading of the
rear surface thereof.
DESCRIPTION OF PREFERRED EMBODIMENT
The present invention as illustrated at FIGS. 1 to 3, for example, is
comprised as a core 21 of an expanded plastic material, such as expanded
polystyrene. The shape of the core 21 determines the shape of the panel
and clearly variations are possible; however, in general the core has a
substantially flat sheet-like configuration with front and back surfaces
22 and 23, respectively. The panel of the present invention may be curved
or planar and the embodiment illustrated in FIGS. 1 to 3 is a planar
panel. In the following description the core 21 is considered to be
substantially flat to distinguish the shape thereof from cylindrical,
spherical, or the like, even though it is realized that the panel may
actually be curved, as further described below.
The panel core 21 is formed of a lightweight moldable material having good
insulating properties and at least a limited structural rigidity so that
the core is, in fact, substantially rigid. The core is preferably formed
of an expanded plastic such as expanded polystyrene, polyethylene or
polyurethane of a density to provide good thermal insulation and
structural strength. For example, the core may be formed of an expanded
polystyrene having a density of the order of one pound per cubic foot to
six pounds per cubic foot and a density of two pounds per cubic foot has
been found to provide very good thermal and physical properties.
Upon the front surface 22 of the core there is disposed a plurality of thin
reinforcing strips 26 including at least horizontal strips 31 and 32
disposed along the top and bottom edges of the front surface and vertical
strips 36 and 37 disposed along the side edges of the front surface.
Additional strips are preferably provided, as indicated by the centrally
located horizontal strip 33 and the centrally located vertical strip 38.
Upon the rear surface 23 of the core there are similarly provided thin
reinforcing strips 41 including at least horizontal strips 42 and 43 on
the top and bottom edges and vertical strips 46 and 47 along the vertical
edges. In the illustrated embodiment of the invention there are also
provided centrally located horizontal and vertical strips 44 and 46,
respectively, upon the back surface of the core, preferably in alignment
with similar front strips. These reinforcing strips may be formed of
metal, wood or plastic.
The thin reinforcing strips described above are bonded to the core,
preferably by the use of an adhesive system, as further described below.
It is possible to physically attach the strips to the core by embedding
the strips in part in the core or having portions of the core extending
over parts of the strips and, of course, a variety of different types of
adhesives may also be employed. It is, however, required that the thin
reinforcing strips shall be firmly attached or bonded to the core surfaces
at least around the edges of the front and rear surfaces. The reinforcing
strips may, for example, be formed of a metal such as aluminum, tin-plated
steel, or the like and need only have a minimal thickness such as 0.010
inch thick steel. The strips are, however, to have a sufficient width to
adhere tightly to the core, although in the illustrations of FIGS. 1 to 3
the width of the strips is exaggerated. In practice a 4 ft..times.6 ft.
panel may, for example, have 3 inch wide strips. In the following
description the strips are considered to be formed of metal.
In order to provide for attachment of panels together to form a wall or the
like, the present invention provides for certain of the thin reinforcing
strips on the front face of the panel to extend beyond the core. In the
embodiment of the invention illustrated in the drawings hereof the
vertical strips 36, 37 and 38 are elongated to depend from the bottom edge
of the core so as to form metal tabs, as indicated at 51. Additionally,
the vertical strip 37 on the front face of the panel is extended laterally
outward from the right edge of the panel, as best illustrated in FIG. 1.
Thus there are provided extensions of the strips along two edges of the
front face of the panel for attachment of the panel to other structures,
such as another panel. With the strips formed of metal and the side strip
37 overlapping a metal strip on a contiguous panel, sheet metal screws,
for example, may be driven through these two strips to join the panels. It
will also be noted that, with thin metal strips extending from the panel
core as tabs 51, these tabs may be bent as desired. Thus the panel of FIG.
1 may be set upon a concrete slab, for example, with the tabs 51 bent
outwardly at right angles to the front surface of the panel and concrete
nails driven through these tabs into the concrete to fix the panel
thereto.
The panel described above is a lightweight structural member which may be
employed in a variety of ways; however, a particularly advantageous method
of employing this panel is to attach a wire mesh 61 to the front face in
offset or spaced relation thereto, as illustrated in FIGS. 1 and 3 of the
drawings. This wire mesh 61 may be attached to the panel by placing small
spacer blocks 62 on the metal strips and driving a sheet metal screw 63,
for example, through the block into the metal strip with the washer 64
under the head of the screw on top of the wire mesh, as illustrated in
FIG. 4. The spacer block 62 may for convenience be formed of the same
material as the core.
The purpose of the wire mesh 61 is to provide an apertured surface for
holding concrete applied to the front face of the panel and for then
comprising reinforcing bar in such concrete. For this purpose the depth of
the spacer blocks may be of the order of one inch when a 3 inch concrete
coating is to be applied. Generally in practice a plurality of panels in
accordance herewith are joined together to form the shape of the desired
structure and then the concrete is applied to the outer surface so that,
upon hardening, the concrete forms a rigid wall or the like attached to
the combination of panels. The panels in this application will be seen to
comprise somewhat of a form for a concrete wall which may, for example, be
applied by commercially available concrete spraying equipment or by hand;
however, the panels of the present invention remain as a portion of the
wall and, in fact, provide a high degree of insulation thereto.
As noted above, the panels of the present invention may be formed in a
variety of configurations and the planar rectangular configuration of FIG.
1, for example, is shown for ease of description. In FIGS. 5, 6 and 7
there are illustrated possible alternative panel configurations. In FIG. 5
there is illustrated a panel 71 having a generally rectangular outline but
having a curved rather than planar configuration. In FIG. 6 there is
illustrated a triangular shaped panel 72 also formed as a curved surface.
In FIG. 7 there is illustrated a panel 73 having a curvature in two
mutually perpendicular directions. It will be seen that the panels of
FIGS. 5, 6 and 7 are each formed in accordance with the present invention
as described above and panels of these shapes are particularly adapted in
multiple combinations to form semispherical surfaces which have maximum
strength for exterior loading as by the application of concrete thereto.
It is also noted that the panels of FIGS. 5, 6 and 7 are illustrated
without the wire mesh thereon; however, it will be appreciated that mesh
is attached thereto, as described above, for applications of the panels
wherein a coating such as concrete is to be applied to the panels'
surfaces.
It would, of course, also be possible to mount a wire mesh on the rear or
back surface of the panel; however, such is normally not necessary unless
it should be desired to have a double concrete wall. Alternative coatings
or the like may be applied to the back surface of the panel if desired
and, for this purpose, the back surface of the panel may be treated to
improve adherence of such a coating. Thus, for example, if a plaster is to
be applied to the back surface of the panels, the core surface may be
roughened or degraded as described below and similarly the thin metal
strips may be roughened as by the application of some type of roughening
agent such as an adhesive or the like thereto.
The present invention also includes the method of manufacture of the panel
or panels described above. This method is advantageous in providing panels
of substantially any desired configuration by molding of the panel core
and produces panels having close dimensional tolerances. The method of the
present invention is illustrated in FIGS. 8 through 15 with regard to the
manufacture of a rectangular planar panel merely for ease of illustration,
for the same process is applicable to the formation of alternatively
shaped panels, such as those illustrated, for example, in FIGS. 5 through
7.
The core 21 of the present invention is formed in accordance herewith by
molding. This molding is carried out in a mold such as that illustrated at
81 of FIG. 8 and having a top 82 for closing the mold. Normally the mold
parts are mounted in equipment which moves them together and apart as
required during processing, although such is not shown in the drawings.
The interior of the mold 81 is shown to have a rectangular configuration
of the dimensions of the resultant panel and a depth of such a panel. With
the mold closed, i.e., the top 82 applied to the bottom portion of the
mold 81, material is inserted in the mold through a pipe or the like 83
extending through a side of the mold. Considering now that the core is to
be formed of expanded polystyrene, the mold is filled with small beads of
expandable polystyrene and these beads are chosen to produce the core
density desired. The beads may be aspirated into the closed mold as by
drawing a vacuum in the mold until the mold is filled. The polystyrene in
the mold is then expanded by the application of heat. Heat may be applied
in a variety of ways; however, the convenient and conventional manner is
to inject steam into the mold and for this purpose a steam line 84 is
shown to extend through a mold wall. In practice steam may be injected in
a substantial number of places in order to ensure an even dispersion of
heat in the material in the mold. With the application of heat the beads
of polystyrene expand to fill the mold and adhere to each other to form
the core 21. Molding of polystyrene, for example, is well known in the art
and thus only the general steps are described herein.
After the core is molded it is removed from the mold and reinforcing strips
are placed on the front and back surfaces of the core. These strips are
placed at least along the edges of the front and back surfaces and may be
temporarily attached to the core in a variety of ways. For example, the
core may be molded with small aligning bumps on the front and back
surfaces and metal strips, for example, placed with the edges thereof
against these bumps and pressed into them to temporarily hold the strips
in place. Other alternatives include cleats on the strips to grip the
core, openings in the strips to grip bumps or projections on the core or
adhesive on the strips. Between the core and strips there is provided a
heat activatable adhesive which may be of conventional composition.
Reinforcing strips 41 are placed on the back surface of the core 21 as
indicated in FIG. 11 and reinforcing strips 26 are placed on the front
surface of the core as indicated in FIG. 12. The front strips 26 are
disposed with tabs 51 thereof extending from the bottom edge of the core
and with the strip 37 along the right edge of the core overhanging the
edge. The core with the strips thereon is replaced in the mold and the
mold top is replaced. The side strip 37 and tabs 51 extend over the sides
of the mold as shown in FIGS. 12 and 13. Heat is again applied to the
mold, as by injecting steam therein through the pipe 84, to bond the
strips to the core by activating the adhesive. It is furthermore noted
that when the core 21 is originally removed from the mold and cools, it
will shrink. This is an almost unavoidable consequence of casting expanded
polystyrene, for example. While it is possible to estimate the amount of
shrinkage and make the mold oversized by this amount, it will be
appreciated that such an approach is only an approximation. The present
invention, on the other hand, provides for re-expansion of the core during
the second heating cycle wherein the core and strips are inserted in the
mold. As the core is re-expanded to completely fill the mold, adherence of
the core to the metal strips along the edges of the core prevents
subsequent contraction of the core so that, when the core and strips
illustrated in FIG. 14 are removed from the mold, the external dimensions
of the core are the same as the internal dimensions of the mold. The
present invention thus provides for attaining dimensional stability in the
casting of the expanded plastic core. A cast expanded polystyrene core,
for example, will eventually lose the capability of re-expanding if it is
stored for an extended period of time before reinsertion in the mold for
bonding of the metal strips thereto. Thus it is necessary for the process
of the present invention to be carried out in an orderly manner whereby
the capability of the core to re-expand is employed.
The above-described process of forming the core with reinforcing strips
bonded thereto may be modified in various ways. Thus, for example, it is
possible to position the reinforcing strips in a mold, inject an
expandable plastic and add heat to form the panel. Bonding of the core and
strips may also be accomplished mechanically as well as chemically as by
forming the strips in such a manner that they are mechanically gripped by
the expanded plastic.
The application of wire mesh to the front surface of the panel has been
described above and may be readily accomplished by attachment thereto with
sheet metal screws, for example. It was also noted above that under some
circumstances a coating of a material such as plaster may be applied to
the back surface of panels of the present invention. Under these
circumstances it is advantageous to provide such surface with advantageous
characteristics for receiving and retaining such a coating. The cast
surfaces of the core 21 are relatively smooth and the adherence of plaster
or the like thereto may be greatly improved by "degrading" the rear
surface of the core. This may be advantageously accomplished by lightly
spraying a solvent on the back surface of the core, as generally
illustrated in FIG. 15. As small droplets of a suitable solvent are
applied as by a spray 91 to the vertical core surface 23, these droplets
will dissolve core material. It will be recalled that the core has been
cast by expanding tiny beads of polystyrene, for example, and thus the
core density actually decreases from each original bead center to the
contact with the next bead and then increases back to the adjacent bead
center. The solvent consequently acts primarily between original bead
centers to dissolve material and it has been found that spraying of a
solvent on a vertical surface of the cast core produces very irregularly
constituted small openings in the core which tend to extend downwardly and
inwardly of the core from the surface. These indentations or small
cavities are admirably suited to receive a coating such as plaster which
then flows into the cavities and securely locks the coating onto the core.
It is noted that the illustration of FIG. 15 does not attempt to show the
strips on the core; however, the degrading of the core surface is
accomplished after the strips are applied. Inasmuch as the reinforcing
strips may be quite smooth, it is also preferable to apply some type of
roughening agent to the strips prior to the application of a coating such
as plaster. Various types of materials are suitable for this such as, for
example, some type of an adhesive material which sticks tightly to the
outer surface of the strips but is not smooth.
There has been described above an improved composite panel structure that
is lightweight, inexpensive and has extremely good insulating properties.
The panel structure is primarily intended for utilization with exterior
coatings; however, such is not absolutely necessary. The application of
wire mesh to the front surface of a panel in accordance with this
invention provides an improved panel particularly adapted to receive
concrete coating.
The present invention as to panel structure and method of manufacture has
been set forth above with respect to particular preferred embodiments of
the panel and steps of manufacture; however, it will be appreciated by
those skilled in the art that modifications and variations thereof are
possible within the scope of the present invention. It is not intended to
limit the present invention to the precise terms of description nor
details of illustration.
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